Intake structure of an internal combustion engine

Abstract

The present disclosure is directed to a configuration that, in an internal combustion engine configured such that an intake channel is divided by a partitioning portion, securing of tumble performance is enabled while enabling relaxing of clearance control of an intake control valve that can also be referred to as a tumble valve. An intake structure S in an internal combustion engine according to an embodiment includes: a main partitioning portion 62 that partitions an intake channel 38 into a first intake channel 64 serving as a tumble channel and a second intake channel 66; a sub-partitioning portion 72 provided so as to form a third intake channel 68 and a fourth intake channel 70 in the first intake channel 64; and an intake control valve 76c provided upstream of the main partitioning portion 62. When the intake control valve 76c is in a state closing off the second intake channel 66 and the fourth intake channel 70, a first gap G1 portion is formed between the sub-partitioning portion 72 and a valve element 76d of the intake control valve 76c, and a second gap portion G2 is formed between an intake channel wall face 77a and the valve element 76d.

Description

[Technical field]

[0001] The present invention relates to an intake structure for an internal combustion engine in which a partition portion is provided to divide an intake passage into a plurality of passages. [Background technology]

[0002] 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 disclosed in 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 an upper main passage and an upper lower auxiliary passage. The lower auxiliary passage becomes the tumble passage, and the tumble valve essentially opens and closes the upper main passage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent No. 6714764 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventionally, for example, when the internal combustion engine is operating in a low load region, the tumble valve is closed to generate a tumble flow in the combustion chamber by the intake air from the tumble passage. However, if the degree of blocking of a passage other than the tumble passage by the tumble valve, for example, the above-mentioned upper main passage, is low, the intake flow leaks into the main passage, which may weaken the generation of the tumble flow by the intake air from the tumble passage.

[0005] On the other hand, in order to increase the degree of closing of the tumble valve when the valve is closed, it is necessary to manage the clearance between the tumble valve and the wall surface of the intake passage, which can lead to an increase in costs.

[0006] The object of the present invention is to provide a configuration in an internal combustion engine in which the intake passage is divided by a partition, which makes it possible to relax clearance management of an intake control valve, which may also be called a tumble valve, while ensuring tumble performance. [Means for solving the problem]

[0007] In order to achieve the above object, one aspect of the present invention is to a main partition portion that partitions an intake passage connected to a combustion chamber of an internal combustion engine into a first intake passage that serves as a tumble flow passage for generating a tumble flow in the combustion chamber, and a second intake passage; a sub-partition provided in the first intake passage so as to define a third intake passage and a fourth intake passage, the fourth intake passage being located between the third intake passage and the second intake passage and having a smaller cross-sectional area than the second intake passage; an intake control valve provided upstream of the main partition; Equipped with When the intake control valve is in a state where it closes the second intake passage and the fourth intake passage, a first gap is formed between the sub-partition portion and a valve body of the intake control valve, and a second gap is formed between the valve body and an intake passage wall surface of the intake control valve on the opposite side to the sub-partition portion. An intake structure for an internal combustion engine to provide.

[0008] According to the above configuration, the first intake passage is provided with a sub-partition portion so as to form a third intake passage and a fourth intake passage, the fourth intake passage is located between the third intake passage and the second intake passage and is formed to have a smaller cross-sectional area than the second intake passage, and when the intake control valve is in a state where it closes the second intake passage and the fourth intake passage, a first gap portion is formed between the sub-partition portion and the valve body of the intake control valve, and a second gap portion is formed between the intake passage wall surface of the intake control valve on the opposite side to the sub-partition portion and the valve body. Therefore, the flow of intake air that has passed through the first and second gap portions can be urged to the fourth intake passage that can become a tumble flow passage. Therefore, the tumble performance can be ensured. In addition, since the intake control valve is designed to form the first and second gap portions, the clearance management of the intake control valve can be relaxed compared to increasing the degree of blockage of the intake control valve when the valve is closed. Therefore, according to the intake structure of the internal combustion engine, it is possible to ensure tumble performance while making it possible to relax the clearance management of the intake control valve.

[0009] Preferably, when the direction of the cylinder axis from the crankshaft side to the cylinder head side is defined as a first direction, the main partition divides the intake passage into the first intake passage and a second intake passage on the first direction side of the first intake passage, and the sub-partition defines, in the first intake passage, the third intake passage and the fourth intake passage on the first direction side of the third intake passage. This configuration makes it possible to more suitably generate a tumble flow.

[0010] Preferably, the first gap is located downstream of the second gap in the intake air flow direction. With this configuration, when the intake control valve closes the second intake passage and the fourth intake passage, the intake air can more effectively flow into the fourth intake passage, which can serve as a tumble flow passage.

[0011] Preferably, each of the first gap and the second gap has a gap width equal to or less than the thickness of the main partition. With this configuration, when the intake control valve is in a state in which the second intake passage and the fourth intake passage are closed, the flow of intake air into the first intake passage including the third intake passage and the fourth intake passage, which can serve as a tumble flow passage, can be further promoted.

[0012] Preferably, the intake structure for the internal combustion engine further includes a junction section where the third intake passage and the fourth intake passage join, and where the first intake passage joins the second intake passage via the junction section. With this configuration, it is possible to provide strong directionality to the intake air from the first intake passage including the third intake passage and the fourth intake passage, and it is possible to further ensure tumble performance.

[0013] Preferably, the junction is formed so that the area of ​​a cross section perpendicular to the flow direction downstream of the upstream end of the junction is smaller than the sum of the cross-sectional areas of the third and fourth intake passages. With this configuration, when the intake air from the third intake passage and the intake air from the fourth intake passage join at the junction and flow into the second intake passage, it is possible to maintain a high flow rate of the intake air.

[0014] Preferably, the junction is formed so that the intake air from the first intake passage through the junction flows into the combustion chamber at a smaller approach angle than the intake air from the second intake passage. With this configuration, the intake air that has passed through the first intake passage can be introduced into the combustion chamber while maintaining a strong directivity, so that a strong tumble flow can be generated in the combustion chamber.

[0015] Preferably, the intake control valve is configured to be able to open and close the second intake passage and the fourth intake passage, and has a first position for closing the second intake passage and the fourth intake passage, a second position for closing the second intake passage and opening the fourth intake passage, and a fully open position. With this configuration, it is possible to preferably generate a tumble flow and more preferably ensure an intake air amount according to an operating state.

[0016] Preferably, the intake control valve is configured with a single valve member that rotates integrally with a valve stem, and a recess that allows movement of the valve member is provided in a wall that defines the intake passage. With this configuration, the amount of intake air can be more easily adjusted by controlling the movement of the single valve member, and the recess can improve the opening and closing function of the valve member.

[0017] Preferably, when the intake control valve closes the second intake passage and the fourth intake passage, one end half of the valve member of the intake control valve is located downstream in the intake flow direction around the valve shaft and forms an obtuse angle with the sub-partition portion on the downstream side of the one end half, and the other end half of the valve member is located upstream and forms an acute angle with the wall portion of the recess on the downstream side of the other end half. With this configuration, when the intake control valve closes the second intake passage and the fourth intake passage, the flow of intake air that has passed through the intake control valve toward the fourth intake passage can be further promoted. Effect of the Invention

[0018] According to the above aspect of the present invention, since the above configuration is provided, in an internal combustion engine in which the intake passage is divided by a partition portion, it becomes possible to relax clearance management of the intake control valve and ensure tumble performance. [Brief description of the drawings]

[0019] [Figure 1] 1 is a cross-sectional view showing a schematic configuration of an internal combustion engine according to an embodiment of the present invention. [Diagram 2] 2 is a diagram showing a three-dimensional model of a portion of an intake passage downstream of a throttle valve in the internal combustion engine of FIG. 1. [Diagram 3] FIG. 3 is a diagram of the three-dimensional model of FIG. 2, seen from a different angle than FIG. 2. [Figure 4] 2 is a diagram showing a valve body of a tumble valve in the internal combustion engine of FIG. 1. [Diagram 5]2 is a diagram showing a three-dimensional model of the internal combustion engine of FIG. 1, including a portion of the intake passage downstream of a throttle valve and a tumble valve, and an exhaust port, as viewed from above. FIG. [Figure 6] 6 is a diagram of the three-dimensional model in FIG. 5 viewed from a direction perpendicular to the cylinder axis and perpendicular to the intake air flow direction. [Figure 7A] 7 is a cross-sectional view of the three-dimensional model of FIG. 6 taken along line VIIA-VIIA. [Figure 7B] 7 is a cross-sectional view of the three-dimensional model of FIG. 6 taken along line VIIB-VIIB. [Figure 7C] 7 is a cross-sectional view of the three-dimensional model of FIG. 6 taken along line VIIC-VIIC. [Figure 7D] 7 is a cross-sectional view of the three-dimensional model of FIG. 6 taken along line VIID-VIID. [Figure 8] FIG. 4 is a diagram for explaining the flow of intake air through a butterfly valve. [Figure 9] FIG. 13 is a further diagram for explaining the flow of intake air through the butterfly valve. [Figure 10] 2 is a diagram for explaining the flow of intake air around a tumble valve, which is an intake control valve, in the internal combustion engine of FIG. 1. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0021] A schematic configuration of an internal combustion engine 10 according to an 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 of a cylinder bore 12b of a cylinder block 12 of the internal combustion engine 10 (cylinder axis).

[0022] 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 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 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.

[0023] The internal combustion engine 10 employs a SOHC type 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 in the cylinder head cover 24, an endless cam chain (not shown) is installed between a camshaft 26 and the crankshaft 17, passing through a cam chain chamber (not shown) provided on one side of the crankshaft direction of the crankcase portion 16, the cylinder block 12, and the cylinder head 14, and 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 and curving in a direction vertically away from each other from the intake valve port 28 and exhaust valve port 30 that open into the combustion chamber ceiling surface 14a. 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.

[0025] The downstream end of the exhaust port 34 opens downward in 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 facing the combustion chamber 20.

[0027] In addition, an exhaust valve 50 slidably supported by an exhaust valve guide 48 that is integrally fitted onto the curved outer wall portion 34 a of the exhaust port 34 in the cylinder head 14 opens and closes the exhaust valve port 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 in contact with the intake cam and the exhaust cam of the camshaft 26, 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, and allowing intake and exhaust to occur at a 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 valve shaft, i.e., a throttle valve shaft 40b, that is perpendicular to the flow direction of the intake air in the intake passage 40a, i.e., that intersects at a right angle with the central axis of the intake passage 40a, 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 the throttle valve shaft 40b and a disk-shaped valve element 40d that is fixed to the throttle valve shaft 40b and rotates integrally therewith.

[0031] The throttle valve 40c can be rotated in the opening direction (counterclockwise in Fig. 1) by the driver's operation, and the valve body 40d is biased in the closing direction (clockwise) by a return spring (not shown) so that the edge of the valve body 40d is positioned at the fully closed position where it abuts against the inner wall surface of the intake passage 40a. Note that the opening and closing directions of the throttle valve 40c may be opposite to each other.

[0032] In the internal combustion engine 10 as described above, an intake structure S is configured to provide a tumble vortex, i.e., a tumble flow, i.e., vertical rotation, of the fuel-air mixture in the combustion chamber 20 in order to obtain more favorable combustion in the combustion chamber 20. That is, the intake passage 38 is divided along the intake flow direction by a partition portion 62 continuing from the inlet pipe 36 to the intake port 32, and is partitioned into a tumble flow passage 64 configured so that the intake air that passes through generates a tumble flow in the combustion chamber 20, and a main flow passage 66 excluding the tumble flow passage 64. The tumble flow passage 64 corresponds to the first intake passage, and the main flow passage 66 corresponds to the second intake passage. The tumble flow passage 64 may be called a sub-passage.

[0033] Furthermore, a partition 72 is provided in the tumble passage 64 so as to continue mainly from the inlet pipe 36 to the intake port 32. By providing the partition 72, two intake passages 68, 70 are partitioned in the tumble passage 64. One of the two intake passages 68, 70 is a first tumble passage 68, and the other is a second tumble passage 70. The first tumble passage 68 corresponds to a third intake passage, and the second tumble passage 70 corresponds to a fourth intake passage.

[0034] Here, the partition 62 separating the tumble passage 64 from the main passage 66 is referred to as the main partition, and the partition 72 separating the first tumble passage 68 from the second tumble passage 70 of the tumble passage 64 is referred to as the sub-partition. The main partition 62 extends in a plate-like manner in the flow direction of the intake air, and the sub-partition 72 also extends in a plate-like manner in the flow direction of the intake air, for example, approximately parallel to the main partition 62. The main partition 62 is provided so as to substantially divide the intake passage 38 in two in the vertical direction, that is, so as to substantially extend on the central axis extending in the flow direction here. The sub-partition 72 is provided so as to substantially divide the tumble passage 64 in two in the vertical direction, that is, so as to substantially extend on the central axis of the tumble passage 64 extending in the flow direction here. As a result, the intake passage 38 is formed with a tumble flow passage 64 and a main flow passage 66 separated by the main partition 62, and the tumble flow passage 64 is formed with a first tumble flow passage 68 and a second tumble flow passage 70 located closer to the main flow passage 66 than the first tumble flow passage 68, that is, between the first tumble flow passage 68 and the main flow passage 66, by the sub-partition 72. Here, as described above, the main partition 62 extends so as to substantially divide the intake passage 38 in half in the vertical direction, and the sub-partition 72 extends so as to substantially divide the tumble flow passage 64 in half in the vertical direction, so that the cross-sectional area of ​​the main flow passage 66 is clearly larger than the cross-sectional area of ​​the second tumble flow passage 70. Note that the sub-partition 72 may be provided so as to be biased, for example, toward either the top or bottom.

