JPH08286584A - Electrophotographic image forming device - Google Patents

Abstract

PURPOSE: To provide an electrophotographic image forming device using an image carrying belt, capable of making the image carrying belt press-contact to and separate from a cleaning member without reducing feeding force in the midst of forming the image, and efficiently forming a faultless image. CONSTITUTION: This device is provided with belt driving devices 15 and 21 for feeding the image carrying belt 20 forming and carrying a toner image on its surface at fixed speed, and a cleaning device 25 having the cleaning member 26 capable of press-contacting to and separating from the belt 20; and it is equipped with belt feeding force increasing devices 16 and 24 increasing the feeding force of the belt 20 when the member 26 press-contacts to the belt 20, or a belt feeding force decreasing device decreasing the feeding force of the belt 20 when the member 26 separates from the belt 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus using an image bearing belt such as a belt photoreceptor or an intermediate transfer belt in the field of the electrophotographic image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, an electrophotographic image forming apparatus using an image bearing belt such as a belt photosensitive member and an intermediate transfer member belt has been used. The image bearing belt can be freely installed as compared with the drum-shaped image bearing member, and can reduce unnecessary space inside the image bearing member, and thus is suitable for downsizing of the apparatus.

The image carrying belt is conveyed by a conveying force transmitted from a driving device of the image carrying belt through a drive transmitting device such as an image carrying belt driving roller. As the cleaning device for the image bearing belt, a cleaning device such as a cleaning blade, a cleaning roller, or a fur brush is usually used to press the image bearing belt to remove unnecessary toner. Further, these cleaning members are configured so that they can be pressed and separated from each other as needed for the purpose of preventing multiple images and deformation of the belt.

[0004]

Image carrier belt clear
When the cleaning member of the cleaning device is brought into pressure contact with the image bearing belt, a load is applied to the image bearing belt and a belt conveying load force is generated. When the belt conveying load force is generated, a slip occurs between the driving device and the image carrying belt, and the conveying force is reduced. When the image formation is performed in the state where the conveyance force is reduced, the image formed is stretched by the reduction in the conveyance force. When the pressure contact and separation of the cleaning member is not performed during image formation, this phenomenon can be eliminated by setting a high conveying force in advance. However, in order to perform image formation efficiently using the image bearing belt, it is necessary to perform belt cleaning during image formation. When the cleaning member is pressed and separated during image formation, the conveyance force decreases during image formation, resulting in image defects. Especially full color
In the case of image formation, four colors of yellow, magenta, cyan, and black are used for image formation, whereas the cleaning member is in pressure contact with a specific one of the four colors. Compared with the other three colors, the image becomes a stretched image, and so-called "color shift" occurs. Such a phenomenon is
In addition to image formation, multi-image formation such as multicolor image formation and composite image formation also occurs.

In view of the above problems, the object of the present invention is to allow the cleaning member to be brought into pressure contact with and separated from the cleaning member during the image formation using the image bearing belt without lowering the conveying force, and there is no image defect. An object is to provide an electrophotographic image forming apparatus capable of forming an image efficiently.

[0006]

In order to solve the above-mentioned problems, an electrophotographic image forming apparatus of the present invention comprises a belt driving device for conveying an image carrying belt for forming and carrying a toner image on its surface at a constant speed. A belt carrying force increasing device for increasing a carrying force of the image carrying belt when the cleaning device has a cleaning member capable of being pressed and separated from the image carrying belt and is brought into pressure contact with the image carrying belt; A belt carrying force reducing device is provided for reducing the carrying force of the image carrying belt when the cleaning member is separated from the carrying belt.

[0007]

According to the electrophotographic image forming apparatus of the present invention, the belt carrying force increasing device compensates the belt carrying force reduced by the cleaning member when the cleaning member is pressed against the image carrying belt, or the image carrying belt is cleaned by the cleaning member. When the belts are separated from each other, the belt conveying force reducing device reduces the belt conveying force, so that the conveying force of the image carrying belt can be kept constant regardless of the pressure contact separation of the cleaning member. By keeping the conveyance force of the image bearing belt constant, it is possible to suppress the occurrence of image defects and obtain good images. Further, even during image formation, the cleaning member can be pressed and separated without affecting the image, so that image formation can be performed efficiently and copy speed can be improved.

[0008]

1 is a sectional view of an electrophotographic image forming apparatus 100 according to the present invention.

The electrophotographic image forming apparatus 100 is an electrophotographic printer that receives data from a host computer (not shown) to form an image.
The intermediate transfer body unit 2, the optical system unit 3, the developing unit 4, the paper feed cassette 5, the copy paper transport unit 6, and the fixing device 7 are included.

The photoconductor unit contains the photoconductor 10 and an image forming element (not shown) such as a charging device and a cleaner disposed around the photoconductor 10, and the photoconductor 10 is provided.
After being cleaned with a cleaner, it is uniformly charged by a charging device.

The print head 3 contains a laser diode, a scanning optical system, etc., and controls the laser diode based on the data from the host computer.
An electrostatic latent image is formed on the photoconductor 10 that is uniformly charged.

The developing unit 4 is rotatably provided around the developing unit shaft 11. Also, the developing unit 4
The developing devices 4Y, 4M, 4C, and 4K are housed in the developing device 4, and the selected developing device faces the photoconductor 10 by the rotation of the developing unit 4. The developing device facing the photoconductor 10 develops the electrostatic latent image formed on the photoconductor 10 to form a toner image.

The paper feed cassette 5 feeds the print paper P stored therein at a predetermined timing and conveys it to the facing portion of the timing rollers 30 and 31.

Next, the detailed structure of the intermediate transfer body unit 2 will be described. FIG. 2 is a cross-sectional view showing the structure of the intermediate transfer body unit 2.

The intermediate transfer body unit 2 is mainly composed of an intermediate transfer belt 20, a driving roller 21 and a biasing roller 22 and 2.
Next transfer counter roller 23, intermediate transfer belt cleaner 2
5, a primary pre-transfer roller 27, and a primary transfer roller 28. The intermediate transfer belt 20 has a circumference of 120.
mm, width 250 mm, endless belt made of polycarbonate. As for the size of the intermediate transfer belt 20, when the maximum size of A4 size paper is used as the print paper P,
50 mm or more in both sub-scanning directions, preferably 1
Use one that is larger than 00 mm.

The intermediate transfer belt 20 is a drive roller-2.
1, energizing roller 22, secondary transfer opposing roller 23, 1
The pre-transfer roller 27 and the primary transfer roller 28 are stretched and suspended.
Is in contact with The surface of the drive roller 21 is made of a rubber material, and the drive is transmitted from the main motor 15 via a drive transmission device (not shown) such as a gear and a timing belt. Rotate in the direction of. Drive low
The rotation of the LA-21 is transmitted to the intermediate transfer belt 20, and the intermediate transfer belt 20 is conveyed in the counterclockwise direction at substantially the same speed as the rotation speed of the photoconductor 10. Also, the energizing roller-22
Is urged in the direction of arrow a, and the intermediate transfer belt 2
It is stretched so that 0 is not loose between the rollers. For this reason, the rotation of the drive roller -21 is caused by the rotation of the intermediate transfer belt 20.
Be efficiently transmitted to.

A belt position detecting mark (not shown) is provided at the end of the intermediate transfer belt 20. The position of the belt intermediate transfer belt 20 can be detected by detecting the belt position detection mark by a belt position detection sensor (not shown). A belt position detecting mark is formed by making a hole in the intermediate transfer belt 20, providing unevenness,
It is provided by a method such as providing regions having different reflectances. As the belt position detection sensor, either a reflection type optical sensor or a transmission type optical sensor is used depending on the form of the belt position detection mark.

The primary transfer roller 28 is urged in the direction of arrow b in order to bring the intermediate transfer belt 20 and the photoconductor 10 into contact with each other, and a primary transfer bias voltage is applied. The toner image formed on the photoconductor 10 is transferred to the intermediate transfer belt 20 by the primary transfer bias voltage applied to the primary transfer roller 28.

The toner image transferred onto the intermediate transfer belt 20 is conveyed to a portion facing the secondary transfer roller 24 while being attached to the intermediate transfer belt 20. A secondary transfer counter roller 23, which is grounded, is provided at a portion of the intermediate transfer belt 20 facing the secondary transfer roller 24. A secondary transfer bias is applied to the secondary transfer roller 24 so that the secondary transfer roller 24 can be pressed against and separated from the intermediate transfer belt 20. The secondary transfer roller 24 has a drive motor 16 provided separately from the main motor 15. The drive motor 16 drives gears, pulleys, timing belts and the like. The drive is transmitted via a transmission device (not shown). The secondary transfer roller 24 is an intermediate drive motor.
By changing the drive voltage of 16 from that of the main motor 15 or changing the gear ratio of the drive transmission device, the intermediate transfer belt 20 rotates at a faster peripheral speed in the direction of the arrow in the figure. Two
The secondary transfer roller 24 is pressed and separated in conjunction with the conveyance of the print paper P, and contacts the secondary transfer facing roller 23 via the intermediate transfer belt 20 during the pressed contact.

The intermediate transfer belt cleaner 25 has a cleaning blade 26 which can be brought into contact with and separated from the intermediate transfer belt 20. The cleaning blade 26 is made of an elastic member such as silicon rubber, and is pressed against the intermediate transfer belt 20 with a total contact force of 200 g during pressing to remove residual toner on the intermediate transfer belt 20.

FIG. 3 shows an image forming apparatus 10 according to the present invention.
It is a block diagram of the control circuit of 0. The CPU is based on input from a host computer, an operation panel, an intermediate transfer belt position detection sensor, etc., and a main motor, a print head 3, an intermediate transfer belt cleaner 25, timing rollers 30, 31, and a secondary transfer roller. 24, each element such as the primary transfer roller 28 is controlled.

FIG. 4 is a timing chart of the full-color image forming operation in the continuous output mode according to the present invention.

The driving of the main motor 15 is started a predetermined time after the print signal is detected, and the first full-color image is formed.
The image of yellow, which is the color, is started. Further, the developing unit 4 makes the first color yellow developing device 4Y for full-color image formation face the photoconductor 10.

By driving the main motor 15, a driving roll is driven.
LA-21 is driven, and the intermediate transfer belt 20 is conveyed. When the belt position detecting mark is detected by the intermediate transfer belt position detecting sensor, the print head 3 is activated after T1 time. The print head 3 forms a first color latent image on the photoconductor 10 based on data from the host computer. The first color latent image formed on the photoconductor 10 is developed by the developing device 4Y to form a yellow toner image.

After a lapse of a predetermined time from the start of operation of the print head 3, the primary transfer roller starts to operate, and the yellow toner image formed on the photoconductor 10 is transferred onto the transfer belt 20 by 1
Next is transcribed. Since the intermediate transfer belt 20 is set to be larger than the size of the image to be formed in both the main scanning direction and the sub scanning direction, the yellow toner image is in a state in which the entire image is held on the transfer belt 20. When the yellow image formation is completed, the developing unit 4 rotates, and the second-color magenta developing device 4M faces the photoconductor 10. The toner remaining on the photoconductor 10 after the primary transfer is removed by a cleaner (not shown).

Next, when the belt position detecting mark is detected again by the intermediate transfer belt position detecting sensor, the formation of magenta which is the second color of the full color image is started.
When the magenta image formation is completed, the cyan developing device 4C for the third color faces the photoconductor 10, and the cyan image formation is started by the detection signal of the intermediate transfer belt position detection sensor.

Further, when the image formation of cyan is completed, the fourth
The black developing device 4K of the color faces the photoconductor 10, and the image formation of black is started by the detection signal of the intermediate transfer belt position detection sensor. When the black toner image is transferred onto the transfer belt 20, the four color toner images of yellow, magenta, cyan and black are superposed on the intermediate transfer belt 20.

