JP2002078386A - Stepping motor drive circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive stepping motor drive circuit, which can suppress noise and vibration by preventing occurrence of more than necessary rotational torque, when it executes through-up or through-down movement of a stepping motor. SOLUTION: When a controller 11 inputs a digital value equivalent to the voltage at a high-speed rotation into a D/A converter 13, a D/A converter 13 generates a voltage, based on the inputted digital value. The voltage change at this time is smoothed with a delay filter 14, and the reference voltage to be inputted into a motor driver 18 changes gradually. The motor driver 18 drives the stepping motor 19 by the current value, corresponding to the reference voltage. Hereby, this stepping motor driving circuit can reduce noise and vibration, by suppressing the reference voltage at a low speed and lessening the rotational torque of the stepping motor 19, and backlashes of mechanical parts caused by excessive rotational torque are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stepping motor drive circuit for driving a stepping motor.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram of a conventional stepping motor drive circuit. In the figure, 11 is a stepping motor drive circuit, 12 is a control unit, 13 is a D / A converter, 1
8 is a motor driver and 19 is a stepping motor. The stepping motor 19 used here is driven by a constant current drive, that is, a so-called chopper drive.

[0003] A control unit 12 outputs a voltage which is a reference of a current value for driving a stepping motor 19 via a D / A (digital / analog) converter 13 to a motor driver 1.
Enter 8 The motor driver 18 includes the D / A converter 1
The stepping motor 19 is driven by a current corresponding to the voltage input from the step 3. Further, the control unit 12 generates a drive signal for determining the rotation speed of the stepping motor 19 and inputs the drive signal to the motor driver 18. As the drive signal, for example, a clock signal having a frequency corresponding to the rotation of the stepping motor 19 is input to the motor driver 18. The motor driver 18 generates an excitation phase and drives the stepping motor 19 based on the input drive signal.

However, the stepping motor 19 cannot be driven at a predetermined rotational speed suddenly or stopped suddenly. Therefore, conventionally, when the rotation of the stepping motor 19 is started, the frequency of the drive signal is gradually increased, and a through-up operation in which the rotation speed of the stepping motor 19 is gradually increased is executed. Further, when stopping, the frequency of the drive signal is gradually reduced, and a through-down operation is performed in which the rotation speed of the stepping motor 19 is gradually reduced.

In general, when the stepping motor is driven at a constant current, the frequency at which the stepping motor 19 is driven is low, and the lower the rotation speed, the less the rotational torque of the motor. As described above, the stepping motor 19
Since the above-described through-up has been performed for a while from the start of the rotation of the drive, the drive frequency is low at the start of the drive, and the rotation torque is not so required. However, conventionally, since the stepping motor 19 is driven at the same current value as that at the time of high-speed rotation from the start of driving, excessive rotation torque is generated at the start of driving. For this reason, the mechanism to which the power is transmitted from the stepping motor 19 rattles, generating noise and vibration. Also, when the rotation of the stepping motor 19 is stopped, the through-down is executed as described above, so that the lower the number of rotations, the more the necessary rotation torque is generated in the stepping motor 19, and the noise is generated due to the rattling of the mechanism. And vibration occurred.

As a method of solving such problems such as noise and vibration, a method of gradually increasing the voltage value input to the motor driver 18 as the drive frequency is increased during execution of the through-up is conceivable. By doing so, the current when the motor driver 18 drives the stepping motor 19 can be gradually increased, the rotating torque immediately after the start of the rotation of the stepping motor 19 is reduced, and then the rotating torque is reduced to a predetermined value. Can be gradually increased. As a result, it is possible to prevent excessive torque from being generated during the execution of the through-up, and to suppress noise and vibration due to rattling or the like. Similarly, when executing the through-down, the drive frequency is lowered and the voltage value input to the motor driver 18 is gradually lowered, so that the rotation torque when the rotation speed is reduced is reduced. Vibration can be suppressed.

However, as described above, in order to gradually change the voltage value input to the motor driver 18 during the slew-up and the slew-down, the voltage value output from the D / A converter 13 is slew-up and slew-down. Need to be fine-tuned during the short time running.
In order to change the voltage value at such a high speed, an expensive D
A / A converter is required, which causes an increase in the manufacturing cost of the stepping motor drive circuit 11. In addition, the control unit 12 needs to control the D / A converter at short intervals, and there is a problem that the load on the control unit 12 increases.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and prevents the generation of an excessive rotation torque when performing a step-up or through-down operation of a stepping motor, thereby reducing noise. It is an object of the present invention to provide an inexpensive stepping motor drive circuit capable of suppressing vibration and vibration.

[0009]

According to the present invention, in a stepping motor driving circuit, a voltage generating means for generating a specified voltage and a stepping motor drive control by designating a voltage to the voltage generating means. Control means, filter means for smoothing the voltage generated by the voltage generation means, and drive means for driving the stepping motor based on the output voltage value from the filter means. For example, when a predetermined voltage is generated by the voltage generating means at the start of driving of the stepping motor, the voltage applied to the driving means is smoothed by the filter means so as to gradually change. Therefore, at the time of the through-up immediately after the start of the driving of the stepping motor, the driving current of the stepping motor becomes small, and the rotational torque is suppressed. As a result, rattling due to excessive torque at a low speed in the mechanism driven by the stepping motor can be suppressed, and generation of noise and vibration can be suppressed. Also, at the time of through-down, the voltage generated by the voltage generating means at the start of through-down is reduced to a predetermined value, or
By doing so, during the subsequent execution of the through-down, a gradually decreasing voltage is applied from the filter means to the drive means. Therefore, at the time when the rotation of the stepping motor becomes slow due to the through-down, the voltage applied to the driving means is small, and the driving current of the stepping motor is small, and the rotation torque is suppressed. Thus, rattling of the mechanism due to excessive torque during low-speed rotation can be suppressed, and noise and vibration can be suppressed. In addition, as a configuration for suppressing the generation of such noise and vibration, a simple configuration in which a filter unit is added is realized, so that a stepping motor drive circuit can be configured at low cost, and the voltage in the control unit can be reduced. There is almost no load for control.

In such a configuration, the control means generates a drive signal related to the rotation speed of the stepping motor, and the drive means generates an excitation phase based on the drive signal generated by the control means to drive the stepping motor. Can be configured. If the delay time of the rise or fall of the voltage by the filter means is set to the time of the slew-up or the slew-down, the control means will perform stepping in accordance with the rise or fall of the voltage by the filter means during the slew-up or the slew-down. The rotation speed of the motor can be controlled, and good through-up and through-down can be realized by simple control.

Further, when the stepping motor performs at least one of a through-up operation and a through-down operation, the control means controls the voltage generation means to change the designation of the voltage during the operation. it can. As a result, the voltage waveform output from the filter unit can be made closer to the target voltage waveform, and the rotation torque control of the stepping motor during the through-up and the through-down can be more accurately performed. Therefore, it is possible to start and stop the stepping motor with lower noise and lower vibration.

[0012]

FIG. 1 is a block diagram showing a stepping motor drive circuit according to a first embodiment of the present invention. In the figure, 11 is a stepping motor drive circuit, 12 is a control unit, 13 is a D / A converter, 14 is a delay filter,
5 is a capacitor, 16 is a resistor, 17 is an amplifier, 18 is a motor driver, and 19 is a stepping motor. The stepping motor drive circuit 11 controls driving of the stepping motor 19. In particular, the stepping motor 19
, The through-up is executed as described above, and when the stepping motor 19 is stopped, the through-down is executed as described above. The stepping motor 19 is
The motor driver 18 is driven by a constant current, and rotates by an input current from the motor driver 18. The stepping motor 19 has two-phase excitation, one-two-phase excitation, three-phase excitation,
Various excitation type motors such as a five-phase motor and a five-phase motor can be applied.

The control section 12 controls the driving of the stepping motor 19 via each section of the stepping motor drive circuit 11. In particular, it outputs to the D / A converter 13 a voltage value that defines a current value that is given to rotationally drive the stepping motor 19. As will be described later, when the stepping motor 19 is started (at the start of through-up), the voltage value is set to the value at the time of rotation of the stepping motor 19, and the set value is maintained during rotation. When the stepping motor 19 is stopped, the voltage is changed to 0 V or a predetermined voltage value at the start of the through-down, and the value is maintained while the stepping motor 19 is stopped. Note that the voltage value may be changed several times during the through-up and the through-down. Further, the control unit 12 generates a drive signal relating to the rotation speed of the stepping motor and outputs the drive signal to the motor driver 18. As the drive signal, for example, the stepping motor 1
9 can be inputted to the motor driver 18 as a clock signal having a frequency corresponding to the rotation of the motor driver 9. Slew-up is performed by gradually increasing the frequency of the drive signal, and thereafter, by outputting a drive signal having a constant frequency, the stepping motor can be rotated at a predetermined speed. When the stepping motor 19 is stopped, the frequency of the drive signal is gradually lowered to execute the through-down. The drive signal need not be given during the stop.
Further, the control unit 12 may be configured to perform various settings such as the setting of the rotation direction and the setting of the excitation mode for the motor driver 18.

The D / A converter 13 functions as voltage generation means for generating a specified voltage based on a digital voltage value input from the control unit 12. The generated voltage is output to the delay filter 14.

The delay filter 14 comprises a capacitor 15, a resistor 16, and an amplifier 17 in this example. The voltage generated by the D / A converter 13 is smoothed by the CR circuit including the capacitor 15 and the resistor 16.
The time required for the voltage to reach a steady state is determined by the time constant of the CR circuit. This time is adjusted to the time required for through-up or through-down, for example, for controlling the current for driving the stepping motor 19. The circuit can be configured to have a corresponding time constant.
Further, when the through-up time and the through-down time are different, a different time constant circuit may be used by switching. The voltage smoothed by the CR circuit is supplied to the amplifier 1
After being amplified at 7, the signal is input to the motor driver 18. The configuration of the delay filter 14 is not limited to such a CR circuit, and an arbitrary filter circuit for smoothing a voltage waveform can be applied.

The motor driver 18 includes a delay filter 14
Is used as a reference voltage, and a current value for driving the stepping motor 19 is determined based on the reference voltage. Further, based on the drive signal sent from the control unit 12, an excitation phase is generated in accordance with a preset excitation method such as two-phase, 1-2-phase or three-phase, and the stepping motor 19 is controlled by the determined current value. Drive. As a result, the stepping motor 19 is rotated by the rotation torque corresponding to the given current value.

FIG. 2 is a diagram illustrating an example of the operation of the stepping motor drive circuit according to the first embodiment of the present invention. In FIG. 2D, the drive signal indicates the number of pulses per second instructed or input to the motor driver 18. In this example, a case where the stepping motor 19 is driven at a constant speed of 600 pulses per second is taken as an example. Is shown. When the stepping motor 19 is operated, as described above, first, the stepping motor 19 is gradually accelerated to a predetermined speed by through-up, and is rotated at a constant speed. In the case of stopping, the vehicle is gradually decelerated by the through-down and stopped. Hereinafter, the operation at the time of through-up and at the time of through-down will be particularly described.

When the driving of the stepping motor 19 is started, first, the control unit 12 sets a digital value corresponding to a reference voltage at the time of constant speed driving in the D / A converter 13. D /
The A converter 13 changes the voltage based on the signal input from the control unit 12 as shown in FIG. The voltage output from the D / A converter 13 is applied to the delay filter 1
4 is input. The delay filter 14 smoothes the voltage input by the CR circuit. As a result, the output voltage from the delay filter 14 changes so as to gradually increase as shown in FIG. 2B, and this voltage is input to the motor driver 18 as a reference voltage. Motor driver 18
Drives the stepping motor 19 with a drive current corresponding to the reference voltage. Therefore, immediately after the start of the rotation of the stepping motor 19, the stepping motor 19 is driven by a small driving current, so that the rotating torque generated by the stepping motor 19 is small. Then, as the drive current gradually increases, the rotation torque generated by the stepping motor 19 increases. In this way, the rotation torque of the stepping motor 19 changes as shown in FIG.

Further, while the reference voltage, the drive current, and the rotation torque are changing in this manner, the drive signal for rotating the stepping motor 19 is changed as shown in FIG. Gradually increase the rotation speed. In this example, an instruction to rotate at 200 pps (pulses / second) is initially sent, and thereafter 300 pps,
The number of pulses instructing driving is increased to 400 pps and 500 pps, and the rotation speed of the stepping motor 19 is increased to a predetermined speed.

In a conventional stepping motor drive circuit,
As in the case of the output voltage waveform of the D / A converter 13 shown in FIG. 2A, a large rotation torque has been generated in the stepping motor 19 from the beginning of the rotation of the stepping motor 19.
For this reason, an unnecessarily large rotation torque is generated even at the time of low-speed rotation immediately after the start of driving, which causes noise and vibration due to rattling of the mechanism. However, in the present invention, as shown in FIG. 2 (C), the rotation torque is small at the time of low-speed rotation, and the occurrence of rattling in a mechanism portion or the like is suppressed, and noise and vibration can be reduced.

When stopping the stepping motor 19, the through-down is performed as described above. In the present invention, the control unit 12 sets the digital value given to the D / A converter 13 to 0 or a predetermined value at the start of the through-down. However, this does not mean that the reference voltage input to the motor driver 18 changes abruptly, and the reference voltage is gradually reduced by the delay filter 14 as shown in FIG. Therefore, the motor driver 18 gradually reduces the drive current to the stepping motor 19. Therefore, the rotational torque generated by the stepping motor 19 also gradually decreases as shown in FIG.

After setting the digital value to be given to the D / A converter 13 to 0 or a predetermined value, the control unit 12
The drive signal sent to the motor driver 18 is changed as shown in FIG. 2D, and the rotation speed of the stepping motor 19 is gradually reduced. In this example, 500 pps, 400 pps, 300 pps, 20
The number of pulses for instructing driving is reduced to 0 pps, and the rotation speed of the stepping motor 19 is reduced and stopped. In this way, it is possible to gradually decrease the rotation torque of the stepping motor 19 while decreasing the rotation speed, thereby performing the through-down.

Conventionally, the output voltage of the D / A converter 13 is kept at the same value until the stepping motor 19 stops. For this reason, even if the rotation of the stepping motor 19 becomes low due to the through-down, the same rotational torque as that at the time of high-speed rotation is generated, and noise and vibration are generated due to rattling of the mechanism. However, in the present invention, FIG.
As shown in (2), when the rotation of the stepping motor 19 becomes low, the generated rotational torque also becomes small, so that the occurrence of rattling in the mechanism and the like can be suppressed, and noise and vibration can be reduced.

As described above, the driving current of the stepping motor 19 can be controlled in accordance with the rotation speed of the stepping motor 19 during the through-up and the through-down.
Drive control can be performed such that a small rotation torque is generated at low speed rotation and a predetermined rotation torque is generated at high speed rotation. Therefore, the mechanism does not rattle due to excessive rotation torque during low-speed rotation, and noise and vibration can be suppressed.

The performance of the stepping motor 19 and the stepping motor drive circuit 11 and the response characteristics of the D / A converter 13 vary, so that even when the rotation of the stepping motor 19 is started, the reference voltage is 0 and the rotation torque is reduced. It is assumed that no torque is generated or the torque disappears before the stepping motor 19 stops, and the stepping motor 19 suddenly stops. In order to avoid such a problem, in the example shown in FIG. 2, when the stepping motor 19 is stopped and the through-down is performed, a predetermined value is given as a digital value to the D / A converter 13 instead of 0, and An offset is provided for the voltage. As a result, the rotation torque does not become 0 immediately after the start of the driving of the stepping motor 19 or immediately before the stop thereof,
Sudden acceleration and sudden stop can be prevented. The method of generating the offset voltage is arbitrary, and various circuits that can generate an offset voltage even when the output of the D / A converter 13 is 0 can be configured.

Similarly, as another method for preventing the running torque from disappearing at the start of the through-up, a predetermined voltage is generated by the D / A converter 13 before the drive signal is applied, and a certain voltage is generated by the delay filter 14. The transmission of the drive signal may be started at the output timing. In this case, the time required for the output voltage of the delay filter 14 to reach the predetermined voltage is set to be slightly longer than the time required for the through-up. Also,
By setting the time required for the output voltage of the delay filter 14 to drop from the predetermined voltage to 0 V somewhat longer than the time required for the through-down, it is possible to prevent the rotation torque from being lost at the end of the through-down. Can be.

FIG. 3 is a block diagram showing a second embodiment of the stepping motor drive circuit according to the present invention. In the figure, the same parts as those in FIG. 20 is a voltage adjuster, 21, 22, 24 are resistors,
23 is a changeover switch. In this second embodiment,
The difference from the first embodiment is that a voltage adjusting unit 20 is provided to switch the reference voltage input to the motor driver 18.

The voltage adjusting section 20 includes resistors 21, 22, 2,
4. A voltage generating means composed of the changeover switch 23, which can switch the generated voltage in two stages.
The generated voltage is output to the delay filter 14.

The resistors 21 and 22 have different resistance values, respectively, and are provided in parallel with the voltage adjusting unit 20. The changeover switch 23 is controlled by the control unit 12 so that only one of the resistors 21 and 22 is connected in series with the resistor 24. The power supply voltage is applied to the resistors 24 and 21.
Alternatively, the voltage is divided by the resistor 22 and output. The resistance value of the resistor 21 is set so that the voltage generated when the resistor 21 is connected to the resistor 24 becomes a voltage required when the stepping motor 19 is driven at a high speed. Further, the resistance value of the resistor 22 is set such that a voltage generated when the resistor 22 is connected to the resistor 24 becomes, for example, a reference voltage as an offset voltage.

When the step-up motor 19 starts through-up, the control unit 12 controls the voltage adjustment unit 20 to connect the resistor 2
2 to the resistor 21, and at the start of the through-down, the switch from the resistor 21 to the resistor 22. As a result, a voltage as shown in FIG. 2A is generated and input to the delay filter 14. The other operations at the time of through-up and at the time of through-down are the same as those of the first embodiment, and therefore the description thereof is omitted.

Next, a description will be given of a third embodiment of the stepping motor drive circuit according to the present invention. Here, it is assumed that the circuit configuration is the same as that shown in FIG.
In the third embodiment, a case will be described in which the voltage generated by the D / A converter 13 can be changed during the through-up or the through-down. FIG. 4 is an explanatory diagram of a voltage waveform when changing the voltage generated during the through-up and a change in torque in the stepping motor. FIG. 4A shows a voltage output generated by the D / A converter 13, that is, a voltage input to the delay filter 14. FIG. 4B shows a change in the reference voltage input to the motor driver 18, and FIG. 4C shows a change in the rotation torque of the stepping motor 19.

In the example shown in FIG. 4, the voltage generated by the D / A converter 13 changes at the time t1 during the through-up. For example, from the start of the through-up to time t1, the voltage can be about 60% of the voltage thereafter.
Of course, this voltage value can be arbitrarily set from the control unit 12.

As described above, by changing the voltage generated in two stages, the output from the delay filter 14 is changed.
Due to the combination of the two smoothed voltage waveforms,
It becomes possible to control the voltage waveform. For example, when it is desired to extend the period of the low rotation torque, the voltage to be generated first is set lower, or the time t until the voltage is switched is t.
1 may be set longer. In particular, rattling in the mechanical section is likely to occur at the beginning of movement, so the time for absorbing this rattling should be set to a low torque state, and then control can be performed to gradually increase the rotating torque. is there. In this way, it is possible to eliminate rattling in the mechanism section and further reduce noise and vibration. Of course, the voltage value to be generated first and the time until the voltage is switched can be set according to the state of each unit.

In the above-described example, the voltage generated at the time of through-up is changed in two steps, but the present invention is not limited to this, and may be three or more steps. However, if it is too fine, D /
It becomes necessary to use a high response characteristic of the A converter 13, resulting in an increase in cost. In the present invention, the delay filter 14 is used.
By using the filter means for smoothing, the change of the voltage generated in the D / A converter 13 can be minimized, and the cost of the D / A converter 13 can be reduced.

In the above example, the through-up operation has been described. However, the same control can be performed during the through-down operation. Further, in the above-described example, the configuration using the D / A converter 13 shown in FIG. 1 has been described. However, for example, as in the configuration shown in FIG. This can be handled by increasing the number of resistors.

[0036]

As is apparent from the above description, according to the present invention, the voltage generated by the voltage generating means is smoothed by the filter means, and the driving means is used as a reference voltage for controlling the driving current of the stepping motor. , So if the voltage generated by the voltage generator is changed,
The reference voltage can be gradually changed. Thus, for example, by gradually changing the reference voltage at the time of through-up or at the time of through-down, the rotation torque at the time of low-speed rotation can be reduced, and the movement can be started or stopped without applying an excessive load to the mechanism. Therefore, it is possible to prevent rattling of the mechanism section and reduce noise and vibration. Further, since such rotation torque control is performed only by providing the filter means, it can be configured at a low cost,
Further, there is no need for a D / A converter or the like having a high response speed, so that a low-cost stepping motor driving circuit can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a stepping motor drive circuit according to the present invention.

FIG. 2 is a diagram illustrating an example of an operation of the stepping motor drive circuit according to the first embodiment of the present invention.

FIG. 3 is a block diagram showing a second embodiment of the stepping motor drive circuit according to the present invention.

FIG. 4 is an explanatory diagram of a voltage waveform when changing a voltage generated during a through-up and a change in torque in a stepping motor.

FIG. 5 is a block diagram of a conventional stepping motor drive circuit.

[Explanation of symbols]

11 ... stepping motor drive circuit, 12 ... control unit, 1
3 D / A converter, 14 delay filter, 15 capacitor, 16 resistor, 17 amplifier, 18 motor driver, 19 stepping motor, 20 voltage regulator,
21, 22, 24 ... resistors, 23 ... changeover switches.

Claims (3)

[Claims] 1. A voltage generating means for generating a designated voltage, a control means for controlling the driving of a stepping motor by designating a voltage with respect to the voltage generating means, and smoothing a voltage generated by the voltage generating means. A stepping motor driving circuit, comprising: a filter means for converting the voltage of the filter means; and a drive means for driving the stepping motor based on an output voltage value from the filter means. 2. The control unit generates a drive signal related to a rotation speed of the stepping motor, and the drive unit generates an excitation phase based on the drive signal generated by the control unit to control the stepping motor. The stepping motor drive circuit according to claim 1, wherein the stepping motor drive circuit is driven. 3. The control means according to claim 1, wherein when the stepping motor performs at least one of a through-up operation and a through-down operation, the control unit changes a voltage designation to the voltage generation unit during the operation. The stepping motor drive circuit according to claim 1 or 2, wherein