Flow measuring device

Abstract

Flow measuring device comprising the following: a housing (3) which has a bypass passage (7) which introduces a portion of the air flowing through a channel (2); and a flow-sensing chip (5) which is placed in the bypass passage and has a scanning surface section (10) which generates an electrical signal in response to a flow volume of air in the channel by means of heat transfer between the scanning surface section and the air flowing through the bypass passage, wherein the scanning surface section is placed along a flow direction (f2) in which the air flows through the bypass passage, the bypass passage is throttled by a throttling section (15, 15u, 15d) such that a cross-sectional area of ​​the bypass passage decreases perpendicular to the flow direction in accordance with a decrease in distance from a centroid of the scanning surface section to a center of the cross-sectional area in a direction parallel to the flow direction, the throttle section is part of a flow passage wall (16a) which faces the scanning surface section, wherein the throttle section throttles the cross-sectional area of ​​the bypass passage such that a distance from the scanning surface section to the flow passage wall on the cross-sectional area decreases in a direction perpendicular to the scanning surface section in accordance with a decrease in the distance from the centroid of the scanning surface section to the center of the cross-sectional area in the direction parallel to the flow direction, a position at which the throttle section starts is referred to as a starting point position (αu, αd), and a position of the throttle section at which the distance between the centroid of the scanning surface section and the throttle section is shortest is referred to as an end point position (βu, βd), and the starting point position and the endpoint position define an imaginary line (γu, γd) and the imaginary line and the flow direction define an angle (δu, δd) which is in a range from 0 degrees to 20 degrees, where the throttle section is an upstream throttle section (15u) which is placed at a position in the bypass passage upstream of the scanning surface section and extends in the flow direction to throttle the bypass passage, and the scanning surface section has a middle part which is placed between the starting point position and the end point position in the flow direction, and wherein the flow measuring device further features a support section (13) which is a plate shape, wherein the support section supports the scanning surface section, the support section extending to a position upstream of the choke section.

Description

TECHNICAL AREA

[0001] The present disclosure relates to a flow measuring device or flow meter which measures a flow volume or flow volume of intake air which is drawn into a machine with internal combustion which is used in a vehicle. BACKGROUND

[0002] According to JP 2014-001954 A, a flow measurement device is conventionally known to comprise a housing and a flow-sensing chip. The housing has a bypass passage that introduces a portion of the air flowing through an intake air duct of an internal combustion engine. The flow-sensing chip is positioned in the bypass passage and has a scanning surface section that generates an electrical signal in response to the airflow volume in the intake air duct by means of heat transfer between the scanning surface section and the air flowing through the bypass passage.

[0003] The scanning surface section is positioned parallel to the direction of airflow through the bypass passage. The bypass passage is throttled by a throttling section such that the cross-sectional area of ​​the bypass passage decreases perpendicular to the direction of airflow, corresponding to a decrease in the distance from the centroid of the scanning surface section to the center of the cross-sectional area in the direction parallel to the direction of airflow.

[0004] Accordingly, if the airflow volume in the air intake duct is relatively small, a sufficient airflow rate can be ensured at the scanning surface section, and adequate heat transfer efficiency and scanning accuracy of the flow volume can be guaranteed. However, if a flow passage wall changes at an acute angle at the throttle section, a vortex or separation in the airflow is created in the vicinity of the throttle area, and the airflow is disturbed, thus eliminating any alignment or straightening function.

[0005] If the vortex is generated in the vicinity of the throttle section, it creates an airflow that flows in the opposite direction to the normal flow direction. In this case, a pressure drop is created in the bypass passage, and the flow volume at the scanning surface section is reduced. Furthermore, if the vortex is generated in the vicinity of the throttle section, and a pulsed flow is generated in response to the operation of a piston in the internal combustion engine, the vortex will reach the scanning surface section, leading to a scanning error.

[0006] Further state-of-the-art information can be found in the following documents.

[0007] JP 2003-315 126 A discloses a flow measuring device. A sub-channel structure of the flow measuring device is characterized in that a mounted plate for supporting a measuring element is arranged parallel to a plane formed by a transit axis of the curved sub-channel, and that the plate for supporting the measuring element is arranged on a channel wall of the sub-channel. The flow resistance of the intake air is low, and an average flow of a pulsating intake flow, which causes backflow, can be detected with high accuracy.

[0008] DE 601 12 002 T2 discloses a flow meter. The flow meter for measuring the fluid flow rate through a fluid channel comprises an outer pipe for forming a bypass channel, a separator dividing the bypass channel into first and second sub-fluid channels, and a thermal flow sensor provided in one of the first and second sub-fluid channels, wherein a projecting part provided in at least one of the first and second sub-fluid channels generates a flow channel resistance difference between the first and second sub-fluid channels, and the projecting part limits the fluid flow through at least one of the sub-fluid channels, so that the flow channel losses of the first and second sub-fluid channels are different from each other as a result of the projecting part.

[0009] US 2012 / 0103086A1 discloses a flow meter. The flow meter comprises a housing, a support, and a flow meter. The housing defines a passage and includes a passage constriction section that reduces the cross-sectional area of ​​the passage in a predetermined portion. The support has a plate-like shape and is oriented along the flow direction of the fluid flowing through the passage. The flow meter is located within the passage constriction section and is positioned on a surface of the support. The flow meter detects the flow rate of the fluid flowing through the passage. The passage constriction section has an inner wall surface that gradually reduces the width of the passage from a central side to both end sides of the passage in a vertical direction perpendicular to the direction of the passage's width.

[0010] DE 11 2013 002 999 T5 discloses a thermal flow meter. To improve the measuring accuracy of a thermal flow meter, the present invention provides a thermal flow meter in which a projection having a constriction surface and a recovery surface is provided on a wall surface of a bypass passage, an intersection line between the constriction surface and the wall surface is arranged on an inlet side from an inlet-side end of a circuit assembly, an intersection line between the recovery surface and the wall surface is arranged on an outlet side from an outlet-side end of the circuit assembly, and a tip of the projection is arranged on an outlet side from a heat transfer surface of an airflow detection section and on an inlet side from the outlet-side end of the circuit assembly.

[0011] DE 102 53 691 A1 discloses a device for measuring flow rate. An air flow meter has a membrane sensor element. The sensor element is supported by a support element such that a sensor surface of the sensor element is parallel to the direction of airflow. The air flow meter has at least one device for protecting the sensor element from dust, such as foreign matter. The protective device is provided with an obstruction element, which is arranged upstream or downstream of the sensor element with respect to the direction of airflow. The sensor element is concealed behind the obstruction element. The obstruction element has gradually expanding or gradually converging surfaces along the direction of airflow. Alternatively, the protective device can be provided with a deflector, a cover element, an air guide element, an inlet, or a dust collector.

[0012] EP 2 306 162 A2 discloses a flow meter. A plate-shaped circuit board is arranged such that fluid passages are formed on a sensor element mounting surface side of the plate-shaped circuit board and on a rear surface side of the same, which is opposite the sensor element mounting surface side, wherein a curved passage section is provided which is arranged upstream of the plate-shaped circuit board and changes its direction so that it forms a curved line. SUMMARY

[0013] It is an object of the present disclosure to provide a flow measuring device which includes a throttle section and a scanning surface section and improves the scanning accuracy of a flow volume at the scanning surface section.

[0014] This problem is solved by the features of claims 1, 5 and 6. Further advantageous embodiments and developments are the subject of the subsequent claims.

[0015] According to a first aspect of the present disclosure, the flow measuring device comprises a housing and a flow sensing chip. The housing has a bypass passage which introduces a portion of the air flowing through a channel. The flow sensing chip is placed in the bypass passage and has a scanning surface section which generates an electrical signal in response to a flow volume of air in the channel by means of heat transfer between the scanning surface section and the air flowing through the bypass passage.

[0016] The scanning surface section is positioned along the direction of airflow through the bypass passage. The bypass passage is throttled by a throttling section such that the cross-sectional area of ​​the bypass passage decreases perpendicular to the direction of airflow, corresponding to a decrease in the distance from the centroid of the scanning surface section to the center of the cross-sectional area in a direction parallel to the direction of airflow.

[0017] The throttle section is part of a flow passage wall facing the scanning surface section. The throttle section restricts the cross-sectional area of ​​the bypass passage such that the distance from the scanning surface section to the flow passage wall decreases along the cross-sectional area in a direction perpendicular to the scanning surface section, corresponding to a decrease in the distance from the centroid of the scanning surface section to the center of the cross-sectional area in a direction parallel to the flow direction. A position where the throttle section begins is referred to as a starting point position, and a position of the throttle section where the distance between the centroid of the scanning surface section and the throttle section is shortest is referred to as an endpoint position, with the starting point and endpoint positions forming an imaginary line.and the imagination line and the flow direction define or limit an angle which is in a range of 0 degrees to 20 degrees, wherein the throttle section is an upstream throttle section which is placed at a position in the bypass passage upstream of the scanning surface section and extends in the flow direction to throttle the bypass passage, and the scanning surface section has a middle section which is placed between the start point position and the end point position in the flow direction, and wherein the flow measuring device further comprises a support section which is a plate shape, wherein the support section supports the scanning surface section, and wherein the support section extends to a position upstream of the throttle section.

[0018] Therefore, since the flow passage wall is varied stepwise within the throttle section, the formation of a vortex or separation in the airflow in the vicinity of the throttle section can be suppressed. Furthermore, disturbances in the intake air flow caused by the throttle section at the scanning surface section can be suppressed. Finally, the scanning accuracy of the flow volume at the scanning surface section in the flow measurement device, which includes the throttle section, can be improved.

[0019] According to a second aspect of the present disclosure, the flow-measuring device comprises a housing and a flow-measuring chip. The housing has a bypass passage which introduces a portion of the air flowing through a channel. The flow-measuring chip is placed in the bypass passage and has a scanning section which generates an electrical signal in response to a flow volume of air in the channel. The bypass passage is throttled by a throttling section such that a cross-sectional area of ​​the bypass passage decreases perpendicular to the flow direction in which the air flows through the bypass passage, corresponding to a decrease in distance from a centroid of the scanning surface section to a center of the cross-sectional area in a direction parallel to the flow direction.

[0020] The throttled section is part of a flow passage wall facing the scanning surface section. The starting point of the throttled section is referred to as its starting point position, and this starting point position is located upstream of the scanning section in the flow direction. The throttled section has a planar surface.The surface of the throttle section and the flow direction define an angle which is in a range of 0 degrees to 20 degrees, wherein the throttle section is an upstream throttle section which is placed at a position in the bypass passage upstream of the scanning surface section and extends in the flow direction to throttle the bypass passage, and the scanning surface section has a middle section which is placed between the start point position and the end point position in the flow direction, and wherein the flow measuring device further comprises a support section which is a plate shape, wherein the support section supports the scanning surface section, and wherein the support section extends to a position upstream of the throttle section.

[0021] Accordingly, similar to the first aspect, a disturbance in the intake air flow, which is generated by the throttle section at the scanning surface section, can be suppressed. Furthermore, the scanning accuracy of the flow volume at the scanning surface section can be improved in the flow measuring device that includes the throttle section. Additionally, the scanning section can have a shape other than planar.

[0022] According to a third aspect of the present disclosure, the flow measuring device comprises a housing which includes a bypass passage that introduces a portion of the air flowing through a channel, and a flow sensing chip located in the bypass passage, and a scanning surface section which generates an electrical signal in response to a flow volume of air in the channel by means of heat transfer between the scanning surface section and the air flowing through the bypass passage. The scanning surface section is positioned along the flow direction in which the air flows through the bypass passage.The bypass passage is throttled by a throttle section such that the cross-sectional area of ​​the bypass passage decreases perpendicular to the flow direction in a direction parallel to the flow direction, corresponding to a decrease in the distance from the centroid of the scanning surface section to the center of the cross-sectional area. The throttle section is part of a flow passage wall contained within the housing and facing the scanning surface section. The throttle section throttles the cross-sectional area of ​​the bypass passage such that the distance from the scanning surface section to the flow passage wall decreases at the cross-sectional area in a direction perpendicular to the scanning surface section, corresponding to a decrease in the distance from the centroid of the scanning surface section to the center of the cross-sectional area in a direction parallel to the flow direction.The position where the throttle section begins is referred to as a starting point position, and the position of the throttle section where the distance between the centroid of the scanning surface section and the throttle section is shortest is referred to as an endpoint position. The starting point position and the endpoint position define an imaginary line, and the imaginary line and the flow direction define an angle that ranges from 0 degrees to 30 degrees.

[0023] Therefore, the same effects as those in the first aspect can be achieved.

[0024] According to a fourth aspect of the present disclosure, the flow-measuring device comprises a housing with a bypass passage that introduces a portion of the air flowing through a channel, and a flow-sensing chip located in the bypass passage that includes a scanning section which generates an electrical signal in response to a flow volume of the air in the channel. The bypass passage is throttled by a throttle section such that a cross-sectional area of ​​the bypass passage decreases perpendicular to the flow direction in which the air flows through the bypass passage, corresponding to a decrease in distance from a centroid of the scanning surface section to a center of the cross-sectional area in a direction parallel to the flow direction. The throttle section is part of a flow passage wall facing the scanning surface section.A position where the throttling section begins is referred to as a starting point position; the starting point position is placed upstream of the sampling section in the flow direction.The throttle section has a surface which is a planar surface, wherein the surface of the throttle section and the flow direction define an angle which is in a range of 0 degrees to 30 degrees, wherein the throttle section is an upstream throttle section which is placed at a position in the bypass passage upstream of the scanning surface section and extends in the flow direction to throttle the bypass passage, and the scanning surface section has a middle section which is placed between the start point position and the end point position in the flow direction, and wherein the flow measuring device further comprises a support section which is plate-shaped, wherein the support section supports the scanning surface section, and wherein the support section extends to a position upstream of the throttle section.

[0025] Therefore, the same effects as those in the first aspect can be achieved.

[0026] According to a fifth aspect of the present disclosure, the flow-measuring device measures a flow volume of air. The flow-measuring device comprises a bypass passage through which the air flows, a sensing section which outputs an electrical signal in response to the flow volume of air in the bypass passage, a pair of flow passage walls facing each other, with the sensing section being placed between the flow passage walls, and a throttling section which throttles the bypass passage by protruding from the flow passage walls in the direction of the sensing section in an arrangement direction in which the pair of flow passage walls is arranged.The throttle section has a protruding dimension or size, increasing incrementally in accordance with a decrease in the distance from the throttle section to the scanning section from an upstream end of the throttle section in the bypass passage in the direction of airflow through the bypass passage. A position at the upstream end of the throttle section is referred to as a starting point position, and a position of the throttle section where the distance between the center of gravity of the scanning surface section and the throttle section is shortest is referred to as an endpoint position. The starting point position and the endpoint position define an imaginary line, and the imaginary line and the flow direction define an angle ranging from 0 degrees to 30 degrees.

[0027] Therefore, effects identical to those in the first aspect can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The above and other functions, features, and advantages of the present disclosure will become clearer from the following detailed description, which is prepared with reference to the accompanying drawings. In the drawings: Fig. Figure 1 is a diagram showing an outline of a flow measuring device viewed from upstream of an intake air flow according to a first embodiment of the present disclosure; Fig. Figure 2 is a cross-sectional view showing the flow measuring device along a flow direction of the intake air according to the first embodiment; Fig. Figure 3 is a cross-sectional view showing the flow measuring device recorded along a III-III line in Fig. 2, according to the first embodiment; Fig. Figure 4 is a graph showing a relationship between a measurement error and an angle in a case where the vibration frequency is 100 Hz according to the first embodiment; Fig. Figure 5 is a graph showing a relationship between the measurement error and the angle in a case where the vibration frequency is 130 Hz according to the first embodiment; Fig. Figure 6 is a cross-sectional view showing the flow measuring device according to a second embodiment of the present disclosure and corresponding to Fig. 3 in the first embodiment; Fig. Figure 7 is a cross-sectional view showing the flow measuring device according to a third embodiment of the present disclosure and corresponding to Fig. 3 in the first embodiment; Fig. Figure 8 is a cross-sectional view showing the flow measuring device according to a fourth embodiment of the present disclosure and corresponding to Fig. 2 in the first embodiment; Fig. Figure 9 is a cross-sectional view showing the flow measuring device and recorded along an IX-IX line in Fig. 8 according to the fourth embodiment; Fig. Figure 10 is a graph showing a relationship between the measurement error and the angle in a case where the vibration frequency is a first frequency according to the fourth embodiment; Fig. Figure 11 is a graph showing a relationship between the measurement error and the angle in a case where the vibration frequency is a second frequency according to the fourth embodiment; Fig. 12 is a cross-sectional view showing the flow measuring device according to a fifth embodiment of the present disclosure and corresponding to Fig. 3 in the first embodiment; Fig. Figure 13 is a cross-sectional view showing the flow measuring device according to a modification example of the present disclosure and corresponding to Fig. 3 in the first embodiment; Fig. Figure 14 is a cross-sectional view showing the flow measuring device according to another modification example of the present disclosure and corresponding to Fig. 3 in the first embodiment; Fig. Figure 15 is a diagram showing an endpoint position according to another modification example of the present disclosure; Fig. Figure 16 is a cross-sectional view showing the flow measuring device according to another modification example of the present disclosure and corresponding to Fig. 3 in the first embodiment; Fig. Figure 17 is a diagram showing the flow measuring device along the flow direction of the intake air according to another modification of the example of the present disclosure; and Fig. Figure 18 is a cross-sectional view showing the flow measuring device and recorded along an XVIII-XVIII line in Fig. 17 shows. DESCRIPTION OF EXECUTION FORMS

[0029] In the embodiments, a part corresponding to an object or element described in a preceding embodiment may be assigned the same reference numeral, and a redundant explanation for the part or element may be omitted. If only one part of a configuration is described in one embodiment, another preceding embodiment may be applied to the other parts of the configuration. The parts may be combined, even if it is not explicitly stated that the parts may be combined. The embodiments may be partially combined, even if it is not explicitly stated that the embodiments may be combined, provided that no harm results from the combination.

[0030] Embodiments of the present disclosure are described below. Furthermore, the present disclosure is not limited to those embodiments which are examples of the present disclosure. [First embodiment]

[0031] Referring to the Fig. 1 and Fig. In Section 2, a flow measuring device 1 according to a first embodiment of the present disclosure will be described. The flow measuring device 1 is attached to an intake air duct 2, which is a duct through which intake air flows, being drawn into an internal combustion engine used in a vehicle. The flow measuring device 1 measures a volumetric flow rate of the intake air flowing through the intake air duct 2. According to the present embodiment, a direction in which the intake air flows in a central section of the intake air duct 2 is referred to as a first flow direction f1. The central section of the intake air duct 2 is a part of the intake air duct 2 that is located at a central region of the intake air duct 2. A wall surface forming the intake air duct 2 in the central section hardly influences the flow of the intake air.The flow measuring device 1 has a housing 3 and a flow scanning chip 5.

[0032] The housing 3 receives the flow-sensing chip 5 and projects inwards in a radial direction towards the intake air duct 2, through which the intake air, which is drawn into the internal combustion engine, flows. The housing 3 is made of a resin material and has a bypass passage 7. The bypass passage 7 has a sub-bypass passage 9, which branches off from the bypass passage 7.

[0033] The bypass passage 7 is a passage that introduces a portion of the intake air flowing through the intake air duct 2 and extends in a direction parallel to the first flow direction f1. The bypass passage 7 has a bypass inlet 7a located at the upstream end of the bypass passage 7 and a bypass outlet 7b located at the downstream end of the bypass passage 7. The bypass passage 7 also has an outlet throttle 7c located adjacent to the bypass outlet 7b, which throttles the flow of intake air passing through the bypass passage 7.

[0034] The sub-bypass passage 9 is a passage that introduces a portion of the intake air flowing through the bypass passage 7. The sub-bypass passage 9 has a sub-bypass inlet 9a through which the portion of the intake air flowing through the bypass passage 7 enters, and a sub-bypass outlet 9b through which the intake air flowing through the sub-bypass passage 9 is returned to the intake air duct 2. The sub-bypass passage 9 rotates the intake air flowing into the sub-bypass inlet 9a in the housing 3 and directs the intake air to the bypass outlet 9b. According to the present invention, the sub-bypass passage 9 extends from the sub-bypass inlet 9a in a direction different from the first flow direction f1. Accordingly, foreign substances or...Foreign material such as dirt or oil, which is contained in the intake air duct 2 and enters the bypass inlet 7a, is separated to the bypass outlet 7b, and it can be suppressed that the foreign material enters the sub-bypass passage 9.

[0035] The flow-sensing chip 5 has a scanning surface section 10, which is located on a surface of the flow-sensing chip 5. The scanning surface section 10 scans the flow volume of the intake air. The scanning surface section 10 is planar. The scanning surface section 10 is of a heat transfer type and measures the flow volume by heat transfer between the scanning surface section 10 and the intake air passing through the under-bypass passage 9. The scanning surface section 10 has a heat generation resistor and a temperature sensing resistor, which are located on a surface of the scanning surface section 10.

[0036] The scanning surface section 10 generates an electrical signal in response to the flow volume of the intake air in the sub-bypass passage 9. The flow scanning chip 5 outputs the electrical signal to the ECU (not shown) via a connection in a connector 11. In other words, the flow scanning chip 5 indirectly outputs an electrical signal in response to the flow volume of the intake air in the intake air duct 2. According to the present embodiment, a direction in which the intake air flows in a central section of the sub-bypass passage 9 is referred to as a second flow direction f2. The central section of the sub-bypass passage 9 is a portion of the sub-bypass passage 9 located at a central region of the passage. A wall surface of a flow passage wall forming the sub-bypass passage 9 has little influence on the intake air flow in the central section.

[0037] The flow-sensing chip 5 is supported by a support section 13, and the scanning surface section 10 is exposed to the under-bypass passage 9. Specifically, the flow-sensing chip 5 is supported by the support section 13 such that the surface of the scanning surface section 10 is positioned in a direction parallel to the second flow direction f2. The scanning surface section 10 is positioned on a portion of the surface of the flow-sensing chip 5. According to the first embodiment, the first flow direction f1 is opposite to the second flow direction f2.

[0038] The underpass passage 9 is throttled by a throttling section 15 such that a cross-sectional area of ​​the underpass passage 9 decreases perpendicular to the second flow direction f2 in accordance with a decrease in the distance from a centroid of the scanning surface section 10 to a center of the cross-sectional area in the direction parallel to the second flow direction f2. The throttling section 15 is part of a first flow passage wall 16a, which forms the underpass passage 9, and faces the scanning surface section 10. A second flow passage wall 16b, which forms the underpass passage 9, is opposite to the first flow passage wall 16a. In other words, the flow scanning chip 5 is supported between a pair of flow passage walls, that is, the first flow passage wall 16a and the second flow passage wall 16b, by the support section 13.According to the present embodiment, the housing 3 has the first flow passage wall 16a and the second flow passage wall 16b.

[0039] The throttle section 15 throttles the cross-sectional area of ​​the under-bypass passage 9 such that the distance from the scanning surface section 10 to the first flow passage wall 16a on the cross-sectional area decreases in a direction perpendicular to the scanning surface section 10, corresponding to a decrease in the distance from the centroid of the scanning surface section 10 to the center of the cross-sectional area in the direction parallel to the second flow direction f2. The throttle section 15 extends in the direction parallel to the second flow direction f2. The throttle section 15 has a first throttle section 15u, which is located upstream of the centroid of the scanning surface section 10 in the second flow direction f2, and a second throttle section 15d, which is located downstream of the centroid of the scanning surface section 10 in the second flow direction f2.The throttle section 15 is a shape which is elongated in the direction parallel to the second flow direction f2.

[0040] A position where the first throttle section 15u starts is referred to as a first starting point position αu, and a position of the first throttle section 15u where the distance between the center of gravity of the scanning surface section 10 and the first throttle section 15u is shortest is referred to as a first endpoint position βu. In this case, the distance is referred to as the shortest distance between the center of gravity of the scanning surface section 10 and the first throttle section 15u. The first starting point position αu and the first endpoint position βu define a first imaginary line γu. The first imaginary line γu and the second flow direction f2 define a first angle δu, which is in a range from 0 degrees to 20 degrees.

[0041] The first starting point position αu is located at the uppermost stream of the first throttle section 15u in the second flow direction f2. According to the present embodiment, the shortest total distance is the sum of the distance between the center of gravity of the scanning surface section 10 and the first flow passage wall 16a on the first throttle section 15u in the direction perpendicular to the scanning surface section 10 and the distance between the center of gravity of the scanning surface section 15u and the first flow passage wall 16a on the first throttle section 15u in the direction parallel to the second flow direction f2.In this case, the total distance is equivalent to the shortest distance between the center of gravity of the scanning surface section 10 and the first throttle section 15u.

[0042] If multiple starting point positions αu exist, the first starting point position αu is the position where the distance between the first starting point position αu and the first endpoint position βu is shortest. In this case, the distance is referred to as the shortest distance between the first starting point position αu and the first endpoint position βu. According to the present embodiment, the shortest total distance is the sum of the distance between the first starting point position αu and the first endpoint position βu in the direction perpendicular to the scanning surface section 10 and the distance between the first starting point position αu and the first endpoint position βu in the direction parallel to the second flow direction f2.In this case, the total distance is equivalent to the shortest distance between the first starting point position αu and the first endpoint position βu.

[0043] A position at which the second throttle section 15d starts is referred to as a second starting point position αd, and a position of the second throttle section 15d at which the distance between the center of gravity of the scanning surface section 10 and the second throttle section 15d is shortest is referred to as a second endpoint position βd. In this case, the distance is referred to as the shortest distance between the center of gravity of the surface scanning section 10 and the second throttle section 15d. The second starting point position αd and the second endpoint position βd define a second imaginary line γd. The second imaginary line γd and the second flow direction f2 define a second angle δd, which is in a range from 0 degrees to 20 degrees. According to the present embodiment, the second flow direction f2 is parallel to the scanning surface section 10.The second starting point position αd is placed furthest downstream (lowermost stream) of the second throttle section 15d in the second flow direction f2.

[0044] The first throttle section 15u and the second throttle section 15d have surfaces that are curved and project inwards in a radial direction towards the under-bypass passage 9. In particular, the throttle section 15, which comprises the first throttle section 15u and the second throttle section 15d, has a side surface facing the scanning surface section 10. In this case, the side surface is also a side surface of a cylinder, which has an axis extending in a vertical direction perpendicular to the second flow direction f2 and parallel to the scanning surface section 10.

[0045] According to the present embodiment, in the flow measuring device 1, the under-bypass passage 9 is throttled by the first throttling section 15u such that the cross-sectional area of ​​the under-bypass passage 9 decreases perpendicular to the second flow direction f2 in accordance with a decrease in distance from the centroid of the scanning surface section 10 to the center of the cross-sectional area in the direction parallel to the second flow direction f2. The first throttling section 15u is part of the first flow passage wall 16a and faces the scanning surface section 10.The first throttling section 15u throttles the cross-sectional area of ​​the under-bypass passage 9 such that the distance from the scanning surface section 10 to the first flow passage wall 16a on the cross-sectional area decreases in the direction perpendicular to the scanning surface section 10 in accordance with a decrease in the distance from the centroid of the scanning surface section 10 to the center of the cross-sectional area in the direction parallel to the second flow direction f2.

[0046] Since the first starting point position αu is a position where the first throttle section 15u starts, and the first endpoint position βu is the position of the first throttle section 15u where the distance between the center of gravity of the scanning surface section 10 and the first throttle section 15u is shortest, the first angle δu, which is defined by the first imaginary line γu and the second flow direction f2, is in a range from 0 degrees to 20 degrees.

[0047] Therefore, since the first flow passage wall 16a is varied stepwise in the first throttle section 15u, the generation of a vortex or separation in the intake air flow in the vicinity of the first throttle section 15u can be suppressed. Furthermore, disturbances in the intake air flow caused by the first throttle section 15u at the scanning surface section 10 can be suppressed. Finally, the scanning accuracy of the flow volume at the scanning surface section 10 in the flow measuring device 1, which includes the first throttle section 15u, can be improved.

[0048] The surface of the first throttle section 15u is curved and projects inwards in the radial direction of the under-bypass passage 9. This allows for a variation relative to the flow direction of the surface of the first throttle section 15u to be maintained, thus reducing the cross-sectional area of ​​the under-bypass passage 9 perpendicular to the second flow direction f2. Furthermore, this suppresses the formation of vortices or separation in the intake air flow in the vicinity of the first throttle section 15u and reduces the pressure drop in the under-bypass passage 9.

[0049] The first throttle section 15u and the second throttle section 15d are positioned upstream and downstream, respectively, of the scanning surface section 10 in the second flow direction f2. Since the second throttle section 15d is positioned downstream of the scanning surface section 10 in the second flow direction f2, the flow measuring device 1 can adequately measure the flow volume in a case where a pulsed flow is generated in response to the actuation of a piston in the internal combustion machine. In other words, if a gas flows from downstream to upstream, a flow rate can be ensured at the scanning surface section 10, and the flow measuring device 1 can adequately measure the flow volume.

[0050] The Fig. 4 and Fig. Figure 5 are graphs that graphically represent the measurement error that occurs when the first angle δu is changed. As in Fig. As shown in Figure 4, if the vibration frequency of the flow volume is low, the measurement error is relatively small without considering the value of the first angle δu, and the flow measuring device 1 has a characteristic that changes in response to a change in the flow volume. With the change in the flow volume, the flow volume increases or decreases. As shown in Fig. As shown in Figure 5, when the vibration frequency of the flow volume is high, the measurement error increases in cases where the first angle δu exceeds 20 degrees, and the characteristic deteriorates. As the vibration frequency increases, eddies or separation are easily generated in the intake air flow, and the influence of the first angle δu on the measurement error becomes greater. According to the present embodiment, the vibration frequency of the flow volume is equivalent to a pulse flow vibration frequency generated in response to the operation of the piston in the internal combustion engine. The vibration frequency of the flow volume has a predetermined central value and indicates a frequency of this value when the flow volume changes at a predetermined vibration amplitude. [Second embodiment]

[0051] Referring to Fig. Section 6 describes components of the flow measuring device 1 according to a second embodiment of the present disclosure, which differ from those of the first embodiment. Additionally, the substantially identical parts and components are indicated as the embodiment in the present disclosure with the same reference numerals. According to the present embodiment, the first throttle section 15u in the flow measuring device 1 has a surface 17u, which is a planar surface. Furthermore, according to the present embodiment, the second throttle section 15d is deleted. Therefore, according to the present embodiment, the first throttle section 15u is referred to as a throttle section 15u.

[0052] Fig. Figure 6 shows a starting point position αu, an endpoint position βu, an imaginary line γu, and an angle δu, which are equivalent to the first starting point position αu, the first endpoint position βu, the first imaginary line γu, and the first angle δu of the first embodiment. In particular, the starting point position αu is located upstream of the scanning surface section 10, which is a scanning section 18 in a flow direction f2 that is equivalent to the second flow direction f2 of the first embodiment. The surface 17u of the throttle section 15u and the flow direction f2 define an angle that is equal to the angle δu.

[0053] Accordingly, a variation relative to a flow direction of the surface of the throttled section 15u can be maintained to ensure stability. The cross-sectional area of ​​the under-bypass passage 9, perpendicular to the flow direction f2, can be reduced at the sampling section 18, and the flow rate at the sampling section 18 can be maintained. Since the cross-sectional area varies stepwise, the magnitude of the flow rate variation generated by the throttled section 15u in the vicinity of the surface 17u is small, thus preventing the generation of a vortex. Because the surface 17u is planar, it is difficult to generate a flow rate variation in a direction perpendicular to a flow traveling along the surface 17u, and separation can be prevented.Additionally, since surface 17u is a planar surface, it is easy to form surface 17u. [Third embodiment]

[0054] Referring to Fig. Section 7 describes components of the flow measuring device 1 according to a third embodiment of the present disclosure, which differ from those of the second embodiment. According to the present embodiment, a second throttle section 20, which differs from the first throttle section 15u, is positioned on the second flow passage wall 16b in the flow measuring device 1. Since at least two throttle sections are provided in the lower bypass passage 9, the cross-sectional area of ​​the lower bypass passage 9 can be further reduced if the angle δu is maintained to be less than 20 degrees. This allows the flow rate of the intake air at the scanning surface section 10 to be further increased, and the heat transfer efficiency and scanning accuracy can be further stabilized.

[0055] If the first throttle section 15u is located on the first flow passage wall 16a, and the vortex directly reaches the scanning surface section 10, the vortex's influence on the intake air flow at the scanning surface section 10 is maximized. In this case, it is unlikely that the vortex, generated by the throttle section being located on a flow passage wall other than the first flow passage wall 16a, will reach the scanning surface section 10, and the vortex's influence on the intake air flow at the scanning surface section 10 decreases. Therefore, the second throttle section 20, located on the second flow passage wall 16b, does not affect the intake air flow at the scanning surface section 10, and the second throttle section 20 can adjust the cross-sectional area of ​​the under-bypass passage 9. [Fourth embodiment]

[0056] According to the first embodiment, if the vibration frequency of the flow volume is high and the first angle δu exceeds 20 degrees, the measurement error increases. According to a fourth embodiment of the present disclosure, if the vibration frequency of the flow volume is high and the first angle δu is 30 degrees, the measurement error remains relatively small. According to the present embodiment, components of the flow measuring device 1, which differ from those of the first embodiment, will be described.

[0057] According to the present embodiment, as in Fig. Figure 8 shows a portion of the bypass passage 7 from the bypass inlet 7a to the bypass outlet 7b, referred to as a passage or through passage 8. The through passage 8 has an upstream end section where the bypass inlet 7a is located and a downstream end section where the bypass outlet 7b is located. The through passage 8 extends in the direction parallel to the first flow direction f1 of the intake air duct 2. According to the present embodiment, the sub-bypass passage 9 can be referred to as a branch passage that branches off from an intermediate part of the through passage 8.

[0058] According to the present embodiment, as shown in Fig. As shown in Figure 9, the first throttle section 15u has an inner circumferential surface extending exactly from the first starting point position αu to the first endpoint position αd, and the second throttle section 15d has an inner circumferential surface extending exactly from the second starting point position βu to the second endpoint position βd. According to the present embodiment, the inner circumferential surface of the first throttle section 15u is equivalent to a surface of the first throttle section 15u according to the first embodiment. According to the present disclosure, the first throttle section 15u and the second throttle section 15d each have inner circumferential surfaces which may have a portion that is recessed, protrudes, or is curved. The first angle δu and the second angle δd are equal to 30 degrees. The first throttle section 15u is equivalent to an upstream throttle section.The scanning surface section 10 is referred to as a scanning section.

[0059] A pair of flow passage walls, comprising the first flow passage wall 16a and the second flow passage wall 16b, are arranged in an orientation direction referred to as a lateral direction X. The first flow passage wall 16a includes the first throttling section 15u and the second throttling section 15d, and the second flow passage wall 16b excludes the first throttling section 15u and the second throttling section 15d. The lateral direction X is an orthogonal direction, perpendicular to the second flow direction f2. The support section 13 is made of a synthetic resin material and is plate-shaped. The support section 13 divides the under-bypass passage 9 into two regions in the lateral direction.The support section 13 is positioned parallel to the first flow passage wall 16a and the second flow passage wall 16b and extends in the direction parallel to the second flow direction f2. The support section 13 is also positioned parallel to the direction in which the first starting point position αu and the second starting point position αd are aligned. The support section 13 has a first opposite surface 13a facing the first flow passage wall 16a and a second opposite surface 13b facing the second flow passage wall 16b. The flow scanning chip 5 and the scanning surface section 10 are positioned on the first opposite surface 13a.

[0060] The support section 13 has a support length L1, which is the length of the support section 13 in the direction parallel to the second flow direction f2, which is equal to a throttle length La, which is the combined length of the first throttle section 15u and the second throttle section 15d in the direction parallel to the second flow direction f2. The flow-sensing chip 5 and the scanning surface section 10 are positioned at the center of the support section 13 in the direction parallel to the second flow direction f2. In other words, the flow-sensing chip 5 and the scanning surface section 10 are positioned such that the centerlines of the flow-sensing chip 5 and the scanning surface section 10, which are parallel to the lateral direction X, coincide with a centerline C of the support section 13, which is perpendicular to the second flow direction f2.A first support distance L2, which is a distance from an upstream end of the support section 13 to the center line C, is equal to a second support distance L3, which is a distance from the center line C to a downstream end of the support section 13.

[0061] The centerline C of the support section 13 is located upstream of the first endpoint position βu and the second endpoint position βd in the second flow direction f2. The upstream end of the support section 13 is located upstream of the first starting point position αu in the second flow direction f2, and the downstream end of the support section 13 is located upstream of the second starting point position αd in the second flow direction f2. The centerline C, the first endpoint position βu, and the second endpoint position βd define a distance in the direction parallel to the second flow direction f2, which is referred to as a center-displacement distance L4. The upstream end of the support section 13 and the first starting point position αu define a distance which is referred to as an upstream displacement distance L5.The downstream end of the support section 13 and the second starting point position αd define a distance to which a downstream displacement distance L6 is referred. Since the support length L1 of the support section 13 is equal to the throttle length La of the first throttle section 15u and the second throttle section 15d, the mean displacement distance L4, the upstream displacement distance L5, and the downstream displacement distance L6 are equal to each other.

[0062] The throttle length La is also a distance from the first starting point position αu to the second starting point position αd. The first throttle section 15u, which is located upstream of the center of gravity of the scanning surface section 10, has a length in the direction parallel to the second flow direction f2, to which reference is made as a first throttle length Lb, and is equal to the length of the second throttle section 15d, which is located downstream of the center of gravity of the scanning surface section 10 in the direction parallel to the second flow direction f2, to which reference is made as a second throttle length Lc. The throttle length La is the sum of the first throttle length Lb and the second throttle length Lc.In this case, the first angle δu is equal to the second angle δd, and the first endpoint position βu and the second endpoint position βd are placed in a midpoint between the first starting point position αu and the second starting point position αd.

[0063] The scanning surface section 10 is positioned between the first start point position αu and the first end point position βu or between the first start point position αu and the second end point position βd in the direction parallel to the second flow direction f2. The scanning surface section 10 is positioned close to the first end point position βu and the second end point position βd, and the scanning surface section 10 does not protrude to a position downstream of the first end point position βu and the second end point position βd in the second flow direction f2. The scanning surface section 10 is positioned close to the first end point position βu and the second end point position βd such that the flow scanning chip 5 protrudes to a position downstream of the first end point position βu and the second end point position βd in the second flow direction f2.In a configuration where the scanning surface section 10 does not protrude to a position downstream of the first endpoint position βu and the second endpoint position βd in the second flow direction f2, half of a scanning length L7, which is a length of the scanning surface section 10 in the direction parallel to the second flow direction f2, is shorter than the center displacement distance L4. In this case, a central part of the scanning surface section 10 is positioned upstream of the first endpoint position βu and the second endpoint position βd.

[0064] The support section 13 is positioned where the first flow passage wall 16a is closer to the support section 13 than the second flow passage wall 16b is in the latitudinal direction X. A first facing distance B1, which is a distance from the first starting point position αu and the second starting point position αd to the support section 13 in the latitudinal direction X, is shorter than a second facing distance B2, which is a distance from the support section 13 to the second flow passage wall 16b in the latitudinal direction X. A gap distance B3, which is a distance from the first endpoint position βu and the second endpoint position βd to the support section 13 in the width direction X, is shorter than a throttle distance B4, which is a distance from the first starting point position αu and the second starting point position αd to the first endpoint position βu and the second endpoint position βd in the width direction X.The first facing distance B1 is the sum of the gap distance B3 and the throttle distance B4. The gap distance B3 is longer than one thickness of the support section 13 and one thickness of the flow-sensing chip 5.

[0065] A space between the first flow passage wall 16a and the support section 13 is referred to as a first region 21a, in which the scanning surface section 10 is located, and a space between the support section 13 and the second flow passage wall 16b is referred to as a second region 21b. According to the present embodiment, the first region 21a is equivalent to a scanning region, and the second region 21b is equivalent to an opposite region. The support section 13 is located between the scanning surface section 10 and the second region 21b. The width of the first region 21a in the lateral direction X increases stepwise from the starting point position αu to the first endpoint position βu in the second flow direction f2, and increases stepwise from the second endpoint position βd to the second starting point position αd in the second flow direction f2.

[0066] The first flow passage wall 16a further comprises an upstream wall surface 22a, which is located upstream of the first starting point position αu, and a downstream wall surface 22b, which is located downstream of the second starting point position αd. Thus, the first region 21a is also defined by the upstream wall surface 22a and the support section 13. The upstream wall surface 22a and the downstream wall surface 22b are each in contact with the first starting point position αu and the second starting point position αd, respectively. The distance from the upstream wall surface 22a and the downstream wall surface 22b to the support section 13 in the lateral direction X is equal to the first adjacent distance B1.

[0067] According to the present embodiment, since the inner circumferential surfaces of the first throttle section 15u and the second throttle section 15d extend straight, the first angle δu is equal to an inclination angle of the inner circumferential surface of the first throttle section 15u relative to the upstream wall surface 22a, and the second angle δd is equal to an inclination angle of the inner circumferential surface of the second throttle section 15d relative to the downstream wall surface 22b.

[0068] The intake air, which flows into the under-bypass passage 9 upstream of the support section 13, is divided into two parts: a first intake air flowing into the first section 21a, and a second intake air flowing into the second section 21b. Since the width of the second section 21b is greater than the width of the first section 21a, foreign matter or substances contained in the intake air flow into the second section 21b more easily than into the first section 21a. In other words, a configuration is achieved that makes it difficult for foreign matter or substances to flow into the first section 21a.Accordingly, it can be suppressed that the scanning accuracy of the scanning surface section 10 is deteriorated or that the scanning surface section 10 is damaged due to foreign substances or foreign bodies that approach or are in contact with the scanning surface section 10.

[0069] Since the support section 13 extends to a position upstream of the first throttle section 15u, the width of an upstream end portion of the first region 21a is equal to the first facing distance B1. The width of the upstream end portion of the first region 21a is greater than that in a configuration where the first throttle section 15u extends to a position upstream of the support section 13. Therefore, in the configuration where the first throttle section 15u extends to a position upstream of the support section 13, the flow area ratio of the first region 21a to the second region 21b is larger, and more intake air can flow into the first region 21a. A throttle rate is a ratio of the upstream end portion of the first region 21a to the downstream end portion of the first region 21a.If the width of the upstream end section increases, it is likely that the throttling rate will increase, and the flow rate of the first intake air reaching the downstream end section of the first region 21a will increase.

