Intake structure of an internal combustion engine

Abstract

To provide an intake structure for an internal combustion engine that enables generation of a stronger tumble flow and reduction of emissions of carbon dioxide by improving combustion efficiency in the intake structure for the internal combustion engine in which an intake passage is partitioned into a main flow passage and a tumble flow passage.SOLUTION: An intake structure for an internal combustion engine includes: an intake flow passage 80; a throttle valve 72, 172, 272; a partitioning member 81 that partitions the intake flow passage 80 in an intake flowing direction; and a main flow passage 80B and a tumble flow passage 80A partitioned by the partitioning member 81. A valve element 74, 174, 274 of the throttle valve 72, 172, 272 comprises one end side half body 74A, 174A, 274A on the tumble flow passage 80A side and the other end side half body 74B, 174B, 274B on the main flow passage 80B side that are divided with a valve stem 73 sandwiched therebetween. When an opening of the throttle valve 72, 172, 272 is small, a first opening part 79A of the one end side half body 74A, 174A, 174A side is opened more largely than a second opening part 79B of the other side half body 74B, 174B, 274B side, so as to generate a stronger tumble flow.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to an intake structure of an internal combustion engine in which an intake passage of the internal combustion engine is partitioned into a main passage and a tumble passage.

Background Art

[0002] Conventionally, efforts aimed at mitigating or reducing the impact of climate change have been continued, and research and development regarding reduction of carbon dioxide emissions have been conducted toward this realization. By the way, in technologies regarding reduction of carbon dioxide emissions, in order to improve the combustion efficiency of an internal combustion engine, it is an issue to generate a stronger tumble flow. Various intake structures of internal combustion engines that generate a tumble flow in a combustion chamber in order to improve the combustion efficiency by enhancing the efficiency of flame propagation after ignition have been proposed (for example, see Patent Document 1).

[0003] For example, in the intake structure of the internal combustion engine of Patent Document 1, a partition plate portion which is a partition portion continuing from an inlet pipe to an intake port is provided on the downstream side of a throttle valve in an intake passage, and the intake passage is partitioned into a lower sub-passage and an upper main passage by this partition plate portion, and the lower sub-passage becomes a tumble passage.

[0004] In the intake structure of the internal combustion engine disclosed in the above patent document, a tumble valve is not provided, but when the throttle valve is gradually opened, that is, in a low opening degree region, due to the negative pressure generated on the downstream side of the valve body by the intake air flowing from the opening of the throttle valve, the intake air on the main passage side flows to the tumble passage side and merges with the intake air on the tumble passage side to generate a tumble flow. However, further enhancement of the tumble flow is desired for improvement of the combustion efficiency.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] In view of the above, the present invention provides an intake structure for an internal combustion engine in which the intake passage of the internal combustion engine is divided into a main passage and a tumble passage, which enables the generation of a more powerful tumble flow, further enhances the efficiency of flame propagation in the combustion chamber, improves combustion efficiency, and reduces carbon dioxide emissions. [Means for solving the problem]

[0007] To solve the above problems, the present invention provides an intake passage through which intake air flows into the combustion chamber, A throttle valve that controls the flow rate of intake air in the intake passage, A partition is provided downstream of the throttle valve, which divides the intake passage in the direction of intake airflow, The intake passage is divided into a main passage and a partitioned section, The intake passage is divided into a tumble passage and the partitioned section, The throttle valve has a valve shaft that is rotatably supported on the throttle body and a valve body that rotates integrally with the valve shaft. The valve body consists of one end half on the tumble flow path side and the other end half on the main flow path side, with the valve stem in between. This intake structure for an internal combustion engine is characterized in that, when the throttle valve is at a low opening, the first opening on one end half is larger than the second opening on the other end half.

[0008] According to the above configuration, when the throttle valve is at a low opening, the first opening on one end half opens wider than the second opening on the other end half. This increases the amount of intake air directed towards the tumble passage, increases the flow velocity within the tumble passage, generates a stronger tumble flow, improves the efficiency of flame propagation in the combustion chamber, enhances combustion efficiency, and enables a reduction in carbon dioxide emissions.

[0009] In the above configuration, the valve body has a valve body main portion offset downstream with respect to the axial center of the valve stem, and a margin portion that gives thickness to the valve body main portion. When the throttle valve begins to open, the one end half of the valve body may rotate to move closer to the tumble flow path.

[0010] According to the above configuration, the valve body has a valve body main body offset downstream with respect to the axis of the valve stem and a margin portion that is thicker than the valve body main body. When the throttle valve starts to open, one end half of the valve body is rotated to move closer to the tumble passage side. As a result, the first opening on the tumble passage side opens wider than the second opening on the main passage side, increasing the amount of intake air directed towards the tumble passage, increasing the flow velocity in the tumble passage, and generating a stronger tumble flow.

[0011] In the above configuration, the margin portion may be provided on the upstream side of the valve body in the intake airflow direction.

[0012] According to the above configuration, since the margin portion is provided on the upstream side of the valve body in the intake airflow direction, when the throttle valve is fully open, the projected area of ​​the valve body is reduced in the intake airflow direction view, which reduces obstruction of the intake airflow by the valve body in the intake passage and improves intake efficiency.