When the developing device 4K is selected and the belt position detecting mark is detected by the intermediate transfer belt position detecting sensor, the secondary transfer roller 24 and the intermediate transfer belt cleaner 25 are activated after T2 time, and T3 The rotation of the timing rollers 30 and 31 starts after a lapse of time. When the secondary transfer roller 24 and the intermediate transfer belt cleaner 25 are operated, the secondary transfer roller 24 and the clear belt are transferred to the transfer belt 20.
Ning blade 26 is pressed at the same time.

On the other hand, the print paper P conveyed from the paper feed cassette 5 is opposed to the intermediate transfer belt 20 and the secondary transfer roller 24 at a predetermined timing by the timing rollers 30 and 31. Be transported to. The copy sheet P conveyed to the facing portion between the intermediate transfer belt 20 and the secondary transfer roller 24 passes between the secondary transfer roller 24 and the intermediate transfer belt 20. At this time, due to the action of the secondary transfer bias applied to the secondary transfer roller 24, the four-color toner image formed on the intermediate transfer belt 20 is secondarily transferred to the print paper P.

Further, the intermediate transfer belt cleaner 25 is provided with a cleaning blade 26 for cleaning the intermediate transfer belt 20.
The toner remaining on the intermediate transfer belt 20 after being transferred from the sheet to the copy sheet P is removed.

The toner image transferred onto the print paper P is
It is conveyed to the fixing device 7 by the copy sheet conveying unit 6. The print paper P is fixed by the fixing device 7 and then discharged to the outside of the machine.

The timing rollers 30 and 31 stop rotating at a predetermined timing after the print paper P has passed.

Further, the secondary transfer roller 24 and the intermediate transfer belt cleaner 25 end their operations at a predetermined timing when the secondary transfer is completed, and the secondary transfer roller 24 is transferred to the transfer belt 20. Then, the cleaning blade 26 is simultaneously separated from the intermediate transfer belt 20.

In the continuous output mode, the first color of the full-color image, yellow, is started again, and a series of image forming processes are repeated. The image forming process is repeated until the preset number of image outputs is reached.

Next, using the electrophotographic image forming apparatus 100, the peripheral speed is changed by changing the diameter of the secondary transfer roller 24 while keeping the rotation speed of the secondary transfer roller 24 constant. I changed it and conducted an experiment.

As an experimental method, the intermediate transfer belt 20 is conveyed, and a predetermined space (282.5) is placed on the intermediate transfer belt 20.
This is a method of measuring the time taken for two points marked with 5 mm) to pass by an optical sensor. The time obtained by this experiment was converted into the transport distance (mm) and the image expansion / contraction (μm).

FIG. 5 and FIG. 6 summarize the results of this experiment. FIG. 5 is a graph showing the relationship between the peripheral speed of the secondary transfer roller 24 and the transport distance of the intermediate transfer belt 20. FIG. 6 is a graph showing the relationship between the peripheral speed of the secondary transfer roller 24 and the expansion and contraction of the image formed on the intermediate transfer belt 20.

From the graphs of FIGS. 5 and 6, when the peripheral speed of the secondary transfer roller 24 is changed, the conveying distance of the intermediate transfer belt 20 and the expansion and contraction of the image formed on the intermediate transfer belt 20. You can see that changes. That is, the secondary transfer roller-2
By changing the peripheral speed of 4, the expansion and contraction of the image can be controlled.

Therefore, the electrophotographic image forming apparatus 10 of the present invention.
0 is the secondary transfer roller 24 in which the peripheral speed is set to an appropriate value.
By using as a speed increasing device for the transfer belt 20, expansion and contraction of an image formed on the transfer belt 20 can be eliminated. This can eliminate the expansion and contraction of the image caused by the cleaning blade 26 being pressed against the transfer belt 20 by the secondary transfer roller 24 pressed at the same time as the cleaning blade 26. Because of that.
In other words, in order to compensate for the decrease in the conveying force of the intermediate transfer belt 20 due to the cleaning blade 26 on the transfer belt 20, 2
The peripheral speed of the next transfer roller 24 is set to be faster than that of the intermediate transfer belt 20, and the intermediate transfer belt 20 is pressed at the same time as the cleaning blade 26 is pressed. You can do it. By preventing the conveyance force of the intermediate transfer belt 20 from decreasing, a good image without expansion and contraction can be obtained. Further, when the present invention is applied to an image forming method of forming a single image by superimposing a plurality of images such as a full-color image, a multicolor image, and a composite image, the image length of the plurality of images is reduced because the images do not expand or contract. It becomes the same, and image defects such as color shift and image shift can be prevented.
Using the electrophotographic image forming apparatus 100 of this embodiment, a clear image is obtained.
An experiment was carried out with the total contact force of the inner blade 26 being 200 gf, and the diameter of the secondary transfer roller 24 was 0.16.
When the size was increased by mm, it was possible to obtain an image without expansion and contraction and color shift.

FIG. 7 is a cross-sectional view of an essential part showing another structural example of the electrophotographic image forming apparatus 100 according to the present invention. This structure is used for the intermediate transfer belt cleaner 25 and the secondary transfer roller.
The lager 24 is incorporated in the transfer / cleaner unit 32, and is pressed and separated at the same time.

FIG. 8 is an upper sectional view showing the structure of the transfer / cleaner unit 32. The transfer / cleaner unit 32 is mainly composed of the transfer / cleaner unit frame 3
3, a transfer / cleaner unit frame 33, an intermediate transfer belt cleaner 25 and a secondary transfer roller 24. The transfer / cleaner unit frame 33 is rotatable about a transfer / cleaner unit shaft 34, and the cleaning blade 26 and the secondary transfer roller 24 are rotated by the rotation of the transfer / cleaner unit frame 33. Press and separate from the intermediate transfer belt.

In this way, the intermediate transfer belt cleaner 2
5 and the secondary transfer roller 24 are incorporated in the transfer / cleaner unit 32, the size and simplification of the apparatus can be achieved.
The pressure contact and separation control of the next transfer roller 24 can also be simplified.

In addition to the intermediate transfer belt, the present invention also
It can also be applied to a belt photoreceptor. Figure 9
FIG. 4 is a cross-sectional view of a main part of an electrophotographic image forming apparatus 200 to which the present invention has been applied to a belt photosensitive member.

The electrophotographic image forming apparatus 200 shown in FIG.
The full-color printer uses the belt photoconductor 40, and the charging charger 4 is provided around the belt photoconductor 40.
1, a print head 42, a developing unit 43, a transfer roller 44, and a cleaning blade 45 are arranged.
Further, the developing unit 43 has developing devices for four colors of yellow, magenta, cyan and black. The transfer roller 44 and the cleaning blade 45 are provided so as to be in pressure contact with and separated from the belt photoconductor 40. Furthermore, the transfer roller 4
4 is rotating at a predetermined speed, which is faster than the belt photosensitive member 40.

The belt photoreceptor 40 is the charging charger 4
After being uniformly charged by 1, the print head 42 exposes it to form a latent image. The latent image formed on the belt photoconductor 40 is developed by one of the developing devices of the developing unit 43. At the time of forming a full-color image, four color toner images of yellow, magenta, cyan, and black are formed and superposed on the belt photoconductor 40. Transfer roller 44
Then, the cleaning blade 45 is separated from the belt photoconductor 40 until the formation of the cyan image of the third color is completed. A predetermined time after the image formation of the cyan image of the third color passes the portion where the belt photosensitive member 40 and the cleaning blade 45 face each other, the transfer roller 44 and the cleaning blade 45 are brought into pressure contact with each other at the same time, and the print paper P contacts the belt photosensitive member 40. The transfer roller 44 is conveyed to the facing portion. When the transfer roller 44 and the cleaning blade 45 are pressed into contact with each other at the same time, the conveyance force of the belt photoconductor 40 reduced by the cleaning blade 45 is compensated by the rotation of the transfer roller 44. Therefore, the conveyance speed of the belt photosensitive member 40 is constant regardless of the pressure contact or separation of the cleaning blade 45.

After the four color toner images are superposed on the belt photosensitive member 40, they are collectively transferred onto the print paper P by the transfer roller 44. Since the four color toner images are superposed on the belt photosensitive member 40 at a constant speed, the transferred image is a good image without expansion and contraction or color misregistration.

