Internal combustion engine admission structure

Description

1 / 33 Internal Combustion Engine Intake Structure TECHNICAL FIELD

[001] The technology disclosed relates to an intake structure of an internal combustion engine. TECHNICAL BACKGROUND

[002] In recent years, research and development to improve fuel efficiency, which contributes to energy efficiency, has been conducted in order to enable more people to have easy and reliable access to sustainable and advanced energy.

[003] Patent Literature 1 discloses a structure in which a tumbling flow path opening is directed to a combustion chamber in order to enhance the tumbling flow from the point of view of improving fuel efficiency. LIST OF QUOTES PATENTARY LITERATURE

[004] PTL 1: International Publication No. 2021 / 186513 SUMMARY OF THE INVENTION TECHNICAL PROBLEM

[005] However, in current technology related to improving fuel efficiency, in a case where, when an intake valve of the combustion chamber is opened, an airflow flowing in one direction from an extended line extending from the opening of the tipping flow path hits a valve stem, a valve seat or the like, there may be a problem that the airflow flowing from the opening of the tipping flow path is diffused, and vortex formation in a cylinder may be inhibited.

[006] One objective of the disclosed technology is to improve the training of a Petition 870250086057, dated 09 / 23 / 2025, pp. 113 / 154 2 / 33 airflow vortex in a cylinder and improve combustion efficiency. Additionally, this contributes to improved fuel efficiency and energy efficiency. SOLUTION TO THE PROBLEM

[007] According to an aspect of the disclosed technology, an intake structure of an internal combustion engine (4) is provided in which a main passage (6B) and an auxiliary passage (6A) are formed by a partition portion (65) that partitions an intake passage (6) vertically along a passage direction, and the intake air is guided to the auxiliary passage (6A) or to the main passage (6B) and the auxiliary passage (6A) according to an operating state of the internal combustion engine (4), characterized in that on a downstream side of the auxiliary passage (6A), an opening (Wa) of an approach section (410) formed in a substantially linear shape is formed to be bifurcated and communicates with a combustion chamber (32) via the main passage (6B), in top view of the combustion chamber (32),Each of the openings (Wa) formed to be bifurcated is formed based on a positional relationship in which a central line (501) of each of the openings (Wa) is eccentric by a defined amount of deviation (503) in a direction that intersects the direction of the passage with respect to a central line (502) of an external width (WA) of the auxiliary passage (6A), in a side view of the combustion chamber (32) in a state where an intake valve (73) is open, the approach section (410) is formed based on a positional relationship in which an axis (419) of the auxiliary passage (6A) in the approach section (410) is inclined by a relative angle (Θ1) defined with respect to, Petition 870250086057, dated 09 / 23 / 2025, pp. 114 / 154 3 / 33 a portion of the stem (73c) of the intake valve (73), in a side view of the combustion chamber (32) in a state where the intake valve (73) is open, a substantially columnar virtual region in which a cross-sectional shape of each of the openings (Wa) of the auxiliary passage (6A) is extended in a direction that extends towards the interior 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), and in a bottom view of the combustion chamber (32) in a state where the intake valve (73) is open, one cross-sectional shape region and the other cross-sectional shape region of the openings (Wa) formed to be bifurcated are formed in a left-right direction with the stem portion (73c) interposed between them so as not to be in contact with the stem portion (73c). ADVANTAGEOUS EFFECTS OF THE INVENTION

[008] According to the disclosed technology, it is possible to provide an intake structure for an internal combustion engine capable of enhancing the formation of an airflow vortex in a cylinder and improving combustion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[009] FIG. 1 is a side view of a vehicle according to an embodiment.

[010] FIG. 2 is a diagram to explain the structure of an internal combustion engine according to the modality.

[011] FIG. 3 is a diagram to explain an internal combustion engine intake structure according to the modality. Petition 870250086057, dated 09 / 23 / 2025, pages 115 / 154 4 / 33

[012] FIG. 4 is a diagram illustrating a structure on a downstream side where a main passage and an auxiliary passage are connected to a combustion chamber in the intake structure of the internal combustion engine according to the embodiment. FIG. 5 is a diagram schematically illustrating the structure of an auxiliary passage in a top view of the combustion chamber in the intake structure of the internal combustion engine according to the embodiment.

[013] FIG. 6A is a diagram illustrating a bottom view of the combustion chamber as seen in the direction of arrow 4A in FIG. 4.

[014] FIG. 6B is a diagram illustrating a bottom view of the combustion chamber seen in the direction of arrow 4A in FIG. 4.

[015] FIG. 7 is a diagram that schematically illustrates a cross-sectional shape of an auxiliary passage 6A.

[016] FIG. 8 is a diagram that schematically illustrates a cross-sectional shape of a portion of intake air guide 409 in the intake structure of the internal combustion engine according to the embodiment.

[017] FIG. 9 is a diagram that schematically illustrates a comparison between intake airflow according to a comparative example and intake airflow through the intake structure according to the modality. DESCRIPTION OF THE MODALITIES

[018] Next, an embodiment will be described in detail with reference to the accompanying drawings. Note that the following embodiment does not limit the invention mentioned in the claims, and not all combinations of attributes described in the embodiment are essential to the invention. Two or more attributes from a plurality of attributes described in the embodiments may optionally be combined. The same reference numeral is given for the Petition 870250086057, dated 09 / 23 / 2025, pp. 116 / 154 5 / 33 same settings or similar settings, and redundant descriptions thereof are omitted.

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

[020] Note that directions such as forward, backward, left, right, up and down in the description and claims of this specification follow a vehicle orientation of the type to be mounted in a case where the internal combustion engine according to this embodiment is mounted on the vehicle of the type to be mounted. In this embodiment, the vehicle of the type to be mounted is, for example, a scooter-type motorcycle (hereinafter simply referred to as “motorcycle”).

[021] In addition, an FR arrow in the drawings indicates a forward direction of the vehicle, LH indicates a left direction of the vehicle, RH indicates a right direction of the vehicle and UP indicates an upward direction of the vehicle. (Sketch of the vehicle, including the intake structure of the internal combustion engine)

[022] FIG. 1 illustrates an outline of a left side surface of a motorcycle 1 including an intake structure of an internal combustion engine according to the present embodiment.

