JP2010200436A - Driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving device that facilitates adjusting prepressurization in accordance with the state of a driven element and preventing a load such as a bending stress from being applied to a piezoelectric element. <P>SOLUTION: The driving device 100 having a smooth impact driving mechanism includes a piezoelectric element 103 having fixed one end and stretched by application of a voltage, a pair of pressing bodies 105 provided on the other end of the piezoelectric element 103 and having pressing forces vertical to the stretching direction of the piezoelectric element 103 and opposite directions to each other, and a driven element having a pair of walls 111a, 111b to be pressed by the pair of pressing bodies 105. The expansion/contraction of the piezoelectric element 103 causes the pair of pressing bodies 105 to smoothly impact-drive the driven element. Thus, adjustment is facilitated in accordance with the state of the driven element. Also, a pressing force is applied in a direction vertical and symmetrical to the stretching direction of the piezoelectric element 103, thereby balance is ensured in the direction of prepressurization to prevent a stress such as a bending stress from being applied to the piezoelectric element 103. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a drive device using a smooth impact drive mechanism.

  In recent years, drive devices using a smooth impact drive mechanism have been developed. The smooth impact driving mechanism is a mechanism that drives the moving body by gently driving one of the expansion and contraction of the piezoelectric element and abruptly driving the other while utilizing the inertia and frictional force of the moving body. A positioning device using such a drive mechanism has been proposed (see, for example, Patent Document 1 and Patent Document 2).

  The positioning device described in Patent Document 1 positions a target object using a moving body and an impact force generation mechanism. In this apparatus, the moving body includes an impact surface that faces the target object via an impact gap. Further, the impact force generation mechanism is composed of a piezoelectric element having one end fixed to the moving body and an inertial body provided at the other end of the piezoelectric element. In this way, accurate minute movement is performed.

  The driving device described in Patent Document 2 is connected in series to a capacitive load, and an inductive element and a resistance element that form a series resonance circuit together with the capacitive load, and a voltage applying unit that applies a rectangular waveform voltage to the series resonance circuit With. As a result, a sawtooth waveform voltage can be applied to the capacitive load with a simple configuration.

Japanese Patent Publication No. 6-87206 Japanese Patent No. 3595808

  However, in the apparatus described in the above-mentioned patent document, it is difficult to adjust the preload because the preload is applied by gravity or the like on the moving body to adjust the frictional force and enable the smooth impact drive. Further, in the conventional apparatus, the direction of the preload is biased, and when the piezoelectric element expands and contracts, bending or tensile stress is generated, which may cause damage to the piezoelectric element. The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a driving device in which preload adjustment according to the situation on the driven body side is easy and the piezoelectric element is not burdened with bending stress or the like. To do.

  (1) In order to achieve the above object, a drive device according to the present invention is a drive device having a smooth impact drive mechanism, which is fixed at one end and expands and contracts by application of a voltage; A pair of pressing bodies provided at the ends and having a pressing force perpendicular to the expansion and contraction direction of the piezoelectric element and opposite to each other; and a driven body having a pair of wall portions pressed by the pair of pressing bodies. The pair of pressing bodies smoothly drives the driven body by the expansion and contraction of the piezoelectric element.

  Thus, the drive device of the present invention drives the driven body using friction based on the pressing force from the drive side when the piezoelectric element expands and contracts. Thereby, it becomes easy to adjust according to the situation by the side of a moving body. Further, a complicated preload mechanism is not necessary. In addition, since a pressing force is applied in a direction that is perpendicular to and symmetrical with respect to the expansion / contraction direction of the piezoelectric element, the preload direction is balanced and stress such as bending is not easily applied to the piezoelectric element. Therefore, the burden on the piezoelectric element is reduced.

  (2) Moreover, the drive device of the present invention is characterized in that the pair of pressing bodies press with a force symmetrical to each other. Thereby, a bending stress is not applied to the piezoelectric element, and the burden on the piezoelectric element can be reduced.

  (3) Moreover, the drive device of the present invention is characterized in that the pair of pressing bodies are leaf springs. Thereby, the front-end | tip of a drive part can be reduced in weight. In addition, the strength of the preload can be easily adjusted.

  (4) Moreover, the drive apparatus of this invention is further provided with the elastic body which gives an elastic force as pressing force of a pair of said press body. As a result, even if the distance between the pair of wall portions and the piezoelectric element changes, if the distance between the pair of wall portions does not change, the preload can be maintained without imposing a burden on the piezoelectric element. Therefore, the present invention can be applied to various forms of driven bodies. Various forms can be adopted for the pair of wall portions. For example, a coil spring can be used as the elastic body.

  (5) Moreover, the drive apparatus of this invention is characterized by the said to-be-driven body having a preload adjustment mechanism which can adjust the preload of a pair of wall part with respect to a pair of said press body. Thereby, the preload can be finely adjusted. Although the preload can be adjusted by the pressing body, fine adjustment and the like can be further performed.

  (6) Moreover, the drive device of the present invention is characterized in that the pair of wall portions of the driven body are formed in a curved shape. This enables driving along a curved path. For example, rotational movement and meandering movement are also possible.

