Image forming apparatus

Abstract

In an image forming apparatus that performs toner ejection, the amount of toner consumed is suppressed. [Solution] The image forming apparatus comprises an image carrier 1, a charging member 2, an exposure apparatus, a developing member 22, an intermediate transfer body 10, a transfer member 14, and a control unit configured to perform a toner ejection operation. In the toner ejection operation, the control unit controls the surface potential and transfer voltage of the image carrier 1 so that the toner on the surface of the image carrier 1 is carried onto the image carrier 1 when the toner supply unit first passes through the transfer unit, controls the surface potential and charging voltage of the image carrier so that the toner on the surface of the image carrier 1 is carried onto the image carrier when the toner supply unit that has passed through the transfer unit passes through the charging unit, and controls the surface potential and transfer voltage of the image carrier 1 so that the toner remaining on the surface of the image carrier 1 that has passed through the developing unit passes through the transfer unit again, moves onto the intermediate transfer body 10.

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus for forming an image on a recording material. [Background technology]

[0002] Conventionally, image forming devices such as photocopiers and laser beam printers are known to have a configuration that includes a developing unit that houses toner and an intermediate transfer unit. In such image forming devices, for example, if images with a low print density are continuously output, the toner in the developing unit will hardly be consumed, which may lead to the toner in the developing unit degrading and causing a decrease in image quality.

[0003] Patent documents 1 and 2 disclose an image forming apparatus capable of performing an operation to eject (force consume) deteriorated toner from within the developing device, separate from the image forming operation. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2006-023327 [Patent Document 2] Japanese Patent Publication No. 2000-310909 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, with the above configuration, during the toner ejection process, both deteriorated toner and fresh toner that is not significantly deteriorated are ejected simultaneously. In other words, toner that can be used without problems in image formation is forcibly ejected, increasing toner consumption and shortening the lifespan of the developing unit and the cartridge containing the developing unit. Furthermore, the waste toner container that holds the ejected toner tends to fill up quickly, increasing the frequency of waste toner container replacement.

[0006] The present invention has been made in view of the above-mentioned problems, and aims to suppress toner consumption in an image forming apparatus that performs a toner ejection operation. [Means for solving the problem]

[0007] To achieve the above-mentioned objectives, the image forming apparatus according to this application is: A rotatable image carrier, A charging member that charges the image carrier, A charging voltage application unit that applies a charging voltage to the charging member, An exposure apparatus that exposes the surface of the image carrier to form an electrostatic latent image, A developing member supplies toner to the image carrier and develops the electrostatic latent image formed on the surface of the image carrier to form a toner image, A developing voltage application unit that applies a developing voltage to the developing member, An intermediate transfer body that comes into contact with the image carrier to form a transfer nip, and in the transfer nip, the toner image formed on the surface of the image carrier is transferred; A transfer member that comes into contact with the intermediate transfer body, A transfer voltage application unit that applies a transfer voltage to the transfer member, A control unit for controlling the charging voltage, the exposure amount of the exposure apparatus, the development voltage, and the transfer voltage, the control unit is configured to perform an image forming operation for forming an image on a recording material, and a toner ejection operation for supplying toner from the developing member to the image carrier, recovering a portion of the supplied toner with the developing member, and moving a portion to the intermediate transfer body. Equipped with, The control unit, in the toner ejection operation, When the toner supply unit, which is supplied with toner for the image carrier, first passes through the transfer unit, which is the contact area between the image carrier and the intermediate transfer unit, the surface potential of the image carrier and the transfer voltage are controlled so that the toner on the surface of the image carrier is carried on the image carrier. The toner supply unit, having passed through the transfer unit, controls the surface potential and charging voltage of the image carrier so that the toner on the surface of the image carrier is carried on the image carrier when the charging member passes through the charging unit that charges the image carrier. When the toner remaining on the surface of the image carrier, which has passed through the developing section (the contact area between the image carrier and the developing member), passes through the transfer section again, the surface potential of the image carrier and the transfer voltage are controlled so that the toner remaining on the surface of the image carrier moves onto the intermediate transfer body. It is characterized by the following: Furthermore, in order to achieve the above-mentioned objectives, the image forming apparatus according to this application is A rotatable image carrier, A charging member that charges the image carrier, A charging voltage application unit that applies a charging voltage to the charging member, An exposure apparatus that exposes the surface of the image carrier to form an electrostatic latent image, A developing member supplies toner to the image carrier and develops the electrostatic latent image formed on the surface of the image carrier to form a toner image, A developing voltage application unit that applies a developing voltage to the developing member, An intermediate transfer body that comes into contact with the image carrier to form a transfer nip, and in the transfer nip, the toner image formed on the surface of the image carrier is transferred; A transfer member that comes into contact with the intermediate transfer body, A transfer voltage application unit that applies a transfer voltage to the transfer member, A control unit for controlling the charging voltage, the exposure amount of the exposure apparatus, the development voltage, and the transfer voltage, characterized in that it is configured to perform an image forming operation for forming an image on a recording material, and a toner ejection operation for supplying toner from the development member to the image carrier, moving a portion of the supplied toner to the intermediate transfer body when the toner supply unit of the image carrier first passes through the transfer unit which is the contact portion between the image carrier and the intermediate transfer body, while leaving the remaining portion in the toner supply unit, and moving the remaining toner to the intermediate transfer body when the remaining toner passes through the transfer unit again. [Effects of the Invention]

[0008] According to the present invention, in an image forming apparatus that performs a toner ejection operation, toner consumption can be suppressed.

Brief Description of the Drawings

[0009] [Figure 1] It is an explanatory diagram of ejection control according to Example 1. [Figure 2] It is a schematic cross-sectional view showing the schematic configuration of the image forming apparatus according to Example 1. [Figure 3] It is an explanatory diagram of the configuration of the engine control unit according to Example 1. [Figure 4] It is an explanatory diagram of weak exposure control according to Example 1. [Figure 5] It is a schematic diagram showing the schematic configuration of the developing device according to Example 1. [Figure 6] It is a diagram showing a configuration example of toner having a convex portion. [Figure 7] It is an explanatory diagram of a method for recovering transfer residual toner according to Example 1. [Figure 8] It is an explanatory diagram of voltage and potential control of ejection control according to Example 1. [Figure 9] It is an explanatory diagram of solid ejection control according to Comparative Example 2. [Figure 10] It is an explanatory diagram of voltage and potential control of deteriorated solid ejection control according to Comparative Example 2. [Figure 11] It is a schematic cross-sectional view showing the schematic configuration of the image forming apparatus according to Example 2. [Figure 12] It is a schematic diagram showing the schematic configuration of the pre-charging exposure device according to Example 2. [Figure 13] It is an explanatory diagram of voltage and potential control of ejection control according to Example 2. [Figure 14] It is an explanatory diagram of the charge amount distribution of fog toner. [Figure 15] It is an explanatory diagram of the back contrast dependency of fog toner. [Figure 16] It is an explanatory diagram of the first fog ejection control according to Example 3. [Figure 17] This is an explanatory diagram of the voltage and potential control of the first fouling discharge control according to Example 3. [Figure 18] This is an explanatory diagram of the first fouling discharge control according to Example 4. [Figure 19] This is an explanatory diagram of the voltage and potential control of the first fouling discharge control according to Example 4. [Figure 20] This is an explanatory diagram of the voltage and potential control of the first fouling discharge control according to Modification Example 1. [Figure 21] This is an explanatory diagram of another configuration example related to Example 4. [Figure 22] This is an explanatory diagram of the rear rotation control according to Example 11. [Figure 23] This is an explanatory diagram of the voltage and potential control for rear rotation control according to Example 11. [Figure 24] This is an explanatory diagram of the voltage and potential control for rear rotation control according to Example 12. [Figure 25] This is an explanatory diagram illustrating an example of adjusting the transfer contrast individually. [Figure 26] This is an explanatory diagram of the method for dividing the paper area according to Example 13. [Figure 27] This is an explanatory diagram of the number of sheets of paper fed, the print rate, and the percentage of degraded toner related to Example 13. [Figure 28] This is an explanatory diagram of the discharge control according to Example 13. [Figure 29] This diagram shows a flowchart of the pre-discharge control according to Example 14. [Figure 30] This is an explanatory diagram of the method for setting the execution interval of discharge control according to Example 14. [Figure 31] This is an explanatory diagram illustrating the relationship between the execution interval of the output control and the aspect ratio. [Figure 32] This is an explanatory diagram of the method for setting the execution interval of the discharge control according to modified example 7. [Figure 33] This figure shows a flowchart of the pre-discharge control related to modified example 8. [Figure 34] This figure shows a flowchart of the pre-discharge control according to Example 14. [Figure 35] This is an explanatory diagram illustrating the relationship between cartridge lifespan and transfer voltage in modified example 9. [Modes for carrying out the invention]

[0010] The embodiments for carrying out this invention will be described in detail below with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in these embodiments should be appropriately modified depending on the configuration of the device to which the invention is applied and various conditions. In other words, the scope of this invention is not intended to be limited to the following embodiments. Furthermore, not all of the features described in the following embodiments are essential to the solution of the invention.

[0011] [Example 1] The following describes an image forming apparatus according to Embodiment 1 to which the present invention can be applied. In the following description, the present invention will be described in the case where it is applied to an image forming apparatus of the electrophotographic image forming method that forms an image on a recording medium using an electrophotographic image forming process. Examples of image forming apparatuses of the electrophotographic image forming method include electrophotographic copiers, electrophotographic printers (LED printers, laser beam printers, etc.), electrophotographic facsimile machines, etc.

[0012] <Image forming apparatus> First, the overall configuration of the electrophotographic image forming apparatus (hereinafter referred to as the image forming apparatus) according to the present invention will be described. The configuration, operation, and control of the image forming apparatus 100 in this embodiment will be explained using Figure 2. Figure 2 is a schematic cross-sectional view showing the general configuration of the image forming apparatus 100 of Embodiment 1.

[0013] The image forming apparatus 100 in this embodiment is a full-color laser printer employing an in-line method and an intermediate transfer method.

[0014] The image forming apparatus 100 can form a full-color image on a recording material P (e.g., recording paper, plastic sheet) according to the image information. The image information is input to the image forming apparatus 100 from an image reading device or a host computer such as a personal computer that is communicatively connected to the image forming apparatus 100.

[0015] The image forming apparatus 100 comprises multiple image forming units for forming images of yellow (Y), magenta (M), cyan (C), and black (K). The image forming apparatus 100 also includes first, second, third, and fourth process cartridges Sa, Sb, Sc, and Sd, which constitute each image forming unit. In this embodiment, the first to fourth process cartridges Sa, Sb, Sc, and Sd are arranged in a line intersecting the vertical direction. In this embodiment, the configuration and operation of the first to fourth process cartridges Sa, Sb, Sc, and Sd are substantially the same, except for the different colors of the images they form. Therefore, in the following description, unless otherwise specified, the subscripts a, b, c, and d, which indicate elements provided for a particular color, will be omitted, and a general description will be provided.

[0016] In this embodiment, the image forming apparatus 100 has four drum-shaped electrophotographic photoreceptors, namely photosensitive drums 1 (1a, 1b, 1c, 1d), arranged in parallel in a direction intersecting the vertical direction, as multiple image carriers. The photosensitive drums 1 are rotationally driven by a photosensitive drum drive source 406, which is a driving means. Around the photosensitive drums 1 are charging rollers 2 (2a, 2b, 2c, 2d), scanner units (exposure devices) 3 (3a, 3b, 3c, 3d), and developing units (developing devices) 4 (4a, 4b, 4c, 4d).

[0017] The charging roller 2 is a charging means (charging member) that uniformly charges the surface of the photosensitive drum 1. The scanner unit 3 is an exposure means (exposure device) that irradiates a laser to form an electrostatic image (electrostatic latent image) on the photosensitive drum 1 based on the output calculated by the CPU 207 from image information input from a host computer such as a personal computer. When the exposure means forms an electrostatic latent image corresponding to the image signal, the photosensitive drum potential is stabilized by uniformly and weakly exposing the non-image area of ​​the surface of the photosensitive drum 1. Hereinafter, the formation of an electrostatic image by the exposure means will be distinguished as exposure, and uniformly exposing the non-image area will be distinguished as weak exposure. The developing unit 4 includes a developing roller 22 as a developing member and is a developing means (developing device) that develops the electrostatic image as a developer (hereinafter referred to as toner) image.

[0018] The photosensitive drum 1, the charging roller 2 which acts as a process means on the photosensitive drum 1, and the developing unit 4 are integrated to form a process cartridge S. The developing unit 4 and the process cartridge S are cartridges that can be attached to and detached from the image forming apparatus 100 via mounting means such as mounting guides and positioning members provided on the image forming apparatus 100.

[0019] An intermediate transfer belt 10 is positioned opposite the four photosensitive drums 1, serving as an intermediate transfer body for transferring the toner image on the photosensitive drums 1 to the recording material P. The intermediate transfer belt 10, formed as an endless belt, contacts all of the photosensitive drums 1 and moves (rotates) in a circular motion in the direction of arrow R3 (clockwise) in Figure 2. The intermediate transfer belt 10 is stretched across a plurality of support members: a drive roller 11, a tension roller 12, and a secondary transfer opposing roller 13. The drive roller 11 is a rotational drive member that rotates in the direction of arrow R2 (clockwise) in Figure 1, thereby driving the intermediate transfer belt 10 to rotate in the direction of arrow R3.

[0020] On the inner circumferential surface of the intermediate transfer belt 10, four primary transfer rollers 14 (14a, 14b, 14c, 14d) are arranged in parallel, facing each photosensitive drum 1, as primary transfer means. The primary transfer rollers 14 contact the intermediate transfer belt 10, pressing the intermediate transfer belt 10 toward the photosensitive drum 1, and the primary transfer portion where the intermediate transfer belt 10 and the photosensitive drum 1 come into contact ( It is a (primary) transfer member that forms a primary transfer nip.

[0021] A primary transfer voltage (primary transfer voltage Vtr = +100V in this embodiment) with the opposite polarity to the normal charging polarity of the toner is applied to the primary transfer roller 14 from the primary transfer power supply 15 (high voltage power supply), which serves as a primary transfer voltage application means. As a result, the toner image on the photosensitive drum 1 is primary transferred onto the intermediate transfer belt 10. When forming a full-color image, the above process is carried out sequentially in the first to fourth process cartridges Sa, Sb, Sc, and Sd, and the toner images of each color are superimposed onto the intermediate transfer belt 10 and primary transferred.

[0022] The primary transfer roller 14 in this embodiment is a cylindrical metal roller with a diameter of φ6 mm, and the material used is nickel-plated SUM material.

[0023] The intermediate transfer belt 10 is an endless belt in which conductivity is imparted by adding a conductive agent to a resin material. It has a circumference of 700 mm and a thickness of 70 μm, and uses an endless polyimide resin mixed with carbon as the conductive agent as the base layer. In terms of electrical properties, it exhibits electronic conductivity and is characterized by small fluctuations in resistance value with respect to ambient temperature and humidity. In this example, the volume resistivity of the intermediate transfer belt 10 is 1 × 10⁻⁶ 9 The value is Ω·cm. Volume resistivity was measured using a HIRESTA-UP (MCP-HT450) from Mitsubishi Chemical Corporation with a ring probe of type UR (model MCP-HTP12). The measurement was performed under the following conditions: room temperature set to 23°C, room humidity 50%, applied voltage 100V, and measurement time 10 sec. Here, volume resistivity is a measure of the conductivity of the intermediate transfer belt 10 as a material.

[0024] A secondary transfer roller 20 is positioned on the outer circumferential surface of the intermediate transfer belt 10 at a location facing the secondary transfer opposing roller 13, serving as a secondary transfer means. The secondary transfer roller 20 is a (secondary) transfer member that presses against the secondary transfer opposing roller 13 via the intermediate transfer belt 10, forming a secondary transfer portion (secondary transfer nip portion) where the intermediate transfer belt 10 and the secondary transfer roller 20 come into contact.

[0025] A voltage opposite to the normal charging polarity of the toner is applied to the secondary transfer roller 20 from the secondary transfer power supply 21 (high-voltage power supply), which serves as a secondary transfer voltage application means. As a result, the four-color toner images on the intermediate transfer belt 10 are transferred collectively onto the recording material P by the action of the secondary transfer roller 20, which is in contact with the intermediate transfer belt 10 via the recording material P. The recording material P stored in the cassette 51 is transported to the secondary transfer section by the feeding means 50 in synchronization with the movement of the intermediate transfer belt 10.

[0026] A cleaning device 16 is positioned opposite the secondary transfer opposing roller 13 via the intermediate transfer belt 10, serving as a cleaning device (removal device) for cleaning (removing) toner on the intermediate transfer belt 10. The cleaning device 16 cleans and removes any residual secondary transfer toner remaining on the intermediate transfer belt 10, and the toner is then collected in the waste toner container 17.

[0027] After the secondary transfer is complete, the recording material P, which carries the four-color toner images, is transported to the fixing device 30, specifically the fixing nip section formed by the fixing roller 31 and the pressure roller 32. There, the recording material P is heated and pressurized, causing the four colors of toner to melt and mix, fixing the recording material P, and it is then discharged from the image forming apparatus 100.

[0028] Furthermore, the image forming apparatus 100 can also form monochrome or multicolor images using only one desired image forming unit, or using only some (but not all) of the image forming units.

[0029] In this embodiment, the image forming apparatus 100 has a process speed of 148 mm / sec and LE This printer supports TTER size paper.

[0030] <Engine Control Section> The configuration of the engine control unit 210, which controls the entire image forming apparatus, will be explained with reference to Figure 3. Figure 3 is an explanatory diagram of the configuration of the engine control unit 210 according to Embodiment 1.

[0031] The image forming apparatus 100 includes an engine control unit 210 as a control unit for controlling the operation of each part during various operations such as printing. As shown in Figure 3, the engine control unit 210 incorporates a CPU circuit unit 150, a ROM 151, and a RAM 152. The CPU circuit unit 150 comprehensively controls the primary transfer control unit 201, the secondary transfer control unit 202, the development control unit 203, the exposure control unit 204, the charging control unit 205, the pre-charging exposure control unit 206, the development blade control unit 401, and the supply roller control unit 403 according to the control program stored in the ROM 151. The RAM 152 temporarily holds control data and is used as a work area for calculation processing associated with the control.

[0032] The primary transfer voltage application unit, which applies a primary transfer voltage (transfer voltage) to the primary transfer roller 14, includes a primary transfer power supply 15 as a primary transfer voltage application means and a primary transfer control unit 201 that controls the primary transfer power supply 15. The secondary transfer voltage application unit, which applies a secondary transfer voltage (transfer voltage) to the secondary transfer roller 20, includes a secondary transfer power supply 21 as a secondary transfer voltage application means and a secondary transfer control unit 202 that controls the secondary transfer power supply 21. The developing voltage application unit, which applies a developing voltage to the developing roller 22, includes a developing power supply 502 as a developing voltage application means and a developing control unit 203 that controls the developing power supply 502. The developing blade voltage application unit (regulating voltage application unit), which applies a developing blade voltage (regulating voltage) to the developing blade 23 of the developing unit 4, includes a developing blade power supply 402 as a developing blade voltage application means (regulating voltage application means) and a developing blade power supply 402 that controls the developing blade power supply 402. The supply voltage application unit that applies a supply voltage to the supply roller 26 of the developing unit 4 includes a supply roller power supply 404 as a supply voltage application means and a supply roller control unit 403 that controls the supply roller power supply 404. The charging voltage application unit that applies a charging voltage to the charging roller 2 includes a charging power supply 501 as a charging voltage application means and a charging control unit 205 that controls the charging power supply 501. The image forming apparatus 100 also includes a photosensitive drum drive source 406 for driving the photosensitive drum 1 and a photosensitive drum control unit 208 that controls the photosensitive drum drive source 406 to control the operation of the photosensitive drum 1.

[0033] When the controller 200 receives print information and print commands from the host computer 199, it sends a video signal to the engine control unit 210. The engine control unit 210 then controls each of the aforementioned control units according to the video signal and performs the image forming operations necessary for the printing operation.

[0034] The image forming apparatus 100 includes an environmental sensor 300 which includes a temperature sensor 301 that acquires temperature information of the installation environment and a humidity sensor 302 that acquires humidity information of the installation environment. The temperature information acquired by the temperature sensor 301 and the humidity information acquired by the humidity sensor 302 are sent to the engine control unit 210 and can be used for controlling the operation of each part.

[0035] <Low exposure control> The control of weak exposure in the non-image area implemented in this embodiment will be explained using Figure 4. Figure 4 is an explanatory diagram of the weak exposure control according to Embodiment 1.

[0036] In Figure 4, the image signal sent from the controller 200 is a multi-level signal (0-255) with 8 bits = 256 gradations in the depth direction. When this signal is 0, the laser light is off; when it is 255, it is fully on; and between 1 and 254, it has a value intermediate between the two. Here, the non-image exposure level can be arbitrarily set by the level of the above multi-level signal. In the following explanation, 32 is used as the level of this multi-level signal, and the non-image exposure level is set accordingly. Light shall be used.

[0037] Non-image portions of the image signal sent from the controller 200, where the signal is 0, are converted to 32 by the image signal conversion circuit 68 in the exposure control unit 204. For image signals with values ​​between 1 and 255, they are compressed and converted from 33 to 255. Subsequently, the frequency modulation circuit 61 converts them into a serial time-axis signal, which in this example is used for pulse width modulation of each dot pulse with a resolution of 600 dots / inch.

[0038] This signal drives the laser driver 62, causing the laser diode 63 to emit light and the laser beam L to be emitted. This laser beam L passes through a correction optical system 67, which includes a polygon mirror 64, a lens 65, and a folding mirror 66, and is then irradiated onto the photosensitive drum 1 as scanning light. The frequency modulation circuit 61 may be located on the controller side, separate from the laser driver 62.

[0039] <Processing Cartridge> Next, the overall configuration of the process cartridge S installed in the image forming apparatus 100 of this embodiment will be described.

[0040] The process cartridge S is composed of a photosensitive unit equipped with a photosensitive drum 1 and a rotatable charging roller 2, and a developing unit (developing device) 4 equipped with a rotatable developing roller 22, etc., integrated into one unit.

[0041] The photosensitive drum 1 is rotatably supported via a bearing (not shown). The photosensitive drum 1 is configured to rotate in the direction of arrow R1 (counterclockwise) in Figure 2 in accordance with the image forming operation, as the driving force of a driving means (driving source) (not shown) is transmitted to the photoreceptor unit. The charging roller 2 is configured to rotate driven by the pressure of a conductive rubber roller portion that makes pressure contact with the photosensitive drum 1. In this embodiment, a charging roller 2 that makes pressure contact with the photosensitive drum 1 is used, but this is not the only option, and a non-contact charging method such as a corona charger may also be used.

[0042] The photosensitive drum 1 consists of a φ20mm aluminum tube on which a photosensitive layer and a surface layer are provided. The surface layer of the photosensitive drum 1 uses a thin film layer with a thickness of 23 μm formed of polyarylate.

[0043] The electrostatic roller 2 has a metal shaft with a diameter of 5.5 mm and a thickness of 1.5 mm, with a volume resistivity of 1 × 10⁻⁶. 6 A roller measuring 228 mm in length and 8.5 mm in diameter was used, which had an elastic layer made of conductive rubber with a conductivity of approximately Ω cm. The charged roller 2 was pressed against the photosensitive drum 1 with a total pressure of 600 gf (300 gf on each side) from bearings (not shown) at both ends of the metal shaft, and rotated while forming a nip width of approximately 300 μm.

[0044] The configuration of the developing unit 4 will be explained using Figure 5. Figure 5 is a schematic cross-sectional view showing the general configuration of the developing unit 4.

[0045] As shown in Figure 5, the developing unit 4 includes a developing roller 22 (developing member) that carries toner T, a developing blade 23 (regulating member), a supply roller 26 (supply member), and a developing frame 24 that fixes these together. The developing frame 24 includes a developing chamber 241 in which the developing roller 22 is located, and an anti-blowing sheet 242 that seals the developing opening (opening) that connects the developing chamber 241 to the outside world. The developing chamber 241 is a toner storage section that stores toner inside.

[0046] One end of the developing blade 23 is fixed to the fixing member 25. The fixing member 25 is fixed to the developing frame 24, thereby integrating the developing blade 23 and the developing frame 24. One end of the rade 23 and the other end opposite it are in contact with the developing roller 22, and the configuration allows for regulation of the amount of toner T coated on the developing roller 22 and the application of charge. The developing roller 22 is located in the developing opening and is positioned so as to be in contact with the photosensitive drum 1. In this embodiment, the image forming apparatus 100 is also equipped with a separation mechanism that moves the developing roller 22 away from and in contact with the photosensitive drum 1.

[0047] The developing roller 22, as shown in Figure 5, is a roller with an outer diameter of φ10 mm, having a structure in which a metal core 221, a base layer 222, and a surface layer 223 are sequentially laminated. The metal core 221 has a diameter of φ6.0 mm. The base layer 222 has a thickness of 2.0 mm and a volume resistivity of 1 × 10⁻⁶. 7 It is made of conductive silicone rubber with a thickness of approximately Ωcm. The surface layer 223 is made of urethane. The developing roller 22 is arranged to rotate in the direction of arrow R4 (clockwise direction) in Figure 2. The developing roller 22 rotates with a speed difference relative to the photosensitive drum 1 in order to control the amount of toner T developed onto the photosensitive drum 1.

[0048] In this embodiment, the development control unit 203 shown in Figure 3 controls the development roller drive source 405. By controlling the development roller drive source 405, the rotation speed of the development roller 22 can be changed relative to the rotation speed of the photosensitive drum 1. In this embodiment, the development roller 22 rotates at 140% of the rotation speed of the photosensitive drum 1.

[0049] As shown in Figure 5, the developing blade 23 (regulating member) is in contact with the developing roller 22 in a direction that is counter to the direction of rotation of the developing roller 22, thereby regulating the amount of toner T coated and imparting charge through triboelectric charging. In other words, the direction from the end of the developing blade 23 on the fixing member 25 side to the end on the contact side with the developing roller 22 is opposite to the direction of rotation of the developing roller 22 at the contact point between the developing blade 23 and the developing roller 22.

[0050] In this embodiment, the developing blade 23, which is a regulating member for the toner T, is a support member with a blade portion provided on a leaf spring-shaped support member. The support member is a leaf spring-shaped SUS plate with a thickness of 50 to 120 μm. The blade portion is formed by coating the surface of the support member with a thin film made of conductive urethane resin. The developing blade 23 is in contact with the developing roller 22 by utilizing the spring elasticity of the support member.

[0051] Furthermore, a predetermined DC voltage (developing blade voltage Vbld) is applied to the developing blade 23, and a developing voltage Vdc (developing roller voltage) is applied to the developing roller 22. By controlling the differential ΔVbld (Vbld-Vdc, developing blade contrast), which is the potential difference between the developing blade voltage Vbld and the developing voltage Vdc, the amount of toner T coated and the amount of toner charged can be controlled. In this embodiment, the voltages are controlled to be Vbld=-500V, Vdc=-300V, and ΔVbld=-200V during the image forming operation.

[0052] The supply roller 26 (supply member) is constructed by providing a foamed urethane layer 262 around a core metal electrode 261 with an outer diameter of φ5.5 mm, which is a conductive support. The total outer diameter of the supply roller 26, including the foamed urethane layer 262, is φ11 mm. The penetration depth between the supply roller 26 and the developing roller 22 is 1.2 mm. At the point of contact with the developing roller 22, the supply roller 26 rotates in a direction (direction of arrow R5 in Figure 2) such that they have opposite velocities. The powder pressure of the toner T present around the foamed urethane layer 262 acts on it, and as the supply roller 26 rotates, the toner T is drawn into the foamed urethane layer 262.

[0053] The supply roller 26 containing toner T supplies toner T to the developing roller 22 at the contact point with the developing roller 22, and further friction imparts a preliminary triboelectric charge to the toner T. In other words, the supply roller 26 is configured to charge the toner T carried on the developing roller 22. On the other hand, the supply roller 26 that supplies toner T to the developing roller 22 is developed in the developing section. It also serves to peel off any toner T that remains on the developing roller 22 without being processed.

[0054] A predetermined DC voltage (supply voltage Vrs) is applied to the supply roller 26. By controlling the potential difference between the supply voltage Vrs and the developing voltage Vdc (difference ΔVrs = Vrs - Vdc), the toner supply amount and the amount of preliminary triboelectric charge can be controlled. In this embodiment, the voltages are controlled to be Vrs = -500V, Vdc = -300V, and ΔVrs = -200V during the image forming operation.

[0055] The toner T according to Example 1 is a non-magnetic toner with a normal charge polarity of negative polarity, manufactured by suspension polymerization, and has a volume-average particle size of 7.0 μm. The toner T becomes negatively charged when supported on the developing roller 22. In addition, in order to modify the surface properties of the toner matrix (referring to the carbon-based composition of the binder resin and release agent contained in the toner particles), silicon dioxide particles at a concentration of about 1.5% of the toner's weight are attached to the surface of the toner as an external additive. The volume-average particle size of the silicon dioxide particles is about 20 to 120 nm.

