WO2009101858A1

WO2009101858A1 - Oscillatory-type drive device, and method for adjusting piezoelectric element and the oscillatory-type drive device

Info

Publication number: WO2009101858A1
Application number: PCT/JP2009/051357
Authority: WO
Inventors: Tomoyuki Yuasa; Ryuichi Yoshida; Takashi Hashimoto
Original assignee: Konica Minolta Opto, Inc.
Priority date: 2008-02-12
Filing date: 2009-01-28
Publication date: 2009-08-20
Also published as: JP5526786B2; JPWO2009101858A1

Abstract

A polarizing voltage capable of polarizing only a layer (3a) having the lowest polarizable voltage is applied to a piezoelectric element (3) prepared by laminating a plurality of layers (3a, 3b and 3c) of different voltages, which can be completely polarized by making either the layer thickness or a piezoelectric material (8) different. If desired extension characteristics are not attained, the polarizing voltage capable of polarizing a next layer (3b) is applied, and the polarizing voltage is stepwise raised until the desired extension characteristics are attained. Thus, it is possible to provide the oscillatory-type drive device which has a small dispersion in performance.

Description

Vibration type drive device, and piezoelectric element and vibration type drive device adjustment method

The present invention relates to a vibration type driving device, and a method for adjusting a piezoelectric element and a vibration type driving device.

For example, Patent Document 1 describes a vibration type driving device that uses a piezoelectric element as a driving source and slides and displaces a moving body by expansion and contraction of the piezoelectric element. In such a vibration type driving device, the driving amount (speed) is determined by the expansion and contraction characteristics of the piezoelectric element.

The piezoelectric element can be manufactured by laminating layers of piezoelectric material as described in Patent Document 2, for example. It is difficult to make the composition of the piezoelectric material and the thickness of the layer strictly uniform, and there is some variation in the expansion / contraction characteristics of the manufactured piezoelectric element.

Particularly, in a vibration type driving apparatus using a piezoelectric element as a driving source, there is a great demand for high accuracy, and performance errors due to variations in the piezoelectric element are regarded as problems. In order to increase the accuracy of the vibration type driving device, the driving amount for each device may be confirmed at the time of manufacture, and the driving voltage may be changed to adjust the driving amount to be constant. However, in order to enable such adjustment, there is a problem that the configuration of the drive circuit becomes complicated and a memory for storing the adjustment value becomes necessary.
JP 2001-103772 A JP 2003-103772 A

In view of the above problems, an object of the present invention is to provide a vibration type driving device with small performance variation, and a method for adjusting a piezoelectric element and a vibration type driving device.

In view of the above problems, the vibration type driving device according to the present invention has a piezoelectric element formed by laminating a plurality of layers of piezoelectric materials having different voltages that can be completely polarized.

According to this configuration, it is possible to leave a non-polarized layer by selecting the polarization processing voltage, thereby reducing the expansion and contraction characteristics of the piezoelectric element. A piezoelectric element having a low expansion / contraction rate can increase the expansion / contraction rate by further polarizing a layer that is not polarized by a higher polarization treatment voltage. As a result, it is possible to provide a vibration type driving device that adjusts the expansion / contraction characteristics of the piezoelectric element and has no variation in driving performance. Further, by adjusting the performance of the piezoelectric element, the driving speed of the vibration type driving device can be adjusted, and a circuit and control program for adjusting the speed are not necessary. Note that layers that cannot contribute to expansion and contraction, such as dummy layers provided at both ends of the piezoelectric element, are not included in “a plurality of layers of piezoelectric materials having different voltages that can be completely polarized” according to the present invention.

Further, in the vibration type driving device of the present invention, the plurality of piezoelectric material layers may include layers having different thicknesses or may include layers of piezoelectric materials having different coercive electric fields.

As the piezoelectric material layer becomes thicker, the electric field strength becomes lower, so that the voltage required for polarization becomes higher. Even if the piezoelectric material layer has the same thickness, the higher the coercive electric field, the higher the voltage required for polarization. By utilizing these properties, the degree of polarization can be made to progress stepwise with respect to the polarization processing voltage, and the driving performance of the vibration type driving device can be easily adjusted by adjusting the expansion / contraction characteristics of the piezoelectric element. .

In addition, the piezoelectric element adjustment method according to the present invention starts with a polarization treatment voltage applied to the piezoelectric element, starting from a voltage lower than that at which the piezoelectric element is completely polarized until the desired expansion and contraction characteristics are obtained. It is a method to raise.

This method can provide a piezoelectric element having no variation in performance.

In the adjustment method of the present invention, the piezoelectric element may be polarized in advance, and the polarization processing voltage may be a voltage that polarizes the piezoelectric element in a reverse direction.

This method can adjust the performance of commercially available piezoelectric elements. In addition, when a piezoelectric element is made by stacking multiple layers of piezoelectric materials with different voltages that can be completely polarized, more stable polarization can be achieved than the number of layers with different voltages that can be polarized, allowing fine adjustments. become.

According to the present invention, the adjustment method of the vibration type driving device that displaces the moving body using the piezoelectric element as a driving source adjusts the piezoelectric element by any one of the above methods, and the desired expansion / contraction characteristic is obtained by the moving body. Confirm by the amount of displacement.

According to this method, since the piezoelectric element is adjusted based on the displacement amount of the moving body, the driving speed of the vibration type driving device can be adjusted to be constant.

According to the present invention, since the expansion / contraction characteristics of the piezoelectric element can be adjusted by changing the polarization processing voltage, there is little variation in the performance of the piezoelectric element, and the performance of the vibration type driving device using the piezoelectric element can be made constant. it can.

Schematic which shows the mode of adjustment of the vibration type drive device of 1st Embodiment of this invention. The graph which shows the reference | standard displacement amount with respect to the polarization process voltage of the piezoelectric element of FIG. Schematic which shows the structure of the piezoelectric element of 2nd Embodiment of this invention. The graph which shows the reference | standard displacement amount with respect to the polarization process voltage of the piezoelectric element of FIG. FIG. 5 is a distribution diagram showing variation of products after polarization at the polarization processing voltage Va in FIG. 4. FIG. 5 is a distribution diagram showing variation of products after polarization at the polarization processing voltage Vb of FIG. 4. FIG. 5 is a distribution diagram showing variation of products after polarization at the polarization processing voltage Vc of FIG. 4. FIG. 4 is a distribution diagram showing product variations after final adjustment of the piezoelectric element of FIG. 3. Schematic which shows the structure of the piezoelectric element of 2nd Embodiment of this invention. The graph which shows the reference | standard displacement amount with respect to the polarization process voltage of the piezoelectric element of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Vibration type drive device 2 ... Weight 3 ...

Piezoelectric element

3a, 3b, 3c ... Block 4 ... Vibration member 5 ... Moving body 6 ...

Power supply

7a, 7b ... Electrode 8 ... Piezoelectric material ta, tb, tc ... Layer Thickness

Embodiments of the present invention will now be described with reference to the drawings.
FIG. 1 shows how the driving speed of the vibration type driving apparatus 1 according to the first embodiment of the present invention is adjusted. The vibration type driving device 1 includes a weight 2, a piezoelectric element 3 having one end fixed to the weight 2 in an expansion / contraction direction, a shaft-like vibration member 4 having one end fixed to the other end of the piezoelectric element 3, and the vibration member 4. And a moving body 5 that is frictionally engaged so as to be able to slide. The piezoelectric element 3 is a laminated piezoelectric element formed by laminating, for example, a piezoelectric material made of PZT and an electrode, and a polarization processing power source 6 is connected to the electrode, and a polarization processing voltage of, for example, about 30 (V) is applied. Then, the piezoelectric material is imparted by polarizing the piezoelectric material.

The vibration type driving device 1 uses the piezoelectric element 3 as a drive source, and applies a driving voltage to the piezoelectric element 3 to cause the piezoelectric element 3 to expand and contract asymmetrically in the extension direction and the contraction direction, thereby vibrating the vibration member 4 asymmetrically. Thus, in the direction in which the vibration member 4 moves slowly, the moving body 5 is moved together with the vibration member 4 being frictionally engaged, and in the direction in which the vibration member 4 moves sharply, the moving body 5 is moved in place by the inertial force. The movable body 5 and the driven object fixed to the movable body 5 are driven by sliding and displacing the vibrating member 4 so as to stay in the movable body 5.

FIG. 2 shows the relationship between the polarization treatment voltage and the expansion / contraction amount (reference displacement amount) at the rated voltage (eg, 3V) as a value indicating the expansion / contraction characteristics of the piezoelectric element 3 after polarization. As shown in the figure, when the polarization processing voltage is low to some extent, the piezoelectric element 3 is not polarized at all and the reference displacement amount is zero. However, when the polarization processing voltage exceeds a certain voltage, the reference displacement amount increases with the voltage. Further, when the polarization processing voltage is increased, the reference displacement amount of the piezoelectric element 3 is saturated and no more increases.

The driving speed of the vibration type driving device 1 and the reference displacement amount of the piezoelectric element 3 are substantially proportional. Therefore, by changing the polarization processing voltage, the reference displacement amount of the piezoelectric element 3 and the driving speed of the vibration type driving device 1 (the displacement amount of the moving body 5 with respect to a constant driving voltage) can be set to desired values.

