Image forming apparatus

Abstract

To prevent passing of toner and an external additive in the initial stage of use of a photoconductor drum.SOLUTION: An image forming apparatus 100 has a photoreceptor 1, a photoreceptor driving unit M1, a charging member 2, an application unit PS1 that applies an AC bias to the charging member 2, a developing member 41, a developing driving unit M2, a cleaning member 61, an acquisition unit N that acquires usage amount information related to a usage amount of the photoreceptor 1, and a control unit 200. During non-image formation in a predetermined period until the usage amount of the photoreceptor 1 from a brand-new state indicated by the usage amount information reaches a predetermined usage amount, the control unit 200 executes, over a predetermined time T, a predetermined operation to apply the AC bias to the charging member 2, and rotate the photoreceptor 1 while generating electric discharge between the charging member 2 and the photoreceptor 1, stops the rotation of the developing device 41 in the predetermined operation, and performs control so as to increase a voltage value of the AC bias applied to the charging member 2 compared to a voltage value of the AC bias applied to the charging member 2 during first image formation after the predetermined operation.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine having a plurality of functions among these, which uses an electrophotographic system. [Background technology]

[0002] Conventionally, as an electrophotographic image forming apparatus, there is known a configuration in which a toner image formed on a photosensitive drum is transferred to an intermediate transfer belt or a recording material, and the toner remaining on the photosensitive drum after the transfer is cleaned by a cleaning blade. The toner image on the photosensitive drum is formed by charging the photosensitive drum with a charging member, exposing the photosensitive drum according to image information to form an electrostatic latent image on the photosensitive drum, and supplying toner to this electrostatic latent image by a developing device.

[0003] In such a configuration, it is known that as the cumulative number of images formed using the photosensitive drum increases, discharge products generated by the discharge phenomenon between the charging member and the photosensitive drum adhere to the surface of the photosensitive drum, and the frictional force (friction coefficient) between the photosensitive drum and the cleaning blade increases. When the frictional force between the photosensitive drum and the cleaning blade increases, a stick-slip phenomenon occurs, which may cause toner and external additives to slip through the cleaning blade (hereinafter, simply referred to as "slip-through").

[0004] To cope with this, it is effective to form unevenness on the surface of the photosensitive drum in advance to reduce the contact area between the photosensitive drum and the cleaning blade. However, if unevenness is formed on the surface of the photosensitive drum in advance so as to reduce the frictional force between the photosensitive drum and the cleaning blade throughout the life of the photosensitive drum, the frictional force between the photosensitive drum and the cleaning blade may become too low in the early stages of use of the photosensitive drum (the early stage after starting to use a new photosensitive drum in an image forming apparatus). If the frictional force between the photosensitive drum and the cleaning blade is too high, as described above, it is problematic, but if it is too low, the contact pressure of the cleaning blade against the photosensitive drum does not increase sufficiently when the photosensitive drum rotates, causing toner and external additives to slip through.

[0005] As described above, if toner or external additives slip through the photosensitive drum during the initial use, the toner or external additives may adhere to the charging member, causing vertical streak-like image defects due to contamination of the charging member.

[0006] Therefore, Patent Document 1 discloses a method for suppressing the slip-through of toner and external additives by lowering the AC bias applied to the charging member during a first period in the early stages of use of the photosensitive drum compared to a second period following the first period. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2016-153875 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, according to the inventors' investigations, although the method described in Patent Document 1 aims to suppress the passage of toner and external additives by lowering the AC bias applied to the charging member, it is difficult to obtain a sufficient effect with this method.

[0009] When using a photosensitive drum whose surface has been polished to further increase the surface roughness, or when using a toner having a small particle size or a toner containing a large amount of external additives, the amount of toner or external additives that slips through tends to increase. Even in such cases, for example, it is desirable to sufficiently suppress the slip-through of toner or external additives to suppress the occurrence of vertical streak-like image defects caused by dirt on the charging member. Thus, the slip-through of toner and external additives in the early stages of use of the photosensitive drum remains an issue that needs to be improved.

[0010] SUMMARY OF THE PRESENTLY PREFERRED EMBODIMENTS An object of the present invention is to suppress the passing of toner and external additives from the photosensitive drum during the initial period of use. [Means for solving the problem]

[0011] The above object is achieved by the image forming apparatus according to the present invention. In summary, a typical configuration of the present invention includes a rotatable photoconductor, a photoconductor drive unit for rotating the photoconductor, a charging member that contacts the surface of the photoconductor and charges the surface of the photoconductor, an application unit for applying an AC bias to the charging member, a rotatable developing member that supplies a developer to the surface of the photoconductor to form a developer image on the surface of the photoconductor, a developing drive unit for rotating the developing member, a cleaning member that contacts the surface of the photoconductor and cleans the surface of the photoconductor, an acquisition unit for acquiring usage information regarding the usage of the photoconductor, and a control unit for controlling the photoconductor to perform an image formation operation for forming the developer image on the photoconductor according to arbitrary image information and a non-image formation operation in which the developer image is not formed on the photoconductor. This image forming apparatus has a photoreceptor driving unit, an application unit, and a control unit capable of controlling the development driving unit, and the control unit is characterized in that during non-image formation during a predetermined period until the usage amount of the photoreceptor from a new state indicated by the usage amount information reaches a predetermined usage amount, the control unit performs a predetermined operation for a predetermined time in which an AC bias is applied to the charging member to rotate the photoreceptor while generating a discharge between the charging member and the photoreceptor, and during the predetermined operation, stops the rotation of the developing member and controls the voltage value of the AC bias applied to the charging member to be greater than the voltage value of the AC bias applied to the charging member during the first image formation after the predetermined operation.

[0012] Also, another representative configuration of the present invention is a photosensitive drum including a rotatable photosensitive drum, a photosensitive drum drive unit for rotating the photosensitive drum, a charging member that contacts the surface of the photosensitive drum and charges the surface of the photosensitive drum, an application unit for applying an AC bias to the charging member, a rotatable developing member that supplies a developer to the surface of the photosensitive drum to form a developer image on the surface of the photosensitive drum, a cleaning member that contacts the surface of the photosensitive drum and cleans the surface of the photosensitive drum, an acquisition unit for acquiring usage information regarding the usage of the photosensitive drum, and a control unit for controlling the photosensitive drum to perform an image formation operation for forming the developer image on the photosensitive drum in accordance with arbitrary image information, and a non-image formation operation in which the developer image is not formed on the photosensitive drum. The image forming apparatus has a photosensitive member driving unit and a control unit capable of controlling the application unit, and further has a detection means for detecting an index value correlated with the driving torque of the photosensitive member driving unit, and the control unit performs a predetermined operation of applying an AC bias to the charging member to rotate the photosensitive member while generating a discharge between the charging member and the photosensitive member during non-image formation during a predetermined period until the usage amount of the photosensitive member from a new state indicated by the usage amount information reaches a predetermined usage amount, and controls the control unit to terminate the predetermined operation when the driving torque indicated by the detection result by the detection means becomes equal to or greater than a threshold value during the execution of the predetermined operation. Effect of the Invention

[0013] According to the present invention, it is possible to suppress the toner and external additives from passing through the photosensitive drum during the initial period of use. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic cross-sectional view of an image forming apparatus. [Diagram 2] FIG. 2 is a schematic cross-sectional view of an image forming unit. [Diagram 3] FIG. 2 is a block diagram for explaining a control configuration of the image forming apparatus according to the first embodiment. [Figure 4] FIG. 2 is a schematic cross-sectional view for explaining an example of a layer structure of a photosensitive drum. [Diagram 5]5 is a schematic cross-sectional view for explaining another example of the layer structure of the photosensitive drum. FIG. [Figure 6] FIG. 11 is a schematic graph for explaining charging AC voltage determination control. [Figure 7] FIG. 1 is a schematic graph for explaining an overview of the problem and the means for solving the problem. [Figure 8] FIG. 4 is a flowchart for explaining a photosensitive drum aging mode in the first embodiment. [Figure 9] FIG. 11 is a timing chart for explaining an example of an operation in a photosensitive drum aging mode. [Figure 10] FIG. 11 is a timing chart for explaining another example of the operation in the photosensitive drum aging mode. [Figure 11] FIG. 11 is a block diagram for explaining a control configuration of an image forming apparatus according to a second embodiment. [Figure 12] FIG. 11 is a flowchart for explaining a photosensitive drum aging mode in the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, the image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

[0016] [Embodiment 1] <Overall Configuration and Operation of Image Forming Apparatus> 1 is a schematic cross-sectional view of an image forming apparatus 100 according to the present embodiment. The image forming apparatus 100 according to the present embodiment is a tandem type laser beam printer employing an intermediate transfer method, capable of forming a full-color image on a sheet-shaped recording material S by electrophotography.

[0017] The image forming apparatus 100 has four image forming units 10Y, 10M, 10C, and 10K as a plurality of image forming units (stations) that form toner images of yellow (Y), magenta (M), cyan (C), and black (K), respectively. Elements having the same or corresponding functions or configurations provided for each color of yellow, magenta, cyan, and black may be generally described by omitting the suffixes Y, M, C, and K of the reference numerals indicating that the elements are for any of the colors. In this embodiment, the image forming unit 10 is configured to include a photosensitive drum 1, a charging roller 2, an exposure device 3, a developing device 4, a primary transfer roller 5, and a cleaning device 6, which will be described later. FIG. 2 is a schematic cross-sectional view showing one representative image forming unit 10. For convenience, the magnitude (high and low) of a voltage or potential refers to the magnitude (high and low) when compared in absolute value, unless otherwise specified. In addition, "~" in a numerical range means that the numerical values ​​before and after it are also included.

[0018] The photosensitive drum 1, which is a rotatable drum-type (cylindrical) photosensitive member (electrophotographic photosensitive member) serving as an image carrier, is rotationally driven at a predetermined peripheral speed (process speed) in the direction of arrow R1 (counterclockwise direction) in FIGS. 1 and 2 by a photosensitive drum drive motor M1 (FIG. 3) serving as a photosensitive member drive means (photosensitive member drive unit). In this embodiment, the photosensitive drum 1 has a length of 340 mm in the rotation axis direction and an outer diameter of 30 mm, and is rotationally driven at a peripheral speed of 200 mm / sec around a central support shaft. The photosensitive drum 1 will be described in further detail later.

[0019] The surface of the rotating photosensitive drum 1 is uniformly charged to a predetermined potential of a predetermined polarity (negative polarity in this embodiment) by the charging roller 2, which is a roller-type charging member serving as a charging means. In this embodiment, the image forming apparatus 100 employs a contact charging method, and the charging roller 2 is an example of a contact-type charging means. In this embodiment, the charging roller 2 has a length of 330 mm in the rotation axis direction and a diameter of 14 mm, and is configured by forming a conductive rubber layer around a stainless steel core. The charging roller 2 is rotatably held by bearing members at both ends in the rotation axis direction of the core, and is biased toward the photosensitive drum 1 by a pressure spring, so that the charging roller 2 is pressed against the surface of the photosensitive drum 1 with a predetermined pressing force. The charging roller 2 rotates in accordance with the rotation of the photosensitive drum 1. In this embodiment, the peripheral speed of the charging roller 2 is 200 mm / sec. The charging roller 2 charges the surface of the photosensitive drum 1 by utilizing a discharge phenomenon that occurs in at least one of the minute gaps between the photosensitive drum 1 and the charging roller 2 formed on the upstream and downstream sides of the contact portion (charging nip) between the photosensitive drum 1 and the charging roller 2 in the rotation direction of the photosensitive drum 1. During image formation (charging process), a predetermined charging bias (charging voltage) is applied to the core of the charging roller 2 by a charging power source (high voltage power source) PS1 (FIG. 3) serving as a charging voltage application means (charging voltage application unit). In this embodiment, the charging power source PS1 is configured to have a DC power source and an AC power source. In this embodiment, during image formation (charging process), a superimposed bias (oscillating voltage) in which a DC bias ("charging DC bias") which is a DC voltage component and an AC bias ("charging AC bias") which is an AC voltage component are superimposed is applied to the charging roller 2 by the charging power source PS1. For example, when the voltage of the charging DC bias ("charging DC voltage") is set to -500V and the voltage of the charging AC bias ("charging AC voltage": peak-to-peak voltage in this embodiment) is set to 1500V, the surface of the rotating photosensitive drum 1 is uniformly charged to approximately -500V. As the waveform of the charging AC bias, a sine wave, a square wave, a triangular wave, etc. can be appropriately applied, or a square wave voltage formed by periodically turning on and off a DC power source may be applied. In addition, the frequency of the charging AC bias is about 1 kHz to 3 kHz.The charging DC bias and charging AC bias applied to the charging roller 2 during image formation are not limited to the above values, but are appropriately set to potentials suitable for good image formation depending on the environment or the usage conditions (amount of usage) of the photosensitive drum 1 and the charging roller 2.

