JPH0834700B2 - Ultrasonic motor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary driving ultrasonic motor.

2. Description of the Related Art In an ultrasonic rotary motor, the friction surface of a ring-shaped vibrating body to which a piezoelectric element is bonded and the friction surface of a moving body are brought into contact and pressed against each other, and the surface displacement of the friction surface of the vibrating body causes an elliptical motion. By controlling the vibration mode of the vibrating body with a piezoelectric element so that the rotational movement is given to the moving body. The ultrasonic motor based on such a driving principle does not generate a magnetic field, whereas a conventional motor rotates due to the interaction of an electric current and a magnetic field. From the principle, it is possible to generate high torque at low speed, the weight of the moving body can be selected small, the response is high because the inertia is small, and the friction is the driving force, so the holding force at the time of stop is great. Yes, it is expected as a general-purpose motor especially for low speed applications.

FIG. 3 is a perspective view of main constituent parts for showing the driving principle of the ultrasonic motor. The vibrator 1 has a ring-shaped protrusion 2 for amplifying the vibration amplitude and increasing the driving efficiency.
Is provided, and a large number of grooves are provided in this projection, and the upper surface of this projection serves as the drive friction surface 3 of the vibrating body. In this vibrating body, a first piezoelectric ceramic 5 provided with an electrode 4 divided into eight in the rotation direction and a second piezoelectric ceramic 7 similarly provided with an electrode divided into eight were arranged at a half of a pitch angle of 45 ° of this electrode. It is made to slip and adhere. By applying alternating voltage with a phase difference of 90 ° to the electrodes, a traveling wave in the rotating direction is generated in the piezoelectric ceramic, and the vibration is transmitted to the vibrating body, causing elliptical vibration on the driving friction surface. On the other hand, a lining material 10 forming a friction surface is adhered to the moving body 9 attached to the rotary shaft 8, and when this is excited while being pressed against the friction surface 3 of the vibrating body, the moving body 9 is rubbed. It receives and rotates. Here, as motor components, the vibrating bodies 1 to 3 function as a stator (stator) 11, and the moving body 9 and the lining material 10 function as a rotor (rotor) 12.

FIG. 4 is a cross-sectional view showing a conventional example of an ultrasonic motor. A lining material 10 adhered to a moving body 9 into which a rotary shaft 8 is press-fitted is attached to a friction surface 3 of a vibrator 1 to which a piezoelectric element 13 is adhered.
Are in contact. In order to generate a pressing force on the drive friction surface 3, a spacer 17 and a plain washer 18 are interposed between an inner ring 15 of a ball bearing 14 mounted on the stator side and a C ring 16 mounted on the end of the rotary shaft 8. A bending washer 19 which acts as a spring is inserted, and the lining material of the rotor is strongly pressed against the drive friction surface 3 by the spring action of the bending washer. The vibrating body 1, which is a stator, is attached to the motor mounting board 20 with screws 21 at a position where it hits a node of the vibration.

Problems to be Solved by the Invention In such a conventional example, the strong thrust force necessary for pressing the drive friction surface is received by the bearing portion of the rotary shaft via the rotary shaft, and particularly in the stationary state, the strong thrust force is always received. Therefore, there was a problem in the life of the bearing. In particular, this is a big problem in the case of a ball bearing which has been conventionally used as a bearing for a small motor. Further, there is a drawback that the thrust load applied to the rotary shaft causes fluctuation in the pressing force of the driving friction surface. The present invention provides an ultrasonic motor that solves the above-mentioned problems by devising the structure of the motor in view of such matters.

Means for Solving the Problems In order to solve such problems, the present invention provides a stator composed of a vibrating body having a piezoelectric element and a rotor serving as a moving body in an axial direction via a friction surface. In the rotary ultrasonic motor that is pressed, the rotor is placed between the two stators,
A plurality of pressing means such as springs corresponding to each of the two opposing friction surfaces are provided, and these friction surfaces are sandwiched by the motor housing, and load fluctuations in the axial direction of the rotating shaft are absorbed by the plurality of pressing means. As a result, the reaction force of the pressing force of the friction surface and the reaction force of the axial load of the rotary shaft are not directly applied to the bearing of the rotary shaft to which the rotor is attached.

Action The present invention thus provides two stators as drive sources,
Therefore, a structure is provided in which two driving friction surfaces are provided, a rotor is arranged between them, and a plurality of pressing means such as springs corresponding to each of the two opposing friction surfaces are provided to sandwich these friction surfaces with the motor housing. Thus, the reaction force of the pressing force of the friction surface can be taken up by the motor housing. In the structure having only one pair of stator and rotor as in the conventional example, the reaction force of the pressing force of the friction surface must be received by the rotary bearing portion of the rotor, but according to the structure of the present invention, the friction surface is used. Since the motor housing bears the reaction force of the pressing force of, the reaction force is not applied to the rotary bearing portion.

Further, particularly, the load fluctuation in the axial direction of the rotating shaft is absorbed by the plurality of pressing means corresponding to each of the two opposing friction surfaces, so that the pressing force of the driving friction surface is changed against the fluctuation of the thrust load of the rotating shaft. It is not subject to fluctuations and can be used stably under a wide range of load conditions.

First Embodiment FIG. 1 is a sectional view of an ultrasonic motor showing a first embodiment of the present invention. In this embodiment, the rotor arranged between the two stators is divided into two parts, each of which is fixed to the rotary shaft by a thin leaf spring. Outer rings of ball bearings 25 and 26 are respectively fitted to a motor cylinder 27 and a side plate 24 which constitute the motor housing 22, and a rotary shaft 8 is fitted to an inner shaft thereof. The vibrating body 1 serving as a stator is supported and fixed to the motor housing at a position corresponding to a node of the vibration (supported and fixed to the motor cylinder 23 at 27 parts and to the side plate 24 at 28 parts. Screws for are not shown). The lining material 10 of the rotor 9 is pressed against the driving friction surface 3 of the stator by a thin leaf spring 29. The thin leaf spring 29 also fixes the rotor 9 to the rotary shaft 8 with a mounting bush 30. It also plays a role in fixing the rotor and rotating shaft in the rotating direction by utilizing the rigidity of the thin leaf spring in the plate thickness direction. In such a configuration, the reaction force of the pressing force of the drive friction surface is taken up by the motor housing, and this reaction force is not applied to the bearing portion of the rotating shaft. As described above, according to this configuration, there is no problem of reliability due to the constant static load applied to the bearing portion at the same time, and even when the thrust load of the rotating shaft fluctuates, this fluctuation directly affects the pressing force of the driving friction surface. Since it has no effect, it can be used for a wide range of load conditions.

FIG. 2 is a sectional view of an ultrasonic motor showing a second embodiment of the present invention, in which the rotor is directly fixed to the rotary shaft and
A spring is provided between one stator and the motor housing. A lining material 10 that contacts the driving friction surface 3 of the stator 1 is adhered to both surfaces of the rotor 9, and the rotor itself is press-fitted and fixed to the rotary shaft 8. On the other hand, the stator 1 is fixed to the housing in the rotational direction by pins 31 and springs 32. The second embodiment requires only one rotor as compared with the first embodiment, so that the structure is simple and the dynamic balance of the rotor portion can be easily obtained. Furthermore, by designing the mechanical impedance between the vibrating body, the lining material, and the moving body appropriately, the rotor can be configured with a small rotor, so the inertial force is small and the response is excellent. Can be generated.

Although the details of the bearings used in these examples have not been described, the present invention is directed to, for example, the axial displacement of the rotary shaft.
It does not prevent the use of additional means such as restraining by applying axial preload to the angular contact type ball bearing. In this case, according to the configuration of the present invention, since the rotary shaft is easily displaced in the axial direction before the preload assembly, the bearing can be conveniently incorporated without being over-constrained by the preload assembly. Further, it goes without saying that there is an effect that the pressing force of the driving friction surface is not affected by the fluctuation of the thrust load of the rotary shaft.

In addition, the present invention, within the scope of the present invention,
For example, providing four stators does not hinder the construction of a higher torque ultrasonic motor by forming multiple components.

EFFECTS OF THE INVENTION As described above, according to the present invention, it is possible to provide an ultrasonic motor having high reliability of the bearing, stable without being affected by the fluctuation of the thrust load, and having high torque and excellent responsiveness. It is a thing.

[Brief description of drawings]

1 and 2 show the first and second aspects of the present invention, respectively.
FIG. 3 is a sectional view of an ultrasonic motor showing an embodiment of the present invention, FIG. 3 is a perspective view illustrating the driving principle of the ultrasonic motor, and FIG. 4 is a sectional view of an ultrasonic motor showing a conventional example. 1 ... vibrating body (stator), 3 ... friction surface of vibrating body, 9 ...
… Movable body (rotor), 10 …… lining material, 13 …… piezoelectric element, 29,32 …… spring, 22 …… motor housing, 25,26
……bearing.

Claims (3)

[Claims] 1. A rotary ultrasonic motor having a stator composed of a vibrating body having a piezoelectric element and a rotor serving as a moving body pressed axially through a friction surface. A rotor is arranged between the children, and a plurality of pressing means such as springs corresponding to each of the two opposing friction surfaces are provided, and the friction surfaces are sandwiched by the motor housing. By absorbing the fluctuations by the plurality of pressing means, the reaction force of the pressing force of the friction surface and the reaction force of the axial load of the rotary shaft are not directly applied to the bearing of the rotary shaft to which the rotor is attached. An ultrasonic motor characterized by the above. 2. A rotor arranged between two stators is divided into two parts, each of which is fixed to a rotary shaft by a thin leaf spring to serve as a friction surface pressing means. The ultrasonic motor according to claim 1. 3. A rotor is directly fixed to a rotary shaft, and a spring is provided between the two stators and the motor housing,
The ultrasonic motor according to claim 1, wherein the ultrasonic motor is a pressing means for the friction surface.