JP2562758B2 - Ultrasonic leak detection method and ultrasonic oscillator used in the method - 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 leak detection method for detecting leakage and failure of mechanical parts by ultrasonic waves, and an ultrasonic oscillator used in the method.

[0002]

BACKGROUND OF THE INVENTION For example, it is known that ultrasonic oscillators and detectors can be used to locate leaks inside pipes. A device of this kind is Harris (Harri).
US Pat. No. 3,978,915 assigned to s). In the above device, the ultrasonic generator is located inside the chamber through which the pipe passes. Ultrasonic detectors are located at both ends of the pipe outside the chamber. Ultrasound enters the interior of the pipe where there is a leak or where the pipe wall is thin and travels along the pipe to the end where the detector is located. Thus, the detector will receive a signal indicating the presence of a leak or weak spot. Ultrasound used for this purpose is generally in the frequency range of 40 KHz.
It is a number , which is higher than the frequency that people can hear. Therefore,
There will be provided means for modulating the wavelength of the detected signal in the audible frequency range to generate a "beat", and various methods can be considered for this purpose.

For example, in the case of detecting a failure of a bearing, the ultrasonic detector is mechanically assembled to the casing of the bearing, and the vibration generated by the defective portion is mechanically transmitted to the detector. With such a configuration,
Frequency is not defined by the ultrasonic generator,
It will be determined by the mechanical vibration itself. Then, in such a case, the ultrasonic detection circuit must be capable of scanning a frequency band within a certain range to detect a frequency characterized by a failure. For this purpose, a "beat" generator circuit, which is often used with a radio receiver, can be modulated in each frequency range.

[0004]

[SUMMARY OF THE INVENTION However, by arranging the ultrasonic generator within the closed chamber, ultrasonic peak and a node that will be generated by from the ultrasonic generator (nod
e) A standing wave with and will be transmitted through the ultrasonic waves through these points when the node coincides with a leaked point or a weakened point.
However, there is a drawback in that it cannot escape outside the closed chamber and therefore leak detection cannot be performed.

Accordingly, the present invention, the conventional disadvantages those to been made to solve, its purpose regardless of the location became leakage points or weak a node position location of the ultrasonic readily ultrasonic leakage It is to provide a method that can detect. Another object of the present invention is to provide an ultrasonic oscillating device capable of oscillating ultrasonic waves so that a node of a standing wave does not always exist at one location on the outer surface of the container.

[0006]

According to the present invention, a container
A method to detect small openings or thin areas,
An ultrasonic transmitter is placed inside the container to generate ultrasonic waves.
And the ultrasonic detector is passed through the outer surface of the container.
To detect the ultrasonic waves leaking from the container
And the step of specifying the leakage position.
In the step of generating the ultrasonic wave,
The frequency of the ultrasonic wave generated by the wave oscillator
Sweeps periodically over a range of frequencies within a certain frequency range
However, the cycle is characterized by being larger than the cycle of the audible band.
An ultrasonic leak detection method is provided.

Also according to the invention, a small opening in the container
Of a container or a thin part,
The process of placing an ultrasonic oscillator inside and generating ultrasonic waves
And passing an ultrasonic detector on the outer surface of the container
The ultrasonic waves leaking from the container are detected by the
The ultrasonic wave generation used in the method consisting of the step of specifying the leakage position.
In the shaker, an oscillation circuit means for generating ultrasonic waves,
The center of the frequency of the ultrasonic waves generated by the oscillator circuit means
Regarding frequency, it is audible within a specified frequency range within the audible band.
Equipped with sweeping means that sweeps at a cycle larger than the band cycle
An ultrasonic oscillator is provided.

A predetermined value within the audible band for the center frequency
Sweeping in the frequency range means, for example, the frequency in the ultrasonic range.
With a center frequency of 40 kHz
With a width of 4 kHz, ie between 38-42 kHz
It means that the frequency is continuously modulated. The audible bandwidth
2 to 5 kHz is preferable . Periodically
Sweep means that the frequency modulation is repeated.
Means that the period is greater than the period of the audible band,
This period is generally called the upper limit period of the audible band.
The period must be 0.05 sec (frequency 20 Hz) or more.
Means and. In the present invention, the cycle is 0.
2 (frequency 5Hz) to 0.05sec (frequency 20H
z) is preferred. Thus limiting the cycle
Allows leaked ultrasonic waves to be detected and workers to hear
When converting to a frequency in the audible band,
The effect is that the width is not changed .

[0009]

The method or device of the present invention is placed inside a container.
The frequency of the ultrasonic waves generated from the ultrasonic transmitter is swept.
As a result, a standing wave cannot occur
It doesn't always exist. Therefore, the ultrasonic waves
Reliably leaks from thinned areas. Also, the leaked super
Converts sound waves into frequencies in the audible band, which workers can hear
If so, the ultrasonic waves are in the audible bandwidth.
Modulated by a number, the operator is not a single tone
You can hear the sound and be sure to recognize the leaked part.
Wear.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram showing an apparatus for detecting mechanical defects such as bearing damage and container leakage by ultrasonic waves. As an example, the container 10 is shown. Inside the container 10, for example, an ultrasonic oscillator 12 that generates ultrasonic waves in the vicinity of 40 KHz is arranged. According to the present invention, this ultrasonic oscillator 12 has, for example, 0.2 to 0.05 sec in the range close to the center frequency of 40 KHz.
A frequency-modulated output is generated with a very narrow cycle of about (5 to 20 Hz) . By modulating the oscillator output, the shape of the standing wave inside the container can be changed so that the nodes of the standing wave are not held in a fixed position.

There is a small hole in the leaking portion 10 'inside the container 10, from which ultrasonic energy escapes and is detected by the ultrasonic transducer 14. Ultrasonic transducer 1
The output of 4 is a preamplifier 1 having a field effect transistor
6, the gain of the preamplifier 16 is applied to the sensitivity controller 1
Under control of 6 ', the sensitivity controller 16' changes the supply voltage to the preamplifier 16 as shown in FIG.

The ultrasonic signal is transmitted from the preamplifier 16 to the transistor excitation amplifier 20, which again amplifies the signal and, via capacitors 29 and 29 ', the input terminal (pin 1) of the function generator 22. Connect to the capacitor. The generator 22 serves to frequency convert the amplified ultrasonic signal into the audible frequency range. The audible signal from the output terminal (pin 2) of the function generator 22 is
Applied to a headphone transistor amplifier 24 including a transistor-coupled configuration. The signal is transmitted from the amplifier 24 through the transformer 25 as a filter to the pair of headphones 2.
It is transmitted to 6. The transformer 25 as a filter functions to remove the frequency of the carrier wave and the frequency of unrelated signals such as the sum signal from the signal applied to the headphones. The output of the function generator 22 is also applied to the frequency compensation meter amplification circuit 35 via the transistor excitation amplifier 23.
A filter inside the frequency compensation meter amplifier circuit 35 functions to cancel the carrier signal and extraneous signals, leaving only an audible signal. A temperature compensating circuit 36 and a meter signal adjusting circuit 37 are connected to the frequency compensating meter amplifying circuit 35, and the output of the meter signal adjusting circuit 37 is applied to a meter 38. Circuit 37 serves to condition the signal for proper display by meter 38.

The temperature compensation circuit 36 includes a thermistor 36 'which is part of a voltage divider network which connects to a meter signal conditioning circuit 37. As a result, as the temperature rises, the meter signal adjusting circuit 3 is arranged so as to compensate the gain change due to the temperature rise.
The ratio of the voltage applied to 7 changes. The meter signal conditioning circuit 37 has two diodes, one of which is a germanium transistor 39 connected as a diode. The function of this diode is to rectify the received AC signal and generate a DC signal to be applied to the meter. This DC signal is applied to the meter, usually through resistor 37 (1). When operating the meter in logarithmic mode, switch 37 (2) is closed and diode 39 'and resistor 37 (3) and resistor 37 (1) are connected in parallel. Resistor 37 (3) is resistor 37 (1)
It is a much smaller resistor, and therefore the scale of the meter changes. In addition, the diode 39 (1) in series with the resistor 37 (3) creates a voltage limit, eliminating noise in the circuit during the sensitive logarithmic scale.

In the arrangement shown in FIG. 1, the ultrasonic signal leaking from the container 10 is intercepted by the ultrasonic transducer 14 and is frequency-converted, so that the user can use the headphones 2
The presence of a leak can be known by the sound heard at 6 and the level displayed on the meter 38. The actual frequency conversion of the ultrasonic signal is performed by the function generator 22. The generator may be a commercially available integrator circuit, such as the EXAR2206, which is pin 7 of the circuit.
Provides a sine wave output at a frequency defined by the tuning resistor 30 connected to and the capacitor 22 'connected to pins 5 and 6. One of the features of this circuit is that it produces an amplitude modulated compressed carrier output when a specific bias is applied to the input terminal (pin 1). This compression carrier modulation is derived from the variable resistor 28. If a capacitor 22 'and a tuning resistor 30 that generate a carrier signal in an audible band whose frequency is different from that of the ultrasonic signal are selected,
The output of the function generator 22 will be audible with respect to the input ultrasound signal and the much higher signal. In particular, the outputs are those corresponding to the sum and difference frequencies of the ultrasonic signal and the carrier signal generated by the function generator 22, but the carrier signal itself is not present in the output. For example, the function generator 22
If the tuning resistor 30 is set so that a signal of 42 KHz is output from the device, and the ultrasonic signal applied to the function generator 22 via the capacitors 29 and 29 'is 40 KHz, the outputs are 2 KHz and 82 KHz. . Since only signals in the audible band are desired, 82 KHz
The transformer 25 as a filter circuit and the frequency compensation meter amplifier circuit 35 are designed so as to remove the sum signal of.

Proper biasing of the input to the function generator 22 removes or compresses the carrier generated by the function generator 22, but this adjustment is an essential requirement, and some of the carrier is subject to temperature changes and voltage changes. May be leaked due to changes. Further, since the frequency of the carrier wave changes due to the change of the setting value of the tuning resistor 30, the circuit operation may change and the carrier wave may appear in the output when the bias is not adjusted. Servo or feedback circuitry is provided to make this adjustment. That is, the output terminal (pin 2) of the function generator 22 is applied via the transistor excitation amplifier 23 to the high pass filter 27 (2) which passes only frequencies above 20 KHz. Filter 27
The output of (2) is applied to the Darlington transistor connection configuration forming amplifier 27. Amplifier 27
Amplifies the received carrier signal, and the capacitor 27
The function (1) serves to integrate, that is, average. This signal is inverted by the amplifier to change the bias from the variable resistor 28 to correct for the carrier present in the output signal. Although there is always a carrier wave to generate an error signal, its level is low enough to avoid erroneous display on the headphones 26 and the meter 38.

In one embodiment of the present invention, a transducer is used that directly detects the vibration from the bearing by mechanically connecting the noise source, such as the housing of the bearing, directly to the crystal of the transducer. . The band of the signal detected in such a case is 20 KHz to 100 KHz, and the position of the tuning resistor 30 is changed to select a specific band of the above frequency range. Generate a carrier frequency that moves with.

In another embodiment, 40 KHz internally
Place the transducer some distance from the hole in the container that holds the oscillator 12. In this case, the detector is preferably 40
Used in KHz operating mode. When operating in the acoustic reception mode, which holds the transducer in a remote position, the tuning resistor 30 is rotated to the scale at one end. Near this scale, the resistance of the tuning resistor 30 drops to near zero. When entering the scale at one end, the switch 34 is displaced,
By connecting the preset resistor 32 to the frequency control line, the resistance of the tuning resistor 30 drops to near zero. When entering the scale at one end, the switch 34 is displaced and the preset resistor 3
2 is connected to the frequency control line to activate the 40 KHz resonance filter 21. The resonance filter 21 is 40KH
It functions to boost the frequency in the z band and remove frequencies outside this frequency band. The preset resistor 32 is
The frequency of the function generator 22 is set to a value near 40 KHz, for example, a frequency of 42 KHz.

Power to the circuit of FIG. 1 originates from a battery 40, and power enters a DC-DC converter 42 via a power switch 50 to provide a 15 volt output applied to each part of the circuit. From the input part of the battery 40 to the DC-DC exchanger 4
On the way to 2, a recharge instruction circuit composed of reference numerals 44 to 47 is arranged. When power switch 50 is closed, the voltage from battery 40 biases transistors 45 and 47 in a Darlington transistor arrangement. The variable resistor 44 is set so that the transistor 45 turns “off” when the transistor 47 turns “on”. However, as the voltage of battery 40 drops, the bias applied to the base of transistor 47 becomes insufficient to keep transistor 47 conductive. When the transistor 47 is turned off,
Transistor 45 turns "on" and current is conducted through light emitting diode 46. This light emitting diode 46
Indicates when the battery must be charged. By using a series arrangement of Darlington transistors, such as transistors 45 and 47, the circuit response is sharp and the setting of variable resistor 44 allows a particular level of battery voltage range attenuation to be set. , The specific level is displayed correctly.

Next, details of the receiver and the frequency conversion circuit will be described. Please refer to the detailed drawing of the ultrasonic oscillator 12 shown in FIG. This oscillator is generally about 4
It is set to generate an output ultrasonic signal of 0 KHz. In order to generate an output ultrasonic signal of 40 KHz, in a feedback circuit of an oscillator including a transistor 110, Panasonic Corporation (Pana
sonic Corp. 40) as manufactured in
A KHz crystal transducer 114 is used. When the circuit is switched on, current flows from the power supply to the transistor 110 through the amplitude control resistor 118 and the primary side of the transformer 112. As a result, the voltage level applied to the crystal transducer 114 becomes a voltage level at which resonance occurs at the fundamental frequency of 40 KHz. The resonant frequency from the crystal transducer 114 flows to the base of the transistor 110 through a filter network consisting of a capacitor 115, a parallel combination of capacitors and resistors 116, and a capacitor 117. The filter network passes signals in the 40 KHz range and removes harmonics (overtones). The reversal of the feedback signal to obtain the positive feedback required for oscillation is provided by the winding on the secondary side of the transformer 112 which is connected midway to the crystal transducer 114.
With such an arrangement, the crystal is excited at a resonant frequency of 40 KHz to generate ultrasonic waves at this frequency.

When the oscillator 12 is placed inside a container such as the container 10 shown in FIG. 1, the ultrasonic energy generated by the crystal fills the container 10 and leaks from the container at an opening such as a leak 10 '. put out. However, inside the container, a constant output from the crystal transducer 114 creates a standing wave inside the container. Therefore, the position of the leak portion 10 'may become a node of the standing wave, and the leak detection may fail. To compensate for this,
By gradually changing the output frequency of the ultrasonic oscillator 12, the waveform of the standing wave is gradually changed. Resistor 12
0, the condenser 122, and the Litronics Flasher model (Litronix Flasher Mo
d. ) With a flasher light emitting diode 124 such as FRL-4403, the output frequency of the oscillator is varied. With this arrangement, current flows through resistor 120 and is stored in capacitor 122. As the charge is stored, the bias applied to the transistor 110 changes, causing frequency conversion of 2 to 5 kHz in the oscillator. When the breakdown voltage of the flasher light emitting diode 124 is reached,
The voltage applied to the capacitor 122 is discharged and this process is repeated. The frequency variation is 0.2 to 0.
The resistor 120 and the capacitor 122 are selected so that the operation is performed in a cycle longer than the audible range of about 05 sec (5 to 20 Hz) . However, other bands can be selected.

Instead of the flasher light emitting diode 124, other types of voltage breakdown devices may be used to modify the circuit of FIG. Further, the secondary side of the transformer 112 may be in the winding state shown in FIG. 2 so that the voltage does not increase. The above arrangement lowers the impedance on the crystal, lowering the Q and increasing the frequency variation that can be achieved. By gradually changing the output frequency, not only the problem of the node position can be avoided, but also the leakage detection becomes psychologically easy for the listener. Further modifications to the receiver circuit to make it responsive only to fluctuating frequencies will make the receiver circuit more sensitive and improve the signal to noise ratio.

A converter and preamplifier for detecting the signal generated by the oscillator of FIG. 2 is shown in FIG. A series connected ultrasonic transducer group which receives ultrasonic waves and converts them into electrical signals is shown in FIG. As each converter, for example, 40KH manufactured by Panasonic Corporation
A z-piezoelectric crystal can be used. Although three crystals are illustrated in FIG. 3, the number of crystals is not limited, and two or three or more crystals can be used. By arranging these transducers adjacent to each other on one plane, each transducer receives an acoustic signal, and since they are connected in series, the electrical signals generated by the acoustic signals are added and one transducer is added. Gives greater output than if used. If the preamplifier impedance is low, the effect of the converter arrangement as described above is diminished. A field effect transistor preamplifier with an input stage field effect transistor 220 is used to avoid diminishing effects. The output of the field effect transistor 220 is applied to the field effect transistor 230 via the capacitor 222. Field effect transistor 230
D is the output of the preamplifier and is connected to the transistor pump amplifier 20 shown in FIG. As already explained, the receiver can be used in a mode of scanning ultrasonic frequencies of 20 KHz to 100 KHz, or in the preferred 40 KHz band. About 40 KH when used in the preferred 40 KHz band
To create a resonant circuit with a frequency response centered on z, capacitors 212 and 214 and an inductance 21
Use 6 and. With this configuration, the voltage of 40 KHz is increased by 40 times, and the frequency deviated from the center frequency band is greatly attenuated. When using this resonance circuit,
It is important that the transistor is a MOS type FET.

The gain of the preamplifier is controlled by the sensitivity controller 16 'shown in FIG. The voltage derived from the variable resistor is applied to the drains D of the input stage field effect transistor 220 and the field effect transistor 230 via the corresponding resistors. In this way, since the amplitude control is performed outside the signal path, the scratching sound of the sensitivity controller 16 'is not heard from the headphone 26. Furthermore, by lowering the voltage level applied to the circuit, the overload of the preamplifier can be easily compensated.

Any number of converters can be used, regardless of the number of converters used.
10 are connected in series and are preferably arranged close together in a flat plane. Placing these transducers next to each other on a flat surface effectively focuses the entire transducer at an infinite distance. If desired, the transducer can be placed on a curved or parabolic surface and focused to receive waves emanating from sources closer than infinity. However, in most cases
No arrangement on the curved surface is required. While the present invention has been illustrated and described with reference to preferred embodiments, it will be apparent to those skilled in the art that many changes can be made in the structure and details without departing from the spirit and scope of the invention. I think it can be done.

[0025]

As described above , according to the present invention,
Since the frequency of the ultrasonic waves generated in the container is swept,
There can be no standing waves and ultrasonic nodes are always present at the container.
We Na Mashimashi. Therefore, whether it is a hole or a thin part of the container
Ultrasonic wave leaks from the
It It also converts leaked ultrasonic waves into audible frequencies.
However, if the operator makes this audible,
Since sound waves that are modulated at a frequency in the audible bandwidth, work
The person can hear the change sound instead of the single sound, and
Can be surely recognized.

[Brief description of drawings]

FIG. 1 is an overall layout diagram of a circuit used in a method of the present invention and a configuration diagram showing a case where the circuit is used for detecting leakage.

FIG. 2 is a schematic explanatory diagram of the ultrasonic oscillator of FIG.

FIG. 3 is a schematic illustration of the converter and preamplifier of FIG.

[Explanation of symbols]

10 Container 10 'Opening (Leakage) 12 Ultrasonic Oscillator 14 Ultrasonic Transducer 16 Preamplifier 22 Function Generator

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Zeno, Jiyoung Richardyard 10011, New York, New York, United States 10011, New York, Twenty Second Street 221 (72) Inventor Boruso, Marty 11218, Burtskrin, Seventy-Fourst, New York, United States Street 1336 (56) Reference JP 58-117434 (JP, A) JP 50-43988 (JP, A) US Pat. No. 3978915 (US, A)

Claims (2)

(57) [Claims] 1. A small opening or thin portion of a container is detected.
The method is to put out an ultrasonic oscillator inside the container.
Place and generate ultrasonic waves on the outer surface of the container
Leakage from the container by passing through an ultrasonic detector
The process of detecting the emitted ultrasonic waves and specifying the leak position
In the method consisting of, in the step of generating the ultrasonic wave, the ultrasonic wave is generated.
Set the frequency of the ultrasonic wave generated by the shaker to a certain center frequency
Then, it sweeps periodically with a predetermined frequency width in the audible band,
The period is greater than the period of the audible band.
Sound wave leakage detection method. 2. A small opening or thin portion of a container is detected.
The method is to put out an ultrasonic transmitter inside the container.
Place and generate ultrasonic waves on the outer surface of the container
Leakage from the container by passing through an ultrasonic detector
The process of detecting the emitted ultrasonic waves and specifying the leak position
And an oscillation circuit means for generating ultrasonic waves in an ultrasonic transmitter used in the method comprising
The frequency of the ultrasonic waves generated by a certain center frequency
Within a certain frequency range within the audible band, and from the audible band period
A sweeping means for sweeping in a large cycle,
Ultrasonic oscillator .