JPH071410B2 - Transfer method and apparatus in electrophotographic copying machine - Google Patents

Description

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

2. Description of the Related Art As shown in the side sectional schematic view of FIG. 4, an electrostatic latent image is formed by exposing a decomposition light source of an original document on a photosensitive drum uniformly charged by a charging charger, and forming an electrostatic latent image on the photosensitive drum. In the color electrophotographic copying machine in which the step of developing with the toner of the above to form a visible image on the drum and transferring the developed image to the transfer paper under the action of the transfer charger is repeated for the number of separation colors. A transfer drum 12 arranged so as to be in contact with each other at a transfer position, and a transfer charger 13 arranged so as to face the photoconductor drum 1 with the cylinder surface of the transfer drum 12 in between.
The transfer drum 12 is formed of a thin cylindrical dielectric sheet and a drum frame that supports the dielectric sheet at both ends, so that the transfer drum 12 rotates synchronously with respect to the photosensitive drum 1 without sliding movement. The transfer means is known as a model number [Ricoh color 5000] in the applicant company before this application. In this machine, transfer failure due to peeling discharge (copy when the transfer paper is peeled from the photosensitive drum 1) In order to prevent (transfer failure) which is technically known as "printing", the transfer charge wire 13a provided in the transfer drum 12 as shown in the partial sectional view of FIG. Is provided on the upstream side in the rotational direction of the transfer drum 1 = about 2 m upside down with respect to the contact position where the photosensitive drum 1 is in pressure contact (the transfer sheet is interposed during transfer). However, in the above-mentioned method, the transfer charge current is most strongly distributed upstream of the pressure contact between the frame of the transfer drum 12 and the photosensitive drum 1, so that the transfer paper comes into close contact with the photosensitive drum 1 at that portion. Must be Especially when the transfer drum is an insulating film (the Ricoh color 5000 uses a 100 μm thick polyester film for the same film), the insulating film is slackened in the circumferential direction of the frame body, When the frame body and the photosensitive drum 1 are in pressure contact with each other, the photosensitive body is located on the upstream side in the rotation direction
The transfer paper and the insulating film must be in close contact with each other.

However, in reality, the contact state is unstable, and sometimes the transfer charge works strongly where the contact is incomplete.
The transfer charge applied to the insulating film is so low that transfer defects may occur.

For example, if there is a gap between the insulating film and the photoconductor drum 1, the electrostatic capacitance between the insulating film and the photoconductor is reduced, and the charge of the transfer insulating film is reduced. If the charging potential is constant, the decrease in electrostatic capacity is reflected in the decrease in the amount of charge.

Aims of the present invention are to eliminate such drawbacks, and a transfer drum in which a flexible insulating film, an insulating (surface) mesh screen, an insulating tension yarn, etc. are fixed at least partially to a drum-shaped frame body. Transfer failure in the system in which the transfer member (transfer paper, mylar, etc., hereinafter referred to as transfer paper) is pressed against the photoconductor and the transfer charge is applied at the same time to transfer the toner image on the photoconductor to the transfer paper. In order to prevent the occurrence of the occurrence of the color, the component of the current flowing to the photoconductor side of the transfer charge (hereinafter referred to as the photoconductor drum current) has a peak value, and the photoconductor, the transfer paper, and the insulating film are brought into close contact with each other. It is intended to provide an electronic copying machine.

Configuration In order to achieve the above-mentioned object, the present invention has the following configuration requirements.

(1) In a charge transfer means using a transfer drum,
The transfer charge wire is provided almost in close proximity to the surface including the rotating shaft of the transfer drum and the contact point where the drum frame is in pressure contact with the photosensitive member, and a current flowing into the shield case of the transfer charger is applied in the rotating direction of the transfer drum. In view of the charge wire, by increasing the amount of the charge wire on the downstream side of the charge wire, the current discharged to the photoconductor side is
A transfer method in an electrophotographic copying machine, characterized in that, as viewed from the direction of rotation of the transfer drum, the charge wire is smaller on the downstream side than on the upstream side.

(2) In a charge transfer means using a transfer drum,
The transfer charge wire is provided in the vicinity of the surface including the rotary shaft of the transfer drum and the contact point where the drum frame is in pressure contact with the photosensitive member, and is downstream of the charge wire when viewed from the rotation direction of the transfer drum. A transfer device in an electrophotographic copying machine, wherein an inner wall of the shield case located at a position closer to the wire on the upstream side.

(3) In a charge transfer means using a transfer drum,
The transfer charge wire is provided in the vicinity of the surface including the rotary shaft of the transfer drum and the contact point where the drum frame is in pressure contact with the photosensitive member, and the transfer charge wire is a charge wire of the transfer charge when viewed from the rotation direction of the transfer drum. On the other hand, a transfer device in an electrophotographic copying machine, characterized in that an insulating member is provided inside the shield case on the downstream side.

Example An example of the present invention will now be described with reference to the drawings.

(Part 1) FIG. 1 (a) is a side sectional view of an embodiment of the device of the present invention.
FIG. 1 (b) is a diagram showing the distribution of the current flowing to the photoconductor side. In FIG. 1 (a), 1 is the photoconductor drum, 12 is a flexible insulating film, an insulating mesh screen or an insulating layer. A transfer drum formed by fixing threads on the drum frame, and the alternate long and short dash line indicates the straight line connecting the centers of rotation of both drums.
Therefore, normally, the contact point between the peripheral surface of the photosensitive drum 1 and that of the transfer drum is mounted on the same line, and the transfer charge wire 13a is also stretched on the same line. Reference numeral 13b denotes a shield case of the charger 13, and the opening of the charger 13 is provided so that the upstream side is wider and the downstream side is substantially narrower than the charge wire 13a when viewed from the rotation direction of the transfer drum 12. That is, the current component flowing from the transfer charger to the shield case 13b is increased on the downstream side rather than 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 peripheral surface. The magnitude of the current is opposite to the charge wire 13a. It is shown that the surface of the photoconductor, and hence the point of contact with the transfer drum, is the largest, and it attenuates as it moves away from the same point on both sides, especially with respect to the charge wire. There is.

According to the present embodiment as described above, the current flowing to the photoconductor side of the transfer charger (hereinafter referred to as the photoconductor drum current). When the component of shows the peak value, surely the photoconductor,
The transfer paper and the insulating film (transfer drum) can be brought into close contact with each other, and there is no risk of defective transfer.

Further, since the current of the photosensitive drum from the peak value to the downstream side is greatly attenuated, peeling discharge can be prevented when the transfer paper leaves the photosensitive drum.

Of course, the apparatus of this embodiment is applied to a predetermined portion of the color copying machine shown in FIG. 4, but the effect of the present invention is not necessarily limited to the type in which the transfer drum is pressed against the photosensitive drum. The present invention can also be applied to the case where an instantaneous discharge occurs when the transfer paper is peeled off from the belt photosensitive member, and is not limited to color copying.

(Part 2) FIG. 2 is a side view of the main part of another embodiment of the present invention.
In the figure, the members denoted by the same reference numerals as those of the first illustration are the same as those described in the embodiment (No. 1). In the case of the present embodiment as well, as in the first embodiment (1), the charge wire is stretched in the plane including the rotary shafts of both drums and the contact points of both drums, but the opening width of the shield case 13b is transferred. Seen from the rotation direction of the drum 12, the upstream side and the downstream side of the wire 13a are the same. However, an insulating member 13c is provided on the inner surface of the case 13b on the downstream side of the wire 13a. For this reason, the presence of the insulating member 13c not only narrows the downstream side with respect to the charge wire 13a, but also sharply cuts the current flowing to the photoreceptor side on the downstream side due to the charge gap caused by the discharge current.

With the above-described structure, the present embodiment can substantially provide the photosensitive drum current characteristics as shown in the first (b) illustration, and accordingly, the object as described in the first embodiment (No. 1) can be obtained. The effect can be achieved.

(No. 3) FIG. 3 is a side view of the main part of another embodiment of the present invention. In this embodiment, the electrodes of the shield case 13b are formed on the inner side of the downstream side via a spacer made of an insulating material. 13d
Is installed and a voltage having the same polarity as the charge polarity is applied to the electrode 13d.

With the above-described structure, in the present embodiment, as in the case of the embodiment (No. 2), the photoconductor drum current characteristics as shown in FIG. 1 (b) can be substantially imparted. The actions and effects described in the embodiment (1) can be obtained.

Advantageous Effects According to the present invention, a flexible insulating film, an insulating mesh screen, an insulating tension yarn, etc. are formed in a drum-shaped frame body,
A transfer drum formed by fixing at least a part of the transfer drum is pressed against a photoconductor with a transfer paper interposed, and at the same time a transfer charge is applied to transfer a toner image to the transfer paper. Can be prevented.

[Brief description of drawings]

FIG. 1 (a), FIG. 2 and FIG. 3 are side views of essential parts of each embodiment of the apparatus for carrying out the method of the present invention, and FIG. FIG. 4 is a diagram showing a distribution characteristic curve with respect to the rotation direction of the drum, FIG. 4 is a side view of a conventionally known transfer device in an electrophotographic copying machine, and FIG. 1 ... photosensitive drum, 12 ... transfer drum, 13 ... transfer charger, 13a ... charge wire, 13b ... shield case, 13c ... insulating material, 13d ... electrode.

Claims (3)

[Claims] 1. A charge transfer means using a transfer drum, wherein a transfer charge wire is provided on a surface including a rotation shaft of the transfer drum and a contact point where the drum frame body is in pressure contact with a photoconductor.
Discharge to the photoconductor side by providing a current that flows into the shield case of the transfer charger more closely to the charge wire on the downstream side than on the upstream side, as viewed from the direction of rotation of the transfer drum, while being installed in close proximity. The transfer method in an electrophotographic copying machine is characterized in that the current applied to the charge wire is smaller on the downstream side of the charge wire than on the upstream side of the charge wire when viewed from the rotation direction of the transfer drum. 2. A charge transfer means using a transfer drum, wherein a transfer charge wire is provided on a surface including a rotation shaft of the transfer drum and a contact point where the drum frame is in pressure contact with a photoconductor.
An electronic photograph characterized in that the shield case inner wall is provided substantially close to the charge wire, and the shield case inner wall is located closer to the wire than the charge wire when viewed from the rotation direction of the transfer drum. Transfer device for copiers. 3. A charge transfer means using a transfer drum, wherein a transfer charge wire is provided on a surface including a rotation shaft of the transfer drum and a contact point where the drum frame is in pressure contact with a photoconductor.
A transfer device in an electrophotographic copying machine, wherein the transfer device is provided in the vicinity of the transfer drum, and an insulating member is provided inside the shield case on the downstream side of the charge wire of the transfer charger when viewed from the rotation direction of the transfer drum.