JP2010283906A - Ultrasonic motor and drive unit using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic motor capable of changing a pressing force against an oscillator. <P>SOLUTION: The ultrasonic motor includes the oscillator 10 for exciting oscillation by the application of an electric signal, an ultrasonic motor body 13 integrated with the oscillator 10 via an elastic section 12, drive sections 12a, 12b integrated with the oscillator 10, and a piezoelectric element 15 expanded and contracted uniaxially by the application of the electric signal, and the oscillator 10 is pressed via the elastic section 12 by the pressing force corresponding to the expansion and contraction of the piezoelectric element 15. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an ultrasonic motor and a driving apparatus using the same.

  When an ultrasonic motor is used as an actuator of a drive device that moves a movable body, a pusher that presses the vibrator and the movable body in contact with the vibrator (contact portion of the vibrator) of the ultrasonic motor is brought into contact with the movable body. It is generally known that it is necessary to apply pressure. Regarding such a technique, for example, Patent Documents 1 and 2 make the following proposals.

  Patent Document 1 proposes an ultrasonic drive device that includes a pressure member that supports a vibration node portion of a vibration member and applies a pressing force that presses the vibration member and a movable body. In this apparatus, the movable member can be moved by the ultrasonic motor by pressurizing the vibrating member with the pressurizing member and generating a frictional force between the vibrating member and the movable member.

  Patent Document 2 proposes a vibration-type driving device in which a magnetic member that presses a vibrating body and a contact member together with a magnetic force is disposed between a first surface of the vibrating body and the contact member. In this apparatus, the vibrating body is configured by joining a vibrating plate, which is an elastic body such as a metal material, and a piezoelectric element plate, and at least a part of the contact member is formed of a ferromagnetic material. In addition, a magnetic force can be generated between the vibrating body (vibrating plate) and the magnetic member, and between the contact member and the magnetic member, and by this magnetic force, the vibrating body and the contact member are press-contacted, A frictional force can be generated between the vibrating body and the contact member.

JP 2001-292484 A JP 2007-31519 A

  Thus, in a drive device using an ultrasonic motor, it is necessary to always bring the vibrator and the movable body into contact with each other and generate a necessary frictional force between the vibrator and the movable body. The frictional force required to move the movable body varies depending not only on the weight of the movable body but also on the load placed on the movable body. Further, when there is a possibility that the drive device is installed in an inclined state, it is necessary to consider a frictional force for preventing the movable body from falling naturally.

  On the other hand, a drive device using an ultrasonic motor is accompanied by wear and friction, and wear and friction increase as the friction force generated between the vibrator and the movable body increases. Therefore, when the frictional force increases, the contact state between the vibrator and the movable body changes, which may affect the driving characteristics and may affect the product life as a driving device.

  In order to reduce the influence of the frictional force on the contact surface between the vibrator and the movable body to the maximum, the weight of the movable body, the load placed on the movable body, the installation state of the drive device (the drive device is tilted diagonally) It is desirable that the frictional force required for driving or the pressing force for pressing the vibrator and the movable body can be changed according to the contact state between the vibrator and the movable body.

However, in the devices described in the above two patent documents, the pressing force that presses the vibrator (vibrating member, vibrating body) and the movable body (contact member) is constant.
In view of the above circumstances, the present invention provides an ultrasonic motor capable of changing the pressing force applied to the vibrator, and a drive device using the ultrasonic motor that can maintain drive characteristics and extend the life of the apparatus. The purpose is to provide.

  In order to achieve the above object, an ultrasonic motor according to a first aspect of the present invention includes an ultrasonic motor that excites vibration by applying an electric signal, and an ultrasonic motor integrated with the vibrator via an elastic portion. A main body, a contact portion integrated with the vibrator, and a pressing means for pressing the vibrator are provided, and the pressing force by the pressing means is variable.

  An ultrasonic motor according to a second aspect of the present invention includes a vibrator that excites vibration by application of an electrical signal, an ultrasonic motor body that is integrated with the vibrator via an elastic portion, and the vibrator. An integrated contact portion; and a piezoelectric element that expands and contracts in one axial direction when an electric signal is applied, and the vibrator is pressed through the elastic portion by a pressing force according to the expansion and contraction of the piezoelectric element. It is characterized by that.

The ultrasonic motor according to a third aspect of the present invention is characterized in that, in the second aspect, an elastic body is disposed between the elastic portion and the piezoelectric element.
An ultrasonic motor according to a fourth aspect of the present invention includes a vibrator that excites vibration by application of an electrical signal, an ultrasonic motor body that is integrated with the vibrator via an elastic portion, and the vibrator. An integrated contact portion; and a piezoelectric element that is coupled to the elastic portion and expands and contracts in a uniaxial direction when an electric signal is applied, and the pressing force according to deformation of the elastic portion accompanying expansion and contraction of the piezoelectric element The vibrator is pressed through the elastic part.

  A drive device using an ultrasonic motor according to a fifth aspect of the present invention includes a base portion, a table disposed so as to be movable parallel to the base portion, and disposed between the base portion and the table. A position detection means comprising: a guide member to be operated; the ultrasonic motor according to the first aspect disposed on the base portion; a scale fixed to the table; and a sensor fixed to the base portion; Control means for applying an electrical signal to the ultrasonic motor and controlling the position of the table and the pressing force by the pressing means of the ultrasonic motor based on the detection signal output from the position detecting means; It is characterized by providing.

  A driving apparatus using an ultrasonic motor according to a sixth aspect of the present invention includes a base portion, a table disposed so as to be movable parallel to the base portion, and disposed between the base portion and the table. The ultrasonic motor according to any one of the second to fourth aspects, a scale fixed to the table, and a sensor fixed to the base portion. An electrical signal is applied to the position detecting means, the vibrator and piezoelectric element of the ultrasonic motor, and the position of the table is controlled and the vibrator is pressed based on the detection signal output from the position detecting means. And a control means for controlling the pressing force at the time.

  According to the present invention, there is provided an ultrasonic motor capable of changing the pressing force to the vibrator, and a driving device using the ultrasonic motor that can maintain the driving characteristics and extend the life of the apparatus. be able to.

It is a top view which shows the structural example of the ultrasonic motor which concerns on Example 1 of this invention. It is a figure which shows the horizontal cross section of the ultrasonic motor shown in FIG. 1, and shows the electrical connection of the ultrasonic motor and a control unit typically. It is a figure which shows the ultrasonic motor which concerns on the modification 1 of Example 1 of this invention. It is a figure which shows the ultrasonic motor which concerns on the modification 2 of Example 1 of this invention. It is a top view which shows the structural example of the drive device using the ultrasonic motor based on Example 2 of this invention. It is AA 'sectional drawing of the drive device shown in FIG. FIG. 6 is a right side view of the drive device shown in FIG. 5, showing a state where the drive device is installed inclined.

  Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 of the present invention relates to an ultrasonic motor.
FIG. 1 is a top view illustrating a configuration example of the ultrasonic motor according to the present embodiment. FIG. 2 is a diagram showing a horizontal section of the ultrasonic motor shown in FIG. 1 and schematically showing an electrical connection between the ultrasonic motor and the control unit.

  In the ultrasonic motor shown in FIGS. 1 and 2, the vibrator 10 is a vibrator that excites vibration by application of an electric signal by the control unit 11. The vibrator 10 is integrated with an ultrasonic motor main body 13 (hereinafter simply referred to as “main body 13”) via an elastic portion (portion indicated by hatching in FIG. 1) 12 at the center of the fixed side surface 10a. ing. Further, on the opposite side surface 10b of the fixed side surface 10a, two identical drive units (an example of a contact unit) 14a and 14b are provided along the longitudinal direction of the vibrator 10, and both the two drive units 14a and 14b are provided. It is integrated and configured. Then, when the vibrator 10 vibrates by the application of an electric signal by the control unit 11, the two drive units 14a and 14b perform an elliptical locus motion.

  In this embodiment, the elastic portion 12 and the main body 13 are formed from a single metal material such as aluminum by wire electric discharge machining or the like. The elastic portion 12 includes a portion that acts as an elastic body and a thick portion 12a that is a central portion that does not act as an elastic body. The thick portion 12a and the vibrator 10 have a high hardness such as a ceramic adhesive. It is bonded with an adhesive. The two drive parts 14a and 14b are formed of a material whose base material is a resin having a relatively small friction coefficient, such as polyacetal or ceramic containing reinforcing fibers.

  The piezoelectric element 15 is a piezoelectric element that expands and contracts in one axial direction (here, the vertical direction in FIG. 2 (or FIG. 1)) by applying an electrical signal from the control unit 11, and is a pressing means that presses the vibrator 10. It is an example. The piezoelectric element 15 is integrated with the mounting seat 16 by bonding or the like, and is attached to the main body 13 via the mounting seat 16. A coil spring (an example of an elastic body) 17 is disposed between the piezoelectric element 15 and the elastic portion (thick portion 12a) 12.

  The control unit 11 is a unit that drives the vibrator 10 and the piezoelectric element 15. The control unit 11 is electrically connected to each of the vibrator 10 and the piezoelectric element 15, and as described above, by applying an electric signal to the vibrator 10, the vibrator 10 is excited to vibrate, and the piezoelectric element 15 The piezoelectric element 15 is expanded and contracted by applying an electric signal.

  According to the above configuration, when an electric signal is applied from the control unit 11 to the piezoelectric element 15, the piezoelectric element 15 expands and contracts in the vertical direction of the sheet of FIG. 2 (or FIG. 1), and the pressing according to the expansion and contraction is performed. The pressure is applied to the vibrator 10 via the coil spring 17 and the elastic part (thick part 12a) 12. Therefore, the pressing force applied to the vibrator 10 can be changed by changing the amount of expansion / contraction of the piezoelectric element 15 by changing an electric signal (for example, voltage) applied to the piezoelectric element 15.

  Further, when an electrical signal is applied from the control unit 11 to the vibrator 10 and vibration is excited in the vibrator 10, the vibration between the vibrator 10 causes the distance between the vibrator 10 and the mounting seat 16 to be minute. However, in the above configuration, since the pressing force is applied to the vibrator 10 through the coil spring 17, the minute distance fluctuation can be absorbed by the coil spring 17, and is caused by the minute distance fluctuation. The fluctuation of the obtained pressing force can be suppressed.

  In addition, although detailed description is abbreviate | omitted in a present Example, when moving a movable body with the ultrasonic motor which concerns on a present Example, after making the movable body contact | abut to two drive parts 14a and 14b, The control unit 11 applies an electric signal to each of the piezoelectric element 15 and the vibrator 10 to apply a pressing force to the vibrator 10 (applying a pressing force to press the vibrator 10 and the movable body), and By causing the driving units 14a and 14b to perform an elliptical locus motion, the movable body can be moved.

  As described above, according to the ultrasonic motor according to the present embodiment, the pressing force applied to the vibrator 10 can be changed by changing the electrical signal (for example, voltage) applied to the piezoelectric element 15 as necessary. It becomes possible.

The ultrasonic motor according to the present embodiment can be modified as follows.
FIG. 3 is a diagram illustrating an ultrasonic motor according to the first modification of the present embodiment. This figure corresponds to FIG. 2 described above.

  As shown in FIG. 3, the ultrasonic motor according to this modification is configured such that the piezoelectric element 15 ′ directly contacts the elastic portion (thick portion 12 a) 12 without providing a coil spring. The piezoelectric element 15 ′ is electrically connected to the control unit 11 in the same manner as the piezoelectric element 15 shown in FIG. 2, and is applied in one axial direction (here, in FIG. This is a piezoelectric element that expands and contracts in the vertical direction of the drawing, and is an example of a pressing means that presses the vibrator 10. The piezoelectric element 15 ′ is also integrated with the mounting seat 16 by bonding or the like, and is attached to the main body 13 via the mounting seat 16.

