Intake structure of an internal combustion engine

Abstract

The present disclosure is intended to provide a configuration with which it is possible to promote the generation of vortex flow in a combustion chamber over a wider operating range while minimizing any increase in the number of components of an internal combustion engine. An intake structure S for an internal combustion engine according to one embodiment comprises: a partition 62 that is provided in an intake passage 38 connected to a combustion chamber 20 so as to separate the intake passage into a first intake passage 64 and a second intake passage 66, and that has a communication part 102 that allows communication between the first intake passage 64 and the second intake passage 66; and a curved part 100 of the intake passage 38 provided upstream of the communication part 102. The curved part 100 is formed such that when a straight line IL parallel to the axis 40AX of an intake path 40a connected to the upstream side of the curved part 100 is determined, the straight line IL passes through the inside of the intake path 40a and extends from the second intake passage 66 to the first intake passage 64 via the communication part 102.

Description

[Technical Field]

[0001] The present invention relates to an intake structure for an internal combustion engine that is provided with a partition in an intake passage that communicates with a combustion chamber. [Background technology]

[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. In the field of internal combustion engines, various studies have been conducted on the possibility of improving fuel combustion efficiency and fuel efficiency by generating swirl, such as tumble vortex, in the combustion chamber by the intake air.

[0003] One example of a configuration aimed at generating a tumble vortex is disclosed in Patent Document 1. In the intake structure for an internal combustion engine disclosed in Patent Document 1, a tumble control valve (TCV, also called an intake distribution valve or intake control valve) is provided downstream of a throttle valve. The intake flow path downstream of the tumble control valve is divided by a partition plate into a main flow path and a tumble flow path configured so that the intake air that passes through it generates a tumble vortex in the combustion chamber, and the ratio of the intake air flowing through the main flow path and the tumble flow path is changed by the tumble control valve.

[0004] Furthermore, a technique described in Patent Document 2 is known as a method for strengthening tumble vortex flow without using a tumble control valve. In the intake structure of an internal combustion engine disclosed in Patent Document 2, the intake passage downstream of the throttle valve is separated by a partition into a tumble passage and a main passage, and the cross-sectional area of ​​the main passage is larger than that of the tumble passage. When the throttle valve, which is a butterfly valve, is gradually opened, the intake air passing through the throttle valve and flowing into the main passage flows back upstream into the tumble passage. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] WO2013 / 146703A1 publication [Patent Document 2] Japanese Patent Application Publication No. 2019-023459 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the intake structure of the internal combustion engine in Patent Document 1 requires a separate tumble control valve downstream of the throttle valve, and an actuator is required to control the operation of the tumble control valve, which increases the number of parts and poses cost issues.

[0007] Furthermore, the intake structure of the internal combustion engine disclosed in Patent Document 2 strengthens the tumble vortex flow by utilizing the backflow of intake air into the tumble flow passage when the throttle valve is slowly opened, i.e., during low-load operation. In other words, the configuration disclosed in Patent Document 2 has an issue with the ability to strengthen the tumble vortex flow when the throttle valve is more open, for example, during medium-load operation.

[0008] As described above, the technology of Patent Document 1, which is concerned with improving fuel efficiency, has a problem in that the number of parts in the intake structure of the internal combustion engine increases. Furthermore, the technology of Patent Document 2 has a problem in that the operating range in which the configuration for strengthening tumble vortexes can be applied is expanded. To solve the above problems, the present application aims to provide a configuration that can promote the generation of vortexes in the combustion chamber over a wider operating range while suppressing an increase in the number of parts in the internal combustion engine. This ultimately contributes to energy efficiency. [Means for solving the problem]

[0009] In order to achieve the above object, one aspect of the present invention is to a partition provided in an intake passage communicating with the combustion chamber so as to separate a first intake passage from a second intake passage, the partition having a communication portion that communicates the first intake passage with the second intake passage; a curved portion of the intake passage provided upstream of the communication portion; Equipped with The curved portion is formed so that when a straight line parallel to the axis of the intake passage connected to the upstream side of the curved portion is defined, the straight line passes through the intake passage and extends from the second intake passage to the first intake passage via the communication portion. An intake structure for an internal combustion engine characterized by to provide.

[0010] According to the above configuration, the curved portion is formed so that when a straight line parallel to the axis of the intake passage connected to the upstream side of the curved portion is determined, the straight line passes through the intake passage and extends from the second intake passage to the first intake passage via the communicating portion. Therefore, the communicating portion is located on an extension of the flow of intake air that flows from the intake passage through the curved portion into the second intake passage. This makes it possible to actively guide the intake air that flows into the second intake passage into the first intake passage via the communicating portion. Furthermore, this flow of intake air from the second intake passage into the first intake passage via the communicating portion can occur regardless of the amount of intake air flowing into the first or second intake passage. Therefore, according to the intake structure for an internal combustion engine of the above aspect, it is not necessary to provide, for example, a tumble control valve, so the increase in the number of parts of the internal combustion engine is suppressed, while the proportion of intake air flowing through the first intake passage can be relatively increased over a wider operating range, thereby more effectively promoting the generation of vortexes such as tumble vortices in the combustion chamber.

[0011] Preferably, when a straight line is defined in a cross section that is along the flow direction of the intake passage and intersects the inner circumferential surface of the curved portion, the straight line extends along an upstream passage wall surface that is connected to the curved inner surface of the inner circumferential surface of the curved portion and deviates from the curved inner surface, the straight line extends through the communicating portion. With this configuration, the intake air flowing into the second intake passage can be more reliably made to flow into the first intake passage through the communicating portion provided in the partition portion.

[0012] Preferably, the first intake passage is a tumble flow path of the intake passage, the second intake passage is a main flow path of the intake passage, and the first intake passage is located on the outer side of the curve of the curved portion than the second intake passage. With this configuration, more intake air can flow into the first intake passage, more effectively generating a tumble flow in the combustion chamber. Note that the center line of the intake passage preferably extends through the second intake passage.

[0013] Preferably, a passage portion of the second intake passage downstream of the curved portion and upstream of the communicating portion is shaped so that its length in a first direction connecting the first intake passage and the second intake passage is shorter and its length in a second direction perpendicular to the first direction is longer than when the cross-sectional shape of the intake passage at that passage portion is circular. With this configuration, the flow path of the intake air passing through the curved portion and flowing from the second intake passage into the first intake passage can be relatively short, and a stronger flow can be imparted to the flow in the first intake passage.

[0014] Preferably, a throttle valve is provided upstream of the curved portion, and the upstream end of the partition portion curves toward the throttle valve along the curved shape of the curved portion. With this configuration, the intake air that has passed through the opening of the throttle valve on the side of the first intake passage more easily flows into the first intake passage, making it possible to more reliably ensure the amount of intake air flowing through the first intake passage.

[0015] Preferably, a protrusion extending toward the second intake passage is formed at a downstream end of the communication portion of the partition. This configuration makes it easier to direct a portion of the intake air flowing through the second intake passage toward the first intake passage, and further prevents a portion of the intake air flowing through the first intake passage from being directed toward the second intake passage.

