JPH03171072A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent generation of filming by moving a transfer drum to a position abutting to a photosensitive body drum with a cam member only at the time of transferring and allowing it to move to a separated position of the transfer drum after the finish of transferring. CONSTITUTION:The cam member 5 which moves the transfer drum 4 to the abutting position by pressurizing a supporting body 3 through a cam follower 10 and a compressed coil spring 6 and allows it to move to the separated position of the transfer drum 4 is attached to a shaft 5a integrally and rotatable in a casing 2. Therefore, since the abutting of the transfer drum 4 to the photosensitive body drum 1 is limited to only when necessary, the abutting time can be shortened. Thus, the generation of filming where toner is stuck to the periphery surface of the photosensitive body drum 4 in a thin film state is prevented.

Description

[Detailed Description of the Invention] Industrial Application Fields The present invention relates to a color image forming apparatus, etc. that transfers toner images of each color of an original carried on a photoreceptor drum onto a transfer paper wound around a transfer drum. The present invention relates to an image forming apparatus.

Problems to be solved by conventional techniques and inventions> In general,
In the above-mentioned color image forming apparatus, a color separated image of an original is formed on the photoreceptor drum, and a plurality of developing devices for each original color are selectively brought close to the photoreceptor drum, and toners for each original color are formed. The image is transferred to transfer paper.

Since it takes a certain amount of time to select the plurality of developing devices and bring them close to the photosensitive drum, the transfer drum is rotated once to synchronize the timing with which the toner image of the next document color is transferred.

When adjusting the timing, if the transfer drum is rotated once while in contact with the photoreceptor drum, the toner that was previously transferred to the transfer drum may return to the photoreceptor drum, or the toner that was transferred to the transfer drum may It may shift. In order to prevent this, the transfer drum is moved away from the photosensitive drum and rotated idly every time a toner image of each original color is transferred to match the above timing.

FIG. 7 shows a support mechanism for a transfer drum of a conventional image forming apparatus, and with reference to the figure, one end 91a of a casing 91 supporting a transfer drum 90 can swing freely about a shaft 92. The other end 91b of the casings 9, 1 is supported by a tension coil spring 9 as a biasing means.
It is urged upward by the urging force of No. 3 via the cams 94 and 95. Normally, the transfer drum 90 is brought into contact with the photosensitive drum 96 by the biasing force of the tension coil spring 93 (the state shown by the solid line in FIG. 7), and the cam 9
7 to push down the casing 91 and remove the transfer drum 9.
0 away from the photoreceptor drum 96 (
(state shown by the two-dot chain line in FIG. 7). When removing the casing 91 from the main body of the image forming apparatus, the engagement between the cams 94 and 95 is released by operating the lever 98 which can rotate integrally with the cam 94, and the transfer drum 90 is removed from the photosensitive drum. It is performed in a state where it is far away from 96.

By the way, in the above-mentioned image forming apparatus, in the normal state,
Since the transfer drum 90 is urged toward the photoreceptor drum 96 and comes into contact with the photoreceptor drum 96, so-called filming occurs, in which toner adheres to the circumferential surface of the photoreceptor drum 96 in the form of a thin film. There was a problem.

In order to solve this problem, the transfer drum is normally forced to move away from the photoreceptor drum by its own weight, and only when necessary (during transfer) is it elastically attached by a cam member. It has also been considered to bring the transfer drum into contact with the photosensitive drum.

However, for example, due to a power outage, the cam member stops with the transfer drum in contact with the photoreceptor drum, and in this state,
If the transfer drum is removed, the photosensitive drum may be damaged.

In view of the above-mentioned problems, it is an object of the present invention to provide an image forming apparatus that can prevent the occurrence of filming and can reliably prevent the photosensitive drum from being damaged when the transfer drum is removed. purpose.

Means for Solving the Problems> In order to achieve the above object, an image forming apparatus according to the present invention is an image forming apparatus that transfers an image by a photoreceptor drum to a transfer paper wound around a transfer drum. A casing that is removable from the apparatus main body and a transfer drum rotatably supported, and a contact position where the transfer drum contacts the photoreceptor drum and a separation position where the transfer drum separates from the photoreceptor drum by the casing or the image forming apparatus main body. A support is supported swingably between the casing and the support, which is interposed between the support and the casing, and at the time of transfer, the support is pressed through an elastic member to move the transfer drum to the contact position. and a cam member that allows the transfer drum to move to the separation position after the transfer is completed, and a lever that manually operates the cam member.
provided in the image forming device main body, and engaged with the lever in a state where the cam member presses the transfer drum to the contact position to restrict removal of the casing from the image forming device main body;
An image forming apparatus comprising: a stopper that allows the transfer drum to be removed while the cam member is allowed to move to the separation position of the transfer drum.

According to the image forming apparatus with the above structure, the cam member moves the transfer drum to the contact position with the photosensitive drum only during transfer, and moves the transfer drum to the separation position after the transfer is completed. In other words, since the transfer drum contacts the photoreceptor drum only when necessary, it is possible to shorten the above-mentioned contact time and prevent the toner from forming a thin film on the circumferential surface of the photoreceptor drum. It is possible to prevent the occurrence of so-called filming.

In addition, when the cam member is pressing the transfer drum to the contact position, the stopper engages with the lever for operating the cam member and restricts the removal of the casing. When movement to the separation position is allowed,
Since the above-mentioned extraction is allowed, the transfer drum and the photosensitive drum are always separated from each other at the time of extraction, and it is possible to prevent damage caused by sliding contact between the two at the time of extraction.

Example Embodiments will be described in detail below with reference to the accompanying drawings showing embodiments.

FIGS. 1 and 2 are schematic diagrams showing the supporting state of the transfer drum of an image forming apparatus according to an embodiment of the present invention, and with reference to FIGS.
The support body 3 supporting the image forming apparatus main body (not shown)
Lb3a, which is removably supported by Lb3a, moves between the contact position where the transfer drum 4 contacts the photoreceptor drum 1 (see Figure 1) and the separation position where it separates from the photoreceptor drum 1 (see Figure 2). The casing 2, which is swingably supported and supported by the image forming apparatus body by the Accuride 9 and can be freely removed from the image forming apparatus main body 1, moves the bin 21 supporting the support body 2 from the support body 3 at the time of extraction. It is loosely fitted into the arc-shaped long groove 31.

Since the center of gravity G of the support body 3 to which the transfer drum 4 is attached is to the right in FIG. It is receiving a biasing force in the rotation direction (movement direction to the separation position).

A compression coil spring 6 as an elastic member is attached to the end plate 32 of the support 3, and a compression coil spring 6 is attached to the lower part of the support 3.
The cam follower 10 that presses the compression coil spring 6 is
It is attached so as to be swingable about the shaft 10a.

A support member 3 is pressed against the casing 2 via the cam follower 10 and the compression coil spring 6 to move the transfer drum 4 to the contact position (see FIG. 1), and also to move the transfer drum 4 to the separation position. A cam member 5 that allows movement (see FIG. 2) is rotatably attached to the shaft 5a.

Referring to FIG. 3, an engagement member 81 is attached to the end of the shaft 5a of the cam member 5 in the opposite direction to the above-mentioned extraction direction, and a drive member 81 is attached to the shaft 5a of the cam member 5. At the end of the shaft 83, an engaged member 84 that is movable in the axial direction and that engages with the engaging member 81 is connected to a compression coil spring 85.
It is attached in a pressed state to the engaging member 81 side. This compression coil spring 85 reduces the impact when the engaging member 81 and the engaging member 84 engage. The drive shaft 83 transmits the drive of a gear 87 connected to the drive system of the image forming apparatus via a spring clutch 88.
The cam member 5 is driven by this driving force. The cam member 5 is driven by the drive shaft 83 so that the home position is a state in which the transfer drum 4 is allowed to move to the separated position. In other words, after the transfer is completed, the transfer drum 4 is always separated from the photosensitive drum 1.

Further, referring to FIGS. 4 to 6, a gear member 1o that rotates integrally with the shaft 5a is disposed at the end of the shaft 5a of the cam member 5 on the extraction direction side.

In addition, the cam member 5 intermittently engages with the gear portion 10a of the rotating gear member 10 only when the cam member 5 moves the transfer drum 4 to the contact position (see FIG. 1).
(see Fig. 5), the clockwise rotating gear 11 is connected to the shaft 13.
Supported by

A lever 7 for manually operating the cam member 5 is attached to the gear 11 via a one-way clutch 12. This one-way clutch 12 transmits the rotation of the lever 7 to the gear 11 only when the lever 7 is rotated clockwise from the vertical state (see Fig. 5) to the inclined state (see Fig. 6). However, it is difficult to transmit the rotation of the gift 11, which rotates counterclockwise in the normal state, to the lever 7.

In addition, when the lever 7 is in the image forming apparatus main body in the casing 2 removal direction, the transfer drum 4 is in the abutting position (
A stopper 8 is provided that restricts removal of the casing 2 when the lever 7 is in a vertical state by engaging with the lever 7. This stopper 8 does not engage with the lever 7 during the above-mentioned extraction when the lever 7 is tilted and the cam member 5 is allowed to move the transfer drum 4 to the separated position.

According to this embodiment, the cam member 5 moves the transfer drum 4 to the contact position with the photosensitive drum 1 only during transfer, and prevents the transfer drum 4 from moving to the separation position after the transfer is completed. It is acceptable. That is, since the transfer drum 4 is brought into contact with the photoreceptor drum 1 only when necessary, the above-mentioned contact time can be shortened, and the toner adheres to the circumferential surface of the photoreceptor drum 1 in the form of a thin film. Therefore, it is possible to prevent the occurrence of so-called filming.

Further, when a selenium drum is used as the photoreceptor drum 1, film roughening due to deterioration of the surface of the photoreceptor drum 1 can be prevented.

Furthermore, if an attempt is made to remove the casing 2 while the cam member 5 is pressing the transfer drum 4 to the abutting position, the stopper 8 engages with the lever 7 for operating the cam member and restricts the removal. In addition, this stopper 8 allows the above-mentioned removal when the cam member 5 allows the transfer drum 4 to move to the separation position, so when removing the transfer drum 4, it is necessary to
The transfer drum 4 and the photosensitive drum 1 are separated from each other, and it is possible to prevent them from coming into sliding contact and being damaged during removal. Even if the transfer drum 4 is stopped in contact with the photoreceptor drum 1 during a power outage, even if the above-mentioned removal is performed, there is no risk of the above-mentioned damage.

In the above embodiment, the support 3 was supported by the main body of the image forming apparatus, but the support 3 was supported by the casing 2.
It can also be supported by

Further, in the above embodiment, the transfer drum 4 is biased in the direction of separation by its own weight, but the transfer drum 4 may be biased in the direction of separation by a biasing means such as a spring.

In addition, the present invention is not limited to the above embodiments, and various design changes can be made without changing the gist of the invention.

<Effects of the Invention> As described above, according to the present invention, the cam member moves the transfer drum to the contact position with the photoreceptor drum only during transfer, and moves the transfer drum to the separation position after the transfer is completed. In other words, since the transfer drum contacts the photoreceptor drum only when necessary, the above-mentioned contact time can be shortened, and the toner forms a thin film on the circumferential surface of the photoreceptor drum. It is possible to prevent so-called filming from occurring. In addition, when the cam member is pressing the transfer drum to the contact position, the stopper engages the lever for operating the cam member and restricts the removal of the casing. When the movement to the separated position is allowed, the above-mentioned extraction is allowed, so the transfer drum and photosensitive drum are always separated from each other at the time of extraction, thereby preventing damage caused by sliding contact between the two at the time of extraction. It has the unique effect of being able to

[Brief explanation of the drawing]

Figure M1 is a schematic view of the main part of an image forming apparatus according to an embodiment of the present invention, showing a state in which a transfer drum is in contact with a photoreceptor drum, and Figure 2 shows a state in which the transfer drum is separated from the photoreceptor drum. A schematic view of the main parts, Figure 3 is a cross-sectional view showing the driving connection part of the cam member, Figure 'M4 is a cross-sectional view showing the connecting mechanism between the cam member and the lever, Figures 5 and 6 are the state in which extraction is restricted by the stopper. and FIG. 7 is a schematic front view showing a conventional transfer drum support mechanism. 1... Photosensitive drum, 2... Casing, 3...
Support body, 4... Transfer drum, 5... Cam member, 6...
...Compression coil spring (elastic member), 7...Lever 8
...stoppa.

Claims (1)

[Claims] 1. Place the photoreceptor on the transfer paper wrapped around the transfer drum. Image formation by transferring images using a drum In the device, A case that can be removed from the image forming apparatus body. -Thing and Supports the transfer drum rotatably, and The above casing or image forming device body , the transfer drum is transferred to the photoreceptor drum. Separate the abutting position from the photoconductor drum. Supports freely swinging between the opposite separation position a support body made of Interposed between this support and the casing During transfer, the support is moved through an elastic member. and press to bring the transfer drum into contact position. and after the transfer is completed, remove the transfer driver. Cam part that allows movement of the cam to the separation position wood and A lever to manually operate this cam member and, Provided in the main body of the image forming apparatus, the cam section material is pressing the transfer drum into contact position. In this state, engage the lever above to close the case. removal from the image forming apparatus main body. and the cam member prevents the separation of the transfer drum. The above while allowing movement to the opposite position. Equipped with a stopper that allows removal. An image forming apparatus characterized by: