Airflow measuring device

Abstract

Air flow measuring device comprising: a housing (4) attached to a channel (2) through which intake air for an internal combustion engine flows in an X-axis direction, wherein the housing (4) is inserted into the channel (2) in a Y-axis direction perpendicular to the X-axis direction and part of the intake air flows through the housing as through-flow air (AF); and a sensor (8) that detects a flow rate of the air flowing through it, wherein the air flow rate measuring device measures a flow rate of the intake air based on a detection result of the sensor, wherein The case contains: a main bypass passage (11) which defines an inlet (13) for drawing in the intake air and an outlet (14) for releasing the flow air drawn in through the inlet; a secondary bypass passage (12) branching off from the main bypass passage at a branching area (21) downstream of the inlet, wherein the sensor is arranged in the secondary bypass passage; and a guide wall (31) which changes the flow direction of the air drawn in through the inlet at a position upstream of the branching area, wherein the inlet and the guide wall are arranged in the X-axis direction, a direction that is perpendicular to both the X-axis direction and the Y-axis direction is defined as a Z-axis direction, and the guide wall contains an inlet side surface (46) opposite the inlet, wherein the inlet side surface (46) is not perpendicular to the X-axis direction when viewed in an XZ-plane defined by the X-axis direction and the Z-axis direction.

Description

AREA OF INVENTION

[0001] The present application relates to an air flow measuring device that is attached to a duct through which intake air for an internal combustion engine flows. BACKGROUND

[0002] An airflow measuring device, which measures the flow rate of intake air for an internal combustion engine, is known. Such devices can include a mounting section attached to a duct and a housing extending vertically from the mounting section into the duct. The housing contains a sensor for detecting the intake air flow rate.

[0003] To improve the accuracy of throughput measurement, a sensor chip containing a plurality of layer resistors arranged on the surface of a semiconductor substrate has been used in recent years.

[0004] Foreign particles, such as dust not removed by an air filter, can mix with the intake air in the duct and be drawn into the housing. If such foreign particles collide with the sensor chip, the chip's resistors can be damaged.

[0005] Against this background, some airflow measuring devices include a main bypass line or passage and a secondary bypass line or passage.

[0006] The main bypass draws in intake air from the duct and then discharges it back into the duct. The secondary bypass branches off from the main bypass and draws in a portion of the intake air from the main bypass, then returns this portion to the main bypass. The sensor chip is located in the secondary bypass (see patent specification JP 2004-012274 A).

[0007] This means that most of the foreign matter, which was sucked in through the inlet along with the intake air, flows only through the main bypass passage without flowing through the secondary bypass passage 12 and is released into channel 2 through the outlet 14 due to inertial force.

[0008] However, if an air filter with lower capture performance is used, or if a vehicle operates in a dusty environment, it is necessary to reduce the amount of foreign matter flowing from the main bypass passage into the secondary bypass passage.

[0009] Further state-of-the-art information can be found in the following documents.

[0010] DE 10 2015 209 337 A1 discloses a flow rate measuring device. To prevent damage to a flow rate detection element due to collisions with dust entering a bypass passage, and to suppress reductions in the airflow velocity passing over the flow rate detection element, a flow rate measuring device is provided which includes: the bypass passage; the flow rate detection element; and a flow rate measuring circuit for measuring the flow rate of a fluid to be measured. The bypass passage includes: an inlet opening; an outlet opening; and a plurality of curved sections formed between the inlet opening and the outlet opening to bend the bypass passage.The majority of the curved sections include the first through third curved sections to form U-shapes and a fourth curved section to bend the tributary passage, which is located at the third curved section so that it lies parallel to the main flow direction. The flow rate detection element is positioned within the tributary passage, in the section after the bend at the fourth curved section. A straight path connecting the outlet orifice and the flow rate detection element is blocked by an inner wall surface of the tributary passage on an outer peripheral side, formed between the first curved section and the second curved section.

[0011] DE 102 45 965 A1 discloses a device for determining at least one parameter of a medium flowing in a conduit. The proposal relates to a device for determining at least one parameter of a medium flowing in a conduit, in particular the intake air mass of an internal combustion engine, comprising a part that has at least one measuring channel for passing through at least a partial flow of the medium flowing in the conduit in a main flow direction and can be inserted into the conduit with a predetermined orientation with respect to the main flow direction, and comprising at least one measuring element arranged in the measuring channel for determining the at least one parameter.It is proposed that the part shall have a channel structure with an inlet area for the entry of a partial flow of the medium and with a measuring channel branching off from the inlet area, the inlet area shall have a discharge zone with a discharge opening and at least two projections shall extend into the inlet area from opposing inner walls of the inlet area.

[0012] DE 10 2007 019 282 A1 discloses a device for measuring flowing media. A device for determining at least one parameter of a medium flowing in a main flow direction, in particular the intake air mass of an internal combustion engine, is proposed. The device has a plug-in part that can be inserted into the flowing medium in a predetermined orientation relative to the main flow direction, with at least one inlet opening and at least one outlet opening, as well as at least one main channel connecting the two openings. Furthermore, at least one measuring channel branching off from the main channel is provided, with at least one sensor element accommodated in the measuring channel for determining the at least one parameter. Upstream of the branch of the measuring channel from the main channel, at least one guide surface is provided to deflect the flow of the medium away from the measuring channel.The guide surface is arranged at least partially at an angle other than 90° to a plane spanned by the main flow direction and the longitudinal axis.

[0013] DE 10 2014 209 094 A1 discloses a flow rate measuring device. Dust with varying particle diameters entering a bypass passage, particularly relatively large dust with a particle diameter of 100 to 200 µm or the like, is reliably brought into collision with a first stepped section, a second stepped section, and a plate-shaped element, thus decelerating it sufficiently to allow it to reach a flow rate detection device with low collision energy. This prevents damage to the flow rate detection device from dust collisions. Furthermore, the position of the plate-shaped element is optimized to suppress air turbulence at the flow rate detection element, thereby achieving a good balance between flow rate detection accuracy and dust tolerance.

[0014] DE 101 39 933 A1 discloses a mass flow meter. A mass flow meter suitable for insertion into a main channel in which a mass flow is present has a housing in which an auxiliary channel is formed, the auxiliary channel having a funnel-shaped inlet opening and an outlet opening, and in which at least one sensor element is arranged, and at least a portion of the wall of the auxiliary channel or the inlet opening of the auxiliary channel has a profile structure designed such that particles in the flowing medium are guided along the wall in a controlled manner.

[0015] DE 10 2004 023 916 A1 discloses a measuring device for the intake air flow rate of an internal combustion engine. A measuring assembly projecting into an intake duct is provided with a branch plate adjacent to a first duct extending from an air inlet to an air outlet. A second duct is formed around the branch plate in such a way that it bypasses the first duct. An air flow rate measuring element is arranged in a second duct. An edge of the branch plate is arranged on or spaced apart from an imaginary line in the direction of the side of the second duct, the imaginary line being parallel to the axis of the intake duct and passing through the top of the air inlet, thus preventing dust or a liquid substance from flowing into the second duct.Alternatively, the branch plate is provided with an inclined section that projects into the first channel such that the inclined section is angled towards the air outlet. In another alternative, the branch plate is provided with an inclined section that is angled towards the air inlet and has a through-opening.

[0016] US 2007 / 0169548 A1 discloses an airflow measuring device. The airflow measuring device comprises a housing with a sub-channel having an inlet and an outlet for an airflow formed in the housing, the sub-channel further comprising a predefined curvature having a downstream maximum point, and a flow measuring element arranged in the sub-channel at a position at least further downstream from the maximum point of the curvature.

[0017] In view of the foregoing, it is an objective of the present application to design an air flow measurement device that can reduce the amount of foreign substances flowing from the main bypass line or passage into the secondary bypass line or passage.

[0018] This problem is solved by the features of claim 1. Further advantageous embodiments and developments are the subject of the subsequent claims. SUMMARY

[0019] One aspect of the present invention comprises an airflow measuring device. The airflow measuring device includes a housing and a sensor. The housing is attached to a duct through which intake air for an internal combustion engine flows. A portion of the intake air flows through the housing as bypass air. The sensor detects the flow rate of this bypass air. The airflow measuring device measures the intake air flow rate based on a sensor reading. The housing includes a main bypass duct, a secondary bypass duct, and a guide vane. The main bypass duct defines an inlet for drawing in the intake air and an outlet for expelling the bypass air drawn in through the inlet. The secondary bypass duct branches off from the main bypass duct at a junction downstream of the inlet. The sensor is located in the secondary bypass duct.The guide vane changes the flow direction of the intake air at a position upstream of the branch section. The inlet and the guide vane are arranged in a direction parallel to the intake air flow direction within the duct. The guide vane includes an inlet side surface that faces the inlet and is not perpendicular to the arrangement direction.

[0020] As described above, the main bypass inlet and the baffle in the housing are positioned along the intake air flow direction within the duct. Therefore, foreign particles drawn in with the intake air through the inlet can come into contact with the baffle. Consequently, the kinetic energy of these particles can be reduced by collisions with the baffle. This makes it less likely that foreign particles will be drawn into the secondary bypass from the branch section, thus reducing the amount of foreign particles drawn from the main bypass into the secondary bypass.

[0021] Therefore, it is possible to prevent foreign objects from colliding with or adhering to the sensor chip.

[0022] Furthermore, the guide wall contains the inlet side surface, which is not perpendicular to the arrangement direction of the inlet and the guide wall.

[0023] Therefore, it is possible to further reduce the kinetic energy of the foreign bodies at a position away from the sensor chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The above and further tasks, features and advantages of the present invention will become even clearer in light of the following detailed description, which is given with reference to the accompanying drawings. The drawings show: Fig. 1 a cross-sectional view of an air flow measuring device attached to a duct (first embodiment); Fig. 2 a cross-sectional view, extending along a II-II line from Fig. 1 is taken from; Fig. 3 an enlarged view of a through A in Fig. 1 marked section; Fig. 4 a cross-sectional view, extending along a IV-IV line from Fig. 1 is taken from; Fig. 5 a cross-sectional view of an air flow measuring device (second embodiment); Fig. 6 a cross-sectional view of an air flow measuring device (third embodiment); Fig. 7 an enlarged view of a guide wall in a main bypass passage (fourth embodiment); Fig. 8 a cross-sectional view of an air flow measuring device attached to a duct (fifth embodiment); Fig. 9 a cross-sectional view of an air flow measuring device attached to a duct (sixth embodiment); Fig. 10 a cross-sectional view of an air flow measuring device attached to a duct (seventh embodiment); Fig. 11 a cross-sectional view of an air flow measuring device attached to a duct (eighth embodiment); Fig. 12 a cross-sectional view of an air flow measuring device attached to a duct (ninth embodiment); Fig. 13 a cross-sectional view of an air flow measuring device attached to a duct (tenth embodiment); Fig. 14 a cross-sectional view of an air flow measuring device attached to a duct (eleventh embodiment); Fig. 15 a cross-sectional view of an air flow measuring device attached to a duct (twelfth embodiment); Fig. 16 a cross-sectional view of an air flow measuring device attached to a duct (thirteenth embodiment); Fig. 17 a cross-sectional view of an air flow measuring device attached to a duct (fourteenth embodiment); Fig. 18 a cross-sectional view of an air flow measuring device attached to a duct (fifteenth embodiment); Fig. 19 a cross-sectional view of an air flow measuring device attached to a duct (sixteenth embodiment); Fig. 20A a cross-sectional view extending along an XX-XX line from Fig. 19 is taken from; Fig. 20B a cross-sectional view along an XX-XX line in Fig. 19 is taken from; Fig. 21 a cross-sectional view of a guide wall of a main bypass passage, from the view through an inlet (first modification); Fig. 22A a cross-sectional view of an air flow measuring device (second modification); Fig. 22B a cross-sectional view of an air flow measuring device (second modification); Fig. 23A a cross-sectional view of an air flow measuring device (third modification); Fig. 23B a cross-sectional view of an air flow measuring device (third modification); Fig. 24A a cross-sectional view of an airflow measuring device (fourth modification); and Fig. 24B a cross-sectional view of an air flow measuring device (fourth modification). DETAILED DESCRIPTION

[0025] It goes without saying that the following embodiments are examples of the present application and that the present application is therefore not limited to these embodiments. Furthermore, the substantially corresponding structures of the embodiments will be identified by the same reference numerals, and the description of the substantially corresponding structures will be omitted in the following embodiments. (First embodiment)

[0026] Fig. Figures 1 to 4 show an air flow measuring device according to a first embodiment of the present application.

[0027] The air flow measuring device 1 is attached to a channel 2 through which a main flow of intake air for an internal combustion engine flows.

[0028] The air flow measuring device 1 comprises a mounting section 3 and a housing 4, as described below. Based on a measurement result from a sensor 8, the air flow measuring device 1 measures the flow rate of intake air.

[0029] Mounting section 3 includes a flat mounting surface 5 for attaching the airflow measuring device 1 to the duct 2. Mounting section 3 is located outside the duct 2. It is attached to a wall 6 of the duct 2 by means of screws 7. The mounting surface 5 is pressed against the wall 6 by the fastening forces of the screws 7, so that it is in contact with a mounting surface of the duct 2 formed on the outside of the wall 6. The mounting surface 5 extends parallel to the direction of airflow in the duct 2.

[0030] The housing 4 accommodates the sensor 8, which detects the flow rate of the intake air flowing through the housing 4 (hereinafter referred to as "air flow AF"). The housing 4 is positioned in the channel 2 such that it extends into the interior of the channel 2 by being inserted into the interior of the channel 2 via an insertion opening 9.

[0031] A fitting section 10 is fitted into the insertion opening 9 between the mounting section 3 and the housing 4. An O-ring is arranged between an outer circumferential surface of the fitting section 10 and an inner wall of the insertion opening 9 to seal the channel 2.

[0032] The housing 4 extends in a direction perpendicular to the mounting surface 5. The housing 4 contains a main bypass passage 11 and a secondary bypass passage 12.

[0033] The main bypass passage 11 draws in intake air from channel 2 and discharges it back into channel 2. The main bypass passage 11 includes an inlet 13 to draw in a portion of the main intake air flow and an outlet 14 to discharge the airflow AF drawn in through inlet 13.

[0034] Inlet 13 is open towards an upstream side, i.e., upstream of an intake passage 2a of channel 2. Inlet 13 is open around the center of channel 2. The opening shape of inlet 13 is square.

[0035] The outlet 14 is open at a downstream end of the housing 4. The outlet 14 is open towards a downstream side of the inlet passage 2a.

[0036] As shown in the figures, the flow direction of the intake air and the throughflow air AF flowing through channel 2 can be referred to as the "X-axis direction".

[0037] Furthermore, a direction perpendicular to the X-axis direction can be referred to as the "Y-axis direction", along which the housing 4 extends into the channel 2.

[0038] A direction that is perpendicular to both the X-axis direction and the Y-axis direction can be called the "Z-axis direction".

[0039] The main bypass passage 11 contains a first curved section 15 and a second curved section 16.

[0040] The first curved section 15 is a passage that first changes the flow direction of the through air AF from the inlet 13 in the main bypass passage 11. The first curved section 15 changes the flow direction of the through air AF from the X-axis direction to the Y-axis direction (i.e., the downstream direction in the figures).

[0041] The second curved section 16 is a passage that changes the flow direction of the airflow AF at a position downstream of the first curved section 15. The second curved section 16 changes the direction of the airflow AF from the Y-axis direction to a downstream direction along the X-axis direction.

[0042] A section of the main bypass passage 11 extends linearly along the X-axis direction from the second curved section 16 to the outlet 14.

[0043] The angle of both the first and second curved sections 15, 16 is 90 degrees.

[0044] The secondary bypass passage 12 draws in the flow air AF from the main bypass passage 11 and then returns the flow air AF to the main bypass passage 11. The secondary bypass passage 12 branches off from the main bypass passage 11 at a branch section 21. The sensor 8 is located in the secondary bypass passage 12.

[0045] The branch section 21 of the secondary bypass passage 12 is located at a position downstream of the first and second curved sections 15, 16.

[0046] The merging area 22 of the secondary bypass passage 12 is located at a position downstream of sensor 8.

[0047] The secondary bypass passage 12 contains a third curved section 23.

[0048] The third curved section 23 is a passage essentially on an upstream side that changes the direction of the flow air AF from the branch section 21 in the secondary bypass passage 12. The third curved section 23 changes the direction of the flow air AF from an upstream direction along the Y-axis to a downstream direction along the Y-axis by 180 degrees. That is, the third curved section 23 has a U-turn structure.

[0049] Therefore, a large proportion of the foreign matter (hereinafter referred to as "dust D") drawn in through the inlet 13 along with the intake air flows only through the main bypass passage 11 without flowing through the secondary bypass passage 12 and is discharged through the outlet 14 into the channel 2 due to its inertial force.

[0050] The sensor 8 contains a sensor carrier 25 and a sensor chip 26. The sensor carrier 25 is made of resin and is integrally formed with a secondary bypass wall 32 of the housing 4. The sensor chip 26 is held by the sensor carrier 25.

[0051] The sensor chip 26 is located in the secondary bypass passage 12 between the branch section 21 and the third curved section 23. The sensor chip 26 contains a plurality of film resistors arranged on an area of ​​a semiconductor substrate. The sensor chip 26 is a thermal flow-measuring sensor that utilizes the excitation of the resistors. One area of ​​the substrate of the sensor chip 26 is aligned parallel to the flow direction of the air AF flowing through the secondary bypass passage 12.

[0052] Housing 4 contains the main bypass passage 11, the secondary bypass passage 12, a guide wall 31 and the secondary bypass wall 32.

[0053] The main bypass passage 11 contains a main inlet passage 41, into which the intake air flows via the inlet 13, a guide passage 42 extending along the guide wall 31 and a common passage extending from the guide passage 42 towards the outlet 14.

[0054] The main inlet passage 41 functions as a first main passage extending from the inlet 13 to the first curved section 15.

[0055] The main passage 42 functions as a second main passage extending from the first curved section 15 to the second curved section 16.

[0056] The common passage 43 functions as a third main passage extending from the second curved section 16 to the outlet 14.

[0057] The secondary bypass passage 12 contains an inlet secondary passage 44, through which the flow air AF from the common passage 43 flows, and an outlet secondary passage 45, from which the flow air AF flows out in the direction of the common passage 43.

[0058] The inlet side passage 44 functions as a first side passage extending from the branch section 21 to the third curved section 23. The sensor 8 is located in the inlet side passage 44.

[0059] The outflow secondary passage 45 functions as a second secondary passage extending from the third curved section in the cross-sectional view to the merging area 22. The outflow secondary passage 45 is fluidically connected to the inflow secondary passage via the third curved section 23.

[0060] The guide vane 31 alters the flow direction of the throughflow air AF, which was drawn in by the inlet 13 at a position upstream of the branch section 21 of the secondary bypass passage 12. The guide vane 31 is located upstream of the secondary bypass passage 12, i.e., upstream of the branch section 21. The guide vane 31 is an outer circumferential surface 33 of the first curved section 15 and forms a section of a passage wall of the guide passage 42.

[0061] The inlet 13 and the guide wall 31 are arranged in the housing 4 along a flow direction of the intake air in the channel 2 (i.e., the X-axis direction).

[0062] The guide wall 31 separates the guide passage 42 from the inflow side passage 44, so that the inflow side passage 44 extends along the guide passage 42.

[0063] The guide wall 31 includes an inlet side surface 46, which is not perpendicular to the arrangement direction in which the inlet 13 and the guide wall 31 are arranged. As in Fig. As shown in Figure 4, the inlet side surface 46 in a cross-sectional view has a curved surface 46a that projects towards a downstream side of a flow direction of the intake air in the main inlet passage 41. It should be noted that the cross-sectional view is along a plane that is perpendicular to an axis of a flow direction in the first curved section 15 (i.e., an XZ plane defined by the X-axis direction and the Z-axis direction).

[0064] The secondary bypass wall 32 separates the inflow secondary passage 44 from the outflow secondary passage 45 such that the outflow secondary passage 45 extends along the inflow secondary passage 44. The secondary bypass wall 32 extends along the guide wall 31 on one side of the inflow secondary passage 44, opposite the guide passage 42. The secondary bypass wall 32 is a section of the inflow secondary passage 44 and a passage wall of the outflow secondary passage 45.

[0065] A flow direction (first direction) of the throughflow air AF in the guide passage 42, which is a section of the main bypass passage 11 from the first curved section 15 to the branch area 21, and a flow direction (second direction) of the throughflow air AF in the inflow secondary passage 44, which is a section of the secondary bypass passage 12 upstream of the sensor chip 26 of the sensor 8, form an angle of 180 degrees.

[0066] The flow direction of the throughflow air AF in the guide passage 42 extends even more precisely from an upper position to a lower position along the Y-axis direction, as shown in Fig. Figure 1 shows the direction of the airflow AF in the secondary inlet passage 44, extending from a lower position to an upper position along the Y-axis direction, as shown in Fig. 1 is shown.

[0067] The direction of the airflow AF in the main passage 42 and the direction of the airflow AF in the secondary inlet passage 44 are therefore opposite each other.

[0068] As described above, the air flow measuring device 1 has the housing 4, which contains the inlet 13 for drawing in intake air and the guide wall 31, which changes the flow direction of the through air AF that is drawn into the inlet secondary passage 41 from the inlet 13.

[0069] Furthermore, the inlet 13 and the guide wall 31 are arranged in the housing 4 along the flow direction of the intake air in the channel 2.

[0070] Therefore, it is possible to bring the dust D, drawn in through inlet 13 along with the intake air, into contact with the guide vane 31, which is located upstream of the branch section 21. This reduces the kinetic energy of the dust D through collisions with the guide vane 31. Consequently, it is less likely that the dust D will be drawn from the branch section 21 into the secondary bypass passage 12, thus significantly reducing the amount of dust D drawn into the secondary bypass passage 12 from the main bypass passage 11.

[0071] Therefore, it is possible to prevent the dust D from colliding with and / or adhering to the sensor chip 26 of the sensor 8.

[0072] The flow direction of the through air AF in the guide passage 42, which is the section of the main bypass passage 11 from the first curved section 15 to the branch area 21, and the flow direction of the through air AF in the inlet secondary passage 44, which is the section of the secondary bypass passage 12 upstream of the sensor chip 26 of the sensor 8, form an angle of 180 degrees.

[0073] The airflow AF must therefore change its direction so significantly at the branch region 21 that it flows into the secondary bypass passage 12, making it even more difficult for the dust D to flow into the secondary bypass passage 12 from the branch region 21. This further improves the effect of preventing the dust D from colliding with and / or adhering to the sensor chip 26.

[0074] It should be noted that the prevention effects achieved by the above-described opposing flow directions of the throughflow air AF can be further improved if the sensor chip 26 is located in the inflow side passage 44 at a position upstream of the third curved section 23.

[0075] The guide wall 31 contains the inlet side surface 46, which is not perpendicular to the arrangement direction of the inlet 13 and the guide wall 31.

[0076] The dust D, accelerated together with the intake air, is reflected by the curved surface 46a or bounces off it when it collides with the curved surface 46a and then collides with the curved surface 46a again, as in Fig. Figure 4 is shown. As a result, the number of collisions of dust D with the inlet side surface 46 increases, and it is therefore possible to reduce the kinetic energy of dust D at a position that is away from the sensor chip 26 of the sensor 8.

[0077] As a result, it is less likely that dust D will be drawn into the secondary bypass passage 12 from the branch area 21, making it possible to reduce the quantity or amount of dust D that is drawn into the secondary bypass passage 12 from the main bypass passage 11.

[0078] Therefore, it is possible to further prevent the dust D from colliding with and / or adhering to the sensor chip 26 of the sensor 8. (Second embodiment)

[0079] Fig. Figure 5 shows an air flow measuring device 1 according to a second embodiment. The components identified by the same reference numerals are the same as those in the first embodiment.

[0080] The inlet side surface 46 of the guide vane 31 has inclined surfaces 46b in a cross-sectional view, forming a V-shaped groove that projects towards a downstream side of the flow direction of the intake air drawn in through the inlet 13. The cross-sectional view is taken along a plane that is perpendicular to an axis of flow in the first curved section 15 (i.e., an XZ plane). (Third embodiment)

[0081] Fig. Figure 6 shows an air flow measuring device 1 according to a third embodiment. The components identified by the same reference numerals are the same as those described in the first embodiment.

[0082] The inlet side surface 46 of the guide vane 31 has, in a cross-sectional view, an inclined surface 46c that forms a tapered or conical groove projecting in the direction of a downstream side of the flow direction of the intake air drawn in through the inlet 13. The cross-sectional view is taken along a plane that is perpendicular to an axis of flow in the first curved section 15 (i.e., an XZ plane). (Fourth embodiment)

[0083] Fig. Figure 7 shows an air flow measuring device 1 according to a fourth embodiment. The components identified by the same reference numerals are the same as those described in the first embodiment.

[0084] The guide wall 31 contains recessed sections 47, which are recessed in a direction away from the inlet side surface 46 of the guide wall 31 in one direction away from the inlet 13.

[0085] The dust D can therefore be captured or trapped by the recessed sections 47 and as a result a quantity of the dust D flowing towards the branch area 21 can be reduced.

[0086] Since the dust D is further slowed down due to the collision with the recessed sections 47, it is possible to prevent the dust D from colliding with and / or adhering to the sensor chip 26 of the sensor 8, even if the dust D flows into the secondary bypass passage 12 from the branch area 21. (Fifth embodiment)

[0087] Fig. Figure 8 shows an airflow measuring device according to a fifth embodiment. The components identified by the same reference numerals are the same as those described in the first embodiment.

[0088] The guide wall 31 projects further towards the common passage 43 than the secondary bypass wall 32 projects towards the common passage 43. In other words, a lower end 31a of the guide wall 31 is lower than a lower end 35 of the secondary bypass wall 32 in the Y-axis direction.

[0089] Consequently, it is less likely that the dust D will collide with wall 51 of the secondary bypass wall 32, and therefore the probability that the dust D will flow into the secondary bypass passage 12 decreases significantly. Therefore, the amount of dust D flowing into the secondary bypass passage 12 can be reduced. (Sixth embodiment)

[0090] Fig. Figure 9 shows an air flow measuring device 1 according to a sixth embodiment. The components identified by the same reference numerals are the same as those described in the first embodiment.

[0091] The secondary bypass wall 32 projects further towards the common passage 43 than the guide wall 31 projects towards the common passage 43. In other words, the lower end 31a of the guide wall 31 is higher than the lower end 35 of the secondary bypass wall 32 in the Y-axis direction.

[0092] Therefore, the dust D collides with the wall surface 51 of the secondary bypass wall 32 and consequently loses further kinetic energy. The dust D then flows into the secondary bypass passage 12. That is, the dust D loses kinetic energy due to the collision immediately after flowing into the secondary bypass passage 12. Therefore, it is possible to reduce the kinetic energy of the dust D at a position upstream of the sensor chip 26 of the sensor 8.

[0093] If the intake air flows back into channel 2 due to pressure pulsation, the dust D can flow through outlet 14. By using the structure described above, the dust D can collide with the wall surface 52 of the secondary bypass wall 32 at a position around the merging area 22, thereby reducing the kinetic energy of the dust D. Therefore, a collision of the dust D with the sensor chip 26 or adhesion of the dust D to it can be prevented, even if a backflow of intake air occurs. (Seventh embodiment)

[0094] Fig. Figure 10 shows an air flow measuring device 1 according to a seventh embodiment. The components identified by the same reference numerals are the same as those described in the first embodiment.

[0095] The secondary bypass passage 12 does not lead into the main bypass passage 11 and contains an outlet opening 53 that is different from the outlet 14 of the main bypass passage 11.

[0096] The main bypass passage 11 contains a section downstream of the branch section 21, which has a cross-section larger than that of the secondary bypass passage 12. Therefore, the pressure loss generated in the section of the main bypass passage 11 is lower than the pressure loss generated in the secondary bypass passage 12.

[0097] As a result, the flow rate of the through air AF flowing into the secondary bypass passage 12 decreases. Therefore, the amount or quantity of dust D flowing into the secondary bypass passage 12 can be reduced. (Eighth embodiment)

[0098] Fig. Figure 11 shows an air flow measuring device 1 according to an eighth embodiment. The components identified by the same reference numerals are the same as those of the first embodiment.

[0099] The secondary bypass passage 12 leads into the main bypass passage 11.

