Image forming apparatus

Abstract

An image forming apparatus is disclosed. The image forming apparatus controls a number of rotations of a photosensitive drum based on usage history information about the photosensitive drum and a suspension time after a rotation operation of rotating the photosensitive drum after a suspension time between a first image forming operation of forming an image on a transfer material and a second image forming operation performed after the first image forming operation.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus using an electrophotographic recording method, such as a laser printer, a copying machine, and a facsimile machine. Background Art

[0002] Electrophotographic image forming devices uniformly charge a photosensitive drum, serving as an image bearing member, and then expose the drum to light based on an image pattern, forming an electrostatic latent image on the drum. The electrostatic latent image on the drum is then developed and visualized using toner, and the resulting image is transferred to a recording material such as a sheet. Untransferred residual toner is then removed from the drum and recovered. While various cleaning methods are known for removing untransferred residual toner, a brush is widely recognized as an effective method.

[0003] Japanese Patent Application Laid-Open No. 2007-65580 discusses a structure having a brush for cleaning toner from a photosensitive drum, with the brush positioned upstream of a charging unit and downstream of a transfer unit in the direction of movement of the photosensitive drum. According to this document, when image formation is interrupted, for example due to a paper jam, the brush is charged to a predetermined polarity to prevent untransferred toner from the photosensitive drum from accumulating on the brush and maintain cleaning performance.

[0004] However, the technology discussed in Japanese Patent Application Laid-Open No. 2007-65580 has the following problem. Specifically, in the case where a recording material is fed through an image forming apparatus having a brush disclosed in Japanese Patent Application Laid-Open No. 2007-65580, moisture in the image forming apparatus adheres to the brush. As the pause time passes, the moisture accumulated on the brush gathers on the surface of the photosensitive drum, forming many water droplets. In the case where the next image forming operation is performed in this state, the many water droplets on the brush move onto the photosensitive drum. This changes the state of the surface of the photosensitive drum and causes image defects in some cases. For example, the many water droplets on the photosensitive drum attract toner at a developing abutment portion that is a contact portion between the photosensitive drum and the developing member, and this sometimes causes toner contamination. Summary of the Invention

[0005] The present invention is directed to reducing image defects caused by toner contamination from water droplets on the brush.

[0006] 14. The image forming apparatus of claim 13, wherein the photosensitive drum is rotated and the developing member is configured to supply toner to the surface of the photosensitive drum charged by the charging member and to form a toner image on the photosensitive drum; a transfer member is configured to contact the photosensitive drum to form a transfer portion and to transfer the toner image formed on the photosensitive drum to a transfer material at the transfer portion; a brush member is configured to contact the surface of the photosensitive drum at a position downstream of the transfer portion and upstream of the charging portion in the rotation direction of the photosensitive drum; a drive unit is configured to rotate the photosensitive drum; a storage unit is configured to store information about the use of the photosensitive drum; and a control unit is configured to control the drive unit, wherein the control unit controls the rotation operation of rotating the photosensitive drum so that a suspension time (suspension time) between a first image forming operation of forming an image on the transfer material and a second image forming operation performed after the first image forming operation has elapsed. time) and before the second image forming operation is performed, and wherein the control unit controls the number of rotations of the photosensitive drum in the rotating operation based on the information and the pause time.

[0007] 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

[0008] Figure 1 is a diagram illustrating an image forming apparatus according to a first exemplary embodiment.

[0009] Figure 2A and Figure 2B is a schematic diagram illustrating a brush member according to a first exemplary embodiment.

[0010] Figure 3 is a control block diagram according to the first exemplary embodiment.

[0011] Figure 4A 、 Figure 4B and Figure 4C is a view illustrating moisture attached to the brush member according to the first exemplary embodiment.

[0012] Figure 5A 、 Figure 5B and Figure 5C is a diagram illustrating a state of a portion around a photosensitive drum during an image output operation according to the first exemplary embodiment.

[0013] Figure 6 A table illustrating the extension time of the front rotation process according to the first exemplary embodiment.

[0014] Figure 7 FIG. 13 is a table illustrating toner contamination results according to a first exemplary embodiment.

[0015] Figure 8 FIG. 14 is a timing chart illustrating a pre-rotation process according to the first exemplary embodiment.

[0016] Figure 9 FIG. 15 is a view illustrating toner and moisture on a brush member according to the first exemplary embodiment.

[0017] Figure 10 FIG. 18 is a table illustrating an extended time of a pre-rotation process according to a second exemplary embodiment.

[0018] Figure 11A and Figure 11B FIG. 22 is a view illustrating a process of measuring a water absorption amount of a brush member according to a fourth exemplary embodiment.

[0019] Figure 12 FIG. 25 is a view illustrating a state of a portion around a photosensitive drum during an image forming process according to a fifth exemplary embodiment.

[0020] Figure 13 FIG. 26 is a view illustrating a state of toner first recovered by a brush member according to the fifth exemplary embodiment. DETAILED DESCRIPTION

[0021] Various exemplary embodiments of the present application will be described below in detail with reference to the accompanying drawings based on examples. It should be noted that the size, material, shape, and relative positions of the components described in the exemplary embodiments will be appropriately changed depending on the structure and various conditions of the apparatus to which the present application is applied. In other words, the scope of the present application is not limited to the exemplary embodiments described below.

[0022] 1. Image forming apparatus

[0023] Figure 1 FIG. 1 is a schematic view illustrating a structure of an image forming apparatus 100 according to a first exemplary embodiment.

[0024] The image forming apparatus 100 according to the present exemplary embodiment is a monochrome laser beam printer using a cleanerless method and a contact charging method. The image forming apparatus 100 includes a photosensitive drum 1. The photosensitive drum 1 is a drum-shaped (cylindrical) electrophotographic photosensitive member serving as a rotatable image bearing member. When an image output operation is started, the photosensitive drum 1 is driven by a driving motor (driving unit) of a driving unit 110 ( Figure 3 ) and rotates in the direction of an arrow R1 in Figure 1 The outer diameter of the photosensitive drum 1 is 24 mm, and the peripheral speed (surface speed) of the photosensitive drum 1 is 140 mm / sec.

[0025] The surface of the rotating photosensitive drum 1 is uniformly charged to a predetermined potential of normal polarity (negative polarity according to this exemplary embodiment) by the charging roller 2 near the charging portion a where the photosensitive drum 1 and the charging roller 2 contact each other. The charging roller 2 is a roller-type charging member that serves as a charging unit. More specifically, the charging roller 2 charges the surface of the photosensitive drum 1 by discharging in at least one of the tiny spaces between the charging roller 2 and the photosensitive drum 1, which are formed upstream and downstream of the contact portion with the photosensitive drum 1 in the rotational direction of the photosensitive drum 1. In this exemplary embodiment, the abutment portion between the charging roller 2 and the photosensitive drum 1 in the rotational direction of the photosensitive drum 1 will be described as the charging portion a.

[0026] The charging roller 2 is an elastic roller including a conductive elastic layer surrounding a core metal. The charging roller 2 is disposed in contact with the photosensitive drum 1 and is driven by a driving motor (not shown). Figure 1 The drive is driven and rotated in the direction of the arrow R2.

[0027] Although the charging roller 2 is driven and rotated according to the present exemplary embodiment, the charging roller 2 may be rotated by the rotation of the photosensitive drum 1. The charging power source E1 ( Figure 3 ) A predetermined charging voltage is applied to the charging roller 2. The predetermined charging voltage is a negative DC voltage. According to this exemplary embodiment, a negative DC voltage is applied to the charging roller 2 as the charging voltage during the charging process. An example of the charging voltage according to this exemplary embodiment is -1200 V. Therefore, according to this exemplary embodiment, the surface of the photosensitive drum 1 is uniformly charged to a dark area potential Vd of -600 V.

[0028] The charged surface of the photosensitive drum 1 is scanned and exposed with a laser beam L modulated based on image data by an exposure unit (laser exposure unit) 4 serving as an exposure unit (electrostatic image forming unit). The exposure device 4 forms an electrostatic latent image on the photosensitive drum 1 by repeatedly exposing the photosensitive drum 1 with the laser beam L in the main scanning direction (rotation axis direction) while also performing exposure in the sub-scanning direction (surface movement direction). According to this exemplary embodiment, the absolute value of the dark area potential Vd of the surface of the photosensitive drum 1 formed due to uniform charging is reduced to a light area potential Vl of -100 V due to exposure by the exposure device 4. The position on the photosensitive drum 1 exposed by the exposure device 4 in the rotational direction of the photosensitive drum 1 is the image exposure portion b. The exposure device 4 is not limited to a laser scanner device. For example, an LED array having a plurality of light emitting diodes (LEDs) arranged along the length of the photosensitive drum 1 can be used.

[0029] The electrostatic latent image formed on the photosensitive drum 1 is developed (visualized) as a toner image by a developing device 3 serving as a developing unit using a toner as a developer. The toner as a developer according to this exemplary embodiment is a spherical non-magnetic toner having an average particle size of 6.4 μm and an average circularity of 0.98. The non-magnetic toner used in this exemplary embodiment ideally has a high average circularity, specifically 0.96 or higher. The average circularity according to this exemplary embodiment is used as a simple way to quantitatively represent the shape of the particles. The particle shape is measured using a flow-type particle image analyzer FPIA-2100 manufactured by TOA Medical Electronics Co., Ltd., and the circularity is calculated using the following formula (1).

[0030]

[0031] In addition, as expressed in the following formula (2), the average circularity is defined as a value obtained by dividing the sum of the measured circularities of all particles by the total number of particles.

[0032]

[0033] The developing device 3 includes a developing roller 31 serving as a developer carrying member, a toner supply roller 32 serving as a developer supply unit, a developer storage chamber 33 storing toner, and a developing blade 34. The toner stored in the developer storage chamber 33 is stirred by a stirring member 35 and supplied to the surface of the developing roller 31 by the toner supply roller 32. The toner supplied to the surface of the developing roller 31 is transported through the contact portion between the developing roller 31 and the developing blade 34. Therefore, the toner is formed into a uniform thin layer and is charged to a negative polarity by friction charging. Although a single-component non-magnetic contact developing method is used in the present exemplary embodiment, the method is not limited thereto, and a two-component non-magnetic contact method or a non-contact developing method may also be used. In addition, a magnetic developing method may be used. In addition, although according to the present exemplary embodiment, the normal polarity of the toner is negative polarity, the normal polarity is not limited to negative polarity. The normal polarity may be positive polarity, and in this case, the voltage relationship described below is appropriately reversed to the opposite polarity. The developing roller 31 is driven by the motor 110 in Figure 1 The photosensitive drum 1 and the developing roller 31 are rotated and driven counterclockwise in the direction of the arrow R3, so that the surface of the photosensitive drum 1 and the surface of the developing roller 31 move in the same direction at the developing portion c where the photosensitive drum 1 and the developing roller 31 contact each other. The driving motor as the driving unit 110 for driving the developing roller 31 may be the same main motor as the driving unit 110 of the photosensitive drum 1, or corresponding different driving motors may rotate the photosensitive drum 1 and the developing roller 31. During development, the developing power source E2 ( Figure 3) A predetermined development voltage (development bias) is applied to the development roller 31. According to this exemplary embodiment, a negative DC voltage is applied to the development roller 31 as the development voltage during development, and the development voltage is set to -300 V. According to this exemplary embodiment, the toner charged to the same polarity as the charged polarity of the photosensitive drum 1 (negative polarity according to this exemplary embodiment) adheres to the exposed surface (image portion), which is the image forming portion on the photosensitive drum 1 and has a reduced absolute value of potential due to exposure after being uniformly charged. This development method is called a reverse development method.

[0034] Furthermore, according to this exemplary embodiment, although the developing roller 31 is always in contact with the photosensitive drum 1 at the developing portion c, the developing roller 31 and the photosensitive drum 1 can be in a contact state and a separated state. In this case, a separate developing contact and separation mechanism can be provided. During the rotation operation, which is the pre-rotation process described below, the photosensitive drum 1 can rotate with the developing roller 31 separated from the photosensitive drum 1.

[0035] The toner image formed on the photosensitive drum 1 is conveyed to the transfer portion d. The transfer portion d is the contact portion of the photosensitive drum 1 and the transfer roller 5 serving as a transfer unit. The transfer roller 5 is a roller-type transfer member. The transfer roller 5 according to the present exemplary embodiment uses a roller including a conductive nitrile rubber (NBR) alcohol-based sponge rubber and having an outer diameter of 12 mm and a hardness of 30° (Asker-C, 500 gf load). The transfer roller 5 according to the present exemplary embodiment is pressed against the photosensitive drum 1 with a predetermined pressure. At the same time, synchronously with the toner image on the photosensitive drum 1, the recording material P, which is the transfer material onto which the toner image is to be transferred, is conveyed from the storage section 6 to the transfer portion d by the conveying roller 8. Then, the toner image on the photosensitive drum 1 is transferred to the recording material P picked up and conveyed by the photosensitive drum 1 and the transfer roller 5 at the transfer portion d under the action of the transfer roller 5. At this time, the transfer power source E3 ( Figure 3 ) applies a predetermined transfer voltage to the transfer roller 5. The predetermined transfer voltage is a DC voltage having a polarity opposite to the normal polarity of the toner (positive polarity according to the present exemplary embodiment). As a result, an electric field is formed between the transfer roller 5 and the photosensitive drum 1, and the toner image is electrostatically transferred from the photosensitive drum 1 to the recording material P. According to the present exemplary embodiment, the transfer voltage during the transfer is, for example, +1000 V. By the action of the electric field formed between the transfer roller 5 and the photosensitive drum 1, the toner image is electrostatically transferred from the photosensitive drum 1 to the recording material P.

[0036] The recording material P having the transferred toner image is conveyed to a fixing device 9 serving as a fixing unit. The fixing device 9 applies heat and pressure to the recording material P, thereby fixing the toner image on the recording material P.

[0037] Meanwhile, untransferred residual toner that is not transferred to the recording material P and remains on the photosensitive drum 1 is conveyed to the brush member 10 located downstream of the transfer roller 5 in the rotation direction of the photosensitive drum 1. The brush member 10 used in the present exemplary embodiment will be described below.

[0038] 2. Configuration of brush components

[0039] Next, the paper dust removing mechanism according to the present exemplary embodiment will be described below. Figure 1 As shown in , the image forming apparatus 100 according to the present exemplary embodiment includes a brush member 10 (recovery member). The brush member 10 is a contact member that serves as a paper dust removal mechanism. According to the present exemplary embodiment, the image forming apparatus 100 includes the brush member 10, and the brush member 10 contacts the surface of the photosensitive drum 1 and forms a brush contact portion (brush contact position) downstream of the transfer portion d and upstream of the charging portion a in the rotation direction of the photosensitive drum 1. According to the present exemplary embodiment, the contact portion between the brush member 10 and the photosensitive drum 1 in the rotation direction of the photosensitive drum 1 will be described as a brush contact portion.

[0040] Figure 2A 1 is a schematic diagram showing the brush member 10 alone along its longitudinal direction (substantially parallel to the rotation axis direction of the photosensitive drum 1). Figure 2B 1 is a schematic diagram illustrating the brush member 10 along the length direction thereof in a state where the brush member 10 abuts against the photosensitive drum 1 .

[0041] The fixed brush 11 constitutes the brush portion of the brush member 10. The fixed brush 11 is fixed and has conductivity. As shown in Figure 2, the brush member 10 includes a pile yarn (also called conductive yarn) 11a and a base cloth 11b that supports the pile yarn 11a. The pile yarn 11a is composed of a plurality of conductive nylon 6 hairs and scrapes the surface of the photosensitive drum 1. As described above, the brush member 10 is arranged to contact the photosensitive drum 1 downstream of the transfer portion d and upstream of the charging portion a in the moving direction (rotational direction) of the photosensitive drum 1.

[0042] The brush member 10 is arranged so that its longitudinal direction is substantially parallel to the rotational axis of the photosensitive drum 1. According to this exemplary embodiment, the fixed brush 11 includes a conductive yarn 11a made of nylon fibers containing a conductive substance and a base fabric 11b made of synthetic fibers containing carbon as a conductive agent, with the conductive yarn 11a being woven into the base fabric 11b. In addition to nylon, rayon, acrylic, and polyester can be used as materials for the conductive yarn 11a.

[0043] like Figure 2AAs shown in , the distance L1 is the distance from the base cloth 11b to the trailing edge of the conductive yarn 11a exposed from the base cloth 11b when the brush member 10 is alone (i.e., in a state where no external force is applied to bend the conductive yarn 11a). According to the present exemplary embodiment, the distance L1 is 6.5 mm. The base cloth 11b is fixed to a supporting member (not shown) deployed at a predetermined position on the image forming device 100 by a fixing material such as a double-sided tape, and the brush member 10 is deployed so that the trailing edge of the conductive yarn 11a is pressed against the photosensitive drum 1 and warped. According to the present exemplary embodiment, the gap between the supporting member and the photosensitive drum 1 is fixed. The distance L2 is the minimum distance from the base cloth 11b of the brush member 10 fixed to the supporting member to the photosensitive drum 1. According to the present exemplary embodiment, the difference between the distances L2 and L1 is defined as the warping amount of the brush member 10 relative to the photosensitive drum 1. According to the present exemplary embodiment, the warping amount of the brush member 10 relative to the photosensitive drum 1 is 1 mm. In addition, according to this exemplary embodiment, as Figure 2A As shown in , the length L3 of the brush member 10 in the circumferential direction of the photosensitive drum 1 (hereinafter referred to as the "width direction") when the brush member 10 is alone is 5 mm. In addition, according to the present exemplary embodiment, the length of the brush member 10 in its longitudinal direction is 216 mm. Therefore, the brush member 10 contacts the entire image forming area (the area where the toner image can be formed) on the photosensitive drum 1 in the direction of the rotation axis of the photosensitive drum 1. In addition, according to the present exemplary embodiment, the conductive yarn 11a has a thickness of 2 deniers and a strength of 280 kF / inch. 2 Density (kF / inch 2 is a unit of brush density and indicates the number of filaments per square inch. As described above, the brush member 10 is supported by a supporting member (not shown), is disposed at a fixed position relative to the photosensitive drum 1, and scrapes the surface of the photosensitive drum 1 as the photosensitive drum 1 moves.

[0044] The brush member 10 captures (recovers) materials such as paper dust that move from the recording material P onto the photosensitive drum 1 at the transfer portion d to reduce the amount of paper dust that moves to the charging portion a and the developing portion c downstream of the brush member 10 in the moving direction of the photosensitive drum 1.

