KR100461587B1 - Image forming apparatus - Google Patents

Abstract

Disclosed is a multi-path color laser printer capable of correcting a deviation of an image forming position for each color in a sub-scanning direction within a predetermined range. The image forming apparatus according to the present invention is an electronic image forming apparatus for forming an image on a print medium. The image forming apparatus includes a power failure in units of one line per horizontal cycle of the horizontal synchronization signal based on an input control signal, a horizontal synchronization signal, and a color image signal. Transfer the photosensitive part for forming a latent image, and a developer supply part for supplying a developer of different colors corresponding to an electrostatic latent image formed on the photosensitive part to form a visible image in the photosensitive part, and overlapping the visible image formed in the photosensitive part for each color. Detects the transfer period for receiving and outputs the page initial position signal, transfers the image which is transferred by overlaying the visible image formed on the photosensitive unit by color, and the photosensitive unit on the basis of the occurrence of the page initial position signal. Outputs the image signal for each color to the photosensitive unit so that the error of each color at the start of forming the electrostatic latent image for each color is less than 1 line And a photosensitive control unit which determines a viewpoint and outputs a horizontal synchronous signal and an image signal to the photosensitive unit. The image forming apparatus according to the present invention configured as described above may correct the image forming position for each color in the sub-scanning direction within a predetermined range.

Description

Image forming apparatus

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic color image forming apparatus of a multipath method, and more particularly, to an image forming apparatus capable of correcting a deviation in a sub-scanning direction of an image formed by superimposing each color within a predetermined range.

In general, electrophotographic development methods are widely used in image forming apparatuses such as copiers, laser beam printers, LPH (LED Print Head) printers, and facsimile machines. The electrophotographic development process is sequentially composed of charging-> photosensitive-> developing-> transfer-> settling process.

1 is a diagram illustrating an image forming process by a general electrophotographic processor.

As shown, the electrophotographic image forming apparatus is largely composed of the photosensitive unit 100, the developing unit 110, the transfer unit 130, 135, and the fixing unit 140, 150, 180, and 190.

The photosensitive portion 100 is composed of a charging roller 102, a photosensitive drum 104, and a laser scanning unit 106.

The charging roller 102 electrically uniformly charges the surface of the photosensitive drum 104 by a contact charging method or the like. The surface of the charged photosensitive drum 104 receives and receives an electrical signal from the laser scanning unit 106 to form an electrostatic latent image for forming an image. The electrostatic latent image formed on the surface of the photosensitive drum 104 is developed with toner supplied from the developing unit 110 to form a visible image. At this time, the laser scanning unit 106 forms a different electrostatic latent image corresponding to the colors of CYAN, Magenta, YELLOW, and BLACK on the photosensitive drum 104. . That is, after the electrostatic latent image corresponding to the shiyan color is first formed on the photosensitive drum 104, the visible image is formed by the first color developing unit (C) 112 of the developer supply unit 110 with the shiyan toner. Since the visible image of the white color formed is transferred to the transfer belt (130). Then, visual images of different colors are formed on the surface of the photosensitive drum 104 by the second, third, and fourth color developing devices 114 to 118, and are overlapped and transferred to the transfer belt 130.

When all the transfer processes for one page are completed with the transfer belt 130, the paper picked up by the pickup roller 160 is moved between the fixing roller 140 and the transfer roller 150 while being superimposed on the transfer belt 130. Receive a visible image.

The paper which has received the visible image is compressed by heat while being moved between the pressing roller 180 and the heating roller 190 and discharged to the outside.

On the other hand, the photosensitive control unit 120 controls the operation of the laser scanning unit 106 to form an electrostatic latent image on the photosensitive drum 104, to the laser scanning unit 106 by different image signals for each color in accordance with a predetermined synchronization signal Output At this time, the sensor 135 of the transfer unit (130, 135) outputs the page initial position signal to the photosensitive controller 120 for each rotation period of the transfer belt (130).

The photosensitive controller 120 performs an electrostatic latent image operation of the laser scanning unit 106 so that the visible images of different colors overlap the transfer belt 130 without being shifted according to the page initial position signal input from the sensor 135. To control.

However, the horizontal (line) synchronization signal for controlling the electrostatic latent image of the laser scanning unit 106 in the photosensitive controller 120 is generated asynchronously with the page initial position signal input from the sensor 135 of the transfer unit, The phases do not match exactly.

Referring to Figures 2a and 2b will be described in more detail the phase relationship of the above-described signals.

FIG. 2A is a diagram illustrating a phase relationship between a page initial position signal and a horizontal synchronization signal in the related art, and FIG. 2B is a diagram showing a phase relationship between signals in a page section corresponding to one color in FIG.

When one horizontal synchronous signal is output from the photosensitive controller 120 to the laser scanning unit 106, the laser scanning unit 106 forms an electrostatic latent image corresponding to one horizontal line on the photosensitive drum 104. That is, one horizontal sync signal section corresponds to one line of electrostatic latent images formed on the photosensitive drum.

As shown in FIG. 2A, the page initial position signal input from the sensor 135 is asynchronously input to the phase of the horizontal synchronous signal for the photosensitive controller 120 to control the electrostatic latent image of the laser scanning unit 106. . 't_1st' is the magnitude of the phase difference between the page initial position signal and the horizontal synchronization signal in the section corresponding to the first color. 't_1st', 't_2nd', 't_3rd', and 't_4th' all have different sizes, and the error range is between 0 lines and less than 1 line.

As illustrated in FIG. 2B, the photosensitive controller 120 counts the number of horizontal synchronization signals generated after the page initial position signal is input from the sensor 135, and when the predetermined number is reached, the vertical synchronization signal is generated (polling edge). ) Is output to the laser scanning unit 106 for each color. Accordingly, the laser scanning unit 106 receives an image signal for each color and forms an electrostatic latent image on the photosensitive drum 104 after a predetermined time elapses from the point of time when the page initial position signal generated from the sensor 135 is generated. After the electrostatic latent images formed on the photosensitive drum 104 are visualized by the developers 112 to 118 of different colors and overlapped with the transfer belt 130, the visible images for each color are about 0 to 1 in the sub-scanning direction. An error corresponding to the open line range occurs. The size of this error is larger when printing at a lower resolution, and when printing at 150 dpi, the maximum is about 170 micrometers, and when printing at 600 dpi, an error of about 43 micrometers is generated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide an image forming apparatus capable of correcting a deviation of a visible image for each color formed on a sheet within a sub-scanning direction.

1 is a view showing an image forming process by a general electrophotographic processor,

2A is a diagram showing a timing relationship between a page initial position signal and a horizontal synchronization signal in the prior art;

FIG. 2B is a diagram showing a timing relationship of each signal in a page section corresponding to one color in FIG. 2A;

3 is a block diagram showing a configuration of an image forming apparatus according to the present invention; and

4 is a diagram showing the timing relationship of each signal in the image forming apparatus according to the present invention;

FIG. 5A is a view showing timing relationships for an example of a page initial position signal, a horizontal synchronization signal, and a vertical synchronization signal generated in synchronization with the conventional art;

5B is a diagram showing the timing relationship between the reference vertical synchronization signal and the vertical synchronization signal in the present invention generated in synchronization with the same page initial position signal and horizontal synchronization signal as in FIG. 5A, and

6A through 6C are timing diagrams illustrating an example in which an error range of a vertical synchronization signal for each color is the largest in the image forming apparatus according to the present invention.