[023] In the motorcycle 1 of the present embodiment, a front vehicle body portion 1A and a rear vehicle body portion 1B are connected to each other via a lower floor portion 1C (foot support portion), and a vehicle body frame 2 forming a vehicle body frame basically includes a lower frame 21 and a main frame 22.

[024] The lower frame 21 extends downward from a head tube 20 of the front portion of vehicle body 1A and is connected to a pair Petition 870250086057, dated 09 / 23 / 2025, pp. 117 / 154 6 / 33 of the lower left and right frame portions 22a of the main frame 22 extending substantially horizontally backward from a lower end of the lower frame 21. The main frame 22 extending obliquely to the rear and upper side from the rear ends of the lower frame portions 22a forms a pair of left and right angled portions 22b, and the upper portions of the angled portions 22b bend further to form a pair of left and right horizontal portions 22c extending substantially horizontally to the rear side.

[025] The inclined portions 22b and the horizontal portions 22c of the main frame 22 support a storage box (also referred to as a helmet box) 11, and an occupant seat 12 is arranged to cover the upper side of the storage box.

[026] In contrast, in the front portion of vehicle body 1A, a steering rod 13 is provided on an upper side of the head tube 20 so as to be pivotally supported, a front fork 14 extends downwards and a front wheel 15 is pivotally supported at a lower end thereof.

[027] A power unit support 23 is provided to project rearward into the inclined portions 22b of the main frame 22, and an oscillating type power unit (hereinafter simply referred to as a “power unit”) 3 is connected and supported to the power unit support 23 via a connecting element 24 so as to be oscillating in a variant manner.

[028] The motorcycle 1 of the present embodiment adopts a support structure of the upper link type of the power unit 3 and, as a result, a space equipped with a catalytic converter 49 below a front portion. Petition 870250086057, dated 09 / 23 / 2025, pp. 118 / 154 7 / 33 of the power of 3 is obtained.

[029] In the front portion of vehicle body 1A, the head tube 20 and the lower frame 21 are covered on the front and rear sides with a front cover 10a and a leg guard 10b of a vehicle body cover 10.

[030] Floor portion 1C is provided in the pair of left and right lower frame portions 22a of the main frame 22 of the vehicle body frame 2. An upper portion of the lower frame portion 22a is covered with a floor cover 10c, the left and right portions thereof are covered with a side floor cover 10d in a front and rear direction, and a lower portion thereof is covered with a lower cover 10e.

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

[032] In power unit 3, an internal combustion engine 4 is provided, and a power transmission portion 5 internally equipped with a continuous belt-type transmission 51 is provided behind the internal combustion engine 4. A reduction gear mechanism 52 that is transmitted by the continuous belt-type transmission 51 is provided in a rear portion of the power transmission portion 5, and the rear wheel 17 is provided on a rear axle 52a which is an output rod of the mechanism. Petition 870250086057, dated 09 / 23 / 2025, pp. 119 / 154 8 / 33 reduction gear.

[033] A rear cushion 18 is interposed between the rear portion of the power transmission portion 5 and the rear horizontal portion 22c of the main frame 22. The internal combustion engine 4 is a 4-stroke, single-cylinder, air-cooled internal combustion engine, in which a crankshaft 41 is rotatably supported by a crankcase 30 so as to be directed in the direction of the width of the vehicle, i.e., the left-right direction, and a cylinder block 42, a cylinder head 43 and a cylinder head cover 44 are sequentially superimposed so as to project from the front portion of the crankcase 30, and the cylinder axis C is fixed to be substantially horizontal and inclined forward.

[034] An intake port 45 is provided on an intake side flange surface 43b to which an intake manifold 61 is attached via an isolator 60.

[035] An intake manifold 61 and a choke body 62 are provided above the power unit 3 and above the cylinder head 43 down to the crankcase 30. The intake manifold 61 is connected to the intake port 45 on an upper portion of the cylinder head 43, which is inclined forward. The intake manifold 61 extends with its upstream side bent backward and is connected to the choke body 62.

[036] The upstream side of the choke body 62 is connected via a connecting tube 63 to an air filter 64 attached to the upper portion of the power transmission portion 5.

[037] An intake passage 6 is formed from the connecting tube 63 through the choke body 62, the intake manifold 61 and the intake port 45 of the cylinder head 43, and leads to a combustion chamber 32. Petition 870250086057, dated 09 / 23 / 2025, pages 120 / 154 9 / 33

[038] In an upstream exhaust pipe 48a connected to an exhaust port outlet 47a in the lower portion of the cylinder head 43, the catalytic converter 49 having a substantially cylindrical shape directed in the direction of the width of the vehicle is interposed, and a catalyst, such as a three-way catalyst for exhaust gas purification, is carried inside it. A downstream exhaust pipe 48b connected to the outlet of the catalytic converter 49 is bent backward, extends rearward along the right side of the vehicle and is connected to a muffler (not shown) on the right side of the rear wheel 17. (Sketch of the intake structure of an internal combustion engine)

[039] FIG. 2 is a right cross-sectional side view of the cylinder block 42, cylinder head 43, cylinder head cover 44 and its periphery of the power unit 3 in FIG. 1, taken along the axis of cylinder C.

[040] The crankcase 30 is configured by combining a left half-body 30L and a right half-body (not illustrated), which are divided into right and left, and the left half-body 30L extends rearward to form a power transmission portion 5 that accommodates a transmission device including the long belt type continuous transmission 51, the reduction gear mechanism 52 and the like between the crankshaft 41 and the rear axle 52a of the rear wheel 17.

[041] A piston 33 reciprocating in a cylinder bore 42a of the cylinder block 42 is connected to a crank pin 41a of the crankshaft 41 of the crankcase 30 by a connecting rod 34.

[042] The combustion chamber 32 is formed between a top surface 33a of the piston 33 slidingly fitted into the cylinder bore 42a of the cylinder block 42 and a roof surface 43a of the cylinder head 43 for the Petition 870250086057, dated 09 / 23 / 2025, pp. 121 / 154 10 / 33 which the top surface 33a faces. As illustrated in FIG. 2, in the present embodiment, the choke body 62 is fixed and connected to the intake manifold 61 connected to the intake port 45 of the cylinder head 43 on the upstream side via a reed valve 8 described later. In the following description, a configuration using the reed valve 8 is described as an example, but the present embodiment can be applied similarly to a configuration that does not include the reed valve 8.

[043] In the choke body 62, a choke valve 62a is incorporated into the intake passage 6 and rotates around a choke valve stem 62b to open and close the intake passage 6 and adjust the intake air flow rate.

[044] In FIG. 2, 31 represents a support portion that projects upwards from the upper portion of the crankcase 30 and suspends the power unit 3 to the vehicle body frame 2.

[045] As illustrated in FIG. 1, the support portion 31 is pivotally supported by a power unit support 23 that projects behind the inclined portion 22b of the main frame 22 via a connecting element 24, and the power unit 3 oscillates up and down relative to the vehicle body frame 2.

[046] The rear end of the vertically oscillating power unit 3 is supported by the horizontal portion 22c of the main frame 22 by the rear pad 18.

[047] As illustrated in FIG. 2, the intake manifold 61 is connected to the front side of the choke body 62, i.e., to the downstream side of the intake air and is curved downwards, and is connected to the intake port 45 in the upper portion of the cylinder head 43 with the isolator 60 interposed between them. Petition 870250086057, dated 09 / 23 / 2025, pages 122 / 154 11 / 33

[048] A fuel injection valve 39 is attached to a downstream end of the intake manifold 61, and fuel is injected towards the intake valve port 35. Fuel injection is carried out in the direction of a central injection line I illustrated in FIG. 2. Because the fuel injection from the fuel injection valve 39 has a constant dispersion, a recess 67a is provided on the outer periphery of a main passage cylinder head inlet opening 67 in order to prevent the injected fuel.

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

[050] In the present embodiment, the internal combustion engine 4 employs a single-cylinder SOHC type two-valve system, and a valve mechanism 9 is provided in the cylinder head 43. The cylinder head 43 is covered with the cylinder head cover 44 so as to cover the valve mechanism 9.

[051] In order to transmit power to the valve mechanism 9 in the cylinder head cover 44, an endless timing chain (not shown) passes through the crankcase 30, through the cylinder block 42 and through a timing chain chamber (not shown) provided on one side of the cylinder head 43 in the direction of the crankshaft 41, and is installed between the camshaft 90 and the crankshaft 41, and the camshaft 90 rotates at a speed of 1 / 2 rotation in synchronization with the crankshaft 41.

[052] Note that in cylinder head 43, an ignition plug is adjusted and inserted on a side opposite the cam chain chamber (the other side in the direction of the crankshaft (41) towards the interior of the combustion chamber 32. Petition 870250086057, dated 09 / 23 / 2025, pp. 123 / 154 12 / 33

[053] In the cylinder head 43, in which the axis of cylinder C is substantially horizontal and inclined forward, the intake port 37 and an exhaust port 38 are formed to extend while being curved in directions vertically away from each other from the intake valve port 35 and an exhaust valve port 36 open to the roof surface 43a of the combustion chamber 32, respectively.

[054] An upstream end of the intake port 37 opens upward from the cylinder head 43 to form the intake port 45 and is connected to the intake manifold 61 to form a continuous intake passage 6. The choke body 62 is connected to the upstream side of the intake manifold 61.

[055] A downstream end of the exhaust port 38 forms an exhaust port outlet 47, opens downwards from the cylinder head 43 and is connected to the upstream exhaust pipe 48a (FIG. 1).

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

[057] In addition, an exhaust valve guide 72 is integrally fitted into a curved portion of the outer wall 38a of the exhaust port 38 in the cylinder head 43, and an exhaust valve 74 slidingly supported by the exhaust valve guide 72 opens and closes the exhaust valve port 36 facing the combustion chamber 32 of the exhaust port 38. Above the combustion chamber 32, the pair of intake valve 73 and exhaust valve 74 is arranged based on a positional relationship in which a portion Petition 870250086057, dated 09 / 23 / 2025, pages 124 / 154 13 / 33 rod 73c and a portion of rod 74c are bent in a V shape.

[058] The intake valve 73 and the exhaust valve 74 are tensioned upwards by the valve springs 75 such that the umbrella portions 73a and 74a close the intake valve port 35 and the exhaust valve port 36 facing the combustion chamber 32. The base ends 73b and 74b of the intake valve 73 and the exhaust valve 74 are pushed downwards by an intake rocker arm 91 and an exhaust rocker arm 92 which rock in contact with an intake cam and an exhaust cam of the camshaft 90, respectively, so that the intake valve 73 and the exhaust valve 74 are opened at a predetermined time to achieve communication between the intake port 37 and the combustion chamber 32 and between the exhaust port 38 and the combustion chamber 32, whereby intake and exhaust are performed at a predetermined time.

[059] The intake manifold 61 is connected to an upstream end of the intake port 37 of the internal combustion engine 4 via the isolator 60 to form the continuous intake passage 6, and the choke body 62 is connected to an upstream side of the intake manifold 61 via the reed valve 8.

[060] The choke body 62 has an intake path 62c having a substantially circular cross-section and constituting a part of the intake passage 6 connected to the combustion chamber 32 of the internal combustion engine 4, and an upstream side thereof is connected to the air filter 64 (see FIG. 1) via the connecting tube 63.

[061] The choke body 62 includes a choke valve 62a. The choke valve 62a is a single butterfly type choke valve that is rotatable and pivotally supported in the choke body 62 by the choke valve stem 62b which is oriented Petition 870250086057, dated 09 / 23 / 2025, pages 125 / 154 14 / 33 vertically to the direction of intake airflow F of intake path 62c, i.e., vertically to the central axis X of intake path 62c, to be substantially horizontal to variably control the intake path flow area of ​​intake path 62c and open and close intake path 62c.

[062] The choke valve 62a is rotatable in a clockwise valve opening direction in FIG. 2 by operation of the driver or similar, and is tensioned in a clockwise valve closing direction by a return spring (not shown). According to the present embodiment, the intake path 62c of the choke body 62 is oriented substantially horizontally. Intake passage 6 is divided vertically along the direction of intake airflow by a partition portion 65 (dividing wall) from the intake manifold 61 to the intake port 37. Intake passage 6 is configured such that the intake air passing through intake passage 6 generates a tumbling flow T in the combustion chamber 32. Intake passage 6 is divided by the partition portion 65 into a tumbling passage 6A on the lower side of intake passage 6 and a main passage 6B on the upper side of intake passage 6.According to the present invention, the "tipping passage" is a passage for intake air to generate the tipping flow T in the combustion chamber 32 when the choke valve 62a has a low opening, i.e., when the internal combustion engine 4 has a low load. In this specification, the tipping passage 6A is also referred to as an auxiliary passage. In the example of FIG. 2, the tipping passage 6A is arranged on the lower side of the intake passage 6, and the main passage 6B is arranged on the upper side of the intake passage 6. However, in the present embodiment,... Petition 870250086057, dated 09 / 23 / 2025, pp. 126 / 154 15 / 33 The vertical arrangement of the 6A overturning passage (auxiliary passage) and the main passage 6B is not limited to the arrangement structure illustrated in FIG. 2.

