JP4604665B2 - Gas security device - Google Patents

Description

  The present invention relates to a gas security device for measuring a gas pressure in a gas passage.

  In recent years, for the purpose of safe use of city gas and LP gas, when the amount of fuel gas (hereinafter referred to as "gas") is measured and the amount of use increases abnormally, it is far from normal use. When it is detected that the gas passage has been used for a long time, a security device that blocks the gas passage has become widespread.

  This type of security device takes a gas flow rate detection signal into a security control circuit, processes it with an internal microcomputer, monitors the gas flow rate, outputs a shut-off signal if there is an abnormality, and closes the shut-off valve.

  For the detection of gas flow rate, a membrane type that measures the passing volume by the number of times the gas ventilates the measuring chamber of a predetermined volume, and an ultrasonic type that measures the flow rate by calculating the gas flow velocity in the gas passage of a predetermined cross-sectional area. There is.

  The principle of ultrasonic flow detection is that the propagation time of the ultrasonic wave between two points in the gas passage is a function including the gas flow velocity. If the propagation time is measured, the gas flow velocity can be calculated backwards. It applies that the flow rate is known from the area.

  There is a strong demand to improve safety performance by adding a pressure monitoring function to eliminate the risk factors related to gas pressure drop in addition to safety by monitoring the flow rate, such as abnormal increase in flow rate and abnormal long-term use as described above. It has become.

Conventionally, a pressure detection device of this type of gas safety device generally has a dedicated pressure sensor installed in the gas passage (see, for example, Patent Document 1).
JP-A-6-258117

  However, in the conventional configuration, a dedicated pressure sensor and a peripheral circuit are indispensable, which puts pressure on the product cost. This gas safety device aims to realize pressure measurement at low cost without using a dedicated pressure sensor.

  In order to solve the above-described conventional problems, the gas security device of the present invention includes an ultrasonic propagation time between at least a pair of ultrasonic transmitters / receivers arranged at intervals in a gas flow direction of a gas passage and the ultrasonic transmitter / receiver. A control gain measurement circuit, and a variable gain amplifier and a received signal peak detection circuit are provided in the control measurement circuit, so that the detection value at the peak detection circuit becomes a constant value. The gain value is adjusted, and the gas pressure in the gas passage is measured based on the gain indication signal value of the variable gain amplifier. The gas pressure in the gas passage is measured based on the value. As a result, the gas pressure can be measured without using a dedicated pressure sensor.

  According to the gas safety device of the present invention, an ultrasonic gas meter measuring unit originally intended for measuring the gas flow rate is used to measure pressure by using the ultrasonic sensor of the component part, so a dedicated pressure sensor is not required. Thus, pressure measurement can be realized at low cost.

  1st invention is equipped with the control measurement circuit which measures the ultrasonic propagation time between the said at least 1 pair of ultrasonic transmitter / receiver arranged at intervals in the gas flow direction of a gas passage, and the said ultrasonic transmitter / receiver, A variable gain amplifier and a received signal peak detection circuit are provided in the control measurement circuit, and the variable gain amplifier is adjusted so that the detection value at the peak detection circuit becomes a constant value. The gas pressure in the gas passage is measured based on the gain instruction signal value of the gain amplifier.

  The propagation gain in the gas uses the fact that the density is proportional to the density of the gas. Since the density is proportional to the pressure in the same gas, the received signal level increases as the gas pressure increases. Therefore, if the received signal is peak-detected by a window comparator or the like and the gain of the variable amplifier circuit is adjusted so that the peak level is constant, the gain instruction signal of the variable amplifier circuit follows the gas pressure. The pressure value is obtained based on this value.

  The second invention is configured such that a threshold value is set for a measurement value of flow rate measurement which is an original function, and pressure measurement is possible only when the value is equal to or less than the set threshold value. In a large flow rate range, the transmission efficiency of ultrasonic waves is reduced and the level is likely to fluctuate. Therefore, pressure measurement is prohibited at a flow rate exceeding the threshold value, and pressure measurement is performed in a stable region at a low flow rate below the threshold value.

  In the third invention, pressure calibration is performed in the state of actual gas and actual pressure after installation, the correction value is written in the memory, and thereafter the gas pressure is measured based on the correction value in the memory. The gas safety device is obliged to inspect the gas pressure in the pipe for the purpose of inspecting the gas leak after installation, and the pressure value measured by the standard pressure gauge at this time is written in the memory in the gas safety device with a setting device or the like. Based on this value, the pressure value in this measurement principle is corrected, and the measurement error due to the sensitivity difference of the ultrasonic transmitter / receiver and the gas difference in the region is corrected.

In the fourth invention, the temperature is detected by a thermistor or the like, and the gas pressure is corrected by the detected temperature. Since the gas density is inversely proportional to the absolute temperature, the measurement pressure is corrected with the detected temperature to prevent measurement errors due to temperature.

  In the fifth aspect of the invention, the altitude data of the installation location is written in the memory, and thereafter the gas pressure is measured based on the correction value in the memory. Since the gas pressure regulator is based on the atmospheric pressure at the installation location, the gas pressure is affected by the atmospheric pressure. The atmospheric pressure difference due to the altitude is corrected, and the measurement error due to the altitude difference is corrected.

  In the sixth invention, the gas pressure is corrected at both the temperature of the fourth invention and the altitude data of the fifth invention, and the measurement accuracy is further improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
In FIG. 1, when the ultrasonic transmitters / receivers 2A and 2B are arranged at an appropriate distance in the gas flow direction in the gas passage 1 and the ultrasonic transmitter / receiver 2A is oscillated via the output drive circuit 3, the ultrasonic waves are generated. The other ultrasonic transmitter / receiver 2B is configured to receive the signal. The received signal is amplified by the variable gain amplifier circuit 4 and input to the peak detection circuit 5.

  The peak detection circuit 5 is composed of a window comparator or the like, and outputs an ER-H signal when the setting window is raised and an ER-L signal when the setting window is lowered.

  The microcomputer 6 adjusts the amplification degree instruction signal (GAIN-CONT) of the variable gain amplifier circuit 4, automatically adjusts so that ER-H and ER-L are not output, and sets the output peak value of the variable gain amplifier circuit 3. Control to fit in the window.

  The ultrasonic wave propagation gain between the ultrasonic transceivers 2A and 2B is proportional to the gas density, and the density is proportional to the pressure. Therefore, the higher the gas pressure, the higher the received signal level.

  Accordingly, if the variable gain amplifier circuit 4 is automatically controlled so as to keep the peak level constant, the amplification degree instruction signal (GAIN-CONT) follows the gas pressure, and the pressure value is obtained based on this value.

  The output of the variable gain amplifying circuit 4 is also connected to the propagation time measuring circuit 7 to measure the ultrasonic propagation time between the ultrasonic transceivers 2A and 2B. The microcomputer 5 has a function of measuring the flow velocity of the gas based on the ultrasonic wave propagation time and calculating the flow rate by multiplying the cross-sectional area of the gas passage 1 and the correction coefficient.

  In the above configuration, the original flow rate can be measured by measuring the ultrasonic propagation time between the ultrasonic transceivers 2A and 2B.

  Further, as described above, the ultrasonic propagation gain between the ultrasonic transmitters / receivers A and 2B is proportional to the gas density, and since the density is proportional to the pressure, the higher the gas pressure, the higher the level of the received signal.

  Therefore, the pressure value can be measured based on the value of the amplification degree instruction signal (GAIN-CONT) by automatically controlling the variable gain amplifier circuit 4 so as to keep the peak level constant.

  Note that ultrasonic transmission / reception may be performed between the ultrasonic transmission / reception units 2A and 2B. For example, if ultrasonic transmission from the ultrasonic transmission / reception unit 2A is received by the ultrasonic transmission / reception unit 2B, ultrasonic transmission / reception is performed next time. It is also conceivable to repeat the measurement several times so that the ultrasonic wave is transmitted from the device 2B and received by the ultrasonic wave transmitter / receiver 2A, and the flow velocity of the gas in the gas passage 1 is measured from the average of the ultrasonic wave propagation time difference.

  In addition, if a threshold value is set for the measurement value of flow measurement, which is the original function, and pressure measurement is possible only when it is below the set threshold value, the transmission efficiency of ultrasonic waves will be reduced in the large flow rate range. In addition, since the level is likely to fluctuate, pressure measurement is prohibited at a flow rate exceeding the threshold value, and pressure measurement can be performed in a stable region at a low flow rate equal to or less than the threshold value.

  Furthermore, pressure calibration may be performed in the state of actual gas and actual pressure after installation, and the correction value may be written into the memory, and thereafter the gas pressure may be measured based on the correction value in the memory.

  In other words, the gas safety device is obliged to inspect the gas pressure in the piping for the purpose of gas leak inspection after installation. The pressure value measured with the standard pressure gauge at this time is stored in the memory in the gas safety device with a setting device. If written, the pressure value in this measurement principle is corrected based on this value, and the measurement error due to the difference in sensitivity of the ultrasonic transmitter / receiver and the gas difference in the region can be corrected.

(Embodiment 2)
FIG. 2 is a graph in which measurement information due to temperature is suppressed by inputting information of the temperature detector 7 such as a thermistor to the microcomputer 6 to correct the gas pressure.

  The same parts as those in FIG. 1 are denoted by the same reference numerals, and the description of the operation and the like uses the first embodiment.

(Embodiment 3)
In FIG. 3, altitude data of the installation location is written in the memory, and the error from the atmospheric pressure is input to the microcomputer 6 by the setting device 8 based on the memory to correct the gas pressure. Suppressed.

  The same parts as those in FIG. 1 are denoted by the same reference numerals, and the description of the operation and the like uses the first embodiment.

  Of course, if the temperature correction of the second embodiment and the correction based on the altitude data of this example are performed simultaneously, it will be obvious that the measurement accuracy can be further improved.

  As described above, the gas safety device according to the present invention is a gas meter with a safety function that has been conventionally monitored only for abnormal increase in flow rate or abnormal long-term use. It can be applied very effectively to supply low-cost and high-safety devices in response to today's demands for improving safety performance by eliminating the risk factors associated with

1 is a block diagram of a gas security device according to Embodiment 1 of the present invention. The block diagram of the gas security device in Embodiment 2 of the present invention The block diagram of the gas security device in Embodiment 3 of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gas passage 2A, 2B Ultrasonic transmitter / receiver 4 Variable gain amplifier circuit 5 Peak detection circuit 7 Propagation time measurement circuit 8 Temperature detector 9 Setting device

Claims (6)

At least a pair of ultrasonic transceivers arranged at intervals in the gas flow direction of the gas passage;
A variable gain amplifier for amplifying a received signal received by the ultrasonic transceiver;
A peak detection circuit for detecting a peak value of the signal amplified by the variable gain amplifier;
A microcomputer,
With
The microcomputer adjusts an amplification value of the variable gain amplifier so that a detection value in the peak detection circuit becomes a constant value, and outputs an ultrasonic wave between the pair of ultrasonic transceivers from an output of the variable gain amplifier. A gas security device for measuring a gas flow rate by measuring a propagation time, and further measuring a gas pressure in a gas passage based on an amplification factor instruction signal value of the variable gain amplifier. The gas security device according to claim 1, wherein a flow rate threshold is provided, and the gas pressure can be measured only when the flow rate is equal to or lower than the threshold flow rate. 2. The gas safety device according to claim 1, wherein comparison data with a reference measurement value is written in a memory, and thereafter the gas pressure is corrected and measured based on the data in the memory. The gas security device according to claim 1, wherein the gas pressure is corrected by the temperature. The gas security device according to claim 1, wherein the gas pressure is corrected by the altitude. The gas security device according to claim 1, wherein the gas pressure is corrected based on the temperature and altitude data.

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