JPS63151264A - Color slurring correcting device in image forming device - Google Patents

Abstract

PURPOSE:To accurately align the developing position of each color by correcting the degree of slur so that dots of magenta toner and dots of cyan toner are arranged in a dot line based on the dots of yellow toner as a reference. CONSTITUTION:Three exposure LED arrays 21, 24, 27 are recorded by using a light timing clock at the same interval of the array 21 over the entire circumference of a photosensitive drum and the recording state of the toner of each color is expanded partially and checked. Each dot of yellow, magenta and cyan is recorded while being slurred in the direction of rotation of the photosensitive drum and the deviation is measured corresponding to an output pulse interval of a rotary encoder 1 based on the dots of yellow color. Then the light timing of the exposure LED array recording magenta and cyan is written in each ROM to form a light timing clock generating means.

Description

[Detailed description of the invention] [Table of contents] Overview Industrial field of application Prior art (Figures 4 and 5) Problems to be solved by the invention Means for solving the problems (Figure 1) Effect Embodiment (Fig. 2, Fig. 3) Effect of the invention [Summary] The present invention provides a color image forming apparatus in which a synchronous image forming apparatus is provided in synchronization with the rotation of an image carrier in order to prevent misalignment of images of each color to be combined. By memorizing the amount of positional deviation of the recording dots that occur and correcting the latent image formation timing of each color image based on this, the positional deviation of each color is eliminated over the entire image area, and a good color image is obtained. It is something.

[Industrial application field]

The present invention relates to a color misregistration correction device in an image forming apparatus such as an electrophotographic recording device, and particularly to a color misregistration correcting device for accurately correcting color misregistration of a multi-color 1.S image.

[Prior Art] A color electrophotographic recording device, for example, as shown in FIG.
On the circumference of the photosensitive drum 20, a charger 21, 24, 27 and a light emitting LED (light emitting diode) are installed.
de) Array 22, 25, 28, yellow developer 23
, a developing device 26 for magenta, and a developing device 29 for cyan are arranged, and the exposure LED arrays 22, 25, 28 are made to emit light in accordance with data stored in a separately prepared image memory, and each color is As the photosensitive drum 20 rotates, yellow, magenta, and cyan toner images are formed by forming a latent image, and developing these latent images using a yellow developer 23, a magenta developer 26, and a cyan developer 29, respectively. A color image is created by sequentially aligning and combining the images, and the color image can be recorded by transferring this onto recording paper 31 using the transfer device 30. Note that 32 is a cleaner, and each exposure LED
Drivers are provided within the blocks of arrays 22, 25, 28.

At this time, if the positions of the yellow, magenta, and cyan toner images are shifted, the colors expressed by the combination of these three colors will also be shifted, resulting in a decrease in image quality. For this reason, it is necessary to record the toner images of each color to be combined with high accuracy.

For this reason, in the conventional color image recording apparatus, as shown in FIG. 5, the surface of the photosensitive drum 20 moves one recording dot by rotating the incremental output pulse signal from the rotary encoder 41 directly connected to the photosensitive drum shaft. The frequency divider 42.
Divide the frequency by 45.48 and each exposure LED array 21.24.2
7 light emission timing clock. For each of these exposure LED arrays 21, 24, 27, image information is read out from the image memory 44, 47, 50 based on the value counted by each of the clock signals by the counter 43, 46, 49, and data for one dot line is stored. Send to exposure LED array 21.24.27.

At this time, when the exposure LED array 21 for yellow is lit first so that the timing differs according to the difference in the mounting position of the exposure LED array 21 that performs image exposure of each color of yellow, magenta, and cyan. , the numerical values of the counters 46 and 49 are shifted so as to delay the image recording timing by the magenta exposure LED array 24 and the cyan exposure LED array 27.

[Problem that the invention seeks to solve]

By the way, in such a conventional color image recording device, the increment output from the rotary encoder is used as the light emission timing clock signal of each exposure LED array 21, 24, 27 for recording each color image of yellow, magenta, and cyan. A signal obtained by dividing a pulse signal into equal intervals is used.

However, in reality, due to causes such as eccentricity of the photosensitive drum, difference in rotation angle due to axis misalignment between the photosensitive drum and rotary encoder, or pinch error of the rotary encoder,
A relative pitch unevenness occurs between the amount of movement of the photosensitive drum surface and the light emission timing clock pulse.

This pitch unevenness is periodic in synchronization with the rotation of the photosensitive drum, but due to the difference in the mounting position of the exposure LED array, the phase of the period of the pitch unevenness is shifted.
There has been a problem in that the positions of recorded dots are shifted between magenta and cyan, resulting in color shift.

Therefore, an object of the present invention is to provide an image forming apparatus free from such color shift.

[Means for solving problems]

In order to achieve the above object, the present invention, as shown in FIG.
T, color shift correction is performed to correct the degree of shift so that the dots CT of cyan toner are lined up. 1st
In the state shown in the figure, the magenta toner dot MT is delayed by three pulses of the output pulse of the rotary encoder from the reference dot line l, and the cyan toner dot CT is also delayed by two pulses. Therefore, in such a case, the light emission timing of the exposure LED array for magenta is performed at a timing that is three pulses ahead of the output pulse of the rotary encoder, and the light emission timing of the exposure LED array for cyan is performed at a timing that is delayed by two pulses.

[Effect]

This allows the development positions of each color to be matched accurately.

〔Example〕

The configuration of an embodiment of the present invention will be described with reference to maps based on FIGS. 2 and 3.

FIG. 2 is a configuration diagram of an embodiment of the present invention, and FIG. 3 is a ROM (Read 0
nly Memory).

In FIG. 2, 1 is a rotary encoder, 2 is a frequency divider, 3 is a counter, 4 is an image memory in which image data for yellow is written, 5 is an exposure LED array for yellow, 6 is a counter, and 7 is a counter. Image memory in which magenta image data is written, 8B magenta exposure LED
9 is a counter, 10 is an image memory in which cyan image data is written, and 11 is an exposure LE for cyan.
D array 12 is a counter 1 that counts the incremental output pulses output from the rotary encoder 1.
3 is a ROM for magenta correction, and 14 is R for cyan correction.
Since these ROMs 13 and 14 are characteristic parts of the present invention, they will be described in detail later.

In this embodiment, the recording dot pinch is 400 dpi, the photosensitive drum diameter is 213 mm, and the rotary encoder 1 outputs a pulse signal of 43,200 pulses per revolution. Frequency divider 2 divides this 43,200 pulse signals per revolution, that is, the pulse signals obtained by dividing one revolution into 43,200 equal parts, into 1
The light emission timing clock is generated by dividing the frequency by /4. A driver is also present in the illustrated block of each exposure LED array 5.8.11.

The counter 12 counts 43,200 pulse signals per rotation output from the rotary encoder 1, that is, increment output pulses, and is reset by a zero signal generated when the rotary encoder 1 rotates once.

The ROM 13 is a ROM in which data for magenta correction is written, and the output pulse of the rotary encoder 1, which indicates the absolute rotational position of the photosensitive drum, is 4 per rotation.
It is accessed by the output of counter 12 which counts 3200 incremental output pulses. Figure 3 (A
) exemplifies the ROM 13 for correcting the states of magenta toner to MT in FIG. That is,
In Figure 1, the magenta toner MT lags behind the reference yellow toner dot YT by 3 pulses in the incremental output pulses of the rotary encoder 1.
If there is no delay, when the absolute rotation device m of the photosensitive drum, that is, the counter 12 that counts the incremental output pulses of the rotary encoder 1, counts m, the magenta toner dot MT of the image will be developed for the yellow toner dot YT. If the exposure LED array 24 for magenta is
The configuration is such that the light is emitted earlier by the amount of the shift.

ROM14 is R in which data for cyan correction is written.
It is OM, and is accessed by the output of the counter 12 similarly to the ROM 13. FIG. 3(B) exemplifies a case in which the state of the cyan toner dots CT shown in FIG. 1 is corrected. That is, as shown in FIG. 1, since the dot YT is two pulses ahead of the yellow toner dot, if the advance is lost, the cyan dot recorded at the absolute rotational position n will be developed two pulses later. n+
".1" is written in the address of the exposure LED array 2 so that the cyan dot is delayed by 2 pulses.
The light emission timing of No. 7 is corrected.

By the way, the correction data in these ROMs 13 and 14 is written in the following manner.

First, as in the conventional case shown in FIG. Check the recording status of color toner by partially enlarging it.

As a result, at a certain position, as shown in FIG. 1, the yellow, magenta, and cyan dots, which should be aligned in a straight line in the axial direction of the photosensitive drum if accurate, are recorded with deviations in the rotational direction of the photosensitive drum. The amount of deviation is measured by the number of pulses relative to the output pulse interval of the rotary encoder 1 with reference to the yellow dot.

As a result, when the absolute rotational position of the photosensitive drum is magenta, m1 is cyan, and n is supposed to match, but when it is deviated as shown in FIG. 1, it is "1" as shown in FIG.
Enter. Of course, on the contrary, set the correction position to "0" and set the other "
1'' and the light emission timing may be set to rOJ.

These operations are performed at, for example, several dozen points distributed evenly over one rotation of the photosensitive drum, and interpolation is performed to write the light emission timing of the exposure LED array for recording magenta and cyan to each ROM and generate a light emission timing clock. It was used as a means.

Of course, the counters 46 and 49 are counted up by this light emission timing clock.

As a result, the light emission timings of the magenta exposure LED array 8 and the cyan exposure LED array 11 are corrected, and based on the image data read out from the image memory 7.10 by the outputs of the counter 6 and the counter 9, A latent image can be formed and developed at an accurate position, and based on this, the recording dot positions of each color can be matched with high precision, and a good color image can be obtained.

In the above embodiment, an example was explained in which three colors of yellow, magenta, and cyan are combined as a color image recording method, but the present invention is of course not limited to this, and other colors may be combined. Furthermore, the number of colors that can be combined can be two or four or more.

Further, the means for detecting the rotational position of the photosensitive drum is not limited to the rotary encoder, and other means having the same function can be used.

〔Effect of the invention〕

According to the present invention, since it is possible to accurately match the recording dot positions of images of each color to be combined, it is possible to obtain an image forming apparatus capable of recording good color images without color shift.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the principle of the present invention; Fig. 2 is a configuration diagram of an embodiment of the present invention; Fig. 3 is an explanatory diagram of a ROM in which correction information is written in the present invention; Fig. 4 is a color electrophotographic recording device. FIG. 5 is an explanatory diagram of a conventional example. 1- Rotary encoder 2- Frequency divider 3-
Counter 4 - Image memory 5 - Exposure LED array for yellow 6 - Counter 7 - Image memory 8 - Exposure LED array for magenta 9 - Count 10 - Image memory 11 - Exposure LED array for cyan 12 - Counter 13-ROM 14-ROM

Claims (1)

[Scope of Claims] An image forming apparatus that forms a toner image on an endless image carrier (20) using a plurality of developing means, and performs image recording by transferring the already synthesized toner image to recording paper at once, comprising: Rotational position detection means for detecting the absolute rotational position of the body (
1), and a storage means for storing latent image formation position correction information corresponding to the absolute rotational position of the image carrier, and a latent image formation timing signal is output based on this position correction information. A color shift correction device for an image forming apparatus.