JP2000019853A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and surely prevent the surface resistivity of an intermediate transfer body from being fluctuated by providing a device with a grinding means grinding the surface of the substrate of the intermediate transfer body and to form an excellent image by eliminating the splash of toner and void. SOLUTION: The toner images T of respective color components formed by respective image forming units 10 are successively primarily transferred on the intermediate transfer belt 20 so as to be superposed. Thereafter, they are secondarily transferred on a paper P. Then, the paper P on which the toner images are transferred is guided to a fixing unit 54 through a carrying belt 53. The grinding means 60 for grinding the substrate itself of the belt 20 is disposed at the downstream side of a belt cleaner 41 and at the upstream side of a primary transfer position. The grinding means 60 is disposed so that a grinding plate which is constituted of a spring material such as stainless steel and whose thickness is about 0.1 mm is pressed to the surface of the belt 20. The abutting part of the grinding plate is made smooth so as to obtain a grinding characteristic that the surface roughness Rz of the surface of the substrate of the ground intermediate transfer body 20 becomes <=3 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, and a multifunction machine provided with an intermediate transfer member.
In particular, the present invention relates to an image forming apparatus that can prevent the surface resistivity of the intermediate transfer body from fluctuating and deteriorating image quality.

[0002]

2. Description of the Related Art Copiers and printers equipped with an intermediate transfer member rotate a toner image formed on an image carrier such as a photosensitive member that is driven by rotation, for example, by an electrophotographic process in synchronization with the image carrier. The image is primarily transferred onto a belt-shaped (or drum-shaped) intermediate transfer body made of a driven dielectric substrate, and then secondary-transferred to a recording material such as recording paper or an OHP sheet via the intermediate transfer body. Forming (copying and printing) is performed.

In particular, when a color image is formed in a copying machine or the like using the intermediate transfer member, a toner image of each of three or four color components constituting the color image is formed on an image bearing member. Since it is possible to transfer images onto a recording material in a batch by accurately superimposing them sequentially on the intermediate transfer body, and to obtain a high-quality color image without color shift due to transfer shift, It is fully adaptable.

[0004] In such a copying machine or the like, usually,
A dedicated cleaning device provided with a scraping blade or the like for removing unnecessary substances such as residual toner adhered to the surface of the intermediate transfer member after the secondary transfer is provided. After the completion, the surface of the substrate of the intermediate transfer member is always kept in a clean state free of unnecessary deposits such as toner.

However, in this type of copying machine or the like,
Despite the provision of the dedicated cleaning device as described above, unnecessary substances such as residual toner are not completely removed from the intermediate transfer body due to poor cleaning or the like, and remain on the intermediate transfer body and accumulate. As a result, there is a problem that a filming layer made of a residual toner or the like is gradually formed on the surface of the intermediate transfer body, so that transfer performance is deteriorated and quality of an obtained image is also deteriorated.

For this reason, conventionally, there has been proposed an image forming apparatus in which a filming layer removing means for removing the filming layer formed on the intermediate transfer member as described above is provided (for example, an image forming apparatus). JP-A-2-262180, JP-A-5-273893). Specifically, such a filming layer removing means is constituted by a cleaning roll or a brush roll which is brought into sliding contact with the surface of the intermediate transfer member on the downstream side of the cleaning device in the intermediate transfer member.

[0007]

However, in a copying machine or the like provided with an intermediate transfer member, even when the filming layer removing means is provided, the image such as toner scattering or white spots is still present. There is a case where a defect occurs and the image quality is reduced.

According to the study of the present inventors, when an image is formed using an intermediate transfer member, the surface resistivity of the intermediate transfer member gradually decreases as the number of image formation (number of sheets) increases. It has been confirmed that in the image area corresponding to the portion of the intermediate transfer member whose surface resistivity has been reduced, the above-mentioned toner scatter and the white spots tend to occur. For example, after continuously forming a large number of A4 size images, and then forming an A3 size image larger than the A4 size, for example, when the A3 size image is obtained, In the area corresponding to the image of the A4 size, the surface resistivity of the intermediate transfer body is reduced, and the above-mentioned image defect occurs.

Further, a study was conducted on such a phenomenon of a decrease in the surface resistivity of the intermediate transfer member. The decrease in the surface resistivity occurs even when there is no unnecessary deposit such as toner attached to the surface of the intermediate transfer member. It has been found.

The decrease in the surface resistivity is not caused by the presence of undesired substances adhering to the surface of the intermediate transfer member, but the surface layer of the substrate itself of the intermediate transfer member is carbonized for some reason and becomes conductive. It became clear that this occurred. In addition, the phenomenon of the decrease in the surface resistivity does not occur when the bias voltage applied in the secondary transfer portion is set to zero, but occurs when the bias voltage is increased. And the recording material has a low water content and is more remarkably generated when the recording material is in a high resistance state. Therefore, the carbonization of the surface layer portion of the base of the intermediate transfer member is caused by the intermediate transfer member and the recording material in the secondary transfer portion. It is presumed that the heat is generated due to the heat generated by the discharge generated during the secondary transfer.

The present invention has been made in view of such circumstances, and an object of the present invention is to simply and reliably prevent a change in the surface resistivity of an intermediate transfer member, and to reduce the change in the surface resistivity. It is an object of the present invention to provide an image forming apparatus capable of performing favorable image formation without causing toner scattering, white spots, and the like caused by the toner.

[0012]

The above object can be achieved.
In the image forming apparatus of the present invention (the invention according to claim 1), after the toner image formed on the rotating image carrier is primarily transferred to the rotating intermediate transfer member, the toner image is transferred onto the intermediate transfer member. An image forming apparatus for forming an image by secondary-transferring a toner image onto a recording material is provided with a polishing means for polishing the surface of the substrate itself of the intermediate transfer body.

Here, the substrate of the intermediate transfer member refers to a component that actually carries the toner image primarily transferred from the image carrier, and is usually formed of a predetermined conductive material on a synthetic resin or rubber base material. In the form of a dielectric film having a predetermined thickness. The intermediate transfer member is formed by forming the film-shaped substrate into a belt shape to form a belt as a whole, or attaching the substrate to the outer peripheral portion of a drum-shaped support to form a drum as a whole. Polishing (polishing amount) of the substrate of the intermediate transfer member by the polishing means is performed within a thickness range in which the substrate does not impair other physical conditions and the like originally required as a substrate of the intermediate transfer member. Further, the polishing amount and the polishing timing may be constant at all times, but it is desirable to set optimal conditions according to various conditions. Further, if necessary, the thickness of the intermediate transfer member may be formed thicker by the thickness corresponding to the polishing amount from the beginning, in consideration of the polishing amount.

According to this image forming apparatus, the substrate of the intermediate transfer member is polished by the polishing means, so that the surface resistivity of the intermediate transfer member does not decrease and becomes stable. The occurrence of image defects such as toner scattering and white spots due to the reduction is prevented.

In this image forming apparatus, when a cleaning means is provided for removing unnecessary substances adhering to the substrate surface of the intermediate transfer body after the secondary transfer, the polishing means is disposed downstream of the cleaning means in the rotation direction of the intermediate transfer body. Side and upstream of the primary transfer section, and polishing of the polishing means so that the surface roughness (Rz) of the substrate of the intermediate transfer body polished by the polishing means is 3 μm or less. It is preferable to set characteristics.

In this case, the intermediate transfer member from which unnecessary substances such as toner are removed in advance by the cleaning device is polished by the polishing means. As a result, the intermediate transfer member is polished by the polishing means. Polishing of the substrate itself is more accurately performed. Further, by setting the polishing characteristics of the polishing means so as to satisfy the above-described conditions, even when using a cleaning means for scraping off unnecessary materials with a blade, the intermediate transfer body substrate always has the surface roughness. As a result, the unnecessary surface of the intermediate transfer member is more reliably removed by the blade.
In addition, as a result, the surface of the substrate of the intermediate transfer member is not stained by unnecessary deposits, so that the polishing of the substrate surface itself by the polishing means is performed more accurately.

Further, in such an image forming apparatus, it is preferable that the polishing means is constituted by a plate-like member which comes into contact with the surface of the base of the intermediate transfer member.

In this case, the substrate of the intermediate transfer member can be reliably and uniformly polished by the polishing means with the simplest configuration. At this time, it is desirable that the plate-shaped member as the polishing means is disposed in a contact posture such that the contact portion with the intermediate transfer member faces downstream in the rotation direction of the intermediate transfer member.

Further, in such an image forming apparatus, the initial surface resistivity of the substrate of the intermediate transfer member is 10 ⁸ Ω /.
□ It is preferable to set the above.

In the case where the substrate of the intermediate transfer member having such an initial surface resistivity is polished by the polishing means, the effect of preventing the fluctuation of the surface resistivity of the substrate can be obtained most effectively.

[0021]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

Embodiment 1 FIG. 1 is a schematic diagram showing an embodiment of a color image forming apparatus to which the present invention is applied. This color image forming apparatus basically has a plurality of image forming units for forming toner images of respective color components (black Bk, yellow Y, magenta M, cyan C) by, for example, an electrophotographic method as shown in FIG. 10 (specifically, 10Bk, 10Y, 10M,
10C) are arranged in parallel, and each of the image forming units 10
After the primary transfer of the respective color component toner images T formed in step (1) so as to be sequentially superimposed on the intermediate transfer belt 20, the transfer toner images multiplex-transferred onto the intermediate transfer belt 20 as the recording material supplied from the supply tray 50 The sheet P is secondarily transferred onto the sheet P, and thereafter, the sheet P after the transfer is guided to the fixing device 54 via the transport belt 53. Thereby, a desired color image is formed.

The image forming unit 10 for each color component includes a photosensitive drum 11 (specifically, 11Bk, 11Y, 11M, 11B) as an image carrier that is driven to rotate in the direction of arrow A in FIG.
Around C), a charger 12 for uniformly charging the photoconductor drum 11, a laser writing device 13 for writing an electrostatic latent image on the photoconductor drum 11, and a toner for each color component are accommodated on the photoconductor drum 11. Developing device 14 for visualizing the electrostatic latent image of
A primary transfer roll 15 for transferring each color component toner image on the photosensitive drum 11 to the intermediate transfer belt 20, a cleaner 16 for removing residual toner and the like on the photosensitive drum, a static eliminator 17 for removing the surface of the photosensitive drum 11, etc. Are sequentially arranged.

For example, when the color image forming apparatus is configured as a digital color copying machine, a document set on a document table (not shown) is read by a color image reading device, and the read signal is converted into a digital signal by image signal processing means. After that, the image is temporarily stored in a memory, and a toner image of each color is formed based on the stored digital image signals of four colors (Bk, Y, M, and C). Further, when the color image forming apparatus is configured as a device such as a printer, a toner image of each color may be formed based on an image signal input to an image signal processing unit from the outside.

The intermediate transfer belt 20 is stretched around a plurality of rolls so as to rotate in the direction of arrow B, and is disposed so as to contact the surface of each photosensitive drum 11. In the figure, reference numeral 21 denotes a driving roll of the intermediate transfer belt 20, reference numeral 22 denotes a support roll, and reference numeral 24 denotes a roll which also serves as an opposing roll (backup roll) for secondary transfer.

The intermediate transfer belt 20 is made of polyimide,
A belt made of a resin such as polycarbonate, polyester, polypropylene and polyethylene terephthalate or various rubbers containing an appropriate amount of a conductive substance such as carbon black and having a thickness of 0.1 mm and a circumference of about 2 m and comprising a single-layer base. The intermediate transfer belt 20 is set so that its surface resistivity is 10 ^11.2 to 10 ^12.4 Ω / □ and its volume resistivity is 10 ⁹ to 10 ¹¹ Ω · cm. Further, the surface of the base of the intermediate transfer belt 20 is formed such that the surface roughness (Rz) is about 1 μm in an initial state.

A primary transfer roll 15 as a primary transfer device is disposed on the back side of the intermediate transfer belt 20 at a position facing the photosensitive drum 11 (primary transfer position). By applying a voltage having a polarity opposite to the charge polarity of the toner to the primary transfer roll 15, the toner image on the photoconductor drum 11 is electrostatically transferred to the intermediate transfer belt 20 side.

A secondary transfer device 40 is provided at a secondary transfer position of the intermediate transfer belt 20 facing the paper P conveyance path. The secondary transfer device 40 includes a secondary transfer roll 25 that is pressed against the toner image bearing surface of the intermediate transfer belt 20.
And a counter roll (backup roll) 24 disposed on the back side of the intermediate transfer belt 20 and serving as a counter electrode of the secondary transfer roll 25. Reference numeral 129 in the figure denotes a paper peeling device provided with a peeling nail for assisting the peeling of the paper P from the intermediate transfer belt 20 after the secondary transfer.

The secondary transfer roll 25 is a grounded conductive roll, and its volume resistivity is set to a low value of 10 ⁷ Ω · cm or less in order to keep its surface potential always the same. Is set. Further, the secondary transfer roll 25 is provided with a cleaning blade 25a made of, for example, urethane rubber in order to remove unnecessary substances adhering to the roll surface. Meanwhile, backup roll 2
Reference numeral 4 denotes a roll in which a semiconductive thin film is coated on a roll having an insulating property. The thin film is formed to a thickness of 10 to 200 μm, and has a surface resistivity of 10 ⁷ to 10 ¹⁰ Ω. Is set to be the resistance region. Further, a bias voltage having the same polarity as the charging polarity of the toner (3 kV in the case of a color image, 2 kV in the case of a monochrome image) is applied to the backup roll 24.
Is supplied stably via the power supply roll 26.

A belt cleaner 41 is provided downstream of the secondary transfer device 40 to remove toner remaining on the intermediate transfer belt 20 without being transferred onto the sheet P. The belt cleaner 41 includes a brush roll 41a and a cleaning blade 41b. Further, on the downstream side of the belt cleaner 41, a reference tape 42 for detecting an image writing timing of the laser writing device 13 attached to an end which is a non-image forming area on the surface side of the intermediate transfer belt 20 is detected. The detection sensor 30 for performing the operation is provided. For example, a polyester film on which aluminum is deposited is used as the reference tape 42, and a reflective photosensor is used as the detection sensor 30.

Further, the paper transport system feeds the paper P from the paper feed tray 50 by the feed roll 51, temporarily stops the positioning by the registration roll (registration roll) 52, and then, at a predetermined timing, the secondary transfer device 40 ( Actually, the secondary transfer roll 25 and the intermediate transfer belt 2
The paper P is fed to the nip portion (0). The sheet P after the secondary transfer is guided to a transfer belt 53 via a sheet transfer guide (not shown), and then transferred to a fixing device 54 by the transfer belt 53. The dashed line in the figure indicates the transport path of the sheet P.

In this color image forming apparatus, as shown in FIGS. 1 and 2, the base itself of the intermediate transfer belt 20 is polished downstream of the belt cleaner 41 and upstream of the primary transfer position. Polishing means 60 is provided. The polishing means 60 is provided such that a polishing plate made of a spring material such as stainless steel and having a thickness of about 0.1 mm is pressed against the surface of the intermediate transfer belt 20 in an abutting posture as shown. In the case of this image forming apparatus, the polishing plate is constantly pressed against the intermediate transfer belt 20. The polishing means 6
The abutting portion of the polishing plate was made smooth so that the polishing properties such that the surface roughness (Rz) of the substrate surface of the intermediate transfer body 20 after the polishing by 0 was obtained was 3 μm or less were obtained.

At this time, it is more desirable to dispose an opposing member such as a roll on the side opposite to the pressing position of the polishing plate as the polishing means 60 against the intermediate transfer belt 20, for example, as in this embodiment. It is preferable to dispose it so as to press against the drive roll 21 of the intermediate transfer belt 20. With this arrangement, accurate rotation of the intermediate transfer belt 20 is not hindered, and thus, there is no risk of image quality defects such as color misregistration of a color image.

In such a color image forming apparatus, an image is formed as follows.

First, the image forming units 10Bk, 1
In 0Y, 10M, and 10C, the photosensitive drums 11Bk, 11Y, 11M, and 11C, which are rotationally driven, are connected to the charger 12B.
k, 12Y, 12M, and 12C are uniformly charged, and the surface of each charged photosensitive drum 11 is
For example, each laser writing device 13 writes an electrostatic latent image corresponding to a digital image signal of each color input from the above-described image signal processing means. Subsequently, the developing devices 14Bk, in which each of these electrostatic latent images contains toner of each color,
The toner images T of the respective color components as described above are formed by the development by 14Y, 14M, and 14C.

