JP2001095268A - Method for control of ultrasonic motor and control circuit thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the control circuit of an ultrasonic motor, capable of attaining high quietness using simple control. SOLUTION: This control circuit 11 is provided with a drive voltage permit circuit 13 of stopping the supply of one high-frequency drive voltage VB and then stopping the supply of the other high-frequency drive voltage VA.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling an ultrasonic motor when rotation is stopped and a control circuit therefor.

[0002]

2. Description of the Related Art An ultrasonic motor is constructed by pressing a rotor rotatably supported by a resilient member against a stator having a piezoelectric element. An A / B phase electrode and a feedback electrode are provided at predetermined positions in the rotational direction of the piezoelectric element, and high frequency driving voltages having phases different from each other by 90 ° are applied to the A / B phase electrodes. When such a drive voltage is applied to each electrode, traveling wave vibration is generated in the stator, and the rotor rotates. When the rotation of the rotor is stopped, the drive voltage applied to the A and B phase electrodes is immediately cut off.

However, if the drive voltage applied to the A and B phase electrodes is immediately cut off and the rotation of the rotor is stopped, the traveling wave vibration generated in the stator is eliminated at a stroke.
The rotor lifted by the vibration collides with the stator by the elastic force of the elastic member, and a collision sound is generated. Due to the generation of such a collision sound, there is a problem that the quietness of the ultrasonic motor is deteriorated.

[0004] A technique for solving such a problem is disclosed in Japanese Patent No. 2797670. According to the control method disclosed in this publication, when the rotation of the rotor is stopped, the frequency of the drive voltage is controlled so as to gradually increase from a predetermined frequency at the time of rotation. With this control, the traveling wave vibration generated in the stator is attenuated, and the rotation of the rotor is stopped while the rotor is in contact with the stator. In this way, since the generation of the collision sound is prevented, the quietness of the ultrasonic motor can be improved.

[0005]

However, the control method for gradually increasing the frequency of the drive voltage is complicated in its control.
That is, since the circuit configuration of the control circuit is complicated, the cost of the circuit increases.

In addition, since the control is complicated, it takes time to change the frequency. Therefore, when the motor is restarted immediately after the motor is stopped, the drive voltage is set to a predetermined value to rotate the motor at a predetermined rotation speed. It takes time to set the frequency. As a result, there was a problem that the response of the motor deteriorated.

[0007] In addition to the method of gradually increasing the frequency, a control method of gradually decreasing the voltage value of the drive voltage is also conceivable, but the same problem as described above occurs. The present invention has been made to solve the above problems, and an object of the present invention is to provide a control method of an ultrasonic motor capable of achieving high quietness with simple control and a control circuit thereof. It is in.

[0008]

According to a first aspect of the present invention, a two-phase high-frequency drive voltage is supplied to a piezoelectric element provided on a stator to solve the above problem. A method for controlling an ultrasonic motor that generates a traveling-wave vibration and rotates a rotor by the traveling-wave vibration.When stopping the rotation of the ultrasonic motor, the supply of one of the high-frequency driving voltages is stopped. The supply of the other high-frequency drive voltage is stopped.

According to a second aspect of the present invention, a two-phase high-frequency drive voltage is supplied to a piezoelectric element provided on the stator to generate a traveling-wave vibration in the stator. A method of controlling an ultrasonic motor to be rotated, wherein when stopping the rotation of the ultrasonic motor, alternately supplying a high-frequency drive voltage of each phase,
The supply of the high-frequency drive voltage for each phase is stopped.

[0010] The invention described in claim 3 is the invention according to claim 1 or 2.
In the control method of the ultrasonic motor described in (1), when the supply of one of the high-frequency driving voltages is stopped when the rotation of the ultrasonic motor is stopped, the generation of the driving voltage is stopped.

According to a fourth aspect of the present invention, a two-phase high-frequency drive voltage is supplied to a piezoelectric element provided on the stator to generate a traveling wave vibration in the stator, and the traveling wave vibration causes the rotor to rotate. The control circuit of the ultrasonic motor to rotate, when stopping the rotation of the ultrasonic motor, stop the supply of one high-frequency drive voltage, and then
A stop circuit for stopping the supply of the other high-frequency drive voltage is provided.

According to a fifth aspect of the present invention, a two-phase high-frequency drive voltage is supplied to a piezoelectric element provided on the stator to generate a traveling-wave vibration in the stator, and the traveling-wave vibration causes the rotor to rotate. The control circuit of the ultrasonic motor to rotate, when stopping the rotation of the ultrasonic motor, alternately supply a high-frequency drive voltage of each phase,
A control circuit for an ultrasonic motor, comprising: a stop circuit for stopping supply of a high-frequency drive voltage of each phase.

The invention according to claim 6 is the invention according to claim 4 or 5.
In the control circuit of the ultrasonic motor according to the, the high-frequency drive voltage is generated by a drive circuit, the stop circuit,
When stopping the supply of one of the high-frequency drive voltages when stopping the rotation of the ultrasonic motor, the drive circuit stops generating the drive voltage.

Therefore, according to the first and fourth aspects of the present invention, the progress of the traveling wave vibration is stopped when the supply of the one driving voltage is stopped, so that the rotation of the rotor is stopped. At this time, the rotor is in a state of being lifted by the vibration based on the other drive voltage. However, since the vibration based on the one drive voltage disappears, the lifting force of the rotor is weakened, and the lift height is reduced. Thereafter, when the vibration is eliminated by the stop of the supply of the driving voltage, the lifted rotor collides with the stator, but the collision noise generated at that time is suppressed to a low level. In addition, such stop control simply delays the timing at which the supply of the drive voltage is stopped, so that the control is simple.

According to the second and fifth aspects of the invention, the progress of the traveling wave vibration is stopped at the time when the driving voltages of the respective phases are alternately supplied, so that the rotation of the rotor is stopped. At this time, 1
Although the rotor is lifted by the vibration based on the drive voltage of only the phase, the force of lifting the rotor is reduced and the height of the lift is reduced by the disappearance of the vibration based on the one-phase drive voltage. Thereafter, when the vibration is eliminated by the stop of the supply of the driving voltage, the lifted rotor collides with the stator, but the collision noise generated at that time is suppressed to a low level. In addition, such a stop control simply stops the supply of the driving voltage alternately, so that the control is simple.

According to the third and sixth aspects of the present invention, when the supply of one drive voltage is stopped when the rotation of the ultrasonic motor is stopped, the generation of the drive voltage is stopped. Does not consume extra power for generation.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows an ultrasonic motor 1 and a control circuit 11 thereof. Ultrasonic motor 1
The stator 2 includes a piezoelectric element 3, and a rotatably supported rotor 4 is pressed against the stator 2 by the elastic force of an elastic member (not shown). The piezoelectric element 3 is formed in an annular shape as shown in FIG. The piezoelectric element 3 has A.
The B-phase electrodes 5a and 5b and the feedback electrode 5c are provided at predetermined positions in the rotation direction. Each of the electrodes 5a to 5c is connected to the control circuit 11.

The high-frequency drive voltage V having a 90 ° phase difference from the control circuit 11 is applied to the A and B phase electrodes 5a and 5b.
When A and VB are supplied, the piezoelectric element 3 vibrates. A traveling wave vibration is generated in the stator 2 based on this vibration, and the rotor 4 rotates in a direction opposite to a traveling direction of the traveling wave vibration. Also, due to the vibration of the piezoelectric element 3,
A detection voltage VC based on the vibration is output from the feedback electrode 5c to the control circuit 11.

The control circuit 11 includes a control signal generation circuit 12,
Drive voltage permission circuit 13 as drive circuit and drive circuit 1
4 is provided. The control signal generation circuit 12 receives the detection voltage VC from the feedback electrode 5c and, based on the detection voltage VC, controls the A / B phase electrodes 5a, 5a during rotation.
It is detected whether or not the high-frequency driving voltages VA and VB applied to 5b have a predetermined frequency close to the resonance point. Then, the control signal generation circuit 12 controls the control signal SA for generating the high-frequency drive voltages VA and VB of a predetermined frequency by the drive circuit 14.
, SB to the drive voltage permission circuit 13. The control signals SA and SB are pulse signals of a predetermined frequency having a phase difference of 90 ° from each other.

The drive voltage permission circuit 13 outputs the input control signals SA and SB to the drive circuit 14 at the subsequent stage during the period of rotation of the motor 1. Then, the drive circuit 14 generates high-frequency drive voltages VA and VB as shown in FIG. 3 which amplify the control signals SA and SB, and converts the drive voltages VA and VB to A · V.
It is supplied to the B-phase electrodes 5a and 5b.

