JP2003194607A - Thermal type flowmeter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal type flowmeter in which measurement output is prevented from being affected by the incident angle of a fluid, and internal leakage can be prevented. <P>SOLUTION: An elbow part 43A bent at 90° is formed in a communication part for communicating a flow passage space 44 with an inlet flow passage 44. A mesh part 51M is provided in a communication part for communicating a main flow passage M with the elbow part 45A. The measurement output is precluded thereby from being affected by the incident angle. A sensor substrate 21 is brought into close contact with a body 41 via seal packing 48 molded integrally with a ring part 48A and a sheet part 48B. Both a leakage to the outside and an internal leakage of the fluid to be measured are prevented thereby. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal type flow meter for measuring a flow rate by using a heating wire. More specifically, the present invention relates to a thermal type flow meter in which the influence of the incident angle of the fluid flowing into the flow meter on the measurement output is eliminated.

[0002]

2. Description of the Related Art Conventionally, as one of thermal type flow meters for measuring a flow rate using a heat wire, there is one which uses a measuring chip manufactured by a semiconductor micromachining processing technique as a sensor section. As this type of thermal flow meter, for example,
Examples include those shown in FIG. The thermal type flow meter 1 of FIG.
In 01, the fluid to be measured that has flowed into the inlet port 102 is rectified by the rectifying mechanism 103, and then the measurement flow path 1
Through the outlet port 105 via 04,
In order to measure the flow rate of the fluid to be measured, the measurement chip 111 connected to the electric circuit 106 is exposed in the measurement channel 104.

In this regard, as shown in FIG. 25, the measuring chip 111 includes a silicon chip 116, in which an upstream temperature sensor 112, a heater 113, a downstream temperature sensor 114, and an ambient temperature sensor 115 (the above-mentioned sensors 112 to 115).
(Corresponding to "heat rays") is provided with semiconductor micromachining processing technology.

Therefore, in the thermal type flow meter 101 of FIG. 24, when the fluid to be measured is not flowing in the measurement channel 104, the temperature distribution of the measurement chip 111 of FIG.
3, the fluid to be measured is the measurement flow path 10
4, the temperature of the upstream temperature sensor 112 decreases and the temperature of the downstream temperature sensor 114 increases.
The symmetry of the temperature distribution of the measurement chip 111 in FIG. 25 collapses according to the flow rate of the fluid to be measured. At this time,
The degree of this collapse appears as a difference in resistance value between the upstream temperature sensor 112 and the downstream temperature sensor 114, so that the flow rate of the fluid to be measured can be measured via the electric circuit 106.

However, the thermal type flow meter 101 shown in FIG.
Then, in the measurement chip 111 of FIG. 25, the six electrodes D1, D2, D3, D4, D5, D6 are provided on the silicon chip 116, and the upstream temperature sensor 112 and the heater 1 are provided.
13, the downstream temperature sensor 114, the ambient temperature sensor 115, and the electric circuit 106 were connected by wire bonding using the six electrodes D1 to D6.

Therefore, in the thermal type flow meter 101 of FIG.
Since the measurement chip 111 is exposed in the measurement pipe 104 and the bonding wire W is interposed in the measurement pipe 104,
When a large flow rate of the measurement target gas flows into the measurement pipe 104, the bonding wire W may be broken due to the wind pressure, and in order to prevent it, a cover mechanism is provided (for example, in Japanese Patent Laid-Open No. 10-2773). "Support 13
a)) had to be taken.

Therefore, in order to solve such a problem, the present applicant uses a measuring chip provided with a heating wire as a sensor part, and relates to a connection between the heating wire of the measuring chip and an electric circuit, a wire. A thermal flowmeter that avoids the use of bonding is proposed in Japanese Patent Application No. 2000-368801.

[0008]

However, in the thermal type flow meter proposed in Japanese Patent Application No. 2000-368801, the output characteristics are affected by the incident angle of the fluid to be measured flowing into the flow meter. Therefore, there is a problem that the output error increases as the measured flow rate increases (see FIG. 12). In the thermal type flow meter 101 of FIG. 24 described above, this problem is solved by providing the rectifying mechanism 103. However, since the rectification mechanism 103 is provided between the inlet port 102 and the measurement flow path 104, the flow meter is increased by that amount.

Further, in the case of measuring a small flow rate in the thermal type flow meter proposed in Japanese Patent Application No. 2000-368801,
The flow rate is measured by closing the main flow path (corresponding to the “bypass flow path” in the claims), but at this time, the fluid to be measured may leak inside the flow meter. When such internal leakage occurs, the flow rate cannot be measured accurately. Therefore, in order to measure a small flow rate with high accuracy, it is necessary to prevent internal leakage.

Therefore, the present invention has been made in order to solve the above-mentioned problems, and there is provided a thermal type flow meter capable of eliminating the influence of the incident angle of the fluid on the measurement output and preventing internal leakage. The challenge is to provide.

[0011]

The thermal type flow meter according to the present invention, which has been made to solve the above-mentioned problems, has a sensor flow path other than a sensor flow path in which a heating wire for measuring a flow rate is installed. In a thermal type flow meter with a bypass flow path for
It is characterized in that it has an elbow portion that connects the inlet flow path through which the fluid flows, the bypass flow path, and the sensor flow path.

In this thermal type flow meter, the fluid to be measured flowing into the flow meter flows through the inlet flow path and is divided into the sensor flow path in which the heating wire is installed and the bypass flow path with respect to the sensor flow path. Here, the inlet passage, the bypass passage, and the sensor passage are communicated with each other by the elbow portion. Therefore, the fluid to be measured that has flowed through the inlet channel, after passing through the elbow portion,
It flows into the sensor channel and the bypass channel. As a result, the flow of the fluid to be measured flowing through the inlet channel is disturbed in the elbow portion, and the flow direction is forcibly changed. For this reason, the fluid to be measured that has passed through the elbow portion is hardly affected by the incident angle. Therefore, the fluid to be measured, which is hardly affected by the incident angle, flows into the sensor channel. Therefore, the measurement output is unlikely to be affected by the incident angle of the fluid to be measured. That is, the output error is suppressed. Also,
Since only the elbow is newly provided, the flowmeter does not become large. The bending angle of the elbow portion may be set to such an angle that the incident angle does not affect the fluid to be measured flowing into the sensor channel.

However, it is desirable that the elbow portion is bent at 90 degrees. This makes it less susceptible to the incident angle of the fluid to be measured on the measurement output, and
This is because the flow of the fluid to be measured can be prevented as much as possible. That is, when the elbow portion is bent at an acute angle, the flow of the fluid to be measured stagnates at the bent portion, which is not preferable. Conversely, when the elbow portion is bent at an obtuse angle, the effect of suppressing the influence of the incident angle is reduced. Is. Further, if the bending angle of the elbow portion is 90 degrees, there is also an advantage that the processing for forming each flow path can be performed very easily.

Further, it is more preferable that a filter is provided at a communication portion between the elbow portion and the bypass flow passage. This is because the influence of the incident angle of the fluid to be measured on the measurement output can be further suppressed. In particular, the filter may be a mesh. By doing this,
This is because the influence of the incident angle of the fluid under measurement flowing into the flowmeter on the measurement output can be almost eliminated. Because the fluid to be measured passes through the mesh,
This is because a large amount of fine turbulence is formed in the flow of the fluid to be measured.

Further, in the thermal type flow meter according to the present invention, a filter in which a plurality of meshes are laminated may be provided between the bypass channel and the sensor channel.

As a result, the fluid to be measured flows into the sensor channel after passing through the laminated filters. Therefore, the flow of the fluid to be measured flowing into the sensor channel is adjusted. This is because the fluid to be measured reduces the turbulence of the flow every time it passes through a plurality of meshes. Therefore, even if the flow of the fluid to be measured flowing into the bypass channel is disturbed, the flow of the fluid to be measured flowing into the sensor channel is adjusted by the filter provided between the bypass channel and the sensor channel. Further, as described above, the flow of the fluid to be measured flowing into the sensor channel is not affected by the incident angle of the fluid to be measured. Therefore, a very stable measurement output can be obtained. Note that it is better to stack the meshes at a predetermined interval rather than directly stacking them. This is because a larger rectifying effect can be obtained.

Further, the thermal type flow meter according to the present invention may have a laminated body in which thin plates having grooves are laminated in the bypass flow passage.

As a result, the bypass flow path is divided into a plurality of small flow paths, and the fluid to be measured flowing into the bypass flow path flows in each groove. Therefore, the flow of the fluid under measurement flowing through the bypass flow path is adjusted. That is, the laminated body serves as a rectifying mechanism. Here, by forming a plurality of grooves in one thin plate, more grooves can be provided in the laminated body, and a greater rectifying effect can be obtained. When forming a plurality of grooves, the grooves may be formed only on one side of the thin plate, or the grooves may be formed on both sides of the thin plate.

As described above, the flow of the fluid to be measured flowing into the sensor channel is not affected by the incident angle of the fluid to be measured. Therefore, a very stable measurement output can be obtained.

Furthermore, in the thermal type flow meter according to the present invention, a shield wall is provided for joining the fluid flowing out from the sensor flow passage and the fluid flowing out from the bypass flow passage in the outlet flow passage formed in the body. The shield wall may be formed by stacking a plurality of shield plates.

As a result, the fluid to be measured flowing out of the sensor flow channel and the fluid to be measured flowing out of the bypass flow channel join together in the outlet flow channel formed in the body. That is, the fluid to be measured outflowing from the sensor channel and the fluid to be measured outflowing from the bypass channel do not merge near the outlet of the sensor channel. That is, the confluence point of the sensor channel and the bypass channel is separated from the heating wire installed in the sensor channel. Therefore, the flow vortex generated at the confluence of the sensor channel and the bypass channel does not disturb the flow of the fluid to be measured in the sensor channel. Further, as described above, the flow of the fluid to be measured flowing into the sensor channel is not affected by the incident angle of the fluid to be measured. Therefore, a very stable measurement output can be obtained.

It should be noted that the shielding wall is large enough to move the vortex of the flow generated at the merging point of the sensor channel and the bypass channel so as not to affect the flow of the fluid to be measured in the sensor channel. All right. Therefore, in some cases, the tip of the shielding wall is located on the upper surface of the outlet channel,
It may be located in the center of the outlet channel.

Here, it is preferable that the outlet channel also be in communication with the bypass channel via the elbow portion. By doing so, the outlet flow passage is not formed on the same straight line as the bypass flow passage, so that the above-described effect obtained by providing the shielding wall becomes greater.

The above-mentioned laminated mesh, laminated body and shielding plate may be combined arbitrarily. This allows
This is because the above effects are synergistically obtained.

In the thermal type flow meter according to the present invention, a substrate on the surface of which an electrode for an electric circuit for connecting to an electric circuit for performing a measurement principle using a heat wire is provided, A bypass chip formed by closely contacting the formed body with a seal packing so as to close the side opening, and a measurement chip provided with a heat ray and a heat ray electrode connected to the heat ray. By bonding the heat wire electrode and the electric circuit electrode and mounting them on the substrate,
A sensor channel formed by a groove provided in at least one of the measurement chip or the substrate, the seal packing, a sheet portion that contacts the measurement chip and the substrate,
And a ring portion arranged in a groove formed along the outer periphery of the side surface opening portion of the body, wherein the seat portion and the ring portion are integrally formed. In the present specification, the “side surface opening” means an opening opened on the side surface of the body (in other words, the surface where the input / output port is not opened) and the surface on which the substrate is mounted.

In such a thermal type flow meter, the heat wire provided on the measuring chip is such that when the measuring chip is mounted on the substrate,
The heat wire electrode provided on the measurement chip and the electric circuit electrode provided on the surface of the substrate are bonded to each other to be connected to an electric circuit for performing the measurement principle using the heat wire. On the other hand, when the substrate is brought into close contact with the body, a bypass flow path is formed inside the body. At this time, since the groove is provided in the substrate or the measurement chip mounted on the substrate, the sensor channel for the bypass channel is also formed inside the body.

Then, the fluid to be measured flowing inside the body is divided into the bypass flow passage and the sensor flow passage according to the cross-sectional area ratio of the bypass flow passage and the sensor flow passage. Therefore, the bypass flow path is closed (fully closed) when measuring a small flow rate.
To be done. Since the heat ray provided on the measurement chip is in the state of being bridged to the sensor flow path, the flow rate of the fluid to be measured flowing through the sensor flow path, by extension, by the electric circuit for performing the measurement principle using the heat ray. The flow rate of the fluid to be measured flowing inside the body can be measured.

Here, when measuring a small flow rate, that is, when the bypass flow passage is closed, it is important to prevent the fluid to be measured from leaking inside the bypass flow passage. The reason is that if such internal leakage occurs, the flow rate of the fluid to be measured cannot be accurately measured.

Therefore, the thermal type flow meter is equipped with a seal packing. Since the ring portion of the seal packing is installed in the groove formed in the body, the seal packing does not move. Therefore, the seat part formed integrally with the ring part does not move. Then, the head of the closing plate for closing the bypass channel is in close contact with one surface of the sheet portion, and the opposite surface of the sheet portion is in close contact with the measurement chip and the substrate. That is, there is no gap between the measuring tip and the closing plate and the measuring tip and the body. Therefore, when the bypass passage is closed, the seat portion of the seal packing completely seals the upper surface of the bypass passage. Moreover, the contact portion between the substrate and the body is completely sealed by the ring portion of the seal packing. That is, the seal packing prevents internal and external leakage of the fluid to be measured. Therefore, since there is no leakage of the fluid to be measured, the flow rate can be measured accurately. In particular, since the internal leakage of the fluid to be measured is prevented, highly accurate flow rate measurement can be performed when measuring a small flow rate.

And, in the sheet portion of the seal packing,
It is desirable that a concave portion be formed in a contact portion with the measurement tip. This is because the adhesion of the sheet portion to the measurement chip and the substrate is enhanced, and internal leakage can be prevented more effectively.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION The most preferred embodiment of the thermal type flow meter of the present invention will be described in detail below with reference to the drawings.

(First Embodiment) First, the first embodiment will be described. Therefore, FIG. 1 shows a schematic configuration of the thermal type flow meter according to the first embodiment. As shown in FIG. 1, the thermal type flow meter 1 according to the present embodiment is roughly classified into a body 41.
And the sensor substrate 21. Then, the sensor substrate 21 is in close contact with the body 41 via the seal packing 48 so as to close the flow path space 44 opening on the upper surface of the body 41. Specifically, the sensor substrate 21
When the substrate holder 31 is screwed to the body 41, the substrate holder 31 comes into close contact with the body 41. As a result, the sensor channel S and the main channel M that is a bypass channel for the sensor channel S are formed. That is, the thermal type flow meter 1 according to the present embodiment is a thermal type flow meter including a sensor flow path and a bypass flow path.

The body 41 has a rectangular parallelepiped shape, as shown in FIGS. 2 is a plan view of the body 41, and FIG. 3 is a sectional view taken along line AA in FIG. An inlet port 42 and an outlet port 46 are formed on both end surfaces of the body 41. An inlet passage 43 is formed from the inlet port 42 toward the center of the body, and an outlet passage 45 is formed from the outlet port 46 toward the center of the body. The inlet channel 4
3 and the outlet channel 45 are formed below the channel space 44.

A flow passage space 44 for forming the main flow passage M and the sensor flow passage S is formed in the upper portion of the body 41. The cross section of the flow path space 44 has a shape in which both short sides of a rectangle are arcuate (semicircle), and an arcuate convex portion 44C is formed in the center thereof. Convex portion 44
C is for positioning the mesh plate 51. Then, a part of the lower surface of the flow path space 44 is provided at the inlet flow path 43.
And communicates with the outlet channel 45. That is, the elbow portions 43A and 4B that are bent at 90 degrees are provided at the communicating portions between the flow passage space 44 and the inlet flow passage 44 and the outlet flow passage 45, respectively.
5A is formed.

As a result, the influence of the incident angle of the fluid to be measured flowing into the inlet channel 43 on the measurement output can be suppressed. This is because the fluid to be measured that has flowed into the inlet flow channel 43 is disturbed by the elbow portion 43A, and the flow is forcibly directed upward (one direction), so that it is less likely to be affected by the incident angle. is there. The bending angle of the elbow portion 43A is set to 90 degrees so that such an effect is great and the flow of the fluid to be measured is prevented as much as possible. Further, if the bending angle of the elbow portion 43A is set to 90 degrees, there is also a manufacturing advantage that the processing for forming each flow path in the body 41 becomes easy. Further, since the elbow portion 43A is only newly provided, the flowmeter does not become large.

In order to suppress the influence of the incident angle of the fluid to be measured on the measurement output, the elbow portion 43A is provided only on the inlet side.
However, in the present embodiment, the elbow portion 45A is also provided on the outlet side. This is to reduce turbulence noise in the measurement output. For more information on this point,
This will be described in the second embodiment.

On the lower surface of the flow path space 44, as shown in FIG.
As shown in, a mesh plate 51 is arranged. The mesh plate 51 is screwed to the body 41 together with the bottom plate 37. As a result, the mesh portion 51M is provided in the communication portion between the main flow passage M and the elbow portion 45A. Here, the mesh plate 51 will be described with reference to FIGS. 4 and 5.
Note that FIG. 4A is a plan view of the mesh plate.
5B is a cross-sectional view taken along the line AA in FIG.
[Fig. 3] is an enlarged view of a mesh portion.

As shown in FIG. 4, the mesh plate 51 has a thickness of 0.3 mm with mesh portions 51M formed at both ends.
It is a thin plate. The projected shape of the mesh plate 51 is the same as the cross-sectional shape of the flow path space 44. The mesh portion 51M has a circular shape with a diameter of 4 mm, and as shown in FIG. 5, the holes (diameter 0.2 mm) forming the mesh have a center-to-center distance of 0.27 mm. That is, the holes are formed so that the centers of the holes are the vertices of an equilateral triangle. The formation of the mesh portion 51M is performed by etching (micromachining process). In addition, the thickness of the mesh portion 51M is thinner than other portions as shown in FIG. 4B, and the thickness thereof is 0.05 to 0.1 mm. In addition, in the mesh portion 51M (right side in FIG. 4) arranged on the outlet side,
A shield 51C is formed. This shield 51C is
It constitutes a part of the shielding wall 47 described in the second embodiment. Therefore, in the present embodiment, the shielding portion 51C may be omitted.

As described above, by providing the mesh portion 51M in the communication portion between the main flow passage M and the elbow portion 45A, the influence of the incident angle of the fluid to be measured flowing into the inlet flow passage 43 on the measurement output is almost eliminated. You can Because
When the fluid to be measured passes through the mesh portion 51M,
This is because very small turbulences are formed in the flow of the fluid to be measured. Further, even if the mesh plate 51 is provided, the flow meter does not become large.

Returning to FIG. 2, a groove 49 is formed on the upper surface of the body 41 along the outer periphery of the flow path space 44. The groove 49 is for mounting the seal packing 48. Here, the seal packing 48 mounted in the groove 49 will be described with reference to FIG. Note that FIG.
6A is a plan view of the seal packing, FIG. 6B is a sectional view taken along the line AA in FIG. 6A, and FIG. 6C is a sectional view taken along the line BB in FIG. 6A. is there.

The seal packing 48 has a ring portion 48A and a seat portion 48B. That is, the ring portion 48A
And the seat portion 48B are integrally molded. The material of the seal packing 48 is fluororubber, NB
Any elastic rubber such as R and silicone rubber may be used. And
A recess 48C is formed in the seat portion 48B so as to fit with the measuring chip 11 described later. As a result, as shown in FIG. 7, the sheet portion 48B comes into close contact with the sensor substrate 21 and the measurement chip 11. Therefore, when the main flow path M is closed, the head portion of the bottom plate 37 comes into close contact with the seat portion 48B. That is, by the seat portion 48B, the measuring tip 11, the body 41 and the measuring tip 11 are
And the gap between the bottom plate 37 disappears. Then, the ring portion 48A of the seal packing 48 is provided with the groove 49 formed in the body 41.
The seal packing 48 does not move because it is attached to the. Therefore, the seat portion 48B also does not move. Seat part 48
This is because B is integrally formed with the ring portion 48A. Therefore, when the main channel M is closed by the bottom plate 37, it is possible to prevent the fluid to be measured from leaking inside the body 41.

Further, the ring portion 48 of the seal packing 48
Since A is mounted in the groove 49 formed in the body 41, the ring portion 48A is arranged along the outer periphery of the fluid flow path 44. Then, in this state, the sensor substrate 21 is brought into close contact with the body 21. Therefore, the ring portion 48A of the seal packing 48 is interposed between the body 21 and the sensor substrate 21. Further, the seal packing 48 does not move as described above. Therefore, the fluid to be measured is prevented from leaking to the outside of the thermal type flow meter 1.

In this way, the ring portion 48A and the seat portion 4 are
By using the seal packing 48 integrally formed with 8B, both external leakage and internal leakage of the fluid to be measured can be prevented.

On the other hand, the sensor substrate 21 outputs the measured flow rate as an electric signal. Therefore, the sensor substrate 2
As shown in FIG. 8, in FIG. 1, a groove 23 is formed in the center of the front surface side (mounting surface side of the body 41) of the printed circuit board 22. And this groove 2
Electrodes 24, 25, 26, 27 for electric circuits are provided on both sides of 3. On the other hand, an electric circuit 32 including electric elements is provided on the back surface side of the printed board 22 (see FIG. 1). Then, in the printed circuit board 22, the electric circuit electrodes 24 to 27 are connected to the electric circuit 32. Further, the measurement chip 11 is mounted on the front surface side of the printed board 22 as described later.

Here, the measuring chip 11 will be described with reference to FIG. 9A is a plan view of the measuring chip, and FIG. 9B is a side view of the measuring chip. The measurement chip 11 is a silicon chip 1 as shown in FIG.
The semiconductor micromachining processing technique is applied to No. 2 and the groove 13 is processed at this time, and the heating wire electrodes 14, 15, 16, 17 are provided on both sides of the groove 13. Further, at this time, the temperature sensor hot wire 18 is extended from the hot wire electrodes 14 and 15 and laid over the groove 13, and the flow velocity sensor hot wire 19 is provided.
Is extended from the heating wire electrodes 16 and 17 and the groove 1
It is erected on top of 3. Further, in the measurement chip 11, the flow rate sensor heating wire 19 is provided on the downstream side of the sensor flow path S, and the run-up section L of the fluid to be measured F2 flowing through the sensor flow path S is provided.
Has been set up for a long time. Fluid to be measured F flowing through the sensor channel S
This is to arrange the flow of 2.

Then, the heating wire electrode 1 of the measuring chip 11 is used.
4, 15, 16, 17 are joined to the respective electrodes 24, 25, 26, 27 (see FIG. 8) for the electric circuit of the sensor substrate 21 by solder reflow, a conductive adhesive, or the like. Are mounted on the sensor substrate 21. Therefore, when the measurement chip 11 is mounted on the sensor substrate 21, the temperature sensor hot wire 18 and the flow velocity sensor hot wire 19 provided on the measurement chip 11 are the hot wire electrodes 14 to 17 of the measurement chip 11 and the sensor substrate 21. Through the electric circuit electrodes 24 to 27 (see FIG. 8) of the sensor substrate 21.
Will be connected to the electric circuit 32 (see FIG. 1) provided on the back side of the.

When the measuring chip 11 is mounted on the sensor substrate 21, the groove 13 of the measuring chip 11 overlaps the groove 23 of the sensor substrate 21A. Therefore, as shown in FIG. 1, when the sensor substrate 21 on which the measurement chip 11 is mounted is brought into close contact with the body 41 via the seal packing 48, the sensor substrate 21 and the measurement chip 11 are separated from each other in the channel space 44 of the body 41. An elongated sensor flow path S including the groove 13 of the measurement chip 11 and the groove 23 of the sensor substrate 21 is formed therebetween. Therefore, the temperature sensor heating wire 18 and the flow velocity sensor heating wire 19 are provided in the sensor flow path S so as to cross the bridge.

Next, the operation of the thermal type flow meter 1 having the above structure will be described. In the thermal type flow meter 1,
As shown in FIG. 1, the inlet channel 4 is connected through the inlet port 42.
The fluid to be measured (F in FIG. 1) that has flown into the flow path 3
At 4, the flow is divided into a flow into the main flow path M (F1 in FIG. 1) and a flow into the sensor flow path S (F2 in FIG. 1). Then, the fluids to be measured flowing out from the main flow passage M and the sensor flow passage S join together and flow out from the outlet port 46 to the outside of the body 41 via the outlet flow passage 45 (F in FIG. 1).

Here, the fluid to be measured (F in FIG. 1) that has flowed into the inlet passage 43 is disturbed in the elbow portion 43A, and the flow direction is forcibly changed upward. Further, it passes through the mesh portion 51M. For this reason,
A large number of minute turbulences are formed in the flow of the fluid to be measured. As a result, the fluid to be measured flowing into the sensor channel S is not affected by the incident angle of the fluid to be measured flowing into the inlet channel 43.

The fluid to be measured (F2 in FIG. 1) flowing through the sensor flow path S draws heat from the temperature sensor heating wire 18 and the flow velocity sensor heating wire 19 bridged in the sensor flow path S.
Then, the electric circuit provided on the back surface side of the sensor substrate 21 causes the temperature sensor heating wire 18 and the flow velocity sensor heating wire 19 to move.
While detecting outputs such as, the temperature sensor hot wire 18 and the flow velocity sensor hot wire 19 are controlled to have a constant temperature difference.

The flow range of the thermal type flow meter 1 is changed by changing the height of the bottom plate 37. For example, to set the minimum flow rate range (0.5 l / min), as shown in FIG.
To close. In this way, the flow rate range can be changed by changing the cross-sectional area of the main flow path M, while the cross-sectional area of the sensor flow path S is constant, and the measured fluid flowing into the main flow path M (FIG. 1 F1) flow rate and sensor flow path S
This is because the flow rate of the fluid to be measured (F1 in FIG. 1) flowing in changes.

FIG. 11 shows an example of the output of the thermal type flow meter 1 at this time. In the graph of FIG. 11, in the thermal type flow meter 1 of the present embodiment, the flow rate of the fluid to be measured flowing into the inlet port 42 of the body 41 is 0.5 (l / min),
1 (l / min), 2 (l / min), 3 (l / mi)
n), 4 (l / min), 5 (l / min), 6 (l / min)
min), 7 (l / min), 8 (l / min), 9
It shows the influence (output error) on the measurement output by the incident angle at (l / min) and 10 (l / min). Further, the graph of FIG. 12 shows the output error of each flow rate under the same conditions as described above in the thermal flowmeter before improvement (proposed by the applicant of the present application in Japanese Patent Application No. 2000-368801). .

Comparing FIG. 11 and FIG. 12, the thermal type flow meter 1 of the present embodiment is compared with the thermal type flow meter before improvement.
It can be seen that the output error is small. Specifically, while the output error in the thermal flow meter before improvement was "± 10%", the output error in the thermal flow meter 1 of the present embodiment was "± 1.5%". became. That is, the output error is about 1
It became / 7. As described above, in the thermal type flow meter 1, the influence of the incident angle of the fluid to be measured is less likely to appear in the measurement output. That is, since the thermal type flow meter 1 is hardly affected by the incident angle of the fluid to be measured, it can be said that the flexibility of piping to the flow meter is very high.

Then, in the case of setting the minimum flow rate range of the thermal type flow meter 1 to 0.5 (l / min), FIG.
As shown in, the main plate M is closed by the bottom plate 37.
At this time, in the thermal type flow meter 1, the head portion of the bottom plate 37 is in close contact with the seat portion 48B of the seal packing 48. Moreover, the seat portion 48B does not move as described above. Therefore, in the thermal type flow meter 1, the fluid to be measured does not leak in the main flow passage M when the main flow passage M is closed. As a result, it is possible to accurately measure the small flow rate.

As described in detail above, according to the thermal type flow meter 1 according to the first embodiment, the elbow portion bent at 90 degrees is provided at the communicating portion between the flow passage space 44 and the inlet flow passage 44. 43
A is formed. As a result, the fluid to be measured that has flowed into the inlet passage 43 is disturbed in the elbow portion 43A,
And the direction of the flow can be forcibly changed upward. Therefore, it becomes difficult for the incident angle to affect the flow of the fluid to be measured flowing through the sensor channel. That is, the influence of the measurement output due to the incident angle is suppressed.

Further, a mesh portion 51M is provided at the communicating portion between the main flow passage M and the elbow portion 45A. For this reason, the fluid to be measured passes through the mesh portion 51M, so that a large amount of fine turbulence is formed in the flow of the fluid to be measured. As a result, the influence of the incident angle on the flow of the fluid to be measured flowing through the sensor flow channel is less likely to occur. Therefore, the incident angle has almost no influence on the measurement output.

Thus, in the thermal type flow meter 1, the inlet flow path 4
3 to connect the main flow path M (and the sensor flow path S) with each other 9
An elbow portion 43A bent at 0 degrees is provided, and a mesh portion 51M is arranged at a communication portion between the elbow portion 43A and the main flow passage M. As a result, even if the incident angle of the fluid to be measured flowing into the inlet channel 42 becomes large, it does not affect the flow of the fluid to be measured flowing through the sensor channel M. Therefore, the measurement output is hardly affected by the incident angle of the fluid to be measured flowing into the inlet channel 42. Moreover, since the elbow portion 43A is only provided and the mesh portion 51M is arranged, the flowmeter does not become large.

Further, according to the thermal type flow meter 1 according to the first embodiment, the sensor substrate 21 is attached to the body 41 via the seal packing 48 in which the ring portion 48A and the seat portion 48B are integrally molded. It is closely attached. The ring portion 48A of the seal packing 48 is mounted in the groove 49 formed in the body 41. Therefore, the ring portion 48A is arranged along the outer circumference of the fluid flow path 44. Therefore, the ring portion 48A of the seal packing 48 is interposed between the body 21 and the sensor substrate 21. This prevents the fluid to be measured from leaking to the outside of the thermal type flow meter 1.

Further, the seat portion 4 of the seal packing 48
A concave portion 48C that fits into the measuring chip 11 is formed in 8B. As a result, the sheet portion 48B comes into close contact with the sensor substrate 21 and the measurement chip 11. Therefore, when the main flow path M is closed, the head portion of the bottom plate 37 is moved to the seat portion 48.
Stick to B. That is, the gaps between the measuring chip 11 and the body 41 and between the measuring chip 11 and the bottom plate 37 are eliminated. Then, the ring portion 48A of the seal packing 48 is attached to the body 41.
Since it is installed in the groove 49 formed in the
The seat portion 48B integrally formed with 8A does not move.
Therefore, when the main channel M is closed by the bottom plate 37, it is possible to prevent the fluid to be measured from leaking inside the body 41.

That is, the ring portion 48A and the seat portion 48
The thermal type flow meter 1 including the seal packing 48 integrally formed with B can prevent both external leakage and internal leakage of the fluid to be measured.

(Second Embodiment) Next, a second embodiment will be described. Therefore, a schematic configuration of the thermal type flow meter according to the second embodiment is shown in FIG. As shown in FIG. 13, the thermal type flow meter 201 according to the second embodiment is
The thermal flowmeter 1 according to the first embodiment has substantially the same structure as that of the thermal type flow meter 1 except that the laminated filter 5 is provided in the flow path space 44.
The difference is that 0 is attached. Therefore, the points different from the first embodiment will be mainly described. Therefore, the same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. Also in the thermal type flow meter 201 of the present embodiment, the effect of providing the elbow portion 43A and the effect of using the seal packing 48 can be obtained as in the first embodiment.

Therefore, the laminated filter 50 is shown in FIG.
4 will be described. As shown in FIG. 14, the laminated filter 50 is made by laminating a total of 11 thin plates of four types. That is, in order from the bottom, the mesh plate 51, the first shield plates 52, 52, 52, 52, the mesh plate 51, the second shield plate 53, the mesh plate 51, the second shield plate 53, the mesh plate 51, and the third shield plate. The plates 54 are laminated and adhered. Each of these shielding plates 52 to 54 has a thickness of 0.5 mm, and each shape is processed (micromachining processing) by etching. The projected shape of each of the shielding plates 52 to 54 is the same as the cross-sectional shape of the flow channel space 44. The projected shape of the mesh plate 51 is also the same as the cross-sectional shape of the flow path space 44 as described above. Therefore, the laminated filter 50 is installed in the flow path space 4
It is designed to be attached to 4 without any gaps.

Here, each shield plate will be described in detail. First, the first shielding plate 52 will be described with reference to FIG. Note that FIG. 15A is a plan view of the first shielding plate, and FIG. 15B is a sectional view taken along line AA in FIG. 15A. The first shield plate 52 is, as shown in FIG. 15, etched so that the outer peripheral portion 52B and the shield portion 52C are left. As a result, the first shield plate 52 is formed with the first opening 61 and the second opening 62. The first shield plate 52 has a thickness of 0.5 mm.

Next, the second shield plate 53 will be described with reference to FIG. 16 (a) is a plan view of the second shielding plate, and FIG. 16 (b) is A- in FIG. 16 (a).
FIG. As shown in FIG. 16, the second shielding plate 53 has an outer peripheral portion 53B, a shielding portion 53C, and a central portion 53D.
Etching is performed so as to leave. That is, an unprocessed portion is left in the center of the first shielding plate 52. Thus, the second shielding plate 53 is formed with the third opening 63, the fourth opening 64, and the second opening 62.

Finally, regarding the third shield plate 54, FIG.
Will be explained. Note that FIG. 17A is a plan view of the third shielding plate, and FIG. 17B is A in FIG. 17A.
FIG. As shown in FIG. 17, the third shielding plate 54 is etched so as to leave the outer peripheral portion 54B and the shielding portion 54C. That is, since the fourth opening 64 is not formed in the second shielding plate 53, the shielding portion 53C and the central portion 53D are integrated to form the shielding portion 54C. As a result, the third opening 63 and the second opening 62 are formed in the third shielding plate 54.

Now, returning to FIG. 13, the mesh plate 51, the first shield plate 52, the second shield plate 53, and the third shield plate 53 as described above.
By mounting the laminated filter 50, which is combined with the shield plate 54 and laminated and adhered as shown in FIG. 14, in the flow path space 44, the first opening 6 provided in the first shield plate 52.
The main flow path M is formed by 1. Also, each thin plate 5
1 to 54, the mesh portion 51 and the first opening portion 6
The 1st and 3rd opening part 63 forms the 1st connection flow path 5 which connects the inlet flow path 43, the main flow path M, and the sensor flow path S.

Then, the elbow portion 43A and the flow path space 44
The mesh portion 51M is arranged in the communication portion with the (main flow passage M). As a result, the effects described in the first embodiment can be obtained. That is, the fluid to be measured flowing into the sensor channel S is not affected by the incident angle of the fluid to be measured flowing into the inlet channel 43.

By mounting the laminated filter 50 in the flow passage space 44, three layers of mesh portions 51M are arranged between the main flow passage M and the sensor flow passage S. The spacing between the mesh portions 51M is 0.7 mm because the mesh plate 51 and the second shielding plate 53 play a role of spacers. As a result, the fluid to be measured whose flow is adjusted every time it passes through each mesh portion 51M can be poured into the sensor flow path S.

In addition, the second connecting flow passage 6 for connecting the main flow passage M and the outlet flow passage 45 by the mesh portion 51, the first opening portion 61, and the fourth opening portion 64 provided in each of the thin plates 51 to 54. Are formed. Furthermore, each thin plate 51-54
By the second opening 62 provided in the, the third communication channel 7 that connects the sensor channel S and the outlet channel 45 is formed. A shielding wall 47 is formed between the second communication channel 6 and the third communication channel 7. This shielding wall 47
Is constituted by the shielding portions 51C, 52C, 53C and 54C provided on the thin plates 51, 52, 53 and 54, respectively. Due to this shielding wall 47, the confluence point of the fluid under measurement flowing out of the sensor channel S and the fluid under measurement flowing out of the main channel M is at the elbow portion 45A and the channel space 4.
It is a communication part with 4.

The outlet channel 45 and the main channel M are connected by the elbow portion 45A. Therefore, the outlet channel 45 is arranged below the main channel M. Therefore, the fluid to be measured flowing out from the sensor channel S and the fluid to be measured flowing out from the main channel M do not merge near the outlet of the sensor channel S. That is, the confluence point of the sensor channel S and the main channel M is kept away from the measurement chip 11 described later. Therefore, the vortex of the flow generated at the confluence of the sensor channel S and the main channel M does not disturb the flow of the fluid to be measured flowing through the portion of the measurement channel 11 in the sensor channel S.

That is, the elbow portion 45A is provided also on the outlet side by forming the above-mentioned shield wall 47 and
This is to increase the effect of preventing the flow vortex generated at the confluence of the main flow path M and the main flow path M from disturbing the flow of the fluid to be measured flowing through the measurement chip 11 in the sensor flow path S.

Then, the thermal type flow meter 20 having the above structure
1, the output was confirmed when the flow rate of the fluid to be measured (F in FIG. 1) flowing into the inlet port 42 of the thermal type flow meter 201 was 10 (l / min). The results are shown in FIGS. 18 and 19. The graph of FIG. 18 shows the output (bridge output) from the thermal type flow meter 1. The graph of FIG. 19 shows the output (amplifier output) after the output from the thermal type flow meter 1 is passed through an electric filter (low-pass filter). 18 and 19, the solid line is the first
The output of the thermal type flow meter 1 according to the embodiment is shown, and the broken line shows the output of the thermal type flow meter before improvement.

As apparent from FIGS. 18 and 19, the second
It can be seen that the thermal flow meter 1 according to the embodiment has a smaller output oscillation width than the thermal flow meter before improvement. Here, when the ratio of the vibration width to the output value is defined as noise, the noise in the thermal flow meter before improvement is “22.36 (% FS)” in FIG.
The noise in the thermal type flow meter 1 according to the embodiment is “2.77 (% FS)”. Further, in FIG. 19, the noise in the thermal type flow meter before improvement is “4.96”.
(% FS) ”, the noise in the thermal type flow meter 1 according to the second embodiment is“ 0.43 (% FS) ”.
Is. That is, according to the thermal type flow meter 1 according to the second embodiment, noise can be reduced to about 1/10.
This is because the flow of the fluid to be measured flowing through the sensor flow path S is very regular as described above.
Regarding the bridge span, the thermal flow meter 1 according to the first embodiment is “0.415 (V)”, and the thermal flow meter before improvement is “0.405 (V)”.

In this way, the laminated filter 50 is installed in the flow path space 4
By mounting the fluid on the sensor channel S, the fluid to be measured can be made to flow through the sensor flow path S with almost no influence of the incident angle, and in which the flow is even. Therefore, the thermal type flow meter 201
The measurement output of is hardly affected by the incident angle and is very stable.

As described above in detail, according to the thermal type flow meter 201 of the second embodiment, the laminated filter 50 is mounted in the flow passage space 44 formed in the body 41. A mesh plate 51 is arranged on the lowermost surface of the laminated filter 50. Therefore, the mesh portion 51M is provided in the communication portion between the main flow passage M and the elbow portion 45A. Then, since the fluid to be measured passes through the mesh portion 51M, a large amount of fine turbulence is formed in the flow of the fluid to be measured. As a result, the influence of the incident angle on the flow of the fluid to be measured flowing through the sensor flow channel is less likely to occur. Therefore, the incident angle has almost no influence on the measurement output.

The thermal type flow meter 201 is also provided with an elbow portion 43A bent at 90 degrees to connect the inlet flow passage 43 and the main flow passage M (and the sensor flow passage S). Further, a mesh portion 51M is arranged in a communication portion between the elbow portion 43A and the main flow passage M. For these reasons, even if the incident angle of the fluid to be measured flowing into the inlet channel 42 becomes large, it does not affect the flow of the fluid to be measured flowing through the sensor channel M. Therefore, the measurement output is hardly affected by the incident angle of the fluid to be measured flowing into the inlet channel 42.

Further, in the laminated filter 50, the three-layered mesh portion 51 arranged between the main flow passage M and the sensor flow passage S is provided.
It has M. Therefore, the fluid to be measured flows into the sensor channel S after passing through the three-layered mesh portion 51M. As a result, the flow of the fluid under measurement flowing into the sensor channel S is adjusted. That is, if the flow of the fluid to be measured flowing into the main flow channel M is disturbed, the fluid to be measured flowing into the sensor flow channel S is prevented by the three-layer mesh portion 51M provided between the main flow channel M and the sensor flow channel S. The flow is adjusted. Moreover, since three layers of the mesh portion 51M are provided,
A larger rectifying effect can be obtained.

Further, the laminated filter 50 is provided with a shielding wall 47 formed by the shielding portions 51C, 52C, 53C and 54C provided on the thin plates 51, 52, 53 and 54 constituting the laminated filter 50. There is. For this reason,
The fluid to be measured flowing out from the sensor flow passage S and the fluid to be measured flowing out from the main flow passage M merge in the outlet flow passage 45 (elbow portion 45A) formed in the body 41. That is, the fluid to be measured flowing out from the sensor channel S and the fluid to be measured flowing out from the main channel M do not merge near the outlet of the sensor channel S. As a result, the confluence of the sensor channel S and the main channel M is kept away from the measurement chip 11. Therefore, the vortex of the flow generated at the confluence of the sensor channel S and the main channel M does not disturb the flow of the fluid to be measured in the sensor channel S.

As described above, the thermal type flow meter 201 is provided with the elbow portion 43A bent at 90 degrees for connecting the inlet flow passage 43 and the main flow passage M (and the sensor flow passage S) to the body 41. By mounting the laminated filter 50 in the formed flow path space 44, the flow of the fluid to be measured in the sensor flow path S is not affected by the incident angle, and the flow is very well regulated. Therefore, a stable measurement output can be obtained without being affected by the incident angle.

(Third Embodiment) Finally, a third embodiment will be described. Therefore, FIG. 20 shows a schematic configuration of the thermal type flow meter according to the third embodiment. As shown in FIG. 20, the thermal type flow meter 301 according to the third embodiment
Has substantially the same configuration as the thermal type flow meter 201 according to the second embodiment, except that a laminated filter 60 is mounted in the flow path space 44 instead of the laminated filter 50. That is, in the thermal type flow meter 301 according to the present embodiment, the laminated filter 60 having a plurality of grooves is mounted in the flow path space 44. In addition, the laminated filter 60
Is different from the laminated filter 50 of the second embodiment in that the mesh portion 51M is not provided. Therefore, the points different from the second embodiment will be mainly described. Therefore, the same components as those in the second embodiment are designated by the same reference numerals and the description thereof will be omitted. Also in the thermal type flow meter 301 of the present embodiment, the effect of providing the elbow portion 43A and the effect of using the seal packing 48 can be obtained as in the first embodiment.

Therefore, the laminated filter 60 is shown in FIG.
This will be described using 1. As shown in FIG. 21, the laminated filter 60 is formed by laminating a total of ten thin plates of three types. That is, in order from the bottom, the mesh plate 51, the groove filters 55, 55, 55, 55, 55, 55, 55, 55,
The third shielding plate 54 is laminated and adhered.

The groove filter 55 is shown in FIG.
Will be explained. 22 (a) is a plan view of the groove filter, and FIG. 22 (b) is A in FIG. 22 (a).
FIG. 22C is a sectional view taken along line A-A, and FIG. 22C is a sectional view taken along line BB in FIG. As shown in FIG. 22, the groove filter 55 is etched so that a groove 55E is formed in the central portion 55D while leaving an outer peripheral portion 55B, a shielding portion 55C, and a central portion 55D. That is, the groove filter 55 includes the central portion 53D of the second shielding plate 53 (see FIG. 16).
The groove 55E is provided in (see). And
In the central portion 55D of the groove filter 55, a total of four grooves 55E are formed, two on each side. The groove 55E has a depth of 0.35 mm and the groove 55E has a width of 0.9 mm. The interval between adjacent grooves is 1.05 mm. The groove filter 55 has a thickness of 0.5 mm.

These mesh plate 51, groove filter 55,
By mounting the laminated filter 60 in which the third shielding plate 54 is laminated and adhered as shown in FIG. 21 in the flow path space 44 formed in the body 41, the elbow portion 43A and the elbow portion 43A are formed as shown in FIG. The mesh portion 51M is arranged in a communication portion with the flow passage space 44 (main flow passage M). As a result, the effects described in the first embodiment can be obtained. That is, the fluid to be measured flowing into the sensor channel S is not affected by the incident angle of the fluid to be measured flowing into the inlet channel 43.

By mounting the laminated filter 60 in the flow passage space 44 formed in the body 41, a large number of fine flow passages are formed in the main flow passage M by the groove 55E formed in the central portion 55D of the groove filter 55. Has been formed. As a result, the fluid to be measured flowing into the main flow path M flows in each groove 55E. Therefore, the flow of the fluid under measurement flowing through the main flow path M is adjusted. Further, in the groove filter 55, the grooves 5 are formed on both sides.
By forming 5E, the laminated body filter 60 can be provided with more grooves 55E, and a greater rectifying effect can be obtained.

The laminated filter 60 includes the thin plates 5
Shields 51C, 54C, 5 provided at 1, 54, 55
There is a shielding wall 47A formed by 5. This shield plate 47A also has the same effect as the shield plate 47 included in the thermal type flow meter 1 according to the first embodiment. That is, the vortex of the flow generated at the confluence of the sensor channel S and the main channel M does not disturb the flow of the fluid to be measured in the sensor channel S.

The thermal type flow meter 30 having the above structure
1 under the same conditions as in the second embodiment (flow rate: 10
(L / min)), the noise at the bridge output is "6.84 (% FS)" and the noise at the amplifier output is "1.42 (% F)".
S) ". Therefore, according to the thermal type flow meter 301 according to the third embodiment, noise can be reduced to about 1/3. The bridge span is "0.679 (V)"
Is. The noise at the bridge output of the thermal flowmeter before improvement is “22.36 (% FS)”, and the noise at the amplifier output is “4.96 (% FS)”.

In this way, the laminated filter 60 is installed in the flow path space 4
By mounting the fluid on the sensor channel S, the fluid to be measured can be made to flow through the sensor flow path S with almost no influence of the incident angle, and in which the flow is even. Therefore, the thermal type flow meter 301
The measurement output of is hardly affected by the incident angle and is very stable.

As described above in detail, according to the thermal type flow meter 301 of the third embodiment, the laminated filter 60 is mounted in the flow passage space 44 formed in the body 41. The mesh plate 51 is arranged on the lowermost surface of the laminated filter 60. Therefore, the mesh portion 51M is provided in the communication portion between the main flow passage M and the elbow portion 45A. Then, since the fluid to be measured passes through the mesh portion 51M, a large amount of fine turbulence is formed in the flow of the fluid to be measured. As a result, the influence of the incident angle on the flow of the fluid to be measured flowing through the sensor channel S is less likely to occur. Therefore, the incident angle has almost no influence on the measurement output.

The thermal type flow meter 301 is also provided with an elbow portion 43A bent at 90 degrees to connect the inlet flow passage 43 and the main flow passage M (and the sensor flow passage S). Further, a mesh portion 51M is arranged in a communication portion between the elbow portion 43A and the main flow passage M. For these reasons, even if the incident angle of the fluid to be measured flowing into the inlet channel 42 becomes large, it does not affect the flow of the fluid to be measured flowing through the sensor channel M. Therefore, the measurement output is hardly affected by the incident angle of the fluid to be measured flowing into the inlet channel 42.

Further, the laminated filter 60 is provided with a groove 55E which divides the main channel M into a plurality of channels. Therefore, the flow of the fluid to be measured flowing into the main channel M is adjusted. Thereby, the flow of the fluid to be measured in the main channel M does not adversely affect the flow of the fluid to be measured in the sensor channel S. That is, the flow of the fluid to be measured in the sensor channel S is always stable.

Further, the laminated filter 60 is provided with a shielding wall 47A formed by the shielding portions 51C, 54C and 55C provided on the respective thin plates 51, 54 and 55 constituting the laminated filter 60. Therefore, the fluid to be measured flowing out from the sensor channel S and the fluid to be measured flowing out from the main channel M join at the outlet channel 45 (elbow portion 45A) formed in the body 41. That is, the fluid to be measured flowing out from the sensor channel S and the fluid to be measured flowing out from the main channel M do not merge near the outlet of the sensor channel S. As a result, the confluence of the sensor channel S and the main channel M is kept away from the measurement chip 11. Therefore, the vortex of the flow generated at the confluence of the sensor channel S and the main channel M does not disturb the flow of the fluid to be measured in the sensor channel S.

As described above, the thermal type flow meter 301 is provided with the elbow portion 43A bent at 90 degrees for connecting the inlet flow passage 43 and the main flow passage M (and the sensor flow passage S) to the body 41. Since the laminated filter 60 is mounted in the formed flow path space 44, the flow of the fluid to be measured in the sensor flow path S is not affected by the incident angle, and the flow is very well regulated. Therefore, a stable measurement output can be obtained without being affected by the incident angle.

The above-described embodiment is merely an example and does not limit the present invention at all, and it goes without saying that various improvements and modifications can be made without departing from the scope of the invention. For example, in the above-described embodiment, the bottom plate 3 is used as an example of changing the flow rate range.
Although the method of changing the height of 7 has been exemplified, as another method, as shown in FIG. 23, the height of the bottom plate 37 is always constant (that is, the height of the main flow path) and the cross-sectional area is changed. May be. Further, the laminated filter is not limited to the one exemplified above, and may be configured by arbitrarily combining the thin plates 51 to 56.

[0094]

As described above, according to the thermal type flow meter of the present invention, the elbow portion that connects the inlet passage, the sensor passage and the bypass passage is formed. As a result, the fluid flowing into the inlet channel is disturbed in the elbow portion and the flow is forcibly changed. Therefore, the flow of the fluid in the sensor channel is less likely to be affected by the incident angle. Therefore, the influence of the incident angle on the measurement output is almost eliminated.

Further, in the thermal type flow meter according to the present invention, a filter is provided at the communicating portion between the elbow portion and the bypass flow passage. Therefore, the fluid flows through the elbow portion and then passes through the filter. At this time, an extremely large number of fine turbulences are formed in the fluid flow. Therefore, the flow angle of the fluid in the sensor channel is less affected by the incident angle. Therefore, the influence of the incident angle on the measurement output is further suppressed. Moreover, the flowmeter does not become large in order to eliminate the influence of the incident angle.

Further, the thermal type flow meter according to the present invention is provided with a seat portion which comes into contact with the measuring chip and the substrate, and a ring portion which is arranged in a groove formed along the outer periphery of the side surface opening of the body. In addition, a seal packing in which the seat portion and the ring portion are integrally formed is provided. Therefore, when the bypass channel is closed by the closing plate, the sheet portion eliminates gaps between the measuring chip and the closing plate and between the measuring chip and the body, and the upper surface of the bypass channel is completely sealed. Therefore, the internal leakage of the fluid is prevented, and the output characteristics at the time of measuring the small flow rate are stable.

Further, the thermal type flow meter according to the present invention includes a filter provided between the bypass flow passage and the sensor flow passage, a laminated body in which thin plates having grooves formed in the bypass flow passage are laminated, Alternatively, it is provided with at least one shield wall that joins the fluid flowing out from the sensor channel and the fluid flowing out from the bypass channel in the outlet channel formed in the body. This makes it possible to stabilize the flow of fluid in the sensor channel. Therefore, the measured output can be stably obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a thermal type flow meter according to a first embodiment.

FIG. 2 is a plan view of a body.

3 is a cross-sectional view taken along the line AA of FIG.

FIG. 4 is a diagram showing a mesh plate, (a) is a plan view,
(B) is AA sectional drawing.

5 is an enlarged view of the mesh portion of FIG.

6A and 6B are views showing a seal packing, FIG. 6A is a plan view, FIG. 6B is a sectional view taken along line AA, and FIG. 6C is a sectional view taken along line BB.

7 is a cross-sectional view taken along the line AA of FIG.

FIG. 8 is a perspective view of a sensor substrate.

9A and 9B are views showing a measurement chip, FIG. 9A is a plan view, and FIG. 9B is a side view.

FIG. 10 is a diagram showing the shape of the bottom plate when the minimum flow rate range is set.

FIG. 11 is a diagram showing an example of the output of the thermal type flow meter.

FIG. 12 is a diagram showing an example of an output of the thermal type flow meter before improvement.

FIG. 13 is a schematic configuration diagram of a thermal type flow meter according to a second embodiment.

FIG. 14 is an exploded perspective view of a laminated filter.

15A and 15B are views showing a first shielding plate, FIG. 15A is a plan view, and FIG. 15B is a sectional view taken along line AA.

16A and 16B are diagrams showing a second shielding plate, FIG. 16A is a plan view, and FIG. 16B is a sectional view taken along line AA.

17A and 17B are diagrams showing a third shielding plate, FIG. 17A is a plan view, and FIG. 17B is a sectional view taken along line AA.

FIG. 18 is a diagram showing an example of an output (bridge output) of the thermal type flow meter.

FIG. 19 is a diagram similarly showing an example of the output (amplifier output) of the thermal type flow meter.

FIG. 20 is a schematic configuration diagram of a thermal type flow meter according to a third embodiment.

FIG. 21 is an exploded perspective view of a laminated filter.

22A and 22B are views showing a groove filter, FIG. 22A is a plan view, FIG. 22B is a sectional view taken along line AA, and FIG.
FIG.

FIG. 23 is a diagram for explaining another method of changing the flow rate range.

FIG. 24 is a cross-sectional view of a conventional thermal type flow meter.

FIG. 25 is a perspective view of a measuring element used in a conventional heat flow meter.

[Explanation of symbols]

1 Thermal flow meter 41 body 43 Inlet channel 43A Elbow part 44 flow path space 47 Shielding wall 48 seal packing 48A ring part 48B seat section 48C recess 50 laminated filter 51 mesh plate 51M mesh part M Main flow path (bypass flow path) S sensor flow path

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Akiichi Kitagawa             250 Ojiki 2-chome, Komaki City, Aichi Prefecture             Inside the company F term (reference) 2F035 EA03 EA04 EA08

Claims (9)

[Claims] 1. A thermal type flow meter including a sensor flow path in which a heat wire for measuring a flow rate is installed, and a bypass flow path for the sensor flow path, wherein an inlet flow path into which a fluid flows and the bypass flow path. A thermal type flow meter having an elbow portion communicating with the sensor flow path. 2. The thermal type flow meter according to claim 1, wherein the elbow portion is bent at 90 degrees. 3. The thermal type flow meter according to claim 1 or 2, wherein a filter is provided in a communication portion between the elbow portion and the bypass flow passage. 4. The thermal type flow meter according to claim 3, wherein the filter is a mesh. 5. The thermal type flow meter according to claim 1, wherein a filter in which a plurality of meshes are laminated is provided between the bypass flow passage and the sensor flow passage. A thermal type flow meter characterized by that. 6. The heat type flow meter according to claim 1, further comprising a laminated body in which thin plates having grooves are laminated in the bypass flow passage. Flow meter. 7. The thermal flowmeter according to claim 1, wherein a fluid flowing out from the sensor flow path and a fluid flowing out from the bypass flow path are formed in a body. A thermal flow meter, comprising a shielding wall that joins at an outlet channel, wherein the shielding wall is formed by laminating a plurality of shielding plates. 8. A substrate on the surface of which an electric circuit electrode for connecting to an electric circuit for performing a measurement principle using a heat wire is provided, with respect to a body in which a fluid channel having a side opening is formed, A bypass flow path formed by closely contacting the side opening through a seal packing, a measurement tip provided with a heat ray and a heat ray electrode connected to the heat ray, the heat ray electrode and the A sensor flow path formed by a groove provided in at least one of the measurement chip or the substrate by mounting an electrode for an electric circuit on the substrate, and the seal packing is the measurement chip. And a sheet portion that contacts the substrate,
And a ring portion arranged in a groove formed along the outer periphery of the side surface opening portion of the body, wherein the seat portion and the ring portion are integrally formed. Total. 9. The thermal type flow meter according to claim 8, wherein a concave portion is formed in a sheet portion of the seal packing at a contact portion with a measuring chip.