[0035] The ratio of the cross-sectional areas of the main flow passage 66 and the tumble flow passage 64 (cross-sectional area of ​​the main flow passage 66:cross-sectional area of ​​the tumble flow passage 64) is preferably in the range of 1:1 to 3:1, and the intake structure S of the internal combustion engine 10 of this embodiment is also designed within this range. The ratio of the cross-sectional areas of the main flow passage 66, the second tumble flow passage 70, and the first tumble flow passage 68 (cross-sectional area of ​​the main flow passage 66:cross-sectional area of ​​the second tumble flow passage 70:cross-sectional area of ​​the first tumble flow passage 68) is preferably in the range of 6:4:2 to 9:1:2.

[0036] The lower part of the intake passage 38 separated by the main partition 62 is the tumble passage 64, the upper part is the main passage 66, the lower part of the tumble passage 64 separated by the sub-partition 72 is the first tumble passage 68, and the upper part is the second tumble passage 70, but in this specification they are not limited to the up-down arrangement. In this specification, "up" and "down" for the intake passage 38 and the like 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. In this specification, the "up" or "up" direction corresponds to the first direction, and the "down" or "down" direction corresponds to the second direction.

[0037] A tumble valve body 76 is connected to the upstream end of the inlet pipe 36 via an insulator 74. The tumble valve body 76 has an intake passage 76a having a generally circular cross section that constitutes part of the intake passage 38, and the aforementioned throttle body 40 is connected to the upstream end of the intake passage 76a.

[0038] The tumble valve body 76 is rotatably supported in the tumble valve body 76 by a valve shaft 76b that is perpendicular to the intake flow direction of the intake passage 76a, i.e., perpendicular to the central axis of the intake passage 76a, and is provided with a tumble valve 76c that can variably control the flow passage area of ​​the intake passage 76a and open and close the upper area of ​​the intake passage 76a in cooperation with the partitions 62, 72. The tumble valve 76c is of a butterfly type and has a valve shaft 76b and a substantially disk-shaped valve body 76d that is fixed to the valve shaft 76b and rotates integrally therewith. In this way, the tumble valve 76c is configured with the valve body 76d, which is a single valve member that rotates integrally with the valve shaft 76b. However, the valve shaft 76b of the tumble valve 76c is parallel to the throttle valve shaft 40b. The tumble valve 76c may also be called a tumble control valve, TCV, etc., and corresponds to the intake control valve of the present invention.

[0039] Here, a three-dimensional model M1 of the portion of the intake passage 38 downstream of the throttle valve 40c is shown in Figs. 2 and 3. Fig. 2 is a perspective view of the three-dimensional model M1 from the downstream side, and Fig. 3 is a view of the three-dimensional model M1 from the left-right direction (perpendicular to the up-down direction). Fig. 3 is a view of the three-dimensional model M1 from a direction perpendicular to the valve axis 46c of the intake valve 46 and perpendicular to the extension direction of the main partition section 62 and the extension direction of the sub-partition section 72. In the three-dimensional model M1, the valve body 76d of the tumble valve 76c is shown. Fig. 4 shows the valve body 76d of the tumble valve 76c. The valve body 76d, which is a single valve member of the tumble valve 76c, is approximately disk-shaped as described above, but the tip portion 76t that swings around the valve axis 76b on the downstream side is approximately linear. This allows the valve body 76d to be in a closed state between the main partition section 62 and the sub-partition section 72.

[0040] The main partition 62 extends continuously from a position immediately downstream of the tumble valve 76c to the intake port 32. Similarly, the sub-partition 72 extends continuously from a position immediately downstream of the tumble valve 76c to the intake port 32. As is clear from FIG. 1, the valve shaft 76b of the tumble valve 76c is positioned above the main partition 62. Naturally, therefore, the valve shaft 76b of the tumble valve 76c is positioned above the sub-partition 72. In addition, the tumble valve 76c is a butterfly-type valve. Therefore, the upstream edge 62a of the main partition 62 is located downstream of the upstream edge 72a of the sub-partition 72. Here, the upstream side of the sub-partition 72 extends into the tumble valve body 76, and its upstream edge 72a is formed in the tumble valve body 76, but this is not limited to this, and the intake structure S may be designed, for example, so that the upstream edge 72a is located in the inlet pipe 36. The downstream edge 62b of the main partition 62 is located downstream of the downstream edge 72b of the sub-partition 72.

[0041] As shown in Fig. 1, the tumble valve body 76 is provided with a recess 77 that allows movement of the valve body 76d of the tumble valve 76c. The recess 77 is provided in a wall portion that defines the intake passage 38, particularly in an upper wall portion 76u of a wall portion 76e of the tumble valve body 76 that defines the intake passage 76a here. Note that the recess 77 is substantially arc-shaped in Figs. 1 and 3.

[0042] The tumble valve 76c configured as described above is configured to be able to open and close the main passage 66 which is the second intake passage and the second tumble passage 70 which is the fourth intake passage. Here, the tumble valve 76c is provided so as not to affect the opening degree of the first tumble passage 68.

[0043] In Fig. 1, the valve body 76d of the tumble valve 76c is positioned so that its downstream side extends to the upstream edge 72a of the sub-partition portion 72. That is, in Fig. 1, the tumble valve 76c substantially closes the main flow path 66 and the second tumble flow path 70, and naturally leaves the first tumble flow path 68 open.

[0044] As shown in FIG. 1, the tumble valve 76c can be positioned in a first position P1 where the downstream tip 76t of the valve body 76d extends to the upstream edge 72a of the sub-partition section 72. In addition to the first position P1 (solid line in FIG. 3), the tumble valve 76c has a fully open position PA (dashed line in FIG. 3) where the valve body 76d of the tumble valve 76c extends in the flow direction, and a second position P2 (dashed line in FIG. 3) where the downstream tip 76t of the valve body 76d extends to the upstream edge 62a of the main partition section 62. When the tumble valve 76c is in the fully open position PA, the tumble flow passage 64 and the main flow passage 66 are fully open. When the tumble valve 76c is in the first position P1, the main flow passage 66 and the second tumble flow passage 70 are substantially closed, and the first tumble flow passage 68 is naturally left open, as previously described based on FIG. 1. When the tumble valve 76c is in the second position P2, the main flow passage 66 is substantially closed, and the second tumble flow passage 70 is open in addition to the first tumble flow passage 68. Thus, the tumble valve 76c is used at a plurality of opening degrees, but the provision of the recess 77 allows the valve body 76d to be suitably positioned at the fully open position PA, the first position P1, or the second position P2. Whether the tumble valve 76c is positioned at the first position P1 or the second position P2, the inner wall surface 77a of the recess 77 is concavely curved so that a gap of approximately the same shape and approximately the same width is formed between the inner wall surface 77a of the recess 77 and a portion (hereinafter, a circular arc portion) 76s (see FIG. 4) of the valve body 76d facing the inner wall surface 77a. The tumble valve 76c can be positioned at any position other than these. These positions of the tumble valve 76c are controlled by the ECU 80, which will be described later, based on the operating state of the internal combustion engine 10.

