JP3805240B2 - Ultrasonic motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention resonates the vibrating body by supplying electric energy to the piezoelectric element, causes the moving body pressed by the vibrating body due to the resonance of the vibrating body, and extracts the rotating motion of the moving body. It is related with the ultrasonic motor used as a motor output by this.
[0002]
[Prior art]
As a conventional ultrasonic motor, as disclosed in Japanese Patent Laid-Open No. 6-178561, a piezoelectric element that generates vibration is polarized by being reversed left and right with a central axis as a boundary. As a set, the phases are divided into the A phase and the B phase, and the phases are arranged differently and laminated. A vibrating body is formed by sandwiching the piezoelectric element between a pair of elastic bodies.
[0003]
When an AC voltage having a specific frequency is applied only to the A phase of the piezoelectric element, the piezoelectric element is reversed in the left-right direction and polarized, so that each region expands and contracts. By this expansion and contraction, the vibrating body is excited by bending natural vibration left and right around the plane including the central axis and the polarization boundary line.
[0004]
When an alternating voltage of a specific frequency is applied only to the B phase, the B phase polarization boundary surface is arranged 90 degrees out of phase with respect to the A phase. Natural vibration is excited in the wrong direction.
[0005]
When the AC voltage applied to the A phase and the B phase is applied with a phase difference of 90 degrees in terms of time, bending vibration is generated such that the end of the vibrating body rotates. At this time, the left and right rotation directions can be selected by selecting either +90 degrees or -90 degrees as the temporal phase.
[0006]
In the ultrasonic motor disclosed in Japanese Patent Laid-Open No. 6-178561, the vibration body has a circumferential groove to increase the displacement of the vibration. As a result, a swivel motion with increased displacement is generated on the end face of the vibrating body, and this swivel vibration corresponds to one traveling wave. Then, the moving body is brought into pressure contact with the end surface portion of the vibrating body to cause a rotational motion in the moving body, and the ultrasonic motor is configured by extracting the rotational motion of the moving body.
[0007]
[Problems to be solved by the invention]
The ultrasonic motor described above is inexpensive and small because the structure of the vibrator is simple. Further, since it is a bolted type, there is no need to bond the piezoelectric element with an adhesive such as a resin material, and there is no problem such as a change in motor performance due to a change in temperature characteristics of the adhesive or a vibration absorption by the adhesive. However, the ultrasonic motor has a low torque, and there is a great demand for a large torque.
[0008]
In order to generate a large torque, it is desirable to set the diameter dimension of the pressure contact surface between the vibrating body and the moving body as large as possible. The ultrasonic motor described above is also close to the maximum outer diameter of the pressure contact surface. Is often provided. However, since it is a rod-shaped ultrasonic motor by swinging vibration, its maximum outer diameter is about the outer diameter of the piezoelectric element.
[0009]
As another means for increasing the torque, there is a method of increasing the pressure applied to the contact portion between the vibrating body and the moving body, but there is a limit because wear of the contact portion may lead to deterioration of durability performance.
[0010]
As described above, although there are some advantages, there is a limit to increasing the torque. Accordingly, an object of the present invention is to provide a motor having a large torque while taking advantage of the ultrasonic motor of the above type.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, according to claim 1, by applying an electrical signal to the rotation center axis, the rotation center axis is orthogonal to the rotation center axis and is 90 degrees different from the center. In addition, in two regions, a thin plate shape having a phase difference of ¼ wavelength temporally with a phase different by ½ wavelength and causing longitudinal vibration in the direction of the rotation axis and having electrodes on both sides, two or more stretchable regions A plurality of piezoelectric elements polarized at different angular phases are laminated, and a vibration source having a columnar shape in which the upper and lower surfaces of the piezoelectric element are sandwiched between a pair of elastic bodies and an end face of the vibration source are coupled to the vibration source. A vibration having a disk shape larger than the maximum outer diameter of the piezoelectric element of the source, and forming an outer peripheral portion that resonates with the longitudinal excitation of the vibration source in the circumferential direction and excites a traveling wave of flexural vibration having a plurality of wave heights. The body and the vibrating body under pressure contact with the traveling wave An ultrasonic motor and a moving body driven in the direction rotation.
