JP7675926B2 - Intake structure of an internal combustion engine - Google Patents

Description

The present invention relates to an intake structure for an internal combustion engine in which an intake passage has a passage for tumble flow and other passages.

Various intake structures for internal combustion engines have been proposed in which the intake passage downstream of the throttle valve is divided into multiple passages by a partition. For example, in the intake structure for an internal combustion engine of Patent Document 1, a tumble valve is provided downstream of the throttle valve, and a partition plate portion, which is a partition portion, is provided downstream of the tumble valve from the inlet pipe to the intake port, and this partition plate portion divides the intake passage into upper and lower lower auxiliary passages and upper main passages. The lower auxiliary passage becomes the tumble passage, and the tumble valve essentially opens and closes the upper main passage. The tumble valve is a valve that can also be called an intake distribution valve or intake control valve, and may not be provided in an internal combustion engine provided with the partition portion (see Patent Document 2, for example).

Patent No. 6714764 Patent No. 6439070

As mentioned above, there is an internal combustion engine in which the intake passage is divided into a tumble passage for generating a tumble flow and an upper main passage which is the other passage. In this internal combustion engine, when the intake valve is opened, the intake from the tumble passage may be interfered with by the intake from the main passage, and the formation of the tumble flow by the intake from the tumble passage may be affected. On the other hand, due to the recent increase in environmental consideration, there is a strong demand for obtaining a strong tumble flow, i.e., a positive tumble flow, in order to further improve the combustibility in the combustion chamber. The object of the present invention is to provide a configuration that makes it possible to generate a stronger tumble flow in the combustion chamber in an internal combustion engine in which a passage for the tumble flow and other passages are provided so as to overlap in the intake passage in the direction of the cylinder axis.

In order to achieve the above object, one aspect of the present invention is to
An intake structure for an internal combustion engine, in which a first intake passage for generating a tumble flow in a combustion chamber and a second intake passage are provided so as to overlap each other in an intake passage communicating with the combustion chamber in a direction of a cylinder axis,
The present invention provides an intake structure for an internal combustion engine, characterized in that the first intake passage is curved in the direction of the cylinder axis so as to move away from the second intake passage, and is curved in a width direction perpendicular to the cylinder axis and perpendicular to the intake and exhaust direction.

According to the above configuration, the first intake passage for generating a tumble flow in the combustion chamber is curved away from the second intake passage in the direction of the cylinder axis, and is curved in the width direction perpendicular to the cylinder axis and perpendicular to the intake and exhaust direction. By forming the first intake passage away from the second intake passage in the direction of the cylinder axis, the intake air from the first intake passage can be smoothly introduced into the combustion chamber to form a tumble flow, and it may be possible to increase the flow rate of the intake air from the first intake passage. In addition, by forming the first intake passage so as to be curved in the width direction perpendicular to the cylinder axis and perpendicular to the intake and exhaust direction, the degree to which the intake air from the first intake passage is interfered with by the intake air from the second intake passage can be reduced. Therefore, according to the above configuration, a stronger tumble flow can be generated in the combustion chamber.

Preferably, when the direction from the crankshaft side to the cylinder head side in the direction of the cylinder axis is defined as the first direction, the second intake passage is provided on the first direction side of the first intake passage. According to this configuration, the second intake passage is provided on the first direction side of the first intake passage, and as described above, the first intake passage is separated from the second intake passage in the direction of the cylinder axis, so that the separation of the intake air from the first intake passage at the point where the first intake passage merges with the second intake passage can be actively promoted. Therefore, it is possible to increase the flow velocity of the intake air from the first intake passage.

Preferably, the junction of the first intake passage with the second intake passage is biased in the width direction with respect to the opening of the intake port. With this configuration, it is possible to give an angle to the flow of intake air from the first intake passage that flows into the combustion chamber when the intake valve opens during the intake stroke, according to the bias. Therefore, it is possible to further reduce the degree to which the intake air from the first intake passage interferes with the intake air from the second intake passage.

Preferably, when a virtual plane is defined that includes the cylinder axis and extends in the intake and exhaust direction, the confluence and the spark plug facing the combustion chamber are disposed on one side of the virtual plane. With this configuration, the intake air from the first intake passage can more quickly transport the spark from the spark plug to the center of the combustion chamber, thereby making it possible to further increase the flame propagation speed.

Preferably, in the width direction, the first intake passage is formed so as to be curved convexly toward the same side as the side to which the junction is biased. This further reduces the degree to which the intake air from the first intake passage interferes with the intake air from the second intake passage, thereby making it possible to more suitably form a tumble flow in the combustion chamber.

Preferably, the first intake passage is formed so as to be curved convexly toward the crankshaft in the direction of the cylinder axis. This actively encourages the intake air from the first intake passage to separate from the intake passage wall surface at the junction of the first intake passage with the second intake passage.

Preferably, the wall surface on the side of the second intake passage that defines the first intake passage is curved so as to be convex toward the crankshaft in the direction of the cylinder axis. With this configuration, the width of the first intake passage in the direction of the cylinder axis can be made roughly the same, and the intake air from the first intake passage can be directed to generate a greater tumble flow.

Preferably, the downstream portion of the first intake passage is formed so that the further downstream in the intake flow direction the portion approaches the cylinder head from the crankshaft side in the direction of the cylinder axis. This makes it possible to more actively encourage the separation of the intake air from the first intake passage from the intake passage wall surface at the junction of the first intake passage with the second intake passage.

Preferably, the downstream wall surface that defines the first intake passage side of the second intake passage has a curved shape that corresponds to the curved shape of the downstream portion of the first intake passage. With this configuration, the intake air from the second intake passage can jump toward the combustion chamber at the downstream wall surface and is directed to smoothly merge with the intake air from the first intake passage. This makes it possible to promote the generation of a stronger tumble flow.

According to the above aspect of the present invention, the above configuration makes it possible to generate a stronger tumble flow in the combustion chamber in an internal combustion engine in which a first intake passage for tumble flow and a second intake passage which is the other passage are arranged so as to overlap in the direction of the cylinder axis.

1 is a schematic configuration diagram of an internal combustion engine according to a reference example. 2 is a plan view of a three-dimensional model of a downstream side of an intake passage of the internal combustion engine of FIG. 1 . FIG. 3 is a front view of the three-dimensional model of FIG. 2 . FIG. 3 is a bottom view of the three-dimensional model of FIG. 2 . FIG. 3 is a rear view of the three-dimensional model of FIG. 2 . FIG. 3 is a right side view of the three-dimensional model of FIG. 2 . FIG. 3 is a left side view of the three-dimensional model of FIG. 2 . FIG. 3 is a left-side perspective view of the three-dimensional model of FIG. 2. FIG. 3 is a right-side perspective view of the three-dimensional model of FIG. 2. FIG. 6 is a perspective view of the three-dimensional model shown in FIG. 5, and is a diagram illustrating a schematic diagram of sprayed fuel injected from a fuel injection valve. FIG. 11 is a perspective view of the three-dimensional model shown in FIG. 2, which is a schematic diagram of the sprayed fuel injected from the fuel injection valve, similar to that shown in FIG. 10. FIG. 11 is a cross-sectional view taken along the intake air flow direction of the three-dimensional model of FIG. 2, and diagrammatically illustrates sprayed fuel injected from a fuel injection valve, similar to that shown in FIG. 10; 11 is a cross-sectional view of the three-dimensional model of FIG. 2 having sprayed fuel injected from a fuel injector similar to that shown in FIG. 10, taken along line SA-SA of FIG. 2. 11 is a cross-sectional view of the three-dimensional model of FIG. 2 having sprayed fuel injected from a fuel injector similar to that shown in FIG. 10, taken along the line SB-SB of FIG. 2. 11 is a cross-sectional view of the three-dimensional model of FIG. 2 having sprayed fuel injected from a fuel injector similar to that shown in FIG. 10, taken along the line SC-SC of FIG. 2. 14 is a perspective view of a portion of the three-dimensional model shown in FIG. 13, and corresponds to the three-dimensional model in FIG. 13A. FIG. 14 is a perspective view of a portion of the three-dimensional model shown in FIG. 13, which corresponds to the three-dimensional model in FIG. 13B. 14 is a perspective view of a portion of the three-dimensional model shown in FIG. 13, and corresponds to the three-dimensional model in FIG. 13C. 1 is a schematic configuration diagram of an internal combustion engine according to a first embodiment. 16 is a plan view of a three-dimensional model of the internal combustion engine shown in FIG. 15 , focusing on a portion from a combustion chamber to an intake system. FIG. 17 is a bottom view of the three-dimensional model of FIG. 16 . FIG. 17 is a side view of the three-dimensional model of FIG. 16. 19 is a side view corresponding to FIG. 18, which illustrates a schematic view of the flow of intake air from the tumble passage. FIG. 6 is a side view of a three-dimensional model incorporating the three-dimensional model of FIG. 5 relating to the internal combustion engine of FIG. 1 according to a reference example. FIG. 11 is a side view of a three-dimensional model having an intake structure for an internal combustion engine according to a second embodiment. FIG. 13 is a diagram showing the results of a computer simulation. FIG. 13 is a diagram showing the results of a computer simulation. FIG. 13 is a diagram showing the results of a computer simulation. FIG. 13 is a diagram showing the results of a computer simulation. FIG. 13 is a diagram showing the results of a computer simulation. 11 is a graph showing experimental results regarding the relationship between the offset amount of the tumble passage and the axial inclination of the tumble flow. 1 is a graph showing experimental results regarding the relationship between the swirl ratio and the axial inclination of the tumble flow. 1 is a graph showing experimental results regarding the relationship between the tumble ratio and the axial inclination of the tumble flow. FIG. 11 is an explanatory diagram for explaining an offset amount of a tumble passage.

Hereinafter, an embodiment of the present invention will be described with reference to the attached drawings. Identical parts (or configurations) are given the same reference numerals, and their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated.

(Reference example)
Before describing an embodiment of the present invention, an internal combustion engine 10 according to a reference example will be described. A schematic configuration of the internal combustion engine 10 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. The internal combustion engine 10 is a single-cylinder engine.

A piston 15 that reciprocates within a cylinder bore 12b of the cylinder block 12 is connected to a crank pin of a crankshaft 17 of a crankcase portion 16 by a connecting rod 18. A combustion chamber 20 is formed between a top surface 15a of the piston 15 that 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 that faces the top surface 15a.

The internal combustion engine 10 employs a two-valve system of the SOHC type, and the cylinder head 14 is provided with a valve train 22. 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 in the cylinder head cover 24, an endless cam chain (not shown) is installed between the camshaft 26 and the crankshaft 17 through a cam chain chamber (not shown) provided on one side of the crankshaft direction of the crankcase 16, the cylinder block 12, and the cylinder head 14, and the camshaft 26 rotates at half the speed of the crankshaft 17 in synchronization with the crankshaft 17. An ignition plug is inserted into the cylinder head 14 from the opposite side of the cam chain chamber (the other side of the crankshaft direction) toward the combustion chamber 20. In FIG. 1, the ignition plug facing the combustion chamber 20 is located on the front side of the paper, and the cam chain chamber is located on the back side of the paper.

In the cylinder head 14, the intake valve port 28 and the exhaust valve port 30, which open to the combustion chamber ceiling surface 14a, are formed with an intake port 32 and an exhaust port 34, which extend while curving upward and downward away from each other. As described above, a two-valve system is used, and a single intake port 32 and a single exhaust port 34 are defined in the cylinder head 14.

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, and 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 can be provided downstream of the exhaust pipe 42.

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 facing the combustion chamber 20.

In addition, an exhaust valve 50 slidably supported on 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.

The intake valve 46 and the exhaust valve 50 are biased upward by a valve spring so that their umbrella portions 46a, 50a close the intake valve port 28 and the exhaust valve port 30 that face 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, and the intake valve 46 and the exhaust valve 50 open at a predetermined timing, connecting the intake port 32 and the combustion chamber 20, and the exhaust port 34 and the combustion chamber 20, and allowing intake and exhaust to occur at a predetermined timing.

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 roughly 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).

The throttle body 40 is rotatably supported within the throttle body 40 by a throttle valve shaft 40b that is perpendicular to the flow direction of the intake air in the intake passage 40a, i.e., perpendicular to the central axis of the intake passage 40a, and is equipped with a throttle valve 40c that can variably control the flow area of the intake passage 40a and open and close the intake passage 40a. The throttle valve 40c is of the butterfly type and has a throttle valve shaft 40b and a disk-shaped valve body 40d that is fixed to the throttle valve shaft 40b and rotates integrally therewith.

Throttle valve 40c can be rotated in the opening direction clockwise in Fig. 1 by the driver's operation, etc., and a return spring (not shown) urges valve body 40d counterclockwise in the closing direction so that its edge abuts on the inner wall surface of intake passage 40a, thereby positioning it in the fully closed position. Throttle valve 40c is controlled so that intake passage 40a is opened to a predetermined small degree in low load operating conditions, and fully opened in high load operating conditions.

In the above internal combustion engine 10, an intake structure S0 is configured to provide a tumble vortex, i.e., tumble flow, i.e., vertical rotation, of the fuel-air mixture in the combustion chamber 20 in order to obtain more favorable combustion of the fuel, i.e., the mixture, in the combustion chamber 20. The intake structure S0 includes a partition 62 provided in the intake passage 38 so as to divide the intake passage 38 into a plurality of passages in the direction of the cylinder axis C. That is, the intake passage 38 is divided along the intake flow direction by the partition 62 continuing from the inlet pipe 36 to the intake port 32, and is divided into a tumble passage 64 configured so that the intake air passing through generates a tumble flow in the combustion chamber 20, and a main passage 66 excluding the tumble passage 64. The tumble passage 64 corresponds to the first intake passage, and the main passage 66 corresponds to the second intake passage. The tumble passage 64 may be called a sub-passage.

The partition 62, which extends like a plate in the intake flow direction, is provided so as to substantially vertically bisect the downstream side of the intake passage 38, here extending substantially parallel to an axis extending in the flow direction. In this reference example, the flow cross-sectional area of the tumble passage 64 is smaller than that of the main passage 66. However, the partition 62 may be provided so that the flow cross-sectional area of the tumble passage 64 is larger than that of the main passage 66, and it is also possible to make them substantially the same.

The lower part of the intake passage 38 separated by the partition 62 is the tumble passage 64, and the upper part is the main passage 66, but in this specification they are not limited to being arranged up and down. In this specification, "up" and "down" for 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 as the "up" or "up" direction, and the direction opposite to this "up" direction, that is, the direction from the cylinder head 14 side to the crankshaft 17 side as the "down" or "down" direction, and do not mean absolute "up" and "down" in space. This "up" or "up" direction corresponds to the first direction, and the "down" or "down" direction corresponds to the second direction.

An intake control valve may be provided upstream of the partition 62 and downstream of the throttle valve 40c. This intake control valve may be provided to variably control the flow area of the main passage 66, for example. The intake control valve may also be called a tumble valve, tumble control valve, or TCV, and is controlled to fully close the main passage 66 in a low load operating condition, and to fully open the main passage 66 in a high load operating condition. The throttle valve 40c is electronically controlled as described below, but is not limited to being electronically controlled and may be a valve that is mechanically controlled by a throttle cable, for example. This also applies when an intake control valve is provided.

The internal combustion engine 10 is provided with fuel injection valves 68 and 70. One fuel injection valve (hereinafter, the first fuel injection valve) 68 is provided upstream of the upstream end 62u of the partition portion 62 and is provided to inject fuel into a portion of the intake passage 38 upstream of the upstream end 62u. The other fuel injection valve (hereinafter, the second fuel injection valve) 70 is provided to inject fuel into the intake port 32. The second fuel injection valve 70 is provided to face the main passage 66, and is provided in the inlet pipe 36 here. In this manner, the second fuel injection valve 70 is provided to inject fuel from the main passage 66 side and supply fuel to the combustion chamber 20 through the intake port 32. As is clear from FIG. 1, the second fuel injection valve 70 is attached to the upper wall of the member that divides the intake passage 38. Note that the present disclosure does not limit the number of fuel injection valves to two, and may be, for example, one. In this case, for example, only the second fuel injector 70 may be provided.

The ECU (electronic control unit) 72 that controls the internal combustion engine 10 has a so-called computer configuration, and includes an intake control unit 74 and a fuel injection control unit 76. In other words, 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 the output from various sensors such as an engine 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 each of the fuel injection valves 68, 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.

2 to 9 show a three-dimensional model M of the downstream side of the intake passage 38. The three-dimensional model M includes the intake port 32 from the downstream end of the inlet pipe 36, and terminates at the intake valve port 28 on the downstream side. Since the three-dimensional model M is a model of the downstream end of the intake passage 38, the outer surface 80 of the three-dimensional model M has a portion 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 members that define the downstream side of the intake passage 38, and a portion corresponds to the surface 62s of the partition portion 62, and a portion corresponds to the surface 90s of the offset portion 90 described later. Therefore, to facilitate understanding, the parts of the three-dimensional model M 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 given their respective reference numerals. The portion where the second fuel injection valve 70 is attached and whose injection port faces the intake passage 38 (hereinafter referred to as the attachment portion) is denoted by the reference symbol "70s." Furthermore, the reference symbol "U" is used for the upper side in the direction of the cylinder axis C, the reference symbol "D" is used for the lower side, the reference symbol "R" is used for the right side when viewed from the upstream side to the downstream side in the intake flow direction, and the reference symbol "L" is used for the left side.

1 and 2 to 9, the partition 62 has a displacement portion 90 on its downstream side, the width of which is narrower in the left-right direction (L-R direction) intersecting the cylinder axis C, i.e., in the width direction, than the upstream end (upstream end) 62u of the partition 62. The displacement portion 90 is a narrow portion of the partition 62 in the width direction that can be defined as the direction extending from one side of the valve axis of the intake valve 46 to the other side when the intake air flows from the upstream side to the downstream side in the intake passage 38, i.e., in the intake flow direction, toward the intake valve 46. As shown in FIG. 4, in the tumble passage 64, the width W2 of the downstream end portion 64d in the width direction is clearly narrower than the width W1 of the upstream end portion located on the upstream end 62u side of the partition 62 among the portions partitioned and formed by the cylinder head 14. Since the partition portion 62 is provided and formed so as to partition the tumble passage 64 in the intake passage 38, the offset portion 90 with respect to the portion of width W2 is relatively narrow.

Furthermore, the offset 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 passage 64 is defined so as to be biased toward the right R side. Therefore, the offset portion 90 downstream of the partition portion 62, which at least partially defines the biased downstream end portion 64d of the tumble passage 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 offset 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. Therefore, the junction 65 of the main passage 66 and the tumble passage 64 is biased toward the right R side.

