JP3093500B2 - Flowmeter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow meter for measuring a flow rate of a fluid such as city gas or LPG gas, and more particularly to a flow meter combining a fluidic element and a hot wire type flow sensor.

[0002]

2. Description of the Related Art Conventionally, this type of flow meter is disclosed in
As disclosed in Japanese Patent Application Laid-Open No. 08921, a fluid sensor for detecting a flow velocity is provided in a fluidic element, and in a small flow rate range, measurement is performed using the output from the flow sensor.
In a large flow rate range, a method of measuring the oscillation frequency of a fluidic element has been proposed, and has a configuration as shown in FIG. 5, for example.

That is, in the conventional flow meter of FIG. 5, 1 is a flow meter main body, 2 is a gas pipe, 3 is a fluidic element,
The flow rate oscillation is generated by using the kinetic energy of the fluid. A piezoelectric sensor 4 detects the frequency of fluid oscillation. Reference numeral 5 denotes a flow sensor that detects a flow velocity of a fluid at a nozzle (not shown) of the fluidic element and generates an analog signal proportional to the flow velocity. Reference numeral 6 denotes a shutoff valve which shuts off gas supply when an abnormal use state is detected. Reference numeral 7 denotes a control device which determines a flow rate from the frequency when the frequency detected by the piezoelectric sensor 4 is equal to or higher than a predetermined value (this value is referred to as F0). From the output of That is, the control device 7 controls the fluid sensor 3 to measure the flow rate with the flow sensor 5 in the small flow rate zone and the fluid sensor 3 in the large flow rate zone because the oscillation is difficult and unstable in the small flow rate zone. Judgment is being performed. The frequency F0 is a value for determining the stability of oscillation.

Since the flow sensor 5 is of a hot wire type, power consumption is relatively large. Therefore, every fixed time (for example, 5
(Every 6 seconds), power is supplied for a short time (several tens of msec), and the flow rate is obtained by intermittent driving.

[0005]

However, in the above-described conventional configuration, the small flow rate region is measured by the flow sensor, but since the flow sensor is driven intermittently,
Even if the flow rate fluctuation occurs during the measurement timing, the fluctuation cannot be captured. Therefore, there is a problem that a measurement error of the flow rate occurs.

[0006] Therefore, the flow meter of the present invention aims to improve the measurement accuracy by capturing the flow rate fluctuation when a large flow rate occurs.

[0007]

In order to solve the above problems, a flow meter according to the present invention is provided with a vibration detecting means for detecting a fluid vibration generated by a fluidic element, and a flow meter intermittently driven at regular intervals. A flow velocity detecting means for detecting a flow velocity of a fluid passing through the fluidic element, and a flow rate is obtained from an output of the vibration detecting means if the output of the vibration detecting means is equal to or more than a predetermined value. In a flowmeter for obtaining a flow rate from the output of the flow velocity detecting means, the power supply has a power supply for driving the flow velocity detecting means, and a power supply controlling means for controlling power supply from the power supply, and the power supply controlling means is provided for each set time. Timer means for activating the power supply, determination means for determining the presence or absence of a flow signal output by the vibration detection means since the previous measurement by the flow velocity detection means, and determination results of the determination means If switching to the available amount signal is obtained and a starting means for starting the power supply.

Further, vibration detecting means for detecting a fluid vibration generated in the fluidic element, and flow velocity detecting means for detecting a flow velocity of the fluid passing through the fluidic element by being intermittently driven at regular time intervals. If the output of the vibration detecting means is equal to or greater than a predetermined value, the flow rate is determined from the output of the vibration detecting means and the flow rate is determined from the output of the flow velocity detecting means if the output is equal to or less than the predetermined value. A power supply for driving; and a power supply control unit for controlling power supply from the power supply. The power supply control unit includes a timer unit for activating the power supply at every set time, and a measurement by the previous flow velocity detection unit. Thereafter, a determination unit that determines the presence or absence of a flow signal output by the vibration detection unit, and the power supply is started when the determination result of the determination unit switches to the presence of a flow signal. Moving means, and if the result of the determination by the determining means is a flow signal, the set time of the timer means is set to a first set value; if there is no flow signal, the set value of the timer means is set to a first set value. Switching means for switching to a shorter second set value.

[0009]

According to the first configuration, the flow meter according to the present invention has the determination means detecting that the amount of gas used has increased and the fluid vibration of the fluidic element has started, and the flow rate detection means is activated by the activation means. Electric power is supplied to determine the flow rate at this point. Therefore, even when the flow rate is measured by the intermittently driven flow rate detecting means, the rise of the flow rate when a large flow rate is generated can be detected, and the measurement accuracy can be improved.

According to the second configuration, when the determination means detects the fluid vibration, the switching time shortens the driving time interval of the flow velocity detection means, so that the change after the rise of the flow rate can be grasped in detail. As a result, measurement accuracy can be improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

In FIG. 1, the same components and elements as those of FIG. 5 are denoted by the same reference numerals. FIG. 1 is a block diagram of a flow meter according to the present invention. In FIG. 1, reference numeral 3 denotes a fluidic element, which is provided in the middle of the gas pipe 2 and uses the kinetic energy of the fluid to generate fluid oscillation. Numeral 8 denotes a vibration detecting means, which comprises a piezoelectric sensor 4 for detecting the oscillation frequency of the fluid as a change in output voltage, and a pulse signal converter 9 for converting the oscillation frequency into a pulse signal having a frequency equivalent to the voltage fluctuation. 1
Numeral 0 denotes a flow rate detecting means, which comprises a flow sensor 5 for generating a voltage proportional to the flow rate, and an A / D converter 11 for generating a pulse number proportional to the output of the flow sensor 5 at regular intervals. Reference numeral 12 denotes a measurement switching unit which determines which of the output of the vibration detection unit 8 and the output of the flow velocity detection unit 10 the flow rate is to be obtained and outputs. Reference numeral 19 denotes a flow rate calculating means, which determines a flow rate according to the switching result of the measurement switching means 12. Reference numeral 20 denotes a flow rate integrating means, which calculates the integrated value of the flow rate by adding the flow rates obtained by the flow rate calculating means. Reference numeral 21 denotes display means for displaying the integrated value obtained by the flow rate integrating means 20. 13
Supplies driving power for the flow velocity detecting means 10 with a power supply. 14
Is a power supply control means for controlling power supply from the power supply 13 to the flow velocity detection means 10.

The configuration of the power control means 14 is as follows. Reference numeral 15 denotes a timer means, and the power supply 13
It operates so that electric power is supplied from. Reference numeral 16 denotes a determination unit which determines the presence or absence of a flow signal from the vibration detection unit 8 at the time of measurement by the flow velocity detection unit 10. Reference numeral 17 denotes an activation unit, which instructs the power supply 13 to supply power to the timer unit 15 at the time when the determination result of the determination unit 16 is switched from no flow signal to presence.

Next, the operation of the above configuration will be described. When the gas starts to be used, the gas in the gas pipe 2 is supplied through the fluidic element 3. At this time, fluid oscillation occurs in the fluidic element 3 due to the Coanda effect, and the fluid oscillation frequency is correlated with the flow rate. The vibration detecting means 8 detects the oscillation frequency via various physical quantities. For example, a pressure change caused by fluid oscillation is detected as a voltage change by a piezoelectric element. Alternatively, as another method, a thermal change caused by fluid oscillation is detected as a resistance change using a thermistor or the like. In this embodiment, the pulse signal converter 9
Generates a pulse signal having a frequency equivalent to the frequency of the voltage change of the piezoelectric sensor 4, and sets the signal frequency f as the fluid oscillation frequency.

The flow velocity detecting means 10 detects the velocity of the fluid flowing through the fluid oscillation element 3. Flow sensor 5
Generates a voltage corresponding to the flow velocity, causes the A / D converter 11 to generate a pulse number proportional to the output voltage of the flow sensor 5 within a predetermined time, and detects the flow velocity from the pulse number p.

The measurement switching means 12 makes a determination for obtaining the flow rate based on the oscillation frequency in the small flow rate range and the oscillation frequency in the middle to large flow rate range. That is, if the output f of the vibration detecting means 8 is equal to or more than a predetermined value, it is determined that the flow rate is to be obtained based on f, and f is output. Conversely, if f is equal to or less than a predetermined value, it is determined that the flow rate is to be obtained based on p, and p is output. Measurement switching means 12
In the case where it is instructed to measure the flow rate based on the flow velocity detecting means 10, that is, in a small flow rate area where the gas usage is small, the normal timer means 15 normally sets a predetermined time T1 (for example, 5 seconds). The power supply 13 supplies power to the power supply and drives the flow velocity detecting means 10 to detect the flow rate.

Here, it is assumed that the flow rate rises and a flow rate signal is generated from the vibration detecting means 8. If the gas usage is smaller than the amount corresponding to the measurement switching, the oscillation is unstable, and the measurement is subsequently performed by the flow velocity detecting means 10. At this time, since the flow velocity detecting means 10 is intermittently driven, the rise in the flow rate is reflected in the integrated value or the like by a maximum of the time T1 set in the timer means 15. Therefore, this change in the flow rate is detected by the power supply control means 14. That is, when the flow rate signal is input from the vibration detection means 8, the determination means 16 outputs a determination signal to the activation means 17. The activating means 17 activates the power supply 13 even if the set time T1 set in the timer means 15 has not elapsed,
As a result, electric power is supplied to the flow velocity detecting means 10, and the flow velocity at this time is detected to obtain a flow value.

FIG. 3 is a timing chart of the above operation, showing the flow rate signal output from the vibration detecting means 8 and the measurement timing of the flow rate detecting means 10. The flow signal is an L output when the fluidic element 3 stops oscillating. When the flow rate increases and the oscillation starts, a pulse corresponding to the oscillation is generated. When the use of the gas is stopped or the amount of gas used is small, no flow signal is generated, so that the determination result of the determination means 16 is no flow signal, and the flow rate is detected every time T1 set in the timer means 15. The measurement is performed by the output of the means 10. It is assumed that the usage amount of the gas increases and a flow rate signal is generated from the vibration detecting means 8 at time t1. The determination means 16 detects the rise of the flow signal and changes the determination result from the absence of the flow signal to the presence of the flow signal. At this time, the flow rate detecting means 10 is driven by the action of the activation means 17 to detect the flow rate, that is, the flow rate. The timer means 15 is restarted at this time, and thereafter, the measurement by the flow velocity detecting means 10 is repeated every T1.

With the above arrangement, in the flow meter of the present invention, the judging means 16 detects the rising of a large flow rate at which the fluidic element starts oscillating, and the flow rate at this time is detected by the action of the activating means 17. As a result, it is possible to catch the fluctuation that occurs during the intermittent driving, which has the effect of improving the measurement accuracy.

Embodiment 2 Next, a second embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG.

FIG. 3 is a block diagram of the power supply control means 14. 3, the same components and elements as those in FIGS. 1 and 5 are denoted by the same reference numerals, and detailed description thereof will be omitted. Reference numeral 18 denotes a switching unit that sets the set time set in the timer unit 15 to a first set time T1 if the result of the determination by the determination unit 16 is no flow signal, and sets the first set time T1 if the result of the determination is a flow signal. Then, the set time of the timer 15 is switched to the second set time T2 shorter than the first set time T1.

Next, the operation of the above configuration will be described. If the flow rate signal from the vibration detecting means 8 has not been generated, the set time of the timer means 15 is T1. When the gas usage increases and a flow signal is generated, the determination result of the determination means switches to the presence of the flow signal. At this time, the flow rate detecting means 10 is driven by the action of the activating means 17 to measure the flow rate, and the set time of the timer means 15 is set to T2 which is shorter than T1, and thereafter the measurement is performed every T2. Therefore, the flow rate at the time when the flow rate fluctuation is detected is measured, and at the same time, the measurement time interval is shortened to measure the fine flow rate fluctuation.

FIG. 4 is a timing chart of the above operation, showing the flow rate signal output from the vibration detecting means 8 and the measurement timing of the flow rate detecting means 10. 4 is a timing chart of the present embodiment. Since the flow rate signal from the vibration detecting means 8 is not generated from the time t2 to the time t3, the determination result of the determining means 16 is no flow rate signal,
Therefore, the measurement is performed by the output of the flow velocity detecting means 10 at every time T1 set in the timer means 15. Time t
3, it is assumed that the flow rate signal is generated from the vibration detecting means 8. Similarly to FIG. 2, the set time of the timer means 15 is reduced to T2 at the same time when the flow rate at this point is detected. Thereafter, if the flow rate signal is continuously output from the vibration detecting means 8, the measurement by the flow velocity detecting means 10 is repeated every T2. Thereafter, when the flow rate signal is no longer output from the vibration detecting means 8 during the time T2 from the time t4 to the time t5, the measurement time interval is extended to T1.

With the above configuration, the flow meter according to the present invention detects the rising of the large flow rate, and then, by the operation of the switching means 18, shortens the measurement time interval of the flow velocity detecting means 10. Since the fluctuation of the flow rate can be finely grasped, there is an effect that the measurement accuracy is improved.

[0025]

As described above, the flow meter according to the present invention has the following effects.

(1) The rising of the large flow rate is detected by the determination means, and the flow rate at this time is detected. Therefore, the fluctuation occurring between the intermittent driving can be detected.
Measurement accuracy can be improved.

(2) Further, after the rising of the large flow rate is detected, the interval of the measurement time of the flow velocity detecting means is shortened by the operation of the switching means. Therefore, measurement accuracy can be improved.

[Brief description of the drawings]

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

FIG. 2 is a timing chart showing the flow meter.

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

FIG. 4 is a timing chart showing the operation of the flow meter.

FIG. 5 is a block diagram illustrating a conventional flow meter.

[Explanation of symbols]

 8 Vibration detection means 10 Flow velocity detection means 13 Power supply 14 Power supply control means 15 Timer means 16 Judgment means 17 Starting means 18 Switching means

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Koichi Takemura 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Koichi Ueki 1006 Kadoma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (56) References JP-A-1-308921 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01F 1/20

Claims (2)

(57) [Claims] An output detecting means for detecting a fluid vibration generated by the fluidic element; a flow rate detecting means for detecting a flow rate of a fluid passing through the fluidic element; In the case of, the flow rate is obtained from the output of the vibration detecting means, and when the flow rate is equal to or less than a predetermined value, the flow rate is obtained from the output of the flow velocity detecting means,
A power supply for driving the flow rate detection means, and a power supply control means for controlling power supply from the power supply, wherein the power supply control means is a timer means for activating the power supply every set time; and Determining means for determining the presence or absence of a flow signal output by the vibration detecting means after measurement by the detecting means, and starting means for starting the power supply when the determination result of the determining means is switched to the presence of a flow signal. A flow meter having 2. A vibration detecting means for detecting a fluid vibration generated by a fluidic element, a flow velocity detecting means for detecting a flow velocity of a fluid passing through the fluidic element, and an output of the vibration detecting means being equal to or more than a predetermined value. In the case of, the flow rate is obtained from the output of the vibration detecting means, and when the flow rate is equal to or less than a predetermined value, the flow rate is obtained from the output of the flow velocity detecting means,
A power supply for driving the flow rate detection means, and a power supply control means for controlling power supply from the power supply, wherein the power supply control means is a timer means for activating the power supply every set time; and Determining means for determining the presence or absence of a flow signal output by the signal detecting means after measurement by the detecting means; and starting means for starting the power supply when the determination result of the determining means is switched to the presence of a flow signal. If the determination result of the determination means is that there is a flow signal, the set time of the timer means is set to a first set value; if there is no flow signal, the set value of the timer means is changed from the first set value. A switching means for switching to a short second set value.