[0012]
According to claim 2 and claim 3, by applying an electrical signal to the rotation center axis, the rotation center axis is orthogonal to the rotation center axis and is 90 degrees different from the center. A thin plate that has a phase difference of ¼ wavelength temporally with a phase difference of ½ wavelength in one region and can cause longitudinal vibration in the direction of the rotation axis. It has electrodes on both sides and is polarized in two or more stretchable regions. A plurality of piezoelectric elements having a predetermined angle phase are stacked, and a vibration source having a pillar shape in which the upper and lower surfaces of the piezoelectric element are sandwiched between a pair of elastic bodies and an end face of the vibration source are coupled to each other. A vibrating body having a disk shape larger than the maximum outer diameter of the piezoelectric element and having an outer peripheral portion that resonates with longitudinal excitation of the vibration source in the circumferential direction and excites a traveling wave of flexural vibration having a plurality of wave heights; , Pressurizing and contacting the vibrating body in a predetermined direction by the traveling wave In claim 2, the vibrating body includes a disk-shaped outer peripheral portion that is larger than the maximum outer diameter of the piezoelectric element and resonates in the longitudinal vibration, and a coupling portion between the vibration source and the vibrating body. A vibrating body portion having a reduced bending rigidity is formed on the way to the pressure contact surface with the moving body, and in claim 3 the shape of the vibrating body is a disk-shaped coupling portion with the vibration source, A cylindrical portion that resonates with the longitudinal vibration with a bending rigidity reduced with the disc-shaped peripheral surface portion as a base end is provided, and a flange-shaped portion is provided at the other end portion of the cylindrical shape. It is an ultrasonic motor characterized by having a pressure contact surface.
[0013]
【Example】
[First Embodiment] FIG. 1 shows a first embodiment of the present invention. FIG. 2 is an exploded perspective view thereof. FIG. 3 is a perspective view showing the electrode arrangement of the piezoelectric element used in the first embodiment.
[0014]
In FIG. 1, a vibration source 4 is a thin and disk-shaped piezoelectric element 1, 2, 3 and lower elastic body 5, an upper elastic body 6, a printed circuit board 7 for connecting each electrode of the piezoelectric element and an external control circuit. It consists of and.
[0015]
As shown in FIG. 3, the piezoelectric element is polarized in the thickness direction in two regions, and is electrically wired so that electrodes 1 a and 1 b are disposed on the upper surfaces of the respective regions and can be energized. Further, a common electrode 8 (not shown) is disposed on the front surface of the piezoelectric element on the opposite side, and is electrically wired so that it can be energized in the same manner.
[0016]
These piezoelectric elements have a set of two piezoelectric elements 1 as an A phase, and a set of two piezoelectric elements 2 arranged by changing the phase by 90 degrees with respect to the A phase become a B phase, for vibration detection. This one piezoelectric element 3 is in the S phase. And each piezoelectric element is laminated | stacked, and each electrode is electrically wired by the printed circuit board.
[0017]
In this embodiment, the A-phase and B-phase piezoelectric elements are each composed of two sheets. However, the voltage can be lowered by reducing the thickness of the piezoelectric elements and stacking more sheets. Needless to say, one A-phase and one B-phase piezoelectric element can be used. Further, instead of using separate piezoelectric elements for the A phase and the B phase as in this embodiment, one electrode is arranged so that one piezoelectric element is divided into four with respect to the axial center, and one of the opposing regions is arranged. May be the A phase and the other may be the B phase.
[0018]
The piezoelectric element configured as described above is sandwiched between the lower elastic body 5 and the upper elastic body 6 together with the printed circuit board 7 as shown in FIGS. 1 and 2, and is tightened by the first screw portion 10 a of the bolt 10. Combined. At this time, it is not preferable to use an adhesive made of a resin material or the like as a coupling means because it causes attenuation of vibration generated from the piezoelectric element or the amount of vibration attenuation at the temperature at which heat is generated. It is also desirable to select a material that does not attenuate vibration energy for the base material of the printed circuit board.
[0019]
In the present embodiment, the disk-shaped vibrating body 9 is integrated with the upper elastic body 6 so that vibration from the vibration source is efficiently transmitted to the vibrating body. Of course, the vibration body 9 and the upper elastic body 6 may be separated and combined with a coupling means. The lower elastic body 5, the upper elastic body 6 and the vibrating body 9 are made of an inexpensive material with excellent processing accuracy such as brass.
[0020]
Next, the movable body 11 is assembled so that the central hole thereof is passed through the connecting shaft portion 10 b of the bolt 10, and the pressure spring 13 is assembled in the storage portion 11 a of the movable body 11. Further, the interlocking gear 12 is assembled so that the convex portion 12b is fitted into the concave portion 11b provided in the moving body 11, and the pressure spring 13 is accommodated in the accommodating portion 12a.
[0021]
Finally, the nut 14 is screwed and fixed to the second screw portion 10c of the bolt 10, whereby the assembly of the movable body 11, the pressure spring 13, and the interlocking gear 12 is completed.
[0022]
Next, the operation will be described.
[0023]
In FIG. 3, a common electrode 8 (not shown) provided on the lower surface side of the piezoelectric element is set to a ground (GND) potential, and a positive potential and a negative potential are applied to the electrodes 1a and 1b provided on the upper surface side, respectively. By making this potential an alternating voltage of a specific frequency, vibrations caused by the A-phase piezoelectric element are caused.
[0024]
In addition, the B phase of the two piezoelectric elements 2 arranged in a set of two sheets with a phase difference of 90 degrees with respect to the two A piezoelectric elements 1 is 1 in time with respect to the A phase. An AC voltage having a specific frequency with a phase difference of / 4 wavelength is applied to cause vibration by a B-phase piezoelectric element having a phase and a position with respect to vibration by the A-phase piezoelectric element.
[0025]
FIG. 4 is a three-dimensional perspective view modeling the shapes of the vibration source 4 and the vibrating body 9. The hatched portions are the piezoelectric elements 1 and 2, the lower elastic body 5 is formed in the lower part, and the upper elastic body 6 and the vibrating body 9 are formed in the upper part. In this model, the central hole shape, the S-phase piezoelectric element, and the like are omitted. This model explains how vibrations occur.
[0026]
As described above, vibration is generated by the A-phase piezoelectric element, and the specific frequency is selected so that the vibrating body 9 excited by the vibration enters a resonance state. Due to this resonance, the vibrating body 9 vibrates left and right so as to repeat the states of FIGS. 5 (a) and 5 (b). Further, when vibration is generated by the B-phase piezoelectric element and the specific frequency is selected so that the vibrating body 9 excited by the vibration is in a resonance state, the resonance causes the vibrating body 9 to be as shown in FIG. Vibrate back and forth so as to repeat the state of (d).
[0027]
Since the vibration caused by the A-phase piezoelectric element and the vibration caused by the B-phase piezoelectric element are temporally different from each other by a quarter wavelength, the wave crest portion 9a formed by the resonance of the vibrating body 9 is represented by (a), (d ), (B), and (c), and the wave height portion 9a moves so as to rotate at the outer peripheral portion of the disc-shaped vibrating body. Further, the wave height portion 9a makes the vibration by the A-phase piezoelectric element and the vibration by the B-phase piezoelectric element different from each other by a quarter wavelength (a), (c), (b), (d). In the order. That is, forward and reverse rotation of the wave height position is possible.
[0028]
As described above, the wave of the vibrating body 9 excited by the vibration source 4 corresponds to a traveling wave having one wave height. The part where the traveling wave is generated is the place where the outer peripheral portion of the vibrating body 9 has the largest amplitude, and the outer diameter of the vibrating body 9 is larger than the maximum outer diameter of the piezoelectric elements 1a and 1b. Large torque can be obtained at low speed.
[0029]
The form of vibration described above can also be described by the following expression.
[0030]
Vibration is generated by the expansion and contraction of the piezoelectric elements 1 and 2, and longitudinal vibrations in the axial direction that are not in the resonance state are symmetric to the lower elastic body 5 and the upper elastic body 6 sandwiching the piezoelectric elements. It is generated with a phase difference of ¼ wavelength in two regions where the vertical vibrations are generated with a phase difference of ½ wavelength in two regions and the two regions where the longitudinal vibrations are different from each other by 90 degrees with respect to the axial center. This longitudinal vibration is a specific frequency that brings the disk-shaped vibrating body 9 into a resonance state, and the vibrating body 9 was excited in the left-right direction standing wave excited in the A phase and the B phase shown in FIG. Since the standing wave in the front-rear direction has a phase difference of ¼ wavelength in time, a traveling wave of bending vibration is created in the circumferential direction.
[0031]
The position where the vibrating body 9 contacts the moving body 11 is this wave height portion 9a. The tangent surface of the wave height portion 9a draws an elliptical orbit and gives the moving body 11 a rotational motion.
[0032]
The moving body 11 has a pressure contact surface 11c with the vibrating body 9 in the vicinity of the outer peripheral portion of the vibrating body 9 so as to effectively obtain the traveling wave and perform a rotational motion. The pressurizing contact load is applied by the pressurizing spring 13. Since the amount of deflection of the pressure spring 13 can be adjusted by the amount of screwing of the nut 14, it is easy to adjust or change the load applied by pressure.
[0033]
The rotational motion of the moving body 11 is transmitted to the interlocking gear 12 because the concave portion 11 b provided on the moving body 11 and the convex portion 12 b provided on the interlocking gear 12 are fitted. The interlocking gear 12 serves as a motion extraction part of this ultrasonic motor, and in this embodiment, the motor output is performed by a gear.
[0034]
As described above, the ultrasonic motor of the present invention is inexpensive because the structure of the vibrating body is simple, and it is not necessary to bond the piezoelectric element with an adhesive made of a resin material or the like. In addition, there is no change in motor performance due to changes in adhesive properties due to changes in temperature or temperature, and a large torque can be obtained at a lower speed than conventional products while having the feature that the vibration source is small.
[0035]
[Second Embodiment] FIG. 6 shows a second embodiment of the present invention.
[0036]
The shape of the vibrating body 9 is different from that in the first embodiment, and the bending rigidity of the vibrating body 9 is reduced in the middle from the connecting portion with the vibration source 4 to the pressure contact surface 11c with the moving body 11. The thinned portion 9b is provided uniformly over the entire circumference.
[0037]
Although the vibrating body 9 is excited in a resonance state by the vibration source 4, the outer peripheral portion 9c of the vibrating body 9 is amplified to a wave having a large amplitude due to the small bending rigidity of the thin portion. This effect increases the energy efficiency of the ultrasonic motor.
[0038]
[Third Embodiment] FIG. 7 shows a third embodiment of the present invention.
[0039]
Similarly to the above, the shape of the vibrating body 9 is different from that of the first embodiment. The vibrating body 9 has a cylindrical shape on the way from the coupling portion with the vibration source 4 to the pressure contact surface 11c with the moving body 11. The thin-walled portion 9b, which has a small bending rigidity, is provided uniformly over the entire circumference, and the pressure contact surface 11c is provided on the outer peripheral portion 9c protruding from the cylindrical shape into a flange shape.
[0040]
The vibrating body 9 is excited in a resonance state by the vibration source 4, and the outer peripheral portion 9c protruding in a flange shape is amplified to a wave having a large amplitude due to the small bending rigidity of the thin cylindrical portion, so that the energy efficiency of the ultrasonic motor is increased. It has led to raising.
[0041]
In the case of the present embodiment, since the thin portion 9b is provided in a cylindrical shape along the outer periphery of the vibration source 4, there is an advantage that the outer diameter of the outer peripheral portion 9c of the vibrating body 9 can be reduced.
[0042]
Further, although the cylindrical thin portion 9b is provided so as to hang down to the vibration source 4 side here, it may be provided so as to protrude toward the movable body 11 side.
[0043]
Further, in the first to third embodiments, the outer peripheral portion 9c of the vibrating body including the pressure contact surface 11c is formed in a comb shape so as to further amplify the amplitude and obtain the effect of removing wear and the like. May be.
[0044]
[Other Embodiments] The traveling wave of the vibrator described above is a traveling wave having one wave height, but a traveling wave having a plurality of wave heights can be created by polarizing the piezoelectric element as follows. it can.
[0045]
FIG. 8A shows a waveform of a vibrating body model having two wave height portions 9a. In order to create a traveling wave having such a waveform, the piezoelectric element is polarized in the thickness direction in four regions as shown in FIG. 8B, and electrodes 1A, 1B, 1C, 1D are formed on the upper surface of each region. And arrange the wiring so that it can be energized. A common electrode 8 (not shown) is arranged on the front surface of the piezoelectric element on the opposite side, and is electrically wired so that it can be similarly energized. Here, for the sake of explanation, the central hole shape, the S-phase piezoelectric element, and the like are omitted.
[0046]
Here, a positive potential is applied to the electrodes 1A and 1B for the A phase of the piezoelectric element 1, a negative potential is applied to the electrodes 1C and 1D, and the common electrode on the opposite surface is set to the GND potential. The B-phase piezoelectric elements are arranged with the phase changed by 45 degrees with respect to the A-phase. A potential having a phase difference of ¼ wavelength is applied to the A-phase piezoelectric element.
[0047]
And by applying the alternating voltage of the said conditions of the specific frequency in which the vibrating body 9 performs the resonance shown to Fig.8 (a) to the electrodes 1A, 1B, 1C, and 1D of the A-phase and B-phase piezoelectric elements, A traveling wave with a wave height can be created.
[0048]
As described in the first embodiment, the number of polarization divisions of the piezoelectric element may be changed to integrate the A-phase and B-phase piezoelectric elements, or a plurality of A-phase and B-phase piezoelectric elements may be stacked. .
[0049]
In order to create a traveling wave having a wave height of three or more waves, the polarization of the piezoelectric element is divided into multiple parts under the same idea as described above, and the phases of the A-phase and B-phase piezoelectric elements are changed accordingly. It only has to be arranged. The waveform shape of the vibrating body having a wave height of 3 waves or more is shown in the solid model of FIG. 9 as an example.
[0050]
When the vibration occurs, the contact portion with the moving body 11 becomes the wave height portion 9a. Therefore, by creating a traveling wave having a plurality of wave heights on the vibration body 9 as described above, the contact portion increases and both are less likely to wear. There are advantages.
[0051]
As described above, the present invention makes it possible to provide a motor having a large torque while taking advantage of a conventional ultrasonic motor.
[Brief description of the drawings]
FIG. 1 is a sectional view of an ultrasonic motor according to a first embodiment of the present invention. FIG. 2 is an exploded perspective view of the ultrasonic motor according to the first embodiment of the present invention. FIG. 4 is a three-dimensional perspective view modeling the shapes of the vibration source 4 and the vibrating body 9. FIG. 5 is an explanatory diagram of a vibration state by the three-dimensional model. FIG. FIG. 7 is a sectional view of an ultrasonic motor according to a third embodiment of the present invention. FIG. 8 is an explanatory diagram of a vibrating body having a wave height of two waves.
FIG. 9 shows a waveform shape of a vibrating body having a wave height of three or more waves by a three-dimensional model.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 A phase piezoelectric element 2 B phase piezoelectric element 4 Vibration source 5 Lower elastic body 6 Upper elastic body 9 Vibration body 9a Wave height part 9b Thin part 9c Outer peripheral part 10 Bolt 11 Moving body 11c Pressing contact surface 12 Interlocking gear 13 Pressing spring 14 nuts

Claims (4)

A rotation center axis;
By applying an electrical signal, the ¼ wavelength is temporally different in phase by ½ wavelength in two regions that are orthogonal to the rotation center axis and symmetrical with respect to the rotation center axis and differ by 90 degrees with respect to the center. A plurality of piezoelectric elements having a phase difference and causing longitudinal vibrations in the direction of the rotation axis and having electrodes on both sides and polarized in two or more stretchable regions are laminated at different predetermined angular phases. A vibration source sandwiching the upper and lower surfaces of the element with a pair of elastic bodies and having a pillar shape;
It is coupled to the end face of the vibration source, has a disk shape larger than the maximum outer diameter of the piezoelectric element of the vibration source, and resonates in the circumferential direction by longitudinal excitation of the vibration source and has a plurality of wave heights. A vibrating body having an outer peripheral portion for exciting traveling waves;
A movable body that is in pressure contact with the vibrating body and is driven to rotate in a predetermined direction by the traveling wave;
Ultrasonic motor with A rotation center axis;
By applying an electrical signal, the ¼ wavelength is temporally different in phase by ½ wavelength in two regions that are orthogonal to the rotation center axis and symmetrical with respect to the rotation center axis and differ by 90 degrees with respect to the center. A plurality of piezoelectric elements having a phase difference and causing longitudinal vibrations in the direction of the rotation axis and having electrodes on both sides and polarized in two or more stretchable regions are laminated at different predetermined angular phases. A vibration source sandwiching the upper and lower surfaces of the element with a pair of elastic bodies and having a pillar shape;
It is coupled to the end face of the vibration source, has a disk shape larger than the maximum outer diameter of the piezoelectric element of the vibration source, and resonates in the circumferential direction by longitudinal excitation of the vibration source and has a plurality of wave heights. A vibrating body having an outer peripheral portion for exciting traveling waves;
A movable body that is in pressure contact with the vibrating body and is rotationally driven in a predetermined direction by the traveling wave;
A vibration body portion having reduced bending rigidity is formed on the way from the connecting portion of the disk-shaped vibration body to the vibration source to the pressure contact surface with the moving body. Sonic motor. A rotation center axis;
By applying an electrical signal, the ¼ wavelength is temporally different in phase by ½ wavelength in two regions that are orthogonal to the rotation center axis and symmetrical with respect to the rotation center axis and differ by 90 degrees with respect to the center. A plurality of piezoelectric elements having a phase difference and causing longitudinal vibrations in the direction of the rotation axis and having electrodes on both sides and polarized in two or more stretchable regions are laminated at different predetermined angular phases. A vibration source sandwiching the upper and lower surfaces of the element with a pair of elastic bodies and having a pillar shape;
It is coupled to the end face of the vibration source, has a disk shape larger than the maximum outer diameter of the piezoelectric element of the vibration source, and resonates with the longitudinal excitation of the vibration source in the circumferential direction and has a plurality of wave heights. A vibrating body having an outer peripheral portion for exciting traveling waves;
A movable body that is in pressure contact with the vibrating body and is rotationally driven in a predetermined direction by the traveling wave;
A cylindrical portion that resonates with the longitudinal vibration is provided with the shape of the vibrating body coupled to the vibration source in a disc shape, and a bending rigidity is reduced with the peripheral surface portion of the disc shape as a base end. An ultrasonic motor characterized in that a flange-shaped portion is provided at the other end of the movable member, and the flange-shaped portion serves as a pressure contact surface of the movable body. The ultrasonic motor according to claim 1, wherein a portion of the vibrating body where the moving body is in pressure contact is formed in a comb shape.

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