JPH0516275B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an ultrasonic motor that rotates a rotor using elastic waves formed on the surface of a solid.

(Prior Art) It is generally known that there are two types of frequencies that propagate in an elastic body: longitudinal waves and transverse waves. These longitudinal waves and transverse waves propagate independently in the elastic body, but on the surface of the elastic body, they intertwine and form elastic waves depending on the boundary conditions.

When a moving solid body is placed on the surface of an elastic body on which elastic waves have been formed, the solid body begins to move along the traveling direction of the elastic waves.

For example, in JP-A No. 58-158682, two vibrators that vibrate a ring-shaped elastic body in different directions are installed, and by vibrating each vibrator at a different phase, the inner part of the ring-shaped elastic body is An ultrasonic motor has been proposed that drives a rotating shaft inserted into the inner periphery of a ring-shaped elastic body by forming elastic waves traveling in the circumferential direction on the circumferential surface.

Also, JP-A-61-49670 and JP-A-61-49670
Japanese Patent No. 54884 discloses a device in which a piezoelectric thickness vibrator is provided with a support beam that is diagonally supported at both ends with diagonal support portions added, and the beam is vibrated to drive a rotor by friction.

(Problems to be Solved by the Invention) The technique disclosed in Japanese Unexamined Patent Publication No. 58-148682 provides a vibrator with an obliquely tapered portion, and this tapered portion frictionally drives the rotor. Therefore, in order to form a surface acoustic wave on the tapered surface of a vibrator, it is necessary to use a plurality of vibrators that vibrate in different directions. Furthermore, since the rotor is coupled by the oblique tapered surface, high pressure cannot be applied between the electrostrictive element, which is a piezoelectric element, and the rotor in order to prevent damage to the rotor.

Also, JP-A-61-49670 and JP-A-61-49670
In the technology disclosed in Publication No. 54884, since a diagonal support part exists between a piezoelectric element such as a thickness vibrator and a rotary element, when high pressure is applied between the piezoelectric element and the rotor, the diagonal support part Deformation and damage of the parts become a problem.

In an ultrasonic motor, it is necessary to apply strong pressure between the piezoelectric element and the rotor in order to obtain high torque. Therefore, in conventional ultrasonic motors, high torque could not be obtained because strong pressure could not be applied between the piezoelectric element and the rotor.

Therefore, the technical object of the present invention is to construct an ultrasonic motor that is driven by a piezoelectric element that vibrates in one direction and can apply strong pressure between the piezoelectric element and the rotor.

[Structure of the invention]

(Means for Solving the Problems) The means taken in the present invention to solve the above-mentioned technical problems consist of a piezoelectric element vibrating in the vertical direction and a rotor provided parallel to the piezoelectric element. In between, there is provided a coupler whose bottom surface is coupled to the piezoelectric element and vibrates together with the piezoelectric element, and this coupler is provided with a vibrating element that extends perpendicularly to the planes of the piezoelectric element and the rotor, and whose end abuts the flat surface of the rotor. The vibrating piece is integrally provided with a plurality of step portions formed on both sides of the vibrating piece and having different distances from the bottom surface.

(Function) When the vibrator vibrates the coupler, a plurality of vibrating pieces integrally formed on the coupler resonate. By the way, a plurality of steps are formed on both sides of this vibrating element, and the distances from the bottom of the connector differ from each other, and the action of these steps creates a difference in internal pressure between the two sides of the plurality of vibrating elements. .

At this time, each of the plurality of vibrating pieces deforms so as to cancel out this difference in internal pressure, and as a result, each of the plurality of vibrations generates a strong bending vibration.

Then, due to the bending vibration of each vibrating piece,
The tip of each vibrating piece moves in an ellipse,
Rotates the rotor that is in contact with the tip of the vibrating piece.

(Example) Examples of the present invention will be described below based on the drawings.

FIG. 1 is a front view depicting an embodiment of the ultrasonic motor of the present invention. FIG. 2 is a right side view of one embodiment of the ultrasonic motor of the present invention, and FIG. 3 is a left side view of one embodiment of the ultrasonic motor of the present invention. Also, Fig. 4 is the - of Fig. 2 or Fig. 3.
FIG.

This will be explained below with reference to FIG.

A piezoelectric ceramic 2a is attached to one end surface of a metal base 1 formed into a substantially cylindrical shape as a vibrator that vibrates in one direction in response to an electric signal. The piezoelectric ceramic 2a and the metal base 1 are mechanically and electrically connected.

Further, a common electrode 3 is formed on the surface of the piezoelectric ceramic 2a facing the base 1. A piezoelectric ceramic 2b is mounted on the surface of the common electrode 3 facing the piezoelectric ceramic 2a. The piezoelectric ceramic 2a and the common electrode 3, and the piezoelectric ceramic 2b and the common electrode 3 are both mechanically and electrically connected. Both piezoelectric ceramics 2a and 2b are cylindrical.

Furthermore, an electrode 22 is attached to the surface of the piezoelectric ceramic 2b facing the common electrode 3. Further, on the surface of the electrode 22 facing the piezoelectric ceramic 2b, a bottom surface 4a of a metallic connector 4 formed in a substantially cylindrical shape is attached. The piezoelectric ceramic 2b and the metallic connector 4 are connected to the electrode 2.
They are mechanically and electrically connected via 2.

The following description will be made with reference to FIG.

A hole 19 is formed along the axis of the base 1 in the end surface of the base 1 on which the piezoelectric ceramic 2a is attached. A female thread is cut into the inner peripheral surface of the hole 19. In addition, the piezoelectric ceramics 2a of the connector 4
A hole 21 is made along the axis of the connector 4 in the end face where the connector 4 is attached. The hole 21 passes through the connector 4, and a female thread is cut on the inner peripheral surface.

The base 1 and the connector 4 are connected by a shaft 9. One end of the shaft 9 is inserted into a hole 19 made in the base 1. A male screw is cut at one end of the shaft 9, and the shaft 9 is fixed by being engaged with a female screw cut into the inner peripheral surface of the hole 19 of the base 1.

A sleeve 20 is inserted into the shaft 9 fixed to the base 1 for insulation, and piezoelectric ceramics 2a and 2b are inserted into the outer periphery of the sleeve 20.

Furthermore, the connector 4 is inserted into the shaft 9.
A male screw is cut on the shaft 9 at a position where the connector 4 is fixed. Connector 4 is connected to hole 2 of connector 4.
By engaging the female screw cut on the inner peripheral surface of shaft 9 with the male screw cut on the outer peripheral surface of shaft 9,
Combined with base 1. And at this time, base 1
The piezoelectric ceramics 2a, 2b are sandwiched and fixed between the connector 4 and the connector 4.

This will be explained below with reference to FIG.

Two vibrating pieces 5 and 6 are formed integrally with the metal connector 4. Further, one ends of the vibrating pieces 5 and 6 are in contact with the rotor 7.

Further, on both sides of the vibrating element 5, a stepped portion 10 and a stepped portion 1 are provided.
1 is formed integrally with the connector 4. Stepped portion 10
and the stepped portion 11 are the bottom surface 4a of the connector 4 (the connector 4
and the piezoelectric ceramics 2b are formed at different distances from the contact surface. Similarly, a stepped portion 12 and a stepped portion 13 are formed integrally with the connector 4 on both sides of the vibrating piece 6. Step portion 12 and step portion 13
The connectors 4 are formed at different distances from the bottom surface 4a.

The stepped portions 10 and 13 are arranged at equal distances from the bottom surface 4a of the connector 4, and the stepped portions 11 and 12 are arranged at equal distances from the bottom surface 4a of the connector 4. is formed.

A rotor 7 is in contact with one end of the vibrating pieces 5 and 6. The rotor 7 is a cylindrical portion with both ends open. The rotor 7 is a metal member, and has an opening having a diameter slightly larger than the diameter of the shaft 9 at one end, and an opening into which the thrust ball bearing 8 is inserted at the other end. .

Elastic members 23a and 23b are bonded to both end surfaces of the thrust ball bearing 8 inserted into the opening of the rotor 7. In this embodiment, the elastic members 23a, 2
Synthetic rubber is used as 3b. The rotor 7 is bonded to the elastic member 23b so that the axes of the thrust ball bearing 8 and the rotor 7 are aligned. and,
By fitting the thrust ball bearing 8 to the outer circumference of the shaft 9, the rotor 7 is rotatably supported on the outer circumference of the shaft 9.

Furthermore, a male screw for fixing the rotor 7 is cut at one end of the shaft 9, and a nut 25 is screwed into this male screw. The rotor 7 has a thrust ball bearing 8, an elastic member 23a and a washer 24.
It is tightened and fixed with a nut 25 via. That is, the rotor 7 is held between the nut 25 and the vibrating pieces 5 and 6, and is rotatably fixed.

In this embodiment, piezoelectric ceramics 2a,
The nut 25 is tightened with a nut 26 to prevent the nut 25 from loosening due to vibrations generated by the nut 2b.

This will be explained below with reference to FIG. FIG. 5 is an electrical circuit diagram for driving the ultrasonic motor of this embodiment.

The drive circuit 14 includes an oscillation circuit 15 that oscillates at the resonant frequency of the vibrating element 11, a voltage amplification circuit 16 that amplifies the output of the oscillation circuit, a power amplification circuit 17 that amplifies the output of the voltage amplification circuit 16, a piezoelectric ceramic 2a, 2b and an impedance conversion circuit 18 for matching the power amplifier circuit 17.

The piezoelectric ceramic 2a expands and contracts in the axial direction of the shaft 9 in accordance with the voltage applied to the metal base 1 and the common electrode 3, and generates vibrations. Similarly, the piezoelectric ceramic 2b also has a common electrode 3 and an electrode 2.
The shaft 9 expands and contracts in the axial direction according to the voltage applied to the shaft 9, thereby generating vibration.

The ultrasonic motor of this embodiment uses the common electrode 3 as a reference plane, and both sides thereof (base 1 side and connector 4 side)
are manufactured so that their masses are approximately equal.
Furthermore, since the two piezoelectric ceramics 2a and 2b are driven by the common drive circuit 14, the two piezoelectric ceramics 2a and 2b repeatedly expand and contract at the same time. Therefore, the base 1 and the coupler 4 vibrate in opposite phases to each other, generating a standing wave with the common electrode 3 as a node.

This will be explained below with reference to FIG. Figure 6 shows
It is a side view of the connector 4 shown in the third figure, viewed from the direction.

The connector 4 is vibrated in the direction of arrow A by the piezoelectric ceramics 2a and 2b attached to the bottom surface 4a, and a standing wave vibrating in the direction of arrow A is formed on the surface of the connector 4. . And at this time,
Changes in internal pressure due to the vibration of the stepped portions 10 and 11 are applied to both sides of the vibrating piece 5.

The change in the internal pressure applied to both sides of the vibrating element 5 is greater at the stepped portion 10, which is located at a longer distance from the bottom surface 4a of the connector 4. Therefore, the vibrating piece 5
Due to the pressure difference applied to both sides of the vibrating piece 5 by pressures 0 and 11, the vibrating piece 5 starts to vibrate in the direction of arrow B, and a bending wave that vibrates in the direction of arrow B is formed at the tip of the vibrating piece 5.

Therefore, a standing wave is formed at the tip of the vibrating element 5, which is a combination of a standing wave in the direction of arrow A and a bending wave in the direction of arrow B. Therefore, the locus of one point C at the tip of the vibrating element 5 will draw a locus that is a combination of vibrations in the direction of arrow A and vibrations in the direction of arrow B. In this embodiment, the vibration in the direction of arrow B is excited by the vibration in the direction of arrow A. Therefore, the vibration in the direction of arrow B and the vibration in the direction of arrow A have a certain relationship, and the locus of one point C at the tip of the vibrating element 5 draws an ellipse.

In exactly the same way, both sides of the vibrating element 6 have stepped portions 12,
A change in internal pressure due to the vibration of 13 is added.

Therefore, like the vibrating element 5, a standing wave is formed at the tip of the vibrating element 6 by combining a standing wave in the direction of arrow A and a bending wave in the direction of arrow B, and a single point at the tip of the vibrating element 5 is drawn. The trajectory becomes an ellipse.

However, as shown in FIG.
2 and 13 are arranged symmetrically with respect to the axis of the shaft 9, so that the bending waves generated in the vibrating element 5 and the bending waves generated in the vibrating element 6 have opposite phases to each other.

The explanation will be given by returning to FIG. 1 again.

As described above, the rotor 7 is in contact with the tips of the vibrating pieces 5 and 6. Further, at the tips of the vibrating pieces 5 and 6, standing waves having mutually opposite phases are formed so as to cause a point C at the tips of the vibrating pieces 5 and 6 to move in an elliptical manner. Therefore, the rotor 7 receives a driving force from the tips of the vibrating pieces 5 and 6 in the circumferential direction of the rotor 7 and starts rotating.

The ultrasonic motor of this embodiment is manufactured so that the masses on both sides of the common electrode 3 are equal, using the common electrode 3 as a reference plane. Therefore, the ultrasonic motor of this embodiment vibrates using the common electrode 3 as a node. Therefore, the stress applied to the piezoelectric ceramics 2a, 2b due to vibrations of the ultrasonic motor can be reduced, and deterioration of the piezoelectric ceramics 2a, 2b over time can be suppressed.

In addition, in this embodiment, piezoelectric ceramics 2a and 2 are used as vibrators that vibrate in one direction in response to an electric signal.
Although an example using piezoelectric ceramics 2a and 2b is shown as the vibrator, it is not necessary to use piezoelectric ceramics 2a and 2b.
For example, a magnetostrictive element that vibrates in response to changes in magnetic force can also be used.

〔Effect of the invention〕

In the present invention, since the vibrating piece provided on the coupler is installed perpendicularly between the rotor and the piezoelectric element, even if a strong force is applied between the piezoelectric element and the rotor, the vibrating piece will deform. , not easy to damage. Therefore,
By applying strong pressure between the piezoelectric element and the rotor, a high torque motor can be obtained. Furthermore, since the vibrating element itself resonates in an elliptical motion mode, strong vibration of the vibrating element occurs, and stronger rotational force can be obtained.

[Brief explanation of drawings]

FIG. 1 is a front view depicting an embodiment of the ultrasonic motor of the present invention. FIG. 2 is a right side view depicting an embodiment of the ultrasonic motor of the present invention. FIG. 3 is a left side view depicting an embodiment of the ultrasonic motor of the present invention. Figure 4 is the − of Figure 2 or Figure 3.
FIG. FIG. 5 is a circuit diagram depicting a drive circuit for driving the ultrasonic motor of the present invention. FIG. 6 is a side view of the connector of the ultrasonic motor shown in FIG. 3, viewed from the direction. DESCRIPTION OF SYMBOLS 1... Base, 2a, 2b... Piezoelectric ceramics (piezoelectric element), 3... Common electrode, 4... Connector, 4a...
Bottom surface of coupler, 5, 6... Vibration piece, 7... Rotor, 8
...Thrust ball bearing, 9...Shaft, 10, 11,
DESCRIPTION OF SYMBOLS 12, 13... Step part, 14... Drive circuit, 15... Oscillation circuit, 16... Voltage amplification circuit, 17... Power amplification circuit, 18... Impedance conversion circuit, 19, 21
...hole, 20...sleeve, 22...electrode, 23a, 2
3b...Elastic member, 24...Washer, 25, 26...
Natsuto.

Claims (1)

[Claims] 1 Piezoelectric elements 2a and 2b on disks fixed to a base 1 and vibrating in the vertical direction in response to an electric signal; , a rotor 7 having a flat surface on the side where the piezoelectric element is present, and a bottom surface 4a disposed between the piezoelectric element and the rotor.
a coupler 4 coupled to the piezoelectric element and vibrating together with the piezoelectric element, the coupler extending perpendicularly to the plane of the piezoelectric element and the rotor, and having an end portion. vibrating pieces 5 and 6 that come into contact with the plane of the rotor, and a plurality of installation parts 1 formed on both sides of the vibrating pieces and having different distances from the bottom surface.
1. An ultrasonic motor characterized by integrally comprising: 0, 11, 12, and 13.