JP2012168314A - Image forming apparatus - Google Patents

Abstract

Provided is an image forming apparatus in which a black transfer unit is brought into contact with a transfer belt and another transfer unit is separated from the transfer belt in a monochrome mode.
In the color mode, the transfer rollers 13K, 13Y, 13M, and 13C are positioned at the transfer position, and in the monochrome mode, the transfer roller 13K of the black image forming unit is at the transfer position, and the other transfer rollers. In the image forming apparatus in which 13Y, 13M, and 13C move to the separated positions, a backup roller 22 that is rotatable and fixed at a position is provided on the side of the intermediate transfer belt 3 on which the transfer roller is provided. When the roller 13 is at the transfer position, it is separated from the intermediate transfer belt 3 and when the transfer roller of the image forming unit for black image is positioned at the transfer position and the other transfer means is moved to the separation position in the monochrome mode. It is provided at a position in contact with the intermediate transfer belt 3.
[Selection] Figure 3

Description

  The present invention relates to an image forming apparatus configured as an electronic copying machine, a printer, a facsimile, or a multifunction machine having at least two of these functions.

  In the image forming apparatus of the above type, a so-called tandem type color copying machine or the like in which a plurality of image forming portions including those for black images are arranged in parallel along one running side of a belt-shaped transfer member has been known. is there. In this type of color image forming apparatus, after the respective color toner images of black, cyan, magenta, and yellow are formed by the developing devices of the respective image forming units, intermediate transfer is sequentially performed on the intermediate transfer belt and superimposed. The color toner image thus obtained is transferred onto a transfer paper of a transfer medium by a transfer device and fixed by a fixing means, thereby forming a color image.

  In this type of image forming apparatus, the cyan, magenta, and yellow primary transfer rollers that are not used in the monochrome mode are used for the intermediate transfer in order to extend the life of the photoreceptor, the intermediate transfer belt, and the primary transfer roller. A technique for performing image formation by retracting the belt inside the loop and separating the intermediate transfer belt from the color photosensitive member is already known.

  Most of the primary transfer rollers for black are arranged at the end of the running side of the intermediate transfer belt. When the above separation is performed, only the primary transfer roller for black contacts the intermediate transfer belt. Since the primary transfer roller for color does not contact, the position of the primary transfer roller for black and the position of the driven roller for supporting the intermediate transfer belt on the side where the primary transfer roller for color is separated. The distance gets longer.

  And if this distance becomes long, the belt at the corresponding location is easily affected by slack and vibration, which makes the running performance of the belt unstable and causes abnormal images such as horizontal stripes and banding due to dot position deviation. There is. Especially in high-speed machines, the above distance tends to become very long due to the increase in the diameter of the photosensitive member used, the enlargement of the developing device, the addition of an image forming unit using special color toners other than black, cyan, magenta, and yellow. In this case, the risk of occurrence of abnormal images increases.

Patent Documents 1 and 2 describe techniques for preventing the running performance of the intermediate transfer belt from becoming unstable as described above.
The technique described in Patent Document 1 includes a pressure roller provided in each color photoconductor, and prevents the vibration of the intermediate transfer belt by contacting the intermediate transfer belt and the pressure roller with a spring during monochrome mode printing. .

  Further, the technique described in Patent Document 2 includes a load applying unit that selectively applies a load to the intermediate transfer belt between the black photoconductor and the nearest color photoconductor. By applying a load to the intermediate transfer belt by the load applying means, the running performance of the intermediate transfer belt is stabilized.

However, the techniques of Patent Documents 1 and 2 have the following problems.
In Patent Document 1, the intermediate transfer belt and the pressure roller are prevented from contacting each other in the monochrome mode to prevent the intermediate transfer belt from vibrating. However, since the contact is made by the spring, the pressure roller is movable and the roller vibrates. There is a risk of disturbing the running performance of the intermediate transfer belt. Further, since the pressure roller is arranged on each photoconductor, the number of parts is increased, and a drive transmission system is required to move the pressure roller, so that the apparatus is complicated and enlarged.

  In Patent Document 2, the running performance of the intermediate transfer belt is stabilized by applying a load to the intermediate transfer belt in the monochrome mode. However, a load applying unit is provided between the black photoconductor and the nearest color photoconductor. Therefore, the belt tension interval is long and it is easy to be affected by slack and vibration. Further, since the load applying means is configured to be movable, there is a possibility that the belt running performance becomes unstable due to the vibration of the load applying means. In addition, there is a problem that a drive transmission system for moving the load applying means is required, resulting in an increase in complexity and size of the apparatus.

  The present invention solves the conventional problems, and in black-and-white mode, even when the black transfer unit is brought into contact with the transfer belt and the other transfer unit is separated from the transfer belt, the belt running performance is unlikely to become unstable. An object is to provide an apparatus.

  In order to solve the above-described problems, the present invention provides a toner image formed on an image carrier of each image forming unit in which a plurality of image forming units including for black images are arranged in parallel along one running side of the transfer belt. An image forming apparatus that is transferred directly onto a transfer belt or onto a recording medium conveyed by the transfer belt by a contact-type transfer unit disposed opposite to the image carrier and the transfer belt. It is provided so as to be movable between a transfer position that abuts on the image carrier via the transfer belt independently, and a separation position between the transfer means and the transfer belt and between the image carrier and the transfer belt. In the color mode for obtaining a color image, each transfer means is located at the transfer position. In the monochrome mode for obtaining a black image, the transfer means of the black image forming unit is at the transfer position, and the other transfer means are separated. In the image forming apparatus that moves to a position, a backup member that is fixed in position is provided on the side of the transfer belt on which the transfer unit is provided, and the transfer member has the transfer belt when the transfer unit of the entire image forming unit is at the transfer position. When the transfer unit of the image forming unit for black image is positioned at the transfer position and the other transfer unit is moved to the separated position in the monochrome mode, the transfer belt is provided at a position where it contacts the transfer belt. An image forming apparatus characterized by this is proposed.

  In the present invention, the black image forming portion is disposed on one end side of one running side of the transfer belt, and the backup member is configured such that the transfer means of the black image forming portion is applied to the transfer belt. It is advantageous if it is disposed at a substantially central portion between the contact position and the position where the support roller for supporting the other end side of one side of the transfer belt is disposed.

Furthermore, the present invention is advantageous when the backup member is a rotatable backup roller.
Furthermore, in the present invention, it is advantageous that the backup roller is a roller having a rubber layer on the surface of a rigid roller body.

  Furthermore, the present invention provides a plurality of transfer means for transferring the color image onto the intermediate transfer member and a transfer means for transferring the black image onto the intermediate transfer member when the transfer device is detached from the image forming apparatus main body. The backup member can be retracted from the image forming unit, and the backup member is advantageously disposed closer to the intermediate transfer body than the retracted position of each transfer unit.

  Furthermore, the present invention is advantageous when the axial width of the backup member is longer than the axial width of the transfer means.

  According to the present invention, the transfer unit of the entire image forming unit is separated from the transfer belt in the color mode of the transfer position, the transfer unit of the image forming unit for black image is positioned at the transfer position, and the other transfer units are separated from each other. In a simple mode, a backup member that can be rotated in a fixed position is provided at a position that comes into contact with the transfer belt in the monochrome mode, and the running performance of the transfer belt can be stabilized in the monochrome mode, and abnormal images are generated. Can be suppressed.

1 is a schematic cross-sectional view showing an embodiment of an image forming apparatus according to the present invention. FIG. 6 is an explanatory diagram illustrating a color mode of an intermediate transfer unit. FIG. 3 is an explanatory diagram showing a monochrome mode of the intermediate transfer unit in FIG. 2. FIG. 3 is a top view illustrating an intermediate transfer unit of the present invention. It is sectional drawing of a backup roller. FIG. 4 is an explanatory diagram illustrating an intermediate transfer unit when the intermediate transfer belt is attached / detached.

Embodiments of the present invention will be described below in detail with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing an example of an image forming apparatus configured as an electronic copying machine, a printer, a facsimile, or a composite machine of these. In the image forming apparatus main body 1 shown here, an image forming unit having first to fourth image carriers 2C, 2M, 2Y, and 2K configured as drum-shaped photoconductors is arranged. An intermediate transfer unit having an intermediate transfer belt 3 made of an endless belt is disposed opposite to the image carrier of the image portion. The intermediate transfer belt 3 is wound around a driving roller 4 and two driven rollers 5, 6, 7, and 8. The driving roller 4 is driven clockwise in FIG. 1 by a driving motor (not shown). Is rotated in the direction of arrow A. Reference numeral 9 denotes a tension roller that presses against the surface of the intermediate transfer belt 3 and applies tension to the intermediate transfer belt 3.

  The image forming apparatus shown in FIG. 1 has the first to fourth four image carriers 2C to 2K, but the number of image carriers may be four or more. The image forming apparatus shown in FIG. 1 has four driven rollers 5, 6, 7, and 8. However, at least one driven roller may be provided.

  The first to fourth image carriers 2C to 2K are rotated in the counterclockwise direction in FIG. 1 while being in contact with the surface of the intermediate transfer belt 3, respectively. At this time, the first image carrier 2C is charged to a predetermined polarity by the charging roller 10, and the charged surface is irradiated with the light-modulated laser beam emitted from the optical writing unit 11. As a result, an electrostatic latent image is formed on the first image carrier 2C, and this electrostatic latent image is visualized as a yellow toner image by the developing device 12. On the other hand, a transfer voltage is applied to the primary transfer roller 13, whereby the toner image on the image carrier 2C is primarily transferred onto the surface of the intermediate transfer belt 3 that is rotationally driven in the direction of arrow A. The residual transfer toner adhering to the image carrier 2C after the toner image transfer is removed by the cleaning device 14.

  In exactly the same manner as described above, a cyan toner image, a magenta toner image, and a black toner image are formed on the second to fourth image carriers 2C, 2M, and 2K, respectively. The toner images are sequentially transferred and transferred onto the transferred intermediate transfer belt 3, and four color superimposed toner images are carried on the intermediate transfer belt 3.

  On the other hand, a paper feeding device 15 is disposed at the lower part of the image forming apparatus main body 1. The paper feeding device 15 includes a paper feeding tray 16 containing a recording medium P made of, for example, transfer paper or a resin film, and an uppermost sheet. The uppermost recording medium P is fed in the direction of arrow B by the rotation of the paper feeding roller 17. The fed recording medium is fed between the intermediate transfer belt 3 and the secondary transfer roller 19 opposed to the intermediate transfer belt 3 at a predetermined timing by the rotation of the registration roller pair 18. At this time, the secondary transfer roller A transfer voltage is applied to 19 so that the superimposed toner image on the intermediate transfer belt 3 is secondarily transferred to the recording medium. The secondary transfer roller 19 is pressed against the driven roller 5 via the intermediate transfer belt 3 and is rotationally driven counterclockwise in FIG. 1 while being in contact with the surface of the intermediate transfer belt 3. The recording medium P is fed between the secondary transfer roller 19 and the intermediate transfer belt 3, and the superimposed toner image on the intermediate transfer belt 3 is secondarily transferred to the recording medium P.

  The recording medium P to which the toner image has been transferred passes through the fixing device 20, and at this time, the toner image on the recording medium is fixed to the recording medium by the action of heat and pressure. The recording medium that has passed through the fixing device 20 is discharged onto a paper discharge tray 21 outside the image forming apparatus main body 1.

  The image forming apparatus described above has a color mode for obtaining a color image shown in FIG. 2 and a monochrome mode for obtaining a black image shown in FIG. In the monochrome mode of FIG. 3, in order to extend the life of the image carrier 2, the intermediate transfer belt 3, and the primary transfer roller 13, the cyan, magenta, and yellow primary transfer rollers 13 that are not used in the monochrome mode are used as intermediate. The transfer belt 3 is retracted inside the loop. Therefore, in the image forming apparatus, the intermediate transfer belt 3 is moved to the transfer position via the displacement means for displacing the primary transfer rollers 13C, 13M, 13Y, and 13K and the driven rollers 7 and 8 so that the intermediate transfer belt 3 is separated from the image carriers 2C to 2K. And is supported so as to be displaceable between the separated positions. In the example shown in the figure, the primary transfer rollers 13C, 13M, 13Y, and 13K and the driven rollers 7 and 8 are supported via displacement means that move up and down, and when these transfer and driven rollers are moved to a lower separation position, The transfer belt 3 is lowered and separated from the image carrier 2. When the above-described monochrome mode is selected, as shown in FIG. 3, the primary transfer rollers 13C, 13M, 13Y and the driven roller 7 are located at the separated positions, and the primary transfer roller 13K and the driven roller 8 are moved. Therefore, it is held at the transfer position.

  Thus, the primary transfer rollers 13C, 13M, 13Y, and 13K and the driven rollers 7 and 8 are displaced, so that the cyan, magenta, and yellow primary transfer rollers 13 that are not used in the monochrome mode are used as the intermediate transfer belt. Thus, the service life of the image carrier 2, the intermediate transfer belt 3, and the primary transfer roller 13 can be extended.

  However, in the monochrome mode shown in FIG. 3, as described above, the position C of the primary transfer roller 13K and the position of the driven roller 7, that is, the primary transfer roller for each color from the black primary transfer roller 13K. Since the distance L to the position D of the driven roller 7 on the side where the 13C, 13M, and 13Y are present becomes too long, the belt is easily affected by slack and vibration, which makes the running performance of the belt unstable. Abnormal images such as horizontal stripes and banding due to misalignment may occur.

  Therefore, in the present invention, as shown in FIGS. 2 and 3, a backup roller 22 as a backup member is provided at a substantially central position between the positions CD. As shown in FIG. 4, the backup roller 22 is mounted on a belt frame 23 on which the driving roller 4 and the driven rollers 5 and 6 around which the intermediate transfer belt 3 is wound, via a bearing 24. The position is fixed but it is rotatable.

  The backup roller 22 is disposed at a position where it does not contact the intermediate transfer belt 3 in the color mode shown in FIG. 2 and abuts against and supports the intermediate transfer belt 3 lowered in the monochrome mode shown in FIG. Yes. That is, the backup roller 22 is not in contact with the intermediate transfer belt 3 in the color mode in which the primary transfer roller 13 of each color is in contact with the intermediate transfer belt 3, and the primary transfer roller 13K and the driven roller 8 are in the intermediate transfer. In the monochrome mode in which the primary transfer rollers 13C, 13M, 13Y and the driven roller 7 are lowered downward while being in contact with the belt 3, they are in contact with the intermediate transfer belt 3.

  Accordingly, in the monochrome mode, the intermediate transfer belt 3 is supported by the backup roller 22 in the middle of the distance L, so that the belt is not easily affected by slack or vibration, and the running performance of the belt may become unstable. Is prevented.

  In the image forming apparatus configured as described above, the intermediate transfer apparatus includes a backup roller 22 supported at the center portion of the distance L so as to be rotatable and immovable. Since the backup roller 22 is disposed at a position not in contact with the intermediate transfer belt 3 during full-color image formation, the cyan, magenta, and yellow primary transfer rollers 13C, 13M, and 13Y are moved from the intermediate transfer belt 3 in the monochrome mode. When retracted and moved to the separation position, the intermediate transfer belt 3 and the image carrier 2 are separated from each other, so that the backup roller 22 supports the intermediate transfer belt 3 at the center portion of the distance L. For this reason, since the distance L is halved, it is difficult to be affected by slack and vibration, and it is possible to prevent an abnormal image caused by the running performance of the intermediate transfer belt 3 becoming unstable.

  As shown in FIG. 5, the backup roller 22 is a rigid roller base. For example, the backup roller 22 is advantageously composed of a roller having a rubber layer 22b on the surface of the metal roller 22a. Further, vibrations of a motor and a fan (not shown) are transmitted to the intermediate transfer belt 2 via the backup roller 22 to prevent the running property from becoming unstable. The rubber layer 22b of the backup roller 22 is preferably, for example, EPDM rubber having a thickness of about 0.5 mm.

  By the way, the intermediate transfer belt 3 can be taken out from the intermediate transfer unit in order to facilitate maintenance and replacement. 6, the primary transfer rollers 13C to 13K and the driven rollers 7 and 8 are retracted from the transfer position to the separation position, and then the intermediate transfer unit is directed outward from the apparatus main body as shown in FIG. Move. Then, the intermediate transfer belt 3 whose tension has been relaxed by retracting the primary transfer roller 13 or the like is taken out from the unit. Then, a new belt is mounted again, but the intermediate transfer belt 10 loosened at this time may interfere with parts inside the transfer unit and cause scratches or breakage. However, in the present invention, as shown in FIG. 6, the backup roller 70 is disposed above the position where the primary transfer rollers 13C to 13K and the driven rollers 7 and 8 are retracted. When the intermediate transfer belt 10 is mounted in a mountain shape with the backup roller at the apex when attaching / detaching from the transfer device, the intermediate transfer belt 10 can be prevented from loosening and interfering with components inside the transfer device, thereby preventing scratches and damage. . In addition, the workability of attaching and detaching the intermediate transfer belt 3 is improved.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited only to the said embodiment, Various modifications can be made. Although the transfer belt is constituted by an intermediate transfer belt, the transfer belt can also be applied to an image forming apparatus of a type in which a recording medium is conveyed by the transfer belt and toner images of respective colors are sequentially transferred during the conveyance.

  In the above embodiment, the backup member is described as the backup roller 22, but instead of the backup roller 22, for example, a plate-like component or resin subjected to flocking treatment so as not to damage the surface contacting the transfer belt. Parts or the like may be used.

3 Intermediate transfer belt
4 Driving roller 5, 6, 7, 8 Driven roller 13 Primary transfer roller 22 Backup roller

JP 2009-271163 A JP 2009-294212 A

Claims (6)

A plurality of image forming sections including those for black images are arranged in parallel along one running side of the transfer belt, and the toner image formed on the image carrier of each image forming section is opposed to the image carrier with the transfer belt interposed therebetween. An image forming apparatus that is directly transferred to a transfer belt by a contact-type transfer means arranged or transferred onto a recording medium conveyed by the transfer belt,
Each of the transfer means can move independently between a transfer position where the transfer means abuts against the image carrier via the transfer belt, and a separation position where the image carrier and the transfer belt are separated from each other. In the color mode for obtaining a color image, each transfer means is positioned at the transfer position, and in the monochrome mode for obtaining a black image, the transfer means of the image forming section for the black image is at the transfer position. In the image forming apparatus in which the transfer unit moves to the separation position,
A backup member fixed on the side of the transfer belt on which the transfer means is provided;
The backup member is separated from the transfer belt when the transfer unit of the entire image forming unit is at the transfer position, and the transfer unit of the image forming unit for black image is positioned at the transfer position in the monochrome mode, and other transfer units are An image forming apparatus, wherein the image forming apparatus is provided at a position in contact with the transfer belt when moved to a separation position.   2. The image forming apparatus according to claim 1, wherein the image forming section for the black image is arranged on one end side of one running side of the transfer belt, and the transfer member of the image forming section for the black image is the backup member. An image forming apparatus, wherein the image forming apparatus is disposed at a substantially central portion between a position where the transfer belt abuts and a position where a support roller for supporting the other end of one running side of the transfer belt is disposed.   3. The image forming apparatus according to claim 1, wherein the backup member is a rotatable backup roller.   The image forming apparatus according to claim 3, wherein the backup roller is a roller having a rubber layer on a surface of a rigid roller body.   4. The image forming apparatus according to claim 1, wherein a plurality of transfer units that transfer the color image onto an intermediate transfer member and a transfer unit that transfers a black image onto the intermediate transfer member include: An image forming apparatus, wherein the backup member can be retracted from the latent image forming means when being attached to and detached from the forming apparatus main body, and the backup member is disposed closer to the intermediate transfer body than the retracted position of each transfer means.   6. The image forming apparatus according to claim 1, wherein the axial width of the backup member is longer than the axial width of the transfer unit.

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