  According to the present invention, it becomes easy to adjust according to the situation on the moving body side, and a complicated preload mechanism is not necessary. In addition, since a pressing force is applied in a direction that is perpendicular to and symmetrical with respect to the expansion / contraction direction of the piezoelectric element, the preload direction is balanced and stress such as bending is not easily applied to the piezoelectric element.

FIG. 3 is a plan sectional view showing the drive device according to the first embodiment. FIG. 3 is a side sectional view showing the drive device according to the first embodiment. FIG. 3 is a front sectional view showing the drive device according to the first embodiment. FIG. 3 is a plan sectional view showing the operation of the drive device according to the first embodiment. FIG. 3 is a plan sectional view showing the operation of the drive device according to the first embodiment. FIG. 6 is a plan sectional view showing a drive device according to a second embodiment. FIG. 6 is a plan sectional view showing a drive device according to a third embodiment. FIG. 6 is a plan sectional view showing a drive device according to a fourth embodiment.

  Next, embodiments of the present invention will be described with reference to the drawings. In order to facilitate understanding of the description, the same reference numerals are given to the same components in the respective drawings, and duplicate descriptions are omitted.

[Embodiment 1]
(Configuration of drive unit)
1A to 1C are a plan cross-sectional view, a side cross-sectional view, and a front cross-sectional view showing the driving device 100. FIG. The views of the cross sections 1B and 1C shown in FIG. 1A viewed from the directions of the arrows respectively correspond to FIGS. 1B and 1C. The driving device 100 drives the driven body 110 by smooth impact driving. As shown in FIGS. 1A to 1C, the driving device 100 includes a fixed portion 101, a piezoelectric element 103, a pair of pressing bodies 105, a driven body 110, a base 120, and bearings 125a and 125b.

  The fixing unit 101 is fixed to the base table 120 and fixes one end of the piezoelectric element 103. One end of the piezoelectric element 103 is fixed to the fixed portion 101 by the connecting portion 102, and the other end is connected to the pair of pressing bodies 105 by the connecting portion 104. The piezoelectric element 103 expands and contracts by applying a voltage, and drives the pair of pressing bodies 105.

  The pair of pressing bodies 105 is provided at the other end of the piezoelectric element 103 and has a pressing force perpendicular to the expansion / contraction direction of the piezoelectric element 103 and opposite to each other. That is, the wall portions 111a and 111b are pressed in a well-balanced manner and a frictional force is generated, thereby enabling smooth impact driving. As described above, since the friction based on the pressing force from the driving side is used when the piezoelectric element 103 expands and contracts, it is easy to adjust according to the situation on the driven side. Further, since the pressing force is applied in a direction that is perpendicular to and symmetrical with respect to the expansion / contraction direction of the piezoelectric element 103, the preload direction is balanced, and the piezoelectric element 103 is not easily subjected to stress such as bending. Therefore, the burden on the piezoelectric element 103 is reduced. As shown in FIG. 1A, a leaf spring can be used for the pair of pressing bodies 105, and the leaf spring has an outward elastic force with respect to the walls 111a and 111b. By using a leaf spring, the strength of the preload can be easily adjusted. Further, the tip of the drive part can be reduced in weight.

  The pair of pressing bodies 105 are preferably pressed with a force symmetrical to each other. For example, the pressing direction of the pair of pressing bodies 105 is set to be horizontally opposite and the strength is the same. Thereby, the bending stress is not applied to the piezoelectric element 103, and the burden on the piezoelectric element 103 can be reduced. Furthermore, it is preferable to have a symmetrical shape. In addition, the pair of pressing bodies 105 are preferably curved so as to protrude outward. The convex portion 105a abuts against the wall portions 111a and 111b, thereby facilitating adjustment of friction and slip suitable for smooth impact driving.

  The driven body 110 has walls 111a and 111b, and is supported by the base 120 via bearings 125a and 125b. The pair of walls 111a and 111b preferably have at least a constant distance between them, and preferably form parallel straight walls. It is preferable to use the driven body 110 for a positioning table. The base table 120 is a fixed table that does not move. The driven body 110 is movably supported.

  The bearings 125 a and 125 b are a kind of ball bearing, and make the driven body 110 movable with respect to the base table 120. In order to enable minute control, it is preferable to employ a bearing, but it is not always necessary to use a bearing as long as the base 120 can support the driven body 110 movably.

(Operation of drive unit)
Next, the operation of the drive device 100 configured as described above will be described. 2A and 2B are plan sectional views showing the operation of the driving apparatus 100. FIG. For example, when a voltage is applied to the piezoelectric element 103, the piezoelectric element 103 expands as shown in FIG. 2A. The voltage applied to the piezoelectric element 103 is gradually increased and does not change abruptly. As a result, the pressed walls 111a and 111b move following the pair of pressing bodies 105 without slipping.

  After that, when the piezoelectric element 103 is gradually expanded and reaches a predetermined voltage, the voltage is rapidly decreased to contract the piezoelectric element 103. For example, it is possible to cause a steep change by reversing the polarity of the voltage. In that case, giving a steep change with the largest change width is efficient for smooth impact driving. However, it is not always necessary to reverse the polarity of the voltage, and the voltage may be lowered all at once to a predetermined value determined in advance. At that time, slip occurs between the driven body 110 and the convex portions 105a of the pair of pressing bodies, and the sent driven body 110 is maintained almost as it is due to inertia. And a pair of press body 105 returns to the original position. In this way, the driven body 110 can be moved by smooth impact driving.

  In the above example, the piezoelectric element 103 is gradually expanded and contracted rapidly by applying a voltage. However, the same applies to the case where the piezoelectric element 103 contracts and expands rapidly. Although depending on the polarization direction of the piezoelectric element 103, the applied voltage when performing smooth impact driving is either gradually increased and decreased rapidly or gradually decreased and increased rapidly. The relationship is represented by a sawtooth graph.

[Embodiment 2]
In the above embodiment, a leaf spring is cited as an example of the pair of pressing bodies, but a pressing force is not applied to the pair of pressing bodies themselves, and an elastic body having an extension force is provided between the pair of pressing bodies. Thus, a pressing force can be applied to each pressing body. In that case, a pressing force in the opposite direction can be generated by utilizing the stretching force of the provided elastic body.

  FIG. 3 is a cross-sectional plan view showing a driving device 200 using a coil spring 230 (elastic body) as a pressing force. The driving device 200 is configured in substantially the same manner as the driving device 100, but in the driving device 200, a coil spring 230 is provided between the pair of pressing bodies 105. The driving device 200 maintains the pressing force to the walls 111a and 111b by the elastic force of the coil spring 230, and enables smooth impact driving. In general, when driving is performed in an unbalanced state in which the distance between one of the walls 111a and 111b and the piezoelectric element 103 is different from the distance between the other and the piezoelectric element 103, the piezoelectric element 103 is subjected to a burden such as bending stress. However, by adopting the above-described configuration, it is possible to transmit the pressing force flexibly, and it is possible to perform a smooth impact drive without giving a load to the piezoelectric element 103.

[Embodiment 3]
In the above embodiment, the preload is obtained by the pair of pressing bodies 105, and no adjustment on the driven body 110 side is particularly necessary. However, since the fine adjustment may be necessary, the driven body 110 may include a preload adjusting mechanism 340 that can adjust the preload from the walls 111a and 111b with respect to the pair of pressing bodies 105. FIG. 4 is a plan view showing a driving device 300 having a preload adjusting mechanism 340. In FIG. 4, the preload adjusting mechanism 340 is schematically indicated by a symbol such as a screw. For example, when there is another wall on the outside of each of the walls 111a and 111b, a screw is screwed into the through hole of the wall, and the tip that is screwed through is applied to the walls 111a and 111b. The pressure to 111a, 111b can be adjusted. Thereby, the preload can be finely adjusted.

[Embodiment 4]
In the above embodiment, the walls 111a and 111b are formed in parallel and linearly, but may be formed in a curved shape. FIG. 5 is a plan view showing the driving device 400 in which the wall portion is formed in a curved shape. As shown in FIG. 5, the configuration of the driving device 400 is substantially the same as the configuration of the driving device 100, but the walls 411 a and 411 b are formed in a curved shape while maintaining a constant spacing therebetween. This enables driving along a curved path. For example, the stage can be rotated or meandered. However, in order to drive accurately, it is preferable that the space | interval of wall part 111a, 111b is constant. In this case, it is preferable that the pair of pressing bodies 105 abut on the inner surfaces of the walls 411a and 411b perpendicularly. Is preferred.

DESCRIPTION OF SYMBOLS 100 Drive apparatus 101 Fixed part 102 Connection part 103 Piezoelectric element 104 Connection part 105 A pair of press body 105a Convex part 110 Driven body 111a, 111b Wall part 120 Base stand 125a, 125b Bearing 200 Drive apparatus 230 Coil spring 300 Drive apparatus 340 Preload Adjustment mechanism 400 Driving device 411a, 411b Wall

Claims (6)

A drive device having a smooth impact drive mechanism,
A piezoelectric element that is fixed at one end and expands and contracts by application of a voltage;
A pair of pressing bodies provided at the other end of the piezoelectric element, each having a pressing force perpendicular to the expansion and contraction direction of the piezoelectric element and opposite to each other;
A driven body having a pair of wall portions pressed against the pair of pressing bodies,
The driving device according to claim 1, wherein the pair of pressing bodies smoothly drives the driven body by expansion and contraction of the piezoelectric element.   The drive device according to claim 1, wherein the pair of pressing bodies are pressed by forces symmetrical to each other.   The drive device according to claim 1, wherein the pair of pressing bodies are leaf springs.   The drive device according to claim 1, further comprising an elastic body that applies an elastic force as a pressing force of the pair of pressing bodies.   5. The driving device according to claim 1, wherein the driven body includes a preload adjusting mechanism capable of adjusting a preload of the pair of wall portions with respect to the pair of pressing bodies.   The drive device according to any one of claims 1 to 5, wherein the pair of wall portions of the driven body are formed in a curved shape.

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