JP6026963B2 - Flow sensor and flow detection system - Google Patents

Description

  The present invention relates to a differential pressure type flow rate sensor used for detecting a flow rate of a fluid flowing in a flow path, and a flow rate detection system including the same.

  A flow velocity sensor that measures a flow velocity based on a change in resistance of a piezoresistive layer provided in the cantilever portion by providing a detection portion having a cantilever portion in a bypass passage, elastically deforming the cantilever portion by a differential pressure in the flow passage Is known (see, for example, Patent Document 1).

JP 2012-145356 A

  The flow velocity sensor has a problem that when the pressure of the fluid applied to the cantilever portion increases, the linearity between the pressure and the resistance change amount of the piezoresistive layer is lost.

  Moreover, since the detection part of said flow-velocity sensor has an up-and-down asymmetric shape, there exists a problem that the sensitivity of a cantilever part will change with the directions through which the fluid flows even if it is the same pressure.

  The problem to be solved by the present invention is to provide a flow rate sensor and a flow rate detection system capable of enlarging the area where the flow rate can be accurately detected and improving the symmetry of sensitivity with respect to the direction of fluid flow. is there.

  [1] A flow sensor according to the present invention is a flow sensor used for detecting a flow rate of a fluid flowing through a main flow path, and has at least one element group including a pair of differential pressure detection elements. And a branch channel provided with the differential pressure detection element, the pair of differential pressure detection elements according to the flow of the fluid. The beam portions of the pair of differential pressure detecting elements are opposite to each other in the branch flow path so as to receive the fluid at opposite surfaces. The flow rate of the fluid is detected based on the output of the bridge circuit.

  [2] In the above invention, one of the differential pressure detection elements may be disposed closer to the one communication port than the other differential pressure detection element in the branch flow path.

  [3] In the above invention, the flow sensor includes a support substrate provided in the branch channel so as to have a through hole and to face the communication port, and the differential pressure detecting element overlaps the through hole. As described above, the differential pressure detection element may be provided on a surface of the support substrate opposite to the surface facing the communication port.

  [4] In the above invention, the differential pressure detecting element includes an opening and a base portion that supports the beam portion, and the beam portion is cantilevered by the base portion so as to protrude into the opening. May be.

  [5] In the above invention, the flow rate sensor may further include a flow rate calculation means for calculating the flow rate of the fluid based on an output of the bridge circuit.

  [6] A flow rate detection system according to the present invention includes the flow rate sensor and flow rate calculation means for calculating the flow rate of the fluid based on an output of the bridge circuit.

  According to the present invention, at least one element group composed of a pair of differential pressure detection elements is provided, and the beam portion of the pair of differential pressure detection elements is divided so as to receive the fluid on opposite surfaces. They are placed in opposite directions in the road.

  For this reason, the pressure received by each differential pressure detection element is reduced, and the area where the linearity between the pressure and the resistance change amount of the piezoresistive layer is relatively expanded relatively increases, so that the flow rate can be accurately set. The detectable area is enlarged.

  In addition, since the asymmetry of the shape of the beam portion with respect to the direction in which the fluid flows is offset, the symmetry of the sensitivity of the flow sensor is also improved.

FIG. 1 is a cross-sectional view showing the overall configuration of a flow rate detection system in an embodiment of the present invention. FIG. 2 is a circuit diagram showing an equivalent circuit of the flow rate detection system in the embodiment of the present invention. FIG. 3A is a plan view of the differential pressure detection element in the embodiment of the present invention, and FIG. 3B is a cross-sectional view taken along the line IIIB-IIIB in FIG. FIG. 4A is a plan view showing a modification of the differential pressure detecting element in the embodiment of the present invention, and FIG. 4B is a cross-sectional view taken along the line IVB-IVB. FIG. 5A is a graph showing the relationship between the pressure and output of the flow sensor in the embodiment of the present invention, and FIG. 5B is a graph showing the relationship between the pressure and output of the flow sensor in the conventional structure. . FIG. 6 is a diagram illustrating a first modification of the flow sensor according to the embodiment of the present invention. FIG. 7 is a circuit diagram showing a first modification of the bridge circuit in the embodiment of the present invention. FIG. 8 is a circuit diagram showing a second modification of the bridge circuit according to the present invention. FIG. 9 is a diagram showing a second modification of the flow sensor in the embodiment of the present invention. FIG. 10 is a diagram showing a third modification of the flow sensor according to the embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing an overall configuration of a flow rate detection system in the present embodiment, and FIG. 2 is a circuit diagram showing an equivalent circuit of the flow rate detection system in the present embodiment.

  As shown in FIG. 1, the flow rate detection system 1 in the present embodiment is a system that measures the flow rate of a fluid flowing through a main flow path 90, and a flow rate sensor 10 attached to the main flow path 90 and an output of the flow rate sensor 10. And a flow rate calculation device 60 that calculates the flow rate of the fluid based on the above.

  As an example of the fluid flowing through the main channel 90, for example, a gas such as air can be exemplified, but a liquid may be used. FIG. 1 illustrates a situation in which the fluid flows in the main channel 90 from the left side to the right side. However, the direction F of the fluid flow is not particularly limited, and the fluid flows in the main channel 90. Sometimes it flows from the right to the left.

  As shown in FIGS. 1 and 2, the flow sensor 10 includes a housing 20 that forms a branch channel 26 that branches from a main channel 90, and a pair of differential pressure detection elements 50 </ b> A and 50 </ b> B provided in the branch channel 26. And a bridge circuit 40 having an element group composed of:

  As shown in FIG. 1, the housing 20 of the flow sensor 10 includes upper and lower box-shaped portions 21 and 25 and a wiring board 30 interposed between the box-shaped portions 21 and 25. .

  The first box-shaped portion 21 has a main body portion 22 having an internal space and a pair of ports 23 and 24. The first port 23 communicates with the internal space of the main body portion 22 through the first opening 221. The second port 24 also communicates with the internal space of the main body portion 22 through the second opening 222. By connecting the two ports 23 and 24 to the main flow path 90, the internal space of the main body portion 22 communicates with the main flow path 90 via the ports 23 and 24. The pair of ports 23 and 24 in the present embodiment corresponds to an example of a pair of communication ports in the present invention.

  The main body 22 has a third opening 223 at the bottom thereof and a partition wall 224 provided between the first opening 221 and the second opening 222. The partition 224 divides the internal space of the main body 22 into two, and a first space 225 and a second space 226 are formed.

  The second box-shaped portion 25 also has an opening 251 at the top thereof so as to correspond to the third opening 223 of the first box-shaped portion 21. The second box-shaped portion 25 is connected to the first box-shaped portion 21 with the wiring board 30 interposed between the openings 223 and 251.

  Two through holes 31 and 32 are formed in the wiring board 30. The first through hole 31 is provided in the wiring substrate 30 so as to face the first opening 221 of the first box-shaped portion 21. On the other hand, the second through hole 32 is provided to face the second opening 222 of the first box-shaped portion 21.

  Therefore, when the two box-like parts 21 and 25 are connected via the wiring board 30, the first port 23 → the first space 225 → the first through hole 31 → the second branch from the main flow path 90. A branch flow path 26 is formed that returns to the main flow path 90 via the internal space 252 of the box-shaped portion 25 → the second through hole 32 → the second space 226 → the second port 24.

  In addition, a pair of differential pressure detection elements 50 </ b> A and 50 </ b> B are mounted on the wiring board 30. The first differential pressure detecting element 50 </ b> A is disposed on the wiring substrate 30 so as to overlap the first through hole 31, and is accommodated in the first space 225 of the first box-shaped portion 21. On the other hand, the second differential pressure detecting element 50 </ b> B is disposed on the wiring substrate 30 so as to overlap the second through hole 32, and is accommodated in the second space 226 of the first box-shaped portion 21. .

  3A and 3B are a plan view and a cross-sectional view of the differential pressure detecting element in the present embodiment, and FIGS. 4A and 4B are diagrams of the differential pressure detecting element in the present embodiment. It is the top view and sectional drawing which show a modification.

  The configuration of the differential pressure detection elements 50A and 50B will be described below with reference to FIGS. 3 (a) and 3 (b). Since the pair of differential pressure detection elements 50A and 50B have the same configuration, the two differential pressure detection elements 50A and 50B will be collectively referred to as “differential pressure detection element 50”.

  As shown in FIGS. 3A and 3B, the differential pressure detecting element 50 includes a base part 51, a cantilever part 52, and electrodes 53 and 54. It is an element. In addition, the cantilever part 52 in this embodiment is equivalent to an example of the beam part in this invention.

  The base 51 and the cantilever 52 are integrally formed by processing an SOI (Silicon on Insulator) wafer. The base 51 includes a first silicon layer 551, a silicon oxide layer 552, and a second It is comprised with the laminated body which consists of the silicon layer 553 of this. An opening 511 that penetrates the base portion 51 is formed in the base portion 51.

  On the other hand, the cantilever part 52 is composed of a second silicon layer 553 and a pair of piezoresistive layers 521 and 522, and is cantilevered by the base part 51 so as to protrude into the opening 511. In the cantilever portion 52, the second silicon layer 553 is located on the free end side, whereas the piezoresistive layers 521 and 522 are located on the fixed end side, and the outer edge of the cantilever portion 52 and the opening 511 A gap (gap) 524 is secured between the inner wall surface. The gap 524 has a narrow width such that almost no fluid flows in the branch flow path 26 and is not particularly limited. For example, the gap 524 may have a width of about 0.1 [μm] to 10 [μm]. preferable.

  The piezoresistive layers 521 and 522 are formed by doping an n-type or p-type impurity into the second silicon layer 553, and the resistance of the piezoresistive layers 521 and 522 is associated with the elastic deformation of the cantilever portion 52. The value changes. For this reason, in the present embodiment, the piezoresistive layers 521 and 522 are provided at the root portion where the distortion is greatest in the cantilever portion 52, and the cantilever portion 52 is connected to the base portion via the piezoresistive layers 521 and 522. 51 is connected to the periphery of the opening 511.

  The piezoresistive layers 521 and 522 are electrically connected in series via connection leads 523 provided on the cantilever portion 52. Note that a piezoresistive layer may be formed on the entire cantilever 52, and in this case, the connection lead 523 is not necessary.

  The electrodes 53 and 54 are provided on the base portion 51. The first electrode 53 is electrically connected to the first piezoresistive layer 521 through the first lead 531. The second electrode 54 is also electrically connected to the second piezoresistive layer 522 through the second lead 541. As will be described later, the electrodes 53 and 54 are connected to the wiring pattern 33 on the wiring board 30 through the wire bonding 34.

  Instead of the cantilever portion 52, as shown in FIGS. 4 (a) and 4 (b), the both-end support beam 52B is supported by the base portion 51 so as to protrude into the opening 511 of the base portion 51. Also good. The both-end supported beam 52B in this example corresponds to an example of a beam portion in the present invention in the present invention.

  As shown in FIG. 1, the pair of differential pressure detecting elements 50 </ b> A and 50 </ b> B described above are disposed in mutually opposite directions in the diversion channel 26 so that the cantilever portion 52 receives the fluid on opposite surfaces. .

  Specifically, in the present embodiment, the first differential pressure detection element 50 </ b> A is configured such that when the fluid flows in the main flow path 90 in the direction shown in FIG. Is disposed in the diversion channel 26 in such a posture as to be received by the surface 525 (see FIG. 3B). Further, the first differential pressure detecting element 50A is provided in a position relatively closer to the first port 23 than the second differential pressure detecting element 50B in the branch flow path 26.

  On the other hand, the second differential pressure detecting element 50B allows the fluid to flow in the direction shown in FIG. 1 when the fluid flows in the second surface 526 on the lower side of the cantilever portion 52 (see FIG. 3B). ), And is disposed in the branch channel 26 in such a posture as to be received in step (3). In addition, the second differential pressure detecting element 50B is provided in the branch channel 26 at a position relatively closer to the second port 24 than the first differential pressure detecting element 50A.

  When a fluid flows through the main flow path 90, pressure loss occurs due to friction with the wall surface and the like, and the pressure becomes lower toward the downstream side. For this reason, when the fluid flows in the direction shown in FIG. 1, the pressure at the opening 241 of the second port 24 becomes relatively lower than the pressure at the opening 231 of the first port 23. On the other hand, when the fluid flows in a direction opposite to the direction shown in FIG. 1, the pressure at the opening 231 of the first port 23 is relative to the pressure at the opening 241 of the second port 24. It becomes low.

  Due to the pressure difference between the ports 23 and 24, the cantilever portions 52 of the pair of differential pressure detecting elements 50A and 50B are elastically deformed, and the piezoresistive layers 521 and 522 are distorted. Specifically, when the fluid is flowing in the direction shown in FIG. 1, the cantilever portion 52 of the first differential pressure detecting element 50 </ b> A has a first surface 525 (FIG. 3 ( b)), the cantilever portion 52 of the second differential pressure detecting element 50B receives the pressure on the second surface 526 (see FIG. 3B). Bend upward in the figure.

  On the other hand, when the fluid is flowing in the direction opposite to the direction shown in FIG. 1, the cantilever part 52 of the second differential pressure detecting element 50B has the first surface 525 (see FIG. 3B). ), The cantilever portion 52 of the first differential pressure detecting element 50A receives pressure on the second surface 526 (see FIG. 3B) and is bent in the drawing. Bends upward.

At this time, in the present embodiment, since two differential pressure detection elements 50 are provided in the branch flow path 26, the pressure (δ _p / 2) applied to each differential pressure detection element 50 is the first This is half of the differential pressure (δ _p ) generated between the second port 24 and the second port 24. Therefore, as shown in FIG. 5A, the pressure and the resistance change amount of the piezoresistive layers 521 and 522 are compared with the conventional structure using only one differential pressure detecting element (see FIG. 5B). In other words, the region where the linearity with respect to (ie, the output of the bridge circuit 40) is maintained (the “linear region” in FIG. 5A) is relatively widened, so that the region where the flow rate can be accurately detected is expanded.

  FIG. 5A is a graph showing the relationship between the pressure and output of the flow sensor in this embodiment, and FIG. 5B is a graph showing the relationship between the pressure and output of the flow sensor in the conventional structure.

  Further, in the present embodiment, since the cantilever portion 52 is in the reverse orientation, the asymmetry of the shape of the differential pressure detecting element 52 with respect to the fluid flow direction F is also canceled, and therefore, as shown in FIG. As described above, the sensitivity symmetry of the flow sensor 10 is also improved as compared with the conventional structure using only one differential pressure detecting element (see FIG. 5B).

  As shown in FIG. 6, the first and second differential pressure detecting elements 50 </ b> A and 50 </ b> B may be provided on the surface 30 b opposite to the surface 30 a facing the ports 23 and 24 in the wiring board 30. Thus, by providing the differential pressure detecting elements 50A and 50B on the lower surface 30b of the wiring board 30, when dust is mixed in the fluid, the dust adheres to the differential pressure detecting elements 50A and 50B. Can be suppressed. FIG. 6 is a cross-sectional view showing a modification of the flow sensor in the present embodiment.

  In addition, if the pair of differential pressure detection elements 50A and 50B are arranged in opposite directions in one element group, the number of element groups provided in the flow sensor is not particularly limited. For example, two sets of element groups are included. It may be provided in the branch channel 26. In this case, two first through holes 31 and two second through holes 32 are provided in the wiring board 30. Then, for example, the first differential pressure detection element 50 </ b> A is disposed in each of the two first through holes 31, and the second differential pressure detection element 50 </ b> B is disposed in each of the two second through holes 32. By increasing the number of element groups in this way, the region where the flow rate can be accurately detected can be further expanded.

  The above-described differential pressure detection elements 50A and 50B are incorporated in the bridge circuit 40. As shown in FIG. 2, the bridge circuit 40 is configured by electrically connecting a first series circuit 41 and a second series circuit 42 in parallel. The first series circuit 41 is configured by electrically connecting the first fixed resistor 411 and the first differential pressure detecting element 50A in series. The second series circuit 42 is configured by electrically connecting the second fixed resistor 421 and the second differential pressure detecting element 50B in series.

  Note that the configuration of the bridge circuit 40 is not limited to that shown in FIG. 2, and may be configured as shown in FIGS. 7 and 8, for example. 7 and 8 are circuit diagrams showing modifications of the bridge circuit in the present embodiment.

  For example, as shown in FIG. 7, a first series circuit 41B is configured by electrically connecting a first fixed resistor 411 and a second fixed resistor 421 in series, and the first differential pressure detecting element The second series circuit 42B may be configured by electrically connecting 50A and the second differential pressure detecting element 50B in series.

  Alternatively, when two sets of element groups are provided in the branch channel 26 as described above, the first differential pressure detecting elements 50A are electrically connected in series as shown in FIG. 8, for example. One series circuit 41C may be configured, and the second differential circuit 42C may be configured by electrically connecting the second differential pressure detecting elements 50B in series.

  As described above, the first and second differential pressure detection elements 50 </ b> A and 50 </ b> B are mounted on the wiring board 30. Although not particularly illustrated, the first and second fixed resistors 411 and 421 are also mounted on the wiring board 30. As shown in FIG. 1, a wiring pattern 33 is formed on the wiring substrate 30. 2 is connected to the wiring pattern 33 via the wire bonding 34, and the fixed resistors 411 and 421 are soldered to the wiring pattern 33, so that the bridge circuit 40 shown in FIG. It is formed on the wiring board 30. 1 shows the structure of the wiring board 30 in an easy-to-understand manner, the arrangement of the wiring pattern 33 and the wire bonding 34 in FIG. 1 does not match the equivalent circuit shown in FIG.

  Further, the wiring board 30 is provided with an external terminal 35 electrically connected to the wiring pattern 33, and the external terminal 35 is led out from the housing 20 to the outside. In the example illustrated in FIG. 1, only one external terminal 35 is illustrated, but actually, four external terminals 35 </ b> A to 35 </ b> D are provided on the wiring board 30 as illustrated in FIG. 2.

  The external terminals 35 </ b> A to 35 </ b> D of the flow rate sensor 10 described above are connected to the flow rate calculation device 60. The flow rate calculation device 60 is a device that calculates the flow rate of the fluid based on the output of the bridge circuit 40 described above. As shown in FIG. 2, a power source 61, a voltmeter 62, and a flow rate calculation unit 63 are provided. I have.

  The power source 61 is a DC power source that applies a voltage Vi to the first and second series circuits 41 and 42. The power source 61 is connected to the first external terminal 35A and the second external terminal 35B of the bridge circuit 40.

  The voltmeter 62 is connected to the third external terminal 35 </ b> C and the fourth external terminal 35 </ b> D of the bridge circuit 40, and the first connection point 412 of the first series circuit 41 and the first series circuit 42 are connected to each other. The potential difference V between the second connection point 422 can be detected. The first connection point 412 is located between the first fixed resistor 411 and the first differential pressure detecting element 50A in the first series circuit 41, and the second connection point 422 is the second connection point 422. The second series resistor 42 is positioned between the second fixed resistor 421 and the second differential pressure detecting element 50B.

The voltmeter 62 detects the potential difference V based on the following equation (1). In the following formula (1), R ₁ is the resistance value of the first fixed resistor 411, R ₂ is the resistance value of the second fixed resistor 421, and R ₃ is the first differential pressure. is the resistance of the piezoresistive layer 521, 522 of the detection element 50A, _{R 4} is the resistance of the piezoresistive layer 521, 522 of the second differential pressure detecting element 50B.

  The flow rate calculation unit 63 calculates the flow rate of the fluid based on the output of the voltmeter 62. Specifically, since the voltage value V corresponding to the differential pressure between the ports 23 and 24 is output from the voltmeter 62, the flow rate calculation unit 63 uses Hagen-Poiseuille's law expressed by the following equation (2). Based on this voltage value V, the flow rate of the fluid flowing in the main flow path 90 is calculated. Such a flow rate calculation unit 63 can be configured by, for example, a computer, a digital circuit, an analog circuit, or the like.

As an example, the relationship between the flow rate and the differential pressure when the main channel 90 in FIG. 1 is a cylindrical tube and the fluid in the tube is a laminar flow having a Reynolds number of 2000 or less is shown. In such a case, Q in the above equation (2) is the flow rate of the fluid flowing per unit time, a is the radius of the main flow path 90, μ is the viscosity of the fluid, and l is the first flow rate. opening 231 of the port 23 and the distance between the aperture 241 of the second port 24, [delta] _p is the pressure difference detected by the flow sensor 10. The main channel 90 may be provided with a throttling mechanism such as an orifice structure for positively generating a differential pressure, or a rectifying guide.

  As shown in FIG. 6, an electronic component 36 may be provided in the flow rate sensor 10 instead of the flow rate calculation device 60.

  The electronic component 36 is mounted in the vicinity of the differential pressure detecting element 50 on the wiring board 40 and is electrically connected to the bridge circuit 40 via a bonding wire 34 and a wiring pattern 33. The electronic component 36 has a flow rate calculation circuit that calculates the flow rate of the fluid from the output of the bridge circuit 40 using the above formula (2) and outputs the calculation result to the outside.

  Further, since the resistance values of the piezoresistive layers 521 and 522 of the cantilever part 52 change depending on the temperature of the fluid, the electronic component 36 calibrates the output of the differential pressure detecting element 50 according to the temperature of the fluid. You may have a circuit. Since this temperature compensation circuit needs to detect the temperature of the fluid with high accuracy, the electronic component 36 is placed in the two through holes 31 on the lower surface 30b of the wiring board 30 so that the electronic component 36 is in direct contact with the fluid flow. , 32 is preferably arranged.

  Instead of the above-described configuration, the electronic component 36 may measure the differential pressure from the output of the bridge circuit 40 and output the measurement result to the flow rate calculation device 60 as a digital signal or an analog signal. Alternatively, after the electronic component 36 calibrates the measurement result according to the temperature of the fluid, the measurement result may be output to the flow rate calculation device 60.

  As described above, in the present embodiment, since the pair of differential pressure detection elements 50A and 50B are arranged in the branch flow path 26 so that the posture of the cantilever portion 52 is reversed, the flow rate can be accurately detected. The area expands. In addition, since the asymmetry of the shape of the differential pressure detecting element 52 with respect to the fluid flow direction F is offset, the symmetry of the sensitivity of the flow sensor 10 is also improved.

  The embodiment described above is described for facilitating the understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

  For example, the structure of the flow sensor 10 is not limited to the above, and may be a structure as shown in FIGS. 9 and 10 are cross-sectional views showing modifications of the flow sensor in the embodiment.

  For example, like the flow sensor 10 B shown in FIG. 9, two ports 23 and 24 are linearly connected by a pipe 27, and two wiring boards 30 are provided in the pipe 27. While mounting the first differential pressure detecting element 50 </ b> A, the second differential pressure detecting element 50 </ b> B may be mounted on the other wiring board 30.

  Alternatively, as in the flow sensor 10C shown in FIG. 10, the two ports 23 and 24 are linearly connected by a pipe 28, and a single wiring board 30 is provided in the pipe 28, and the wiring board 30 is placed on the wiring board 30. A pair of differential pressure detection elements 50A and 50B may be mounted.

  9 and 10, the first differential pressure detecting element 50 </ b> A is in such a posture that the fluid is received by the first surface 525 (see FIG. 3B) of the cantilever portion 52, 26. On the other hand, the second differential pressure detecting element 50B is arranged in the branch channel 26 in such a posture that the fluid is received by the second surface 526 (see FIG. 3B) of the cantilever portion 52.

  In other words, the pair of differential pressure detection elements 50A and 50B are disposed in the direction opposite to each other in the diversion channel 26 so that the cantilever portion 52 receives the fluid at the opposite surfaces. For this reason, while the area | region which can detect a flow volume correctly expands, the symmetry of the sensitivity of the flow sensor 10 also improves.

DESCRIPTION OF SYMBOLS 1 ... Flow rate detection system 10 ... Flow rate sensor 20 ... Housing | casing 21 ... 1st box-shaped part 23 ... 1st port 24 ... 2nd port 25 ... 2nd box-shaped part 26 ... Split flow path 30 ... Wiring board 31 ... 1st through-hole 32 ... 2nd through-hole 40 ... Bridge circuit 50, 50A, 50B ... Differential pressure detection element 51 ... Base part 511 ... Opening 52 ... Cantilever part 521,522 ... Piezoresistive layer 525 ... 1st Surface 526 ... Second surface 60 ... Flow rate calculation device 90 ... Main flow path

Claims (6)

A flow sensor used to detect a flow rate of a fluid flowing through a main flow path,
A bridge circuit having at least one element group composed of a pair of differential pressure detection elements;
A communication channel capable of communicating with the main channel through a pair of communication ports, and provided with the differential pressure detection element,
The pair of differential pressure detection elements each include a beam portion that is deformable according to the flow of the fluid and has a piezoresistive layer,
The beam portions of the pair of differential pressure detection elements are disposed in opposite directions in the branch flow path so as to receive the fluid at opposite surfaces.
A flow rate sensor, wherein the flow rate of the fluid is detected based on an output of the bridge circuit. The flow sensor according to claim 1,
One said differential pressure detection element is arrange | positioned in the said branch flow path at the one said communicating port side rather than the said other said differential pressure detection element. The flow sensor according to claim 2,
The flow sensor includes a support substrate provided in the branch channel so as to have a through hole and face the communication port.
The differential pressure detection element is mounted on the support substrate so as to overlap the through hole,
The flow rate sensor, wherein the differential pressure detecting element is provided on a surface of the support substrate opposite to a surface facing the communication port. The flow sensor according to any one of claims 1 to 3,
The differential pressure detection element includes a base portion having an opening and supporting the beam portion,
The beam sensor is cantilevered by the base so as to protrude into the opening. The flow sensor according to any one of claims 1 to 4,
The flow sensor further comprises a flow rate calculation means for calculating a flow rate of the fluid based on an output of the bridge circuit. A flow sensor according to any one of claims 1 to 4,
And a flow rate calculation means for calculating the flow rate of the fluid based on the output of the bridge circuit.

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