JP3017831B2 - Fluidic flow meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid flow meter for detecting a flow rate by detecting an alternating pressure wave generated by a vibration phenomenon of a fluid such as gas ejected from an ejection nozzle into a flow path.

[0002]

2. Description of the Related Art A fluidic flow meter installed in a general household or the like for measuring a gas flow rate is disclosed in, for example,
It is known from JP-A-313018 and JP-A-1-250725.

In this fluidic flow meter, an ejection nozzle is provided on the inlet side of a flow path, and when a fluid is ejected from the ejection nozzle into the flow path, the ejection fluid flows, for example, along the right side wall due to the Coanda effect.

[0004] A part of the fluid flowing to the right side wall becomes a return fluid, and the fluid energy of the return fluid is applied to the ejected fluid, so that the ejected fluid flows along the left side wall. A part of the fluid flowing to the side wall becomes a return fluid, and the fluid energy of the return fluid is applied to the ejection fluid, so that the ejection fluid flows again along the right side wall.

That is, an alternating pressure wave is generated by the vibration phenomenon of the fluid ejected from the ejection nozzle into the flow path. The alternating pressure wave is detected by the piezoelectric film sensor, and the flow rate is calculated from the frequency to detect the flow rate of the fluid.

However, a general household gas flow meter needs to be able to measure over a wide range from the maximum use flow rate to a flow rate of 1/1000 to 1/2000, but a piezoelectric film sensor for detecting an alternating pressure wave. The measurable range of the fluidic flow meter using the standard is the pressure loss at the maximum use flow rate, so it is about 1/50 of the maximum use flow rate, and measurement in the micro flow rate range is impossible. . Therefore, a fluidic flow meter has been developed in which a large flow area is detected by a piezoelectric film sensor and a minute flow area is detected by a flow sensor.

However, the flow sensor needs to be provided at a position where the flow path is narrowed in the flow meter and the flow velocity is highest, that is, at the ejection nozzle, in order to measure a minute flow rate region.

Therefore, conventionally, a flow sensor is attached as shown in FIG. That is, reference numeral 1 denotes a flow path main body that forms the flow path 2, and a jet nozzle 6 is provided in a partition wall 5 that partitions the upstream flow path 3 and the downstream flow path 4 of the flow path main body 1. A flow sensor 7 is attached to the partition 5 located at the end of the ejection nozzle 6, and a sensor chip 8 faces the ejection nozzle 6.

[0009]

However, the sensor chip 8 in the flow sensor 7 of the fluidic flow meter constructed as described above has one heating part and the upstream and downstream sides of the heating part. It consists of a pair of installed temperature sensing units, and measures the flow velocity based on the temperature difference between the two. The heating unit and the temperature sensing unit are provided in an exposed state.

[0010] Therefore, careless handling or contact with the sensor chip will damage the sensor chip. In addition, the quality of the fluid measurement member is
Although a metal is used, the sensor chip installed in the narrowest part of the flow path has a small gap between the sensor chip and the metal case, and thus has poor electrical characteristics such as withstand voltage.

The present invention has been made in view of the above circumstances, and has as its object to facilitate the handling of the flow sensor and to improve the workability of assembling the flow sensor with respect to the flow path main body. It is another object of the present invention to provide a fluidic flowmeter capable of performing accurate measurement while the flow sensor is electrically insulated.

[0012]

In order to achieve the above object, the present invention is directed to a first aspect of the present invention, wherein a flow rate of a fluid is detected by detecting a flow velocity of a fluid at an ejection nozzle for ejecting the fluid into a flow path. In a fluidic flow meter provided with a flow sensor for detecting a flow rate, a concave portion is provided in a flow path main body located at an end of an ejection nozzle, and an insulating case for accommodating the flow sensor is housed in the concave portion. The case is provided with a groove forming a part of the ejection nozzle, and the sensor chip of the flow sensor faces the groove.

When the flow sensor is housed in the recessed portion of the flow path main body while housed in the insulating case, the flow sensor can be electrically insulated and the sensor chip can be protected during assembly. A second aspect of the present invention resides in that an engagement concave portion is provided in the concave portion and an engagement convex portion that engages with the engagement concave portion is provided in the insulating case to position the insulating case.

[0014]

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

FIGS. 3 and 4 show the whole of a fluidic flow meter, in which 11 is a case. This case 1
1 is a rectangular box-shaped case body 12 and this case body 12
And a lid 13 that closes the opening of the cover.

At the lower part of the case body 12, a gas inlet 1 is provided.
4 and a gas outlet 15 are arranged side by side, and a display window 16
Is provided. A fluidic element 17 and a shutoff valve 18, which will be described later, are installed in a lower part of the case 11, and a battery 19, a pressure switch 20, a seismic sensor 21, and an integrating display substrate 22 facing the display window 16 are provided in an upper part.
Is installed.

The fluidic element 17 will be described. Reference numeral 23 denotes a flow passage main body formed by die casting or the like.
The flow path 26 is configured by being closed by the lid 25 through the cover 4.

The flow path 26 is defined by a partition wall 27, and the upstream flow path 28 communicates with the gas inlet 14.
The downstream flow passage 29 communicates with the gas outlet 15. A valve seat 30 is provided in the middle of the upstream flow path 28, and the valve body 31 of the shutoff valve 18 faces the valve seat 30. That is, when the pressure switch 20 and the seismic sensor 21 detect an abnormality, the flow path 26 can be shut off by the shutoff valve 18.

As shown in FIG. 3, a jet nozzle 32 is provided on the partition wall 27 of the flow path main body 23. The ejection nozzle 32 has a slit shape that opens over the entire depth direction of the flow path main body 23, and has protrusions 32 a and 32 b that protrude into the upstream flow path 28 on both sides of the opening in the longitudinal direction.
The nozzle passage length is extended.

A first target 33 for stabilizing the switching of the flow direction of the fluid is provided in the downstream flow path 29 facing the ejection nozzle 32. Side walls 34a and 34b are provided symmetrically on both sides of the first target 33.

Further, a second target 35 is provided at a central portion located downstream of the first target 33, and a return wall 36 extending in the width direction of the downstream flow path 29 is further downstream. Is provided. Return passages 37a, 37b are formed outside the side walls 34a, 34b, and discharge passages 38a,
38b are provided.

Therefore, when the fluid is ejected from the ejection nozzle 32 toward the downstream flow path 29, the ejected fluid flows, for example, along the inside of the right side wall 34a by the Coanda effect.

Most of the fluid flowing to the right side wall 34a goes to the discharge passage 38a, but a part of it becomes return fluid and goes to the return passage 37a. The fluid energy of the return fluid is applied to the ejected fluid, and the ejected fluid is supplied to the left side wall 34.
b, and a part of the fluid that has flowed to the left side wall 34b becomes return fluid, and the fluid energy of this return fluid is applied to the ejected fluid, and the ejected fluid returns to the right side wall 34a. Will flow along the inside of the. That is, the configuration is such that an alternating pressure wave is generated by the vibration phenomenon of the fluid ejected from the ejection nozzle 32 into the downstream flow path 29.

Further, a flow sensor 40 and a piezoelectric film sensor 41 are provided on the side surface of the flow path main body 23 corresponding to the jet nozzle 32. The flow sensor 40
As shown in FIG. 1 and FIG. 2, in order to measure a minute flow rate region, the flow path is narrowed and installed at a position where the flow velocity is the highest.

That is, it is composed of a sensor main body 42 and a sensor chip 43 provided with a detecting section composed of a heating section and a temperature sensing section, and is fixed to the flow path main body 23. A pair of concave portions 44, 44 are symmetrically provided on the flow path main body 23 located at one end of the ejection nozzle 32 with the ejection nozzle 32 interposed therebetween.

A rectangular insulating case 45 formed of a synthetic resin material is accommodated in the recesses 44, 44 so as to straddle the jet nozzle 32. A concave groove 46 having the same width as the jet nozzle 32 is provided at the bottom of the insulating case 45, and the concave groove 46 forms a part of the jet nozzle 32.

The sensor chip 43 faces the concave groove 46, and measures the flow velocity of the fluid passing through the ejection nozzle 32. In this case, the recess 4
The distance between the inner surfaces of the sensor case 42 and the inner surface of the sensor case 42 is close to that of the outer surface of the insulating case 45. The insulating case 45 and the sensor main body 42 are positioned closely by matching closely with each other.

The piezoelectric film sensor 41 is for measuring a large flow rate region, and comprises a sensor main body 47 and a pressure wave introducing section 48.
3 and the pressure wave introduction part 48 is connected to the ejection nozzle 32.
Is installed at the position where the alternating pressure wave generated by the vibration phenomenon is optimally taken out near the outlet.

On the other hand, a flat first straightening plate 51 made of a wire mesh and a mountain-shaped second straightening plate 52 made of a wire mesh are installed in the upstream flow path 28. It is provided detachably.

Next, the operation of the fluidic flow meter configured as described above will be described. Gas inlet body 14
Flows through the upstream flow path 28 of the flow path 26, is further rectified by the first rectifying plate 51 and the second rectifying plate 52, and then flows toward the ejection nozzle 32.

Since the flow path of the ejection nozzle 32 is narrowed, the flow velocity of the fluid increases, and the fluid is ejected from the ejection nozzle 32 to the downstream flow path 29. When the fluid passes through the ejection nozzle 32, its flow velocity is detected by the flow sensor 40. When the fluid is ejected from the ejection nozzle 32 toward the downstream flow path 29, the ejected fluid flows, for example, along the inside of the right side wall 34a due to the Coanda effect.

Most of the fluid flowing to the right side wall 34a goes to the discharge passage 38a, but a part of it becomes return fluid and goes to the return passage 37a. The fluid energy of the return fluid is applied to the ejected fluid, and the ejected fluid is supplied to the left side wall 34.
b, and a part of the fluid that has flowed to the left side wall 34b becomes return fluid, and the fluid energy of this return fluid is applied to the ejected fluid, and the ejected fluid returns to the right side wall 34a. Will flow along the inside of the.

That is, the downstream flow path 2
An alternating pressure wave is generated due to the vibration phenomenon of the fluid ejected into 9. The alternating pressure wave, that is, the pressure change caused by the change in the flow direction of the jet from the jet nozzle 32 is detected by the piezoelectric film sensor 41. The waveform signals from the flow sensor 40 and the piezoelectric film sensor 41 are used to calculate the fluid flow rate from the frequency and are displayed on the integration display board 22.

When assembling the flow sensor 40 to the flow path main body 23, first, the sensor main body 42 is housed in the insulating case 45, and the sensor chip 43 is inserted into the concave groove 46.
Face.

In this case, since the sensor chip 43 does not protrude below the bottom surface of the insulating case 45, the fingers of the operator come into contact with the sensor chip 43 during assembly and
3 is not damaged, the handling is easy, and the insulating case 45 is formed in the concave portions 44, 44 formed in the flow path main body 23.
The flow sensor 40 can be mounted at a predetermined position of the ejection nozzle 32 simply by storing the flow sensor 40 in the ejection nozzle 32. Therefore, the workability of assembling the flow sensor 40 with respect to the flow path main body 23 can be improved, and the workability is also improved during maintenance inspection and repair.

In the above embodiment, the flow path main body 23 is provided with the concave portions 44, 44, and the concave portions 44, 44 are provided.
The insulating case 45 is positioned so that it fits tightly. However, as shown in FIG. 5, the concave portions 44, 44 are provided with engaging concave portions 53, 53, respectively. Engagement projections 5 engaging engagement recesses 53, 53
The insulating case 45 can be positioned and fixed at a predetermined position with respect to the flow path main body 23 by providing the four and the four 54 and engaging with each other.

[0037]

As described above, according to the first aspect of the present invention, a concave portion is provided in the flow path body located at the end of the ejection nozzle, and the insulating case for accommodating the flow sensor is provided in the concave portion. By housing the insulating case and providing a concave groove that constitutes a part of the ejection nozzle in the insulating case so that the sensor chip faces the concave groove, it is easy to handle the flow sensor, and the workability of assembling the flow sensor with respect to the flow path body is improved. It is possible to achieve an improvement and to perform accurate measurement in a state where the flow sensor is electrically insulated.

According to the second aspect, since the concave portion is provided with the engaging concave portion and the insulating case is provided with the engaging convex portion which engages with the engaging concave portion, the insulating case is fixed to the flow path main body. There is an effect that the position can be determined.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a mounted state of a flow sensor according to one embodiment of the present invention.

FIG. 2 is a sectional view of the flow sensor according to the embodiment in an attached state.

FIG. 3 is a vertical sectional front view of the fluidic flow meter of the embodiment.

FIG. 4 is a vertical side view of the fluidic flow meter of the embodiment.

FIG. 5 is a cross-sectional view showing a mounted state of a flow sensor according to another embodiment of the present invention.

FIG. 6 is a perspective view showing a state in which a flow sensor is mounted in a conventional fluidic flow meter.

[Explanation of symbols]

23: flow path main body, 32: ejection nozzle, 40: flow sensor, 43: sensor chip, 44: concave portion, 45: insulating case, 46: concave groove, 53: engaging concave portion, 54: engaging convex portion.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideyuki Oike 1-3-2 Shimura, Itabashi-ku, Tokyo Inside Kinmon Manufacturing Co., Ltd. No. 70 Inside Aichi Watch Electric Co., Ltd. (72) Inventor Tadao Shibuya 2-10-16 Higashi Kobashi, Higashi-Nari-ku, Osaka-shi, Osaka Inside Kansai Gas Meter Co., Ltd. (56) References JP-A-1-308921 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) G01F 1/20 G01F 7/00

Claims (2)

(57) [Claims] An ejection nozzle for ejecting a fluid into a flow path, a sensor chip facing an end of the ejection nozzle, detecting a flow velocity of the fluid flowing through the ejection nozzle, and adjusting a flow rate in a minute flow rate region. In a fluidic flow meter provided with a flow sensor for detection, a concave portion is provided in a flow path main body located at an end of the ejection nozzle, and an insulating case for accommodating the flow sensor is housed in the concave portion. A fluid groove that forms a part of the ejection nozzle, and a sensor chip of the flow sensor faces the concave groove. 2. A fluidic according to claim 1, wherein said recess is provided with an engagement recess, and said insulation case is provided with an engagement projection engaging said engagement recess to position said insulation case. Flowmeter.