JPS6122777A - Piezoelectric motor - Google Patents

Abstract

PURPOSE:To obtain a piezoelectric motor which has a simple construction and high efficiency by providing two piezoelectric vibrators at a stator, dividing the direction of polarization into a pair of regions, and displacing by half range. CONSTITUTION:The stator 6 of a piezoelectric motor has a vibration displacing amplifying member 1 made of synthetic resin material, a rectangular first piezoelectric vibrator 3 and the second piezoelectric vibrator 4, and a stator base 2. A forcible excitation drive frequency determined by the stator 6 is oscillated by an oscillator 7, one is input directly to an amplifier 8, and the other is input through a phase shifter 9 to an amplifier 10, the first and second piezoelectric vibrators 3, 4 are driven to generate standing wave at the member 1. An elastic unit 15 and the slider 14 of an acoustic member 16 coupled with the unit 15 are contacted with the stator 6, and when the stator 6 is driven, a force having lateral component is applied to the vibrator 14 to obtain rotary motion.

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 or the like.

Conventional configurations and their problems 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 they have a high energy density. has been done.

A conventional piezoelectric motor that utilizes these ultrasonic vibrations will be described below with reference to the drawings.

In conventional piezoelectric motors published in Nikkei Mechanical (57, 2, 28), etc., a stator is constructed by bonding a thin piezoelectric element ring to the surface of a thick metal ring or the like. This piezoelectric motor uses Rayleigh waves, also called surface acoustic waves. This wave is a wave that propagates near the surface of the material, and the wave has both longitudinal and transverse wave components.
Using the same principle as a phase motor, when a phase-shifted alternating current signal is applied, the piezoelectric body expands and contracts in the circumferential direction, and a surface wave is generated in the stator. Figure 1 is an enlarged depiction of the contact situation between the stator and a moving object in contact with the stator surface of a conventional piezoelectric motor, which is well-known as the elliptical motion of particles accompanying surface waves (for example, Nobuo Mikoshiba's "Sonic Waves"). (Refer to “Physical Properties” published by Sanseidosha in 1971). Focusing on one point A on the surface of the elastic body, point A is drawing a locus on an ellipse with a major axis 2W and a minor axis 2u. At the vertex where the elastic body contacts the moving body, point A is X
It has a velocity of V-2πfu in the negative direction of the axis. As a result,
The moving body is driven by the frictional force with the elastic body at a speed ■ in the direction opposite to the propagation of the wave. By drawing an elliptical locus as a thrust on the surface of an elastic body, a conventional piezoelectric motor applies rotational force to a moving body (rotor) in contact with the piezoelectric motor. Piezoelectric motors that utilize surface waves have the same principle as two-phase and three-phase motors, and the direction of rotation can be easily switched using a phase-shifted power source.

However, the above configuration has the following problems.

(1) The stress required to obtain the vibration mode that is the driving principle is:
The maximum value is shown on the stator surface. In a stator with three thicknesses, the normal stress is about 2000 to 9/mjr, and the required electric power is about 100 to 1000 times the normal theoretical value for a bimorph.

(2) Since the neutral surface of the vibration is inside the elastic body such as the metal that constitutes the stator, the piezoelectric material used as an electro-mechanical transducer does not provide efficient node drive, but rather produces inefficient drive. Even if it is limited to the piezoelectric body that is driven by the abdomen and serves as the driving source, more than 5/8 of the total energy is ineffective energy according to this driving principle.

(3) In addition, in order to extract thrust from a minute amplitude of approximately 0.25 μm or less, the moving body is in uniform contact with the peaks and valleys of the stator, which have different amplitudes and different speeds and directions. Therefore, the speed of the moving body is low, unlike the integral value. In order to obtain practical rotation speed and torque, it is necessary to
It requires about 00 times more power.

It had the following problems.

Purpose of the Invention The purpose of the present invention is to focus on highly efficient spatial waves or bulk waves excited by piezoelectric ceramic vibrators, to use this as a direct driving force, and to use a vibration displacement amplifying member to create an extremely efficient and practical device. The purpose of this invention is to provide a piezoelectric motor.

Structure of the Invention According to the present invention, 4 piezoelectric elements 1-' and 29') piezoelectric vibration; a vibrator containing dirt and an acoustic material, which are stacked in the thickness direction; and an integrated structure with the vibrator. It includes a stator having a vibration displacement amplifying member, and a slider that is overlapped in the thickness direction and makes surface contact with the stator. Both piezoelectric vibrators have thickness direction polarization consisting of one or more pairs of divided regions divided in the slider movement direction or the longitudinal direction of the rectangular plate, and these polarizations have opposite directions in adjacent regions. It is. Both piezoelectric vibrators are arranged so that the vicinity of the boundary of each polarization region on one side is located near the center of each polarization region on the other side. When the piezoelectric vibrators configured as described above are driven with voltages of predetermined forced excitation frequencies that are out of phase with each other, the combined vibration of the stator caused by both piezoelectric vibrators is caused by the vibration displacement amplifying member material and the piezoelectric vibrator. Alternatively, the displacement increases with the ratio of the Young's modulus to the stator base, and the maximum amplitude position moves in a certain direction over time, and the slider in contact with the apex receives a driving force in that direction.

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

The stator has a structure as shown in FIGS. 2a and 2b, for example. The stator is composed of a vibration displacement amplifying unit 1 made of a synthetic resin material such as ABS or nylon, a rectangular first piezoelectric vibrator 3, a second piezoelectric sensor 4, and a stator base body 2. For example, six electrodes 3a are provided on the surface of the first piezoelectric vibrator 30, which are divided into regions every several millimeters.

This electrode 3a is formed on the surface of the first piezoelectric vibrator 3 by a method such as printing, vapor deposition, or plating using a conductive material such as 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 3 configured as described above differ from each other in the thickness direction. As a result, as shown in FIGS. 2a and 2b, three sets of six-pole forced excitation vibrators each consisting of regions having alternately positive or negative polarity are constructed. The electrode 3a does not need to be divided after polarization,
Connected so that voltage can be applied all at once. The rectangular second piezoelectric vibrator 4 also has the same structure as the first piezoelectric vibrator 3, and has six poles having alternately positive polarity or negative polarity.

Three sets of forced excitation vibrators are configured.

The minimum amplitude position of the first piezoelectric vibrator 3 or the second piezoelectric vibrator 4 is near the boundary between adjacent electrodes, and the maximum amplitude position is near the center of each electrode. Then, both piezoelectric vibrators 3°4 have a second piezoelectric vibrator 4 located near the center of the electrode, which is the maximum amplitude position of the first piezoelectric vibrator 3.
The minimum amplitude positions of the electrodes are overlapped so that the boundaries between adjacent electrodes are located.

The first piezoelectric vibrator 3 and the second piezoelectric vibrator 4 configured as described above are mounted on a stator base 2 having a stone or equivalent thickness or about 10 times the thickness of the piezoelectric vibrator. The stator base 2 is formed using an acoustic acoustic material 1 made of aluminum, brass, iron, stainless steel/hardened steel, ceramic material, glass material, or a composite material made of these materials. . Further, the stator base 2
One end is shaped into a horn shape that changes exponentially, as shown in FIG. As shown in FIG. 2, it is in contact with the vibration displacement amplifying part 1 at an arbitrary inclination 5 to form an integral structure.

The structure constructed as described above is used as the stator 6 shown in FIG. As shown in FIG. 3, the output signal oscillated by the oscillator 7 at the forced excitation drive frequency determined by the stator 6 is branched, one is directly sent to the amplifier 8, and the other is sent to the amplifier 10 via the phase shifter 9. Enter. The phase shifter 9 inputs and amplifies the signal to the ±amplifier 8 used for forward rotation or reverse rotation as will be described later, and sends the amplified signal to the lead wire 11.
The voltage is applied to the first piezoelectric vibrator 3 by 12. As a result, forced excitation waves of three wavelengths corresponding to six poles and three sets of forced excitation vibrators are generated in the stator 6, with each pair of regions having polarization polarity of the first piezoelectric vibrator 30 being one wavelength. This wave propagates through the main part formed into a horn shape, via an arbitrary slope 5, and generates a standing wave in the vibration displacement amplifying member 1.

The second piezoelectric vibrator 4 also connects the output of the amplifier 10 to the lead wire 12.
It is similarly driven by applying it through 13.

A standing wave is generated in the vibration displacement amplifying member 1 in the same manner.

FIG. 4 shows the results of measuring the strain in the vertical direction as a change in the longitudinal direction of the piezoelectric vibrators when an electric signal is applied to the first piezoelectric vibrator 3 and the second piezoelectric vibrator 4.

The measurement was performed by irradiating the measurement location with a He-Ne gas laser beam and using an interference method of incident light and reflected light. FIG. 4a shows the measurement results when the first piezoelectric vibrator 3 was started to be driven by applying signals to the lead wires 11 and 12. For example 5
When 0V was applied, the amplitude was about ±0.871m. The minimum amplitude position is located near the boundary between adjacent electrodes, and the maximum amplitude position is located near the center of each electrode. FIG. 4 shows the results of longitudinal strain measured when the second piezoelectric vibrator 4 was driven in the same manner. For example 5
When 0V was applied, the amplitude was approximately 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, FIG. 4C shows the measurement results when the first piezoelectric vibrator 3 and the second piezoelectric vibrator 4 were simultaneously driven using the configuration shown in FIGS. 2 and 3. 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. The maximum amplitude of strain in the sizing direction is approximately 1.3 times larger. Here, as described above, the second piezoelectric vibrator 4 has an angle of ±10° to ±170° with respect to the first piezoelectric vibrator.
Unless it is driven with a zero phase shift, the maximum amplitude position of the composite wave C moves in a constant direction with time.

At this time, a similar composite wave C is obtained in the vibration displacement amplification member 1. Similarly, the maximum amplitude position of the composite wave C moves in a constant direction with time.

The piezoelectric vibrator and stator base 2 have a Young's modulus of 720.
The vibration displacement amplifying member 1 is made of a material with a relatively large Young's modulus of 0-216ooKg/m,j, whereas the vibration displacement amplifying member 1 has a Young's modulus of 1Q○~2o○○Kq/ma.
It is made of a material with a relatively small Young's modulus. From the above, it can be seen that the Young's modulus of each of the above-mentioned substances differs by a factor of 10 to 100 or more.

The Young's modulus of a material is expressed as the quotient of the stress generated and the amount of mechanical strain output as shown in the following equation. That is, assuming Young's modulus: E, strain: s, and Okani T, the overall ring ratio of the two examples of stator substrates: E1. ．． Distortion: S1. Okani T1 is El-T1/51S1-T1/51S1-8
1°E1. Next, Young's modulus of vibration displacement amplification member 1:
E2° distortion: 82. Similarly, for Okani T2, E2=T2/52S2=T2/E2T2;s2·E2. Since T-T, distortion: 82 is S on the E2 side.
2-E1/E2・Sl. In other words, when the excitation of mechanical strain caused by a material with a large Young's modulus is propagated into a material with a relatively small Young's modulus, if the stress in the system is kept constant, the amount of mechanical strain increases in proportion to the Young's modulus, so the vibration displacement The amount of mechanical strain S2 of the amplifying member 1 is 52=E1/E2・S
The displacement is amplified by the ratio of l to Young's modulus, and as a result, the amount of displacement increases. When the stator 2 was made of aluminum and the vibration displacement amplification member 1 was made of ABS resin, the vibration displacement was approximately 5 to 5 times the displacement of the stator 2 in the vibration displacement amplification member 1. An increase of about 10 degrees was obtained.

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

The slider 14 is composed of an elastic body 15 made of a friction material, an elastic material, or the like, 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 repeats positional movement by the lateral component using the drive frequency determined by the stator 6, and as a result, it is possible to obtain rotational motion in the range of several to several thousand revolutions per minute. . The generated torque varies depending on the acoustic material that constitutes the stator, the friction coefficient and contact area of the slider that makes surface contact with the stator, the magnitude of the load, etc. Number 10μ
For those with chrome plating etc. consisting of
It was possible to obtain torques in the range of several thousand qf-saws from α.

For the direction of slight rotation, +100 relative to the reference signal.
For example, if the rotation obtained when the second piezoelectric vibrator is driven by applying a phase-shifted signal in the range of 1700 to +1700 is a positive rotation, then the rotation will be 1CP to -1 with respect to the reference signal.
The direction of rotation obtained when driving by simultaneously applying signals with phase shifts in the range of 1700 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.

Further, according to the configurations shown in FIGS. 2 and 3, the heavy load of distorting metal with a large Young's modulus in the conventional system is eliminated. In the conventional method, it is considered possible to increase the minor axis 2u of the elliptical locus by further increasing the thickness of the metals to be bonded together. The size of the dynamic range of the resonance characteristic represents the level of strong excitation, and for each increase in the metal thickness, the resonance characteristic increases by 15d.
Since it is attenuated by about B, driving with large electric power is required to actually increase the short axis 2u which becomes the thrust. 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.

Since all the mechanical load is applied to the vibration displacement amplifying member 1, there is no mechanical load on the stator base 2 and both piezoelectric vibrators, and the drive conditions do not change depending on the magnitude of the load, resulting in extremely efficient operation. A good drive is now possible.

FIG. 6 shows a stator with another configuration. In this configuration, between the first piezoelectric vibrators 17, 18゜19, 20 and the second piezoelectric vibrators 21, 22, 23゜24, there is a fixed piece having an old or equivalent thickness or about 10 times the thickness of the piezoelectric vibrators. A child base body 25 is mounted, and there is, for example, A
A vibration displacement amplifying member 26 made of synthetic resin material such as BS or nylon, with 26', 27. 27' on the back
, 28, 28', 29. on the back. The basic configuration is that 29' is attached to the back side. The materials and structures of each member are the same as those in the embodiment shown in FIG. First piezoelectric vibrator 17,1
8, 19.20 and second piezoelectric vibrator 21.22, 23.
The relative arrangement of the polarizations 24 is exactly the same as that of the stator 6 shown in FIGS. 2 and 3.

The reason why the two piezoelectric vibrators are divided into four groups is to achieve a drive with less loss by obtaining strong vibrations. Further, as the drive circuit for this stator, the exact same configuration as the circuit shown in FIG. 3 can be used, so a detailed explanation will be omitted. The slider is a vibration displacement amplifying member 26, 2.7, 28.29 or the like.

26', 27', 2! Since the rotation is guided by contact with 8/ and 2 g/, there is no mechanical load on both piezoelectric vibrators, and the drive conditions do not change depending on the size of the load, making extremely efficient drive possible. It became.

FIG. 6 shows a stator in yet another embodiment. In this embodiment, on the upper part of the annular first piezoelectric vibrator 3o and the annular second piezoelectric vibrator 31, an annular fixing device having a thickness equal to or about 10 times the Tδ of the piezoelectric vibrator is fixed. The basic configuration is that a child base 32 and a vibration displacement amplifying member 33 made of synthetic resin such as ABS or nylon are attached. The materials and structures of each member are the same as those in the embodiment shown in FIG. The relative arrangement of polarization of the first piezoelectric vibrator 30 and the second piezoelectric vibrator 31 is shown in FIGS.
It is exactly the same as the stator 6 having the configuration shown in the figure, and is as illustrated in FIG. 6. Further, as the drive circuit for this stator, the same structure as the circuit shown in FIG. 3 can be used, so a detailed explanation will be omitted.

When the vibration displacement amplifying member made of synthetic resin material such as ABS or nylon, or elastic rubber shown in Fig. 2, Fig. 3, Fig. 5, Fig. 6, and Fig. 8 is integrated with a piezoelectric vibrator. Figure 7 shows the admittance-frequency characteristics of . a has a material Young's modulus of 20000Kq/
Characteristics when using a material with a material with a Young's modulus of approximately 10,000 to 2 o○○ OKq/-
d is the characteristic when using a material with a Young's modulus of about 10 to 1000 Kq/ma, and e is the characteristic when using a material with a Young's modulus of about 1 Kq/vra or less. The characteristics of each material when integrated with a piezoelectric vibrator are shown. 7th
From figures d and e, the Young's modulus of the material is approximately 1oooKq/ma
It can be seen that by using a material of a certain level or less as the vibration displacement amplifying member, no change is observed in the frequency characteristic of admittance, which is generally called resonance characteristic. This includes the piezoelectric material and, for example, aluminum, brass,
The Young's modulus of a stator made of acoustic materials such as iron, stainless steel, hardened steel, ceramic materials, glass materials, or composite materials made of these materials, and the material used for the vibration displacement amplifying member. This is because the Young's modulus of the drive body differs by a factor of 10 to 100 or more, and as a result, as shown in FIG. 7, there is no vibrational component of the driving body. Therefore, by using the vibration displacement amplifying member of the present invention, it has become possible to obtain only the amplification effect of the excited vibration displacement.

FIG. 8 shows a stator in yet another embodiment. In this embodiment, the annular first piezoelectric vibrator 34 and the annular second piezoelectric vibrator 35 are connected to a thin plate 36 made of a conductive material.
They are facing each other across.

The basic configuration is that an annular vibration displacement amplifying member 37 having a thickness of 6 to 10 times the thickness of the piezoelectric vibrator or about 10 times that of the piezoelectric vibrator is mounted on top of both piezoelectric vibrators.

The materials and structures of each member are the same as those in the embodiment shown in FIG. The relative arrangement of the polarizations of the first piezoelectric vibrator 34 and the second piezoelectric vibrator 36 constitutes a forced excitation vibrator consisting of regions having alternately positive polarity or negative polarity, as shown in FIG. In addition, the polarization directions of the first piezoelectric vibrator 34 and the second piezoelectric vibrator 35 are arranged to be the same at each position, and the outer electrodes are configured as two sets and short-circuited, and this and the center electrode are connected to an electrical terminal. By doing so, a parallel bimorph is constructed. The electrode located at the center shown in FIG. 8 has a circumferential length that is 0.5 to 1.5 times longer than the length of the other electrodes located in the circumferential direction.
It is formed to be 5 times as large. By sandwiching the two electrodes and connecting seven electrodes each having a positive polarity or a negative polarity on the left and right sides,
Two sets of electrodes, which together form one set, can be formed.

These two sets of electrodes are drive electrodes with a positional phase shift of 90°, that is, a reference signal and a ±10° relative to the reference signal.
It is arranged on an electrode for applying an electrical signal whose phase is shifted in the range of 0 to ±1700.

Moreover, the above-mentioned pair of piezoelectric vibrators doubles the mechanical displacement at a constant voltage, and is extremely advantageous during actual driving. Further, as the drive circuit for this stator, the exact same configuration as the circuit shown in FIG. 3 can be used, so a detailed explanation will be omitted.

Using the drive circuit shown in Fig. 3, the stators shown in Figs. 5 to 8 are
When driven at the forced excitation frequency determined by each stator, the vertical strain has exactly the same distribution as shown in Figure 4, and the peak values are approximately 5 to 10 on the vibration displacement amplifying member. Obtained an increase in degrees. In addition, when these stators were mounted and driven using a configuration similar to that of the piezoelectric motor made by the misfired Akira shown in Fig. 3, the results were as follows:
It was possible to obtain rotational motion in the range of several revolutions to several thousand revolutions per minute. The generated torque varies depending on the acoustic material that constitutes the stator, the friction coefficient and contact area of the slider etc. that makes surface contact with the stator, or the magnitude of the load received, but it varies by several tens of cm (if"cm). From several thousand qf-
We were able to obtain torque within the α range.

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, and is approximately 1o○○r.
Torque within several thousand qf -α can be generated at low to medium speed rotation within pm.

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, 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. Since the structure is very simple, the price is low.

Effects of the Invention As described above, the piezoelectric motor according to the present invention includes two piezoelectric vibrators in the stator, and both piezoelectric vibrators have at least a pair of piezoelectric vibrators whose polarization directions are alternately reversed in the slider movement direction. The stator is divided into two regions, and the sliders are in contact with the stator via a vibration displacement amplifying member. By applying a voltage of a predetermined frequency, a vibration wave moving in a certain direction is generated in the stator, and this vibration displacement is amplified by the vibration displacement amplifying member. The mover is driven. Therefore, a highly efficient motor can be constructed with an extremely simple structure, and a small and responsive motor can be realized.

[Brief explanation of the drawing]

Figure 1 is a perspective view showing the operation of a conventional piezoelectric motor;
Figure a is a plan view of a stator of a piezoelectric motor according to an embodiment of the present invention, Figure 2 is a front view of the stator, and Figure 3 is an overview of a piezoelectric motor using the same stator and its first drive. FIG. 4 is a diagram showing the strain distribution of the piezoelectric motor stator of FIG. 3 during driving, and FIGS. 5 d and b show fixation of the piezoelectric motor in other embodiments according to the present invention, respectively. 6 and 8 are exploded perspective views of a stator of a piezoelectric motor according to another embodiment of the present invention, and FIG. 7 shows a vibration displacement amplifying member integrated with the stator. FIG. 3 is a characteristic diagram showing frequency characteristics of admittance. 3.4, 7, 18, 19, 20.2'j, 22°23
．． 24...Piezoelectric vibrator 1. ? , 25... stator base, 1 , 26 , 26', 27, 27',
28.28'. 29.29'... Vibration displacement amplification member, 3a...
... Electrode, 6 ... Stator, 14 ... Slider, 7 ... Oscillator, 8.10 ... Amplifier, 9
...Phase shifter. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Fig. 42 (cL) Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7
the law of nature

Claims (5)

[Claims] (1) In a piezoelectric motor that generates a driving force by the vibration of a stator configured using a piezoelectric vibrator and drives a slider that makes surface contact with the stator, the stator is made of materials with different Young's moduli. and a vibration displacement amplifying member, the ratio of the Seng rate inherent in the former material to the latter material is about 10 or more, and the piezoelectric vibrator generates vibration in the base material and absorbs the vibration. is transmitted to the vibration displacement amplifying member, and the slider is driven by contact with the vibration displacement amplifying member. (2) The stator includes a vibrator component including a piezoelectric body and a base, and a vibration displacement amplifying member, is in contact with the slider, and is coupled to the vibrator component via a mechanical vibration introducing main part. 2. The piezoelectric motor according to claim 1, wherein the piezoelectric motor comprises a rotating or traveling body component. (3) A piezoelectric motor according to claim 1, characterized in that piezoelectrics are mounted at a plurality of locations on the stator base in a distributed manner, and a vibration displacement amplifying member is disposed between the piezoelectrics. (4) The piezoelectric motor according to claim 1, wherein a drive body including a piezoelectric vibrator and a stator base is stacked in multiple layers with a vibration displacement amplification member to constitute a stator. (5) The driving body including the piezoelectric vibrator is composed of a plurality of piezoelectric bodies, and the plurality of piezoelectric bodies have a parallel bimorph configuration, and have a vibration displacement amplifying member on the slider contact surface. A piezoelectric motor as claimed in claim 1.