[0100] The flow direction of the intake air at the outlet 14 is angled to the flow direction of the through air AF, which is drawn in through the inlet 13.

[0101] The flow of intake air exiting through outlet 14 collides with the flow of intake air inside channel 2 at a right angle, and as a result, the outlet of intake air through outlet 14 can be prevented. Therefore, it is possible to prevent intake air from being drawn in through inlet 13, thus preventing dust D from entering housing 4. (Ninth embodiment)

[0102] Fig. Figure 12 shows an air flow measuring device 1 according to a ninth embodiment. The components identified by the same reference numerals are the same as those described in the first, sixth, and eighth embodiments.

[0103] The outlet 14 of the main bypass passage 11 is open at the lowest position of the housing 4 in the Y-axis direction.

[0104] A direction of airflow AF, flowing through a region of the main bypass passage 11 from the second curved section 16 to the outlet 14 of the main bypass passage 11, is gradually separated from a flat surface B (hereinafter referred to as the "reference plane B") along which the mounting surface 5 extends. In other words, the main bypass wall 34 of the main bypass passage 11 from the second curved section 16 to the outlet 14 is inclined such that the main bypass wall 34 is gradually separated from an end 35 of the secondary bypass wall 32 near the common passage 35.

[0105] Therefore, the flow axis of the main bypass passage 11 can be angled such that the axis is gradually separated from the branch region 21 towards a downstream side of the main bypass passage 11. Consequently, the dust D cannot flow into the secondary bypass passage 12 as long as the dust D does not significantly change its flow direction at the branch region 21. Therefore, it is possible to improve the effect of preventing the dust D from colliding with or adhering to the sensor chip 26.

[0106] It should be noted that the angle of the first curved section 15 is 90 degrees, while the angle of the second curved section 16 is greater than 90 degrees. (Tenth embodiment)

[0107] Fig. Figure 13 shows an air flow measuring device 1 according to a tenth embodiment. The components identified by the same reference numerals are the same as those described in the first embodiment.

[0108] In the air flow measuring device 1 according to the present embodiment, the sensor chip 26 is arranged in the middle of the third curved section 23.

[0109] Alternatively, the sensor chip 26 can be located in a region of the secondary bypass passage 12 from the third curved section 23 to the merging area 22 or the outlet 14. Furthermore, a passage extending in the X-axis direction can be formed in the center of the third curved section 23. (Eleventh embodiment)

[0110] Fig. Figure 14 shows an air flow measuring device 1 according to an eleventh embodiment. The components identified by the same reference numerals are the same as those described in the first embodiment.

[0111] In the air flow measuring device 1 according to the present embodiment, a recessed area is formed by the curvature of the outer circumferential surface 33 of the first curved section 15 from the X-axis direction to the Y-axis direction.

[0112] Consequently, the dust D is deflected along the flow direction in the first curved section 15 as it collides with the outer circumferential surface 33 of the first curved section 15. The number of collisions of dust D with the guide vane 31 therefore increases, and the kinetic energy of dust D can thus be further reduced before the dust D reaches the branching region 21.

[0113] It should be noted that the shape of the circumferential wall of the second curved section 16 can be a recessed curved shape. (Twelfth embodiment)

[0114] Fig. Figure 15 shows an air flow measuring device 1 according to a twelfth embodiment. The components identified by the same reference numerals are the same as those described in the first and tenth embodiments.

[0115] The secondary bypass passage 12 contains an impact plate 54, which is located upstream of the sensor chip 26 of the sensor 8 and extends along the direction of flow of the throughflow air AF passing through the inlet secondary passage 44.

[0116] Even though the dust D is slightly accelerated by absorbing kinetic energy from the main intake airflow, even when the dust D is drawn with increased kinetic energy from the main bypass passage 11 into the secondary bypass passage 12 upstream of the sensor chip 26, the flow rate of dust D is reduced due to its collision with the impact plate 54. As a result, the kinetic energy of the dust D being drawn from the branch area 21 into the secondary bypass passage 12 can be reduced before the dust D reaches the branch area 21. (Thirteenth embodiment)

[0117] Fig. Figure 16 shows an air flow measuring device 1 according to a thirteenth embodiment. The components identified by the same reference numerals are the same as those described in the first and eleventh embodiments.

[0118] As in the twelfth embodiment, the secondary bypass passage 12 includes an impact plate 54 which is located upstream of the sensor chip 26 of the sensor 8 and extends along the direction of flow of the throughflow air AF which flows through the inflow secondary passage 44. (Fourteenth embodiment)

[0119] Fig. Figure 17 shows an air flow measuring device 1 according to a fourteenth embodiment. The components identified by the same reference numerals are the same as those described in the first and tenth embodiments.

[0120] The secondary bypass passage 12 contains a third curved section 23 which changes the flow direction of the throughflow air AF drawn in from the main bypass passage 11 at a position upstream of the sensor chip 26.

[0121] The housing 4 contains a plurality of recessed sections 55, which are recessed from an outer circumferential surface of the third curved section 23 in a direction radially outwards of the third curved section 23.

[0122] Although the dust D is easily accelerated by absorbing kinetic energy from the main flow, even when the dust D is drawn with increased kinetic energy from the main bypass passage 11 into the secondary bypass passage 12 upstream of the sensor chip 26, the throughput of dust D is reduced due to collisions of the dust D with the recessed sections 55. As a result, the kinetic energy of the dust D being drawn from the branch region 21 into the secondary bypass passage 12 can be reduced before the dust D reaches the branch region 21. (Fifteenth embodiment)

[0123] Fig. Figure 18 shows an air flow measuring device 1 according to a fifteenth embodiment. The components identified by the same reference numerals are the same as those described in the first and twelfth embodiments.

[0124] As in the fourteenth embodiment, the housing 4 contains a plurality of recessed sections 55 which are recessed from an outer circumferential surface of the third curved section 23 in a direction radial outwards of the third curved section 23. (Sixteenth embodiment)

[0125] Fig. 19 and Fig. Figure 20 shows an air flow measuring device 1 according to a sixteenth embodiment. The components identified by the same reference numerals are the same as those described in the first embodiment.

[0126] The airflow measuring device 1 according to the present embodiment includes a curved section 15 that changes the flow direction of the air AF from the X-axis direction to the Z-axis direction. The airflow measuring device 1 includes a second curved section 16 that changes the flow direction of the air AF from the Z-axis direction to the X-axis direction.

[0127] The curvature direction of the first curved section 15 can be a downstream direction in Fig. 20A from the X-axis direction to the Z-axis direction. The curvature direction of the second curved section 16 can be a downstream direction from the X-axis direction to the Z-axis direction, as in Fig. 20A is shown.

[0128] Alternatively, the curvature direction of the first curved section 15 can be an upstream direction in Fig. 20B from the X-axis direction to the Y-axis direction. Furthermore, the curvature direction of the second curved section 16 can be a downstream direction from the Z-axis direction to the X-axis direction, as shown in Fig. 20B is shown. (Modifications)

[0129] In the first to the sixteenth embodiment, the air flow measuring device 1 includes the mounting section 3, which is attached to the wall 6 of the duct 2 by means of screws 7. Alternatively, the air flow measuring device 1 can include the mounting section 3, which is attached to the wall 6 of the duct 2 by means of welding or gluing.

[0130] It should be noted that welding means that the fastening section 3 is attached to the wall 6 by melting a section or the entirety of the fastening surface 5.

[0131] It should also be noted that gluing means that the fastening section 3 is attached to the wall 6 using an adhesive.

[0132] In the airflow measuring device 1 of the first embodiment, the opening shape of the inlet 13 is square. Alternatively, the opening shape of the inlet 13 can be elliptical, with a major axis running along the Y-axis direction and a minor axis running along the Z-axis direction, as shown in Fig. 21 is shown as the first modification.

[0133] Alternatively, the opening shape of the inlet 13 can be circular, oval, or rectangular. Furthermore, the opening shape of the outlet 14, the outlet opening 53, the branch section 21, and the merging section 22 can each be square, elliptical, circular, oval, or rectangular.

[0134] Furthermore, the cross-sectional shape of the main bypass passage 11 and the secondary bypass passage 12 can each be square, elliptical, circular, oval or rectangular.

[0135] In the airflow measuring device 1 of the first to sixteenth embodiments, the shape of an outer wall near the inlet 13 is planar, extending linearly along the X-axis direction. Alternatively, the shape of the outer wall 61 near the inlet 13 can be planar, extending gradually from an opening end of the inlet 13 towards a downstream side in an outward direction from the housing 4, as shown in Fig. 22A and Fig. 22B is shown.

[0136] Fig. Figure 22A shows a second modification which includes a conical surface 61 on the outer wall near the inlet 13. As in Fig. As shown in 22B, a curved surface 61 can be used in contrast, which protrudes from the outer wall near the inlet 13.

[0137] Therefore, it is possible to reduce the pressure loss of the intake air flowing through channel 2.

[0138] In Fig. 22A and Fig. 22B contains the guide wall 31 the curved surface 46a, which is recessed in a downstream direction, but the guide wall 31 can also contain the inclined surfaces 46b, as in Fig. Figure 5 is shown. Furthermore, the guide wall 31 can contain the inclined surface 46c, as shown in Figure 5. Fig. 6 is shown.

[0139] In the airflow measuring device 1 of the first to sixteenth embodiments, the shape of the inner wall 62 near the inlet 13 has a form that extends linearly along the X-axis direction. Alternatively, the shape of the inner wall 62 near the inlet 13 can have a form that gradually reduces the cross-section of the main bypass passage 11 from an opening edge of the inlet 13 towards a downstream side of the main bypass passage 11, as shown in Fig. 23A and Fig. 23B is shown as the third modification.

[0140] Fig. Figure 23A shows the third modification, which includes a conical surface on the inner wall 62 near the inlet 13. The in Fig. The third modification shown in 23B includes a curved surface that protrudes outwards on the inner wall 62 near the inlet 13.

[0141] As a result, the dust D collides with the inner wall 62 near the inlet 13. Therefore, the kinetic energy of the dust D can be further reduced before the dust D reaches the branching area 21.

[0142] It should be noted that the guide wall 31 contains the curved surface 46a, which extends in a downstream direction into Fig. 23A and Fig. 23B is recessed, but the guide wall 31 can also contain the inclined surfaces 46b, as in Fig. Figure 5 is shown. Furthermore, the guide wall 31 can contain the inclined surface 46c, as shown in Figure 5. Fig. 6 is shown.

[0143] In the airflow measuring device 1 of the first to third embodiments, the guide wall 31 includes the curved surface 46a, which has a curved groove shape, or the inclined surfaces 46b, which have a V-shaped groove shape. As in Fig. As shown in Figure 24A, a fourth modification of the guide wall 31 can include two curved surfaces 46d, each having a semicircular groove shape and a flat surface 46e. More precisely, the guide wall 31 can have a shape in which the flat surface 46e lies between the two curved surfaces 46d.

[0144] Alternatively, the guide wall 31 can contain a recessed curved surface 47f which has a semicircular groove shape, as in Fig. 24B is shown.

[0145] Therefore, the same operation and effects can be achieved as with the first to third embodiments.

[0146] In the airflow measuring device 1 of the first to sixteenth embodiments, the flow direction of the through-air AF in a section of the main bypass passage 11 and the flow direction of the through-air AF in a section of the secondary bypass passage 12 form an angle of 180 degrees. Alternatively, the flow direction of the through-air AF in the section of the main bypass passage 11 and the flow direction of the through-air AF in the section of the secondary bypass passage 12 form an angle greater than 180 degrees.

[0147] In the airflow measuring device 1 of the first to sixteenth embodiments, the number of bends in the main bypass passage 11 due to the first and second curved sections 15, 16 is two, and the number of bends in the secondary bypass passage 12 due to the third curved section 23 is one. However, the number of bends in the main bypass passage 11 and the secondary bypass passage 12 is not necessarily limited. For example, the number of bends in the main bypass passage 11 can be one, three, or more, and the number of bends in the secondary bypass passage 12 can be three or more.

[0148] According to the first embodiment of the air flow measuring device 1, the angle of the first curved section 15 and the angle of the second curved section 16 are 90 degrees and the angle of the second curved section 16 is greater than 90 degrees in the air flow measuring device 1 according to the Fig.12. The ninth embodiment shown. However, the angles need not necessarily be limited to those.

[0149] That is, the angle of the first curved section 15 can be greater than 90 degrees and that of the second curved section 16 can be less than 90 degrees.

[0150] In the air flow measuring device 1 according to the first to sixteenth embodiments, the angle of the third curved section 23 is 180 degrees. However, the angle of the third curved section 23 can be a value other than 180 degrees.

Claims

[1] Air flow measuring device comprising: a housing (4) attached to a channel (2) through which intake air for an internal combustion engine flows in an X-axis direction, wherein the housing (4) is inserted into the channel (2) in a Y-axis direction perpendicular to the X-axis direction and part of the intake air flows through the housing as through-flow air (AF); and a sensor (8) that detects a flow rate of the air flowing through it, wherein the air flow rate measuring device measures a flow rate of the intake air based on a detection result of the sensor, wherein The case contains: a main bypass passage (11) which defines an inlet (13) for drawing in the intake air and an outlet (14) for releasing the flow air drawn in through the inlet; a secondary bypass passage (12) branching off from the main bypass passage at a branching area (21) downstream of the inlet, wherein the sensor is arranged in the secondary bypass passage; and a guide wall (31) which changes the flow direction of the air drawn in through the inlet at a position upstream of the branching area, wherein the inlet and the guide wall are arranged in the X-axis direction, a direction that is perpendicular to both the X-axis direction and the Y-axis direction is defined as a Z-axis direction, and the guide wall contains an inlet side surface (46) opposite the inlet, wherein the inlet side surface (46) is not perpendicular to the X-axis direction when viewed in an XZ-plane defined by the X-axis direction and the Z-axis direction. [2] Air flow measuring device according to claim 1, wherein the bypass passage includes an impact plate (54) at a position upstream of the sensor, and The impact plate extends along a flow direction of the airflow in the secondary bypass passage. [3] Air flow measuring device according to claim 1 or 2, wherein the secondary bypass passage contains a curved section (23) which changes the flow direction of the air drawn in from the main bypass passage at a position upstream of the sensor, and the housing contains a plurality of recessed sections (55) which are recessed from an outer wall of the curved section in a direction radial outwards of the curved section. [4] Air flow measuring device according to one of claims 1 to 3, wherein the guide wall is an outer circumferential surface (33) of a curved section (15) which changes the flow direction of the intake air drawn in through the inlet in the main bypass passage, and the airflow through a section of the main bypass passage from the curved section to the branch area flows in a first direction, the airflow through a section of the secondary bypass passage upstream of the sensor flows in a second direction, and The first direction and the second direction form an angle of 180 degrees or more. [5] Air flow measuring device according to one of claims 1 to 4, wherein The guide wall is an outer circumferential surface of a curved section that changes the direction of the intake air drawn in through the inlet in the main bypass passage, and the guide wall contains a plurality of recessed sections (47) which are recessed in a direction away from the inlet side surface (46) of the guide wall. [6] Air flow measuring device according to one of claims 1 to 5, wherein the main bypass passage includes a guide passage (42) extending along the guide wall and a common passage (43) extending from the guide passage towards the outlet, the secondary bypass passage includes an inlet secondary passage (44) through which the flow air from the common passage flows, and an outlet secondary passage (45) from which the flow air flows out in the direction of the common passage, The guide wall separates the guide passage from the secondary inflow passage in such a direction that the secondary inflow passage extends along the guide passage. the housing contains a secondary bypass wall (32) which separates the outflow secondary passage from the inflow secondary passage such that the inflow secondary passage extends along the outflow secondary passage, and The sensor is located in the secondary inlet passage to detect the flow rate of the air passing through it. [7] Air flow measuring device according to claim 6, wherein the secondary bypass wall extends along the guide wall on one side of the secondary inflow passage opposite the main inflow passage, and The secondary bypass wall protrudes more towards the common passage than the guide wall protrudes towards the common passage. [8] Air flow measuring device according to claim 6, wherein the secondary bypass wall extends along the guide wall on one side of the secondary inflow passage opposite the main inflow passage, and the guide wall protrudes more towards the common passage than the side bypass wall protrudes towards the common passage. [9] Air flow measuring device according to any one of claims 1 to 8, wherein the secondary bypass passage, which does not lead into the main bypass passage, contains an outlet opening (53) that differs from the outlet of the main bypass passage, and a pressure loss in a section of the main bypass passage downstream of the branch area is less than a pressure loss in the secondary bypass passage. [10] Air flow measuring device according to one of claims 1 to 8, wherein a direction of the intake air flowing through the outlet is inclined to a direction of the intake air flowing through the inlet. [11] Air flow measuring device according to any one of claims 1 to 10, further comprising a mounting surface (5) which attaches the air flow measuring device to the duct, wherein the guide wall is an outer circumferential surface (33) of a first curved section (15) which changes the direction of the intake air drawn in through the inlet in the main bypass passage, the main bypass passage includes a second curved section (16) which changes the direction of the airflow at a position downstream of the first curved section, and a direction of the flowing air through a region of the main bypass passage from the second curved section to the outlet is gradually separated from a flat surface (B) along which the mounting surface extends.

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