[0016] Preferably, the curved inner surface of the curved portion has a protrusion with a radius of curvature smaller than that of the curved inner surface. This configuration promotes separation of intake air at the curved inner surface of the curved portion and more actively promotes the flow of intake air from the second intake passage to the first intake passage through the communication portion, thereby making it possible to further increase the amount of intake air flowing from the second intake passage to the first intake passage, for example.

[0017] Preferably, downstream of the communication portion, the first intake passage is defined so that the cross-sectional area of ​​the downstream outlet of the first intake passage is smaller than the cross-sectional area of ​​the downstream end of the communication portion. This makes it possible to simultaneously take intake air from the second intake passage into the first intake passage at the communication portion and increase the flow velocity of the intake air from the first intake passage to the combustion chamber. [Effects of the Invention]

[0018] According to the above aspect of the present invention, since the above configuration is provided, it is possible to promote the generation of vortexes in the combustion chamber over a wider operating range while suppressing an increase in the number of parts in the internal combustion engine. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic diagram of an internal combustion engine according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a front view of a three-dimensional model of the internal combustion engine of FIG. 1, from a part of the intake passage to the exhaust port. [Figure 3] FIG. 3 is a plan view of a three-dimensional model of the downstream side of the intake passage of the internal combustion engine of FIG. [Figure 4] FIG. 4 is a front view of the three-dimensional model of FIG. [Figure 5] FIG. 5 is a bottom view of the three-dimensional model of FIG. [Figure 6] FIG. 6 is a rear view of the three-dimensional model of FIG. [Figure 7] FIG. 7 is a left side view of the three-dimensional model of FIG. [Figure 8]FIG. 8 is a right side view of the three-dimensional model of FIG. [Figure 9] FIG. 9 is a perspective view of the three-dimensional model of FIG. 3 from the left side. [Figure 10] FIG. 10 is a perspective view of the three-dimensional model of FIG. 3 from the right side. [Figure 11] FIG. 11 is a perspective view of the three-dimensional model shown in FIG. 6, and is a diagram schematically showing the sprayed fuel injected from the fuel injection valve. [Figure 12] FIG. 12 is a perspective view of the three-dimensional model shown in FIG. 3, which schematically shows the sprayed fuel injected from the fuel injection valve, similar to that shown in FIG. [Figure 13] FIG. 13 is a cross-sectional view of the three-dimensional model of FIG. 3 taken along the intake air flow direction, and schematically shows the sprayed fuel injected from the fuel injection valve, similar to that shown in FIG. [Figure 14A] 14A is a cross-sectional view of the three-dimensional model of FIG. 3 having atomized fuel injected from a fuel injection valve in the same manner as shown in FIG. 11, taken along the line SA-SA in FIG. [Figure 14B] 14B is a cross-sectional view of the three-dimensional model of FIG. 3 having sprayed fuel injected from the fuel injection valve in the same manner as shown in FIG. 11, taken along the line SB-SB in FIG. [Figure 14C] 14C is a cross-sectional view of the three-dimensional model of FIG. 3 having atomized fuel injected from the fuel injection valve in the same manner as shown in FIG. 11, taken along the line SC-SC in FIG. [Figure 15A] FIG. 15A is a perspective view of a portion of the three-dimensional model shown in FIG. 14A. [Figure 15B] FIG. 15B is a perspective view of a portion of the three-dimensional model shown in FIG. 14B. [Figure 15C] FIG. 15C is a perspective view of the portion of the three-dimensional model shown in FIG. 14C. [Figure 16] FIG. 16 is a perspective view of a three-dimensional model of the intake passage of the internal combustion engine of FIG. [Figure 17] FIG. 17 is a front view of the three-dimensional model of FIG. [Figure 18] FIG. 18 is a bottom view of the three-dimensional model of FIG. [Figure 19] FIG. 19 is a plan view of the three-dimensional model of FIG. [Figure 20] FIG. 20 is a cross-sectional view of the three-dimensional model of FIG. 19 taken along line XX-XX. [Figure 21] FIG. 21 is a cross-sectional view of the three-dimensional model of FIG. 19 taken along line XXI-XXI. [Figure 22] FIG. 22 is a schematic diagram of the cross-sectional view of FIG. [Figure 23] FIG. 23 is a front view of a three-dimensional model of an intake passage of an internal combustion engine according to the second embodiment. [Figure 24] FIG. 24 is a schematic diagram of the intake passage of FIG. [Figure 25] FIG. 25 is a front view showing a modified example of the intake passage of the internal combustion engine according to the second embodiment. [Figure 26] FIG. 26 is a perspective view of a three-dimensional model of an intake passage of an internal combustion engine according to the third embodiment. [Figure 27] FIG. 27 is a front view of the three-dimensional model of FIG. [Figure 28] FIG. 28 is a plan view of a portion of the three-dimensional model of FIG. [Figure 29] 29 is a cross-sectional view of the three-dimensional model of FIG. 26 taken along the line XXIX-XXIX in FIGS. 27 and 28. FIG. [Figure 30] FIG. 30 shows the results of a computer simulation. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The same components (or configurations) are denoted by the same reference numerals, and the names and functions of these components are also the same. Therefore, detailed description thereof will not be repeated.

[0021] A schematic configuration of an internal combustion engine 10 according to a first embodiment of the present invention is shown in Fig. 1. Fig. 1 is a cross-sectional view of the internal combustion engine 10 taken along an axis C (cylinder axis) of a cylinder bore 12b of a cylinder block 12 of the internal combustion engine 10. Note that the internal combustion engine 10 is a single-cylinder engine, but the internal combustion engine to which the present invention is applied is not limited to single-cylinder engines and may be a multi-cylinder engine.

[0022] A piston 15 reciprocates within a cylinder bore 12b of the cylinder block 12 and is connected to a crank pin of a crankshaft 17 in a crankcase portion 16 by a connecting rod 18. A combustion chamber 20 is defined between a top surface 15a of the piston 15, which is slidably fitted within the cylinder bore 12b of the cylinder block 12, and a combustion chamber ceiling surface 14a of the cylinder head 14, which faces the top surface 15a.

[0023] The internal combustion engine 10 employs a SOHC two-valve system, and a valve train 22 is provided in the cylinder head 14. A cylinder head cover 24 is placed over the cylinder head 14 to cover the valve train 22. To transmit power to the valve train 22 within the cylinder head cover 24, an endless cam chain (not shown) is installed between a camshaft 26 and the crankshaft 17, passing through the crankcase 16, the cylinder block 12, and a cam chain chamber (not shown) provided on one side of the cylinder head 14 in the crankshaft direction. The camshaft 26 rotates in synchronization with the crankshaft 17 at half the rotational speed. An ignition plug is inserted into the cylinder head 14 from the opposite side of the cam chain chamber (the other side in the crankshaft direction) toward the combustion chamber 20.

[0024] In the cylinder head 14, an intake port 32 and an exhaust port 34 are formed by extending, curving upward and downward, from an intake valve port 28 and an exhaust valve port 30 that open to the combustion chamber ceiling surface 14a. As described above, a two-valve system is employed, and a single intake port 32 and a single exhaust port 34 are defined and formed in the cylinder head 14.

