Image forming apparatus

Abstract

An image forming apparatus is disclosed. In an image forming apparatus, a charging member charges an image bearing member; an exposure unit that exposes a surface of the image bearing member to develop the electrostatic latent image; and the developer image on the image bearing member is transferred onto the recording material. The control portion is capable of executing a first operation mode for rotating the image bearing member at a first circumferential speed and a second operation mode for rotating the image bearing member at a second circumferential speed lower than the first circumferential speed, the first operation mode being a mode in which the exposure unit exposes the surface of the image bearing member at a first exposure intensity, and the second operation mode being a mode in which the exposure unit exposes the surface of the image bearing member at a second exposure intensity. The second operation mode is a mode in which the exposure unit exposes the surface of the image bearing member at a second exposure intensity higher than the first exposure intensity.

Description

Technical Field

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

[0002] An electrophotographic system is known as an image recording system for an image forming apparatus such as a laser printer, a copier, and a facsimile machine. The electrophotographic system is a system in which a laser beam is applied to form an electrostatic latent image on a photosensitive drum and the electrostatic latent image is developed by a developer (hereinafter referred to as "toner") which is a charged color material to form a toner image. By transferring and fixing the toner image thus formed onto a recording material, an image is formed on the recording material.

[0003] The toner is contained in the developer container, and when the image formation is repeated, the toner in the developer container is gradually consumed. Therefore, the following configuration is known: the developer container is detachably attached to the device body of the image forming device as an independent unit alone or as part of the processing box, and is replaceable as needed. Then, in recent years, in order to reduce the environmental load and reduce the printing cost, an image forming device having the following configuration has been proposed: when the remaining toner amount in the developer container is reduced, the developer container is directly replenished with only the toner (Japanese Patent Application Publication No. 2022-027631). Summary of the invention

[0004] One of the causes of image failure such as fogging is toner degradation. One of the causes of toner degradation is the flow and agitation of the toner in the developer container. In the image forming operation, the toner in the developer container flows, but the toner used for development is a part of the toner in the developer container, and most of the toner is not used for development but remains in the developer container. When the toner is not used for development but continues to remain in the developer container each time the image forming operation is performed, the toner degradation further proceeds.

[0005] An object of the present invention is to provide a technology capable of reducing the influence of toner degradation on image formation.

[0006] In order to solve the above problems, the image forming device in the present invention includes:

[0007] an image bearing member configured to rotate;

[0008] a charging member configured to contact the image bearing member to charge a surface of the image bearing member;

[0009] a charging voltage applying section configured to apply a charging voltage to the charging member;

[0010] an exposure unit configured to expose the surface of the image bearing member to form an electrostatic latent image on the surface of the image bearing member;

[0011] a developer accommodating portion configured to accommodate a developer therein;

[0012] a developer carrying member configured to carry the developer accommodated in the developer accommodating portion, the developer carrying member configured to rotate and supply the developer to a surface of the image bearing member;

[0013] a driving portion configured to drive the image bearing member and the developer bearing member; and

[0014] a control section configured to control the driving section, the charging voltage applying section and the exposure unit,

[0015] wherein the image forming device transfers a developer image obtained by developing the electrostatic latent image using a developer carried by the developer carrying member onto a recording material to form an image on the recording material, and

[0016] Among them, the control part can execute the following modes:

[0017] a first operation mode for rotating the image bearing member at a first peripheral speed, the first operation mode being a mode in which the exposure unit exposes the surface of the image bearing member at a first exposure intensity; and

[0018] A second operation mode for rotating the image bearing member at a second peripheral speed lower than the first peripheral speed, the second operation mode being a mode in which the exposure unit exposes the surface of the image bearing member at a second exposure intensity higher than the first exposure intensity.

[0019] According to the present invention, the influence of toner degradation on image formation can be reduced.

[0020] 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

[0021] Figure 1 is an explanatory diagram of an image forming apparatus according to an example of the present invention;

[0022] Figure 2 is an explanatory diagram of a control configuration of an image forming apparatus according to an example of the present invention;

[0023] Figure 3A and Figure 3Bis a schematic front view of a toner pack and a schematic cross-sectional view of an image forming apparatus in a state where the toner pack is installed;

[0024] Figure 4 This is an illustration of a grayscale table.

[0025] Figure 5A and Figure 5B is an explanatory diagram of the expansion process; and

[0026] FIG. 6A to FIG. 6C is a diagram showing a configuration example of a remaining toner amount panel. DETAILED DESCRIPTION

[0027] Example 1

[0028] With reference to the accompanying drawings, based on examples, the modes for embodying the present invention are described in detail below in exemplary form. However, the size, material, shape, and relative arrangement of the components described in the embodiments should be appropriately changed depending on the configuration and various conditions of the device to which the present invention is applied. In other words, the size, material, shape, and relative arrangement of the components are not intended to limit the scope of the present invention to the following embodiments.

[0029] Schematic Configuration of Image Forming Apparatus

[0030] refer to Figure 1 , describes a schematic configuration of an image forming apparatus in an example of the present invention. Figure 1 : is a schematic cross-sectional view of the image forming apparatus 100 in this example. The image forming apparatus 100 in this example is a monochrome laser printer capable of forming a black monochrome image on a sheet-like recording material P by using an electrophotographic system.

[0031] The image forming portion 9 has a photosensitive drum 1 as a rotatable drum-shaped (cylindrical) photosensitive member (electrophotographic photosensitive member) serving as an image bearing member. Further, the image forming portion 9 has a charging roller 2 as a roller-shaped charging member of a charging portion and a developing device 8 as a developing unit around the photosensitive drum 1. Further, the image forming portion 9 has a brush member 12 as a paper dust collecting member and a static eliminating device 11 as a static eliminating unit around the photosensitive drum 1. Further, the image forming portion 9 has a toner amount sensor 18 as a developer amount detecting member. The charging roller 2, the developing roller 4 as a developer bearing member included in the developing device 8, and the brush member 12 are disposed so as to be in contact with the surface (peripheral surface) of the photosensitive drum 1.

[0032] Furthermore, the image forming apparatus 100 has a transfer roller 13 as a roller-type transfer member of a transfer portion, an exposure device (exposure unit) 10 of a laser scanner as an exposure portion, and a fixing device 14 as a fixing unit as a part of the image forming portion 9. The transfer roller 13 is disposed in contact with the surface of the photosensitive drum 1.

[0033] Figure 2 304 is a block diagram illustrating a control form (printer system configuration) of the image forming apparatus 100 in this example. The image forming apparatus 100 has a printer control device 304 as a control section (control unit). The printer control device 304 uses a controller interface 305 described later so that the printer control device 304 is connected to a host computer 300 as an external host device of the image forming apparatus 100 to perform communication therebetween.

[0034] The printer control device 304 roughly has a controller section 301 and an engine control section 302. In the controller section 301, a controller interface 305 and an image processing section 303 are provided. In the engine control section 302, a video interface 310, a CPU 311, a ROM 312, a RAM 313, an ASIC 314, a fixing control section 320, a feeding and conveying control section 330, and an image forming control section 340 are provided. The image forming control section 340 includes a charging voltage applying section 341, a developing voltage applying section 342, a transfer voltage applying section 343, an exposure control section 344, and a drive control section 345. The charging voltage applying section 341 includes a charging voltage applying power source and a charging voltage applying circuit as a unit for applying a charging voltage (charging bias) to the charging roller 2. The developing voltage applying section 342 includes a developing voltage applying power source and a developing voltage applying circuit as a unit for applying a developing voltage (developing bias) to the developing roller 4. The transfer voltage applying section 343 includes a transfer voltage applying power source and a transfer voltage applying circuit as a unit for applying a transfer voltage (transfer bias) to the transfer roller 13. The exposure control section 344 controls the exposure operation of the exposure device 10. The drive control section (drive section) 345 controls the drive of the drive motor 70 as a drive source and the transmission of the drive from the drive motor 70 to control the drive of the photosensitive drum 1, the developing roller 4, the supply roller 5, and the stirring member 7.

[0035] In the controller section 301, the image processing section 303 receives the print job information from the host computer 300 through the controller interface 305. The image processing section 303 performs image processing on the image data included in the print job information so that an image can be formed by the image forming section 9. The image processing section 303 determines a black image and a halftone image mainly composed of text or lines included in the image data, and performs halftone processing on the halftone image. The image processing section 303 has a grayscale table for halftones corresponding to the density of the halftone image, and performs halftone processing so that the density of the image to be formed by the image forming section 9 is adjusted to the density of the halftone image included in the image data. Then, the image processing section 303 transmits image information including the image data after the image processing to the video interface 310 in the engine control section 302.

[0036] The above-mentioned image information includes information for controlling the opening timing of the exposure device 10 as a laser scanner, information about the print mode for controlling the processing conditions such as temperature adjustment and transfer bias, and information about the image size. The information about the opening timing of the exposure device 10 is transmitted to the ASIC (Application Specific Integrated Circuit) 314. The ASIC 314 performs a part of the control of the image forming section 9 (such as the exposure device 10) controlled by the image formation control section 340. On the other hand, the above-mentioned information about the print mode and the information about the image size are transmitted to the CPU (Central Processing Unit) 311.

[0037] The CPU 311 performs, for example, the following control. Specifically, the CPU 311 performs control of the temperature of the fixing device 14 in the fixing control section 320 and control of the operation of the feeding section 30 (such as the operation interval (feeding interval)) in the feeding and conveying control section 330. In addition, the CPU 311 performs control in the image forming control section 340, such as the processing speed, various voltages (such as the developing voltage, the charging voltage, and the transfer voltage), and the operation of the contact / separation mechanism (not shown) (the contact or separation of the developing roller 4 with the photosensitive drum 1). Note that the CPU 311 performs the above-mentioned control by storing information in the RAM 313, using the programs stored in the ROM 312 and the RAM 313, and referring to the information stored in the ROM 312 and the RAM 313 as needed.

[0038] Furthermore, the controller section 301 sends a print command or a cancel command to the engine control section 302 according to an instruction executed by a user (operator) on the host computer 300, thereby controlling operations such as start or stop of the printing operation.

[0039] The operation panel 60 has a display section for displaying information to an operator such as a user or a service representative by controlling the printer control device 304 , and an input section for inputting information to the printer control device 304 in response to the operator's operation.

[0040] Image forming operation

[0041] Next, the image forming operation in the image forming apparatus 100 in this example is described.

[0042] A driving force is transmitted from a driving motor (not shown) as a driving source to the photosensitive drum 1, and the photosensitive drum 1 is Figure 1 The photosensitive drum 1 is driven to rotate in the direction of arrow R1 (counterclockwise) so that the surface of the photosensitive drum 1 has a predetermined peripheral speed. The peripheral speed of the photosensitive drum 1 in this example is 140 mm / sec.

[0043] The charging roller 2 contacts the surface of the photosensitive drum 1 with a predetermined contact pressure to form a charging portion. Figure 2 ) applies a predetermined charging voltage (charging bias) as a DC voltage to the charging roller 2. In this way, the charging roller 2 uniformly charges the surface of the photosensitive drum 1 to a predetermined potential with a predetermined polarity (negative polarity in this example). In this example, the charging roller 2 is applied with a charging voltage of -1400V, so that the surface potential (pre-exposure potential VD) of the photosensitive drum 1 becomes -800V. Note that in this example, a DC voltage is used as the charging voltage, but the voltage is not limited to this. An oscillating voltage obtained by superimposing a DC voltage and an AC voltage may be used as the charging voltage.

[0044] The uniformly charged surface of the photosensitive drum 1 is scanned and exposed by being applied with laser light based on image information by the exposure device 10 as a laser scanner, so that an electrostatic latent image (electrostatic image) is formed on the photosensitive drum 1. In this example, the exposure device 10 is 0.35 μJ / cm 2 Laser light is applied to the surface of the photosensitive drum 1 at a predetermined exposure amount.

[0045] The electrostatic latent image formed on the photosensitive drum 1 is supplied with a toner as a developer by the developing device 8 and is developed (visualized), so that a 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 contacts the surface of the photosensitive drum 1 with a predetermined contact pressure to form a developing portion. On the developing roller 4, a toner layer is formed by the toner 3 charged to a predetermined polarity (negative polarity in this example). From the developing voltage applying portion 342 ( Figure 2) applies a predetermined developing voltage (developing bias) as a DC voltage to the developing roller 4. In this way, the toner 3 is attached to the electrostatic latent image on the photosensitive drum 1 at the developing portion. In this way, a toner image (developer image) is formed on the photosensitive drum 1. In this example, the developing roller 4 is applied with a developing voltage of -400V.

[0046] In this example, the toner 3 that has been charged to the same polarity as the charging polarity of the photosensitive drum 1 (negative polarity in this example) is attached to the exposed area (image portion) on the photosensitive drum 1 where the absolute value of the potential has been reduced due to the photosensitive drum 1 being exposed after being uniformly charged (reversal development type). In this example, the normal charging polarity of the toner 3 (which is the main charging polarity of the toner 3 during development) is negative polarity.

[0047] The transfer roller 13 contacts the photosensitive drum 1 with a predetermined contact pressure to form a transfer portion. The toner image formed on the photosensitive drum 1 is transferred at the transfer portion to the recording material P that has been conveyed while being sandwiched by the photosensitive drum 1 and the transfer roller 13. During the transfer, a transfer voltage is applied from the transfer voltage applying portion 343 ( Figure 2 ) applies a predetermined transfer voltage (transfer bias) as a DC voltage to the transfer roller 13. In this example, the transfer voltage of +1500V is applied to the transfer roller 13.

[0048] The recording material (transfer material, recording medium, sheet) P is supplied to the transfer portion from a feeding portion 30 provided at the lower portion of the apparatus body M. The feeding portion 30 has a cassette 31 as a recording material containing portion and a feeding roller 32 as a feeding member. The recording materials P contained in the cassette 31 are fed from the cassette 31 by the feeding roller while being separated one by one. The recording material P is conveyed to the transfer portion by a conveying roller (registration roller) 50 as a conveying member in synchronization with the toner image on the photosensitive drum 1.

[0049] The recording material P on which the toner image is transferred is conveyed to the fixing device 14 as a fixing unit. The fixing device 14 applies heat and pressure to the recording material P, thereby fixing (melting, fixing) the toner image on the recording material P. The recording material P on which the toner image is fixed is discharged (output) onto a tray 40 as a discharge portion provided outside the image forming apparatus 100.

[0050] Cleaner-less toner collection

[0051] On the other hand, the toner (transfer residual toner) that has not been transferred onto the recording material P in the transfer process but remains on the photosensitive drum 1 is removed from the photosensitive drum 1 in the following manner.

[0052] The static electricity on the surface of the photosensitive drum 1 after the transfer process is removed by the static electricity eliminating device (static electricity eliminating lamp) 11 so that the surface potential becomes 0V, and then the surface of the photosensitive drum 1 enters the charging portion. In the transfer residual toner remaining on the photosensitive drum 1, the toner charged to the positive electrode and the toner charged to the negative electrode but not having sufficient charge are mixed. These kinds of transfer residual toner are charged to the negative polarity by discharge at the charging portion.

[0053] The transfer residual toner that has been charged to the negative polarity at the charging portion reaches the developing portion as the photosensitive drum 1 rotates. In this case, an electrostatic latent image corresponding to the image information is formed on the surface of the photosensitive drum 1 that has reached the developing portion. The transfer residual toner attached to the non-exposed area (non-image portion) on the photosensitive drum 1 moves from the photosensitive drum 1 to the developing roller 4 at the developing portion due to the potential difference between the pre-exposure potential VD on the photosensitive drum 1 and the developing voltage, and is collected in the developing chamber 8b in the developing device 8. Note that the toner collected in the developing chamber 8b is used again for image formation.

[0054] On the other hand, the transfer residual toner attached to the exposed area (image portion) on the photosensitive drum 1 does not move from the photosensitive drum 1 to the developing roller 4 at the developing portion, but constitutes a toner image together with the toner that has moved from the developing roller 4 to the photosensitive drum 1. Then, this toner is transferred onto the recording material P at the transfer portion, and is removed from the photosensitive drum 1.

[0055] Paper dust collection

[0056] A brush member 12 is provided, which is a paper dust collecting member for removing paper dust fibers that have been generated from the recording material P and attached to the photosensitive drum 1 from the recording material P in the transfer process. The brush member 12 is disposed to contact the photosensitive drum 1 on the downstream side of the transfer portion and the upstream side of the charging portion in the rotation direction of the photosensitive drum 1. The brush member 12 rubs the surface of the photosensitive drum 1 as the photosensitive drum 1 rotates, thereby capturing the paper dust fibers on the photosensitive drum 1 and removing the paper dust fibers from the photosensitive drum 1.

[0057] Detailed Configuration of the Development Device 8

[0058] The detailed configuration of the developing device 8 in the image forming apparatus 100 in this example is described.

[0059] In this example, 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 developer container (frame) 80, which includes a toner accommodating chamber 8a as a developer accommodating chamber and a developing chamber 8b in which a developing roller 4 as a developer carrying member is disposed. The developing chamber 8b and the toner accommodating chamber 8a are connected to each other. In the developing chamber 8b, in addition to the developing roller 4, a supply roller 5 as a supply member for supplying the toner 3 to the developing roller 4 and a developing scraper 6 as a limiting member are provided. The developing scraper 6 is configured to limit the amount of toner on the developing roller 4 while applying the toner 3 to the developing roller 4 with an electric charge having a predetermined polarity.

[0060] The developing roller 4 is disposed in the opening portion of the developing chamber 8b (developer container 80) so as to be rotatable. A portion of the outer peripheral surface of the developing roller 4 is exposed to the outside of the developer container 80 through the opening portion, and is opposed to the photosensitive drum 1 in the area exposed to the outside of the developer container 80. The developing roller 4 transports the toner 3 from the inside of the developing chamber 8b (developer container 80) to the outside by rotating while carrying the toner 3. In the toner containing chamber 8a, the toner 3 as the developer is contained. In addition, the toner containing chamber 8a is provided with a stirring member 7, which is configured to transport the toner 3 from the toner containing chamber 8a to the developing chamber 8b while stirring the toner 3 in the toner containing chamber 8a.

[0061] In this example, the developing roller 4 is configured by sequentially coating the outer circumference of a core rod having a diameter of 6 mm with a base layer of silicone rubber and a surface layer of polyurethane rubber so as to have an outer diameter of 15 mm. 4 Ω to 1×10 12 The resistance value is Ω.

[0062] In addition, in this example, the supply roller 5 is a conductive elastic sponge roller configured by forming a foam layer on the outer periphery of a core rod having a diameter of 6 mm. 4 Ω to 1×10 8 The resistance value is Ω and the hardness is 200 gf. The hardness of the supply roller 5 is a value obtained by measuring a load when a plate having a longitudinal width of 50 mm is made to enter the surface of the supply roller 5 by 1 mm.

[0063] In this example, the developing scraper 6 is a SUS plate made of metal, has a thickness of 0.1 mm and has a predetermined length in the longitudinal direction along the rotation axis direction of the developing roller 4 and in the transverse direction approximately orthogonal to the longitudinal direction. The developing scraper 6 is deployed to contact the developing roller 4 so that its free end in the transverse direction points to the upstream side of the rotation direction of the developing roller 4, and the side surface close to the free end is along the longitudinal direction. In this example, a scraper obtained by cutting the distal end (free end) of the SUS plate from the contact surface side of the developing roller 4 is used as the developing scraper 6. The distal end portion of the developing scraper 6 is bent in the cutting direction by cutting, and the bending amount of the distal end of the developing scraper 6 corresponding to the curvature radius R is 0.02 mm.

[0064] The movement of the toner 3 in the developing device 8 during driving is described. The driving force is transmitted to the developing device 8 from the driving motor 70, which is a driving source provided to the device body M and constitutes a driving unit. In this way, the developing roller 4, the supply roller 5, and the stirring member 7 rotate in the direction of the arrow R2 (clockwise direction), the direction of the arrow R3 (clockwise direction), and the direction of the arrow R4 (counterclockwise direction) in the figure.

[0065] In this case, when the ratio of the peripheral speed of the surface of the developing roller 4 to the peripheral speed of the surface of the photosensitive drum 1 is defined as a developing peripheral speed ratio, the surface of the developing roller 4 is rotationally driven at a predetermined peripheral speed so that the developing peripheral speed ratio is 1.4.

[0066] When the stirring member 7 in the toner containing chamber 8a rotates, the toner 3 in the toner containing chamber 8a is stirred and conveyed toward the supply roller 5 in the developing chamber 8b. The toner 3 held by the foaming layer of the supply roller 5 is sent to the contact portion with the developing roller 4 as the supply roller 5 rotates. Then, the toner 3 that has reached the contact portion is rubbed by the surface of the developing roller 4 and the surface of the supply roller 5 moving in opposite directions at the contact portion, and a part of the toner adheres to the surface of the developing roller 4. Note that the supply roller 5 may rotate in the same rotation direction as that of the developing roller 4, and the moving direction of the supply roller 5 and the developing roller 4 at the contact portion may be a forward direction.

[0067] The toner 3 attached 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 limits the amount of the toner 3 attached to the surface of the developing roller 4 to form a uniform thin layer and frictionally charges the toner 3. The thinned toner 3 is sent to the contact portion 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.

[0068] The toner 3 that has not been used for development and 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 containing chamber 8a and is stirred and mixed with the toner 3 in the toner containing chamber 8a.

[0069] Toner replenishment configuration

[0070] A toner replenishment configuration of the developer container 80 in the developing device 8 in this example is described. Figure 3A : is a schematic front view of the toner pack 16 as the toner replenishing container in this example. Figure 3B 1 is a schematic cross-sectional view illustrating a state in which the toner pack 16 is mounted to the developer container 80 in the developing device 8 .

[0071] like Figure 1 and Figure 3B As shown in FIG. 8 , a supplementary protrusion 8 c is formed at the developer container 80. The supplementary protrusion 8 c has a hollow interior and is formed to communicate with the toner accommodating chamber 8 a through a supply port 8 d. At the upper portion of the device body M, a top cover 17 is provided to be openable and closable. Note that the top surface of the top cover 17 constitutes the above-mentioned tray 40.

[0072] like Figure 3A As shown in FIG. 1 , in this example, the toner pack 16 has a deformable plastic package 16a and a coupling portion 16b provided at one end of the package 16a. The interior of the package 16a and the interior of the coupling portion 16b are connected to each other. Figure 3B As shown in , the image forming apparatus 100 is configured so that when the top cover 17 is opened so that the space above the supplementary protrusion 8c is opened (in the direction of retreating from above the supplementary protrusion 8c), the supplementary protrusion 8c is exposed to the outside of the apparatus. At the end of the supplementary protrusion 8c, the toner pack 16 (its coupling portion 16b) can be installed. When the toner pack 16 is installed to the supplementary protrusion 8c, the toner containing chamber 8a can be replenished with the toner from the toner pack 16. The toner pack 16 is coupled to the supplementary protrusion 8c by the connecting portion 16b in a state where the top cover 17 is opened, so that the toner pack 16 is installed to the supplementary protrusion 8c in a state where at least a portion of the package 16a at one end of the side opposite to the coupling portion 16b is exposed to the outside of the image forming apparatus 100.

[0073] More specifically, when the toner pack 16 is mounted to the replenishing protruding portion 8c, the interior of the toner pack 16 (packing 16a, coupling portion 16b) and the interior of the replenishing protruding portion 8c are communicated with each other. Then, the toner contained in the toner pack 16 is discharged to the interior of the replenishing protruding portion 8c through an opening (not shown) provided in the coupling portion 16b of the toner pack 16, and the toner is replenished from the replenishing protruding portion 8c to the toner accommodating chamber 8a through the replenishing port 8d.

[0074] Note that in this example, the toner pack 16 as the toner replenishing container has a deformable plastic package, but the configuration is not limited to this. For example, the toner replenishing container may include a bottle container having a substantially conical shape or a substantially cylindrical shape. In addition, for example, the toner replenishing container may have a paper container made of paper.

[0075] As a method for discharging the toner from the toner replenishing container, when the container is a toner pack 16 or a paper container as in this example, it is preferred that the operator squeezes the container, and when the container is a bottle container, it is preferred that the operator knocks and vibrates the container. In order to discharge the toner from the bottle container, the bottle container may be provided with a discharge mechanism. The discharge mechanism may be engaged with a drive mechanism provided to the image forming apparatus 100 so as to receive a drive from the drive mechanism.

[0076] To prevent toner from leaking from the toner replenishing container, the toner replenishing container may be provided with a rotating or sliding shutter member. In addition, the shutter member may be configured so as to break when mounted to the replenishing port of the developing device 8, or may have a removable cover structure such as a seal.

[0077] The top cover 17 only needs to be configured so that at least the space above the replenishment protrusion 8c (replenishment port 8d) can be opened. For example, the top cover 17 does not necessarily need to be used as the tray 40, or the top cover 17 may constitute a part of the tray 40.

[0078] Toner refill indicator

[0079] When the image forming operation is repeated, the toner contained in the toner containing chamber 8a is consumed. When the remaining amount of toner in the developer container 80 decreases and the toner amount detected by the toner amount sensor 18 becomes less than a preset toner low threshold value, the engine control part 302 displays a toner low indication on the display part 61 of the operation panel 60. The toner low indication is an indication that the remaining amount of toner in the developer container 80 is small. When the image forming operation is further repeated from the timing of the detection of the toner low and the toner amount detected by the toner amount sensor 18 becomes less than a preset toner empty threshold value, the engine control part 302 displays a toner empty indication on the display part 61 of the operation panel 60. The toner empty indication is an indication that the toner in the developer container 80 is empty. In addition, the engine control part 302 also displays an indication prompting the realization of toner replenishment together with the toner empty indication.

[0080] You can use FIG. 6A to FIG. 6C As the display configuration of the remaining toner amount, the configuration shown in FIG. 6A to FIG. 6C As shown in , the display configuration is provided on a part of the casing of the apparatus body M of the image forming apparatus 100 . Fig. 6A 2 is a perspective view illustrating a toner remaining amount panel 400 in which a remaining amount indication of toner is at a low level. Figure 6B 1 is a perspective view of the toner remaining amount panel 400 showing a middle level of the toner remaining amount indication. Figure 6C 4 is a perspective view of a toner remaining amount panel 400 indicating a full level of the remaining amount of toner. The toner remaining amount panel 400 is a panel member including marks 400a to 400c as a plurality of (three in this case) indicators arranged side by side in the up-down direction. When the toner remaining amount indicates a low level, as shown in FIG. Fig. 6A As shown in FIG. 4 , only the mark 400a is turned on. When the remaining amount of toner indicates a medium level, as shown in FIG. Figure 6B As shown in FIG. 1 , the mark 400a and the mark 400b are turned on. When the remaining amount of toner indicates the full level, all the marks 400a to 400c are turned on.

[0081] question

[0082] In the case where the image forming operation with a low image coverage is repeated, the amount of toner in the developer container 80 reaches the toner exhaustion threshold, and before the toner is replenished, image failures such as fogging may occur. The image forming operation with a low image coverage refers to an image forming operation in which the ratio of the printing area (the area where the toner is placed in the image formable area) to the sheet area (the area of ​​the image formable area of ​​the recording material) (hereinafter referred to as "image coverage") is small and the toner consumption is small. Typical examples of image formation with a low image coverage include image formation in which the image includes only text or lines so that the image coverage is low.

[0083] Note that in the case where the same image coverage is provided between a recording material having a small size and a recording material having a large size, the printing area in the small-sized recording material is relatively small compared to the printing area in the large-sized recording material, and therefore the above-mentioned image failure such as fogging is more likely to occur. In this example, control of an image forming operation based on the image coverage of a recording material having an LTR size as a small-sized recording material is described. The 100% image coverage in this example corresponds to a print amount when a solid black image is formed in the entire image formable area on a single LTR-sized recording material.

[0084] One of the causes of image failure such as fogging is toner degradation, and one of the causes of toner degradation is the flow and agitation of toner in the developer container during the image forming operation. During the image forming operation, the toner in the developer container 80 is repeatedly rubbed by the supply roller 5 and the developing blade 6, and the release and embedding of the external additive to the toner base or the deformation of the toner base itself occurs and the toner degrades. The toner used for development during the image forming operation is a part of the toner in the developer container, and most of the toner is not used for development and remains in the developer container 80. Such a toner residue becomes more obvious when the image forming operation with a low image coverage continues. As the image coverage of the image formation becomes lower, a larger amount of toner in the developer container 80 is not consumed and remains in the developer container 80, and a large number of image forming operations are repeated before the toner replenishment in the developer container 80 is performed. Each time the image forming operation is performed, when the toner continues to remain in the developer container without being used for development, the toner degradation proceeds. Therefore, since the image formation has a lower image coverage, the colorant in the developer container 80 deteriorates more rapidly before the amount of colorant in the developer container is consumed to a predetermined amount at which the user is prompted to replenish the colorant, and image failures such as fogging are likely to occur before toner replenishment is performed.

[0085] feature

[0086] In view of the above, in the present example, a low image coverage ratio support mode is provided so as to prevent the occurrence of image failures such as fogging before the toner amount in the developer container 80 reaches the toner end threshold and toner replenishment is performed even when an image forming operation with a low image coverage ratio is repeated. Specifically, the image forming apparatus 100 in the present example is capable of executing a normal mode (first operation mode) that supports the above-mentioned normal image forming operation and a low image coverage ratio support mode (second operation mode) that supports an image forming operation with a low image coverage ratio as options.

[0087] The low image coverage ratio support mode can be selected through the input portion 62 in the operation panel 60. When the user selects the low image coverage ratio support mode through the input portion 62 in the operation panel 60, the fact that the low image coverage ratio support mode has been selected is transmitted to the engine control portion 302, and the fact that the low image coverage ratio support mode has been selected is stored in the engine control portion 302.

[0088] Then, when the low image coverage ratio supporting mode is selected, the engine control portion 302 changes the normal mode corresponding to the normal image forming operation as follows.

[0089] First, when the low image coverage support mode is selected, the peripheral speed of the photosensitive drum 1 (the moving speed of the peripheral surface of the photosensitive drum 1) is set to 2 / 3 times that of the normal image forming operation. In addition, when the low image coverage support mode is selected, by setting the peripheral speed of the developing roller 4 to 2 / 3 times that of the normal image forming operation, the developing peripheral speed ratio is set to 1.4 similar to the normal image forming operation.

[0090] The configuration in which the peripheral speeds of the photosensitive drum 1 and the developing roller 4 are variable can be realized by, for example, independently providing a driving configuration of the photosensitive drum 1 and a driving configuration of the developing roller 4 and independently controlling the photosensitive drum 1 and the developing roller 4 by the engine control section 302 (image formation control section 340). In other words, the photosensitive drum 1 and the developing roller 4 are driven by different drive motors (drive sources). Note that in the case where the developing peripheral speed ratio is maintained constant between the normal mode and the low image coverage support mode as in this example, the photosensitive drum and the developing roller can be driven by the same drive motor (common drive source).

[0091] In addition, when the low image coverage support mode is selected, the exposure intensity of the laser from the exposure device 10 to the surface of the photosensitive drum 1 is set to 1.2 times that of the normal image forming operation. Examples of methods for increasing the exposure intensity include methods for increasing the laser output of the exposure device 10 (the amount of light per unit area of ​​the surface of the photosensitive drum 1). Specifically, in the normal mode, as described above, the output (amount of light) of the laser of the exposure device 10 is set to 0.35 μJ / cm as a predetermined exposure amount (first exposure amount). 2 (First exposure intensity) On the other hand, in the low image coverage support mode, the output of the laser light of the exposure device 10 is increased to 0.42 μJ / cm as the second exposure amount. 2 (Second exposure intensity).

[0092] Other controls performed when the low image coverage support mode is selected are the same as those in the normal image forming operation, and thus description thereof is omitted.

[0093] Effect

[0094] Next, the effect of the low image coverage support mode in this example is described.

[0095] In the low image coverage support mode, the peripheral speed of the photosensitive drum 1 is reduced compared with the normal image forming operation, so the time period during which the photosensitive drum 1 is exposed by the exposure device 10 is increased, and the exposure amount per unit area of ​​the photosensitive drum 1 can be increased to increase the exposure amount of the surface of the photosensitive drum 1. In addition, in the low image coverage support mode, the exposure intensity of the surface of the photosensitive drum 1 by the exposure device 10 is increased compared with the normal image forming operation, so the exposure amount of the surface of the photosensitive drum 1 in this image forming operation can be increased compared with the normal image forming operation. Then, in this way, in the low image coverage support mode, the exposure amount of the surface of the photosensitive drum 1 is greater than the exposure amount in the normal image forming operation, so a latent image deeper than the latent image in the normal image forming operation can be formed on the surface of the photosensitive drum 1. The deep latent image refers to an electrostatic latent image having a large potential difference between the potential of the image portion formed by the exposure of the exposure device 10 on the peripheral surface of the photosensitive drum 1 and the potential of the non-image portion that is not exposed by the exposure device 10 or formed by extremely slight exposure. Therefore, the development amount of the toner of the latent image on the surface of the photosensitive drum 1 from the developing roller 4 increases, and the toner consumption amount in the developer container 80 in the image forming operation can be increased.

[0096] Furthermore, in the low image coverage support mode, in addition to reducing the peripheral speed of the photosensitive drum 1 compared to the normal image forming operation, the peripheral speed of the developing roller 4 is also reduced so that the developing peripheral speed ratio is 1.4 similar to the normal image forming operation. On the other hand, if the developing peripheral speed ratio is not maintained constant, and the developing peripheral speed ratio in the low image coverage support mode is set to be greater than the normal image forming operation, the developing roller 4 rotates faster than the photosensitive drum 1, and the chance of friction of the toner on the developing roller 4 increases. According to this example, the chance of such friction of the toner can be prevented from increasing, and the acceleration of toner deterioration due to the increase in the chance of friction of the toner can be prevented. Note that from the viewpoint of toner deterioration, it is preferable to maintain the developing peripheral speed ratio or set the developing peripheral speed ratio to be small, but depending on the conditions, the developing peripheral speed ratio can also be controlled to be large in consideration of toner deterioration.

[0097] Effect confirmation

[0098] In order to confirm the effect of the low image coverage support mode in this example, the following test was performed.

[0099] In this test, in the image forming apparatus of this example, in a state where the low image coverage support mode is specified, an operation of printing text images with an image coverage of 1.5% on LTR size sheets is repeated two by two under a normal environment of 23°C and 50% until toner exhaustion is indicated. The sheet used is "Vitality 75 (manufactured by Xerox Corporation)". In the developer container 80 before the test, toner in an amount that indicates toner exhaustion when printing about 5,000 images with an image coverage of 4.0% on LTR size sheets is loaded.

[0100] As a comparative example, in an image forming apparatus having the same configuration as that of the image forming apparatus in this example, the same test as that in this example was performed in a state in which the low image coverage support mode was not specified.

[0101] First, in the image forming apparatus in this example, the low image coverage support mode is specified, so the toner consumption per image forming operation increases compared to the case where the normal mode is specified. Therefore, in the image forming apparatus in this example, toner exhaustion is displayed at a timing of about 11,000 prints from the start of the test, and image failures such as fogging do not occur until toner exhaustion is displayed.

[0102] In addition, by setting the rotation of the photosensitive drum to be low and increasing the exposure, an electrostatic latent image with a steeper boundary between the image portion potential and the non-image portion potential can be formed. In this way, especially in text images, an image with a clear boundary between the image portion and the non-image portion can be formed, and the image quality can be improved.

[0103] On the other hand, in the image forming apparatus in the comparative example, the low image coverage support mode is not specified, so the amount of toner consumed per image forming operation is smaller than that of the image forming apparatus in the present example in which the low image coverage support mode is specified. Therefore, in the image forming apparatus in the comparative example, image failure due to fogging occurs at a timing of about 13,000 prints from the start of the test, and thereafter toner exhaustion is displayed at a timing of about 14,000 prints.

[0104] As described above, in the low image coverage support mode in this example, even when image forming operations with low image coverage are repeated, the amount of colorant in the developer container 80 can be prevented from reaching the colorant exhaustion threshold, so that image failures such as fogging can be prevented from occurring before the toner is replenished.

[0105] Furthermore, in the present example, the low image coverage ratio support mode is selected by the input section 62 provided in the operation panel 60 of the image forming apparatus, but the method for selecting the low image coverage ratio support mode is not limited to the selection by using the input section 62 in the operation panel 60. For example, the low image coverage ratio support mode may be selected by an information device (such as a personal computer, a smartphone, a tablet terminal) as a host computer connected to the image forming apparatus.

[0106] Furthermore, in this example, the configuration in which the operator selects the low image coverage ratio support mode has been described, but the image forming apparatus may automatically select the low image coverage ratio support mode depending on the image coverage ratio of the image to be formed. Alternatively, the image forming apparatus may automatically select the low image coverage ratio support mode depending on the consumption speed of the toner in the developer container 80 detected by the toner amount sensor 18.

[0107] At the time of automatic switching of the operation mode depending on the image coverage, the image coverage can be detected by the following method. Specifically, a measuring unit (pixel count) capable of counting the number of pixels caused to emit light by the exposure device 10 can be used to obtain the image coverage based on the number of pixels relative to the printing area (the amount of colorant consumed in the printing of one recording material). The measuring unit can be configured by the engine control part 302, or can be provided separately from the engine control part 302. Pixel counting refers to counting the individual image signals of the image dots that form the image to be formed based on the image data after image processing included in the image information transmitted from the image processing part 303 to the engine control part 302. Regarding the amount of colorant required to develop the image, the engine control part 302 (image formation control part 340) estimates the toner consumption x [%] used for printing one recording material based on the number of pixels caused to emit light by the exposure device 10.

[0108] In addition, in the automatic switching of the operation mode depending on the image coverage, the threshold of the image coverage (predetermined image coverage) can be 1.5% to 2.0%. In other words, when the detected image coverage is equal to or lower than the predetermined image coverage, the low image coverage support mode can be selected and executed.

[0109] Example 2

[0110] In the image forming apparatus in Example 2 of the present invention, when the low image coverage support mode is selected, the developing roller 4 is rotationally driven at a peripheral speed of 1.3 at the development peripheral speed ratio. The other configurations are the same as those in Embodiment 1, and thus descriptions thereof are omitted.

[0111] In the configuration of this example, the development peripheral speed ratio (1.3) when the low image coverage support mode is selected is smaller than the development peripheral speed ratio (1.4) in normal image forming operation, so the chance of friction with the colorant on the developing roller 4 can be reduced to prevent toner degradation.

[0112] In this example, the development peripheral speed ratio when the low image coverage support mode is selected is 1.3, but if the development peripheral speed ratio is too small, the toner consumption amount cannot be increased in some cases even when the low image coverage support mode is selected by forming a darker electrostatic latent image than the normal image forming operation on the surface of the photosensitive drum 1. In other words, if the development peripheral speed ratio is too small, toner deterioration may be accelerated on the contrary, so it is preferable to set the reduction width of the development peripheral speed ratio depending on the characteristics of the image forming apparatus.

[0113] Example 3

[0114] In the image forming apparatus of Example 3 of the present invention, the grayscale table for halftone (grayscale correction) used by the image processing section 303 is changed between selecting the low image coverage ratio support mode and not selecting the low image coverage ratio support mode. The grayscale table used when the low image coverage ratio support mode is selected is a table in which the grayscale on the side having a lower density than the grayscale table used when the low image coverage ratio support mode is not selected in the halftone of the halftone image data having the same density is selected. The other configuration is the same as that in Example 1, and therefore the description thereof is omitted.

[0115] like Figure 4 As shown in , in normal mode, use the display Figure 4 The grayscale curve indicated by the dashed line in the table for the normal mode (the first grayscale table), while in the low image coverage support mode, the display Figure 4 The table (second grayscale table) for the low image coverage support mode of the grayscale curve indicated by the dotted line. In the two grayscale tables, the output data density of the same input data is different. Specifically, regarding the value (density) of the output data corresponding to a certain input data, the value of the output data when using the table for the low image coverage support mode is smaller (lighter) than the value of the output data when using the table for the normal mode.

[0116] If the same grayscale table as in the normal image forming operation is used so that when the low image coverage support mode is selected, the electrostatic latent image on the surface of the photosensitive drum 1 is formed darker than in the normal image forming operation (so that the potential difference between the image portion and the non-image portion is larger), a halftone image portion having a higher density than in the normal image forming operation can be formed. As in this example, by using different grayscale tables depending on the operation mode, it is possible to prevent the density of the formed image from being too high.

[0117] As a grayscale table used when the low image coverage support mode is selected, a halftone grayscale lower than the grayscale table used when the low image coverage support mode is not selected is preferably determined depending on the characteristics of the image forming apparatus itself. In this example, a case where only one grayscale table for the low image coverage support mode is provided has been illustrated, but a plurality of grayscale tables with a step size may be provided. For example, the grayscale table to be used may be switched between a plurality of grayscale tables for the low image coverage support mode depending on the size of the image coverage so that the density gradually decreases.

[0118] Example 4

[0119] In the image forming apparatus of Example 4 of the present invention, when the low image coverage support mode is selected, image processing (expansion processing) is performed by the image processing section 303 so that the periphery of the image portion that has been determined as text or line in the image data is exposed by the exposure device 10. The other configurations are the same as those in Example 1, and thus descriptions thereof are omitted.

[0120] Image data includes information on the attributes of objects constituting an image, such as text (characters), lines, graphics, and photographs, the number of pixels, the grayscale value of each pixel, and coordinates in the image.

[0121] Figure 5A 2 is a schematic diagram illustrating pixel data constituting a character "A" as an example of an object whose attribute is text. Figure 5A As shown in, for example, when a character "A" is included in the image data, the area in the image where the character "A" is formed includes an image portion pixel P1 constituting the character "A" and a non-image portion pixel P0 constituting the background of the character "A". The image portion pixel P1 is typically a black image portion that forms a black dot, and is, for example, a pixel having a grayscale value of 255 and to which a laser is applied during exposure so that a toner is attached. The non-image portion pixel P0 is typically a white image portion that forms a white dot or a light-colored dot close to white, and is a pixel having a grayscale value of 0 or approximately 0 and to which a laser is not applied or is lightly applied with a laser having a low output during exposure.

[0122] Figure 5B It is a diagram of the composition Figure 5A Schematic diagram of image data after the pixel data of the character "A" shown in FIG. Figure 5B As shown in, as an example of expansion processing, the image processing section 303 changes the image data so that among the non-image portion pixels P0 included in the formation area of ​​the character "A" in the image, the non-image portion pixel P0 adjacent to the image portion pixel P1 is replaced with the image portion pixel P2. The image portion pixel P2 is a pixel that constitutes the character "A" together with the image portion pixel P1. The grayscale value of the image portion pixel P2 may be the same as the grayscale value of the image portion pixel P1, or may be different.

[0123] By performing image processing such that the periphery of the black image portion is exposed by the exposure device 10 as in this example, when the low image coverage support mode is selected, the toner consumption in the black image portion can be increased without increasing the density of the halftone image portion.

[0124] In this example, when the low image coverage ratio support mode is selected, in addition to the operation in the low image coverage ratio support mode in Example 1, the image processing section 303 performs image processing (expansion processing) so that the periphery of the black image portion is exposed by the exposure device 10, but the configuration is not limited thereto. For example, when the low image coverage ratio support mode is selected, the image processing section 303 may perform only image processing for exposing the periphery of the black image portion by the exposure device 10, instead of reducing the peripheral speed of the photosensitive drum 1 or increasing the exposure intensity of the photosensitive drum 1 as in Example 1.

[0125] In the selection of the low image coverage support mode, how to set the range of the periphery of the black image portion to be exposed by the exposure device 10 is preferably set by the image processing section 303 depending on the image quality of the text image or the line image and the toner consumption increase rate. The specific method of the above-mentioned extension processing is only an example, and various conventional known image processing can be appropriately adopted instead of the above-mentioned method as long as the image processing can increase the toner consumption in the low image coverage support mode compared with the usual mode.

[0126] In this example, a device configuration of a contact development type in which the photosensitive drum 1 and the developing roller 4 are in contact with each other to form a developing portion has been described, but the present invention is also applicable to a non-contact development type image forming device. Specifically, the present invention is also applicable to an image forming device in which the photosensitive drum 1 and the developing roller 4 are not in contact with each other, the closest opposing portions of the photosensitive drum 1 and the developing roller 4 form a developing portion, and development is performed by causing the toner to fly from the developing roller 4 to the electrostatic latent image on the outer peripheral surface of the photosensitive drum 1.

[0127] Furthermore, in the present embodiment, a so-called monochrome type image forming apparatus, i.e., an image forming apparatus including a single image forming portion, has been exemplified, but the image forming apparatus to which the present invention is applicable is not limited thereto. For example, the present invention is preferably applied to a so-called full-color type image forming apparatus, i.e., an image forming apparatus including a plurality of image forming portions. The difference in the apparatus configuration between a monochrome image forming apparatus and a color image forming apparatus includes the difference in the number of colors and colors of the image to be formed. Specifically, a monochrome image forming apparatus can form an image of a single color (usually, black), but a color image forming apparatus can form an image of a freely selectable hue by superimposing a plurality of developer images having different colors. Furthermore, in an intermediate transfer type color image forming apparatus, a developer image is first transferred from a photosensitive member as an image bearing member to an intermediate transfer member (also referred to as a second image bearing member) as a first transfer member, and is transferred from the intermediate transfer member to a recording material as a second transfer member. On the other hand, in a monochrome image forming apparatus and a direct transfer type color image forming apparatus, a developer image is directly transferred from a photosensitive member to a recording material.

[0128] The configurations and control methods in the above examples can be combined as much as possible.

[0129] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. An image forming device, comprising: an image bearing member configured to rotate; a charging member configured to contact the image bearing member to charge a surface of the image bearing member; a charging voltage applying section configured to apply a charging voltage to the charging member; an exposure unit configured to expose the surface of the image bearing member to form an electrostatic latent image on the surface of the image bearing member; a developer accommodating portion configured to accommodate a developer therein; a developer carrying member configured to carry the developer accommodated in the developer accommodating portion, the developer carrying member configured to rotate and supply the developer to a surface of the image bearing member; a driving portion configured to drive the image bearing member and the developer bearing member; as well as a control section configured to control the driving section, the charging voltage applying section and the exposure unit, wherein the image forming device transfers a developer image obtained by developing the electrostatic latent image using a developer carried by the developer carrying member onto a recording material to form an image on the recording material, and Among them, the control part can execute the following modes: a first operation mode for rotating the image bearing member at a first peripheral speed, the first operation mode being a mode in which the exposure unit exposes the surface of the image bearing member at a first exposure intensity; and A second operation mode for rotating the image bearing member at a second peripheral speed lower than the first peripheral speed, the second operation mode being a mode in which the exposure unit exposes the surface of the image bearing member at a second exposure intensity higher than the first exposure intensity.

2. The image forming apparatus according to claim 1, wherein: Regarding the image coverage ratio which is a ratio of the developer image to the image formable area of ​​the recording material, the image coverage ratio in the second operation mode is lower than that in the first operation mode.

3. The image forming apparatus according to claim 1 or 2, wherein: Regarding a peripheral speed ratio which is a ratio of a peripheral speed of the developer bearing member to a peripheral speed of the image bearing member, the peripheral speed ratio in the first operation mode and the peripheral speed ratio in the second operation mode are equal to each other.

4. The image forming apparatus according to claim 1 or 2, wherein: Regarding a peripheral speed ratio which is a ratio of a peripheral speed of the developer bearing member to a peripheral speed of the image bearing member, the peripheral speed ratio in the second operation mode is smaller than that in the first operation mode.

5. The image forming apparatus according to claim 1 or 2, in, As a grayscale table for grayscale correction of image data to be used for forming an image, the image forming apparatus has: a first grayscale table used in the first operation mode; as well as a second grayscale table used in the second operation mode, and However, with respect to the same input data, the density of output data when the second grayscale table is used is lower than the density of output data when the first grayscale table is used.

6. The image forming device according to claim 1 or 2 further includes an image processing part, which is configured to process image data in the second operating mode so that among the non-image partial pixels included in the formation area of ​​text or lines in the image, the non-image partial pixels adjacent to the image partial pixels are replaced with image partial pixels. 7 . The image forming apparatus according to claim 1 , further comprising an input section configured to receive an input of selection of an operation mode for an image forming operation from a user.

8. The image forming apparatus according to claim 2, further comprising an acquisition section configured to acquire the image coverage before an image forming operation is performed, in, The control section is configured to: performing the image forming operation in the first operation mode in a case where the image coverage ratio acquired by the acquisition section is higher than a predetermined image coverage ratio; as well as In a case where the image coverage ratio acquired by the acquisition section is equal to or lower than the predetermined image coverage ratio, the image forming operation is performed in the second operation mode.

9. The image forming apparatus according to claim 1 or 2, wherein: The image forming apparatus is configured so that the developer which has not been transferred to the recording material but remains on the image bearing member can be collected in the developer accommodating portion by the developer bearing member.

10. The image forming apparatus according to claim 1 or 2, wherein: Regarding the light amount per unit area of ​​laser light applied to the surface of the image bearing member by the exposure unit, the light amount in the second operation mode is greater than the light amount in the first operation mode.

11. The image forming apparatus according to claim 1 or 2, wherein: Regarding a potential difference between an image portion potential formed by exposure by the exposure unit and a non-image portion potential on the image bearing member, the potential difference in the second operation mode is greater than the potential difference in the first operation mode.

12. The image forming apparatus according to claim 1 or 2, wherein: The developer carrying member is configured to be in contact with the image bearing member to supply the developer to a surface of the image bearing member.

Images