JP2009025407A - Drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive device capable of preventing the tilt of a driving shaft to a predetermined reference line. <P>SOLUTION: In the drive device 1, the tilt of the driving shaft 6 to the reference line FL is regulated by a regulation member 20 provided in bearing grooves 11a and 12a of a holder 3. More specifically, the driving shaft 6 is positioned by supporting the driving shaft 6 at three spots by two inner surfaces of the respective bearing grooves 11a and 12a and a pressing part 22 pressing the driving shaft 6 on the inner surfaces. Accordingly, a situation that a piezoelectric element 4 is supported by the holder 3 in such a state that the driving shaft 6 is tilted to the reference line FL is surely prevented. <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 in the extending direction of a predetermined reference line, a drive shaft attached to one end of the electromechanical conversion element in the extending direction of the predetermined reference line, A device including a driven body frictionally engaged with a drive shaft and a holder that supports an electromechanical conversion element and has a bearing hole of the drive shaft is known (for example, see Patent Documents 1 and 2). .

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 body is stationary with respect to the drive shaft due to friction, and conversely, when the electromechanical conversion element is deformed at a high speed, the driven body is transformed into the drive shaft by inertia. Move against. Therefore, by repeatedly applying a drive pulse having a sawtooth waveform to the electromechanical transducer, the driven body can be intermittently moved at a fine pitch.
JP 2002-142470 A JP 2007-74889 A

  However, in the drive device as described above, since there is a clearance between the outer surface of the drive shaft and the inner surface of the bearing hole, the electromechanical conversion element is in a state where the drive shaft is tilted with respect to a predetermined reference line. May be supported by the holder. In particular, when driving a lens or the like in a camera-equipped mobile phone or a small digital camera, extremely high optical performance is required. Therefore, even if a tilt of the drive shaft with respect to a predetermined reference line is slight, it is serious. It becomes a problem.

  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 prevent the drive shaft from falling over a predetermined reference line.

  In order to achieve the above object, a drive device according to the present invention includes an electromechanical transducer that expands and contracts in the extending direction of a predetermined reference line, and a drive shaft attached to one end of the electromechanical transducer in the extending direction. , A driven body frictionally engaged with the drive shaft, a holder for supporting the electromechanical conversion element, a bearing having a bearing portion of the drive shaft, and a regulation provided on the bearing portion to regulate the inclination of the drive shaft with respect to the reference line And a member.

  In this drive device, the inclination of the drive shaft with respect to a predetermined reference line is restricted by a restriction member provided in a bearing portion of the holder. Therefore, it is possible to prevent the electromechanical conversion element from being supported by the holder in a state where the drive shaft is tilted with respect to the predetermined reference line.

  In the drive device according to the present invention, it is preferable that the regulating member is attached to the opening side of the bearing portion formed in the holder as a groove. In this case, it is possible to dispose the drive shaft from the opening side of the bearing portion formed in the holder as a groove and then attach the regulating member to the opening side of the bearing portion. Therefore, it is possible to improve the assembly of the drive device.

  In the drive device according to the present invention, the restricting member has a fixed portion fixed to the holder, and a pressing portion that presses the drive shaft on the inner surface of the bearing portion, and the drive shaft includes an inner surface of the bearing portion in the bearing portion. And it is preferable that it is supported by at least three places by the pressing part. Thus, the drive shaft is positioned by the support shaft being supported at least in three places by the inner surface of the bearing portion and the pressing portion that presses the drive shaft against the inner surface. Therefore, it is possible to more reliably prevent the drive shaft from falling with respect to the predetermined reference line.

  At this time, the pressing part may be a screw screwed to the fixing part, or may be a spring attached to the fixing part. When the pressing portion is a screw, the pressing force of the drive shaft against the inner surface of the bearing portion can be adjusted depending on the tightening condition. When the pressing portion is a spring, the pressing force of the drive shaft against the inner surface of the bearing portion can be adjusted by changing the spring constant.