[0045] 1 and 3, the valve body 76d of the tumble valve 76c is inclined. At this time, the one end half 76f located below the valve body 76d of the tumble valve 76c is located downstream in the intake flow direction F around the valve shaft 76b, and forms an obtuse angle α with the corresponding sub-partition portion 72 on the downstream side of the one end half 76f. At this time, the other end half 76g located above the valve body 76d of the tumble valve 76c is located upstream in the intake flow direction F around the valve shaft 76b, and forms an acute angle β with the upper wall 76u of the wall 76e of the corresponding recess 77, i.e., the inner wall surface 77a of the recess 77, which is the intake passage wall surface, on the downstream side of the other end half 76g. This angular relationship also holds when the valve body 76d of the tumble valve 76c is in the second position P2, and at this time, the one-end half 76f located below the valve body 76d of the tumble valve 76c forms an obtuse angle with the corresponding main partition portion 62 on the downstream side thereof.

[0046] The internal combustion engine 10 is provided with a fuel injection valve 78. The fuel injection valve 78 is provided downstream of the throttle valve 40c and the tumble valve 76c. Here, the fuel injection valve 78 is provided in the inlet pipe 36 so as to face the main flow passage 66, and is provided so as to inject fuel toward the intake port 32. More specifically, the fuel injection valve 78 is provided so as to inject fuel toward the intake valve 46 via the main flow passage 66. The amount of fuel injection from this fuel injection valve 78 and its injection timing are controlled in association with the control of the throttle valve 40c and the tumble valve 76c, respectively.

[0047] The throttle valve 40c is not limited to being electronically controlled, and may be a valve that is mechanically controlled, for example, by a throttle cable, and the same is true for the tumble valve 76c. In addition to the fuel injection valve 78, an additional fuel injection valve may be provided. In this case, the additional fuel injection valve may be provided so as to inject fuel into the intake passage downstream of the throttle valve 40c and upstream of the tumble valve 76c. When the additional fuel injection valve is provided, the fuel injection amount and injection timing of the additional fuel injection valve may be controlled in the same manner as the fuel injection amount and injection timing of the fuel injection valve 78, or in association with the fuel injection amount and injection timing of the fuel injection valve 78.

[0048] An ECU (electronic control unit) 80 that controls the internal combustion engine 10 has a configuration as a so-called computer, and includes an intake control unit 82 and a fuel injection control unit 84. The ECU 80 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 each of the throttle valve 40c and the tumble valve 76c by the intake control unit 82. For example, the throttle valve 40c is controlled to an opening degree according to the accelerator operation by the driver. Furthermore, the ECU 80 controls the operation of the fuel injection valve 78 by the fuel injection control unit 84 based on the analyzed operating state of the internal combustion engine 10. The ECU 80 stores programs and various data for these controls.

[0049] Here, the control of the tumble valve 76c will be described in detail. For example, when the operating state of the internal combustion engine 10 is in the low load region, the ECU 80 controls the operation of the tumble valve 76c to be located at the first position P1 so that intake air is substantially taken in only from the first tumble passage 68. This ensures an intake air amount appropriate for the low load region, and causes the intake air from the first tumble passage 68 to form a tumble flow in the combustion chamber 20. Since the first tumble passage 68 has a relatively small cross-sectional area, the flow rate can be increased even with an intake air amount appropriate for the low load region, and a strong tumble flow can be formed. Here, when the operating state of the internal combustion engine 10 is in the low load region, the fuel injection from the fuel injection valve 78 is controlled so that the air-fuel ratio is lean, but by forming a tumble flow, combustion can be effectively caused.

[0050] Also, for example, when the operating state of the internal combustion engine 10 is in the medium load region, the ECU 80 controls the operation of the tumble valve 76c to be located at the second position P2 so that intake air is taken in from the first tumble passage 68 and the second tumble passage 70, i.e., from the tumble passage 64. This ensures an intake air amount appropriate for the medium load region, and forms a tumble flow in the combustion chamber 20 with the intake air from the first and second tumble passages 68, 70. Since the tumble flow is formed with the intake air from the first and second tumble passages 68, 70, a strong tumble flow can be formed while ensuring a necessary intake air amount even in the medium load region where a larger intake air amount is required than in the low load region. Here, when the operating state of the internal combustion engine 10 is in the medium load region, the fuel injection from the fuel injection valve 78 is controlled so that the air-fuel ratio is lean, but by forming the tumble flow, combustion can be effectively caused.

[0051] Furthermore, for example, when the operating state of the internal combustion engine 10 is in the high load region, the ECU 80 controls the operation of the tumble valve 76c to be positioned at the full open position PA so that intake air is taken in from the tumble passage 64 including the first tumble passage 68 and the second tumble passage 70 and the main passage 66. This ensures an intake air amount appropriate for the high load region, and realizes a preferable tumble flow in the combustion chamber 20 with the intake air from the first and second tumble passages 68, 70, or a suitable in-cylinder flow velocity if not. Here, when the operating state of the internal combustion engine 10 is in the high load region, the fuel injection from the fuel injection valve 78 is controlled so that the air-fuel ratio becomes stoichiometric, and furthermore, by realizing a suitable in-cylinder flow velocity, combustion can be more effectively caused.

[0052] For example, when the operating state of the internal combustion engine 10 is in the high load region, the operation of the tumble valve 76c is controlled to be located at the fully open position PA, and intake air is taken in through the tumble passage 64 and the main passage 66. At this time, the intake structure S of the internal combustion engine 10 has a further configuration and shape so as to increase the intake air volume by intake from the main passage 66 and to more suitably ensure the tumble performance by intake from the tumble passage 64. This will be further explained below.

[0053] A junction section 86 is defined and formed downstream of the tumble passage 64. The junction section 86 is provided at a point where the first tumble passage 68 and the second tumble passage 70 join downstream. The tumble passage 64 joins the main passage 66 via the junction section 86. The junction section 86 is formed in the cylinder head 14. Here, the junction section 86 is formed as a part of the intake port 32.

[0054] 5 and 6 show a three-dimensional model M2 including the portion of the intake passage 38 downstream of the throttle valve 40c and the tumble valve 76c and the exhaust passage of the exhaust port 34. Fig. 5 is a view from above the three-dimensional model M2, and Fig. 6 is a view of the three-dimensional model M2 from a direction perpendicular to the cylinder axis C and perpendicular to the intake air flow direction. Furthermore, Fig. 7A shows a cross-sectional view of the three-dimensional model M2 taken along line VIIA-VIIA in Fig. 6, Fig. 7B shows a cross-sectional view of the three-dimensional model M2 taken along line VIIB-VIIB in Fig. 6, Fig. 7C shows a cross-sectional view of the three-dimensional model M2 taken along line VIIC-VIIC in Fig. 6, and Fig. 7D shows a cross-sectional view of the three-dimensional model M2 taken along line VIID-VIID in Fig. 6. Line VIIA-VIIA in Fig. 6 passes near the upstream edge of the main partition 62, line VIIB-VIIB in Fig. 6 passes near the upstream end of the intake port 32, line VIIC-VIIC in Fig. 6 passes near the downstream edge of the sub-partition 72, and line VIID-VIID in Fig. 6 passes near the downstream edge of the main partition 62. All of line VIIA-VIIA to line VIID-VIID in Fig. 6 are parallel to the cylinder axis C in Fig. 6.

[0055] In Fig. 7A, Fig. 7B, and Fig. 7C, the first tumble flow passage 68 and the second tumble flow passage 70 have approximately the same shape and size. In this way, the first tumble flow passage 68 and the second tumble flow passage 70 smoothly reach from the upstream side to the downstream side without changing their shape or size significantly in the intake air flow direction. The first tumble flow passage 68 and the second tumble flow passage 70 are connected to a junction 86. The junction 86 is connected to the main flow passage 66 downstream of the downstream edge 62b of the downstream end of the main partition 62 (see Fig. 1 and Fig. 6). With this configuration, the first tumble flow passage 68 and the second tumble flow passage 70 are connected to the main flow passage 66 via the junction 86 downstream of the downstream edge 72b of the sub-partition 72. Therefore, the intake air that has passed through the first tumble flow passage 68 and the second tumble flow passage 70 of the tumble flow passage 64 can have strong directionality.

[0056] In FIG. 6, a line L1 determined to extend in the intake flow direction at the junction 86 intersects with the cylinder axis C at an angle θ1 close to a right angle, whereas a line L2 determined to extend in the flow direction at the downstream end of the main flow passage 66 intersects with the cylinder axis C at an angle θ2 smaller than the angle θ1. In this manner, the junction 86 is partitioned so that the intake air from the tumble flow passage 64 via the junction 86 flows into the combustion chamber 20 at a smaller approach angle than the intake air from the main flow passage 66. With this configuration, the intake air that has passed through the tumble flow passage 64 can be introduced into the combustion chamber 20 while maintaining a strong directivity, and for example, a strong tumble flow can be generated in the combustion chamber 20. The approach angle here refers to the angle of the intake air flowing toward the combustion chamber 20 into the combustion chamber 20. For example, the larger the angle between the intake air and the cylinder axis C in FIG. 6 viewed from a direction perpendicular to the cylinder axis C and perpendicular to the intake flow direction, the smaller the approach angle.

[0057] 1, 3, and 6, the tumble flow passage 64 is defined so as to have a curved shape convex downward, and the main flow passage 66 is defined so as to have a curved shape convex upward. With this configuration, as described above, it becomes possible to guide the intake air from the tumble flow passage 64 to the combustion chamber 20 at a smaller approach angle, and it becomes possible to guide the intake air from the main flow passage 66 to the combustion chamber 20 more effectively.

[0058] FIG. 7C shows where the first tumble flow path 68 and the second tumble flow path 70 communicate with the upstream end of the confluence portion 86. Here, for reference, FIG. 7C shows a cross-section 68A of the first tumble flow path 68, a cross-section 70A of the second tumble flow path 70, and one side TA1 of a virtual plane defined at the upstream end 86u of the confluence portion 86, that is, a cross-section at this virtual plane. The side TA1 of the upstream end 86u of the confluence portion 86 is clearly longer than the vertical length of the cross-section 68A of the first tumble flow path 68 and the vertical length of the cross-section 70A of the second tumble flow path 70, respectively. In this way, the confluence portion 86 is partitioned such that the cross-sectional areas (areas S1 and S2 in FIG. 7C) of the first tumble flow path 68 and the second tumble flow path 70 are smaller than the cross-sectional area S3 of the upstream end 86u of the confluence portion 86 (the area of the cross-section partially defined by the side TA1) (S1 < S3, S2 < S3). With this configuration, the intake air from the first tumble flow path 68 and the intake air from the second tumble flow path 70 can suitably flow into the confluence portion 86. More specifically, when the tumble valve 76c is in the second position P2 and intake air is flowing through the first tumble flow path 68 and the second tumble flow path 70, since the cross-sectional area of the confluence portion 86 is larger than the cross-sectional areas of the first tumble flow path 68 and the second tumble flow path 70 respectively, the intake air amount is less likely to be restricted at the confluence portion 86, and an intake air amount suitable for the operation region in the medium load region can be ensured.

[0059] Also, for example, the side TA2 in FIG. 7D is shorter than the side TA1 in FIG. 7C. That is, the cross-sectional area of ​​the junction 86 of the tumble passage 64 tends to become smaller at the cross-sectional location in FIG. 7D than at the side TA1 in FIG. 7C toward the downstream side. In this manner, in the internal combustion engine 10, the junction 86 is partitioned so as to taper from the upstream end of the junction 86 toward the downstream side. With this configuration, the area (cross-sectional area) of the cross section perpendicular to the flow direction downstream of the upstream end 86u of the junction 86 is smaller than the sum of the cross-sectional areas of the first tumble passage 68 and the second tumble passage 70 (for example, the sum of the area S1 of the cross-section 68A and the area S2 of the cross-section 70A). This makes it possible to maintain the flow velocity of the intake air high when the intake air from the first tumble passage 68 and the intake air from the second tumble passage 70 join at the junction 86 and flow into the main passage 66. Therefore, the intake air from the tumble passage 64 flows into the combustion chamber 20 at a high flow rate, and preferably forms a tumble flow. Note that making the area of ​​the cross section perpendicular to the flow direction downstream of the upstream end of the junction 86 smaller than the sum of the cross-sectional areas of the first tumble passage 68 and the second tumble passage 70 may be achieved by means other than tapering.

[0060] As described above, the tumble valve 76c can be positioned at the first position P1 or the second position P2. When positioned at either of these positions, at least one intake passage is closed to actively generate a tumble flow with intake air from the remaining intake passage. However, in order to increase the degree of closure of at least one intake passage when the tumble valve 76c is closed, it is necessary to improve the design accuracy of the valve body 76d and / or the accuracy of the wall surface that defines the intake passage 76a of the tumble valve body 76. Therefore, in this embodiment, particularly when the tumble valve 76c is positioned in the first position P1 and is in a state of closing the main flow path 66, which is the second intake passage, and the second tumble flow path 70, which is the fourth intake passage, a gap (first gap) G1 is actively formed between the sub-partition 72 and the valve body 76d, and a gap (second gap) G2 is actively formed between the wall surface that defines the intake passage 76a extending opposite to the sub-partition 72 of the tumble valve 76c, i.e., upward, i.e., the intake passage wall surface, and the valve body 76d of the tumble valve 76c. In other words, at that time, the upstream end 72a of the sub-partitioning portion 72 is separated from the facing tip portion 76t of the valve body 76d by a predetermined distance (first predetermined distance) corresponding to the first gap portion G1, and the wall surface defining the intake passage 76a extending above the tumble valve 76c is separated from the facing edge portion, i.e., the arc-shaped portion 76s, of the valve body 76d of the tumble valve 76c by a predetermined distance (second predetermined distance) corresponding to the second gap portion G2. Here, the wall surface defining the intake passage 76a extending above the tumble valve 76c refers to the upper wall portion 76u of the wall portion 76e of the tumble valve body 76, i.e., the inner wall surface 77a of the recess 77. Note that, when the valve body 76d of the tumble valve 76c is inclined at the first position P1 shown in FIG. 1 and FIG. 3, the first gap portion G1 is located downstream of the second gap portion G2 in the intake flow direction F.

[0061] Each of the first gap G1 and the second gap G2 has a gap width equal to or smaller than the thickness of the main partition 62. The thickness of the main partition 62 is preferably the average thickness of the main partition 62 extending in the intake air flow direction. Specifically, each of the first gap G1 and the second gap G2 has a gap width equal to or smaller than 3 mm (0<gap width≦3 mm), more preferably equal to or smaller than 2 mm (0<gap width≦2 mm). Here, the sub-partition 72 is also formed to have substantially the same thickness as the main partition 62. That is, in this embodiment, each of the first gap G1 and the second gap G2 has a gap width equal to or smaller than the thickness of the sub-partition 72. The first gap G1 has a maximum width in FIG. 1 and FIG. 3, and the gap width is preferably smaller toward the left and right (in the direction perpendicular to the paper surface in FIG. 1 and FIG. 3). Similarly, the second gap G2 has the maximum width in Figures 1 and 3, and the gap width should be smaller toward the left and right. These gaps G1 and G2 are designed to realize the flow of intake air (see, for example, the arrow in Figure 10) described later. Here, in Figures 1 and 3, the gaps G1 and G2 have a gap width of about 2 mm, but are not limited to this.

[0062] Before describing the effects of providing the gaps G1 and G2, a related phenomenon will be described below with reference to Figures 8 and 9. Note that a description similar to the following description based on Figures 8 and 9 is described in detail in JP 2019-23459 A.

[0063] Fig. 8 is a diagram showing the intake air flow when a partition 106 is provided in the intake passage 100 to separate the tumble passage 102 and the main passage 104, and a butterfly valve 108 is provided upstream of the partition 106. Fig. 9 is a diagram showing mainly the pressure downstream of the butterfly valve 108 shown in Fig. 8 when the butterfly valve 108 is gradually opened.

[0064] The butterfly valve 108 is capable of rotating in the counterclockwise direction R in Figure 8 in the valve opening direction, and is biased clockwise in the valve closing direction by a return spring (not shown) so that the rotating one end half 108b of the valve body 108a abuts against the inner wall surface 110 that defines the intake passage 100, and the rotating other end half 108c abuts against the same inner wall surface 110 in a fully closed position.

[0065] In the fully closed state, one end half 108b of the butterfly valve 108 forms an obtuse contact angle with the inner wall surface 110 of the intake passage 100 on the downstream side of the intake flow direction F, and the other end half 108c forms an acute contact angle with the inner wall surface 110 of the intake passage 100 on the downstream side of the intake flow direction F. In other words, the butterfly valve 108 is inclined, with one end half 108b located downstream of the intake passage 100 about the valve shaft 108d, and the other end half 108c of the butterfly valve 108 located upstream of the intake passage 100. When the butterfly valve 108 moves from the fully closed position in such a state to the gradually opened position as shown in Fig. 8, the intake air flows from the upstream side of the intake passage 100 to the downstream side through a gap (hereinafter, obtuse angle side gap) 110a formed between the one end half 108b and the inner wall surface 110 that defines the intake passage 100, and a gap (hereinafter, acute angle side gap) 110b formed between the other end half 108c and the inner wall surface 110. At this time, as shown in Figs. 8 and 9, the angle α1 between the one end half 108b of the butterfly valve 108 and the inner wall surface 110 of the intake passage 100 is an obtuse angle, and the angle β1 between the other end half 108c and the inner wall surface 110 of the intake passage 100 is an acute angle.

[0066] At this time, as shown in Figure 9, a strong negative pressure is generated in the area 112 immediately downstream of the obtuse angle side gap 110a and the acute angle side gap 110b (black area in Figure 9), and a wide negative pressure area 114 (dotted hatched area in Figure 9) is generated in the downstream range of the butterfly valve 108 including the valve stem 108d of the butterfly valve 108. That is, as shown in FIG. 9, the portion of the intake flow path 100 downstream of the butterfly valve 108 is partitioned into two flow paths 102, 104 with large and small cross-sectional areas by a partition 106 having a surface that is approximately parallel to the valve axis 108d of the butterfly valve 108 along the intake flow direction F, and the flow path 104 with the larger cross-sectional area is located downstream of the other end half 108c, and the flow path 102 with the smaller cross-sectional area is located downstream of the one end half 108b. When the butterfly valve 108 is slowly opened, the momentum of the intake air that passes through the butterfly valve 108 and flows into the flow path 104 with the larger cross-sectional area tends to weaken, and the intake air that has lost momentum and flows into the flow path 104 with the larger cross-sectional area is attracted to the negative pressure generated in the immediate downstream portions 112 (black portions in FIG. 9) of each end of the one end half 108b and the other end half 108c of the butterfly valve 108, and flows back upstream. The backflowing intake air is attracted to the negative pressure generated in the immediate downstream portion 112 of the one end half 108b on the side of the flow path 102 with the smaller cross-sectional area, and then flows into the flow path 102 with the smaller cross-sectional area together with the intake air that has passed through the butterfly valve 108, and the amount of intake air flowing through the flow path 102 increases.

[0067] Therefore, by using the flow passage 104 with the larger cross-sectional area as the main flow passage and using the flow passage 102 with the smaller cross-sectional area as the tumble flow passage, i.e., by setting the cross-sectional area of ​​the main flow passage 104 larger than the cross-sectional area of ​​the tumble flow passage 102, the intake air that once flows into the main flow passage 104 can be guided to the tumble flow passage 102. In other words, by setting the cross-sectional area of ​​the main flow passage 104 larger than the cross-sectional area of ​​the tumble flow passage 102, the intake air flowing through the tumble flow passage 102 can be strengthened.

[0068] Furthermore, in a cross-sectional view along the central axis X of the intake passage 100 at a right angle to the valve stem 108d of the butterfly valve 108, when fully closed, one end half 108b of the butterfly valve 108 contacts the inner wall surface 110 at an obtuse angle, and the other end half 108c of the butterfly valve 108 contacts the inner wall surface 110 at an acute angle, with the tumble flow passage 102 located downstream of the one end half 108b, and the main flow passage 104 located downstream of the other end half 108c. In this manner, the one end half 108b of the butterfly valve 108 when fully closed is disposed so as to contact the downstream inner wall surface 110 at an obtuse angle, so that the one end half 108b is inclined from the main flow path 104 toward the tumble flow path 102 on the downstream side of the butterfly valve 108, and when the butterfly valve 108 is gradually opened, the backflow of the main flow path 104 is easily guided to the tumble flow path 102 side, and the partition portion 106 can be brought close to the one end half 108b, so that the distance from the one end half 108b to the partition portion 106 in the intake flow direction F is shorter than the distance from the other end half 108c to the partition portion 106. Therefore, the intake air that has passed through the one end half 108b side easily flows into the tumble flow path 102, and the amount of intake air flowing into the tumble flow path 102 can be increased.

[0069] Here, we return to the description of the above embodiment of the present invention. As described above, when the tumble valve 76c is in the first position P1 shown in Fig. 3, it is inclined, and the one end half 76f located below the valve body 76d of the tumble valve 76c is located downstream in the intake flow direction F with the valve shaft 76b as the center and forms an obtuse angle α with the corresponding sub-partition portion 72 on the downstream side, and the other end half 76g located above the valve body 76d of the tumble valve 76c is located upstream and forms an acute angle β with the corresponding wall portion 76e of the recess 77 on the downstream side. The cross-sectional area of ​​the main flow path 66 is larger than the cross-sectional area of ​​the second tumble flow path 70, and the second tumble flow path 70 is arranged downstream of the one end half 76f of the valve body 76d of the tumble valve 76c, and the main flow path 66 is arranged downstream of the other end half 76g of the valve body 76d. 8 can be made to correspond to the tumble valve 76c, the second tumble passage 70, and the main passage 66 in this embodiment. Therefore, by designing the tumble valve 76c to form the first gap G1 and the second gap G2 as described above, the intake structure S for an internal combustion engine of this embodiment can realize the flow of intake air described with reference to FIG.

[0070] As shown in Fig. 10, according to the intake structure S of the internal combustion engine 10 of Fig. 1, when the tumble valve 76c is in the first position P1, the first gap G1 and the second gap G2 are formed as described above. The flow of the intake air at this time is shown by arrows in Fig. 10. The intake air that has passed through the second gap G2 may flow once to the main flow passage 66 side, but a part of it, preferably the entirety of it, returns to the second tumble flow passage 70 side and flows through the second tumble flow passage 70 together with the intake air that has passed through the first gap G1. In this way, the intake air that has flowed downstream of the tumble valve 76c in the first position P1 enters the second tumble flow passage 70 and eventually flows into the tumble flow passage 64.

[0071] In the intake structure S of the internal combustion engine 10 described above, when the tumble valve 76c is positioned at the first position P1, a first gap G1 is formed between the sub-partition portion 72 and the valve body 76d of the tumble valve 76c, and a second gap G2 is formed between the wall surface 77a that defines the upper intake passage of the tumble valve 76c and the valve body 76d. As a result, as described above, when the tumble valve 76c is controlled to the first position P1, the flow of intake air is promoted to the second tumble passage 70 in addition to the first tumble passage 68 that is mainly opened, and thus the flow of intake air is promoted to the tumble passage 64 including them, so that the formation of the tumble flow in the intake air through the first tumble passage 68 is not inhibited, but the tumble flow can be suitably strengthened. Therefore, the tumble performance can be suitably secured.

[0072] In this way, the tumble valve 76c is not designed to increase the degree of blocking, but is designed to form the first and second gaps G1 and G2. Since the first and second gaps G1 and G2 can have a certain width as described above, designing the tumble valve 76c to form the gaps G1 and G2 in this way is easier than increasing the degree of blocking of the tumble valve 76c when closed. This makes it possible to ease the clearance management of the tumble valve 76c.

[0073] Therefore, according to the intake structure S of the internal combustion engine 10, it is possible to ease the clearance management of the tumble valve 76c and ensure the tumble performance.

[0074] When the tumble valve 76c is controlled to the first position in this manner, the intake air flowing into the second tumble passage 70 merges with the intake air in the first tumble passage 68, whose main purpose at that time is to carry the intake air, at the junction 86, and is drawn into the combustion chamber 20. Therefore, at this time, it is possible to impart strong directionality to the intake air from the tumble passage 64, including the intake air flowing through the second tumble passage 70, and it is possible to suitably strengthen the tumble flow in the combustion chamber 20, and it is possible to further ensure tumble performance.

[0075] When the tumble valve 76c is in the second position P2, the tumble valve 76c is inclined in the same manner as when it is in the first position P1, and a gap is formed between the main partition portion 62 and the valve body 76d, and a gap is also formed between the wall surface that defines the intake passage 76a extending above the tumble valve 76c and the valve body 76d of the tumble valve 76c. At this time, the intake air that has passed through the tumble valve 76c can flow into the main passage 66, but at this time, the aforementioned junction portion 86 can provide strong directionality to the intake air that has passed through the first tumble passage 68 and the second tumble passage 70 of the tumble passage 64, so that sufficient tumble performance can be obtained overall.

[0076] The intake structure S of the internal combustion engine 10 is provided with a main partition 62 that separates the tumble passage 64 from the main passage 66, and a sub-partition 72 that separates the tumble passage 64 into first and second tumble passages 68, 70. This intake structure S is provided with the main passage 66 and the tumble passage 64, and can divide the tumble passage 64 into the first tumble passage 68 and the second tumble passage 70. Thus, by using any or all of them depending on the operating state of the internal combustion engine, it is possible to ensure an intake air amount according to the operating state.

[0077] The number of sub-partitions is not limited to one, and may be multiple. By providing multiple sub-partitions in the tumble passage 64, it is possible to divide the tumble passage 64 into three or more intake passages, i.e., intake passage portions, including a third intake passage corresponding to the first tumble passage 68 and a fourth intake passage corresponding to the second tumble passage 70. The divided multiple intake passage portions may be connected to the main passage 66 via a junction 86, similar to the above-mentioned first and second tumble passages 68 and 70, and then to the combustion chamber 20. In this case, the multiple sub-partitions may be provided in the tumble passage 64 at intervals in the vertical direction. In this case, a tumble valve may be provided to actively utilize the backflow phenomenon of intake air into the tumble passage described based on Figures 8 to 10.

