JPS633660A - Ultrasonic motor with pressed surface lubricated - Google Patents

Abstract

PURPOSE:To increase life of an ultrasonic motor, by a method wherein lubrication means for forming an oil film to a pressed surface between a stator and a rotor is installed. CONSTITUTION:An ultrasonic motor comprises a torsional coupler 1, a piezoelectric thickness vibrator 2, a stator foot portion 3, a rotor 5 and the like. In this case, for lubrication to a pressed surface of the ultrasonic motor, an oil cup 6 of lubrication means and an oil impregnated pad 7 are provided, and wiping application of oil to the rotor 5 is performed and a new oil film is always formed. In this constitution, an oil film is formed on a pressed surface between the stator 3 and the rotor 5 that generates ultrasonic elliptic vibration, and frictional force of the rotor 5 is increased and output torque is also increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic motor, and more particularly to an improvement in the crimp surfaces of its stator and rotor.

[Conventional technology]

Recently, research into the practical application of rotating machines that utilize ultrasonic vibrations, that is, ultrasonic motors, has been accelerated. Among them, the spiral mode piezoelectric vibrator proposed by the present invention (Japanese Patent Application No. 1983-
148671)) using a piezoelectric motor (patent application No. 148671)
69364) is an idea that by configuring a rotor to be crimped onto the end face of a stator that is excited by a piezoelectric vibrator and generates ultrasonic elliptical vibrations, the rotor receives rotational torque and a motor that rotates powerfully can be realized. was provided. A piezoelectric motor using a cantilevered ultrasonic torsional elliptical vibrator (Patent Application No. 172,429/1989) attracted attention for its simple structure and high efficiency among the various plans that implemented this idea. Although this method has excellent properties in practical use, since it uses frictional force to generate rotational torque, it has drawbacks such as uneven rotation, creaking noise, and easy wear of the crimping surface.

[Problem that the invention attempts to solve]

This invention solves the drawbacks of the conventionally proposed ultrasonic motors, such as uneven rotation, squeaking noise, and abrasion of the crimping surface. 2) Ultrasonic motors with excellent rotational stability, low noise, and long life The purpose is to provide motors.

[Means to solve the problem]

An ultrasonic motor is a motor that outputs rotational torque through abrasion force, and in order to obtain a stable high output, the frictional force generated between the stator and rotor is required to exhibit a large constant value. The frictional force is determined by the pressing force P and the friction coefficient, but in a motor configured so that the pressing force always remains at a constant value, it depends on the friction coefficient. In a normal ultrasonic motor, the crimping surface is made of different materials and shapes, so it is unlikely that the coefficient of friction will differ from place to place as the motor rotates.

However, in reality, uneven rotation, squeaking, etc. occur when a slip occurs between the crimped surfaces as the motor rotates, and the ultrasonic vibrations damage the surface and change the coefficient of friction. This is thought to be due to the local distribution of the friction coefficient. Therefore, the first thing to do is to maintain the condition of the crimping surface in a smooth state in which both the coefficients of static friction and dynamic friction, which are the causes of slippage, are equal and at the same time have large coefficients.

〔Example〕

A role model for considering specific measures that meet the above-mentioned guidelines is a roller-type rolling mill. The roller to be crimped must not slip or wear out.

For this reason, the surface of the roller is made of a hard material with a smooth mirror finish. Therefore, in the present invention, the rotor crimping surface of the aluminum stator was hard coated, plated, and mirror-polished, and the die steel rotor was hardened and then the crimping surface was polished. When a motor was constructed by crimping a rotor to the stator thus completed and operated, it was found that uneven rotation, wear, etc. were significantly improved, and a large value of output torque was obtained.

Fig. 3 is a diagram showing this ultrasonic motor, in which 1 is a torsion coupler, 2 is a piezoelectric thickness vibrator, 3 is a stator leg, and 4
5 is a terminal plate, and 5 is a rotor.

However, although it was said to be a significant improvement, when the rotor was removed from the stator after continuous operation for - hours and the crimped surface was examined, scratches were found. After re-crimping the rotor to the stator and restarting operation, uneven rotation appeared about 10 hours later.The operation was stopped and the motor was disassembled and inspected. A protruding spot 8 is seen on the surface 5a, and when this spot comes into contact with the stator, -
It was found that uneven rotation occurred twice during rotation. These spots are thought to be caused by ultrafine abrasion particles on the crimped surface that harden while rolling while being crimped, causing subtle rotational irregularities and squeaks, and are baked into one spot on the rotor surface.

It is well known in Ti processing technology that machine oil is effective in preventing such seizure. Therefore, it seems that the cause of uneven rotation can be removed and the problem solved by refueling.

However, refueling devices that utilize frictional force, such as brakes, is strictly prohibited. Therefore, when we measured the change in frictional force when the crimping surface of the ultrasonic motor was lubricated in a non-energized state, that is, the limit at which static friction changed to dynamic friction, we obtained the unexpected results shown in Figure 2. .

It was found that when machine oil is supplied, the frictional force increases rather than decreases, and in particular, as the pressure increases, the friction coefficient increases by several tens of percent.On the other hand, machine oil has a large difference between the static friction coefficient and the kinetic friction coefficient. As shown in the curve in Figure 2 12゜13, when the crimp pressure exceeds 100 kgf/cI]t, 10
Since the whiteout is exceeded, when the rotor rotates, it causes periodic uneven rotation, or vibration. - On the other hand, in case No. 15 was refueled with grease, the friction coefficient was almost the same as in state 1) without an oil film before refueling, but the difference between the static and dynamic friction coefficients was small and the rotation became smooth.

In light of the above, it is ideal to supply oil with a large pressure force (when applied, the static and dynamic friction coefficients are both equal and large). Traction oils have been developed for lubricating the rollers of continuously variable transmissions (CVTs) developed for this purpose.Among these traction oils, the ones with excellent temperature characteristics are as shown by the curve in Figure 2, 14. No difference was observed in the coefficient of static/dynamic friction.The oil was filled in the oil supply pot 6 shown in Fig. 1, and was wiped onto the rotor 5 while constantly forming a new oil film.
A 10-month continuous load torque test of 10 kg was carried out, and the wear was less than 1 μm, and the rotation unevenness was 1 r, p,
We obtained a good result of less than m. 7 in the figure is an oil-impregnated pad.

〔Effect of the invention〕

As explained above, the present invention applies oil to the crimped surfaces of the stator and rotor in an ultrasonic motor that utilizes the rotational torque received by the frictional force of the rotor crimped to the end surface of the stator that generates ultrasonic elliptic vibrations, thereby forming an oil film. The formed configuration was taken. As a result, the frictional force of the rotor increases, the output torque increases (and the generation of squeaking noises etc. is eliminated).
In particular, when using oil with a difference between the static friction coefficient and the dynamic friction coefficient of 10% or less, rotational unevenness will be 1 r, p, m.
The following remarkable effects were obtained. Furthermore, by providing a lubricating means for forming an oil film on the crimped surfaces of the stator and rotor, a new oil film is constantly formed on the crimped surfaces of the rotor, which has the effect of significantly improving the life of the ultrasonic motor.

[Brief explanation of drawings]

FIG. 1 is a front view showing an embodiment of the ultrasonic motor according to the present invention in which the crimp surface is lubricated and is equipped with a lubricating means, and FIG. 2 is the crimp surface of the ultrasonic morph shown in FIG. Figure 3 is an explanatory external view of an example of an ultrasonic motor, Figure 4 is an illustration of the ultrasonic motor shown in Figure 3 but without it. FIG. 4 is an explanatory diagram showing spots of foreign matter on the crimping surface of the rotor, which was inspected after the rotor had been operated for a long time with refueling. 1... Torsional coupler, 2... Piezoelectric thickness vibrator, 3...
... Stator body, 6... Rotor, 6... Oil pot, 7
...Oil-impregnated pad. Figure 1 Figure 2 Figure 3 Figure 4

Claims (3)

[Claims] (1) In an ultrasonic motor that utilizes the rotational torque received by the frictional force of a rotor that is crimped to the end face of a stator that generates ultrasonic elliptical vibrations, an oil film is formed on the crimped surfaces of the stator and rotor. Features an ultrasonic motor. (2) An ultrasonic motor according to claim (1), characterized in that the ultrasonic motor is equipped with an oil supply means for forming an oil film on the contact surfaces of the stator and rotor. (3) When the specifications of the oil suitable for lubricating as described in claim (1) are applied to a crimped surface of 100 kg/cm^2, both the coefficient of static friction and the coefficient of kinetic friction are increased compared to the surface in an unlubricated state. An ultrasonic motor characterized in that an oil film is formed of oil in which the difference between the two is 10% or less.