JPH01217382A - Separation claw device of copying machine - Google Patents

Abstract

PURPOSE:To prevent adhesion of the unfixed toner on transfer paper to a separation claw for separating transfer paper from a photosensitive body by holding the separation claw at the same potential against a copying machine body or at the potential of the same polarity as that of developing toner. CONSTITUTION:At the timing when the leading end of transfer paper P is about to reach the vicinity of a separation charger 8, a separation claw 11 is pressurized contact with a photosensitive drum 1 and the leading edge of the transfer paper P is separated from the drum 1. When the leading edge of the paper P passes the claw 11 by about 5cm, the pressure-contacting state of the claw 11 to the drum 1 is cancelled. At the time of the cancellation, a negative voltage E, the polarity of which is the same as that of the toner used for development by means of a developing device 6, is applied across the claw member 22 of the separation claw 11. Therefore, the toner is electrostatically repulsed by the claw member 22, even if the transfer paper P is attracted by the member 22. Therefore, the unfixed toner on the transfer paper P does not adhere to the claw member 22 and disturbance of the picture on the transfer paper P can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a separation claw device for separating transfer paper from a photoreceptor in an electrophotographic copying machine.

[Conventional technology and its problems]

In an electrophotographic copying machine, as a method of separating the transfer paper charged by a transfer charger and electrostatically attracted to the surface of the photoreceptor drum from the photoreceptor drum, the charger removes the transfer paper's charge by corona discharge from the photoreceptor drum. There are two methods: one method is to weaken the adhesion force to the material and separate the other, and the other method is to install a separation claw in addition to the separation charger and mechanically force the separation using the separation claw.

In the former method, the separation performance is easily affected by paper quality (for example, paper stiffness or paper thickness) or humidity, and separation reliability is low.

In the latter method, separation reliability is high, but the separation claw comes into contact with the photoreceptor drum, which scratches the photoreceptor drum and causes image noise, which also shortens the life of the photoreceptor drum. .

Therefore, in copiers that adopt the latter method, in order to prevent as much as possible the occurrence of scratches caused by the contact of the separation claws with the photoreceptor drum, the contact time of these claws is reduced or the contact portion is placed on the photoreceptor drum. Efforts have been made to avoid concentrating on one place.

Here, a conventional separating claw device will be explained with reference to FIG.

In FIG. 3, 1 is a photosensitive drum, 7 is a transfer charger, 8 is a separation charger, 9 is a cleaning device, and 11
12 is a separating claw, and 12 is a transport heald that transports the separated transfer paper P toward the fixing roller.

The separation claw 11 is constructed by attaching a metal claw member to a holder made of insulating resin, and the claw member that contacts the photosensitive drum and the transfer paper P is insulated from the machine body. It is in.

The toner image on the surface of the photoreceptor drum 1 is transferred onto a transfer paper P by a transfer charger 7 , and then the transfer paper P is neutralized by a separation charger 8 and separated by a separation claw 11 .

When the transfer paper P comes near the position of the separation charger 8, the separation claw 11 separates the photoreceptor drum 1 by the elastic force of a spring.
(indicated by the broken line in FIG. 2), whereby the transfer paper P attached to the photosensitive drum 1 is separated from its leading edge. After the leading edge of the transfer paper P is separated, in order to prevent the photosensitive drum 1 from being scratched, when the leading edge of the transfer paper P passes the separating claw 11 by a few centimeters, the photosensitive drum of the separating claw 11 is removed. The pressure contact with the drum 1 is released (the state shown by the solid line in FIG. 2).

However, at this time, the separation claw 11 is retracted into the transport path of the transfer paper P, and the surface of the moving transfer paper P may come into contact with the vicinity of the lower surface of the tip of the separation claw 11. In particular, when the transfer paper P is a thin paper with weak stiffness, even after the leading edge is separated, it moves along the photosensitive drum 1. are likely to come into contact with each other.

Therefore, the unfixed toner on the surface of the transfer paper P is removed by the separation claw 1.
The toner is peeled off by the transfer sheet 1, and the image in that area is removed, resulting in image dropout or image loss, resulting in a disturbed image.In addition, the toner adheres to the separation claw 11, staining the separation claw 11, and this separation claw 11 is used to transfer the next transfer paper. There was the problem of contaminating the

In order to solve this problem, Japanese Patent Application Laid-Open No. 60-208782
In the separation claw device described in the publication, a regulating member is provided for regulating the amount of movement of the separation claw 11 in the release direction when the pressure contact is released, and the separation claw 11 reaches into the transport path of the transfer paper P. I try not to.

However, in this conventional separating claw device, in order to limit the amount of movement at the tip of the separating claw to a minute amount of, for example, about 0.5 mm, it is necessary to increase the precision of each part, and the machining,
It is not easy to assemble and adjust, and if the vM degree decreases or the adjustment goes out of order due to wear due to use, etc., the separation claw 11 may move a large amount and come into contact with the transfer paper P, or On the other hand, there is a possibility that a situation may occur in which the separation claw 11 remains in contact with the photoreceptor drum 1 and does not separate from it.

[Technical means for solving the problem] In view of the above-mentioned problem, the present invention prevents unfixed toner on the transfer paper even if the separation claw comes into contact with the transfer paper when the pressure contact of the separation claw is released. The purpose is to prevent it from adhering to the separation claw,
The technical means for this purpose is characterized in that a separating claw for separating the transfer paper from the photoreceptor is held at the same potential with respect to the machine body or with the same polarity potential as the developing toner.

[For production]

Since the separation claw is held at the ground potential or the potential of the same polarity as the developing toner, there is no electrostatic attraction between the separation claw and the toner, or there is no electrostatic attraction between them. Electric repulsive force acts to prevent the toner on the transfer paper from moving toward the separation claw.

To maintain the separation claw at ground potential or a potential of the same polarity as the toner, either ground the separation claw to the machine body, or insulate the separation claw from the machine body, and then apply a voltage of several hundred ports using a DC power supply. Apply.

In the present invention, various means may be employed to form a latent image on the photoreceptor, such as exposure using reflected light from an original or exposure using deflection scanning of a laser beam modulated in brightness. be able to.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing the structure around a photosensitive drum of a copying machine.

Around the photosensitive drum 1, which is arranged approximately in the center of the copying machine body, there are an eraser pump 2, a charger 3, a developing device 6, a transfer charger 7, a separation charger 8, a blade-type cleaning device 9, and a separation device. Claws 11 and the like are provided.

The photoreceptor drum 1 has a photoreceptor layer provided on its surface, and the surface is uniformly charged by passing through an eraser lamp 2 and a charger 3, and image exposure is performed from an optical system (not shown) as indicated by an arrow. As a result, an electrostatic latent image is formed, which is developed by the developing device 6.

A paper feed section (not shown) is provided on the left side of the copying machine main body.
The transfer paper fed from the paper feed section is passed through a timing roller pair 1.
0, the toner image is sent to the transfer position in synchronization with the toner image on the photoreceptor drum 1. The toner image on the photoreceptor drum l is transferred to the fed transfer paper P by the transfer charger 7, and then the transfer paper P is neutralized by the separation charger 8 and separated from the photoreceptor drum 1 by the separation claw 11. The image is transported by the transport heald 12 and fixed by a fixing device (not shown).

As an example of the structure of the separation claw 11 is shown in FIG.
A claw member 22 made of hardened metal is fitted into a holder 21 made of an insulating material such as a synthetic resin and fixed, and a support shaft 23 passes through a shaft hole provided in the holder 21. The holder 21 and the claw member 22 are rotatably supported on the body.

The holder 21 is biased in the direction of arrow B by a spring 24 so as to come into pressure contact with the surface of the photoreceptor drum 1, and is configured to be released from the pressure contact with the photoreceptor drum 1 by a release mechanism (not shown).

The claw member 22 is insulated from the fuselage by the holder 21, and is connected to a DC power supply 25 via a flexible electric wire 26.
A voltage E having the same polarity as the developing toner is applied. These separation claws 11 and power supply device 25 constitute a separation claw device 13.

When the photoreceptor drum 1 is made of, for example, a selenium photoreceptor, its surface is positively charged by the charger 3, and negatively charged toner is transferred to the surface of the photoreceptor drum 1 after exposure in the developing device 6. It is attached and developed. Therefore, in this case, the voltage E applied to the claw member 22
has negative polarity, and its value is about -100 to -800 volts.

Next, the operation of the separating claw device 13 configured as described above will be explained.

When the leading edge of the transfer paper P reaches the vicinity of the separation charger 8, the separation claw 11 comes into pressure contact with the photosensitive drum 1. As a result, the leading end of the transfer paper P is separated from the photosensitive drum 1 as shown by the solid line in FIG. When the leading edge of the transfer paper P passes the separation claw 11 by about 5 cm, the separation claw 1
1 is released from pressure contact with the photoreceptor drum 1. By this time, if the transfer paper P is ordinary plain paper, it will separate from the photoreceptor drum 1 near the separation charger 8 due to its own elasticity and gravity, as shown by the broken line in FIG. If the paper P is a thin paper with weak stiffness, it may come into contact with the separation claw 11.

However, since a negative voltage E having the same polarity as the toner used for development by the developing device 6 is applied to the claw member 22 of the separation claw 11, the transfer paper is attached to the separation claw 11 whose pressure contact is released. Even if the toner and the claw member 22 may come into contact with each other,
The unfixed toner on the transfer paper P will not adhere to the claw member 22, and the image on the transfer paper P will not be disturbed.

The present inventor conducted experiments described below using two types of photoreceptors to determine how the image on the transfer paper P changes depending on the voltage applied to the claw member 22.

In the case of photoconductor drum (A) Photoconductor... OPC photoconductor charging polarity... Negative polarity Vo-minus 500 volts Polarity of toner used... Positive polarity transfer charger 7 polarity... Negative polarity separation charger 8 ...AC corotron photoreceptor drum (
In case of B), photoreceptor...Selenium photoreceptor charging polarity...Positive polarity ■. - Plus 650 volts Polarity of toner used... Negative polarity Transfer charger 7 polarity... Positive polarity separation charger 8... AC corotron For each of these photoreceptor drums (A) and (B), iron The applied voltage E to the claw member 22 was set to various values, and the transfer paper P with a weight of 52 g/m2 was passed in a CD direction (the paper was passed in a direction perpendicular to the lines of the paper), and the state of the image after transfer was observed. did.

The results are shown in Table 1.

Table 1××× Δ △ ◎ ◎ ◎ ◎ ◎ ○○ However, ◎ ・・・・・・No disturbance in the image was found○ ・
...Disturbances in the image cannot be detected with normal attentiveness (
No problems in use Δ... Lines appear on the image ×... Small circular white spots appear on the image According to Table 1, photoreceptor drums (A) and (B) In either case, when the potential of the claw members 22 is maintained at the same polarity potential as the toner used for each, there is almost no disturbance of the image on the transfer paper P, and there is no problem at all in practice. It is shown.

In the above embodiment, to ground the claw member 22, the claw member 22 may be electrically connected via the support shaft 23 without using the electric wire 26. In addition, separation claw 1
The structure of 1, the material of each part, the number of separation claws 11, etc. can be varied.

〔Effect of the invention〕

According to the present invention, even if the separation pawl comes into contact with the transfer paper, unfixed toner on the transfer paper is prevented from adhering to the separation pawl as much as possible.

Therefore, it is possible to prevent the image from being disturbed due to image loss on the transfer paper, and to prevent the separation claw from being contaminated with toner and staining the next transfer paper.

[Brief explanation of the drawing]

1 and 2 show an embodiment of the present invention, FIG. 1 is a schematic diagram of the area around the photosensitive drum of a copying machine equipped with the separating claw device of the present invention, and FIG. 2 shows the structure of the separating claw. A perspective view showing an example, and FIG. 3 is a schematic configuration diagram of a conventional separating claw device. 1... Photosensitive drum, 7... Transfer charger, 8...
...Separation charger, 11...Separation claw, 13...Separation claw device, 21...Holder, 22...Claw member, 2
5... Power supply device, 26... Electric wire, P... Transfer paper. Applicant Minolta Camera Co., Ltd. Agent Patent Attorney Yukio Kubo Figure 2 Figure 3/8

Claims (1)

[Claims] A separating claw device for a copying machine, characterized in that a separating claw for separating transfer paper from a photoreceptor is held at a ground potential or a potential of the same polarity as a developing toner.