JP4412663B2 - Piezoelectric actuator and electronic device using the same - Google Patents

Description

  The present invention relates to a piezoelectric actuator that changes a displacement speed or acceleration of a piezoelectric element, transmits only a displacement in one direction to a moving body, and drives the moving body, and an electronic apparatus using the piezoelectric actuator.

  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 the torque becomes extremely weak even if the motor is miniaturized. 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 operation. In this case, there is a merit that the operating member can be operated directly, but the generated force is small and there is a risk that the operating part will move if the actuator mounting device falls or vibrates. It was. Therefore, as a countermeasure, it is conceivable to increase the frictional force between the working member and the shaft. In this case, in order to drive the working member, a large voltage must be applied to the piezoelectric element. There is a risk of increasing the power and complicating and increasing the size of the drive circuit such as a booster circuit. In addition, there is a possibility that the degree of freedom in design is restricted due to the structure that requires the shaft for guiding the operating member, which may be an obstacle to mounting on the equipment.

According to a first aspect of the present invention for solving the above problem, a movable body, a piezoelectric element that expands and contracts, a fixing member that fixes the piezoelectric element, and a direction orthogonal to the direction of expansion and contraction of the piezoelectric element protrude. A friction member provided; a pressure member that applies pressure to the fixed member to apply contact pressure between the movable body and the friction member; and a drive circuit that outputs a signal for reciprocally displacing the piezoelectric element. The drive circuit is a signal for displacing the piezoelectric element so that the acceleration or velocity of the displacement in the first direction is different from the acceleration or velocity of the displacement in the second direction which is opposite to the first direction. in pressure conductive actuator and drives the movable body by outputting.

According to a second aspect of the present invention, in the piezoelectric actuator according to the first aspect, the fixing member is rotatably supported and the pressing force of the pressure member acts .

According to a third aspect of the present invention, in the piezoelectric actuator according to the first or second aspect, the fixing member is a part of the piezoelectric element .

According to a fourth aspect of the present invention, there is provided the piezoelectric actuator according to any one of the first to third aspects, an output shaft that rotates in conjunction with driving of the movable body, and the output shaft that operates in conjunction with rotation of the output shaft. The drive mechanism is characterized by having a moving body that moves in the direction of the rotation center axis .

According to a fifth aspect of the present invention, there is provided an electronic apparatus characterized in that the operating member is operated by the movement of the moving body of the piezoelectric actuator according to any one of the first to third aspects.

According to a sixth aspect of the present invention, there is provided an electronic apparatus characterized in that the operating member is operated by the moving body of the driving mechanism according to the fourth aspect.

  According to the present invention, since the piezoelectric element can be driven in a non-resonant state, a rotary type piezoelectric actuator with a small current consumption and a small driving circuit can be realized. In addition, since the support mechanism and the pressure mechanism are simple and can be easily downsized, the entire actuator can be easily downsized. The output characteristics (rotation speed, torque) can be set arbitrarily by simply changing the outer shape of the rotating body.

  In addition, linear drive can be realized by providing a drive mechanism having an output shaft that rotates in conjunction with rotation of the rotating body and a moving body that moves in the direction of the rotation center axis of the output shaft in conjunction with rotation of the output shaft. A large generated force can be output. Further, it is possible to have a large holding force that does not operate even when an impact such as a drop or vibration is applied.

  Then, the operating member is operated by the rotation of these rotating bodies, or the operating member is operated by the moving body of the driving mechanism, whereby the downsizing and low power consumption of the electronic device can be realized.

  Accordingly, the piezoelectric actuator of the present invention has a rotating body, a piezoelectric element arranged at one end fixed to a fixing member, and the other end being in contact with a side surface located on a radial extension of the rotating body, and a rotating piezoelectric element. It consists of a pressure member that applies contact pressure to the body, and rotates by displacing the acceleration or speed of displacement in the first direction of the piezoelectric element so that the acceleration or speed of displacement in the second direction is different. Drive the body.

  Here, the fixing member is supported so as to be rotatable in a radial plane of the rotating body, and the pressing force of the pressurizing member works. Alternatively, the fixing member is guided so as to be movable in the radial direction of the rotating body, and the pressing force of the pressing member is applied.

  Further, the driving mechanism has an output shaft that rotates integrally with the rotation of the rotating body, and a moving body that moves in the direction of the rotation center axis of the output shaft in conjunction with the rotation of the output shaft.

The operating member is operated by the rotation of the rotating body, or the operating member is operated by the moving body of the driving mechanism.
(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 100 according to the first embodiment of the present invention. One end of a bimorph 1 composed of a piezoelectric element is fixed to the fixing member 3. A disc-shaped rotating body 2 serving as a moving body has a central axis 2a and is rotatably supported by a bearing (not shown). A bearing portion 3a having a hole is provided at one end of the fixed member 3, and is supported so as to be rotatable about a shaft (not shown). The piezoelectric element 1 and the rotating body 2 are in pressure contact with the other end 3b of the solid member 3 by a pressure member 4 made of a leaf spring. As shown in FIG. 1, a friction member 5 such as an engineering plastic such as engineering plastics or alumina having excellent wear resistance is joined to the contact portion of the rotating body 3 of the piezoelectric element 1. good.

Next, the driving principle of the piezoelectric actuator 100 of the present invention will be described with reference to FIGS. The bimorph 1 made of a piezoelectric element is, for example, a tangential direction orthogonal to the radial direction of the rotating body 2 (
The piezoelectric elements 1a and 1b polarized in the direction of the arrow in FIG. Electrodes (not shown) are provided on the bonding surface and the other surface of the piezoelectric elements 1a and 1b. Here, the lead 2b connected to the electrode on the bonding surface of the piezoelectric elements 1a and 1b is set to GND, and the lead 2a that short-circuits the electrode on the other surface of the piezoelectric elements 1a and 1b is applied with a voltage by a drive circuit not shown When one is applied, one piezoelectric element expands and one piezoelectric element contracts, so that the piezoelectric element 1 exhibits bending displacement as a whole. When the polarity of the voltage is changed, the direction of deformation is also reversed. Here, the operation of rapidly deforming from the state of FIG. 1 (b) to the state of FIG. 1 (c) and the act of gently deforming from the state of FIG. 1 (c) to the state of FIG. 1 (b) are alternately performed. For example, in the former operation, slip occurs between the rotating body 2 and the piezoelectric element 1, and in the latter operation, the rotating body 2 also rotates as the piezoelectric element 1 is deformed, so that the rotating body moves in one direction. Actually, even if slippage and movement coexist in both operations, the rotating body 2 can be moved in one direction as a result if the ratios are different.

  In order to cause the piezoelectric element 1 to perform such driving, the drive signal is changed to an alternating voltage, and the speed at which the voltage is increased and the speed at which the voltage is decreased are changed to change the deformation speed and acceleration of the piezoelectric element 1. The first direction, which is the direction to be changed, and the second direction, which is the opposite direction to the first direction. For example, the rotation direction of the rotating body 2 can be changed by applying the drive signal shown in FIG. 2B or 2C between the leads 2a and 2b. Here, a drive signal having only + polarity is applied, but a drive signal in which + and -polarities are alternately repeated may be applied. In this case, since the piezoelectric element 1 is displaced to the left and right with the state of FIG. 1A as the center, a large displacement can be obtained.

  In this way, the moving amount of the rotating body 3 generated by the deformation of the piezoelectric element 1 in the first direction and the moving amount of the rotating body 3 generated by the second direction (the direction opposite to the first direction) are made different. 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 a bimorph element. Since a large displacement can be obtained by using the bending deformation of the piezoelectric element 1 as in this embodiment, the piezoelectric element 1 can be driven at a low voltage.

  Further, the support method is not limited to that of the present embodiment, and support methods of other embodiments described below may be used.

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 third embodiment of the present invention will be described with reference to the drawings. FIG. 3 shows the configuration of the piezoelectric actuator 200 according to the second embodiment of the present invention. Basic piezoelectric actuator 200
Since the configuration is the same as that shown in the first embodiment, only the differences will be described.

In FIG. 3, one end of the piezoelectric element 6 is fixed to one end 8 a of the fixing member 8. The disk-shaped rotating body 7 has a central shaft 7a and is rotatably supported by a bearing (not shown).
The fixed member 8 is guided by the guide members 9a and 9b and supported so as to be movable only in the radial direction of the rotating body 7. By pressing the other end 8b of the fixing member 8 with a pressing member 10 made of a coil spring, the piezoelectric element 6 and the rotating body 7 are in pressure contact. As shown in FIG. 3, a friction member 11 such as an engineering plastic such as engineering plastics or alumina having excellent wear resistance is joined to the contact portion of the piezoelectric element 6 with the rotating body 7. Also good.

  Next, the driving principle of the piezoelectric actuator 200 of the present invention will be described with reference to FIGS. The piezoelectric element 6 is polarized, for example, in the radial direction of the rotating body 2 (the direction of the arrow in FIG. 4). When a voltage is applied to an electrode (not shown) provided on a surface orthogonal to the direction orthogonal to the polarization direction of the piezoelectric element 6 by a drive circuit (not shown) through leads 12a and 12b, the piezoelectric element 6 undergoes shear deformation. . When the polarity of the voltage is changed, the direction of deformation is also reversed. Here, if the operation of rapidly deforming from the state of FIG. 3B to the state of (c) and the act of gently deforming from the state of FIG. 3C to the state of (b) are alternately performed, the former In the operation, slip occurs between the rotating body 7 and the piezoelectric element 6, and in the latter operation, the rotating body 7 also rotates with the deformation of the piezoelectric element 6, so that the rotating body moves in one direction. Actually, even if slip and movement coexist in both operations, if the ratios are different, the rotating body 7 can be moved in one direction as a result.