[063] Partition portion 65 is configured so that an intake manifold side partition portion 65A, an isolator side partition portion 65B and an intake port side partition portion 65C are positioned continuously from the upstream to the downstream side of the intake airflow.

[064] The main passage 6B on the upper side in the drawing and the tipping passage 6A on the lower side in the drawing are formed by the vertical partition of the intake passage 6 by the partition portion 65.

[065] As illustrated in FIG. 2, the blade valve 8 is provided between the choke body 62 and the inlet manifold 61.

[066] 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 a reed valve element 87 is attached to a reed valve body 81.

[067] The blade valve 8 includes the blade valve body 81 which forms the whole shape, and a mounting flange portion 85 is interposed and secured between a downstream end portion of the choke body 62 and an upstream end portion of the inlet manifold 61.

[068] An inlet opening 82 coinciding with a downstream opening 62d of the choke body 62 is provided on a surface of the blade valve body 81 to be attached to the choke body 62, and the valve intake path 80 communicating with the intake path 62c of the choke body 62 is formed in the blade valve body 81.

[069] In the downstream end portion 83 of the valve body of Petition 870250086057, dated 09 / 23 / 2025, pages 127 / 154 16 / 33 blade 81, an opening 84 is formed which is in contact with an upstream end 65Aa of the partition portion 65A and corresponds to an upstream end opening 6Aa of the tipping passage 6A. The upper portion of the blade valve body 81 is formed to be inclined from the rear portion of the mounting flange portion 85 to the lower portion on the downstream side of the blade valve 8, and an inclined surface 81a is formed with an opening 86 that communicates with the valve intake path 80 in the blade valve body 81 and the main passage 6B.

[070] One end 87a of the blade valve element 87 is fixed to the mounting flange portion 85 by a screw 87c so as to cover the opening 86. The other end 87b of the blade valve element 87 is a swinging free end, and the other end 87b of the blade valve element 87 is in contact with the downstream end portion 83 formed on the downstream side of the blade valve body 81. When the choke valve 62a has a low opening, i.e., when the negative pressure on the downstream side of the blade valve element 87 is less than a certain value, the other end 87b of the blade valve element 87 maintains a state in which the opening 86 is closed, and the intake air flows exclusively from the valve intake path 80 in the blade valve body 81 to the tipping passage 6A of the intake manifold 61.

[071] When the choke valve 62a has a high opening, that is, when the internal combustion engine 4 has a high load and the negative pressure on the downstream side of the blade valve element 87 becomes greater than a certain value, the other end 87b of the blade valve element 87 bends to open the opening 86, and the intake air flows from the intake valve path 80 in the blade valve body 81 to the main passage 6B of the intake manifold 61. Petition 870250086057, dated 09 / 23 / 2025, pp. 128 / 154 17 / 33 (Downstream intake structure connected to combustion chamber 32)

[072] FIG. 4 is a diagram illustrating a downstream intake structure in which the main passage 6B and the auxiliary passage 6A are connected (communicate) to the combustion chamber 32. FIG. 4 illustrates a side view of the combustion chamber 32 in a state where the intake valve 73 is open. FIG. 5 is a diagram schematically illustrating a structure of the auxiliary passage 6A in a top view of the combustion chamber 32 of the internal combustion engine 4.

[073] In the intake structure of the internal combustion engine 4 of the present embodiment, the main passage 6B and the auxiliary passage 6A are formed by the partition portion 65 which divides the intake passage 6 vertically along the direction of the passage, and the intake air is guided to the auxiliary passage 6A or to the main passage 6B and the auxiliary passage 6A according to the operating state of the internal combustion engine 4.

[074] On one side downstream of auxiliary passage 6A, an opening Wa of an approach section 410 formed in a substantially linear shape communicates with the combustion chamber 32 via the main passage 6B.

[075] As illustrated in FIG. 4, in a side view of the combustion chamber 32 in a state where the intake valve 73 is open, the approach section 410 is formed based on a positional relationship in which an axis 419 of the auxiliary passage 6A in the approach section 410 is inclined by a relative angle Θ1 defined with respect to the stem portion 73c of the intake valve 73 in the open state. Additionally, a relative angle Θ2 indicates, for example, a relative angle of the approach section 410 with respect to the mounting surface for attaching the cylinder head 43 to the cylinder block 42. Petition 870250086057, dated 09 / 23 / 2025, pp. 129 / 154 18 / 33

[076] The intake structure of the internal combustion engine 4 includes a fusion portion 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 auxiliary passage 6A to the combustion chamber 32 merge. A substantially linear flat surface 416 is provided on a surface of the main passage 6B on the side of the auxiliary passage 6A in the fusion portion 420. An opening to guide the intake airflow f from the side of the auxiliary passage 6A to the fusion portion 420 is formed in the flat surface 416. The flat surface 416 is formed substantially parallel to the stem portion 73c of the intake valve 73.

[077] The auxiliary passage 6A is provided with a substantially linear intake air guide portion 409 which guides the intake air flow f from an opening end 506 of the opening Wa towards the melting portion 420 or the combustion chamber 32.

[078] As illustrated in FIG. 5, in a top view of the combustion chamber 32 of the internal combustion engine 4, the Wa opening of the approach section 410 of the auxiliary passage 6A formed on the downstream side in the direction of the passage communicates with the combustion chamber 32 via the main passage 6B.

[079] The Wa opening is formed based on a positional relationship in which a central line 501 of the Wa opening is eccentric by a first eccentric quantity (deviation quantity 503) defined in a direction that intersects (substantially orthogonal to) the direction of the passage with respect to a central line 502 of an external width WA of the auxiliary passage 6A. The Wa opening is formed based on a positional relationship in which the central line 501 of the Wa opening is eccentric by a second eccentric quantity (deviation quantity 505) with respect to the central line 504 (central line along Petition 870250086057, dated 09 / 23 / 2025, pp. 130 / 154 19 / 33 of the passage direction) of the 73c stem portion of the 73 intake valve.

[080] That is, the intake structure (positional relationship) of the auxiliary passage 6A is a positional relationship in which the centerline 501 of Wa is eccentric by the first eccentric amount (deviation amount 503) with respect to the centerline 502 of the external width WA of the auxiliary passage 6A. A relative arrangement structure (positional relationship) between the auxiliary passage 6A and the intake valve 73 is a positional relationship in which the centerline 501 of the opening Wa is eccentric by the second eccentric amount (deviation amount 505) with respect to a centerline 504 (centerline along the direction of the passage) of the stem portion 73c of the intake valve 73.

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

[082] The projection surface of the opening Wa is formed as a substantially columnar virtual region (hereinafter also referred to as the cross-sectional shape region of the opening Wa) in which the cross-sectional shape of the opening Wa of the auxiliary passage 6A is extended in a direction extending from the end of the opening 506 towards the interior of the combustion chamber 32. The projection surface of the opening Wa (cross-sectional shape region of the opening Wa) is projected substantially linearly from the end of the opening 506 towards the combustion chamber 32 and has a spatial extension in a direction perpendicular to the surface of the paper. The intake airflow f flowing through the auxiliary passage 6A is emitted (provided) by the end of the opening 506 of the opening. Petition 870250086057, dated 09 / 23 / 2025, pp. 131 / 154 20 / 33 Wa from auxiliary passage 6A to combustion chamber 32 so as to flow in the substantially columnar virtual region (cross-sectional shape region of opening Wa).

[083] The Wa aperture has, as a cross-sectional shape, a substantially elliptical shape or a substantially rectangular shape that extends horizontally in the direction of the deviation quantity 503.

[084] The intake airflow f is emitted from the opening Wa through the linearly formed approach section 410 on the downstream side of the auxiliary passage 6A. The intake airflow f emitted from the opening Wa flows through the approach section 410 to become a substantially linearly directed flow. The intake air guide portion 409 provides the intake airflow f emitted from the opening Wa to the combustion chamber 32 as a flow in which the substantially linear orientation is additionally maintained.

[085] As illustrated in FIG. 4, the substantially columnar virtual region having a spatial extent according to the cross-sectional shape of the opening Wa (cross-sectional shape region of the opening Wa) is formed in the combustion chamber 32 so as not to come into contact with the umbrella portion 73a of the intake valve 73 or the roof surface 43a of the combustion chamber 32 in a side view of the combustion chamber 32 in a state where the intake valve 73 is open. In addition, as illustrated in FIG. 5, the substantially columnar virtual region (cross-sectional shape region of the opening Wa) formed as a projection surface of the opening Wa is formed in the combustion chamber 32 so as not to come into contact with the stem portion 73c of the intake valve 73 in the open state in a top view of the combustion chamber 32 of the internal combustion engine 4. That is, the substantially columnar virtual region Petition 870250086057, dated 09 / 23 / 2025, pp. 132 / 154 21 / 33 columnar (cross-sectional shape region of the Wa opening) formed as a projection surface of the Wa opening is not in contact with the stem portion 73c of the intake valve 73 in the open state, and is not in contact with the umbrella portion 73a of the intake valve 73 in the open state of the intake valve 73. The Wa opening and the approach section 410 of the auxiliary passage 6A are formed in such a way that the substantially columnar virtual region (cross-sectional shape region of the Wa opening) is formed in the combustion chamber 32.

[086] FIG. 6A is a diagram illustrating a bottom view of the combustion chamber 32 seen in the direction of an arrow 4A in FIG. 4. In FIG. 6A, a hatched portion exemplifies a projection surface of the opening Wa of the auxiliary passage 6A. The intake airflow f flowing through the auxiliary passage 6A is emitted (provided) by the opening Wa of the auxiliary passage 6A to the combustion chamber 32 so as to flow on the projection surface of the opening Wa in the combustion chamber 32. As illustrated in FIGS. 4 and 6A, the substantially columnar virtual region (cross-sectional shape region of the opening Wa) formed as a projection surface of the opening Wa is formed in the combustion chamber 32 so as not to be in contact with a valve seat edge 77 of the intake valve 73 in the open state in a side view and a bottom view of the combustion chamber 32 in a state where the intake valve 73 is open.In addition to the stem portion 73c and the umbrella portion 73a of the intake valve 73 in the open state, the substantially columnar virtual region (cross-sectional shape region of the opening Wa) is formed so as not to be in contact with the valve seat edge 77 of the intake valve 73. The opening Wa and the approach section 410 of the auxiliary passage 6A are formed in such a way that the substantially columnar virtual region (cross-sectional shape region) Petition 870250086057, dated 09 / 23 / 2025, pages 133 / 154 22 / 33 transverse of the Wa opening) is formed in the combustion chamber 32.

[087] Although FIG. 6A illustrates an example where the projection surface of the opening Wa is one, the opening Wa can be formed to be bifurcated. For example, as illustrated in FIGS. 4 and 6A, one projection surface and the other projection surface of the opening Wa of the auxiliary passage 6A formed to be bifurcated can be formed in the combustion chamber 32 so as not to come into contact with the valve seat edge 77 of the intake valve 73 in the open state in a side view and a bottom view of the combustion chamber 32 in a state where the intake valve 73 is open. In this case, one projection surface (one cross-sectional shape region of the opening Wa) and the other projection surface (the other cross-sectional shape region of the opening Wa) of the opening Wa of the auxiliary passage 6A formed to be bifurcated are formed in a left-right direction of the paper surface with the rod portion 73c interposed between them.Even when the opening is formed to be bifurcated, a substantially columnar virtual region (a cross-sectional shape region of the opening Wa) formed as one projection surface of the opening Wa and a substantially columnar virtual 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 be in contact with the valve seat edge 77 of the intake valve 73, apart from the stem portion 73c and the umbrella portion 73a of the intake valve 73 in the open state (FIG. 6B). (Auxiliary passage cross-section format 6A)

[088] FIG. 7 is a diagram that schematically illustrates a cross-sectional format of auxiliary passage 6A. In FIG. 7, a direction perpendicular to the paper surface indicates a direction of passage of the Petition 870250086057, dated 09 / 23 / 2025, pages 134 / 154 23 / 33 intake passage 6, and a left-to-right direction on the paper surface indicates a width direction of the internal combustion engine 4 that intersects (substantially orthogonally to) the passage direction. In addition, an up-and-down direction on the paper surface indicates an up-and-down direction of the internal combustion engine 4 that intersects (substantially orthogonally to) the passage direction and the intersection direction.

