JP4369720B2 - Piezoelectric actuator and electronic device using the same - Google Patents

Description

  The present invention relates to a piezoelectric actuator that transmits only a displacement in one direction to a moving body by a deformation of a piezoelectric element and drives the moving body, and an application thereof.

  In recent years, electronic devices have been miniaturized, and actuators used there have also been required to be miniaturized. As a typical example of this actuator, a system in which an operating member is driven via a reduction gear train by the rotational force of an electromagnetic motor is generally performed, and miniaturization of DC motors and stepping motors used therein is progressing.

On the other hand, actuators based on a new principle have been actively developed, and expectations are also high for those using piezoelectric elements with a large generated force. For example, the inertia of the working member generated when a frictional force is generated between the working member and the shaft that guides the working member so as to be movable in one direction, and the piezoelectric element provided at the tip of the shaft is periodically deformed. A method of operating the operating member by force has been developed (see, for example, Non-Patent Document 1). Further, such an actuator has been tried to be applied to a zoom mechanism and an autofocus mechanism of a camera.
Ryuichi Yoshida, Yasuhiro Okamoto, Journal of Precision Engineering, Vol. 68, NO. 5,2002

  However, the electromagnetic motor is not only difficult to miniaturize, but even if the motor is miniaturized, the torque becomes extremely weak. Therefore, a reduction gear train is required, and it is difficult to reduce the size of the mechanism itself.

  In addition, devices using the inertial force generated by the deformation of the piezoelectric element are limited in equipment to be applied because of the linear motion. In this case, there is a merit that the operating member can be operated directly, but there is a possibility that the operating part may move when a device in which the actuator is mounted is dropped or vibrated. Therefore, it is conceivable to increase the frictional force between the working member and the shaft as a countermeasure. In this case, in order to drive the working member, a large voltage must be applied to the piezoelectric element. As a result, there is a risk that the drive circuit such as a booster circuit becomes complicated and large in size. In addition, the structure that requires a shaft that guides the operating member limits the degree of freedom in design, which may hinder the installation of the device.

According to a first aspect of the present invention for solving the above-mentioned problems, a rotating body arranged rotatably, one end is fixed to the same fixing member, and the other end is in contact with the end surface in the rotation axis direction of the rotating body , Two piezoelectric elements reciprocally displaced in a tangential direction perpendicular to the radial direction of the rotating body, acceleration or speed of displacement of the two piezoelectric elements in a first direction, and a second opposite to the first direction There is a piezoelectric actuator comprising a drive circuit that supplies a drive signal to the piezoelectric element such that the acceleration or speed of the direction displacement is different and the displacement directions of the two piezoelectric elements are opposite to each other .

According to a second aspect of the present invention, in the first aspect, a rotating body that is rotatably arranged;
A fixed plate disposed in the rotation axis direction of the rotating body; two fixed ends that are in contact with the fixed plate, the other end fixed to the rotating body, and reciprocally displaced in a tangential direction perpendicular to the radial direction of the rotating body. The acceleration or speed of displacement in the first direction of the two piezoelectric elements is different from the acceleration or speed of displacement in the second direction opposite to the first direction, and the two piezoelectric elements The piezoelectric actuator is characterized by comprising a drive circuit for supplying a drive signal with displacement directions opposite to each other to the piezoelectric element .

  According to a third aspect of the present invention, in the piezoelectric actuator according to the first or second aspect, the piezoelectric element bends and deforms.

  According to a fourth aspect of the present invention, in the piezoelectric actuator according to the first or second aspect, the piezoelectric element undergoes shear deformation.

  A fifth aspect of the present invention is the piezoelectric actuator according to any one of the first to fourth aspects, wherein a restriction member for restricting a displacement amount of the piezoelectric element is provided.

  According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the cam includes a cam provided on the rotating body, and a moving body that moves linearly in conjunction with the movement of the cam. It is in the piezoelectric actuator.

  According to a seventh aspect of the present invention, there is provided an electronic apparatus including the piezoelectric actuator according to any one of the first to sixth aspects.

  According to the present invention, a specific component of the deformation of the piezoelectric element fixed to the rotating body or the fixed member is transmitted to the rotating body, the rotating body can be rotated, and the inertial force of the rotating body itself can be used as a driving force. Power is obtained. By using such a principle, current consumption can be suppressed as compared with, for example, an ultrasonic motor or an ultrasonic motor using resonance, and power is not consumed at all when stopped. By using a piezoelectric element that bends and deforms, a large deformation of the piezoelectric element can be obtained, and driving at a low voltage is possible. Further, by using a shear deformation piezoelectric element having a large piezoelectric constant, not only a large driving force can be obtained at a low voltage, but also a high frequency can be driven and a high-speed operation of the rotating body can be realized.

  By providing a regulating member that regulates the amount of displacement of these piezoelectric elements, it is possible to prevent large deformation or even destruction of the piezoelectric elements caused by dropping or vibration.

  Further, if the mechanism has a cam provided on the rotating body and a moving body that moves linearly in conjunction with the movement of the cam, the moving body can be moved directly. The autofocus mechanism and zoom mechanism can be realized with an extremely small configuration. The configuration using such a cam can not only operate a heavy moving body with a small amount of electric power, but also has a large holding force and is less likely to be displaced when a drop or vibration occurs.

  In this way, by using the piezoelectric actuator of the present invention as a drive source of an electronic device, it is possible to reduce the size and simplification of the drive circuit, reduce the size of the electronic device, reduce power consumption, and improve reliability.

  The present invention comprises a rotating body and a piezoelectric element arranged so that one end is fixed to a fixing member and the other end is in contact with the rotating body. The acceleration or speed of displacement in the first direction of the piezoelectric element and the second By causing the piezoelectric element to deform such that the acceleration or speed of the displacement in the direction is different, only the displacement component of one of the piezoelectric elements is transmitted to the rotating body, and the rotating body is driven.

  As another example, a rotating body and a piezoelectric element arranged so that one end is fixed to the rotating body and the other end is in contact with the fixing member, the acceleration or speed of displacement of the piezoelectric element in the first direction By deforming so that the acceleration or velocity of the displacement in the second direction is different, only one displacement component of the piezoelectric element is transmitted to the fixed member, and the rotating body is driven.

Here, in particular, a piezoelectric element that is bent or sheared is used. And the impact resistance is improved by providing a regulating member that regulates the displacement amount of the piezoelectric element.
In addition, by adopting a structure having a cam provided on the rotating body and a moving body that moves linearly in conjunction with the movement of the cam, the moving body can be moved directly.
(Embodiment 1)
Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of a piezoelectric actuator 10 according to Embodiment 1 of the present invention. One end of bimorphs 1 a and 1 b made of piezoelectric elements is fixed to the fixed plate 4. The inner peripheral part of the cylindrical rotating body 3 is rotatably guided by a step part 4 a provided in the thickness direction of the fixed plate 4. Here, although not shown, the rotating body 3 is brought into pressure contact with the other ends of the bimorphs 1a and 1b by a pressure spring or the like, and an appropriate frictional force is secured between the two.

  Next, the driving principle of the piezoelectric actuator 10 of the present invention will be described with reference to FIGS. In FIG. 3, the bimorph element 1 is configured, for example, by superposing and joining piezoelectric elements 6 a and 6 b polarized in a tangential direction (in the direction of the arrow in the figure) perpendicular to the radial direction of the rotating body 3. Electrodes 5a, 5b, and 5c are provided in order from the other surface side of the piezoelectric element 6a on the bonding surface and the other surface of the piezoelectric elements 6a and 6b. Here, when the electrode 5b is GND, the electrodes 5a and 5c are short-circuited, and when a voltage is applied by a drive circuit (not shown), one piezoelectric element expands and one piezoelectric element contracts, so that the bimorph element 1 is bent and displaced as a whole. Indicates. When the polarity of the voltage is changed, the direction of deformation is also reversed. Here, as shown in FIG. 3B, when the drive signal is an alternating voltage and the speed at which the voltage is raised and the speed at which the voltage is lowered are changed, the deformation speed of the bimorph element 1 is also the first direction in which the deformation occurs. And a second direction that is opposite to the first direction.

  For example, the drive signal shown in FIG. 3A is applied to the bimorph element 1. The bimorph element 1 improves durability by bonding a friction material 2 made of a resin or ceramic having excellent wear resistance to the tip of the piezoelectric element 5. Due to the deformation of the bimorph element 1, the rotating body 3 in contact with the friction material 2 also moves. However, when the deformation speed of the bimorph element 1 is high, slip occurs between the rotating body 3 and the friction material 2, and the rotating body 3. The amount of movement is very small or does not move. After the bimorph element 1 is rapidly deformed from the state of FIG. 2A to the state of FIG. 2B, it can be returned to the state of FIG. 2A more slowly than the deformation speed at that time. If there is, if it stops suddenly there, the rotating body can be rotated in the CW direction of FIG. When using the large inertial force of the rotating body 3, in order to stop the displacement of the bimorph element 1 abruptly, for example, a drive signal shown in FIG. 3C may be applied. Further, as shown in FIG. 3D, when the speed at which the voltage is raised and the speed at which the voltage is lowered are reversed with respect to the drive signal of FIG. 3A, the rotating direction of the rotating body 3 is also reversed (CCW direction). Become.

  In this way, the moving amount of the rotating body 3 generated by the deformation of the bimorph element 1 in the first direction is different from the moving amount of the rotating body 3 generated by the second direction (the direction opposite to the first direction). Such a drive signal is not limited to that shown in FIG. Appropriate ones may be adopted according to required output specifications and circuit configurations. Moreover, you may use what comprised the unimorph using elastic members, such as a piezoelectric element and a metal, instead of the bimorph element 1. FIG. The number of bimorph elements 1 is not limited.

In the present embodiment, the piezoelectric element is polarized in a tangential direction orthogonal to the radial direction of the rotating body. However, even if the polarization direction and the method of applying voltage are different, as a result, the radial direction of the rotating body Any configuration may be used as long as the deformation is generated in the tangential direction orthogonal to the line.
(Embodiment 2)
A second embodiment of the present invention will be described with reference to the drawings. FIG. 4 shows the configuration of the piezoelectric actuator 20 according to the second embodiment of the present invention. Since the basic configuration of the piezoelectric actuator 20 is the same as that shown in the first embodiment, only the differences will be described.

  In FIG. 4, one ends of the bimorph elements 1 a and 1 b formed of piezoelectric elements are fixed to support portions 7 a and 7 b provided on the side surface of the rotating body 7. An inner peripheral portion of the cylindrical rotating body 7 is rotatably guided by a step portion 4 a provided in the thickness direction of the fixed plate 4. The other ends of the bimorph elements 1a and 1b are in contact with the fixed plate 4 and are driven in the same manner as in the first embodiment, whereby the rotating body 7 is rotated. In other words, the deformation of the bimorph element 1 in the first direction is abruptly caused to slip as much as possible between the bimorph element 1 and the deformation in the second direction (the direction opposite to the first direction). The rotating body 7 is moved between the other end of the bimorph element 1 and the fixed plate 4 without causing any slippage.

Incidentally, restricting members 7c and 7d are provided on the side surface of the rotating body 7, and the bimorph element 1 is accommodated in the groove portions of the restricting members 7c and 7d. The regulating members 7c and 7d regulate the deformation amount of the bimorph element 1, and are gaps that are larger than the deformation amount due to the drive signal and smaller than the deformation amount leading to destruction. Therefore, although the groove portions of the regulating members 7c and 7d do not have any influence in normal operation, the highly reliable piezoelectric actuator 20 that regulates the deformation of the bimorph element that occurs at the time of dropping or external vibration and is not destroyed by these is provided. Realized.
(Embodiment 3)
A third embodiment of the present invention will be described with reference to the drawings. FIG. 5 is a diagram showing a part of the configuration of the piezoelectric actuator 30 according to the third embodiment of the present invention. Since the configuration is basically the same as that of the second embodiment, only the difference, that is, the relationship between the rotating body 8 and the piezoelectric element 9 and the operation of the piezoelectric element will be described. One end of the piezoelectric elements 9 a and 9 b is fixed to the lower surface of the cylindrical rotating body 8. The inner peripheral portion of the rotating body 8 is rotatably guided by a step portion 4a provided in the thickness direction of the fixed plate 4 (not shown). Here, although not shown, the rotating body 8 is brought into pressure contact with the fixed plate 4 by a pressure spring or the like, and an appropriate frictional force is secured between the two.

  Next, the driving principle of the piezoelectric actuator 30 according to the present invention will be described with reference to FIG. 6 in which the rotating body 8 is viewed from the piezoelectric elements 9a and 9b side. The piezoelectric element 9 is polarized in the tangential direction orthogonal to the radial direction of the rotating body 8 and in the direction indicated by the arrow in FIG. Electrodes 12a, 12b and 12c, 12d are provided on the surface of the piezoelectric elements 9a, 9b opposite to the rotating body 8 and the surface on the rotating body 8, respectively, and each rotating body is driven by a drive circuit (not shown). When a voltage is applied between the electrodes on the surface opposite to the surface 8 and the surface on the rotating body 8 side, the piezoelectric elements 9a and 9b undergo shear deformation. Here, when the electrodes 12b and 12d are set to GND and a voltage is applied to the electrodes 12a and 12c, the piezoelectric elements 9a and 9b are deformed as shown in FIG. 6B. Accordingly, the deformation speed of the piezoelectric elements 9a, 9b from the state of FIG. 6 (a) to the state of FIG. 6 (b) and the piezoelectric elements 9a, 9a, 9b from the state of FIG. 6 (b) to the state of FIG. The rotating body 8 rotates based on the principle shown in the second embodiment by making the deformation speed of 9b different and causing these two states to be performed alternately and continuously.

  Here, the form of the drive signal applied to the piezoelectric elements 9a and 9b may be the same as that shown in FIG. 3, but is not limited thereto. That is, it is only necessary to apply a drive signal so that the acceleration of deformation in the first direction of the piezoelectric elements 9a and 9b and the acceleration of deformation in the second direction (reverse direction) are different. May be optimized according to the output characteristics. Further, when the rotating body 8 is reversely rotated, a drive signal is applied so that the relationship between the acceleration of deformation in the first direction and the acceleration of deformation in the second direction (reverse direction) at the time of forward rotation is reversed. That's fine. In other words, there is a difference between the amount of movement of the rotating body 8 caused by the deformation of the piezoelectric element 9 in the first direction and the amount of movement of the rotating body 8 caused by the second direction (the direction opposite to the first direction). If the piezoelectric element 9 is deformed as described above, the method is not limited. The piezoelectric element 9 may be fixed to the fixed plate 4 side.

In the present embodiment, the piezoelectric element is polarized in a tangential direction orthogonal to the radial direction of the rotating body. However, even if the polarization direction and the method of applying voltage are different, as a result, the radial direction of the rotating body Any configuration may be used as long as the deformation is generated in the tangential direction orthogonal to the line.
(Embodiment 4)
This embodiment shows an example in which the piezoelectric actuator of the present invention is applied to a drive source of an electronic device. By adopting a configuration in which the pin provided on the moving body engages with the groove provided on the rotating body of the piezoelectric actuator, the moving body can move up and down as the rotating body rotates. Therefore, for example, if the moving body is a lens, a zoom mechanism, an autofocus mechanism, or the like of the camera can be realized.

  FIG. 7 shows an example using the piezoelectric actuator 10 shown in the first embodiment. A groove (cam) 3 a that is inclined with respect to the circumferential direction is provided on a side surface of the rotating body 3. A moving body 13 is disposed on the inner periphery of the rotating body 3, and a pin 14 is connected to a side surface of the moving body 13. The pin 14 is guided by a guide groove (not shown) so as to be movable only in the thickness direction of the moving body 13 (in the direction of the arrow in the figure), and is engaged with a groove (cam) 3a of the rotating body 3, so It can move in the direction of the arrow in the figure along with the rotation.

  Here, an example using the piezoelectric actuator 10 according to the first embodiment has been described, but the piezoelectric actuator is not particularly limited as long as it is based on the principle of the present invention. In addition, by combining the structures described in Embodiment Mode 2, a highly reliable electronic device can be realized.

  If the moving body of the piezoelectric actuator of the present invention is a lens, for example, it can be applied to electronic devices such as a zoom mechanism and an autofocus mechanism of a camera.

It is a figure which shows the structure of the piezoelectric actuator concerning Embodiment 1 of this invention. It is a figure which shows the mode of operation | movement of the piezoelectric element of the piezoelectric actuator concerning Embodiment 1 of this invention. It is a figure which shows the example of the drive signal of the piezoelectric actuator concerning Embodiment 1 of this invention. It is a figure which shows the structure of the piezoelectric actuator concerning Embodiment 2 of this invention. It is a figure which shows the structure of the piezoelectric actuator concerning Embodiment 3 of this invention. It is a figure which shows the drive principle of the piezoelectric actuator concerning Embodiment 3 of this invention. It is a figure which shows the example which applied the piezoelectric actuator concerning Embodiment 1 to 3 of this invention to the electronic device.

Explanation of symbols

3, 7, 8 Rotating body 4 Fixed plate 13 Moving body 14 Pin 6, 9 Piezoelectric element 5, 12 Electrode

Claims (7)

A rotating body arranged rotatably,
One end is fixed to the same fixing member arranged in the rotation axis direction of the rotating body, the other end extends in the rotation axis direction of the rotating body , contacts the end surface of the rotating body, and is orthogonal to the radial direction of the rotating body. Two piezoelectric elements that reciprocate in the tangential direction;
The acceleration or velocity of the displacement in the first direction of the two piezoelectric elements is different from the acceleration or velocity of the displacement in the second direction opposite to the first direction, and the displacement directions of the two piezoelectric elements are mutually different. A piezoelectric actuator comprising a drive circuit for supplying a drive signal in the opposite direction to the piezoelectric element. A rotating body arranged rotatably,
A fixed plate arranged in the rotation axis direction of the rotating body;
One end fixed to said rotary member, and two piezoelectric elements for reciprocally displaced in the tangential direction the other end is perpendicular to the radial direction of the rotating body in contact with rolled out the fixing plate to the fixed plate direction,
The acceleration or velocity of the displacement in the first direction of the two piezoelectric elements is different from the acceleration or velocity of the displacement in the second direction opposite to the first direction, and the displacement directions of the two piezoelectric elements are mutually different. A piezoelectric actuator comprising a drive circuit for supplying a drive signal in the opposite direction to the piezoelectric element.   The piezoelectric actuator according to claim 1, wherein the piezoelectric element is bent and deformed.   The piezoelectric actuator according to claim 1, wherein the piezoelectric element undergoes shear deformation.   The piezoelectric actuator according to any one of claims 1 to 4, further comprising a regulating member that regulates a displacement amount of the piezoelectric element. 6. The piezoelectric actuator according to claim 1, further comprising: a cam provided on the rotating body; and a moving body that linearly moves in conjunction with the movement of the cam.   The electronic device provided with the piezoelectric actuator as described in any one of Claim 1 to 6.

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