FIG. 10 is a cross-sectional view of essential parts showing another example of the electrophotographic image forming apparatus 100 according to the present invention. FIG.
In the example of 0, instead of supplementing the carrying force of the image carrying belt when the cleaning blade is pressed, the carrying force of the image carrying belt is reduced when the cleaning blade is separated so that the carrying force of the image carrying belt is kept constant. It is configured. Also, the basic configuration of the example of FIG.
The electrophotographic image forming apparatus 100 is substantially the same as the electrophotographic image forming apparatus 100, except for the configuration of the intermediate transfer belt cleaner 46.

FIG. 11 is an enlarged perspective view showing an end portion of the intermediate transfer belt cleaner 46 in this example. The intermediate transfer belt cleaner 46 mainly includes an intermediate transfer belt cleaner frame 49, a cleaning blade 26, and a belt conveyance load blade 47.
The intermediate transfer belt cleaner frame 49 is composed of an L-shaped member made of aluminum, stainless steel, plastic or the like, and the cleaning blade 26 and the belt conveyance load blade 47 are provided with an adhesive at both ends of the L-shape. It is fixed by. At the center of the L-shaped intermediate transfer belt cleaner frame 49, the intermediate transfer belt 2
An intermediate transfer belt cleaner shaft 48 is fixed at a fixed distance from 0. Cleaning Blade 2
6 and the belt conveyance load blade 47 rotate about the intermediate transfer belt cleaner shaft 48, and when the cleaning blade 26 is pressed against the intermediate transfer belt 20,
When the belt conveying load blade 47 is separated, and conversely, the cleaning blade 26 is separated, the belt conveying load blade 47 is in pressure contact. Further, the cleaning blade 26 is pressed so as to cover the image area of the intermediate transfer belt 20, and the belt conveyance load blade 47 is provided so as to be pressed only in the non-image area. The belt conveying load blade 47 is made of the same material as the cleaning blade 26, and has the same shape and blade.
The contact conditions such as the total contact force and contact angle of the blades are set so that the same load as the cleaning blade 26 applies to the intermediate transfer belt 20. In addition, the belt transport load blade 4 is used for jam handling and maintenance.
The cleaning blade 7 and the cleaning blade 26 can both be brought into non-pressure contact with each other, and an unnecessary load on the intermediate transfer belt 20 can be prevented. Incidentally, the intermediate transfer belt 20 and the belt conveyance load blade 47 and the clear belt are formed during image formation.
Since it is always decelerated by the training blade 26, the carrying force of the intermediate transfer belt 20 is set in consideration of the belt carrying load blade 47 and the deceleration by the cleaning blade 26. In addition, the secondary transfer roll
The speed of the roller 24 is set to a speed that does not affect the conveying force of the intermediate transfer belt 20.

FIG. 12 shows the continuous output mode in this example.
3 is a timing chart of the full-color image forming operation of the printer.
The operation of the timing chart of FIG. 12 is exactly the same as that of the timing chart shown in FIG. 4 except for the operation control of the belt conveyance load blade 47, and therefore the operation control of the belt conveyance load blade 47 will be mainly described here. .

The belt conveyance load blade 47 is held in pressure contact with the intermediate transfer belt 20 from the time when image formation is started to the time when the cleaning blade 26 is pressed, and the speed of the intermediate transfer belt 20 is kept constant. Maintain the same speed as when pressing the cleaning blade 26. When the developing device 4K is selected, when the belt position detection mark is detected by the intermediate transfer belt position detection sensor, the secondary transfer roll is started after T2 time.
The liner 24 and the intermediate transfer belt cleaner 25 are activated,
The secondary transfer roller 24 and the cleaning blade 26 are pressed against the transfer belt 20, and the belt conveying load blade 4
7 is separated from the intermediate transfer belt 20.

Thus, the cleaning blade 26,
Further, by constantly applying a constant load to the intermediate transfer belt 20 by the belt conveyance load blade 47, the conveyance speed of the intermediate transfer belt 20 is kept constant, and there is no image defect such as image expansion and contraction or color misregistration. You can get a nice image.

In FIG. 13, a belt carrying load roller 50 is used instead of the belt carrying load blade 47.
In this way, by using rollers as the belt conveying load member instead of the blade, the durability of the image bearing belt can be improved. FIG. 14 is an enlarged perspective view showing an end portion of the intermediate transfer belt cleaner 46 using the belt conveyance load roller 50. The belt carrying load roller 50 is provided on the intermediate transfer belt cleaner frame 49 so as to face the non-image portion of the intermediate transfer belt 20, like the belt carrying load blade 47.

This method can also be applied to an electrophotographic image forming apparatus using a belt photosensitive member instead of the intermediate transfer belt. FIG. 15 is a sectional view of an essential part of an electrophotographic image forming apparatus 300 using a belt photosensitive member according to the present invention.

The electrophotographic image forming apparatus 30 shown in FIG.
The basic configuration of 0 is the same as that of the electrophotographic image forming apparatus 200 of FIG. 9 except that a belt photosensitive member cleaner 51 is provided instead of the cleaning blade 45. or,
The rotation speed of the transfer roller 44 of the electrophotographic image forming apparatus 300 is the same as that of the electrophotographic image forming apparatus 200 of FIG.
Unlike the above, the speed is set close to the belt photoconductor 40 so as not to affect the conveyance speed of the belt photoconductor 40.

The structure of the belt photosensitive member cleaner 51 is almost the same as that of the intermediate transfer belt cleaner 46 shown in FIGS.
Is mainly composed of a belt photosensitive member cleaner frame 54, a cleaning blade 45, and a belt carrying load blade 52. The belt photosensitive member cleaner frame 54 is formed of a trapezoidal member made of aluminum, stainless steel, plastic, or the like, and the cleaning blade 45 and the belt conveyance load blade 52 are fixed to a portion corresponding to the bottom of the trapezoid. There is. A belt photoconductor cleaner shaft 53 is fixed to the belt photoconductor cleaner frame 54, and the cleaning blade 45 and the belt carrying load blade 52 rotate about the belt photoconductor cleaner shaft 53. When the cleaning blade 45 is pressed against the belt photosensitive member 40, the belt conveying load blade 52 is separated, and conversely, when the cleaning blade 45 is separated, the belt conveying load blade 52 is pressed. Is configured. The cleaning blade 45 is pressed against the belt photosensitive member 40 so as to cover the image area of the belt photosensitive member 40.
2 is provided so as to be in pressure contact with the non-image area. Therefore, when not cleaning, cleaning blade 4
5, the belt carrying load blade 52 reduces the carrying force of the belt photoconductor 40, so that the photoconductor belt 40
It is possible to maintain a constant transport speed. Photoconductor belt 4
Since the conveying speed of 0 is constant regardless of contact / separation of the cleaning blade 45, it is possible to obtain a good image without expansion and contraction of the toner image formed on the belt photosensitive member and color misregistration. Further, also for the belt photosensitive member, a roller may be used as the belt conveying load means instead of the blade.

In this embodiment, the cleaning blade is used as the intermediate transfer belt, and the cleaning means for the belt photosensitive member and the belt conveying load means. However, other brush cleaners, cleaning rolls, fur brushes, etc. The cleaning member may be used. Further, in this embodiment, 1
Although roller transfer was used as the next transfer means, other transfer methods such as charger transfer and brush transfer may be used.

Further, in the present invention, the speed increasing device of the image bearing belt is also used as the transfer roller for the purpose of downsizing and simplification of the device. A device for increasing the driving force of the carrier belt itself may be provided. Further, a brush, sponge, friction plate or the like may be used as the deceleration means of the image bearing belt in addition to the blade and the roller, and a device for reducing the driving force of the image bearing belt itself may be provided.

[0058]

According to the present invention, it is possible to prevent the belt-type image carrier carrying force from being lowered, and it is possible to obtain a good image without expansion and contraction. Further, when the present invention is applied to an image forming method of forming a single image by superimposing a plurality of images such as a full-color image, a multicolor image, and a composite image, the image length of the plurality of images is reduced because the images do not expand or contract. It becomes the same, and image defects such as color shift and image shift can be prevented.

