JP2018025549A - Flow rate measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the accuracy of detecting a flow rate in a detection surface part in a flow rate measurement device having a restriction part.SOLUTION: In a flow rate measurement device, a restriction part 15u is configured such that the distance between a detection surface part 10 and a passage wall 16a perpendicular to the detection surface part 10 is progressively narrowed in correspondence to closeness to the detection surface part 10 along a flow direction f2. Assuming that a position where the restriction part 15u begins is a start position αu and a position of the restriction part 15u shortest in distance from the detection surface part 10 is an end position βu, an angle formed by a virtual line γu linking the start position αu and the end position βu and the flow direction f2 in the restriction part 15u is larger than 0 degree and smaller than 20 degrees. Thus, since a change of the passage wall 16a in the restriction part 15u is moderated, it is possible to suppress the occurrence of an eddy or a separation in the flow of air near the restriction part 15u. Therefore, in the flow rate measurement device having the restriction part 15u, it is possible to improve the accuracy of detecting a flow rate in the detection surface part 10.SELECTED DRAWING: Figure 3

Description

  The disclosure according to this specification relates to a flow rate measuring device for measuring a flow rate of intake air taken into a vehicle internal combustion engine.

  2. Description of the Related Art Conventionally, a flow rate measuring device including a housing and a flow rate sensor chip described below has been known (for example, see Patent Document 1). The housing has a bypass flow path that takes in part of the air flowing through the intake path of the internal combustion engine. The flow rate sensor chip has a detection surface portion that is arranged in the bypass flow path and generates an electrical signal corresponding to the flow rate of air in the intake path by heat transfer accompanying the air flow velocity flowing through the bypass flow path.

  Here, the detection surface portion is arranged along a flow direction that is a flow of air flowing through the bypass flow path. Further, the bypass channel is narrowed by the throttle portion so that the cross-sectional area perpendicular to the flow direction decreases as the cross-sectional area approaches the detection surface portion along the flow direction.

  Thereby, even when the air flow rate in the intake passage is small, the flow velocity on the detection surface portion can be sufficiently ensured, the heat transfer performance is stabilized, and the flow rate detection accuracy is ensured. However, when the flow path wall in the throttle part changes at a steep angle, vortex and separation occur in the air flow in the vicinity of the throttle part, the air flow is disturbed, and the rectifying effect is reduced. was there.

  In addition, if a vortex is generated in the vicinity of the throttle portion, a flow component in the reverse flow direction is generated in the air flow, pressure loss occurs in the bypass flow path, and the flow rate at the detection surface portion is reduced. . Furthermore, if a vortex is generated in the vicinity of the throttle part, when the throttle part and the detection surface part are close to each other, when a pulsating flow is generated in conjunction with the operation of the piston of the internal combustion engine, the vortex is generated on the detection surface part. This may cause a detection error of the flow rate.

JP 2014-001954 A

  The present disclosure has been made in view of the above problems, and an object of the present disclosure is to improve flow rate detection accuracy in a detection surface portion in a flow rate measuring device having a throttle portion.

  The flow rate measuring device according to the first aspect includes a housing and a flow rate sensor chip described below. The housing has a bypass passage that takes in a part of the air flowing inside the duct. The flow rate sensor chip has a detection surface portion that is arranged in the bypass flow path and generates an electrical signal corresponding to the flow rate of air in the duct by heat transfer with the air flowing through the bypass flow path.

  Here, the detection surface portion is arranged along a flow direction that is a flow of air flowing through the bypass flow path. Further, the bypass channel is narrowed by the throttle portion so that the cross-sectional area perpendicular to the flow direction decreases as the cross-sectional area approaches the detection surface portion along the flow direction.

  Here, the throttle part is a part of the flow path wall facing the detection surface part. The narrowing portion narrows the distance between the detection surface portion perpendicular to the detection surface portion and the flow path wall as it approaches the detection surface portion along the flow direction. Then, if the position where the diaphragm starts is the start point, and the position where the shortest distance from the detection surface of the diaphragm is the end point, the angle formed by the imaginary line connecting the start point and the end point and the flow direction in the diaphragm is 0. Greater than 20 degrees and less than 20 degrees.

  Thereby, since the change of the flow path wall in the throttle part becomes gentle, it is possible to suppress the occurrence of vortex and separation in the air flow near the throttle part. For this reason, it is possible to suppress the disturbance of the air flow in the detection surface portion due to the throttle portion. As a result, in the flow rate measuring device having the throttle portion, the flow rate detection accuracy in the detection surface portion can be improved.

  The flow rate measuring device according to the second aspect includes a housing and a flow rate sensor chip described below. The housing has a bypass passage that takes in a part of the air flowing inside the duct. The flow sensor chip has a detection unit that is arranged in the bypass flow path and generates an electrical signal corresponding to the flow rate of air in the duct. The bypass channel is throttled by the throttle unit so that the cross-sectional area perpendicular to the flow direction decreases as the cross-sectional area approaches the detection unit along the flow direction.

  Here, the throttle part is a part of the flow path wall facing the detection part. If the position where the throttle section starts is the start position, the start position is on the upstream side in the flow direction of the detection section. In addition, the surface of the diaphragm is a flat surface. The angle formed between the surface of the throttle portion and the flow direction at the throttle portion is greater than 0 degree and smaller than 20 degrees.

  Thereby, like the 1st mode, disturbance of the air flow in the detecting part by a restricting part can be controlled. As a result, in the flow rate measuring device having the throttle unit, the flow rate detection accuracy in the detection unit can be improved. In addition, the detection part does not need to be planar.

The flow rate measuring device of the third aspect is
A housing (3) having a bypass flow path (7) for taking in part of the air flowing inside the duct (2);
A flow rate sensor chip (5) having a detection surface portion (10) that is arranged in the bypass flow path and generates an electrical signal corresponding to the flow rate of air in the duct by heat transfer with air flowing through the bypass flow path;
The detection surface portion is arranged along a flow direction (f2) that is a flow of air flowing through the bypass flow path,
In the flow rate measuring device (1), the bypass flow path is throttled by the throttle portions (15, 15u, 15d) so that the cross-sectional area perpendicular to the flow direction decreases as it approaches the detection surface portion along the flow direction.
The throttle part is a part of the flow path wall (16a) facing the detection surface part, and narrows the distance between the detection surface part perpendicular to the detection surface part and the flow path wall as the detection surface part is approached along the flow direction. ,
Assuming that the starting position of the diaphragm portion is the start point position (αu, αd) and the position of the shortest distance from the detection surface portion of the diaphragm portion is the end point position (βu, βd),
An angle (δu, δd) formed by an imaginary line (γu, γd) connecting the start point position and the end point position and the flow direction in the throttle portion is greater than 0 degree and less than 30 degrees.

