JP2005354832A - Actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an actuator for moving a driven member accurately while reducing the size. <P>SOLUTION: Two drive units 32A and 32B constituting the actuator are arranged in the driving direction of a driven board 30. The drive units 32A and 32B comprises piezoelectric elements 34A and 34B and drive members 36A and 36B provided integrally wherein the drive members 36A and 36B engage frictionally with the driven board 30. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an actuator, and more particularly to an actuator that is mounted on a small precision device such as a digital camera or a mobile phone and drives a zoom lens and a focus lens.

  There is an actuator using a piezoelectric element as a driving device for a lens unit of a digital camera or the like. For example, in the actuator of Patent Document 1, a driving rod is fixed to the end face of a piezoelectric element, and a lens barrel is slidably supported by the driving rod. A leaf spring is attached to the lens barrel, and a frictional force acts between the plate spring and the drive rod by the elastic force of the leaf spring. A drive pulse having a substantially sawtooth waveform is applied to the piezoelectric element, and the piezoelectric element is deformed at different speeds in the extending direction and the contracting direction. For example, when the piezoelectric element is gently deformed, the lens barrel moves together with the drive rod. Conversely, when the piezoelectric element deforms quickly, the lens barrel stops at the same position due to the inertia of its mass. Therefore, the lens barrel can be moved intermittently at a fine pitch by repeatedly applying a drive pulse having a substantially sawtooth waveform to the piezoelectric element.

  However, since the actuator described in Patent Document 1 transmits a driving force through a long drive rod, the vibration of the piezoelectric element is absorbed and attenuated by the drive rod, and the lens barrel is moved accurately. There was a problem that I could not. In particular, high-frequency vibration has a large attenuation factor due to the drive rod, and therefore the response of the lens barrel is deteriorated. Therefore, the actuator of Patent Document 1 can be controlled only with a low-frequency drive pulse, and there is a problem that the number of movements of the lens barrel per unit time is reduced. For this reason, in order to increase the moving speed of the lens barrel in the actuator of Patent Document 1, it is necessary to increase the applied voltage to increase the amount of displacement of the piezoelectric element and to increase the amount of movement of the lens barrel once. .

  In Patent Document 2, by increasing the power supply voltage of 5 V to 30 V, the amount of movement at one time is increased, and the moving speed of the lens barrel is increased. For this reason, in patent document 2, there existed a problem that a pressure | voltage rise apparatus was needed, the apparatus enlarged, and complicated control was needed.

In the actuator described in Patent Document 3, an engagement member is attached to the end face of the piezoelectric element in the displacement direction, the engagement member is frictionally engaged with the moving plate, and the lens barrel is attached to the moving plate. . Then, by applying a driving pulse to the piezoelectric element, vibration is transmitted through the engaging member, and the moving plate and the lens barrel are moved.
Japanese Patent No. 2633066 Japanese Patent Laid-Open No. 2000-50660 Japanese Patent Laid-Open No. 10-232337

  By the way, the actuators described in Patent Documents 1 to 3 include the frictional force between the drive member (the drive member and the engagement member described above) and the driven member (the lens barrel and the movable plate described above), It is necessary to set a speed difference between when the piezoelectric element is extended and when it is contracted so that the magnitude relationship with the inertial force is reversed when the piezoelectric element is extended and contracted. Therefore, there is a problem that it is very difficult to select a spring force that frictionally engages the driven member and the driving member with an appropriate friction force. In particular, in Patent Document 3, since the spring force is generated by the shape of the drive member (engagement member), it is very difficult to set an appropriate spring force. For this reason, in Patent Document 3, there is a risk that the driven member may not move accurately because the frictional force increases and the driven member does not slip, or the frictional force decreases and the driven member stops moving. was there.

  As a method for solving such a problem, the inventors of the present invention devised a method of providing a plurality of piezoelectric elements and driving members. By using this method, an appropriate frictional force can always be applied between the driving member and the driven member, and the driven member can be accurately moved.

  However, this method has a problem that the entire actuator is enlarged because a plurality of drive units are provided.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an actuator that can accurately move a driven member and can be miniaturized.

  In order to achieve the above object, the invention described in claim 1 is a piezoelectric element, a driving member integrally attached to the piezoelectric element, frictionally engaged with the driving member and extended in the driving direction. In the actuator including the driven member, a plurality of the piezoelectric elements and a driving unit including the driving member are provided along the driving direction.

  According to the first aspect of the present invention, since the plurality of drive units are provided in the drive direction, the drive units can be arranged without difficulty along the driven member, and space saving can be achieved.

  According to the first aspect of the present invention, since the driving force is transmitted from a plurality of locations to the driven member extending in the driving direction, the driven member can be moved smoothly and stably.

  According to the first aspect of the present invention, the driven member extends in the driving direction, and the friction engagement surface between the driven member and the driving member is always in a fixed positional relationship with respect to the piezoelectric element. Therefore, the friction engagement surface can always be arranged in the vicinity of the piezoelectric element. Therefore, the vibration of the piezoelectric element is not attenuated by the driving member, and can be controlled by a high frequency driving pulse. Thereby, even if it is a low voltage, a to-be-driven member can be moved at high speed.

  Furthermore, according to the first aspect of the present invention, since the plurality of piezoelectric elements and the driving member are provided, the output can be increased.

  According to a second aspect of the present invention, in the first aspect of the invention, the actuator is a lens moving actuator that moves a lens frame integrally attached to the driven member along an optical axis. And

  According to the actuator of the present invention, the plurality of drive units having the piezoelectric element and the drive member are arranged along the drive direction, so that space can be saved and the driven member can be stably and accurately provided. Can be moved.

  Hereinafter, preferred embodiments of an actuator according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a perspective view showing a configuration of a lens apparatus to which an actuator according to the present invention is applied. The actuator shown in the figure is provided inside a box-shaped case 12. A fixed lens 16 is attached to the side surface of the case 12.

  A lens frame 20 is provided inside the case 12, and a moving lens 18 such as a zoom lens is held on the lens frame 20.

  On the outer peripheral surface of the lens frame 20, an engaging portion 22 is formed so as to protrude. An arcuate groove 23 is formed in the engaging portion 22, and a guide rod 24 is engaged with the groove 23. The guide rod 24 is disposed in parallel with the optical axis of the fixed lens 16 (hereinafter simply referred to as the optical axis), and is fixed to the case 12. Further, a guide portion (not shown) is provided on the outer peripheral surface of the lens frame 20 on the opposite side of the engaging portion 22, and a guide rod 26 is inserted through a through hole formed in the guide portion. The guide bar 26 is disposed in parallel with the optical axis, like the guide bar 24, and is fixed to the case 12. As a result, the lens frame 20 is guided by the guide rods 24 and 26 and supported so as to be slidable in the optical axis direction.

  Further, a pair of fixing portions 28, 28 are formed to protrude from the outer peripheral surface of the lens frame 12, and a driven plate (corresponding to a driven member) 30 is sandwiched and fixed between the fixing portions 28, 28. The driven plate 30 is formed in an elongated rectangular shape, and is arranged so that its longitudinal direction is parallel to the optical axis. The material of the driven plate 30 is not particularly limited, but a lightweight and strong material such as ceramic is selected.

  The actuator of the present embodiment includes two drive units 32A and 32B. The drive units 32 </ b> A and 32 </ b> B are arranged on the same side (lower side in FIG. 1) with respect to the driven plate 30 and are arranged along the driven plate 30. That is, the drive units 32A and 32B are arranged in the moving direction (drive direction) of the driven plate 30.

  The drive unit 32A includes a piezoelectric element 34A, a drive member 36A, and a compression spring 38A, and the piezoelectric element 34A is disposed so that the displacement direction thereof is parallel to the optical axis. One end face (left end face in FIG. 1) in the displacement direction of the piezoelectric element 34A is brought into contact with a presser plate 40A fixed to the case 12. Further, the driving member 36A is fixed to the other end face (the end face on the right side in FIG. 1) in the displacement direction of the piezoelectric element 34A. The drive member 36A is formed in a substantially rectangular block shape, and is made of a light and rigid material, for example, ceramic, like the driven plate 30 described above. The piezoelectric element 34 </ b> A and the driving member 36 </ b> A are biased toward the driven plate 30 by the compression spring 38 </ b> A, and the driving member 30 </ b> A is frictionally engaged with the lower surface of the driven plate 30.

  On the other hand, the drive unit 32B includes a piezoelectric element 34B, a drive member 36B, and a compression spring 38B, similarly to the drive unit 32A. The piezoelectric element 34B is disposed so that the displacement direction thereof is parallel to the optical axis. One end face (left end face in FIG. 1) in the displacement direction of the piezoelectric element 34B is in contact with a presser plate 40B fixed to the case 12. Further, the driving member 36B is fixed to the other end face (the right end face in FIG. 1) in the displacement direction of the piezoelectric element 34B. Similarly to the driven plate 30 and the driving member 36A described above, the driving member 36B is made of a lightweight and highly rigid material such as ceramic. The piezoelectric element 34B and the driving member 36B are urged toward the driven plate 30 by the compression spring 38B, and the driving member 36B is frictionally engaged with the lower surface of the driven plate 30.

  Although FIG. 1 shows an example in which the piezoelectric elements 34A and 34B are biased by the compression springs 38A and 38B, the driving members 36A and 36B may be biased by the compression springs 38A and 38B. Further, the biasing means is not limited to the compression springs 38A and 38B, and may be an elastic body such as a leaf spring or rubber.

  2A and 2B show examples of drive pulses applied to the piezoelectric elements 34A and 34B. 2A is a drive pulse for moving the lens frame 20 of FIG. 1 in the right direction, and FIG. 2B is a drive pulse for moving the lens frame 20 of FIG. 1 in the left direction. .

  In the case of FIG. 2A, a substantially sawtooth drive pulse that gently rises from time α1 to time α2 and falls sharply at time α3 is applied to the piezoelectric element 34A. The piezoelectric element 34B is applied with a substantially sawtooth drive pulse that rises gently from time α1 to time α2 and suddenly falls at time α4. Therefore, from time α1 to time α2, the piezoelectric elements 34A and 34B are gently extended at the same time, so that the driving members 36A and 36B in FIG. 1 move gently in the right direction. At this time, since the driving members 36A and 36B move gently, the driven plate 30 is held by the frictional force with the driving members 36A and 36B, and moves to the left together with the driving members 36A and 36B. On the other hand, only the piezoelectric element 34A contracts rapidly at time α3, and only the piezoelectric element 34B contracts rapidly at time α4. Accordingly, at time α3 and time α4, each of the driving members 36A and 36B in FIG. 1 moves suddenly in the left direction independently. When the drive members 36A and 36B move suddenly in this way, slip occurs between the driven plate 30 and only the drive members 36A and 36B move while the driven plate 30 is stopped. Therefore, at time α3 and time α4, the piezoelectric elements 34A and 34B can be contracted and returned to the original state while the driven plate 30 is stopped. From the above, when the drive pulse of FIG. 2A is repeatedly applied, the driven plate 30 of FIG. 1 repeats the movement and the stop in the right direction, so that the lens frame 20 can be moved in the right direction.

  In the case of FIG. 2B, a substantially sawtooth drive pulse that gently falls from time α5 to time α6 and suddenly rises at time α7 is applied to the piezoelectric element 34A. Then, a substantially sawtooth drive pulse that gently falls from time α5 to time α6 and suddenly rises at time α8 is applied to the piezoelectric element 34B. Accordingly, from time α5 to time α6, the piezoelectric elements 34A and 34B are gradually and simultaneously contracted, so that the drive members 34A and 34B in FIG. 1 move slowly in the left direction. At this time, since the driving members 36A and 36B move gently, the driven plate 30 is held by the frictional force with the driving members 36A and 36B, and moves to the left together with the driving members 36A and 36B. On the other hand, only the piezoelectric element 34A rapidly expands at time α7, and only the piezoelectric element 34B expands rapidly at time α8. Accordingly, at time α7 and time α8, each of the drive members 36A and 36B in FIG. 1 moves suddenly in the right direction. When the drive members 36A and 36B move suddenly in this way, slip occurs between the driven plate 30 and only the drive members 36A and 36B move while the driven plate 30 is stopped. Therefore, at time α7 and time α8, the piezoelectric elements 34A and 34B can be extended and returned to the original state while the driven plate 30 is stopped. From the above, when the drive pulse of FIG. 2B is repeatedly applied, the driven plate 30 of FIG. 1 repeats the movement and the stop in the left direction, so that the lens frame 20 can be moved in the left direction.

  By the way, when the voltage is controlled as described above, the timing at which the piezoelectric element 34A suddenly deforms is slightly different from the timing at which the piezoelectric element 34B suddenly deforms. That is, in the case of FIG. 2A, the piezoelectric element 34A is rapidly contracted at time α3, and the piezoelectric element 34B is rapidly contracted at time α4 with a slight delay. Similarly, in the case of FIG. 2B, the piezoelectric element 34A expands rapidly at time α7, and the piezoelectric element 34B expands at time α8 with a slight delay. Therefore, when the drive member 36A moves suddenly, the drive member 36B stops, and when the drive member 36B moves suddenly, the drive member 36A stops. For this reason, the driven plate 30 is not easily moved by being driven by the driving members 36A and 36B, and the driven plate 30 can be surely stopped. Therefore, by applying a voltage like the above drive pulse, the movement and stop of the driven plate 30 can be controlled reliably, and the drive control of the driven plate 30 can be performed accurately.

  Next, the operation of the actuator configured as described above will be described.

  In the present embodiment, two drive units 32A and 32B are arranged side by side in the moving direction (ie, drive direction) of the driven plate 30. Therefore, since the drive units 32A and 32B are collectively arranged on one side of the driven plate 30, the entire lens device can be reduced in size.

  In the present embodiment, the driving force is transmitted from two places in the driving direction to the driven plate 30 extending in the driving direction. Therefore, the driving force is reliably transmitted to the driven plate 30, and the driven plate 30 can be moved smoothly.

  Furthermore, according to the present embodiment, the driven plate 30 is extended in the driving direction, and the frictional engagement surface between the driving members 36A and 36B and the driven plate 30 is always with respect to the piezoelectric elements 34A and 34B. Since the structure is maintained in a fixed positional relationship, the friction engagement surface can always be disposed in the vicinity of the piezoelectric elements 34A and 34B. As a result, the vibrations of the piezoelectric elements 34A and 34B can be reliably transmitted to the driven plate 30 and can be controlled by a high-frequency driving pulse. Therefore, the driven plate 30 can be moved at a high speed even with a low voltage.

  In addition, the shape of the waveform of the drive pulse applied to the piezoelectric elements 34A and 34B is not limited to the rectangular shape described above. For example, as shown in FIGS. 3A and 3B, drive pulses having the same shape may be simultaneously applied to the piezoelectric elements 34A and 34B. In FIG. 3A, a substantially sawtooth drive pulse that gently rises from time β1 to time β2 and falls sharply at time β3 is applied to the piezoelectric elements 34A and 34B. In FIG. 3B, a substantially sawtooth drive pulse that gently falls from time β4 to time β5 and suddenly rises at time β6 is applied to the piezoelectric elements 34A and 34B. Thus, the piezoelectric elements 34A and 34B may be rapidly deformed at the same timing.

  Moreover, although embodiment mentioned above used the driven plate 30 formed in the rectangular plate shape as a driven member, the shape of a driven member is not limited to this, A shape long in a moving direction If it is. Therefore, for example, the driven member may be formed in a columnar shape or a triangular prism shape.

  In the above-described embodiment, the two drive units 32A and 32B are provided. However, the number of drive units is not limited to two, and three or more drive units may be provided. Even when three or more drive units are provided, the drive units can be arranged side by side in the drive direction to save space, and the driven member can be moved reliably.