[0025] The upstream end of the intake port 32 opens toward the top of the cylinder head 14 and connects to an inlet pipe 36 to form a continuous intake passage 38. A throttle body 40 is connected to the upstream side of the inlet pipe 36. The downstream end of the exhaust port 34 opens toward the bottom of the cylinder head 14 and is connected to an exhaust pipe 42. An exhaust purification device and a silencer may be provided downstream of the exhaust pipe 42.

[0026] A cylindrical intake valve guide 44 is fitted integrally to the curved outer wall portion 32a of the intake port 32 in the cylinder head 14. An intake valve 46 slidably supported by the intake valve guide 44 opens and closes the intake valve opening 28 of the intake port 32 that faces the combustion chamber 20.

[0027] In addition, an exhaust valve 50 slidably supported by an exhaust valve guide 48 integrally fitted to the curved outer wall portion 34a of the exhaust port 34 in the cylinder head 14 opens and closes the exhaust valve opening 30 of the exhaust port 34 facing the combustion chamber 20.

[0028] The intake valve 46 and the exhaust valve 50 have their head portions 46a, 50a biased upward by valve springs so as to close the intake valve port 28 and the exhaust valve port 30 facing the combustion chamber 20. The stem ends 46b, 50b of the intake valve 46 and the exhaust valve 50 are pushed down by the intake rocker arm 56 and the exhaust rocker arm 58, which swing against the intake cam and the exhaust cam of the camshaft 26, respectively, opening the intake valve 46 and the exhaust valve 50 at a predetermined timing, connecting the intake port 32 and the combustion chamber 20, and connecting the exhaust port 34 and the combustion chamber 20, thereby allowing intake and exhaust to occur at the predetermined timing.

[0029] An inlet pipe 36 is connected to the upstream end of the intake port 32 of the internal combustion engine 10 via an insulator 60 to form a continuous intake passage 38, and a throttle body 40 is connected to the upstream side of the inlet pipe 36. The throttle body 40 has an intake passage 40a with a substantially circular cross section that forms part of the intake passage 38 leading to the combustion chamber 20 of the internal combustion engine 10, and its upstream side is connected to an air cleaner device (not shown).

[0030] The throttle body 40 is provided with a throttle valve 40c that is rotatably supported within the throttle body 40 by a throttle valve shaft 40b that is perpendicular to the flow direction of intake air in the intake passage 40a, i.e., that intersects the central axis of the intake passage 40a at a right angle, and that variably controls the flow area of ​​the intake passage 40a to open and close the intake passage 40a. The throttle valve 40c is of a butterfly type and has a throttle valve shaft 40b and a disk-shaped valve element 40d that is fixed to the throttle valve shaft 40b and rotates integrally with it.

[0031] The throttle valve 40c can be rotated counterclockwise in Figure 1 in the valve opening direction by operation by the driver, etc., and a return spring (not shown) urges the valve body 40d clockwise in the valve closing direction so that it is positioned at the fully closed position where its edge abuts against the inner wall surface of the intake passage 40a.

[0032] In the internal combustion engine 10 described above, an intake structure S is configured to impart a tumble vortex, i.e., tumble flow, i.e., vertical rotation, to the fuel-air mixture in the combustion chamber 20, thereby improving fuel combustion efficiency and fuel economy. The intake structure S includes a partition 62 provided in the intake passage 38. Here, the partition 62 is provided in the intake passage 38 so as to divide the intake passage 38 into multiple sections in the direction of the cylinder axis C. That is, the intake passage 38, particularly the portion of the intake passage 38 downstream of the throttle valve 40c, is divided along the intake air flow direction by the partition 62 extending from the inlet pipe 36 to the intake port 32, and is partitioned into a tumble passage 64 configured to generate a tumble flow in the combustion chamber 20 after the intake air passes through, and a main passage 66 excluding the tumble passage 64. The tumble passage 64 corresponds to a first intake passage, and the main passage 66 corresponds to a second intake passage. The tumble passage 64 may also be called a sub-passage.

[0033] The partition 62, which extends like a plate in the intake air flow direction, is provided so as to substantially vertically divide the downstream side of the intake passage 38 into two, here extending substantially parallel to the axis extending in the flow direction. In this embodiment, the flow path cross-sectional area of ​​the tumble flow path 64 is smaller than the flow path cross-sectional area of ​​the main flow path 66. However, the partition 62 may be provided so that the flow path cross-sectional area of ​​the tumble flow path 64 is larger than the flow path cross-sectional area of ​​the main flow path 66, or the flow path cross-sectional area of ​​the tumble flow path 64 may be substantially the same.

[0034] The lower portion of the intake passage 38 separated by the partition 62 becomes the tumble passage 64, and the upper portion becomes the main passage 66, but in this specification they are not limited to being arranged up and down. In this specification, "up" and "down" with respect to the intake passage 38 etc. refer to the direction from the crankshaft 17 side to the cylinder head 14 or cylinder head cover 24 side in the direction of the cylinder axis C, and refer to the direction opposite to this "up" direction, that is, from the cylinder head 14 side to the crankshaft 17 side, and do not mean absolute "up" and "down" in space.

[0035] The internal combustion engine 10 is provided with a fuel injection valve 70. The fuel injection valve 70 is provided to inject fuel into the intake port 32. The fuel injection valve 70 is provided to face the main flow passage 66, and in this case, is provided in the inlet pipe 36. In this manner, the fuel injection valve 70 is provided to inject fuel from the main flow passage 66 side and supply fuel to the combustion chamber 20 via the intake port 32. As is clear from FIG. 1 , the fuel injection valve 70 is attached to an upper wall portion of a member that defines the intake passage 38. Note that the present disclosure does not limit the number of fuel injection valves to one, and may be, for example, two. For example, a second fuel injection valve may be provided to inject fuel into a portion of the intake passage 38 upstream of the partition portion 62.

[0036] The ECU (electronic control unit) 72 that controls the internal combustion engine 10 has a configuration as a so-called computer, and includes an intake control unit 74 and a fuel injection control unit 76. That is, the ECU 72 includes a processor (e.g., a CPU) and memory (e.g., a ROM and a RAM). The ECU 72 analyzes the operating state of the internal combustion engine 10 based on outputs from various sensors such as an engine rotation speed sensor and an engine load sensor, and controls the operation of the throttle valve 40c using the intake control unit 74. The ECU 72 also controls the operation of the fuel injection valve 70 using the fuel injection control unit 76 based on the analyzed operating state of the internal combustion engine 10. The ECU 72 stores programs and various data for these controls. Although the throttle valve 40c is electronically controlled here, this is not limited to electronic control, and the throttle valve 40c may be a valve that is mechanically controlled, for example, by a throttle cable.