[0070] The flow rate of the initial intake air entering the first region 21a is gradually increased while the initial intake air is throttled between the support section 13 and the first throttle section 15u, after the initial intake air is aligned or straightened between the support section 13 and the upstream wall surface 22a. A portion of the first region 21a between the support section 13 and the upstream wall surface 22a acts as an alignment or straightening region, aligning or straightening the initial intake air. It is difficult for the disturbance, which is the vortex or separation, to be generated in the initial intake air within the first region 21a between the support section 13 and the first throttle section 15u. The scanning surface section 10 scans the flow volume based on a temperature change generated according to the flow volume of the initial intake air.Accordingly, if the temperature change is generated due to the disturbance of the flow applied to the scanning surface section 10, the scanning accuracy of the flow volume is deteriorated by using the scanning surface section 10.

[0071] Since the first region 21a is enlarged downstream of the first endpoint position βu and the second endpoint position βd in the second flow direction f2, the disturbance, which is the vortex or the separation, is readily generated in the first intake air passing through the first endpoint position βu and the second endpoint position βd in the first region 21a. When the first intake air flowing along the first throttle section 15u passes the first endpoint position βu and the second endpoint position βd, the disturbance is generated at a position immediately downstream of the first endpoint position βu and the second endpoint position βd due to a portion of the first intake air flowing along the second throttle section 15d and a portion of the first intake air flowing towards the support section 13.

[0072] Since the scanning surface section 10 is located upstream of the first endpoint position βu and the second endpoint position βd, it is unlikely that the flow generated at a position downstream of the first endpoint position βu and the second endpoint position βd will affect the initial intake air between the scanning surface section 10 and the first throttle section 15u. Therefore, it is unlikely that the scanning accuracy of the scanning surface section 10 will be degraded by the flow generated in the initial intake air downstream of the first endpoint position βu and the second endpoint position βd.

[0073] Recently, as the cylinder of the internal combustion engine has been miniaturized in response to a reduction in the number of components or a reduction in weight, the influence on the intake air in the intake air duct 2 is slightly reduced, and the vibration of the flowing air relative to a flow direction is slightly increased. When the vibration frequency, which is a frequency of the vibration, is increased, the disturbance generated in the intake air in the first area 21a is increased. Then the measurement error of the flow measuring device 1 is slightly increased. According to the present embodiment, the unit of measurement error is %.In a configuration where the scanning surface section 10 is placed in the sub-bypass passage 9 in the bypass passage 7, without being placed in the passage 8 in the bypass passage 7, the measurement error is readily increased in a case where the disturbance generated when the intake air flows from the passage 8 into the sub-bypass passage 9 reaches the first area 21a.

[0074] As in Fig. Figure 10 is similar to the first embodiment, where the vibration frequency is a relatively low first frequency, and the measurement error is within a permissible range in a case where the first angle δu is greater than 20 degrees. In this case, a measurement result from the flow measuring device 1 indicates a characteristic that changes in response to a change in the intake air in the intake air duct 2. As shown in Fig. As shown in Figure 10, if the first angle δu is up to 30 degrees or 40 degrees, the measurement error remains within the permissible range. According to the present embodiment, the first frequency can be 100 Hz, and the permissible range of the measurement error can be less than or equal to 3%.

[0075] According to the first embodiment, if the vibration frequency is a second frequency which is relatively high, it is assumed that the measurement error is sharply increased to be outside the permissible range in a case where the first angle δu exceeds 20 degrees. According to the present embodiment, as in Fig. As shown in Figure 11, the measurement error remains within the permissible range in a case where the first angle δu exceeds 20 degrees and is up to a value that slightly exceeds 30 degrees, and the measurement error increases sharply to be outside the permissible range in a case where the first angle δu exceeds the value that slightly exceeds 30 degrees. In this case, it is difficult to assume that the disturbance in the first intake air is generated in the first region 21a in a case where the support section 13 faces the upstream wall surface 22a in the first region 21a, and the scanning surface section 10 is placed upstream of the first endpoint position βu and the second endpoint position βd.

[0076] According to the present embodiment, since the first angle δu and the second angle δd are set to 30 degrees by the first throttle section 15u and the second throttle section 15d, the measurement error of the flow measuring device 1 can be reduced more than in a case where the first angle δu and the second angle δd are set to be greater than 30 degrees.

[0077] According to the present embodiment, since the scanning surface section 10 is positioned between the first start point position αu and the first end point position βu, it is difficult for the disturbance generated in the flow downstream of the first end point position βu to affect the scanning surface section 10. Therefore, the degradation of the scanning accuracy of the scanning surface section 10 due to the disturbance generated in the flow downstream of the first end point position βu can be suppressed. Furthermore, since the scanning surface section 10 is positioned close to the first end point position βu and the second end point position βd, where the flow rate of the first intake air is readily increased in the first region 21a, the flow rate of the first intake air exerted on the scanning surface section 10 is also readily increased.Accordingly, the scanning accuracy of the scanning surface section 10 can be improved.

[0078] According to the present embodiment, the support section 13 extends to a position upstream of the first starting point position αu. Thus, the first intake air flowing into the first region 21a flows between the support section 13 and the upstream wall surface 22a to be aligned before reaching the first throttle section 15u. Therefore, it is difficult for the disturbance to be generated in the first intake air and reach the scanning surface section 10.

[0079] According to the present embodiment, the gap distance B3 is shorter than the throttle distance B4. In this case, since the flow rate of the first intake air, which reached the first endpoint position βu and the second endpoint position βd in the first region 21a, is increased more easily than the flow rate of the first intake air, which passes the first starting point position αu, the scanning accuracy of the scanning surface section 10 can be improved.

[0080] According to the present embodiment, the first facing distance B1 is shorter than the second facing distance B2. In this case, since the width of the first area 21a is smaller than the width of the second area 21b, the probability of the foreign substance entering the first area 21a can be reduced. Therefore, the deterioration of the scanning accuracy of the scanning surface section 10 or damage to the scanning surface section 10 due to the foreign substance can be prevented. [Fifth embodiment]

[0081] According to the fourth embodiment, the first endpoint position βu coincides with the second endpoint position βd. According to a fifth embodiment of the present disclosure, as in Fig. As shown in Figure 12, the first endpoint position βu and the second endpoint position βd are separated from each other in the direction parallel to the second flow direction f2. According to the present embodiment, components of the flow measuring device 1, which differ from those according to the fourth embodiment, are described.

[0082] According to the present embodiment, a connecting section 23, which is connected to the first throttle section 15u and the second throttle section 15d, is positioned between the first throttle section 15u and the second throttle section 15d. The connecting section 23 has an inner circumferential surface that extends in a direction parallel to the upstream wall surface 22a and the downstream wall surface 22b. The connecting section 23 has a connection length Ld, which is the length of the connecting section in the direction parallel to the second flow direction f2. The connection length Ld is also the distance from the first endpoint position βu to the second endpoint position βd.

[0083] The scanning surface section 10 is positioned facing the connecting section 23. Specifically, the scanning surface section 10 is located between the first endpoint position βu and the second endpoint position βd in the direction parallel to the second flow direction f2. The connecting length Ld is longer than a chip length L8, which is a length of the flow-sensing chip 5 in the direction parallel to the second flow direction f2. The scanning surface section 10 is positioned close to the first endpoint position βu such that the flow-sensing chip 5 extends to a position upstream of the first endpoint position βu in the second flow direction f2. The connecting section 23 has an upstream end located upstream of the first endpoint position βu and a downstream end located downstream of the second endpoint position βd.

[0084] According to the present embodiment, the gap distance B3 is equal to the throttle distance B4. However, the gap distance B3 can be longer than the throttle distance B4. In this case, since the width of the first region 21a decreases stepwise in the lateral direction X in accordance with a decrease in the distance between a position of the first opposing surface 13a on a cross-sectional area that includes the width and the center of gravity of the scanning surface section 10 in the direction parallel to the second flow direction f2, the flow rate of the first intake air flowing between the connecting section 23 and the support section 13 can be suitably increased.

[0085] According to the present embodiment, a space in the first region 21a between the connecting section 23 and the support section 13 is referred to as a most throttled region. Since the surface scanning section 10 is located in the most throttled region, the flow rate of the first intake air, which is exerted or applied to the scanning surface section 10, can be sufficiently increased. Furthermore, since the scanning surface section 10 is located upstream of the second endpoint position βd, which is the same as that in the fourth embodiment, it is difficult for disturbances such as vortices, which are generated in the flow when the intake air passes through the second endpoint position βd, to be prevented.Accordingly, it can be suppressed that the scanning accuracy of the scanning surface section 10 is degraded due to the disturbance of the flow, which is generated downstream of the second endpoint position βd. [Other embodiment]

[0086] The above embodiments can be modified into various embodiments within the scope and intent of the present disclosure. According to the first embodiment, the first throttle section 15u and the second throttle section 15d have surfaces which are curved surfaces. As in Fig. As shown in Figure 13, according to a sixth embodiment of the present disclosure, which is a modification of the first embodiment, the first throttle section 15u and the second throttle section 15d have surfaces which are planar surfaces.

