JP2006271167A - Piezoelectric actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric actuator which is enhanced in responsiveness and is suitable for highly accurately performing positioning of a mobile body. <P>SOLUTION: The piezoelectric actuator 7 comprises piezoelectric elements 12, two electrodes films 10a, 10b provided to one face of the piezoelectric elements 12, an electrode film 10c provided to the other face of the piezoelectric element 12, power sources 22a, 22b applying voltage to the electrode films 10a, 10b, and a control unit 26 controlling the power sources 22a, 22b. The control unit 26 controls the power sources 22a, 22b so that the voltage having two voltage waveforms, wherein the frequency is less than the resonance frequency of the piezoelectric elements 12 and the phase is different by 90°, is applied respectively to the electrode films 10a, 10b. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a piezoelectric actuator that drives a movable body by vibration of a piezoelectric element, and more particularly, to a piezoelectric actuator that improves responsiveness and is highly accurate for positioning the movable body.

Conventionally, as a piezoelectric actuator, for example, a micromotor described in Patent Document 1 is known.
FIG. 8 is a diagram showing the structure of a conventional piezoelectric actuator.
As shown in FIG. 8, the piezoelectric actuator 7 is formed on almost the entire surface of the piezoelectric element 12, the electrode films 10 a to 10 d that are divided into four on one surface of the piezoelectric element 12, and the other surface of the piezoelectric element 12. An electrode film (not shown) provided and a finger 8 provided at the tip of the piezoelectric element 12 are provided.
The piezoelectric element 12 is housed in a housing, and the side surface is supported at four points inside the housing. Further, the finger 8 is pressed against the traveling plate 6 by a coil spring 14 provided between the rear end of the piezoelectric element 12 and the housing.

FIG. 9 is a diagram illustrating a driving state of a conventional piezoelectric actuator.
In the electrode films 10a to 10d, the electrode film 10a and the electrode film 10d, which are diagonally located, and the electrode film 10b and the electrode film 10c are connected to each other. A voltage having a voltage waveform having a frequency different from the resonance frequency of the piezoelectric element 12 and a phase of 180 ° is applied to the electrode film 10a and the electrode film 10b, and the electrode film disposed on the other surface is grounded. As shown in FIG. 9, longitudinal vibration and lateral vibration are alternately generated in the piezoelectric element 12, and the fingers 8 are elliptically moved by synthesizing these vibrations. Thereby, the vibration of the piezoelectric element 12 is transmitted to the traveling plate 6 through the finger 8 so that the movable body installed on the traveling plate 6 is driven.
JP 7-184382 A

However, in the invention described in Patent Document 1, since the resonance principle is applied, in order to execute the feeding operation from the stopped state to the movable body, power is injected until the combined vibration is aligned at the tip of the piezoelectric element 12. There is a problem that there is a dead zone for the applied voltage.
Further, since it is difficult to stop the vibration of the piezoelectric element 12 during one cycle of resonance vibration, even if the optimum position of the movable body is detected, the movable body cannot be stopped accurately at that position. Therefore, there has been a problem that the movable body cannot be positioned with high accuracy.
Therefore, the present invention has been made paying attention to such an unsolved problem of the prior art, and is a piezoelectric actuator suitable for improving responsiveness and positioning a movable body with high accuracy. The purpose is to provide.

  In order to achieve the above object, a piezoelectric actuator according to claim 1 of the present invention is the piezoelectric actuator that vibrates the piezoelectric element by applying a voltage to the piezoelectric element and drives the movable body by the vibration. A first electrode and a second electrode provided on one of the two opposing surfaces of the piezoelectric element; a third electrode provided on the other of the two opposing surfaces of the piezoelectric element; the first electrode and the Voltage applying means for applying a voltage to the second electrode, wherein the voltage applying means applies voltages of two voltage waveforms whose frequencies are less than the resonance frequency of the piezoelectric element and whose phases are different by 90 ° to the first electrode and the Each is applied to the second electrode.