  According to the present invention, it is possible to prevent the drive shaft from falling over a predetermined reference line.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the same or an equivalent part, and the overlapping description is abbreviate | omitted.

  FIG. 1 is a perspective view showing an embodiment of a drive device according to the present invention, and FIG. 2 is a partial cross-sectional view taken along the line II-II shown in FIG. As shown in FIGS. 1 and 2, the driving device 1 is a device for driving a lens held by a lens frame (driven body) 2 along the optical axis OA. It is suitable for a digital camera or the like.

  The driving device 1 includes a holder 3 that accommodates the lens frame 2. The holder 3 supports a piezoelectric element (electromechanical conversion element) 4 that expands and contracts in the extending direction of a reference line FL parallel to the optical axis OA. Specifically, the piezoelectric element 4 is elastically held by the holder 3 by being held from the side with respect to the extending direction of the reference line FL by a silicone cap 5 bonded to the holder 3 with a silicone adhesive. It is supported. The piezoelectric element 4 is provided with input terminals 4a and 4b for applying drive pulses.

  A driving shaft 6 is fixed to one end of the piezoelectric element 4 in the extending direction of the reference line FL with an adhesive so as to extend along the reference line FL. The drive shaft 6 is formed in a columnar shape from a graphite composite in which graphite crystals are firmly combined, such as carbon graphite. On the other hand, a weight member 8 is fixed to the other end of the piezoelectric element 4 in the extending direction of the reference line FL with an adhesive. The weight member 8 is for preventing the other end of the piezoelectric element 4 from being displaced more than one end by applying a load to the other end of the piezoelectric element 4. The weight member 8 preferably has a mass larger than that of the drive shaft 6 in order to efficiently transmit the expansion and contraction of the piezoelectric element 4 to the drive shaft 6.

  One end portion of the drive shaft 6 is disposed in a bearing groove (bearing portion) 11 a formed in the partition portion 11 included in the holder 3. On the other hand, the other end portion of the drive shaft 6 is disposed in a bearing groove (bearing portion) 12 a formed in the partition portion 12 included in the holder 3. Thereby, the drive shaft 6 can reciprocate along the reference line FL.

  The driving shaft 6 is frictionally engaged with the engaging portion 2a of the lens frame 2 whose movement region is regulated between the partitioning portions 11 and 12. Specifically, a plate member 13 having a V-shaped cross section fixed to the engaging portion 2a and a plate member 13 biased toward the plate member 13 by a plate spring 14 locked to the engaging portion 2a. Since the plate member 15 sandwiches the drive shaft 6, the engaging portion 2 a is attached to the drive shaft 6 so that a constant frictional force is generated during the movement. A shaft 9 disposed in a groove having a U-shaped cross section of the lens frame 2 is stretched over the holder 3 along the extending direction of the reference line FL. That is, the drive shaft 6 also functions as a guide shaft for the lens frame 2, and the shaft 9 functions as a rotation stop shaft for the lens frame 2.

  Further, a regulating member 20 that regulates the inclination of the drive shaft 6 with respect to the reference line FL is provided on the opening side of the bearing grooves 11 a and 12 a and is attached to the holder 3. The restricting member 20 has a fixed portion 21 fixed to the holder 3 and a pressing portion 22 that presses the drive shaft 6 on the inner surfaces of the bearing grooves 11a and 12a. The pressing portion 22 urges the drive shaft 6 against the inner surfaces of the bearing grooves 11a and 12a so that a force acts in a direction substantially orthogonal to the reference line FL. As shown in FIG. 3, the drive shaft 6 is supported at three locations by two inner surfaces 11 b formed in a V-shaped cross section in the bearing groove 11 a and an inner surface 22 a of the pressing portion 22. Such a configuration is the same in the bearing groove 12a. Note that the pressing force of the drive shaft 6 against the inner surfaces of the bearing grooves 11a and 12a is large enough not to hinder the reciprocation of the drive shaft 6 along the reference line FL.

  In the drive device 1 configured as described above, the inclination of the drive shaft 6 with respect to the reference line FL is restricted by the restriction member 20 provided in the bearing grooves 11a and 12a of the holder 3. More specifically, the drive shaft 6 is positioned by supporting the drive shaft 6 at three locations by the two inner surfaces of the bearing grooves 11a and 12a and the pressing portions 22 that press the drive shaft 6 against the inner surfaces. The Accordingly, it is possible to reliably prevent the piezoelectric element 4 from being supported by the holder 3 when the drive shaft 6 is tilted with respect to the reference line FL. Thereby, when driving a lens etc. in a mobile phone with a camera, a small digital camera, etc., for example, extremely high optical performance can be obtained.

  Further, since the inclination of the drive shaft 6 with respect to the reference line FL is restricted by the restricting member 20, the drive shaft 6 can be used as the guide shaft of the lens frame 2 simply by providing the shaft 9 as the rotation stop shaft of the lens frame 2. Is possible. Thereby, even if a guide shaft for the lens frame 2 is not provided separately in addition to the drive shaft 6, it is possible to prevent deterioration of optical performance when driving a lens or the like in a camera-equipped mobile phone or a small digital camera, for example. .

  The restricting member 20 is attached to the opening side of the bearing grooves 11a and 12a. Thereby, the drive shaft 6 can be arrange | positioned from the opening side to the bearing grooves 11a and 12a, and the control member 20 can be attached to the opening side of the bearing grooves 11a and 12a after that. Therefore, it is possible to improve the assemblability of the drive device 1.

  Here, the operation of the driving device 1 will be described. FIG. 4 is a circuit diagram of a drive circuit for operating the piezoelectric element shown in FIG. FIG. 5 is a waveform diagram of an input signal input to the drive circuit shown in FIG. 4, and FIG. 6 is a waveform diagram of an output signal output from the drive circuit shown in FIG.

  As shown in FIG. 4, the drive circuit 31 is provided in the control unit 30. The control unit 30 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 drive circuit 31 functions as a drive circuit for the piezoelectric element 4 and outputs an electrical signal for driving to the piezoelectric element 4. The drive circuit 31 receives a control signal from the control signal generation unit of the control unit 30 and outputs a drive electric signal for the piezoelectric element 4 by amplifying the control signal with voltage or current. As the drive circuit 31, for example, an input stage configured by logic circuits U1 to U3 and an output stage including field effect transistors (FETs) Q1 and Q2 is used. The transistors Q1 and Q2 can output Hi output (high potential output), Lo output (low potential output), and OFF output (open output) as output signals.

  FIG. 5A shows an input signal that is input when the lens frame 2 is moved so that the engaging portion 2a approaches the piezoelectric element 4, and FIG. 4 is an input signal that is input when the lens frame 2 is moved away from the lens 4. 6A shows an output signal output when the lens frame 2 is moved so that the engaging portion 2a approaches the piezoelectric element 4, and FIG. 6B shows the output signal of the engaging portion 2a. This is an output signal that is output when the lens frame 2 is moved away from the piezoelectric element 4.

  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 4 a and 4 b of the piezoelectric element 4. A pulse signal having a sawtooth waveform may be input to the input terminals 4a and 4b. However, as shown in FIG. 6, even if a pulse signal having a rectangular waveform is input, the piezoelectric element 4 Can be activated. In this case, since the drive signal of the piezoelectric element 4 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 extension speed and the contraction speed of the piezoelectric element 4 can be made different, and the engaging portion 2a and thus the lens frame 2 can be moved.

For example, in FIGS. 6A and 6B, after one signal is changed 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).

  As the output signals shown in FIGS. 6A and 6B, that is, electric signals for operating the piezoelectric element 4, signals having frequencies exceeding the audible frequency are used. In FIGS. 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 4.

  As described above, the driving device 1 operates as follows. That is, an electric signal is input to the piezoelectric element 4, and the piezoelectric element 4 repeats expansion and contraction by the input of the electric signal. The drive shaft 6 reciprocates in accordance with the expansion and contraction. At this time, the speed at which the drive shaft 6 moves in one direction is different from the speed at which it moves in the other direction by making the extension speed and the contraction speed of the piezoelectric element 4 different. Thereby, the engaging part 2a and by extension the lens frame 2 are moved in a desired direction.

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

  For example, as shown in FIG. 7, the drive shaft 6 includes three inner surfaces 11 b formed in a U-shaped section in the bearing groove 11 a and two inner surfaces 22 a formed in a V-shaped section in the pressing portion 22. It may be supported at points. Such a configuration is the same in the bearing groove 12a. In addition, since the drive shaft 6 is positioned if it is supported at least at three places, it may be supported at four or more places.

  Further, the pressing portion 22 may be a screw screwed to the fixing portion 21 as shown in FIG. 8, or the pressing portion 22 may be compressed to the fixing portion 21 as shown in FIG. It may be an attached spring. When the pressing portion 22 is a screw, the pressing force of the drive shaft 6 against the inner surfaces of the bearing grooves 11a and 12a can be adjusted according to the tightening condition. When the pressing portion 22 is a spring, the pressing force of the drive shaft 6 against the inner surfaces of the bearing grooves 11a and 12a can be adjusted by changing the spring constant.

  The pressing portion 22 is not limited to pressing the drive shaft 6 against the inner surfaces of the bearing grooves 11a and 12a, but reduces the clearance between the outer surface of the drive shaft 6 and the inner surfaces of the bearing grooves 11a and 12a. There may be. Also in this case, since the inclination of the drive shaft 6 with respect to the reference line FL is restricted by the restriction member 20, it is possible to prevent the drive shaft 6 from falling with respect to the reference line FL.

  Further, when the piezoelectric element 4 is supported by the holder 3 from the side with respect to the extending direction of the reference line FL, the weight member 8 may not be fixed to the other end of the piezoelectric element 4. Further, the support of the piezoelectric element 4 by the holder 3 is not limited to the support from the side with respect to the extending direction of the reference line FL, and the other end of the piezoelectric element 4 is fixed to the holder 3. It may be supported from the other side in the extending direction.

It is a perspective view which shows one Embodiment of the drive device which concerns on this invention. It is a fragmentary sectional view along the II-II line shown in FIG. It is a front view of the bearing groove vicinity shown by FIG. 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. It is a front view of the bearing groove vicinity of other embodiment of the drive device which concerns on this invention. It is a front view of the bearing groove vicinity of other embodiment of the drive device which concerns on this invention. It is a front view of the bearing groove vicinity of other embodiment of the drive device which concerns on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Drive device, 2 ... Lens frame (driven body), 3 ... Holder, 4 ... Piezoelectric element (electromechanical conversion element), 6 ... Drive shaft, 11a, 12a ... Bearing groove (bearing part), 20 ... Restriction member , 21 ... fixed part, 22 ... pressing part, FL ... reference line.

Claims (5)

An electromechanical transducer that expands and contracts in the extending direction of a predetermined reference line;
A drive shaft attached to one end of the electromechanical transducer in the extending direction;
A driven body frictionally engaged with the drive shaft;
A holder that supports the electromechanical transducer and has a bearing portion of the drive shaft;
And a regulating member that is provided in the bearing portion and regulates an inclination of the driving shaft with respect to the reference line.   The drive device according to claim 1, wherein the restriction member is attached to the opening side of the bearing portion formed in the holder as a groove. The restricting member has a fixed portion fixed to the holder, and a pressing portion that presses the drive shaft on the inner surface of the bearing portion,
3. The drive device according to claim 1, wherein the drive shaft is supported in at least three places in the bearing portion by an inner surface of the bearing portion and the pressing portion.   The driving device according to claim 3, wherein the pressing portion is a screw screwed into the fixing portion.   The driving device according to claim 3, wherein the pressing portion is a spring attached to the fixing portion.

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