Image forming apparatus

Abstract

An image forming apparatus is disclosed. An image forming apparatus includes an image bearing member, a charging member, a developing member, a developer accommodating portion, a first acquiring portion acquiring developer amount information related to an amount of developer accommodated in the developer accommodating portion, a second acquiring portion acquiring development driving information related to a movement distance of a surface of the developing member, and a control section capable of executing, as image forming modes, a first mode and a second mode in which a frequency at which the developing member is driven is lower than a frequency at which the developing member is driven in the first mode. The control portion proposes or determines a change of the image forming mode from the first mode to the second mode based on the developer amount information and the development driving information.

Description

Technical Field

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

[0002] In an image forming apparatus that forms an image on a recording material by using an electrophotographic system (electrophotographic process), a cleaner-less method is proposed for the purpose of size reduction of the apparatus, in which a cleaning member that contacts the surface of an image bearing member and cleans the image bearing member is eliminated. The cleaner-less method is a method in which a developer (toner) remaining on the surface of an image bearing member after a transfer process is cleaned by a developing member at the same time as development, and the developer on the image bearing member is removed, recovered, and reused.

[0003] In an image forming apparatus of a cleaner-less method, a charging member or a transfer member in contact with an image bearing member may be contaminated by a developer remaining on the image bearing member. Japanese Patent Application Publication No. 2010-26198 discloses a configuration in which a cleaning operation is performed so that a developer adhering to the surface of a member in contact with an image bearing member is moved to the surface of the image bearing member by changing a voltage applied to the charging member or the transfer member, and the member is cleaned. Summary of the invention

[0004] However, as in the above-mentioned configuration, for example, when the developing member or the supply member that supplies the developer to the developing member rotates during the cleaning operation as an operation other than the image forming operation, the developer in the developing device is repeatedly brought into sliding contact. Then, the developer may be deteriorated due to removal, embedding (buried), etc. of an external additive added to the developer. In particular, if the consumption of the developer is small relative to the driving time of the developing device, the deterioration of the developer is promoted. And the deterioration of the developer causes a decrease in the amount of charge, etc., and there is a concern that a defective image such as so-called fogging (in which the toner adheres to the white background of the recording material) is caused.

[0005] In addition, in particular, in a configuration in which the image bearing member and the developing member are driven also in a non-image forming operation such as a cleaning operation, since the developing device is driven every time the cleaning operation is performed, toner degradation is easily promoted. In a configuration in which the image bearing member or the developing member is repeatedly driven in a non-image forming operation as above, there is a concern that the occurrence of defective images is accelerated.

[0006] The present invention has been made in view of the above-mentioned problems, and has an object to provide an image forming apparatus that can suppress the occurrence of defective images.

[0007] In order to achieve the above object, the image forming device according to the present application includes:

[0008] an image bearing member, the image bearing member being rotatable;

[0009] a charging member that is rotatable and charges the image bearing member;

[0010] a developing member that is rotatable and supplies a developer to a surface of the image bearing member;

[0011] a developer accommodating portion that accommodates therein a developer supplied to the developing member;

[0012] a first acquisition section that acquires developer amount information related to an amount of developer accommodated in the developer accommodating section;

[0013] a second acquisition section that acquires development drive information related to a movement distance on a surface of the development member; and

[0014] A control part, which is capable of executing a first mode and a second mode as image forming modes, wherein the frequency of driving the developing member in the second mode is lower than that in the first mode, and the control part proposes or determines a change of the image forming mode from the first mode to the second mode based on the developer amount information and the developer drive information.

[0015] According to the present invention, it is possible to provide an image forming apparatus that can suppress the occurrence of defective images.

[0016] Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic cross-sectional view of the image forming apparatus of Example 1;

[0018] Figure 2 is a schematic front view of the light guide member of Example 1;

[0019] Figure 3 is a circuit diagram of the sensor portion of Example 1;

[0020] Figure 4 is a schematic block diagram illustrating a control system of the image forming apparatus of Embodiment 1;

[0021] Figure 5 is a diagram illustrating a cleaning operation of the charging roller of Embodiment 1;

[0022] Figure 6 is a perspective view of a developing device that can replenish toner;

[0023] Figure 7 is a flowchart for facilitating the change of the printing mode of Embodiment 1;

[0024] Figure 8 is a flowchart for calculating the degree of toner degradation of Embodiment 2; and

[0025] Fig. 9 1 is a flowchart for facilitating the change of the printing mode of the second embodiment. DETAILED DESCRIPTION

[0026] Hereinafter, description will be given of embodiments (examples) of the present invention with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described in the embodiments may be appropriately changed according to the configuration of the device to which the present invention is applied, various conditions, etc. Therefore, the dimensions, materials, shapes, relative arrangements, etc. of the components described in the embodiments are not intended to limit the scope of the present invention to the following embodiments. In addition, not all of the features described in the following embodiments are necessary for the solutions provided by the present invention.

[0027] Example 1

[0028] Schematic Configuration of Image Forming Apparatus

[0029] First, a schematic configuration of an image forming apparatus 100 of Embodiment 1 will be described. Figure 1 : is a schematic cross-sectional view of an image forming apparatus 100 of Embodiment 1. The image forming apparatus 100 of Embodiment 1 is a monochrome laser printer capable of forming a black monochrome image on a sheet-like recording material P by using an electrophotographic system, and is configured so that a process cartridge 9 is detachable relative to an apparatus main body M. Here, the apparatus main body M is a component other than the process cartridge 9 in the image forming apparatus 100.

[0030] Note that the image forming apparatus to which the present invention can be applied is not limited to the image forming apparatus having the basic configuration shown in Embodiment 1. For example, the present invention can be applied to a color laser printer that detachably has a plurality of process cartridges 9 and forms a full-color image by transferring a plurality of color toner images to a recording material P using an intermediate transfer body such as an intermediate transfer belt. Furthermore, the image forming apparatus 100 of Embodiment 1 has a configuration in which the process cartridge 9 is detachable, but the present invention can also be applied to an image forming apparatus in which a process unit is provided in an apparatus main body and has a configuration similar to that of the process cartridge 9 in Embodiment 1.

[0031] The process cartridge 9 has a photosensitive drum 1 which is a rotatable drum-type (cylindrical) photosensitive body (electrophotographic photosensitive body) as an image bearing member. Furthermore, the process cartridge 9 has a charging roller 2 as a roller-type charging member and a developing device 8 as a developing member around the photosensitive drum 1. Furthermore, the process cartridge 9 has a brush member 12 as a paper powder recovery member and a charge removal device 11 as a charge removal member around the photosensitive drum 1. Furthermore, the process cartridge 9 has a memory 15 as a nonvolatile storage member. Furthermore, the process cartridge 9 has a toner amount sensor (toner remaining amount sensor) 20 as a developer amount detection member.

[0032] The charging roller 2, the brush member 12, and the developing roller 4 as a developer carrying member provided in the developing device 8 are disposed in contact with the surface (peripheral surface) of the photosensitive drum 1. The process cartridge 9 is configured to be easily and detachably attached as a whole to the apparatus body M via attachment parts (not shown) such as an attachment guide, a positioning member, etc. provided in the apparatus body M and the process cartridge 9.

[0033] Furthermore, the image forming apparatus 100 has a transfer roller 13 as a transfer means, an exposure device 10 as an exposure means, and a fixing device 14 as a fixing means (fixing unit). The transfer roller 13 is a roller-type transfer member disposed in contact with the surface of the photosensitive drum 1.

[0034] Furthermore, the image forming apparatus 100 has a control section 200 that manages control of the entire image forming apparatus 100, an operation panel 60 as an operation section, etc. The operation panel 60 is configured by having a display section for displaying information to an operator such as a user and a service person by control of the control section 200, an input section for inputting information to the control section 200 according to the operation of the operator, etc.

[0035] Image forming operation

[0036] Subsequently, an image forming operation in the image forming apparatus 100 of Embodiment 1 will be described. Figure 1 The conveyance path of the recording material P in the image forming operation is illustrated by a dotted line.

[0037] The photosensitive drum 1 is rotated / driven in the direction of arrow A1 in the figure (counterclockwise direction) at a predetermined process speed by a driving force transmitted from a driving motor (not shown) as a driving source constituting a driving member provided in the apparatus body M. Here, the process speed corresponds to the peripheral speed (surface movement speed) of the photosensitive drum 1. The process speed of the photosensitive drum 1 in Embodiment 1 is 140 rpm.

[0038] The charging roller 2 is a rotatable charging member for charging the photosensitive drum 1, and forms a charging portion ES by contacting the surface of the photosensitive drum 1 with a predetermined contact pressure. A predetermined charging voltage (charging bias) as a DC voltage is applied to the charging roller 2 from a charging voltage applying circuit (not shown) provided in the device body M as a voltage applying portion (charging voltage applying member). As a result, the charging roller 2 uniformly performs a charging process of the surface of the photosensitive drum 1 to a predetermined potential of a predetermined polarity (negative polarity in Embodiment 1). In Embodiment 1, a charging voltage of -1400V is applied to the charging roller 2 so that the surface potential of the photosensitive drum 1 (the potential VD before exposure) is -800V. Note that in Embodiment 1, a DC voltage is used as the charging voltage, but this is not restrictive, and a vibration voltage in which a DC voltage and an AC voltage are overlapped may also be used as the charging voltage.

[0039] The surface of the photosensitive drum 1 subjected to the uniform charging process is scanned and exposed by the exposure device 10 based on the image information by irradiating with a laser beam, and an electrostatic latent image (electrostatic image) is formed on the photosensitive drum 1. In Embodiment 1, the exposure device 10 is constituted by a scanner unit. Image information input to the image forming device 100 from an external device (not shown) such as a personal computer connected to the image forming device 100 is converted into a time-series electrical digital image signal by a video controller (not shown) provided in the image forming device 100. The exposure device 10 is controlled by the control section 200, emits a laser beam demodulated corresponding to the above-mentioned time-series electrical digital image signal, and scans and exposes the surface of the photosensitive drum 1. As a result, an electrostatic latent image corresponding to the image information is formed on the photosensitive drum 1.

[0040] In Example 1, the exposure device 10 is used with a 0.45 μJ / cm 2 The laser beam with a light amount of 100 Ω irradiates the surface of the photosensitive drum 1 , so that the potential VL of the surface of the photosensitive drum 1 after exposure becomes −100 V.

[0041] The electrostatic latent image formed on the photosensitive drum 1 is developed (visualized) by a toner as a developer supplied by a developing device 8, and a toner image (toner image, developer image) is formed on the photosensitive drum 1. The developing device 8 has a developing roller 4 as a developer carrying member. The developing roller 4 is a developing member that is rotatable and supplies toner to the photosensitive drum 1.

[0042] The developing roller 4 forms a developing portion DS by contacting the surface of the photosensitive drum 1 with a predetermined contact pressure. On the developing roller 4, a toner layer formed of the toner 3 charged to a predetermined polarity (negative polarity in Embodiment 1) is formed. A predetermined developing voltage (developing bias) as a DC voltage is applied to the developing roller 4 from a developing voltage applying circuit (not shown) as a developing voltage applying member provided in the apparatus main body M. As a result, the toner 3 adheres to the electrostatic latent image on the photosensitive drum 1 in the developing portion DS, and a toner image is formed on the photosensitive drum 1.

[0043] In Embodiment 1, a developing voltage of -400 V is applied to the developing roller 4. And, the toner 3 charged to the same polarity as the charging polarity of the photosensitive drum 1 (negative polarity in Embodiment 1) adheres to the exposed portion (image portion) on the photosensitive drum 1 whose absolute value of the potential is lowered by being exposed after being subjected to the uniform charging process (reversal development method). In Embodiment 1, the normal charging polarity of the toner 3, which is the main charging polarity of the toner 3 at the time of development, is negative polarity.

[0044] The transfer roller 13 is brought into contact with the photosensitive drum 1 at a predetermined contact pressure, and a transfer portion TS is formed. At the transfer portion TS, the toner image formed on the photosensitive drum 1 is transferred to the recording material P sandwiched and conveyed by the photosensitive drum 1 and the transfer roller 13. At the time of transfer, a predetermined transfer voltage (transfer bias) as a DC voltage is applied to the transfer roller 13 from a transfer voltage applying circuit (not shown) as a transfer voltage applying member. In Embodiment 1, a transfer voltage of +1500V is applied to the transfer roller 13.

[0045] The recording material (transfer material, recording medium, sheet) P is supplied to the transfer section TS from the feeding section 30. The feeding section 30 is constituted by having a box 31 as a recording material accommodating section, a feeding roller 32 as a feeding member, etc. The recording materials P accommodated in the box 31 are separated one by one and sent out from the box 31 by the feeding roller 32, etc. The timing at which the toner image of this recording material P on the photosensitive drum 1 reaches the transfer section TS is synchronously conveyed to the transfer section TS by the conveying roller (resist roller) 50 as a conveying member.

[0046] The recording material P to which the toner image has been transferred is conveyed to a fixing device 14 as a fixing member. The fixing device 14 fixes (melts, causes adhesion) the toner image to the recording material P by applying heat and pressure to the recording material P. The recording material P to which the toner image has been fixed is discharged (output) onto a tray 40 as a discharge portion provided outside the apparatus main body M.

[0047] On the other hand, the toner (untransferred toner) that has not been transferred to the recording material P at the transfer portion TS in the transfer process and remains on the photosensitive drum 1 is removed from the photosensitive drum 1 as follows.

[0048] The surface portion of the photosensitive drum 1 of the transfer portion TS after the transfer process is destaticized (destatic lamp) 11 so that the surface potential becomes 0V and enters the charging portion ES. In the untransferred toner remaining on the photosensitive drum 1, the toner charged with positive polarity and the toner charged with negative polarity but not having sufficient charge are mixed. The untransferred toner is charged with negative polarity by discharge in the charging portion ES.

[0049] The untransferred toner charged with negative polarity in the charging portion ES reaches the developing portion DS as the photosensitive drum 1 rotates. Here, on the surface portion of the photosensitive drum 1 that has reached the developing portion DS, an electrostatic latent image corresponding to the image information is formed. The untransferred toner adhering to the non-exposed portion (non-image portion) on the photosensitive drum 1 moves from the photosensitive drum 1 to the developing roller 4 at the developing portion DS by the potential difference between the potential VD before exposure on the photosensitive drum 1 and the developing voltage, and is recovered in the developing chamber 8b of the developing device 8. As described above, the untransferred toner on the photosensitive drum 1 that has not been transferred to the recording material P at the transfer portion TS is recovered by the developing device 8. Note that the toner recovered in the developing chamber 8b is used again for image formation.

[0050] On the other hand, the untransferred toner of the exposed portion (image portion) adhered to the photosensitive drum 1 does not move from the photosensitive drum 1 to the developing roller 4 at the developing portion DS, but constitutes a toner image together with the toner that has moved from the developing roller 4 to the photosensitive drum 1. And, this toner is transferred onto the recording material P at the transfer portion TS, and is removed from the photosensitive drum 1.

[0051] Furthermore, there is provided a brush member 12 as a paper powder recovery member for removing powder fibers generated from the recording material P at the time of the transfer process and adhering from the recording material P to the photosensitive drum 1. The brush member 12 is disposed so as to contact the photosensitive drum 1 on the downstream side of the transfer portion TS and the upstream side of the charging portion ES in the rotation direction of the photosensitive drum 1. The brush member 12 captures the paper powder fibers on the photosensitive drum 1 and removes them from the photosensitive drum 1 by frictionally sliding on the surface of the photosensitive drum as the photosensitive drum 1 rotates.

[0052] Note that the image forming apparatus 100 according to Embodiment 1 does not have a development contact / separation mechanism capable of achieving contact between the development roller 4 and the photosensitive drum 1 at an appropriate time, but is configured so that the development roller 4 and the photosensitive drum 1 are always in contact. Therefore, Embodiment 1 is configured so that the voltage applying portion can apply a voltage of a polarity opposite to the negative polarity from a power source for applying a development voltage to the development roller 4. That is, it is configured so that if development is not performed, by applying a voltage of a positive polarity opposite to the negative polarity which is the normal polarity of the toner to the development roller 4, the transfer of the toner to the photosensitive drum 1 is suppressed. As a result, the same effect as the case where the development roller and the photosensitive drum are separated when development is not performed in an image forming apparatus having a development contact / separation mechanism can be obtained. Note that a configuration having a development contact / separation mechanism in which the development roller 4 can contact and separate from the photosensitive drum 1 can be used.

[0053] Detailed configuration of main components of image forming apparatus

[0054] Subsequently, the detailed configuration of main components in the image forming apparatus 100 in Embodiment 1 will be described.

[0055] Photosensitive drum 1

[0056] In Example 1, the photosensitive drum 1 has an OPC (organic photoconductor) photosensitive layer formed on the outer peripheral surface of a cylindrical conductive drum. In Example 1, the photosensitive drum 1 is a rigid body constituted by sequentially coating a resistance layer, an undercoat layer, a charge generation layer, and a charge transport layer on the outer periphery of an aluminum cylinder having a diameter of 24 mm by a dip coating method. In Example 1, the film thickness of the charge transport layer is 22 μm.

[0057] Charging roller 2

[0058] In Example 1, the charging roller 2 is formed by coating a polyepichlorohydrin rubber base layer and a polyurethane surface layer in sequence on the outer periphery of a core metal having a diameter of 6 mm so as to have an outer diameter of 12 mm. In addition, in Example 1, the resistance value of the charging roller 2 is 1×10 6 Ω or less, and the hardness of the charging roller 2 is 40 degrees when measured by an Asker C rubber hardness meter of KOBUNSHI KEIKI CO., LTD.

[0059] Exposure equipment 10

[0060] In Embodiment 1, exposure device 10 is a scanner unit capable of changing the light amount of a laser beam irradiating the surface of photosensitive drum 1. The wavelength of the laser beam emitted by exposure device 10 is 800 nm. In Embodiment 1, the light source of exposure device 10 is a semiconductor laser.

[0061] Transfer roller 13

[0062] In Example 1, the transfer roller 13 is constituted by providing a base layer of ion conductive sponge on the outer periphery of a core metal having a diameter of 6 mm so that the outer diameter becomes 15 mm. In addition, in Example 1, in an environment having a temperature of 22° C., the resistance value of the transfer roller 13 is 4×10 7 Ω, and when measured by Asker C rubber hardness meter of KOBUNSHI KEIKI Co., Ltd., the hardness is 30 degrees.

[0063] Development equipment 8

[0064] In Embodiment 1, the developing device 8 is a single-component contact developing device using a non-magnetic single-component developer (toner) as a developer. The developing device 8 has a developing container (frame) 80 constituted by including a developing chamber 8b as a developing member accommodating chamber (developing member accommodating portion) and a toner accommodating chamber 8a as a developer accommodating chamber (developer accommodating portion). The developing chamber 8b and the toner accommodating chamber 8a are connected to each other via an opening portion.

[0065] In the developing chamber 8b, a developing roller 4, a supply roller 5 as a supply member, and a developing blade 6 as a limiting member are provided. The developing roller 4 is rotatably disposed at the opening portion of the developing chamber 8b (developing container 80), and conveys the toner 3 from the inside of the developing chamber 8b (developing container 80) to the outside by rotating while carrying the toner 3. The supply roller 5 supplies the toner 3 to the developing roller 4. The developing blade 6 limits the amount of toner on the developing roller 4, while giving a charge of a predetermined polarity to the toner 3 on the developing roller 4.

[0066] In the toner accommodating chamber 8a, toner 3 as a developer is accommodated. Further, in the toner accommodating chamber 8a, a stirring member 7 for conveying the toner 3 from the toner accommodating chamber 8a to the developing chamber 8b while stirring the toner 3 in the toner accommodating chamber 8b is provided.

[0067] Note that in Embodiment 1, a contact developing method in which the photosensitive drum 1 and the developing roller 4 are arranged in contact with each other is used for the developing device 8, but this is not restrictive. The developing device 8 may use a two-component developing method using a two-component developer or a non-contact developing method in which the photosensitive drum 1 and the developing roller 4 are arranged relative to each other with a predetermined gap.

[0068] In Example 1, the developing roller 4 is formed by coating a base layer of silicone rubber and a surface layer of polyurethane rubber in this order on the outer periphery of a core metal having a diameter of 6 mm so that the outer diameter becomes 15 mm. In addition, in Example 1, the resistance value of the developing roller 4 is 1×10 4 Up to 1x10 12 Ω.

[0069] In Example 1, the supply roller 5 is a conductive elastic sponge roller formed by forming a foam layer on the outer periphery of a core metal having a diameter of 6 mm. In addition, in Example 1, the resistance value of the supply roller 5 is 1×10 4 Up to 1x10 8 Ω, and the hardness is 200 gf. Note that the hardness of the supply roller 5 is a value obtained by measuring a load when a flat plate having a longitudinal width of 50 mm is made to intrude 1 mm from the surface of the supply roller 5.

[0070] In Embodiment 1, the developing blade 6 is a SUS metal sheet made of metal having a thickness of 0.1 mm, and has a predetermined length in the longitudinal direction disposed along the rotation axis direction of the developing roller 4 and in the short side direction substantially orthogonal to the longitudinal direction. With respect to this developing blade 6, the free end in the short side direction points to the upstream side in the rotation direction of the developing roller 4, and the side surface near the free end is disposed in contact with the developing roller 4 in the longitudinal direction. In Embodiment 1, for the developing blade 6, a developing blade obtained by cutting and processing the distal end (free end) of the SUS metal sheet from the contact surface side relative to the developing roller 4 is used. The distal end portion of the developing blade 6 is bent in the cutting direction by cutting and processing, and the amount of bending at the distal end of the developing blade 6 corresponding to the radius of curvature R is 0.02 mm.

[0071] The movement of the toner 3 in the driven developing device 8 will be described. In the developing device 8, the driving force is transmitted from a driving motor (not shown) provided in the apparatus main body M as a driving source constituting a driving part. As a result, the developing roller 4 rotates in the arrow A2 direction (clockwise direction) in the figure, the supply roller 5 rotates in the arrow A3 direction (clockwise direction) in the figure, and the stirring member 7 rotates in the arrow A4 direction (counterclockwise direction) in the figure. Note that the driving source of the photosensitive drum 1 and each rotating member of the developing device 8 (developing roller 4, supply roller 5, stirring member 7) can be shared.

[0072] When the stirring member 7 in the toner containing chamber 8a rotates, the toner 3 in the toner containing chamber 8a is stirred, and is also conveyed toward the supply roller 5 in the developing chamber 8b. The toner 3 held by the foam layer of the supply roller 5 is sent to the contact portion with the developing roller 4 by the rotation of the supply roller 5. Then, the toner 3 having reached this contact portion is brought into sliding contact in this contact portion by the surface of the developing roller 4 and the surface of the supply roller 5 moving in opposite directions to each other, and a part thereof adheres to the surface of the developing roller 4.

[0073] The toner 3 adhering to the surface of the developing roller 4 is sent to the contact portion with the developing blade 6 as the developing roller 4 rotates. The developing blade 6 forms a uniform thin layer by limiting the amount of the toner 3 adhering to the surface of the developing roller 4, and frictionally charges the toner 3. The toner 3 made into a thin layer is sent to the contact portion (developing portion DS) with the photosensitive drum 1 as the developing roller 4 rotates, and is used to develop the electrostatic latent image formed on the photosensitive drum 1. The toner 3 that is not used for development but remains on the surface of the developing roller 4 is conveyed to the contact portion with the supply roller 5, and is removed from the surface of the developing roller 4 by the supply roller 5. The removed toner 3 is sent to the toner accommodating chamber 8a and is stirred and mixed with the toner 3 in the toner accommodating chamber 8a.

[0074] Toner Amount Sensor

[0075] Subsequently, a toner amount sensor 20 as a developer amount detecting means for detecting a toner amount (toner remaining amount) in the developing device 8 in Embodiment 1 will be described. The toner amount sensor 20 is an optical sensor constituted by the light guide member 18 and the sensor portion 19. Figure 2 1 is a schematic front view of the light guide member 18 in Embodiment 1. Figure 3 is a circuit diagram of the sensor portion 19 in Embodiment 1. Figure 4 1 is a schematic block diagram illustrating a control system of the image forming apparatus 100 in Embodiment 1.

[0076] like Figure 1 As shown in FIG. 1 , in the developing device 8, a light guide member 18 constituting a toner amount sensor 20 is provided. Figure 2 As shown in FIG. 1 , the light guide member 18 has a light emitting side light guide portion 18 a and a light receiving side light guide portion 18 b. The light emitting side light guide portion 18 a guides light emitted from a light emitting element 19 a of a sensor portion 19 to be described later into the developing container 80. The light receiving side light guide portion 18 b guides light having passed through the light emitting side light guide portion 18 a and a spatial light path Q inside the developing container 80 into a light receiving element 19 b of the sensor portion 19 to be described later.

[0077] In addition, if Figure 1 As shown in FIG. 1 , in the developing device 8, a sensor portion 19 constituting a toner amount sensor 20 is provided. Figure 3As shown in , the sensor part 19 has a light emitting element 19a as a light emitting part that emits light and a light receiving element 19b as a light receiving part that receives light emitted from the light emitting element 19a. In addition, the sensor part 19 has a board (not shown) on which the light emitting element 19a and the light receiving element 19b are provided. In Embodiment 1, an LED is used as the light emitting element 19a, and a phototransistor is used as the light receiving element 19b. The phototransistor enters an ON state by light from the LED. In addition, a cable connector (not shown) is provided on the board. The sensor part 19 is connected to a control part 200, which will be described later, provided in the device body M of the image forming device 100 via this cable connector.

[0078] Subsequently, the deployment of the toner amount sensor 20 in Embodiment 1 will be described. The toner amount sensor 20 composed of the light guide member 18 and the sensor portion 19 is deployed on the side of the toner holding chamber 8a of the developing container 80. In Embodiment 1, the toner amount sensor 20 (light guide member 18 and sensor portion 19) is provided at the center portion in the longitudinal direction (rotation axis direction of the developing roller 4) of the toner holding chamber 8a (developing container 80). In some cases, the toner inside the toner holding chamber 8a is unevenly distributed in the longitudinal direction of the toner holding chamber 8a, but at the center portion in the longitudinal direction of the toner holding chamber 8a, the uneven distribution of the toner is small. Therefore, by providing the toner amount sensor 20 (light guide member 18 and sensor portion 19) at the center portion in the longitudinal direction of the toner holding chamber 8a, the toner amount with the influence of the uneven distribution of the toner suppressed can be detected.

[0079] Subsequently, a method of detecting the toner amount by the toner amount sensor 20 will be described. Figure 3 In the embodiment, a switch (not shown) is provided between the light emitting element 19a and the power supply voltage Vcc1, and when this switch enters the ON state, a voltage is applied from the power supply voltage Vcc1 to the light emitting element 19a, and the light emitting element 19a enters the conducting state. On the other hand, a switch (not shown) is also provided between the light receiving element 19b and the power supply voltage Vcc, and when this switch enters the ON state, the light receiving element 19b enters the conducting state, and a current according to the amount of light detected by the light receiving element 19b flows.

[0080] The power supply voltage Vcc1 and the current limiting resistor R1 are connected to the light emitting element 19a, and the light emitting element 19a emits light by the current determined by the current limiting resistor R1. The light emitted from the light emitting element 19a passes through the spatial optical path Q and is received by the light receiving element 19b. The power supply voltage Vcc2 is connected to the collector terminal of the light receiving element 19b, and the detection resistor R2 is connected to the emitter terminal of the light receiving element 19b. The light receiving element 19b, which is a phototransistor, receives the light emitted from the light emitting element 19a and outputs a signal (current) according to the amount of light received. This signal is converted into a voltage by the detection resistor R2 and is input to the A / D conversion part 202 of the control part 200, which will be described later. That is, the light receiving element 19b changes the output value according to the amount of toner contained in the toner containing chamber 8a. The toner amount sensor 20 is powered from a power supply provided in the device body M.

[0081] The toner amount calculation section 300 (to be described later) of the control section 200 determines whether the light receiving element 19b has received the light from the light emitting element 19a based on the voltage level input to the control section 200 by the toner amount sensor 20 and converted into a digital signal by the A / D conversion section 202. Then, when the toner in the developing container 80 is stirred by the stirring member 7 for a predetermined period of time, the toner amount calculation section 300 calculates the length of time for which the toner amount sensor 20 detects the light. In the ROM 203 (to be described later) of the control section 200, toner amount determination information for determining (calculating, predicting, estimating) the toner amount is pre-stored as a table indicating the relationship between the above-mentioned time and the toner amount. And, the toner amount calculation section 300 calculates the toner amount in the developing container 80 based on the voltage level input to the control section 200 by the toner amount sensor 20 and converted by the A / D conversion section 202 and the information of the above-mentioned table.

[0082] More specifically, the spatial optical path Q of the toner amount sensor 20 is set so as to intersect with the rotation trajectory of the stirring member 7 when viewed from the rotation axis direction of the stirring member 7 in the toner containing chamber 8a. And, when the stirring member 7 rotates once, the time during which the spatial optical path Q is blocked by the toner conveyed by the stirring member 7-that is, the time during which the light receiving element 19b does not detect the light from the light emitting element 19a changes depending on the amount of toner remaining. In addition, the light reception intensity at the light receiving element 19b also changes depending on the amount of toner remaining.

[0083] That is, when the amount of toner remaining is small, the time that the spatial optical path Q is blocked by the toner 3 is short, and therefore, the time that the light receiving element 19b receives light becomes longer, and the light receiving intensity of the light received by the light receiving element 19b becomes larger. On the other hand, when the amount of toner remaining is large, the time that the light receiving element 19b receives light becomes shorter, and the light receiving intensity of the light received by the light receiving element 19b becomes weaker. Therefore, the control part 200 can determine the level of the amount of toner remaining based on the light receiving time or light receiving intensity of the light receiving element 19b as described above.

[0084] The toner amount calculation section 300 causes the toner amount in the developing container 80 calculated based on the detection result of the toner amount sensor 20 to be stored in the memory 15. Note that in Embodiment 1, in the memory 15, the toner remaining amount T accommodated in the toner accommodating chamber 8a when the developing device 8 (process cartridge 9) is new (starting use, unused state) is stored in advance as the toner initial remaining amount T0.

[0085] In Embodiment 1, when the image forming operation is performed, the toner remaining amount T1 detected most recently by the toner amount sensor 20 at the end of the image forming operation is calculated by the toner amount calculation section 300. And, when the calculated toner remaining amount T1 is smaller than the toner remaining amount T stored in the memory 15, the toner amount calculation section 300 updates the toner remaining amount T stored in the memory 15 to T1 (stored in the memory 15 as T=T1).

[0086] Note that the method for detecting / estimating the amount of toner residue is not limited to the above-mentioned optical toner residue detection system, but various known methods for detecting / estimating the amount of toner residue can be used. For example, the amount of toner residue can be detected / estimated by disposing two or more metal plates or conductive resin sheets extending in the longitudinal direction of the developing roller on the inner wall of the developing container 80 as a frame, and by measuring the electrostatic capacity between the two metal plates or conductive resin sheets. Alternatively, a weighing sensor is provided in the form of supporting the developing device 8 from below, so that the CPU 201 described later subtracts the weight of the developing device 8 when the toner is empty from the weight measured by the weighing sensor, so that the amount of toner residue is calculated. In addition, in the present embodiment, the amount of toner residue is detected by one sensor of the optical toner residue detection system, but the amount of toner residue can be detected by multiple sensors.

[0087] Control Configuration

[0088] like Figure 4As shown in FIG. 1 , in the apparatus body M of the image forming apparatus 100, a control section 200 as a control section is provided. The control section 200 is constituted by a CPU 201 having an operation processing section as a core element for performing operation processing, an A / D conversion section 202, a ROM 203 and a RAM 204 as storage sections (storage media), an input / output circuit (not shown), and the like. The A / D conversion section 202 converts an analog signal input to the control section 200 into a digital signal. In the ROM 203, a control program, a pre-acquired data table, and the like are stored. In the RAM 204, information input to the control section 200, detected information, calculation results, and the like are stored. The input / output circuit controls input / output of signals between the control section 200 and the devices connected thereto.

[0089] Each part (various driving devices, various power supplies, various sensors, etc.) of the image forming apparatus 100 is connected to the control part 200. The control part 200 controls the operation of each part by bidirectionally communicating with each part of the image forming apparatus 100. The control part 200 controls each part of the image forming apparatus 100 based on a signal (start signal, image signal) input from an external device (not shown) such as a personal computer according to an operation of an operator (user), and performs an image forming operation.

[0090] Furthermore, in the control section 200, a toner amount calculation section 300 is provided. The toner amount calculation section 300 calculates the toner amount (toner remaining amount) in the developing container 80 based on the detection result of the above-mentioned toner amount sensor 20. In Embodiment 1, the toner amount calculation section 300 is realized by the CPU 201 executing a program stored in the ROM 203.

[0091] Furthermore, in the control section 200, a travel distance detection device 400 is provided as a developing roller travel distance detection member. The travel distance detection device 400 counts the travel distance of the developing roller 4, and is implemented by the CPU 201 executing a program stored in the ROM 203. The travel distance of the developing roller 4 counted by the travel distance detection device 400 is stored in the memory 15 as a cumulative travel distance R0. The travel distance is a moving distance of the surface of the developing roller 4, and the cumulative travel distance R0 is a cumulative moving distance of the surface of the developing roller 4. Note that when the developing device 8 is new, R0=0.

[0092] Furthermore, in the control section 200, there is provided a print sheet number detection section 500 for detecting the number of formed images of the recording material P for which the image forming operation is performed (print sheet number). The print sheet number detection section 500 counts the number of image forming operations since the apparatus is new, which is realized by the CPU 201 executing a program stored in the ROM 203. The number of image forming operations counted by the print sheet number detection section 500 is stored as the accumulated print sheet number N0 in the memory 15. Note that when the developing device 8 is new, N0=0.

[0093] Furthermore, which one of a normal printing mode (to be described later) and a text printing mode the printing mode currently set (in use) is is recorded in the memory 15 .

[0094] Toner contamination on the charging roller

[0095] As described above, the untransferred toner remaining on the surface of the photosensitive drum 1 in the transfer process is brought into contact with the charging portion ES, which is a contact portion between the photosensitive drum 1 and the charging roller 2, before the developing portion DS. In the above configuration, the charging roller 2 may be contaminated in some cases in the case where the developing device 8 is new, a long time has passed since the last printing, the toner has deteriorated due to repeated image forming operations, etc.

[0096] The above phenomenon will be described in detail. In the above case, if the charging characteristic of the toner in the toner holding chamber 8a is low, the toner cannot be held on the surface of the developing roller 4 only by the potential difference formed between the photosensitive drum 1 and the developing roller 4, and the amount of toner moved to the surface of the photosensitive drum 1 becomes large. The phenomenon that the toner moves to the surface of the photosensitive drum 1 relative to the potential difference formed between the potential VD before exposure of the photosensitive drum 1 and the developing voltage is called atomization, and the toner that moves to the surface of the photosensitive drum 1 when atomized is called atomized toner. Since the atomized toner that has moved to the photosensitive drum 1 as described above has a low charging characteristic, even if the potential difference formed between the charging roller 2 and the photosensitive drum 1 is such that it is difficult for the toner to move to the charging roller 2 side, the atomized toner contaminates the charging roller 2. If the amount of contamination of the charging roller 2 with the mist toner is large, the difference in the degree of contamination becomes large depending on the position on the surface of the charging roller 2 due to factors such as the shape of the charging roller 2, the contact pressure between the charging roller 2 and the photosensitive drum 1, the roughness of the surface layer of the charging roller 2, etc. This difference in the degree of contamination induces latent non-uniformity of the potential VD before exposure, and results in the generation of an image having non-uniformity of image density of the cycle of the charging roller 2.

[0097] Cleaning operation on the charging roller surface

[0098] Subsequently, the cleaning operation control in Embodiment 1 will be described. In order to facilitate understanding of various types of potential control in the cleaning operation control in Embodiment 1, the cleaning operation control in Embodiment 1 will be described by using Figure 5 To explain. Figure 5 1 is a diagram illustrating a cleaning operation of the charging roller 2 in the image forming apparatus 100 in Embodiment 1. Figure 5 , the time change of each of the driving signal of the motor, the charging voltage applied to the charging roller 2, the surface potential in the charging portion ES of the photosensitive drum 1, and the difference between the surface potential of the photosensitive drum 1 and the charging voltage applied to the charging roller 2 is shown in order from top to bottom. Note that Figure 5 The motor whose driving signal is shown in FIG. 1 is a motor for driving the driving portion of the photosensitive drum 1, the charging roller 2, and the developing roller 4. Figure 5 The horizontal axis is time.

[0099] In the cleaning operation, first, -1200V is applied only to the portion of the length of the charging roller 2 corresponding to one circumference of the photosensitive drum 1, and the charging roller 2 charges the surface of the photosensitive drum 1 to -600V. After that, an operation of alternately applying two voltages to the charging roller 2, i.e., -1200V and 0V (OFF), is performed 10 times for each voltage. By giving a potential difference of 600V to each of the toner of the positive polarity and the toner of the negative polarity with respect to the surface potential of -600V of the photosensitive drum 1, the toner is moved from the charging roller 2 to the surface of the photosensitive drum 1. When the toner of both the positive polarity and the negative polarity on the surface of the charging roller 2 moves to the photosensitive drum 1 side by the potential difference formed between the surface of the photosensitive drum 1 and the charging roller 2, the amount of toner contamination on the surface of the charging roller 2 is reduced. The toner that has moved to the photosensitive drum 1 is then recovered by the developing roller 4 and is accommodated in the developing device 8.

[0100] As described above, in the cleaning operation, a charging voltage of 0 V and a smaller charging voltage of -1200 V, which are greater than the surface potential of the photosensitive drum 1, are alternately applied to the charging roller 2 by the charging voltage applying circuit. By regularly performing the cleaning operation as above, the amount of toner contamination of the charging roller 2 is reduced, and the generation of images having image density unevenness having a generation period in halftone images and the like can be suppressed.

[0101] If the cleaning operation of the charging roller surface is performed at a high frequency, the effect of suppressing the image density unevenness generated in the halftone image is improved, but the development drive distance relative to the number of printed sheets increases, and therefore, the toner deterioration progresses. In particular, in the case where image formation with a small toner usage amount relative to the number of printed sheets is mainly performed so that the halftone image is not printed, etc., the progress of the toner deterioration degree is remarkable. That is, the high-frequency cleaning operation can suppress the generation of image density unevenness of the halftone image, but there is a concern that defective images such as fogged images on the white background portion caused by the reduced charge amount of the toner due to the progress of the toner deterioration may appear at an early stage.

[0102] Furthermore, in a configuration in which the photosensitive drum 1 and the developing roller 4, the supply roller 5, etc. are synchronously driven by a common driving source, each time the cleaning operation is performed, the driving time of the developing device 8 is extended, and toner degradation may be particularly prone to progress. However, for users who do not perform printing of images in which image density unevenness may generally matter (such as halftone images), the cleaning operation does not necessarily have to be performed.

[0103] Therefore, the image forming device 100 of Embodiment 1 is configured to be able to execute two modes - that is, a first mode and a second mode as printing modes (image forming modes). The first mode is a normal printing mode, having the main purpose of not generating image density unevenness of a halftone image by periodically performing a cleaning operation of the surface of the charging roller. Here, the term periodically refers to, for example, every predetermined number of jobs, every predetermined driving time, each start of the image forming device 100, etc. The second mode is a text printing mode, having the main purpose of excluding the periodic cleaning operation of the surface of the charging roller and suppressing the progression of toner deterioration. For users who can allow the generation of image density unevenness on a halftone image, the generation of a fogged image can be suppressed by using the text printing mode.

[0104] In a text image, the toner consumption is generally less than that of a halftone image, etc., and the print percentage is low. Therefore, the text printing mode may also be referred to as a low print percentage mode or a low consumption mode.

[0105] The print percentage can be detected by a measuring means (pixel count) capable of counting the number of pixels (pixels) of light emitted by the scanner unit of the exposure device 10. The measuring means of the print percentage may be configured by the control section 200, or may be provided separately from the control section 200. The pixel count counts individual image signals of image dots forming an image to be formed. The control section 200 estimates the amount of toner required for developing an image as a toner consumption used for printing per sheet of paper based on the number of pixels of light emitted by the scanner unit.

[0106] Note that the print percentage detection means is not limited to the print percentage detection system by pixel counting described above. For example, when the image forming apparatus 100 is configured to be able to replenish toner using a toner pack or the like, detection can be performed based on the detection result of the developer container weight at the previous toner replenishment timing, the detection result of the current developer container weight, and the number of sheets passed during the period.

[0107] Hereinafter, an example of a toner replenishing configuration of the image forming apparatus 100 configured to replenish toner will be described. The image forming apparatus 100 is configured to replenish toner by forming a replenishing port 53a for replenishing developer to the toner containing chamber 8a in the developing device 8, for example. Figure 6 It is a perspective view of the developing device 8 of the image forming apparatus 100 configured to be able to replenish toner.

[0108] Figure 6 The developing device 8 shown in FIG. 1 has a first protruding portion 37 as a protruding portion protruding upward from one end portion in the longitudinal direction of the toner accommodating chamber 8a and communicating with the toner accommodating chamber 8a, and a second protruding portion 38 protruding upward from the other end portion in the longitudinal direction of the toner accommodating chamber 8a. An attachment portion 53 capable of attaching a toner pack 51 is provided on an upper end portion (distal end portion) of the first protruding portion 37, and a replenishment port 53a for replenishment of the developer from the toner pack 51 to the toner accommodating chamber 8a is formed in the attachment portion 53. The toner pack 51 can be attached to the attachment portion 53 in a state exposed to the outside of the device. From the viewpoint of operability of toner replenishment, it is particularly preferred that the developing device 8 is constructed so that the toner replenished through the replenishment port 53a reaches the stirring member 7 only by its own weight.

[0109] In addition, the developing device 8 includes a grip portion 39 having a handle portion 39a that can be grasped by a user by hooking a finger. The handle portion 39a is formed by protruding upward from the top surface of the grip portion 39. The first protruding portion 37 is formed with a hollow shape inside, and a replenishing port 53a is formed on the upper surface. In addition, the space inside the first protruding portion 37 is communicated with the toner accommodating chamber 8a. The replenishing port 53a is configured to be connected to the toner bag 51.

[0110] The toner pack 51 is configured to be detachably attached to the attachment portion 53 of the first protruding portion 37. In addition, the toner pack 51 has a shutter member 51a provided at the opening portion and capable of opening / closing, and a plurality of (three in the present embodiment) protrusions 51b formed corresponding to a plurality of (three in the present embodiment) groove portions 53b formed in the attachment portion 53. When the user replenishes the developing device 8 with toner, positioning is performed so that the protrusions 51b of the toner pack 51 pass through the groove portions 53b of the attachment portion 53, and the toner pack 51 is connected to the attachment portion 53. And by rotating the toner pack 51 180 degrees in this state, the shutter member 51a of the toner pack 51 abuts against the abutting portion (not shown) of the attachment portion 53, and rotates relative to the main body of the toner pack 51, and the shutter member 51a opens. As a result, the toner contained in the toner pack 51 leaks out of the toner pack 51, and the leaked toner enters the hollow-shaped first protruding portion 37 through the replenishment port 53a. Note that the shutter member 51a may be provided on the replenishment port 53a side. The present application invention may also be applied to the image forming apparatus 100 configured as above.

[0111] Print mode change operation

[0112] Subsequently, the change of the printing mode based on the travel distance (also referred to as the surface movement distance, the number of rotations, the rotation distance, etc.) of the developing roller 4 and the amount of toner used will be described. In Embodiment 1, the printing mode is set to the normal printing mode in the initial setting. And the control section 200 is configured to be able to propose a change of the printing mode from the normal printing mode to the text printing mode based on the developing amount information related to the amount of toner 3 accommodated in the toner accommodation chamber 8a and the developing drive information related to the moving distance of the surface of the developing roller 4.

[0113] In Embodiment 1, the developer amount information is the toner remaining amount T contained in the toner containing chamber 8a and the toner initial remaining amount T0 and is acquired by the toner amount sensor 20 as the first acquisition section. In addition, the developer drive information is the cumulative travel distance R0 of the developing roller 4 and is acquired by the travel distance detection device 400 as the second acquisition section. Hereinafter, a method of proposing a change in the printing mode based on the above information will be described in more detail.

[0114] In Embodiment 1, when the cumulative number of printed sheets NO reaches a predetermined number of printed sheets, if the ratio of the toner usage amount to the travel distance of the developing roller 4 (= toner usage rate TR) is lower than a threshold value, a change from the normal printing mode to the text printing mode is prompted. This is because the fact that the toner usage rate TR is low is considered to indicate that text printing, in which the toner consumption is generally smaller than that of a halftone image, is mainly performed, and there is a high probability that the cleaning operation of the charging roller 2 is excessively performed.

[0115] The toner usage rate (developer usage rate) TR is calculated based on the cumulative travel distance R0 of the developing roller 4 stored in the memory 15 and the toner usage amount since the developing device 8 is new. The toner usage amount can be calculated based on the difference between the toner initial remaining amount T0 stored in advance in the memory 15 and the toner remaining amount T calculated by the toner amount calculation part 300. In Embodiment 1, the toner usage rate TR is calculated by TR=(T0-T) / R0. Note that the toner initial remaining amount T0 is the toner remaining amount when the developing device 8 is new.

[0116] In Embodiment 1, when the cumulative number of printed sheets N0 reaches 5000, if the toner usage rate TR is lower than 1.5 μg / mm, a change (switching) of the printing mode from the normal printing mode to the text printing mode is prompted.

[0117] Will be used by Figure 7 The method of prompting the print mode to change (switch) in the first embodiment is described. Figure 7 This is a flowchart for prompting a change in printing mode in the first embodiment.

[0118] First, when the power of the image forming apparatus 100 is turned on (S100), the control part 200 determines whether the printing mode is a text printing mode. Here, if the printing mode is a text printing mode, the process proceeds to S110, and the image forming operation is performed. On the other hand, if the printing mode is not a text printing mode but a normal printing mode, the process proceeds to S102.

[0119] At S102, the control section 200 communicates with the memory 15 (memory tag) of the process cartridge 9 and reads out the cumulative number of printed sheets N0. This cumulative number of printed sheets N0 is information when the image forming apparatus 100 was stopped last time, and corresponds to the number of sheets printed since the developing device 8 was new.

[0120] Subsequently, at S103, the control section 200 determines whether the cumulative number of printed sheets N0 is equal to or greater than a threshold value. Here, if the cumulative number of printed sheets N0 is less than the threshold value and the number of printed sheets has not yet reached a predetermined number of sheets, the process proceeds to S110, and the image forming operation is performed. On the other hand, if the cumulative number of printed sheets N0 is equal to or greater than the threshold value and has reached a predetermined number of printed sheets, the process proceeds to S104.

[0121] At S104, the control section 200 communicates with the memory 15 of the process cartridge 9 and reads out the toner remaining amount T and the initial toner remaining amount T0 when the developing device 8 is new. This toner remaining amount T is information when the image forming apparatus 100 was stopped last time and is a value calculated by the toner amount calculation section 300.

[0122] Subsequently, at S105, the control section 200 communicates with the memory 15 of the process cartridge 9 and reads out the cumulative travel distance R0 of the developing roller 4. This cumulative travel distance R0 is information when the image forming apparatus 100 was stopped last time and is a value counted by the travel distance detection device 400.

[0123] Subsequently, at S106, the control section 200 calculates the toner usage rate TR based on the toner remaining amount T, the toner initial remaining amount T0 and the cumulative travel distance R0. The toner usage rate TR is calculated by TR=(T0-T) / R0 as described above.

[0124] Subsequently, at S107, the control section 200 determines whether the toner usage rate TR is less than a predetermined threshold value. Here, if the toner usage rate TR is equal to or greater than the threshold value, the process proceeds to S110, and the image forming operation is performed without any notification to the user. On the other hand, if the toner usage rate TR is less than the threshold value, the process proceeds to S108.

[0125] At S108, the user is asked to select whether to change the print mode to the text print mode. In Embodiment 1, the proposal of mode change to the user is performed through a display on the operation panel 60. If the user chooses not to change the print mode to the text print mode, that is, when the user chooses to continue the print mode as the normal print mode, the process proceeds to S110, and the image forming operation is performed in the normal print mode.

[0126] On the other hand, at S108, if the user selects to change the printing mode to the text printing mode, the process proceeds to S109, the printing mode is changed to the text printing mode, and the text printing mode is recorded as the printing mode in the memory 15. Then, the process proceeds to S110, and the image forming operation is performed in the text printing mode.

[0127] Notice, Figure 7The flowchart in is only an example of the operation proposed for the print mode change, and the method, order, etc. of each process may be appropriately changed. For example, the readout (S104) of the toner remaining amount T and the toner initial remaining amount T0 may be performed after the readout (S105) of the cumulative travel distance R0. In addition, for example, the readout (S104) of the toner remaining amount T and the toner initial remaining amount T0 and the readout (S105) of the cumulative travel distance R0 may be performed at the same time as the readout (S102) of the cumulative number of printed sheets N0. In addition, for example, the processing from the readout (S104) of the toner remaining amount T and the toner initial remaining amount T0 to the determination (S107) of whether the toner usage rate TR is less than the threshold value may be performed before the readout (S102) of the cumulative number of printed sheets N0.

[0128] In Embodiment 1, the suggestion to the user to change the printing mode or the user's selection instruction to change the printing mode is performed through the operation panel 60, but it may be performed through other display parts or operation parts of the image forming apparatus 100 or external devices.

[0129] Evaluation Experiment

[0130] Subsequently, in Embodiment 1, an evaluation experiment performed to verify the effect when a change is made from the normal printing mode to the text printing mode will be described. In this experiment, with respect to Embodiment 1 and Comparative Example 1, a printing operation of 2 sheets per job for 10,000 recording materials was continuously performed under an environment of 25°C / 50%RH. For the printing operation, a horizontal line with an image printing percentage of 1.0% was used as image data.

[0131] In the normal printing mode of Example 1, it is configured so that a cleaning operation on the surface of the charging roller 2 is performed every ten print sheets (every five print jobs) in the printing operation. It is configured so that in the normal printing mode, by executing the cleaning sequence as above, the developing drive distance of each print sheet becomes 1.5 times that of the text printing mode. As a result, the toner usage rate TR in the normal mode in this evaluation experiment is 1.3μg / mm and the toner usage rate TR in the text printing mode is 2.0μg / mm. In addition, as the developing device 8 in Example 1, a developing device in which 100g of toner is contained in the toner containing chamber 8a when the device is new is used. Comparative Example 1 is configured similarly to Example 1 except that the printing mode is not changed.

[0132] In the evaluation experiment, for Example 1 and Comparative Example 1, the number of printed sheets at which fogged images appeared and the toner residual amount T at the timing of fogged images appearing were evaluated. In Example 1, when the cumulative number of printed sheets N0 reached 5000, the printing mode was changed to the text printing mode. In Comparative Example 1, the change of the printing mode was not performed, and the image forming operation was continued in the normal printing mode. Table 1 illustrates the evaluation results of Example 1 and Comparative Example 1.

[0133] [Form 1]

[0134]

[0135] As shown in Table 1, in Example 1, fogged images occurred when the cumulative number of printed sheets N0 was 8000, and the remaining amount of toner at this time was 60.0 g. On the other hand, in Comparative Example 1, fogged images occurred when the cumulative number of printed sheets N0 was 7000, and the remaining amount of toner at this time was 65.0 g.

[0136] As can be seen from the above results, the timing of the appearance of the fogged image of Example 1 is slower than that of Comparative Example 1 (the cumulative number of printed sheets N0 is larger), and the toner residual amount T becomes smaller. That is, in Example 1 in which the printing mode is changed to the text printing mode, the deterioration of the toner is suppressed, and therefore, the appearance of the fogged image can be suppressed, and the amount of toner usable before the deterioration is increased compared with Comparative Example 1.

[0137] As described above, the image forming apparatus 100 according to Embodiment 1 is configured to be able to execute the normal printing mode and the text printing mode, and prompts the user to make a change from the normal printing mode to the text printing mode based on the toner usage rate TR calculated according to the user's usage. That is, according to the configuration of Embodiment 1, since the printing mode is configured to be able to be changed to the text printing mode excluding the cleaning sequence, the occurrence of fogged images can be suppressed.

[0138] Note that Embodiment 1 is configured so that the cleaning operation on the surface of the charging roller is excluded in the text printing mode, but may be configured to perform the cleaning operation at a lower frequency than in the normal printing mode. In the above configuration, compared with the image forming apparatus 100 that performs only the normal printing mode, the contamination of the charging roller 2 is suppressed, the occurrence of fogged images is suppressed, and the amount of toner that can be used before deterioration is increased.

[0139] Example 2

[0140] Subsequently, Embodiment 2 according to the present invention will be described. The basic configuration and operation of the image forming apparatus 100 of Embodiment 2 are similar to those of the image forming apparatus 100 in Embodiment 1. In the following description, the same symbols are given to configurations similar to those in Embodiment 1, and the description will be omitted, and the characteristic portion of Embodiment 2 will be mainly described. Embodiment 2 is different from Embodiment 1 in that the user is prompted to change the print mode based on the toner deterioration degree W.

[0141] The change of the printing mode based on the travel distance of the developing roller 4 and the amount of toner used in Embodiment 2 will be described. In Embodiment 2, the printing mode is set to the normal printing mode as an initial setting. And the control section 200 proposes a change of the printing mode based on the developer amount information related to the amount of toner 3 contained in the toner containing chamber 8a, the developer drive information related to the moving distance of the surface of the developing roller 4, and the developer consumption information related to the consumed toner amount. More specifically, the control section 200 proposes a change of the printing mode from the normal printing mode to the text printing mode based on the toner deterioration degree W calculated from the developer amount information, the developer drive information, and the developer consumption information.

[0142] In Embodiment 2, the developer amount information is the toner remaining amount T contained in the toner containing chamber 8a and is obtained by the toner amount sensor 20 as the first obtaining section. In addition, the development drive information is the section travel distance Rc which is the travel distance of a predetermined section of the developing roller 4 and is obtained by the travel distance detection device 400 as the second obtaining section. In addition, the developer consumption amount information is the toner consumption amount Tc consumed in the predetermined section and can be calculated by the toner remaining amount T obtained by the toner amount sensor 20 and the like. Hereinafter, a method of proposing a change in the printing mode based on these information will be described in more detail.

[0143] Toner deterioration degree

[0144] As described above, in Embodiment 2, the user is prompted to change the print mode based on the toner degradation degree (developer degradation degree) W. Therefore, first, the details of the toner degradation degree W will be described. The toner degradation degree W is a value having an initial value of "0", which counts up as the developing roller 4 is driven in rotation, and gradually rises as the toner degradation progresses. In addition, since the toner degradation degree W in Embodiment 2 is the average degradation degree of the entire toner in the developing device expressed in numerical values, if the amount of toner in the developing device 8 is small, the progression speed of the degradation degree becomes high, and the toner degradation degree W may easily become large.

[0145] In Embodiment 2, by actually measuring or estimating these parameters, the toner deterioration degree W can be calculated based on a calculation method to be described below. In Embodiment 2, the following method is used: each time two sheets of paper as recording materials (recording media) are output as a predetermined section, the toner deterioration degree W is calculated.

[0146] The formula (1) used to calculate the toner degradation degree W in Example 2 is as follows:

[0147] W n = W n-2 + (1 / T n-2 ) * (Rc / Tc) ... Formula (1)

[0148] Each parameter used in formula (1) is as follows:

[0149] Toner degradation degree at the end of driving of the n-th print sheet: W n

[0150] Toner degradation degree at the end of driving of the n-2th printing sheet: W n-2

[0151] Segment travel distance of the developing roller driven on the n-1th and nth printing sheets: Rc

[0152] Remaining amount of toner at the end of driving the n-2th printing sheet: T n-2

[0153] Amount of toner consumed during image forming operations of the n-1th and nth print sheets: Tc

[0154] According to formula (1), if the developing roller driving distance per printing sheet is large, the segment travel distance Rc of the developing roller 4 becomes large, and therefore, the degree of increase in the degree of toner deterioration W becomes large. In addition, if the amount of toner consumed per printing sheet is small, the amount of toner consumed during driving Tc becomes small, and therefore, the degree of increase in the degree of toner deterioration becomes large.

[0155] Note that the predetermined section for calculating the toner degradation degree W does not necessarily have to be calculated every two sheets, but may be each job, each predetermined number of sheets, or each expected developing roller travel distance. That is, the toner degradation degree W2 immediately after the end of the predetermined section may be calculated based on the toner residual amount T1 and the toner degradation degree W1 immediately before the start of the predetermined section, the travel distance (movement distance) Rc of the developing roller 4 in the predetermined section, and the toner consumption amount Tc consumed in the predetermined section. By applying these parameters to formula (1), the toner degradation degree (developer degradation degree) W2 immediately after the end of the predetermined section is expressed by the following formula (2):

[0156] W2 = W1 + (1 / T1) * (Rc / Tc) ... Formula (2)

[0157] Calculation method of toner deterioration degree

[0158] Will be used by Figure 8 The calculation method of the toner degradation degree W in Example 2 will be described. Figure 8 This is a flowchart of a calculation method for calculating the degree of toner degradation in Embodiment 2. The calculation method example described here is for the case of printing two sheets in one job for the sake of convenience.

[0159] First, when the power of the image forming apparatus 100 is turned on (S200), at S201, the control section 200 communicates with the memory 15 of the process cartridge 9 and reads out the toner remaining amount T n-2 and toner degradation degree W n-2 . Toner Remaining Amount T n-2 and toner degradation degree W n-2 It is information when the image forming apparatus 100 was stopped last time and information when the printing operation of the number of printed sheets n-2 is completed.

[0160] Subsequently, at S202, the image formation preparation operation is started. Then, at S203, the rotational drive of the developing roller 4 is started, and the counting of the segment travel distance Rc of the developing roller 4 is started.

[0161] Subsequently, at S204, as an image forming operation, a printing operation of two recording materials is performed. Here, an image forming operation of the n-1th printing sheet and the nth printing sheet is performed. Then, at S205, the image forming operation is completed. Then, at S206, the rotation drive of the developing roller 4 is completed, and the counting of the segment travel distance Rc of the developing roller 4 is stopped.

[0162] Subsequently, at S207, the control section 200 calculates the toner consumption amount Tc during the rotational drive of the developing roller 4. The toner consumption amount Tc is calculated by taking the toner remaining amount Tc stored in the memory 15. n-2 The toner remaining amount T detected by the toner amount sensor 20 immediately before n Note that in Embodiment 2, the calculation of the toner consumption amount Tc is performed after the image formation is completed, but it may be performed during the image forming operation (before S206).

[0163] Subsequently, at S208, the control section 200 determines the toner degradation degree W based on the toner degradation degree W. n-2 , Toner Remaining Amount T n-2 , the segment travel distance Rc of the developing roller 4 and the toner consumption Tc, and calculate the toner degradation degree W at the time point when the printing of the nth sheet ends n Then, the control section 200 communicates with the memory 15 of the process cartridge 9 and writes the toner degradation degree W at the n-th sheet printing end time point. n and the remaining amount T of toner in the toner containing chamber 8a n Related information.

[0164] Print mode change operation based on toner deterioration degree

[0165] Subsequently, the change of the printing mode based on the toner deterioration degree W will be described. In Embodiment 2, a configuration is made so that if the toner deterioration degree W exceeds a threshold value for a predetermined number of printed sheets, a change of the printing mode from the normal printing mode to the text printing mode is prompted. In Embodiment 2, a plurality of predetermined cumulative numbers of printed sheets N0 and a plurality of threshold values ​​of the toner deterioration degree W corresponding to the predetermined numbers of sheets are set. Table 2 shows the relationship between the cumulative number of printed sheets N0 and the threshold value of the toner deterioration degree W.

[0166] [Form 2]

[0167]

[0168] As shown in Table 2, in Embodiment 2, configuration is made so that if the toner deterioration degree W is 15 or more when the cumulative number of printed sheets N0 reaches 2000, a change from the normal printing mode to the text printing mode is prompted. Similarly, the threshold value of the toner deterioration degree W when the cumulative number of printed sheets N0 is 4000 is 35, the threshold value of the toner deterioration degree W when the cumulative number of printed sheets N0 is 6000 is 55, and the threshold value of the toner deterioration degree W when the cumulative number of printed sheets N0 is 80 is 80.

[0169] Will be used by Fig. 9 The method of prompting a change in printing mode in the second embodiment is described below. Fig. 9 This is a flowchart for prompting a change in printing mode in the second embodiment.

[0170] First, when the power of the image forming apparatus 100 is turned on (S300), the control part 200 determines whether the printing mode is a text printing mode. Here, if the printing mode is a text printing mode, the process proceeds to S308, where an image forming operation is performed. On the other hand, if the printing mode is not a text printing mode but a normal printing mode, the process proceeds to S302.

[0171] At S302, the control section 200 communicates with the memory 15 of the process cartridge 9 and reads out the toner deterioration degree W. This toner deterioration degree W is information when the image forming apparatus 100 was stopped last time, and corresponds to Figure 8 The toner degradation degree W described in the flowchart in n .

[0172] Subsequently, at S303, the control section 200 communicates with the memory 15 of the process cartridge 9 and reads out the cumulative printed sheet number N0. This cumulative printed sheet number N0 is information when the image forming apparatus 100 was last stopped, and corresponds to the number of sheets printed since the developing device 8 was in a new state.

[0173] Subsequently, at S304, the control section 200 determines whether the cumulative number of printed sheets N0 is equal to or greater than a threshold value. In Embodiment 2, the threshold values ​​of the cumulative number of printed sheets N0 are 2000, 4000, 6000, and 8000 as shown in Table 2 above. If the cumulative number of printed sheets N0 has not yet reached the threshold value, the process proceeds to S308, and the image forming operation is performed without notifying the user of anything. On the other hand, if the cumulative number of printed sheets N0 is equal to or greater than the threshold value, the process proceeds to S305. This determination process is performed each time the cumulative number of printed sheets N0 reaches each threshold value.

[0174] Subsequently, at S305, the control section 200 determines whether the toner degradation degree W is equal to or greater than a threshold value. In Embodiment 2, the threshold value of the toner degradation degree W is shown in the above-mentioned Table 2, and varies depending on the cumulative number of printed sheets N0. If the toner degradation degree W is less than the threshold value, the process proceeds to S308, and the image forming operation is performed without notifying the user of anything. On the other hand, if the toner degradation degree W is equal to or greater than the threshold value, the process proceeds to S306.

[0175] At S306, the user is asked to select whether to change the print mode to the text print mode. In Embodiment 2, a proposal of mode change to the user is made through a display on the operation panel 60. If the user selects that the print mode is not to be changed to the text print mode, that is, if the user selects to continue the print mode of the normal print mode, the process proceeds to S308, and the image forming operation is performed in the normal print mode.

[0176] On the other hand, if the user selects to change the printing mode to the text printing mode in S306, the process proceeds to S307, the printing mode is changed to the text printing mode, and the text printing mode is recorded as the printing mode in the memory 15. And the process proceeds to S308, and the image forming operation is performed in the text printing mode.

[0177] Notice, Fig. 9 The flowchart in the figure merely presents an example of the operation for the print mode change, and the method, order, etc. of each process may be changed appropriately. For example, the readout (S302) of the toner deterioration degree W may be performed after the determination (S304) of whether the cumulative number of printed sheets N0 is equal to or greater than the threshold value. Furthermore, for example, the determination (S305) of whether the toner deterioration degree W is equal to or greater than the threshold value may be performed before the readout (S303) of the cumulative number of printed sheets N0.

[0178] Evaluation Experiment

[0179] Subsequently, an evaluation experiment performed to verify the effect when a change is made from the normal printing mode to the text printing mode in Embodiment 2 will be described. In this experiment, a printing operation of 2 sheets per job for 10,000 recording materials was continuously performed under an environment of 25°C / 50%RH with respect to Embodiment 2 (2-1, 2-2, 2-3, 2-4) and Comparative Example 2. For the printing operation, a horizontal line with an image printing percentage of 1.0% was used as image data.

[0180] In the normal printing mode of Embodiment 2, it is configured so that the cleaning operation on the surface of the charging roller 2 is performed every ten printing sheets (every five printing jobs) in the printing operation. It is configured so that in the normal printing mode, by performing the cleaning sequence as above, the developing drive distance of each printing sheet becomes 1.5 times that of the text printing mode. In addition, as the developing device 8 in Embodiment 2, a developing device in which 100 g of toner is accommodated in the toner accommodating chamber 8a when the device is new is used. Comparative Example 2 is configured similarly to Embodiment 2 except that the printing mode is not changed.

[0181] In the evaluation experiment, for Example 2 and Comparative Example 2, the number of printed sheets at which fogged images appeared and the residual toner amount T and the degree of toner deterioration W at the timing of the fogged images appearing were evaluated. In this experiment, for Example 2, Examples 2-1, 2-2, 2-3, and 2-4 in which the timing of the printing mode being changed from the normal printing mode to the text printing mode was changed were evaluated. In Example 2-1, since the developing device 8 was new (starting), the printing mode was set to the text printing mode. When the cumulative number of printed sheets N0 reached 2000 sheets in Example 2-2, when the cumulative number of printed sheets N0 reached 4000 sheets in Example 2-3, and when the cumulative number of printed sheets N0 reached 6000 sheets in Example 2-4, the printing mode was changed to the text printing mode, respectively. In Comparative Example 2, no change in the printing mode was made, and the image forming operation was continued in the normal printing mode. Table 3 shows the evaluation results of Examples 2-1, 2-2, 2-3, 2-4 and Comparative Example 2.

[0182] [Form 3]

[0183]

[0184] As shown in Table 3, in Example 2-1 where the printing mode is always the text printing mode, fogged images do not appear even when the cumulative number of printed sheets N0 reaches 10,000. Also, the toner residual amount T when the cumulative number of printed sheets N0 of Example 2-1 is 10,000 is 50.0 g, and the toner deterioration degree W is 110.

[0185] In Example 2-2 in which the print mode was switched to the text print mode when the cumulative number of printed sheets N0 was 2000, fogged images occurred when the cumulative number of printed sheets N0 reached 9500. The toner remaining amount T at this time was 52.5 g, and the toner deterioration degree W was 115.

