JP2003241540A - Apparatus and method for offset transfer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and a method for offset transfer for stably obtaining high-quality prints. <P>SOLUTION: The offset transfer apparatus is provided with: a photoreceptor drum 1; a charger for charging the surface of the photoreceptor drum 1; an exposure for forming an electrostatic latent image by exposing and scanning the surface of the photoreceptor drum 1 charged by the charger; a developer for forming an image by developing the electrostatic latent image by supplying toner to the surface of the photoreceptor drum exposed by the exposure; and an offset drum 20 to which the image is transferred by pressing its surface to the surface of the photoreceptor drum 1 having the image formed thereon during development and rotating it. The offset transfer apparatus is further provided with: a clutch 31 which provides a rotating load 30 in the state of being attachable and detachable to/from the photoreceptor drum 1: an actuator 42 for controlling the clutch; and a controller 41. Thus, the variation of the speed of the photoreceptor drum 1 is reduced, thereby the high-quality prints can stably be obtained. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an offset transfer device for transferring an image formed on a photosensitive drum using electronic technology to an offset drum and further transferring the image from the offset drum to an output medium such as printing paper. And about the method.

[0002]

2. Description of the Related Art FIG. 3 shows a structure of a conventional offset transfer device using a liquid toner. The surface of the photoconductor drum 1 charged by the charging device 2 is exposed and scanned by the laser of the laser drawing device 3 which is an exposure device based on the drawing data to create an electrostatic latent image. The formed electrostatic latent image is developed by supplying the liquid toner 6.

The liquid toner 6 is housed in the developing tub 5 after being mixed with a solvent and a resin and a pigment, and given with electrical characteristics so as to be positively or negatively charged. A developing roller 4 is installed in the developing tub 5, and the lower surface of the developing roller 4 is immersed in the liquid toner 6.

In FIG. 3, four process colors (yellow,
Four developing tubs 5 each containing a liquid toner 6 of magenta, cyan, and black) are installed. The developing tub 5 horizontally moves corresponding to each color electrostatic latent image formed on the photoconductor 1, and the developing roller 4 installed in the developing tub 5 moves the developing roller 4 to the bottom of the photoconductor 1. The upper surface stops at a position separated by a predetermined distance.

By the rotation of the developing roller 4, the liquid toner 6 in the developing tub 5 adheres to the developing roller 4 to form a layer around the developing roller 4 and is supplied to the surface of the photosensitive drum 1.
Since the liquid toner 6 has electric characteristics,
The electrostatic latent image on the photoconductor drum 1 also moves by being pulled by the electrostatic latent image (also referred to as electrophoresis) and electrostatically attracted to the electrostatic latent image to form an image.

This charging, exposure and development are repeated for each color to form a color image by sequentially superposing the colors of yellow, magenta, cyan and black on the surface of the photosensitive drum 1 and then offsetting to the photosensitive drum 1. The image is transferred to the offset drum 20 by pressing and rotating the drum 20. The offset drum 20 is composed of, for example, an iron core and a rubber blanket wound around the surface of the iron core.

After that, the printing paper 22 is sandwiched between the offset drum 20 and the backup drum 21, and the offset drum 20 and the backup drum 21 are rotated, so that the image on the offset drum 20 is transferred to the printing paper 22.

[0008]

The photosensitive drum 1 is driven by a motor (not shown). The rotation load of the motor during exposure and development is small because it is only the photosensitive drum 1. When the image formed on the photoconductor drum 1 is transferred to the offset drum 20, a force is applied to the offset drum 20 to press it against the photoconductor drum 1.
May reach. In this case, the rotation load of the motor becomes several hundred times larger than that during exposure and development.

A servomotor is often used for rotating the photosensitive drum 1 in order to perform each process at an accurate timing. However, a rotational load variation of several hundred times is usually within a range in which the control of the servomotor is allowable. It is difficult to obtain the required rotation accuracy in all processes of exposure, development and transfer.

The rotation accuracy of the photosensitive drum 1 affects the quality of the printed matter, and if the predetermined rotation accuracy cannot be obtained in all processes of exposure, development and transfer, the printed matter will have stripes of light and shade of toner. It is difficult to obtain high quality printed matter.

If the heavy photosensitive drum 1 is used, fluctuations in rotational load during exposure, development, and transfer can be reduced to some extent, but it is necessary to increase the rigidity of the frame in order to incorporate the photosensitive drum 1, and the offset transfer apparatus is therefore required. Is large and heavy, which is not preferable. Further, since the photoconductor drum 1 is a consumable item, it takes time and effort to replace it.

The present invention meets the demand for high quality images possessed by such a conventional device, and improves the rotational accuracy of the photosensitive drum in all printing processes of exposure, development and transfer. It is an object of the present invention to provide an offset transfer apparatus and method capable of improving the quality of printed matter.

[0013]

The present invention adopts the following constitution in order to achieve the above object. The offset transfer device according to claim 1, wherein the photosensitive drum, a charger for charging the surface of the photosensitive drum, and an electrostatic latent image by exposing and scanning the surface of the photosensitive drum charged by the charger. An exposing unit for forming an image, a developing unit for developing the electrostatic latent image to form an image by supplying toner to the surface of the photosensitive drum exposed by the exposing unit, and the developing unit for forming the image. In an offset transfer device including an offset drum to which the image is transferred by pressing the surface against the surface of the photoconductor drum and rotating the mechanism, a mechanism that applies a rotational load to the photoconductor drum so that the image is transferred to and from the photoconductor drum, And a control means for controlling a load applying mechanism.

