JPS62247771A - Oscillatory-wave motor - Google Patents

Abstract

PURPOSE:To improve drive efficiency by providing oscillation-detecting electrodes so that each electrode lies between an antinode and a node of any of A and B phase standing waves and by driving the electrodes in such manner that there exists a required phase relation between them. CONSTITUTION:A stator is composed of a ring-shaped diaphragm 1 and a piezoe lectric element plate 2 consisting of piezoelectric ceramics and so on secured on one side of said diaphragm, which element plate is provided with electrodes Al-B2 relative to first group (A phase) and second group (B phase) piezoelectric elements respectively and with an electrode Sl relative to an oscillation-detecting piezoelectric element (S phase). Said A phase electrodes A1-A2 and B phase electrodes Bl-B2 are respectively arranged at a pitch of 1/2 wavelength and these A and B phase electrodes are formed so as to deviate from each other by 90 deg. (l/4 wavelength) in a positional phase. Also, an oscillation at the S phase center point is made to have + or -45 deg. or + or -135 deg. time phase difference from an oscillation at the center point of the A phase electrode A1 according to the direction of rotation of a motor. In this way, it is made possible to improve a phase detection sensitivity.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a vibration wave motor that frictionally drives a moving body using progressive vibration waves, and particularly relates to a vibration wave motor that generates vibration waves in a stable resonance state. This paper relates to the arrangement and size of a mechano-electrical transducer element for detecting vibration in a circuit.

[Background of the invention]

Photographic wave motors that use progressive vibration waves to frictionally drive moving objects have recently been put into practical use, and the basic principle thereof is as follows.

The stator is made by fixing two groups of piezoelectric elements arranged in the circumferential direction to one side of a ring-shaped diaphragm made of an elastic material whose total circumferential length is an integral multiple of the length λ. . These piezoelectric elements are arranged so that there is a shift within each group. Both groups of piezoelectric elements are each provided with an electrode film. If an AC voltage is applied to only one of the groups, λ on the diaphragm will be the center point of each piezoelectric element in the group and the antinode position at every i point from there, and the center point between the positions of the layers. A standing wave (wavelength λ) of bending vibration is generated around the entire circumference of the diaphragm, where is the position of the node. If an AC voltage is applied only to the other group, a standing wave will be generated in the same way, but the positions of its antinodes and nodes will be different from the standing wave. When an AC voltage with the same frequency and a temporal phase difference of 1 is simultaneously applied to both groups, as a result of the synthesis of both standing waves, the diaphragm has a progressive wave of bending vibration (wavelength λ) that advances in the circumferential direction. ) occurs,
At this time, each point on the other thick surface of the diaphragm moves in a kind of ellipse. Therefore, if a ring-shaped moving body as a rotor is brought into pressure contact with the other surface of the diaphragm, the moving body receives circumferential frictional force from the diaphragm and is rotationally driven. The direction of rotation can be reversed by switching the phase difference between the AC voltages applied to both piezoelectric element groups to positive or negative. The above is an overview of the principle of this type of vibration wave motor.

In this type of vibration wave motor, the above two groups of piezoelectric elements (
In addition to this, a piezoelectric element for vibration detection is fixed to the diaphragm, and the frequency of the AC voltage applied to the piezoelectric drive element is automatically adjusted according to the detection output of the piezoelectric element for vibration detection. A drive circuit that can most efficiently drive a vibration wave motor by setting the resonant frequency to 0 is proposed by the present applicant in Japanese Patent Application No. 59-276962. However, in this proposal, the piezoelectric element for vibration detection is fixed at a position having the same spatial phase as the position of any one group of the driving piezoelectric elements. That is, the piezoelectric elements for vibration detection were fixed so that the center point of the piezoelectric element for vibration detection was located at a position shifted by an integral multiple of 1 from the center point of one section of the piezoelectric element for driving of the -λ group. However, voltages due to leakage of other frequency voltages for vibration driving appear in the piezoelectric element for vibration detection installed in such a position, and the AC voltage applied to the piezoelectric element for driving does not match the desired phase. Sometimes it would come off.

[Purpose of the invention]

It is an object of the present invention to eliminate the above-mentioned conventional drawbacks and at the same time improve phase detection sensitivity.

[Summary of the invention]

Two groups of drive electro-mechanical λ energy conversion element sections are arranged on a diaphragm made of an elastic material, at equal pitches 7 within each group, and so that the polarity of expansion and contraction when voltage is applied is alternately reversed. The arrangement is fixed so that there is an odd multiple of i between the groups, and AC voltages having a temporal phase difference of 90° are applied to the two groups of the drive electro-mechanical energy conversion element sections, respectively. By applying this, a progressive oscillation wave of wavelength λ is generated as a composite of two standing waves (wavelength λ) generated by each of the above-mentioned groups that are shifted by a distance from each other, and thus a progressive vibration wave of wavelength λ is generated. In a vibration wave motor configured to frictionally drive a movable body that is in pressurized contact with a diaphragm, an electro-mechanical energy conversion element section for vibration detection is provided on the diaphragm between the group of electric-mechanical energy conversion element sections for driving. The alternating current voltage applied to the driving electromechanical transducer section group is provided at the midpoint between the adjacent antinodes and nodes of both of the standing waves, and the alternating current voltage applied to the drive electromechanical transducer section group is used for vibration detection according to the rotational direction of the vibration wave motor. A vibration wave motor having a phase difference of ±45° or ±135° with respect to a detection voltage of an electro-mechanical energy conversion element section, and having an electro-mechanical energy signature for vibration detection.

[Embodiments of the invention]

Examples of the present invention will be described below. FIG. 1 (turtle) is a side view showing a portion of the stator, and FIG. 1(b) is a plan view showing the portion of the stator.

In Figure 1, 1 is a ring-shaped diaphragm, 2 is a diaphragm 1
This is a piezoelectric element plate made of piezoelectric ceramics or the like that is fixed to one side of the piezoelectric element plate. A1. A2 and B1°B2 are the first
Group (referred to as A phase) piezoelectric elements and second group (B phase)
This is an electrode for the piezoelectric element, and S is an electrode for the vibration detection piezoelectric element (this is referred to as an S-phase piezoelectric element). Each part of the piezoelectric element plate 2 corresponding to these electrodes is polarized in advance to form a group of divided piezoelectric elements 6). The A-phase electrodes A15A2it are arranged at a pitch of 7 wavelengths, and the polarization directions of the corresponding 8 piezoelectric elements are opposite to each other, and the B-phase 1 poles 81*B2 are also arranged at a pitch of 1 wavelength, and the corresponding polarization directions are opposite to each other. The polarization directions of the piezoelectric element sections are opposite to each other, the A-phase piezoelectric element group and the B-phase piezoelectric element group have a positional phase, and the circumferential length of the electrode S is smaller than one wave. be. The standing wave vibration excited by applying an AC voltage to the human-phase electrode is called an A-phase standing wave, and the standing wave vibration excited by applying a full AC voltage of the same frequency to the S-phase electrode is called a B-phase standing wave. It is called a phase standing wave.

By simultaneously generating an A-phase standing wave and a B-phase standing wave of the same amplitude and setting their temporal phase difference to 90°, a progressive filament wave is excited as a result of the synthesis of both standing waves.

The center position @aa' of the electrode A1 is the antinode of the A-phase standing wave and the node of the B-phase standing wave. Also, the center position b of the electrode B1
-b' (this is an imaginary position shifted by one wavelength from the position a-a') is the antinode of the B-phase standing wave and a node of the standing wave of the human phase. Center position e - e' of detection electrode (S phase electrode) S
is located at a position shifted by one wavelength from positions a-a' and b-b'. Therefore, the position e''e' is neither a node nor an antinode of either the A-phase or B-phase standing wave.

Position d - d', which is one wavelength closer to position e - e' from position a - a' (this is a node of the A-phase standing wave and an antinode of the B-phase standing wave), in the circumferential direction If the origin of the position coordinate X is taken as the origin, the force due to the A-phase standing wave is IrA, and the force due to the B-phase standing wave is tm, then the following is obtained. Here, λ is the wavelength, TVi period, t is an arbitrary time, and double number corresponds to the rotation direction of the vibration wave motor.

When the center position C-C' of the vibration detection electrode (S-phase electrode) S is F, the vibration at position tc-e' is ±45° with respect to the vibration at position Jd-d'. It has a temporal phase difference of position d-d
Since the vibration at ' has a temporal phase difference of ±90° with respect to the center position a-a' of the human-phase electrode A1, it ends up at the position C-c'
The vibration at position has a temporal phase difference of ±1356, depending on the motor rotation direction, with respect to the imaging at position &-11'.