However, it is difficult to strictly control the composition of the piezoelectric material, the layer thickness, the electrode state, and the like of the piezoelectric element 3, and even if the polarization voltage is constant, the reference displacement amount of the piezoelectric element 3 and The driving speed of the vibration type driving device 1 varies. Therefore, first, the piezoelectric element 3 is polarized by a polarization processing voltage sufficiently lower than the voltage at which the piezoelectric element 3 is completely polarized (saturation of polarization), and a rated voltage is applied to the piezoelectric element 3 to provide a reference for the piezoelectric element 3. Only when the amount of displacement (or the amount of movement of the vibrating member 4) is measured and does not reach the predetermined expansion / contraction amount, the polarization is advanced by applying a higher polarization treatment voltage until the predetermined reference displacement amount is reached. By increasing the polarization processing voltage stepwise, the expansion / contraction amount of the piezoelectric element 3 and the driving speed of the vibration type driving device 1 can be set to substantially desired values.

FIG. 3 shows the structure of the piezoelectric element 3 that facilitates the adjustment of the reference displacement amount according to the second embodiment of the present invention. The piezoelectric element 3 of the present embodiment has a plurality of layers of the piezoelectric material 8 sandwiched between the

electrodes

7a and 7b, and the first block 3a having the thickness of the layer of the piezoelectric material 8 of ta, The piezoelectric material 8 includes a second block 3b having a thickness of tb and a third block 3c having a thickness of the piezoelectric material 8 of tc.

For example, the thickness of each layer of the first block 3a is 10 μm and the number of stacked layers is 80, the thickness of each layer of the second block 3b is 20 μm, the number of stacked layers is 20, and the thickness of each layer of the third block 3c is 30 μm. The number of layers is 20 layers.

Generally, if the piezoelectric material 8 is homogeneous, the polarization proceeds according to the strength of the electric field applied by the polarization processing voltage. Therefore, the polarization processing voltage at which each

block

3a, 3b, 3c is polarized is proportional to the thicknesses ta, tb, tc of each layer, and the reference displacement amount of the entire piezoelectric element 3 of the present embodiment depends on the polarization processing voltage. It changes as shown in FIG.

Specifically, the first block 3a having the smallest layer thickness starts polarization at the lowest voltage, and is completely polarized and displaced at a lower voltage than the second block 3b and the third block 3c start polarization. The amount is saturated. When the polarization processing voltage is further increased, the second block 3b is subsequently polarized, and the displacement amount becomes the second saturation state. When the polarization processing voltage is further increased, the third block 3c is polarized, and the reference displacement amount is further increased.

In the present embodiment, first, the polarization processing power source 6 is connected in a state where the piezoelectric element 3 is incorporated in the vibration type driving device 1, and the polarization processing voltage Va (V) is applied so that only the first block 3a is completely polarized. Then, polarization is performed, and a driving voltage of the rated voltage is applied to the piezoelectric element 3 to measure the driving speed of the vibration type driving device 1. FIG. 5 shows the drive speed distribution of individual products (vibration type drive device 1) when the piezoelectric elements 3 of a large number of vibration type drive devices 1 are polarized with the polarization processing voltage Va (V). The driving speed of the vibration type driving device 1 mainly depends on the expansion / contraction characteristics of the piezoelectric element 3, and exhibits a distribution like a normal distribution as shown in the figure due to variations in the expansion / contraction characteristics of the piezoelectric element 3.

Here, when the lower limit of the allowable range of the driving speed of the vibration type driving device 1 is 7.0 mm / sec, a product group in the range indicated by hatching in the figure having a driving speed higher than this value is regarded as an acceptable product. The other piezoelectric elements 3 of the vibration type driving device 1 are further polarized by a polarization voltage Vb (V) that can completely polarize the second block 3b. Then, again, the driving speed of the vibration type driving device 1 with the driving voltage of the rated voltage is measured. Then, as shown in FIG. 6, the driving speed distribution of the vibration type driving device 1 is a distribution that is stacked by an increase in vibration due to the polarization of the second block 3 b.

Here, too, the product group in the range indicated by the oblique line having the driving speed equal to or higher than the lower limit (7.0 mm / sec) is regarded as an acceptable product, and the piezoelectric element 3 of the remaining product can be polarized to the third block 3c completely. Further polarization is caused by the voltage Vc (V). Then, the driving speed of the vibration type driving device 1 further increases to show a distribution as shown in FIG.

The overall drive speed of the vibration type drive device 1 and the vibration type drive device 1 that has been accepted after the previous two polarizations has a distribution as shown in FIG. 8, and the drive speed variation is small. In the illustrated embodiment, the variation in expansion / contraction characteristics of the original piezoelectric element 3 is relatively large. However, the thicknesses ta and tb of the layers of the

blocks

3a, 3b, and 3c are adjusted in accordance with the processing accuracy of the piezoelectric element 3. , Tc and the number of stacked layers are preferably selected.

In this embodiment, the voltage at which the

blocks

3a, 3b, 3c are polarized is set by the layer thicknesses ta, tb, tc, but the layer thicknesses ta, tb, tc of the

blocks

3a, 3b, 3c are set. The voltage at which the

blocks

3a, 3b, and 3c are polarized can also be varied by changing the composition of the piezoelectric material 8 while keeping the constant.

In general, among piezoelectric materials, what is called a soft material having a low Curie temperature has a low coercive electric field (electric field intensity at which polarization starts), and what is called a hard material having a high Curie temperature has a high coercive electric field. . Therefore, for example, if a soft material is used for the first block 3a, a hard material is used for the third block 3c, and an intermediate piezoelectric material is used for the second block 3b, the relationship between the polarization processing voltage and the reference displacement amount similar to FIG. Is obtained. Of course, the composition of the piezoelectric material 8 may be further varied after changing the thicknesses ta, tb, tc of the layers of the

blocks

3a, 3b, 3c.

Further, FIG. 9 shows the configuration of the piezoelectric element 3 according to the third embodiment of the present invention. The piezoelectric element 3 according to this embodiment includes two blocks, a first block 3a formed by stacking layers having a small thickness ta, and a second block 3b formed by stacking layers having a large thickness tb. The compositions of the piezoelectric materials 8 of 3a and 3b are the same.

In the present embodiment, when both the

blocks

3a and 3b are completely polarized, the contribution of the second block 3b polarized at a high voltage in the reference displacement amount of the entire piezoelectric element 3 is the third polarized at a low voltage. It is designed to be larger than the contribution of the block 3a.

In the present embodiment, after both

blocks

3a and 3b are completely polarized, a polarization processing voltage of opposite polarity is applied in a stepwise manner so that the reference displacement amount of the piezoelectric element 3 is reduced to three stable values as shown in FIG. A state is obtained. Specifically, the reference displacement amount of the piezoelectric element 3 in which both the

blocks

3a and 3b are completely polarized is in the first stable state. If this reference displacement amount is too large, the polarization of the first block 3a only disappears. By applying a polarization processing voltage Van (V) in the opposite direction to that when prepolarized, a second stable state with a reference displacement amount that depends only on the amount of expansion / contraction of the second block 3b can be obtained. Furthermore, if this reference displacement amount is too large, the first block 3a can be polarized in the reverse polarity, and the polarization processing voltage Aap (V) having a voltage at which the polarization of the second block 3b does not disappear can be applied to the first block 3a. The block 3c can be polarized so as to expand and contract in the opposite direction to the second block 3b. Accordingly, the reference displacement amount of the entire piezoelectric element 3 is a value obtained by subtracting the expansion / contraction amount of the first block 3a from the expansion / contraction amount of the second block 3b.

When a higher polarization voltage Vbn (V) that eliminates the polarization of the second block 3b is applied, the displacement direction of the piezoelectric element 3 is reversed. If only the absolute value of the reference displacement amount is seen, this state can be used as the fourth stable state. However, in the state incorporated in the vibration type driving device 1, the reversal of the expansion / contraction direction of the piezoelectric element 3 is caused in the driving direction. Since it means inversion, it is necessary to reverse the polarity of the drive circuit, so care must be taken.

Claims

A vibration type driving device having a piezoelectric element formed by laminating a plurality of layers of piezoelectric materials having different voltages that can be completely polarized.
The vibration type driving device according to claim 1, wherein the layers of the plurality of piezoelectric materials include layers having different thicknesses.
3. The vibration type driving device according to claim 1, wherein the plurality of layers of the piezoelectric material include layers of piezoelectric materials having different coercive electric fields.
A method for adjusting a piezoelectric element, characterized in that a polarization treatment voltage applied to the piezoelectric element starts from a voltage lower than that at which the piezoelectric element is completely polarized and is increased stepwise until a desired expansion / contraction characteristic is obtained. .
5. The method of adjusting a piezoelectric element according to claim 4, wherein the piezoelectric element is previously polarized, and the polarization processing voltage is a voltage that polarizes the piezoelectric element in a reverse direction.
The method of adjusting a piezoelectric element according to claim 4 or 5, wherein the piezoelectric element is formed by laminating a plurality of layers having different thicknesses.
The method for adjusting a piezoelectric element according to any one of claims 4 to 6, wherein the piezoelectric element is formed by laminating a plurality of layers of piezoelectric materials having different coercive electric fields.
An adjustment method of a vibration type driving device that displaces a moving body using a piezoelectric element as a driving source,
A piezoelectric element is adjusted by the method according to any one of claims 4 to 7,
The adjustment method of the vibration type driving device, wherein the desired expansion / contraction characteristic is confirmed by a displacement amount of the moving body.