JP3173902B2 - Ultrasonic linear motor and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic linear motor driven by an electromechanical energy conversion element such as a laminated piezoelectric element, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, an ultrasonic motor has attracted attention as a new motor replacing an electromagnetic motor. This ultrasonic motor has the following advantages over a conventional electromagnetic motor. (1) Low speed and high thrust can be obtained without gears. (2) Large holding force. (3) Long stroke and high resolution. (4) It is quiet. (5) It does not generate electromagnetic noise and is not affected by noise. Here, ultrasonic motors are divided into rotary type and linear type,
As a linear type ultrasonic motor, for example, a paper feed device N using a flat motor using a longitudinal-bending multi-mode vibrator in 1988,
o. A-223 (S63.3)) is known.

As shown in FIG. 13, in a vibrator in such a linear ultrasonic motor, three piezoelectric ceramics 103, 104, 3 are provided between an elastic body 101 made of a stainless steel plate or the like and a support 102 made of silicon rubber or the like. 105 is adhered. Here, the piezoelectric ceramic 104 has a longitudinal vibration mode (Longitudinal-mode: L
2) of piezoelectric ceramics 103 and 105
The sheet is for a bending vibration mode (Bending mode). The vibrator is designed in such a shape that the resonance frequencies of these two modes match, and an alternating voltage (AC) of the resonance frequency is applied to each of the piezoelectric ceramics 103 to 105. If an appropriate phase difference is provided between these alternating voltages, elliptical vibration can be excited in the shaded portions in FIGS. Then, when the paper 107 as the driven body is pressed by the pressure roll 106, the paper 107 can be transported right and left.

[0004]

However, in the above-described conventional ultrasonic linear motor, the piezoelectric ceramics 103 to 1 are provided.
Since the vibration was excited using the piezoelectric lateral effect of No. 05, there was a problem that the efficiency was low. That is, in general, the piezoelectric ceramic has an electro-mechanical coupling coefficient of 60 to 70% due to the piezoelectric longitudinal effect, whereas the piezoelectric transverse effect has a considerably low value of 30 to 40%. Here, the low electro-mechanical coupling coefficient means that the electro-mechanical conversion efficiency is low, and the driving input voltage is also several tens Vrms to 100 Vrm.
A voltage as high as s is required.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and utilizes an ultrasonic linear motor which has high electro-mechanical conversion efficiency and can be driven at a low voltage by utilizing the piezoelectric longitudinal effect of a piezoelectric element. It is intended to provide a manufacturing method thereof.

[0006]

In order to achieve the above object, in an ultrasonic linear motor according to the present invention, an electric-mechanical energy conversion element is used as a drive source, and a longitudinal vibration and a bending vibration are applied to an elastic body. An ultrasonic vibrator that generates and synthesizes these vibrations to generate ultrasonic elliptical vibration, and a driven member that is pressed by a part of the ultrasonic vibrator and moves relatively to the ultrasonic vibrator In the ultrasonic linear motor, the ultrasonic vibrator includes at least two laminated piezoelectric elements as a driving source, a basic elastic body as an elastic body, and a holding member joined to the basic elastic body. An elastic body is provided, and both end portions of each of the stacked piezoelectric elements are joined and held against the holding elastic body.

According to a second aspect of the present invention, there is provided an ultrasonic linear motor according to the first aspect, wherein a surface orthogonal to a nodal line of the elastic wave in the basic elastic body or a surface including a traveling direction of the elastic wave. A piezoelectric element for vibration detection which is entirely polarized in the thickness direction for independently detecting longitudinal vibration and bending vibration of the basic elastic body, or a vibration detection piezoelectric element which is alternately polarized in the thickness direction. The elements are joined.

According to a third aspect of the present invention, there is provided an ultrasonic linear motor according to the first aspect, wherein an ultrasonic vibrator is provided near a portion where the basic elastic body and the driven member come into contact with each other. A piezoelectric element for detection, which is entirely polarized in the thickness direction and detects contact pressure, is joined thereto.

According to a fourth aspect of the present invention, there is provided the method of manufacturing an ultrasonic linear motor according to any one of the first to third aspects, wherein the holding is performed by abutting between the holding elastic bodies of the laminated piezoelectric element. An ultrasonic linear motor is manufactured by fixing the holding elastic body while applying mechanical pressure from both side surfaces of the elastic body.

[0010]

The ultrasonic linear motor of the present invention having the above-described structure operates as follows. That is, in the ultrasonic linear motor according to the first aspect, an alternating voltage having a resonance frequency of the longitudinal vibration of the vibrator is applied to the laminated piezoelectric element. Here, when the phase difference between the alternating voltages applied to the two stacked piezoelectric elements is appropriately determined, each part of the ultrasonic vibrator generates an elliptical vibration. If the driven body is pressed against the part where the elliptical vibration is generated, the driven body is driven linearly. Note that a DC voltage may be applied to the stacked piezoelectric element in a manner superimposed on the alternating voltage. As a result, a compressive force is constantly applied to the laminated piezoelectric element, thereby preventing the piezoelectric element from being broken.

Also, since the ultrasonic motor utilizes the resonance phenomenon of the elastic body, the drive frequency must be tracked when the resonance frequency changes due to a temperature rise. Therefore, in the ultrasonic linear motor according to the second aspect, the longitudinal vibration or the bending vibration of the elastic body is detected by the piezoelectric element having the elastic body bonded to the surface. Since this detection signal is correlated with the amplitude and phase of the vibration, it is fed back to track the drive frequency. In particular, in the present invention, since the longitudinal vibration and the bending vibration can be detected independently, it is possible to track the resonance frequency of either vibration.

Further, in the ultrasonic linear motor according to the third aspect, the contact pressure between the ultrasonic vibrator and the driven member is detected by the detecting piezoelectric element joined near the elastic sliding member. Therefore, a change in the contact pressure when the resonance frequency changes due to a change over time is directly detected. If this signal is detected and fed back, the vibration of the ultrasonic transducer can be controlled. Further, the contact pressure can be made constant when making the ultrasonic linear motor.

Several embodiments of an ultrasonic linear motor according to the present invention will be described below with reference to the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.

[0014]

Embodiment 1 First, Embodiment 1 of the present invention will be described. FIG.
Is a perspective view showing an ultrasonic transducer, and FIG. 2 is a front view. As shown in the figure, this ultrasonic vibrator 10 has three holding elastic bodies 12 fixed on the upper surface of a basic elastic body 11, and a laminated piezoelectric element 13 sandwiched and fixed between the respective holding elastic bodies 12. It is.

The basic elastic body 11 is formed by processing a brass material into a rectangular parallelepiped shape, and the holding elastic bodies 12 are epoxy-coated at three positions (a portion corresponding to a secondary bending vibration node) at both ends and a center portion of the upper surface. It is fixed with a system adhesive and further fixed with screws 14. Then, the laminated piezoelectric element 13 is held between the respective holding elastic bodies 12 in contact with each other. That is, the laminated piezoelectric element 13 is bonded and fixed to the holding elastic body 12 so as not to contact the basic elastic body 11. The side surface of the multilayer piezoelectric element 13 is coated with a resin. Here, the electrodes to the laminated piezoelectric element 13 on the left side of FIG.
And will be referred to as phase A. Similarly, electrodes on the right side of the laminated piezoelectric element 13 are denoted by B and G, and will be called a B phase.

A sliding member 15 is bonded to both ends of the bottom surface of the basic elastic body 11. The sliding member 15 is made of polyimide mixed with carbon fiber (20% by weight) and mica (30% by weight) as a filler, and has a thickness of about 0.1%.
It is 1 mm.

The dimensions of the basic elastic body 11 are 30 mm in width and 8 m in height, referring to the specifications of the ultrasonic transducer.
m, depth 4 mm, and the size of the holding elastic body 12 is width 4
mm, height 3 mm, depth 4 mm, and the laminated piezoelectric element 13 is NLA-2 × 3 × 9 by Tokin Corporation, and the dimensions are 2 mm × 3.1 mm × 9 mm.

Next, the operation of the ultrasonic transducer will be described. According to the computer simulation, the ultrasonic resonator having the above dimensions has substantially the same primary resonance longitudinal vibration as shown in FIG. 3A and the secondary resonance bending vibration as shown in FIG. 3B. Can be excited by frequency. The frequency is 53.
5 kHz. Then, a DC voltage of 30 V is applied to the A phase and the B phase to apply a compression preload to the multilayer piezoelectric element 13, and the A phase and the B phase have a frequency of 53.5 kHz and an amplitude of 10 Vp.
-P alternating voltage is applied. Here, when the phases of the A phase and the B phase are set to be the same, a primary resonance longitudinal vibration as shown in FIG. 3A is excited. Next, when the phases of the A phase and the B phase are reversed, the secondary resonance bending vibration as shown in FIG. 3B is excited. Next, when the phases of the A phase and the B phase were shifted by 90 degrees, ultrasonic elliptical vibration could be excited near the sliding member 15.

Next, an ultrasonic linear motor using the above-described ultrasonic transducer will be described. FIG. 4 is a front view of the ultrasonic linear motor. As shown in the figure, in this ultrasonic linear motor, the ultrasonic vibrator 10 runs on the rail 21 left and right by itself, and a linear guide fixing part 22 is provided on the back surface of the rail 21 to guide the ultrasonic vibrator 10. On the other hand, a linear guide moving portion 23 is provided at the lower end of the support mechanism of the ultrasonic transducer 10.

The ultrasonic vibrator 10 is held by a vibrator holding member 24 made of an aluminum material via silicon rubber (not shown) having a thickness of 1 mm. The vibrator holding member 24 has a U-shape, and has a connecting rod 25 connected thereto. A spring receiver 26 is formed at the upper end of the connecting rod 25. On the other hand, the rail 21 is made of stainless steel whose surface is quenched and hardened, the surface is polished smoothly, and the linear guide fixing part 22 is integrally fixed to the back surface. A frame 30 is fixed to the linear guide moving section 23 and is integral with the upper frame 31. A tap is cut at the center of the upper frame 31, and a bolt 29 is screwed therein. A spring retainer 28 is attached to the bolt 29 so that the length of the spring 27 can be adjusted and the contact pressure between the ultrasonic vibrator 10 and the rail 21 can be adjusted.

Next, the operation of the ultrasonic linear motor will be described. As described above, an alternating voltage is applied to the A-phase and the B-phase of the ultrasonic transducer 10 so that the phase difference is 90 degrees (or -90 degrees).
Degrees). Then, ultrasonic elliptical vibration is excited on the sliding surface of the ultrasonic transducer 10 and moves rightward (or leftward) with respect to the rail. The motor characteristics of this example were a no-load speed of 150 mm / sec and a starting thrust of 2N. This performance was maintained after 100,000 reciprocations.

The present embodiment may be modified as follows. (1) In the above embodiment, a DC voltage is superimposed to apply a preload to the laminated piezoelectric element, but the holding elastic body is fixed while applying mechanical pressure from both sides of the holding elastic body during assembly. (2) Similarly, in order to apply a preload, the laminated piezoelectric element is assembled in a depolarized state before assembly, and then polarized by applying a voltage of 100 V DC. At this point, since a preload is applied to the multilayer piezoelectric element, it is not necessary to apply a DC voltage during driving. (3) When driving with a small vibration amplitude, a preload does not need to be applied because the tensile force applied to the laminated piezoelectric element is small.

As described above, according to the ultrasonic linear motor of this embodiment, since the piezoelectric longitudinal effect is used, the electro-mechanical conversion efficiency is greatly improved. In addition, since the laminated piezoelectric element is operated while applying a preload, the durability of the ultrasonic vibrator is also improved.

[0024]

Second Embodiment Next, a second embodiment of the present invention will be described. FIG.
Is a front view showing an ultrasonic vibrator, and FIG. 6 is a front view showing an ultrasonic linear motor. The ultrasonic transducer of FIG. 5 differs from that of the first embodiment in that the sliding member 16 is attached to another antinode of the resonance bending vibration and that the material is made of amorphous carbon. In the ultrasonic linear motor of FIG. 6, the ultrasonic vibrator 10 is fixed, and the rod-shaped driven body 34 is driven left and right.

The ultrasonic vibrator 10 is fixed to a base (not shown) by a fixing member 32. As shown in FIG.
As shown in the side view of (b), urethane rubber 33 is stuck on the inner surface holding the ultrasonic vibrator in a U-shaped cross section for vibration isolation. Next, the driven body 34 has a shape shown in the cross-sectional view of FIG. 6C, and is obtained by hardening a stainless steel material and then smoothly polishing the contact surface 41 with the ultrasonic vibrator 10. The contact surface and the upper surface 42 are connected by thin portions 39 and 40. By doing so, the thin portion 39,
Since the vibration is reflected at 40, the vibration energy does not leak to the outside, and the efficiency of the ultrasonic linear motor can be improved.

Next, a linear guide moving portion 35 is integrally fixed on the upper surface of the driven body 34, and the linear guide fixing portion 3 is fixed.
6 is pressed downward. 37 is a leaf spring for applying a pressing force, and 38 is a spring holding portion fixed to a base (not shown).

Next, the operation of the ultrasonic linear motor will be described. As in the first embodiment, an alternating voltage is applied to the A phase and the B phase of the ultrasonic vibrator 10, and the phase difference is 90 degrees (or -9 degrees).
0 degrees). Then, ultrasonic elliptical vibration is excited on the sliding surface of the ultrasonic transducer 10, and the driven body 34 moves rightward (or leftward). The motor characteristics of this example were a no-load speed of 200 mm / sec and a starting thrust of 3N.
This performance was maintained after 100,000 reciprocations.

[0028]

Third Embodiment Next, a third embodiment of the present invention will be described. FIG.
FIG. 3 is a front view showing an ultrasonic vibrator. As shown in the figure, in the ultrasonic transducer 10, the piezoelectric elements 17 and 18 for detecting vibration are used.
Was adhered to the side surface of the basic elastic body 11. Piezoelectric element for detection 1
Reference numerals 7 and 18 are made of PZT ceramics and have a thickness of 0.2 mm with silver electrode treatment on both surfaces. And
The detecting piezoelectric element 17 is polarized in the same direction over the entire surface, and the detecting piezoelectric element 18 is polarized in the opposite direction at the center. Lead wires F1 and F2 are connected to the respective detecting piezoelectric elements 17 and 18, and a common ground line paired with the lead wires F1 and F2 is connected to the basic elastic body 11.

Next, the operation of this embodiment will be described. When an alternating voltage is applied to the laminated piezoelectric element 13 to excite the primary longitudinal vibration in the same manner as in the first embodiment, a sinusoidal signal proportional to the vibration amplitude is obtained from the F1 terminal, and a signal is generated from the F2 terminal. Could not be obtained. Next, when the secondary bending vibration was excited in the laminated piezoelectric element 13, no signal was obtained from the F1 terminal, but a sinusoidal signal proportional to the vibration amplitude was obtained from the F2 terminal. Next, when the primary longitudinal vibration and the secondary bending vibration are simultaneously excited to excite the ultrasonic elliptical vibration, F
Sinusoidal signals were obtained from both the 1 and F2 terminals. In this case, the signal from the F1 terminal is proportional to the primary longitudinal vibration, and the signal from the F2 terminal is proportional to the secondary bending vibration.

When the ultrasonic vibrator is driven for a long time, the temperature of the vibrator rises and the resonance frequency changes. Therefore, in order to keep the vibration state of the vibrator constant, the frequency must be tracked. In this embodiment, tracking is performed by a circuit configuration as shown in FIG. That is, the output of the alternating voltage from the oscillator is amplified and applied to the A phase, and after passing through the phase shifter, amplified and applied to the B phase. Then, the signal of the F1 terminal (or F2 terminal) is amplified and compared with the signal of the oscillator as the monitor voltage, and the oscillation frequency is adjusted so that the phase difference between the two becomes constant, or the monitor voltage is always maximized. The oscillation frequency may be adjusted as described above.

The mounting position of the detecting piezoelectric element may be as shown in FIG. That is, in FIG. 9, the detecting piezoelectric element 1 is used.
7 and 18 were bonded to the bottom surface of the basic elastic body 11. As the monitor signal, the F2 signal may be used, or the F2 signal may be used.
Frequency tracking is also possible using the sum of one signal and F2 signal.

As described above, according to the present embodiment, the vibration state can be kept constant regardless of the temperature rise of the vibrator, and the motor characteristics can be stabilized.

[0033]

Fourth Embodiment Next, a fourth embodiment of the present invention will be described. FIG.
0 is a front view of the ultrasonic transducer. As shown, in this embodiment, the detecting piezoelectric elements 19 and 20 are connected to the basic elastic body 11.
And the sliding member 15. The piezoelectric elements 19 and 20 for detection are made of PZT ceramics,
Silver electrode treatment on both sides 0.2mm thick x 2mm wide
X 4 mm deep, polarized in the thickness direction.
Then, bonding was performed so that the directions of polarization were opposite between the piezoelectric elements 19 and 20 for detection. The same sliding member 15 as in Example 1 was adhered to these bottom surfaces. Further, lead wires F3 and F4 are connected to the respective piezoelectric elements 19 and 20, and a common ground wire paired with the lead wires F3 and F4 is connected to the basic elastic body 11.

Using the ultrasonic transducer of this embodiment, an ultrasonic linear motor similar to that shown in FIG. 4 was constructed. When the ultrasonic linear motor is driven, a piezoelectric effect is generated by the contact pressure between the sliding member 15 and the rail, and a voltage is generated at the terminals F3 and F4. This voltage has a waveform shown in FIG. Further, since the phases of the output voltages of F3 and F4 are different by 180 degrees and the signs are opposite, the sum of both is shown in FIG.
It becomes a sine wave like

In the present embodiment, this signal is used to
Frequency tracking is performed by such a circuit configuration. That is, the output of the alternating voltage from the oscillator is amplified and applied to the A phase, and after passing through the phase shifter, amplified and applied to the B phase. Then, the signals of the F3 terminal and the F4 terminal are added and amplified, and compared with the signal of the oscillator as the monitor voltage, the oscillation frequency is adjusted so that the phase difference between the two becomes constant, or the monitor voltage is always maximized. The oscillation frequency may be adjusted so that

As described above, according to the present embodiment, it is possible to detect the contact pressure between the vibrator and the driven body with a simple structure. As a result, the frequency can be tracked, and the vibration state can be kept constant irrespective of the temperature rise of the vibrator, and the motor characteristics can be stabilized. In this embodiment, the contact pressure between the vibrator and the driven body can be detected, and the contact pressure between the two can be adjusted and controlled.

[0037]

As described above, according to the ultrasonic linear motor of the present invention, the following effects can be obtained. That is, since the piezoelectric longitudinal effect was utilized using the laminated piezoelectric element, the electro-mechanical conversion efficiency was improved, and low voltage driving was possible. In addition, it is possible to obtain an ultrasonic linear motor that has a very simple configuration and is compact, yet has a large output, and that it is used while preloading the laminated piezoelectric element, thereby improving the durability of the ultrasonic linear motor. Can be. Further, it is possible to independently detect the longitudinal vibration and the bending vibration of the ultrasonic transducer, and it is possible to automatically track the driving frequency based on the signal. Further, it is also possible to detect the contact pressure between the ultrasonic vibrator and the moving body and perform automatic frequency tracking.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an ultrasonic transducer according to a first embodiment of the present invention.

FIG. 2 is a front view showing the ultrasonic transducer according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating the operation of the ultrasonic transducer according to the first embodiment.

FIG. 4 is a front view showing the ultrasonic linear motor according to the first embodiment of the present invention.

FIG. 5 is a front view showing an ultrasonic transducer according to a second embodiment of the present invention.

FIG. 6 is a front view showing an ultrasonic linear motor according to a second embodiment of the present invention.

FIG. 7 is a front view showing an ultrasonic transducer according to a third embodiment of the present invention.

FIG. 8 is a drive circuit diagram of the ultrasonic transducer according to the third embodiment.

FIG. 9 is a bottom view illustrating a modified example of the ultrasonic transducer according to the third embodiment.

FIG. 10 is a front view showing an ultrasonic transducer according to a fourth embodiment of the present invention.

FIG. 11 is a diagram illustrating an operation of the ultrasonic transducer according to the fourth embodiment.

FIG. 12 is a drive circuit diagram of an ultrasonic transducer according to a fourth embodiment.

FIG. 13 is a front view showing a conventional ultrasonic linear motor.

FIG. 14 is a diagram showing a longitudinal vibration mode of a conventional ultrasonic linear motor.

FIG. 15 is a diagram showing a bending vibration mode of a conventional ultrasonic linear motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Ultrasonic vibrator 11 Basic elastic body 12 Elastic body for holding 13 Laminated piezoelectric element 14 Screw 15, 16 Sliding member 17, 18 Piezoelectric element for detection 19, 20 Piezoelectric element for detection 21 Rail 22 Linear guide fixing part 23 Linear Guide moving part 24 Vibrator holding member 25 Connecting rod 26, 28 Spring receiver 27 Spring 29 Bolt 30 Frame 31 Upper frame 32 Fixed member 33 Urethane rubber 34 Driven body 35 Linear guide moving part 36 Linear guide fixed part 37 Leaf spring 38 Spring Holding part 39 Thin part 40 Thin part 41 Contact surface 42 Upper surface 101 Elastic body 102 Supporter 103, 104, 105 Piezoelectric ceramic 106 Pressure roll 107 Paper

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takashi Ouchi 2-43-2 Hatagaya, Shibuya-ku, Tokyo Inside O-Limpus Optical Industry Co., Ltd. (72) Inventor Yoshihisa Taniguchi 2-43-2 Hatagaya, Shibuya-ku, Tokyo No. Olympus Optical Co., Ltd. (56) References JP-A-3-261385 (JP, A) JP-A-6-6989 (JP, A) JP-A-3-178581 (JP, A) JP-A-63 −277477 (JP, A) JP-A-2-7876 (JP, A) JP-A-3-142888 (JP, A) JP-A-4-68495 (JP, U) (58) Fields investigated (Int. . ^7, DB name) H02N 2/08 H02N 2/16

Claims (4)

(57) [Claims] An ultrasonic vibrator that uses an electro-mechanical energy conversion element as a driving source, generates longitudinal vibration and bending vibration in an elastic body, combines the vibrations to generate ultrasonic elliptical vibration, and an ultrasonic vibrator. A driven member that is pressed by a part of the vibrator and moves relatively to the ultrasonic vibrator, wherein the ultrasonic vibrator has at least two stacked Type piezoelectric element, a basic elastic body as an elastic body, and a holding elastic body joined to the basic elastic body, and both ends of each laminated piezoelectric element are attached to the holding elastic body. An ultrasonic linear motor characterized in that the ultrasonic linear motor is held in contact with and held. 2. The ultrasonic linear motor according to claim 1, wherein a plane perpendicular to a nodal line of the elastic wave or a plane including a traveling direction of the elastic wave in the basic elastic body is provided with a longitudinal vibration of the basic elastic body. A vibration detecting piezoelectric element that is fully polarized in the thickness direction for independently detecting bending vibration or a vibration detecting piezoelectric element whose direction is alternately polarized in the thickness direction is joined. Ultrasonic linear motor. 3. The ultrasonic linear motor according to claim 1, wherein the entire surface of the ultrasonic vibrator is polarized in the thickness direction near a portion where the basic elastic body and the driven member are in contact with each other, and the contact pressure is reduced. An ultrasonic linear motor, wherein a detection piezoelectric element for detection is joined. 4. The method according to claim 1, wherein the multilayer piezoelectric element is held between the holding elastic bodies by abutting the holding piezoelectric bodies, and the holding elastic bodies are fixed while applying mechanical pressure from both side surfaces of the holding elastic bodies. The method for manufacturing an ultrasonic linear motor according to claim 1, wherein: