JPH09285154A - Vibration actuator drive device and vibration actuator drive method - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To stably drive a vibration actuator even if the environmental temperature changes. A vibration actuator 100 having a vibrator that vibrates by an electromechanical conversion element and a relative motion member that makes pressure contact with the vibrator to perform relative motion with the vibrator.
In the driving device, the temperature detection unit (4) that detects the temperature of the environment that drives the vibration actuator 100, and the power control unit that controls the power supplied to the electromechanical conversion element based on the temperature detected by the temperature detection unit. (4, 5, 6 etc.)
With.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration actuator having a vibrator that vibrates by an electromechanical conversion element and a relative motion member that makes pressure contact with the vibrator and performs relative motion with the vibrator. The present invention relates to a driving device and a driving method of a vibration actuator.

[0002]

2. Description of the Related Art A vibration actuator is an elastic body which is brought into pressure contact with an electromechanical conversion element by supplying an electric signal to the electromechanical energy conversion element (hereinafter referred to as "electromechanical conversion element") such as a piezoelectric body. A vibration is generated in the, and the moving body is frictionally driven by the vibration. Conventionally, as a vibration actuator, (1) an annular ultrasonic traveling wave motor, (2) a linear ultrasonic motor using a traveling wave, and (3) a traveling wave is generated in a cylindrical elastic body. An ultrasonic motor of a type that drives a moving element, (4) a rod-type vibration wave motor that generates a standing wave in a cylindrical elastic body and drives the moving element by the standing wave, and the like are known.

FIG. 4 is a sectional view showing an example of an annular ultrasonic motor which is one of conventional vibration actuators.
The elastic body 101 has a support portion on a flange extending to the outer peripheral side, and this support portion is fixed to a predetermined member (not shown). A piezoelectric body 102, which is a type of electromechanical conversion element, is fixed to the lower side of the elastic body 101. The piezoelectric body 102 has two electrode groups (not shown) formed by assembling segment electrodes. The segment electrodes are alternately polarized in opposite directions, and each electrode group is arranged so as to have a phase difference of π / 2.

The moving body 103 comprises a rotor 105 and a sliding member 104 fixed to the rotor 105. The moving body 103 is brought into pressure contact with the elastic body 101 by a pressing means (not shown). The elastic body 101,
The piezoelectric body 102 and the moving body 103 (the rotor 105 and the sliding member 104) form a vibration actuator 100.

When a driving AC signal having a phase difference of π / 2 is applied to each electrode group of the piezoelectric body 102, the elastic body 101
Is excited by the vibration of the piezoelectric body 102, and the elastic body 102
A traveling wave is generated. Due to this traveling wave, the elastic body 102
The moving body 103 that is brought into pressure contact with is frictionally driven.

FIG. 5 is an external view showing an example of a conventional rod-type vibration actuator having a cylindrical shape.
Between the elastic bodies 110 and 111, the piezoelectric bodies 112 and 1
13 is sandwiched. Also, the elastic bodies 110 and 111
And are mechanically coupled with the piezoelectric body 112 interposed therebetween.
The piezoelectric bodies 112 and 113 are types of electromechanical conversion elements for generating longitudinal vibration and torsional vibration, respectively. The mover is composed of an elastic body 110, a rotor 114, and a sliding member 115, and the rotor 114 and the elastic body 111 are in pressure contact with each other. Piezoelectric bodies 112 and 1
By giving a driving AC signal having a phase difference to each other, an oscillating wave is generated on the surface in contact with the moving element, and the moving element is frictionally driven.

Description of other vibration actuators will be omitted. However, in any type of vibration actuator,
The moving element or the load is frictionally driven by the vibration generated in the elastic body. These vibration actuators use an elastic body as a resonance vibration state due to the vibration of the electromechanical conversion element. Therefore, the amplitude of vibration of the elastic body can be changed by changing the frequency of the driving AC signal. The drive speed of the vibration actuator is set by changing the amplitude of this vibration.

[0008]

However, the above-mentioned conventional vibration actuator has the following problems. FIG.
[Fig. 4] is a graph showing an example of characteristics of a vibration actuator at room temperature (25 ° C). In FIG. 6, in the normally used resonance frequency band, the drive speed of the vibration actuator can be set by changing the frequency of the drive AC signal. Then, if the frequency is high, the driving speed becomes slow, and if the frequency is low, the driving speed becomes fast. As the frequency is lowered, the vibration actuator reaches the very vicinity of the resonance frequency of the vibration actuator, and the driving becomes unstable at this position. When the frequency is further lowered, the driving speed becomes slower and eventually stops. The magnitude of the drive AC signal is set so that the drive efficiency of the vibration actuator is good.

With the characteristics shown in FIG. 6, the vibration actuator can be driven from an extremely low speed. However, when the environment for driving the vibration actuator becomes low in temperature, the characteristics change greatly. Figure 7 shows low temperature (-20 ° C)
6 is a graph showing a first example of characteristics of the vibration actuator in FIG. In the case of having the characteristics shown in FIG. 7, the frequency of the drive AC signal is started from the high frequency side (at low speed) to start the vibration actuator, and the frequency of the drive AC signal is changed in the direction of the arrow in the figure (to the low frequency side). , If the drive speed is increased, the drive suddenly stops at the frequency f1.

FIG. 8 is a graph showing a second example of the characteristic of the vibration actuator at low temperature (−20 ° C.). In the case of having the characteristics shown in FIG. 8, when the frequency of the drive AC signal is changed to the high frequency side in order to slow the drive speed of the vibration actuator that was driven at the frequency f0 of the drive AC signal, the frequency f2 Suddenly stops at.

Furthermore, FIG. 9 is a graph showing a third example of the characteristic of the vibration actuator at a low temperature (−20 ° C.). In the case of having the characteristics shown in FIG. 9, when the frequency of the driving AC signal is changed from the high frequency side to the low frequency side in order to change the driving speed from the low speed to the high speed, the frequency does not start up to the frequency f3 and the frequency changes. When it reaches f3, it starts suddenly. And when the frequency is changed to the low frequency side,
The drive becomes unstable at the frequency f4 and suddenly stops. This occurs when it becomes very close to the resonance frequency of the vibration actuator, and it occurs at a frequency different from that at room temperature.

In the above FIGS. 7 to 9, low temperature (-20 ° C.)
An example of the characteristics of the vibration actuator in
Even in an environment at a high temperature (60 ° C.), similar characteristics, in particular, characteristics as shown in FIG. 9 may change. The cause of the change in the characteristic of the vibration actuator due to the change in the ambient temperature is deformation due to the difference in expansion coefficient between the elastic body and the piezoelectric body, the change in the characteristic of the piezoelectric body, and the adhesion for fixing the elastic body and the piezoelectric body. Changes in the physical properties of the agent, changes in the coefficient of friction between the sliding material and the elastic body, changes in the physical properties of the sliding material, changes in the frictional characteristics, etc. are considered to be caused by these factors being intertwined. . 1 without forming a mover from the rotor and sliding material
The same problem occurs when the mover is formed from two materials.

When such a phenomenon occurs, there is a problem in that the vibration actuator cannot be started normally, or suddenly stops while the driving speed is being controlled, so that normal driving cannot be performed. There is also a problem that the target drive speed cannot be obtained. Especially, the drive speed of the vibration actuator is detected by an encoder,
When the frequency of the drive AC signal of the vibration actuator is feedback-controlled by comparing with the target drive speed, there is a problem that the relationship between the frequency, which is a control parameter, and the drive speed becomes discontinuous. The above phenomenon occurs in any of the circular, cylindrical, and linear vibration actuators. Further, depending on the material used and the like, there are cases where the degree of change is different from the above-mentioned change, but since it is a phenomenon that changes with temperature, it can be considered in the same way.

An object of the present invention is to make it possible to stably drive a vibration actuator even if the environmental temperature changes.

[0015]

According to a first aspect of the present invention, there is provided a vibrator which vibrates by an electromechanical conversion element, and a relative motion member which makes pressure contact with the vibrator and performs relative motion with the vibrator. In a drive device for a vibration actuator, the temperature detection part (4-1) for detecting the temperature of the environment for driving the vibration actuator, and the temperature detection part supplies the electromechanical conversion element based on the temperature detected by the temperature detection part. And a power control unit (4-2, 5, 6, etc.) for controlling the power to be used.

According to a second aspect of the present invention, in the drive device for the vibration actuator according to the first aspect, a drive speed detecting section for detecting a drive speed of the vibration actuator, and a speed and a target detected by the drive speed detecting section. And a frequency control unit for performing feedback control of the frequency of the electric signal supplied to the electromechanical conversion element by comparing with the driving speed.

According to a third aspect of the present invention, the driving of the vibration actuator includes a vibrator that vibrates by the electromechanical conversion element, and a relative motion member that makes pressure contact with the vibrator and performs relative motion with the vibrator. In the method, the temperature of the environment for driving the vibration actuator is detected, and the electric power supplied to the electromechanical conversion element is controlled based on the detected temperature.

[0018]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. First, in the present invention, it has been found that in a low temperature environment, the vibration actuator can be driven without causing the above-mentioned problems by setting the voltage value of the driving AC signal higher than that at room temperature. Further, it has been found that even under a high temperature environment, the vibration actuator can be driven by controlling the voltage value of the driving AC signal without the above-mentioned problems. Further, in the relationship between the voltage value of the driving AC signal and the driving efficiency of the vibration actuator, it was also found that when the same output is obtained, the higher the voltage value, the higher the efficiency.

Therefore, if the voltage value is constantly increased under any circumstances, the vibration actuator may be driven in a state where the driving efficiency is poor. By the way, the voltage value of the driving AC signal in each of FIGS. 6 to 9 is 30 (VRMS). FIG. 10 shows a low temperature (−20
It is a graph which shows an example of a characteristic when the voltage of a drive AC signal is 40 (VRMS) at (° C). As shown in FIG. 10, when the voltage value is 40 (VRMS), the above-mentioned problem does not occur. This is because by applying a high voltage to the piezoelectric body, the vibration generated in the elastic body becomes large and the driving force is enhanced. Then, changes in the characteristics under low temperature environment such as changes in the friction coefficient between the elastic body and the sliding material, deformation due to temperature changes in the elastic body and the sliding material, and changes in characteristics due to the temperature of the piezoelectric element are compensated for. is there.

FIG. 11 is a graph showing the relationship between the environmental temperature of the vibration actuator and the drive voltage at which the above-mentioned problems do not occur. Here, these relationships differ depending on the shape, material, manufacturing method, and the like of the vibration actuator. Therefore, the present invention controls the electric power of the drive AC signal input to the vibration actuator according to the environmental temperature for driving the vibration actuator.

FIG. 1 is a block diagram showing a first embodiment of a drive device for a vibration actuator according to the present invention.
The vibration actuator in the present embodiment is exemplified by the vibration actuator 100 (FIG. 4) shown in the conventional example. The speed setting means 1 is a means for outputting a voltage for setting the output frequency of the voltage controlled oscillator 2. The output voltage of the speed setting means 1 can be set arbitrarily, and its output is input to the voltage controlled oscillator (VCO) 2. The voltage control oscillator 2 changes the frequency of the output signal according to the input voltage. The output signal of the voltage control oscillator 2 is a rectangular wave signal, and its frequency is the vibration actuator 1.
The frequency is set to be n times the frequency of the drive AC signal for driving 00.

The output of the voltage control oscillator 2 is the frequency divider / phaser 3
Is input to, and its frequency becomes 1 / n, and is converted into two sine wave signals having a phase difference of π / 2 with each other. The frequency of this signal is the same as the frequency of the drive AC signal for driving the vibration actuator 100. The output signal of the frequency divider / phaser 3 is input to the power amplifiers 5 and 6. The power amplifiers 5 and 6 are supplied with power from the power supply 7,
The vibration is amplified so that the driving AC signal is necessary for driving the vibration actuator 100.
As shown in FIG. 2, the power amplifier 5 includes a voltage controlled amplifier (VCM) 5-1 and a power amplifier 5-2 (the same applies to the power amplifier 6). As a result, the power amplifier 5
Will be determined by the amplification factor of the voltage control amplifier 5-1 and the amplification factor of the power amplifier 5-2.
Therefore, by changing the amplification factor of the voltage controlled amplifier 5-1, it is possible to control the drive AC signal applied to the vibration actuator 100.

The amplification factor of the voltage control amplifier 5-1 is determined by the output voltage of the AC signal control means 4. As shown in FIG. 2, the AC signal control means 4 includes a temperature detecting element 4-1.
And an amplification / correction circuit 4-2. Temperature detection element 4
-1 is based on a conventionally known semiconductor temperature detector, thermistor, thermocouple, etc., which is installed in an environment using a vibration actuator and detects the environmental temperature. The amplification / correction circuit 4-2 includes a voltage control amplifier 5-1.
In order to control the temperature of the temperature detecting element 4-1, the output of the temperature detecting element 4-1 is amplified to a required voltage, and the temperature detected by the temperature detecting element 4-1 is converted into a necessary driving AC signal. The output characteristic of is corrected.

As this method, for example, the following configuration may be adopted. First, the output of the temperature detection element 4-1 is used as it is, or is amplified and A / D converted and taken into a microprocessor to determine the temperature. Next, the amplification factor of the voltage controlled amplifier 5-1 required to obtain the driving AC signal required in that environment is obtained from experimental data given in advance. Then, the correction data is output via the D / A converter so that the value corresponding to it is given to the voltage controlled amplifier 5-1. Here, since the required value of the drive AC signal differs depending on the type of the vibration actuator and the like, it is necessary to make a correction suitable for the vibration actuator. In the case where the amplification factor of the voltage control amplifier 5-1 may be linearly changed by the temperature change, it may be configured to simply amplify and output. With the above-described configuration, the vibration actuator 10
Even if the environmental temperature for driving 0 is changed, stable driving can always be performed.