[0013] In the above configuration, the margin portion may be provided on the downstream side of the valve body in the intake airflow direction.

[0014] According to the above configuration, when the throttle valve starts to open, the valve body rotates to move closer to the tumble passage side, and the margin portion is provided on the downstream side of the valve body in the intake airflow direction. This allows the end of the margin portion to be brought closer to the tumble passage side, ensuring that intake air is reliably delivered to the tumble passage and generating a stronger tumble flow.

[0015] In the above configuration, the margin portion of the one-end half may have a chamfered portion.

[0016] According to the above configuration, by chamfering the margin portion of the one - end - side half - body, that is, chamfering the margin portion on the tumble flow path side, the flow velocity in the tumble flow path when the throttle valve is at a low opening degree is increased, and a stronger tumble flow can be generated.

[0017] In the above configuration, the margin portion of the other - end - side half - body may have a relief portion for preventing interference with the throttle body when the throttle valve opens and closes.

[0018] According to the above configuration, since a relief portion is provided on the main flow path side far from the tumble flow path so as to prevent interference with the throttle body when the throttle valve opens and closes, when the throttle valve is at a low opening degree, it is possible to reduce the opening on the main flow path side of the throttle valve, and intake air can flow through the opening on the tumble flow path side, and a stronger tumble flow can be generated.

[0019] In the above configuration, the margin portion of the other - end - side half - body may have a chamfered portion.

[0020] According to the above configuration, in the region when the throttle valve is at a low opening degree, as the intake air flow changes due to the chamfered portion, the flow velocity on the tumble flow path side is increased, and a stronger tumble flow is generated.

[0021] In the above configuration, when the throttle valve is closed, the upstream edge of the other - end - side half - body may contact and close the inner wall surface of the throttle body, and the downstream edge of the other - end - side half - body may be spaced apart from the inner wall surface of the throttle body. The valve body may be provided with a chamfered portion directed from the upstream side to the downstream side.

[0022] According to the above configuration, when the throttle valve is at a low opening degree, the intake air flowing from the opening of the other - side half - body of the throttle valve is guided along the chamfered portion to the tumble flow path side, and a stronger tumble flow is generated.

[0023] The valve body of the present invention has a valve body main body portion offset upstream with respect to the axial center of the valve shaft, and a margin portion having a thickness provided on the valve body main body portion. The margin portion is provided on the upstream side in the intake air flow direction of the valve body main body portion. An intake structure of an internal combustion engine is characterized in that when the throttle valve starts to open, the other end side half body of the valve body rotates so as to approach the main flow path side.

[0024] According to the above configuration, when the throttle valve is at a low opening degree, the opening on the main flow path side is blocked by the other end side half body far from the tumble flow path, and the flow velocity increases due to the throttling effect on the tumble flow path side by the one end side half body close to the tumble flow path. As the flow velocity in the tumble flow path increases, a stronger tumble flow is generated.

[0025] In the above configuration, the margin portion and the valve body main body portion may be an integral member.

[0026] According to the above configuration, since the margin portion and the main body portion are integrally formed, the number of processing steps is reduced, and it can be manufactured at a low cost.

[0027] In the above configuration, the margin portion may be a separate member from the valve body main body portion.

[0028] According to the above configuration, since the margin portion can be made of a lighter metal or resin, etc., the weight of the valve body can be reduced, and the responsiveness when the throttle valve opens and closes can be improved.

Effect of the Invention

[0029] According to the intake structure of the internal combustion engine of the present invention, when the throttle valve is at a low opening degree, the first opening on the one end side half body side opens larger than the second opening on the other end side half body side. Therefore, the intake air volume toward the tumble flow path increases, the flow velocity in the tumble flow path increases, a stronger tumble flow is generated, the efficiency of flame propagation in the combustion chamber is improved, the combustion efficiency is improved, and the reduction of carbon dioxide emissions can be achieved.

Brief Description of the Drawings

[0030] [Figure 1] This is the right side view of a motorcycle equipped with a power unit featuring the intake structure of the internal combustion engine of the present invention. [Figure 2] This is the rear right side of the motorcycle shown in Figure 1, with the body cover removed. [Figure 3] This is a side cross-sectional view of a power unit equipped with an intake structure for an internal combustion engine of Embodiment 1, taken out of Figure 2 and shown in substantially the same orientation as shown in Figure 2. [Figure 4] This is an enlarged view of the main part of Figure 3. [Figure 5] This is an enlarged view of the main part of Figure 4, showing the throttle valve in a low opening position. [Figure 6] This diagram shows the opening of the throttle valve in a low-opening state, viewed from the upstream side of the intake airflow. [Figure 7] This diagram shows the throttle valve in a low-opening state, viewed from the downstream side of the intake airflow. [Figure 8] This diagram shows the throttle valve in a partially open position, viewed from the downstream side of the intake airflow. [Figure 9] This diagram shows the throttle valve in a low-opening state, viewed from the upstream side of the intake airflow. [Figure 10] This is a perspective view of the main part of the throttle valve, seen from the downstream side of the intake airflow. [Figure 11] This is a perspective view of the main part of the throttle valve, seen from the upstream side of the intake airflow. [Figure 12] This diagram shows the throttle valve in a blocked state. [Figure 13] This is a cross-sectional view showing a first modified example of the first embodiment. [Figure 14] This is a cross-sectional view showing a second modified example of the first embodiment. [Figure 15] This is a perspective view of the main part of the throttle valve of the second modified example of the first embodiment, viewed from the downstream side of the intake airflow. [Figure 16] This is a perspective view of the main part of the throttle valve of the second modified example of the first embodiment, viewed from the upstream side of the intake airflow. [Figure 17]This is a cross-sectional view showing the throttle valve of the second embodiment. [Figure 18] This is a cross-sectional view showing a modified throttle valve of the second embodiment. [Figure 19] This is a cross-sectional view showing the throttle valve of the third embodiment. [Modes for carrying out the invention]

[0031] The intake structure of an internal combustion engine according to the first embodiment of the present invention will be described based on Figures 1 to 12. In this specification, the directions such as front, rear, left, right, up, and down in the description and claims refer to the orientation of the vehicle when the power unit equipped with the intake structure of the internal combustion engine according to this embodiment is mounted on the vehicle. In this embodiment, the vehicle is a small vehicle, specifically a motorcycle. However, with respect to the intake passage 70 and intake passage 80 of the throttle body 7, the upper part of the partition 81 that divides them along the intake flow direction will be described as the "upper" side, and the lower part as the "lower" side. (See Figures 3 and 4). In addition, in the diagram, arrows FR indicate the front of the vehicle, LH indicates the left side of the vehicle, RH indicates the right side of the vehicle, and UP indicates the top of the vehicle. The same applies to the second and third embodiments.

[0032] Figure 1 shows the right side view of a motorcycle 1 equipped with a power unit 3 having an intake structure for an internal combustion engine 30 according to the first embodiment of the present invention. Figure 2 shows the rear right side view of the motorcycle 1 in Figure 1 with the body cover 10 removed.

[0033] Motorcycle 1 is a so-called scooter-type motorcycle, with the front part 1A and the rear part 1B of the vehicle body connected via a low floor part 1C, and the vehicle frame 2 which forms the skeleton of the vehicle body consists of a down tube 21 and a main pipe 22 (see Figure 2). Specifically, a down tube 21 extends downward from the head pipe 20 of the front part 1A of the vehicle body, and the down tube 21 bends horizontally at its lower end and extends rearward below the floor part 1C. As shown in Figure 2, a pair of left and right main pipes 22 are connected at the rear end via a connecting frame 23 which is arranged in the width direction of the vehicle, and the main pipes 22 rise diagonally rearward from the connecting frame 23 as an inclined section 22a, and then bend to ease the inclination along the way and extend rearward.

[0034] A storage box 11 and a fuel tank 12 are supported above the inclined portion 22a of the main pipe 22. The storage box 11 and fuel tank 12 are covered by a crew seat 13 mounted above them, and the area below the crew seat 13, including the storage box 11 and fuel tank 12, is covered by a vehicle body cover 10. On the other hand, in the front part 1A of the vehicle body, a handlebar 14 is provided above, pivotally supported by the head pipe 20, and a front fork 15 extends downward, with the front wheel 16 pivotally supported at its lower end.

[0035] As shown in Figure 2, which illustrates the rear right side of the motorcycle 1 with the body cover 10 removed, a bracket 24 is provided protruding from near the lower end of the inclined portion 22a of the main pipe 22, and a power unit 3 is pivotably connected and supported to the bracket 24 via a link member 25. The power unit 3 has a single-cylinder, four-stroke, air-cooled internal combustion engine (hereinafter simply referred to as "internal combustion engine") 30 at its front. The crankshaft 51 is rotatably supported at the front of the power unit case 50 which constitutes the crankcase section 50a, with the cylinder axis L tilted forward to a nearly horizontal position. The end of a hanger arm 52, which protrudes forward from the lower end of the power unit case 50, is connected to a link member 25 attached to a bracket 24 of the main pipe 22 so as to be able to swing up and down. The internal combustion engine 30 in this embodiment is an air-cooled internal combustion engine, but it may also be a water-cooled internal combustion engine.

[0036] In the power unit 3, the cylinder block 31, cylinder head 32, and cylinder head cover 33, which constitute the internal combustion engine 30, are fastened to the front of the power unit case 50 that constitutes the crankcase section 50a, tilting significantly forward and almost horizontally. In addition, a power transmission case section 55 equipped with a belt-type continuously variable transmission, etc., extends integrally from the crankcase section 50a to the left rear, and the rear axle 56, which is the output shaft of the power unit 3, is provided at the rear, to which the rear wheel 17 is attached. In other words, the power unit 3 is a so-called swing unit, and a rear cushion (not shown) is interposed between the power transmission case section 55 at the rear of the power unit 3 and the rear of the main pipe 22.

[0037] As shown in Figure 2, at the top of the power unit 3, an inlet pipe 6 extends from the top of the significantly forward-tilted cylinder head 32 of the internal combustion engine 30 and curves backward. A throttle body 7 connected to the inlet pipe 6 is located above the cylinder block 31, and an air cleaner device 86 connected to the throttle body 7 via a connecting tube 85 is positioned above the power transmission case 55. Meanwhile, the exhaust pipe 38, which extends downward from the lower part of the cylinder head 32, bends backward, is biased to the right, and extends backward to connect to the muffler 39 on the right side of the rear wheel 17.

[0038] Figure 3 is a side cross-sectional view of the power unit 3, taken out of Figure 2 and shown in approximately the same orientation as in Figure 2. In the power unit 3, the internal combustion engine 30 is shown with a cross-section of the left half of the cylinder block 31, cylinder head 32, and cylinder head cover 33, and the power unit case 50 is shown with the left case half 50L facing the front of the illustration with the mating surface 50b with the right case half (not shown).

[0039] The power unit case 50 is composed of a left case half 50L and a right case half (not shown) which are split into left and right halves. The right case half forms the right half of the crankcase section 50a, and the front part of the left case half 50L forms the left half of the crankcase section 50a, while the rear part extends to form a power transmission case section 55 which houses a long belt-type continuously variable transmission (not shown) and a reduction gear mechanism 57, etc., between the crankshaft 51 and the rear axle 56 of the rear wheel 17. The reduction gear mechanism 57 is housed inside the right-side open surface 55R at the rear of the power transmission case 55 and is covered by a reduction gear case (not shown). The output shaft of the reduction gear mechanism 57 is the rear axle 56 of the rear wheel 17. The rotational power of the crankshaft 51 of the crankcase section 50a of the internal combustion engine 30 is transmitted to the rear wheel 17 via a belt-type continuously variable transmission and a reduction gear mechanism 57 in the power transmission case section 55.

[0040] The piston 34, which reciprocates within the cylinder bore 31a of the cylinder block 31, is connected to the crankpin 51a of the crankshaft 51 in the crankcase section 50a by a connecting rod 35. A combustion chamber 36 is formed between the top surface 34a of the piston 34, which is slidably fitted into the cylinder bore 31a of the cylinder block 31, and the combustion chamber ceiling surface 32a of the cylinder head 32, which faces the top surface 34a.

[0041] In the first embodiment, the internal combustion engine 30 employs a SOHC type 2-valve system, and a valve train 9 is provided in the cylinder head 32. A cylinder head cover 33 is placed over the cylinder head 32 so as to cover the valve train 9. In this embodiment, the internal combustion engine 30 is an SOHC type, but it may also be a DOHC type. In addition, in this embodiment, the internal combustion engine 30 employs a 2-valve type internal combustion engine with one intake valve 46 and one exhaust valve 47, but there may be multiple intake valves 46 and exhaust valves 47. In order to transmit power to the valve train 9 inside the cylinder head cover 33, an endless cam chain (not shown) is installed between the camshaft 91 and the crankshaft 51, passing through the crankcase portion 50a, the cylinder block 31, and a cam chain chamber (not shown) provided on one side of the cylinder head 32 with respect to the crankshaft 51 direction. The camshaft 91 rotates at half the rotational speed in synchronization with the crankshaft 51. In the cylinder head 32, a spark plug 49 is fitted into the combustion chamber 36 as an ignition means.

[0042] As shown in Figure 3 and Figure 4, which is an enlarged view of the main part of Figure 3, in a cylinder head 32 in which the cylinder axis L is tilted forward to be nearly horizontal, an intake port 42 and an exhaust port 43 are formed extending from the intake valve port 40 and exhaust valve port 41 that open to the combustion chamber ceiling surface 32a, respectively, curving in a direction that separates them vertically from each other.

[0043] The upstream end of the intake port 42 opens upward toward the cylinder head 32 and connects to the inlet pipe 6 to form a continuous intake passage 80, and the throttle body 7 is connected to the upstream side of the inlet pipe 6. The downstream end of the exhaust port 43 opens downwards toward the cylinder head 32 and is connected to the exhaust pipe 38 (see Figure 2), forming the exhaust passage 60 downstream of the exhaust valve port 41.

[0044] A cylindrical intake valve guide 44 is integrally fitted to the curved outer wall portion 42a of the intake port 42 in the cylinder head 32, and an intake valve 46, which is slidably supported by the intake valve guide 44, opens and closes the intake valve opening 40 of the intake port 42 that faces the combustion chamber 36. Furthermore, an exhaust valve 47, which is slidably supported by an exhaust valve guide 45 integrally fitted to the curved outer wall portion 43a of the exhaust port 43 in the cylinder head 32, opens and closes the exhaust valve opening 41 of the exhaust port 43 that faces the combustion chamber 36.

[0045] The intake valve 46 and exhaust valve 47 have their umbrella portions 46a and 47a biased upward by valve springs 48 so as to close the intake valve port 40 and exhaust valve port 41 facing the combustion chamber 36. However, as shown in Figure 3, the intake rocker arms 94 and exhaust rocker arms 95, which contact and oscillate with the intake cam 92 and exhaust cam 93 of the camshaft 91, push down the stem ends 46b and 47b of the intake valve 46 and exhaust valve 47, causing the intake valve 46 and exhaust valve 47 to open at a predetermined timing, connecting the intake port 42 with the combustion chamber 36 and the exhaust port 43 with the combustion chamber 36, and enabling intake and exhaust at the predetermined timing.

[0046] In the internal combustion engine 30 described above, an intake structure is configured to provide a tumble vortex flow T, i.e., vertical rotation, of the fuel-air mixture in the combustion chamber 36 in order to obtain more favorable combustion in the combustion chamber 36. In other words, an inlet pipe 6 is connected to the upstream end of the intake port 42 of the internal combustion engine 30 via an insulator 61, forming a continuous intake passage 80 with a substantially circular cross-section, and a throttle body 7 is connected to the upstream side of the inlet pipe 6. The throttle body 7 has an intake passage 70 with a substantially circular cross-section that forms part of the intake passage 80 connected to the combustion chamber 36 of the internal combustion engine 30, and its upstream side is connected to an air cleaner device 86 (see Figure 2) via a connecting tube 85.

[0047] As shown in Figures 4 to 12, the throttle body 7 is rotatably supported within the throttle body 7 by a valve shaft 73 that is perpendicular to the intake airflow direction F of the intake passage 70, i.e., perpendicular to the central axis X of the intake passage 70 and oriented substantially horizontally, and is equipped with a throttle valve 72 that can variably control the flow area of ​​the intake passage 70 and open and close the intake passage 70.

[0048] As shown in Figures 10 and 11, the throttle valve 72 is of the butterfly type. The throttle valve 72 has a valve stem 73 and a disc-shaped valve body 74 that is fixed to the valve stem 73 by a screw 96 and rotates integrally with it. The valve body 74 is divided in two on either side of the valve stem 73, and consists of a semi-disc-shaped one-end half 74A and a semi-disc-shaped other-end half 74B.

[0049] The throttle valve 72 can be rotated counterclockwise in the opening direction as shown in Figure 5 by the driver's operation, and the return spring 97 shown in Figures 10 and 11 biases the valve body 74 counterclockwise in the closing direction, as shown in Figure 12, so that one rotating end half 74A abuts against the inner surface of the intake passage 70, i.e., the inner wall surface 70a of the throttle body 7, and the other rotating end half 74B abuts against the inner wall surface 70a, so that it is in a fully closed position. The other half 74B may also be set to be kept in a slightly open state in order to maintain the idling speed. The intake passage 70 of the throttle body 7 is oriented approximately horizontally, with the lower end valve body being one end half 74A and the upper end valve body being the other end half 74B.

[0050] In the first embodiment, the intake passage 80 is divided along the intake flow direction by a partition 81 that continues from the inlet pipe 6 to the intake port 42, and is divided into a tumble passage 80A configured to generate a tumble vortex flow T in the combustion chamber 36 as the intake air passes through, and a main passage 80B excluding the tumble passage 80A. In the first embodiment, the "tumble passage" is an intake air passage for generating a tumble vortex flow T in the combustion chamber 36 when the throttle valve 72 is at a low opening, that is, when the internal combustion engine 30 is under low load. In addition, the internal combustion engine 30 in the first embodiment does not have a tumble control valve to control the flow of the tumble flow, but it may be an internal combustion engine equipped with a tumble control valve.

[0051] In the first embodiment, the lower portion of the intake passage 80 partitioned by the partition portion 81 becomes the tumble passage 80A, and the upper portion becomes the main passage 80B. However, the present invention is not limited to this vertical arrangement. Furthermore, in this specification, "up" and "down" with respect to the intake passage 80, intake passage 70, and throttle valve 72 refer to the direction of the cylinder head 32 or cylinder head cover 33 as "up" and the direction of the crankshaft 51 as "down" in the direction of the cylinder axis L, and do not refer to absolute "up" and "down" in space.

[0052] The partition section 81 is configured such that the inlet pipe side partition section 81A, the insulator side partition section 81B, and the intake port side partition section 81C are continuously positioned from the upstream side to the downstream side of the intake airflow. The main passage 80B on the upper side and the tumble passage 80A on the lower side are separated by a partition 81 that runs vertically from the inlet pipe 6 to the intake port 42, thereby dividing the intake passage 80 downstream of the throttle valve 72 into upper and lower sections as shown in the figure. Furthermore, the surface of the partition portion 81 in the width direction of the intake passage 80 and the valve stem 73 are parallel.

[0053] Therefore, the inlet opening 80Aa of the tumble passage 80A of the intake passage 80 of the inlet pipe 6 connected to the downstream side of the intake passage 70 of the throttle body 7 is located downstream of one end half 74A of the throttle valve 72, and the inlet opening 80Ba of the main passage 80B is located downstream of the other end 71B of the throttle valve 72. Furthermore, a fuel injector 87 is attached to the inlet pipe 6, which penetrates the main passage 80B from above and is positioned to inject fuel toward the intake valve port 40. In this embodiment, the fuel injector 87 is located in the inlet pipe 6, but a direct injection structure may also be used, in which the fuel injector 87 is located in the cylinder head 32 or the cylinder block 31 and fuel is injected into the combustion chamber 36.

[0054] Furthermore, as shown in Figure 4, the downstream end 81b of the partition 81, that is, the downstream end 81b located within the intake port 42 of the cylinder head 32, is bent toward the cylinder block 31 and integrally formed in the cylinder head 32, and the end 80Ab of the tumble passage 80A is formed to face the combustion chamber ceiling surface 32a of the cylinder head 32. Therefore, as shown by the small arrow in Figure 4, the intake air flowing through the tumble passage 80A can pass over the umbrella portion 46a of the intake valve 46 before flowing into the cylinder bore 31a, making it easier for tumble vortex T to be generated in the combustion chamber 36. In this way, the tumble passage 80A is configured so that the intake air that passes through it generates tumble vortex T.

[0055] As shown in Figures 10 and 11, the valve body 74 of the throttle valve 72 in the first embodiment is divided into two halves, one end 74A on the tumble passage 80A side and the other end 74B on the main passage 80B side, with the valve stem 73 in between.

[0056] Referring also to Figures 5 and 12, the valve body 74 has a substantially disc-shaped valve body portion 75 fixed to the valve stem 73 by a screw 96, and a margin portion 76 that gives the valve body portion 75 a predetermined thickness t. The valve body portion 75 is positioned offset downstream with respect to the axial center C of the valve stem 73. The margin portion 76 is formed to a predetermined width t on the surface of the valve body portion 75 on the valve stem 73 side, that is, the margin portion 76 is formed on the upstream side with respect to the intake air flow direction. The entire valve body 74, including the valve body portion 75 and the margin portion 76, is positioned offset downstream with respect to the axial center C of the valve stem 73.

[0057] In this embodiment, the valve body portion 75 and the margin portion 76 are formed integrally, but the valve body portion 75 and the margin portion 76 may be made of separate components. If the margin portion 76 is made of a separate component from the valve body portion 75, and the margin portion 76 is made of a lightweight material such as lightweight metal or resin, the overall weight of the valve body 74 can be reduced, thereby improving the responsiveness of the opening and closing of the throttle valve 72.

[0058] As shown in Figure 12, when the throttle valve 72 is closed, the peripheral end of the valve body 74 abuts against the inner wall surface 70a of the throttle body 7, thereby closing the intake passage 70. One end half 74A of the valve body 74 is located downstream of the other end half 74B.

[0059] As shown in Figure 5, when the throttle valve 72 begins to open, the valve body 74 rotates counterclockwise, meaning that one end half 74A of the valve body 74 begins to rotate toward the tumble passage 80A, while the other end half 74B begins to rotate toward the main passage 80B.

[0060] As shown in Figure 12, the valve body 72 is positioned offset downstream with respect to the axial center C of the valve stem 73, and when the valve is closed, the other end half 74B on the main passage 80B side is located upstream of the one end half 74A on the tumble passage 80A side. Therefore, when the throttle valve 72 is at a low opening, as shown in Figure 5, the distance d2 between the other end half 74B of the valve body 74 and the inner wall surface 70a of the throttle body 7 is smaller than the distance d1 between the one end half 74A of the valve body 74 and the inner wall surface 70a of the throttle body 7 in a view along the valve axis.

[0061] Figure 7 shows the throttle valve 72 immediately after it opens, viewed from the downstream side. Figure 8 shows the throttle valve 72 further opened, viewed from the downstream side. Figure 9 shows the throttle valve 72 in the state shown in Figure 7, viewed from the upstream side. As shown in Figure 6, the opening area A1 of the first opening 79A on one end of the throttle valve 72 is larger than the opening area A2 of the second opening 79B on the other end of the throttle valve 72.

[0062] Since the intake structure of the internal combustion engine in the first embodiment is configured as described above, it produces the following effects.

[0063] The intake structure of the internal combustion engine of the first embodiment includes an intake passage 80 through which intake air flows into the combustion chamber 36, a throttle valve 72 that controls the flow rate of intake air in the intake passage 80, a partition 81 disposed downstream of the throttle valve 72 that divides the intake passage 80 in the direction of intake air flow, a main passage 80B through which the intake passage 80 is divided by the partition 81, and a tumble passage 80A through which the intake passage 80 is divided by the partition 81. The throttle valve 72 has a valve shaft 73 that is rotatably supported on the throttle body 7, and a valve body 74 that rotates integrally with the valve shaft 73. The valve body 74 consists of one end half 74A on the tumble passage 80A side and the other end half 74B on the main passage 80B side, with the valve stem 73 in between. When the throttle valve 72 is at a low opening, the opening area A1 of the first opening 79A on the one end half 74A side of the throttle valve 72 is larger than the opening area A2 of the second opening 79B on the other end half 74B side of the throttle valve 72. As a result, the amount of intake air directed towards the tumble passage 80A increases, the flow velocity in the tumble passage 80A increases, a stronger tumble flow is generated, the efficiency of flame propagation in the combustion chamber 36 is improved, combustion efficiency is enhanced, and carbon dioxide emissions can be reduced.

[0064] Furthermore, the valve body 74 has a valve body main portion 75 offset downstream with respect to the axial center C of the valve stem 73, and a margin portion 76 which is thicker than the valve body main portion 75. When the throttle valve 72 starts to open, the valve body 74 rotates to move closer to the tumble passage 80A side. As a result, the opening area A1 of the first opening 79A on the tumble passage 80A side of the throttle valve 72 becomes larger than the opening area A2 of the second opening 79B on the main passage 80B side of the throttle valve 72. This increases the amount of intake air directed towards the tumble passage 80A, increases the flow velocity in the tumble passage 80A, and generates a stronger tumble flow.

[0065] Furthermore, since the margin portion 76 is provided on the upstream side of the valve body portion 75 in the intake airflow direction, the projected area of ​​the throttle valve 72 becomes smaller when the throttle valve 72 is fully open and viewed in the intake airflow direction. This prevents obstruction of the intake airflow and improves intake efficiency.

[0066] Next, Figure 13 shows a first modified example of the first embodiment. In the throttle valve 72 of the first modified example, a chamfered portion 77A is formed on one end half 74A to round off the upstream corner of the margin portion 76. Similarly, a chamfered portion 77B is formed on the other end half 74B to round off the upstream corner of the margin portion 76. The chamfered portion 77A on one end half 74A increases the flow velocity in the tumble passage 80A when the throttle valve 72 is at a low opening, thereby generating a stronger tumble flow.

[0067] Next, a second modified example of the first embodiment is shown in Figures 14 to 16. In the throttle valve 72 of the second modified example, as shown in Figure 14, when the throttle valve 72 is closed, the upstream edge of the other end half 74B abuts against the inner wall surface 70a of the throttle body 7 and closes, and the downstream edge of the other end half 74B is spaced apart from the inner wall surface 70a of the throttle body 7, so that a chamfered portion 77B is formed on the valve body, extending from the upstream side to the downstream side. Also, as shown in Figure 16, the upstream margin portion 76 of one end half 74A of the valve body 74 is provided with a chamfered portion 77A that rounds off the corner of the lower part of the valve body, extending from the upstream side to the downstream side.

[0068] In other words, when the throttle valve 72 is closed, the margin portion 76 of the other end half 74B is in contact with the inner wall surface 70a, but the valve body portion 75 has a chamfered portion 77B formed so that it is away from the inner wall surface 70a. Therefore, when the throttle valve 72 is at a low opening, the intake air flowing from the second opening 79B of the other end half 74B of the throttle valve 72 is guided along the chamfered portion 77B towards the tumble flow path 80A, which can generate a stronger tumble flow.

[0069] In the first embodiment, the margin portion 76 of the valve body 72 is provided on both the one-end half 74A and the other-end half 74B. However, the margin portion 76 on the one-end half 74A may be omitted, and the margin portion 76 may be provided only on the other-end half 74B. Even if the margin portion 76 is omitted only on the other-end half 74B, the second opening 79B can be made smaller than the first opening 79A, thereby strengthening the tumble flow and reducing the weight of the valve body 74, thereby improving the responsiveness of the throttle valve 72.

[0070] Next, the second embodiment will be described with reference to Figure 17. In the first embodiment, the valve body 74 of the throttle valve 72 has a margin portion 76 formed on the upstream side of the valve body main portion 75, but in the second embodiment, the throttle valve 172 has a margin portion 176 provided on the downstream side of the valve body main portion 175. In addition, a relief portion 178 is formed in the margin portion 176 of the other end half 174B of the valve body 174 to prevent interference with the throttle body 7 when the throttle valve 172 is opened and closed.

[0071] Since the margin portion 176 is provided on the downstream side of the valve body portion 175 in the intake airflow direction, when the throttle valve 172 starts to open, the valve body 174 rotates to approach the tumble passage 80A side, and because the margin portion 176 is provided on the downstream side of the valve body portion 175 in the intake airflow direction, the end of the margin portion 176 can be brought towards the tumble passage 80A side, ensuring that intake air is reliably delivered to the tumble passage 80A, thereby enabling the generation of a stronger tumble flow.

[0072] Furthermore, a relief portion 178 is provided on the other end half 174B on the main passage 80B side, which is farther from the tumble passage 80A, to prevent interference with the throttle body 7 when the throttle valve 172 is opened and closed. As a result, when the throttle valve 172 is at a low opening, the opening of the throttle valve 172 on the main passage 80B side can be reduced, allowing intake air to flow through the opening on the tumble passage 80A side, thereby generating a stronger tumble flow.

[0073] Next, a modified example of the second embodiment will be described with reference to Figure 18. In the second embodiment, the downstream side of one end half 174A of the valve body 174 is formed in a shape that follows the inner wall surface 70a, and the downstream side of the other end half 174B is provided with a chamfered portion 177B.

[0074] According to the above configuration, in the low-opening region of the throttle valve 172, the intake air flow passing downstream of the other half 174B and the diffusion of the intake air passing through the chamfered portion 177B of the other end half 174B increase the flow velocity on the tumble passage 80A side, generating a stronger tumble flow.

[0075] Figure 19 shows the intake structure of an internal combustion engine according to a third embodiment of the present invention. In the intake structure of the internal combustion engine according to the third embodiment, the valve body 274 has a valve body main portion 275 offset upstream with respect to the axis center C of the valve stem 73, and a margin portion 276 which is thickened on the valve body main portion 275. The margin portion 276 is provided on the upstream side of the valve body main portion 275 in the intake flow direction, and when the throttle valve 272 starts to open, the other end half 274B of the valve body 274 rotates to approach the main passage 80B side. A relief portion 278 is formed in the margin portion 276 of the other end half 274B, and a chamfered portion 277 is formed in the margin portion 276 of the one end half 274A.

[0076] With this configuration, when the throttle valve 272 is at a low opening, the other end half 274B on the side farther from the tumble passage 80A closes the opening on the main passage 80B side, and the throttling effect on the tumble passage side by the one end half on the side closer to the tumble passage increases the flow velocity. As a result, a stronger tumble flow is generated due to the increased flow velocity in the tumble passage.

[0077] As described above, the intake structures for internal combustion engines of the first embodiment 1, the second embodiment, and the third embodiment of the present invention are applied to an internal combustion engine 30 in which the cylinder axis L is oriented substantially horizontally, but they can also be applied to an internal combustion engine in which the cylinder axis L is oriented substantially vertically. Furthermore, the present invention is not limited to the embodiments described above, and various design modifications are possible without departing from its spirit. Naturally, the scope of the present invention includes vehicles, internal combustion engines, etc., that can be implemented in a variety of ways. For the sake of explanation, the left-right arrangement of the illustrated embodiment has been described, but even if the left-right arrangement is different, it is still included in the present invention as long as it falls within the scope of the gist of the invention. [Explanation of Symbols]

[0078] 7...Throttle body, 30...Internal combustion engine, 72...Throttle valve, 73...Valve stem, 74...Valve body, 74A...One end half, 74B...The other end half, 75...Valve body main body, 76...Margin part, 77...Chamfered part, 78...Relief part, 79A...First opening, 79B...Second opening, 80...Intake passage, 80A...Tumble passage, 80B...Main passage, 81...Partition part 172...Throttle valve, 174...Valve body, 174A...One end half, 174B...The other end half, 175...Valve body main body, 176...Margin part, 177...Chamfered part, 178...Relief part, 272...Throttle valve, 274...Valve body, 274A...One end half, 274B...The other end half, 275...Main body portion of the valve body, 276...Margin portion, 277...Chamfered portion, 278...Relief portion.

Claims

1. An intake passage (80) through which intake air flows into the combustion chamber (36), A throttle valve (72, 172) controls the flow rate of intake air in the intake passage (80), A partition (81) is provided downstream of the throttle valve (72, 172) and divides the intake passage (80) in the direction of intake flow, The intake passage (80) is divided into a main passage (80B) and a partition (81), The intake passage (80) is divided into a tumble passage (80A) which is divided into a partition (81), The throttle valve (72, 172) has a valve shaft (73) that is rotatably supported on the throttle body (7), and a valve body (74, 174) that is offset downstream of the axial center (C) of the valve shaft (73) and rotates integrally with the valve shaft (73). It does not have a tumble valve for opening and closing the main flow path (80B), The valve body (74, 174) consists of one end half (74A, 174A) on the tumble passage (80A) side, which is divided in two by the valve stem (73), and the other end half (74B, 174B) on the main passage (80B) side. The aforementioned one-end half (74A, 174A) abuts against the inner circumferential surface (70a) of the intake passage (80), and has a chamfered portion (77A) formed on its upstream edge, and rotates to move closer to the tumble passage (80A) when the throttle valve (72, 172) opens. An intake structure for an internal combustion engine, characterized in that, when the throttle valves (72, 172) are at a low opening, the first opening (79A) on the one-end half (74A, 174A) side opens wider than the second opening (79B) on the other-end half (74B, 174B) side.

2. The valve body (74,174) has a valve body main portion (75,175) that is offset downstream with respect to the axial center (C) of the valve stem (73), and a margin portion (76,176) that is thicker than the valve body main portion (75,175). The intake structure for an internal combustion engine according to claim 1, characterized in that when the throttle valve (72, 172) begins to open, the one-end half (74A, 174A) of the valve body (74, 174) rotates to move closer to the tumble passage (80A) side.

3. The intake structure for an internal combustion engine according to claim 2, characterized in that the margin portion (76) is provided on the upstream side of the valve body portion (75) in the intake air flow direction.

4. The intake structure for an internal combustion engine according to claim 2, characterized in that the margin portion (176) is provided on the downstream side of the valve body portion (175) in the intake airflow direction.

5. The intake structure for an internal combustion engine according to claim 3 or 4, characterized in that the margin portion (76, 176) of the one-end half (74A, 174A) has a chamfered portion (77, 177).

6. The intake structure for an internal combustion engine according to claim 4, characterized in that the margin portion (176) of the other end half (174B) has a relief portion (178) to prevent interference with the throttle body (7) when the throttle valve (172) is opened or closed.

7. The intake structure for an internal combustion engine according to claim 3 or 4, characterized in that the margin portion (76, 176) of the other end half (74B, 174B) has a chamfered portion (77, 177).

8. The intake structure for an internal combustion engine according to claim 2 or 3, characterized in that when the throttle valve (72, 172) is closed, the upstream edge of the other end half (74B, 174B) abuts against the inner wall surface (7a) of the throttle body (7) and closes, and the downstream edge of the other end half (74B, 174B) is spaced apart from the inner wall surface (70a) of the throttle body (7), the valve body (74, 174) has chamfered portions (77B, 177B) oriented from the upstream side to the downstream side.

9. The intake structure for an internal combustion engine according to claim 2 or 3, characterized in that the margin portion (76, 176) is an integral member with the valve body portion (75, 175).

10. The intake structure for an internal combustion engine according to claim 2 or 3, characterized in that the margin portion (76, 176) is a separate component from the valve body portion (75, 175).

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