JPH11262296A - Stepping motor driving equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce vibrations and noises, without decreasing the output torque, and improve both the output torque characteristic and vibration characteristic. SOLUTION: Current limit setting change signals IRCA and IRCB are outputted to drivers 2 and 3 from an excitation control circuit 6. When the signals IRCA and IRCB are in 'H' period, the drivers 2 and 3 change a current limit setting value which defines the upper limit of absolute value of currents flowing in stator coils 4 and 5 into a lower side current limit setting value. While a current value of the stator coil 5 increases up to the upper side current limit setting value, in a period from a time t1 to a time t2, a current value of the stator coil 4 decreases and is maintained to be a lower side current limit setting value. Comparatively weak hysteresis break of the stator coil 4 is applied to a rotor for a comparatively long term, so that the rotor rotates smoothly and the output torque is not drastically deteriorated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device for supplying driving power to a stepping motor, and more particularly to a driving device for improving the output torque characteristics and vibration characteristics of the stepping motor.

[0002]

2. Description of the Related Art In a stepping motor in which the rotation angle of the rotor is controlled by switching the excitation phase of the stator based on the positional relationship between the stator and the rotor, the rotor is not provided with a winding, and the load is reduced in a load state. Regardless, since constant energy is always supplied from the stator, it is not possible to generate a torque corresponding to a load change. For this reason, it is necessary to select a stepping motor that generates as much torque as possible in the range of load fluctuation.
On the other hand, along with a demand for downsizing of an apparatus using the stepping motor, a demand for downsizing of the stepping motor is also strong, and it is desired that the relative output torque characteristics of the stepping motor be improved.

Generally, in a stepping motor, the output torque is reduced by a so-called hysteresis brake in which the magnetic force of the coil of the stator, which the rotor has passed, acts on the rotor in a direction opposite to the rotation direction.

Therefore, in a conventional stepping motor driving device, as shown in FIGS. 11 and 12, the A-phase coil 42 or B-phase coil 42 or B-phase coil 41 after the teeth of the rotor 41 face the A-phase coil 42 or B-phase coil 43 of the stator. The current limit control period ta of the phase coil 43 is shortened, and the current value of the A-phase coil 42 or the B-phase coil 43 of the stator after the teeth of the rotor 41 pass is sharply reduced, so that the hysteresis brake operates time. Is shortened to improve output torque.

However, if the period during which the hysteresis brake operates is shortened by setting the current limit control period ta of the A-phase coil 42 to, for example, the point a to the point b shown in FIG. 11, the point b at the point b shown in FIG. The hysteresis brake hardly acts on the rotor in a relatively wide range from point to point d. During this time, the rotor rotates rapidly, causing a problem that the stepping motor generates vibration and noise.

On the other hand, as a means for reducing the vibration and noise of the stepping motor, in the configuration disclosed in Japanese Patent Application Laid-Open No. 8-331896, two-phase excitation to one-phase excitation, and
During the change from the phase excitation to the two-phase excitation, the exciting current is changed from 1 to 1
/ 2 → 0 → −1 / 2 → −1 and create an intermediate excitation mode in 1-2 phase excitation to make 3 steps in 1-2 phase excitation 5 steps and smooth rotation of the rotor I'm trying to get

In the conventionally known micro-step driving method, an AV for determining the set current of the A-phase and the B-phase is used.
By applying a voltage obtained by full-wave rectification of a sine wave to the R terminal and the BVR terminal at intervals of, for example, 1/4 cycle, the current set value during one step of movement is changed linearly, and the current flowing to the motor is changed to a sine waveform. And a smooth rotation state of the rotor is obtained. This micro-step driving method is also disclosed in Japanese Unexamined Patent Publication No.
This is the same as the configuration disclosed in Japanese Patent No. 1896.

[0008]

However, in the configuration disclosed in Japanese Patent Application Laid-Open No. Hei 8-331896 and the micro-step drive system, the rotation of the rotor is smoothly performed by a hysteresis brake in the intermediate excitation mode. This results in a decrease in output torque due to a longer operation period of the hysteresis brake during rotation. Therefore, the conventional driving device has a problem that vibration and noise cannot be reduced without lowering the output torque.