Explanation of symbols on the main parts of the drawings

106: laser scanning unit 120: photosensitive control unit

122: clock generator 124: central processing unit (CPU)

126: memory 135: sensor

An image forming apparatus according to the present invention for achieving the above object, in the electronic image forming apparatus for forming an image on a print medium, 1 of the horizontal synchronous signal based on the input control signal, horizontal synchronous signal and color image signal The photosensitive part for forming the electrostatic latent image on a line-by-line basis, and the developer supplying part for supplying the developer of different colors corresponding to the electrostatic latent image formed on the photosensitive part to form a visible image on the photosensitive part, and the visible part formed on the photosensitive part Detecting a transfer cycle for receiving images by superimposing the images by color, outputting a page initial position signal, and transferring a transferred image to a print medium by overlaying the visible image formed on the photosensitive unit by color, and generating a page initial position signal. Colorization is performed such that the error per color of the starting point at which the photosensitive part forms an electrostatic latent image for each color is less than one line based on the viewpoint. To determine when to output a signal to the photosensitive, a photosensitive agent fisherman for outputting a horizontal synchronizing signal and the image signal to the photosensitive.

The photosensitive controller generates a horizontal synchronous signal and outputs the image signal to the photosensitive unit in synchronization with the horizontal synchronous signal, and starts outputting the image signal corresponding to each color based on the point of time when the page initial position signal is generated. It is preferable to include a central processing unit (CPU) for storing information on a viewpoint and determining an output time point of an image signal for each color in synchronization with a horizontal synchronization signal in a section where the error is less than one line based on the information.

The photosensitive controller may further include a memory configured to temporarily store information on an output start time of the image signal corresponding to the color based on a control signal of the CPU, and output the temporary information to the controller.

In addition, the photosensitive portion is a photosensitive drum for forming an electrostatic latent image, a laser scanning unit for converting a color-specific image signal into a laser beam based on the horizontal synchronous signal and color image signal input from the photosensitive controller to radiate the photosensitive drum, and a photosensitive drum It is preferable to include a charging drum for charging a high voltage to the.

The transfer unit preferably includes a transfer belt which transfers the visible image formed on the photosensitive unit by color to be transferred to the print medium, and a sensor that outputs a page initial position signal for each color to the photosensitive controller every one rotation period of the transfer belt. Do.

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.

The present invention will be described with reference to the drawings showing an image forming process by the general electrophotographic processor shown in FIG. 1, and the same parts as those shown in FIG. 1 are given the same reference numerals.

1 is a view showing an image forming process by a general electrophotographic processor, Figure 3 is a block diagram showing the configuration of an image forming apparatus according to the present invention.

The image forming apparatus according to the present invention includes a photosensitive unit 100, a developer supply unit 110, a transfer unit 130 and 135, and a photosensitive control unit 120.

First, the photosensitive unit 100 applies an electrostatic latent image to the photosensitive drum 104 in units of one line in one period of the horizontal synchronization signal based on a control signal, a horizontal synchronization signal, and a color image signal input from the photosensitive controller 120. Form.

The developer supply unit 110 supplies a developer having a different color corresponding to an electrostatic latent image formed on the photosensitive unit 100 to form a visible image in the photosensitive unit 100.

The transfer units 130 and 135 overlap the visible images formed on the photosensitive unit 100 for each color to detect a transfer period for receiving the transfer, and output a page initial position signal for each color to the photosensitive controller 120. The transfer units 130 and 135 overlap the visible images formed on the photosensitive unit 100 for each color and are transferred to a print medium such as paper.

The photosensitive controller 120 outputs the image signal for each color such that an error for each color of the start point at which the photosensitive unit 100 forms an electrostatic latent image for each color is less than one line based on the occurrence of the page initial position signal. A time point for outputting is determined, and the horizontal synchronizing signal and the image signal are output to the photosensitive unit 100.

The photosensitive unit 100 includes a photosensitive drum 104, a laser scanning unit 106, and a charging drum 102.

The photosensitive drum 104 forms an electrostatic latent image by a laser beam incident from the laser scanning unit 106 while being uniformly charged by the charging drum 102 at a constant voltage.

The laser scanning unit 106 converts an image signal for each color into a laser beam on a line-by-line basis in synchronization with the horizontal synchronous signal input from the photosensitive controller 120 to radiate the photosensitive drum 104.

The charging drum 102 uniformly charges the high pressure voltage to the photosensitive drum 104.

The photosensitive controller 120 includes a clock generator 122, a memory 126, and a central processing unit (CPU) 124.

The clock generator 122 generates a horizontal (line) synchronization signal based on a control signal input from the central processing unit (CPU) 124 and transmits it to the laser scanning unit 106 and the central processing unit (CPU) 124. Output

The central processing unit (CPU) 124 outputs an image signal to the photosensitive unit 100 in synchronization with the horizontal synchronizing signal input from the clock generator 122, but at the time of generation of the page initial position signal input from the sensor 135. On the basis of this, information on the start point of output of the image signal corresponding to each color is stored in the memory 126, and the point of time of outputting the image signal for each color in synchronization with the horizontal synchronous signal in the section where the error is less than one line. The image signal of the color corresponding to the determined output time point is output to the photosensitive unit 100.

The memory 126 temporarily stores information on the start point of output of the image signal corresponding to each color based on the control signal of the central processing unit (CPU), and outputs it to the central processing unit (CPU) 124. do.

A process of determining the output time point of the image signal performed by the central processing unit (CPU) 124 will be described in more detail with reference to FIG.

4 is a diagram showing the timing relationship of each signal in the image forming apparatus according to the present invention.

The central processing unit (CPU) 124 corresponds to the first color from the occurrence of the falling edge of the page initial position signal corresponding to the first color among the color initial page position signals output from the sensor 135. Information on the time up to the output time of the image signal is output to the memory 126 as the first reference output time information Tp1 and stored.

Thereafter, the CPU 124 performs a time corresponding to -0.5 lines to +0.5 lines from the stored first reference output time Tp1 based on the occurrence time of the page initial position signal corresponding to the second color. Generates a reference vertical synchronization signal that maintains a high level during the range.

Then, the CPU 124 uses the reference vertical synchronization signal corresponding to the generated first color as an enable signal so that the falling edge of the horizontal synchronization signal input while the reference vertical synchronization signal is at a high level. Is determined as the output time of the image signal corresponding to the second color.

The determination process of the output time point of the image signal corresponding to the third color is as follows.

The CPU 124 corresponds to the second color from the time when the falling edge of the page initial position signal corresponding to the second color among the color initial page position signals output from the sensor 135 is generated. The information on the time until the output time of the image signal is output to the memory 126 as the second reference output time information Tp2 and stored.

Thereafter, the CPU 124 performs a first reference output time Tp1 and a second reference output time Tp2 stored in the memory 126 on the basis of the occurrence time of the page initial position signal corresponding to the third color. Generates a reference vertical synchronization signal that maintains a high level for a time range corresponding to -0.5 line to +0.5 line from the average value of?).

Then, the central processing unit (CPU) 124 uses the reference vertical synchronization signal corresponding to the generated third color as an enable signal so that a falling edge of the horizontal synchronization signal input while the reference vertical synchronization signal is at a high level. Is determined as the output time of the image signal corresponding to the third color.

The determination process of the output time point of the image signal corresponding to the fourth color is as follows.

The CPU 124 corresponds to the third color from the time when the falling edge of the page initial position signal corresponding to the third color among the page initial position signals for each color output from the sensor 135 is generated. Information on the time up to the output point of the image signal is output to the memory 126 as the third reference output time information Tp2 and stored.

Thereafter, the CPU 124 performs the first reference output time Tp1 and the second reference output time Tp2 stored in the memory 126 on the basis of the occurrence point of the page initial position signal corresponding to the fourth color. And a reference vertical synchronous signal that maintains a high level for a time range corresponding to -0.5 line to +0.5 line from the average value of the smallest and largest one among the third reference output time Tp3.

Then, the CPU 124 uses the reference vertical synchronization signal corresponding to the generated fourth color as an enable signal so that the falling edge of the horizontal synchronization signal input while the reference vertical synchronization signal is at a high level. Is determined at the time of outputting the image signal corresponding to the fourth color.

The difference between the timing of outputting the image signal in the prior art and the present invention with respect to the same page initial position signal and the horizontal synchronization signal will be described with reference to FIGS. 5A and 5B.

FIG. 5A illustrates a timing relationship of an example of a page initial position signal, a horizontal synchronous signal, and a vertical synchronous signal generated in synchronization with the conventional art, and FIG. 5B is the same as the page initial position signal and horizontal same as that of FIG. 5A. The timing relationship between the reference vertical synchronizing signal and the vertical synchronizing signal in the present invention generated in synchronization with the synchronizing signal is shown.

As shown in FIG. 5A, in the related art, the photosensitive controller 120 counts a certain number of horizontal sync signals inputted from a polling edge occurrence point of a page initial position signal, thereby vertically syncing a polling edge occurrence point of a specific horizontal sync signal. A signal is generated and an image signal is output in synchronization with it.

However, as shown in Fig. 5B, in the present invention, after the output time point of the image signal corresponding to the first color is determined, the output time point of the next color is determined based on the time information at this time, so The error range with respect to the output time of the image signal is narrowed to 0.85 lines or less.

6A to 6C, the case where the error in the output time of the image signal corresponding to each color is the greatest in the present invention will be described.

6A through 6C are timing diagrams illustrating an example in which an error range of a vertical synchronization signal for each color is the largest in the image forming apparatus according to the present invention.

In the case shown in Fig. 6A, the output time point of the image signal corresponding to the second color is determined 0.5 lines after the output point of the image signal corresponding to the first color, and the output time point of the image signal corresponding to the third color is determined. It is determined 0.5 lines after the average of the output time points of the image signals corresponding to the first and second colors, and the output time point of the image signals corresponding to the fourth color is the output time point of the image signals corresponding to the first and third colors. The case is decided 0.5 lines after the average value. At this time, the error range at the time of outputting the image signal corresponding to each color is 0.85 lines.

In the case shown in Fig. 6B, the output time point of the image signal corresponding to the second color is determined 0.5 lines after the output point of the image signal corresponding to the first color, and the output time point of the image signal corresponding to the third color is determined. It is determined 0.5 lines before the average of the output time points of the image signals corresponding to the first and second colors, and the output time point of the image signals corresponding to the fourth color is the output time point of the image signals corresponding to the second and third colors. The case is decided 0.5 lines after the average value. At this time, the maximum error range at the time of outputting the image signal corresponding to each color is 0.85 lines.

In the case shown in Fig. 6C, the output time point of the image signal corresponding to the second color is determined 0.5 lines after the output time point of the image signal corresponding to the first color, and the output time point of the image signal corresponding to the third color is determined. It is determined 0.5 lines after the average of the output time points of the image signals corresponding to the first and second colors, and the output time point of the image signals corresponding to the fourth color is the output time point of the image signals corresponding to the first and third colors. The case is decided 0.5 lines after the average value. At this time, the maximum error range at the time of outputting the image signal corresponding to each color is 0.85 lines.

On the other hand, the image signal output at the time determined by the above process is output to the laser scanning unit 106, the laser scanning unit (LSU) 106 to the horizontal synchronous signal input from the clock generator 122 In synchronization, a polygon mirror motor (not shown) rotates and scans a laser beam on the photosensitive drum 104.

The image forming apparatus according to the present invention, in the multi-path electronic color image forming apparatus, can correct the deviation in the sub-scanning direction of the image superimposed for each color within the predetermined range.

Although the preferred embodiments of the present invention have been illustrated and described above, the present invention is not limited to the specific embodiments described above, and the present invention is not limited to the specific embodiments of the present invention without departing from the spirit of the present invention as claimed in the claims. Anyone skilled in the art can make various modifications, as well as such modifications are within the scope of the claims.

Claims (8)

An electronic image forming apparatus for forming an image on a print medium, A photosensitive unit configured to form an electrostatic latent image in units of one line in one period of the horizontal synchronization signal based on an input control signal, a horizontal synchronization signal, and a color image signal; A developer supply unit supplying a developer of different colors corresponding to the electrostatic latent images formed on the photosensitive unit to form a visible image on the photosensitive unit; Transferring a page initial position signal by detecting a transfer period for receiving a transfer by overlapping the visible image formed on the photosensitive unit for each color, and transferring the transferred image to the print medium by overlapping the visible image formed on the photosensitive unit by color. part; And Determining a point in time to output the image signal for each color to the photosensitive unit so that the error per color of the start point of the photosensitive unit to form the electrostatic latent image for each color is less than the one line on the basis of the occurrence of the page initial position signal, And a photosensitive controller for outputting the horizontal synchronous signal and the image signal to the photosensitive unit. The method of claim 1, wherein the photosensitive control unit A clock generator for generating the horizontal synchronization signal and outputting the horizontal synchronization signal; The image signal is output to the photosensitive unit in synchronization with the horizontal synchronization signal, and an error between the start point of output of the image signal corresponding to each color is less than the one line based on the occurrence point of the page initial position signal. And a central processing unit (CPU) for determining an output time point of the color image signal in synchronization with a horizontal synchronization signal in a section. The method of claim 1, wherein the photosensitive control unit From the time when the falling edge of the page initial position signal corresponding to the first color among the page initial position signals for each color output from the transfer unit occurs from the time of outputting the image signal corresponding to the first color Information is stored as first reference output time information, and within a time range corresponding to -0.5 lines to +0.5 lines from the stored first reference output time on the basis of the occurrence of the page initial position signal corresponding to the second color. And a point at which a falling edge of the input horizontal sync signal is generated as an output point of an image signal corresponding to a second color. The method of claim 3, wherein the photosensitive control unit From the time when the falling edge (falling edge) of the page initial position signal corresponding to the second color among the page initial position signals for each color output from the transfer unit from the time of output of the image signal corresponding to the second color Information about the first reference output time and the second reference output time based on the occurrence time of the page initial position signal corresponding to the third color. And a time point at which a falling edge of the horizontal synchronization signal inputted within a time range corresponding to 0.5 lines is determined as an output time point of an image signal corresponding to a third color. The method of claim 4, wherein the photosensitive control unit From the time when the falling edge of the page initial position signal corresponding to the third color among the page initial position signals for each color output from the transfer unit from the time of outputting the image signal corresponding to the third color Information is stored as third reference output time information, and among the stored first reference output time, second reference output time, and third reference output time on the basis of the occurrence of the page initial position signal corresponding to the fourth color. Determining when the falling edge of the horizontal synchronous signal inputted within a time range corresponding to -0.5 to +0.5 lines from the average value of the smallest and largest is output time of the image signal corresponding to the fourth color. An image forming apparatus. The method of claim 3, wherein the photosensitive control unit And a memory which temporarily stores the reference output time information and outputs the information to the controller. The method of claim 1, wherein the photosensitive portion A photosensitive drum forming an electrostatic latent image; A laser scanning unit which converts the image signal for each color into a laser beam based on the horizontal synchronization signal and the image signal for each color input from the photosensitive controller, and emits the laser beam to the photosensitive drum; And And a charging drum for charging the high voltage to the photosensitive drum. The method of claim 1, wherein the transfer unit A transfer belt which transfers the visible image formed on the photosensitive unit by color and is transferred to the print medium; And And a sensor for outputting the page initial position signal for each color to the photosensitive controller every one rotation period of the transfer belt.