Patent Description:
There has been conventionally proposed a gas safety device including a gas meter that measures the amount of gas usage and determines anomaly to cut off a gas passage to ensure safety (see PTL <NUM>). The gas safety device includes an ultrasonic flow rate measurement unit in which an ultrasonic sensor and a circuit board provided with an ultrasonic sensor drive circuit are integrated, and a pressure sensor that measures differential pressure between supply pressure and atmospheric pressure. The gas safety device further includes a control function of cutting off a flow path and stopping supply of gas, and a function of warning, when it is determined that the differential pressure between the supply pressure and the atmospheric pressure measured by the pressure sensor is abnormal.

The pressure sensor incorporated in the gas safety device is a differential pressure measurement type that measures pressure of gas on the basis of atmospheric pressure, so that the pressure sensor has a through-hole through which the gas is introduced into the pressure sensor, and thus the gas may leak from the through-hole when temperature around the gas safety device excessively increases. Thus, examples of structure that does not require a through-hole include means for measuring change in gas supply pressure from a difference between measurement values of an absolute pressure sensor that measures atmospheric pressure and an absolute pressure sensor that measures gas pressure.

Unfortunately, driving the two sensors increases power consumption, and thus causing a problem that the gas safety device, which is typically driven by a battery, is required to increase capacity of the battery.

The invention is defined by the subject-matter of independent claim <NUM>. The dependent claims are directed to advantageous embodiments.

The present disclosure enables a gas safety device preventing gas from being ejected even at high temperature around the gas safety device to reduce power consumption even when two absolute pressure sensors are provided.

Hereinafter, exemplary embodiments will be described in detail with reference to the drawings. However, an unnecessarily detailed description may be eliminated.

Hereinafter, a first exemplary embodiment will be described with reference to <FIG> and <FIG>.

<FIG> illustrates a gas safety device <NUM> including: a flow path <NUM> through which gas flows; a shutoff valve <NUM> that shuts off the flow path <NUM>; a flow rate measurement unit <NUM> that measures a flow rate of the gas flowing through the flow path <NUM>; and a control circuit <NUM> that integrates the amount of gas usage using flow rate measurement data measured by the flow rate measurement unit <NUM>. Gas safety device <NUM> also includes a gas-side absolute pressure sensor <NUM> being a first pressure sensor that measures absolute pressure of gas, an atmosphere-side absolute pressure sensor <NUM> being a second pressure sensor that measures absolute pressure of atmosphere, an electronic circuit <NUM> installed in gas atmosphere, and a pressure value transition detector <NUM> that detects an absolute pressure transition state measured by the gas-side absolute pressure sensor <NUM>. Gas safety device <NUM> further includes a sensor drive controller <NUM> that controls driving of the atmosphere-side absolute pressure sensor <NUM> according to a predetermined transition value detected by the pressure value transition detector <NUM>, and a gas pressure determination unit <NUM> that calculates gas supply pressure from a difference between two pressure values measured by the gas-side absolute pressure sensor <NUM> and the atmosphere-side absolute pressure sensor <NUM>.

Gas-side absolute pressure sensor <NUM> being the first pressure sensor is mounted as an electronic component on electronic circuit <NUM> installed in gas atmosphere inside flow path <NUM>, and measures absolute pressure of the gas in flow path <NUM> using a signal from control circuit <NUM>. Atmosphere-side absolute pressure sensor <NUM> being the second pressure sensor is mounted as an electronic component on control circuit <NUM> installed on an atmospheric side outside flow path <NUM>, and measures atmospheric absolute pressure using a signal from control circuit <NUM>.

Next, specific operation of pressure value transition detector <NUM> and sensor drive controller <NUM> will be described with reference to <FIG>.

<FIG> illustrates an example of change in absolute pressure on a gas side and in absolute pressure on the atmospheric side, and of measurement timing of gas-side absolute pressure sensor <NUM> being the first pressure sensor and atmosphere-side absolute pressure sensor <NUM> being the second pressure sensor, in an identical period.

As illustrated in <FIG>, gas-side absolute pressure sensor <NUM> is always driven at predetermined intervals (e.g., two seconds to ten seconds) to perform measurement. That is, the predetermined intervals are intervals of the measurement timing of gas-side absolute pressure sensor <NUM>. When gas-side pressure value transition detector <NUM> detects that absolute pressure measured by gas-side absolute pressure sensor <NUM> has changed by a predetermined value (e.g., <NUM> kPa) or more, sensor drive controller <NUM> drives atmosphere-side absolute pressure sensor <NUM> to measure pressure on the atmospheric side. Then, when the change in the absolute pressure measured by gas-side absolute pressure sensor <NUM> is less than the predetermined value, the measurement is stopped without driving atmosphere-side absolute pressure sensor <NUM>.

That is, pressure change at each predetermined interval is less than <NUM> kPa until measurement timing Tn-<NUM> of gas-side absolute pressure sensor <NUM>, so that atmosphere-side absolute pressure sensor <NUM> is not driven. However, pressure difference ΔPgn between absolute pressure Pgn-<NUM> at measurement timing Tn-<NUM> and absolute pressure Pgn at measurement timing Tn is <NUM> kPa or more, and atmosphere-side absolute pressure sensor <NUM> is driven to measure atmospheric absolute pressure Pan at measurement timing Tn. Then, at next measurement timing Tn+<NUM>, pressure difference ΔPgn+<NUM> between absolute pressure Pgn at measurement timing Tn using gas-side absolute pressure sensor <NUM> and absolute pressure Pgn+<NUM> at measurement timing Tn+<NUM> is less than <NUM> kPa, and thus driving of atmosphere-side absolute pressure sensor <NUM> is stopped. After that, pressure change at each measurement timing of gas-side absolute pressure sensor <NUM> is less than <NUM> kPa, so that driving of atmosphere-side absolute pressure sensor <NUM> is stopped.

Thus, when gas-side absolute pressure sensor <NUM> measures absolute pressure Pgn on the gas side and atmosphere-side absolute pressure sensor <NUM> measures absolute pressure Pan on the atmosphere side at measurement timing Tn, gas pressure determination unit <NUM> can calculate gas supply pressure from a difference between the two measured pressure values. Control circuit <NUM> determines the flow rate measurement data measured by flow rate measurement unit <NUM>, the gas supply pressure, and change in the gas supply pressure to determine whether there is an anomaly such as gas leakage. When determining that there is an anomaly, control circuit <NUM> causes shutoff valve <NUM> to shut off flow path <NUM> to stop gas supply.

As described above, in the present exemplary embodiment, only gas-side absolute pressure sensor <NUM> being the first pressure sensor usually measures absolute pressure on the gas side, and driving and stopping of atmosphere-side absolute pressure sensor <NUM> being the second pressure sensor are controlled depending on whether a predetermined pressure change or more is detected. Such a configuration allows fluctuation of gas supply pressure to be detected using a difference between pressure values detected by the two absolute pressure sensors capable of reducing power consumption and measuring absolute pressure, so that a through-hole necessary for using a pressure sensor of a differential pressure measurement type is unnecessary, and thus a highly safe gas safety device can be fabricated.

Although in the present exemplary embodiment, pressure value transition detector <NUM> uses a method for detecting a pressure difference between measurement timings using gas-side absolute pressure sensor <NUM>, available methods include a method for detecting a pressure transition using a pressure difference between separated measurement timings, an average pressure difference of a plurality of measurement timings, a change pattern, or the like.

Although the present exemplary embodiment describes the configuration in which gas-side absolute pressure sensor <NUM> measures pressure to control stopping and driving of atmosphere-side absolute pressure sensor <NUM>, it is needless to say that a configuration in which stopping and driving of gas-side absolute pressure sensor <NUM> are controlled on the basis of pressure measurement of atmosphere-side absolute pressure sensor <NUM> can be equivalent to the configuration above.

It is needless to say that even when flow rate measurement unit <NUM> is used for ultrasonic flow rate measurement in the present exemplary embodiment, an equivalent measurement can be performed.

Although the present exemplary embodiment describes the structure in which gas-side absolute pressure sensor <NUM> is mounted on electronic circuit <NUM> installed in the gas atmosphere inside flow path <NUM>, it is needless to say that absolute pressure sensor <NUM> may be mounted anywhere inside flow path <NUM>. Although the structure is described in which atmosphere-side absolute pressure sensor <NUM> is mounted on control circuit <NUM> installed on the atmospheric side outside flow path <NUM>, a mounting place is not limited as long as atmospheric pressure can be measured.

Hereinafter, an example will be described with reference to <FIG> that does form part of the invention.

In <FIG>, the same components described in <FIG> are denoted by the same reference numerals, and duplicated description thereof is eliminated.

Gas safety device <NUM> includes flow path <NUM>, shutoff valve <NUM>, flow rate measurement unit <NUM> that measures a flow rate of the gas flowing through flow path <NUM>, and control circuit <NUM> that integrates the amount of gas usage using flow rate measurement data measured by flow rate measurement unit <NUM>. Gas safety device <NUM> also includes gas-side absolute pressure sensor <NUM> being a first pressure sensor, atmosphere-side absolute pressure sensor <NUM> being a second pressure sensor, electronic circuit <NUM> installed in gas atmosphere, and sensor drive controller <NUM> that controls driving of gas-side absolute pressure sensor <NUM> and atmosphere-side absolute pressure sensor <NUM>. Gas safety device <NUM> also includes a gas-side pressure value collector <NUM> that collects a pressure value measured by gas-side absolute pressure sensor <NUM> n times, and atmosphere-side pressure value collector <NUM> that collects a pressure value measured by atmosphere-side absolute pressure sensor <NUM> n times. Gas safety device <NUM> further includes gas-side previous value comparator <NUM> that compares a previous pressure value and a current pressure value that are obtained by gas-side pressure value collector <NUM>, atmosphere-side previous value comparator <NUM> that compares a previous pressure value and a current pressure value that are obtained by atmosphere-side pressure value collector <NUM>, and drive-stop determination unit <NUM> that determines stop of driving gas-side absolute pressure sensor <NUM> and atmosphere-side absolute pressure sensor <NUM> from results of gas-side previous value comparator <NUM> and atmosphere-side previous value comparator <NUM>. Gas safety device <NUM> further includes gas pressure determination unit <NUM> that calculates gas supply pressure from a difference between an absolute pressure value collected by gas-side pressure value collector <NUM> and an absolute pressure value collected by atmosphere-side pressure value collector <NUM>.

Next, specific operation will be described with reference to <FIG> that does not form part of the invention. The same components described in <FIG> and <FIG> are denoted by the same reference numerals.

As illustrated in <FIG>, gas pressure determination unit <NUM> periodically measures pressure at predetermined time intervals T (e.g., two seconds to ten seconds). <FIG> illustrates pressure measurement times T1 and T2 that each indicate timing of pressure measurement. At pressure measurement time T1, gas-side pressure value collector <NUM> collects absolute pressure values from pressure value Pg(<NUM>) measured first to pressure value Pg(n) measured at a maximum n-th time by gas-side absolute pressure sensor <NUM> at predetermined intervals (e.g., <NUM>). Atmosphere-side pressure value collector <NUM> collects absolute pressure values from pressure value Pa(<NUM>) measured first to pressure value Pa(n) measured at a maximum n-th time by atmosphere-side absolute pressure sensor <NUM> at the same timing as gas-side absolute pressure sensor <NUM>.

When gas-side pressure value collector <NUM> collects a pressure value at the second time, gas-side previous value comparator <NUM> compares first pressure value Pg(<NUM>) with second pressure value Pg(<NUM>), and thereafter, every time a measurement value is collected, gas-side previous value comparator <NUM> compares the measurement value with the previous value. Similarly, when atmosphere-side pressure value collector <NUM> collects second pressure value Pa(<NUM>), atmosphere-side previous value comparator <NUM> compares first pressure value Pa(<NUM>) with second pressure value Pa(<NUM>), and thereafter, every time a pressure value is collected, atmosphere-side previous value comparator <NUM> compares the pressure value with the previous pressure value.

When it is determined that the pressure values on the gas side and the atmosphere side are both stably measured as a result of comparisons using gas-side previous value comparator <NUM> and atmosphere-side previous value comparator <NUM>, drive-stop determination unit <NUM> stops driving gas-side absolute pressure sensor <NUM> and atmosphere-side absolute pressure sensor <NUM>.

That is, in the middle of n times measurements, when it is determined that not only a pressure value on the gas side is stable by comparison between pressure value Pg(k) on the gas side in the k-th measurement and pressure value Pg(k+<NUM>) on the gas side in the (k+<NUM>)-th measurement, but also a pressure value on the atmosphere side is stable by comparison between pressure value Pa(k) on the atmosphere side in the k-th measurement and pressure value Pa(k+<NUM>) on the atmosphere side in the (k+<NUM>)-th measurement, the (k+<NUM>)-th and subsequent measurements are stopped.

It is determined whether a pressure value is stably measured by determining whether a difference between a pressure value acquired this time and a pressure value acquired last time is smaller than a predetermined value. The predetermined value may be equal or set individually on each of the gas side and the atmosphere side.

Gas pressure determination unit <NUM> calculates gas supply pressure from a difference between a pressure value on the gas side in the (k+<NUM>)-th measurement with gas-side pressure value collector <NUM> when it is determined that measured pressure values are stable and a pressure value on the atmosphere side in the (k+<NUM>)-th measurement acquired by atmosphere-side pressure value collector <NUM>. Then, control circuit <NUM> determines whether there is an anomaly such as gas leakage by determining flow-rate measurement data measured by flow rate measurement unit <NUM>, gas supply pressure, and change in the gas supply pressure. When determining that there is an anomaly, control circuit <NUM> causes shutoff valve <NUM> to shut off flow path <NUM> to stop supplying the gas.

When it is determined that pressure values are unstable even after n repetitions as a result of comparisons using gas-side previous value comparator <NUM> and atmosphere-side previous value comparator <NUM> at pressure measurement time T1, as a result, gas pressure determination unit <NUM> does not calculate gas supply pressure from a difference between two absolute pressure values at pressure measurement time T1. Operation similar to that described above is also performed at pressure measurement time T2.

As described above, although in the present exemplary embodiment, measurements are performed by driving two absolute pressure sensors (gas-side absolute pressure sensor <NUM> being the first pressure sensor and atmosphere-side absolute pressure sensor <NUM> being the second pressure sensor) at predetermined time intervals T, power consumption can be reduced due to control of driving and stopping of the two absolute pressure sensors, the control being performed by determining whether pressure values measured by the two absolute pressure sensors are stable.

That is, when measured values are unstable due to an external factor such as noise, an accurate pressure value can be measured by performing measurement until the measured values become stable. Since noise or the like due to an external factor temporarily occurs, thus, in normal measurement without noise or the like, a number of times of driving the absolute pressure sensor in one pressure measurement time can be reduced, so that power consumption can be greatly reduced.

Additionally, a through-hole required for using a pressure sensor of a differential pressure measurement type becomes unnecessary, so that a gas safety device with higher safety can be fabricated.

Although in the present example that does not form part of the invention, gas-side previous value comparator <NUM> and atmosphere-side previous value comparator <NUM> have been described as a method for comparing two measurement results at the previous time and the current time, it is needless to say that the same can be performed when drive-stop determination unit <NUM> performs sensor drive control by comparing an average of values at multiple times up to the previous time and a measurement value at the current time.

Although the present exemplary embodiment describes the structure in which gas-side absolute pressure sensor <NUM> is mounted on electronic circuit <NUM> installed in the gas atmosphere inside flow path <NUM>, it is needless to say that gas-side absolute pressure sensor <NUM> may be mounted anywhere inside flow path <NUM>. Although the structure is described in which atmosphere-side absolute pressure sensor <NUM> is mounted on control circuit <NUM> installed on the atmospheric side outside flow path <NUM>, a mounting place is not limited as long as atmospheric pressure can be measured.

Claim 1:
A gas safety device (<NUM>) comprising:
a flow path (<NUM>) for allowing gas to flow;
a flow rate measurement unit (<NUM>) for measuring a flow rate of the gas flowing through the flow path (<NUM>);
a first pressure sensor (<NUM>) disposed inside the flow path (<NUM>) to measure absolute pressure of the gas;
characterized by
a second pressure sensor (<NUM>) disposed outside the flow path (<NUM>) to measure absolute pressure of atmospheric pressure;
a pressure value transition detector (<NUM>) that detects a transition state of the absolute pressure measured by the first pressure sensor (<NUM>) or the second pressure sensor (<NUM>);
a sensor drive controller (<NUM>) that controls driving of the second pressure sensor (<NUM>) according to a predetermined transition value of the pressure value transition detector (<NUM>) for the absolute pressure measured by the first pressure sensor (<NUM>) or that controls driving of the first pressure sensor (<NUM>) according to a predetermined transition value of the pressure transition detector (<NUM>) for the absolute pressure measured by the second pressure sensor (<NUM>);
a gas pressure determination unit (<NUM>) that calculates gas supply pressure from a difference between pressure values measured when the first pressure sensor (<NUM>) and the second pressure sensor (<NUM>) are both driven;
a shutoff valve (<NUM>) that shuts off the flow path (<NUM>); and
a control circuit (<NUM>) that controls the flow rate measurement unit (<NUM>) and causes the shutoff valve (<NUM>) to shut off the flow path (<NUM>) when determining anomaly from the flow rate measured by the flow rate measurement unit (<NUM>) or the gas supply pressure calculated by the gas pressure determination unit (<NUM>).