JP3078217B2 - Fluidic flow meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to the present invention, wherein a periodic fluid vibration is generated in a flow of a jet fluid ejected from a nozzle flow path, and a proportional relationship exists between the frequency of the periodic fluid oscillation and the flow rate of the ejected fluid. The present invention relates to a fluid flow meter that detects a flow rate of a fluid based on the existence thereof, and more particularly to a fluid flow meter that prevents occurrence of a flow rate detection error due to fluid noise.

[0002]

2. Description of the Related Art Generally, a gas meter is widely used as a gas meter. This membrane gas meter detects the flow rate by converting the reciprocating motion of the diaphragm into rotary motion, but the structure is complicated and the manufacturing cost is high, and since there are many mechanically movable parts, a large number of personnel are required for maintenance and inspection. And there were inconveniences such as requiring costs.

[0003] Therefore, attempts have been made to apply a fluidic flow meter which has no mechanically movable parts, has a low manufacturing cost, and has a high flow rate detection accuracy to a gas meter.
As this fluidic flow meter, for example, there is a fluidic flow meter F as shown in FIG. The fluidic flow meter F includes a housing 1, nozzle members 2 a and 2 b provided in the housing 1, a target member 3 and a pressure outlet 4.

[0004] The housing 1 has a rectangular parallelepiped space 1a, and is connected to another flow path via an inlet 1b and an outlet 1c. Nozzle members 2a, 2b
Has a symmetrical shape and is constituted by a pair of members, and is provided so as to occupy a downstream portion of the space 1a. For this reason, the nozzle member 2 is provided in the housing 1.
An inflow space 1d is configured on the upstream side of a and 2b. Further, the nozzle members 2a and 2b constitute the nozzle flow path 21 after the upstream portion thereof is symmetrically adjacent to each other to form the contraction portion 1e, and the flow rate is set to the downstream side of the nozzle flow path 21. A measurement space 22 for detection is configured. The measurement space 22 is provided at the nozzle outlet 2 of the nozzle flow path 21.
Wall surfaces 22a, 22b that expand in an arc shape symmetrically from left to right from 1a
It has a structure with.

[0005] The target member 3 is located in the measurement space 22 and on an extension of the nozzle flow path 21. The pressure outlet 4 is provided in the measurement space 22 at a position symmetrical with respect to the extension of the nozzle flow path 21, so that the fluid oscillation of the flow of the jet fluid from the nozzle flow path 21 is generated by the jet flow. It is determined by detecting the static pressure on both sides.

The housing 1 is hermetically sealed by a seal packing and a cover (not shown). Therefore, the fluid flowing into the inflow port 1b flows out of the outflow port 1c through the inflow space 1d, the nozzle flow path 21, and the measurement space 22.

In the fluidic flowmeter configured as described above, the flow of the jet fluid, for example, propane gas, flowing out of the nozzle flow path 21 periodically vibrates. That is, at a certain time, the ejected fluid flows along one wall surface 3a of the target member 3 and collides with the bottom portion 22c of the wall surface, and a part of the flow flows to one wall surface 22a of the measurement space 22.
And return to the nozzle outlet 21a.
It flows out of the system through c. At the next point in time, the ejected fluid flows as if drawn along the other wall surface 3b of the target member 3 and has the same flow state as described above. Such ejection fluid vibrations occur periodically in the measurement space 22.

Since there is a proportional relationship between the fluid oscillation frequency at which the ejected fluid undergoes fluid oscillation and the flow rate of the ejected fluid, the static pressure of the ejected fluid is detected by the pressure sensor through the pressure outlet 4. By calculating the fluid vibration frequency,
The flow rate of the fluid can be measured.

The above-mentioned fluidic flow meter is a so-called simplified type having one target member in a measuring space, and a similar type is disclosed in JP-A-4-278421.
And JP-A-4-278422. In addition, JP-A-63-139213 discloses a complicated fluidic flow meter provided with a pair of partitions in addition to one target member.

[0010]

As shown in the above-mentioned known example, the position at which the pressure sensor is mounted and the static pressure of the jet is detected is set between the nozzle outlet and the target member in the simple type. , And the complicated type may be provided after the target member. As described above, the pressure detection position is provided at various positions according to the configuration state of the measurement space, but if this position is not properly selected, pulse output due to accurate static pressure fluctuation due to the influence of fluid noise. Cannot be obtained, and a detection error of the number of pulses occurs.

That is, FIG. 8 is a diagram showing the time on the horizontal axis and the signal output on the vertical axis, showing the case where the fluid noise signal is not superimposed on the pressure fluctuation detection signal 41. Output can be detected. On the other hand, FIG. 9 shows a case in which a noise signal 42 due to fluid noise is superimposed on the pressure fluctuation detection signal 41. In practice, an output of 4 pulses is counted as 7 pulses, resulting in erroneous detection. In general, the output waveform is not disturbed by the fluid noise in the high flow rate region, but the waveform is disturbed by the fluid noise in the low flow rate region, and a waveform crack that causes a counting error occurs.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fluid flow meter capable of accurately detecting the frequency of fluid vibration without being affected by fluid noise even in a low flow rate range.

[0013]

In order to achieve the above object, the present invention has a nozzle flow path and one target member which is spaced apart from a nozzle outlet of the nozzle flow path. Fluidic flow meter that detects the flow rate of a fluid because periodic fluid vibration occurs in the ejected fluid to be ejected, and there is a proportional relationship between the frequency of the periodic fluid oscillation and the flow rate of the ejected fluid. A pressure fluctuation detecting position for detecting the fluid vibration frequency is provided upstream of the target member and symmetrically with respect to a center axis of the nozzle flow path, and a straight line connecting the pressure fluctuation detecting positions with the center axis being the X axis. Is the Y axis, the distance from the intersection of the Y axis and the X axis orthogonal to each other is x, the distance between the two pressure fluctuation detection positions is ± y, and the width of the nozzle flow path is w, w = 1.
2 mm or more and 3.0 mm or less, x / w = 0.67 or more and 3.75 or less, and y / w = 0.67 or more and 3.75 or less.

That is, the fluidic flow meter of the present invention has a simplified configuration similar to that of the conventional example, and has two pressure fluctuation detecting positions located upstream of the target member and with respect to the center axis of the nozzle flow path. They are provided at symmetrical positions. Then, the relationship between the pressure fluctuation detection position and the occurrence of the waveform crack in the low flow rate region is obtained by an experiment, and the pressure fluctuation detection position is set at a position where w, x, y satisfies the above-described relationship. It has been found that a fluid flow meter which prevents generation of waveform cracks and has no detection error can be obtained.

In the present invention, the nozzle width w is limited to a range of 1.2 mm or more and 3.0 mm or less. However, considering the flow rate of a conventional gas meter, the nozzle width w is preferably about 2.5 mm. Therefore, it is set with a width provided before and after the center. Since the measurement accuracy decreases as the width w decreases, the lower limit is set to 1.2 mm or more. In addition, the upper limit is limited to 3.0 mm or less. When the thickness of the flow meter is about 10 mm, the cross section becomes closer to a circle by increasing the upper limit of the nozzle width. The two-dimensional jet is no longer formed and changes to a three-dimensional jet flow. This is to prevent this and maintain the characteristics of the nozzle having a rectangular cross section.

Further, x / w and y / w should be 0.67 or more.
The reason for limiting to 75 or less is that x / w, y /
at least one of w is less than 0.67, or 3.7
This is because, if it exceeds 5, waveform cracks occur in the low flow rate range. In other words, the closer the pressure fluctuation detection position is to the target member and the further away from the nozzle center axis, the more easily the influence of fluid noise is exerted.

The results of the above experiment are shown by AA ', BB', CC 'and DD' shown in FIG.
The case where the four positions are set as pressure fluctuation detection positions will be described.

In the case of A-A ', w = 2.5 mm x = 2 mm x / w = 0.8 y = ± 2 mm y / w = ± 0.8 The flow rate Q is 4.8185 m ^{3 /} h to 0.0726 m ³ No waveform cracking in / h range.

In the case of BB ′ w = 2.0 mm x = 4.5 mm x / w = 2.25 y = ± 4.5 mm y / w = ± 2.25 The flow rate Q is from 4.8185 m ³ / h. No waveform cracking in the range of 0.09132 m ³ / h. In the case of C−C ′, w = 2.0 mm x = 14 mm x / w = 7 y = ± 5 mm y / w = ± 2.5 Waveform cracking occurs when the flow rate Q is 0.9783 m ³ / h or less.

In the case of DD ′ (position immediately downstream of the target member) w = 2.0 mm x = 20 mm x / w = 10 y = ± 11 mm y / w = ± 5.5 The flow rate Q is 2.1167 m ³ / Wave cracks occur below h.

That is, when x / w and y / w do not fall within the above-mentioned limits, waveform cracks are generated, and therefore, the pressure fluctuation detection position is not possible.

The fluidic flow meter of the present invention regulates the width of the nozzle flow path and sets the pressure fluctuation detection position in a region where no waveform break occurs with respect to the width of the nozzle flow path. The flow rate can be accurately measured over a wide flow rate range from a large flow rate range to a minute flow rate range without being affected by noise.

Therefore, when used as a general gas meter, it is possible to provide a gas meter which is inexpensive, highly accurate, and easy to maintain.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments with reference to the drawings. FIG. 1 is an explanatory view of a configuration of an embodiment of the present invention, FIG. 2 is a cross-sectional explanatory view of a main part (a static pressure extracting part of a flow detecting means), and FIG. 3 is a block diagram of the main part (a flow detecting means). FIG. 4 is a waveform explanatory diagram in a large flow rate region, FIG. 5 is a waveform explanatory diagram in a low flow rate region,
FIG. 6 is an enlarged explanatory view of a main part for explaining a relationship between a pressure fluctuation detection position and a waveform, FIG. 7 is an explanatory diagram of a configuration of a conventional example, FIG. 8 is an explanatory diagram of a fluid vibration detection signal having no waveform crack, and FIG. FIG. 5 is an explanatory diagram of a waveform of a fluid vibration detection signal in which a waveform crack has occurred.

The fluidic flow meter E according to the embodiment of the present invention has a nozzle flow path 21 and one target member 3 which is spaced apart from and opposed to the nozzle outlet 21a of the nozzle flow path 21. Fluidic flowmeters that measure the flow rate of a fluid due to periodic fluid oscillations occurring in the ejected fluid flowing out of the fluid, and since there is a proportional relationship between the frequency of the periodic fluid oscillations and the flow rate of the ejected fluid. Then, the pressure fluctuation detection position 61 for detecting the frequency is located on the upstream side of the target member 3 and in the nozzle flow path 21.
Is provided so as to be symmetrical with respect to the central axis 21b, and the central axis 21b is defined as the X axis, a straight line connecting the two pressure fluctuation detection positions 61 is defined as the Y axis, and the intersection between the Y axis and the X axis is orthogonal. Assuming that the distance to the nozzle outlet 21a on the X axis is x, the distance from the intersection to both the pressure fluctuation detection positions 61 on the Y axis is ± y, and the width of the nozzle flow path 21 is w, w = 1.
2 mm or more and 3.0 mm or less, and x / w = 0.67 or more.
75 or less and y / w = 0.67 or more and 3.75 or less.

In this embodiment, w = 2.
0 mm, x = 4.5 mm, y = ± 4.5 mm,
B and B 'in FIG. 6 are the pressure fluctuation detection positions 61. Even in a low flow rate region, no waveform break occurs, and the flow rate can be accurately measured over a wide flow rate range.

The fluidic flow meter E has a main body F
And flow rate detecting means K. Since the main body F has the same configuration as the conventional example shown in FIG. 7, the same parts of the main body F are given the same reference numerals to simplify the description, but the flow rate detecting means K is the most important component of the present invention. Hereinafter, mainly the flow rate detecting means K will be described in detail.

The flow rate detecting means K comprises a pressure extracting section 6 for extracting the static pressure of the jet, and a circuit section 7 for calculating the flow rate based on a signal from the pressure extracting section 6. The take-out unit 6 has two pressure fluctuation detection positions 61 (BB-B 'in FIG. 6) provided symmetrically on both sides of a center axis 21b (see FIG. 6) passing through the center of the nozzle outlet 21a of the nozzle flow path 21. Position), for example, a pressure detection hole 6 having a diameter of 0.5 mm.
The pressure detection hole 62 is connected to a pipe 63 having, for example, an inner diameter of 1.5 mm. This pipe 6
The static pressure is taken out through 3 and the static pressure of the jet is detected by two pressure sensors (not shown) connected to these pipes 63 respectively.

The circuit section 7 has a pressure detecting circuit 71. The pressure detecting circuit 71 detects the static pressure of the jet by a pressure sensor, and outputs an obtained output signal to a waveform shaping circuit 72. The waveform shaping circuit 72 converts the signal converted into the voltage into
Unnecessary components such as noise are removed to obtain a waveform-shaped fluid vibration detection signal, which is further converted into a flow rate detection signal and output to the frequency detection circuit 73.

The frequency detection circuit 73 detects a frequency based on the input waveform-detected flow rate detection signal, and outputs the detected frequency signal to the next flow rate calculation circuit 74.
The flow rate calculation circuit 74 is configured to calculate the flow rate from the relationship between the frequency and the flow rate input in advance using the input frequency. Further, the flow rate calculation circuit 74 is connected to a flow rate display device 75. The flow rate display device 75 can display the flow rate, the used flow rate, the integrated flow rate, and the like calculated by the flow rate calculation circuit 74 on a display every moment, and can print out the information as needed.

In FIG. 1, reference numeral 101 denotes a screw insertion hole for fixing a cover and a packing (not shown) to the housing 1, and reference numeral 102 denotes a screw for fixing the nozzle members 2a and 2b to the housing 1. It is an insertion hole.

In the flow meter constructed as described above, a fluid such as propane gas flows into the main body F of the fluidic flow meter E from a hose (not shown). Fluid vibration that the jet fluid ejected from the nozzle flow path 21 flows along one wall surface 3a of the target member 3 at a certain time and flows along the other wall surface 3b at a certain time is periodically generated. I do.

This periodic fluid vibration is detected by a change in the static pressure of the jet introduced from the pressure detection hole 62 provided at each pressure fluctuation detection position 61. The static pressure is input to a pressure detection circuit 71, where the pressure is converted into an electric signal by a pressure sensor. As described above, the output of the pressure detection circuit 71 is
, The signal is input to the frequency detection circuit 73,
3, the frequency is detected. The flow rate is calculated by the flow rate calculation circuit 74 based on this frequency. Further, a flow rate display device 75 is connected to the flow rate calculation circuit 74, and the used flow rate and the integrated flow rate are constantly displayed on the display, and the used amount can be printed out as necessary.

The fluid vibration detection signal and the flow rate detection signal in the above embodiment will be described with reference to FIGS. In both figures, the horizontal axis represents time ms, and the vertical axis represents output voltage v. FIG. 4 shows the case of a large flow rate region where the flow rate Q = 4.8185 m ³ / h, and the lower waveform diagram shows two pressure fluctuation detection positions 61.
Is a fluid vibration detection signal obtained by synthesizing the static pressure signals obtained through the respective pressure detection holes 62. The upper waveform diagram is a flow rate detection signal obtained by converting the lower waveform diagram into a pulse wave. No waveform break is seen in the upper figure, and a good pulse number (frequency) is obtained.

FIG. 5 shows a flow rate Q = 0.09132 m ^3.
In the case of the low flow rate range of / h, the lower waveform diagram is a fluid vibration detection signal obtained by synthesizing the static pressure signals obtained through the respective pressure detection holes 62 at the two pressure fluctuation detection positions 61. It is. The upper waveform diagram is a flow rate detection signal obtained by converting the lower waveform diagram into a pulse wave. No waveform break is seen in the upper figure, and a good pulse number (frequency) is obtained.

In the present embodiment, propane gas is described as a fluid, but the present invention is not limited to this, and may be air or another gas, or water, oil or another liquid (Newtonian fluid).

[0037]

As described in detail above, the fluidic flow meter of the present invention regulates the width of the nozzle flow path and detects the pressure fluctuation in the area where no waveform break occurs with respect to the width of the nozzle flow path. Since the position is set, the flow rate can be accurately measured over a wide range from a large flow rate range to a minute flow rate range without being affected by fluid noise.

Therefore, when used as a general gas meter, it is possible to provide a gas meter which is inexpensive, highly accurate, and easy to maintain.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory diagram of an embodiment of the present invention.

FIG. 2 is an explanatory sectional view of a main part (a part for extracting a static pressure of a flow rate detecting means).

FIG. 3 is a block diagram of a main part (flow rate detecting means).

FIG. 4 is an explanatory diagram of output signals in a large flow rate region.

FIG. 5 is an explanatory diagram of an output signal in a low flow rate region.

FIG. 6 is an enlarged explanatory view of a main part, similarly illustrating a relationship between a pressure detection position and a waveform of fluid vibration.

FIG. 7 is a configuration explanatory view of a conventional example.

FIG. 8 is an explanatory diagram of a waveform of a fluid vibration detection signal having no waveform crack.

FIG. 9 is an explanatory diagram of a waveform of a fluid vibration detection signal in which a waveform crack has occurred.

[Explanation of symbols]

 w Width of nozzle flow path 3 Target member 21 Nozzle flow path 21a Nozzle outlet 21b Nozzle center axis 61 Pressure fluctuation detection position

Claims (1)

(57) [Claims] 1. A nozzle having a nozzle flow path and a target member spaced apart from and facing a nozzle outlet of the nozzle flow path, wherein a periodic fluid vibration is generated in a jet fluid ejected from the nozzle flow path. Fluid flow rate that detects the flow rate of the fluid because there is a proportional relationship between the frequency of the typical fluid vibration and the flow rate of the ejected fluid, the pressure fluctuation detection position that detects the fluid vibration frequency is the target Upstream from the member and provided symmetrically with respect to the center axis of the nozzle flow path, the center axis is the X axis,
The straight line connecting both pressure fluctuation detection positions is defined as the Y axis, the distance from the intersection of the Y axis and the X axis perpendicular to the nozzle outlet is x, the distance between the two pressure fluctuation detection positions is ± y, and the width of the nozzle flow path is w
Where w = 1.2 mm or more and 3.0 mm or less, x / w = 0.67 or more and 3.75 or less, and y / w = 0.67 or more and 3.75 or less. Total.