Image forming apparatus

Abstract

To provide a technique that can reduce the influence of deterioration of toner on image formation.SOLUTION: An image forming apparatus develops an electrostatic latent image on a surface of an image carrier formed by a charging member electrostatically charging the surface of the image carrier and an exposure unit exposing the surface of the image carrier, by using developer carried on a developer carrier, and transfers, to a recording material, a developer image on the surface of the image carrier formed through the development, thereby forming an image on the recording material. The image forming apparatus has: a first operation mode for rotating the image carrier at a first peripheral speed, and exposing, by the exposure unit, the surface of the image carrier at a first exposure intensity; and a second operation mode for rotating the image carrier at a second peripheral speed slower than the first peripheral speed, and exposing, by the exposure unit, the surface of the image carrier at a second exposure intensity higher than the first exposure intensity.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus that forms an image on a recording material by using an electrophotographic method. [Background technology]

[0002] Electrophotography is known as an image recording method used in image forming devices such as laser printers, copiers, and facsimiles. In electrophotography, a laser beam is irradiated onto a photosensitive drum to form an electrostatic latent image, which is then developed with a developer (hereinafter referred to as toner) as a charged color material to form a toner image. The toner image thus formed is transferred to a recording material and fixed thereon, forming an image on the recording material.

[0003] Toner is contained in a developing container, and the toner in the developing container is gradually consumed as image formation is repeated. For this reason, a well-known configuration is one in which the developing container is configured as an independent unit, either alone or as part of a process cartridge, so that it can be attached to and detached from the main body of the image forming apparatus and can be replaced as necessary. In recent years, in order to reduce environmental impact and printing costs, an image forming apparatus has been proposed in which only toner is directly replenished to the developing container when the amount of toner remaining in the developing container becomes low (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2022-027631 Summary of the Invention [Problem to be solved by the invention]

[0005] Here, toner deterioration is cited as a cause of image defects such as fogging. One of the factors of toner deterioration is the flow and agitation of toner in the developing container. During an image forming operation, the toner in the developing container flows, but the toner used for development is only a portion of the toner in the developing container, and most of the toner remains in the developing container without being used for development. The deterioration of toner progresses further as the toner continues to remain in the developing container without being used for development every time an image forming operation is performed.

[0006] An object of the present invention is to provide a technique capable of reducing the influence of toner deterioration on image formation. [Means for solving the problem]

[0007] In order to solve the above problems, the image forming apparatus of the present invention comprises: A rotating image carrier; a charging member that contacts the image bearing member and charges the surface of the image bearing member; a charging voltage application unit that applies a charging voltage to the charging member; an exposure unit for exposing a surface of the image carrier to light to form an electrostatic latent image on the surface of the image carrier; a developer container for containing a developer; a rotating developer carrier that carries the developer contained in the developer container and supplies the carried developer to a surface of the image carrier; a drive unit that drives the image carrier and the developer carrier; the driving unit, the charging voltage application unit, the charging voltage application unit, and the exposure unit, A control unit for controlling the an image forming apparatus comprising: a developer carrying member that develops the electrostatic latent image with a developer image, the developer image being transferred onto a recording material to form an image on the recording material; The control unit: a first operation mode in which the image carrier is rotated at a first peripheral speed and the exposure unit exposes a surface of the image carrier with a first exposure intensity; a second operation mode in which the image carrier is rotated at a second peripheral speed slower than the first peripheral speed, and the exposure unit exposes a surface of the image carrier with a second exposure intensity stronger than the first exposure intensity; The present invention is characterized by having the following. Effect of the Invention

[0008] According to the present invention, it is possible to reduce the influence of toner deterioration on image formation. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is an explanatory diagram of an image forming apparatus according to an embodiment of the present invention; [Diagram 2] FIG. 2 is an explanatory diagram of a control configuration in the image forming apparatus according to the embodiment of the present invention. [Diagram 3] FIG. 1 is a schematic front view of a toner pack and a schematic cross-sectional view of an image forming apparatus with the toner pack attached thereto; [Figure 4] Gradation table illustration [Diagram 5] Diagram of expansion process [Figure 6] Diagram of the toner remaining amount panel configuration example DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Example 1 Hereinafter, the embodiment of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative positions of the components described in the embodiment may be changed as appropriate depending on the configuration and various conditions of the device to which the invention is applied. In other words, the scope of the present invention is not limited to the following embodiment.

[0011] <General Configuration of Image Forming Apparatus> A schematic configuration of an image forming apparatus according to an embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a schematic cross-sectional view of an image forming apparatus 100 according to this embodiment. The image forming apparatus 100 according to this embodiment is a monochrome laser printer capable of forming a black monochrome image on a sheet-shaped recording material P using an electrophotographic method.

[0012] The image forming unit 9 has a photosensitive drum 1 which is a rotatable drum-type (cylindrical) photosensitive body (electrophotographic photosensitive body) serving as an image carrier. The image forming unit 9 also has a charging roller 2 which is a roller-type charging member serving as a charging means, and a developing device 8 serving as a developing means, around the photosensitive drum 1. The image forming unit 9 also has a brush member 12 serving as a paper dust collecting member, and a static eliminator 11 serving as a static eliminator, around the photosensitive drum 1. The image forming unit 9 also has a toner amount sensor 18 serving as a developer amount detection means. The charging roller 2, the developing roller 4 serving as a developer carrier provided in the developing device 8, and the brush member 12 are arranged in contact with the surface (outer circumferential surface) of the photosensitive drum 1.

[0013] The image forming apparatus 100 also includes, as part of the image forming section 9, a transfer roller 13 which is a roller-type transfer member serving as a transfer means, an exposure device (exposure unit) 10 which is a laser scanner serving as an exposure means, and a fixing device 14 serving as a fixing means. The transfer roller 13 is disposed in contact with the surface of the photosensitive drum 1.

[0014] 2 is a block diagram showing a control mode (printer system configuration) of the image forming apparatus 100 in this embodiment. The image forming apparatus 100 has a printer control device 304 as a control unit (control means). The printer control device 304 uses a controller interface 305 (described later) to connect to a host computer 300 as a host device outside the image forming apparatus 100 and communicates with the host computer 300.

