JP3436826B2 - Gas meter - Google Patents

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 safety function of shutting off gas when an abnormality occurs.

[0002]

2. Description of the Related Art FIG. 8 is an explanatory diagram showing the structure of a gas meter with a safety function equipped with a conventional microcomputer. This gas meter has a housing 100,
In this housing 100, from the inlet portion 111 to the outlet portion 11
A gas flow path 110 up to 2 is provided. Gas channel 1
The valve 10 is provided with a shutoff valve 114 for shutting off gas, a flow rate measuring unit 115 for measuring the flow rate, and a pressure switch 116 for outputting a signal when the pressure is equal to or higher than a predetermined value, in order from the inlet section 111 side. . A control unit 117 using a microcomputer for inputting output signals of the flow rate measuring unit 115 and the pressure switch 116 and controlling the shutoff valve 114 is provided in the housing 100.

In the gas meter shown in FIG. 8, when the flow rate measuring unit 115 detects a gas flow rate of a predetermined amount or more, or when the gas flow rate is detected for a predetermined period of time or more, the control unit 117 controls the gas meter. The shutoff valve 114 is driven to shut off the gas. When the gas is shut off in this way, a gas leak test is performed, and if there is a gas leak, recovery work is performed, and when the abnormality is resolved, a shutoff valve 114 is restored by pressing a return button (not shown). As shown in FIG. 9, when the shutoff valve 114 is restored, the control unit 117 causes the pressure switch 116 to operate the gas flow path 110.
It is monitored whether the internal pressure has recovered to, for example, 60 mmH ₂ O. The pressure recovery monitoring period for this monitoring is about 3 minutes at maximum when the pressure recovery cannot be confirmed. Control unit 1
If the pressure recovery can be confirmed within the pressure recovery monitoring period, 17 confirms the presence or absence of gas leakage based on the output of the flow rate measurement unit 115. Then, when there is no leakage, the normal state in which the gas can be used is entered. If there is a leak, the control unit 117 drives the shutoff valve 114 to shut off the gas again.
When the pressure recovery cannot be confirmed within the pressure recovery monitoring period, the control unit 117 drives the shutoff valve 114 to shut off the gas again.

By the way, there is a shut-off valve that electrically shuts off and returns. Further, some of such shut-off valves have a double valve structure in order to reduce the load at the time of return. The shut-off valve having a double-valve structure has a main valve for covering an opening provided in the gas flow path, a hole provided in the main valve, a sub valve capable of closing the hole, and a hole when shutting off. By urging the auxiliary valve in the closing direction, the main valve covers the opening and the auxiliary valve closes the hole, and when returning, it has a drive means for urging the auxiliary valve in the direction of opening the hole. ,
When returning, the main valve is biased in the direction to cover the opening by the pressure difference when the pressure difference between the upstream side and the downstream side of the opening exceeds a certain value, and is opened by the spring when the pressure difference is below a certain value. It is urged in the direction to open the part. Therefore,
In the shutoff valve of this double valve structure, at the time of return, since the differential pressure between the upstream side and the downstream side of the opening is large at first, the main valve covers the opening and the auxiliary valve opens the hole, and When the pressure difference on the downstream side becomes small, the main valve opens the opening.

[0005]

However, when the shutoff valve having the double valve structure described above is used, after the shutoff valve returns,
When the instrument plug is opened or the gas hose is disconnected, only the hole provided in the main valve is opened at the beginning, so the pressure loss in this hole is large, the pressure does not recover, and the maximum is about 3 minutes. There was a problem that the gas would flow out during the pressure recovery monitoring period.

The present invention has been made in view of the above problems, and an object thereof is to prevent gas outflow by promptly determining that pressure does not recover in pressure recovery monitoring after return of the shutoff valve. It is to provide a gas meter that can be used.

[0007]

A gas meter according to claim 1, wherein a flow rate detecting means for detecting a flow rate of the gas flowing through the gas flow passage, and a shut-off valve for shutting off the gas flow passage in the event of an abnormality are provided.
Return means for returning the shut-off valve, and detecting whether or not the gas pressure has recovered to a predetermined value or more after the shut-off valve has been returned by the return means.
Therefore, the detected flow rate decreases more than a predetermined amount within a predetermined time.
If not, pressure recovery monitoring means for determining that the gas pressure will not recover, and leakage determination means for determining the presence or absence of gas leakage when the pressure recovery monitoring means detects that the gas pressure has recovered. , When the pressure recovery monitoring means detects that the gas pressure does not recover above a predetermined value, when the pressure recovery monitoring means determines that the gas pressure does not recover, and when the leak determination means determines that gas has leaked. When it is turned off, the shutoff valve is driven to shut off the gas flow path again.

In this gas meter, after the shut-off valve is returned by the returning means, the pressure recovery monitoring means detects whether or not the gas pressure has recovered to a predetermined value or more.
The flow rate detected by the flow rate detection means is within a predetermined time
When the gas pressure does not decrease by the predetermined amount or more, it is determined that the gas pressure does not recover. When it is detected that the gas pressure has recovered, the leakage determination means determines whether or not there is a gas leakage. When the pressure recovery monitoring means detects that the gas pressure does not recover above the predetermined value, when the pressure recovery monitoring means determines that the gas pressure does not recover, and when the leakage determination means determines that gas has leaked. In this case, the shutoff valve is driven by the reshutting means to shut off the gas flow path again. In this way, in the pressure recovery monitoring after return of the shutoff valve, when the flow rate does not decrease below the preset value within the predetermined time, it is judged that the gas pressure does not recover, and thus the shutoff valve having the double valve structure is used. Even in this case, it is possible to quickly determine that the pressure does not recover without being affected by the pressure loss in the shutoff valve.

[0009]

A gas meter according to a second aspect is the gas meter according to the first aspect , in which the flow rate detecting means generates a fluidic oscillation by a gas ejected from a nozzle provided in the gas passage. And a fluidic oscillation detection sensor that detects the fluidic oscillation generated by this fluidic oscillation generation unit, a flow velocity sensor that detects the flow velocity of the gas flowing through the gas flow path, and a fluidic oscillation detection sensor according to the flow rate. The pressure recovery monitoring means has a flow rate calculating means for calculating the flow rate based on the output of at least one of the flow rate sensors, and the pressure recovery monitoring means uses the flow rate calculated by the flow rate detecting means based on the output of the flow rate sensor to determine the gas pressure. It is configured to judge that it will not recover.

The gas meter according to claim 3 is the gas meter according to claim 1.
Or 2 , the shutoff valve includes a main valve for covering an opening provided in the gas flow path, a hole provided in the main valve, and a sub valve capable of closing the hole. , Drives to energize the auxiliary valve in the direction of closing the hole when shutting off so that the main valve covers the opening and the auxiliary valve closes the hole, and to urge the auxiliary valve in the direction of opening the hole when returning. The main valve is urged in a direction to cover the opening by the differential pressure when the differential pressure between the upstream side and the downstream side of the opening exceeds a certain value when returning, and the differential pressure is less than the certain value. In this state, it is configured so as to be biased in the direction of opening the opening.

[0012]

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

FIG. 2 is a sectional view showing the structure of a gas meter according to an embodiment of the present invention. The gas meter comprises a body 10 having an inlet 11 for receiving gas and an outlet 12 for discharging gas. A partition wall 13 is provided in the main body 10.
Is provided, a gas flow path 14 is formed between the partition wall 13 and the inlet portion 11, and a gas flow path 15 is formed between the partition wall 13 and the outlet portion 12. An opening 16 is provided in the partition wall 13, and a shutoff valve 50 that can close the opening 16 is provided on the upstream side of the opening 16.

In the gas passage 15, there is provided a nozzle 21 which allows the gas received from the inlet portion 11 to pass therethrough to generate a jet flow. A flow sensor 30 which is a thermal type flow velocity sensor is arranged in the passage of the nozzle 21. Although not shown, the flow sensor 30 has a heat generating part and two temperature sensors arranged on the upstream side and the downstream side of the heat generating part, and keeps a constant temperature difference detected by the two temperature sensors. Therefore, the flow rate corresponding to the flow velocity is calculated from the power supplied to the heat generating section, or the heat generating section is heated with a constant current or constant power, and the flow rate is calculated from the temperature difference detected by the two temperature sensors. There is. In addition,
The flow sensor 30 is not limited to the one having the heat generating part and the two temperature sensors as described above, but has, for example, one heat generating part and generates heat required to keep the temperature (resistance) of the heat generating part constant. To obtain the flow velocity from the power supplied to the part,
It is also possible to heat the heat generating portion with a constant current or constant power and obtain the flow velocity from the temperature (resistance) of the heat generating portion.

On the downstream side of the nozzle 21, a pair of side walls 23 and 24 forming an enlarged flow path are provided. A target 25 is provided on the upstream side and a target 26 is provided on the downstream side with a predetermined gap between the side walls 23 and 24. A return guide 29 is formed outside the side walls 23 and 24 to form a pair of feedback flow paths 27 and 28 for returning the gas passing through the nozzle 21 to the ejection port side of the nozzle 21 along the outer peripheral portions of the side walls 23 and 24. Is provided. A pair of discharge passages 31 and 32 are formed between the outlet portions of the feedback flow passages 27 and 28 and the outlet portion 12 by the back surface of the return guide 29 and the main body 10. A pressure guiding hole 3 is provided in the vicinity of the nozzle 21 ejection port.
3, 34 are provided, and a piezoelectric film sensor 35 (not shown in FIG. 2) for detecting the pressure difference between the pressure guiding hole 33 and the pressure guiding hole 34 is provided outside the bottom portion of the main body 10.

The main body 10 is provided with a pressure guiding hole 39 communicating with the gas flow path 15 on the upstream side of the nozzle 21, and the gas in the gas flow path 15 is provided outside the main body 10 via the pressure guiding hole 39. A pressure sensor 40 that detects pressure is provided.

FIG. 1 is a block diagram showing the configuration of the circuit portion of the gas meter shown in FIG. As shown in this figure,
The gas meter is an A / D that converts the output signal of the flow sensor 30 from analog to digital (hereinafter referred to as A / D).
A converter 41, an analog amplifier 42 that amplifies the output signal of the piezoelectric film sensor 35, and a waveform shaping circuit 43 that shapes the output of the analog amplifier 42 to generate a pulse.
And a flow rate calculation unit 44 that inputs the output of the A / D converter 41 and the output of the waveform shaping circuit 43 and calculates the flow rate and the integrated flow rate based on at least one of the outputs according to the flow rate, and the flow rate calculation unit 44. And a display unit 45 that displays the integrated flow rate calculated by. The flow rate calculation unit 44 calculates the flow rate and the integrated flow rate based on the output of the flow sensor 30 (the output of the A / D converter 41) in the small flow rate range in which the range is set in advance, and the large flow rate in which the range is set in advance. In the region, the flow rate and the integrated flow rate are calculated based on the output of the piezoelectric film sensor 35 (output of the waveform shaping circuit 43).

The gas meter further determines the presence / absence of gas leakage based on the shutoff valve drive circuit 46 for driving the shutoff valve 50 and the flow rate calculated by the flow rate calculation unit 44, and drives the shutoff valve when it is determined that there is a leak. The circuit 46 is controlled to drive the shutoff valve 50 to shut off the gas, and at the same time, the leakage determination unit 47 that issues an alarm display on the display unit 45 and the shutoff valve drive circuit 46.
A return switch 48 for instructing the return of the shutoff valve 50 and a signal from the return switch 48,
After the shutoff valve 50 is restored, a pressure recovery monitor 49 is provided for monitoring whether or not the gas pressure has recovered to a predetermined value based on the output of the pressure sensor 40 and the output of the flow rate calculator 44. The flow rate calculation unit 44, the leakage determination unit 47, and the pressure recovery monitoring unit 49 are configured by, for example, a microcomputer.

After the shutoff valve 50 is restored, the pressure recovery monitoring section 49 has a maximum pressure recovery monitoring period of, for example, 3 minutes.
Based on the output of the pressure sensor 40, the gas pressure has a predetermined value,
For example, when it is detected whether or not the flow rate has been recovered to 60 mmH ₂ O or more and the flow rate calculated based on the output of the flow sensor 30 in the flow rate calculation unit 44 does not decrease below a preset value within a predetermined time. It is determined that the gas pressure will not recover even before the pressure recovery monitoring period has elapsed.

When the pressure recovery monitoring unit 49 detects that the gas pressure has recovered to a predetermined value or higher, the leakage determination unit 47 determines the presence or absence of gas leakage based on the presence or absence of the flow rate calculated by the flow rate calculation unit 44. It is supposed to do. When the pressure recovery monitoring unit 49 detects that the gas pressure has not recovered to a predetermined value or higher after the pressure recovery monitoring period has elapsed, the leakage determination unit 47 uses the pressure recovery monitoring unit 49 before the pressure recovery monitoring period elapses. When it is determined that the gas pressure does not recover, and when the pressure recovery monitoring unit 49 detects that the gas pressure has recovered and gas leakage has occurred, the shutoff valve drive circuit 46 is controlled to shut off the shutoff valve 50. Is driven to shut off the gas again and an alarm is displayed on the display unit 45. Shutoff valve 50
When the pressure recovery monitoring unit 49 detects that the gas pressure has recovered and the leakage determination unit 47 determines that there is no gas leakage after the return of the above, the gas is in a normal state in which the gas can be used. The leak determination unit 47 corresponds to the leak determination means and the re-cutoff means in the present invention.

3 to 5 show the structure and operation of the shutoff valve 50. As shown in FIG. As shown in these drawings, the shutoff valve 50 includes a housing 51 fixed to the outside of the main body 10 of the gas meter. The housing 51 has a hollow portion, and the permanent magnet 5 is provided at the rear end in the hollow portion.
2 is provided, and further, a core piece 53 joined to the front end of the permanent magnet 52 is provided. Housing 5
In the hollow part of No. 1, a plunger 54 made of a magnetic material
Has been inserted. Inside the housing 51, a coil 55 serving as an electromagnet is provided. The plunger 54 has three parts having a diameter smaller toward the tip side, that is, a small diameter part 54a on the tip side, a middle diameter part 54b in the center, and a large diameter part 54c on the rear end side. . Between the small diameter portion 54a and the medium diameter portion 54b, and between the medium diameter portion 54b and the large diameter portion 54c, tapered surfaces having gradually changing diameters are formed. The taper surface between the small diameter portion 54a and the medium diameter portion 54b constitutes a sub valve 56.

The shutoff valve 50 further includes a main valve 57 that abuts on a valve seat 16a formed around the opening 16 and covers the opening 16. The main valve 57 has a ring-shaped support member 57a and a rubber valve body 57b fixed to the front end surface of the support member 57a. Rubber valve body 57b
A hole 58 having an inner diameter larger than the outer diameter of the small-diameter portion 54a and smaller than the outer diameter of the medium-diameter portion 54b is provided in the central portion of the. The small diameter portion 54a of the plunger 54 is inserted into the hole 58. On the rear end side of the rubber valve body 57b, a tapered surface whose inner diameter is gradually increased is formed continuously with the hole 58, and the auxiliary valve 56 formed on the plunger 54 abuts on this tapered surface, Sub valve 56
The hole 58 is closed by the. A spring 59 that biases the main valve 57 toward the opening 16 is provided around the middle diameter portion 54b between the rear end surface of the support member 57a and the inner wall of the main body 10. A flange member 61 is fixed to the tip of the small diameter portion 54a, and the small diameter portion 54a is surrounded by the flange member 61 and the rubber valve body 57b.
A spring 62 that biases the main valve 57 toward the side opposite to the opening 16 is provided.

This shut-off valve 50 is normally used for the coil 5
5, the plunger 54 moves the core piece 5 into the core piece 5 due to the magnetic force of the permanent magnet 52, as shown in FIG.
Adsorbed on 3. Further, the force of the spring 62 is stronger than the force of the spring 59, and the balance of the spring load allows the main valve 57 to open the opening 56 and allow the gas to pass through the opening 16. To shut off the gas from this state,
A current is passed through the coil 55 so as to cancel the magnetic force of the permanent magnet 52, and the force of the spring 59 causes the plunger 54 to project, as shown in FIG. As a result, the main valve 57 covers the opening 56, the auxiliary valve 56 closes the hole 58, and the gas is shut off. When the shutoff valve 50 is returned from this state, an electric current is applied to the coil 55 in the opposite direction to that at the time of shutoff, and the plunger 54 is attracted to the core piece 53 side as shown in FIG. At the time of this restoration, the opening 1 is initially
Since the pressure on the upstream side of 6 is larger than the pressure on the downstream side and the pressure difference between the two is large, the pressure difference urges the main valve 57 in the direction to cover the opening 16. Therefore, at the beginning, the main valve 5
7 covers the opening 16 and the auxiliary valve 56 opens the hole 58, and the gas flows through the hole 58 to the downstream side of the opening 16. When the pressure difference between the upstream side and the downstream side of the opening 16 becomes smaller, the spring 62 becomes stronger than the biasing force due to the pressure difference.
The urging force of the main valve 57 becomes larger than the opening 1
6 and the main valve 57 is in the state shown in FIG. 3 in which the opening 56 is opened.

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

The gas received from the inlet 11 of the gas meter is supplied to the gas passage 14, the opening 16 and the gas passage 1.
After going through 5 in order, it enters the nozzle 21. The output signal of the flow sensor 30 arranged in the passage of the nozzle 21 is converted into digital data by the A / D converter 41 and the flow rate calculation unit 4
4 is input. The flow rate calculation unit 44 is A /
The flow rate and the integrated flow rate are calculated based on the output of the D converter 41. The display unit 45 displays the integrated flow rate calculated by the flow rate calculation unit 44.

The gas passing through the nozzle 21 becomes a jet stream and is jetted from the jet outlet. The gas ejected from the ejection port flows along one side wall due to the Coanda effect. Here, it shall first flow along the side wall 23. The gas flowing along the side wall 23 is further returned to the ejection port side of the nozzle 21 via the feedback flow path 27.
It is discharged from the outlet 12 via the discharge passage 31. At this time, the gas ejected from the nozzle 21 is changed in direction by the gas flowing through the feedback flow path 27, and now flows along the other side wall 24. This gas further passes through the feedback flow path 28, and the nozzle 21
Is discharged to the jet outlet side of the nozzle, and is discharged from the outlet portion 12 via the discharge passage 32. Then, the direction of the gas ejected from the nozzle 21 is changed by the gas flowing through the feedback flow path 28, and the gas flows again along the side wall 23 and the feedback flow path 27. By repeating the above operation, the gas passing through the nozzle 21 performs fluidic oscillation which alternately flows through the pair of feedback flow paths 27 and 28. The frequency of this fluidic oscillation,
The cycle has a relationship with the flow rate.

The fluidic oscillation is detected by the piezoelectric film sensor 35, the output of the piezoelectric film sensor 35 is amplified by the analog amplifier 42, pulsed by the waveform shaping circuit 43, and input to the flow rate calculation unit 44. The flow rate calculation unit 44 calculates the flow rate and the integrated flow rate based on the output of the waveform shaping circuit 43 in the large flow rate range.

The leakage determination unit 47 controls the shut-off valve drive circuit 46 in the event of an abnormality such as when the flow rate calculation unit 44 detects a gas flow rate of a predetermined amount or more, or when the gas flow rate is detected for a predetermined period or more. Then, the shutoff valve 50 is changed from the state shown in FIG. 3 to the state shown in FIG. 4 to shut off the gas, and an alarm display is displayed on the display unit 45. When the gas is shut off in this way, a gas leak test is performed, and if there is a gas leak, recovery work is performed. When the abnormality is resolved, the return switch 48 is pressed to turn off the shut-off valve 5 to the shut-off valve drive circuit 46.
Instruct to return 0. In response to this instruction, the shutoff valve drive circuit 46 changes the shutoff valve 50 from the state shown in FIG. 4 to the state shown in FIG. 5, and restores the shutoff valve 50.

As shown in FIG. 6, when the shutoff valve 50 is restored, the pressure recovery monitoring unit 49 controls the gas pressure based on the output of the pressure sensor 40 during the pressure recovery monitoring period of, for example, 3 minutes at the maximum. Is detected to be equal to or greater than a predetermined value, for example 60 mmH ₂ O, and the flow rate calculated based on the output of the flow sensor 30 in the flow rate calculation unit 44 is reduced to a value equal to or less than a preset value within a predetermined time. If not, it is determined that the gas pressure does not recover even before the pressure recovery monitoring period has elapsed. The leak determination unit 47 determines that the pressure recovery monitoring unit 49 determines that the gas pressure does not recover before the pressure recovery monitoring period elapses, and that the pressure recovery monitoring period elapses and the pressure recovery monitoring unit 49 determines that the gas pressure does not recover. When it is detected that the predetermined value or more is not recovered, the shut-off valve drive circuit 46 is controlled to drive the shut-off valve 50 to shut off the gas again, and an alarm is displayed on the display unit 45.

FIG. 7 shows the change in the flow rate after the shutoff valve 50 is returned. Reference numeral 71 indicates that the gas does not flow out on the downstream side of the gas meter, and reference numeral 72 indicates that the gas flows out on the downstream side of the gas meter. It shows the case. As shown in this figure, after the shutoff valve 50 returns, if there is no gas outflow on the downstream side of the gas meter, the flow rate sharply decreases and the pressure recovers, but there is gas outflow on the downstream side of the gas meter. In this case, the flow rate does not decrease and the pressure does not recover. Therefore, it can be determined that the gas pressure will not recover unless the flow rate decreases with the passage of time after the shutoff valve 50 returns. In view of this, in the present embodiment, when the flow rate calculated by the pressure recovery monitoring section 49 based on the output of the flow sensor 30 in the flow rate calculation section 44 does not decrease below a preset value Q ₁ within a predetermined time T. Has decided not to recover the gas pressure even before the pressure recovery monitoring period has elapsed. Here, after the shutoff valve 50 returns, when the gas does not flow out on the downstream side of the gas meter, the time until the flow rate decreases to zero is, for example, about 20 to 30 seconds, so the predetermined time T is, for example, 20 to 30. It is set to about a second. Also, the set value Q
_{No. 1} is that the flow rate is sufficiently lower than the gas flow rate within a predetermined time T when there is no gas flow-out on the downstream side of the gas meter, and the flow rate is not below this when there is gas flow-out on the gas meter downstream side. Is set to any value.

When the pressure recovery monitoring unit 49 detects that the gas pressure has recovered, the leakage determination unit 47, as shown in FIG. 6, during the next leakage confirmation period,
The presence or absence of gas leakage is determined based on the presence or absence of the flow rate calculated by the flow rate calculation unit 44. When it is determined that there is a gas leak, the shutoff valve drive circuit 46 is controlled to shut off the shutoff valve 5.
0 is driven, the gas is cut off again, and an alarm is displayed on the display unit 45. When it is determined that there is no gas leakage, the gas is in a normal state in which it can be used.

As described above, in the present embodiment, after the shutoff valve 50 is restored, the flow rate calculated by the pressure recovery monitoring section 49 based on the output of the flow sensor 30 in the flow rate calculation section 44 is within a predetermined time. When the pressure does not decrease below a preset value, it is determined that the gas pressure will not recover even before the pressure recovery monitoring period elapses, and the gas is shut off. After the shutoff valve 50 returns, when the gas does not flow out on the downstream side of the gas meter, the time for the flow rate to decrease to zero is, for example, about 20 to 30 seconds, so the gas pressure does not recover within this time. It is possible to judge that. Therefore, according to the present embodiment, even when the shutoff valve 50 having the double valve structure as shown in FIGS. 3 to 5 is used, the shutoff valve 50 is used in the pressure recovery monitoring after the shutoff valve 50 is restored.
It is possible to prevent gas from flowing out by promptly judging that the pressure does not recover without being affected by the pressure loss in the above.

Further, according to the present embodiment, when the flow rate calculated by the flow rate calculation unit 44 based on the output of the flow sensor 30 after the shutoff valve 50 is returned decreases to a value equal to or less than a preset value within a predetermined time. In addition, since the pressure recovery monitoring unit 49 detects whether or not the gas pressure has recovered to a predetermined value or higher, and if the gas pressure has recovered to a predetermined value or higher, the presence or absence of gas leakage is determined. It is possible to accurately determine the presence or absence of gas leakage.

The present invention is not limited to the above embodiment,
For example, in the pressure recovery monitoring unit 49, the flow rate calculation unit 44
When the flow rate calculated based on the output of the flow sensor 30 does not decrease below a preset value within a predetermined time, the flow rate calculation unit 44 outputs the output of the flow sensor 30 instead of determining that the gas pressure does not recover. It may be determined that the gas pressure is not recovered when the flow rate calculated based on the above does not decrease by a predetermined amount or more within a predetermined time.

Instead of the pressure sensor 40, a pressure switch that outputs a signal when the gas pressure recovers to a predetermined value, for example, 60 mmH ₂ O or more, may be used.

[0036]

As described above, according to the gas meter of the present invention, in the pressure recovery monitoring after the return of the shutoff valve, when the flow rate does not decrease below a preset value within a predetermined time, or when the flow rate is within a predetermined time. Since it is determined that the gas pressure will not be restored if the pressure does not decrease by more than a predetermined amount and the gas flow path is shut off, even if a shut-off valve with a double valve structure is used, it will be affected by the pressure loss at the shut-off valve. In other words, there is an effect that gas outflow can be prevented by promptly judging that the pressure will not recover.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of a gas meter according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a configuration of a gas meter according to an embodiment of the present invention.

3 is a cross-sectional view showing a normal state of the shutoff valve in FIG.

FIG. 4 is a cross-sectional view showing a state when the shutoff valve in FIG. 1 is shut off.

5 is a cross-sectional view showing a state immediately after the cutoff valve in FIG. 1 is restored.

FIG. 6 is an explanatory diagram showing an operation of the gas meter according to the embodiment of the present invention after the shutoff valve is returned.

FIG. 7 is a characteristic diagram showing a change in flow rate after returning from the shutoff valve of the gas meter according to the embodiment of the present invention.

FIG. 8 is an explanatory diagram showing a configuration of a conventional gas meter.

FIG. 9 is an explanatory diagram showing an operation of the conventional gas meter after returning from the shutoff valve.

[Explanation of symbols]

30 flow sensor 35 Piezoelectric film sensor 40 pressure sensor 44 Flow rate calculator 45 Display 46 Shut-off valve drive circuit 47 Leakage judgment part 48 Return switch 49 Pressure recovery monitor 50 shutoff valve

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-5-157594 (JP, A) JP-A-51-118133 (JP, A) JP-A-6-117955 (JP, A) 5055 (JP, U) Patent 3051577 (JP, B2) Patent 2837082 (JP, B2) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01F 1/00 G01F 1/20 G01F 3/22

Claims (3)

(57) [Claims] 1. A flow rate detecting means for detecting a flow rate of a gas flowing through a gas flow path, a shut-off valve for shutting off the gas flow path in the event of an abnormality, a returning means for returning the shut-off valve, and the returning means After the shutoff valve is restored, it is detected whether or not the gas pressure has recovered to a predetermined value or more, and the flow rate detected by the flow rate detecting means is at a predetermined time.
If the pressure does not decrease more than the specified amount within the
Pressure recovery monitoring means for judging that the gas does not recover, leakage judgment means for judging whether or not there is a gas leak when the pressure recovery monitoring means detects that the gas pressure has recovered, and gas recovery by the pressure recovery monitoring means. When it is detected that the pressure of does not recover to a predetermined value or more, when it is determined that the pressure of the gas does not recover by the pressure recovery monitoring means, and when it is determined that there is a gas leak by the leakage determination means, A gas meter, comprising: a re-shutoff unit that drives the shut-off valve to shut off the gas flow path again. 2. The flow rate detection means includes a fluidic oscillation generation section that generates fluidic oscillation by gas ejected from a nozzle provided in a gas flow path, and a fluidic oscillation generation section that is generated by the fluidic oscillation generation section. A fluidic oscillation detection sensor that detects Dick oscillation, a flow velocity sensor that detects the flow velocity of the gas flowing through the gas flow path, and a flow rate based on the output of at least one of the fluidic oscillation detection sensor and the flow velocity sensor according to the flow rate. And a flow rate calculation means for calculating
Gas meter according to claim 1, wherein the determining that the pressure of the gas is not recovered with a flow rate calculated by the flow rate detecting means based on an output of the flow sensor. 3. The shutoff valve includes a main valve for covering an opening provided in a gas flow path, a hole provided in the main valve, a sub valve capable of closing the hole, and a shutoff valve when shutting off. By urging the auxiliary valve in the direction of closing the hole, the main valve covers the opening and the auxiliary valve closes the hole, and at the time of return, the drive means for urging the auxiliary valve in the direction of opening the hole. The main valve is urged in a direction to cover the opening by the differential pressure when the differential pressure between the upstream side and the downstream side of the opening exceeds a certain value at the time of return, and the differential pressure is below a certain value. The gas meter according to claim 1 or 2, wherein the gas meter is biased in a direction to open the opening.