JPS61269176A - Transfer device of color copying machine - Google Patents

Abstract

PURPOSE:To obtain a color copy reduced at its color shear and to reduce the size of a device by constituting a paper carrier for transferring and carrying paper while circumscribing the paper carrier with plural photosensitive drums and copying points as a copying drum consisting of a cylindrical rigid body. CONSTITUTION:The transfer paper carrier constituted of a semiconductive resin film, a supporting body and electrodes is formed like a rigid drum. Consequently, paper to be transferred can be adsorbed to an optional position on the rigid drum 35, respective sheets can be relatively close to each other independently of the longitudinal size of the paper, so that the copying speed can be increased. In addition, respective toner images on the drums can be precisely transferred to the paper by transfer brushes 44-50 at the transfer points of respective photosensitive drums 36-39, the rigid drum is not expanded or contracted and no error is generated in a paper carrying distance, so that toner images on respective photosensitive drums 36-39 can be superposed just at a set position and the color images inputted to the photosensitive drums can be precisely transferred to the paper.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a transfer device for transferring toner images formed on a plurality of photosensitive drums of a color copying machine onto a sheet of paper in superimposed colors.

BACKGROUND ART In general, as a means of obtaining color images by electrophotography, an electrostatic latent image formed on a single photosensitive drum is developed in three stages using toners of three colors, for example, yellow, magenta, and cyan. A method is provided in which a transferred image is obtained by transferring these developed images onto a sheet of paper three times, and a method in which yellow, magenta, and cyan developed images are formed on a plurality of, for example, three photosensitive drums, respectively.
There is a method of obtaining a transferred image by transferring these developed images to paper three times at different transfer points (Japanese Patent Laid-Open No. 56-12
No. 2067, No. 49-84446).

As a transfer device that independently forms and transfers toner images onto three photosensitive drums, the applicant has proposed, for example, a device as shown in FIGS. 3 to 6. When the transfer paper 3 is conveyed from the paper feed cassette 1 onto the conveyance belt 4 by the conveyance roll 2, the feeding of the paper to the conveyance belt 4 is detected by a paper feed sensor (not shown), and based on this detected paper feed signal, the photosensitive drums 5 to 4 are transferred. 7 rotation timing is determined. The electrostatic latent images formed on the photosensitive drums 5 to 7 are made visible by a developing device (not shown) that supplies cyan, magenta, and yellow toners, and this visible image travels on the conveyor belt 4 as shown in FIG. The image is transferred at a predetermined timing onto a transfer sheet that is moved in the direction of the arrow. On the surface of the conveyor belt 4 opposite to the photosensitive drums 5 to 7, suction brushes 10 to 12 for sucking paper onto the conveyor belt 4 are provided corresponding to the photosensitive drums 5 to 7, respectively. ~12
Transfer brushes 13 to 15 are attached to the downstream side of the photosensitive drums 5 to 7, respectively, for transferring the toner images on the photosensitive drums 5 to 7 onto the paper. On the downstream side of each transfer point of the photosensitive drums 5 to 7,
Transfer the specified color toner image! F-turn? For M/
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Peeling claws 16 to 18 are provided for peeling off the transfer paper from the drum surface to prevent it from sticking.

As shown in FIGS. 3 and 4, the conveyor belt 4 has a thickness of 0.
It is constructed by adhering a support 21 to the back side of a semiconductive resin film with a volume resistivity of 5N and a volume resistivity of 1010Ω・cm.
5 and 26 are arranged alternately. At the ends of the electrodes 25 and 26, terminals 25a and 26a are exposed on both sides of the back surface of the support 21, and as the conveyor belt 4 moves, suction brushes 10 to 12 are attached to these terminals 25a and 26a from the bottom surface.
Alternatively, the transfer brushes 13 to 15 are brought into contact with each other.

When the electrodes 25 and 26 contact the suction brushes 10 to 12, for example, the grounded brush contacts the terminal 25a of the electrode 25, and the DC power source 2 contacts the terminal 26a of the other electrode 26.
A positive voltage is applied through the electrodes 7 and the switch 28, so that the electrostatic attraction generated between the electrodes 25 and 26 causes the paper to be attracted to the surface of the semiconductive resin film 20. It has become. When the electrodes 25 and 26 come into contact with the transfer brushes 13 to 15, a positive voltage is applied to both the electrodes 25 and 26 via the DC power supply 29 and the switch 30. The negatively charged toner images on the photosensitive drums 5 to 7 are transferred onto the transfer paper.

In this way, the paper is attracted onto the conveyor belt 4 by the suction brush 10, and the cyan toner image is transferred onto the photosensitive drum 5 at the transfer point by the transfer brush 13, and then onto the conveyor belt by the suction belt 11. The transfer paper is transferred while being adsorbed, and the transfer brush 14 transfers the magenta toner image on the photosensitive drum 6 in a superimposed color.The transfer paper is then transferred to the conveyor belt 4 while being adsorbed by the suction brush 12. The yellow toner image on the photosensitive drum 7 is superimposed on the transfer paper using the transfer brush 15.
After the desired color image is formed on the transfer paper, the color image is fixed by a fixing device (not shown).

However, in the transfer device of such a conventional color copying machine, the conveyance body for the transfer paper is constituted by the conveyor belt 4, and therefore, due to the flexible nature of the belt, there are There is a problem in that the so-called belt creep causes color misregistration when three colors of toner are superimposed on a sheet of transfer paper. Furthermore, in the conventional apparatus, since the cyan, magenta, and yellow toner images are transferred onto the horizontal surface of the conveyor belt 4 by independent photosensitive drums 5 to 7, these photosensitive drums 5 to 7 There was a problem in that the arrangement state became long in a straight line, and the size of the device itself was unavoidable.

An object of the present invention is to solve the above-mentioned problems, and to obtain a color image without color shift using a relatively small-sized device.

Means for Solving the Problems In order to solve the problems of the prior art, the transfer device of the color copying machine of the present invention has a semicircular half that rotates closely at the transfer position to the transfer paper to which the toner image of the photosensitive drum is transferred. An S conductive resin film, a plurality of electrodes arranged on a support at regular intervals in the tangential direction to the inner peripheral surface of the semiconductive resin film, and an electrode on the upstream side of the transfer position on the inner peripheral side. A suction brush that slides and applies a DC voltage to the electrode to electrostatically attract the transfer paper to the semiconductive resin crotch, and a suction brush that slides on the inner peripheral side of the electrode when the electrode moves to the transfer position and is placed on the photosensitive drum. A transfer brush is provided for transferring the toner by applying a voltage of opposite polarity to the toner, and a transfer paper conveying body composed of the semiconductive resin film, a support, and an electrode is formed on a rigid drum.

According to the present invention, by energizing the suction brush at a predetermined timing, the paper to be transferred is attracted to an arbitrary position on the rigid drum, and the gap between the sheets is removed regardless of the size of the paper in the longitudinal direction. can be brought relatively close to each other, and the copying speed can be increased accordingly. In addition, at the transfer point of each photosensitive drum, the transfer brush accurately transfers each toner image on the drum onto the paper, and the rigid drum does not expand or contract, making it possible to reduce the conveyance distance of the paper. Since this error does not occur, the toner images on each photosensitive drum can be superimposed in color at the preset positions, and the color image input on the photosensitive drum can be accurately transferred onto paper.

The rigid drum serving as the transfer drum is formed into a cylindrical shape, and therefore, it is possible to arrange multiple photosensitive drums circumscribing this drum, making it possible to effectively utilize the internal space of the copying machine main body, allowing the device to It is possible to reduce the size of the device itself.

Example Embodiments of the present invention will be described below based on the drawings.

As shown in FIG. 1, the paper stacked in the paper feed cassette 1 is fed out by the paper feed roll 2 and conveyed by the transport roll 40.4.
1, the paper is supplied through a chute 42 to a rigid drum 35 as a transfer drum. As shown in FIGS. 2 to 4, this rigid drum 35 has a support 21 made of an insulating material on the back side of a semiconductive resin film 20 having a thickness of 0.5 N1 and a volume resistivity of 1010 Ω·1. Electrodes 25 and 26 having a width of, for example, 1all are arranged alternately with a gap 1#l1ll in the conveying direction of the support 21, and terminals 25a and 26a are attached to the support 21, respectively.
It is exposed on the underside of the eave as shown in Figure 2.

On the inside of the support body 21 facing the terminals 25a and 26a of the electrodes 25 and 26, as shown in FIG. 45a, 47a, 49a and suction brushes 43b, 45b, 47b, 49b are arranged upstream of the transfer points of the photosensitive drums 36-39, respectively. The suction brushes 43a, 45a147a, and 49a are grounded, and the other suction brush 43b145b.

A positive voltage is applied to 47b and 49b via the DC power supply 27 and switch 28. Each transfer drum 36 to downstream of these suction brushes 43, 45, 47, 49
39, there is a transfer brush 4 as shown in FIG.
4,46, 48, and 50 are arranged on both sides facing the terminals 25a and 268, and these transfer brushes are applied with a predetermined positive voltage via the DC power supply 29 and the switch 30. It has become.

The rigid drum 35 is rotated at a constant speed in the clockwise direction in FIG. 1 by a motor (not shown), and a transfer drum cleaner 51 is provided upstream of the chute 42 to clean the drum surface. . The suction brushes and transfer brushes 43 to 50 are formed by implanting conductive fibers having a specific resistance of 102Ω·1 and a length of 511III into a conductive support cloth.

To explain the operation of this embodiment, first, paper is transferred from the paper feed cassette 1 to the chute 42 via the transport rolls 40 and 41.
The paper fed onto the transfer drum 35 at a predetermined timing is adsorbed onto the transfer drum 35 by an adsorption brush 43. In this first suction section, the switch 28
When turned on, a voltage of, for example, 1000 volts is applied from the DC power supply 27 to the suction brush 43b, and this suction brush 4
A predetermined eight voltages are applied to the electrode 25 via the terminal 25a that is in sliding contact with the terminal 25a that is in sliding contact with the other suction brush 43a.
By grounding the electrode 26 of 6a, the electrode 25
A potential difference is generated between and 26 to generate a predetermined electric field pattern on the surface of the semiconductive resin film 20, thereby attracting the paper onto the semiconductive resin film 20.