[0087] A space within the under-bypass passage 9 between the first throttle section 15u and the second throttle section 15d, in the direction parallel to the second flow direction f2, is a constant region in which the cross-sectional area of ​​the under-bypass passage 9 is minimal and constant perpendicular to the second flow direction f2. The scanning surface section 10 is located within this constant region.

[0088] According to the second embodiment, the cross-sectional area of ​​the under-bypass passage 9 is perpendicular to the second flow direction f2 and is minimal at the scanning surface section 10. As in Fig. As shown in Figure 14, according to a seventh embodiment of the present disclosure, which is a modification of the second embodiment, the cross-sectional area of ​​the under-bypass passage 9 is minimal at a position downstream of the scanning surface section 10, perpendicular to the second flow direction f2.

[0089] The distance between the first position p1 and the scanning surface section 10 is the sum of the first distance d1 and the second distance d2 (d1+d2). A first distance d1 is a distance between the first position p1 and the scanning surface section 10 in a direction perpendicular to the surface of the scanning surface section 10 and the second flow direction f2. A second distance d2 is a distance between the first position p1 and the surface scanning section 10 in a direction parallel to the second flow direction f2. A third distance d3 is a distance obtained by subtracting the first distance d1 from a distance between the second position p2 and the scanning surface section 10 in a direction perpendicular to the surface of the scanning surface section 10 and the second flow direction f2. As in Fig. As shown in Figure 15, the length of the second line L2 is equal to the distance between the second position p2 and the scanning surface section 10 in the direction perpendicular to the surface of the scanning surface section 10 and the second flow direction f2. Therefore, the distance between the second position p2 and the scanning surface section 10 is equal to the sum of the first distance d1 and the third distance d3 (d1+d3). Since the first angle δu is in a range from 0 degrees to 20 degrees, the second distance d2 is longer than the third distance d3. Then, the distance between the first position p1 and the scanning surface section 10 is longer than the distance between the second position p2 and the scanning surface section 10. Therefore, the first endpoint position βu is set to be located at the second position p2, which is likewise in Fig. 14 is shown. As in Fig. As shown in Figure 15, a first position p1 is a position of the surface of the first flow passage wall 16a, and the first position p1 and the centroid of the scanning surface section 10 define a first line L1 perpendicular to the surface of the first flow passage wall 16a. A second position p2 is a position of the surface of the first flow passage wall 16a, and the second position p2 and the centroid of the scanning surface section 10 define a second line L2 perpendicular to the surface of the scanning surface section 10.

[0090] According to an eighth embodiment of the present disclosure, which is another modification of the second embodiment, as in the Fig. 13 and Fig. As shown in Figure 16, the first throttle section 15u is placed upstream of the scanning surface section 10 in the second flow direction f2.

[0091] According to a ninth embodiment of the present disclosure, which is another modification of the second embodiment, as in the Fig. 17 and Fig. As shown in Figure 18, the first throttle section 15u is positioned non-coaxially with the scanning surface section 10 in the direction parallel to the second flow direction f2. The distance between the scanning surface section 10 and the first throttle section 15u is the distance between the centroid of the scanning surface section 10 and the first throttle section 15u.According to the present embodiment, the shortest total distance is the sum of the distance between the center of gravity of the scanning surface section 10 and the first flow passage wall 16a on the first throttle section 15u in the direction perpendicular to the scanning surface section 10 and the distance between the center of gravity of the scanning surface section 10 and the first flow passage wall 16a on the first throttle section 15u in the direction parallel to the second flow direction f2. In this case, the total distance is equivalent to the shortest distance between the center of gravity of the scanning surface section 10 and the first throttle section 15u.

[0092] If multiple starting point positions αu exist, the first starting point position αu is the position where the distance between the first starting point position αu and the first endpoint position βu is shortest. In this case, the distance is referred to as the shortest distance between the first starting point position αu and the first endpoint position βu. According to the present embodiment, the shortest total distance is the sum of the distance between the first starting point position αu and the first endpoint position βu in the direction perpendicular to the scanning surface section 10 and the distance between the first starting point position αu and the first endpoint position βu in the direction parallel to the second flow direction f2.In this case, the total distance is equivalent to the shortest distance between the first starting point position αu and the first endpoint position βu.

[0093] According to the third embodiment, the second throttle section 20 is positioned on the second flow passage wall 16b facing the first flow passage wall 16a. According to a tenth embodiment of the present disclosure, which is a modification of the third embodiment, the second throttle section 20 is positioned on a flow passage wall other than the second flow passage wall 16b. Since the vortex only slightly or minimally affects the scanning surface section 10 when a flow passage wall is separated from the scanning surface section 10 by a predetermined distance, the second throttle section 20 can be positioned on the first flow passage wall 16a.

[0094] According to the first, second, and third embodiments, the housing 3 has the sub-bypass passage 9, which is part of the bypass passage 7. According to an eleventh embodiment of the present disclosure, which is a modification of the first, second, and third embodiments, the housing 3 excludes the sub-bypass passage 9.

[0095] According to a twelfth embodiment of the present disclosure, which is a modification of the fourth and fifth embodiments, the first angle δu and the second angle δd are less than 30 degrees. If the first angle δu and the second angle δd are in a range from 0 degrees to 30 degrees, a configuration can be achieved in which the measurement error is not sharply increased until the first angle δu exceeds 30 degrees, as shown in Fig. Figure 11 shows that a similar configuration can be achieved in which the measurement error is not increased sharply until the second angle δd exceeds 30 degrees.

[0096] According to a thirteenth embodiment of the present disclosure, which is a further modification of the fourth and fifth embodiments, the support length L1 differs from the throttle length La. In a configuration where the support length L1 is longer than the throttle length La, the support section 13 extends to a position upstream of the first throttle section 15u and downstream of the second throttle section 15d in the second flow direction f2. In a configuration where the support length L1 is shorter than the throttle length La, the support section 13 extends to a position upstream of the first throttle section 15u.

[0097] According to a fourteenth embodiment of the present disclosure, which is a further modification of the fourth and fifth embodiments, the flow-sensing chip 5 and scanning surface section 10 are positioned upstream or downstream of a central position of the support section 13 in the second flow direction f2. Furthermore, the scanning surface section 10 is positioned upstream or downstream of a central position of the flow-sensing chip 5 in the second flow direction f2.

[0098] According to a fifteenth embodiment of the present disclosure, which is another modification of the fourth embodiment, the entire flow-sensing chip 5 is placed upstream of the first endpoint position βu and the second endpoint position βd. In this case, the scanning surface section 10 can be placed at a position close to the first endpoint position βu and the second endpoint position βd in the direction parallel to the second flow direction f2.

[0099] According to a sixteenth embodiment of the present disclosure, which is another modification of the fifth embodiment, at least a part of the scanning surface section 10 is located upstream of the first endpoint position βu. For example, the entire scanning surface section 10 is located upstream of the first endpoint position βu. In this case, the scanning surface section 10 does not face the connecting section 23 and faces the first choke section 15u, the same as that according to the fourth embodiment.

[0100] According to a seventeenth embodiment of the present disclosure, which is another modification of the fourth and fifth embodiments, the first angle δu and the second angle δd are less than 30 degrees. For example, the first angle δu is less than the second angle δd, or the first angle δu is greater than the second angle δd. In this case, since a configuration can be achieved in which the measurement error is not sharply increased until the first angle δu exceeds 30 degrees, as described in Fig.As shown in Figure 11, the scanning accuracy of the scanning surface section 10 and the measurement accuracy of the flow measuring device 1 can be adequately maintained. Furthermore, similarly, since a configuration can be achieved in which the measurement error is not sharply increased until the second angle δd exceeds 30 degrees, the scanning accuracy of the scanning surface section 10 and the measurement accuracy of the flow measuring device 1 can be adequately maintained.

[0101] According to an eighteenth embodiment of the present disclosure, which is a further modification of the fourth and fifth embodiments, the support section 13 is not located upstream of the first starting point position αu. In this case, if the support section 13 is located at a position where the first flow passage wall 16a is closer to the support section 13 than other flow passage walls are in the lateral direction X, the measurement error is not sharply increased until the first angle δu or the second angle δd exceeds 30 degrees. In a configuration where the support section 13 is located at a position where the first flow passage wall 16a is closer to the support section than other flow passage walls are in the lateral direction X, the first facing distance B1 is shorter than the second facing distance B2.

[0102] According to a nineteenth embodiment of the present disclosure, which is a further modification of the fourth and fifth embodiments, the support section 13 is not placed at a position where the first flow passage wall 16a is closer to the support section 13 than other flow passage walls in the lateral direction X. In this case, if the support section 13 is placed upstream of the first starting point position αu in the second flow direction f2, the measurement error is not sharply increased until the first angle δu or the second angle δd exceeds 30 degrees.

[0103] According to one aspect of the present disclosure, the flow-measuring device comprises a housing with a bypass passage that introduces a portion of the air flowing through a channel, and a flow-sensing chip located in the bypass passage that has a support section which generates an electrical signal in response to a flow volume of the air in the channel. The bypass passage is throttled by a throttle section such that a cross-sectional area of ​​the bypass passage decreases perpendicular to the flow direction in which the air flows through the bypass passage, corresponding to a decrease in distance from a centroid of the sensing surface section to a center of the cross-sectional area in a direction parallel to the flow direction. The throttle section is part of a flow passage wall facing the sensing surface section.The position at which the throttle section starts is referred to as the starting point position, which is located upstream of the sampling section in the flow direction. The throttle section has a planar surface, and the surface of the throttle section and the flow direction define an angle between 0 and 30 degrees.

[0104] According to another aspect of the present disclosure, the flow-measuring device measures a flow volume of air. The flow-measuring device comprises a bypass passage through which the air flows, a sensing section which outputs an electrical signal in response to the flow volume of air in the bypass passage, a pair of flow passage walls facing each other, with the sensing section being placed between the flow passage walls, and a throttling section which throttles the bypass passage by protruding from the flow passage walls in the direction of the sensing section, in an arrangement direction in which the pair of flow passage walls is arranged.The throttle section has a protruding dimension that increases incrementally in accordance with a decrease in the distance from the throttle section to the scanning section from an upstream end of the throttle section in the bypass passage in the direction of airflow through the bypass passage. A position of an upstream end of the throttle section is referred to as a starting point position, and a position of the throttle section where the segment between the centroid of the scanning surface section and the throttle section is shortest is referred to as an endpoint position. The starting point position and the endpoint position define an imaginary line, and the imaginary line and the flow direction define an angle in the range of 0 degrees to 30 degrees.

[0105] While the present disclosure has been described with reference to its embodiments, it is to be understood that the disclosure is not limited to these embodiments and constructions. The present disclosure is intended to encompass various modifications and equivalent arrangements. In addition to the various combinations and configurations which are preferred, other combinations and configurations comprising more, fewer, or only a single element are likewise within the scope and intent of the present disclosure.

Claims

[1] Flow measuring device comprising the following: a housing (3) which has a bypass passage (7) which introduces a portion of the air flowing through a channel (2); and a flow sensing chip (5) which is placed in the bypass passage and has a scanning surface section (10) which generates an electrical signal in response to a flow volume of air in the channel by means of heat transfer between the scanning surface section and the air flowing through the bypass passage, wherein the scanning surface section is placed along a flow direction (f2) in which the air flows through the bypass passage, the bypass passage is throttled by a throttling section (15, 15u, 15d) such that a cross-sectional area of ​​the bypass passage decreases perpendicular to the flow direction in accordance with a decrease in distance from a centroid of the scanning surface section to a center of the cross-sectional area in a direction parallel to the flow direction, the throttle section is part of a flow passage wall (16a) which faces the scanning surface section, wherein the throttle section throttles the cross-sectional area of ​​the bypass passage such that a distance from the scanning surface section to the flow passage wall on the cross-sectional area decreases in a direction perpendicular to the scanning surface section in accordance with a decrease in the distance from the centroid of the scanning surface section to the center of the cross-sectional area in the direction parallel to the flow direction, a position at which the throttle section starts is referred to as a starting point position (αu, αd), and a position of the throttle section at which the distance between the centroid of the scanning surface section and the throttle section is shortest is referred to as an end point position (βu, βd), and the starting point position and the endpoint position define an imaginary line (γu, γd) and the imaginary line and the flow direction define an angle (δu, δd) which is in a range from 0 degrees to 20 degrees, where the throttle section is an upstream throttle section (15u) which is placed at a position in the bypass passage upstream of the scanning surface section and extends in the flow direction to throttle the bypass passage, and the scanning surface section has a middle part which is placed between the starting point position and the end point position in the flow direction, and wherein the flow measuring device further features a support section (13) which is a plate shape, wherein the support section supports the scanning surface section, the support section extending to a position upstream of the choke section. [2] Flow measuring device according to claim 1, wherein the throttle section has a surface which is a planar surface or a curved surface. [3] Flow measuring device according to claim 1 or 2, wherein another throttle section (20), which is different from the throttle section (15), is placed in the bypass passage. [4] Flow measuring device according to one of claims 1 to 3, wherein the throttle section extends in the direction parallel to the flow direction, the throttle section having a first part which is placed upstream of the center of gravity of the scanning surface section in the flow direction, and a second part which is placed downstream of the center of gravity of the scanning surface section in the flow direction. [5] Flow measuring device comprising the following: a housing (3) which has a bypass passage (7) which introduces a portion of the air flowing through a channel (2); and a flow-sensing chip (5) which is placed in the bypass passage and has a scanning section (18) which generates an electrical signal in response to a flow volume of air in the channel, wherein the bypass passage is throttled by a throttle section (15u) such that a cross-sectional area of ​​the bypass passage decreases perpendicular to a flow direction (f2) in which the air flows through the bypass passage in accordance with a decrease in distance from a center of mass of the sampling section to a center of the cross-sectional area in a direction parallel to the flow direction, the throttle section is part of a flow passage wall (16a) which faces the sampling section, A position at which the throttle section starts is referred to as a starting point position (αu), wherein the starting point position is placed upstream of the sampling section in the flow direction, and the throttle section has a surface (17u) which is a planar surface, wherein the surface of the throttle section and the flow direction define an angle which is in a range from 0 degrees to 20 degrees, wherein the throttling section is an upstream throttling section (15u) which is placed at a position in the bypass passage upstream of the sampling section and extends in the flow direction to throttle the bypass passage, and the scanning section has a middle section which is placed between the starting point position and the end point position in the direction of flow, and wherein the flow measuring device further features a support section (13) which is a plate shape, wherein the support section supports the scanning section, the support section extending to a position upstream of the throttle section. [6] Flow measuring device comprising the following: a housing (3) which has a bypass passage (7) which introduces a portion of the air flowing through a channel (2); and a flow sensing chip (5) which is placed in the bypass passage and has a scanning surface section (10) which generates an electrical signal in response to a flow volume of air in the channel by means of heat transfer between the scanning surface section and the air flowing through the bypass passage, wherein the scanning surface section is placed along a flow direction (f2) in which the air flows through the bypass passage, the bypass passage is throttled by a throttling section (15, 15u, 15d) such that a cross-sectional area of ​​the bypass passage decreases perpendicular to the flow direction in accordance with a decrease in distance from a centroid of the scanning surface section to a center of the cross-sectional area in a direction parallel to the flow direction, the throttle section is part of a flow passage wall (16a) which is contained in the housing and faces the scanning surface section, wherein the throttle section throttles the cross-sectional area of ​​the bypass passage such that that the distance from the scanning surface section to the flow passage wall on the cross-sectional area decreases in a direction perpendicular to the scanning surface section in accordance with a decrease in the distance from the centroid of the scanning surface section to the center of the cross-sectional area in the direction parallel to the flow direction, a position at which the throttle section starts is referred to as a starting point position (αu, αd), and a position of the throttle section at which the distance between the centroid of the scanning surface section and the throttle section is shortest is referred to as an end point position (βu, βd), and the starting point position and the endpoint position define an imaginary line (γu, γd) and the imaginary line and the flow direction define an angle (δu, δd) which is in a range from 0 degrees to 30 degrees, where the throttle section is an upstream throttle section (15u) which is placed at a position in the bypass passage upstream of the scanning surface section and extends in the flow direction to throttle the bypass passage, and the scanning surface section has a middle part which is placed between the starting point position and the end point position in the flow direction, and wherein the flow measuring device further features a support section (13) which is a plate shape, wherein the support section supports the scanning surface section, the support section extending to a position upstream of the choke section. [7] Flow measuring device according to claim 6, wherein a distance (B3) from the endpoint position to the support section (13) which supports the scanning surface section is shorter than a distance (B4) from the starting point position to the endpoint position in an orthogonal direction (X) perpendicular to the flow direction. [8] Flow measuring device according to claim 6 or 7, wherein the flow passage wall is a first flow passage wall (16a), wherein the housing has a second flow passage wall (16b) which faces the first flow passage wall, wherein the support section (13) which supports the scanning surface section is placed between the first flow passage wall and the second flow passage wall, the scanning surface section is placed on a surface (13a) of the support section which faces the first flow passage wall, a distance (B1) from the starting point position of the first flow passage wall to the support section is shorter than a distance (B2) from the support section to the second flow passage wall.

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