JPH0442783A - Driving apparatus of 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 provides the following methods for efficiently starting an ultrasonic motor:
The present invention relates to an ultrasonic motor drive device that controls a drive signal applied to a piezoelectric element.

[Prior art] In an ultrasonic motor, a piezoelectric element provided on a ring-shaped stator is divided into two parts, and high-frequency voltages with different phases are applied to each piezoelectric element to generate traveling waves on the surface of the stator. , there is one that drives a rotor that is in pressure contact with a stator.

From the relationship between the rotational speed of the motor and the driving frequency shown in the curve diagram in Figure 3, in order to drive this ultrasonic motor, the driving frequency must be changed from a starting signal of a somewhat high value to a driving signal of a low value at the time of startup. The drive efficiency of the motor can be increased by performing feedback control so that the drive signal can be swept and fixed at a drive frequency that provides an appropriate rotational speed.

[Problems to be Solved by the Invention] However, in the above method for driving an ultrasonic motor, when the motor stops due to the state of the load applied to the output shaft of the motor, feedback control is activated while the motor remains stopped.
The drive frequency is swept from a start signal with a certain high value to a drive signal with a low value, and the drive frequency is fixed at a low value by the limiter. Therefore, even if the load is removed, the motor will not rotate and will not restart.

The present invention was made to solve these problems, and an object of the present invention is to provide an ultrasonic motor drive device that can easily restart the motor even if the motor is stopped due to a load or the like.

[Means for Solving the Problems] The ultrasonic motor driving device of the present invention applies high frequency voltages with different phases to piezoelectric elements provided in two sections in a ring-shaped stator, and also applies driving at the time of startup. In an ultrasonic motor drive device that sweeps the frequency from a startup signal with a certain high value to a drive signal with a low value, and drives a rotor that is pressed against the stator using an appropriate drive signal, the rotation state of the rotor is detected and a detection signal is generated. A rotation sensor that outputs a rotation sensor, a stop detection circuit that is activated by a motor start command signal, detects a stopped state of the rotor based on a detection signal from the rotation sensor, and outputs an alarm signal during the stopped state, and a stop detection circuit that outputs an alarm signal. A drive circuit includes a timer that operates only while receiving the signal and outputs a control signal at fixed time intervals, and a means for returning a drive signal with a low drive frequency to a start signal by receiving the control signal from the timer. It consists of

[Function] In the above ultrasonic motor drive device, when the motor start switch is turned on, the start command signal oscillates, the stop detection circuit is activated, and the motor drive circuit detects that the motor drive frequency is high to some extent. It sweeps from a value activation signal to a lower value drive signal and is fixed at an appropriate drive signal. At this time, when some load is applied to the output shaft and the motor comes to a stop state, the stop detection circuit detects the stop state of the motor based on the detection signal from the rotation sensor.

When the stop detection circuit confirms that the motor is stopped, an alarm signal is output while the motor is stopped, and the timer is activated only during that time. By operating this timer, as shown in the graph showing the relationship between frequency and time in Figure 2, while the motor is in a stopped state,
), and in the drive circuit that receives this control signal, the frequency control means operates to return the drive signal of the drive frequency to the activation signal (f, ). Therefore, when the motor is stopped due to a load or the like, the drive frequency is returned to the starting signal many times until the motor is restarted.

[Embodiment 1] An embodiment of the ultrasonic motor driving device of the present invention will be described below.

FIG. 1 is a block diagram showing the overall configuration of this drive device.

In this figure, an ultrasonic motor l (not shown in detail) has a piezoelectric element provided in two sections on a ring-shaped stator, and high-frequency voltages with different phases output from a drive circuit 2 are applied to the piezoelectric element, which is pressed into contact with the stator. The structure is such that the rotor rotates.

In the drive circuit 2, when the switch for starting the motor is turned on, the drive frequency applied to the piezoelectric element of the ultrasonic motor l is swept from a somewhat high value to a low value drive signal, which is ideal for obtaining a constant speed. A control is activated to fix the drive signal to a certain drive signal.

A rotation sensor 3 is provided at the rotation output section of the rotor of the ultrasonic motor 1, and when the motor stops due to the state of the load on the output shaft, the rotation sensor 3 also oscillates a pulse signal, etc. ing. This pulse signal is then output to the stop detection circuit 4 connected to the output terminal of the rotation sensor 3. Note that an encoder may be provided instead of the rotation sensor 3.

The stop detection circuit 4 is interlocked with a motor start switch, is activated upon receiving a start command signal, and detects the stop state of the motor using a pulse signal from the rotation sensor 3. When the stop detection circuit 4 confirms that the motor is in a stopped state, an alarm signal is output while the motor is in a stopped state. The timer 5 connected to the output terminal of the stop detection circuit 4 operates only while this alarm signal is being output, and outputs a control signal to the drive frequency control circuit of the drive circuit 2 (not shown) at fixed time intervals.

In the drive frequency control circuit of the drive circuit 2, when receiving the control signal from the timer 5, as shown in FIG. In this state, the drive frequency of the motor is returned to the starting signal many times until it is restarted. As a result, when the motor stops, the drive frequency is repeatedly controlled to sweep the drive signal from a high value to a low value.

[Effects of the Invention] In the ultrasonic motor drive device of the present invention, when a rotation sensor or the like detects a stopped state of the motor, the drive frequency returns from a low value drive signal state to a high value start signal state. Therefore, even if the motor is stopped due to a load applied to the output shaft of the motor, the motor will not be restarted, and the motor can be easily restarted by removing the load that caused the motor to stop. Therefore, the ultrasonic motor can be started efficiently.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the overall configuration of an embodiment of the present invention, Fig. 2 is a graph showing the relationship between the drive frequency and time by the drive device of the present invention, and Fig. 3 is a graph showing the relationship between the rotational speed of the motor and the drive frequency. It is a curve diagram showing the relationship. l; Ultrasonic motor 2; Drive circuit 3; Rotation sensor 4; Stop detection circuit 5; Timer Applicant: Fukori Co., Ltd. Taisei Electric Co., Ltd. Agent: Patent attorney Katsutsugu Maki

Claims (1)

[Claims] High-frequency voltages with different phases are applied to the piezoelectric elements provided in two sections on the ring-shaped stator, and at the time of startup, the drive frequency is swept from a somewhat high value starting signal to a low value driving signal, and an appropriate value is set. In an ultrasonic motor drive device that drives a rotor pressed against a stator using a drive signal, there is a rotation sensor that detects the rotational state of the rotor and outputs a detection signal, and a rotation sensor that is activated by a motor start command signal and receives a signal from the rotation sensor. a stop detection circuit that detects a stopped state of the rotor based on a detection signal and outputs an alarm signal during the stopped state; a timer that operates only while receiving the alarm signal and outputs a control signal at fixed time intervals; 1. A driving device for an ultrasonic motor, comprising: a driving circuit having means for returning a driving signal having a low driving frequency to a starting signal by receiving a control signal from a timer.