JP2000094739A - Image-forming apparatus and method for controlling image-forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To register write positions of color component images even when a rotational speed of a photosensitive body or the like shifts due to influence of a load change, a backlash of a drive transmission gear or the like. SOLUTION: A latch circuit 1303 detects a phase difference between an ITOP signal and a BD signal when an image is formed at a first rotation (first color). Based on the detected phase difference, a subtraction circuit 1308, a data load type down counter 1302, a JK flip-flop 1313 process to delay the ITOP signal when the image is formed after the first rotation (first color) and later.

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 forming a multi-color image by sequentially superimposing color component images formed based on image information for each color component, and a method of controlling the image forming apparatus. is there.

[0002]

2. Description of the Related Art Conventionally, as a color image forming apparatus for printing out color image data, a main scanning means such as a laser beam printer (LBP) for scanning laser irradiation light on a photoreceptor with a rotary polygon mirror, such as a laser beam printer (LBP). Then, a latent image for each line is formed on the photoconductor, and the latent image is, for example, magenta (M),
An image is formed for each color element by using a developer of a color element such as cyan (C), yellow (Y), and black (BK). 2. Description of the Related Art There is known an apparatus for forming a color image by superimposing and transferring an image for each color element on a sheet fixed on a transfer drum.

There is also a system in which an image for each color element formed on a photoreceptor is temporarily overlaid on an intermediate transfer member, and the color image on the intermediate transfer member is collectively transferred to a sheet.

In these apparatuses, the photosensitive member and the transfer drum or the intermediate transfer member are driven at a constant speed in a direction perpendicular to the main scanning direction (sub-scanning direction), and the photosensitive drum, the transfer drum and the intermediate transfer member make one rotation. The color is superimposed on the paper on the transfer drum and the intermediate transfer body one by one in synchronization with the sub-scanning start signal generated every time.

There is also a system in which an image for each recording color element is formed on a photoreceptor in a superimposed manner, and is collectively transferred to recording paper.

In the conventional color image forming technique as described above, in order to prevent deterioration of the image quality of a color image due to a shift of the superposition position of each color image, a method of controlling the position at which each color image is superimposed is used. It becomes important.

As an example of this position control method, the number of sub-scanning start signals (ITOP signals) obtained during one rotation of the photosensitive member or the intermediate transfer member and the number of main scanning recording line signals (BD signals) synchronized therewith are given. (Refer to FIG. 12B described later), and a method of synchronizing rotations of a motor for driving the photoconductor and the intermediate transfer member and a scanner motor for driving main scanning has been proposed. .

FIG. 12 is a schematic diagram of a main scanning line formed on a photosensitive member or an intermediate transfer member of a conventional image forming apparatus.

In FIGS. 12A and 12B, reference numeral 801
Denotes an image bearing member such as a photosensitive member or an intermediate transfer member, which will be described below as a photosensitive member. An ITOP sensor 802 detects a sensor flag 803 provided at a predetermined position on the side surface of the photoconductor 801 every time the photoconductor 801 makes one rotation, and generates a sub-scanning start signal (ITOP signal).

FIG. 12A shows that the number of main scanning start signals (BD signals) obtained during one rotation of the photosensitive member 801 and the number of main scanning recording line signals synchronized therewith are "n + (1/1)".
2) ”(n; integer), and the first line, the second line,..., The (n−1) th line, the nth line, and the second line when the photoconductor 801 rotates twice. The first line of the rotation and the main scanning recording line signal position are shown.

[0011] As shown in FIG.
While one rotates one time, that is, while the ITOP signal is generated,
Since the main scanning recording line signal generates “n + (１ ／)” lines, the first line of the first rotation and the first line of the second rotation are shifted by a fraction of “１ ／” line. .

In order to prevent such a shift between the first rotation and the second rotation, in the conventional image forming apparatus, the main scanning start signal (B) obtained during one rotation of the photosensitive member or the intermediate transfer member described above.
A method has been proposed in which the number of main scan recording line signals synchronized therewith is an integral number.
Hereinafter, an example is shown in FIG.

FIG. 12B shows a configuration in which the number of main scanning start signals (BD signals) obtained during one rotation of the photosensitive member 801 and the number of main scanning recording line signals synchronized therewith are n (integer). , The first line, the second line,..., The (n−1) th line, n when the photoconductor 801 makes two rotations
The first line of the second line, the second rotation, and the main scanning recording line signal position are shown.

[0014] As shown in FIG.
While 1 is rotated once, that is, while the ITOP signal is generated once, the main-scanning recording line signal is n (integer) lines. Therefore, the first line of the first rotation and the first line of the second rotation are separated. , Without overlapping.

Referring to FIGS. 13 and 14, a method of synchronizing rotations of a motor for driving a photosensitive member or an intermediate transfer member and a scanner motor for driving main scanning in a conventional image forming apparatus will be described. explain.

A first method is to divide the frequency of a main scanning start signal (BD signal) generated with the rotation of the scanner motor,
It is used as a reference clock for a motor for driving the photosensitive member and the intermediate transfer member. Hereinafter, an example of the configuration will be described.

FIG. 13 is a diagram showing a configuration of a conventional image forming apparatus, and corresponds to the first method.

In FIG. 1, reference numeral 901 denotes a photosensitive member, which is rotationally driven by a photosensitive member drive motor 907 via a drive belt 908. A scanner motor 902 includes an oscillator 9
PLL circuit 91 based on the reference clock given from
The rotation of the polygon mirror 903 is rotationally controlled by 0. The polygon mirror 903 deflects the laser beam emitted from the laser 904 and performs line scanning on the surface of the photosensitive member 901 via a lens 905.

Reference numeral 906 denotes a beam detect sensor (BD sensor), which is arranged in a non-image area on a line scan line of a laser beam, and is a main scan start signal (BD signal) synchronized with each laser line scan, that is, in synchronization with the rotation of the scanner motor. Occurs. A PLL circuit 909 performs constant speed control of the photoconductor driving motor 907 using a BD signal generated by the BD sensor 906 as a reference clock. Thus, the rotation of the scanner motor 902 and the rotation of the photoconductor driving motor 907 can be synchronized.

Next, a second method uses a common clock for a reference clock of a motor for driving the photosensitive member and the intermediate transfer member and a reference clock of a scanner motor for driving main scanning. Hereinafter, an example of the configuration will be described.

FIG. 14 is a diagram showing a configuration of a conventional image forming apparatus, and corresponds to the above-mentioned second method.

In the figure, reference numeral 1001 denotes a photosensitive member, which is rotationally driven by a photosensitive member drive motor 1007 via a drive belt 1008. 1002 is a scanner motor,
PL based on the reference clock given from the oscillator 1011
The constant speed rotation is controlled by the L circuit 1010, and the polygon mirror 1003 is rotationally driven. Polygon mirror 1003
Scans the surface of the photosensitive member 1001 with a laser beam emitted from a laser 1004 via a lens 1005.

Reference numeral 1009 denotes a PLL circuit which controls the photoconductor driving motor 1007 at a constant speed based on a reference clock generated by a transmitter 1011 used for PLL control of the scanner motor 1002. Thus, the rotation of the scanner motor 1002 and the rotation of the photoconductor driving motor 1007 can be synchronized.

As described above, according to the first and second methods, the number of main scanning start signals (BD signals) obtained during one rotation of the photosensitive member or the intermediate transfer member and the number of main scanning recording line signals synchronized therewith are an integral number. By synchronizing the rotation of the motor for driving the photoconductor and the scanner motor for driving the main scanning, the sub-scanning start position is shifted regardless of the rotation of the photoconductor and the intermediate transfer body. Positioning can be performed without any problem.

As another example of the sub-scanning start position control, the main scanning start signal (BD signal) obtained during one rotation of the photosensitive member or the intermediate transfer member and the number of main scanning recording line signals synchronized therewith Is not limited to an integer, and there is a third method of phase adjustment between the main scanning start signal and the sub-scanning start signal, which can perform alignment. Hereinafter, an example of the configuration will be described.

FIG. 15 is a diagram showing a configuration of a conventional image forming apparatus, and corresponds to the third method.

In the figure, reference numeral 1101 denotes a photosensitive member, which is rotationally driven by a photosensitive member drive motor 1107 via a drive belt 110. A PLL circuit 1109 controls the photoconductor drive motor 1107 at a constant speed based on a reference clock supplied from the oscillator 1114. An ITOP sensor 115 generates an ITOP signal when the sensor flag 1116 shields the ITOP sensor 1115 from light every time the photoconductor 1101 makes one rotation. Based on the ITOP signal, the writing position of the first line of the photosensitive member 1101 is determined.

Reference numeral 1112 denotes a phase matching circuit,
The reference clock transmitted by the reference 13 is an ITOP sensor 1.
Synchronize with the ITOP signal transmitted by 115. Reference numeral 1110 denotes a PLL circuit.
Controls the low speed rotation of the scan motor 1102 based on the reference clock phase-synchronized with the ITOP signal.

As described above, the phase of the ITOP signal and the reference clock are matched by the phase matching circuit 1112, so that the rotation phase of the scanner motor 1102 is
The same correction is always made for each signal. Therefore, the rotational phase of the polygon mirror 1103 driven by the scanner motor 1102 is synchronized with the ITOP signal, and the position where the laser beam emitted from the laser 1104 is line-scanned on the surface of the photoconductor 1101 via the lens 1105 is defined as ITOP. Match based on signal.

FIG. 16 is a schematic diagram showing the relationship between an actual main scanning line (main scanning start signal) and an ITOP signal (sub-scanning start signal) on a photosensitive member of a conventional image forming apparatus.

In the figure, reference numeral 1601 denotes an image bearing member such as a photosensitive member or an intermediate transfer member.
Reference numeral 1602 denotes an ITOP sensor which detects a sensor flag 1603 provided at a predetermined position on the side surface of the photoconductor 1601 every time the photoconductor 1601 makes one rotation, and detects a sub-scanning start signal (I
TOP signal).

Further, the photosensitive member 1601 has "n + (1 /
2) One (1) rotation is performed on the (n; integer) main scanning line. The ITOP sensor 1602 generates a sub-scanning start signal at a predetermined position for each rotation of the photoconductor 1601. In this configuration, a main scan line of "n + (1/2)" lines is generated for one rotation of the photosensitive drum, and therefore, as shown in FIG. The first line of the second rotation is shifted by a fraction of "1/2" lines.

However, each time the ITOP signal (sub-scanning start signal) is generated, the rotation phase of the scanner motor 1102 for driving the main scanning line (sub-scanning start signal) is changed by the phase matching circuit 1112 as shown in FIG. By synchronizing with the above, the position of the first line for each ITOP signal can be adjusted as shown in the figure.

This makes it possible to perform alignment without causing a shift regardless of the rotation of the photosensitive member or the intermediate transfer member.

[0035]

However, the technique for preventing misalignment by the above device configuration is a technology on the assumption that all device environments are ideal. Therefore, in practice, the above-described technology for preventing displacement is not enough.

For example, the rotation speed of the photoreceptor slightly fluctuates due to the influence of load fluctuation, backlash of the drive transmission gear, and the like. This speed fluctuation causes a fluctuation in the phase difference between the main scanning start signal and the sub-scanning start signal, and in the above-described method of keeping the position of the laser scanning line of the photoconductor constantly constant by the conventional image forming apparatus, the fluctuation amount Will appear as a color shift. This fluctuation can be suppressed to a fraction of a line by a method such as minimizing the load fluctuation of the motor or improving the accuracy of the mechanical drive transmission system.

However, when the generation phase of the sub-scanning start signal for each of the recording colors of the color superimposition occurs across the main scanning start signal, even though the shift is actually a fraction of a line, A shift of one line occurs.

FIG. 17 is a timing chart for explaining the image forming timing of the conventional image forming apparatus, and corresponds to the case where the generation phase of the sub-scanning start signal for each recording color is generated across the main scanning start signal.

As shown in the figure, since the sub-scanning start signal 1204 for the first rotation is generated just before the main scanning start signal, the first line (12) is synchronized with the main scanning start signal.
06) scanning is started, and 2 is synchronized with the main scanning start signal.
The scanning of the line (1207) is started, the scanning of the third line (1208) is started in synchronization with the main scanning start signal, and the photosensitive member is sequentially scanned.

However, the sub-scanning start signal 120 for the second rotation
5 is generated slightly after the main scanning start signal,
Since the main scanning start signal cannot be recognized, the scanning of the first line (1207) is started in synchronization with the main scanning start signal, and the scanning of the second line (1207) is synchronized with the main scanning start signal.
The scanning of 8) is started, and scanning is sequentially performed on the photoconductor.

Accordingly, a shift of one line occurs between the first rotation and the second rotation (hereinafter, shown in FIG. 18).

FIG. 18 is a schematic diagram showing a case where the generation phase of the sub-scanning start signal for each recording color of the conventional image forming apparatus is generated across the main scanning start signal. Are attached.

In the figure, reference numeral 1201 denotes an image bearing member such as a photosensitive member or an intermediate transfer member.
Reference numeral 1202 denotes an ITOP sensor which is shielded from light by a sensor flag 1203 in accordance with the rotation of the photoconductor 1201 and generates a sub-scanning start signal.

The first rotation sub-scanning start signal 1204
The generation position is slightly before the main scanning start signal, and the generation position of the sub-scanning start signal 1205 in the second rotation is slightly after the main scanning start signal, and the first line 1206 in the first rotation and the one line in the second rotation. The eye 1207 is shifted by one line. Less than,
This will be described in detail with reference to FIG.

FIG. 19 is a timing chart showing the image forming timing of the conventional image forming apparatus, which corresponds to the detailed timing chart of the timing chart shown in FIG. 17, and the same parts as those in FIG. It is attached.

Here, the conventional image forming apparatus sets the video clock (video CL) to "n" in synchronization with the main scanning start signal.
After counting, an interval occurs in which the memory read signal counts “m” of the video CLK, reading of recording data from a memory (not shown) is started in synchronization with the memory read signal, and data read from the memory is: The laser beam is scanned line by line and recorded on the photosensitive member. The sub-scanning start signal is generated at a predetermined position for each rotation of the image carrier, and becomes effective from the main scanning start signal after the sub-scanning start signal changes from "L" to "H" level. Generate a read signal.

In a color image forming apparatus in which a latent image or transfer is performed by superposing a plurality of colors, the latent image or transfer is repeated several times. FIG. 19 shows an example in which repetition is performed twice. In the first rotation, the sub-scanning start signal is generated shortly before the main scanning start signal period. In the second rotation, the sub-scanning start signal is slightly different from the main scanning start signal. This is an example of a case that occurs later.

As shown in the figure, the sub-scanning start signal 1204 generated at the first rotation is generated shortly before the main scanning start signal.
The timing of the memory read signal on the line is synchronized with the main scanning start signal. For this reason, as shown in the figure, the memory read signal of the first rotation is generated from the point where the number of video clocks is counted "n" from the main scanning start signal.

Next, the sub-scanning start signal 1206 generated in the second rotation is shifted backward with respect to the first rotation due to a timing shift caused by rotation fluctuation of the image carrier.

In this case, since the sub-scanning start signal is generated shortly after the main scanning start signal, the main scanning start signal is not detected, and the memory read timing of the first line of the image is synchronized with the main scanning signal. For this reason, as shown in the figure, the memory read signal for the second rotation is generated from the point where the video clock is counted "n" from the main scanning start signal.

Therefore, there is a shift of one line between the memory read signal of the first rotation and the memory read timing of the second rotation. Therefore, when the image data read out from the memory based on the timing is sequentially line-recorded on the photoconductor, the first line which should originally overlap is deviated, and the first line and the second line of the first rotation are deviated. The second line overlaps, causing color misregistration.

As described above, in the conventional color matching technology, the sub-scanning start signal and the main scanning start signal generated by the fluctuation of the rotation speed of the photosensitive member or the like due to the load fluctuation or the back crash of the drive transmission gear. However, there is a problem that a shift of one or more lines may occur in the image writing position of the color component due to the variation of the phase difference of

The present invention has been made to solve the above problems, and an object of the first to tenth inventions according to the present invention is to form an image at a first rotation (first color). The phase difference between the sub-scanning start signal and the main scanning start signal at the time is detected, and the first rotation (the first rotation) is performed based on the detected phase difference.
By performing the delay processing of the sub-scanning start signal at the time of image formation after the color tone, even if the rotation speed of the photosensitive member or the like is shifted due to the influence of load fluctuation or back crash of the drive transmission gear, An object of the present invention is to provide an image forming apparatus and a control method of the image forming apparatus, which can form a high-quality image without color shift by matching the image writing positions of the respective color components.

[0054]

According to a first aspect of the present invention, there is provided an image forming apparatus for forming a multicolor image by sequentially superimposing color component images formed based on image information for each color component. A rotating polygon mirror (polygon mirror 103 shown in FIG. 2) that scans an image carrier that is rotated and driven by deflecting a light beam based on image information for each color component, and a light beam that is scanned by the rotating polygon mirror Main-scanning start signal generating means (BD sensor 107 shown in FIG. 1) for generating a main-scanning start signal by detecting a sub-scanning start signal for synchronizing the rotation of the image carrier. Means (ITOP sensor 110 shown in FIG. 2), detecting means (latch circuit 1303 shown in FIG. 4) for detecting a phase difference between the sub-scanning start signal and the main scanning start signal at a first timing, and the detecting means By the first There is provided delay means (a subtraction circuit 1308, a data load down counter 1312, and a JK flip-flop 1313 shown in FIG. 4) for delaying the sub-scanning start signal at the second timing based on the phase difference detected by the imaging. Things.

The second invention according to the present invention is directed to the delay means (subtraction circuit 1308, data load down counter 1312, JK flip-flop 1313 shown in FIG. 4).
Is based on the phase difference detected at the first timing by the detecting means so that the sub-scanning start signal generated by the sub-scanning start signal generating means is generated at the center of the main scanning start signal cycle. (The subtraction circuit 130 shown in FIG.
8) calculates the delay amount of the sub-scanning start signal and, based on the calculated delay amount, (by the data load down counter 1312 and the JK flip-flop 1313 shown in FIG. 4).
The sub-scanning start signal is delayed at the second timing.

According to a third aspect of the present invention, in the delay means (the subtraction circuit 1308 shown in FIG. 4), the phase difference detected at the first timing by the detection means and the period of the main scanning start signal cycle are calculated. The difference from 3/2 "is calculated as the delay amount of the sub-scanning start signal.

According to a fourth aspect of the present invention, the first timing is a timing at which a sub-scanning start signal is generated when the first image formation is performed, and the second timing is
This is the timing for generating the sub-scanning start signal when performing the first and subsequent image formation.

In a fifth aspect according to the present invention, the first timing is a timing at which a sub-scanning start signal is generated when forming an image of a first color, and the second timing is
This is the timing for generating the sub-scanning start signal when forming the image of the first color and thereafter.

According to a sixth aspect of the present invention, there is provided an image forming apparatus for forming a multicolor image by sequentially superimposing color component images formed based on image information for each color component. A rotating polygon mirror (polygon mirror 103 shown in FIG. 2) that scans an image carrier that is rotated and driven by deflecting a light beam based on information, and detects a light beam scanned by the rotating polygon mirror to perform main scanning. Main scanning start signal generating means (BD sensor 107 shown in FIG. 1) for generating a start signal, and sub-scanning start signal generating means (FIG. 2) for generating a sub-scanning start signal in synchronization with the rotation of the image carrier. ITOP sensor 1
10) and detecting means (a latch circuit 17 shown in FIG. 10) for detecting a phase difference between the sub-scanning start signal and the main scanning start signal.
03) and when the phase difference detected by the detection means is less than “１ ／” times the main scanning start signal cycle, the phase difference is “１ ／” times the main scanning start signal cycle. The sub-scanning start signal is delayed by the difference of the above. If the phase difference is "1/2" times or more of the main scanning start signal cycle, "3/2" of the phase difference and the main scanning start signal cycle. Delay means for delaying the sub-scanning start signal by the difference from the double (comparator 1708, first subtraction circuit 1709,
It has a first subtraction circuit 1710 and a selector 1710).

According to a seventh aspect of the present invention, the sub-scanning start signal generating means (ITOP sensor 110 shown in FIG. 2)
Generates a plurality of sub-scanning start signals in one rotation of the image carrier in synchronization with the rotation of the image carrier, and generates a plurality of sub-scanning start signals in one rotation of the image carrier by the sub-scanning start signal generating means. Detection means (a latch circuit 130 shown in FIG. 4) for detecting a phase difference between the sub-scanning start signal and the main scanning start signal at a first timing for each of the sub-scanning start signals to be performed.
3), and the delay means (the subtraction circuit 13 shown in FIG. 4)
08, a data load type down counter 1312, and a JK flip-flop 1313) delay each sub-scanning start signal at a second timing based on each phase difference detected by each of the detecting means.

According to an eighth aspect of the present invention, the image information for each color component is stored in the image scanner unit 20 shown in FIG.
1) is read from the document.

According to a ninth aspect of the present invention, the image information for each color component is input from an information processing device (an external device such as a computer (not shown)) via a predetermined communication medium.

According to a tenth aspect of the present invention, there is provided a control method of an image forming apparatus for forming a multicolor image by sequentially superimposing color component images formed based on image information for each color component. A detection step of detecting, at a first timing, a phase difference between a sub-scanning signal generated in synchronization with the rotation of the laser beam and a main scanning start signal generated by detecting a light beam scanned by the rotary polygon mirror (FIG. 5, the step (6), the step (6) in FIG. 7, and the step (8) in FIG. 9), and based on the detected phase difference, at a second timing, the sub-scanning start signal causes the main scanning to start. A calculation step (step (7) in FIG. 5, step (7) in FIG. 7, step (9) in FIG. 9) for calculating the delay amount of the sub-scanning start signal so as to occur at the center of the start signal cycle; Generated for each image formation based on the calculated delay amount Delay step of delaying the sub-scanning start signal (step of FIG. 5 (8), (9), Step (8 in FIG. 7), (9), the steps of FIG. 9 (10), (11))
And

[0064]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] FIG. 1 is a sectional view for explaining the structure of an image forming apparatus according to a first embodiment of the present invention.

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

In the image scanner section 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.

210 is a three-line sensor (hereinafter referred to as CCD)
And a red (R) sensor 210-1, a green (G) sensor 210-2, and a blue (B) sensor 210-3.
7. Lens 208 including 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 is formed of R, G, B
The data is read by the sensors 210-1 to 210-3 and correction data is generated. 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,
The output data of the visible sensors of the B sensors 210-1 to 210-3 are corrected. Reference numeral 230 denotes an optical sensor,
9 together with the image tip signal VTOP.

In the printer section 200, reference numeral 101 denotes an image writing timing control circuit.
01 and a semiconductor laser 102 based on magenta (M), cyan (C), yellow (Y), and black (BK) image signals input from an external device such as a computer (not shown) via a predetermined communication medium. Drive modulation. 103
Is a polygon mirror, which is driven to rotate by the polygon motor 106, reflects the laser beam emitted from the semiconductor laser 102, and reflects the f-θ lens 104 and the return mirror 216.
Scans on the photosensitive drum 105 via the.

The photosensitive drum 105 is a polygon mirror 10
3 forms an electrostatic latent image by laser scanning. 107
Is a BD sensor, which is provided near the scanning start position of one line of laser light, detects line scanning of laser light, and outputs a main scanning start signal (scanning start reference signal (B
D signal)).

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 an electrostatic latent image on the photosensitive drum 105 to form a toner image. Reference numeral 108 denotes a transfer drum, which is a paper cassette 224 or 2
The recording paper 109 fed from the printer 25 is conveyed by suction, and the toner image formed on the photosensitive drum 105 is transferred onto the recording paper 109.

Reference numeral 110 denotes an ITOP sensor, which is a transfer drum 1
By detecting the passage of the flag 111 fixed in the transfer drum 108 by the rotation of 08, a sub-scanning start signal for each color (a signal indicating the leading end position of the recording sheet adsorbed on the transfer drum 108 (ITOP signal)) Generate 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 glass 203 is irradiated with light from a halogen lamp 205, and the reflected light from the original is guided to mirrors 206 and 207, and forms an image on a CCD 210 by a lens 208. Next, the CCD 210 performs color separation of the light information from the document, reads the full-color information red (R), green (G), and blue (B) components, and sends the read components to the signal processing unit 209. Note that 205 and 206 are speeds “v” and 207 is speed “v / 2” mechanically in a direction perpendicular to an electrical scanning direction (hereinafter, main scanning direction) of the line sensor (hereinafter, sub-scanning direction). To scan the entire surface of the document.

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, 230 is an optical sensor,
The image tip signal VTOP is generated 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 original scanning (scan) 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 a computer (not shown) via the image scanner unit 201 or a predetermined communication medium is sent to the image writing timing control circuit 101. The image writing timing control circuit 101 modulates and drives the semiconductor laser 102 according to magenta (M), cyan (C), yellow (Y), and black (BK) image signals. 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, is reflected by the return mirror 216, scans the photosensitive drum 105, and scans the photosensitive drum 105. An electrostatic latent image is formed.

Further, while the photosensitive drum 105 rotates four times, the four developing machines 219 to 222 alternately operate the photosensitive drum 10.
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
The recording paper 9 is wound around the transfer drum 108, and after the four colors M, C, Y, and BK of the toner image developed by the developing machine are sequentially transferred, the recording paper passes through the fixing unit 226 and is discharged.

FIG. 2 is a diagram for explaining the configuration of the printer unit 200 of the image forming apparatus shown in FIG. 1, and 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. Reference numeral 122 denotes a phase matching circuit which is an ITOP signal from the ITOP sensor 110 and a B signal from the BD sensor 107.
The D signal and the data load enable signal from the CPU 130 are input, and the ITOP signal is delayed and output so as to be generated at the center of the BD signal cycle.

An image writing timing control circuit 101 receives an ITOP signal output from the phase matching circuit 122 and outputs an image signal at a timing synchronized with the ITOP signal. Reference numeral 117 denotes an OR gate which outputs an image signal from the image writing timing control circuit 101 or a laser lighting signal for BD signal detection from the laser lighting signal generation circuit 120 to the semiconductor laser 102,
02 is modulated. A frequency dividing circuit 119 divides the BD signal from the BD sensor 107 at a predetermined frequency dividing ratio and transmits a photosensitive drum motor driving pulse (reference CLK). 1
Reference numeral 18 denotes a PLL circuit that detects a phase difference and a frequency deviation between the FG pulse and the reference CLK so that the phase of the motor FG pulse output with the rotation of the photosensitive drum motor 115 matches the phase of the reference CLK, and compares them. PLL control for controlling the drive voltage to the photosensitive drum motor 115 is performed. Note that the CPU 130 has a ROM and a RAM inside,
The overall control of the image forming apparatus is performed based on the program stored in M.

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) via a predetermined communication medium is sent to the image writing timing control circuit 101 and the image writing timing The control circuit 101 supplies the 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 is reflected by the rotating polygon mirror 103, fθ-corrected by the f-θ lens 104, reflected by the return mirror 216 (shown in FIG. 1), scans the photosensitive drum 105, and scans the photosensitive drum 105. An electrostatic latent image is formed.

The polygon motor 106 is driven to rotate by a polygon motor driving pulse (reference CLK-P) generated by dividing the frequency of 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. PLL control for controlling the drive voltage to the controller is performed.

The BD sensor 107 provided in the vicinity of the scanning start position of one line of the laser light detects the line scanning of the laser light, and a scanning start reference signal of each line having the same period as shown in FIG. BD signal). Also,
An ITOP sensor 110 in the transfer drum 108 detects a flag 111 fixed in the transfer drum 108 by rotation of the transfer drum 108, and an ITOP signal for each color (recording on the transfer drum 108) as shown in FIG. Paper 1
09 indicating the position of the tip of 09). Further, the photosensitive drum motor 115 includes a laser lighting signal generation circuit 120.
The laser lighting signal for BD signal detection from the frequency dividing circuit 11
The motor driving pulse (reference CLK) divided by 9 is PL
The rotation is driven by being sent to the L circuit 118.

The PLL circuit 118 includes the photosensitive drum motor 1
The phase difference and the frequency deviation between the FG pulse and the reference CLK are detected so that the phase of the motor FG pulse from the reference 15 and the phase of the reference CLK coincide with each other.
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 writing timing control circuit 1
01 counts the BD signal a predetermined number of times and generates a sub-scanning start signal (for m BD signals determined by the length of the recording paper) in synchronization with the rising edge of the nth BD signal;
The image signal is irradiated on the photosensitive drum 105 as laser modulated light.

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 transmitted from an ITOP sensor 110 in the transfer drum 108 to the transfer drum 108.
The flag 1 fixed in the transfer drum 108 by the rotation of
Transfer drum 108 output by detecting 11
This signal indicates the position of the leading edge of the upper recording sheet 109, and 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 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 the rising edge of the ITOP signal is detected.
The signal is sent to the semiconductor laser 102 via the OR gate 117 in synchronization with the rise of the D signal. That is, ITOP
"N" th (predetermined number) after detecting rising of signal
A sub-scanning start signal is generated in synchronization with the rising edge of the BD signal, and the image signal corresponding to the “m” -th BD signal is irradiated onto the photosensitive drum 105 as laser modulated light.

In this embodiment, exactly an integral number of BD signals are output during one rotation of the photosensitive drum 105 so that the scanning light of the laser on the photosensitive drum 105 is always at the same position every rotation. The number of BD signals output during one rotation of the photosensitive drum determined from the process speed and the resolution is 8,192. The photosensitive drum motor 115 has a gear ratio such that the photosensitive drum motor 115 rotates 64 times for one rotation.
Since the number of FG pulses per rotation is 32, one rotation of the photosensitive drum motor 115 requires 32 reference clocks.

Therefore, in order for the photosensitive drum 105 to make one rotation, the reference clock is 64 rotations × 32 pulses = 2048.
A pulse is required. For this reason, by dividing the BD signal by ４ and using it as the reference CLK of the photosensitive drum motor 115, the photosensitive drum 105 makes one rotation when 8192 BD signals are output. Note that this gear ratio n
Is set to be a natural number. This is because the monitor and the reduction gear are rotated an integer while the photosensitive drum 105 makes one rotation, so that the influence of the motor shaft and the knitting center of the reduction gear for each rotation of the photosensitive drum 105 is obtained. Is always the same, and the color shift due to these eccentricities is made zero.

Hereinafter, an example of the phase matching method will be described.

FIG. 4 shows the phase matching circuit 12 shown in FIG.
2 is a circuit diagram illustrating a configuration of FIG.

In the figure, reference numeral 1301 denotes a rising detection circuit which detects the rising of the ITOP signal emitted from the ITOP sensor 110 in the transfer drum 108. 130
Reference numeral 2 denotes an UP counter, which is a free-run counter that is cleared to "0" by a BD signal and repeats the UP count, and the count number of this counter becomes a BD signal cycle.

Reference numeral 1306 denotes a 3CLK delay circuit.
The signal obtained by delaying the signal by 3CLK is AND gate 1314
Output to A flip-flop 1307 synchronizes the output of the rising edge detection circuit 1301 with the clock timing.

Reference numeral 1303 denotes a latch circuit, which is a UP counter 1 at the timing of the output of the rising edge detection circuit 1301.
Latch the output of 302. Thus, the latched count data indicates the rising edge position of the ITOP signal in the BD signal cycle. That is, the data indicates the phase difference between the ITOP signal and the BD signal. The latch circuit 13
The output of the rising edge detection circuit 1301 and the output of the AND gate 1305 of the data load enable signal set by the CPU 130 (controller) shown in FIG. 2 are connected to the latch enable terminal LE of 03.
When the data load enable signal is at "L" level, I
The latch operation is not performed even if the rising edge of the TOP signal is detected.

A subtraction circuit 1308 subtracts the count data latched by the latch circuit 1303 from the data set by the CPU 130. In the present embodiment, the setting data is 1.5 times (3/2) T, where T is the count number of the BD signal cycle (a known value uniquely determined by the apparatus). The result of this subtraction processing is the required delay from the input of the ITOP signal to the center of the next BD signal cycle. That is, assuming that the count number of the BD signal cycle is T = “100” and the ITOP signal is input at the position of the count “80 (= latch data)”, “(3/2) T−80 = 150−80 = If the ITOP signal is delayed by the "70" count, it can be adjusted so that the ITOP signal is input to the center position of the next BD signal cycle.

Reference numeral 1312 denotes a data load type down counter (hereinafter referred to as a down counter).
7, the subtraction circuit 1 is synchronized with the output of the rising edge detection circuit 501 of the ITOP signal after the timing is adjusted.
The output data of 308 is loaded from the data load terminal.

When the down counter 1312 finishes counting the loaded data, it outputs an RC output to the JK flip-flop 1313. This down counter 131
The counting time of 2 is a delay time for the phase adjustment of the ITOP signal. JK flip-flop 131
3 is reset at the rising edge of the ITOP signal,
The Q output ITOPDLY becomes an “L” level output, and holds the “L” level state until RC of the down counter 1312 is output and set.

That is, the "L" level is maintained for the required delay time from the rise of the ITOP signal.
By outputting the ITOPDLY output and a signal obtained by delaying the ITOP signal by a predetermined time (3 CLK in this embodiment) for timing adjustment through an AND gate 1314, the ITOP signal can be generated at the center of the BD signal cycle. it can.

Further, only the phases of the BD signal and the ITOP signal in the first rotation are sampled by the data load enable signal described above, and the delay is performed so that the ITOP signal is generated at the center of the BD signal cycle. By setting the data load enable signal to the “L” level in the rotations to the n-th rotation, the same data as in the first delay can be held. As a result, the ITOP signal position of the first rotation is generated at the center position of the BD signal period, and the second and subsequent times are generated by deviating from the center by a variation due to the rotation accuracy of the photosensitive drum motor 115 and the like.

Hereinafter, the phase matching process of the image forming apparatus according to the first embodiment of the present invention will be described with reference to FIGS.

FIG. 5 is a flowchart showing a phase matching processing procedure of the image forming apparatus according to the first embodiment of the present invention. Note that (1) to (10) indicate each step.

First, when the image forming sequence operation is started, the CPU 130 determines whether or not the signal is the first (first) ITOP signal (1). If it is determined that the signal is not the first ITOP signal, the data loading is performed. The enable signal is set to the "L" level (data load enable disabled) (3). If it is determined that the signal is the first ITOP signal, the data load enable signal input to the AND gate 1305 is set to the "H" level ( (Data load enable permission) is set (2).

Next, the rising edge of the ITOP signal is
It is determined whether or not the signal is detected by the rising edge detection circuit 1301 (4).
Returning to step (1), if it is determined that the data load enable signal is detected, the state of the data load enable signal is determined (5). The phase position of the ITOP signal is latched in the latch circuit 1303 (6), and the value set by the CPU 130 in the subtraction circuit 1308,
For example, assuming that the count number of the BD signal period (a known value uniquely determined by the apparatus) is T, the phase position data latched is subtracted from 1.5 times (3/2) T to calculate the ITOP signal. The delay amount is calculated (7), and the calculated delay amount is loaded into the data load type down counter 1312, and the ITOP is calculated based on the data loaded delay amount.
A signal delay process is performed (8), and a delayed ITOP signal is output (9). Next, it is determined whether or not the output sequence has been completed. If it is determined that the output sequence has not been completed, the process returns to step (1). If it is determined that the output sequence has been completed, the process is terminated (this operation is performed). This is repeated until the output sequence operation is completed) (10).

On the other hand, if it is determined in step (5) that the data load enable signal is not in the enabled state (the data load enable signal is in the disabled state), the ITOP is determined based on the data already latched in the latch circuit 1303. The signal is delayed (8), and a delayed ITOP signal is output (9). Next, the CPU 130 determines whether or not the output sequence has been completed. If it is determined that the output sequence has not been completed, the process returns to step (1). If it is determined that the output sequence has been completed, the process ends. The operation is repeated until the output sequence operation ends) (10).

FIG. 6 is a timing chart showing a phase matching process of the image forming apparatus according to the first embodiment of the present invention.

In the figure, 1 is set shortly before the main scanning start signal.
When the sub-scanning start signal (ITOP signal) of the first rotation is generated, the CPU 130 shown in FIG. 2 sets the data load enable signal to the “H” level, and thus the amount of delay of the sub-scanning start signal of the first rotation A is calculated. Based on the calculated delay amount A, the sub-scanning start signal for the first rotation is
As shown in the drawing, the delay occurs at the main scanning synchronization center position.

The sub-scanning start signal (ITOP signal) for the second rotation is generated shortly after the main scanning start signal.
Since the PU 130 sets the data load enable signal to the “L” level, the delay amount of the second rotation sub-scanning start signal is not calculated, and the delay amount A calculated by the first sub-scanning start signal is held. Therefore, the sub-scanning start signal in the second rotation is also generated based on the delay amount A as shown in the figure, as in the first rotation.

Similarly, the sub-scanning start signal at the n-th rotation is generated by delaying the sub-scanning start signal at the n-th rotation by the delay amount A as shown in FIG.

As described above, the sub-scanning start signal before the delay is
Although it fluctuated before and after the main scanning start signal, by delaying each sub-scanning start signal based on the delay amount A calculated at the first rotation, the fluctuation of the sub-scanning start signal is changed by the period of the scanning start signal. Near the center of With this processing, it is possible to increase the margin for the fluctuation of the sub-scanning.

Therefore, if image writing is started based on this ITOP signal, the phase difference between the ITOP signal and the BD signal is always constant for each color, so that the image writing positions from the first color to the Nth color can be accurately determined. And a high-quality image without color shift can be obtained.

[Second Embodiment] When a plurality of color images are formed in one image forming sequence, the amount of delay of the ITOP signal is calculated by forming an image of the first color for forming an image for each sheet. Independently calculated ITOP signals may be used, and the ITOP signals for the second and subsequent colors may be configured to be delayed based on the delay amount calculated for each image forming sheet.

Thus, the center of the BD signal period is
A P signal can be generated.

Further, only the phases of the BD signal and the ITOP signal of the first color are sampled by the above-mentioned data load enable signal, and the delay is performed so that the ITOP signal is generated at the center of the BD signal cycle. By setting the data load enable signal to the “L” level for the nth color, the same data as the delay of the first color can be held. As a result, the ITOP signal position of the first color is generated at the center position of the BD signal period, and the second to subsequent nth colors are generated from the center thereof by deviating from the center thereof by a variation due to the rotation accuracy of the photosensitive drum motor 115 and the like. become. Hereinafter, the embodiment will be described.

Hereinafter, the phase matching process of the image forming apparatus according to the second embodiment of the present invention will be described with reference to FIGS.

FIG. 7 is a flowchart showing a phase matching processing procedure of the image forming apparatus according to the second embodiment of the present invention. Note that (1) to (11) indicate each step.

First, when the image forming sequence operation is started, the CPU 130 determines whether or not the signal is the first color ITOP signal (1). If it is determined that the signal is not the first color ITOP signal, the data load enable is determined. Set the signal to "L" level (data load enable disabled) (3)
If it is determined that the signal is the ITOP signal of the first color, A
Set the data load enable signal input to ND gate 1305 to "H" level (data load enable enabled)
(2).

Next, the rising edge of the ITOP signal is
It is determined whether or not the signal is detected by the rising edge detection circuit 1301 (4).
Returning to step (1), if it is determined that the data load enable signal is detected, the state of the data load enable signal is determined (5). The phase position of the ITOP signal is latched in the latch circuit 1303 (6), and the value set by the CPU 130 in the subtraction circuit 1308,
For example, assuming that the count number of the BD signal period (a known value uniquely determined by the device) is T, the phase position data latched is subtracted from 1.5 times (3/2) T, and the data is obtained. The delay amount of the ITOP signal is calculated (7), and the calculated delay amount is loaded into the data load type down counter 1312, and the ITOP signal delay processing is performed based on the data loaded delay amount (8).
An OP signal is output (9).

Next, the CPU 130 determines whether or not the image formation up to the n-th color has been completed (10). If it is determined that the image formation has not been completed, the process returns to step (1) (this operation is the n-th operation). This is repeated until the color image forming operation is completed.)

On the other hand, if it is determined in step (10) that the image formation up to the nth color has been completed, the CPU 130 determines whether or not the output of the N portion (Nth sheet) has been completed (11). If it is determined that the process has not been completed, the process returns to step (1), and if it is determined that the process has been completed, the process is terminated (this operation is performed until the image formation of the N-th (N-th) image is completed). repeat).

FIG. 8 is a timing chart showing a phase matching process of the image forming apparatus according to the second embodiment of the present invention. FIG. 8A shows the IT when a plurality of images are formed.
(B) shows the timing of the OP signal, the data load enable, and the latched delay data.
The generation timing of the ITOP signal of one image sequence of the signal is shown.

In the figure, the CPU 130 shown in FIG. 2 sets the data load enable signal to the "H" level when the sub-scanning start signal (ITOP signal) of the first color of the first sheet is generated. The delay amount Dl of the sub-scanning start signal of the first color in the image sequence operation for one frame is calculated. Based on the calculated delay amount Dl, a sub-scanning start signal is generated by delaying the sub-scanning start signal of the first color and the first color as described above.

Sub-scanning start signals for the second and subsequent colors of the first sheet (the ITOP signal is a delay of the sub-scanning start signal for the second sheet of the first sheet because the CPU 130 sets the data load enable signal to "L" level). Since the amount calculation is not performed and the delay amount Dl calculated by the sub-scanning start signal of the first color is held, the sub-scanning start signal of the second color is also based on the delay amount D1 similarly to the first color. As described above, a sub-scanning start signal is generated by delaying the sub-scanning start signal of the second color.

Similarly, for the n-th color, a sub-scanning start signal is generated by delaying the n-th color sub-scanning start signal based on the delay amount D1 as shown in FIG. This operation is repeated in the second, third,..., N-th image forming sequence.

By starting the image writing based on the ITOP signal by performing the above processing, the ITOP signal and B
Since the phase difference of the D signal is always constant for each color in one image formation, 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. Obtainable.

[Third Embodiment] In the above-described second embodiment, when a color image formation mode of two or more colors and a single color image formation mode of only one color are provided, in the case of the single color mode, the IT
The OP signal delay amount calculation is performed in the first ITO for image formation.
You may comprise so that it may calculate based on a P signal. Hereinafter, the embodiment will be described.

