JP2007274816A - Drive unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive unit where the effective drive distance of a driven member is extended. <P>SOLUTION: In this drive unit 1 equipped with an actuator 10 that has a drive element 15 consisting of a piezoelectric element 12 and fixed to a fixing frame 24 and a drive shaft 14 driven according to the expansion and contraction of the drive element 15, and shifts a driven member 16 frictionally engaged with the drive shaft 14 along the drive shaft 14, the fixing frame 24 supports the drive shaft 14 of the actuator 10 only in the end position opposite to the drive element 15 side of the drive shaft 14. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a drive device using an actuator, and more particularly to a drive device that drives an optical member such as a relatively small lens mounted on a small digital camera, a web camera, a mobile phone with a camera, or the like.

As a lens driving device for a digital camera or the like, a device using an actuator using an electromechanical transducer is known. For example, the actuators of Patent Documents 1 to 3 are composed of an electromechanical conversion element, a drive member (drive friction member), and the like, and the drive member is fixed to one end face in the expansion / contraction direction of the electromechanical conversion element. The driven member (engagement member) is frictionally engaged with each other. The actuator is housed in a housing, and both ends of the drive member are supported by the support portion of the housing. In the driving device, when a pulse voltage is applied to the electromechanical conversion element, the movement of the electromechanical conversion element in the extending direction and the contracting direction is transmitted to the driving member. When the electromechanical transducer is deformed at a slow speed, the driven member moves together with the drive member, and when the electromechanical transducer is deformed at a high speed, the driven member is moved to the same position due to the inertia of its mass. Stop. Therefore, by repeating the application of the pulse voltage, the relative position of the driven member with respect to the housing can be intermittently moved at a fine pitch.
JP 2002-142470 A Japanese Patent No. 3171187 JP 2002-95274 A

  However, in the above-described conventional driving device, the actuator is supported by the support portions of the housing at both ends of the drive member, so that the driven member moves to the drive element side by the support portion on the drive element side. Was restricted. Specifically, when the driven member moves to the driving element side and contacts the supporting part on the driving element side, the movement of the driven member is hindered by the supporting part, and the driven member further exceeds I couldn't move. That is, because of the support portion provided at the end of the drive member on the drive element side, the effective drive distance of the driven member is shortened at least by the thickness of the support portion. Therefore, in order to secure a desired effective driving distance, it is necessary to use a driving member in which the thickness of the support portion is added to the distance, which hinders downsizing of the driving device.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a driving device in which an effective driving distance of a driven member is extended.

  A drive device according to the present invention includes a drive element that includes an electromechanical conversion element and is fixed to a housing, and a drive member that is driven according to expansion and contraction of the drive element, and is driven to be frictionally engaged with the drive member. In a drive device including an actuator that moves a member along a drive member, the housing supports the drive member of the actuator only at an end position of the drive member opposite to the drive element side.

  In this drive device, the housing supports the drive member of the actuator only at the end position opposite to the drive element side of the drive member, and the housing supports the drive member on the drive element side end portion of the drive member. Not supported in position. Therefore, when the driven member is moved to the driving element side, there is nothing that obstructs the driven member unlike the conventional support portion, and the driven member can be moved to a position in contact with the driving element. As a result, the effective driving distance of the driving device can be increased.

  Further, the housing may include a first support portion, and the first support portion may support the driving member of the actuator at an end position on the side opposite to the driving element side of the driving member. The housing may further include a second support portion that supports the actuator at the position of the drive element. Moreover, it is preferable that a 2nd support part supports an actuator in the position of the electromechanical conversion element of a drive element.

  Moreover, it is preferable that a 2nd support part supports an actuator in the edge part position by the side of the drive member of an electromechanical conversion element. In this case, since the actuator is supported near the drive member of the entire drive element, it is possible to effectively suppress the axial deviation of the drive member.

  The drive element may include a weight portion attached to an end surface of the electromechanical conversion element opposite to the drive member side, and the second support portion may support the actuator at the position of the weight portion. Further, the drive element may be fixed to the housing on the side surface orthogonal to the drive direction of the drive element. Further, the drive element may be fixed to the housing at an end face opposite to the drive member side end face of the drive element.

  ADVANTAGE OF THE INVENTION According to this invention, the drive device with which the effective drive distance of the driven member was extended is provided.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments that are considered to be the best for carrying out the invention will be described in detail with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected about the same or equivalent element, and the description is abbreviate | omitted when description overlaps.

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 embodiment drives the moving lens 70 using the moving lens 70 as a moving object, and includes an actuator 10 and a fixed frame 24 to which the actuator 10 is assembled. Configured.
(Actuator)

First, the actuator 10 of the drive device 1 will be described. The actuator 10 includes a piezoelectric element 12 (corresponding to an electromechanical conversion element), a drive shaft 14, a driven member 16, and a weight member 18.
(Piezoelectric element)

The piezoelectric element 12 is a laminated piezoelectric element and is an electromechanical conversion element in the present invention. The piezoelectric element 12 is provided with two input terminals 72A and 72B, and the piezoelectric element 12 and the control unit 71 are connected via the 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.
(Drive shaft)

The drive shaft 14 corresponds to a drive member, and a base end portion 14a thereof is bonded and fixed 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. The drive shaft 14 is a long cylindrical member, and is attached so that the shaft is directed in the arrow direction (that is, the expansion / contraction direction of the piezoelectric element 12). The material of the drive shaft 14 is suitable for light and high rigidity, and beryllium is ideal for 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. (Here, the graphite composite means a composite of graphite, which is a hexagonal plate crystal of carbon, and a substance other than graphite, and carbon graphite means a substance made of graphite and amorphous carbon. Graphite is also called graphite.) This graphite composite, carbon graphite, has properties similar to beryllium (the specific gravity of beryllium is about 1.85 and the specific gravity of carbon graphite is about 1.8). Unlike beryllium, it is relatively inexpensive and easy to process. The shape of the drive shaft 14 is not limited to a cylindrical shape, and may be a prismatic shape.
(Weight member)

  The weight member 18 is provided on the other end surface 12B of the piezoelectric element 12 in a state where it is not supported and fixed to the fixed frame 24 by an adhesive (not shown). That is, the weight member 18 is not directly supported or fixed to the fixed frame 24, and is not supported or fixed so that the movement is restricted to the fixed frame 24 via an adhesive or a resin material. It is provided in the state. The weight member 18 applies a load to the end surface 12B of the piezoelectric element 12 to prevent the end surface 12B from being displaced more than the end surface 12A, and is preferably heavier than the drive shaft 14. Further, by providing the weight member 18 having a mass larger than that of the drive shaft 14, the expansion and contraction of the piezoelectric element 12 can be efficiently transmitted to the drive shaft 14 side. For example, when the drive shaft 14 is 8 mg and the piezoelectric element 12 is 30 mg, a 20 mg weight member 18 is used. As an adhesive for fixing the weight member 18 and the piezoelectric element 12, an elastic adhesive is preferably used. The combined portion of the piezoelectric element 12 and the weight member 18 corresponds to the drive element 15, and the weight member 18 corresponds to the weight portion of the drive element 15.

The weight member 18 is made of a soft material, so that the resonance frequency in the actuator 10 can be made sufficiently smaller than the drive frequency of the piezoelectric element 12, and the influence of resonance is reduced. As a constituent material of the weight member 18, a material having a Young's modulus smaller than that of the piezoelectric element 12 and the drive shaft 14 (for example, a material having a Young's modulus of 1 GPa or less is preferable, and a material having a 300 MPa or less is more preferable). Further, the specific gravity of the weight member 18 is preferably as high as possible in order to reduce the size of the apparatus, and is set to about 8 to 12, for example. Therefore, as the constituent material of the weight member 18, a material in which a metal powder having a large specific gravity is mixed with an elastic body such as rubber, for example, a material in which tungsten powder is mixed with urethane rubber or urethane resin is used. The weight member 18 has a Young's modulus of about 60 MPa and a specific gravity of about 11.7. When it is desired to design the volume of the weight member 18 to be as small as possible, a combination weight member 18 having a large specific gravity and a small Young's modulus is optimal, but the weight member 18 is larger than the specific gravity of the drive shaft 14 (specific gravity 1.8 or more). ) And a Young's modulus of 1 GPa or less can be used. That is, if the value obtained by dividing the specific gravity by the Young's modulus (specific gravity / Young's modulus) is 1.8 × 10 ⁻⁹ or more, it is suitable as the weight member 18.
(Fixed frame)

The actuator 10 described above is supported by being assembled to the fixed frame 24. Hereinafter, the support of the actuator 10 by the fixed frame 24 will be specifically described.
(Partition)

  The actuator 10 is supported by two partition portions 24B and 24C extending inward from the fixed frame 24 so as to be movable along the longitudinal direction. One partition 24B functions as a portion that supports the piezoelectric element 12. The other partition portion 24 </ b> C is a portion that partitions a moving region of the driven member 16 described later, and also functions as a portion that supports the drive shaft 14. The two partition parts 24B and 24C correspond to a second support part and a first support part, respectively.

  A through hole 24A is formed in each of the partition parts 24B and 24C, the drive shaft 14 is inserted into the through hole 24A of the partition part 24C, and the piezoelectric element 12 is inserted into the through hole 24A of the partition part 24B. It penetrates. One partition portion 24 </ b> B supports the piezoelectric element 12 in the vicinity of the drive shaft 14 mounting portion of the piezoelectric element 12, that is, at the end portion on the one end face 12 </ b> A side of the piezoelectric element 12. 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. When the drive shaft 14 is attached to the piezoelectric element 12, the drive shaft 14 reciprocates along its longitudinal direction in accordance with repeated operations of expansion and contraction of the piezoelectric element 12.

The fixed frame 24 having the two partition portions 24B and 24C functions as a housing for accommodating the actuator 10, and also functions as a frame or a frame member for assembling the actuator 10.
(Support member)

  The actuator 10 is supported on the fixed frame 24 by the support member 60. The support member 60 supports the actuator 10 from the side with respect to the expansion / contraction direction of the piezoelectric element 12, and is disposed between the fixed frame 24 that houses the actuator 10 and 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 shown on both sides of the piezoelectric element 12, but these support members 60, 60 are shown in two by taking a cross section of one continuous support member 60. is there.

  When the piezoelectric element 12 expands and contracts, vibration due to the expansion and contraction occurs. However, since the actuator 10 including the piezoelectric element 12 is supported by the support member 60 from the side in the expansion and contraction direction, the piezoelectric element 12 expands and contracts. The generated vibration is difficult to be transmitted to the outside of the actuator 10. For this reason, it is suppressed that the actuator 10 resonates with external members, 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 made of an elastic body, and is formed to be larger than between the fixed frame 24 and the piezoelectric element 12 and is press-fitted between them. Thereby, the support member 60 is disposed in close contact with the fixed frame 24 and the piezoelectric element 12. In this case, the piezoelectric element 12 is pressed by the support member 60 from both sides in the direction orthogonal to the expansion / contraction direction. As a result, the actuator 10 is supported.

In addition, although the case where the supporting member 60 was formed with a silicone resin was demonstrated above, you may comprise the supporting member 60 with a spring member. For example, a spring member may be arranged 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 this spring member.
(Driven member)

A 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.
(Control part)

  Here, the electric signal input from the control unit 71 to the piezoelectric element 12 will be described in more detail with reference to FIG.

  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 that gently rises from time α1 to time α2 and suddenly falls at time α3 is applied to the piezoelectric element 12 (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 to the right of the arrow in 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.

  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. Electric signals are input and output. The 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 outputs a drive electric signal for the piezoelectric element 12 by voltage or current amplification of the control signal. 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 the 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 t _OFF 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.
(Moving lens)

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.
(Detector)

  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.

  6 and 7 are diagrams showing specific examples of detectors in the driving apparatus according to the present embodiment.

  As shown in FIG. 6, the detector 75 includes, for example, a reflector 75A, a detection unit 75B, an interrupter 75C, and a detection unit 75D. The reflector 75A and the interrupter 75C are attached to the lens frame 68 and move together with the lens frame 68 and the moving lens 70. A detection unit 75B is disposed at a position facing the reflector 75A. The detection unit 75B detects the amount of reflection of light from the reflector 75A that changes with the movement of the moving lens 70, and detects the amount of movement of the moving lens 70. The detection unit D is arranged at a position where the interrupter 75C passes. The detection unit D detects the passage of the interrupter 75C and detects the passage of the moving lens 70 at a predetermined position.

  Further, as shown in FIG. 7, the reflector 75A and the detection unit 75B are arranged so that the reflector 75A approaches or separates from the detection unit 75B according to the movement of the moving lens 70, and the relative distance of the reflector 75A to the detection unit 75B. Accordingly, the moving position of the moving lens 70 may be detected. In this case, the position of the moving lens 70 can be detected linearly.

  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 structure of the driven member 16 will be described in detail with reference to FIG. FIG. 8 is a cross-sectional view of the driven member 16 taken along line VIII-VIII in FIG.

  As shown in FIG. 8, the driven member 16 includes, for example, 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. 8, the sliding portion 16 </ b> C is configured as 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.

  In the drive device 1 according to the embodiment of the present invention configured as described above, the partition portion 24B supports the actuator 10 at the position of the piezoelectric element 12, as shown in FIG. Therefore, the effective driving distance of the driven member 16 is D1. On the other hand, in the drive device having the conventional configuration shown in FIG. 9B, the partition portion 24 </ b> B supports the actuator 10 at the position of the drive shaft 14. Therefore, the effective driving distance of the driven member 16 is D2. As a result, in the driving device 1 of the present invention, the effective driving distance of the driven member 16 is extended by the length D, which is the difference between D1 and D2D in FIG. 9, as compared with the conventional driving device. That is, since the drive device 1 having the configuration according to the present invention effectively uses the length of the drive shaft 14 in the drive direction, the effective drive distance of the driven member 16 is extended. When compared with the drive device of the conventional configuration, the effective drive distance can be extended when the drive device is the same size, and when the effective drive distance is the same length, the drive shaft 14 is Since it is shortened, the apparatus can be downsized. Therefore, by adopting this driving device 1 for a small digital camera or the like, it is possible to increase the degree of freedom in designing the optical member such as a lens, and it is possible to reduce the size of the entire product.

  In addition, in the drive device having the conventional configuration shown in FIG. 9B, the partition portion 24B that supports the actuator 10 is present at the base end portion 14a of the drive shaft 14, and therefore the drive timing is set in the following process. There is also the problem of delay. When the driven member 16 moves to the right in FIG. 9 and comes into contact with the partition portion 24B, a force that pulls the drive shaft 14 toward the tip end portion 14b is generated in the driven member 16 due to the contact. As a result, the piezoelectric element 12 connected to the drive shaft 14 is also drawn toward the tip end portion 14 b of the drive shaft 14 by the driven member 16. When the driven member 16 is driven in the left direction in FIG. 9 in this state, the drive timing is delayed by the amount that the piezoelectric element 12 is attracted. On the other hand, in the case of the configuration of the present invention shown in FIG. 9A, the driven member 16 does not contact the partition portion 24B even if it moves in the right direction in FIG. Therefore, a situation in which the piezoelectric element 12 is attracted toward the tip end portion 14b of the drive shaft 14 does not occur, and the drive timing is not delayed even when the driven member 16 is driven leftward in FIG. Therefore, with the configuration of the present invention, a highly reliable driving device can be realized.

  Furthermore, the partition part 24 </ b> B supports the actuator 10 at the end part on the end face 12 </ b> A side of the piezoelectric element 12. That is, since the partition portion 24B supports the actuator 10 at a position close to the base end portion 14a of the drive shaft 14, it is possible to effectively prevent the shaft displacement of the drive shaft 14. Therefore, the driving device 1 according to the present embodiment can move the driven member 16 at high speed and stably. Therefore, by adopting the driving device 1 for a small digital camera or the like, Reliability can be improved.

  In the above-described embodiment, the partition portion 24B supports the actuator 10 at the position of the piezoelectric element 12, but is not limited to such a configuration, and may be an embodiment as shown in FIGS.

  The drive device 1A shown in FIG. The partition portion 24C in the fixed frame 124 supports the actuator 10 at the position of the distal end portion 14b of the drive shaft 14 in the same manner as the partition portion 24C in FIG. Further, the partition portion 24 </ b> B in the fixed frame 124 supports the actuator 10 at the position of the weight member 18. Even in such a configuration, when the driven member 16 moves to the base end portion 14a side of the drive shaft 14, the movement of the driven member 16 is not hindered by the partition portion 24B. The effective driving distance can be extended.

  The drive device 1 </ b> B illustrated in FIG. 11 includes a fixed frame 224. The fixed frame 224 has only the partition portion 24C and does not have the partition portion 24B described above. Therefore, the fixed frame 224 supports the drive shaft 14 of the actuator 10 only at the partition portion 24 </ b> C at the position of the tip end portion 14 b of the drive shaft 14. Further, the fixed frame 224 supports the actuator 10 at the position of the piezoelectric element 12 by the support member 60. Also in this drive device 1B, when the driven member 16 moves to the base end portion 14a side of the drive shaft 14, the driven member 16 is naturally not hindered from moving because the partition portion 24B does not exist. Therefore, the driven member 16 can move to a position where it comes into contact with the piezoelectric element 12, and the effective driving distance is extended.

  The drive device 1 </ b> C illustrated in FIG. 12 includes a fixed frame 324. The fixed frame 324 has only the partition portion 24C and does not have the partition portion 24B described above. In the actuator 10 </ b> A in the driving device 1 </ b> C, an end surface 12 </ b> B opposite to the driving shaft 14 side of the piezoelectric element 12 that is a driving element is fixed to the fixed frame 324 with an adhesive 17. Therefore, the actuator 10A is supported in a balanced manner by the fixed frame 324 at both ends thereof (that is, the end portion 14b of the drive shaft 14 and the end portion on the end face 12B side of the piezoelectric element 12). Also in this drive device 1C, when the driven member 16 moves to the base end portion 14a side of the drive shaft 14, the driven member 16 is naturally not hindered from moving because the partition portion 24B does not exist. Therefore, the driven member 16 can move to a position where it comes into contact with the piezoelectric element 12, and the effective driving distance is extended. In the driving device 1C, as long as the end of the driving element of the actuator 10 is fixed to the fixed frame 324, the driving device 1C can be appropriately changed to the aspect including the partition 24B, the support member 60, and the weight member 18 described above. .

  Note that each of the above-described embodiments shows an example of a drive device according to the present invention. The drive device according to the present invention is not limited to the drive device according to these embodiments, and the drive device according to the embodiment may be modified or otherwise changed without changing the gist described in each claim. It may be applied to. 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, only the case where the partition portion 24B and the partition portion 24C that support the drive shaft 14 are integrated with the fixed frame is shown. However, the partition portions 24B and 24C are separate from the fixed frame. May be attached to the fixed frame. Even in the case of separate bodies, the same functions and effects as in the case of being integrated can be obtained. In this case, the whole of the fixed frame and the partition portions 24B and 24C separate from the fixed frame functions as a housing for accommodating the actuator.

  Moreover, in the said embodiment, the weight member 18 is provided in the other end side in the expansion-contraction direction of the piezoelectric element 12, and this weight member 18 is made soft and heavy as it is especially preferable, However, It is not limited to this. In addition, the weight member 18 further enhances the mobility of the drive shaft 14 in the extending and contracting direction, but the weight member 18 may be omitted.

  In the above embodiment, the frequency of the pulse voltage applied to the piezoelectric element 12 is the same when the moving lens 70 moves forward and backward, but 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.

  Moreover, in the said embodiment, although the other end side in the expansion-contraction direction of the piezoelectric element 12 is made into the free end, this edge part of this other end side may be fixed to the fixed frame 24, and may be used as a fixed end.

  Furthermore, in the above-described embodiment, the electromechanical conversion element 12 is particularly preferably supported and elastically supported by the fixed frame 24 via an adhesive having elasticity. You may make it support to the fixed frame 24 through an agent.

  The application of the driving device 1 or 1A can be applied to small precision devices such as digital cameras and mobile phones. In particular, a mobile phone needs to be driven at a low voltage of 3 V or less, but by using the driving device 1 or 1A, 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 move at speed. 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 the purpose of moving a 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 a perspective view which shows the position detector in the drive device which concerns on embodiment. It is a figure which shows the modification of the position detector in the drive device which concerns on embodiment. It is sectional drawing which shows the to-be-driven member in the drive device which concerns on embodiment. It is the figure which showed the effective drive distance of a to-be-driven member, (a) is the drive device which concerns on this invention, (b) is the conventional drive device. It is sectional drawing which shows the drive device which concerns on the modification of embodiment. It is sectional drawing which shows the drive device which concerns on the modification of embodiment. It is sectional drawing which shows the drive device which concerns on the modification of embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1A, 1B, 1C ... Drive apparatus, 10, 10A ... Actuator, 12 ... Electromechanical conversion element (piezoelectric element), 14 ... Drive shaft, 14a ... Base end part of a drive shaft, 14b ... Tip part of a drive shaft, DESCRIPTION OF SYMBOLS 15 ... Drive element, 16 ... Driven member, 18 ... Weight member, 24, 124, 224, 324 ... Fixed frame, 24A ... Through-hole, 24B, 24C ... Partition part, 60 ... Support member, 65 ... Imaging element, 68 ... Lens frame, 70 ... Moving lens, 71 ... Control unit, 72A, 72B ... Input terminal

Claims (8)

A driving element including an electromechanical conversion element and fixed to a housing; and a driving member that is driven according to expansion and contraction of the driving element, and a driven member that is frictionally engaged with the driving member is used as the driving member. In a drive device comprising an actuator that moves along,
The housing supports the drive member of the actuator only at an end position of the drive member opposite to the drive element side. The housing includes a first support portion,
2. The driving device according to claim 1, wherein the first support portion supports the driving member of the actuator at an end position of the driving member opposite to the driving element side.   The drive device according to claim 1, wherein the housing further includes a second support portion that supports the actuator at a position of the drive element.   The drive device according to claim 3, wherein the second support portion supports the actuator at a position of the electromechanical conversion element of the drive element.   The drive device according to claim 4, wherein the second support portion supports the actuator at an end portion position of the electromechanical conversion element on the drive member side. The drive element has a weight portion attached to an end surface of the electromechanical conversion element opposite to the drive member side,
The drive device according to claim 3, wherein the second support portion supports the actuator at a position of the weight portion.   The drive device according to claim 1, wherein the drive element is fixed to the housing at a side surface orthogonal to a drive direction of the drive element. The driving device according to claim 1, wherein the driving element is fixed to the housing at an end surface of the driving element opposite to the driving member side end surface.

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