JPH02148076A - Preventing method for contamination of transfer member - Google Patents

Abstract

PURPOSE:To prevent the contamination of a transfer member by constituting the transfer member so that is can be brought into contact and separated against an image carrying body, and when a developer remains between a developing position of the carrying body and a transfer member position due to generation of abnormality, the transfer member is separated until the developer moves to the outside of a transfer area. CONSTITUTION:When a toner 11 which is not transferred to transfer paper due to a jam remains behind on the surface of a photosensitive drum 1, when a power source is turned on again and the drum rotates in the (a) direction, a cam 3 also comes into contact by a rubber member 3b and rotates in the (b) direction, and when the toner 11 passes through a transfer position completely, a transfer roller 2 comes into contact with the drum 1. Thereafter, the toner 11 is collected by a cleaner and to the roller 2, a transfer use bias can be applied through a contact spring 8 from a power source 9. When a cover unit A is released due to a jam, etc., the cam 3 returns to an initial position by force of a spring 4 and comes into contact with the drum 1 by resetting the unit A, and it does not occur that the residual toner 11 contaminates the roller 2.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to preventing the transfer member of an image forming apparatus using an electrostatic transfer process such as an electrostatic copying machine or a printer from becoming dirty.
It is about how to

[Conventional technology]

A transfer roller is usually pressed against an image carrier which has a rotating cylindrical structure and runs in an endless manner, and a sheet-like transfer material such as paper is passed between the two, and the toner image formed on the surface of the image carrier is transferred to the transfer roller. An image forming apparatus configured to transfer images onto a transfer material by the action of a bias applied to the image is conventionally well known.

This is shown in Figure 4. In the figure, 1 is a photosensitive drum that is an image carrier, 2 is a transfer roller that is a transfer member, and 2a is an EP
2b is a metal core for applying a transfer voltage from an external power source (not specified) via a spring 13, which is a conductive rubber made by foaming carbon in a DM or the like. The spring 13 also has the role of pressing the transfer roller 2 against the photosensitive drum 1 with a constant pressure. Further, 7 is a developing sleeve, and 11 is toner, which is the toner that was between the developing sleeve and the transfer roller at the time of a jam and was not transferred to the transfer material.

[Problems to be Solved by the Invention] In such devices, there are problems such as legal problems when a jam or a momentary power interruption occurs.

If the printer body stops due to a jam or a momentary power outage, untransferred developer will remain in the area between the developing sleeve on the photosensitive drum and the transfer roller.

Next, when the jammed transfer material is removed and the power of the printer body is turned on again and the photosensitive drum starts rotating, the developer remaining on the surface of the photosensitive drum ends up on the surface of the transfer roller.

On the other hand, it is possible to prevent the developer from landing on the transfer roller by making the polarity of the bias applied to the transfer roller the same as that of the developer only at this time, but even if such measures are taken, the transfer roller In cases where the photosensitive drum 1 is made of a sponge-like material, residual toner from the photosensitive drum 1 gets into the sponge, resulting in significant contamination.

As a result, there have been problems in that the back surface of the transfer material for the first stitch after the jam treatment is stained or the transfer bias is substantially insufficient, resulting in poor transfer.

[Means for Solving the Problems] The present invention has been made in view of the above, and the present invention has been made in view of the above problem, and it solves the problem that after jam removal, the residual toner remaining between the developing sleeve and the transfer position is removed from the front of the image bearing member. It is characterized in that the transfer roller is pressed against the image carrier after passing the transfer position as it rotates, thereby preventing the transfer roller from becoming dirty.

〔Example〕

FIG. 1a to FIG. 1C show implementation views of the present invention. In FIG. 1a, part A shows the front cover unit side that supports the transfer roller, and part B shows the main body side that holds the photosensitive drum.

In the figure, 1 is a cylindrical electrophotographic photosensitive drum, and 2 is a transfer roller consisting of a conductive sponge 2a made of foamed EPDM and a core metal 2b to which a voltage necessary for transfer is applied from the outside. 3
The main body 3a is used to press and release the transfer roller from the photosensitive drum 1 using a cam, and the rubber member 3b is used to rotate the main body 3a in accordance with the rotation of the photosensitive drum 1. The cams 3 are located on both sides of the transfer roller 2 and are in contact with the photosensitive drum 1 in the non-image area.

Further, 4 is a spring for returning the cam 3 to a predetermined position when the front cover is opened, and 5 is a part of the front cover unit that supports the spring 4. 6 is a support pin for the spring 4 which is attached to the cam 3. 7 is a developing sleeve for developing the electrostatic latent image on the photosensitive drum. Reference numeral 11 indicates residual toner remaining between the developing sleeve 7 and the transfer position at the time of jam.

Further, in FIG. 1c, 8 is a contact spring for applying a transfer bias to the transfer roller core metal 2b, and 9 is a power source for the bias.

Now, in the configuration shown in FIGS. 1a to 1b, the state immediately after the jammed paper is processed is as shown in the figure. In other words, the toner 11 that was not transferred to the transfer paper due to the jam remains on the surface of the photosensitive drum.

Next, when the photosensitive drum starts to rotate forward after the power is turned on again, the photosensitive drum rotates in the direction of arrow a, and the cam 3 rotates in the direction of arrow A. Since the rubber member 3b is tensioned at the photosensitive drum contact point of the cam 3, the cam 3 also rotates as the photosensitive drum l rotates (see FIG. 1b).

The transfer roller 2 comes into contact with the photosensitive drum 1 only when the residual toner 11 has completely passed through the transfer position.

Thereafter, this residual toner 11 is partially collected by the cleaner. Then, a transfer bias can be applied to the transfer roller from a power source 9 via a contact spring 8 .

Further, the force of the spring 4 to return the cam 3 to the position shown in FIG. 1a is weaker than the force of the photosensitive drum 1 to rotate the cam 3, so when the photosensitive drum rotates and the transfer roller is partially pressed against the photosensitive drum, It becomes possible to maintain this state (see Figure 1c).
.

Next, when the front cover unit A is partially released due to jamming or the like, the cam 3 is returned to the position shown in FIG. 1a by the force of the spring 4. Thereafter, when the jammed transfer material is removed and the front cover is reset (arrow C), the cam 3 comes into contact with the photosensitive drum in the same state as in FIG. 1a.

Therefore, with this configuration, even if the transfer material jams during the transfer process, it is possible to partially release the front cover unit A, remove the transfer material, and reset the front cover unit A. If you do this, the transfer roller will be set after the residual toner has passed, so the residual toner 11
However, it does not contaminate the transfer roller 2.

[Other Examples]

FIG. 2 shows another embodiment. Explanation of the same symbols as in FIG. 1 will be omitted. In the figure, 14 is a solenoid for pressing and releasing the transfer roller 2 from the photosensitive drum 1, 10 is a support member for the transfer roller 2, 10a is an arm made of a conductive material, and 10b is a solenoid for pressing the transfer roller 2 against the photosensitive drum 1. The spring 10c for pressure contact is a joint part with the solenoid 14 and is made of insulating plastic. 12 indicates the residual toner after the photoconductor rotates.

Fig. 3 shows the main switch of the main body, the drum motor transfer roller set, and the reset timing sequence.

In the above configuration, first turn on the main switch of the main unit. At the same time, the transfer roller is reset and released from the drum. Then, after a while, the tram motor starts rotating. Here, if t seconds is the time it takes for the remaining toner on the photosensitive drum 1 to completely escape from the transfer area, the transfer roller is brought into pressure contact with the photosensitive drum t seconds after the photosensitive drum 1 starts rotating (the third (See timing chart in figure).

At this time, the transfer roller moves in the direction of arrow d from the position shown by the solid line in FIG. 2, and moves to the position shown by the broken line in FIG.

This movement is performed by the solenoid 14, and at the same time, the remaining toner 11 on the photoreceptor moves to a position 12 indicated by a broken line.

Because of the above configuration, in the event that a jam occurs, the transfer roller is always released from its negative position by turning the main body switch OFF and then ON.

Then, when the transfer roller is set next time, the remaining toner 11 on the photosensitive drum has passed through the transfer section, so it will not contaminate the transfer roller. Furthermore, in this case, unlike the above embodiment, even if the jammed transfer material is pulled out from the paper ejection port side without releasing the front cover A when removing the jammed transfer material, the power to the main body will be turned off immediately. As long as the transfer roller is released from the photosensitive drum, the transfer roller will not be stained with residual toner.

This becomes effective when, in the event of a jam, the main body switch is turned off, the jammed transfer material is pulled out from the paper ejection port, and the main body is left as it is. In other words, even if the main body is left jammed, turning on the main body switch will automatically release the transfer roller and prevent the transfer roller from getting dirty.

Although the transfer roller has been described above as the transfer portion, a belt-like member may be pressed against and released from an image bearing member such as an electrophotographic photoreceptor.

〔Effect of the invention〕

As explained above, in the present invention, even if the printer stops due to a transfer material jam or a momentary power cut, the toner remaining on the photoreceptor between the development position and the transfer position can be removed. It has become possible to eliminate contamination of the transfer material.

As a result, there is no staining on the back of the transfer material after the jam treatment, and since the surface of the transfer material is not contaminated, there is no increase in the resistance of the transfer material (as a result, no transfer defects occur).

1) Since there is no increase in resistance due to surface contamination of the transfer material, the durability of the transfer material has also been greatly improved.

[Brief explanation of the drawing]

Figures 1a, 1b, 1c, and 1d are explanatory diagrams of the operation of an embodiment of the present invention, Figure 2 is a side view of another embodiment, Figure 3 is a timing chart thereof, and Figure 4. FIG. 2 is an explanatory diagram showing a conventional example. In the figure, (2) is a photosensitive drum, 2 is a transfer roller, 3 is a cam, 7 is a developing sleeve, 8 is a bias application contact, and 9 is a bias power source.

Claims (1)

[Claims] (1) In an image forming apparatus having a transfer member configured to be able to approach and separate from the image carrier, when an abnormality occurs, the developer remaining between the development position on the image carrier and the position of the transfer member may A method for preventing staining of a transfer member, which comprises bringing the transfer member into contact with the image carrier again after the transfer member moves outside the transfer area as the carrier rotates.