FIG. 9 is a flowchart showing a phase matching processing procedure of the image forming apparatus according to the third embodiment of the present invention. In addition, (1) to (12) indicate each step.

First, when the image forming sequence operation is started, the CPU 130 determines whether the mode is the monochrome mode or the color mode (1). If the mode is determined to be the color mode, the CPU 130 shifts to the color image sequence operation shown in FIG. (2) If it is determined that the mode is the monochrome mode, the process proceeds to step (3).

In step (3), the CPU 130 determines whether or not the signal is the first (first) ITOP signal. If it is determined that the signal is not the first ITOP signal, the CPU 130 sets the data load enable signal to the “L” level (data level). (5) The data load enable signal input to the AND gate 1305 is set to "H" level (data load enable permission) when it is determined that the signal is the first ITOP signal (5). 4).

Next, the rising edge of the ITOP signal is
It is determined whether or not the signal is detected by the rising edge detection circuit 1301 (6).
Returning to step (3), if it is determined that the data load enable signal has been detected, the state of the data load enable signal is determined (7). The phase position of the ITOP signal is latched in the latch circuit 1303 (8), and the value set by the CPU 130 in the subtraction circuit 1308,
For example, assuming that the count number of the BD signal cycle (unambiguous value determined uniquely by the apparatus) is T, the phase position data latched is subtracted from 1.5 times (3/2) T to obtain the ITOP signal. (9), the calculated delay amount is loaded into the data load type down counter 1312, and the ITO is calculated based on the data loaded delay amount.
A P signal delay process is performed (10), and a delayed ITOP signal is output (11). Next, the CPU 130 determines whether or not the image formation of the number of output copies N has been completed (12). If it is determined that the image formation has not been completed, the process returns to step (3). The process is terminated (this operation is repeated until the image formation for the N-th set (N-th sheet) is completed).

On the other hand, if it is determined in step (7) that the data load enable signal is not in the permitted state (the data load enable signal is in the disabled state), the ITOP is determined based on the data already latched in the latch circuit 1303. The signal is delayed (10), and the delayed ITOP is
A signal is output (11). Next, the CPU 130 determines whether or not the image formation of the number of output copies N has been completed (12). If it is determined that the image formation has not been completed, the process returns to step (3). , And terminates the process (this operation is repeated until the image formation of the N sets is completed).

According to the above processing, in the image forming apparatus having the color mode for forming a color image with two or more colors and the single color mode for forming a single color image of only one color, in the case of the color mode, the ITOP signal delay amount is calculated. Is calculated based on the ITOP signal of the first color for forming an image. In the case of the single color mode, the amount of delay of the ITOP signal is calculated based on the first ITOP signal for forming an image. As a result, the optimum image writing timing can be adjusted, and a high-quality image without image shift can be obtained.

[Fourth Embodiment] In the first embodiment, the delay amount of the ITOP signal is calculated so that the ITOP signal of the first rotation is aligned with the center of the next BD signal period, and the calculated amount is calculated. The case where each ITOP signal is delayed based on the delay amount has been described. However, when the center of the BD signal cycle has not yet come when the first rotation ITOP signal is generated, the timing of the first rotation ITOP signal is changed. That B
You may comprise so that it may be set to the center of a D signal period. Hereinafter, the embodiment will be described.

FIG. 10 shows the phase matching circuit 1 shown in FIG.
FIG. 2 is a circuit diagram illustrating a configuration of a second embodiment.

Referring to FIG. 17, reference numeral 1701 denotes a rising edge detection circuit, and an ITO sensor 110 in the transfer drum 108.
The rising edge of the generated ITOP signal is detected.
Reference numeral 1702 denotes an UP counter, which is a free-run counter that is cleared to "0" by a BD signal and repeats the UP count, and the count number of this counter becomes a BD signal cycle. Reference numeral 1703 denotes a latch circuit, which outputs an UP counter 170 based on the output timing of the rising edge detection circuit 1701.
2 is latched. Thus, the latched count data indicates the rising edge position of the ITOP signal during the BD signal cycle, that is, data indicating the phase difference between the ITOP signal and the BD signal. The output of the rising edge detection circuit 1701 and the output of the AND gate 1715 of the data load enable signal set by the CPU 130 (controller) shown in FIG. 2 are connected to the latch enable terminal LE of the latch circuit 1703. When the load enable signal is at “L” level, ITOP
Even when the rising edge of the signal is detected, the latch operation is not performed.

The latched count data is input to a comparator 1708, a first subtraction circuit 1709, and a second subtraction circuit 1710. Reference numeral 1708 denotes a comparator which compares the data set by the CPU 130 with the magnitude of the data latched by the latch circuit 1703. If the latch data is smaller or equal to the set data, the comparator sets an "H"level; Is output. That is, when the output is “H” level, it indicates that the generation of the ITOP signal is before the center of the BD signal cycle, and when the output is “L” level, the generation of the ITOP signal is after the center of the BD signal cycle. Indicates that there is.

The first subtraction circuit 1709 is connected to the CPU 13
The latched count data is subtracted from the data set by 0. In this embodiment, the setting data is B
Assuming that the count number of the D signal cycle (a known value uniquely determined by the apparatus) is T, 1.5 times (3/2) T
And

The result of this subtraction processing is that the ITOP signal is B
This is the required delay amount from the input of the ITOP signal in the case of entering after the center of the D signal cycle to the center of the next BD signal cycle. That is, the count number of the BD signal cycle is T = 10
Assuming that the ITOP signal is input at the position of the count 80 (= latch data), "(3/2) T-8
If the ITOP signal is delayed by the count of “0 = 150−80 = 70”, the ITOP signal is shifted to the center position of the next BD signal cycle.
It can be adjusted so that a signal is input.

In the second subtraction circuit 1710, the CPU 1
The subtraction of the latched count data from the data set by 30 is performed. In the present embodiment, the setting data is set to T / 2, which is 既知 times as large as T, where T is the count number of the BD signal cycle (a known value uniquely determined by the device). If the result of this subtraction processing is that the ITOP signal is before or equal to the center of the BD signal cycle, it becomes the necessary delay amount from the input of the ITOP signal to the center of the cycle of the BD signal cycle.

The outputs of the first subtraction circuit 1709 and the second subtraction circuit 1710 are respectively input to a selector 1711. The selector 1711 outputs the first subtraction circuit 1709 and the second subtraction circuit based on the output result from the comparator 1708. The output of the UP counter 17 is selected by selecting the output of the
12 to the data load terminal.

When the output result from comparator 1708 is at the "L" level, that is, after the center of the BD signal cycle,
When the P signal is generated, the result of the first subtraction circuit 1709 is selected, and the output result from the comparator 1708 is set to the “H” level, that is, the ITO signal is output before the center of the BD signal cycle.
When the P signal is generated, the result of the second subtraction circuit 1710 is selected and output to the data load terminal of the UP counter 1712.

Hereinafter, with reference to FIG. 11, the difference in the phase adjustment when the ITOP signal is generated in the first half and the second half of the BD signal cycle will be described.

FIG. 11 is a timing chart showing the phase matching process of the image forming apparatus according to the fourth embodiment of the present invention. FIG. 11A shows an example in which the ITOP signal enters the first half of the BD signal period. (B) shows an example in which the ITOP signal enters the latter half of the BD signal cycle.

In (a), assuming that T is the BD signal period, the phase difference A between the ITOP signal and the BD signal becomes "A <(1/2) T" as shown in the figure, and occurs in the first half of the BD signal period. It is determined that it has been done.

At this time, since the center of the BD signal cycle in which the ITOP signal is generated has not yet come, when the timing of the ITOP signal is adjusted to the center of the BD signal cycle, the BD
What is necessary is just to match with the center of a signal period. Therefore, the delay data is "(1/2) TA", and the ITOP signal is changed to "(1
/ 2) T-A "can be adjusted to the center of the BD signal cycle.

In (b), if T is the BD signal period, the phase difference B between the ITOP signal and the BD signal becomes “B> (１ ／) T” as shown in FIG. It is determined that this has occurred.

At this time, since the center of the BD signal cycle in which the ITOP signal has been generated has passed, when the timing of the ITOP signal is set to the center of the BD signal cycle, it must be set to the center of the next BD signal cycle. No. Therefore, the delay data becomes “(3/2) TB”, and the ITOP
If the signal is delayed by "(3/2) T-B", it can be adjusted to the center of the BD signal cycle.

As described above, when the input of the ITOP signal in the first rotation comes into the first half of the BD signal cycle, the BD
When the ITOP signal is set at the center of the signal cycle and the second half of the BD signal cycle is entered, the BD signal can be used effectively by adjusting the ITOP signal at the center of the next BD signal cycle.

The output data of the selector 1711 is input to the data load terminal of the down counter 1712, and the data after the timing is adjusted by the flip-flop 1707.
The signal is loaded into the down counter 1712 in synchronization with the output of the rising edge detection circuit 1701 of the OP signal. When the down counter 1712 has finished counting the loaded data, it outputs an RC output to the JK flip-flop 1713. The time counted by the down counter 1712 is a delay time for adjusting the phase of the ITOP signal. The JK flip-flop 1713 is reset at the rising edge of the ITOP signal and its Q output, ITO,
PDLY outputs "L" level and the down counter 1
The “L” level state is maintained until RC of 712 is output and set.

That is, the "L" level is maintained for the required delay time from the rise of the ITOP signal. By outputting the ITOPDLY output and a signal obtained by delaying the ITOP signal by a predetermined time (3 CLK in this embodiment) for timing adjustment via an AND gate 1714, the ITOP signal can be generated at the center of the BD signal cycle. it can.

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 light written based on the BD signal of the first scan of the first rotation. , And the scanning lines of the first scan in the first rotation and the second rotation overlap each other for every 8192 BD signals. Furthermore, I
When the input of the TOP signal comes in the first half of the BD signal cycle, align the ITOP signal with the center of the BD signal cycle,
When entering the latter half of the BD signal cycle, the BD signal can be used effectively by adjusting the ITOP signal to the center of the next BD signal cycle. By setting the position where the ITOP signal is generated at the center of the BD signal cycle, a large margin can be provided for fluctuations caused by uneven rotation of the photosensitive drum motor 115, and the accuracy of the motor and the driving mechanism can be sufficiently accommodated.

Therefore, if image writing is started based on the ITOP signal, the phase difference between the ITOP signal and the BD signal is always constant for each color, so that the image writing positions from the first color to the Nth color can be accurately determined. And a high-quality image without color shift can be obtained.

[Fifth Embodiment] The first to fourth embodiments described above.
In the embodiment, the main scanning start signal (BD signal) is frequency-divided and used as a reference clock for the photosensitive drum 105, the transfer drum 108, and the photosensitive drum motor 115 for driving the intermediate transfer member. Drum 108
Main scanning start signal (BD signal) obtained during one rotation of
And the case where the number of main scanning recording line signals synchronized therewith is set to an integer value, the reference clock of the photosensitive drum motor 115 for driving the photosensitive drum 105, the transfer drum 108, and the intermediate transfer member, and the main scanning May be configured to synchronize the scanner motor 106 with the photosensitive drum 105, the transfer drum 108, and the intermediate transfer member by using a clock common to the reference clock of the scanner motor 106 that drives the scanner motor 106.

Thus, the present invention is applied, and the first
The same effects as in the fourth to fourth embodiments can be obtained.

[Sixth Embodiment] The first to fourth embodiments described above.
In the embodiment, the main scanning start signal (BD signal) is frequency-divided and used as a reference clock for the photosensitive drum 105, the transfer drum 108, and the photosensitive drum motor 115 for driving the intermediate transfer member. Drum 108
Main scanning start signal (BD signal) obtained during one rotation of
And the case where the number of main scanning recording line signals synchronized therewith is set to an integer value. However, every time a sub-scanning start signal (ITOP signal) is generated, the main scanning start signal (B
By synchronizing the phase of the D signal) with the phase of the sub-scanning start signal, the synchronization of the photosensitive drum 105, the transfer drum 108, the intermediate transfer member and the scanner motor 106 may be synchronized.

As a result, the present invention is applied and the first
The same effects as in the fourth to fourth embodiments can be obtained.

[Seventh Embodiment] The first to sixth embodiments described above.
In the embodiment, one rotation of the photosensitive drum 105 corresponds to one rotation.
Although the case where one ITO signal is issued has been described, a plurality of ITO
When a P signal is issued, the ITOP signal delay amount calculation is independently calculated for each ITOP signal, and
The TOP signal may be configured to be delayed based on the calculated delay amount.

In this way, even when a plurality of latent images are formed and transferred with one rotation of the photosensitive drum, the writing positions of the first to Nth images can be accurately adjusted, and color misregistration can be achieved. No high quality images can be obtained.

In the first embodiment, the case where the ITO sensor 110 detects the flag 111 fixed in the transfer drum and transmits the sub-scanning start signal (ITOP signal) has been described. A timekeeping unit that measures the cycle of the drum etc. is provided, and based on the timekeeping of the timekeeping unit,
The sub-scanning start signal (ITOP signal) may be transmitted.

As described above, the generation position of the ITOP signal within the BD signal cycle is detected, the phase difference from the generation position serving as a reference, for example, the generation position of the ITOP signal of the first color, is detected, and the sub-scanning line is accordingly detected. By controlling the count value of the counter, if the relative generation timing of the sub-scanning start signal and the main scanning start signal fluctuates from the theoretical value only with the misregistration prevention technology by the device configuration, for example, load fluctuation or drive transmission Even if the rotational speed of the photoconductor or the like is shifted due to the effects of gear back crash, the start position of the image of each color on the paper matches the position of the first color without shifting the timing of the sub-scanning start signal. As a result, a high-quality image without color shift can be obtained.

Also, regardless of the timing at which the sub-scanning start signal is generated, the delay means always adjusts the sub-scanning start signal to the center of the cycle of the main scanning start signal. Even if it fluctuates, the start position of the image of each color on the paper can be matched with the position of the first color without shifting the timing of the main scanning start signal, and a high-quality image without color shift can be obtained.

In each of the above embodiments, a case has been described where the control shown in each of the flowcharts is implemented by hardware, but the control may be implemented by software.

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 CPU or 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.

Further, the present invention may be applied to a system composed of a plurality of devices or an apparatus composed of one 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 out a program represented by software for achieving the present invention from a database on a network using a communication program, the system or apparatus can be
It is possible to enjoy the effects of the present invention.

[0173]

As described above, the first embodiment according to the present invention is described.
According to the invention, the detecting means detects the phase difference between the sub-scanning start signal and the main scanning start signal at the first timing,
The delay means delays the sub-scanning start signal at the second timing based on the phase difference detected at the first timing by the detection means. Adjust the scan start signal,
Even when the sub-scanning start signal fluctuates, the start positions of the images of the respective colors can be matched without shifting the timing of the main scanning start signal.

According to the second invention and the third invention, the delay means is arranged such that the sub-scanning start signal generated by the sub-scanning start signal generating means is generated at the center of the main scanning start signal cycle. The delay amount of the sub-scanning start signal is calculated based on the phase difference detected at the first timing by the detection means, and the sub-scanning start signal is calculated at the second timing based on the calculated delay amount. Therefore, no matter what timing the sub-scanning start signal is generated, the sub-scanning start signal is adjusted to match the center of the cycle of the main scanning start signal. The start position of the image of each color can be matched without shifting the timing of the start signal.

According to the fourth aspect, the first timing is a timing at which a sub-scanning start signal is generated at the time of performing the first image formation, and the second timing is a timing at which the first and subsequent images are formed. Since the sub-scanning start signal is generated at the time of formation, the writing start position of each image can be made to coincide with the initial position.

According to the fifth aspect, the first timing is a timing at which a sub-scanning start signal is generated at the time of forming an image of the first color, and the second timing is a timing of generating an image of the first color and thereafter. Since the sub-scanning start signal is generated at the time of formation, the writing start position of each color can be matched with the position of the first color.

According to the sixth aspect, the detecting means detects a phase difference between the sub-scanning start signal and the main scanning start signal, and the delaying means detects the phase difference detected by the detecting means. When the phase difference is less than “１ ／” times the start signal cycle, the sub-scanning start signal is delayed by a difference between the phase difference and “１ ／” times the main scanning start signal cycle. If the period is equal to or longer than "1/2" of the main scanning start signal period, the sub-scanning start signal is delayed by the difference between the phase difference and "3/2" times of the main scanning start signal period. Regardless of the timing at which the signal is generated, the sub-scanning start signal is adjusted to be aligned with the center of the cycle of the main scanning start signal, so that the timing of the main scanning start signal does not shift even if the sub-scanning start signal varies. , The writing position of each color image can be matched Kill.

According to the seventh aspect, the sub-scanning start signal is generated at the first timing by the sub-scanning start signal generating means with respect to each sub-scanning start signal generated by one rotation of the image carrier. Detecting means for detecting a phase difference from the main scanning start signal is provided, and the delay means delays each sub-scanning start signal at a second timing based on each phase difference detected by each detecting means. Therefore, even if the sub-scanning start signal for each color component of the image forming apparatus capable of forming a plurality of images by generating a plurality of sub-scanning start signals per rotation of the image carrier is generated, Is adjusted, the writing start positions of the images of the respective colors can be made to coincide with each other without shifting the timing of the main scanning start signal even if the sub-scanning start signal fluctuates.

According to the eighth aspect, since the image information for each color component is read from the original, the image writing position of each color component of the image read from the original can be matched.

According to the ninth aspect, since the image information for each color component is input from the information processing device via a predetermined communication medium, the image writing of each color component of the image input from the information processing device is performed. The positions can be matched.

According to the tenth aspect, in the control method of the image forming apparatus for forming a multicolor image by sequentially superimposing the color component images formed based on the image information for each color component, At a first timing, a phase difference between a sub-scanning start signal generated in synchronization with the main scanning start signal and a main scanning start signal generated by detecting a light beam scanned by the rotating polygon mirror is detected. Based on the phase difference, at a second timing, a delay amount of the sub-scanning start signal is calculated so that the sub-scanning start signal is generated at the center of the main scanning start signal cycle. Since the sub-scanning start signal generated for each image formation is delayed on the basis of the timing, the sub-scanning start signal is adjusted at any timing and the sub-scanning start signal is adjusted even if the sub-scanning start signal fluctuates. The timing of the main scanning start signal is Without, it is possible to match the writing position of each color image.

Therefore, even if the rotational speed of the photosensitive member or the like is deviated due to the influence of load fluctuations or back crash of the drive transmission gear, the image writing positions of the respective color components are matched, and there is no color deviation. There is an effect that a high-quality image can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of an image forming apparatus according to a first 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 circuit diagram illustrating a configuration of a phase matching circuit illustrated in FIG. 2;

FIG. 5 is a flowchart illustrating a phase matching processing procedure of the image forming apparatus according to the first exemplary embodiment of the present invention.

FIG. 6 is a timing chart illustrating a phase matching process of the image forming apparatus according to the first exemplary embodiment of the present invention.

FIG. 7 is a flowchart illustrating a phase matching processing procedure of the image forming apparatus according to the second exemplary embodiment of the present invention.

FIG. 8 is a timing chart illustrating a phase matching process of the image forming apparatus according to the second exemplary embodiment of the present invention.

FIG. 9 is a flowchart illustrating a phase matching processing procedure of the image forming apparatus according to the third exemplary embodiment of the present invention.

FIG. 10 is a circuit diagram illustrating a configuration of a phase matching circuit illustrated in FIG. 2;

FIG. 11 is a timing chart illustrating a phase matching process of the image forming apparatus according to the fourth exemplary embodiment of the present invention.

FIG. 12 is a schematic diagram of a main scanning line formed on a photosensitive member or an intermediate transfer member of a conventional image forming apparatus.

FIG. 13 is a diagram illustrating a configuration of a conventional image forming apparatus.

FIG. 14 is a diagram illustrating a configuration of a conventional image forming apparatus.

FIG. 15 is a diagram illustrating a configuration of a conventional image forming apparatus.

FIG. 16 is a schematic diagram showing a relationship between an actual main scanning line (main scanning start signal) and an ITOP signal (sub-scanning start signal) on a photosensitive member of a conventional image forming apparatus.

FIG. 17 is a timing chart showing image forming timing of a conventional image forming apparatus.

FIG. 18 is a schematic diagram when a generation phase of a sub-scanning start signal for each recording color of the conventional image forming apparatus is generated across a main scanning start signal.

FIG. 19 is a timing chart showing image forming timing of a conventional image forming apparatus.

[Explanation of symbols]

 101 Image writing timing control circuit 103 Polygon mirror 107 BD sensor 110 ITOP sensor 122 Phase matching circuit 130 CPU 1303 Latch circuit 1308 Subtraction circuit 1302 Data load down counter 1313 JK flip-flop

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H04N 1/113 H04N 1/04 104A F-term (Reference) 2C362 BB29 BB32 BB37 BB46 BB47 BB48 BB50 CA18 CA22 CA38 2H027 DA21 DA22 DA23 DE02 DE09 EA18 EC06 ED02 ED06 EE02 EF06 EH08 2H030 AA01 AD17 BB02 BB16 5C072 AA03 BA19 CA06 EA05 HA02 HA13 HB11 JA07 JA08 UA18 XA01 XA05

Claims (10)

[Claims] An image forming apparatus for forming a multi-color image by sequentially superimposing color component images formed based on image information for each color component, wherein a light beam based on the image information for each color component is deflected. A rotating polygon mirror that scans an image carrier that is driven to rotate, a main scanning start signal generating unit that detects a light beam scanned by the rotating polygon mirror and generates a main scanning start signal, and the image carrier. A sub-scanning start signal generating unit that generates a sub-scanning start signal in synchronization with the rotation of the scanning unit; a detecting unit that detects a phase difference between the sub-scanning start signal and the main scanning start signal at a first timing; A delay unit that delays the sub-scanning start signal at a second timing based on the phase difference detected at the first timing. 2. The delay unit according to claim 1, wherein the sub-scanning start signal generated by the sub-scanning start signal generating unit is generated at a first timing by the detecting unit such that the sub-scanning start signal is generated at the center of the main scanning start signal cycle. 2. A sub-scanning start signal is delayed at the second timing based on the detected phase difference, the delay amount of the sub-scanning start signal being calculated based on the detected phase difference. The image forming apparatus as described in the above. 3. A delay amount of the sub-scanning start signal, wherein the delay unit calculates a difference between a phase difference detected at a first timing by the detecting unit and "3/2" times of a period of the main scanning start signal. The image forming apparatus according to claim 2, wherein the calculation is performed as: 4. The first timing is a sub-scanning start signal generation timing at the time of performing the first image formation, and the second timing is the sub-scanning start signal generation timing at the time of performing the first and subsequent image formation. 2. The image forming apparatus according to claim 1, wherein the timing is a timing at which a scanning start signal is generated. 5. The first timing is a sub-scanning start signal generation timing at the time of forming an image of the first color, and the second timing is a sub-scanning start signal at the time of forming an image of the first color and thereafter. 2. The image forming apparatus according to claim 1, wherein the timing is a timing at which a scanning start signal is generated. 6. An image forming apparatus for forming a multicolor image by sequentially superimposing color component images formed based on image information for each color component, wherein a light beam based on the image information for each color component is deflected. A rotating polygon mirror that scans an image carrier that is driven to rotate, a main scanning start signal generating unit that detects a light beam scanned by the rotating polygon mirror and generates a main scanning start signal, and the image carrier. Sub-scanning start signal generating means for generating a sub-scanning start signal in synchronization with the rotation of the detecting means; detecting means for detecting a phase difference between the sub-scanning start signal and the main scanning start signal; and a position detected by the detecting means. When the phase difference is less than “１ ／” times the main scanning start signal cycle, the sub-scanning start signal is delayed by a difference between the phase difference and “１ ／” times the main scanning start signal cycle; The phase difference is the main scanning start signal cycle. An image forming apparatus comprising: a delay unit that delays a sub-scanning start signal by a difference between the phase difference and “3/2” times the period of the main scanning start signal when the ratio is equal to or more than １ ／ times. . 7. The sub-scanning start signal generating means generates a plurality of sub-scanning start signals for one rotation of the image carrier in synchronization with the rotation of the image carrier. Generating means for detecting a phase difference between the sub-scanning start signal and the main scanning start signal at a first timing with respect to each of the sub-scanning start signals generated by one rotation of the image carrier; The image forming apparatus according to claim 1, wherein the delay unit delays each sub-scanning start signal at a second timing based on each phase difference detected by each of the detection units. 8. The image forming apparatus according to claim 1, wherein the image information for each color component is read from a document. 9. The image forming apparatus according to claim 1, wherein the image information for each color component is input from an information processing apparatus via a predetermined communication medium. 10. A control method of an image forming apparatus for forming a multi-color image by sequentially superimposing color component images formed based on image information for each color component, wherein the multi-color image is generated in synchronization with rotation of an image carrier. Detecting a phase difference between a sub-scanning signal and a main scanning start signal generated by detecting a light beam scanned by the rotary polygon mirror at a first timing; and detecting a phase difference based on the detected phase difference. Then, at the second timing,
A calculating step of calculating a delay amount of the sub-scanning start signal so that the sub-scanning start signal is generated at the center of the main scanning start signal cycle; and a calculating step for each image formation based on the calculated delay amount. A delaying step of delaying a sub-scanning start signal.