If it is such a structure, the voltage of a voltage waveform will be applied to the 1st electrode and the 2nd electrode by the voltage application means, and the voltage of two voltage waveforms from which the phase differs by 90 degrees will be respectively applied. As a result, the piezoelectric element is driven non-resonantly to generate longitudinal vibration and lateral vibration alternately, and the movable body is driven by the synthesis of the vibration.
Since the driving of the piezoelectric element is non-resonant driving, the vibration can be started without waiting for the combined vibration to be aligned at the tip of the piezoelectric element, and the vibration of the piezoelectric element can be easily stopped in one cycle. Can do. In addition, since the phases of the voltage waveforms applied to the first electrode and the second electrode differ by 90 °, four displacements are formed in the piezoelectric element, and circular motion can be formed instead of elliptical motion.

Furthermore, a piezoelectric actuator according to a second aspect of the present invention is the piezoelectric actuator according to the first aspect, further comprising polarity inverting means for inverting the polarity of the voltage waveform applied to the first electrode and the second electrode.
With such a configuration, the polarity of the voltage waveform applied to the first electrode and the second electrode is reversed by the polarity reversing means. Thereby, the rotation direction of the piezoelectric element is reversed.

Furthermore, a piezoelectric actuator according to a third aspect of the present invention is the piezoelectric actuator according to any one of the first and second aspects, further comprising a housing for installing the piezoelectric element, and an end portion of the piezoelectric element. Of these, the end opposite to the movable body is fixed to the casing.
With such a configuration, since the end of the piezoelectric element opposite to the movable body is fixed, the vibration of the piezoelectric element can be efficiently transmitted to the movable body.

Furthermore, a piezoelectric actuator according to a fourth aspect of the present invention is the piezoelectric actuator according to the third aspect, further comprising a spring member, wherein the end portion of the piezoelectric element is fixed to the housing via the spring member. ing.
With such a configuration, the piezoelectric element is pressed against the movable body by the spring member, so that the vibration of the piezoelectric element can be efficiently transmitted to the movable body.

Furthermore, the piezoelectric actuator according to claim 5 according to the present invention is the piezoelectric actuator according to any one of claims 3 and 4, further comprising a support, wherein the surface perpendicular to the displacement direction of the piezoelectric element is the piezoelectric actuator. It is fixed to the housing via a support.
With such a configuration, vibration in a direction orthogonal to the displacement direction of the piezoelectric element is suppressed by the support.

Furthermore, a piezoelectric actuator according to a sixth aspect of the present invention is the piezoelectric actuator according to any one of the first to fifth aspects, wherein a traveling plate on which the movable body is installed and an end portion of the piezoelectric element. A driving body provided at an end facing the movable body, and the piezoelectric element is installed by pressing the driving body against the travel plate.
With such a configuration, since the driving body is pressed against the traveling plate, the vibration of the piezoelectric element can be efficiently transmitted to the movable body.

Furthermore, a piezoelectric actuator according to a seventh aspect of the present invention is the piezoelectric actuator according to any one of the first to sixth aspects, comprising a plurality of the piezoelectric elements, and vibrating the plurality of piezoelectric elements. The movable body is driven by vibration.
With such a configuration, a plurality of piezoelectric elements are driven, and the movable body is driven by the vibrations. Therefore, even if one piezoelectric element is separated from the movable body or the traveling plate, the other piezoelectric elements are movable bodies. Or since it drives in contact with a travel plate etc., a movable body can always be hold | maintained and the more stable drive is attained.

  As described above, according to the piezoelectric actuator according to the first aspect of the present invention, since the driving of the piezoelectric element is non-resonant driving, the vibration is not waited for the combined vibration to be aligned at the tip of the piezoelectric element. While being able to start, the vibration of the piezoelectric element can be easily stopped in one cycle. Therefore, the response can be improved and the movable body can be positioned with high accuracy as compared with the prior art.

Embodiments of the present invention will be described below with reference to the drawings. 1 to 7 are diagrams showing an embodiment of a piezoelectric actuator according to the present invention.
First, the structure of the piezoelectric actuator 7 according to the present invention will be described.
FIG. 1 is a side view showing the structure of the piezoelectric actuator 7.
As shown in FIG. 1, the piezoelectric actuator 7 includes a piezoelectric element 12. As the piezoelectric element 12, a non-stacked rectangular parallelepiped piezoelectric element is used. Thereby, durability of piezoelectric element 12 itself can be improved.

As shown in FIG. 1A, electrode films 10a and 10b are provided side by side on one surface of the piezoelectric element 12. Conductive wires 11a and 11b for applying a voltage are provided on the electrode films 10a and 10b. It is connected. As shown in FIG. 1B, an electrode film 10c is provided on the other surface of the piezoelectric element 12 so as to cover the entire surface, and a conductive wire 11c for grounding is connected to the electrode film 10c. ing.
A finger 8 for transmitting the vibration of the piezoelectric element 12 to the movable body is provided at the tip of the piezoelectric element 12. The finger 8 and the piezoelectric element 12 may be formed integrally, or the finger 8 and the piezoelectric element 12 may be formed of individual parts and joined together.

FIG. 2 is a perspective view showing the structure of the piezoelectric actuator 7.
FIG. 3 is a side view showing the structure of the piezoelectric actuator 7.
The piezoelectric element 12 is housed in a housing 16 as shown in FIG. Further, the rear end of the piezoelectric element 12 is fixed to the housing 16 via a leaf spring 18, and the finger 8 is pressed against the traveling plate 6 by the leaf spring 18 as shown in FIG. 3. As a method for fixing the piezoelectric element 12, an elastic hinge may be used instead of the leaf spring 18, or one end of the piezoelectric element 12 may be completely fixed like a cantilever. The pressing pre-pressure of the traveling plate 6 is set according to the driving conditions.

As shown in FIG. 2, the side surface orthogonal to the displacement direction of the piezoelectric element 12 is fixed to the housing 16 via support members 20a and 20b. In the example of FIG. 2, only one place is supported for one side surface, but a plurality of support members may be used for one side surface.
FIG. 4 is a block diagram showing the structure of the piezoelectric actuator 7.
As shown in FIG. 4, the piezoelectric actuator 7 includes a power source 22a that is connected to the conductive wire 11a and applies a voltage to the electrode film 10a, a power source 22b that is connected to the conductive wire 11b and applies a voltage to the electrode film 10b, and power sources 22a and 22b. The polarity reversing unit 24 for reversing the polarity of the voltage waveform and the control unit 26 for controlling the power supplies 22a and 22b and the polarity reversing unit 24 are configured.

The control unit 26 generates two voltage waveforms whose phases are different by 90 °, and controls the power supplies 22a and 22b so as to apply the voltages having the generated voltage waveforms to the electrode films 10a and 10b, respectively. The frequency of the voltage waveform is set in a range from DC (0 [Hz]) to less than the resonance frequency of the piezoelectric element 12. This is because, when the piezoelectric element 12 is used in the resonance frequency region, the piezoelectric element 12 causes resonance vibration, which is suppressed.
When the control unit 26 reverses the rotation direction of the finger 8, the polarity reversing unit 24 reverses the polarity of the voltage waveform.

Next, the driving principle of the piezoelectric actuator 7 will be described.
FIG. 5 is a diagram illustrating a driving state of the piezoelectric actuator 7.
The example of FIG. 5 is a case where pulse voltages having a phase difference of 90 ° are applied to the electrode films 10a and 10b.
First, when a negative voltage is applied to each of the electrode films 10a and 10b, as shown in FIG. 5A, the left half surface of the piezoelectric element 12 (the portion where the electrode film 10a is provided) and the right half surface (electrode) The part where the film 10a is provided) extends, and the finger 8 is displaced upward.
Next, when the voltage applied to the electrode film 10b becomes positive, as shown in FIG. 5B, the right half surface contracts with the left half of the piezoelectric element 12 extended, and the finger 8 is displaced in the right direction.

Next, when the voltage applied to the electrode film 10a becomes positive, as shown in FIG. 5C, the left half surface contracts while the right half of the piezoelectric element 12 contracts, and the finger 8 is displaced downward.
When the voltage applied to the electrode film 10b becomes positive, as shown in FIG. 5D, the right half surface expands with the left half surface of the piezoelectric element 12 contracted, and the finger 8 is displaced in the left direction.
By repeating these four displacements, the tip of the finger 8 is driven to draw a circular motion. The movable body can be moved by this movement. The speed of movement can be adjusted by changing the frequency of the voltage applied to the electrode films 10a and 10b. Further, the voltage waveform applied to the electrode films 10a and 10b is not limited to the pulse wave, but may be a sine wave or a triangular wave.

FIG. 6 is a diagram illustrating a driving state when the piezoelectric actuator 7 is DC-driven.
When the piezoelectric actuator 7 is DC-driven, for example, as shown in FIG. 6, a positive voltage is applied to one of the electrode films 10a and 10b and a negative voltage is applied to the other to displace the piezoelectric element 12. Can do. Further, the piezoelectric element 12 can be displaced by applying a positive or negative voltage only to one of the electrode films 10a and 10b.

During fine movement, the amount of movement can adjust the amount of displacement of the piezoelectric element 12 by changing the magnitude of the applied voltage. As a result, the movable body can be moved with a very small amount of displacement.
Thus, in the present embodiment, the piezoelectric element 12, the two electrode films 10a and 10b provided on one surface of the piezoelectric element 12, and the electrode film 10c provided on the other surface of the piezoelectric element 12 are used. A power source 22a, 22b for applying a voltage to the electrode films 10a, 10b, and a control unit 26 for controlling the power source 22a, 22b. The control unit 26 has a frequency lower than the resonance frequency of the piezoelectric element 12 and a phase. The power supplies 22a and 22b are controlled so that voltages of two voltage waveforms different by 90 ° are applied to the electrode films 10a and 10b, respectively.

Thereby, since the driving of the piezoelectric element 12 is non-resonant driving, the vibration can be started without waiting for the combined vibration to be aligned at the tip of the piezoelectric element 12, and the vibration of the piezoelectric element 12 can be started during one cycle. Can be stopped easily. Therefore, the response can be improved and the positioning of the movable body can be performed with high accuracy as compared with the conventional case.
Further, in the present embodiment, a polarity reversing unit 24 that reverses the polarity of the voltage waveform applied to the electrode films 10a and 10b is provided.

Thereby, the rotation direction of the piezoelectric element 12 can be reversed.
Further, in the present embodiment, the rear end of the piezoelectric element 12 is fixed to the housing 16 via the leaf spring 18, and the finger 8 is pressed against the traveling plate 6 by the leaf spring 18.
Thereby, the vibration of the piezoelectric element 12 can be efficiently transmitted to the movable body.
Furthermore, in the present embodiment, the side surface orthogonal to the displacement direction of the piezoelectric element 12 is fixed to the housing 16 via the support members 20a and 20b.
Thereby, the vibration of the direction orthogonal to the displacement direction of the piezoelectric element 12 can be suppressed by the support members 20a and 20b.

In the above embodiment, the electrode film 10a corresponds to the first electrode according to claim 1 or 2, the electrode film 10b corresponds to the second electrode according to claim 1 or 2, and the electrode film 10c corresponds to the claim. The power supplies 22a and 22b and the control unit 26 correspond to the voltage applying means according to the first aspect. The polarity reversing section 24 corresponds to the polarity reversing means according to claim 2, the finger 8 corresponds to the driving body according to claim 6, and the support members 20 a and 20 b correspond to the support body according to claim 5. It corresponds.
In the above-described embodiment, the movable body is driven using one piezoelectric element 12, but the present invention is not limited to this, and the movable body is driven using a plurality of piezoelectric elements 12. You can also.

FIG. 7 is a diagram illustrating a case where a movable body is driven using two piezoelectric elements 12.
When the movable body is driven using the two piezoelectric elements 12, the piezoelectric elements 12 are driven with a phase difference as shown in FIG. As a result, even when one piezoelectric element 12 is separated from the traveling plate 6, the other piezoelectric element 12 is driven in contact with the traveling plate 6, so that the traveling plate 6 can always be held and more stable driving can be achieved. It becomes possible. When the driving force is increased, a larger number of piezoelectric elements 12 may be used.

In the above embodiment, the two electrode films 10a and 10b are provided on one surface of the piezoelectric element 12. However, the present invention is not limited to this, and a plurality of electrode films may be provided. In this case, two electrode films may be set, and a voltage may be applied to the electrode film by the same voltage application method as in the above embodiment for each set. Further, when the number of electrode films is n (n ≧ 3), a voltage having a voltage waveform whose phase is different by π / n may be applied to each electrode film. Thereby, 2n displacements can be formed in the piezoelectric element 12.
The piezoelectric actuator according to the present invention is not limited to the above-described embodiment, and can be applied to other cases without departing from the gist of the present invention.

3 is a side view showing the structure of a piezoelectric actuator 7. FIG. 3 is a perspective view showing a structure of a piezoelectric actuator 7. FIG. 3 is a side view showing the structure of a piezoelectric actuator 7. FIG. 3 is a block diagram showing a structure of a piezoelectric actuator 7. FIG. FIG. 3 is a diagram showing a driving state of a piezoelectric actuator. It is a figure which shows the drive state at the time of carrying out DC drive of the piezoelectric actuator. It is a figure which shows the case where a movable body is driven using two piezoelectric elements. It is a figure which shows the structure of the conventional piezoelectric actuator. It is a figure which shows the drive state of the conventional piezoelectric actuator.

Explanation of symbols

7 Piezoelectric actuator 6 Traveling plate 8 Fingers 10a to 10c Electrode film 12 Piezoelectric element 16 Housing 18 Leaf springs 20a and 20b Support members 22a and 22b Power supply 24 Polarity reversing unit 26 Control unit

Claims (7)

In the piezoelectric actuator that vibrates the piezoelectric element by applying a voltage to the piezoelectric element and drives the movable body by the vibration.
A first electrode and a second electrode provided on one of the two opposing surfaces of the piezoelectric element; a third electrode provided on the other of the two opposing surfaces of the piezoelectric element; and the first electrode and Voltage applying means for applying a voltage to the second electrode,
The voltage applying means applies voltages of two voltage waveforms whose frequencies are less than the resonance frequency of the piezoelectric element and whose phases are different by 90 ° to the first electrode and the second electrode, respectively. A piezoelectric actuator. In claim 1,
A piezoelectric actuator, further comprising polarity inverting means for inverting the polarity of a voltage waveform applied to the first electrode and the second electrode. In any one of Claim 1 and 2,
A housing for installing the piezoelectric element;
A piezoelectric actuator, wherein an end of the piezoelectric element opposite to the movable body is fixed to the casing. In claim 3,
A spring member;
The piezoelectric actuator, wherein the end of the piezoelectric element is fixed to the housing via the spring member. In any one of Claims 3 and 4,
Further comprising a support,
A piezoelectric actuator characterized in that a surface orthogonal to the displacement direction of the piezoelectric element is fixed to the housing via the support. In any one of Claims 1 thru | or 5,
A travel plate for installing the movable body; and a driving body provided at an end of the piezoelectric element facing the movable body,
A piezoelectric actuator, wherein the piezoelectric element is installed by pressing the driving body against the traveling plate. In any one of Claims 1 thru | or 6,
A plurality of the piezoelectric elements;
A piezoelectric actuator characterized in that the plurality of piezoelectric elements are vibrated and the movable body is driven by the vibrations.

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