  According to the 3rd aspect, there can exist an effect similar to the said 1st aspect.

The flow rate measuring device of the fourth aspect is
A housing having a bypass flow path for taking in part of the air flowing inside the duct;
A flow rate sensor chip having a detection unit (18) that is arranged in the bypass flow path and generates an electrical signal corresponding to the flow rate of air in the duct;
The bypass channel is a flow rate measuring device that is throttled by the throttle unit so that the cross-sectional area perpendicular to the flow direction (f2), which is the flow of air flowing through the bypass channel, decreases as it approaches the detection unit along the flow direction. In
The throttle part is a part of the flow path wall facing the detection part,
Assuming that the starting position of the throttle part is the starting point position, this starting point position is on the upstream side in the flow direction of the detecting part,
The surface (17u) of the throttle part is a flat surface, and the angle formed by the flow direction between the surface and the throttle part is larger than 0 degree and not larger than 30 degrees.

  According to the 4th aspect, there exists an effect similar to the said 1st aspect.

The flow rate measuring device of the fifth aspect is
A flow rate measuring device (1) for measuring a flow rate of air,
A bypass passage (7) through which air flows;
A detection unit (10) for outputting an electrical signal corresponding to the flow rate of air in the bypass flow path;
A pair of flow path walls (16a, 16b) facing each other across the detection unit;
In the arrangement direction (X) in which the pair of flow path walls are arranged, a throttle part (15u) for narrowing the bypass flow path by projecting from the flow path wall toward the detection unit;
With
The projecting dimension of the throttle part gradually increases as it approaches the detection part from the upstream side in the bypass flow path,
Assuming that the position of the upstream end of the throttle part is the start point position (αu, αd) and the position of the shortest distance from the detection part of the throttle part is the end point position (βu, βd),
The angle (δu, δd) formed between the virtual line (γu, γd) connecting the start point position and the end point position and the flow direction (f2) that is the flow of air flowing through the bypass flow path is greater than 0 degree and less than 30 degrees is there.

  According to the 5th aspect, there exists an effect similar to the said 1st aspect.

  In addition, the code | symbol in the parenthesis described in a claim and this clause only shows a corresponding relationship with the specific means as described in the Example mentioned later, and does not limit a technical range.

FIG. 1 is an overall view of a flow rate measuring device viewed from the upstream side of an intake air flow (Example 1). (Example 1) which is sectional drawing of the flow volume measuring apparatus along the flow direction of intake air. FIG. 3 is a sectional view taken along line III-III in FIG. 2 (Example 1). It is the graph which showed the relationship between the measurement error and angle in case a vibration frequency is 100 Hz (Example 1). 10 is a graph showing the relationship between measurement error and angle when the vibration frequency is 130 Hz (Example 1). FIG. 4 is a cross-sectional view corresponding to FIG. 3 (Example 2). FIG. 4 is a cross-sectional view corresponding to FIG. 3 (Example 3). FIG. 4 is a cross-sectional view corresponding to FIG. 3 (Example 4). (Example 4) which is sectional drawing which follows the IX-IX line | wire in FIG. (Example 4) which is the graph which showed the relationship between the measurement error and angle in case a pulsation frequency is a 1st frequency. (Example 4) which is the graph which showed the relationship between the measurement error and angle in case a pulsation frequency is a 2nd frequency. FIG. 6 is a cross-sectional view corresponding to FIG. 3 (Example 5). It is sectional drawing corresponding to FIG. 3 (modification). It is sectional drawing corresponding to FIG. 3 (modification). It is explanatory drawing of an end point position (modification). It is sectional drawing corresponding to FIG. 3 (modification). It is sectional drawing of the flow volume measuring apparatus along the flow direction of intake air (modification). It is sectional drawing which follows the XVIII-XVIII line in FIG. 17 (modification).

  Hereinafter, modes for carrying out the present disclosure will be described using examples. In addition, an Example discloses a specific example, and it is needless to say that the present disclosure is not limited to the Example.

[Configuration of Example 1]
A flow rate measuring apparatus 1 according to the first embodiment will be described with reference to FIGS. 1 and 2. The flow rate measuring device 1 is mounted on an intake passage 2 which is a duct through which intake air sucked into an internal combustion engine for a vehicle flows, and measures the flow rate of intake air flowing through the intake passage 2. Hereinafter, the direction in which the intake air flows in the central portion of the intake passage 2 may be referred to as a flow direction f1. The central portion of the intake passage 2 means a central portion where the influence of the wall surface forming the intake passage 2 is small. The flow rate measuring device 1 includes a housing 3 and a flow rate sensor chip 5 described below.

  The housing 3 holds the flow sensor chip 5 and protrudes to the inner periphery of the intake passage 2 through which intake air drawn into the internal combustion engine flows. The housing 3 is provided with a resin material, and a bypass channel 7 is formed therein. Here, the bypass flow path 7 has a sub bypass flow path 9 branched from itself.

  The bypass flow path 7 is a flow path that takes in part of the intake air flowing through the intake path 2 and is formed along the flow direction f1. An intake port 7 a is provided on the upstream side of the bypass flow path 7, and a discharge port 7 b is provided on the downstream side of the bypass flow path 7. A discharge port restrictor 7 c that restricts the flow of intake air passing through the bypass passage 7 is formed on the downstream side of the bypass passage 7.

  The sub-bypass channel 9 is a channel that takes in a part of the intake air flowing through the bypass channel 7 restricted by the outlet restrictor 7c, and an inlet 9a into which a part of the taken-in intake air flows, And an outlet 9b for returning the intake air that has passed through the bypass passage 9 to the intake passage 2. Then, the intake air flowing from the inlet 9a is rotated inside the housing 3 and guided to the outlet 9b. Here, by providing the inlet 9a in a direction different from the flow direction f1, dust, oil, foreign matter and the like contained in the intake passage 2 entering from the intake 7a are separated into the discharge port 7b, and the sub-bypass passage 9 Intrusion of foreign matter or the like into the body can be suppressed.

  The flow sensor chip 5 has a detection surface portion 10 that is sensitive to the flow rate of the intake air on its surface. Here, the detection surface portion 10 is formed in a flat shape, and is a heat transfer type that measures the flow rate by the heat transfer of the intake air that passes through the sub-bypass flow path 9. It has a well-known configuration having a resistor on the surface.

  The detection surface unit 10 generates an electrical signal corresponding to the flow rate of the intake air in the sub-bypass flow path 9, and the flow rate sensor chip 5 sends the electrical signal to an ECU (not shown) via a connection terminal in the connector 11. Etc. That is, the flow sensor chip 5 indirectly outputs an electrical signal corresponding to the flow rate of the intake air in the intake passage 2. Hereinafter, the direction in which the intake air flows in the central portion of the sub-bypass channel 9 may be referred to as a flow direction f2. In addition, the center part of the sub bypass flow path 9 means the center part of the flow path where the influence of the wall surface of the flow path wall forming the sub bypass flow path 9 is small.

  Here, the flow rate sensor chip 5 is supported by the support portion 13 so that the detection surface portion 10 is exposed to the sub-bypass channel 9. More specifically, the flow sensor chip 5 is held by the support portion 13 so that the surface of the detection surface portion 10 is along the flow direction f2. The detection surface portion 10 occupies a partial area on the surface of the flow sensor chip 5. In Example 1, the flow direction f2 in the support portion 13 is the same as the flow direction f1, and the upstream side and the downstream side are opposite.

[Features of Example 1]
Next, a characteristic configuration of the first embodiment will be described with reference to FIG. The sub-bypass passage 9 is restricted by the restriction portion 15 so that the cross-sectional area perpendicular to the flow direction f2 decreases as the cross-sectional area approaches the detection surface portion 10 along the flow direction f2. Here, the throttle unit 15 is a part of the flow channel wall 16 a that forms the sub-bypass channel 9 that faces the detection surface unit 10. Further, the flow path wall facing the flow path wall 16a is defined as a flow path wall 16b. That is, the flow rate sensor chip 5 is supported by the support portion 13 between the pair of flow path walls 16 a and 16 b facing each other. Note that, “approaching the detection surface portion 10” means “approaching the center of gravity of the detection surface portion 10”.

  The narrowing portion 15 narrows the distance between the detection surface portion 10 perpendicular to the detection surface portion 10 and the flow path wall 16a as it approaches the detection surface portion 10 along the flow direction f2. Further, the throttle unit 15 is provided on the upstream side and the downstream side of the detection surface unit 10 in the flow direction f2. Here, the upstream throttle 15 in the flow direction f2 is referred to as a throttle 15u, and the downstream throttle 15 is referred to as a throttle 15d. Here, the upstream side and the downstream side in the flow direction f2 of the detection surface portion 10 mean the upstream side and the downstream side in the flow direction f2 of the center of gravity position of the detection surface portion 10. The diaphragm 15 has a shape that is continuous in the same shape in the vertical direction of the drawing.

  Then, assuming that the starting position of the diaphragm 15u is the start point position αu and the position of the shortest distance from the detection surface 10 of the diaphragm 15u is the end point position βu, a virtual line γu connecting the start point position αu and the end point position βu and the diaphragm unit 15u. The angle δu formed by the flow direction f2 at is greater than 0 degree and smaller than 20 degrees.

  The starting point position αu is the most upstream position in the flow direction f2 of the throttle portion 15u. Further, the distance from the detection surface portion 10 is a distance from the center of gravity of the detection surface portion 10. The shortest distance from the detection surface portion 10 is the shortest distance obtained by adding the distance perpendicular to the detection surface portion 10 between the detection surface portion 10 and the flow path wall 16a in the throttle portion 15u and the distance along the flow direction f2. It means that

  When a plurality of start point positions αu are considered, the start point position αu is a position where the distance from the end point position βu is the shortest distance. Here, the shortest distance between the starting point position αu and the ending point position βu is a distance perpendicular to the detection surface portion 10 between the starting point position αu and the ending point position βu and a distance along the flow direction f2. Means that the distance is the shortest.

  Similarly, assuming that the starting position of the stop 15d is the start position αd and the position of the shortest distance from the detection surface 10 of the stop 15d is the end position βd, a virtual line γd connecting the start position αd and the end position βd and the stop The angle δd formed by the flow direction f2 at 15d is larger than 0 degree and smaller than 20 degrees. Here, the flow direction f2 in the throttle portions 15u and 15d is a direction along the detection surface portion 10. The start position αd is the most downstream position in the flow direction f2 of the throttle portion 15d.

  The surfaces of the throttle portions 15u and 15d are formed of curved surfaces that protrude toward the inner peripheral side of the sub-bypass channel 9. More specifically, the diaphragm unit 15 including the diaphragm units 15 u and 15 d is formed such that a cylindrical side surface with the vertical direction on the paper surface as an axial direction faces the detection surface unit 10.

[Effect of Example 1]
According to the flow rate measuring device 1 of the first embodiment, the sub-bypass channel 9 is throttled by the throttle unit 15u so that the cross-sectional area perpendicular to the flow direction f2 decreases as it approaches the detection surface unit 10 along the flow direction f2. ing. Here, the narrowed portion 15 u is a part of the flow path wall 16 a facing the detection surface portion 10. The narrowed portion 15u narrows the distance between the detection surface portion 10 perpendicular to the detection surface portion 10 and the flow path wall 16a as it approaches the detection surface portion 10 along the flow direction f2.

  Then, assuming that the starting position of the diaphragm 15u is the start point position αu and the position of the shortest distance from the detection surface 10 of the diaphragm 15u is the end point position βu, a virtual line γu connecting the start point position αu and the end point position βu and the diaphragm unit 15u. The angle δu formed by the flow direction f2 at is greater than 0 degree and smaller than 20 degrees.

  Thereby, since the change of the flow path wall 16a in the throttle part 15u becomes gentle, it is possible to suppress the occurrence of vortex and separation in the air flow in the vicinity of the throttle part 15u. For this reason, the disturbance of the air flow in the detection surface part 10 by the aperture | diaphragm | squeeze part 15u can be suppressed. As a result, in the flow rate measuring device 1 having the throttle unit 15u, the flow rate detection accuracy in the detection surface unit 10 can be improved.

  Further, the surface of the throttle portion 15u is formed by a curved surface that protrudes toward the inner peripheral side of the sub-bypass channel 9. Thereby, the cross-sectional area perpendicular to the flow direction f2 can be reduced while keeping the change in the flow direction on the surface of the throttle portion 15u smooth. For this reason, it is possible to suppress the occurrence of vortices and separation in the air flow in the vicinity of the throttle portion 15u, and the pressure loss generated in the sub-bypass channel 9 can be reduced.

  The throttle portions 15u and 15d are provided on the upstream side and the downstream side in the flow direction f2 of the detection surface portion 10, respectively. As a result, not only the upstream side of the detection surface 10 in the flow direction f2 but also the downstream side has the throttle portion 15d, so that the flow rate can be appropriately controlled even when a pulsating flow linked to the operation of the piston of the internal combustion engine occurs. Can be measured. That is, even when a flow from the downstream side to the upstream side occurs, a sufficient flow velocity on the detection surface portion 10 can be secured and the flow rate can be measured appropriately.

  Here, graphs plotting measurement errors when the angle δu is changed are shown in FIGS. When the vibration frequency of the flow rate is low, even if the value of the angle δu is large, the measurement error is small and good follow-up to the increase and decrease of the flow rate is shown (see FIG. 4). However, if the vibration frequency of the flow rate increases, the measurement error increases when the value of the angle δu exceeds 20 degrees, and the followability to increase / decrease in the flow rate is greatly deteriorated (see FIG. 5). This is because vortices and separation easily occur in the air flow as the vibration frequency increases, and the influence of the angle δu on the measurement error increases. The vibration frequency of the flow rate corresponds to the vibration frequency of the pulsating flow generated in conjunction with the operation of the piston of the internal combustion engine, and the frequency when the flow rate increases or decreases with a predetermined amplitude with a predetermined value as the center value. Show.

[Example 2]
A flow measurement device 1 according to the second embodiment will be described with reference to FIG. In the following embodiments, the same functions as those in the first embodiment are denoted by the same reference numerals. In the flow rate measuring device 1 according to the second embodiment, the surface 17u of the throttle portion 15u is configured from a flat surface. In the second embodiment, the diaphragm portion 15d does not exist.

  Here, the start point position αu, the end point position βu, the virtual line γu, and the angle δu are as shown in FIG. That is, the starting point position αu is on the upstream side in the flow direction f2 of the detection surface unit 10 that is the detection unit 18, and the angle formed by the surface 17u of the throttle unit 15u and the flow direction f2 is equal to the angle δu.

  Thereby, the cross-sectional area perpendicular to the flow direction f2 in the detection unit 18 can be reduced while keeping the change in the flow direction of the surface 17u of the throttle unit 15u smooth, and the flow velocity in the detection unit 18 can be secured. In addition, since the change of the cross-sectional area is gradual, the difference in the change amount of the flow velocity by the throttle portion 15u in the vicinity of the surface 17u is not large, so that the generation of vortex can be suppressed. Further, since the surface 17u is a flat surface, the speed change in the direction perpendicular to the flow along the surface 17u hardly occurs, and the occurrence of peeling can be suppressed. Since the surface 17u is a flat surface, it can be easily formed.

[Example 3]
A flow measurement device 1 according to the third embodiment will be described with reference to FIG. In the flow rate measuring device 1 according to the third embodiment, a throttle unit 20 different from the throttle unit 15u is also provided in the flow path wall 16b. Thereby, by providing a plurality of throttle portions, the cross-sectional area of the sub-bypass channel 9 can be further reduced while the angle δu is kept smaller than 20 degrees, and the flow velocity of the intake air at the detection surface portion 10 is further increased. Thus, the heat transfer performance and detection accuracy can be further stabilized.

  It should be noted that the influence on the air flow in the detection surface portion 10 is greatest when the generated vortex or the like can reach the detection surface portion 10 directly, so that the flow path wall 16a is provided with a throttle portion 15u or the like. For this reason, for example, even if a throttle part is provided in the flow path wall other than the flow path wall 16a, the possibility that the generated vortex or the like reaches the detection surface part 10 is reduced, and the influence on the detection surface part 10 is reduced. As a result, the different throttle parts 20 provided on the flow path wall 16b can adjust the cross-sectional area of the sub bypass flow path 9 without affecting the air flow to the detection surface part 10.

[Example 4]
In the first embodiment, when the vibration frequency of the flow rate increases, the measurement error increases when the angle δu exceeds 20 degrees. However, in the fourth embodiment, the measurement error occurs even when the vibration frequency of the flow rate is high and the angle δu is 30 degrees. The structure that is difficult to increase is realized. The fourth embodiment will be described focusing on the differences from the first embodiment.

  In Example 4, as shown in FIG. 8, a portion of the bypass channel 7 that spans the intake port 7 a and the discharge port 7 b is referred to as a passage channel 8. The passage channel 8 has an upstream end portion that forms the intake port 7a and a downstream end portion that forms the discharge port 7b, and extends in the flow direction f1 of the intake passage 2. In this case, the sub-bypass channel 9 can also be referred to as a branch channel branched from the intermediate portion of the passage channel 8.

  In the fourth embodiment, unlike the first embodiment, as shown in FIG. 9, the inner peripheral surfaces of the throttle portions 15u, 15d extend straight so as to connect the start point positions αu, αd and the end point positions βu, βd. Yes. Here, a configuration in which the inner peripheral surfaces of the throttle portions 15u and 15d have some unevenness, and a configuration in which the inner peripheral surfaces extend straight are also included in the configuration in which the inner peripheral surfaces extend straight. Further, both the upstream angle δu and the downstream angle δd are 30 degrees. The upstream throttle portion 15u corresponds to the upstream throttle portion. Moreover, the detection surface part 10 can also be called a detection part.

  The flow path wall 16a including the throttle portions 15u and 15d is referred to as a first flow path wall 16a, and the flow path wall 16b that does not include the throttle portions 15u and 15d is referred to as a second flow path wall 16b. The arrangement direction of 16a and 16b is referred to as a width direction X. The width direction X corresponds to an orthogonal direction orthogonal to the flow direction f2. The support portion 13 is formed in a plate shape from a synthetic resin material or the like, and divides the sub-bypass channel 9 into two in the width direction. The support portion 13 is disposed so as to extend in the flow direction f2 and parallel to the flow path walls 16a and 16b. Moreover, the support part 13 is arrange | positioned in parallel also in the alignment direction of the starting point position (alpha) u and (alpha) d. The support unit 13 includes a first facing surface 13a facing the first flow path wall 16a and a second facing surface 13b facing the second flow path wall 16b. Is attached to the first facing surface 13a.

  In the flow direction f2, the length dimension L1 of the support portion 13 is the same as the total length Fa of the throttle portions 15u and 15d. The flow sensor chip 5 and the detection surface portion 10 are disposed at the center of the support portion 13 in the flow direction f2. That is, the flow rate sensor chip 5 and the detection surface portion 10 are arranged at positions where the respective center lines in the flow direction f <b> 2 coincide with the center line C of the support portion 13. In the support portion 13, the separation distance L <b> 2 between the upstream end portion and the center line C is the same as the separation distance L <b> 3 between the downstream end portion and the center line C.

  The center line C of the support portion 13 in the flow direction f2 is disposed at a position shifted to the upstream side from the end point positions βu and βd in the flow direction f2. In the support portion 13, the upstream end portion is disposed upstream of the upstream start point position αu, and the downstream end portion thereof is disposed upstream of the downstream start point position αd. When the distance between the center line C and the end point positions βu, βd in the flow direction f2 is referred to as a shift distance L4, the upstream end portion and the downstream end portion of the support portion 13 are shifted from the start position αu, αd by a shift distance L5, respectively. It is shifted by L6. Due to the fact that the length L1 of the support portion 13 and the total length Fa of the throttle portions 15u and 15d are the same, these shift distances L4 to L6 have the same value.

  The full length Fa of the throttle portions 15u and 15d is a separation distance between the end point positions βu and βd. The length Lb of the upstream throttle portion 15u is the same as the length Lc of the downstream throttle portion 15d, and the total length of these length dimensions Lb and Lc is Fa. In this case, the angle δu upstream from the end point position βu and the angle δd downstream from the end point position βu have the same value, and the end point positions βu, βd are arranged at the center of the start point positions αu, αd. ing.

  The detection surface portion 10 is disposed between the upstream start point position αu and the end point positions βu, βd in the flow direction f2. The detection surface portion 10 is disposed near the end point positions βu and βd, but does not protrude further downstream than the end point positions βu and βd. The detection surface portion 10 is close to the end point positions βu and βd so that the flow rate sensor chip 5 protrudes downstream from the end point positions βu and βd. The configuration in which the detection surface portion 10 does not protrude downstream from the end point positions βu and βd is realized by the fact that the length dimension L7 of the detection surface portion 10 in the flow direction f2 is smaller than the deviation distance L4. In this case, the central portion of the detection surface portion 10 is disposed upstream of the end point positions βu and βd.

  The support portion 13 is disposed at a position near the first flow path wall 16a in the width direction X. In the width direction X, the separation distance B1 between the support portion 13 and the starting position αu, αd is smaller than the separation distance B2 between the support portion 13 and the second flow path wall 16b. In the width direction X, the separation distance B3 between the end point positions βu, βd and the support portion 13 is smaller than the separation distance B4 between the start point positions αu, αd and the end point positions βu, βd, and these separation distances B3. , B4 is the separation distance B1. The separation distance B3 between the end point positions βu and βd and the support portion 13 is larger than the thickness dimension of the support section 13 and the thickness dimension of the flow rate sensor chip 5.

  An area between the support part 13 and the first flow path wall 16a is referred to as a detection side area 21a provided with the detection surface part 10, and an area between the support part 13 and the second flow path wall 16b is referred to as a support part. 13 is referred to as an opposite side region 21b that is opposite to the detection surface portion 10 with 13 therebetween. The width dimension of the detection-side region 21a in the width direction X gradually decreases from the upstream start point position αu toward the end point positions βu, βd in the flow direction f1, and downstream from the end point positions βu, βd. It gradually increases as it approaches the position αd.

  For the first flow path wall 16a, the upstream wall surface from the upstream start point position αu is referred to as the upstream wall surface 22a, and the downstream wall surface from the downstream start point position αd is referred to as the downstream wall surface 22b. 21a is also formed between the support part 13 and the upstream wall surface 22a. Similarly to the start point positions αu and αd, the upstream wall surface 22a and the downstream wall surface 22b include a portion in which the separation distance from the support portion 13 is the separation distance B1 in the width direction X. It is continuous with αu and αd.

  As described above, in Example 4, the inner peripheral surfaces of the throttle portions 15u and 15d with respect to the upstream wall surface 22a and the downstream wall surface 22b due to the inner peripheral surfaces of the throttle portions 15u and 15d extending straight. Are inclined at angles δu and δd.

  Next, a mode in which intake air flows through the sub-bypass channel 9 will be described. The intake air that has approached the support portion 13 in the sub-bypass channel 9 is divided into intake air that flows into the detection-side region 21a and intake air that flows into the opposite-side region 21b. Here, since the width dimension of the opposite side area 21b is larger than the width dimension of the detection side area 21a, the foreign matter contained in the intake air enters the opposite side area 21b rather than the detection side area 21a. It has become easier. That is, a configuration in which foreign matter or the like hardly enters the detection side region 21a is realized. For this reason, it is suppressed that the detection accuracy of the detection surface part 10 falls or the detection surface part 10 is damaged by the contact and approach of a foreign substance etc. to the detection surface part 10.

  Since the support portion 13 extends to the upstream side of the upstream throttle portion 15u, the width dimension of the upstream end portion of the detection side region 21a is the same as the separation distance B1 between the first flow path wall 16a and the support portion 13. It has become. In this case, for example, the width of the upstream end portion of the detection-side region 21a is larger than the configuration in which the throttle portion 15u extends to the upstream side of the support portion 13. For this reason, the flow-path area ratio of the detection side area | region 21a with respect to the opposite side area | region 21b becomes large, and more intake air can be flowed into the detection side area | region 21a. In addition, when the ratio of the downstream end portion to the upstream end portion in the detection side region 21a is referred to as a restriction ratio, the restriction ratio increases as the width dimension of the upstream end portion increases, and reaches the downstream end portion in the detection side region 21a. The flow rate of intake air tends to increase.

  Moreover, the intake air that has flowed into the detection-side region 21a is rectified between the support portion 13 and the upstream wall surface 22a, and then gradually squeezed between the support portion 13 and the upstream throttle portion 15u, thereby gradually accelerating. It will be done. As described above, in the detection-side region 21a, the region between the support unit 13 and the upstream wall surface 22a serves as a rectifying region for rectifying the intake air. It becomes difficult to generate in the intake air between the portion 15u. Here, the detection surface unit 10 is configured to detect the flow rate based on a temperature change caused by the flow rate of the intake air. For this reason, when the turbulence of the airflow is applied to the detection surface portion 10, a temperature change corresponding to the turbulence occurs, and the detection accuracy of the flow rate by the detection surface portion 10 is lowered.

  Due to the expansion of the detection side region 21a downstream of the end point positions βu and βd, the intake air that has passed through the end point positions βu and βd in the detection side region 21a is likely to be disturbed such as vortex or separation. . In particular, the action of the air flowing along the downstream throttle portion 15d and the air flowing toward the support portion 13 due to the intake air flowing along the upstream throttle portion 15u passing the end point positions βu and βd. As a result, disturbance occurs immediately downstream of the end point positions βu and βd.

  On the other hand, since the detection surface portion 10 is arranged on the upstream side of the end point positions βu and βd, even if a disturbance occurs on the downstream side of the end point positions βu and βd, the disturbance is detected with the detection surface portion 10. It is difficult to be transmitted to the intake air between the throttle portion 15u on the downstream side. For this reason, it is unlikely to occur that the detection accuracy of the detection surface portion 10 is lowered due to the disturbance of the intake air generated downstream from the end point positions βu and βd.

  Here, in recent vehicles, due to the reduction in the number of parts and the reduction in the weight of the internal combustion engine due to the reduction in weight, there is less intake interference inside the intake passage 2 and the inflow air in the flow direction is reduced. Vibration tends to increase. When this vibration frequency is referred to as a vibration frequency, the disturbance of the intake air in the detection-side region 21a increases as the vibration frequency increases, and as a result, the measurement error [%] of the flow rate by the flow rate measuring device 1 tends to increase. In particular, in the configuration in which the detection surface portion 10 is provided in the sub-bypass channel 9 instead of the through-channel 8 in the bypass channel 7, the disturbance that occurs when the intake air flows into the sub-bypass channel 9 from the passing channel 8. The measurement error tends to increase by reaching the detection side region 21a.

  For example, when the vibration frequency is at the first frequency that is relatively low, as shown in FIG. 10, the measurement error is included in the allowable range even when the upstream angle δu is larger than 20 degrees, as in the first embodiment. . This indicates that the measurement result of the flow measuring device 1 is highly sensitive to the actual increase and decrease of the intake air in the intake passage 2. In the example shown in FIG. 10, even if the angle δu is large such as 30 degrees or 40 degrees, the measurement error is included in the allowable range. The first frequency is, for example, 100 Hz, and the allowable range of measurement error is several percent.

  In addition, when the vibration frequency is at the first frequency that is relatively high, the measurement error may rapidly increase and deviate from the allowable range when the upstream angle δu exceeds 20 degrees as in the first embodiment. is assumed. On the other hand, in Example 4, as shown in FIG. 11, even if the upstream angle δu exceeds 20 degrees, the measurement error is included in the allowable range until it exceeds 30 degrees, and 30 degrees The measurement error gradually increases around the time of exceeding and falls outside the allowable range. As described above, this is because, in the detection side region 21a, the support portion 13 faces the upstream wall surface 22a, or the detection surface portion 10 is upstream of the end point positions βu and βd. This shows that the disturbance of intake air is less likely to occur.

  According to the fourth embodiment, since the angles δu and δd by the throttle portions 15u and 15d are set to 30 degrees, compared to the configuration in which the angles δu and δd are set to a value larger than 30 degrees, the flow rate measuring device 1 Measurement error can be reduced.

  According to the fourth embodiment, since the detection surface unit 10 is provided between the upstream start point position αu and the end point position βu, airflow disturbance generated downstream of the end point position βu is generated in the detection surface unit 10. It is difficult to be granted. For this reason, it can suppress that the detection accuracy of the detection surface part 10 falls by disturbance of the airflow which generate | occur | produced downstream from the end point position (beta) u. In addition, since the detection surface portion 10 is disposed at a position near the end point positions βu and βd where the flow velocity of the intake air tends to increase in the detection side region 21a, the flow velocity of the intake air applied to the detection surface portion 10 is moderately large. Prone. For this reason, the detection accuracy of the detection surface unit 10 can be increased.

  According to the fourth embodiment, the support portion 13 extends to the upstream side from the upstream start point position αu. For this reason, the intake air that has flowed into the detection-side region 21a is rectified by flowing between the support portion 13 and the upstream wall surface 22a at a stage prior to reaching the upstream throttle portion 15u. Therefore, it is possible to realize a configuration in which the intake air reaching the detection surface portion 10 is less likely to be disturbed.

  According to the fourth embodiment, the separation distance B3 between the end point positions βu, βd and the support portion 13 is smaller than the separation distance B4 between the start point positions αu, αd and the end point positions βu, βd. In this case, since the flow velocity of the intake air that has reached the end point positions βu and βd in the detection side region 21a is likely to be larger than the flow velocity of the intake air that passes through the upstream start point position αu, the detection accuracy of the detection surface unit 10 is improved. Can be increased.

  According to the fourth embodiment, the separation distance B1 between the support portion 13 and the start position αu, αd is smaller than the separation distance B2 between the support portion 13 and the second flow path wall 16b. In this case, since the front end of the detection side region 21a is smaller than the front end of the opposite side region 21b, the probability that a foreign substance or the like enters the detection side region 21a can be reduced. Thereby, it can suppress that the detection accuracy of the detection surface part 10 falls by the foreign material etc., or the detection surface part 10 is damaged.

[Example 5]
In the fourth embodiment, the end point position βu on the upstream side and the end point position βd on the downstream side coincide with each other. However, in the fifth embodiment, as shown in FIG. 12, these end point positions βu and βd are in the flow direction f2. They are separated from each other. The fifth embodiment will be described focusing on the differences from the fourth embodiment.

  In the fifth embodiment, a connecting portion 23 for connecting the throttle portions 15u and 15d is provided between the upstream throttle portion 15u and the downstream throttle portion 15d. The inner peripheral surface of the connecting portion 23 extends in parallel with the upstream wall surface 22a and the downstream wall surface 22b, and the length dimension Ld of the connecting portion 23 is a separation distance between the end point positions βu and βd in the flow direction f2. .

  The detection surface portion 10 is provided at a position facing the connection portion 23. Specifically, the detection surface portion 10 is disposed between the upstream end point position βu and the downstream end point position βd in the flow direction f2. The length dimension Ld of the connecting portion 23 is larger than the length dimension L8 of the flow rate sensor chip 5 in the flow direction f2, and the detection surface portion 10 is located upstream of the end point position βu on the upstream side of the flow rate sensor chip 5. It is arranged close to the end point position βu so as to protrude. In the connection portion 23, the upstream end portion is disposed upstream from the upstream end point position βu, and the downstream end portion is disposed downstream from the downstream end position βd.

  In the fifth embodiment, the separation distance B3 between the end point positions βu, βd and the support portion 13 is the same value as the separation distance B4 between the start point positions αu, αd and the end point positions βu, βd. The separation distance B3 may be larger than the separation distance B4. Even in these cases, the width dimension of the detection-side region 21a gradually decreases as the detection surface portion 10 is approached in the flow direction f2, so that the intake air flowing between the connection portion 23 and the support portion 13 is reduced. The structure which raises a flow rate appropriately can be realized.

  According to Example 5, in the detection side region 21a, the region between the connection portion 23 and the support portion 13 is the most narrowed region, and the detection surface portion 10 is provided in this most narrowed region. The flow velocity of the intake air applied to the detection surface portion 10 can be sufficiently increased. In addition, as in the fourth embodiment, since the detection surface portion 10 is arranged on the upstream side of the downstream end point position βd, the turbulence of air current such as vortex generated when the intake air passes the end point position βd is disturbed. It is difficult to be applied to the detection surface portion 10. Therefore, it can be suppressed that the detection accuracy of the detection surface portion 10 is lowered due to the turbulence of the airflow generated downstream of the downstream end position βd.

[Modification]
Various modifications can be considered for each of the above embodiments without departing from the scope of the invention. In the first embodiment, the surfaces of the aperture portions 15u and 15d are curved surfaces, but the surfaces of the aperture portions 15u and 15d may be flat as shown in FIG. In this case, start point positions αu and αd, end point positions βu and βd, virtual lines γu and γd, and angles δu and δd are as illustrated.

  In addition, between the restricting portion 15u and the restricting portion 15d, a cross-sectional area perpendicular to the flow direction f2 is minimized and does not change, and the detection surface portion 10 has a minimum cross-sectional area perpendicular to the flow direction f2. It exists in an area that does not change.

  In the second embodiment, the cross-sectional area perpendicular to the flow direction f2 is the smallest on the detection surface portion 10, but the cross-sectional area perpendicular to the flow direction f2 is the smallest on the downstream side of the detection surface portion 10 as shown in FIG. It may be. In this case, the start point position αu, the end point position βu, the virtual line γu, and the angle δu are as illustrated.

  Here, as shown in FIG. Considering the distance from the detection surface portion 10 at the positions p1 and p2, the distance from the detection surface portion 10 at the position p1 is the sum of d1 and d2. d1 is a distance perpendicular to the detection surface portion 10 between the detection surface portion 10 and the flow path wall 16a, and d2 is a distance along the flow direction f2. Since the distance from the detection surface portion 10 at the position p2 is d1 + d3 and d1 + d2> d1 + d3, the end point position βu is the position p2 as shown in FIG. In addition, p1 is a position corresponding to the gravity center position of the detection surface portion 10 perpendicular to the surface of the flow path wall 16a, and p2 is a position corresponding to the gravity center of the detection surface portion 10 perpendicular to the detection surface portion 10.

  Further, the aperture 15u does not have to extend to the detection surface 10 as shown in FIGS. In this case, the start point position αu, the end point position βu, the virtual line γu, and the angle δu are as illustrated.

  Further, as shown in FIGS. 17 and 18, the throttle portion 15 u may not exist on the same axis in the flow direction f <b> 2 in the detection surface portion 10. In this case, the start point position αu, the end point position βu, the virtual line γu, and the angle δu are as illustrated. The distance from the detection surface portion 10 is a distance from the center of gravity position of the detection surface portion 10. The shortest distance from the detection surface portion 10 is the shortest distance obtained by adding the distance perpendicular to the detection surface portion 10 between the detection surface portion 10 and the flow path wall 16a in the throttle portion 15u and the distance along the flow direction f2. It means that

  When a plurality of start point positions αu are considered, the start point position αu is a position where the distance from the end point position βu is the shortest distance. Here, the shortest distance between the starting point position αu and the ending point position βu is a distance perpendicular to the detection surface portion 10 between the starting point position αu and the ending point position βu and a distance along the flow direction f2. Means that the distance is the shortest.

  In the third embodiment, the different throttle portions 20 are provided on the flow channel wall 16b facing the flow channel wall 16a, but may be provided on a flow channel wall other than the flow channel wall 16b. Furthermore, if the distance from the detection surface portion 10 is increased, the influence of the generated vortex and the like on the detection surface portion 10 is reduced. Therefore, a different throttle portion 20 may be provided on the flow path wall 16a.

  In the first to third embodiments, the housing 3 has the sub-bypass channel 9 that is a part of the bypass channel 7 formed therein. However, the housing 3 may not have the sub-bypass channel 9 formed therein. .

  In the fourth and fifth embodiments, the angles δu and δd may be smaller than 30 degrees. Thus, even when the angles δu and δd are larger than 0 degree and smaller than 30 degrees, as shown in FIG. 11, the measurement error does not increase rapidly until the angle δu exceeds 30 degrees (see FIG. 11). Can be realized.

  In the fourth and fifth embodiments, the length L1 of the support portion 13 may be different from the total length Fa of the throttle portions 15u and 15d. For example, in a configuration in which the length dimension L1 is larger than the full length Fa, the support portion 13 may protrude beyond both the throttle portions 15u and 15d on both the upstream side and the downstream side. Further, even in a configuration in which the length L1 is smaller than the full length Fa, the support portion 13 may extend to the upstream side of the upstream throttle portion 15u.

  In the fourth and fifth embodiments, the flow rate sensor chip 5 and the detection surface portion 10 may be arranged at positions shifted from the center position of the support portion 13 to the upstream side or the downstream side in the flow direction f2. Moreover, the detection surface part 10 may be arrange | positioned in the position which shifted | deviated to the upstream or downstream from the center position of the flow sensor chip 5 in the flow direction f2.

  In the fourth embodiment, the entire flow rate sensor chip 5 may be disposed upstream of the end point positions βu and βd. Even in this case, it is possible to realize a configuration in which the detection surface portion 10 is disposed at positions near the end point positions βu and βu in the flow direction f2.

  In the fifth embodiment, at least a part of the detection surface portion 10 may be arranged upstream of the upstream end position βu. For example, it is assumed that the entire detection surface portion 10 is disposed upstream of the upstream end point position βu. In this configuration, the detection surface portion 10 does not face the connection portion 23, but faces the upstream throttle portion 15u as in the fourth embodiment.

  In the fourth and fifth embodiments, the angles δu and δd may be smaller than 30 degrees. For example, the upstream angle δu is smaller than the downstream angle δd, or the upstream angle δu is larger than the downstream angle δd. Even in this configuration, the measurement error does not increase abruptly until the angle δu exceeds 30 degrees (see FIG. 11), so that the detection accuracy of the detection surface unit 10 and the measurement accuracy of the flow rate measuring device 1 are kept appropriate. Can do.

  In the fourth and fifth embodiments, the support portion 13 may not be arranged on the upstream side from the upstream start point position αu. Even in this case, the inventor does not increase the measurement error abruptly until the angle δu exceeds 30 degrees as long as the support portion 13 is disposed at a position near the first flow path wall 16a in the width direction X. (See FIG. 11). In addition, the structure by which the support part 13 is arrange | positioned in the position close | similar to the 1st flow-path wall 16a is implement | achieved when the separation distance B1 is smaller than the separation distance B4.

  In the fourth and fifth embodiments, the support portion 13 may not be disposed at a position near the first flow path wall 16a in the width direction X. Even in this case, the present inventor does not increase the measurement error abruptly until the angle δu exceeds 30 degrees as long as the support portion 13 is arranged upstream from the upstream start position αu (FIG. 11). See)).

DESCRIPTION OF SYMBOLS 1 ... Flow measuring device, 2 ... Intake passage (duct), 3 ... Housing, 5 ... Flow rate sensor chip, 7 ... Bypass flow path, 10 ... Detection surface part as a detection part, 13 ... Support part, 15 ... Restriction part, 15u ... Upstream restrictor, 15d ... restrictor, 16a ... first channel wall as a channel wall, 16b ... second channel wall, 17u ... surface, 18 ... detector, B1, B2, B3, B4 ... separation distance , F2 ... flow direction, αu, αd ... start point position, βu, βd ... end point position, γu, γd ... virtual line, δu, δd ... angle, X ... width direction as orthogonal direction.

Claims (12)

A housing (3) having a bypass flow path (7) for taking in part of the air flowing inside the duct (2);
A flow rate sensor chip (5) having a detection surface portion (10) disposed in the bypass flow path and generating an electrical signal corresponding to the flow rate of air in the duct by heat transfer with air flowing through the bypass flow path; Prepared,
The detection surface portion is arranged along a flow direction that is a flow of air flowing through the bypass flow path,
The flow rate measuring device (1) in which the bypass channel is throttled by a throttle portion (15, 15u, 15d) so that a cross-sectional area perpendicular to the flow direction decreases as the cross section approaches the detection surface portion along the flow direction. )
The throttle part is a part of the flow path wall (16a) facing the detection surface part, and the distance between the detection surface part perpendicular to the detection surface part and the flow path wall is detected along the flow direction. It gets narrower as you get closer to the face,
When the starting position of the diaphragm portion is a start position (αu, αd) and the position of the shortest distance from the detection surface portion of the diaphragm portion is an end point position (βu, βd),
The flow rate measuring device, wherein an angle (δu, δd) formed by an imaginary line (γu, γd) connecting the start point position and the end point position and the flow direction in the throttle portion is larger than 0 degree and smaller than 20 degrees.   The flow rate measuring device according to claim 1, wherein a surface of the throttle portion is a flat surface or a curved surface.   The flow rate measuring device according to claim 1 or 2, wherein a throttle part (20) different from the throttle part is provided in the bypass channel.   The flow rate measuring device according to any one of claims 1 to 3, wherein the throttle portion is provided on an upstream side and a downstream side of the detection surface portion in the flow direction. A housing having a bypass flow path for taking in part of the air flowing inside the duct;
A flow rate sensor chip having a detection part (18) arranged in the bypass flow path and generating an electrical signal corresponding to the flow rate of air in the duct;
The bypass channel is a flow rate measurement that is throttled by a throttle unit so that a cross-sectional area perpendicular to the flow direction, which is a flow of air flowing through the bypass channel, decreases as the detection unit approaches the detection unit along the flow direction. In the device
The throttle part is a part of a flow path wall facing the detection part,
When the starting position of the throttle unit is a starting point position, this starting point position is upstream of the flow direction of the detection unit,
The flow rate measuring device, wherein a surface (17u) of the throttle part is a flat surface, and an angle formed between the surface and the flow direction in the throttle part is larger than 0 degree and smaller than 20 degrees. A housing (3) having a bypass flow path (7) for taking in part of the air flowing inside the duct (2);
A flow rate sensor chip (5) having a detection surface portion (10) disposed in the bypass flow path and generating an electrical signal corresponding to the flow rate of air in the duct by heat transfer with air flowing through the bypass flow path; Prepared,
The detection surface portion is arranged along a flow direction (f2) that is a flow of air flowing through the bypass flow path,
The flow rate measuring device (1) in which the bypass channel is throttled by a throttle portion (15, 15u, 15d) so that a cross-sectional area perpendicular to the flow direction decreases as the cross section approaches the detection surface portion along the flow direction. )
The throttle part is a part of the flow path wall (16a) facing the detection surface part, and the distance between the detection surface part perpendicular to the detection surface part and the flow path wall is detected along the flow direction. It gets narrower as you get closer to the face,
When the starting position of the diaphragm portion is a start position (αu, αd) and the position of the shortest distance from the detection surface portion of the diaphragm portion is an end point position (βu, βd),
The flow rate measuring device, wherein an angle (δu, δd) formed by an imaginary line (γu, γd) connecting the start point position and the end point position and the flow direction in the throttle portion is greater than 0 degree and less than 30 degrees. As the restricting portion, an upstream restricting portion (15u) that restricts the bypass passage from the upstream side to the downstream side of the detection surface portion in the bypass passage,
The flow rate measuring device according to claim 6, wherein a central portion of the detection surface portion is provided between the start point position and the end point position with respect to the upstream throttle portion in the flow direction.   The flow rate measuring device according to claim 7, wherein the plate-like support portion (13) supporting the detection surface portion extends to the upstream side of the start point position of the upstream throttle portion.   In the orthogonal direction (X) orthogonal to the flow direction, the separation distance (B3) between the end point position and the support part (13) that supports the detection surface portion is the separation distance (B4) between the end point position and the start point position. The flow rate measuring device according to any one of claims 6 to 8, which is smaller. The flow path wall is a first flow path wall (16a), and a second flow path wall (16b) is provided opposite the first flow path wall with a support portion (13) supporting the detection surface portion interposed therebetween. And
The detection surface portion is attached to a surface (13a) facing the first flow path wall in the support portion,
The separation distance (B1) between the starting point position of the first flow path wall and the support section is smaller than the separation distance (B2) between the second flow path wall and the support section. The flow measuring device according to claim 1. A housing having a bypass flow path for taking in part of the air flowing inside the duct;
A flow rate sensor chip having a detection part (18) arranged in the bypass flow path and generating an electrical signal corresponding to the flow rate of air in the duct;
The bypass channel is squeezed by a throttle unit so that a cross-sectional area perpendicular to the flow direction (f2), which is a flow of air flowing through the bypass channel, decreases as it approaches the detection unit along the flow direction. In the flow measurement device
The throttle part is a part of a flow path wall facing the detection part,
When the starting position of the throttle unit is a starting point position, this starting point position is upstream of the flow direction of the detection unit,
The flow rate measuring device characterized in that the surface (17u) of the throttle part is a plane, and the angle formed by the surface and the flow direction in the throttle part is greater than 0 degree and not more than 30 degrees. A flow rate measuring device (1) for measuring a flow rate of air,
A bypass flow path (7) through which the air flows;
A detection unit (10) for outputting an electrical signal corresponding to the flow rate of the air in the bypass channel;
A pair of flow path walls (16a, 16b) opposed across the detection unit;
In the arrangement direction (X) in which the pair of flow path walls are arranged, a throttle part (15u) for narrowing the bypass flow path by projecting from the flow path wall toward the detection unit;
With
The protruding dimension of the throttle part gradually increases as it approaches the detection part from the upstream side in the bypass flow path,
When the position of the upstream end portion of the aperture portion is a start point position (αu, αd) and the position of the shortest distance from the detection portion of the aperture portion is an end point position (βu, βd),
An angle (δu, δd) formed by an imaginary line (γu, γd) connecting the start point position and the end point position and a flow direction (f2) that is a flow of air flowing through the bypass flow path is larger than 0 degree and 30 Flow rate measuring device that is less than or equal to degrees

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