JPH0628687U - Gas leak detector - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a gas leakage detection device for detecting gas leakage over time using ultrasonic waves even when ambient noise is large. [Structure] A piezoelectric ultrasonic sensor 1 that receives ultrasonic waves generated when gas leaks from a gasket of an engine 12.
4, the detector 1 detects the received signal representing the received ultrasonic wave.
The signal is detected at 6 and input to the peak detector 18. The peak detector 18 detects a peak value within the predetermined time interval of the input detection signal at predetermined time intervals, converts the peak value into a gas leakage amount by the converter 20, and records the gas leakage amount by the recording device 22.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a device for detecting gas leakage using ultrasonic waves, and for example, to a gas leakage detection device suitable for detecting gas leakage from a gasket of an engine.

[0002]

[Prior art]

 It has been conventionally known that the flow rate of gas leaking from a minute hole is proportional to the sound pressure level of ultrasonic waves generated when the gas leaks from the minute hole (Sensor Technology, 1 987 October issue, Vol 7, N0.11, pp. 19-20). Therefore, various devices for detecting gas leaks using ultrasonic waves have been devised in the past.For example, an ultrasonic sensor attached to the tip of a freely movable articulated arm can be used to detect gas from various devices and pipes. A device for detecting leakage is known (Japanese Patent Laid-Open No. 60-82829). In addition, a leak detection device (Japanese Patent Laid-Open No. 63-88424) for detecting leaks in an automobile body by ultrasonic waves, and a gas is sealed in the hollow container to inspect the airtightness of the hollow container and the like, and ultrasonic waves are applied. A leak inspection device for inspecting gas leakage from the hollow container (Japanese Patent Laid-Open No. 1-308936) and a leak detection device for detecting gas leakage from the gas filled communication cable by ultrasonic waves (Japanese Patent Laid-Open No. 2-143134). Etc. are known.

The conventional gas leakage detection device using ultrasonic waves is a device used in a place where ambient noise is relatively small, and measurement error due to ambient noise is not taken into consideration. Therefore, the various conventional gas leak detection devices described above are not suitable as devices for detecting gas leak from the gasket of an operating engine, for example, because of the large ambient noise.

As a method of detecting gas leakage from a gasket of an operating engine, in order to accurately measure the leaked gas, the engine and the gas detection device are integrally kept in an airtight state to measure the gas leakage amount. There are known methods of performing gas leaks and methods of determining gas leakage by human hearing.

[0005]

[Problems to be solved by the device]

 However, the method of measuring the amount of gas leakage using the gas detection device has a problem that the entire measurement device is large-scaled and the gas leakage that changes with time cannot be detected. In addition, the method of judging gas leakage by human hearing requires skill to be able to judge accurately.

In view of the above circumstances, it is an object of the present invention to provide a gas leakage detection device that easily detects gas leakage that changes with time even when ambient noise is large.

[0007]

[Means for Solving the Problems]

 In order to achieve the above object, a gas leakage detection device of the present invention comprises an ultrasonic sensor for receiving an ultrasonic wave caused by a gas leakage, and a detection means for detecting a reception signal representing the ultrasonic wave received by the ultrasonic sensor. A peak value detecting means for detecting a peak value within the predetermined time interval of the detection signal output from the detecting means, and a recording means for recording the peak value detected by the peak value detecting means. It is characterized by having and.

Further, it is preferable that the ultrasonic sensor receives an ultrasonic wave having a center frequency of 50 KHz or more and 100 KHz or less. More preferably, the center frequency is in the range of 70 to 90 KHz. Further, the ultrasonic sensor is preferably a piezoelectric type. Furthermore, it is preferable to include a conversion unit that converts the peak value detected by the peak value detection unit into a sound pressure value or a gas leakage amount.

[0009]

First, the principle of the gas leakage detection device of the present invention will be described. Generally, there is a relationship of P∝ (ρVD / μ) and ρ∝ (4γ / μπD) between the gas flow rate γ ejected from the minute holes and the sound pressure P of the ultrasonic wave generated at the time of this ejection. It has been known.

Here, ρ: gas density V: flow velocity D: average diameter of pores μ: viscosity Therefore, when D is constant, the gas flow rate γ and the gas density ρ are in a proportional relationship, whereby the sound pressure P changes to the gas. The flow rate γ can be measured.

According to the present invention, for example, the ultrasonic wave generated when the gas leaks from the minute hole is received by the ultrasonic sensor. The received signal representing the received ultrasonic wave is detected by the detecting means and input to the peak value detecting means. The peak value detecting means detects the peak value of the detection signal within a predetermined time interval. This peak value is recorded by the recording means, and the degree of gas leakage which changes with time is detected.

When the center frequency of the ultrasonic wave received by the ultrasonic sensor is 50 KHz or more and 100 KHz, particularly 70 to 90 KHz, the ultrasonic wave generated when the gas leaks can be distinguished relatively easily from the ambient noise. it can. Further, when the ultrasonic sensor is a piezoelectric type, the frequency received by the sensor is determined, so that it is not necessary to separately provide a filter or the like.

Further, in the case of including a converting means for converting the peak value detected by the peak value detecting means into a sound pressure value or a gas leakage amount, the sound pressure value or the gas leakage amount which changes with time elapses. Desired.

