JP2001264674A - Image forming device and its control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To print an image without deteriorating a rotation jitter when digital PLL control is performed to correct a writing position in a sub-scanning direction in an electrophotographic image forming device. SOLUTION: A rotation reference signal for controlling the rotational speed of a scanner motor 19 is generated, the accelerating or decelerating signal of the scanner motor 19 is generated by a speed control part 11 from the rotational position signal of the scanner motor 19, which is detected by a horizontal synchronizing signal detecting part 18, a phase comparing part 12 compares the phase of the rotational position signal with that of the rotation reference signal to generate a phase delay or advance signal, the rotation of the scanner motor 19 is controlled based on the accelerating or decelerating signal during printing the image and, then, the rotation of the scanner motor 19 is controlled based on the accelerating or decelerating signal and the phase delay or advance signal during printing no image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a color printer,
TECHNICAL FIELD The present invention relates to an image forming apparatus in which the rotation speed control of a scanner motor for deflecting a light beam is improved in a color copying machine or the like, particularly an electrophotographic image forming apparatus having a plurality of laser scanners and photosensitive drums, and a control method thereof. is there.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram schematically showing a general electrophotographic image forming apparatus for performing color printing.

FIG. 6 shows a color printer provided with image forming means for four colors, namely, yellow Y, magenta M, cyan C, and black K. In the figure, reference numerals 1a, 1b, 1c, and 1d denote photosensitive drums (a, b, c, and d respectively represent K, C, and
M, Y) 2a, 2b, 2c, 2d perform exposure of each color in accordance with an image signal, and each of the photosensitive drums 1a, 1
A laser scanner 3 for forming an electrostatic latent image on b, 1c, 1d is an endless transport belt for sequentially transporting the paper to the image forming section of each color, and also serves as a transfer belt.

Reference numeral 4 denotes a driving roller connected to driving means, not shown, comprising a motor and gears for driving the conveyor belt 3, and a driven roller 5 which rotates according to the movement of the conveyor belt 3 and applies a constant tension to the conveyor belt 3. , 6a and 6b are a pair of optical sensors for detecting a misregistration detection pattern formed on the conveyor belt 3, and are provided on both sides of the conveyor belt 3.

Next, the operation of the color printer having the above configuration will be described.

When data to be printed is sent from a PC (Personal Computer) to the printer, and image formation according to the printer engine system is completed and the printer is ready for printing, paper is supplied from a paper cassette and the paper is conveyed. Upon reaching the belt 3, the sheets are sequentially conveyed to the image forming units of each color by the conveying belt 3. Image signals of each color are sent to each of the laser scanners 2a, 2b, 2c and 2d in synchronism with the sheet conveyance by the conveyance belt 3, and respective electrostatic latent images are formed on the photosensitive drums 1a, 1b, 1c and 1d. The toner is developed in each developing device. This toner image is transferred onto a sheet at a transfer unit (not shown).

In the apparatus shown in FIG. 6, images are sequentially formed in the order of Y, M, C, and K. Thereafter, the sheet is separated from the transport belt 3, and the toner image is fixed on the sheet by heat in a fixing device (not shown), and is discharged to the outside.

Here, in the laser scanner of each image forming section of the image forming apparatus having the above configuration, a light beam generating means, a light beam control means for controlling the light beam to be turned on by an image signal, and the light beam A scanner motor for deflecting and scanning the beam on the photosensitive drum, scanner motor driving means for rotating and driving the scanner motor, and detecting a light beam deflected and scanned by the scanner motor at a predetermined position and outputting a horizontal synchronization signal Horizontal synchronization signal detection means, rotation reference signal generation means for generating a rotation reference signal of the scanner motor, and rotation position detection means for detecting the rotation position of the scanner motor, and the rotation reference signal and the output signal of the rotation position detection means , And controls each driving means so that each scanner motor rotates at a constant speed.

[0009] Then, the images formed by the respective image forming units are superimposed and transferred on paper. At this time, in order to transfer the respective images accurately on the paper, the image formation start positions of the respective images on the respective photosensitive drums in the main scanning direction and the sub scanning direction must be accurately adjusted.