  Even with such a configuration, it is possible to change the pressing force applied to the vibrator 10 by changing an electric signal (for example, voltage) applied to the piezoelectric element 15 ′ as necessary.

  However, in this configuration, since the coil spring is not provided, the above minute distance fluctuation that may occur when vibration is excited in the vibrator 10 cannot be absorbed by the coil spring. Therefore, the expansion and contraction of the piezoelectric element 15 ′ is varied in accordance with the minute distance variation (the piezoelectric element 15 ′ is vibrated in the expansion and contraction direction) so that the pressing force to the vibrator 10 does not vary due to the minute distance variation. )There is a need. The degree of the minute distance variation can be predicted by an electric signal applied to the vibrator 10 by the control unit 11. Therefore, in the present configuration, based on the prediction, the vibrator 10 is caused by the minute distance variation by varying the electric signal (for example, voltage) applied to the piezoelectric element 15 ′ to vary the expansion and contraction of the piezoelectric element 15 ′. It is configured so that the pressing force to the fluctuates does not fluctuate.

FIG. 4 is a diagram illustrating an ultrasonic motor according to a second modification of the present embodiment. This figure also corresponds to FIG. 2 described above.
As shown in FIG. 4, the ultrasonic motor according to the present modification includes two identical piezoelectric elements 18a on the vibrator side surface of the elastic portion 12 and symmetrical positions sandwiching the thick portion 12a. 18b is connected by the surface, and they are integrated. Each of the two piezoelectric elements 18a and 18b is electrically connected to the control unit 11, and is applied with an electric signal by the control unit 11 in the direction of the joint surface with the elastic portion 12 (here, the paper surface of FIG. 4). It is a piezoelectric element that expands and contracts in the left-right direction) and is an example of a pressing means that presses the vibrator 10. The shape of the piezoelectric element is not limited to two of 18a and 18b, but may be a ring-shaped integrated structure.

  According to such a configuration, when the electric signal is applied from the control unit 11 to the two piezoelectric elements 18a and 18b and the two piezoelectric elements 18a and 18b expand and contract, the thick portion 12a is expanded and contracted as shown in FIG. The elastic portion 12 is deformed so as to move in the vertical direction, and a pressing force corresponding to the deformation is applied to the vibrator 10 via the elastic portion (thick portion 12a) 12. Accordingly, the pressing force applied to the vibrator 10 is changed by changing the expansion / contraction amount of the piezoelectric elements 18a and 18b by changing the electrical signals (for example, voltage) applied to the piezoelectric elements 18a and 18b as necessary. It becomes possible. For example, when both of the two piezoelectric elements 18a, 18 are contracted by applying an electric signal, the elastic portion 12 is deformed so that the thick portion 12a moves upward in the drawing. As a result, the pressing force increases. In this case, the pressing force to the vibrator 10 generated by the deformation of the elastic portion 12 is changed by changing the contraction degree of both the two piezoelectric elements 18a and 18b by changing the applied electric signal (for example, voltage). It becomes possible.

  Note that this configuration does not include a configuration in which the piezoelectric element 15 as shown in FIG. 2 is attached to the main body 13 via the mounting seat 16, and as shown in FIG. 4, the main body (ultrasonic motor main body) 13. ′ Is not provided with a space for storing them.

Embodiment 2 of the present invention relates to a drive device using an ultrasonic motor.
FIG. 5 is a top view illustrating a configuration example of the drive device according to the present embodiment. FIG. 6 is a cross-sectional view of the drive device shown in FIG. FIG. 7 is a right side view of the drive device shown in FIG. 5, showing a state in which the drive device is installed inclined.

  For convenience of explanation, FIG. 5 partially includes a perspective view and a cross-sectional view. 5 and 7, the description of the control unit is omitted. FIG. 6 schematically shows the control unit and the electrical connection with the control unit.

  5 and 6, guide members 22a and 22b such as linear guides are disposed between a base portion 20 and a table 21 serving as a movable body. One of the guide members 22 a and 22 b is fixed to the base portion 20, and the other is fixed to the table 21. As a result, the table 21 can be translated relative to the base portion 20. Further, a scale 23 is fixed to the side surface of the table 21, and a sensor 24 is fixed to the upper surface of the base portion 20 so as to face the scale 23, so that the position of the table 21 can be detected by the scale 23 and the sensor 24. It has become. The scale 23 and the sensor 24 are an example of position detection means. In FIG. 5, a part of the scale 23 is shown as a perspective view.

  The ultrasonic motor 25 has the same configuration as the ultrasonic motor according to the first embodiment described with reference to FIGS. 1 and 2, and is disposed on the base portion 20. Of course, the ultrasonic motor 25 having the same configuration as that of the ultrasonic motor according to the modification of the first embodiment described with reference to FIGS. 3 and 4 can be applied. In FIG. 5, the elastic part 12, the ultrasonic motor main body 13, the piezoelectric element 15, the mounting seat 16, and the coil spring 17 of the ultrasonic motor 25 are shown as sectional views. The two drive portions 14a and 14b of the ultrasonic motor 25 have their drive surfaces in contact with the table 21, and a pressing force corresponding to expansion and contraction of the piezoelectric element 15 is transmitted through the coil spring 17 and the thick portion 12a. 10, the friction force can be generated between the two drive units 14a and 14b and the table 21. Further, at this time, the vibration is excited in the vibrator 10 and the elliptical locus motion of the two drive units 14 a and 14 b is performed, so that the frictional force generated between the two drive units 14 a and 14 b and the table 21 is generated. Thus, the table 21 can be driven (moved).

  The control unit 26 is electrically connected to each of the vibrator 10, the piezoelectric element 15, and the sensor 24. The control unit 26 has a function of applying an electrical signal to each of the vibrator 10 and the piezoelectric element 15 and controlling the position of the table 21 based on a signal (detection signal) obtained from the sensor 24 at that time.

  The control unit 26 also has a function of detecting an actual driving characteristic at a predetermined timing and changing an electric signal (for example, voltage) applied to the piezoelectric element 15 according to the detection result. For example, when a constant electrical signal is applied to the piezoelectric element 15 and a periodic electrical signal is applied to the vibrator 10 to drive the table 21, this function operates as follows. First, from the signal (detection signal) obtained from the sensor 24, the table movement amount in a predetermined signal cycle is measured as the actual drive characteristic, and compared with a threshold value. Here, the threshold value is a threshold value of drive characteristics stored in the control unit 26 in advance, and indicates a table movement amount in a predetermined signal cycle when the table 21 is driven as described above. The threshold value can also be determined as a range, such as an allowable range of table movement. When the measured value is smaller than the threshold value as a result of the comparison with the threshold value, the piezoelectric element 15 extends to the current state, that is, the pressing force to the vibrator 10 becomes larger than the current state. The electric signal to be applied is changed (for example, the voltage applied to the vibrator 10 is made larger than the current voltage). Thereby, the frictional force between the two drive parts 14a and 14b and the table 21 becomes larger than the present, and the table movement amount per predetermined signal period can be made larger than the present. On the other hand, when the measured value is larger than the threshold value, an electric signal applied to the vibrator 10 is applied so that the piezoelectric element 15 is contracted from the current state, that is, the pressing force to the vibrator 10 is smaller than the current state. (For example, the voltage applied to the vibrator 10 is made smaller than the current state). Thereby, the frictional force between the two drive parts 14a and 14b and the table 21 becomes smaller than the present, and the table movement amount per predetermined signal period can be made smaller than the present.

  As described above, the control unit 26 measures the table movement amount in a predetermined signal cycle, and changes the electric signal (for example, voltage) applied to the piezoelectric element 15 according to the table movement amount, thereby causing the vibrator 10 to move. Since the applied pressing force can be changed, as a result, the frictional force generated between the two drive units 14a and 14b and the table 21 can be changed. Therefore, the minimum frictional force for driving the table 21 can be generated between the two drive units 14a and 14b and the table 21, and the drive characteristics of the drive device can be maintained. For example, since the load placed on the table 21 is large and the measured table movement amount is smaller than the threshold value, the pressing force to the vibrator 10 is increased, so the two drive units 14a, The frictional force generated between 14b and the table 21 is increased, and the drive characteristics of the drive device can be maintained. Even if the friction coefficient changes due to a change in the contact state between the two drive units 14a and 14b and the table 21, the vibration is transferred to the vibrator 10 according to the comparison result between the measured table movement amount and the threshold value. Since the pressing force is changed, the driving characteristics of the driving device can be maintained. Further, as shown in FIG. 7, for example, even when the drive device is installed in an inclined state, the pressing force to the vibrator 10 is changed according to the comparison result between the measured table movement amount and the threshold value. As a result, the drive characteristics of the drive device can be maintained. In this case, naturally, the table 21 can be prevented from falling naturally.

  As described above, according to the driving apparatus according to the present embodiment, the pressing force applied to the vibrator 10 is changed according to the comparison result between the measured table movement amount and the threshold value. The frictional force between the two drive units 14a, 14b and the table 21 can be changed according to the installation state of the drive device, the contact state between the two drive units 14a, 14b and the table 21, etc. . Therefore, since the minimum frictional force necessary for driving can always be generated between the two driving units 14a and 14b and the table 21, the driving characteristics of the driving device can be maintained, and the friction, Since the wear is reduced, the life of the device is extended, and the drive device can be used for a long time.

  The present invention has been described in detail above. However, the present invention is not limited to the above-described embodiments, and various modifications and changes may be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Vibrator 11 Control unit 12 Elastic part 13 Ultrasonic motor main body 14a, 14b Drive part 15 Piezoelectric element 16 Mounting seat 17 Coil spring 18a, 18b Piezoelectric element 20 Base part 21 Table 22a, 22b Guide member 23 Scale 24 Sensor 25 Ultrasonic motor 26 Control unit

Claims (6)

A vibrator that excites vibration by applying an electrical signal;
An ultrasonic motor main body integrated with the vibrator via an elastic part;
A contact portion integrated with the vibrator;
Pressing means for pressing the vibrator;
With
The pressing force by the pressing means is variable.
An ultrasonic motor characterized by that. A vibrator that excites vibration by applying an electrical signal;
An ultrasonic motor main body integrated with the vibrator via an elastic part;
A contact portion integrated with the vibrator;
A piezoelectric element that expands and contracts in one axial direction by application of an electrical signal;
With
The vibrator is pressed through the elastic portion by a pressing force corresponding to the expansion and contraction of the piezoelectric element.
An ultrasonic motor characterized by that. An elastic body is disposed between the elastic portion and the piezoelectric element.
The ultrasonic motor according to claim 2. A vibrator that excites vibration by applying an electrical signal;
An ultrasonic motor main body integrated with the vibrator via an elastic part;
A contact portion integrated with the vibrator;
A piezoelectric element that is coupled to the elastic portion and expands and contracts in a uniaxial direction by application of an electrical signal;
With
The vibrator is pressed through the elastic portion by a pressing force according to the deformation of the elastic portion accompanying expansion and contraction of the piezoelectric element.
An ultrasonic motor characterized by that. A base part;
A table arranged to be parallel to the base part;
A guide member disposed between the base portion and the table;
The ultrasonic motor according to claim 1, wherein the ultrasonic motor is disposed on the base portion.
Position detecting means having a scale fixed to the table and a sensor fixed to the base part;
Control means for applying an electric signal to the ultrasonic motor and controlling the position of the table and controlling the pressing force by the pressing means of the ultrasonic motor based on the detection signal output from the position detecting means;
A drive device using an ultrasonic motor. A base part;
A table arranged to be parallel to the base part;
A guide member disposed between the base portion and the table;
The ultrasonic motor according to any one of claims 2 to 4, which is disposed on the base portion;
Position detecting means having a scale fixed to the table and a sensor fixed to the base part;
An electric signal is applied to the vibrator and piezoelectric element of the ultrasonic motor, and the position of the table is controlled and the pressing force when the vibrator is pressed based on the detection signal output from the position detecting means. Control means for controlling
A drive device using an ultrasonic motor.

Images