[0037] 2 shows a three-dimensional model M of the internal combustion engine 10, extending from the intake passage 38 shown in FIG. 1 through the combustion chamber 20 to the exhaust port 34. The three-dimensional model M includes the intake passage 40a of the throttle body 40 to the exhaust port 34. This three-dimensional model M has a characteristic configuration of the intake structure S of the internal combustion engine 10. In addition to having a partition 62, the intake structure S of the internal combustion engine 10 is also configured to have a curved portion 100 and a communicating portion 102 provided in relation to the partition 62. Below, first, the configuration of the intake structure S other than the curved portion 100 and the communicating portion 102 will be mainly described, and then the curved portion 100 and the communicating portion 102 will be described.

[0038] 3 to 10 show a three-dimensional model M1 of the downstream side of the intake passage 38. The three-dimensional model M1 extends from the downstream end of the inlet pipe 36 to the intake port 32, and terminates downstream at the intake valve port 28. Since the three-dimensional model M1 is a model of the downstream end of the intake passage 38, the outer surface 80 of the three-dimensional model M1 has portions corresponding to the inner surface 36s of the inlet pipe 36, the inner surface 60s of the insulator 60, and the inner wall surface 14s of the cylinder head 14, which are components that define the downstream side of the intake passage 38. A portion of the outer surface 80 of the three-dimensional model M1 corresponds to the surface 62s of the partition portion 62, and a portion corresponds to the surface 90s of the offset portion 90, which will be described later. Therefore, to facilitate understanding, the portions of the three-dimensional model M1 that correspond to the inner surface 36s of the inlet pipe 36, the inner surface 60s of the insulator 60, the inner wall surface 14s of the cylinder head 14, the surface 62s of the partition portion 62, and the surface 90s of the offset portion 90 are denoted by their corresponding reference numerals. The portion where the fuel injection valve 70 is attached and where its injection port faces the intake passage 38 (hereinafter referred to as the attachment portion) is denoted by the reference symbol "70s." Furthermore, the upper side in the direction of the cylinder axis C is denoted by the reference symbol "U," the lower side by the reference symbol "D," and the right side when viewed from upstream to downstream in the intake air flow direction is denoted by the reference symbol "R," and the left side by the reference symbol "L." This also applies to the drawings of the three-dimensional models M2 and M4 described later.

[0039] 1 and 3 to 10, the partition 62 has a deviation portion 90 on its downstream side that is narrower in the left-right direction (LR direction) intersecting the cylinder axis C, i.e., in the width direction, than other portions of the partition 62, such as the upstream end 62u. The deviation portion 90 is a narrow portion of the partition 62 in the width direction, which can be defined as the direction extending from one side of the valve axis of the intake valve 46 to the other when facing the intake valve 46 in the direction in which intake air flows from upstream to downstream through the intake passage 38, i.e., in the intake air flow direction. As shown in FIG. 5, in the tumble flow passage 64, the width W2 of a downstream end portion 64d is clearly narrower than the width W1 of an upstream end portion 62u' located on the upstream end 62u side of the partition 62, within the portion defined by the cylinder head 14. The partition portion 62 is provided and formed so as to define the tumble flow passage 64 in the intake passage 38, so that the offset portion 90 with respect to the portion of width W2 is relatively narrow.

[0040] Furthermore, the deviation portion 90 is biased in one direction in the left-right direction, i.e., the width direction. Here, the downstream end portion 64d of the tumble flow path 64 is defined so as to be biased toward the right R side. Therefore, the deviation portion 90 downstream of the partition portion 62, which at least partially defines the biased downstream end portion 64d of the tumble flow path 64, is biased toward the right R side here. Therefore, in FIG. 1, the cylinder axis C extends parallel to the paper surface and the width direction extends approximately perpendicular to the paper surface, so the deviation portion 90 extending downstream of the partition portion 62 does not appear and is therefore shown by a two-dot dashed line instead of a solid line.

[0041] 7 and 8, the mounting portion 70s of the fuel injection valve 70 is positioned on the left side L of the intake passage 38. In this way, the fuel injection valve 70 is provided at a position offset in a direction opposite to the offset direction of the offset portion 90. In this way, the fuel injection valve 70 is provided so as to be able to inject fuel in a direction different from, and more preferably in the opposite direction to, the offset direction of the offset portion 90. The fuel injection valve 70 is provided on the upper side, i.e., on the main flow path 66 side, and injects fuel from the main flow path 66 side.

[0042] 11, which is a perspective view of the three-dimensional model M1 shown in FIG. 6, schematically illustrates the sprayed fuel F injected from the fuel injection valve 70, which is located off to the left (L). Similarly to FIG. 11, a perspective view of the three-dimensional model M1 is shown in FIG. 12, which also schematically illustrates the sprayed fuel F injected from the fuel injection valve. Similarly to FIG. 11, a cross-sectional view of the three-dimensional model M taken along the intake air flow direction is shown in FIG. 13, which also schematically illustrates the sprayed fuel F injected from the fuel injection valve 70. From FIGS. 11 to 13, it can be seen that the fuel F injected from the fuel injection valve 70 is not blocked by the partition 62, but at least a portion of the fuel, particularly at least a majority of the fuel, and more preferably all of the fuel, first flows through the main flow passage 66, then flows to the confluence of the main flow passage 66 and the tumble flow passage 64, and then directly reaches the intake valve port 28 and is introduced into the combustion chamber 20. The arrangement of the fuel injection valve 70 and the shape of the partition portion 62 including the offset portion 90 are designed to enable such fuel injection. In particular, the partition main body portion 92 of the partition portion 62 terminates on its downstream side to enable the main flow path 66 and the tumble flow path 64 to merge, and the partition main body portion 92 and the offset portion 90 of the partition portion 62 are designed so that the fuel F injected from the fuel injection valve 70 reaches the intake valve port 28 along a surface 90s of the offset portion 90, preferably without touching the offset portion 90 (see, for example, FIG. 12 ).

[0043] Here, cross-sectional views of the three-dimensional model M1 including the injected fuel F of Fig. 11 are shown in Fig. 14A to Fig. 15C. Fig. 14A is a cross-sectional view of the three-dimensional model M1 taken along line SA-SA of Fig. 3, Fig. 14B is a cross-sectional view of the three-dimensional model M1 taken along line SB-SB of Fig. 3, and Fig. 14C is a cross-sectional view of the three-dimensional model M1 taken along line SC-SC of Fig. 3. Fig. 15A is a perspective view of a portion of the three-dimensional model M1 of Fig. 14A, Fig. 15B is a perspective view of a portion of the three-dimensional model M1 of Fig. 14B, and Fig. 15C is a perspective view of a portion of the three-dimensional model M1 of Fig. 14C.

[0044] 14A and 15A, the tumble flow path 64 and the main flow path 66 are completely separated. At the position of line SA-SA in Fig. 3, the partition portion 62 extends to the inner surface 36s of the inlet pipe 36 at both ends in the width direction between the tumble flow path 64 and the main flow path 66, and a partition main body portion 92 connecting to the upstream side of the deviation portion 90 extends thereto. Note that in Figs. 14A and 15A, the surface 62s of the partition portion 62 and the surface 92s of the partition main body portion 92 therein are denoted by the same reference numerals.

[0045] 14B and 15B, the tumble flow passage 64 and the main flow passage 66 are partially connected. Also, in the cross sections of FIGS. 14B and 15B, the surface 62s of the partition 62 extends in the width direction and also in the up-down direction, and is biased to the right. From this, it can be seen that, at the position of line SB-SB in FIG. 3, the partition 62 transitions from the partition main body 92 to the offset portion 90, and the offset portion 90 extends from the right side of the inner wall surface 14s of the cylinder head 14 to the left in the intake port 32, without completely separating the tumble flow passage 64 and the main flow passage 66. In other words, the tumble flow passage 64 and the main flow passage 66 are partitioned so that the main flow passage 66 and the tumble flow passage 64 are connected in the region where the offset portion 90 extends in the intake air flow direction. In other words, the deviation portion 90 connected to the partition main body portion 92 extends downstream of the partition main body portion 92 of the partition portion 62 so as to extend a portion of the partition main body portion 92 in the flow direction downstream of the partition main body portion 92. Note that in Figures 14B and 15B, the portions corresponding to the surface 62s of the partition portion 62 and the surface 90s of the deviation portion 90 thereon are denoted by the same reference numerals, and this is also true in Figures 14C and 15C.

[0046] 14C and 15C, the deviation portion 90 protrudes less to the left from the inner wall surface 14s of the cylinder head 14 than at the cut portions of FIGS. 14B and 15B. Thus, the deviation portion 90 is formed so as to narrow more downstream in the intake air flow direction. This results in a greater degree of communication between the main flow passage 66 and the tumble flow passage 64 at the cut portions of FIGS. 14C and 15C than at the cut portions of FIGS. 14B and 15B. In other words, the degree of connection between the tumble flow passage 64 and the main flow passage 66 at the cut portions of FIGS. 14C and 15C is greater than the degree of connection between them at the cut portions of FIGS. 14B and 15B. More specifically, the tumble flow passage 64 and the main flow passage 66 are partitioned so that the main flow passage 66 extends downward to the side of the deviation portion 90 in the region where the deviation portion 90 extends in the intake air flow direction. This downward expansion of the main flow path 66 is performed in the direction opposite to the direction in which the deviation section 90 is biased, and in this case, it is performed on the left side L of the deviation section 90. Note that this downward expansion of the main flow path 66 and the resulting merging of the main flow path 66 and the tumble flow path 64 are more pronounced downstream of the deviation section 90.

[0047] 14A to 15C, the fuel injection valve 70, which is arranged to inject fuel F from the main flow path 66 toward the combustion chamber 20, is arranged to inject fuel in the direction opposite to the biased direction of the deviation portion 90. Therefore, the partition portion 62, and particularly the deviation portion 90, can be extended further downstream in the intake flow direction. The tumble flow path 64 is then defined and formed so as to be biased downstream of the biased direction of the deviation portion 90. Therefore, the deviation portion 90 of the partition portion 62, which is extended further downstream in the intake flow direction, can impart stronger directionality to the intake air from the tumble flow path 64.

[0048] Thus, the partition 62 is designed to completely separate the main flow path 66 from the tumble flow path 64 with the partition body 92 located upstream. The downstream portion of the partition 62 has a deviation portion 90, which connects the main flow path 66 and the tumble flow path 64 while characterizing the flow from the tumble flow path 64 further downstream. Furthermore, the fuel injection valve 70 is positioned offset from the direction of the deviation portion 90. Here, the fuel injection valve 70 is positioned on the opposite side in the width direction. This allows fuel to be injected in a direction different from the deviation portion 90, allowing fuel to be introduced into the combustion chamber 20 generally directly through the intake valve port 28. In other words, the supply of fuel to the combustion chamber can be ensured effectively. Therefore, the deviation portion 90, which is the downstream portion of the partition 62, can be extended further downstream. This allows for stronger directionality to be imparted to the flow from the tumble flow path 64. This directionality is directed between the intake valve port 28 and the head portion 46a of the intake valve 46 when the valve is open so as to form a stronger tumble flow in the combustion chamber 20, so that the intake air from the tumble flow passage 64 can form a tumble flow more suitably in the combustion chamber 20.

[0049] The tumble flow passage 64 and the main flow passage 66 are partitioned so that the tumble flow passage 64 communicates with the main flow passage 66 downstream of the downstream edge of the partition portion 62, i.e., the downstream edge 90d of the deviation portion 90, to form a single intake passage leading to the combustion chamber 20. This allows intake air from the tumble flow passage 64 to be introduced into the combustion chamber 20 together with intake air from the main flow passage 66, making it possible to supply fuel to the combustion chamber 20 and form a tumble flow with intake air from the single intake port 32, which is a single intake passage. This configuration also makes it possible to suppress an increase in the number of parts and is advantageous in terms of cost.

[0050] As described above, the intake structure S of the internal combustion engine 10 includes a curved portion 100 and a communicating portion 102 (FIGS. 1 and 2). The curved portion 100 is provided immediately downstream of the throttle valve 40c. The curved portion 100 is a part of the intake passage 38, and is a portion that is bent in a substantially V-shape. The communicating portion 102 is formed at a location of the partition portion 62 downstream of the curved portion 100.

[0051] The communicating portion 102 communicates the tumble flow passage 64 with the main flow passage 66 at the partition portion 62, which is provided in the intake passage 38 connected to the combustion chamber 20 so as to separate the tumble flow passage 64 from the main flow passage 66. In other words, because the partition portion 62 is flat, the communicating portion 102 may also be called a gap, a hole, an opening, or the like. The communicating portion 102 extends from one end to the other end of the partition portion 62 in a direction perpendicular to the intake air flow direction. In other words, the communicating portion 102 is an elongated hole that extends to the inner surface 36s of the inlet pipe 36 at both ends in the width direction. The communicating portion 102 divides the partition portion 62 into an upstream partition portion 62a located upstream of the communicating portion 102 and a downstream partition portion 62b located downstream of the communicating portion 102. In other words, the communication portion 102 is a gap between the upstream partition portion 62a and the downstream partition portion 62b. Note that the configuration described above with reference to Figures 3 to 15C relates to the downstream partition portion 62b.

[0052] 16 to 21 show a three-dimensional model M2 of the portion of the three-dimensional model M shown in FIG. 2 from the throttle valve 40c of the intake passage 38 to the partition portion 62. FIG. 16 is a perspective view of the three-dimensional model M2, FIG. 17 is a front view of the three-dimensional model M2, FIG. 18 is a bottom view of the three-dimensional model M2, FIG. 19 is a plan view of the three-dimensional model M2, FIG. 20 is a cross-sectional view of the three-dimensional model M2 of FIG. 19 taken along line XX-XX, and FIG. 21 is a cross-sectional view of the three-dimensional model M2 of FIG. 19 taken along line XXI-XXI. For ease of explanation, the insulator 60, the mounting portion 70s of the fuel injection valve 70, and the offset portion 90 are omitted from the three-dimensional model M2. The downstream end of the downstream-side partition portion 62b of the partition portion 62 is shown as terminating at the partition main body portion 92. However, this does not exclude the possibility of providing the offset portion 90 at the downstream end of the partition main body portion 92. 2 and 16 to 21, similarly to the three-dimensional model M1, for ease of understanding, the three-dimensional models M and M2 of the internal combustion engine 10 are assigned reference numerals to portions of the three-dimensional model M2 that correspond to, for example, the inner surface 36s of the inlet pipe 36, the inner wall surface 14s of the cylinder head 14, the inner wall surface 40s that defines the intake passage 40a of the throttle body 40, the surface 62s of the partition 62, the surface 62as of the upstream partition 62a, and the surface 62bs of the downstream partition 62b.

[0053] In the intake passage 38, the curved portion 100 is provided upstream of the communicating portion 102. The curved portion 100 is formed so that the communicating portion 102 is located on an extension of the flow of intake air that has flowed into the main passage 66. In other words, the intake passage that connects to the upstream side of the curved portion 100 is the intake passage 40a of the throttle body 40 in this case. Therefore, when a straight line IL (see FIG. 1) that is parallel to the axis 40AX of the intake passage 40a is defined, the curved portion 100 is formed so that the straight line IL passes through the intake passage 40a and extends from the main passage 66 to the tumble passage 64 via the communicating portion 102. 21 shows a cross section along the flow direction of the intake passage 38 and intersecting the inner circumferential surface 104 of the curved portion 100, particularly a cross section extending across the curved inner surface 106 and the curved outer surface 108 of the inner circumferential surface 104. When a straight line L1 is defined to extend along the upstream pipe inner wall surface connected to the curved inner surface 106 of the inner circumferential surface 104 of the curved portion 100 (here, the inner wall surface 40s that defines the intake passage 40a of the throttle body 40) and deviate from the curved inner surface 106, this straight line L1 extends through the communicating portion 102. This straight line L1 is an example of a straight line IL that is parallel to the axis 40AX of the intake passage 40a. The curved inner surface 106 of the inner circumferential surface 104 is the inner portion in the curved direction of the curved portion 100, and the curved outer surface 108 of the inner circumferential surface 104 is the outer portion in the curved direction of the curved portion 100. Therefore, the tumble flow path 64 is located on the outer side of the curve of the curved portion 100 than the main flow path 66 .

[0054] 21, which is also a cross section of the partition portion 62 cut in the vertical direction, the line L1 extends directly to the communicating portion 102. This means that the line L1, which extends so as to deviate from the curved inner surface 106, passes through the main flow path 66, passes through the communicating portion 102, and extends to the tumble flow path 64.

[0055] 1, 2, 17, and 21, the upstream end of the partition 62, i.e., the upstream partition 62a, curves toward the throttle valve 40c along the curved shape of the curved portion 100. It is preferable that this upstream partition 62a extends to a position closer to the throttle valve 40c, but this is not limited thereto and various designs are possible.

[0056] Furthermore, the inner curved surface 106 of the curved portion 100 has a protrusion 110 having a radius of curvature R2 (R1 > R2) smaller than the radius of curvature R1 of the inner curved surface 106. As particularly shown in FIG. 21, the protrusion 110 protrudes toward the intake passage 38 on the inner curved surface 106.

[0057] Also, on the downstream side of the communication portion 102, the tumble flow path 64 is partitioned such that the cross-sectional area Se of the downstream outlet portion 64e of the tumble flow path 64 is smaller than the cross-sectional area Si at the downstream end portion 64i of the communication portion 102, that is, the cross-sectional area Si at the upstream end of the downstream partition portion 62b (Se < Si). Note that the difference between the cross-sectional area Se and the cross-sectional area Si may be slight.

[0058] The operation and effect of the intake structure S of the internal combustion engine 10 having the above configuration will be described below. In the following description, the schematic diagram of FIG. 22 is used.

[0059] First, in the internal combustion engine 10, the partition portion 62 provided so as to separate the tumble flow path 64, which is the first intake passage, and the main flow path 66, which is the second intake passage, in the intake passage 38 connected to the combustion chamber 20 has a communication portion 102 that connects the tumble flow path 64 and the main flow path 66. When a straight line IL parallel to the axis 40AX of the intake passage 40a connected to the upstream side of the curved portion 100 is defined, the curved portion 100 is formed such that the straight line IL passes through the intake passage 40a and extends from the main flow path 66 to the tumble flow path 64 through the communication portion 102.

[0060] The schematic diagram of Figure 22 is a diagram that schematically illustrates the cross-sectional view of Figure 21, and, like Figures 16 to 21, the tumble valve 40c is opened to a small opening. The intake air that passes through the opening 40e on the curved outer surface 108 side of the curved portion 100 of the tumble valve 40c (see arrow A1 in Figure 22) flows toward the lower side of the upstream partition portion 62a and can enter the tumble flow path 64. On the other hand, the intake air that passes through the opening 40f on the curved inner surface 106 side of the curved portion 100 of the tumble valve 40c (see arrow A2 in Figure 22) flows toward the upper side of the upstream partition portion 62a and can enter the main flow path 66. As described above, the curved portion 100 is formed so that a straight line IL parallel to the axis 40AX of the intake passage 40a connected to the upstream side of the curved portion 100 passes through the intake passage 40a and extends from the main passage 66 to the tumble passage 64 via the communicating portion 102. In other words, the curved portion 100 of the intake passage 38, which is provided upstream of the communicating portion 102, is formed so that the communicating portion 102 is located on an extension of the flow of intake air that has flowed into the main passage 66. Therefore, the intake air that has passed through the opening 40f on the curved inner surface 106 side flows into the main passage 66 so as to separate at the curved inner surface 106 of the curved portion 100 and can directly reach the communicating portion 102. Therefore, the intake air that has flowed into the main passage 66 can be actively guided to the tumble passage 64 and can be merged in the tumble passage 64 with the intake air that has passed through the opening 40e on the curved outer surface 108 side. 21 and 22, the flow of intake air into the tumble flow passage 64 via the communication portion 102 can occur not only when the tumble valve 40c is opened to a small degree, but also when the tumble valve 40c is opened to a large degree. Therefore, according to the intake structure S of the internal combustion engine 10, it is possible to suppress an increase in the number of parts of the internal combustion engine because it is not necessary to provide a tumble control valve, for example, and it is possible to relatively increase the proportion of intake air flowing through the tumble flow passage 64 over a wider operating range, and therefore it is possible to more suitably promote the generation of vortices such as tumble vortices in the combustion chamber 20.

[0061] 21 (and 22), when a straight line L1 is defined so as to extend along the inner wall surface 40s of the throttle body 40 that defines the intake passage 40a, which is the upstream passage wall surface connected to the curved inner surface 106 of the inner circumferential surface 104 of the curved portion 100, and deviate from the curved inner surface 106, the straight line L1 extends through the communicating portion 102. Therefore, as shown in FIG. 22, at least a portion of the intake air that passes through the opening 40f of the tumble valve 40c on the curved inner surface 106 side of the curved portion 100 (arrow A2 in FIG. 22) can directly flow toward the communicating portion 102 due to its inertia. This allows the intake air flowing into the main flow path 66 to more reliably flow into the tumble flow path 64 through the communicating portion 102 provided in the partition portion 62.

[0062] The tumble flow passage 64 is located at the curved portion 100 on the outer side of the curve than the main flow passage 66. Therefore, by generating a flow of intake air from the main flow passage 66 to the tumble flow passage 64 via the communication portion 102, more intake air can be made to flow into the tumble flow passage 64, and a tumble flow can be more suitably generated in the combustion chamber 20.

[0063] 1 and 21, the intake air that has passed through the opening 40e on the tumble flow path 64 side of the throttle valve 40c is more likely to flow into the tumble flow path 64, making it possible to more reliably ensure the amount of intake air that flows through the tumble flow path 64.

[0064] Furthermore, the inner curved surface 106 of the curved portion 100 has a protrusion 110 having a radius of curvature smaller than the radius of curvature of the inner curved surface 106. Therefore, the intake air passing through the opening 40f on the inner curved surface 106 side of the curved portion 100 of the throttle valve 40c can be more effectively promoted to peel off at the inner curved surface 106 of the curved portion 100. Thus, the flow of the intake air flowing from the main flow path 66 to the tumble flow path 64 can be more actively promoted, and for example, the amount of the intake air flowing from the main flow path 66 to the tumble flow path 64 can be further increased.

[0065] Also, on the downstream side of the communication portion 102, the tumble flow path 64 is partitioned such that the cross-sectional area Se of the downstream outlet portion 64e of the tumble flow path 64 is smaller than the cross-sectional area Si at the downstream end portion 64i of the communication portion 102, that is, the cross-sectional area Si at the upstream end of the downstream partition portion 62b (Se < Si). In FIG. 22, the line corresponding to the cross-sectional area Se is marked with the symbol "Se", and the line corresponding to the cross-sectional area Si is marked with the symbol "Si". Thereby, it becomes possible to achieve both taking in the intake air from the main flow path 66 side into the tumble flow path 64 and increasing the flow velocity of the intake air from the tumble flow path 64 to the combustion chamber 20. The ratio between the cross-sectional area Se of the downstream outlet portion 64e of the tumble flow path 64 and the cross-sectional area Si at the downstream end portion 64i of the communication portion 102 can be variously set, but for example, it is preferably about 14: about 15.

[0066] In the intake structure S of the internal combustion engine 10, the bending angle θ (see FIG. 二十二条) of the curved portion 100 can be variously set. Here, the bending angle θ is a line L2 defined so as to extend in the intake air flow direction in the intake passage portion 38a where the communication portion 102 is located (here, this line L2 is the center line in the intake air flow direction), and a line L3 defined so as to extend in the intake air flow direction through the valve shaft 40b of the throttle body 40, that is, the intersection angle with the axis 40AX of the intake passage 40a. Here, it is about 25°, but it may be an angle larger than 25°, such as 30°, 40°, 45°, etc. For example, the bending angle θ can be an angle of 20° to 50°, preferably in the range of 25° to 45°, but can be set according to the characteristics or specifications of the internal combustion engine 10.

[0067] Next, a second embodiment will be described. The intake structure S1 for an internal combustion engine according to the second embodiment will be described with reference to FIGS. 23 and 24. FIG. 23 is a front view of a three-dimensional model M3 of an intake passage for an internal combustion engine according to the second embodiment, corresponding to FIG. 17 of the internal combustion engine 10 according to the first embodiment. FIG. 24 is a schematic diagram of the intake passage for an internal combustion engine according to the second embodiment, corresponding to FIG. 22 of the internal combustion engine 10 according to the first embodiment. This internal combustion engine has substantially the same configuration as the internal combustion engine 10, but differs in that the intake structure S1 does not include the protrusion 106 but includes a protrusion 112. However, this does not exclude the intake structure S1 for this internal combustion engine from also including the protrusion 106; the intake structure S1 for an internal combustion engine according to the second embodiment can also include the protrusion 106. The following description will mainly focus on the protrusion 112, which is the difference. Components corresponding to components already described will be designated by the same reference numerals, and redundant description will be omitted as much as possible.

[0068] The protrusion 112 is formed at the downstream end 102d of the communicating portion 102 of the partition portion 62 so as to extend toward the main flow path 66. In FIG. 23, the portion corresponding to the surface 112s of the protrusion 112 is denoted by the reference symbol "112s." Specifically, the protrusion 112 is formed as the upstream end 62bu of the downstream partition portion 62b (see FIG. 24). The protrusion 112 extends toward the main flow path 66 and upstream from the upstream end 62bu of the downstream partition portion 62b, and partially covers the communicating portion 102 from the main flow path 66 side. Note that the protrusion 112 is provided at the upstream end 62bu of the downstream partition portion 62 of the partition portion 62 so as to protrude therefrom, but may be discontinuous with the downstream partition portion 62b of the partition portion 62.

[0069] A protrusion 112 extending toward the main flow path 66 is formed at the downstream end 102d of the communication portion 102 of the partition portion 62, making it easier to direct a portion of the intake air flowing through the main flow path 66 toward the tumble flow path 64. Furthermore, by providing the protrusion 112, it becomes possible to more actively prevent a portion of the intake air flowing through the tumble flow path 64 from being directed toward the main flow path 66.

[0070] 25, the intake passage 38 may be further curved midway along the inlet pipe 36. This increases the degree of freedom in mounting on the vehicle.

[0071] Next, a third embodiment will be described. An intake structure S2 for an internal combustion engine according to the third embodiment will be described with reference to FIGS. 26 to 29. FIG. 26 is a perspective view of a three-dimensional model M4 of an intake passage for an internal combustion engine according to the third embodiment, FIG. 27 is a front view of the three-dimensional model M4, FIG. 28 is a plan view of the three-dimensional model M4, and FIG. 29 is a cross-sectional view of the three-dimensional model M4 taken along line XXIX-XXIX in FIGS. 27 and 28, which corresponds to FIG. 20 of the internal combustion engine 10 according to the first embodiment. The intake structure S2 for this internal combustion engine differs from the intake structure S for an internal combustion engine according to the first embodiment in that it does not include a protrusion 106 and in the cross-sectional shape of the intake passage 38. However, this does not exclude the intake structure S2 for an internal combustion engine from further including the protrusion 106; the intake structure S2 for an internal combustion engine may further include the protrusion 106. Furthermore, the intake structure S2 for an internal combustion engine according to the third embodiment, i.e., the three-dimensional model M4 of the intake passage thereof, can also be provided with the protrusion 112 that provides the above-described effects. The following mainly describes the differences, and the same reference numerals are used for components that correspond to components already described, and redundant explanations will be omitted as much as possible.

[0072] In the intake structure S2 for an internal combustion engine, a passage portion 66b in the main flow path 66 downstream of the curved portion 100 and upstream of the communicating portion 102 has a shape that is squashed vertically without changing the cross-sectional area, compared to a passage portion 66ba (see FIGS. 17 and 20) in the intake structure S for the internal combustion engine 10. That is, the passage portion 66b in the main flow path 66 downstream of the curved portion 100 and upstream of the communicating portion 102 is shaped so that its length in the up-down direction (UD direction in FIG. 27), which is a first direction connecting the tumble flow path 64 and the main flow path 66, is shorter and its length in the width direction (left-right direction, i.e., LR direction in FIG. 28), which is a second direction perpendicular to the first direction, is longer, compared to a case in which the cross-sectional shape of the intake passage 38 in the passage portion 66b is circular, that is, the passage portion 66ba in the internal combustion engine 10 of the first embodiment. In the three-dimensional model M4 of Fig. 27, dashed lines indicate the outlines of the intake passage 38, the upstream partition 62a, and the downstream partition 62b of the internal combustion engine 10 according to the first embodiment. Therefore, the widthwise length d2 (d2 / d1) relative to the vertical length d1 of the passage portion 66ba of the intake structure S of the internal combustion engine 10 according to the first embodiment shown in Fig. 20 is smaller than the widthwise length d4 (d4 / d3) relative to the vertical length d3 of the passage portion 66b of the intake structure S2 of the internal combustion engine.

[0073] Therefore, the length of the flow path of the intake air that passes through the curved portion 100 and flows from the main flow path 66 into the tumble flow path 64 via the communicating portion 102 (corresponding to the distance d5 in FIG. 27 ) can be made relatively shorter compared to that in the intake structure S of the internal combustion engine 10 of the first embodiment. Thus, the intake air can be guided from the main flow path 66 to the tumble flow path 64 via the communicating portion 102 over a shorter distance without reducing the strength of the flow, and it is possible to impart a stronger flow to the flow in the tumble flow path 64.

[0074] The above-mentioned features of the intake structure S2 of the internal combustion engine according to the third embodiment can be applied to both the intake structure S of the internal combustion engine according to the first embodiment and the intake structure S1 of the internal combustion engine according to the second embodiment, and can provide similar effects.

[0075] (Experimental example) FIG. 30 shows the results of a computer simulation of the intake structure S of the internal combustion engine 10, with the throttle valve 40c slightly open. As shown in FIG. 30, the intake air that passed through the opening 40e on the curved outer surface 108 side of the curved portion 100 of the tumble valve 40c flows downward toward the upstream partition 62a and into the tumble flow passage 64. On the other hand, the intake air that passed through the opening 40f on the curved inner surface 106 side of the curved portion 100 of the tumble valve 40c flows upward toward the upstream partition 62a, separates at the curved inner surface 106 of the curved portion 100, flows into the main flow passage 66, and then directly reaches the communication portion 102 and merges with the intake air in the tumble flow passage 64. Similar results were obtained when the throttle valve 40c was opened more widely.

[0076] Although the embodiments and their modifications according to the present invention have been described above, the present invention is not limited thereto. Various substitutions and modifications are possible without departing from the spirit and scope of the present invention as defined by the claims of this application. For example, the intake structure S for an internal combustion engine of the first embodiment, the intake structure S1 for an internal combustion engine of the second embodiment, and the intake structure S2 for an internal combustion engine of the third embodiment can be combined in whole or in part with each other as long as no technical contradiction arises.

[0077] In the above embodiment, the tumble flow channel 64 is located on the outer side of the curved portion 100, and the main flow channel 66 is located on the inner side of the curved portion 100, but the present invention does not exclude the possibility of this relationship being reversed. However, the tumble flow channel 64 is preferably located on the outer side of the curved portion 100 than the main flow channel 66. [Explanation of symbols]

[0078] 10...internal combustion engine, 12...cylinder block 14...cylinder head, 15...piston 20... combustion chamber, 28... intake valve port, 30... exhaust valve port 32...intake port, 34...exhaust port 38...intake passage, 40...throttle body 46...intake valve, 50...exhaust valve 62...partition portion, 62a...upstream side partition portion, 62b...downstream side partition portion 64...Tumble passage (first intake passage) 66...Main passage (second intake passage) 70...Fuel injection valve 100... curved portion, 102... communication portion M, M1, M2, M3, M4...3D model, S, S1, S2...intake structure

Claims

1. a partition (62) provided in an intake passage (38) communicating with a combustion chamber (20) so as to separate a first intake passage (64) from a second intake passage (66), the partition (62) having a communication portion (102) that communicates the first intake passage (64) with the second intake passage (66); a curved portion (100) of the intake passage (38) provided upstream of the communication portion (102); Equipped with The curved portion (100) is formed so that, when a straight line (IL) parallel to the axis (40AX) of the intake passage (40a) connected to the upstream side of the curved portion (100) is determined, the straight line (IL) passes through the intake passage (40a) and extends from the second intake passage (66) to the first intake passage (64) via the communication portion (102). An intake structure (S, S1, S2) for an internal combustion engine (10).

2. when a straight line (L1) is defined so as to extend along an upstream passage wall surface (40s) connected to a curved inner surface (106) of the inner peripheral surface (104) of the curved portion (100) in a cross section along the flow direction of the intake passage (38) and intersecting with the inner peripheral surface (104) of the curved portion (100) and deviate from the curved inner surface (106), the straight line (L1) extends through the communication portion (102); 2. The intake structure (S, S1, S2) of an internal combustion engine (10) according to claim 1.

3. the first intake passage (64) is a tumble flow path of the intake passage, and the second intake passage (66) is a main flow path of the intake passage; The first intake passage (64) is located on the curved portion (100) on the outer side of the curve of the second intake passage (66).

3. The intake structure (S, S1, S2) of an internal combustion engine (10) according to claim 1 or 2.

4. A passage portion (66b) of the second intake passage (66) downstream of the curved portion (100) and upstream of the communication portion (102) is shaped so that the length in a first direction connecting the first intake passage (64) and the second intake passage (866) is shorter and the length in a second direction perpendicular to the first direction is longer than when the cross-sectional shape of the intake passage (38) in the passage portion (66b) is circular.

3. The intake structure (S2) of an internal combustion engine (10) according to claim 1 or 2.

5. a throttle valve (40c) is provided upstream of the curved portion (100); an upstream end (62u) of the partition portion (62) curves toward the throttle valve (40c) along the curved shape of the curved portion (100); 3. The intake structure (S, S1, S2) of an internal combustion engine (10) according to claim 1 or 2.

6. a protrusion (112) extending toward the second intake passage (66) is formed at a downstream end (102d) of the communication portion (102) of the partition portion (62); 3. The intake structure (S1) of an internal combustion engine (10) according to claim 1 or 2.

7. The curved inner surface (106) of the curved portion (100) has a protrusion (110) having a radius of curvature smaller than the radius of curvature of the curved inner surface (106).

3. The intake structure (S) of an internal combustion engine (10) according to claim 2.

8. downstream of the communication portion (102), the first intake passage (64) is partitioned so that a cross-sectional area (Se) of a downstream outlet portion of the first intake passage (64) is smaller than a cross-sectional area (Si) of a downstream end portion of the communication portion (102).

3. The intake structure (S) of an internal combustion engine (10) according to claim 1 or 2.

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