In the main scanning direction, the writing timing of each image is adjusted for each image forming section based on the horizontal synchronizing signal of each light beam, so that even if the surface phases of the scanner motors do not coincide with each other. Image shift can be corrected.

In the sub-scanning direction, the distance between the image forming units is set to an integral multiple of the image pitch in the sub-scanning direction.
By adjusting the timing of writing each image for each light beam scanning cycle, it is possible to adjust to an image shift of one pixel pitch or less. However, if the surface phase of the scanner motor does not match exactly, a shift of one pixel pitch or less occurs. In order to solve this problem, PLL control of each scanner motor is performed using a common rotation reference signal supplied to each scanner motor control unit.

FIG. 7 shows a block diagram of a digital PLL controller of such a scanner motor. In the figure, 19
Is a scanner motor integrated with the polygon mirror, and the rotational position detecting means 18 detects the rotational position of the scanner motor 19 and outputs a rotational position signal S2. The speed control unit 11 sets the / VACC signal S3 to the L (low) level only during a period in which the cycle of the position signal S2 is longer than a predetermined period based on the rotation position signal S2. Only for a short period of time / VDEC signal S4
To L level.

The phase comparator 12 compares the phase of the rotation reference signal S1 output from the rotation reference signal generating means (not shown) with the phase of the rotation position signal S2, and determines whether the rotation position signal S2 is delayed from the rotation reference signal S1. Only the / lag signal S5 is set to the L level, and the / lead signal S6 is set to the L level only during a period that is ahead of the rotation reference signal S1. Gate 13
The / lag signal S5 is superimposed on the / VACC signal S3,
Generate a CC signal S7. The gate 14 superimposes the / lead signal S6 on the / VDDED signal S4 and outputs the / DEC signal S4.
8 is generated.

The charge pump 15 is provided with a / ACC signal S7
And the capacitor 16 is charged / discharged according to the Low period of the / DEC signal S8 to generate the motor control voltage S12.
The motor drive unit 17 drives the scanner motor 19 based on the motor control voltage. Then, by the operation described above, the rotation driving of the scanner motor 19 is controlled in a state where the rotation is in phase with the rotation reference signal.

[0015]

However, in the above-described image forming apparatus, digital PLL control of the scanner motor is performed by superimposing the output pulse of the phase comparison means on the output pulse of the speed discrimination. In order to superimpose the phase lag and phase advance signals, which are the output signals of the phase control unit, on the acceleration signal and deceleration signal of the speed discrimination, respectively, the rotation is compared with the case where the rotation speed of the scanner motor is controlled only by the speed control loop. There is a problem that the speed jitter becomes large.

The present invention has been made in view of the above-described problems. Even in the case where the writing phase in the sub-scanning direction is corrected by performing digital PLL control, the image can be reproduced without deteriorating the rotation jitter. It is an object to provide an image forming apparatus capable of performing printing and a control method thereof.

[0017]

An image forming apparatus and a control method therefor according to the present invention are configured as follows.

(1) An electrophotographic image forming apparatus, comprising: a scanner motor for scanning a photosensitive drum with a light beam; and a rotation reference signal for controlling the rotation speed of the scanner motor to a predetermined value. A rotation reference signal generating means for outputting, a rotation position detection means for detecting a rotation position of the scanner motor and outputting a rotation position signal, and a speed control means for outputting an acceleration or deceleration signal of the scanner motor from the rotation position signal And phase control means for comparing the phase of the rotation position signal and the rotation reference signal and outputting a phase delay or phase advance signal, and during image printing, based on an acceleration or deceleration signal from the speed control means. The rotation of the scanner motor is controlled, and during non-printing, the acceleration or deceleration signal from the speed control means and the phase delay or phase from the phase control means are controlled. And to control the rotation of the scanner motor based proceeds to the signal.

(2) In the above (1), there is provided a cycle measuring means for measuring the cycle of the rotational position signal, and the target cycle is set so that the difference between the measured cycle of the rotational position signal and the target cycle becomes small. I did it.

(3) A method for controlling an electrophotographic image forming apparatus, wherein a rotation reference signal for controlling a rotation speed of a scanner motor for scanning a photosensitive drum with a light beam to a predetermined value is generated. Along with this, the rotational position of the scanner motor is detected to obtain a rotational position signal, an acceleration or deceleration signal of the scanner motor is generated from the rotational position signal, and the rotational position signal and the phase of the rotational reference signal are compared. Generates a phase delay or phase advance signal, controls the rotation of the scanner motor based on the acceleration or deceleration signal during image printing, and outputs the acceleration or deceleration signal and the phase delay or phase advance signal during non-printing. The rotation of the scanner motor is controlled based on this.

(4) In the above (3), the period of the rotational position signal is measured, and the target period is set so that the difference between the measured period of the rotational position signal and the target period becomes small.

[0022]

Embodiments of the present invention will be described below with reference to the drawings.

As an image forming apparatus according to the present invention, as shown in the perspective view of FIG. 6, a four-drum type color having four color image forming portions of yellow Y, magenta M, cyan C and black K is used. The image forming apparatus will be described.

(First Embodiment) FIG. 1 is a block diagram showing a configuration of a first embodiment of the present invention, and shows a main part of a scanner motor control unit. In this embodiment, yellow Y,
Each of the four color image forming units of magenta M, cyan C, and black K is provided with a laser scanner, and FIG. 1 shows only one scanner motor control unit.

In FIG. 1, reference numeral 11 denotes a scanner motor 19.
/ VA is an acceleration signal for controlling the rotational drive of the motor at a constant speed.
CC signal (S3), / VDEC signal (S
A speed controller (means) 12 comprising a speed discriminator circuit for generating 4), a / RefBD signal (S1) as a rotation reference signal and a rotation position detection signal (S2) such as a horizontal synchronization signal.
And a phase delay corresponding to the phase difference is shown.
The phase comparison unit (means) 13 for generating the lag signal (S5) and the / lead signal (S6) indicating the phase advance,
An AND circuit that combines the VACC signal and the / lag signal to generate an / ACC signal (S7) that becomes an actual acceleration signal;
An AND circuit 14 combines the / VEDD signal and the / lead signal to generate a DEC signal (S8) which is an actual deceleration signal.

Reference numeral 15 denotes a charge pump for charging / discharging the capacitor 16 based on the / ACC signal and / DEC signal. Reference numeral 17 denotes a motor for driving the scanner motor 19 based on a predetermined voltage determined by the capacitor 16. The drive unit 18 detects a laser beam (not shown) reflected by the polygon mirror in accordance with the rotation of the scanner motor 19, and generates a horizontal synchronization signal (hereinafter, referred to as a / BD signal) as a reference of a writing position in the main scanning direction. This is a horizontal synchronization signal detection unit (hereinafter referred to as a BD sensor) for detecting.
The sensor 18 functions as means for detecting the rotational position of the scanner motor 19. Reference numeral 20 denotes a frequency divider for dividing (1 / m) the / BD signal output from the BD sensor 18, and reference numerals 25 and 26 denote valid / invalid outputs of the phase comparator 12.
This is a gate for controlling invalidation.

In step S11, the gate is turned on / off.
, And S9 and S10 are outputs after the outputs S5 and S6 of the phase comparator 12 have been turned on / off by the gates 25 and 26, respectively.

Although not shown, this embodiment has a photosensitive drum for carrying an electrostatic latent image, a light beam generating means, and a light beam control means for controlling the light beam to be turned on by an image signal. Then, the scanner motor 19 deflects and scans the light beam on the photosensitive drum. And a rotation reference signal generating means for generating a rotation reference signal for controlling the rotation speed of the scanner motor 19 within a predetermined range. The phase of the rotation reference signal is compared with the phase
To generate a phase lag and phase lead signal,
A plurality of image forming means comprising scanner motor control means comprising means for generating a control signal for controlling the motor drive section 17 by combining the acceleration and deceleration signals of the scanner motor 19 and the phase delay and phase advance signals thereof; I have.

The scanner motor control means includes a mode for controlling the rotation of the scanner motor 19 only by the speed control unit 11 and a mode for controlling the rotation of the scanner motor 19 by combining the speed control unit 11 and the phase control unit 12. The control mode switching means controls the rotation of the scanner motor 19 by the speed control unit 11 during image printing, and the speed control unit 11 and the phase control unit 12 when image printing is not performed. Are switched so that the rotation of the scanner motor 19 is controlled.

FIG. 2 is a timing chart showing the operation of this embodiment. Next, the operation of the scanner motor control unit in FIG. 1 will be described using this timing chart. S1, S2, S3, S7, and S9 of FIG.
It corresponds to S2, S3, S7, S9.

Based on the / BD signal from the BD sensor 18, the speed controller 11 sets the / ACC signal to a LOW (low) level for a period in which the period of the / BD signal is longer than a preset period T1. Further, the / DEC signal is set to the LOW level only during a period in which the cycle of the / BD signal is shorter than T1. The charge pump 15 charges the capacitor 16 when the / ACC signal is at a low level and the / DEC signal is at a high (high) level, and charges the capacitor 16 when the / ACC signal is at a high level and the / DEC signal is at a low level. To discharge. The motor drive unit 17 drives the scanner motor 19 based on the voltage of the capacitor 16.
Therefore, the scanner motor 19
Is driven to rotate such that the cycle of the / BD signal is a predetermined cycle T1.

Next, the phase comparator 12 will be described.
/ RefBD signal (S1), which is a rotation reference signal set to have a predetermined cycle, and BD
The / BD signal (S2) output from the sensor 18 is divided by the frequency divider 2
The frequency is divided by m by 0 and input to the phase comparison unit 12 (m is a natural number). The phase comparison section 12 compares the phases of the two signals and
The / lag signal is set to the LOW level only when the signal is behind the phase of the / RefBD signal, and the / lead signal is set to the LOW level only when the phase is advanced.

In FIG. 2, when the rotation speed of the scanner motor 19 is lower than a predetermined rotation speed, that is, / VAC
The signal when the C signal is at the LOW level is shown. Also, the signal when the phase of the / BD signal is delayed with respect to the rotation reference signal / RefBD is shown.

The AND circuit 13 controls the charge pump 15 based on the / VACC signal and the / lag signal.
The AND circuit 14 combines the / VDEC signal and the / lead signal into a charge pump 1.
5 and a circuit for synthesizing the DEC signal. FIG.
As shown in (1), the / ACC signal is synthesized by adding the / VACC signal and the / lag signal by the AND circuit 13.

By combining the / ACC signal as described above, the / ACC signal can be output in consideration of not only the speed information but also the phase information. When the phase of the / BD signal of the scanner motor 19 matches the phase of the / RefBD signal, the / lag signal becomes HIGH level,
The scanner motor 19 rotates according to a predetermined speed and phase.

FIG. 3 shows a scanner motor 1 according to the first embodiment.
9 is a diagram showing the timing of performing the PLL control of FIG.
Reference numeral 3 denotes a / TOP signal indicating the start of printing. When a video controller (not shown) outputs image data in synchronization with the / TOP signal S13, the image forming apparatus controls lighting of a laser diode (not shown) based on the image data to print an image. S14 is a signal indicating the printing state of the image forming apparatus. S15 is the scanner motor 1
9 is a signal indicating the control state.

FIG. 3 shows a print sequence in the case where continuous printing is performed. The hatched portion in the signal S14 indicates a period from the end of image printing until the / TOP signal of the next page comes (between the paper interval and the paper interval). Call). The laser is turned off between the sheets.

In the first embodiment, during image printing (signal S1
4), only the speed control is performed as shown by the vertical line portion in the signal S15, and the speed control is performed only during the non-printing period where the image is not printed (the period of the horizontal line portion in the signal S15). Digital PLL control is used together. With the digital PLL control between the sheets, the surface phase of the polygon of each scanner motor 19 can be controlled to a predetermined phase. afterwards,
By performing only speed control during image printing, image printing can be performed without deterioration of jitter.

At this time, the digital PLL control is turned ON / OFF.
The turning off can be realized by setting the signal S11 to a LOW level or a HIGH level by an engine controller (not shown). That is, when the scanner motor 19 is started, the signal S11 is set to a low level, digital PLL control is used together, and after detecting a / TOP signal, the signal S11 is set to a high level to control the scanner motor 19 only by speed control. . Then, at the timing when the output of the image data ends, the signal S11 is set to the LOW level again, whereby the digital PLL is output.
Use control together. Thereafter, this operation is repeated.

The above-mentioned scanner motor control unit is yellow,
By applying the / RefBD signal to a common signal for each of the scanner motor control units for magenta, cyan, and black, it is possible to perform rotation drive control with the polygon phase of each scanner motor 19, Digital PL
Even in the case of performing the L control, it is possible to eliminate the image shift in the sub-scanning direction between the image forming units without deteriorating the jitter. In addition, signals having the same cycle but different phases are converted into / R
The color shift in the sub-scanning direction may be corrected by supplying the signal as an efBD signal and shifting the surface phase of the polygon.

Since digital PLL control is not applied during image printing, the rotation speed of the scanner motor 19 for each color differs by the steady speed deviation of each scanner motor 19. However, since the deviation is small, the phase shift during printing one page is small. Since the digital PLL control is always performed before starting the image signal of each page, the surface phase of the polygon of each scanner motor 19 is kept almost constant.

(Second Embodiment) A second embodiment of the present invention will be described. Also in this embodiment, a four-drum type color image forming apparatus having four color image forming units is provided.
FIG. 4 shows a configuration related to the scanner motor control unit. FIG. 4 shows a scanner motor control unit of one of the four-color laser scanners.
1 having the same operations as those shown in the embodiment of FIG. The detailed operation of each unit is the same as in the first embodiment, and a description thereof will be omitted.

In this embodiment, a cycle setting unit 22 is provided in addition to the scanner motor control unit of the first embodiment. The cycle setting unit 22 includes a BD sensor 1 that is a rotational position detector.
8 serves as a period measuring means for measuring the period of the rotation position signal S2 from the control unit 8. If there is a rotational speed deviation in the scanner motor 19 and there is a difference between the actual measured value and the target period, the period setting unit 22 changes the set value of the speed discrimination so as to eliminate the difference.

FIG. 5 shows a scanner motor 1 according to the second embodiment.
9 is a diagram showing timing for performing digital PLL control of No. 9, and S13 is a / TOP signal indicating the start of printing. A video controller (not shown) uses the / TOP signal S13
When the image data is output in synchronization with the image data, the image forming apparatus controls the lighting of a laser diode (not shown) based on the image data to perform image printing. S14 is a signal indicating the printing state of the image forming apparatus. S15 is a signal indicating the control state of the scanner motor 19.

FIG. 5 shows a print sequence in the case where continuous printing is performed. The hatched portion on the upper right of the signal S14 indicates the / TOP of the next page after the image printing is completed.
The period until the signal comes (between sheets) is shown. The laser is turned off between the sheets.

In the second embodiment, before image printing is performed (during the period of the slanted portion of the signal S14 falling to the right), the scanner motor 19 is controlled by using the digital PLL control together with the speed control as shown by the horizontal line of the signal S15. to start. Thereafter, during image printing (the period of the white portion of the signal S14) and the sheet interval (the signal S1
4), only speed control is performed. The phase control of the polygon of the scanner motor 19 can be controlled to a predetermined phase by the PLL control at the time of the start. Thereafter, by performing only the speed control, image printing can be performed without deteriorating jitter.

At this time, the digital PLL control is turned ON.
Although not shown, / OFF can be realized by setting the signal S11 to a LOW level or a HIGH level by an engine controller. That is, when the scanner motor 19 is started, the signal S11 is set to the LOW level, and the speed control and the digital PLL control are used together.
By setting the signal S11 to the HIGH level after detecting the / TOP signal, the scanner motor 19 is controlled only by the speed control.

The above-described scanner motor control unit is yellow,
By applying the / RefBD signal to each of the scanner motor control units of magenta, cyan, and black and making the / RefBD signal a common signal, the polygon motors of the scanner motors 19 can be rotated and controlled with the same phase. PL
Even in the case of performing the L control, it is possible to eliminate the image shift in the sub-scanning direction between the image forming units without deteriorating the jitter. In addition, signals having the same cycle but different phases are applied to each color with / R
The color shift in the sub-scanning direction may be corrected by supplying as an efBD signal and using this signal to shift the surface phase of the polygon.

At this time, the cycle setting value of each scanner motor 19 is set to an optimum value for each scanner motor 19 by the cycle setting unit 22 of each scanner motor 19, and the rotational speed deviation between the scanner motors is set. Is small. Therefore, even when continuous printing is performed, image printing can be performed while the color shift in the sub-scanning direction is small.

(Third Embodiment) A third embodiment of the present invention will be described. Also in this embodiment, a four-drum type color image forming apparatus having four color image forming units is provided.
The scanner motor control section of this embodiment has the same configuration as that of the second embodiment, and will be described with reference to FIG. FIG. 4 shows a scanner motor control unit of one of the four color laser scanners. The detailed operation of each unit is the same as that of the second embodiment, and a description thereof will be omitted.

In this embodiment, in addition to the scanner motor controller of the second embodiment, a signal S11 for controlling ON / OFF of PLL control is controlled based on a print sequence.

The timing chart of FIG. 3 shows the timing for performing digital PLL control of the scanner motor 19 in the present embodiment, which is the same as that used in describing the first embodiment. S13 indicates printing start / T
OP signal. Video controller not shown is / TO
When the image data is output in synchronization with the P signal S13, the image forming apparatus controls the lighting of a laser diode (not shown) based on the image data and prints an image. S14 is a signal indicating the printing state of the image forming apparatus. Also, S15
Is a signal indicating the control state of the scanner motor 19.

FIG. 3 shows a print sequence in the case where continuous printing is performed. The hatched portion in the signal S14 indicates a period from the end of image printing until the / TOP signal of the next page comes (paper interval). Is shown. The laser is turned off between the sheets.

In the third embodiment, during image printing (signal S1
4), only the speed control indicated by the hatched portion in the signal S15 is performed, and the digital PLL control is used for the speed control only when the image printing is not performed (the period of the horizontal line portion in the signal S15). To be used together. By the digital PLL control between the sheets, the surface phase of the polygon of each scanner motor 19 can be controlled to a predetermined phase. Thereafter, by performing only the speed control during the image printing, the image printing can be performed without deteriorating the rotational speed jitter.

At this time, ON / O of digital PLL control is performed.
Although not shown, the FF can be realized by setting the signal S11 to a low level or a high level by the engine controller. That is, when the scanner motor 19 is started, the signal S11 is set to the LOW level to perform the PLL control, and after detecting the / TOP signal, the signal S11 is set to the HIGH level, so that the scanner motor 19 is controlled only by the speed control. . Thereafter, at the timing when the output of the image data ends, the signal S11 is again
By setting to W level, digital PLL control is used together with speed control. Thereafter, this operation is repeated.

The above-mentioned scanner motor control unit is yellow,
By applying the / RefBD signal to each of the magenta, cyan, and black scanner motor control units, the polygon motors of the scanner motors 19 can be rotated and controlled with the same phase, and the digital PLL control can be performed. Also in this case, it is possible to eliminate the image shift in the sub-scanning direction between the image forming units without deteriorating the rotational speed jitter. Alternatively, signals having the same cycle but different phases may be supplied as / RefBD signals of the respective colors, and the color shift in the sub-scanning direction may be corrected by shifting the surface phase of the polygon using the signals.

Since the digital PLL control is not applied during the image printing, the rotation speeds of the scanner motors 19 for the respective colors are slightly different. However, the cycle setting value of each scanner motor 19 at this time is set to an optimum value for each scanner motor 19 by the cycle setting unit 22 of each scanner motor 19, and the rotational speed deviation between the scanner motors is small. Therefore, the phase shift during printing one page is slight. Since the digital PLL control is always performed before the image printing of each page is started, the surface phase of the polygon of each scanner motor 19 is kept almost constant.

[0058]

As described above, according to the present invention,
Even in the case where the writing position in the sub-scanning direction is corrected by performing the digital PLL control, the image can be printed without deteriorating the rotational speed jitter.

Further, according to the present invention, by independently setting the speed setting values of the scanner motor control units of the respective colors, even when the writing position in the sub-scanning direction is corrected by performing digital PLL control, the rotation speed can be reduced. Image printing can be performed without deteriorating jitter.

According to the present invention, the speed of the scanner motor control unit for each color is set independently, and the digital PLL control is performed between sheets of paper.
Also in the case where the write start position in the sub-scanning direction is corrected by performing the L control, the image can be printed without deteriorating the rotational speed jitter.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is a timing chart showing the operation of the first embodiment.

FIG. 3 is a timing chart showing the operation of the first and third embodiments.

FIG. 4 is a block diagram showing the configuration of the second and third embodiments of the present invention.

FIG. 5 is a timing chart showing the operation of the second embodiment.

FIG. 6 is a perspective view illustrating a schematic configuration of an image forming apparatus.

FIG. 7 is a block diagram showing a configuration of a conventional example.

[Explanation of symbols]

 1a, 1b, 1c, 1d Photosensitive drums 2a, 2b, 2c, 2d Laser scanner 11 Speed controller 12 Phase comparator 13 AND circuit 14 AND circuit 15 Charge pump 17 Motor driver 18 Horizontal period signal detector (rotational position detector ) 19 Scanner motor 22 Period setting unit (period measurement unit) 25 gate 26 gate

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02P 5/00 301 G03G 21/00 372 9A001 H04N 1/113 H04N 1/04 104A F-term (Reference) 2C362 BA32 BA33 BA34 2H027 DA16 DA50 EB04 ED06 EE01 EE03 EE04 ZA07 2H045 AA01 AA53 AA56 CA88 CA98 5C072 AA03 BA15 HA02 HA13 HB08 HB11 HB16 5H550 AA10 AA14 AA15 GG04 GG07 GG08 JJ23 LL30 GG23 GG30

Claims (4)

[Claims] 1. An electrophotographic image forming apparatus, comprising:
A scanner motor for scanning the photosensitive drum with a light beam, rotation reference signal generating means for outputting a rotation reference signal for controlling the rotation speed of the scanner motor to a predetermined value, and detecting a rotation position of the scanner motor A rotation position detection means for outputting a rotation position signal, a speed control means for outputting an acceleration or deceleration signal of the scanner motor from the rotation position signal, and comparing the phases of the rotation position signal and the rotation reference signal. Phase control means for outputting a phase delay or phase advance signal, wherein during image printing the rotation of the scanner motor is controlled based on an acceleration or deceleration signal from the speed control means, and during non-printing the speed control means Controlling the rotation of the scanner motor based on an acceleration or deceleration signal from the controller and a phase delay or phase advance signal from the phase controller. Image forming apparatus characterized by. 2. The apparatus according to claim 1, further comprising a period measuring means for measuring a period of the rotation position signal, wherein the target period is set so that a difference between the measured period of the rotation position signal and the target period is reduced. Item 2. The image forming apparatus according to Item 1. 3. A method for controlling an electrophotographic image forming apparatus, comprising: generating a rotation reference signal for controlling a rotation speed of a scanner motor for scanning a photosensitive drum with a light beam to a predetermined value; Detecting the rotational position of the scanner motor to obtain a rotational position signal, generating an acceleration or deceleration signal of the scanner motor from the rotational position signal, and comparing the rotational position signal with the phase of the rotational reference signal. Generate a delay or phase advance signal, control the rotation of the scanner motor based on the acceleration or deceleration signal during image printing, and based on the acceleration or deceleration signal and the phase delay or phase advance signal during non-printing. Controlling the rotation of the scanner motor by controlling the rotation of the scanner motor. 4. The method according to claim 3, wherein the period of the rotation position signal is measured, and the target period is set so that a difference between the measured period of the rotation position signal and the target period becomes small. A method for controlling an image forming apparatus.