JPH06310771A - Displacement amplifying mechanism for piezoelectric element and driving method therefor - Google Patents

Abstract

PURPOSE:To provide a miniature amplifying mechanism excellent in high speed response at low cost wherein the amplification factor of one piezoelectric element is equal to or lower than that of a conventional piezoelectric displacement amplifying mechanism. CONSTITUTION:An amplifying part comprising two buckling springs 2A/2B welded into a ring is boded directly to two driving end faces 3a/3b of a piezoelectric element 1 generating distortion through piezoelectric effect depending on a driving voltage being applied externally. Distortion of the element 1 in the direction of an arrow A is amplified by the elongation of the buckling springs upon elongation of the element 1 and the displacement in the direction of an arrow B is taken out from the bridge-like apex of the buckling springs 2A/2B thus decreasing the number of components as compared with a conventional mechanism where the amplification is carried out in two stages through a lever arm. Two piezoelectric may be fixed to the outside of the amplifying part in order to compress the buckling springs. The buckling springs may have asymmetric shape and may be odd in number.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric element displacement amplification mechanism which uses a piezoelectric element as a displacement source and amplifies a minute strain generated by the piezoelectric element to transmit the amplified minute strain to the outside.

[0002]

2. Description of the Related Art A piezoelectric element is an element that converts electric energy into mechanical energy by utilizing the strain generated by a piezoelectric ceramic or the like in accordance with a driving voltage. Other elements such as a servo motor, a step motor, or a coil are used. Compared with electric actuators, it has excellent characteristics such as extremely high response speed and good displacement control accuracy. However, since the amount of strain itself that can be generated by the piezoelectric element is limited to about several tens of μm, the displacement amplifying means (piezoelectric element displacement amplifying mechanism. It is necessary to amplify the minute strain generated by the piezoelectric element to a displacement amount according to the application by means of an amplification mechanism).

FIG. 7 shows a perspective view of an example of this type of amplification mechanism. The amplification mechanism shown in this figure is disclosed in JP-A-2-11927.
This is disclosed in Japanese Patent Publication No. Referring to FIG. 7, in the amplification mechanism shown in this figure, both ends of the piezoelectric element 1 are
Two lever arms 6 by two hinges 5a / 5b
It is connected to one end of each a / 6b. The lever arms 6a / 6b each have two hinges 10a as fulcrums.
/ 10b respectively, and is connected to the substrate 7.
A bridge-shaped buckling spring 2 is provided at the other end of each of the lever arms 6a / 6b.
It is fixed by each of the two rivets 8a / 8b so as to be sandwiched between.

With this structure, a minute strain of about several tens of μm generated in the piezoelectric element 1 in the direction indicated by the arrow A in FIG. 7 is amplified by the lever arms 6a / 6b and further buckled.
Then, the peak of the buckling spring 2 is finally displaced about 0.5 mm, which is amplified several tens of times in the direction indicated by the arrow B in FIG.

When the strain of the piezoelectric element is expanded to this extent, that is, several tens of times, it can be used for applications such as opening and closing a gas valve and tracking adjustment of a video tape recorder. In order to obtain such an amplification factor, it is usually necessary to perform amplification twice, that is, amplification by the lever arm and amplification by the buckling spring as described above.

[0006]

As described above, in order to amplify the displacement of the piezoelectric element by several tens of times, amplification by the lever arm and amplification by the buckling spring are necessary. In order to realize this amplification, Parts such as lever arms, hinges, and boards are essential. Although these parts are manufactured by wire electric discharge machining or precision press working, cost reduction is difficult due to the complicated shape and the large number of parts. Moreover, in order to increase the amplification factor, it is necessary to lengthen the lever arm, which makes it difficult to reduce the size because of the large number of parts. Further, if the lever arm is long, the resonance frequency there is lowered, which is disadvantageous in that the high speed response of the piezoelectric element itself cannot be fully utilized. These problems in the conventional amplification mechanism are due to the fact that the amplification factor required for this amplification mechanism is at least several tens of times or more.

On the other hand, from the viewpoint of the required performance of the amplifying mechanism, it is expected that the demand for the amplifying mechanism having a lower amplifying factor than the conventional one will increase in the future while the demand for the higher amplifying factor becomes stronger than the conventional one. Be done. In other words, the application range of this kind of actuator has been widened in recent years, and for example, a displacement amount of about 0.1 mm is sufficient for applications such as mirror positioning control and XY stage position control in optical equipment. Also, actuators using piezoelectric elements have come to be used. For such applications, amplification by the amplification mechanism is sufficient at most about several times. Further, the piezoelectric element is being actively improved and the amount of generated strain itself is also increasing. As a result, to obtain the same displacement as the conventional displacement described above,
Amplification by the amplification mechanism is becoming smaller than before. Under such circumstances, it is strongly desired that the piezoelectric element amplifying mechanism has a small size, a low cost, and an improved high-speed response, as well as an increased amplification factor.

Therefore, an object of the present invention is to provide an amplifying mechanism which is small in size and excellent in high-speed response, at a low cost, in which the amplification factor per piezoelectric element is less than that of the conventional piezoelectric element displacement amplifying mechanism. It is what

[0009]

A piezoelectric element displacement amplification mechanism of the present invention comprises a piezoelectric element that generates strain by a piezoelectric effect according to a driving voltage applied from the outside, and two piezoelectric elements whose one ends face each other. At least one buckling spring effectively fixed directly to one of the drive end faces is included.

The piezoelectric element displacement amplification mechanism of the present invention is
The first piezoelectric element and the second piezoelectric element are arranged so as to be in series so as to be in series with respect to the strains respectively generated, and between the driving end surfaces of the respective piezoelectric elements facing the driving end surfaces of the other piezoelectric elements. Further, at least one buckling spring is provided in a bridge shape.

Further, the piezoelectric element displacement amplification mechanism of the present invention is
In the second piezoelectric element displacement amplification mechanism, a third piezoelectric element is connected in series with the first piezoelectric element and the second piezoelectric element with respect to the strain in the space formed by the first piezoelectric element and the second piezoelectric element. And the one driving end surface of the third piezoelectric element and the driving end surface to which the buckling spring of the first piezoelectric element is fixed are fixed to each other via the buckling spring. The other drive end face and the drive end face to which the buckling spring of the second piezoelectric element is fixed are fixed via the buckling spring.

The piezoelectric element displacement amplification mechanism driving method according to the present invention drives the first piezoelectric element and the second piezoelectric element in phase with respect to the third piezoelectric element displacement amplification mechanism, It is characterized in that the third piezoelectric element is driven in a phase opposite to that of the first piezoelectric element and the second piezoelectric element.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a first embodiment of the present invention. With reference to FIG. 1, in the present embodiment, a displacement generating portion composed of a piezoelectric element 1 that generates a small strain in the direction of an arrow indicated by A in the figure by a piezoelectric effect, and two bridge-shaped buckling springs 2A / 2B are provided. The displacement amplification section has a ring-shaped composite structure (hereinafter referred to as an amplification section).

The piezoelectric element 1 is a laminated type element in which layers of piezoelectric ceramic containing lead zirconate titanate as a main raw material and internal electrode layers are alternately laminated. The element 1 is provided with a pair of external electrodes that electrically connect every other one of the above internal electrode layers. When a driving voltage is applied between the two external electrodes, the internal electrodes adjacent to each other with the ceramic layer sandwiched therebetween in the laminated structure act as opposing electrodes, so that distortion due to the piezoelectric effect occurs in each ceramic layer, Strain of several μm to several tens of μm occurs in the direction of arrow A in FIG. In the present embodiment, the piezoelectric element 1 is a rectangular parallelepiped having a cross section perpendicular to the strain direction of 5 mm × 5 mm and a length of 20 mm along the strain direction, and the generated strain amount when a driving voltage of 150 DCV is applied. It is 20 μm. The piezoelectric ceramic material is not limited to the lead zirconate titanate, but other materials such as lead titanate can be used.

The buckling springs 2A / 2B constituting the amplifying section are formed by pressing a stainless steel plate having a thickness of 0.08 mm and a width of 5 mm to form a bridge shape. These two buckling springs are spotted. Weld into a ring shape. A flat portion is provided on this ring so as to be a plane parallel to a vertical cross section passing through the bridge-shaped vertices of the two buckling springs 2A / 2B, and the driving end surface of the element 1 (element 1
The end faces perpendicular to the strain direction A) 3a / 3b and the ring are bonded.

In this embodiment, the overall shape is 10 mm.
It is × 5 mm × 20 mm (= 1 cm ³ ). Piezoelectric element 1
When a drive voltage of 150 DCV is applied to the
A strain of 0 μm is generated, and this strain causes the buckling springs 2A / 2B to be stretched. As a result, the buckling springs 2A / 2B are bridged with the arrow B in FIG.
A displacement of 0.3 mm occurs in the direction indicated by. Therefore, the amplification factor is 15 times. The resonance frequency in this example was 3 kHz.

On the other hand, in the conventional structure shown in FIG. 7, in the amplification mechanism having the amplification factor of 30 times using the same element as the piezoelectric element in this embodiment, the shape is 30 mm × 30 mm × 5 mm (=
It was 4.5 cm ³ ), which was 4.5 times that of this example, and its resonance frequency was 1 kHz, which was 1/3 of this example.

Although this embodiment has a lower amplification factor than the conventional amplification mechanism, it can be said that it is superior to the conventional one in terms of downsizing and high-speed response. Further, since the number of parts is small and the number of assembling steps is also small, it can be manufactured at low cost.

In this embodiment, the apex of the buckling springs 2A / 2B in the bridge shape is bent at one place as shown in FIG. 2 (a), but the present invention is not limited to this. It is not something that can be done. As shown in FIG. 2 (b), it may be bent at two places to provide a flat surface perpendicular to the displacement direction. Further, as shown in FIG. 2C, the same effect as that of the present embodiment can be obtained even if processing is performed so as to form a curved surface instead of an acute angle.

Also, an example has been described in which the two flat portions of the ring-shaped amplifying portion are both fixed to the two drive end faces 3a / 3b of the piezoelectric element 1, but the flat portion may be fixed to only one of them. Good. For example, even if the flat portion on the drive end face 3a side of the ring-shaped amplifying portion is not fixed to the element 1 but is fixed to a frame of an apparatus using this amplifying mechanism, the drive end face 3a of the element 1 is relatively fixed to this frame. If fixed so as not to cause movement, the flat portion of the ring-shaped amplifying portion is effectively fixed to the drive end surface 3a of the element 1, so that the same effect as this embodiment can be obtained.

In the first embodiment described above, the direction of displacement generation with respect to the expansion of the piezoelectric element 1 is as shown by the arrow B in FIG.
Although the amplification mechanism facing the direction of the element 1 has been described, the displacement direction can be set in the opposite direction to the first embodiment as in the second embodiment shown below. FIG. 3 is a perspective view showing the structure of the second embodiment of the present invention.

Referring to FIG. 3, in this embodiment, stainless steel end fittings 9a / 9b are adhered to both end faces 3a / 3b of the piezoelectric element 1, and buckling springs 2A / 2B are provided respectively. It differs from the first embodiment in that it is attached in a bridge shape between the two end fittings 9a / 9b, and that the apex of the bridge faces inward (toward the element 1). Buckling springs 2A / 2B and end fittings 9a
/ 9b is joined by laser welding. In the case of the present embodiment, when a driving voltage is applied to the element 1, the element 1 will be
A strain is generated in the direction of the middle arrow A, which is amplified by the extension of the buckling spring, and a displacement is amplified at the apex of the bridge of the buckling spring 2A / 2B in the direction of the arrow B in the figure.

In this embodiment, the two buckling springs 2A /
2B is not directly fixed to both drive end faces 3a / 3b of the piezoelectric element 1, but is fixed to the end fittings 9a / 9b. In this case, the end fittings 9a / 9b are not active at all. However, the buckling springs 2A / 2B are not provided with an amplifying effect, but are merely for creating a space for inwardly directing the apexes of the bridges of the buckling springs 2A / 2B.
It can be said that B is effectively directly fixed to both ends 3a / 3b of the element 1.

In the above-mentioned two embodiments, the buckling spring expands in response to the expansion of the piezoelectric element 1, but the structure exhibits an amplifying effect. However, according to the present invention, the buckling spring is compressed. As a result, the strain generated by the element 1 can be amplified. Referring to FIG. 4, which shows a perspective view of a third embodiment of the present invention, the third embodiment shown in this figure is the flat portion of the ring-shaped amplifying portion in the first embodiment (see FIG. 1). The two elements 1A / 1B from the outside of the ring
The respective drive end surfaces 3Aa / 3Bb are adhered. The other driving end surface of each of the elements 1A / 1B is fixed to the bases 4a / 4b. still,
The bases 4a / 4b are part of the housing or part of the frame of the device that uses this amplification mechanism.

In this embodiment, two piezoelectric elements 1A /
When a drive voltage is externally applied to each of 1B, each element generates strain in the direction indicated by arrow A in FIG. Then, this strain is amplified by the bending of the buckling springs 2A / 2B, and the amplified displacement in the direction indicated by arrow B in the figure is extracted at the apex of the bridge of each buckling spring. In this embodiment, when the same element and buckling spring as those in the first embodiment shown in FIG. 1 are used, the amount of deflection (displacement) at the tip of the buckling spring is 0.6 mm. Is twice as large as the example. When the displacement amount is 0.3 mm as in the first embodiment, the length of the two elements 1A / 1B can be reduced to about 1/2.
According to this embodiment, the shape is slightly larger than that of the first embodiment, but the direction of displacement can be changed, so that the adaptability to the application can be expanded.

In this embodiment, two piezoelectric elements are used to compress the buckling spring, but one element may be used.
In this case, one of the two flat portions of the ring-shaped amplification section is directly fixed to the base 4a or 4b.

Referring now to FIG. 5, which shows a perspective view of a fourth embodiment of the present invention, the fourth embodiment shown in this figure is the apex of each bridge of two buckling springs 2A / 2B. However, it differs from the third embodiment in that it faces the inside of the ring-shaped amplifying portion formed by these two buckling springs. Therefore, in this embodiment, the relationship between the strain direction of the piezoelectric elements 1A / 1B and the amplified displacement direction is opposite to that in the third embodiment.

Next, a fifth embodiment in which the present invention is applied to an amplifying mechanism using three piezoelectric elements will be described. FIG. 6 is a perspective view of the fifth embodiment of the present invention. With reference to the figure, this embodiment is different from the third embodiment shown in FIG. 4 in that a piezoelectric element 1C is further provided inside a ring-shaped amplifying portion made of two buckling springs 2A / 2B. There is. Element 1C
The two driving end faces 3Ca / 3Cb are adhered to respective flat portions provided on the ring-shaped amplifying portion. The two piezoelectric elements 1A / 1B in this embodiment are
Has a length of 10 m, which is 1/2 that of the third embodiment.
Therefore, the amount of strain generated when a driving voltage of 150 DCV is applied is half that of 10 μm.
m. On the other hand, the element 1C newly provided inside the ring-shaped amplifier has a length of 20 mm and a generated strain amount of 2 mm.
The thickness is 0 μm.

In this embodiment, the driving end surface 3Aa of the piezoelectric element 1A and the driving end surface 3Ca of the piezoelectric element 1C face each other across the flat portion of the ring-shaped amplifying portion, and the driving end surface 3Bb of the piezoelectric element 1B and the piezoelectric element 1C are opposed to each other. The drive end surface 3Cb is also structured to face each other. With such a configuration, the phase of the drive voltage applied to the two elements 1A / 1B outside the ring amplification section and the phase of the drive voltage applied to the element 1C inside the amplification section are made opposite to each other, that is, the element 1A
When 1B extends, element 1C contracts, and element 1A /
When the respective elements are driven so that the element 1C expands when the element 1B contracts, the two flat portions of the ring-shaped amplifier are always tightly supported by the element 1A and the element 1C and the element 1B and the element 1C, respectively. However, since the buckling springs 2A and 2B are deformed, the springs are less likely to be deformed even when an external force is applied to the buckling springs 2A / 2B, and the displacement control accuracy is improved.

Although all of the above embodiments are amplification mechanisms having a set of buckling springs which are displaced in opposite directions,
The number and shape of buckling springs need not be particularly symmetrical.

[0031]

As described above, the piezoelectric element displacement amplification mechanism of the present invention amplifies the strain generated by the piezoelectric element as the displacement generating source by the buckling spring directly attached to the driving end face of this element. There is.

Thus, according to the present invention, a piezoelectric element displacement amplifying mechanism which is small in size and excellent in high-speed responsiveness can be manufactured at low cost for applications that do not require a large amplification factor as compared with the conventional amplifying mechanism. Can be provided.

Further, three piezoelectric elements are used, and the two ends of the buckling spring are closely supported by the two piezoelectric elements, so that the elements adjacent to each other are driven by the drive voltages of opposite phases. If so, the displacement control accuracy can be further improved.

[Brief description of drawings]

FIG. 1 is a perspective view of a first embodiment of the present invention.

FIG. 2 is a diagram showing three examples of the shape of the buckling spring in the first embodiment of the present invention.

FIG. 3 is a perspective view of a second embodiment of the present invention.

FIG. 4 is a perspective view of a third embodiment of the present invention.

FIG. 5 is a perspective view of a fourth embodiment of the present invention.

FIG. 6 is a perspective view of a fifth embodiment of the present invention.

FIG. 7 is a perspective view of an example of a conventional piezoelectric element displacement amplification mechanism.

[Explanation of symbols]

1, 1A, 1B, 1C Piezoelectric element 2, 2A, 2B Buckling spring 3a, 3b, 3Aa, 3Bb, 3Ca, 3Cb Driving end face 4a, 4b Base 5a, 5b Hinge 6a, 6b Lever arm 7 Substrate 8a, 8b Rivet 9a , 9b End fittings 10a, 10b Hinge

Claims (6)

[Claims] 1. A piezoelectric element that generates strain by a piezoelectric effect in response to a driving voltage applied from the outside, and at least one of which one end is effectively directly fixed to one of two opposing driving end faces of the piezoelectric element. A piezoelectric element displacement amplification mechanism including one or more buckling springs. 2. A piezoelectric element, one end of which is effectively directly fixed to one of the two driving end surfaces of the piezoelectric element, and the other end of which is effectively directly fixed to the other of the two driving end surfaces, A piezoelectric element displacement amplification mechanism, comprising: at least one buckling spring mounted in a bridge shape between the two driving end surfaces of the element. 3. A first piezoelectric element and a second piezoelectric element, which are arranged so as to maintain a space in series with respect to strains respectively generated by the first piezoelectric element and the second piezoelectric element, and the first piezoelectric element and the second piezoelectric element. A piezoelectric element displacement amplification mechanism including at least one or more buckling springs provided in a bridge shape between the driving end surfaces of the opposing piezoelectric element and the driving end surfaces facing each other. 4. The piezoelectric element displacement amplifying mechanism according to claim 3, wherein a third piezoelectric element is provided in the space formed by the first piezoelectric element and the second piezoelectric element with respect to the strain. A piezoelectric element and the second piezoelectric element are arranged in series, and one driving end surface of the third piezoelectric element and one end of the buckling spring of the first piezoelectric element are fixed to the driving end surface. Is fixed via one end of the buckling spring, and the other driving end surface of the third piezoelectric element and the driving end surface of the second piezoelectric element to which the other end of the buckling spring is fixed are buckled. A piezoelectric element displacement amplification mechanism characterized by being fixed via the other end of a spring. 5. The first piezoelectric element and the second piezoelectric element are driven in the same phase, and the third piezoelectric element is driven by the first piezoelectric element.
The piezoelectric element displacement amplification mechanism driving method according to claim 4, wherein the piezoelectric element and the second piezoelectric element are driven in a phase opposite to that of the piezoelectric element. 6. The piezoelectric element displacement amplifying mechanism according to claim 2, claim 3 or claim 4, wherein a set of buckling springs made up of two buckling springs that deform in opposite directions are provided. Piezoelectric element displacement amplification mechanism.