JP3871566B2 - Thermal flow meter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thermal flow meter that measures a flow rate using a hot wire. More specifically, the present invention relates to a thermal flow meter that eliminates the influence on the measurement output due to the incident angle of the fluid flowing into the flow meter.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as one type of thermal flow meter that measures a flow rate using a hot wire, there is one that uses a measurement chip manufactured by a semiconductor micromachining processing technique as a sensor unit. An example of this type of thermal flow meter is shown in FIG. In the thermal flow meter 101 of FIG. 24, the fluid to be measured that has flowed into the inlet port 102 is rectified by the rectifying mechanism 103, and then flows out from the outlet port 105 via the measurement channel 104. In order to measure the flow rate of the measurement fluid, the measurement chip 111 connected to the electric circuit 106 is exposed to the measurement flow path 104.
[0003]
In this regard, as shown in FIG. 25, the measurement chip 111 includes an upstream temperature sensor 112, a heater 113, a downstream temperature sensor 114, and an ambient temperature sensor 115 (the above-described sensors 112 to 115 are “heat rays” as shown in FIG. 25. Etc.) are provided with processing technology for semiconductor micromachining.
[0004]
Therefore, in the thermal flow meter 101 of FIG. 24, when the fluid to be measured does not flow into the measurement flow path 104, the temperature distribution of the measurement chip 111 of FIG. When the fluid is flowing through the measurement flow path 104, the temperature of the upstream temperature sensor 112 decreases and the temperature of the downstream temperature sensor 114 increases, so the symmetry of the temperature distribution of the measurement chip 111 in FIG. It will collapse according to the flow rate of the fluid. At this time, the degree of the 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.
[0005]
However, in the thermal flow meter 101 of FIG. 24, in the measurement chip 111 of FIG. 25, six electrodes D1, D2, D3, D4, D5, D6 are provided on the silicon chip 116, and the upstream temperature sensor 112, heater 113, the downstream temperature sensor 114, the ambient temperature sensor 115 and the electric circuit 106 are connected by wire bonding using the six electrodes D1 to D6.
[0006]
Therefore, in the thermal flow meter 101 of FIG. 24, the measurement chip 111 is exposed in the measurement pipe 104 and the bonding wire W is interposed in the measurement pipe 104. In order to prevent the bonding wire W from being cut due to the wind pressure or the like, it is necessary to take measures such as providing a cover mechanism (for example, “support 13a” of JP-A-10-2773). It was.
[0007]
Therefore, in order to solve such a problem, the present applicant uses a measurement chip provided with a heat ray as a sensor unit, and relates to the connection between the heat wire of the measurement chip and an electric circuit, and uses wire bonding. Japanese Patent Application No. 2000-368801 proposed a thermal flow meter that avoids the above.
[0008]
[Problems to be solved by the invention]
However, in the thermal type flow meter proposed in the above-mentioned 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 flow meter 101 of FIG. 24 described above, this problem is solved by providing the rectifying mechanism 103. However, since the rectifying mechanism 103 is provided between the inlet port 102 and the measurement flow path 104, the flowmeter is increased accordingly.
[0009]
In addition, when measuring a small flow rate in the thermal flow meter proposed in Japanese Patent Application No. 2000-368801, the main flow channel (corresponding to the “bypass flow channel” in the claims) is closed to measure the flow rate. At this time, the fluid to be measured may leak inside the flowmeter. If 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.
[0010]
Accordingly, the present invention has been made to solve the above-described problems, and provides a thermal flow meter capable of eliminating the influence on the measurement output due to the incident angle of the fluid and preventing internal leakage. Is an issue.
[0011]
[Means for Solving the Problems]
The thermal flow meter according to the present invention, which has been made to solve the above problems, has a thermal flow rate provided with a bypass flow path for the sensor flow path in addition to the sensor flow path provided with a hot wire for measuring the flow rate. The meter is characterized by having an elbow portion for communicating the inlet flow channel into which the fluid flows, the bypass flow channel, and the sensor flow channel.
[0012]
In this thermal flow meter, the fluid to be measured that has flowed into the flow meter flows through the inlet flow channel and is divided into a sensor flow channel in which a heat ray is installed and a bypass flow channel with respect to the sensor flow channel. Here, the inlet flow path, the bypass flow path, and the sensor flow path are communicated with each other through the elbow portion. For this reason, the fluid to be measured that has flowed through the inlet flow path flows into the sensor flow path and the bypass flow path after passing through the elbow portion. As a result, the fluid to be measured flowing through the inlet channel is disturbed in the elbow portion, and the direction of the flow is forcibly changed. For this reason, the fluid to be measured that has passed through the elbow part is hardly affected by the incident angle. Therefore, the fluid to be measured that is hardly affected by the incident angle flows into the sensor flow path. Therefore, it is difficult for the measurement output to be affected by the incident angle of the fluid to be measured. That is, output error is suppressed. Moreover, since the elbow part is only newly provided, the flow meter does not become large. The bending angle of the elbow part may be set to an angle that does not affect the incident angle on the fluid to be measured flowing into the sensor flow path.
[0013]
However, it is desirable that the elbow part bends at 90 degrees. By doing so, the influence of the incident angle of the fluid to be measured on the measurement output is hardly affected, and the flow of the fluid to be measured can be prevented as much as possible. That is, if the elbow portion is bent at an acute angle, the flow of the fluid to be measured is undesirably stagnated at the bent portion. Conversely, if the elbow portion is bent at an obtuse angle, the effect of suppressing the influence of the incident angle is reduced. It is. Further, if the elbow portion has a bending angle of 90 degrees, there is an advantage that the processing for forming each flow path can be performed very easily.
[0014]
Furthermore, it is more desirable that a filter is provided at the communication part between the elbow part and the bypass flow path. 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. This is because the influence on the measurement output due to the incident angle of the fluid to be measured flowing into the flowmeter can be almost eliminated. This is because, when the fluid to be measured passes through the mesh, very small disturbances are formed in the flow of the fluid to be measured.
[0015]
In the thermal type flow meter according to the present invention, a filter in which a plurality of meshes are stacked may be provided between the bypass flow path and the sensor flow path.
[0016]
Thereby, the fluid to be measured flows into the sensor flow path after passing through the stacked filters. For this reason, the flow of the fluid to be measured flowing into the sensor flow path is adjusted. This is because the turbulence of the fluid to be measured decreases every time it passes through a plurality of meshes. Therefore, even if the flow of the fluid to be measured flowing into the bypass flow path is disturbed, the flow of the fluid to be measured flowing into the sensor flow path is adjusted by the filter provided between the bypass flow path and the sensor flow path. 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. In addition, it is better to overlap each mesh at a predetermined interval rather than directly. This is because a larger rectifying effect can be obtained.
[0017]
Furthermore, the thermal flow meter according to the present invention may have a laminated body in which thin plates having grooves are laminated in the bypass flow path.
[0018]
Thereby, the bypass channel is divided into a plurality of small channels, and the fluid to be measured flowing into the bypass channel flows through each groove. For this reason, the flow of the fluid to be measured flowing through the bypass channel is adjusted. That is, the laminate is a rectifying mechanism. Here, by forming a plurality of grooves in one thin plate, the stacked body can be provided with more grooves, and a larger rectification effect can be obtained. In addition, when forming a some groove | channel, a groove | channel may be formed only in the single side | surface of a thin plate, and a groove | channel may be formed in both surfaces of a thin plate.
[0019]
As described above, the flow of the fluid to be measured flowing into the sensor flow path is not affected by the incident angle of the fluid to be measured. Therefore, a very stable measurement output can be obtained.
[0020]
Furthermore, in the thermal flow meter according to the present invention, the thermal flow meter has a shielding wall that joins the fluid flowing out from the sensor flow path and the fluid flowing out from the bypass flow path in the outlet flow path formed in the body, The shielding wall may be formed by stacking a plurality of shielding plates.
[0021]
As a result, the fluid to be measured flowing out from the sensor flow path and the fluid to be measured flowing out from the bypass flow path merge at the outlet flow path formed in the body. That is, the fluid to be measured flowing out from the sensor flow path and the fluid to be measured flowing out from the bypass flow path do not merge near the outlet of the sensor flow path. That is, the confluence point of the sensor flow path and the bypass flow path is kept away from the heat ray installed in the sensor flow path. Therefore, the vortex of the flow generated at the confluence of the sensor flow path and the bypass flow path does not disturb the flow of the fluid to be measured in the sensor flow path. 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.
[0022]
Note that the shielding wall has a size that allows the vortex of the flow generated at the confluence point of the sensor flow path and the bypass flow path to keep the confluence point far enough not to affect the flow of the fluid to be measured in the sensor flow path. That's fine. Therefore, the tip of the shielding wall may be located on the upper surface of the outlet channel, or may be located in the center of the outlet channel.
[0023]
Here, the outlet channel is preferably communicated with the bypass channel via the elbow. By doing so, the outlet channel is not formed on the same straight line with respect to the bypass channel, and thus the above-described effect obtained by providing the shielding wall becomes larger.
[0024]
Note that the above-described laminated mesh, laminated body, and shielding plate may be arbitrarily combined. This is because the above-described effects can be obtained synergistically.
[0025]
The thermal flow meter according to the present invention has a substrate on which a circuit electrode connected to an electrical circuit for performing a measurement principle using a hot wire is provided on a surface, and a fluid flow path including a side opening is formed. A measuring chip provided with a bypass channel formed by close contact with a body through a seal packing so as to close a side opening, a heating wire and a heating wire electrode connected to the heating wire is used for heating wire. An electrode and an electric circuit electrode are bonded and mounted on a substrate to provide a sensor flow path formed by a groove provided in at least one of the measurement chip or the substrate, and the seal packing is attached to the measurement chip and the substrate. It has a seat part that contacts and a ring part that is disposed in a groove formed along the outer periphery of the side opening of the body, and the sheet part and the ring part are integrally formed. It is an feature. In the present specification, the “side opening” means an opening that is open on the side of the body (in other words, the surface where the input / output port is not open) and the substrate is mounted.
[0026]
In such a thermal flow meter, when the measurement chip is mounted on the substrate, the heat wire provided on the measurement chip includes a heat wire electrode provided on the measurement chip and an electric circuit electrode provided on the surface of the substrate. Is bonded to an electric circuit for performing a measurement principle using a hot wire. On the other hand, when the substrate is in close contact with the body, a bypass channel is formed inside the body. At this time, since the groove is provided in the substrate or the measurement chip mounted on the substrate, a sensor flow path for the bypass flow path is also formed inside the body.
[0027]
Then, the fluid to be measured flowing inside the body is divided into the bypass channel and the sensor channel according to the cross-sectional area ratio between the bypass channel and the sensor channel. Therefore, the bypass flow path is closed (fully closed) when measuring a small flow rate. And since the heat ray provided in the measurement chip is in a 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 the electric circuit for performing the measurement principle using the heat ray, and consequently The flow rate of the fluid to be measured flowing inside the body can be measured.
[0028]
Here, when measuring a small flow rate, that is, when the bypass channel is closed, it is important to prevent the fluid to be measured from leaking in the bypass channel. This is because when such internal leakage occurs, the flow rate of the fluid to be measured cannot be measured accurately.
[0029]
Therefore, this thermal flow meter is equipped with a seal packing. Since the ring portion of the seal packing is mounted in the groove formed in the body, the seal packing does not move. Accordingly, the seat portion formed integrally with the ring portion does not move. And while the head of the closing plate for closing a bypass channel closely_contact | adheres to the single side | surface of a sheet | seat part, the opposite surface of a sheet | seat part closely_contact | adheres to a measurement chip and a board | substrate. That is, there is no gap between the measurement tip and the closing plate and between the measurement tip and the body. For this reason, when the bypass channel is closed, the upper surface of the bypass channel is completely sealed by the seat portion of the seal packing. In addition, 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 leakage and external leakage of the fluid to be measured. Accordingly, since there is no leakage of the fluid to be measured, the flow rate can be accurately measured. In particular, since internal leakage of the fluid to be measured is prevented, highly accurate flow rate measurement can be performed at the time of small flow rate measurement.
[0030]
And it is desirable for the sheet | seat part of seal packing to form the recessed part in the contact part with a measurement chip | tip. This is because the adhesion of the sheet portion to the measurement chip and the substrate is enhanced, and internal leakage can be more effectively prevented.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a most preferred embodiment that embodies a thermal flow meter of the present invention will be described in detail with reference to the drawings.
[0032]
(First embodiment)
First, the first implementation will be described. Therefore, FIG. 1 shows a schematic configuration of the thermal flow meter according to the first embodiment. As shown in FIG. 1, the thermal flow meter 1 according to the present embodiment is roughly composed of a body 41 and a sensor substrate 21. 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 opened on the upper surface of the body 41. Specifically, the sensor substrate 21 is brought into close contact with the body 41 by fixing the substrate pressing member 31 to the body 41 with screws. Thereby, the main flow path M which is a bypass flow path with respect to the sensor flow path S and the sensor flow path S is formed. That is, the thermal flow meter 1 according to the present embodiment is a thermal flow meter including a sensor flow path and a bypass flow path.
[0033]
Here, as shown in FIGS. 2 and 3, the body 41 has a rectangular parallelepiped shape. 2 is a plan view of the body 41, and FIG. 3 is a cross-sectional view taken along line AA in FIG. The body 41 is formed with an inlet port 42 and an outlet port 46 on both end faces. An inlet channel 43 is formed from the inlet port 42 toward the center of the body. Similarly, an outlet channel 45 is formed from the outlet port 46 toward the center of the body. The inlet channel 43 and the outlet channel 45 are formed below the channel space 44.
[0034]
In addition, a channel space 44 for forming the main channel M and the sensor channel 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 the rectangle are arcuate (semicircle), and an arcuate convex part 44C is formed at the center. The convex portion 44 </ b> C is for positioning the mesh plate 51. A part of the lower surface of the channel space 44 communicates with the inlet channel 43 and the outlet channel 45. That is, elbow portions 43A and 45A bent at 90 degrees are formed at the communication portion between the channel space 44, the inlet channel 44, and the outlet channel 45, respectively.
[0035]
Thereby, the influence on the measurement output by the incident angle of the fluid to be measured flowing into the inlet channel 43 can be suppressed. This is because the fluid to be measured that has flowed into the inlet channel 43 is disturbed by the elbow part 43A, and the flow is forcibly directed upward (in one direction), so that it is not easily affected by the incident angle. is there. The elbow portion 43A has a bending angle of 90 degrees so that such an effect is great and the flow of the fluid to be measured is not disturbed as much as possible. Further, if the bending angle of the elbow portion 43A is 90 degrees, a manufacturing advantage that processing for forming each flow path in the body 41 becomes easy can be obtained. Moreover, since the elbow part 43A is newly provided, the flow meter does not become large.
[0036]
In order to suppress the influence of the incident angle of the fluid to be measured on the measurement output, it is only necessary to provide the elbow portion 43A only on the inlet side, but in this embodiment, the elbow portion 45A is also provided on the outlet side. Yes. This is to reduce turbulence noise in the measurement output. Details of this point will be described in the second embodiment.
[0037]
A mesh plate 51 is disposed on the lower surface of the flow path space 44 as shown in FIG. The mesh plate 51 is screwed to the body 41 together with the bottom plate 37. Thereby, the mesh part 51M is provided in the communication part of the main flow path M and the elbow part 45A. Here, the mesh board 51 is demonstrated using FIG. 4, FIG. 4A is a plan view of the mesh plate, FIG. 4B is a cross-sectional view taken along the line AA in FIG. 4A, and FIG. 5 is an enlarged view of the mesh portion.
[0038]
As shown in FIG. 4, the mesh plate 51 is a thin plate having a thickness of 0.3 mm in which mesh portions 51M are formed at both ends. The projected shape of the mesh plate 51 is the same as the cross-sectional shape of the flow path space 44. The mesh part 51M has a circular shape with a diameter of 4 mm, and is formed so that the distance between the centers of the holes (diameter 0.2 mm) constituting the mesh is 0.27 mm as shown in FIG. That is, the holes are formed so that the centers of the holes are the vertices of the equilateral triangle. The formation of the mesh portion 51M is performed by etching (micromachining process). In addition, the thickness of the mesh part 51M is thinner than other parts as shown in FIG.4 (b), The thickness is 0.05-0.1 mm. Further, a shielding part 51C is formed on the mesh part 51M (on the right side in FIG. 4) arranged on the outlet side. This shielding part 51C constitutes a part of the shielding wall 47 described in the second embodiment. Therefore, in this embodiment, the shielding part 51C may not be provided.
[0039]
Thus, by providing the mesh part 51M at the communication part between the main flow path M and the elbow part 45A, the influence on the measurement output due to the incident angle of the fluid to be measured flowing into the inlet flow path 43 can be almost eliminated. This is because, when the fluid to be measured passes through the mesh part 51M, a great amount of fine disturbances are formed in the flow of the fluid to be measured. Further, the flow meter is not increased by providing the mesh plate 51.
[0040]
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. This 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. 6A is a plan view of the seal packing, FIG. 6B is a cross-sectional view taken along line AA in FIG. 6A, and FIG. 6C is a cross-sectional view taken along line B- in FIG. It is B sectional drawing.
[0041]
The seal packing 48 includes a ring portion 48A and a seat portion 48B. That is, the ring portion 48A and the seat portion 48B are integrally formed. The material of the seal packing 48 may be an elastic rubber such as fluorine rubber, NBR, or silicon rubber. And the recessed part 48C is formed in the sheet | seat part 48B so that it may fit in the measurement chip | tip 11 mentioned later. Thereby, as shown in FIG. 7, the sheet portion 48 </ b> B comes into close contact with the sensor substrate 21 and the measurement chip 11. For this reason, when the main flow path M is closed, the head of the bottom plate 37 is in close contact with the seat portion 48B. That is, the gap between the measurement chip 11 and the body 41 and between the measurement chip 11 and the bottom plate 37 is eliminated by the sheet portion 48B. Since the ring portion 48A of the seal packing 48 is mounted in the groove 49 formed in the body 41, the seal packing 48 does not move. Accordingly, the seat portion 48B does not move. This is because the seat portion 48B is formed integrally with the ring portion 48A. For this reason, when the main channel M is closed by the bottom plate 37, leakage of the fluid to be measured inside the body 41 can be prevented.
[0042]
Further, since the ring portion 48 </ b> A of the seal packing 48 is mounted in the groove 49 formed in the body 41, the ring portion 48 </ b> A is disposed along the outer periphery of the fluid flow path 44. In this state, the sensor substrate 21 is brought into close contact with the body 21. Accordingly, the ring portion 48 </ b> A of the seal packing 48 is interposed in the close contact portion between the body 21 and the sensor substrate 21. Further, as described above, the seal packing 48 does not move. Therefore, the fluid to be measured is prevented from leaking outside the thermal flow meter 1.
[0043]
As described above, by using the seal packing 48 in which the ring portion 48A and the seat portion 48B are integrally formed, both external leakage and internal leakage of the fluid to be measured can be prevented.
[0044]
On the other hand, the sensor substrate 21 outputs the measured flow rate as an electrical signal. For this reason, as shown in FIG. 8, the sensor substrate 21 has a groove 23 formed in the center thereof on the surface side (the mounting surface side to the body 41) of the printed circuit board 22 serving as a base. Electric circuit electrodes 24, 25, 26, and 27 are provided on both sides of the groove 23. On the other hand, an electrical circuit 32 composed of electrical elements is provided on the back side of the printed circuit board 22 (see FIG. 1). 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 surface side of the printed circuit board 22 as described later.
[0045]
Here, the measurement chip 11 will be described with reference to FIG. FIG. 9A is a plan view of the measurement chip, and FIG. 9B is a side view of the measurement chip. As shown in FIG. 9, the measurement chip 11 is obtained by performing a semiconductor micromachining processing technique on the silicon chip 12. At this time, the groove 13 is processed and the hot wire electrodes 14, 15, 16 and 17 are provided on both sides of the groove 13. Further, at this time, the temperature sensor hot wire 18 extends from the hot wire electrodes 14 and 15 and is laid over the groove 13, and the flow velocity sensor hot wire 19 extends from the hot wire electrodes 16 and 17. And is installed on the groove 13. Further, in the measurement chip 11, the flow rate sensor hot 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 F 2 flowing through the sensor flow path S is long. This is for adjusting the flow of the fluid to be measured F2 flowing through the sensor flow path S.
[0046]
Then, the electrodes 14, 15, 16, 17 for the hot wire of the measuring chip 11 are respectively connected to the electrodes 24, 25, 26, 27 (see FIG. 8) for the electric circuit of the sensor substrate 21, solder reflow, conductive adhesive, etc. The measurement chip 11 is mounted on the sensor substrate 21 by bonding at the above. 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 connected to the hot wire electrodes 14 to 17 of the measurement chip 11 and the sensor substrate 21. The electrical circuit electrodes 24 to 27 (see FIG. 8) are connected to an electrical circuit 32 (see FIG. 1) provided on the back side of the sensor substrate 21.
[0047]
When the measurement chip 11 is mounted on the sensor substrate 21, the groove 13 of the measurement chip 11 overlaps with 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 disposed in the flow path space 44 of the body 41. An elongated sensor flow path S composed of the groove 13 of the measuring chip 11 and the groove 23 of the sensor substrate 21 is formed therebetween. Therefore, in the sensor flow path S, the temperature sensor hot wire 18 and the flow velocity sensor hot wire 19 are provided so as to cross the bridge.
[0048]
Then, the effect | action of the thermal type flow meter 1 which has an above-described structure is demonstrated. In the thermal flow meter 1, as shown in FIG. 1, the fluid to be measured (F in FIG. 1) that flows into the inlet channel 43 via the inlet port 42 flows to the main channel M in the channel space 44. The flow is divided into a flow (F1 in FIG. 1) and a flow into the sensor flow path S (F2 in FIG. 1). Then, the fluids to be measured that have flowed out of the main flow path M and the sensor flow path S merge and flow out of the body 41 from the outlet port 46 via the outlet flow path 45 (F in FIG. 1).
[0049]
Here, the fluid to be measured (F in FIG. 1) flowing into the inlet channel 43 is disturbed in the elbow portion 43A and the direction of the flow is forcibly changed upward. Furthermore, it passes through the mesh part 51M. For this reason, very small fine disturbances are formed in the flow of the fluid to be measured. As a result, the fluid under measurement flowing into the sensor channel S is not affected by the incident angle of the fluid under measurement flowing into the inlet channel 43.
[0050]
Then, the fluid to be measured (F2 in FIG. 1) flowing through the sensor flow path S deprives the heat from the temperature sensor hot wire 18 and the flow velocity sensor hot wire 19 bridged in the sensor flow path S. Then, while the electric circuit provided on the back surface side of the sensor substrate 21 detects the outputs of the temperature sensor hot wire 18 and the flow velocity sensor hot wire 19, the temperature sensor hot wire 18 and the flow velocity sensor hot wire 19 are constant. Control the temperature difference.
[0051]
In order to change the flow range in the thermal flow meter 1, the height of the bottom plate 37 is changed. For example, in order to make the minimum flow rate range (0.5 l / min), the main flow path M is closed by the bottom plate 37 as shown in FIG. The flow rate range can be changed in this way because the cross-sectional area of the sensor flow path S is constant, but the cross-sectional area of the main flow path M is changed, and accordingly, the fluid to be measured that flows into the main flow path M (see FIG. This is because the flow rate of F1 of No. 1 and the flow rate of the fluid to be measured (F1 of FIG. 1) flowing into the sensor flow path S change.
[0052]
An example of the output in the thermal type flow meter 1 at this time is shown in FIG. The graph of FIG. 11 shows that 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 in the thermal flow meter 1 of the present embodiment. (L / min), 3 (l / min), 4 (l / min), 5 (l / min), 6 (l / min), 7 (l / min), 8 (l / min), 9 ( It shows the influence (output error) on the measurement output due to the incident angle at the time of (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 above in the thermal flow meter before improvement (proposed by the present applicant in Japanese Patent Application No. 2000-368801). .
[0053]
Comparing FIG. 11 and FIG. 12, it can be seen that the thermal flow meter 1 of the present embodiment has a smaller output error than the thermal flow meter before improvement. Specifically, the output error in the thermal flow meter before improvement was “± 10%”, whereas the output error in the thermal flow meter 1 of the present embodiment was “± 1.5%”. became. That is, the output error was about 1/7. As described above, in the thermal flow meter 1, the influence of the incident angle of the fluid to be measured is difficult to appear in the measurement output. That is, the thermal flow meter 1 is hardly affected by the incident angle of the fluid to be measured, so it can be said that the degree of freedom of piping to the flow meter is very high.
[0054]
And when setting to 0.5 (l / min) which is the minimum flow range of the thermal type flow meter 1, the main flow path M is closed by the bottom plate 37, as shown in FIG. At this time, in the thermal flow meter 1, the head of the bottom plate 37 is in close contact with the seat portion 48 </ b> B of the seal packing 48. Moreover, as described above, the seat portion 48B does not move. Therefore, in the thermal flow meter 1, the fluid to be measured does not leak in the main channel M when the main channel M is closed. Thereby, a small flow rate can be measured with high accuracy.
[0055]
As described above in detail, according to the thermal flow meter 1 according to the first embodiment, the elbow portion 43A bent at 90 degrees is formed in the communication portion between the flow path space 44 and the inlet flow path 44. Has been. Thereby, the fluid to be measured that has flowed into the inlet channel 43 is disturbed in the elbow portion 43A, and the direction of the flow is forcibly changed upward. Therefore, the influence of the incident angle is less likely to occur on the flow of the fluid to be measured flowing through the sensor flow path. That is, the influence of the measurement output due to the incident angle is suppressed.
[0056]
Further, a mesh part 51M is provided at the communication part between the main flow path M and the elbow part 45A. For this reason, since the fluid to be measured passes through the mesh portion 51M, a very large amount of fine disturbance is formed in the flow of the fluid to be measured. Thereby, the influence of the incident angle is less likely to occur in the flow of the fluid to be measured flowing through the sensor flow path. Therefore, the influence on the measurement output by the incident angle is almost eliminated.
[0057]
As described above, the thermal flow meter 1 is provided with the elbow portion 43A bent at 90 degrees for communicating the inlet channel 43 and the main channel M (and the sensor channel S). The mesh part 51M is arranged at the communication part. Thereby, even if the incident angle of the fluid to be measured flowing into the inlet channel 42 is increased, the flow of the fluid to be measured flowing through the sensor channel M is not affected. Therefore, the measurement output is hardly affected by the incident angle of the fluid to be measured flowing into the inlet channel 42. In addition, since the elbow portion 43A is provided and the mesh portion 51M is only disposed, the flowmeter does not increase.
[0058]
Further, according to the thermal flow meter 1 according to the first embodiment, the sensor substrate 21 is brought into close contact with the body 41 via the seal packing 48 in which the ring portion 48A and the seat portion 48B are integrally formed. Yes. A ring portion 48 </ b> A of the seal packing 48 is mounted in a groove 49 formed in the body 41. For this reason, the ring portion 48 </ b> A is disposed along the outer periphery of the fluid flow path 44. Accordingly, the ring portion 48 </ b> A of the seal packing 48 is interposed in the close contact portion between the body 21 and the sensor substrate 21. As a result, the fluid to be measured is prevented from leaking outside the thermal flow meter 1.
[0059]
Further, the seat portion 48B of the seal packing 48 is formed with a recess 48C that fits into the measurement chip 11. Thereby, the sheet part 48 </ b> B comes into close contact with the sensor substrate 21 and the measurement chip 11. For this reason, when the main flow path M is closed, the head of the bottom plate 37 is in close contact with the seat portion 48B. That is, the gap between the measurement chip 11 and the body 41 and between the measurement chip 11 and the bottom plate 37 is eliminated. Since the ring portion 48A of the seal packing 48 is mounted in the groove 49 formed in the body 41, the seat portion 48B formed integrally with the ring portion 48A does not move. Therefore, when the main flow path M is closed by the bottom plate 37, leakage of the fluid to be measured inside the body 41 can be prevented.
[0060]
That is, in the thermal flow meter 1 including the seal packing 48 in which the ring portion 48A and the seat portion 48B are integrally formed, both external leakage and internal leakage of the fluid to be measured can be prevented.
[0061]
(Second Embodiment)
Next, a second embodiment will be described. Therefore, FIG. 13 shows a schematic configuration of the thermal type flow meter according to the second embodiment. As shown in FIG. 13, the thermal flow meter 201 according to the second embodiment has substantially the same configuration as the thermal flow meter 1 according to the first embodiment. 44 is different in that a multilayer filter 50 is attached to 44. For this reason, it demonstrates centering on a different point from 1st Embodiment. Accordingly, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted. In the thermal type flow meter 201 of the present embodiment, the effect obtained by providing the elbow part 43A and the effect obtained by using the seal packing 48 can be obtained in the same manner as in the first embodiment.
[0062]
Therefore, the multilayer filter 50 will be described with reference to FIG. As shown in FIG. 14, the multilayer filter 50 is obtained by laminating a total of 11 sheets of four types of thin plates. That is, in order from the bottom, the mesh plate 51, the first shielding plates 52, 52, 52, 52, the mesh plate 51, the second shielding plate 53, the mesh plate 51, the second shielding plate 53, the mesh plate 51, and the third shielding. A plate 54 is laminated and bonded. Each of these shielding plates 52 to 54 has a thickness of 0.5 mm, and each shape is processed (micromachining) by etching. The projected shapes of the shielding plates 52 to 54 are the same as the cross-sectional shape of the flow path space 44. The projected shape of the mesh plate 51 is also the same as the cross-sectional shape of the channel space 44 as described above. Accordingly, the multilayer filter 50 is mounted in the flow path space 44 without a gap.
[0063]
Here, each shielding plate will be described in detail. First, the first shielding plate 52 will be described with reference to FIG. FIG. 15A is a plan view of the first shielding plate, and FIG. 15B is a cross-sectional view taken along line AA in FIG. As shown in FIG. 15, the first shielding plate 52 is etched so as to leave the outer peripheral portion 52B and the shielding portion 52C. Thereby, the first shielding plate 52 is formed with a first opening 61 and a second opening 62. In addition, the thickness of the 1st shielding board 52 is 0.5 mm.
[0064]
Next, the second shielding plate 53 will be described with reference to FIG. In addition, Fig.16 (a) is a top view of a 2nd shielding board, FIG.16 (b) is AA sectional drawing in Fig.16 (a). As shown in FIG. 16, the second shielding plate 53 is etched so as to leave the outer peripheral portion 53B, the shielding portion 53C, and the central portion 53D. That is, an unprocessed portion is also left in the center of the first shielding plate 52. As a result, a third opening 63, a fourth opening 64, and a second opening 62 are formed in the second shielding plate 53.
[0065]
Finally, the 3rd shielding board 54 is demonstrated using FIG. FIG. 17A is a plan view of the third shielding plate, and FIG. 17B is a cross-sectional view taken along line AA in 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, by not forming the fourth opening 64 in the second shielding plate 53, the shielding part 53C and the central part 53D are integrated to form the shielding part 54C. As a result, a third opening 63 and a second opening 62 are formed in the third shielding plate 54.
[0066]
Returning to FIG. 13, a laminated filter 50 in which the mesh plate 51, the first shielding plate 52, the second shielding plate 53, and the third shielding plate 54 are combined and laminated and bonded as shown in FIG. 14. Is attached to the flow path space 44, so that the main flow path M is formed by the first opening 61 provided in the first shielding plate 52. In addition, the first communication flow for communicating the inlet flow path 43 with the main flow path M and the sensor flow path S by the mesh portion 51, the first opening portion 61, and the third opening portion 63 provided in each of the thin plates 51 to 54. A path 5 is formed.
[0067]
And the mesh part 51M is arrange | positioned in the communication part of 43 A of elbow parts, and the flow path space 44 (main flow path M). Thereby, the effect described in the first embodiment can be obtained. That is, the fluid to be measured that flows into the sensor flow path S is not affected by the incident angle of the fluid to be measured that has flowed into the inlet flow path 43.
[0068]
In addition, by attaching the multilayer filter 50 to the flow path space 44, three layers of mesh portions 51 </ b> M are disposed between the main flow path M and the sensor flow path S. The interval between the mesh portions 51M is 0.7 mm, with the mesh plate 51 and the second shielding plate 53 serving as spacers. Thereby, the fluid under measurement whose flow is adjusted every time it passes through each mesh portion 51M can be poured into the sensor flow path S.
[0069]
In addition, the second communication flow path 6 that connects the main flow path M and the outlet flow path 45 is formed by the mesh portion 51, the first opening 61, and the fourth opening 64 provided in each of the thin plates 51 to 54. ing. Furthermore, a third communication channel 7 that connects the sensor channel S and the outlet channel 45 is formed by the second opening 62 provided in each of the thin plates 51 to 54. A shielding wall 47 is formed between the second communication channel 6 and the third communication channel 7. The 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. The shielding wall 47 serves as a communication portion between the elbow portion 45 </ b> A and the flow path space 44 at the junction of the measured fluid flowing from the sensor flow path S and the measured fluid flowing from the main flow path M.
[0070]
And the outlet flow path 45 and the main flow path M are connected by the elbow part 45A. For this reason, the outlet channel 45 is disposed below the main channel M. Therefore, the fluid to be measured flowing out from the sensor flow path S and the fluid to be measured flowing out from the main flow path M do not merge near the outlet of the sensor flow path S. That is, the junction point of the sensor flow path S and the main flow path M is kept away from the measurement chip 11 described later. Therefore, the vortex of the flow generated at the junction of the sensor flow path S and the main flow path M does not disturb the flow of the fluid to be measured flowing through the measurement chip 11 in the sensor flow path S.
[0071]
In other words, the elbow portion 45A is also provided on the outlet side because the above-described shielding wall 47 is formed, and the vortex of the flow generated at the confluence of the sensor flow path S and the main flow path M is measured in the sensor flow path S. This is to increase the effect of not disturbing the flow of the fluid to be measured flowing through the portion of the chip 11.
[0072]
And the output when the flow volume of the fluid to be measured (F in FIG. 1) flowing into the inlet port 42 of the thermal flow meter 201 was 10 (l / min) was confirmed with the thermal flow meter 201 having the above-described configuration. The results are shown in FIGS. The graph of FIG. 18 shows the output (bridge output) from the thermal flow meter 1. The graph of FIG. 19 shows the output (amplifier output) after passing the output from the thermal flow meter 1 through an electrical filter (low-pass filter). 18 and 19, the solid line indicates the output of the thermal flow meter 1 according to the first embodiment, and the broken line indicates the output of the thermal flow meter before improvement.
[0073]
As is apparent from FIGS. 18 and 19, the thermal flow meter 1 according to the second embodiment has a smaller output vibration width than the thermal flow meter before improvement. Here, if 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 flow meter 1 according to the form is “2.77 (% FS)”. In FIG. 19, the noise in the thermal flow meter before improvement is “4.96 (% FS)”, whereas the noise in the thermal flow meter 1 according to the second embodiment is “0. 43 (% FS) ". That is, according to the thermal flow meter 1 according to the second embodiment, the 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 well-prepared as described above. The bridge span is “0.415 (V)” for the thermal flow meter 1 according to the first embodiment, and “0.405 (V)” for the thermal flow meter before improvement.
[0074]
By mounting the multilayer filter 50 in the flow path space 44 in this way, it is possible to flow a measured fluid that is hardly affected by the incident angle and that has a uniform flow through the sensor flow path S. Therefore, the measurement output of the thermal flow meter 201 is hardly affected by the incident angle and is very stable.
[0075]
As described above in detail, according to the thermal flow meter 201 according to the second embodiment, the multilayer filter 50 is mounted in the flow path space 44 formed in the body 41. A mesh plate 51 is disposed on the lowermost surface of the multilayer filter 50. For this reason, the mesh part 51M is provided in the communication part of the main flow path M and the elbow part 45A. Since the fluid to be measured passes through the mesh portion 51M, a very large amount of fine disturbance is formed in the flow of the fluid to be measured. Thereby, the influence of the incident angle is less likely to occur in the flow of the fluid to be measured flowing through the sensor flow path. Therefore, the influence on the measurement output by the incident angle is almost eliminated.
[0076]
The thermal flow meter 201 is also provided with an elbow portion 43A bent at 90 degrees for communicating the inlet channel 43 and the main channel M (and the sensor channel S). Further, a mesh portion 51M is disposed at a communication portion between the elbow portion 43A and the main flow path M. For these reasons, even if the incident angle of the fluid to be measured flowing into the inlet channel 42 is increased, the flow of the fluid to be measured flowing through the sensor channel M is not affected. Therefore, the measurement output is hardly affected by the incident angle of the fluid to be measured flowing into the inlet channel 42.
[0077]
The multilayer filter 50 includes a three-layer mesh portion 51M disposed between the main flow path M and the sensor flow path S. For this reason, the fluid to be measured flows into the sensor flow path S after passing through the three-layer mesh portion 51M. Thereby, the flow of the fluid to be measured flowing into the sensor flow path S is adjusted. That is, assuming that the flow of the fluid to be measured flowing into the main channel M is disturbed, the three-layer mesh portion 51M provided between the main channel M and the sensor channel S causes the fluid to be measured to flow into the sensor channel S. The flow is trimmed. Moreover, since the mesh part 51M is provided in three layers, a larger rectification effect can be obtained.
[0078]
Furthermore, the multilayer filter 50 includes 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 multilayer filter 50. For this reason, the fluid to be measured flowing out from the sensor flow path S and the fluid to be measured flowing out from the main flow path M merge at the outlet flow path 45 (elbow part 45A) formed in the body 41. That is, the fluid to be measured flowing out from the sensor flow path S and the fluid to be measured flowing out from the main flow path M do not merge near the outlet of the sensor flow path S. Thereby, the junction point of the sensor flow path S and the main flow path M is kept away from the measurement chip 11. Therefore, the vortex of the flow generated at the junction of the sensor flow path S and the main flow path M does not disturb the flow of the fluid to be measured in the sensor flow path S.
[0079]
As described above, the thermal flow meter 201 is provided with the elbow portion 43A bent at 90 degrees for communicating the inlet channel 43 and the main channel M (and the sensor channel S), and is formed in the body 41. Since the multilayer filter 50 is mounted in the 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-ordered. Therefore, a stable measurement output can be obtained without being affected by the incident angle.
[0080]
(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 flow meter 301 according to the third embodiment has substantially the same configuration as that of the thermal flow meter 201 according to the second embodiment. 44 differs in that a multilayer filter 60 is mounted instead of the multilayer filter 50. That is, in the thermal flow meter 301 according to the present embodiment, the multilayer filter 60 having a plurality of grooves is mounted in the flow path space 44. The multilayer filter 60 is also different from the multilayer filter 50 of the second embodiment in that the mesh part 51M is not provided. For this reason, it demonstrates centering on a different point from 2nd Embodiment. Therefore, the same components as those in the second embodiment are denoted by the same reference numerals and description thereof is omitted. In the thermal flow meter 301 of the present embodiment, the effect of providing the elbow part 43A and the effect of using the seal packing 48 can be obtained in the same manner as in the first embodiment.
[0081]
Therefore, the multilayer filter 60 will be described with reference to FIG. As shown in FIG. 21, the multilayer filter 60 is obtained by laminating a total of ten types of thin plates. That is, the mesh plate 51, the groove filters 55, 55, 55, 55, 55, 55, 55, 55 and the third shielding plate 54 are laminated and bonded in order from the bottom.
[0082]
Here, the groove filter 55 will be described with reference to FIG. 22A is a plan view of the groove filter, FIG. 22B is a cross-sectional view taken along the line AA in FIG. 22A, and FIG. 22C is a cross-sectional view taken along the line B- in FIG. It is B sectional drawing. 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 the outer peripheral portion 55B, the shielding portion 55C, and the central portion 55D. That is, the groove filter 55 is provided with a groove 55E in the central portion 53D (see FIG. 16) of the second shielding plate 53. A total of four grooves 55E are formed on the center portion 55D of the groove filter 55, two on each side. The depth of the groove 55E is 0.35 mm, and the width of the groove 55E is 0.9 mm. The interval between adjacent grooves is 1.05 mm. The thickness of the groove filter 55 is 0.5 mm.
[0083]
A laminated filter 60 in which the mesh plate 51, the groove filter 55, and the third shielding plate 54 are laminated and bonded as shown in FIG. 21 is attached to the flow path space 44 formed in the body 41, so that FIG. As shown in FIG. 5, the mesh portion 51M is disposed at the communication portion between the elbow portion 43A and the flow path space 44 (main flow path M). Thereby, the effect described in the first embodiment can be obtained. That is, the fluid to be measured that flows into the sensor flow path S is not affected by the incident angle of the fluid to be measured that has flowed into the inlet flow path 43.
[0084]
Further, by mounting the multilayer filter 60 in the flow path space 44 formed in the body 41, a large number of fine flow paths are formed in the main flow path M by the grooves 55E formed in the central portion 55D of the groove filter 55. Yes. As a result, the fluid to be measured flowing into the main flow path M flows through each groove 55E. For this reason, the flow of the fluid to be measured flowing through the main flow path M is adjusted. Further, in the groove filter 55, by forming the grooves 55E on both surfaces, the multilayer filter 60 can be provided with more grooves 55E, and a larger rectifying effect can be obtained.
[0085]
The multilayer filter 60 includes a shielding wall 47A formed by shielding portions 51C, 54C, 55 provided on the thin plates 51, 54, 55. This shielding plate 47A also has the same effect as the shielding plate 47 provided in the thermal flow meter 1 according to the first embodiment. That is, the vortex of the flow generated at the junction of the sensor flow path S and the main flow path M does not disturb the flow of the fluid to be measured in the sensor flow path S.
[0086]
Then, when the thermal flow meter 301 having the above-described configuration was checked for output under the same conditions (flow rate: 10 (l / min)) as in the second embodiment, the noise at the bridge output was “6.84. (% FS) ”, and the noise at the amplifier output was“ 1.42 (% FS) ”. Therefore, according to the thermal type flow meter 301 concerning 3rd Embodiment, a noise can be made into about 1/3. The bridge span is “0.679 (V)”. The noise at the bridge output of the thermal flow meter before improvement is “22.36 (% FS)”, and the noise at the amplifier output is “4.96 (% FS)”.
[0087]
By mounting the multilayer filter 60 in the flow path space 44 in this way, it is possible to flow a measured fluid that is hardly affected by the incident angle and that has a good flow through the sensor flow path S. Therefore, the measurement output of the thermal flow meter 301 is hardly affected by the incident angle and is very stable.
[0088]
As described above, according to the thermal type flow meter 301 according to the third embodiment, the multilayer filter 60 is mounted in the flow path space 44 formed in the body 41. A mesh plate 51 is disposed on the lowermost surface of the multilayer filter 60. For this reason, the mesh part 51M is provided in the communication part of the main flow path M and the elbow part 45A. Since the fluid to be measured passes through the mesh portion 51M, a very large amount of fine disturbance is formed in the flow of the fluid to be measured. As a result, the influence of the incident angle is less likely to occur in the flow of the fluid to be measured flowing through the sensor flow path S. Therefore, the influence on the measurement output by the incident angle is almost eliminated.
[0089]
The thermal flow meter 301 is also provided with an elbow portion 43A bent at 90 degrees for communicating the inlet channel 43 and the main channel M (and the sensor channel S). Further, a mesh portion 51M is disposed at a communication portion between the elbow portion 43A and the main flow path M. For these reasons, even if the incident angle of the fluid to be measured flowing into the inlet channel 42 is increased, the flow of the fluid to be measured flowing through the sensor channel M is not affected. Therefore, the measurement output is hardly affected by the incident angle of the fluid to be measured flowing into the inlet channel 42.
[0090]
The multilayer filter 60 includes a groove 55E that divides the main channel M into a plurality of channels. For this reason, the flow of the fluid to be measured flowing into the main flow path 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 flow path S is always stable.
[0091]
Further, the multilayer filter 60 is provided with a shielding wall 47A formed by the shielding portions 51C, 54C, and 55C provided on the thin plates 51, 54, and 55 constituting the multilayer filter 60. For this reason, the fluid to be measured flowing out from the sensor flow path S and the fluid to be measured flowing out from the main flow path M merge at the outlet flow path 45 (elbow part 45A) formed in the body 41. That is, the fluid to be measured flowing out from the sensor flow path S and the fluid to be measured flowing out from the main flow path M do not merge near the outlet of the sensor flow path S. Thereby, the junction point of the sensor flow path S and the main flow path M is kept away from the measurement chip 11. Therefore, the vortex of the flow generated at the junction of the sensor flow path S and the main flow path M does not disturb the flow of the fluid to be measured in the sensor flow path S.
[0092]
As described above, the thermal flow meter 301 is provided with the elbow portion 43A bent at 90 degrees that allows the inlet channel 43 and the main channel M (and the sensor channel S) to communicate with each other, and is formed on the body 41. Since the multilayer filter 60 is mounted in the 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-ordered. Therefore, a stable measurement output can be obtained without being affected by the incident angle.
[0093]
It should be noted that the above-described embodiment is merely an example, and does not limit the present invention in any way, and various improvements and modifications can be made without departing from the scope of the invention. For example, in the above-described embodiment, the method of changing the height of the bottom plate 37 is illustrated as an example of changing the flow rate range, but as another method, as shown in FIG. It is also possible to change the cross-sectional area while keeping the length constant (that is, the height of the main flow path). Further, the multilayer filter is not limited to those exemplified above, and can be configured by arbitrarily combining the thin plates 51 to 56.
[0094]
【The invention's effect】
As described above, according to the thermal flow meter of the present invention, the elbow portion that connects the inlet channel, the sensor channel, and the bypass channel is formed. Thereby, the fluid flowing into the inlet channel is disturbed in the elbow portion, and the flow is forcibly changed. Therefore, the flow of fluid in the sensor flow path is not easily affected by the incident angle. Therefore, the influence on the measurement output by the incident angle is almost eliminated.
[0095]
Moreover, the thermal type flow meter according to the present invention is provided with a filter at a communication part between the elbow part and the bypass flow path. For this reason, the fluid passes through the filter after flowing through the elbow portion. At this time, a very large amount of fine turbulence is formed in the fluid flow. Accordingly, the flow of fluid in the sensor flow path is less affected by the incident angle. Therefore, the influence on the measurement output due to the incident angle is further suppressed. Moreover, the flow meter does not become large in order to eliminate the influence of the incident angle.
[0096]
Further, the thermal flow meter according to the present invention is provided with a sheet portion that contacts the measurement chip and the substrate, and a ring portion that is disposed in a groove formed along the outer periphery of the side opening of the body. A seal packing in which a seat portion and a ring portion are integrally formed is provided. For this reason, when the bypass channel is closed by the closing plate, the gap between the measuring chip and the closing plate and the measuring chip and the body is eliminated by the seat portion, and the upper surface of the bypass channel is completely sealed. Accordingly, the internal leakage of the fluid is prevented, and the output characteristics at the time of measuring a small flow rate are stabilized.
[0097]
Further, the thermal flow meter according to the present invention includes a filter provided between the bypass flow path and the sensor flow path, a laminate in which thin plates formed with grooves arranged in the bypass flow path are stacked, or a sensor flow There is provided at least one shielding wall that joins the fluid flowing out from the passage and the fluid flowing out from the bypass channel in an outlet channel formed in the body. Thereby, the flow of the fluid in a sensor channel can be stabilized. Therefore, the measurement output can be obtained stably.
[Brief description of the 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 the body.
3 is a cross-sectional view taken along the line AA in FIG.
4A and 4B are diagrams illustrating a mesh plate, in which FIG. 4A is a plan view and FIG. 4B is a cross-sectional view taken along line AA.
FIG. 5 is an enlarged view of the mesh portion of FIG. 4;
6A and 6B are views showing a seal packing, in which FIG. 6A is a plan view, FIG. 6B is a cross-sectional view along AA, and FIG. 6C is a cross-sectional view along BB.
7 is a cross-sectional view taken along the line AA in FIG.
FIG. 8 is a perspective view of a sensor substrate.
9A and 9B are diagrams showing a measurement chip, where 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 range is set.
FIG. 11 is a diagram showing an example of an output of a thermal flow meter.
FIG. 12 is a diagram showing an example of an output of a thermal 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 multilayer filter.
FIGS. 15A and 15B are diagrams showing a first shielding plate, in which FIG. 15A is a plan view and FIG.
16A and 16B are views showing a second shielding plate, in which FIG. 16A is a plan view and FIG. 16B is a cross-sectional view taken along line AA.
FIGS. 17A and 17B are views showing a third shielding plate, where FIG. 17A is a plan view and FIG. 17B is a cross-sectional view taken along line AA.
FIG. 18 is a diagram showing an example of an output (bridge output) of a thermal flow meter.
FIG. 19 is a diagram similarly showing an example of an output (amplifier output) of a thermal 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 multilayer filter.
22A and 22B are views showing a groove filter, wherein FIG. 22A is a plan view, FIG. 22B is an AA cross-sectional view, and FIG. 22C is a BB cross-sectional view.
FIG. 23 is a diagram for explaining another method of changing the flow range.
FIG. 24 is a cross-sectional view of a conventional thermal 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
44 Channel space
47 Shielding wall
48 Seal packing
48A Ring part
48B seat part
48C recess
50 Multilayer filter
51 mesh board
51M mesh section
M Main channel (Bypass channel)
S Sensor flow path

Claims (9)

In addition to the sensor flow path provided with a heat wire for measuring the flow rate, in the thermal flow meter provided with a bypass flow path for the sensor flow path,
An elbow section for communicating the inlet flow path into which the fluid flows, the bypass flow path and the sensor flow path;
A thermal flow meter , wherein a filter is provided at a communication portion between the elbow portion and the bypass flow path . In the thermal type flow meter according to claim 1,
  The thermal flow meter, wherein the filter is a mesh having a thickness of 0.5 mm or less. In the thermal type flow meter according to claim 2,
  The thermal flow meter, wherein the mesh is formed by etching. In the thermal type flow meter according to any one of claims 1 to 3,
  A thermal flow meter comprising a laminate in which a plurality of meshes are laminated between the bypass channel and the sensor channel. In the thermal type flow meter according to any one of claims 1 to 4.
  The laminated body includes a thin plate in which a groove is formed, and the groove is disposed in the bypass flow path. In the thermal type flow meter according to claim 4 or claim 5,
  The thermal flow meter, wherein the filter is incorporated in the laminate. In the thermal type flow meter according to any one of claims 1 to 6,
A shielding wall for joining the fluid flowing out from the sensor flow path and the fluid flowing out from the bypass flow path in an outlet flow path formed in the body;
The thermal flow meter, wherein the shielding wall is formed by laminating a plurality of shielding plates. In the thermal type flow meter according to any one of claims 1 to 7,
The bypass is a substrate provided on the surface with an electrode for an electric circuit connected to an electric circuit for performing a measurement principle using a flow path heat wire, with respect to a body in which a fluid flow path including a side opening is formed. Formed by close contact through a seal packing so as to close the side opening,
The sensor flow path is formed by mounting a measurement chip provided with a hot wire and a hot wire electrode connected to the hot wire on the substrate by bonding the hot wire electrode and the electric circuit electrode. It is formed by a groove provided in at least one of the chip or the substrate ,
The seal packing is
A sheet portion in contact with the measurement chip and the substrate, and a ring portion disposed in a groove formed along the outer periphery of the side opening of the body,
The thermal flow meter, wherein the seat portion and the ring portion are integrally formed. The thermal flow meter according to claim 8,
A thermal flow meter, wherein a recess is formed in a contact portion with the measurement chip in the sheet portion of the seal packing.

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