JP2008253106A - Drive unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive unit capable of improving drive characteristics of an actuator while suppressing resonance between the actuator and a casing. <P>SOLUTION: The drive unit 1 is provided with an actuator 10 having a piezoelectric element 12 and a drive shaft 14, and reciprocating the drive shaft 14 in response to the expansion/shrinkage of the piezoelectric element 12. The drive unit 1 is further provided with a protective plate 51 and a plate spring 52, a convex portion 53 protruding inward in an attaching state is provided on the protective plate 51, and the convex portion 53 contacts another end surface 12B of the piezoelectric element 12. A convex portion 54 protruding inward in an attaching state is formed on the plate spring 52, and the convex portion 54 contacts a tip surface 14c of the drive shaft 14. Thus, the protective plate 51 and the plate spring 52 sandwich the actuator 10 at point contact and support it on a fixed frame 24. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a driving apparatus using an electromechanical transducer such as a piezoelectric element, and more particularly to a driving apparatus that drives an optical member such as a small lens mounted on a small digital camera, a web camera, a mobile phone with a camera, or the like.

Conventionally, as a drive device, an electromechanical conversion element, and an actuator that has a drive shaft (drive member) attached to the electromechanical conversion element and drives the drive shaft to reciprocate according to expansion and contraction of the electromechanical conversion element, What is provided is known (for example, refer patent document 1). In such a drive device, the expansion / contraction amount of the electromechanical conversion element is increased by supporting the actuator on the housing (stationary member) so that a constant pressing force is applied to the electromechanical conversion element.
JP-A-7-298654

  However, in the drive device as described above, since both end portions of the actuator are in contact with the casing, vibration generated by the actuator is directly transmitted to the casing, and the actuator and the casing resonate. . As a result, in the drive device as described above, for example, the drive shaft may be displaced in a direction other than the expansion / contraction direction of the piezoelectric element due to an adverse effect due to the resonance.

  Therefore, an object of the present invention is to provide a drive device that can improve the drive characteristics of the actuator while suppressing the resonance between the actuator and the housing.

  In order to solve the above problems, a drive device according to the present invention has an electromechanical conversion element and a drive shaft attached to the electromechanical conversion element, and reciprocates the drive shaft according to the expansion and contraction of the electromechanical conversion element. An actuator to be driven and support means for holding the actuator in a telescopic direction and supporting the actuator on a housing are provided, and the actuator and the support means are in point contact or line contact.

  In the drive device according to the present invention, the support means supports the actuator to the case by point contact or line contact, so that vibration due to expansion and contraction of the electromechanical conversion element in the actuator can be suppressed from being transmitted to the case. . In addition, it becomes possible to bias the electromechanical conversion element in the expansion / contraction direction by holding the actuator in the expansion / contraction direction by the support means. Therefore, according to the present invention, it is possible to improve the drive characteristics of the actuator while suppressing the resonance between the actuator and the housing.

  Here, it is preferable that the supporting means is an urging means for urging the actuator in the expansion / contraction direction. In this case, the electromechanical conversion element can be positively biased in the extending and contracting direction, and the driving characteristics of the actuator can be further improved.

  Moreover, the weight member attached to the edge part on the opposite side to the edge part to which the drive shaft of an electromechanical conversion element is attached may be provided. The actuator preferably moves the driven member that frictionally engages the drive shaft.

  The drive device according to the present invention can improve the drive characteristics of the actuator while suppressing the resonance between the actuator and the housing.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or equivalent elements will be denoted by the same reference numerals, and redundant description will be omitted.

  FIG. 1 is a sectional view of a driving apparatus according to an embodiment of the present invention. As shown in FIG. 1, the driving device 1 according to the present embodiment drives the moving lens 70 using the moving lens 70 as a moving object, and includes an actuator 10 and a fixed frame (housing) that houses the actuator 10. Body) 24.

  First, the actuator 10 of the drive device 1 will be described. The actuator 10 includes a piezoelectric element (electromechanical conversion element) 12, a drive shaft 14, and a driven member 16.

  The piezoelectric element 12 is a stacked piezoelectric element. The shape of the piezoelectric element 12 is a long cylindrical shape extending in the stacking direction, and its diameter is D1. In addition, the piezoelectric element 12 is provided with two input terminals 72A and 72B, and a control unit 71 is connected via these input terminals 72A and 72B. The piezoelectric element 12 expands and contracts in the stacking direction in accordance with an electric signal input from the control unit 71. For example, when the voltage applied to the input terminals 72A and 72B is repeatedly increased or decreased, the piezoelectric element 12 repeats expansion and contraction.