[0045] While the length L3 of the brush member 10 in the circumferential direction of the photosensitive drum 1 (hereinafter referred to as the "width direction") is set to L3 = 5 mm according to this exemplary embodiment, the length L3 is not limited to this value. The length L3 can be appropriately changed, for example, depending on the life of the image forming apparatus 100 or the process cartridge. Obviously, a brush member 10 having a longer widthwise length can capture paper dust for a longer period of time.

[0046] Although the length of the brush member 10 in the longitudinal direction according to the present exemplary embodiment is set to 216 mm, the length is not limited to this value. For example, the length can be appropriately changed according to the maximum width of the sheet to be fed in the image forming apparatus 100.

[0047] Although the brush member 10 according to the present exemplary embodiment has a fineness of 220T / 96F (indicating a bundle of 96 yarns each having a thickness equal to 220g / 10000m), the fineness is ideally set in consideration of the passing characteristics of paper dust. A brush member 10 with a smaller fineness has a poor ability to block paper dust, and paper dust easily slips through. This inhibits the charging roller 2 from charging the photosensitive drum 1 and causes image defects. On the other hand, a brush member 10 with excessive fineness cannot recycle toner and fine paper dust. This results in uneven concentration due to uneven toner adhesion along the length of the charging roller 2 and image defects due to charging defects at the portion with paper dust.

[0048] Although the density of the brush member 10 according to the present exemplary embodiment is set to 280 kF / inch 2 (kF / inch 2 is a unit of brush density and indicates the number of filaments per square inch), but the density is ideally set in consideration of the toner permeability and paper dust capturing characteristics. Specifically, a brush member 10 with too high a density allows less toner to penetrate, and the toner sticks. The stuck toner spreads and causes defects such as contamination in the device. In addition, a brush member 10 with too low a density has difficulty capturing paper dust. Therefore, from the viewpoint of paper dust capturing characteristics, the conductive filament 11a preferably has a thickness of 1 denier to 6 denier and 150 kF / inch 2 ~350kF / inch 2 From the viewpoint of long life, the length of the brush member 10 in the width direction is preferably 3 mm or more. In addition, the brush power supply E4 ( Figure 3 ) is connected to the brush member 10.

[0049] 3. Image output operation

[0050] The image forming apparatus 100 according to this exemplary embodiment performs an image output operation (job), which is a series of operations for forming an image on a single recording material P or multiple recording materials P based on a single start command from an external device (not shown), such as a personal computer. A job generally includes an image forming process (printing process), a pre-rotation process, a sheet separation process during image formation on multiple recording materials P, and a post-rotation process. The image forming process is the period of forming an electrostatic image on the photosensitive drum 1, developing the electrostatic image (forming a toner image), transferring the toner image, and fixing the toner image. This period is referred to as the image forming period. More specifically, the timing of the image forming period varies depending on the locations of electrostatic image formation, toner image formation, toner image transfer, and toner image fixing. Therefore, the image forming operation can be defined as either the operation until the toner image is transferred or the operation until the toner image is fixed. This definition is applicable because the image forming operation on the photosensitive drum 1 ends and the switching of the photosensitive drum 1's operation from image forming to non-image forming does not affect the image already transferred to the recording material P. The pre-rotation process is a period during which preparatory operations are performed before the image forming process. The sheet separation process is a period between recording materials P when the image forming process is continuously performed on multiple recording materials P (continuous image forming period). The post-rotation process is a period during which arrangement operations (preparatory operations) are performed after the image forming process. The non-image forming period is a period that does not include the image forming period but includes the pre-rotation process, sheet separation process, post-rotation process, and preparatory rotation process. The preparatory rotation process is a preparatory operation when the image forming apparatus 100 is turned on or resumes from a sleep state.

[0051] 4. Control configuration

[0052] Figure 3is a schematic block diagram illustrating a control configuration for controlling the main parts of the image forming apparatus 100 according to the present exemplary embodiment. The image forming apparatus 100 includes a control unit 150. The control unit 150 includes a central processing unit (CPU) 151, a memory (storage element) 152, and an input / output unit (not shown). The CPU 151, which serves as a calculation control unit, is a central element that performs calculation processing. The memory 152 is a storage unit such as a read-only memory (ROM) and a random access memory (RAM). The input / output unit controls signal transmission and reception with various components connected to the control unit 150. The RAM stores sensor detection results and calculation results, and the ROM stores pre-acquired control programs and data tables. According to the present exemplary embodiment, the memory 152 stores the number of rotations of the photosensitive drum 1 as information on the usage history of the photosensitive drum 1. In other words, the memory 152 stores the number of rotations of the photosensitive drum 1 as information on the usage of the photosensitive drum 1. The usage history information about the photosensitive drum 1 is not limited to the above-described information and may be any information that changes with the use of the photosensitive drum 1, such as the rotation time of the photosensitive drum 1, the amount of printed recording material P, and layer thickness information about the photosensitive drum 1. The control unit 150 also includes a measuring unit 153. The measuring unit 153 measures a suspension time for determining a condition for performing a pre-rotation process described below.

[0053] The control unit 150 is a control unit that generally controls the operation of the image forming apparatus 100. The control unit 150 controls the sending and receiving of various electrical information signals and the drive timing, and performs a predetermined image forming sequence. The components of the image forming apparatus 100 are connected to the control unit 150. For example, with respect to the present exemplary embodiment, the charging power source E1, the developing power source E2, the transfer power source E3, the brush power source E4, the drive motor 110, and the exposure unit 4 are connected to the control unit 150. In particular, with respect to the present exemplary embodiment, the control unit 150 controls the on / off and output values ​​of the various power sources E1, E2, E3, and E4, and performs an operation of extending the following front rotation process. According to the present exemplary embodiment, the normal front rotation process time is set to 2 seconds. The front rotation process time is appropriately set.

[0054] 5. Extended Anterior Rotation Process

[0055] In the case where the image forming apparatus 100 performs a job of continuously feeding the recording material P and then performs a normal forward rotation process when performing the next job after pausing for a predetermined time, toner contamination occurs. This is caused by moisture attached to the brush member 10 during sheet feeding in the previous job. Specifically, Figure 4A Moisture on the brush member 10 shown in FIG begins to accumulate as time passes immediately after the pause ( Figure 4B), and eventually form an aggregate of water droplets on the surface of the photosensitive drum 1 ( Figure 4C ). Depending on the environment in which the image forming apparatus 100 is used and the number of sheets fed in the previous job, the water droplets have different sizes. For example, in a high temperature and high humidity environment, the water content of the recording material P is high, and therefore the size of the water droplets increases as the number of sheets fed in the previous job increases. In addition, after a predetermined time has passed, the water droplets evaporate over time due to the atmospheric temperature in the image forming apparatus 100. Specifically, immediately after the pause after feeding the recording material P, moisture gathers over time and forms an aggregate of water droplets, and after a predetermined time has passed, the water droplets evaporate and disappear over time. In the case of using the brush member 10 according to this exemplary embodiment, thirty seconds after the drive of the photosensitive drum 1 is paused, water droplets of the largest size exist on the surface of the photosensitive drum 1. The pause time varies depending on the length (L1), width, and density of the brush member 10 because the speed at which water droplets are formed, the speed at which water droplets evaporate, and the size of the formed water droplets vary according to the length (L1), width, and density of the brush member 10.

[0056] Figures 5A to 5C The figure shows the state of the portion around the photosensitive drum 1 in the case where the next job is executed while water droplets are collected on the surface of the photosensitive drum 1. When the job starts, Figure 5A The aggregate of water droplets shown in FIG moves in the direction of arrow R1 as the photosensitive drum 1 rotates, and at the charging portion a, a portion of the aggregate of water droplets adheres to the charging roller 2. In addition, the water droplets that have passed through the charging portion a attract the toner ( Figure 5B Due to this phenomenon, image defects due to charging defects occur, and the toner adsorbed to the photosensitive drum 1 is transferred to the recording material P conveyed to the transfer portion d and is visualized as toner contamination ( Figure 5C ).

[0057] Therefore, according to the present exemplary embodiment, when the next job is executed after pausing for a predetermined time after executing a job for continuously feeding the recording material P, an operation of extending the pre-rotation process is executed. Specifically, the number of rotations of the photosensitive drum 1 during the pre-rotation process is controlled based on the pause time between a first image forming operation for forming an image on the recording material P and a second image forming operation executed after the first image forming operation.

[0058] The conditions and extension time for performing the operation of the extension pre-rotation process will be described below.

[0059] Figure 6 The figure shows the extended time of the front rotation process according to this exemplary embodiment. Figure 6As shown in , according to the first exemplary embodiment, the conditions for the forward rotation process are determined based on the number of sheets fed in the previous job, and the extension time of the forward rotation process is set to be longer for a larger number of fed sheets. Specifically, the number of rotations of the photosensitive drum 1 is controlled to increase as the number of fed sheets increases. Furthermore, it is understood that the extension time of the forward rotation process reaches its maximum at the 30-second pause time after the previous job and decreases thereafter. The reason for this will be described below.

[0060] Figure 6 Each abort time in indicates the case where the abort time is a maximum value, and Figure 6 Each of the numbers of fed sheets in indicates a case where the number of fed sheets is the maximum value. Specifically, a pause time of 5 seconds indicates that the pause time is 0 seconds to 5 seconds, and a pause time of 10 seconds indicates that the pause time is longer than 5 seconds and does not exceed 10 seconds. In addition, linear interpolation can be performed on the rotation time values ​​between the pause times and between the numbers of fed sheets. In addition, although not shown, the same fixing temperature control as that of the image forming process is applied to the fixing device 9 during the pre-rotation process. According to the present exemplary embodiment, the temperature is controlled at 180°C during the pre-rotation and image forming processes. The fixing temperature control during the pre-rotation process can be appropriately changed according to the fixing temperature control during the image forming process.

[0061] Figure 7 The diagram shows the result of toner contamination occurring in the case of feeding a sheet having a high moisture content according to the first exemplary embodiment and the result of toner contamination occurring in the case of feeding a sheet having a high moisture content and the case of not extending the front rotation process (comparative example). Figure 7 In the graph, the symbol "○" represents "none", indicating that no adverse effect of toner adhesion to the surface of the photosensitive drum 1 occurs on the image, the symbol "△" represents "slight", indicating that slight toner adhesion to the surface of the photosensitive drum 1 occurs but has no adverse effect on the image, and the symbol "×" represents "significant", indicating that a significant adverse effect on the image occurs. In the sheet feeding experiment, a sheet with a gram weight of 75 g / m 2 Letter-sized Xerox Vitality Multipurpose sheets were used as recording media, and before use, the sheets were removed from the wrapping paper and left for two days in an environment with an ambient temperature of 30°C and a humidity of 80%. The moisture content of the sheets was measured using a moisture analyzer Moistrex MX-8000 manufactured by NDC Infrared Engineering, and the result was 9.2%. In addition, for comparison, the moisture content immediately after removal from the wrapping paper was measured, and the result was 5.7%. Figure 7As shown in , the greater the number of sheets fed in the previous job, the worse the toner contamination level in the comparative example. Furthermore, the toner contamination level is at its lowest level when the pause time is 30 seconds and improves thereafter. This is due to the following reasons. Specifically, as the pause time increases, water droplets form aggregates, but after a predetermined time, which is 30 seconds or longer according to this exemplary embodiment, the water droplets begin to evaporate. Therefore, the impact of the water droplets decreases as the elapsed time increases. Therefore, the time period with the most severe toner contamination level is approximately 30 seconds after the sheets are fed. Furthermore, the toner contamination level remains unchanged when the number of sheets fed is 100 or more, because when moisture is generated due to the sheet feeding, the moisture evaporates due to the atmospheric temperature in the image forming apparatus 100. In contrast, in the first exemplary embodiment, although slight toner contamination occurs when the number of sheets fed in the previous job is 50 or more and the pause time is approximately 30 seconds, toner contamination does not occur in other cases. This is due to the extended time of the front rotation process which is set based on the number of sheets fed in the previous job and the pause time.

[0062] 6. Effects of the present exemplary embodiment

[0063] As described above, according to this exemplary embodiment, the forward rotation process is extended by a necessary time based on the number of sheets fed in the previous job and the pause time after the previous job. This promotes evaporation of water droplets on the surface of the photosensitive drum 1 and provides a stable image without image defects (such as toner contamination).

[0064] Although the present exemplary embodiment will be described as an example in which the image forming device 100 using a direct current (DC) charging method is used, the present invention can also be applied to an image forming device using an alternating current (AC) charging method, in which an oscillating voltage in which a direct current voltage (direct current component) and an alternating current voltage (alternating current component) are superimposed is used as a charging voltage.

[0065] In addition, although only the DC component of the developing voltage is described in the present exemplary embodiment, the developing voltage may be an oscillating voltage in which a DC voltage (DC component) and an AC voltage (AC component) are superimposed.

[0066] In addition, although toner, which is a non-magnetic one-component developer, is used as the developer in the present exemplary embodiment, a magnetic one-component developer may also be used.

[0067] In addition, although the present exemplary embodiment uses a "cleanerless method" in which no unit for cleaning the photosensitive drum 1 is used, the method is not limited thereto. For example, a "blade cleaning method" may be used in which a blade is used as a cleaning unit, and the cleaning unit is disposed downstream of the brush member 10 and upstream of the charging roller 2 in the conveyance direction of the photosensitive drum 1.

[0068] In addition, although the extension time is changed based on the number of sheets fed in the previous job according to the present exemplary embodiment, the configuration is not limited thereto. For example, the extension time may be changed based on the time or distance that the recording material P passes on the photosensitive drum 1.

[0069] As a result of the above description, the configuration described below is adopted according to the present exemplary embodiment.

[0070] The image forming apparatus 100 according to this exemplary embodiment includes a rotating photosensitive drum 1 and a charging roller 2 configured to charge the surface of the photosensitive drum 1 at a charging portion a. The image forming apparatus 100 includes a developing roller 31 configured to supply toner to the surface of the photosensitive drum 1 charged by the charging roller 2 and form a toner image. The image forming apparatus 100 includes a transfer roller 5 configured to contact the photosensitive drum 1 to form a transfer portion d and transfer the toner image formed on the photosensitive drum 1 to a recording material P at the transfer portion d. The image forming apparatus 100 includes a brush member 10 configured to contact the surface of the photosensitive drum 1 downstream of the transfer portion d and upstream of the charging portion a in the rotational direction of the photosensitive drum 1, and a drive motor 110 configured to rotate the photosensitive drum 1. The image forming apparatus 100 includes a memory 152 configured to store usage history information about the photosensitive drum 1 and a control unit 150 configured to control the drive motor 110. The image forming apparatus 100 includes a measuring unit 153 configured to measure a pause time between a first image forming operation of forming an image on a recording material P and a second image forming operation performed after the first image forming operation.

[0071] After a pause time has elapsed between a first image forming operation for forming an image on recording material P and a second image forming operation performed after the first image forming operation, a rotation operation for rotating the photosensitive drum 1 is controlled to be performed before the second image forming operation is performed. The number of rotations of the photosensitive drum 1 in the rotation operation performed before the second image forming operation is controlled based on the usage history information about the photosensitive drum 1 and the pause time. The target of control is not limited to the number of rotations of the photosensitive drum 1, and may be the rotation time of the photosensitive drum 1.

[0072] In addition, when the amount of recording material P conveyed by the transfer portion d in the first image forming operation is a first value, the number of rotations of the photosensitive drum 1 in the rotating operation is controlled to be smaller than when the amount of recording material P is a second value larger than the first value.

[0073] The pause time is the time from when the photosensitive drum 1 changes from a driven state in which the photosensitive drum 1 rotates to a pause state in which the rotation of the photosensitive drum 1 is paused after the first image forming operation, to when the photosensitive drum 1 changes from the pause state to a driven state in order to start the second image forming operation. The pause time according to this exemplary embodiment is not limited to that described above and may be a time period that correlates with the accumulation of water droplets on the brush member 10. For example, the pause time may be the time period from immediately after the first image forming operation ends to immediately before the second image forming operation begins. The pause time may be any period of time as long as it includes the time during which the photosensitive drum 1 is paused.

[0074] In addition, the suspension time can not only be measured by the measuring unit 153 but also be predicted based on the decay condition of the surface potential of the photosensitive drum 1 , the temperature transition of the image forming apparatus 100 , and the temperature change of the fixing device 9 .

[0075] In addition, although according to this exemplary embodiment, Figure 6 As shown in FIG, the extension time of the pre-rotation process is stored in a table in the memory 152. However, the table may store not the extension time value but the extension time and the total time of the pre-rotation process or the extension ratio relative to the pre-rotation process time. In addition, coefficients corresponding to the amount of printed recording material P and the suspension time may be stored, and the extension time may be calculated each time without preparing a table.

[0076] Next, another exemplary embodiment of the present invention will be described below. The basic configuration and operation of the image forming apparatus according to this exemplary embodiment are similar to those of the image forming apparatus 100 according to the first exemplary embodiment. Therefore, components of the image forming apparatus according to this exemplary embodiment having functions or configurations similar to or corresponding to those of the components of the image forming apparatus 100 according to the first exemplary embodiment are given the same reference numerals as those of the components of the image forming apparatus 100 according to the first exemplary embodiment, and redundant detailed descriptions thereof are omitted.

[0077] 1. Features of the second exemplary embodiment

[0078] The second exemplary embodiment is characterized in that the extension time of the front rotation process is variable based on the use environment of the image forming apparatus 100. The image forming apparatus 100 used in the second exemplary embodiment includes an environmental sensor 300, and determines the extension time of the front rotation process described in the first exemplary embodiment based on environmental information as a detection result of the environmental sensor 300. The environmental information includes absolute water content information about the environment calculated by the CPU 151 based on the detection results of the temperature sensor and the humidity sensor (neither of which is shown) of the environmental sensor 300. According to the second exemplary embodiment, the absolute water content obtained from the environmental sensor 300 is expressed in 0.1 g / m 3 Then, when the image forming apparatus 100 receives an image output operation (job) signal, the control unit 150 determines whether the absolute water content is higher or lower than the threshold value 10.5 g / m 3 When the absolute water content is higher than the threshold value of 10.5g / m 3 In the case of , the same operation of extending the front rotation process as in the first exemplary embodiment is performed. The extension time of the front rotation process is the same as that according to the first exemplary embodiment. Figure 6 The extended time described is similar, so the repeated description thereof is omitted. On the other hand, when the absolute water content is lower than the threshold value of 10.5 g / m 3 , the operation of extending the pre-rotation process is not performed. This prevents unnecessary rotation of the photosensitive drum 1 in environments other than those with a high absolute moisture content. The absolute moisture content used to determine whether to change the extension time of the pre-rotation process based on the usage environment is not limited to the above value and can be changed as appropriate.

[0079] 2. Functional Effects of the Second Exemplary Embodiment

[0080] As described above, according to the second exemplary embodiment, the control described below is performed based on the absolute water content obtained from the detection result of the environmental sensor 300. 3 In the case of a job that has not yet been completed, the forward rotation process is extended for a necessary time based on the number of sheets fed in the previous job and the pause time after the previous job. This prevents unnecessary rotation of the photosensitive drum 1 in environments other than those with a high absolute moisture content, and performs an operation for effectively evaporating water droplets on the surface of the photosensitive drum 1 as needed.

[0081] As a result of the above description, the configuration described below is adopted according to the second exemplary embodiment.

[0082] Image forming apparatus 100 includes an environmental sensor 300 configured to detect the environment in which image forming apparatus 100 is installed, and controls the number of rotations based on the environment. As used herein, the term "installation environment" refers to the temperature or humidity and absolute moisture content detected by environmental sensor 300. Absolute moisture content can be calculated based on the temperature and humidity detection results. Alternatively, absolute moisture content can be calculated by predicting the temperature or humidity.

[0083] According to the second exemplary embodiment, based on the absolute moisture content obtained from the detection results of the environmental sensor 300, the operating environment of the image forming apparatus 100 is divided into two environments: an environment with a high absolute moisture content and an environment other than an environment with a high absolute moisture content, thereby determining whether to extend the pre-rotation process. However, this configuration is not limited to this. For example, the operating environment of the image forming apparatus 100 can be divided into multiple environments, such as three environments, based on the absolute moisture content, and the extension time of the pre-rotation process can be appropriately changed according to the environment. Specifically, multiple thresholds can be set. In addition, the extension time of the pre-rotation process can be appropriately changed based on the absolute moisture content. In other words, when the absolute moisture content is detected as a first absolute moisture content, the number of rotations of the photosensitive drum 1 can be controlled to be greater than when a second absolute moisture content lower than the first absolute moisture content is detected.

[0084] In addition, although the environment sensor 300 is used as a unit for detecting the use environment of the image forming apparatus 100 according to the second exemplary embodiment, this is not a restrictive configuration. For example, the use environment can be determined based on the detection of the resistance value of the transfer roller 5 (the result of the automatic transfer voltage control (transfer ATVC)).

[0085] 1. Brush voltage control

[0086] This exemplary embodiment is characterized in that Figure 3 The brush power source E4 in the front rotation process applies a brush voltage to the brush member 10 during the front rotation process. The brush voltage control during the front rotation process will be described below.

[0087] According to the present exemplary embodiment, the control unit 150 applies a predetermined brush voltage to the brush member 10. The predetermined brush voltage is a negative polarity DC voltage. The brush voltage applying unit E4 can apply, for example, a voltage on which a DC component and an AC component are superimposed. According to the present exemplary embodiment, the brush voltage during the image forming process is -300V. At the same time, the surface potential of the photosensitive drum 1 after passing through the transfer section d is approximately -50V. Therefore, the untransferred residual colorant transported from the transfer section d and charged to the positive polarity is first recovered by the brush member 10 due to the potential difference between the brush voltage at the brush section e and the surface potential of the photosensitive drum 1. On the other hand, the colorant charged to the negative polarity is attracted toward the photosensitive drum 1 at the brush section e and passes through the brush section e. The toner passing through the brush section e has the desired negative polarity charge due to the uniform discharge at the charging section a and is transported to the developing section c. Of the toner transported to the developing section c, the toner in the non-image area (non-exposed area) moves to the developing roller 31 due to the potential difference between the dark area potential (Vd) of the surface of the photosensitive drum 1 and the development bias (Vdc), and is recovered by the developing device 3. According to this exemplary embodiment, as in the first exemplary embodiment, the dark area potential (Vd) is approximately -600 V and the development bias (Vdc) is -300 V. On the other hand, the toner in the image area (exposed area) does not move to the developing roller 31 due to the potential difference between the light area potential (Vl) of the surface of the photosensitive drum 1 and the development bias (Vdc), and is transported to the transfer section d as an image portion as the photosensitive drum 1 rotates, and is transferred to the recording material P. As in the first exemplary embodiment, the light area potential (Vl) according to this exemplary embodiment is approximately -100 V.

[0088] 2. Prolonged operation during the front rotation process

[0089] Figure 8 is a timing diagram illustrating a forward rotation process according to this exemplary embodiment. Figure 8 , timing A is the timing at which the image forming apparatus 100 receives an image output operation (job) signal from an external device and starts the front rotation process. At this time, the control unit 150 determines the extension time of the front rotation process based on the number of fed sheets in the previous job and the pause time after the previous job. Then, at timing A, the drive of the drive motor 110 is started, and the output of the charging voltage and the output of the brush voltage are turned on. In addition, the fixing device 9 starts outputting, thereby controlling the fixing temperature to be the same as that of the image forming process (180°C). Depending on the power-on time, the timing of turning on the charging voltage and the brush voltage may be earlier or later. In addition, depending on the responsiveness of the fixing device 9, the timing of outputting the fixing temperature control may be earlier or later.

[0090] The output value of the charging voltage is the same as during the image forming process, -1200V, so that the surface potential of the photosensitive drum 1 is uniformly equal to the dark area potential (-600V). While the surface potential of the photosensitive drum 1 is maintained at the value of the dark area potential (-600V), the surface of the photosensitive drum 1 passes through the developing section c and reaches the transfer section d. At this time, no transfer voltage is applied to the transfer roller 5, so the surface of the photosensitive drum 1 reaches the brush section e in a state of maintaining the dark area potential (-600V). The output value of the brush voltage is the same as during the image forming process, -300V. Therefore, the positive polarity toner remaining on the brush member 10 is discharged to the surface of the photosensitive drum 1 due to the potential difference between the brush voltage and the dark area potential (-600V) of the photosensitive drum 1.

[0091] While the cleaning operation of discharging the untransferred residual toner first recovered by the brush member 10 during the image forming process is performed during the post-rotation process according to the present exemplary embodiment, some toner remains on the brush member 10 even thereafter. Therefore, the residual toner having a positive polarity on the brush member 10 is actively discharged after timing A and thereafter. At this time, moisture is present around the toner, and the toner is discharged from the brush member 10 together with the moisture. Figure 9 The state of the toner and the moisture in the brush member 10 at this time is illustrated. From Figure 9 It is understood that the moisture adheres to the toner on the brush member 10 and is discharged together with the toner discharged from the brush member 10. As described above, the discharge of the residual toner on the brush member 10 promotes the discharge of the moisture adhering to the brush member 10.

[0092] According to the present exemplary embodiment, while no transfer voltage is applied at timing A, the brush voltage (-300V) will be set to a value that does not lower the surface potential of the photosensitive drum 1, i.e., a voltage value having the same negative polarity as the surface potential of the photosensitive drum 1 and having a small absolute value.

[0093] Next, at timing B in Figure 8 the output of the transfer voltage is turned on. The output value of the transfer voltage at this time is +1000V. Therefore, the surface potential of the photosensitive drum 1 after passing through the transfer section d is approximately -50V. At the same time, the output value of the brush voltage is still maintained at -300V, so that the negative polarity toner remaining on the brush member 10 at this time is discharged to the surface of the photosensitive drum 1 due to the potential difference between the brush voltage and the surface potential of the photosensitive drum 1 (-50V). Then, similarly, the discharge of the moisture adhering to the brush member 10 is promoted. Timing B is set to secure time for discharging the positive polarity toner in the brush member 10, and according to the present exemplary embodiment, timing B is set 500ms after timing A.

[0094] As described above, the brush voltage is applied and the positive and negative polarity residual toners in the brush member 10 are discharged due to the potential difference from the surface potential of the photosensitive drum 1 to promote the discharge of moisture.

[0095] Figure 8 The timing C in the figure is the timing at which the image forming process starts when the pre-rotation process is not extended. When it is determined at the timing A that the pre-rotation process is to be extended, the extension operation starts from the timing C, and the image forming process starts from the timing D. Specifically, Figure 8 The time from timing C to timing D is the extended time of the front rotation process.

[0096] Figure 10 The figure shows the extended time of the front rotation process according to this exemplary embodiment. Figure 10 It can be understood that the extended time of the front rotation process is different from the extended time of the front rotation process according to the first exemplary embodiment ( Figure 6 This is because according to the third exemplary embodiment, moisture is actively discharged together with the residual toner in the brush member 10 by the brush voltage, thereby promoting evaporation of water droplets during the front rotation.

[0097] 3. Effects of the present exemplary embodiment

[0098] As described above, according to this exemplary embodiment, the residual toner in the brush member 10 is discharged by the brush voltage simultaneously with the start of the pre-rotation process. At the same time, the pre-rotation process is extended by the necessary time based on the number of sheets fed in the previous job and the pause time since the previous job. Since the water is discharged along with the residual toner in the brush member 10, water droplets on the surface of the photosensitive drum 1 evaporate efficiently, and the extension time of the pre-rotation process is reduced.

[0099] Therefore, while increasing the lifespan of the image forming apparatus 100 , a stable image with reduced image defects such as toner contamination is provided.

[0100] As a result of the above description, the configuration described below is adopted according to the third exemplary embodiment.

[0101] The image forming apparatus 100 includes a brush power supply (brush voltage applying unit) E4 configured to apply a brush voltage to the brush member 10. The brush member 10 is a conductive brush, and the brush voltage applying unit E4 is controlled so that a brush voltage having the same polarity as the toner charged to the normal polarity is applied to the brush member 10 while a rotation operation is performed.

[0102] The brush voltage applying unit E4 is controlled so that while the rotation operation is performed, the potential difference between the brush voltage applied to the brush member 10 and the surface potential of the photosensitive drum 1 gradually increases at the brush portion e where the surface of the photosensitive drum 1 and the brush member 10 contact each other.

[0103] The brush voltage applying unit E4 is controlled so that the brush voltage applied to the brush member 10 has the same polarity as the surface potential of the photosensitive drum 1, and the absolute value of the brush voltage is larger than the absolute value of the surface potential of the photosensitive drum 1. Alternatively, the brush voltage applying unit E4 is controlled so that the brush voltage applied to the brush member 10 has the same polarity as the surface potential of the photosensitive drum 1, and the absolute value of the brush voltage is smaller than the absolute value of the surface potential of the photosensitive drum 1.

[0104] In addition, the image forming apparatus 100 includes a transfer power source (transfer voltage applying unit) E3 configured to apply a transfer voltage to the transfer roller 5. The transfer voltage applying unit E3 is controlled so that the brush voltage applied to the brush member 10 has the same polarity as the surface potential of the photosensitive drum 1 at the transfer portion d, and the surface potential of the photosensitive drum 1 at the transfer portion d is lower than the brush voltage applied to the brush member 10.

[0105] While the surface potential of the photosensitive drum 1 is controlled by varying the transfer voltage and the brush voltage according to this exemplary embodiment, this is not a limiting configuration. For example, the transfer voltage and the brush voltage may be varied while the photosensitive drum 1 is grounded to set the surface potential to ground (0 V). Alternatively, the potential relationship between the transfer roller 5 and the brush member 10 may be controlled by applying a voltage directly to the photosensitive drum 1.

[0106] Although the image forming apparatus 100 using a direct current (DC) charging method is described as an example in this exemplary embodiment, the present invention can also be applied to an image forming apparatus using an alternating current (AC) charging method, in which an oscillating voltage obtained by superimposing a DC voltage (DC component) and an AC voltage (AC component) is used as a charging voltage.

[0107] In addition, although only the DC component of the developing voltage is described according to the present exemplary embodiment, the developing voltage may be an oscillating voltage in which a DC voltage (DC component) and an AC voltage (AC component) are superimposed.

[0108] In addition, although the toner which is a magnetic one-component developer is used as the developer according to the present exemplary embodiment, a non-magnetic one-component developer may also be used.

[0109] In addition, although the present exemplary embodiment uses a "cleanerless method" in which no unit for cleaning the photosensitive drum 1 is used, this is not a limiting method. For example, a "blade cleaning method" may be used in which a blade is used as a cleaning unit, and the cleaning unit is disposed downstream of the brush member 10 and upstream of the charging roller 2 in the conveyance direction of the photosensitive drum 1.

[0110] In addition, although the extension time is changed based on the number of sheets fed in the previous job according to the present exemplary embodiment, this is not a restrictive configuration. For example, the extension time may be changed based on the time or distance that the sheet passes through the photosensitive drum 1.

[0111] In addition, although the recording material P as a transfer material to which the toner image is transferred is conveyed to the transfer portion d and undergoes transfer according to the present exemplary embodiment, a conveying belt for conveying the recording material P to the transfer portion d may be provided.

[0112] In addition, according to this exemplary embodiment, a pre-exposure unit can be provided for exposing the surface of the photosensitive drum 1 at a position downstream of the transfer portion d and upstream of the charging portion a in the rotational direction of the photosensitive drum 1. The pre-exposure unit can be disposed upstream or downstream of the brush portion (contact portion) e where the brush member 10 and the photosensitive drum 1 come into contact with each other. In the case where the pre-exposure unit is disposed upstream of the contact portion e, the surface potential of the photosensitive drum 1 can be controlled by the pre-exposure unit.

[0113] Next, a fourth exemplary embodiment will be described below. Figure 1 As shown in FIG, the image forming apparatus 100 according to this exemplary embodiment includes a paper dust capture mechanism and a brush member 10 (recovery member) constituting a contact member serving as a moisture recovery mechanism. In the image forming apparatus 100 according to this exemplary embodiment, the brush member is arranged to contact the surface of the photosensitive drum 1 at a position downstream of the transfer portion d and upstream of the charging portion a in the rotational direction of the photosensitive drum 1. In this exemplary embodiment, the brush contact portion refers to the portion where the brush member 10 contacts the photosensitive drum 1 in the rotational direction of the photosensitive drum 1.

[0114] Figure 1 and Figure 12 The diagram illustrates a layout in which the image forming apparatus 100 is placed on a flat installation surface, as is the normal intended installation state. The left-right direction of the diagram corresponds to the horizontal direction of the image forming apparatus 100, and the top-bottom direction of the diagram corresponds to the top-bottom direction (gravity direction, vertical direction) of the image forming apparatus 100.

[0115] Comparison of brush water absorption and image evaluation

[0116] Next, the water absorption amount and image evaluation of the brush member 10 according to the present exemplary embodiment will be described in detail below together with comparative examples. The water absorption amount of the brush member 10 according to the present exemplary embodiment was measured by the following methods. The measurement methods are not limited to those described herein.

[0117] Measurement of water absorption

[0118] A fixed brush 11 as shown in Figure 2 is used, which includes a plurality of conductive yarns 11a made of fibers of various materials and different densities and woven into a base cloth 11b. The shape and size of the fixed brush 11 are similar to L1 = 6.5 mm, L3 = 5 mm, and the length in the longitudinal direction = 216 mm.

[0119] FIG11 illustrates the measurement of the amount of water absorption of the brush member 10 according to the present exemplary embodiment. After measuring the initial weight (W0) of the fixed brush 11, the contact surface of the fixed brush 11 to be in contact with the photosensitive drum 1 is moved toward the water surface at 20° C. so that the contact surface is parallel to the water surface ( Figure 11A ), and only the trailing edge of the fixed brush 11 of 1mm is immersed in water for 10 seconds ( Figure 11B ). The contact surface of the fixed brush 11 in contact with the photosensitive drum 1 is a term used to compare the collection of the trailing edges of the plurality of conductive yarns 11a cut into approximately the same length to a surface. The contact surface can be understood as a virtual surface including each trailing edge of the plurality of fiber yarns 11a. Specifically, the fixed brush 11 (contact surface) is brought close to the water surface while keeping the contact surface parallel to the water surface, so that the trailing edges of the plurality of fiber yarns 11a enter the water at approximately the same timing and there is no difference in the degree of immersion of the plurality of fiber yarns 11a. Even if they are different, the difference is not large because only the area 1 mm away from the trailing edge of each fiber yarn 11a is reliably immersed in water. Thereafter, the fixed brush 11 is lifted from the water surface, and the weight (W) of the sample is measured at a timing when water droplets no longer drip from the sample. Then, the water absorption is calculated using the following formula.

[0120] Water absorption (g) = W-W0

[0121] Comparison of water absorption

[0122] An experiment for comparing water absorption was conducted using the conductive yarn 11 a of the following material and density as the fiber material of the conductive yarn 11 a.

[0123] (Table 1)

[0124]

[0125] It can be understood from the items A, B, C and F in Table 1 that from the perspective of fiber materials, and 6nylon have a greater water absorption than SFCP and This shows a trend corresponding to the value of the water absorption rate (the weight change rate of a sample immersed in water at 23°C for 24 hours) measured according to the American Society for Testing and Materials (ASTM) D570 test procedure, and the higher the water absorption rate of the fiber material, the greater the water absorption amount of the fiber material.

[0126] In addition, it can be understood from items C, D, E, F, and G that, when the same fiber material is used, the higher the density of the conductive yarn 11a, the greater the water absorption. This is because the higher the density of the conductive yarn 11a, the larger the surface area and the greater the amount of attached moisture per unit area.

[0127] Although 6nylon is used as the fiber material according to this exemplary embodiment, the fiber material is not limited to 6nylon. Any fiber material with high water absorption can be used, and the water absorption rate measured according to the ASTM D570 test procedure is desirably 0.5% or higher, more desirably 1.1% or higher.

[0128] Image evaluation comparison

[0129] Next, a comparative image evaluation test was conducted in the case of feeding a plurality of recording materials stored under a high temperature and high humidity environment. In the image evaluation, a recording medium with a grammage of 75 g / m 2 Letter-sized Xerox Vitality Multipurpose sheets were removed from their wrapping and left for two days in an environment with an ambient temperature of 30°C and a humidity of 80%. The moisture content of the sheets was measured using a Moistrex MX-8000 moisture analyzer manufactured by NDC Infrared Engineering and found to be 9.2%. For comparison, the moisture content of the sheets was measured immediately after removal from the wrapping and found to be 5.7%.

[0130] (Table 2)

[0131]

[0132] Table 2 illustrates the results of toner-stained images when 100 sheets of the above-mentioned recording material were continuously fed. In Table 2, "None" indicates that no toner staining occurred on the image, "Slight" indicates that a toner-stained image slightly occurred on the image, and "Remarkable" indicates that a toner-stained image significantly occurred on the image.

[0133] From the items A, B, C and F in Table 2, it can be understood that the use of SFCP and When 10 sheets were continuously fed, significant toner contamination of the image occurred, while the use of the M and 6nylon greatly reduces toner contamination of images.

[0134] In addition, it can be understood from items C, D and E, F and G in Table 2 that the toner contaminated image appears at different timings for different densities. In the case of 6nylon with a density of 70kF, a slight toner contaminated image appears on the 50th sheet. In the case of 6nylon with a density of 150kF, a slight toner contaminated image appears on the 100th sheet. In the case of 6nylon with a density of 240kF, no toner contaminated image appears even on the 100th sheet. This indicates that the higher the density, the less likely the toner contaminated image will appear. This is for the following reason. Specifically, the higher the density, the greater the water absorption, so the brush member 10 can store moisture therein even when feeding a recording material with a high water content.

[0135] In the present exemplary embodiment, in the case of a recording material expected to have a high water content, the measured water absorption amount of the fixed brush 11 is desirably 2.4 g or more, and the water absorption amount per unit area is desirably 2.2 mg / mm 2 or more. Therefore, when using M In the case of using nylon (water absorption = 0.5%), the density of the conductive yarn 11a is desirably 240 kF or higher, and in the case of using 6nylon (water absorption = 1.1%), the density of the conductive yarn 11a is desirably 150 kF or higher.

[0136] Here, the water absorption per unit area refers to the value obtained by dividing the measured moisture content of the fixed brush 11 by the contact area between the fixed brush 11 and the photosensitive drum 1. The contact area between the fixed brush 11 and the photosensitive drum 1 is the aggregate of the contact areas between the trailing edges of the plurality of conductive yarns 11a and the photosensitive drum 1. At a microscopic level, gap regions exist between adjacent trailing edges of the plurality of conductive yarns 11a, where the gap regions do not contact the surface of the photosensitive drum 1. Therefore, it is technically difficult to unambiguously define the contact area between the fixed brush 11 and the photosensitive drum 1 as a single region. However, it is possible to define a single region by, for example, ignoring the gap regions and determining the overall outline of the aggregate of the contact areas between the plurality of conductive yarns 11a and the photosensitive drum 1 as an approximate contact area, and the area of ​​this region can be used as the contact area.

[0137] According to the present exemplary embodiment, the contact area is calculated as follows. Specifically, it is assumed that an area corresponding to a warping amount (L1-L2) of 1 mm in length (which is a portion of the 6.5 mm length (L1) of the conductive yarn 11a) abuts against the peripheral surface of the photosensitive drum 1. In addition, the length (L3) of the brush member 10 of 5 mm in the circumferential direction of the photosensitive drum 1 is assumed to be the length (width) of the bundle of the conductive yarn 11a in the same direction. It is assumed that the conductive yarn 11a that contacts the peripheral surface of the photosensitive drum 1 with a contact area of ​​1 mm forms a plurality of rows within a range of 5 mm in the circumferential direction of the photosensitive drum 1 and these plurality of rows extend in the longitudinal direction of the peripheral surface of the photosensitive drum 1 within a range of 216 mm of the width of the brush member 10 in the longitudinal direction. Therefore, according to the present exemplary embodiment, the contact area is determined to be 1 mm × 5 mm × 216 mm = 1080 mm 2 The water absorption per unit area of ​​items A, B, C, D, E, F, and G according to this embodiment is 0.27 mg / mm 2 , 0.74mg / mm 2 , 1.38mg / mm 2 , 2.22mg / mm 2 , 1.85mg / mm 2 , 2.22mg / mm 2 and 2.68 mg / mm 2 The above-described way of defining the contact area is not the only way, and any other way may be used.

[0138] Effects in this exemplary embodiment

[0139] As described above, according to the present exemplary embodiment, the water absorption per unit area is 2.2 mg / mm 2 The brush member 10 is positioned downstream of the transfer section d and upstream of the charging section a in the rotational direction of the photosensitive drum 1. Therefore, even when continuously feeding recording material with a high moisture content, the brush member 10 can sufficiently recover moisture adhering to the surface of the photosensitive drum 1. This prevents image defects such as toner contamination caused by moisture.

[0140] Although the image forming device 100 using a direct current (DC) charging method is described as an example in this exemplary embodiment, it is also possible to apply the present invention to an image forming device using an alternating current (AC) charging method, in which an oscillating voltage in which a DC voltage (DC component) and an AC voltage (AC component) are superimposed is used as a charging voltage.

[0141] In addition, although only the DC component of the developing voltage is described according to the present exemplary embodiment, the developing voltage may be an oscillating voltage in which a DC voltage (DC component) and an AC voltage (AC component) are superimposed.

[0142] In addition, although the toner which is a non-magnetic one-component developer is used as the developer according to the present exemplary embodiment, a magnetic one-component developer may also be used.

[0143] In addition, although the present exemplary embodiment uses a "cleanerless method" in which no unit for cleaning the photosensitive drum 1 is used, this is not a limiting method. For example, a "blade cleaning method" may be used in which a blade is used as a cleaning unit, and the cleaning unit is disposed downstream of the brush member 10 and upstream of the charging roller 2 in the conveyance direction of the photosensitive drum 1.

[0144] Furthermore, while the density of the conductive yarn 11a is determined according to this exemplary embodiment based on the situation where a recording material with a high moisture content is continuously fed, this is not a restrictive configuration. Depending on the operating environment of the image forming apparatus 100 (e.g., a high-humidity environment), the time between sheets during continuous sheet feeding can be set longer than normal. In this case, even if the amount of water absorbed by the brush member 10 is low, toner contamination of the image is prevented, allowing the density of the conductive yarn 11a to be appropriately set based on the time between sheets.

[0145] Next, a fifth exemplary embodiment of the present invention will be described below. The basic configuration and operation of the image forming apparatus according to this exemplary embodiment are similar to those of the image forming apparatus 100 according to the fourth exemplary embodiment. Therefore, components of the image forming apparatus according to this exemplary embodiment having functions or configurations similar to or corresponding to those of the components of the image forming apparatus 100 according to the fourth exemplary embodiment are given the same reference numerals as those of the components of the image forming apparatus 100 according to the fourth exemplary embodiment, and redundant detailed descriptions thereof are omitted.

[0146] This exemplary embodiment is characterized by Figure 3 The brush power source E4 shown in FIG. 1 applies a brush voltage to the brush member 10. Next, control of the brush voltage during image formation will be described.

[0147] 1. Brush voltage control

[0148] According to the present exemplary embodiment, the control unit 150 controls the brush power supply E4 to apply a predetermined brush voltage to the brush member 10. The predetermined brush voltage is a negative polarity DC voltage. The brush power supply E4 used as a brush voltage applying unit can, for example, apply a voltage on which a DC component and an AC component are superimposed. According to the present exemplary embodiment, the brush voltage during the image forming process is -300V. At the same time, the surface potential of the photosensitive drum 1 after passing through the transfer section d is approximately -50V. Therefore, due to the potential difference between the brush voltage at the brush section e and the surface potential of the photosensitive drum 1, the untransferred residual colorant transported from the transfer section d and charged to the positive polarity is first recovered by the brush member 10. On the other hand, the colorant charged to the negative polarity is attracted to the photosensitive drum 1 at the brush section e and passes through the brush section e. The colorant passing through the brush section e has the desired negative polarity charge due to the uniform discharge at the charging section a and is transported to the developing section c. Of the toner transported to the developing section c, the toner in the non-image area (non-exposed area) moves to the developing roller 31 due to the potential difference between the dark area potential (Vd) of the surface of the photosensitive drum 1 and the development bias (Vdc), and is recovered by the developing device 3. According to this exemplary embodiment, as in the fourth exemplary embodiment, the dark area potential (Vd) is approximately -600 V and the development bias (Vdc) is -300 V. On the other hand, the toner in the image area (exposed area) does not move to the developing roller 31 due to the potential difference between the light area potential (Vl) of the surface of the photosensitive drum 1 and the development bias (Vdc), and is transported to the transfer section d as an image portion as the photosensitive drum 1 rotates, and is transferred to the recording material P. The light area potential (Vl) according to this exemplary embodiment is approximately -100 V, as in the fourth exemplary embodiment.

[0149] Figure 12 The figure shows the state of a portion around the photosensitive drum 1 during the image forming process. Figure 12 It is understood that the untransferred residual toner having positive polarity is first recovered by the brush member 10 , while the untransferred residual toner having negative polarity passes through the brush portion e and the charging portion a and moves to the developing roller 31 .

[0150] Figure 13 The figure shows the state of the toner first recovered by the brush member 10. Figure 13 It can be understood that moisture adheres to the toner that is first recovered by the brush member 10. As described above, moisture adhering to the surface of the photosensitive drum 1 is not only recovered by the brush member 10 along with the untransferred residual toner, but is also transported along with the toner toward the base cloth 11b of the brush member 10 (opposite the trailing edge of the brush) due to the brush voltage. Therefore, the brush member 10 can recover a larger amount of moisture compared to a configuration in which no brush voltage is applied.

[0151] 2. Image Evaluation and Comparison

[0152] An experiment for comparing image evaluations in the case of feeding a plurality of recording materials stored under a high temperature and high humidity environment was conducted as in the fourth exemplary embodiment. Detailed conditions are similar to those in the fourth exemplary embodiment, and therefore repeated descriptions thereof are omitted.

[0153] (Table 3)

[0154]

[0155]

[0156] The results of occurrence of toner-stained images when 200 sheets of the above-mentioned recording materials are continuously fed are shown in Table 3. The image levels in Table 3 are similar to those according to the fourth exemplary embodiment.

[0157] As can be seen from Table 3, the appearance of toner-stained images is delayed for all fiber materials. Specifically, the occurrence of toner-stained images resulting from an increase in the number of sheets fed continuously is reduced. This is due to the following reasons. Specifically, the brush voltage causes moisture to move along with the toner toward the base fabric 11b of the brush member 10 (opposite the trailing edge of the brush), resulting in a larger amount of moisture being recovered compared to when no brush voltage is applied.

[0158] 3. Effects of the present exemplary embodiment

[0159] As described above, according to the present exemplary embodiment, the brush voltage causes moisture adhering to the surface of the photosensitive drum 1 to move together with untransferred residual toner toward the base cloth 11b of the brush member 10. Therefore, the brush member 10 can recover a large amount of moisture, and toner contamination of the image resulting from an increase in the number of sheets continuously fed is reduced.

[0160] As a result of the above description, the configuration described below is adopted according to the fifth exemplary embodiment.

[0161] The image forming apparatus 100 includes a brush power source E4 as a brush voltage applying unit that applies a brush voltage to the brush member 10. The brush member 10 is a conductive brush, and the control unit 150 controls the brush voltage applied from the brush power source E4 to the brush member 10 so that a brush voltage having the same polarity as the toner charged to the normal polarity is applied to the brush member 10 while an image forming operation is performed.

[0162] The control unit 150 controls the voltage applied from the brush power source E4 to the brush member 10 so that the brush voltage applied to the brush member 10 has the same polarity as the surface potential of the photosensitive drum 1 and the absolute value of the brush voltage is greater than the absolute value of the surface potential of the photosensitive drum 1.

[0163] In addition, the image forming apparatus 100 includes a transfer power source E3 as a transfer voltage applying unit that applies a transfer voltage to the transfer roller 5. The control unit 150 controls the transfer power source E3 so that the brush voltage applied to the brush member 10 has the same polarity as the surface potential of the photosensitive drum 1 at the transfer portion d and the surface potential of the photosensitive drum 1 at the transfer portion d is lower than the brush voltage applied to the brush member 10.

[0164] While the surface potential of the photosensitive drum 1 is controlled by changing the transfer voltage or the brush voltage according to this exemplary embodiment, this is not a limiting configuration. For example, the transfer voltage and the brush voltage may be changed while the photosensitive drum 1 is grounded to set the surface potential to ground (0 V). Alternatively, the potential relationship between the transfer roller 5 and the brush member 10 may be controlled by applying a voltage directly to the photosensitive drum 1.

[0165] Although the present exemplary embodiment will be described as an example in which the image forming device 100 using a direct current (DC) charging method is used, the present invention can also be applied to an image forming device using an alternating current (AC) charging method, in which an oscillating voltage in which a DC voltage (DC component) and an AC voltage (AC component) are superimposed is used as a charging voltage.

[0166] In addition, although only the DC component of the developing voltage is described according to the present exemplary embodiment, the developing voltage may be an oscillating voltage in which a DC voltage (DC component) and an AC voltage (AC component) are superimposed.

[0167] In addition, although the toner which is a non-magnetic one-component developer is used as the developer according to the present exemplary embodiment, a magnetic one-component developer may also be used.

[0168] In addition, although the present exemplary embodiment uses a "cleanerless method" in which no unit for cleaning the photosensitive drum 1 is used, this is not a limiting method. For example, a "blade cleaning method" may be used in which a blade is used as a cleaning unit, and the cleaning unit is disposed downstream of the brush member 10 and upstream of the charging roller 2 in the conveyance direction of the photosensitive drum 1.

[0169] In addition, although the recording material P as the transfer material to which the toner image is transferred is conveyed to the transfer portion d and undergoes transfer according to the present exemplary embodiment, a conveying belt for conveying the recording material P to the transfer portion d may be provided.

[0170] In addition, according to this exemplary embodiment, a pre-exposure unit can be provided for exposing the surface of the photosensitive drum 1 at a position downstream of the transfer portion d and upstream of the charging portion a in the rotational direction of the photosensitive drum. The pre-exposure unit can be disposed upstream or downstream of the contact portion e where the brush member 10 and the photosensitive drum 1 come into contact with each other. When the pre-exposure unit is disposed upstream of the contact portion e, the surface potential of the photosensitive drum 1 can be controlled by the pre-exposure unit.

[0171] Furthermore, while the density of the conductive yarn 11a is determined according to this exemplary embodiment based on the situation where a recording material with a high moisture content is continuously fed, this is not a restrictive configuration. Depending on the operating environment of the image forming apparatus 100 (e.g., a high-humidity environment), the time between sheets during continuous sheet feeding can be set longer than normal. In this case, even if the amount of water absorbed by the brush member 10 is low, toner contamination of the image is prevented, allowing the density of the conductive yarn 11a to be appropriately set according to the time between sheets.

[0172] 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 apparatus, comprising: Rotating photosensitive drum; a charging member configured to charge the surface of the photosensitive drum at the charging portion; a developing member configured to supply toner to the surface of the photosensitive drum charged by the charging member and form a toner image on the photosensitive drum; a transfer member configured to be in contact with the photosensitive drum to form a transfer portion and to transfer the toner image formed on the photosensitive drum to a transfer material at the transfer portion; a brush member that contacts the surface of the photosensitive drum at a position downstream of the transfer portion and upstream of the charging portion in the rotational direction of the photosensitive drum; a driving unit configured to rotate the photosensitive drum; a storage unit configured to store information regarding usage of the photosensitive drum; as well as a control unit configured to control the drive unit, wherein the control unit controls a rotation operation of rotating the photosensitive drum so that the rotation operation is performed after a pause time between a first image forming operation of forming an image on a transfer material and a second image forming operation performed after the first image forming operation has elapsed and before the second image forming operation is performed, wherein the control unit controls the number of rotations of the photosensitive drum in the rotating operation based on the information and the pause time, and When the pause time is less than a predetermined time, the number of rotations of the photosensitive drum in the rotation operation increases as the pause time increases, and when the pause time is greater than the predetermined time, the number of rotations of the photosensitive drum in the rotation operation decreases as the pause time increases.

2. The image forming apparatus according to claim 1, wherein The suspension time is the time from the following first change to the following second change, wherein the first change is the change from the driving state of the photosensitive drum rotating to the suspension state in which the rotation of the photosensitive drum is suspended after the first image forming operation, and the second change is the change from the suspension state to the driving state of the photosensitive drum in order to start the second image forming operation.

3. The image forming apparatus according to claim 1 or 2, further comprising: A measuring unit configured to measure a pause time between a first image forming operation of forming an image on a transfer material and a second image forming operation performed after the first image forming operation.

4. The image forming apparatus according to claim 1 or 2, further comprising: an environment detection sensor configured to detect an installation environment of the image forming apparatus, The control unit controls the number of rotations based on the installation environment.

5. The image forming apparatus according to claim 4, wherein The installation environment is the temperature or humidity detected by the environment detection sensor.

6. The image forming apparatus according to claim 4, wherein The installation environment is the absolute moisture content detected by the environmental detection sensor.

7. The image forming apparatus according to claim 6, wherein: The control unit controls the number of rotations so that the number of rotations in the rotation operation performed when the absolute water content is detected as a first absolute water content is greater than the number of rotations in the rotation operation performed when a second absolute water content lower than the first absolute water content is detected.

8. The image forming apparatus according to claim 1 or 2, wherein: The information is the amount of transfer material conveyed through the transfer portion in the first image forming operation.

9. The image forming apparatus according to claim 1 or 2, further comprising: a brush voltage applying unit configured to apply a brush voltage to the brush member, wherein the brush member is a conductive brush, and Here, the control unit controls the brush voltage applying unit so that a brush voltage having the same polarity as the toner charged to the normal polarity is applied to the conductive brush during performance of the rotating operation.

10. The image forming apparatus according to claim 9, wherein The control unit controls the brush voltage applying unit so that a potential difference between the brush voltage applied to the brush member and the surface potential of the photosensitive drum gradually increases at a contact portion where the surface of the photosensitive drum and the brush member contact each other during execution of the rotation operation.

11. The image forming apparatus according to claim 9, wherein The control unit controls the brush voltage applying unit so that the brush voltage applied to the brush member has the same polarity as the surface potential of the photosensitive drum and an absolute value of the brush voltage is larger than an absolute value of the surface potential of the photosensitive drum.

12. The image forming apparatus according to claim 9, wherein The control unit controls the brush voltage applying unit so that the brush voltage applied to the brush member has the same polarity as the surface potential of the photosensitive drum and an absolute value of the brush voltage is smaller than an absolute value of the surface potential of the photosensitive drum.

13. The image forming apparatus according to claim 9, further comprising: a transfer voltage applying unit configured to apply a transfer voltage to the transfer member, Herein, the control unit controls the transfer voltage applying unit so that the brush voltage applied to the brush member has the same polarity as the surface potential of the photosensitive drum at the transfer portion, and the surface potential of the photosensitive drum at the transfer portion is lower than the brush voltage applied to the brush member.

14. The image forming apparatus according to claim 1 or 2, wherein: The control unit controls the number of rotations of the photosensitive drum in the rotation operation so that the number of rotations when the amount of transfer material conveyed through the transfer portion in the first image forming operation is a first value is smaller than the number of rotations when the amount of transfer material is a second value greater than the first value.

15. The image forming apparatus according to claim 1 or 2, wherein: The control unit controls a rotation time of the rotating operation to control the number of rotations of the photosensitive drum in the rotating operation.

16. The image forming apparatus according to claim 1 or 2, wherein: The developing member recovers the toner that has not been transferred from the photosensitive drum to the transfer material at the transfer portion and remains on the photosensitive drum.

17. The image forming apparatus according to claim 1 or 2, wherein: Toner is a single-component developer.

Images