JP5309001B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that outputs a toner image from a photosensitive drum to a sheet through an intermediate transfer member.

  In this type of image forming apparatus, an electrophotographic system is used. When the charger precharges the photosensitive drum and the exposure unit irradiates light on the surface of the photosensitive drum, an electrostatic latent image is formed on the surface. It is formed. The developing unit carries toner, and the toner adheres to the electrostatic latent image to form a toner image. The toner image is primary-transferred to the intermediate transfer member, and then secondary-transferred to the paper and fixed.

  Here, a small amount of toner may remain on the surface of the photosensitive drum without being transferred to the sheet, and needs to be removed before the next image formation. For this reason, a technique for cleaning the surface of the photosensitive drum with a cleaning blade using an abrasive is disclosed (for example, see Patent Document 1).

JP 2008-129450 A

  By the way, the charging characteristics are deteriorated in the initial drum, specifically, in the photosensitive drum close to the unused state. This phenomenon is such that when the surface potential of the photosensitive drum is taken on the vertical axis and the number of printed sheets is taken on the horizontal axis, the surface potential is approximately V of the alphabet even though a desired voltage is applied to the photosensitive drum from charging. It appears in a curved shape like a letter (hereinafter referred to as a V-shaped phenomenon).

This is because the surface of the photoconductive drum has high surface smoothness when it is not used, so that the progress of wear is slow, so that deposits are difficult to remove. This is because the presence of deposits further hinders the progress of wear and makes it difficult to scrape the photosensitive drum.
As described above, since the surface potential is remarkably lowered until the photosensitive drum is removed from the unused state, it is necessary to adjust the operating conditions in consideration of the V-shaped phenomenon. Only the edge of the drum contacts the drum.

In other words, the abrasive near the edge of the cleaning blade adheres to the toner from the developing unit and the residual toner scraped off by the cleaning blade and is easily collected. There is a problem that it is not possible to actively promote the wear of the photosensitive drum close to the state.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus that solves the above-described problems and can quickly eliminate the deterioration state of the charging characteristics of the photosensitive drum that is close to an unused state.

A first invention for achieving the above object is applied to an image forming apparatus that forms a toner image by developing a latent image formed on a surface of a photosensitive drum through charging or exposure with toner.
Then, the transfer belt has a transfer surface facing the surface of the photosensitive drum, and is applied to the transfer belt to which the toner image is transferred. The abrasive is supplied to the transfer surface of the transfer belt for photosensitivity. V-shaped phenomenon elimination means for accelerating the wear of the photosensitive drum and eliminating the deterioration state of the charging characteristics due to the surface property of the photosensitive drum when not in use.

According to the first invention, a toner image obtained by developing the latent image with toner is formed on the surface of the photosensitive drum by driving the photosensitive drum, and the toner image is primarily transferred onto the transfer surface of the transfer belt. The The toner image is superimposed on the transfer surface and secondarily transferred onto the paper.
Here, the present invention pays attention to the V-shaped phenomenon in which the charging characteristic deteriorates in the photosensitive drum close to the unused state.

  According to the present invention, the V-shaped phenomenon eliminating means is applied to the transfer belt, and the abrasive is supplied to the transfer surface of the transfer belt to actively promote the wear of the initial drum that is close to the unused state. . As a result, along with the difference in linear velocity between the transfer belt and the photosensitive drum, the surface of the photosensitive drum is worn, and the deterioration of the charging characteristics is quickly eliminated. As a result, it becomes a state close to a drum (hereinafter referred to as a “durable drum”) that has been promptly printed from an unused time and has no decrease in surface potential, and a desired surface potential can be obtained.

The second invention is characterized in that, in the configuration of the first invention, the V-characteristic elimination means supplies an abrasive to the transfer surface of the transfer belt in an unused state.
According to the second invention, in addition to the action of the first invention, it is possible to further improve the polishing action of the unused transfer belt. When the transfer belt is in use, a large amount of abrasive is adhered to the transfer surface, and the surface of the photosensitive drum can be polished with this abrasive. On the other hand, when the transfer belt is in an unused state, for example, when the transfer belt is newly replaced, the adhesion of the abrasive cannot be expected, and there is a concern that the surface of the photosensitive drum cannot be accelerated. is there. However, if the V-shaped phenomenon eliminating means supplies an abrasive to the transfer surface of an unused transfer belt, there is no concern.

According to a third aspect of the present invention, in the configuration of the first or second aspect, the V-characteristic elimination means restores the charging characteristic from the initial state where the charging characteristic of the photosensitive drum deteriorates when the abrasive is supplied to the transfer belt. It is prohibited to move with the transition to the durable state.
According to the third invention, in addition to the effects of the first and second inventions, the supply of the abrasive to the transfer belt is performed in the initial drum state, but is prohibited in the durable drum state. The progress of wear of this durable drum is slowed. Therefore, the life of the photosensitive drum can be extended and good image formation can be performed over a long period of time.

According to a fourth invention, in any one of the first to third inventions, the abrasive is a metal oxide.
According to the fourth invention, in addition to the effects of the first to third inventions, the wear of the initial drum is surely accelerated by using a metal oxide abrasive.

According to a fifth invention, in any one of the first to fourth inventions, the photosensitive drum is a photosensitive drum having an organic photosensitive layer on a surface thereof.
According to the fifth invention, in addition to the effects of the first to fourth inventions, an effective polishing action can be exhibited by combining a photosensitive drum having an organic photosensitive layer. In addition, a photosensitive drum having an organic photosensitive layer is inexpensive and easily mass-produced. However, the surface is extremely smooth, and the surface smoothness has a great influence on the initial drum. On the other hand, there is a concern that the surface is easily scraped and the wear has a big influence on the durable drum. , The characteristics of the photosensitive drum can be maintained over a long period of time, and a particularly remarkable effect is achieved.

According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the apparatus further includes a charger that contacts and charges the surface of the photosensitive drum.
According to the sixth invention, in addition to the effects of the first to fifth inventions, the contact charging type charger is more effective. The contact charging type charger does not generate ozone or nitrogen oxide compared to the case of the corona discharge type charging device, so that the image quality can be improved, but the charging characteristics of the initial drum are remarkably deteriorated. To do. However, if the above-described V-shaped phenomenon eliminating means is provided, a desired surface potential can be obtained even if a contact charging type charger is used, and correction of the charging current during image formation becomes unnecessary.

  According to the present invention, the abrasive is supplied to the transfer surface of the transfer belt to actively promote the wear of the photoconductor drum, and the photoconductor drum close to the unused state can be quickly transferred to the durable drum state. An image forming apparatus can be provided.

1 is a schematic configuration diagram of a printer according to an embodiment. It is a block diagram including the controller of the printer of FIG. FIG. 2 is a cross-sectional view around the image forming unit in FIG. 1. It is a flowchart of the wear promotion control by the controller of FIG. It is an experimental result regarding the surface potential of the photosensitive drum and the number of printed sheets.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.
FIG. 1 schematically shows the structure of a printer 1 capable of color printing, which is an example of an image forming apparatus. The cross section shown in the figure is seen from the left side of the printer 1. For this reason, the front surface of the printer 1 is positioned on the right side and the rear surface of the printer 1 is positioned on the left side.

As shown in the figure, a paper discharge tray 36 is provided above the apparatus main body 2 of the printer 1, and a plurality of operation keys used for various operations by the user are provided near the paper discharge tray 36. A front cover 5 on which a screen for displaying various types of information is arranged is provided.
Further, a sheet feeding cassette 4 is disposed below the apparatus main body 2, and sheets of sheets are stored in the storage unit 40 in a stacked state. As shown in the figure, a paper feed roller 46 is provided on the upper right side of the accommodating portion 40.

Then, the sheet is sent toward the upper right of the sheet feeding cassette 4 in the figure, and the sent sheet is conveyed upward along the front surface of the printer 1 inside the apparatus main body 2.
Further, the paper feed cassette 4 is configured to be able to be pulled out to the front side of the printer 1, that is, in the right direction in FIG. 1, and in this pulled out state, a new sheet can be replenished to the storage section 40. The paper can be replaced with another type of paper.

Inside the apparatus main body 2, a transport roller 10, a registration roller 14, an image forming unit 16, and a secondary transfer unit 30 are sequentially arranged on the downstream side in the paper transport direction from the paper feed cassette 4.
The image forming unit 16 includes four image forming units 17 arranged in parallel, and each unit 17 is provided with a photosensitive drum 18 (FIGS. 1 and 3). The photosensitive drum 18 is rotatably installed and is driven clockwise in FIGS. 1 and 3 by a driving motor (not shown).

The photosensitive drum 18 of the present embodiment is a single-layer OPC drum (OPC: Organic Photoconductor) having a diameter of, for example, 30 mm and having an organic photosensitive layer on the surface thereof.
An exposure unit 15 is provided between the photosensitive drum 18 and the paper feed cassette 4 (FIG. 1), and laser light is irradiated from the exposure unit 15 toward the photosensitive drums 18 respectively. Is done. As shown in FIGS. 1 and 3, a charger 20, a developing device 24, an intermediate transfer roller 13, and a cleaning unit 50 are provided at appropriate positions around each photosensitive drum 18.

  As shown in FIG. 3, the charger 20 is positioned below the image forming unit 17 and includes a charging roller 21 that is in contact with the photosensitive drum 18 and a brush that cleans the surface of the charging roller 21 by grinding and rubbing. A rubbing roller 22 is provided to charge the surface of the photosensitive drum 18. The charging roller 21 is made of, for example, epichlorohydrin rubber, and has a diameter of, for example, φ12 mm.

The developing device 24 is disposed on the left side of the image forming unit 17 and has a developing roller 25 that faces the photosensitive drum 18. The developing roller 25 is driven counterclockwise in the figure by a driving motor (not shown).
The reference numeral 26 in FIG. 3 is a gap regulating roller. The gap regulating rollers 26 are provided at both ends of the developing roller 25, and set a gap between the developing roller 25 and the photosensitive drum 18 along with the photosensitive drum 18.

  The image forming unit 16 includes an intermediate transfer belt (transfer belt) 12 made of, for example, rubber. The intermediate transfer belt 12 is disposed above each photosensitive drum 18, and the intermediate transfer belt 12 and the paper discharge tray 36 are connected to each other. Four toner containers 23 are disposed between them (FIG. 1). These toner containers 23 are arranged in the order of magenta, cyan, yellow, and black from the back side to the front side of the printer 1, and the toner container for black has the largest capacity. Is done.

The secondary transfer unit 30 includes a secondary transfer roller 31, and the transfer roller 31 is configured to be able to press against the transfer belt 12 from obliquely below. The transfer belt 12 and the secondary transfer roller 31 form a nip portion for transferring a toner image onto a sheet.
A fixing unit 32, a discharge branching unit 34, and a paper discharge tray 36 are sequentially arranged on the downstream side of the secondary transfer unit 30 in the paper transport direction.

In this embodiment, a duplex printing conveyance path 38 is formed between the secondary transfer unit 30 and the manual feed tray 3. The duplex printing conveyance path 38 branches from the discharge branching portion 34 on the front side of the apparatus main body 2 and extends downward, and is connected to the upstream side of the registration roller 14.
Here, a small amount of abrasive (metal oxide such as titanium oxide, silica, and alumina) is added to the toner of this embodiment. As shown in FIG. 3, the cleaning unit 50 includes a housing 51 that opens toward the photosensitive drum 18 on the downstream side of the transfer position with the intermediate transfer roller 13 as viewed in the rotational direction of the photosensitive drum 18. And a cleaning blade 52 and a toner recovery unit 80 are provided at appropriate positions of the housing 51.