[0186] In Embodiment 2-3 in which the printing mode was switched to the text printing mode when the cumulative number of printed sheets N0 was 4000, fogged images occurred when the cumulative number of printed sheets N0 was 9000. The toner remaining amount T at this time was 55.0 g, and the toner deterioration degree W was 116.

[0187] In Embodiment 2-4 in which the print mode is switched to the text print mode when the cumulative number of printed sheets N0 is 6000, fogged images occur when the cumulative number of printed sheets N0 is 8000. The toner remaining amount T at this time is 60.0 g, and the toner deterioration degree W is 115.

[0188] In Comparative Example 2 where the print mode is always the normal print mode, fogged images occur when the cumulative number of printed sheets N0 is 7000. The toner remaining amount T at this time is 65.0 g, and the toner deterioration degree W is 115.

[0189] As described above, in these experiments, it is known that a fogged image on a white background portion appears at the cumulative number of printed sheets N0 at which the degree of toner deterioration reaches 115. Moreover, in each example of Embodiment 2, the timing of the appearance of the fogged image is later (the cumulative number of printed sheets N0 is larger) compared with Comparative Example 2, and the toner residual amount T becomes smaller. Moreover, the printing mode change from the normal printing mode to the text printing mode is made at an earlier stage, the timing of the appearance of the fogged image becomes later, and the toner residual amount T becomes smaller. That is, in Embodiment 2 where the printing mode can be changed to the text printing mode, the progression of the degree of toner deterioration is suppressed, and the usable toner amount is increased, compared with Comparative Example 2.

[0190] As described above, the image forming apparatus 100 according to Embodiment 2 is configured to be able to execute the normal printing mode and the text printing mode, and prompts the user to change from the normal printing mode to the text printing mode based on the toner deterioration degree W calculated according to the user's usage. That is, according to the configuration of Embodiment 2, since the configuration is performed so that the printing mode can be changed to the text printing mode excluding the cleaning sequence, the occurrence of fogged images can be suppressed.

[0191] Note that Embodiments 1 and 2 are configured so that the normal printing mode can be changed to the text printing mode, but are preferably configured so that the text printing mode cannot be changed (returned) to the normal printing mode. This is because, by using in the text printing mode, the toner contamination of the charging roller 2 progresses more than the state of use in the normal printing mode, and it is difficult to improve the toner contamination to the same extent as the case of continuous use of the image density unevenness of the halftone image in the normal printing mode. However, if the time period for performing the image forming operation in the text printing mode is short, the toner contamination of the charging roller 2 does not progress to the state where the toner contamination is too heavy to be used, and therefore, it can be configured so that the text printing mode can be changed to the normal printing mode.

[0192] Note that, Embodiments 1 and 2 are configured so that the cleaning operation on the surface of the charging roller is not performed in the text printing mode, but can be configured so that the cleaning operation is performed at a frequency lower than that of the normal printing mode. In the above configuration, compared with the image forming apparatus 100 that performs only the normal printing mode, the contamination of the charging roller 2 is suppressed, and the occurrence of fogged images can be suppressed.

[0193] In addition, Embodiment 2 is configured to prompt a change in the printing mode when the pre-set degree of toner degradation for each of the number of printed sheets is equal to or greater than a threshold value, but can be configured so that a change in the printing mode is prompted (proposed) in the initial setting operation. Here, the initial setting operation includes a user setting operation when a new image forming device 100 is started for the first time and a pre-shipment setting operation for determining the settings when the product is shipped. In the initial setting operation, the user or service personnel decides whether to change the printing mode. Specifically, for example, it can be configured so that at the start of the image forming device 100, when the toner residual amount T is the initial toner residual amount T0 and the cumulative travel distance R0 of the developing roller 4 is zero, a change in the printing mode is proposed. The above configuration is particularly effective when it is known in advance that a use will be made to reduce the toner usage rate TR.

[0194] In addition, Embodiments 1 and 2 are configured to be able to propose a change in the printing mode, and whether the printing mode is to be changed is left to the user to decide, but the control section 200 may be configured to be able to determine whether the printing mode is to be changed. For example, in Embodiment 2, it may be configured so that if the toner degradation degree W is equal to or greater than the threshold value when the predetermined cumulative number of printed sheets N0 is reached, the control section 200 decides on the change in the printing mode and changes the normal printing mode to the text printing mode. Alternatively, by associating the proposal for a change in the image forming mode with maintenance, it may be configured so that when the service personnel is to perform maintenance, the change in the image forming mode is proposed to the service personnel.

[0195] In addition, Embodiments 1 and 2 are configured so that the first mode and the second mode in which the frequencies of performing the cleaning operation of the charging member are different can be executed as the printing mode, and the change of the printing mode is prompted based on the developer amount information and the development drive information, but they are not restrictive. For example, instead of the cleaning operation, by focusing on the operation other than the image forming operation driven by the development device 8 and which can promote the deterioration of the toner, the image forming mode can be divided into the first mode and the second mode, and the frequency of driving the developing roller 4 in the second mode is lower than that in the first mode. In the above configuration, the change of the printing mode is also promoted or determined according to the use of the image forming apparatus 100, so that the occurrence of defective images can be suppressed.

Claims

1. An image forming device, comprising: an image bearing member, the image bearing member being rotatable; a charging member that is rotatable and charges the image bearing member; a developing member that is rotatable and supplies a developer to a surface of the image bearing member; a developer accommodating portion that accommodates therein a developer supplied to the developing member; a first acquisition section that acquires developer amount information related to an amount of developer accommodated in the developer accommodating section; a second acquisition section that acquires development drive information related to a movement distance on a surface of the development member; as well as A control part, which is capable of executing a first mode and a second mode as image forming modes, wherein the frequency of driving the developing member in the second mode is lower than that in the first mode, and the control part proposes or determines a change of the image forming mode from the first mode to the second mode based on the developer amount information and the developer drive information.

2. The image forming apparatus according to claim 1, wherein In the first mode, a cleaning operation is performed regularly, in which the developer adhering to the surface of the charging member is moved to the image bearing member to clean the charging member, while in the second mode, the cleaning operation is performed at a frequency lower than that of the first mode or the cleaning operation is not performed.

3. The image forming apparatus according to claim 2, wherein The developer amount information is the remaining amount of developer contained in the developer containing portion, the developer drive information is the cumulative moving distance, the cumulative moving distance is the cumulative moving distance of the surface of the developing member, and assuming that the remaining amount of developer is T, the cumulative moving distance is R0, and the initial remaining amount of developer pre-contained in the developer containing portion is T0, the control portion proposes a change from the first mode to the second mode based on the developer usage rate TR calculated by TR=(T0-T) / R0.

4. The image forming apparatus according to claim 3, wherein The control portion proposes a change from the first mode to the second mode in a case where the developer usage rate TR is smaller than a predetermined threshold value.

5. The image forming apparatus according to claim 4, wherein The control portion determines whether the developer usage rate TR is smaller than the threshold value in a case where the cumulative number of printed sheets of the recording material reaches a predetermined number of sheets.

6. The image forming apparatus according to claim 2, wherein A change from the first mode to the second mode is proposed based on a degree of developer deterioration inside a developing device consisting of the developer accommodating portion and a developing member accommodating chamber accommodating the developing member, wherein the degree of developer deterioration is obtained based on the developer amount information and the developing drive information.

7. The image forming apparatus according to claim 6, wherein The developer amount information is the residual amount of developer contained in the developer containing portion, and the developer drive information is the moving distance of a predetermined section of the surface of the developing member, and assuming that the residual amount of developer immediately before the start of the predetermined section is T1, the cumulative moving distance of the predetermined section is Rc, the colorant consumption in the predetermined section is Tc, the degree of developer deterioration immediately before the start of the predetermined section is W1, and the degree of developer deterioration immediately after the predetermined section is W2, the control portion proposes a change from the first mode to the second mode based on the degree of developer deterioration W2 calculated by W2=W1+(1 / T1)*(Rc / Tc).

8. The image forming apparatus according to claim 7, wherein The control portion proposes a change from the first mode to the second mode in a case where the developer degradation degree W2 is equal to or greater than a predetermined threshold value.

9. The image forming apparatus according to claim 8, wherein In a case where the accumulated number of printed sheets of recording material has reached a predetermined number of sheets, the control portion determines whether the developer deterioration degree W2 is equal to or greater than the threshold value.

10. The image forming apparatus according to claim 9, wherein The predetermined number of sheets of the cumulative number of printed sheets and the threshold value of the developer deterioration degree W2 corresponding to the predetermined number of sheets are set in plural.

11. The image forming apparatus according to claim 1, wherein The image forming apparatus is configured such that a change from the second mode to the first mode cannot be made after the first mode is changed to the second mode.

12. The image forming apparatus according to claim 2, further comprising: a voltage applying portion that applies a charging voltage to the charging member, wherein In the cleaning operation, the voltage applying portion alternately applies a charging voltage greater than a surface potential of the image bearing member and a charging voltage less than a surface potential of the image bearing member to the charging member.

13. The image forming apparatus according to claim 1, wherein The control section proposes a change from the first mode to the second mode to a user in an initial setting operation of the image forming apparatus.

14. The image forming apparatus according to claim 1, further comprising: A memory that records whether a currently set image forming mode is any one of the first mode and the second mode.

15. The image forming apparatus according to claim 2, wherein The first acquisition portion is an optical sensor having a light emitting portion that emits light and a light receiving portion that receives the light that is emitted from the light emitting portion and has passed through the inside of the developer accommodating portion, and The optical sensor is provided at a central portion of the developer accommodating portion in a rotation axis direction of the developing member.

16. The image forming apparatus according to claim 2, wherein The developer that has moved from the charging member to the image bearing member in the cleaning operation is recovered by the developing member.

Images