  The drive shaft 14 is bonded and fixed to the piezoelectric element 12 using an adhesive (not shown) in a state where the base end portion 14a is in contact with the one end surface 12A of the piezoelectric element 12. As described above, the drive shaft 14 is attached to the piezoelectric element 12 so as to reciprocate along the longitudinal direction (axial direction) in accordance with repeated operations of expansion and contraction of the piezoelectric element 12. The drive shaft 14 is a long cylindrical member having a diameter D2 (> D1), and the axial direction of the drive shaft 14 is in the expansion / contraction direction of the piezoelectric element 12 (the direction of the arrow in the figure, hereinafter, simply referred to as “extension / contraction direction”). It is attached along. In addition, the cross-sectional shape seen from the axial direction of the drive shaft 14 is not limited to a circle, and may be an ellipse or a rectangle.

  As the material of the drive shaft 14, a light and high rigidity material is suitable, and beryllium is ideal as a material satisfying the condition. However, since this material is a rare metal, it is expensive and has poor workability. have. Therefore, in the present embodiment, a graphite composite in which graphite crystals are firmly combined, for example, carbon graphite is used.

  A graphite composite means a composite of graphite (graphite), which is a hexagonal plate-like crystal of carbon, and a substance other than graphite, and carbon graphite means a substance made of graphite and amorphous carbon. Carbon graphite, which is a graphite composite, has characteristics similar to beryllium (beryllium has a specific gravity of about 1.85 and carbon graphite has a specific gravity of about 1.8), but is relatively inexpensive unlike beryllium. It has the characteristic of being easy to process. Alternatively, a carbon resin composite in which a carbon resin is firmly combined may be used as the material of the drive shaft 14.

  The fixed frame 24 supports the actuator 10 by assembling it. Hereinafter, the support of the actuator 10 by the fixed frame 24 will be specifically described.

  The fixed frame 24 functions as a frame body or a frame member for assembling the actuator 10. The fixed frame 24 is provided with two partition parts 24B and 24C extending inward from the fixed frame 24. These partition parts 24B and 24C support the actuator 10 so that the drive shaft 14 can move along the longitudinal direction. Further, these partition parts 24 </ b> B and 24 </ b> C are parts that partition the moving region of the driven member 16, and also function as parts that support the drive shaft 14.

  A protective plate 51 formed by, for example, bending a thin plate into a U-shape is attached to the rear end of the fixed frame 24 on the right side of the figure, while a thin plate is attached to the rear end of the fixed frame 24 on the left side of the figure. A leaf spring 52 is attached which is bent in an L shape. The protective plate 51 and the leaf spring 52 hold the actuator 10 in the expansion / contraction direction and support the actuator 10 in the expansion / contraction direction.

  Each of the partition parts 24B and 24C is formed with a through hole 24A that allows the drive shaft 14 to pass therethrough. One partition portion 24B supports the drive shaft 14 in the vicinity of the portion where the piezoelectric element 12 is attached to the drive shaft 14, that is, at the position of the base end portion 14a of the drive shaft 14. The other partition portion 24 </ b> C supports the drive shaft 14 at the position of the tip end portion 14 b of the drive shaft 14.

  FIG. 1 shows a state in which the drive shaft 14 is supported at two locations of the base end portion 14a and the tip end portion 14b by the partition portions 24B and 24C, but the drive shaft 14 is supported at the base end portion 14a or the tip end. It may be supported by either one of the parts 14b. For example, by forming the through hole 24A on the partition portion 24B side larger than the outer diameter of the drive shaft 14, the drive shaft 14 is supported only by the tip portion 14b by the partition portion 24C. In addition, by forming the through hole 24A on the partition portion 24C side larger than the outer diameter of the drive shaft 14, the drive shaft 14 is supported only by the base end portion 14a by the partition portion 24B.

  Alternatively, there may be a case where partition portions 24 </ b> B and 24 </ b> C that are separate from the fixed frame 24 are attached to the fixed frame 24. Even in the case of this separate body, the same functions and effects as when integrated are obtained.

  The support member 60 is for supporting the actuator 10 on the fixed frame 24. The support member 60 is disposed between the fixed frame 24 that houses the actuator 10 and the piezoelectric element 12, and supports the actuator 10 from the side with respect to the expansion and contraction direction of the piezoelectric element 12. In this case, the actuator 10 is preferably supported from a direction orthogonal to the expansion / contraction direction of the piezoelectric element 12. The support member 60 functions as an attachment member that supports and attaches the actuator 10 from the side.

  The support member 60 is formed of an elastic body having a predetermined or higher elastic characteristic, for example, a silicone resin. The support member 60 is configured by forming an insertion hole 60A through which the piezoelectric element 12 is inserted, and is assembled to the fixed frame 24 in a state where the piezoelectric element 12 is inserted through the insertion hole 60A. The support member 60 is fixed to the fixed frame 24 by bonding with an adhesive (not shown). Further, the fixing between the support member 60 and the piezoelectric element 12 is also performed by bonding with an adhesive (not shown). By configuring the support member 60 with an elastic body, the actuator 10 can be supported so as to be movable in the expansion / contraction direction of the piezoelectric element 12. In FIG. 1, two support members 60 are illustrated on both sides of the piezoelectric element 12, but the support members 60 and 60 are illustrated in two by taking a cross section of one continuous support member 60. Is.

  Here, when the piezoelectric element 12 expands and contracts, vibration due to the expansion and contraction occurs. As described above, the actuator 10 including the piezoelectric element 12 is supported by the support member 60 from the side in the expansion and contraction direction. Vibration generated by the expansion and contraction of the element 12 is not easily transmitted to the outside of the actuator 10. Therefore, the actuator 10 is suppressed from resonating with an external member such as the fixed frame 24, and the influence of the resonance can be reduced. Therefore, the driven member 16 and the moving lens 70 can be accurately moved.

  The fixing of the support member 60 to the fixed frame 24 and the fixing to the piezoelectric element 12 may be performed by pressing the support member 60 between the fixed frame 24 and the piezoelectric element 12 and pressing the support member 60. For example, the support member 60 is formed of an elastic body, and is formed larger than between the fixed frame 24 and the piezoelectric element 12, and the support member 60 is press-fitted between the support frame 60 and the support member 60. It is disposed in close contact with the piezoelectric element 12. In this case, the piezoelectric element 12 is pressed from both sides in the direction orthogonal to the expansion / contraction direction by the support member 60, and the actuator 10 is supported.

  Incidentally, although the support member 60 is formed of silicone resin in the present embodiment, for example, the support member 60 may be formed of a spring member. That is, a spring member may be disposed between the fixed frame 24 and the piezoelectric element 12 and the actuator 10 may be supported with respect to the fixed frame 24 by the spring member.

  The driven member 16 is movably attached to the drive shaft 14 of the actuator 10 described above. The driven member 16 is attached by friction engagement with the drive shaft 14 and is movable along the longitudinal direction of the drive shaft 14. For example, the driven member 16 is engaged with the drive shaft 14 with a predetermined friction coefficient, and is pressed against the drive shaft 14 with a constant pressing force so that a constant friction force is generated during the movement thereof. It is attached. Note that the frictional force between the driven member 16 and the drive shaft 14 is such that, when a slowly changing voltage is applied to the piezoelectric element 12, the static frictional force is greater than the driving force and applied to the piezoelectric element 12. It is set so that the static friction force becomes smaller than the driving force when a voltage with a sudden change is applied.

  As shown in FIG. 6, the driven member 16 includes a main body portion 16A, a pressing portion 16B, and a sliding portion 16C. The main body portion 16A is pressed against the drive shaft 14 with a constant force by the pressing portion 16B. A V-shaped groove 16D is formed in the main body portion 16A. The drive shaft 14 is accommodated in the groove 16D while being sandwiched between the two sliding portions 16C and 16C. The sliding portions 16C and 16C are plate bodies having a V-shaped cross section, are arranged with the concave portions facing each other, and are provided with the drive shaft 14 interposed therebetween. Thus, by accommodating the drive shaft 14 in the V-shaped groove 16D, the driven member 16 can be stably attached to the drive shaft 14.

  As the pressing portion 16B, for example, a leaf spring material having an L-shaped cross section is used. The one side of the pressing portion 16B is hooked to the main body portion 16A, and the other side is arranged at a position opposite to the groove 16D, so that the drive shaft 14 accommodated in the groove 16D by the other side is connected to the main body portion 16A and the sliding portion It can be inserted together with 16C. Thereby, 16 A of main-body parts can be pressed to the drive shaft 14 side.

  Thus, the driven member 16 is frictionally engaged with the drive shaft 14 by attaching the main body portion 16A to the drive shaft 14 side with a certain force by the pressing portion 16B. That is, the driven member 16 is attached so that the main body portion 16A and the pressing portion 16B are pressed against the driving shaft 14 with a constant pressing force, and a constant frictional force is generated during the movement.

  Further, by sandwiching the drive shaft 14 by the sliding portions 16C and 16C having a V-shaped cross section, the driven member 16 comes into line contact with the drive shaft 14 at a plurality of locations, and the drive shaft 14 is stably frictioned. Can be engaged. Further, since the driven member 16 is engaged with the drive shaft 14 by a plurality of line contact states, substantially the same relationship as when the driven member 16 is engaged with the drive shaft 14 in a surface contact state. In this state, stable friction engagement can be realized.

  In FIG. 6, the sliding portion 16 </ b> C is configured by a plate body having a V-shaped cross section, but the sliding portion 16 </ b> C may be configured as a plate body having an arc-shaped cross section and brought into surface contact with the drive shaft 14. . In this case, since the driven member 16 is engaged with the driving shaft 14 in a surface contact state, the driven member 16 can be more stably frictionally engaged with the driving shaft 14.

  A voltage having a waveform shown in FIGS. 2A and 2B is applied to the piezoelectric element 12 by the controller 71. Here, FIGS. 2A and 2B show examples of pulse waveforms applied to the piezoelectric element 12. 2A shows a pulse waveform when the driven member 16 is moved in the left direction of the arrow in FIG. 1 (that is, the direction away from the piezoelectric element 12 along the drive shaft 14). (B) is a pulse waveform when moving the driven member 16 in the right direction of the arrow in FIG. 1 (that is, the direction approaching the piezoelectric element 12 along the drive shaft 14).

  When the driven member 16 is moved in the left direction of the arrow, a substantially sawtooth drive pulse is applied to the piezoelectric element 12 that rises gently from time α1 to time α2 and falls sharply at time α3 (FIG. 2). (See (A)). Therefore, from time α1 to time α2, the piezoelectric element 12 extends gently. At that time, since the drive shaft 14 moves at a moderate speed, the driven member 16 moves together with the drive shaft 14. As a result, the driven member 16 moves to the left of the arrow in FIG. At time α3, the piezoelectric element 12 is rapidly contracted, so that the drive shaft 14 moves to the right of the arrow in FIG. At that time, since the drive shaft 14 moves suddenly, only the drive shaft 14 moves while the driven member 16 stops at that position due to inertia. Accordingly, by repeatedly applying the sawtooth drive pulse shown in FIG. 2A, the driven member 16 repeatedly moves and stops in the left direction of the arrow in FIG. Can be moved to.

  On the other hand, when the driven member 16 is moved in the right direction of the arrow, a substantially sawtooth drive pulse that suddenly rises at time β1 and gently falls from time β2 to time β3 is applied to the piezoelectric element 12. (See FIG. 2B). Therefore, at the time β1, the piezoelectric element 12 expands rapidly, and the drive shaft 14 moves to the left of the arrow in FIG. At that time, since the drive shaft 14 moves suddenly, only the drive shaft 14 moves while the driven member 16 stops at that position due to inertia. From time β2 to time β3, the piezoelectric element 12 is gradually contracted. At that time, since the drive shaft 14 is gently displaced, the driven member 16 moves together with the drive shaft 14. Thereby, the driven member 16 can be moved in the right direction of the arrow of FIG. Accordingly, by repeatedly applying the sawtooth drive pulse shown in FIG. 2B, the driven member 16 repeatedly moves and stops in the right direction of the arrow in FIG. Can be moved to.

  Note that a lubricant is applied to the sliding contact portion between the drive shaft 14 and the driven member 16 in order to stabilize the operation and improve the durability when repeatedly driven. This lubricant is preferably one whose performance hardly changes depending on the temperature so that the sliding drive resistance between the drive shaft 14 and the driven member 16 does not increase even at low temperatures. Further, a type that does not generate dust that adversely affects optical components and mechanical components is preferable.

  Incidentally, the sawtooth drive pulse signal described above is schematically used for simplicity of explanation, and is actually shown in FIGS. 4 and 5 by the control unit 71 having a circuit as shown in FIG. An electric signal is input / output (this output signal is equivalent to the sawtooth drive pulse signal described above). Further, the drive frequency used is preferably about 20 to 200 kHz, more preferably 50 if it is selected in consideration of avoiding an audible frequency range in which the drive frequency is recognized as an abnormal sound and low power consumption. ~ 100 kHz is used.

  FIG. 3 is a circuit diagram of a drive circuit that operates the piezoelectric element 12. As shown in FIG. 3, the drive circuit 77 is disposed and provided in the control unit 71. The drive circuit 77 functions as a drive circuit for the piezoelectric element 12 and outputs an electric signal for driving to the piezoelectric element 12. The drive circuit 77 receives a control signal from a control signal generation unit (not shown) of the control unit 71, and amplifies the control signal by voltage or current to output an electric signal for driving the piezoelectric element 12. As the drive circuit 77, for example, an input stage having logic circuits U1 to U3 and an output stage having field effect transistors (FETs) Q1 and Q2 are used. The transistors Q1 and Q2 are configured to output H output (high potential output), L output (low potential output), and OFF output (open output) as output signals.

  4 shows an input signal inputted to the drive circuit 77, and FIG. 5 shows an output signal outputted from the drive circuit 77. 4A shows an input signal that is input when the driven member 16 is moved in the direction in which the driven member 16 approaches the piezoelectric element 12 (the right direction in FIG. 1), and FIG. 4B shows the driven member 16. Is an input signal that is input when moving in the direction away from the piezoelectric element 12 (leftward in FIG. 1). 5A shows an output signal that is output when the driven member 16 is moved in the direction in which the driven member 16 approaches the piezoelectric element 12 (the right direction in FIG. 1). FIG. 5B shows the driven signal. This is an output signal that is output when the member 16 is moved in a direction away from the piezoelectric element 12 (leftward in FIG. 1).

  The output signals in FIGS. 5A and 5B are pulse signals that turn on and off at the same timing as the input signals in FIGS. 4A and 4B. Two signals in FIGS. 5A and 5B are input to the input terminals 72 </ b> A and 72 </ b> B of the piezoelectric element 12. A signal having a trapezoidal waveform as shown in FIG. 2 may be input to the input terminals 72A and 72B. However, the piezoelectric element 12 can be operated by inputting a rectangular pulse signal as shown in FIG. . In this case, since the drive signal of the piezoelectric element 12 may be a rectangular pulse signal, signal generation is facilitated.

  The output signals in FIGS. 5A and 5B are composed of two rectangular pulse signals having the same frequency. These two pulse signals are different in phase from each other, so that the potential difference between the signals increases stepwise and decreases rapidly, or the potential difference increases rapidly and decreases stepwise. . By inputting these two signals, the expansion speed and contraction speed of the piezoelectric element 12 can be made different, and the driven member 16 can be moved.

  For example, in FIGS. 5A and 5B, one signal is set to H (high) and then lowered to L (low), and then the other signal is set to H. In these signals, when one signal becomes L, the other signal is set to H after a certain time lag tOFF has elapsed. When both the two signals are L, the output is turned off (open state).

  5A and 5B, that is, an electric signal for operating the piezoelectric element 12, a signal having a frequency exceeding the audible frequency is used. 5A and 5B, the frequency of the two signals is a frequency signal exceeding the audible frequency, for example, a frequency signal of 30 to 80 kHz, and more preferably 40 to 60 kHz. In this way, by using the frequency signal, it is possible to reduce the operating sound in the audible region of the piezoelectric element 12.

  A movable lens 70 is attached to the driven member 16 described above via a lens frame 68. The moving lens 70 constitutes a photographing optical system of the camera and is a moving object of the driving device. The moving lens 70 is integrally coupled to the driven member 16 and is provided so as to move together with the driven member 16. On the optical axis O of the moving lens 70, a fixed lens (not shown) and the like are arranged to constitute a camera optical system. An image sensor 65 is disposed on the optical axis O. The image pickup element 65 is an image pickup means for converting an image formed by the photographing optical system into an electric signal, and is constituted by a CCD, for example. The image sensor 65 is connected to the control unit 71 and outputs an image signal to the control unit 71.

  The driving device 1 is provided with a detector 75 that detects the movement position of the driven member 16. As the detector 75, for example, an optical detector is used, and a photo reflector, a photo interrupter, or the like is used. Specifically, when the detector 75 including the reflector 75A and the detection unit 75B is used, the reflector 75A is attached to the lens frame 68 formed integrally with the driven member 16, and the detection unit 75B is moved toward the reflector 75A. The detection light is emitted, and the reflected light reflected on the reflector 75A side is detected by the detection unit 75B, thereby detecting the movement positions of the driven member 16 and the moving lens 70.

  The detector 75 is connected to the control unit 71. The output signal of the detector 75 is input to the control unit 71. The control unit 71 controls the entire drive device, and includes, for example, a CPU, a ROM, a RAM, an input signal circuit, an output signal circuit, and the like. The control unit 71 includes a drive circuit for operating the piezoelectric element 12 and outputs an electrical signal for driving to the piezoelectric element 12.

  Further, as a method for controlling the movement of the moving lens 70, the moving lens 70 may be moved based on the output signal of the image sensor 65. For example, the high-frequency component of the video signal output from the image sensor 65 is detected, and the moving lens 70 is moved to a position where the level is maximum. By performing movement control of the moving lens 70 in this way, position detection by the detector 75 becomes unnecessary.

  Next, the support in the expansion / contraction direction of the actuator 10 described above will be described in more detail.

  As described above, the protective plate 51 and the leaf spring 52 are attached to the front end and the rear end of the fixed frame 24, and the actuator 10 is sandwiched and supported in the expansion / contraction direction by these.

  The protective plate 51 has a convex portion 53 that protrudes in a hemispherical shape in the attached state, and this convex portion 53 is in contact with the other end surface 12 </ b> B of the piezoelectric element 12. The leaf spring 52 is formed with a convex portion 54 that protrudes in a hemispherical shape in the attached state, and this convex portion 54 is in contact with the tip surface 14 c of the drive shaft 14. In other words, the protection plate 51 and the leaf spring 52 hold the both ends of the expansion / contraction direction in the actuator 10 by point contact and support the actuator 10 by point contact in the expansion / contraction direction.

  Further, the protection plate 51 and the leaf spring 52 sandwich the actuator 10 as described above, thereby urging the actuator 10 in the expansion / contraction direction and urging the piezoelectric element 12 in the expansion / contraction direction. That is, the piezoelectric element 12 is pressed by the protective plate 51 and the leaf spring 52 in the shrinking direction. Further, the leaf spring 52 has an elastic force in the expansion / contraction direction in the attached state, and with this elastic force, the actuator 10 is positively biased in the expansion / contraction direction, and the piezoelectric element 12 is positively expanded in the expansion / contraction direction. Is energized.

  When attaching the protection plate 51 and the leaf spring 52, first, the leaf spring 52 is attached to the fixed frame 24, and then the actuator 10 is attached to the fixed frame 24 while making point contact with the convex portion 54 of the leaf spring 52. Then, the convex portion 53 is brought into point contact with the actuator 10 while the protective plate 51 is attached to the fixed frame 24. As a result, the actuator 10 is held and supported by point contact in the expansion and contraction direction. The protective plate 51 may be attached to the fixed frame 24 first.

  Here, the above-mentioned point contact means that contact is made with a contact area sufficiently smaller than the contact area of both end faces of the actuator 10. In the drive device 1, the area of the convex portion 53 of the protection plate 51 is sufficiently smaller than the area of the other end face 12 </ b> B of the piezoelectric element 12 (for example, about 10% of the other end face 12 </ b> B). The area of the convex portion 54 is smaller than the area of the front end surface 14c of the drive shaft 14 (for example, about 10% of the front end surface 14c). Further, the point contact here substantially means a contact state in which the vibration of the actuator 10 is not easily transmitted to the fixed frame 24 as compared with the case where both ends of the actuator 10 abut.

  That is, the support of the actuator 10 in the expansion / contraction direction is not limited to the above configuration, and various configurations can be employed. Hereinafter, another example of supporting the actuator 10 in the expansion / contraction direction will be described. In the following description, the vicinity of the contact portion between the drive shaft 14 and the leaf spring 52 will be mainly described, but the same applies to the vicinity of the contact portion between the piezoelectric element 12 and the protection plate 51.

  FIG. 7 is a diagram illustrating another example of the vicinity of the contact portion between the drive shaft and the leaf spring. As shown in FIG. 7, in this other example, the tip surface 14 c of the drive shaft 14 is formed with a concave portion 55 that is cut into a hemispherical shape, and the convex portion 53 of the leaf spring 52 is formed in the concave portion 55. Is touched by point contact. In this case, the axis deviation of the actuator 10 can be prevented.

  Alternatively, the uneven relationship may be reversed. That is, as shown in FIG. 8, a concave portion 58 that is cut in a hemispherical shape is formed inside the leaf spring 52 in the attached state, and a convex portion that protrudes in a hemispherical shape on the tip surface 14 c of the pressure drive shaft 14. 59 may be formed and these may be contacted by point contact. The point of reversing the concave / convex relationship is also possible in the example described later.

  FIG. 9 is a view showing still another example of the vicinity of the contact portion between the drive shaft and the leaf spring. As shown in FIG. 9, in still another example, a convex portion 56 that protrudes in a substantially conical shape is formed inside the leaf spring 52 in the attached state, and a quadrangular pyramid is formed on the tip surface 14 c of the drive shaft 14. A concave portion 57 that is cut into a shape is formed. And the convex part 56 is engaged with the recessed part 57, and is contacting. In this case, the axis deviation of the actuator 10 can be further prevented.

  In the above embodiment, the other end surface 12B of the piezoelectric element 12 and the protective plate 51 are in point contact with each other. As shown in FIG. 11, a weight member is attached to the other end surface 12B via an adhesive or a resin material. 81 is provided, and the weight member 81 and the protection plate 51 may be in point contact with each other.

  In the driving device 1 according to the present embodiment that does not include the weight member, a space for providing the weight member is not required inside the fixed frame 24. Therefore, the fixed frame 24 can be reduced in the extending / contracting direction, and the driving device 1 can be reduced. Thinning and miniaturization can be realized. Further, since the space for providing the weight member is not necessary in this way, the piezoelectric element 12 can be formed thicker in the stacking direction, and the displacement amount of the piezoelectric element 12 can be increased and the capacitance can be reduced. It is possible to save power and to easily cope with leadless piezoelectric element 12.

  On the other hand, when the weight member is provided, a load is applied to the end surface 12B of the piezoelectric element 12 by the weight member, so that it is possible to further prevent the end surface 12B from being displaced more than the end surface 12A. In this case, for example, the resonance frequency of the actuator can be freely adjusted by adjusting the Young's modulus of the weight member.

  As described above, according to the driving device 1, the protection plate 51 and the leaf spring 52 support the actuator 10 on the fixed frame 24 by point contact, so that vibration due to expansion and contraction of the piezoelectric element 12 in the actuator 10 is transmitted to the fixed frame 24. Can be suppressed. In addition, as described above, the protection plate 51 and the leaf spring 52 pinch the actuator 10 in the expansion / contraction direction, whereby the piezoelectric element 12 can be urged in the expansion / contraction direction. Therefore, while suppressing the resonance between the actuator 10 and the fixed frame 24, the expansion / contraction amount and generated force of the piezoelectric element 12 can be increased, and the drive characteristics (for example, the displacement amount and the drive speed) of the actuator 10 can be enhanced.

  Further, as described above, the actuator 10 is biased in the expansion / contraction direction by the elastic force of the leaf spring 52, so that the piezoelectric element 12 is positively biased in the expansion / contraction direction. Can be further enhanced.

  In general, the diameters of the partition portions 24B and 24C are slightly larger than the diameter of the drive shaft 14 from the viewpoint of manufacturing and assembly, for example. The drive shaft 14 may be slightly tilted due to the posture difference (the axial direction is slightly inclined with respect to the expansion / contraction direction). Since it is supported in the expansion and contraction direction, such a fall can be prevented.

  Incidentally, in the drive device 1, as described above, in order to sandwich the actuator 10 in the expansion / contraction direction and reliably support the expansion / contraction direction, the partition portions 24 </ b> B and 24 </ b> C are thinned or either one of them, or the support member 60. Can be thinned. As a result, it is also possible to configure the drive device 1 without providing the partition portions 24B and 24C or to configure the drive device 1 without providing the support member 60 (see FIG. 10). In these cases, the fixed frame 24 can be reduced in the extending / contracting direction, and the drive device 1 can be further reduced in thickness and size.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment.