  In order to cause the piezoelectric element 6 to perform such driving, while changing the driving signal to an alternating voltage and changing the speed at which the voltage is raised and the speed at which the voltage is lowered, the deformation speed and acceleration of the piezoelectric element 6 are It differs depending on the first direction that is the direction of deformation and the second direction that is opposite to the first direction. For example, the rotation direction of the rotating body 7 can be changed by applying the drive signal shown in FIG. 4A or 4B between the leads 12a and 12b.

  Thus, there is a difference between the amount of movement of the rotating body 7 caused by the deformation of the piezoelectric element 6 in the first direction and the amount of movement of the rotating body 7 caused by the second direction (the direction opposite to the first direction). The driving signal is not limited to that shown in FIG. Appropriate ones may be adopted according to required output specifications and circuit configurations. As in the present embodiment, by using the shear deformation of the piezoelectric element 6, a large generated force can be obtained, and since it can be driven at a high frequency, a large torque and speed can be generated.

Further, the supporting method is not limited to the one in this embodiment, and the supporting method in another embodiment according to the present invention may be used.
(Embodiment 3)
A third embodiment of the present invention will be described with reference to the drawings. FIG. 5 shows the configuration of the piezoelectric actuator 300 according to the third embodiment of the present invention. Since the basic configuration of the piezoelectric actuator 300 is the same as that shown in the first embodiment, only the differences will be described.

  In FIG. 5, one end of the piezoelectric element 13 is fixed to the fixing member 14. The disk-shaped rotating body 15 has a central shaft 15a and is rotatably supported by a bearing (not shown). A bearing portion 14a having a hole is provided at one end of the fixing member 14, and is supported rotatably about a shaft (not shown). The piezoelectric element 13 and the rotating body 15 are in pressure contact with the other end 14b of the solid member 14 by a pressure member 16 made of a leaf spring. As shown in FIG. 5, a friction member 17 such as an engineering plastic such as engineering plastic or alumina having excellent wear resistance is joined to the contact portion of the piezoelectric element 13 with the rotating body 15. Also good.

  Next, the driving principle of the piezoelectric actuator 300 of the present invention will be described with reference to FIG. For example, the piezoelectric element 13 is polarized in a tangential direction (in the direction of the arrow in FIG. 6) perpendicular to the radial direction of the rotating body 15. When a voltage is applied to the piezoelectric element 13 by a drive circuit (not shown), the piezoelectric element 13 expands and contracts. When the polarity of the voltage is changed, the direction of deformation is reversed. If the operation of rapidly deforming from the state of FIG. 6A to the state of FIG. 6B and the act of gently deforming from the state of FIG. 6B to the state of FIG. In the former operation, slip occurs between the rotating body 15 and the piezoelectric element 13, and in the latter operation, the rotating body 15 also rotates with the deformation of the piezoelectric element 13, so that the rotating body moves in one direction. Actually, even if slip and movement coexist in both operations, if the ratios are different, the rotating body 15 can be moved in one direction as a result.

  In order to cause the piezoelectric element 13 to perform such driving, the drive signal is changed to an alternating voltage, and the speed at which the voltage is increased and the speed at which the voltage is decreased are changed, so that the deformation speed and acceleration of the piezoelectric element 13 are changed. The first direction, which is the direction to be changed, and the second direction, which is the opposite direction to the first direction. Basically, it may be the same as that shown in the first and second embodiments.

  As in the present embodiment, a large generated force can be obtained by using the expansion and contraction deformation of the piezoelectric element 13, and a large torque and speed can be obtained because the piezoelectric element 13 can be driven at a higher frequency than that using the bending displacement.

Further, the supporting method is not limited to the one in this embodiment, and the supporting method in another embodiment according to the present invention may be used.
(Embodiment 4)
Next, an example in which the piezoelectric actuator of the present invention is applied to an electronic device will be described with reference to FIG.
This embodiment shows an example in which the piezoelectric actuator of the present invention is applied to a drive source of an electronic device. The driving source includes a rotating body 20, a piezoelectric element 18 that is in pressure contact with a pressing mechanism (not shown), a fixing member 19 that supports the piezoelectric element 18, and a rotating body that is provided on the rotation center axis of the rotating body 20. The output shaft 21 that rotates integrally with the shaft 20, and the bearings 22 and 23 that guide the rotation of the output shaft 21 and the rotating body 20 with the rotating body 20 and shaft portions 21a and 21b provided integrally with the output shaft. And a moving body 23 having a female screw portion 23a that is provided on the side surface of the output shaft 21 and that engages with the external thread portion 21c, and a guide shaft that engages with a hole-shaped guide portion 23b provided in the moving body 23. 25.

  When the rotating body 20 rotates with the operation of the piezoelectric element 18, the output shaft 21 also rotates integrally, and the moving body 23 operates in the direction of the rotation center axis of the output shaft 21. The operating direction of the moving body 23 is changed by changing the rotating direction of the rotating body 20. In this manner, the inertia moment of the rotating portion is the sum of the inertia moments of the rotating body 20 and the output shaft 21, and becomes large. Therefore, even if the deformation of the piezoelectric element is completed, a large output can be obtained using this inertia. .

  Therefore, for example, if the operating body 24 joined to the hole 23c provided in the moving body 23 is a lens, a zoom mechanism, an autofocus mechanism, or the like of the camera can be realized. By adopting such a structure, since the moving mechanism of the moving body 23 is small with respect to the moving angle of the rotating body 20, a highly accurate positioning is possible, and against external impacts and vibrations. However, the mobile object 23 can realize a highly reliable electronic device that is difficult to move.

  Thus, by rotating the output shaft 21 integrally with the rotating body 20, high-accuracy positioning is possible without backlash. However, in order to take out a large output, the rotating shaft 20 can be positioned between the rotating body 20 and the output shaft 21. A reduction mechanism such as a gear may be used.

By the way, the form of the piezoelectric element 18 is not limited as long as it is based on the operation principle of the first to third embodiments according to the present invention.
(Embodiment 5)
Next, an example in which the piezoelectric actuator of the present invention is used as a linear type piezoelectric actuator will be described with reference to FIG.
This embodiment shows a configuration example of a linear type piezoelectric actuator. Instead of the rotating body shown in the first to fourth embodiments, a moving body 28 that linearly moves in the direction of arrow 30 is used as the moving body. The moving body 28 is guided by the roller member 29 so as to be movable only in the direction of the arrow 30. A friction member 29 is provided at one end of the piezoelectric element 25, and receives a pressing force from the pressing member 27 to come into contact with the moving body 28. The unpolarized portion 25a of the piezoelectric element is guided by the guide member 26 and is guided so as to be movable only in the contact pressure direction.
By the way, the form of the piezoelectric element 28 is not limited as long as it is based on the operation principle of the first to third embodiments according to the present invention. The moving body 28 can move in the direction of the arrow 30 by using the piezoelectric element 25 having such a configuration. Here, by using the non-polarized portion 25a of the piezoelectric element 25 as a fixed member, not only the number of components but also the piezoelectric actuator can be miniaturized.
By the way, even if it is not an unpolarized part, any part where the displacement of the piezoelectric element does not occur, such as a part where no drive signal is applied, may be treated as a fixed member because it does not affect the guide or pressurization of the piezoelectric element. .

  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 structure and drive signal of a piezoelectric actuator which concern on 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 drive signal 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 of this invention to the electronic device. It is a figure which shows the example which used the piezoelectric actuator of this invention as a linear type piezoelectric actuator.

Explanation of symbols

2, 7, 15, 28 Moving body 3, 8, 14 Fixed member 23 Driving body 24 Operating member 4, 10, 16 Pressure member 1, 6, 13 Piezoelectric element

Claims (5)

A piezoelectric element that expands and contracts, a fixing member that fixes and rotates the piezoelectric element, a friction member that protrudes in a direction orthogonal to the direction of expansion and contraction of the piezoelectric element, and a protrusion of the friction member A movable body provided in a direction, a pressure member that applies pressure to the fixed member to apply a contact pressure between the movable body and the friction member, and a drive circuit that outputs a signal for reciprocally displacing the piezoelectric element The drive circuit is displaced so that the acceleration or velocity of the displacement in the first direction of the piezoelectric element is different from the acceleration or velocity of the displacement in the second direction which is opposite to the first direction. A piezoelectric actuator characterized in that the moving body is driven by outputting a signal to be operated. The piezoelectric actuator according to claim 1, wherein the fixing member is a part of the piezoelectric element . A piezoelectric actuator according to claim 1, an output shaft that rotates in conjunction with driving of the movable body, and a movable body that moves in the direction of the rotation center axis of the output shaft in conjunction with rotation of the output shaft. A drive mechanism comprising: An electronic device in which an operation member is operated by movement of a moving body of the piezoelectric actuator according to claim 1. An electronic device, wherein the operating member is operated by the moving body of the driving mechanism according to claim 3 .

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