JPH02273085A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To improve reliability by arranging a spring between a tightening nut and a spacer in order to pressure contact an element and arranging a belleville spring between a seat pressure contacting with a rotor through a bearing and the nut. CONSTITUTION:Since loosening or deformation of a nut 15 causes considerable change of characteristics, the nut 15 must be tightened perfectly to a shaft 17a. An insulator 18a, a longitudinal vibrator 11, an insulator 18b, a supporting board 30, a torsional vibrator 12, a metal block 14 and a belleville spring 16 are applied onto the shaft 17a then they are adhered firmly to the end face of a head mast 13 through epoxy series organic adhesive or through soldering, thereatter they are pressure contacted by means of the nut 15 through the belleville spring 16. Since the longitudinal vibrator 11 vibrates with magnitude of several mum and the characteristics fluctuate remarkably due to thermal variation of the members, a belleville spring 23 is arranged on the pushing face of a nut 24 such that the belleville spring 23 elongates/contracts to accomodate thermal variation of the members thus preventing extreme variation of the pushing force of the nut 24.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic motor, and more particularly to an ultrasonic motor that excites ultrasonic vibrations in a piezoelectric vibrator and thereby generates a driving force.

[Conventional technology]

Recently developed ultrasonic motors are motors based on a new principle of obtaining rotational force through ultrasonic vibrations, and are characterized by lower speed and higher torque than conventional electromagnetic motors, which are based on the interaction of current and magnetic fields. There is. In other words, the torque per unit volume is much larger than that of an electromagnetic motor.
Moreover, it has the advantage of being gearless and brakeless when used at low speeds, and has excellent responsiveness due to its small mechanical properties and large static holding force of the rotor.

Various ultrasonic motors have been proposed so far, for example, in the Proceedings of the Acoustical Society of Japan (October 1986), pp.
21-822, such as "Ultrasonic motor using vertical-torsional compound vibration". Such an ultrasonic motor is practical because it has a small diameter and can obtain high torque.

FIG. 2 is a cross-sectional structural diagram showing the right half of an ultrasonic motor as an example of such a conventional ultrasonic motor.

As shown in Fig. 2, the conventional ultrasonic motor has a stator 6.
0 and a rotor 70, and the stator 60 is a longitudinal oscillator (hereinafter referred to as a longitudinal oscillator) made of a laminated piezoelectric actuator.
61, a Langevin type torsional vibration excitation piezoelectric element (hereinafter referred to as a torsional vibrator) 62, a head mass 63, a metal block 64, a nut 65, a shaft 67a and insulators 66a and 66b (hereinafter referred to as a longitudinal vibrator) 61). This stator 60 is driven in a torsional resonance mode, and the longitudinal vibrator 61 is driven by the stator 60.
is excited non-resonantly in a manner that matches the resonant frequency of. Furthermore, the stator 60 operates in a mode in which a round bar is torsionally deformed, similar to the movement of wringing a rag, as is well known in the operation of the transducer portion of a mechanical channel filter using a torsional mode. Furthermore, the head mass 63 further amplifies the momentum. Therefore, the end face of the head mass 63 where the stator 60 and the rotor 70 come into contact can generate rotational forces in the clockwise and counterclockwise directions at the resonance frequency.

Here, a case will be described in which the rotor 70 is rotated counterclockwise. When the end face of the head mass 63 that contacts the rotor 70 is deformed counterclockwise so that the stator 60 that has been tightened with the nut applies a counterclockwise rotational force to the rotor 70, the vertical vibrator 61 is rotated in synchronization with the torsional vibration. extending in the direction of
A voltage is applied from another power source so as to cause deformation, and the rotor 70 and the heladomas 63 are momentarily brought into strong pressure contact. The friction force at this time allows the rotor 70 to obtain a large rotational force in the counterclockwise direction. Further, when the surface of the head mass 63 that comes into contact with the rotor 70 rotates clockwise, the vertical vibrator 61 is contracted in the axial direction, and the pressure contact force between the rotor 70 and the head mass 63 is temporally reduced to zero, and the clock is rotated. It is sufficient to make the clutch function so as not to transmit the torsional vibration displacement of the surroundings to the rotor 70. Therefore, by a series of operations of the torsional vibration of the stator 60 and the stretching vibration of the longitudinal vibrator 61 disposed in a part of the stator, , the rotor 70 can smoothly rotate counterclockwise.

On the other hand, when the rotor 70 is rotated clockwise, the stator 60 is simply excited at the torsional resonance frequency, and when the clutch operation is performed, one oscillator 61 is rotated counterclockwise. All you have to do is change the phase so that the degree phase is different. In this case as well, the rotor 70 can rotate smoothly clockwise.

The above-mentioned longitudinal vibrator 61 and torsional vibrator 62 are both made of piezoelectric ceramic, and as is well known, this piezoelectric ceramic is extremely strong against compressive force, but extremely fragile against tension. It is necessary to constantly apply a large compressive bias stress to the longitudinal vibrator 61 and the torsional vibrator 62 by means of the nut. In addition, in order to transmit the rotation of the stator 60 to the rotor 70, it is essential that the helad mass 63 and the rotor 70 are strongly pressed together, and the bolt 67b
Connect the head mass 63 and rotor 70 using a strong coil spring 72 and nut 73 to the pedestal 74 and bearing 7.
1 and held by pressure. Further, in order for the stator 60 to perform torsional vibration, the heradomas 63. The longitudinal vibrator 61 and the torsional vibrator 62 must be firmly coupled.

Therefore, in the conventional ultrasonic motor, the longitudinal vibrator 61 and the torsional vibrator 62 are connected to the head mask 63 by bolts.

[Problem to be solved by the invention]

The conventional ultrasonic motor described above uses a strong coil spring 72 to hold the head mass 63 and the rotor 70, and for this purpose, a spring with a strong spring constant is required.

However, when a compression coil spring is used, there are problems in that the radial direction is restricted due to stress, the wire diameter becomes thinner, and the length becomes longer. Further, when the wire diameter is shortened by using a compression coil spring in the form of a leaf spring, there is a problem in that the end surface of the spring does not sit well and uniform pressure contact cannot be obtained. Therefore, in any case, the use of a coiled spring has the disadvantage that the ultrasonic motor becomes inevitably long.

In addition, it is necessary to constantly apply a large compressive bias stress to the longitudinal vibrator 61 and the torsional vibrator 62, and a structure is used in which the spacer is directly pressed with nuts and bolts, and the vertical and torsional vibrators are uniformly pressed together through the spacer. Therefore, when a temperature change occurs in the ultrasonic motor, thermal contraction occurs and the metal and vibrator (
Since the coefficient of thermal expansion is different from that of ceramic (ceramic), there is a disadvantage that the pressing force changes and the characteristics change. Furthermore, by directly bolding the vibrator, the stator becomes a rigid body, and the expansion and contraction of the vertical vibrator applies repeated tensile loads in the axial direction to the bolts, which causes stress concentration in the structurally weak threaded parts, which can lead to fatigue failure. There is a drawback that.

An object of the present invention is to provide a stable and highly reliable ultrasonic motor that can even out the spring load force applied to the rotor and compression and torsion oscillators, and that is resistant to thermal deformation and has no change in characteristics over a long period of time. There is a particular thing.

[Means to solve the problem]

The ultrasonic motor of the present invention includes a stator of a vertical and torsional composite piezoelectric vibrator, a head mass that transmits vertical and torsional operation modes, and a rotor that rotates in forward and reverse directions in response to the vertical and torsional vibrations.
An ultrasonic motor comprising the stator and the rotor with a central shaft tightened with the head mass sandwiched therebetween, and a pedestal that presses the rotor through a bearing by providing a spring between the tightening nut and the spacer to press the element. It is characterized by providing a flat spring between it and the nut.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional structural diagram showing the right half of an ultrasonic motor as an embodiment of the present invention.

As shown in FIG. 1, the stator 10 in this embodiment is a stator portion that is tightened with a nut and can output displacement in both longitudinal and torsional directions. The torsional vibrator 12, which is a ring-shaped piezoelectric element, is entirely polarized in the circumferential direction. These piezoelectric elements are firmly laminated and bonded using an organic adhesive such as epoxy, solder, etc., with an electrode plate 12a made of Cu or the like interposed therebetween. Furthermore, each of the -plates is polarized in opposite directions.

For example, if the 1st and 3.5th stages are polarized clockwise, the 2nd, 4th and 6th stages are polarized counterclockwise. Furthermore, electrodes are applied to the upper and lower surfaces by sputtering, plating, vapor deposition, or the like, and electrical terminals are taken out in parallel.

As is well known, based on the principle of a torsional oscillator, it is known that in a torsional vibration conversion section made up of more layers of piezoelectric elements, the polarization directions of adjacent piezoelectric elements are opposite to each other.

Further, the longitudinal vibrator 11 consisting of a ring-shaped laminated piezoelectric actuator constituting the stator 10 has an insulator 18a,
It is electrically insulated from the torsional vibration element 12 by 18b. The head mass 13 has one end surface fixed to the end surface of the vertical vibrator 11 via an insulator 18a, amplifies the amplitude output from the vertical vibrator 11 and the torsional vibrator 12, and has a sliding material 22 on the contact surface with the upper part. Output via . metal block 14
The shaft 17a, counter spring 16 and nut 15 apply static pressure to the longitudinal vibrator 11, torsional vibrator 12 and insulator 1.
This is a member that uniformly applies voltage to portions 8a and 18b. Note that the flat spring 16 is provided to minimize changes in the pressure applied to the piezoelectric element due to temperature changes due to differences in the coefficient of thermal expansion of each member constituting the stator 10.

On the other hand, the rotor 20 has a cylindrical shape, a bearing 21 is provided in the cylinder, and the rotor 20 is rotatably supported by the shaft 17b with a degree of freedom in the axial direction. Moreover, the force that presses the end surface of the rotor 2o against the stator 10 is reduced by the flat spring 2.
3 through the pedestal 25 and the bearing 21.

The sliding material 22 is a member with excellent wear resistance, and is bonded to the end surface of the head mass 13 as described above. In order to enable the ultrasonic motor to operate, the stator 10 and rotor 2o must be pressed against each other with strong static pressure when not in operation.

Shaft 17b, flat spring 23. The nut 24 and the pedestal 25 are
The pedestal 25 is in pressure contact with the end surface of the inner ring of the bearing 21, and the rotor 20 is in pressure contact with the end surface of the inner ring of the bearing 21.
It is configured to be pressed into contact with the outer ring of No. 1. Therefore, when the rotor 20 rotates, the member serving as the pressure applying means does not rotate.

As is clear from the above configuration, the stator 10 operates in a mode in which the round rod is torsionally deformed, similar to the movement of wringing a rag. By the way, loosening, deformation, etc. of the nut 15 can significantly change the characteristics, so the nut 15 and shaft 17a
must be fully concluded. Therefore, an insulator 18a and a longitudinal vibrator 11. Insulator 18b, support plate 30.
Torsional oscillator 12. Metal block 14. A counter spring 16 is inserted and firmly adhered to the end face of the head mass 13 using an organic adhesive such as epoxy or solder, and the nut 15 is pressed through the counter spring 16 to optimize the elliptical movement of the head mass 13. It is effective to adjust the condition and fix the connecting screw part n1 of the shaft 17a and the nut 15 by spot welding the joint screw part at several places around the joint thread part. For spot welding, electric spot welding can be used in addition to laser spot welding. Furthermore, since the longitudinal vibrator 11 undergoes stretching vibration of several micrometers, the characteristics will change markedly when a thermal change occurs in the member. Even if a thermal change occurs, the flat spring 16 expands and contracts, so that the pressing force of the nut 15 does not change drastically. Further, since the rotor 2o rotates due to frictional force due to the elliptical motion of the heladium mass 13, it can be seen that the force when the rotor 20 is pressed against the heladium mass 13 significantly affects the characteristics. Therefore, it is necessary to optimally adjust the pressing force using the nut 24 and to completely fix the nut 24 to the shaft 17b. Therefore, similarly to the fastening of the nut 15 of the stator 1o, it is effective to melt and fix the joint threaded portion n2 of the shaft 17b and the nut 24 at several points by spot welding. Furthermore, as mentioned above, since the longitudinal vibrator 11 undergoes stretching vibration of several micrometers, the characteristics will change significantly when the member undergoes a thermal change. The counter spring 23 expands and contracts even if a thermal change occurs in the member, so that the pressing force of the nut 24 does not change drastically.

〔Effect of the invention〕

As explained above, the ultrasonic motor of the present invention can equalize the pressure contact force to the rotor by providing a flat spring in the rotor pressure contact part, thereby minimizing rotational fluctuations and achieving high efficiency and high torque. Not only that, but the total length of the motor can be reduced and it can be mounted compactly in the device.

Furthermore, by pressing the vibrator with a flat spring, the ultrasonic motor of the present invention not only alleviates stress concentration on weak members and prevents aging and fatigue failure, but also prevents thermal deformation of the motor. However, the Saraspring follows the deformation error,
Since there is no extreme change in the force that presses the vibrator, the characteristics of the motor do not change, resulting in longer life and improved reliability.

[Brief explanation of drawings]

FIG. 1 is a structural diagram showing a right half of an ultrasonic motor as an example of the present invention in cross section, and FIG. 2 is a structural diagram showing a right half of a conventional ultrasonic motor in cross section. 10... Stator, 11... Vertical vibrator, 12...
Torsional vibrator, 13... Head mass, 14... Metal block, 15... Nut, 16... Sara spring, 17
a17b...shaft, 18a, 18b...insulator, 2o
... Rotor, 21... Bearing, 22... Sliding material, 23... Flat spring, 24... Nut, 25...
・Pedestal, 3o...Support plate. Agent Patent Attorney Uchihara Jinliang District 2nd Ward

Claims (1)

[Claims] a stator of a vertical and torsional composite piezoelectric vibrator, a head mass that transmits the vertical and torsional operating modes, a rotor that rotates in forward and reverse directions in response to the vertical and torsional vibrations, and a center that tightens the stator and rotor with the head mass sandwiched therebetween. An ultrasonic motor configured with a shaft, characterized in that a spring is provided between a tightening nut and a spacer to press the element, and a flat spring is provided between the nut and a pedestal that presses the rotor via a bearing. Ultrasonic motor.