  Specifically, the cleaning blade 52 includes a main body of a galvanized steel plate fixed to the lower end of the housing 51, and a polyurethane rubber blade portion welded to the main body. It extends along the rotation axis. Then, the edge contacts in the counter direction at a position lower than the rotation axis of the photoconductive drum 18, and scrapes off residual toner including an abrasive and a discharge product adhering to the surface of the photoconductive drum 18.

Residual toner or the like scraped off from the surface of the photosensitive drum 18 by the cleaning blade 52 is recovered from the toner recovery unit 80.
Specifically, the toner recovery unit 80 has a screw 88 near the bottom surface of the housing 51. The screw 88 is installed on the right side of the cleaning blade 52 as viewed in FIG. 3, extends along the rotational axis direction of the photosensitive drum 18, and has a tip connected to a drive motor (not shown). When the drive motor is driven, residual toner and the like in the housing 51 are collected in a collection container via the screw 88.

On the other hand, the intermediate transfer belt 12 described above is cleaned by a cleaning unit (V-characteristic elimination means) 70.
The cleaning unit 70 of this embodiment is provided on the side opposite to the pressure contact position between the intermediate transfer belt 12 and the secondary transfer roller 31 (FIG. 1).
More specifically, the cleaning unit 70 is provided on the upstream side of the magenta image forming unit 17 disposed on the back side of the printer 1 when viewed in the traveling direction of the transfer belt 12, and includes a cleaning roller, a scraper, and the like. .

The cleaning roller is formed of, for example, a conductive nylon brush, and is rotated by a drive motor (not shown) to contact and clean the transfer surface of the rubber transfer belt 12.
As a result, the cleaning roller removes residual toner including abrasives adhering to the transfer surface of the transfer belt 12, paper dust from the paper, and the like, and cleans the transfer surface of the transfer belt 12. Further, the scraper is scraped off in contact with the cleaning roller, and the toner scraped off from the cleaning roller is collected in another collecting container using a feed roller, for example.

By the way, the surface of the photosensitive drum 18 can be actively accelerated and suppressed in accordance with the state of use.
In this embodiment, an abrasive supply unit 71 is installed in the vicinity of the cleaning roller of the cleaning unit 70. The container of the abrasive supply unit 71 has an opening through which the abrasive can be supplied to the peripheral wall of the cleaning roller. Have.

The supply of the abrasive to the cleaning roller is selectively used according to the use state of the photosensitive drum 18 and the use state of the transfer belt 12, and this is performed by a drive signal from the controller 90 shown in FIG. Is done.
Specifically, the controller 90 includes an initial state determination unit 92 and a polishing execution unit (V-shaped phenomenon eliminating unit) 93.

The initial state determination unit 92 determines whether it is an initial drum and whether it is an initial belt, and outputs the determination result to the polishing execution unit 93. The polishing execution unit 93 supplies an abrasive when the polishing rate of the intermediate transfer belt 12 with respect to the initial drum is increased.
Referring to FIG. 4, a flowchart of the wear promotion control by the controller 90 is shown. Hereinafter, the operation of the printer 1 according to the present invention will be described.

In step S401 in FIG. 4, it is determined whether or not the initial state determination unit 92 is an initial drum. For example, the surface potential of the photosensitive drum 18 does not reach a desired voltage, and the photosensitive member has deteriorated charging characteristics. It is determined whether or not the drum 18 has reached a reference predetermined number of sheets (for example, 10,000 sheets in total) that can be simulated.
For example, when it is determined that the output for a total of 5,000 sheets has been completed, it can be assumed that the initial drum whose charging characteristics are deteriorating due to a decrease in the surface potential of the photosensitive drum 18 is determined as YES. Then, the process proceeds to step S402.

Next, in step S402, it is determined whether or not the initial state determination unit 92 is an initial belt. Specifically, the contact period with the photosensitive drum 18 is short, and the surface of the photosensitive drum 18 is covered with the intermediate transfer belt 12. It is determined whether or not it is in an unused state that cannot be polished sufficiently.
The initial state determination unit 92 is a case where the initial belt, for example, a new intermediate transfer belt 12 has just been replaced, and even if the intermediate transfer belt 12 in this state comes into contact with the photosensitive drum 18, the surface potential thereof. When lowering, the determination is YES, the process proceeds to step S403, and the polishing execution unit 93 executes wear promotion control.

  Specifically, the polishing execution unit 93 in step S403 outputs a drive signal for opening the container of the abrasive supply unit 71 to the cleaning unit 70 described above. As a result, the abrasive is supplied from the container to the cleaning roller and adheres to the transfer surface of the intermediate transfer belt 12. Then, the surface of the photosensitive drum 18 is polished by contact with the transfer belt 12 using the newly supplied abrasive and exits a series of routines.

  On the other hand, when the intermediate transfer belt 12 is a durable belt that is not an initial belt in step S402, for example, when a considerable period has elapsed since the replacement of the intermediate transfer belt 12 with a new intermediate transfer belt 12, or the printing mode of the printer 1 is high. When there is a large amount of abrasive that polishes the photosensitive drum 18 with the density set, or even when the printing mode is set to a low density, the toner deteriorated inside the developing device 24 is discharged, and this toner is removed. When the toner discharge mode to be collected by the cleaning unit 50 is set or the like, if the intermediate transfer belt 12 in this state comes into contact with the photosensitive drum 18, the surface potential can be held or raised at the same value, the process proceeds to step S404. The polishing execution unit 93 also executes wear promotion control.

  However, the polishing execution unit 93 in step S404 does not output a drive signal for opening the container of the abrasive supply unit 71 to the cleaning unit 70 described above. In this case, the abrasive contained in the toner from the developing device 24 can adhere to the transfer surface of the intermediate transfer belt 12. Then, the surface of the photosensitive drum 18 is polished by contact with the transfer belt 12 using an abrasive already attached to the transfer surface of the transfer belt 12, and then exits a series of routines.

  In addition, when it is determined in step S401 described above that the output of a predetermined reference number (for example, 10,000 sheets in total) that can be assumed to be the photosensitive drum 18 having the above-described deterioration in charging characteristics has been completed. It can be assumed that the surface potential of the photosensitive drum 18 has risen to the state of a durable drum. Therefore, the polishing execution unit 93 controls the wear suppression, more specifically, if the abrasive from the abrasive container is supplied to the cleaning roller, the supply of the abrasive is prohibited and the series of routines are quickly exited. .

  Returning to FIG. 1 again, when the printer 1 performs printing, the paper feed roller 46 separates and feeds the paper from the paper feed cassette 4 one by one. The sent paper reaches the registration roller 14. The registration roller 14 corrects the oblique feeding of the paper and measures the image transfer timing with the toner image formed by the image forming unit 16, while feeding the paper to the secondary transfer unit 30 at a predetermined paper feed timing. Send it out.

On the other hand, the input port 91 in FIG. 2 is configured to be able to receive image data as a printing source from the outside. This image data is data in which various images such as characters, codes, figures, symbols, diagrams, and patterns are converted into data. Based on this data, the controller 90 controls light irradiation and the like.
Specifically, the eraser lamp 19 is turned on for each photosensitive drum 18 (FIG. 3), and the charger 20 charges the surface of the photosensitive drum 18 respectively.

Next, when the exposure unit 15 irradiates the surface of the photosensitive drum 18 with laser light, an electrostatic latent image is formed on the surface of each photosensitive drum 18, and a toner image of each color is formed from the electrostatic latent image. The
Each toner image is superimposed on the intermediate transfer belt 12 (primary transfer) and is secondarily transferred to a sheet by the secondary transfer unit 30. The toner remaining on the surface of the photosensitive drum 18 is removed by the cleaning unit 50, and the toner remaining on the transfer surface of the intermediate transfer belt 12 is removed by the cleaning unit 70 described above.

Subsequently, the sheet is fed toward the fixing unit 32 with an unfixed toner image carried thereon, and is heated and pressed by the fixing unit 32 to fix the toner image. Thereafter, the sheet sent from the fixing unit 32 is discharged to the discharge tray 36 via the discharge roller 35 and stacked in the height direction.
When double-sided printing is performed on this single-sided printing, the conveyance direction of the paper discharged from the fixing unit 32 is switched by the discharge branching unit 34.

That is, the sheet printed on one side is pulled back into the apparatus main body 2 and conveyed to the duplex printing conveyance path 38. Subsequently, the sheet is sent toward the upstream side of the registration roller 14 and is sent again toward the secondary transfer unit 30. As a result, the toner image is transferred to the surface of the paper that has not been printed.
By the way, the above-described initial state determination unit 92 measures the number of printed sheets and determines the usage state of the photosensitive drum 18, but is not necessarily limited to this example. The potential can be monitored and the state of the initial drum and the state of the durable drum can be determined based on the detection result.

  On the other hand, in the above-described embodiment, the powder abrasive is described. However, the abrasive formed in a rod shape is applied to the transfer surface of the intermediate transfer belt 12 based on the drive signal from the polishing execution unit 93. It may be contacted and separated. In addition, when a roller having a polishing function is disposed on the intermediate transfer belt, a rod-shaped abrasive may be brought into contact with and separated from the polishing roller.

As described above, according to this embodiment, a toner image obtained by developing the latent image with toner is formed on the surface of the photosensitive drum 18 by driving the photosensitive drum 18, and this toner image is transferred to the intermediate transfer belt 12. First transfer is performed on the transfer surface. The toner image is superimposed on the transfer surface and secondarily transferred onto the paper.
Here, even if a silicon compound is added and a single-layer OPC drum having the property of being easily worn with a small number of printed sheets is selected, the number of printed sheets can be increased to about 20,000 with the conventional intermediate transfer belt 12 alone. Until it reaches, the surface of the photosensitive drum 18, more specifically, the extreme surface layer portion that is exposed to the gas generated during charging and oxidatively deteriorates is difficult to be scraped.

  Then, the charging characteristics deteriorate in the initial drum. As shown by the one-dot chain line in FIG. 5, this phenomenon is caused by applying a desired voltage to the photosensitive drum 18 from the charging by taking the surface potential of the photosensitive drum 18 as the vertical axis and the number of printed sheets as the horizontal axis. In spite of this, the surface potential appears in a curved shape like an approximate V-shape of the alphabet (V-shaped phenomenon).

The broken line in the figure is a case using a corona discharge type charger. The decreasing tendency of the surface potential is the same as that of the charger 20 in direct contact with the photosensitive drum 18. However, it can be seen that the V-shaped phenomenon appears more markedly in the contact charger 20 shown in this embodiment than in the corona discharge method.
More specifically, a period of about 1/10 of the expected usage period (endurance guarantee) of the photosensitive drum 18 has elapsed, for example, until the number of printed sheets reaches about 10,000, or this photosensitive drum. Until the surface of 18 is worn by about 1-2 μm (1 μm = 1 × 10 ⁻⁶ m), the surface potential continues to decrease and reaches a minimum value. This is a characteristic of the initial drum. Thereafter, the surface potential starts to rise and shifts from the initial drum to a durable drum state. Subsequently, when the surface potential further rises and, for example, the number of printed sheets reaches about 50,000, it recovers to a desired value.

  Therefore, in this embodiment, the V-shaped phenomenon eliminating means is applied to the intermediate transfer belt 12, and abrasive is supplied to the transfer surface of the transfer belt 12 to actively promote the wear of the initial drum. As a result, the linear velocity difference between the transfer belt 12 and the photoconductor drum 18 is combined with the wear of the surface of the photoconductor drum 18 to quickly eliminate the deterioration of the charging characteristics. As a result, it becomes a state close to a durable drum immediately from the unused time, and a desired surface potential can be obtained.

  This point will be described in detail. When the abrasive is supplied from the container of the abrasive replenisher 71 of the cleaning unit 70, as shown by the solid line in FIG. 5, the wear of the photosensitive drum 18 proceeds until the number of printed sheets reaches about 10,000, and the photosensitive drum 18 is exposed. The surface potential of the body drum 18 starts to rise. Next, the surface potential further increased until reaching about 20,000 sheets, and a large decrease in the surface potential of the photosensitive drum 18 could be suppressed.

  In addition, when the intermediate transfer belt 12 is not the initial belt, that is, when the transfer belt 12 is in use, a large amount of abrasive is adhered to the transfer surface, and the surface of the photosensitive drum 18 is removed with this abrasive. Can be polished. On the other hand, in the state of the initial belt, for example, when the transfer belt 12 is newly replaced, the transfer belt 12 in an unused state cannot be expected to adhere this abrasive, and promotes the surface wear of the photosensitive drum 18. There are concerns that cannot be made. However, if the polishing execution unit 93 outputs a signal for supplying an abrasive to the transfer surface of the transfer belt 12 in an unused state, there is no concern.

Further, the supply of the abrasive to the intermediate transfer belt 12 is performed in the state of the initial drum, but is prohibited in the state of the durable drum, and the progress of wear of the durable drum is delayed. Therefore, the life of the photosensitive drum 18 can be extended, and good image formation can be performed over a long period of time, and the reliability of the printer 1 is improved.
Furthermore, the use of an abrasive such as titanium oxide ensures that the initial drum wears faster.

  The OPC drum 18 having an organic photosensitive layer is inexpensive and easy to mass-produce. However, the surface is extremely smooth, and the surface smoothness has a great influence on the initial drum. On the other hand, there is a concern that the surface is easily scraped and the wear has a big influence on the durable drum. , The characteristics of the OPC drum 18 can be maintained over a long period of time, and a particularly remarkable effect is achieved.

  Further, since the contact charging type charger 20 does not generate ozone or nitrogen oxide as compared with the case of the corona discharge type charging device, the image quality can be improved, but the charging characteristic of the initial drum is low. Deteriorates significantly. However, if the above-described V-shaped phenomenon eliminating means is provided, a desired surface potential can be obtained even if the contact charging type charger 20 is used, and it becomes unnecessary to correct the charging current during image formation.

The present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the claims.
For example, in the above-described embodiment, an example in which the image forming apparatus is embodied in a printer is shown. However, the image forming apparatus of the present invention can naturally be applied to a multifunction machine, a copier, a facsimile machine, and the like.

  Also in this case, similarly to the above, there is an effect that the deterioration state of the charging characteristic of the photosensitive drum close to the unused state can be quickly eliminated.

1 Printer (image forming device)
12 Intermediate transfer belt (transfer belt)
18 Photosensitive drum 20 Charger 70 Cleaning unit (V-shaped phenomenon eliminating means)
93 Polishing execution part (V-shaped phenomenon elimination means)

Claims (5)

An image forming apparatus that forms a toner image by developing a latent image formed on a surface of a photosensitive drum through charging or exposure with toner,
A transfer belt having a transfer surface facing the surface of the photosensitive drum and onto which the toner image is transferred;
The transfer belt is applied to the transfer belt, and an abrasive is supplied to the transfer surface of the transfer belt to promote the wear of the photosensitive drum. The charging characteristic is deteriorated due to the surface property of the photosensitive drum when not in use. V-shaped phenomenon elimination means for eliminating the state ,
The V-characteristic elimination means prohibits the supply of the abrasive to the transfer belt as it shifts from an initial state where the charging characteristics deteriorate to a durable state where the charging characteristics recover. Forming equipment. The image forming apparatus according to claim 1,
The V-shaped phenomenon eliminating means supplies an abrasive to the transfer surface of an unused transfer belt. The image forming apparatus according to claim 1, wherein
The image forming apparatus, wherein the abrasive is a metal oxide . The image forming apparatus according to any one of claims 1 to 3,
The photosensitive drum, the image forming apparatus which is a photosensitive drum having a photosensitive layer of an organic on its surface. An image forming apparatus according to any one of claims 1 to 4,
An image forming apparatus , further comprising a charger for charging the surface of the photosensitive drum in contact with the surface .

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