JPS61106076A - Piezoelectric motor - Google Patents

Abstract

PURPOSE:To efficiently produce propulsion energy by providing a vibration transmitter to a slider on the surface of a stator. CONSTITUTION:8 electrodes 1a, 2a which are divided on the front and back surfaces of the first and second piezoelectric vibrators 1, 2 of disc shape are provided at a stator to form four sets of forcible vibration vibrators. A stator base 3 having a thickness equivalent to the vibrators 2 or approx. 100 times is superposed and mounted on the vibrators 2. In this case, a projection 4 of a vibration transmitting member is provided, for example, at approx. 1/2 position of diameter is formed on the surface of the base 3, and a shaft 5 is formed at the center. Thus, the projection 4 acts to enlarge longitudinal and lateral distortions at operating time to obtain mechanical vibration exceeding the surface roughness of two articles contacted with one another.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a motor that generates driving force using a piezoelectric material.

2. Description of the Related Art In recent years, piezoelectric motors, which obtain rotational or running motion by exciting various ultrasonic vibrations using electromechanical transducers such as piezoelectric ceramics, have attracted attention because of their high energy density. .

Below, with reference to the drawings, these conventional piezoelectric motors that utilize ultrasonic vibration will be described.

Published in Nikkei Mechanical (5B, 2.28) etc. □
In conventional piezoelectric motors, a piezoelectric element ring is integrated with the surface of a thick metal ring or the like to form a stator. This piezoelectric motor uses Rayleigh waves, also called surface acoustic waves.

This wave is a wave that propagates near the surface of a material, and the wave has both longitudinal and transverse wave components.

A conventional piezoelectric motor configured as described above.

Using the same principle as a two-phase or three-phase motor, when a phase-shifted AC signal is applied, the stator expands and contracts in the circumferential direction, and a surface wave is generated in the stator. Figure 12 is an enlarged depiction of the contact situation between the stator of a conventional piezoelectric motor and a moving object that comes into contact with its surface. If we focus on one point A on the surface of an elastic body, point A draws an elliptical locus with a major axis 2w and a minor axis 2u. At the vertex where the elastic body contacts the moving body, point A has a velocity of V=2πfu in the negative direction of the I axis.

As a result, the moving body is driven at a speed V in the direction opposite to the wave propagation due to the frictional force with the elastic body. By drawing an elliptical trajectory as thrust on the surface of the elastic body in this manner, the conventional piezoelectric motor guides the rotation of the moving body (rotor) with which it comes into contact.

Furthermore, this piezoelectric motor that uses surface waves uses the same principle as two-phase and three-phase motors, and the direction of rotation can be easily switched using phase-shifted power supplies.

These driving principles are also clarified in the published patent No. 58-32618, and when the longitudinal vibration and lateral vibration occurring in the friction contact part are excited at the same frequency but with different phases, a force directed in the lateral direction is generated. Therefore, the concept of a traveling wave, which is a combination of longitudinal waves and transverse waves, is disclosed as an object moving in contact with it.

Problems to be Solved by the Invention The above configuration has the following problems.

(1) The stress required to obtain the vibration mode that is the driving principle has a maximum value on the stator surface. In a stator with a thickness of three blades, the vertical stress is about 20001J/-, and the electric power required to resist this is about 100 to 1000 times the normal theoretical value for a bimorph.

(2) -! Since the neutral surface of the vibration is located inside the elastic body such as metal that constitutes the stator, the piezoelectric material used as an electro-mechanical transducer does not provide efficient nodal drive, but rather inefficient abdominal drive. Furthermore, in this driving principle, more than 5/8 of the total energy of the piezoelectric material serving as the driving source is ineffective energy.

(3) In addition, in order to extract thrust from a minute amplitude of about 0.26 μm or less, the moving object uniformly contacts the peaks and troughs of the stator, which have different amplitudes at different speeds and directions. The speed is low, close to the integral value. Therefore, in order to obtain a practical rotation speed, torque, etc., a large amount of electric power, about 10 to 100 times that of a conventional motor, is required.

(4) In the conventional piezoelectric motor with a surface waveform, the drive electrodes are divided into two sets, and the waves excited by the A electrode are propagated to the B electrode side, or conversely, the waves excited by the B electrode are transmitted to the A side. The wave is propagated to the electrode side as a wave having a longitudinal wave component and a transverse wave component, generating an elliptical locus on the surface of the elastic body. Due to this driving principle, the effective drive area never exceeds 50%, so only weak vibrations can be excited, and the stator has no choice but to have an endless configuration. This configuration uses the secondary effect after excitation, which has an extremely narrow range of application. In other words, the direct and
It had many of the problems mentioned above, such as the inability to use powerful thrust.

Means for Solving the Problem Two plate-shaped piezoelectric vibrators are divided into at least one pair of regions, and the polarization direction of each region is alternately reversed. A stator is arranged so that the boundaries of the respective regions of the other plate-shaped piezoelectric vibrator are located near the section, and a stator is constructed by stacking a base made of an acoustic material or the like in multiple layers together with both piezoelectric vibrators, and its fixing. A pickup transmission member, comprising a slider facing the slider, and which does not cause an apparent mechanical load on the surface of the stator by contacting the slider, for example, a member having a hollow cross-sectional shape, in the circumferential direction U. 'Divided into multiple pieces, or light metal materials such as aluminum 9 Synthetic resin materials.

Alternatively, it is characterized in that it is made of a rubber material or the like.

By providing the vibration transmission part to the working slider on the stator surface, the longitudinal strain and the lateral strain are magnified during operation, and the mechanical amplitude is obtained by exceeding the surface roughness of the two objects in contact. , rotational energy or propulsion energy can be extracted most efficiently.

Example Details of embodiments of the present invention will be described with reference to the drawings.

The stator has a structure as shown in FIG. 1, for example. On the surface of the disk-shaped first piezoelectric vibrator 1, eight electrodes 1a divided into, for example, 46° areas are provided. This electrode 1a is formed on the surface of the first piezoelectric vibrator 1 by a method such as printing, vapor deposition, or plating using a conductive material such as gold, silver, silver palladium, rhodium, or nickel. The electrode (not shown) provided on the back surface may or may not be divided like the front electrode.

Polarization is performed so that the polarization directions of adjacent electrodes of the first piezoelectric vibrator 1 configured as described above are different from each other in the thickness direction. As a result, as shown in FIG. 1, four sets of forced excitation vibrators with eight poles each consisting of regions having alternately positive or negative polarity are constructed. After polarization, the electrodes 1a do not need to be divided and are connected so that a voltage can be applied all at once. The disk-shaped second piezoelectric vibrator 2 has the same structure as the first piezoelectric vibrator 1, and includes four sets of forced excitation vibrators with eight poles having alternating positive and negative polarities.

The minimum amplitude position of the first piezoelectric vibrator 1 or the second piezoelectric vibrator 2 is near the boundary between adjacent electrodes, and the maximum amplitude position is near the center of each electrode. Both piezoelectric vibrators 1°2 have a second piezoelectric vibrator 2 located near the center of the electrode, which is the maximum amplitude position of the first piezoelectric vibrator 1.
The electrodes are superimposed so that the boundary between adjacent electrodes is located at the minimum amplitude position.

The first piezoelectric vibrator 1 and the second piezoelectric vibrator 2 configured as described above are attached to a stator base 3 having a thickness equal to or about 100 times as thick as that of the piezoelectric vibrator.

The stator base 3 is made of an acoustic material or a friction material made of aluminum, brass, iron, stainless steel, hardened steel, synthetic resin material such as nylon, ceramic material, glass material, or a composite material made of these materials. It is formed using Further, on the surface of the stator base body 3, a projection 4, which is an image capturing and transmitting member, is formed in the vicinity of a position corresponding to, for example, about % of the diameter, and a shaft 6 is formed at the center.

Details of various aspects of the projection 4, which is the vibration transmitting member, are shown in FIGS. 2, 3, and 4.

The same parts as in FIG. 1 are given the same numbers and the explanation is omitted.

FIG. 2 shows a cross-sectional view of the stator base 3 made of an acoustic material or the like. Near the position of about % of the diameter,
A protrusion 4a, which is a vibration transmitting member, is formed integrally with the stator base body 3, having a wall thickness of, for example, about 0.6 mm and a height and width of about 3 mm.

According to such a configuration, despite the formation of the protrusion 4a which is the vibration transmitting member, the dynamic range of the mechanical resonance characteristic representing the level of strong excitation does not change, and the vertical direction in the radial direction does not change. The maximum position of directional strain did not shift to the outside of the protrusion 4a, and it was possible to obtain an effect that apparently no mechanical load was applied. This allows rotational energy to be extracted most efficiently.

FIG. 3 shows another embodiment, and shows a plan view of a stator base 3 made of an acoustic material or the like. Protrusions 4b, which are integrally structured with the stator base 3 and have a height of approximately 3 mm and a width of approximately 2 blades, are located in the vicinity of the position of about % of the diameter, and are vibration transmitting members divided into sections, for example, every 15 degrees. is formed.

According to such a configuration, despite the formation of the protrusion 4b which is the vibration transmitting member, the dynamic range of the mechanical resonance characteristic representing the level of strong excitation does not change, and the radial vertical direction does not change. The position of maximum directional strain is protrusion 4
By b, it was possible to obtain the effect that no mechanical load was applied to the outside without being transferred to the outside. This allows rotational energy to be extracted most efficiently.

FIG. 4 shows a perspective view of a stator base 3 made of an acoustic material or the like, which is still another embodiment. A protrusion 4C, which is a photo-transmission member made of a light metal material such as aluminum 9 and a synthetic resin material or a rubber material, coated with an abrasion-resistant material and having a surface of about 3 fl in both width and width, is fixed.

According to such a configuration, despite the formation of the protrusion 4C which is the vibration transmission member, the dynamic range of the mechanical resonance characteristic representing the level of strong excitation does not change, and the radial vertical direction does not change. The position of maximum directional strain is protrusion 4
By C, it was possible to obtain the effect that no mechanical load was applied to the outside without being transferred to the outside. This allows rotational energy to be extracted most efficiently.

Note that the slider 1 of the protrusion 4 configured as shown in FIG.
Etching is performed on the contact surface with the slider 14 in the radial direction perpendicular to the direction of movement of the slider 14, consisting of a plurality of etchings with a depth of several μm to several tens of holes, for example, every 10 or several tens of degrees. Alternatively, machined knife-etched grooves (not shown) may be provided. Thereby, the effect of cleaning the precipitated powder due to rotational wear of the protrusion 4, slider 14, etc. by using the groove can be obtained. The precipitated powder is guided inside the groove and transported to the outside. As a result, the friction coefficient of both the contact surfaces of the protrusion 4 and the slider 14 could maintain the initial friction coefficient and contact area, and the generated torque was always constant.

The structure constructed as described above is used as the stator 6 shown in FIG. As shown in FIG. 5, the output signal oscillated by the oscillator 7 at the forced excitation drive frequency determined by the stator 6 is branched, one being directly sent to the amplifier 8 and the other being sent to the amplifier 10 via the phase shifter 9. input. The phase shifter 9 shapes a signal whose phase is shifted within a range of ±10° to ±170°, which is used for forward rotation or reverse rotation as described later. The output signal of the oscillator 7 is directly input to the amplifier 8, and the amplified signal is applied to the first piezoelectric vibrator 1 through lead wires 11 and 12. As a result, stator 6
In this case, forced excitation waves of 4 wavelengths corresponding to 8 poles and 4 sets of forced excitation vibrators are generated, with each pair of regions of the first piezoelectric vibrator 1 having different positive polarity or negative polarity as one wavelength. be done. The second piezoelectric vibrator 2 is similarly driven by applying the output of the amplifier 10 via the lead wires 12,13.

Figure 6 shows the strain in the vertical direction when an electric signal is applied to the first piezoelectric vibrator 1 and the second piezoelectric vibrator 2 as a change in the circumferential position at a position of about 70% with respect to the maximum diameter. The measured results are shown. The measurement was performed by irradiating the measurement location with a He-Ne gas laser beam and using an interference method between incident light and reflected light. FIG. 6a shows the measurement results when the first piezoelectric vibrator 1 was driven by applying signals to the lead wires 11 and 12. When soV was applied, the amplitude was approximately ±O, Sμm. The minimum amplitude position is near the boundary between adjacent electrodes, and the maximum amplitude position is near the center of each electrode. The results of vertical strain measured when the second piezoelectric vibrator 2 was driven in the same manner are shown in FIG. s
When oV was applied, the amplitude was about ±0.8 μm. The minimum amplitude position is near the boundary position between adjacent electrodes,
The maximum amplitude position is near the center of each electrode.

Next, the measurement results when the first piezoelectric vibrator 1 and the second piezoelectric vibrator 2 are driven simultaneously according to the configuration shown in FIG.
Shown in Figure C. In the strain distribution in the vertical direction, the position where the amplitude is maximum has moved to an intermediate position between a and b. Furthermore, the maximum amplitude of vertical strain is approximately 1.3 times larger. Here, as mentioned above, the second piezoelectric vibrator 2
Since it is driven with a phase shift of ±10' to ±17o0 with respect to the piezoelectric vibrator, the maximum amplitude position of the composite wave C moves in a constant direction with time.

A slider 14 is in contact with the top of the stator 6.

The slider 14 is composed of an elastic body 16 made of a friction material or an elastic material, and an acoustic material 16 coupled thereto.

When the stator 6 is driven as described above, the apex of the vibration on the side of the stator 6 facing the slider 14 comes into contact with the slider 14, and since the apex moves with time, the slider 14 A force having a lateral component is applied to the In this way, the slider 14 repeatedly moves in position due to the lateral component according to the drive frequency determined by the stator 6, and as a result, the slider 14 obtains rotational motion in the range of approximately several to several thousand revolutions per minute. I can do it. The generated torque varies depending on the acoustic material that makes up the stator, the friction coefficient and contact area of the slider that makes surface contact with the stator, or the magnitude of the load received, but it ranges from several tens of g+α to several thousand. gf ar
It was possible to obtain torque in the range of m. Regarding the direction of rotation, +10° to +170° relative to the reference signal.
If the rotation obtained when driving the second piezoelectric vibrator by applying a signal with a phase shift in the range of 0 is, for example, positive rotation, then the phase is shifted in the range of -10' to -170 degrees with respect to the reference signal. The rotation direction obtained when driving by simultaneously applying signals is rotation in the opposite direction. Further, the rotation speed can be arbitrarily selected by selecting the magnitude or phase of the applied signal, or the magnitude of the load received by the contact portion.

According to the configuration of the present invention, the heavy load that causes distortion of metal with a large Young's modulus in the conventional method is eliminated. In the conventional method, it is considered possible to increase the short axis 2u of the elliptical locus by increasing the thickness of the metal to be bonded over the entire surface.

The size of the dynamic range of the resonance characteristics indicates the level of strong excitation, but the resonance characteristics are attenuated by about 15 dB for each increase in the metal thickness, so in reality, the short axis 2u, which is the thrust force, is increased. requires driving with large electric power. In this case, since the structure has extremely poor linearity, a high amount of heat is generated, but the increase in thrust is extremely small.

FIG. 7 shows a virtual image of the vertical distortion of the stator 6' when an electric signal is applied to the stator 6 according to the present invention.
The results are shown as changes in the cross-sectional direction. The measurement was carried out using the interferometry method using laser light, similar to the measurement in the circumferential direction. During soV application, the protrusion 4 which is a vibration transmission member
The maximum scratch width was approximately 1.8 μm in the vicinity. The amplitude phase shift turning point, the so-called vibration node, has a diameter of 100%.
Assuming this, it changes almost linearly at a position of 80 to 85 inches, and the amplitude at the end is about 2.6 μm. In addition, lead wires 11 and 12 for applying electrical signals from the vicinity of the vibration node.
．． When I took out No. 13, there was no disconnection due to vibration fatigue. Further, as shown in FIG. 11, which will be described later, as a practical structure, a buffer body 1γ is provided at the lower part of the stator 6. In that case, the stator 6 is curved as shown in FIG. 7 using the buffer body 1γ as a base, so that an effect is obtained in which the apparent amplitude is enlarged. Furthermore, if the support position is located near the vibration node, a drive with less loss can be realized.

As a result, the lateral component which becomes the thrust of the slider 14 increases in the protrusion 4, and the slider 14 moves very efficiently in a certain direction.

FIG. 8 shows the relationship between the driving voltage and the rotation speed of the piezoelectric motor according to the present invention. For comparison, the characteristics of a conventional surface wave type piezoelectric motor are shown in (a). (b) is the characteristic of a piezoelectric motor having the same structure as the present invention but without protrusions, and (C) is
(d) shows the characteristics when the length of the protrusion in the vertical direction of the piezoelectric motor according to the present invention is 4 mm, and (d) shows the characteristic when the length of the protrusion in the vertical direction of the piezoelectric motor according to the present invention is 8 mm. . By changing the vertical length of the protrusion 4 of the stator member in this way, a desired running speed could be obtained. From these facts, it can be seen that the piezoelectric motor according to the present invention is extremely efficient. In Fig. 8, the maximum speed is 36 Orpm, but in a prototype model with a larger diameter, a model with a smaller diameter of the rib 36, or a prototype model with a thinner piezoelectric vibrator, the maximum speed is 11000 rpm to 200 Orpm. I was able to measure the speed.

Moreover, the power consumption at this time was about 1/1 to 1/10 Q compared to a conventional piezoelectric motor. Furthermore, the power efficiency was also relatively better than that of DC micro motors and the like.

FIG. 9 shows changes in operating time when the materials of the projection 4 and the elastic body 15 of the slider 14 are changed. a indicates the operating time when the elastic body 16 is made of a composite material such as asbestos with a rubber binder. b indicates the operating time when a structural material such as hardened steel is used as the material of the protrusion 4.

C indicates the operating time when the elastic body 16 is made of a material □ which is a composite of pulp, silica, etc. with a synthetic resin binder. d shows the operating time when the protrusion 4 is provided with a knife-etched groove for cleaning precipitated powder due to rotational wear, and the initial characteristics can be guaranteed even after approximately 1000 hours or more of actual rotational loss.

The number of revolutions of a conventional piezoelectric motor is limited to a few revolutions to about 3° rpm. This is based on the drive principle of surface waveforms that use minute amplitudes of submicrons, and conventional piezoelectric motors are characterized by low speed and are intended for driving camera lenses and the like.

FIG. 1 shows a piezoelectric motor that directly uses spatial waves or bulk waves that produce strong vibrations according to the present invention.

For example, when the protrusion 4 shown in FIGS. 2, 3, and 4 has a height of about 8 mm, the soV driving voltage is 22 mm high.
The rotation speed is about Orpm. FIG. 10 shows the relationship between the diameter and the number of rotations when the diameter of the protrusion 4 is changed. As is clear from Fig. 1Q, the piezoelectric motor according to the present invention can obtain any desired number of revolutions by selecting the diameter or height of the protrusion 4, from several revolutions per minute to about 1,000 revolutions per minute. I can do it. Furthermore, the driving voltage is 20
Since it has an IJ air characteristic up to about 0■, the rotation speed can be increased to about 2000 rpm by increasing the voltage. In addition, since the construction principle or component parts do not have any magnetic means such as magnets or coils, piezoelectric motors with a speed of about 400 rpm or 700 rpm, for example, can be used as motors for magnetic recording and reproducing equipment such as floppy disks or video tape recorders. An ideal motor with no magnetic influence can be obtained.

FIG. 11 shows a more specific structure of the piezoelectric motor in one embodiment of the present invention. The same parts as in FIG. 5 are given the same numbers. The stator 6 provided with lead wires 11°, 12, and 13 is mounted on a frame (not shown) via a buffer 17 so as to be able to vibrate freely. A slider 14 is in contact with the top of the stator 6 via a bearing 18 pushed into the shaft 5.

