JP2006201417A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus in which image deletion is suppressed by increasing the effect of polishing a surface of a photoreceptor drum in continuous image formation and which forms high quality images. <P>SOLUTION: An image forming process in continuous image formation comprises an arrow A in which the surface of the photoreceptor drum 1 is charged by a charging unit 2 for a predetermined time, an arrow B in which an image formed on the photoreceptor drum 1 is transferred onto a sheet 11, and a paper interval C until the subsequent sheet 11 is transported, wherein an arrow D obtained by joining the arrows B and C together becomes output interval per one record. In the paper interval C, a charge stop time T1 in which the charging unit 2 is turned off and a pre-charge time T2 are set. In the charge stop time T1, the surface of the photoreceptor drum 1 is polished by a rubbing roller 6 in a state where the surface of the photoreceptor drum 1 is not charged, accordingly generation of ionic products due to discharge of the charging unit 2 is suppressed and effective polishing is made possible. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus using a photosensitive drum, and in particular, a method for polishing a surface of a photosensitive drum capable of suppressing image flow when an amorphous silicon (hereinafter referred to as a-Si) photosensitive drum is used. It is about.

  In recent years, an a-Si photosensitive drum has been widely used as an image carrier of an image forming apparatus using an electrophotographic process. The a-Si photoconductor drum has high hardness and excellent durability, and its characteristics as a photoconductor are hardly deteriorated even after long-term use. In addition, the image carrier is excellent in environmental safety.

  In an image forming apparatus using such an a-Si photosensitive drum, it is known that image flow tends to occur due to its characteristics. That is, when charging is performed using the charging unit, ozone is generated by discharging of the charging unit. The components in the air are decomposed by the ozone, and ion products such as NOx and SOx are generated. Since the adhesion force of the ion product to the photoconductor is very strong, it is difficult to remove it by a general-purpose cleaning system used in an image forming apparatus using an a-Si photoconductor drum. As a result, it adheres to the photosensitive drum and enters into the roughness structure of about 0.1 μm on the surface of the photosensitive drum, so that it cannot be removed by a cleaning system used in a general-purpose machine. The resistance of the surface of the photosensitive drum is reduced by taking in moisture therein. As a result, the lateral flow of the potential occurs at the edge portion of the electrostatic latent image formed on the surface of the photosensitive drum, and as a result, the image flow may occur.

  Conventionally, by putting a heater in the photoconductor drum, energy is given to release the moisture taken in by the ion products, and the resistance decrease on the surface of the photoconductor drum in a high-humidity environment is suppressed. ing. However, in such an apparatus, the number of parts for configuring the heater is increased, a heater mounting space is required, and power consumption is increased, leading to an increase in size and cost of the apparatus. In addition, it takes time for the surface of the photoreceptor to be heated to a predetermined temperature, which requires a long processing time and is not preferable from the viewpoint of safety.

  In view of this, a method for reducing the image flow by suppressing a decrease in resistance on the surface of the photosensitive drum with a simple configuration has been proposed. In Patent Documents 1 and 2, as shown in FIG. 7, development in which an abrasive is mixed is proposed. The ozone product is removed without using a heater or the like by executing a refresh mode at a predetermined timing to polish the photosensitive member by the interaction between the agent (hereinafter referred to as toner) and the polishing means (sliding roller and cleaning blade). A method is disclosed.

  In FIG. 7, the image forming unit 15 includes a charging unit 2, an exposure unit 3, a developing unit 4, a transfer roller 5, a rubbing roller 6, and a cleaning blade along the rotation direction (arrow A direction) of the photosensitive drum 1. 9. A static eliminating device 10 is provided. The photosensitive drum 1 is formed, for example, by laminating a photosensitive layer made of a-Si on an aluminum drum, and the charging unit 2 charges the surface. Then, an electrostatic latent image in which charging is attenuated is formed on the surface that has received the laser beam from the exposure unit 3. The charging unit 2 charges the surface of the photosensitive drum 1 by discharging (for example, corona discharge). For example, the charging unit 2 is discharged by applying a high voltage using a thin wire or the like as an electrode. .

  The exposure unit 3 irradiates the photosensitive drum 1 with a light beam (for example, a laser beam) based on the image data to form an electrostatic latent image on the surface of the photosensitive drum 1. The developing unit 4 includes a developing sleeve 4a disposed opposite to the photosensitive drum 1, and the toner accommodated in the developing unit 4a is attached to the electrostatic latent image on the photosensitive drum 1 by the developing sleeve 4a to form a toner image. Is.

  As is well known, an electrostatic latent image is recorded by the exposure unit 3 on the photosensitive drum 1 uniformly charged by the charging unit 2 after static elimination by the static eliminator 10, and the electrostatic latent image is developed by reversal development. In step 4, the toner image is visualized and the toner image is transferred onto the sheet 11 by the transfer roller 5. Untransferred toner that has not been transferred by the transfer roller 5 is removed from the surface of the photosensitive drum 1 by the rubbing roller 6 and the cleaning blade 9 as residual toner, and the removed residual toner is illustrated by a toner recovery device such as a recovery screw 8. Not transported to waste bottle.

  A cleaning device 14 includes a rubbing roller 6 which is a polishing system for polishing the photosensitive drum 1 and a cleaning blade 9, and has a spring 7 for pressing the rubbing roller 6 to the surface of the photoconductor. . The rubbing roller 6 has a configuration in which the periphery is covered with foamed urethane rubber with the shaft as the center, and is rotated at a predetermined linear speed difference with respect to the peripheral speed of the photosensitive drum 1 by a motor (not shown). In addition, as the abrasive toner, titanium oxide, strontium titanate, alumina, or the like as an abrasive is embedded in the toner particle surface and held so as to partially protrude on the surface, or the abrasive is electrostatically applied to the toner surface. What is attached to is used.

  This technology is an image forming apparatus having a configuration in which the surface roughness of an a-Si photosensitive drum is polished so as to be Rz500 angstroms or less. By polishing to this surface roughness, ion generation as described above is performed. Even if an object adheres to the surface of the photosensitive drum, it can be removed. However, even if the methods of Patent Documents 1 and 2 are used, ion products cannot be sufficiently removed only by polishing the surface of the photosensitive drum 1 with the rubbing roller 6 especially at high temperatures and high humidity. It has been difficult to completely prevent image defects.

  FIG. 8 is a timing chart showing the operation control of the charging unit during continuous image formation in the conventional image forming apparatus. With reference to FIG. 7, an image forming process in the case where continuous image formation is instructed by the user will be described with reference to FIG. 8. First, a main motor (not shown) that drives the photosensitive drum 1 and the transfer roller 5 and the static eliminator 10 are turned on, and then charging of the surface of the photosensitive drum 1 is started by the charging unit 2. The initial charging by the charging unit 2 is continuously performed for a predetermined time (arrow A in FIG. 8). After the surface of the photosensitive drum 1 is uniformly charged, the electrostatic latent image is formed and developed by the exposure unit 3. The toner images are sequentially formed by the unit 4.

  Thereafter, the image formed on the photosensitive drum 1 is transferred onto the sheet 11 (arrow B in FIG. 8). A predetermined interval (between sheets) is secured until the next sheet 11 is conveyed (arrow C in FIG. 8), and the residual toner and residual charge on the photosensitive drum 1 are removed by the cleaning device 14 and the sublimation device 10. The toner image is removed and a new toner image is formed. That is, the time when the arrows B and C are combined is an output interval per recording sheet (arrow D in FIG. 8), and thereafter, the above process is repeated until a preset number of images are formed.

  On the other hand, polishing of the surface of the photosensitive drum by the rubbing roller 6 is continuously performed during image formation. However, as described above, the ion product is easily attached due to the charging of the photosensitive drum 1, and thus the photosensitive drum. In order to polish the surface effectively, it is desirable to keep the charging unit 2 in the OFF state when charging is unnecessary. When the charging unit 2 is turned off and then turned on again, before the next image is formed in order to prevent uneven charging on the surface of the photosensitive drum 1 due to the influence of the residual charge that could not be removed by the static eliminator 10. Therefore, it is necessary to ensure a so-called pre-charging time, in which charging is performed continuously for a predetermined time.

However, since the output interval D is usually shortened to increase the number of processed sheets per time, the paper interval C is also set as small as possible. For this reason, when the charging unit 2 is turned off, a sufficient pre-charging time cannot be secured, and it is necessary to keep the charging unit 2 in the ON state even during the paper interval C. Further, Patent Document 3 discloses a method of concentrating and polishing a portion of the surface of the photosensitive drum facing the charging unit when the power is turned on or when returning from the sleep mode. However, although the method of Patent Document 3 is effective in preventing image flow when the apparatus is started up, it has not been able to sufficiently suppress image flow when image formation is continuously performed.
Japanese Patent Laid-Open No. 11-3014 JP-A-11-133462 JP 2003-307986 A

  In view of the above problems, an object of the present invention is to provide an image forming apparatus that suppresses image flow and forms a high-quality image by enhancing the polishing effect on the surface of the photosensitive drum during continuous image formation. .

  To achieve the above object, the present invention provides a photosensitive drum, a charging unit for uniformly charging the surface of the photosensitive drum, an exposure unit for writing an electrostatic latent image on the surface of the photosensitive drum, and the photosensitive member. A developing unit that forms a toner image corresponding to the electrostatic latent image by attaching a toner containing an abrasive to the drum surface; and a transfer unit that transfers the toner image formed by the developing unit onto a recording medium. In an image forming apparatus including an image forming unit and a polishing unit that is pressed against the photoconductor drum with a predetermined pressure and polishes the surface of the photoconductor drum, the charging is performed after each image formation during continuous image formation is completed. A charging stop time for stopping charging by the unit is provided, and after the charging stop time has elapsed, a pre-charging time for performing pre-charging by the charging unit until the start of the next image formation, It is characterized in that to secure the photosensitive drum 1 rotation of even without.

  According to the present invention, in the image forming apparatus configured as described above, the image forming speed in the image forming unit is a speed at which the charging stop time and the pre-charging time can be ensured without reducing the number of processed sheets per predetermined time. It is characterized by.

  According to the present invention, in the image forming apparatus configured as described above, the photosensitive drum is made of amorphous silicon.

  According to the first configuration of the present invention, the surface of the photosensitive drum is not charged in the charging stop time, and polishing by the polishing unit is performed, thereby suppressing the generation of ion products due to the discharge of the charging unit. Thus, effective polishing becomes possible. Further, by providing a pre-charging time for at least one rotation of the photosensitive drum, there is no possibility of uneven charging on the surface of the photosensitive drum due to the influence of the residual charge.

  Further, according to the second configuration of the present invention, in the image forming apparatus having the first configuration, the image forming speed can secure the charging stop time and the pre-charging time without reducing the number of processed sheets per predetermined time. Therefore, effective polishing can be performed without reducing the image forming efficiency as a whole.

  According to the third configuration of the present invention, in the image forming apparatus having the first or second configuration, the life of the photoconductor is extended by using the a-Si photoconductor drum as the photoconductor drum, Contributes to higher image quality and lower running costs for image forming devices.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing the configuration of the image forming apparatus of the present invention. Portions common to FIG. 7 of the conventional example are denoted by the same reference numerals and description thereof is omitted. In FIG. 1, reference numeral 100 denotes an image forming apparatus, and here, a digital multifunction peripheral is shown as an example.

  In the image forming apparatus 100, when performing a copying operation, an electrostatic latent image based on the original image data read by the image reading unit 20 is formed in the image forming unit 15 in the multifunction peripheral body, and the developing unit 4 performs electrostatic discharge. Toner is attached to the latent image to form a toner image. The toner is supplied from the toner container 21 to the developing unit 4. In such an image forming apparatus 100, the image forming process for the photosensitive drum 1 is executed while rotating the photosensitive drum 1 clockwise (in the direction of arrow A) in FIG. The image forming process is the same as that of the conventional example shown in FIG.

  The sheet 11 is conveyed from the sheet feeding mechanism 22 to the image forming unit 15 via the sheet conveying path 23 and the resist roller pair 24 toward the photosensitive drum 1 on which the toner image is formed as described above. In the portion 15, the toner image on the surface of the photosensitive drum 1 is transferred to the sheet 11 by the transfer roller 5 (transfer means). Then, the sheet 11 on which the toner image is transferred is separated from the photosensitive drum 1 and conveyed to a fixing unit 26 having a fixing roller pair 26a to fix the toner image.

  The sheet 11 that has passed through the fixing unit 26 is sent to a paper conveyance path 27 branched in a plurality of directions, and has a plurality of path switching mechanisms 30, 31, and 32 that have a plurality of path switching guides provided at branch points of the paper conveyance path 27. , The transport direction is sorted, and the sheet is discharged to the sheet discharge section of the first discharge tray 29a, the second discharge tray 29b, or the third discharge tray 29c as it is (or after being sent to the sheet transfer path 28 and copied on both sides). The

  Further, a static elimination device 10 (see FIG. 7) for removing residual charges on the surface of the photosensitive drum 1 is provided on the downstream side of the cleaning device 14. Further, the paper feed mechanism 22 is detachably attached to the MFP main body, and includes a plurality of paper feed cassettes 22a and 22b for storing the sheets 11, and a stack bypass (manual feed tray) 22c provided thereabove. These are connected to the image forming unit 15 including the photosensitive drum 1, the developing unit 4 and the like by the paper conveyance path 23. Reference numeral 33 denotes a platen (original presser) that presses and holds an original placed on the image reading unit 20.

  Specifically, the sheet conveyance path 27 is first branched into left and right bifurcations on the downstream side of the fixing roller pair 26a, and one path (a path branched in the right direction in FIG. 1) communicates with the first discharge tray 29a. It is configured as follows. The other path (the path that branches in the left direction in FIG. 1) branches into the upper and lower forks via the conveying roller pair 35, and the other path (the path that branches in the upper direction in FIG. 1) is the second discharge. It is configured to communicate with the tray 29b.

  On the other hand, the other path (the path that branches downward in FIG. 1) is bifurcated immediately below the branch point, and one path passes through the discharge roller pair 36 to the third discharge tray 29c. 11, and the other path is configured to communicate with the sheet conveyance path 28. The sheet conveyance path 28 is a path through which the sheet 11 on which one side of the image is formed is switched back and conveyed, and another one side is formed again by the image forming unit 15 and discharged (double-sided copying).

  FIG. 2 is a block diagram showing the configuration of the image forming apparatus of the present invention. Portions common to those in FIG. 1 are denoted by the same reference numerals. The image forming apparatus 100 includes an image forming unit 15, an image reading unit 20, a paper feeding mechanism 22, a fixing unit 26, a control unit 32, a storage unit 33, an operation panel 34, and the like.

  The image reading unit 20 includes a scanner lamp that illuminates the document during copying, a scanning optical system equipped with a mirror that changes the optical path of reflected light from the document, and a condensing lens that focuses the reflected light from the document to form an image. , And a CCD that converts the imaged image light into an electrical signal. The image signal read by the image reading unit 20 is sent to the control unit 32, and image processing such as gradation processing is appropriately performed to convert the image signal into image data.

  The image forming unit 15 includes a photosensitive drum 1, a charging unit 2, an exposure unit 3, a developing unit 4, and the like. An electrostatic latent image is formed on the photosensitive drum 1 based on the image data converted by the control unit 32. Form. Reference numeral 36 denotes a main motor for rotationally driving the photosensitive drum 1, the transfer roller 5, the fixing roller 26 a in the fixing unit 26, and the control unit 32 transmits a control signal to the main motor 36 to send the photosensitive drum 1. And the rotation and stop of the transfer roller 5 and the fixing roller 26a are controlled. The control unit 32 also controls each part of the image forming apparatus such as the image reading unit 20, the paper feeding mechanism 22, the charging unit 2, the exposure unit 3, and the developing unit 4 according to the set program.

  The storage unit 33 stores a control program for each unit used by the control unit 32. Further, a charging stop time T1 and a pre-charging time T2 (both described later) when continuous printing is set are also stored. The operation panel 34 includes operation keys for the user to set device functions, printing conditions, and the like, and a display unit (none of which is shown) that displays the setting conditions, device states, and the like.

  FIG. 3 is a timing chart showing the operation control of the charging unit during continuous image formation in the image forming apparatus of the present invention. Portions common to FIG. 8 of the conventional example are denoted by the same reference numerals and description thereof is omitted. In the present invention, a charging stop time T1 in which charging of the surface of the photosensitive drum 1 is stopped by turning off the charging unit 2 between the trailing edge C of the previous image and the time when the next image is formed, A pre-charging time T2 is provided.

  As a result, during the charging stop time T1, polishing by the rubbing roller 6 is performed in a state in which the surface of the photosensitive drum 1 is not charged, and the generation of ion products due to the discharge of the charging unit 2 is suppressed. Polishing is possible. In addition, by providing the pre-charging time T2, there is no possibility of uneven charging on the surface of the photosensitive drum 1 due to the influence of the residual charge.

  Since the generation of ion products is reduced as the charging stop time T1 is longer, it is possible to secure the charging stop time T1 by increasing the paper interval C. However, if the paper interval C is increased, the output interval is increased accordingly. Since D is also long, the image forming efficiency is lowered. On the other hand, in order to reliably prevent uneven charging on the drum surface, it is necessary to secure the pre-charging time T2 for at least the time required for the photosensitive drum 1 to make one revolution.

  Therefore, it is preferable to secure the charging stop time T1 and the pre-charging time T2 without increasing the image forming efficiency by increasing the image forming speed (process speed). Further, in order to suppress the generation of the ion product and effectively prevent the image flow phenomenon, the ratio (T1 / D) of the charging stop time T1 to the total polishing time (= D) in the output interval D is 10% or more. It is preferable to set the charging stop time T1 so that

  FIG. 4 is a flowchart showing the operation of the image forming apparatus of the present invention. The image forming process of the image forming apparatus according to the present invention will be described with reference to FIGS. When the user starts image formation, the image reading unit 20 reads the original image and converts it into an image signal (step S1). This image signal is digitized by an AD converter (not shown) and converted into print data (step S2). Next, the surface of the photosensitive drum 1 is initially charged by the charging unit 2 for a predetermined time (arrow A in FIG. 3) (step S3).

  Next, image formation is performed on the photosensitive drum 1 based on the print data converted in step S2 (step S4), and the formed toner image is transferred onto the sheet 11 (arrow B in FIG. 3). . Then, after the image formation is completed, the charging unit 2 is turned off to stop the charging of the photosensitive drum 1 (step S5).

  Thereafter, it is determined whether or not printing is completed (step S6). If printing is continued, after a predetermined charging stop time (T1 in FIG. 3), the charging unit 2 is turned on again to perform photosensitivity. The pre-charging of the surface of the body drum 1 is continued for a predetermined time (T2 in FIG. 3) (step S7). Then, the process returns to step S4 again, and the same processing is repeated until printing is completed (steps S4 to S6). If printing of a predetermined number of pages has been completed in step S6, the processing is terminated as it is.

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning of this invention. For example, in the above embodiment, the case where the rubbing roller 6 and the cleaning blade 9 are used as the polishing means for the surface of the photosensitive drum has been described. However, the present invention is not limited to this, and only the rubbing roller 6 or only the cleaning blade 9 is used. It may be a configuration provided with a fur brush instead of the cleaning blade 9.

  Although the digital multi-function peripheral has been described here as an example, the present invention is a tandem color image forming apparatus, an analog monochrome image forming apparatus, or another image forming apparatus such as a facsimile or printer. Furthermore, the present invention can be applied to an image forming apparatus in which a photosensitive drum other than a-Si is mounted, such as OPC.

  When the charging stop time T1 and the pre-charging time T2 are provided as shown in FIG. 3 using the image forming apparatus as shown in FIG. 1 (the present invention), the charging unit is always turned on as shown in FIG. The apparatus setting in the case (conventional example) is shown in FIGS. Hereinafter, the process control of the present invention will be described in detail with reference to FIGS. 5 and 6 with reference to the timing charts of FIGS. As test machines, Kyocera Mita Co., Ltd. KM-2550 and KM-3530 were used. FIG. 5 shows the device settings of KM-2550, and FIG. 6 shows the device settings of KM-3530.

  As shown in FIG. 5, conventionally, with KM-2550 (A4 paper, 25 sheets / min), the process speed was set to 127 mm / second, so the paper passing time B was 210 (mm) / 127 (mm / second). ) = 1.654 seconds, and the output interval D is 2.4 seconds. Therefore, the sheet interval C is 2.4-1.654 = 0.746 seconds. On the other hand, the photosensitive drum diameter is 30 mm. Therefore, the time required for one rotation of the drum is 30 (mm) × 3.14 / 127 (mm / second) = 0.742 seconds. The pre-charging time T2 could not be secured.

  Therefore, in the present invention, by setting the process speed to 150 mm / second, the sheet passing time B is 210 (mm) / 150 (mm / second) = 1.4 seconds, and the sheet interval C is 2.4-1. 4 = 1.0 seconds. Further, since the time required for one round of the drum is 30 (mm) × 3.14 / 150 (mm / second) = 0.628 seconds, 1.0−0.628 = 0.372 seconds within the paper gap C. Charging stop time T1 and a precharging time T2 of 0.628 seconds, which is one revolution of the drum, can be provided.

  Further, since the surface of the drum surface is continuously polished by the rubbing roller, the ratio of the charging stop time T1 to the total polishing time (T1 / D) is 15.5%, which lowers the image forming efficiency compared to the conventional example. It was possible to secure the time for polishing in the non-charged state without using it.

  Also in FIG. 6, by changing the process speed of KM-3530 (A4 paper, 35 sheets / minute) from the conventional 178 mm / second to 230 mm / second, the paper passing time B is 1.18 seconds to 0.1 mm. 913 seconds, and the paper interval C is from 0.535 seconds to 0.801 seconds. Further, since the time required for one round of the drum is from 0.706 seconds to 0.546 seconds, the charging stop time T1 of 0.801−0.546 = 0.255 seconds within the sheet interval C, and one drum round A pre-charging time T2 of 0.546 seconds can be provided. As a result, as in the case of FIG. 5, the ratio (T1 / D) of the charging stop time T1 to the total polishing time could be about 15%.

  The above embodiment is merely an example of the present invention, and the charging stop time T1 and the pre-charging time T2 can be appropriately set according to the number of processed sheets of the image forming apparatus, the process speed, and the photosensitive drum diameter. it can.

  The present invention includes a photosensitive drum, a charging unit for uniformly charging the surface of the photosensitive drum, an exposure unit for writing an electrostatic latent image on the surface of the photosensitive drum, and a toner containing an abrasive on the surface of the photosensitive drum. An image forming unit including a developing unit that adheres to form a toner image corresponding to the electrostatic latent image, a transfer unit that transfers the toner image formed by the developing unit onto a recording medium, and a predetermined drum In an image forming apparatus provided with a polishing unit that is pressed by pressure and polishes the surface of the photosensitive drum, a charging stop time for stopping charging by the charging unit is provided after each image formation at the time of continuous image formation is completed. After the stop time has elapsed, at least one rotation of the photosensitive drum is ensured as a pre-charging time for pre-charging by the charging unit until the start of the next image formation.

  As a result, during the charging stop time, polishing by the polishing means is performed in a state where the surface of the photosensitive drum is not charged, and at least a pre-charging time for one rotation of the photosensitive drum is secured. It is possible to provide an image forming apparatus capable of effectively polishing by suppressing the generation of ion products due to electric discharge and not causing unevenness in image density due to uneven charging on the surface of the photosensitive drum.

  Also, if the charging stop time and pre-charging time are secured by increasing the image forming speed, the number of processed sheets per predetermined time does not decrease, the occurrence of image flow phenomenon is suppressed, and high image forming efficiency is maintained. can do.

  Further, by using a photosensitive drum made of a-Si, it is possible to provide a high-quality image forming apparatus having a long life and low running cost.

FIG. 1 is a schematic cross-sectional view showing an overall configuration of an image forming apparatus of the present invention. 1 is a block diagram showing a configuration of an image forming apparatus of the present invention. These are timing charts showing the operation control of the charging unit during continuous image formation in the image forming apparatus of the present invention. These are flowcharts showing an image forming operation of the image forming apparatus of the present invention. 4 is a table showing a setting example of the image forming apparatus of the present invention. 4 is a table showing another setting example of the image forming apparatus of the present invention. These are the schematic diagrams which show the structure of the image forming part of the conventional image forming apparatus. These are timing charts showing the operation control of the charging unit during continuous image formation in the conventional image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 3 Exposure unit 4 Developing unit 4a Developing sleeve 5 Transfer roller (transfer means)
6 Rub roller (polishing means)
7 Spring 8 Recovery screw 9 Cleaning blade (polishing means)
DESCRIPTION OF SYMBOLS 10 Static elimination apparatus 14 Cleaning apparatus 15 Image forming part 20 Image reading part 32 Control part 33 Memory | storage part 100 Image forming apparatus T1 Charge stop time T2 Pre-charge time

Claims (3)

A photosensitive drum; a charging unit for uniformly charging the surface of the photosensitive drum; an exposure unit for writing an electrostatic latent image on the surface of the photosensitive drum; and a toner containing an abrasive on the surface of the photosensitive drum. An image forming unit including a developing unit that forms a toner image corresponding to the electrostatic latent image and a transfer unit that transfers the toner image formed by the developing unit onto a recording medium; An image forming apparatus comprising: a polishing unit that is pressed against the surface of the photosensitive drum by pressure of
After each image formation at the time of continuous image formation is completed, a charging stop time for stopping charging by the charging unit is provided, and after the charging stop time has elapsed, pre-charging by the charging unit until the start of the next image formation. An image forming apparatus characterized in that a charging time before performing at least one rotation of the photosensitive drum is secured.   2. The image forming apparatus according to claim 1, wherein the image forming speed in the image forming unit is a speed capable of securing the charging stop time and the pre-charging time without reducing the number of processed sheets per predetermined time. .   The image forming apparatus according to claim 1, wherein the photosensitive drum is made of amorphous silicon.

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