JPH04178181A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To make a controllability of an ultrasonic motor at a low speed favorable, by generating a bending vibration in one of a plurality of driving members, and by so vibrating bending vibrators and longitudinal vibrators in the other driving members that they are synchronized with the generated vibration, and further, by moving a member to be driven relatively to a fixed member. CONSTITUTION:To sense the vibration states of respective bending vibrators 11A, 11B, 11C, piezoelectric elements 21A, 21B, 21C are fastened respectively on the respective vibrators 11A, B, C. Further, the signals fed from the piezoelectric elements 21A, 21B, 21C are inputted to an oscillator 15, and its oscillation frequency is so controlled that the bending vibrators vibrate always stably at a frequency approximate to their resonance frequencies. Also, hereupon. considered in the bending vibration of a bending vibrator 11A of a driving body 12A, which is one of a plurality of driving bodys. Then, the other vibrators 11B, 11C and associated longitudinal vibrators 4A, 4B, 4C can be so driven that their vibration phases are shifted from the vibration phase of the vibrator 11A. Thereby, the driving at a low speed is made easy. Moreover, by virtue of driving the plurality of curvature vibrators by the only one oscillator, the driving timings of the longitudinal vibrators can be taken accurately, and the vibrators can be driven efficiently.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to an ultrasonic motor, specifically, a combination of a bending vibrator and a longitudinal vibrator, and the longitudinal vibrator is attached on the nodal line of the bending vibration of the bending vibrator. The present invention relates to an ultrasonic motor.

[Prior Art] Ultrasonic motors, which have been attracting attention recently, have the characteristics of being easy to drive at low speeds and producing high torque output, and some motors have already been commercialized. . However, this commercialized ultrasonic motor is a rotary type motor, and a small linear type motor that has a high degree of design freedom and can easily be converted into a rotary type motor has not yet been commercialized. The reason for this is that it is difficult to produce a small linear type ultrasonic motor with high efficiency and high output. In linear ultrasonic motors, in order to efficiently generate traveling waves, it is necessary to use a closed-loop bending transducer, which results in a very large transducer and a complicated support mechanism for the transducer. The efficiency itself is only a few percent, so it is not necessarily a small linear type ultrasonic motor with high efficiency.

In addition, in the case of a linear type ultrasonic motor that combines the bending resonance of a plate and the longitudinal resonance vibration in the longitudinal direction of the plate, as disclosed in Japanese Patent Application Laid-Open No. 63-277477, the bending resonance of the plate Unless the resonant frequency of the vertical resonance and the vertical resonance match, a highly efficient motor cannot be realized, and its size and shape are restricted.

Therefore, it has not been easy to downsize and increase efficiency.

Furthermore, this motor uses the transverse effect of the piezoelectric material, that is, the fact that the driving direction is perpendicular to the voltage application direction, to generate vibrations to generate frictional force, so it is not possible to increase the crimping force. However, it also has the disadvantage of not being able to generate a large driving force.

Therefore, in order to eliminate the above-mentioned drawbacks of the conventional ultrasonic motor of this type, the present applicant has generated a resonant bending standing wave in a plate-shaped bending vibrator to which a piezoelectric material is attached, and the nodes of the bending vibration are A longitudinal vibrator made of a laminated piezoelectric material that vibrates in a direction perpendicular to the neutral axis of the bending vibration is provided at the position, and the phase of the bending vibration generated by the bending vibrator and the longitudinal vibration generated by the longitudinal vibration is set to A small linear type ultrasonic motor is configured to generate elliptical vibration at the tip of the vertical vibrator by shifting the vertical vibrator, thereby moving a moving body crimped to the tip of the vertical vibrator in a predetermined direction. I proposed it earlier (Patent application No. 2-7
No. 9800).

