JP2000122445A - Transfer roller pressurizing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transfer roller pressurizing device capable of uniformly maintaining the pressurizing force by a spring in the transfer roller shaft direction, even if the pressuring force on a rear part side end part of the transfer roller is reduced. SOLUTION: A gear section 2b of a photoreceptor drum 1 and the gear 10 of the transfer roller 5 engage each other to be driven in connection. The upward spring force is applied to bearing members at both end parts on the transfer roller 5 by pressure members 6 and 7. When defining a component of the force in the spring extension and contraction direction of the driving force F1 generated in the teeth gear surface tangent direction at the driving time as F2, the spring force of the pressure member 6 as F3, and the spring force of the pressure member 7 as F4, they are set so that F3=F4+F2 is satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer roller pressing device in an image forming apparatus such as a copying machine, a printer, a facsimile, and a multifunction machine thereof.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, process units such as charging, exposure (light writing), development, transfer (and separation), cleaning, and charge removal are arranged around a photoreceptor. Examples of the transfer unit include a non-contact type transfer charger, a contact type transfer roller, and a transfer belt. When a transfer roller is used, a driven transmission gear provided at one end thereof is connected to a drive transmission gear at an end of the photosensitive drum which is rotationally driven by a drive source of the main body,
In addition, the pair of pressure members are urged toward the photosensitive drum via bearing members at both ends.

A sheet fed from a sheet feeding section is fed to a transfer section at a timing with a toner image on a photosensitive drum, and is conveyed while being sandwiched by a nip between the photosensitive drum and a transfer roller. In the process, a bias voltage having a polarity opposite to that of the toner is applied to the back surface of the sheet by the transfer roller, and the toner image is transferred to the surface of the sheet.

When a transfer roller is used, it is desirable that the pressing force of the transfer roller against the photoreceptor is uniform in the roller axis direction in order to prevent image transfer unevenness or the like. However, in a method in which springs as pressing members are provided at both ends of the transfer roller and pressure is applied to both ends of the roller shaft, an error in the pressing force is likely to occur.

In view of the above, Japanese Patent Application Laid-Open No.
A technique described in Japanese Patent Application Publication No. 06-2006 is proposed. This is an image forming apparatus in which a transfer material is pressed against a transfer member (transfer roller) against an image carrier on which a transferable image is formed and supported, thereby transferring the transferable image on the image carrier to the transfer material side. A support member that supports the shafts at both ends of the member with one member,
The provision of a pressure member for pressing the central portion of the support member in the direction in which the transfer member is pressed against the image carrier causes image transfer unevenness due to uneven pressing force in the axial direction of the transfer member. To form a good image.

[0006]

As described above, there has been proposed a technique in which the shafts at both ends of the transfer roller are supported by one support member, and a pressing member is disposed between the center of the support member and the bottom plate chassis. However, a large supporting member for supporting the entire transfer roller is required, and since it is supported by a spring at a central point, there is a disadvantage that the supporting mechanism becomes unstable. For this reason, the present invention is based on the premise that a spring having the same spring force is interposed between the shaft portions at both ends of the transfer roller. Here, when the gear at the end of the transfer roller and the gear at the end of the photosensitive drum engage, the transfer roller receives the driving force from the photosensitive drum side. The driving force acts in the linear direction, and the component force in the spring expansion and contraction direction of the force acts to reduce the pressing force,
The pressing force is not uniform in the transfer roller axial direction.

Accordingly, the present invention provides a transfer roller pressurizing device which can maintain the pressurized force of a spring evenly in the axial direction of the transfer roller even if the pressurized force at the gear portion side end of the transfer roller is reduced. As a first object.

[0008] In addition, since several components are involved in the structure for pressing the transfer roller against the photosensitive drum,
The pressing force of the transfer roller varies between machines. Economically, due to the wear of the transfer roller bearing and the incorporation of toner and paper dust,
The driving torque of the transfer roller fluctuates. That is, the component of the driving force acting in the normal direction of the tooth surface of the gear at the time of driving in the spring expansion and contraction direction changes, and the pressing force of the transfer roller is not uniform in the axial direction of the transfer roller.

Therefore, a second object of the present invention is to keep the pressing force uniform in the axial direction of the transfer roller at all times in response to variations between machines and changes over time.

[0010]

According to a first aspect of the present invention, there is provided a photosensitive drum in which a driven transmission gear provided at one end is rotated by a driving source of a main body. A transfer roller connected to an end drive transmission gear and urged in the direction of the photosensitive drum by a pair of pressurizing members via bearing members at both ends. The pressing force of the pressure member is set higher by a component force in the spring expansion and contraction direction of the driving force acting in the normal direction of the gear tooth surface during driving.

According to a second aspect of the present invention, in order to achieve the second object, in the transfer roller pressing device according to the first aspect, the pressing force of at least one pressing member can be adjusted. It is characterized by the following.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a perspective view showing a driving connection between a photosensitive drum and a transfer roller and a pressing mechanism.
As shown in FIG. 1, the photosensitive drum 1 is supported by support portions 4a and 4b of a machine body frame 4 via a shaft portion 2a of a flange 2 and a shaft portion 3a of a flange 3 at its end.

The transfer roller 5 has shaft portions 5a and 5 at both ends thereof.
b is fitted and held by the bearing members 8a and 8b. Bearing members 8a, 8b are fitted and installed in a pair of guides 4c, 4d provided upright on the main body frame 4,
The bearing members 8a and 8b are vertically movable along the guides 4c and 4d. Therefore, the bearing members 8a, 8b
Transfer roller 5 fixed to shaft members 5a and 5b via shaft portions 5a and 5b
Can also be moved up and down.

Pressing members (coil springs) 6 and 7 are interposed between the bottom surfaces of the guides 4c and 4d and the bearing members 8a and 8b, respectively, in a compressed state. , 7 urge the bearing members 8a, 8b upward, so that the transfer roller 5 is pressed against the photosensitive drum 1 with an appropriate pressing force.

In the photosensitive drum 1, the gear portion 3b of the flange 3 is driven by the main body driving connection gear 9, and the transfer roller 5 is driven by the gear 10 from the gear portion 2b of the flange 2 of the photosensitive drum 1. ing. That is, the gear 3b at one end of the photosensitive drum 1 meshes with the main body drive connection gear 9, and the gear 2b at the other end of the photosensitive drum 1 meshes with the gear 10 at the opposite end of the transfer roller 5.

With such a drive connection mechanism, the driving force from the drive source of the main body is transmitted to the photosensitive drum 1 via the main body drive connection gear 9, and the photosensitive drum 1 is rotationally driven, and at the same time, the gear portion 2b, The power is transmitted to the transfer roller 5 via the gear 10, and the transfer roller 5 is driven to rotate.

FIG. 2 is a diagram showing a vector of a force acting on the transfer roller when the photosensitive drum and the transfer roller are rotated. As shown in FIG. 2, when the photosensitive drum 1 rotates in the direction A (clockwise), the gear portion 2 of the flange 2 is rotated.
The transfer roller 5 is also driven in the direction B (counterclockwise) by the connection between the gear b and the gear 10. At this time, the driving force F1 acts in the normal direction of the gear tooth surface. Then, the component force F2 of F1 is applied in the direction of expanding and contracting the pressing member 6 (vertical downward direction in FIG. 2).
Works. Therefore, if this component force F2 is not considered, a uniform pressing force cannot be obtained in the axial direction of the transfer roller 5.

FIG. 3 is a configuration diagram of the transfer roller pressing device according to the first embodiment. As described above, since the component force of F2 is applied downward on the gear 10 side in the transfer roller 5, the spring force of the pressing member 6 must be larger than that of the pressing member 7 by that amount. A uniform pressing force cannot be obtained. Therefore, when the spring force of the pressing member 7 is F4, the spring force of the pressing member 6 is set to a value larger by F2 than that. That is, the spring force F3 of the pressing member 6 is expressed as F3 =
It is represented by F4 + F2. In the first embodiment, the spring constant is set such that the spring force of the pressing member 6 is F3 and the spring force of the pressing member 7 is F4 at the same compression length.

FIG. 4 is a configuration diagram of a transfer roller pressing device according to a second embodiment. In this embodiment, the pressing member 6
Is set to F3 (= F4 + F2) and the spring force of the pressing member 7 is set to F4. However, unlike the first embodiment, the spring constant is set to be the same and the compression length is set. (Compressed length of pressing member 6 <compressed length of pressing member 7) to obtain F3 and F4.

FIG. 5 is a configuration diagram of a transfer roller pressing device according to a third embodiment. In this embodiment, the spring force of the pressing member can be adjusted.
The spring force adjusting member 11 includes a screw portion 11a and a knob portion 11a.
b and a position restricting portion 11c of the pressing member 6. When the knob 11b is rotated in the C direction, the spring force adjusting member 11 moves in the D direction due to the engagement of the screw portion 11a, and the spring force of the pressing member 6 is increased. Conversely, if the knob 11b is rotated in the direction opposite to the direction C,
The spring force of the pressing member 6 can be reduced. Note that the spring force of the pressing member 7 may be adjusted.

[0021]

According to the first aspect of the present invention, the pressing force of the pressing member on the driven transmission gear side at the time of locking is changed by the spring expansion / contraction direction of the driving force acting in the normal direction of the gear tooth surface during driving. , The pressure of the pressurizing member on the driven transmission gear side is reduced by the component force, and the pressure can be evenly applied in the axial direction of the transfer roller. Therefore,
The transfer speed of the transfer paper becomes equal in the left and right directions,
The occurrence of transfer unevenness or the like due to uneven pressing force can be prevented.

According to the second aspect of the present invention, since the pressing force of at least one of the pressing members can be adjusted, it is possible to cope with variations between machines and changes with time, and the above effect is further enhanced. be able to.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a drive connection mechanism and a pressure mechanism between a photosensitive drum and a transfer roller.

FIG. 2 is a diagram illustrating a vector of a force acting on a transfer roller when a photosensitive drum and a transfer roller are rotated.

FIG. 3 is a configuration diagram of a transfer roller pressing device according to the first embodiment of the present invention.

FIG. 4 is a configuration diagram of a transfer roller pressing device according to a second embodiment of the present invention.

FIG. 5 is a configuration diagram of a transfer roller pressing device according to a third embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 photosensitive drum 2, 3 flange 2a, 3a shaft 2b, 3b gear 4 machine body frame 4a, 4b support 4c, 4d guide 5 transfer roller 5a, 5b shaft 6,7 pressure member 8a, 8b bearing member 9 Body drive coupling gear 10 Gear

Claims (2)

[Claims] 1. A driven transmission gear provided at one end is connected to a drive transmission gear at an end of a photosensitive drum that is rotationally driven by a drive source of a main body, and is connected via bearing members at both ends.
A transfer roller which is urged in the direction of the photosensitive drum by a pair of pressing members, wherein the pressing force of the pressing member on the driven transmission gear side at the time of locking acts in the normal direction of the gear tooth surface when driven. A transfer roller pressurizing device, wherein the driving force is set higher by a component force in a spring expansion / contraction direction. 2. The transfer roller pressing device according to claim 1, wherein the pressing force of at least one pressing member is adjustable.