  Furthermore, although embodiment mentioned above demonstrated the example which drives a to-be-driven member to an optical axis direction, the drive direction of a to-be-driven member is not limited to this. For example, the lens device shown in FIG. 4 is an example of driving in a direction orthogonal to the optical axis. This lens device includes a lens frame 52 that holds a lens group including a moving lens 50 and a lens frame 56 that holds a lens group including a moving lens 54. Each lens frame 52, 56 is slidably supported by two guide rods 58, 60 arranged in the optical axis direction. The lens frames 52 and 56 are provided with cam pins 62 and 64, respectively. The cam pins 62 and 64 are engaged with cam grooves 68 and 70 formed in the moving plate 66. The moving plate 66 is supported so as to be slidable in the vertical direction in FIG. 4, and two drive units 32 </ b> A and 32 </ b> B are arranged vertically along the moving plate 66. Each drive unit 32A, 32B includes piezoelectric elements 34A, 34B and drive members 36A, 36B, and the piezoelectric elements 34A, 34B are attached so that their displacement directions are up and down. A pressing plate (not shown) is provided on the upper surface of each piezoelectric element 34A, 34B, and driving members 36A, 36B are integrally attached to the lower surface. When the voltage of the driving pulse described above is applied to the piezoelectric elements 34A and 34B, the moving plate 66 is driven in the vertical direction, and each lens frame 20 is moved in the optical axis direction. Also in the case of the lens device configured as described above, since the two drive units 32A and 32B are arranged side by side in the driving direction of the movable plate 66, space can be saved and the movable plate 66 can be reduced. It can be moved smoothly.

  In the lens apparatus shown in FIG. 5, cam pins 62 and 64 formed on the lens frames 52 and 56 are engaged with cam grooves 74 and 76 formed on the swing plate 72. A hole 78 is formed in the swing plate 72, and the swing plate 72 is swingably supported through a shaft member (not shown) inserted through the hole 78. The lens frames 52 and 56 are moved in the optical axis direction by swinging the swing plate 72. The drive units 32 </ b> A and 32 </ b> B are arranged side by side in the swing direction (that is, the drive direction) of the swing plate 72. Therefore, space can be saved and the swing plate 72 can be moved smoothly.

  The lens apparatus shown in FIG. 6 has a fixed cylinder 80, and a lens frame 84 of a moving lens 82 is supported inside the fixed cylinder 80 so as to be slidable in the optical axis direction. A driving cylinder 86 is rotatably supported outside the fixed cylinder 80, and the lens frame 84 is configured to move back and forth in the optical axis direction by rotating the driving cylinder 86. . A flange 88 is formed in the drive cylinder 86, and two drive units 32 </ b> A and 32 </ b> B are disposed along the flange 88. Also in the lens apparatus configured as described above, the drive units 32A and 32B are arranged side by side in the rotation direction (that is, the drive direction) of the drive cylinder 86, so that space can be saved and the drive cylinder 86 can be made smooth. Can be moved to.

  The application of the actuator of the present invention can be applied to small precision devices such as digital cameras and mobile phones. In particular, the cellular phone needs to be driven at a low voltage of 3 V or less, but by using the actuator of the present invention, it can be driven even at a high frequency of about 20 kHz, and the lens frame 20 can be driven at 2 mm / s or more. It can be moved at high speed. Therefore, even a zoom lens that needs to move about 10 mm can be moved quickly.

1 is an exploded perspective view showing a configuration of a lens apparatus to which an actuator according to the present invention is applied. Waveform diagram of drive pulse applied to piezoelectric element of FIG. Waveform diagram of drive pulse different from FIG. The perspective view which shows the main structures of the lens apparatus different from FIG. The perspective view which shows the main structures of the lens apparatus different from FIG. The perspective view which shows the main structures of the lens apparatus different from FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 20 ... Lens frame, 30 ... Driven plate, 32A, 32B ... Drive unit, 34A, 34B ... Piezoelectric element, 36A, 36B ... Drive member, 38A, 38B ... Compression spring

Claims (2)

In an actuator comprising a piezoelectric element, a driving member integrally attached to the piezoelectric element, and a driven member frictionally engaged with the driving member and extended in the driving direction,
An actuator comprising a plurality of drive units each including the piezoelectric element and the drive member along the drive direction.   The actuator according to claim 1, wherein the actuator is a lens moving actuator that moves a lens frame integrally attached to the driven member along an optical axis.

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