JPH1138738A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a color image free from color shear between images of different colors by aligning the image draw start position of each color image accurately. SOLUTION: A beam of light based upon the fed image information is deflected, and therewith a polygon mirror 103 scans a photoreceptor drum 105 which is rotated by a photoreceptor drum motor 115, and the scanning beam from the polygon mirror 103 is sensed by a BD sensor 107 to generate a scan start reference signal (BD signal) for each line having the same period, the BD signal, which is divided by a frequency dividing circuit 119 by the specified frequency dividing proportion so that the drum 105 makes one turn accurately while a certain integer number of BD signals is generated, generates a reference CLK which are driving pulses for the drum motor 115, and a PLL circuit 118 makes drive control of the motor 115 on the basis of the reference CLK for the motor 115.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for developing an electrostatic latent image based on each color image on an image carrier and superimposing and transferring the color image on a recording medium to form a color image. .

[0002]

2. Description of the Related Art Conventionally, a color image forming apparatus which prints out color image data, for example, a laser beam printer (LBP), scans a photosensitive member with a rotating polyhedron by scanning a laser irradiation light on the photosensitive member. A latent image for each line is formed on the line, and the latent image is formed into an image for each color element using a developer for a color element such as magenta (M), cyan (C), yellow (Y), black (BK), or the like. Then, a color image is formed by superimposing and transferring the image of each color element onto a sheet fixed on a transfer drum.

There has also been an image forming apparatus in which an image for each color element formed on a photoreceptor is temporarily overlaid on an intermediate transfer member, and the color images on the intermediate transfer member are collectively transferred to paper. .

In these conventional image forming apparatuses, the photosensitive member and the transfer drum or the intermediate transfer member are driven at a constant speed in a direction (sub-scan direction) orthogonal to the main scanning direction, and the transfer drum and the intermediate transfer member make one rotation. Each time, one color is overlaid on the paper on the transfer drum or the intermediate transfer body. There is also an image forming apparatus that forms an image for each recording color element on a photoconductor in a superimposed manner and collectively transfers the image to recording paper.

In the above-described conventional color image forming apparatus, there is a problem that the image quality of the color image is degraded due to the shift of the superposition position of each color image. In order to prevent the shift of the superposition position of each color image, each color image is superimposed. The method of controlling the position at the time was important.

[0006]

However, in the above-mentioned conventional color image forming apparatus, the main scanning drive for driving the main scanning means such as a rotating polyhedron and the sub-scanning driving for driving the photoreceptor, the intermediate transfer body and the transfer drum are required. Are often independent,
For this reason, the main scanning recording position (that is, the image writing position of each color image) on the photoconductor where the rotating polyhedron is laser-scanned at the start of recording each color image is not guaranteed, and as a result, the color of the maximum main scanning one line in the sub scanning direction is There has been a problem that displacement occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the first and second inventions according to the present invention is to detect a light beam scanned by a rotating polyhedron. The first pulse signal is frequency-divided at a predetermined frequency division ratio such that the image carrier makes one rotation without excess or decrement while the generated first pulse signal is generated by a predetermined integer. By generating a second pulse signal as a drive pulse and controlling the drive of the image carrier based on the second pulse signal, the image writing position of each color image is accurately adjusted, and An object of the present invention is to provide an image forming apparatus that forms a color image with no color shift between them.

[0008]

According to a first aspect of the present invention, there is provided an image carrier (photosensitive drum 105 shown in FIG. 2) for holding an electrostatic latent image, and a predetermined transmission of the image carrier. Drive means (photosensitive drum motor 115 shown in FIG. 2) which is driven to rotate via means (a gear belt 116 shown in FIG. 2), and a light beam based on input image information is deflected and driven to rotate by the drive means. A rotating polyhedron (polygon mirror 103 shown in FIG. 2) for scanning on the image carrier and a light beam scanned by the rotating polyhedron are detected to generate a first pulse signal (BD signal shown in FIG. 2). First pulse generating means (BD sensor 107 shown in FIG. 2), a first pulse generating means for detecting a light beam by scanning the rotating polyhedron and generating a pulse signal, and the first pulse signal A predetermined integer (shown in FIG. 6) During the generation of 8192 BD signals), the first pulse signal is frequency-divided at a predetermined frequency division ratio (１ ／) so that the image carrier makes one rotation without excess or shortage. A second pulse signal which is a driving pulse (FIG. 2
Second pulse generating means for generating a reference CLK of the photosensitive drum motor 115 shown in FIG. 2 (frequency dividing circuit 119 shown in FIG. 2)
And control means (PLL circuit 118 shown in FIG. 2) for controlling the driving of the driving means based on the second pulse signal.

According to a second aspect of the present invention, the transmission means (the gear belt 116 shown in FIG. 2) is configured such that the driving means (the photosensitive drum motor 115 shown in FIG. 2) rotates a predetermined integer number of times (the drum motor shown in FIG. 6). The drive of the driving means is transmitted to the image carrier (the photosensitive drum 105 shown in FIG. 2) so that the image carrier makes one full rotation during 64 rotations.

[0010]

FIG. 1 is a sectional view illustrating the structure of an image forming apparatus according to an embodiment of the present invention.

In FIG. 1, reference numeral 201 denotes an image scanner which reads a document and performs digital signal processing. 200
A printer unit prints a full-color image of a document read by the image scanner unit 201 or an image based on image data transferred from an external device such as a computer (not shown) on recording paper.

In the image scanner unit 201, 20
An original pressing plate 2 presses the original 204 on the original platen glass 203 onto the original platen glass 203. Reference numeral 205 denotes a halogen lamp which irradiates a document 204 on a document table glass 203 with light.

Reference numeral 210 denotes a three-line sensor (hereinafter, CCD)
And a red (R) sensor 210-1, a green (G) sensor 210-2, and a blue (B) sensor 210-3.
7. Lens 208 with far-infrared cut filter 231
The optical information formed on the CCD through the CCD is color-separated to read the red (R), green (G), and blue (B) components of the full-color information. 209 is a signal processing unit;
The R, G, B signals read by the G, B sensors 210-1 to 210-3 are electrically processed, and magenta (M),
It is decomposed into cyan (C), yellow (Y), and black (BK) components and sent to the printer unit 200.

Reference numeral 211 denotes a standard white plate which reads reflected light from the standard white plate 211 by R, G, B sensors 210-1 to 210-3 and generates data correction data. The standard white plate 211 has substantially uniform reflection characteristics from visible light to infrared light, and has white color when visible. Using this standard white plate, R, G, B sensors 210-1 to 210-210
The correction of the output data of the visible sensor of -3 is performed. 230 is an optical sensor, together with the flag plate 229, an image tip signal VT.
Create an OP.

In the printer unit 200, reference numeral 101 denotes an image writing timing control circuit.
01 or a semiconductor laser 10 based on magenta (M), cyan (C), yellow (Y), and black (BK) image signals input from an external device such as a computer (not shown).
2 is modulated. Reference numeral 103 denotes a polygon mirror, which is rotationally driven by a polygon motor 106.
2 reflects the laser light emitted from the
4, via the folding mirror 216, the photosensitive drum 105
Scan above.

The photosensitive drum 105 includes a polygon mirror 10
6 holds an electrostatic latent image formed on the photosensitive drum 105 by laser scanning. A BD sensor 107 is provided near a scanning start position of one line of laser light, detects line scanning of laser light, and generates a scanning start reference signal (BD signal) of each line in the same cycle.

219 is a magenta (M) developing device, 220 is a cyan (C) developing device, 221 is a yellow (Y) developing device,
A black (BK) developing unit 222 develops the electrostatic latent image on the photosensitive drum 105 to form a toner image. A transfer drum 108 sucks and conveys a recording sheet 109 fed from a sheet cassette 224 or 225, and transfers a toner image formed on the photosensitive drum 105 to the recording sheet 109.
Transfer to

Reference numeral 110 denotes a sensor which is provided in the transfer drum 108, and which rotates the transfer drum 108 when the transfer drum 108 rotates.
When the passage of the flag 111 fixed in 08 is detected, an ITOP signal for each color (representing the leading end position of the recording sheet adsorbed on the transfer drum 108) is generated. A fixing unit 226 fixes the toner image transferred onto the recording paper by the transfer drum 108.

The operation of each section will be described below.

The original 204 on the original platen glass 203 is irradiated with light from a halogen lamp 205, and the reflected light from the original 204 is guided to mirrors 206 and 207, and a lens 208
Forms an image on the CCD 210. Next, the CCD 210
Scans the light information from the document 204 to read full-color information red (R), green (G), and blue (B) components, and sends them to the signal processing unit 209. Note that the halogen lamp 205 and the mirror 206 operate at the speed “v”,
Reference numeral 7 scans the entire surface of the document by mechanically moving the line sensor at a speed "v / 2" in a direction perpendicular to the electrical scanning direction (hereinafter, main scanning direction) of the line sensor (hereinafter, sub-scanning direction).

Further, using the standard white plate 211, R, G,
The output data is corrected by the visible sensors of the B sensors 210-1 to 210-3. Further, the optical sensor 230 generates the image leading edge signal VTOP together with the flag plate 229. The signal processing unit 209 electrically processes the read R, G, and B signals to separate them into magenta (M), cyan (C), yellow (Y), and black (BK) components. Send to

It should be noted that M, C, Y, and BK per one scan of a document in the image scanner unit 201.
Are sent to the printer 200, and one printout is completed by a total of four document scans.

An image signal sent from an external device such as the image scanner unit 201 or a computer (not shown) is sent to the image writing timing control circuit 101. The image writing timing control circuit 101 includes magenta (M), cyan (C), yellow (Y), and black (B
The semiconductor laser 102 is modulated and driven according to the image signal K). The laser light emitted from the semiconductor laser 102 is reflected by the rotating polygon mirror 103, fθ-corrected by the f-θ lens 104, reflected by the return mirror 216, and scans the photosensitive drum 105 to scan the photosensitive drum 1.
05, an electrostatic latent image is formed.

Further, while the photosensitive drum 105 rotates four times, the four developing devices 219 to 222 are alternately operated.
5, M, C, and C formed on the photosensitive drum 105.
Develop with toner corresponding to the electrostatic latent images of Y and BK. Recording paper 10 fed from paper cassette 224 or 225
9 is wound around the transfer drum 108, and after the four colors of M, C, Y, and BK of the toner image developed by the developing device are sequentially transferred, the recording paper 109 is discharged through the fixing unit 226. .

FIG. 2 is a diagram for explaining the configuration of the printer unit 200 of the image forming apparatus shown in FIG. 1. The same components as those in FIG. 1 are denoted by the same reference numerals.

In the figure, reference numeral 112 denotes an oscillator which outputs a clock having a predetermined frequency. A frequency dividing circuit 113 divides a clock output from the oscillator 112 by a predetermined frequency dividing ratio and transmits a polygon motor driving pulse (reference CLK-P). Reference numeral 114 denotes a PLL circuit which controls the polygon motor 10
FG pulse output along with rotation of No. 6 and reference C
The FG pulse and the reference CLK are adjusted so that the phase of LK-P matches.
−P which detects the phase difference and frequency deviation of −P, compares them, and controls the drive voltage to the polygon motor 106.
L control is performed.

Reference numeral 121 denotes an oscillator which outputs a clock having a predetermined frequency. A laser lighting signal generation circuit 120 inputs a clock from the oscillator 121 and a BD signal from the BD sensor 107, and outputs a laser lighting signal for detecting a BD signal. An OR gate 117 outputs a logical sum of an image signal from the image writing timing control circuit 101 and a laser lighting signal for detecting a BD signal from the laser lighting signal generation circuit 120 to the semiconductor laser 102, and modulates and drives the semiconductor laser 102. I do. A frequency dividing circuit 119 divides the laser lighting signal for BD signal detection from the laser lighting signal generating circuit 120 by a predetermined frequency dividing ratio and transmits a photosensitive drum motor driving pulse (reference CLK). Reference numeral 118 denotes a PLL circuit that adjusts the phase of the motor FG pulse output with the rotation of the photosensitive drum motor 115 to the reference CLK.
A phase difference and a frequency deviation between the FG pulse and the reference CLK are detected, and a PLL control for controlling a driving voltage to the photosensitive drum motor 115 is performed by comparing them.

The operation of each section will be described below.

An image signal transferred from the image scanner unit 201 shown in FIG. 1 or an external device such as a computer (not shown) is sent to the image writing timing control circuit 101, and the image writing timing control circuit 101 performs an OR operation.
Through the gate 117, magenta (M), cyan (C),
According to the yellow (Y) and black (BK) image signals,
The semiconductor laser 102 is modulated and driven. The laser light is reflected by the rotating polygon mirror 103, and the f-θ lens 10
4 is fθ-corrected, and the return mirror 216 (FIG. 1)
, And scans the photosensitive drum 105,
An electrostatic latent image is formed on the photosensitive drum 105.

The polygon motor 106 is driven to rotate by a polygon motor driving pulse (reference CLK-P) generated by dividing the clock of the oscillator 112 by the frequency dividing circuit 113 to the PLL circuit 114. . The PLL circuit 114 detects a phase difference and a frequency deviation between the FG pulse and the reference CLK-P so that the phase of the motor FG pulse from the polygon motor 106 matches the phase of the reference CLK-P, compares them, and compares them. PLL control for controlling the drive voltage to the controller is performed.

The BD sensor 107 is provided in the vicinity of the scanning start position of one line of the laser beam, detects the scanning of the line of the laser beam, and detects the scanning start reference signal (BD) of each line of the same cycle as shown in FIG. Signal).

The sensor 110 in the transfer drum 108
Is detected by detecting the flag 111 fixed in the transfer drum 108 by the rotation of the transfer drum 108, and an ITOP signal for each color (a signal indicating the leading end position of the recording paper 109 on the transfer drum 108) as shown in FIG. ).

Further, the photosensitive drum motor 115 sends to the PLL circuit 118 a motor driving pulse (reference CLK) obtained by dividing the laser lighting signal for BD signal detection from the laser lighting signal generating circuit 120 by the frequency dividing circuit 119. Is driven to rotate.

The PLL circuit 118 includes the photosensitive drum motor 1
The phase difference between the FG pulse and the reference CLK and the frequency deviation are detected so that the phase of the motor FG pulse from the reference 15 and the phase of the reference CLK match, and they are compared with each other to detect the photosensitive drum motor 11.
PLL control for controlling the drive voltage to 5 is performed. The photosensitive drum 105 is rotationally driven by a photosensitive drum motor 115 via a gear belt 116 in a direction indicated by an arrow. (Sub-scan)
It is driven to rotate in the direction. The BD signal and the ITOP signal are input to the image writing timing control circuit 101, and send the image signal to the semiconductor laser 102 at the following timing, for example. That is, after detecting the rising edge of the ITOP signal, the image signal is radiated on the photosensitive drum 105 as laser-modulated light in synchronization with the rising edge of the n-th BD signal, as shown in FIG.

FIG. 3 is a timing chart showing the image forming timing of the printer section 200 of the image forming apparatus shown in FIG.

In the figure, an ITOP signal is a recording sheet on the transfer drum 108 which is output when a sensor 110 in the transfer drum 108 detects a flag 111 fixed in the transfer drum 108 by rotation of the transfer drum 108. A signal representing the position of the front end 109 is output for each color.

The BD signal is a scanning start reference signal for each line of the same cycle, which is output when the BD sensor 107 provided near the scanning start position of one line of the laser light detects the line scanning of the laser light. It is.

As for the image signal, the BD signal and the ITOP signal are input to the image writing timing control circuit 101, and, for example, the nth B signal after detecting the rise of the ITOP signal is detected.
The signal is sent to the semiconductor laser 102 via the OR gate in synchronization with the rise of the D signal. That is, the image signal is emitted as laser modulated light onto the photosensitive drum 105 in synchronization with the rise of the “n” th BD signal after detecting the rise of the ITOP signal.

In order to detect a BD signal, the BD signal
The laser must be turned on until a signal is detected. However, if the laser is turned on at all times, the laser light scans in the image forming area on the photosensitive drum 105 together with the problem of the life of the laser. Problems arise. Since the period of the BD signal is known in advance from the rotation speed of the polygon motor and the number of surfaces of the polygon mirror, the period “t0 + α” is longer by “α” than the period “t0” of the BD signal, as shown in FIG. The laser lighting signal is sent from the laser lighting signal generation circuit 120 to the semiconductor laser 102 through the OR gate 117.

When the laser beam scans the BD sensor 107 at the laser lighting timing, that is, when the BD signal is detected, the cycle of the laser lighting signal is changed to the same cycle "t0" as the cycle of the BD signal. Since the photosensitive drum motor 115 is rotationally driven by a reference clock obtained by dividing the laser lighting signal, the laser does not always scan the same place, and the deterioration of the photosensitive drum 105 can be prevented.

FIG. 4 is a block diagram for explaining the configuration of the laser lighting signal generation circuit 120 shown in FIG. 2, and the same components as those in FIG. 2 are denoted by the same reference numerals.

In the figure, reference numeral 131 denotes a 13-bit down counter which counts the clock of the oscillator 121 and
The period “t0” longer by “α” than the period “t0” of the D signal
After + α ”, a ripple carry (RC) is output. Therefore, for example, 5000 corresponding to “t0 + α” in the number of clocks of the oscillator 121 is input as a preset value of the down counter 131. 133 is a 12-bit up counter for counting the clock of the oscillator 121. A comparator 134 generates a laser lighting signal such as “H (laser lighting)” when the count value of the up counter 133 is 100 or less, and “L (laser turning off)” after 101.

The down counter 131 is cleared by the BD signal from the BD sensor 107, and the up counter 133 is cleared by the RC output from the down counter 131 or the BD signal from the BD sensor 107 through the OR gate 132. Therefore, once the BD signal is input, the down counter 131 outputs B
Since the signal is cleared by the D signal, as shown in FIG. 5 described later, a laser lighting signal having a period “t0” of the BD signal is output thereafter.

FIG. 5 is a timing chart showing a laser lighting signal output timing by the laser lighting signal generation circuit 120 shown in FIG.

In the figure, the laser lighting signal has a period “t0 + α” longer by “α” than the period “t0” of the BD signal.
From the laser lighting signal generation circuit 120 to the OR gate 117
Is transmitted to the semiconductor laser 102 via the.

When the laser beam scans the BD sensor 107 at the time of laser lighting, that is, when a BD signal is transmitted, the laser lighting signal generation circuit 120 sets the cycle of the laser lighting signal to the same cycle as the cycle of the BD signal. Change to “t0”.

Here, the reference clock of the photosensitive drum motor 115 is generated by dividing the laser lighting signal generated by the laser lighting signal generation circuit 120 by the frequency divider 119. “t0” changes from “t0 + α” to “t0”, and the switched cycle “t0”
It is necessary to consider the convergence time until the speed stabilizes, such that image writing cannot be performed until the speed stabilizes.

However, since the fluctuation amount of the cycle of the reference clock before and after the switching is always constant, the convergence time is also always constant, so that it is easy to consider this convergence time.

FIG. 6 is a view for explaining the configuration of the printer unit 200 of the image forming apparatus shown in FIG. 2. In particular, the photosensitive drum motor 115 when the photosensitive drum 105 makes one rotation.
And the relationship between BD signals. The same components as those in FIG. 2 are denoted by the same reference numerals.

The photosensitive drum 10 is moved so that the scanning line of the laser on the photosensitive drum 105 is always at the same position for each rotation.
The number of BD signals output during one rotation of the photosensitive drum determined from the process speed and the resolution is, for example, configured to output an integer number of BD signals during one rotation of the photosensitive drum 5. Is “8192” (that is, the rotation speed of the polygon mirror 103 is “1024”).

The gear ratio of the gear belt 116 (“1:64”) is such that the photosensitive drum motor 115 rotates “64” for one rotation of the photosensitive drum 105.
Further, the photosensitive drum motor 115 has a FG per rotation.
Since the number of pulses is configured to output “32” pulses, the reference CLK of the photosensitive drum motor 115 needs “32” pulses for one rotation of the photosensitive drum motor 115.

Therefore, in order for the photosensitive drum 105 to make one rotation, the reference CLK of the photosensitive drum motor 115 is set to “64”.
(Rotation) × 32 (pulse) = 2048 (pulse) ”. Therefore, the laser lighting signal output from the laser lighting signal generation circuit 120 which is equivalent to the BD signal is set to “2”.
048/8192 = 1/4 "and used as the reference CLK for the photosensitive drum motor 115, so that every time" 8192 "BD signals are output, the photosensitive drum 10
5 makes one rotation.

That is, the dividing ratio is “n”, and the photosensitive drum 105
Is the number of rotations of the photosensitive drum motor 115 per rotation of “N”, and FG per rotation of the photosensitive drum motor 115 is
Assuming that the number of pulses is “X” and the number of BD signals per rotation of the photosensitive drum 105 is “M”, the relationship “n = N × X / M” is established.

The gear ratio of the gear belt 116 is configured to be a natural number, and this is
By rotating the motor and the reduction gear by an integer during one rotation of 5, the influence of the eccentricity of the motor shaft and the reduction gear for each rotation of the photosensitive drum 105 is always the same (constant), and the color shift due to these eccentricities is zero. In order to

As a result, on the photosensitive drum 105, the scanning line of the first scan of the second rotation overlaps with the scanning line of the laser beam written based on the BD signal of the first scan of the first rotation. , The first rotation, the second
The scanning lines of the first scan of the rotation are overlapped.

Therefore, as shown in FIG.
The phase difference between the signal and the BD signal is always constant for each color ("T
0 "), so that if image writing is started based on ITOP, the writing positions of the images from the first color to the Nth color can be accurately adjusted, and a high-quality image without color shift can be obtained. Can be.

With the simple configuration as described above, the writing start position of each image on the paper is matched with the position of the first color, and a high-quality image without color shift can be obtained.

Further, since the photosensitive drum motor 115, the reduction gear and the reduction gear belt 116 for transmitting the drive to the photosensitive drum 105 always return to the same position each time the photosensitive drum 105 makes one rotation, the photosensitive drum is rotated. Drum 1
The influence of the eccentricity of the motor shaft and the reduction gear for each rotation of 05 is always the same (constant), and the color shift due to these eccentricities can be made zero.

As described above, the storage medium storing the program codes of the software for realizing the functions of the above-described embodiments is supplied to the system or the apparatus, and the computer (or the CPU or the MP) of the system or the apparatus is supplied.
It goes without saying that the object of the present invention is also achieved when U) reads out and executes the program code stored in the storage medium.

In this case, the program code itself read from the storage medium realizes the novel function of the present invention, and the storage medium storing the program code constitutes the present invention.

As a storage medium for supplying the program code, for example, a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM, C
DR, magnetic tape, nonvolatile memory card, RO
M, EEPROM and the like can be used.

When the computer executes the readout program code, not only the functions of the above-described embodiment are realized, but also the OS (Operating System) running on the computer based on the instruction of the program code. ) And the like perform part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, based on the instructions of the program code, The CPU provided in the function expansion board or function expansion unit performs part or all of the actual processing,
It goes without saying that a case where the function of the above-described embodiment is realized by the processing is also included.

The present invention may be applied to a system constituted by a plurality of devices or to an apparatus constituted by a single device. Needless to say, the present invention can be applied to a case where the present invention is achieved by supplying a program to a system or an apparatus. In this case, by reading a storage medium storing a program represented by software for achieving the present invention into the system or the apparatus, the system or the apparatus can enjoy the effects of the present invention. .

Further, by downloading and reading a program represented by software for achieving the present invention from a database on a network by a communication program, the system or apparatus can be
It is possible to enjoy the effects of the present invention.

[0066]

As described above, the first embodiment according to the present invention is described.
According to the invention, the rotating polyhedron scans the image carrier that is rotated and driven by the driving unit by deflecting the light beam based on the input image information, and scans the light beam scanned by the rotating polyhedron. Upon detection, the first pulse generating means generates a first pulse signal, and the image carrier makes one rotation without excess or shortage while the first pulse generating means generates the first pulse signal for a predetermined integer. As described above, the first pulse signal is frequency-divided at a predetermined frequency division ratio, and the second pulse generating means generates a second pulse signal which is a driving pulse of the driving means,
Since the control means drives and controls the driving means based on the second pulse signal generated by the second pulse generation means, the scanning start position by the rotating polyhedron can be accurately determined for each rotation of the image carrier with a simple structure. It becomes possible to match.

According to the second aspect, the transmission means controls the driving of the image carrier so that the image carrier makes one full rotation while the driving means rotates a predetermined integer. Therefore, the driving means and the transmitting means always return to the same position every time the image carrier rotates, and the effect of the eccentricity of the driving means and the transmitting means every time the image carrier rotates can be made constant.

Therefore, there is an effect that a color image without color shift can be formed between the respective color images by accurately aligning the image writing positions of the respective color images.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of an image forming apparatus according to an exemplary embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of a printer unit of the image forming apparatus illustrated in FIG.

FIG. 3 is a timing chart illustrating image forming timing of a printer unit of the image forming apparatus illustrated in FIG. 1;

FIG. 4 is a block diagram illustrating a configuration of a laser lighting signal generation circuit illustrated in FIG. 2;

FIG. 5 is a timing chart showing a laser lighting signal output timing by the laser lighting signal generation circuit shown in FIG. 4;

6 is a diagram illustrating a configuration of a printer unit of the image forming apparatus illustrated in FIG.

[Explanation of symbols]

 Reference Signs List 102 semiconductor laser 103 polygon mirror 104 f-θ lens 105 photosensitive drum 106 polygon motor 110 sensor 111 flag 112 oscillator 113 frequency dividing circuit 114 PLL circuit 115 photosensitive drum motor 116 gear belt 117 BD sensor 118 PLL circuit 119 frequency dividing circuit 121 oscillator

Claims (2)

[Claims] An image carrier that holds an electrostatic latent image; a driving unit that rotationally drives the image carrier via a predetermined transmission unit; and a light beam that deflects a light beam based on input image information. A rotating polyhedron that scans the image carrier that is rotationally driven by the driving means; and a first pulse generating means that detects a light beam scanned by the rotating polyhedron and generates a first pulse signal; While the first pulse signal is generated by a predetermined integer, the first pulse signal is frequency-divided at a predetermined frequency division ratio so that the image carrier makes one rotation without excess or shortage. An image forming apparatus comprising: a second pulse generating unit that generates a second pulse signal that is a driving pulse; and a control unit that controls driving of the driving unit based on the second pulse signal. 2. The image forming apparatus according to claim 1, wherein the transmitting unit transmits the drive of the driving unit to the image carrier such that the image carrier makes one full rotation while the driving unit rotates a predetermined integer. The image forming apparatus according to claim 1.