JPH03182355A - Multi-color electrophotographic printing apparatus - Google Patents

Abstract

PURPOSE:To prevent misregistration among a plurality of image writing parts thereby to improve the printing quality by controlling the rotation of a motor so that beam detecting signals have no phase difference to a common reference clock. CONSTITUTION:Each of image writing parts 12a, 12b is provided with a light source 120 driven in accordance with a video signal, an optical scanning part 121 rotated by a motor 124 to scan the light of the light source 120, a beam detecting part 123 which detects the scanned light and outputs a beam detecting signal, and a rotation controlling part 2a or 2b which controls the rotation of the motor 124 so that the beam detecting signals have no phase difference to a common reference clock. Accordingly, the optical scanning parts 121 of the image writing parts 12a, 12b are synchronously rotated, thereby preventing misregistration.

Description

[Detailed description of the invention] [Table of contents] Overview Industrial field of application Conventional technology (Figures 4 and 5) Means for solving the problems to be solved by the invention (Figure 1) Working examples (al Description of one embodiment (Fig. 2, Fig. 3) (bl
Description of other embodiments Effects of the invention [Summary] Regarding a multicolor electrophotographic printing device that forms multicolor toner images on a photoreceptor by repeating charging, image writing, and development processes a plurality of times. In order to prevent printing misalignment between printing areas and improve printing quality, a plurality of chargers, image writing units, and developing units are arranged around the photoconductor, and the photoconductor is charged and image written. repeating the development sequence multiple times to form toner images of multiple colors on the photoreceptor,
In a multicolor electrophotographic printing device that transfers images onto a print medium, the multiimage writing unit includes a light emitting source driven in accordance with a video signal and an optical scanning device that is rotated by a motor to optically scan the light from the light emitting source. a beam detection section that detects the optically scanned light and outputs a beam detection signal; and a rotation control that controls the rotation of the cough motor so that the beam detection signal has no phase difference with respect to a common reference clock. It has a department.

[Industrial Field of Application] The present invention relates to a multicolor electrophotographic printing device that forms a multicolor toner image on a photoreceptor by repeating charging, image writing, and development steps multiple times.

Electrophotographic printing devices are widely used in copying machines, facsimile machines, printers, and the like.

Such electrophotographic printing apparatuses are also required to be colored, that is, to have multiple colors, and are required to have no color misregistration.

[Conventional technology]

FIGS. 4 and 5 are explanatory diagrams of the prior art.

A multicolor electrophotographic printing apparatus, for example, a two-color electrophotographic printing apparatus, is configured as shown in FIG. 4(A).

After charging the photosensitive drum 10 with the first pre-charger 11a, the first
The image writing unit 12a exposes and writes a light image to form an electrostatic latent image, and the first color developer 13a forms a first color toner image on the photosensitive drum IO.

After charging the photosensitive drum 10 again with the second pre-charger 11b,
A second image writing unit 12b exposes and writes a light image to form an electrostatic latent image, and a second color developer 13b forms a second color toner image on the photosensitive drum 10; A two-color toner image is obtained.

The multicolor toner image on the photosensitive drum 10 is transferred onto the paper PP by a transfer charger 14 to obtain a multicolor toner image on the paper PP, which is fixed by a flash fixing section 18.

On the other hand, the photosensitive drum 10 is cleaned with a fur brush of a cleaner 17 after being neutralized by a static eliminator 15 and a static eliminator lamp 16 .

That is, by repeating the steps of charging, exposure writing, and development twice, two-color toner images are formed on the photosensitive drum IO.

As shown in FIG. 4(B), the image writing unit 12aS12b modulates and drives a laser light source 120 such as a semiconductor laser with a video signal, and converts the light of the laser light source 120 into a polygon mirror (rotating polygon a) rotated by a motor. ) etc. optical scanning unit 1
21, the photosensitive drum 10 is scanned with light, and a reflecting mirror 122 provided at the end of the photosensitive drum 10 reflects the scanning light and guides it to a beam detector 123, where it is used as a synchronizing signal for a video signal. A beam detection signal BD is obtained.

The optical scanning section 121 of each image writing section 12a, 12b like this
The rotation speeds of the two were controlled to be the same, but they were rotating asynchronously.

[Problem to be solved by the invention]

Conventionally, in each of the image writing sections 12a and 12b, the video signal is sent to the laser light source 120 after a certain period of time from the beam detection signal BD.
The optical scanning unit 1 of each image writing unit 12a, 12b is controlled so that printing of one line starts.
21 are rotating asynchronously, a phase difference δ occurs in each beam detection signal BD, as shown in FIG. 5(A).

As a result, the first image writing section 12a and the second image writing section 12
If printing with b is connected line by line, Figure 5 (B)
As described above, there is a problem in that the position of the second toner image due to the exposure of the second image writing section 12b is shifted from the original position, resulting in a decrease in print quality.

Therefore, an object of the present invention is to provide a multicolor electrophotographic printing apparatus that can prevent printing misalignment between a plurality of image writing units and improve print quality.

[Means to solve the problem]

FIG. 1 is a diagram showing the principle of the present invention.

As shown in FIG. 1, the present invention provides a plurality of chargers 11a,
11b, image writing sections 12a, 12b, developing devices 13a, 13
b is arranged around the photoreceptor IO, and the photoreceptor 10 is charged,
The sequence of image writing and development is repeated multiple times, and the photoreceptor 1 is
In a multicolor electrophotographic printing apparatus that forms toner images of a plurality of colors on 0 and transfers them to a printing medium, each image writing section 12a
, 12b is a light emitting source 12 driven according to a video signal.
0 and rotated by a motor 124, the light emitting source 12
an optical scanning section 121 that optically scans the zero light, and a beam detection section 1 that detects the optically scanned light and outputs a beam detection signal.
23, and rotation control units 2a and 2b that control the rotation of the motor 124 so that the beam detection signals have no phase difference with respect to a common reference clock.

[Effect]

In order to eliminate printing misalignment caused by the plurality of image writing units 12a, 12b, the optical scanning units 121 of each image writing unit 12a, 12b may be rotated synchronously.

To perform this synchronous rotation, it is necessary to eliminate the phase difference between the beam detection signals of each image writing section 12a, 12b.

Therefore, in the present invention, the motor 121a is controlled so that there is no phase difference in the beam detection signal BD with respect to the same common reference clock.
Rotation control units 2a and 2b are provided to control the rotation of the image writing units 12a and 12b, and the optical scanning units 121 of each image writing unit 12a and 12b are rotated synchronously.
This is to prevent printing misalignment.

〔Example〕

(al　Explanation of one embodiment FIG. 2 is a configuration diagram of an embodiment of the present invention.

In the figure, the same parts as shown in Figures 1 and 4 are:
3 is a control unit, which is composed of a microprocessor (MPU) and controls the entire device, and also outputs video signals of each color after a certain period of time in accordance with each beam detection signal BDi to BD2. Each image writing section 12a, 1
What outputs to the laser light source 120 of 2b, 20 is a PLL
(phase synchronization) circuit, which generates a control signal such that the phases of the reference clock CL and the beam detection signals BDI, BD2 are synchronized, that is, there is no phase difference; 21 is a motor drive circuit; PLL circuit 20; The motor 124 is driven to rotate in response to the control signal.

FIG. 3 is an explanatory diagram of the operation of one embodiment of the present invention.

The PLL@path 20 generates a control signal that synchronizes the input reference clock with the beam detection signals BDI and BD2, and controls the rotation of the motor 124 via the motor drive circuit 21, as shown in FIG. Furthermore, the phase difference between the rising edge of the reference clock CL and each of the beam detection signals BDI and BD2 can be eliminated.

The fact that the beam detection signals BDI, BD2 of the first image writing section 12a and the second image writing section 12b have no phase difference with respect to the same reference clock CL means that each of the image writing sections 12a, 12b
This means that the optical scanning units 121 of are rotating synchronously.

Therefore, the printing misalignment as shown in FIG. 5(B) does not occur, and the second image writing section 12b writes the image at the original position to form a toner image.

(b) Description of other embodiments In the above embodiments, an example was explained in which the optical scanning unit was configured with a polygon mirror (rotating polygon mirror), but it may also be applied to a device that performs optical scanning by rotation, such as a hologram. .

Moreover, although the example of two-color printing has been described, three or more colors may be used.

Although the present invention has been described above using examples, the present invention can be modified in various ways according to the gist of the present invention, and these are not excluded from the present invention.

〔Effect of the invention〕

As explained above, according to the present invention, each image writing section 12a
, 12b can be synchronized, so that it is possible to prevent printing misalignment by each image writing section 12a, 12b and improve the quality of multicolor printing.

[Brief explanation of drawings]

Fig. 1 is a diagram of the principle of the present invention, Fig. 2 is a configuration diagram of an embodiment of the invention, Fig. 3 is an explanatory diagram of the operation of an embodiment of the invention, Figs.
The figure is an explanatory diagram of the prior art. , 2b--rotation control section, ---photoreceptor, a, 1lb--pre-charger, a, 12b--image writing section, a, 13b--developing device, 0-m--light source, 1---light Scanning unit, ■ 3 Beam detection unit, 4-Motor.

Claims (1)

[Claims] A plurality of chargers (11a, 11b), an image writing section (12a,
12b), the developing device (13a, 13b) is connected to the photoreceptor (10)
The sequence of charging, image writing, and development is repeated multiple times on the photoconductor (10) to form a multi-color toner image on the photoconductor (10) and transfer it to a printing medium. In the multicolor electrophotographic printing device, each of the image writing units (12a, 12b) includes a light emitting source (120) driven in accordance with a video signal, and a light emitting source (120) rotated by a motor (124).
0), a beam detection section (123) that detects the scanned light and outputs a beam detection signal, and detects the beam with respect to a common reference clock. A multicolor electrophotographic printing apparatus comprising a rotation control section (2a, 2b) that controls the rotation of the motor (124) so that the signals have no phase difference.