JPH01267454A - Air bubble detector - Google Patents

Abstract

PURPOSE:To test airtightness by detecting air bubbles, by emitting an ultrasonic wave into a liquid at a definite cycle and detecting the temporary reflecting echo from rising air bubbles. CONSTITUTION:An ultrasonic wave having predetermined frequency is sent to a vibrator 11 from an ultrasonic transmitting circuit 12 while the ultrasonic wave received by the vibrator 11 is converted to an electric signal by an ultrasonic wave receiving circuit 13. A count circuit 14 receives the signal from the second transmitting circuit 15 to count the signal from the receiving circuit 13 corresponding to the cycle of said signal. The count signal of the count circuit 14 is temporarily stored in a memory circuit 16 to be inputted to a comparing circuit 17 at any time. The comparing circuit 17 inputs the count signal from the memory circuit 16 during a time when a probe operating signal generating circuit 18 receives the signal during the stoppage of a probe to compare the same with the transmission number of repeating signals and, when a comparing result is not same, an alarm signal showing the detection of air bubbles is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a bubble detection device suitable for underwater airtightness testing of compressors and the like.

[Conventional technology]

BACKGROUND ART Conventionally, airtightness inspections have been performed for devices and devices that require airtightness, such as compressors, to confirm airtightness. The airtightness inspection method includes, for example, "High Pressure Gas J vol.
, 19 hh6 (1982) p. 7-13, there are many types. Among these, the underwater airtightness test applies internal pressure to the test object and tests the airtightness by checking for the presence or absence of bubbles in the water, and is used in a wide range of fields because it is easy to perform.

[Problem to be solved by the invention]

However, in conventional underwater airtightness tests, bubbles are basically observed visually, which increases inspection costs and
Furthermore, there was a risk of overlooking minute air bubbles.

In view of this situation, the present invention aims to provide a bubble detection device that can reliably automatically detect even minute bubbles.

[Means to solve the problem]

As shown in FIG. 1, the device of the present invention includes an ultrasonic oscillator 11 immersed in a liquid, an ultrasonic transmitting circuit 12 and an ultrasonic receiving circuit 13 connected to the ultrasonic oscillator 11. , a second transmitting circuit 15 that outputs a repetitive signal of a constant period.
, a counting circuit 14 for detecting and counting reflected echoes received by the receiving circuit 13 corresponding to the transmission period of the repetitive signal transmitted by the second transmitting circuit 15; and a memory for the reflected echoes detected and counted by the counting circuit 14. a circuit 16; a comparator circuit 17 that compares the count number of reflected echoes stored in the memory circuit 16 with the number of emitted repeat signals for a certain period;
and a determination circuit 19 that outputs a bubble detection signal when it receives a comparison result that is not equal to the number of transmissions and is not the same as the number of transmissions.

[Function] The device of the present invention detects air bubbles using the principle of ultrasonic flaw detection.

Ultrasonic waves travel straight through materials with specific directionality, and are reflected when they collide with foreign materials. Ultrasonic flaw detection detects the presence of foreign substances by emitting ultrasonic waves from a vibrator and receiving the ultrasonic waves (reflected echoes) that collide with foreign substances and are reflected by the vibrator.

Now, considering underwater airtightness inspection, the acoustic impedance Z1 of water is 1500 m/5XIX10' kg/d, and the acoustic impedance Zt of air is 340 m/s xo, o 0
Since the zero reflectance ν of 12 Air bubbles can be detected from the surface using ultrasonic waves.

Zz Z+ 2, +2° Also, if a bubble is considered to be a sphere, the limit detectability is approximately 2 of the wavelength λ of the ultrasonic wave. When using 5MH2 ultrasound,
Since the wavelength is 0.3 nm, bubbles with a diameter of about 0.15 nm or more can be detected. If ultrasonic waves with a frequency of about 5 MH or higher are used, it is possible to detect bubbles by ultrasonic flaw detection in terms of the detection limit.

The device of the present invention also detects reflected echoes from bubbles separately from reflected echoes from test objects and the like.

When detecting air bubbles using ultrasonic waves in underwater airtightness tests, the ultrasonic waves emitted from the ultrasonic oscillator reflect not only on the air bubbles but also on the test object, etc., and air bubbles cannot be detected accurately just by detecting the reflected echoes. .

In the device of the present invention, reflected echoes are detected and counted in accordance with the transmission cycle of the repetitive signal transmitted by the second transmission circuit 15 (count circuit 14).

If this is done for a certain period of time, the count will be O if there is no bubble or test object in the detectable range in front of the ultrasonic oscillator. If only the test object is present,
Since there is no movement of the test object, counting is performed continuously during a certain period of time in accordance with the transmission cycle of the repeated signal.

If only bubbles are present, the bubbles float in the liquid, so counting is performed for a part of the fixed period.

If a bubble and a test object are present, temporary reflection echoes from the bubble are counted in addition to continuous reflection echoes from the test object. In any case, if a bubble exists in the detectable range in front of the oscillator, temporary reflected echoes from the bubble are detected and counted.

In the apparatus of the present invention, a comparison circuit 17 and a determination circuit 19 identify and detect temporary reflected echoes from air bubbles by comparing counts, and automatically detect even minute air bubbles with high precision.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 2 is a schematic diagram showing an outline of the apparatus according to the embodiment.

In FIG. 2, 1 indicates a water tank, and 2 indicates a compressor which is set in the water tank 1 and is an object to be inspected.

Air piping 4.4 is connected to the compressor 2 via a coupler 3.3.
is connected and high pressure air is supplied.

5 is an ultrasonic probe, and water is applied to the support ring 6! It is suspended and supported within a support ring 6, and is configured to horizontally rotate in a predetermined range stepwise at a predetermined angle by means of a pulse motor 7 connected to the upper end of a support ring 6.

8 is a bubble detection mechanism connected to the ultrasonic transducer 11 (see FIG. 2) in the ultrasonic probe 5, and its configuration is shown in FIG.

According to FIG. 1, an ultrasonic wave of a predetermined frequency is sent from an ultrasonic transmitting circuit 12 to a transducer 11, while an ultrasonic wave received by the transducer 11 is converted into an electrical signal by an ultrasonic receiving circuit 13.

The output of the receiving circuit 13 is input to the counting circuit 14.

In addition to the output from the receiving circuit 13, the counting circuit 14 receives the second
A signal from the transmitter circuit 15 is input. Second transmitting circuit 15
outputs a repeating signal of a constant period to the count circuit 14. The counting circuit 14 counts the signals from the receiving circuit 13 in accordance with the cycle of the repetitive signal input from the second transmitting circuit 15.

The count signal output by the count circuit 14 is sent to the memory circuit 1.
6 and -temporarily stored. The signals stored in the memory circuit 16 are input to the comparison circuit 17 at any time according to instructions from the comparison circuit 17.

In addition to the signals from the memory circuit 16, the comparison circuit 17 receives signals from the probe operation signal generation circuit 1. The probe operation signal generation circuit 18 is a pulse motor that drives the probe 5.
7 (not shown), and outputs a signal indicating that the probe is rotating or stopped to the comparison circuit 17.

The comparison circuit 17 compares the period corresponding to the period in which it receives the probe stop signal from the probe operation signal generation circuit 18.
The number of count signals is input manually from the memory circuit 16, and this is compared with the number of repeated signal transmissions. The comparison result is sent to the judgment circuit 19.
When a comparison result in which the number of count signals is not 0 and the number of repeated signals is not the same as the number of repeated signals is input from the comparison circuit 18, the judgment circuit 19 outputs an alarm signal for bubble detection.

3 and 4 show the count circuit 14 and the comparison circuit 17.
, a flowchart and a waveform diagram showing the operation of the determination circuit 19.

From the probe operation signal generation circuit 18 to the comparison circuit 17, a fourth
A signal indicating that the H1 probe is rotating while the probe is stopped is input as shown in FIG. From the second oscillation circuit 15 to the count circuit 14
is a repetitive signal PRF of a constant period shown in Fig. 4 (b).
is input.

When the compressor 2 is placed in the water tank 1 and the compressor 412 is pressurized, bubbles will be generated if the compressor 2 has a leak. When the compressor 2 and air bubbles are present within the detectable range of the probe 5, a reflected echo is generated.

In section ■ in Fig. 4, the probe 5 is stopped;
During this period, a detection count of reflected echoes is performed corresponding to the transmission period of the repetitive signal PRF. Since the compressor 2 and air bubbles exist within the detectable range of the fifth probe, the reflected echoes from the compressor 2 and the reflected echoes from the air bubbles are detected and counted. Compressor 2 is stationary during the inspection period, so section! It produces reflected echoes throughout the period. As the bubble floats up, a reflected echo is generated during a part of section I.

As shown in Fig. 4 (e), when the number of counts in one section is 5 and the count numbers are processed for both reflected echoes, the processing result will be (00000) or (11111) if there is no bubble. In the 0 interval ■, the temporary count due to air bubbles is added to the continuous count by the compressor, so (1
A processing result of (2211) is obtained, which is converted to (00000
), (11111), the presence of bubbles is detected.

In section H, the probe 5 is rotating in order to perform detection in the next zone, and no count comparison of reflected echoes is performed.

In section ■, there are no bubbles or compressor 2, so
Despite performing a count comparison of reflected echoes, the data processing result is (00000) and no bubble detection signal is transmitted.

In sections ■, Vl, ■, and X, the probe 5 is in rotation, and no count comparison of reflected echoes is performed.

In sections V and IX, only compressor-2 exists, and (
In the 6th interval (3) where a data processing result of (11111) is obtained, only bubbles exist, and a data processing result of (01110) is obtained. The data processing result is (00
000) and (11111), a bubble detection signal is transmitted.

〔Effect of the invention〕

As is clear from the above description, the bubble detection device of the present invention utilizes the fact that bubbles float in liquid to automatically detect minute bubbles while clearly distinguishing them from fixed objects behind and around them. Therefore, when applied to, for example, an underwater airtight inspection of a compressor, it is highly effective in streamlining the inspection process, reducing inspection costs, and improving inspection accuracy.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of an example of the device according to the present invention, FIG. 2 is a schematic diagram showing the outline of the device, and FIGS. 3 and 4 show the operation of the main parts of the device. 3 is a flowchart and a waveform diagram shown in FIG. In the figure, l: water tank, 2: object to be inspected, 5: ultrasonic probe, 11: ultrasonic oscillator, 12: ultrasonic transmitter circuit, 13:
Ultrasonic receiving circuit, 14: Count circuit, 15: Second transmitting circuit, 16: Memory circuit, 17: Comparison circuit, 19: Judgment circuit. Figure 2

Claims (1)

[Claims] 1. An ultrasonic oscillator (11) immersed in a liquid, and an ultrasonic oscillator (12) connected to the ultrasonic oscillator (11).
and an ultrasonic receiving circuit (13), a second transmitting circuit (15) that outputs a repetitive signal of a constant period, and the receiving circuit corresponding to the transmitting period of the repetitive signal transmitted by the second transmitting circuit (15). (13) detects and counts reflected echoes received by the count circuit (14);
4) Memory circuit for reflected echoes detected and counted (16)
and a comparator circuit (17) that compares the count number of reflected echoes stored in the memory circuit (16) with the number of emitted repeated signals in a certain interval, and a determination circuit that outputs a bubble detection signal when receiving a comparison result that is not the same as the number of transmissions (
19) A bubble detection device comprising: