JP3504310B2 - Image forming device - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention transfers a toner image formed on an image bearing member to an intermediate transfer member, and then transfers the toner image from the intermediate transfer member to a transfer material such as paper by using a transfer means, and further after that. The present invention relates to an image forming apparatus such as an electrophotographic copying machine, a laser beam printer, or a FAX, which fixes a toner image on a transfer material by using a fixing unit.

[0002]

2. Description of the Related Art Conventionally, as an image forming apparatus using such an intermediate transfer member, for example, toner images of different colors sequentially formed on an image carrier are sequentially transferred to the intermediate transfer member. 2. Description of the Related Art A color image forming apparatus is known in which, after being superposed, they are collectively transferred from an intermediate transfer member to a transfer material such as paper. Further, it is also known that the intermediate transfer member is composed of a plurality of supporting rollers and an endless intermediate transfer belt that is stretched around these supporting rollers.

[0003]

However, in the above-mentioned prior art, when the image forming apparatus is left for a certain period of time or more, and then the apparatus power is turned on to drive the intermediate transfer belt to rotate, the supporting roller is used while the apparatus is left standing. A supporting roller habit is easily formed on the supported portion of the intermediate transfer belt. This support roller habit tends to cause damage to the surface of the image carrier. In addition, a difference occurs between the surface speed of the image carrier and the surface speed of the intermediate transfer member, so when the image carrier and the intermediate transfer member come into contact with each other and image transfer is performed, slippage occurs between the two and the transfer occurs. There has been a problem that the generated toner image is blurred. The problem of the former is already filed (Japanese Patent Application No. 5-18205).
Although a solution is proposed by the technology of (see No. 2),
The latter problem remained.

[0004]

SUMMARY OF THE INVENTION Therefore, the present invention is to solve this remaining problem. That is, the present invention is applied to a toner image transferred so that there is no difference between the surface speed of the image carrier and the surface speed of the intermediate transfer member when the toner image is transferred from the image carrier to the intermediate transfer member. An object of the present invention is to provide an image forming apparatus that eliminates the problem of fading.

[0005]

In order to achieve the above object, the present invention is to transfer a toner image formed on an image bearing member to an intermediate transfer member, and then transfer the toner image from the intermediate transfer member using a transfer unit. In an image forming apparatus for transferring onto a transfer material such as paper and fixing the transfer material onto a transfer material using a fixing unit, the intermediate transfer member is composed of a plurality of support rollers and an endless intermediate transfer belt which is supported by the support rollers. Configure and pair with the above image carrier
Rotate the facing first support roller and second support roller
Swingably supporting a first supporting member and a third supporting member.
A third supporting roller that rotatably supports the holding roller.
A spring that biases the above-mentioned intermediate transfer belt in the circumferential direction.
A swingable second support member for supporting, and a first support portion
An eccentric cam arranged between the material and the second support member.
The half rotation of the eccentric cam causes the first support member and the
The second support member swings so that the intermediate transfer member moves to the image.
Contact position to contact the carrier, and separate from the image carrier
Move to and from the separated position, and
As the urging force of the ring becomes stronger than the contact position above,
The tension of the intermediate transfer belt becomes stronger than the contact position.
The most important feature is that it is an image forming apparatus. The image forming apparatus regulates the rotation of the eccentric cam.
Is provided to prevent the eccentric cam from rotating.
Is regulated to selectively change the urging force of the spring.
In addition, the tension of the intermediate transfer belt can be changed selectively.
The most important feature is that it has a configuration that allows it. The image forming apparatus includes the swingable first support portion.
The main feature is that the material is replaced by the fixed first support member .

[0006]

In the image forming apparatus constructed as described above, the tension of the intermediate transfer belt is weakened when the intermediate transfer body comes into contact with the image carrier. At the time of transferring the toner image to the transfer body, there is no difference between the surface speed of the image carrier and the surface speed of the intermediate transfer body, thereby eliminating the problem that the toner image to be transferred is blurred. . Further, the contacting / separating mechanism means of the intermediate transfer member to the image carrier and the tension varying mechanism means of the intermediate transfer belt have the same mechanism, so that the intermediate transfer member is moved from the image carrier. It is possible to provide an image forming apparatus which can easily obtain a good image without blurring of a toner image when the toner image is transferred to and from the contacting / separating portion and the timing of selectively changing the tension of the intermediate transfer belt. To do so.

[0007]

Embodiments of the present invention will now be described with reference to the drawings. Here, an example in which the present invention is applied to a color copying apparatus which is an image forming apparatus will be described. In FIG. 1, this color copying apparatus is roughly composed of a color image reading apparatus 6 and a color image recording apparatus 7.
First, the color image reading device 6 forms an image of the document 50 on the contact glass CG on the color sensor 54 via the illumination lamp 51, the mirror group 52, and the lens 53, and the color image information of the document 50. Is, for example, blue (hereinafter referred to as B), green (Green)
n, hereinafter G), red (Red, hereinafter R)
Each color separation light is read and converted into an electrical image signal. Then, based on the B, G, and R color-separated image signal intensity levels obtained by the color image reading device 6,
Color conversion processing is performed by an image processing unit (not shown), and black (hereinafter, referred to as Bk), cyan (Cyan, hereinafter, C)
Color image data of magenta (hereinafter referred to as M) and yellow (hereinafter referred to as Y).

Next, in the color image recording apparatus 7, the writing optical unit 11 is used to read the color image reading apparatus 6
The color image data from is converted into an optical signal, and the optical writing corresponding to the original image is performed to form an electrostatic latent image on the image carrier 10 composed of a photosensitive drum or the like. The surface of the image carrier (photoreceptor drum) 10 rotates counterclockwise as indicated by the arrow, and around it, an image carrier cleaning unit (including a pre-cleaning charge eliminator) 12, a discharge lamp 13, Charging device 14, potential sensor 15, Bk developing device 1
6, a C developing device 17, an M developing device 18, a Y developing device 19, an optical sensor 20 for detecting a development density pattern, an intermediate transfer belt 3 and the like are arranged. Each developing device rotates a developing sleeve (16a, 17a, 18a, 18a, 18a, 18a, 18b) which rotates by bringing a brush of the developer into contact with the surface of the image carrier 10 to develop the electrostatic latent image.
19a, see FIG. 2) and the developing paddles (16b, 17b, 18b, 19) that rotate to pump up and stir the developer.
b, see FIG. 2), and a toner concentration sensor (1
6c, 17c, 18c, 19c, see FIG. 2) and the like.

The outline of the copying operation will be described below by taking the case where the developing operation order (color toner image forming order) is Bk, C, M, and Y as an example (however, the image forming order is not limited to this. is not). When the copy operation is started, the color image reading device 6 starts reading Bk image data from a predetermined timing, and optical writing by a laser beam and latent image formation start based on this image data (hereinafter, referred to as Bk image data). The electrostatic latent image is referred to as a Bk latent image. C, M, and Y are referred to as a C latent image, an M latent image, and a Y latent image, respectively). Before the latent image front end reaches the developing position of the Bk developing device 16, which allows development from the front end of the Bk latent image, the developing sleeve 16a is started to rotate, and Bk
The latent image is developed with Bk toner. After that, the developing operation of the Bk latent image area is continued, and when the trailing edge of the latent image passes the Bk developing position, the developing operation is disabled. This transition to the inoperative state is completed at least before the leading edge of the C latent image by the next C image data arrives.

Next, the Bk toner image formed on the image carrier 10 is transferred onto the surface of the intermediate transfer belt 3 which is driven at the same speed as the image carrier 10. The toner image transfer from the image carrier 10 to the intermediate transfer belt 3 is called belt transfer. This belt transfer belongs to the support roller 2 in a state where the image carrier 10 and the intermediate transfer belt 3 are in contact with each other. This is performed by applying a predetermined bias voltage to the transfer bias rollers 2b and 2c. In addition, on the intermediate transfer belt 3, the Bk, C, M, and Y toner images sequentially formed on the image carrier 10 are sequentially aligned on the same surface to form a belt transfer image of four-color superposition. Then, batch transfer is performed on the transfer paper. This intermediary transcript 1
Will be described later.