The above is a case where the S-phase lost point is at the position shown in Figure 1, but generally the S-phase lost point is at the midpoint between the adjacent antinodes and nodes of the A-phase standing wave and the B-phase standing wave. In some cases, when the amplitudes of both standing waves are equal, the vibration at the point lost in the S phase is ±45° or ±45° with respect to the vibration at the center point of the A phase electrode A1, depending on the motor rotation direction. It has a temporal phase difference of 135°. Whether this temporal phase difference is 456 degrees or 135 degrees depends on which point in the S phase the lost point is located between which adjacent angle and node.

In piezoelectric ceramics, the driving AC voltage and the displacement speed are in the same phase at the resonance point, and the phase of the detected AC voltage is 90' (100) phase ahead of the displacement speed.

Even considering this point, the temporal phase difference is ±45° or ±
It is 1356.

Conversely, in the case of such an S-phase position, phase-locked driving is performed to provide the above-mentioned temporal phase difference between the S-phase detection voltage and the human-phase drive voltage, depending on the motor rotation direction. For example, the amplitudes of the standing waves of both the A and B phases can be made equal. Of course, it is not a problem to provide a positive or negative temporal phase difference of 906 between the A-phase drive voltage and the B-phase drive voltage depending on forward rotation or reverse rotation.

A drive circuit f is shown in FIG. 2, which performs phase locking so that there is a temporal phase difference of 45°, positive or negative, depending on the motor rotation direction, between the S-phase detection voltage and the human-phase drive voltage. 6,18.24
is a comparator, 7,12゜19 is a phase comparator (pc)
, 8, 13.20 are resistors, 9.14.21 are capacitors, 10, 15.22 are voltage controlled oscillators (V, C, O),
11.23 is an amplifier, 16 is an n-frequency divider circuit, 17 is an n-stage shift register, 17a to d are output terminals of the 5-stage shift register 17, and 25 is a double switch for switching forward/reverse rotation.

The S-phase signal from the vibration detection electrode 5 is converted to a logic level by the comparator 6 and input to the edge trigger type phase comparator 7. is input using the dual switch 25 for forward/reverse switching. These two inputs to the digital phase comparator 7 are in phase and at the same frequency.

edge) IJ type phase comparator 12, integrating resistor 13,
By connecting the integrating capacitor 14, the voltage-controlled oscillator 15, and the n-frequency divider circuit as shown in the figure, a signal with a frequency n times the human phase drive frequency can be generated, and the clock of the five-stage shift register 17 can be generated. Input as a signal. Further, as data to the five-stage shift register 17, the A-phase driving voltage is inputted by the comparator 18. The B-phase drive voltage is applied to the shift register 17 via the dual switch 25.
The output 17e or 17d is given by the illustrated circuit configuration.

With such a circuit configuration, the human phase drive voltage is generated by combining the S phase signal from the detection electrode 5 and the output terminal 17 of the n-stage shift register.
Since the signal from a or 17b has the same phase, the phase is shifted by the shift register 17 and the detection electrode 5
deviates from the S-phase signal from. n=8, 16, 24.
32. (360°745°=8), n is 8
By taking a multiple of , the output of the shift register 17 can generate a phase shift of 45 degrees with respect to the human phase driving voltage.

Therefore, the output of the shift register 17 is 17 m * 17
-45 for b-17e and 17d, respectively, with respect to the A-phase drive voltage.
°.

By having phase shifts of -315°, -90°, and -270@, the time difference between the A-phase drive voltage, B-phase drive voltage, and S-phase detection voltage as described above can be adjusted according to forward and reverse rotations. Phase lock can be achieved.

It is clear that a drive circuit that achieves 135° phase lock between the S-phase signal and the human-phase drive voltage can be easily realized in the same manner as shown in FIG.

FIG. 3 is a diagram showing the electrode arrangement of this embodiment.

A1 to A5 are human phase drive electrodes, B1 to B5 are B phase drive electrodes, 81 or 82 are vibration detection electrodes, and C is an electrode electrically connected to the back surface, that is, a ground electrode.

Human phase drive electrodes A1 to A5, B phase drive electrodes B1 to B5
It is desirable to make the area as large as possible from the point of view of the efficiency of exciting vibrations. In such an arrangement, in the above embodiment, the electrode S1 or the electrode S2 having the arrangement relationship shown in FIG. 3 is employed as the vibration detection electrode (S-phase electrode).

FIG. 4 is an enlarged view of the vicinity of the perturbation detection electrode Sl in FIG. 3. The circumferential length of the electrode S1 is t, and the radial length λ is ω. t is set to satisfy 0<1<-2, and in order to increase the phase sensitivity, t is made as short as possible in the present invention. However, from the point of view of the output voltage, if t is too short, the output will become small, so t should be kept within a certain range of magnitude in relation to the input resistance of the comparator 6 so that the output is not too small. shorten. When t is short, the detection electrode S1 may obtain a signal with a resonance frequency higher than the drive frequency of the vibration wave motor. For this reason, it is desirable to limit the voltage controlled oscillators 10, 15, and 22 so that they do not oscillate at high-order resonance frequencies.

FIG. 5(,) shows the vibration detection electrode S1.

This electrical equivalent circuit is shown in the same figure (b). ■ is the current source, and Cd is the braking capacity. ■ The current flowing from l
Then, the voltage v8 appearing on the vibration detection electrode S1 is where i = i o65'''' ω is the angular frequency during driving.

When a capacitor C (to reduce the pressure without changing the phase when the output voltage of the piezoelectric element for vibration detection is high) is connected in parallel to the electrode S1, 1[C pressure υ8' is therefore vs'/M
IB is reduced in pressure by capacitor C, but the braking capacity is 191
If cd is large, the capacitance of capacitor C must be made large. However, if the area of the electrode S1 is small, the size of the pressure reducing capacitor C can be made small.

Although piezoelectric elements were used in the above embodiments, other electro-mechanical energy conversion elements, such as electrostrictive elements, may also be used.

[Effects of the Invention] In the present invention, a pole is provided in the imaging detection device 1 so as to be located at an intermediate position between the antinode and the node when viewed from either the A-phase or B-phase standing waves, and one pole is provided for vibration detection. By shortening the length of the detection electrode in the circumferential direction, it is possible to drive the human phase/B phase driving piezoelectric element with the required phase relationship based on the signal from the detection electric sign, and the phase detection sensitivity is improved. be able to.

Further, the human phase driving electrode and the B phase driving electrode can be made as wide as possible, and driving efficiency is improved. In addition, by narrowing the vibration detection electrode, the capacitance of the decompression capacitor can be reduced.
ii can be reduced.

[Brief explanation of drawings]

1(a) and 1(b) are a side view and a plan view, respectively, showing a part of the stator of a vibration wave motor according to an embodiment of the present invention, and FIG. 2 is a diagram showing a drive circuit that performs phase locking, and FIG. 3
The figure is a plan view showing the electrode arrangement, FIG. 4 is an enlarged plan view near the vibration detection electrode S1 in FIG. 3, and FIG. 5 (a) + (b)
) e (c) is a diagram showing a piezoelectric confectionery for vibration detection, several circuits thereof, and a circuit when a decompression capacitor is connected to the piezoelectric confectionery. A1-A5...A-phase electrode, B1-B5...S-phase electrode, Sl, S2...imaging detection electrode (S-phase electrode), 6
．． 11(,24...Konoyareta, 7.12.19
... Phase comparator, 10.15.22 ... Voltage controlled oscillator, 11.23.
...Amplifier, 16...n frequency divider, 17...n stage shift register, 25...forward/reverse selector switch.

Claims (1)

[Claims] Two groups of drive electric-mechanical energy conversion element sections are arranged on a diaphragm made of an elastic material, with equal pitch λ/2 within each group, and so that the polarity of expansion and contraction when voltage is applied is alternately opposite. The arrangement is fixed so that there is a shift of an odd multiple of λ/4 between the groups, and an AC voltage having a temporal phase difference of 90° is applied to the two groups of the drive electro-mechanical energy conversion element sections. By applying these to each group, a progressive vibration wave of wavelength λ is generated as a composite of two standing waves (wavelength λ) generated by each of the groups and shifted by λ/4 from each other, and as follows. In a vibration wave motor that frictionally drives a movable body that is in pressure contact with the diaphragm, an electro-mechanical energy conversion element for vibration detection is provided on the diaphragm between the group of sections of the electro-mechanical energy conversion element for driving. The division is provided at the midpoint between the adjacent antinodes and nodes of both of the standing waves, and the AC voltage applied to the drive electromechanical transducer division group changes to the vibration excitation detection electricity according to the rotational direction of the vibration wave motor. - A phase difference of ±45° or ±135° is established with respect to the detection voltage of the mechanical energy conversion cord section, and the length of the vibration detection electro-mechanical energy conversion element section is made smaller than λ/4. A vibration wave motor characterized by: