JPH04101675A - ultrasonic motor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an ultrasonic motor.

[Conventional technology]

An ultrasonic motor is a motor based on a new principle in which rotational force is obtained by the vibration of an ultrasonic vibrator made of a piezoelectric element. This ultrasonic motor is based on the interaction between electric current and magnetic field.Compared to conventional electromagnetic motors, it is smaller, lighter, and has a lower speed, and has a larger torque per unit volume, and is capable of statically holding the rotor. It is characterized by great strength. Therefore, when used at low speeds, it can be gearless or brakeless, and its small inertial mass provides excellent responsiveness, so it has recently been attracting attention as a drive source for various control devices. There is. Various ultrasonic motors have been proposed so far, but for example, a traveling wave ultrasonic motor that can easily switch the rotation direction is disclosed in Japanese Patent Application Laid-open No. 58-148682 and No. 59-9.
This method is disclosed in Japanese Patent No. 6881 and the like. The traveling wave type ultrasonic motor utilizes bending vibrations around the circumference of a stator C, which has a piezoelectric ceramic plate B attached to a disk elastic body A, as shown in Figs. 6(A) and (B>). , a traveling wave moving over time is excited in the stator C by a two-phase or multi-phase drive method, and the rotor D is pressed against the rotor C.
It rotates.

[Problems to be solved by the invention] However, these conventional traveling wave ultrasonic motors
Since both methods used bending traveling waves, the compliance of the stator as seen from the rotor was large, and while it was relatively easy to obtain a medium driving force, it was difficult to obtain a high driving force. . Furthermore, since progressive vibration waves were used, it was necessary to install a large number of piezoelectric elements in circulation in order to allow the vibration waves to progress without interruption, and as a result, a large number of lead wires had to be installed. There was also the problem of not getting any. Furthermore, in conventional ultrasonic motors that use progressive vibration waves, it is necessary in principle to always maintain a constant proportional relationship between the longitudinal wave amplitude and the transverse wave amplitude. It is difficult to freely control the longitudinal wave amplitude, which should be the driving force, and the transverse wave amplitude, which should be the supporting force of the rotor, and there is also the problem that it is difficult to control it in response to changes in the required load and speed. there were. If you try to obtain large torque with this type of ultrasonic motor, you will generally need to increase the voltage applied to the piezoelectric element, or you will need a high-voltage power supply or a high-voltage piezoelectric element, which will require a drive circuit. This poses many problems in practice, as it not only increases the size of the device but also significantly increases the cost of the device. Furthermore, since this type of ultrasonic motor uses a bending traveling wave, there are no vibration nodes in the stator, making it difficult to fix the position of the stator. Therefore, there is a problem that the vibration of the stator is transmitted to other machines outside and has an adverse effect. The present invention was made in view of these conventional problems, and it is possible to obtain a larger torque with a simpler structure, and also to prevent the propagation of ultrasonic vibrations to the outside as much as possible. The purpose is to provide an ultrasonic motor that can be used. [Means for Solving the Problems] The present invention provides an ultrasonic motor that includes a rotor, a substantially cylindrical resonator made of an elastic material that contacts the rotor, and one or more resonators that vibrate the resonator in the axial direction. an ultrasonic vibrator, and a drive circuit for vibrating the ultrasonic vibrator, the resonator and the rotor! # Generate a motion on the tactile surface equivalent to a motion combining a plurality of oscillations of the swash plate, and divide the resonator into two resonators, a first and a second resonator, to generate the ultrasonic vibrator. The first resonator is sandwiched between the first and second resonators, and the first resonator has a lower rigidity and is used to generate a vibration mode equivalent to the oscillating motion of the swash plate, and the second resonator has a higher rigidity. As a general rule, the above purpose was achieved by using it for fixing to the casing. Further, the present invention achieves the above object by forming a flange on the second resonator and using the flange for fixing to the casing in an ultrasonic motor.

【Example】

Embodiments of the present invention will be described in detail below based on the drawings. In FIG. 1, a rotor 1 is fixed to a rotating shaft 2, and the rotating shaft 2 is provided in a casing 3 via a bearing B so as to be movable in the axial direction and rotatable. A resonator 4 made of an elastic material is provided in partial contact with the end face 11 of the rotor 1 . In this embodiment, the resonator 4 is divided into a first resonator 41 and a second resonator 42, and two layers of ultrasonic transducers ( Note that the ultrasonic transducer 5 may have one or more layers. The first resonator 41 is made of an elastic material<a material with low Wl property to generate "a motion equivalent to a motion that combines multiple oscillations of the swash plate" in response to the vibrations of the ultrasonic transducer 5. has been done. Further, the first resonator 41 is provided with a conical recess 12, which is designed to reduce machinability. On the other hand, the second resonator 42 is made of a material that is the same as or more rigid than the first resonator 41. This second resonator 42 has been subjected to minimal processing, and together with the fact that the flange 7 is formed, it is designed to have higher rigidity than the first resonator 41. If such a design is carried out, the natural frequency of the first co-expanding member 41 with low rotation and ratio becomes smaller than the natural frequency of the second resonator 42 with high rigidity, so Depending on the frequency of vibration, it is possible to excite a mode in which only the first resonator 41 with low rigidity vibrates violently (a mode in which only the second resonator 42 with high thermal rigidity vibrates, or a mode in which only the second resonator 42 with high thermal rigidity vibrates). ). By providing the first and second resonators 41 and 42 with a difference in machinability, the second resonator 4□ can be made to hardly vibrate. By fixing the resonator 42 to the casing 3 via the flange 7, an ultrasonic motor in which almost no vibrations are transmitted to the casing 3 can be obtained. By the way, as described above, the first resonator 41 has the conical recess 12 formed therein, and the open end surface 13 of the first resonator 41 comes into contact with the end surface 11 of the rotor 1. Although the cross-sectional shape of the open end surface 13 is arcuate in this embodiment, it may be tapered or the like. Since the end face 11 of the rotor 1 contacts the resonator 4 while being deformed, it is formed into a slightly inclined conical face in order to effectively take out the vibration displacement of the resonator 4.
The open end surface 13 is subjected to surface hardening treatment to prevent wear, such as heat treatment, alumite treatment, hard chrome plating treatment, etc. Note that the inclination of the rotor 1 is not necessarily a necessary configuration, and may be a flat surface. 2. On the rotating shaft 2. A nut 9 is screwed into the screw 21. Also, two spacers 11, which are urged in the direction of separation by the spring 10, are provided in contact with the bearing B and the shaft 9, and by rotating the nut 9, the urging force of the spring 10 is changed, and the rotor 1
The pressing force between the end face 11 of the resonator 4 and the open end face 13 of the resonator 4 is made variable. As shown in FIG. 2, the ultrasonic vibrator 5 is provided with eight fan-shaped piezoelectric elements 51 to 58 divided on the circumference and wired as shown in the figure. Moreover, each piezoelectric element 5
A hole 15 through which the bolt 6 passes is formed in the center of each of the holes 1 to 58. The ultrasonic transducer 5 may include a plurality of fan-shaped piezoelectric elements arranged in the circumferential direction (eight pieces in the illustrated example);
The polarization directions of the piezoelectric elements may be divided into sectors. Next, the operation of this embodiment will be explained. The apparatus shown in FIG. 1 was modeled as shown in FIG. 3, and the results of FEM natural vibration analysis (computer analysis using the finite element method) are shown in FIG. No. 4121
(A) is a front view seen from the open end surface side, and (B) is a side view. As is clear from FIG. 4, the first resonator 41
The part where the conical recess 12 is formed (the open end surface 13+-132) vibrates as if two swash plates were joined vertically, while the part of the second resonator 42 It can be seen that there is almost no vibration. From this we can say the following. First, since an ultrasonic motor generally drives a rotor by the vibration of a vibrator, when the vibrator is held in a casing or the like, the vibration of the vibrator propagates to the outside,
This often had a negative impact on other i-machines. However, according to the embodiment described above, the second resonator 42 that does not vibrate
By coupling with the casing 3 at this portion, it is possible to prevent vibrations from propagating to the outside. That is, resonator 4
The resonant frequency of is determined from the toughness value depending on the shape of the first resonator 41 (the shape of the recess 12), etc., and is hardly dependent on the shape of the second resonator 42. By providing the flange 7 on the second resonator 42 and fixing it to the casing 3, a very quiet ultrasonic motor can be obtained. Second, rotational force can be efficiently extracted from the vibration mode on the first resonator 41 side. That is, in this embodiment, the configuration of the ultrasonic transducer 5 is as shown in FIG.
There are 2 pieces based on the principle of the oscillating movement of the swash plate.
It is possible to generate a phenomenon that makes it appear as if the rotors are individually connected and rotating, and rotational force can be extracted from this to the rotor 1. According to this embodiment, since the structure of the vibration source is such that the ultrasonic diaphragm 5 is held between the first and second resonators 47 and 42 and is strongly tightened with the bolts 6, It has a simple structure, low cost, high efficiency, and long life, and can secure an extremely large output per unit volume or unit weight. That is, with this structure, driving force is obtained by vibration in the axial direction, so it is possible to obtain a much higher driving force than a conventional traveling wave type ultrasonic motor. Furthermore, by changing the toughness of the first resonator 41 and the second resonator 42, the second resonator 42 can be made to hardly vibrate, and therefore the flange 7 is provided on the side of the second resonator 42. and is fixed to the casing 3 via the flange 7, it is possible to prevent the vibrations generated by the vibrator from propagating to the casing 3, making it possible to obtain an extremely quiet ultrasonic motor. can. FIG. 5 shows an FEM analysis diagram of the third vibration mode of the recess 12. From this, it can be seen that driving can be performed in the same way even if higher-order modes higher than second order are used.

【Effect of the invention】

As explained above, according to the present invention, it is possible to easily obtain a larger torque than the conventional one with a simple configuration, and furthermore, it is possible to obtain a quiet ultrasonic motor.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of an ultrasonic motor according to the driving method of the present invention, FIG. 2 is a plan view showing the configuration of the ultrasonic vibrator of the above embodiment, and FIG. Figure 4 is an FEM analysis diagram of the modeled equipment; Figure 5 is a line section showing the FEM analysis diagram of the third-order vibration mode; Figure 6 is FIG. 2 is a perspective view for explaining the principle of a conventional traveling wave type ultrasonic motor. 1... Rotor, 2... Rotating shaft, 3...
・Casing, B...Bearing, 4...Resonator,
41... First resonator, 42... Second resonator, 5... Ultrasonic vibrator, 51-56... Piezoelectric element, 12... Concave portion, 13... Open end surface. Figure 1 Sub-Agent Nori Makino Hiromatsu Kei Yama Yutakaya Theory Figure (A) (B) Figure (A) (B) Figure 1

Claims (2)

[Claims] (1) A rotor, a substantially cylindrical resonator made of an elastic material that contacts the rotor, one or more ultrasonic vibrators that vibrate the resonator in the axial direction, and vibrate the ultrasonic vibrator. a drive circuit, which generates a motion equivalent to a motion combining a plurality of oscillations of the swash plate on the contact surface between the resonator and the rotor, and drives the resonator into a first and a second two. The ultrasonic transducer is divided into resonators, and the ultrasonic transducer is sandwiched between the first and second resonators, and the first resonator has a lower rigidity to generate a vibration mode equivalent to the oscillating motion of the swash plate. 1. An ultrasonic motor, characterized in that the second resonator has a higher rigidity and is used for fixing to a casing. (2) The ultrasonic motor according to claim 1, wherein a flange is formed on the second resonator, and the flange is used for fixing to the casing.