JPH08114480A - Gas meter - Google Patents

Abstract

PURPOSE: To obtain a gas meter which enhances a gas safe cutoff function more by a method wherein gas leak at a very small flow rate can be inspected in a short time. CONSTITUTION: When a gas flow passage cutoff means (a gas cutoff valve) 31 is returned, the flow rate is detected by a gas flow rate detection means (a flow sensor) 30 in a returned state. Then, the detection result (an integrated flow rate) by the gas flow rate detection means 30 is monitored by a judgement means 33 for a prescribed time. It is judged that gas leaks when a gas flow rate (the integrated flow rate) is larger than a reference flow rate, and it is judged that gas does not leak when the gas flow rate is at the reference flow rate or lower. When it is judged by the judgement means 33 that gas leaks, the gas flow-passage cutoff means (the gas cutoff valve) 31 is driven by a recurrent drive means 34, and a gas flow passage is cut off again.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas meter having a gas safety shutoff function by a microcomputer.

[0002]

2. Description of the Related Art In recent years, household gas meters have a function of detecting the flow rate of gas passing through them by a flow meter, and when a gas flow rate of a predetermined amount or more is detected or a gas flow rate of a predetermined period or more is detected. In some cases, various types have been developed that have a gas safety shutoff function that drives a gas shutoff valve to close the gas flow path. As a result, gas leaks in the pipes and unnatural gas outflows are detected to prevent accidents and ensure safety.

By the way, when the gas flow path is cut off by such a gas safety cutoff function, a gas leak inspection is carried out and a recovery operation is carried out. When the recovery work is completed, the shutoff valve is returned by the return lever. Then, after the shut-off valve is returned, a situation where the gas is not used for a predetermined time (for example, 2 minutes) (for example, the flow rate is 50 liters /
If less than h) continues, the gas leak inspection is terminated because there is no gas leak on the downstream side from the gas meter. On the other hand, the use of gas is detected within 2 minutes (for example, the flow rate is 50 liter / h).
If the above is done, it is judged that there is still a gas leak due to a construction error or the like, and the gas cutoff valve is driven again to close the gas flow path.

[0004]

However, in such a conventional gas meter, a leak inspection time is long (2 minutes) after the gas cutoff valve is returned, and a gas leak of a minute flow rate of 50 liter / h or less is required. There is a problem that it is difficult to detect.

The present invention has been made in view of the above problems, and an object thereof is to provide a gas meter capable of performing a gas leak inspection of a minute flow rate in a short time and further improving a gas safety cutoff function. is there.

[0006]

The gas meter of the present invention comprises:
A gas flow rate detecting means for detecting a gas flow rate flowing through the gas flow path, a gas flow path blocking means for blocking the gas flow path according to a detection result of the gas flow rate detecting means, and a return for returning the gas flow path blocking means. Means and the gas flow path blocking means are returned by the returning means, the detection result of the gas flow rate detecting means is monitored for a predetermined time, and when the gas flow rate is larger than a preset value, gas leakage occurs. Judging means for judging that there is no gas leakage when it is less than or equal to a preset value, and re-driving means for driving the gas flow path blocking means again when it is judged by this judging means that there is gas leakage. Is equipped with.

In this gas meter, the gas flow rate detecting means detects the flow rate of the gas flowing through the gas flow path, and the gas flow path blocking means blocks the gas flow path in accordance with the detection result of the gas flow rate detecting means. After the restoration work is performed, when the gas flow path blocking means is restored by the returning means and the gas flow path is opened, the determination means monitors the detection result of the gas flow rate detection means for a predetermined time in this state, When the gas flow rate is larger than a preset value, it is determined that there is a gas leak, and when it is less than the preset value, it is determined that there is no gas leak. When the determination unit determines that there is a gas leak, the re-driving unit drives the gas flow passage blocking unit again to shut off the gas flow passage. Although the integrated flow rate may be used or the instantaneous flow rate may be used as the detection result of the gas flow rate detection means, the integrated flow rate is advantageous in that the noise component can be removed.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows a schematic configuration of a gas meter according to an embodiment of the present invention. This gas meter 10
Inside the housing 11, a gas pipe 12 for supplying the gas a to a gas appliance (not shown) is arranged. The gas pipe 12 is provided with a gas shutoff valve 13 for shutting off the gas flow path at the time of abnormality and a gas flow meter 14 for detecting the flow rate of gas passing through the gas flow path in this order. . Further, in the housing 11, a control unit 15 for controlling the gas cutoff valve 13 by determining the presence or absence of gas leakage by using the output signal of the gas flow meter 14 as an input is provided.

As the gas flow meter 14, for example, a thermal type flow velocity sensor (hereinafter referred to as a flow sensor) suitable for measuring a minute flow rate is used. This flow sensor is a sensor that obtains the flow velocity by utilizing the fact that the movement of heat in the pipe is related to the flow velocity of the fluid flowing in the pipe.

FIG. 2 shows a control unit 1 which constitutes the gas meter 10.
FIG. 5 is a block diagram showing the configuration of 5 and its surroundings. As shown in this figure, the control unit 15 includes a CPU (central processing unit) 2
0, ROM (Read Only Memory) 21, RAM
A (random access memory) 22, a clock 23 for clocking, and an input / output port 24 are provided, and these are connected to each other by a bus 25. A gas flow meter 14 and a drive circuit 26 for driving the gas cutoff valve 13 are connected to the input / output port 24. When the gas cutoff valve 13 is driven and cuts off the gas flow path, the return lever 27 returns the initial state after the restoration work. In the control unit 15, the CPU 20 realizes a function as a gas meter by executing a program stored in the ROM 21 by using the RAM 22 as a working area.

FIG. 3 shows a functional configuration of the gas meter 10 of this embodiment. That is, this gas meter 10
Is a gas flow rate detecting means 30 for detecting the gas flow rate flowing through the gas flow path, a gas flow path blocking means 31 for blocking the gas flow path according to the detection result of the gas flow rate detecting means 30, and a gas flow path blocking means 31. The detection result of the gas flow rate detection means 30 is monitored for a predetermined time while the return means 32 for returning the means 31 and the gas flow path blocking means 31 are returned by the return means 32, and the gas flow rate is set to a preset value. If there is a gas leak, it is judged that there is a gas leak, and if it is below a preset value, there is no gas leak, and if this judgment means 33 judges that there is a gas leak, a gas flow path blocking means. And a re-driving unit 34 for driving 31 again.

The gas flow rate detecting means 30 is a gas flow rate meter 14,
The gas flow path cutoff means 31 is realized by the gas cutoff valve 13 and the drive circuit 26, and the return means 32 is realized by the return lever 27. Further, the judging means 33 and the re-driving means 34
Are respectively realized by the control unit 15.

In FIG. 4, the gas flow path blocking means 31 is the restoring means 3
Elapsed time after being returned by 2 and gas flow rate detecting means 3
A shows the relationship with the flow rate detected by 0 (integrated flow rate), where A is the normal state without gas leakage, and B is the abnormal state with minute gas leakage. As is clear from this figure, in the normal state (A), the integrated flow rate does not change, whereas in the abnormal state with minute gas leakage (B)
When, the integrated flow rate increases with the elapsed time. In the gas meter 10 of this embodiment, an appropriate flow rate between the integrated flow rate in the normal state and the integrated flow rate in the abnormal state at the time when a predetermined time (T1) has passed is set as the reference flow rate (Q1) in advance in the RAM2.
It is stored in No. 2, and whether or not there is a minute gas leak is determined depending on whether or not the integrated flow rate after restoration has reached this reference flow rate (Q1).

Next, the operation of the gas meter 10 of this embodiment will be described with reference to the flow chart shown in FIG.

The gas flow rate detecting means 30 detects the gas flow rate flowing through the gas flow path, and the gas flow rate detecting means 30
After the gas flow path is blocked by the gas flow path blocking means 31 according to the detection result of the above, and the restoration work is performed, the returning means 32
The gas flow path blocking means 31 is restored (step S500) as in the conventional case. In this embodiment, thereafter, in this return state, the gas flow rate detecting means (flow sensor) 30 detects a minute flow rate, and the determining means 33 monitors the detection result of the gas flow rate detecting means 30 for a predetermined time (T1). (Step S501). And
The determination means 33 determines that there is a gas leak when the gas flow rate (integrated flow rate) is larger than the reference flow rate (Q1), and determines that there is no gas leak when the gas flow rate is less than the reference flow rate (Q1) (step S502). When the determination unit 33 determines that there is a gas leak (step S502; Y), the re-driving unit 34 drives the gas flow path blocking unit 31 to block the gas flow path again (step S503).
After that, recovery work is performed again.

On the other hand, when the determination means 33 determines that there is no gas leakage (step S502; N), the return state of the gas flow path blocking means 31 is left as it is, and the gas leakage inspection is completed.

As described above, according to the gas meter 10 of this embodiment, the change in the flow rate after the return is measured by the gas flow rate detecting means (flow sensor) 30, and after a lapse of a predetermined time, the flow rate is set to a preset value (Q1). Since it is determined whether or not there is a gas leak depending on whether or not the gas flow rate has reached, the gas leak test with a minute flow rate can be accurately performed in real time in a short time. This further improves the safety function of the gas meter 10.

In the above-described embodiment, the operator manually returns the gas shutoff valve 13 by using the return lever 27 (returning means 32). However, the gas shutoff valve 13 is electrically turned on and off. A valve (bidirectional valve) that can be automatically operated may be used to automatically return by the control of the control unit 15. In this case, the returning means 32
Are realized by the control unit 15. Further, in the above embodiment, the presence or absence of gas leakage is determined by the integrated flow rate after the lapse of a predetermined time, but the presence or absence of gas leakage may be determined by comparing the instantaneous flow rate with a predetermined value. .

[0020]

As described above, according to the gas meter of the present invention, after the gas flow path blocking means is restored by the restoring means, the detection result of the gas flow rate detecting means is monitored for a predetermined time in this state, and the gas flow rate is monitored. , It is judged that there is a gas leak when it is larger than a preset value, it is judged that there is no gas leak when it is less than or equal to the preset value, and when it is judged that there is a gas leak, the gas flow path is shut off again. Therefore, it is possible to perform a gas leak inspection with a small flow rate with high accuracy in a short time, and there is an effect that the safety function is further improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic configuration of a gas meter according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a control unit and its periphery in the gas meter of FIG.

FIG. 3 is a functional block diagram showing a functional configuration of the gas meter shown in FIG.

FIG. 4 is a characteristic diagram showing a relationship between an elapsed time after the gas cutoff valve of the gas meter of FIG. 1 is restored and an integrated flow rate.

5 is a flow chart for explaining the operation of the gas meter of FIG. 1. FIG.

[Explanation of symbols]

 10 Gas Meter 11 Housing 12 Gas Pipe 13 Gas Cutoff Valve 14 Gas Flowmeter 15 Control Part 30 Gas Flow Rate Detection Means (Flow Sensor) 31 Gas Flow Cutoff Means 32 Return Means 33 Judgment Means 34 Redrive Means

Claims (1)

[Claims] 1. A gas flow rate detecting means for detecting a gas flow rate flowing through the gas flow path, a gas flow path blocking means for blocking the gas flow path according to a detection result of the gas flow rate detecting means, and the gas flow path blocking means. A resetting means for resetting the means, and a state in which the gas flow path blocking means is restored by the resetting means, the detection result of the gas flow rate detecting means is monitored for a predetermined time, and the gas flow rate is higher than a preset value. When it is large, it is judged that there is a gas leak, and when it is less than a preset value, there is no gas leak, and when this judgment means judges that there is a gas leak, the gas flow blocking means is driven again. And a re-driving means for driving the gas meter.