It is an object of the present invention to provide a stepping motor driving device capable of reducing vibration and noise without lowering output torque and improving both output torque characteristics and vibration characteristics.

[0010]

According to the first aspect of the present invention, an absolute value of a current flowing through a stator coil during excitation in a range in which a magnetic force of a stator coil acts in a direction opposite to a rotation direction of a rotor is determined. The present invention is characterized in that current limit value lowering control is performed to lower the absolute value of the current flowing through the stator coil during excitation in a range in which the magnetic force acts in the rotation direction of the rotor.

According to the first aspect of the present invention, in a range where the magnetic force of the stator coil acts in the direction opposite to the rotation direction of the rotor, the absolute value of the current flowing in the stator coil is reduced, and the magnetic force generated in the stator coil is weakened. Become.
Therefore, the hysteresis brake acting on the rotor from the stator coil in the direction opposite to the rotation direction is reduced, and the output torque is not significantly reduced.

That is, as shown in FIG. 13, the current value of the A-phase stator coil is within a range in which the magnetic force of the A-phase stator coil acts in the direction opposite to the rotation direction of the rotor after the rotor has passed through the A-phase stator coil. Is decreased from the set value Sa to the set value Sb, and the hysteresis brake acting on the rotor is weakened in a relatively wide range from the point a to the point c as shown in a diagram Lb of FIG. Therefore, the action of the hysteresis brake on the rotor is weaker than when the set value Sa of the current value of the A-phase stator coil is maintained in a range where the magnetic force of the A-phase stator coil acts in the direction opposite to the rotation direction of the rotor. Therefore, the amount of attenuation of the output torque of the stepping motor can be reduced.

Further, as compared with a configuration in which the period during which the hysteresis brake acts on the rotor is shortened by shortening the current limit control time of the stator coil (see FIG. 12), the range in which the rotor rotates rapidly is narrowed. The rotation of the rotor can be made smooth, and the vibration characteristics and noise characteristics of the stepping motor can be improved.

The invention described in claim 2 is characterized in that the application of the voltage to the stator coil is stopped at the time of starting the current limit value lowering control.

According to the second aspect of the present invention, the application of the voltage to the stator coil is stopped at the start of the current limit value lowering control for reducing the absolute value of the current flowing through the stator coil. Therefore, at the start of the current limit value lowering control, the absolute value of the current of the stator coil quickly decreases.

The invention described in claim 3 is characterized in that a reverse voltage is applied to the stator coil at the start of the current limit value lowering control.

According to the third aspect of the present invention, a reverse voltage is applied to the stator coil at the start of the current limit value lowering control for reducing the absolute value of the current flowing through the stator coil. Therefore, at the start of the current limit value lowering control, the absolute value of the current of the stator coil decreases more quickly.

According to a fourth aspect of the present invention, a signal for commanding the application of a voltage to the stator coil or the application of a reverse voltage to the stator coil is provided by an excitation command signal for the stator coil or a decrease in the current limit value. It is characterized by being superimposed on a signal for instructing start of control.

According to the fourth aspect of the present invention, the signal for stopping the application of the voltage to the stator coil or for applying the reverse voltage to the stator coil is an excitation command signal or the start of the current limit value lowering control. Is superimposed on the signal instructing Therefore, a signal for stopping the application of the voltage to the stator coil or for applying a reverse voltage to the stator coil is output in exact synchronization with the excitation command signal or the signal for instructing the start of the current limit value lowering control. You.

According to a fifth aspect of the present invention, when the application of the voltage to the stator coil is stopped or the reverse voltage is applied to the stator coil, the value of the current flowing through the stator coil is decreased in the current limit value decreasing control. It is characterized in that it is executed until the value matches.

According to the fifth aspect of the present invention, the stop of the application of the voltage to the stator coil or the application of the reverse voltage to the stator coil, which is started together with the control of decreasing the current limit value, causes the current value flowing through the stator coil to be equal to the current value. The process is continued until the current value set in the limit value lowering control matches the current value. Therefore, at the time of the current limit value lowering control, the current value of the stator coil quickly and reliably decreases to the predetermined current value.

According to a sixth aspect of the present invention, there is provided a comparator for comparing a current value flowing through the stator coil with a reference value during the current limit value lowering control, and a voltage of the stator coil based on an output signal of the comparator. And switching means for turning on / off the application.

According to the present invention, a comparator for comparing the value of the current flowing through the stator coil with a reference value, and switching for turning on / off the application of a voltage to the stator coil based on an output signal of the comparator. The means controls the application of the voltage to the stator coil such that the current value of the stator coil matches the set value during the current limit value lowering control. Therefore, it is not necessary to output a signal only for instructing the stop of the application of the voltage to the stator coil or the application of the reverse voltage to the stator coil at the start of the current limit value lowering control.

[0024]

FIG. 1 is a diagram showing a configuration of a stepping motor driving device according to a first embodiment of the present invention. The stepping motor drive device 10 according to this embodiment includes an A-phase driver 2, a B-phase driver 3, and an excitation control circuit 6. The A-phase driver 2 drives the A-phase stator coil 4 of the stepping motor 1. The B-phase driver 3 drives the B-phase stator coil 5. The excitation control circuit 6 sends an A-phase excitation command signal APL and an A-phase current limit setting change signal I to the A-phase driver 2.
RCA, and outputs a B-phase excitation command signal BPL and a B-phase current limit setting change signal IRCB to the B-phase driver 3.
Is output.

FIG. 2 is a timing chart of each signal at the time of two-phase excitation in the stepping motor driving device. Excitation control circuit 6 of stepping motor drive device 10
The A-phase excitation command signal APL and the B-phase excitation command signal BPL output to the A-phase driver 2 and the B-phase driver 3, respectively, are set to “H” during two steps with four steps as one cycle. Signal. B-phase excitation command signal B
PL is output one step behind A-phase excitation command signal APL. The A-phase driver 2 and the B-phase driver 3
For the A-phase stator coil 4 and the B-phase stator coil 5, the A-phase excitation command signal APL and the B-phase excitation command signal BP
In the “H” period of L, a positive polarity voltage is applied, and “L”
During the period, a negative voltage is applied.

The A-phase current limit setting change signal IRCA and the B-phase current limit setting change signal IRCB output from the excitation control circuit 6 are signals that are set to “H” during one step with two steps as one cycle. And rises at an intermediate timing between the “H” and “L” periods in the A-phase excitation command signal APL and the B-phase excitation command signal BPL. B-phase current limit setting change signal IRCB
Is output one step behind the A-phase current limit setting change signal IRCA. The A-phase driver 2 and the B-phase driver 3 control the current flowing through the A-phase stator coil 4 and the B-phase stator coil 5 during the period when the A-phase current limit setting change signal IRCA and the B-phase current limit setting change signal IRCB are “H”. Of the current limit setting value that defines the upper limit of the absolute value of is reduced to, for example, 値.

That is, the upper limit of the absolute value of the current flowing through the A-phase stator coil 4 and the B-phase stator coil 5 is determined by “L” or “H” of the A-phase current limit setting change signal IRCA and the B-phase current limit setting change signal IRCB. Is set to either the larger current limit setting value or the smaller current limit setting value. Below, the larger current limit setting is the upper current limit setting,
The smaller current limit setting is called the lower current limit setting.

By controlling each signal output from the excitation control circuit 6 as described above, for example, as shown in FIG. 2, the current value of the B-phase stator coil 5 is changed from time t1 to time t2. While rising to the upper current limit set value, the current value of the A-phase stator coil 4 falls and is maintained at the lower current limit set value. The rotor of the stepping motor 1 comes closest to the A-phase stator coil 4 after a lapse of a short time from the time t1 when the current value of the A-phase stator coil 4 matches the upper current limit set value, and at the time t2
And moves to the position closest to the B-phase stator coil 5 until a minute time elapses.

Therefore, the current value of the B-phase stator coil 5 is increasing, and while the rotor is moving toward the position closest to the B-phase stator coil 5, A
When a constant current flows through the phase stator coil 4,
The hysteresis brake of the A-phase stator coil 4 acts on the rotor for a relatively long time, and the rotor rotates smoothly. At this time, since the current value of the A-phase stator coil 4 is defined by the lower current limit setting value, the hysteresis brake acting on the rotor from the A-phase stator coil 4 is relatively weak, and the output torque of the stepping motor 1 is significantly reduced. Never.

FIG. 3 is a diagram showing a configuration of a stepping motor driving device according to a second embodiment of the present invention. The excitation control circuit 6 of the stepping motor drive device 10 according to this embodiment is configured to control the A-phase excitation command signal AP shown in FIG.
L and A phase current limit setting change signal IRCA, B phase excitation command signal BPL and B phase current limit setting change signal IR
In addition to CB, it outputs an A-phase excitation stop signal ENA to the A-phase driver 2 and outputs a B-phase excitation stop signal ENB to the B-phase driver 3.

FIG. 4 is a timing chart of each signal during two-phase excitation in the stepping motor driving device. Excitation control circuit 6 of stepping motor drive device 10
The A-phase excitation command signal APL, the B-phase excitation command signal BPL, the A-phase current limit setting change signal IRCA, and the B-phase current limit setting change signal IRCB output to the A-phase driver 2 and the B-phase driver 3 respectively from , Signals similar to those shown in FIG.

The A-phase excitation stop signal ENA and the B-phase excitation stop signal ENB output from the excitation control circuit 6 are signals that are set to "H" during, for example, 1/2 step with two steps as one cycle. It rises at an intermediate timing between the “H” and “L” periods in the A-phase excitation command signal APL and the B-phase excitation command signal BPL. The B-phase excitation stop signal ENB is output one step behind the A-phase excitation stop signal ENA. The A-phase driver 2 and the B-phase driver 3 provide an A-phase excitation stop signal ENA and a B-phase excitation stop signal E
During the “H” period of NB, the A-phase stator coils 4 and B
The application of the voltage to the phase stator coil 5 is stopped.

During the "H" period of the A-phase excitation stop signal ENA and the B-phase excitation stop signal ENB, the absolute value of the current flowing through the A-phase stator coil 4 and the B-phase stator coil 5 is changed by the A-phase current limit setting change. A period until the lower current limit set value is set is set by the signal IRCA and the B-phase current limit setting change signal IRCB.

By controlling each signal output from the excitation control circuit 6 as described above, the B-phase stator coil 5
Or, while the current value of the A-phase stator coil 4 rises to the upper current limit set value, the A-phase stator coil 4 or B
The current value of the phase stator coil 5 can be quickly decreased by the lower current limit set value.

That is, in the stepping motor driving apparatus according to the first embodiment shown in FIGS. 1 and 2, the A-phase drivers 2 and B are controlled by the A-phase current limit setting change signal IRCA and the B-phase current limit setting change signal IRCB. The phase driver 3 includes an A-phase stator coil 4 and a B-phase stator coil 5
Even if the upper limit of the absolute value of the current flowing through the A-phase stator coil 4 and the B-phase stator coil 5 cannot be reduced quickly by the already stored electric energy.

Therefore, in the stepping motor driving device according to the present embodiment, the actual current values of the A-phase stator coil 4 and the B-phase stator coil 5 are set lower by the A-phase excitation stop signal ENA and the B-phase excitation stop signal ENB. By stopping the application of the voltage to the A-phase stator coil 4 and the B-phase stator coil 5 until the current limit set value is reached, the accumulated electric energy is diverted to thereby disperse the A-phase stator coil 4 and the B-phase stator coil. 5 is made to match the lower current limit set value earlier.

FIG. 5 is a timing chart of signals when the stepping motor driving device according to the third embodiment of the present invention is driven by two-phase excitation bipolar. In the stepping motor driving device according to this embodiment, the A-phase excitation command signal APL and the B-phase excitation command signal BP shown in FIG.
L indicates the A-phase excitation stop signal ENA and the B-phase excitation stop signal EN
The content of the signal B is superimposed and output from the excitation control circuit 6. Specifically, as the “H” period and the “L” period of the A-phase excitation command signal APL and the B-phase excitation command signal BPL, A
A period is provided until the current values of the phase stator coil 4 and the B-phase stator coil 5 fall from the upper current limit set value to the lower current limit set value.

A-phase excitation command signals APL and B shown in FIG.
By outputting the phase excitation command signal BPL from the excitation control circuit 6, the A-phase driver 2 and the B-phase driver 3
During a certain period during which the polarity voltage or the negative polarity voltage is to be applied, the negative polarity voltage or the positive polarity voltage is applied. Thus, voltages of opposite polarities are applied to the A-phase stator coil 4 and the B-phase stator coil 5 until the current values of the A-phase stator coil 4 and the B-phase stator coil 5 fall to the lower current limit set value. By doing so, even when the current descending speed is slow due to the influence of the coil characteristics, the number of rotations of the rotor, and the like, the current value of the B-phase stator coil 5 or the A-phase stator coil 4 is increased to the upper current limit set value. , The actual current value of the A-phase stator coil 4 or the B-phase stator coil 5 can be reliably reduced to the lower current limit set value.

The A-phase excitation stop signal EN shown in FIG.
The A and B phase excitation stop signal ENB is the A phase excitation command signal A
Although it is necessary to reliably synchronize with the PL and B-phase excitation command signals BPL, the contents of the A-phase excitation stop signal ENA and the B-phase excitation stop signal ENB are superimposed on the A-phase excitation command signal APL and the B-phase excitation command signal BPL. Thus, both can be reliably synchronized, and the number of signal lines can be reduced.

The contents of the A-phase excitation stop signal ENA and the B-phase excitation stop signal ENB are changed to the A-phase current limit setting change signal IRCA and the B-phase current limit setting change signal IRCB.
May be superimposed.

FIG. 6 is a timing chart of each signal at the time of 1-2 phase excitation of the stepping motor driving device according to the second embodiment of the present invention. The A-phase excitation command signal APL and the B-phase excitation command signal BPL output from the excitation control circuit 6 of the stepping motor drive device 10 to each of the A-phase driver 2 and the B-phase driver 3 are 4 steps with 8 steps as one cycle. This signal is set to “H” during the step. The B-phase excitation command signal BPL is output two steps later than the A-phase excitation command signal APL. The A-phase driver 2 and the B-phase driver 3 include an A-phase stator coil 4
A positive polarity voltage is applied to the A-phase excitation command signal APL and the B-phase excitation command signal BPL to the B-phase stator coil 5 during the “H” period, and a −polarity voltage is applied to the B-phase stator coil 5 during the “L” period.

The A-phase current limit setting change signal IRCA and the B-phase current limit setting change signal IRCB output from the excitation control circuit 6 are signals that are set to “H” during one step with four steps as one cycle. And rises at an intermediate timing between the “H” and “L” periods in the A-phase excitation command signal APL and the B-phase excitation command signal BPL. B-phase current limit setting change signal IRCB
Is output two steps later than the A-phase current limit setting change signal IRCA. The A-phase driver 2 and the B-phase driver 3 control the current flowing through the A-phase stator coil 4 and the B-phase stator coil 5 during the period when the A-phase current limit setting change signal IRCA and the B-phase current limit setting change signal IRCB are “H”. Set the current limit set value that determines the upper limit of the absolute value of the lower current limit set value.

Further, A output from the excitation control circuit 6
The phase excitation stop signal ENA and the B phase excitation stop signal ENB are
With four steps as one cycle, the signal is set to “H” during a half step, for example, from the middle timing between the “H” and “L” periods in the A-phase excitation command signal APL and the B-phase excitation command signal BPL. , Are set to “L” during the next half step and set to “H” during the next one step. The B-phase excitation stop signal ENB is output two steps later than the A-phase excitation stop signal ENA. The A-phase driver 2 and the B-phase driver 3 provide an A-phase excitation stop signal ENA
During the “H” period of the B-phase excitation stop signal ENB, the application of voltage to the A-phase stator coil 4 and the B-phase stator coil 5 is stopped.

With the above configuration, during the 1-2-phase excitation, the A-phase driver 2 and the B-phase driver 3 continuously make the same for the A-phase stator coil 4 and the B-phase stator coil 5 during three steps. Polarity current is supplied and this 3
During the last one step of the step period, the A-phase current limit setting change signal IRCA and the B-phase current limit setting change signal IRCB are set to “H”, and in the first half of the last one step, the A-phase excitation stop signal ENA And the B-phase excitation stop signal ENB is set to “H”. Therefore, during the 1-2-step excitation, the A-phase stator coil 4 and the B-phase stator coil 5 during the three-step period in which the current of the same polarity is continuously supplied to the A-phase stator coil 4 and the B-phase stator coil 5 In the last step during which the hysteresis brake acts on the rotor, the current limit set values of the A-phase stator coil 4 and the B-phase stator coil 5 can be accurately reduced, and the application of voltage is stopped. can do. As a result, even during the 1-2-phase excitation, the hysteresis brake having a small influence can be reliably applied for a relatively long period of time, and a smooth rotation operation can be obtained without a significant decrease in output torque. .

The A-phase current limit setting change signal IR
The lower current limit set value set in the A-phase stator coil 4 and the B-phase stator coil 5 from the A-phase driver 2 and the B-phase driver 3 when the CA and the B-phase current limit setting change signal IRCB is input is the stator in the stepping motor 1. It can be determined from the relationship between the current drop rate of the coil, the output torque attenuation rate, and the noise reduction rate. For example,
The relationship between the current drop rate of the stator coil in the stepping motor 1, the output torque attenuation rate, and the noise reduction rate is as follows.
When represented as shown in FIGS. 7 and 8, respectively,
As the lower current limit setting value, 20 to 80% of the upper current limit setting value is selected so that the output torque attenuation is as small as possible and the noise reduction amount is large. Here, the relationship between the voltage drop rate and the noise reduction rate shown in FIG. 8 is obtained by converting the vibration generated by the stepping motor 1 into noise when the stepping motor 1 is mounted on the resonance plate and the current value of the stator coil is changed. This is the result of measurement.

When the "H" period in the A-phase excitation stop signal ENA and the B-phase excitation stop signal ENB is fixedly set, the actual current value of the stator coil is reduced to the lower current limit due to the individual difference of the stepping motor 1. There is a possibility that a case where it does not decrease to the set value may occur. Therefore, a current detection resistor for detecting a current value flowing through the stator coil is provided,
The voltage of the current detection resistor is compared with a reference voltage corresponding to the lower current limit set value, and the A-phase excitation stop signal ENA and the B-phase excitation stop signal ENB are set to “H” until they match. This configuration ensures that the actual current value of the stator coil always matches the lower current limit setting value regardless of the individual difference of the stepping motor 1.

For example, as shown in FIG. 9, the A-phase driver 2 includes a current detection resistor R1 for detecting a current value flowing through the A-phase stator coil 4, a comparator CMP1 for comparing the voltage at the current detection resistor R1 with a reference voltage, Resistors R2 and R3 for setting an upper reference voltage in the comparator CMP1, and a reference voltage changing resistor for lowering the reference voltage of the comparator CMP1 to a lower value based on a current limit setting change signal IRCA output from the excitation control circuit 6. R4
The output of the comparator CMP1 and the excitation control circuit 6 are connected to the base terminals of the transistors TR1 and TR2 on the power supply VM side among the bipolar drive transistors TR1 to TR4 for driving the stator coil 4 and the transistor TR5.
Gates AND1 and AND2 for supplying as a drive signal the logical product of the excitation command signal APL and the excitation command signal APL output therefrom are provided.

With this configuration, when the current limit setting change signal IRCA is output from the excitation control circuit 6, the transistor TR5 is turned on, the reference voltage of the comparator CMP1 is reduced by the resistor R4, and the output of the comparator CMP1 is reduced. Then, the drive signal output from the gate AND1 or AND2 to the drive transistor TR1 or TR2 on the power supply side becomes "L", and current is not supplied from the power supply VM to the stator coil 4.

On the other hand, among the bipolar driving transistors TR1 to TR4 for driving the stator coil 4, the driving transistor TR3 or TR4 on the ground side receives the excitation command signal APL.
, And the stator coil 4 is grounded via the drive transistor TR3 or TR4 and the current detection resistor R1. Therefore, the coil energy remaining in the stator coil 4 is released via the drive transistor TR3 or TR4 and the current detection resistor R1, and the current value of the stator coil 4 decreases.

As a result, when the value of the current flowing through the current detection resistor R1 decreases and the voltage at the current detection resistor R1 becomes lower than the smaller reference voltage set in the comparator CMP1, the output of the comparator CMP1 increases.
The drive signal output from the gate AND1 or AND2 becomes “H”, and a current is supplied from the power supply VM to the stator coil 4 via the drive transistor TR1 or TR2 on the power supply VM side.

Therefore, when the supply of power is stopped and the absolute value of the current in the stator coil 4 is decreased, the coil energy remaining in the stator coil 4 is transferred to the ground-side drive transistor TR3 or TR4 and the current detection resistor R1. And the current value of the stator coil 4 can be rapidly reduced. Also,
By turning on / off the drive transistors TR1 and TR2 on the power supply side based on the output of the comparator CMP1 that compares the voltage value of the current detection resistor R1 with the reference voltage, the excitation control circuit 6 does not output the excitation stop signal ENA. The power supply to the stator coil 4 can be stopped accurately until the actual current value of the stator coil 4 matches the smaller current limit set value. The above configuration and effect are the same for the B-phase stator coil 5.

When the stator coils 4 and 5 of the stepping motor 1 are driven via the unipolar drive transistor, the unipolar drive transistor TR11 is arranged between the power supply VM and the stator coil 4 as shown in FIG. And GND and the unipolar drive transistor T
A diode D1 is inserted between R11 and the stator coil 4. As a result, when the transistor TR11 is turned off, the coil energy remaining in the stator coil 4 flows to GND as shown by the arrow in the figure, and the current value of the stator coil 4 can be quickly reduced.

Further, in order to improve the output torque characteristics of the stepping motor 1, it is desirable to shorten the time required for the actual current value of the stator coil to reach the upper current limit set value as short as possible. To do this,
The inductance of the windings of the stator coils 4 and 5 should be reduced to make the rise of the current flowing through the coils faster.
Thereby, the effect of suppressing the heat generation amount of the stator coil can also be obtained.

In addition, in order to rotate the stepping motor 1 smoothly, the A-phase current limit setting change signal IR
The CA and B-phase current limit setting change signal IRCB needs to be completely synchronized with the A-phase excitation command signal APL and the B-phase excitation command signal BPL. Therefore, the A-phase current limit setting change signal IRCA and the B-phase current limit setting change signal IRCB are based on the same operation clock as the output circuit of the A-phase excitation command signal APL and the B-phase excitation command signal BPL. It is possible to output from.

[0055]

According to the first aspect of the present invention, the absolute value of the current flowing through the stator coil is reduced in a range in which the magnetic force of the stator coil acts in the direction opposite to the rotation direction of the rotor, and is generated in the stator coil. By weakening the magnetic force, it is possible to reduce the hysteresis brake acting on the rotor from the stator coil in the direction opposite to the rotation direction, thereby reducing the output torque attenuation and controlling the stator coil current limit. Compared to a configuration that shortens the period in which the hysteresis brake acts on the rotor by shortening the time, the range in which the rotor rotates rapidly can be narrowed, and the rotation of the rotor can be smooth. And noise characteristics can be improved.

According to the second aspect of the present invention, the application of the voltage to the stator coil is stopped at the start of the current limit value lowering control for reducing the absolute value of the current flowing through the stator coil, so that the current limit value lowers. At the start of the control, the absolute value of the current of the stator coil can be quickly reduced.

According to the third aspect of the present invention, at the start of the current limit value lowering control for reducing the absolute value of the current flowing through the stator coil, a reverse voltage is applied to the stator coil to thereby reduce the current limit value lowering control. , The absolute value of the stator coil current can be reduced more quickly.

According to the fourth aspect of the present invention, the signal for commanding the stop of the voltage application to the stator coil or the application of the reverse voltage to the stator coil is used as the excitation command signal or the current limit value lowering control. By superimposing on the signal for instructing the start, the application of the signal for instructing the application of the reverse voltage to the stator coil to stop the application of the voltage to the stator coil, or the excitation instruction signal, or instructing the start of the current limit value lowering control. The output can be accurately synchronized with the signal, and the absolute value of the current flowing through the stator coil can always be reduced at an accurate timing.

According to the fifth aspect of the present invention, the stop of the application of the voltage to the stator coil or the application of the reverse voltage to the stator coil, which is started together with the current limit value lowering control, is performed by changing the current value flowing through the stator coil. By continuing until the current value matches the current value set in the current limit value lowering control, the current value of the stator coil can be quickly and reliably reduced to a predetermined current value during the current limit value lowering control.

According to the invention described in claim 6, the comparator for comparing the value of the current flowing through the stator coil with the reference value,
Switching means for turning on / off the application of the voltage to the stator coil based on the output signal of the comparator; and controlling the voltage applied to the stator coil so that the current value of the stator coil matches the set value during the current limit value lowering control. By controlling the application, it is not necessary to stop the application of the voltage to the stator coil at the start of the current limit value lowering control or to output a signal only for instructing the application of the reverse voltage to the stator coil. Control of the applied voltage can be simplified.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a stepping motor driving device according to a first embodiment of the present invention.

FIG. 2 is a timing chart of each signal during two-phase excitation in the stepping motor driving device.

FIG. 3 is a diagram showing a configuration of a stepping motor driving device according to a second embodiment of the present invention.

FIG. 4 is a timing chart of signals at the time of two-phase excitation in the stepping motor driving device.

FIG. 5 is a timing chart of signals during two-phase excitation of a stepping motor drive device according to a third embodiment of the present invention.

FIG. 6 is a timing chart of each signal at the time of 1-2 phase excitation of the stepping motor drive device according to the second embodiment of the present invention.

FIG. 7 is a diagram showing a relationship between a current decrease rate of a stator coil and a damping rate of an output torque in a stepping motor driven by a driving device according to an embodiment of the present invention.

FIG. 8 is a diagram showing a relationship between a current decrease rate of a stator coil and a noise reduction rate in a stepping motor driven by the driving device according to the embodiment of the present invention.

FIG. 9 is a diagram illustrating a configuration of a stepping motor driving device when applied to a bipolar driving stepping motor.

FIG. 10 is a diagram showing a configuration of a stepping motor drive device when applied to a monopolar drive stepping motor.

FIG. 11 is a diagram illustrating a rotation state of a rotor in a general stepping motor.

FIG. 12 is a diagram showing a change in current of an A-phase stator coil and a B-phase stator coil of a stepping motor driven by a conventional driving device.

FIG. 13 is a diagram showing a change in current of an A-phase stator coil and a B-phase stator coil for explaining the operation of the present invention.

[Explanation of symbols]

 1-Stepping motor 2-A-phase driver 3-B-phase driver 4-A-phase stator coil 5-B-phase stator coil 6-Excitation control circuit 10-Stepping motor driving device

Claims (6)

[Claims] An absolute value of a current flowing through a stator coil during excitation in a range in which a magnetic force of a stator coil acts in a direction opposite to a rotation direction of a rotor is determined by an excitation in a range in which a magnetic force of the stator coil acts in a rotation direction of the rotor. A stepping motor driving device for executing a current limit value lowering control for lowering an absolute value of a current flowing through a middle stator coil. 2. The stepping motor drive device according to claim 1, wherein the application of the voltage to the stator coil is stopped when the current limit value lowering control is started. 3. The stepping motor drive device according to claim 1, wherein a reverse voltage is applied to the stator coil at the time of starting the current limit value lowering control. 4. A signal for commanding stop of voltage application to said stator coil or application of reverse voltage to said stator coil, comprising: an excitation command signal for said stator coil;
4. The stepping motor driving device according to claim 2, wherein the stepping motor driving device is superimposed on a signal for instructing the start of the current limit value lowering control. 5. 5. The method according to claim 1, further comprising: stopping application of a voltage to said stator coil or applying a reverse voltage to said stator coil.
5. The stepping motor driving device according to claim 2, wherein the stepping motor driving is performed until the value of the current flowing through the stator coil coincides with the value decreased in the current limit value decreasing control. 6. A comparator for comparing a current value flowing through a stator coil with a reference value at the time of the current limit value lowering control, and switching for turning on / off application of a voltage to the stator coil based on an output signal of the comparator. 6. The stepping motor drive device according to claim 5, further comprising: means.