JPH10228219A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of a photoreceptor, for example, sticking of residual toner and foreign matter, at the time of forming an image by introducing a cleaningless system, and to prevent a chemical change caused by the aforesaid situation. SOLUTION: In the case of forming an image by using an electrophotographic copying process and introducing the cleaningless system, the surface of a photoreceptor is ground by a grinding member 22 installed on a transfer/carrying belt 10 so that the foreign matter may be removed. Thus, the foreign matter such as the residual toner, etc., is removed from the surface of the photoreceptor without excessively grinding the surface of the photoreceptor, then, even in the case of forming the image by introducing the cleaningless system, the deterioration of the image quality caused by the introduction of the cleaningless system is prevented. In this case, as for the grinding member 22, only one end on a downstream side in the rotating direction A of the transfer/carrying belt 10 at the transfer operation time is covered with a sheet like cover 23 fixed on the transfer/carrying belt 10, then, the surface of the photoreceptor is usually prevented from being ground.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus for performing image formation using an electrophotographic process in a cleaningless manner.

[0002]

2. Description of the Related Art In image formation by an electrophotographic method, a photoreceptor surface is uniformly charged, exposed to form an electrostatic latent image, and toner is adhered to the electrostatic latent image and developed. This is performed using an electrophotographic process of transferring an image to a recording medium. At this time, the toner remaining on the photoreceptor after the transfer process becomes a cause of preventing the toner from being whitened and causing the recording medium to become dirty during the subsequent electrophotographic process. Therefore, such residual toner is removed. Cleaning treatment is required. As such a cleaning process,
Conventionally, a so-called blade cleaning method in which a urethane rubber blade or the like is brought into contact with a photoreceptor after a transfer process to scrape off residual toner has been most widely used. However, in the cleaning process using the blade cleaning method, there is a problem that the life of the photoconductor is shortened because the photoconductor is shaved. Further, since the film shaving of the photoreceptor changes the capacitance of the photoreceptor, the image forming conditions in the electrophotographic process are fluctuated, and there is a problem that the image quality is reduced. Furthermore, since a space for installing a cleaning device including a urethane rubber blade or the like is required around the photoconductor, there is a current situation that the diameter of the photoconductor, which has been rapidly increasing in recent years, cannot be coped with.

[0003] Under such circumstances, a cleaning-less type image forming apparatus based on a new concept of simultaneous development cleaning has been researched and developed.
No. 300 and the Journal of the Society of Electrophotography Vol. 31 No. 3 (199
2), pages 190 to 195. Such a cleaningless system generally uses a resilient conductive roller as a developing roller, which is a developer carrying member, to perform development by a one-component non-magnetic developing system so that toner adheres to an exposed portion on a photoconductor and The photoconductor is cleaned on the principle that the toner remaining on the non-exposed portion is collected by the developing roller. This will be described in more detail with reference to FIG.

First, it is assumed that the potential after charging is -800 V, the potential after exposure is -100 V, and the developing bias is -500 V. When the charger 102 charges the surface of the photoconductor 101 by corona discharge, the surface potential of the photoconductor 101 becomes -800 V uniformly (FIG. 11A). afterwards,
When the photosensitive member 101 after uniform charging is exposed, the black potential portion after exposure becomes -100V. The unexposed white potential portion remains at -800 V (FIG. 11B). Then, when this is developed with a developing bias of -500 V, an electric field toward the photoconductor 101 acts on the black potential portion, and an electric field toward the developing roller 103 acts on the white potential portion. This allows
In the black potential portion, the toner moves from the developing roller 103 to the photosensitive member 101, or the toner remaining on the photosensitive member 101 stays as it is, and in the white potential portion, the toner remaining on the photosensitive member 101 moves to the developing roller 103 (FIG. 11
(C)). In this manner, a process called simultaneous development and cleaning is performed.

[0005]

However, in the image forming apparatus of the cleaningless type, there is a problem that the surface of the photosensitive member is apt to deteriorate. In other words, the toner adheres to the surface of the photoreceptor with a physical force such as van der Waals force and causes filming, or a discharge product such as a nitric acid compound generated in a charging device or a transfer device adheres to the photoreceptor to expose the photoconductor. The surface resistance of the body may be reduced to cause image deletion, or such discharge products may chemically erode the surface of the photoreceptor and deteriorate the electrostatic characteristics of the photoreceptor. In the blade cleaning method, the photoreceptor surface is scraped off so that a new surface is always exposed to the photoreceptor surface, so that such deterioration of the photoreceptor surface is suppressed. However, the cleaningless method is vulnerable to such photoreceptor deterioration. Has the disadvantage that

In the case where image formation is performed by a cleaning-less method, if foreign matter such as residual toner adheres to the photoreceptor, at least the charging device and the exposing device need to be connected while the foreign material travels from the transfer section to the developing section. This would cause problems at each of these parts. That is, when the contact charging method is adopted as the charging device, there is a problem that foreign matters such as residual toner adhere to the charging device, and the charging potential becomes unstable or image unevenness occurs. In addition, at the exposure position, a portion where foreign matter such as residual toner is present is not sufficiently exposed, so that there is a problem that white spots and the like are likely to occur in that portion.

SUMMARY OF THE INVENTION It is an object of the present invention to prevent deterioration of the surface of a photoreceptor while performing image formation of a cleaningless system.

[0008]

According to the first aspect of the present invention,
A photoreceptor having a photosensitive layer on the surface, a charging device for uniformly charging the surface of the photoreceptor, an image exposure device for exposing the photoreceptor after uniform charging to form an electrostatic latent image, A developing device for developing the electrostatic latent image formed on the photoreceptor and simultaneously collecting the residual toner on the photoreceptor, and transferring the developed image on the photoreceptor to a recording medium conveyed by a transfer conveyer belt And a polishing means having a polishing member provided on the transfer / conveying belt and polishing the surface of the photoreceptor to an extent necessary for removing foreign matter. Therefore, the developing device performs simultaneous development cleaning. For this reason,
Deterioration of the surface of the photoreceptor, such as adhesion of foreign matter such as residual toner, is likely to occur. In the present invention, however, the surface of the photoreceptor is polished by a polishing member of a polishing means using a transfer conveyance belt. Foreign matter such as residual toner is removed from the toner. In addition, the polishing member polishes the surface of the photoconductor to such an extent that foreign substances such as residual toner can be removed from the surface of the photoconductor, so that the surface of the photoconductor is not excessively shaved.

According to a second aspect of the present invention, in the image forming apparatus of the first aspect, the polishing member comprises a sheet or plate-like member containing an abrasive and fixed on the transfer conveyance belt. During the transfer operation, only one end on the downstream side in the rotation direction was covered with a sheet-like cover fixed on the transfer / conveying belt. Therefore, the polishing member is covered with the sheet cover when the transfer conveyance belt rotates in the rotation direction during the transfer operation, so that the surface of the photoconductor is not polished by the polishing member during the normal transfer operation.

According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, the polishing member is moved to the photosensitive member by rotating the polishing / transporting belt in a direction opposite to the rotation direction during the transfer operation during polishing. A means for controlling the rotation of the photosensitive member while stopping the positioning at the contact position. Therefore, when the transfer conveyance belt is rotated in the direction opposite to the rotation direction during the transfer operation, the sheet-like cover is turned up and the polishing member is exposed, so that the surface of the photosensitive member can be polished by the polishing member. Then, by positioning and stopping the polishing member at a position in contact with the photoconductor and rotating the photoconductor, the photoconductor and the polishing member are rubbed at the nip portion of both members, and the surface of the photoconductor is polished.

According to a fourth aspect of the present invention, in the image forming apparatus of the third aspect, there is provided detecting means for detecting a rotational position of the transfer conveyance belt based on a detection signal of a mark provided on the transfer conveyance belt, The polishing means stops the transfer conveyance belt at a position where the polishing member comes into contact with the photoreceptor based on the detected detection signal of the mark. Therefore, by detecting the mark on the transfer conveyance belt, the positional relationship between the photoconductor and the friction member can be controlled.
The polishing member can be stopped at a position where it comes into contact with the photoconductor, and preparation before the polishing operation can be completed in a short time.

According to a fifth aspect of the present invention, in the image forming apparatus of the fourth aspect, the mark is formed by a polishing member or a part of a sheet-like cover. Therefore, a part of the polishing member or the sheet-like cover can be used as a mark, so that the cost can be reduced.

According to a sixth aspect of the present invention, there is provided an image forming apparatus in which a plurality of cleaningless electrophotographic processing units are arranged along a transfer / conveying belt for conveying a recording medium to form a color image, and A sheet-like or plate-like member fixed on the transfer / transport belt, and only one end on the downstream side in the rotation direction during the transfer operation of the transfer / transport belt is covered by a sheet-like cover fixed on the transfer / transport belt. A polishing member for polishing the surface of the photoreceptor of each of the electrophotographic process units to a degree necessary for removing foreign substances, and a direction opposite to a rotation direction during the transfer operation of the transfer conveyance belt during polishing. The control to stop the positioning of the polishing member at the position in contact with the photoreceptor and to rotate the photoreceptor by one rotation of the transfer conveyance belt And so as to sequentially performed from the downstream side of the photosensitive member in at the transfer operation during rotation direction. Therefore, since the polishing means of the present invention is applied to an image forming apparatus for forming a color image in a so-called tandem system, the surface of each photoconductor is polished by a polishing member. In this case, it takes time to polish a plurality of photoconductors, but since the polishing operation is completed during one rotation of the transfer / conveying belt, processing can be performed in a short time. In particular, since the polishing process is performed sequentially from the photosensitive member on the downstream side in the rotation direction during the transfer operation, the processing time can be minimized.

The invention according to claim 7 is the invention according to claims 2, 3, and 4.
In the image forming apparatus described in Item 6, the polishing means rotates the transfer conveyance belt once in the rotation direction during the transfer operation in order to return the sheet-like cover onto the polishing member after the completion of the polishing operation and before starting the image formation. Control is performed. Therefore, the sheet-shaped cover is returned to the state in which the polishing member is covered before the image formation is started, so that the surface of the photoconductor is not polished by the polishing member during the original transfer operation.

[0015] The invention according to claim 8 is the first or second invention.
In the image forming apparatus described in 3, 4, 5, 6 or 7, the photoreceptor after uniformly charged is exposed based on binary data in a saturated region of its light attenuation characteristic. In other words, if the photoconductor is 2
Exposure to saturation at the value. Such a saturated exposure, for example, to the photoreceptor after uniform charging, the maximum exposure amount within the exposure diameter is exposed with a light beam set to a value that sufficiently reduces the differential sensitivity of the photosensitive layer, The maximum exposure amount within the exposure diameter is performed by exposing the photosensitive layer with a light beam set to a value that reduces the differential sensitivity of the photosensitive layer to a value of 1/3 or less of the maximum value. The “differential sensitivity” means the surface potential V (E) of the photoconductor and the exposure amount E obtained when the photoconductor is uniformly exposed to a light beam having the same wavelength as the light beam irradiated by the image exposure apparatus.
Is defined in relation to Specifically, when the photoconductor is exposed at a certain exposure amount E and the surface potential of the photoconductor when the exposure amount E is increased by a small value ΔE from the exposure value is defined as V (E + ΔE), the differential sensitivity Is defined as | V (E + △ E) −V (E) | / △ E. In general, the differential sensitivity decreases as the exposure E increases. The “value that sufficiently reduces the differential sensitivity” means a value of the exposure amount that can use a region of the attenuation characteristic of the photoconductor sufficient to obtain the required stability. The “sought stability” in this case means stability such that the image quality does not deteriorate even when the photosensitive layer of the photosensitive member is abraded due to aging and the capacitance is increased. Such a “value for sufficiently reducing the differential sensitivity” is, for example, that the differential sensitivity of the photosensitive layer is one of its maximum value of 1
It is a value that decreases to a value of / 3 or less.

Therefore, even if the photosensitive layer is abraded by polishing of the photoreceptor and the electrostatic capacity of the photoreceptor increases, the instability of the image forming state due to this is absorbed by the saturated exposure of the photoreceptor. Image quality is maintained. In particular, in a system that does not perform saturated exposure, unevenness is conspicuous in halftone, but if saturation exposure is performed using binary data, it is possible to sufficiently lower the potential directly below the toner with the sneak-through light even if the light is somewhat difficult to hit. Therefore, generation of an afterimage can be suppressed, which is advantageous in obtaining a high-quality image. In other words, by performing saturated exposure with binary data, a high-quality image can be obtained even if the transfer residual toner on the photoconductor is not completely cleaned, so that the cleaning-less method is suitable.

[0017]

FIG. 1 shows a first embodiment of the present invention.
This will be described with reference to FIG. The present embodiment is an image forming apparatus like a multifunction machine that also functions as a digital copying machine.

FIG. 2 is a schematic view of the image forming apparatus. As shown in FIG. 2, a paper feed path 3 for connecting a paper feeder 2 for storing a transfer paper 1 as a recording medium and a discharge unit (not shown).
An image processing section 5 as an electrophotographic processing section including a fixing device 4 is provided in the paper passage path 3.

The image processing section 5 is mainly composed of a photosensitive member 6 having a photosensitive drum configuration. Around the photosensitive member 6, a charging device 7, a developing device 8, and a transfer device 9 are sequentially arranged. An exposure position EX is provided between the charging device 7 and the developing device 8, and the image processing unit 5 is provided with an image exposure device (not shown) that irradiates the exposure position EX with a light beam as a laser beam.

In the image processing unit 5, the photosensitive member 6 is uniformly charged to one polarity by charging by the charging device 7. Since the photoconductor 6 is uniformly charged at the exposure position EX, an electrostatic latent image is formed on the photoconductor 6 by irradiating the exposure position EX with a light beam from an image exposure apparatus according to image information. It is formed. That is, in the photosensitive member 6, a potential difference from the charged potential is generated in a portion irradiated with the light beam, and this portion becomes an electrostatic latent image. The developing device 8 attaches toner having a potential difference from the electrostatic latent image to the electrostatic latent image formed on the photoconductor 6 at the exposure position EX to visualize the image, and collects the toner remaining on the photoconductor 6. Then, the photoconductor 6 is cleaned. The principle of simultaneous development and cleaning in this case is the same as the principle described with reference to FIG. Therefore, the description is omitted. The transfer device 9 is configured to transfer the transfer paper 1 while electrostatically sucking the transfer paper 1.
In addition to the transfer roller 9a, the transfer roller 9a is provided at a position facing the photoconductor 6, and the toner image on the photoconductor 6 visualized at the position of the transfer roller 9a is sucked by a potential difference. The toner image is transferred onto the transfer paper 1 conveyed at the timing adjusted by the registration rollers 3a. The fixing device 4 is arranged on the downstream side of the transfer device 9 in the paper passing path 3, and the transfer paper 1 after passing through the transfer device 9.
The unfixed toner adhering to the sheet is fixed by a heating / pressing action.