[0020] The surface of the rotating photosensitive drum 1 that has been charged is scanned and exposed by an exposure device 3 as an exposure means (information writing means), and an electrostatic latent image (electrostatic image) corresponding to image information is formed on the photosensitive drum 1. In this embodiment, the exposure device 3 is a laser beam scanner using a semiconductor laser. The laser beam scanner outputs a laser beam modulated in response to an image signal (image information) sent to the image forming apparatus 100 from an external device (host processing device) such as an image reading device or a personal computer (not shown), and performs laser scanning and exposure on the surface of the rotating photosensitive drum 1 that has been uniformly charged. This laser scanning and exposure reduces the potential of the portion of the surface of the photosensitive drum 1 that has been irradiated with the laser beam, and an electrostatic latent image corresponding to the image information is sequentially formed on the surface of the rotating photosensitive drum 1.

[0021] The electrostatic latent image formed on the photosensitive drum 1 is developed (visualized) by supplying toner by the developing device 4 as a developing means, and a toner image (toner image, developer image) is formed on the photosensitive drum 1. In this embodiment, the developing device 4 adheres toner charged with the same polarity (negative polarity in this embodiment) as the charging polarity of the photosensitive drum 1 to an exposed portion (image portion) in which the potential is reduced by being exposed after being uniformly charged, thereby forming a toner image (reversal development method). In this embodiment, the developing device 4 is configured to have a developing sleeve 41 as a developer carrier (developing member), a developing container 42, and a regulating blade 43 as a regulating member. The developing container 42 contains a two-component developer containing toner (non-magnetic toner particles) and carrier (magnetic carrier particles) as a developer. The developing sleeve 41 is arranged opposite to the photosensitive drum 1. In this embodiment, the developing sleeve 41 is arranged opposite to the photosensitive drum 1 in close proximity so as to maintain the closest distance (S-Dgap) between the developing sleeve 41 and the photosensitive drum 1 at 350 μm. The developing sleeve 41 is rotated in the direction of the arrow R3 in FIG. 2 (clockwise direction) by a developing drive motor M2 (FIG. 3) as a developing drive means (developing drive section). That is, in this embodiment, the developing sleeve 41 rotates so that the moving direction of the surface of the photosensitive drum 1 and the moving direction of the surface of the developing sleeve 41 are the same direction in the developing section where the photosensitive drum 1 and the developing sleeve 41 face each other. A regulating blade 43 faces the developing sleeve 41 with a predetermined gap. The regulating blade 43 forms a thin layer of developer on the developing sleeve 41 as the developing sleeve 41 rotates. The developing sleeve 41 holds a magnetic brush made of a two-component developer, and develops the electrostatic latent image on the photosensitive drum 1 by rotating the magnetic brush in contact with the photosensitive drum 1 in the developing section.

[0022] In this embodiment, the normal charge polarity of the toner, which is the main charge polarity of the toner during development, is negative. In this embodiment, the toner used is a toner with an average particle size of about 5 μm obtained by kneading a pigment into a resin binder mainly made of polyester and pulverizing and classifying the mixture. In this embodiment, the average charge amount of the toner attached to the photosensitive drum 1 during development is about -30 μC / g. An external additive (particles added as auxiliary particles to the toner particles or external additive particles) is added to the toner. When this external additive migrates to the surface of the photosensitive drum 1 and is supplied to the contact portion (hereinafter also referred to as the "cleaning portion") between the photosensitive drum 1 and a cleaning blade 61 described later, lubricity is imparted, and the frictional force (friction coefficient) between the photosensitive drum 1 and the cleaning blade 61 decreases. When the rotation of the developing sleeve 41 stops and the supply of the external additive to the cleaning portion stops, the lubricity is lost and the frictional force between the photosensitive drum 1 and the cleaning blade 61 increases.

[0023] During image formation (development), a predetermined development bias (development voltage) is applied to the development sleeve 41 by a development power source (high voltage power source) PS2 (FIG. 3) as a development voltage application means (development voltage application section). In this embodiment, the development power source PS2 is configured to have a DC power source and an AC power source. Then, in this embodiment, during image formation (development), a superimposed bias (oscillating voltage) in which a DC bias ("development DC bias") which is a DC voltage component and an AC bias ("development AC bias") which is an AC voltage component are superimposed is applied to the development sleeve 41 by the development power source PS2. For example, the development bias is a superimposed bias (oscillating voltage) in which a development DC bias and a development AC bias of a square wave with a frequency of 8.0 kHz and a peak-to-peak voltage of 1800 V are superimposed. The development DC bias is appropriately set so as to be an appropriate fog removal potential with respect to the potential of the non-image portion on the photosensitive drum 1 in the development section. In this embodiment, the development DC bias is set to -400 V. In this embodiment, the potential of the non-image area on the photosensitive drum 1 in the developing section is about -500V.

[0024] Opposing the four photosensitive drums 1, an intermediate transfer belt 7 formed of an endless belt as an intermediate transfer body is disposed. The intermediate transfer belt 7 is stretched around a driving roller 71, a tension roller 72, and a secondary transfer opposing roller 73 as a plurality of tension rollers, and stretched with a predetermined tension. The intermediate transfer belt 7 rotates (moves orbitally, moves circulatingly) in the direction of arrow R2 (clockwise direction) in FIG. 1 by being driven to rotate by a belt driving motor M3 (FIG. 3) as an intermediate transfer body driving means (intermediate transfer body driving section). On the inner peripheral surface side of the intermediate transfer belt 7, primary transfer rollers 5Y, 5M, 5C, and 5K as roller-type primary transfer members as primary transfer means are disposed corresponding to each photosensitive drum 1. The primary transfer roller 5 is brought into contact with the photosensitive drum 1 via the intermediate transfer belt 7 with a predetermined pressing force so as to sandwich the intermediate transfer belt 7 between the photosensitive drum 1 and the primary transfer roller 5. As a result, a primary transfer section (primary transfer nip) T1, which is a contact section between the photosensitive drum 1 and the intermediate transfer belt 7, is formed. The tension rollers other than the driving roller 71 and each primary transfer roller 5 are rotated by the rotation of the intermediate transfer belt 7. The toner image formed on the photosensitive drum 1 is transferred (primary transfer) onto the rotating intermediate transfer belt 7 as a transfer target by the action of the primary transfer roller 5 at the primary transfer portion T1. During image formation (primary transfer), a predetermined primary transfer bias (primary transfer voltage) which is a DC voltage of the opposite polarity (positive polarity in this embodiment) to the normal charging polarity of the toner is applied to the primary transfer roller 5 by a primary transfer power source (high voltage power source) PS3 (FIG. 3) as a primary transfer voltage application means (primary transfer voltage application portion). In this embodiment, during image formation (primary transfer), a primary transfer bias of +600V is applied to the primary transfer roller 5. For example, during the formation of a full-color image, the toner images of each color of yellow, magenta, cyan, and black formed on each photosensitive drum 1 are transferred sequentially onto the intermediate transfer belt 7 so as to be superimposed on each other.

[0025] In this embodiment, the intermediate transfer belt 7 is an endless belt (film) having a two-layer structure of a resin layer and a surface layer. The resin material constituting the resin layer may be polycarbonate, fluororesin (ETFE, PVDF), or the like. However, the material constituting the resin layer is not limited to the above-mentioned materials. A conductive agent for adjusting the electrical resistance value is added to the resin layer. There is no particular restriction on the conductive agent for adjusting the electrical resistance value, but for example, carbon black, graphite, or the like may be used. In this embodiment, the resin layer is made of a material having a surface resistivity of 10 12 A 100μm thick PI (polyimide) resin with Ω / □ (using a JIS-K6911 compliant probe, applied voltage 100V, application time 60sec, 23°C / 50%RH) was used. However, this is not limited to this and other materials, volume resistivities and thicknesses may be used. There are no particular limitations on the material that constitutes the surface layer, but it is desirable to use a material that reduces the adhesion of toner to the surface of the intermediate transfer belt 7 and enhances secondary transferability. Examples of materials that can be used to constitute the surface layer include polyurethane and polyester.

[0026] A secondary transfer roller 8, which is a roller-type secondary transfer member serving as a secondary transfer means, is disposed at a position facing the secondary transfer opposing roller 73 on the outer peripheral surface side of the intermediate transfer belt 7. The secondary transfer roller 8 is brought into contact with the secondary transfer opposing roller 73 via the intermediate transfer belt 7 with a predetermined pressing force so as to sandwich the intermediate transfer belt 7 between the secondary transfer opposing roller 73. This forms a secondary transfer portion (secondary transfer nip) T2, which is a contact portion between the intermediate transfer belt 7 and the secondary transfer roller 8. The secondary transfer roller 8 may be configured to rotate following the rotation of the intermediate transfer belt 7, or may be configured to be rotated by a driving means. The toner image formed on the intermediate transfer belt 7 is transferred (secondarily transferred) by the action of the secondary transfer roller 8 onto the recording material S, which is a transfer target material being conveyed while being sandwiched between the intermediate transfer belt 7 and the secondary transfer roller 8, at the secondary transfer portion T2. During image formation (secondary transfer), a predetermined secondary transfer bias (secondary transfer voltage) that is a DC voltage of the polarity opposite to the normal charging polarity of the toner (positive polarity in this embodiment) is applied to the secondary transfer roller 8 by a secondary transfer power source (high voltage power source) PS4 (FIG. 3) serving as a secondary transfer voltage application means (secondary transfer voltage application unit). In this embodiment, a secondary transfer bias of +800V is applied to the secondary transfer roller 8 during image formation (secondary transfer). The secondary transfer opposing roller 73 is connected to a ground potential. Note that a secondary transfer bias of the same polarity as the normal charging polarity of the toner may be applied to an inner roller corresponding to the secondary transfer opposing roller 73 in this embodiment, and an outer roller corresponding to the secondary transfer roller 8 in this embodiment may be connected to a ground potential. A recording material (transfer material, recording medium, sheet) S such as recording paper is stored in a cassette 11 serving as a recording material storage unit. The recording material S is sent out one by one from the cassette 11 at a predetermined control timing by a feeding roller 12 serving as a feeding member, and is transported to a pair of registration rollers 13 serving as a transport member. Then, this recording material S is conveyed by a pair of registration rollers 13 to a secondary transfer portion T2 in synchronization with the toner image on the intermediate transfer belt .

[0027] The image forming apparatus 100 has a contact / separation mechanism 75 (FIG. 3) capable of bringing the intermediate transfer belt 7 into contact with and separating from each photosensitive drum 1. In this embodiment, the contact / separation mechanism 75 is configured to separate the intermediate transfer belt 7 from the photosensitive drum 1 by moving the primary transfer roller 5 in a direction away from the photosensitive drum 1. Also, in this embodiment, the contact / separation mechanism 75 is configured to bring the intermediate transfer belt 7 into contact with the photosensitive drum 1 by moving the primary transfer roller 5 in a direction approaching the photosensitive drum 1.

[0028] The recording material S onto which the toner image has been transferred is conveyed to a fixing device 14 serving as a fixing means. In this embodiment, the fixing device 14 is a heat roller fixing device, which applies heat and pressure to the recording material S carrying the unfixed toner image, thereby fixing (melting and bonding) the toner image onto the recording material S. After the toner image has been fixed by the fixing device 14, the recording material S is discharged (output) to the outside (outside the machine) of the image forming apparatus 100 as an image formed product (print, copy).

[0029] Meanwhile, toner remaining on the photosensitive drum 1 after the primary transfer (primary transfer residual toner) is removed from the photosensitive drum 1 and collected by a cleaning device 6 serving as a cleaning means. The cleaning device 6 will be described in further detail later. In addition, toner remaining on the intermediate transfer belt 7 after the secondary transfer (secondary transfer residual toner) and deposits such as paper powder are removed from the intermediate transfer belt 7 and collected by a belt cleaning device 74 serving as an intermediate transfer body cleaning means.

[0030] <Photosensitive drum> Next, a further description will be given of the photosensitive drum 1. As the photosensitive drum 1, an organic photosensitive body (OPC (organic photoconductor) photosensitive body), an amorphous silicon photosensitive body, or the like can be used.

[0031] ·Organic photoreceptor An organic photoreceptor constituting the photosensitive drum 1 used in this embodiment (experimental example to be described later) will be described. FIG. 4 is a schematic cross-sectional view showing an example of the layer structure of the organic photoreceptor 1a. In this embodiment, the organic photoreceptor 1a constituting the photosensitive drum 1 is constructed by coating a charge generating layer 52 made of an organic material, a charge transport layer 53 (about 20 μm thick), and a surface layer 54 on the surface of an aluminum cylinder (conductive drum substrate) 51 in this order from the bottom. Here, the surface layer 54 is a hardened layer (8 μm thick) using a hardening resin as a binder resin. In this embodiment, the hardened layer 54 using a hardening resin is used as the surface hardening treatment of the organic photoreceptor 1a, but is not limited to this. For example, a charge transport hardened layer formed by hardening and polymerizing a monomer having a carbon-carbon double bond and a charge transport monomer having a carbon-carbon double bond by heat or light energy, a charge transport hardened layer formed by hardening and polymerizing a hole transport compound having a chain polymerizable functional group in the same molecule by electron beam energy, etc. can be used. Also, an organic photoreceptor 1a that does not have a hardening layer can be used.

[0032] In this embodiment, the photosensitive drum 1 formed of the organic photosensitive body 1a has a surface roughness Ra of 0.02 μm to 0.10 μm on the surface (outer periphery) in a new (unused) state. If the surface roughness Ra of the photosensitive drum 1 in a new state is less than 0.02 μm, it becomes difficult to suppress the slip-through of toner and external additives caused by the stick-slip phenomenon until the end of the life of the photosensitive drum 1. If the surface roughness Ra of the photosensitive drum 1 in a new state exceeds 0.10 μm, the slip-through of toner and external additives is likely to occur throughout the entire life of the photosensitive drum 1. In this embodiment, the unevenness of the surface of the photosensitive drum 1 formed of the organic photosensitive body 1a is formed by polishing the surface (outer periphery) of the surface layer 54 with a polishing sheet, and the surface roughness Ra is adjusted. Here, the surface roughness Ra refers to the "arithmetic mean roughness" specified in JIS B 0601:2013, and is a value based on the result of measurement in the rotation axis direction of the photosensitive drum 1.

[0033] Amorphous silicon photoconductor A photoconductor that is mainly composed of amorphous silicon (amorphous silicon) and is generally called an amorphous silicon photoconductor (a-Si photoconductor) and that constitutes the photoconductor drum 1 used in this embodiment (experimental example described later) will be described. FIG. 5 is a schematic cross-sectional view showing an example of the layer structure of the amorphous silicon photoconductor 1b. The amorphous silicon photoconductor 1b that constitutes the photoconductor drum 1 has a photoconductive layer mainly composed of amorphous silicon (amorphous silicon). The amorphous silicon photoconductor 1b shown in FIG. 5(a) has a photosensitive film 82 provided on a photoconductor support 81. The photosensitive film 82 is composed of a photoconductive layer 83 that is made of a-Si:H,X (H is a hydrogen atom, and X is a halogen atom) and has photoconductivity. The amorphous silicon photoconductor 1b shown in FIG. 5(b) has a photosensitive film 82 provided on a photoconductor support 81. The photosensitive film 82 is composed of a photoconductive layer 83 made of a-Si:X, X and having photoconductivity, and an amorphous silicon-based surface layer 84. The amorphous silicon photoconductor 1b shown in FIG. 5(c) has a photosensitive film 82 provided on a photoconductor support 81. The photosensitive film 82 is composed of a photoconductive layer 83 made of a-Si:H, X and having photoconductivity, an amorphous silicon-based surface layer 84, and an amorphous silicon-based charge injection blocking layer 85. The amorphous silicon photoconductor 1b shown in FIG. 5(d) has a photosensitive film 82 provided on a photoconductor support 81. The photosensitive film 82 is composed of a charge generating layer 86 and a charge transport layer 87 made of a-Si:H, X, which constitute the photoconductive layer 83, and an amorphous silicon-based surface layer 84.

[0034] These photoconductive layer, surface layer, charge injection blocking layer, charge generating layer, charge transport layer, etc. may be layers constituting amorphous silicon photoconductors commonly used in the art.

[0035] The support used for the amorphous silicon photoreceptor 1b may be either conductive or electrically insulating. Examples of conductive supports include metals such as Al, Cr, Mo, Au, In, Nb, Te, V, Ti, Pt, Pd, and Fe, and alloys thereof, such as stainless steel. In addition, electrically insulating supports such as synthetic resin films or sheets, such as polyester, polyethylene, polycarbonate, cellulose acetate, polypropylene, polyvinyl chloride, polystyrene, and polyamide, glass, and ceramic supports, at least the surface of which on which the photosensitive film is formed, may be conductively treated. This is also true for the organic photoreceptor 1a described above. However, in this embodiment, the photoreceptor is a drum type.

[0036] In this embodiment, the photosensitive drum 1 made of the amorphous silicon photosensitive body 1b has a surface roughness Ra of 0.02 μm to 0.10 μm on the surface (outer circumferential surface) in a new (unused) state, similar to the photosensitive drum 1 made of the above-mentioned organic photosensitive body 1a. The surface roughness Ra of the photosensitive drum 1 made of the amorphous silicon photosensitive body 1b can be adjusted by roughening the outer circumferential surface of an aluminum raw tube as a support by blasting or the like, and forming an amorphous silicon layer (photosensitive layer) thereon. Alternatively, a polishing process may be used similar to the photosensitive drum 1 made of the above-mentioned organic photosensitive body 1a.

[0037] <Cleaning device> Next, the cleaning device 6 in this embodiment will be further described.

[0038] The cleaning device 6 has a cleaning blade 61 as a cleaning member, and a cleaning container 62. The cleaning blade 61 comes into contact with the surface of the photosensitive drum 1 to form a contact portion (cleaning portion) between the photosensitive drum 1 and the cleaning blade 61. The cleaning device 6 uses the cleaning blade 61 to scrape and remove primary transfer residual toner from the surface of the rotating photosensitive drum 1, and stores it in the cleaning container 62.

[0039] In this embodiment, the cleaning blade 61 includes a flat rubber member 61a made of polyurethane, which is an elastic member, and a support member 61b made of sheet metal. The rubber member 61a is attached and fixed to the support member 61b with an adhesive. The rubber member 61a is a plate-like member that is substantially rectangular in plan view and has a predetermined length in the longitudinal direction arranged along the rotation axis direction of the photosensitive drum 1 and in the lateral direction substantially perpendicular to the longitudinal direction, and has a predetermined thickness. A part of the fixed end side, which is one end of the rubber member 61a in the lateral direction, is fixed to the support member 61b, and an edge part of the free end side, which is the other end, abuts against the surface of the photosensitive drum 1. In this embodiment, the rubber member 61a is attached to the support member 61b so that the thickness is 2 mm and the free length (the length of the part not fixed to the support member 61b in the lateral direction) is 8 mm. In this embodiment, the rubber member 61a has a length of 330 mm in the longitudinal direction. The cleaning blade 61 (more specifically, the rubber member 61a) is pressed against the surface of the photosensitive drum 1 with a contact pressure in the range of 0.0002 N / mm to 0.0005 N / mm. The contact pressure of the cleaning blade 61 against the photosensitive drum 1 (herein, simply referred to as "contact pressure") is expressed as a contact load (N) per unit length (1 mm) in the direction of the rotation axis of the photosensitive drum 1 (longitudinal direction of the cleaning blade 61) when the photosensitive drum 1 is stopped. If the contact pressure of the cleaning blade 61 is smaller than 0.0002 N / mm, it becomes difficult for the cleaning blade 61 to block the primary transfer residual toner, and the toner may slip through. Conversely, if the contact pressure of the cleaning blade 61 is larger than 0.0005 N / mm, the frictional force between the photosensitive drum 1 and the cleaning blade 61 increases, and problems such as chattering, wear, and chipping of the cleaning blade 61 may occur. In other words, if the contact pressure of the cleaning blade 61 is not within the range of 0.0002 N / mm to 0.0005 N / mm, poor cleaning performance may occur and good cleaning performance may not be obtained.

[0040] <Control configuration> FIG. 3 is a block diagram for explaining the control configuration of the image forming apparatus 100 in this embodiment.

[0041] The image forming apparatus 100 is provided with a control unit 200 as a control means for controlling the overall operation of each unit of the image forming apparatus 100. The control unit 200 has a CPU 201 as an arithmetic processing means (arithmetic processing unit) and a memory 202 configured with a ROM, a RAM, a non-volatile memory, etc. as a storage means (storage unit). The ROM stores a control program, a data table obtained in advance by experiments, etc. Furthermore, the RAM temporarily stores the detection results of the sensors, the calculation results, etc. Furthermore, the non-volatile memory constitutes a counter, etc., which will be described later, and stores various usage history information such as count values, various setting information, etc.

[0042] The control unit 200 controls the operation of each unit of the image forming apparatus 100 by the CPU 201 performing processing according to the programs and data stored in the memory 202. For example, the control unit 200 controls the ON / OFF of various motors M1, M2, and M3, the ON / OFF and output values ​​of various power sources PS1, PS2, PS3, and PS4, the contact and separation state of the intermediate transfer belt 7 with respect to the photosensitive drum 1 by the contact and separation mechanism 75, and the like, to perform image formation or a photosensitive drum aging mode described later. In addition, a photosensitive drum replacement detection circuit 401 is connected to the control unit 200 as a replacement detection means for detecting that the photosensitive drum 1 has been replaced. In addition, a charging AC current detection circuit 403 is connected to the control unit 200 as a charging AC current detection means for detecting a charging AC current described later. In addition, a temperature sensor 404 and a humidity sensor 405 are connected to the control unit 200 as environment detection means for detecting an environment (usage environment) that is at least one of the temperature and humidity inside or outside the image forming apparatus 100. The photosensitive drum replacement detection circuit 401, charging AC current detection circuit 403, temperature sensor 404, and humidity sensor 405 each input a signal (information) indicating a detection result to the control unit 200. Furthermore, an operation unit 406 is connected to the control unit 200. The operation unit 406 is configured to include a display unit that displays information under the control of the control unit 200, and an input unit that inputs information to the control unit 200 based on the operation of an operator such as a user or a service representative. The operation unit 406 may be configured to include a touch panel that functions as both a display means and an input means.

[0043] The photosensitive drum replacement detection circuit 401 can detect that the photosensitive drum 1 has been replaced with a new one based on replacement information indicating that the photosensitive drum 1 has been replaced, which is input from the operation unit 406 or an external device (not shown), for example. The photosensitive drum replacement detection circuit 401 can also detect that the photosensitive drum 1 has been replaced with a new one based on information (including the presence or absence of predetermined information) in a memory serving as a storage unit (storage unit) provided in the photosensitive drum 1 (or a unit including the photosensitive drum 1). In this embodiment, the temperature sensor 404 detects the temperature inside the image forming apparatus 100 and inputs a signal (temperature information) indicating the detection result to the control unit 200. In this embodiment, the humidity sensor 405 detects the humidity inside the image forming apparatus 100 and inputs a signal (humidity information) indicating the detection result to the control unit 200.

[0044] The control unit 200 also has a sheet number counter 300 that counts the number of sheets on which images are formed. In this embodiment, the sheet number counter 300 is configured by a memory 202 (such as a non-volatile memory) that is a storage unit. The CPU 201 of the control unit 200 accumulates and stores the number of sheets on which images are formed in the sheet number counter 300 every time a toner image is formed on one side of the recording material S. In particular, in this embodiment, the sheet number counter 300 is configured to have a photosensitive drum usage counter N as a counting means that counts an index value that correlates with the usage amount of the photosensitive drum 1. The control unit 200 can be controlled to execute a photosensitive drum aging mode, which will be described later, based on the count value (accumulated number of sheets on which images are formed) of the photosensitive drum usage counter N. The count value of the photosensitive drum usage counter N is reset to an initial value (0 in this embodiment) when the photosensitive drum replacement detection circuit 401 detects that the photosensitive drum 1 has been replaced with a new one.

[0045] The control unit 200 also has a function of controlling the ON / OFF of the DC power supply and the AC power supply of the charging power supply PS1, respectively, to apply either one of the charging DC bias and the charging AC bias, or a superimposed bias of the charging DC bias and the charging AC bias to the charging roller 2. The control unit 200 also has a function of controlling the value of the charging DC bias voltage ("charging DC voltage") applied to the charging roller 2 from the DC power supply of the charging power supply PS1, and the value of the charging AC bias voltage ("charging AC voltage") Vac or the value of the AC current ("charging AC current") Iac applied to the charging roller 2 from the AC power supply of the charging power supply PS1. In this embodiment, the charging AC voltage Vac represents a peak-to-peak voltage. Note that the charging AC voltage Vac can be any of the peak-to-peak voltage, maximum voltage, minimum voltage, and effective voltage value. The control unit 200 receives information on the detected charging AC current Iac from a charging AC current detection circuit 403 that detects the charging AC current Iac flowing to the charging roller 2 via the photosensitive drum 1.

[0046] Here, the image forming apparatus 100 executes a job (print job, image forming operation) which is a series of operations for forming and outputting an image on a single or multiple recording materials S in response to one start instruction. A job generally includes an image forming process, a pre-rotation process, a paper-interval process in the case of forming an image on multiple recording materials S, and a post-rotation process. The image forming process is a period in which an electrostatic latent image of an image to be actually formed on the recording material S is formed, a toner image is formed, and the toner image is primarily transferred or secondary transferred, and this period is referred to as the time of image formation (normal image formation). More specifically, the timing of image formation differs depending on the position where each process of charging, exposure, development, primary transfer, and secondary transfer is performed. The pre-rotation process is a period in which a preparatory operation is performed before the image forming process from when a start instruction is input to the image forming apparatus 100 until the image actually starts to be formed. The paper-interval process is a period corresponding to the period between recording materials S when the image forming process is continuously performed on multiple recording materials S (continuous image formation). The post-rotation process is a period in which a tidying operation (preparatory operation) is performed after the image forming process. The non-image forming time is a period other than the image forming time, and includes the above-mentioned pre-rotation process, the sheet interval process, the post-rotation process, and further the pre-multiple rotation process which is a preparatory operation when the image forming apparatus 100 is turned on or when it returns from a sleep state. The photosensitive drum aging mode described later is a control executed in the pre-rotation process or pre-multiple rotation process at the beginning of use of the photosensitive drum 1 (typically, when starting to use a new photosensitive drum 1).

[0047] <Charging AC voltage determination control> Next, a charging AC voltage determination control for determining the charging AC voltage Vac during image formation in this embodiment or during a photosensitive drum aging mode, which will be described later, will be described.

[0048] The condition for the charging AC voltage Vac at which sustained discharge occurs in the minute gap between the charging roller 2 and the photosensitive drum 1 is when the charging AC voltage Vac exceeds twice the discharge start voltage Vth (the voltage at which discharge starts when a DC voltage is applied (discharge threshold)) which is determined by the configuration of the photosensitive drum 1 and the charging roller 2. In the configuration of this embodiment, the discharge start voltage Vth is 500 V. Therefore, a charging AC bias with a charging AC voltage Vac of less than 1000 V is defined as an "undischarged bias," and a charging AC bias with a charging AC voltage Vac of 1000 V or more is defined as a "discharge bias."

[0049] FIG. 6(a) is a graph showing the relationship between the charging AC voltage Vac and the charging AC current Iac flowing into the photosensitive drum 1. When the charging AC voltage Vac increases, the charging AC current Iac increases, and the relationship between the charging AC voltage Vac and the charging AC current Iac has an inflection point at the point where the charging bias approaches the discharging bias from the undischarged bias. The increase (slope) of the charging AC current Iac with respect to the increase in the charging AC voltage Vac is larger in the discharging bias region than in the undischarged bias region. This is because the charging AC current Iac flowing with respect to the discharging bias is added with the "undischarged current" assumed from the relationship between the charging AC voltage Vac and the charging AC current Iac in the undischarged bias region, since the condition for the continuous discharge caused by the charging AC voltage Vac is satisfied. In order to set the charging AC voltage Vac that does not cause image defects, it is preferable to control the discharge current to a predetermined value.

[0050] In this embodiment, the image forming apparatus 100 executes charging AC voltage determination control for setting a charging AC voltage Vac at which the discharge current becomes a predetermined value before starting image formation or before starting a photosensitive drum aging mode described later. In this embodiment, the control unit 200 applies a plurality of undischarged biases and a plurality of discharge biases as test biases to the charging roller 2 while rotating the photosensitive drum 1 by operating the photosensitive drum driving motor M1 in the charging AC voltage determination control, and detects the charging AC current Iac at that time. Specifically, the control unit 200 applies a test bias with charging AC voltages Vac of 500V and 900V as the undischarged bias and a test bias with charging AC voltages Vac of 1100V, 1500V, and 1900V as the discharge bias to the charging roller 2, and detects the charging AC current Iac at that time. Then, the control unit 200 calculates the discharge current Idis by subtracting the undischarged current predicted (calculated) from the relationship between the undischarged bias in the undischarged bias region and the charging AC current Iac from the charging AC current Iac in the discharge bias region.

[0051] The control unit 200 determines the charging AC voltage Vac that provides the target discharge current Itarget that is determined in advance and stored in the memory 202, based on the relationship between the discharge bias and the discharge current Idis calculated as described above. In this embodiment, the predetermined target discharge current Itarget1 during image formation (normal image formation) is set to 100 μA. In addition, in this embodiment, the predetermined target discharge current Itarget2 during a photosensitive drum aging mode, which will be described later, is set to 150 μA. Then, as shown in FIG. 6(b), the charging AC voltage Vac1 during image formation is set to, for example, 1500 V by the charging AC voltage determination control. In addition, as shown in FIG. 6(b), the charging AC voltage Vac2 during the photosensitive drum aging mode is set to, for example, 1800 V by the charging AC voltage determination control. The photosensitive drum aging mode and the target discharge current Itarget2 during the photosensitive drum aging mode will be described later in more detail.

[0052] <Summary of the problem and solution> As described above, when the cumulative number of images formed using the photosensitive drum 1 increases, the frictional force (friction coefficient) between the photosensitive drum 1 and the cleaning blade 61 increases due to adhesion of discharge products to the surface of the photosensitive drum 1. Then, the stick-slip phenomenon occurs, which may cause toner and external additives to slip through. In addition to the toner and external additives that slip through due to the stick-slip phenomenon, chattering, wear, chipping, etc. of the cleaning blade 61 may also occur.

[0053] In response to this, it is effective to form unevenness on the surface of the photosensitive drum 1 in advance to reduce the contact area between the photosensitive drum 1 and the cleaning blade 61. However, if unevenness is formed on the surface of the photosensitive drum 1 in advance so as to reduce the frictional force between the photosensitive drum 1 and the cleaning blade 61 throughout the life of the photosensitive drum 1, the frictional force between the photosensitive drum 1 and the cleaning blade 61 may become too low in the early stages of use of the photosensitive drum 1. If the frictional force between the photosensitive drum 1 and the cleaning blade 61 is too high, as described above, it is problematic, but if it is too low, the contact pressure of the cleaning blade 61 against the photosensitive drum 1 does not increase sufficiently when the photosensitive drum 1 rotates, causing the toner and external additives to slip through. If the toner and external additives slip through in the early stages of use of the photosensitive drum 1, the toner and external additives may adhere to the charging roller 2, and vertical streak-like image defects (streak-like image density unevenness extending along the moving direction of the surface of the photosensitive drum) caused by dirt on the charging roller 2 may occur.

[0054] Fig. 7(a) is a graph illustrating the relationship between the cumulative number of images formed using the photosensitive drum 1 and the frictional force between the photosensitive drum 1 and the cleaning blade 61, in order to explain the conventional problems. Curve (1) in Fig. 7(a) shows the above relationship when the surface roughness Ra of the surface of a new photosensitive drum 1 is 0.01 μm, and curve (2) in Fig. 7(a) shows the above relationship when the surface roughness Ra of a new photosensitive drum 1 is 0.10 μm.

[0055] When the cumulative number of images formed using the photosensitive drum 1 increases, in addition to the deposition of discharge products on the surface of the photosensitive drum 1, the surface of the photosensitive drum 1 gradually wears and becomes smooth, and the frictional force between the photosensitive drum 1 and the cleaning blade 61 increases. Therefore, as shown by the curve (1) in FIG. 7(a), if the surface roughness Ra of a new photosensitive drum 1 is too low, the frictional force between the photosensitive drum 1 and the cleaning blade 61 becomes too high in the latter half of the life of the photosensitive drum 1. Then, problems such as slip-through of toner and external additives due to the stick-slip phenomenon or chattering may occur. In contrast, if the surface roughness Ra of the photosensitive drum 1 is set so as to suppress the occurrence of the above problems in the latter half of the life of the photosensitive drum 1, the frictional force between the photosensitive drum 1 and the cleaning blade 61 becomes too low in the early stage of use of the photosensitive drum 1 (the period from 0 to 1000 cumulative images formed in the illustrated example), and the toner and external additives may slip-through, as shown by the curve (2) in FIG. 7(b). For example, this may be the case when the surface roughness Ra of the photosensitive drum 1 is the maximum value in the manufacturing variations.

[0056] Therefore, in this embodiment, the image forming apparatus 100 executes a photosensitive drum aging mode, which is a predetermined operation, at the beginning of use of the photosensitive drum 1 (typically, when starting to use a brand new photosensitive drum 1).

[0057] Fig. 7(b) is a graph diagram showing a typical relationship between the cumulative number of images formed using the photosensitive drum 1 and the frictional force between the photosensitive drum 1 and the cleaning blade 61, in order to explain the effect of the photosensitive drum aging mode. Fig. 7(b) shows the above relationship when the surface roughness Ra of a new photosensitive drum 1 is 0.10 µm. As shown in Fig. 7(b), in this embodiment, by executing the photosensitive drum aging mode, the frictional force between the photosensitive drum 1 and the cleaning blade 61 is increased to a degree that can suppress the slipping through of toner and external additives in the initial period of use of the photosensitive drum 1.

[0058] The initial use of the photosensitive drum 1 refers to the initial stage of the life of the photosensitive drum 1 from the start of use of the new photosensitive drum 1 in the image forming apparatus 100 until a predetermined period determined by the number of sheets of image formation has elapsed. The predetermined period of the initial use of the photosensitive drum 1 can be arbitrarily set based on the period during which toner or external additives may pass through if the photosensitive drum aging mode is not executed, depending on the configuration of the photosensitive drum 1 and the cleaning blade 61. For example, as shown in FIG. 7(a), the predetermined period of the initial use of the photosensitive drum 1 can be exemplified by a period until the cumulative number of sheets of image formation from the new state of the new photosensitive drum 1 reaches 1000 sheets. Typically, as in this embodiment, the photosensitive drum aging mode may be executed after the new photosensitive drum 1 is installed in the image forming apparatus 100 until the start of the first image formation (first job) according to any image information specified by the user using the new photosensitive drum 1. However, within the above-mentioned predetermined period, the photosensitive drum aging mode can be executed to suppress the subsequent pass-through of toner or external additives. In this embodiment, the photosensitive drum aging mode needs to be executed only once at the beginning of use of the photosensitive drum 1.

[0059] <Photosensitive drum aging mode> The photosensitive drum aging mode in this embodiment will be described.

[0060] In this embodiment, the image forming apparatus 100 executes a photosensitive drum aging mode at the beginning of use of the photosensitive drum 1. In particular, in this embodiment, the image forming apparatus 100 executes the photosensitive drum aging mode from when the photosensitive drum 1 is new (unused) until the first image is output.

[0061] In the photosensitive drum aging mode, the photosensitive drum drive motor M1 is operated for a predetermined time to rotate the photosensitive drum 1, while a charging AC bias is applied to the charging roller 2 by the charging power source PS1 to generate a discharge between the charging roller 2 and the photosensitive drum 1.

[0062] In the photosensitive drum aging mode, by generating a discharge between the charging roller 2 and the photosensitive drum 1, a discharge product adheres to the surface of the photosensitive drum 1, and the frictional force (friction coefficient) between the photosensitive drum 1 and the cleaning blade 61 increases. As a result, the edge of the cleaning blade 61 is pulled into the surface of the rotating photosensitive drum 1, and the contact pressure of the cleaning blade 61 against the photosensitive drum 1 increases. This makes it possible to suppress the passing of toner and external additives during image formation in the initial period of use of the photosensitive drum 1 after the photosensitive drum aging mode has been executed, and to suppress image defects such as vertical streaks.

[0063] In this embodiment, the target discharge current Itarget2 in the photosensitive drum aging mode is set to be larger than the target discharge current Itarget1 during image formation (normal image formation). This effectively increases the frictional force between the photosensitive drum 1 and the cleaning blade 61, and shortens the time required for the photosensitive drum aging mode. As described above, in this embodiment, the target discharge current Itarget1 during image formation is 100 μA, and the target discharge current Itarget2 during the photosensitive drum aging mode is 150 μA (1.5 times the target discharge current Itarget1 during image formation). Then, by the charging AC voltage determination control, the charging AC voltage Vac1 during image formation is set to, for example, 1500 V, and the charging AC voltage Vac2 during the photosensitive drum aging mode is set to, for example, 1800 V (FIG. 6B). The charging AC voltage to be set changes depending on the environment, or the usage status (usage amount) of the photosensitive drum 1 or the charging roller 2. The charging AC voltage Vac in the photosensitive drum aging mode and during image formation may be compared between the photosensitive drum aging mode and during image formation immediately thereafter.

[0064] Here, the target discharge current Itarget2 in the photosensitive drum aging mode is preferably 1.5 times or more, more preferably 2.0 times or more, of the target discharge current Itarget1 in the image formation. However, in general, the charging power source PS1 is set with an upper limit value of the charging AC current Iac determined by the output performance of the high voltage power source. Then, when the charging power source PS1 tries to output the charging AC current Iac in excess of the upper limit value, the charging power source PS1 is designed so that the charging AC current Iac flows through the protection circuit. Therefore, the upper limit value of the target discharge current Itarget may be set so as not to flow the charging AC current Iac that exceeds the upper limit value of the charging AC current Iac. In the configuration of this embodiment, the target discharge current Itarget2 in the photosensitive drum aging mode is preferably less than 5 times the target discharge current Itarget1 in the image formation. In other words, the charging AC voltage Vac2 in the photosensitive drum aging mode is preferably set to a value 50 V or more higher than the charging AC voltage Vac1 during image formation by controlling the discharge current, more preferably set to a value 100 V or more higher, and even more preferably set to a value 200 V or more higher. However, for the same reason as in the case of the target discharge current, the charging AC voltage Vac2 in the photosensitive drum aging mode is typically set to a value 400 V or less higher than the charging AC voltage Vac1 during image formation.

[0065] In addition, the upper limit of the target discharge current Itarget2 in the photosensitive drum aging mode is determined by the output performance of the high-voltage power supply, and can be set arbitrarily depending on the configuration of the charging power supply PS1, etc. The same applies to the upper limit of the charging AC voltage Vac2 in the photosensitive drum aging mode.

[0066] Furthermore, the rate of increase in the frictional force between the photosensitive drum 1 and the cleaning blade 61 per unit travel distance (unit surface movement distance) of the photosensitive drum 1 varies depending on the temperature detected by the temperature sensor 404 and the humidity detected by the humidity sensor 405. Therefore, the relationship between the target discharge current Itarget1 during image formation and the target discharge current Itarget2 in the photosensitive drum aging mode may be set differently for each environment.

[0067] In the present embodiment, a configuration is adopted in which the charging AC voltage Vac is determined to obtain a predetermined discharge current by executing the charging AC voltage determination control, but the present invention is not limited to such an embodiment. In a configuration in which a charging AC current detection means is not provided, the charging AC voltage Vac during image formation or the charging AC voltage Vac during the photosensitive drum aging mode can be determined according to the environment (for example, at least one of the temperature and humidity around the photosensitive drum 1). Then, in the same environment, the charging AC voltage Vac during the photosensitive drum aging mode can be set higher than the charging AC voltage Vac during image formation.

[0068] On the other hand, in the photosensitive drum aging mode, it is preferable to apply a charging AC bias to the charging roller 2 while rotating the photosensitive drum 1 with the rotation of the developing sleeve 41 of the developing device 4 stopped, to generate a discharge between the charging roller 2 and the photosensitive drum 1. This makes it possible to more effectively increase the frictional force between the photosensitive drum 1 and the cleaning blade 61, and to further shorten the time required for the photosensitive drum aging mode. In other words, by making the target discharge current Itarget2 higher than that during image formation, it becomes easier for sticky discharge products to adhere to the surface of the photosensitive drum 1, and by stopping the rotation of the developing sleeve 41, the supply of external additives to the cleaning blade 61 is stopped. This makes it easier for the frictional force between the photosensitive drum 1 and the cleaning blade 61 to increase. However, as shown in the experimental example described later, depending on the configuration of the photosensitive drum 1, even if a charging AC bias is applied to the charging roller 2 while rotating the photosensitive drum 1 with the development sleeve 41 of the developing device 4 rotated in the photosensitive drum aging mode, to generate a discharge between the charging roller 2 and the photosensitive drum 1, the desired effect of the photosensitive drum aging mode can be obtained in a sufficiently short time.

[0069] In this embodiment, during execution of the photosensitive drum aging mode, the charging DC bias is not applied to the charging roller 2, and the developing bias (developing DC bias, developing AC bias) is not applied to the developing sleeve 41. Furthermore, during the photosensitive drum aging mode, exposure by the exposure device 3 is not performed. However, for example, in a case where the developing sleeve 41 is rotated during execution of the photosensitive drum aging mode, the charging DC bias similar to that during image formation may be applied to the charging roller 2, and the developing bias (developing DC bias, developing AC bias) similar to that during image formation may be applied to the developing sleeve 41 during execution of the photosensitive drum aging mode.

[0070] Also, a configuration may be adopted in which the developing member contacts the photosensitive drum 1 to perform development, and a developing contact / separation mechanism is provided for contacting and separating the developing member with respect to the photosensitive drum 1. In such a configuration, if the rotation of the developing member is stopped during execution of the photosensitive drum aging mode, the developing member may be separated from the photosensitive drum 1 during execution of the photosensitive drum aging mode. Also, if the developing member can be rotated during execution of the photosensitive drum aging mode, it can be brought into contact with the photosensitive drum 1 during execution of the photosensitive drum aging mode.

[0071] FIG. 8 is a flow chart showing an outline of the control procedure of the pre-multiple rotation process in this embodiment.

[0072] When the image forming apparatus 100 is powered on or the image forming apparatus 100 is restored from a sleep state (S101), the CPU 201 of the control unit 200 controls the image forming apparatus 100 to start a pre-rotation process (S102). When starting the pre-rotation process, the CPU 201 judges whether the count value (accumulated number of images formed) of the photosensitive drum usage counter N is 0 or not, thereby judging whether the photosensitive drum 1 is new or not (S103). When the CPU 201 judges in S103 that the count value of the photosensitive drum usage counter N is 0, that is, that the photosensitive drum 1 is new ("Yes"), it executes charging AC voltage determination control to determine a target charging AC voltage Vac1 during image formation and a target charging AC voltage Vac2 during the photosensitive drum aging mode (S104). After that, the CPU 201 executes the photosensitive drum aging mode (S105). After the photosensitive drum aging mode is completed, the CPU 201 executes other operations in the pre-rotation process (S106) and ends the pre-rotation process. If the CPU 201 determines in S103 that the photosensitive drum usage counter N is not 0, that is, that the photosensitive drum 1 is not new ("No"), the CPU 201 executes the normal pre-rotation process without executing the photosensitive drum aging mode (S106) and ends the pre-rotation process.

[0073] In the procedure shown in FIG. 8, the photosensitive drum aging mode is executed in the pre-rotation process, but the photosensitive drum aging mode may also be executed in the pre-rotation process after the image forming apparatus 100 receives job information and before starting image formation.

[0074] 8, in the pre-rotation process, the photosensitive drum aging mode is executed first, and then other operations in the pre-rotation process are executed, but the order of these operations may be reversed. For example, in the pre-rotation process, the photosensitive drum aging mode may be executed after an adjustment operation of forming a test image (patch) for adjusting image density on the photosensitive drum 1 is executed.

[0075] FIG. 9 is a sequence chart for explaining the transition of the state of each part during the photosensitive drum aging mode (and during subsequent image formation) when the rotation of the developing sleeve 14 is stopped in the photosensitive drum aging mode (Experimental Examples 1, 3, and 5 described later). In this case, when the photosensitive drum aging mode is started, the photosensitive drum drive motor M1 is driven and the charging AC bias is applied to the charging roller 2 by the charging power source PS1. At this time, the development drive motor M2 is stopped, the application of the development bias (developing DC bias, developing AC bias) to the developing sleeve 41 by the development power source PS2 is stopped, and the application of the charging DC bias to the charging roller 2 by the charging power source PS1 is stopped. At this time, the charging AC bias is controlled to the charging AC voltage Vac2 (for example, 1800 V) during the photosensitive drum aging mode determined in advance by the charging AC voltage determination control. Then, after a preset execution time T of the photosensitive drum aging mode (here, simply referred to as "execution time") has elapsed, the charging AC bias is turned OFF and the driving of the photosensitive drum driving motor M1 is stopped. When image formation is started after the photosensitive drum aging mode ends, the setting of the charging AC bias is changed to the charging AC voltage Vac1 during image formation determined in advance by the charging AC voltage determination control. As described above, during image formation, the driving of the photosensitive drum driving motor M1 and the developing driving motor M2 is turned ON, and the charging power source SP1 applies the charging bias (charging DC bias, charging AC bias) to the charging roller 2, and the developing power source SP2 applies the developing bias (developing DC bias, developing AC bias) to the developing sleeve 41.

[0076] In this embodiment, the execution time T is set according to the time of the photosensitive drum aging mode required when the surface roughness Ra of the photosensitive drum 1 is a maximum of 0.010 μm and the contact pressure of the cleaning blade 61 is a minimum of 0.0002 N / mm, so as to prevent the toner and external additives from passing through during the initial use of the photosensitive drum 1 even if there are manufacturing variations in the surface roughness Ra of the photosensitive drum 1 and the contact pressure of the cleaning blade 61. This execution time T will be described in more detail using an experimental example described later.

[0077] 10 is a sequence chart for explaining the transition of the state of each part during the photosensitive drum aging mode (and during subsequent image formation) when the developing sleeve 14 is rotated in the photosensitive drum aging mode (Experimental Examples 2 and 4 described later). In this case, when the photosensitive drum aging mode is started, the photosensitive drum drive motor M1 and the development drive motor M2 are driven, and a charging AC bias is applied to the charging roller 2 by the charging power source PS1. Other points are the same as those in the sequence chart shown in FIG. 9.

[0078] The photosensitive drum aging mode can be executed simultaneously in all image forming units 10 when starting to use a brand new image forming apparatus 100. However, when a photosensitive drum 1 is replaced while the image forming apparatus 100 is in operation, the photosensitive drum aging mode can be executed for each corresponding image forming unit 10. In addition, in a configuration in which a plurality of photosensitive drums 1 rotate in conjunction with each other, the photosensitive drums 1 can be idle-rotated without applying a charging bias, rotating the developing sleeve 41, etc., in the image forming units 10 other than the image forming unit 10 requiring the photosensitive drum aging mode.

[0079] In addition, in this embodiment, during execution of the photosensitive drum aging mode, the intermediate transfer belt 7 is separated from the corresponding photosensitive drum 1 by the contact / separation mechanism 75 (the intermediate transfer belt 7 may be separated from all the photosensitive drums 1). However, in a configuration in which the contact / separation mechanism 75 is not provided, the intermediate transfer belt 7 may rotate in contact with the photosensitive drum 1 during execution of the photosensitive drum aging mode.

[0080] In this embodiment, the rotation speed of the photosensitive drum 1 during the photosensitive drum aging mode is the same as that during image formation, but may be different from that during image formation. For example, the rotation speed of the photosensitive drum 1 during the photosensitive drum aging mode may be slower than the rotation speed during image formation to increase the amount of discharge per unit area of ​​the surface of the photosensitive drum 1.

[0081] <Experimental Example> Next, some experimental examples conducted to confirm the effect of the photosensitive drum aging mode in this embodiment will be described.

[0082] Experimental Method Here, in the image forming apparatus 100 having the configuration of the present embodiment described above, the setting of the photosensitive drum aging mode was changed to evaluate the occurrence of image defects due to the slip-through of toner and external additives in the early stages of use of the photosensitive drum 1. The slip-through of toner and external additives was evaluated by printing 5,000 A4-sized halftone images with a print rate of 50% in an environment of 23°C and 50%, and determining whether or not image defects in the form of vertical streaks occurred on the halftone images during the printing of the 5,000 sheets. Then, if an image defect occurred within 5,000 sheets, it was evaluated as "× (bad)", and if it did not occur, it was evaluated as "◯ (good)".

[0083] If the execution time T is too short, it becomes difficult to obtain a sufficient effect of suppressing image defects caused by the slip-through of toner or external additives in the initial use of the photosensitive drum 1. Therefore, in the configuration of this embodiment, under any conditions of the minimum to maximum value of the surface roughness Ra of the photosensitive drum 1 when considering the manufacturing variation and the minimum to maximum value of the contact pressure of the cleaning blade 61 when considering the manufacturing variation, the minimum execution time T necessary to suppress image defects caused by the slip-through of toner or external additives in the initial use of the photosensitive drum 1 was obtained. Note that, in the configuration of this embodiment, the minimum value of the surface roughness Ra of the photosensitive drum 1 when considering the manufacturing variation is 0.02 μm and the maximum value is 0.10 μm when considering the manufacturing variation. Also, in the configuration of this embodiment, the minimum value of the contact pressure of the cleaning blade 61 when considering the manufacturing variation is 0.0002 N / mm and the maximum value is 0.0005 N / mm. In this embodiment, the minimum necessary time of the photosensitive drum aging mode is set as the execution time T. The execution time T is typically 2 minutes or more, and is desirably less than 5 minutes from the viewpoint of preventing the time spent waiting for the photosensitive drum aging mode to end from becoming too long.

[0084] Experimental Example 1 In experimental example 1, an organic photoconductor was used as the photoconductor drum 1, and the rotation of the developing sleeve 41 was stopped during execution of the photoconductor drum aging mode. Also, in experimental example 1, the target discharge current Itarget2 during the photoconductor drum aging mode was set to 1.5 times the target discharge current Itarget1 during image formation.

[0085] Table 1 shows the results of Experimental Example 1.

[0086] [Table 1]

[0087] As shown in Table 1, in the configuration of Experimental Example 1, when the contact pressure of the cleaning blade 61 is within the range of 0.0002 N / mm to 0.0005 N / mm, if the surface roughness Ra of the photosensitive drum 1 is 0.02 μm, image defects due to the passage of toner and external additives during the initial use of the photosensitive drum 1 can be suppressed by setting the execution time T to 150 sec or more. Also, when the surface roughness Ra of the photosensitive drum 1 is 0.10 μm, image defects due to the passage of toner and external additives during the initial use of the photosensitive drum 1 can be suppressed by setting the execution time T to 210 sec or more.

[0088] Therefore, in the configuration of experimental example 1, by setting the execution time T to 210 sec, even if there are manufacturing variations in the surface roughness Ra of the photosensitive drum 1 and the cleaning blade 61, it is possible to suppress vertical streak-like image defects caused by the passage of toner or external additives during the initial use of the photosensitive drum 1.

[0089] In the configuration of Experimental Example 1, the target discharge current Itarget2 in the photosensitive drum aging mode is set to 1.5 times the target discharge current Itarget1 during image formation, but this can be changed depending on the output performance of the charging power source PS1, etc. In addition, in the configuration of Experimental Example 1, the execution time T is not limited to being set to 210 sec, and may be set to be longer than 210 sec.

[0090] Experimental Example 2 In the second experimental example, an organic photoconductor was used as the photoconductor drum 1, and the developing sleeve 41 was rotated during the execution of the photoconductor drum aging mode.

[0091] Table 2 shows the results of Experimental Example 2.

[0092] [Table 2]

[0093] As shown in Table 2, in the configuration of Experimental Example 2, when the contact pressure of the cleaning blade 61 is within the range of 0.0002 N / mm to 0.0005 N / mm, if the surface roughness Ra of the photosensitive drum 1 is 0.02 μm, an execution time T of 240 sec or more can suppress image defects caused by the passage of toner and external additives during the initial use of the photosensitive drum 1. Also, when the surface roughness Ra of the photosensitive drum 1 is 0.10 μm, an execution time T of 300 sec or more can suppress image defects caused by the passage of toner and external additives during the initial use of the photosensitive drum 1.

[0094] Therefore, in the configuration of experimental example 2, in order to suppress vertical streak-like image defects caused by the passage of toner or external additives during the initial use of the photosensitive drum 1, even if there are manufacturing variations in the surface roughness Ra of the photosensitive drum 1 and the cleaning blade 61, the execution time T needs to be set to 300 sec.

[0095] Thus, in the configuration of Experimental Example 2, it is necessary to make the execution time T longer than in the configuration of Experimental Example 1. This is thought to be because, by rotating the developing sleeve 41 during execution of the photosensitive drum aging mode, the external additive is supplied to the surface of the photosensitive drum 1, and it takes time to increase the frictional force between the photosensitive drum 1 and the cleaning blade 61.

[0096] Experimental Example 3 In Experimental Example 3, an amorphous silicon photosensitive member was used as the photosensitive drum 1, and the rotation of the developing sleeve 41 was stopped during the photosensitive drum aging mode. Also, in Experimental Example 3, the target discharge current Itarget2 during the photosensitive drum aging mode was set to 1.5 times the target discharge current Itarget1 during image formation.

[0097] Table 3 shows the results of Experimental Example 3.

[0098] [Table 3]

[0099] As shown in Table 3, in the configuration of Experimental Example 3, when the contact pressure of the cleaning blade 61 is within the range of 0.0002 N / mm to 0.0005 N / mm, if the surface roughness Ra of the photosensitive drum 1 is 0.02 μm, an execution time T of 90 sec or more can suppress image defects caused by the passage of toner and external additives during the initial use of the photosensitive drum 1. Also, when the surface roughness Ra of the photosensitive drum 1 is 0.10 μm, an execution time T of 150 sec or more can suppress image defects caused by the passage of toner and external additives during the initial use of the photosensitive drum 1.

[0100] Therefore, in the configuration of experimental example 3, by setting the execution time T to 150 sec, even if there are manufacturing variations in the surface roughness Ra of the photosensitive drum 1 and the cleaning blade 61, it is possible to suppress vertical streak-like image defects caused by the passage of toner or external additives during the initial use of the photosensitive drum 1.

[0101] In this way, the configuration of Experimental Example 3 can shorten the execution time T compared to the configuration of Experimental Example 1. This is thought to be because the surface of an amorphous silicon photoconductor is less susceptible to abrasion compared to an organic photoconductor, and therefore the frictional force between the photoconductor drum 1 and the cleaning blade 61 is more likely to increase by adhering discharge products in the photoconductor drum aging mode. In this way, it can be said that the photoconductor drum aging mode of this embodiment works more advantageously when an amorphous silicon photoconductor is used than when an organic photoconductor is used.

[0102] In the configuration of Experimental Example 3, the target discharge current Itarget2 in the photosensitive drum aging mode is set to 1.5 times the target discharge current Itarget1 during image formation, but this can be changed depending on the output performance of the charging power source PS1, etc. Also, in the configuration of Experimental Example 3, the execution time T is not limited to being set to 150 sec, and may be set to be longer than 150 sec.

[0103] Experimental Example 4 In the experimental example 4, an amorphous silicon photosensitive member was used as the photosensitive drum 1, and the developing sleeve 41 was rotated during the execution of the photosensitive drum aging mode.

[0104] Table 4 shows the results of Experimental Example 4.

[0105] [Table 4]

[0106] As shown in Table 4, in the configuration of Experimental Example 4, when the contact pressure of the cleaning blade 61 is within the range of 0.0002 N / mm to 0.0005 N / mm, if the surface roughness Ra of the photosensitive drum 1 is 0.02 μm, image defects due to the passage of toner and external additives during the initial use of the photosensitive drum 1 can be suppressed by setting the execution time T to 150 sec or more. Also, when the surface roughness Ra of the photosensitive drum 1 is 0.10 μm, image defects due to the passage of toner and external additives during the initial use of the photosensitive drum 1 can be suppressed by setting the execution time T to 210 sec or more.

[0107] Therefore, in the configuration of experimental example 4, by setting the execution time T to 210 sec, even if there are manufacturing variations in the surface roughness Ra of the photosensitive drum 1 and the cleaning blade 61, it is possible to suppress vertical streak-like image defects caused by the passage of toner or external additives during the initial use of the photosensitive drum 1.

[0108] Thus, in the configuration of Experimental Example 4, even when the developing sleeve 41 is rotated during execution of the photosensitive drum aging mode, the same effect can be obtained with the same execution time T as in Experimental Example 1, in which an organic photoconductor is used as the photosensitive drum 1 and the rotation of the developing sleeve 41 is stopped during execution of the photosensitive drum aging mode. This is thought to be because, as described above, the surface of an amorphous silicon photoconductor is less prone to being scraped off than an organic photoconductor, and therefore the adhesion of discharge products in the photosensitive drum aging mode makes it easier for the frictional force between the photosensitive drum 1 and the cleaning blade 61 to increase.

[0109] Experimental Example 5 In the experimental example 5, an organic photoconductor was used as the photoconductor drum 1, and the target discharge current Itarget2 (i.e., charging AC voltage Vac2) in the photoconductor drum aging mode was set to be the same as the target discharge current Itarget1 (i.e., charging AC voltage Vac1) during image formation (target discharge current Itarget2=150 μA, charging AC voltage Vac2=1500 V). Other points were the same as in the experimental example 1.

[0110] Table 5 shows the results of Experimental Example 5.

[0111] [Table 5]

[0112] As shown in Table 5, in the configuration of Experimental Example 5, when the contact pressure of the cleaning blade 61 is within the range of 0.0002 N / mm to 0.0005 N / mm, if the surface roughness Ra of the photosensitive drum 1 is 0.02 μm, image defects due to the passage of toner and external additives during the initial use of the photosensitive drum 1 can be suppressed by setting the execution time T to 420 sec or more. Also, when the surface roughness Ra of the photosensitive drum 1 is 0.10 μm, image defects due to the passage of toner and external additives during the initial use of the photosensitive drum 1 can be suppressed by setting the execution time T to 480 sec or more.

[0113] Therefore, in the configuration of experimental example 5, in order to suppress vertical streak-like image defects caused by the passage of toner or external additives during the initial use of the photosensitive drum 1, even if there are manufacturing variations in the surface roughness Ra of the photosensitive drum 1 and the cleaning blade 61, the execution time T needs to be set to 480 sec.

[0114] Thus, in the configuration of Experimental Example 5, it is necessary to make the execution time T longer than in the configuration of Experimental Example 1. This is thought to be because in Experimental Example 5, the target discharge current Itarget2 (i.e., charging AC voltage Vac2) in the photosensitive drum aging mode is lower than in Experimental Example 1, so it takes time to increase the frictional force between the photosensitive drum 1 and the cleaning blade 61.

[0115] Experimental Example 6 In Experimental Example 6, in the configurations of Experimental Example 1 (organic photoconductor) and Experimental Example 3 (amorphous silicon photoconductor), the photoconductor drum aging mode was not executed even though the photoconductor drum 1 was new.

[0116] As a result, when the contact pressure of the cleaning blade 61 was 0.0002 N / mm and 0.0005 N / mm and the surface roughness Ra of the photosensitive drum 1 was 0.02 μm and 0.10 μm, image defects occurred during printing of 5,000 sheets.

[0117] Comparison of experimental examples Table 6 compares the execution times T set in the configurations of the above-mentioned experimental examples 1 to 6, and the evaluation results of image defects caused by the passing through of toner and external additives in the early stages of use of the photosensitive drum 1 when the photosensitive drum aging mode is executed for the execution time T. Note that in experimental example 6, the photosensitive drum aging mode was not executed, and image defects occurred due to the passing through of toner and external additives in the early stages of use of the photosensitive drum 1.

[0118] [Table 6]

[0119] As shown in Table 6, in Experimental Example 1, the execution time T can be made shorter than in Experimental Example 2 and Experimental Example 5. In addition, in Experimental Example 3, the execution time T can be made shorter than in Experimental Example 1, and in Experimental Example 4, the execution time T can be made equivalent to that of Experimental Example 1.

[0120] <Effects> Thus, in this embodiment, the image forming apparatus 100 includes a rotatable photoconductor 1, a photoconductor drive unit M1 that rotates the photoconductor 1, a charging member 2 that contacts the surface of the photoconductor 1 and charges the surface of the photoconductor 1, an application unit PS1 that applies an AC bias to the charging member 2, a rotatable developing member 41 that supplies developer to the surface of the photoconductor 1 to form a developer image on the surface of the photoconductor 1, a development drive unit M2 that rotates the developing member 41, a cleaning member 61 that contacts the surface of the photoconductor 1 and cleans the surface of the photoconductor 1, an acquisition unit (photoconductor drum usage counter) N that acquires usage information (count value of the photoconductor drum usage counter) regarding the usage of the photoconductor 1, and a control unit 200 that can control the photoconductor drive unit M1, the application unit PS1, and the development drive unit M2 to perform an image formation operation in which a developer image is formed on the photoconductor 1 according to arbitrary image information, and a non-image formation operation in which a developer image is not formed on the photoconductor 1. In this embodiment, during the non-image formation during a predetermined period (initial period of use) until the usage amount of the photoconductor 1 from a new state indicated by the usage amount information reaches a predetermined usage amount, the control unit 200 executes a predetermined operation (photoconductor drum aging mode) for a predetermined time T in which an AC bias is applied to the charging member 2 to rotate the photoconductor 1 while generating a discharge between the charging member 2 and the photoconductor 1, and during the predetermined operation, the rotation of the developing member 41 is stopped and the voltage value of the AC bias applied to the charging member 2 is controlled to be larger than the voltage value of the AC bias applied to the charging member 2 during the first image formation after the predetermined operation. Furthermore, in the case where the photoconductor 1 is an amorphous silicon photoconductor, the control unit 200 may perform a predetermined operation (photoconductor drum aging mode) for a predetermined time T during the non-image formation during a predetermined period (initial period of use) until the usage amount of the photoconductor 1 from a new state indicated by the usage amount information reaches a predetermined usage amount, in which an AC bias is applied to the charging member 2 to rotate the photoconductor 1 while generating a discharge between the charging member 2 and the photoconductor 1, and control the voltage value of the AC bias applied to the charging member 2 during the predetermined operation to be larger than the voltage value of the AC bias applied to the charging member 2 during the first image formation after the predetermined operation.

[0121] In addition, in this embodiment, the control unit 200 controls the value of the discharge current flowing between the charging member 2 and the photoconductor 1 in the predetermined operation to be at least 1.5 times the value of the discharge current flowing between the charging member 2 and the photoconductor 1 during the first image formation after the predetermined operation. The control unit 200 may also control the voltage value of the AC bias applied to the charging member 2 in the predetermined operation to be at least 50 V higher than the voltage value of the AC bias applied to the charging member 2 during the first image formation after the predetermined operation. In this embodiment, the control unit 200 controls to execute the predetermined operation before starting the operation during the first image formation after the acquisition unit N acquires the usage amount information indicating that the photoconductor 1 is new.

[0122] As described above, in the photosensitive drum aging mode, the frictional force between the photosensitive drum 1 and the cleaning blade 61 can be increased by generating a discharge between the charging roller 2 and the photosensitive drum 1. This makes it possible to suppress the slipping of toner and external additives during image formation in the initial stage of use of the photosensitive drum 1 after the photosensitive drum aging mode is executed, and suppresses image defects such as vertical stripes. In this embodiment, the target discharge current Itarget2 (i.e., charging AC voltage Vac2) during the photosensitive drum aging mode is set to be larger than the target discharge current Itarget1 (i.e., charging AC voltage Vac1) during image formation (normal image formation). This effectively increases the frictional force between the photosensitive drum 1 and the cleaning blade 61, and the time required for the photosensitive drum aging mode can be sufficiently shortened. In addition, when the photosensitive drum 1 is an organic photoconductor, in order to effectively increase the frictional force between the photosensitive drum 1 and the cleaning blade 61 in a sufficiently short time, the rotation of the developing sleeve 41 is stopped in the photosensitive drum aging mode. However, when the photosensitive drum 1 is an amorphous silicon photosensitive body, even if the developing sleeve 41 is rotated in the photosensitive drum aging mode, the frictional force between the photosensitive drum 1 and the cleaning blade 61 can be effectively increased in a sufficiently short time.

[0123] [Embodiment 2] Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the image forming apparatus of embodiment 1. Therefore, in the image forming apparatus of this embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus of embodiment 1 are given the same reference numerals as those of embodiment 1, and detailed explanations are omitted.

[0124] <Outline of this embodiment> As described in the first embodiment, the time of the photosensitive drum aging mode required to suppress the passing of toner and external additives during the initial use of the photosensitive drum 1 differs depending on the surface roughness Ra of the photosensitive drum 1 and the contact pressure of the cleaning blade 61. Therefore, in the configuration of the first embodiment, in order to prevent the passing of toner and external additives during the initial use of the photosensitive drum 1 even if there is manufacturing variation, the execution time T is set in accordance with the time of the photosensitive drum aging mode required when the surface roughness Ra of the photosensitive drum 1 is a maximum of 0.010 μm and the contact pressure of the cleaning blade 61 is a minimum of 0.0002 N / mm.

[0125] Therefore, in the configuration of embodiment 1, depending on the surface roughness Ra of the photosensitive drum 1 installed in the image forming apparatus 100 and the contact pressure of the cleaning blade 61 installed in the image forming apparatus 100, an execution time T longer than necessary is set.

[0126] Therefore, the photosensitive drum aging mode of this embodiment sets a more appropriate execution time T depending on the surface roughness Ra of the photosensitive drum 1 installed in the image forming device 100 and the contact pressure of the cleaning blade 61 installed in the image forming device 100.

[0127] <Control configuration> FIG. 11 is a block diagram for explaining the control configuration of the image forming apparatus 100 in this embodiment.

[0128] The control configuration in this embodiment shown in Fig. 11 is similar to the control configuration in the first embodiment shown in Fig. 3, but in this embodiment, a photosensitive drum driving torque detection circuit 402 as a torque detection means is further connected to the control unit 200. The photosensitive drum driving torque detection circuit 402 is configured to detect the driving torque A of the photosensitive drum driving motor M1 when the photosensitive drum 1 is driven by the photosensitive drum driving motor M1. The photosensitive drum driving torque detection circuit 402 inputs a signal (information) indicating the detection result of the driving torque A of the photosensitive drum driving motor M1 to the control unit 200.

[0129] The CPU 201 of the control unit 200 stores information indicating the driving torque (photosensitive drum detected torque) A detected by the photosensitive drum driving torque detection circuit 402 in the memory (RAM) 202. Then, the CPU 201 is configured to be able to control the photosensitive drum aging mode based on the data of this driving torque A, as will be described in detail later.

[0130] In this embodiment, the photosensitive drum driving torque detection circuit 402 detects the output current value (driving current value) of the photosensitive drum driving motor M1, and detects the driving torque A based on the relationship between the output current value and the driving torque A that is obtained in advance. Then, the photosensitive drum driving torque detection circuit 402 inputs a signal indicating the detection result of the driving torque A to the control unit 200. Note that the CPU 201 may be configured to obtain the driving torque A from the signal indicating the detection result of the output current value of the photosensitive drum driving motor M1 input from the photosensitive drum driving torque detection circuit 402. Note that, as the torque detection means, any available means, such as a publicly known one, can be used. Also, the torque detection means may be any means that detects an index value that correlates with the driving torque of the photosensitive drum driving unit, and for example, a current value or a voltage value (such as the output current value of the photosensitive drum driving unit) can be used for control as a substitute value for the driving torque of the photosensitive drum driving unit.

[0131] In this embodiment, before the cleaning device 6 is installed in the image forming apparatus 100, the contact pressure of the cleaning blade 61 is measured in advance, and information indicating the contact pressure is stored in the memory (ROM or non-volatile memory) 202 of the control unit 200. As a means for measuring the contact pressure of the cleaning blade 61, any available means, such as a publicly known means, can be used.

[0132] <Photosensitive drum aging mode> In this embodiment, a more appropriate execution time T is set according to the surface roughness Ra of the photosensitive drum 1 installed in the image forming apparatus 100 and the contact pressure of the cleaning blade 61 installed in the image forming apparatus 100. To this end, in this embodiment, information on the contact pressure of the cleaning blade 61 during execution of the photosensitive drum aging mode is acquired. In this embodiment, the driving torque A of the photosensitive drum driving motor M1 detected by the photosensitive drum driving torque detection circuit 402 is used as a substitute value for the relevant contact pressure. Then, in this embodiment, the execution time T is determined based on the driving torque A.

[0133] Other points of this embodiment are similar to those of the first embodiment, particularly the configuration of the first experimental example. That is, an organic photoconductor is used as the photosensitive drum 1, and the photosensitive drum aging mode is executed from when the photosensitive drum 1 is new (unused) until the first image output is performed. In addition, in the photosensitive drum aging mode, a charging AC bias is applied to the charging roller while the photosensitive drum 1 is rotated with the rotation of the developing sleeve 41 stopped, to generate a discharge between the charging roller 2 and the photosensitive drum 1. In addition, the target discharge current Itarget2 in the photosensitive drum aging mode is set to 1.5 times the target current Itarget1 during image formation. As a result, the charging AC voltage Vac2 in the photosensitive drum aging mode is 1800V, which is higher than the charging AC voltage Vac1 of 1500V during image formation.

[0134] Table 7 shows the relationship between the execution time T when the photosensitive drum aging mode is executed under the above conditions, the driving torque A reached in the photosensitive drum aging mode for the execution time T, and the occurrence state of image defects due to the slip-through of toner or external additives in the early stages of use of the photosensitive drum 1 when the driving torque A is reached. The evaluation method and evaluation criteria for image defects are the same as those in the experimental example described in the first embodiment.

[0135] [Table 7]

[0136] As shown in Table 7, it was found that, regardless of the surface roughness Ra of the photosensitive drum 1, when the contact pressure of the cleaning blade 61 is 0.0002 N / mm, it is possible to suppress image defects caused by the passage of toner and external additives during the initial period of use of the photosensitive drum 1 when the driving torque A is 0.079 N m or more. Similarly, it was found that, regardless of the surface roughness Ra of the photosensitive drum 1, when the contact pressure of the cleaning blade 61 is 0.0005 N / mm, it is possible to suppress image defects caused by the passage of toner and external additives during the initial period of use of the photosensitive drum 1 when the driving torque A is 0.168 N m or more.

[0137] Therefore, in this embodiment, a driving torque target value Atarget is set based on the contact pressure of the cleaning blade 61, and the photosensitive drum aging mode is executed until the driving torque target value Atarget is reached. As a result, even if there is manufacturing variation in the surface roughness Ra of the photosensitive drum 1 and the contact pressure of the cleaning blade 61, it is possible to suppress image defects due to the slip-through of toner and external additives in the initial period of use of the photosensitive drum 1 while suppressing the occurrence of excess or deficiency in the execution time T. In this embodiment, the relationship between the contact pressure P of the cleaning blade 61 and the driving torque target value Atarget is expressed by the following formula (1). That is, in this embodiment, the driving torque target value Atarget is determined by the following formula (1) using the contact pressure P of the cleaning blade 61 that has been measured in advance. Atarget=298×P+0.0212 ···(1)

[0138] As can be seen from Table 7, in this embodiment, when the contact pressure of the cleaning blade 61 is 0.0002 N / mm, the execution time T is set to 150 sec when the surface roughness Ra of the photosensitive drum 1 is 0.02 μm, and when the surface roughness Ra of the photosensitive drum 1 is 0.10 μm, the execution time T is set to 210 sec. Also, when the contact pressure of the cleaning blade 61 is 0.0005 N / mm, the execution time T is set to 120 sec when the surface roughness Ra of the photosensitive drum 1 is 0.02 μm, and when the surface roughness Ra of the photosensitive drum 1 is 0.10 μm, the execution time T is set to 180 sec.

[0139] FIG. 12 is a flow chart showing an outline of the control procedure of the pre-multiple rotation process in this embodiment.

[0140] When the image forming apparatus 100 is powered on or the image forming apparatus 100 is restored from a sleep state (S201), the CPU 201 of the control unit 200 controls the image forming apparatus 100 to start a pre-rotation process (S202). When starting the pre-rotation process, the CPU 201 judges whether the photosensitive drum 1 is new by judging whether the count value (accumulated number of images formed) of the photosensitive drum usage counter N is 0 or not (S203). When the CPU 201 judges in S203 that the count value of the photosensitive drum usage counter N is 0, that is, that the photosensitive drum 1 is new ("Yes"), it reads the contact pressure P of the cleaning blade 61 stored in the memory 202 (S204). Then, the CPU 201 determines the driving torque target value Atarget by the above-mentioned formula (1) (S205). Next, the CPU 201 executes charging AC voltage determination control to determine a target AC voltage Vac1 during image formation and a target AC voltage Vac2 during the photosensitive drum aging mode (S206). After that, the CPU 201 starts the photosensitive drum aging mode (S207). Then, the CPU 201 judges (monitors) whether the driving torque A of the photosensitive drum driving motor M1 detected by the photosensitive drum driving torque detection circuit 402 during execution of the photosensitive drum aging mode becomes equal to or greater than the driving torque target value Atarget (S208). When the CPU 201 judges in S208 that the driving torque A becomes equal to or greater than the driving torque target value Atarget ("Yes"), it ends the photosensitive drum aging mode (S210). After ending the photosensitive drum aging mode, the CPU 201 executes other operations in the pre-multiple rotation process (S211) and ends the pre-multiple rotation process. Furthermore, when the CPU 201 determines in S208 that the driving torque A is not equal to or greater than the driving torque target value Atarget ("No"), it continues the photosensitive drum aging mode until the driving torque A becomes equal to or greater than the driving torque target value Atarget (S209, S208). After that, it executes other predetermined operations in the pre-multiple rotation process (S211) and ends the pre-multiple rotation process.Furthermore, if the CPU 201 determines in S203 that the photosensitive drum usage counter N is not 0, i.e., that the photosensitive drum 1 is not new ("No"), it executes the normal pre-multiple rotation process without executing the photosensitive drum aging mode (S211) and ends the pre-multiple rotation process.

[0141] In the procedure shown in FIG. 12, the photosensitive drum aging mode is executed in the pre-rotation process, but the photosensitive drum aging mode may also be executed in the pre-rotation process before the image forming apparatus 100 starts image formation after receiving job information.

[0142] In the above description of this embodiment, the rotation of the developing sleeve 41 is stopped during the execution of the photosensitive drum aging mode, but the developing sleeve 41 may be rotated during the execution of the photosensitive drum aging mode. In this embodiment, when the surface roughness Ra of the photosensitive drum 1 and the contact pressure P of the cleaning blade 61 are within the range of manufacturing variations, the execution time T can be shortened in many cases compared to the first embodiment. Therefore, in this embodiment, even if the developing sleeve 41 is rotated during the execution of the photosensitive drum aging mode in many cases, image defects due to the slippage of toner or external additives at the beginning of use of the photosensitive drum 1 can be suppressed with a sufficiently short execution time T, regardless of whether an organic photoconductor or an amorphous silicon photoconductor is used as the photosensitive drum 1. However, when the developing sleeve 41 is rotated during the execution of the photosensitive drum aging mode, the time required for the driving torque A to reach the driving torque target value Atarget (i.e., the execution time T) becomes longer than when the rotation is stopped. For the same reason, in this embodiment, even if the target discharge current Itarget2 in the photosensitive drum aging mode (i.e., charging AC voltage Vac2) is not made larger than the target discharge current Itaget1 during image formation (i.e., charging AC voltage Vac1) (or even if the degree of increase is made smaller than in embodiment 1), it may be possible to suppress image defects due to the slip-through of toner or external additives in the initial stage of use of the photosensitive drum 1 with a sufficiently short execution time T. However, in that case, the time it takes for the driving torque A to reach the driving torque target value Atarget (i.e., execution time T) will be longer than when the target discharge current (charging AC voltage) is set as in embodiment 1.

[0143] In this embodiment, an upper limit may be set on the execution time T. This makes it possible to prevent the execution time T from becoming too long. In addition, an upper limit may be set on the execution time T of one photosensitive drum aging mode, and the photosensitive drum aging mode may be executed multiple times. For example, if the driving torque does not reach the driving torque target value in one photosensitive drum aging mode, the photosensitive drum aging mode may be executed again during a predetermined period in the initial period of use, while waiting for a job, or the like.

[0144] Furthermore, as in this embodiment, the execution time T can be set more accurately and without excess or deficiency by setting the driving torque target value Atarget based on the contact pressure of each cleaning blade 61. However, a predetermined driving torque target value Atarget based on the contact pressure (average value, minimum value, etc.) of a predetermined cleaning blade 61 may also be used.

[0145] Table 8 compares the execution time T set in the configuration of Experimental Example 1 of Embodiment 1 and the configuration of this embodiment, and the evaluation results of image defects caused by the passage of toner and external additives during the initial use of the photosensitive drum 1 when the photosensitive drum aging mode is executed for that execution time T.

[0146] [Table 8]

[0147] As shown in Table 8, in this embodiment, when the surface roughness Ra of the photosensitive drum 1 is 0.02 μm, and when the surface roughness Ra of the photosensitive drum 1 is 0.10 μm and the contact pressure P of the cleaning blade 61 is 0.0005 N / mm, the execution time T can be further shortened compared to Experimental Example 1 of Embodiment 1. Therefore, in this embodiment, in many cases, the execution time T can be shortened compared to Experimental Example 1 of Embodiment 1 (execution time T = 210 sec). Similarly, when an amorphous silicon photosensitive body is used as the photosensitive drum 1 in this embodiment, the execution time T can be shortened compared to Experimental Example 3 of Embodiment 1 in many cases.

[0148] Thus, in this embodiment, the image forming apparatus 100 has a detection means (photosensitive drum driving torque detection circuit) 402 that detects an index value correlated with the driving torque of the photosensitive drum driving unit M1, and the control unit 200 executes a predetermined operation (photosensitive drum aging mode) in which an AC bias is applied to the charging member 2 to rotate the photosensitive drum 1 while generating a discharge between the charging member 2 and the photosensitive drum 1 during non-image formation during a predetermined period (initial period) until the usage amount of the photosensitive drum 1 from a new state indicated by the usage amount information (count value of the photosensitive drum usage counter) reaches a predetermined usage amount, and controls the predetermined operation to end when the driving torque indicated by the detection result by the detection means 402 during the execution of the predetermined operation becomes equal to or greater than a threshold value. In this embodiment, the image forming apparatus 100 has a storage unit 202 that stores contact pressure information regarding the contact pressure of the cleaning member 61 against the photosensitive drum 1 measured in advance, and the control unit 100 changes the threshold value based on the contact pressure information. In this embodiment, the control unit 200 changes the threshold value so that the threshold value is larger when the contact pressure indicated by the contact pressure information is a second contact pressure that is larger than the first contact pressure than when the contact pressure indicated by the contact pressure information is a first contact pressure. Also, in this embodiment, the control unit 200 controls the voltage value of the AC bias applied to the charging member 2 in the predetermined operation to be larger than the voltage value of the AC bias applied to the charging member 2 during the first image formation after the predetermined operation. Also, in this embodiment, the image forming apparatus 100 has a development drive unit M2 that is controlled by the control unit 200 and rotates the development member 41, and the control unit 200 controls the development member 41 to stop rotating in the predetermined operation.

[0149] [others] Although the present invention has been described above with reference to specific examples, the present invention is not limited to the above examples.

[0150] In the above-described embodiment, the number of images formed is used as an index value correlating with the usage amount of the photosensitive drum, but the present invention is not limited to this, and the number of rotations (travel distance) of the photosensitive drum, rotation time, charging processing time, etc. may also be used.

[0151] In the above embodiment, the case where unevenness is formed on the surface of the photosensitive drum by a roughening treatment such as a polishing treatment has been described as an example, but the present invention is not limited to such an embodiment. When the friction force between the photosensitive drum and the cleaning blade is too low at the beginning of use of the photosensitive drum, causing toner and external additives to slip through, the present invention can also be applied even when the surface of the photosensitive drum has unevenness due to manufacturing reasons, for example.

[0152] In the above embodiment, the charging AC voltage is increased by increasing the target discharge current of the charging AC bias as a means for increasing the discharge current value between the charging roller and the photosensitive drum in the photosensitive drum aging mode compared to that during image formation. In contrast, the frequency of the charging AC bias may be increased as a means for increasing the discharge current value between the charging roller and the photosensitive drum in the photosensitive drum aging mode compared to that during image formation. The frequency of the charging AC bias in the photosensitive drum aging mode can be appropriately set so that the discharge current value in the photosensitive drum aging mode is similar to that in the above embodiment, for example, to 1.5 times the frequency of the charging AC bias during image formation (normal image formation). In this case, for example, the frequency of the charging AC bias in the photosensitive drum aging mode is preferably 1.5 times or more, more preferably 2 times or more, and typically less than 5 times, the frequency of the charging AC bias during image formation. In other words, the control unit 200 can control the frequency of the AC bias applied to the charging member 2 in a predetermined operation (photosensitive drum aging mode) to be higher than the frequency of the AC bias applied to the charging member 2 during the first image formation after the predetermined operation.

[0153] Furthermore, in the above embodiment, the present invention has been described as being applied to a color image forming apparatus, but the present invention can also be applied to, for example, a monochrome image forming apparatus having only one photosensitive drum.

[0154] The photoconductor is typically a drum-type photoconductor drum, but may be a belt-type photoconductor belt. [Explanation of symbols]

[0155] 1 Photosensitive drum 2. Charge roller 4. Developing device 6 Cleaning device 41 Developing sleeve 61 Cleaning blade 100 Image forming device 200 Control section

Claims

1. A rotatable photoreceptor; A photoconductor driving unit that rotates the photoconductor; a charging member that contacts the surface of the photoconductor and charges the surface of the photoconductor; an application unit that applies an AC bias to the charging member; a rotatable developing member that supplies a developer to a surface of the photoreceptor to form a developer image on the surface of the photoreceptor; A developing drive unit that rotates the developing member; a cleaning member that comes into contact with the surface of the photoreceptor and cleans the surface of the photoreceptor; an acquisition unit that acquires usage information regarding a usage amount of the photoconductor; a control unit capable of controlling the photoconductor driving unit, the application unit, and the development driving unit so as to execute an operation during image formation in which the developer image is formed on the photoconductor in accordance with arbitrary image information, and an operation during non-image formation in which the developer image is not formed on the photoconductor; In an image forming apparatus having the control unit executes a predetermined operation for a predetermined time during non-image formation in a predetermined period until the usage amount of the photoconductor from a new state indicated by the usage amount information reaches a predetermined usage amount, in which an AC bias is applied to the charging member to rotate the photoconductor while generating a discharge between the charging member and the photoconductor, and during the predetermined operation, stops the rotation of the developing member and controls the voltage value of the AC bias applied to the charging member to be greater than the voltage value of the AC bias applied to the charging member during the first image formation after the predetermined operation.

2. A rotatable photoreceptor; A photoconductor driving unit that rotates the photoconductor; a charging member that contacts the surface of the photoconductor and charges the surface of the photoconductor; an application unit that applies an AC bias to the charging member; a rotatable developing member that supplies a developer to a surface of the photoreceptor to form a developer image on the surface of the photoreceptor; a cleaning member that comes into contact with the surface of the photoreceptor and cleans the surface of the photoreceptor; an acquisition unit that acquires usage information regarding a usage amount of the photoconductor; a control unit capable of controlling the photoconductor driving unit and the application unit to execute an image forming operation for forming the developer image on the photoconductor in accordance with arbitrary image information and a non-image forming operation for not forming the developer image on the photoconductor; In an image forming apparatus having the photoreceptor is an amorphous silicon photoreceptor, the control unit executes a predetermined operation for a predetermined time during non-image formation in a predetermined period until the usage amount of the photosensitive member from a new state indicated by the usage amount information reaches a predetermined usage amount, in which an AC bias is applied to the charging member to rotate the photosensitive member while generating a discharge between the charging member and the photosensitive member, and controls a voltage value of the AC bias applied to the charging member during the predetermined operation so that it is greater than a voltage value of the AC bias applied to the charging member during the first image formation after the predetermined operation.

3. A rotatable photoreceptor; A photoconductor driving unit that rotates the photoconductor; a charging member that contacts the surface of the photoconductor and charges the surface of the photoconductor; an application unit that applies an AC bias to the charging member; a rotatable developing member that supplies a developer to a surface of the photoreceptor to form a developer image on the surface of the photoreceptor; A developing drive unit that rotates the developing member; a cleaning member that comes into contact with the surface of the photoreceptor and cleans the surface of the photoreceptor; an acquisition unit that acquires usage information regarding a usage amount of the photoconductor; a control unit capable of controlling the photoconductor driving unit, the application unit, and the development driving unit so as to execute an operation during image formation in which the developer image is formed on the photoconductor in accordance with arbitrary image information, and an operation during non-image formation in which the developer image is not formed on the photoconductor; In an image forming apparatus having an image forming apparatus characterized in that, during non-image formation during a predetermined period until the usage amount of the photoconductor from a new state indicated by the usage amount information reaches a predetermined usage amount, the control unit executes a predetermined operation for a predetermined time, in which an AC bias is applied to the charging member to rotate the photoconductor while generating a discharge between the charging member and the photoconductor, and during the predetermined operation, stops the rotation of the developing member and controls the frequency of the AC bias applied to the charging member to be higher than the frequency of the AC bias applied to the charging member during the first image formation after the predetermined operation.

4. A rotatable photoreceptor; A photoconductor driving unit that rotates the photoconductor; a charging member that contacts the surface of the photoconductor and charges the surface of the photoconductor; an application unit that applies an AC bias to the charging member; a rotatable developing member that supplies a developer to a surface of the photoreceptor to form a developer image on the surface of the photoreceptor; a cleaning member that comes into contact with the surface of the photoreceptor and cleans the surface of the photoreceptor; an acquisition unit that acquires usage information regarding a usage amount of the photoconductor; a control unit capable of controlling the photoconductor driving unit and the application unit to execute an image forming operation for forming the developer image on the photoconductor in accordance with arbitrary image information and a non-image forming operation for not forming the developer image on the photoconductor; In an image forming apparatus having the photoreceptor is an amorphous silicon photoreceptor, the control unit executes a predetermined operation for a predetermined time during non-image formation in a predetermined period until the usage amount of the photosensitive member from a new state indicated by the usage amount information reaches a predetermined usage amount, in which an AC bias is applied to the charging member to rotate the photosensitive member while generating a discharge between the charging member and the photosensitive member, and controls a frequency of the AC bias applied to the charging member during the predetermined operation to be higher than a frequency of the AC bias applied to the charging member during the first image formation after the predetermined operation.

5. A rotatable photoreceptor; A photoconductor driving unit that rotates the photoconductor; a charging member that contacts the surface of the photoconductor and charges the surface of the photoconductor; an application unit that applies an AC bias to the charging member; a rotatable developing member that supplies a developer to a surface of the photoreceptor to form a developer image on the surface of the photoreceptor; a cleaning member that comes into contact with the surface of the photoreceptor and cleans the surface of the photoreceptor; an acquisition unit that acquires usage information regarding a usage amount of the photoconductor; a control unit capable of controlling the photoconductor driving unit and the application unit to execute an image forming operation for forming the developer image on the photoconductor in accordance with arbitrary image information and a non-image forming operation for not forming the developer image on the photoconductor; In an image forming apparatus having a detection means for detecting an index value correlated with a driving torque of the photoconductor driving unit; the control unit, during non-image formation during a predetermined period until the usage amount of the photosensitive member from a new state indicated by the usage amount information reaches a predetermined usage amount, performs a predetermined operation of applying an AC bias to the charging member to rotate the photosensitive member while generating a discharge between the charging member and the photosensitive member, and controls the predetermined operation to be terminated when the driving torque indicated by the detection result by the detection means becomes equal to or greater than a threshold value during the execution of the predetermined operation.

6. a storage unit that stores contact pressure information regarding a contact pressure of the cleaning member against the photoconductor that is measured in advance; The image forming apparatus according to claim 5 , wherein the control unit changes the threshold value based on the contact pressure information.

7. The image forming apparatus according to claim 6, characterized in that the control unit changes the threshold value so that the threshold value is larger when the contact pressure indicated by the contact pressure information is a second contact pressure that is larger than the first contact pressure than when the contact pressure indicated by the contact pressure information is a first contact pressure.

8. 7. The image forming apparatus according to claim 6, wherein the control unit controls the voltage value of the AC bias applied to the charging member during the specified operation so as to be greater than the voltage value of the AC bias applied to the charging member during the first image formation after the specified operation.

9. 9. The image forming apparatus according to claim 8, wherein the control unit controls the voltage value of the AC bias applied to the charging member during the specified operation to be at least 50 V higher than the voltage value of the AC bias applied to the charging member during the first image formation after the specified operation.

10. 7. The image forming apparatus according to claim 6, wherein the control unit controls the frequency of the AC bias applied to the charging member during the specified operation so as to be higher than the frequency of the AC bias applied to the charging member during the first image formation after the specified operation.

11. a developing drive unit that is controlled by the control unit and rotates the developing member; 7. The image forming apparatus according to claim 6, wherein the control section controls the developing member to stop rotating during the predetermined operation.

12. The image forming apparatus according to any one of claims 1 to 11, characterized in that the control unit controls the discharge current value flowing between the charging member and the photosensitive member during the specified operation to be at least 1.5 times the discharge current value flowing between the charging member and the photosensitive member during the first image formation after the specified operation.

13. 3. The image forming apparatus according to claim 1, wherein the control unit controls the voltage value of the AC bias applied to the charging member during the specified operation to be at least 50 V higher than the voltage value of the AC bias applied to the charging member during the first image formation after the specified operation.

14. The image forming apparatus according to any one of claims 1 to 11, characterized in that the control unit controls the predetermined operation to be executed before starting the operation for the first image formation after the usage information indicating that the photosensitive member is new is acquired by the acquisition unit.

Images