The offset transfer method according to claim 2 is
An exposure step of charging the surface of the photosensitive drum and exposing and scanning the surface of the charged photosensitive drum to form an electrostatic latent image;
The developing step of developing the electrostatic latent image to form an image by supplying toner to the exposed surface of the photosensitive drum, and the surface of the photosensitive drum by pressing and rotating the surface of the offset drum. In the offset transfer method, the transfer step of transferring the image is performed, a rotational load is applied to the photosensitive drum during the exposure and development steps, and the rotational load is removed during the transfer step.

In the inventions of both claims, fluctuations in the rotational load in the printing process such as exposure, development and transfer can be suppressed and fluctuations in the rotational load can be reduced, so that the photosensitive drum can be rotated with high accuracy and the quality of the printed matter can be improved. can do.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. The basic structure of the offset transfer device to which the present invention is applied is the same as that shown in FIG. Figure 1
1 shows an embodiment of a photosensitive drum, an offset drum, and a backup drum of an offset transfer device according to the present invention. The rotation load 30 is connected to the photosensitive drum 1 via a clutch 31. The clutch 31 can be engaged and disengaged by an actuator 42. The timing of this contacting / separating operation is performed by an electric signal output from the control device 41.

Further, the control device 41 of the servomotor 40 that drives the photosensitive drum 1 with the clutch 31 connected in advance and the photosensitive drum 1 and the rotational load 30 connected to each other is adjusted, and appropriate control parameters such as a feedback gain are set. Set it.

At the time of exposure and development, the actuator 42 is operated by an electric signal from the control device 41 to operate the clutch 3
1 to connect the photoconductor drum 1 and the rotary load 30,
An image is formed on the photosensitive drum 1. At the time of transfer, similarly, the actuator 42 is operated to disengage the clutch 31 to separate the photosensitive drum 1 from the rotational load 30, and the offset drum 20 is pressed against the photosensitive drum 1 to apply a force. By performing the process in this way, the fluctuation of the rotational load can be reduced and can be kept within the control range of the servomotor 40.

FIG. 2 shows gears 32A, 3 instead of clutches.
It is a figure using 2B and 32C. The photosensitive drum 1 and the rotary load 30 are connected via gears 32A, 32B, 32C. The gear 32C can be moved in the rotation axis direction by operating the actuator 42 by an electric signal from the control device 41. Depending on the position of the gear 32C, the photosensitive drum 1 and the rotary load 30 are connected or separated. At the time of exposure and development, the gear 32C is meshed to connect the rotational load 30 and the photosensitive drum 1, and at the time of transfer, the gear 32C is removed to separate the rotational load 30 and the photosensitive drum 1.

As a result, fluctuations in the rotational load of the photoconductor drum can be reduced regardless of the printing process of exposure, development, and transfer, and fluctuations in the speed of the photoconductor drum can be suppressed, and streaks can be formed on the printed matter. It is possible to stably improve the quality of the image.

Here, the method of contacting and separating the rotational load with a clutch or a gear has been described, but in addition to this, a rotational load of the photosensitive drum can be changed by providing a brake such as friction or electromagnetic force.

[0022]

As can be understood from the above description, the offset transfer device and method of the present invention can reduce fluctuations in the rotational speed of the photosensitive drum in any printing process such as exposure, development and transfer. It is possible to provide high quality printed matter.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an offset transfer device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of an offset transfer device according to another embodiment of the present invention.

FIG. 3 is a schematic view showing a conventional offset transfer device.

[Explanation of symbols]

1 photoconductor drum 2 charger 3 Laser drawing device 4 developing roller 5 development tub 6 Liquid toner 20 offset drum 21 backup drum 22 Printing paper 30 rotation load 31 clutch 32A, 32B, 32C gear 40 servo motor 41 Control device 42 Actuator

Claims (2)

[Claims] 1. A photoconductor drum, a charger for charging the surface of the photoconductor drum, and an exposure device for forming an electrostatic latent image by exposing and scanning the surface of the photoconductor drum charged by the charger. A developing device that develops the electrostatic latent image to form an image by supplying toner to the surface of the photosensitive drum exposed by the exposing device; and the surface of the photosensitive drum on which the image is formed during development. An offset transfer device comprising: an offset drum to which the image is transferred by pressing the surface of the drum against the surface of the drum and rotating the image; Control means for controlling
An offset transfer device comprising: 2. An exposing step of charging the surface of the photosensitive drum and exposing and scanning the charged surface of the photosensitive drum to form an electrostatic latent image, and supplying toner to the exposed surface of the photosensitive drum. Offset transfer including a developing step of developing the electrostatic latent image to form an image and a transfer step of transferring the image on the surface of the photosensitive drum by pressing and rotating the surface of the offset drum. In the method, an offset transfer method is characterized in that a rotational load is applied to the photosensitive drum during the exposure and development steps, and the rotational load is removed during the transfer step.