JPH0458771A - Overload stopper for ultrasonic motor - Google Patents

Abstract

PURPOSE:To interrupt power supply to a driving circuit by receiving monitor signals from a monitor electrode and the like mounted on the piezoelectric element of stator and operating an overload interrupting circuit upon elapse of a predetermined time after detection of an overload state. CONSTITUTION:Piezoelectric element for an ultrasonic motor 1 is provided with a monitor electrode 3b for stopping overload having an output terminal connected with a voltage regulating circuit 6 which has an output terminal connected with a shaping circuit 7. A judgment is made that an overload state has occurred if a predetermined time elapses before any pulse signal is provided from the shaping circuit 7 and a switching element S2 in a time controlled monostable multivibrator 8 produces an operational signal. The operational signal causes to function a drive ON/OFF circuit 10 comprising a relay RY2 for interrupting the power supply to an ultrasonic wave motor driving circuit 2 and the like through an overload interrupting circuit 9. Consequently, power supply to the driving circuit is interrupted when overload state of motor sustains for a predetermined time.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides an ultrasonic motor that automatically turns off the power of the ultrasonic motor drive circuit when the ultrasonic motor stops due to a large load. This invention relates to an overload stop device.

[Conventional technology 1] In an ultrasonic motor, a piezoelectric element having two electrode groups is attached to a ring-shaped stator, 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.

When driving this ultrasonic motor, if a large load is applied to the 8-force axis of the motor and the motor stops, the overload stop device is activated to turn off the power to the drive circuit and prevent the motor from overheating. There is. A conventional overload stop device includes a rotation sensor or an encoder provided on the output shaft of an ultrasonic motor, detects an overload state of the motor based on a signal from the rotation sensor, and performs controls such as cutting off power to a drive circuit.

[Problem to be solved by the invention] However, with an overload stop device that uses a sensor or encoder, the installation position must be secured on or near the output shaft of the motor, so the ultrasonic motor itself becomes large. There's a problem. In addition, optical sensors and the like are susceptible to heat, dust, etc., and have the problem of malfunctioning.

This invention was made to solve these problems, and when the motor stops due to overload, etc., it accurately determines the overload state of the motor and appropriately turns off the power to the drive circuit. It is an object of the present invention to provide an overload stop device for an ultrasonic motor that works.

[Means for Solving the Problems] The overload stop device for an ultrasonic motor of the present invention includes a piezoelectric element having two electrode groups attached to a stator, and high frequency voltages having different phases applied to the piezoelectric element. In an ultrasonic motor that drives a rotor that is pressed against a stator, a piezoelectric element is provided with a monitor electrode that outputs an electric signal, and a voltage regulator that adjusts the voltage of the electric signal is connected to the monitor electrode.
A waveform shaping circuit is connected to the output terminal of the voltage regulator, which shapes the electrical signal into a pulse signal and also outputs a pulse signal with a voltage value of zero when the motor stops due to overload. When a pulse signal is not output from the circuit for a certain period of time, a means is provided for outputting an activation signal to an overload cutoff circuit, and an overload cutoff circuit is provided that cuts off the power to the drive circuit of the ultrasonic motor in response to the activation signal.

In addition, a monitor electrode is provided to output an electric signal to the piezoelectric element,
A voltage adjustment circuit that adjusts the voltage of the electrical signal is connected to the monitor electrode, and an oscillation circuit that outputs an end frequency signal when the motor's rotational output decreases is provided.The end frequency signal of this oscillation circuit and the output from the voltage adjustment circuit are connected to the monitor electrode. A synchronous rectifier circuit is installed that compares and judges the output signal and outputs an activation signal if the output signal is below the end frequency for a certain period of time, and the overload cutoff function cuts off the power to the drive circuit using the activation signal from the synchronous rectifier circuit. An overload stop device provided with a circuit may also be used.

Furthermore, a monitor electrode for outputting an electric signal is provided on the piezoelectric element, a voltage adjustment circuit for adjusting the voltage of the electric signal is connected to the monitor electrode, and a comparator circuit is connected to the output terminal of this voltage adjustment circuit via a rectifier circuit. , a level setting circuit is provided that oscillates a voltage level signal to a comparator circuit when the motor stops due to overload, and the comparator circuit compares and judges the output voltage from the level setting circuit and the output voltage from the rectifier circuit. Even if the device is configured to output an activation signal if the voltage of good.

[Function] The above-mentioned ultrasonic motor overload stop device detects the overload state of the ultrasonic motor by extracting a monitor signal from a monitor electrode provided on a piezoelectric element of the stator,
It functions to turn off the power to the drive circuit after a certain period of time has passed.

The overload state is detected by comparing the values of the voltage, frequency, and potential difference of the monitor signal with the values of the motor stopped state. The overload state is detected in the circuit of each device, and when a certain period of time has passed in that state, the overload cutoff circuit of each device is activated and cuts off the power to the drive circuit, so the overload can be easily removed. In the event of a failure or malfunction, the power to the drive circuit cannot be shut off.

[Example] Hereinafter, an example of the overload stop device for an ultrasonic motor of the present invention will be described.

FIG. 1 is a block diagram of a first embodiment of an overload stop device for an ultrasonic motor, and FIG. 2 is a circuit diagram of the same embodiment.

Although not shown in the diagram, the ultrasonic motor 1 has a piezoelectric element having two electrode groups attached to the stator, and high-frequency voltages with different phases are applied to the piezoelectric element to generate a traveling wave in the stator. This is to drive the rotor which is pressed against the stator.

The overload stop device is a device that accurately determines the overload condition and turns off the power to the drive circuit 2 of the ultrasonic motor when an overload is applied to the output shaft of the ultrasonic motor 1. The ultrasonic motor drive circuit 2 includes a tracking monitor electrode 3a provided on the piezoelectric element of the ultrasonic motor 1, and a feedback circuit for extracting the monitor voltage output from the monitor electrode 3a for automatic tracking. A circuit 4 and an oscillation circuit 5 are attached, and a control signal is sent from the oscillation circuit 5 to the drive circuit 2.

In order to provide an overload stop device, the piezoelectric element of the ultrasonic motor 1 is provided with an overload stop monitor electrode 3b in addition to the tracking monitor electrode 3a. The voltage of the monitor electric signal is connected to the output terminal of the monitor electrode 3b through a variable resistor VR+.
A voltage adjustment circuit 6 is connected to the output terminal of the voltage adjustment circuit 6, and the output terminal of the voltage adjustment circuit 6 is connected to a diode D that converts an electric signal into a waveform-shaped pulse signal, and a switching element S1.
A waveform shaping circuit 7 equipped with the following is connected. The output signals of the diode D and switching S1 during motor drive and overload stop are as shown in FIGS. 5 and 6, and the voltage value of the pulse signal output from this waveform shaping circuit 7 is as follows. The voltage adjustment circuit 6 can adjust the voltage so that it becomes zero when the ultrasonic motor l stops due to overload.

A capacitor C is connected to the output terminal of the waveform shaping circuit 7.

A time-controlled monomulti circuit 8 using a microcomputer M1 is connected to the circuit 8, so that a pulse signal from the waveform shaping circuit 7 can be received. This time-controlled monomulti circuit 8 is comprised of a microcomputer M1, a capacitor C1, a switching element 82, etc., and determines that an overload condition exists when a pulse signal from the waveform shaping circuit 7 cannot be received for a certain period of time. However, an actuation signal is output from the switching element S2.

The output terminal of the time-controlled monomulti circuit 8 includes a switching element S3, a diode D2 . D3. Relay RY.

A drive 0 equipped with a relay RY2 etc. that cuts off the power of the drive circuit 2 of the ultrasonic motor via an overload cutoff circuit 9 equipped with a
The N-OFFFF circuit is connected. The overload cutoff circuit 9 operates upon receiving a signal output from the time-controlled monomulti circuit 8.

Next, the overload stop device of the second embodiment will be explained using FIG.

Note that, like the first embodiment, this embodiment is also a device that extracts a monitor voltage from the monitor electrode 3b and controls the drive ON/OFF circuit IO.

The circuit configuration other than the monitor electrode 3b to the drive ON/OFF circuit 10 is the same as that of the first embodiment, and therefore will not be described below. A voltage adjustment circuit 6 for adjusting the voltage of the electric signal is connected to the output terminal of the monitor electrode 3b, and a synchronous rectification circuit 11 is connected to the output terminal of the voltage adjustment circuit 6.

Furthermore, an oscillation circuit 12 that presses the end frequency when the rotational output of the ultrasonic motor decreases is connected to the synchronous rectification circuit 11,
The output signal of this oscillation circuit 12 can be input.

In the synchronous rectifier circuit 11, the end frequency signal is used as a reference signal, and it is compared with the output signal from the voltage adjustment circuit 6, and when the output signal from the voltage adjustment circuit 6 is below the end frequency signal for a certain period of time, it is activated. Pressure signal.

A DC amplifier 13 is connected to the output terminal of this synchronous rectifier circuit 11.
An overload cutoff circuit 9 is connected to the overload cutoff circuit 9, and the overload cutoff circuit 9 receives the actuation signal output from the synchronous rectification circuit 11 and outputs the drive circuit of the ultrasonic motor via the drive 0N-OFF circuit IO. 2 power can be cut off.

A third embodiment of the overload stop device will be described using FIG. 4.

Incidentally, as in the second embodiment, the drive is turned on and off from the monitor electrode 3b.
OFFFF circuit 1 The circuit configuration other than the liquid circuit configuration is omitted.

A voltage adjustment circuit 6 that adjusts the voltage of the electric signal is connected to the monitor electrode 3b, and the output terminal of this voltage adjustment circuit 6 is
A comparator circuit 15 is connected through the rectifier circuit 14, and further connected to the comparator circuit 15 is a level setting circuit 16 that oscillates a voltage level when the motor stops due to overload.

The comparator circuit 15 compares and determines the voltage value of the level setting circuit 16 and the voltage value from the rectifier circuit 14, and
When the voltage of the rectifier circuit 14 is lower than the voltage of the level setting circuit 16 for a certain period of time, an activation signal is applied. The output terminal of the comparator circuit 15 is connected to the overload cutoff circuit 9 via the DC amplifier 13, and the output terminal of the overload cutoff circuit 9 is connected to the drive ON/OFF circuit l.

The overload cutoff circuit 9 is activated by receiving the operating signal of the comparator circuit via the DC amplifier 13, and cuts off the power to the drive circuit 2 of the ultrasonic motor l via the drive ON/OFF circuit IO.

[Effects of the Invention] In the ultrasonic motor overload stop device of the present invention, the overload state of the motor is accurately determined based on the monitor signal of the monitor electrode provided on the piezoelectric element, and when the overload state continues for a certain period of time,
Functions to turn off the power to the drive circuit. Therefore, malfunctions are reduced compared to optical sensors and the like. Further, since the drive circuit is operated to turn off the power after a certain period of time has elapsed, it is possible to accurately detect an overload state of the motor. Furthermore, since a monitor electrode or the like can be used, the overload stop device can be downsized, and the ultrasonic motor can also be downsized.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a first embodiment of the invention, Fig. 2 is a circuit diagram of the same embodiment, Fig. 3 is a block diagram of a second embodiment of the invention, and Fig. 4 is a block diagram of a third embodiment of the invention. A block diagram of an embodiment,
5 and 6 are graphs showing output signals of the main circuit elements of the first embodiment. 1; Ultrasonic motor 2; Drive circuit 3a, 3b; Monitor electrode 4; Feedback circuit 6; Voltage adjustment circuit 8: Mono-multi circuit for time control IO; Drive ON/OFF circuit 12, oscillation circuit 14: Rectifier circuit 16: Level Setting circuit 5: Oscillation circuit Waveform shaping circuit Overload cutoff circuit Synchronous rectification circuit DC amplifier comparator circuit

Claims (3)

[Claims] (1) In an ultrasonic motor in which a piezoelectric element having two electrode groups is attached to the stator and high-frequency voltages with different phases are applied to the piezoelectric element to drive a rotor that is in pressure contact with the stator, an electric signal is sent to the piezoelectric element. A monitor electrode for output is provided, a voltage regulator is connected to the monitor electrode to adjust the voltage of the electrical signal, and the output terminal of the voltage regulator is used to shape the electrical signal into a waveform and convert it into a pulse signal. When the circuit stops, a waveform shaping circuit that outputs a pulse signal with a voltage value of zero is connected, and when a pulse signal is not output from the waveform shaping circuit for a certain period of time, a means is provided to output an activation signal to the overload cutoff circuit. An overload stop device for an ultrasonic motor, comprising an overload cutoff circuit that cuts off the drive circuit power of the ultrasonic motor in response to a signal. (2) In an ultrasonic motor in which a piezoelectric element having two electrode groups is attached to the stator and high-frequency voltages with different phases are applied to the piezoelectric element to drive a rotor that is in pressure contact with the stator, an electric signal is sent to the piezoelectric element. A monitor electrode for output is provided, a voltage adjustment circuit for adjusting the voltage of the electrical signal is connected to the monitor electrode, an oscillation circuit is provided for outputting an end frequency signal when the rotational output of the motor decreases, and the end frequency signal of this oscillation circuit and A synchronous rectifier circuit is provided that compares and judges the output signal from the voltage adjustment circuit and outputs an activation signal when the output signal is below the end frequency for a certain period of time. An overload stop device for an ultrasonic motor, characterized by being provided with an overload cutoff circuit that cuts off power. (3) In an ultrasonic motor in which a piezoelectric element having two electrode groups is attached to the stator and high-frequency voltages with different phases are applied to the piezoelectric element to drive a rotor that is in pressure contact with the stator, an electric signal is sent to the piezoelectric element. A monitor electrode for output is provided, a voltage adjustment circuit that adjusts the voltage of the electrical signal is connected to the monitor electrode, and a comparator circuit is connected to the output terminal of this voltage adjustment circuit via a rectifier circuit. A level setting circuit that oscillates a voltage level signal to a comparator circuit is provided, and the comparator circuit compares and judges the output voltage from the level setting circuit and the output voltage from the rectifier circuit, and the voltage of the rectifier circuit is set at the level for a certain period of time. An overload stop for an ultrasonic motor, characterized in that an overload cutoff circuit is configured to output an activation signal when the voltage is lower than the circuit voltage, and shuts off power to the drive circuit based on the activation signal of a comparator circuit. Device.