JPS6070469A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the surface of a drum from being damaged by removing a toner adhering only to the surface of the drum corresponding to the end part of a transfer member, and simultaneously, removing a foreign matter such as paper powder, etc., at the time of a blank exposure. CONSTITUTION:The drum surface is exposed by a blank exposure source 13 whose lighting timing is controlled by a microswitch placed on a cassette 9 except when an original is exposed while the drum 1 is being rotated. Subsequently, the size of a transfer member 8 is detected, and by this detecting signal, a charge is made to remain behind by reducing the blank exposure quantity of the drum surface corresponding to the end part of the transfer member at the time of a blank exposure, and by this residual charge, a toner is made to adhere like a belt to the drum surface, therefore, when removing this adhering toner from the drum surface, a foreign matter such as the paper powder, etc. can also be removed together.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus that uses a photoreceptor such as an electrophotographic copying machine, and in particular to an image forming apparatus that uses a photoreceptor such as an electrophotographic copying machine. After transferring to the transfer member,
The present invention relates to an image forming apparatus in which a photoreceptor is cleaned and used repeatedly.

In conventional image forming apparatuses of this type, such as electrophotographic copying machines, foreign matter such as paper dust coming out from the end surface of the transfer member collects at the contact portion between the cleaner and the photoreceptor. However, since the end of the transfer member is mostly a white part, toner does not adhere to the photoreceptor surface corresponding to the end of the transfer member, and foreign matter that has gathered at the contact area is easily transferred through the toner. could not be scraped off the photoreceptor. As a result, the photoreceptor may be damaged by foreign matter such as paper dust, or in the worst case, cleaning failure may occur.

An object of the present invention is to eliminate the above-mentioned disadvantages, and at the time of blank exposure, charges remain on the photoreceptor at a position corresponding to the end of the transfer member, and this residual charge causes toner to adhere to the above position. When the toner is cleaned in the cleaner part, foreign matter such as paper powder that has collected in the cleaner part is scraped off from the surface of the photoreceptor along with the toner.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a very schematic configuration of the image forming apparatus of the present invention.
is a photoreceptor on a drum (hereinafter referred to as a drum) supported rotatably in the direction of the arrow by an axis Ja, and around this is a charger 2.
, a developing device 3, a transfer charger 4, a cleaner 5, a pre-exposure lamp 6, and other image forming process equipment are sequentially arranged.

In the above configuration, the drum 1 is positively or negatively charged by the charger 2 during its rotation, and then receives the image light i at the image exposure section 7, thereby forming an electrostatic latent image. This electrostatic latent image is visualized as a toner image by the developing device 3,
This toner image is transferred to a transfer member 8 by a transfer charger 4. This transfer member 8 is sent out from the cassette 9 by a paper feed roller (not shown), and sent toward the transfer charger 4 on guide plates 11 and 12 by a timing roller 10 in synchronization with the rotation of the drum 1. 1 to perform the transfer, it is separated from the drum surface, passes through a fixing section (not shown), and is discharged outside the machine as a copy. After the transfer member has been separated, the drum surface is cleaned of residual toner by a cleaner 5, and is used repeatedly for image formation.

On the other hand, when the drum surface is rotating and the document is not exposed, the blank exposure [1] whose lighting timing is controlled by a microswitch (not shown) arranged in the cassette 9.
3 (for example, a plurality of lamps, light emitting diodes, etc. arranged linearly in the axial direction of the drum l).

The present invention detects the size of the transfer member 8 (the size in the axial direction of the drum l), and uses this detection signal to reduce the blank exposure amount on the tram surface corresponding to the end of the transfer member during blank exposure so that charges remain. This residual charge causes toner to adhere to the drum surface in a band-like manner.

In FIG. 1, a transfer member size detector (for example, a photocoupler array) 22 is provided across the transfer member path from the cassette 9 to the timing roller 10, and the detection signal of this detector 22 is supplied to the blank exposure source driving circuit 14. However, the blank exposure source 13 at the position corresponding to the end of the transfer member 8 is turned off to prevent blank exposure from being performed on the drum surface corresponding to the end of the transfer member.

Moreover, instead of controlling the blank exposure source 13 to turn off as described above, the position of the light shielding plate 15 is controlled as shown in FIG. 2 so that blank exposure is not performed on the drum surface corresponding to the end of the transfer member. It may also be something that does. That is, drum 1
A guide groove 17 parallel to the drum axis is provided in the reflective case 16 arranged in parallel with the drum shaft, and a light shielding plate 1 is provided in this guide 1i11.7.
5 and one end of the light shielding plate is brought into contact with the outer surface of the case. Then, a wire 19 is hung around pulleys 18a to 18d provided close to the four corners of the reflection case 16, and both ends of the wire are attached to the other end of the light shielding plate 15.
A motor control circuit 21 receives a detection signal from a transfer member size detector 22 as input for the motor 2° that drives the pulley 18a.
The configuration is such that the light shielding plate 15 is stopped at a position corresponding to the end of the transfer member 8.

A specific example of the present invention, as described above, does not turn on the blank exposure source 13 corresponding to the end of the transfer member during blank exposure (
(Fig. 1), or even if the light is turned on, the light does not reach the drum surface corresponding to the end of the transfer member (Fig. 2), so that an electric charge remains on the drum surface in a width of about 10 mm, and this residual Since the toner is attached in a band shape by electric charge (hereinafter referred to as blackout), when this blackout toner is removed from the drum surface, foreign matter such as paper dust can also be removed together with it.

As a result of a durability experiment, it was found that in a conventional apparatus that does not perform blackout during blank exposure, streak-like scratches were generated on the drum surface corresponding to the end of the transfer member after several f times of image formation. However, in the apparatus of the present invention that performs L blackout, no streak-like scratches were observed on the drum surface until the formation of images on several sides. In other words, with the apparatus of the present invention, it has become possible to extend the life of the drum by more than one order of magnitude.

The illustrated cleaner 5 uses a blade cleaning method having a brush □-F5a, but it can also be applied to a far plan cleaning method or a magnetic brush cleaning method. Although a transfer member size detector such as a photocoupler array is disposed in the path of the transfer member, a detection signal from a loaded cassette may also be used as a size detection signal for the transfer member.

As described above, according to the present invention, toner is deposited only on the drum surface corresponding to the end of the transfer member during blank exposure, and foreign matter such as paper dust is removed at the same time as the adhering toner is removed. This has the effect of greatly extending the life of the drum by preventing damage.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of the image forming apparatus of the present invention, and FIG. 2 is a perspective view of a blank exposure source applied to the apparatus. l is a drum, 8 is a transfer member, 13 is a blank exposure source, 2
2 is a transfer member size detector.

Claims (1)

[Claims] (1) In an image forming apparatus in which the image formed on the photoreceptor is transferred to a transfer member by subjecting the photoreceptor to the steps of charging, photoimage exposure, and development, the photoreceptor is cleaned and used repeatedly. A size detector that detects the size of the member, and blank exposure control means that receives a detection signal from the size detector and reduces the amount of blank exposure to the photoreceptor surface corresponding to the end of the transfer member. image forming apparatus.