JPH04172975A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To accurately obtain synchronization of forward and reverse rotation by arranging the first detecting element between the first/second set vibrators further the second detecting element in both ends of the first detecting element. CONSTITUTION:Voltage in accordance with a deflection amount of a stator part 12 is generated by a detecting element 50, and its output is input to an oscillating circuit OSC through a smoothing circuit SC1 of a driving circuit 100. Voltage in accordance with a traveling wave is generated in the detecting element 50 by a traveling wave, generated in the stator part 12, and fed back to the oscillating circuit OSC through the smoothing circuit SC1. When the voltage is low generated in the detecting element 50 (when amplitude of the traveling wave is small), the amplitude of the traveling wave is controlled in a direction of increasing by oscillating a frequency by the oscillating circuit OSC to approach a resonance frequency of the stator part 12. On the other hand, when the voltage is high generated in the detecting element 50 (when the amplitude of the traveling wave is large), the amplitude of the traveling wave is decreased by separating the frequency, oscillated by the oscillating circuit OSC, from the resonance frequency of the stator part 12.

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 the configuration of a vibrator of an ultrasonic motor.

(Prior Art) The prior art related to the present invention will be explained with reference to FIGS. 4 to 6.

FIG. 4 shows the structure of an ultrasonic motor M described in Japanese Unexamined Patent Publication No. 63-73887. The structure of the ultrasonic motor M will be explained below.

An inner hole of a ring-shaped stator section 12 is fitted into the base 11, and the inner circumferential side of the stator section 12 is prevented from vibrating via countersunk screws 13.

The stator section 12 is composed of an elastic body 12a and a piezoelectric vibrating body 12b. The piezoelectric vibrating body 12b is ring-shaped and is bonded 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 moved to the stator portion 1 by the pressing force of the disc spring 17.
It is constantly in pressure contact with 2. A friction material 16a is adhered to the rotor 16, and the friction material 16a is in contact with the stator portion 12. Further, a rubber sheet 18 is sandwiched between the disc spring 17 and the rotor 16. The disc spring 17 is held by a holder portion 20a of the rotating shaft 20. The driving force of the rotor 16 is transmitted to the rotating shaft 20 through the disc spring 17 and the holder portion 20a. The rotating shaft 20 is the base 11
It is rotatably supported by a bearing 23 fixed to the housing 15 and a bearing 19 fixed to the housing 15.

By applying an alternating current 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 section 12. The generated traveling wave gives a rotational moment to the rotor 16, causing the rotor 16 to rotate.

Next, using FIG. 5 and FIG.
The ultrasonic motor described in No. 3 will be explained. Fifth
The figure shows a system diagram showing the arrangement of the input control device and electrodes of the ultrasonic motor, and FIG. 5 shows a front view of the stator section 12.

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

A feedback electrode 33 is disposed between the two divided drive vibrators 31 and 32.

This feedback electrode 33 detects the amount of elastic deformation of the stator section 12.

(Problems to be Solved by the Invention) Conventionally, ultrasonic motors have been required to be rotatable in both forward and reverse directions, and have been required to synchronize the rotational speeds during forward and reverse rotations. In order to satisfy this requirement, a feedback electrode is provided between the driving oscillators to detect the vibration state of the elastic body vibrated by the two driving oscillators to control the rotation speed. There is.

However, in the conventional technology, when a standing wave is generated in the stator by vibrating an elastic body using a drive vibrator, no consideration is given to the placement position 1 of the feedback electrodes, making it difficult to perform accurate feedback control. The problem was that it couldn't be done.

The present invention has been made to solve the problems of the prior art, and its technical object is to provide a new configuration and arrangement method for feedback control electrodes.

[Structure of the invention]

(Means for Solving the Problems) The technical means taken to solve these technical problems are as follows: An annular elastic body; A first set of vibrators fixed on the elastic body; , In an ultrasonic motor having a stator portion configured by a second set of vibrators fixed on the elastic body spaced apart from the 1m-th vibrator, the first set of vibrators and the second set A first detection element is disposed between the vibrators, and second detection elements are disposed on the elastic body at both ends of the first detection element.

(Function) With the above technical means, the feedback detection element is not affected by the leakage electric field from the adjacent piezoelectric element, and the piezoelectric phenomenon of the feedback detection element due to the standing wave excited by the stator is also suppressed. Now I can do it. Therefore, the ultrasonic motor can accurately synchronize forward and reverse rotations.

(Example) Next, a preferred example of the present invention will be described with reference to the drawings. In the following description, the same members as in the conventional device are given the same numbers and symbols, and the description thereof is omitted.

FIG. 1 is a plan view of a stator section 12 to which the present invention is applied, and FIG. 2 is a front view of the stator section 12. The stator section 12 is composed of an elastic body 12a and a piezoelectric vibrating body 12b. The elastic body 12a has an annular shape, and a large number of comb teeth (not shown) are formed on one surface. On the surface of the elastic body 12b on which comb teeth are not formed, a first set of vibrators 30 and a second set of vibrators 40 are placed at positions spaced apart from each other.
is fixed via a ground electrode 45. The first set of vibrators 30 and the second mth vibrator are made of piezoelectric elements.

The first set of vibrators 30 further includes eight drive elements 31 to 3.
It has 8. The driving elements 31 to 38 are polarized so that the polarization directions of adjacent vibrating elements are opposite to each other. Similarly, the second set of vibrators 40 includes eight vibrating elements 41 to 48. And the vibration element 41~
48 is polarized so that adjacent vibrating elements are in opposite directions. A predetermined distance 5.6 is set between the first set of vibrators 30 and the second set of vibrators 40.

A ground electrode 45 is provided over the entire surface of the elastic body 12a.
is formed. Then, on the ground electrode 45, a first
, a second set of vibrators 30, 40 are arranged. A first detection element 50 is located between the first and second transducers 30 and 40.
, second detection elements 51 and 52 are disposed. The first detection element 50 and the second detection element 5L52 function as detection elements that detect the amount of elastic deformation of the stator section 12. moreover,
1st. Each vibrating element 31 to 3 of the second set of vibrator 30.40
8.41 to 48, electrodes 46 are formed on the surfaces of each of the detection elements 50, 51 and 52, respectively.

If the wavelength of the traveling wave generated on the elastic body 12a is defined as λ, then the length of each vibrating element 31 to 38 and 41 to 48 is designed to be equivalent to (λ/2). The distance 5 between the first set of transducers 30 and the second m-th transducer 40 is (3
λ/4). Further, the distance 6 between the first set of vibrators 30 and the second set of vibrators 40 is (λ/4
).

That is, in this embodiment, the length of the elastic body 12a corresponds to nine wavelengths.

The first detection element 50 and the second detection element 51, 52 are polarized in the same direction. Among these three detection elements, the one actually used as a detection element is the first detection element 50 disposed at the center of the interval 5. The first detection element 50 and the second detection element 51, 52 are arranged within the interval 5.
They may be arranged densely as shown in the figure. Further, as long as the first detection element 50 is located at the center of the interval 5, the method of arrangement thereof and the size of each detection element are not limited.

Referring again to FIG. 1, the first and second sets of vibrators 30
．． When a pair of AC voltages having electrical phases different by 906 are applied to the stator 40, each vibrator generates vibration in the stator section 12. The generated vibrations interfere with each other within the elastic body 12a and generate traveling waves within the elastic body 12a.

The traveling wave then rotates the rotor 16 disposed on the stator section 12.

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

A stator section 12 and a switch SW are connected to the drive circuit 100. Switch SW is used to determine the rotation direction of rotor 16. The state of the switch SW is input to the phase shift circuit PH3 and the oscillation circuit oSC through the input circuit IF.

When the contact CW is grounded by the switch SW, the phase shift circuit PH3 delays the phase of the wake signal supplied to the drive circuit DRV2 by 90 degrees with respect to the AC signal supplied to the drive circuit DRVI, thereby rotating the rotor 16 clockwise. . switch S
When the contact CCW is grounded by W, the phase shift circuit PH3
rotates the rotor 16 counterclockwise by delaying the phase of the AC signal supplied to the drive circuit DRVI by 90 degrees with respect to the AC signal supplied to the drive circuit DRv2. When the contact 5TOP is grounded by the switch SW, the phase shift circuit PH3 stops the rotor 16. Switch SW is contact 5TOP
Immediately after switching from the contact CW to the contact CCW, the oscillation circuit O8C performs processing for starting the rotor 16.

The oscillation circuit O3C is a circuit that outputs an alternating current signal of a predetermined frequency. The AC signal output by the oscillation circuit O3C is supplied to the phase shift circuit PH3. The phase shift circuit PH3 divides the frequency of the AC signal and outputs a pair of signals having mutually different phases. The AC signal outputted by the phase shift circuit PH3 is sent to the drive circuits DRVI and DR.
After being amplified by V2, it is supplied to the first and second sets of oscillators 30 and 40. At this time, a traveling wave is generated in the stator section 12.

The detection element 50 disposed on the stator section 12 generates a voltage according to the amount of deflection of the stator section 12, and its output is passed through the smoothing circuit S01 of the drive circuit 100 to the oscillation circuit O.
Connected to 3C.

The traveling wave generated in the stator section 12 causes the detection element 50 to
A voltage corresponding to the traveling wave is generated. The voltage generated in the detection element 50 is fed back to the oscillation circuit O3C through the smoothing circuit SCI in the drive circuit 100. Detection element 50
When the voltage of is low (when the amplitude of the traveling wave is small),
The frequency oscillated by the oscillation circuit O3C is controlled to be close to the resonant frequency of the stator section 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 frequency at which the oscillation circuit O8C oscillates is moved away from the resonant frequency of the stator section 12 to reduce the amplitude of the traveling wave. Through the above control, the traveling wave of the stake portion 12 is controlled to an optimal state, and the rotor 16 is driven with high precision.

Furthermore, it goes without saying that even when the ultrasonic motor M is driven in reverse, the rotor 16 is feedback-controlled by the voltage generated in the detection element 50.

In this embodiment, the detection elements 50, 51, 52 were all polarized to positive polarities, but all the detection elements may be polarized to negative polarities.

As in the present invention, the detection elements 50, 51, 52 are placed within the interval set between the first set of transducers 30 and the second &u transducers 40, and at a position farthest from each transducer. Due to this arrangement, the detection element 50 is located at a position away from the nodes of the traveling wave, and is at the most stable position when driven in forward and reverse directions, so that accurate feedback control can be performed. In addition, since the detection elements 51' and 52 polarized in the same direction are arranged on both sides of the detection element 50, the leakage electric field of the detection element 50 can be suppressed, which also allows for accurate rotation control during both forward and reverse driving. became possible.

〔Effect of the invention〕

As explained above, since the feedback detection element of the present invention suppresses the effects of traveling waves and leakage electric fields, it is possible to accurately control the rotation speed to the desired rotation speed when driving the ultrasonic motor in forward and reverse directions. You will be able to do this.

[Brief explanation of 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 the stator section of the ultrasonic motor. FIG. 3 is a block diagram showing a drive circuit capable of driving an ultrasonic motor according to an embodiment of the present invention. FIG. 4 is a cross-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 the arrangement of an input control device and detection elements for an ultrasonic motor according to the prior art. FIG. 6 is a front view of a stator section of an ultrasonic motor according to the prior art. 12a... Elastic body, 30... First set of vibrators, 40... Second set of vibrations 12... Stator section, 50... First detection element, 51.52... th 2 detection elements. 12 Figure 2 Otsuq

Claims (4)

[Claims] (1) 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, also spaced apart from the first set of vibrators. In the ultrasonic motor having a stator section constituted by a child, a first detection element is disposed between the first set of transducers and the second set of transducers, and further, both ends of the first detection element are arranged between the first set of transducers and the second set of transducers. An ultrasonic motor characterized in that a second detection element is disposed on the elastic body. (2) The first detection element and the second detection element are fixed to each other continuously on the stator between the first and second sets of vibrators. For ultrasonic motors. (3) The ultrasonic motor according to claim 1, wherein the first detection element and the second detection element are polarized to the same polarity. (4) The ultrasonic motor according to claim (1), wherein the first and second sets of vibrators are separated by a wavelength of λ/4 of a standing wave excited by both the vibrators.