Here, on the side of the image carrier 10, the Bk process is followed by the C process, but the C image data reading by the color image reading device 6 starts at a predetermined timing, and the laser light writing by the image data causes C latent image formation is performed. The C developing device 17 starts rotating the developing sleeve 17a after the trailing end of the previous Bk latent image has passed and before the leading end of the C latent image has reached the developing position, and the C developing device 17 is rotated. Is developed with C toner. After that, the development of the C latent image area is continued, and when the trailing edge of the latent image passes, the development inoperative state is set in the same manner as the previous Bk developing device. This is also the next M
Complete before the latent image tip reaches. Note that M and Y
For each step of, each image data reading,
The latent image forming and developing operations are performed in the same manner as the steps Bk and C described above.

Next, the intermediate transfer member 1 will be described. In FIG. 2, the intermediate transfer belt 3 includes a driving roller 2d, transfer bias rollers 2b and 2c, and driven rollers 2a and 2a.
It is stretched around e and is driven by a drive motor (not shown). Further, a contact / separation mechanism means 5 is provided so that the intermediate transfer belt 3 can contact and separate from the image carrier 10. Further, there is a variable mechanism means 4 for changing the tension of the intermediate transfer belt 3 in accordance with the contact / separation state of the intermediate transfer belt 3. In this example, the variable mechanism means 4 and the contact / separation mechanism means 5
Are shown to be the same, but are not particularly limited. The movement of both will be described later.

A belt cleaning unit 21 is provided at a predetermined position facing the surface of the intermediate transfer belt 3. The belt cleaning unit 21 includes a brush roller 21a, a rubber blade 21b, and a cleaning contact / separation mechanism 21c from the belt. The belt cleaning unit 21 transfers the second, third, and fourth colors after the belt transfer of the first-color Bk image. During belt transfer, the cleaning contact / separation mechanism 21c
Is separated from the belt surface by, and at a predetermined timing thereafter, the surface of the intermediate belt 3 is contacted and cleaning is performed.
Further, a paper transfer unit 22 is provided so as to face the portion of the intermediate transfer belt 3 wound around the drive roller 2d. The paper transfer unit 22 is composed of a paper transfer roller 22a, a roller cleaning blade 22b, a paper transfer contact / separation mechanism 22c from the belt, and the like.

The paper transfer roller 22a is normally separated from the surface of the intermediate transfer belt 3, but the intermediate transfer belt 3 is not provided.
The above-mentioned paper transfer contact / separation mechanism 22c is timed when the four-color superposed images formed on
Then, a predetermined bias voltage is applied to the paper transfer roller 22a to transfer the paper onto the paper. Note that, in FIG. 1, the transfer paper P includes a paper feed roller 23 and a registration roller 24.
Thus, the leading end of the four-color superimposed image on the surface of the intermediate transfer belt 3 is fed at the timing of reaching the paper transfer position.

As a method of driving the intermediate transfer belt 3, the following three methods are conceivable as an operation method after the belt transfer of the Bk toner image of the first color is completed up to the end, and one of these methods is used. Or in terms of copy speed, the intermediate transfer belt 3 is driven by efficiently combining a plurality of these methods according to the copy size. (1) First, a constant speed forward movement method will be described as a first method. Even after the Bk toner image is transferred onto the belt, it continues to move at a constant speed. When the front end position of the Bk image on the surface of the intermediate transfer belt 3 again reaches the belt transfer position which is the contact portion with the image carrier 10, the image carrier 10 side displays the next C toner image. An image is formed with a timing so that the front end portion is exactly at that position. As a result, the C image is belt-transferred on the surface of the intermediate transfer belt 3 while being accurately aligned with the Bk image. After that, the same operation is followed to the M and Y image process,
A belt transfer image of four colors is obtained. After the transfer process of the Y toner image belt for the fourth color, the four color toners on the belt surface are collectively transferred to the transfer paper P as described above while moving forward.

(2) Next, a skip forward method will be described as a second method. When the belt transfer of the Bk toner image is completed, the image carrier 1
The intermediate transfer belt 3 is separated from the surface of 0, and the intermediate transfer belt 3 is skipped at high speed in the forward movement direction as it is, and after moving a predetermined amount, the initial forward movement speed is restored. Further, after that, the intermediate transfer belt 3 is brought into contact with the image carrier 10 again. When the front end position of the Bk image on the surface of the intermediate transfer belt 3 reaches the belt transfer position again, the image carrier 10 side takes timing so that the front end part of the next C toner image comes to that position. Image is formed. As a result, the image of C is accurately aligned with the Bk image and transferred onto the belt in a superimposed manner. After that, the same operation is performed to proceed to the M and Y image process.
Obtain a belt transfer image with color overlap. Subsequent to the Y-color toner image belt transfer step for the fourth color, the four-color superimposed toner image on the surface of the intermediate transfer belt 3 is transferred onto the transfer paper P all together at the same forward speed.

(3) Next, a reciprocating (quick return) system will be described as a third system. When the belt transfer of the Bk toner image is completed, the image carrier 1
The intermediate transfer belt 3 is separated from the surface of 0, and the forward movement is stopped, and at the same time, the high speed return is performed in the opposite direction. In the return, the front end position of the Bk image on the surface of the intermediate transfer belt 3 passes the position corresponding to the belt transfer in the opposite direction, and after moving by a preset distance, it is stopped and put in a standby state. Next, when the front end of the C toner image on the image carrier 10 side reaches a predetermined position before the belt transfer position, the intermediate transfer belt 3 is restarted in the forward direction. Further, the intermediate transfer belt 3 is brought into contact with the surface of the image carrier 10 again. Also in this combination, the C image is controlled and transferred under the condition that the C image exactly overlaps the Bk image on the surface of the intermediate transfer belt 3. After that, the same operation is performed to proceed to the Y and M image process.
Obtain a belt transfer image with color overlap. Subsequent to the belt transfer process of the Y color toner image of the fourth color, the four color superposed toner images on the surface of the intermediate transfer belt 3 are collectively transferred onto the transfer paper P by moving forward at the same speed without returning.

As described above, the transfer paper P on which the four-color superposed toner images are collectively transferred from the surface of the intermediate transfer belt 3 is conveyed to the fixing device 26 by the paper conveying unit 25 and controlled to a predetermined temperature. Fixing roller 26a and pressure roller 26
In b, the toner image is fused and fixed and stored in the copy tray 27 to obtain a full-color copy. The surface of the image carrier 10 after the belt transfer is cleaned by an image carrier cleaning unit 12 (pre-cleaning static eliminator 12a, brush roller 12b, rubber blade 12c, see FIG. 2), and the static erasing lamp is also used. The charge is uniformly removed at 13. Further, the intermediate transfer belt 3 after the toner image is transferred onto the transfer paper P is
The belt cleaning unit 21 is again pressed by the cleaning contact / separation mechanism 21c to clean the surface.

At the time of repeat copying, the operation of the color image reading device 6 and the image formation on the image carrier 10 are continued to the Y (fourth color) image process of the first sheet, and then the second sheet at a predetermined timing. Proceed to the Bk (first color) image process. Further, in the intermediate transfer belt 3, after the batch transfer process of the first four-color superimposed image onto the transfer paper P, the surface is set to the area cleaned by the belt cleaning unit 21.
The Bk toner image of the first sheet is transferred on the belt. After that, the same operation as the first sheet is performed.

The transfer paper cassette 28 (28a, 28a
b, 28c, 28d) contain transfer sheets of various sizes, which are fed and conveyed toward the registration rollers 24 at a timing from a storage cassette of a size designated by an operation panel (not shown). It In addition, a manual feed tray 29 is separately provided for OHP paper, thick paper, and the like.

The above is the description of the copy mode for obtaining four full colors. However, the combination of the three-color copy mode and the two-color copy mode is performed for the designated number of colors and the number of times.
The same operation as above will be performed. In addition, in the single-color copy mode, until the copying of the predetermined number of sheets is completed, only the phenomenon device of that color is in the developing operation (agent stand) state, and the intermediate transfer belt 3 is the image carrier 10. The surface is driven at a constant speed in the forward direction while being in contact with the surface of No. 2, and the copying operation is performed while the belt cleaning unit 21 is also in contact with the intermediate transfer belt 3.

Next, the operation of the intermediate transfer belt 3 according to the embodiment of the present invention will be described in detail with respect to (2) skip forward movement method and (3) reciprocating movement (quick return) method.
FIG. 3A is an example showing the state of the intermediate transfer body 1 in the case of belt transfer for both the (2) skip forward method and the (3) reciprocating (quick return) method.
An eccentric cam 60 has an eccentric position of 60a. The transfer bias rollers 2b and 2c are the rotation support shaft 6
Bias roller support member 62 ("
(Corresponding to "1 support member") , it moves with the rotation of the member 62. In the state shown in the drawing, the surface of the image carrier 10 is in contact with the intermediate transfer belt 3 with a nip width 1 (ell). A driven roller supporting member 64 (corresponding to a "second supporting member") that supports the driven roller 2a .
That) is rotatable around the rotation support shaft 63, a driven roller 2a in this state has given a predetermined tension is pressurized to the intermediate transfer belt 3 (shown to not) in the spring 65. The tension has a relationship corresponding to the length A of the spring 65 when it is pressed.

In FIG. 3B, the eccentric cam 60 is rotated counterclockwise (arrow) by about 90 ° to bring the eccentric position 60a to the position shown in the figure, and while the eccentric position 60a moves. In addition, the transfer bias rollers 2b and 2c rotate in the direction away from the surface of the image carrier 10 (arrow). At the same time, the driven roller support member 64 is pressed by the eccentric cam 60.
Rotates in the counterclockwise (arrow) direction around the rotation support shaft 63, so that the driven roller 2a moved by the driven roller support member 64 strongly contacts the intermediate transfer belt 3. Therefore, the tension of the intermediate transfer belt 3 is equal to that of the transfer bias roller 2
The movement of the driven rollers 2a strengthens the movement of the driven rollers 2a by the amount of weakening caused by the movements of b and 2c.
And the length A of the spring 65 when the spring 65 is pressed are almost unchanged.

FIG. 3C shows a result obtained by further rotating the eccentric cam 60 in the counterclockwise (arrow) direction.
It is a figure which shows the state which moved about 180 degree from the position of (a). The eccentric position 60a moves to the position shown in the figure, and the bias roller support member 62 hardly moves during this time.
Since the driven roller support member 64 is largely rotated in the counterclockwise (arrow) direction around the rotation support shaft 63, the length of the spring 65 is shortened from A to B state, and the tension of the intermediate transfer belt 3 is reduced. It becomes larger than the tension in the case of FIGS. Then, in the state where the surface of the image carrier 10 of FIG. 3C and the intermediate transfer belt 3 are separated from each other, the skip forward movement of the skip forward movement method of (2) above and the reciprocating movement of (3) (quick return). It is possible to make a quick return of the method. Actually, the eccentric cam 60 has the eccentric position 180 and the eccentric position 60a of FIG.
The two eccentric positions 60a of FIG. 3 (c) facing each other can be selectively taken. For example, this is 18
An electromagnetic spring clutch having a ratchet stopper at a position opposed to 0 ° (hereinafter referred to as a belt contact / separation clutch 83
This can be easily achieved by using (refer to FIG. 4 ) (corresponding to “regulating means”) .

By using the intermediate transfer member 1 of the present invention configured as described above, when the intermediate transfer belt 3 comes into contact with the surface of the image carrier 10 and the belt transfer is performed, it is shown in FIG. 3 (a). As described above, the tension of the intermediate transfer belt 3 is set to be weak,
The surface speed of the intermediate transfer belt 3 in the nip width 1 portion is the variable length of the spring 65 of the driven roller 2a due to the electrostatic attraction effect in the nip width 1 where the surface of the image carrier 10 and the intermediate transfer belt 3 are in contact with each other. Since it matches the surface velocity of the image carrier 10 within the pressure change range, it is possible to obtain a good image that is free from image deterioration such as blurring of the toner image due to the disagreement between the two and the insect transfer due to belt transfer failure.

Further, since the intermediate transfer belt 3 is separated from the image carrier 10 after the belt transfer of each color is completed, the tension of the intermediate transfer belt 3 is set to be strong as shown in FIG. (2) When the high-speed operation such as the skip forward movement of the skip forward movement method and the quick return of the (3) reciprocating movement (quick return) method is required, the intermediate transfer belt 3 slides on the drive roller 2d and the position thereof. It eliminates the problem of not being able to make a good match.

Further, as can be seen from FIG. 3A, the contact / separation mechanism means 5 and the intermediate transfer belt 3 are moved in accordance with the separating operation so that the intermediate transfer belt 3 can contact and separate from the image carrier 10. By making the variable mechanism means 4 for changing the tension of No. 3 the same, it helps to provide an image forming apparatus that obtains a good image in which there is no error or deviation in the switching timing of both functions. Further, since the components are commonly used, it is possible to obtain an effect of obtaining a low cost, downsized, and highly reliable image forming apparatus.

In the example of the above description, of the three operation modes of the intermediate transfer belt 3, the constant speed forward motion method of (1) was excluded, but in order to apply the present invention to the constant speed forward motion method. Is the transfer bias roller 2 in FIG.
The bias roller support members 62 of b and 2c are attached to the eccentric cam 60.
The bias roller support member 62 may be fixed so that the bias roller support member 62 is always in non-contact with. In this state, the intermediate transfer belt 3 remains in contact with the image carrier 10 and the tension of the intermediate transfer belt 3 can be changed by the operation of the eccentric cam 60. Therefore, during the belt transfer, the intermediate transfer belt 3 is moved. The tension may be set to be weak and strong during non-belt transfer.

FIG. 4 is a block diagram showing the essential parts of the electrical system of the color image recording apparatus 7, and the parts closely related to the present invention will be described. The system controller 80 controls the entire color image recording device 7. An intermediate transfer belt drive motor control unit 82 to which the belt drive motor 81 for the drive roller 2d of the intermediate transfer belt 3 is connected, and a mechanism for performing the contact / separation operation of the intermediate transfer belt 3 with respect to the image carrier 10 is possible. A belt contact / separation clutch 83, a paper transfer roller contact solenoid 84 for driving a paper transfer contact / separation mechanism 22c for contacting / separating the paper transfer roller 22a with respect to the drive roller 2d, and a contact / separation for the belt cleaning unit 21. A belt cleaner contact solenoid 85 for driving the cleaning contact / separation mechanism 21c, various driving loads 86 of the color image recording apparatus 7, various process loads 87, etc. are connected. The various driving loads 86 include a motor for driving the fixing roller 26a and the pressure roller 26b of the fixing device 26, a motor for driving the paper carrying unit 25 for carrying the transfer material to the fixing device 26, and the like.

