JP2008252982A - Drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive device capable of surely suppressing the dispersion in drive characteristics of a driven member. <P>SOLUTION: In the drive device 1, a drive member 14 is sandwiched by slide members 16C, 16D. By biasing the slide member 16C to the slide member 16D side by a biasing member 16B under the sandwiched state, the driven member 16 is made to engage with the drive member 14 by friction. Then, the slide member 16C is in a surface contact with the drive member 14 on two slide planes formed on the drive member 14. Accordingly, compared with a case where curved surfaces come into a surface contact with each other, the surface contact between the slide member 16C and the drive member 14 is ensured and the attitude of the slide member 16C to the drive member 14 is stabilized. Thereby, a friction force which occurs between the slide member 16C and the drive member 14 is stabilized, so that dispersion in drive characteristics of the driven member 16 can surely be suppressed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a driving device suitable for driving a lens or the like in, for example, a mobile phone with a camera or a small digital camera.

  As a conventional driving device in the technical field, an electromechanical conversion element that expands and contracts along a predetermined expansion / contraction direction, a drive member attached to one end of the electromechanical conversion element in the expansion / contraction direction, and frictionally engaged with the drive member And a driven member. And the drive member which is a cylindrical axis | shaft whose centerline corresponds substantially with the expansion-contraction direction is pinched | interposed by two sliding members which have a semi-cylindrical groove, and one sliding member is a biasing member in that state A driving device is known in which the driven member is frictionally engaged with the driving member by being biased toward the other sliding member (see, for example, Patent Document 1).

In such a drive device, a drive pulse having a sawtooth waveform is applied to the electromechanical conversion element, and the electromechanical conversion element is deformed in a state where the expansion speed and the contraction speed are different. When the electromechanical conversion element is deformed at a slow speed, the driven member is stationary with respect to the driving member due to friction, and conversely, when the electromechanical conversion element is deformed at a high speed, the driven member is transformed into the driving member by inertia. Move against. Therefore, by repeatedly applying a drive pulse having a sawtooth waveform to the electromechanical transducer, the driven member can be moved intermittently at a fine pitch.
JP 7-274543 A

  However, in the drive device as described above, the side surface of the drive member, which is a cylindrical shaft, and the inner surface of the semi-cylindrical groove of the sliding member are both curved surfaces. In order to make surface contact, both curved surfaces must be formed with extremely high accuracy. That is, if the formation accuracy of both curved surfaces is reduced even slightly, the frictional force generated between the two curved surfaces becomes unstable due to the change in the state of surface contact, and as a result, the driving characteristics of the driven member may vary.

  Therefore, the present invention has been made in view of such circumstances, and an object of the present invention is to provide a drive device that can reliably suppress variations in drive characteristics of driven members.

  In order to achieve the above object, a drive device according to the present invention includes an electromechanical conversion element that expands and contracts along a predetermined expansion / contraction direction, a drive member attached to one end of the electromechanical conversion element in the expansion / contraction direction, and a drive member A driven member frictionally engaged with the first sliding member and the second sliding member that are in contact with the driving member with the driving member interposed therebetween. An urging member that urges the first sliding member toward the second sliding member, and the first sliding member has two first sliding planes formed on the driving member. And the drive member is in surface contact.

  In this driving device, the driving member is sandwiched between the first sliding member and the second sliding member, and in this state, the first sliding member is biased toward the second sliding member by the biasing member. As a result, the driven member is frictionally engaged with the driving member. At this time, the first sliding member is in surface contact with the driving member on two first sliding planes formed on the driving member. Therefore, compared with the case where the curved surfaces are to be brought into surface contact, the surface contact between the first sliding member and the driving member is ensured, and the posture of the first sliding member with respect to the driving member is stabilized. As a result, the frictional force generated between the first sliding member and the driving member is stabilized, so that variations in driving characteristics of the driven member can be reliably suppressed.

  In the drive device according to the present invention, the drive member is a cylindrical shaft whose center line substantially coincides with the expansion / contraction direction, and the two first sliding planes are formed on the side surfaces of the drive member so as to be separated from each other. It is preferable. According to this configuration, since the curved surface exists between the two first sliding planes, it is possible to prevent the corners of the driving member from being lost.

  In the drive device according to the present invention, the drive member is a columnar axis whose center line substantially coincides with the expansion / contraction direction, and the two first sliding planes have an obtuse angle at the intersection on the center line side. Preferably, it is formed on the side surface of the drive member. According to this configuration, even when the two first sliding planes directly intersect with each other, and when the two first sliding planes do not intersect directly (that is, the two first sliding planes). Even when a curved surface exists between the two, the crossing angle on the center line side becomes an obtuse angle, so that the corners of the driving member can be prevented from being lost.

  In the drive device according to the present invention, the drive member is preferably made of a graphite composite. The graphite composite is not only light and highly rigid, but also a relatively inexpensive material with excellent workability. Moreover, if the two first sliding planes are formed on the driving member that is a cylindrical shaft as described above, the corners of the driving member are prevented from being lost even if a relatively fragile graphite composite is used. can do.

  In the driving device according to the present invention, it is preferable that the second sliding member is in surface contact with the driving member in at least one second sliding plane formed on the driving member. According to this configuration, the surface contact between the second sliding member and the drive member is ensured as compared with the case where the curved surfaces are to be brought into surface contact. As a result, the frictional force generated between the second sliding member and the driving member is stabilized, so that variations in driving characteristics of the driven member can be more reliably suppressed.

  According to the present invention, it is possible to reliably suppress variations in driving characteristics of driven members.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view showing an embodiment of a drive device according to the present invention.

  As shown in FIG. 1, the driving device 1 drives the moving lens 70 using the moving lens 70 as a moving object, and is suitable for, for example, a mobile phone with a camera or a small digital camera. The drive device 1 includes an actuator 10 having a piezoelectric element (electromechanical conversion element) 12, a drive member 14, a driven member 16, and a weight member 18, and a support member 60 that supports the actuator 10.

  The piezoelectric element 12 can be expanded and contracted along a predetermined expansion / contraction direction. The piezoelectric element 12 is connected to the control unit 71 and expands and contracts when an electric signal is input by the control unit 71. For example, by repeatedly increasing or decreasing the voltage applied to the input terminals 72A and 72B installed in the piezoelectric element 12, the piezoelectric element 12 repeatedly expands and contracts.

  The drive member 14 is a cylindrical shaft, and is attached to the one end 12 </ b> A of the piezoelectric element 12 in a state where the center line CL is substantially coincident with the expansion / contraction direction of the piezoelectric element 12. For example, the drive member 14 is bonded by the adhesive 27 in a state where the base end thereof is in contact with the one end 12 </ b> A of the piezoelectric element 12.

  The drive member 14 is formed of a graphite composite in which graphite crystals are firmly combined, such as carbon graphite. The graphite composite is not only light and highly rigid, but also a relatively inexpensive material with excellent workability. The graphite composite means a composite of graphite (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. To do.

  The drive member 14 is supported by partition portions 24B and 24C extending inward from the fixed frame 24 so as to be movable along the direction of the center line CL. The partition portions 24 </ b> B and 24 </ b> C are members for partitioning the moving region of the driven member 16 and also function as support members for the driving member 14. The fixed frame 24 functions as a housing for housing the actuator 10.

  Each partition portion 24B, 24C is formed with a through hole 24A through which the drive member 14 passes. The partition portion 24 </ b> B supports the vicinity of the piezoelectric element 12 in the driving member 14, that is, the base end portion of the driving member 14. The partition portion 24 </ b> C supports the tip portion of the drive member 14. The fixed frame 24 functions as a frame or a frame member for assembling the actuator 10. When the driving member 14 is attached to the piezoelectric element 12, the driving member 14 reciprocates along the direction of the center line CL according to repeated operations of expansion and contraction of the piezoelectric element 12.

  Note that the driving member 14 may be supported on one of the distal end side and the proximal end side, not on both the distal end side and the proximal end side. For example, if the through hole 24A of the partition portion 24B is formed larger than the outer diameter of the drive member 14, the drive member 14 is supported only at the tip portion by the partition portion 24C. Further, if the through hole 24A of the partition portion 24C is formed larger than the outer diameter of the drive member 14, the drive member 14 is supported only at the base end portion by the partition portion 24B. Further, the partition portions 24 </ b> B and 24 </ b> C may not be integrated with the fixed frame 24 but may be formed separately from the fixed frame 24 and attached to the fixed frame 24. Even in the case of separate bodies, functions and effects similar to those in the case of integration can be obtained.

  The driven member 16 is movably attached to the driving member 14. The driven member 16 is frictionally engaged with the driving member 14 and is movable along the direction of the center line CL. For example, the driven member 16 is engaged with the driving member 14 with a predetermined coefficient of friction, and is pressed against the driving member 14 with a constant pressing force, so that a constant friction force is generated during the movement thereof. It is attached as follows. When a moving force exceeding the frictional force is applied to the driven member 16, the driven member 16 moves along the driving member 14 against the frictional force.

  The weight member 18 is attached to the other end 12 </ b> B of the piezoelectric element 12 while being separated from the fixed frame 24. For example, the weight member 18 is bonded to the piezoelectric element 12 with an adhesive while being in contact with the other end 12 </ b> B of the piezoelectric element 12.

  The weight member 18 applies a load to the other end 12B of the piezoelectric element 12, thereby preventing the other end 12B from being displaced more than the one end 12A. As the weight member 18, one having a mass larger than that of the driving member 14 is preferable. Thereby, the expansion and contraction of the piezoelectric element 12 can be efficiently transmitted to the drive member 14 side.

  The support member 60 is disposed between the fixed frame 24 that houses the actuator 10 and the piezoelectric element 12, and from the side with respect to the expansion / contraction direction of the piezoelectric element 12 (for example, substantially orthogonal to the expansion / contraction direction of the piezoelectric element 12). The piezoelectric element 12 is supported (from the direction).

  The support member 60 is formed of an elastic body (for example, silicone resin) having an elastic coefficient equal to or greater than a predetermined value. Thereby, the piezoelectric element 12 is elastically supported by the support member 60. The support member 60 has 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 bonded to the fixed frame 24 with an adhesive 61, and the piezoelectric element 12 is bonded to the support member 60 with an adhesive 62.

  The support member 60 is fixed to the fixed frame 24 and the piezoelectric element 12 is fixed to the support member 60 by pressing the support member 60 between the fixed frame 24 and the piezoelectric element 12 and pressing the support member 60. Also good. For example, the support member 60 is formed of an elastic body so as to be slightly larger than the gap between the fixed frame 24 and the piezoelectric element 12, and the support member 60 is press-fitted and installed in the gap. 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 a direction substantially orthogonal to the expansion / contraction direction, and the actuator 10 is supported. Further, the support member 60 may be configured by a spring member instead of the silicone resin. In this case, for example, a spring member is disposed between the fixed frame 24 and the piezoelectric element 12, and the actuator 10 is supported with respect to the fixed frame 24 by the spring member.

  A movable lens 70 is attached to the driven member 16 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. A fixed lens (not shown) or the like is disposed on the optical axis O of the moving lens 70, and constitutes a photographing optical system of the camera. An image sensor 65 is disposed on the optical axis O. The image pickup element 65 is an image pickup means for converting an image formed by the photographing optical system into an electric signal, and is constituted by a CCD, for example. The image sensor 65 is connected to the control unit 71 and outputs an image signal to the control unit 71.

  The control unit 71 performs overall control of the driving device 1 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.

  2 is a cross-sectional view taken along the line II-II shown in FIG. 1, and FIG. 3 is a perspective view of the drive member shown in FIG.

  As shown in FIG. 2, the driven member 16 has a main body portion 16A, an urging member 16B, a sliding member (first sliding member) 16C, and a sliding member (second sliding member) 16D. is doing. The main body portion 16A is pressed against the drive member 14 by a biasing member 16B with a constant force. A V-shaped groove 16E is formed in the main body portion 16A. In the groove 16E, the driving member 14 is disposed in a state of being sandwiched between the two sliding members 16C and 16D. Thus, by arranging the driving member 14 in the V-shaped groove 16E, the driven member 16 can be attached to the driving member 14 stably.

  As the urging member 16B, for example, a leaf spring material having a C-shaped cross section is used. One side of the urging member 16B is hooked on the main body portion 16A, and the other side is disposed at a position opposite to the groove 16E, so that the driving member 14 disposed in the groove 16E is moved to the main body portion 16A and the other side by the other side. It can be inserted together with the sliding members 16C and 16D. Thereby, 16 A of main-body parts can be pressed to the drive member 14 side.

  The sliding members 16 </ b> C and 16 </ b> D are plate bodies having a V-shaped cross section, and are disposed with the concave portion side (inner side) facing the center line CL side of the driving member 14. The sliding members 16C and 16D are in contact with the driving member 14 with the driving member 14 interposed therebetween. 16 C of sliding members are arrange | positioned by the upper body inclined to the side which the urging | biasing member 16B which is a leaf | plate spring material with a C-shaped cross section opens, and is urged | biased by the urging member 16B to the sliding member 16D side. ing. The sliding member 16D is disposed along the inner surface of the groove 16E of the main body portion 16A.

  As shown in FIGS. 2 and 3, the sliding member 16 </ b> C is in surface contact with the driving member 14 at two sliding planes (first sliding planes) 14 </ b> A and 14 </ b> A formed on the driving member 14. More specifically, each of the two flat surfaces on the concave side of the sliding member 16C is in surface contact with each sliding flat surface 14A of the driving member 14. The two sliding planes 14A and 14A are formed on the side surface of the driving member 14 so that they are separated from each other and the crossing angle A on the center line CL side is an obtuse angle.

  The sliding member 16D is in surface contact with the driving member 14 at two sliding planes (second sliding planes) 14B and 14B formed on the driving member 14. More specifically, each of the two flat surfaces on the concave portion side of the sliding member 16D is in surface contact with each sliding plane 14B of the driving member 14. The two sliding planes 14B and 14B are formed on the side surface of the driving member 14 so that they are separated from each other and the crossing angle B on the center line CL side is an obtuse angle.

  In this way, the driven member 16 has the driving member 14 sandwiched between the sliding members 16C and 16D, and in this state, the sliding member 16C is biased toward the sliding member 16D by the biasing member 16B. The drive member 14 is frictionally engaged. That is, the driven member 16 is attached to the driving member 14 so that a constant frictional force is generated when the driven member 16 is moved.

  FIG. 4 is a circuit diagram of a drive circuit for operating the piezoelectric element shown in FIG.

  As shown in FIG. 4, the drive circuit 77 is disposed and provided in the control unit 71. The drive circuit 77 functions as a drive circuit for the piezoelectric element 12 and outputs an electric signal for driving to the piezoelectric element 12. The drive circuit 77 receives a control signal from a control signal generation unit (not shown) of the control unit 71, and amplifies the control signal by voltage amplification or current amplification to output an electric signal for driving the piezoelectric element 12. As the drive circuit 77, for example, an input stage having logic circuits U1 to U3 and an output stage having field effect transistors (FETs) Q1 and Q2 are used. The transistors Q1 and Q2 are configured to be able to output Hi output (high potential output), Lo output (low potential output), and OFF output (open output) as output signals.

  FIG. 5 is a waveform diagram of an input signal input to the drive circuit shown in FIG. 4. FIG. 5A shows an input input when the driven member 16 is moved so as to approach the piezoelectric element 12. FIG. 5B shows an input signal that is input when the driven member 16 is moved away from the piezoelectric element 12. FIG. 6 is a waveform diagram of an output signal output from the drive circuit shown in FIG. 4, and is output when the driven member 16 is moved so as to approach the piezoelectric element 12 in FIG. (B) shows an output signal that is output when the driven member 16 is moved away from the piezoelectric element 12.

  The output signals in FIGS. 6A and 6B are pulse signals that are turned ON / OFF at the same timing as the input signals in FIGS. 5A and 5B. The two signals shown in FIGS. 6A and 6B are input to the input terminals 72A and 72B of the piezoelectric element 12. A pulse signal having a sawtooth waveform may be input to the input terminals 72A and 72B. However, as shown in FIG. 6, a pulse signal having a rectangular waveform is input to operate the piezoelectric element 12. Can be made. In this case, since the drive signal for the piezoelectric element 12 may be a pulse signal having a rectangular waveform, signal generation is facilitated.

  The output signals in FIGS. 6A and 6B are composed of two pulse signals having the same frequency. These two pulse signals have different phases, so that the potential difference between the signals increases stepwise and decreases rapidly, or the potential difference between the signals increases rapidly and decreases stepwise. It becomes the signal which becomes. By inputting such 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. 6A and 6B, after one signal changes from Hi (high) to Lo (low), the other signal is set to Hi. These signals are set so that when one signal becomes Lo, the other signal becomes Hi after a certain time lag t _OFF has elapsed. When both signals are Lo, the output is turned off (open state).

  Signals having a frequency exceeding the audible frequency are used as output signals in FIGS. 6A and 6B, that is, electric signals for operating the piezoelectric element 12. 6A and 6B, the frequency of the two signals is a frequency signal exceeding the audible frequency, for example, a frequency signal of 30 to 80 kHz, more preferably 40 to 60 kHz. By using a signal having such a frequency, it is possible to reduce the operation sound in the audible region of the piezoelectric element 12.

  The drive device 1 configured as described above operates as follows. That is, an electric signal is input to the piezoelectric element 12, and the piezoelectric element 12 repeats expansion and contraction by the input of the electric signal. The drive member 14 reciprocates according to the expansion and contraction. At this time, the speed at which the drive member 14 moves in one direction is different from the speed at which the drive member 14 moves in the other direction by making the extension speed and contraction speed of the piezoelectric element 12 different. Thereby, the driven member 16 and the moving lens 70 are moved in a desired direction.

  As described above, in the driving device 1, the driving member 14 is sandwiched between the sliding members 16C and 16D, and in this state, the sliding member 16C is urged toward the sliding member 16D by the urging member 16B. Thus, the driven member 16 is frictionally engaged with the driving member 14. At this time, the sliding member 16C is in surface contact with the driving member 14 on the two sliding planes 14A and 14A formed on the driving member 14, and the sliding member 16D is formed on the two sliding surfaces 16A and 14A. The sliding members 14B and 14B are in surface contact with the driving member 14. Therefore, compared with the case where the curved surfaces are to be brought into surface contact, the surface contact between the sliding members 16C and 16D and the driving member 14 is ensured, and the posture of the sliding member 16C with respect to the driving member 14 is stabilized. As a result, the frictional force generated between the sliding members 16C, 16D and the driving member 14 is stabilized, so that variations in the driving characteristics of the driven member 16 can be reliably suppressed. The drive member 14 that is a cylindrical shaft having the sliding planes 14A and 14B can be easily manufactured by extrusion.

  Since the contact area between the driving member 14 and the driven member 16 is increased, the driving member 14 can be prevented from being scraped, and the displacement transmission efficiency of the piezoelectric element 12 with respect to the driven member 16 is improved. Can be made.