The paper suctioned onto the semiconductive resin 11120 by the first suction section is conveyed to the first transfer section. In the first transfer section, when the switch 30 is turned on at a predetermined transfer timing, a predetermined transfer voltage is applied from the DC power supply 29 to the transfer brushes 44a, 44b.
A transfer voltage is applied to the electrodes 25, 26 of the terminals 25a, 26a that are in sliding contact with the photosensitive drum 36, thereby transferring the yellow toner image on the photosensitive drum 36 onto the paper at the transfer point by electrostatic attraction.

The electrostatic latent image formed on the photosensitive drum 36 in this case is
For example, an image is imprinted using a laser, and this imprinted electrostatic latent image is developed by a yellow developing roll (not shown) and becomes visible. Transfer points are set so that conveyance of the paper on the transfer drum 35 takes a predetermined timing.

The paper on which the yellow toner image has been transferred is conveyed to the second suction section, where it is suctioned onto the transfer drum 35 by energizing the second suction brushes 45a and 45b, and then transferred to the next second transfer section. transported to.

In the second transfer section, the magenta toner image formed on the photosensitive drum 37 at the transfer point is transferred at a predetermined timing by energizing the transfer brush 46, and the magenta toner image is transferred onto the yellow toner image. The image is overlaid with colors. When transferring the next third and fourth photosensitive drums 3B and three respective cyan toner images and black toner images onto the paper, the suction brush 47.49 and the transfer brush 48.50 are used in the same manner. A cyan toner image from the photosensitive drum 38 and a black toner image from the photosensitive drum 39 are transferred onto the paper on the drum 35 in superimposed colors.

In this way, the color image obtained by superimposing the four-color toner images on the photosensitive drums 36 to 39 passes through a conveyance roll (not shown) and is fixed by a fixing device (not shown), and the obtained color image is transferred to the transfer drum. Since the image forming apparatus 35 is formed from a rigid drum, an accurate color copy can be made according to the image information without any color shift.

Each photosensitive drum 36 to 3 arranged around the outer periphery of the transfer drum 35
If 9 is composed of a xerographic photoreceptor, the diameter of the photoreceptor drum can be, for example, 401! If the image exposure to the photosensitive drums 36 to 39 is performed using a semiconductor laser, for example, It is possible to further promote miniaturization of the copying machine itself.

Unlike conventional transfer drums, this embodiment does not have a gripper, so the transfer drum 35 can be set at any position on the transfer drum regardless of the relative position between the paper and the longitudinal direction of the paper. By setting the distance between sheets to a desired narrow interval regardless of the size of the direction, copying speed can be significantly increased.

Effects of the Invention According to the present invention, the paper conveyance body that transfers and conveys the paper while circumscribing a plurality of photosensitive drums at transfer points is configured as a transfer drum made of a cylindrical rigid body. It is possible to obtain color copies with less misregistration, and because the photosensitive drum is disposed around the transfer drum, it is possible to further reduce the size of the apparatus. Also,
On the inner circumferential side of the transfer drum, there is a structure in which the toner image is reliably transferred at the transfer point while attracting the paper onto the transfer drum using electrostatic attraction based on suction brushes and transfer brushes corresponding to the plurality of photosensitive drums. This allows you to obtain color images with fewer color shifts, and also allows you to set the position of each sheet of paper that is transported from one to the next to any position depending on the timing when the brush is energized, greatly increasing the copying speed. There is also this effect.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of an embodiment of the present invention, Fig. 2 is a partially cutaway sectional view of the transfer drum, Fig. 3 is a partially new view of the transfer drum, and Fig. 4 is a diagram showing the transfer drum. FIG. 5 is a circuit diagram showing the wiring of the power supply shown in FIG. 1, and FIG. 6 is a schematic diagram of the conventional example. 1: Paper feed cassette 20: Semi-conductive resin film 21: Support 25. 26: Electrode 27. 29: DC power supply 35: Transfer drum (rigid drum) 36 to 39: @ optical drum

Claims (1)

[Claims] A semi-conductive resin film that circulates in close contact with the transfer paper at the transfer position on which the toner image from the photosensitive drum is transferred, and a support that is arranged at regular intervals in a tangential direction to the inner peripheral surface of the semi-conductive resin film. a plurality of electrodes; a suction brush that slides on the inner peripheral side of the electrode upstream of the transfer position and supplies a DC voltage to the electrode to electrostatically attract the transfer paper onto the semiconductive resin film; In the transfer device of a color copying machine, the transfer brush is provided with a transfer brush that slides on the electrode on the inner peripheral side when the electrode moves to the transfer position and transfers the toner on the photosensitive drum by applying a voltage of opposite polarity to the toner on the photosensitive drum. 1. A transfer device for a color copying machine, characterized in that a transfer paper transport body composed of a semiconductive resin film, a support, and an electrode is formed on a rigid drum.