JPH01177568A - Multicolored image recorder - Google Patents

Abstract

PURPOSE:To prevent deviation of position at the time of multi-transferring by providing copying paper adsorbing device on either side of inlet or outlet of marking unit group. CONSTITUTION:At least on either inlet side of the marking unit 1a of uppermost stream or outlet side of the making unit 1b of lowermost stream, photosensitive drums 2a-2d and the copying paper adsorbing devices 13a and 13b which have equal function to copying paper adsorbing function by transferring devices 7a-7d are provided. Accordingly, during transferring, the attitude and the actions of copying paper are the same every transferring position. That is, at the time of copying by using longer copying paper than the set interval of the photosensitive drums 2a-2d, copying paper is always adsorbed by plural photosensitive drums 2a-2d or the copying paper adsorbing devices 13a and 13b during transferring. Thus, deviation in position of copying paper is eliminat ed among each transfer position.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image recording apparatus that uses a plurality of photosensitive drums and a transfer device to obtain color images by electrophotography.

[Conventional technology]

A multicolor image recording device using an electrophotographic method uses a photoreceptor drum, as described in, for example, Japanese Patent Application Laid-Open No. 47-37434, Japanese Patent Application Laid-Open No. 52-67337, and Japanese Patent Application Laid-Open No. 57-85066. A plurality of image forming devices (hereinafter referred to as marking units) each equipped with a charging device, an exposure device, a developing device, and a cleaning device are arranged at regular intervals, and a different color is assigned to each marking unit. A method is adopted in which a multicolor image is created by sequentially superimposing and transferring images onto copy paper using a plurality of transfer devices provided corresponding to each marking unit.

FIG. 5 shows an example of a conventional multicolor image recording device.

The marking unit 1a includes a photosensitive drum 2a, a charging device 3a, an exposure device 4a, a developing device 5a, and a cleaning device 6a. marking unit)l
Marking units 1a to 1d are sequentially arranged around the transfer drum 8 at equal intervals. Inside the transfer drum 8, transfer devices 7a to 7 are provided at positions facing each of the photoreceptor drums 2a to 2d.
d are arranged in sequence. The copy paper a stored in the paper feed tray 9 is sent to the transfer drum 8 by the paper feed device 10 and the paper transport device 11, rotates together with the transfer drum 8, and is transferred to each of the photoreceptor drums 2a to 2d and the transfer devices 7a to 7d. As a result, toner images of each color are sequentially transferred onto copy paper a in a superimposed manner. After the final transfer is completed, the copy paper a is fed to the fixing device 20, where the transferred toner image is fixed.

[Issues that Hathu tries to solve]

In the multicolor image recording apparatus shown in FIG. 5, when the copy paper a is transferred while rotating together with the transfer drum 8, when the length of the copy paper a in the conveying direction is longer than the distance between the photoreceptor drums. In this case, the leading edge of copy paper a is on photosensitive drum 2.
The copy paper a is attracted to at least two photoreceptor drums from the time when it reaches the position b until the rear end passes the photoreceptor drum 2C. However, until the leading edge of copy paper a reaches the position of photoreceptor drum 2b, copy paper a
is attracted only to the photoreceptor drum 2a, and after the trailing edge of the copy paper a leaves the position of the photoreceptor drum 2C, the copy paper a is attracted only to the photoreceptor drum 2d.

Therefore, when the leading edge of copy paper a reaches the position of photoreceptor drum 2b and when the rear end of copy paper a leaves the position of photoreceptor drum 2d, the suction state of copy paper a by the photoreceptor drum is as follows. This will cause a temporary change in position from the previous state. The degree of this positional shift differs between the positions of the photoreceptor drums 2a and 2b, and also differs between the positions of the photoreceptor drums 2d and 20. As a result, there is a problem in that the positional deviation of each color toner image occurs, resulting in defects such as color unevenness and blurring of the image.

On the other hand, if the distance between the photoreceptor drums 2a to 2d is increased so that the copy paper does not straddle the two photoreceptor drums, the above-mentioned misalignment will not occur. If the apparatus is made larger, the size of the transfer drum and the entire multicolor image recording apparatus will be increased, and the copying speed will be reduced, which is not preferable.

The present invention maintains the posture and movement of a copy sheet constant during multiple transfer by a multicolor image recording device while the copy sheet passes through each transfer device, thereby eliminating positional deviation of each color toner image and causing color unevenness in one image. The purpose is to record high-quality multicolor images without blur.

[Means to solve the problem]

In order to achieve the object, the multicolor image recording apparatus of the present invention includes a charging device and an exposure device on a photoreceptor drum.

In a multicolor image recording device in which a plurality of marking units equipped with a developing device and a cleaning device and a plurality of transfer devices corresponding to the marking units are sequentially arranged,
A copy paper suction device having a function equivalent to the copy paper suction function of the photosensitive drum and the transfer device is provided on at least one side of the inlet side of the most upstream marking unit and the outlet side of the most downstream marking unit. Features.

Here, as the above-mentioned copy paper suction device, a suction device consisting of a rotating drum to which a bias voltage is applied and a corotron can be used.

[Effect]

In the multicolor image recording apparatus of the present invention, a copy paper suction device consisting of, for example, a rotating drum to which a bias voltage is applied and a corotron is provided on at least one of the entry side and the exit side of the marking unit group consisting of a plurality of marking units. The posture and movement of the copy paper during transfer are the same at each transfer position. That is, when copying is performed using copy paper that is longer than the installation interval of the photoreceptor drums, in the apparatus of the present invention, the copy paper is always adsorbed by a plurality of photoreceptor drums or copy paper adsorption devices during transfer. , there is no misalignment of the copy paper between each transfer position.

[Example] Hereinafter, the features of the present invention will be specifically explained based on the example apparatus shown in FIG. In addition, in the same figure, parts corresponding to those shown in FIG. 5 are indicated by the same reference numbers.

In the apparatus of this embodiment, a copy paper suction device 13a is provided on the inlet side of the marking unit 1a, and a copy paper suction device 13b is provided on the output side of the marking unit 1d. The distance between the copy paper suction device 13a and the marking unit 1a and the distance between the copy paper suction device 13b and the marking unit ld are the same as the distance between each marking unit (200 mm in this embodiment).

The copy paper suction devices 13a, 13b have the same function as the copy paper suction function of the photosensitive drum and the transfer device during transfer, and in this embodiment, the copy paper suction devices 14a, 14b to which a bias voltage is applied are used. It was composed of a corotron 15a and a corotron 15b.

In the marking unit (1a), the photoreceptor drum 2a is charged by a charging device 3a, and then an image pattern corresponding to each color is irradiated by an exposure device 4a to record an electrostatic latent image. Thereafter, development is performed by the developing device 5a, and toner images of each color are formed on the photoreceptor drum 2a. Toner images are similarly formed on the photoreceptor drums 2b to 2d for the marking units 1h to 1d. On the other hand, the uppermost copy paper a is fed by a paper feed device 10 from a paper feed tray 9 containing a large number of copy papers a, and is fixed on a rotating transfer drum 8 via a paper transport device 11. . The copy paper a is sent by the transfer drum 8 to transfer devices 7a to 7d provided at each marking unit position, and toner images are multiple-transferred onto the paper.

The behavior of copy paper a during this transfer will be explained in detail. As shown in the perspective view of FIG. 3, the transfer drum 8 has a gripper 16 for gripping the copy paper a, a mesh 17 for suctioning and fixing the copy paper a, and a gripper 16 for gripping the copy paper a and a mesh 17 for fixing the copy paper a in openings (three in the example shown) on the circumference. It has a cylindrical shape. Here mesh 17
For example, a polyester thread having a diameter of 0.15 mm is used. As shown in FIG. 4, the surface 18 of each photoreceptor drum 2a to 2d and the surface 19 of the transfer drum 8 are arranged with a slight gap G, and the copy paper a is placed in the transfer device 7a to 7d during transfer. Due to the action of the electric field, the inside of the gap G becomes as shown in the figure.
The toner image is transferred by moving while being attracted to the photoreceptor drum.

At this time, electrostatic adsorption based on the charge supplied by the paper adsorption charger 12 acts on the copy paper a and the mesh 17, and the copy paper a and each of the photoreceptor drums 2a to 2d are
The adsorption force works according to the potential of the photosensitive drum, the potential of the copy paper, and the electric field formed by the transfer device. When the leading edge of the copy paper a reaches the transfer position, the copy paper a within the gap G behaves as follows due to the action of the suction force.

(1) Copy paper a is adsorbed to the photosensitive drum while being adsorbed to mesh 17 (the state shown in Fig. 4), and the movement of copy paper a at this time affects the upstream side, and transfer is performed on the upstream side. When this is being done, the copy paper a is temporarily misaligned with respect to the photoreceptor drum. This phenomenon occurs at the photosensitive drum 2a section on the upstream side when the leading edge of the copy paper a reaches the photosensitive drum 2h, and at the photosensitive drum 2b section when the leading edge of the copy paper a reaches the photosensitive drum 2C. This occurs at the photosensitive drum 20 portion when the photosensitive drum 2d is reached.

(2) Marking units) When an A3 size copy paper a is fed vertically through a device in which the intervals between la to 1d are approximately 200 mm, the copy paper a straddles a maximum of three marking units. Therefore, the leading edge of the copy paper a reaches the photoreceptor drum 2c or 2d, and the copy paper a
When the leading edge of the copy paper a is attracted to the photoreceptor drum 2c or 2d, at two points, the upstream photoreceptor drums 2b and 2a, or the photoreceptor drums 2C and 2b, -
A positional shift occurs.

(3) Before the leading edge of the copy paper a reaches the photoconductor drum 2b and after the rear end of the copy paper a leaves the photoconductor drum 2c, the photoconductor drum adsorbs the copy paper a onto one photoconductor. It is performed only by the position of the drum.

In (1) to (3) above, when the copy paper a is attracted to a plurality of photoreceptor drums at the same time, the posture and movement of the copy paper a as shown in FIG. , and even if copy paper a is misaligned, the degree of misalignment is the same between each photosensitive drum. However, when the leading edge of the copy paper a reaches the photoreceptor drum 2b, a positional shift occurs independently at the position of the photoreceptor drum 2a.

Also, when the trailing edge of the copy paper a leaves the photosensitive drum 2C,
A positional shift occurs independently at the position of the photoreceptor drum 2d. As a result, an image shift occurs after a position corresponding to the distance between the photosensitive drums (200+nm in this embodiment) from the leading edge of the copy paper a.

FIG. 2 et al.) are diagrams showing examples of image shifts. Now, when a document on which many lines are drawn at constant intervals d is copied using the multicolor image recording device shown in Fig. 5, a length corresponding to the installation interval of the photoreceptor drums from the leading edge of the copy paper a is obtained. (200m
Although no image shift occurs in the m) range, image shift occurs thereafter as shown in the figure. This image shift is caused by copy paper a
When the leading edge of the copy paper a reaches the photoconductor drum 2b, the copy paper a temporarily shifts its position at the photoconductor drum 2a position due to the effect of suction by the photoconductor drum 2b, and the copy paper a
This occurs because the copy paper a is temporarily displaced at the position of the photoreceptor drum 2d due to the effect of the trailing edge exiting the photoreceptor drum 2c. Here, for example, the marking unit 1a is yellow, the marking unit y)
Assuming that magenta is assigned to tl, cyan is assigned to marking unit 1c, and black is assigned to marking unit 1d, the thick line in FIG.
The photosensitive drums 2a to 2c and 2
This is a copy image of four colors, yellow, magenta, cyan, and black, which are multiple-transferred at each position of d without any image shift, and the line spacing is d. The broken line is 200 meters from the leading edge of copy paper a.
This is a yellow copy image transferred at the photosensitive drum 2a position after mm, and the initial deviation is dl from the thick line.
The image appears as follows, and is then transferred at intervals of d. The thin line is a copy image of magenta, cyan, and black that is multiple-transferred at each position of the photoreceptor drums 2b, 2c, and 2d between the leading edge 200 mm and the trailing edge 20On+m of the copy paper a, and does not shift. The spacing is d. The one-dot chain line indicates the photosensitive drum 2b after 200 mm from the rear edge of the copy paper a.
This is a copy image of two colors, magenta and cyan, which are multiple-transferred at each position of 20 and 20 without any image shift, and the line spacing is d. The dotted line is the black copy image transferred at the photosensitive drum 2d position after 200 mm from the rear edge of the copy paper a,
The first deviation appears as the interval d2, and thereafter the interval d
It is transcribed by . As a result, as shown in the figure, an image becomes blurry with image shift occurring beyond 200 mm from the leading edge of the copy sheet a.

In the apparatus of this embodiment, a copy paper suction device 13a is provided on the inlet side of the marking unit)la, and the marking unit)ld
A copy paper suction device 13b is provided on the exit side of the copy paper suction device 13b, and the paper suction function of the copy paper suction devices 13a and 13b is made to be equivalent to the paper suction function of the photoconductor drum and the transfer device. In the case of long copy paper a, the copy paper is always in the same state as being attracted to two or more photoreceptor drums during transfer,
Therefore, no image shift occurs.

FIG. 2(a) shows one copy image obtained by the apparatus of this embodiment.
Give an example. The original is a group of lines with an interval d, and the copied image has a group of lines with the same interval d as the original except for a position 200 mm from the leading edge of the paper. The reason why the distance between the lines at the position 200 mm from the leading edge of the paper is d2, which is larger than d, is because the leading edge of copy paper a reaches the downstream photosensitive drum position from the upstream photosensitive drum position. This is because the posture and movement of copy paper a change at the position of the photosensitive drum on the downstream side. However, since the changes in the posture and movement of the copy paper a at this time are the same regardless of the photoreceptor drum position, there is no positional shift between the photoreceptor drums in the copy image, and visually there is no color unevenness. No image blurring.

In the above embodiment, a device consisting of a rotating drum to which a bias voltage was applied and a corotron was used as a copy paper suction device, but it is not possible to use a device that has a suction function equivalent to the copy paper suction function of a photosensitive drum and a transfer device. if there is,
Other devices may also be used.

Furthermore, even if this copy paper suction device is installed only on either the inlet side of the most upstream photoreceptor drum or the outlet side of the most downstream photoreceptor drum, color unevenness and image blurring can be significantly improved. .

〔Effect of the invention〕

As explained above, in the present invention, a copy paper suction device is provided on at least one of the entry side and the exit side of the marking unit group of a multicolor image recording device in which a plurality of marking units and transfer devices are sequentially arranged. The posture and movement of the copy paper during transfer are made to be the same at each transfer position. As a result, it is possible to eliminate relative positional shift when multiple transfer is performed using a plurality of transfer devices, and to obtain a high-quality multicolor image with less color unevenness and image blur.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a multicolor image recording apparatus in an embodiment of the present invention, FIG. 2 is a diagram showing an example of a copied image, and FIG. 3 is a perspective view showing the structure of a transfer drum. 4 is a diagram for explaining the suction state of copy paper. On the other hand, FIG. 5 is a diagram showing an example of the configuration of a conventional copying machine. ■a to 1d, mill 1d, marking unit photosensitive drum 3a to 3d: charging device 4a
~4d: Exposure device 5a~5d: Developing device 68~
6d° Cleaning devices 7a to 7d: Transfer device 8: Transfer drum 9: Paper feed tray 10. Paper feeding device 11゛Paper conveying device
12: Paper adsorption charger 13a, 13b: Copy paper adsorption device 14a, 14b: Rotating drum 15a, 15b:
ml D-tron 16: Gripper 17 = Mesh 20: Fixing device a: Copy paper patent applicant
Fuji Xerox Co., Ltd. Managing Director Kobori
Masu (and 2 others) Figure 2 Figure 3

Claims (1)

[Claims] 1. A multicolor image in which a plurality of marking units each having a charging device, an exposure device, a developing device, and a cleaning device attached to a photoreceptor drum and a plurality of transfer devices corresponding to the marking units are sequentially arranged. In the recording device, a copy paper suction device having a function equivalent to the copy paper suction function of the photosensitive drum and the transfer device is provided on at least one side of the inlet side of the most upstream marking unit and the outlet side of the most downstream marking unit. A multicolor image recording device characterized by: 2. The multicolor image recording apparatus according to claim 1, wherein the copy paper suction device comprises a rotating drum to which a bias voltage is applied and a corotron.