On the other hand, when a stop command signal is input to the drive voltage permission circuit 13 to stop the rotation of the motor 1, the circuit 13 stops the generation of the high frequency drive voltage VB supplied to the B-phase electrode 5b. A drive stop signal STB is output to the drive circuit 14. As a result, the drive circuit 14 stops generating the high-frequency drive voltage VB. When a predetermined time t has elapsed from the input of the stop command signal, the circuit 14 outputs a drive stop signal STA to the drive circuit 14 to stop generating the high frequency drive voltage VA supplied to the A-phase electrode 5a. As a result, the drive circuit 14 stops generating the high-frequency drive voltage VA.

That is, as shown in FIG. 3, when a stop command signal is input to the drive voltage permission circuit 13, the drive circuit 14
Is the high-frequency drive voltage VB immediately supplied to the B-phase electrode 5b.
Is stopped, and the generation of the high-frequency driving voltage VA to be supplied to the A-phase electrode 5a is stopped after a predetermined time t has elapsed.

When the stop command signal is input to stop the rotation of the ultrasonic motor 1, the control circuit 11 configured as described above immediately stops generating the high-frequency drive voltage VB supplied to the B-phase electrode 5 b. . Then, only the vibration based on the drive voltage VA is generated in the stator 2, and the vibration based on the drive voltage VB disappears. That is, the traveling wave vibration generated in the stator 2 does not progress. Therefore, the rotation of the rotor 4 eventually stops due to the frictional force with the stator 2.

In this case, the rotor 4 has one drive voltage VA
Is raised from the position of the rotor 4 at the time of rotation stop due to vibration based on the driving voltage VB, but the lifting force becomes weaker as the vibration based on the driving voltage VB disappears. Accordingly, the height at which the rotor 4 is lifted by vibration is reduced.

When a predetermined time t has elapsed, the control circuit 11 sets the high-frequency drive voltage VA supplied to the A-phase electrode 5a.
Stop generating Then, the vibration based on the drive voltage VA disappears, and the rotor 4 lifted by the vibration collides with the stator 2. At this time, the rotor 4
Since the height at which the rotor 4 is lifted is low, collision noise generated when the rotor 4 collides with the stator 2 can be suppressed to a small level.

As described above, according to the present embodiment,
It has the following effects. (1) When stopping the rotation of the ultrasonic motor 1, the control circuit 11 stops the supply of one drive voltage VB and waits for a predetermined time t.
After the elapse, the operation is performed so as to stop the supply of the other drive voltage VA. In this way, after the predetermined time t has elapsed and the vibration has disappeared due to the stoppage of the supply of the drive voltage VA, the lifted rotor 4 collides with the stator 2, but since the lifted height is reduced, Collision noise generated in the vehicle can be kept low.

(2) The stop control of the control circuit 11 is a simple control in which the timing of stopping the supply of the drive voltage VA is delayed from the drive voltage VB. Therefore, the control circuit 11 can have a simple circuit configuration. As a result, the cost of the control circuit 11 can be reduced.

(3) The stop control of the control circuit 11 does not change the frequencies or voltage values of the drive voltages VA and VB. Therefore, when the motor 1 is restarted immediately after the motor 1 is stopped, the stop time is short. The rotation speed of the motor 1 can be set to a predetermined rotation speed. Therefore, the response of the motor 1 is not deteriorated.

(4) When the supply of one drive voltage VB is stopped when the rotation of the ultrasonic motor 1 is stopped, the generation of the drive voltage VB is stopped, so that no extra power is consumed. Therefore, the power consumption of the control circuit 11 can be reduced.

The embodiment of the present invention may be modified as follows. In the above embodiment, the stop of the supply of the drive voltage VA to the piezoelectric element 3 is delayed based on the stop command signal. However, the drive voltages VA and VB to the piezoelectric element 3 are alternately supplied. The supply of the voltages VA and VB may be stopped.

In this case, the driving voltages VA, VB
The rotation of the rotor 4 is stopped because the traveling wave oscillation stops at the point of alternate supply. At this time, the rotor 4 is lifted by the vibration based on the one-phase drive voltage VA (VB), but the one-phase drive voltage VA (VB)
), The force of lifting the rotor 4 becomes weaker, and the height of the lifting becomes lower.

Therefore, since it is the same as the above embodiment,
The collision sound when the lifted rotor 4 collides with the stator 2 can be suppressed low. Further, since such a stop control is a simple control, the circuit configuration of the control circuit is not complicated.

In the above embodiment, the drive voltage permission circuit 13 drives the drive stop signals STA and STA based on the stop command signal.
STB is output to the drive circuit 14 so that the drive circuit 14 does not generate the drive voltages VA and VB. However, the present invention is not limited to this. For example, the control signal generation circuit 12
May stop outputting the control signals SA and SB. Further, a circuit for interrupting the supply of the drive voltage VB from the circuit 14 to the piezoelectric element 3 based on the stop command signal is provided at a stage subsequent to the drive circuit 14.
In step 4, the generation of the driving voltages VA and VB may be stopped.

In the above embodiment, the supply of the driving voltage VB to the piezoelectric element 3 is immediately stopped based on the stop command signal, and the driving voltage V
Although the supply of A is stopped, the time may be changed depending on the situation.

[0035]

As described in detail above, according to the present invention,
It is possible to provide an ultrasonic motor control method and a control circuit thereof that can achieve high quietness with simple control.

[Brief description of the drawings]

FIG. 1 is a block diagram of an ultrasonic motor and a control circuit according to the present embodiment.

FIG. 2 is a plan view illustrating a configuration of a piezoelectric element.

FIG. 3 is a waveform chart showing control of a control circuit.

[Explanation of symbols]

2 ... stator, 3 ... piezoelectric element, 4 ... rotor, 13 ... drive voltage permission circuit as stop circuit, 14 ... drive circuit, VA
, VB ... high frequency drive voltage.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H680 AA08 AA09 AA18 BB03 BB16 CC02 CC07 DD01 DD15 DD23 DD35 DD53 DD66 DD72 DD87 EE24 FF25 FF30 FF33

Claims (6)

[Claims] 1. A piezoelectric element provided on a stator,
A method for controlling an ultrasonic motor that generates a traveling-wave vibration in the stator by supplying a two-phase high-frequency driving voltage and rotates the rotor by the traveling-wave vibration, wherein the rotation of the ultrasonic motor is stopped. In this case, the supply of one high-frequency drive voltage is stopped, and then the supply of the other high-frequency drive voltage is stopped. 2. A piezoelectric element provided on a stator,
A method for controlling an ultrasonic motor that generates a traveling-wave vibration in the stator by supplying a two-phase high-frequency driving voltage and rotates the rotor by the traveling-wave vibration, wherein the rotation of the ultrasonic motor is stopped. In this case, a high-frequency driving voltage of each phase is alternately supplied, and then the supply of the high-frequency driving voltage of each phase is stopped. 3. The method of controlling an ultrasonic motor according to claim 1, wherein when the supply of one of the high-frequency driving voltages is stopped when the rotation of the ultrasonic motor is stopped, the generation of the driving voltage is performed. A method for controlling an ultrasonic motor, wherein the method is performed by stopping. 4. A piezoelectric element provided on a stator,
A control circuit for an ultrasonic motor that generates a traveling-wave vibration in the stator by supplying a two-phase high-frequency driving voltage, and rotates the rotor by the traveling-wave vibration, and stops the rotation of the ultrasonic motor. A control circuit for the ultrasonic motor, comprising: a stop circuit for stopping the supply of one high-frequency drive voltage and thereafter stopping the supply of the other high-frequency drive voltage. 5. A piezoelectric element provided on a stator,
A control circuit for an ultrasonic motor that generates a traveling-wave vibration in the stator by supplying a two-phase high-frequency driving voltage, and rotates the rotor by the traveling-wave vibration, and stops the rotation of the ultrasonic motor. A control circuit for an ultrasonic motor, comprising: a stop circuit for alternately supplying a high-frequency drive voltage for each phase and thereafter stopping the supply of the high-frequency drive voltage for each phase. 6. The control circuit for an ultrasonic motor according to claim 4, wherein the high-frequency drive voltage is generated by a drive circuit, and wherein the stop circuit stops the rotation of the ultrasonic motor. A control circuit for an ultrasonic motor, wherein when the supply of one of the high-frequency drive voltages is stopped, the drive circuit stops generating the drive voltage.