JPH01308921A - Gas flowmeter - Google Patents

Abstract

PURPOSE:To widen a measurable flow rate range and to enhance reliability by providing a fluidic oscillation element, a sensor and a flow sensor. CONSTITUTION:It is judged whether the frequency of the electric signal of a sensor 10 for detecting the fluidic vibration of a fluidic oscillation element 7 is equal to, more than or less than a definite value and, when said frequency is the definite value or less, drive power is supplied to a flow sensor 12 intermittently. At the time of a large flow rate of the definite value or more, a flow rate is calculated on the basis of the signal of the element 7 and, at the time of a flow rate of the definite value or less, the flow rate is calculated on the basis of the signal of the sensor 12 and the power consumption of the sensor 12 is reduced. As a sensor for detecting fluidic vibration, the sensor 10 having a pair of pressure introducing ports 14, 14 is used, and the introducing ports 15, 15' and a pair of pressure introducing ports 14, 14' provided to the element 7 are allowed to communicate with each other by a pair of the pressure introducing ports 9, 9.. provided to the airtight member constituting the element 7. By this method, fluidic vibration is effectively detected and a degree of freedom can be provided to the mount position of the sensor.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to improvements in gas flow meters.

[Prior art and its problems]

A small and easy-to-install gas flowmeter that can replace a conventional model gas meter, that is, a fluidic flowmeter using a fluidic oscillator (e.g., JP-A-57-663)
13) has the advantage of being small and has excellent durability because it has no moving parts, but the measurable flow rate range is about 50 times that of the model gas meter No. 3 meter. It is not possible to measure a flow rate range of 3 to 30001/h, that is, a flow rate range that is 1000 times larger.

Therefore, we used a fluidic oscillator element that measures medium to large flow rates and another fluidic element that measures small flow rates, and used a switching valve to switch both fluidic elements according to the size of the flow rate. A so-called parent-child type flowmeter for use is proposed in Japanese Patent Laid-Open No. 61-223517.

However, even if two fluidic oscillation elements are provided, 10
It is difficult to measure a flow rate range of 00 times, and when a switching valve is used, the moving part of the switching valve itself may cause valve leakage.
When trying to measure a minute flow rate of about 1/h, durability was a problem.

Furthermore, since the operating force of the switching valve is determined by the area of the pressure-receiving diaphragm, the shape of the diaphragm must be enlarged in order to operate at minute pressure ti such as in a gas meter, making it difficult to downsize and mechanically There was a problem that the structure became complicated.

In view of these problems, this invention has been developed as a No. 3 gas meter. A wide measurement range that allows measurement of flow rates from /h to 30001/h, and a maximum pressure drop of 13nllz, which is such that a gas meter is required to have zero pressure loss.
The purpose is to propose a gas flowmeter that can realize O.

In order to achieve this objective, the present invention uses a flow sensor based on the same principle as that used in so-called thermal flowmeters to measure a minute flow rate range, and uses a flow sensor to measure a larger flow rate range. It is a parent-child flowmeter that uses a Dick oscillation element and is switched by an electronic circuit.

[Means to solve the problem]

In order to achieve the above object, the gas flowmeter of the present invention includes a fluidic oscillation element 7, a sensor 10 that detects the fluid vibration of the fluidic oscillation element and converts it into an electrical signal, and a Element nozzle part 2
Flow sensor 12 that detects the flow velocity and converts it into an electrical signal
and an electronic circuit 11 for calculating the integrated flow rate by calculating the signals of the fluid vibration detection sensor 10 and the flow sensor 12 for flow velocity detection, and a display 13 for displaying the integrated flow rate obtained by the electronic circuit. It is.

It determines whether the frequency of the electric signal of the sensor that detects the fluid imaging of the fluidic oscillation element is above or below a certain value, and when the frequency is below a certain value, driving power is intermittently supplied to the flow sensor, and when the frequency is above or below a certain value. It is effective to determine the flow rate using the signal from the fluidic oscillation element when the flow rate is large, and from the signal from the flow sensor when the flow rate is below a certain value, because it reduces the power consumed by the flow sensor.

In addition, a polymer piezoelectric film sensor having a pair of pressure inlets is used as a sensor for detecting fluid vibration, and this pressure inlet and a pair of pressure inlets provided in a fluidic oscillation element constitute a fluidic oscillation element. Communication through a pair of pressure introduction passages provided in the airtight member is effective in effectively detecting fluid vibrations and providing flexibility in the mounting position of the sensor.

Furthermore, arranging the flow sensor above the nozzle of the fluidic oscillation element is effective in eliminating the adverse effects of drain and the like. Moreover, providing a step portion that reduces the flow path immediately upstream of the flow sensor is effective in preventing dust from directly hitting the flow sensor.

〔Example〕

The fluid vibration phenomenon of a fluidic flowmeter using a fluidic oscillation element will be explained with reference to FIG.

Gas flowing in from the inlet 1 of the channel and ejected from the nozzle 2 flows along the side wall 3 or 3' due to the Coanda effect. When this flow reaches the feedback channel population 4 or 4'', pressure is transmitted to the nozzle section 2 and the flow is switched. This switching occurs alternately, resulting in fluid vibrations with a frequency proportional to the flow rate. 5 is the jet nozzle. A columnar object (target) is located at the center downstream of 1, and 6 is an exit.

Reference numeral 7 indicates the entire fluidic oscillation element.

In the embodiment of FIG. 1, the side 2 of the fluidic oscillation element 7 is
3. Although a' is cylindrical in shape and has a different shape from that shown in the principle diagram of FIG. 2, and the shape of other parts of the element is also somewhat different, the operating principle as an oscillation element is the same. Gas enters from the inlet of the fluidic oscillation element as indicated by arrow A, and is ejected downstream from the nozzle 2, generating fluid vibrations as explained in FIG.

8 is the case body that forms the fluidic oscillation element;
By devising the shape of this element, the density can be increased to +r/r+? 0.8, which is acceptable for a No. 3 gas meter. Maximum pressure t with gas
Under the limitation of ffi13+ntlzO, we were able to expand the oscillation range to 55-30001/h. This fluid vibration is guided to the sensor 10 by the pressure introduction paths 9, 9', converted into an electrical signal, and transmitted to the electronic circuit 11.

12 is a flow sensor placed in the nozzle 2, which detects the flow velocity that has become faster due to constriction at the nozzle portion, and converts it into an analog electrical signal proportional to the flow velocity. This electrical signal is processed by the electronic circuit 11 together with the electrical signal from the sensor 10, and is displayed on the display 13 as an integrated flow rate value.

Note that FIG. 1 shows the fluidic oscillation element with the lid removed for easy understanding.

The sensor lO for detecting fluid vibrations communicates one end of each of the pressure introduction passages 9, 9'' with a pair of pressure introduction ports 14, 14' opening to the feedback passages 4 and 4''. By communicating the other ends of the two pressure inlets to a pair of pressure inlets of the sensor 10, pulsating pressure caused by fluid vibration is differentially applied to both sides of the polymer piezoelectric film 16 of the sensor 10.

As shown in FIG. 3, the sensor 10 has a structure using a polymer piezoelectric film, and the pressure inlets 15 and 15' are connected as shown in FIG. It is also possible to detect the differential pressure between them.

As shown in an enlarged view in FIG. 4, the flow sensor 12 has a temperature sensor 12a and a heater 12b on the surface facing the gas flow.
and a temperature sensor 12c are arranged in this order, and are heated by passing a current through the heater 12b. When there is no flow, the temperature distribution is symmetrical around the heater (that is, symmetrical in both the upstream and downstream directions of the flow), but when there is flow, the temperature sensor 12c on the downstream side is hotter than the temperature sensor 12a on the upstream side. An analog electrical signal corresponding to the flow rate (flow velocity at the nozzle portion) is generated from changes in the electrical resistance of both temperature sensors 12a and 12b.

In the block diagram of FIG. 5, reference numeral 17 is an analog-to-digital conversion circuit, which has a function of converting an analog electrical signal in a small flow rate range detected by the flow sensor 12 into an electrical pulse signal with a frequency proportional to the flow rate. 18 is a counter for temporarily stocking high-speed electric pulses (signal B) output from the analog-to-digital conversion circuit 17 for inputting them to the microcomputer 19; 20 is a power supply;
1 is a power supply control circuit that controls the driving voltage supplied to the piezoelectric film circuit section 22 and the flow sensor circuit section 23; 24 is an analog amplifier that amplifies the electrical signal of the sensor 10; and 25 is a rectangular waveform that converts the output signal of the analog amplifier 24. The waveform shaping circuit 26 is a signal judgment circuit which receives the signal A which is the output of the waveform shaping circuit as an input and determines whether the frequency is above a certain value, and when the frequency is above the certain value, the signal A
as a signal J of the same frequency as the microcomputer 19
to be transmitted. A clock control circuit 27 sends a clock signal H for A/D conversion to the analog-to-digital conversion circuit 17 in response to instructions from the microcomputer 19.

Next, the operation of the electronic circuit shown in FIG. 5 will be explained using FIGS. 6 to 8.

The signals A-H in FIG. 6 correspond to the signals A-H in FIG. 5, respectively.

The diagram at the top of FIG. 6 is a diagram with the horizontal axis as the time axis and the vertical axis as the flow rate. In the diagram, signal B shown by a solid line shows how the signal of the flow sensor 12 changes depending on the flow rate. shows. Also, 2
A signal A indicated by a dashed dotted line indicates that the signal from the piezoelectric film sensor 10 changes depending on the flow rate. In the figure, A indicates the point where the signal B of the flow sensor 12 is switched to the signal A of the sensor 10 when the flow rate increases, and the opening indicates the signal A of the sensor 10 when the flow rate M decreases.
The point at which the signal is switched from to the signal B of the flow sensor 12 is shown.
While the flow rate is from zero to point A, power is intermittently supplied to the flow sensor circuit section 23 as shown in Figures 6 to 6. Since the current consumed by the flow sensor 12 is relatively large with a maximum value of 5 mA, the average current is reduced by supplying power for a short time T1 of 40 m5 every 5 seconds TO. This situation is shown in Figure 6. The flow sensor 12, which is disposed in the nozzle part 2 and generates an analog signal proportional to the gas flow rate, receives a signal of 32 KIIz, which is supplied from the clock control circuit 27 only during the 1ffi period of T1 in synchronization with the power supply signal. In synchronization with the clock signal H, a flow rate signal B having a pulse number proportional to the flow rate is output. This signal B has an interval (period) T.

The number of pulses each time is the flow rate 0ffi/h.
O pulse, flow rate 150 i! The characteristics of the analog-to-digital converter circuit 17 are determined so that the number of pulses per hour is 200. 30 pulses at flow rate O1/h, 1501/h
It is also possible to detect the backflow caused by the pressure difference in the piping by shifting the zero point like 230 pulses. The piezoelectric film sensor that detects fluid vibrations of the fluidic oscillation element has the ability to detect fluid vibrations in a flow rate slightly downstream of the point A, and in the flow rate region between the point A and A, the sensor 10 detects the flow. Power is supplied to both sensors 12, and both sensors detect the flow rate to prevent measurement errors due to minute changes in the flow rate near the switching flow rate. In a flow rate range lower than point A, the flow sensor 12 is energized,
Since the piezoelectric film sensor 10 is energized in a flow rate range larger than the point A, both sensors are energized in a flow rate range between the point A and the mouth. When the flow rate decreases from a region larger than point A to zero, energization to the flow sensor 12 is started at the flow rate at point A, and energization to the piezoelectric film sensor 10 is turned off at the flow rate at the mouth.

An example of the signal determination circuit 26 in FIG. 5 is shown in FIG.
8 is a 1/N counter, 29 is a monostable multi-bi break, 30 and 31 are D flip-flops, and 32 is an AND gate connected as shown.

Next, the operation of the circuit shown in FIG. 7 will be explained with reference to FIG.

The 1/N counter 28 converts the signal A into 1/N and outputs it to the port f. The output of Ql is two D flip-flops 30
According to 31, when a number of signals A larger than a predetermined value N (for example, 8) is input during the measurement time To (5 seconds), the output Q1 becomes H level. If there is no N pulse signal input during time To, mouth 1 remains at L level.
It is. 01 when the number of pulses of signal A is greater than N
becomes H level, the D flip-flop 30 holds this H level signal, and this H level output Q2 of the D flip-flop is then transferred to the second stage D flip-flop 31 at the rising edge of the signal G, and the D flip-flop 30 holds this H level signal. Set the output to H level,
AND gate 32 is opened. Therefore, signal A passes through AND gate 32 and is output as signal J. In this way, when a signal A with a frequency of 8 pulses or more is input during the 5 second time To, the signal determination circuit outputs the signal A as the signal J. This signal J is calculated by the microcomputer 19 and becomes the flow rate integrated value.

Further, if the number of signals A during the time To is less than N pulses, the signal B based on the flow sensor 12 is stored in the counter 18 and then calculated by the microcomputer 19 to become the flow rate integrated value. In other words, in the microflow N 112, the signal B based on the flow sensor 12 is calculated, and in the flow rate region above a certain value, the signal A detected by the sensor 10 is the frequency of the fluidic oscillation element, and the microcomputer 19 calculates the total flow rate integrated value. Desired.

In addition, in Fig. 7, if the signal A is a temporary one such as a disturbance,
If N pulses are not exceeded during the time To, the signal J will not be output, so there is no risk of erroneously counting such disturbances. That is, the disturbance can be distinguished from the original signal A.

Note that the signal discrimination circuit shown in FIG. 7 can also be performed by software within a microcomputer. An example of a flowchart in this case is shown in FIG. In FIG. 9, n is a pulse number counter, and 8 of the judgment step where n=8.
has the same meaning as N (for example, 8) in FIG.

FIG. 10 shows switching between measurement using the frequency of the fluidic oscillation element and measurement using the flow sensor 12. Switching from the flow sensor to the fluidic oscillation element is performed when the frequency of the fluidic oscillation element, that is, the period of signal A, is 220 m5 or less (that is, the flow rate is 1421 m5 or less).
h or more), and when eight consecutive pulses are detected, the device switches to the fluidic oscillation element. Switching from the fluidic oscillation element to the flow sensor 12 is performed when the frequency of the fluidic oscillation element, that is, the period of the signal is 2.
If the flow rate is 40 m5 or more (that is, the flow rate is 1351/h or more), the flow sensor 12 is used.

FIGS. 11 and 12 show another embodiment of a gas meter using the present invention. In the figure, ■ is the inlet of the flow path, 2 is the nozzle, 3, 3゛ is the side wall, 5 is the target, 4,
4'' is the inlet of the feedback flow path, 7 is the fluidic oscillation element, 8 is the case body, 33 is the cutoff valve disposed downstream of the fluidic oscillation element, and 34 is the valve that opens after the cutoff valve closes ( 35 is a lithium battery,
36 is a seismic sensor, 37 is a pressure sensor, 38 is a light emitting diode, 39 is a printed circuit board for a safety function circuit, 41 is a printed circuit board for a circuit that processes the electrical signal of the flow sensor 12,
Reference numeral 40 denotes a printed circuit board for a circuit that processes electrical signals from a sensor 10 that detects fluid vibrations of the fluidic oscillation element 7, and also includes a signal discrimination circuit, a microcomputer, a display, and the like. 42 is an airtight gasket that is in contact with the upper surface of the case body 8, and 43 is a lid that is in contact thereon.
The lid 43 is a metal plate and is fixed to the main body 8 with six screws 44 (not shown). 44'' are six female threaded portions provided on the main body 8 for tightening these screws.

45 is a cover.

The sensor 10 is attached to the top surface of the lid 43 with two screws 46, and these screws 46 pass through holes (not shown) in the lid 43 and the packing 42, and are inserted into the female thread 3a+ of the side wall 3 in FIG.
It is screwed and fixed to 3ta.

The sensor 10 and the flow sensor 12 are attached to the fluidic oscillation element 7 as shown in FIGS. 13 and 14.
The sensor 10 is screwed to the side wall 3.3' (not shown) via the lid 43 and the gasket 42 using the screws 46 as described above. Pressure inlet 15, 15' of sensor 10
is a pressure introduction path 9,9′ formed by the packing 42 and the lid 43, and the pressure introduction port 14 formed in the packing 42
．． 14'. Pressure introduction path 9゜9゛ is the lid 4
3, and the lower surface is surrounded by a packing 42 to form a pressure introduction path. In this way, the pressure introduction path 9,
Reference numeral 9' is provided on a gasket 42 and a lid 43 as airtight members constituting the fluidic oscillation element 7.

The flow sensor 12 is provided above the nozzle 2. As shown in FIG. 16, the flow sensor 12 has a structure in which a heater and a temperature sensor are integrated on the bottom surface of a square ceramic substrate in the above-described structure, and six electrical connection wires are installed on the top surface of the substrate. A pin 12a protrudes as shown in FIG.
Mount it by pressing it with 43. Flow sensor 1
The wall 2 forming the nozzle 2 is
A square recess 2c whose side is slightly longer than the length of one side of the square ceramic substrate of the flow sensor 12 is formed on the upper end surfaces of a and 2b.
c! The square ceramic substrate of the flow sensor 12 is f! i
i? Z and implement. The flow sensor 12 is mounted while being held down by the lid 43, and is connected to an electronic circuit by fitting a connector to the pin 12a.

In order to make it easier to understand the pressure introduction path 9 that communicates the two pressure introduction ports 14 and 15, FIG. 17 shows a cross section taken vertically along the center of the width of the pressure introduction path. Note that the sensor 10 is not cut in this cross-sectional view.

The flow sensor 12 is mounted on the upper end of the nozzle walls 2a and 2b, but as shown in FIG.
7 is provided. This stepped portion 47 is located slightly below the lower surface of the flow sensor 12, that is, the sensing portion, to prevent dust floating in the gas entering from the inlet 1 and ejected from the nozzle 2 from directly hitting the sensing portion of the sensor 10. To prevent.

In the embodiment, as explained in FIGS. 5 and 6, power is intermittently supplied to the flow sensor 12 only when the flow rate is small, and power is supplied to the sensor 10 only when the flow rate is medium to large. Even though the sensor 12 is used, the flow sensor part has a current of 10μA and the part related to the sensor 10 has a current of 20μA.
A. The microcomputer part can be operated with as little current consumption as 20 μA, and we have created a gas meter that can operate on batteries for 10 years.

〔Effect of the invention〕

In this invention, the frequency of the fluidic oscillation element is detected by the sensor 10, and the flow velocity at the nozzle part of the fluidic oscillation element is detected by the flow sensor 12, and medium to large flow rate and small flow rate are detected by the sensor 10 and the flow sensor, respectively. 12
Since the flow rate is detected and measured from small to large flow rates, it is possible to realize a small and highly reliable flow meter that can obtain a measurable flow rate range 1000 times wider than that required by a gas meter.

Further, in the invention of claim 2, since the flow sensor 12 is intermittently supplied with power only when the flow rate is small, the current consumption can be reduced, and there is an advantage that the flow sensor 12 can be operated for a long time with a battery.

Further, in the invention of claim 3, since the pressure introduction path is provided, there is an effect that the degree of freedom in the mounting position of the polymer piezoelectric film sensor is increased. Therefore, the piezoelectric film sensor can be fixed to the side wall, which is originally essential to the fluidic oscillation element, so there is no need to make the lid or the like particularly thick, and the overall size can be reduced accordingly.

Further, in the invention of claim 4, since the flow sensor is disposed above the nozzle portion, there is no possibility of being adversely affected by drainage in the fluid, and the life of the flowmeter can be expected to be extended.

Furthermore, in the invention of claim 5, since the stepped portion is provided immediately upstream of the flow sensor, dust in the fluid will not collide with the sensing surface of the flow sensor, so a longer life can be expected in this respect as well. .

Furthermore, with such a configuration, the fluidic in the large flow area and the flow sensor in the small flow area, the important point is that in the measurement of the large flow rate, the sensor for measuring the small flow rate is It should not get in the way of large flow rates. Also, when measuring in a small flow rate range, a sensor in a large flow rate range should not interfere. The present invention is particularly advantageous in that, in the former case, there is nothing in the fluid passages that obstructs each other.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the entire embodiment of the present invention, Fig. 2 is a diagram explaining the operation of a fluidic oscillation element, and Fig. 3 shows another example of a sensor that converts fluid vibration into an electrical signal. Figure 4 is an explanatory diagram of the flow sensor, Figure 5 is a block diagram of the electric circuit, Figure 6 is a diagram explaining the operation of the electronic circuit,
FIG. 7 is a signal determination circuit, FIG. 8 is a timing chart explaining the operation of the signal determination circuit, FIG. 9 is a flowchart, FIG. 1θ is a diagram explaining switching operation, and FIG. 11 is a front view of another embodiment. A portion of the cover is shown cut away. 12 is a cross section taken along the line A-A in FIG. 11, FIG. 13 is a top view of the main part of the embodiment shown in FIG. 12, and FIG. 14 is a cross-section taken along the line B--
B cross section, FIG. 15 is a slope view of the nozzle part, FIG. 16 is a slope view of the flow sensor obliquely viewed from above, and FIG. 17 is a longitudinal sectional view showing the vicinity of the pressure introduction path.

Claims (1)

[Claims] 1. A fluidic oscillation element (7), a sensor (10) that detects fluid vibration of the fluidic oscillation element and converts it into an electrical signal, and a nozzle section (2) of the fluidic oscillation element. ) for detecting the flow velocity of the flow sensor (12) and converting it into an electrical signal, and an electronic circuit ( 11) and a display (13) for displaying the integrated flow rate determined by the electronic circuit. 2. Determine whether the frequency of the electrical signal of the fluid vibration detection sensor (10) is above or below a certain value, and when it is below the certain value, intermittently supply driving power to the flow sensor (12) for flow velocity detection. , the flow rate is determined by a signal from a fluidic oscillation element (7) for a large flow rate above a certain value, and by a signal from a flow sensor (12) for a small flow rate below a certain value. Gas flow meter as described. 3. A polymer piezoelectric film sensor having a pair of pressure inlets (15), (15') is used as the fluid vibration detection sensor (10), and this pressure inlet is connected to a fluidic oscillation element (7).
) communicates with a pair of pressure introduction ports (14) and (14') provided in the pressure introduction passages (9) and (9'), and
2. The gas flowmeter according to claim 1, wherein the pair of pressure introduction passages are provided in an airtight member constituting the fluidic oscillation element (7). 4. The gas flow meter according to claim 1, wherein the flow sensor (12) for detecting flow velocity is arranged above the nozzle (2) constituting the fluidic oscillation element (7). 5. Immediately upstream of the flow sensor (12) for detecting flow rate,
The gas flowmeter according to claim 4, further comprising a stepped portion (47) that reduces the flow path.