Air intake structure for internal combustion engine

Abstract

According to the present invention, an air intake structure for an internal combustion engine is such that a main passage and a sub passage are formed by a partitioning part that vertically partitions an air intake passage along a passage direction, and intake air is guided to the sub passage, or to the main passage and the sub passage, in accordance with an operating state of the internal combustion engine. In a top view of a combustion chamber, an opening Wa is formed on the basis of a positional relationship in which a center line of the opening is eccentric, in relation to a center line of an outer shape width of the sub passage, by an offset amount set in a direction intersecting the passage direction.. In a side view of the combustion chamber in a state in which an air intake valve is open, an inlet zone is formed on the basis of a positional relationship in which an axial line of the sub passage in the inlet zone is inclined by a relative angle set with respect to a shaft part of the air intake valve. A virtual substantially columnar region in which the cross-sectional shape of the opening of the sub passage is extended in a direction extending toward the inside of the combustion chamber is formed so as not to contact a valve seat edge of the air intake valve in a side view of the combustion chamber in which the air intake valve is opened.

Description

Intake structure of an internal combustion engine

[0001] The disclosed technology relates to an intake structure for an internal combustion engine.

[0002] In recent years, research and development has been conducted into improving fuel efficiency, which contributes to energy efficiency, in order to ensure that more people have access to affordable, reliable, sustainable and advanced energy.

[0003] Patent Document 1 discloses a structure in which the opening of a tumble flow passage is directed toward the combustion chamber in order to strengthen the tumble flow from the viewpoint of improving fuel efficiency.

[0004] International Publication No. 2021 / 186513

[0005] However, in this technology for improving fuel efficiency, when the intake valve of the combustion chamber opens, if the airflow flowing in the direction of the extension line extending from the tumble flow passage opening hits the valve stem, valve seat, etc., the airflow flowing in from the tumble flow passage opening may be diffused, which may hinder the formation of a vortex inside the cylinder, which may be a problem.

[0006] The disclosed technology aims to enhance the formation of airflow vortices within the cylinder and improve combustion efficiency, which in turn contributes to improved fuel economy and energy efficiency.

[0007] An intake structure for an internal combustion engine according to one aspect of the disclosed technology includes a partition (65) that separates an intake passage (6) into upper and lower sections along a passage direction, forming a main passage (6B) and a secondary passage (6A), and directing intake air to the secondary passage (6A) or to the main passage (6B) and the secondary passage (6A) depending on the operating state of the internal combustion engine (4), wherein an opening (Wa) of an inlet section (410) formed in a substantially linear shape downstream of the secondary passage (6A) communicates with a combustion chamber (32) via the main passage (6B), and the opening (Wa) is formed such that, in a top view of the combustion chamber (32), a center line (501) of the opening (Wa) is eccentric with respect to a center line (502) of an outer width (WA) of the secondary passage (6A) by an offset amount (503) set in a direction intersecting the passage direction, In a side view of the combustion chamber (32) with the intake valve (73) open, the axis of the sub-passage (6A) in the inlet section (410) is inclined at a relative angle (θ1) set with respect to the shaft portion (73c) of the intake valve (73) in the open state, thereby forming the inlet section (410), and a virtual, approximately cylindrical region obtained by extending the cross-sectional shape of the opening (Wa) of the sub-passage (6A) in a direction extending toward the inside of the combustion chamber (32) is formed so as not to come into contact with a valve seat edge (77) of the intake valve (73) in a side view of the combustion chamber (32) with the intake valve (73) open.

[0008] According to the disclosed technology, it is possible to provide an intake structure for an internal combustion engine that can strengthen the formation of air vortices within a cylinder and improve combustion efficiency.

[0009] 4A. A side view of a vehicle according to an embodiment. A diagram illustrating the structure of an internal combustion engine according to an embodiment. A diagram illustrating the intake structure of an internal combustion engine according to an embodiment. A diagram illustrating the downstream structure where a main passage and an auxiliary passage connect to a combustion chamber in the intake structure of an internal combustion engine according to an embodiment. A diagram schematically illustrating the structure of the auxiliary passage in a top view of the combustion chamber in the intake structure of an internal combustion engine according to an embodiment. A diagram illustrating a bottom view of the combustion chamber as seen from the direction of arrow 4A in FIG. 4. A diagram illustrating a bottom view of the combustion chamber as seen from the direction of arrow 4A in FIG. 4. A diagram schematically illustrating the cross-sectional shape of an auxiliary passage 6A. A diagram schematically illustrating the cross-sectional shape of an intake guide portion 409 in the intake structure of an internal combustion engine according to an embodiment. A diagram schematically illustrating a comparison of the intake flow of a comparative example and the intake flow of the intake structure of the embodiment.

[0010] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention as claimed, and not all combinations of features described in the embodiments are necessarily essential to the invention. Two or more of the features described in the embodiments may be arbitrarily combined. Furthermore, the same reference numerals are used for the same or similar components, and redundant explanations will be omitted.

[0011] An intake structure for an internal combustion engine according to one embodiment of the present invention will be described with reference to FIGS. 1 to 9. FIG.

[0012] In the description of the specification and the claims, the directions of front, rear, left, right, up, down, etc. are determined to correspond to the directions of the vehicle when the internal combustion engine according to this embodiment is mounted on a saddle-ride type vehicle. In this embodiment, the saddle-ride type vehicle is, for example, a scooter-type motorcycle (hereinafter simply referred to as a "motorcycle").

[0013] In the drawings, arrows FR indicate the front of the vehicle, LH indicate the left side of the vehicle, RH indicate the right side of the vehicle, and UP indicate the top of the vehicle.

[0014] (Outline of a Vehicle Equipped with an Intake Structure for an Internal Combustion Engine) FIG. 1 shows an outline of a left side view of a motorcycle 1 equipped with an intake structure for an internal combustion engine according to this embodiment.

[0015] In the motorcycle 1 of this embodiment, the front body 1A and the rear body 1B are connected via a low floor portion 1C (footrest portion), and the body frame 2, which forms the skeleton of the body, is generally composed of a down frame 21 and a main frame 22.

[0016] A down frame 21 extends downward from a head pipe 20 in the front portion 1A of the vehicle body, and lower frame portions 22a of a pair of left and right main frames 22 are connected to the lower end of the down frame 21 and extend rearward and approximately horizontally. The main frames 22 extend diagonally rearward and upward from the rear ends of the lower frame portions 22a and form a pair of left and right inclined portions 22b, and the upper portions of the inclined portions 22b are further bent to form a pair of left and right horizontal portions 22c that extend rearward and approximately horizontally.

[0017] A storage box (also called a helmet box) 11 is supported on the inclined portion 22b and horizontal portion 22c of the main frame 22, and a rider seat 12 is disposed above and covers the storage box.

[0018] On the other hand, at the front body 1A, a handlebar 13 is provided above and journalled on a head pipe 20, and a front fork 14 extends below and journalled at its lower end to a front wheel 15.

[0019] A power unit support bracket 23 protrudes rearward from the inclined portion 22b of the main frame 22, and a swing-type power unit (hereinafter simply referred to as the "power unit") 3 is connected and supported to the power unit support bracket 23 via a link member 24 so that it can swing up and down.

[0020] The motorcycle 1 of this embodiment employs an upper link type support structure for the power unit 3, and as a result, a space for providing a catalytic converter 49 is available below the front of the power unit 3.

[0021] At the front body portion 1A, the head pipe 20 and the down frame 21 are covered from the front and rear by the front cover 10a and leg shield 10b of the body cover 10.

[0022] The floor section 1C is provided on the left and right pair of lower frame sections 22a of the main frame 22 of the vehicle body frame 2, and the upper part of the lower frame section 22a is covered by a floor cover 10c, and the left and right sides are covered in the front-to-rear direction by floor side covers 10d, and the lower part is covered by an under cover 10e.

[0023] In the vehicle body rear 1B, a fuel tank 16 is mounted on a horizontal portion 22c of a main frame 22 below the rear of the passenger seat 12 and above the rear wheel 17, and the inclined portion 22b and horizontal portion 22c of the main frame 22 are covered on the left, right, and rear sides by a body cover 10f. A front fender 10g is also provided above the front wheel 15. Each of the covers 10a to 10g that make up the body cover 10 is formed of an appropriate material such as a resin material.

[0024] The power unit 3 is provided with an internal combustion engine 4, and a power transmission section 5 having a belt-type continuously variable transmission 51 installed therein, extending rearward from the internal combustion engine 4. A reduction gear mechanism 52 that transmits power from the belt-type continuously variable transmission 51 is provided at the rear of the power transmission section 5, and the rear wheels 17 are mounted on a rear axle 52a that is the output shaft of the reduction gear mechanism 52.

[0025] A rear cushion 18 is interposed between the rear of the power transmission unit 5 and the horizontal portion 22 c at the rear of the main frame 22 .

[0026] The internal combustion engine 4 is a single-cylinder, air-cooled, four-stroke cycle internal combustion engine, and has a crankshaft 41 rotatably supported in a crankcase 30 and oriented in the vehicle width direction, i.e., the left-right direction. A cylinder block 42, a cylinder head 43, and a head cover 44 are stacked in this order so as to protrude from the front of the crankcase 30, and are fastened together with the cylinder axis C tilted forward and approximately horizontal.

[0027] An intake port 45 is provided on the intake side flange surface 43b to which an inlet manifold 61 is fastened via an insulator 60.

[0028] An inlet manifold 61 and a throttle body 62 are provided above the power unit 3, above the area from the cylinder head 43 to the crankcase 30. The inlet manifold 61 is connected to the intake port 45 at the top of the forward-inclined cylinder head 43, and the upstream side of the inlet manifold 61 bends backward and extends, connecting to the throttle body 62.

[0029] The upstream side of the throttle body 62 is connected via a connecting tube 63 to an air cleaner 64 attached to the upper part of the power transmission unit 5 .

[0030] An intake passage 6 is formed from the connecting tube 63 through the throttle body 62 , the inlet manifold 61 and the intake port 45 of the cylinder head 43 , and communicates with the combustion chamber 32 .

[0031] An approximately cylindrical catalytic converter 49 oriented in the vehicle width direction is installed in an upstream exhaust pipe 48a connected to an exhaust port outlet 47a at the bottom of the cylinder head 43. A catalyst for purifying exhaust gas, such as a three-way catalyst, is installed inside the upstream exhaust pipe 48a. A downstream exhaust pipe 48b connected to the outlet of the catalytic converter 49 bends rearward and extends rearward along the right side of the vehicle, connecting to a muffler (not shown) on the right side of the rear wheel 17.

[0032] (Outline of Intake Structure of Internal Combustion Engine) FIG. 2 is a right cross-sectional side view taken along the cylinder axis C of the cylinder block 42, cylinder head 43, head cover 44 and their surrounding areas of the power unit 3 in FIG.

[0033] The crankcase 30 is formed by combining a left case half 30L and a right case half (not shown), and the left case half 30L extends rearward to form a power transmission section 5 that houses a transmission device including a long belt-type continuously variable transmission 51 and a reduction gear mechanism 52, etc., in the front and rear between the crankshaft 41 and the rear axle 52a of the rear wheel 17.

[0034] A piston 33 reciprocates within a cylinder bore 42 a of the cylinder block 42 and is connected to a crank pin 41 a of a crankshaft 41 of the crankcase 30 by a connecting rod 34 .

[0035] A combustion chamber 32 is defined between a top surface 33a of the piston 33 slidably fitted in a cylinder bore 42a of the cylinder block 42 and a ceiling surface 43a of the cylinder head 43 opposite the top surface 33a.

[0036] 2, in this embodiment, an inlet manifold 61 is connected to the intake port 45 of the cylinder head 43, and a throttle body 62 is fastened to the upstream side of the inlet manifold 61 via a reed valve 8, which will be described later. In the following explanation, a configuration using the reed valve 8 is used as an example, but this embodiment can also be applied to a configuration that does not use the reed valve 8.

[0037] The throttle body 62 has a throttle valve 62a mounted in the intake passage 6, which rotates around a throttle valve shaft 62b to open and close the intake passage 6 and adjust the intake air flow rate.

[0038] In FIG. 2, reference numeral 31 denotes a bracket portion that protrudes upward from the upper portion of the crankcase 30 and that suspends the power unit 3 on the body frame 2 .

[0039] As shown in FIG. 1, a bracket portion 31 is journaled via a link member 24 to a power unit support bracket 23 that protrudes rearward from the inclined portion 22b of the main frame 22, and the power unit 3 swings up and down relative to the body frame 2.

[0040] The rear end of the power unit 3, which swings up and down, is supported on the horizontal portion 22c of the main frame 22 by the rear cushion 18.

[0041] As shown in FIG. 2, an inlet manifold 61 is connected to the front of the throttle body 62, i.e., on the downstream side of the intake air, and bends downward to connect to the intake port 45 at the top of the cylinder head 43 with an insulator 60 sandwiched between them.

[0042] A fuel injection valve 39 is attached to the downstream end of the inlet manifold 61, and injects fuel toward the intake valve port 35. The fuel is injected in the direction of the injection center line I shown in Figure 2. Because the fuel injected from the fuel injection valve 39 has a certain spread, a recess 67a is provided on the outer periphery of the main passage head inlet opening 67 to avoid the injected fuel.

[0043] A fuel hose (not shown) connected to the fuel injection valve 39 is routed rearward and connected to the fuel tank 16 provided above the rear wheel 17 via a fuel pump device (not shown).

[0044] In this embodiment, the internal combustion engine 4 employs a single-cylinder SOHC type two-valve system, and a valve train 9 is provided in a cylinder head 43. A head cover 44 is placed on the cylinder head 43 to cover the valve train 9.

[0045] To transmit power to the valve train 9 inside the head cover 44, an endless cam chain (not shown) is stretched between the camshaft 90 and the crankshaft 41, passing through a cam chain chamber (not shown) provided on one side of the crankcase 30, the cylinder block 42, and the cylinder head 43 in the direction of the crankshaft 41, and the camshaft 90 rotates in synchronization with the crankshaft 41 at half the rotational speed.

[0046] An ignition plug is inserted into the cylinder head 43 from the opposite side of the cam chain chamber (the other side in the direction of the crankshaft 41 ) toward the combustion chamber 32 .

[0047] In a cylinder head 43 in which the cylinder axis C is tilted forward approximately horizontally, an intake valve port 35 and an exhaust valve port 36 that open to the ceiling surface 43a of the combustion chamber 32 are formed such that they extend, curving upward and downward, from each other.

[0048] The upstream end of the intake port 37 opens upward into the cylinder head 43 to form an intake port 45, which is connected to an inlet manifold 61 to form a continuous intake passage 6, and a throttle body 62 is connected to the upstream side of the inlet manifold 61.

[0049] The downstream end of the exhaust port 38 forms an exhaust port outlet 47, which opens downward in the cylinder head 43 and is connected to an upstream exhaust pipe 48a (FIG. 1).

[0050] A cylindrical intake valve guide 71 is integrally fitted to the curved outer wall portion 37a of the intake port 37 in the cylinder head 43, and an intake valve 73 slidably supported by the intake valve guide 71 opens and closes the intake valve opening 35 of the intake port 37 facing the combustion chamber 32.

[0051] The exhaust valve guide 72 is integrally fitted to the curved outer wall portion 38a of the exhaust port 38 in the cylinder head 43, and an exhaust valve 74 slidably supported by the exhaust valve guide 72 opens and closes the exhaust valve opening 36 of the exhaust port 38 that faces the combustion chamber 32. Above the combustion chamber 32, the pair of intake valve 73 and exhaust valve 74 are arranged based on a positional relationship in which the shafts 73c and 74c are inclined in a V-shape.

[0052] The intake valve 73 and the exhaust valve 74 are biased upward by a valve spring 75 so that their head portions 73a, 74a close the intake valve port 35 and the exhaust valve port 36 facing the combustion chamber 32. The stem ends 73b, 74b of the intake valve 73 and the exhaust valve 74 are pushed down by an intake rocker arm 91 and an exhaust rocker arm 92 that swing against the intake cam and the exhaust cam of a camshaft 90, respectively, and the intake valve 73 and the exhaust valve 74 open at a predetermined timing, connecting the intake port 37 and the combustion chamber 32, and connecting the exhaust port 38 and the combustion chamber 32, allowing intake and exhaust to occur at the predetermined timing.

[0053] An inlet manifold 61 is connected to the upstream end of the intake port 37 of the internal combustion engine 4 via an insulator 60, forming a continuous intake passage 6, and a throttle body 62 is connected to the upstream side of the inlet manifold 61 via a reed valve 8.

[0054] The throttle body 62 has an intake passage 62c with a substantially circular cross section that forms part of the intake passage 6 connected to the combustion chamber 32 of the internal combustion engine 4, and its upstream side is connected to an air cleaner 64 (see Figure 1) via a connecting tube 63.

[0055] The throttle body 62 is equipped with a throttle valve 62a. The throttle valve 62a is a single butterfly-type throttle valve that is rotatably supported within the throttle body 62 by a throttle valve shaft 62b that is oriented substantially horizontally and perpendicular to the intake air flow direction F of the intake passage 62c, i.e., perpendicular to the central axis X of the intake passage 62c, and that variably controls the flow area of ​​the intake passage 62c to open and close the intake passage 62c.

[0056] The throttle valve 62a can be rotated clockwise in the valve opening direction as viewed in FIG. 2 by the driver's operation, and is biased clockwise in the valve closing direction by a return spring (not shown).

[0057] In this embodiment, the intake passage 62c of the throttle body 62 is oriented approximately horizontally. The intake passage 6 is divided into upper and lower sections along the intake air flow direction by a partition 65 (partition wall) from the inlet manifold 61 to the intake port 37. The intake passage 6 is configured so that the intake air passing through the intake passage 6 generates a tumble flow T in the combustion chamber 32. The intake passage 6 is divided by the partition 65 into a tumble passage 6A on the lower side of the intake passage 6 and a main passage 6B on the upper side of the intake passage 6.

[0058] In this embodiment, the "tumble passage" refers to an intake passage for generating a tumble flow T in the combustion chamber 32 when the throttle valve 62a is at a low opening, that is, when the internal combustion engine 4 is under low load. In this specification, the tumble passage 6A is also referred to as an auxiliary passage. In the example of Figure 2, the tumble passage 6A is arranged below the intake passage 6 and the main passage 6B is arranged above the intake passage 6, but in this embodiment, the vertical arrangement of the tumble passage 6A (auxiliary passage) and the main passage 6B is not limited to the arrangement shown in Figure 2.

[0059] The partition section 65 is configured so that an inlet manifold-side partition section 65A, an insulator-side partition section 65B, and an intake port-side partition section 65C are continuous from the upstream side to the downstream side of the intake flow.

[0060] The main passage 6B on the upper side in the figure and the tumble passage 6A on the lower side in the figure are each formed by dividing the intake passage 6 into upper and lower sections by a partition portion 65.

[0061] As shown in FIG. 2, a reed valve 8 is provided between the throttle body 62 and the inlet manifold 61 .

[0062] ST31 in Fig. 3 is a perspective view of the downstream side of the reed valve 8. ST32 in Fig. 3 is a perspective view of the downstream side of the reed valve 8 in a state where the reed valve element 87 is fastened to the reed valve body 81.

[0063] The reed valve 8 has a reed valve body 81 that forms the entire reed valve, and an attachment flange portion 85 is sandwiched and fastened between the downstream end of the throttle body 62 and the upstream end of the inlet manifold 61 .

[0064] An inlet opening 82 that coincides with the downstream opening 62d of the throttle body 62 is provided on the surface where the reed valve body 81 is attached to the throttle body 62, and a valve intake passage 80 that communicates with the intake passage 62c of the throttle body 62 is formed within the reed valve body 81.

[0065] An opening 84 is formed at a downstream end 83 of the reed valve body 81. The opening 84 abuts against the upstream end 65Aa of the partition portion 65A and coincides with the upstream end opening 6Aa of the tumble passage 6A.

[0066] The upper part of the reed valve body 81 is formed to slope from the back of the mounting flange portion 85 to the lower downstream part of the reed valve 8, and an opening 86 is formed in the sloped surface 81a, which connects the valve intake passage 80 inside the reed valve body 81 to the main passage 6B.

[0067] One end 87a of the reed valve element 87 is fastened to the mounting flange portion 85 by a screw 87c so as to cover the opening 86. The other end 87b of the reed valve element 87 is a free swinging end, and the other end 87b of the reed valve element 87 is in contact with a downstream end portion 83 formed on the downstream side of the reed valve body 81. When the throttle valve 62a is at a low opening, that is, when the negative pressure on the downstream side of the reed valve element 87 is smaller than a certain value, the other end 87b of the reed valve element 87 maintains a state in which it closes the opening 86, and intake air flows from the valve intake passage 80 in the reed valve body 81 exclusively to the tumble passage 6A of the inlet manifold 61.

[0068] As the throttle valve 62a opens to a high degree, that is, as the internal combustion engine 4 enters a high load state and the negative pressure downstream of the reed valve body 87 exceeds a certain value, the other end 87b of the reed valve body 87 bends to open the opening 86, and intake air flows from the valve intake passage 80 in the reed valve body 81 to the main passage 6B of the inlet manifold 61.

[0069] (Downstream-Side Intake Structure Connected to Combustion Chamber 32) Figure 4 is a diagram showing the downstream-side intake structure where the main passage 6B and the sub-passage 6A connect (communicate) with the combustion chamber 32. Figure 4 shows a side view of the combustion chamber 32 with the intake valve 73 open. Figure 5 is a diagram schematically showing the structure of the sub-passage 6A in a top view of the combustion chamber 32 of the internal combustion engine 4.

[0070] In the intake structure of the internal combustion engine 4 of this embodiment, a main passage 6B and a sub-passage 6A are formed by a partition section 65 that separates the intake passage 6 into upper and lower sections along the passage direction, and intake air is guided to the sub-passage 6A or to both the main passage 6B and the sub-passage 6A depending on the operating state of the internal combustion engine 4.

[0071] An opening Wa of the approach section 410 formed in a substantially straight line downstream of the sub-passage 6A communicates with the combustion chamber 32 via the main passage 6B.

[0072] 4, in a side view of the combustion chamber 32 with the intake valve 73 open, the inlet section 410 is formed based on a positional relationship in which the axis 419 of the secondary passage 6A in the inlet section 410 is inclined at a relative angle θ1 set with respect to the shaft portion 73c of the open intake valve 73. Furthermore, the relative angle θ2 indicates, for example, the relative angle of the inlet section 410 with respect to the fastening surface that attaches the cylinder head 43 to the cylinder block 42.

[0073] The intake structure of the internal combustion engine 4 has a confluence section 420 where intake air 407 flowing from the main passage 6B to the combustion chamber 32 and intake air 408 flowing from the secondary passage 6A to the combustion chamber 32 converge. A substantially linear flat surface 416 is provided on the surface of the main passage 6B on the secondary passage 6A side of the confluence section 420. An opening is formed in the flat surface 416 to guide the intake air flow f from the secondary passage 6A side to the confluence section 420. The flat surface 416 is formed substantially parallel to the shaft 73c of the intake valve 73.

[0074] The sub-passage 6A is provided with a substantially linear intake guide portion 409 that guides the intake flow f from the opening end 506 of the opening Wa toward the junction portion 420 or the combustion chamber 32 .

[0075] As shown in FIG. 5, in a top view of the combustion chamber 32 of the internal combustion engine 4, an opening Wa of the inlet section 410 of the sub-passage 6A, which is formed on the downstream side in the passage direction, communicates with the combustion chamber 32 via the main passage 6B.

[0076] The opening Wa is formed based on a positional relationship in which the center line 501 of the opening Wa is eccentric with respect to a center line 502 of the outer width WA of the auxiliary passage 6A by a first eccentricity amount (offset amount 503) set in a direction intersecting (substantially perpendicular to) the passage direction. Also, the opening Wa is formed based on a positional relationship in which the center line 501 of the opening Wa is eccentric with respect to a center line 504 (center line along the passage direction) of the shaft portion 73c of the intake valve 73 by a second eccentricity amount (offset amount 505).

[0077] That is, in the intake structure (positional relationship) of the secondary passage 6A, the center line 501 of the opening Wa is eccentric to the center line 502 of the outer width WA of the secondary passage 6A by a first eccentricity amount (offset amount 503). Also, in the relative arrangement (positional relationship) between the secondary passage 6A and the intake valve 73, the center line 501 of the opening Wa is eccentric to the center line 504 (center line along the passage direction) of the shaft portion 73c of the intake valve 73 by a second eccentricity amount (offset amount 505).

[0078] In Figures 4 and 5, the hatched portion extending from the opening end 506 of the opening Wa of the bypass passage 6A to the right side of the paper indicates the projection plane of the opening Wa (the projection plane of the cross-sectional shape in a direction perpendicular to the direction in which the approach section 410 of the bypass passage 6A extends).

[0079] The projection plane of the opening Wa is formed as an imaginary, substantially cylindrical region (hereinafter also referred to as the cross-sectional region of the opening Wa) obtained by extending the cross-sectional shape of the opening Wa of the bypass passage 6A in a direction extending from the opening end 506 toward the inside of the combustion chamber 32. The projection plane of the opening Wa (the cross-sectional region of the opening Wa) is projected in a substantially linear manner from the opening end 506 toward the combustion chamber 32, and has a spatial extent in a direction perpendicular to the plane of the drawing. The intake flow f flowing through the bypass passage 6A is output (supplied) from the opening end 506 of the opening Wa of the bypass passage 6A into the combustion chamber 32 so as to flow within the imaginary, substantially cylindrical region (the cross-sectional region of the opening Wa).

[0080] The opening Wa has a cross-sectional shape that is substantially oval or rectangular and extends laterally in the direction of the offset amount 503 .

[0081] The intake air flow f passes through a linear inlet section 410 downstream of the secondary passage 6A and is output from the opening Wa. The intake air flow f output from the opening Wa becomes a flow directed in a substantially linear direction by flowing through the inlet section 410. The intake air guide section 409 supplies the intake air flow f output from the opening Wa into the combustion chamber 32 while maintaining the substantially linear direction.

[0082] As shown in Fig. 4 , a virtual, substantially cylindrical region (cross-sectional region of the opening Wa) having a spatial extent corresponding to the cross-sectional shape of the opening Wa is formed in the combustion chamber 32 so as not to come into contact with the head portion 73a of the intake valve 73 or the ceiling surface 43a of the combustion chamber 32 when the intake valve 73 is open, as viewed from the side of the combustion chamber 32. Furthermore, as shown in Fig. 5 , a virtual, substantially cylindrical region (cross-sectional region of the opening Wa) formed as a projection of the opening Wa is formed in the combustion chamber 32 so as not to come into contact with the shaft portion 73c of the intake valve 73 when open, as viewed from above the combustion chamber 32 of the internal combustion engine 4. That is, the virtual, substantially cylindrical region (cross-sectional region of the opening Wa) formed as a projection of the opening Wa is formed so as not to come into contact with the shaft portion 73c of the intake valve 73 when open, and so as not to come into contact with the head portion 73a of the intake valve 73 when the intake valve 73 is open. The opening Wa of the sub-passage 6A and the inlet section 410 are formed so that an imaginary, substantially cylindrical area (the cross-sectional area of ​​the opening Wa) is formed in the combustion chamber 32 .

[0083] FIG. 6A is a bottom view of the combustion chamber 32 as viewed from the direction of arrow 4A in FIG. 4. In FIG. 6A, the hatched portion illustrates the projected surface of the opening Wa of the secondary passage 6A. The intake air flow f flowing through the secondary passage 6A is output (supplied) from the opening Wa of the secondary passage 6A into the combustion chamber 32 so as to flow within the projected surface of the opening Wa. The imaginary, substantially cylindrical region (cross-sectional area of ​​the opening Wa) formed as the projected surface of the opening Wa is formed within the combustion chamber 32 so as not to contact the valve seat edge 77 of the intake valve 73 when the intake valve 73 is open, as shown in FIGS. 4 and 6A in side and bottom views of the combustion chamber 32 with the intake valve 73 open. Furthermore, the imaginary, substantially cylindrical region (cross-sectional area of ​​the opening Wa) is formed so as not to contact the stem 73c and head 73a of the intake valve 73 when the intake valve 73 is open, as well as the valve seat edge 77 of the intake valve 73. The opening Wa of the sub-passage 6A and the inlet section 410 are formed so that an imaginary, substantially cylindrical area (the cross-sectional area of ​​the opening Wa) is formed in the combustion chamber 32 .

[0084] 6A shows an example in which the opening Wa has only one projected surface, the opening Wa may be bifurcated. For example, one projected surface and the other projected surface of the bifurcated opening Wa of the auxiliary passage 6A may be formed in the combustion chamber 32 so as not to contact the valve seat edge 77 of the open intake valve 73 in a side view and a bottom view of the combustion chamber 32 with the intake valve 73 open, as shown in FIGS. 4 and 6A, respectively. In this case, one projected surface (one cross-sectional shape region of the opening Wa) and the other projected surface (the other cross-sectional shape region of the opening Wa) of the bifurcated opening Wa of the auxiliary passage 6A are formed in the left-right direction of the page, sandwiching the shaft portion 73c. Even when the opening Wa is formed as a bifurcated portion, the imaginary, approximately cylindrical region (one cross-sectional shape region of the opening Wa) formed as one projection surface of the opening Wa, and the imaginary, approximately cylindrical region (the other cross-sectional shape region of the opening Wa) formed as the other projection surface of the opening Wa are formed so as not to come into contact with the shaft portion 73c and umbrella portion 73a of the intake valve 73 in the open state, as well as the valve seat edge 77 of the intake valve 73 (Figure 6B).

[0085] (Cross-sectional shape of the bypass passage 6A) Figure 7 is a diagram schematically showing the cross-sectional shape of the bypass passage 6A. In Figure 7, the direction perpendicular to the paper surface indicates the passage direction of the intake passage 6, and the left-right direction of the paper surface indicates the width direction of the internal combustion engine 4 which intersects (substantially perpendicular to) the passage direction. Furthermore, the up-down direction of the paper surface indicates the up-down direction of the internal combustion engine 4 which intersects (substantially perpendicular to) the passage direction and the intersecting direction.

[0086] The sub-passage 6A has a cross-sectional shape in which a substantially oval opening Wa or a substantially rectangular opening Wa is formed, extending laterally in the direction of the offset amount 503. In Fig. 7 , ST71 shows an example in which the opening Wa of the sub-passage 6A is formed in a substantially oval shape, and ST72 shows an example in which the opening Wa of the sub-passage 6A is formed in a substantially rectangular shape. In ST71 and ST72 of Fig. 7 , the opening Wa is formed in a positional relationship in which the center line 501 of the opening Wa of the sub-passage 6A is eccentric by a first eccentricity amount (offset amount 503) with respect to the center line 502 of the outer width WA of the sub-passage 6A.

[0087] 4, the intake guide portion 409 extends in a substantially straight line from the opening end 506 of the opening Wa toward the combustion chamber 32, and is formed so as to be able to connect to the inner surface of the opening Wa without any steps. To connect to the inner surface of the opening Wa without any steps, a recess having a curvature that matches the cross-sectional shape of the opening Wa is formed on the upper surface 409a of the intake guide portion 409.

[0088] Fig. 8 is a diagram schematically showing the cross-sectional shape of the intake guide portion 409. The coordinate system in Fig. 8 is the same as Fig. 7, with the direction perpendicular to the paper surface indicating the passage direction of the intake passage 6, and the left-right direction on the paper surface indicating the width direction of the internal combustion engine 4 which intersects (substantially perpendicular to) the passage direction. Furthermore, the up-down direction on the paper surface indicates the up-down direction of the internal combustion engine 4 which intersects (substantially perpendicular to) the passage direction and the intersecting direction.

[0089] In order to connect the inner surface of the opening Wa of the secondary passage 6A and the upper surface 409a of the intake guide section 409 without any steps, recesses (801, 802) having a curvature that matches the shape of the opening Wa are formed on the upper surface 409a of the intake guide section 409.

[0090] 8, ST81 shows the cross-sectional shape of the intake guide portion 409 corresponding to the example (ST71) in which the opening Wa is formed in a substantially oval shape, and ST82 shows the cross-sectional shape of the intake guide portion 409 corresponding to the example (ST72) in which the opening Wa is formed in a substantially rectangular shape.

[0091] In ST81, a recess 801 having a curvature that matches the cross-sectional shape of the lower part of the opening Wa (for example, the shape of the lower half of the approximately oval shape in the vertical direction) is formed on the upper surface 409a of the intake guide section 409 so that it connects seamlessly with the inner surface of the approximately oval opening Wa.

[0092] In addition, in ST82, a recess 802 having a curvature that matches the cross-sectional shape of the lower part of the opening Wa (for example, the shape of the lower half of the approximately rectangular shape in the vertical direction) is formed on the upper surface 409a of the intake guide section 409 so that it connects without any steps with the inner surface of the approximately rectangular opening Wa.

[0093] By forming recesses 801, 802 having a curvature that matches the cross-sectional shape of the lower part of opening Wa on the upper surface 409a of intake guide portion 409, it becomes possible to connect recesses 801, 802 (inner surfaces of the recesses) of intake guide portion 409 and the lower part of opening Wa (inner surface of the lower part) without any steps at the connecting portion in the passage direction. This allows intake flow f to be supplied to combustion chamber 32 without disturbing the flow that is directed approximately linearly along the passage direction.

[0094] Furthermore, the intake air flow f, which has a spatial expansion corresponding to the cross-sectional shape of the opening Wa, flows through the recesses 801, 802 (the inner peripheral surfaces of the recesses), thereby maintaining a flow directed in a substantially linear manner along the passage direction and suppressing the expansion of the intake air flow in the intersecting direction. This allows the intake air flow f to be supplied into the combustion chamber 32 without coming into contact with the stem 73c (FIG. 5) of the open intake valve 73.

[0095] In this embodiment, the main passage 6B, the sub-passage 6A, and the intake guide portion 409 may be formed, for example, by casting together with the cylinder head 43, or may be formed by machining after the cylinder head 43 is formed.

[0096] (Comparison of intake air flow) Figure 9 is a diagram showing a comparison of the intake air flow in a comparative example and the intake air flow in the intake structure of the embodiment, where ST91 is a diagram showing the flow of the intake air flow f in the comparative example, and ST92 is a diagram showing the flow of the intake air flow f in the intake structure of the internal combustion engine 4 in this embodiment.

[0097] In ST91, a curved portion 900 having an arc shape with a predetermined curvature is provided at the confluence portion 420 instead of the flat surface 416 of the main passage 6B. The curved portion 900 has an arc shape with a predetermined curvature that curves downward from the open end of the secondary passage 6A toward the combustion chamber 32. In the intake structure shown in ST91, the intake flow f output (supplied) from the secondary passage 6A leaves the curved portion 900 and is divided into an intake flow f1 that flows toward the combustion chamber 32 and an intake flow f2 that flows upward of the intake valve 73. Of the supplied intake flow f, only the intake flow f1 that flows toward the combustion chamber 32 is used for combustion, which may reduce combustion efficiency.

[0098] ST92 is a diagram schematically illustrating the flow of the intake air flow f in the intake structure for the internal combustion engine 4 according to this embodiment. As shown in ST92, the intake air flow f output (supplied) from the secondary passage 6A flows over the upper surface of the intake guide portion 409 and is supplied to the combustion chamber 32 while maintaining a substantially linearly directed flow along the passage direction. In the intake structure for the internal combustion engine 4 according to this embodiment (ST92), the flat surface 416 is formed on the main passage 6B, so that the open end 506 of the secondary passage 6A can be positioned closer to the combustion chamber 32. Compared to the comparative example (ST91), the intake structure for the internal combustion engine 4 according to this embodiment (ST92) can supply the intake air flow f to the combustion chamber 32 while maintaining a substantially linearly directed flow of the intake air flow f. That is, the intake structure for the internal combustion engine 4 according to this embodiment (ST92) can supply the intake air flow f to the combustion chamber 32 to achieve more favorable combustion in the combustion chamber 32.

[0099] According to the intake structure of the internal combustion engine 4 of this embodiment as described above, a vertical rotating vortex (a rotating vortex on a plane along the cylinder axis C), i.e., a tumble flow T, of the fuel-air mixture can be provided in the combustion chamber 32 in order to obtain more favorable combustion in the combustion chamber 32. The disclosed technology can provide an intake structure for an internal combustion engine that can strengthen the formation of airflow vortices inside the cylinder and improve combustion efficiency.

[0100] <Summary of the embodiment> (Item 1) In the intake structure for an internal combustion engine of the above embodiment, a main passage (6B) and a sub-passage (6A) are formed by a partition (65) that separates the intake passage (6) into upper and lower sections along the passage direction, and intake air is guided to the sub-passage (6A) or to the main passage (6B) and the sub-passage (6A) depending on the operating state of the internal combustion engine (4), wherein an opening (Wa) of an inlet section (410) formed in a substantially linear shape downstream of the sub-passage (6A) communicates with a combustion chamber (32) via the main passage (6B), and in a top view of the combustion chamber (32), The opening (Wa) is formed based on a positional relationship in which a center line (501) of the opening (Wa) is eccentric with respect to a center line (502) of an outer width (WA) of the secondary passage (6A) by an offset amount (503) set in a direction intersecting with the passage direction, and in a side view of the combustion chamber (32) with an intake valve (73) open, the inlet section (410) is formed based on a positional relationship in which an axis (419) of the secondary passage (6A) in the inlet section (410) is inclined by a relative angle (θ1) set with respect to a shaft portion (73c) of the intake valve (73), and an imaginary, approximately cylindrical region obtained by extending the cross-sectional shape of the opening (Wa) of the secondary passage (6A) in a direction extending toward inside the combustion chamber (32) is formed based on a positional relationship in which an axis (419) of the secondary passage (6A) in the inlet section (410) is inclined by a relative angle (θ1) set with respect to a shaft portion (73c) of the intake valve (73), and in a side view of the combustion chamber (32) with an intake valve (73) open, It is formed so as not to come into contact with the valve seat edge (77) of the intake valve (73).

[0101] According to the intake structure for an internal combustion engine of Item 1, it is possible to reduce obstruction of the intake air flow from the open end 506 of the secondary passage 6A toward the inside of the cylinder, strengthen the formation of an air vortex inside the cylinder, and improve combustion efficiency.

[0102] (Item 2) The region is formed so as not to come into contact with the stem portion (73c) of the intake valve (73) when viewed from the top, and so as not to come into contact with the umbrella portion (73a) of the intake valve (73) when viewed from the side.

[0103] According to the intake structure for an internal combustion engine of item 2, the intake air flow from the open end 506 of the secondary passage 6A toward the inside of the cylinder can be prevented from being obstructed by contact with the valve seat edge 77, thereby improving combustion efficiency. This strengthens the formation of an airflow vortex inside the cylinder, making it possible to improve combustion efficiency.

[0104] (Item 3) The combustion chamber (32) further includes a junction (420) where the intake air (407) flowing from the main passage (6B) to the combustion chamber (32) and the intake air (408) flowing from the sub-passage (6A) to the combustion chamber (32) join together, and a substantially linear flat surface (416) is provided on a surface of the main passage (6B) on the sub-passage (6A) side of the junction (420).

[0105] According to the intake structure for an internal combustion engine of item 3, by providing the flat surface 416, the position of the open end 506 of the secondary passage 6B can be brought closer to the junction 420 compared to the structure (ST91) provided with the curvature portion 900 having an arc shape with a predetermined curvature. This makes it easier to adjust the insertion angle (relative angle θ1: Figure 1) of the secondary passage 6A toward the junction 420 and the combustion chamber 32, and further improves the directionality of the intake flow f. This strengthens the formation of air vortices inside the cylinder, making it possible to improve combustion efficiency.

[0106] (Item 4) The flat surface (416) has an opening formed therein for guiding the intake air flow (f) from the sub-passage (6A) side to the junction (420).

[0107] According to the intake structure for an internal combustion engine of item 4, the position of the opening end 506 of the secondary passage 6B can be brought closer to the junction 420, and the intake flow f can be supplied to the junction 420 through the opening formed in the flat surface 416. This strengthens the formation of air vortices inside the cylinder, making it possible to improve combustion efficiency.

[0108] (Item 5) The flat surface (416) is formed substantially parallel to the shaft portion (73c) of the intake valve (73).

[0109] According to the intake structure for an internal combustion engine of item 5, the position of the open end 506 of the secondary passage 6B can be brought closer to the junction 420. This makes it easier to adjust the insertion angle (relative angle θ1: Figure 1) of the secondary passage 6A toward the junction 420 and the combustion chamber 32, and further improves directivity. This strengthens the formation of air vortices within the cylinder, making it possible to improve combustion efficiency.

[0110] (Item 6) The sub-passage (6A) is provided with a substantially linear intake guide portion (409) that guides the intake flow (f) from the opening end (506) of the opening (Wa) toward the combustion chamber (32).

[0111] According to the intake structure for an internal combustion engine of item 6, the intake air flow f output from the opening Wa flows through the linearly formed inlet section 410, and is thereby directed in a substantially linear manner. Furthermore, by forming the intake guide section 409, the intake air flow f output from the opening Wa can be supplied into the combustion chamber 32 as a flow that further maintains its substantially linear direction. This strengthens the formation of air vortices within the cylinder, making it possible to improve combustion efficiency.

[0112] (Item 7) The sub-passage (6A) has a cross-sectional shape in which a substantially oval opening (Wa) or a substantially rectangular opening (Wa) is formed, which is elongated horizontally in the direction of the offset amount (503), and in order to connect the inner surface of the opening (Wa) and the upper surface (409a) of the intake guide section (409) without any steps, recesses (801, 802) having a curvature matching the shape of the opening (Wa) are formed on the upper surface (409a) of the intake guide section (409).

[0113] According to the intake structure for an internal combustion engine of item 7, the intake flow f, which has a spatial expansion corresponding to the cross-sectional shape of the opening Wa, flows through a recess (the inner surface of the recess) having a curvature that matches the shape of the opening (Wa). This maintains a flow directed approximately linearly along the passage direction, and suppresses the expansion of the intake flow in the cross direction. This allows the intake flow to be supplied into the combustion chamber without coming into contact with the stem of the open intake valve. This reduces obstruction of the intake flow from the open end of the secondary passage into the cylinder, strengthens the formation of an airflow vortex inside the cylinder, and improves combustion efficiency.

[0114] The present invention is not limited to the above-described embodiment, and various modifications and variations are possible within the scope of the gist of the present invention.

[0115] 4: internal combustion engine, 6: intake passage, 6A: sub-passage, 6B: main passage, 65: partition portion, 32: combustion chamber, 73: intake valve, 73a: head portion, 73c: stem portion, 77: valve seat edge, 410: inlet section, 506: opening end, 409: intake induction portion, 420: confluence portion

Claims

1. An intake structure for an internal combustion engine (4), comprising: a partition (65) that separates an intake passage (6) into upper and lower sections along a passage direction, and forms a main passage (6B) and a sub-passage (6A), and the intake air is guided to the sub-passage (6A) or to the main passage (6B) and the sub-passage (6A) depending on an operating state of the internal combustion engine (4), An opening (Wa) of an inlet section (410) formed in a substantially straight line downstream of the sub-passage (6A) is bifurcated and communicates with the combustion chamber (32) via the main passage (6B), When viewed from above, the combustion chamber (32) Each of the openings (Wa) is formed based on a positional relationship in which a center line (501) of each of the openings (Wa) formed by branching into two branches is eccentric with respect to a center line (502) of the outer width (WA) of the sub-passage (6A) by an offset amount (503) set in a direction intersecting the passage direction, In a side view of the combustion chamber (32) with the intake valve (73) open, the inlet section (410) is formed based on a positional relationship in which an axis (419) of the sub-passage (6A) in the inlet section (410) is inclined at a relative angle (θ1) set with respect to a shaft portion (73c) of the intake valve (73), The cross-sectional shape of each of the openings (Wa) of the sub-passage (6A) is extended in a direction toward the inside of the combustion chamber (32), forming an imaginary substantially cylindrical region, In a side view of the combustion chamber (32) when the intake valve (73) is open, It is formed so as not to come into contact with the valve seat edge (77) of the intake valve (73), When viewed from below of the combustion chamber (32) with the intake valve (73) open, one cross-sectional shape region and the other cross-sectional shape region of the bifurcated opening (Wa) are formed in the left-right direction across the shaft portion (73c) so as not to come into contact with the shaft portion (73c).

2. 2. The intake structure for an internal combustion engine according to claim 1, wherein the region is formed so as not to contact the stem portion (73c) of the intake valve (73) when viewed from the top, and so as not to contact the umbrella portion (73a) of the intake valve (73) when viewed from the side.

3. The combustion chamber (32) further includes a confluence portion (420) where intake air (407) flowing from the main passage (6B) to the combustion chamber (32) and intake air (408) flowing from the sub-passage (6A) to the combustion chamber (32) are confluenced, 2. The intake structure of an internal combustion engine according to claim 1, wherein a substantially linear flat surface is provided on a surface of the main passage on the side of the sub-passage at the junction.

4. 4. The intake structure for an internal combustion engine according to claim 3, wherein an opening is formed in the flat surface (416) for guiding the intake flow (f) from the secondary passage (6A) side to the junction (420).

5. 4. The intake structure for an internal combustion engine according to claim 3, wherein the flat surface (416) is formed substantially parallel to the shaft portion (73c) of the intake valve (73).

6. 5. The intake structure for an internal combustion engine according to claim 4, wherein the sub-passage (6A) is provided with a substantially linear intake guide portion (409) that guides the intake flow (f) from the opening end (506) of each of the openings (Wa) toward the combustion chamber (32).

7. The sub-passage (6A) has a cross-sectional shape formed with a substantially oval opening (Wa) or a substantially rectangular opening (Wa) that is elongated horizontally in the direction of the offset amount (503), In order to connect the inner surface of each of the openings (Wa) and the upper surface (409a) of the intake air guide portion (409) without any step, An intake structure for an internal combustion engine as described in claim 6, characterized in that recesses (801, 802) having curvatures that match the shapes of each of the openings (Wa) are formed on the upper surface (409a) of the intake guide portion (409).