JPH0777447A - Gas meter - Google Patents

Abstract

PURPOSE:To provide a gas meter capable of finding a slight gas leakage at an early stage and giving no trouble to the use of a gas appliance. CONSTITUTION:A controller 15 temporarily cuts off a gas passage 11 with a gas shut-off valve 12 when a gas flow to be judged for the use of a gas utensil is not measured by a gas flowmeter 13 for a prescribed period or longer, monitors the gas pressure with a gas pressure detecting sensor 14, and inspects the presence or absence of a slight gas leakage based on the change quantity of the gas pressure. When the controller 15 detects an abrupt change of the gas pressure during an inspection, it judges that a gas appliance is used, and it interrupts the inspection and opens the gas shut-off valve 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas meter for measuring the flow rate of gas supplied upstream of a gas appliance such as a gas stove, and more particularly to a gas meter capable of detecting a slight gas leak.

[0002]

2. Description of the Related Art In recent years, as a gas meter for home use, a meter equipped with a microcomputer and a safety function in addition to the function of measuring the flow rate of passing gas has been put into practical use. The safety function of this gas meter is to detect the flow rate of gas above a predetermined amount using a flow meter, to detect the flow rate above a predetermined time for a certain period of time, or to supply a pressure above a predetermined pressure using a gas pressure detection sensor. When there is no pressure, it has a function of driving the gas shutoff valve to shut off the gas flow path. With these functions, leaks in piping and outflow of unnatural gas can be detected to prevent accidents.
It is designed to guarantee safety.

As a safety function of a gas meter equipped with a microcomputer, in addition to the above-mentioned function, there is a function of detecting a slight gas leak. The conventional gas meter has a function of detecting a small amount of gas leakage, for example, when a situation where the gas is not used for a predetermined time, for example, one hour or more cannot be detected for a predetermined number of days, for example, 30 days, a small amount of gas is detected on the downstream side of the gas meter. It was judged that there was a gas leak and shut off the gas.

[0004]

However, with the conventional function for detecting a small amount of gas leakage as described above, it takes a long period of 30 days to detect a small amount of gas leakage, and therefore a small amount of gas leakage is detected. There is a problem that it is not possible to detect it early.

Therefore, the applicant of the present invention temporarily shuts off the gas flow path and uses the gas pressure detection sensor when the gas flow rate at which it can be determined that the gas appliance is used is not measured for a predetermined time or longer. It proposes a technique for monitoring the gas pressure and inspecting for the presence or absence of a slight gas leak based on the amount of fluctuation of the gas pressure.

According to this technique, it is possible to detect a small amount of gas leakage earlier than in the prior art, but a gas appliance is used because the gas flow path is blocked during the inspection of the small amount of gas leakage. There was a problem that it could not be done, and there was room for improvement.

The present invention has been made in view of the above problems, and an object thereof is to make it possible to detect a small amount of gas leakage at an early stage and not to hinder the use of a gas appliance. It is to provide a gas meter.

[0008]

A gas meter according to claim 1, wherein a gas passage through which a gas passes, a gas cutoff valve provided in the gas passage, for shutting off the gas passage, and a gas flow. A gas flow meter provided in the passage for measuring the flow rate of the gas passing through the gas passage, a gas pressure detection sensor provided in the gas passage for detecting the pressure of the gas in the gas passage, and a predetermined time As described above, when the gas flow rate at which it can be determined that the gas appliance is being used is not measured by the gas flow meter, the gas shutoff valve is driven to shut off the gas flow path, and the gas pressure is detected using the gas pressure detection sensor. Of the gas detected by the gas pressure detection sensor during the inspection by the trace gas leak inspection means for monitoring whether or not there is a trace gas leak based on the fluctuation amount of the pressure of the gas Sudden change in pressure A pressure fluctuation detecting means for detecting,
When a sudden change in gas pressure is detected by this pressure fluctuation detection means, it is judged that a gas appliance has been used, and the inspection by the trace gas leak inspection means is interrupted, and the inspection interruption means for opening the gas cutoff valve is used. It is equipped with.

In this gas meter, when the gas flow rate at which the gas flow rate can be judged to be using the gas appliance is not measured by the gas flow meter for a predetermined period of time or longer, the gas flow path is blocked by the trace gas leakage inspection means, The pressure of the gas is monitored using a pressure detection sensor, and the presence or absence of a slight gas leak is inspected based on the amount of change in the pressure of the gas. Further, during this inspection, when the pressure fluctuation detecting means detects a rapid change in the gas pressure, the inspection suspending means determines that the gas appliance has been used and suspends the inspection by the trace gas leak inspection means. Then, the gas cutoff valve is opened.

A gas meter according to a second aspect of the present invention is the gas meter according to the first aspect, in which the pressure fluctuation detecting means calculates the rate of change of the fluctuation gradient of the gas pressure detected by the gas pressure detecting sensor, and When the rate of change of the fluctuation gradient obtained by the calculation means exceeds a predetermined range, it has a judgment means for judging that the gas pressure has suddenly changed.

In this gas meter, the calculation means
The rate of change of the variation gradient of the gas pressure is calculated, and when the rate of variation of the variation gradient exceeds a predetermined range, the determination means determines that the gas pressure has changed rapidly.

A gas meter according to a third aspect is the gas meter according to the first or second aspect, in which the trace gas leakage inspection means determines the decrease amount and the decrease gradient of the gas pressure in a predetermined period after the gas flow path is blocked. At least one of them is detected as a fluctuation amount of the gas pressure, and when this fluctuation amount exceeds a preset value, it is judged that a slight gas leak exists.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings. 1 to 4 relate to an embodiment of the present invention.

FIG. 1 is an explanatory view showing a schematic structure of a gas meter according to this embodiment. As shown in this figure, a gas flow passage 11 having a gas inlet 16 and a gas outlet 17 is provided inside the gas meter 10 of this embodiment. The gas 20 flows into the gas flow path 11 through a pipe (not shown), and the gas 20 is supplied to a gas appliance such as a gas stove (not shown). In the gas flow path 11, the gas flow path 1 is sequentially arranged from the gas inlet 16 side.
1, a gas shutoff valve 12 for shutting off 1, a gas flow meter 13 for measuring the flow rate of the gas passing through the gas flow path 11, and a gas pressure detection sensor 14 for detecting the pressure of the gas in the gas flow path 11. Is provided.

A control unit 15 is provided in the gas meter 10 for controlling the gas cutoff valve 12 and the like while receiving the outputs of the gas flow meter 13 and the gas pressure detection sensor 14.

FIG. 2 is a block diagram showing the configuration of the control unit 15 and its peripherals in the gas meter 10 of this embodiment.
As shown in this figure, the control unit 10 includes a CPU (central processing unit) 30, a ROM (read only memory) 31,
A RAM (random access memory) 32, a clock 33 for clocking time, and an input / output port 34 are provided, and these are connected to each other by a bus 35.
In addition to the gas flow meter 13 and the gas pressure detection sensor 14 described above, the input / output port 34 is connected to a drive circuit 36 that drives the gas cutoff valve 12 and a warning lamp 37 that warns the occurrence of a minute amount of gas leakage. Has been done.

In the control unit 15, the CPU 30 controls the RA
By executing a program stored in the ROM 31 with M32 as a working area, a safety function such as an inspection for a small amount of gas leakage is realized.

The control unit 15 has a function relating to the inspection of a slight amount of gas leakage, in particular, when the gas flow rate which can be judged that the gas appliance is used is not measured by the gas flow meter 13 for a predetermined time or longer, the gas shutoff is performed. A trace gas for driving the valve 12 to shut off the gas flow path 11, monitoring the gas pressure using the gas pressure detection sensor 14, and inspecting for the presence or absence of a slight gas leak based on the amount of fluctuation of the gas pressure. Leakage inspection means, pressure fluctuation detection means for detecting a rapid change in gas pressure detected by the gas pressure detection sensor 14 during the inspection by the trace gas leakage inspection means, and gas pressure detection means for detecting gas pressure detected by the pressure fluctuation detection means. When a rapid change is detected, it is determined that the gas appliance is used, the inspection by the trace gas leak inspection means is interrupted, and the gas cutoff valve 12 is opened. It has the ability. The pressure fluctuation detection means calculates the change rate of the fluctuation gradient of the gas pressure detected by the gas pressure detection sensor 14, and the change rate of the fluctuation gradient calculated by the calculation means exceeds a predetermined range. In this case, it has a judging means for judging that the pressure of the gas has changed abruptly.

Next, the operation of the gas meter of this embodiment will be described.

The gas meter of this embodiment is a gas flow meter 13
The gas flow rate of the gas passing through the gas flow path 11 is measured by the gas flow path 11
The pressure of the gas inside is detected. And
As in the conventional case, when the gas flow meter 13 detects a gas flow rate of a predetermined amount or more, when the predetermined gas flow rate is detected for a predetermined time or more, or when the gas pressure detection sensor 14 is used to supply a pressure of a predetermined pressure or more. It has a safety function of driving the gas shutoff valve 12 to shut off the gas flow path 11 when there is no pressure. In addition to these safety functions, the gas meter of this embodiment has a function of inspecting the presence or absence of a small amount of gas leakage as described below.

FIG. 3 is a flow chart showing the operation of inspecting for the presence or absence of a slight gas leak. In this operation, first, the control unit 1
5, it is determined whether to start the trace gas leak inspection mode (step S101). Specifically, a state in which it can be determined that the gas appliance is unused, that is, a state in which the gas flow rate that can be determined that the user is using the gas appliance in the normal usage state is not measured by the gas flow meter 13 continues for a predetermined time. If so, the trace gas leak inspection mode is started. When the trace gas leak inspection mode is not started (N), the above determination (step S101) is repeated.

When the trace gas leak inspection mode is started (step S101; Y), the gas cutoff valve 12 is driven through the drive circuit 36 to shut off the gas flow path 11, and the gas pressure detection sensor 14 is used. Monitoring of the gas pressure is started (step S102). The pressure detected by the gas pressure detection sensor 14 is sequentially stored in the RAM 32 in the control unit 15. Next, the control unit 15 determines whether or not a predetermined time required for the trace gas leak inspection has elapsed (step S103). If it has not elapsed (N), the fluctuation gradient of the pressure of the gas detected by the gas pressure detection sensor 14 is calculated (step S104), and then the change rate of this fluctuation gradient is calculated (step S105). It is determined whether the rate of change is within a predetermined range (step S10).
6). When the rate of change is within the predetermined range (Y), the process returns to step S103. On the other hand, when the rate of change is not within the predetermined range (N), it is determined that the gas appliance is used,
The minute gas leak inspection mode is interrupted, the gas shutoff valve 12 is opened (step S107), and the operation is ended. This allows the use of gas appliances.

If the predetermined time required for the trace gas leak inspection has passed without interruption of the trace gas leak inspection mode (step S103; Y), the inspection result is processed (step S108), and the operation is performed. To finish. The processing of the inspection result is specifically performed as follows. That is, from the pressure of the gas at each time point within the predetermined time required for the trace gas leak inspection, the amount of decrease in the pressure of the gas and the decrease gradient are calculated as the amount of change in the pressure of the gas within the predetermined time,
It is determined whether or not there is a slight amount of gas leakage by determining whether or not at least one of the decrease amount and the decrease gradient of the gas pressure exceeds a preset value. When there is a slight gas leak, the control unit 15 continues to shut off the gas flow path 11 by the gas shutoff valve 12, outputs a warning signal and turns on the warning lamp 37, and ends the operation. If there is no minute gas leak, the control unit 15
Ends the operation by returning or opening the gas shutoff valve 12.

FIG. 4 is a characteristic diagram for explaining a method for inspecting a small amount of gas leakage and a method for determining interruption of the inspection in this embodiment. The horizontal axis shuts off the gas passage 11 by the gas shutoff valve 12. The elapsed time since then, the vertical axis represents the gas pressure. As shown in this figure, when there is a small amount of gas leakage due to a hole in the pipe on the downstream side of the gas meter 10, etc., the gas pressure increases as the elapsed time after the gas flow path 11 is blocked increases. I know it will drop. Therefore, in this embodiment, the pressure of the gas is monitored within a predetermined period, the decrease amount and the decrease gradient of the pressure of the gas in the predetermined period are calculated, and at least one of the decrease amount and the decrease gradient of the pressure of the gas is calculated in advance. When exceeding the set value, it is judged that there is a slight gas leak. It is also possible to estimate the size of the hole from the size of the pressure drop gradient. Since the decrease gradient of the gas pressure has a negative value, the decrease gradient of the gas pressure exceeding the preset value means that the decrease gradient is below the preset negative value or the decrease gradient. It means that the absolute value of exceeds a preset positive value.

If the user starts to use the gas appliance during the inspection for such a slight gas leak, the gas pressure may drop and the gas appliance may become unusable. Therefore, in this embodiment, during the inspection of a slight amount of gas leakage,
The rate of change of the fluctuation gradient of the gas pressure is obtained, and when the rate of change of the fluctuation gradient exceeds a predetermined range, that is, when the pressure of the gas fluctuates rapidly (decreases), the user starts using the gas appliance. I decided that I did, and immediately interrupted the inspection,
The gas shutoff valve 12 is opened. In the example of FIG. 4, the inspection is interrupted at the time indicated by the symbol a, and the gas cutoff valve 1
2 can be opened. In addition, in FIG. 4, a curve after the time point a indicates a change in pressure when the gas cutoff valve 12 is not opened.

As described above, in this embodiment, when the gas flow rate, which can be judged to be the gas appliance is not measured, continues for a predetermined time, the gas flow passage 11 is temporarily shut off and the gas pressure is monitored. By doing so, it is determined whether or not there is a slight gas leak. Therefore, when it is assumed that a gas leak test can be performed at any time when the gas appliance has not been used for a predetermined time or longer, and a condition where the gas appliance has not been used for a predetermined time or longer exists within 30 days (many This is considered to be the case), and as compared with the conventional function of detecting a small amount of gas leakage, it is possible to detect a small amount of gas leakage earlier and improve safety.

Further, in the present embodiment, when it is determined that a minute amount of gas leakage has not occurred, the gas shutoff valve 12 is automatically opened as soon as the inspection of the minute amount of gas leakage is completed. The gas appliance can be used without bothering the user.

Further, in the present embodiment, the inspection of a small amount of gas leakage is performed when the gas appliance is not used, and when it is determined that the small amount of gas leakage has not occurred, the inspection is automatically performed after the inspection is completed. Since the gas shutoff valve 12 is opened, and the gas shutoff valve 12 is opened promptly even when the use of the gas appliance is started during the inspection, the use of the gas appliance is not hindered.

The present invention is not limited to the above embodiment,
For example, a small amount of gas leakage may be detected by calculating only one of the gas pressure decrease amount and the decrease gradient. Further, in the embodiment, when at least one of the amount of decrease in gas pressure and the decrease gradient exceeds a preset value, it is determined that a slight amount of gas leakage has occurred. It may be determined that a slight amount of gas leakage has occurred when both the amount and the decrease gradient exceed preset values.

Further, the warning method when it is judged that a slight amount of gas leakage exists is not limited to the lighting of the warning lamp, and other methods such as sounding a buzzer may be used.

[0031]

As described above, according to the gas meter of the first to third aspects, when the gas flow rate at which it can be judged that the gas appliance is used is not measured by the gas flow meter for a predetermined time or longer, The gas flow path is blocked by the trace gas leak inspection means, the gas pressure is monitored using the gas pressure detection sensor, and the presence or absence of a trace gas leak is inspected based on the fluctuation amount of the gas pressure. Therefore, when a gas appliance has not been used for a predetermined time or longer, a small amount of gas leak can be inspected at any time, and a small amount of gas leak can be detected early, improving safety. is there. Further, during the inspection, when a rapid change in the gas pressure is detected by the pressure change detection means, the inspection interruption means judges that the gas appliance is used, interrupts the inspection, and opens the gas cutoff valve. Therefore, there is an effect that it does not hinder the use of the gas appliance.

[Brief description of drawings]

FIG. 1 is an explanatory diagram 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 in FIG. 1 and its peripherals.

FIG. 3 is a flowchart showing an operation of inspecting the gas meter of FIG. 1 for the presence or absence of a slight gas leak.

FIG. 4 is a characteristic diagram for explaining a method of inspecting a slight amount of gas leakage and a method of determining interruption of inspection in the gas meter of FIG.

[Explanation of symbols]

 10 gas meter 11 gas flow path 12 gas cutoff valve 13 gas flow meter 14 gas pressure sensor 15 controller

Claims (3)

[Claims] 1. A gas passage through which a gas passes, a gas cutoff valve provided in the gas passage for shutting off the gas passage, and provided in the gas passage and passing through the gas passage. A gas flow meter for measuring the flow rate of the gas, a gas pressure detection sensor provided in the gas flow passage for detecting the pressure of the gas in the gas flow passage, and a gas appliance is used for a predetermined time or longer. When the gas flow rate that can be judged is not measured by the gas flow meter, the gas cutoff valve is driven to cut off the gas flow path, and the gas pressure is monitored by using the gas pressure detection sensor. A trace gas leak inspection means for inspecting the presence or absence of a trace gas leak based on the amount of pressure fluctuation, and a sudden change in the gas pressure detected by the gas pressure detection sensor during the inspection by the trace gas leak inspection means. Pressure to detect When a rapid change in gas pressure is detected by the motion detecting means and the pressure change detecting means, it is judged that a gas appliance has been used, the inspection by the trace gas leak inspection means is interrupted, and the gas shutoff is performed. A gas meter, comprising: an inspection interruption means for opening a valve. 2. The pressure fluctuation detecting means calculates the change rate of the fluctuation gradient of the gas pressure detected by the gas pressure detecting sensor, and the change rate of the fluctuation gradient calculated by the calculating means. The gas meter according to claim 1, further comprising: a determining unit that determines that the gas pressure has suddenly changed when the pressure exceeds a predetermined range. 3. The trace gas leak inspection means detects at least one of a decrease amount and a decrease gradient of the gas pressure in a predetermined period after the gas flow path is blocked, as a change amount of the gas pressure, and the change is detected. The gas meter according to claim 1 or 2, wherein it is determined that a slight amount of gas leakage is present when the amount exceeds a preset value.