JP3278954B2 - Ultrasonic motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic motor having an improved joining structure between an elastic body constituting a stator and an electromechanical transducer.

[0002]

2. Description of the Related Art Conventionally, a traveling-wave type ultrasonic motor of this type has an electro-mechanical converter for converting electric energy into mechanical motion, for example, a piezoelectric body, as is well known in Japanese Patent Publication No. 1-17354. Element (hereinafter, sometimes referred to as piezoelectric body)
A traveling wave is generated on the drive surface of the elastic body by utilizing the expansion and contraction of the elastic body, and the traveling body is driven by the traveling wave under pressure contact with the drive surface.

The elastic body is integrated by joining to the piezoelectric body, whereby the elastic body is excited by the vibration of the piezoelectric body. Since the piezoelectric body and the elastic body are different materials, they often have different coefficients of thermal expansion, and the amount of expansion with respect to the temperature change is different, so that the stator may be deformed due to temperature fluctuation. To prevent this phenomenon, see
As disclosed in Japanese Patent Application No. 0-62883, it has been proposed to make the thermal expansion coefficients of an elastic body and an electrostrictive element substantially the same.

[0004]

However, in the above-mentioned prior art, the thermal expansion coefficients of the elastic body and the piezoelectric body are made substantially the same, but the adhesive layer existing therebetween is not considered. The thermal expansion coefficient of the adhesive is generally 1 to 2 orders of magnitude larger than the thermal expansion coefficients of metals and piezoelectrics. Therefore, the thermal expansion coefficient of the adhesive layer is often different from that of the elastic body or the piezoelectric body. In this case, the deformation amount of the adhesive layer with respect to the temperature change is different from the deformation amount of the elastic body or the piezoelectric body. I was Since the adhesive used for bonding has a role of reliably transmitting vibration of the piezoelectric body to the elastic body, it is preferable that the adhesive has relatively hardness. Could not be absorbed, which could deform the stator.

FIG. 2 is a view for explaining deformation of the stator when the temperature of the adhesive layer is higher than that of the elastic body or the piezoelectric body when the coefficient of thermal expansion is larger than that of the elastic body or the piezoelectric body. Adhesive layer 13
Since the amount of deformation is larger than that of the elastic body 11 or the piezoelectric body 12, the joint surface 11b of the elastic body 11 is subjected to shear stress, and the joint surface 11b is pulled to the outer diameter side.
Since no external force is applied to the elastic body 11 except for the joining surface 11b, the inner surface of the driving surface 11a (the left side in FIG. 2) is eventually deformed into a concave shape.

The adhesive layer 13 exists between the elastic body 11 and the piezoelectric body 12, but when the rigidity of the elastic body 11 and the piezoelectric body 12 is compared, the elastic body 11 is larger due to the material, thickness and the like. The driving surface of the elastic body 11 (referred to as an elastic body driving surface)
The inner diameter side of 11a is concavely deformed. Therefore, as shown in FIG. 2, when the elastic body driving surface 11a is brought into contact with the sliding surface 22a of the moving element 2 (referred to as a moving element sliding surface), the outer diameter side of the moving element 2 comes into contact with the inner diameter side. Is separated from the elastic body driving surface 11a, and a gap 22b is generated.

[0007] As described above, the contact area between the slider sliding surface 22a and the elastic body driving surface 11a decreases as the temperature fluctuates, thereby reducing the starting torque and power consumption of the ultrasonic motor, the power consumption of the slider, and the like. There has been a problem that the performance of the driving efficiency fluctuates.

The present invention has been made in order to solve the above problems.
By reducing the deformation of the elastic body due to temperature fluctuation, it is possible to secure the bonding area with the moving element, and even if the temperature fluctuates, it is possible to reduce the starting torque, the power consumption, and the change in the driving efficiency of the moving element. It is an object of the present invention to provide an ultrasonic motor capable of obtaining substantially the same performance.

[0009]

According to a first aspect of the present invention, there is provided an electro-mechanical conversion element which is excited by a drive signal and a driving surface which is joined to the electro-mechanical conversion element and which is driven by the excitation. An ultrasonic motor comprising: a stator having an elastic body that generates a traveling vibration wave at a position thereof; and a moving member that comes into pressure contact with a driving surface of the elastic body and is driven by the traveling vibration wave. joining the the transducer the elastic body, the electro - an adhesive layer using an adhesive having substantially the same thermal expansion coefficient as mechanical converting element or said elastic member is provided, the adhesive hardening of the adhesive used in the adhesive layer By setting the subsequent coefficient of thermal expansion to 5.0 × 10 ⁻⁵ / ° C. or less ,
The elastic body can be used both when driven at normal temperature and when driven at high temperature.
An ultrasonic motor wherein surface contact between the moving element and the moving element is maintained .

According to a second aspect of the present invention, there is provided a stator having an electro-mechanical transducer which is excited by a drive signal and an elastic member which is joined to the electro-mechanical transducer and generates a progressive vibration wave on a drive surface by the excitation. A moving member that is brought into pressure contact with a driving surface of the elastic body and is driven by the traveling vibration wave;
In the ultrasonic motor including, the electro-mechanical conversion element and the elastic body is bonded, an adhesive layer using an adhesive having substantially the same thermal expansion coefficient as the electro-mechanical conversion element or the elastic body is provided, Adhesive curing of the adhesive used for the adhesive layer
Making the thermal expansion coefficient after the 9.0 × 10 ^-5 / ° C or less
The front of both the room temperature drive and the high temperature drive
An ultrasonic motor characterized in that surface contact between the elastic body and the moving element is maintained .

[0011]

According to the above means, the piezoelectric body 12 and the elastic body 1
Since the thermal expansion coefficient of the adhesive used for bonding with the first and second piezoelectric elements 1 and 2 is substantially the same as that of the piezoelectric body 12 and the elastic body 11, the expansion amount and the contraction amount of the elastic body 11, the piezoelectric body 12 or the adhesive layer 13 due to the temperature change. Can be made almost the same. Thereby, the deformation of the elastic body 11 can be prevented, the reduction in the contact area between the elastic body driving surface 11a and the slider sliding surface 22a due to the temperature fluctuation is improved, and even if the temperature fluctuates, the starting torque and the power consumption are reduced. Thus, the change in the driving efficiency of the moving element 2 can be reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments will be described in more detail with reference to the drawings and the like. FIG. 1 is a view showing a first embodiment of an ultrasonic motor according to the present invention. Stator 1
A piezoelectric body 12 excited by a drive signal;
And an elastic body 11 that generates a progressive vibration wave on the drive surface 11a by the excitation. Stator 1
Are supported by a support (not shown).

The moving element 2 is joined to a moving element base material 21 connected to a moving target object (not shown),
The sliding member 22 is in pressure contact with the driving surface 11a of the elastic body 11 by the sliding surface 22a. The piezoelectric body 12 and the elastic body 11 are formed of an adhesive layer 13 using an adhesive having substantially the same coefficient of thermal expansion as the piezoelectric body 12 or the elastic body 11.
Are joined by

According to the above configuration, the adhesive used for joining the piezoelectric body 12 and the elastic body 11 has a substantially same thermal expansion coefficient as that of the piezoelectric body 12 or the elastic body 11, so that the temperature of the adhesive is low. The amount of expansion and contraction of the elastic body 11, the piezoelectric body 12, and the adhesive layer 13 due to the fluctuation can be made substantially the same. Thereby, the deformation of the elastic body 11 can be prevented, and the elastic body driving surface 11a and the moving element sliding surface 2 due to the temperature fluctuation can be prevented.
The decrease in the contact area with the movable member 2a is improved, the starting torque is sufficiently obtained, and the driving efficiency of the moving member 2 can be improved.

There is also an effect described below. Elastic body 1
The state in which the piezoelectric body 1 and the piezoelectric body 12 are deformed by the adhesive is that residual strain is generated in the elastic body 11 and the piezoelectric body 12.
In particular, if there is residual strain in the piezoelectric body 12, extra power consumption may be required for the expansion and contraction of the piezoelectric body 12. Therefore, even by reducing the deformation of the piezoelectric body 12, it is possible to prevent an increase in current consumption and improve the driving efficiency.

Since the material of the elastic body 11 has a low coefficient of thermal expansion such as 0.1 × 10 ^{−5 to} 0.5 × 10 ⁻⁵ / ° C. at room temperature, the piezoelectric body (piezoelectric element) A material having a coefficient of thermal expansion approximately equal to 12 is commonly used. For example, invar material (about 0.1 × 10 ^{−5 to} 0.3 at room temperature range)
× 10 ^-5 / ° C) and nickel-based alloys such as 42 alloy (about 0.4 × 10 ^{-5 to} 1.0 × 10 ^-5 / ° C at room temperature)
Or an iron-based alloy such as SUS (about 0.9 × 10
^{−5 to} 1.8 × 10 ⁻⁵ / ° C.).

When bonding the piezoelectric body 12 and the elastic body 11 described above, it is preferable that the adhesive used for the adhesive layer 13 has a thermal expansion coefficient equal to that of the piezoelectric body 12 or the elastic body 11.
Specifically, as shown in Table 1, 5.0 × 10 ⁻⁵ / °
The adhesive having a thermal expansion coefficient of C or less can reduce the deformation of the stator 1 due to the temperature fluctuation, and can reduce the change in performance such as the starting torque of the ultrasonic motor, the power consumption, and the driving efficiency of the moving element 2. Good results are obtained in the reduction.

[0018]

[Table 1]

(Modifications) The present invention is not limited to the embodiments described above, and various modifications and changes are possible, which are also within the scope of the present invention. In the present embodiment, a large effect was obtained when the coefficient of thermal expansion of the adhesive was 5.0 × 10 ⁻⁵ / ° C. or less. For example, 7.0 × 10 ⁻⁵ / ° C. Even with an adhesive having a relatively small coefficient of thermal expansion such as 9.0 × 10 ⁻⁵ / ° C., the deformation of the stator 1 when the temperature fluctuates can be reduced to a certain extent, and the starting torque of the ultrasonic motor can be reduced. And the change in performance such as power consumption, driving efficiency of the moving element, and the like can be sufficiently reduced. In this embodiment, the electromechanical transducer is described as a piezoelectric element, but may be an electrostrictive element.

[0020]

As described above, according to the present invention, the temperature fluctuation can be achieved by making the thermal expansion coefficient of the adhesive used for joining the elastic body and the piezoelectric body substantially the same as that of the elastic body or the piezoelectric body. In this case, the deformation of the stator can be reduced. As a result, it is possible to prevent a reduction in the contact area between the elastic body driving surface and the slider sliding surface, and to reduce changes in performance such as the starting torque and power consumption of the ultrasonic motor and the driving efficiency of the slider. Became.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a first embodiment of an ultrasonic motor according to the present invention.

FIG. 2 is a diagram illustrating deformation of a stator when the temperature fluctuates.

[Description of sign]

 DESCRIPTION OF SYMBOLS 1 Stator 2 Moving element 11 Elastic body 11a Driving surface 12 Piezoelectric body 13 Adhesive layer 21 Moving element base material 22 Sliding material 22a Sliding surface

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-197271 (JP, A) JP-A-2-56260 (JP, A) JP-A-60-62883 (JP, A) 176496 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02N 2/00

Claims (2)

(57) [Claims] A stator having an electro-mechanical conversion element excited by a drive signal and an elastic body joined to the electro-mechanical conversion element and generating a progressive vibration wave on a driving surface by the excitation; A moving member that is brought into pressure contact with a driving surface and is driven by the traveling vibration wave; wherein the electro-mechanical conversion element and the elastic body are joined to each other; almost an adhesive layer using an adhesive of the same thermal expansion coefficient is provided, wherein the thermal expansion coefficient after bonding the curing of the adhesive and 5.0 × 10 ^-5 / ° C or less for use in the adhesive layer and the elastic member By normal temperature
In both driving and high-temperature driving, the elastic body
An ultrasonic motor characterized in that surface contact with the moving element is maintained . 2. A stator having an electro-mechanical conversion element excited by a drive signal and an elastic body joined to the electro-mechanical conversion element and generating a progressive vibration wave on a driving surface by the excitation; A moving element that is brought into pressure contact with a driving surface and driven by the traveling vibration wave; wherein the electro-mechanical conversion element and the elastic body are joined to each other, an adhesive layer using an adhesive having substantially the same thermal expansion coefficient as the elastic member is provided, wherein the thermal expansion coefficient after bonding the curing of the adhesive and 9.0 × 10 ^-5 / ° C or less for use in the adhesive layer By normal temperature
In both driving and high-temperature driving, the elastic body
An ultrasonic motor characterized in that surface contact with the moving element is maintained .