JP2002072606A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the positional deviation of an image without changing the write starting order of a beam in a multi-beam color image forming device. SOLUTION: The positional deviation of the toner image of each color in a subscanning direction is detected based on a phase difference between the synchronization detected signal 58 of a top beam detected by a synchronization detection sensor and a belt mark signal 57 detected by a mark sensor 33, so that the rotational target position of a motor M to rotate a photoreceptor 11 and/or an intermediate transfer belt body 13 is controlled by a motor controlling part 62 so as to correct the positional shifting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for simultaneously deflecting a plurality of beams by a common deflector to form a plurality of lines of images on a photosensitive member, and forming toner images of respective colors formed on the photosensitive member. The present invention relates to a color image forming apparatus that transfers images in a manner superimposed on an intermediate transfer member, and particularly to correction of misregistration of toner images of respective colors in the sub-scanning direction.

[0002]

2. Description of the Related Art A plurality of beams are simultaneously deflected by a common deflector (polygon mirror) to form an image of a plurality of lines on a photoreceptor, and a toner image of each color formed on the photoreceptor is intermediately transferred. In a color image forming apparatus in which the transfer is performed while being superimposed on the body, the rotation of the optical deflector cannot be synchronized with the photosensitive body, so that when the toner image is transferred a plurality of times, the number of the beams on the photosensitive body is reduced. A positional shift may necessarily occur in the sub-scanning direction by the beam interval.

FIG. 6 shows a line synchronization detection signal detected by deflecting two beams by an optical deflector and a belt mark signal detected from the intermediate transfer belt. Times Δt1 and Δt2 from the belt mark signal to the writing start position are as follows. As shown in FIG. 7, a displacement of up to two lines occurs. For example, if the number of beams is two and the resolution is 600 dpi,
Since the memory pitch is 42.3 μm, 4 * 42.3 μm
= Possible displacement of about 84.6 μm. When the number of beams is 4 and the resolution is 600 dpi,
4 * 42.3 μm = approximately 170 μm displacement may occur. This shift amount increases in proportion to the number of beams.

Therefore, as a conventional example of reducing the displacement by reducing the displacement to a distance equal to or less than the resolution (42.3 μm in the case of 600 dpi), Japanese Patent Application Laid-Open No. H10-239939 is disclosed.
Japanese Patent Application Laid-Open Publication No. H11-163,199 discloses a position detecting member provided at one position of an intermediate transfer belt (or a photoreceptor), a position of a belt mark signal detected by a sensor for detecting the position detecting member during rotation, and a position of a synchronous detection signal of a polygon mirror. A method of switching the writing order of the beams (LD1, LD2) based on the phase difference as shown in FIG. 8 has been proposed.

[0005]

However, in the above prior art, the beam writing order is randomly determined by the phase difference between the belt mark signal and the synchronization detection signal.
Power is switched between multiple beams
Is small, the light energy applied to the photoreceptor has a deviation for each color even though the image data is the same, and the color balance is lost.
In particular, when a halftone gray is reproduced, it has a remarkable adverse effect, and at the worst, there is a drawback that the gray color is not grayed and is discolored for each copy. FIG. 9 shows LD1 and L2 when the power deviation of LD2 with respect to LD1 is 10%.
This shows a case where the writing order of D2 is switched, and eight patterns occur even for the same image data. When an image was formed by increasing or decreasing the LD power experimentally, 2
% Color deviation could be visually observed.

The present invention has been made in view of the above-mentioned problems of the prior art, and
It is an object of the present invention to provide a color image forming apparatus capable of preventing an image from being displaced without switching the writing order of the images.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method in which a plurality of beams are deflected by a common deflector to simultaneously form a plurality of lines of images on a photoreceptor. In a color image forming apparatus for transferring a toner image of each color formed on the intermediate transfer body in a superimposed manner, a synchronization detection sensor that detects a leading beam deflected by the deflector and outputs a synchronization detection signal, A mark sensor for detecting a reference mark serving as a reference for positioning when superposing toner images of each color on the intermediate transfer member; a motor for rotating the photosensitive member and / or the intermediate transfer member; Based on the phase difference between the synchronization detection signal detected by the synchronization detection sensor and the reference mark signal detected by the mark sensor, the displacement of the toner image of each color in the sub-scanning direction is detected, and the displacement is detected. To correct Characterized in that a motor control means for controlling the rotational target position of the motor.

[0008] In this case, the rotation target position of the motor is controlled by a speed control loop and a position control loop. Also, a phase difference detection circuit for detecting the phase difference and a circuit for calculating a correction amount based on the phase difference are provided in a circuit for driving the motor. Further, the motor control is completed between the end of the transfer of the effective image area of the previous color and the start of the transfer of the effective transfer area of the next color. The correction amount is set to be equal to or less than the distance corresponding to the number of beams in the sub-scanning direction on the photoconductor.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing a color printer of an embodiment of a color image forming apparatus according to the present invention, FIG. 2 is a configuration diagram showing a writing device of FIG. 1, FIG. 3 is a block diagram showing a control system, and FIG. FIG. 2 is a block diagram illustrating a motor control unit that is a main part of the color image forming apparatus according to the invention.

One embodiment of the present invention is an electrophotographic digital color image forming apparatus comprising an electrophotographic digital color copying machine. This color copier includes a color printer as an electrophotographic image forming unit that forms an image on transfer paper as a transfer material by an electrophotographic process, and a plurality of colors, for example, red, by scanning a document and reading the image. A scanner as original reading means for obtaining blue and green image signals and converting them into digital image signals;

FIG. 1 shows the main structure of the above color printer. The color printer includes a photoconductor 11 and a rotating device 12.
And an intermediate transfer belt 13 as an intermediate transfer member, and a writing device 14 as exposure means. Photoconductor 11
Used a photosensitive drum, but a photosensitive belt or the like may be used. The intermediate transfer belt 13 may use an intermediate transfer member such as an intermediate transfer drum and an intermediate transfer roller.

A slow-current lamp (hereinafter referred to as QL) 1 is provided around the photosensitive member 11 as a slow-charge means for removing charge from the photosensitive member 11.
5 and a scorotron charger (hereinafter referred to as a charging charger) 1 as charging means for uniformly charging the photoconductor 11
6, a writing device 14, a potentiometer 17 for detecting the surface potential of the photoconductor 11, a rotating device 12, and a photosensor as a density detecting unit for optically detecting the amount (density) of toner attached to the photoconductor 11. (Hereinafter referred to as P sensor) 18, a pre-transfer slow-charging lamp (hereinafter referred to as PTL) 19 for gradually reducing the charge of the photoconductor 11 before transferring the toner image, and transferring the toner image on the photoconductor 11 to the intermediate transfer belt 13. A belt transfer charger 20 as a transfer unit and a cleaning device 21 for cleaning the photoconductor 11 are provided.

The rotating device 12 holds a plurality of developing devices for developing the electrostatic latent images of the respective colors on the photoconductor 11 into toner images of the respective colors. Developing device 22 to produce a black toner image and photoconductor 11
A developing device 23 that develops the electrostatic latent image on the photoconductor 11 to produce a cyan toner image; a developing device 24 that develops the electrostatic latent image on the photoconductor 11 to produce a magenta toner image; Developing device 25 that develops an electrostatic latent image into a yellow toner image
And the plurality of developing devices 22 to 25 are selectively driven to a developing position by being rotationally driven by a revolver motor as a driving unit.

Each of the plurality of developing devices 22 to 25 has a developing sleeve 22a to 25a at a developing position during a developing operation.
Faces the photoreceptor 11, and the developing sleeves 22a to 25a are rotated by a developing motor to convey the developer in the developing devices 22 to 25 to a developing area between the photoreceptor 11 and the developing sleeves 22a to 25a. The electrostatic latent image on the photoconductor 11 is developed. A revolver home position sensor (hereinafter, referred to as a revolver HP sensor) 26 detects that the rotating device 12 is located at the reference stop position.

The intermediate transfer belt 13 includes a plurality of rollers 27
And a predetermined roller among these rollers 27 to 32 is rotationally driven by a drum motor to rotate the intermediate transfer belt 13. On the inner side of the intermediate transfer belt 13, a reference mark serving as a reference for aligning the toner images of each color on the photoconductor 11 on the intermediate transfer belt 13 for each screen when the images are superimposed and transferred is superimposed. One is provided.

In the vicinity of the intermediate transfer belt 13, a belt mark sensor (hereinafter, referred to as a mark sensor) 33 as mark detection means for detecting a reference mark on the intermediate transfer belt 13 along the rotation direction of the intermediate transfer belt 13. A lubricant application device 34 for applying a lubricant on the intermediate transfer belt 13 by contacting the intermediate transfer belt 13 when the lubricant application solenoid is turned on, and a transfer unit for transferring a color image on the intermediate transfer belt 13 to transfer paper The paper transfer device 35 as a cleaning device and the intermediate transfer belt 13
A belt cleaning device 36 is disposed as cleaning means for removing the upper toner.

The belt cleaning device 36 is constituted by, for example, a cleaning member such as a cleaning blade, and is brought into contact with and separated from the intermediate transfer belt 13 by turning on / off a solenoid for contacting and separating the belt cleaning device. At the time of contact, the toner on the intermediate transfer belt 13 is removed. The paper transfer device 35 is arranged to face the lowermost portion of the intermediate transfer belt 13, and the belt cleaning device 36 is arranged between the paper transfer device 35 and the belt transfer charger 20. Belt cleaning device 3
Reference numeral 6 designates an intermediate transfer belt cleaning solenoid that can be brought into contact with and separated from the intermediate transfer belt 13 by turning on and off, and a lubricant applying device 34 applies a lubricant to the intermediate transfer belt 13 by turning on and off the lubricant applying solenoid. Whether it is possible or not is possible.

The circumferential length of the intermediate transfer belt 13 is a length obtained by adding two A4-size papers and an interval between transfer materials (transport interval between transfer materials). Is twice as long. One rotation of the photoconductor 11 forms one A4 horizontal color image, and two rotations of the photoconductor 11 transfer two screen images of the same color onto the intermediate transfer belt 13.

In the transport path along which the transfer paper is transported, a registration roller 37 is disposed upstream of the paper transfer device 35, and a transport belt 38 is disposed downstream of the paper transfer device 35. Further downstream, a fixing device having a fixing roller and a pressing roller pressed against the fixing roller is arranged. The conveyor belt 38 and the fixing roller of the fixing device are driven to rotate by a main motor, and the registration roller 37 is driven to rotate by a main motor via a registration clutch. The registration sensor 39 detects the transfer paper just before the registration roller 37. Transfer paper is fed to the registration roller 37 from a paper feeder selected from a plurality of paper feeders.

FIG. 2 shows a scanning optical system of the writing device 14. In the writing device 14, a plurality of beams emitted from a light source unit 41 that generates a light beam (hereinafter, simply referred to as a beam) composed of a plurality of laser beams enter a rotary polygon mirror 43 as a scanning unit via a cylinder lens 42. I do. Each beam incident on the rotating polygon mirror 43 is
The scanning is performed by the rotation of the rotating polygon mirror 43, and the fθ lens 4 is scanned.
4. Exposure and scanning are simultaneously performed in the main scanning direction on the photoconductor 11 at a beam pitch P in the sub-scanning direction via the scanning optical system including the toroidal lens 45 and the folding mirror 46.

The rotary polygon mirror 43 is driven to rotate by a polygon motor, and a synchronization detector (not shown) as a line synchronization signal generating means detects a beam from the toroidal lens 45 at a predetermined position outside the writing area of the photoconductor 11. This synchronization detector is provided by the light source 41 to the cylinder lens 4.
2. Detect a plurality of beams incident through the rotating polygon mirror 43, the fθ lens 44, and the toroidal lens 45, and output one output signal for the plurality of beams as a line synchronization signal.

Here, the light source section 41 normally emits a plurality of beams modulated according to the image signals by driving the light sources 41a and 41b composed of, for example, two semiconductor lasers with the image signals. Further, the light source unit 41 is provided with a pitch adjusting mechanism for adjusting the beam pitch in the sub-scanning direction, and the pitch adjusting mechanism rotates the light source unit 41 to adjust the beam pitch in the sub-scanning direction. Light source 4
1, a light source 41 composed of two semiconductor lasers
The beams emitted from a and 41b are collimated lenses 4
The light is converted into parallel light by 1c and 41d, and is shaped into a predetermined light beam diameter by passing through a slit of an aperture member (not shown).

The beam from one of these aperture members is rotated by 90 degrees in the polarization direction by a half-wave plate 41e, enters a beam combining prism 41f as a beam combining means, and is incident on a slope of the beam combining prism 41f. The beam is internally reflected, is reflected by the polarization beam splitter surface of the beam combining prism 41f, and is combined with a beam from the other aperture member serving as a reference in the vicinity of the optical axis thereof.

The two beams from the beam combining prism 41f are emitted at a predetermined angle θm in the main scanning direction, and are collimated by the semiconductor laser 41a.
By rotating the light source unit 41 around the optical axis by slightly decentering the optical axis with the main scanning direction, a sub-scanning angle component of the emission angle between the two beams is obtained, and Beam pitch adjustment is performed. Assuming that the rotation angle of the light source unit 41 is α, Δθs = θm · sinα. The number of the light sources 41a and 41b is two, but may be three or more.

FIG. 3 shows a control section of the color printer. The CPU 47 executes a process such as an operation according to the contents of the control program, and the ROM 48 has a built-in control program. The RAM 49 is used for storing and saving data,
The CPU 47, the ROM 48, and the RAM 49 are connected by a data bus and an address bus. The serial communication controller 50 includes a control unit of the scanner and the CPU 4.
7, and is connected to the CPU 47 by a data bus and an address bus.

A write control IC 51 as a write control section for controlling the exposure of the photoconductor 11 is connected to the CPU 47 by a data bus and an address bus.
The exposure LD control unit 52 and the polygon motor 43a are controlled by being connected to the D control unit 52 and the polygon motor 43a. The exposure LD control unit 52 controls lighting of the LDs 41 a and 41 b in the writing device 14 based on an input signal from the writing control IC 51. I / O
The controller 53 controls input and output of the CPU 47. C
The PU 47, the ROM 48, the RAM 49, the serial communication controller 50, the write control IC 51, and the I / O controller 53 constitute a control unit of the color printer.

The fixing device 54 has a fixing thermistor for detecting the surface temperature of the fixing roller, and a fixing heater for heating the fixing roller. The CPU 47 A / D converts a temperature detection signal of the fixing thermistor and A / D converts the signal. Based on the converted value, a pulse width modulation (PWM) pulse for controlling the fixing heater is output to control the fixing heater on / off, thereby controlling the surface temperature of the fixing roller to be constant.

The CPU 47 converts the output voltage fed back from the power pack unit 55 as a high-voltage power supply to A
/ D conversion, and outputs a PWM signal to the power pack unit 55 based on the A / D conversion value, and
5 is controlled. Power pack unit 55
Apply a high voltage to the charging charger 16, the belt transfer charger 20, and the paper transfer device 35, and apply a grid voltage to the charging charger 16;
Are applied to the developing sleeves 22a to 25a, respectively.

An electrometer circuit 56 including the electrometer 17 detects the surface potential of the photoconductor 11, and the output signal of the electrometer 17 is CP.
It is input to the A / D input terminal of U47. P including a P sensor 18 composed of a light emitting diode and a phototransistor
The sensor circuit 57 optically detects the toner adhesion amount (density) of the photoconductor 11, and a phototransistor output signal of the P sensor 18 is input to an A / D input terminal of the CPU 47. C
PU47 is a light emitting diode drive circuit for the P sensor 18
The lighting control of the light emitting diode is performed by outputting the WM pulse.

The main motor 58 rotationally drives a transfer material transport system for transporting the transfer material, and the drum motor 59 rotationally drives the photosensitive member 11 and the intermediate transfer belt 13. The developing motor 60 is connected to the developing sleeve 22 of the developing devices 22 to 25.
a to 25a for rotating the motors. These motors are ON signals from the CPU 47, a half-speed signal for reducing the speed by half, and a lock for judging that the speed has reached the target speed. A signal is input.

The revolver motor 61 rotates the rotating device 12 equipped with the developing devices 22 to 25 in response to a four-phase output signal input from the CPU 47, and develops a developing device of the developing devices 22 to 25 that performs development of a designated color. Stop in position. The toner supply motor 62 supplies black, cyan, magenta,
The CPU 47 controls the ON time of the toner supply motor 62 in accordance with the amounts of black, cyan, magenta, and yellow toners on the photoconductor 11 based on the input signal from the P sensor 18 based on the input signal from the P sensor 18. I do.

The output signal of the mark sensor 33 as an intermediate transfer reference signal, which is used as a reference for the alignment of each toner image at the time of image superposition, is input to an interrupt terminal of the CPU 47 because strict precision is required in terms of timing. You. The output signal of the revolver HP sensor 26, which serves as a reference for the stop position of the rotating device 12, requires strict precision in timing to switch the output pulse (four-phase output signal) from the CPU 47 to the revolver motor 61 while the rotating device 12 is rotating. Is input to the interrupt terminal of the CPU 47.

In this embodiment, for example, A4 horizontal size (A4 size in which the transfer material transport direction is shortened)
The basic sequence in the case of continuously forming the full-color image of, for example, four screens will be described. In the color printer, in the stop state, the rotating device 12 is stopped in a state where the developing device 22 whose developing color is black is located at the developing position. When a color image forming start (print start) command is received from the system control unit, the control unit of the color printer (hereinafter referred to as a printer control unit)
The QL 15 and the drum motor 59 are turned on. For this reason,
The drum motor 59 rotates to rotate the photoconductor 11 and the intermediate transfer belt 13, and the photoconductor 11 is discharged by the QL 15.

The printer control unit controls the QL1 on the photoconductor 11
The charging charger 16 is turned on when the neutralization start position 5 reaches the position where the charging of the charging charger 16 is performed. Next, when the position on the photoconductor 11 where charging by the charging charger 16 is started reaches the developing position, the printer control unit turns on the developing bias in the power pack unit 55 and simultaneously rotates the developing motor 60.

The printer control unit determines that the position facing the developing position when the developing bias on the photoconductor 11 is turned on is the belt transfer position (the position where the toner image on the photoconductor 11 is transferred to the intermediate transfer belt 13). Is reached, the belt transfer charger 20 is turned on. The period from the start of the rotation of the photoconductor 11 to this point is the pre-rotation of the photoconductor 11.

At the same time, when the mark sensor 33 detects a reference mark on the intermediate transfer belt 13 by rotation of the intermediate transfer belt 13, a mark detection signal of the mark sensor 33 is input to the interrupt terminal of the CPU 47 as an intermediate transfer reference signal, and The control unit performs an interrupt process on the program. The printer control unit transmits a scan start command for the first color of the first screen (black) to the control unit of the scanner (hereinafter, referred to as a scanner control unit) during the interrupt processing.

When the scanner control unit receives a scan start command for the first color of the first screen from the printer control unit, it causes the scanner to read a document for obtaining an image signal of the first color of the first screen, For example, red, blue,
The image signal of (green) is converted into an image signal of the first color of the first screen and transferred to the printer control unit.

The printer controller transfers the image signal transferred from the scanner controller to the write control IC 51,
The write control IC 51 converts the image signal into exposure data for the first color of the first screen (data for driving the semiconductor laser with the writing device 14 to perform the first color exposure) and outputs the data to the exposure LD control unit 52. . The LD control unit for exposure 52 is the first screen 1 from the write control IC 51.
LD 41 in the writing device 14 according to the color exposure data
a, 41b to control the first screen 1 on the photoconductor 11
By writing a color image, an electrostatic latent image for the first color of the first screen is formed.

The printer controller causes the developing motor 60 to start rotating the developing sleeve 22a of the developing device 22 for developing the first color of the first screen prior to the start of writing by the writing device 14. When the electrostatic latent image of the first color on the first screen on the photoconductor 11 reaches the developing position, the developing device 22 starts development of the electrostatic latent image to form a toner image of the first color on the first screen.

When the toner image of the first color on the first screen on the photoconductor 11 reaches the first transfer position (belt transfer position), it is transferred onto the intermediate transfer belt 13 by the belt transfer charger 20. When the scanner finishes reading the original for obtaining the image signal of the first color on the first screen, the scanner quickly returns to the home position and starts reading the original for obtaining the image signal of the next first color (black) on the second screen. Wait at home position until.

Next, the printer control unit transmits a scan start command for the first color of the second screen to the scanner control unit.
Upon receiving the scan start command for the first color of the second screen from the printer control unit, the scanner control unit
An original is read to obtain an image signal of the first color on the screen, and the read image signals of a plurality of colors (for example, red, blue, and green) are converted into an image signal of the first color on the second screen and transferred to the printer control unit. .

The printer control unit transfers the image signal transferred from the scanner control unit to the write control IC 51,
The writing control IC 51 converts the image signal into exposure data for the first color of the second screen and outputs the data to the exposure LD control unit 52. The exposure LD control unit 52 controls the lighting of the LDs 41 a and 41 b in the writing device 14 based on the exposure data of the second screen first color from the writing control IC 51, and writes the image of the second screen first color on the photoconductor 11. As a result, an electrostatic latent image of the first color of the second screen is formed.

The developing sleeve 22a of the developing device 22 for developing the first color is rotated without stopping even after the development of the first-color electrostatic latent image on the first screen is completed. are doing. When the electrostatic latent image of the first color of the second screen on the photoconductor 11 reaches the developing position, the developing device 22 starts developing the electrostatic latent image to form a toner image of the first color of the second screen.

When the first color toner image on the second screen on the photoconductor 11 reaches the first transfer position (belt transfer position), the toner image is transferred onto the intermediate transfer belt 13 by the belt transfer charger 20. When the scanner finishes reading the document for obtaining the image signal of the first color on the second screen, the scanner quickly returns to the home position and starts reading the document for obtaining the image signal of the second color (cyan) on the first screen. Wait at home position until.

When the development of the first-color electrostatic latent image on the second screen is completed, the printer control unit controls the revolver motor 61 so that the developing device 23 for developing the second color (cyan) comes to the developing position and stops. The rotating device 12 is rotated. Further, the printer control unit causes the belt cleaning device contacting / separating solenoid 66 to separate the belt cleaning device 36 from the intermediate transfer belt 13 so that the image on the intermediate transfer belt 13 is not erased.

Thereafter, the printer control unit detects that the mark sensor 33 has detected the reference mark on the intermediate transfer belt 13 and
When a mark detection signal from the mark sensor 33 is input to the interrupt terminal of the PU 47 as an intermediate transfer reference signal, an interrupt process is started and a scan start command for the second color (cyan) of the first screen is transmitted to the scanner control unit.

When the scanner control unit receives the scan start command for the second color of the first screen from the printer control unit, it causes the scanner to read the original to obtain an image signal for the second color of the first screen. The image signal is converted to an image signal of the second color of the first screen and transferred to the printer control unit.

The printer control unit transfers the image signal transferred from the scanner control unit to the writing control IC 51,
The write control IC 51 converts the image signal into exposure data for the second color of the first screen and outputs the data to the exposure LD control unit 52. The exposure LD control unit 52 controls the lighting of the LDs 41 a and 41 b in the writing device 14 based on the exposure data of the first screen second color from the writing control IC 51 to write the image of the first screen second color on the photoconductor 11. As a result, an electrostatic latent image of the second color of the first screen is formed.

The printer controller controls the rotation of the developing sleeve 23a of the developing device 23 for developing the second color by the developing motor 6
0 is started prior to the start of writing by the writing device 14. When the electrostatic latent image of the second color of the first screen on the photoreceptor 11 reaches the developing position, the developing device 23 starts developing the electrostatic latent image to obtain a toner image of the second color of the first screen.

When the second-color toner image on the first screen on the photosensitive member 11 reaches the first transfer position, the belt transfer charger 20
As a result, the toner image of the first color of the first screen is transferred onto the intermediate transfer belt 13 at the same position as the toner image of the first color of the first screen. When the scanner finishes reading the document for obtaining the image signal of the second color on the first screen, the scanner quickly returns to the home position and starts reading the document for obtaining the image signal of the second color (cyan) on the second screen. Wait at home position until.

Next, the printer control unit transmits a scan start command for the second color of the second screen to the scanner control unit.
Upon receiving the scan start command for the second color of the second screen from the printer control unit, the scanner control unit
An original is read to obtain an image signal of the second color on the screen, and the read image signals of a plurality of colors are converted into an image signal of the second color on the second screen and transferred to the printer control unit.

The printer control unit transfers the image signal transferred from the scanner control unit to the write control IC 51,
The write control IC 51 converts the image signal into exposure data for the second color of the second screen and outputs the data to the exposure LD control unit 52. The exposure LD control unit 52 controls the lighting of the LDs 41 a and 41 b in the writing device 14 based on the exposure data of the second screen second color from the writing control IC 51 to write the image of the second screen second color on the photoconductor 11. Thereby, an electrostatic latent image of the second color of the second screen is formed.

The developing sleeve 23a of the developing device 23 for developing the second color is rotated without stopping even after the development of the electrostatic latent image of the second color on the first screen is rotated. are doing. When the electrostatic latent image of the second color on the second screen on the photoconductor 11 reaches the developing position, the developing device 23 starts developing the electrostatic latent image to form a toner image of the second color on the second screen.

When the toner image of the second color on the second screen on the photosensitive member 11 reaches the first transfer position, the belt transfer charger 20
Thus, the toner image of the second color on the second screen is transferred onto the intermediate transfer belt 13 at the same position as the toner image of the first color on the second screen. Upon completion of reading the document for obtaining the image signal of the second color on the second screen, the scanner quickly returns to the home position and starts reading the document for obtaining the image signal of the next third color (magenta) on the first screen. Wait at home position until. When the development of the second-color electrostatic latent image on the second screen is completed, the printer control unit controls the revolver motor 61 so that the developing device 24 for developing the third color (magenta) comes to the developing position and stops. To rotate.

Thereafter, the printer control section detects that the mark sensor 33 has detected the reference mark on the intermediate transfer belt 13 and
When a mark detection signal is input from the mark sensor 33 to the interrupt terminal of the PU 47, an interrupt process is started and a scan start command for the third color (magenta) of the first screen is transmitted to the scanner control unit.

Upon receiving the scan start command for the third color of the first screen from the printer control unit, the scanner control unit causes the scanner to read an original to obtain an image signal for the third color of the first screen, The image signal is converted into an image signal for the third color of the first screen and transferred to the printer control unit.

The printer control unit transfers the image signal transferred from the scanner control unit to the write control IC 51,
The write control IC 51 converts the image signal into exposure data for the third color of the first screen and outputs it to the exposure LD control unit 52. The exposure LD control unit 52 controls the lighting of the LDs 41 a and 41 b in the writing device 14 based on the exposure data of the first screen third color from the writing control IC 51, and writes the first screen third color image on the photoconductor 11. As a result, an electrostatic latent image of the third color of the first screen is formed.

The printer control unit controls the rotation of the developing sleeve 24a of the developing device 24 for developing the third color by the developing motor 6
0 is started prior to the start of writing by the writing device 14. When the electrostatic latent image of the third color on the first screen on the photoconductor 11 reaches the developing position, the developing device 24 starts developing the electrostatic latent image to obtain a toner image of the third color on the first screen.

When the toner image of the third color on the first screen on the photosensitive member 11 reaches the first transfer position, the belt transfer charger 20
As a result, the first screen 1 is located at the same position as the first screen first color toner image and the first screen second color toner image on the intermediate transfer belt 13.
The toner image of the color and the toner image of the second color on the first screen are superimposed and transferred. When the scanner finishes reading the document for obtaining the image signal of the third color on the first screen, the scanner quickly returns to the home position and starts reading the document for obtaining the image signal of the next third color (magenta) on the second screen. Wait at home position until.

Next, the printer control unit transmits a scan start command for the third color of the second screen to the scanner control unit.
Upon receiving the scan start command for the third color of the second screen from the printer control unit, the scanner control unit
An original is read to obtain an image signal of the third color on the screen, the read image signals of a plurality of colors are converted into an image signal of the third color on the second screen, and transferred to the printer control unit.

The printer control unit transfers the image signal transferred from the scanner control unit to the write control IC 51,
The writing control IC 51 converts the image signal into exposure data for the third color of the second screen and outputs it to the exposure LD control unit 52. The exposure LD control unit 52 controls the lighting of the LDs 41 a and 41 b in the writing device 14 based on the exposure data of the second screen third color from the writing control IC 51, and writes the image of the second screen third color on the photoconductor 11. As a result, an electrostatic latent image of the third color of the second screen is formed.

The developing sleeve 24a of the developing device 24 for developing the third color rotates without stopping even after the development of the electrostatic latent image of the third color on the first screen, and rotates while the writing device 14 is writing. are doing. When the electrostatic latent image of the third color on the second screen on the photoconductor 11 reaches the developing position, the developing device 24 starts developing the electrostatic latent image to form a toner image of the third color on the second screen.

When the toner image of the second color on the second screen on the photosensitive member 11 reaches the first transfer position, the belt transfer charger 20
As a result, the second screen 1 is located at the same position as the second screen first color toner image and the second screen second color toner image on the intermediate transfer belt 13.
The color toner image and the second screen second color toner image are transferred in an overlapping manner.

When the scanner finishes reading the original for obtaining the image data of the third color on the second screen, the scanner quickly returns to the home position and obtains the original for obtaining the image data of the next fourth color (yellow) on the first screen. Wait at the home position until reading starts. The printer control unit has a second
When the development of the electrostatic latent image of the third color on the screen is completed, the rotating device 12 is rotated by the revolver motor 61 so that the developing device 25 for developing the fourth color (yellow) comes to the developing position and stops.

Thereafter, the printer control unit detects that the mark sensor 33 has detected the reference mark on the intermediate transfer belt 13 and
When a mark detection signal from the mark sensor 33 is input to the interrupt terminal of the PU 47 as an intermediate transfer reference signal, the process enters an interrupt process and transmits a scan start command for the first screen fourth color to the scanner control unit.

When the scanner control unit receives the scan start command for the fourth color of the first screen from the printer control unit, it causes the scanner to read the original to obtain image data for the fourth color of the first screen. The image data is converted into image data of the fourth color of the first screen and transferred to the printer control unit.

The printer control unit transfers the image data transferred from the scanner control unit to the write control IC 51, and the write control IC 51 converts the image data into exposure data for the first screen, the fourth color, and converts the image data into an exposure LD control unit. 52. The exposure LD control unit 52 controls the lighting of the LDs 41 a and 41 b in the writing device 14 based on the exposure data of the first screen fourth color from the writing control IC 51 to write the image of the first screen fourth color on the photoconductor 11. As a result, an electrostatic latent image of the fourth color of the first screen is formed.

The printer control unit controls the rotation of the developing sleeve 25 a of the developing device 25 for developing the fourth color by the developing motor 6.
0 is started prior to the start of writing by the writing device 14. When the electrostatic latent image of the first screen fourth color on the photoreceptor 11 reaches the developing position, the developing device 25 starts developing the electrostatic latent image to obtain a toner image of the first screen fourth color.

When the toner image of the fourth color on the first screen on the photosensitive member 11 reaches the first transfer position, the belt transfer charger 20
As a result, the first screen first color toner image and the first screen second color toner image are located at the same positions as the first screen first color toner image, the first screen second color toner image, and the first screen third color toner image on the intermediate transfer belt 13. The full-color image of the first screen is formed by being transferred so as to be superimposed on the toner image of the first color and the toner image of the third color on the first screen.
When the scanner finishes reading the document for obtaining the image data of the first screen fourth color, the scanner quickly returns to the home position and starts reading the document for obtaining the image data of the next second screen fourth color (yellow). Wait at home position until.

Next, the printer control unit transmits a scan start command for the fourth color of the second screen to the scanner control unit.
Upon receiving the scan start command for the fourth color of the second screen from the printer control unit, the scanner control unit
An original is read to obtain the image data of the fourth color on the screen, the read image data of a plurality of colors is converted into image data of the fourth color on the second screen, and transferred to the printer control unit.

The printer control unit transfers the image data transferred from the scanner control unit to the write control IC 51, and the write control IC 51 converts the image data into exposure data for the second color of the fourth screen, and converts the image data into an exposure LD control unit. 52. The exposure LD control unit 52 controls the lighting of the LDs 41 a and 41 b in the writing device 14 based on the exposure data of the second screen fourth color from the writing control IC 51 to write the image of the second screen fourth color on the photoconductor 11. As a result, an electrostatic latent image of the fourth color of the second screen is formed.

The developing sleeve 25a of the developing device 25 for developing the fourth color rotates without stopping after the development of the electrostatic latent image of the fourth color on the first screen. are doing. When the electrostatic latent image of the second color on the second screen on the photoconductor 11 comes to the developing position, the developing device 25 starts developing the electrostatic latent image to obtain a toner image of the second color on the second screen.

When the toner image of the fourth color on the second screen on the photosensitive member 11 reaches the first transfer position, the belt transfer charger 20
As a result, the toner image of the second color of the second screen is located at the same position as the toner image of the second color of the second screen, the toner image of the second color of the second screen, and the toner image of the third color of the second screen on the intermediate transfer belt 13. The toner image of the second color and the toner image of the third color of the second screen are transferred and superimposed to form a full-color image of the second screen.
When the scanner finishes reading the document for obtaining the image data of the second screen fourth color, the scanner quickly returns to the home position and starts reading the document for obtaining the next third screen first color (black) image data. Wait at home position until.

The printer controller completes the development of the electrostatic latent image of the fourth color on the second screen, and transfers the toner image of the fourth color on the second screen to the belt (transfer from the photoconductor 11 to the intermediate transfer belt 13).
Is completed, the full-color image on the intermediate transfer belt 13 is transferred to the paper transfer position between the intermediate transfer belt 13 and the paper transfer device 35 in order to transfer the full-color image on the intermediate transfer belt 13 to the transfer material. The transfer device 35 is turned on, and the paper transfer device 35 transfers the full-color image on the intermediate transfer belt 13 to a transfer material.

When the secondary transfer (transfer of the full-color image from the intermediate transfer belt 13 to the transfer material) of the full-color image on the first screen and the full-color image on the second screen is completed, the printer control unit determines the first color (black). The revolver motor 6 is moved so that the developing device 22 for developing comes to the developing position and stops.
1, the rotating device 12 is rotated.

The transfer of the full-color image of the first screen and the full-color image of the second screen from the intermediate transfer belt 13 to the transfer material for the first screen and the transfer material for the second screen are continued.
The transfer material for the first screen and the transfer material for the second screen to which the full-color image of the screen and the full-color image of the second screen are respectively transferred are transported to the fixing device by the transport belt 38, and the full-color image of the first screen is transferred by the fixing device. The full-color image on the second screen and the full-color image on the second screen are respectively fixed, and are discharged to a discharge tray.

When the mark sensor 33 detects a reference mark on the intermediate transfer belt 13 due to the rotation of the intermediate transfer belt 13, the printer control section inputs a mark detection signal from the mark sensor 33 to the interrupt terminal of the CPU 47 as an intermediate transfer reference signal. When this is done, the program enters an interrupt process on the program, and sends a scan start command for the first color of the third screen (black) to the scanner control unit.

When the scanner control unit receives the scan start command for the first color of the third screen from the printer control unit, the scanner control unit causes the scanner to read an original to obtain image data of the first color of the third screen. The image data is converted into image data of the first color of the third screen and transferred to the printer control unit.

The printer control unit transfers the image data transferred from the scanner control unit to the writing control IC 51, and the writing control IC 51 converts the image data into exposure data for the first color of the third screen, and converts the image data into an exposure LD control unit. 52. The exposure LD control unit 52 controls the lighting of the LDs 41 a and 41 b in the writing device 14 based on the exposure data of the third screen first color from the writing control IC 51 to write the image of the third screen first color. As a result, an electrostatic latent image of the first color of the third screen is formed.

Hereinafter, the steps from the development of the electrostatic latent image of the first color of the third screen to the transfer of the toner image of the fourth color of the fourth screen to the belt are described above. The process is performed in the same manner as the process up to the belt transfer of the fourth color toner image on the screen. Thereafter, similarly to the formation of the full-color image of the first screen and the full-color image of the second screen, the formation of the full-color image of the third screen and the full-color image of the fourth screen are performed.

When the development of the electrostatic latent image of the fourth color on the fourth screen is completed and the belt transfer of the toner image of the fourth color on the fourth screen is completed, the printer control unit transfers the full-color image on the intermediate transfer belt 13 to the transfer material. The full color image on the intermediate transfer belt 13 is transferred to the intermediate transfer belt 13 and the paper transfer device 3
5 immediately before reaching the paper transfer position between
Is turned on, and the paper transfer device 35 transfers the full-color image on the intermediate transfer belt 13 to a transfer material.

Thereafter, the printer control unit turns on the solenoid 66 for contacting and separating the belt cleaning device to bring the belt cleaning device 36 into contact with the intermediate transfer belt 13, thereby causing the belt cleaning device 36 to start cleaning the intermediate transfer belt 13.

When the secondary transfer of the full-color image on the third screen and the full-color image on the fourth screen is completed, the printer control unit stops the developing device 22 for developing the first color (black) at the developing position. Then, the rotating device 12 is rotated by the revolver motor 61. After that, the printer control unit
By turning off the solenoid 66 for contacting and separating the belt cleaning device, the belt cleaning device 36 is moved to the intermediate transfer belt 13.
Away from Further, the printer control unit controls the drum motor 59 to control the stop position of the intermediate transfer belt 13, and thereafter, this embodiment is in a standby state.

In this embodiment, two reference marks on the intermediate transfer belt 13 may be provided at predetermined intervals (for example, equal intervals) in the rotation direction of the intermediate transfer belt 13. In this case, the printer control unit transmits a scan start command to the scanner control unit for each color on the basis of the time when the first reference mark on the intermediate transfer belt 13 is detected by the mark sensor 33. An original is read to obtain image data, and a full-color image of one screen to be formed first among two full-color images on the intermediate transfer belt 13 is formed, and a second reference mark on the intermediate transfer belt 13 is formed. By transmitting a scan start command to the scanner control unit on the basis of the time of detection by the mark sensor 33, the scanner is caused to read a document for obtaining image data of another one screen, and the two screens on the intermediate transfer belt 13 are scanned. Control is performed so that a full-color image of one screen to be formed later among the full-color images is formed.

Next, the motor control section 62, which is a main part of the present invention, will be described with reference to FIG. In the control unit 62,
Phase detector 61, correction amount calculator 60, motor driver 5
9 are provided. The phase comparison circuit 64 in the phase detector 61 receives the synchronization detection signal 58 of the leading beam from the synchronization detector of the writing device 14 and the belt mark signal 57 from the mark sensor 33 as an intermediate transfer reference signal. And the phases are compared. The counter 63 is cleared by the synchronization detection signal 58 and counts up a clock from an internal clock generator (not shown), and outputs the count value to the phase comparison circuit 64.

The phase comparison circuit 64 outputs the belt mark signal 57
It operates when the belt mark signal 57 is input in order to compare the phase with the synchronization detection signal 58. When the synchronization detection signal 58 is input, the count value of the counter 63 (immediately before the reset by the synchronization detection signal 58) Count value)
And outputs this value to the correction operation unit 60 as the phase difference between the belt mark signal 57 and the synchronization detection signal 58.

Here, the photosensitive member 11 and the intermediate transfer belt 13
5 are driven mechanically, that is, connected by a timing belt 40 as shown in FIG. 5 and driven by a common drum motor 59 (hereinafter referred to as a motor M), the respective rotational relative positions do not deviate. 11 may be installed. Also, the photoconductor 11 and the intermediate transfer belt 13
Are independently driven, the photoconductor 11 rotates at a constant speed, an intermediate transfer motor M whose position is controllable is provided on the intermediate transfer belt 13, and a mark is provided on the intermediate transfer belt 13. A sensor 33 is provided.

The correction calculation section 60 calculates the amount of phase shift from the above count value, and further converts the phase shift into a distance.
The amount of shift to the intermediate transfer motor M (position correction amount). Phase shift amount = total count value of the synchronization interval (fixed value) / count value Shift amount = (1−phase shift amount) * (movement distance in the sub-scanning direction at synchronization interval time (ta)) = Δt1 / ta * (Moving distance in the sub-scanning direction at the time (ta) of the synchronization interval) Next, the obtained shift amount is sent to the motor drive unit 59 and added to the target position by the adder 101. The target position is given by a CPU (not shown). The addition result of the adder 101 is applied to the motor M via the gain adjusting unit 102 and the servo amplifier 104 to control the target position of the motor M. Vessel 1
05, the current position is detected, the speed is calculated by the differentiating circuit 106, and this speed is subtracted from the output of the gain adjustment unit 102 by the adder 103 to form a speed control loop, and the position is calculated by the position sensor 107. This position is subtracted from the target position by the adder 101 to form a position control loop.

Here, the motor drive section 59 has an analog servo configuration, and the shift amount calculated by the correction operation section 60 is DA-converted and input as an analog signal. If it is a system, it will be input as a digital value. (Actually, the minimum control resolution count number of the motor M is sent from the distance.) By inputting the shift amount, the rotational position is apparently delayed by the shift amount (position correction amount).

The mechanical position of the mark sensor 33 is smaller than the distance (L1) from the beam irradiation position on the photosensitive member 11 to the transfer position in FIG. The distance from the position to the mark detection position is set to be longer by L2, and in this example, L2 = about 60 m
m. That is, the belt mark signal 57
Is output, and after the synchronization detection signal 58 is input, a writing operation is started after a lapse of L2. In this example, the linear speed of the intermediate transfer belt 11 is about 200 mm /
s, this time is t0 = 60/200 =
Writing starts after 0.3 s. (The belt mark signal is detected immediately after the transfer of the previous color is completed.) That is, after detecting the belt mark signal 57, the shift amount is calculated, and within the time until the start of writing the next color (this example) Then, the shift amount is input to the transfer motor M within about 0.3 sec, and if the rotation is stabilized, the position correction is completed by the time of writing the next color. The transferred image on the intermediate transfer belt 13 and the toner image on the photosensitive member of the next color, which have been subjected to the above-described position correction, are not shifted by one line at the time of transfer and remain at the same position. Transcribed.

In the case of this example, since it is an example of two beams,
The maximum value of the shift amount (position correction amount) is a maximum of two lines (42.3 μm * 2 = 8 in the case of 600 dpi).
4.6 μm). If the number of beams increases, a shift amount (position correction amount) corresponding to the number of beams is required. However, by setting the shift amount to be equal to or less than the maximum correction amount, the motor for inputting the shift amount is required. The load on M can be minimized.

[0092]

As described above, according to the first aspect of the present invention, the position shift of the image in the sub-scanning direction is detected based on the phase difference between the synchronization detection signal and the reference mark signal, and the position shift is detected. Since the rotation target position of the motor for rotating the photosensitive member and / or the intermediate transfer member is controlled so as to make correction, it is possible to prevent the image from being displaced without switching the beam writing order. Further, since the displacement can be prevented without switching the writing order of the two beams, the coloring of the gray between the copies can be prevented at the same time.

According to the second aspect of the present invention, since the rotation target position of the motor can be controlled by the speed control loop and the position control loop, the displacement of the image can be accurately prevented.

According to the third aspect of the invention, the external circuit configuration is simplified, and the cost can be reduced.

According to the fourth aspect of the present invention, the motor control is completed between the end of the transfer of the effective image area of the previous color and the start of the transfer of the effective transfer area of the next color. It is possible to prevent displacement of a plurality of beams without finding an image of the area.

According to the fifth aspect of the present invention, since the correction amount is equal to or less than the distance corresponding to the number of beams in the sub-scanning direction on the photosensitive member, the load fluctuation on the motor can be reduced as much as possible, and the image is adversely affected. Can be prevented.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a color printer of an embodiment of a color image forming apparatus according to the present invention.

FIG. 2 is a configuration diagram illustrating the writing device of FIG. 1;

FIG. 3 is a block diagram showing a control system.

FIG. 4 is a block diagram showing a motor control unit which is a main part of the color image forming apparatus according to the present invention.

FIG. 5 is a configuration diagram showing in detail a driving mechanism of a photoconductor and an intermediate transfer belt of FIG. 1;

FIG. 6 is an explanatory diagram showing a position shift due to rotation asynchronous between the optical deflector and the photosensitive member.

FIG. 7 is an explanatory diagram showing a position shift due to rotation asynchronous between the optical deflector and the photosensitive member.

FIG. 8 is an explanatory diagram showing conventional displacement correction.

FIG. 9 is an explanatory diagram showing a color shift due to a position shift.

[Explanation of symbols]

 REFERENCE SIGNS LIST 11 photoconductor 13 intermediate transfer belt 33 mark sensor 59 motor drive unit 60 correction amount calculation unit 61 phase detection unit M motor

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 1/113 H04N 1/04 104A F-term (Reference) 2C362 BA52 BA56 BA66 BA71 BB32 BB34 BB46 BB47 BB50 CA22 CA23 CA38 CB59 CB80 2H027 DA02 DA10 DA21 DE02 DE07 ED06 EE03 EE04 EE06 ZA07 2H030 AA01 AD17 BB02 BB16 BB24 BB42 BB56 5C072 AA03 BA19 HA02 HA06 HA13 HB08 HB13 HB15 QA14 QA17 RA20 UA14 XA01 X05

Claims (5)

[Claims] 1. A plurality of beams are simultaneously deflected by a common deflector to form a plurality of lines of images on a photoreceptor, and toner images of respective colors formed on the photoreceptor are superimposed on an intermediate transfer member. A synchronous detection sensor for detecting a leading beam deflected by the deflector and outputting a synchronous detection signal; and a method for superimposing toner images of respective colors on the intermediate transfer body. A mark sensor for detecting a reference mark serving as a reference for positioning, a motor for rotating the photosensitive member and / or the intermediate transfer member, a synchronization detection signal detected by the synchronization detection sensor, and the mark sensor A motor control means for detecting a displacement in the sub-scanning direction of the toner image of each color based on the detected phase difference of the reference mark signal, and controlling a rotation target position of the motor so as to correct the displacement. Color image forming apparatus comprising the and. 2. The color image forming apparatus according to claim 1, wherein the rotation target position of the motor can be controlled by a speed control loop and a position control loop. 3. A circuit for driving the motor, comprising: a phase difference detection circuit for detecting the phase difference; and a circuit for calculating a correction amount based on the phase difference. 3. The color image forming apparatus according to 1 or 2. 4. The motor control according to claim 1, wherein the motor control is completed after the transfer of the effective image area of the previous color is completed and before the transfer of the effective transfer area of the next color is started. A color image forming apparatus according to any one of the preceding claims. 5. The color image forming apparatus according to claim 1, wherein the correction amount is equal to or less than a distance corresponding to the number of beams in the sub-scanning direction on the photoconductor.