JPH0652460B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus using a photoconductor such as an electrophotographic copying machine, and in particular, an image formed on the photoconductor by subjecting the photoconductor to the steps of charging, photoimage exposure and development. After transferring the
The present invention relates to an image forming apparatus in which a photoreceptor is cleaned and used repeatedly.

In this type of image forming apparatus, for example, an electrophotographic copying machine, there is a problem that paper powder adheres to the photoconductor when the toner image is transferred from the photoconductor to the recording paper. This paper dust is likely to be generated from the cut portion of the paper, that is, the edge of the paper. If the paper dust remains attached to the photoconductor, it damages the photoconductor and causes cleaning failure.In addition, the paper dust absorbs water to lower the electrical resistance of the photoconductor.
The photoconductor cannot be charged to the desired potential. Therefore, it is necessary to remove the paper dust.

Since the front end and the rear end of the recording material in the rotating direction of the photoconductor contact the image area in the direction of the photoconductor bus, the paper dust generated from the front end and the rear end can be removed together with the residual toner after the transfer. However, the end portion of the recording material in the direction perpendicular to the rotating direction of the photoconductor comes into contact with the non-image area where the residual toner is small. Therefore, it is difficult to remove the paper dust in this portion.

Therefore, the present invention which solves this problem is to develop a rotating photosensitive member, a charging unit for applying an electric charge to the surface of the photosensitive member to charge it, and develop an electrostatic latent image formed on the photosensitive member by image exposure with toner. Developing means, a cleaning blade for cleaning the residue remaining on the surface of the photoconductor after the toner image is transferred from the photoconductor to the recording material, and a non-image area outside the image-exposed area in the photoconductor rotating direction. And a non-image area in which an end portion of the recording material in a direction perpendicular to the rotation direction of the photoconductor is in contact with the detection means for detecting the size of the recording material. In order to form a cleaning toner image of a certain width in the inner position along the rotation direction of the photoconductor, the blank exposure means and the present toner are attached so that the toner is attached to the surface of the photoconductor while leaving a charge. A control means for controlling the means, a control means is the formation position of the cleaning toner image which is characterized in that switching to the size of the recording material in which the detection unit detects.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a very schematic structure of the image forming apparatus of the present invention.
Is a drum-shaped photosensitive member (hereinafter, referred to as a drum) rotatably supported by a shaft 1a in an arrow direction, and a charging device 2, a developing device 3, a transfer charging device 4, a cleaner 5, a pre-exposure lamp are provided around the photosensitive member. Image forming process equipments such as 6 are sequentially arranged.

In the above-described structure, the drum 1 is positively or negatively charged by the charger 2 in the course of its rotation, and is then image-exposed by the image exposure unit 7, so that an electrostatic latent image is formed. This electrostatic latent image is visualized as a toner image by the developing device 3,
This toner image is transferred to the transfer member 8 by the transfer charger 4. The transfer member 8 is sent out from the cassette 9 by a paper feed roller (not shown), and is sent on the guide plates 11 and 12 toward the transfer charger 4 in synchronization with the rotation of the drum 1 by the timing roller 10, and the drum 1 After the transfer is performed by contacting with the sheet, the sheet is separated from the drum surface, passes through a fixing unit (not shown), and is ejected outside the apparatus as a copy. The cleaner 5 removes residual toner after transfer from the drum surface after separating the transfer member, and is repeatedly used for image formation.

On the other hand, the drum surface is rotated by the drum 1 except when the original is exposed, that is, in the non-toner image area following the area on the photoconductor on which the toner image is formed, by a micro switch (not shown) arranged in the cassette 9. Exposure is performed by a blank exposure source 13 whose lighting timing is controlled (for example, a plurality of lamps, light emitting diodes, and the like, which are linearly arranged in the axial direction of the drum 1).

In this embodiment, the size of the transfer member 8 (size in the axial direction of the drum 1) is detected, and the detection signal is used to reduce the blank exposure amount of the drum surface corresponding to the end portion of the transfer member at the time of blank exposure so that the electric charge remains. The residual charge causes the toner to adhere to the drum surface in a band shape.

In FIG. 1, a transfer member size detector (for example, a photocoupler array) 22 is provided across the transfer member passage extending from the cassette 9 to the timing roller 10, and a detection signal of the 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 so that blank exposure is not performed on the drum surface corresponding to the end of the transfer member.

Further, instead of controlling the blank exposure source 13 to be turned 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. You can choose That is, drum 1
A guide groove 17 parallel to the drum shaft is provided in the reflection case 16 arranged in parallel, and the light shield plate 15 is passed through the guide groove 17 so that a bent piece 15a at one end of the light shield plate is brought into contact with the outer surface of the case. Then, the wire 19 is suspended around the pulleys 18a to 18d provided near 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, so that the pulley 1
The transfer member size detector 2 is provided with a motor 20 that drives 8a.
The light-shielding plate 15 is stopped at a position corresponding to the end of the transfer member 8 by being controlled by the motor control circuit 21 which receives the second detection signal as an input.

As described above, the embodiment of the present invention does not turn on the blank exposure source 13 corresponding to the end portion of the transfer member during blank exposure (FIG. 1) or, even if the blank exposure source 13 is turned on, the light thereof corresponds to the end portion of the transfer member. As shown in Fig. 2 (Fig. 2), the electric charge is left on the drum surface in a width of about 10 mm, and the toner is adhered to the belt by the residual electric charge (hereinafter referred to as "blackening"). When removing the toner from the drum surface, it is possible to remove foreign matter such as paper dust.

Since a large amount of paper dust is present on the surface of the photoconductor in contact with the edge of the recording material, the edge of the recording material in the direction perpendicular to the rotating direction of the photoconductor is formed as in this embodiment that forms a belt-shaped toner image having a width of about 10 mm. By forming a cleaning toner image of a certain width along the rotation direction of the photoconductor at a position in the non-image area where the parts contact, paper dust can be removed without consuming unnecessary toner.

As a result of an endurance test, a streak-like scratch was generated on the drum surface corresponding to the end portion of the transfer member in the conventional apparatus that does not black out during blank exposure after thousands of times of image formation. However, in the apparatus of the present invention for blackening out, no streak-like scratch was observed on the drum surface until the image formation was performed tens of thousands of times. That is, according to the device of the present invention, the life of the drum can be extended by one digit or more.

The cleaner 5 in the illustrated example is a blade cleaning system having a blade 5a, but a fur brush cleaning system or a magnetic brush cleaning system can be similarly applied. In the illustrated example, a transfer member size detector such as a photocoupler array is arranged in the passage of the transfer member to detect the width size of the transfer member. It can also be used as.

As described above, according to the present invention, the size of the recording material is detected, and the toner of a certain width is attached along the rotation direction only to the drum surface corresponding to the end portion of the recording material. Since foreign matter such as paper dust is removed, the surface of the photoconductor can be maintained in a good condition regardless of the size of the recording material used.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an image forming apparatus of the present invention, and FIG. 2 is a perspective view of a blank exposure source applied to the apparatus. 1 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. A rotating photoconductor, charging means for applying a charge to the surface of the photoconductor to charge it, and developing means for developing an electrostatic latent image formed on the photoconductor by image exposure with toner.
A cleaning blade that cleans the residue remaining on the surface of the photoconductor after transferring the toner image from the photoconductor to the recording material, and attenuates the electrostatic charge in the non-image area outside the image-exposed area in the photoconductor rotation direction. In an image forming apparatus having a blank exposing unit, a detecting unit that detects the size of the recording material, and a position in the non-image area where the end of the recording material in the direction perpendicular to the photosensitive member rotating direction is in contact, Control means for controlling the blank exposing means and the developing means so that the toner is attached to the surface of the photoconductor so as to leave a charge on the surface of the photoconductor so as to form a cleaning toner image having a constant width along the rotation direction of the photoconductor. The image forming apparatus is characterized in that the control means switches the formation position of the cleaning toner image according to the size of the recording material detected by the detection means.