[0078] In addition, various members that define the intake passage of the internal combustion engine 10, particularly the intake passage downstream of the throttle valve 40c, may be mainly manufactured by casting. This makes it possible to realize various shapes, such as a tumble passage 64 that is convex downward and a main passage 66 that is convex upward. Note that this disclosure does not exclude the manufacturing of members that define the intake passage by methods other than casting.

[0079] Although the embodiment and its modified examples 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.

[0080] In the intake structure for an internal combustion engine according to the above embodiment, the second tumble passage is formed above the first tumble passage, and the main passage is provided above the tumble passages including these. However, the second tumble passage may be formed below the first tumble passage, and the main passage may be provided below the tumble passages including these. In this case, however, it is preferable that the tumble valve 76c is turned upside down and directed in the opposite direction in the drawing corresponding to FIG. 1. [Explanation of symbols]

[0081] 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 (main partition portion), 64: Tumble flow passage (first intake passage) 66... ​​main passage (second intake passage), 68... first tumble passage (third intake passage) 70... second tumble passage (fourth intake passage), 72... partition portion (sub-partition portion) 76... tumble valve body, 76c... tumble valve (intake control valve), 86... junction, S... intake structure G1: First gap, G2: Second gap

Claims

1. a main partition portion (62) that partitions an intake passage (38) communicating with a combustion chamber (20) of an internal combustion engine (10) into a first intake passage (64) that serves as a tumble flow path for generating a tumble flow in the combustion chamber (20) and a second intake passage (66); a sub-partition (72) provided in the first intake passage (64) to define a third intake passage (68) and a fourth intake passage (70), the fourth intake passage (70) being located between the third intake passage (68) and the second intake passage (66) and formed to have a smaller cross-sectional area than the second intake passage; an intake control valve (76c) provided upstream of the main partition portion (62); a junction (86) where the third intake passage (68) and the fourth intake passage (70) join, and the first intake passage (64) joins the second intake passage (66) through the junction (86); and Equipped with the intake control valve (76c) is configured to be able to open and close the second intake passage (66) and the fourth intake passage (70), and has a first position (P1) that closes the second intake passage (66) and the fourth intake passage (70), a second position (P2) that closes the second intake passage (66) and opens the fourth intake passage (70), and a fully open position (PA); When the intake control valve (76c) is in a state in which it closes the second intake passage (66) and the fourth intake passage (70), a first gap (G1) is formed between the sub-partition (72) and a valve body (76d) of the intake control valve (76c), and a second gap (G2) is formed between the valve body (76d) and an intake passage wall surface (77a) of the intake control valve (76c) on a side opposite to the sub-partition (72), In the intake air flow direction (F), the first gap (G1) is located downstream of the second gap (G2), The intake control valve (76c) is a butterfly type valve having a single valve member (76d) that rotates integrally with a valve shaft (76b), A recess (77) that allows the movement of the valve member (76d) is provided in a wall that defines the intake passage (38), The intake passage wall surface (77a) of the recess (77) is concavely curved, The junction (86) is partitioned so that the area of ​​a cross section perpendicular to the flow direction downstream of an upstream end (86u) of the junction (86) is smaller than the sum of the cross-sectional areas (S1, S2) of the third intake passage (68) and the fourth intake passage (70). An intake structure (S) for an internal combustion engine (10).

2. a main partition portion (62) that partitions an intake passage (38) communicating with a combustion chamber (20) of an internal combustion engine (10) into a first intake passage (64) that serves as a tumble flow path for generating a tumble flow in the combustion chamber (20) and a second intake passage (66); a sub-partition (72) provided in the first intake passage (64) to define a third intake passage (68) and a fourth intake passage (70), the fourth intake passage (70) being located between the third intake passage (68) and the second intake passage (66) and formed to have a smaller cross-sectional area than the second intake passage; an intake control valve (76c) provided upstream of the main partition portion (62); Equipped with the intake control valve (76c) is configured to be able to open and close the second intake passage (66) and the fourth intake passage (70), and has a first position (P1) that closes the second intake passage (66) and the fourth intake passage (70), a second position (P2) that closes the second intake passage (66) and opens the fourth intake passage (70), and a fully open position (PA); When the intake control valve (76c) is in a state in which it closes the second intake passage (66) and the fourth intake passage (70), a first gap (G1) is formed between the sub-partition (72) and a valve body (76d) of the intake control valve (76c), and a second gap (G2) is formed between the valve body (76d) and an intake passage wall surface (77a) of the intake control valve (76c) on a side opposite to the sub-partition (72), In the intake air flow direction (F), the first gap (G1) is located downstream of the second gap (G2), The intake control valve (76c) is a butterfly type valve having a single valve member (76d) that rotates integrally with a valve shaft (76b), A recess (77) that allows the movement of the valve member (76d) is provided in a wall that defines the intake passage (38), The intake passage wall surface (77a) of the recess (77) is concavely curved, When the intake control valve (76c) is in a state in which it closes the second intake passage (66) and the fourth intake passage (70), in the intake flow direction (F) around the valve shaft (76b), one end half (76f) of the valve member (76d) of the intake control valve (76c) is located on the downstream side and forms an obtuse angle (α) with the sub-partition portion (72) on the downstream side of the one end half (76f), and the other end half (76g) of the valve member (76d) is located on the upstream side and forms an acute angle (β) with the wall portion (76e) of the recess (77) on the downstream side of the other end half (76g). An intake structure (S) for an internal combustion engine (10).

3. 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, the main partition portion (62) divides the intake passage (38) into the first intake passage (64) and a second intake passage (66) on the first direction side of the first intake passage (64), The sub-partition portion (72) is provided in the first intake passage (64) so ​​as to define the third intake passage (68) and the fourth intake passage (70) on the first direction side of the third intake passage (68).

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

4. Each of the first gap (G1) and the second gap (G2) has a gap width equal to or smaller than the thickness of the main partition portion (62).

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

5. a junction (86) where the third intake passage (68) and the fourth intake passage (70) join, and the first intake passage (64) joins the second intake passage (66) through the junction (86); Further comprising An intake structure (S) for an internal combustion engine (10) according to claim 2.

6. The junction (86) is partitioned so that the area of ​​a cross section perpendicular to the flow direction downstream of an upstream end (86u) of the junction (86) is smaller than the sum of the cross-sectional areas (S1, S2) of the third intake passage (68) and the fourth intake passage (70). An intake structure (S) for an internal combustion engine (10) according to claim 5.

7. The confluence portion (86) is formed so that the intake air from the first intake passage (64) through the confluence portion (86) flows into the combustion chamber (20) at a smaller approach angle than the intake air from the second intake passage (66). An intake structure (S) for an internal combustion engine (10) according to any one of claims 1, 5 and 6.

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