  For example, in the present embodiment, an apparatus applied to a driving device that drives a moving lens has been described. However, the present invention may be applied to a driving device that drives an object other than the moving lens (for example, a lens frame that holds the moving lens). .

  In the above-described embodiment, the protection plate 51 and the leaf spring 52 are in contact with both end faces of the actuator 10 by point contact, but are in contact with each other in an area sufficiently smaller than the area of both end faces of the actuator 10 (actuator 10 As long as the vibration of the actuator 10 is in a contact state in which the vibration of the actuator 10 is difficult to be transmitted to the fixed frame 24 as compared to the case where the two end surfaces are in contact with each other, contact may be made by line contact. Furthermore, in the said embodiment, although each contacted by one place contact in each end surface, if it is this contact state, you may contact in multiple places and may contact by surface contact.

  Moreover, in the said embodiment, although the frequency of the pulse voltage applied to the piezoelectric element 12 is made equal in the case where the moving lens 70 moves forward and backward, it may be different.

  Furthermore, although the piezoelectric element 12 is used as the electromechanical conversion element, an artificial muscle polymer or the like may be used as long as it can be expanded and contracted by inputting an electric signal.

  Further, in the above embodiment, the plate spring 52 is used as the supporting means, and the actuator 10 is positively biased in the expansion / contraction direction by the plate spring 52. Any means can be used. Further, instead of the leaf spring 52, a member that does not have a biasing force itself (for example, the same member as the protective plate 51) may be used. Incidentally, the support means may be formed integrally with the housing.

  Furthermore, in the above-described embodiment, the piezoelectric element 12 is particularly preferably supported by the fixing frame 24 via an elastic adhesive. For example, when the expansion / contraction amount of the piezoelectric element is small, Alternatively, it may be supported on the fixed frame 24 via a hard adhesive.

The application of the drive device 1 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 driving device 1, it can be driven at a high frequency of about 20 kHz, and the driven member 16 can be driven at a high speed of 2 mm / s or more. Can be moved. Therefore, even a zoom lens that needs to move about 10 mm can be moved quickly. Further, the use of the actuator 10 according to the present invention is not limited to the use of moving a moving lens such as a focus lens or a zoom lens, but may be used for moving the CCD.

It is sectional drawing which shows the drive device which concerns on embodiment. It is a wave form diagram of the drive pulse applied to a piezoelectric element. It is a circuit diagram which shows the drive circuit in the drive device which concerns on embodiment. FIG. 4 is a waveform diagram of an input signal input to the drive circuit of FIG. 3. FIG. 4 is a waveform diagram of an output signal output from the drive circuit of FIG. 3. It is sectional drawing which shows the to-be-driven member in the drive device which concerns on embodiment. It is the schematic which shows the other example of the contact part vicinity of a drive shaft and a leaf | plate spring. It is the schematic which shows the further another example of the contact part vicinity of a drive shaft and a leaf | plate spring. It is the schematic which shows the further another example of the contact part vicinity of a drive shaft and a leaf | plate spring. It is sectional drawing which shows the other example of the drive device which concerns on embodiment. It is sectional drawing which shows the other example of the drive device which concerns on embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Drive device, 10 ... Actuator, 12 ... Electromechanical conversion element (piezoelectric element), 14 ... Drive shaft, 16 ... Driven member, 24 ... Fixed frame (housing), 51 ... Protection plate (support means), 52 ... leaf spring (support means), 81 ... weight member.

Claims (4)

An electromechanical transducer and a drive shaft attached to the electromechanical transducer, and an actuator that reciprocates the drive shaft according to the expansion and contraction of the electromechanical transducer;
Supporting means for holding the actuator in the expansion / contraction direction and supporting the actuator in a housing,
The driving device according to claim 1, wherein the actuator and the support means are in point contact or line contact.   The drive device according to claim 1, wherein the support means is an urging means that urges the actuator in the expansion and contraction direction.   The drive device according to claim 1, further comprising a weight member attached to an end portion opposite to an end portion to which the drive shaft of the electromechanical conversion element is attached.   The drive device according to claim 1, wherein the actuator moves a driven member that frictionally engages the drive shaft.

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