The mounting portion 70s of the second fuel injection valve 70 is positioned on the left L side of the intake passage 38, as is clear from Figures 6 and 7. In this way, the second 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 second fuel injection valve 70 is provided so as to be able to inject fuel in a direction different from the offset direction of the offset portion 90, more preferably in the opposite direction. The second fuel injection valve 70 is provided on the upper side, i.e., on the main passage 66 side, and injects fuel from the main passage 66 side.

Here, in FIG. 10, which is a perspective view of the three-dimensional model M shown in FIG. 5, the sprayed fuel F injected from the second fuel injection valve 70, which is provided at a position biased to the left L side, is shown typically. FIG. 11 is a perspective view of the three-dimensional model M, which shows the sprayed fuel F injected from the fuel injection valve as in FIG. 10. FIG. 12 is a cross-sectional view of the three-dimensional model M along the intake flow direction, which shows the sprayed fuel F injected from the fuel injection valve as in FIG. 10. From FIG. 10 to FIG. 12, it can be seen that the fuel F injected from the second fuel injection valve 70 is not blocked by the partition 62, and at least a part of it, particularly at least a majority of it, and more preferably all of it, first flows through the main passage 66, then flows to the junction 65 of the main passage 66 and the tumble passage 64, and then directly reaches the intake valve port 28 and is introduced into the combustion chamber 20. The arrangement of the second 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 body portion 92 of the partition portion 62 terminates on its downstream side to enable the main passage 66 and the tumble passage 64 to merge, and the partition body portion 92 and the offset portion 90 of the partition portion 62 are designed so that the fuel F injected from the second 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 FIG. 11, for example).

Here, cross-sectional views of the three-dimensional model M including the injected fuel F in Figure 10 are shown in Figures 13A to 14C. However, Figure 13A is a cross-sectional view of the three-dimensional model M at a position along the SA-SA line in Figure 2, Figure 13B is a cross-sectional view of the three-dimensional model M at a position along the SB-SB line in Figure 2, and Figure 13C is a cross-sectional view of the three-dimensional model M at a position along the SC-SC line in Figure 2. Figures 14A to 14C are perspective views of a portion of the three-dimensional model M in Figures 13A to 13C, and the three-dimensional model in Figure 14A corresponds to the three-dimensional model in Figure 13A, the three-dimensional model in Figure 14B corresponds to the three-dimensional model in Figure 13B, and the three-dimensional model in Figure 14C corresponds to the three-dimensional model in Figure 13C.

At the cut locations in Figures 13A and 14A, the tumble passage 64 and the main passage 66 are completely separated. At the position of line SA-SA in Figure 2, 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 passage 64 and the main passage 66, and the partition body portion 92 that is connected to the upstream side of the deviation portion 90 extends thereto. Note that in Figures 13A and 14A, the portions corresponding to the surface 62s of the partition portion 62 and the surface 92s of the partition body portion 92 therein are given the same reference numerals.

In the cutaway portions of Figures 13B and 14B, the tumble passage 64 and the main passage 66 are partially connected. Also, in the cutaway portions of Figures 13B and 14B, the surface 62s of the partition 62 extends in the width direction as well as in the vertical direction, and is biased to the right. From this, it can be seen that at the position of line SB-SB in Figure 2, the partition 62 transitions from the partition body portion 92 to the offset portion 90, and the offset portion 90 extends leftward from the right side of the inner wall surface 14s of the cylinder head 14 to the intake port 32, to the extent that it does not completely separate the tumble passage 64 and the main passage 66. In other words, the tumble passage 64 and the main passage 66 are partitioned so that the main passage 66 and the tumble passage 64 are connected in the region where the offset portion 90 extends in the intake flow direction. In other words, the deviation portion 90 connected to the partition main body portion 92 is formed to extend downstream of the partition main body portion 92 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 of the partition portion 62. Note that in Figures 13B and 14B, the portions corresponding to the surface 62s of the partition portion 62 and the surface 90s of the deviation portion 90 thereon are given the same reference numerals, and this is also true in Figures 13C and 14C.

13C and 14C, the amount of leftward protrusion of the deviation portion 90 from the inner wall surface 14 of the cylinder head 14 is reduced compared to the cut portions of FIGS. 13B and 14B. Thus, the deviation portion 90 is formed so as to become narrower toward the downstream side in the intake flow direction. As a result, the degree of communication between the main passage 66 and the tumble passage 64 is greater at the cut portions of FIGS. 13C and 14C than at the cut portions of FIGS. 13B and 14B. In other words, the amount of connection between the tumble passage 64 and the main passage 66 at the cut positions of FIGS. 13C and 14C is greater than the amount of connection between them at the cut positions of FIGS. 13B and 14B. More specifically, the tumble passage 64 and the main passage 66 are partitioned so that the main passage 66 extends downward to the side of the deviation portion 90 in the region where the deviation portion 90 extends in the intake flow direction. This downward expansion of the main passage 66 is performed in the direction opposite to the direction in which the deviation portion 90 is biased, and in this case, it is performed on the left L side of the deviation portion 90. Note that this downward expansion of the main passage 66 and the resulting merging of the main passage 66 and the tumble passage 64 are more noticeable downstream of the deviation portion 90.

Furthermore, as shown in Figures 13A to 14C, the second fuel injection valve 70, which is provided to inject fuel F from the main passage 66 toward the combustion chamber 20, is provided to inject fuel in the direction opposite to the biased direction of the offset portion 90. Therefore, the partition portion 62, and in particular the offset portion 90, can be extended further downstream in the intake flow direction. The tumble passage 64 is then partitioned and formed so as to be biased downstream in the biased direction of the offset portion 90. Therefore, the offset portion 90 of the partition portion 62 extended further downstream in the intake flow direction can impart stronger directionality to the intake air from the tumble passage 64.

In this way, the partition 62 is designed to completely separate the main passage 66 and the tumble passage 64 with the partition body 92 on the upstream side, and to have the offset portion 90 on the downstream side, so that the flow from the tumble passage 64 is characterized further downstream while realizing the connection between the main passage 66 and the tumble passage 64. In addition, the second fuel injection valve 70 is arranged in a biased position opposite to the bias of the offset portion 90, and is arranged on the opposite side in the width direction here, so that fuel can be injected in a direction different from the offset portion 90, and fuel can be introduced into the combustion chamber 20 almost directly through the intake valve port 28. In other words, the supply of fuel to the combustion chamber can be well ensured. Therefore, the offset portion 90, which is the downstream portion of the partition 62, can be extended further downstream. Therefore, a stronger directivity can be given to the flow from the tumble passage 64. This directionality is directed between the intake valve port 28 and the umbrella 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 passage 64 can more suitably form a tumble flow in the combustion chamber 20.

The tumble passage 64 and the main passage 66 are partitioned so that the tumble passage 64 communicates with the main passage 66 downstream of the downstream edge of the partition 62, i.e., the downstream edge 90d of the offset portion 90, to form a single intake passage leading to the combustion chamber 20. This allows intake air from the tumble passage 64 to be introduced into the combustion chamber 20 together with intake air from the main 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 also excellent in terms of cost.

First Embodiment
As described above, the intake structure S0 of the internal combustion engine 10 having the above configuration provides excellent functions and effects. The internal combustion engine 110 according to the first embodiment of the present invention, particularly the intake structure S thereof, which is provided with a configuration aimed at further strengthening the tumble flow in addition to the above configuration, will be described below. The intake structure S of the internal combustion engine 110 generally includes the above configuration of the intake structure S0 of the internal combustion engine 10, and has additional configurations, i.e., features. Therefore, the following description will focus mainly on the internal combustion engine 110 with respect to differences from the internal combustion engine 10, and the same reference numerals as those already used for components equivalent to or corresponding to those already described in the internal combustion engine 110 will be used to omit further overlapping description. Note that the internal combustion engine 110 is a single-cylinder engine, but the internal combustion engine to which the present invention is applied is not limited to a single-cylinder engine, and may be a multi-cylinder engine.

15, compared to internal combustion engine 10, internal combustion engine 110 does not include the first fuel injection valve 68, but includes a fuel injection valve 70a equivalent to the second fuel injection valve. Note that internal combustion engine 110 may include the first fuel injection valve 68, as with internal combustion engine 10. Internal combustion engine 110 also includes the aforementioned tumble valve 94c to open and close the main passage 66 partitioned by partition portion 62. A tumble valve body 94 is connected to the upstream end of inlet pipe 36 via insulator 95. This tumble valve body 94 has an intake passage 94a with a substantially circular cross section that constitutes part of intake passage 38, and the aforementioned throttle body 40 is connected to its upstream end.

The tumble valve body 94 is supported rotatably in the tumble valve body 94 by a valve shaft 94b that is perpendicular to the intake flow direction of the intake passage 94a, i.e., perpendicular to the central axis of the intake passage 94a, and is provided with a tumble valve 94c that can variably control the flow area of the intake passage 94a and open and close the upper area of the intake passage 94a in cooperation with the partition part 62. The operation of the tumble valve 94c is electronically controlled here according to the operating state of the internal combustion engine 110, but is not limited to this. For example, the tumble valve 94c is controlled so that the main passage 66 is fully closed in a low load operating state and the main passage 66 is fully opened in a high load operating state. The tumble valve 94c is of a butterfly type and has a valve shaft 94b and a substantially disk-shaped valve body 94d that is fixed to the valve shaft 94b and rotates integrally therewith. In this manner, the tumble valve 94c is configured to include a valve body 94d that is a single valve member that rotates integrally with the valve shaft 94b. However, the valve shaft 94b of the tumble valve 94c is parallel to the throttle valve shaft 40b.

The internal combustion engine 110 is characterized by the tumble passage 64. The tumble passage 64 will be described with reference to Figures 16 to 18.

16 to 18 show a three-dimensional model M1 from the top of the combustion chamber 20 of the internal combustion engine 110 to the downstream side of the intake system, for example, the intake port 32. FIG. 16 is a plan view or top view of the three-dimensional model M1, which corresponds to the plan view of the internal combustion engine 10 (FIG. 2), FIG. 17 is a bottom view of the three-dimensional model M1, which corresponds to the bottom view of the internal combustion engine 10 (FIG. 4), and FIG. 18 is a side view of the three-dimensional model M1, which corresponds to the rear view of the internal combustion engine 10 (FIG. 5). In the internal combustion engine 110, as in the internal combustion engine 10, the intake passage 38 connected to the combustion chamber 20 is divided by a partition 62 into a tumble passage 64, which is the first intake passage, and a main passage 66, which is the second intake passage, in the direction of the cylinder axis C. The main passage 66 is provided above the tumble passage 64 in the direction of the cylinder axis C. In top view (FIG. 16) seen from the direction of the cylinder axis C, the tumble passage 64 roughly overlaps with the main passage 66, and the junction 65 of the tumble passage 64 with the main passage 66 is biased with respect to the opening of the intake port 32, i.e., the intake valve port 28, and here, as already explained, is biased toward the right R side. In addition, in the internal combustion engine 110, the tumble passage 64 provided to generate a tumble flow in the combustion chamber 20 is curved so as to move away from the main passage 66 in the direction of the cylinder axis C, and is curved in the width direction perpendicular to the cylinder axis C and perpendicular to the intake and exhaust direction.

16 and 17, a virtual plane IS is drawn that includes the cylinder axis C and extends in the intake and exhaust direction. This virtual plane IS extends in the intake and exhaust direction, passes through the centers of the intake valve port 28 and the exhaust valve port 30, and includes the cylinder axis C. In FIG. 16 and FIG. 17, it is represented as a line (center line) Lx. By comparing with this center line Lx, it can be seen that the main passage 66 is formed so that the width in the left-right direction simply narrows from the upstream side to the downstream side, that is, toward the combustion chamber 20, as it moves downstream. On the other hand, in the three-dimensional model M1 of the internal combustion engine 110 of this embodiment, the right-side contour 64r of the tumble passage 64 is not parallel to the center line Lx, but curves convexly to the right outward. As the contour 64r moves from the upstream side to the downstream side in the intake flow direction, it first expands so as to protrude outward to the right, and then extends to approach the center line Lx side through the maximum right protrusion 64s. 16, the tumble passage 64 is formed so as to be curved convexly toward the same side as the side to which the junction 65 is biased. In this manner, in the internal combustion engine 110, the tumble passage 64 is formed so as to be curved in the width direction, i.e., the left-right direction, which is perpendicular to the cylinder axis C and perpendicular to the intake/exhaust direction, i.e., the line Lx.

Furthermore, as shown in FIG. 18, in the three-dimensional model M1, the tumble passage 64 is curved away from the main passage 66. The partition 62 is provided in the middle of the intake passage 38, where the tumble passage 64 branches off from the main passage 66 and joins the main passage 66 downstream. As the tumble passage 64 curves away from the main passage 66, the tumble passage 64 curves convexly on the opposite side to the main passage 66. More specifically, the tumble passage 64 is formed so as to curve convexly toward the crankshaft 17 in the direction of the cylinder axis C, that is, it curves convexly downward. In FIG. 18, a surface, that is, a line Ly, which is perpendicular to the cylinder axis C and tangent to the lower contour 64t of the tumble passage 64 is drawn. The contour 64t first protrudes downward from the upstream side to the downstream side in the intake flow direction, passes through the maximum downward protrusion 64u, and then extends upward. The contour 64t is in contact with the line Ly not at both ends but at the maximum protruding portion 64u. The vertical width of the tumble passage 64 does not change significantly from the upstream side to the downstream side in the intake flow direction. Therefore, in the internal combustion engine 110, in a side view (FIG. 18) seen from a direction perpendicular to the cylinder axis C, the tumble passage 64 is curved in the direction of the cylinder axis C, and more specifically, is curved in a substantially U-shape so as to be curved so as to be most convex downward in the direction of the cylinder axis C around the maximum downward protruding portion 64u. Therefore, in FIG. 18, the downstream portion 64L of the tumble passage 64 is formed so as to approach the cylinder head 24 side from the crankshaft 17 side in the direction of the cylinder axis C as it approaches the downstream side in the intake flow direction. In particular, the downstream portion 64L of the tumble passage 64 includes a portion of the tumble passage 64 downstream of the maximum protruding portion 64u. Since the vertical width of the tumble passage 64 does not change significantly from the upstream side to the downstream side in the intake air flow direction, the curved shape of this contour 64t is the same in the wall surface ds of the partition portion 62 that defines the tumble passage 64 in a side view seen from a direction perpendicular to the cylinder axis C, i.e., in Figure 18, the wall surface ds of the partition portion 62 that defines the tumble passage 64 is curved so as to convex toward the crankshaft 17 in the direction of the cylinder axis C.

As shown in Figure 16, that is, in a top view seen from the direction of the cylinder axis C, a confluence portion 65 and an ignition plug facing the combustion chamber 20 are arranged on one side of an imaginary plane IS that includes the cylinder axis C and extends in the intake and exhaust directions, in this case on the right R side. Figure 16 shows the ignition portion p of the spark plug.

The intake structure S of the internal combustion engine 110 having the above-mentioned configuration provides the following effects.

For example, in an operating state in which the tumble valve 94c is closed, the intake air from the tumble passage 64 is allowed to flow into the combustion chamber 20 during the intake stroke, thereby generating a tumble flow in the combustion chamber 20. However, between one intake stroke and the next, the intake air becomes stagnant in the main passage 66 through the junction 65. Figure 20 shows a three-dimensional model M2 incorporating the three-dimensional model M of the intake structure S0 of the internal combustion engine 10 of the reference example. In the three-dimensional model M2 of Figure 20, the throttle valve 40c and the tumble valve 94c downstream thereof are provided on the upstream side of the tumble passage 64 and the main passage 66, as already explained. When the throttle valve 40c is opened and the tumble valve 94c is fully closed, as shown in Figure 20, when the intake valve is opened during the intake stroke, the intake air that has passed around the throttle valve 40c flows into the tumble passage 64 and flows into the combustion chamber 20 (see arrow A1). At this time, the intake air remaining in the main passage 66 is also drawn into the combustion chamber 20, but flows in a manner that crosses the intake air from the tumble passage 64 (see arrow A2). Therefore, there is a possibility that the intake air flow from the main passage 66 will affect the intake air flow from the tumble passage 64. In contrast, the intake structure S1 of the internal combustion engine 110 configured as described above has the above-described configuration, and therefore can alleviate this effect.

In the intake structure S of the internal combustion engine 110, the intake passage 38 is divided by the partition 62, and the main passage 66 is formed above the tumble passage 64. That is, in the direction of the cylinder axis C, the intake passage 38 connected to the combustion chamber 20 is provided so that the tumble passage 64 for generating a tumble flow in the combustion chamber 20 and the main passage 66 overlap. The tumble passage 64 is formed so as to be curved in the width direction perpendicular to the cylinder axis C and perpendicular to the intake and exhaust direction. Therefore, for example, when the throttle valve 40c is opened and the tumble valve 94c is closed (for example, during light load operation) and the intake valve 46 is opened, the intake from the tumble passage 64 flows into the combustion chamber 20 from the right side through the junction 65 with respect to the intake from the main passage 66. As a result, the intake from the tumble passage 64 is less interfered with by the intake from the main passage 66, making it possible to favorably form a tumble flow in the combustion chamber. Furthermore, the tumble passage 64 is curved away from the main passage 66 in the direction of the cylinder axis C. Therefore, the intake air from the tumble passage 64 can smoothly flow into the combustion chamber 20 to form a tumble flow. Therefore, a stronger tumble flow can be generated in the combustion chamber.

In particular, in the intake structure S, the junction 65 is biased relative to the opening 28 of the intake port 32 in the top view of Figure 16. This makes it possible to give the flow of intake air that flows into the combustion chamber when the intake valve 46 opens during the intake stroke an angle that corresponds to the bias. Furthermore, the tumble passage 64 is formed so as to be curved convexly on the same side as the junction 65 is biased. This further reduces the degree to which the intake air from the tumble passage 64 interferes with the intake air from the main passage 66, making it possible to favorably form a tumble flow in the combustion chamber.

Furthermore, in FIG. 18, the tumble passage 64 is formed so as to be curved convexly toward the crankshaft 17 in the direction of the cylinder axis C. Therefore, it is possible to actively encourage the intake air from the tumble passage 64 to separate from the wall portion that forms the tumble passage 64 at the junction 65, particularly the wall portion 64w that defines the lower contour 64t of the tumble passage 64. The flow of intake air from the tumble passage 64 at this time is shown by arrow A3 in FIG. 19. This makes it possible to increase the flow rate of the intake air from the tumble passage 64 and generate a stronger tumble flow. And since the tumble passage 64 is formed so as to be curved convexly toward the crankshaft 17 in the direction of the cylinder axis C, the position of the junction 65 is located above the portion 46s where the umbrella portion 46a of the intake valve 46 hits, as shown in FIG. 19. By further adjusting the position of this junction 65 based on experiments, etc., the direction of the intake air from the tumble passage 64 can be optimized, and the generation of the tumble flow can be further promoted.

18, the downstream portion 64L of the tumble passage 64 is formed so that the further downstream in the intake flow direction it is, the closer it is to the cylinder head 24 in the direction of the cylinder axis C from the crankshaft 17. This makes it possible to more actively encourage the intake air from the tumble passage 64 to separate from the wall portion 64w that defines the lower contour 64t of the tumble passage 64.

18, the wall surface ds of the partition 62 that defines the tumble passage 64 is curved so as to be convex toward the crankshaft 17 in the direction of the cylinder axis C. Therefore, the width of the tumble passage in the vertical direction can be made roughly the same, and the intake air from the tumble passage 64 can be directed to generate a greater tumble flow. The wall surface ds is the wall surface on the side of the main passage 66 that defines the tumble passage 64.

16, on one side of an imaginary plane IS that includes the cylinder axis C and extends in the intake and exhaust direction, in this case on the right R side, a junction 65 and an ignition plug facing the combustion chamber 20 are arranged. Therefore, the intake air from the tumble passage 64 can transport the spark from the ignition plug more quickly to the center of the combustion chamber, thereby making it possible to further increase the flame propagation speed.

Second Embodiment
Next, a second embodiment will be described. In the following, differences between the first embodiment and the second embodiment, that is, features of the second embodiment will be mainly described. However, in the following, components equivalent to or corresponding to components already described will be denoted by the same reference numerals already used, and further duplicated description will be omitted.

The internal combustion engine of the second embodiment has the features of the internal combustion engine 110 of the first embodiment, such as the above-mentioned configuration of the tumble passage 64, but has an additional feature in the configuration of the main passage 66 compared to the internal combustion engine 110. This feature will be explained with reference to Figure 21. Figure 21 shows a three-dimensional model M3 having the intake structure S1 of the internal combustion engine of the second embodiment. In Figure 21, a throttle valve 40c and a tumble valve 94c (not shown) are provided upstream of the tumble passage 64 and the main passage 66, and the throttle valve 40c is fully open and the tumble valve 94c is fully closed.

In the intake structure S1 of the internal combustion engine according to the second embodiment, in FIG. 21, which is a side view seen from a direction perpendicular to the cylinder axis C, the downstream wall surface us of the partition portion 62 that defines the main passage 66 is a downstream wall surface that defines the tumble passage 64 side of the main passage 66, and has a curved shape corresponding to the curved shape of the downstream portion 64L of the tumble passage 64. This means that the curved shape of the downstream wall surface us is similar to or close to, preferably the same as, the curved shape of the downstream portion 64L. As previously explained based on FIG. 18, the downstream portion 64L of the tumble passage 64 is formed so that the further downstream it is in the intake flow direction, the closer it is to the cylinder head 24 side from the crankshaft 17 side in the direction of the cylinder axis C. In particular, the downstream wall surface us of the partition portion 62 that defines the main passage 66 has this curved shape that faces upward. By having the downstream wall surface us have this curved shape, the downstream wall surface us has a curved shape that is convex downward or similar.

By having the above-mentioned configuration of the downstream wall surface us of the partition 62 that defines the main passage 66, for example, when the tumble valve 94c is in an operating state where it is closed, the intake air in the main passage 66 (see arrow A4) can jump toward the combustion chamber 20 at the downstream wall surface us and is directed to smoothly merge with the intake air from the tumble passage 64 (see arrow A5). This makes it possible to promote the generation of a stronger tumble flow.

(Experimental Example)
A computer simulation was performed on the intake structure S of the internal combustion engine according to the first embodiment. As a comparative example, a computer simulation was also performed on the intake structure S0 of the internal combustion engine of the reference example. In the computer simulation, the throttle valve 40c was fully opened, and the tumble valve 94c was fully closed.

First, the results of the first computer simulation are shown in Figures 22 to 24. In the first computer simulation, in order to verify the effect of the curvature of the tumble passage 64 in the direction of the cylinder axis C, particularly the downward convex curvature (see Figures 18 and 19), the intake air flow from the intake port 32 side to the combustion chamber 20 when looking at the combustion chamber 20 side from a direction perpendicular to the cylinder axis C was calculated. In Figures 22 to 24, the intake air flow is shown so that the faster the flow speed, the darker the intake air flow. Note that 360° of the crank angle (deg) corresponds to top dead center.

In the comparative example of the intake structure S0 of the internal combustion engine 10, the intake air also flows strongly into the combustion chamber 20 from the intake side of the intake valve port 28 (see, for example, the circle R1 in FIG. 22). In contrast, in the embodiment of the intake structure S of the internal combustion engine 110, the intake air from the intake side of the intake valve port 28 into the combustion chamber 20 is suppressed, and the intake air from the exhaust side of the intake valve port 28 into the combustion chamber 20 is strengthened. As a result, in the embodiment, the counterclockwise forward tumble flow in FIG. 22 to FIG. 24 is made faster and stronger (see, for example, the circle R2 in FIG. 24). From these, it can be understood that the intake structure S of the internal combustion engine 110 can reduce the reverse tumble flow and strengthen the forward tumble flow, thereby improving the flow in the cylinder.

Next, the results of the second computer simulation are shown in Figures 25 and 26. In the second computer simulation, in order to verify the effect of the curvature of the tumble passage 64 in the width direction perpendicular to the cylinder axis C and perpendicular to the intake and exhaust direction, i.e., curvature to the right (see Figures 16 and 17), the flow of intake air from the intake port 32 side to the combustion chamber 20 when looking at the combustion chamber 20 side from above in the direction of the cylinder axis C was calculated. In Figures 25 and 26, the intake air flow is shown with a black line indicating a faster flow rate. Note that 360° of crank angle (deg) corresponds to top dead center.

Compared to the comparative example of the intake structure S0 of the internal combustion engine 10, in the embodiment of the intake structure S of the internal combustion engine 110, the fast intake air from the intake tumble passage 64 flows into the combustion chamber 20 at an angle from the right side. For example, as shown in FIG. 26, the inflow path of the black line in the comparative example is generally in the intake and exhaust direction (see direction mark R3), but the inflow path of the black line in the embodiment is inclined relative to the intake and exhaust direction, and is angled from the right side to the left side (see direction mark R4). From this, it can be understood that according to the intake structure S of the internal combustion engine 110, the flow into the cylinder during the intake stroke can be angled by the curvature of the width direction of the tumble passage 64, the rotation axis of the normal tumble flow can be inclined, and the intake air from the tumble passage 64 can be made to flow into the combustion chamber 20 from the right side. This is suitable for promoting flame propagation from the spark plug on the right side where the tumble passage 64 is biased.

From the above computer simulation results, the inclination (axial inclination) of the rotation axis of the normal tumble flow, the swirl ratio, and the tumble ratio were calculated. The results are shown in Figures 27 to 29. The "offset amount" on the horizontal axis corresponds to the distance RO between the imaginary plane IS, which includes the cylinder axis C and extends in the intake and exhaust direction, that is, the center line Lx, and the tangent line L1 of the right-side contour 64r of the tumble passage 64, which is parallel to the center line Lx, as shown in Figure 30. Therefore, an increase in the offset amount means that the degree of curvature of the tumble passage 64 to the right increases. In the model of Figure 30, the degree of curvature of the tumble passage 64 to the right is stronger than the degree of curvature of the tumble passage 64 to the right in the model M1 of Figure 16, and a part of the tumble passage 64 (for example, the maximum right protrusion 64s) does not overlap with the main passage 66.

Figures 27 to 29 show the results of five simulations. Three of the five simulations were performed using a model having the configuration of the internal combustion engine 110 of the first embodiment, and the curvature of the tumble passage 64 in the direction of the cylinder axis C (see Figure 18) was the same, but the degree of curvature of the tumble passage 64 to the right was changed. The results are shown in Figures 27 to 29 as plots P1 to P3. That is, for example, plot P1 in Figures 27 to 29 was obtained by the same simulation. As a comparative example, the results obtained by the simulation using a model having the configuration of the internal combustion engine 10 of the reference example are shown by dashed lines in Figures 27 to 29, and the results obtained by the simulation using a model in which the tumble passage 64 is curved in the direction of the cylinder axis C as shown in Figure 18 but not to the right are shown by plot RP in Figures 27 to 29.

To strengthen the tumble flow, i.e., the positive tumble flow, it is better to have a small swirl ratio and a large tumble ratio. Also, to more effectively spread the flame, it is better to have the axis of rotation of the tumble flow tilted to the right where the ignition plug is located, and the more the axis of rotation of the tumble flow tilts to the right, the greater the axial tilt of the vertical axis in Figure 27 becomes.

27 to 29 show that the swirl ratio can be lowered and the tumble ratio can be raised by curving the tumble passage 64 in the direction of the cylinder axis. It can also be seen that the axis of rotation of the tumble flow can be tilted to the right while lowering the swirl ratio and raising the tumble ratio by curving the tumble passage 64 to the right.

The above describes the embodiments and their modifications of the present invention, but 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.

In the intake structures S, S1 of the internal combustion engine of the first and second embodiments, the tumble passage 64 is curved with a bias toward the right, but it may be curved with a bias toward the left. In this case, the junction 65 and the spark plug may be provided on the left side of the imaginary plane IS. The intake structures S, S1 of the internal combustion engine of the first and second embodiments have the characteristics of the intake structure S0 of the reference example, such as the offset portion 90, but it is also possible not to have this offset portion. For example, the tumble passage 64 of the intake structures S, S1 may be formed so as to be completely independent from the main passage 66 up to the junction 65 with the main passage 66.

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
40c…Throttle valve
46...intake valve, 50...exhaust valve
62…Partition
64…Tumble passage (first intake passage)
66…Main passage (second intake passage)
68: first fuel injector, 70: second fuel injector
70a…Fuel injection valve
94c…Tumble valve
M, M1, M2, M3...3D model, S0, S, S1...intake structure

Claims (8)

An intake structure (S, S1) for an internal combustion engine (110) in which a first intake passage (64) and a second intake passage (66) for generating a tumble flow in the combustion chamber (20) are provided so as to overlap with each other in an intake passage (38) communicating with the combustion chamber (20) in a direction of a cylinder axis (C),
the first intake passage (64) is curved in the direction of the cylinder axis (C) so as to move away from the second intake passage (66), and is curved in a width direction perpendicular to the cylinder axis (C) and perpendicular to the intake and exhaust direction,
The first intake passage (64) is formed so as to be curved convexly toward the crankshaft (17) in the direction of the cylinder axis (C),
An intake structure (S1) for an internal combustion engine (110), characterized in that a downstream wall surface (us) that defines the first intake passage (64) side of the second intake passage (66) has a curved shape that corresponds to the curved shape of the downstream portion (64L) of the first intake passage (64). When a direction from the crankshaft (17) side to the cylinder head (14) side in the direction of the cylinder axis (C) is defined as a first direction,
2. The intake structure (S1) of an internal combustion engine (110) according to claim 1, wherein the second intake passage (66) is provided on the first direction side of the first intake passage (64). The intake structure (S1) of an internal combustion engine (110) as described in claim 1 or 2, characterized in that a junction (65) of the first intake passage (64) with the second intake passage (66) is biased in the width direction with respect to an opening (28) of the intake port (34). When a virtual plane (IS) including the cylinder axis (C) and extending in the intake and exhaust direction is defined,
The intake structure (S1) of an internal combustion engine (110) according to claim 3, characterized in that the confluence portion (65) and an ignition plug facing the combustion chamber (20) are arranged on one side of the imaginary plane (IS). The intake structure (S1) of an internal combustion engine (110) as described in claim 3 or 4, characterized in that, in the width direction, the first intake passage (64) is formed so as to be convexly curved toward the same side as the side to which the junction portion (65) is biased. (delete) An intake structure (S1) for an internal combustion engine (110) as described in any one of claims 1 to 5, characterized in that a wall surface (ds) on the side of the second intake passage (66) that defines the first intake passage (64) is curved so as to be convex toward the crankshaft (17) in the direction of the cylinder axis (C). The intake structure (S1) of an internal combustion engine (110) according to any one of claims 1 to 5 and 7, characterized in that the downstream portion (64L) of the first intake passage (64) is formed so as to approach from the crankshaft (17) side to the cylinder head (24) side in the direction of the cylinder axis (C) as it approaches the downstream side in the intake flow direction.

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