JPH02206373A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To contrive the improvement of response characteristics or especially the shortening of a necessary time for stopping by a method wherein a voltage, produced by reversing the phase of a driving voltage, is impressed on a vibrating body upon stopping an ultrasonic motor. CONSTITUTION:A voltage, produced by reversing the phase of a driving voltage, is impressed on a vibrating body. An ordinary oscillation circuit is short- circuited by a shunt resistors, connected in parallel to the ordinary oscillation circuit, in order to stop the vibration of the vibrating body. The vibration is stopped in a shorter period of time by impressing the voltage, produced by reversing the phase of a driving frequency. In order to determine the optimum value of the product of an impressing time of the voltage by an impressing voltage, whose phase is reversed to the phase of the driving frequency, the vibration of the vibrating body is detected at all times and the voltage is controlled in accordance with the detected vibration of the vibrating body. According to this method, a rotary type and a linear type ultrasonic motor may be stopped more speedily.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an ultrasonic motor that utilizes ultrasonic vibrations.

Conventional technology In conventional motors, in order to obtain a motor with high-speed response characteristics, it is common to use a motor with an output greater than the output required as an equilibrium value, and then control that motor to obtain high-speed response. be. This leads to an increase in the size of the device. 2. Description of the Related Art As semiconductor devices progress and electrical equipment becomes smaller, motors are also required to be smaller. However, since the properties of the materials that make up motors have not advanced as much as semiconductor devices, the motor has always been the largest component of the device. Therefore, the demand for miniaturization has been met by increasing processing accuracy.

Rotary type and linear type ultrasonic motors are attracting attention as a solution to these drawbacks. This ultrasonic motor inherently allows for a faster response motor than conventional motors. The reason for this is that the response characteristics of a motor are determined by the torque, the moment of inertia of the motor, and the achieved speed, and ultrasonic motors are superior no matter which values are compared.

Problems to be Solved by the Invention However, such an ultrasonic motor does not always have a high-speed response, and has the disadvantage that there are cases in which the response is only comparable to that of conventional motors.

Note that one of the factors that lowers the response characteristics of these ultrasonic motors is the response characteristics of the vibrating body (the stator of the ultrasonic motor). When power is cut off to the stator, the response speed is degraded by the vibration energy of the stator itself, in other words, the energy corresponding to the Q value of the vibrating body. Specifically, it corresponds to a time several tens to hundreds of times the period of vibration. When the position period is 30 microseconds, the value reaches several tens of milliseconds in the case of a large value, which is by no means a small value, and the problem has been how to reduce this value.

The present invention provides an ultrasonic motor that can shorten response characteristics, particularly the time required for stopping.

Means for Solving the Problems In order to solve the above-mentioned conventional problems, the present invention applies a voltage with the phase of the drive voltage inverted to the vibrating body.

In order to stop the vibration of the vibrating body, a shunt resistor is used to short-circuit the vibration circuit in parallel. Further, in order to further shorten the stopping time, the present invention applies a voltage with the phase of the drive frequency reversed, thereby stopping the vibration in an even shorter time.

In an ultrasonic motor, in order to generate a traveling wave in the vibrating body, 2
Although two waves with different phases are combined and generated, the present invention may apply an inverted signal to the two waves, or may apply an inverted signal to only one phase.

When applying the above-mentioned reverse voltage, there is always an optimum value for the product of the application time and the applied voltage, and application of a reverse voltage more than necessary may rather lead to deteriorated characteristics.

In order to easily determine the optimum value, the vibration of the vibrating body is constantly detected and the voltage is controlled accordingly, thereby making it possible to stop the motor in a much shorter time.

Function The present invention improves the driving voltage and phase of the ultrasonic motor to improve the falling characteristic when the motor stops, in order to make the rotary type and linear type ultrasonic motor respond faster. This makes it possible to improve the stopping characteristics of the vehicle.

Embodiment FIG. 1 shows response characteristics when a reverse voltage is applied to a rotary type and a linear type ultrasonic motor using a phase inversion circuit. In this case, the drive time and voltage for phase inversion were controlled by a circuit.

Figure 2 shows the vibration damping when the rotary ultrasonic motor is stopped. One of the damping characteristic factors of the ultrasonic motor is the inertial force of the rotor, and the other is the inertial force that is a composite of the instantaneous inertial force of stator imaging, which determines the damping times shown in FIGS. 1 and 2. In the embodiment shown in Figures 1 and 2, the driving frequency is 40 kll.
Since z is used, one imaging period is 25 microseconds.

The ultrasonic motor continues to vibrate several tens of times for 25 microseconds.

Meanwhile, the ultrasonic motor continues to move and stops at a location different from the initial stop position. This value poses a problem for the high-speed response of ultrasonic motors.

FIG. 3 shows a block diagram of a circuit for applying a phase-inverted voltage when stopped. Further, FIG. 4 shows a circuit for detecting vibrations from a part of the piezoelectric body or a vibration current detection circuit of an ultrasonic motor and minimizing the signal. Furthermore, FIG. 5 shows a circuit diagram in which the ultrasonic motor is connected to the optimum resistance at the same time as the switching circuit stops, thereby damping the vibrations of the stator.

FIG. 6 shows an example of the response characteristics of the rotary type and linear type ultrasonic motors of the present invention.

As is clear from FIG. 6, in this example, high-speed response of 1 millisecond or less is possible for both rise and fall.

Effects of the Invention The present invention enables rotary and linear ultrasonic motors to stop faster and improves response characteristics. Conventionally, it took several milliseconds to stop, but the ultrasonic motor of the present invention It has become possible to reduce the downtime to about one-tenth.

[Brief explanation of the drawing]

Figure 1 is a vibration response speed characteristic diagram when the ultrasonic motor is stopped, Figure 2 is a response characteristic diagram of another ultrasonic motor, Figure 3 is a block diagram of the phase inversion circuit, and Figure 4 is the stator of the ultrasonic motor. Figure 5 is a circuit diagram when a shunt resistor is inserted, Figure 6 is a diagram of the ultrasonic motor of the present invention and its rise when the circuit is stopped. , is a falling characteristic diagram. Name of agent: Patent attorney Shigetaka Awano and 1 other person Figure 20/″sec H2 Akira Kaden Akaden Omote

Claims (5)

[Claims] (1) In an ultrasonic motor that uses ultrasonic vibration as a driving force source, when the ultrasonic motor is stopped, a voltage with the phase of the driving voltage reversed is applied to the vibrating body to stop the ultrasonic motor. (2) In an ultrasonic motor that uses ultrasonic vibration as a driving force source, when the ultrasonic motor is stopped, a resistor is connected to a driving piezoelectric body in a stator, which is a driving body, to stop the ultrasonic motor. (3) The ultrasonic motor according to claim 1 or 2, further comprising a circuit that applies a voltage whose phase is reversed simultaneously with the stop command. (4) The ultrasonic motor according to claim 1 or 2, further comprising an ultrasonic motor stop circuit in which the application time of the reverse voltage is applied to the fall time of vibration of the ultrasonic motor. (5) The ultrasonic motor according to any one of claims 1, 2, and 3, further comprising an ultrasonic motor stop circuit that detects the vibration of the vibrating body and controls the phase and voltage so that the vibration becomes zero.