JPH11132818A - Flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a flowmeter having an easily and cheaply producible flow passage and capable of stably holding rectifier members and accurately detecting the flow rate. SOLUTION: The flow passage 2 has a larger inlet cross sectional area than the outlet cross sectional area and is tapered down from the inlet cross section to the outlet one, allowing dies to be easily drawn off from the passage 2 after casting. This makes it possible to easily and cheaply produce it by the injection forming or diecasting method. The passage 2 is provided with protrusions 5 for holding rectifier members 4, 6 to avoid playing them, thereby accurately detecting the flow rate.

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 detecting a flow rate of a fluid.

[0002]

2. Description of the Related Art FIG.
No. 48 is a cross-sectional view showing a flow meter disclosed therein, and FIG. 12 is a cross-sectional view showing another flow meter disclosed by the present applicant in Japanese Patent Application Laid-Open No. 9-68448. 11 and 12, reference numeral 100 denotes a body; 101, an inlet flow path; 102, a large flow rate measurement flow path having a larger flow path diameter than the inlet flow path 101;
Numeral 03 denotes a small flow rate measuring channel having a smaller channel diameter than the large flow rate measuring channel 102, 105 denotes a flow rate sensor unit, 105
a to 105c are flow rate sensors for detecting the flow rate of the fluid to be measured, 106 is a flow rate sensor unit, 106a to 106c
Is a flow rate sensor for detecting the flow rate of the fluid to be measured, and 107 and 108 are rectifying members.

Next, the operation will be described. Inlet channel 10
The fluid to be measured introduced from 1 is rectified through the rectifying member 107 and the like, and the flow velocity is detected by the flow velocity sensors 105a to 105c and the flow velocity sensors 106a to 106c. Then, the flow rate is calculated by a calculation means (not shown) based on the detected flow velocity signal.

[0004]

Since the conventional flowmeter is constructed as described above, it is necessary to form the cross-sectional area of the flow passage so as to increase from the inlet side to the outlet side and then to decrease. In addition, there is a problem that the processing of the flow path is troublesome, and the production cost tends to increase.
In particular, when the flow path is manufactured by the injection molding method or the die casting method, it is difficult to manufacture using the molding method because the mold cannot be easily pulled out from the flow path after the molding. There was a problem that it was difficult to provide a flow meter having a flow path that can be easily and inexpensively manufactured.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has as its object to obtain a flow meter having a flow path which can be easily and inexpensively manufactured.

Another object of the present invention is to provide a flow meter which has a flow path which can be easily and inexpensively manufactured, can stably hold a rectifying member, and can accurately detect a flow rate.

[0007]

According to the flowmeter of the present invention, the cross-sectional area on the inlet side of the flow path is formed larger than the cross-sectional area on the outlet side, and the cross-sectional area of the flow path is measured from the inlet side. At least a part of the flow path is formed in a tapered shape so as to decrease toward the outlet side.

In the flow meter according to the present invention, a protrusion for holding the outer peripheral portion of the rectifying member provided in the flow path on the inlet side is provided on the inner wall of the flow path on the inlet side.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. Embodiment 1 FIG. FIG. 1 is a vertical sectional view showing a flow meter according to Embodiment 1 of the present invention, FIG. 2 is a front view showing a protruding portion viewed from an inlet of a flow channel, and FIG. 3 is an enlarged cross-sectional view showing a structure near the protruding portion. FIG. 4 is an exploded perspective view showing the flow meter. In FIG. 1, reference numeral 1 denotes a body formed by injection molding or die-casting of, for example, a glass fiber reinforced thermoplastic resin, and has an index portion 1a on a side surface for designating a flowing direction of a fluid to be measured. Reference numeral 2 denotes a flow path having a circular cross-section through which the fluid to be measured flows. The cross-sectional area on the inlet side is formed larger than the cross-sectional area on the outlet side, and the gradient is such that the inner diameter decreases from the inlet side to the outlet side. It is formed in a taper shape of about 1 degree. That is, by forming the flow path 2 in a tapered shape so that the mold can be easily pulled out from the flow path 2 after molding, it is possible to manufacture easily and inexpensively using an injection molding method or a die casting method. It is like that. The fluid to be measured in this embodiment is, for example, a gas such as air, nitrogen, argon, carbonic acid, or oxygen. However, the subject of the present invention is not limited to this, and may be a flow meter for a liquid. You may.

Reference numeral 3 denotes a stepped portion for retaining a ring-shaped aluminum spacer (rectifying member) 4, and 5 is provided on the inner wall on the inlet side of the flow channel 2 so as to face each other and abut on the outer peripheral portion of the spacer 4. Are two pairs of protruding portions that hold this. That is, as shown in an enlarged manner in FIG. 3, since the inlet side of the flow path 2 is also formed in a tapered shape, the spacer 4 having the same outer diameter reaches the step portion 3 without any treatment. When the spacers 4 are successively inserted, a gap is formed between the spacer 4 located on the inlet side of the flow path 2 and the inner wall of the flow path 2. Disturbing the flow of the measurement fluid makes it difficult to detect the flow rate with high accuracy. Therefore, in order to fill the gap, the protruding portion 5 is connected to the flow channel 2.
Are formed on the inner wall to prevent rattling of the spacer 4 and the rectifying wire mesh 6.

Reference numeral 6 denotes a rectifying wire mesh (rectifying member) made of stainless steel, which is held between the spacers 4 and regulates the flow of the fluid to be measured.
Reference symbol a denotes a stainless steel wire mesh for a filter that removes dust and the like in the fluid to be measured when the fluid to be measured flows backward. Reference numeral 7 denotes a sensor mounting hole formed so as to communicate with the flow path 2 and engaged with a sensor chip fixing substrate 11 of a sensor unit (flow rate sensor) 8 described later.

The sensor unit 8 includes a micro flow sensor chip 9 for detecting the flow velocity of the fluid to be measured, and a lead wire 10 for fixing the micro flow sensor chip 9 on one surface and extracting a detection signal of the micro flow sensor chip 9 from the other surface. And a metal sensor chip fixing substrate 11 that derives the above. The lead wire 10 is inserted into the sensor chip fixing substrate 11 and is fixed by a glass sealing material.

As the micro flow sensor chip 9, for example, a semiconductor diaphragm configuration disclosed by the present applicant in the specification of Japanese Patent Application No. 3-106528 can be used. That is, the micro flow sensor chip 9 has a heat generating portion and two temperature detecting portions disposed upstream and downstream of the heat generating portion, although illustration is omitted. The flow rate corresponding to the flow velocity is obtained from the power supplied to the heat generating portion necessary to keep the difference between the detected temperatures constant, or the heat generating portion is heated with a constant current or constant power and detected by the two temperature detecting portions. It is formed so that the flow rate can be obtained from the temperature difference. Since the micro flow sensor chip 9 employs a very thin diaphragm structure that is thermally insulated, it has features of high-speed response and low power consumption.

Reference numeral 14 denotes the sensor unit 8 in which the sensor mounting hole 7 is mounted.
And a press-formed stainless steel plate. The bracket 14 has a main body fixing plate 14a fixed to the body 1 by a screw 18 via an O-ring 17 near an outer peripheral edge of the sensor mounting hole 7 on the side opposite to the flow path 2, and a protruding portion provided on the main body fixing plate 14a. A board supporting piece 14b having an engaging hole 15c to be engaged with an engaging protrusion 27b of a circuit board 27 described later, a protruding plate 14c protruding from the main body fixing plate 14a toward the flow path 2, and a protruding plate. Sensor chip fixed substrate 1 provided at the tip of 14c
1 and a sensor fixing plate 14d for fixing the same. Although only one screw 18 is shown in FIG. 4 with the number omitted, it goes without saying that four screws are used in this embodiment. Substrate support piece 14b
Is formed integrally with the main body fixing plate 14a by press-forming a stainless steel plate, so that it can be elastically deformed. Reference numeral 15a denotes a lead wire insertion hole through which the lead wire 10 is inserted, and 15b denotes a screw hole through which the screw 18 is inserted. The sensor chip fixing board 11 is provided with a sensor fixing plate 14d.
On the other hand, metal bonding is performed in an airtight manner by, for example, electric resistance welding, solder bonding, eutectic bonding, or electron beam welding.

Reference numeral 16 denotes a recess provided near the outer peripheral edge of the sensor mounting hole 7 on the side opposite to the flow path 2 so as to be coaxial with the sensor mounting hole 7 and to have an inner diameter larger than the inner diameter of the sensor mounting hole 7. The bracket positioning portion engages with the protruding plate 14c of the bracket 14. In FIGS. 1 and 4, reference numeral 19 denotes two bracket positioning ridges formed on the inner wall surface of the body 1 so as to engage with the board supporting pieces 14b of the bracket 14. The two bracket positioning projections 19, 19 are provided in parallel, and the interval therebetween is substantially the same as the width of the substrate support piece 14b, whereby a groove for guiding the substrate support piece 14b is formed. .
That is, when the micro flow sensor chip 9 previously fixed to the sensor fixing plate 14 d of the bracket 14 is inserted into the sensor mounting hole 7 of the body 1 and exposed to the flow path 2, the substrate support piece 14 b of the bracket 14 is The micro flow sensor chip 9 passes through substantially the center of the sensor mounting hole 7 and is accurately and easily positioned at a predetermined position by engaging with the guide groove formed by the bracket positioning ridges 19 and 19 and sliding. The micro flow sensor chip 9 having an extremely fine structure can be prevented from contacting the edge of the sensor mounting hole 7 or the inner wall surface of the body 1 and being damaged.

Reference numeral 20 denotes an aluminum flange formed by die-casting for connecting the body 1 to a pipe (not shown), and has an engaging hole 22 for engaging an engaging projection 21 provided on the body 1. , And is fixed by the engaging projection 21 and the screw 23. 24 and 25 are O-rings made of synthetic rubber, for example.

Reference numeral 27 denotes a lead wire mounting hole 27a through which the lead wire 10 of the sensor unit 8 is conductively fixed, an operation circuit of the sensor unit 8, and an engagement hole 15 of the board support piece 14b.
c is a circuit board having an engaging protrusion 27b engaging with the connector c and a connector 27c. This operation circuit includes, for example, a resistance bridge circuit, an amplification circuit, an A / D conversion circuit, and the like. The circuit board 27 is fixed to the body 1 by fixing means 28a and 28b. In addition, the width of the circuit board 27 is
It is almost equal to the dimension between b and 14b. Therefore, the circuit board 27 uses a connector, a cable member, or the like by elastically deforming the engagement protrusion 27b outwardly of the board support pieces 14b, 14b of the bracket 14 and engaging with the engagement holes 15c. And can be easily connected to the sensor unit 8 without performing
14b.

Reference numeral 30 denotes an arithmetic unit (not shown) for calculating the flow rate of the fluid to be measured based on the detection signal of the micro flow sensor chip 9 and used when the arithmetic unit corrects the flow characteristics according to the type of the fluid to be measured. And a circuit board including a memory (not shown) that stores correction coefficients to be corrected in advance. Algorithms and the like for setting operations and arithmetic processing are also written in advance in these not-shown arithmetic devices and memories, for example, display mode setting, gas type setting,
A control program for realizing a setting mode for setting various functions such as analog scaling and parameter setting, and a measurement mode for executing a flow rate calculation such as an instantaneous flow rate, an integrated flow rate, and a reverse integrated flow rate is written in advance.
In addition, the memory can store measured flow rate data and the like at any time. The circuit board 30
The circuit board 27 is connected to the connector 27c by a cable (not shown) or the like. 31 is the body 1
And fixing means for fixing the circuit board 30.
Reference numeral 32 denotes a connector for external output, which is formed, for example, by a cable connection with a personal computer (not shown) so that communication is possible.

Reference numeral 34 denotes a cover formed of a glass fiber reinforced thermoplastic resin or the like and formed so as to be attachable to the body 1. The cover has a push button switch 36 for inputting various settings to an arithmetic unit (not shown). And a liquid crystal display 38 for displaying the settings made by the computer and the output results of the arithmetic unit. Also, this cover 34
The lower part of the center of the side of the
1 that elastically engages with a pair of engaging projections 35, 35
A pair of engagement holes 34a, 34a are provided. The engagement protrusions 35, 35 and the engagement holes 34a, 34a are provided at positions where they are engaged even when the mounting direction of the cover 34 is reversed with respect to the body 1. That is, the cover 3
4 is mounted on the body 1 before shipment, but due to restrictions on the installation location of the body 1, the directions of the push button switch 36 of the cover 34 and the liquid crystal display 38 are reversed for the user, which causes inconvenience in operation. However, in such a case, the cover 34 can be easily mounted on the body 1 by reversing the mounting direction and engaging with the body 1.

Reference numeral 39 denotes a protection film provided so as to cover the upper surface of the push button switch 36 provided on the cover 34, and reference numeral 40 denotes a circuit board provided with the push button switch 36, an operation circuit of the liquid crystal display 38, and the like. Are connected to the circuit board 30 by connectors (not shown) and cables. The circuit board 40 is fixed to the cover 34 by fixing means 42a and 42b provided in the cover 34.

Next, the procedure for assembling the flow meter will be described. Spacers 4 and rectifying wire meshes 6 are alternately inserted into the inlet side flow path 2. Then, attach the flange 20 to the O-ring 2
It is fixed to the body 1 by screws 23 via 4 and 25. On the other hand, a wire mesh 6a for a filter is arranged on the outlet side of the flow path 2, and the flange 20 is fixed to the body 1 by a screw 23 via an O-ring 25. When the micro flow sensor chip 9 previously fixed to the sensor fixing plate 14d of the bracket 14 is inserted into the sensor mounting hole 7 of the body 1 and exposed to the flow path 2, the substrate supporting piece 1 of the bracket 14
The micro flow sensor chip 9 passes through substantially the center of the sensor mounting hole 7 and is accurately positioned at a predetermined position by engaging the slide 4b with the guide groove formed by the two bracket positioning protrusions 19, 19 and sliding the same. Further, the micro flow sensor chip 9 which can be easily accommodated and has an extremely fine structure can be prevented from contacting the edge of the sensor mounting hole 7 or the inner wall surface of the body 1 and being damaged. In addition, by engaging the protruding plate 14c of the bracket 14 with the bracket positioning portion 16 of the body 1, the positioning can be easily performed with respect to the sensor mounting hole 7, and the assembling work is easy. In addition, since the sensor chip fixing substrate 11 is air-tightly metal-bonded to the sensor fixing plate 14d in advance, the air-tightness at the bonding portion is sufficiently ensured. Further, the bracket 14 is connected to the screw 1 via the O-ring 17.
8, the airtightness between the body fixing plate 14a and the body 1 is sufficiently secured.

Further, by forming the protruding plate 14c on the bracket 14, the effective length of the screw 18 with respect to the body 1 can be easily and sufficiently secured. Therefore, screw 18
In order to secure the effective length, the situation in which the screw hole penetrates the flow path 2 can be avoided. Accordingly, even when the large-diameter flow path 2 is provided in the body 1, the length of the protruding plate 14 c of the bracket 14 and the thickness of the portion of the body 1 where the screw hole is provided are set to the effective length of the screw 18. If the body 1 is appropriately adjusted and manufactured, it is not necessary to increase the size of the entire body 1, which also contributes to reduction in manufacturing cost due to reduction in size and weight.

The circuit board 27 uses the elastic deformation of the board supporting piece 14b to engage the engaging protrusion 27b with the engaging hole 15c and insert the lead wire 10 of the sensor unit 8 into the lead wire mounting hole 27a. By soldering
It can be easily and quickly connected to the sensor unit 8 without using a connector or a cable member. Further, since the circuit board 27 is fixed to the body 1 by the fixing means 28a and 28b, and is also supported by the board supporting piece 14b, stable fixing is possible.

The circuit board 30 is fixed to the body 1 by fixing means 31. The circuit board 30 and the circuit board 27 are connected to the connector 27c by a cable (not shown) or the like.

The cover 34 is attached to the body 1 by engaging the engagement holes 34a with the engagement projections 35 of the body 1. As described above, the cover 34 is attached to the body 1 in advance and shipped. However, due to restrictions on the installation location of the body 1, the push button switch 36 and the liquid crystal display 38 of the cover 34 are reversed with respect to the user, and the operation is performed. May cause inconvenience. In such a case, the cover 34 may be mounted on the body 1 with the mounting direction reversed at the installation site, and the display on the liquid crystal display 38 or the like can be easily viewed.

Next, the operation will be described. The memory (not shown) previously stores the correction coefficient used when correcting the flow rate characteristic according to the type of the fluid to be measured by the arithmetic unit (not shown). A predetermined fluid to be measured is selected and set by a predetermined operation of the button switch 36. The fluid to be measured is introduced into the flow channel 2 from the inlet side of the flow channel 2 and is rectified by the rectifying wire mesh 6. The flow rate of the fluid to be measured is detected by the micro flow sensor chip 9 of the sensor unit 8, and the detection signal is transmitted from the lead wire 10 to the circuit board 27.
Output to The detection signal is taken into an arithmetic unit (not shown) of the circuit board 30 through predetermined signal conversion and amplification, and the flow rate data is calculated through linearization and correction. The output of the flow rate data is performed by, for example, a 4-20 mA output or an integrated pulse output, and is also displayed on the liquid crystal display 38.

As described above, according to the first embodiment, the cross-sectional area on the inlet side of the flow path 2 is formed larger than the cross-sectional area on the outlet side, and the inner diameter increases from the inlet side to the outlet side. Since the taper is formed with a gradient of about 1 degree so as to reduce the size, the mold can be easily pulled out from the flow path 2 after molding, and can be easily and inexpensively manufactured by using an injection molding method or a die casting method. The effect that can be obtained is obtained. Further, by forming the flow path 2 in a tapered shape, the flow of the fluid to be measured is restricted, and the flow velocity distribution can be kept uniform by inhibiting the development of the boundary layer, so that the flow rate can be accurately detected. Is obtained. Furthermore, regardless of injection molding,
Even in the case where the flow path 2 is formed by hollowing out the block member, the taper direction is only one direction, and an effect that cutting can be easily performed can be obtained. Further, since the projecting portion 5 is formed on the inner wall of the flow path 2 to prevent the spacer 4 and the rectifying wire mesh 6 from rattling, the flow of the fluid to be measured passing through the rectifying wire mesh 6 is not disturbed, and the accuracy is improved. The effect that the flow rate can be detected well is obtained.

Embodiment 2 FIG. 5 is a vertical sectional view schematically showing a body and a flow channel of a flow meter according to a second embodiment of the present invention, and FIG. 6 is a front view showing a protruding portion as viewed from an inlet direction of the flow channel. In FIG. 5, reference numeral 46 denotes a rectifying member for adjusting the flow of the fluid to be measured, which is constituted by the above-described rectifying wire mesh 6, the spacer 4, or the like, or is constituted by a honeycomb member having a large number of small channels in the channel direction. Is what you do. Hereinafter, members that are the same as or correspond to those already described are denoted by the same reference numerals, and description thereof will be omitted or simplified. In the first embodiment, the step portion 3 is provided in the flow path 2 having a circular cross section, and the inner diameter of the flow path 2 is formed in an enlarged tapered shape from the step portion 3 toward the inlet side. In the second embodiment, the step 2 is not provided in the flow path 2 and the flow path 2
Is formed in a tapered shape with a gradient of about 1 degree so that the inner diameter decreases from the entrance side to the exit side. That is, even in the second embodiment, by forming the flow path 2 in a tapered shape so that the mold can be easily pulled out from the flow path 2 after the molding, the injection molding or the die casting method is used. It can be easily and inexpensively manufactured. In this case, since the movement of the flow regulating member 46 toward the outlet side is regulated by the tapered flow path 2, rattling in the flow direction of the flow regulating member 46 occurs even if the step 3 is not particularly provided. Absent. Other components and operation examples are the same as those in the first embodiment, and a description thereof will not be repeated.

As described above, according to the second embodiment, the same effects as in the first embodiment can be obtained, and the flow path 2 has a simpler shape that does not require the step 3. Therefore, the shape of the mold can be simplified, and the effect of further reducing the manufacturing cost can be obtained.

Embodiment 3 FIG. 7 is a vertical sectional view schematically showing a body of a flow meter according to Embodiment 3 of the present invention. In FIG. 7, reference numeral 47 denotes an inner diameter near the inlet in the flow path 2 having a circular cross section in the flow direction. The parallel portions are formed in the same manner, and the inner diameter thereof is formed so that the rectifying member 46 can be inserted thereinto. Numeral 48 denotes a parallel portion in which the inner diameter near the outlet in the flow channel 2 is formed to be the same in the flow direction and the inner diameter is formed smaller than the flow channel inner diameter in the parallel portion 47. A gradient 49 is 1 between the parallel portions 47 and 48 so that the inner diameter decreases from the inlet side to the outlet side of the flow path 2.
It is a taper portion formed in a taper shape of about degree. In this case, the rectifying member 46 is inserted and held in the parallel portion 47, so that the rattling in the vertical direction with respect to the flow path 2 does not need to be provided as in the case of the first embodiment. Does not occur.
Further, since the movement of the rectifying member 46 toward the outlet side is restricted by the tapered portion 49 having a reduced diameter, the rectifying member 46 can be provided without providing the stepped portion 3 as in the first embodiment.
No rattling in the direction of the flow path occurs. Other components and operation examples are the same as those in the first embodiment, and a description thereof will not be repeated.

As described above, according to the third embodiment, the same effects as those of the first embodiment can be obtained, and the flow path 2 is simpler than the case where the step portion 3 and the projecting portion 5 are not required. With such a shape, the shape of the mold can be simplified, and the effect of further reducing the manufacturing cost can be obtained.

Embodiment 4 FIG. FIG. 8 is a perspective view schematically showing a body of a flow meter according to Embodiment 4 of the present invention.
Is a horizontal sectional view of the body including the central axis of the flow path, and FIG. 10 is a vertical sectional view of the body including the central axis of the flow path. As shown in FIG. 8, the cross section of the flow channel 2 is formed in a square shape.
Further, as shown in FIG. 9, the cross-sectional area of the flow path 2 on the inlet side is formed larger than the cross-sectional area of the outlet side, and the distance between the upper inner wall and the lower inner wall of the flow path 2 is from the inlet side to the outlet side. Is formed in a tapered shape with a gradient of about 1 degree so as to decrease toward. Then, as shown in FIG. 10, the side walls of the flow path 2 are formed in parallel. Note that a rectifying member (not shown) having a shape that can be inserted into the flow path 2 without a gap can be provided near the inlet of the flow path 2. Other components and operation examples are the same as those in the first embodiment, and a description thereof will not be repeated.

As described above, according to the fourth embodiment, the same effect as that of the first embodiment can be obtained, and moreover, the flow path 2 does not need the step portion 3 and the projecting portion 5 and is simpler. With such a shape, the shape of the mold can be simplified, and the effect of further reducing the manufacturing cost can be obtained.

[0034]

As described above, according to the present invention, the cross-sectional area on the inlet side of the flow path is formed to be larger than the cross-sectional area on the outlet side, and the cross-sectional area of the flow path increases from the inlet side. Since at least a part of the flow path is formed in a tapered shape so as to decrease toward the outlet side, the mold can be easily pulled out from the flow path after molding, and the injection molding method or the die casting method can be used. There is an effect that it can be manufactured easily and at low cost. In addition, since the flow path is formed in a tapered shape, the flow of the fluid to be measured is restricted, and the flow velocity distribution can be kept uniform by inhibiting the development of the boundary layer. is there. Furthermore, even if the flow path is formed by hollowing out the block member without using injection molding or the like, the taper direction is only one direction,
There is also an effect that cutting can be easily performed.

According to the present invention, since the protrusion for holding the outer peripheral portion of the rectifying member provided in the inlet side flow path is provided on the inner wall of the inlet side flow path, the rectifying member rattles. As a result, the flow of the fluid to be measured passing through the rectifying member is not disturbed, and the flow rate can be accurately detected.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view showing a flow meter according to Embodiment 1 of the present invention.

FIG. 2 is a front view showing a protruding portion as viewed from an inlet direction of a flow channel.

FIG. 3 is an enlarged sectional view showing a structure near a protrusion.

FIG. 4 is an exploded perspective view showing a flow meter.

FIG. 5 is a vertical sectional view schematically showing a body and a flow path of a flow meter according to a second embodiment of the present invention.

FIG. 6 is a front view showing a protruding portion as viewed from an inlet direction of the flow channel.

FIG. 7 is a vertical sectional view schematically showing a body of a flow meter according to Embodiment 3 of the present invention.

FIG. 8 is a perspective view schematically showing a body of a flow meter according to Embodiment 4 of the present invention.

FIG. 9 is a horizontal sectional view of a body including a central axis of a flow path.

FIG. 10 is a vertical sectional view of a body including a central axis of a flow path.

FIG. 11 is a sectional view showing a flow meter disclosed by the present applicant in Japanese Patent Application Laid-Open No. 9-68448.

FIG. 12 is a sectional view showing another flow meter disclosed in Japanese Patent Application Laid-Open No. 9-68448 by the present applicant.

[Explanation of symbols]

 2 Flow path 4 Spacer (rectifying member) 5 Projection 6 Rectifying wire mesh (rectifying member) 8 Sensor unit (flow rate sensor)

Claims (2)

[Claims] 1. A flowmeter having a flow path through which a fluid to be measured flows and a flow rate sensor provided in the flow path and detecting a flow rate of the fluid to be measured, wherein a cross-sectional area on an inlet side of the flow path is determined by an outlet. And at least a portion of the flow path is formed in a tapered shape such that the cross-sectional area of the flow path decreases from the inlet side toward the outlet side. Flow meter. 2. The flowmeter according to claim 1, wherein a protrusion for holding an outer peripheral portion of the rectifying member provided in the inlet side flow path is provided on an inner wall of the inlet side flow path.