JP2010145774A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of preventing a transfer belt from being deflected by loosening the tension of the transfer belt. <P>SOLUTION: The image forming apparatus includes: two rollers around which a transfer belt is stretched in tension; a slide member having a roller moving means which is slid approximately parallel with the tension direction of the transfer belt to move one of the rollers reversely to a belt tension direction; and a slide member moving means for sliding the slide member in the reverse direction of the tension direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that prevents wrinkles of a transfer belt.

  In a conventional image forming apparatus, an electrophotographic method is known as one of image forming methods. In such an image forming apparatus, a transfer belt is mounted to form a toner image directly on a sheet on the transfer belt or directly on the transfer belt.

  Since the transfer belt stretches the transfer belt other than during image formation, various deformations such as curling and stretching occur, resulting in fatigue failure, image deterioration, and the like.

  Thus, for example, Patent Document 1 and Patent Document 2 disclose a configuration in which a transfer belt is loosened using a solenoid or the like.

Further, Patent Document 3 discloses a configuration that prevents the transfer belt from being wrinkled during long-term storage by providing a separate fixing member.
JP 2002-258692 A JP 2006-053492 A JP 2005-049678 A

  However, Patent Document 1 and Patent Document 2 have a demerit that a separate drive member is required, which increases costs.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus in which a tension is loosened and a transfer belt can be prevented from being wrinkled.

  In order to solve the above-described problem, an image forming apparatus according to the present invention includes two rollers for stretching a transfer belt, and slides substantially parallel to the stretching direction of the transfer belt, and one of the rollers is opposite to the belt stretching direction. It comprises a slide member having a roller moving means for moving, and a slide member moving means for sliding the slide member in the reverse direction of the tension.

  Further, the slide member moving means is characterized in that it slides by rotating a cam and pressing a contact surface provided on the slide member.

  Also, the slide member has a long hole in the stretching direction into which the shaft of one roller is inserted, and slides more than a certain value to press the roller shaft at one end of the hole and move one roller. It is characterized by.

  Further, the contact surface is provided at a position where the contact surface does not contact when the distance between the contact portion with the cam and the center axis of the cam is less than a predetermined value.

  An L-shaped transfer arm that is rotatably fixed at the center and is rotated by an elastic member, and the transfer arm is slid by the second contact surface provided on the slide member by sliding the slide member. Thus, the elastic member is rotated in the direction opposite to the direction of action of the elastic member.

  There is a belt drop-off prevention member that prevents the roller from dropping off when one of the rollers is moved in the direction opposite to the belt stretching direction, and the transfer belt is sandwiched between the one roller and the belt drop-off prevention member. It is characterized by that.

  The belt drop-off preventing member is provided in the slide member and has an elastic layer.

  According to the present invention, the tension can be loosened when image formation is not being performed, and the transfer belt can be prevented from being wrinkled.

  Next, the best mode for carrying out the invention will be described in detail with reference to the drawings.

  FIG. 1 is a configuration diagram of an image forming apparatus. In the image forming apparatus, a paper feed cassette 2 that stores paper 29 as a recording material is disposed at the bottom of the image forming apparatus main body 1 serving as a base, and the image forming unit 3 is provided above the paper cassette.

  The image forming unit 3 includes an intermediate transfer unit 7, an image forming unit 8, an optical writing unit 15, and a fixing unit 22.

  The intermediate transfer unit 7 includes a plurality of rollers 4, 5, 6 and an intermediate transfer belt 7 a as an intermediate transfer member configured by a flexible endless belt wound around the rollers. Is done.

  The image forming unit 8 includes four image forming units 8Y, 8C, 8M, and 8BK as a plurality of image forming means including an image carrier.

  The optical writing unit 15 is an optical writing unit that performs optical writing on each image carrier. The fixing unit 22 fixes the toner image on the paper 29.

  A transport path for transporting the paper 29 is formed between the paper feeding unit 2 and the fixing unit 22, and the roller 6 is disposed facing the transport path.

  The intermediate transfer unit 7, the image forming unit 8, the optical writing unit 15, and the fixing unit 22 constitute constituent elements inside the apparatus, and are arranged at the approximate center in the apparatus main body 1.

  The space between the roller 4 and the roller 5 of the intermediate transfer belt 7a corresponds to the lower belt running side of the belt 7a. The intermediate transfer belt 7a is disposed so that a secondary transfer roller 20 serving as a secondary transfer device faces a conveyance path at a portion facing the roller 6, and a belt cleaning device that cleans the belt surface at a portion facing the roller 4. 21 is disposed.

  The image forming unit 8 is disposed so as to face the lower running side, and is disposed below the intermediate transfer belt 7a. Each image forming unit includes a photosensitive drum 10 as an image carrier in contact with the intermediate transfer belt 7a.

  Around each photosensitive drum 10, a charging device 11, a developing device 12, and a cleaning device 13 are arranged. Transfer rollers 14 serving as transfer means for performing primary transfer are provided inside the intermediate transfer belt 7a at positions where the respective photosensitive drums 10 are in contact with the intermediate transfer belt 7a.

  The image forming units 8Y, 8C, 8M, and 8BK have the same structure. In FIG. 1, only the configuration of the image forming unit 8BK is given a reference numeral for each component. In each image forming unit, only the color of toner as a developer stored in each developing device 12 is different.

  Each developing device 12 including the image forming units 8Y, 8C, 8M, and 8BK stores yellow, cyan, magenta, and black toners, respectively. When the toner decreases, each developing device 12 is supplied with replenishing toner from toner replenishing bottles T1, T2, T3, and T4 disposed on the upper portion of the apparatus main body 1, respectively.

  The optical writing unit 15 irradiates the surface of each photoconductive drum with light modulated laser light L to form a latent image for each color on the surface of the photoconductive member, and is disposed below the image forming unit 8. The

  The toner supply bottles T1, T2, T3, and T4, the intermediate transfer unit 7, the image forming unit 8, and the optical writing unit 15 are disposed in the apparatus main body 1 so as to be inclined in the same direction. The installation area is reduced as compared with the case where it is horizontally arranged.

  When the image forming operation is started, the photosensitive drums 10 of the respective image forming units 8 are rotationally driven clockwise by a driving device (not shown), and the surface of each photosensitive drum is uniformly made to have a predetermined polarity by the charging device 11. Charged.

  The surface of each charged photosensitive drum is irradiated with laser light L from the optical writing unit 15 to form an electrostatic latent image on each surface. At this time, the image information to be exposed on each photosensitive drum is single-color image information obtained by separating a desired full-color image into color information of yellow, cyan, magenta, and black. The electrostatic latent image formed in this way is visualized as a toner image by the toner of each developing device 12 when passing between each photoconductor and the developing device 12.

  Of the plurality of rollers 4, 5, 6 around which the intermediate transfer belt 7a is wound, one roller is rotationally driven counterclockwise by a driving device (not shown), whereby the intermediate transfer belt 7a is counterclockwise indicated by an arrow. Driven in the clockwise direction, the other rollers are driven to rotate. A yellow toner image formed by the image forming unit 8Y including the developing device 12 having yellow toner is transferred by the transfer roller 14 to the intermediate transfer belt 7a that travels in this manner.

  To the transferred yellow toner image, a cyan toner image, a magenta toner image and a black toner image formed by the image forming units 8C, 8M and 8BK are sequentially transferred and transferred by the transfer roller 14, and the intermediate transfer belt 7a is formed on the surface thereof. Supports a full-color toner image.

  Residual toner adhering to the surface of each photosensitive drum after the toner image is transferred is removed from the surface of the photosensitive drum by each cleaning device 13, and then the surface is subjected to a static eliminating action by a static eliminating device (not shown). The surface potential is initialized and prepared for the next image formation.

  The sheet 29 fed from the sheet feeding unit 2 is sent to the conveyance path, and the sheet feeding timing is measured by the registration roller pair 24 arranged on the sheet feeding side with respect to the secondary transfer roller 20. The sheet is fed to a portion facing the secondary transfer roller 20. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the surface of the intermediate transfer belt is applied to the secondary transfer roller 20, whereby the toner image on the surface of the intermediate transfer belt 7 a is collectively collected on the paper 29. Transcribed.

  The paper 29 to which the toner image has been transferred is conveyed to the fixing means 22 and when passing through the fixing means 22, heat and pressure are applied to melt and fix the toner image. The printed material 29A on which the toner image is fixed is located at the end of the transport path, is transported to the discharge unit 23 configured by the upper part of the apparatus main body 1, and is discharged to the stacking unit 25 configured at the upper part of the apparatus main body 1. Is done. After the toner image is transferred onto the paper 29, the toner remaining on the intermediate transfer belt 7a is removed from the cleaning device 21.

  This image forming apparatus is provided with four image forming units 8Y, 8M, 8C and 8BK facing the intermediate transfer belt 7a, and sequentially transfers the toner images of the respective colors onto the intermediate transfer belt 7a. The image forming time can be greatly reduced as compared with a type in which a single four-color developing device is used and a toner image is transferred onto an intermediate transfer belt and then transferred onto a sheet. In addition, since the stacking unit 25 is configured on the upper portion of the apparatus main body 1, the stacking unit 25 does not jump out from the apparatus main body 1, and the installation area and the occupied area are reduced.

  The above is an image forming operation when a full-color image is formed on the paper 29. A single color image can be formed using any one of the image forming units of the image forming unit 8, or two colors or three colors. It is also possible to form an image. When monochrome printing is performed using this image forming apparatus, an electrostatic latent image is formed only on the photosensitive drum of the image forming unit 8BK, developed by the unit, transferred to the paper 29, and fixing means. Fixing at 22 is sufficient.

  Next, the transfer belt unit in the embodiment of the present invention will be described in detail with reference to FIGS.

  In this color tandem printer, transfer portions of three colors of y, m, and c out of four colors of k (black), y (yellow), m (magenta), and c (cyan) are in contact with each photoconductor 30.・ Separate.

  A drive roller 31 for stretching and driving the transfer belt 39 on the transfer frame 40 which is the main body of the transfer belt unit, and a tension roller 32 (hereinafter referred to as tension roller) movable for stretching are brackets 36. The bracket 36 is pressed against the frame 40 in the belt stretching direction by a spring (not shown). As a result, the transfer belt 40 is stretched.

  The transfer belt unit includes a slide member 33 and a cam member 34. The slide member 33 comes into contact with the cam member 34 at 33b, and when the cam member 34 rotates and presses 33b, the entire slide member 33 slides, and the tension roller 32 is moved in the direction opposite to the stretching direction. And pull. As a result, the transfer belt 39 is released from the stretched state, and creep deformation during long-term storage or standby of the transfer belt 39 can be prevented.

  The cam member 34 is roughly divided into three areas, and each surface determines the position of the slide member 33 in each mode. As the mode is switched from 1st to 2nd to 3rd, the position of the slide member 33 moves in the reverse direction of the tension. This is because the distance from the axial center of the contact surface of the cam member 34 is set to be larger in the order of first → second → third. The cam member 34 rotates and is fixed to a state determined for each mode. As a result, the slide member 33 moves in the direction opposite to the stretching direction by an amount determined for each mode.

  In addition, an oblong hole 35 that is long in the lateral direction is formed at a position where the slide member 33 is in contact with the tension roller, and the shaft of the tension roller 32 is inserted. This is configured so that the tension roller 32 is not pulled unless the slide member 33 is pressed by the cam member 34 and slides in the opposite direction of the tension, and there is no slide beyond a certain value. Then, when the shaft of the tension roller 32 is pushed to the right of the oval hole 35 of the slide member 33, the tension roller 32 is pulled and the tension state of the transfer belt 39 is released.

  Note that the slide member is not provided with an oval-shaped hole, and for example, when the distance between the cam contact surface and the central axis is short, the position configuration is such that 33b and the cam do not contact each other. It may be configured such that the slide member and the tension roller always slide together as a position configuration in which the distance between the slide member 33b and the cam is in contact with each other when the distance between the slide member and the cam is in contact with each other.

  Further, the slide member 33 is provided with a contact surface 33a with the contact portion of the primary transfer arm 38 of each color. The primary transfer arm 38 provided on the frame 40 is configured to be fixed at the center by a spring member and rotate counterclockwise, but the end is in contact with 33a and is pushed by the slide member. Thus, a clockwise force is applied and the sheet is accommodated inside the transfer belt.

  FIG. 2 shows a first mode (color mode) in which all four colors are in contact with each other. The transfer nip portion is formed by press-contacting each color photoconductor 30 facing the transfer belt 39 in a stretched state. In order to optimize the transfer nip pressing force and nip amount of each color and to apply a transfer voltage, a primary transfer roller 37 is arranged for each color, and a primary transfer arm 38 is provided with a primary transfer arm 38 to support them. A transfer roller 37 is inserted.

  Although each primary transfer arm 38 is pressed in the belt stretching direction by a spring member (not shown), the primary transfer arm 38 is rotated by being supported by the shaft from the frame 40, and holds the primary transfer roller 37. The transfer belt 39 is rotated in the direction in which the transfer belt 39 is stretched to come into contact with a photoconductor unit (not shown) provided with each color photoconductor 30 to be in a fixed position.

  In the first mode, the cam member 34 is fixed at a position where the distance from the rotating shaft to the contact portion 33b with the slide member 33 is the shortest, and the transfer belt 39 is maintained in a stretched state. The

  Next, the second mode (monochrome mode) will be described with reference to FIG. In the second mode, the three colors y, m, and c are separated.

  In the first mode, since the slide member 33 is slid in the stretching direction, the primary transfer arm 38 does not come into contact with 33a of the slide member 33 because the primary transfer arm 38 stops in the middle of contact with the photosensitive unit. In the second mode, since the slide member 33 is slid in the reverse direction by the cam member 34, 33a comes into contact with the contact portion of the primary transfer arm 38, and the primary transfer arm 38 is rotated clockwise. And housed in the transfer belt.

  Next, the third mode will be described with reference to FIG.

  In the first and second modes, since the slide of the slide member 33 is small, even if the position of the slide member 33 changes, the shaft of the tension roller 32 only moves in the oval hole 35. In this mode, the slide member 33 largely moves in the reverse direction of the tension, so that the oval hole and the shaft of the tension roller 32 come into contact with each other, and the tension roller 32 is forcibly transferred with the movement of the slide member 33. It is moved in the direction opposite to the stretching direction. As a result, the belt tension state is released, and creep deformation during long-term storage or standby of the transfer belt 39 can be prevented.

  Further, if the tension of the transfer belt 39 is released and the belt is removed from the roller, the transfer belt 39 may cause a running failure when the image formation is resumed. Therefore, the belt pressing member 41 is provided on the slide member 33. The belt pressing member 41 has an elastic sponge 41a, which is also set to a gap that sandwiches the transfer belt 39 with the tension roller 32 only in the third mode.

  It should be noted that the mode selection described so far may be configured to be controlled automatically or by user selection.

  As described above, by relaxing and eliminating the deformation stress applied to the transfer belt other than during image formation, it is possible to maintain the transfer belt in a good state, improve durability and eliminate image quality defects. .

  Also, by automatically selecting the mode, it is possible to maintain the transfer belt in a good state, improve durability and eliminate image quality defects.

  The present invention has been described above by the preferred embodiments of the present invention. While the invention has been described with reference to specific embodiments thereof, various modifications and changes can be made to these embodiments without departing from the broader spirit and scope of the invention as defined in the claims. is there.

1 is a configuration diagram of an image forming apparatus according to an embodiment of the present invention. It is explanatory drawing in a 1st mode. It is explanatory drawing in a 2nd mode. It is explanatory drawing in a 3rd mode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 30 Photoconductor 31 Drive roller 32 Tension roller 33 Slide member 34 Cam member 35 Oval hole 36 Bracket 37 Primary transfer roller 38 Primary transfer arm 39 Transfer belt 40 Transfer frame 41 Belt pressing member

Claims (7)

Two rollers that stretch the transfer belt,
A slide member having roller moving means that slides substantially parallel to the stretching direction of the transfer belt and moves one of the rollers in the direction opposite to the belt stretching direction;
An image forming apparatus comprising: slide member moving means for sliding the slide member in the opposite direction of the tension.   The image forming apparatus according to claim 1, wherein the slide member moving means slides by rotating a cam and pressing a contact surface provided on the slide member.   The slide member includes a hole that is elongated in the stretching direction into which the shaft of the one roller is inserted, and slides more than a predetermined value to press the shaft of the roller at one end of the hole, thereby the one roller. The image forming apparatus according to claim 1, wherein the image forming apparatus is moved.   3. The image forming apparatus according to claim 2, wherein the contact surface is provided at a position where the contact surface does not contact when a distance between a contact portion with the cam and a central axis of the cam is less than a predetermined value. An L-shaped transfer arm that is rotatably fixed at the center and is rotated by an elastic member,
The transfer arm is rotated in the direction opposite to the direction of action of the elastic member when the slide member slides and one end is pressed by a second contact surface provided on the slide member. The image forming apparatus according to any one of claims 1 to 4. A belt drop-off preventing member that prevents the roller from dropping off from the roller when one of the rollers is moved in the direction opposite to the belt stretching direction by the roller moving means;
The image forming apparatus according to claim 1, wherein the transfer belt is sandwiched between the one roller and the belt fall-off prevention member.   The image forming apparatus according to claim 6, wherein the belt drop-off preventing member is provided on the slide member and has an elastic layer.

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