WO2010067774A1

WO2010067774A1 - Ultrasonic motor

Info

Publication number: WO2010067774A1
Application number: PCT/JP2009/070476
Authority: WO
Inventors: 梢平今井; 昭広沖; 隆松尾; 明小坂; 茂昭栃本; 勝一浦谷
Original assignee: コニカミノルタオプト株式会社
Priority date: 2008-12-12
Filing date: 2009-12-07
Publication date: 2010-06-17

Abstract

The ultrasonic motor is equipped with a vibrating body (12) in which a piezoelectric element (12a) vibrates at a high frequency, and a moving body which is brought into pressure contact with the vibrating body (12) and is moved by the aforementioned high-frequency vibration. The shape of the contact part (12d) of the vibrating body (12) that contacts the moving body is formed to be longer in the direction to intersect the direction the moving body moves than the length in the direction the moving body moves. With the ultrasonic motor that has such a construction, the vibrating body (12) and the moving body are brought into linear contact by the contact part (12d), so deformation and abrasion of the contact part can be limited by a reduction in the contact stress caused by increased contact area, and the transmission of torque can be improved while detection sensitivity and resolution are maintained.

Description

Ultrasonic motor

The present invention relates to an ultrasonic motor, and is particularly suitably used for a lens drive mechanism of a micro camera unit (MCU) that can be mounted on a digital still camera (DSC), a mobile phone, or the like, or an optical pickup unit such as a DVD. The present invention relates to a small ultrasonic motor.

Ultrasonic motors have advantages such as high torque, high holding power when stopped, and low noise compared to electromagnetic motors. On the other hand, when performing speed control or position control, an ultrasonic motor needs to be separately equipped with a position detection sensor. For this reason, when the ultrasonic motor is applied to a small apparatus as described above, it is disadvantageous compared to an electromagnetic stepping motor or a voice coil motor in terms of its arrangement and size. was there. However, if this point is improved, the ultrasonic motor will be very superior to the electromagnetic type in terms of torque and efficiency.

Therefore, in order to cope with such a problem, Patent Document 1 proposed a self-sensing ultrasonic motor. In this conventional ultrasonic motor, a protrusion is provided on the rotor, and a detection piezoelectric element is sandwiched between piezoelectric elements on the stator side. The ultrasonic motor calculates the amount of rotation of the rotor from a detection signal corresponding to the orientation of the non-uniform structure and the detection piezoelectric element that appears in the output of the vibration detector due to unevenness of the surface pressure generated by the protrusion. Detected.

The above-described conventional technique is excellent in that it is not necessary to provide a means for detecting the rotation amount or the rotation position of an encoder or the like. However, in this prior art, since the change in the vibration state of the stator (vibrating body) due to the change in the contact state between the rotor and the stator (vibrating body) is detected by the piezoelectric element, the detection sensitivity increases if the rotor contact portion is reduced. As a result, adverse effects such as a decrease in driving performance are caused. More specifically, the smaller the protrusion, the higher the detection sensitivity and S / N. However, the area of the portion where the driving force can be transmitted becomes smaller, the torque becomes insufficient, the contact stress of the protrusion increases, and the wear increases. It becomes easy to do.

JP-A-6-133570

The present invention has been made in view of the above circumstances, and its purpose is to improve the torque transmission while suppressing deformation and wear of the contact portion while maintaining detection sensitivity and resolution. And providing an ultrasonic motor capable of detecting a position.

The ultrasonic motor according to the present invention includes a vibrating body in which a piezoelectric element performs high-frequency vibration, and a moving body that is in pressure contact with the vibrating body and is moved by the high-frequency vibration, and the vibration in contact with the moving body. The shape of the contact part of the body is formed longer in the direction intersecting the moving direction of the moving body than the length of the moving body in the moving direction. In the ultrasonic motor having such a configuration, the contact portion is a line contact formed by extending from the point contact so as to intersect the moving direction of the moving body. Therefore, the ultrasonic motor having such a configuration can suppress the deformation and wear of the contact portion by reducing the contact stress due to the increase in the contact area while maintaining the detection sensitivity and the resolution, and can transmit the torque (corrosion). ) Can be improved.

The above and other objects, features and advantages of the present invention will become apparent from the following detailed description and the accompanying drawings.

It is a schematic block diagram of the lens drive unit using the ultrasonic motor which concerns on one Embodiment of this invention. FIG. 2 is an axial sectional view showing a structure of the ultrasonic motor shown in FIG. 1. FIG. 6 is a six-sided view of a vibrating body in the ultrasonic motor shown in FIG. 1. FIG. 4 is a plan view and a bottom view showing both front and back surfaces of each layered piezoelectric element in the vibrating body shown in FIG. 3. It is a perspective view which shows the mode of a deformation | transformation of the bending primary mode of the piezoelectric element in the vibrating body shown in FIG. It is a figure which shows the mode of the vibration of the said vibrating body by the deformation | transformation of the piezoelectric element in the vibrating body shown in FIG. It is a perspective view of the moving body in the ultrasonic motor shown in FIG. FIG. 4 is a development view for explaining driving of the moving body by vibration of the vibrating body shown in FIG. 3. It is a graph for demonstrating the detection mechanism of the rotation position of the moving body shown in FIG. It is a wave form diagram for demonstrating a mode that position detection is performed from the phase difference in the ultrasonic motor shown in FIG. FIG. 3 is a block diagram of a drive circuit that performs position detection based on an amplitude value of a detection voltage according to an embodiment of the present invention. It is a block diagram of the drive circuit which performs a position detection based on the phase difference of the detection voltage of other one Embodiment of this invention. It is a perspective view which shows the structure of the contact part of one Embodiment of this invention. It is a figure which shows typically the comparison of the structure of the detection element in patent document 1 and this Embodiment. It is a perspective view which shows the structure of the contact part of the 1st modification in one Embodiment of this invention. It is a perspective view which shows the structure of the contact part of the 2nd modification in one Embodiment of this invention. It is a perspective view which shows the structure of the contact part of the 3rd modification in one Embodiment of this invention. It is a perspective view which shows the structure of the contact part of the 4th modification in one Embodiment of this invention. It is a figure which shows typically a mode that the mobile body which concerns on the further another form of implementation of this invention is driven with a vibrating body. It is a figure for demonstrating the positional relationship (angle) of the contact part and detection area of a vibrating body.

Hereinafter, an embodiment according to the present invention will be described with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted suitably.
(Configuration of the embodiment)

[Embodiment 1]
FIG. 1 is a schematic configuration diagram of a lens driving unit 2 using an ultrasonic motor 1 according to an embodiment of the present invention. This lens driving unit 2 is used for zooming of a digital still camera (DSC) or a digital video camera, or for correcting aberrations of a pickup lens of a DVD, and is a small ultrasonic wave having a thickness W1 of about 3 to 5 mm, for example. It is a motor. A cylindrical ultrasonic motor 1 is attached to a frame 3 of a lens unit, an output shaft of which is a lead screw 11, and a linear motion lens feed mechanism that directly moves a lens 7 via a guide member 6. Is configured. The frame 3 is provided with

guide shafts

4 and 5 in parallel with the lead screw 11, and a lens 7 is held by a guide member 6 slidable on the

guide shafts

4 and 5. A lead screw 11 is engaged with the guide member 6, and when the lead screw 11 rotates, the guide member 6, and thus the lens 7, is moved to the lead screw 11 (ultrasonic motor 1) and the

guide shafts

4, 5. Is displaced in the direction of the axis (left and right in the figure).

FIG. 2 is an axial sectional view showing the structure of the ultrasonic motor 1. The ultrasonic motor 1 includes a vibrating body (stator) 12 in which a piezoelectric element 12a performs high-frequency vibration, a moving body (rotor) 13 that is in pressure contact with the vibrating body 12 and moved by the high-frequency vibration, and a vibrating body 12. A pressure member 14 that presses against the moving body 13, a bottomed cylindrical case 15 that accommodates them, a lead screw 11 that is fixed to the moving body 13 integrally or by caulking, and the lead screw 11 is pivotally supported. And a pair of bearing

members

16, 17.

One bearing member 16 closes the open end of the bottomed cylindrical case 15 and supports the base end portion 11a at one end of the lead screw 11 in the radial direction. The other bearing member 17 is composed of a ball bearing that fits into a cap 18 attached to the frame 3. A concave surface 11 c formed at the free end portion 11 b of the other end of the lead screw 11 is fitted into the radial end of the free end portion 11 b. Support in direction and thrust direction.

The vibrating body 12 includes a piezoelectric element 12a, a contact member 12b on the moving body 13 side, and a weight member 12c for stability on the opposite side, and is rotated with respect to the case 15 by a regulating member (not shown). Is controlled, and the axis of the movable body 13 is positioned and held. The vibrating body 12 is urged toward the moving body 13 (right side in the figure) by the pressing member 14, and the contact member 12 b is pressed against the moving body 13. On the other hand, the second bearing member 17 receives the reaction force from the cap 18 due to the pressing force from the moving body 13 to the lead screw 11 at the center of rotation so that the friction loss can be minimized. It is configured. A screw 18a is engraved between the cap 18 and the frame 3, and the pressing force can be adjusted by moving the cap 18 in the left-right direction in the figure by the amount of rotation of the screw 18a. Yes. Then, after the adjustment, for example, the cap 18 is fixed to the frame 3 by adhesion.

FIG. 3 is a hexahedral view of the vibrating body 12, (a) is a top view, (b) is a front view, (c) is a side view, and (d) is a bottom view. . In FIG. 3, as described above, the vibrating body 12 includes a stacked piezoelectric element 12a in which a plurality of piezoelectric layers 12f are stacked, a contact member 12b on the moving body 13 side, and a weight member 12c on the opposite side. They are composed by bonding. For the adhesive, an epoxy adhesive having high rigidity and high adhesive strength is used. The contact member 12b is made of ceramics such as alumina and zirconia having high wear resistance. In this contact member 12 b, three spherical contact portions 12 d are arranged at equal intervals (120 ° intervals) in the circumferential direction of the piezoelectric element 12, and are pressed by the pressing force of the pressure member 14 described above. Each vertex 12e of the contact portion 12d contacts the moving body 13. The weight member 12c is made of tungsten having a high specific gravity or a copper or iron-based tungsten alloy or the like in order to suppress the deflection on the base end side due to the bending vibration of the piezoelectric element 12a as described later.

FIG. 4 is a plan view and a bottom view showing both front and back surfaces per layer of the multilayer piezoelectric element 12a. Each piezoelectric layer 12f has a piezoelectric layer 12g made of PZT (lead zirconate titanate) sandwiched between one surface (FIG. 4A) at equal intervals in the circumferential direction (90 ° intervals). A plurality of drive electrodes IA, IB, IC, ID to which a drive signal from a drive circuit that is not input is input are formed and arranged, and include a region on the outer peripheral side as much as possible with the largest bending displacement of the piezoelectric element described later. In addition, a detection electrode IS for outputting a detection signal to a detection circuit (not shown) is formed and arranged by dividing into a plurality of drive electrodes IA, IB, IC, ID. One surface (FIG. 4A) of the piezoelectric layer 12f (piezoelectric layer 12g) is divided into a plurality of regions, and the drive electrodes IA, IB, IC, ID, and detection electrodes are divided into the divided regions. IS is arranged. The plurality of drive electrodes IA, IB, IC, ID are four in the example shown in FIG. In the example shown in FIG. 4A, between the two drive electrodes ID and IC arranged adjacent to each other in the four drive electrodes IA, IB, IC, ID arranged at intervals of 90 ° in the circumferential direction, A detection electrode IS is arranged. A solid GND electrode IG is formed on the other surface (FIG. 4B) in common. These internal electrodes IA, IB, IC, ID; IS and IG are formed by silver palladium printing or the like, and between the laminated piezoelectric layers 12g, the drive electrodes IA, IB, IC, ID and detection electrodes IS and GND electrodes IG are alternately formed.

The electrodes IA, IB, IC, ID; IS and IG in each piezoelectric layer 12f are common to the external electrodes OA, OB, OC, OD; OS and OG formed by screen printing or vapor deposition of silver or gold. (FIGS. 3B, 3C, and 4). The external electrodes OA, OB, OC, OD; OS and OG are joined with a lead wire, a flexible substrate (lead wire 12h in the example of FIG. 3), etc. by solder, a conductive adhesive, etc. A drive signal is input and a detection signal is output to and from the detection circuit. In order to easily form these external electrodes OA, OB, OC, OD; OS and OG, the piezoelectric element 12a is preferably a cylinder or a prism, particularly a quadrangular prism. Each piezoelectric layer 12f and electrodes IA, IB, IC, ID; IS and IG formed thereon are polarized in the same direction after lamination.

With respect to the piezoelectric element 12a configured in this manner, a phase corresponding to the equal interval (90 ° interval) between the drive circuit (not shown) and each of the drive electrodes IA, IB, IC, ID and the GND electrode IG. Are applied with high-frequency electric fields that are shifted from each other by 90 °, the regions of the drive electrodes IA, IB, IC, and ID perform stretching vibrations that are 90 ° out of phase. Then, when the frequency of the drive signal is brought close to the resonance frequency, the bending primary mode vibration as shown in FIG. 5 is excited in the piezoelectric element 12a with the 90 ° phase shift.

Here, as described above, the weight member 12c is attached to the proximal end side of the piezoelectric element 12a and is substantially fixed to the case 15 via the pressure member 14, and the contact portion on the distal end side is caused by the bending vibration. 12d performs a predetermined motion corresponding to the bending vibration, for example, a revolving motion (oscillating vibration). As a result, elliptical vibrations whose phases are shifted from each other by 120 ° are generated at the apexes 12e of the contact portion 12d, as indicated by reference numeral 12r in FIG. The frictional force generated by the elliptical vibration 12r is rotationally driven around the axis of the piezoelectric element 12a. Similar to FIG. 3, FIG. 6A is a top view of the vibrating body 12, and FIG. 6B is a front view.

On the other hand, FIG. 7 is a perspective view of the moving body 13, and FIG. 8 is a cross-sectional view illustrating the vicinity of the contact portion between the moving body 13 and the contact member 12b of the vibrating body 12. Note that FIGS. 7 and 8 are upside down with respect to FIGS. 3 and 6. The moving body 13 includes a lead screw 11 as a shaft for taking out the rotation, a moving body main body 13a fixed to the lead screw 11, and a cover plate 13b stacked on the moving body main body 13a. On the surface of the main body 13a on the cover plate 13b side, grooves 13c are formed at equal intervals in the circumferential direction extending in the radial direction. And this groove | channel 13c is a structurally non-uniform | heterogenous part, and becomes the detection area 13d. Further, a portion where the groove 13c is not formed is a structurally uniform portion, and becomes a drive (normal) region 13e.

The moving body 13 is created by forming a groove 13c on a moving body main body 13a made of a metal such as stainless steel by machining or etching and then laminating a thin cover plate 13b made of stainless steel or the like. The cover plate 13b is subjected to nitriding treatment or the like in order to improve wear resistance. Lamination of the cover plate 13b to the movable body main body 13a is performed by joining with a thin adhesive layer or the like or by spot welding or the like, and the movable body main body 13a and the cover plate 13b rotate integrally without any deviation. It only has to be like this. By comprising in this way, the ultrasonic motor 1 of the same shape as the normal cylindrical motor from which an output shaft extends from a cylindrical main body is realizable.

In the ultrasonic motor 1 configured as described above, FIG. 8 is a diagram schematically showing how the moving body 13 is driven by the vibrating body 12. Referring to FIG. 8, when the piezoelectric element 12a is driven in a resonance state, the moving body 13 is moved (rotated) to the left in the figure indicated by the arrow 13f by the elliptical vibration 12r of the vertex 12e of the contact portion 12d. The apex 12e passes alternately over the drive area 13e and the detection area 13d of the moving body 13. Here, the groove 13c, that is, the detection area 13d, is arranged so that the vertex 12e passes at the same timing, that is, the detection area 13d is 120 ° / n (n is an integer, with respect to the vertex 12e every 120 °. 8 is formed every n = 4).

According to this, the voltage and the phase of the detection voltage output from the detection electrode IS are as shown in FIG. 9A and FIG. 9B, respectively. First, FIG. 9A shows the amplitude value of the detection voltage, corresponding to the case where the reference symbol α11 (solid line) is in the drive region 13e, and corresponding to the case where the reference symbol α12 (broken line) is in the detection region 13d. ing. The frequency f0 at which the detected voltage is the maximum value, that is, the distortion is the maximum, is the resonance point, and the amplitude value greatly changes in the vicinity thereof. Driving is performed at a frequency f0 'in the vicinity thereof. When the apex 12e enters the detection region 13d, the resonance frequency shifts to f0 ″ on the low frequency side, and the amount of distortion of the piezoelectric element 12a decreases. This reduces the amplitude by ΔV. This is because the spring constant of the contact portion of the moving body 13 is different between the drive area 13e and the detection area 13d. In the drive area 13e, the moving body main body 13a is located directly below the cover plate 13b. On the other hand, in the detection area 13d, the space immediately below the cover plate 13b is a space, and the structure is such that the pressure at the contact point is supported by the elasticity of the cover plate 13b, and the rigidity is reduced. Thus, the resonance frequency of the piezoelectric element 12a decreases, and the resonance state of the piezoelectric element 12a changes between the drive area 13e and the detection area 13d.

FIG. 9B shows the phase difference of the detection voltage with respect to the drive signal, corresponding to the case where the reference symbol α21 (solid line) is the drive region 13e, and the case where the reference symbol α22 (broken line) is the detection region 13d. It corresponds to. For the same reason as described above, when the vertex 12e enters the detection region 13d and the resonance frequency shifts to the low frequency side, the phase of the detection voltage advances by Δθ. FIGS. 10A and 10B are diagrams for explaining the phase difference. FIG. 10A shows that the driving area 13e is passing, and FIG. 10B shows that the detecting area 13d is passing. In both FIGS. 10A and 10B, the drive signal is indicated by a solid line, and the detection voltage is indicated by a broken line. The deviation θ2 is large during the passage of the detection area 13d in which the rigidity is lowered with respect to the deviation θ1 while passing through the drive area 13e, that is, the phase difference (delay) is large.

Using this, the

drive circuits

21 and 31 of the ultrasonic motor 1 are configured as shown in FIGS. 11 and 12, for example. FIG. 11 shows a drive circuit 21 that detects the position of the detection electrode IS based on the amplitude value of the detection voltage shown in FIG. 9A. FIG. 12 shows the phase difference shown in FIG. The drive circuit 31 which performs position detection based on it is shown. Each of the

drive circuits

21 and 31 includes

drive units

22 and 22, position detection units 23 and 33, and control units 24 and 34.

The drive unit 22 has a configuration common to the

drive circuits

21 and 31, and includes a drive voltage generation unit 25, a phase shift unit 26, and a filter unit 27. The drive voltage generator 25 can generate a high-frequency signal with sufficient power to drive the piezoelectric element 12a. The high-frequency signal is input to the phase shift unit 26 to create a four-phase drive signal whose phases are shifted from each other by 90 ° as described above, and each of the drive electrodes IA, It is applied between IB, IC, ID and the GND electrode IG.

The position detector 23 includes an amplitude detector 28, a deviation calculator 29, and a position calculator 30 in order to detect the amplitude. The amplitude detection unit 28 detects the amplitude value (output voltage) of the detection voltage output from the detection electrode IS, and the deviation calculation unit 29 calculates the amplitude value and the known ideal amplitude value (optimum drive amplitude value). The deviation is calculated, and the position calculation unit 30 detects the rotation position (rotation amount) and rotation speed of the moving body 13 from the calculation result. The control unit 24 causes the drive voltage generation unit 25 to generate the drive signal in a desired direction.

On the other hand, the other position detection unit 33 includes a phase difference detection unit 38, a deviation calculation unit 39, and a position calculation unit 40 in order to perform the phase detection. The phase difference detection unit 38 detects the phase difference between the detection voltage output from the detection electrode IS and the drive signal to any phase, and the deviation calculation unit 39 detects the phase difference and a predetermined phase difference (optimum). The position calculation unit 40 detects the rotation position (rotation amount) and rotation speed of the moving body 13 from the calculation result.

As shown in FIG. 7 and FIG. 8, the ultrasonic motor 1 configured as described above has a moving body 13 in which the moving body 13 is moved in the moving direction (the arrow shown above) in order to change the vibration state of the vibrating body 12. Grooves 13c are formed at equal intervals in the moving direction 13f of the moving body 13 and extending in a direction orthogonal to the direction of the reference numeral 13f and its opposite direction (hereinafter referred to as the moving direction including the reverse direction). Then, the detection unit detects a change in the vibration state of the vibration body 12 caused by the contact portion 12d of the vibration body 12 passing through the groove 13c as a vibration change of the piezoelectric element 12a constituting the vibration body 12. Thus, the ultrasonic motor 1 is a self-sensing ultrasonic motor that can detect the rotational position (rotation amount) and rotational speed of the moving body 13 without a sensor such as an encoder. In the present embodiment, the contact portion 12d is formed so as to extend in the direction 13g perpendicular to the moving direction 13f of the moving body 13, and makes line contact with the moving body 13.

FIG. 13 is a perspective view showing the structure of the contact portion 12d. Referring to FIGS. 3 and 6 and FIG. 13, contact portion 12 d of the present embodiment divides the sphere into half cracks along moving direction 13 f of moving body 13, and between these half-broken hemispheres 12 x. The connecting portion 12y extends in a direction 13g perpendicular to the moving direction 13f. That is, the contact portion 12d has a shape in which the hemisphere 12x is fitted into both ends of a connecting portion 12y having a hook-back shape obtained by horizontally extruding the arch (U). Furthermore, in other words, the contact portion 12d is shaped such that each hemisphere 12x is coupled to both ends of a semi-cylindrical connecting portion 12y obtained by cutting the cylinder along the axial direction. Thereby, a structure in which the contact portion 12d is in line contact with the moving body 13 in the direction 13g orthogonal to the moving direction 13f of the moving body 13 is realized.

With this configuration, the contact portion 12d does not extend in the moving direction 13f of the moving body 13, so that detection sensitivity and resolution can be maintained. And the contact part 12d can suppress the deformation | transformation and wear of the contact part 12d by the reduction of the contact stress by the increase in the contact area by the connection part 12y of the contact part 12d, and improves torque transmission (biting). Can do. In the above description, the extending direction of the contact portion 12d is the direction 13g orthogonal to the moving direction 13f of the moving body 13. However, the deviation from the orthogonal direction 13g causes a decrease in detection sensitivity and resolution. It does not have to be orthogonal to, and it is sufficient if it intersects. The range of the extent deviated from the orthogonal direction 13g is defined according to an allowable range such as a rotational position (amount of rotation) in the ultrasonic motor 1 and a detection accuracy of the rotational speed, which is determined in advance by, for example, specifications.

Here, FIG. 14 schematically shows a comparison of the structure of the detection element between Patent Document 1 and the present embodiment. FIG. 14A shows the structure in Patent Document 1. In Patent Document 1, the elastic body 101 resonates due to the displacement of the piezoelectric element, and the structure expands the displacement of the piezoelectric element. ing. One or two electrodes for detection over the entire surface of the piezoelectric element are formed outside the piezoelectric element. That is, the electrode for detection in Patent Document 1 is not formed by dividing the surface of the piezoelectric element. In the case of two layers, signal processing is performed layer by layer in order to increase the position resolution, so the configuration is substantially as shown in FIG.

On the other hand, in the present embodiment, the piezoelectric element 12a itself expands the resonance displacement and has a laminated structure as described above. As shown in FIG. 4, each piezoelectric layer 12f (12g) has a drive electrode IA. , IB, IC, ID are divided into regions to form the detection electrode IS, and the detection electrode IS is formed in the same phase position across a plurality of layers and connected in parallel by the external electrode OS.

Therefore, assuming that the capacitance between the detection electrode IS and the GND electrode OS formed on the opposite surface across the piezoelectric layer 12g is equal and the strain of each piezoelectric layer 12f is equal, the present embodiment is Assuming that charges are generated n times the number of layers and the same amount of noise (Qn in the figure) is generated, an S / N of about n times the number of layers can be obtained. In addition, since the detection electrode IS is formed at the most strained portion in each piezoelectric layer 12f, a signal can be extracted efficiently, and this also increases sensitivity.

Further, in the case of Patent Document 1, the antinode of vibration with the largest strain is in the central portion 101a of the rod-like elastic body 101, and the amount of strain that can be detected by the piezoelectric element provided at the end is relatively small. Therefore, the ultrasonic motor of Patent Document 1 does not have a structure that can efficiently extract electric charges. On the other hand, in the case of the present embodiment, the piezoelectric element 12a itself resonates and the piezoelectric element 12a expands its displacement, and two nodes (both ends) in the vibration of the bending primary mode are used. The detection electrode IS is formed in the vicinity of the central portion 12k, which is the antinode of vibration with the largest deformation between the two). For this reason, the ultrasonic motor 1 of the present embodiment can increase the detection sensitivity and can cope with high resolution.

Furthermore, in the configuration of Patent Document 1, it is necessary to separately provide a piezoelectric layer for detection, and the vibrating body becomes long. On the other hand, in the present embodiment, since the detection electrode IS is arranged by dividing the region in the same plane as the drive electrodes IA, IB, IC, ID, the vibrating body (piezoelectric element 12a) is lengthened. There is no need to do. In addition, since the ultrasonic motor 1 of the present embodiment can arrange both the drive electrodes IA, IB, IC, ID and the detection electrode IS at the position of the antinode of the vibration, it can excite the vibration efficiently and has a sensitivity. Detection can be performed well.

Further, as in Patent Document 1, in the case of a configuration in which a detection electrode is not provided and a change in voltage applied to the piezoelectric element is detected using an impedance matching element (coil), the frequency characteristics of the impedance matching element and the vibrating body The degree of change is determined by both of the frequency characteristics of the signal and it is difficult to detect it easily and stably due to individual differences. In the case of the above configuration, it is necessary to add the impedance matching element, which increases the circuit scale. On the other hand, the ultrasonic motor 1 of the present embodiment can perform stable detection without being influenced by the individual difference or the like.

In the above description, although the output from the detection electrode IS is extracted as a voltage, the output may be extracted by current detection that short-circuits between the detection electrode IS and the GND electrode IG. In this case, the detection is stronger than the extraction by voltage with respect to the external noise Qn. However, in Patent Document 1, since the amount of generated charge is small, the current level is very small and the detection becomes difficult.

[Embodiment 2]
FIG. 15 is a perspective view of a contact portion 12d ′ according to another embodiment of the present invention. The contact portion 12d ′ is similar to the contact portion 12d described above, and the corresponding portions are denoted by the same reference numerals and description thereof is omitted. Here, in the present embodiment, the contact portion 12d ′ is divided into two in the direction 13g in which the contact portion 12d is orthogonal to the moving direction 13f of the moving body 13. Therefore, although the contact area decreases and the contact stress increases, according to this configuration, it is possible to easily discharge the dust generated by the contact of the moving body 13 with the cover plate 13b.

[Embodiment 3]
FIG. 16 is a perspective view of a contact portion 42 according to still another embodiment of the present invention. The contact portion 42 is similar to the contact portion 12d described above, and corresponding portions are denoted by the same reference numerals, and description thereof is omitted. Here, in the present embodiment, the contact portion 42 has a triangular prism shape, and the long axial direction of the triangular prism (direction from one surface (bottom surface) to the other surface (top surface) of the triangle) The moving body 13 is formed in a shape (matched and aligned) in a direction 13g intersecting with the moving direction 13f. Even if it forms in this way, the line contact in the direction 13g orthogonal to the moving direction 13f of the said mobile body 13 is realizable.

On the other hand, FIG. 17 shows a contact portion 42 ′ in which the contact surface (vertex 12 e) is chamfered and the cross section perpendicular to the axis is formed in a trapezoidal shape. By forming in this way, although the detection sensitivity and resolution are lowered, the contact area can be increased and the contact stress can be reduced.

[Embodiment 4]
FIG. 18 is a perspective view of a contact portion 52 according to still another embodiment of the present invention. The contact portion 52 is similar to the contact portion 12d described above, and corresponding portions are denoted by the same reference numerals, and description thereof is omitted. Here, in the present embodiment, the contact portion 52 has a shape obtained by rotating an ellipse having a major axis 53 in a direction 13g perpendicular to the moving direction 13f of the moving body 13 into a semicircular arc around the major axis. is doing. Accordingly, the contact portion 52 has a semicircular arc shape having curvatures in the moving direction 13f and the orthogonal direction 13g of the moving body 13, and the orthogonal direction 13g has a larger curvature than the moving direction 13f. Even if it forms in this way, the line contact in the direction 13g orthogonal to the moving direction 13f of the moving body 13 is realizable.

[Embodiment 5]
FIG. 19 is a diagram schematically illustrating a state in which the moving body 13x according to still another embodiment of the present invention is driven by the vibrating body 12. The vibrating body 12 is the same as that in FIG. In the present embodiment, the moving body 13x has a low friction coefficient layer 13z extending in the radial direction and having a predetermined friction coefficient at equal intervals in the circumferential direction instead of the groove 13c on the moving body main body 13y. This low friction coefficient layer 13z is formed as the structurally non-uniform detection area 13d. The low friction coefficient layer 13z is formed by patterning a material having a low friction coefficient such as DLC. As a result, the low friction coefficient layer 13z becomes lower than the friction coefficient of the drive region 13e in the movable body main body 13y. The detection electrode IS detects a change in the vibration state due to the difference in friction coefficient. In this case, the vibration state does not change the resonance frequency as described above, and the vibration attenuation due to the slip is mainly caused. Although a change occurs, the position detection units 22 and 33 can perform position detection in the same manner. Even in this case, an ultrasonic motor having the same shape as that of a normal cylindrical motor having an output shaft extending from the cylindrical main body can be realized.

In addition, as shown in FIG. 20, each

contact part

12d, 12d ', 42, 42', 52 of the vibrating body 12 has a predetermined width W1, and is orthogonal to the moving direction 13f of the moving

bodies

13, 13x. The maximum width W2 in the movement direction 13f may be configured to straddle the structurally non-uniform detection area 13d by the groove 13c or the low friction coefficient layer 13z, but the detection area 13d Since the detection sensitivity decreases as the distance straddling is increased, each

contact portion

12d, 12d ′, 42, 42 ′, 52 of the vibrating body 12 does not straddle the detection region 13d and is structurally between the detection regions 13d. It is preferable to fit within a uniform drive region 13e.

This specification discloses various modes of technology as described above, and the main technologies are summarized below.

An ultrasonic motor according to one aspect includes a piezoelectric element, the vibrating element that performs high-frequency vibration, a moving body that is in pressure contact with the vibrating body and moved by the high-frequency vibration, and a detection unit. An ultrasonic motor provided, wherein the moving body extends in a direction intersecting with a moving direction of the moving body in order to change a vibration state of the vibrating body and is predetermined in a moving direction of the moving body. A structurally non-uniform portion is formed at a predetermined interval, and the detection unit is in a vibration state of the vibrating body due to a contact portion of the vibrating body contacting the moving body passing through the non-uniform portion. The position information or movement information of the moving body can be detected by detecting the change in the moving body, and the shape of the contact portion of the vibrating body is larger than the length of the moving body in the moving direction. Long in the direction that intersects the direction It is formed.

In the ultrasonic motor having such a configuration, the contact portion is formed so as to extend from the point contact so as to intersect the moving direction of the moving body, and is in line contact. Therefore, the ultrasonic motor having such a configuration can suppress the deformation and wear of the contact portion by reducing the contact stress due to the increase in the contact area while maintaining the detection sensitivity and the resolution, and can transmit the torque (corrosion). ) Can be improved.

In another aspect, in the above-described ultrasonic motor, preferably, the structurally non-uniform portion is a groove or a ridge.

With such a configuration, as an example, a structurally non-uniform portion is realized by a groove or a protrusion.

In another aspect, in the above-described ultrasonic motor, preferably, the piezoelectric element is formed by laminating a plurality of piezoelectric layers in which a plurality of drive electrodes divided in the circumferential direction are arranged, and each drive electrode Is provided with a high-frequency electric field whose phases corresponding to the positional displacement amount of the drive electrode are shifted from each other from the drive circuit, so that the vibrating body performs a motion corresponding to a predetermined vibration mode, The moving body is rotated around the axis of the vibrating body by the contact portion attached to the tip of the vibrating body, and the moving body is a disk-shaped disk member having an output shaft for taking out rotation fixed to the center. It is to be.

According to this configuration, since the moving body is provided with the disk-shaped disk member in which the output shaft for extracting the rotation is fixed at the center, an ultrasonic motor similar to a normal motor in which the output shaft extends is realized. Preferably, the piezoelectric element is configured by laminating a plurality of piezoelectric layers in a columnar or prismatic shape. As a result, an ultrasonic motor having the same shape as a normal cylindrical motor whose output shaft extends from the cylindrical main body is realized.

In another aspect, in the above-described ultrasonic motor, preferably, the detection unit includes an antinode region of vibration due to the high-frequency vibration in the plurality of piezoelectric layers, and is divided into the drive electrode and the region. And a detection electrode that can detect the vibration state, and a position detection unit that detects position information of the moving body from the amplitude or phase of the detection voltage at the detection electrode.

According to this configuration, in each of the plurality of piezoelectric layers, the detection electrode includes an antinode region of vibration due to high-frequency vibration and is divided into regions from the drive electrode, so that the vibration state can be detected. Therefore, the detection electrode can detect the passage of the non-uniform portion with high sensitivity, that is, high resolution, and the detection unit can reliably detect the position information. In addition, according to this configuration, the detection unit can detect the non-uniform portion and the uniform portion with high sensitivity, so that the difference between them does not have to be larger than necessary. A decrease in driving performance due to the formation of a rough portion is minimized.

In another aspect, in the above-described ultrasonic motors, preferably, the detection electrodes are formed at the in-phase positions of the piezoelectric layers and connected in parallel to each other.

According to this configuration, when the piezoelectric element is configured by laminating a plurality of n layers of piezoelectric layers, the detection electrodes are formed in the respective piezoelectric layers at the same phase position, and these are connected in parallel to each other. . For this reason, the capacitance between the detection electrode and the GND electrode formed on the opposite surface across the piezoelectric layer increases n times. Therefore, according to this configuration, the ultrasonic motor can further increase the detection sensitivity and increase the resistance to noise.

Moreover, in another aspect, in the above-described ultrasonic motor, preferably, the contact portion divides the sphere in half along the moving direction of the moving body to form a half-cracked portion, and these half-cracked portions In other words, they are connected by a connecting portion extending so as to intersect the moving direction of the moving body.

According to this configuration, the line contact in the direction intersecting the moving direction of the moving body can be realized by the contact portion having the shape including the half crack portion and the connecting portion therebetween.

Moreover, in another aspect, in the above-described ultrasonic motors, preferably, the contact portion has a triangular prism shape, and a direction in which a long axis direction of the triangular prism intersects a moving direction of the movable body It is a shape that matches.

According to this configuration, the line contact in the direction intersecting the moving direction of the moving body can be realized by the contact portion of the triangular prism.

In another aspect, in the above-described ultrasonic motor, preferably, the contact portion rotates an ellipse having a major axis in a direction intersecting the moving direction of the movable body in a semicircular arc around the major axis. It is the shape made to do.

According to this configuration, the moving direction of the moving body and the intersection thereof have curvature, respectively, and the semicircular arc-shaped contact portion in which the curvature in the moving direction of the moving body and the direction of intersection is larger than the curvature of the moving direction, Line contact in a direction intersecting with the moving direction of the moving body can be realized.

This application is based on Japanese Patent Application No. 2008-317219 filed on Dec. 12, 2008, the contents of which are included in the present application.

In order to express the present invention, the present invention has been properly and fully described through the embodiments with reference to the drawings. However, those skilled in the art can easily change and / or improve the above-described embodiments. It should be recognized that this is possible. Accordingly, unless the modifications or improvements implemented by those skilled in the art are at a level that departs from the scope of the claims recited in the claims, the modifications or improvements are not covered by the claims. It is interpreted that it is included in

According to the present invention, an ultrasonic motor can be provided.

Claims

A vibrating body comprising a piezoelectric element, wherein the piezoelectric element performs high-frequency vibration;
A moving body that is in pressure contact with the vibrating body and is moved by the high-frequency vibration;
An ultrasonic motor including a detection unit,
The moving body is structurally indefinite to extend so as to intersect the moving direction of the moving body in order to change the vibration state of the vibrating body and at a predetermined interval in the moving direction of the moving body. A uniform part is formed,
The detection unit detects positional change or movement of the moving body by detecting a change in a vibration state of the vibrating body caused by a contact portion of the vibrating body contacting the moving body passing through the non-uniform portion. Information can be detected,
The shape of the contact part of the said vibrating body is formed longer in the direction crossing the moving direction of the said moving body than the length of the moving direction of the said moving body.
The ultrasonic motor according to claim 1, wherein the structurally nonuniform portion is a groove or a protrusion.
The piezoelectric element includes a plurality of piezoelectric layers in which a plurality of driving electrodes divided in the circumferential direction are stacked, and each driving electrode has a phase corresponding to a positional deviation amount of the driving electrode from a driving circuit. By applying a high-frequency electric field that is shifted from each other, the vibrating body moves in accordance with a predetermined vibration mode at the tip, and the moving body is vibrated by the contact portion attached to the tip of the vibrating body. Rotated around the body axis,
The ultrasonic motor according to claim 1, wherein the moving body is a disk-shaped disk member in which an output shaft for extracting rotation is fixed in the center.
The detection unit includes a detection electrode that includes an antinode region of vibration due to the high-frequency vibration in the plurality of piezoelectric layers, is divided into regions from the drive electrode, and can detect the vibration state; and the detection electrode The ultrasonic motor according to claim 3, further comprising: a position detection unit configured to detect position information of the moving body from an amplitude or a phase of a detection voltage at.
The ultrasonic motor according to claim 3, wherein the detection electrodes are formed at in-phase positions of the piezoelectric layers and are connected in parallel to each other.
The contact portion is divided by a half along the moving direction of the moving body to form a half-cracked portion, and is connected by a connecting portion extending between the half-cracked portions so as to intersect the moving direction of the moving body. The ultrasonic motor according to claim 1, wherein the ultrasonic motor is formed.
2. The ultrasonic wave according to claim 1, wherein the contact portion has a triangular prism shape, and has a shape in which a long axial direction of the triangular prism is matched with a direction intersecting a moving direction of the moving body. motor.
2. The ultrasonic motor according to claim 1, wherein the contact portion has a shape obtained by rotating an ellipse having a major axis in a direction intersecting a moving direction of the moving body into a semicircular arc around the major axis. .