JPH08189851A - Gas meter - Google Patents

Abstract

PURPOSE: To quickly perform leak inspection of gas in a minute rate of flow and enhance the safe shutting function for gas by furnishing a judging means to judge as to whether gas leak exists or not on the basis of the size of the rate of gas pressure change. CONSTITUTION: A gas flow-path shutting means 31 shuts a gas flow-path in accordance with the result from sensing made by a gas flow sensing means 30 and is restituted electrically. A memory means 33 stores the change rate of gas pressure sensed by a gas pressure sensing means 32 corresponding to the size of the obtained change rate upon dividing into a plurality of stages. After restitution of the shutting means 31, a judging means 34 determines the rate of pressure change on the basis of the sensing result of the means 30 and performs discrimination to know in which area of the pressure change rate stored in the memory means 33 the obtained rate of pressure change lies. When the rate of pressure change is greater than a predetermined reference value, judgment as 'no gas leak' is decided, and when the rate lies within the reference value, a judgment as 'gas leak' is decided. A restituting means 35 restitutes the shutting means 31 in the former case.

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 devices having a so-called safety function of driving a gas cutoff valve to close the gas flow path have been developed. 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]

A gas meter according to a first aspect of the present invention includes a gas flow rate detecting means for detecting a gas flow rate flowing through the gas flow path, and the gas flow path is shut off in accordance with a detection result of the gas flow rate detecting means. Along with the gas flow path interrupting means capable of being electrically restored, a gas pressure detecting means for detecting a variation in gas pressure in the gas flow path, and a rate of change of the gas pressure detectable by the gas pressure detecting means is set to the magnitude thereof. According to each of these distinguished pressure change rates, a plurality of inspection times of a size inversely proportional to the magnitude of the pressure change rate are stored, and a storage means is stored. Before the gas flow path blocking means returns, a pressure change rate is obtained based on the detection result of the gas pressure detection means, and the pressure change rate corresponds to which range of the pressure change rate stored in the storage means. Or not Further, it is determined whether or not the pressure fluctuation value within the inspection time corresponding to the range is within a predetermined reference value, and when the pressure fluctuation value is larger than the reference value, it is determined that there is no gas leakage. Further, it is provided with a judging means for judging that there is a gas leak when it is within the reference value, and a returning means for returning the gas flow path blocking means when the judging means judges that there is no gas leak.

In this gas meter, the gas flow rate flowing through the gas flow path is detected by the gas flow rate detecting means, and the gas flow path shutting means (gas shutoff valve) shuts off the gas flow path in accordance with the detection result of the gas flow rate detecting means. To be done. Then, after the recovery work is performed and before the gas flow path shutoff means is restored, the determination means obtains the pressure change rate based on the detection result of the gas pressure detection means according to the temperature change, and the pressure It is distinguished whether the change rate corresponds to a range of the pressure change rate stored in advance in the storage means, and the inspection time corresponding to the range (that is, when the pressure change rate is large, a short inspection time, a pressure change). When the rate is small, it is determined whether the pressure fluctuation value within a long inspection time) is within a predetermined reference value. When the pressure fluctuation value is larger than the reference value, it is determined that there is no gas leakage, and when it is within the reference value, it is determined that there is gas leakage. When the determination means determines that there is no gas leakage, the gas flow path blocking means is restored.

A gas meter according to a second aspect of the present invention is the gas meter according to the first aspect, further comprising an informing means for informing that when there is a gas leak by the determining means.

A gas meter according to a third aspect of the present invention is the gas meter according to the first or second aspect, wherein the reference value of the pressure fluctuation is set to be constant regardless of the magnitude of the pressure change rate, and the judging means determines the pressure change rate. Regardless of the size, the same reference value is used to determine the presence or absence of gas leakage.

A gas meter according to a fourth aspect is the gas meter according to the first or second aspect, wherein the reference value of the pressure fluctuation is set in a plurality of stages in accordance with the magnitude of the pressure change rate, and the judging means determines the pressure. It is configured to determine the presence or absence of gas leakage using different reference values according to the magnitude of the rate of change.

[0011]

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 includes a gas shutoff valve 13 for shutting off the gas flow path at the time of abnormality, a gas flow meter 14 for detecting the flow rate of the gas passing through the gas flow path, and a gas in the gas flow path. The pressure sensor 15 for detecting the pressure is arranged in this order. Further, the housing 11 is provided with a control unit 16 for controlling the gas cutoff valve 13 by determining the presence / absence of gas leakage by using the output signals of the gas flow meter 14 and the pressure sensor 15 as inputs.

The gas shutoff valve 13 is constituted by a valve (bidirectional valve) capable of electrically shutting off and returning. 2 and 3 show this gas cutoff valve (bidirectional valve) 1
3 shows a specific configuration of No. 3. Here, FIG. 2 shows an open state (return state), and FIG. 3 shows a closed state (blocking state). In the following description, the positional relationship between the opening 12a and the gas cutoff valve 13 in the gas flow path in the gas pipe 12 is described with the opening 12a side being the upper side and the gas cutoff valve 13 side being the lower side. .

The gas shutoff valve 13 has a housing 41 made of a magnetic material. This housing 41
Has a small diameter cylindrical shape on the upper side and a large diameter cylindrical shape on the lower side, and the upper end is open and the lower end is closed. A flange portion 42 is provided outside the central portion of the housing 41 in the vertical direction.
Has been fixed. The flange portion 42 is fixed to the main body (housing 11) of the gas meter 10 in FIG. A cylindrical permanent magnet 4 is provided on the upper side of the housing 41.
3 is provided, and a coil 44 serving as an electromagnet is provided below the housing 41. The plunger 4 is placed in the hollow portion formed by the permanent magnet 43 and the coil 44.
5 is inserted so as to be movable in the axial direction. Plunger 4
5 has an upper magnetic part 45a made of a magnetic material and a lower non-magnetic part 45b made of a non-magnetic material. The upper end of the plunger 45 projects from the upper end of the housing 41, and a rubber valve body 46 capable of closing the opening 12a in FIG. 1 is attached to the upper end of the plunger 45. A spring 47 for urging the rubber valve body 46 upward is provided between the rubber valve body 46 and the flange portion 42.

No current flows through the coil 44 of the gas cutoff valve 13 in normal times. Further, as shown in FIG. 2, the magnetic force of the permanent magnet 43 acts as shown by the arrow 48, the plunger 45 is drawn in, and the opening 12a is opened. As a result, the gas passes through the opening 12a as indicated by the arrow 49. To put the gas shutoff valve 13 into the shutoff state, a current is passed through the coil 44 to generate a magnetic field that cancels the magnetic field generated by the permanent magnet 43, as shown in FIG. The magnetic force generated by the coil 44 is indicated by a dashed arrow 50. Then, the force of the spring 47 causes the plunger 45 to project, and the rubber valve element 46 closes the opening 12 a. On the other hand, in order to return the gas cutoff valve 13, a current in the opposite direction to that in the cutoff state is passed through the coil 44 to generate a magnetic field that strengthens the magnetic field by the permanent magnet 43. As a result, the plunger 45 overcomes the force of the spring 47 and is retracted, and as a result, the opening 12a is opened.

FIG. 4 shows a control unit 1 constituting the gas meter 10.
6 is a block diagram showing the configuration of 6 and its surroundings. FIG. As shown in this figure, the control unit 16 includes a CPU (central processing unit) 2
0, ROM (Read Only Memory) 21, RAM
A (random access memory) 22, a clock 23 and an input / output port 24, which are connected to each other by a bus 25.
Connected by. A gas flow meter 14, a pressure sensor 16, and a drive circuit 26 for driving the gas cutoff valve 13 are connected to the input / output port 24. In the control unit 16, the CPU 20 realizes a function as a gas meter by executing a program stored in the ROM 21 with the RAM 22 as a working area.

FIG. 5 shows a functional configuration of the gas meter 10 of this embodiment. The gas meter 10 includes a gas flow rate detecting means 30 for detecting a gas flow rate flowing through a gas flow path,
A gas flow path shutoff means 31 that shuts off the gas flow path and can be electrically restored according to the detection result of the gas flow rate detection means 30, and a gas pressure detection means 32 that detects a variation in gas pressure in the gas flow path. The rate of change of the gas pressure (the amount of pressure fluctuation for each predetermined time period) that can be detected by the gas pressure detecting unit 32 is stored in a plurality of stages according to the magnitude thereof, and the differentiated rate of pressure change is stored. Corresponding to each, after the storage means 33 in which a plurality of inspection times of a size inversely proportional to the magnitude of the pressure change rate and the gas flow path blocking means 31 are restored, the detection result of the gas flow rate detection means 30 The pressure change rate is obtained based on the above, and the range of the pressure change rate stored in the storage unit 33 is distinguished, and the pressure fluctuation within the inspection time corresponding to the range is determined. value A judgment means 34 for judging whether or not it is within a predetermined reference value, judging that there is no gas leakage when the pressure fluctuation value is larger than the reference value, and judging that there is a gas leakage when it is within the reference value. The determining means 34 includes a returning means 35 for returning the gas flow path blocking means 31 when it is determined that there is no gas leakage.

The gas flow rate detecting means 30 is a gas flow meter 14,
The gas flow path shutoff means 31 is implemented by the gas shutoff valve (bidirectional valve) 13 and the drive circuit 26, the gas pressure detection means 32 is implemented by the pressure sensor 15, and the storage means 33 is implemented by the RAM 22. The determining unit 34 and the returning unit 35 are realized by the control unit 16.

In FIG. 6, the gas flow path shut-off means 31 (gas shut-off valve 13) is shut off and then restored, before the gas flow path shut-off means 31 is restored, that is, when the gas flow path is in a sealed state. The relationship between the elapsed time and the pressure in the gas flow path is shown. A and B show a normal state without gas leakage, and C shows an abnormal state with minute gas leakage.
That is, in the state where the gas flow passage is sealed before the recovery, as is clear from this figure, the pressure changes according to the temperature change of the environment at the normal time (A, B) without gas leakage. (Especially day and night changes greatly). On the contrary,
At the abnormal time (C) with minute gas leakage, the pressure does not change regardless of the temperature change. In the gas meter 10 of this embodiment, an appropriate pressure lower than the normal pressure at the time when a predetermined time has elapsed is previously stored in the RAM as the reference pressure (P0).
It is stored in No. 22 and whether or not there is a minute gas leak is determined by whether or not the pressure after shutting down and before returning is larger than this reference pressure (P0).

Here, there are cases where the pressure changes greatly as shown by A in FIG. 6 (that is, when the pressure change rate (the amount of pressure fluctuation for each predetermined time) is large), and in FIG. As shown in B, there is a case where the change is gradual (that is, the pressure change rate is small).

In the gas meter 10 of this embodiment, the pressure change rate is calculated before the gas flow path shut-off means (bidirectional valve) 31 is restored. This pressure change rate is preliminarily RA according to its magnitude, for example, by distinguishing between two stages, large and small.
Corresponding to each of the pressure change rates that are stored in M22 and are classified into these two, two types of inspection time having a size inversely proportional to the magnitude of the pressure change rate (short inspection time when the pressure change rate is large) (Small time T1) and long inspection time (large time T2) when the pressure change rate is small are stored. That is, in the present embodiment, before the gas flow path shutoff means (bidirectional valve) 31 returns, the rate of pressure change is obtained, the magnitude thereof is distinguished, and the pressure within the inspection time of a length corresponding to the rate of pressure change. Calculate the variation value. Then, it is judged whether or not this pressure fluctuation value is within a predetermined value (reference value) (P0 in FIG. 6). If the pressure fluctuation value is larger than the reference value, it is judged that there is no gas leakage, and the pressure fluctuation value is When is within the reference value, it is judged that there is a gas leak.

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

As in the prior art, the gas flow path is blocked by the gas flow path blocking means (bidirectional valve) 31 in accordance with the detection result of the gas flow rate detecting means 30 and the restoration work is performed.
In the present embodiment, thereafter, gas flow path shutoff means (bidirectional valve)
Before the gas pressure 31 is restored, the gas pressure detection means 32 detects the pressure fluctuation in the gas passage in the sealed state. Then, the determination unit 34 monitors the detection result of the gas pressure detection unit 32 for a certain period of time (step S700), calculates the pressure change rate, and distinguishes the magnitude of the pressure change rate (step S701). When the pressure change rate is large (Y), it is determined whether the pressure fluctuation value is within the reference value (P0) (step S702). The pressure fluctuation value is within the reference value (Y) and the predetermined inspection time (small time T1)
When the time has elapsed (step S703; Y), it is determined that there is a gas leak (abnormal) and the cutoff state is maintained (step S7).
04). When the predetermined inspection time (small time T1) has not elapsed (step S703; N), the process returns to step S702. When the pressure fluctuation value is larger than the reference value (step S702; N), it is determined that there is no gas leak, and the gas flow path shutoff means (bidirectional valve) 31 is restored by the restoration means 35 (step S705). This completes the gas leak inspection.

On the other hand, when the pressure change rate is small (step S701; N), it is also determined whether the pressure fluctuation value is within the reference value (step S706). If the pressure fluctuation value is within the reference value (Y) and the predetermined inspection time (large time T2) has passed (step S707; Y), it is determined that there is gas leakage (abnormal) and the cutoff state is maintained (step S707). S7
04). If the predetermined inspection time (large time T2) has not elapsed (step S707; N), the process returns to step S706. When the pressure fluctuation value is larger than the reference value (step S706; N), it is determined that there is no gas leakage, and the gas flow path shutoff means (bidirectional valve) 31 is restored by the restoration means 35 (step S705). This completes the gas leak inspection.

As described above, in the gas meter 10 of this embodiment, when the gas flow path before the gas flow path shut-off means (bidirectional valve) 31 is restored is in a closed state, the pressure change rate due to the temperature change can be measured in real time. Whether or not there is a gas leak is determined by measuring and determining the magnitude of the pressure change rate and checking whether the pressure fluctuation value within the inspection time of a size corresponding to the pressure change rate is larger than a predetermined reference value. to decide. That is, since the length of the inspection time is changed according to the magnitude of the pressure change rate, it is possible to accurately perform the gas leak inspection with a minute flow rate in a short time. This further improves the safety function of the gas meter 10. Further, in the present embodiment, since the pressure change due to the temperature change is detected, the gas leak inspection can be performed without pressurizing with gas or other method, and the inspection work is easy.

Next, a second embodiment of the present invention will be described.

In the first embodiment, the reference value of the pressure fluctuation is the same (P0 in FIG. 6) regardless of the magnitude of the pressure change rate. However, in this embodiment, the reference value of the pressure change depends on the magnitude of the pressure change rate. The size of the reference value of pressure fluctuation is changed with the inspection time. That is, when the pressure change rate is large as shown in the characteristic diagram of FIG.
At P1, the reference value for pressure fluctuation is large (hereinafter referred to as the first reference value). On the other hand, when the rate of pressure change is small, the reference value for pressure fluctuation is shown at P2 in the figure. Smaller (hereinafter referred to as the second reference value)
By setting it, the inspection time can be further shortened.

Next, the operation of the gas meter according to the second embodiment will be described with reference to the flow chart of FIG.

The gas passage is shut off by the gas passage shut-off means (bidirectional valve) 31 in accordance with the detection result of the gas flow rate detecting means 30, and the restoration work is performed as in the conventional case.
In the present embodiment, thereafter, gas flow path shutoff means (bidirectional valve)
Before the gas pressure 31 is restored, the gas pressure detection means 32 detects the pressure fluctuation in the gas passage in the sealed state. The determination unit 34 monitors the detection result of the gas pressure detection unit 32 for a certain period of time (step S900), calculates the pressure change rate, and distinguishes the magnitude of the pressure change rate (step S901). When the pressure change rate is large (Y), it is determined whether the pressure fluctuation value is within the first reference value (P1) (step S902). When the pressure fluctuation value is within the first reference value (Y) and the predetermined inspection time (small time T1) has elapsed (step S903; Y).
Indicates that there is a gas leak (abnormal) and the cutoff state is maintained (step S904). Predetermined inspection time (small time T1)
When the time has not elapsed (step S903; N), the process returns to step S902. When the pressure fluctuation value is larger than the first reference value (step S902; N), it is determined that there is no gas leak, and the gas flow path shutoff means (bidirectional valve) 31 is restored by the restoration means 35 (step S905). .
This completes the gas leak inspection.

On the other hand, when the rate of pressure change is small (step S901; N), the pressure fluctuation value is the second reference value (P2).
It is determined whether it is within the range (step S906). When the pressure fluctuation value is within the second reference value (Y) and the predetermined inspection time (large time T2) has elapsed (step S907;
In Y), the gas leakage is present (abnormal) and the cutoff state is maintained (step S904). When the predetermined inspection time (large time T2) has not elapsed (step S907; N), the process returns to step S906. When the pressure fluctuation value is larger than the second reference value (step S906; N),
Assuming that there is no gas leakage, the gas flow path shutoff means (bidirectional valve) 31 is restored by the restoration means 35 (step S90
5). This completes the gas leak inspection.

According to the present embodiment, not only the inspection time but also the magnitude of the reference value of the pressure fluctuation is changed according to the magnitude of the pressure change rate. Therefore, for example, as shown in FIG. Inspection time (large time) T2 when pressure change rate is small
Can be further shortened as indicated by T2 ', and the inspection time can be further shortened.

The present invention has been described with reference to the examples.
The present invention is not limited to the above embodiment, but can be variously modified. For example, in the above-described embodiment, the detected pressure change rate is divided into two large and small sizes, and the inspection time is set to two large and small according to the magnitude of these pressure change rates. The rate is divided into 3 or more, and the inspection time is 3 depending on the pressure change rate.
The pressure may be set separately in the above magnitudes, and the reference value of the pressure fluctuation may be changed correspondingly.

Further, in the above embodiment, when it is judged that there is a gas leak, the blocked state of the gas flow path is maintained, but an alarm notifying means for notifying that there is a gas leak is further provided. It may be configured.

[0034]

As described above, according to the gas meter of the present invention, when the gas flow passage before closing the gas flow passage shut-off means (shut-off valve) is closed, the pressure change due to the temperature change is detected. Then, the pressure change rate is calculated, and the presence or absence of gas leakage is judged depending on whether the pressure fluctuation value during the inspection time according to the magnitude of this pressure change rate exceeds the reference value. In addition, it is possible to perform a gas leak inspection with a small flow rate with high accuracy, and to further improve the safety function.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view for explaining the operation of the bidirectional valve in the gas meter of FIG.

FIG. 3 is a cross-sectional view for explaining the operation of the bidirectional valve in the gas meter of FIG.

FIG. 4 is a block diagram showing a configuration of a control unit and its periphery in the gas meter of FIG.

5 is a functional block diagram for explaining the function of the gas meter of FIG. 1. FIG.

FIG. 6 is a characteristic diagram showing a relationship between an elapsed time and a flow rate after the gas cutoff valve of the gas meter of FIG. 1 is restored.

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

FIG. 8 is a characteristic diagram for explaining the operation of the gas meter according to the second embodiment of the present invention.

FIG. 9 is a flow chart for explaining the operation of the gas meter according to the second embodiment of the present invention.

[Explanation of symbols]

 10 Gas Meter 11 Housing 13 Gas Cutoff Valve (Bidirectional Valve) 14 Gas Flowmeter 15 Pressure Sensor 16 Control Section 30 Gas Flow Rate Detection Means (Flowmeter) 31 Gas Flow Path Cutoff Means (Bidirectional Valve) 32 Gas Pressure Detection Means 33 Memory Means 34 Judging Means 35 Returning Means

Claims (4)

[Claims] 1. A gas flow rate detecting means for detecting a gas flow rate flowing through a gas flow path, and a gas flow path shutting means capable of shutting off the gas flow path and electrically returning the gas flow path according to a detection result of the gas flow rate detecting means. And a gas pressure detecting means for detecting fluctuations in gas pressure in the gas flow path, and a rate of change in gas pressure detectable by the gas pressure detecting means is stored in a plurality of stages in accordance with the magnitude of the change. , Corresponding to each of these differentiated pressure change rates, storage means in which a plurality of inspection times of a size inversely proportional to the magnitude of the pressure change rate are stored, and before the gas flow path blocking means returns, The pressure change rate is obtained based on the detection result of the gas pressure detection means, and the range of the pressure change rate stored in the storage means is distinguished, and the range is further determined. Corresponding inspection It is determined whether or not the pressure fluctuation value within the interval is within a predetermined reference value.If the pressure fluctuation value is greater than the reference value, it is determined that there is no gas leak, and if it is within the reference value, there is a gas leak. Judgment means for judging, and when this judgment means judges that there is no gas leakage,
A gas meter, comprising: a resetting unit that resets the gas flow path blocking unit. 2. The gas meter according to claim 1, further comprising notifying means for notifying that there is a gas leak when the judging means judges that there is a gas leak. 3. A reference value of pressure fluctuation is set to be constant regardless of the magnitude of the pressure change rate, and the determination means uses the same reference value regardless of the magnitude of the pressure change rate to determine the presence or absence of gas leakage. The gas meter according to claim 1 or 2, wherein the gas meter is judged. 4. The reference value of pressure fluctuation is set in a plurality of stages according to the magnitude of the pressure change rate, and the judging means uses different reference values according to the magnitude of the pressure change rate to determine whether or not there is a gas leak. The gas meter according to claim 1 or 2, wherein