JP2007274776A - Drive unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive unit which can suppress the velocity dispersion of a driven member. <P>SOLUTION: In this drive unit 1, a drive shaft 14 is pressed at the rib-shaped projection 19 of the energizing part 17 of a leaf spring 16B, therefore this rib-shaped projection 19 can press the drive shaft 14 both when the energizing part 17 is not inclined back and forth and when inclined. Accordingly, in this drive unit 1, the fluctuation of frictional force between the driven member 16 and the drive shaft 14 is suppressed, and the suppression of the velocity dispersion of the driven member 16 is materialized. In addition, the fluctuation of frictional force between the product of the drive unit 1 where the energizing part 17 is inclined back and forth of the drive shaft 14 and the product of the drive unit 1 where it is not inclined is suppressed, so that the velocity dispersion among every product is obviously suppressed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a driving device using an electromechanical conversion element such as a piezoelectric element, and more particularly to a driving device that drives an optical member such as a small lens mounted on a small digital camera, a web camera, or a camera-equipped mobile phone.

Conventionally, a lens driving device using a piezoelectric element is described in, for example, Patent Document 1 below. The drive device described in this publication is a device that moves the lens barrel, and the lens barrel that is a driven member is frictionally engaged with the drive shaft by sandwiching the drive shaft between the lens barrel and the friction plate. It is. In the driving device, a spring for pressing the friction plate against the lens barrel is attached to the lens barrel.
JP 7-274543 A

  However, the conventional driving device described above has the following problems. That is, if the spring can be pressed uniformly in the extending direction of the drive shaft, the driven member is frictionally engaged with the drive shaft with a stable force, but the spring is driven for reasons such as a spring mounting failure. In some cases, the shaft tilted in the longitudinal direction. In this case, the pressing position of the spring in the extending direction of the drive shaft moves to the edge position of the front end portion or the rear end portion of the spring, and the frictional force between the driven member and the drive shaft changes significantly. End up. As a result, the amount of displacement and the speed of the driven member vary greatly, and this also causes the speed variation of each product.

  Therefore, the present invention has been made to solve such technical problems, and an object thereof is to provide a drive device in which speed variation of a driven member is suppressed.

  A drive device according to the present invention is a drive device in which a drive shaft is reciprocated according to expansion and contraction of an electromechanical conversion element, and a driven member frictionally engaged with the drive shaft is moved along the drive shaft. And a leaf spring having an urging portion that presses the drive shaft in the direction of the driven member, and the urging portion of the leaf spring is driven in a cross section orthogonal to the extending direction. The pressing portion includes a pressing portion that is convex toward the shaft side, and the biasing portion presses the drive shaft at the pressing portion.

  In this drive device, the drive shaft is pressed at the pressing portion of the urging portion of the leaf spring. The pressing portion is a portion that is convex toward the drive shaft side in a cross section orthogonal to the extending direction of the urging portion. Therefore, even when the urging portion is not inclined in the front-rear direction of the drive shaft or when it is inclined, the drive shaft can be pressed by this pressing portion. Therefore, in this drive device, the frictional force blur between the driven member and the drive shaft is suppressed, and the speed variation of the driven member is suppressed.

  Moreover, it is preferable that a press part is a rib-shaped protrusion extended along the extension direction of an urging | biasing part. In this case, it is possible to easily design the pressing portion that presses the drive shaft as compared with the bump-shaped protrusion.

  Further, the pressing portion may be a curved surface portion provided on the urging portion of the leaf spring. In this case, even if the urging portion is greatly inclined in the front-rear direction of the drive shaft, the drive shaft can be pressed by the pressing portion, so that the frictional force between the driven member and the drive shaft is blurred. Suppressed with higher accuracy.

  Further, the urging portion of the leaf spring may be a mode in which the driving shaft is pressed through a covering member having a substantially V-shaped cross section that is covered along the driving shaft. In this case, the frictional force on the drive shaft is increased.

  Further, it is preferable that the urging portion of the leaf spring and the covering member are in point contact. In this case, the frictional force between the driven member and the drive shaft is stabilized.

  ADVANTAGE OF THE INVENTION According to this invention, the drive device by which suppression of the speed variation of the to-be-driven member was achieved 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, 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 is bonded and fixed using an adhesive 27 with the base end 14 a in contact with the one end surface 12 </ b> A 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 the adhesive 20. 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 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 has a drive shaft 14 supported by two partition portions 24B and 24C extending inward from the fixed frame 24 so as to be movable along the longitudinal direction. These partition portions 24B and 24C are portions that partition a moving region of the driven member 16 described later, and also function as portions that support the drive shaft 14. The fixed frame 24 functions as a housing for accommodating the actuator 10, and also functions as a frame or a frame member for assembling the actuator 10.

  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 24 </ b> B supports the drive shaft 14 in the vicinity of the piezoelectric element 12 mounting portion of the drive shaft 14, that is, at the position of the base end portion 14 a 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. 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.

  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 in the partition portion 24B 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. Further, by forming the through hole 24A of the partition portion 24C 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.

1 shows the case where the partition portions 24B and 24C for supporting the drive shaft 14 are integrated with the fixed frame 24, these partition portions 24B and 24C are separate from the fixed frame 24. You may attach to the fixed frame 24 and provide. Even in the case of separate bodies, functions and effects similar to those in the case of being integrated can be obtained.
(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 adhesion with an adhesive 61. Further, the fixing between the support member 60 and the piezoelectric element 12 is also performed by bonding with an adhesive. 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.

  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 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 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 1. 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 1 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 leaf spring 16B, and a sliding portion (covering member) 16C.

  The main body portion 16A is pressed against the drive shaft 14 with a constant force by a leaf spring 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.

  The leaf spring 16B has a substantially L-shaped cross section, and one end 16a is hooked to the main body 16A, and the biasing portion 17 on the other end 16b side is a groove forming surface 16c of the main body 16A. It extends parallel to. Further, the urging portion 17 extends in a direction (Y direction in FIG. 8) intersecting the drive shaft 14 extending in the X direction in FIG. 8 so as to face the groove 16D. Therefore, the leaf spring 16B sandwiches the drive shaft 14 together with the main body portion 16A and the sliding portion 16C, and the biasing portion 17 presses the drive shaft 14 accommodated in the groove 16D in the direction of the main body portion 16A.

  Thus, since the driven member 16 is attached so as to press the driving shaft 14 with a constant force via the sliding portion 16C, the driven member 16 is frictionally engaged with the driving shaft 14. That is, in the driven member 16, the sliding portion 16C is pressed against the drive shaft 14 with a constant pressing force, and a constant frictional force is generated during the movement.

  Since the sliding portion 16C has a V-shaped cross section, the driven member 16 comes into line contact with the driving shaft 14 at a plurality of locations, and can be stably frictionally engaged with the driving shaft 14. Further, an increase in the frictional force with respect to the drive shaft 14 is realized as compared with the case where the leaf spring 16B directly contacts the drive shaft 14. Further, since the driven member 16 is engaged with the drive shaft 14 by a plurality of line contact states, the relationship is substantially the same as when the driven member 16 is engaged with the drive shaft 14 in a surface contact state. Thus, a stable friction engagement is realized. In FIG. 8, 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 may be 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.

  Note that the lower sliding portion 16C shown in FIG. 8 is attached so as to stick to the inside of the groove 16D formed in the main body portion 16A. The part 16A may be integrally formed by insert molding. In this case, the displacement of the sliding portion 16C with respect to the main body portion 16A does not substantially occur, so that more stable friction engagement and driving characteristics can be obtained. In addition, the manufacturing process can be simplified and the manufacturing time can be shortened by reducing the number of parts.

  Here, a rib-like projection 19 is formed on the biasing portion 17 on the drive shaft 14 side, and the drive shaft 14 is pressed by the rib-like projection 19 via the sliding portion 16C. Hereinafter, the rib-shaped protrusion 19 will be described with reference to FIG. FIG. 9 is a cross-sectional view of the urging portion 17 shown in FIG. 8 taken along the line IX-IX, that is, a cross-sectional view orthogonal to the extending direction of the urging portion 17.

  As shown in FIG. 9, the urging portion 17 is a half protruding toward the drive shaft 14 in a cross section (XZ cross section) orthogonal to the extending direction (Y direction) of the urging portion 17. A circular pressing portion 17a is formed, and the pressing portion 17a is formed over the entire length of the urging portion 17, so that a dome-shaped rib-like projection 19 is formed along the extending direction of the urging portion 17. ing. That is, the rib-like protrusion 19 of the urging portion 17 is formed along a direction (Y direction in the figure) orthogonal to the drive shaft 14, as with the urging portion 17.

  9, the rib-like protrusion 19 of the urging portion 17 extending in the Y direction in the drawing extends in the X direction in the drawing, and the upper sliding portion 16C having an inverted V-shaped cross section and the drawing. A point contact is made substantially at the position of the point P. By such point contact, even when the biasing portion 17 is inclined by a predetermined angle α (α> 0 °) in the front-rear direction (X direction in the figure) of the drive shaft 14, the sliding portion 16C and the drive shaft 14 is suppressed. Even if the urging portion 17 is not inclined in the front-rear direction of the drive shaft 14 (see the solid line in FIG. 9) or is inclined (see the two-dot chain line in FIG. 9), the pressing portion 17a (that is, This is because the rib-like projections 19) press the drive shaft 14, and the pressing position and pressing force are not substantially changed.

  On the other hand, as shown in FIG. 10, when the pressing portion as described above is not formed in the biasing portion, the biasing portion 17Z is not inclined in the front-rear direction of the drive shaft 14 (FIG. 10). The pressing position and the pressing force of the urging portion 17Z are greatly changed between the case of being inclined (see the solid line) and the case of being inclined (see the two-dot chain line in FIG. 10). That is, when the urging portion 17Z is not inclined in the front-rear direction of the drive shaft 14, the urging portion 17Z has a uniform pressing force in the X direction over the entire lower surface (surface on the drive shaft 14 side). However, when the biasing portion 17Z is inclined by a predetermined angle α in the front-rear direction of the drive shaft 14, the pressing force concentrates on one edge position Q on the lower surface thereof. As a result, the frictional force between the driven member 16 and the drive shaft 14 changes significantly. Such a change in the frictional force causes a large variation in the displacement amount and speed of the driven member 16, and also causes a variation in speed for each product.

  That is, in the drive device 1, the drive shaft 14 is pressed by the rib-like protrusion 19 of the urging portion 17 of the leaf spring 16 </ b> B, so that even when the urging portion 17 is not inclined in the front-rear direction of the drive shaft 14. Even in this case, the drive shaft 14 can be pressed by the rib-shaped protrusion 19. Therefore, in this drive device 1, the frictional friction between the driven member 16 and the drive shaft 14 is suppressed, and the speed variation of the driven member 16 is suppressed. In addition, the frictional force blur between the product of the drive device 1 in which the urging portion 17 is inclined in the front-rear direction of the drive shaft 14 and the product of the drive device 1 that is not inclined is also suppressed. Needless to say, is suppressed.

  In the driving device 1, 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. Vibration generated by the expansion and contraction of the piezoelectric element 12 is not easily 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 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 the purpose of moving a CCD.

  In addition, the shape of the urging | biasing part mentioned above can be suitably changed into an aspect as shown in FIGS.

  FIG. 11 is a diagram showing an urging portion 17A that differs from the urging portion 17 described above only in its cross-sectional shape. That is, the urging portion 17A shown in FIG. 11 also extends in a direction orthogonal to the drive shaft 14 (Y direction in the figure), and is convex toward the drive shaft 14 in a cross section orthogonal to the extending direction. The pressing portion 17a is formed over the entire length of the urging portion 17, so that a sharp rib-shaped protrusion 19A along the extending direction of the urging portion 17 is formed. Has been.

  The rib-like protrusion 19A of the urging portion 17A is also substantially in point contact with the upper sliding portion 16C at the position of point P in the figure, like the rib-like protrusion 19 of the urging portion 17 described above. Therefore, even if the urging portion 17A is inclined by a predetermined angle α in the front-rear direction of the drive shaft 14 (X direction in FIG. 11), the frictional force blur between the sliding portion 16C and the drive shaft 14 is also eliminated. Is suppressed.

  Therefore, also in the driving device 1 of such a mode, the frictional force blur between the driven member 16 and the driving shaft 14 is suppressed, and the speed variation of the driven member 16 is suppressed, The speed variation for each product is also suppressed.

  FIG. 12 is a diagram showing an urging portion 17B that differs from the urging portion 17 described above only in its cross-sectional shape. That is, the urging portion 17B shown in FIG. 12 also extends in a direction orthogonal to the drive shaft 14 (Y direction in the figure), and the lower surface of the urging portion 17B is entirely directed toward the drive shaft 14 in the cross section orthogonal to the extending direction. The pressing portion 17a has a convex shape, and the pressing portion 17a is formed over the entire length of the urging portion 17, so that a curved surface portion 19B along the extending direction of the urging portion 17 is formed. ing.

  The curved surface portion 19B of the urging portion 17B is also substantially in point contact with the upper sliding portion 16C at the position of the point P in the figure, like the rib-like protrusion 19 of the urging portion 17 described above. Therefore, even if the urging portion 17B is inclined by a predetermined angle α in the front-rear direction of the drive shaft 14 (X direction in FIG. 12), the frictional force fluctuation between the sliding portion 16C and the drive shaft 14 is also reduced. Is suppressed.

  Therefore, also in the driving device 1 of such a mode, the frictional force blur between the driven member 16 and the driving shaft 14 is suppressed, and the speed variation of the driven member 16 is suppressed, The speed variation for each product is also suppressed. In the protrusions 19 and 19A described above, when the biasing portions 17 and 17A are greatly inclined in the front-rear direction of the drive shaft 14, the edges may come into contact with the sliding portion 16C. In 19B, the drive shaft 14 can be surely pressed without such a situation, so that the frictional force blur between the driven member 16 and the drive shaft 14 is suppressed with higher accuracy. .

  FIG. 13 is a diagram showing an urging portion 17C partially having the same cross-sectional shape as the urging portion 17 described above. That is, the urging portion 17C shown in FIG. 13 also partially extends in the direction orthogonal to the drive shaft 14 (Y direction in the figure), and in the cross section orthogonal to the extending direction, the entire urging portion toward the drive shaft 14 side. The pressing portion 17a is convex, and the pressing portion 17a is formed along the extending direction of the urging portion 17C, so that the bump-shaped protrusion along the extending direction of the urging portion 17 is formed. 19C is formed.

  The projection 19C of the urging portion 17C is also substantially shorter at the position of the upper sliding portion 16C and the point P in the drawing, like the rib-like projection 19 of the urging portion 17 described above, although the length thereof is shortened. Point contact. Therefore, even if the urging portion 17C is inclined by a predetermined angle α in the front-rear direction of the drive shaft 14 (X direction in FIG. 13), the frictional force fluctuation between the sliding portion 16C and the drive shaft 14 is also reduced. Is suppressed.

  Therefore, also in the driving device 1 of such a mode, the frictional force blur between the driven member 16 and the driving shaft 14 is suppressed, and the speed variation of the driven member 16 is suppressed, The speed variation for each product is also suppressed. As described above, even if the protrusion 19C is used, the displacement of the pressing position caused by the inclination of the urging portion 17C is suppressed, so that the frictional force between the driven member 16 and the drive shaft 14 is effectively suppressed. However, the rib-like protrusions 19 and 19A are preferable in that the pressing portion 17a that presses the drive shaft 14 can be easily designed as compared with the bump-like protrusion 19C.

  The cross-sectional shape of the urging portion 17C at the position of the pressing portion 17a is not limited to the cross-sectional shape of the urging portion 17 shown in FIG. 9, but the cross-sectional shape of the urging portion 17A shown in FIG. It can be changed to the cross-sectional shape of the urging portion 17B shown in FIG.

  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 above-described embodiment, the mode in which the leaf spring is included in the driven member has been described. However, the embodiment may be appropriately changed to a leaf spring provided separately from the driven member.

  Further, only the device applied to the driving device that drives the moving lens has been described, but 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). Further, in the above-described embodiment, the weight member 18 is provided on the other end side in the expansion / contraction direction of the piezoelectric element 12, and the weight member 18 is particularly soft and heavy, but is not limited thereto.

  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. Furthermore, 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 it may be different.

  Further, 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.

  In the above embodiment, the other end side in the expansion / contraction direction of the piezoelectric element 12 is a free end, but the end on the other end side may be fixed to the fixed frame 24 to be a fixed end. In the above embodiment, the electromechanical transducer 12 is particularly preferably supported by the fixing frame 24 via an elastic adhesive, but the effect is somewhat reduced, but a hard adhesive is used. You may make it support to the fixed frame 24 via.

It is sectional drawing which shows the drive device which concerns on embodiment of this invention. It is a wave form diagram of the drive pulse applied to the piezoelectric element of FIG. It is a circuit diagram which shows the drive circuit of a control part. 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 of FIG. It is a figure which shows the modification of the position detector in the drive device of FIG. It is a VIII-VIII sectional view taken on the line of the driven member of FIG. It is the IX-IX sectional view taken on the line of the urging | biasing part of FIG. It is sectional drawing which showed the biasing part of the aspect different from the biasing part of FIG. It is sectional drawing which showed the biasing part of the aspect different from the biasing part of FIG. It is sectional drawing which showed the biasing part of the aspect different from the biasing part of FIG. It is sectional drawing which showed the biasing part of the aspect different from the biasing part of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Drive device, 10 ... Actuator, 12 ... Piezoelectric element, 14 ... Drive shaft, 16 ... Driven member, 16B ... Leaf spring, 17, 17A, 17B, 17C ... Biasing part, 17a ... Pressing part, 18 ... Weight Member, 19, 19A ... rib-like projection, 19B ... curved surface portion, 19C ... projection.

Claims (5)

In the drive device that reciprocates the drive shaft according to the expansion and contraction of the electromechanical conversion element, and moves the driven member frictionally engaged with the drive shaft along the drive shaft.
A leaf spring having a biasing portion extending in a direction intersecting the drive shaft and pressing the drive shaft in the direction of the driven member;
The urging portion of the leaf spring includes a pressing portion that is convex toward the drive shaft side in a cross section orthogonal to the extending direction, and the urging portion is driven by the pressing portion. A drive device that presses a shaft.   The driving device according to claim 1, wherein the pressing portion is a rib-like protrusion extending along an extending direction of the urging portion.   The driving device according to claim 1, wherein the pressing portion is a curved surface portion provided in the urging portion of the leaf spring.   The said biasing part of the said leaf | plate spring presses the said drive shaft via the coating | coated member of the substantially V-shaped cross section covered along the said drive shaft. The drive device according to item. The driving device according to claim 4, wherein the urging portion of the leaf spring and the covering member are in point contact.

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