JPH0710193B2 - Ultrasonic motor - Google Patents

Description

The present invention relates to an ultrasonic motor having a piezoelectric element that expands and contracts as a drive source.

[Conventional technology]

FIG. 3 shows an example of a conventional ultrasonic motor using a stretchable piezoelectric element.

FIG. 3 is a perspective view showing an example of a conventional ultrasonic motor, in which a vibration plate 11 is fixed to an upper portion of a ring-shaped piezoelectric body 12 and these are attached to a case 14. The disc surface of the vibrating plate 11 is opposed to the disc surface of the rotating disc 10 so that the disc surface is brought into close contact, and the disc spring 9 is pressed from the side face of the rotating disc 10 so as to firmly fix it. Are fixed with a presser plate 8 and are integrally attached to a shaft 13 so as to be rotatable. As shown in FIG. 4, the structure of the piezoelectric body 12 is divided into eight expanding and contracting piezoelectric elements on a circular ring, and the portion in the figure has a function of being polarized so that it is extended by applying a voltage and the portion is contracted. The elements of this are alternately arranged and connected to each other to form section A, and this block is divided into eight elements which are alternately connected to this block with a 3/4 wavelength (on) interval. And the electric wire for division A so that each element is energized.
The ultrasonic motor is integrally constructed by connecting 15 and the wire 15 'for B division. 15 ″ is a phase converter.

When a pulsed DC power supply is supplied from the electric wire 15 of section A of the ultrasonic motor configured as described above, since the expanding and contracting elements are connected, unevenness is displaced in the thickness direction and a standing wave is generated. . This standing wave propagates throughout the ring.
At the same time as supplying power to section A, the same frequency is applied to section B as well.
When a voltage is applied to the power source of the section with a phase delay of 90 degrees, uneven waves are generated here as well, and because the wave overlaps with the wave of section A and the phase is shifted by 90 °, the standing wave becomes a traveling wave. On the disk surface of the vibrating plate 11 integrally fixed to the piezoelectric body 12, the wave motion makes an elliptic motion. The rotating disk 10 pressed against this surface naturally rotates due to the frictional force. For example, if the rotating disk 10 is rotated to the right at this time (the power supply pulse of the section B is delayed by 90 degrees), the phase may be advanced by 90 degrees with respect to the power supply pulse of the section A to rotate the disk 10 to the left. That is, in order to freely rotate left and right, it is necessary to supply power to the two systems at the same frequency and with a phase delay and lead of 90 degrees.

[Problems to be Solved by the Invention]

However, in the above-mentioned configuration, in order to obtain left and right freely rotating directions, two systems require a power source of the same frequency and a phase difference of 90 degrees. On the other hand, the frequency in the ultrasonic range is at least 20.
At a frequency of KHz, a practical ultrasonic motor has a high frequency of about 40 KHz.

Assuming that a phase difference of 90 degrees is accurately applied to this high frequency, as an example, at a drive frequency of 40 KHz (1/40 KHz)
× (90 ° / 360 °) = 6.25 × 10 ^{-6 It} is necessary to supply power with a pulse difference of 10 ^-6 seconds, but this accuracy cannot be secured, and efficient rotation drive and stable rotation direction cannot be obtained. . Further, this power supply device becomes extremely expensive, which poses a serious problem in putting the ultrasonic motor into practical use.

The present invention has been made in view of the above points, and an object of the present invention is to propose an ultrasonic motor that is highly efficient, stable in rotation, and economical.

[Means for Solving the Problems]

In other words, the means for achieving the object is that two expanding and contracting piezoelectric elements are paired and arranged in parallel, independent inertial members are arranged at one end, and two piezoelectric elements are linked at the other end. As shown in Fig.2, one driving body is arranged and these are integrated by bolts etc. to obtain a driving unit. In an ultrasonic motor using this as a driving source, the surplus wave in the transverse wave is driven on the upper part of the inertial body. Sometimes, a cutout is provided in the shape of a letter to form a reflection path that does not interfere with it, and its upper surface is aligned, and the driving body is formed in a substantially M shape. Is inclined at 45 degrees, and a groove is provided in the upper part of the center, so that both ends of the M-shape and the bases of the center are in a straight line so that the excess wave does not hinder driving and at the same time enhances the resonance effect of the longitudinal wave. A machine that allows the inertial body to elastically press downward at all times. Assemble the piezoelectric element, the inertial body, and the driving body so as to have a high-performance output, and assemble the driving unit by pushing the tip of the driving body by applying elastic force to the rotating drum. A shaft, a bearing, and the like are pivotally supported to integrally form these members, and by supplying power to either one of a pair of piezoelectric elements, the forward and reverse rotations of the rotational vibration are obtained.

[Work]

 The operation will be described in combination with the embodiment described below.

〔Example〕

FIG. 1 is a front view of a main part of an ultrasonic motor showing an embodiment of the present invention, and FIG. 2 is a side view thereof. In FIG. 1 and FIG. 2, two expanding and contracting piezoelectric elements 1-a and 1-a are arranged in a pair in the left-right direction, and independent inertial bodies 1-
c is arranged, and one driving body 1-b is arranged at the other end so as to link two piezoelectric elements 1-a and 1-a to obtain a driving unit 1 integrally constructed by bolts or the like. Driver 1-b is approximately M
It is formed in a letter shape and the angle of both inclined surfaces 1-b ₁ is 45
And a groove is provided, and the bottom surfaces of the both sides and the center of the three members are aligned in a straight line to obtain a required shape and dimension. Further, the upper portion of the inertial body 1-c has a surplus wave during transverse wave motion. Forming the inclined surface 1-c ₁ by providing a "L" -shaped notch of a required dimension that becomes a reflection path that does not obstruct when driving,
And without the upper surface in alignment, further the width of the upper surface 1-c ₃ of the outer portion, the bottom surface 1-b ₃ of the outer portion of the drive member 1-b
And have almost the same width, and the width 1 of the upper surface of the central portion of the inertial body 1-c
-C ₂ and the width 1-b ₂ of the bottom surface of the central portion of the driving body 1-b are set to have substantially the same width to form the driving body 1-b and the inertia body 1-c, respectively, and these and the piezoelectric element 1-a. The three members are fastened with bolts 7.

Further, arms are formed in an L-shape 1-c ₄ by both sides of the inertial body 1-c so as to elastically press the inertial body 1-c downward.
A spring 5 is provided at the tip of each of them, and a guide rod 6 is arranged so that the inertial body 1-c can freely move in the vertical direction and is fixedly held in the other directions.

The tip of the driving body 1-b is applied to the rotating drum 2 by the action of the spring 5 so that the driving drum 1-b is elastically pressed and pushed.
Is integrally supported by rotatingly supporting the shaft 3 and the bearing 4.

Next, the operation will be described.

First, the case of counterclockwise rotation will be described.

Of the left and right piezoelectric elements 1-a, 1-a arranged in pairs, only the right side is supplied with the pulsed high frequency power source E through the electric wire 1-d, and the right side piezoelectric element 1-a extends vertically. Displace. This displacement is vibrated and propagated to the driving body 1-b, and propagates downward as Y, Y ′, Y ″ longitudinal waves.

This wave propagation is due to the 45-degree inclined surface 1- on the right side of the driver 1-b.
When the longitudinal wave Y included in b ₁ hits the surface cut off at 45 degrees,
When the acoustic impedance of the medium in contact with this surface, that is, the product of the density ρ and the wave propagation velocity C, ρ · C is extremely different, for example, since aluminum was used for the driver 1-b in the experiment, the density ρ = 2.7 g / cm ³ , wave velocity C = approx. 4
In contrast to 000m / s, air is ρ = 1.3 × 10 ^-3 g / cm ³ , C = 340m / s, and this ρ ・ C is very different, so the existence of the medium is ignored, and if the surface is smooth, it is inclined. Almost 100% on surface 1-b ₁
Is reflected. The angle of reflection in this case is treated exactly the same as that of light, and is propagated in the horizontal direction at a right angle to the incident angle on the inclined surface 1-b _{1 of} 45 degrees, and becomes Yokohama Yx and proceeds to the left. Then, the longitudinal wave Y ′ traveling on the front end surface 1-b ₂ of the driving body 1-b and the wave intersect at a right angle, and the wave is combined and the wave has an elliptic motion with a vector velocity (Q in FIG. 1). And the tip surface 1-
At the b ₂ site, a slight displacement from right to left occurs in the pulse cycle of the power supply. Since the rotary drum 2 is pressed against the tip surface 1-b ₂ , the rotary drum 2 moves from the right to the left due to the frictional force. That is, it rotates counterclockwise.

The longitudinal wave Y ″ on the right side of the longitudinal wave travels downward as it is, is reflected by the bottom surface 1-b ₃ of the driving body 1-b, and travels upward. Further, this wave is generated by the inertial body 1-c. Opposite to the upper surface 1-c ₃ , the waves travel downward, that is, the longitudinal waves Y ′ and Y ″ from the piezoelectric element 1-a are the upper surfaces 1-c ₂ and 1-c ₃ of the inertial body 1-c and the driver 1. -B propagates repeatedly at a natural frequency f depending on the distance L of the opposing surfaces of the bottom surfaces 1-b ₂ and 1-b ₃ of -b. Assuming that the propagation velocity of the longitudinal wave is C ₀ , this natural frequency f is f = (C ₀ / λ) = C ₀ / 2L ………… (1) λ: wavelength, and this natural frequency f The driving unit 1 resonates by supplying the same number of pulse power supplies to the piezoelectric element 1-a. As a result, the inflow value of the current of the piezoelectric element 1-a becomes 3 to 15 times larger due to the resonance effect, and the inflow energy is converted from electricity to mechanical kinetic energy. Correspondingly, the strain and force of the piezoelectric element 1-a increase. Generally piezoelectric element 1
-A has a low thermal property, and the piezoelectric property is impaired at about 150 ° C. When the volume is determined, the maximum current value is determined, and accordingly the strain and force are also determined. Moreover, this value is extremely low. For example, if strain is not resonated, the value is about 1 μm or less, which is an obstacle to practical use as an actuator.

The formation of the L dimension of the parallel planes in the drive unit 1 of the present invention (the distance between the 1-b ₃ plane and the 1-c ₃ plane in the figure) is extremely useful for obtaining the above resonance effect. If driver 1-b 45
When the 1-b ₁ surface is extended and the 1-b ₃ parallel surface is absent, longitudinal wave motion
Of the Y, Y ′, Y ″, the part of L dimension that contributes to resonance is 1-c
_Since only the longitudinal wave Y'of the ₂ to 1-b ₂ plane participates in the vibration propagation of the fundamental wave, the resonance effect on the piezoelectric element 1-a becomes small, and as a result, a large output cormorant cannot be obtained. Of course, if the parallel surface 1-b ₃ is too large, the amount of the transverse wave Yx becomes small, and the synthetic elliptic wave Q cannot be obtained appropriately. Therefore, it is necessary to design with good balance.

The wave Yx that has become the transverse wave is not vectorized completely (elliptic wave Q) due to time difference and other freedom, and a surplus wave Z is generated. This propagates to the 45-degree inclined surface 1-b ₁ on the left side, is reflected, and propagates upward. Further, it passes through the left piezoelectric element 1-a, and the inclined surface 1-c _{1 of the} inertial body 1-c is formed in a "L" shape.
, And is reflected here, and is reflected on the left side surface of the drive unit 1 .

Further, the surplus wave ZHF is reflected by the surface of the groove W in the center and travels, and is reflected by the 45-degree surface 1-b _{1 of} the left driver 1-b. That is, the surplus wave Z takes a path from Z _{1 to} Z ₅ , and the part and the traveling direction of the wave Z take a path without interfering with the vectorized elliptical wave that directly contributes to the driving force of the central portion, and drive. Does not hinder. The path of the surplus wave of the elliptic wave Q vectorized at the upper portion is different from the path of Z _{1 to} Z ₅ of the surplus wave Z. That is, the path from Z ₁ ′ to Z ₄ ′ is the same, but after Z ₅ ′, instead of the left reflecting surface 1-b ₁ of the driving body 1-b, the light is reflected by the M-shaped left side surface, and so on. And then Z ₅ ′ ~
Wave propagation up to Zi '.

As a result, in combination with the above, the surplus waves Z and Z'are processed without obstructing the elliptic wave Q that contributes to driving in all regions.

Therefore, the formation of the both sides of the M-letter is performed for the two purposes of improving the resonance effect of the longitudinal wave Y ″ and preventing the driving inhibition of the surplus wave Z ′. In the case where there is no “” -shaped inclined surface 1-c ₁ and the surface is made flush, the surplus wave Z ₁ is reflected by this surface and changes its direction to change to the driving body 1-b.
It enters the 45-degree surface 1-b ₁ on the left side of, and is reflected here and propagates in waves from left to right.

Thus, this wave is an elliptic wave Q that contributes to rotation during driving.
The transverse wave Yx that synthesizes is acted in the direction completely opposite to that of the transverse wave Yx, so that the drive is extremely hindered and the performance is deteriorated. That is, the gist of the usefulness of the present invention is also here.

Next, when rotating to the right, the pulsed high frequency power source E may be supplied to the piezoelectric element 1-a on the left side and the right side may be turned off. That is, an arbitrary left / right rotation can be easily and surely obtained by switching energization to either the right side or the left side of the pair of piezoelectric elements 1-a.

Now, even if a plurality of drive units 1 are arranged on the rotary drum 2 and the friction thereof is not uniform, and the drive friction surface 1-b ₂ also fluctuates in the radial direction due to the eccentricity of the rotary drum 2, the drive unit 1 Since 1 independently follows and is elastically applied by the spring 5 so as to be always pressed against the rotary drum 2, even a slight distortion of the wave efficiently leads to the driving force, and even when used for a long time, The driving performance is stable and long life is obtained.

〔The invention's effect〕

As described above, according to the present invention, conventionally, in order to obtain an arbitrary left / right rotation and stable rotation, for example, with respect to a drive frequency of 40 KHz, a phase difference of 90 degrees at the same frequency of two systems, that is, 1/40 KHz) × (90 ° / 360 °) = 6.25 × 10 ⁻⁶ sec. It was necessary to accurately supply a power source, but in the present invention, two piezoelectric elements 1-a and 1-a are required. Since it suffices to supply power to one side and turn off the other side, the operation is simple and a stable left and right rotation can be obtained. Furthermore, compared to the same type of embodiment,
Due to the "L" -shaped depression and the M-shaped formation of the inertial body and the driving body, what was conventionally hindered by the surplus wave Z during driving, for example, is guided to a harmless wave path, and longitudinal waves Y ', Y The driving performance has been dramatically improved by increasing the resonance effect of the ″. In terms of economic efficiency, only one system is required for two power sources, and a minimum time of 6.25 × 10 ⁻⁶ seconds is achieved. Since the phase difference is not required, the power supply device is extremely inexpensive, and the ultrasonic motor of the present invention is useful in that it has great technical and economic advantages.

[Brief description of drawings]

1 is a main front view showing an embodiment of the present invention, FIG. 2 is a side view thereof, FIG. 3 is a perspective view showing an example of the prior art, and FIG. 4 is a structure of the piezoelectric body in FIG. It is explanatory drawing which shows each power supply relationship. 1 ... Drive unit, 1-a ... Piezoelectric element, 1-b ...
Driver, 1-c ... Inertia, 1-d ... Electric wire, 2 ... Rotating drum, 3 ... Shaft, 4 ... Bearing, 5 ... Spring,
6 ... guide rod, 7 ... bolt, 8 ... presser foot, 9 ...
Disc springs, 10 ... rotating discs, 11 ... diaphragms, 12 ... piezoelectric bodies, 13 ... shafts, 14 ... cases, 15,15 '... electric wires.

Claims (1)

[Claims] 1. A pair of expanding and contracting piezoelectric elements are arranged in parallel, one independent body is provided at one end of the piezoelectric element, and the other piezoelectric element is connected to the other end of the piezoelectric element. In an ultrasonic motor using a body arranged and integrated with bolts or the like to obtain a drive unit, and using this as a drive source, surplus wave during transverse wave does not hinder during driving. A L-shaped notch with a required size to be a reflection path is provided, and the upper surface thereof is aligned, and the driving body is formed in a substantially M shape, and both M-shaped inclined surfaces are inclined at 45 degrees. In addition, a groove is provided at the upper center, and both ends of the M-shape and the bases of the center are formed in a straight line so as to enhance the resonance effect of the longitudinal wave without disturbing the excessive wave at the time of driving. It has a function that the body elastically presses downward all the time. The piezoelectric element, the inertial body, and the driving body are integrated to assemble a driving unit capable of obtaining a high-performance output, and the tip of the driving body is elastically applied to the rotating drum so as to push the rotating drum. An ultrasonic motor characterized by being configured such that they are integrally supported by means of, for example, and power is supplied to either one of a pair of piezoelectric elements to obtain normal and reverse rotation of rotational vibration.