Further, even during image formation, the cleaning member can be pressed and separated without affecting the image, so that image formation can be performed efficiently and copy speed can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an electrophotographic image forming apparatus according to the present invention.

FIG. 2 is a sectional view showing a configuration of an intermediate transfer member unit.

FIG. 3 is a block diagram of a control circuit of the image forming apparatus according to the present invention.

FIG. 4 is a timing chart of an image forming operation of the image forming apparatus according to the present invention.

FIG. 5 is a graph showing the relationship between the secondary transfer roller peripheral speed and the intermediate transfer belt conveyance distance.

FIG. 6 is a graph showing a relationship between secondary transfer roller peripheral speed and image expansion / contraction on the intermediate transfer belt.

FIG. 7 is a cross-sectional view of essential parts showing another configuration example of the electrophotographic image forming apparatus according to the present invention.

FIG. 8 is an upper sectional view showing a structure of a transfer / cleaner unit.

FIG. 9 is a cross-sectional view of essential parts of an electrophotographic image forming apparatus according to the present invention.

FIG. 10 is a cross-sectional view of essential parts showing an electrophotographic image forming apparatus of another example related to the present invention.

FIG. 11 is an enlarged perspective view of an end portion of an intermediate transfer belt cleaner according to another example of the present invention.

FIG. 12 is a timing chart of an image forming operation of another example according to the present invention.

FIG. 13 is a cross-sectional view of essential parts showing another example of an electrophotographic image forming apparatus according to the present invention.

FIG. 14 is an enlarged perspective view of an end portion of an intermediate transfer belt cleaner according to another example of the present invention.

FIG. 15 is a cross-sectional view of essential parts of another example of an electrophotographic image forming apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor unit 2 Intermediate transfer body unit 3 Printhead 4 Developing unit 5 Paper feed cassette 6 Copy paper transport unit 7 Fixing device 10 Photoconductor 11 Developing unit shaft 15 Main motor 16 Drive motor 20 Intermediate transfer belt 21 Drive roll -Raler 22 Energizing Roller 23 Secondary Transfer Opposing Roller 24 Secondary Transfer Roller 25 Intermediate Transfer Belt Cleaner 26 Cleaning Blade 27 Primary Pre-Transfer Roller 28 Primary Transfer Roll Lar 30 Timing Roller 31 Timing Roller 32 Transfer / Cleaner Unit 33 Transfer / Cleaner Unit Frame 34 Transfer / Cleaner Unit Shaft 40 Belt Photoreceptor 41 Charging Charger 42 Printhead 43 Developing Unit 44 Transfer Roller 45 Cleaning Blade 46 Intermediate transfer belt 47 Belt transport load blade 48 Intermediate transfer belt cleaner shaft 49 Intermediate transfer belt cleaner frame 50 Belt transport load roller 51 Belt photosensitive cleaner 52 Belt transport load blade 53 Belt photosensitive cleaner shaft 54 Belt photosensitive cleaner frame 100 Electrophotographic type Image device 200 Electrophotographic image forming device 300 Electrophotographic image forming device P Print paper

Claims (2)

[Claims] 1. An image carrying belt for carrying a toner image on its surface, a belt driving device for carrying the image carrying belt at a constant speed, and a cleaning device having a cleaning member which can be pressed into contact with and separated from the image carrying belt. An electrophotographic image forming apparatus including a belt conveying force increasing device for increasing a conveying force of the image supporting belt when a cleaning member is pressed against the image supporting belt. 2. An image carrying belt carrying a toner image on the surface thereof, a belt driving device for carrying the image carrying belt at a constant speed, and a cleaning member pressable to and separable from the image carrying belt. Sometimes a cleaning device for removing the developer on the image bearing belt, and a cleaning member separated from the image bearing belt,
An electrophotographic image forming apparatus equipped with a belt conveying force reducing device for reducing the conveying force of an image carrying belt.