JP2524281Y2 - Ultrasonic motor - Google Patents

Description

[Detailed description of the invention] [Industrial applications]

The present invention relates to an ultrasonic motor that excites a resonator by vibration of an ultrasonic vibrator and uses the vibration of the resonator to extract a rotational force from a rotor.

[Prior art]

An ultrasonic motor is a motor based on a new principle of obtaining a rotational force by the vibration of an ultrasonic transducer made of a piezoelectric element. This ultrasonic motor is smaller, lighter, slower, has a larger torque per unit volume, and has a lower static holding force than a conventional electromagnetic motor based on the interaction between a current and a magnetic field. It has the feature of being large. Therefore, when used at low speeds, gearless and brakeless operations are possible, and the responsiveness is excellent due to the small inertial mass. Until now, various ultrasonic motors have been proposed.For example, traveling wave ultrasonic motors that can easily switch the rotation direction are disclosed in JP-A-58-148682 and JP-A-59-96881. ing. As shown in FIGS. 2 (A) and 2 (B), the traveling wave type ultrasonic motor utilizes bending vibration on the circumference of a stator C in which a piezoelectric ceramic plate B is pasted on a disk elastic body A. The traveling wave moving with time to the stator C is excited by a two-phase or multi-phase driving method, and the rotor D pressed against the face is rotated. However, in the conventional ultrasonic motor, the resonator, that is, the material of the ultrasonic resonance vibration generating portion is often made of aluminum, duralumin, etc., which have good acoustic vibration characteristics due to their properties. The contact surface between the rotor and the rotor, that is, the friction torque transmission surface to the rotor, is liable to be worn when the contact torque is transmitted to the rotor, and the performance of the ultrasonic motor tends to deteriorate quickly with time. Had. To cope with this problem, for example, a method of coating the resonator with ceramics or manufacturing the resonator by itself (Japanese Patent Application Laid-Open No. 60-109776), an oil film is formed on the vibrating surfaces of the rotor and the resonator. Forming method (Japanese Patent Application Laid-Open No. 63-3660), providing an elastic thin film between the rotor and the resonator (Japanese Patent Application Laid-Open No. 63-124785), using a friction torque transmitting pin or vibrating element on the resonator. A method of embedding and transmitting the torque via the friction torque transmitting pin or the projecting vibrating piece has been proposed.

[Problems to be solved by the invention]

However, the above-described prior arts are not satisfactory because they have the following problems. That is, first, the technique of coating the resonator with ceramics has a problem that the current technique requires expensive equipment to perform such coating, and the cost is extremely high. In addition, the technique of manufacturing the resonator itself with ceramic is considered to be more expensive than the above-described ceramic coating in terms of cost. In the method of forming an oil film on the sliding surfaces of the rotor and the resonator, it is extremely difficult to supply a constant oil film over a long period of time so that its function can be maintained, and to control the film thickness. In addition, an oil supply device that satisfies such conditions is required, and in this case, the cost is unavoidable. In the technology of providing an elastic thin film between the rotor and the resonator, the elastic thin film generally has a problem in terms of abrasion resistance as compared with metal, so that the torque is transmitted by friction sliding between the resonator and the rotor. It is considered that the elastic thin film wears remarkably when performing the above, and therefore, the wear resistance of the elastic thin film greatly affects the life of the ultrasonic motor itself. Further, there is a problem that the adhesion between the metal and the elastic thin film is apt to be peeled off at the bonding interface due to the difference between the respective coefficients of linear expansion. In this method, the contact area between the rotor and the pin or the vibrating piece is reduced, and when the torque is transmitted through the small contact portion, the contact surface pressure is reduced. There is a problem that it is necessarily high. This is disadvantageous in terms of wear resistance, and it is considered that the limit of the torque that can be transmitted tends to be low. The present invention has been made in view of such conventional problems, and provides an ultrasonic motor having a simple configuration, excellent wear resistance and excellent acoustic vibration characteristics, good performance, low cost, and long life. The purpose is to do.

[Means for Solving the Problems]

The present invention provides an ultrasonic motor that excites a resonator by the vibration of an ultrasonic vibrator and takes out a rotational force from a rotor using the vibration of the resonator, wherein the resonator has a substantially cylindrical acoustic vibration characteristic. To transmit the excitation of the resonator to the rotor by tightly fitting a ring made of excellent material and having higher strength and higher wear resistance than the material of the resonator, and bringing the end face of the ring into contact with the rotor. As a result, the above object has been achieved.

[Action]

In the present invention, since the vibration generated at the tip of the resonator is transmitted to the rotor through a high-strength ring closely fitted to the tip, it has wear resistance and excellent acoustic vibration characteristics. Characteristics that are not necessarily compatible with each other can be shared by the resonator and the ring, and the wear resistance and the acoustic vibration characteristics can be compatible at a high level. That is, since the resonator itself is formed of a material having excellent acoustic vibration characteristics, the original performance of the ultrasonic motor can be maintained high, while the hardness of the ring is high and the “end face of the ring” As a result, vibration can be transmitted, so that an appropriate contact area with the rotor can be secured, and excellent wear resistance can be maintained. As a result, the rotation conditions on the sliding surface (torque transmitting surface) are stabilized, and the life of the ultrasonic motor itself can be maintained long, and
By stabilizing the rotation, the occurrence of abnormal noise can be eliminated.

【Example】

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In FIG. 1, a rotor 101 is fixed to a rotating shaft 102, and the rotating shaft 102 is provided on a casing 103 via a bearing B so as to be axially movable and rotatable. In this embodiment, the resonator 104 is divided into a first resonator 104a and a second resonator 104b, and the first resonator 104a and the second resonator 104b are separated from each other.
A two-layer ultrasonic transducer (diaphragm) 105 between the resonator 104b and the resonator 104b
Is pinched. Note that the ultrasonic transducer 105 may have at least one layer. The first resonator 104a is made of a material having excellent acoustic vibration characteristics (elastic) so that it vibrates in response to the vibration of the ultrasonic transducer 105. On the other hand, the second resonator 104b is made of the same material as or more rigid than the first resonator 104a. The second resonator 104b has undergone only minimal processing, and the first resonator 104b has the first
It is designed to have higher rigidity than the resonator 104a. When such a design is performed, the value of the natural frequency of the portion of the low-rigidity first resonator 104a differs from the value of the natural frequency of the portion of the high-rigidity second resonator 104b. Can excite a mode in which only the low-rigidity first resonator 104a vibrates violently. Therefore, the casing 103 is provided via the flange 107 and the fixing bolt 108 provided on the second resonator 104b which hardly vibrates.
Thus, an ultrasonic motor that hardly transmits vibration to the casing 103 can be obtained. The first and second resonators 104a and 104b are integrally fixed by bolts 106 with the ultrasonic oscillator 105 therebetween. By the way, the first resonator 104a is formed with a conical concave portion 112, and the vibration is amplified by the horn effect. A ring 114 is tightly fitted to the tip of the recess 112. The cross-sectional shape of the ring end surface 114a is an arc shape in this embodiment, but may be a tapered shape or the like. Since the end surface 101a of the rotor 101 comes into contact with the ring 114 while being deformed, the end surface 101a is a conical surface that is slightly inclined in order to effectively extract the vibration displacement of the ring 114. Note that the inclination of the rotor 101 is not always a necessary configuration,
It may be a plane. The ring 114 is made of a material having a high hardness, for example, a material such as steel or ceramics to prevent abrasion. It should be noted that even if the ring 114 is not necessarily made of a material of high hardness itself, the end surface 114a is subjected to a surface effect treatment for wear prevention, such as heat treatment, alumite treatment, hard chrome plating treatment, or the like. It may be something. Note that a screw 102a is cut in the rotating shaft 102, and a nut 109 is screwed into the screw 102a. Also, two spacers 111 urged in the separating direction by the spring 110
Is provided in contact with the bearing B and the nut 109, and the nut 109
, The urging force of the spring 110 is changed, and the pressing force between the end surface 101a of the rotor 101 and the end surface 114a of the ring 114 is made variable. According to this embodiment, since the resonator itself is formed of a material having excellent acoustic vibration characteristics, the vibration of the vibrator can be transmitted to the rotor satisfactorily, and an efficient ultrasonic motor can be realized. be able to. On the other hand, since the hardness of the ring 114 is high and the ring 114 has abrasion resistance, the effect of stabilizing the rotation condition with the vibration force (torque transmitting surface) and extending the life of the ultrasonic motor can be obtained. Further, the generation of abnormal noise can be reduced by stabilizing the rotation.

【The invention's effect】

As described above, according to the present invention, it is possible to achieve both improvement of wear resistance and improvement of acoustic vibration characteristics with a simple configuration, and to obtain an inexpensive and long-life ultrasonic motor. An excellent effect is obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a configuration of an ultrasonic motor according to an embodiment of the present invention, and FIGS. 2A and 2B are views for explaining the principle of a conventional traveling wave type ultrasonic motor. It is a perspective view. 101 ... rotor, 102 ... rotating shaft, 103 ... casing,
B ... bearing, 104 ... resonator, 104a ... first resonator, 104
b: second resonator, 105: ultrasonic transducer, 112: recess, 114: ring, 114a: ring end face.

Claims (1)

(57) [Scope of request for utility model registration] 1. An ultrasonic motor which excites a resonator by vibration of an ultrasonic vibrator and takes out a rotational force from a rotor using the vibration of the resonator, wherein the resonator has a substantially cylindrical acoustic vibration characteristic. And a ring having higher strength and higher wear resistance than the material of the resonator is closely fitted to the rotor contact part of the resonator, and the end face of the ring is brought into contact with the rotor. An ultrasonic motor for transmitting excitation of a resonator to a rotor.