[0056] Due to prolonged friction with the developing blade, the toner T may deform in shape, or the external additives on the toner surface may peel off or become embedded. The deformation of the toner shape increases the contact area between the toner T and the photosensitive drum 1. Additionally, the peeling off of the external additives on the toner surface causes the resin component of the toner to come into contact with the photosensitive drum 1, and the embedding of the external additives into the toner further increases the contact area between the toner and the photosensitive drum 1. As a result, the non-electrostatic adhesion force to the photosensitive drum 1 becomes higher compared to when it is new. In the following explanation, this phenomenon will be referred to as the deterioration of toner T.

[0057] The change in non-electrostatic adhesion force due to deformation of the toner shape can be represented by a change in the average circularity (aspect ratio) of the toner T. In this embodiment, the average circularity in a new state is approximately 0.95, and a state where it falls below approximately 0.90 is considered a deteriorated state. The average circularity of the toner can be measured using the flow-type particle image analyzer "FPIA-3000" (manufactured by Sysmex Corporation).

[0058] Furthermore, changes in the surface condition due to peeling or embedding of external additives contained in toner T can be quantitatively understood using the BET value. In this embodiment, QuadraSorb SI manufactured by Cantachrome was used to measure the BET value of toner T. The BET value of toner T, used as an indicator of the change in the adhesion state of external additives to the toner surface, indicates the amount of external additives attached to the toner surface. As the amount of external additives present on the toner surface decreases, the BET value of toner T decreases. In other words, when an external additive with a high BET value is added to the toner matrix surface, the BET value of the toner increases, but the BET value of toner T decreases due to the embedding of the external additives into the toner resin or their detachment from the toner surface. When the external additive is completely removed from the toner surface, the BET value of toner T becomes the same as the BET value of the toner matrix. In this embodiment, the BET value of a new product was 2.8m 2 It is approximately / g, and 2.0m 2 A state where the value falls below approximately / g is considered a deteriorated state.

[0059] Changes in non-electrostatic adhesion can be measured using other indicators; for example, by directly measuring the amount of toner remaining after primary transfer (primary transfer residue), changes in non-electrostatic adhesion can be determined by an increase in the primary transfer residue.

[0060] In this embodiment, toner T was used in which an external additive was added to the base material, but this is not limited to this. For example, toner T may be used in which a toner base material has a protrusion Ta containing an organosilicon polymer having a substructure represented by the following formula (1). R0-SiO3 / 2 (Equation 1) (R0 is an alkyl group or phenyl group with 1 to 6 carbon atoms)

[0061] Figure 6 shows an example of the configuration of toner T having protrusions Ta. The convex spacing G, which is the distance between adjacent convex portions Ta on the toner surface, and the convex height H, which is the height of the convex portion Ta from the base material, can be measured using a scanning probe microscope (hereinafter referred to as SPM). The SPM is equipped with a probe, a cantilever that supports the probe, and a displacement measurement system that detects the bending of the cantilever, and observes the shape of the sample surface by detecting the interatomic force (attractive or repulsive force) between the probe and the sample.

[0062] <Toner development and collection of leftover toner> The development of toner and the recovery of residual toner in the developing unit will be explained using Figures 7(a) to 7(d). Figures 7(a) to 7(d) are explanatory diagrams of the method for recovering residual toner. In Figures 7(a) and 7(c), circles enclosed by solid lines represent the toner after movement, and circles enclosed by dashed lines represent the toner before movement.

[0063] First, we will explain toner development using Figures 7(a) and 7(b). Figure 7(a) is a schematic diagram of the potential relationship when toner is developed. Figure 7(b) is a schematic diagram of the vicinity of the developing unit when toner is developed.

[0064] In this embodiment, the charging voltage Vpri applied to the charging roller 2 during the image formation operation is -1200V, and the surface potential (post-charging potential Vp, post-charging drum potential) of the photosensitive drum 1 after charging is approximately -700V. Furthermore, the post-weak exposure potential Vd (post-weak exposure drum potential) formed in the non-image area of ​​the photosensitive drum 1 due to weak exposure is approximately -480V. The developing voltage Vdc applied to the developing roller 22 is -300V, and the post-exposure potential VL (exposed drum potential) of the photosensitive drum 1 after the charge has decayed due to exposure is approximately -150V.

[0065] Primary transfer is performed by the transfer contrast ΔVtr1 (primary transfer contrast), which is the potential difference between the post-exposure potential VL and the primary transfer voltage Vtr. As shown in Figures 7(a) and (b), the potential difference between the development voltage Vdc and the post-exposure potential VL (hereinafter referred to as the development contrast ΔVc) causes the electrostatic latent image to be revealed in the development section where the negatively charged toner comes into contact with the photosensitive drum 1, thereby forming a toner image. In addition, the potential difference between the development voltage Vdc and the post-weak exposure potential Vd formed by weak exposure (hereinafter referred to as the back contrast ΔVb) electrically holds the toner on the development roller 22 so that it does not transfer to the non-image area.

[0066] Next, we will explain how to process the toner that remains on the surface of the photosensitive drum 1 without being transferred to the intermediate transfer belt 10 during the primary transfer process (hereinafter referred to as residual toner).

[0067] In this embodiment, the remaining toner is recovered by the developing roller 22 and reused. The method of recovering the remaining toner by the developing roller 22 (hereinafter referred to as developing and recovering) will be explained using Figures 7(c) and 7(d). Figure 7(c) is a schematic diagram of the potential relationship during developing and recovering. Figure 7(d) is a schematic diagram of the vicinity of the developing unit during developing and recovering.

[0068] Of the toner developed on the photosensitive drum 1, the toner with a low charge and nearly neutral polarity cannot be transferred to the intermediate transfer belt 10 in the primary transfer process and remains on the surface of the photosensitive drum 1 as transfer residue toner. As shown in Figures 7(c) and (d), the transfer residue toner is charged to a normal charge polarity by the charging voltage Vpri when it passes through the contact area with the charging roller 2. At the same time, a post-charge potential Vp is formed on the surface of the photosensitive drum 1 by the charging voltage Vpri, and subsequently a post-weak exposure potential Vd is formed by weak exposure.

[0069] A potential difference (back contrast ΔVb) is generated between the potential of the developing roller 22 (developing voltage Vdc) formed by applying a DC voltage to the developing roller 22 and the potential Vd after weak exposure. The residual toner on the drum surface, where a potential Vd has been formed after weak exposure, is charged with the normal charging polarity. The residual toner on the drum surface, where a potential Vd has been formed after weak exposure, is collected by the developing roller 22 by the electric field caused by the potential difference (back contrast ΔVb). The toner collected by the developing roller 22 is then reused.

[0070] <Discharge control> The image forming apparatus 100 according to Example 1 is configured to efficiently discharge and process deteriorated toner generated as a result of using the process cartridge S from the developing unit 4 (developing container) without discharging a large amount of toner that has not deteriorated significantly. In the following description, toner that has not deteriorated significantly will be referred to as fresh toner, and toner that has deteriorated as a result of using the process cartridge S will be referred to as deteriorated toner.

[0071] In this embodiment, the image forming apparatus 100 is configured to perform an image forming mode for image forming operations and a toner ejection mode for toner ejection operations for processing degraded toner. In the toner ejection operation, the toner in the developing unit 4 (including both degraded toner and fresh toner) is ejected onto the photosensitive drum 1. Subsequently, the fresh toner is selectively recovered in the developing unit, and the degraded toner is recovered into the waste toner container 17 by the cleaning device 16. Hereinafter, the operation control of the toner ejection operation, which is different from such image forming operations, will be referred to as degraded toner ejection control (ejection control).

[0072] The image forming apparatus 100 according to Example 1 can selectively discharge deteriorated toner from within the developing unit 4 while recovering a portion of the fresh toner into the developing unit 4 through deteriorated toner discharge control (deteriorated toner discharge operation). Therefore, efficient discharge can be achieved, and unnecessary toner consumption can be suppressed.

[0073] The degraded toner ejection control (ejection operation) will be explained in more detail below using Figures 1(a) to (f) and Figure 8. Hereafter, the toner ejected from the developing unit 4 will be referred to as ejected toner. Figures 1(a) to (f) are explanatory diagrams of the degraded toner ejection control, and are schematic diagrams showing the movement of the ejected toner when the ejection control is performed. Figure 8 is an explanatory diagram of the voltage and potential control of the ejection control, and is a schematic diagram that shows the changes in the potential of the photosensitive drum 1, the developing voltage, the primary transfer voltage, and the movement of the toner along the time axis during the ejection control. Figure 8 shows a graph with potential / voltage on the vertical axis and time on the horizontal axis, and the surface potential (photosensitive drum potential) of a predetermined location that moves with the rotation of the photosensitive drum 1 is shown by a thick line, and the toner attached to that part is also shown. In each of the diagrams used in the following explanation, fresh toner is shown by a black circle, and degraded toner is shown by a white circle. Additionally, circles enclosed by solid lines represent the toner after it has moved, while circles enclosed by dashed lines represent the toner before it has moved.

[0074] This control process can be broadly divided into the following steps: A. Toner ejection from the developing unit 4, B. Passage of ejected toner through the primary transfer section, C. Passage of ejected toner through the charging section, D. Toner sorting in the developing section, E. Transfer of degraded toner, and F. Cleaning (processing) of degraded toner. Each step will be explained below. Note that each step from A to F corresponds to Figures 1(a) to (f), and the ranges corresponding to each step from A to E are also indicated by arrows in Figure 8.

[0075] (A. Toner ejection from the developing unit 4) Figure 1(a) shows the toner ejection process within the developing unit 4. The toner ejection process is the process in which toner is supplied from the developing roller 22 to the photosensitive drum 1. When the ejection control operation is started, the photosensitive drum 1 is uniformly charged to a predetermined negative potential by the charging roller 2 during the rotation process, and then exposed by the scanner unit 3. As a result, a latent image potential of post-exposure potential VL is formed on the photosensitive drum 1. In this embodiment, Assume the electrophoretic potential Vp = -700V and the post-exposure potential VL = -100V.

[0076] Subsequently, as shown in Figure 1(a), at the position where the developing roller 22 and the photosensitive drum 1 come into contact, the toner carried on the developing roller 22 is ejected onto the photosensitive drum 1 by the potential difference between the developing voltage Vdc and the post-exposure potential VL (developing contrast ΔVc). At this time, the ejected toner contains a mixture of degraded toner and fresh toner. In this embodiment, the developing voltage Vdc is set to -300V. That is, the absolute value of the developing contrast ΔVc is 200V.

[0077] In this ejection control, the exposure amount by the scanner unit 3 is different from that during the image formation operation. Compared to the image formation operation, the post-exposure potential VL is increased (from -150V to -100V) (approaching a positive value), and the absolute value of the development contrast ΔVc is increased (from 150V to 200V). This is to ensure that the toner on the development roller 22 is properly developed onto the photosensitive drum 1.

[0078] In the rotational direction of the photosensitive drum 1, the length of toner ejected at one time (in one ejection control) is preferably at least the length of one rotation of the developing roller 22, and preferably within the length of one rotation of the photosensitive drum 1. Since toner near the developing roller 22 is expected to be consumed, the length of the ejected toner is preferably at least the length of one rotation of the developing roller 22 in order to eject all the toner coated on the developing roller 22 immediately before ejection control. On the other hand, due to the potential relationship of the photosensitive drum, if the ejection of toner contained in the developing unit 4 and the recovery of fresh toner in the developing section described later are performed simultaneously, the recovery efficiency may decrease. Therefore, the length of the ejected toner is preferably within the length of one rotation of the photosensitive drum 1.

[0079] In this embodiment, during the ejection control, toner equivalent to two rotations of the developing roller 22, totaling 44.8 mm (= 10 mm × 3.14 ÷ 1.4 × 2), is ejected. The length of one rotation of the photosensitive drum 1 is 62.8 mm (= 20 mm × 3.14), and the length in the rotational direction of the photosensitive drum 1 from which the toner is ejected is less than the length of one rotation of the photosensitive drum 1. Although there is a limit to the length of toner ejected at one time in the rotational direction of the photosensitive drum 1, the total amount of toner ejected can be adjusted by repeating this ejection control.

[0080] (B. Passage of ejected toner through the primary transfer section) Figure 1(b) shows the process of the ejected toner passing through the primary transfer section. The primary transfer section is the process in which the toner supply section of the photosensitive drum 1, which is supplied with toner from the developing roller 22, first passes through the primary transfer section, which is the contact section between the photosensitive drum 1 and the intermediate transfer belt 10. When the ejected toner passes through the primary transfer section, a voltage of -600V is applied from the primary transfer power supply 15 to the primary transfer roller 14, which is a metal roller. As shown in Figure 8, a potential difference ΔV1 is formed between the post-exposure potential VL and the potential formed between the photosensitive drum 1 and the intermediate transfer belt 10 in the primary transfer section, such that the ejected toner (normally charged polarity) remains on the photosensitive drum 1. As a result, as shown in Figure 1(b), the toner ejected onto the toner supply section passes through the primary transfer section while remaining supported on the photosensitive drum 1.

[0081] If the potential formed on the intermediate transfer belt 10 is negative and its absolute value is greater than the absolute value of the post-exposure potential VL of the photosensitive drum 1, the ejected toner can be left on the photosensitive drum 1. This is because the ejected toner is charged to a normal charge polarity (negative polarity) due to friction with the developing blade 23. In other words, the toner is electrostatically attracted to the photosensitive drum 1 by the intermediate transfer belt 10, which has a negative potential greater than the absolute value of the potential of the photosensitive drum 1 (post-exposure potential VL). As for the potential difference, if it is about the same as or greater than the transfer contrast ΔVtr1 during image formation, the ejected toner can be left on the photosensitive drum 1. However, if the potential difference ΔV1 is too large, an abnormal discharge will occur in the primary transfer section and the toner will be ejected. In this embodiment, the potential difference ΔV1 is preferably less than 1500V because there is a risk of reversing the polarity of the dispensed toner. In this embodiment, a potential of -600V was formed on the intermediate transfer belt 10 by the primary transfer power supply 15 so that the absolute value of the potential difference ΔV1 was 500V.

[0082] (C. Passage of the charged part of the ejected toner) Figure 1(c) shows the process of the ejected toner passing through the charged section. The process of passing through the charged section is the process in which the toner supply section of the photosensitive drum 1, which is supplied with toner from the developing roller 22, passes through the charged section, which is the contact point between the photosensitive drum 1 and the charging roller 2. The ejected toner that has passed through the primary transfer section passes through the position where the charging roller 2 charges the photosensitive drum 1, and where the charging roller 2 and the photosensitive drum 1 are in contact (the charged section). As shown in Figure 8, when the ejected toner passes through the charged section, a negative voltage of -1200V is applied to the charging roller 2. As a result, the ejected toner passes through without adhering to the charging roller 2 due to the potential difference between the potential of the photosensitive drum 1 and the voltage of the charging roller 2 (hereinafter referred to as the charging contrast ΔV2). At this timing, the formation of the post-charging potential Vp and the imparting of charge to the ejected toner also occur simultaneously.

[0083] Furthermore, from any of the above viewpoints, it is preferable for the charge contrast ΔV2 to be somewhat large, and it is sufficient if it is equal to or greater than the charge contrast during image formation. On the other hand, if the charge contrast ΔV2 is too large, abnormal discharge may occur in the charged area, reversing the toner polarity and potentially causing it to adhere to the charged roller 2. For this reason, in this embodiment, the charge contrast ΔV2 was set to 1100V.

[0084] (D. Toner sorting in the developing department) Figure 1(d) shows the toner sorting process in the developing section. The toner sorting process is a process in which a portion of the toner on the surface of the photosensitive drum 1 supplied from the developing roller 22, that is, a portion of the toner from the toner supply section, is recovered by the developing roller 22. After the ejected toner passes through the charged section, sorting of deteriorated toner and fresh toner takes place at the position where the developing roller 22 and the photosensitive drum 1 come into contact (hereinafter referred to as the developing section). The ejected toner that has passed through the charged section then passes through the developing section as the photosensitive drum 1 rotates. At this time, as shown in Figure 8, a developing voltage Vdc = -300V is applied to the developing roller 22, and a Vd = -600V is formed on the surface of the photosensitive drum due to weak exposure. The ejected toner is recovered by the back contrast ΔVb, which is the potential difference between this post-weak exposure potential Vd and the developing voltage Vdc.

[0085] The ejected toner contains a mixture of fresh toner and degraded toner. Degraded toner is toner whose shape has been deformed due to prolonged friction with the developing blade 23, or whose external additives on the toner surface have been peeled off or embedded. The deformation of the toner shape increases the contact area between the toner and the photosensitive drum 1. For example, when the external additive on the toner surface peels off, the resin component of the toner comes into contact with the photosensitive drum 1, and the external additive becomes embedded in the toner, increasing the contact area between the toner and the photosensitive drum 1. As a result, degraded toner has a higher non-electrostatic adhesion force to the photosensitive drum 1 compared to fresh toner. On the other hand, fresh toner has less degradation, and therefore has a lower non-electrostatic adhesion force to the photosensitive drum 1, the opposite of degraded toner.

[0086] As described above, there is a difference in the non-electrostatic adhesion force between degraded toner and fresh toner. Therefore, when the ejected toner is recovered in the developer unit, fresh toner is more easily recovered, while degraded toner is less easily recovered. In Example 1, this difference in the non-electrostatic adhesion force between degraded toner and fresh toner is used to selectively recover fresh toner in the developer unit (and selectively recover degraded toner), as shown in Figure 1(d). With this configuration, a large amount of fresh toner with less degradation can be recovered from the ejected toner, thus extending the lifespan of the developer unit 4 without wasting toner. For example, the BET value for Fresh Toner is 2.8m 2 The value is approximately / g, and the BET value of the degraded toner is 2.0m 2 The amount was set to approximately 0.8 m / g or less. However, in this toner sorting process, the difference in non-electrostatic adhesion force was 0.8 m in BET value. 2Even when the toner level is below / g, it is possible to sort the toner, and toner sorting can be performed from the early stages of use of the process cartridge S (when it is in a near-new condition). As the usage time of the process cartridge S increases and it approaches the end of its lifespan, the proportion of degraded toner increases. Therefore, toner sorting is more effective when performed in the latter half of the process cartridge S's lifespan, when the proportion of degraded toner is high.

[0087] The recovery efficiency of the ejected toner when it is collected by the developing roller 22 can be controlled by the back contrast ΔVb. First, as the absolute value of the back contrast ΔVb increases within the range below the discharge threshold, the electric field that moves the ejected toner toward the developing roller 22 becomes stronger, thus improving the recovery efficiency. However, if the back contrast ΔVb is greater than the discharge threshold between the developing roller 22 and the photosensitive drum 1, the polarity of the ejected toner is reversed due to discharge, and the recovery efficiency decreases.

[0088] On the other hand, if the absolute value of the back contrast ΔVb is small, not only does the recovery efficiency decrease, but the toner coated on the developing roller 22 cannot be retained on the developing roller 22 and is developed onto the photosensitive drum 1. This unintended development is called fogging. Therefore, the back contrast ΔVb must be set to be below the discharge threshold, within a range where fogging does not occur, and so that fresh toner is selectively recovered by the developing roller 22. Specifically, the back contrast ΔVb should be between 100V and 500V, and should be adjusted appropriately according to the properties of the toner being used (adhesion, charge amount, shape, and degree of degradation).

[0089] In this embodiment, the voltage applied to the developing roller 22 (developing voltage Vdc) was set to -300V so that the absolute value of the back contrast ΔVb was 300V. In other words, the absolute value of the back contrast ΔVb in the ejection control is set to be greater than that during the image formation operation. In this embodiment, the back contrast ΔVb was formed by weak exposure, but the configuration is not limited to this. For example, in the case of an image forming apparatus that does not have (or cannot perform) weak exposure, an appropriate charging contrast ΔV2 and back contrast ΔVb can be secured by adjusting the charging voltage.

[0090] As described above, by controlling various voltages and exposure levels, a large portion of the fresh toner can be recovered by the developing roller 22, while a large portion of the degraded toner can be left on the photosensitive drum 1.

[0091] (E. Transfer of degraded toner) Figure 1(e) shows the degraded toner transfer process. The degraded toner transfer process is a process in which the toner supply section of the photosensitive drum 1, which has been supplied with toner from the developing roller 22, passes through the transfer section again, and any remaining toner moves from the photosensitive drum 1 to the intermediate transfer belt 10. In other words, after the sorting and recovery process of the developing section, the degraded toner remaining on the photosensitive drum 1 is transferred to the intermediate transfer belt 10. The degraded toner that has passed through the developing section is charged with negative polarity (normal charge polarity). Therefore, as shown in Figure 1(e), a positive primary transfer voltage is applied to the primary transfer roller 14 to transfer the degraded toner to the intermediate transfer belt 10. At this time, as shown in Figure 8, the potential of the surface of the photosensitive drum 1 where the degraded toner remains is the post-weak exposure potential Vd. Then, the degraded toner is transferred to the intermediate transfer belt 10 by the transfer contrast ΔVtr2, which is the potential difference between the post-weak exposure potential Vd and the primary transfer voltage Vtr.

[0092] As described above, degraded toner has a higher adhesion force to the photosensitive drum 1 compared to fresh toner. Therefore, when transferring degraded toner to the intermediate transfer belt 10, the degraded toner is less likely to transfer to the intermediate transfer belt 10 with the same potential difference as during normal image formation. Therefore, the transfer contrast ΔVtr2 needs to be set so that degraded toner can be transferred to the intermediate transfer belt 10.

[0093] The degraded toner remaining on the photosensitive drum 1 is toner that was not collected by the developing roller 22 at the back contrast ΔVb during the previous recovery by the developing roller 22. Therefore, it is preferable that the transfer contrast ΔVtr2 be greater than or equal to the back contrast ΔVb during the development and recovery of fresh toner. Furthermore, as described above, the degraded toner has a high adhesion force to the photosensitive drum 1 and is difficult to transfer. For this reason, it is preferable that it be greater than the transfer contrast ΔVtr1 during normal image formation operation. In other words, it is preferable that the transfer contrast ΔVtr2 be greater than the larger of the back contrast ΔVb during the development and recovery of fresh toner and the transfer contrast ΔVtr1 during normal image formation operation. However, if the transfer contrast ΔVtr2 is too large, there is a risk of abnormal discharge occurring in the primary transfer section, so it is preferable that the transfer contrast ΔVtr2 be less than 2000V.

[0094] In this example, when transferring the degraded toner to the intermediate transfer belt 10, the transfer contrast ΔVtr2 = 900V is set between the post-weak exposure potential Vd = -600V and the primary transfer voltage Vtr = +300V.

[0095] (F. Cleaning deteriorated toner) Figure 1(f) shows the cleaning process for degraded toner. The degraded toner transferred to the intermediate transfer belt 10 is sent to the cleaning device 16 by the rotation of the intermediate transfer belt 10, and collected in the waste toner container 17 for processing.

[0096] Thus, in Example 1, a portion of the ejected toner, which contains a large amount of degraded toner, can be sent to the waste toner container 17. Therefore, compared to the case where all ejected toner is sent to the waste toner container 17, the time it takes for the waste toner container 17 to become full can be delayed. As a result, the frequency of the user having to replace the waste toner container can be reduced.

[0097] In this embodiment, once the ejected toner has finished passing through the developing section (between Figure 1(e) and Figure 1(f)), the developing roller 22 is immediately separated from the photosensitive drum 1 by the separation mechanism, and then the rotation of the developing roller 22 is stopped. This is because, as the developing roller 22 rotates, the toner on the developing roller 22 rubs against the developing blade 23. The purpose of this is to immediately separate the developing roller 22 when contact with the photosensitive drum 1 is no longer necessary, thereby avoiding unnecessary rubbing.

[0098] In this embodiment, when the degraded toner, which is negatively charged on the intermediate transfer belt 10, is sent to the cleaning device 16, a negative voltage is applied to the secondary transfer roller 20. This prevents the degraded toner on the intermediate transfer belt 10 from adhering to the secondary transfer roller 20 and allows it to pass through.

[0099] If the absolute value of the voltage applied to the secondary transfer roller 20 when the degraded toner on the intermediate transfer belt 10 passes through the contact area with the secondary transfer roller 20 is too low, the degraded toner will adhere to the secondary transfer roller 20. Conversely, if the absolute value of the applied voltage is too high, the toner polarity will reverse due to abnormal discharge, causing the degraded toner to adhere to the secondary transfer roller 20. Therefore, the voltage applied to the secondary transfer roller 20 is preferably around -300 to -1000V. In this embodiment, a voltage of -500V is applied to the secondary transfer roller 20. In this embodiment, although the secondary transfer roller 20 is in contact with the intermediate transfer belt 10, if there is a mechanism for separating the secondary transfer roller 20, the secondary transfer roller 20 may be separated from the intermediate transfer belt 10 to prevent the degraded toner from adhering to the secondary transfer roller 20.

[0100] Furthermore, the degraded toner transferred onto the intermediate transfer belt 10 does not necessarily need to be sent to the cleaning device 16 during the ejection control. For example, the ejection control may be terminated once the degraded toner has been transferred onto the intermediate transfer belt 10. In this case, the degraded toner remaining on the intermediate transfer belt 10 may be sent to the cleaning device 16 for collection and processing by the rotation of the intermediate transfer belt 10 during the next normal image forming operation. Doing so makes it possible to perform ejection control without causing unnecessary downtime.

[0101] In this embodiment, during output mode, the development voltage Vdc is operated at the same Vdc=-300V as during image formation, and the charging voltage and exposure amount are different from those during image formation. However, the configuration is not limited to this. For example, the development voltage Vdc may be changed to change the back contrast ΔVb or the development contrast ΔVc.

[0102] <Execution timing of discharge control> The ejection mode (toner ejection operation) is preferably performed after the completion of the image formation operation or between sheets of paper of recording material P when forming images on multiple recording materials P consecutively (when the image formation operation is not being performed) to avoid delays in the start of the image formation operation.

[0103] Furthermore, in order to selectively eject most of the degraded toner from the developing unit 4 (developing device), it is preferable to perform ejection control in the latter half of the lifespan of the process cartridge S, when the degraded toner accumulates in the developing unit 4. Also, as explained above, toner ejection control requires the developing roller 22 to rotate at least one full rotation of the photosensitive drum. Therefore, performing ejection control more than necessary will result in excessive rotation of the developing roller 22 (i.e., friction between the developing blade 23 and the toner). For this reason, in this embodiment, ejection control is performed every 50 sheets after the halfway point of the lifespan of the process cartridge S (for example, the remaining toner amount or the rotation distance of the developing roller). However, the method for determining the timing of toner ejection control is not limited to this configuration, and a detection unit may be provided to detect the lifespan or usage time of any of the photosensitive drum 1, charging roller 2, or developing roller 22, and the control may be performed based on the detection result of the detection unit.

[0104] By implementing the ejection control described above, efficient ejection can be achieved by selectively ejecting most of the degraded toner generated during the use of process cartridge S from the developing unit 4. This, in turn, reduces unnecessary toner consumption and simultaneously reduces the frequency of replacing the waste toner container.

[0105] <Evaluation Test> This section describes the evaluation tests conducted to confirm the toner consumption reduction effect and the effect of reducing the frequency of replacing the waste toner container in this embodiment.

[0106] First, to confirm the toner consumption reduction effect, the following tests were conducted on the configuration of Example 1 and the configuration of Comparative Example 1 below, based on the cartridge print yield measurement standard ISO / IEC 19798. In an environment of 23°C / 50% relative humidity, a 5000-sheet paper feed test was performed using Xerox Business 4200 LETTER size (Xerox, product name) as the recording material P, and the presence or absence of image defects was verified. Example 1: Paper ejection control implemented (implemented every 50 sheets after the 2500th sheet) Comparative Example 1: No discharge control was implemented.

[0107] The configuration and operation of the image forming apparatus 100 in Comparative Example 1 are substantially the same as those of the image forming apparatus 100 in Example 1, except that ejection control is not performed.

[0108] Table 1 below shows the evaluation results of this test. Table 1 shows the occurrence of image defects on the first sheet and every 1000 sheets for Example 1 and Comparative Example 1. Image defects were judged based on poor recovery in the developing unit due to deterioration of primary transferability caused by toner degradation (hereinafter referred to as poor development and recovery). Here, no poor development and recovery occurred is rated as A, minor poor development and recovery occurred as B, and unacceptable poor development and recovery occurred as C. Ranks A and B are judged as no problems, and rank C is judged as image defects occurred.

[0109] [Table 1]

[0110] In the configuration of Comparative Example 1, the transfer quality deteriorated as the number of sheets passed through increased. Specifically, development and recovery failures occurred after 3000 sheets. In particular, unacceptable (C-rank) development and recovery failures occurred at 5000 sheets.

[0111] On the other hand, in the configuration of Example 1, where ejection control is performed periodically in the latter half of the lifespan of the process cartridge S, no development and recovery failure occurred even when the number of sheets fed reached 5,000. In other words, in Example 1, the degraded toner was ejected from within the development unit 4, resulting in a difference compared to Comparative Example 1 from the 3,000th sheet of paper fed onwards.

[0112] Next, in order to confirm the effect of reducing the frequency of replacement of the waste toner container in this embodiment, an evaluation test was conducted on the configuration of Embodiment 1 and Comparative Example 2 described below. First, the configuration of Comparative Example 2 will be explained using Figures 9(a), (b) and 10.

[0113] In Comparative Example 2, the ejection control described below (hereinafter referred to as solid ejection control to distinguish it from the ejection control in Example 1) is performed. Figures 9(a) and (b) are explanatory diagrams of the solid ejection control in Comparative Example 2, and are schematic diagrams showing the movement of ejected toner when the solid ejection control is performed. Figure 10 is an explanatory diagram of the voltage and potential control in the solid ejection control in Comparative Example 2, and is a schematic diagram that shows the changes in the potential of the photosensitive drum 1, the developing voltage, the primary transfer voltage, and the movement of toner along the time axis in the solid ejection control. Figure 10 shows a graph with potential / voltage on the vertical axis and time on the horizontal axis, and the surface potential (photosensitive drum potential) of a predetermined location that moves with the rotation of the photosensitive drum 1 is shown by a thick line, and the toner attached to that part is also shown. A and B in Figure 10 correspond to Figures 9(a) and (b), respectively.

[0114] The solid color ejection control can be broadly divided into two steps: A. Toner ejection from the developing unit 4, and B. Transfer of the ejected toner. Steps A and B correspond to Figures 9(a) and 9(b), respectively, and the range corresponding to each step is also indicated by arrows in Figure 10.

[0115] (A. Toner ejection) Figure 9(a) shows the toner ejection process. In solid toner ejection control, first, as shown in Figure 9(a), the toner in the developing unit 4 is ejected onto the photosensitive drum 1. The potential relationships of each part in the ejection process during solid toner ejection control are the same as in Example 1A. Ejection Process (Figure 8(a)), as shown in Figure 10.

[0116] (B. Transfer of ejected toner) Figure 9(b) shows the toner transfer process. After the toner ejection process, as shown in Figure 9(b), the toner ejected onto the photosensitive drum 1 is transferred directly to the intermediate transfer belt 10. The transferred toner is then cleaned and stored by the cleaning device 16 and the waste toner container 17. In the toner transfer process according to Comparative Example 2, the primary transfer voltage is set to 700V so that the transfer contrast ΔVtr3 becomes ΔVtr3 = 800V (= ΔVtr2) in order to transfer the toner ejected onto the photosensitive drum 1 to the intermediate transfer belt 10.

[0117] Evaluation tests were conducted on Comparative Example 2, which uses solid toner ejection control, and Example 1, which uses (degraded toner) ejection control. In the test, 250,000 sheets of Xerox Business 4200 LETTER size (Xerox, product name) were fed as recording material P in an environment of 23°C / 50% relative humidity, and the number of times the waste toner container 17 was replaced was compared. In Example 1, ejection control was performed every 50 sheets, while in Comparative Example 2, solid toner ejection control was performed every 50 sheets.

[0118] In Comparative Example 2, high-print toner was ejected every 50 sheets and sent to the waste toner container, so the waste toner container was replaced a total of three times during the 250,000-sheet paper-passing test.

[0119] On the other hand, in the ejection control of Example 1, although high-print toner is ejected every 50 sheets, the fresh toner is recovered to the developing unit 4, so the amount of toner sent to the waste toner container 17 was reduced compared to Comparative Example 2. Specifically, in the configuration of Example 1, about 50% of the toner ejected in one ejection control was recovered to the developing unit 4. As a result, in a paper feed test of 250,000 sheets, the test was completed with a total of one replacement of the waste toner container, which was fewer replacements than in Comparative Example 2.

[0120] As described above, by performing the ejection control described in the description, a large portion of the degraded toner generated during the use of the process cartridge S can be selectively ejected from the developing unit 4, thereby achieving efficient ejection. Consequently, it is possible to provide an image forming apparatus that reduces unnecessary toner consumption while simultaneously reducing the frequency of replacing the waste toner container.

[0121] [Example 2] Next, Example 2 of the present invention will be described. Hereinafter, only the differences between the configuration and effects of Example 2 and Example 1 will be described. Components in Example 2 that are the same as those in Example 1 are denoted by the same reference numerals, and their descriptions are omitted.

[0122] In Example 1, as the ejected toner passed through the charging section, a voltage of -1200V was applied to the charging roller 2 from the charging power supply 501, thereby charging the ejected toner while preventing it from adhering to the charging roller 2, and simultaneously forming a post-charging potential Vp. In contrast, Example 2 differs from Example 1 in that it provides a pre-charging exposure device to control the drum potential by pre-charging exposure before the ejected toner passes through the charging section. Furthermore, in terms of potential and voltage, it differs from Example 1 in that a voltage of -1100V, which has a smaller absolute value than -1200V, is applied to the charging roller 2. Except for the voltage value applied to the charging roller 2 when the ejected toner passes through the charging section, and the post-charging potential Vp of the photosensitive drum 1 charged by the charging voltage, the control in the ejection control is the same as in Example 1.

[0123] <Explanation of pre-charging exposure equipment> First, the pre-charging exposure apparatus 6 will be described. Figure 11 is a schematic cross-sectional view showing the general configuration of the image forming apparatus 100 of Example 2. The image forming apparatus 100 of Example 2 has the same configuration as Example 1, except that it includes the pre-charging exposure apparatus 6.

[0124] The pre-charging exposure device 6 is positioned opposite the photosensitive drum 1 and is configured to expose the surface of the photosensitive drum 1. In the rotational direction of the photosensitive drum 1, the pre-charging exposure device 6 is located downstream of the primary transfer roller 14 and upstream of the charging roller 2. In other words, the image forming apparatus 100 is equipped with a scanner unit 3 as a first exposure device and a pre-charging exposure device 6 as a second exposure device.

[0125] Figure 12 is a schematic diagram showing the configuration of the pre-charging exposure apparatus 6 according to Example 2. The pre-charging exposure apparatus 6 is composed of a light-emitting element 601 and a light guide 602.

[0126] The light-emitting element 601 is installed in the main body of the image forming apparatus 100. On the other hand, the light guide 602 is a light guide member for irradiating the light from the light-emitting element 601 onto the photosensitive drum 1, and is provided on the cartridge tray (not shown) that holds the process cartridge S. The light guide 602 is positioned downstream of the primary transfer roller 14 and upstream of the charging roller 2 in the rotational direction of the photosensitive drum 1.

[0127] The light guide 602 is positioned such that its axial direction (longitudinal direction) is approximately parallel to the axial direction of the photosensitive drum 1. One end of the light guide 602 in the axial direction is provided with a light incident section 603 that receives light emitted from the light-emitting element 601.

[0128] The amount of light emitted from the light-emitting element 601 is controlled at a predetermined timing by a light emission amount control means (not shown). The light guided to the light guide 602 becomes diffused light from the side of the light guide 602 and irradiates the photosensitive drum 1, thereby removing static electricity from the surface potential of the photosensitive drum 1. This is to remove the surface charge of the photosensitive drum 1 after the primary transfer process and smooth the surface potential. With this configuration, the pre-charging exposure apparatus 6 removes static electricity from the surface potential of the photosensitive drum 1 to a predetermined potential (approximately 0V in this embodiment). In other words, the pre-charging exposure apparatus 6 in this embodiment is a static electricity removal device that removes static electricity from the surface of the photosensitive drum 1.

[0129] In this embodiment, the amount of light emitted during pre-charging exposure is adjusted to a predetermined amount, but the configuration is not limited to this. For example, a light-receiving element for detecting the amount of light emitted during pre-charging exposure may be placed near the light-emitting element 601, the light guide 602, and the photosensitive drum 1, and a mechanism for adjusting the amount of light emitted by the pre-charging exposure device 6 may be provided. With such a configuration, the amount of light emitted by the pre-charging exposure device 6 can be adjusted in response to deterioration of the light-emitting element 601, dirt on the light guide 602, and changes in the light-receiving sensitivity of the photosensitive drum 1.

[0130] Furthermore, although the configuration of placing the light guide 602 on the cartridge tray has been described, the configuration is not limited to this. For example, the light guide 602 may be installed on the process cartridge S, an LED array may be used instead of the light guide 602, or, for further simplification of the apparatus, the photosensitive drum 1 may be directly illuminated with light without using the light guide 602.

[0131] <Discharge control> In Example 2, the movement of the ejected toner in the ejection control is the same as in Example 1. That is, the ejected toner in the ejection control according to Example 2 moves in the same way as the ejected toner in Example 1 shown in Figures 1(a) to (f). Only the potential and charging voltage of the photosensitive drum 1 in the ejection control of Example 2 differ from those of Example 1, so the differences from Example 1 will be explained using Figure 13.

[0132] Figure 13 is an explanatory diagram of the voltage and potential control of the ejection control according to Example 2, showing the changes in the potential of the photosensitive drum 1, the developing voltage, the primary transfer voltage, and the movement of the toner during ejection control. This is a schematic diagram along the inter-axis. Figure 13 shows a graph with potential / voltage on the vertical axis and time on the horizontal axis. The surface potential (photosensitive drum potential) of a predetermined location that moves with the rotation of the photosensitive drum 1 is shown by a thick line, and the toner adhering to that area is also shown. In Figure 13, the range corresponding to each step of the ejection control shown in Figures 1(a) to (e) is indicated by arrows.

[0133] In Example 2 and Example 1, the relationship between voltage and potential differs in the ejection control process, specifically from B. after the ejected toner passes through the primary transfer section to D. before toner sorting in the developing section. In Example 2, after the ejected toner passes through the primary transfer section (between B. the ejected toner passing through the primary transfer section and C. the ejected toner passing through the charging section), the drum potential is discharged to 0V by the pre-charging exposure device 6. Since the difference between the charging voltage Vpri and the drum potential entering the charging section is the charging contrast ΔV2, the charging contrast ΔV2 can be increased by the amount of potential discharged by the pre-charging exposure device 6.

[0134] By performing static discharge using the pre-charging exposure device 6, greater flexibility can be given to the selection of the charging voltage Vpri. As explained in Example 1, the charging contrast ΔV2 has multiple roles, and increasing the charging contrast ΔV2 within an appropriate range is preferable in terms of ensuring the chargeability of the ejected toner, preventing adhesion to the charging roller 2, and forming the back contrast ΔVb. However, as in Example 1, if the drum potential before the charging section enters is the post-exposure potential VL (-100V in Example 1), it becomes necessary to increase the charging voltage Vpri in order to increase the charging contrast ΔV2. If the charging voltage Vpri is too high, the high-voltage element of the charging power supply 501 is more likely to be overloaded, increasing the risk of high-voltage oscillation and current leakage to the photosensitive drum 1. By providing the pre-charging exposure device 6 as in this embodiment, the potential of the photosensitive drum 1 is reduced to approximately 0V by pre-charging exposure, and the charging contrast ΔV2 can be increased without increasing the charging voltage Vpri.

[0135] Although the charging voltage Vpri is lower than in Example 1, resulting in a smaller post-charging potential Vp, the same potential as the post-weak exposure potential Vd = -600V in Example 1 is formed. Therefore, in this example, the same back contrast ΔVb as in Example 1 can be secured, and the same effects and advantages as in Example 1 can be obtained.

[0136] As described above, by performing the ejection control described in the description, a large portion of the degraded toner generated during the use of the process cartridge S can be selectively ejected from the developing unit 4, thereby achieving efficient ejection. Consequently, it is possible to provide an image forming apparatus that reduces unnecessary toner consumption while simultaneously reducing the frequency of replacing the waste toner container.

[0137] [Example 3] Next, Example 3 of the present invention will be described. Below, only the differences between the configuration and effects of Example 3 and Example 1 will be described. Components in Example 3 that are the same as those in Example 1 are denoted by the same reference numerals and their descriptions are omitted. The configuration of the image forming apparatus 100 in Example 3 is the same as that of Example 2, and the image forming apparatus 100 includes a pre-charging exposure apparatus 6.

[0138] Example 3 describes a control method for efficiently processing degraded toner using a different method than that used in Examples 1 and 2. Degraded toner is toner with a mixture of positive and negative polarity. In Example 3, such degraded toner with a mixture of positive and negative polarity is discharged (developed) from the developing roller 22 of the developing unit 4 to the photosensitive drum 1. In the primary transfer section, the negative polarity toner is left on the photosensitive drum 1, and the positive polarity toner is transferred to the intermediate transfer belt 10. The negative polarity toner left on the photosensitive drum 1 is then transferred to the intermediate transfer belt 10 after one rotation without being recovered again by the developing roller 22. This allows the cleaning device 16 to clean the toner of both polarities, and the toner is then returned to the waste toner container 17. Collect and process.

[0139] In the control of Example 3, as in Examples 1 and 2, degraded toner can be ejected from within the developing unit 4. As a result, unnecessary toner consumption can be suppressed. At the same time, the amount of toner collected in the waste toner container 17 can be reduced, thus reducing the frequency of replacing the waste toner container. To distinguish it from Examples 1 and 2, the toner ejected from the developing unit 4 is referred to as "fouled toner," and the series of operations is referred to as the first fouled toner ejection control.

[0140] <cover> First, flicker will be explained using Figures 14 and 15. Figure 14 is an explanatory diagram of the charge distribution of the flicker toner. Figure 15 is an explanatory diagram of the back contrast ΔVb dependence of the flicker toner according to Example 3.

[0141] When toner deteriorates (due to toner deformation, external coating peeling, external coating embedding, etc.), the triboelectric charge generated by friction with the developing blade 23 decreases. For example, if toner deformation or external coating embedding progresses, the fluidity of the toner decreases, reducing the rolling ability when the developing blade 23 and developing roller 22 rub against each other. If the external coating peeling of the toner progresses, the toner matrix is ​​exposed, making it impossible to exhibit the desired electrostatic charge. Thus, as toner deterioration progresses, the triboelectric charge generated with the developing blade 23 decreases due to the decrease in fluidity and electrostatic charge. As a result, the deteriorated toner is in a state where positive and negative polarity with small charge amounts are mixed, with the charge amount centered around 0.

[0142] During toner development, the back contrast ΔVb, which is the potential difference between the development voltage Vdc and the photosensitive drum 1 potential (charged potential Vp, or weak exposure potential Vd), should electrically hold the toner on the development roller 22 so that it does not transfer to the non-image area. However, if degraded toner with a mixture of positive and negative polarity is contained in the development unit 4, the toner with the opposite polarity to the normal charging polarity (positive polarity in this embodiment) will be developed by the back contrast ΔVb. Furthermore, even toner with the normal charging polarity (negative polarity in this embodiment) may move to the photosensitive drum 1 if the charge amount is small and the mirroring force with the development roller 22 is weak, as it cannot be held on the development roller 22 by the back contrast ΔVb. Thus, toner that is developed differently from the toner developed by the development contrast ΔVc is called "fogging toner," and the phenomenon of development is called "fogging."

[0143] Figure 14 shows the results of measuring the charge distribution of 3,000 capsule toners generated from a degraded developing unit 4 using an E-Spert analyzer manufactured by Hosokawa Micron. Figure 14 is a graph with the ratio of abundance on the vertical axis and the toner charge amount [μC / g] on the horizontal axis. As mentioned earlier, the graph can be seen to confirm that the charge amount of the capsule toners is a mixture of positive and negative polarity, centered around 0.

[0144] Figure 15 is a graph with back contrast ΔVb [V] on the horizontal axis and fogging concentration [OD] (fogging amount) on the vertical axis. The graph shows the fogging amount when using new (fresh) toner as a dashed line and diamond plot, and the fogging amount when using degraded toner as a solid line and circular plot. The fogging amount is the result of measurement using a Macbeth densitometer (manufacturer: Gretag Macbeth Corporation), and a larger value indicates a larger fogging amount.

[0145] As shown in Figure 15, in both new and deteriorated conditions, the amount of toner fill is lowest when the back contrast ΔVb is around 150-180V, and the fill increases as the back contrast ΔVb increases. The fill on the side with a large back contrast ΔVb is called inverted fill. Note that the fill on the side with a small back contrast ΔVb is normal development. This is the same phenomenon, and is called ground-level fog to distinguish it from inversion fog.

[0146] As shown in Figure 15, the reason why the amount of fogging around ΔVb = 150~180V increases in the deteriorated state compared to the new state is due to a decrease in the mirroring force on the developing roller 22 due to toner deterioration. Furthermore, the reason why the reverse fogging increases in the deteriorated state compared to the new state is due to the effect of the decrease in triboelectricity due to toner deterioration, which makes it difficult for the toner to be charged with the normal charging polarity, resulting in positive polarity toner, which is the opposite of the normal charging polarity, being developed on the photosensitive drum 1 with a potential difference of ΔVb. Moreover, as mentioned above, even the negative polarity toner, which is the normal charging polarity, among the deteriorated toner is developed on the photosensitive drum 1 with a potential difference of ΔVb because the amount of charge is small. Thus, fogging toner contains a mixture of both positive and negative polarities and contains a large amount of deteriorated toner.

[0147] The image forming apparatus 100 according to Example 3 is configured to perform a first fogging discharge control using the fogging characteristics with respect to the back contrast ΔVb for fogging toner containing a large amount of degraded toner and mixed polarity. In Example 3, both positive and negative polarity fogging toner discharged from the developing roller 22 is transferred to the intermediate transfer belt 10 and cleaned and removed by the cleaning device 16.

[0148] <First type of fouling discharge control> Next, the first fogging discharge control of this embodiment will be explained using Figures 16(a) to (e) and Figure 17. Figures 16(a) to (e) are explanatory diagrams of the first fogging discharge control, and are schematic diagrams showing the movement of discharged toner when the discharge control is performed. Figure 17 is an explanatory diagram of the voltage and potential control of the first fogging discharge control, and is a schematic diagram that shows the changes in the potential of the photosensitive drum 1, the developing voltage, the primary transfer voltage, and the movement of toner along the time axis during the first fogging discharge control. Figure 17 shows a graph with potential / voltage on the vertical axis and time on the horizontal axis, and the surface potential (photosensitive drum potential) of a predetermined location that moves with the rotation of the photosensitive drum 1 is shown by a thick line, and the toner adhering to that part is also shown. In the drawings used in the following explanation, when distinguishing between positive polarity toner and negative polarity toner, positive polarity toner is shown by a circle with a "+" written on it, and negative polarity toner is shown by a circle with a "-" written on it.

[0149] This control process can be broadly divided into the following steps: A. Discharge of cabritone from the developing unit 4, B. Polarity separation of cabritone in the primary transfer section, C. Passage of negative polarity cabritone through the charged section, D. Transfer of negative polarity cabritone, and E. Cleaning of cabritone. Each step will be explained below. Note that each step from A to E corresponds to Figures 16(a) to (e), and the ranges corresponding to each step from A to D are also indicated by arrows in Figure 17.

[0150] (A. Ejection of capritner from developing unit 4) Figure 16(a) shows the process of ejecting the capritner from the developing unit 4. When the operation of the first capritner ejection control is started, the photosensitive drum 1 is uniformly charged to a predetermined negative potential (post-charging potential Vp = -700V) by the charging roller 2 during its rotation. Almost simultaneously, a predetermined voltage (developing voltage Vdc = -300V) is applied to the developing roller 22. The surface of the photosensitive drum 1, which has been charged to the predetermined post-charging potential Vp, is adjusted to a predetermined potential (post-weak exposure potential Vd = -600V) by weak exposure of the non-image area. When the drum surface, which has been charged to the post-weak exposure potential Vd, passes through the contact area with the developing roller 22, the capritner, which has a mixture of positive and negative polarity, is developed due to the back contrast ΔVb = 300V (it moves onto the surface of the photosensitive drum 1).

[0151] In this embodiment, when generating fogging in the first fogging discharge control, the back contrast ΔVb is set to 300V, making the absolute value of the back contrast ΔVb larger than during the image formation operation (ΔVb = 180V in this embodiment). This is because, as explained in Figures 14 and 15, a large amount of fogging toner with a positive polarity different from the normal charging polarity is developed. That is the case.

[0152] Furthermore, the length of the fouling toner ejected at one time (in a single fouling ejection control) in the rotational direction of the photosensitive drum 1 is preferably greater than or equal to the length of one rotation of the developing roller 22, and preferably within the length of one rotation of the photosensitive drum 1. Since it is assumed that toner near the developing roller 22 is easily consumed, the length of the fouling toner ejected is preferably greater than or equal to the length of one rotation of the developing roller 22 in order to eject all the toner coated on the developing roller 22 immediately before the first fouling ejection control. On the other hand, in order to prevent the fouling toner from being recovered by the developing roller 22 after one rotation of the photosensitive drum 1, the length of the fouling toner ejected is preferably within the length of one rotation of the photosensitive drum 1.

[0153] In this embodiment, a length of 44.8 mm (= 10 mm × 3.14 ÷ 1.4 × 2) of fouling toner, equivalent to two rotations of the developing roller 22, is ejected at once. The length of one rotation of the photosensitive drum 1 is 62.8 mm (= 20 mm × 3.14), and the length of the fouling toner ejected at once in the rotational direction of the photosensitive drum 1 is less than the length of one rotation of the photosensitive drum 1.

[0154] After developing a predetermined length of cabritone, the developing roller 22 is immediately separated from the photosensitive drum 1, and the rotation of the developing roller 22 is stopped. This is to prevent the toner on the developing roller 22 from unnecessarily rubbing against the developing blade 23, and at the same time to prevent the cabritone from being collected on the developing roller 22 after one rotation of the photosensitive drum 1.

[0155] (B. Polarity separation in the primary transfer section of the Cabritone) Figure 16(b) shows the polarity separation process in the primary transfer section of the cabriolet toner. In this process, the negative polarity toner passes through the transfer section and the positive polarity toner is transferred to the intermediate transfer belt 10.

[0156] When the cabritone first passes through the primary transfer section, a voltage of -1000V is applied from the primary transfer power supply 15 to the primary transfer roller 14. As shown in Figure 17(b), a potential difference ΔV3 is formed between the photosensitive drum 1 and the intermediate transfer belt 10 in the primary transfer section, such that the negative polarity toner remains on the photosensitive drum 1 and the positive polarity toner is transferred to the intermediate transfer belt 10. The potential difference ΔV3 is the potential difference between the surface potential of the photosensitive drum 1 (potential after weak exposure Vd) and the primary transfer voltage Vtr, and in this embodiment, ΔV3 = Vd - Vtr = 400V. As a result, as shown in Figure 16(b), of the discharged cabritone, the negative polarity toner remains supported on the photosensitive drum 1, while only the positive polarity toner is transferred to the intermediate transfer belt 10.

[0157] If the potential formed on the intermediate transfer belt 10 is negative and greater than the absolute value of the surface potential of the photosensitive drum 1, a potential difference ΔV3 is formed that allows the negative polarity toner to remain on the photosensitive drum 1 while the positive polarity toner to be transferred to the intermediate transfer belt 10. The absolute value of the potential difference ΔV3 is preferably greater than or equal to the transfer contrast ΔVtr1 during image formation (250V in this embodiment). As mentioned above, the cabritone contains a lot of degraded toner and has high non-electrostatic adhesion. Therefore, if the potential difference ΔV3 is around the normal transfer contrast ΔVtr1 during image formation, there is a risk that the cabritone (positive polarity cabritone in this embodiment) cannot be transferred to the intermediate transfer belt 10. By making the potential difference ΔV3 greater than or equal to the transfer contrast ΔVtr1 during image formation, the negative polarity toner can be left on the photosensitive drum 1, and at the same time, the positive polarity toner can be transferred to the intermediate transfer belt 10. Furthermore, if the potential difference ΔV3 is too large, abnormal discharge may occur in the primary transfer section, potentially reversing the polarity of the ejected toner. Therefore, in the configuration of this embodiment, a potential difference ΔV3 of less than 1500V is preferable. In this embodiment, a potential of -1000V was formed on the intermediate transfer belt 10 by the primary transfer power supply 15 such that the absolute value of the potential difference ΔV3 was 400V.

[0158] (C. Passage through the charged section of the negative polarity cabriolet) Figure 16(c) shows the process of negative polarity cabritone passing through the charged section. The movement of the negative polarity cabritone remaining on the photosensitive drum 1 after passing through the primary transfer section will be explained. The processing method for the positive polarity cabritone transferred to the intermediate transfer belt 10 will be explained separately together with the processing method for the negative polarity cabritone.

[0159] The negative polarity capritor remaining on the photosensitive drum 1 must pass through the charged area so as not to adhere to the charging roller 2. At this time, the charging contrast ΔV2, which is the potential difference between the surface potential of the photosensitive drum 1 and the charging voltage Vpri, causes the capritor to pass through the position where the charging roller 2 and the photosensitive drum 1 come into contact (the charged area).

[0160] In this embodiment, the potential of the photosensitive drum 1 may be slightly displaced due to the potential difference ΔV3 = 400V in step B. Furthermore, in order to ensure a sufficiently large charge contrast ΔV2, the potential of the photosensitive drum 1 is neutralized to approximately 0V by the pre-charging exposure device 6. As shown in Figure 17, when the negative polarity cabritone passes through the charging section, a negative voltage of -1200V is applied to the charging roller 2, and the charge contrast ΔV2 is controlled to be 1200V. As a result, as shown in Figure 16(c), the negative polarity cabritone passes through the charging section while remaining supported on the photosensitive drum 1. Simultaneously, the post-charging potential Vp is formed, resulting in a photosensitive drum potential of -700V. A charge contrast ΔV2 is sufficient if it is equal to or greater than the charge contrast during image formation (in this embodiment, the charge contrast ΔV2 during image formation is 1200V).

[0161] In the case of an image forming apparatus that does not have a pre-charging exposure apparatus 6 as described in Example 1, the charging contrast ΔV2 may be secured by increasing the charging voltage Vpri.

[0162] (D. Transfer of negative polarity cabriolet toner) Figure 16(d) shows the transfer process of negative polarity cabritone. The negative polarity cabritone that has passed through the charged section reaches the primary transfer section again and is transferred to the intermediate transfer belt 10. As described above, since the developing roller 22 is separated from the photosensitive drum 1, the cabritone reaches the primary transfer section without being collected by the developing roller 22.

[0163] In this process, a positive primary transfer voltage Vtr is applied to transfer the negative polarity toner to the intermediate transfer belt 10. The negative polarity toner on the photosensitive drum 1 is transferred to the intermediate transfer belt 10 by the transfer contrast ΔVtr2 between the photosensitive drum potential and the primary transfer voltage Vtr. Since the cabriolet toner contains a large amount of degraded toner with increased non-electrostatic adhesion, it is difficult to transfer it to the intermediate transfer belt 10 with the same potential difference as during normal image formation. Therefore, the transfer contrast ΔVtr2 needs to be set so that the degraded toner can be transferred to the intermediate transfer belt 10. Specifically, it is preferable to set the transfer contrast ΔVtr2 to be greater than the transfer contrast ΔVtr1 during normal image formation operation. However, if the transfer contrast ΔVtr2 is too large, there is a risk of abnormal discharge in the primary transfer section, so it is preferable that the transfer contrast ΔVtr2 be less than 2000V.

[0164] In this embodiment, during the transfer process of degraded toner to the intermediate transfer belt 10, the transfer is performed with a transfer contrast ΔVtr2 = 1000V between the post-charge potential Vp = -700V and the primary transfer voltage Vtr = +300V. In this embodiment, the photosensitive drum potential is not adjusted by weak exposure, but this is not a requirement; the drum potential may be adjusted by weak exposure if an appropriate transfer contrast ΔVtr2 can be ensured.

[0165] (Cleaning E. Cabriton) Figure 16(e) shows the cleaning process of the cabritone. Intermediate transfer belt 10 The processing of the transcribed Cabritone is described below.

[0166] The positive and negative polarity capritners transferred to the intermediate transfer belt 10 are sent to the cleaning device 16 by the rotation of the intermediate transfer belt 10, and are collected and processed in the waste toner container 17.

[0167] As described above, the configuration of Example 3 allows only the toner containing a large amount of degraded toner to be sent to the waste toner container 17, thereby reducing the proportion of degraded toner in the developing unit 4. As a result, unnecessary toner consumption is suppressed, extending the lifespan of the developing unit 4. At the same time, the amount of toner sent to the waste toner container 17 can be reduced compared to Example 1, thus reducing the frequency of the waste toner container replacement by the user.

[0168] As described above, by implementing the first fogging discharge control, a large portion of the degraded toner generated during the use of the process cartridge S can be selectively discharged from the developing unit 4, thereby achieving efficient discharge. Consequently, an image forming apparatus can be provided that reduces unnecessary toner consumption while simultaneously reducing the frequency of replacing the waste toner container. Furthermore, the control in Example 3 exhibits even more remarkable effects when combined with the control in Example 1. Specifically, by combining Example 3 and Example 1, the quality of the degraded toner discarded in the cleaning device 16 can be improved. By implementing the control in Example 3 in conjunction with the control in Example 1, the proportion of degraded toner is reduced, thereby increasing the amount of toner that can be recovered.

[0169] [Example 4] Next, Example 4 of the present invention will be described. Hereinafter, only the differences between the configuration and effects of Example 4 and Example 3 will be described. Components in Example 4 that are the same as those in Example 3 are denoted by the same reference numerals, and their descriptions are omitted.

[0170] Example 4 describes a control method for efficiently processing cabritone (degraded toner) by a different means, similar to Example 3. In Example 3, a control method was described in which, of the cabritone containing a large amount of degraded toner, the positive polarity toner was first transferred to the intermediate transfer belt 10, the negative polarity toner was temporarily left on the photosensitive drum 1, and then transferred to the intermediate transfer belt 10 without being recovered by the developing roller 22. In Example 3, all of the cabritone was processed by the cleaning device 16. In Example 4, unlike Example 3, a control method is described in which, of the cabritone, the negative polarity toner is first transferred to the intermediate transfer belt 10, the positive polarity toner was temporarily left on the photosensitive drum 1, and then transferred to the intermediate transfer belt 10 without being recovered by the developing roller 22.

[0171] According to the control in Example 4, the toner cap can be ejected from the developing unit 4 with an efficiency equal to or greater than that of Example 3. As a result, unnecessary toner consumption can be suppressed more effectively. To distinguish it from Examples 1, 2, and 3, the ejection control performed in Example 4 is referred to as the second toner cap ejection control, and the same reference numerals are used for parts that are the same as in Examples 1, 2, and 3, and their explanation is omitted. The following explanation will be based on the image forming apparatus of Example 2.

[0172] <Second fouling discharge control> The second fogging discharge control of this embodiment will be explained using Figures 18(a) to (f) and Figure 19. Figures 18(a) to (f) are explanatory diagrams of the second fogging discharge control, and are schematic diagrams showing the movement of discharged toner when the discharge control is performed. Figure 19 is an explanatory diagram of the voltage and potential control of the second fogging discharge control, and is a schematic diagram that shows the changes in the potential of the photosensitive drum 1, the developing voltage, the primary transfer voltage, and the movement of toner along the time axis during the second fogging discharge control. Figure 19 shows a graph with potential / voltage on the vertical axis and time on the horizontal axis. The surface potential (photosensitive drum potential) of a predetermined location that moves as the photosensitive drum 1 rotates is shown by a thick line, and the toner adhering to that area is also shown.

[0173] This control process can be broadly divided into the following steps: A. Toner fogging discharge from the developer, B. Polarity separation of fogging toner in the primary transfer section, C. Collection of positive polarity fogging toner by the charging roller, D. Discharging of positive polarity fogging toner by the charging roller, E. Transfer of positive polarity fogging toner, and F. Cleaning of fogging toner. Each step will be explained below. Note that each step from A to F corresponds to Figures 18(a) to (f), and the ranges corresponding to each step from A to E are also indicated by arrows in Figure 19.

[0174] (A. Toner fogging discharge from the developing unit) Figure 18(a) shows the process of ejecting the cabritone in the developing unit 4. Similar to the first cabritone ejection control in Example 3, when the operation of the second cabritone ejection control is started, the photosensitive drum 1 is charged to a predetermined potential (post-charging potential Vp = -700V) by the charging roller 2. At almost the same time, a predetermined voltage (developing voltage Vdc = -300V) is also applied to the developing roller 22. The surface of the photosensitive drum 1, which is charged to a post-charging potential Vp = -700V, is adjusted to a predetermined potential (post-weak exposure potential Vd = -600V) by weak exposure of the non-image area. When the drum surface, which is charged to a post-weak exposure potential Vd, passes through the contact area with the developing roller 22, the cabritone with mixed positive and negative polarities is developed (moves onto the surface of the photosensitive drum 1). In this example as well, similar to Example 3, when generating cabritone, the back contrast ΔVb is set to 300V, which is greater than the back contrast ΔVb = 180V during image formation.

[0175] Furthermore, the length of the fouling toner ejected in one go (in one fouling toner ejection control) in the rotational direction of the photosensitive drum 1 is preferably at least the length of one rotation of the developing roller 22, as in Example 3. However, unlike Examples 1, 2, and 3, the length of the ejected toner may be at least the length of one rotation of the photosensitive drum 1, and the length of the fouling toner can be increased as long as it is sufficient to collect positive polarity fouling toner with the charging roller 2. As a result, the amount of degraded toner that can be ejected in one control is increased compared to Examples 1, 2, and 3. Consequently, the configuration of Example 4 reduces the number of times this control is performed throughout the lifespan of the process cartridge S, thus reducing downtime throughout its lifespan.

[0176] In this embodiment, the system is set to discharge 267 mm (8.5 mm × 3.14 mm × 10 mm) of toner at once, which is the length of 10 rotations of the charging roller 2. However, the amount of toner discharged is not limited to this and can be set appropriately according to the amount of toner.

[0177] (B. Polarity separation in the primary transfer section of the Cabritone) Figure 18(b) shows the polarity separation process in the primary transfer section of the cabriolet toner. In this process, the positive polarity toner passes through the transfer section and the negative polarity toner is transferred to the intermediate transfer belt 10.

[0178] When the capri toner first passes through the primary transfer section, a voltage of +100V is applied from the primary transfer power supply 15 to the primary transfer roller 14. As shown in Figure 19(b), a potential difference ΔV4 is formed between the photosensitive drum 1 and the intermediate transfer belt 10 in the primary transfer section, such that negative polarity toner is transferred onto the intermediate transfer belt 10 and positive polarity toner remains on the photosensitive drum 1. At this time, if the potential formed on the intermediate transfer belt 10 is positive compared to the photosensitive drum potential, the positive polarity toner of the capri toner can be left on the photosensitive drum 1, and the negative polarity toner can be transferred to the intermediate transfer belt 10.

[0179] The absolute value of the potential difference ΔV4 is the transfer of negative polarity cabriolet toner containing a large amount of degraded toner and From this perspective, a transfer contrast ΔVtr1 (250V in this embodiment) or higher during image formation is preferable. However, if the potential difference ΔV4 is too large, there is a risk that abnormal discharge will occur in the primary transfer section, reversing the polarity of the ejected toner, or that the drum potential after transfer will become positive. Therefore, in the configuration of this embodiment, a potential difference ΔV4 of less than 1500V is preferable. In this embodiment, a potential of +100V (primary transfer voltage Vtr) was formed on the intermediate transfer belt 10 by the primary transfer power supply 15 so that the absolute value of the potential difference ΔV4 was 700V.

[0180] (C. Positive polarity cabritone charge roller collection) Figure 18(c) shows the process of collecting positive polarity cabritone on the charging roller. The movement of the positive polarity cabritone that has passed through the primary transfer section and remains on the photosensitive drum 1 will be explained. The processing method for the negative polarity cabritone transferred to the intermediate transfer belt 10 will be explained separately together with the processing method for the positive polarity cabritone.

[0181] In the second fray ejection control, the positively polarized fray toner remaining on the photosensitive drum 1 is temporarily collected by the charging roller 2 to which a negatively polarized voltage is applied. At this time, the charging contrast ΔV2 between the photosensitive drum 1 and the charging voltage Vpri moves the positively polarized fray toner from the photosensitive drum 1 to the charging roller 2. In this embodiment, the surface potential of the photosensitive drum 1 is not discharged by the pre-charging exposure device 6. This is because it is necessary to eject the positively polarized fray toner from the charging roller 2 to the photosensitive drum 1 in a later process. Therefore, the photosensitive drum potential that reaches the charged area in this process is a potential that is slightly displaced from the post-weak exposure potential Vd (-600V) by a potential difference ΔV4 (700V) (referred to as the post-transfer potential Va). In this embodiment, the post-transfer potential Va is set to a potential of -500V.

[0182] Therefore, in this embodiment, the charge contrast ΔV2 is the difference between the post-transfer potential Va = -500V and the charging voltage Vpri = -1200V, and in this embodiment, the charge contrast ΔV2 is set to 700V. As a result, as shown in Figure 18(c), the charge contrast ΔV2 causes the positive polarity capri toner to adhere from the photosensitive drum 1 to the charging roller 2. It is preferable that the charge contrast ΔV2 be below the discharge initiation voltage. While increasing the potential difference allows more toner to adhere to the charging roller 2, there is a risk that the polarity of the toner will reverse when discharge occurs. Furthermore, during the subsequent rotation of the photosensitive drum 1, there is a risk that the toner on the charging roller 2 side may become negative (become negatively polarized) due to friction. Therefore, it is preferable that the charge contrast ΔV2 in the charging roller collection process be smaller than the charge contrast during image formation.

[0183] (D. Positive polarity cabritone discharge from the charged roller) Figure 18(d) shows the process of ejecting positive polarity cabritone from the charging roller. After a certain amount of positive polarity cabritone is collected by the charging roller 2, the collected positive polarity cabritone is ejected from the charging roller 2 to the photosensitive drum 1. Prior to ejecting the positive polarity cabritone, the developing roller 22 is separated from the photosensitive drum 1. This is to prevent the cabritone ejected from the charging roller 2 from being collected by the developing roller 22.

[0184] In this embodiment, approximately 0V is applied to the charging roller 2 in order to discharge positive polarity cabritone from the charging roller 2. The surface potential of the photosensitive drum 1 when it reaches the charged area is the post-transfer potential Va = -500V. Due to the potential difference ΔV5 (ΔV5 = 500V in this embodiment) between the post-transfer potential Va (-500V) and the charging voltage Vpri (approximately 0V), the positive polarity cabritone collected from the charging roller 2 is discharged onto the photosensitive drum 1, as shown in Figure 18(d).

[0185] The absolute value of the potential difference ΔV5 is the transfer contrast ΔVtr1 (250 in this embodiment) during image formation in order to eject positive polarity cabriolet toner containing a large amount of degraded toner to the photosensitive drum 1. V) or higher is preferable. In this embodiment, a potential difference ΔV5 was formed by applying 0V to the charging voltage Vpri, but this is not the only way; both the post-transfer potential Va and the charging voltage Vpri may be adjusted so that the potential difference ΔV5 is equal to or greater than the transfer contrast ΔVtr1.

[0186] The surface of the photosensitive drum 1, from which the positive polarity cabritone is discharged, is neutralized to approximately 0V by the scanner unit 3 (hereinafter referred to as forced emission). This ensures a transfer contrast ΔVtr4, which is the potential difference (the difference between the surface potential of the photosensitive drum 1 and the primary transfer voltage Vtr) in the transfer of the positive polarity cabritone in the next process.

[0187] (E. Transfer of positive polarity cabriolet toner) Figure 18(e) shows the transfer process of positive polarity cabritone. The positive polarity cabritone discharged from the charging roller 2 reaches the primary transfer section again and is transferred to the intermediate transfer belt 10. At this time, since the developing roller 22 is separated from the photosensitive drum 1, the cabritone reaches the primary transfer section without being collected by the developing roller 22.

[0188] In this process, a negative primary transfer voltage Vtr is applied to transfer the positive polarity toner. The positive polarity toner is transferred to the intermediate transfer belt 10 by the transfer contrast ΔVtr4 between the potential of the photosensitive drum 1 (approximately 0V) and the primary transfer voltage Vtr. Since the cabriolet toner contains a large amount of degraded toner with high non-electrostatic adhesion, it is difficult to transfer it to the intermediate transfer belt 10 with the same potential difference as during normal image formation. Therefore, the transfer contrast ΔVtr4 needs to be set so that the degraded toner can be transferred to the intermediate transfer belt 10. Specifically, it is preferable that the transfer contrast ΔVtr4 is greater than the transfer contrast ΔVtr1 (250V in this embodiment) during normal image formation operation. However, if the transfer contrast ΔVtr4 is too large, there is a risk of abnormal discharge in the primary transfer section, so it is preferable that the transfer contrast ΔVtr4 is less than 2000V.

[0189] In this embodiment, the transfer of positive polarity cabritone to the intermediate transfer belt 10 is performed with a transfer contrast ΔVtr4 = 1000V between the photosensitive drum potential of approximately 0V after forced illumination and the primary transfer voltage Vtr = -1000V. In this embodiment, the photosensitive drum potential is neutralized to 0V by forced illumination, but this is not mandatory; if an appropriate transfer contrast ΔVtr4 can be secured, it is not necessary to neutralize the photosensitive drum potential to 0V.

[0190] (Cleaning of F. Cabritner) Figure 18(f) shows the cleaning process of the cabritone. The processing of the cabritone transferred onto the intermediate transfer belt 10 will be explained.

[0191] The positive and negative polarity capritners transferred to the intermediate transfer belt 10 are sent to the cleaning device 16 by the rotation of the intermediate transfer belt 10, and are collected and processed in the waste toner container 17.

[0192] Based on the above, the configuration of Example 4 allows only the toner containing a large amount of degraded toner to be sent to the waste toner container 17, thus achieving the same effects as Examples 1, 2, and 3. Furthermore, in Example 4, temporary collection is possible with the charged roller 2, allowing for a longer toner discharge length in a single control cycle compared to Example 3. As a result, the frequency of downtime can be reduced. In addition, the control in Example 4, like the control in Example 3, exhibits even more remarkable effects when combined with the control in Example 1. Specifically, combining Example 3 and Example 1 can improve the quality of the degraded toner discarded in the cleaning device 16. By implementing the control in Example 3 in combination with the control in Example 1, the proportion of degraded toner is reduced, thus increasing the amount of toner that can be recovered.

[0193] <Example 1> Next, a modified example 1 of Example 4 will be described. In Example 4, pre-charging exposure is not performed immediately before the collection of positive polarity cabritone by the charging roller 2, but the potential of the photosensitive drum 1 may be discharged by pre-charging exposure. The differences in control in that case compared to Example 4 will be explained using Figure 20.

[0194] Figure 20 is an explanatory diagram of the voltage and potential control of the second fogging discharge control according to Modification 1, and schematically represents the changes in the potential of the photosensitive drum 1, the developing voltage, the primary transfer voltage, and the movement of toner along the time axis during the second fogging discharge control. Figure 20 shows a graph with potential / voltage on the vertical axis and time on the horizontal axis, and the surface potential (photosensitive drum potential) of a predetermined location that moves with the rotation of the photosensitive drum 1 is shown by a thick line, along with the toner adhering to that part.

[0195] First, if pre-charging exposure is applied immediately before the collection of positively polarized capritor at the charging roller 2, the positively polarized capritor moves to the charging roller 2, similar to Example 4. Subsequently, when the positively polarized capritor is discharged from the charging roller 2, it is necessary to move the positively polarized capritor from the charging roller 2 to the surface of the photosensitive drum 1, which has been de-charged to approximately 0V. Therefore, in Modification 1, a positive voltage is applied to the charging roller 2. At this time, the positively polarized capritor moves from the charging roller 2 to the photosensitive drum 1, and simultaneously the photosensitive drum potential is charged to a positive polarity. In this Modification, a charging voltage Vpri of +1000V is applied to the charging roller 2 when the positively polarized capritor is discharged from the charging roller 2, and the surface potential of the photosensitive drum 1 formed at that time is +500V. Therefore, in this Modification, similar to Example 4, forced emission is performed by the scanner unit 3 to de-charge to approximately 0V again. This results in the same state as in Figures 18(e) and 19E in Example 4. The subsequent operations are the same as in Example 4, so the explanation will be omitted.

[0196] <Other configurations> In Example 4, positive polarity cabritone was temporarily collected by the charging roller 2, but the configuration is not limited to this. For example, instead of the charging roller 2, a collection member may be provided that contacts the photosensitive drum 1 and charges the photosensitive drum 1 to temporarily collect positive polarity cabritone. In this case, the voltage applied to the collection member should be controlled by the engine control unit 210 in the same way as the other applied voltages. Preferably, the temporary collection member is positioned upstream of the charging roller 2 (charging part) and downstream of the primary transfer roller 14 (transfer part) in the rotational direction of the photosensitive drum 1.

[0197] Figures 21(a) and (b) are explanatory diagrams of other configuration examples related to Embodiment 4. Figure 21(a) shows a configuration in which a urethane sponge roller 27 is arranged as a temporary collection member. Figure 21(b) shows a configuration in which a brush-shaped collection member 28 is arranged as a temporary collection member. Furthermore, the temporary collection member may be a non-contact type charging member instead of a contact type. Moreover, when a primary collection member is provided, the charging member such as the charging roller 2 does not need to be a contact type, and a non-contact type charging member may be used.

[0198] As described above, by implementing the second fogging discharge control, a large portion of the degraded toner generated during the use of the process cartridge S can be selectively discharged from the developing unit 4, thereby achieving efficient discharge. Consequently, it is possible to provide an image forming apparatus that reduces unnecessary toner consumption while simultaneously reducing the frequency of replacing the waste toner container.

[0199] [Example 5] Next, Example 5 of the present invention will be described. Below, only the differences between the configuration and effects of Example 5 and Example 1 will be described. The same symbols are used for the composition of the characters, and explanations are omitted.

[0200] In this embodiment, ejection control is performed in the same manner as in Embodiment 1, but the absolute value of the difference between the voltage applied to the regulating member and the voltage applied to the developing means is larger during toner ejection formation than during image formation, which is a difference from Embodiment 1.

[0201] As described in Example 1, the developing blade 23, acting as a regulating member, regulates the amount of toner coating formed on the developing roller 22, which acts as a developing means, and also imparts charge. A voltage with the same polarity as the developing roller 22 and a large absolute value is applied to the developing blade 23. Due to this voltage, the toner T on the developing roller 22 rubs against the developing blade 23, becoming triboelectrically charged, and is also charged by charge injection from the developing blade 23. Hereinafter, the operation of charging the toner carried by the developing roller 22 with the developing blade 23 to form toner for discharge from the developing roller 22 will be referred to as discharged toner formation. In this embodiment, both the developing blade voltage Vbld and the developing voltage Vdc are negative values, and the relationship |Vbld|>|Vdc| exists.

[0202] The larger the absolute value of the difference ΔVbld (=Vbld-Vdc) between the developing blade voltage Vbld applied to the developing blade 23 and the developing voltage Vdc applied to the developing roller 22, the greater the amount of charge injected from the developing blade 23 to the toner T. As the amount of charge injected into the toner T increases, the amount of charge on the toner T on the developing roller 22 increases. However, if the difference ΔVbld exceeds a predetermined threshold (in this embodiment, |ΔVbld|=approximately 500V), discharge begins. Therefore, the difference ΔVbld must be kept within a range where discharge does not occur. Furthermore, the larger the difference ΔVbld, the stronger the electric field from the developing blade 23 to the developing roller 22. As a result, the toner T receives a strong Coulomb force from the developing blade 23 towards the developing roller 22, increasing the amount of toner passing through the restricted area between the developing blade 23 and the developing roller 22. Consequently, the amount of toner coating on the developing roller 22 increases.

[0203] <Discharge control> The toner ejection control in this embodiment is basically the same as in Embodiment 1, including toner movement and potential relationships. The movement of ejected toner explained using Figures 1(a) to (f) and the potential relationships explained using Figure 8 in Embodiment 1 are also the same as in Embodiment 1.

[0204] During image formation, a developing blade voltage Vbld = -500 V is applied to the developing blade 23, and a developing voltage Vdc = -300 V is applied to the developing roller 22. Therefore, the difference ΔVbld is ΔVbld = Vbld - Vdc = -200 V.

[0205] On the other hand, during the formation of ejected toner during ejection control (corresponding to part A in Fig. 1(a) and Fig. 8), a developing blade voltage Vbld = -700 V is applied to the developing blade 23, and a developing voltage Vdc = -300 V is applied to the developing roller 22. Therefore, the difference ΔVbld is ΔVbld = Vbld - Vdc = -400 V. Thus, by increasing the absolute value of the difference ΔVbld compared to during image formation, the toner coating amount and the charge amount of the toner T on the developing roller 22 increase.

[0206] The weight M (g / m 2 ) per unit area and the charge amount Q (C / g) per unit weight of the ejected toner formed on the surface of the photosensitive drum 1 at the timing of Fig. 1(a) were confirmed by changing ΔVbld. When ΔVbld = -200 V, M = 4.6 g / m 2 , and Q = 0.040 C / g. On the other hand, when ΔVbld = -400 V, M = 4.9 g / m 2 , and Q = 0.045 C / g.

[0207] As described in Example 1, the deteriorated toner has the external additive on the toner surface peeled off or embedded This refers to toner that has been deformed or whose shape has been altered. Some external additives are added to the toner for the purpose of imparting charge to it, and the amount of charge in the toner decreases when these external additives peel off or become embedded. In addition, when the shape of the toner is altered, it becomes more difficult for the toner to roll on the developing roller 22, the opportunity for triboelectric charging is lost, and the amount of charge in the toner decreases. Therefore, degraded toner tends to have a lower charge amount compared to normal toner. Degraded toner with a low charge amount is less likely to be developed because it receives a smaller Coulomb force from the potential difference formed between the developing roller 22 and the exposure potential of the photosensitive drum 1. In this ejection control, as described in Example 1, the development contrast ΔVc during toner formation (corresponding to Figure 1(a)) is made larger than during image formation, making it easier to develop the toner T on the photosensitive drum 1 than during image formation. However, simply increasing the development contrast ΔVc may result in some degraded toner having an extremely low charge amount and remaining on the developing roller 22.

[0208] According to the configuration of this embodiment, the differential ΔVbld is increased during toner ejection, resulting in a larger charge even for degraded toner, making it easier to develop. Therefore, the total amount of degraded toner contained in the ejected toner can be increased compared to Example 1. In addition, the ratio of degraded toner to fresh toner in the ejected toner can be increased. As a result, the number of times this ejection control is performed throughout the lifespan of the process cartridge can be reduced, resulting in a reduction in downtime throughout its lifespan.

[0209] The period during which the difference ΔVbld is increased is the period during which toner is ejected onto the photosensitive drum 1 (part A in Figure 8). Specifically, the applied voltages are controlled so that toner that has passed at least once through the contact area between the developing blade 23 and the developing roller 22, where the modified difference ΔVbld is formed, is transported to the contact area between the developing roller 22 and the exposure surface of the photosensitive drum 1, and ejected.

[0210] Here, we will explain why it is difficult to keep the difference ΔVbld large during image formation. If the difference ΔVbld is large during normal operation, such as during image formation, the toner may become excessively charged. Toner that has passed through the contact area between the developing blade 23 and the developing roller 22 many times has many opportunities to be charged by injection from the developing blade 23, and also has many opportunities to roll on the developing roller 22 and rub against the developing blade 23, so the amount of charge tends to increase. In addition, a large difference ΔVbld increases the amount of charge injected from the developing blade 23, so the amount of charge increases even further. If the amount of charge becomes excessively large, image defects may occur, such as the image density becoming lighter over the distance of one rotation of the developing roller 22. For this reason, it is better not to make the difference ΔVbld excessively large during image formation. In this embodiment, a good image was obtained by keeping ΔVbld = -200V during image formation.

[0211] On the other hand, during toner formation in ejection control, even if the difference ΔVbld is large, the toner is immediately ejected around the entire circumference of the developing roller, so the toner does not pass through the contact area between the developing blade 23 and the developing roller 22 multiple times while the difference ΔVbld is large. Therefore, toner overcharging is less likely to occur during ejection control. Furthermore, even if the toner becomes overcharged, during ejection control, the toner is ejected onto the photosensitive drum 1, collected by the developing roller 22, or transferred to the intermediate transfer belt 10 and then collected in the waste toner container 17, so it is not transferred to the recording material and causes image defects. Therefore, it is possible to set a larger difference ΔVbld during ejection control compared to during image formation.

[0212] <Evaluation Test> To confirm the effectiveness of this embodiment in efficiently ejecting degraded toner and reducing downtime throughout its lifespan, the following tests were conducted. In an environment of 23°C / 50% relative humidity, a 5000-sheet paper feed test was performed using Xerox Business 4200 LETTER size (Xerox, product name) as the recording material P, and the presence or absence of image defects was verified.

[0213] In this evaluation test, in Example 5, the difference ΔVbld was set to -400V, and the same control as in Example 1 was used to perform ejection control every 50 sheets after the 2500th sheet. Furthermore, in this evaluation test, the number of ejection controls was reduced, and an ejection control was performed every 100 sheets after the 2500th sheet. Table 2 shows the evaluation results of this test. Table 2 shows whether or not image defects occurred on the first sheet and every 1000 sheets for the two control types in Example 5. Image defects were judged based on poor recovery in the developing unit (development and recovery failure) due to deterioration of primary transferability caused by toner degradation. The evaluation criteria are the same as those for the evaluation test in Example 1.

[0214] [Table 2]

[0215] As shown in Table 2, in this embodiment, when ejection control was performed every 50 sheets after the 2500th sheet, no development and recovery failure occurred even when the number of sheets fed reached 5000, similar to Example 1. Thus, it was confirmed that the control in this embodiment, similar to Example 1, has the effect of efficiently ejecting deteriorated toner while suppressing unnecessary toner consumption.

[0216] Furthermore, as shown in Table 2, even when the frequency of ejection control was reduced and ejection control was performed every 100 sheets after the 2500th sheet, no development and recovery failures occurred even when the number of sheets fed reached 5000. Thus, in this embodiment, by increasing the difference ΔVbld during toner ejection formation, the proportion and total amount of degraded toner ejected in each ejection control increased, making it possible to reduce the ejection frequency. As a result, the frequency of downtime caused by ejection control was reduced.

[0217] As explained above, in this embodiment, control was implemented to increase the absolute value of the difference ΔVbld during toner ejection compared to image formation. By implementing this control, efficient ejection was achieved, similar to Embodiment 1, reducing unnecessary toner consumption and simultaneously reducing the frequency of replacing the waste toner container. In addition to these effects, the control in this embodiment was able to increase the proportion and total amount of degraded toner in the ejected toner. As a result, the number of times this ejection control is executed can be reduced, resulting in reduced downtime throughout the lifespan.

[0218] <Modification 2> A modified example 2 relating to Example 5 will now be described. In this modified example, the difference ΔVbld is increased in stages during toner ejection. Specifically, during toner ejection, the absolute value of the difference ΔVbld is increased for each rotation of the developing roller 22 in the rotational direction of the photosensitive drum 1. Hereafter, parts (configuration, effects, etc.) that are the same as in Example 5 will be denoted by the same reference numerals and their explanation will be omitted.

[0219] <Toner on the developing roller during ejection> The toner T on the developing roller 22 becomes charged as it passes through the contact area between the developing blade 23 and the developing roller 22. Therefore, if there is no printing for an extended period, the toner T on the developing roller 22 tends to become highly charged (hereinafter referred to as white toner). On the other hand, once the toner T on the developing roller 22 moves onto the photosensitive drum 1, such as after a high-resolution image (hereinafter referred to as a solid image) has been printed around the entire circumference of the developing roller 22, it is then coated onto the developing roller 22. Since toner T (hereinafter referred to as black toner) passes through the contact area between the developing blade 23 and the developing roller 22 only once, the amount of charge it accumulates is low. Also, if a solid image is continuously printed over multiple rotations of the developing roller 22, the amount of toner coating on the developing roller 22 may decrease in proportion to the number of rotations due to a shortage of toner near the developing roller 22.

[0220] <Discharge control> In Example 1, when ejection control was performed, a length of 44.8 mm (= 10 mm × 3.14 ÷ 1.4 × 2), equivalent to two rotations of the developing roller 22, was ejected. However, in this modified example, a length of 60 mm, or approximately 2.7 rotations of the developing roller, of toner is ejected.

[0221] In this modified example, a developing voltage Vdc = -300V is always applied to the developing roller 22. During toner ejection, a developing blade voltage Vbld is applied to the developing blade 23, which is -700V for the first rotation, -720V for the second rotation, and -740V for the third rotation. That is, the difference ΔVbld(Vbld-Vdc) is -400V for the first rotation, -420V for the second rotation, and -440V for the third rotation. In this modified example, the developing voltage Vdc and the developing blade voltage Vbld are controlled so that the absolute value of the difference ΔVbld increases in accordance with the increase in the rotation distance of the developing roller 22.

[0222] As described above, in this modified example, control was implemented to gradually increase the absolute value of the difference ΔVbld between the developing blade voltage Vbld and the developing voltage Vdc during ejection control, compared to the image formation process. As a result, according to the control of this embodiment, in addition to the effects of Embodiment 5, the difference in charge amount between the white toner and the black toner is reduced, making it possible for the black toner to be sufficiently charged and ejected. Furthermore, it becomes possible to suppress the decrease in the amount of toner on the developing roller 22 in proportion to the number of rotations during toner ejection.

[0223] [Example 6] Next, Example 6 of the present invention will be described. Hereinafter, only the differences between the configuration and effects of Example 6 and Example 1 will be described. Components in Example 6 that are the same as those in Example 1 are denoted by the same reference numerals, and their descriptions are omitted.

[0224] In this embodiment, ejection control is performed in the same manner as in Embodiment 1, but the characteristic feature is that the relative rotation speed of the developing means with respect to the image carrier is greater during toner ejection formation than during image formation, which is different from Embodiment 1. Parts that are the same as in Embodiment 1 (such as configuration and effects) are denoted by the same reference numerals and their explanation is omitted.

[0225] The developing roller 22 as a developing means rotates with a speed difference relative to the photosensitive drum 1 as an image carrier. When the relative rotational speed of the developing roller 22 with respect to the photosensitive drum 1 is increased, the distance where the toner layer on the developing roller 22 contacts the exposed surface of the photosensitive drum 1 increases. As a result, when the development contrast ΔVc, which is the potential difference between the exposed portion of the photosensitive drum 1 and the developing roller 22, is sufficiently large, the amount of toner developed from the developing roller 22 to the photosensitive drum 1 increases. As described in Example 1, in the ejection control, the exposure amount by the exposure means is made different from that during the image forming operation, and the development contrast ΔVc is made larger than that during the image forming operation. Therefore, in the ejection control, when the relative rotational speed of the developing roller 22 with respect to the photosensitive drum 1 is increased, the total amount of toner T developed increases.

[0226] <Ejection control> The ejection control of this embodiment is basically the same as that of Example 1 in terms of the movement of toner, potential relationship, etc. The movement of the ejected toner described using FIGS. 1(a) to (f) and the potential relationship described using FIG. 8 in Example 1 are also the same as those in Example 1. Hereinafter, the rotational speed of the developing roller 22 when the rotational speed of the photosensitive drum 1 is 100% is expressed as a percentage and is called the relative developing roller speed. That is, the relative developing roller speed is synonymous with the ratio of the rotational speed of the developing roller 22 to the rotational speed of the photosensitive drum 1. During normal operations other than ejection control, such as during image formation, the relative developing roller speed is 140%. In this embodiment, during the formation of ejected toner (corresponding to FIG. 1(a) and part A in FIG. 8), the relative developing roller speed is set to 160%. By performing such control, the total amount of toner developed from the developing roller 22 to the photosensitive drum 1 increases. The weight M (g / m

[0227] ) per unit area of the ejected toner formed on the surface of the photosensitive drum 1 at the timing of FIG. 1(a) was confirmed by changing the relative developing roller speed. When the relative developing roller speed was 140%, M = 4.6 g / m 2 ) and when the relative developing roller speed was 160%, M = 6.8 g / m 2On the other hand, when the relative developing roller speed was 160%, M = 5.2 g / m 2 It was.

[0228] Thus, by increasing the rotational speed of the developing roller 22 with respect to the photosensitive drum 1 at the time of forming the ejected toner, the total amount of toner developed from the developing roller 22 to the photosensitive drum 1 can be increased. As a result, the total amount of deteriorated toner contained in the ejected toner can be increased. As a result, the number of times of executing this ejection control throughout the life of the process cartridge can be reduced, and the effect of reducing downtime throughout the life can be obtained.

[0229] <Evaluation Test> In order to confirm the effect of efficiently ejecting the deteriorated toner and the effect of reducing downtime throughout the life of the present embodiment, the same test as in Example 5 was conducted. Specifically, in Example 6, the relative developing roller speed at the time of forming the ejected toner was set to 160%, and control for performing ejection control every 50 sheets after the 2500th sheet of paper passing and control for performing ejection control every 100 sheets after the 2500th sheet of paper passing were executed. Table 3 shows the evaluation results of this test. Table 3 shows the presence or absence of image defects for the first sheet of paper passed and every 1000 sheets in the two types of controls of Example 6. The evaluation criteria are the same as those in the evaluation tests of Examples 1 and 5.

[0230]

Table 3

[0231] [[ID=,24]]As shown in Table 3, in the control of the present embodiment, when the ejection control was performed every 50 sheets after the 2500th sheet, as in Example 1, no developing recovery failure occurred even when the number of sheets passed reached 5000. Thus, in the control of the present embodiment, as in Example 1, it was confirmed that there is an effect of efficiently ejecting the deteriorated toner while suppressing wasteful toner consumption.

[0232] Furthermore, as shown in Table 3, even when the frequency of ejection control was reduced and ejection control was performed every 100 sheets after the 2500th sheet, no development and recovery failures occurred even when the number of sheets fed reached 5000. Thus, in this embodiment, by increasing the peripheral speed of the developing roller 22 (relative developing roller speed) during toner ejection, the total amount of deteriorated toner ejected in each ejection control increased, making it possible to reduce the ejection frequency. As a result, the frequency of downtime caused by ejection control was reduced.

[0233] As explained above, in this embodiment, the development process during toner ejection is more important than the development process during image formation. The rotational speed of the roller 22 relative to the photosensitive drum 1 was increased. By performing this control, similar to Example 1, efficient toner ejection is achieved, reducing unnecessary toner consumption and simultaneously reducing the frequency of replacing the waste toner container. In addition to these effects, the control in this embodiment can increase the total amount of degraded toner in the ejected toner. As a result, the number of times this ejection control is performed can be reduced, resulting in reduced downtime throughout the lifespan of the process cartridge S.

[0234] <Variation 3> In Example 6, the relative developing roller speed during toner ejection was increased in the ejection control described in Example 1. Below, as Modification 3 of Example 6, an example is described in which the first fogging ejection control described in Example 3 or the second fogging ejection control described in Example 4 is performed instead of the ejection control described in Example 1. In Modification 3, the relative developing roller speed is increased during the ejection of fogging toner (at the timings shown in Figures 16(a) and 18(a)) in the fogging ejection control. Hereafter, parts (configuration, effects, etc.) that are the same as in Example 6 are denoted by the same reference numerals and their explanation is omitted.

[0235] In this modified example, the relative developing roller speed is set to 140% during image formation and to 160% during toner ejection. By implementing this control, the total amount of toner ejected onto the photosensitive drum 1 increases compared to during image formation, thus increasing the amount of degraded toner ejected in a single toner ejection control. As a result, in this modified example, in addition to the effects of Examples 3 and 4, the number of times toner ejection control is performed can be reduced, resulting in reduced downtime throughout the lifespan.

[0236] [Example 7] Next, Example 7 of the present invention will be described. Hereinafter, only the differences between the configuration and effects of Example 7 and Example 1 will be described. Components in Example 7 that are the same as those in Example 1 are denoted by the same reference numerals and their descriptions are omitted.

[0237] In this embodiment, ejection control is performed in the same manner as in Embodiment 1, but the absolute value of the difference between the voltage applied to the developer supply means and the voltage applied to the developing means during toner ejection is larger than during image formation, which is a difference from Embodiment 1.

[0238] As described in Example 1, the supply roller 26, which serves as a developer supply means, has a supply voltage Vrs applied to it as a predetermined DC voltage. The supply voltage Vrs is a voltage with the same polarity as the developing voltage Vdc applied to the developing roller 22, which serves as a developing means, and has a larger absolute value. In this embodiment, both the supply voltage Vrs and the developing voltage Vdc are negative values, and the relationship |Vrs| > |Vdc| exists.

[0239] The toner on the developing roller 22 is charged by charge injection from the supply roller 26. Therefore, increasing the absolute value of the voltage difference ΔVrs (=Vrs-Vdc, supply roller contrast) between the supply roller 26 and the developing roller 22 increases the amount of charge on the toner T on the developing roller 22. Increasing the difference ΔVrs also increases the amount of toner that moves from the supply roller 26 to the developing roller 22, increasing the amount of coating on the developing roller 22. As a result, when the development contrast ΔVc, which is the potential difference between the exposed area of ​​the photosensitive drum 1 and the developing roller 22, is sufficiently large, the amount of toner developed from the developing roller 22 to the photosensitive drum 1 increases. However, if the difference ΔVrs exceeds a threshold (approximately |ΔVrs|=500V in this embodiment), discharge begins. Therefore, ΔVrs must be set to a range where discharge does not occur.

[0240] <Discharge control> The toner ejection control in this embodiment is basically the same as in Embodiment 1, including toner movement and potential relationships. The movement of ejected toner explained using Figures 1(a) to (f) and the potential relationships explained using Figure 8 in Embodiment 1 are also the same as in Embodiment 1.

[0241] During image formation, a supply voltage Vrs = -500V is applied to the supply roller 26, and a development voltage Vdc = -300V is applied to the development roller 22. Therefore, the difference ΔVrs is ΔVrs = Vrs - Vdc = -200V.

[0242] On the other hand, during toner ejection (corresponding to parts A in Figure 1(a) and Figure 8), a supply voltage Vrs = -700V is applied to the supply roller 26 and a development voltage Vdc = -300V is applied to the development roller 22. At this time, the difference ΔVrs is ΔVrs = Vrs - Vdc = -400V. By performing this control, the amount of toner T on the development roller 22 increases, and the total amount of toner T developed from the development roller 22 to the photosensitive drum 1 increases.

[0243] The weight M (g / m²) of ejected toner formed on the surface of the photosensitive drum 1 at the timing shown in Figure 1(a) is the weight per unit area. 2) was confirmed by changing the differential ΔVrs. When ΔVrs = -200V, M = 4.6g / m 2 , Q = 0.040C / g. On the other hand, when ΔVrs = -400V, M = 4.9g / m 2 , Q = 0.045C / g. Thus, by increasing the potential difference between the supply roller 26 and the developing roller 22 during the formation of the ejected toner, the total amount of toner T developed from the developing roller 22 to the photosensitive drum 1 can be increased. As a result, the amount of deteriorated toner discharged per ejection control increases.

[0244] However, if the differential ΔVrs is kept large except during the formation of the ejected toner, such as during image formation, the toner T may be overcharged. Therefore, it is preferable to increase the differential ΔVrs at the timing before the formation of the ejected toner and return it to the original magnitude after the formation of the ejected toner.

[0245] <Evaluation Test> In order to confirm the effect of efficiently ejecting the deteriorated toner and the effect of reducing downtime through the life in this example, the same tests as in Examples 5 and 6 were conducted. Specifically, in Example 7, the absolute value of the differential ΔVrs during the formation of the ejected toner was set to 400V, which is larger than during image formation, and controls were executed in which ejection control was performed every 50 sheets after the 2500th sheet of paper passed and in which ejection control was performed every 100 sheets after the 2500th sheet of paper passed.

[0246] As a test result, in any of the tests, no developing recovery failure occurred. From this result, it was confirmed that the control in this example has the effect of efficiently ejecting the deteriorated toner while suppressing wasteful toner consumption, similar to Example 6, and the effect of suppressing the frequency of occurrence of downtime due to ejection control.

[0247] As explained above, in this embodiment, control was performed to increase the potential difference between the supply roller 26 and the developing roller 22 during toner ejection formation compared to image formation. By performing such control, the total amount of toner T developed from the developing roller 22 to the photosensitive drum 1 increases, and the total amount of degraded toner contained in the ejected toner can be increased. As a result, similar to Embodiment 1, efficient ejection is achieved, reducing unnecessary toner consumption and simultaneously reducing the frequency of replacing the waste toner container. In addition to these effects, the number of times this ejection control is performed throughout the lifespan of the process cartridge S can be reduced, resulting in reduced downtime throughout its lifespan.

[0248] <Modification 4> Modification 4 of Example 7 will be described. In the configuration of this modification, ejected toner formation Sometimes, ΔVrs is increased in stages. Specifically, during toner ejection, the absolute value of the difference ΔVrs is increased with each rotation of the developing roller 22 in the rotational direction of the photosensitive drum 1. In the following, parts (configuration, effects, etc.) that are the same as in Example 7 are denoted by the same reference numerals and their explanation is omitted.

[0249] As explained in Modification 2 of Example 5, in the toner on the developing roller 22, there may be a difference in the amount of charge between the white toner and the black toner, or the solid image may continue over multiple turns of the developing roller 22, which may lead to a decrease in the amount of toner on the developing roller 22.

[0250] Increasing the potential difference ΔVrs between the supply roller 26 and the developing roller 22 increases the charge level of the toner T on the developing roller 22. Therefore, by increasing the difference ΔVrs for the black toner compared to the white toner, the difference in charge levels between the white and black toners can be reduced. Furthermore, if a solid image continues over multiple turns of the developing roller 22, gradually increasing the difference ΔVrs can prevent a decrease in the amount of toner on the developing roller 22.

[0251] In Example 1, when ejection control was performed, a length of 44.8 mm (= 10 mm × 3.14 ÷ 1.4 × 2), equivalent to two rotations of the developing roller 22, was ejected. However, in this modified example, a length of 60 mm, or approximately 2.7 rotations of the developing roller, of toner is ejected.

[0252] In this modified example, a developing voltage Vdc = -300V is always applied to the developing roller 22. During toner ejection, a supply voltage Vrs is applied to the supply roller 26 as follows: -700V for the first pass, -720V for the second pass, and -740V for the third pass. That is, the difference ΔVrs(Vrs-Vdc) is -400V for the first pass, -420V for the second pass, and -440V for the third pass.

[0253] By implementing this control, in addition to the effects of Example 7, the difference in charge levels between the white toner and the black toner is reduced, allowing the black toner to be sufficiently charged and ejected. Furthermore, it becomes possible to suppress the decrease in the amount of toner on the developing roller 22 in proportion to the number of rotations during toner ejection.

[0254] <Modification 5> A second modification 5 relating to Example 7 will now be described. In this modification, the absolute value of the difference ΔVrs is kept lower compared to the image formation stage until just before the ejected toner is formed, and then the absolute value of the difference ΔVrs is increased at the timing of toner ejection. Hereafter, parts that are the same as in Example 7 (such as configuration and effects) will be denoted by the same reference numerals and their explanation will be omitted.

[0255] In this modified version, a developing voltage Vdc = -300V is always applied to the developing roller 22. During image formation, a supply voltage Vrs = -500V is applied to the supply roller 26, resulting in a difference of ΔVrs = -200V.

[0256] A supply voltage Vrs = -400V is applied to the supply roller 26 before the start of ejection control, resulting in a difference ΔVrs = -100V. In this way, by reducing the absolute value of the difference ΔVrs before the start of ejection control compared to during image formation, the amount of toner on the developing roller 22 decreases. At this time, fresh toner with low non-electrostatic adhesion preferentially moves off the developing roller 22. Therefore, by reducing the difference ΔVrs, the ratio of degraded toner on the developing roller 22 before the start of ejection control can be increased.

[0257] Subsequently, when ejection control is started and the ejected toner is moved onto the photosensitive drum 1, a supply voltage Vrs = -700V is applied to the supply roller 26, i.e., the difference ΔVrs = -400V, making the absolute value of the difference ΔVrs larger than during image formation. In this way, development is performed. The amount of toner on the roller is increased, and the amount of degraded toner discharged in a single ejection control is increased. The timing for reducing the difference ΔVrs before the start of ejection control should be at least before the start of ejection control, and it is desirable to rotate the developing roller 22 one full turn while the difference ΔVrs is reduced.

[0258] By implementing this control, the amount of degraded toner discharged in this modified example is greater than in Example 7. As a result, compared to Example 7, the number of times this discharge control is performed throughout the lifespan of the process cartridge can be reduced, resulting in a reduction in downtime throughout the lifespan.

[0259] <Variation 6> In Example 7, the differential ΔVrs, which is the potential difference between the supply roller 26 and the developing roller 22, was increased compared to the discharge control described in Example 1. Below, as Modification 6 of Example 7, an example is described in which the first fogging discharge control described in Example 3 or the second fogging discharge control described in Example 4 is performed instead of the discharge control described in Example 1. In Modification 6, in the fogging discharge control, the absolute value of the differential ΔVrs is increased when the fogging toner is discharged (timing in Figures 16(a) and 18(a)). Hereafter, parts that are the same as in Example 7 (configuration, effects, etc.) are denoted by the same reference numerals and their explanation is omitted.

[0260] In this modified example, the difference ΔVrs is set to -200V during image formation and to -400V during cap toner ejection. By implementing this control, the amount of toner coating on the developing roller 22 increases during cap toner ejection. Of the toner T held on the developing roller 22, a certain proportion of toner T moves onto the photosensitive drum 1 as cap toner. Therefore, as the amount of toner coating on the developing roller 22 increases, the amount of cap toner also increases.

[0261] In this way, by implementing control to increase the difference ΔVrs during toner ejection, the total amount of toner that moves onto the photosensitive drum 1 increases, thus increasing the amount of degraded toner ejected with a single toner ejection control. As a result, the number of times ejection control is performed can be reduced, resulting in a reduction in downtime throughout the lifespan.

[0262] [Example 8] Next, Example 8 of the present invention will be described. Hereinafter, only the differences between the configuration and effects of Example 8 and Example 1 will be described. Components in Example 8 that are the same as those in Example 1 are denoted by the same reference numerals, and their descriptions are omitted.

[0263] In this embodiment, ejection control is performed in the same manner as in Embodiment 1. However, in this embodiment, at the timing when the ejected toner on the image carrier passes through the transfer section, the charging section, and then again through the developing section, the absolute value of the difference between the voltage applied to the regulating member and the voltage applied to the developing means is smaller than that during the image forming operation. Hereinafter, this timing when the ejected toner on the image carrier passes through the developing section again will be referred to as the developing section passing timing. Embodiment 8 is characterized in that, at the developing section passing timing, the difference between the voltage applied to the regulating member and the voltage applied to the developing means is smaller than that during the image forming operation, and this point differs from Embodiment 1.

[0264] As explained in Example 1, the ejection control in Example 1 allows for selective ejection of degraded toner while returning a large amount of fresh toner to the developing unit 4. However, some fresh toner may be ejected and consumed along with the degraded toner. In this example, the amount of fresh toner developed and recovered at the timing when the ejected toner passes through the developing unit is increased, and the amount of toner consumed by the ejection control is reduced. As a result, the frequency of replacing the waste toner container can be reduced.

[0265] <Discharge control> The toner ejection control in this embodiment is basically the same as in Embodiment 1, including toner movement and potential relationships. The movement of ejected toner explained using Figures 1(a) to (f) and the potential relationships explained using Figure 8 in Embodiment 1 are also the same as in Embodiment 1.

[0266] As explained in Example 5, charge injection from the developing blade 23 to the toner T is performed by the difference ΔVbld between the developing blade voltage Vbld applied to the developing blade 23 and the developing voltage Vdc applied to the developing roller 22. Therefore, reducing the absolute value of the difference ΔVbld reduces the amount of charge on the toner T on the developing roller 22. Also, the smaller the absolute value of the difference ΔVbld, the weaker the electric field from the developing blade 23 to the developing roller 22. As a result, the Coulomb force acting on the toner T from the developing blade 23 towards the developing roller 22 weakens, increasing the amount of toner that cannot pass through the restrictive section between the developing blade 23 and the developing roller 22. Consequently, the amount of toner coating on the developing roller 22 decreases.

[0267] During image formation, a developing blade voltage Vbld = -500V is applied to the developing blade 23, which acts as a regulating member, and a developing voltage Vdc = -300V is applied to the developing roller 22, which acts as a developing means. Therefore, the difference ΔVbld is ΔVbld = Vbld - Vdc = -200V.

[0268] On the other hand, in the ejection control, at the timing when the ejected toner passes through the developer section (corresponding to section D in Figure 1(d) and Figure 8), a developer blade voltage Vbld = -400V and a developer voltage Vdc = -300V are applied to the developer blade 23 and the developer roller 22, respectively. Therefore, the difference ΔVbld is ΔVbld = Vbld - Vdc = -100V. In this way, reducing the absolute value of the difference ΔVbld reduces the amount of charge on the toner T on the developer roller 22 and also reduces the amount of toner coated on the developer roller 22. As the amount of toner coated on the developer roller 22 decreases, the amount of toner recovered by the developer roller 22 at the timing when the ejected toner passes through the developer section increases. Fresh toner has a lower non-electrostatic adhesion force than degraded toner, so it is preferentially recovered over degraded toner. Therefore, by performing the control in this embodiment, it is possible to reduce the amount of fresh toner consumed by the ejection control.

[0269] As mentioned above, the timing for reducing the difference ΔVbld is the timing at which the ejected toner passes through the developing section (corresponding to section D in Figure 1(d) and Figure 8). Specifically, the applied voltages are controlled so that the surface of the developing roller 22, which has passed at least once through the contact area between the developing roller 22 and the developing blade 23 where the modified difference ΔVbld is formed, comes into contact with the ejected toner on the photosensitive drum 1.

[0270] <Evaluation Test> To confirm the effectiveness of the ejection control in this embodiment in suppressing image defects caused by the ejection of degraded toner, the following test was conducted. In an environment of 23°C / 50% relative humidity, a 5000-sheet paper feed test was performed using Xerox Business 4200 LETTER size (Xerox, product name) as the recording material P, and the presence or absence of image defects was verified. Ejection control was performed at intervals of once every 50 sheets after 2500 sheets had been fed. In other words, this evaluation test was the same as that described in Example 1.

[0271] Table 4 below shows the evaluation results of this test. Table 4 also shows the test results for Example 1 and Comparative Example 1 (where ejection control was not implemented) for comparison. Table 4 shows the occurrence of image defects on the first sheet and every 1000 sheets for the configurations of Example 8, Example 1, and Comparative Example 1. Image defects were judged based on development and recovery failures. The evaluation criteria were the same as those for the evaluation test of Example 1.

[0272] [Table 4]

[0273] As shown in Table 4, in Example 8, similar to Example 1, no development and recovery failures occurred even when the number of sheets fed reached 5,000. In other words, Example 8 has the effect of selectively ejecting degraded toner compared to Comparative Example 1.

[0274] Furthermore, the average circularity (aspect ratio) of the toner at the 5000th sheet was checked using the FPIA-3000 model. The average circularity (aspect ratio) was 0.901 for Example 8, 0.903 for Example 1, and 0.851 for Comparative Example 1. In other words, there was no significant difference between Example 8 and Example 1, but the average circularity was higher for both Example 8 and Example 1 compared to Comparative Example 1. This result also confirms that the configuration of Example 8 is more effective in ejecting degraded toner compared to the configuration of Comparative Example 1.

[0275] Next, to confirm the effect of reducing the frequency of waste toner container replacement in this embodiment, the following test was conducted. In an environment of 23°C / 50% relative humidity, a 300,000-sheet paper feed test was performed using Xerox Business 4200 LETTER size (Xerox, product name) as the recording material P, and the number of waste toner container replacements was compared. Ejection control was performed every 50 sheets. In this test, in addition to the configuration of Example 8, the configuration of Example 1 was also evaluated as a comparison.

[0276] In the control method of Example 1, the waste toner container needed to be replaced a total of two times during a 300,000-sheet paper-feed test. On the other hand, in the ejection control method of this embodiment, the waste toner container needed to be replaced a total of one time during a 300,000-sheet paper-feed test. Thus, compared to Example 1, the ejection control method of this embodiment reduces the amount of toner consumed per ejection control cycle, thereby reducing the frequency of waste toner container replacement.

[0277] As described above, in this embodiment, control was implemented to reduce the potential difference between the regulating member and the developing means as the ejected toner passes through the developing unit during ejection control. By performing this control, in addition to the effects of Embodiment 1, it was possible to reduce unnecessary toner consumption during ejection control and reduce the frequency of replacing the waste toner container.

[0278] Furthermore, in this embodiment, the difference between the voltage applied to the regulating member and the voltage applied to the developing means was made smaller at the timing of passing through the developing unit in ejection control than at the time of image formation, but the configuration is not limited to this. For example, by making the difference smaller at the timing of passing through the developing unit in ejection control than at the time of ejection toner formation in ejection control, the effect of suppressing unnecessary toner consumption during ejection control can be obtained.

[0279] To suppress unnecessary toner consumption in the ejection control, it is particularly preferable to set the following conditions: (Difference ΔVbld of timing of passing through the developing unit) < (Difference ΔVbld during image formation) < (Difference ΔVbld during ejection toner formation).

[0280] [Example 9] Next, Example 9 of the present invention will be described. Hereinafter, only the differences between the configuration and effects of Example 9 and Example 1 will be described. Components in Example 9 that are the same as those in Example 1 are denoted by the same reference numerals, and their descriptions are omitted.

[0281] In this embodiment, ejection control is performed in the same manner as in Embodiment 1, but it is characterized in that the relative rotational speed of the developing means with respect to the image carrier is greater at the timing of passing through the developing unit than at the time of image formation, and this is the difference from Embodiment 1. The timing of passing through the developing unit is the timing when the ejected toner on the image carrier passes through the developing unit after passing through the transfer unit and the charging unit.

[0282] <Discharge control> The toner ejection control in this embodiment is basically the same as in Embodiment 1, including toner movement and potential relationships. The movement of ejected toner explained using Figures 1(a) to (f) and the potential relationships explained using Figure 8 in Embodiment 1 are also the same as in Embodiment 1.

[0283] During normal operation other than ejection control, such as during image formation, the relative developing roller speed, which is the relative rotation speed of the developing roller 22 when the rotation speed of the photosensitive drum 1 is set to 100%, is 140%. On the other hand, in this embodiment, at the timing when the ejected toner passes through the developing section during ejection control (corresponding to Figures 1(d) and 8D), the relative developing roller speed is set to 160%. By performing this control, the distance at which the developing roller 22 and the surface on the photosensitive drum 1 where the ejected toner is present are in contact increases in the rotation direction of the developing roller 22. As a result, the amount of toner returning from the photosensitive drum 1 to the developing roller 22 at the timing when the ejected toner passes through the developing section increases.

[0284] Because fresh toner has a lower non-electrostatic adhesion force than degraded toner, fresh toner is preferentially collected over degraded toner when passing through the developing unit. Therefore, by implementing the control in this embodiment, it is possible to reduce the amount of fresh toner consumed by the ejection control.

[0285] <Evaluation Test> To confirm the effectiveness of the ejection control in this embodiment in suppressing image defects caused by the ejection of degraded toner, the same test as in Example 8 was conducted. Specifically, in Example 9, the relative development roller speed at the timing of passing through the development section was set to 160%, and a total of 5,000 sheets of paper were fed through in a test where ejection control was performed every 50 sheets after 2,500 sheets. As a result, no development and recovery defects occurred even when the number of sheets fed through reached 5,000, and the same effect as in Example 8 was obtained with the configuration of this embodiment as well.

[0286] Furthermore, to confirm the effect of reducing the frequency of waste toner container replacement in this embodiment, a paper-feed test of 300,000 sheets was conducted, similar to Example 8, with ejection control performed every 50 sheets, and the number of waste toner container replacements was compared. As a result, in Example 1, a total of two replacements were required, but with the configuration of this embodiment, only one replacement was needed.

[0287] As described above, in this embodiment, when the ejected toner passes through the developing unit during ejection control, the relative rotation speed of the developing means with respect to the image carrier is controlled to be greater than that during the image forming operation. By implementing this control, in addition to the effects of Embodiment 1, it was possible to reduce unnecessary toner consumption and decrease the frequency of replacing the waste toner container.

[0288] [Example 10] Next, Example 10 of the present invention will be described. Below, only the differences between the configuration and effects of Example 10 and Example 1 will be described. For configurations similar to those in 1, the same reference numerals are used, and the explanation is omitted.

[0289] In this embodiment, ejection control is performed in the same manner as in Embodiment 1, but the absolute value of the difference between the voltage applied to the developer supply means and the voltage applied to the developing means at the timing of passing through the developing unit is smaller than at the time of image formation, which is a difference from Embodiment 1. The timing of passing through the developing unit is the timing when the ejected toner on the image carrier passes through the transfer unit and the charging unit and then passes through the developing unit again.

[0290] <Discharge control> The toner ejection control in this embodiment is basically the same as in Embodiment 1, including toner movement and potential relationships. The movement of ejected toner explained using Figures 1(a) to (f) and the potential relationships explained using Figure 8 in Embodiment 1 are also the same as in Embodiment 1.

[0291] During image formation, a supply voltage Vrs = -500V is applied to the supply roller 26, which serves as the developer supply means, and a developing voltage Vdc = -300V is applied to the developing roller 22, which serves as the developing means. Therefore, the difference ΔVrs is ΔVrs = Vrs - Vdc = -200V.

[0292] On the other hand, in the ejection control, at the timing when the ejected toner passes through the developer section (corresponding to Figures 1(d) and 8D), a supply voltage Vrs = -400V is applied to the supply roller 26 and a development voltage Vdc = -300V is applied to the development roller 22. At this time, the difference ΔVrs is ΔVrs = Vrs - Vdc = -100V. In this way, by reducing the absolute value of the difference ΔVrs at the timing when the ejected toner passes through the developer section compared to image formation, the amount of charge on the toner T on the development roller 22 decreases at the timing when the ejected toner passes through the developer section. Furthermore, the amount of toner coating on the development roller 22 decreases at the same time.

[0293] The weight per unit area M (g / m²) of ejected toner formed on the surface of the photosensitive drum 1 at the timing shown in Figure 1(d). 2 This was confirmed by varying the difference ΔVrs. When ΔVrs = -200V, M = 4.6 g / m 2 Q was 0.040 C / g. On the other hand, when ΔVrs = -100 V, M = 4.3 g / m 2 The Q value was 0.035 C / g. In this way, as the amount of toner coating on the developing roller 22 decreases at the timing when the ejected toner passes through the developing section, the amount of toner recovered by the developing roller 22 from the ejected toner on the photosensitive drum 1 increases. Since fresh toner has a lower non-electrostatic adhesion force than degraded toner, it is recovered preferentially over degraded toner. As a result, by controlling the system in this embodiment, it is possible to reduce the amount of fresh toner consumed by the ejection control.

[0294] As mentioned above, the timing for reducing the difference ΔVrs is the timing at which the ejected toner passes through the developing section (corresponding to section D in Figure 1(d) and Figure 8). Specifically, the applied voltages are controlled so that the surface of the developing roller 22, which has passed at least once through the contact area between the developing roller 22 and the developing blade 23 where the modified difference ΔVrs is formed, comes into contact with the ejected toner on the photosensitive drum 1.

[0295] <Evaluation Test> To confirm the effectiveness of the ejection control in this embodiment in suppressing image defects caused by the ejection of degraded toner, a test similar to that in Example 8 was conducted. Specifically, in Example 10, the difference ΔVrs of the timing of passing through the developing unit was set to -100V, and a total of 5000 sheets of paper were fed through, with ejection control being performed every 50 sheets after 2500 sheets. As a result, no developing and recovery defects occurred even when the number of sheets fed reached 5000, and the same effect as in Example 8 was obtained with the configuration of this embodiment.

[0296] Furthermore, to confirm the effect of reducing the frequency of waste toner container replacement in this embodiment, a paper-feed test of 300,000 sheets was conducted, similar to Example 8, with ejection control performed every 50 sheets, and the number of waste toner container replacements was compared. As a result, in Example 1, a total of two replacements were required, but with the configuration of this embodiment, only one replacement was needed.

[0297] As described above, in this embodiment, when the ejected toner passes through the developing unit during ejection control, control was performed to reduce the difference between the voltage applied to the developer supply means and the voltage applied to the developing means compared to the image forming operation. By performing such control, in addition to the effects of Embodiment 1, it was possible to reduce unnecessary toner consumption and decrease the frequency of replacing the waste toner container.

[0298] [Example 11] Next, Example 11 of the present invention will be described. The configuration of the image forming apparatus 100 according to Example 11 is the same as that of Example 2, and the image forming apparatus 100 is equipped with a pre-charging exposure apparatus 6. Hereinafter, only the differences between the configuration and effects of Example 11 and Example 2 will be described. Components in the configuration of Example 11 that are the same as those in Example 2 are denoted by the same reference numerals and their descriptions are omitted.

[0299] Examples 1 to 10 describe control methods for efficiently processing degraded toner. Example 11 describes a method for effectively transferring degraded toner remaining on the photosensitive drum 1 from the ejected toner to the intermediate transfer belt 10.

[0300] According to the control in Example 11, while achieving the same effects as in Examples 1 to 10, it becomes possible to transfer more degraded toner that may remain on the photosensitive drum to the intermediate transfer belt 10, thereby suppressing material contamination such as toner fusion to the photosensitive drum 1. Toner fusion to the photosensitive drum 1 occurs when toner remaining on the photosensitive drum 1 is crushed on the photosensitive drum 1 and firmly fixed to it as it repeatedly passes through the charging section, developing section, and transfer section. Once firmly fixed on the photosensitive drum 1, toner further adheres to the crushed and fixed toner (where the toner matrix is ​​exposed and the non-electrostatic adhesion force is high), and as it is crushed and accumulates, it grows to a height of about 10 to 15 μm. This state of toner accumulation and growth is called toner fusion to the photosensitive drum 1, and may result in image defects such as white spots in the image due to poor charging (hereinafter referred to as white spots).

[0301] According to the configuration of this embodiment, contamination of components such as toner fusion to the photosensitive drum 1 can be suppressed. To distinguish it from the control described in Examples 1 to 10, the control of Example 11, described below, will be referred to as rear-rotation control.

[0302] <Reverse rotation control> In this embodiment, post-rotation control is performed to effectively transfer toner that may remain on the photosensitive drum 1 after the transfer process of degraded toner in the ejection control (remaining toner after transfer of degraded toner) to the intermediate transfer belt 10. The process up to the toner sorting process in the developing unit of the ejection control according to Embodiment 11 is the same as in Embodiment 2, so the explanation is omitted, and the process from the transfer process of degraded toner in the ejection control onward will be explained in more detail.

[0303] In the degraded toner transfer process, toner containing a large amount of degraded toner remaining on the photosensitive drum 1 after toner sorting in the developing unit is transferred to the intermediate transfer belt 10. Because degraded toner has a high adhesion force to the photosensitive drum 1, the transfer process for degraded toner is performed at a potential difference higher than that during normal image formation. However, because degraded toner has a high adhesion force to the photosensitive drum 1, if the amount is large, it may not all be transferred to the intermediate transfer belt 10 and some may remain on the photosensitive drum 1. This toner remaining on the photosensitive drum 1 is then transferred to the normal transfer residue toner. To distinguish it from other materials, it is called "remote toner discharged during transfer."

[0304] As a post-rotation control method according to this embodiment, the control method for transferring the remaining toner after ejection transfer to the intermediate transfer belt 10 without leaving any residue on the photosensitive drum 1 will be explained using Figures 22(a) to (d) and Figure 23. Figures 22(a) to (d) are explanatory diagrams of the post-rotation control, and are schematic diagrams showing the movement of ejected toner in the processes after the transfer process of deteriorated toner in the ejection control. Figure 23 is an explanatory diagram of the voltage and potential control of the post-rotation control, and is a schematic diagram that shows the changes in the potential of the photosensitive drum 1, the developing voltage, the primary transfer voltage, and the movement of toner along the time axis in the post-rotation control. Figure 23 shows a graph with potential / voltage on the vertical axis and time on the horizontal axis, and the surface potential (photosensitive drum potential) of a predetermined location that moves with the rotation of the photosensitive drum 1 is shown by a thick line, and the toner adhering to that part is also shown. In Figures 22(a) to (d), the remaining toner after ejection transfer is shown as dots.

[0305] Post-rotation control is performed after the E. degraded toner transfer process and before the F. degraded toner cleaning process according to Example 2. In other words, post-rotation control can be considered as a part of the ejection control. Post-rotation control can be broadly divided into the following steps: E2. Recharging of the ejected transfer residue toner, and E3. Transfer of the ejected transfer residue toner. Note that each of the steps E, E2, E3, and F corresponds to Figures 22(a) to (d), and the ranges corresponding to each of the steps E, E2, and E3 are also indicated by arrows in Figure 23.

[0306] (E. Transfer of degraded toner) Figure 22(a) shows the process of transferring degraded toner. In the degraded toner transfer process, the toner on the surface of the photosensitive drum 1 is moved to the intermediate transfer belt 10. However, in this process, not all of the toner on the surface of the photosensitive drum 1 is moved to the intermediate transfer belt 10, and some toner may remain on the surface of the photosensitive drum 1. The symbol × on the dashed arrow shown in Figure 23 schematically represents the toner that should have been transferred to the intermediate transfer belt 10 but remained on the photosensitive drum 1 without being transferred. This toner remaining on the photosensitive drum 1 is called discharge transfer residue toner. In this embodiment, the toner remaining after the toner supply unit, which supplied the toner to the photosensitive drum 1, has passed through the transfer unit twice corresponds to discharge transfer residue toner.

[0307] Once the ejected toner has finished passing through the developing section, the developing roller 22 is immediately separated from the photosensitive drum 1, as shown in Figure 22(a), and the rotation of the developing roller 22 is stopped. This is to prevent the toner on the developing roller 22 from unnecessarily rubbing against the developing blade 23, and at the same time to prevent the ejected transfer residue toner from being collected by the developing roller 22. The transport length of the ejected toner is preferably less than the length of one rotation of the photosensitive drum 1. Therefore, the separation operation of the developing roller 22 should be performed at a timing when the ejected transfer residue toner corresponding to the leading end of the ejected toner reaches the developing section again, and after the trailing end of the ejected toner has completed the collection process by the developing roller 22.

[0308] (E2. Recharging of residual toner after ejection transfer) Figure 22(b) shows the recharging process of the ejected transfer toner. When the ejected transfer toner reaches the charging section, as shown in Figures 22(b) and 23, a voltage above the discharge threshold is applied to the charging roller 2, and the surface of the photosensitive drum 1 is charged to the post-charging potential Vp. At the same time, the ejected transfer toner is recharged by discharge in the charging section. At this time, a negative voltage with the same polarity as the normal charging polarity of the toner is applied to prevent it from adhering to the charging roller 2.

[0309] In this embodiment, the photosensitive drum potential reaching the charged section is discharged to approximately 0V by the pre-charging exposure device 6, and a charging voltage Vpri = -1200V, which is above the discharge threshold, is applied to the charging roller 2. The charging contrast ΔV2 is set to 1200V. At the same time as charging the residual toner after ejection, the surface of the photosensitive drum 1 is charged to a post-charging potential Vp = -700V.

[0310] The recharging of residual toner after ejection will be explained in detail. As mentioned above, degraded toner has reduced frictional charging properties on the developing blade 23 due to decreased fluidity. Although ejected toner containing such degraded toner with low frictional charging is charged by discharge during the charging section passage process in ejection control (corresponding to Figure 1(c)), if the amount of toner is large, sufficient charge may not be imparted to the toner in the lower layer. Therefore, degraded toner located in the lower layer of ejected toner has high non-electrostatic adhesion and a small amount of charge, making it more likely to remain on the photosensitive drum 1 during the transfer process of degraded toner shown in Figure 22(a), and thus more likely to become residual toner after ejection.

[0311] However, the amount of discharged toner remaining before reaching the charged section is less than the amount of discharged toner, as shown in Figure 22(b), because it has gone through the developer section sorting process and the degraded toner transfer process. Therefore, sufficient charge can be imparted to the discharged toner remaining before passing through the charged section by discharge. This imparting of charge to the discharged toner remaining before passing through makes it easier for the discharged toner remaining before passing through to the intermediate transfer belt 10 in subsequent processes.

[0312] (E3. Transfer of residual toner after ejection) Figure 22(c) shows the transfer process of the discharged transfer residue toner. The discharged transfer residue toner, which has been charged by passing through the charging section, does not come into contact with the developing roller 22 because the developing roller 22 is separated from the photosensitive drum 1. Then, as the photosensitive drum 1 rotates, the discharged transfer residue toner reaches the transfer section again, as shown in Figure 22(c), and is transferred to the intermediate transfer belt 10 by the transfer contrast ΔVtr5 (potential difference between the charged potential Vp and the primary transfer voltage Vtr). Since the discharged transfer residue toner is recharged and charged by passing through the charging section, an appropriate transfer contrast ΔVtr5 is provided, and an electrostatic force greater than the non-electrostatic adhesion force to the photosensitive drum 1 is obtained, making it possible to transfer the discharged transfer residue toner. As a result, less toner remains on the photosensitive drum 1, and material contamination such as toner fusion caused by toner accumulation on the photosensitive drum 1 can be suppressed.

[0313] It is preferable that the transfer contrast ΔVtr5 when the toner supply unit, to which the toner from the photosensitive drum 1 has been supplied, passes through the transfer unit for the third time is greater than the transfer contrast ΔVtr2 when the toner supply unit passes through the transfer unit for the second time (during the transfer process of degraded toner). This is because the ejected transfer residue toner is toner that could not be transferred due to a potential difference of ΔVtr2 during the transfer of degraded toner. In this embodiment, compared to the transfer contrast ΔVtr2 = 900V in Example 2, the primary transfer voltage Vtr = +300V, the post-charging potential Vp of the photosensitive drum 1 after charging = -700V, and the transfer is performed with a transfer contrast ΔVtr5 = 1000V. With this control, the toner remaining on the photosensitive drum 1 after passing through the transfer unit twice can be moved to the intermediate transfer belt 10. In this embodiment, the transfer contrast ΔVtr5 when the toner supply unit passes through the transfer unit for the third time is greater than the transfer contrast ΔVtr2 when the toner supply unit passes through the transfer unit for the second time, but this is not limited to this. For example, the transfer contrast when the toner supply unit passes through the transfer unit for the fourth and fifth time may be made greater than the transfer contrast ΔVtr2. In other words, the transfer contrast at any point when the toner supply unit passes through the transfer unit from the third time onward should be made greater than the transfer contrast ΔVtr2.

[0314] (F. Cleaning deteriorated toner) Figure 22(d) shows the cleaning process for degraded toner. Here, the degraded toner includes the residual toner that has been transferred to the intermediate transfer belt 10. The processing of the toner transferred to 10 is the same as in Example 2. As shown in Figure 22(d), the rotation of the intermediate transfer belt 10 sends deteriorated toner, such as residual toner from the discharged transfer, to the cleaning device 16, where it is collected and processed in the waste toner container 17.

[0315] Through the above control, a larger portion of the ejected toner that may remain on the photosensitive drum 1 can be transferred to the intermediate transfer belt 10, thereby preventing toner fusion that occurs when toner remains on the photosensitive drum 1.

[0316] Although this embodiment describes the image forming apparatus 100 and the post-rotation control method in ejection control of Example 2, it is not limited to this, and post-rotation control can be performed similarly when negative polarity toner may remain on the photosensitive drum 1, as in Examples 1 and 3.

[0317] <Evaluation Test> To confirm the toner fusion suppression effect on the photosensitive drum 1 in Example 11, the following tests were conducted on Example 11 and Comparative Example 3 below. In an environment of 23°C / 50% relative humidity, a 5000-sheet paper feed test was performed using Xerox Business 4200 LETTER size (Xerox, product name) as the recording material P, and the presence or absence of white spots due to toner fusion on the photosensitive drum 1 was verified. Example 11: Control: Ejection control is performed, frequency: every 50 sheets after the 2500th sheet, rear rotation control: rear rotation control is performed simultaneously with ejection control. Comparative Example 3: Control: Solid ejection control was implemented, frequency: every 50 sheets after the 2500th sheet, post-rotation control: not implemented.

[0318] The configuration and operation of the image forming apparatus 100 in Comparative Example 3 are substantially the same as those of the image forming apparatus 100 in this embodiment, except for the points mentioned above.

[0319] Table 5 below shows the evaluation results of this test. Table 5 shows the results of checking for the occurrence of white spots on the first sheet and every 1000 sheets for Example 11 and Comparative Example 3. If a white spot occurred, it is indicated as "yes," and if it did not occur, it is indicated as "no."

[0320] [Table 5]

[0321] In the configuration of Comparative Example 3, no white spots occurred up to the 3000th sheet, but toner fusion to the photosensitive drum 1 occurred from the 4000th sheet onward, and white spots also occurred.

[0322] On the other hand, in the configuration of Example 11, since post-rotation control was performed in conjunction with ejection control, the amount of toner remaining on the photosensitive drum 1 could be minimized, and no white spots caused by toner fusion to the photosensitive drum 1 occurred up to 5000 sheets, resulting in no image defects.

[0323] As described above, the configuration of Example 11 allows for a greater portion of the ejected toner that may remain on the photosensitive drum 1 to be transferred to the intermediate transfer belt 10, thereby preventing toner fusion that occurs when toner remains on the photosensitive drum 1.

[0324] [Example 12] Next, Example 12 of the present invention will be described. The configuration of the image forming apparatus 100 according to Example 12 is the same as that of Example 2, and the image forming apparatus 100 includes a pre-charging exposure apparatus 6.

[0325] Example 11 described a control method that suppresses material contamination such as toner fusion to the photosensitive drum 1 by transferring more degraded toner that may remain on the photosensitive drum to the intermediate transfer belt 10. Example 12 describes a method that achieves similar effects by a different means. Below, only the differences between the configuration and effects of Example 12 and Example 11 will be described. Components in Example 12 that are the same as those in Example 11 are denoted by the same reference numerals and their descriptions are omitted.

[0326] The toner movement in the ejection control and post-rotation control according to Example 12 is the same as in Example 11 (Figures 22(a) to (d)). However, in Example 12, the potential relationship of some components in the post-rotation control differs from that of Example 11. Therefore, the post-rotation control according to Example 12 will be explained focusing on the differences from Example 11.

[0327] Figure 24 is an explanatory diagram of voltage and potential control in the post-rotation control, schematically representing the changes in the potential of the photosensitive drum 1, the developing voltage, the primary transfer voltage, and the movement of toner along the time axis during post-rotation control. Figure 24 shows a graph with potential / voltage on the vertical axis and time on the horizontal axis, where the surface potential (photosensitive drum potential) of a predetermined location that moves with the rotation of the photosensitive drum 1 is shown by a thick line, and the toner adhering to that area is also shown.

[0328] In Example 12, when the ejected transfer residue toner reaches the charged section, a larger charging voltage Vpri is applied to the charging roller 2 compared to Example 11, as shown in Figure 24, and a discharge is performed with a charging contrast ΔV2 greater than or equal to that of Example 11. This increases the post-charging potential Vp on the surface of the photosensitive drum 1, and further allows the ejected transfer residue toner to be recharged by a discharge greater than or equal to that of Example 11. In other words, in Example 12, more charge is applied to the ejected transfer residue toner than in Example 11, making it easier for the ejected transfer residue to be transferred to the intermediate transfer belt 10 in subsequent processes.

[0329] Furthermore, when the drum surface, which has been charged to the post-charging potential Vp, reaches the developing unit, the developing roller 22 is separated from the photosensitive drum 1. Therefore, the post-charging potential Vp of the photosensitive drum 1, which is higher than in Example 11, can be used to ensure the transfer contrast ΔVtr6 in the subsequent transfer process of the ejected transfer residue toner.

[0330] In this embodiment, the photosensitive drum potential reaching the charged section is discharged to approximately 0V by the pre-charging exposure device 6, and a charging voltage Vpri = -1500V, which is above the discharge threshold, is applied to the charging roller 2, resulting in a charging contrast ΔV2 = 1500V. In other words, the absolute value of the charging contrast ΔV2 is set to be greater when the toner supply section to which the toner of the photosensitive drum 1 is supplied passes through the charged section again (Figure 22(b)) than when it first passes through the charged section (Figure 1(c)). At the same time as charging the remaining toner after ejection and transfer, the surface of the photosensitive drum 1 is charged to a post-charging potential Vp = -1000V. In Embodiment 11, the charging voltage Vpri = -1200V and the charging contrast ΔV2 = 1200V, and in Embodiment 12, these values ​​are larger than those in Embodiment 11.

[0331] The discharged transfer residue toner, which has been charged after passing through the charging section, reaches the transfer section again, as shown in Figure 22(c), similar to Example 11, and is transferred to the intermediate transfer belt 10 by the transfer contrast ΔVtr6, similar to Example 11. As a result, similar to Example 11, less toner remains on the photosensitive drum 1, and contamination of components such as toner fusion caused by toner accumulation on the photosensitive drum 1 can be suppressed.

[0332] Furthermore, the transfer contrast ΔVtr6 at this time is preferably greater than the transfer contrast ΔVtr2 during the transfer process of degraded toner, for the same reasons as in Example 11. In this example, compared to the transfer contrast ΔVtr2 = 900V in Example 2, the primary transfer voltage Vtr = 0V and the post-charging potential Vp = -1000V, and the transfer is performed with a transfer contrast ΔVtr6 = 1000V.

[0333] The processing of the toner transferred to the intermediate transfer belt 10 is the same as in Examples 2 and 11. That is, the toner transferred to the intermediate transfer belt 10 is sent to the cleaning device 16 by the rotation of the intermediate transfer belt 10, and is collected and processed in the waste toner container 17.

[0334] Although this embodiment describes the image forming apparatus 100 and the post-rotation control method in ejection control of Example 2, it is not limited to this, and post-rotation control can be performed similarly when negative polarity toner may remain on the photosensitive drum 1, as in Examples 1 and 3.

[0335] Through the above control, a portion of the ejected toner that may remain on the photosensitive drum 1 can be transferred to the intermediate transfer belt 10, thereby preventing toner fusion that occurs when toner remains on the photosensitive drum 1.

[0336] <Other examples> The image forming apparatus 100 includes multiple image forming units, each corresponding to a different color toner. In the case where the primary transfer voltage Vtr is applied by a common primary transfer power supply 15 at each station constituting the image forming unit, as in the image forming apparatus 100 of this embodiment, the transfer contrast may be adjusted by individually adjusting the charging voltage Vpri at each station. A station refers to a unit that constitutes the image forming unit, and in this embodiment, four stations are provided in the image forming apparatus 100. That is, while the stations performing ejection control form the transfer contrast ΔVtr5 necessary for transfer, unnecessary discharge can be suppressed by reducing the transfer contrast at stations that are not performing ejection control.

[0337] A method for individually adjusting the transfer contrast is explained exemplified below. Figures 25(a) and (b) illustrate examples of individually adjusting the transfer contrast. Figure 25(a) shows an example of voltage control for a station that performs ejection control. Figure 25(b) shows an example of voltage control for a station that does not perform ejection control.

[0338] The following explanation will use the example of a case where there is a first station (first image forming unit) that performs ejection control and a second station (second image forming unit) that does not perform ejection control. In the following explanation, the sign of each potential (voltage) at the first station that performs ejection control will be denoted with A, and the sign of each potential (voltage) at the second station that does not perform ejection control will be denoted with B to distinguish them. However, since the primary transfer voltage Vtr is common to both stations, no special distinction will be made.

[0339] For example, as shown in Figure 25(a), in Example 12, in the first station where discharge control is performed, the transfer contrast ΔVtr5A in post-rotation control is formed by the primary transfer voltage Vtr=+0V and the post-charge potential VpA=-1000V.

[0340] On the other hand, as shown in Figure 25(b), in the second station where ejection control is not performed, it is not necessary to form a transfer contrast ΔVtr5 = 1000V. Therefore, in the second station where ejection control is not performed, the charging voltage VpriB = -800V is controlled, and the post-charging potential VpB = -300V. Thus, in the second station where ejection control is not performed At the second station, the transfer contrast ΔVtr5B becomes 300V, allowing for a potential difference smaller than ΔVtr5 = 1000V. This type of control suppresses discharge at stations (image forming units) where discharge control is not performed, thereby preventing the generation of discharge products. If the charging voltage cannot be adjusted individually at each station as described above (for example, when the charging power supply is shared), the transfer contrast ΔVtr5 may be adjusted by individually adjusting the exposure amount at each station.

[0341] Furthermore, in Examples 11 and 12, the transfer contrast is increased in order to transfer toner containing a large amount of degraded toner from the photosensitive drum 1 to the intermediate transfer belt 10, but this is not limited to this. For example, if the rotation speed of the intermediate transfer belt 10 can be controlled by the engine control unit 210 and the rotation speed of the intermediate transfer belt 10 can be changed individually, a speed difference may be created relative to the photosensitive drum 1 to physically transfer the toner from the photosensitive drum 1.

[0342] This section specifically describes an example of physically transferring toner from the photosensitive drum 1 by changing the rotation speed of the intermediate transfer belt 10 to create a speed difference with respect to the photosensitive drum 1. Let v1 be the rotation speed of the photosensitive drum 1 at the time of transferring the ejected toner, v2 be the rotation speed of the intermediate transfer belt 10, v3 be the rotation speed of the photosensitive drum 1 at the time of transferring the remaining toner after ejection, and v4 be the rotation speed of the intermediate transfer belt 10. In this case, the speed difference |v3-v4| between the rotation speed of the photosensitive drum 1 and the intermediate transfer belt 10 at the time of transferring the remaining toner after ejection is increased compared to the speed difference |v1-v2| between the rotation speed of the photosensitive drum 1 and the intermediate transfer belt 10 at the time of transferring the ejected toner. This generates a physical peeling force from the photosensitive drum 1, improving the transfer performance. Note that in order to generate a physical peeling force due to the speed difference, the rotation speed of the photosensitive drum 1 may be faster than the rotation speed of the intermediate transfer belt 10, or vice versa. Here, the rotational speed of the photosensitive drum 1 and the intermediate transfer belt 10 refers to the moving speed of the surface of each component.

[0343] Furthermore, although the transfer of residual toner after ejection is completed in a single pass in Examples 11 and 12, this is not limited to this. For example, the transfer may be repeated until even more residual toner after ejection is transferred to the intermediate transfer belt 10. Alternatively, the transfer contrast ΔVtr5 may be increased with each passing cycle to transfer even more residual toner after ejection to the intermediate transfer belt 10.

[0344] Through the above control, a portion of the ejected toner that may remain on the photosensitive drum 1 can be transferred to the intermediate transfer belt 10, thereby preventing toner fusion that occurs when toner remains on the photosensitive drum 1.

[0345] [Example 13] Next, Example 13 of the present invention will be described. Hereinafter, only the differences between the configuration and effects of Example 13 and Example 1 will be described. Components in Example 13 that are the same as those in Example 1 are denoted by the same reference numerals, and their descriptions are omitted.

[0346] <Average printing rate> The ratio of degraded toner to fresh toner on the developing roller 22 and in the developing unit 4 varies depending on the history of the image being printed. In the longitudinal direction of the developing roller 22, which intersects (orthogonal in this example) the transport direction of the recording material P, areas with high toner usage have a low proportion of degraded toner because fresh toner is consumed during the transition to degraded toner. On the other hand, areas with low toner usage have a high proportion of degraded toner because toner stays on the developing unit 4 and developing roller for longer periods.

[0347] The longitudinal direction of the developing roller 22 is the axis of rotation of the developing roller 22, and the photosensitive drum 1, etc. The longitudinal direction is parallel to the longitudinal direction of the developing roller. Furthermore, the longitudinal direction of the developing roller 22 is approximately parallel to the width direction of the recording material P that is transported within the image forming apparatus 100.

[0348] In Example 13, the paper area, which corresponds to the recording material P of the developing roller 22, is divided into multiple areas along the longitudinal direction of the developing roller 22 (the direction perpendicular to the paper transport direction), and the average print rate is obtained for each area. Based on the obtained average print rate, the percentage of degraded toner for each area is then obtained. The method for obtaining the percentage of degraded toner for each area divided along the longitudinal direction of the paper area will be described below. In the following description, the direction parallel to the longitudinal direction of the developing roller 22 that divides the paper area will be referred to as the division direction E.

[0349] Figures 26(a) and (b) are explanatory diagrams of the method for dividing the paper area according to Example 13. Figure 26(a) shows an example of dividing the paper area (A4 paper area) when using A4 paper. In this example, the A4 paper area is divided into three parts in the division direction E. Each divided area is defined as D1, D2, and D3, starting from one end of the division direction E (the left side in Figure 26(a)). The A4 paper area is 210 mm wide x 297 mm. Each divided area is the same size, and the size of each area is set to 70 mm x 297 mm. For example, at 600 dpi, each area is composed of 1654 x 7016 = 11,604,464 pixels. However, the configuration is not limited to this, and the size of each area may be different, or the number of divisions may be increased.

[0350] Figure 26(b) shows an example of an image formed on an A4 sheet of paper in the division example shown in Figure 26(a). The pixel counting rule will be explained using the image shown in Figure 26(b) as an example. In this example, the case of process cartridge S with toner color Bk will be explained.

[0351] Each pixel has density information ranging from 0 to 255. The total number of pixels with density information greater than 0 is calculated in each of the D1, D2, and D3 regions. Since this counts the number of pixels where toner is present, the calculated total is called the total toner pixel count.

[0352] The image shown in Figure 26(b) is a solid black image across the entire D1 region, a solid black image across half of the D2 region, and no pixels with density information in the D3 region. "Solid" refers to a collection of pixels with density information 255. The total number of toner pixels in each region is 11,604,464 in the D1 region, 5,802,232 in the D2 region, and 0 in the D3 region. The value obtained by dividing the total number of toner pixels by the total number of pixels in each region and multiplying by 100 is called the print rate. For each sheet of paper, the print rate for each region is calculated, and the average print rate for each region is calculated. Thus, the print rate acquisition unit, which divides the paper region (the longitudinal region corresponding to the recording material P of the developing roller 22) and obtains the average print rate for each region, may be provided as such in the engine control unit 210, for example. Alternatively, a separate control unit that functions as a print rate acquisition unit may be provided in addition to the engine control unit 210.

[0353] <Average print coverage and percentage of degraded toner> An evaluation test was conducted to investigate the relationship between print density and toner degradation rate. In the test, three types of images with different print density levels (1%, 5%, and 10%) were prepared, and 1000 sheets of paper were fed through the printer repeatedly. The density information of all printed pixels was set to 255.

[0354] Figure 27 is an explanatory diagram illustrating the relationship between the number of sheets fed, the print density, and the percentage of degraded toner, and shows the results of the evaluation test. Figure 27 shows a graph with the number of sheets fed [×1000 sheets] on the horizontal axis and the percentage of degraded toner [%] on the vertical axis, showing the number of sheets fed and the percentage of degraded toner on the developing roller 22.

[0355] During the process of feeding 1000 sheets of paper, toner is collected from the developing roller 22 and deformed. The percentage of degraded toner was calculated. To calculate the percentage of degraded toner, the average circularity (aspect ratio) of the collected toner was checked using the flow-type particle image analyzer "FPIA-3000" (manufactured by Sysmex Corporation). As mentioned above, toner with an average circularity of less than 0.90 was defined as degraded.

[0356] As shown in Figure 27, it was confirmed that the higher the print density, the smaller the proportion of degraded toner. When the print density is high, the toner coated on the surface of the developing roller 22 moves to the photosensitive drum 1, and then to the intermediate transfer belt 10, where it is transferred and fixed to the paper before it changes from fresh toner to degraded toner. Therefore, it is thought that when the print density is high, the toner has fewer opportunities to degrade, resulting in a smaller proportion of degraded toner. Conversely, when the print density is low, the toner coated on the surface of the developing roller 22 has fewer opportunities to move to the paper. Therefore, it is thought that the number and frequency of friction between the developing roller 22 and the photosensitive drum 1 are higher, resulting in a larger proportion of degraded toner.

[0357] Furthermore, the print coverage rate and the percentage of degraded toner were not proportional. Here's a discussion of why the print coverage rate and the percentage of degraded toner were not proportional. When the print coverage rate is low, the area outside the printable area is large. And in this area, cap toner is ejected. However, the print coverage rate is not a value that takes this cap toner into account. The amount of cap toner varies depending on the print coverage rate. Therefore, it is thought that the print coverage rate and the percentage of degraded toner were not proportional.

[0358] <Toner degradation level and toner ejection pattern> As mentioned above, when we examined the relationship between the average print density and degraded toner, we found that the lower the average print density, the higher the proportion of degraded toner. In toner ejection control, the toner ejection pattern can be executed with the same density across the entire area, but if the proportion of degraded toner can be calculated, it is desirable to perform toner ejection control with a toner ejection pattern that corresponds to that proportion.

[0359] Therefore, in Example 13, the relationship between a predetermined average print rate and the density of the toner ejection pattern is used to perform ejection control based on the average print rate obtained from the print history of the image forming operation before the ejection control is performed. Figures 28(a) to (c) are explanatory diagrams of the ejection control according to Example 13, showing the relationship between the average print rate and the density of the toner ejected by the toner ejection control.

[0360] Figure 28(a) shows the relationship between the average print density and the density of the toner ejection pattern. Figure 28(a) shows a graph with the average print density [%] on the horizontal axis and the density of the toner ejection pattern (maximum value 255) on the vertical axis. Figure 28(a) shows that the average print density and the density of the toner ejection pattern are inversely proportional. In Example 13, this relationship is used to determine the density of the toner ejection pattern in each divided region during ejection control based on the average print density of each divided region. Specifically, when the average print density is low and there is a lot of degraded toner, the density of the ejection pattern is controlled to be high, and when the average print density is high and there is little degraded toner, the density of the ejection pattern is controlled to be low. In other words, it can be said that the amount of toner ejected during ejection control (the amount of toner moved from the developing roller 22 to the photosensitive drum 1) is determined based on the average print density. The density of the ejection pattern, that is, the amount of toner ejected, is adjusted by controlling various applied voltages and exposure amounts.

[0361] Figure 28(b) shows the average print density of three divided regions D1, D2, and D3. Figure 28(b) shows an example where the average print density of region D1 is 50%, region D2 is 5%, and region D3 is 50%.

[0362] Figure 28(c) shows the toner ejection pattern determined based on the average print density of the example shown in Figure 28(b). The ejection pattern corresponds to the D1 and D3 areas. The shaded area represents the toner density, and the black area represents the toner ejection pattern at the position corresponding to the D2 area. The density information for the shaded area is 40, and the density information for the black area is 194. Thus, in Example 13, in the ejection control, the paper area is divided, and the toner ejection pattern (density) is determined based on the average print density of each paper area.

[0363] This section explains the reason for adjusting the toner ejection pattern density according to the average print density. During toner ejection control, the basic principle is to move only degraded toner to the intermediate transfer belt 10, but a small amount of fresh toner may also move to the intermediate transfer belt 10 at the same time. If there is little degraded toner in the ejected toner image, it is desirable to control the density of the toner ejection pattern to a low level, considering the risk of losing fresh toner. On the other hand, if it is known that there is a lot of degraded toner in the toner ejection pattern, it is necessary to remove a large amount of degraded toner in a single toner ejection control. Therefore, it is desirable to control the density of the toner ejection pattern to a high level. Thus, in order to efficiently process degraded toner while suppressing the processing of fresh toner, it is desirable to adjust the density of the toner ejection pattern based on the average print density.

[0364] With the toner ejection control described above, the density of the toner ejection pattern can be changed according to the percentage of degraded toner, thereby reducing the risk of losing fresh toner while achieving highly efficient removal of degraded toner.

[0365] [Example 14] Next, Example 14 of the present invention will be described. Hereinafter, only the differences between the configuration and effects of Example 14 and Example 1 will be described. Components in Example 14 that are the same as those in Example 1 are denoted by the same reference numerals, and their descriptions are omitted.

[0366] In Example 1, a 5000-page print test was conducted based on the ISO / IEC 19798 standard for measuring the number of printable pages in a cartridge. By implementing toner ejection control at a frequency of once every 50 pages from 2500 pages onward, which is the latter half of the cartridge's lifespan, degraded toner was ejected, and good images were obtained without any development and recovery failures up to 5000 pages, the lifespan of the process cartridge.

[0367] However, when the toner print density is low, the amount of toner consumed from the developing unit 4 is small, so the number of printable pages tends to increase compared to printing images with a high print density. For example, in a print test based on ISO / IEC 19798, if the print density of each color toner is 1%, the number of printable pages increases, making it possible to print approximately 5,000 or more pages compared to Example 1. When the number of printable pages increases, the friction time of the toner between the developing roller 22 and the developing blade 23 increases, resulting in toner that deteriorates more rapidly in the later stages of durability.

[0368] Therefore, in Example 14, we will describe a method for reducing the occurrence of development and recovery defects that is particularly suitable when the print density is low and the number of printed pages increases. In this example, we will describe the control performed assuming a case where the print density of each color toner in LETTER size is lower than ISO / IEC 19798, specifically when the print density of each color toner is 1%.

[0369] In this embodiment, we will describe a control method that adjusts the execution interval of the toner ejection control according to the degree of toner degradation, so as not to cause image defects even at low print rates such as 1% for each color.

[0370] Figure 29 is a flowchart of the pre-discharge control performed before the discharge control according to Example 14. Using Figure 29, the operations up to the implementation of discharge control in this example are explained below. Let me explain. In this example, I will explain the case where the printing operation is performed using only the yellow station. Also, the calculations and drive control in each of the following steps can be performed by control units such as the engine control unit 210.

[0371] Pre-ejection control can be started, for example, when a print job begins. When pre-ejection control is started, first, as STEP 1, the engine control unit 210 acquires (calculates) the toner degradation level. In this embodiment, the number of printed pages is used as an indicator of the toner degradation level, but other indicators may also be used. Other indicators that can be used include, for example, the amount of toner consumed from within the developing unit 4 (the amount of toner developed on the photosensitive drum 1), the rotation speed and driving time of the developing roller 22, and the rotation speed and driving time of the photosensitive drum 1. In any case, it is sufficient that the execution interval is set to shorten as the toner degradation progresses.

[0372] Next, in STEP 2, the engine control unit 210 sets the execution interval for ejection control based on the toner degradation level obtained in STEP 1. In this embodiment, the execution interval for ejection control is defined as the interval between the number of prints for which ejection control is performed. The interval determination unit that determines the execution interval for ejection control based on an index indicating the toner degradation level may be provided in the engine control unit 210, or another control unit may be provided that functions as the interval determination unit.

[0373] Embodiment 14 is configured to change the execution interval of the ejection control according to the cumulative number of printed pages. The method for determining the execution interval of the ejection control in this embodiment will be explained using Figure 30. Figure 30 is an explanatory diagram of the method for setting the execution interval of the ejection control according to Embodiment 14. Figure 30 shows a graph with the number of printed pages [×1000 pages] on the horizontal axis and the ejection control interval [number of pages] on the vertical axis.

[0374] Figure 30 shows several intervals corresponding to the number of prints. Interval A is the interval from 0 to 2500 prints, in which no ejection control is performed. Interval B is the interval from 2500 to 5000 prints, in which ejection control is performed at intervals of once every 50 prints. Interval C is the interval from 5000 to 7500 prints, in which ejection control is performed at intervals of once every 40 prints. Interval D is the interval from 7500 to 10000 prints, in which ejection control is performed at intervals of once every 30 prints. Thus, in Example 14, the ejection control interval is controlled to decrease in stages as the number of prints increases.

[0375] Next, in STEP 3, the engine control unit 210 sets the timing for the next ejection control. In this embodiment, it defines the number of prints for which the next ejection control will be performed. The timing for the next ejection control is determined based on the execution interval of the ejection control determined in STEP 2.

[0376] Next, in STEP 4, the engine control unit 210 performs a print operation. After each print, in STEP 5, the engine control unit 210 determines whether the timing for executing the ejection control has been reached. If the timing has not been reached, it returns to STEP 4, and the engine control unit 210 performs the next print operation. If the timing has been reached, it proceeds to STEP 6, and the engine control unit 210 performs the ejection control. Once the ejection control is performed, the series of operations ends. When a new print job is received, it returns to START, and the toner degradation level calculation in STEP 1 is performed again.

[0377] Furthermore, if a print job includes multiple image forming operation instructions, and the timing for executing the ejection control in STEP 5 is reached while the print job is running, the print job will be interrupted. The process then proceeds to STEP 6, where the engine control unit 210 performs ejection control. After the ejection control is completed, the remaining print jobs are executed. After the ejection control is completed, the remaining print jobs are executed. Alternatively, after STEP 6, a determination may be made as to whether the print jobs have been completed, and the process may return to STEP 4 based on the result of that determination.

[0378] In the example shown in Figure 29, if the ejection control execution timing is not reached in STEP 5, the process returns to STEP 4 and printing continues. However, it is also possible to return to STEP 1 and recalculate the toner degradation level. Reasons for recalculating the toner degradation level in the middle of a print job include cases where the print rate is included as a parameter in the toner degradation calculation. When performing print jobs with varying print rates, the rate of toner degradation differs for each print. By recalculating the toner degradation level after each print, it becomes possible to perform ejection control at a timing that more accurately reflects the actual toner degradation.

[0379] Next, the effect of changing the ejection control execution interval on the aspect ratio will be explained using Figure 31. Figure 31 is an explanatory diagram of the relationship between the ejection control execution interval and the aspect ratio. Figure 31 shows the amount of toner aspect ratio recovery when printing 1000 sheets while changing the ejection control execution interval, when printing with a print density of 1% for each color. Figure 31 shows a graph with the aspect ratio before ejection control on the horizontal axis and the amount of aspect ratio recovery on the vertical axis. Figure 31 plots the results when the ejection control execution interval is set to 30 sheets, 35 sheets, 40 sheets, and 50 sheets. Note that the amount of aspect ratio recovery is a quantity that shows how much the average aspect ratio has recovered (improved). For example, as shown in Figure 31, when the ejection control execution interval is 50 sheets, the aspect ratio recovery amount when the aspect ratio is 0.75 is approximately 0.10. This means the aspect ratio of 0.75 recovers by 0.10 to become 0.85.

[0380] As shown in Figure 31, a tendency was observed for the aspect ratio recovery amount to increase as the execution interval of the ejection control decreased. Furthermore, regardless of the execution interval, the aspect ratio recovery amount when ejection control was performed tended to decrease as the aspect ratio increased. This is because, when the aspect ratio is large, the proportion of degraded toner in the developing unit 4 is small, so even when ejection control is performed, very little degraded toner is ejected to the photosensitive drum 1.

[0381] Considering this, it is desirable to change the execution interval of the toner ejection control according to the degree of toner degradation, as in Example 14. In other words, when the number of printed pages is small, it is desirable not to perform ejection control until the toner has degraded to a certain extent from its new state, and to shorten the execution interval of the ejection control as the toner degrades more rapidly in the latter half of its lifespan. By implementing such control, it is possible to maintain good image quality while minimizing downtime.

[0382] Note that the trend shown in Figure 30 is just one example, and the amount of aspect ratio recovery will vary depending on various toner characteristics such as the shape of the developer, the amount of toner filled in the developer, and the hardness of the toner. However, the tendency for the amount of aspect ratio recovery to increase as the execution interval of the ejection control is shortened remains unchanged.

[0383] <Evaluation Test> Table 6 shows the changes in image rank and toner aspect ratio with respect to the number of prints per day, based on the results of various print tests. The evaluation criteria for image rank, i.e., the presence or absence of image defects, are the same as those used in the evaluation test of Example 1, and a rank of D is used for development and recovery defects (image defects) that are more serious than rank C.

[0384] Table 6 first shows the results of a print test similar to the evaluation test of Example 1, based on ISO / IEC 19798. In this test, the maximum number of sheets fed was 5000. Table 6 also shows the results of Comparative Example 4, where a print test was performed up to 10,000 sheets with the same configuration as Example 1, but with a print density of 1% for each color. In both Example 1 and Comparative Example 4, ejection control was performed at a frequency of once every 50 sheets after 2500 sheets in each print test. Table 6 also shows the results of Example 14, where a print test was performed up to 10,000 sheets with a print density of 1% for each color. In Example 14, the frequency of ejection control was changed according to the number of printed sheets, as shown in Figure 30.

[0385] [Table 6]

[0386] As shown in Table 6, in Example 1, the image rank remained at A rank until the lifespan of the developing unit 4 reached 5000 sheets in the print test based on ISO / IEC 19798. This is because the rate of decrease in aspect ratio was reduced by implementing ejection control, and the aspect ratio remained above 0.9 even at 5000 sheets.

[0387] In Comparative Example 4, where the print density for each color is 1%, the image rank was A for up to 5000 sheets of paper fed, and no image defects occurred. Furthermore, the aspect ratio change was almost the same as in the case of ISO / IEC 19798. This is because there was a large amount of toner remaining in the developing unit 4, and the probability of it being rubbed by the developing roller 22 and developing blade 23 was low.

[0388] On the other hand, in Comparative Example 4, a B-rank image defect occurred after 6,000 sheets, a C-rank defect after 7,000 sheets, and a D-rank image defect after 8,000 sheets. In this embodiment, the lifespan of the process cartridge S is defined as 10,000 sheets when print tests are conducted with a print density of 1% for each color. The lifespan of the process cartridge S does not necessarily have to be determined by the amount of toner remaining in the developing unit 4, but may also be defined by the degree of deterioration of various components, such as the amount of abrasion of the surface of the photosensitive drum 1, or the accumulation of deposits on the surface of the developing roller 22 and the deterioration of surface quality due to rotation. In this embodiment, the lifespan is defined as 10,000 sheets, taking into account the amount of abrasion of the surface of the photosensitive drum 1.

[0389] As shown in Table 6, in Example 14, where ejection control was performed at the execution interval shown in Figure 30, no image defects occurred and the image rank was A even after reaching 10,000 sheets of paper with a print density of 1% for each color. Furthermore, the aspect ratio was maintained at 0.9 or higher throughout the test.

[0390] Based on the above, the control method of Example 14 can suppress the occurrence of image defects by adjusting the execution interval of the ejection control according to the state of toner deterioration, even when the toner printing rate is low and the toner deteriorates over a long period of time.

[0391] <Example 7> In Example 14, the execution interval of the ejection control was changed every 2500 sheets as shown in Figure 31, but the configuration is not limited to this. Below, as Modification 7 of Example 14, a control example in which the method of setting the execution interval of the ejection control is changed will be described. Hereafter, parts that are the same as in Example 14 (configuration, effects, etc.) will be denoted by the same reference numerals and their explanation will be omitted.

[0392] Figure 32 is an explanatory diagram of the method for setting the execution interval of the ejection control according to Modification 7. Figure 32 shows a graph with the number of printed pages [×1000 pages] on the horizontal axis and the ejection control interval [number of pages] on the vertical axis.

[0393] Figure 32 shows several intervals corresponding to the number of printed pages. Interval A is the interval from 0 to 2500 printed pages, in which ejection control is not performed. Interval B is the interval from 2500 to 7500 printed pages, in which the execution interval of ejection control gradually decreases as the number of printed pages increases. In Interval B, the execution interval of ejection control is proportional to the number of printed pages, with ejection control performed once every 50 pages when the number of printed pages is 2500, and once every 30 pages when the number of printed pages is 7500. Interval C is the interval from 7500 to 1000 printed pages, in which ejection control is performed once every 30 pages.

[0394] Thus, in Modification 7, the ejection control interval is controlled to decrease sequentially as the number of printed pages increases in a specific section. Even with this control method, even when the toner printability is low and the toner deteriorates over a long period of time, the execution interval of the ejection control can be adjusted according to the deterioration state of the toner to suppress the occurrence of image defects.

[0395] <Differentiation Example 8> Furthermore, in Example 14, as shown in Figure 29, the print job was interrupted and ejection control was performed when the ejection control execution timing was reached, but the configuration is not limited to this. Below, as Modification 8 of Example 14, a control example in which ejection control is performed after a series of print jobs have been completed without interrupting the print job midway will be described. Hereafter, parts (configuration, effects, etc.) that are the same as in Example 14 will be denoted by the same reference numerals and their explanation will be omitted.

[0396] Figure 33 is a flowchart of the pre-ejection control performed before the ejection control in Modification Example 8. The pre-ejection control in Modification Example 8 differs from the pre-ejection control in Example 14 in that it determines whether the print job has finished in STEP 6.

[0397] In the modified example 8, if the print job is running in STEP 6 and it is determined that the print job is not yet complete, the process proceeds to STEP 7 and printing continues. Once printing is complete, the process returns to STEP 6 for further evaluation. On the other hand, if the print job is determined to be complete in STEP 6, the process proceeds to STEP 8 and ejection control is performed.

[0398] Even with this control method, if the toner print coverage is low and the toner deteriorates over a long period, the execution interval of the ejection control can be adjusted according to the toner's deterioration state to suppress the occurrence of image defects. In addition, since the print job is not interrupted midway, the execution time of the print job can be suppressed.

[0399] Note that in Example 14 and Modification 8, when printing operations are performed at a single station... This was explained as an example. If printing operations are performed at four stations, when it is time to execute ejection control at any of the four stations, ejection control may be performed at all stations, and the print count until the next execution may be reset.

[0400] Using Figure 34, an example of pre-ejection control when printing operations are performed at all four stations will be explained. Figure 34 is a flowchart of pre-ejection control according to Embodiment 14, showing the operation of pre-ejection control when printing operations are performed at all four stations.

[0401] First, steps 1-4 are essentially the same as those shown in the flowchart in Figure 29. Specifically, in step 1, the toner degradation level of each of the four stations is calculated; in step 2, the ejection control interval for each of the four stations is set; and in step 3, the timing of the next ejection control for each of the four stations is set. Then, in step 4, printing is performed at all four stations.

[0402] Next, in STEP 5, it is determined whether the timing for executing the ejection control has been reached at any station. If the timing for executing the ejection control has not been reached at any station, the process returns to STEP 4 and the print operation is performed again. On the other hand, if the timing has been reached, the process proceeds to STEP 6 and the ejection control is performed. In this case, the ejection control in STEP 6 is performed at all stations.

[0403] Next, in STEP 7, the number of prints until the next ejection is cleared for all stations except the station that has reached the timing for executing the ejection control.

[0404] Once the ejection control is performed, the series of operations ends, and the process returns to START, where the toner degradation level calculation from STEP 1 is performed again.

[0405] By implementing discharge control at all stations when the timing for discharge control is reached at any station, frequent downtime due to discharge control can be prevented. However, if the interval between discharge control executions is long and the impact of downtime is not a major concern, discharge control may be implemented only at the station that has reached the timing for discharge control.

[0406] In that case, the ejection control in STEP 6 should be performed only at the station that has reached the ejection control timing, and in STEP 7, the counter for the number of prints until the next ejection should only be cleared at the station where the ejection control was performed.

[0407] <Modification 9> Next, we will explain how to set the potential of the photosensitive drum 1 and the developing voltage Vdc when implementing ejection control.

[0408] The ejection control described in this embodiment assumed that the potential of the photosensitive drum 1 and the primary transfer voltage settings were the same for all ejection intervals. However, even with the same aspect ratio, as the lifespan of the process cartridge S progresses, toners of various degrees of degradation may be mixed together, potentially worsening the ejection performance from the photosensitive drum 1 to the intermediate transfer belt 10. Therefore, in each of the embodiments described above, the primary transfer voltage Vtr setting may be controlled to change according to the lifespan of the process cartridge S and the degree of toner degradation. Below, as Modification 9, an example in which the primary transfer voltage Vtr setting is changed according to the lifespan of the process cartridge S will be described. The following is the same as in Embodiment 1. For parts (such as composition or effects), the same symbol is used, and the explanation is omitted.

[0409] Figure 35 is an explanatory diagram illustrating the relationship between the lifespan of the process cartridge S (cartridge life) and the primary transfer voltage Vtr in Modification 9. As shown in Figure 35, in Modification 9, the setting of the primary transfer voltage Vtr is changed according to the lifespan of the process cartridge S. In this example, the lifespan of the process cartridge S is determined by the number of printed pages.

[0410] In Modification 9, in toner ejection control, the primary transfer voltage Vtr was set to +300V in the first half of the print life and to +400V in the second half of the print life. Since the post-charging potential Vp remains unchanged at -600V, the transfer contrast ΔVtr2 in the first half of the print life is 900V, and the transfer contrast ΔVtr2 in the second half of the print life is 1000V.

[0411] Thus, in this modified configuration, the absolute value of the transfer contrast ΔVtr2 is increased as the lifespan of the process cartridge S progresses, that is, as the degree of toner degradation increases. By implementing this control, a larger proportion of the toner, even if it has degraded, can be ejected onto the intermediate transfer belt 10 by electrostatic force. Consequently, it becomes possible to maintain good ejection control throughout the lifespan of the process cartridge S.

[0412] Furthermore, the configurations of each of the above embodiments and modified examples can be combined in any way.

[0413] This embodiment includes the following configuration. (Composition 1) A rotatable image carrier, A charging member that charges the image carrier, A charging voltage application unit that applies a charging voltage to the charging member, An exposure apparatus that exposes the surface of the image carrier to form an electrostatic latent image, A developing member supplies toner to the image carrier and develops the electrostatic latent image formed on the surface of the image carrier to form a toner image, A developing voltage application unit that applies a developing voltage to the developing member, An intermediate transfer body that comes into contact with the image carrier to form a transfer nip, and in the transfer nip, the toner image formed on the surface of the image carrier is transferred; A transfer member that comes into contact with the intermediate transfer body, A transfer voltage application unit that applies a transfer voltage to the transfer member, A control unit for controlling the charging voltage, the exposure amount of the exposure apparatus, the development voltage, and the transfer voltage, the control unit is configured to perform an image forming operation for forming an image on a recording material, and a toner ejection operation for supplying toner from the developing member to the image carrier, recovering a portion of the supplied toner with the developing member, and moving a portion to the intermediate transfer body. Equipped with, The control unit, in the toner ejection operation, When the toner supply unit, which is supplied with toner for the image carrier, first passes through the transfer unit, which is the contact area between the image carrier and the intermediate transfer unit, the surface potential of the image carrier and the transfer voltage are controlled so that the toner on the surface of the image carrier is carried on the image carrier. The toner supply unit, having passed through the transfer unit, controls the surface potential and charging voltage of the image carrier so that the toner on the surface of the image carrier is carried on the image carrier when the charging member passes through the charging unit that charges the image carrier. When the toner remaining on the surface of the image carrier, which has passed through the developing section (the contact area between the image carrier and the developing member), passes through the transfer section again, the surface potential of the image carrier and the transfer voltage are controlled so that the toner remaining on the surface of the image carrier moves onto the intermediate transfer body. An image forming apparatus characterized by the following features. (Configuration 2) The control unit, in the toner ejection operation, When the toner supply section of the image carrier first passes through the transfer section, the transfer voltage is controlled to be negative, and the absolute value of the transfer voltage is greater than the absolute value of the post-exposure potential, which is the surface potential of the image carrier exposed by the exposure apparatus. The image forming apparatus according to configuration 1, characterized in that the value of the transfer voltage is controlled to become positive when the toner remaining on the surface of the image carrier passes through the transfer section again. (Composition 3) The image forming apparatus according to configuration 1 or 2, characterized in that the control unit controls each voltage and the exposure amount in the toner ejection operation such that the potential difference between the development voltage and the post-exposure potential, which is the surface potential of the image carrier exposed by the exposure device, is greater than that during the image forming operation. (Composition 4) The image forming apparatus according to any one of configurations 1 to 3, characterized in that, in the toner ejection operation, the control unit exposes the non-image area of ​​the image carrier with the exposure device after the toner supply unit of the image carrier first passes through the transfer unit and before it passes through the developing unit. (Composition 5) The image forming apparatus according to any one of configurations 1 to 4, characterized in that the control unit controls each voltage and the exposure amount so that, in the toner ejection operation, when the toner supply unit of the image carrier passes through the developing unit, the absolute value of the potential difference between the surface potential of the toner supply unit and the developing voltage is greater than that during the image forming operation. (Composition 6) The image forming apparatus according to configuration 5, characterized in that the control unit controls each voltage such that, in the toner ejection operation, the potential difference between the surface potential of the toner supply unit and the transfer voltage when the toner supply unit passes through the transfer unit is greater than the potential difference between the surface potential of the toner supply unit and the development voltage when the toner supply unit passes through the development unit. (Composition 7) The image forming apparatus according to any one of configurations 1 to 6, characterized in that the control unit controls each voltage and the exposure amount such that, in the toner ejection operation, the potential difference between the surface potential of the toner supply unit and the transfer voltage when the toner supply unit of the image carrier passes through the transfer unit is greater than the potential difference between the surface potential of the image carrier exposed by the exposure device during the image forming operation and the transfer voltage. (Composition 8) The image carrier is further provided with a static elimination device positioned downstream of the transfer member and upstream of the charging member in the rotational direction of the image carrier, which removes static electricity from the surface of the image carrier. The image forming apparatus according to any one of configurations 1 to 7, characterized in that, in the toner ejection operation, the control unit uses the static elimination device to de-energize the toner supply unit of the image carrier before the toner supply unit passes through the charged unit. (Composition 9) The developing member is further provided with a separation / contacting mechanism that moves it to separate from and into contact with the image carrier, The image forming apparatus according to any one of configurations 1 to 8, characterized in that the separation mechanism separates the developing member from the image carrier after the toner supply unit of the image carrier has passed through the developing unit during the toner ejection operation. (Composition 10) A restricting member for restricting the thickness of toner supported on the developing member, comprising a restricting member that charges the toner supported on the developing member, A regulating voltage application unit that applies a regulating voltage to the regulating member, Furthermore, The image forming apparatus according to any one of configurations 1 to 9, characterized in that the control unit is configured to control the regulating voltage, and in the toner ejection operation, when the regulating member charges the toner to be moved from the developing member to the image carrier, the regulating member charges each voltage such that the absolute value of the potential difference between the developing voltage and the regulating voltage is greater than that during the image forming operation. (Composition 11) The image forming apparatus according to configuration 10, characterized in that the control unit controls each voltage in the toner ejection operation such that the absolute value of the potential difference between the developing voltage and the regulating voltage gradually increases. (Composition 12) The developing member is configured to be rotatable, The image forming apparatus according to configuration 11, characterized in that the control unit controls each voltage in the toner ejection operation such that the absolute value of the potential difference between the developing voltage and the regulating voltage gradually increases in accordance with the increase in the rotation distance of the developing member. (Composition 13) The developing member is configured to be rotatable, The image forming apparatus according to any one of configurations 1 to 12, characterized in that the control unit is configured to control the rotation speed of the image carrier and the developing member, and in the toner ejection operation, when moving toner from the developing member to the image carrier, the control unit controls each rotation speed such that the ratio of the rotation speed of the developing member to the rotation speed of the image carrier is greater than that during the image forming operation. (Composition 14) A supply member that supplies toner to the developing member, comprising a supply member that charges the toner carried on the developing member, A supply voltage application unit that applies a supply voltage to the supply member, Furthermore, The image forming apparatus according to any one of configurations 1 to 13, characterized in that the control unit is configured to control the supply voltage, and in the toner ejection operation, when the supply member charges the toner to be moved from the developing member to the image carrier, the voltages are controlled such that the absolute value of the potential difference between the supply voltage and the developing voltage is greater than that during the image forming operation. (Composition 15) The image forming apparatus according to configuration 14, characterized in that the control unit controls each voltage in the toner ejection operation such that the absolute value of the potential difference between the supply voltage and the developing voltage gradually increases. (Composition 16) The developing member is configured to be rotatable, The image forming apparatus according to configuration 15, characterized in that the control unit controls each voltage in the toner ejection operation such that the absolute value of the potential difference between the supply voltage and the developing voltage gradually increases in accordance with the increase in the rotation distance of the developing member. (Composition 17) The image forming apparatus according to configuration 14, characterized in that the control unit controls each voltage before the start of the toner ejection operation so that the absolute value of the potential difference between the supply voltage and the developing voltage is smaller than that during the image forming operation. (Composition 18) A restricting member for restricting the thickness of toner supported on the developing member, comprising a restricting member that charges the toner supported on the developing member, A regulating voltage application unit that applies a regulating voltage to the regulating member, Furthermore, The image forming apparatus according to any one of configurations 1 to 17, characterized in that the control unit is configured to control the regulating voltage, and in the toner ejection operation, when the toner supply unit of the image carrier passes through the developing unit, the control unit controls each voltage and the exposure amount such that the absolute value of the potential difference between the regulating voltage and the developing voltage becomes smaller than that during the image forming operation. (Composition 19) A restricting member for restricting the thickness of toner supported on the developing member, comprising a restricting member that charges the toner supported on the developing member, A regulating voltage application unit that applies a regulating voltage to the regulating member, Furthermore, The control unit is configured to control the regulating voltage, and in the toner ejection operation, when the toner supply unit of the image carrier passes the developing unit, the control unit controls each voltage and the exposure amount such that the absolute value of the potential difference between the regulating voltage and the developing voltage becomes smaller than when the regulating member charges the toner that is moved from the developing member to the image carrier. This is the image forming apparatus according to any one of the configurations 1 to 18. (Composition 20) The developing member is configured to be rotatable, The image forming apparatus according to any one of configurations 1 to 19, characterized in that the control unit is configured to control the rotation speed of the image carrier and the developing member, and in the toner ejection operation, when the toner supply unit of the image carrier passes the developing unit, the control unit controls each rotation speed such that the ratio of the rotation speed of the developing member to the rotation speed of the image carrier is greater than that during the image forming operation. (Composition 21) A supply member that supplies toner to the developing member, comprising a supply member that charges the toner carried on the developing member, A supply voltage application unit that applies a supply voltage to the supply member, Furthermore, The image forming apparatus according to any one of configurations 1 to 20, characterized in that the control unit is configured to control the supply voltage, and in the toner ejection operation, when the toner supply unit of the image carrier passes through the developing unit, the voltages are controlled such that the absolute value of the potential difference between the supply voltage and the developing voltage becomes smaller than that during the image forming operation. (Composition 22) The image forming apparatus according to any one of configurations 1 to 21, characterized in that the control unit controls the voltages so that, in the toner ejection operation, the toner supply unit of the image carrier passes through the transfer unit twice, and the toner remaining in the toner supply unit is recharged by the charging member. (Composition 23) The image forming apparatus according to configuration 22, characterized in that the control unit controls the charging voltage and the transfer voltage so that, in the toner ejection operation, the toner remaining in the toner supply unit and recharged after the toner supply unit has passed through the transfer unit twice is moved to the intermediate transfer body. (Composition 24) The image forming apparatus according to configuration 22 or 23, characterized in that the control unit controls each voltage such that, in the toner ejection operation, at any timing when the toner supply unit passes the transfer unit for the third time or later, the absolute value of the potential difference between the surface potential of the toner supply unit and the transfer voltage is greater than when the toner supply unit passes the transfer unit for the second time. (Composition 25) The control unit, in the toner ejection operation, when the toner supply unit passes the charging unit again, the potential difference between the surface potential of the toner supply unit and the charging voltage is such that the toner An image forming apparatus according to any one of the configurations 22 to 24, characterized in that each voltage is controlled so that the supply voltage is greater than the voltage when it first passes through the charging section. (Composition 26) The system comprises multiple image forming units, each consisting of the image carrier, the charging member, the developing member, and the transfer member. The image forming apparatus according to configuration 24, characterized in that, among the plurality of image forming units, if the first image forming unit performs the toner ejection operation and the second image forming unit does not perform the toner ejection operation, when the toner supply unit of the second image forming unit passes the transfer unit for the third time, each voltage is controlled so that the absolute value of the potential difference between the surface potential of the toner supply unit and the transfer voltage becomes smaller than that during the image forming operation. (Composition 27) The intermediate transfer body is configured to be rotatable, The image forming apparatus according to any one of configurations 1 to 26, wherein the control unit is configured to control the rotation speed of the intermediate transfer body, and in the toner ejection operation, the rotation speed is controlled such that when the toner supply unit of the image carrier passes the transfer unit for the third time, the speed difference between the image carrier and the intermediate transfer body is greater than when the toner supply unit passes the transfer unit for the second time. (Composition 28) The developing member is provided with a print rate acquisition unit that divides the region of the developing member corresponding to the recording material into multiple regions in the longitudinal direction, and acquires the average print rate of each of the multiple regions based on the print history of the image forming operation. The image forming apparatus according to any one of configurations 1 to 27, characterized in that, in the toner ejection operation, the amount of toner to be moved from each of the multiple regions from the developing member to the image carrier is determined based on the average print density. (Composition 29) The developing member and the developing unit including a toner storage section for storing toner, An interval determination unit that determines the execution interval of the ejection operation based on an index indicating the degree of deterioration of the toner stored in the toner storage unit, the interval determination unit that narrows the execution interval as the deterioration of the toner progresses, An image forming apparatus according to any one of the configurations 1 to 28, further comprising the above. (Composition 30) The image forming apparatus according to configuration 29, characterized in that the indicator showing the degree of deterioration of the toner is the number of recording materials on which the image forming operation was performed. (Composition 31) The image forming apparatus according to configuration 29, characterized in that the indicator showing the degree of deterioration of the toner is the operating time of the developing member. (Composition 32) The image forming apparatus according to configuration 29, characterized in that the indicator showing the degree of toner degradation is the amount of toner consumed from the developing unit. (Composition 33) The image forming apparatus according to any one of configurations 1 to 32, characterized in that when the control unit reaches the timing for executing the ejection control during the execution of a print job which includes a plurality of image forming operation instructions, it interrupts the print job and starts the ejection control. (Composition 34) The image forming apparatus according to any one of configurations 1 to 32, characterized in that, when the control unit reaches the timing for executing the ejection control during the execution of a print job including a plurality of image forming operation instructions, it starts the ejection control after the print job is completed. (Composition 35) The developing members comprise a plurality of the above-mentioned developing members, The image forming apparatus according to any one of configurations 1 to 34, characterized in that the control unit executes the ejection control for all of the developing members when the timing for executing the ejection control is reached for any of the plurality of developing members. (Composition 36) The developing members comprise a plurality of the above-mentioned developing members, The image forming apparatus according to any one of the configurations 1 to 34, characterized in that the control unit, when the timing for executing the ejection control is reached for any of the plurality of developing members, executes the ejection control only for the developing member that has reached the execution timing. (Composition 37) The developing unit further includes the developing member and a toner storage section for storing toner, The image forming apparatus according to any one of configurations 1 to 36, characterized in that, in the toner ejection operation, the control unit increases the absolute value of the potential difference between the surface potential of the image carrier and the transfer voltage when moving the toner supplied to the image carrier that was not recovered by the developing member to the intermediate transfer body as the degree of deterioration of the toner stored in the toner storage unit progresses. (Composition 38) The image forming apparatus according to configuration 37, characterized in that the control unit increases the absolute value of the potential difference by changing the transfer voltage. (Composition 39) The image forming apparatus according to any one of configurations 1 to 38, further comprising a removal device for removing toner transferred to the intermediate transfer body from the intermediate transfer body. (Composition 40) The system further comprises a detection unit for detecting the lifespan or usage time of at least one of the image carrier, the charging member, and the developing member. The image forming apparatus according to any one of configurations 1 to 39, characterized in that the control unit performs the toner ejection operation based on the detection result of the detection unit. (Composition 41) The image forming apparatus according to any one of the configurations 1 to 40, characterized in that the control unit performs the toner ejection operation after the completion of the image forming operation. (Composition 42) The image forming apparatus according to any one of configurations 1 to 41, characterized in that the control unit performs the toner ejection operation when the image forming operation is not being performed. (Composition 43) A rotatable image carrier, A charging member that charges the image carrier, A charging voltage application unit that applies a charging voltage to the charging member, An exposure apparatus that exposes the surface of the image carrier to form an electrostatic latent image, A developing member supplies toner to the image carrier and develops the electrostatic latent image formed on the surface of the image carrier to form a toner image, A developing voltage application unit that applies a developing voltage to the developing member, An intermediate transfer body that comes into contact with the image carrier to form a transfer nip, and in the transfer nip, the toner image formed on the surface of the image carrier is transferred; A transfer member that comes into contact with the intermediate transfer body, A transfer voltage application unit that applies a transfer voltage to the transfer member, A control unit that controls the charging voltage, the exposure amount of the exposure apparatus, the development voltage, and the transfer voltage, comprising: an image forming operation that forms an image on a recording material; and supplying toner from the development member to the image carrier, and when the toner supply unit to which the toner of the image carrier is supplied first passes through the transfer unit which is the contact part between the image carrier and the intermediate transfer unit, a portion of the supplied toner is moved to the intermediate transfer unit, while the remaining portion remains in the toner supply unit, and the remaining toner An image forming apparatus characterized by being configured to perform a toner ejection operation that moves any remaining toner to the intermediate transfer body when the toner passes through the transfer section again. (Composition 44) The image forming apparatus according to configuration 43, characterized in that the control unit controls each voltage and the exposure amount so that when the toner supply unit first passes through the transfer unit, toner with the opposite polarity to the normal charge of the toner supply unit is moved to the intermediate transfer body, while the toner with the normal charge of the toner supply unit is held on the image carrier, and when the toner with the normal charge of the toner passes through the transfer unit again, the toner with the normal charge of the toner is moved to the intermediate transfer body. (Composition 45) The image forming apparatus according to configuration 43 or 44, characterized in that, in the toner ejection operation, the control unit exposes the non-image area of ​​the image carrier with the exposure device after the toner supplied to the image carrier first passes through the transfer section and before it passes through the developing section, which is the contact area between the image carrier and the developing member. (Composition 46) The image forming apparatus according to any one of the configurations 43 to 45, characterized in that the control unit controls each voltage and the exposure amount so that when the developing member supplies toner to the image carrier during the toner ejection operation, the absolute value of the potential difference between the surface potential of the image carrier and the developing voltage is greater than that during the image forming operation. (Composition 47) The image forming apparatus according to any one of the configurations 43 to 46, characterized in that the control unit controls each voltage and the exposure amount so that, in the toner ejection operation, the absolute value of the potential difference between the surface potential of the toner supply unit and the transfer voltage when the toner supply unit of the image carrier passes through the transfer unit which is the contact portion between the image carrier and the intermediate transfer unit is greater than that during the image forming operation. (Composition 48) The image carrier is further provided with a static elimination device positioned downstream of the transfer member and upstream of the charging member in the rotational direction of the image carrier, which removes static electricity from the surface of the image carrier. The image forming apparatus according to any one of configurations 43 to 47, characterized in that, in the toner ejection operation, the control unit discharges the toner supply unit of the image carrier using the static discharge device before the charging member passes through the charging unit that charges the image carrier. (Composition 49) The image forming apparatus according to any one of the configurations 43 to 48, characterized in that the control unit controls each voltage and the exposure amount such that, in the toner ejection operation, the potential difference between the surface potential of the toner supply unit and the transfer voltage when the remaining toner passes through the transfer unit again is greater than the potential difference between the surface potential of the image carrier exposed by the exposure device during the image forming operation and the transfer voltage. (Composition 50) The image forming apparatus according to any one of the configurations 43 to 49, characterized in that the control unit controls the voltage and exposure amount such that when the toner supply unit first passes through the transfer unit, the toner with the normal charge polarity of the toner supply unit is moved to the intermediate transfer body, while the toner with the opposite charge polarity of the toner supply unit is held in the image carrier, and when the toner with the opposite polarity passes through the transfer unit again, the toner with the opposite polarity is moved to the intermediate transfer body. (Composition 51) The image forming apparatus according to configuration 50, characterized in that the control unit controls the charging voltage so that the charging member collects the toner of the opposite polarity from the toner supply unit during the toner ejection operation. (Composition 52) In the rotational direction of the image carrier, the upstream side of the charging member and the downstream side of the transfer member The collection member is positioned and, while in contact with the image carrier, charges the image carrier and temporarily collects the toner from the toner supply unit. The image forming apparatus according to configuration 51, characterized in that the control unit controls the voltage applied to the collection member. (Composition 53) The developing member is configured to be rotatable, The image forming apparatus according to any one of configurations 43 to 52, characterized in that the control unit is configured to control the rotation speed of the image carrier and the developing member, and in the toner ejection operation, the rotation speeds are controlled such that the ratio of the rotation speed of the developing member to the rotation speed of the image carrier is greater than that during the image forming operation. (Composition 54) A supply member that supplies toner to the developing member, comprising a supply member that charges the toner carried on the developing member, A supply voltage application unit that applies a supply voltage to the supply member, Furthermore, The image forming apparatus according to any one of the configurations 43 to 53, characterized in that the control unit is configured to control the supply voltage, and in the toner ejection operation, when the supply member charges the toner to be moved from the developing member to the image carrier, the control member controls each voltage such that the absolute value of the potential difference between the supply voltage and the developing voltage is greater than that during the image forming operation. [Explanation of Symbols]

[0414] 1...Photosensitive drum (image carrier), 2...Charging roller (charging component), 3...Scanner unit (exposure device), 10...Intermediate transfer belt (intermediate transfer body), 100...Image forming apparatus, 201...Engine control unit (control unit)

Claims

1. A rotatable image carrier, A charging member that charges the image carrier, A charging voltage application unit that applies a charging voltage to the charging member, An exposure apparatus that exposes the surface of the image carrier to form an electrostatic latent image, A developing member supplies toner to the image carrier and develops the electrostatic latent image formed on the surface of the image carrier to form a toner image, A developing voltage application unit that applies a developing voltage to the developing member, An intermediate transfer body that comes into contact with the image carrier to form a transfer nip, and in the transfer nip, the toner image formed on the surface of the image carrier is transferred; A transfer member that comes into contact with the intermediate transfer body, A transfer voltage application unit that applies a transfer voltage to the transfer member, A control unit for controlling the charging voltage, the exposure amount of the exposure apparatus, the development voltage, and the transfer voltage, the control unit is configured to perform an image forming operation for forming an image on a recording material, and a toner ejection operation for supplying toner from the developing member to the image carrier, recovering a portion of the supplied toner with the developing member, and moving a portion to the intermediate transfer body. Equipped with, The control unit, in the toner ejection operation, When the toner supply unit, which is supplied with toner for the image carrier, first passes through the transfer unit, which is the contact area between the image carrier and the intermediate transfer unit, the surface potential of the image carrier and the transfer voltage are controlled so that the toner on the surface of the image carrier is carried on the image carrier. The toner supply unit, having passed through the transfer unit, controls the surface potential and charging voltage of the image carrier so that the toner on the surface of the image carrier is carried on the image carrier when the charging member passes through the charging unit that charges the image carrier. When the toner remaining on the surface of the image carrier, which has passed through the developing section (the contact area between the image carrier and the developing member), passes through the transfer section again, the surface potential of the image carrier and the transfer voltage are controlled so that the toner remaining on the surface of the image carrier moves onto the intermediate transfer body. An image forming apparatus characterized by the following features.

2. The control unit, in the toner ejection operation, When the toner supply section of the image carrier first passes through the transfer section, the transfer voltage is controlled to be negative, and the absolute value of the transfer voltage is greater than the absolute value of the post-exposure potential, which is the surface potential of the image carrier exposed by the exposure apparatus. The image forming apparatus according to claim 1, characterized in that the value of the transfer voltage is controlled to become positive when the toner remaining on the surface of the image carrier passes through the transfer section again.

3. The image forming apparatus according to claim 1, characterized in that the control unit controls each voltage and the exposure amount in the toner ejection operation such that the potential difference between the development voltage and the post-exposure potential, which is the surface potential of the image carrier exposed by the exposure device, is greater than that during the image forming operation.

4. The image forming apparatus according to claim 1, characterized in that, in the toner ejection operation, the control unit exposes the non-image area of ​​the image carrier with the exposure device after the toner supply unit of the image carrier first passes through the transfer unit and before it passes through the developing unit.

5. The control unit controls the voltages and exposure amount during the toner ejection operation such that, when the toner supply unit of the image carrier passes through the developing unit, the absolute value of the potential difference between the surface potential of the toner supply unit and the developing voltage is greater than that during the image forming operation. The image forming apparatus according to claim 1, characterized by the following:

6. The image forming apparatus according to claim 5, characterized in that the control unit controls each voltage such that, in the toner ejection operation, the potential difference between the surface potential of the toner supply unit and the transfer voltage when the toner supply unit passes through the transfer unit is greater than the potential difference between the surface potential of the toner supply unit and the development voltage when the toner supply unit passes through the development unit.

7. The image forming apparatus according to claim 1, characterized in that the control unit controls each voltage and the exposure amount such that, in the toner ejection operation, the potential difference between the surface potential of the toner supply unit and the transfer voltage when the toner supply unit of the image carrier passes through the transfer unit is greater than the potential difference between the surface potential of the image carrier exposed by the exposure apparatus during the image forming operation and the transfer voltage.

8. The image carrier is further provided with a static elimination device positioned downstream of the transfer member and upstream of the charging member in the rotational direction of the image carrier, which removes static electricity from the surface of the image carrier. The image forming apparatus according to claim 1, characterized in that the control unit, in the toner ejection operation, removes static electricity from the toner supply unit of the image carrier using the static electricity removal device before the toner supply unit passes through the charged unit.

9. The developing member is further provided with a separation / contacting mechanism that moves it to separate from and into contact with the image carrier, The image forming apparatus according to claim 1, characterized in that the separation mechanism separates the developing member from the image carrier after the toner supply unit of the image carrier has passed through the developing unit during the toner ejection operation.

10. A restricting member for restricting the thickness of toner supported on the developing member, comprising a restricting member that charges the toner supported on the developing member, A regulating voltage application unit that applies a regulating voltage to the regulating member, Furthermore, The image forming apparatus according to claim 1, characterized in that the control unit is configured to control the regulating voltage, and in the toner ejection operation, when the regulating member charges the toner to be moved from the developing member to the image carrier, the regulating member controls each voltage such that the absolute value of the potential difference between the developing voltage and the regulating voltage is greater than that during the image forming operation.

11. The image forming apparatus according to claim 10, characterized in that the control unit controls each voltage in the toner ejection operation such that the absolute value of the potential difference between the developing voltage and the regulating voltage gradually increases.

12. The developing member is configured to be rotatable, The image forming apparatus according to claim 11, characterized in that the control unit controls each voltage in the toner ejection operation such that the absolute value of the potential difference between the developing voltage and the regulating voltage gradually increases in accordance with the increase in the rotation distance of the developing member.

13. The developing member is configured to be rotatable, The image forming apparatus according to claim 1, wherein the control unit is configured to control the rotation speed of the image carrier and the developing member, and in the toner ejection operation, when moving toner from the developing member to the image carrier, the control unit controls each rotation speed such that the ratio of the rotation speed of the developing member to the rotation speed of the image carrier is greater than that during the image forming operation.

14. A supply member that supplies toner to the developing member, comprising a supply member that charges the toner carried on the developing member, A supply voltage application unit that applies a supply voltage to the supply member, Furthermore, The image forming apparatus according to claim 1, characterized in that the control unit is configured to control the supply voltage, and in the toner ejection operation, when the supply member charges the toner to be moved from the developing member to the image carrier, the control unit controls each voltage such that the absolute value of the potential difference between the supply voltage and the developing voltage is greater than that during the image forming operation.

15. The image forming apparatus according to claim 14, characterized in that the control unit controls each voltage in the toner ejection operation such that the absolute value of the potential difference between the supply voltage and the developing voltage gradually increases.

16. The developing member is configured to be rotatable, The image forming apparatus according to claim 15, characterized in that the control unit controls each voltage in the toner ejection operation such that the absolute value of the potential difference between the supply voltage and the developing voltage gradually increases in accordance with the increase in the rotation distance of the developing member.

17. The image forming apparatus according to claim 14, characterized in that the control unit controls each voltage before the start of the toner ejection operation such that the absolute value of the potential difference between the supply voltage and the developing voltage becomes smaller than that during the image forming operation.

18. A restricting member for restricting the thickness of toner supported on the developing member, comprising a restricting member that charges the toner supported on the developing member, A regulating voltage application unit that applies a regulating voltage to the regulating member, Furthermore, The image forming apparatus according to claim 1, characterized in that the control unit is configured to control the regulating voltage, and in the toner ejection operation, when the toner supply unit of the image carrier passes through the developing unit, the control unit controls each voltage and the exposure amount such that the absolute value of the potential difference between the regulating voltage and the developing voltage becomes smaller than that during the image forming operation.

19. A restricting member for restricting the thickness of toner supported on the developing member, comprising a restricting member that charges the toner supported on the developing member, A regulating voltage application unit that applies a regulating voltage to the regulating member, Furthermore, The control unit is configured to control the regulating voltage, and in the toner ejection operation, when the toner supply unit of the image carrier passes the developing unit, the control unit controls each voltage and the exposure amount such that the absolute value of the potential difference between the regulating voltage and the developing voltage becomes smaller than the value when the regulating member charges the toner that is moved from the developing member to the image carrier. This is the image forming apparatus according to claim 1.

20. The developing member is configured to be rotatable, The image forming apparatus according to claim 1, wherein the control unit is configured to control the rotation speed of the image carrier and the developing member, and in the toner ejection operation, when the toner supply unit of the image carrier passes the developing unit, the control unit controls each rotation speed such that the ratio of the rotation speed of the developing member to the rotation speed of the image carrier is greater than that during the image forming operation.

21. A supply member that supplies toner to the developing member, wherein the toner carried on the developing member A supply member that is charged, A supply voltage application unit that applies a supply voltage to the supply member, Furthermore, The image forming apparatus according to claim 1, characterized in that the control unit is configured to control the supply voltage, and in the toner ejection operation, when the toner supply unit of the image carrier passes the developing unit, the control unit controls each voltage such that the absolute value of the potential difference between the supply voltage and the developing voltage becomes smaller than that during the image forming operation.

22. The image forming apparatus according to claim 1, characterized in that the control unit controls the voltages so that, in the toner ejection operation, the toner supply unit of the image carrier passes through the transfer unit twice, and the toner remaining in the toner supply unit is recharged by the charging member.

23. The image forming apparatus according to claim 22, characterized in that the control unit controls the charging voltage and the transfer voltage in the toner ejection operation such that, after the toner supply unit has passed through the transfer unit twice, the toner remaining in the toner supply unit and recharged is moved to the intermediate transfer body.

24. The image forming apparatus according to claim 22, characterized in that the control unit controls each voltage such that, in the toner ejection operation, at any timing when the toner supply unit passes the transfer unit for the third time or later, the absolute value of the potential difference between the surface potential of the toner supply unit and the transfer voltage is greater than when the toner supply unit passes the transfer unit for the second time.

25. The image forming apparatus according to claim 22, characterized in that the control unit controls each voltage such that, in the toner ejection operation, when the toner supply unit passes through the charging unit again, the potential difference between the surface potential of the toner supply unit and the charging voltage is greater than when the toner supply unit first passes through the charging unit.

26. The system comprises multiple image forming units, each consisting of the image carrier, the charging member, the developing member, and the transfer member. The image forming apparatus according to claim 24, characterized in that, among the plurality of image forming units, if the first image forming unit performs the toner ejection operation and the second image forming unit does not perform the toner ejection operation, when the toner supply unit of the second image forming unit passes the transfer unit for the third time, each voltage is controlled so that the absolute value of the potential difference between the surface potential of the toner supply unit and the transfer voltage becomes smaller than that during the image forming operation.

27. The intermediate transfer body is configured to be rotatable, The control unit is configured to control the rotation speed of the intermediate transfer body, and in the toner ejection operation, the rotation speed is controlled such that when the toner supply unit of the image carrier passes the transfer unit for the third time, the speed difference between the image carrier and the intermediate transfer body is greater than when the toner supply unit passes the transfer unit for the second time, as described in claim 1.

28. The developing member is provided with a print rate acquisition unit that divides the region of the developing member corresponding to the recording material into multiple regions in the longitudinal direction, and acquires the average print rate of each of the multiple regions based on the print history of the image forming operation. The image forming apparatus according to claim 1, characterized in that, in the toner ejection operation, the amount of toner to be moved from each of the plurality of regions from the developing member to the image carrier is determined based on the average print density.

29. The developing member and the developing unit including a toner storage section for storing toner, An interval determination unit that determines the execution interval of the ejection operation based on an index indicating the degree of deterioration of the toner stored in the toner storage unit, the interval determination unit that narrows the execution interval as the deterioration of the toner progresses, The image forming apparatus according to claim 1, further comprising the following:

30. The image forming apparatus according to claim 29, characterized in that the indicator showing the degree of deterioration of the toner is the number of recording materials on which the image forming operation was performed.

31. The image forming apparatus according to claim 29, characterized in that the indicator showing the degree of deterioration of the toner is the driving time of the developing member.

32. The image forming apparatus according to claim 29, characterized in that the indicator showing the degree of deterioration of the toner is the amount of toner consumed from the developing unit.

33. The image forming apparatus according to claim 1, characterized in that when the control unit reaches the timing for executing the ejection control during the execution of a print job which includes a plurality of image forming operation instructions, it interrupts the print job and starts the ejection control.

34. The image forming apparatus according to claim 1, characterized in that, if the control unit reaches the timing for executing the ejection control during the execution of a print job including a plurality of image forming operation instructions, it starts the ejection control after the print job is completed.

35. The developing members comprise a plurality of the above-mentioned developing members, The image forming apparatus according to claim 1, characterized in that when the control unit reaches the timing for executing the ejection control for any of the plurality of developing members, it executes the ejection control for all of the developing members.

36. The developing members comprise a plurality of the above-mentioned developing members, The image forming apparatus according to claim 1, characterized in that the control unit, when the timing for executing the ejection control is reached for any of the plurality of developing members, executes the ejection control only for the developing member that has reached the execution timing.

37. The developing unit further includes the developing member and a toner storage section for storing toner, The image forming apparatus according to claim 1, characterized in that, in the toner ejection operation, as the degree of deterioration of the toner contained in the toner storage section progresses, the control unit increases the absolute value of the potential difference between the surface potential of the image carrier and the transfer voltage when moving the toner supplied to the image carrier that was not recovered by the developing member to the intermediate transfer body.

38. The image forming apparatus according to claim 37, characterized in that the control unit increases the absolute value of the potential difference by changing the transfer voltage.

39. The image forming apparatus according to claim 1, further comprising a removal device for removing toner transferred to the intermediate transfer body from the intermediate transfer body.

40. The system further comprises a detection unit for detecting the lifespan or usage time of at least one of the image carrier, the charging member, and the developing member. The image forming apparatus according to claim 1, characterized in that the control unit performs the toner ejection operation based on the detection result of the detection unit.

41. The image forming apparatus according to claim 1, characterized in that the control unit performs the toner ejection operation after the completion of the image forming operation.

42. The image forming apparatus according to claim 1, characterized in that the control unit performs the toner ejection operation when the image forming operation is not being performed.

43. A rotatable image carrier, A charging member that charges the image carrier, A charging voltage application unit that applies a charging voltage to the charging member, An exposure apparatus that exposes the surface of the image carrier to form an electrostatic latent image, A developing member supplies toner to the image carrier and develops the electrostatic latent image formed on the surface of the image carrier to form a toner image, A developing voltage application unit that applies a developing voltage to the developing member, An intermediate transfer body that comes into contact with the image carrier to form a transfer nip, and in the transfer nip, the toner image formed on the surface of the image carrier is transferred; A transfer member that comes into contact with the intermediate transfer body, A transfer voltage application unit that applies a transfer voltage to the transfer member, An image forming apparatus characterized in that it is configured to perform an image forming operation in which an image is formed on a recording material, and an image ejection operation in which toner is supplied from the developing member to the image carrier, and when the toner supply section of the image carrier to which the toner has been supplied first passes through the transfer section which is the contact section between the image carrier and the intermediate transfer body, a portion of the supplied toner is moved to the intermediate transfer body, while the remaining portion remains in the toner supply section, and when the remaining toner passes through the transfer section again, the remaining toner is moved to the intermediate transfer body.

44. The image forming apparatus according to claim 43, characterized in that the control unit controls the voltage and exposure amount such that when the toner supply unit first passes through the transfer unit, toner with the opposite polarity to the normal charge of the toner supply unit is moved to the intermediate transfer body, while the toner with the normal charge of the toner supply unit is held on the image carrier, and when the toner with the normal charge of the toner passes through the transfer unit again, toner with the normal charge of the toner is moved to the intermediate transfer body.

45. The image forming apparatus according to claim 43, wherein the control unit, in the toner ejection operation, exposes the non-image area of ​​the image carrier with the exposure device after the toner supplied to the image carrier first passes through the transfer section and before it passes through the developing section, which is the contact area between the image carrier and the developing member.

46. The image forming apparatus according to claim 43, characterized in that the control unit controls each voltage and the exposure amount in the toner ejection operation such that when the developing member supplies toner to the image carrier, the absolute value of the potential difference between the surface potential of the image carrier and the developing voltage is greater than that during the image forming operation.

47. The image forming apparatus according to 43, characterized in that the control unit controls each voltage and the exposure amount in the toner ejection operation such that the absolute value of the potential difference between the surface potential of the toner supply unit and the transfer voltage when the toner supply unit of the image carrier passes through the transfer unit which is the contact portion between the image carrier and the intermediate transfer unit is greater than that during the image forming operation.

48. The image carrier is further provided with a static elimination device positioned downstream of the transfer member and upstream of the charging member in the rotational direction of the image carrier, which removes static electricity from the surface of the image carrier. The control unit, in the toner ejection operation, the toner supply unit of the image carrier The image forming apparatus according to claim 43, characterized in that the toner supply unit is de-energized by the de-energizing device before the charged member passes through the charged unit that charges the image carrier.

49. The image forming apparatus according to 43, characterized in that the control unit controls each voltage and the exposure amount such that, in the toner ejection operation, the potential difference between the surface potential of the toner supply unit and the transfer voltage when the remaining toner passes through the transfer unit again is greater than the potential difference between the surface potential of the image carrier exposed by the exposure device during the image forming operation and the transfer voltage.

50. The image forming apparatus according to 43, characterized in that the control unit controls the voltage and exposure amount such that when the toner supply unit first passes through the transfer unit, the toner with the normal charge polarity of the toner supply unit is moved to the intermediate transfer body, while the toner with the opposite charge polarity of the toner supply unit is held in the image carrier, and when the toner with the opposite polarity passes through the transfer unit again, the toner with the opposite polarity is moved to the intermediate transfer body.

51. The image forming apparatus according to claim 50, characterized in that the control unit controls the charging voltage so that the charging member collects the toner of the opposite polarity from the toner supply unit during the toner ejection operation.

52. The image carrier is further provided with a collection member positioned upstream of the charging member and downstream of the transfer member in the rotational direction of the image carrier, which contacts the image carrier and charges the image carrier to temporarily collect toner from the toner supply unit. The image forming apparatus according to claim 50, characterized in that the control unit controls the voltage applied to the collection member.

53. The developing member is configured to be rotatable, The image forming apparatus according to claim 43, wherein the control unit is configured to control the rotation speed of the image carrier and the developing member, and in the toner ejection operation, the control unit controls each rotation speed such that the ratio of the rotation speed of the developing member to the rotation speed of the image carrier is greater than that during the image forming operation.

54. A supply member that supplies toner to the developing member, comprising a supply member that charges the toner carried on the developing member, A supply voltage application unit that applies a supply voltage to the supply member, Furthermore, The image forming apparatus according to claim 43, characterized in that the control unit is configured to control the supply voltage, and in the toner ejection operation, when the supply member charges the toner to be moved from the developing member to the image carrier, the voltages are controlled such that the absolute value of the potential difference between the supply voltage and the developing voltage is greater than that during the image forming operation.

Images