[0030]

Since the image forming apparatus configured as described above has a structure in which the tension of the intermediate transfer belt is weakened when the intermediate transfer body comes into contact with the image carrier, the intermediate transfer body moves from the image carrier to the intermediate transfer body. When the toner image is transferred to, the difference between the surface speed of the image carrier and the surface speed of the intermediate transfer member does not occur, and the problem that the transferred toner image is blurred is eliminated. Further, since the contacting / separating mechanism means for the intermediate transfer body to the image carrier and the tension varying mechanism means for the intermediate transfer belt are the same, it is possible to transfer the toner image from the image carrier to the intermediate transfer body. Thus, it is possible to provide an image forming apparatus that can obtain a good image with no toner image blurring, because it is easy to set the timing of contact and separation and the timing of selectively changing the tension of the intermediate transfer belt.

[Brief description of drawings]

FIG. 1 is a side view of the entire main part of a color copying apparatus showing an embodiment of the present invention.

FIG. 2 is a side view of essential parts of an image carrier and an intermediate transfer member of a color copying apparatus showing an embodiment of the present invention.

3 (a), (b) and (c) are explanatory views of essential parts of the intermediate transfer member of the present invention.

FIG. 4 is a block diagram of an electrical system main part of a color image recording apparatus showing an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Intermediate transfer body, 2 ... Support roller, 3 ... Intermediate transfer belt, 4 ... Variable mechanism means, 5 ... Contact / separation mechanism means, 6 ... Color image reading device, 7 ... Color image recording device, 10 ... Image carrier, 11 ... Writing optical unit, 12 ... Image carrier cleaning unit, 13 ... Static elimination lamp, 14 ... Charger,
15 ... Potential sensor, 16 ... Bk developing device, 17
... C developing device, 18 ... M developing device, 19 ... Y developing device, 20 ... Optical sensor, 21 ... Belt cleaning unit, 22 ... Paper transfer unit, 23 ...
..Feeding rollers, 24 ... Registration rollers,
25 ... Paper transport unit, 26 ... Fixing device, 27 ...
..Copy tray, 28 ... Transfer paper cassette, 29 ...
..Manual feed tray, 50 ... Originals, 51 ... Illumination lamp, 52 ... Mirror group, 53 ... Lens, 5
4 ... Color sensor, 60 ... Eccentric cam, 61.
..Rotation support shafts, 62 ... Bias roller support members,
63 ... Rotation support shaft, 64 ... Followed roller support member, 65 ... Spring, 80 ... System control unit, 81 ... Belt drive motor, 82 ... Intermediate transfer belt drive motor control unit , 83 ... Belt contact / separation clutch, 84 ... Paper transfer roller contact solenoid, 85 ...
-Belt cleaner contact solenoid, 86 ... Various drive loads, 87 ... Various process loads.

Claims (3)

(57) [Claims] 1. A toner image formed on an image carrier is transferred to an intermediate transfer member, then transferred from the intermediate transfer member to a transfer material such as paper by using a transfer unit, and then transferred by a fixing unit. In the image forming apparatus for fixing to the first supporting roller, the intermediate transfer member is composed of a plurality of supporting rollers and an endless intermediate transfer belt which is stretched around and supported by the supporting rollers, and the first supporting roller is opposed to the image bearing member. And the second branch
A swingable first support that rotatably supports the holding roller.
And rotatably support the member and the third support roller.
Energize the third support roller in the circumferential direction of the intermediate transfer belt.
Swingable second support member for supporting the spring
And between the first support member and the second support member
An eccentric cam is provided, and the first support member and the second eccentric cam are rotated by half rotation.
Support member swings, and the intermediate transfer member holds the image
Contact position to contact the body and separation to separate from the image carrier
Move to and from the position, and in the spaced position, the spring
The urging force of the
So that the tension of the transfer belt becomes stronger than the contact position
An image forming apparatus characterized in that. 2. A regulating means for regulating the rotation of the eccentric cam.
The provided, the regulating means regulates the rotation of the eccentric cam, the scan
Selectively change the pulling force, and
The image forming apparatus according to claim 1 , wherein the tension of the transfer belt is selectively changed . 3. Fixing the swingable first support member
The image forming apparatus according to claim 1 or 2, wherein the image forming apparatus is replaced with the first supporting member that is formed.