FIG. 3 is a block diagram showing the electrical connection of each part. The image forming apparatus according to the present embodiment includes, as a basic configuration, a controller 11 having a microcomputer configuration for controlling each unit and an engine control unit 12. The controller 11 is a microcomputer including a storage device such as an image memory 13 and a font bank 14. A host computer 15 is connected to the controller 11 via bidirectional Centronics. The controller 11 receives image information transmitted from the host computer 15 and performs processing for a printer function. Further, the scanner 16 operates in response to a drive signal from the engine control unit 12.
The image information read by the scanner 16 is transmitted to the controller 11, whereby the controller 11 performs a process for a digital copier function. That is, the controller 11 receiving the image signal from the host computer 15 or the scanner 16 expands the image signal in the image memory 13 and transmits the control / write data to the engine control unit 12 in accordance with the drive signal from the operation panel 17. . At this time, if the image signal is text data from the host computer 15, an appropriate font is called from the font bank 14 as necessary, and image data (character data) according to the called font is stored in the image memory 1.
Expand to 3. On the other hand, the engine control unit 12 that has received the control / write data from the controller 11 includes a drive motor, a clutch, and a solenoid, which are drive sources for various movable units such as the sheet feeding device 2 and the photoconductor 6, that is, the drive unit. A drive signal is given to 18 to drive and control them, and a high-voltage power supply circuit 19 for the charging device 7 and the developing device 8 is provided with a drive signal to drive and control them. Specifically, a driving unit 18 and an engine control unit 12 for controlling the rotation direction and the speed of the transfer conveyance belt 10 (including the stop control) are also included. A cleaning device 21 of a blade type for cleaning the surface of the transfer conveyance belt 10 is also provided.
Also, the transfer / conveyance belt 10 can be freely contacted / separated under the control of the engine control unit 12 by a contact / separation mechanism (not shown). At the time of the reverse rotation driving of the transfer / conveying belt 10 before polishing and the time of polishing described later, the cleaning device 2
1 is controlled so as to be separated from the transfer conveyance belt 10.

FIG. 4 is a sectional view of the photosensitive layer 20 of the photosensitive member 6. The photoreceptor 6 is an organic photoreceptor, and the photosensitive layer 20 of the photoreceptor 6 includes a charge generation layer 20a disposed on the base side of the photoreceptor 6 and a charge transport layer 20b disposed on the surface side. Such a photosensitive layer 20 has a thickness Tp of 13 μm. The thickness Tp of the photosensitive layer 20 and the exposure diameter Db of the light beam are set to have a relationship of 2Tp <Db <8Tp. Here, the exposure diameter D of the light beam
b is the energy distribution P (x, y, light beam) of the light beam on the photoconductor 6 when the surface coordinates of the photoconductor 6 are (x, y).
t) Exposure distribution E (x, y) [jule / m ² ] defined as a value obtained by integrating [watt / m ² ] with the exposure time, that is, E (x, y) = ∫P (x, y) , T) defined as the minimum diameter at 1 / e ² from the peak value of dt. FIG. 5A is a graph showing an energy distribution (beam profile) of a light beam applied to the photoconductor 6, and FIG. 6A is a graph showing an exposure amount distribution on the photoconductor 6. In the present embodiment, in the beam profile, the diameter of the light beam at 1 / e ² from the peak value of the exposure amount distribution is, for example, 30 μm in the main scanning direction and 38 μm in the sub-scanning direction (FIG. 5B). reference). That is, the energy distribution of the light beam has a Gaussian distribution of 30 μm in the main scanning direction and 38 μm in the sub-scanning direction. When the photosensitive member 6 is exposed by a length of about 20 μm in the sub-scanning direction in order to form an electrostatic latent image of one pixel on the photosensitive member 6, the exposure diameter of the light beam in the exposure amount distribution becomes The size in both the direction and the sub-scanning direction is about 38 μm (see FIG. 6B).
That is, a Gaussian distribution of approximately 38 μm is shown in both the main and sub scanning directions. Therefore, 1 / e ^{2 is} smaller than the peak value of the exposure amount distribution.
The exposure diameter Db of the light beam, defined as the minimum diameter at, is 38 μm.

