JP3232656B2 - Electric motor speed control apparatus and copying apparatus having the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed control device for a DC motor or office equipment equipped with the speed control device. The present invention relates to a highly reliable DC motor speed control device capable of performing a stable operation and rotating at a constant speed in accordance with a commanded speed, or a copying apparatus including the speed control device.

[0002]

2. Description of the Related Art As a speed control device for a DC motor, phase comparison means for comparing the phases of a speed reference signal and a speed detection signal to output a phase control signal, and comparing the cycle of the speed reference signal and the speed detection signal. It is generally known to provide a speed comparison means for outputting a speed control signal, and to control the speed by adding a speed control signal to the phase control signal.

[0003]

In the prior art, when the load changes, the drive current is increased or decreased by changing the voltage level of the phase control signal, and the speed is kept constant even when the load changes. It is a configuration to do.

[0004] Therefore, in an electric motor in which the instantaneous load fluctuation is small and the gain of the control device is small, the rotational unevenness of the motor is small. Therefore, a change in the viscous friction load of the bearing due to a change in the ambient temperature or a change in the viscous friction load of the bearing due to speed change. , When there is a change in load such as hysteresis loss and windage loss,
If the gain setting of the control device is set too small for the purpose of reducing the rotation unevenness, there is a problem that the load cannot be changed and the synchronous stable state is deviated.

[0005] Further, there is a problem that the copy quality is degraded in the copying apparatus if there is uneven speed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a highly reliable DC motor control apparatus or a high-quality copying apparatus capable of stably performing pull-in even if a load changes due to a speed change or an ambient temperature change. Is to provide.

[0007]

The object of the present invention is to provide a driving means for driving a DC motor, a means for giving a predetermined speed command to the DC motor, and a speed detection signal having a frequency proportional to the rotation speed of the DC motor. Speed detection means, reference signal generation means for generating a predetermined speed reference signal, phase comparison means for comparing the phases of the speed reference signal and the speed detection signal and outputting a phase control signal, and the speed reference signal And a speed control device of a DC motor including a speed comparison unit that compares the period of the speed detection signal and outputs a speed control signal, wherein a phase difference between the speed reference signal and the speed detection signal is set to a predetermined value; Means for controlling the phase difference to be maintained at the predetermined value when there is a change in the predetermined phase difference due to a load change of the DC motor or the like; By it is accomplished by providing a means for a constant speed of the DC motor in accordance with the speed commanded by the.

[0008]

When the load on the DC motor increases, the speed of the DC motor decreases below the target speed according to the amount of change. As a result, the speed control signal rises to increase the drive current of the DC motor. Similarly, the phase control signal rises to increase the drive current of the DC motor. The increased speed control signal and phase control signal are added by a subsequent adding means. The added speed control signal and phase control signal are
The proportional term and the integral term are transmitted to a means for outputting the driving means to the electric motor. The output of the means for outputting the proportional term and the integral term holds the increment of the speed control signal and the phase control signal, and increases the drive current of the DC motor. The speed of the DC motor returns to the target speed, and the speed control signal and the phase control signal also return to the original voltage levels.

[0009]

FIG. 1 shows an embodiment in which the present invention is applied to a direct current brushless motor.

In FIG. 1, a magnetic detecting element 1, a magnetic detecting element 2, and a magnetic detecting element 3 detect a magnetic flux of a permanent magnet magnetized to eight poles provided in a rotor 4, and respond to the detected magnetic flux. The output signal is supplied to the distributor 5. The distributor 5
A drive command signal is given to the drive device 6 in response to the outputs of the magnetic detection elements 1, 2 and 3. The driving device 6 supplies a driving current to the coils 7, 8, and 9 from a power supply according to a driving command signal output from the distributor 5.

The rotor 4 having permanent magnets magnetized to eight poles generates torque and rotates by interaction between the magnetic flux of the permanent magnet and the magnetic fields generated by the coils 7, 8, and 9. The speed detection device 10 detects a change in the magnetic flux of the permanent magnet 4 and transmits a speed detection signal 11 having a frequency proportional to the speed of the motor to the amplifier 12.

The output signal of the amplifier 12, that is, the amplified speed detection signal 13 is transmitted to a control device 14.

The control device 14 incorporates a vibrator 15 having an oscillation circuit connected to operate the control device in synchronization with a clock signal, and a frequency divider circuit for the clock signal. Create a reference signal for

The control device 14 has a built-in phase control circuit for comparing the phase difference between the reference signal and the speed detection signal 13 and outputting the phase difference as a voltage level. The output signal of the phase control circuit, that is, the phase control signal 27 is
4 is output to the terminal P.

The control device 14 has a built-in speed control circuit for comparing the speed difference between the reference signal and the speed detection signal 13 and outputting the speed difference as a voltage level. The output signal of the speed control circuit, that is, the speed control signal 24 is
4 is output to the terminal F.

The resistor P is connected to the terminal P, and the resistor F is connected to the terminal F.
Is connected to a non-inverting input terminal of an operational amplifier 18 while the terminals on the opposite sides of the resistors 16 and 17 are connected to each other.

A reference voltage is applied to an inverting input terminal of the operational amplifier 18 via a resistor 19.

The output terminal of the operational amplifier 18 is connected to one end of a resistor 20, and the other end of the resistor 20 is connected to one end of a capacitor 21. Capacitor 21
Is connected to the inverting input terminal of the operational amplifier 18.

Further, the output terminal of the operational amplifier 18 is connected to the non-inverting input terminal of the comparator 22. Further, a triangular waveform voltage is applied to the inverting input terminal of the comparator 22.

A control signal in the form of a rectangular wave is output from the output terminal of the comparator 22 and is supplied to the driving device 6.

FIG. 2 shows the characteristics of the speed control circuit built in the control device 14, that is, how the speed control signal changes with respect to the speed detection signal.

When the frequency of the speed detection signal is within a certain range with respect to the target speed (hereinafter referred to as a lock range), the following is performed.

When the speed of the motor is at the target speed, the speed control signal is VF1.

If the speed of the motor exceeds the target speed,
The speed control signal drops.

When the speed of the motor falls below the target speed, the speed control signal rises.

When the frequency of the speed detection signal is lower than the lock range, that is, in the underspeed state, the speed control signal is fixed at the high level.

When the frequency of the speed detection signal is equal to or higher than the lock range, that is, in the overspeed state, the speed control signal is fixed at the low level.

FIG. 3 shows the characteristics of the phase control circuit built in the control device 14, that is, how the phase control signal changes with respect to the phase difference.

When the frequency of the speed detection signal is within the lock range, the following is performed.

When the phase difference is 0, the phase control voltage is at the minimum voltage level Low state.

When the phase difference is 2π, the phase control voltage is at the maximum voltage level High state.

When the phase difference is between 0 and 2π, FIG.
Has a linear characteristic.

When the frequency of the speed detection signal is out of the lock range, the following is performed.

When the frequency of the speed detection signal is equal to or lower than the lock range, that is, in the underspeed state, the phase control signal is fixed at the high level.

When the frequency of the speed detection signal is equal to or higher than the lock range, that is, in an overspeed state, the phase control signal is fixed at the low level.

FIG. 4 shows a time chart of the speed control signal.

The speed control circuit includes a speed control reference signal 23.
A difference between the cycles of the speed detection signal 13 and the speed detection signal 13, that is, a speed difference is detected at the rising timing of the speed detection signal 13, and the speed difference is output as a speed control signal 24 at a voltage level.

FIG. 5 shows a time chart of the phase control signal.

The phase control circuit includes a phase control reference signal 25.
26 obtained by dividing the speed detection signal 13 by 1/2
Is detected at the rising timing of the signal 26, and the phase difference is output as a phase control signal 27 at a voltage level.

FIG. 6 shows operation waveforms in the configuration of the present invention.

First, the case where the load on the motor is reduced will be described.

When the load of the motor decreases from load T1 to load T2 at time t1, the speed of the motor increases, and time t2 at which the rising edge of speed detection signal 13 comes.
Thus, the speed control signal 24 drops from VF1 to VF2. At time t2, the phase control signal 27 also changes to VP1.
From VP2 to VP2. As a result, the operational amplifier 18
Has a non-inverting amplifier configuration in the configuration of FIG. 1, the output signal 28 drops in voltage from VC1 to VC2 and is transmitted to the non-inverting input terminal of the comparator 22 in the subsequent stage.
The comparator 22 outputs a rectangular wave in comparison with the triangular waveform voltage applied to the inverting input terminal. However, since the input voltage of the non-inverting terminal drops to VC2, the duty of the rectangular wave decreases, The device 6 accordingly operates as coil 7, coil 8,
The drive current supplied to the coil 9 is reduced. as a result,
The motor speed decreases and returns to the target value, and the speed control signal returns to VF1 at time t3. The phase control signal returns to VP1 at time t4.

Here, one end of a resistor 20 is connected to the output terminal of the operational amplifier 18, and one end of a capacitor 21 is connected to the terminal on the opposite side of the resistor 20.
Is connected to the inverting input terminal of the operational amplifier 18, so that even if the speed control signal 27 and the phase control signal 24 return, the capacitor 21 holds the decrease as a voltage. I do. Therefore, even if the speed control signal 27 and the phase control signal 24 return, the output signal 28 of the operational amplifier 18 keeps the level of VC2.

Next, the case where the load of the motor increases will be described.

When the load of the motor increases from load T2 to load T3 at time t5, the speed of the motor decreases and the rising edge of speed detection signal 13 comes at time t6.
The voltage of the speed control signal 24 rises from VF1 to VF3. At time t6, the phase control signal 27 also changes to VP1.
From VP3 to VP3. As a result, the operational amplifier 18
Has a non-inverting amplifier configuration in the configuration of FIG. 1, so that the output signal 28 increases in voltage from VC2 to VC3,
The signal is transmitted to the non-inverting input terminal of the comparator 22 at the subsequent stage. The comparator 22 outputs a rectangular wave as compared with the triangular wave voltage applied to the inverting input terminal. However, since the input voltage of the non-inverting terminal has risen to VC3, the duty of the rectangular wave increases, The driving device 6 increases the driving current supplied to the coils 7, 8 and 9 accordingly. As a result, the speed of the motor increases, returns to the target value, and the speed control signal returns to VF1 at time t7. The phase control signal returns to VP1 at time t8.

Here, one end of a resistor 20 is connected to the output terminal of the operational amplifier 18, and one end of a capacitor 21 is connected to the terminal on the opposite side of the resistor 20.
Is connected to the inverting input terminal of the operational amplifier 18, so that even if the speed control signal 27 and the phase control signal 24 return, the capacitor 21 holds the increase as a voltage. I do. Therefore, even if the speed control signal 27 and the phase control signal 24 return, the output signal 28 of the operational amplifier 18 keeps the level of VC3.

That is, since the capacitor 21 holds the voltage corresponding to the load change, the phase control signal can return to the original level VP1. For this reason, even if the load of the motor changes, the phase can be kept constant, and the speed of the motor can be maintained at the target value.

This operation is achieved when the resistor 20 shown in FIG. 1 acts as a proportional term and the capacitor 21 acts as an integral term.

From this, the load T according to the configuration of the present invention is
-The phase control voltage VP characteristic is, as shown in FIG.
, The phase control voltage VP becomes a constant value, and even if the load changes, synchronization can be stably performed, and a highly reliable DC motor or office equipment using the same can be used. Can be provided.

Next, FIG. 8 shows a conventional configuration diagram.

FIG. 8 differs from FIG. 1 of the present invention in that the capacitor 21 is missing.

FIG. 9 shows operation waveforms according to the conventional configuration of FIG.

First, the case where the load on the motor is reduced will be described.

