JPS6214673A - Method and device for transfer in electrophotographic copying machine - Google Patents

Abstract

PURPOSE:To prevent a defect in transfer from occurring by making a current which is discharged to the side of a photosensitive body smaller on the upstream side of a charge wire in the rotating direction of a transfer drum than on the downstream side. CONSTITUTION:An alternate long and two short dash line indicates a straight line which connects the centers of rotation of both drums together, the point of contact between the peripheral surface of the photosensitive drum 1 and that of the transfer drum is put on the straight line, and a transfer charger wire 13a is extended on the straight line. The gap of the opening part of the shield case 13b of the charger 13 is made wider on the upstream side of the charging wire 13a in the rotating direction of the transfer drum 12 and substantially narrower on the downstream side. Namely, the current component flowing from the transfer charger to the shield case 13b is made smaller on the downstream side than on the upstream side. Consequently, the photosensitive body, transfer paper, and insulating film (transfer drum) are brought into contact with one another securely where the current component flowing to the photosensitive body side of the transfer charger has a peak value, and a defect in transfer never occurs.

Description

TECHNICAL FIELD The present invention relates to a charge transfer method and apparatus using a transfer drum.

Prior art As shown in FIG. 4, a side cross-sectional view of the photosensitive drum is uniformly charged by a charger, and an electrostatic latent image is formed by exposing the original to a light source that separates the original. In a color electrophotographic copying machine, a process of developing with toner to form a developed image on the drum and transferring the developed image to transfer paper under the action of a transfer charger is repeated as many times as the number of separated colors. It has a transfer drum 12 arranged so as to be in contact with each other at the transfer position, and a transfer charger 13 arranged opposite to the photosensitive drum 1 with the cylindrical surface of the transfer drum 12 in between. The transfer means is formed of a thin dielectric sheet and a drum frame supporting the dielectric sheet at both ends (t==both sides), and the transfer drum 12 rotates synchronously with respect to the photoreceptor drum 1 without sliding movement. Toyama Ganjin Co., Ltd.'s model number [known before this application as Ricoh Color 50001, and in this machine, transfer failure due to peeling discharge that occurs when the transfer paper is peeled off from the photoreceptor drum 1 (commonly known in copying technology as "print print") In order to prevent transfer defects (referred to as "transfer defects"), as shown in the partial cross-sectional view shown in FIG. The contact point is provided upside down by about t=2 points on the upstream side in the rotational direction of the transfer drum with respect to the contact point that comes into pressure contact (with transfer paper interposed during transfer). However, in the above method, the transfer charge current is distributed most strongly upstream of the pressure contact point between the transfer drum 12 frame and the photoreceptor drum 1, so the transfer paper is in close contact with the photoreceptor drum 1 in that area. must be maintained. In particular, the transfer drum is made of an insulating film (for Ricoh Color 5000, the film is made of 100%
Adopts a μm thick polyester film. ), the insulating film is pasted so as to sag in the circumferential direction of the frame, and when the frame and the photoreceptor drum 1 come into pressure contact, the photoreceptor, transfer paper, and insulating film are attached on the upstream side in the rotational direction. The three parts of the film must be brought into close contact.

However, in reality, the adhesion is unstable, and sometimes the transfer charge acts strongly where the adhesion is incomplete.
There is a drawback that the transfer charge applied to the insulating film may become substantially low, resulting in poor transfer.

For example, if there is a gap between the insulating film and the photoreceptor drum 1, the capacitance between the insulating film and the photoreceptor decreases, and the charge on the insulating film for transfer decreases. Assuming that the charging potential is constant, a decrease in capacitance appears as a decrease in the amount of charge.

Purpose The present invention aims to eliminate such drawbacks, and the present invention is directed to a method in which at least a portion of a flexible insulating film, an insulating (human blood) mesh screen, an insulating tension thread, etc. is fixed to a drum-shaped frame. A method in which a transfer drum is pressed against a photoconductor with a transfer member (transfer paper, Mylar, etc., hereinafter referred to as transfer paper) interposed, and at the same time a transfer charge is applied to transfer the developed toner image on the photoconductor to the transfer paper. In order to prevent the occurrence of transfer defects, the photoconductor, transfer paper, and insulating film are brought into close contact at the point where the component of the current flowing toward the photoconductor side of the transfer charge (hereinafter referred to as photoconductor drum current) reaches its peak value. The purpose of the present invention is to provide a color electronic copying machine that has the following features.

Configuration In order to achieve the above-mentioned object, the present invention includes the configuration requirements described below.

(1) In the charge transfer method using a transfer drum,
A transfer charge wire is provided substantially close to a surface including the rotation axis of the transfer drum and a contact point where the drum frame comes into pressure contact with the photoreceptor, and the current discharged to the photoreceptor side is controlled when viewed from the rotation direction of the transfer drum. A transfer method for an electrophotographic copying machine, characterized in that the charge wire is smaller on the downstream side than on the upstream side.

(2) The electronic device according to item (1) above, in which the current flowing into the shield case of the transfer charger is made larger on the downstream side of the charge wire than on the upstream side when viewed from the transfer drum rotation direction. Transfer method in photocopying machines.

(3) In a charge transfer means using a transfer drum,
A transfer charge wire is provided substantially close to a surface including the rotation axis of the transfer drum and a contact point where the drum frame comes into pressure contact with the photoreceptor, and is located downstream with respect to the charge wire when viewed from the rotation direction of the transfer drum. 1. A transfer device for an electrophotographic copying machine, characterized in that an inner wall of a shield case is provided closer to the wire than an inner wall of the shield case on an upstream side.

(4) In a charge transfer means using a transfer drum,
The transfer charge wire is provided substantially close to the surface including the rotation axis of the transfer drum and the contact point where the drum frame comes into pressure contact with the photoreceptor, and is located downstream of the charge wire of the transfer charger when viewed from the rotation direction of the transfer drum. A transfer device for an electrophotographic copying machine, characterized in that an insulating member is applied to the inside of a side shield case.

Embodiments An embodiment of the present invention will now be described with reference to the drawings.

(Part 1) Fig. 1(a) is a side sectional view of one embodiment of the device of the present invention.
(b) is a diagram showing the current distribution flowing to the photoconductor side, and in FIG. This is a transfer drum formed by fixing thread, etc. to a drum frame, and the dashed line indicates a straight line connecting the rotation centers of both drums.
Therefore, normally, the contact points between the circumferential surface of the photosensitive drum 1 and the transfer drum are placed on the same straight line, and the transfer charge wire 13 & is also stretched on the same line. 13b is
In the shield case of the charger 13, the gap between the openings is wide on the upstream side and substantially narrow on the downstream side with respect to the charge wire 13a when viewed from the rotational direction of the transfer drum 12. In other words, from the transfer charger to the shield case 1
The current component flowing through 3b is made to be larger on the downstream side than on the upstream side.

FIG. 1(b) is a distribution curve showing the relationship between the current flowing from the charge wire to the photoconductor side in the transfer device and the rotation direction of the photoconductor circumferential surface, and the magnitude of the current is opposite to the charge wire 13a. It has been shown that the maximum attenuation is at the point of contact with the surface of the photoreceptor and therefore the transfer drum, and the attenuation decreases as it moves away from the same point on both sides, with the attenuation rate being especially large on the downstream side with respect to the charge wire.

As described above, according to this embodiment, the photoreceptor, transfer paper, and insulating film (transfer drum ) can be brought into close contact with each other, and there is no risk of defective transfer.

Furthermore, since the photosensitive drum current attenuates from the peak value toward the downstream side, it is possible to prevent peeling discharge when the transfer paper separates from the photosensitive main drum.

Of course, the device of this embodiment is applied to a predetermined part of the color copying machine shown in FIG. 4, but the effects of the present invention are not necessarily limited to the type in which the transfer drum is in full pressure contact with the photoreceptor drum. , it can also be applied to cases where instantaneous discharge occurs when the transfer paper is peeled off from the belt photoreceptor, and therefore is not limited to color copying.

(Part 2) FIG. 2 is a side view of main parts of another embodiment of the present invention,
In the figure, members indicated by the same reference numerals as those shown in the first drawing are the same as those described in the embodiment (part 1). In the case of this embodiment, as in the embodiment (part 1), the charge wire is stretched in a plane that includes the rotating shafts of both drums and the contact points of both drums, but the opening width of the shield case 13b is larger than that of the transfer drum. When viewed from the rotation direction of the wire 12, the upstream and downstream sides of the wire 13a are the same. However, an insulating member 13G is provided inside and on the side surface of the case downstream of the wire 13a of the case 13b. Therefore, the insulating member 1
3c does not necessarily make the downstream side narrower with respect to the charge wire 13aK, but the current flowing toward the photoreceptor side on the downstream side is abruptly cut off due to charge-up due to the discharge current.

With the above configuration, this embodiment can substantially provide the photosensitive drum current characteristics as shown in FIG. be able to.

(Part 3) FIG. 3 shows a complete side view of the main part of another embodiment of the present invention. In this embodiment, a spacer made of an insulating material is provided inside the shield case 13b on the downstream side with respect to the wire. Electrode 1
3d, and a voltage of the same polarity as the charger polarity is applied to the same electrode 13d.

With the above configuration, this embodiment can substantially provide the photoreceptor drum current characteristics as shown in FIG. The functions and effects described in 1) can be achieved.

According to the present invention, a flexible insulating film, an insulating mesh screen, an insulating tension thread, etc. are mounted on a drum-shaped frame.
A method and apparatus for transferring a developed toner image to the transfer paper by pressing a transfer drum, which is formed at least partially fixed, against a photoreceptor with a transfer paper interposed therebetween and applying a transfer charge at the same time, and to prevent transfer defects occurring in the apparatus. It can be prevented.

[Brief explanation of the drawing]

1(a), 2, and 3 are side views of essential parts of each embodiment of the apparatus for carrying out the method of the present invention, and FIG. 1(b) is the same diagram of the photoreceptor drum current in the apparatus of the present invention. FIG. 4 is a side view of a conventional transfer device in an electrophotographic copying machine; FIG.
The figure is a detailed view of the main parts. 1... Photosensitive drum, 12... Transfer drum, 13.
...Transfer charger, 13a...Charge bow wire, 13b...Shield case, 13c...Insulating material,
13d...electrode.

Claims (1)

[Claims] 1. In a charge transfer means using a transfer drum, a transfer charge wire is provided substantially close to a surface including a rotating shaft of the transfer drum and a contact point where the drum frame comes into pressure contact with a photoreceptor; , the current discharged to the photoreceptor side, when viewed from the rotational direction of the transfer drum, is relative to the charge wire.
A transfer method for an electrophotographic copying machine, characterized in that the number of copies on the downstream side is smaller than on the upstream side. 2. The current flowing into the shield case of the transfer charger,
2. The transfer method for an electrophotographic copying machine according to claim 1, wherein the number of charge wires is larger on the downstream side than on the upstream side of the charge wire when viewed from the rotational direction of the transfer drum. 3. In a charge transfer means using a transfer drum, a transfer charge wire is provided substantially close to a surface including the rotation axis of the transfer drum and a contact point where the drum frame comes into pressure contact with the photoreceptor, and the transfer charge wire is provided in the rotation direction of the transfer drum. A transfer device for an electrophotographic copying machine, characterized in that an inner wall of the shield case located on the downstream side with respect to the charge wire when viewed from above is provided closer to the wire than that on the upstream side. 4. In a charge transfer means using a transfer drum, a transfer charge wire is provided substantially close to a surface including the rotation axis of the transfer drum and a contact point where the drum frame comes into pressure contact with the photoreceptor, and the transfer charge wire is provided in the rotation direction of the transfer drum. A transfer device for an electrophotographic copying machine, characterized in that an insulating member is provided inside a shield case on the downstream side with respect to a charge wire of a transfer charger.