FIG. 3 is a block diagram showing a second embodiment of the drive device for the vibration actuator according to the present invention.
In the first embodiment, a sine wave is given as a drive AC signal for the vibration actuator 100, but in the second embodiment, a pulse waveform or a pseudo sine wave waveform is given as a drive AC signal. Here, in order to make the pulse waveform into a pseudo-sinusoidal waveform, the pulse waveform is made to resonate with the self-capacitance of the piezoelectric body via the inductance.

In the second embodiment, the output signal of the frequency division phase shifter 3 is a rectangular wave. The power amplifier 5 is a signal that requires the output signal of the frequency division phase shifter 3 for switching the output switching elements (MOS-FETs) 5-11 and 5-12 and the output switching elements 5-11 and 5-12. A level conversion circuit 5-13 for converting the level. The power amplifier 5 amplifies the signal to the power supply voltage level supplied from the power supply 7. The amplified signal is supplied to the vibration actuator 100 via the inductance 5-14. The power amplifier 6 is also similar to the power amplifier 5.
The other configuration is the same as that of the first embodiment, and the description is omitted.

In the second embodiment, the output voltage of the power supply 7 may be controlled using the output of the AC signal control means 4 as shown in FIG. In this case, the power supply 7 is a conventionally known variable output power supply. When the output voltage of the power supply 7 increases, the value of the driving AC signal increases, and when the output voltage of the power supply 7 decreases, the value of the driving AC voltage decreases. Therefore, the drive AC signal can be controlled by the AC signal control means 4 as in the first embodiment.

As described above, one embodiment of the present invention has been described. However, the present invention is not limited to the above-described embodiment, and the following various modifications are possible within an equivalent range. For example, in the second embodiment, a duty ratio control circuit for controlling the on / off duty ratio of the output switching elements 5-11 and 5-12 is provided, and the duty ratio control circuit is controlled by the output of the AC signal control means 4. May be.
Further, in the present embodiment, the voltage value of the drive AC signal is controlled, but the same effect can be obtained by controlling the current value.

[0029]

According to the present invention, the vibration actuator can be driven stably and efficiently even if the environmental temperature changes.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of a drive device for a vibration actuator according to the present invention.

FIG. 2 is a block diagram showing a detailed configuration of an AC signal control means 4 and a power amplifier 5 of FIG.

FIG. 3 is a block diagram showing a second embodiment of a drive device for a vibration actuator according to the present invention.

FIG. 4 is a cross-sectional view showing an example of an annular ultrasonic motor that is one of conventional vibration actuators.

FIG. 5 is an external view showing an example of a conventional rod-type vibration actuator having a cylindrical shape.

FIG. 6 is a graph showing an example of characteristics of the vibration actuator at room temperature (25 ° C.).

FIG. 7 is a graph showing a first example of characteristics of the vibration actuator at low temperature (−20 ° C.).

FIG. 8 is a graph showing a second example of characteristics of the vibration actuator at low temperature (−20 ° C.).

FIG. 9 is a graph showing a third example of characteristics of the vibration actuator at low temperature (−20 ° C.).

FIG. 10 is a graph showing an example of characteristics when the voltage of the driving AC signal is 40 (VRMS) at low temperature (−20 ° C.).

FIG. 11 is a graph showing the relationship between the environmental temperature of the vibration actuator and the drive voltage at which no problem occurs.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Speed setting means 2 Voltage control oscillator 3 Dividing phase device 4 AC signal control means 4-1 Temperature detection element 4-2 Amplification / correction circuit 5 Power amplifier 5-1 Voltage control amplifier 5-2 Power amplifier 6 Power amplifier 7 Power supply 100 Vibration actuator

Claims (3)

[Claims] 1. A drive device for a vibration actuator, comprising: a vibrator vibrated by an electromechanical conversion element; and a vibration actuator having a relative motion member that makes pressure contact with the vibrator to perform relative motion with the vibrator. It is characterized by comprising a temperature detection unit that detects the temperature of the environment that drives the actuator, and a power control unit that controls the power supplied to the electromechanical conversion element based on the temperature detected by the temperature detection unit. Vibration actuator drive device. 2. The drive apparatus for the vibration actuator according to claim 1, wherein a drive speed detection unit that detects a drive speed of the vibration actuator is compared with a speed detected by the drive speed detection unit and a target drive speed. And a frequency control unit that feedback-controls the frequency of the electric signal supplied to the electromechanical conversion element. 3. A method for driving a vibration actuator, comprising: a vibrator vibrated by an electromechanical conversion element; and a vibration actuator having a relative motion member that makes pressure contact with the vibrator to perform relative motion with the vibrator. A method for driving a vibration actuator, comprising detecting a temperature of an environment for driving the actuator and controlling electric power supplied to the electromechanical conversion element based on the detected temperature.