[0014]

【Example】

 Next, an embodiment of the gas leakage detection device of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of the gas leakage detection device of this embodiment. The gas leakage detection device 10 is provided with a piezoelectric ultrasonic sensor 14 that receives ultrasonic waves generated when gas leaks from a hole in a gasket (not shown) of the engine 12. Since ultrasonic waves are attenuated relatively quickly in air, the ultrasonic sensor 14 is placed near the hole for inspecting gas leakage, for example, about 10 cm from the hole. The received signal representing the ultrasonic wave received by the ultrasonic sensor 14 is detected by the wave detector 16 and input to the peak detector 18. The peak detector 18 sequentially detects the peak value of the input detection signal within each predetermined time interval. The peak value detected by the peak detector 18 is converted into a gas leakage amount in the converter 20 and recorded by the recording device 22. As a result, the gas leak amount corresponding to the peak value within the predetermined time interval set by the peak detector 18 is sequentially detected, and the change in the gas leak amount with the passage of time can be detected.

Next, actual measurement values in the gas leak detection device 10 will be described with reference to the drawings. FIG. 2 is a graph in which the SN ratio of the received signal is obtained when the ultrasonic sensor 14 is replaced with a different central frequency of the ultrasonic waves received by the ultrasonic sensor 14. As shown in FIG. 2, when the center frequency of the ultrasonic waves received by the ultrasonic sensor 14 is 50 KHz or more and 100 KHz or less, the SN ratio becomes large, so that the ultrasonic waves due to ambient noise and gas leakage are accurately identified, and The leak can be detected with high accuracy. In particular, the SN ratio becomes high near 80 KHz.

FIG. 3 is a graph showing the waveform of the ultrasonic wave received by the ultrasonic sensor 14 when the center frequency of the ultrasonic wave received by the ultrasonic sensor 14 is 80 KHz. The waveforms of the portions indicated by the peaks 30, 32, 34, 36, etc. are the waveforms of the ultrasonic waves at the time of gas leakage, and the waveforms of the other portions are the waveforms due to ambient noise such as engine noise. Further, FIG. 3 shows the waveform of the ultrasonic wave received during 4 mSEC, and the peak value indicated by the peak 34 is detected by the peak detector 18 as the peak value during 4 mSEC.

Similar to FIG. 3, when the center frequency of the ultrasonic wave received by the ultrasonic sensor 14 is set to 80 KHz, FIG. 4 shows the peak value for every 4 mSEC interval detected by the peak detector 18 as a converter. 20 is a graph in which the amount of gas leakage is converted at 20 and is sequentially recorded by the recording device 22 as time passes. In FIG. 4, a region 38 from the scale 0 to about 10 on the horizontal axis shows a peak value during idling of the engine, and it can be seen that the amount of gas leakage is small. It was found that when the engine was loaded, the peak value rapidly increased, and the maximum gas leakage amount was shown at peak 40, after which the gasket became more familiar and the gas leakage amount gradually decreased.

FIG. 5 shows that when the center frequency of the ultrasonic wave received by the ultrasonic sensor 14 is set to about 40 KHz, the peak value at every 4 mSEC interval detected by the peak detector 18 is converted into the gas leakage amount by the converter 20. The graphs are converted into the graphs and sequentially recorded by the recording device 22 as time passes. As shown in FIG. 5, when the center frequency of the ultrasonic wave received by the ultrasonic sensor 14 is out of the predetermined range, the difference in gas leakage amount between when the engine is idling and when the engine is loaded is clear. It turned out not to be.

[0019]

[Effect of device]

 As described in detail above, according to the gas leakage detection device of the present invention, the peak value of the ultrasonic wave received within the predetermined time interval is detected and recorded at each predetermined time interval. The change in gas leakage rate over time is found.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a gas leakage detection device according to an embodiment of the present invention.

FIG. 2 is a graph in which an SN ratio between a received signal and noise is obtained when the center frequency of the ultrasonic wave received by the ultrasonic sensor is changed by changing the ultrasonic sensor.

FIG. 3 is a graph showing a waveform of an ultrasonic wave received by the ultrasonic sensor when the center frequency of the ultrasonic wave received by the ultrasonic sensor is 80 KHz.

[Fig. 4] Fig. 4 is a graph of 4 detected by the peak detector when the center frequency of the ultrasonic wave received by the ultrasonic sensor is set to 80 KHz.
6 is a graph in which a peak value within an mSEC interval is converted into a gas leakage amount by a conversion device and sequentially recorded by a recording device as time passes.

FIG. 5: When the center frequency of the ultrasonic wave received by the ultrasonic sensor is set to about 40 KHz, the peak value within the 4 mSEC interval detected by the peak detector is converted into the gas leakage amount by the conversion device, and as time passes, 6 is a graph sequentially recorded by a recording device.

[Explanation of symbols]

 10 Gas Leakage Detection Device 14 Ultrasonic Sensor 16 Wave Detector 18 Peak Detector 20 Converter 22 Recording Device

Claims (4)

[Scope of utility model registration request] 1. An ultrasonic sensor for receiving an ultrasonic wave caused by gas leakage, a detection means for detecting a reception signal representing the ultrasonic wave received by the ultrasonic sensor, and a detection signal output from the detection means. Gas leakage comprising: a peak value detecting means for detecting a peak value within the predetermined time interval at every predetermined time interval; and a recording means for recording the peak value detected by the peak value detecting means. Detection device. 2. The ultrasonic sensor is 50 KHz or higher 1
The gas leakage detection device according to claim 1, wherein the gas leakage detection device receives an ultrasonic wave having a center frequency of 00 KHz or less. 3. The gas leakage detection device according to claim 1, wherein the ultrasonic sensor is a piezoelectric type. 4. The gas leakage detection apparatus according to claim 1, further comprising a conversion unit that converts the peak value detected by the peak value detection unit into a sound pressure value or a gas leakage amount. .