According to this ultrasonic motor, the motor efficiency is high and it can be configured to be thinner, making it extremely useful. In other words, since this small linear type ultrasonic motor is small, it is easy to create a small rotary type ultrasonic motor by arranging them in a circle or by making the bending vibrator itself into an annular or disk shape. It is possible to realize an ultrasonic motor, and since a vertical vibrator of laminated piezoelectric material is used in the direction in which the crimping force is applied to generate frictional force, it is possible to generate a large driving force even though it is small. It had many advantages.

Furthermore, as proposed by the present applicant, Japanese Patent Application Laid-Open No. 1-291
The ultrasonic motors disclosed in JP-A No. 676 and JP-A-1-234073 vary the speed by changing the drive frequency or the pulse width of the drive signal to change the amplitude of the elliptical vibration generated on the stator. was to be controlled.

[Problems to be Solved by the Invention] However, in the above-mentioned ultrasonic motor that the present applicant previously proposed in Japanese Patent Application No. 2-7980, the output power is determined by utilizing minute rotational motion around the nodes of the bending vibrator. In order to increase the It has been difficult to provide efficient motors. Furthermore, in terms of space, it is necessary to increase the length of the bending vibrator in the longitudinal direction, which reduces the degree of freedom in design. Furthermore, in order to stably control the ultrasonic motor, it is necessary to design each circuit to match the drive body, since the electrical characteristics of the drive body change.

Furthermore, JP-A-1-291676 and JP-A-1-
The ultrasonic motor disclosed in Japanese Patent No. 234073 controls the speed by changing the amplitude of the vibration that contributes to driving as described above, so the amplitude must be reduced in order to reduce the speed.

Therefore, if the vibration amplitude becomes smaller than the surface roughness of the contact surface between the driving body and the driven body, it will stop operating and low-speed operation at a vibration amplitude below the above-mentioned vibration amplitude will become impossible.

Furthermore, there are some ultrasonic motors, such as the ultrasonic motor disclosed in Japanese Patent Laid-Open No. 63-7174, that attempt to control the speed by intermittently applying a drive signal, but since the signals are intermittently applied, the operation itself is slow. Like an electromagnetic stepping motor, there are problems in that the operation becomes intermittent vibrations at low speeds, and when operated at high speeds, vibrations and audible sounds occur at intervals of time from intermittent drive to intermittent drive.

Furthermore, a speed control method that combines the above-mentioned driving methods can be considered, but it is not possible to eliminate the problems specific to each method.

On the other hand, as a method of simply increasing the driving force,
The ultrasonic motor disclosed in Japanese Patent No. 60488 uses a method in which the driving force of a plurality of motors is applied to a single driven body to increase the driving force. If the motors are not synchronized, speed differences will occur between the motors. The speed difference causes slippage between the driving body and the driven body, reducing efficiency and generating unpleasant audible sounds. Further, in this ultrasonic motor, the vibration in the driving direction and the vibration in the pressing direction are not independent, making speed control difficult.

As mentioned above, it is difficult to achieve stable speed control by simply reducing the amplitude.

The object of the present invention has been made to solve the above-mentioned problems, and it is possible to obtain a large driving force with high efficiency, and also to have good controllability at low speeds. It is easy to provide an ultrasonic motor.

[Means and effects for solving the problem] The ultrasonic motor of the present invention includes an elastic body and an electro-mechanical conversion element fixed to the plurality of elastic bodies, and an alternating current voltage is applied to the electro-mechanical conversion element. a bending vibrator that generates standing wave type bending vibration on the elastic body by applying a plurality of drive members each comprising a longitudinal vibrator that is oscillated about a nodal line and expands and contracts in the amplitude direction of the bending vibration when an alternating current voltage is applied; a fixed member that holds the plurality of drive members; and a driven member that is pressed against the tip surface of the vertical vibrator, and in synchronization with the bending vibration generated in one of the plurality of drive members, the bending vibrator of the other drive member and the vertical It is characterized in that the driven member is moved relative to the fixed member by vibrating the vibrator.

[Example] The present invention will be explained below with reference to illustrated embodiments.

FIG. 1.2 is a longitudinal sectional view of an ultrasonic motor showing a first embodiment of the present invention. This ultrasonic motor is mainly composed of a plurality of driving members, namely a driving body and a fixed member. and,
The plurality of driving bodies 12A, 12B, and 12C are longitudinal vibrators 4A, 4B, and 4C and bending vibrators 11A, IIB, and I, respectively.
It is composed of an IC.

Further, the fixing members are the driving bodies 12A and 12B.

It is composed of holders 7A, 7B, and 7C that hold 12C, respectively, and a motor support frame 1. The above bending vibrator 11
Since A, IIB, and IIC each have a similar structure, one of them, the bending vibrator 11A, will be described in detail.

The bending vibrator 11A has a thin piezoelectric body 6A, which is an electro-mechanical transducer polarized in the thickness direction, on the upper and lower surfaces of a relatively thick plate-shaped elastic body 5A having a rectangular planar shape. They are glued together so that they are oriented in the same direction. When a high frequency voltage is applied to the surface electrode of the piezoelectric body 6A, the bending vibrator 11A generates bending vibration, and when a signal of a specific frequency is further applied, it causes resonance bending standing wave vibration.

In the case of this embodiment, the bending vibrator is configured so that first-order bending resonance vibration is most efficiently excited.

On the other hand, the longitudinal vibrator 4A is formed of a laminated piezoelectric material having approximately the same width as the bending vibrator 11A (see FIG. 2), and has two nodes of the first-order bending vibration of the bending vibrator 11A. It is fixed in a groove 5b provided in the plate width direction of the joint elastic body 5 passing through positions NAI and NA2, and vibrates in the plate thickness direction of the bending vibrator 11A when a high frequency voltage is applied. Further, a slider 4a made of a wear-resistant friction material is fixed to the tip surface of the vertical vibrator 4A.

The driving body 12A is configured as described above, and the other driving bodies 12B and 12C also have similar configurations. and,
It is assumed that these driving bodies are arranged in a line along the driving direction. And the driving bodies 12A, 12B, 12
The sliders 4a fixed to C are pressed into frictional contact with a slide plate 3 formed of a wear-resistant friction material fixed to the upper surface of a rail member 2 fixed to a driven member (not shown). There is.

Note that the other bending vibrators 11B and IIC are also made of elastic body 5B.
, 5C and piezoelectric bodies 6B and 6C.

Similarly, the driving bodies 12B and 12C are also connected to the bending vibrator 11B.
, IIC and longitudinal vibrators 4B and 4C.

On the other hand, on the surface of the rail member 2 on the side to which the slide plate 3 is not fixed, linear guide grooves 2a having a semicircular cross section are arranged in two rows in the direction in which the drive bodies 12A, B, and C are driven. They are bored parallel to each other and corresponding to each drive body 12A, 12B, 12C.

Also, a part of the rail member 2 and the bending vibrator 1
1A, B, and C are arranged in a motor support frame 1, and this motor support frame 1 has a U-shaped cross section so as to surround a part of the rail member 2 and the bending vibrators 11A, B, and C. It is formed of a channel-shaped member. This support frame 1 has linear parallel ball storage with ends facing the guide groove 2a and having a semicircular cross-section similar to the guide groove 2a in each section where each drive body presses against the slide plate 3. ? II 1 a are perforated in each case. A plurality of bearing balls 13 are disposed within both the ball storage groove 1a and the guide groove 2a. As a result, the support frame 1 is configured to be movable only in the direction of the guide groove 2a of the rail member 2 while holding the ball 13 in the ball storage groove 1a.

The bending vibrators 11A, B, and C are connected to the support frame 1.
It is attached as follows:

Note that the three bending vibrators 11A, B, and C are all attached to the support frame 1.
Since the installation method is the same, one bending vibrator 1
Only 1A will be explained. That is, the position NAI of the bending vibration node of the bending vibrator 11A.

In the NA2, four cylindrical shaft-shaped support parts 5a protruding in the width direction of the bending vibrator 11A are provided integrally with the elastic body 5A at symmetrical positions. A support member 14 with a flange is fixed or fitted to the outer periphery of the protruding support portion 5a, and a holder attached to the support frame 1 with screws 10 is inserted into a groove provided on the outer circumference of the support member 14. The bending vibrator 11A is attached to the support frame 1 by fitting the engagement notch 7b of the body 7A. Note that other curved surface vibrators 11B,
IIC is similarly supported via holders 7B and 7C.

The holding body 7A is made of a channel-shaped member formed in an inverted U-shape in cross section so as to surround the bending vibrator 11A from above, and the holding body 7A has the above-mentioned channel-like member formed in an inverted U-shape in cross section so as to surround the bending vibrator 11A from above. An engagement notch 7b is provided. The middle portions of both left and right edges are bent upward and horizontally protrude outward to the left and right in the width direction of the mounting piece 7a.
is formed.

Then, both mounting pieces 7a of the holding body 7A with the engaging notches 7b fitted into the protruding support portions 5a are placed on the upper surface of the support frame 1, and the screws 10 are attached via the disc springs 8 and spacers 9. The holder 7 is fixed to the support frame 1 by passing through the piece 7a and screwing it into the upper surface of the support frame 1. Further, in this attached state, the design is such that there is a slight gap between the attachment piece 7a and the upper surface of the support frame. Therefore, the disc spring 8
If the elastic force of the slider 4a is adjusted by the spacer 9, the pressing force generated by the spring 8 will directly apply to the vibrator 12A, thereby increasing the pressing force of the slider 4a against the contact surface of the slide plate 3 of the drive body 12A.

Optimum adjustment can be made for each of B and C.

Further, in this embodiment, the support member 14 is made of a soft elastic member such as rubber, urethane, or felt.

Further, in this embodiment, the rail 2 is connected to the driven member, but the motor support frame 1 side may be the driven side.

FIG. 3 is a block diagram of a drive circuit for the ultrasonic motor, and shows drive circuits for three drive bodies 12A, B, and C. First, the voltage of the high frequency signal generated by the oscillator 15 is amplified by the amplifier 18a, and the voltage is amplified by the piezoelectric bodies 6A, 6.
B, 6C to generate primary bending vibration in the bending vibrators 11A, B, and C. Furthermore, the high frequency signal generated by the oscillator 15 is transmitted through phase shifters 16Aa, 16Ab, 16Ba, 1
Also input to 6Bb, 16Ca, l 6Cb. After that, the phase of each is changed, and furthermore, the amplifier L 8
Ab, 18Ac, 18Bb, 18Bc, 18Cb, 18
Cc amplified and each longitudinal oscillator 4A, 4B, 4C
is applied to Then, longitudinal vibration occurs which has a phase different from that of the bending vibration. In addition, the phase shifters 16Aa, 16A
The phases set by b, 16Ba, 16Bb, 16Ca, and 16Cb are the output signals S1 and S2 of the speed control circuit 17.
, S3, S4, S5, and S6.

Further, the position of the support frame 1 is detected by a sensor 20 fixed to the support frame 1 by dividing the division scale of a scale 19 fixed to the side surface of the rail 2.

Then, the detection signal is input to the speed control circuit 17,
Used for speed control and position control.

In the speed control circuit 17, a speed signal is obtained by differentiating the position detection signal.

The combination of the scale 19 and sensor 20 is as follows:
For example, there are those that combine a magnetic scale that is magnetized at a constant pitch with a magnetic head, a magnetoresistive element, a Hall element, etc., or those that use an optical or electrostatic detector.

On the other hand, the speed control circuit 17 receives the position and speed signals,
Furthermore, phase shifters 16Aa, 16Ab, 16Ba, and 16Bb are provided so that optimum operation of the driving bodies 12A, 12B, and 12C can be obtained according to a speed command signal and a position command signal (not shown).
, 16Ca, 16Cb output signals S1, S2-S3, S4, S5, S6
Output each.

Furthermore, the control circuit 17 includes bending vibrators 11A, 11
Each vibrator 11A is used to detect the vibration state of B and 11C.
, B, C, respectively, piezoelectric elements 21A, 21B
, 21C are input, and the bending vibrators 11A, 1
The oscillation frequency of the oscillator 15 is controlled so that 1B and 11C always vibrate stably near the resonance point. For details of these phase setting circuits and oscillation frequency control circuits, please refer to Japanese Patent Application No. 1330161 or Japanese Patent Application No. 1-1.
No. 59247.

In the ultrasonic motor of this embodiment, the bending vibrator 11A
, 11B, and 11C have their shapes and materials selected so that their respective resonance frequencies are approximately the same. However, even if the same shape is manufactured, there will be a frequency variation of about 100H2, so it is desirable that the frequency set by the oscillator 15 be set to the average value of the variation.If configured in this way, the frequency will vary by about 100H2. When a single driven body is driven by a plurality of driving bodies, there is no need to provide an oscillator for each driving body, and control can be performed with one oscillation X, which is advantageous in terms of circuit configuration.

Furthermore, in this ultrasonic motor, in response to the bending vibration of one of the plurality of drive bodies, that is, the bending vibrator 11A of the drive body 12A, the other bending vibrators 11B, 11C and the longitudinal vibrator 4A, Since 4B and 4C can be driven with their phases shifted, low-speed driving becomes easy. Furthermore, since the bending vibrator is driven by one oscillator, the driving timing of the vertical vibrator can be accurately determined and the vertical vibrator can be driven efficiently.

For example, even if bending vibrators are manufactured with high precision, if the operating frequency of each bending vibrator changes, the phase will change with respect to the drive signal near the resonance point. Therefore, if an oscillator is provided for each bending vibrator as in a conventional motor, it becomes necessary to align the phases of each element, and if this adjustment is not done, the timing of driving the driven object of each driving object will be different, causing the driving This will result in slippage between the two, reducing efficiency, but these problems will be solved.

Furthermore, in the motor of this embodiment, the phase of the longitudinal vibration can be set individually for the bending vibration, so even if the phase between the bending vibrators is out of phase, the vibration phase of the longitudinal vibrator can be adjusted. is also possible.

As for the speed control in the motor of this embodiment, there is a control method in which the phase of all longitudinal vibrations is shifted by a certain amount with respect to the phase of bending vibration, and a control method in which the phase of all longitudinal vibrations is shifted by a certain amount with respect to the phase of bending vibration. It is possible to adopt a control method in which the phase of the vibration of other longitudinal oscillators is appropriately selected by providing a child, or a more sophisticated Maf method in which the amplitude of some of the longitudinal oscillations is appropriately selected.

FIG. 4 is a block configuration diagram of an ultrasonic motor drive circuit showing a second embodiment of the present invention. The motor mechanism of this embodiment is the same as that of the first embodiment, but the drive circuit is different, and the difference is that the bending vibrator 11B
, IIC are provided with phase shifters 23a and 23b, respectively.

As a result, as in the case of the first embodiment, the longitudinal oscillators 4A, B are connected to the respective bending oscillators 11A, B, C.

It becomes unnecessary to adjust the phase of the vibration of C to maximize the speed of the motor. That is, each bending vibrator IIA, B, C
The above-mentioned transfer device 81
Optimal driving conditions can be obtained by adjusting 3a and 23b.

Furthermore, in the speed control according to this embodiment, in addition to the three speed control methods of the above-mentioned embodiment, each bending vibrator 11A,
A method can be adopted in which the phases of the bending vibrations B and C are shifted to change the speed. Note that speed control can also be performed by changing the amplitude of the bending vibration, but in this case, the driving force will be reduced as in the conventional speed control using amplitude control.

5 and 6 are longitudinal sectional views of an ultrasonic motor showing a third embodiment of the present invention. In the first embodiment, one rail and a plurality of drive bodies, which are drive members, are arranged in a single row in the driving direction, but in the present embodiment, two rails and a plurality of drive members are arranged in a single row. It is characterized by its body arranged in double rows. That is,
FIG. 6 is a sectional view seen from the front in the driving direction, and as shown in this figure, two rails 32 and 33 are installed in parallel, and a plurality of driving bodies 34A are mounted on the rails 32.

34B and a plurality of drivers 35A on the rail 33.

35B can be attached to increase its driving force.

Note that the driving bodies 34A, B or 35A, B are held by holding bodies 37A, B or 38A, B as in the first embodiment. Furthermore, those holders 37A, B and 3
8A and B are connected to a single motor support frame 31 by screws 40.
The driving body is connected to each rail via a disc spring or the like, and the driving body is pressed against each rail. In addition, the driving bodies 34A, B and 35A
, B are each composed of a bending vibrator and a longitudinal vibrator as in the first embodiment. Further, the drive circuit of this ultrasonic motor is the same as that of the first embodiment.

Although first-order bending vibration is used as the bending vibration of the motor in each of the embodiments described above, it is also possible to use other higher-order bending vibrations. Further, the gist of the present invention can be applied not only to linear type ultrasonic motors but also to rotary type ultrasonic motors in which the drive body is disposed in a circumferential manner.

[Effects of the Invention] As explained above, the ultrasonic motor of the present invention operates the flexural oscillator and longitudinal oscillator of the other driving member in synchronization with the flexural vibration generated in one of the plurality of driving members. This device drives a driven member by vibrating it, and the device of the present invention provides high efficiency and high output.Furthermore, since each vibrator is synchronized, slippage does not occur in each drive member. It has many remarkable effects, such as no unnecessary vibrations or audible sounds, and stable speed control even at low speeds.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of the ultrasonic motor showing the first embodiment of the present invention, FIG. 2 is a longitudinal sectional view of the ultrasonic motor shown in FIG. FIG. 1 is a block configuration diagram of an ultrasonic motor drive circuit, FIG. 4 is a block configuration diagram of an ultrasonic motor drive circuit according to a second embodiment of the present invention, and FIG. FIG. 6 is a vertical cross-sectional view of the ultrasonic motor shown in FIG. 5, viewed from the driving direction. 1...Motor support frame (fixing member) 4A, B, C...Longitudinal vibrator 5A, B, C... ... Multiple elastic bodies 6A, B, C.
...Piezoelectric electro-mechanical conversion element)7...
.........Holding body (fixing member) 1, IA
, B, C...Bending vibrator 12A, B, C... Plural driving bodies (plural driving members)
Third eye

Claims (1)

[Claims] Consisting of an elastic body and an electro-mechanical conversion element fixed to the plurality of elastic bodies, the electric-mechanical conversion element can be fixed on the elastic body by applying an alternating voltage to the electro-mechanical conversion element. A bending vibrator that generates wave-shaped bending vibration, and a surface of the elastic body, which is provided on the nodal line of the bending vibration, is oscillated about the nodal line by the bending vibration, and applies an alternating voltage. a plurality of drive members each comprising a longitudinal vibrator that expands and contracts in the amplitude direction of the bending vibration when the vibration is applied; a fixed member that holds the plurality of drive members; and a driven member that is pressed against the tip surface of the longitudinal vibrator. member, and vibrates the bending vibrator and the longitudinal vibrator of the other drive member in synchronization with the bending vibration generated in one of the plurality of drive members. An ultrasonic motor, characterized in that the ultrasonic motor moves the motor relative to the fixed member.