JPH06105571A - Ultrasonic linear motor and manufacture thereof - Google Patents

Abstract

PURPOSE:To drive an ultrasonic linear motor at a low voltage with high electro- mechanical conversion efficiency by utilizing the piezoelectric longitudinal effect of a piezoelectric element. CONSTITUTION:An ultrasonic linear motor comprises an ultrasonic vibrator 10 having a plurality of holding elastic elements 12 fixed to the upper surface of a basic elastic element 11 of a rectangular parallelepiped shape and a laminated piezoelectric element 13 interposed to be held fixedly between the members 12.

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 having an electromechanical energy conversion element such as a laminated piezoelectric element as a drive source.

[0002]

2. Description of the Related Art In recent years, ultrasonic motors have attracted attention as new motors to replace electromagnetic motors. This ultrasonic motor has the following advantages over conventional electromagnetic motors. (1) Low speed and high thrust can be obtained without gears. (2) Large holding power. (3) The stroke is long and the resolution is high. (4) It is very quiet. (5) Electromagnetic noise is not generated and is not affected by noise. Here, the ultrasonic motor is divided into a rotary type and a linear type,
As a linear type ultrasonic motor, for example, the 1988 IEICE Spring National Convention (2.21 paper feed device N using a plate-shaped motor using a longitudinal-bending multimode oscillator)
o. A-223 (S63.3)) is known.

In the vibrator of such a linear ultrasonic motor, as shown in FIG. 13, three piezoelectric ceramics 103, 104 are provided between an elastic body 101 made of a stainless steel plate or the like and a support 102 such as silicon rubber. 105 is adhered. Here, the piezoelectric ceramic 104 has a longitudinal vibration mode (L).
2) of piezoelectric ceramics 103 and 105
The sheet is for bending vibration mode (Bending-mode: hereinafter referred to as B mode). A vibrator is designed in a shape in which the resonance frequencies of both modes match, and an alternating voltage (AC) of the resonance frequencies is applied to each of the piezoelectric ceramics 103 to 105. Then, if an appropriate phase difference is provided to these alternating voltages, elliptical vibration can be excited in the shaded portions in FIGS. 14 and 15. Then, by pressing the paper 107 as the driven body by the pressure roll 106, the paper 107 can be conveyed left and right.

[0004]

However, in the above-mentioned conventional ultrasonic linear motor, the piezoelectric ceramics 103 to 1 are used.
Since the piezoelectric transverse effect of No. 05 is used to excite the vibration, there is a problem that the efficiency is low. That is, in general, in piezoelectric ceramics, the electro-mechanical coupling coefficient due to the piezoelectric longitudinal effect is 60 to 70%, whereas in the piezoelectric lateral effect, it is as low as 30 to 40%. Here, the low electro-mechanical coupling coefficient means that the electro-mechanical conversion efficiency is low, and the drive input voltage is also several tens Vrms to 100 Vrm.
A high voltage of about s is required.

The present invention has been made in view of the above problems, and an ultrasonic linear motor having a high electro-mechanical conversion efficiency and capable of being driven at a low voltage by utilizing the piezoelectric longitudinal effect of a piezoelectric element. It is intended to be provided.

[0006]

In order to achieve the above object, in the ultrasonic linear motor of the present invention according to claim 1, an electric-mechanical energy conversion element is used as a drive source, and longitudinal vibration and bending vibration are applied to an elastic body. An ultrasonic transducer that generates and synthesizes those vibrations to generate an ultrasonic elliptical vibration, and a driven member that is pressed by a part of the ultrasonic transducer and moves relatively to the ultrasonic transducer. In the ultrasonic linear motor, the ultrasonic transducer includes at least two laminated piezoelectric elements as drive sources, a basic elastic body as an elastic body, and a holding elastic body bonded to the basic elastic body. It is characterized in that it is composed of a body and both ends of each of the laminated piezoelectric elements are joined and held by abutting against the holding elastic body.

According to a second aspect of the present invention, in addition to the above first aspect, the ultrasonic linear motor of the present invention has a surface orthogonal to the nodal line of the elastic wave in the basic elastic body or a surface including a traveling direction of the elastic wave. In addition, a piezoelectric element for vibration detection entirely polarized in the thickness direction for independently detecting longitudinal vibration and bending vibration of the basic elastic body, or a piezoelectric element for vibration detection in which the direction is alternately polarized with respect to the thickness direction. The elements are joined together.

The ultrasonic linear motor according to a third aspect of the present invention is, in addition to the first aspect, the entire surface in the thickness direction thereof is polarized in the vicinity of the portion where the ultrasonic vibrator and the driven member are in contact with each other. The piezoelectric element for pressure detection is joined.

According to a fourth aspect of the present invention, when the ultrasonic linear motor of the first to third aspects is assembled, the laminated piezoelectric element is set in a depolarized state in advance, and the laminated piezoelectric element is polarized after the assembly. The compressive stress is applied to the laminated piezoelectric element.

[0010]

The ultrasonic linear motor of the present invention having the above construction operates as follows. That is, in the ultrasonic linear motor according to the first aspect, the alternating voltage having the resonance frequency of the longitudinal vibration of the vibrator is applied to the laminated piezoelectric element. Here, when the phase difference of the alternating voltage applied to the two laminated piezoelectric elements is appropriately set, each part of the ultrasonic transducer causes elliptical vibration. When the driven body is brought into pressure contact with the portion where the elliptical vibration is generated, the driven body is linearly driven. It should be noted that a DC voltage may be applied to the laminated piezoelectric element by superimposing it on the alternating voltage. As a result, a compressive force is constantly applied to the laminated piezoelectric element to prevent the piezoelectric element from being broken.

Further, since the ultrasonic motor utilizes the resonance phenomenon of the elastic body, it is necessary to track the drive frequency when the resonance frequency changes due to 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 that is surface-bonded to the elastic body. Since this detection signal correlates with the amplitude and phase of vibration, this is fed back to track the drive frequency. In particular, in the present invention, the longitudinal vibration and the bending vibration can be detected independently, so that the resonance frequency of either vibration can be tracked.

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

Some embodiments of the 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]

First Embodiment First, a first embodiment of the present invention will be described. Figure 1
Is a perspective view showing an ultrasonic transducer, and FIG. 2 is a front view. As shown in the figure, this ultrasonic transducer 10 is one in which three holding elastic bodies 12 are fixed to the upper surface of a basic elastic body 11, and a laminated piezoelectric element 13 is sandwiched and fixed between each holding elastic body 12. Is.

The basic elastic body 11 is formed by processing a brass material into a rectangular parallelepiped shape. Epoxy retaining elastic bodies 12 are provided at three points on the upper surface and at the central portion (a portion corresponding to a node of secondary bending vibration). In addition to fixing with a system adhesive, the screw 14 is also fixed. Then, the laminated piezoelectric element 13 is abutted and held between the holding elastic bodies 12. That is, the laminated piezoelectric element 13 is adhesively fixed to the holding elastic body 12 so as not to contact the basic elastic body 11. The side surface of the laminated piezoelectric element 13 is resin-coated. Here, the electrodes to the laminated piezoelectric element 13 on the left side of FIG.
Let's call it Phase A. Similarly, the electrodes to the laminated piezoelectric element 13 on the right side are referred to as B and G and are referred to as the B phase.

Sliding members 15 are adhered 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.
It is 1 mm.

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

Next, the operation of the ultrasonic transducer will be described. According to a computer simulation, the ultrasonic transducer having the above-described size has substantially the same primary resonance longitudinal vibration as shown in FIG. 3A and the same secondary resonance bending vibration as shown in FIG. 3B. Can be excited at frequency. Its frequency is 53.
It is 5 kHz. Therefore, a direct current voltage of 30 V is applied to the A phase and the B phase to apply compression preload to the laminated piezoelectric element 13, and the A phase and the B phase have a frequency of 53.5 kHz and an amplitude of 10 Vp.
Apply an alternating voltage of -p. Here, if the phases of the A phase and the B phase are made to be the same phase, the primary resonance longitudinal vibration as shown in FIG. 3A is excited. Next, when the phases of the A phase and the B phase are made opposite to each other, a secondary resonance bending vibration as shown in FIG. 3B is excited. Next, by shifting the phases of the A phase and the B phase by 90 degrees, ultrasonic elliptical vibration could be excited near the sliding member 15.

Next, an ultrasonic linear motor using the above ultrasonic vibrator 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 transducer 10 is designed to be self-propelled to the left and right on the rail 21, and a linear guide fixing portion 22 is provided on the back surface of the rail 21 to guide this. On the other hand, the linear guide moving unit 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 a silicon rubber (not shown) having a thickness of 1 mm. The vibrator holding member 24 has a U-shape and is connected with a connecting rod 25. A spring receiver 26 is formed on the upper end of the connecting rod 25. On the other hand, the rail 21 is made of a stainless material whose surface is hardened by quenching, the surface is smoothly polished, and the linear guide fixing portion 22 is integrally fixed to the rear surface. A frame 30 is fixed to the linear guide moving portion 23 and is integrated with the upper frame 31. A tap is cut in the central portion 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 transducer 10 and the rail 21 can be adjusted.

Next, the operation of this 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 and the phase difference is 90 degrees (or -90).
Degree). Then, ultrasonic elliptical vibration is excited on the sliding surface of the ultrasonic transducer 10 and moves to the right (or left) 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 even after 100,000 reciprocating operations.

The present embodiment may be modified and implemented as follows. (1) In the above embodiment, a DC voltage was superimposed to apply a preload to the laminated piezoelectric element, but the holding elastic body should be fixed while applying mechanical pressure from both side surfaces 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 assembling, and then a voltage of DC100V is applied to polarize. At this point, since a preload is applied to the laminated piezoelectric element, it is not necessary to apply a DC voltage during driving. (3) Further, when driving with a small vibration amplitude, since the tensile force applied to the laminated piezoelectric element is small, it is not necessary to apply preload.

As described above, according to the ultrasonic linear motor of this embodiment, the piezoelectric longitudinal effect is utilized, so that the electromechanical conversion efficiency is significantly improved. Moreover, since the laminated piezoelectric element is operated while applying a preload, the durability of the ultrasonic transducer is also improved.

[0024]

Second Embodiment Next, a second embodiment of the present invention will be described. Figure 5
Is a front view showing an ultrasonic transducer, and FIG. 6 is a front view showing an ultrasonic linear motor. The ultrasonic vibrator of FIG. 5 is different from that of the first embodiment in that the sliding member 16 is attached to another antinode of the resonance bending vibration and the material is amorphous carbon. Further, 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 transducer 10 is fixed to a base (not shown) by a fixing member 32. The fixing member 32 is shown in FIG.
As shown in the side view of (b), urethane rubber 33 is attached to the inner surface of the U-shaped cross section for holding the ultrasonic transducer for vibration damping. Next, the driven body 34 has a shape shown in the cross-sectional view of FIG. 6C, and is obtained by quenching a stainless material and then smoothly polishing the contact surface 41 with the ultrasonic transducer 10. The contact surface and the upper surface 42 are connected by the thin portions 39 and 40. By doing this, the thin portion 39,
Since the vibration is reflected by 40, the vibration energy does not leak to the outside and the efficiency of the ultrasonic linear motor can be improved.

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

Next, the operation of this ultrasonic linear motor will be described. Similar to the first embodiment, alternating voltage is applied to the A phase and the B phase of the ultrasonic transducer 10 and the phase difference is 90 degrees (or -9).
0 degree). Then, ultrasonic elliptical vibration is excited on the sliding surface of the ultrasonic transducer 10, and the driven body 34 moves to the right (or to the left). 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 even after 100,000 reciprocating operations.

[0028]

Third Embodiment Next, a third embodiment of the present invention will be described. Figure 7
FIG. 4 is a front view showing an ultrasonic transducer. As shown in the figure, in this ultrasonic transducer 10, piezoelectric elements 17 and 18 for vibration detection are used.
Was adhered to the side surface of the basic elastic body 11. Piezoelectric element for detection 1
Nos. 7 and 18 are made of PZT ceramics and have a thickness of 0.2 mm, both surfaces of which are treated with silver electrodes. And
The detection piezoelectric element 17 is polarized in the same direction over the entire surface, and the detection piezoelectric element 18 is polarized in the opposite direction with the central portion as a boundary. Lead wires F1 and F2 are connected to the respective detecting piezoelectric elements 17 and 18, and a common ground wire 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 in the same manner as in Example 1 to excite the primary longitudinal vibration, a sinusoidal signal proportional to the vibration amplitude is obtained from the F1 terminal and a signal is obtained from the F2 terminal. I couldn't get it. Next, when a 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. The signal from the F1 terminal in this case 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 the 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 also amplified after passing through the phase shifter and applied to the B phase. Then, the signal at the F1 terminal (or F2 terminal) is amplified and compared with the signal from the oscillator as a 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 follows.

The mounting position of the detecting piezoelectric element may be as shown in FIG. That is, in FIG. 9, the detecting piezoelectric element 1
7 and 18 were adhered to the bottom surface of the basic elastic body 11. Further, 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 1 signal and F2 signal.

As described above, according to this 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. Figure 1
0 is a front view of the ultrasonic transducer. As shown, in this embodiment, vibration detecting piezoelectric elements 19 and 20 are interposed between the basic elastic body 11 and the sliding member 15. The detection piezoelectric elements 19 and 20 are made of PZT ceramics and have a thickness of 0.2 mm and a width of 2 with silver electrode treatment on both surfaces.
mm × 4 mm in depth, polarized in the thickness direction. Then, the piezoelectric elements for detection 19 and 20 were bonded so that the directions of polarization were opposite to each other. The sliding member 15 similar to that in Example 1 was adhered to the bottom surface of these. Furthermore, the lead wires F3 and F are connected to the respective piezoelectric elements 19 and 20 for detection.
4 are connected to each other, and a common ground wire paired therewith is connected to the basic elastic body 11.

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

This embodiment utilizes this signal in FIG.
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 also amplified after passing through the phase shifter and applied to the B phase. Then, the signals of the F3 and F4 terminals are added together and 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 so that

As described above, according to this 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 was tracked, the vibration state could be kept constant regardless of the temperature rise of the vibrator, and the motor characteristics could be stabilized. Further, in this embodiment, the contact pressure between the vibrator and the driven body can be detected, and the contact pressure between the both can be adjusted and controlled.

[0037]

As described above, the ultrasonic linear motor of the present invention has the following effects. That is, since the piezoelectric vertical effect was used by using the laminated piezoelectric element, the electromechanical conversion efficiency was improved and low voltage driving was possible. Further, it is possible to obtain an ultrasonic linear motor having a large output with a very simple structure and a large output, and since the laminated piezoelectric element is used while being preloaded, the durability of the motor can be improved. Further, it is possible to independently detect the longitudinal vibration and the bending vibration of the ultrasonic vibrator, and the signal can be used to automatically track the driving frequency. Further, the frequency automatic tracking can be performed by detecting the contact pressure between the ultrasonic transducer and the driven body.

[Brief description of 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 of the first embodiment according to the present invention.

FIG. 3 is a diagram for explaining the operation of the ultrasonic transducer of the first embodiment.

FIG. 4 is a front view showing an ultrasonic linear motor according to a 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 of the third embodiment.

FIG. 9 is a bottom view showing a modified example of the ultrasonic transducer of 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 the operation of the ultrasonic transducer of the fourth embodiment.

FIG. 12 is a drive circuit diagram of the ultrasonic transducer of the 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]

 10 Ultrasonic Transducer 11 Basic Elastic Body 12 Holding Elastic Body 13 Laminated Piezoelectric Element 14 Screws 15,16 Sliding Member 17,18 Detection Piezoelectric Element 19,20 Detection Piezoelectric Element 21 Rail 22 Linear Guide Fixing Section 23 Linear Guide moving part 24 Transducer holding member 25 Connecting rod 26, 28 Spring receiver 27 Spring 29 Bolt 30 Frame 31 Upper frame 32 Fixing member 33 Urethane rubber 34 Driven body 35 Linear guide moving part 36 Linear guide fixing part 37 Leaf spring 38 Spring Holding portion 39 Thin portion 40 Thin portion 41 Contact surface 42 Upper surface 101 Elastic body 102 Support body 103, 104, 105 Piezoelectric ceramic 106 Pressure roll 107 Paper

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Ouchi 2-43-2 Hatagaya, Shibuya-ku, Tokyo Olympus Optical Co., Ltd. (72) Inventor Yoshihisa Taniguchi 2-43-2 Hatagaya, Shibuya-ku, Tokyo Olympus Optical Industry Co., Ltd.

Claims (4)

[Claims] 1. An ultrasonic transducer which uses an electro-mechanical energy conversion element as a drive source to generate longitudinal vibration and bending vibration in an elastic body and synthesizes those vibrations to generate ultrasonic elliptical vibration, and this ultrasonic wave. An ultrasonic linear motor comprising: a driven member that is pressed by a part of an oscillator and moves relative to the ultrasonic oscillator, wherein the ultrasonic oscillator includes at least two laminated types as drive sources. The piezoelectric element is composed of a basic elastic body as an elastic body and a holding elastic body joined to the basic elastic body. Both ends of each laminated piezoelectric element are abutted against the holding elastic body. An ultrasonic linear motor characterized by being joined and held. 2. The ultrasonic linear motor according to claim 1, wherein a longitudinal vibration of the basic elastic body is generated on a surface orthogonal to a nodal line of the elastic wave in the basic elastic body or on 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 bending vibration, or a piezoelectric element for vibration detection, which is alternately polarized in the thickness direction, is joined. Ultrasonic linear motor. 3. The ultrasonic linear motor according to claim 1, wherein a piezoelectric element for pressure detection, which is entirely polarized in its thickness direction, is bonded in the vicinity of a portion where the ultrasonic vibrator and the driven member are in contact with each other. Ultrasonic linear motor characterized by 4. When the ultrasonic linear motor is assembled, the laminated piezoelectric element is previously depolarized, and the laminated piezoelectric element is polarized after the assembly so that a compressive stress is applied to the laminated piezoelectric element. The method of manufacturing an ultrasonic linear motor according to claim 1, wherein