JPH0844219A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent slipping caused by deficiency in driving force for driving an intermediate transfer body. CONSTITUTION:This device provided with the intermediate transfer body 28 extended on plural rollers and rotated and transferring a toner image on an image carrier 12 onto the intermediate transfer body 28 and further, a transfer material is provided with a means for deciding whether the driving force of the intermediate transfer body 28 is deficient or not and a means for compensating the driving force for driving the intermediate transfer body 28 at the time of transferring the toner image thereon to the transfer material, when it is decided that the driving force for driving the intermediate transfer body 28 is deficient by the deciding means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a printer, a facsimile, etc. for transferring a toner image formed on an image carrier onto an intermediate transfer member and transferring the toner image on the intermediate transfer member onto a transfer material. The present invention relates to an image forming apparatus.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a printer or a facsimile, a toner image is formed on an image carrier, and the toner image on the image carrier is transferred onto an intermediate transfer member. There is one that carries the toner image and conveys it to the next step and transfers the toner image on the intermediate transfer member to a transfer material.
Here, the intermediate transfer member is an intermediate transfer belt or the like that is formed in an endless belt shape and is stretched around a plurality of rollers and rotated. The intermediate transfer body carries the toner image transferred from the image carrier and conveys it by rotation, and the toner image on the intermediate transfer body is transferred to a transfer material such as transfer paper by the transfer material transfer means. Further, the intermediate transfer member is cleaned by the cleaning unit after transferring the toner image onto the transfer material.

In the image forming apparatus having such an intermediate transfer member, when the toner image on the intermediate transfer member is transferred to the transfer material by the transfer material transfer means, the transfer material comes into contact with the intermediate transfer member and the intermediate transfer member. A large load is applied to the intermediate transfer member, and the driving force for driving the intermediate transfer member becomes insufficient, which may cause the intermediate transfer member to slip with respect to the drive roller that drives the intermediate transfer member.

Further, the cleaning means for cleaning the intermediate transfer member comes into contact with the intermediate transfer member and a large load is applied to the intermediate transfer member,
As a result, the driving force for driving the intermediate transfer body becomes insufficient, and the intermediate transfer body may slip with respect to the drive roller that drives the intermediate transfer body. Therefore, when the toner image on the intermediate transfer body is transferred to the transfer material or when the intermediate transfer body is cleaned, the intermediate transfer body is brought into contact with the image carrier or the transfer material transfer means is used as the intermediate transfer body. An image forming apparatus has been proposed in which the above problem is solved by bringing the above into contact with the above.

[0005]

In the image forming apparatus having the intermediate transfer member, the driving force for driving the intermediate transfer member has no problem for a while after the maintenance, and the toner and the paper dust in the apparatus are scattered during the use of the machine. Or, it becomes a problem with time due to abrasion powder of the intermediate transfer member, abrasion and dirt of the roller. However, in the above image forming apparatus, when the toner image on the intermediate transfer body is transferred to the transfer material or when the intermediate transfer body is cleaned, the intermediate transfer body is brought into contact with the image carrier or the transfer material is transferred. Since the transfer means is brought into contact with the intermediate transfer body, the intermediate transfer body is brought into contact with the image carrier even when the driving force for driving the intermediate transfer body is sufficiently obtained, or the transfer material transfer means is used. Since the intermediate transfer body is brought into contact with the intermediate transfer body, abrasion of the intermediate transfer body, rollers, etc. is promoted, and the amount of toner adhered to the transfer material transfer means is increased to reduce the margin for back stain of the transfer material. The problem arises.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of preventing slippage due to insufficient driving force for driving an intermediate transfer member and minimizing the occurrence of the above problems.

[0007]

In order to achieve the above object, the invention according to claim 1 is formed into an endless belt,
It has an intermediate transfer member that is stretched and rotated by a plurality of rollers, transfers the toner image formed on the image carrier onto the intermediate transfer member, and transfers the toner image on the intermediate transfer member onto a transfer material. In an image forming apparatus for transfer, a driving force shortage determination unit that determines whether or not the driving force that drives the intermediate transfer member is insufficient, and a driving force that drives the intermediate transfer member by the driving force shortage determination unit. When it is determined that the toner image on the intermediate transfer body is insufficient, a driving force assisting means for supplementing the driving force for driving the intermediate transfer body when transferring the toner image on the intermediate transfer body is provided.

According to a second aspect of the present invention, there is provided an intermediate transfer member which is formed in an endless belt shape and is stretched around a plurality of rollers and rotated. The toner image formed on the image carrier is transferred to the intermediate transfer member. In the image forming apparatus, in which the toner image on the intermediate transfer member is transferred to the transfer material by the transfer material transfer unit, and the intermediate transfer member is cleaned by the cleaning unit, a driving force for driving the intermediate transfer member. The driving force shortage determining means for determining whether the intermediate transfer body is insufficient, and when the driving force shortage determining means determines that the driving force for driving the intermediate transfer body is insufficient, And a driving force assisting means for supplementing the driving force for driving the intermediate transfer member when cleaning the toner.

The invention according to claim 3 is the invention according to claim 1 or 2.
In the image forming apparatus described above, the driving force shortage determination means measures a slip amount between a drive roller that drives the intermediate transfer member and the intermediate transfer member, and when the slip amount exceeds a reference value. It is determined that the driving force for driving the intermediate transfer member is insufficient.

According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the slip amount is measured by the driving force shortage determining means when the image forming apparatus main body is powered on.

The invention according to claim 5 is the invention according to claim 1 or 2.
In the image forming apparatus described above, the driving force shortage determination means measures an accumulated operation time of the intermediate transfer body after maintenance of an intermediate transfer unit including the intermediate transfer body, and the accumulated operation time exceeds a reference value. In this case, it is determined that the driving force for driving the intermediate transfer member is insufficient.

The invention according to claim 6 is the invention according to claim 1 or 2.
In the image forming apparatus described above, the driving force assisting means brings the intermediate transfer member into contact with the image carrier,
It complements the driving force for driving the intermediate transfer member.

According to a seventh aspect of the invention, in the image forming apparatus according to the sixth aspect, the image carrier which is in contact with the intermediate transfer body is charged.

According to an eighth aspect of the invention, in the image forming apparatus according to the second aspect, the driving force assisting means drives the intermediate transfer body by bringing the intermediate transfer body into contact with the transfer material transfer means. This is to supplement the driving force to drive.

According to a ninth aspect of the present invention, in the image forming apparatus according to the eighth aspect, the transfer material transfer means in contact with the intermediate transfer member is charged.

[0016]

According to the present invention, the driving force shortage determining means determines whether or not the driving force for driving the intermediate transfer body is insufficient, and the driving force shortage determining means drives the intermediate transfer body. If it is determined that the toner is insufficient, the driving force assisting means supplements the driving force for driving the intermediate transfer member when the toner image on the intermediate transfer member is transferred to the transfer material.

According to the second aspect of the present invention, the driving force shortage determining means determines whether or not the driving force for driving the intermediate transfer body is insufficient, and the driving force shortage determining means drives the intermediate transfer body. When it is determined that the toner is insufficient, the driving force for driving the intermediate transfer member when cleaning the toner on the intermediate transfer member is supplemented by the driving force assisting means.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the driving force shortage determining means measures the slip amount between the drive roller driving the intermediate transfer member and the intermediate transfer member. Then, when this slip amount exceeds the reference value, it is determined that the driving force for driving the intermediate transfer member is insufficient.

According to a fourth aspect of the invention, in the image forming apparatus according to the third aspect, the measurement of the slip amount by the driving force shortage determining means is performed when the power of the image forming apparatus main body is turned on.

According to a fifth aspect of the present invention, in the image forming apparatus according to the first or second aspect, the driving force deficiency determining unit indicates the cumulative operating time of the intermediate transfer member after the maintenance of the intermediate transfer unit including the intermediate transfer member. When the accumulated operation time exceeds the reference value by measurement, it is determined that the driving force for driving the intermediate transfer member is insufficient.

According to a sixth aspect of the present invention, in the image forming apparatus according to the first or second aspect, the driving force assisting means brings the intermediate transfer member into contact with the image carrier to drive the intermediate transfer member. To make up for.

According to a seventh aspect of the invention, in the image forming apparatus according to the sixth aspect, the image carrier that is in contact with the intermediate transfer body is charged.

According to an eighth aspect of the present invention, in the image forming apparatus according to the second aspect, the driving force assisting means applies the driving force for driving the intermediate transfer body by bringing the intermediate transfer body into contact with the transfer material transfer means. compensate.

According to a ninth aspect of the present invention, in the image forming apparatus according to the eighth aspect, the transfer material transfer means in contact with the intermediate transfer member is charged.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention has an intermediate transfer member formed in the shape of an endless belt and stretched around a plurality of rollers and rotated, and the toner image formed on an image carrier such as a photoconductor is intermediately transferred to the intermediate transfer member. The present invention relates to an image forming apparatus that transfers onto a transfer body and transfers the toner image on the intermediate transfer body onto a transfer material such as transfer paper,
Examples in which an intermediate transfer belt is used as the intermediate transfer member will be described below.

FIG. 1 schematically shows a first embodiment of the present invention,
FIG. 2 is an enlarged view showing a portion around the photosensitive drum and the intermediate transfer belt, and FIGS. 3 and 4 show operation timings of the first embodiment. The first embodiment is defined by claims 1, 3,
4 is an embodiment of the invention described in 4, 6, 7 and is an example of an electrophotographic image forming apparatus including a color copying apparatus. Color image reading device (hereinafter referred to as color scanner) 1
Illuminates the original 3 on the original table 2 with the illumination lamp 4,
The reflected light image is formed on the color sensor 9 via the mirror groups 5 to 7 and the lens 8 to read the color image information of the original by color separation for each of blue, green and red, and read it as an electric image signal. Convert.

The color sensor 9 includes color separation means for separating the color image information of the original into, for example, blue, green and red.
An image pickup device, such as a CCD, which converts the image information of each color separated by the color separation means into an electric image signal.
It is configured by and to obtain image signals of each color of blue, green and red. The image signal of each color obtained by the color sensor 9 is subjected to color conversion processing by an image processing unit (not shown) based on the intensity level thereof, and black (hereinafter referred to as BK), cyan (hereinafter referred to as C)
,), Magenta (hereinafter, referred to as M), and yellow (hereinafter, referred to as Y) color image data.

An electrophotographic color image recording apparatus (hereinafter referred to as a color printer) 10 forms a visible image of BK, C, M and Y by the color image data from the image processing section and makes a final color copy. create. Where BK,
Color scanner 1 for obtaining C, M, Y image data
1 receives the scanner start signal in timing with the operation of the color printer 10 from the control unit, and in FIG. 1, the illumination lamp 4 and the optical systems 5 to 7 are driven by the scanner motor to move to the left to move the document table. Two
The upper original is scanned, and image data of one color is obtained each time the original is scanned. The color scanner 1 performs 4 such operations in total.
By repeating this, the image processing unit sequentially outputs BK,
Image data of four colors of C, M and Y are obtained. Then, every time image data of each color is obtained, the color printer 10 sequentially forms a visible image with the image data and superimposes them to create a four-color full-color image.

Next, the color printer 10 will be described. The writing optical unit 11 converts the color image data from the image processing unit into an optical signal and performs optical writing corresponding to the original image on the image carrier 12 formed of a photosensitive drum to form an electrostatic latent image. The writing optical unit 11 includes a laser 13, a light emission drive control unit (not shown) that controls light emission of the laser 13, a polygon mirror 14 that deflects the laser light from the laser 13, a motor 15 that rotates the polygon mirror 14, and f / θ. The laser light from the polygon mirror 14 is formed of a lens 16, a reflection mirror 17, etc., and is imaged on the photosensitive drum 12 via the f / θ lens 16 and the reflection mirror 17.

The photoconductor drum 12 is driven by a photoconductor drum drive motor and rotates counterclockwise as shown by an arrow, around which a photoconductor cleaning device (including a pre-cleaning charge eliminator 18) 19 and a discharge lamp 20 are provided. , Charger 21, potential sensor 22, BK developing device 23, C developing device 2
4, an M developing device 25, a Y developing device 26, a development density pattern detector 27, an intermediate transfer member 28 including an intermediate transfer belt, and the like are arranged.

Each of the developing devices 23 to 26 includes a photosensitive drum 12
A developing sleeve 23 in which the brush of the developer is brought into contact with the surface of the photosensitive drum 12 to rotate in order to develop the electrostatic latent image thereon.
a, 24a, 25a, 26a, and developing paddles 23b, 24 that rotate to scoop up and agitate the developer inside
b, 25b, 26b and toner concentration detection sensors 23c, 24c, 25c, 2 for detecting the toner concentration of the developer
6c and the like. In the standby state, all of the four developing devices 23 to 26 have the developing sleeves 23a, 24a, 25.
Although the developer on the a and 26a is cut off (development inoperative), the order of the development operations of the developing devices 23 to 26 (B
K, C, M, Y image formation order) is BK, C, M, Y
The order is to develop the electrostatic latent image. However, the order of image formation of each color is not limited to this, and may be any order.

At the start of the copying operation, the photosensitive drum 12
Rotates and is uniformly charged by the charger 21. Then, the color scanner 1 starts the reading for obtaining the BK image data at a predetermined timing, the image processing unit obtains the BK image data from the image data from the color scanner 1, and the writing optical based on the BK image data. The unit 11 performs optical writing with a laser beam on the photoconductor drum 12 to form a latent image. Hereinafter, the electrostatic latent image based on this BK image data is referred to as a BK latent image. The electrostatic latent images based on the C, M, and Y image data are also C latent images, M latent images,
It is called a Y latent image. In order to develop this BK latent image from its tip, the developing sleeve 23a starts rotating before the tip of the BK latent image reaches the developing position of the BK developing device 23, and the developer is spiked. BK latent image is developed with BK toner.

Thereafter, the developing operation of the BK latent image area on the photoconductor drum 12 is continued, but when the rear end portion of the BK latent image passes the BK developing position, the developing sleeve 23a of the BK developing device 23 is immediately swept. The developer is cut off and the development is disabled. This is completed at least before the leading edge of the C latent image by the next C image data arrives. The developer is cut off by changing the rotation direction of the developing sleeve 23a to the opposite direction to that during the developing operation. At this time, the other developing units 24 to 26 remain in the non-developing state.

The BK toner image on the photoconductor drum 12 is transferred onto the surface of the intermediate transfer belt 28 which is driven at the same speed as the photoconductor drum 12 (hereinafter, from the photoconductor drum 12 to the intermediate transfer belt 28). Toner image transfer is called belt transfer). The belt transfer is performed in the state where the photosensitive drum 12 and the intermediate transfer belt 28 are in contact with each other.
This is performed by applying a predetermined bias voltage from the high voltage power source to the transfer bias roller 29 which is in contact with the transfer bias roller 29. The intermediate transfer belt 28 is pressed against the photoconductor drum 12 by the contact / separation mechanism when the belt transfer is performed, and is separated from the photoconductor drum 12 when the belt transfer is not performed.

After the BK toner image is transferred, the photoconductor drum 12 is destaticized and cleaned by the photoconductor cleaning device 19 including the pre-cleaning decharger 18, is decharged by the decharging lamp 20, and is recharged uniformly by the charger 21. . It should be noted that the intermediate transfer belt 28 is formed by transferring the BK, C, M, and Y toner images sequentially formed on the photosensitive drum 12 to the same surface in order and transferred.
A belt transfer image of color superposition is formed, and then this belt transfer image is collectively transferred to a transfer paper. The configuration and operation of the intermediate transfer belt unit including the intermediate transfer belt 28 will be described later.

On the side of the photosensitive drum 12, the BK image forming process is followed by the C image forming process. In this C image forming process, the color scanner 1 starts reading for obtaining C image data at a predetermined timing. , The image processing unit obtains C image data from the image data from the color scanner 1 and
Based on the image data, the writing optical unit 11 performs optical writing on the photoconductor drum 12 with laser light, and C
Form a latent image.

In the C developing device 24, the developing sleeve 24a starts rotating after the rear end of the previous BK latent image has passed and before the front end of the C latent image has reached the developing position, and the developing agent is developed. The C latent image is developed with C toner. After that,
The C developing device 24 continues to develop the C latent image area on the photosensitive drum 12, but when the rear end of the C latent image passes,
As in the case of the K developing device 23, the developer on the C developing sleeve 24a is cut off. This is also completed before the leading edge of the next M latent image arrives.

The C toner image on the photosensitive drum 12 is the intermediate transfer belt 2 which is driven at the same speed as the photosensitive drum 12.
8 is transferred to the surface. After the transfer of the C toner image, the photoconductor drum 12 is destaticized and cleaned by the photoconductor cleaning device 19 including the pre-cleaning decharger 18, is decharged by the decharging lamp 20, and is uniformly charged again by the charger 21.

On the photosensitive drum 12 side, the C image forming process is followed by the M image forming process. In this M image forming process, the color scanner 1 starts reading for obtaining M image data at a predetermined timing, and The image processing unit obtains M image data from the image data from the scanner 1, and the writing optical unit 11 causes the photoconductor drum 12 based on the M image data.
An optical latent image is formed by performing optical writing with a laser beam.

With respect to the developing position of the M developing device 25, the developing sleeve 25a starts rotating after the rear end portion of the previous C latent image has passed and before the front end of the M latent image has reached the developing position. The M latent image is developed with M toner. After that, M
The developing device 25 continues to develop the M latent image area on the photoconductor drum 12, but when the rear end portion of the M latent image passes, the developing device 25 continues to develop on the M developing sleeve 25a as in the case of the C developing device 24. The developer is cut off. This is also completed before the leading edge of the next Y latent image arrives.

The M toner image on the photosensitive drum 12 is the intermediate transfer belt 2 which is driven at the same speed as the photosensitive drum 12.
8 is transferred to the surface. After the transfer of the M toner image, the photoconductor drum 12 is destaticized and cleaned by the photoconductor cleaning device 19 including the pre-cleaning decharger 18, is decharged by the decharging lamp 20, and is uniformly charged again by the charger 21.

On the side of the photoconductor drum 12, the M image forming process is followed by the Y image forming process. In this Y image forming process, the color scanner 1 starts reading for obtaining Y image data at a predetermined timing, and a color image is formed. The image processing unit obtains Y image data from the image data from the scanner 1, and the writing optical unit 11 causes the photoconductor drum 12 based on the Y image data.
Then, optical writing is performed by laser light to form a Y latent image.

In the Y developing device 26, the developing sleeve 26a starts rotating after the rear end portion of the previous M latent image has passed and before the front end of the Y latent image reaches the developing position, and the developing sleeve 26a starts developing. And the Y latent image is developed with Y toner. After that, Y
The developing device 26 continues to develop the Y latent image area on the photoconductor drum 12, but when the trailing end of the Y latent image passes, the developing device 26 is on the Y developing sleeve 26a as in the case of the M developing device 25. The developer is cut off. This is also completed after the trailing edge of the Y latent image has arrived. The Y toner image on the photosensitive drum 12 is transferred to the intermediate transfer belt 28 that is driven at the same speed as the photosensitive drum 12.
Is transferred to the surface of.

Next, the intermediate transfer belt unit will be described. The intermediate transfer belt 28 includes a driving roller 31, a belt transfer bias roller 29, and driven roller groups 32 and 3.
The drive roller 31 is driven by a drive motor (not shown) to rotate the intermediate transfer belt 28. Belt cleaning device (belt cleaner) 35
Is composed of a brush roller 35a, a rubber blade 35b, a contact / separation mechanism 35c, etc., and transfers the C image, M image, and Y image to the belt transfer bias roller 29 after the BK image of the first color is transferred onto the belt. In the interval, the brush roller 35a and the rubber blade 35b are separated from the belt transfer bias roller 29 by the contact / separation mechanism 35c.

Transfer material transfer means 3 comprising a paper transfer unit
Reference numeral 6 includes a paper transfer bias roller 36a, a roller cleaning blade 36b, a contact / separation mechanism 36c, and the like. The paper transfer bias roller 36a is normally separated from the intermediate transfer belt 28. However, when the four-color superposed images formed on the intermediate transfer belt 28 are collectively transferred to the transfer paper, the paper transfer bias roller 36a contacts the transfer paper at a timing. It is pressed by the separating mechanism 36c and comes into contact with the intermediate transfer belt 28, and a predetermined transfer bias voltage is applied to the paper transfer bias roller 36a from a high voltage power source to pass between the paper transfer bias roller 36a and the intermediate transfer belt 28. The four-color superimposed image on the intermediate transfer belt 28 is transferred onto the transfer paper.

In this case, the transfer paper is the transfer paper cassette 37-
The selected one of 40 is fed to the registration roller 45 by one of the paper feed rollers 41 to 44, or is fed from the manual paper feed tray 46 to the registration roller 45 by the paper feed roller 41. The transfer paper is sent at the timing when the leading end of the four-color superimposed image on the intermediate transfer belt 28 reaches the paper transfer position.

The movement of the intermediate transfer belt 28 is 1
The following constant speed forward movement method, skip forward movement method, and reciprocating movement (quick return) method can be considered as the operation method after the belt transfer of the BK toner image of the color is completed up to the rear end portion. A method, or a method in which these are efficiently combined (in terms of copy speed, etc.) according to the copy size is used.

1) -Constant-speed forward movement method Even after the intermediate transfer belt 28 has transferred the BK toner image onto the belt, it continues to move forward at a constant speed. On the photoconductor drum 12 side, when the BK image front end position on the intermediate transfer belt 28 again reaches the belt transfer position of the contact portion with the photoconductor drum 12, the front end part of the next C toner image is just at the belt transfer position. An image is formed with a timing so that the image becomes dark. As a result, the C image is accurately aligned with the BK image and is transferred onto the intermediate transfer belt 28 in a superposed manner. After that, the M image forming process and the Y image forming process are performed by similar operations, and a belt transfer image of four colors is obtained on the intermediate transfer belt 28. Following the step in which the intermediate transfer belt 28 performs the belt transfer of the Y toner image of the fourth color, the four-color superimposed toner image is collectively transferred to the transfer paper as described above while moving forward.

2) Skip Forward Method The intermediate transfer belt 28 is separated from the photosensitive drum 12 when the belt transfer of the BK toner image is completed, and is skipped at a high speed in the forward direction to move a predetermined amount. Return to forward speed. Then, the intermediate transfer belt 28 is brought into contact with the photosensitive drum 12 again. On the photoconductor drum 12 side, when the BK image front end position on the intermediate transfer belt 28 reaches the belt transfer position again, the timing is adjusted so that the front end portion of the next C toner image comes to the belt transfer position. It is formed. as a result,
The C image is accurately aligned with the BK image and transferred onto the belt in a superimposed manner. After that, the M image forming process and the Y image forming process are performed by similar operations, and a belt transfer image of four colors is obtained on the intermediate transfer belt 28. The intermediate transfer belt 28 collectively transfers the four-color superposed toner image onto the transfer paper at the same forward speed as the belt transfer process of the Y toner image of the fourth color.

3) Reciprocating motion (quick return) system When the intermediate transfer belt 28 finishes the belt transfer of the BK toner image, it is separated from the photosensitive drum 12 and stops the forward movement, and at the same time, returns in the reverse direction at a high speed. In this return, the front end position of the BK image on the intermediate transfer belt 28 passes through the position corresponding to the belt transfer in the opposite direction, and after moving for a preset distance, it is stopped and becomes a standby state. Next, on the side of the photoconductor drum 12, when the front end portion of the C toner image reaches a predetermined position before the belt transfer position, the intermediate transfer belt 28 is restarted in the forward direction and comes into contact with the photoconductor drum 12 again. . Also in this case, the condition is controlled such that the C image accurately overlaps the BK image on the intermediate transfer belt 28. After that, the M image forming process and the Y image forming process are performed by similar operations, and a belt transfer image of four colors is obtained on the intermediate transfer belt 28. Following the belt transfer process of the Y toner image of the fourth color, the intermediate transfer belt 28 moves forward at the same speed without returning, and transfers the four-color superimposed toner image to the transfer paper in a batch.

The transfer paper on which the four-color superposed toner images are collectively transferred from the intermediate transfer belt 28 is conveyed to the fixing device 48 by the paper conveying unit 47 and is controlled to a predetermined temperature of the fixing device 48. The toner image is fused and fixed by the fixing roller 48a and the pressure roller 48b and is carried out to the copy tray 49 as a full-color copy. Further, the photoconductor belt 12 after the belt transfer is uniformly discharged by the pre-cleaning static eliminator 18 by the photoconductor cleaning device 19, the surface is cleaned by the brush roller 19a and the rubber blade 19b, and the charge is uniformly discharged by the static erasing lamp 20. It Further, the surface of the intermediate transfer belt 28 after the toner image is transferred onto the transfer paper is cleaned by the cleaning unit 35, and at this time, the brush roller 19a.
The rubber blade 19b is pressed against the intermediate transfer belt 28 by the contact / separation mechanism 35c.

At the time of repeat copying in which copying is continuously performed, the operation of the color scanner 1 and the image formation on the photosensitive drum 12 are started following the Y (fourth color) image forming process of the first sheet, and at a predetermined timing. Proceed to the second BK (first color) image formation process. Further, the intermediate transfer belt 28 has its surface cleaned by the cleaning device 35 following the step of collectively transferring the four-color superposed image onto the first transfer paper, and the second BK toner image on the surface of the photosensitive drum. The belt is transferred from 12. After that, the same operation as that for the first sheet is performed, and thereafter, the same operation is performed for each sheet.

The transfer paper cassettes 37-40 contain transfer papers of various sizes, and the paper feed rollers 41-44.
Thus, the transfer paper is fed to the registration roller 45 at a timing from the transfer paper cassette in which the transfer paper of the size specified by the operation panel (not shown) is stored. The manual feed tray 46 is used for feeding OHP paper or thick paper in the manual feed mode.

The above-mentioned operation is the operation in the copy mode for obtaining a full-color copy in four colors.
When obtaining a copy in the color copy mode, the same operation as described above is performed for the number of colors and the number of times designated by the operation unit. Also, in the case of the monochromatic copy mode for obtaining a monochromatic copy, only the monochromatic developing device is in the development operation (development of developer) state until the copying of a predetermined number of sheets is completed,
The intermediate transfer belt 28 is driven in the forward direction at a constant speed while being in contact with the photosensitive drum 12, and the belt cleaning unit 35 is also kept in contact with the intermediate transfer belt 28 to perform a copying operation.

In the above-mentioned structure, the intermediate transfer belt 2
The driving force for driving 8 (specifically, the frictional force between the driving roller 31 and the intermediate transfer belt 28) decreases with the passage of time, and a high load is eventually applied to the intermediate transfer belt 28. When the upper toner image is transferred onto the transfer paper, slip occurs between the drive roller 31 and the intermediate transfer belt 28.

Therefore, in the first embodiment, which is an embodiment of the invention described in claim 1, there is provided a driving force shortage determination means for determining whether or not the driving force for driving the intermediate transfer member 28 is insufficient, and this driving is performed. When the force shortage determination means determines that the driving force for driving the intermediate transfer body 28 is insufficient, a drive for driving the intermediate transfer body 28 when the toner image on the intermediate transfer body 28 is transferred to the transfer paper. By compensating the force with the first driving force assisting means, the slip between the driving roller 31 and the intermediate transfer belt 28 is prevented. Therefore, the adverse effect of the slip between the drive roller 31 and the intermediate transfer belt 28, that is, the acceleration of the abrasion of the intermediate transfer member and the roller, and the increase in the amount of toner adhered to the paper transfer bias roller 36a, stain the back of the transfer material. It is possible to minimize a problem such as a decrease in the margin for.

In the first embodiment, which is an embodiment of the invention described in claim 3, the driving force shortage determination means measures the slip amount between the drive roller 31 and the intermediate transfer belt 28, and the measured slip amount. Is compared with a predetermined reference value, and when the slip amount exceeds the reference value, it is determined that the driving force for driving the intermediate transfer member 28 is insufficient, so that the drive roller 31 and the intermediate transfer belt 28 are separated from each other. It is determined whether or not the slip amount between them is at a problem level.

In this driving force shortage determination means, for example, FIG.
As shown in FIG. 3, the mark 50 attached on the intermediate transfer belt 28 is read by the mark detection sensor 51 at a fixed position, and the encoder 52 integrally attached to the drive roller 21 rotates the rotation speed (rotation speed of the drive roller 31). ) Is detected and pulses are generated in a number proportional to the number of times. The slip amount measuring device 53 counts the pulses from the encoder 52 with a slip measuring counter, and the intermediate transfer belt 28 rotates once by the output signal of the mark detection sensor 51 in a state where nothing touches the intermediate transfer belt 28. Each time the mark 50 is read by the mark detection sensor 51, the value of the slip measurement counter is read after being read by the mark detection sensor 51, and the value of the slip measurement counter is cleared to 0. When the paper transfer bias roller 36a is in contact with the mark detection sensor 51,
Output signal, the intermediate transfer belt 28 makes one rotation and is triggered every time the mark 50 is read by the mark detection sensor 51 to read the value of the slip measurement counter and then clear the value of the slip measurement counter to zero. .

Then, the slip amount measuring device 53 measures the count value read from the slip measuring counter in a state where nothing touches the intermediate transfer belt 28, and the intermediate transfer belt 2
8, the paper transfer bias roller 36a of the paper transfer unit 36
In the state of contacting with, the count value read from the slip measuring counter is compared, and the difference between these count values is measured as the slip amount between the drive roller 31 and the intermediate transfer belt 28. In this way, the driving force shortage determination means is
By measuring the slip amount between the drive roller 31 and the intermediate transfer belt 28, it can be accurately determined that the driving force for driving the intermediate transfer body 28 is insufficient.

In the first embodiment, which is an embodiment of the invention described in claim 4, the slip amount measuring device 53 performs the operation of measuring the slip amount between the driving roller 31 and the intermediate transfer belt 28 in this embodiment. This is performed during warm-up after turning on the power of the image forming apparatus main body. As described above, the slip amount is measured by the driving force shortage determination means when the power of the image forming apparatus main body is turned on, so that the copying operation is performed to measure the slip amount between the drive roller 31 and the intermediate transfer belt 28. The measurement operation can be performed at an appropriate frequency without interruption, and it can be reliably detected that the driving force for driving the intermediate transfer member 28 is insufficient.

In the first embodiment, which is an embodiment of the invention described in claim 6, the first driving force assisting means determines that the driving force insufficient determination means has insufficient driving force for driving the intermediate transfer member 28. In this case, when the toner image on the intermediate transfer body 28 is transferred to the transfer paper, the intermediate transfer body 28 is brought into contact with the image carrier 12 to supplement the driving force for driving the intermediate transfer body 28. In this case, the first driving force assisting means is the contact / separation mechanism 36.
Simultaneously with the press contact of the paper transfer bias roller 36a with the intermediate transfer belt 28 by c, the contact / separation mechanism that brings the intermediate transfer belt 28 into contact with the photoconductor drum 12 is operated to move the paper transfer bias roller 36a to the intermediate transfer belt 28. The pressure contact and the contact of the intermediate transfer belt 28 with the photosensitive drum 12 are simultaneously performed.

FIG. 6 shows the result of measuring how many pulses it takes for the intermediate transfer belt 28 to make one rotation on the assumption that the driving roller 31 for driving the intermediate transfer belt 28 makes one rotation with 5000 pulses, and the intermediate transfer belt 28. Shows the relationship with the drive linear velocity ratio. The drive linear velocity ratio of the intermediate transfer belt 28 is
It is obtained by (linear velocity of intermediate transfer belt 28) / (linear velocity of photoconductor drum 12).

In FIG. 6, a curve A indicates the intermediate transfer belt 2.
8 to the photosensitive drum 12, the cleaning unit 35,
The curve B shows the change in the number of drive roller pulses (the number of pulses for driving the drive roller 31) when the paper transfer unit 36 is separated (hereinafter referred to as the free state), and the curve B presses the paper transfer unit 36 against the intermediate transfer belt 28. The change in the number of drive roller pulses at the time is shown. A curve C shows that the photosensitive drum 12 and the paper transfer unit 36 both contact the intermediate transfer belt 28 (however, the charging of the portion of the photosensitive drum 12 contacting the intermediate transfer belt 28 does not occur. Changes in the number of drive roller pulses when the switch is off).

As shown by the curve A in FIG. 6, the intermediate transfer belt 28
As compared with the number of drive roller pulses when the sheet is rotating in the free state, the change in the number of drive roller pulses when the paper transfer unit 36 is pressed against the intermediate transfer belt 28 is large as shown by the curve B in FIG. When the paper transfer unit 36 is pressed against the intermediate transfer belt 28, the driving force for driving the intermediate transfer belt 28 is insufficient and the intermediate transfer belt 28 is driven by the driving roller 3
It is considered that the slip has occurred between 1 and 1. On the other hand, as shown by the curve C in FIG. 6, when the photosensitive drum 12 and the paper transfer unit 36 come into contact with the intermediate transfer belt 28, the intermediate transfer belt 28 rotates in the free state at the driving roller pulse number. It can be seen that the number of pulses of the driving roller becomes close to that at the time, and the slip between the intermediate transfer belt 28 and the driving roller 31 is reduced. By bringing the intermediate transfer belt 28 into contact with the photosensitive drum 12 in this manner, it is possible to compensate for the lack of driving force for driving the intermediate transfer belt 28.

In the first embodiment, which is an embodiment of the invention described in claim 7, the first driving force assisting means is such that the driving force shortage determining means drives the intermediate transfer member 28 insufficiently. If determined, the intermediate transfer body 28 is brought into contact with the image carrier 12 and the charger 21 is operated to transfer the toner image on the intermediate transfer body 28 onto the transfer sheet, and the intermediate transfer belt 2 is operated.
The photosensitive drum 12 which is in contact with 8 is charged.

The curve D in FIG. 6 is the intermediate transfer belt 28.
7 shows changes in the number of drive roller pulses when the photosensitive drum 12 that is in contact with is charged. In this case, the number of drive roller pulses is greater than the number of drive roller pulses when the photosensitive drum 12 is not charged as shown by the curve C in FIG. 6, and the intermediate transfer belt 28 is in the free state as shown by the curve A in FIG. Is approaching the number of drive roller pulses when rotating at
It can be seen that a larger driving force is applied to the intermediate transfer belt 28 and the slip between the intermediate transfer belt 28 and the driving roller 31 is reduced. Thus, when the photosensitive drum 12 is brought into contact with the intermediate transfer belt 28, the photosensitive drum 1
By charging 2 to the intermediate transfer belt 28, a larger driving force is applied to the intermediate transfer belt 28 and the driving roller 3
The slip between 1 and 1 can be reduced.

The second embodiment of the present invention is the same as the first embodiment except that the driving force deficiency determining means is used for the intermediate transfer belt 2.
When it is determined that the driving force for driving the intermediate transfer belt 8 is insufficient, the second driving force assisting means drives the intermediate transfer belt 28 when the toner on the intermediate transfer belt 28 is cleaned by the cleaning unit 35. To make up for.

The second embodiment is an embodiment of the invention described in claim 2 and is the first embodiment when the driving force shortage determining means determines that the driving force for driving the intermediate transfer belt 28 is insufficient. Since the second driving force assisting means supplements the driving force for driving the intermediate transfer belt 28 when the toner on the intermediate transfer belt 28 is cleaned by the cleaning unit 35,
Slip between the drive roller 31 and the intermediate transfer belt 28 can be prevented. Therefore, the adverse effect of the slip between the drive roller 31 and the intermediate transfer belt 28, that is, the acceleration of the abrasion of the intermediate transfer member and the roller, and the increase in the amount of toner adhered to the paper transfer bias roller 36a, stain the back of the transfer material. It is possible to minimize a problem such as a decrease in the margin for.

In the second embodiment, which is an embodiment of the present invention as defined in claim 8, the second driving force assisting means lacks the driving force for driving the intermediate transfer member 28 by the driving force shortage determining means. When it is determined that the toner on the intermediate transfer belt 28 is cleaned by the cleaning unit 35, the paper transfer bias roller 36a of the paper transfer unit 36 is brought into contact with the intermediate transfer belt 28, so that the intermediate transfer body 28
Supplements the driving force to drive the.

In this case, the second driving force assisting means presses the paper transfer bias roller 36a against the intermediate transfer belt 28 at the same time as the brush roller 19a and the rubber blade 19b are pressed against the intermediate transfer belt 28 by the contact / separation mechanism 35c. The contact / separation mechanism 36c for contact is operated to simultaneously press the brush roller 19a and the rubber blade 19b against the intermediate transfer belt 28 and simultaneously contact the paper transfer bias roller 36a with the intermediate transfer belt 28. FIG. 7 shows a result of measuring how many pulses it takes for the intermediate transfer belt 28 to make one rotation on the assumption that the driving roller 31 for driving the intermediate transfer belt 28 makes one rotation with 5000 pulses, and the drive line of the intermediate transfer belt 28. The relationship with the speed ratio is shown.

In FIG. 7, the curve A is the intermediate transfer belt 2.
8 shows the change of the drive roller pulse number in the free state, curve B shows the change of the drive roller pulse number when the cleaning unit 35 is pressed against the intermediate transfer belt 28,
The curve C indicates the cleaning unit 3 on the intermediate transfer belt 28.
5 and the paper transfer bias roller 36a of the paper transfer unit 36
Shows the change in the number of drive roller pulses when both are in contact with each other (however, the charging of the intermediate transfer belt 28 is off).

As shown by the curve A in FIG. 7, the intermediate transfer belt 28
Of the driving roller pulse when the cleaning unit 35 is pressed against the intermediate transfer belt 28 as shown by the curve B in FIG. It is considered that when the cleaning unit 35 is pressed against the intermediate transfer belt 28, the driving force for driving the intermediate transfer belt 28 is insufficient and the intermediate transfer belt 28 slips with the driving roller 31. On the other hand, as shown by the curve C in FIG. 7, the cleaning unit 35 and the paper transfer unit 3 are attached to the intermediate transfer belt 28.
The drive roller pulse number when the paper transfer bias rollers 36a of 6 contact each other is close to the drive roller pulse number when the intermediate transfer belt 28 is rotating in a free state, and the intermediate transfer belt 28 and the drive roller 31 It can be seen that the slip between them is decreasing. In this way, when the driving force shortage determination means determines that the driving force for driving the intermediate transfer member 28 is insufficient, when the toner on the intermediate transfer belt 28 is cleaned by the cleaning unit 35, the paper transfer unit 36 is cleaned. By bringing the paper transfer bias roller 36 a into contact with the intermediate transfer belt 28,
It is possible to compensate for the lack of driving force for driving the. When the driving force shortage determination means determines that the driving force for driving the intermediate transfer member 28 is insufficient, the intermediate transfer belt 28 is exposed to light when the toner on the intermediate transfer belt 28 is cleaned by the cleaning unit 35. You may make it contact | abut with the body drum 12.

In the second embodiment, which is an embodiment of the invention described in claim 9, the second driving force assisting means is such that the driving force insufficient determination means is insufficient in driving force for driving the intermediate transfer member 28. When the determination is made, when the toner on the intermediate transfer belt 28 is cleaned by the cleaning unit 35, the paper transfer bias roller 36a of the paper transfer unit 36 is brought into contact with the intermediate transfer belt 28 and the paper with which the intermediate transfer belt 28 is brought into contact. The transfer bias roller 36a is charged by the charging means. The charging means charges the paper transfer bias roller 36a by applying a bias to the core of the paper transfer bias roller 36a, for example.

The curve D in FIG. 7 is the intermediate transfer belt 28.
5 shows a change in the number of drive roller pulses when the paper transfer bias roller 36a that is in contact with is charged. In this case, the number of drive roller pulses is greater than the number of drive roller pulses when the paper transfer bias roller 36a is not charged as shown by the curve C in FIG. 7, and further as shown by the curve A in FIG.
8 is approaching the number of drive roller pulses when rotating in a free state, and a larger drive force is applied to the intermediate transfer belt 2
8 that the slip between the intermediate transfer belt 28 and the driving roller 31 is reduced. By charging the paper transfer bias roller 36a when the paper transfer bias roller 36a is brought into contact with the intermediate transfer belt 28 as described above, a larger driving force is applied to the intermediate transfer belt 28, and the intermediate transfer belt 28 and the driving roller 31 are connected to each other. The slip between can be reduced.

By the way, in the above embodiment, the driving force between the intermediate transfer belt 28 and the driving roller 31 is the most during maintenance of the intermediate transfer belt unit (cleaning of the driving roller 31, replacement of the intermediate transfer belt 28, etc.). It is high, and as the image forming operation (copying operation) is repeated, it gradually decreases due to toner and paper dust floating inside the apparatus, dirt on the driving roller 31 due to shavings of the intermediate transfer belt 28, and the like.

Therefore, the embodiment of the invention described in claim 5 is as follows:
In each of the first and second embodiments, instead of the driving force shortage determination means, the accumulated operation time from the maintenance of the intermediate transfer belt unit and the driving force for driving the intermediate transfer belt 28 (intermediate transfer belt 28 and the slip amount between the drive roller 31) are previously obtained by experiments to determine the cumulative operation time corresponding to the limit value of the driving force for driving the intermediate transfer belt 28. The cumulative operating time from the maintenance is counted and measured by the counter, and when the cumulative operating time reaches the previously determined cumulative operating time, it is determined that the driving force of the intermediate transfer belt 28 is insufficient, and the intermediate transfer belt unit is determined. The driving force shortage determination means for clearing the counter when the maintenance of is completed is used.

In this embodiment, the driving force shortage determining means counts the accumulated operation time from the maintenance of the intermediate transfer belt unit to judge whether or not the driving force shortage of the intermediate transfer belt 28 occurs. The time when the driving force of the intermediate transfer belt 28 becomes insufficient can be easily known without providing a mechanism. The driving force shortage determination means measures other characteristics, such as the number of copies and the operation time of the photosensitive drum 12, from the maintenance of the intermediate transfer belt unit instead of the accumulated operation time from the maintenance of the intermediate transfer belt unit. Alternatively, it may be determined that the driving force of the intermediate transfer belt 28 is insufficient when the measured value reaches the limit value. The present invention is not limited to the above embodiments, but can be similarly applied to image forming apparatuses such as printers and facsimiles other than the above embodiments.

[0078]

As described above, according to the first aspect of the invention, the intermediate transfer member is formed in the shape of an endless belt and is stretched around a plurality of rollers and rotated, and is formed on the image carrier. It is determined whether or not the driving force for driving the intermediate transfer body is insufficient in an image forming apparatus that transfers the formed toner image onto the intermediate transfer body and transfers the toner image on the intermediate transfer body onto a transfer material. And a driving force shortage determining means that determines that the driving force for driving the intermediate transfer body is insufficient, and the toner image on the intermediate transfer body is transferred to the transfer material. Since the driving force assisting means for compensating the driving force for driving the intermediate transfer member is provided, the adverse effect caused by the slip between the roller driving the intermediate transfer member and the intermediate transfer member, that is, the intermediate transfer member or the roller. Acceleration of abrasion such as It is possible to minimize the problem, such as reduction of margin for.

According to the second aspect of the present invention, the toner image formed on the image carrier is provided with an intermediate transfer member which is formed in an endless belt shape and is stretched around a plurality of rollers and rotated. An image forming apparatus in which an intermediate transfer member is transferred, a toner image on the intermediate transfer member is transferred to a transfer material by a transfer material transfer unit, and the intermediate transfer member is cleaned by a cleaning unit, and the intermediate transfer member is driven. Insufficient driving force determining means for determining whether or not the driving force is insufficient, and if the driving force insufficient determination means determines that the driving force for driving the intermediate transfer member is insufficient, the intermediate transfer member Since the driving force assisting means for compensating the driving force for driving the intermediate transfer member when cleaning the upper toner is provided, an adverse effect due to a slip between the roller for driving the intermediate transfer member and the intermediate transfer member, that is,
It is possible to minimize problems such as acceleration of wear of the intermediate transfer body and rollers, and reduction of the margin for back stain of the transfer material.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the driving force deficiency determining means is provided between the drive roller for driving the intermediate transfer body and the intermediate transfer body. The slip amount of the intermediate transfer member is measured, and when the slip amount exceeds the reference value, it is determined that the driving force for driving the intermediate transfer member is insufficient. Can be accurately determined.

According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the measurement of the slip amount by the driving force shortage determining means is performed when the image forming apparatus main body is powered on. The image forming operation is not interrupted for the operation of measuring the slip amount between the roller driving the intermediate transfer member and the intermediate transfer member, and the measuring operation can be performed at an appropriate frequency. It can be reliably detected that the driving force for driving is insufficient.

According to a fifth aspect of the present invention, in the image forming apparatus according to the first or second aspect, the driving force deficiency determining means includes the intermediate transfer body from the maintenance of the intermediate transfer unit including the intermediate transfer body. The cumulative operating time of is measured, and when the cumulative operating time exceeds the reference value, it is determined that the driving force for driving the intermediate transfer member is insufficient. Therefore, it is possible to easily perform the intermediate operation without providing a special mechanism. It is possible to know when the driving force of the transfer body is insufficient.

According to a sixth aspect of the present invention, in the image forming apparatus according to the first or second aspect, the driving force assisting means brings the intermediate transfer member into contact with the image carrier to thereby transfer the intermediate transfer member. Since the driving force for driving the body is compensated, the lack of the driving force for driving the intermediate transfer body can be compensated.

According to the seventh aspect of the invention, in the image forming apparatus according to the sixth aspect, since the image carrier that is in contact with the intermediate transfer body is charged, a larger driving force is applied to the intermediate transfer body. It is possible to reduce the slip between the roller for driving the intermediate transfer member and the intermediate transfer member.

According to the eighth aspect of the invention, in the image forming apparatus according to the second aspect, the driving force assisting means brings the intermediate transfer body into contact with the transfer material transfer means, thereby the intermediate transfer body Since the driving force for driving the intermediate transfer member is compensated, the lack of the driving force for driving the intermediate transfer member can be compensated.

In the image forming apparatus according to the present invention, since the transfer material transfer means in contact with the intermediate transfer body is charged, a larger driving force is applied to the intermediate transfer body to transfer the intermediate transfer body. The slip between the drive roller and the intermediate transfer member can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view showing a part of the first embodiment.

FIG. 3 is a timing chart showing the operation timing of the first embodiment.

FIG. 4 is a timing chart showing another operation timing of the first embodiment.

FIG. 5 is a perspective view showing a part of the first embodiment.

FIG. 6 is a characteristic curve diagram for explaining the first embodiment.

FIG. 7 is a characteristic curve diagram for explaining the second embodiment of the present invention.

[Explanation of reference numerals] 12 photoconductor drum 28 intermediate transfer belt 31 drive roller 35 belt cleaning unit 36 paper transfer unit 50 mark 51 mark detection sensor 52 encoder 53 slip amount measuring instrument

Claims (9)

[Claims] 1. An intermediate transfer member, which is formed into an endless belt shape and is stretched around a plurality of rollers and rotated, and transfers a toner image formed on an image carrier onto the intermediate transfer member. In an image forming apparatus that transfers a toner image on the intermediate transfer body to a transfer material, a driving force shortage determination unit that determines whether the driving force that drives the intermediate transfer body is insufficient, and the driving force shortage determination unit. When it is determined that the driving force for driving the intermediate transfer body is insufficient, the driving force for driving the intermediate transfer body is supplemented when the toner image on the intermediate transfer body is transferred to the transfer material. An image forming apparatus comprising a driving force assisting means. 2. An intermediate transfer member, which is formed in an endless belt shape and is stretched and rotated by a plurality of rollers, and the toner image formed on an image carrier is transferred onto the intermediate transfer member. Whether the driving force for driving the intermediate transfer body is insufficient in the image forming apparatus that transfers the toner image on the intermediate transfer body to the transfer material by the transfer material transfer means and cleans the intermediate transfer body by the cleaning means. When the toner on the intermediate transfer body is cleaned, the driving force shortage determining means for determining that the intermediate transfer body is insufficient, and the driving force shortage determining means determines that the driving force for driving the intermediate transfer body is insufficient. An image forming apparatus comprising: a driving force assisting unit that supplements a driving force for driving the intermediate transfer member. 3. The image forming apparatus according to claim 1, wherein the driving force shortage determination means measures a slip amount between a drive roller for driving the intermediate transfer body and the intermediate transfer body, and An image forming apparatus, wherein it is determined that the driving force for driving the intermediate transfer member is insufficient when the slip amount exceeds a reference value. 4. The image forming apparatus according to claim 3, wherein the measurement of the slip amount by the driving force shortage determination means is performed when the power of the image forming apparatus main body is turned on. 5. The image forming apparatus according to claim 1, wherein the driving force deficiency determining unit measures an accumulated operating time of the intermediate transfer member after maintenance of an intermediate transfer unit including the intermediate transfer member, An image forming apparatus characterized in that when the accumulated operation time exceeds a reference value, it is determined that the driving force for driving the intermediate transfer member is insufficient. 6. The image forming apparatus according to claim 1, wherein the driving force assisting means supplements the driving force for driving the intermediate transfer member by bringing the intermediate transfer member into contact with the image carrier. An image forming apparatus characterized by the above. 7. The image forming apparatus according to claim 6, wherein the image carrier that is in contact with the intermediate transfer member is charged. 8. The image forming apparatus according to claim 2, wherein the driving force assisting means supplements the driving force for driving the intermediate transfer body by bringing the intermediate transfer body into contact with the transfer material transfer means. An image forming apparatus characterized by. 9. The image forming apparatus according to claim 8, wherein the transfer material transfer means in contact with the intermediate transfer member is charged.