JP2010128319A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily fix the direction on which the pressure of a transfer roller on an image carrier acts. <P>SOLUTION: The image forming apparatus includes: a transfer roller 8 that presses a transfer material against the image carrier 1, thereby transferring a toner image, held on the image carrier, to the transfer material; and a support device 9 that supports the transfer roller so that it is freely rotated. The support device is held so as to be movable toward and away from the image carrier. A coil spring 23 for pressing the transfer roller to the image carrier is attached to the image forming apparatus. The image forming apparatus is provided with a guide part 22 that guides the support device so as to linearly move toward and away from the image carrier. The coil spring is attached so that the spring axis X is parallel to the moving direction of the support device. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention includes a transfer roller capable of transferring a toner image carried on an image carrier to the image carrier by pressing the material to be transferred to the image carrier, and a support member that rotatably supports the transfer roller. And an image forming apparatus in which a coil spring that presses the transfer roller against the image carrier is mounted, the support being held movably in the perspective direction with respect to the image carrier.

In the conventional image forming apparatus, a transfer belt serving as an image carrier is wound around a backup roller, and a guide portion that guides a support tool so as to linearly move in a perspective direction with respect to the transfer belt portion wound around the backup roller. Is provided on the swing arm, and a coil spring that presses the transfer roller supported by the support against the transfer belt portion is mounted across the support and the swing arm.
Then, by the swinging operation of the swing arm, the transfer roller is pressed against the transfer belt portion by the biasing force of the coil spring along the arcuate movement locus, and the transfer roller is separated from the transfer belt portion. It is configured so that it can be switched and moved to the non-transfer position (for example, see Patent Document 1).

JP 10-293478 A

For this reason, if the position of the transfer roller relative to the backup roller at the transfer position deviates from a predetermined position along the arc-shaped movement locus of the transfer roller due to an assembly error of the swing arm or the transfer roller, the pressing force Since the direction of action on the transfer belt portion slightly changes, there is a drawback that it is difficult to maintain a constant image quality.
The present invention has been made in view of the above circumstances, and an object of the present invention is to make it easy to make the acting direction of the pressing force pressing the transfer roller against the image carrier constant.

  The first characteristic configuration of the present invention is a transfer roller capable of transferring a toner image carried on an image carrier to the image carrier by pressing the material to be transferred to the image carrier, and rotatably supporting the transfer roller. An image forming apparatus, wherein the support is held so as to be movable in a perspective direction with respect to the image carrier, and a coil spring that presses the transfer roller against the image carrier is mounted. And a guide portion for guiding the support device so as to linearly move in the perspective direction with respect to the image carrier, and the coil spring is mounted with its spring axis being parallel to the moving direction of the support device. There is in point.

[Action and effect]
The support that rotatably supports the transfer roller is guided by the guide portion so as to linearly move in the perspective direction with respect to the image carrier.
The coil spring that presses the transfer roller against the image carrier is mounted with its spring axis being parallel to the moving direction of the support.
Therefore, even if the axial position of the transfer roller relative to the backup roller at the transfer position is deviated from a predetermined position along the moving direction of the support, the direction of the pressing force that presses the transfer roller against the image carrier is constant. Easy to convert.

Embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
FIG. 1 shows a main part of a transfer unit in a full-color electrophotographic image forming apparatus such as a copying machine, a printer, or a fax machine, and includes an intermediate transfer belt unit A and a transfer conveyance unit B.

  The intermediate transfer belt unit A includes an intermediate transfer belt 1 as an image carrier, and a driving roller 2, a driven roller 3, a tension roller 4 and a secondary transfer counter roller 5 around which the intermediate transfer belt 1 is wound. .

  The intermediate transfer belt 1 is sandwiched between photosensitive drums 6a to 6d and primary transfer rollers 7a to 7d corresponding to the respective colors of yellow, magenta, cyan, and black, and toner formed for each of the photosensitive drums 6a to 6d. Images are transferred in layers.

  The transfer conveyance unit B includes a secondary transfer roller 8 that faces the secondary transfer counter roller 5 with the intermediate transfer belt 1 interposed therebetween, and a support 9 that rotatably supports the secondary transfer roller 8. The outer peripheral portion of the roller 8 is formed of a soft material such as rubber so that a predetermined nip portion can be formed.

  The support 9 includes a bearing 10 that rotatably supports the secondary transfer roller 8, and a support plate portion 11 that fixes a lower portion of the bearing 10.

  The secondary transfer roller 8 conveys the recording paper P as a transfer material sandwiched between the secondary transfer roller 1 and the intermediate transfer belt 1 by driving and rotating the intermediate transfer belt 1, and moves the recording paper P toward the intermediate transfer belt 1. The toner image carried on the intermediate transfer belt 1 can be transferred onto the recording paper P by being pressed.

  The secondary transfer roller 8 is supported by support members 9 at both ends of the rotary shaft member 12 via bearings 10, and each support device 9 is held so as to be linearly movable in the perspective direction with respect to the intermediate transfer belt 1. A pair of guide units 13 is provided (only one guide unit 13 is shown in FIG. 2).

  Each of the guide units 13 is along a substrate portion 15 screwed to a peripheral wall member (an example of a stationary member) 14 of the transfer conveyance unit B and a pair of mutually parallel first guide portions 16 formed on the substrate portion 15. And a movable member 17 that can move linearly in the perspective direction (vertical direction) with respect to the intermediate transfer belt 1 and a lifting operation mechanism 18 that moves the movable member 17 up and down along the first guide portion 16.

  The movable member 17 connects the pair of guided portions 20 including the fitting portions 19 that are slidably fitted to the first guide portions 16 and the lower end sides of the pair of guided portions 20. It is formed in a substantially upward U shape in a side view including the bottom plate portion 21.

  The support 9 is mounted on the movable member 17, and therefore the support 9 is guided along the first guide portion 16 so as to linearly move along with the movable member 17 in the perspective direction with respect to the intermediate transfer belt 1.

  A second guide portion 22 that guides the support 9 relative to the movable member 17 so as to be relatively movable in the same direction as the movement direction thereof is provided at a portion of the pair of guided members 20 facing each other. A coil spring 23 that presses the roller 5 against the intermediate transfer belt 1 is mounted between the support 9 and the bottom plate portion 21 with its spring axis X parallel to the moving direction of the support 9.

  On the inner side of the coil spring 23, a rod 24 for restricting the expansion / contraction direction to a direction along the spring axis X is mounted concentrically with the spring axis X, and one end side of the rod 24 is a support plate of the support 9. A through hole 25 that is fixed to the portion 11 and allows the withdrawal from the movable member 17 on the other end side is formed in the bottom plate portion 21.

  The raising / lowering operation mechanism 18 makes the cam surface of the eccentric cam 27 rotated by the rotation operation of the rotation operation shaft 26 contact the lower surface of the bottom plate portion 21, and moves the movable member 17 by the rotation operation of the eccentric cam 27. 16 is configured to be moved up and down along the line 16.

  3A, the secondary transfer roller 8 is moved to a non-transfer position away from the intermediate transfer belt 1, and the lower surface of the bottom plate portion 21 is pressed by the large-diameter cam surface of the eccentric cam 27. Therefore, as the eccentric cam 27 is rotated, the movable member 17 moves upward toward the intermediate transfer belt 1 together with the support 9.

  When the secondary transfer roller 8 is in contact with the intermediate transfer belt 1 and further presses the lower surface of the bottom plate portion 21 with the large-diameter cam surface, the movable member 17 is moved to the intermediate transfer belt 1 while the coil spring 23 is compressed and deformed. As shown in FIG. 3B, the secondary transfer roller 8 is moved to the transfer position pressed against the intermediate transfer belt 1 by the urging force of the coil spring 23.

  As shown in FIG. 3B, the eccentric cam 27 is rotated so that the small-diameter cam surface of the eccentric cam 27 contacts the lower surface of the bottom plate portion 21 from the state where the secondary transfer roller 8 has moved to the transfer position. As a result, the movable member 17 descends by its own weight together with the support 9, and the secondary transfer roller 8 moves to the non-transfer position as shown in FIG.

[Second Embodiment]
FIG. 4 shows a modification of the lifting operation mechanism 18 in the first embodiment, and includes a downward inclined surface 28 formed on the bottom plate portion 21 of the movable member 17 and an upward inclined surface 29 slidably in contact with the downward inclined surface 28. The wedge member 30, the guide plate 31 for guiding the moving direction of the wedge member 30 in the horizontal direction, and the eccentric cam 27 for moving the wedge member 30 in the horizontal direction so as to enter between the movable member 17 and the guide plate 31. And are provided.

  The guide plate 31 is fixed to the substrate portion 15, and the eccentric cam 27 is moved from the state where the secondary transfer roller 8 is moved to the non-transfer position separated from the intermediate transfer belt 1 as shown in FIG. As the eccentric cam 27 is rotated so as to press the side surface of the wedge member 30 with the large-diameter cam surface, the movable member 17 moves upward toward the intermediate transfer belt 1 together with the support 9.

  As the secondary transfer roller 8 comes into contact with the intermediate transfer belt 1 and further presses the side surface of the wedge member 30 with the large-diameter cam surface, the movable member 17 moves to the intermediate transfer belt 1 while the coil spring 23 is compressed and deformed. As shown in FIG. 4B, the secondary transfer roller 8 moves to the transfer position pressed against the intermediate transfer belt 1 by the urging force of the coil spring 23.

As shown in FIG. 4B, the eccentric cam 27 is rotated so that the small-diameter cam surface of the eccentric cam 27 contacts the side surface of the wedge member 30 from the state where the secondary transfer roller 8 has moved to the transfer position. As a result, the movable member 17 is lowered by its own weight together with the support 9, and the secondary transfer roller 8 is moved to the non-transfer position as shown in FIG.
Other configurations are the same as those of the first embodiment.

[Third Embodiment]
FIG. 5 shows a modification of the elevating operation mechanism 18 in the first embodiment, and a swing arm 32 for pushing up the bottom plate portion 21 of the movable member 17 and an eccentric cam 27 for swinging the swing arm 32 up and down. Is provided.

  The swing arm 32 is supported on the substrate portion 15 so as to be swingable up and down around the swing axis Y, and the eccentric cam 27 is supported on the substrate portion 15 via the rotation operation shaft 26 so as to be rotatable. .

  As shown in FIG. 5A, the swinging arm 32 faces upward on the large-diameter cam surface of the eccentric cam 27 from the state where the secondary transfer roller 8 has moved to the non-transfer position separated from the intermediate transfer belt 1. As the eccentric cam 27 is rotated to swing, the movable member 17 moves upward together with the support 9 toward the intermediate transfer belt 1.

  As the secondary transfer roller 8 comes into contact with the intermediate transfer belt 1 and further swings the swing arm 32 upward on the large-diameter cam surface, the movable member 17 is subjected to intermediate transfer while the coil spring 23 is compressed and deformed. As shown in FIG. 5B, the secondary transfer roller 8 moves to the transfer position pressed against the intermediate transfer belt 1 by the urging force of the coil spring 23, as shown in FIG.

As shown in FIG. 5B, the eccentric cam 27 is rotated so that the small-diameter cam surface of the eccentric cam 27 is brought into contact with the swing arm 32 from the state where the secondary transfer roller 8 is moved to the transfer position. Along with this, the movable member 17 is lowered by its own weight together with the support 9, and the secondary transfer roller 8 moves to the non-transfer position as shown in FIG.
Other configurations are the same as those of the first embodiment.

[Other Embodiments]
1. In the image forming apparatus according to the present invention, a transfer roller pressed against the photosensitive drum as an image carrier may be rotatably supported by a support.
2. In the image forming apparatus according to the present invention, an intermediate transfer belt to which a toner image carried on a photosensitive drum as an image carrier is transferred is provided as a transfer material, and the intermediate transfer belt is pressed against the photosensitive drum side. A transfer roller capable of transferring the toner image carried on the photosensitive drum to the intermediate transfer belt may be rotatably supported by the support.

Side view showing the main part of the transfer section in the image forming apparatus Perspective view of main parts Side view of the main part Side view of essential parts of second embodiment Side view of essential parts of third embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image carrier 8 Transfer roller 9 Support tool 22 Guide part 23 Coil spring P Transfer material X Spring axis

Claims (1)

A transfer roller capable of transferring the toner image carried on the image carrier to the image carrier by pressing the material to be transferred to the image carrier, and a support tool for rotatably supporting the transfer roller;
The support is held movably in a perspective direction with respect to the image carrier;
An image forming apparatus equipped with a coil spring that presses the transfer roller against the image carrier,
A guide portion is provided for guiding the support so as to linearly move in a perspective direction with respect to the image carrier;
The image forming apparatus, wherein the coil spring is mounted with a spring axis thereof parallel to a moving direction of the support.

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