JP4860565B2 - Drive device - Google Patents

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 (see, for example, Patent Documents 1 to 3). .

  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.

In addition, as a driving device for improving the support stability of the electromechanical conversion element, an electromechanical conversion element that expands and contracts in the extending direction of the predetermined reference line, and an electromechanical conversion element in the extending direction of the predetermined reference line An electric machine that supports the drive shaft disposed on one end side, the driven body frictionally engaged with the drive shaft, the electromechanical conversion element and the drive shaft, and the electromechanical conversion element and the drive shaft come into contact with each other. A device including a holder that biases the other end of the conversion element and one end of the drive shaft is known (see, for example, Patent Document 4). However, in such a drive device, the other end of the electromechanical conversion element and one end of the drive shaft are urged by the holder so that the electromechanical conversion element and the drive shaft come into contact with each other. Although the support stability of the element is improved, it is difficult to increase the expansion and contraction of the electromechanical conversion element. On the other hand, in order to increase the expansion / contraction of the electromechanical conversion element, a technique of elastically supporting the electromechanical conversion element on the holder is effective (see, for example, Patent Document 5).
JP 2002-142470 A JP-A-10-337055 JP 2006-31794 A JP 2006-91210 A JP 2007-74889 A

  By the way, in a drive device that employs a technique for elastically supporting the electromechanical conversion element on the holder, it is desired to further improve the support stability of the electromechanical conversion element. 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, if the electromechanical conversion element is displaced due to an impact caused by dropping or the like, the displacement This is because even a small amount is a serious problem.

  Accordingly, the present invention has been made in view of such circumstances, and can drive the electromechanical conversion element that can further expand and contract and can further improve the support stability of the electromechanical conversion element. An object is to provide an apparatus.

  In order to achieve the above object, a drive device according to the present invention includes an electromechanical conversion element that expands and contracts in the extending direction of a predetermined reference line, and a hollow drive that is attached to one end of the electromechanical conversion element in the extending direction. A shaft, a driven body frictionally engaged with the drive shaft, a holder that supports the electromechanical conversion element and has a bearing portion of the drive shaft, and a fixed portion that is provided on the bearing portion and fixed to the holder, And a support member having a fitting portion fitted into the drive shaft from one end side, and disposed between the electromechanical conversion element and the fitting portion in the drive shaft, and urges the electromechanical conversion element in the extending direction. And an urging member.

  In this drive device, the electromechanical conversion element can be elastically supported by the holder, whereby the expansion and contraction of the electromechanical conversion element can be further increased. At this time, the electromechanical conversion element is urged in the expansion and contraction direction by the urging member disposed between the electromechanical conversion element and the fitting portion of the support member in the hollow drive shaft. The support stability of the element can be further improved.

  In the drive device according to the present invention, it is preferable that the biasing member is a spring disposed in a compressed state between the electromechanical conversion element and the fitting portion in the drive shaft. In this case, by changing the spring constant of the spring, it is possible to adjust the support stability of the electromechanical conversion element and the drive performance of the drive device.

  According to the present invention, the expansion and contraction of the electromechanical conversion element can be further increased, and the support stability of the electromechanical conversion element can be further improved.

  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 hollow drive shaft 6 is fixed to one end of the piezoelectric element 4 in the extending direction of the reference line FL by an adhesive 7 so as to extend along the reference line FL. The drive shaft 6 is formed in a cylindrical shape from a graphite complex in which graphite crystals are firmly combined, such as carbon graphite.

  One end portion of the drive shaft 6 is fitted into a bearing hole (bearing portion) 11 a formed in the partition portion 11 of the holder 3. On the other hand, the other end portion of the drive shaft 6 is inserted through a through hole 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 support member 20 that supports the drive shaft 6 is provided in the bearing hole 11 a of the partition portion 11. The support member 20 has a rectangular plate-like fixing portion 21 that is bonded and fixed to the holder 3 and a fitting portion 22 that is fitted into the drive shaft 6 from one end thereof. A clearance is provided between the other end surface of the fixed portion 21 and one end surface of the drive shaft 6 so that the piezoelectric element 4 does not come into contact even when it is most expanded. A spring (biasing member) 26 is arranged in a compressed state between one end surface of the piezoelectric element 4 and the other end surface of the fitting portion 22 in the drive shaft 6. The spring 26 biases the piezoelectric element 4 to the other side in the extending direction of the reference line FL. The fixing of the fixing portion 21 to the holder 3 is not limited to adhesive fixing, and may be screwed or the like.

  In the driving device 1 configured as described above, the piezoelectric element 4 is elastically supported by the holder 3. Therefore, for example, compared with the case where the other end of the piezoelectric element 4 and one end of the drive shaft 6 are urged by the holder 3 so that the piezoelectric element 4 and the drive shaft 6 come into contact with each other, the piezoelectric element 4 is more expanded and contracted. Can be bigger. Moreover, the other side of the piezoelectric element 4 in the extending direction (stretching direction) of the reference line FL is caused by the spring 26 disposed between the piezoelectric element 4 and the fitting portion 22 of the support member 20 in the hollow drive shaft 6. Is biased to the side. Therefore, for example, the support stability of the piezoelectric element 4 by the holder 3 can be further improved as compared with a case where a weight member is attached to the other end of the piezoelectric element 4 without providing the spring 26. This prevents the piezoelectric element 4 from being displaced due to an impact caused by dropping or the like, so that extremely high optical performance is maintained when driving a lens or the like in a camera-equipped mobile phone or a small digital camera, for example. It becomes possible.

  In addition, as hardness (for example, hardness of the silicone cap 5) at the time of making the piezoelectric element 4 elastically support the holder 3, durometer A90 or less is suitable, and durometer A20-60 is more suitable.

  Furthermore, by changing the spring constant of the spring 26, the support stability of the piezoelectric element 4 by the holder 3 and the driving performance of the driving device 1 can be adjusted.

  Here, the operation of the driving device 1 will be described. FIG. 3 is a circuit diagram of a drive circuit for operating the piezoelectric element shown in FIG. 4 is a waveform diagram of an input signal input to the drive circuit shown in FIG. 3, and FIG. 5 is a waveform diagram of an output signal output from the drive circuit shown in FIG.

  As shown in FIG. 3, 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.

  4A shows an input signal input when the lens frame 2 is moved so that the engaging portion 2a approaches the piezoelectric element 4, and FIG. 4B shows an input signal when the engaging portion 2a is a piezoelectric element. 4 is an input signal that is input when the lens frame 2 is moved away from the lens 4. 5A shows an output signal that is output when the lens frame 2 is moved so that the engaging portion 2a approaches the piezoelectric element 4, and FIG. 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. 5A and 5B are pulse signals that are turned ON / OFF at the same timing as the input signals in FIGS. 4A and 4B. The two signals shown in FIGS. 5A and 5B 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. 5, 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. 5A and 5B 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. 5A and 5B, 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).

  As the output signals shown in FIGS. 5A and 5B, that is, electric signals for operating the piezoelectric element 4, 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, 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, an elastic member such as rubber may be disposed in a compressed state between one end surface of the piezoelectric element 4 and the other end surface of the fitting portion 22 in the drive shaft 6. Also in this case, since the piezoelectric element 4 is biased to the other side in the extending direction of the reference line FL by the elastic member, for example, a weight member is attached to the other end of the piezoelectric element 4 without providing the elastic member. Compared to such a case, the support stability of the piezoelectric element 4 by the holder 3 can be further improved.

  Moreover, in the said embodiment, although the piezoelectric element 4 was urged | biased by the other side in the extension direction of the reference line FL, it is not limited to this. As an example, by attaching a tension spring or the like between one end surface of the piezoelectric element 4 and the other end surface of the fitting portion 22 in the drive shaft 6, the piezoelectric element 4 is placed on one side in the extending direction of the reference line FL. It may be energized.

  Further, the one end surface of the piezoelectric element 4 and the other end surface of the fitting portion 22 are not directly pressed or pulled in the drive shaft 6, and the other end surface of the piezoelectric element 4 or the other end surface of the fitting portion 22 is not interposed. The piezoelectric element 4 may be urged in the extending direction of the reference line FL by indirectly pressing or pulling.

  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 support in the extending direction of the reference line FL can be used as long as it is an elastic support. It may be supported from the side.

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 circuit diagram of the drive circuit which operates the piezoelectric element shown by FIG. FIG. 4 is a waveform diagram of an input signal input to the drive circuit shown in FIG. 3. FIG. 4 is a waveform diagram of an output signal output from the drive circuit shown in FIG. 3.

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 ... Bearing hole (bearing part), 20 ... Support member, 21 ... fixed part, 22 ... fitting part, 26 ... spring (biasing member), FL ... reference line.

Claims (2)

An electromechanical transducer that expands and contracts in the extending direction of a predetermined reference line;
A hollow 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;
A support member that is provided on the bearing portion, and has a fixed portion that is fixed to the holder, and a fitting portion that is fitted from one end into the drive shaft;
A drive device comprising: an urging member disposed between the electromechanical conversion element and the fitting portion in the drive shaft and urging the electromechanical conversion element in the extending direction; .   The drive device according to claim 1, wherein the biasing member is a spring disposed in a compressed state between the electromechanical conversion element and the fitting portion in the drive shaft.

Images