JPH06343200A - Ultrasonic transmitter - Google Patents

Abstract

(57) [Summary] [Purpose] To provide an ultrasonic transmitter capable of transmitting an ultrasonic wave having a stable sound pressure while preventing a change in output sound pressure due to a change in ambient temperature. A loop for automatically tracking a drive frequency such that a mechanical arm current flowing into a piezoelectric body 2 of an ultrasonic transmitter is detected, its amplitude or phase is detected, and its magnitude becomes a predetermined magnitude. Make up. Alternatively, a part of the electrodes of the piezoelectric body 2 is separated as a sensor, and a loop is configured so that the drive frequency is automatically tracked so that the amplitude or phase difference of the sensor becomes a predetermined value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic transmitter using a piezoelectric ceramic.

[0002]

2. Description of the Related Art Conventionally, various measuring instruments using a distance sensor using ultrasonic waves and an ultrasonic wave detector attached to a moving body to detect irregularities on a traveling road surface have been commercialized. Generally, the frequency of the voltage signal applied to the ultrasonic diaphragm during transmission is fixed near the resonance frequency of the diaphragm measured in advance and then transmitted.

[0003]

However, although an ultrasonic wave is generated by applying an AC voltage having a resonance frequency of the diaphragm to the diaphragm composed of the piezoelectric ceramic and the metal plate, the ultrasonic wave used in the ultrasonic transmitter is used. The resonance frequency of the diaphragm changes depending on the ambient temperature of the ultrasonic diaphragm. Therefore, when the piezoelectric ceramic is driven at a constant frequency and a constant voltage, the output sound pressure of the generated ultrasonic waves greatly changes depending on the temperature. For example, when used with a distance sensor, the S / N of the received waveform
There was a problem that the ratio became unstable and the measurement became unstable.

In consideration of the above problems of the conventional ultrasonic transmitter, the present invention prevents the change of the output sound pressure due to the temperature change of the surroundings and the like, and enables transmission of the ultrasonic wave of stable sound pressure. The purpose is to provide a sound wave transmitter.

[0005]

According to the present invention, there is provided an ultrasonic wave transmitting plate composed of a piezoelectric ceramic for generating an ultrasonic wave and a diaphragm, and an oscillator for outputting a signal of a predetermined frequency according to a frequency command signal from the outside. Among the currents flowing into the piezoelectric ceramic, a mechanical arm current detector that detects a mechanical arm current that contributes to the displacement speed of the piezoelectric ceramic, a rectifier circuit that detects the amplitude of the mechanical arm current, and an amplitude of the mechanical arm current. And a device arm current amplitude setting value as an input, and a controller that outputs a frequency command signal is provided, and the frequency command signal is output so that the amplitude of the machine arm current and the device arm current amplitude setting value match. .

Further, the present invention provides an ultrasonic wave transmitting plate composed of a piezoelectric ceramic for generating ultrasonic waves and a diaphragm, an oscillator for outputting a signal of a predetermined frequency according to a frequency command signal from the outside, and the piezoelectric ceramic. Of the inflowing current, a mechanical arm current detector that detects a mechanical arm current that contributes to the displacement speed of the piezoelectric ceramic, and a phase detector that detects the phase difference between the mechanical arm current and the voltage applied to the piezoelectric ceramic. A phase difference and a phase difference setting value are input, and a controller that outputs a frequency command signal is provided, and the frequency command signal is output so that the phase difference of the mechanical arm current and the phase difference setting value match. is there.

Further, the present invention is an ultrasonic wave transmitting plate composed of a piezoelectric ceramic and a vibration plate for generating an ultrasonic wave, an oscillator for outputting a signal of a predetermined frequency according to a frequency command signal from the outside, and the inside of the piezoelectric ceramic. The sensor provided to detect the displacement speed, and the controller that receives the output and installation value of the sensor as input and outputs the frequency command signal, so that the output of the sensor and the installation value match. The frequency command signal is output.

Also, the present invention provides an ultrasonic wave transmitting plate composed of a piezoelectric ceramic and a vibration plate for generating ultrasonic waves, an oscillator for outputting a signal of a predetermined frequency according to a frequency command signal from the outside, and the inside of the piezoelectric ceramic. A sensor for detecting the displacement speed provided in, a phase detector for detecting the phase difference between the sensor output and the voltage applied to the piezoelectric ceramic, and the phase difference and the phase difference setting value as an input,
A controller that outputs a frequency command signal is provided, and the frequency command signal is output so that the phase difference of the sensor and the phase installation value match.

[0009]

In the present invention, the machine arm current detector for detecting the machine arm current that contributes to the displacement speed of the piezoelectric ceramic is provided, and the frequency command signal is provided so that the amplitude of the machine arm current and the predetermined machine arm current installation value match. By outputting, the sound pressure output from the diaphragm can be made stable and have a predetermined magnitude regardless of the ambient temperature.

Further, according to the present invention, a mechanical arm current detector for detecting a mechanical arm current contributing to the displacement speed of the piezoelectric ceramic, and a phase for detecting a phase difference between the mechanical arm current and the voltage applied to the piezoelectric ceramic. Equipped with a detector, by outputting the frequency command signal so that the phase difference of the mechanical arm current and the phase difference installation value match, the output sound pressure from the diaphragm is stable regardless of the ambient temperature. And it can be made into a predetermined size.

Further, according to the present invention, there is provided a sensor for detecting the displacement speed provided in the piezoelectric ceramic,
By outputting the frequency command signal so that the output of the sensor and the predetermined installation value match, the sound pressure output from the diaphragm can be made stable and have a predetermined magnitude regardless of the ambient temperature. it can.

Further, according to the present invention, a sensor provided in the piezoelectric ceramic for detecting the displacement speed thereof and a phase detector for detecting the phase difference between the sensor output and the voltage applied to the piezoelectric ceramic are provided. By outputting the frequency command signal so that the phase difference of the sensor and the phase installation value match, the output sound pressure from the diaphragm can be made stable and to a predetermined magnitude regardless of the ambient temperature. You can

As described above, by making the output from the diaphragm stable and constant, the operation of various measurements using ultrasonic waves is stable, and it is possible to prevent deterioration of measurement accuracy.

[0014]

EXAMPLES Details of the present invention will be described below with reference to examples.

FIG. 1 shows the configuration of an embodiment of the present invention. 1 is a transmitter, 2 is a piezoelectric disk, 3 is a diaphragm,
Reference numeral 4 is an amplifier for outputting a voltage for driving the transmitter 3, 5 is a frequency variable oscillator for outputting an AC signal 101 having a predetermined frequency in response to an external frequency command signal 108, 6 mechanical arm current detector, 7 is mechanical arm current A rectifier circuit for detecting the amplitude of the signal, and a controller 8.

FIG. 5 shows an electrically equivalent circuit of the piezoelectric body, and FIG. 6 shows the admittance characteristic of the mechanical arm current. The mechanical arm current is introduced, for example, in Japanese Patent Application No. 62-95614 (ultrasonic motor device). As shown in FIG. 6, the magnitude of the amplitude of the mechanical arm current becomes maximum at the resonance frequency f0, and the phase of the drive voltage 102 and the mechanical arm current becomes 90 in the vicinity thereof.
It changes greatly from ° to -90 °.

The sound pressure output of the transmitter 1 is substantially proportional to the magnitude of the mechanical arm current flowing into the piezoelectric body. The oscillator 5 supplies the amplifier 4 with an AC signal 10 having a frequency near the transmitter resonance frequency.
1 is output, and the amplifier 4 amplifies the signal to a predetermined voltage and drives the transmitter 1 to generate ultrasonic waves.

Of the currents flowing into the vibrating body 1, the machine arm current detector 6 which directly contributes to the piezoelectric effect is detected by the device arm current detector 6. In the mechanical arm current detector 6, the capacitor 103 and the current detection resistor 1 equivalent to the capacitor capacity of the electric arm that does not contribute to the piezoelectric effect of the electric equivalent circuit of the piezoelectric body shown in FIG.
No. 04 is prepared, the current flowing through the piezoelectric body and the current flowing through the capacitor 103 are obtained using the current detecting resistors 104 and 105, respectively, as shown in the inside of the mechanical arm current detector 6 of FIG. 1, and the difference between them is calculated. As a result, the current flowing through the electric arm is canceled to detect the voltage 106 proportional to the mechanical arm current (hereinafter referred to as mechanical arm current proportional voltage). The device arm current proportional voltage 106, which is the output of the device arm current detector 6, is an alternating current, and is converted by the rectifier 7 into a voltage 107 proportional to its amplitude.

In the controller 8, the transmitter 5 has a device arm current amplitude setting value 1 which is a voltage proportional to the machine arm current desired to flow.
09 and a voltage 107 proportional to the amplitude, which is a voltage proportional to the amplitude, and a voltage 107 proportional to the amplitude are input, and a frequency command signal 108 is output to the variable frequency oscillator 5 so that the both match. For example, equipment arm current amplitude setting value 1
The difference between 09 and the voltage 107 proportional to the amplitude is taken as an error, and the sum of the integrated value, the proportional value, and the differential value of the error is used as the frequency command signal 108, so that the two coincide with each other by what is called PID control. Can be configured. When the transmitter 1 is driven in this way, the frequency of the frequency variable oscillator 5 is automatically tracked so that the amplitude of the device arm current flowing into the piezoelectric body 1 becomes a predetermined magnitude.

FIG. 2 shows the configuration of the second embodiment of the present invention. Description of the same components as in FIG. 1 will be omitted. As shown in FIG. 6, the phase difference between the mechanical arm current proportional voltage 106 and the drive signal 102 greatly changes in the vicinity of the resonance frequency. Therefore, the phase detector 7 uses the mechanical arm current proportional voltage 106 and the drive signal 102.
The phase difference signal 119 is detected and the phase difference signal 119 is output. In the controller 8, a predetermined phase difference set value 110 and a phase difference signal 111
The frequency command signal 108 is output to the variable frequency oscillator 5 so that 9 match. This control can also be realized by, for example, PID control in consideration of the change in the phase difference 107 with respect to the change in frequency.

FIG. 3 shows the configuration of the third embodiment of the present invention. Description of the same components as those in FIGS. 1 and 2 is omitted.
A part of the electrodes of the piezoelectric body is separated to form a sensor electrode 10 for detecting displacement of the piezoelectric body. The sensor voltage detection unit 9 that detects the output of the sensor electrode 10 performs impedance conversion to detect the sensor output voltage 121 (hereinafter referred to as sensor voltage). FIG. 7 shows frequency characteristics of the amplitude of the sensor voltage 121 and the phase difference between the sensor voltage and the drive voltage. The amplitude of the sensor voltage becomes maximum at the resonance frequency f0, and the phase difference greatly changes from 90 ° to −90 ° near the resonance frequency. Similar to the mechanical arm current, the sound pressure output of the transmitter 1 is substantially proportional to the magnitude of the amplitude of the sensor voltage 121. The oscillator 5 outputs an AC signal 101 having a frequency near the transmitter resonance frequency to the amplifier 6, and the amplifier 4 amplifies the signal to a predetermined voltage and drives the transmitter 1 to generate ultrasonic waves. The rectifier 7 detects the voltage 122 proportional to the amplitude of the sensor voltage 121. The controller 8 receives the setting value 111 of the amplitude of the sensor voltage and the amplitude value 122 of the sensor voltage as input, and makes the frequency command signal 1
08 is output to the variable frequency oscillator 5. For example, the difference between the sensor voltage setting value 111 and the voltage 122 proportional to the amplitude is used as an error, and the sum of the integral value, proportional value, or differential value of the error is used as the frequency command signal 108, so-called PID control, whereby both are Can be configured to match. When the transmitter 1 is driven in this way, the frequency of the variable oscillator 5 is automatically tracked so that the amplitude of the sensor voltage for detecting the amplitude of the piezoelectric body provided on a part of the electrode of the piezoelectric body becomes a predetermined magnitude. To be done.

FIG. 4 shows the configuration of the fourth embodiment of the present invention. Descriptions of the same components as those in FIGS. 1, 2, and 3 are omitted. Similar to FIG. 3, a part of the electrodes of the piezoelectric body is separated to form a sensor electrode 10 for detecting the displacement of the piezoelectric body. The detection unit 9 that detects the output of the sensor electrode 10 performs impedance conversion and detects the output voltage 121 of the sensor.
As shown in FIG. 7, the amplitude of the sensor voltage is maximum at the resonance frequency f0, and the phase difference is 90 ° in the vicinity of the resonance frequency.
It changes greatly up to 90 °. Therefore, the phase detector 7 detects the phase difference between the sensor voltage 121 and the drive signal 102, and outputs the phase difference signal 123. The controller 8 outputs the frequency command signal 108 to the variable frequency oscillator 5 so that the phase difference set value 124 of the predetermined sensor voltage and the phase difference signal 123 match. Also in this controller, as shown in FIG. 7, in consideration of the change of the phase difference 107 with respect to the frequency change, for example, P
It can be realized by ID control. The variable frequency oscillator 5 causes the amplifier 6 to receive an AC signal 101 having a frequency near the transmitter resonance frequency.
Then, the amplifier 4 amplifies the signal to a predetermined voltage and drives the transmitter 1 to generate ultrasonic waves. When the transmitter 1 is driven in this way, the frequency of the variable frequency oscillator 5 is automatically adjusted so that the amplitude of the sensor voltage for detecting the amplitude of the piezoelectric body provided on a part of the electrode of the piezoelectric body becomes a predetermined magnitude. Be tracked.

In the above four examples, the disk-shaped piezoelectric body and the vibrating body have been described, but the structure of the transmitter is not limited to the disk-shaped, and ultrasonic waves are excited by the piezoelectric body. It may have any shape as long as it has a structure.

[0024]

As is apparent from the above description,
As described above, according to the present invention, the sound pressure of the transmitter that outputs the ultrasonic pulse is set to the amplitude of the mechanical arm current, the phase difference between the mechanical arm current and the driving voltage, the sensor output, or the sensor output and the driving voltage. By automatically tracking the drive frequency so that the phase difference becomes a predetermined value, it is possible to prevent a change in output sound pressure due to a change in ambient temperature and the like, and to transmit ultrasonic waves having a stable sound pressure.

When a plurality of ultrasonic wave transmitters are used, the sound pressures of the ultrasonic wave transmitters are stabilized and the directivity of the transmitted ultrasonic waves is stabilized. As a result, it is possible to improve the reliability and stability of measurement in an application field such as a distance sensor using ultrasonic waves, and its practical effect is great.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a third embodiment of the present invention.

FIG. 4 is a configuration diagram of a fourth embodiment of the present invention.

FIG. 5 is an electrical equivalent circuit of the piezoelectric body used in the present invention.

FIG. 6 is a frequency response characteristic diagram of a phase difference between a magnitude of a mechanical arm current flowing in a piezoelectric body used in the present invention and a driving voltage.

FIG. 7 is a frequency response characteristic diagram of a phase difference between an output amplitude and a drive voltage of a sensor electrode provided with a piezoelectric body used in the present invention.

[Explanation of symbols]

 1 Transmitter 2 Piezoelectric body 3 Vibration plate 4 Amplifier 5 Frequency variable oscillator 6 Mechanical arm current detector 7 Rectifier circuit 8 Controller 9 Sensor voltage detection unit 10 Sensor electrode 101 AC signal 102 Drive signal 103 Capacitor 104 Current detection resistance 106 Mechanical arm Current proportional voltage 107 Machine arm current amplitude 108 Frequency command signal 109 Machine arm current amplitude setting value 110 Machine arm current phase difference setting value 119 Machine arm current phase difference 111 Sensor voltage amplitude setting value 121 Sensor voltage 122 Sensor voltage amplitude 123 Sensor voltage level Phase difference 124 Sensor voltage setting value

Claims (4)

[Claims] 1. An ultrasonic wave transmitting plate composed of a piezoelectric ceramic and a vibration plate for generating an ultrasonic wave, an oscillator for outputting the frequency signal for driving the piezoelectric ceramic according to a frequency command signal from the outside, and an inflow into the piezoelectric ceramic. Among the currents to be used, a mechanical arm current detector that detects a mechanical arm current that contributes to the displacement speed of the piezoelectric ceramic, and the amplitude of the mechanical arm current and the equipment arm current amplitude installation value are input, and the amplitude of the mechanical arm current and An ultrasonic transmitter, comprising: a controller that outputs the frequency command signal so that the device arm current amplitude installation values match. 2. An ultrasonic wave transmitting plate composed of a piezoelectric ceramic and a vibration plate for generating an ultrasonic wave, an oscillator for outputting the frequency signal for driving the piezoelectric ceramic according to a frequency command signal from the outside, and an inflow into the piezoelectric ceramic. Among the currents to be used, a mechanical arm current detector that detects a mechanical arm current that contributes to the displacement speed of the piezoelectric ceramic, and a phase detector that detects the phase difference between the mechanical arm current and the voltage applied to the piezoelectric ceramic, An ultrasonic transmission, comprising: a controller that inputs the phase difference and the phase difference installation value and outputs the frequency command signal so that the phase difference of the mechanical arm current and the phase difference installation value match. vessel. 3. An ultrasonic wave transmitting plate composed of a piezoelectric ceramic and a vibrating plate for generating an ultrasonic wave, an oscillator for outputting the piezoelectric ceramic driving frequency signal in response to a frequency command signal from the outside, and an inside of the piezoelectric ceramic. A sensor for detecting the displacement speed provided and a controller for inputting the output of the sensor and a predetermined installation value and outputting the frequency command signal so that the output of the sensor matches the installation value are provided. An ultrasonic transmitter characterized in that 4. An ultrasonic wave transmitting plate composed of a piezoelectric ceramic and a vibration plate for generating an ultrasonic wave, an oscillator for outputting the frequency signal for driving the piezoelectric ceramic according to a frequency command signal from the outside, and the inside of the piezoelectric ceramic. A sensor for detecting the displacement speed provided, a phase detector for detecting the phase difference between the sensor output and the voltage applied to the piezoelectric ceramic, and the sensor using the phase difference and the phase difference setting value as input. And a controller that outputs the frequency command signal so that the phase difference of the above and the phase installation value match.