Next, the toner images T of the respective color components formed by the respective image forming units 10 are primarily transferred such that they are sequentially superimposed on the intermediate transfer belt 20 at a primary transfer position facing the primary transfer roll 15. Thereafter, the toner image transferred to the intermediate transfer belt 20 is fed between the intermediate transfer belt 20 and the secondary transfer roll 25 (nip portion) at a secondary transfer position where the secondary transfer device 40 is provided. Is secondarily transferred to the paper P to be transferred. Finally,
The paper P on which the toner image has been transferred is then transferred to the transport belt 5
3, the toner image is fixed to the intermediate transfer belt 20 after the completion of the secondary transfer.
The belt cleaner 41 removes unnecessary substances such as residual toner adhering to the surface. Thus, basic image formation is completed.

In this color image forming apparatus, since the polishing means 60 as described above is provided,
After the intermediate transfer belt 20 after the completion of the secondary transfer, the surface of the belt base is constantly polished by the polishing means 60 after the unnecessary deposits are removed by the belt cleaner 41. At this time, the surface roughness (Rz) of the substrate surface of the intermediate transfer belt 20 after being polished by the polishing means 60 is always 3 μm.
As a result, the unnecessary adhering matter on the belt surface is removed by the belt cleaner 41 using a blade or the like, and the surface of the belt base is polished by the polishing means 60 more reliably.

Therefore, according to this color image forming apparatus, during the next image forming process, the intermediate transfer belt 20
Will be used with its substrate surface constantly polished. Thereby, the intermediate transfer belt 2 as described later
The surface resistivity of 0 can be stabilized, and a high-quality image free from image defects such as toner scattering and white spots can be stably obtained.

Next, the following test was conducted using this color image forming apparatus.

First, the image forming unit 10 is not operated (each photosensitive drum 11 is separated from the intermediate transfer belt 20), and the A3 size paper P is collected for a total of 12,0.
The surface resistivity of the intermediate transfer belt 20 when the intermediate transfer belt 20 and its peripheral components (polishing means 60) are operated by feeding paper to the secondary transfer position by an amount equivalent to 00 sheets is measured, and the surface resistivity is measured. The state of change was examined. The environmental conditions at this time were a humidity of 15% RH and a temperature of 10 ° C.
Further, the measurement of the surface resistivity was performed under an application of 100 V using an HR probe and a measuring device (manufactured by Mitsubishi Yuka: Hiresta IP). For comparison, the state of the change in the surface resistivity of the intermediate transfer belt 20 when the polishing by the polishing means 60 was not performed at all was similarly examined. The results are shown in FIG.

Incidentally, when the thickness of the intermediate transfer belt 20 after the feeding of 120,000 sheets was measured, it was 3 μm thinner than the initial thickness (0.1 mm). Therefore, the polishing amount by the polishing means 60 in this case is 3 μm. On the other hand, when the thickness of the intermediate transfer belt for comparison was also measured, the thickness was the same as the initial thickness and did not change.

As shown in FIG. 3, in the case of an intermediate transfer belt which is not polished for comparison (Comparative Example), the surface resistivity sharply decreases from its initial value, whereas Intermediate transfer belt 2 polished by polishing means 60
In the case of 0 (Example), it was confirmed that the surface resistivity hardly changed, and the initial value remained stable for a long time. The surface resistivity of the non-sheet passing area (corresponding to the non-image forming area) of the intermediate transfer belt 20 hardly changed in both the example and the comparative example.

Next, the image forming unit 10 is operated by the color image forming apparatus, and the A3 size paper P
The test prints were repeatedly performed on the print samples, and the image quality of the obtained print samples was examined. As a result, when the polishing of the intermediate transfer belt 20 is not performed (Comparative Example),
After 000 sheets, the density of the secondary transfer image decreases,
In addition, it has been confirmed that image defects such as toner scattering and white spots have occurred as the number of fed sheets has increased. On the other hand, when the intermediate transfer belt 20 is polished (Example), The occurrence of image defects such as toner scattering and white spots as in the comparative example was not particularly observed.

Here, as shown in FIG. 3, since the surface resistivity in the comparative example is stable after decreasing to about 10 ⁸ Ω / □, the initial surface resistivity of the intermediate transfer belt 20 is 3 × Each of the belts set at 10 ¹⁰ Ω / □ and 3 × 10 ⁸ Ω / □ was prepared, and the state of change in the surface resistivity of each intermediate transfer belt was similarly examined. as a result,
It was confirmed that the intermediate transfer belt having any surface resistivity was stable after the surface resistivity decreased and finally decreased to about 10 ⁸ Ω / □.
Therefore, the effect of polishing the intermediate transfer belt 20 to prevent its surface resistivity from fluctuating is that the initial surface resistivity is 10%.
It has been found that when set to ⁸ Ω / □ or more, it can be obtained effectively.

Embodiment 2 FIG. 4 is a schematic diagram showing another embodiment of a color image forming apparatus to which the present invention is applied. In this color image forming apparatus, basically, as shown in FIG. 1, a photosensitive drum 11 on which toner images of respective color components (black Bk, yellow Y, magenta M, and cyan C) are sequentially formed by, for example, an electrophotographic method. After the primary transfer of each color component toner image T formed on the photosensitive drum 11 so as to be sequentially superimposed on the intermediate transfer belt 20, the transfer toner image multi-transferred onto the intermediate transfer belt 20 is supplied. The secondary transfer is performed on paper P as a recording material supplied from a tray 50, and thereafter, the transferred paper P is guided to a fixing device 54 via a transport belt 53. Thereby, a desired color image is formed.

In the color image forming apparatus, the same components as those in the first embodiment have the same contents except for the following differences.

That is, the polishing means 60 is a resin plate in which a synthetic resin is formed into a plate shape, and a polishing paper for low polishing (imperial wrapping film, 9 μm thick, manufactured by Sumitomo 3M) is fixed on the surface of the resin plate. ,
4 is used while being pressed against the area of the intermediate transfer belt 20 supported by the driving roll 21 in a contact posture as shown in FIG. Have been. Further, the arrangement position of the polishing means 60 is substantially the same as in the above-described embodiment,
This is a position downstream of the belt cleaner 41 and upstream of the primary transfer position.

The secondary transfer roll 25, the belt cleaner 41, and the polishing means 60 are each disposed so as to be able to freely contact and separate from the intermediate transfer belt 20 by a retraction device (not shown). These components 25, 41, and 6 are provided before the toner image on the intermediate transfer belt 20 completes the secondary transfer before the toner image passes through the intermediate transfer belt 20.
Each of the reference numerals 0 is separated from the intermediate transfer belt 20.

Next, the following tests were performed using the color image forming apparatus having the above-described configuration.

First, the intermediate transfer belt 2 of the polishing means 60
With respect to the contact / separation condition with respect to 0, in the case of full-color image formation, the polishing means 60 is brought into contact with the intermediate transfer belt for one rotation every time the image forming process of 200 sheets is completed. The setting was such that the polishing means 60 was brought into contact only for one rotation of the intermediate transfer belt every time the image forming process of 2,000 sheets was completed. Under such setting conditions, when the full-color image formation is performed for 60,000 sheets and the monochrome image formation is performed for 60,000 sheets, the state of the change in the surface resistivity of the intermediate transfer belt 20 will be described. The same test as that of No. 1 was conducted and examined.

As a result, first, the final polishing amount of the intermediate transfer belt 20 was about 10 μm. The surface resistivity of the intermediate transfer belt 20 did not change (decrease) in any image formation.

Subsequently, the intermediate transfer belt 2 of the polishing means 60
Regarding the contact / separation condition with respect to 0, in the case of single-sided formation of a full-color image, the polishing means 60 is brought into contact only for one rotation of the intermediate transfer belt each time 1,000 image forming processes are completed. 2 in case of formation
Every time the image forming process of 00 sheets is completed, the intermediate transfer belt 1
It was set so that the polishing means 60 was in contact only during the circumference. Under such setting conditions, one-sided full-color image formation is performed for 60,000 sheets, and the two-sided formation is performed for 30,000 sheets.
The same test was performed to determine how the surface resistivity of the intermediate transfer belt 20 changed at that time.

As a result, first, the final polishing amount of the intermediate transfer belt 20 was about 7 μm. The surface resistivity of the intermediate transfer belt 20 did not change (decrease) in any image formation.

Embodiment 3 In this embodiment, a roll in which an ionic conductive agent is added to a urethane foam to adjust the volume resistance thereof is used as the primary transfer roll 15 in the embodiment 2,
As the polishing means 60, a resin plate coated and fixed with a # 500 paper file is used.
A color image forming apparatus having the same configuration as that of the second embodiment except that the contact / separation condition with respect to the transfer belt 20 of 0 was set according to the humidity environment condition was prepared.

In particular, as for the contact / separation condition of the polishing means 60 with respect to the transfer belt 20, the voltage of the primary transfer roll 15 to which a bias voltage for primary transfer is applied is measured by a constant current control method, and the measured value is set in advance. After comparing the threshold value with the threshold value, if it is determined that the environment is a high humidity environment (humidity 70% RH or more), the polishing means 60 is not contacted.
When it is determined that the environment is low humidity, the setting is made so that the polishing means 60 is brought into contact with the intermediate transfer belt only for one rotation every time 500 image forming processes are completed. Under such setting conditions, image forming is performed for 120,000 sheets,
The state of the change in the surface resistivity of the intermediate transfer belt 20 at that time was examined by performing the same test as in the second embodiment.

As a result, first, the final polishing amount of the intermediate transfer belt 20 was about 15 μm. The surface resistivity of the intermediate transfer belt 20 did not change (decrease) at all.

◎ Other Embodiments In the first to third embodiments, the case where a belt-shaped intermediate transfer belt 20 is used as the intermediate transfer body is exemplified, but the drum-shaped intermediate transfer body is used as the intermediate transfer body. (Intermediate transfer drum) may be used. Further, in the first embodiment, the configuration in which the polishing plate of the polishing means 60 is always brought into contact with the intermediate transfer belt 20 has been described. However, the polishing plate is fixed to a predetermined position by the retract mechanism as illustrated in the second and third embodiments. At the timing described above, the intermediate transfer belt 20 may be brought into contact with or separated from the intermediate transfer belt 20. Further, the polishing means in the present invention is not limited to a plate-like form as exemplified in each of the above-described embodiments, but may be any other form as long as it can realize the required purpose and function. And may be, for example, a cylinder or a column.

[0058]

As described above, according to the image forming apparatus of the present invention, the variation of the surface resistivity of the intermediate transfer member can be reduced by only polishing the substrate surface itself of the intermediate transfer member by the polishing means. It is simple and reliable, and can be prevented for a long time. As a result, it is possible to stably perform good image formation without causing image defects such as toner scattering and white spots due to such fluctuations in surface resistivity. Can be.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a color image forming apparatus according to a first embodiment.

FIG. 2 is an enlarged view of a main part showing an arrangement state of a polishing means.

FIG. 3 is a graph showing measured data on the surface resistivity of an intermediate transfer member.

FIG. 4 is a schematic diagram illustrating a color image forming apparatus according to a second embodiment.

[Explanation of symbols]

11 photoreceptor drum (image carrier), 20 intermediate transfer belt (intermediate transfer member), 41 belt cleaner (cleaning means), 60 polishing means.

Claims (4)

[Claims] 1. A method according to claim 1, wherein the toner image formed on the rotating image carrier is primarily transferred to a rotating intermediate transfer member, and then the toner image transferred on the intermediate transfer member is secondarily transferred to a recording material. An image forming apparatus for forming an image according to claim 1, further comprising a polishing means for polishing a surface of the substrate of the intermediate transfer body itself. 2. The apparatus according to claim 1, further comprising a cleaning unit for removing unnecessary substances attached to the surface of the base of the intermediate transfer body after the secondary transfer. The intermediate transfer member is disposed at a position downstream of the rotation direction and upstream of the primary transfer position, and the surface roughness (Rz) of the substrate of the intermediate transfer member polished by the polishing means is 3 μm or less. An image forming apparatus, wherein the polishing characteristics of the means are set. 3. An image forming apparatus according to claim 1, wherein said polishing means is constituted by a plate-like member which comes into contact with a surface of a substrate of said intermediate transfer member. 4. The apparatus according to claim 1, wherein the substrate of the intermediate transfer member has an initial surface resistivity of 10 ^8.
An image forming apparatus characterized by being set to Ω / □ or more.