FIG. 7 is a graph showing the light attenuation characteristics of the photosensitive member 6 with respect to the exposure amount. In the present embodiment, the image exposure apparatus has a light beam having a wavelength of 670 nm,
The exposure power is adjusted to be 0.23 mW on the surface of the photoconductor 6. As a result, the image exposure apparatus exposes the photoreceptor 6 in a saturated region of the light attenuation characteristic. That is, the exposure amount at the peak value of the exposure amount distribution, that is, the maximum exposure amount within the exposure diameter Db is a value that sufficiently reduces the differential sensitivity of the photosensitive layer 20. The “differential sensitivity” refers to the surface potential V (E) of the photoconductor 6 and the exposure amount E obtained when the photoconductor 6 is uniformly exposed to a light beam having the same wavelength (670 nm) as the light beam irradiated by the image exposure apparatus. Is defined in relation to Specifically, when the photosensitive member 6 is exposed at a certain exposure amount E, and the exposure amount E is increased by a minute value ΔE from the exposure amount, and the surface potential of the photosensitive member 6 is V (E + ΔE), The differential sensitivity is defined as | V (E + △ E) −V (E) | / △ E. Further, "a value that sufficiently reduces the differential sensitivity" means a value of the exposure amount E that can use a region of the light attenuation characteristic of the photoreceptor sufficient to obtain the required stability. In this case, the “sought stability” means a stability such that the image quality does not decrease even when the photosensitive layer 20 of the photosensitive member 6 is abraded due to aging and the capacitance is increased. Such a “value that sufficiently reduces the differential sensitivity” is, for example, a value at which the differential sensitivity of the photosensitive layer 20 decreases to a value equal to or less than １ ／ of the maximum value. For reference, in the light attenuation characteristic of the photoreceptor 6 illustrated in FIG. 6, the exposure value E of the peak value (peak exposure value) of the exposure value distribution is 21 mJ / m ² , and the differential sensitivity corresponding thereto is: 5 V · m ² / mJ. Therefore, it is about 1/5 of the maximum differential sensitivity.

In such a basic configuration, in this embodiment, as shown in FIG. 1, a polishing member 22 constituting a part of the polishing means is fixed to a part of the transfer / conveying belt 10. . The polishing member 22 is in the form of a strip sheet or a plate containing an abrasive, and has a length that covers almost the entire width of the transfer conveyance belt 10. A sheet-like cover 23 is provided on the polishing member 22. The sheet-like cover 23 has an area that covers the entire surface of the polishing member 22 and is made of the same material (or substantially the same material) as the transfer and conveyance belt 10.
The transfer belt 10 has an affixing portion 23a on the downstream side in the rotation direction (direction of the arrow A) during the transfer operation of the transfer conveyor belt 10, and has only one end fixed to the surface of the transfer conveyor belt 10. Therefore, the other end 23b of the sheet-like cover 23 is a free end that can freely contact and separate from the transfer conveyance belt 10, but usually, the transfer conveyance belt 10 is electrostatically actuated.
Is adsorbed on the surface. On the other hand, when the transfer conveyance belt 10 is rotated in the reverse direction (the direction of the arrow B), FIG.
As shown in (b), the free end 23b side is separated from the transfer / transport belt 10 by the curvature of the drive roller 24 for the transfer / transport belt 10 and the weight of the sheet-like cover 23 in the direction of gravity, thereby exposing the polishing member 22. It has a possible structure.

As shown in FIG. 8, a mark 25 used for detecting the rotational position of the transfer / transport belt 10 is provided at a predetermined position in relation to the polishing member 22. ing. In response to this,
A light reflection type sensor 26 functioning as a detecting means for optically detecting the mark 25 is provided near the transfer conveyance belt 10.
Is provided.

In such a configuration, the photosensitive layer 20 of the photosensitive member 6 is charged by the charging device 7, and an electrostatic latent image based on image information is formed on the charged photosensitive member 6 at the exposure position EX. When the toner supplied from the developing device 8 adheres to the latent image, the electrostatic latent image is developed and visualized. At the same time, the developing device 8 collects the toner remaining on the photoconductor 6. Then, a visualized developed image, that is, a toner image is transferred to the transfer paper 1 conveyed to the electrophotographic process unit 5 at a predetermined timing. Thereafter, the transferred image is fixed by the fixing device 4, whereby an image is formed on the transfer paper 1. At the time of such image formation, as shown in FIG. 1A, the polishing member 22 is covered with a sheet-like cover 23, and the polishing member 22 does not come into contact with the photoconductor 6, so that the surface of the photoconductor 6 should be polished. There is no.

When the engine controller 12 recognizes that the predetermined number of images have been formed, the photosensitive member 6 is polished under the condition that no image is formed. this is,
It is not necessary to perform the polishing operation every time the transfer paper 1 is used, and the polishing operation is performed once every several image forming operations, based on the adhesion speed of the deposit on the surface of the photoconductor 6 in the system. This is for good reason. For this polishing process, first, the driving roller 24 is rotated in the direction of arrow B by the driving unit 18 to drive the sheet-like cover 23 that moves with the rotation of the transfer conveyance belt 10 as shown in FIG. The polishing member 22 is exposed by turning over and separating from the transfer / conveying belt 10 at the curvature portion by the roller 24. Then, by rotating the transfer conveyance belt 10 by a predetermined amount based on the position where the light reflection type sensor 26 detects the mark 25 with the rotation of the transfer conveyance belt 10, the polishing member 22 is brought into contact with the photosensitive member 6 (transfer). Position) to stop the transfer / conveyance belt 10. When the photoconductor 6 is rotated clockwise in this state, rubbing occurs at a nip portion between the photoconductor 6 and the polishing member 22. Here, the transfer conveyance belt 10 is normally rotated at the same speed as the photoconductor 6, and a sufficient nip width for the transfer is set between the transfer conveyance belt 10 and the photoconductor 6. Is rubbed with a sufficient nip width. As a result, the surface of the photoconductor 6 is polished, and foreign matters such as residual toner are removed from the surface of the photoconductor 6. This stabilizes the image forming state and prevents the image quality from deteriorating even when the image formation of the cleaningless system is performed.

At this time, the photoreceptor 6 is polished with a force capable of removing foreign matters such as residual toner from the photoreceptor 6, and the polishing amount of the photoreceptor 6 is much smaller than, for example, a blade cleaning method. Therefore, the amount of film shaving of the photosensitive layer 20 of the photoconductor 6 is minimized, and the durability of the photoconductor 6 is not impaired. In addition, although the photosensitive layer 20 of the photosensitive member 6 is slightly etched, the capacitance of the photosensitive member 6 is increased. However, the influence of this on the image forming state is absorbed by the saturated exposure of the photosensitive member 6. . That is, since the photoconductor 6 is saturatedly exposed, the charged potential of the photoconductor 6 after exposure is stabilized, and the image forming state is stabilized. Thereby, the image quality is maintained. In addition, since the control for stopping the positioning of the polishing member 22 at the transfer position in contact with the photoconductor 6 is also based on the detection of the mark 25,
This can be performed easily and reliably, and preparation processing before the polishing operation can be performed in a short time.

After the polishing operation is completed, prior to the image forming operation,
As shown in FIG. 1 (c), by rotating the transfer conveyance belt 10 in the rotation direction (direction of arrow A) during the normal transfer operation, the sheet-like cover 23 is rotated while the polishing member 22 is rotated.
And the free end 23b is returned to a state where the free end 23b is electrostatically attracted onto the transfer conveyance belt 10 again. As a result, the polishing member 22 is not exposed during the image forming operation, and the surface of the photoconductor 6 is not unnecessarily polished by the polishing member 22.

In this embodiment, the mark 25 is provided on the transfer / conveying belt 10 alone.
As shown in FIG.
A part of the polishing member 22 may be used as the mark 27 by extending the end of the polishing member 22 to the end of the zero.
According to this, it is not necessary to provide the mark 25 alone,
In addition to cost reduction, the mark 27 itself and the photoconductor 6
The position of the polishing member 22 at which the polishing member 22 should be stopped can be controlled based on the positional relationship between the two.

The marking function is not limited to a part of the polishing member 22, but may be a part of the sheet-like cover 23, particularly the sticking part 23a.

A second embodiment of the present invention will be described with reference to FIG. FIG. 7 is a schematic diagram of the image forming apparatus.
Note that the same parts as those described in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

This embodiment is an example of application to a color image forming apparatus. That is, the image forming apparatus of the present embodiment
This is a tandem-type color image forming apparatus in which four image processing units 5K, 5Y, 5M, and 5C for black, yellow, magenta, and cyan are arranged along the transfer conveyance belt 10. The transfer conveyance belt 10 is stretched between a driving roller 24 and a driven roller 28, and a transfer brush 9 is provided at a position corresponding to each photoconductor 6 in each image processing unit 5.
b is provided. The transfer conveying belt 10 is provided with a transfer bias from the transfer brushes 9b.

The transfer / conveying belt 10 can be freely moved toward and away from each of the image processing units 5 by a contact / separation mechanism (not shown). The contact / separation mechanism is a clutch or a drive in a drive unit 18 driven and controlled by the engine control unit 12. Driven by a drive motor or the like, the transfer / conveying belt 10 and the image processing unit 5 are selectively brought into and out of contact with each other.

Here, a part of the processing executed by the microcomputer operation of the engine control unit 12 will be described. This process is a process for a polishing means for polishing the surface of the photoreceptor 6 to an extent necessary for removing foreign substances by the polishing member 22 and a cleaning means for cleaning the surface of the transfer conveyance belt 10.

As processing for the polishing means, the engine control unit 12 searches for conditions for polishing the photosensitive member 6 by various management functions. This condition is an AND condition between the condition that the formation of a predetermined number of images has been completed and the condition that no image is formed. When the CPU (not shown) of the engine control unit 12 recognizes that these conditions are satisfied, the polishing of the photoconductor 6 is performed.

For the polishing process, first, the driving unit 24 rotates the driving roller 24 in the direction of arrow B to move the sheet-like cover 23 with the rotation of the transfer / conveying belt 10 as shown in FIG. The polishing member 22 is exposed by turning off and separating from the transfer conveyance belt 10 at the curvature portion by the driving roller 24 as in the case of FIG.
Then, the transfer member 10 is further rotated by a predetermined amount based on the position where the light reflection type sensor 26 detects the mark 25 with the rotation of the transfer member 10 so that the polishing member 22 is moved to the most downstream position in the rotation direction during the transfer operation. Is moved to a position (transfer position) in contact with the photosensitive member 6 (the photosensitive member for the image process 5K in the figure) located at the position (1), and the transfer conveyance belt 10 is stopped. By rotating the photoconductor 6 clockwise in this state, rubbing occurs at the nip portion between the photoconductor 6 and the polishing member 22. Here, the transfer conveyance belt 10
Is normally rotated at the same speed as the photoconductor 6, a nip width sufficient for transfer is set between the photoconductor 6 and the nip width when the polishing member 22 abuts. It will be rubbed. As a result, the surface of the photoconductor 6 is polished, and foreign matters such as residual toner are removed from the surface of the photoconductor 6. Thereafter, the polishing member 22 is moved to and stopped at the position of the photoconductor 6 for the image process 5Y located immediately upstream, and the photoconductor 6 is polished in the same manner. Similarly, the other two photoconductors 6 for the image processes 5M and 5C are sequentially polished by the polishing member 22 in the same manner. This stabilizes the image forming state and prevents the image quality from deteriorating even when the image formation of the cleaningless system is performed.

In this case, although it takes time to polish the plurality of photoconductors 66, since the polishing operation is completed during one rotation of the transfer / conveyance belt 10, processing can be performed in a short time. In particular, since the polishing process is performed sequentially from the photoconductor 6 on the downstream side in the rotation direction during the transfer operation, the processing time can be minimized. In addition, since the transfer conveyance belt 10 is stopped, there is no movement of foreign matter such as residual toner removed, and color mixing and damage of the toner in the downstream image processing unit 5 are prevented.

Next, as a process for the cleaning means, when the engine control unit 12 recognizes the completion of polishing of the photoreceptor 6 by the time management function of the engine control unit 12,
The transfer conveyance belt 10 is separated from the image processing unit 5. Then, the transfer conveyance belt 10 is driven to rotate, and the surface of the polishing member 22 is cleaned by sliding of the polishing member 22 and the cleaning device 21 on the transfer conveyance belt 10 at this time. At this time, since the transfer conveyance belt 10 is separated from each of the image processing units 5K, 5Y, 5M, and 5C, foreign matter such as residual toner that is removed from the photoconductor 6 and remains on the polishing member 22 of the transfer conveyance belt 10 is removed. The toner does not reach the image processing unit 5, and color mixing and damage of the toner are prevented.

[0040]

According to the first aspect of the present invention, when performing a cleaning-less type image formation using an electrophotographic process, the polishing member provided on the transfer / conveying belt removes foreign matter on the surface of the photoreceptor. Since the surface is polished to a necessary degree, foreign substances such as residual toner can be removed from the surface of the photoconductor without excessively shaving the surface of the photoconductor. You can prevent the image quality from deteriorating,
In addition, it is possible to suppress an increase in the capacitance of the photoconductor due to remarkable shaving of the photosensitive layer, and to stabilize an image forming state.

According to the second aspect of the present invention, the polishing member is a sheet-like or plate-like member containing an abrasive and fixed on the transfer / conveying belt, and the downstream side in the rotation direction during the transfer operation of the transfer / conveying belt. Since only one side end is covered by a sheet-like cover fixed on the transfer / transport belt, the polishing member is covered by the sheet-like cover when the transfer / transport belt rotates in the rotation direction during the transfer operation. It is possible to simply and reliably prevent the surface of the photoconductor from being polished by the polishing member during the transfer operation of the above.

According to the third aspect of the present invention, the polishing means stops the positioning of the polishing member at the position in contact with the photosensitive member by rotating the transfer conveying belt in the direction opposite to the rotation direction during the transfer operation during polishing. Since the means for controlling the rotation of the photoreceptor is used, the sheet-like cover is turned up by rotating the transfer conveyance belt in the direction opposite to the rotation direction during the transfer operation, so that the polishing member is exposed. The surface of the photoreceptor can be polished.Therefore, the polishing member is positioned and stopped at a position in contact with the photoreceptor, and the photoreceptor and the polishing member are rubbed at the nip portion of both by rotating the photoreceptor. The surface of the photoreceptor can be polished well.

According to a fourth aspect of the present invention, there is provided a detecting means for detecting a rotational position of the transfer / conveying belt based on a detection signal of a mark provided on the transfer / conveying belt, and a polishing means for detecting the detected mark. The transfer conveyance belt is stopped at a position where the polishing member comes into contact with the photoconductor based on the detection signal, so that the positional relationship between the photoconductor and the friction member is controlled by detecting the mark on the transfer conveyance belt. Since the polishing member can be stopped at a position where the polishing member is in contact with the photoconductor, preparation before the polishing operation can be completed in a short time.

According to the fifth aspect of the present invention, the mark is
Since it is formed by a part of the polishing member or the sheet-shaped cover, a part of the polishing member or the sheet-shaped cover can be used as a mark, and cost can be reduced.

According to the sixth aspect of the present invention, a so-called tandem type image forming apparatus in which a plurality of cleaningless type electrophotographic processing units are arranged along a transfer / conveying belt for conveying a recording medium to form a color image. Since the polishing means according to the third aspect of the present invention is applied to the apparatus, the surface of each photoconductor can be sequentially polished by the polishing member on the transfer / conveying belt. In this case, it takes time to polish a plurality of photoconductors. However, since the polishing operation is completed during one rotation of the transfer conveyance belt, the processing can be performed in a short time. In particular, by performing the polishing processing sequentially from the photosensitive member on the downstream side in the rotation direction during the transfer operation, the processing time is minimized. Can be

According to the seventh aspect of the invention, the polishing means rotates the transfer conveyance belt during the transfer operation to return the sheet-like cover to the polishing member after the completion of the polishing operation and before starting the image formation. Control is performed so that the sheet-like cover covers the polishing member before image formation is started, and the photosensitive member surface is polished by the polishing member during the original transfer operation. Can be prevented.