[089] The auxiliary passage 6A is formed with an opening Wa having, as a cross-sectional shape, a substantially elliptical shape or a substantially rectangular shape that extends horizontally in the direction of the deviation quantity 503. In FIG. 7, ST71 illustrates an example in which the opening Wa of the auxiliary passage 6A is formed in a substantially elliptical shape, and ST72 illustrates an example in which the opening Wa of the auxiliary 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 centerline 501 of the opening Wa of the auxiliary passage 6A is eccentric by the first eccentric quantity (deviation quantity 503) with respect to the centerline 502 of the external width WA of the auxiliary passage 6A.

[090] As illustrated in FIG. 4, the intake air guide portion 409 extends substantially linearly from the opening end 506 of the opening Wa towards the combustion chamber 32 and is formed so as to be connectable to the inner surface of the opening Wa without a step. In order to connect to the inner surface of the opening Wa without a step, a recess having a curvature corresponding to the cross-sectional shape of the opening Wa is formed on a top surface 409a of the intake air guide portion 409.

[091] FIG. 8 is a diagram that schematically illustrates a format Petition 870250086057, dated 09 / 23 / 2025, pages 135 / 154 24 / 33 cross-section of the intake air guide portion 409. The coordinate system in FIG. 8 is similar to that in FIG. 7: a direction perpendicular to the paper surface indicates a direction of passage of the intake passage 6, and a left-to-right direction of the paper surface indicates a width direction of the internal combustion engine 4 that intersects (substantially orthogonally to) the direction of passage. In addition, an up and down direction of the paper surface indicates an up and down direction of the internal combustion engine 4 that intersects (substantially orthogonally to) the direction of passage and the direction of intersection.

[092] In order to connect the inner surface of the Wa opening of the auxiliary passage 6A and the top surface 409a of the intake air guide portion 409 without a step, a recess (801, 802) having a curvature corresponding to the shape of the Wa opening is formed on the top surface 409a of the intake air guide portion 409. In FIG. 8, ST81 indicates a cross-sectional shape of the intake air guide portion 409 corresponding to an example (ST71) in which the Wa opening is formed in a substantially elliptical shape. ST82 indicates a cross-sectional shape of the intake air guide portion 409 corresponding to an example (ST72) in which the Wa opening is formed in a substantially rectangular shape.

[093] In ST81, in order to connect to the inner surface of the Wa opening having a substantially elliptical shape without a step, the recess 801 having a curvature corresponding to the cross-sectional shape (for example, the shape of the lower half of the substantially elliptical shape in the upward and downward direction) of the lower portion of the Wa opening is formed on the top surface 409a of the intake air guide portion 409.

[094] In ST82, in order to connect to the inner surface of the substantially rectangular opening Wa without a step, the recess 802 having a Petition 870250086057, dated 09 / 23 / 2025, pages 136 / 154 25 / 33 curvature corresponding to the cross-sectional shape (e.g., the shape of the lower half of the substantially rectangular shape in the upward and downward directions) of the lower portion of the Wa opening is formed on the top surface 409a of the intake air guide portion 409.

[095] By forming recesses 801 and 802 having a curvature corresponding to the cross-sectional shape of the lower portion of the opening Wa on the top surface 409a of the intake air guide portion 409, recesses 801 and 802 (inner surfaces of the recesses) of the intake air guide portion 409 and the lower portion (inner surface of the lower portion) of the opening Wa can be connected without a step in the connecting portion in the direction of passage. As a result, intake airflow f can be provided to the combustion chamber 32 without disturbing the flow directed substantially linearly along the direction of passage.

[096] In addition, the intake airflow f having a spatial distribution according to the cross-sectional shape of the opening Wa flows through recesses 801 and 802 (inner peripheral surfaces of the recesses), so that a substantially linearly directed flow is maintained along the passage direction, and the distribution of the intake airflow in the intersection direction can be suppressed. As a result, the intake airflow f can be provided to the combustion chamber 32 so as not to come into contact with the stem portion 73c (FIG. 5) of the intake valve 73 in the open state.

[097] In the present embodiment, the main passage 6B, the auxiliary passage 6A and the intake air guide portion 409 can be formed together with the cylinder head 43, for example, by casting, or they can be formed by machining after the cylinder head 43 has been formed. (Comparison of intake airflows) Petition 870250086057, dated 09 / 23 / 2025, pages 137 / 154 26 / 33

[098] FIG. 9 is a diagram that schematically illustrates a comparison between intake airflow according to a comparative example and intake airflow through the intake structure of the embodiment, where ST91 is a diagram that illustrates intake airflow f in the comparative example, and ST92 is a diagram that illustrates intake airflow f through the intake structure of the internal combustion engine 4 in the present embodiment.

[099] In ST91, instead of the flat surface 416 of the main passage 6B, a 90° curvature portion having an arc shape of a predetermined curvature is provided in the fusion portion 420. The 90° curvature portion has an arc shape curved downwards from the opening end of the auxiliary passage 6A towards the combustion chamber 32 and having a predetermined curvature. In the intake structure illustrated in ST91, the intake airflow f emitted (provided) from the auxiliary passage 6A is separated from the 90° curvature portion and divided into an intake airflow f1 flowing towards the combustion chamber 32 and an intake airflow f2 flowing upwards towards the intake valve 73. Of the provided intake airflow, the intake airflow f1 flowing towards the combustion chamber 32 is used for combustion, and the combustion efficiency may be reduced.

[100] ST92 is a diagram that schematically illustrates the flow of intake airflow f through the intake structure of the internal combustion engine 4 in the present embodiment. As illustrated in ST92, the intake airflow f emitted (provided) from the auxiliary passage 6A flows on the top surface of the intake air guide portion 409 and is provided to the combustion chamber 32 in a state where a substantially linearly directed flow is maintained along the direction of the passage. In the structure of Petition 870250086057, dated 09 / 23 / 2025, pp. 138 / 154 27 / 33 intake (ST92) of internal combustion engine 4 according to the embodiment, as the flat surface 416 is formed in the main passage 6B, the opening end 506 of the auxiliary passage 6A can be arranged close to the side of the combustion chamber 32. According to the intake structure (ST92) of internal combustion engine 4 according to the embodiment, compared with the comparative example (ST91), the intake airflow f can be provided to the combustion chamber 32 in a state where the substantially linearly directed flow of the intake airflow f is maintained. That is, according to the intake structure (ST92) of internal combustion engine 4 according to the embodiment, the intake airflow f to obtain a more preferable combustion in the combustion chamber 32 can be provided to the combustion chamber 32.

[101] According to the intake structure of the internal combustion engine 4 of the present embodiment described above, in order to obtain combustion more preferentially in the combustion chamber 32, a longitudinal rotation vortex (rotation vortex in a plane along the axis of cylinder C) of the air-fuel mixture, i.e., a tumbling flow T, can be given in the combustion chamber 32. According to the disclosed technology, it is possible to provide an intake structure of an internal combustion engine capable of enhancing the formation of an airflow vortex in a cylinder and improving combustion efficiency. <Resumo das Modalidades> (Item 1)

[102] According to one aspect of the disclosed technology, an intake structure of an internal combustion engine (4) is provided in which a main passage (6B) and an auxiliary passage (6A) are formed by a partition portion (65) that partitions an intake passage (6) Petition 870250086057, dated 09 / 23 / 2025, pp. 139 / 154 28 / 33 vertically along a passage direction, and the intake air is guided to the auxiliary passage (6A) or to the main passage (6B) and the auxiliary passage (6A) according to an operating state of the internal combustion engine (4), characterized in that on a downstream side of the auxiliary passage (6A), an opening (Wa) of an approach section (410) formed in a substantially linear shape communicates with a combustion chamber (32) via the main passage (6B), in a top view of the combustion chamber (32), the opening (Wa) is formed based on a positional relationship in which a centerline (501) of the opening (Wa) is eccentric by a defined amount of deviation (503) in a direction that intersects the passage direction relative to a centerline (502) of an external width (WA) of the auxiliary passage (6A), in a side view of the combustion chamber (32) in a state where an intake valve (73) is open,The approach section (410) is formed based on a positional relationship in which an axis (419) of the auxiliary passage (6A) in the approach section (410) is inclined by a relative angle (Θ1) defined in relation to a stem portion (73c) of the intake valve (73), and in side view of the combustion chamber (32) in the state where the intake valve (73) is open, a substantially columnar virtual region in which a cross-sectional shape of the opening (Wa) of the auxiliary passage (6A) is extended in a direction that extends towards the interior of the combustion chamber (32) is formed so as not to be in contact with a valve seat edge (77) of the intake valve (73).

[103] According to the internal combustion engine intake structure of Item 1, it is possible to reduce the inhibition of intake airflow of Petition 870250086057, dated 09 / 23 / 2025, pages 140 / 154 29 / 33 opening end 506 of auxiliary passage 6A towards the inside of the cylinder, and it is possible to enhance the formation of the airflow vortex in the cylinder to improve combustion efficiency. (Item 2)

[104] Internal combustion engine intake structure, according to disclosed technology, characterized in that the region is formed so as not to be in contact with the stem portion (73c) of the intake valve (73) in the top view, and not to be in contact with an umbrella portion (73a) of the intake valve (73) in the side view.

[105] According to the internal combustion engine intake structure of Item 2, the intake airflow from the opening end 506 of the auxiliary passage 6A towards the interior of the cylinder can be prevented from being inhibited by contact with the valve seat edge 77, and combustion efficiency can be improved. As a result, it is possible to enhance the vortex formation of the airflow in the cylinder to improve combustion efficiency. (Item 3)

[106] The intake structure of the internal combustion engine, according to the disclosed technology, is characterized by a fusion portion (420) being additionally provided in which the intake air (407) flowing from the main passage (6B) to the combustion chamber (32) and the intake air (408) flowing from the auxiliary passage (6A) to the combustion chamber (32) merge, and a substantially linear flat surface (416) is provided on a surface of the main passage (6B) on the side of the auxiliary passage (6A) in the fusion portion (420).

[107] According to the internal combustion engine intake structure of Item 3, once the flat surface 416 is provided, the position of Petition 870250086057, dated 09 / 23 / 2025, pages 141 / 154 The opening end 506 of the auxiliary passage 6A can be brought closer to the fusion portion 420 compared to the structure (ST91) in which the curvature portion 900 having the arc shape of the predetermined curvature is provided. Therefore, the insertion angle (relative angle θ1: FIG. 1) of the auxiliary passage 6A towards the fusion portion 420 and the combustion chamber 32 can be easily adjusted, and the directivity of the intake airflow f can be further improved. As a result, it is possible to enhance the vortex formation of the airflow in the cylinder to improve combustion efficiency. (Item 4)

[108] The intake structure of the internal combustion engine, according to the disclosed technology, is characterized by the fact that the flat surface (416) is formed with an opening to guide an intake airflow (f) from the auxiliary passage side (6A) to the fusion portion (420).

[109] According to the internal combustion engine intake structure of Item 4, the position of the opening end 506 of the auxiliary passage 6A can be approximated to the fusion portion 420, and the intake airflow f can be provided to the fusion portion 420 through the opening formed in the flat surface 416. As a result, it is possible to enhance the formation of the airflow vortex in the cylinder to improve combustion efficiency. (Item 5)

[110] The intake structure of the internal combustion engine according to the disclosed technology is characterized by the fact that the flat surface (416) is formed substantially parallel to the stem portion (73c) of the intake valve (73).

[111] According to the internal combustion engine intake structure of Item 5, the position of the opening end 506 of the passage Petition 870250086057, dated 09 / 23 / 2025, pages 142 / 154 Auxiliary passage 6A (31 / 33) can be brought closer to the fusion portion 420. Therefore, the insertion angle (relative angle θ1: FIG. 1) of auxiliary passage 6A towards the fusion portion 420 and the combustion chamber 32 can be easily adjusted, and its directivity can be further improved. As a result, it is possible to enhance the formation of the airflow vortex in the cylinder to improve combustion efficiency. (Item 6)

[112] The intake structure of the internal combustion engine, according to the disclosed technology, is characterized in that the auxiliary passage (6A) is provided with a substantially linear intake air guide portion (409) that guides the intake air flow (f) from an opening end (506) of the opening (Wa) towards the combustion chamber (32).

[113] According to the internal combustion engine intake structure of Item 6, the intake airflow f emitted from the opening Wa flows through the linearly formed approach section 410 to become a substantially linearly directed flow. Additionally, by forming the intake air guide portion 409, the intake airflow f emitted from the opening Wa can be provided to the combustion chamber 32 as a flow in which the substantially linear orientation is maintained. As a result, it is possible to enhance the vortex formation of the airflow in the cylinder to improve combustion efficiency. (Item 7)

[114] The intake structure of the internal combustion engine, according to the disclosed technology, is characterized by the fact that the auxiliary passage (6A) is formed with an opening (Wa), as a cross-sectional shape, having a substantially elliptical shape or an opening (Wa) having a substantially rectangular shape extending horizontally in a Petition 870250086057, dated 09 / 23 / 2025, pages 143 / 154 32 / 33 direction of the amount of deviation (503), and a recess (801, 802) having a curvature corresponding to an opening shape (Wa) is formed on a top surface (409a) of the intake air guide portion (409) in order to connect an inner surface of the opening (Wa) and the top surface (409a) of the intake air guide portion (409) without a step.

[115] According to the internal combustion engine intake structure of Item 7, the intake airflow f having a spatial distribution corresponding to the cross-sectional shape of the opening Wa flows through the recess (inner surface of the recess) having a curvature according to the shape of the opening (Wa), so that the substantially linear flow direction is maintained along the passage direction, and the intake airflow distribution in the intersection direction can be suppressed. As a result, the intake airflow can be provided to the combustion chamber so as not to come into contact with the intake valve stem portion in the open state. It is possible to reduce the inhibition of intake airflow from the opening end of the auxiliary passage towards the interior of the cylinder, and it is possible to enhance the vortex formation of the airflow in the cylinder to improve combustion efficiency.

[116] The present invention is not limited to the above embodiments, and various modifications and alterations may be made within the scope of the essence of the present invention. LIST OF REFERENCE SIGNS Internal combustion engine Admission passage 6A Auxiliary passage 6B Main passage Petition 870250086057, dated 09 / 23 / 2025, pages 144 / 154 33 / 33 Partition portion Combustion chamber Intake valve 73a Umbrella Portion 73c Stem portion Valve seat rim 410 Approach Section 506 Opening end 409 Intake air guide portion 420 Melting Portion Petition 870250086057, dated 09 / 23 / 2025, pages 145 / 154

Claims

1 / 3 CLAIMS 1. Intake structure of an internal combustion engine (4) in which a main passage (6B) and an auxiliary passage (6A) are formed by a partition portion (65) that partitions an intake passage (6) vertically along a passage direction, and the intake air is guided to the auxiliary passage (6A) or to the main passage (6B) and the auxiliary passage (6A) according to an operating state of the internal combustion engine (4), characterized in that on a downstream side of the auxiliary passage (6A), an opening (Wa) of an approach section (410) formed in a substantially linear shape is formed to be bifurcated and communicates with a combustion chamber (32) via the main passage (6B), in top view of the combustion chamber (32),Each of the openings (Wa) formed to be bifurcated is formed based on a positional relationship in which a central line (501) of each of the openings (Wa) is eccentric by a defined amount of deviation (503) in a direction that intersects the direction of the passage with respect to a central line (502) of an external width (WA) of the auxiliary passage (6A), in a side view of the combustion chamber (32) in a state where an intake valve (73) is open, the approach section (410) is formed based on a positional relationship in which an axis (419) of the auxiliary passage (6A) in the approach section (410) is inclined by a relative angle (Θ1) defined with respect to a portion of the stem (73c) of the intake valve (73), in a side view of the combustion chamber (32) in a state where the intake valve (73) is open, a substantially columnar virtual region in which a section shape Petition 870250086057, dated 09 / 23 / 2025,pg. 146 / 154 2 / 3 transverse of each of the openings (Wa) of the auxiliary passage (6A) is extended in a direction that extends into the interior of the combustion chamber (32) is formed so as not to be in contact with a valve seat edge (77) of the intake valve (73), and in a bottom view of the combustion chamber (32) in a state where the intake valve (73) is open, one cross-sectional shaped region and the other cross-sectional shaped region of the openings (Wa) formed to be bifurcated are formed in a left-right direction with the stem portion (73c) interposed between them so as not to be in contact with the stem portion (73c)., 2. Internal combustion engine intake structure according to claim 1, characterized in that the region is formed so as not to be in contact with the stem portion (73c) of the intake valve (73) in the top view, and not to be in contact with an umbrella portion (73a) of the intake valve (73) in the side view.

3. Internal combustion engine intake structure according to claim 1, characterized in that a fusion portion (420) is additionally provided in which the intake air (407) flowing from the main passage (6B) to the combustion chamber (32) and the intake air (408) flowing from the auxiliary passage (6A) to the combustion chamber (32) fuse, and a substantially linear flat surface (416) is provided on a surface of the main passage (6B) on the side of the auxiliary passage (6A) in the fusion portion (420).

4. Internal combustion engine intake structure according to claim 3, characterized in that the flat surface (416) is formed with an opening to guide an intake airflow (f) from the auxiliary passage side (6A) to the fusion portion (420). Petition 870250086057, dated 23 / 09 / 2025, pp. 147 / 154 3 / 3 5. Internal combustion engine intake structure according to claim 3, characterized in that the flat surface (416) is formed substantially parallel to the stem portion (73c) of the intake valve (73).

6. Internal combustion engine intake structure, according to claim 4, characterized in that the auxiliary passage (6A) is provided with a substantially linear intake air guide portion (409) that guides the intake air flow (f) from an opening end (506) of each of the openings (Wa) towards the combustion chamber (32).

7. Internal combustion engine intake structure according to claim 6, characterized in that the auxiliary passage (6A) is formed with each opening (Wa) having a substantially elliptical cross-sectional shape or an opening (Wa) having a substantially rectangular shape extending horizontally in a direction of the amount of deviation (503), and a recess (801, 802) having a curvature corresponding to the shape of each of the openings (Wa) is formed on a top surface (409a) of the intake air guide portion (409) in order to connect an inner surface of each of the openings (Wa) and the top surface (409a) of the intake air guide portion (409) without a step. Petition 870250086057, dated 23 / 09 / 2025, pp. 148 / 154

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