[0015] The printer control device 304 is roughly divided into a controller unit 301 and an engine control unit 302. The controller unit 301 is provided with a controller interface 305, an image processing unit 303, and the like. The engine control unit 302 is provided with a video interface 310, a CPU 311, a ROM 312, a RAM 313, an ASIC 314, a fixing control unit 320, a paper feed conveyance control unit 330, an image formation control unit 340, and the like. The image formation control unit 340 includes a charging voltage application unit 341, a developing voltage application unit 342, a transfer voltage application unit 343, an exposure control unit 344, a drive control unit 345, and the like. The charging voltage application unit 341 includes a charging voltage application power supply and a charging voltage application circuit as means for applying a charging voltage (charging bias) to the charging roller 2. The developing voltage application unit 342 includes a developing voltage application power supply and a developing voltage application circuit as means for applying a developing voltage (developing bias) to the developing roller 4. The transfer voltage application unit 343 includes a transfer voltage application power source and a transfer voltage application circuit as means for applying a transfer voltage (transfer bias) to the transfer roller 13. The exposure control unit 344 controls the exposure operation of the exposure device 10. The drive control unit (drive unit) 345 controls the drive of the drive motor 70 serving as a drive source and the drive transmission from the drive motor 70, thereby controlling the drive of the photosensitive drum 1, the developing roller 4, the supply roller 5, the stirring member 7, etc.

[0016] In the controller unit 301, the image processing unit 303 receives print job information from the host computer 300 via the controller interface 305. The image processing unit 303 performs image processing on the image data included in the print job information so that the image can be formed by the image forming unit 9. The image processing unit 303 distinguishes between black images and halftone images, mainly including text and lines, included in the image data, and performs halftoning on the halftone images. The image processing unit 303 has a gradation table for halftoning processing corresponding to the density of the halftone image, and performs halftoning so that the density of the image formed by the image forming unit 9 matches the density of the halftone image included in the image data. Then, the image processing unit 303 transmits image information including the image data after image processing to the video interface 310 of the engine control unit 302.

[0017] The image information includes information for controlling the timing of turning on the exposure device 10, which is a laser scanner, information on the print mode for controlling process conditions such as temperature control and transfer bias, and information on the size of the image. The information on the timing of turning on the exposure device 10 is transmitted to an ASIC (Application Specific Integrated Circuit) 314. The ASIC 314 controls a part of the image forming unit 9, such as the exposure device 10, which is controlled by an image formation control unit 340. Meanwhile, the information on the print mode and the image size are transmitted to a CPU (Central Processing Unit) 311.

[0018] The CPU 311 performs the following controls, for example. That is, it controls the temperature of the fixing device 14 in the fixing control unit 320, and controls the operation of the paper feed unit 30 (such as operation intervals (paper feed intervals)) in the paper feed transport control unit 330. It also controls the process speed, various voltages (development voltage, charging voltage, transfer voltage, etc.), and the operation of the contact / separation mechanism (not shown) (contact or separation of the developing roller 41 with respect to the photosensitive drum 1) in the image formation control unit 340. Note that the CPU 311 stores information in the RAM 313 as necessary, uses programs stored in the ROM 312 or RAM 313, and reads information stored in the ROM 312 or RAM 313. The above control is performed by referring to the above.

[0019] Furthermore, the controller unit 301 transmits print commands, cancel commands, and the like to the engine control unit 302 in response to instructions given by a user (operator) on the host computer 300, and controls operations such as starting and stopping a print operation.

[0020] The operation panel 60 is configured to include a display section for displaying information to an operator such as a user or a service representative under the control of 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.

[0021] <Image formation operation> Next, the image forming operation in the image forming apparatus 100 of this embodiment will be described.

[0022] The photosensitive drum 1 is rotated in the direction of arrow R1 (counterclockwise direction) in the figure by a driving force transmitted from a driving motor (not shown) as a driving source so that the surface of the photosensitive drum 1 has a predetermined peripheral speed. The peripheral speed of the photosensitive drum 1 in this embodiment is 140 mm / sec.

[0023] The charging roller 2 contacts the surface of the photosensitive drum 1 with a predetermined contact pressure to form a charging section. A predetermined charging voltage (charging bias) which is a DC voltage is applied to the charging roller 2 from a charging voltage application circuit of a charging voltage application section 341 (FIG. 2) as a charging voltage application means. As a result, the charging roller 2 uniformly charges the surface of the photosensitive drum 1 to a predetermined potential of a predetermined polarity (negative polarity in this embodiment). In this embodiment, a charging voltage of −1400 V is applied to the charging roller 2 so that the surface potential (potential VD before exposure) of the photosensitive drum 1 becomes −800 V. In this embodiment, a DC voltage is used as the charging voltage, but the present invention is not limited to this, and an oscillating voltage in which a DC voltage and an AC voltage are superimposed may be used as the charging voltage.

[0024] The surface of the photosensitive drum 1 that has been uniformly charged is scanned and exposed to laser light based on image information by an exposure device 10 that is a laser scanner, and an electrostatic latent image (electrostatic image) is formed on the photosensitive drum 1. In this embodiment, the exposure device 10 uses a predetermined exposure amount of 0.35 μJ / cm 2 The surface of the photosensitive drum 1 is irradiated with laser light.

[0025] The electrostatic latent image formed on the photosensitive drum 1 is developed (visualized) by the developing device 8, which supplies toner as a developer, 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 carrier. The developing roller 4 contacts the surface of the photosensitive drum 1 with a predetermined contact pressure to form a developing section. A toner layer is formed on the developing roller 4 by the toner 3 charged to a predetermined polarity (negative polarity in this embodiment). A predetermined developing voltage (developing bias), which is a DC voltage, is applied to the developing roller 4 from a developing voltage application circuit of a developing voltage application section 342 (FIG. 2) as a developing voltage application means. As a result, the toner 3 adheres to the electrostatic latent image on the photosensitive drum 1 in the developing section. As a result, a toner image (developer image) is formed on the photosensitive drum 1. In this embodiment, a developing voltage of −400 V is applied to the developing roller 4.

[0026] In this embodiment, toner 3 charged with the same polarity as the charge polarity of the photosensitive drum 1 (negative polarity in this embodiment) adheres to an exposed portion (image portion) on the photosensitive drum 1, the absolute value of the potential of which has been reduced by exposure after being uniformly charged (reverse development method). In this embodiment, the normal charge polarity of the toner 3, which is the main charge polarity of the toner 3 during development, is negative polarity.

[0027] 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 to a recording material P, which is being conveyed while being sandwiched between the photosensitive drum 1 and the transfer roller 13, in the transfer portion. A predetermined transfer voltage (transfer bias) which is a DC voltage is applied from a transfer voltage application circuit of a transfer voltage application unit 343 (FIG. 2) as a transfer voltage application means to the transfer roller 13. In this embodiment, a transfer voltage of +1500 V is applied to the transfer roller 13.

[0028] A recording material (transfer material, recording medium, sheet) P is supplied to the transfer section from a paper feed section 30 at the bottom of the device main body M. The paper feed section 30 is configured to have a cassette 31 as a recording material storage section, a feed roller 32 as a feeding member, and the like. The recording material P stored in the cassette 31 is separated one by one by the feed roller 32 and sent out from the cassette 31. This recording material P is transported to the transfer section by a transport roller (registration roller) 50 as a transport member so as to be synchronized with the toner image on the photosensitive drum 1.

[0029] The recording material P onto which the toner image has been transferred is conveyed to a fixing device 14 serving as a fixing means. The fixing device 14 applies heat and pressure to the recording material P to fix (melt and adhere) the toner image onto the recording material P. The recording material P onto which the toner image has been fixed is discharged (output) onto a tray 40 serving as a discharge unit provided outside the image forming apparatus 100.

[0030] <<Cleanerless toner collection>> On the other hand, the toner (transfer residual toner) remaining on the photosensitive drum 1 without being transferred to the recording material P during the transfer step is removed from the photosensitive drum 1 in the following manner.

[0031] After the transfer process, the surface of the photosensitive drum 1 is neutralized by a neutralization device (discharging lamp) 11 so that the surface potential becomes 0 V, and then the photosensitive drum 1 enters the charging section. The residual toner remaining on the photosensitive drum 1 includes a mixture of positively charged toner and negatively charged toner that does not have a sufficient charge. This residual toner is charged negatively by discharge in the charging section.

[0032] The transfer residual toner, negatively charged in the charging section, reaches the developing section as the photosensitive drum 1 rotates. Here, an electrostatic latent image corresponding to image information is formed on the surface of the photosensitive drum 1 that has reached the developing section. The transfer residual toner adhering to the non-exposed area (non-image area) on the photosensitive drum 1 moves from the photosensitive drum 1 to the developing roller 4 in the developing section 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 of the developing device 8. The toner collected in the developing chamber 8b is used again for image formation.

[0033] On the other hand, the residual toner adhering to the exposed area (image area) on the photosensitive drum 1 does not move from the photosensitive drum 1 to the developing roller 4 in the developing section, but forms 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 in the transfer section and removed from the photosensitive drum 1.

[0034] <<Paper dust collection>> In addition, a brush member 12 is provided as a paper dust collecting member to remove paper dust fibers generated from the recording material P that adhere to the photosensitive drum 1 from the recording material P during the transfer process. The brush member 12 is disposed so as to come into contact with the photosensitive drum 1 downstream of the transfer unit in the rotation direction of the photosensitive drum 1 and upstream of the charging unit. As the photosensitive drum 1 rotates, the brush member 12 rubs against the surface of the photosensitive drum 1, thereby picking up and removing the paper dust fibers on the photosensitive drum 1 from the photosensitive drum 1.

[0035] <Detailed configuration of developing device 8> The detailed configuration of the developing device 8 in the image forming apparatus 100 of this embodiment will be described.

[0036] In this embodiment, the developing device 8 is a single-component developer that uses a non-magnetic single-component developer (toner). It is a component contact developing device. The developing device 8 has a developing container (frame) 80 that is configured with a toner storage chamber 8a as a developer storage chamber, and a developing chamber 8b in which the developing roller 4 as a developer carrier and the like are disposed. The developing chamber 8b and the toner storage chamber 8a are mutually communicated. In addition to the developing roller 4, the developing chamber 8b is provided with a supply roller 5 as a supply member for supplying toner 3 to the developing roller 4, and a developing blade 6 as a regulating member. The developing blade 6 is configured to regulate the amount of toner on the developing roller 4 while applying a charge of a predetermined polarity to the toner 3 on the developing roller 4.

[0037] The developing roller 4 is rotatably disposed in the opening of the developing chamber 8b (developing container 80), a part of the circumferential surface is exposed to the outside of the developing container 80 through the opening, and the area exposed to the outside of the developing container 80 faces the photosensitive drum 1. The developing roller 4 carries the toner 3 and rotates to transport the toner 3 from the inside to the outside of the developing chamber 8b (developing container 80). The toner storage chamber 8a stores the toner 3 as a developer. The toner storage chamber 8a is provided with an agitating member 7 for agitating the toner 3 in the toner storage chamber 8a and transporting the toner 3 from the toner storage chamber 8a to the developing chamber 8b.

[0038] In this embodiment, the developing roller 4 is configured by coating a base layer of silicone rubber and a surface layer of urethane 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. Also, in this embodiment, the electrical resistance value of the developing roller 4 is 1×10 4 ~1×10 12 It is Omega.

[0039] In this embodiment, the supply roller 5 is a conductive elastic sponge roller that is configured by forming a foam layer on the outer periphery of a core metal having a diameter of 6 mm. In this embodiment, the electrical resistance of the supply roller 5 is 1×10 4 ~1×10 8 The hardness of the supply roller 5 is measured by applying a load of 1 mm to a flat plate having a longitudinal width of 50 mm on the surface of the supply roller 5.

[0040] In this embodiment, the developing blade 6 is a 0.1 mm thick SUS sheet metal made of metal, having a predetermined length in a longitudinal direction aligned with the rotation axis direction of the developing roller 4 and in a lateral direction substantially perpendicular to the longitudinal direction. This developing blade 6 is arranged so that a free end in the lateral direction faces the upstream side in the rotation direction of the developing roller 4, and a side surface near the free end contacts the developing roller 4 along the longitudinal direction. In this embodiment, the developing blade 6 is made of a SUS sheet metal whose tip (free end) is cut from the contact surface side with the developing roller 4. The tip portion of the developing blade 6 is bent in the cutting direction by the cutting process, and the amount of bending of the tip of the developing blade 6 corresponding to the curvature radius R is 0.02 mm.

[0041] The movement of toner 3 in developing device 8 during operation will be described. Driving force is transmitted to developing device 8 from a driving motor 70 serving as a driving source constituting a driving means provided in device main body M. As a result, developing roller 4, supply roller 5, and stirring member 7 rotate in the directions of arrows R2 (clockwise), R3 (clockwise), and R4 (counterclockwise) in the figure, respectively.

[0042] Here, if 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 the developing peripheral speed ratio, the peripheral speed of the surface of the developing roller 4 is rotated at a predetermined peripheral speed so that the developing peripheral speed ratio becomes 1.4.

[0043] As the agitator 7 in the toner storage chamber 8a rotates, the toner 3 in the toner storage chamber 8a is agitated and transported toward the supply roller 5 in the development chamber 8b. The toner 3 held in the foam layer of the supply roller 5 is transported to the contact portion with the development roller 4 by the rotation of the supply roller 5. The toner 3 that has reached this contact portion is then spun in opposite directions at this contact portion. The toner particles are rubbed by the surface of the developing roller 4 and the surface of the supply roller 5 which are moving in the forward direction, and part of the toner particles adheres to the surface of the developing roller 4. Note that the supply roller 5 may be rotated in the same rotation direction as the developing roller 4, so that the moving directions of the supply roller 5 and the developing roller 4 at the contact portion are the forward directions.