According to the eighth aspect of the present invention, the photosensitive member after uniform charging is exposed based on the binary data in the saturated region of the light attenuation characteristic, so that the photosensitive layer is polished by polishing the surface of the photosensitive member. Even if the film is scraped and the capacitance of the photoconductor increases,
The influence on the image quality due to such fluctuation is absorbed by the saturated exposure, and the image quality can be maintained.

[Brief description of the drawings]

FIG. 1 is an enlarged schematic view showing a part of a transfer conveyance belt and a polishing member according to a first embodiment of the present invention.

FIG. 2 is a schematic view of an image forming apparatus according to the first embodiment of the present invention.

FIG. 3 is a block diagram showing an electrical connection.

FIG. 4 is a sectional view of a photosensitive layer in the photosensitive member.

FIG. 5 is a graph showing an energy distribution (beam profile) of a light beam.

FIG. 6 is a graph showing an exposure amount distribution.

FIG. 7 is a graph showing a light attenuation characteristic of a photoconductor with respect to an exposure amount.

FIG. 8 is a perspective view showing a transfer conveyance belt.

FIG. 9 is a perspective view showing a modified example thereof.

FIG. 10 is a schematic view of an image forming apparatus according to a second embodiment of the present invention.

FIG. 11 is a schematic diagram for explaining the principle of simultaneous cleaning of development.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Recording medium 6 Photoconductor 7 Charging device 8 Developing device 9 Transfer device 10 Transfer conveyance belt 20 Photosensitive layer 22 Polishing member 23 Sheet-shaped cover 25, 27 mark

Claims (8)

[Claims] 1. A photoreceptor having a photosensitive layer on its surface, a charging device for uniformly charging the surface of the photoreceptor, and an image for forming an electrostatic latent image by exposing the photoreceptor after uniformly charged An exposure device, a developing device that develops an electrostatic latent image formed on the photoconductor and simultaneously collects residual toner on the photoconductor, and a recording medium that conveys the developed image on the photoconductor by a transfer conveyance belt An image forming apparatus comprising: a transfer device for transferring the image on the transfer belt; and a polishing unit having a polishing member provided on the transfer / conveying belt and polishing the surface of the photoconductor to a necessary degree for removing foreign matter. apparatus. 2. The polishing member comprises a sheet-like or plate-like member containing an abrasive and fixed on a transfer conveyance belt, and only one end of the transfer conveyance belt on the downstream side in the rotation direction at the time of a transfer operation is transferred to the transfer conveyance belt. The image forming apparatus according to claim 1, wherein the image forming apparatus is covered by a sheet-like cover fixed thereon. 3. The polishing means performs control to stop the positioning of the polishing member at the position in contact with the photoconductor and to rotate the photoconductor by rotation of the transfer conveyance belt in the direction opposite to the rotation direction during the transfer operation of the transfer conveyor belt during polishing. The image forming apparatus according to claim 2, wherein the image forming apparatus is a unit. 4. A detecting means for detecting a rotational position of the transfer / conveying belt based on a detection signal of a mark provided on the transfer / conveying belt, and the polishing means includes a polishing member based on the detected detection signal of the mark. 4. The image forming apparatus according to claim 3, wherein the transfer belt stops at a position where the transfer belt contacts the photosensitive member. 5. The mark is formed by a polishing member or a part of a sheet-like cover.
The image forming apparatus as described in the above. 6. An image forming apparatus in which a plurality of cleaningless electrophotographic process units are arranged along a transfer conveyance belt for conveying a recording medium to form a color image. A polishing member comprising a sheet-like or plate-like member fixed to the transfer conveyance belt, and only one end on the downstream side in the rotation direction during the transfer operation of the transfer conveyance belt is covered by a sheet-like cover fixed on the transfer conveyance belt. A polishing means for polishing the surface of the photoreceptor of each of the electrophotographic process units to a degree necessary for removing foreign substances; and during the polishing, the polishing is performed by rotating the transfer / conveyor belt in a direction opposite to the rotation direction during the transfer operation. The position of the member is stopped at a position where the member contacts the photoconductor, and the control of rotating the photoconductor is performed during the rotation of the transfer conveyance belt during one rotation of the transfer conveyance belt. An image forming apparatus characterized in that so as to successively performed from the downstream side of the photoreceptor in the direction. 7. The polishing means performs control of rotating the transfer conveyance belt once in the rotation direction during the transfer operation in order to return the sheet-like cover to the polishing member after the completion of the polishing operation and before starting image formation. The image forming apparatus according to claim 2, 3, 4, or 6, wherein 8. The photoconductor according to claim 1, wherein the photoreceptor after uniform charging is exposed based on binary data in a saturation region of the light attenuation characteristic. Image forming device.