JP2000316286A - Piezoelectric actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To change the drive frequency quickly in response to the change of a resonance frequency. SOLUTION: A piezoelectric actuator has a displacement mechanism unit 103 which has a free end, a drive piezoelectric device 104 and a sensing piezoelectric device 108 which are bonded to one of the surfaces of the displacement mechanism unit 103 and whose other surface are brought into contact with a moving unit 102. Further, the piezoelectric actuator has a superposing means which superposes an AC voltage with a further lower frequency upon an AC voltage supplied to the drive piezoelectric device 104 bonded to the displacement mechanism unit 103 or a voltage detected by the sensing piezoelectric device 108. Directions of the deviation of the present frequency of a drive AC voltage and an actual resonance frequency can be simultaneously detected, so that the drive frequency can follow the resonance frequency immediately.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a piezoelectric actuator using a piezoelectric element.

[0002]

2. Description of the Related Art An ultrasonic motor is a typical actuator using a piezoelectric element.

In a conventional ultrasonic motor, there is known a structure in which a vibrating body is constituted by a piezoelectric element made of piezoelectric ceramics and an elastic body such as a metal, and a moving body is pressed against the surface of the vibrating body. As the vibrating body, for example, a ring-type ultrasonic motor that forms a vibrating body by bonding a driving piezoelectric element to one surface of a ring-shaped metal body, or for example, driving a piezoelectric element on one surface of a disk-shaped metal body Disk-type ultrasonic motors and the like that form a vibrating body by bonding a piezoelectric element are known, and many applications and practical applications have been made as actuator devices that replace conventional electromagnetic motors.

[0004] These conventional ultrasonic motors are 1) low-speed and high-torque, 2) simple in structure, 3) large in holding torque, and 4) non-magnetic material compared to conventional electromagnetic motors.
5) It has characteristics such as excellent responsiveness.

The principle of operation of a conventional ultrasonic motor is that vibration is propagated to a vibrating body by controlling the amplitude of a piezoelectric element material that is bonded to one surface of a metal vibrating body and is polarized for driving, and an applied electric field is applied. From the phase difference to the moving body as a traveling wave. The moving body is frictionally driven and moves by the traveling wave. This traveling wave is generated by converting the vertical vibration of the vibrating body into a horizontal vibration depending on the thickness, and creating an elliptical motion in the vibrating body. When the moving body is placed in pressure contact with the vibrating body, the lateral movement of the surface of the vibrating body is transmitted to the moving body by frictional force. Since the amplitude value of this vertical vibration is extremely small, about several microns, drive at a frequency that maximizes the amplitude, and contact the vibrating body and moving body in that state to extract the mechanical output However, it has been important in a conventional piezoelectric actuator such as an ultrasonic motor.

[0006]

However, in a conventional piezoelectric actuator such as an ultrasonic motor, the impedance seen from the drive terminal is capacitive, and the drive frequency is limited to a specific narrow range. Therefore, an automatic frequency tracking circuit or the like for tracking a resonance frequency that changes delicately depending on the surrounding temperature or the moving state of the moving object is required.

This automatic frequency tracking circuit changes the drive frequency with respect to the change in the resonance frequency so as to keep the relationship between the resonance frequency and the drive frequency of the vibrating body which changes under the influence of the load, temperature and the like constant. In order to achieve this function, it is necessary to detect the output voltage value of the sensor electrode formed on the piezoelectric element together with the drive electrode.

However, in order to track the resonance frequency,
Although it is necessary to track the maximum value of the output voltage value of the sensor power, even if the drive frequency shifts from the resonance frequency to the high frequency side or to the low frequency side, the sensor power similarly decreases,
Whether the frequency should be controlled to the high frequency side or the low frequency side cannot be determined by one sensing, and there is a disadvantage that it takes time for tracking.

[0009]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above, and an object of the present invention is to provide a piezoelectric actuator capable of rapidly changing a driving frequency with respect to a change in a resonance frequency. Aim.

In order to achieve the above object, a piezoelectric actuator according to the present invention has a free end, and a driving and sensing piezoelectric element is attached to one surface and a moving body contacts the other surface. A driving circuit including a superimposing means for superimposing an AC voltage having a lower frequency on an AC voltage supplied to a driving piezoelectric element attached to the displacement mechanism, in the piezoelectric actuator having the displacement mechanism. It is characterized by having.

Alternatively, in order to achieve the above object, a piezoelectric actuator according to the present invention has a free end, and a driving and sensing piezoelectric element is attached to one surface and a moving body is attached to the other surface. A piezoelectric actuator having a displacement mechanism, wherein an AC voltage having a lower frequency than an AC voltage supplied to a driving piezoelectric element attached to the displacement mechanism is attached to the displacement mechanism. Or a low-frequency AC generating means for supplying to the provided piezoelectric element for sensing, or superimposing a low-frequency AC voltage on a voltage generated by the piezoelectric element for sensing attached to the displacement mechanism. It is characterized by having a sensing circuit including a circuit.

Further, the piezoelectric actuator of the present invention is characterized in that it has a sensing circuit for sensing the amplitude or phase of the voltage generated by the sensing piezoelectric element.

Further, in the piezoelectric actuator of the present invention, the driving piezoelectric element and the sensing piezoelectric element are the same, and switching means for selectively connecting the driving circuit and the sensing circuit to the piezoelectric element is provided. It is characterized by.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. The present invention is not limited by the embodiment. (Embodiment 1) FIG. 1 is a schematic view showing one embodiment of a piezoelectric actuator according to the present invention. FIG. 2 is a view for explaining the operation of the displacement mechanism of FIG. 1, and FIG. FIG. 4 is an explanatory view for explaining the vibration of the piezoelectric element for displacing the displacement mechanism shown in FIGS. 1 and 2, FIG. 4 is a configuration diagram showing the configuration of the drive circuit and the sensing circuit in the present invention, and FIG. FIG. 9 and FIG. 10 are explanatory diagrams for explaining the relationship between the voltage supplied to the piezoelectric element and the detection state of the sensing piezoelectric element. FIGS. 9 and 10 are configuration diagrams showing other examples of the configuration of the drive circuit and the sensing circuit in the present invention. is there.

In FIG. 1, reference numeral 101 denotes a drive block, and a drive mechanism 101 having a free end formed by a U-shaped hole 106 is formed in the drive block 101. The driving piezoelectric element 104 and the sensing piezoelectric element 108 are attached to the displacement mechanism 103, and the driving piezoelectric element 1
An electrode 105 is provided on the surface opposite to the surface on which the piezoelectric element 104 is attached. The electrode 105 is connected to the drive circuit 111 through an electric wire or the like. And is connected to the sensing circuit 112 through an electric wire or the like. Drive block 10
No. 1 driving piezoelectric element 104 and sensing piezoelectric element 10
The moving body 102 is installed on the surface opposite to the surface on which the moving body 8 is attached, and the driving block 101 and the moving body 102
02 is in pressure contact with its own weight or spring force.
The drive block 101 is grounded through a contact 107. The drive circuit 111 and the sensing circuit 112 are connected to a control circuit 113, and the control circuit 113 is grounded through a contact 114.

In FIG. 1 and FIG.
In FIG. 1, the displacement mechanism 103 is formed to have a free end by a U-shaped hole 106. Although a stainless steel material is used for the drive block in the present embodiment, beryllium steel, phosphor bronze, brass, duralumin, titanium, silicon material, or the like may be used. A drive piezoelectric element 104 made of a PZT (lead zirconate titanate) thin film is attached to one surface of the displacement mechanism, and when an AC voltage is applied to the drive piezoelectric element 104, the drive piezoelectric element 104 is attached.
Generates a stretching force, but the displacement mechanism 10
Since 3 has a free end, this stretching force appears as a bending force including the driving piezoelectric element 104 and the displacement mechanism 103. The displacement of the displacement mechanism 103 caused by the bending force acts on the moving body 102. Although PZT is used for the piezoelectric element in the present embodiment, barium titanate, lithium niobate, lead zircon titanate, or the like may be used instead.

FIG. 3 shows the vibration behavior of the displacement mechanism 103 from the side connected to the drive block 101 to the free end when an AC voltage is applied. The left end to the right end of the horizontal axis is the effective length from the side of the displacement mechanism 103 connected to the drive block 101 to the free end. The vertical axis represents the vibration amplitude of the displacement mechanism 103. The positive and negative signs shown on the vertical axis indicate the phases of the input AC voltage and the vibration of the displacement mechanism, and when the phase of the free end is positive, a phase different by 2π is shown as negative for convenience.
When the vibration amplitude is 0, it indicates that the vibration is not excited. The displacement mechanism 103 generates a vibration in which a minute displacement and a force are mixed depending on the application condition of the input AC voltage, and excites the longitudinal vibration and the elliptical motion. Displacement mechanism 10
At the free end of 3, the absolute value of the vibration amplitude is maximum,
Motion is transmitted from the displacement mechanism 103 to the moving body 102. The moving direction of the moving body 102 is determined by the lateral component of the elliptical motion in FIG.

1 and 2, the displacement mechanism 10
3, a sensing piezoelectric element 108 is attached alongside the driving piezoelectric element 104. When the displacement mechanism 103 performs a bending motion, the bending motion generates a stress on the sensing piezoelectric element 108, and thus the sensing piezoelectric element 108 generates a voltage. Piezoelectric element for sensing 108
As the driving piezoelectric element 104, PZT, barium titanate, lithium niobate, lead zircon titanate, or the like can be used.

FIG. 4 shows the configuration of the driving circuit 111, sensing circuit 112, and control circuit 113 in FIG. 1 in more detail. In the drive circuit 111, an AC generation means 603 such as a VCO and a modulation frequency generation means 604 are controlled by a drive control means 605, and the signals generated by each become a signal superimposed by the superimposition means 602. The superimposed signal output is amplified by the amplification means 601 and output from the output terminal 6.
It is output from 10. The sensing circuit 112 amplifies the signal input from the input terminal 611 by the amplifier 606 and inputs the amplified signal to the detector 607. The output of the detection means 607 and the control signal of the drive control means 605
O means 608, and is connected to arithmetic means 6 such as a CPU.
09 can be controlled.

FIG. 5 shows an output signal of the drive circuit 111 and a detection waveform of the sensing circuit 112 in FIG. FIG. 5A is a diagram showing the modulation of the frequency of the AC voltage for causing the driving piezoelectric element 104 to vibrate near the resonance point by a change in the frequency with respect to the reference frequency. As described above, the signal having the frequency near the resonance point generated by the AC generator 603 and the signal having the lower frequency generated by the modulation frequency generator 604 are superimposed by the superimposing unit 602 to form a signal waveform. The actual driving voltage amplified by the means 601 has a waveform as shown in FIG. 5B and is input to the driving piezoelectric element 104. The driving piezoelectric element 104 causes the displacement mechanism 103 to vibrate according to the input waveform 702. However, since the input waveform 702 is modulated at a low frequency near the resonance frequency, the vibration of the displacement mechanism 103 causes resonance. When the frequency is near the point, the frequency increases, and when the frequency deviates, the vibration decreases. This vibration state can be detected by the sensing piezoelectric element 108,
FIG. 5C shows an example of the detected amplitude. Displacement mechanism 10
When 3 is vibrating greatly near the resonance point, the amplitude detected by the sensing piezoelectric element 108 becomes large as indicated by 705, but when it deviates from the resonance point, the amplitude detected by the sensing piezoelectric element 108 is increased. Becomes smaller. This allows the control circuit 113 to immediately know the frequency near the resonance point and whether the current driving frequency is shifted to a higher frequency or a lower frequency.
The resonance point can always be followed. In addition, in order to perform detection with higher accuracy, it is possible to gradually reduce the change in frequency shown in FIG. FIG.
FIG. 5C shows an example in which the amplitude of the voltage generated by the sensing piezoelectric element 108 is detected. However, as shown in FIG. It is also possible to detect how far the phase of the AC voltage supplied to the piezoelectric element 104 advances and follow the resonance point. Since the phase of the AC voltage detected by the sensing piezoelectric element 108 changes rapidly in the vicinity of the resonance point, the peak of the resonance point can be detected more clearly by detecting the phase. The resonance frequency is determined by the characteristics of the driving piezoelectric element 104,
In addition, it slightly changes depending on the state of attachment with the displacement mechanism 103, the state of contact with the moving body 102, the environmental temperature, and the like. However, according to the present embodiment, the output of the sensing piezoelectric element 108 can be detected by modulating the AC voltage input to the driving piezoelectric element 104 in a timely manner during driving, so that the amplitude always has a peak value. Control circuit 113
, The frequency of the AC voltage output by the drive circuit 111 can be changed, and the relationship between the AC voltage to be driven and the resonance frequency can be kept constant. Further, according to the present invention, since the direction of the deviation between the current frequency of the driving AC voltage and the actual resonance frequency can be detected simultaneously, it is possible to immediately follow the resonance frequency.

As apparent from the above description, the superposing means 602 superimposes a signal having a lower frequency on the AC voltage for vibrating the driving piezoelectric element 104 near the resonance point, thereby obtaining the sensing piezoelectric element. In element 108,
Since the amount and direction of the deviation between the current driving AC voltage frequency and the actual resonance frequency can be detected simultaneously, it is possible to immediately follow the resonance frequency.

Up to this point, an example has been described in which a modulation frequency is applied to the driving piezoelectric element 104 as shown in FIG. 4 as a configuration of the driving circuit 111, the sensing circuit 112, and the control circuit 113. FIG. 9 or FIG.
As shown in the configuration diagram of FIG.
8, or added to the sensing circuit 112.

In FIG. 9, the drive circuit 111 controls the AC generation means 803 such as a VCO by the drive control means 805, and the generated signal output is amplified by the amplification means 801 and output from the output terminal 810. Sensing circuit 112
Amplifies the signal input from the input terminal 811
The signal is amplified at 6 and input to the detection means 807, but the AC generated by the low-frequency AC generation means 804 controlled by the control circuit 113 is also applied to the input terminal 811. This enables detection similar to that described with reference to FIG.

In FIG. 10, the drive circuit 111 controls the AC generation means 903 such as a VCO by the drive control means 905, and the generated signal output is amplified by the amplification means 901 and output from the output terminal 910. Sensing circuit 11
2 amplifies the signal input from the input terminal 911
At step 06, the signal is amplified and inputted to the detecting means 907. Meanwhile, the AC generated by the low-frequency AC generating means 904 controlled by the control circuit 113 is superimposed by the superimposing means 902. Thus, even in this configuration, FIG.
The same detection as that described above can be performed.

As described above, the low-frequency AC generating means 80 for supplying the AC voltage having a lower frequency than the AC voltage supplied to the driving piezoelectric element 104 to the sensing piezoelectric element 108.
4 or by having the sensing circuit 112 including a superimposing circuit 902 that superimposes a low frequency AC voltage on the voltage generated by the sensing piezoelectric element 108, the current driving AC voltage frequency and actual Since the amount and direction of the deviation from the resonance frequency can be detected simultaneously,
It is possible to immediately follow the resonance frequency.

In the description of the present embodiment, the case where the moving body 102 is moved by the single displacement mechanism 103 has been described. However, even if there are a plurality of displacement mechanisms, the effect of the present invention is exactly the same. The effect of the present invention is the same even when the plurality of displacement mechanisms are arranged in different directions.

In this embodiment, the driving circuit 1
11. Both the sensing circuit 112 and the amplifying means 6
However, the amplification means is not always necessary. In the present embodiment, control circuit 113 includes I / O means 608 and arithmetic means 60.
9 is described, but is not limited to this configuration. (Embodiment 2) In this embodiment, the displacement mechanism 1 of the piezoelectric actuator described in Embodiment 1 is described.
03 shows another example.

FIG. 6A shows a displacement mechanism 103 similar to that of the first embodiment, in which a driving piezoelectric element 104 and a sensing piezoelectric element 108 are attached in parallel.

However, the driving piezoelectric element 104 only needs to have a configuration capable of applying a vibration force to the displacement mechanism 103, and the sensing piezoelectric element 108 need only have a configuration capable of detecting the vibration of the displacement mechanism 103. The driving piezoelectric element 104 and the sensing piezoelectric element 108 as shown in FIG.
The same effect as that of the first embodiment can be obtained by using the displacement mechanism 103 in which the.

Furthermore, the same effect as in the first embodiment can be obtained by using the displacement mechanism 103 as shown in FIG. 6C in which the sensing piezoelectric element 108 is attached at a position distant from the displacement mechanism 103. Obtained.

Also, the driving piezoelectric element 10 is amplified so that the sensing piezoelectric element 108 can amplify and detect mechanical vibration.
In FIG. 6D affixed to another displacement mechanism 103 different from the fourth embodiment, the same effect as in the first embodiment was obtained.

Although the present embodiment has been described with respect to four examples of the displacement mechanism 103, the driving piezoelectric element 104 is configured to apply an oscillating force to the displacement mechanism 103. It is needless to say that the same effect can be obtained with another configuration as long as the element 108 can detect the vibration of the displacement mechanism 103. (Embodiment 3) FIG. 7 is a schematic view showing one embodiment of a piezoelectric actuator according to the present invention. In FIG. 7, reference numeral 201 denotes a drive block,
In FIG. 1, displacement mechanism parts 203 and 213 having free ends are formed by U-shaped holes 206 and 216. Each of the displacement mechanisms 203 and 213 includes a piezoelectric element 20.
4,214 are attached, and the piezoelectric elements 204,214
The electrodes 205 and 215 are provided on the surface opposite to the surface on which the switching circuit 2 is attached.
21 and 222. A moving body 202 is provided on a surface of the driving block 201 opposite to the surface on which the piezoelectric elements 204 and 214 are attached, and the driving block 201 and the moving body 202 are pressurized by the weight of the moving body 202 or a spring force. Has been contacted. The drive block 201 is grounded through a contact 227. Switching circuits 221 and 22
2 have electrodes 231, 232, 233 and 2 respectively.
34, 235 and 236, and by switching the connection between these electrodes, the electrodes 205 and 215 provided on the piezoelectric elements 204 and 214 and the drive circuit 22
3 or the connection with the sensing circuit 224 can be selected. The sensing circuit 224 is connected to the control circuit 225 and can input a signal. The drive circuit 223 is connected so as to be controlled by the control circuit 225. The control circuit 225 is grounded through a contact 226.

In FIG. 7, a stainless steel material is used for the drive block 201 as in the first embodiment, but beryllium steel, phosphor bronze, brass, duralumin, titanium,
A silicon material or the like may be used. Also, the piezoelectric elements 204, 2
Although PZT (lead zirconate titanate) was used for 14, barium titanate, lithium niobate, lead zirconate titanate or the like may be used.

The driving circuit 223, the sensing circuit 224,
The control circuit 225 has the configuration shown in FIG. 4 as in the first embodiment.

In the present embodiment, the displacement mechanism 20
Since 3 and 213 are configured in opposite directions, the moving body 2
02 can be moved in both directions. Therefore,
The displacement mechanisms used when moving the moving body 202 in the respective directions are different displacement mechanisms. Therefore, in the present embodiment, when moving the moving body 202 using the displacement mechanism 203, the piezoelectric element 204 is used as a driving piezoelectric element, and the piezoelectric element 214 not used for driving is used as a sensing piezoelectric element. Can be used as When moving the moving body 202 in the opposite direction, the piezoelectric element 214 is used as a driving piezoelectric element, and the piezoelectric element 20 is moved.
4 can be used as the sensing piezoelectric element.
The respective piezoelectric elements 204 and 214 and the driving circuit 22
3. The connection with the sensing circuit 224 is performed by the switching circuit 221,
222 can be used for switching.

The voltage supplied to the driving piezoelectric element and the signal detected by the sensing piezoelectric element in the present embodiment are shown in FIG. 5 as in the first embodiment. The signal of the frequency near the resonance point generated by the AC generation means 603 and the signal of the frequency generated by the modulation frequency generation means 604 lower than that have a signal waveform superimposed by the superimposition means 602, and are amplified by the amplification means 601. The actual driving voltage thus obtained has a waveform as shown in FIG. 5B and is input to the piezoelectric element 204 via the switching circuit 221. According to the input waveform 702, the piezoelectric element 2
04 vibrates the displacement mechanism 203. Since the input waveform 702 is modulated at a low frequency near the resonance frequency, the vibration of the displacement mechanism 203 increases when the frequency is near the resonance point, and decreases when the frequency deviates. This vibration state can be detected by the piezoelectric element 214 attached to the displacement mechanism 213. FIG. 5 shows an example of the detected amplitude.
It is shown in (c). When the displacement mechanism section 203 is vibrating greatly near the resonance point, large vibration is transmitted to the displacement mechanism section 213, and the amplitude detected by the piezoelectric element 214 increases as indicated by 705, but deviates from the resonance point. At this time, the amplitude detected by the piezoelectric element 214 becomes small. This allows the control circuit 225 to immediately know the frequency near the resonance point and whether the frequency is shifted to a higher frequency or a lower frequency with respect to the current driving frequency. Can be. The phase can be detected with the same configuration as described in the first embodiment.

As is clear from the above, by superimposing a signal having a lower frequency on the AC voltage for vibrating one of the piezoelectric elements 204 or 214 near the resonance point by using the superimposing means 602, One piezoelectric element 2
In 04 or 214, the amount and direction of the deviation between the current frequency of the driving AC voltage and the actual resonance frequency can be detected at the same time, so that the resonance frequency can be immediately followed. Further, in the present embodiment, the moving body 202
It is possible to switch the piezoelectric elements 204 and 214 between the driving piezoelectric element and the sensing piezoelectric element by using the switching means 221 and 222 depending on the moving direction of. It is possible to follow the resonance frequency without making the following.

Up to this point, the configuration of the drive circuit 223, the sensing circuit 224, and the control circuit 225 has been described as an example in which the modulation frequency is supplied to the drive piezoelectric element as shown in FIG. As shown in the configuration diagram of FIG. 9 or FIG. 10, the current can be supplied to the sensing piezoelectric element or the sensing circuit. In this case, the current driving AC voltage frequency and the actual resonance frequency can also be supplied. And the direction of the displacement can be detected at the same time, so that it is possible to immediately follow the resonance frequency, and to drive the piezoelectric elements 204 and 214 by using the switching means 221 and 222 depending on the moving direction of the moving body 202. Since it is possible to switch between the piezoelectric element for sensing and the piezoelectric element for sensing, there is no need for a special structure. The number of follow-up is possible. (Embodiment 4) FIG. 8 is a schematic view showing an embodiment of a rotary piezoelectric actuator according to the present invention.

The rotary piezoelectric actuator according to the present embodiment has a rotary moving body 302 having a shaft projection 331.
And vibrating body block 3 having hole 332 through which a shaft projection passes
01 and a base chassis 3 that supports the vibrating body block 301 and slidably supports the shaft protrusion 331.
33.

The vibrating body block 301 is formed with displacement mechanisms 303 and 313 having free ends. The displacement mechanisms 303 and 313 include a piezoelectric element 304,
314 is attached, and electrodes 305, 315 are provided on the surface opposite to the attachment surface of the piezoelectric elements 304, 314, respectively.
1,322. The rotary moving body 302 is disposed on the surface of the vibrating body block 301 opposite to the surface on which the piezoelectric elements 304 and 314 are attached, and is brought into pressure contact with the displacement mechanism portions 303 and 313 by its own weight, spring force, magnetic force, or the like. I have. The vibrating body block 301 is grounded through a contact 327. The switching between the piezoelectric elements 304 and 314 and the driving circuit 323 or the sensing circuit 324 can be selected by the switching circuits 321 and 322. The sensing circuit 324 is connected to the control circuit 325 and can input a signal. The drive circuit 323 includes the control circuit 32
5 to be controlled.

In this embodiment, a stainless steel material is used for the vibrating body block 301 as in the first embodiment. Also, PZT was used for the piezoelectric elements 304 and 314 as in the first embodiment. However, it goes without saying that the same effect can be obtained by using other materials. When an AC voltage is applied to the piezoelectric element 304, the piezoelectric element 304 generates a stretching force. However, since the attached displacement mechanism 303 has a free end, the stretching force is applied to the piezoelectric element 304 and the displacement mechanism 3.
It appears as a bending force including 03. The displacement of the displacement mechanism 303 caused by the bending force acts on the rotary moving body 302. Similarly, when an AC voltage is applied to the piezoelectric element 314, a bending force appears in the displacement mechanism 313. Displacement mechanism 3
The vibration behaviors 03 and 313 are the same as in FIG. 3 described in the first embodiment. The displacement mechanisms 303 and 313 are arranged in the same direction, but the rotation moving body 30
2 rotates, the rotation of the rotary moving body 302 is different between when the piezoelectric element 304 attached to the displacement mechanism 303 is driven and when the piezoelectric element 314 attached to the displacement mechanism 313 is driven. Go in the opposite direction. Although the displacement mechanisms 303 and 313 have substantially the same shape in the present embodiment, it is needless to say that they do not necessarily have to have the same shape and the same dimensions.

The driving circuit 323, the sensing circuit 324,
The configuration of control circuit 325 is equivalent to the configuration of FIG. 4 described in the first embodiment. When the AC voltage output of the drive circuit 323 is connected to the piezoelectric element 304 by the switching circuit 321, the displacement mechanism 303 vibrates due to expansion and contraction of the piezoelectric element 304. This vibration is transmitted through the rotary moving body 302 and the vibrating body block 301, and induces vibration in another displacement mechanism 313. A piezoelectric element 314 is attached to the displacement mechanism 313, and an electromotive force is generated in the piezoelectric element 314 by the induced vibration of the displacement mechanism 313. The generated electromotive force is connected to the sensing circuit 324 by the switching circuit 322, so that the generated electromotive force can be used to control the driving circuit 323 through the control circuit 325.

The voltage supplied to the driving piezoelectric element and the signal detected by the sensing piezoelectric element in the present embodiment are shown in FIG. 5 as in the first embodiment. The signal of the frequency near the resonance point generated by the AC generation means 603 and the signal of the frequency generated by the modulation frequency generation means 604 lower than that have a signal waveform superimposed by the superimposition means 602, and are amplified by the amplification means 601. The actual driving voltage thus obtained has a waveform as shown in FIG. 5B, and is input to the piezoelectric element 304 via the switching circuit 321. According to the input waveform 702, the piezoelectric element 3
04 vibrates the displacement mechanism 303. Since the input waveform 702 is modulated at a low frequency near the resonance frequency, the vibration of the displacement mechanism 303 increases when the frequency is near the resonance point, and decreases when the frequency deviates. This vibration state can be detected by the piezoelectric element 314 attached to the displacement mechanism 313. FIG. 5 shows an example of the detected amplitude.
It is shown in (c). When the displacement mechanism 303 vibrates greatly near the resonance point, a large vibration is transmitted to the displacement mechanism 313, and the amplitude detected by the piezoelectric element 314 increases as indicated by 705, but deviates from the resonance point. At this time, the amplitude detected by the piezoelectric element 314 becomes small. This allows the control circuit 325 to immediately know the frequency near the resonance point and whether the frequency is shifted to a higher frequency or a lower frequency with respect to the current driving frequency. Can be. The phase can be detected with the same configuration as described in the first embodiment.

Up to this point, the case where the rotary moving body 302 is rotationally moved by the vibration of the displacement mechanism 303 has been described. However, the case where the rotary moving body 302 is rotationally moved in the opposite direction using another displacement mechanism 313 is also described. Needless to say, the same effect as described above can be obtained.

In this embodiment, a case is described in which two displacement mechanisms are formed in the vibrating body block 301. However, a plurality of displacement mechanisms may be formed.

As is clear from the above, the superposition means 602 superimposes a signal having a lower frequency on an AC voltage for causing one of the piezoelectric elements 304 or 314 to vibrate near the resonance point. One piezoelectric element 3
In 04 or 314, since the amount and direction of the deviation between the current frequency of the driving AC voltage and the actual resonance frequency can be simultaneously detected, it is possible to immediately follow the resonance frequency. Further, in the present embodiment, the rotary moving body 3
Switching means 321 and 322 depending on the rotation direction
It is possible to switch the piezoelectric elements 304 and 314 between the driving piezoelectric element and the sensing piezoelectric element by using the piezoelectric element, so that a dedicated structure is unnecessary, and the resonance frequency can be followed without a complicated configuration. Become.

[0047]

As described above, the piezoelectric actuator according to the present invention has a free end and has a driving and sensing piezoelectric element attached to one surface and a moving body in contact with the other surface. In a piezoelectric actuator having a displacement mechanism unit, a driving circuit including superimposing means for superimposing an AC voltage having a lower frequency on an AC voltage supplied to a driving piezoelectric element attached to the displacement mechanism unit is provided. With such a configuration, it is possible to provide a piezoelectric actuator that can change and follow a drive frequency with respect to a change in resonance frequency.

Alternatively, in the piezoelectric actuator according to the present invention, a displacement is characterized in that a piezoelectric element for driving and sensing is affixed to one surface and a moving body contacts the other surface. In a piezoelectric actuator including a mechanism, an AC voltage having a lower frequency than an AC voltage supplied to a driving piezoelectric element attached to the displacement mechanism,
Either it has low-frequency AC generation means for supplying to the sensing piezoelectric element affixed to the displacement mechanism, or a low-frequency AC voltage is generated by the sensing piezoelectric element affixed to the displacement mechanism. It is possible to provide a piezoelectric actuator that can change the drive frequency and follow the change in the resonance frequency by including the sensing circuit including the superimposing circuit that superimposes the voltage on the applied voltage.

Further, the piezoelectric actuator according to the present invention is characterized in that it has a sensing circuit for sensing the amplitude or phase of the voltage generated by the sensing piezoelectric element. It is possible to provide a piezoelectric actuator that can change the driving frequency quickly.

Further, in the piezoelectric actuator according to the present invention, the driving piezoelectric element and the sensing piezoelectric element are the same, and switching means for selectively connecting the driving circuit and the sensing circuit to the piezoelectric element is provided. Therefore, a simple configuration that does not require a special electrode or the like is suitable for miniaturization, and the detection circuit can change the drive frequency and follow the change in the resonance frequency without obstructing the drive characteristics. It is possible to provide a piezoelectric actuator.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an example of a piezoelectric actuator according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram for explaining an operation of the displacement mechanism shown in FIG. 1;

FIG. 3 is an explanatory diagram for explaining vibration of the piezoelectric element shown in FIGS. 1 and 2.

FIG. 4 is an explanatory diagram illustrating a configuration of a circuit unit illustrated in FIG. 1;

FIG. 5 is an explanatory diagram for explaining a relationship between a driving signal and a sensing signal according to the first embodiment of the present invention.

FIG. 6 is an explanatory diagram for explaining another configuration example of the displacement mechanism used in the first embodiment of the present invention.

FIG. 7 is a schematic diagram illustrating an example of a piezoelectric actuator according to a third embodiment of the present invention.

FIG. 8 is a schematic diagram illustrating an example of a rotary piezoelectric actuator according to a fourth embodiment of the present invention.

FIG. 9 is an explanatory diagram for explaining another configuration of the circuit section shown in FIG. 1;

FIG. 10 is an explanatory diagram for describing another configuration of the circuit section illustrated in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Drive block 102 Moving body 103 Displacement mechanism part 104 Drive piezoelectric element 105 Electrode 108 Sensing piezoelectric element 109 Electrode 111 Drive circuit 112 Sensing circuit 113 Control circuit 107, 114 Contact point 106 Hole 201 Drive block 202 Moving body 221, 222 Switching circuit 223 Drive circuit 224 Sensing circuit 225 Control circuit 226, 227 Contact point 203, 213 Displacement mechanism section 204, 214 Piezoelectric element 205, 215 Electrode 206, 216 hole 301 Vibrator block 302 Rotating moving body 303, 313 Displacement mechanism section 304, 314 Piezoelectric Element 305, 315 Electrode 321, 322 Switching circuit 323 Drive circuit 324 Sensing circuit 325 Control circuit 331 Shaft projection 332 Hole 333 Base chassis 601 Amplification means 602 Superposition Means 603 AC generation means 604 Modulation frequency generation means 605 Drive control means 606 Amplification means 607 Detection means 702 Waveform 703 Amplitude 704 Phase change 801 901 Amplification means 803 903 AC generation means 805 905 Drive control means 806 906 Amplification means 807, 907 detection means 804, 904 low frequency AC generation means 902 superposition means

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yoko Suzuki 1-8-1, Nakase, Mihama-ku, Chiba-shi, Chiba Inside SII IRD Center (72) Inventor Seiji Watanabe Nakase, Mihama-ku, Chiba-shi 1-8-8 SII IRD Center

Claims (7)

[Claims] 1. A piezoelectric actuator comprising a displacement mechanism having a free end and having driving and sensing piezoelectric elements attached to one surface and a moving body in contact with the other surface. A piezoelectric actuator, comprising: a driving circuit including superimposing means for superimposing an AC voltage having a lower frequency on an AC voltage supplied to a driving piezoelectric element attached to the displacement mechanism. 2. A piezoelectric actuator comprising a displacement mechanism having a free end and having driving and sensing piezoelectric elements affixed to one surface and a movable body in contact with the other surface. A low-frequency AC generator that supplies an AC voltage having a lower frequency than an AC voltage supplied to the driving piezoelectric element attached to the displacement mechanism to the sensing piezoelectric element attached to the displacement mechanism; A piezoelectric actuator characterized in that: 3. A piezoelectric actuator comprising a displacement mechanism having a free end and having driving and sensing piezoelectric elements attached to one surface and a moving body in contact with the other surface. A superposition circuit that superimposes an AC voltage having a lower frequency than an AC voltage supplied to a driving piezoelectric element attached to the displacement mechanism section on a voltage generated by a sensing piezoelectric element attached to the displacement mechanism section. A piezoelectric actuator having a sensing circuit including: 4. The piezoelectric actuator according to claim 1, further comprising a sensing circuit for sensing an amplitude of a voltage generated by the sensing piezoelectric element. 5. The piezoelectric actuator according to claim 1, further comprising a sensing circuit for sensing a phase of a voltage generated by the sensing piezoelectric element. 6. The driving piezoelectric element and the sensing piezoelectric element are the same, and the piezoelectric element includes a switching unit for selectively connecting the driving circuit and the sensing circuit to the piezoelectric element. The piezoelectric actuator according to any one of claims 1 to 5. 7. The piezoelectric actuator according to claim 1, wherein the moving body is a rotary moving body.