When the load on the motor decreases from load T1 to load T2 at time t9, the speed of the motor increases and the rising edge of speed detection signal 13 comes at time t10.
Then, the voltage of the speed control signal 24 drops from VF1 to VF4. At time t10, the voltage of the phase control signal 27 also drops from VP1 to VP4. As a result, since the operational amplifier 18 has the configuration of the non-inverting amplifier in the configuration of FIG. 8, the output signal 28 drops in voltage from VC1 to VC4 and is transmitted to the non-inverting input terminal of the comparator 22 in the subsequent stage.
The comparator 22 outputs a rectangular wave as compared with the triangular wave voltage applied to the inverting input terminal. However, since the input voltage of the non-inverting terminal has dropped to VC4, the duty of the rectangular wave has decreased. The driving device 6 accordingly reduces the driving current supplied to the coils 7, 8 and 9. As a result, the speed of the motor decreases, returns to the target value, and the speed control signal returns to VF1 at time t11.

However, in the configuration of FIG.
, And is not configured to output the integral term,
The phase control signal does not return to VP1 even at time t11 and remains at the level of VP4 in order to maintain the drive current of the motor.

At time t11, the output signal 28 of the operational amplifier 18 rises to VC5 because the speed control signal 24 returns from VF4 to VF1.

Next, the case where the load of the motor increases will be described.

When the load of the motor increases from load T2 to load T3 at time t12, the speed of the motor decreases, and time t1 at which the rising edge of speed detection signal 13 comes.
At 3, the voltage of the speed control signal 24 increases from VF1 to VF5. At time t13, the voltage of the phase control signal 27 also increases from VP4 to VP5. As a result, since the operational amplifier 18 has the configuration of the non-inverting amplifier in the configuration of FIG. 8, the output signal 28 rises in voltage from VC5 to VC6 and is transmitted to the non-inverting input terminal of the comparator 22 in the subsequent stage. The comparator 22 outputs a rectangular wave as compared with the triangular wave voltage applied to the inverting input terminal. However, since the input voltage of the non-inverting terminal has risen to VC6, the duty of the rectangular wave increases, The drive 6 is accordingly driven by a coil 7,
The drive current supplied to the coils 8 and 9 is increased.
As a result, the motor speed increases and returns to the target value,
The speed control signal returns to VF1 at time t14.

However, in the configuration shown in FIG. 8, since the capacitor 21 is not provided, the phase control signal is maintained at VP1 even at time t14 to maintain the drive current of the motor.
, And remains at the level of VP5.

As is apparent from the above operation, in the configuration shown in FIG. 8, it is necessary to change the phase in order to change the drive current according to the load change of the motor and to keep the speed constant. You can see that there is.

Therefore, as shown in FIG. 10, when the load T changes, the phase control voltage VP changes in accordance with the characteristics of the load T and the phase control voltage VP in the conventional configuration.

Such a conventional configuration is applied to an electric motor, such as office equipment, in which the load fluctuation of a bearing or the like is small instantaneously and the gain of the control device is set to be as small as possible to reduce the rotation unevenness, such as office equipment. When applied to a driving motor for driving a polygon mirror, it has not been satisfactory. That is, in the configuration shown in FIG.
When there is a change in the viscous friction load of the bearing due to a change in the ambient temperature, or a change in the viscous friction load of the bearing due to speed switching and a load change such as windage loss and hysteresis loss, the control device is controlled for the purpose of reducing the rotation unevenness. If the gain setting is too small, there is a technical problem that it is not possible to cope with the above-mentioned change in the load amount, and it is not possible to achieve a stable synchronization state.

On the other hand, in the present invention, as shown in FIG. 1, the provision of the capacitor 21 can solve the technical problem caused by the conventional structure shown in FIG.

FIG. 11 shows the characteristic indicating the load change of the motor.

Reference numeral 29 denotes a speed characteristic, and reference numeral 30 denotes a current characteristic.

FIG. 11 shows a case where the speed is not switched, but the viscous friction load of the bearing changes due to a change in the ambient temperature. At normal temperature, the load becomes T1 and the current becomes I1.
At low temperatures, the viscous friction load of the bearing increases and the load is T1M
AX, and the current increases to I1MAX. At high temperatures, the viscous friction load of the bearing decreases, the load becomes T1MIN, and the current decreases to I1MIN.

As described above, even when the speed switching is not performed, a load variation occurs.

Next, FIG. 12 shows a characteristic indicating a load change of the motor when the speed is changed. Speed is N1 / N
It is assumed that two-stage switching of 2 is performed.

When the speed is set to a low speed N2, the current characteristic becomes lower than 30, as indicated by 31. this is,
This is because, in the case of the speed N2, compared with the speed N1, the output is reduced because the speed is low even when compared under the same load. Furthermore, in the case of the speed N2, the loss of the bearing, the loss due to the hysteresis, and the windage loss are reduced as compared with the case of the speed N1, so when the same motor is switched in two stages of the speed N1 / N2, The load changes from T2MIN to T1MAX, and the current changes from I2MIN to I1MAX.

That is, the load change amount of the motor when the speed is switched is larger than that when the speed is not switched.

Under these circumstances, if the gain of the control device is reduced in order to reduce the rotation unevenness, FIG.
As shown in the following, in order to apply a reference voltage to the resistor 19,
The control power supply 32 may be divided by a trimmer resistor 33 and a resistor 34 and applied, and a reference voltage may be adjusted by adjusting the trimmer resistor to cope with variations in circuit constants.

On the other hand, in the configuration according to the present invention, FIG.
As shown in FIG. 4, to apply a reference voltage to the resistor 19,
The control power supply 32 can be supplied by dividing the voltage between the resistor 35 and the resistor 34. This is because, in the configuration according to the present invention, since the phase has a constant value, even if the gain of the control device is set low, variation in circuit constants such as resistance does not matter.

Further, according to the present invention, even when the speed is switched, it is possible to perform a stable synchronization pull-in.

FIG. 15 is a block diagram showing one embodiment of the present invention, showing a configuration for performing speed switching.

The basic configuration is the same as that of FIG. 1, but the reference signal creation part is different.

In FIG. 15, a vibrator 36 includes an oscillator 37
, And the output of the oscillator 37 is input to the selector 40. The oscillator 38 is connected to an oscillator 39, and the output of the oscillator 39 is also input to the selector 40. Further selector 4
The speed switching command signal is input to 0, and the selector 40
Supplies either the output of the oscillator 37 or the output of the oscillator 39 to the control device 14 according to the speed switching command signal.

The operation in the case of FIG. 15 is the same as the operation of FIG.

FIG. 16 is a block diagram showing a case where the motor to which the present invention is applied is applied to a polygon mirror driving motor of office equipment such as a printer, a facsimile or a copying machine.

The system controller 41 controls a laser light source 42, and the laser light source 42 irradiates a polygon mirror (polygon mirror) 43 with laser light to expose a photosensitive drum 44. The polygon mirror 43 is driven by a polygon mirror driving motor 45. The controller 46 drives the motor 45 for driving the polygon mirror, and since this motor has very small uneven rotation, scanning of the laser beam can be performed at a uniform speed. Then, a print pattern imaged on the photosensitive drum 44 by a uniform laser beam is transferred to the transfer drum 47.
And the developer 48 is adhered thereto. The developing motor 49 is used to attach the developer 48 to the transfer drum 47. The paper 51 on the tray 50 is sent to the inside of a printer, a facsimile or a copying machine by an electric motor 52 for feeding paper. Developer 4 attached to transfer drum 47
After the transfer of 8 to the paper 51, the paper 51 is fed by the paper feed belt 53. The document or image transferred to the paper 51 is subjected to a fixing process by a fixing device 54 with a developer 48,
It is sent out of a printer, facsimile, or copier.

Although the present invention has been described with reference to the embodiment in which the direct current brushless motor is applied, the present invention is also applicable to a direct current brush motor. Further, the control device can be applied even if the characteristics of the built-in speed control device and phase control device are slightly different from those of FIGS. 2, 3, 4, and 5. Also, an embodiment of a system for performing speed control by a PWM (pulse width modulation control) system has been described.
The method is also applicable. In addition, FG
(Frequency Generator) Although the embodiment to which the frequency generator is applied has been described, the configuration of the present invention can be applied to a case where the speed is detected by an encoder system or the speed is detected by a magnetic detecting element.

[0081]

According to the present invention, drive means for driving a DC motor, means for giving a predetermined speed command to the DC motor, and speed detection for outputting a speed detection signal having a frequency proportional to the rotation speed of the DC motor Means, a reference signal generating means for generating a predetermined speed reference signal, phase comparing means for comparing the phases of the speed reference signal and the speed detection signal to output a phase control signal, and the speed reference signal and the speed. A DC motor speed control device including a speed comparison unit that compares a cycle of a detection signal and outputs a speed control signal, wherein a DC motor includes a unit that sets a phase difference between the speed reference signal and the speed detection signal to a predetermined value; Means for controlling the phase difference to be maintained at the predetermined value when there is a change in the predetermined phase difference set as described above due to a load change or the like. Since the speed of the DC motor and a means for the constant to match the speed instructed by said, even if a change in load due to speed switching and ambient temperature changes,
Synchronization can be stably performed, and a highly reliable DC motor or a copying apparatus using the same can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention.

FIG. 2 is a change state diagram of a speed control signal with respect to a speed detection signal.

FIG. 3 is a diagram illustrating a change state of a phase control signal with respect to a phase difference.

FIG. 4 is a time chart of a speed control signal.

FIG. 5 is a time chart of a phase control signal.

FIG. 6 is a time chart of a control signal according to the configuration of the present invention.

FIG. 7 is a T-VP characteristic diagram of the configuration of the present invention.

FIG. 8 is a conventional configuration diagram.

FIG. 9 is an operation waveform diagram of a conventional configuration.

FIG. 10 is a T-VP characteristic diagram of a conventional configuration.

FIG. 11 is a characteristic diagram showing a load change of the electric motor.

FIG. 12 is a characteristic diagram showing a load change of the electric motor.

FIG. 13 is a configuration diagram related to the present invention.

FIG. 14 is a configuration diagram showing another embodiment of the present invention.

FIG. 15 is a configuration diagram showing another embodiment of the present invention.

FIG. 16 is a configuration diagram of a copying apparatus including the electric motor of the present invention.

[Explanation of symbols]

1, 2, 3 ... magnetic detection element, 4 ... rotor having permanent magnets magnetized in multiple poles, 5 ... distributor, 6 ... drive device,
7, 8, 9: coil, 10: speed detection device, 11: speed detection signal, 12: amplifier, 13: amplified speed detection signal, 14: control device, 15: vibrator, 16, 17, 1
9, 20, 34, 35 ... resistor, 18 ... operational amplifier, 2
DESCRIPTION OF SYMBOLS 1 ... Capacitor, 22 ... Comparator, 23 ... Speed control reference signal, 24 ... Speed control signal, 25 ... Phase control reference signal, 26 ... Signal obtained by dividing the speed detection signal by 1/2, 27 ...
Phase control signal, 28... Output signal of operational amplifier 18, 29
... speed characteristics of the motor, 30 ... current characteristics of the motor (for N1), 31 ... current characteristics of the motor (for N2), 32
... Control power supply, 33 ... Trimmer resistor, 36, 38 ... Vibrator, 37,39 ... Oscillator, 40 ... Selector, 41 ... System controller, 42 ... Laser emission source, 43 ... Polygon mirror, 44 ... Photoconductor drum, 45: motor for driving a polygon mirror, 46: control device, 47: transfer drum, 48
... developer, 49 ... motor for development, 50 ... tray, 51 ...
Paper, 52: electric motor for feeding paper, 53: paper feed belt, 54: fixing machine.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Sueo Akashi 1-1-1, Higashitaga-cho, Hitachi City, Ibaraki Prefecture Inside the Taga Plant, Hitachi, Ltd. No. 1 Inside the Taga Plant, Hitachi, Ltd. (72) Inventor Manabu Kihara 1-1-1, Higashitaga-cho, Hitachi City, Ibaraki Prefecture Inside the Taga Plant, Hitachi, Ltd. No. 1-1, Hitachi, Ltd. Taga Factory (72) Inventor Tatsuo Matsumoto 1-1-1, Higashitaga-cho, Hitachi City, Ibaraki Prefecture Inside Taga Factory, Hitachi, Ltd. (56) References JP-A-3-78490 ( JP, A) JP-A-2-299496 (JP, A) JP-A-2-188179 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02P 6/06 B41J 2/44 G02B 26/10 H02P 6/16

Claims (4)

(57) [Claims] 1. A drive means for driving a DC motor, a means for giving a predetermined speed command to the DC motor, a speed detection means for outputting a speed detection signal having a frequency proportional to the rotation speed of the DC motor, a predetermined speed Reference signal generating means for generating a reference signal, phase comparing means for comparing the phases of the speed reference signal and the speed detection signal and outputting a phase control signal, and comparing the periods of the speed reference signal and the speed detection signal A speed control device for a DC motor including a speed comparison unit that outputs a speed control signal, and a unit that sets a phase difference between the speed reference signal and the speed detection signal to a predetermined value; Means for controlling the phase difference to be maintained at the predetermined value when there is a change in the predetermined phase difference set in the step (c), and by making the phase difference constant, the speed of the DC motor Means for keeping the speed constant in accordance with the speed commanded above, and means for switching a speed reference signal.
Speed control of the DC motor to be. A drive means for driving the DC motor; a means for giving a predetermined speed command to the DC motor; a speed detection means for outputting a speed detection signal having a frequency proportional to the rotation speed of the DC motor; Reference signal generating means for generating a reference signal, phase comparing means for comparing the phases of the speed reference signal and the speed detection signal and outputting a phase control signal, and comparing the periods of the speed reference signal and the speed detection signal A speed control device for a DC motor including a speed comparison unit that outputs a speed control signal to the speed control unit, wherein a unit that adds a speed control signal to the phase control signal,
Further comprising means for outputting the phase control signal added as described above, the proportional term and the integral term of the speed control signal to the drive means of the DC motor, and having a speed reference signal switching means. Characteristic DC motor speed control device. A drive means for driving the DC motor; a means for giving a predetermined speed command to the DC motor; a speed detection means for outputting a speed detection signal having a frequency proportional to the rotation speed of the DC motor; Reference signal generating means for generating a reference signal, phase comparing means for comparing the phases of the speed reference signal and the speed detection signal and outputting a phase control signal, and comparing the periods of the speed reference signal and the speed detection signal A speed control device for a DC motor including a speed comparison means for outputting a speed control signal, and an operational amplifier for adding a speed control signal to the phase control signal; and a resistor connected to a feedback section of the operational amplifier. Switching of speed reference signal with a series circuit of capacitors
Speed control of the DC motor, characterized in that it comprises a e means. 4. A copying or printing section and the copying or printing section.
Drives a polygon mirror that irradiates laser light to the printing unit
DC motor and speed control for controlling the speed of this DC motor
Control circuit and this speed control circuit drive the DC motor
Drive means and a frequency proportional to the rotational speed of the DC motor.
Speed detection means for outputting a speed detection signal;
Reference signal generating means for generating a reference signal;
Compare the phase of the signal and the speed detection signal to output the phase control signal.
Phase comparing means for applying, and said speed reference signal and speed
Speed at which the speed control signal is output by comparing the period of the detection signal
Means for adding a speed control signal to said phase control signal in a copying apparatus having a comparing means ;
The output signal of the phase comparison means added as described above and the speed ratio
Means for outputting the proportional term and the integral term of the output signal of the comparing means.
A copying apparatus comprising: