JPH1194612A - Flow rate measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the power consumption without lowering the flow measuring accuracy, by setting up driving conditions for driving a flow-rate measuring means according to output of a change detecting means. SOLUTION: A hot-wire type flow-rate measuring part 10 causes a heating element in a channel 11 to generate heat by signal of a flow measurement starting means 12, measures temperature change thereof, and outputs its measured result to a signal processing mean 13. Since flow velocity of fluid is found by using a characteristic that the larger the flow velocity in the channel is, the more the heat generated in the heating element is lost, the temperature change becomes smaller, and a flow rate computing means 14 computes the flow rate of a fluid flowing in the channel 11 by using the flow velocity, the cross section area of the channel 11, sampling period, and the like. The sampling period is normally set up to be several seconds to several tens seconds from the viewpoint of lower power consumption. Driving conditions for driving the flow-rate measuring part are set up by a condition set-up means 16 by using an output signal of a pressure sensor 15 as a change detecting means for detecting change of fluid condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an external synchronous type flow rate measuring device for measuring a flow rate of a fluid using a hot wire or an ultrasonic wave.

[0002]

2. Description of the Related Art Conventionally, as this type of external synchronous type fluid measuring device, a hot-wire type fluid flow meter as shown in FIG. 8 is well known. A concave portion 2 is formed on the surface of a base 1 such as a semiconductor by a fine processing technique such as etching, and an electrically insulating thin film 3 is formed thereon in a bridge shape. A slit 6 is formed in the electrically insulating thin film 3 so that the resistance thermometers 4 and 5 are thermally insulated from each other.
A fluid temperature detecting element 7 composed of a temperature measuring resistor for detecting the temperature of the fluid is provided on the upper portion, and a hot wire type fluid flow meter is used. A fluid is allowed to flow from the direction of the arrow 8, a constant current from a constant current source is allowed to flow through the resistance temperature detectors 4 and 5 for a predetermined time, and the temperature is increased by heating. And each temperature is measured from the resistance value of each of the resistance temperature detectors 4 and 5 due to the cooling effect depending on the flow velocity of the fluid, and the flow velocity of the fluid is measured from the temperature difference. (See Japanese Patent Publication No. 6-25684).

[0003]

However, in the above-mentioned conventional externally-synchronized flow rate measuring apparatus, intermittent sampling is performed in order to suppress power consumption. There is a problem that power consumption increases due to increased measurement. For example, in the case of a hot-wire type fluid flow meter having a heat-generating portion, if the calculation is performed on the assumption that the measurement time is 10 [msec], the measurement current is 10 [mA], and the number of times of measurement is 1 [times / sec], about 900
0 [mA · Hr], and if a lithium battery or the like that is usually used has a capacity of about 5000 [mA · Hr], operation for about 10 years cannot be guaranteed.

Another problem is that if the fluid starts flowing during intermittent sampling, the flow rate cannot be measured accurately. For this reason, with a flow meter that also has a safety function such as shutting off the flow path when abnormal use is used, such as a gas meter, it uses a battery with low power consumption and realizes accurate flow measurement in a short time to ensure safety Was a challenge. In addition, in the case of a large water heater or the like in which the flow pattern immediately after the start of use is a pattern unique to the device, it has been difficult to accurately measure the flow pattern with an external synchronous type flow meter.

[0005]

In order to solve the above problems, a flow rate measuring device according to the present invention includes a flow rate measuring means for measuring a fluid flow rate, and a change detecting means for detecting a change in a fluid state such as a pressure sensor or a gas sensor. And condition setting means for setting driving conditions for driving the flow rate measuring means according to the output of the change detecting means. With this configuration, during normal measurement, the flow rate is measured at a fixed interval, for example, a sampling interval of several seconds to several tens of seconds, but when a pressure change or the like occurs, it is synchronized with that, and the sampling interval is several seconds or less. Can be set to measure the flow rate. Therefore, low power consumption can be realized without lowering the flow rate measurement accuracy. In addition, since the flow measurement can be started in synchronization with the rise of the flow, the flow can also be accurately measured.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a flow rate measuring means for measuring a fluid flow rate, a change detecting means for detecting a change in a fluid state, such as a pressure sensor or a gas sensor, The configuration is provided with condition setting means for setting driving conditions for driving the measuring means. With this configuration, during normal measurement, the flow rate is measured at a fixed interval, for example, a sampling interval of several seconds to 10 seconds. However, when a pressure change or the like occurs, the flow is measured in synchronization with the sampling interval, and a sampling interval of several seconds or less. Can be set to measure the flow rate. Therefore, low power consumption can be realized without lowering the flow rate measurement accuracy. In addition, since the flow measurement can be started in synchronization, the flow can also be accurately measured.

Further, the present invention provides a flow rate measuring means for measuring a fluid flow rate, a change generating means for changing a fluid state such as a valve opening / closing operation, and a drive means for driving the flow rate measuring means in accordance with the operation of the change generating means. And a condition setting means for setting a driving condition to be performed. With this configuration, the flow rate can be measured at an optimal sampling interval in synchronization with the opening / closing operation of a valve of a large water heater or the like, or the ignition operation. Therefore, since a change in flow rate and a change in pressure for several tens of seconds immediately after the start of use can be measured in detail, it is possible to specify a device to be used and to enhance the security function. In addition, since the measurement can be started at the same time when the cock is opened (filling starts), such as at the time of gas filling, the filling amount and the like can be accurately measured.

Further, according to the present invention, since a measuring device including a heating element and a temperature sensor for detecting a temperature change by the heating element is provided in the flow path of the fluid, a sampling interval as short as several tens of milliseconds is required. The flow rate can be measured with high accuracy. In addition, measurement can be easily performed in synchronization with an external signal.

Further, the present invention provides a pair of ultrasonic transceivers for transmitting and receiving ultrasonic waves upstream and downstream of a flow path through which a fluid flows, wherein the ultrasonic transmitter and receiver transmit ultrasonic waves from the upstream side to the downstream side and from the downstream side to the upstream side. Since it is configured with an ultrasonic flow rate measuring unit that measures the sound wave propagation time, calculates the flow velocity of the fluid from the time difference, and measures the flow rate, a wide range of flow rate can be measured in synchronization with an external signal, and low consumption is achieved. A high-precision gas meter using electric power can be realized.

Further, according to the present invention, immediately after a change in state such as pressure, or immediately after a valve is opened, a sampling cycle is shortened, and a driving condition is set such that the sampling cycle is lengthened with time or as the flow rate change becomes smaller. It was configured to be able to. Therefore, only when necessary,
Since the sampling time can be shortened and the flow rate can be measured, a change in the flow rate in a transient state can be accurately measured with low power consumption.

Further, the present invention has a structure provided with a discriminating means for discriminating the state of the flow path on the downstream side from the output of the fluid state change detecting means such as a pressure sensor and the flow rate measurement result of the flow rate measuring means. . With this configuration, immediately after the fluid state changes, the time change of the pressure and the time change of the flow rate can be accurately measured, the state of the flow path on the downstream side can be reliably determined, and the safety of the flow path is ensured. Can do things.

Further, according to the present invention, when the pressure value is large and the flow rate is large, a device is mounted on the downstream side, it can be determined that the gas is in use, and the safety on the downstream side is ensured. be able to.

Further, according to the present invention, when the pressure value is small and the flow rate is large, it is determined that the gas is being discharged without load on the downstream side, so that a shutoff command can be transmitted to a shutoff valve or the like. This makes it possible to prevent danger on the downstream side.

Further, in the present invention, when the pressure value is large and the flow rate is small, it is determined that a very small amount of gas is used or leaked through the device, so that if this state is maintained for a long time, Since it is possible to display or notify that a very small amount of gas, such as a pilot flame, is being used, or that there is a possibility of leakage, it is possible to prevent danger on the downstream side.

Further, in the present invention, when the pressure value is large and the flow rate is zero, the downstream side is determined to be in a completely closed state, so that safety on the downstream side can be secured in a short time.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a flow meter 9 according to a first embodiment of the present invention. Reference numeral 10 denotes a hot wire type flow rate measuring unit provided as flow rate measuring means provided in the flow path 11. The hot wire type flow measurement unit 10 includes a flow measurement start unit 12.
The heat generation element in the flow path 11 is caused to generate heat by the signal of (1), the temperature change is measured, and the measurement result is output to the signal processing means 13. The larger the flow velocity in the flow path, the more the heat generated by the heating element is cooled. Therefore, the flow velocity of the fluid is determined from the characteristic that the temperature change is reduced, and the cross-sectional area of the flow path 11 or the sampling period is further determined. The flow rate calculating means 14 calculates the flow rate of the fluid flowing through the flow path 11. Normally, the sampling period is set to several seconds to several tens of seconds from the viewpoint of low power consumption. Reference numeral 15 denotes a pressure sensor as a change detecting means for detecting a change in the fluid state. The driving condition for driving the flow rate measuring unit is set by the condition setting unit 16 based on the output signal of the pressure sensor 15.

In such a configuration, for example, when the fluid state and the flow rate change as shown in FIG. 2 occur, that is, in FIG. 2, the horizontal axis indicates the elapsed time, and the vertical axis indicates the pressure 17 and the flow rate 18. Of the characteristic values of FIG.
It should be noted that T _O in the figure indicates a point in time when a pressure change occurs. 1
Reference numeral 9 denotes a synchronization signal for starting measurement at an interval of several seconds to several tens of seconds in a normal state. In this case, since the point in time when the flow rate rises cannot be detected, even if the gas with a large flow rate is started to be used, the flow rate value at that time cannot be measured, so that a large error occurs in the measured value. In addition, since the flow rate cannot be accurately measured, there may be a case where the state deviates from a preferable state in terms of security. For example, in the case of the present invention, the flow rate (1
By monitoring the increase (8) of the output (17) of the pressure sensor at intervals of, for example, 0.2 seconds, a change in the flow rate can be detected from a change (pressure) in the state of the fluid. On the basis of, for example, the flow meter measurement, as shown at 20, the measurement was normally started at intervals of several seconds to several tens of seconds, for example, it can be changed to start at intervals of 1 second, Measurement accuracy is improved. Further, in this case, since the start point of the increase in the flow rate can be reliably detected with an error of 0.2 seconds, even if a large flow rate gas is released due to, for example, a broken pipe, the detection is immediately performed. Security performance is also improved.

In this case, the pressure sensor and the like, which consume less power, are frequently operated, and the hot wire type flow rate measuring unit, which consumes more power, is operated an optimum number of times. Security performance can be ensured. For example, in the case of a pressure sensor composed of a strain gauge or the like, the time required for measurement is 2 [ms].
ec], assuming that the current required for measurement is 10 [μA] and the number of measurements is 5 [times / sec], the current capacity required for operation for 10 years is about 9 [mA · Hr], which is commonly used. About 5000 [mA]
[Hr], which is a sufficiently achievable capacity.

(Embodiment 2) FIG. 3 is a block diagram of a flow meter 21 according to Embodiment 2 of the present invention. The difference from the first embodiment is that a cock 22 of a gas appliance such as a water heater is provided as a fluid state change generating means instead of the fluid state change detecting means such as a pressure sensor. Furthermore, a condition setting means 17 for setting driving conditions is linked to the cock 22. Therefore, it is possible to set the driving conditions in synchronization with the opening and closing of the cock 22. That is, in the normal case, from the viewpoint of low power consumption, the sampling cycle is set to several seconds to several tens of seconds, and when the cock 22 is opened, for example, if measurement is started at 0.5 second intervals,
Sufficient weighing accuracy can be realized. In addition, if the normal sampling period is returned in synchronization with the closing of the cock 22, high-precision flow measurement can be realized while realizing low power consumption.
In addition, since the flow measurement can be started in synchronization with the opening and closing of the cock 22, the flow pattern at the time of ignition, for example, can be measured in detail. Therefore, in a large-sized water heater, it is possible to confirm a flow pattern at the time of ignition specific to each, and it is also possible to determine what kind of large-sized water heater has ignited. In addition, because of such a configuration, for example, even when filling a gas cylinder or the like with a gas, it is possible to repeat the flow rate measurement in a short time in synchronization with the opening of the cock, so that the filling amount can be accurately determined. Can be measured.

(Embodiment 3) FIG. 4 is a block diagram of a flow meter 23 according to Embodiment 3 of the present invention. The difference from the first embodiment is that, instead of the hot wire type flow measurement unit 10, an ultrasonic flow measurement unit is provided with an upstream ultrasonic transceiver 24 and a downstream ultrasonic transceiver 25 to switch between transmission and reception. The switching means 26 is provided. In this configuration, for example, when a measurement start signal is given from 12 to the switching unit 26, the switching unit 26 operates the upstream ultrasonic transceiver 24 as a transmitter and sends the signal to the downstream transceiver 25. Sound waves are transmitted into the flow path. Downstream transceiver 25
Operates as a receiver, receives transmitted ultrasound,
The propagation time of the ultrasonic wave transmitted from the upstream side to the downstream side is measured. Next, the switching means 26 causes the downstream transceiver 25 to operate as a transmitter and the upstream transceiver 2 to operate as a receiver.

In this way, the propagation time of the ultrasonic wave transmitted from the downstream side to the upstream side is measured. The measured propagation times of the ultrasonic waves are given to the signal processing means 13. The flow rate calculating means 14 calculates the average flow velocity from the time difference, and calculates the flow rate of the fluid from the sampling period, the effective area of the flow path, and the like. Generally, ultrasonic flow measurement has a wide measurement range and high measurement accuracy, but is said to consume slightly higher power. Therefore, as in the first embodiment, the pressure sensor and the like that consume less power are frequently operated, the state of the fluid is frequently monitored, and the ultrasonic flow rate measuring unit that consumes more power and is operated at the optimum number of times is operated. By doing so, it is possible to achieve measurement accuracy and security performance over a wide measurement range while realizing low power consumption.

(Embodiment 4) FIG. 5 shows a time change of a measurement start signal in Embodiment 4 of the present invention. The flow rate measurement start signal of the first embodiment is different from 20 in FIG. 2 in that it is synchronized with the change 17 in the pressure characteristic value from the pressure sensor as indicated by 26 in FIG. Then, the measurement start signal is set to be output sparsely with time. With this configuration, immediately after the change, the flow rate measurement is repeated more closely, and the flow rate measurement is repeated sparsely with time, so that a more accurate flow rate measurement can be realized with lower power consumption. In the above description, the measurement time interval is changed with time. However, for example, the measurement time interval may be linked with the change width of the characteristic value 17 of the pressure sensor. Also, the change width of the flow rate value 18 may be linked. In this case, the frequency of the flow rate measurement is high when the change is large, and is low when the change is small, which is very rational. Therefore,
High power flow measurement with low power consumption.

(Embodiment 5) FIG. 6 shows a flow rate measuring device 27 according to Embodiment 5 of the present invention. The difference from the second embodiment lies in that, instead of the cock 22 such as a gas appliance, a valve 28 such as a shutoff valve is provided, and a determination means 29 for determining security on the downstream side is provided. Note that the valve 28 may be located on either the upstream side or the downstream side of the flow rate measuring unit. In this configuration, for example, if a valve 28 such as a shut-off valve provided on the downstream side of the flow measuring unit operates for some reason and shuts off, gas is supplied to the flow measuring unit. Is a state in which the gas pressure is applied. In this case, the valve 28 cannot be opened unless the downstream pipe end of the valve 28 is in a closed state. If the valve 28 is opened with the piping end open, the gas will be released freely from the piping end, resulting in a very dangerous condition. Therefore, it is very important to determine the state of the piping terminal. In this case, according to the present invention, at the same time when the valve 28 is opened, the output value of the pressure sensor 15 and the output value of the
Give to. The determination means 29 makes the following determination.

For example, (1) when the pressure change or pressure drop is small, the pressure value is larger than a preset value, and the flowing flow value is relatively large, the gas having a large gas consumption is supplied to the pipe terminal. It can be determined that a device, for example, a device such as a large gas water heater, is connected and gas is being released through the device. Therefore, in this case, for example, it is possible to notify that the cock of the large device is closed. (2) The pressure change or pressure drop is large, the pressure value is smaller than a preset value, and
If the value of the flowing flow rate is relatively large, the pipe terminal may be in an open state, for example, broken. In this case,
If a large flow of gas reports a danger of release, or valve 2
8 can be closed quickly. (3) When the pressure change or pressure drop is small, the pressure value is larger than a preset value, and the flowing flow rate value is relatively small, a gas device with a small gas consumption at a pipe terminal, for example, A device such as a small gas water heater is connected, and it can be determined that a very small amount of gas, for example, a gas used for pilot fire is released through the device.

Therefore, in this case, it is possible to notify that a small amount of gas is released or to notify that gas is leaking. (4) When the pressure change or the pressure drop is small, the pressure value is larger than a preset value, and the flowing flow value is zero, it can be determined that the pipe terminal is in the closed state. . Therefore, in this case, it can be determined that safety on the downstream side has been ensured even if the valve 28 is opened. FIG. 7 shows the cases (1), (2), (3) and (4) described above. That is, in the figure, the horizontal axis shows the gas flow rate, and the vertical axis shows the gas pressure. Symbols in the figure, (1),
(2), (3) and (4) show the areas in the case described above, respectively. The broken lines in the figure indicate the boundaries between the respective regions. As described above, by monitoring the flow rate and the pressure, the safety of the piping terminal can be confirmed.

[0027]

As is clear from the above description, the following effects can be obtained according to the flow rate measuring device of the present invention.

(1) Since driving conditions can be set in accordance with the output of the detecting means, for example, 5
The measurement is performed at a constant interval of about seconds, but when a pressure change or the like occurs, the measurement can be performed in synchronization with the change, for example, at a measurement interval of 1 second or less. Therefore, power consumption can be reduced without deteriorating measurement accuracy.

(2) Since the measurement conditions can be set according to the operation such as the opening and closing operation of the valve, the flow rate immediately after use, for example, in a large water heater, can be accurately measured, and the specification of the appliance is easy. Becomes In addition, since the measurement can be started at the same time when the cock is opened, such as at the time of gas filling, the filling amount and the like can be accurately measured.

(3) Since the flow rate is measured by the hot wire type flow meter, the flow rate can be measured in a short time with low power consumption in synchronization with an external signal.

(4) Since the flow rate is measured by an ultrasonic flow meter, a wide range of flow rate can be measured in a short time with low power consumption in synchronization with an external signal.

(5) Immediately after the fluid state change, the sampling cycle is shortened, and the sampling cycle is lengthened with time, so that the flow rate change in the transient state can be accurately measured with low power consumption.

(6) The state of the downstream flow path can be determined from the output of the pressure sensor and the like and the flow rate measurement result, so that the safety of the downstream flow path can be ensured.

(7) If the pressure value is large and the flow rate is large, it can be determined that the gas is in use via the device, so that it can be notified that the gas is being used by the device or the valve of the device is open. The performance is improved.

(8) If the pressure value is small and the flow rate is large, it is possible to determine that gas is being discharged without any load on the terminal, so that it is possible to determine that the gas pipe on the downstream side is broken and close the valve. In addition, safety can be improved.

(9) When the pressure value is large and the flow rate is small, it is possible to determine that a very small amount of gas is being used or leaked through the device. The safety can be improved.

(10) When the pressure value is large and the flow rate is zero, it is possible to determine that the downstream side is in a completely closed state, and it is possible to secure and confirm the safety of the downstream side.

[Brief description of the drawings]

FIG. 1 is a block diagram of a flow rate measuring device according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a pressure change and a flow rate change in the same device.

FIG. 3 is a block diagram of a flow rate measuring device according to a second embodiment of the present invention.

FIG. 4 is a block diagram of a flow rate measuring device according to a third embodiment of the present invention.

FIG. 5 is a characteristic diagram showing a pressure change and a flow rate change in Embodiment 4 of the present invention.

FIG. 6 is a block diagram of a flow rate measuring device according to a fifth embodiment of the present invention.

FIG. 7 is a characteristic diagram illustrating the relationship between gas pressure and gas flow rate in the apparatus.

FIG. 8 is a diagram showing a conventional flow measurement device.

[Explanation of symbols]

 Reference Signs List 10 Flow rate measuring means 15 Change detecting means 16 Condition setting means 17 Pressure change 18 Flow rate change 22 Cock 24,25 Ultrasonic transceiver 26 Switching means 28 Valve 29 Discriminating means

Claims (10)

[Claims] 1. A flow rate measuring means for measuring a fluid flow rate, a change detecting means such as a pressure sensor or a gas sensor for detecting a change in a fluid state, and a drive for driving the flow rate measuring means in accordance with an output of the change detecting means. A flow rate measuring device comprising condition setting means for setting conditions. 2. A flow rate measuring means for measuring a fluid flow rate, a change generating means for changing a fluid state such as a valve opening / closing operation, and a driving condition for driving the flow rate measuring means in accordance with an operation of the change generating means. A flow rate measuring device comprising condition setting means for setting. 3. The flow rate measuring device according to claim 1, wherein the flow rate measuring means is a hot wire type flow rate measuring means comprising a heating element and a temperature sensor for detecting a temperature change caused by the heating element. 4. The flow rate measuring means is provided with a pair of ultrasonic transceivers for transmitting and receiving ultrasonic waves at an upstream side and a downstream side of a flow path through which a fluid flows, and a pair of ultrasonic transmitters and receivers from upstream to downstream and from downstream to upstream. The flow rate measuring device according to claim 1, wherein the flow rate measuring device is an ultrasonic flow rate measuring unit that measures an ultrasonic propagation time, calculates a flow velocity of the fluid from the time difference, and measures a flow rate. 5. The flow rate measuring device according to claim 1, wherein a driving condition for shortening the sampling cycle immediately after the change of the fluid state and increasing the sampling cycle with time is set. 6. The flow rate measurement device according to claim 1, further comprising a determination means for determining a flow path state on the downstream side based on an output of the fluid state change detection means such as a pressure sensor and a flow rate measurement result of the flow rate measurement means. apparatus. 7. The flow rate measuring apparatus according to claim 6, wherein when the pressure value is large and the flow rate is large, it is determined that the gas is in use via the device. 8. The flow rate measuring device according to claim 6, wherein when the pressure value is small and the flow rate is large, it is determined that gas is being released without a load on the terminal. 9. The flow rate measuring apparatus according to claim 6, wherein when the pressure value is large and the flow rate is small, it is determined that a very small amount of gas is being used or leaked via the device. 10. When the pressure value is large and the flow rate is zero,
7. The flow measuring device according to claim 6, wherein the downstream side is determined to be in a completely closed state.