JP2000316292A - Motor drive device, its control method and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress rotation unevenness of a rotary unit which is produced when the rotary unit is turned by driving a motor at a low cost. SOLUTION: The revolution of a DC brushless motor 40 is detected with a magnetic pattern 45 and an MR sensor 41 which are formed on the outer circumference of a rotor 44. The rotation unevenness information of a rotary unit which is turned by driving the motor is detected with a DSP 20 in accordance with the revolution information of the DC brushless motor 40. The DSP 20 generates control data for suppressing the rotation unevenness of the rotary unit in accordance with the rotation unevenness information. The revolution of the DC brushless motor is controlled with the control data via an AND gate 33 and a driver 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor driving apparatus for driving a motor to rotate a rotating body, a control method therefor, and, for example, an electrophotographic image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, in a color image forming apparatus provided with image forming means for four colors, that is, yellow Y, magenta M, cyan C, and black BK, for example, as shown in FIG. , C, d are BK, C, M, Y, respectively.
Is rotated by driving the motor 6,
The photosensitive drum 1 is scanned by the laser scanner 2 according to an image signal.
The top is exposed to form an electrostatic latent image of each color, developed for each color, then transferred to paper, the toner image is heat-fixed by a fixing device 5, and discharged outside to obtain a color image. .

The photosensitive drums 1a, 1b, 1c,
Motors 6a, 6b, 6 for rotating 1d respectively
DC brushless motors and the like are used as c and 6d. However, uneven rotation occurs as shown in FIG. 12A due to the influence of torque ripple of the motor, eccentricity and pitch error of the gear, eccentricity of the rotating shaft, and the like. Therefore, the laser scan positions of the respective colors are as shown in FIG. 12B, and banding and color misregistration occur when the image is finally transferred to the sheet, thereby deteriorating the image quality.

In view of the above, in the related art, for example, a flywheel is used to suppress rotational unevenness to improve image quality.

There is also a method in which a rotary encoder is provided on a shaft of a rotating body, and a motor is controlled based on the detection result.

[0006]

However, the above conventional example has the following problems.

In the method using a flywheel, it is necessary to use a flywheel of several tens of kilograms in order to obtain a sufficient suppression effect, which has led to an increase in the size and cost of the apparatus.

In the method using a rotary encoder, a high-precision rotary encoder and high mechanical accuracy are required in order to obtain a sufficient suppression effect, resulting in an increase in the cost of the apparatus.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has a low-cost structure capable of suppressing rotation unevenness of a rotating body, a control method thereof, and an image forming apparatus. The purpose is to provide.

[0010]

SUMMARY OF THE INVENTION A motor driving apparatus, a control method thereof, and an image forming apparatus according to the present invention are configured as follows.

(1) In a motor driving device, a motor, control means for controlling the driving of the motor, a rotating body rotated by driving the motor, speed detecting means for detecting a rotation speed of the motor, and a motor Rotation unevenness information detecting means for detecting rotation unevenness information of the rotating body from rotation speed information of the motor, wherein the control means drives the motor so as to suppress the rotation unevenness of the rotating body based on the rotation unevenness information. Control is performed.

(2) In the motor driving device of the above (1), the uneven rotation information detecting means makes the frequency to be detected variable according to the rotation speed of the motor.

(3) In the motor driving device of (1) or (2), the uneven rotation information detecting means detects the uneven rotation information of the rotating shaft of the motor and detects the uneven rotation information separately from the uneven rotation information of the rotating body. I did it.

(4) In any one of (1) to (3) above, the control means controls the speed of the motor based on the detected information on the rotational unevenness so as to eliminate the rotational unevenness of the rotating body. I made it.

(5) In the motor driving device according to the above (3) or (4), the control means determines the frequency of the uneven rotation of the rotating body and the frequency of the uneven rotation of the motor shaft detected according to the rotation speed of the motor. The frequency to be suppressed is selected.

(6) In any one of (1) to (5) above, the control means is constituted by a DSP.

(7) In the control method of the motor driving device, the rotation speed of the motor is detected, and the rotation speed information of the rotating body rotated by driving the motor is detected from the rotation speed information of the motor, and the rotation unevenness information is detected. Based on the above, drive control of the motor is performed so as to suppress uneven rotation of the rotating body.

(8) In the control method of the motor drive device of the above (7), the motor speed is controlled based on the detected rotation unevenness information so as to eliminate the rotation unevenness of the rotating body.

(9) In the method for controlling a motor driving device according to the above (7) or (8), the frequency of the rotation unevenness of the rotating body and the frequency of the rotation unevenness of the motor shaft detected according to the rotation speed of the motor are determined. The frequency to be suppressed is selected.

(10) In the image forming apparatus, a motor, control means for controlling the driving of the motor, a rotating body rotated by driving the motor, speed detecting means for detecting a rotation speed of the motor, and the motor Rotation unevenness information detecting means for detecting rotation unevenness information of the rotating body from rotation speed information of the motor, wherein the control means drives the motor so as to suppress the rotation unevenness of the rotating body based on the rotation unevenness information. Control is performed.

(11) In the image forming apparatus of the above (10), the uneven rotation information detecting means makes the frequency to be detected variable according to the rotation speed of the motor.

(12) In the image forming apparatus according to the above (10) or (11), the uneven rotation information detecting means detects the uneven rotation information of the rotating shaft of the motor and detects the uneven rotation information separately from the uneven rotation information of the rotating body. I did it.

(13) In the image forming apparatus of any one of the above (10) to (12), the control means controls the speed of the motor based on the detected rotation unevenness information so as to eliminate the rotation unevenness of the rotating body. I made it.

(14) In the image forming apparatus according to the above (12) or (13), the control means determines the frequency of the rotational unevenness of the rotating body and the frequency of the rotational unevenness of the motor shaft detected according to the rotational speed of the motor. The frequency to be suppressed is selected.

(15) In any one of the above-mentioned image forming apparatuses (10) to (14), the control means is constituted by a DSP.

[0026]

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

FIG. 1 shows four colors according to a first embodiment, namely, yellow Y, magenta M, cyan C,
FIG. 1 is a cross-sectional view showing the overall configuration of a color (multicolor) image forming apparatus provided with a black BK image forming unit, in which 1 denotes a photosensitive drum (a, b, c,
d is for BK, C, M, and Y), and 6 is a DC brushless motor which is a drive motor for rotating each photosensitive drum.

Reference numeral 2 denotes a laser scanner which forms an electrostatic latent image on the photosensitive drum 1 by exposing in accordance with an image signal, and 3 denotes an endless end which also serves as a transfer belt and which sequentially conveys a sheet to an image forming section of each color. The transport belt 4 is connected to a drive unit including a motor and gears (not shown), and a driving roller for driving the transport belt 3 is a fixing device for melting and fixing the toner transferred to the sheet.

When data to be printed is sent from the PC to the printer, image formation according to the printer engine system is completed, and the printer becomes ready for printing, paper is supplied from the paper cassette and reaches the transport belt 3 where the transport belt 3 , The paper is sequentially conveyed to the image forming units of each color. Image signals of the respective colors are sent to the respective laser scanners 2 at the same time as the sheet conveyance by the conveyor belt 3 to form an electrostatic latent image on the photosensitive drum 3, and the toner is developed by a developing unit (not shown), and is not shown. The image is transferred onto the paper at the transfer unit. FIG.
In this example, images are sequentially formed in the order of Y, M, C, and BK. Thereafter, the sheet is separated from the transport belt, and the toner image is fixed on the sheet by heat in the fixing device 5 and is discharged to the outside.

FIG. 2 is a block diagram showing a schematic configuration of a control system of the color image forming apparatus according to the first embodiment.

In FIG. 2, reference numeral 10 denotes a printer as an image forming apparatus. A printer control unit 11 controls each device in the printer. Reference numeral 12 denotes a power supply for supplying power to each device in the printer. Reference numeral 13 denotes sensors for detecting the status of each unit in the printer. Reference numeral 14 denotes a motor control unit that controls motors according to instructions from the printer control unit.

Reference numeral 15 denotes motors, which are power sources for each device in the printer. A display unit 16 notifies the user of the operation status of the printer. A communication controller 17 performs communication between the printer and the host computer. Reference numeral 18 denotes a host computer that transfers data to be printed to the printer 10.

FIG. 3 is an explanatory diagram showing the configuration of a main part (drive unit) according to the first embodiment, and FIG. 4 is a circuit diagram thereof.

In FIG. 3, reference numeral 1 denotes the photosensitive drum.
Gear 46 fixed to the drive shaft of C brushless motor 40
And a gear 47 fixed to the rotating shaft of the photosensitive drum 1. The gear ratio is 8: 240.

Reference numeral 20 denotes a DSP, which controls phase switching by a rotor position signal from the DC brushless motor 42, starts the motor 40 by a control signal from the printer control unit,
Control means for performing stop control and comparing the speed signal from the printer control unit with the output of the speed detecting means to perform speed control and rotational unevenness suppression control are provided.

FIG. 5 is a block diagram showing the configuration of the DSP 20. In FIG. 5, reference numeral 21 denotes a program controller, 22 denotes an arithmetic unit,
C22a and an ALU 22b that performs addition, subtraction, and logical operations. 23 is a data memory, 24 is a program memory, 25 is a data memory bus, 26 is a program memory bus, 27 is a serial port, 28 is a timer, and 29 is an I / O port.

As described above, the memory is made independent for the data and the program, the bus is also divided into the data bus and the program bus, and the multiplication and the addition are executed in one machine cycle.
Having C allows high-speed calculations.

The DC brushless motor 40 has a U-, V-, and W-phase three-phase star-connected coil 43 and rotor 44. Further, the rotor 4 is used as a means for detecting the position of the roller 44.
Four Hall elements 42 for detecting four magnetic poles are provided, and the outputs are connected to the DSP 20. Also, the rotor 44
And a rotational speed detecting means (speed detecting means) comprising a magnetic pattern 45 and an MR sensor 41 provided on the outer periphery of the DSP 20. The output is connected to the DSP 20.

Reference numeral 30 denotes a driver for driving the DC brushless motor 40. The driver 30 includes three high-side transistors 31 and three low-side transistors 32, which are connected to U, V, and W of the coil 43, respectively.

The DSP 20 specifies the rotor position based on the rotor position signals HU to W generated by the Hall element 42,
Generate a phase switching signal. Phase switching signals UU to W,
LU to W control the on / off control of each transistor of the driver, sequentially switch the phase to be excited, and rotate the rotor.

Further, the DSP 20 compares the rotation speed target value with the rotation speed information, and generates and outputs a PWM signal. PW
The M signal is ANDed by the phase switching signals UU to W and the AND gate 33 to chop the drive current and
0 rotation speed is controlled.

When the photosensitive drum rotation drive mechanism is driven by feedback control based on the rotation speed, the motor shaft and the photosensitive drum rotation shaft generate uneven rotation. For example, when the gear ratio between the motor shaft and the rotating shaft of the photosensitive drum is 8: 240 and the motor is driven at 10 rps, the frequency components are as shown in FIGS.

When the rotation unevenness correction is not performed as described above,
Rotational unevenness due to the gear pitch and rotational unevenness due to periodic load fluctuation due to eccentricity of the rotary shaft occur on the photosensitive drum rotary shaft, and appear as banding or the like in an image.

FIG. 6 is an explanatory view showing rotation unevenness on the motor shaft side according to the first embodiment, and FIG. 7 is a view showing rotation unevenness on the photosensitive drum rotating shaft side. As can be seen from FIGS. Can be detected on the motor shaft side. For example, by multiplying the frequency component of the motor shaft by the frequency component ratio of the motor shaft side and the photosensitive drum rotating shaft side as shown in FIG. Can be

FIG. 9 is a flowchart showing a control operation for suppressing uneven rotation according to the first embodiment. FIG. 10 is an explanatory diagram showing signal waveforms during motor operation according to the first embodiment. Based on the circuit configuration shown in FIG. Note that this operation is executed based on an instruction from the program controller 21 based on a program stored in the program memory 24.

When the rotation of the motor is instructed from the printer control unit 11, the DSP 20 does not perform the rotation unevenness suppression control.
The motor is driven by the feedback control based on the rotation speed (step S1 in FIG. 9), the pulse interval output from the MR sensor 41 as the rotation speed detecting means is measured by a timer unit (timer 28), and the rotation speed information of the motor is measured. (Step S2 in FIG. 9, FIG. 10
(A)). When the motor 40 reaches the target rotation speed (step S3 in FIG. 9), the rotation speed information is subjected to an FFT operation (not shown) of the DSP (rotational unevenness information detecting means) 20, and is included in the rotation speed information as the rotation unevenness information. Obtain the amplitude and phase of the frequency component (step S4 in FIG. 9, FIG.
(B)).

Next, a frequency component for suppressing rotation unevenness is extracted. In this embodiment, frequencies from the drum shaft rotation speed to the drum shaft rotation speed × 240 are extracted so as to suppress the rotation unevenness due to the load fluctuation of the drum shaft. Further, the motor shaft rotation frequency is not extracted.

Hereinafter, description will be made assuming that the frequency component shown in FIG. 10B is corrected.

First, frequency components for which rotation unevenness is to be suppressed are extracted (step S5 in FIG. 9 and shown in FIG. 10C).

Next, a coefficient stored in advance is selected according to the motor rotational speed and the extracted frequency (step S6 in FIG. 9), and the coefficient is multiplied by a frequency component to be corrected (step S6 in FIG. 9). As shown in FIG. 10C), a frequency component of the rotation unevenness of the photosensitive drum rotating shaft is obtained (Step S7 in FIG. 9).

For example, when manufacturing the image forming apparatus, a measuring device such as a rotary encoder (not shown) is attached to the motor shaft and the drum shaft to measure the frequency component ratio, and the coefficients used for the calculation are stored as coefficients.

From the obtained information on the rotation unevenness of the photosensitive drum,
Generate motor control data for suppressing rotation unevenness (FIG. 9)
Step S8). In this embodiment, as shown in FIG. 10D, PWM data corresponding to the same amplitude and opposite phase as the frequency component of the uneven rotation frequency of the photosensitive drum rotating shaft is generated.

The drive current is chopped based on the PWM data to control the motor 40 (step S9 in FIG. 9).

In this embodiment, the multi-color image forming apparatus has been described. However, the present invention can be applied to a photosensitive drum of a single-color image forming apparatus.

(Second Embodiment) FIG. 11 is a flowchart showing a rotation unevenness suppression control operation according to a second embodiment. The rotation unevenness suppression operation performed by the circuit configuration of FIG. 4 according to the present embodiment based on FIG. The control operation will be described. This operation is performed based on the program stored in the program memory 24.
It is executed based on the instruction.

The configuration of the image forming apparatus of this apparatus, the schematic configuration of the control system, and the configuration of the main part are the same as those of the first embodiment, and therefore the description is omitted.

In this embodiment, the first point is that when the rotation speed of the motor 40 is low, uneven rotation of the motor 40 is also suppressed.
Is different from the embodiment.

When the rotation of the motor is instructed from the printer control unit 11, the DSP 20 does not perform the rotation unevenness suppression control.
The motor 40 is controlled by the feedback control based on the rotation speed.
Is driven (step S11 in FIG. 11), the interval of pulses output from the MR sensor 41 as the rotation speed detecting means is measured by a timer unit (timer 28), and the rotation speed information of the motor 40 is calculated (FIG. 11). Step S
12). When the motor 40 reaches the target rotation speed (step S13 in FIG. 11), the rotation speed information is subjected to FFT calculation to obtain the amplitude and phase of the frequency component included in the rotation speed information as rotation unevenness information (step S13 in FIG. 11). S1
4).

Next, a frequency component for suppressing rotation unevenness is extracted. In this embodiment, the frequency from the drum shaft rotation speed to the drum shaft rotation speed × 240, and the motor shaft rotation during the low speed rotation are controlled so as to suppress the rotation unevenness due to the load fluctuation of the drum shaft and the motor shaft rotation at the low speed rotation. Extract the frequency of the speed.

First, the rotational speed of the motor is determined (FIG. 11).
In step S15, a rotation speed frequency component is extracted so as to suppress the rotation unevenness in the rotation cycle of the motor shaft at the time of low speed rotation (step S16 in FIG. 11).

Next, a frequency component of uneven rotation of the drum shaft to be suppressed is extracted (step S17 in FIG. 11).

Subsequently, a coefficient stored in advance is selected according to the motor rotation speed and the extracted frequency (step S18 in FIG. 11), and the coefficient is multiplied by a frequency component to be corrected (step S19 in FIG. 11). ), To obtain a frequency component of uneven rotation of the photosensitive drum rotating shaft.

The coefficients used in the calculation are, for example, attached to a motor shaft and a drum shaft by a measuring device such as a rotary encoder (not shown) at the time of manufacturing the image forming apparatus, and the frequency component ratio is measured and stored as a coefficient.

From the obtained information on the uneven rotation of the photosensitive drum,
Generate motor control data that suppresses rotational unevenness (see FIG. 1).
Step S20). In the present embodiment, PWM data corresponding to the same amplitude and opposite phase as the rotational unevenness frequency component of the photosensitive drum rotating shaft is generated.

The drive current is chopped based on the PWM data to control the motor 40 (step S21 in FIG. 11).

Although the multi-color image forming apparatus has been described in the present embodiment, the present invention can be applied to a photosensitive drum of a single-color image forming apparatus.

As described above, in the first and second embodiments,
Since uneven rotation information of the rotating body is detected from the motor shaft rotation speed information and the uneven rotation of the rotating body is suppressed based on the uneven rotation information, the uneven rotation of the rotating body can be suppressed with an inexpensive configuration. .

Further, when detecting the rotation unevenness information of the rotating body, the frequency to be detected is made variable according to the motor rotation speed, so that the correction can be made with higher accuracy and without burdening the processing of the DSP and the like.

Further, at the time of low-speed rotation, the uneven rotation component of the motor is also detected, so that the uneven rotation can be suppressed with higher accuracy.

[0070]

As described above, according to the present invention,
There is an effect that rotation unevenness of the rotating body can be suppressed at low cost.

Further, since the component to be extracted is variable depending on the rotation speed (rotation speed), there is an effect that the correction can be performed with higher accuracy and without burdening the processing of the DSP or the like.

Further, since the uneven rotation component of the motor is also detected, there is an effect that the uneven rotation can be suppressed with higher accuracy.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an overall configuration of a color image forming apparatus according to a first embodiment.

FIG. 2 is a block diagram illustrating a schematic configuration of a control system of the color image forming apparatus according to the first embodiment.

FIG. 3 is an explanatory diagram showing a configuration of a main part according to the first embodiment.

FIG. 4 is a circuit diagram showing a configuration of a main part according to the first embodiment.

FIG. 5 is a block diagram showing a configuration of a main part according to the first embodiment;

FIG. 6 is an explanatory view showing rotation unevenness on the motor shaft side according to the first embodiment.

FIG. 7 is an explanatory diagram showing rotation unevenness on the photosensitive drum rotating shaft side according to the first embodiment.

FIG. 8 is an explanatory diagram showing a rotation unevenness frequency component ratio between the motor shaft and the photosensitive drum rotation shaft according to the first embodiment.

FIG. 9 is a flowchart showing a rotation unevenness suppression control operation according to the first embodiment;

FIG. 10 is a diagram showing signal waveforms during motor operation according to the first embodiment.

FIG. 11 is a flowchart showing a rotation unevenness suppression control operation according to a second embodiment.

FIG. 12 is an explanatory diagram showing a scan position error due to uneven rotation of a motor.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photosensitive drum 2 laser scanner 3 transport belt 4 drive roller 5 fixing device 6 DC brushless motor 10 printer 11 printer control unit 13 sensors 14 motor control unit 20 DSP (control means, uneven rotation detection means) 21 program controller 22 arithmetic unit 28 Timer 30 Driver 31 High-side transistor 32 Low-side transistor 33 AND gate 40 DC brushless motor 41 MR sensor (speed detection means) 42 Hall element 43 Coil 44 Rotor 45 Magnetic pattern (speed detection means)

Continued on the front page F-term (reference) 2H027 DA16 DA17 ED02 EE03 EE04 5H550 AA10 BB05 CC01 DD08 FF03 FF07 GG03 HA07 HB11 HB16 JJ03 JJ18 JJ25 JJ26 KK04 LL09 LL35 5H560 AA03 BB04 BB07 TT01 X02 9A001 HH34 KK31 KK32

Claims (15)

[Claims] A motor, control means for controlling the driving of the motor, a rotating body rotated by driving the motor, speed detecting means for detecting a rotation speed of the motor, and A rotation unevenness information detecting unit that detects rotation unevenness information of the rotating body, wherein the control unit performs drive control of the motor based on the rotation unevenness information so as to suppress the rotation unevenness of the rotating body. Motor drive device. 2. The motor drive device according to claim 1, wherein the uneven rotation information detecting means changes a frequency to be detected in accordance with a rotation speed of the motor. 3. The motor drive device according to claim 1, wherein the rotation unevenness information detecting means detects the rotation unevenness information of the rotating shaft of the motor and detects the rotation unevenness information separately from the rotation unevenness information of the rotating body. . 4. The motor driving device according to claim 1, wherein the control means controls the speed of the motor based on the detected rotation unevenness information so as to eliminate the rotation unevenness of the rotating body. 5. The method according to claim 3, wherein the control means selects a frequency to be suppressed from among the frequency of the rotational unevenness of the rotating body and the frequency of the rotational unevenness of the motor shaft, which is detected according to the rotational speed of the motor. 5. The motor driving device according to 4. 6. The motor drive device according to claim 1, wherein the control means is constituted by a DSP. 7. A rotational speed of a motor is detected, and information on rotational unevenness of a rotating body rotated by driving the motor is detected from information on rotational speed of the motor, and rotational unevenness of the rotary body is detected based on the rotational unevenness information. A method for controlling a motor driving device, comprising: controlling the driving of the motor so as to suppress the occurrence of the motor. 8. The control method for a motor drive device according to claim 7, wherein the speed control of the motor is performed based on the detected rotation unevenness information so as to eliminate the rotation unevenness of the rotating body. 9. The method according to claim 7, wherein a frequency to be suppressed is selected from among the frequency of the rotation unevenness of the rotating body and the frequency of the rotation unevenness of the motor shaft detected according to the rotation speed of the motor. Control method of motor drive device. 10. A motor, control means for controlling driving of the motor, a rotating body rotated by driving the motor,
Speed detecting means for detecting the rotation speed of the motor, and uneven rotation information detecting means for detecting uneven rotation information of the rotating body from the rotation speed information of the motor, the control means based on the uneven rotation information An image forming apparatus, wherein drive control of the motor is performed so as to suppress uneven rotation of the rotating body. 11. The image forming apparatus according to claim 10, wherein the rotation unevenness information detecting means changes a frequency to be detected according to a rotation speed of the motor. 12. The rotation unevenness information detecting means detects rotation unevenness information of a rotating shaft of a motor and detects the rotation unevenness information separately from rotation unevenness information of a rotating body.
Or the image forming apparatus according to 11. 13. The image forming apparatus according to claim 10, wherein the control unit controls the speed of the motor based on the detected rotation unevenness information so as to eliminate the rotation unevenness of the rotating body. 14. The control device according to claim 12, wherein the control means selects a frequency to be suppressed from among the frequency of the rotational unevenness of the rotating body and the frequency of the rotational unevenness of the motor shaft detected according to the rotational speed of the motor. 14. The image forming apparatus according to claim 13. 15. An image forming apparatus according to claim 10, wherein said control means is constituted by a DSP.