  The drive member 14 is a cylindrical shaft whose center line CL substantially coincides with the expansion / contraction direction, and the sliding planes 14A and 14B are driven so that the crossing angle on the center line CL side is an obtuse angle. It is formed on the side surface of the member 14. As a result, a curved surface exists between the sliding planes 14A and 14B, and the crossing angle on the center line CL side formed by the sliding planes 14A and 14B becomes an obtuse angle, which is relatively fragile. Even when the graphite composite is used, the corners of the drive member 14 can be prevented from being lost.

  The present invention is not limited to the embodiment described above.

  For example, although the driving device 1 drives the moving lens 70 in the above-described embodiment, the driving device 1 may drive a moving object other than the moving lens 70.

  Further, the driving device 1 is not limited to the one in which the weight member 18 is attached to the other end 12 </ b> B of the piezoelectric element 12. As an example, the other end 12B of the piezoelectric element 12 is in a no-load state (that is, nothing is attached to the other end 12B and nothing is in contact), or the other end of the piezoelectric element 12 12B may be fixed to some member (for example, the fixed frame 24).

  Further, the formation positions and areas of the sliding planes 14A and 14B formed on the drive member 14 can be appropriately determined so that desired drive characteristics can be obtained.

  Further, if each sliding plane 14A, 14B is formed on the side surface of the driving member 14 so as to be separated from each other, or if it is formed on the side surface of the driving member 14 so that the intersection angle on the center line CL side becomes an obtuse angle, It is possible to prevent the corner portion of the driving member 14 from being lost.

  Furthermore, the drive member 14 is not limited to a cylindrical axis, and may be an axis whose side surface is a curved surface (for example, an elliptical columnar axis). The material of the driving member 14 is not limited to the graphite composite, and may be a metal such as beryllium, a carbon resin composite in which a carbon resin is firmly combined, or the like.

It is sectional drawing which shows one Embodiment of the drive device which concerns on this invention. It is sectional drawing along the II-II line | wire shown by FIG. FIG. 2 is a perspective view of a driving member shown in FIG. 1. It is a circuit diagram of the drive circuit which operates the piezoelectric element shown by FIG. FIG. 5 is a waveform diagram of an input signal input to the drive circuit shown in FIG. 4. FIG. 5 is a waveform diagram of an output signal output from the drive circuit shown in FIG. 4.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Drive device, 12 ... Piezoelectric element (electromechanical conversion element), 14 ... Drive member, 14A ... Sliding plane (first sliding plane), 14B ... Sliding plane (second sliding plane), 16 ... driven member, 16B ... biasing member, 16C ... sliding member (first sliding member), 16D ... sliding member (second sliding member).

Claims (5)

An electromechanical conversion element that expands and contracts along a predetermined expansion / contraction direction; a drive member attached to one end of the electromechanical conversion element in the expansion / contraction direction; and a driven member frictionally engaged with the drive member. A driving device comprising:
The driven member includes a first sliding member and a second sliding member that are in contact with the driving member with the driving member interposed therebetween, and the first sliding member is the second sliding member. A biasing member biasing to the side,
The driving device according to claim 1, wherein the first sliding member is in surface contact with the driving member in two first sliding planes formed on the driving member. The drive member is a cylindrical shaft whose center line substantially coincides with the expansion / contraction direction,
The drive device according to claim 1, wherein the two first sliding planes are formed on side surfaces of the drive member so as to be separated from each other. The drive member is a cylindrical shaft whose center line substantially coincides with the expansion / contraction direction,
2. The driving device according to claim 1, wherein the two first sliding planes are formed on a side surface of the driving member such that an intersection angle on the center line side is an obtuse angle.   The drive device according to claim 1, wherein the drive member is made of a graphite composite.   The said 2nd sliding member is in surface contact with the said driving member in the at least 1 2nd sliding plane formed in the said driving member, The any one of Claims 1-4 characterized by the above-mentioned. The drive device described.

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