JP3010591B2 - Ultrasonic transmitter - Google Patents

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 piezoelectric ceramic.

[0002]

2. Description of the Related Art Conventionally, various types of measuring instruments using ultrasonic sensors, such as a distance sensor using an ultrasonic wave and an ultrasonic detector attached to a moving body and detecting unevenness on a traveling road surface, have been commercialized. In general, 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 transmitted.

[0003]

However, an ultrasonic wave is generated by applying an AC voltage having a resonance frequency of the vibration plate to a vibration plate made of a piezoelectric ceramic and a metal plate. The resonance frequency of the diaphragm changes depending on the temperature around 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 wave 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 was not stable and the measurement became unstable.

[0004] The present invention takes into consideration such problems of the conventional ultrasonic transmitter, and prevents a change in output sound pressure due to a change in ambient temperature or the like, and enables transmission of ultrasonic waves with stable sound pressure. It is intended to provide a sound wave transmitter.

[0005]

According to the present invention, there is provided an ultrasonic transmitting plate comprising a piezoelectric ceramic and a vibration plate for generating ultrasonic waves, a transmitter for outputting a signal of a predetermined frequency in response to an external frequency command signal, Of the current 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 <br/> machinery inputs the arm current amplitude installed value, comprising a controller for outputting a frequency command signal, said frequency command signal so that the amplitude and the machine arm current amplitude installed value of the mechanical arm current matches Is output.

[0006]

According to the present invention, there is provided a mechanical arm current detector for detecting a mechanical arm current that contributes to the displacement speed of the piezoelectric ceramic, and a frequency command signal is provided so that the amplitude of the mechanical arm current and a predetermined mechanical arm current setting value match. Is output, the sound pressure output from the diaphragm can be stably set to a predetermined value regardless of the ambient temperature.

As described above, by making the output from the diaphragm stable and constant, various measurement operations using ultrasonic waves can be stabilized, and a decrease in measurement accuracy can be prevented.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below along with embodiments.

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 denotes an amplifier for outputting a voltage for driving the transmitter 3; 5, a frequency variable oscillator for outputting an AC signal 101 having a predetermined frequency in response to an external frequency command signal 108; 6, a mechanical arm current detector; A rectifier circuit for detecting the amplitude of the control signal;

FIG. 5 shows an electrical equivalent circuit of the piezoelectric body, and FIG. 6 shows the admittance characteristics 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, at the resonance frequency f0, the magnitude of the amplitude of the mechanical arm current becomes maximum, and the drive voltage 102 and the phase of the mechanical arm current become 90 around that.
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 and the amplifier 4 amplifies the signal to a predetermined voltage and drives the transmitter 1 to generate an ultrasonic wave.

A mechanical arm current which directly contributes to the piezoelectric effect among the currents flowing into the vibrating body 1 is detected by an equipment arm current detector 6. The mechanical arm current detector 6 includes a capacitor 103 and a current detection resistor 1 equivalent to the capacitor of the electric arm which does not contribute to the piezoelectric effect of the electric equivalent circuit of the piezoelectric body shown in FIG.
4, the current flowing in the piezoelectric body and the current flowing in the capacitor 103 are obtained by using current detection resistors 104 and 105, respectively, as shown inside the mechanical arm current detector 6 in FIG. As a result, the current flowing through the electric arm is canceled to detect a voltage 106 proportional to the mechanical arm current (hereinafter, referred to as a mechanical arm current proportional voltage). The device arm current proportional voltage 106 output from the device arm current detector 6 is an alternating current, and is converted by the rectifier 7 into a voltage 107 proportional to the amplitude thereof.

The controller 8 supplies the transmitter 5 with the equipment arm current amplitude setting value 1 which is a voltage proportional to the mechanical arm current to be flowed.
09 and an apparatus arm current amplitude setting value 109 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 frequency variable oscillator 5 so that the two coincide. For example, the device arm current amplitude setting value 1
The difference between the voltage 09 and the voltage 107 proportional to the amplitude is defined 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, that is, so-called PID control so that the two values match. Can be configured. When the transmitter 1 is driven in this manner, the frequency of the variable frequency 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 a configuration of a technique related to the present invention . The description of the same components as those in FIG. 1 is omitted. As shown in FIG. 6, the phase difference between the mechanical arm current proportional voltage 106 and the drive signal 102 greatly changes near the resonance frequency. Then, the phase detector 7 detects the mechanical arm current proportional voltage 106 and the drive signal 102.
, And a phase difference signal 119 is output. The controller 8 sets a predetermined phase difference setting value 110 and a phase difference signal 111
The frequency command signal 108 is output to the variable frequency oscillator 5 so that 9 coincides. This control can also be realized by, for example, PID control in consideration of a change in the phase difference 107 with respect to a frequency change.

FIG. 3 shows the configuration of another example related to the present invention .
Show. The description of the same components as those in FIGS. 1 and 2 is omitted. A part of the electrode of the piezoelectric body is separated to constitute a sensor electrode 10 for detecting displacement of the piezoelectric body. The sensor electrode 10
The output of the sensor is detected by a sensor voltage detecting unit 9 that detects an output, and an output voltage 121 (hereinafter, referred to as a sensor voltage) of the sensor is detected. FIG. 7 shows the frequency characteristics of the amplitude of the sensor voltage 121 and the phase difference between the sensor voltage and the drive voltage. At the resonance frequency f0, the amplitude of the sensor voltage becomes maximum, 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 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 a 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 inputs, and sets the frequency command signal 1 so that the two coincide.
08 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 regarded as an error, and the integral of the error, the proportional value, and the sum of the differential values are used as the frequency command signal 108, so-called PID control. Can be configured to match. When the transmitter 1 is driven in this manner, 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 member provided on a part of the electrode of the piezoelectric member becomes a predetermined value. Is done.

FIG. 4 shows a configuration of another example related to the present invention .
Show. The description of the same components as those in FIGS. 1, 2, and 3 will be omitted. A part of the electrode of the piezoelectric body is separated as in FIG.
The sensor electrode 10 for detecting the displacement of the piezoelectric body is formed.
The detection unit 9 that detects the output of the sensor electrode 10 performs impedance conversion and detects an output voltage 121 of the sensor. As shown in FIG. 7, the amplitude of the sensor voltage becomes maximum at the resonance frequency f0, and the phase difference is 90 # near the resonance frequency.
To -90 #. Then, the phase detector 7 detects the phase difference between the sensor voltage 121 and the drive signal 102,
The phase difference signal 123 is output. The controller 8 sends the frequency command signal 10 to the variable frequency oscillator 5 such that the phase difference set value 124 of the predetermined sensor voltage matches the phase difference signal 123.
8 is output. This controller can also be realized by, for example, PID control in consideration of a change in the phase difference 107 with respect to a frequency change as shown in FIG. The variable frequency oscillator 5 supplies the amplifier 6 with an AC signal 1 having a frequency near the transmitter resonance frequency.
01, the amplifier 4 amplifies the signal to a predetermined voltage and drives the transmitter 1 to generate an ultrasonic wave. When the transmitter 1 is driven in this manner, the frequency of the frequency variable oscillator 5 is automatically adjusted so that the amplitude of the sensor voltage for detecting the amplitude of the piezoelectric member provided on a part of the electrode of the piezoelectric member becomes a predetermined value. Will be tracked.

In the above four examples, the explanation has been made with reference to the figures of the disk-shaped piezoelectric body and the vibrating body. However, the configuration of the transmitter is not limited to the disk-shaped one, and ultrasonic waves are excited by the piezoelectric body. Any shape may be used as long as it has a structure.

[0018]

As is apparent from the above description,
According to the present invention prevents a change in the output sound pressure due to temperature changes in the peripheral, it is possible to transmit ultrasound stable sound pressure.

When a plurality of ultrasonic transmitters are used, the directivity of the transmitted ultrasonic waves is stabilized by stabilizing the sound pressure of each. As a result, in application fields such as a distance sensor using ultrasonic waves, the reliability and stability of measurement can be improved, and the practical effect is great.

[Brief description of the drawings]

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

FIG. 2 is a configuration diagram of an example of a technique related to the present invention.

FIG. 3 is a configuration diagram of an example of a technique related to the present invention.

FIG. 4 is a configuration diagram of an example of a technique related to the present invention.

FIG. 5 is an electrical equivalent circuit of a 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 through a piezoelectric body used in the present invention and a drive voltage.

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

[Explanation of symbols]

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

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H04R 17/00 331 B06B 1/06 G01S 7/521 G01S 7/524 H03B 5/32

Claims (1)

(57) [Claims] An ultrasonic transmission plate comprising a piezoelectric ceramic for generating ultrasonic waves and a vibration plate; a transmitter for outputting a frequency signal for driving the piezoelectric ceramic in response to an external frequency command signal; of current, and a mechanical arm current detector for detecting a contributing mechanical arm current displacement speed of the piezoelectric ceramic, an input amplitude and <br/> machinery arm current amplitude installed value of the mechanical arm current, the machine ultrasonic transmitter characterized by comprising a controller for the amplitude and the machine arm current amplitude installed value of the arm current outputs said frequency command signal to match.