[0044] The toner 3 adhering to the surface of the developing roller 4 is sent to the contact point with the developing blade 6 as the developing roller 4 rotates. The developing blade 6 regulates the amount of toner 3 adhering to the surface of the developing roller 4 to form a uniform thin layer, and also frictionally charges the toner 3. The thin layer of toner 3 is sent to the contact point 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.

[0045] The toner 3 remaining on the surface of the developing roller 4 without being used for development is transported 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 into the toner storage chamber 8a, and is stirred and mixed with the toner 3 in the toner storage chamber 8a.

[0046] <Toner supply configuration> The toner supply configuration to the developing container 80 of the developing device 8 in this embodiment will be described. Fig. 3(a) is a schematic front view of a toner pack 16 as a toner supply container in this embodiment. Fig. 3(b) is a schematic cross-sectional view showing a state in which the toner pack 16 is attached to the developing container 80 of the developing device 8.

[0047] As shown in Fig. 1 and Fig. 3(b), the developer container 80 is formed with a supply protrusion 8c. The supply protrusion 8c is hollow and communicates with the toner storage chamber 8a via a supply port 8d. A top cover 17 is provided on the top of the device main body M so as to be able to open and close. The upper surface of the top cover 17 constitutes the above-mentioned tray 40.

[0048] As shown in FIG. 3(a), in this embodiment, the toner pack 16 is configured to have a plastic bag 16a that is easily deformed and a connecting portion 16b provided at one end of the bag 16a. The inside of the bag 16a and the inside of the connecting portion 16b are in communication with each other. As shown in FIG. 3(b), the image forming apparatus 100 is configured such that the top cover 17 is opened so that the top of the supply protrusion 8c is opened (in the direction of retracting from the top of the supply protrusion 8c) so that the supply protrusion 8c is exposed to the outside of the apparatus. The toner pack 16 (the connecting portion 16b) can be attached to the end of the supply protrusion 8c. When the toner pack 16 is attached to the supply protrusion 8c, toner can be supplied from the toner pack 16 to the toner storage chamber 8a. With the top cover 17 open, the toner pack 16 is connected to the supply protrusion 8c by the connecting portion 16b, so that at least a portion of the end side of the bag 16a opposite the connecting portion 16b is exposed to the outside of the image forming device 100.

[0049] More specifically, when the toner pack 16 is attached to the supply protrusion 8c, the inside of the toner pack 16 (wrapping bag 16a, connecting portion 16b) and the inside of the supply protrusion 8c are in communication with each other. Then, the toner contained in the toner pack 16 is discharged from an opening (not shown) provided in the connecting portion 16b of the toner pack 16 into the supply protrusion 8c, and this toner is supplied from the supply protrusion 8c to the toner storage chamber 8a through the supply port 8d.

[0050] In this embodiment, the toner pack 16 serving as a toner supply container is configured to have a plastic bag that is easily deformed, but is not limited to this. For example, the toner supply container may be configured to have a bottle container having a substantially conical or cylindrical shape. Also, for example, the toner supply container may be configured to have a paper container made of paper.

[0051] In addition, the method of discharging the toner from the toner supply container is preferably such that, in the case of the toner pack 16 or a paper container as in this embodiment, the operator squeezes the container with his / her fingers, and in the case of a bottle container, the operator preferably discharges the toner by vibrating the container by tapping it, etc. In order to discharge the toner from the bottle container, a discharge mechanism may be provided in the bottle container. The discharge mechanism may be configured to engage with a drive mechanism provided in the image forming apparatus 100 and receive drive from the drive mechanism.

[0052] In order to prevent toner from leaking from the toner supply container, a rotating or sliding shutter member may be provided on the toner supply container. The shutter member may be configured to be destroyed when attached to the supply port of the developing device 8, or may have a removable cover structure such as a seal.

[0053] Furthermore, the top cover 17 may be configured so that at least the portion above the supply protrusion 8c (supply port 8d) can be opened. For example, the top cover 17 may not also function as the tray 40, or the top cover 17 may constitute a part of the tray 40.

[0054] <Toner supply instructions> By repeating the image forming operation, the toner contained in the toner storage chamber 8a is consumed. When the remaining amount of toner in the developing container 80 decreases and the toner amount detected by the toner amount sensor 18 falls below a preset toner low threshold, the engine control unit 302 displays a toner low display on the display unit 61 of the operation panel 60. The toner low display is a display indicating that the remaining amount of toner in the developing container 80 is low. Furthermore, when the image forming operation is further repeated from the timing when the toner low is detected and the toner amount detected by the toner amount sensor 18 falls below a preset toner out threshold, the engine control unit 302 displays a toner out display on the display unit 61 of the operation panel 60. The toner out display is a display indicating that the toner in the developing container 80 has run out. Furthermore, the engine control unit 302 displays a notation prompting the user to replenish toner together with the toner out display.

[0055] The toner remaining amount display configuration may be as shown in FIG. 6(a) to FIG. 6(c). As shown in FIG. 6(a) to FIG. 6(c), the toner remaining amount display is provided in a part of the housing of the device main body M of the image forming device 100. FIG. 6(a) is a perspective view of the toner remaining amount panel 400 that displays the toner remaining amount at a low level, and FIG. 6(b) is a perspective view of the toner remaining amount panel 400 that displays the toner remaining amount at a mid level. FIG. 6(c) is a perspective view of the toner remaining amount panel 400 that displays the toner remaining amount at a full level. The toner remaining amount panel 400 is a panel member including multiple (three in this case) scales 400a to 400c as indicators arranged vertically. When displaying that the toner remaining amount is at a low level, only the scale 400a is lit as shown in FIG. 6(a). When displaying that the toner remaining amount is at a mid level, the scales 400a and 400b are lit as shown in FIG. 6(b). When indicating that the remaining amount of toner is at the full level, all of the scales 400a to 400c are lit.

[0056] (assignment) Here, when an image forming operation with a low print ratio is repeated, image defects such as fogging may occur before the amount of toner in the developing container 80 reaches the toner Out threshold and toner replenishment is performed. An image forming operation with a low print ratio is an image forming operation in which the ratio (hereinafter referred to as the print ratio) of the print area (the area of ​​the portion of the image formable area where toner is placed) to the paper area (the area of ​​the image formable area of ​​the recording material) is small, and the amount of toner consumed is small. A typical example of image formation with a low print ratio is image formation in which the image is composed only of text and lines, resulting in a low print ratio.

[0057] In addition, when the printing rate is the same for a small-sized recording material and a large-sized recording material, the printing area of ​​the small-sized recording material is relatively smaller than that of the large-sized recording material, so image defects such as the above-mentioned fogging are more likely to occur. In this embodiment, control of the image forming operation based on the printing rate of an LTR-sized recording material as a small-sized recording material will be described. In this embodiment, a printing rate of 100% corresponds to the printing amount when a solid black image is formed in the entire image formable area on one LTR-sized recording material.

[0058] Deterioration of the toner is one of the causes of image defects such as fogging, and one of the factors of toner deterioration is the flow and stirring of the toner in the developing container during the image forming operation. The toner in the developing container 80 is repeatedly rubbed by the supply roller 5 and the developing blade 6 during the image forming operation, and the external additive is separated or embedded in the toner matrix, and the toner matrix itself is deformed, and the toner deteriorates. The toner used for development during the image forming operation is only a part of the toner in the developing container, and most of the toner remains in the developing container 80 without being used for development. Such toner residue becomes more noticeable when image forming operations with a low printing rate are continued. The lower the printing rate of the image formation, the more toner in the developing container 80 remains in the developing container 80 without being consumed, and many image forming operations are repeated until toner is replenished into the developing container 80. The deterioration of the toner progresses as the toner continues to remain in the developing container without being used for development every time an image forming operation is performed. Therefore, the lower the printing rate of image formation, the more the toner deterioration in the developing container 80 is accelerated before the amount of toner in the developing container is consumed to a predetermined amount that prompts the user to replenish toner, and the more likely image defects such as fogging are to occur before toner replenishment is performed.

[0059] (Features) Therefore, in this embodiment, a low print rate compatible mode is provided to suppress the occurrence of image defects such as fogging before the toner amount in the developing container 80 reaches the toner Out threshold and toner replenishment is performed even when image forming operations with low print rates are repeated. That is, the image forming apparatus 100 of this embodiment is configured to be executable as options between the normal mode (first operation mode) corresponding to the normal image forming operations described above and the low print rate compatible mode (second operation mode) corresponding to the image forming operations with low print rates.

[0060] The low print rate compatible mode can be selected at the input unit 62 of the operation panel 60. When the user selects the low print rate compatible mode at the input unit 62 of the operation panel 60, the selection of the low print rate compatible mode is transmitted to the engine control unit 302, and the selection of the low print rate compatible mode is stored in the engine control unit 302.

[0061] When the low print rate compatible mode is selected, the engine control unit 302 makes the following changes to the normal mode corresponding to the normal image forming operation.

[0062] First, when the low print rate compatible mode is selected, the circumferential speed of the photosensitive drum 1 (movement speed of the circumferential surface of the photosensitive drum 1) is set to 2 / 3 times that of the normal image forming operation. Furthermore, when the low print rate compatible mode is selected, the circumferential speed of the developing roller 4 is also set to 2 / 3 times that of the normal image forming operation, so that the developing circumferential speed ratio is 1.4, which is the same as that of the normal image forming operation.

[0063] The configuration in which the circumferential speeds of the photosensitive drum 1 and the developing roller 4 are variable can be realized, for example, by making the drive configuration of the photosensitive drum 1 and the drive configuration of the developing roller 4 independent of each other and having the engine control unit 302 (image formation control unit 340) control each of them individually. That is, the photosensitive drum 1 and the developing roller 4 are driven by different drive motors (drive sources). Note that, when the development circumferential speed ratio is maintained constant between the normal mode and the low printing rate compatible mode as in this embodiment, the photosensitive drum and the developing roller may be driven by the same drive motor (common drive source).

[0064] Furthermore, when the low printing rate compatible mode is selected, the exposure intensity of the laser light from the exposure device 10 on the surface of the photosensitive drum 1 is set to 1.2 times that of the normal image forming operation. One method for increasing the exposure intensity is, for example, to increase the output of the laser light from the exposure device 10 (amount of light per unit area on the surface of the photosensitive drum 1). That is, in the normal mode, as described above, the output (amount of light) of the laser light from the exposure device 10 is set to 0.35 μJ / cm, which is the predetermined exposure amount (first exposure amount). 2On the other hand, in the low printing rate compatible mode, the output of the laser light from the exposure device 10 is set to 0.42 μJ / cm 2 , which is the second exposure amount. 2 (second exposure intensity).

[0065] Other controls when the low printing rate compatible mode is selected are the same as those in the normal image forming operation, and therefore a description thereof will be omitted.

[0066] (effect) Next, the effect of the low print rate compatible mode of this embodiment will be described.

[0067] In the low printing rate compatible mode, the peripheral speed of the photosensitive drum 1 is reduced compared to the normal image forming operation, so that the time during which the photosensitive drum 1 is exposed to light from the exposure device 10 is longer, the amount of exposure per unit area of ​​the photosensitive drum 1 is increased, and the amount of exposure on the surface of the photosensitive drum 1 can be increased. In the low printing rate compatible mode, the exposure intensity of the exposure device 10 on the surface of the photosensitive drum 1 is increased compared to the normal image forming operation, so that the amount of exposure on the surface of the photosensitive drum 1 during the image forming operation can be increased compared to the normal image forming operation. In this way, in the low printing rate compatible mode, the amount of exposure on the surface of the photosensitive drum 1 is increased compared to the normal image forming operation, so that a deeper latent image can be formed on the surface of the photosensitive drum 1 than in the normal image forming operation. A deep latent image is an electrostatic latent image in which the potential difference between the image portion potential formed by the exposure of the exposure device 10 on the peripheral surface of the photosensitive drum 1 and the non-image portion potential formed by the exposure of the exposure device 10 that is not exposed to the exposure device 10 or is very little exposed to the exposure device 10 is larger. Therefore, the amount of toner developed from the developing roller 4 onto the latent image on the surface of the photosensitive drum 1 increases, and the amount of toner consumed within the developing container 80 during the image forming operation can be increased.

[0068] In the low printing rate compatible mode, the peripheral speed of the developing roller 4 is also reduced in accordance with the reduction in the peripheral speed of the photosensitive drum 1 compared to the normal image forming operation, and the developing peripheral speed ratio is set to 1.4, which is the same as that in the normal image forming operation. In contrast, if the developing peripheral speed ratio is not kept constant and is increased in the low printing rate compatible mode compared to the normal image forming operation, the developing roller 4 is rotated faster relative to the photosensitive drum 1, and the opportunity for the toner to rub against the developing roller 4 increases. According to this embodiment, it is possible to suppress such an increase in the opportunity for the toner to rub against the developing roller 4 and suppress the promotion of toner deterioration due to the increase in the opportunity for the toner to rub against the developing roller 4. From the viewpoint of toner deterioration, it is preferable to maintain or reduce the developing peripheral speed ratio, but depending on the conditions, the developing peripheral speed ratio may be controlled to be increased in consideration of the toner deterioration.

[0069] (Effectiveness check) In order to confirm the effect of the low print rate compatible mode of this embodiment, the following test was carried out.

[0070] The test was performed in the image forming apparatus of this embodiment, with the low print rate compatible mode specified, in a normal environment of 23°C and 50%, by repeatedly printing text images with a print rate of 1.5% on LTR size paper every two sheets until Toner Out was displayed. The paper used was "Vitality75 (manufactured by Xxrox)". Before the test, the developer container 80 was filled with an amount of toner that would cause Toner Out to be displayed when about 5,000 sheets of images with a print rate of 4.0% were printed on LTR size paper.

[0071] As a comparative example, the above test was carried out in an image forming apparatus having the same configuration as the image forming apparatus of this embodiment, without specifying the low print rate compatible mode.

[0072] First, in the image forming apparatus of this embodiment, the low print rate compatible mode is specified, so the amount of toner consumed in one image forming operation is greater than when the normal mode is specified. Therefore, in the image forming apparatus of this embodiment, the Toner Out message is displayed when about 11,000 sheets have been printed since the start of the test, and no image defects such as fogging occurred until the Toner Out message is displayed.

[0073] Furthermore, by slowing down the rotation speed of the photosensitive drum and increasing the amount of exposure, it is possible to form an electrostatic latent image with a sharper gradient at the boundary between the potential of the image area and the potential of the non-image area, which makes it possible to form an image with a clearer boundary between the image area and the non-image area, particularly in a text image, thereby improving the image quality.

[0074] On the other hand, in the image forming apparatus of the comparative example, the low print rate compatible mode is not specified, so the toner consumption during one image forming operation is less than that of the image forming apparatus of this embodiment in which the low print rate compatible mode is specified. Therefore, in the image forming apparatus of the comparative example, an image defect due to fogging occurred when about 13,000 sheets were printed from the start of the test, and then a Toner Out message was displayed when about 14,000 sheets were printed.

[0075] As described above, according to the low printing rate compatible mode of this embodiment, even if image formation operations with low printing rates are repeated, it is possible to prevent image defects such as fogging from occurring before toner replenishment is performed due to the toner amount in the developing container 80 reaching the Toner Out threshold.

[0076] In addition, in this embodiment, the low print rate compatible mode is configured to be selected from the input unit 62 of the operation panel 60 provided in the image forming apparatus, but the method of selecting the low print rate compatible mode is not limited to the configuration of selecting from the input unit 62 of the operation panel 60. For example, the low print rate compatible mode may be selected from an information device such as a personal computer, smartphone, tablet terminal, etc., serving as a host computer connected to the image forming apparatus.

[0077] In addition, in this embodiment, the configuration in which the operator selects the low print rate compatible mode has been described, but the image forming apparatus may be configured to automatically select the low print rate compatible mode according to the print rate of the image to be formed. Alternatively, the image forming apparatus may be configured to automatically select the low print rate compatible mode according to the toner consumption pace in the developing container 80 detected by the toner amount sensor 18.

[0078] The automatic switching of the operation mode according to the printing rate may be configured to detect the printing rate by the following method. That is, a measuring means (pixel count) capable of counting the number of pixels emitted by the exposure device 10 may be used to obtain the printing rate based on the number of pixels relative to the printing area (the amount of toner consumed in printing one sheet of recording material). The measuring means may be configured by the engine control unit 302, or may be provided separately from the engine control unit 302. The pixel count is to count individual image signals forming image dots of an image to be formed from image data after image processing contained in the image information transmitted from the image processing unit 303 to the engine control unit 302. The amount of toner required to develop a certain image is estimated by the engine control unit 302 (image formation control unit 340) from the number of pixels emitted by the exposure device 10 as the toner consumption amount x [%] used in printing one sheet of recording material.

[0079] In addition, the threshold value of the print rate in the automatic switching of the operation mode according to the print rate (predetermined print rate ) may be set to 1.5 to 2.0%. In other words, when the detected print rate is equal to or lower than a predetermined print rate, the low print rate compatible mode may be selected and executed.

[0080] Example 2 In the image forming apparatus according to the second embodiment of the present invention, when the low print rate compatible mode is selected, the developing roller 4 is rotated at a peripheral speed such that the developing peripheral speed ratio is 1.3. Since the rest of the configuration is the same as that of the first embodiment, the description will be omitted.

[0081] In the configuration of this embodiment, the development peripheral speed ratio (1.3) when the low print rate compatible mode is selected is smaller than the development peripheral speed ratio (1.4) during normal image formation operation, thereby reducing the opportunities for rubbing of the toner on the development roller 4 and preventing toner deterioration.

[0082] In this embodiment, the developing circumferential speed ratio when the low printing rate compatible mode is selected is set to 1.3, but if the developing circumferential speed ratio is made too small, it may not be possible to increase the amount of toner consumed even if the electrostatic latent image on the surface of the photosensitive drum 1 is formed deeper than during normal image forming operations when the low printing rate compatible mode is selected. In other words, if the developing circumferential speed ratio is made too small, it may actually promote toner deterioration, so it is preferable to set the reduction range of the developing circumferential speed ratio in accordance with the characteristics of the image forming apparatus.

[0083] Example 3 In the image forming apparatus according to the third embodiment of the present invention, the gradation table for halftoning (gradation correction) used by the image processing unit 303 is changed between when the low printing rate compatible mode is selected and when the low printing rate compatible mode is not selected. The gradation table used when the low printing rate compatible mode is selected is set to select a gradation on the lighter side when performing halftoning on image data of intermediate tones of the same density, compared to the gradation table used when the low printing rate compatible mode is not selected. The rest of the configuration is the same as that of the first embodiment, so a description thereof will be omitted.

[0084] As shown in Fig. 4, in normal mode, a normal mode table (first gradation table) with a gradation curve shown by a dashed line in the figure is used, and in low printing rate compatible mode, a low printing rate compatible mode table (second gradation table) with a gradation curve shown by a dashed line in the figure is used. These two gradation tables have different densities of output data for the same input data. Specifically, for the value (density) of output data corresponding to certain input data, the value of the output data when the low printing rate compatible mode table is used is smaller (lighter) than the value of the output data when the normal mode table is used.

[0085] If the electrostatic latent image on the surface of the photosensitive drum 1 is formed deeper (the potential difference between the image portion and the non-image portion is made larger) than in the normal image forming operation when the low print rate compatible mode is selected using the same gradation table as in the normal image forming operation, the halftone image portion may be formed with a higher density than in the normal image forming operation. By using different gradation tables depending on the operation mode as in this embodiment, it is possible to prevent the density of the formed image from becoming too high.

[0086] It is preferable to determine, in accordance with the characteristics of the image forming apparatus itself, how much lighter halftone gradation should be selected as the gradation table used when the low printing rate compatible mode is selected, compared to the gradation table used when the low printing rate compatible mode is not selected. In addition, in this embodiment, the case where only one gradation table for the low printing rate compatible mode is provided is exemplified, but multiple gradation tables may be provided in stages. For example, the gradation table to be used may be switched between multiple gradation tables for the low printing rate compatible mode so that the density is gradually lowered according to the size of the printing rate.

[0087] Example 4 In the image forming apparatus according to the fourth embodiment of the present invention, when the low print rate compatible mode is selected, image processing (expansion processing) is performed so that the periphery of an image portion determined to be text or a line in the image data by the image processing unit 303 is exposed by the exposure device 10. The rest of the configuration is the same as that of the first embodiment, so a description thereof will be omitted.

[0088] Image data includes information about the attributes of each object, such as the text (characters), lines, graphics, and photographic parts that make up the image, the number of pixels, the gradation value of each pixel, and coordinates within the image.

[0089] FIG. 5(a) is a schematic diagram showing pixel data constituting the character "A" as an example of an object whose attribute is text. As shown in FIG. 5(a), for example, when the character "A" is included in image data, the area in the image where the character "A" is formed is composed of image portion pixel P1 constituting the character "A" and 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 black dots, has a gradation value of, for example, 255, is a pixel that is irradiated with laser light during exposure and toner adheres to it. The non-image portion pixel P0 is typically a white image portion that forms white or pale colored dots, has a gradation value of 0 or a value close to 0, is a pixel that is not irradiated with laser light during exposure, or is a pixel that is irradiated with weak laser light at a weak output.

[0090] Fig. 5(b) is a schematic diagram showing image data after performing expansion processing on pixel data constituting the character "A" shown in Fig. 5(a). As shown in Fig. 5(b), as an example of expansion processing, the image processing unit 303 changes the image data so that, among non-image portion pixels P0 included in the formation area of ​​the character "A" in the image, non-image portion pixel P0 adjacent to image portion pixel P1 is replaced with image portion pixel P2. Image portion pixel P2 is a pixel that constitutes the character "A" together with image portion pixel P1. The gradation value of image portion pixel P2 may be the same as or different from the gradation value of image portion pixel P1.

[0091] By performing image processing so that the periphery of the black image area is exposed by exposure device 10 as in this embodiment, when the low printing rate compatible mode is selected, it is possible to increase the amount of toner consumed in the black image area without increasing the density of the halftone image area.

[0092] In this embodiment, when the low printing rate compatible mode is selected, in addition to the operation of the low printing rate compatible mode of the first embodiment, the image processing unit 303 performs image processing (expansion processing) so that the periphery of the black image portion is exposed by the exposure device 10, but the present invention is not limited to such a configuration. For example, when the low printing rate compatible mode is selected, it is also possible to simply perform image processing in the image processing unit 303 so that the periphery of the black image portion is exposed by the exposure device 10 without reducing the circumferential speed of the photosensitive drum 1 or increasing the exposure intensity as in the first embodiment.

[0093] When the low printing rate compatible mode is selected, it is preferable to determine the extent to which the exposure device 10 exposes the periphery of the black image portion in the image processing unit 303 in accordance with the image quality of the text image or line image and the rate of increase in toner consumption. Moreover, the specific method of the expansion process described above is merely an example, and any of various types of image processing known in the art may be appropriately adopted instead of the above method as long as the image processing is capable of increasing the amount of toner consumption when the low printing rate compatible mode is implemented compared to the normal mode.

[0094] In this embodiment, the device configuration of the contact development type in which the photosensitive drum 1 and the developing roller 4 come into contact with each other to form the developing portion has been described, but the present invention is also applicable to an image forming apparatus of a non-contact development type. That is, the photosensitive drum 1 and the developing roller 4 do not come into contact with each other, and the closest opposing portions form the developing portion, and the toner is transferred from the developing roller 4 to the photosensitive drum 1. This is an image forming device that develops an electrostatic latent image on a peripheral surface by scattering toner particles.

[0095] In addition, in this embodiment, a so-called monochrome type image forming apparatus, that is, an image forming apparatus having a single image forming unit, is exemplified, but the image forming apparatus to which the present invention can be applied is not limited to this. For example, the present invention is also suitably applied to a so-called full-color type image forming apparatus, that is, an image forming apparatus having a plurality of image forming units. The difference in device configuration between a monochrome image forming apparatus and a color image forming apparatus is, first, that the color and number of colors of the image formed are different. That is, a monochrome image forming apparatus can form an image of a single color (typically black), but a color image forming apparatus can form an image of any color by superimposing a plurality of developer images of different colors on each other. In addition, in an intermediate transfer type color image forming apparatus, a developer image is first transferred from a photosensitive body as an image carrier to an intermediate transfer body (which can also be called a second image carrier) as a first transferee, and then transferred from the intermediate transfer body to a recording material as a second transferee. In contrast, in a monochrome image forming apparatus or a direct transfer type color image forming apparatus, a developer image is transferred directly from a photosensitive body to a recording material.

[0096] The configurations and control methods of the above-described embodiments can be combined with each other as much as possible.

[0097] The disclosure of the embodiments of the present invention includes the following configurations. (Configuration 1) A rotating image carrier; a charging member that contacts the image bearing member and charges the surface of the image bearing member; a charging voltage application unit that applies a charging voltage to the charging member; an exposure unit for exposing a surface of the image carrier to light to form an electrostatic latent image on the surface of the image carrier; a developer container for containing a developer; a rotating developer carrier that carries the developer contained in the developer container and supplies the carried developer to a surface of the image carrier; a drive unit that drives the image carrier and the developer carrier; a control unit that controls the drive unit, the charging voltage application unit, the charging voltage application unit, and the exposure unit; an image forming apparatus comprising: a developer carrying member that develops the electrostatic latent image with a developer image, the developer image being transferred onto a recording material to form an image on the recording material; The control unit: a first operation mode in which the image carrier is rotated at a first peripheral speed and the exposure unit exposes a surface of the image carrier with a first exposure intensity; a second operation mode in which the image carrier is rotated at a second peripheral speed slower than the first peripheral speed, and the exposure unit exposes a surface of the image carrier with a second exposure intensity stronger than the first exposure intensity; An image forming apparatus comprising: (Configuration 2) Regarding the printing rate, which is the ratio of the developer image to the imageable area of ​​the recording material, 2. The image forming apparatus according to claim 1, wherein the printing rate in the second operation mode is lower than the printing rate in the first operation mode. (Configuration 3) Regarding the peripheral speed ratio, which is the ratio of the peripheral speed of the developer carrier to the peripheral speed of the image carrier, 3. The image forming apparatus according to claim 1, wherein the peripheral speed ratio in the first operation mode is equal to the peripheral speed ratio in the second operation mode. (Configuration 4) Regarding the peripheral speed ratio, which is the ratio of the peripheral speed of the developer carrier to the peripheral speed of the image carrier, 3. The image forming apparatus according to claim 1, wherein the peripheral speed ratio in the second operation mode is smaller than the peripheral speed ratio in the first operation mode. (Configuration 5) As a gradation table used when correcting the gradation of image data used for forming an image, a first gradation table used in the first operation mode; a second gray scale table used in the second operation mode; having The image forming apparatus according to any one of configurations 1 to 4, characterized in that for the same input data, the density of the output data when the second gradation table is used is lighter than the density of the output data when the first gradation table is used. (Configuration 6) The image forming apparatus according to any one of configurations 1 to 5, further comprising an image processing unit that processes image data in the second operating mode so as to replace non-image pixels adjacent to image pixels among non-image pixels included in a text or line formation area in the image with image pixels. (Configuration 7) 7. The image forming apparatus according to any one of configurations 1 to 6, further comprising an input unit that receives an input from a user regarding a selection of an operation mode to be used in an image forming operation. (Configuration 8) an acquisition unit that acquires the printing rate before an image forming operation is performed; The control unit is When the printing rate acquired by the acquisition unit is higher than a predetermined printing rate, the image forming operation is performed in the first operation mode. The image forming apparatus according to any one of configurations 1 to 7, characterized in that, when the printing rate acquired by the acquisition unit is equal to or lower than a predetermined printing rate, the image forming operation is performed in the second operation mode. (Configuration 9) The image forming apparatus according to any one of configurations 1 to 8, characterized in that the developer remaining on the image carrier without being transferred to the recording material is configured to be recoverable in the developer accommodating section via the developer carrier. (Configuration 10) Regarding the amount of light per unit area of ​​the laser light irradiated by the exposure unit onto the surface of the image carrier, 10. The image forming apparatus according to any one of configurations 1 to 9, wherein the amount of light in the second operation mode is greater than the amount of light in the first operation mode. (Configuration 11) Regarding the potential difference between the image portion potential formed by the exposure of the exposure unit and the non-image portion potential in the image carrier, 11. The image forming apparatus according to any one of configurations 1 to 10, wherein the potential difference in the second operation mode is larger than the potential difference in the first operation mode. (Configuration 12) 12. The image forming apparatus according to any one of Configurations 1 to 11, wherein the developer carrier contacts the image carrier and supplies the developer to the surface of the image carrier. [Explanation of symbols]

[0098] 1: photosensitive drum, 2: charging roller, 4: developing roller, 8: developing device, 16: toner pack, 18: toner amount sensor, 60: operation panel, 300: host computer, 304: print control device

Claims

1. A rotating image carrier; a charging member that contacts the image bearing member and charges the surface of the image bearing member; a charging voltage application unit that applies a charging voltage to the charging member; an exposure unit for exposing a surface of the image carrier to light to form an electrostatic latent image on the surface of the image carrier; a developer storage unit that stores a developer; a rotating developer carrier that carries the developer contained in the developer container and supplies the carried developer to a surface of the image carrier; a drive unit that drives the image carrier and the developer carrier; a control unit that controls the drive unit, the charging voltage application unit, the charging voltage application unit, and the exposure unit; an image forming apparatus comprising: a developer carrying member that develops the electrostatic latent image with a developer image, the developer image being transferred onto a recording material to form an image on the recording material; The control unit: a first operation mode in which the image carrier is rotated at a first peripheral speed and the exposure unit exposes a surface of the image carrier with a first exposure intensity; a second operation mode in which the image carrier is rotated at a second peripheral speed slower than the first peripheral speed, and the exposure unit exposes a surface of the image carrier with a second exposure intensity stronger than the first exposure intensity; An image forming apparatus comprising:

2. Regarding the printing rate, which is the ratio of the developer image to the imageable area of ​​the recording material, 2. The image forming apparatus according to claim 1, wherein the printing rate in the second operation mode is lower than the printing rate in the first operation mode.

3. Regarding the peripheral speed ratio, which is the ratio of the peripheral speed of the developer carrier to the peripheral speed of the image carrier, 2. The image forming apparatus according to claim 1, wherein the peripheral speed ratio in the first operation mode is the same as the peripheral speed ratio in the second operation mode.

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

5. As a gradation table used when correcting the gradation of image data used for forming an image, a first gradation table used in the first operation mode; a second gradation table used in the second operation mode; having 2. The image forming apparatus according to claim 1, wherein the density of the output data when the second gradation table is used is lower than the density of the output data when the first gradation table is used for the same input data.

6. 2. The image forming apparatus according to claim 1, further comprising an image processing unit that processes image data so as to replace, in the second operating mode, non-image pixels adjacent to image pixels included in a text or line formation area in the image with image pixels.

7. 2. The image forming apparatus according to claim 1, further comprising an input unit for receiving an input from a user regarding a selection of an operation mode to be used in the image forming operation.

8. an acquisition unit that acquires the printing rate before an image forming operation is performed; The control unit is When the printing rate acquired by the acquisition unit is higher than a predetermined printing rate, the image forming operation is performed in the first operation mode. The image forming apparatus according to claim 2 , wherein when the printing rate acquired by the acquisition unit is equal to or lower than a predetermined printing rate, the image forming operation is performed in the second operation mode.

9. 2. The image forming apparatus according to claim 1, wherein the developer remaining on the image carrier without being transferred to the recording material is recoverable in the developer accommodating section via the developer carrier.

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

11. Regarding the potential difference between the image portion potential formed by the exposure of the exposure unit and the non-image portion potential in the image carrier, 2. The image forming apparatus according to claim 1, wherein the potential difference in the second operation mode is greater than the potential difference in the first operation mode.

12. 2. The image forming apparatus according to claim 1, wherein the developer carrying member contacts the image carrying member to supply the developer to a surface of the image carrying member.

Images