A pressing force adjustment screw 19 is attached to the upper end of the shaft 5, and when the screw is tightened, the chrysanthemum-shaped leaf spring 20 is bent, and the stator 6 and the slider 14 can be brought into contact with an arbitrary pressing force. As a result, it was possible to obtain a torque ranging from several tens of gfez to several thousand qf-α.

Further, a fixed ring 21 is fixed on the slider 14, and rotation is transmitted to the rotated body by sandwiching the rotated body between it and a guide ring 22 shown by a virtual line. .

The piezoelectric motor with the above configuration not only does not take up much of its apparent storage space, but also can be driven in forward or reverse directions at will by simply changing the phase of the drive signal.
rl) several thousand 9f11 at low and medium speed rotations within m
Torque within the range of α can be generated. Further, the rotation speed can be arbitrarily selected up to approximately several thousand rotations by selecting the magnitude or phase of the applied signal, the magnitude of the load received by the contact portion, the length and diameter of the protrusion, etc. Therefore, there is no need for a speed reducer or the like. Moreover, since it always forms a contact friction pair, there is no moment of inertia, it is rich in minute pulse operation, and is excellent in compactness. Furthermore, since the structure is extremely simple, the price is low.

Effects of the Invention The piezoelectric motor according to the present invention has a structure in which a lateral component that becomes thrust is obtained by directly exciting a disc-shaped bulk wave, so that the mechanical displacement can be increased several times at a constant voltage. Since the entire deflection in the cross-sectional direction is output, it is possible to extract the peak speed without averaging the speed.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view of a stator of a piezoelectric motor according to an embodiment of the present invention, and FIGS. 2, 3, and 4 are sectional views and plan views showing different embodiments of the motor stator base, respectively. 6 is a cross-sectional view showing an outline of a piezoelectric motor using the same stator and its drive circuit, and FIGS. 6 and 7 are distortions during driving of the piezoelectric motor stator shown in FIG. 6. FIG. 8 is a graph showing the characteristics of the rotation speed versus drive voltage of the piezoelectric motor according to the present invention, FIG. 9 is a graph showing the operating time characteristics of the same motor, and FIG. 10 is a graph showing the characteristics of the piezoelectric motor according to the present invention. FIG. 11 is a graph showing the characteristics of the rotation speed with respect to the diameter of the main part of the stator. FIG. 11 is a partially cross-sectional front view showing the specific structure of a piezoelectric motor according to an embodiment of the present invention. FIG. FIG. 2 is a perspective view showing the operation of a conventional piezoelectric motor. 1.2... Piezoelectric vibrator, 1a... Electrode, 3... Stator base, 4... Protrusion, 6
...Stator, 14...Slider, 7...
...Oscillator, 8,10...Amplifier, 9...
...Phase shifter. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Figure 3 Figure 3 Basic stator Figure 4 Figure 3 Stator bowl Figure 5 Figure 6-11+ Figure 7 Figure 8 M movement v Mr. Cvr-r) Figure 9 Figure 10 C'''r )0
20 4D ω 80
to. Diameter (-

Claims (4)

[Claims] (1) Two plate-shaped piezoelectric vibrators are divided into at least one pair of regions, and the polarization direction of each region is alternately reversed. The plate-shaped piezoelectric vibrator is arranged so that the boundaries of each region are located, and a base made of an acoustic material or the like is placed.
The stator includes a stator configured in multiple layers together with the piezoelectric vibrators, and a slider that faces the stator, and the surface of the stator is in contact with the slider and has an apparent mechanical load. 1. A piezoelectric motor characterized by having a vibration transmitting member that does not act as a vibration transmitter. (2) The piezoelectric motor according to claim 1, wherein the vibration transmitting member integrally constructed with the base body has a hollow cross-sectional shape. (3) The piezoelectric motor according to claim 1, wherein the vibration transmission member is divided into a plurality of parts in the circumferential direction. (4) The piezoelectric motor according to claim 1, wherein the vibration transmission member is made of a light metal material, a synthetic resin material, or a rubber material.