JPH02303372A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To suppress fluctuation of rotation and torque by arranging an auxiliary pressurizing member between a spring means and a mover. CONSTITUTION:An ultrasonic motor comprises a housing 1, a stator having a piezoelectric element 14, a rotary shaft 20, a mover 24 and a bellevile spring 30 mounted on the rotary shaft 20, and the like. An auxiliary pressurizing member 34 is placed between the belleville spring 30 and the mover 24 and the ring projection 35 thereof is engaged with the mover 24 from a position immediately above the contact faces of the stator 6 and the mover 24. By such arrangement, the stator 6 and the mover 24 are prevented from curving.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an ultrasonic motor configured to drive a movable element by elastic traveling waves generated in a stator. This relates to a structure that pressurizes the child.

[Prior art] As a conventional ultrasonic motor of this type, there is a
One example is the technology published in Publication No. 887.

FIG. 3 is a vertical sectional view showing a conventional ultrasonic motor, FIG. 4 is a partial sectional view showing an enlarged contact area between the stator and the movable element in the ultrasonic motor shown in FIG. 3, and FIG. 5 is an explanatory diagram showing the distribution of the pressing force of the disc spring used in the ultrasonic motor of FIG. 4. FIG.

In FIG. 3, 41 is a case that forms the outer shell of the ultrasonic motor, 42 is a cover that closes the case 41, 43 is a stator,
44 is a piezoelectric element disposed on the stator 43, 45 is a movable element connected to the stator 43 via a liner 46, and 47 is a rotating shaft that rotates together with the movable element 45. A movable element 4 is provided on the lower side of the large diameter flange 48 of the rotating shaft 47.
A disc spring 50 that presses against the thin wall portion 49 of 5 is disposed.

Further, a shim 52 is held at the lower part of the rotating shaft 47 by a snap ring 51, and by selecting the thickness of the shim 52, the pressing force of the disc spring 50 can be adjusted as appropriate.

In the conventional ultrasonic motor configured as above,
When a high frequency voltage is applied to the piezoelectric element 44, the piezoelectric element 4
As the stator 4 deforms, an elastic traveling wave is generated in the stator 43, and this elastic traveling wave causes an elliptical motion to occur at a mass point on the surface of the stator 43. As a result of this elliptical movement, a frictional force is generated on the contact surface between the stator 43 and the movable element 45, and a rotational moment acts on the movable element 45 due to the frictional force, and the rotating shaft 47 is rotated integrally with the movable element 45. be rotated.

[Problems to be Solved by the Invention] Incidentally, the torque output of this type of ultrasonic motor is generally determined by the friction coefficient between the stator 43 and the movable element 45 and the disc spring 5.
It depends on the pressing force of 0. However, in the conventional ultrasonic motor, the pressing force of the disc spring 50 acts on the inside of the contact portion of the stator 43 and the movable element 45, so the pressing force causes the motor to move, as shown in an enlarged view in FIG. Thin wall part 4 of child 45
9 and the thin wall portion 54 of the stator 43 are respectively curved, and the stator 43 and the movable element 45 are pressed into contact with each other in a state of partial contact.

Furthermore, the disc spring 50 has a fifth characteristic due to its own spring characteristics.
As shown by the arrows in the figure, since the pressing force in the circumferential direction is non-uniform, it is difficult to press the movable element 45 against the stator 43 with uniform force at each part. Therefore, stator 4
The friction coefficient and pressure contact force between the movable element 3 and the movable element 45 become unstable, and uneven rotation or torque tends to occur.As a result, the ultrasonic motor cannot achieve high output.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an ultrasonic motor in which a stator and a movable element are always brought into pressure contact with each other at a stable contact surface to prevent uneven rotation and torque, and thereby to obtain high output. .

[Means for Solving the Problems] An ultrasonic motor according to the present invention includes a stator that generates an elastic traveling wave using a piezoelectric element, and a movable motor that is arranged so as to be in elastic contact with the stator and is driven by the elastic traveling wave. a spring means for pressurizing the movable element toward the stator; and a spring means interposed between the spring means and the movable element, the pressing force of the spring means being applied to a position approximately equal to the contact surface of the stator and the movable element. and an auxiliary member for applying pressure to the contact surface.

[Function] According to the ultrasonic motor of the present invention, the pressurizing auxiliary member is interposed between the spring means and the movable element, and applies the pressurizing force of the spring means at approximately the same position as the contact surfaces of the stator and the movable element. In order to transmit the force to the contact surfaces, the stator and mover are prevented from bending, and the pressing force of the spring means acts uniformly on each part of the contact surfaces of the stator and mover. Therefore, the stator and the movable element are always pressed against each other via a stable contact surface, rotational unevenness and torque unevenness are suppressed, and as a result, high output can be obtained.

[Example] Hereinafter, an example embodying the present invention will be described based on the drawings.

FIG. 1 is a vertical sectional view of an ultrasonic motor according to an embodiment of the present invention, and FIG. 2 is an ultrasonic motor according to another embodiment of the present invention in which the connection structure between the movable element and the rotating shaft is different from that in FIG. 1. FIG. 3 is a longitudinal cross-sectional view showing the motor.

As shown in FIG. 1, the housing 1 of the ultrasonic motor of this embodiment includes a substantially disk-shaped base 2, a side wall tube 3 erected and fixed on the outer periphery of the base 2, and a side wall tube 3. It consists of a lid member 4 screwed onto the inner periphery of the upper end.

An inner hole 7 of a stator 6 is inserted into the central annular portion 5 of the base 2 . The stator 6 is integrally constructed of a small-diameter ring portion 8, a large-diameter ring portion 9, and a thin-walled portion 10 made of an elastic metal material such as phosphor bronze. The small-diameter ring portion 8 is fixed to the support surface 11 of the base 2 by screws 12 while being joined to the support surface 11 of the base 2 . A large number of comb teeth 13 are protruded from the upper surface of the ring portion 9 at a constant pitch over the entire circumference.

A piezoelectric element 14 formed into a ring shape from a ceramic material or the like is fixed to the lower surface of the large-diameter ring portion 9 of the stator 6 via a conductive adhesive (not shown). and,
When a high frequency voltage is applied to the piezoelectric element 14, elastic traveling waves, that is, ultrasonic vibrations, are generated in the large diameter ring portion 9 of the stator 6 as the piezoelectric element 14 expands and contracts.

A bearing 17 is press-fitted into the central opening 16 of the base 2. Further, an insertion hole 18 is formed in the center of the lid member 4, and a bearing 19 is fixed thereto. The rotating shaft 2 is connected to the bearing 17 and the bearing 19.
0 is inserted and supported. The rotary ring 20 includes an output portion 21 that projects outside the housing 1 and a large-diameter collar portion 22 that contacts the bearing 19, and movement toward the output portion 21 is restricted by the large-diameter collar portion 22. .

A movable element 24 is inserted through the rotary ring 20 so as to be joined to the stator 6 from above.

The movable element 24 is made of a metal material such as aluminum, and has a ring-shaped protrusion 26 projecting downward from its outer periphery. The lower surface of the ring-shaped convex portion 26 is in contact with the comb teeth 13 of the stator 6 via the liner 28.

A disc spring 30 , a first rubber sheet 31 , and a pressurizing auxiliary member 34 are provided between the movable element 24 and the large diameter flange 22 of the rotating shaft 20 .
and a second rubber sheet 29 are stacked vertically.

The disc spring 30 is provided with a locking hole 33 that fits into a plurality of locking protrusions 32 protruding from the lower surface of the large-diameter collar portion 22, and is prevented from rotating with respect to the rotating shaft 20 by the locking hole 33. This results in
The movable element 24 is connected to the rotating shaft 20 via a pressurizing auxiliary member 34 so as to be integrally rotatable therewith. The disc spring 30 constitutes the spring means of this embodiment, and its elastic force causes the pressurizing auxiliary member 3 to
4 pressurizes the movable element 24 against the stator 6. Note that the pressing force of the disc spring 30 is adjusted as appropriate by adjusting the amount of tightening of the lid member 4.

The pressurizing auxiliary member 34 is made of a metal material such as iron, which has higher rigidity than the movable element 24 made of aluminum or the like, and has a larger mass than the movable element 24. Furthermore, a ring-shaped protrusion 35 is provided on the outer periphery of the pressurizing auxiliary member 34 so as to protrude downward, the ring-shaped protrusion 35 coming into contact with the upper surface of the ring-shaped protrusion 26 of the movable element 24 via the second rubber sheet 29 . The pressurizing auxiliary member 34 is interposed between the disc spring 30 and the movable element 24, and the ring-shaped protrusion 35 allows the disc spring 3 to
It is configured to transmit a pressing force of 0 to the contact surfaces of the stator 6 and the movable element 24 at substantially the same position as the contact surfaces.

Note that the first rubber sheet 31 prevents vibration noise between the disc spring 30 and the pressurizing auxiliary member 34 due to the vibration of the movable element 24. Further, the second rubber sheet 29 prevents vibration noise between the movable element 24 and the pressurizing auxiliary member 34.

Next, the operation of the ultrasonic motor of this embodiment configured as described above will be explained.

When high frequency power is applied to the piezoelectric element 14 fixed to the stator 6, the piezoelectric element 14 is expanded and contracted, and an elastic traveling wave is generated in the stator 6. This elastic traveling wave is transmitted to the stator 6
In the process, the amplitude of the elliptical motion that generates an elastic traveling wave is expanded by the comb teeth 13 of the large-diameter ring portion 9 . Then, due to the elliptical movement of the second mass point on the surface of the L tooth 13, the stator 6 and the mover 24
Frictional force is generated on the contact surface. Then, a rotational moment acts on the movable element 24 due to this frictional force, whereby the movable element 24 and the rotating shaft 20 are rotated together.

By the way, in the ultrasonic motor of this embodiment, the pressurizing auxiliary member 34 is interposed between the disc spring 30 and the movable element 24, and its ring-shaped protrusion 35 contacts the contact surface of the stator 6 and the movable element 24. Since the movable element 24 is engaged from the position directly above, unlike the conventional case, the stator 6 and the movable element 24 are prevented from bending, and the pressing force of the disc spring 30 is applied along the ring-shaped protrusion 35 to the stator. 6 and the movable element 24, it acts uniformly on each part of the contact surface. Therefore, the stator 6 and the movable element 24 are always pressed into contact with each other through a stable contact surface, rotational unevenness and torque unevenness are suppressed, and as a result, high output can be obtained.

Further, a pressurizing auxiliary member 34 is interposed between the disc spring 30 and the movable element 24 to apply the pressing force of the disc spring 30 to the ring-shaped protrusion 35.
Even if the voltage applied to the piezoelectric element 14 is set high, there is no risk of natural vibrations having a frequency different from that of the stator 6 occurring in the movable element 24 . Therefore, the output of the ultrasonic motor can be increased while preventing abnormal noise from the disc spring 30 and the like. Moreover, in this embodiment, the pressurizing auxiliary member 34 is made of a material with higher rigidity than the movable element 24 and has a larger mass than the movable element 24, so that the vibration of the movable element 24 is The pressure is less likely to be transmitted to the auxiliary member 34, disc spring 30, etc.

In the above embodiment, the mover 24 is integrally and rotatably connected to the rotary shaft 20 through the connection between the large-diameter collar portion 22 and the disc spring 30, but the present invention is not limited to this. Instead, it is also possible to connect the movable element 24 and the rotating shaft 20 with the structure shown in FIG. That is, in another embodiment shown in FIG. 2, the lower part 37 of the rotating shaft 20 is formed into a drum-like cross section with both sides cut away, and the mover 24 is attached to the lower part 37 of the rotating shaft 20 so that it cannot rotate relative to the lower part 37 of the rotating shaft 20. is inserted into. According to this connection structure, the movable element 24 is connected to the rotating shaft 2.
0, the rotational moment of the movable element 24 can be efficiently transmitted to the rotating shaft 20. Further, unlike the example shown in FIG. 2, the same effect as described above can be obtained even if the lower part of the rotary shaft 20 is formed into a spline shape and the movable element 24 is inserted therein so as not to be relatively rotatable.

Furthermore, although the ultrasonic motor of the above embodiment is configured so that the movable element 24 performs rotational motion, the present invention can be applied to a linear type ultrasonic motor in which the movable element is configured to perform linear motion. It is also possible to convert

[Effects of the Invention] As described in detail above, the ultrasonic motor of the present invention includes a stator that generates an elastic traveling wave by deformation of a piezoelectric element, and a stator that is arranged so as to come into elastic contact with the stator. A movable element driven by a movable element, a spring means for pressurizing the movable element toward the stator, and a spring means interposed between the spring means and the movable element, the pressing force of the spring means being applied to the contact between the stator and the movable element. Since it is composed of an auxiliary member that applies pressure to the contact surface at almost the same position as the surface, the stator and mover can always be brought into pressure contact with a stable contact surface, preventing uneven rotation and torque. This provides an excellent effect in that high output can be obtained.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of an ultrasonic motor according to an embodiment of the present invention, and FIG. 2 is an ultrasonic motor according to another embodiment of the present invention in which the connection structure between the movable element and the rotating shaft is different from that in FIG. 1. FIG. 3 is a vertical cross-sectional view showing a conventional ultrasonic motor.
FIG. 4 is a partial cross-sectional view showing an enlarged view of the contact area between the stator and the movable element in the ultrasonic motor shown in FIG. 3, and FIG.
FIG. 3 is an explanatory diagram showing the distribution of the pressing force of the disc spring used in the ultrasonic motor shown in the figure. In the figure, 6: stator, 14: piezoelectric element, 24: mover, 30: disc spring, 34: pressurizing auxiliary member. In the drawings, the same reference numerals and the same symbols indicate the same or equivalent parts. Patent applicant: 1 person other than Aisin Seiki Co., Ltd.

Claims (2)

[Claims] (1) A stator that generates an elastic traveling wave by deformation of a piezoelectric element, a movable element that is arranged to come into elastic contact with the stator and is driven by the elastic traveling wave, and a movable element that moves the movable element in the direction of the stator. A pressurizing auxiliary member that is interposed between the spring means and the movable element and transmits the pressurizing force of the spring means to the contact surfaces of the stator and the movable element at substantially the same position as the contact surfaces of the stator and the movable element. An ultrasonic motor comprising: (2) The ultrasonic motor according to claim 1, wherein the pressurizing auxiliary member is made of a material having higher rigidity than the movable element and has a larger mass than the movable element.