JP3089324B2 - Ultrasonic motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a traveling wave type ultrasonic motor, and more particularly to a configuration of a vibrator of an ultrasonic motor.

(Prior Art) A prior art related to the present invention will be described with reference to FIGS. 4 to 6. FIG.

FIG. 4 shows the structure of the ultrasonic motor M described in Japanese Patent Application Laid-Open No. 63-73887. Hereinafter, the structure of the ultrasonic motor M will be described.

An inner hole of a ring-shaped stator portion 12 is fitted to the base 11 so that the inner peripheral side of the stator portion 12 cannot be vibrated via a countersunk screw 13. The stator part 12 is an elastic body 12a
And the piezoelectric vibrating body 12b. The piezoelectric vibrating body 12b has a ring shape and is adhered to one surface of the elastic body 12a. A large number of comb teeth 12c are formed on the elastic body 12a of the stator section 12.

The rotor 16 is constantly pressed against the stator section 12 by the pressure of the disc spring 17. A friction material 16a is adhered to the rotor 16, and the friction material 16a is in contact with the stator portion 12. Also,
A rubber sheet 18 is sandwiched between the disc spring 17 and the rotor 16. The disc spring 17 is held by the holder 20a of the rotating shaft 20. The driving force of the rotor 16 is the disc spring 17 and the holder 20
The rotation is transmitted to the rotation shaft 20 through a. The rotating shaft 20 is rotatably supported by a bearing 23 fixed to the base 11 and a bearing 19 fixed to the housing 15.

By applying an AC voltage to the piezoelectric vibrating body 12b bonded to the elastic body 12a, the piezoelectric vibrating body 12b repeats expansion and contraction, and as a result, a traveling wave is generated in the stator unit 12. The generated traveling wave gives a rotational moment to the rotor 16,
Rotate 16

Next, referring to FIG. 5 and FIG.
The ultrasonic motor described in the above item will be described. FIG. 5 is a system diagram showing the arrangement of the input control device and the electrodes of the ultrasonic motor, and FIG. 5 is a front view of the stator unit 12.

A piezoelectric vibrating body 12b is bonded to one end surface of the elastic body 12a. The positive and negative electrodes 30 are alternately and continuously arranged on the outer surface of the piezoelectric vibrating body 12b. Piezoelectric vibrator 12b
Are divided into two sets of semicircular vibrators with an interval therebetween at a boundary position, forming a first driving vibrator 31 and a second driving vibrator 32.

A feedback electrode 33 is disposed between the two divided driving vibrators 31 and 32. The feedback electrode 33 detects the amount of elastic deformation of the stator 12.

(Problems to be Solved by the Invention) Conventionally, ultrasonic motors have been required to have rotational properties in both forward and reverse directions, and to synchronize the rotational speeds during forward and reverse rotations. To satisfy this demand,
By providing a feedback electrode between the driving vibrators,
The number of rotations is controlled by detecting a vibration state of an elastic body vibrating by two driving vibrators.

However, in the related art, when a standing wave is generated in the stator by vibrating the elastic body by the driving vibrator, the arrangement position of the feedback electrode is not considered, and accurate feedback control cannot be performed. There was a problem.

The present invention has been made in order to solve such problems of the related art, and has as its technical object to provide a novel configuration and arrangement method of a feedback control electrode.

[Configuration of the invention]

(Means for Solving the Problems) The technical measures taken to solve such technical problems include an annular elastic body, a first set of vibrators fixed on the elastic body, A second set of vibrators fixed on the elastic body, spaced apart from the first set of vibrators; and on the elastic body between the first set of vibrators and the second set of vibrators. An ultrasonic motor having a stator portion comprising: a first detection element; and a second detection element disposed on both sides of the first detection element. The first detection element and the second detection element are disposed so as to be polarized to have the same polarity, and the second detection element is electrically released.

In addition to the above, the first detection element and the second detection element are within an interval on the elastic body set between the first set of transducers and the second set of transducers. And at a position farthest from the first set of transducers and the second set of transducers.

(Operation) By the above technical means, the feedback detecting element is not affected by the leakage electric field due to the adjacent piezoelectric element, and the piezoelectric phenomenon of the feedback detecting element due to the standing wave excited by the stator is suppressed. Now you can do it. Therefore, the ultrasonic motor can accurately obtain the synchronization between the normal rotation and the reverse rotation.

Next, a preferred embodiment of the present invention will be described with reference to the drawings. In the following description, the same members as those of the conventional device are denoted by the same reference numerals, and the description thereof is omitted.

FIG. 1 is a plan view of the stator section 12 to which the present invention is applied, and FIG. 2 is a front view of the stator section 12. Stator section
Numeral 12 includes an elastic body 12a and a piezoelectric vibrating body 12b. The elastic body 12a has an annular shape, and has a plurality of comb teeth (not shown) formed on one surface. Then, on the surface of the elastic body 12b where the comb teeth are not formed, the first set of vibrators 30 and the second set of vibrators 40 are located at positions separated from each other.
Has been fixed through. The first set of transducers 30 and the second set of transducers are composed of piezoelectric elements.

The first set of transducers 30 further includes eight drive elements 31 to 38. The driving elements 31 to 38 are polarized so that the polarization directions of the adjacent vibration elements are opposite to each other.
Similarly, the second set of vibrators 40 includes eight vibrating elements 41 to 48.
It has. The vibrating elements 41 to 48 are polarized so that adjacent vibrating elements are in opposite directions.
Predetermined intervals 5 and 6 are set between the first set of transducers 30 and the second set of transducers 40.

A ground electrode 45 is formed on the entire surface of the elastic body 12a. The first and second sets of vibrators 30 and 40 are disposed on the ground electrode 45. First and second
The first detection element 50 and the second detection element 5
1,52 are arranged. 1st detecting element 50, 2nd detecting element
Reference numerals 51 and 52 function as detecting elements for detecting the amount of elastic deformation of the stator section 12. Further, electrodes 46 are formed on the surfaces of the respective vibrating elements 31 to 38 and 41 to 48 of the first and second sets of vibrators 30 and 40 and the respective detecting elements 50, 51 and 52. When the wavelength of the traveling wave generated on the elastic body 12a is defined as λ, each of the vibration elements 31 to
The lengths of 38 and 41 to 48 are designed to be equivalent to (λ / 2). The interval 5 between the first set of transducers 30 and the second set of transducers 40 is set to be (3λ / 4). The interval 6 between the first set of transducers 30 and the second set of transducers 40 is (λ / 4). That is, in the present embodiment, the elastic body 12a
The length corresponding to nine wavelengths is used.

The first detection element 50 and the second detection elements 51 and 52 are polarized in the same direction. Among these three detection elements,
The element actually used as the detecting element is the first detecting element 50 disposed at the center of the space 5. First detection element
50 and the second detection elements 51 and 52 may be densely arranged within the interval 5 as shown in FIG. In addition, as long as the first detection element 50 is located at the center of the space 5, the arrangement method and the size of each detection element are not limited.

Referring again to FIG. 1, the first and second sets of transducers 3
When a pair of AC voltages having electric phases different by 90 ° are applied to 0 and 40, vibrations are generated in the stator unit 12 by the respective vibrators. The generated vibrations interfere with each other in the elastic body 12a to generate a traveling wave in the elastic body 12a. Then, the traveling wave rotates the rotor 16 provided on the stator unit 12.

FIG. 3 is a block diagram of a driving circuit 100 capable of driving the stator section 12 according to the embodiment.

The drive circuit 100 is connected to the stator unit 12 and a switch SW. The switch SW is used to determine the rotation direction of the rotor 16. The state of the switch SW is input to the phase shift circuit PHS and the oscillation circuit OSC through the input circuit IF.

When the contact CW is grounded by the switch SW, the phase shift circuit PH
S sets the phase of the downstream signal supplied to the drive circuit DRV2 to the drive circuit D
90 ° delay from the AC signal supplied to RV1
Turn clockwise. Contact CCW by switch SW
Is grounded, the phase shift circuit PHS rotates the rotor 16 counterclockwise by delaying the phase of the AC signal supplied to the drive circuit DRV1 by 90 ° with respect to the AC signal supplied to the drive circuit DRV2. When the contact STOP is grounded by the switch SW, the phase shift circuit PHS stops the rotor 16. Switch SW is contact STO
Immediately after switching from P to ground CW or contact CCW, the oscillation circuit OSC performs a process for starting the rotor 16.

The oscillation circuit OSC is a circuit that outputs an AC signal having a predetermined frequency. The AC signal output from the oscillation circuit OSC is converted to a phase shift circuit PHS
Supplied to The phase shift circuit PHS divides the AC signal and outputs a pair of signals having different phases. The AC signal output from the phase shift circuit PHS is amplified by the drive circuits DRV1 and DRV2, and then supplied to the first and second sets of transducers 30 and 40. At this time, a traveling wave is generated in the stator unit 12.

The detection element 50 disposed on the stator section 12 generates a voltage corresponding to the amount of deflection of the stator section 12, and its output is connected to the oscillation circuit OSC through the smoothing circuit SC1 of the drive circuit 100.

A voltage corresponding to the traveling wave is generated in the detection element 50 by the traveling wave generated in the stator unit 12. The voltage generated in the detection element 50 is supplied to the oscillation circuit OS through the smoothing circuit SC1 in the drive circuit 100.
Feeded back to C. When the voltage of the detection element 50 is low (when the amplitude of the traveling wave is small), the frequency at which the oscillation circuit OSC oscillates is controlled to approach the resonance frequency of the stator unit 12 to increase the amplitude of the traveling wave. On the other hand, when the voltage of the detection element 50 is high (when the amplitude of the traveling wave is large), the oscillation frequency of the oscillation circuit OSC is kept away from the resonance frequency of the stator section 12 to reduce the amplitude of the traveling wave. By the above control, the traveling wave of the stator section 12 is controlled to an optimum state, and the rotor 16 is driven with high accuracy.

Needless to say, even when the ultrasonic motor M is driven in the reverse direction, the rotor 16 is feedback-controlled by the voltage generated at the detecting element 50.

In this embodiment, the detection elements 50, 51, and 52 are all subjected to polarization processing on the positive electrode. However, the detection elements 50, 51, and 52 may be all polarization elements subjected to polarization processing on the negative electrode.

As in the present invention, the detecting elements 50, 51, 52 are connected to the first set of vibrators.
The detection element 50 is located at a position apart from the node of the traveling wave by being disposed within the distance set between the vibrator 30 and the second set of vibrators 40 and at the most distant position from each vibrator. The position becomes the most stable position when the motor is driven forward and reverse, so that accurate feedback control can be performed. Further, detection elements 51 and 52 polarized in the same direction on both sides of the detection element 50 are provided.
Since the leakage electric field of the detection element 50 can be suppressed because of the arrangement, the rotation control with high accuracy at the time of both forward and reverse driving is possible.

〔The invention's effect〕

As described above, the detection element of the present invention includes the first detection element and the second detection elements disposed on both sides of the first detection element, and includes the first detection element and the second detection element. The elements are arranged to be polarized to the same polarity, and the second detection element is electrically released, so that the influence of the leakage electric field of the detection element can be suppressed,
When the ultrasonic motor is driven forward and reverse, the desired rotational speed can be controlled with high accuracy.

Further, the first detection element and the second detection element are within an interval on the elastic body set between the first set of transducers and the second set of transducers, and the first set The transducers and the second set of transducers are arranged at the positions farthest away from each other, so that the detecting element is at the position farthest from the node of the traveling wave and is most stable when the ultrasonic motor is driven forward and reverse. Since it is located at the position, the effect of the traveling wave can be suppressed, and there are effects that accurate feedback control can be performed.

[Brief description of the drawings]

FIG. 1 is a plan view of a stator section showing an embodiment of an ultrasonic motor to which the present invention is applied. FIG. 2 is a front view of a stator portion of the ultrasonic motor. FIG. 3 is a block diagram showing a driving circuit capable of driving an ultrasonic motor according to the embodiment of the present invention. FIG. 4 is a sectional view showing the structure of an ultrasonic motor according to the present invention and the prior art. FIG. 5 is a system diagram showing an arrangement state of an input control device and a detection element of an ultrasonic motor according to the prior art. FIG. 6 is a front view of a stator portion of a conventional ultrasonic motor. 12a: elastic body, 30: first set of vibrators, 40: second set of vibrations 12: stator section, 50: first detection element, 51, 52 ... second detection element.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shinji Sagara 1-333 Futatsuya, Kitamoto City, Saitama Prefecture 2-325 Hydens Examiner Koji Shimohara (56) References JP-A-2-237479 (JP, A) JP Hei 2-206371 (JP, A) JP-A 64-12881 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02N 2/00

Claims (2)

(57) [Claims] An annular elastic body, a first set of vibrators fixed on the elastic body, and a second set of vibrators fixed on the elastic body apart from the first set of vibrators An ultrasonic motor having a stator portion comprising: a vibrator; and a detection element fixed on the elastic body between the first set of vibrators and the second set of vibrators. A first detecting element; second detecting elements disposed on both sides of the first detecting element;
An ultrasonic motor, wherein the first detection element and the second detection element are disposed so as to be polarized to the same polarity, and the second detection element is electrically released. . 2. The method according to claim 1, wherein the first detecting element and the second detecting element are within an interval on the elastic body set between the first set of transducers and the second set of transducers, 2. The ultrasonic motor according to claim 1, wherein the ultrasonic motor is arranged at a position farthest from the first set of transducers and the second set of transducers. 3.