Intake structure for 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 for 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 technology]

[0002] Efforts aimed at mitigating or reducing the impact of climate change have been ongoing for some time, and research and development into reducing carbon dioxide emissions has been carried out to achieve this. Incidentally, in the technology for reducing carbon dioxide emissions, it is an issue to generate a stronger tumble flow in order to improve the combustion efficiency of an internal combustion engine. BACKGROUND ART Various intake structures for internal combustion engines have been proposed that generate a tumble flow in the combustion chamber in order to improve combustion efficiency by increasing the efficiency of flame propagation after ignition (see, for example, Patent Document 1).

[0003] For example, in the intake structure of an internal combustion engine disclosed in Patent Document 1, a partition plate portion serving as a partition portion is provided in the intake passage downstream of the throttle valve, continuing from the inlet pipe to the intake port, and this partition plate portion divides the intake passage into an upper and lower lower auxiliary passage and an upper main passage, with the lower auxiliary passage serving as a tumble flow path.

[0004] The intake structure of the internal combustion engine disclosed in the above patent document does not have a tumble valve, but when the throttle valve is gradually opened, i.e., in the low opening range, the intake air flowing from the opening of the throttle valve generates negative pressure downstream of the valve body, causing the intake air on the main flow path to flow into the tumble flow path and merge with the intake air on the tumble flow path, generating a tumble flow. However, it is desirable to further strengthen the flow of the tumble flow to improve combustion efficiency. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-23459 Summary of the Invention [Problem to be solved by 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 flow path and a tumble flow path, which enables the generation of a stronger tumble flow, further increases the efficiency of flame propagation in the combustion chamber, improves combustion efficiency, and enables a reduction in carbon dioxide emissions. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides an intake air flow path through which intake air flows into a combustion chamber, a throttle valve that controls the flow rate of intake air in the intake passage; a partition portion disposed downstream of the throttle valve and dividing the intake passage into intake air flow directions; a main flow path in which the intake flow path is divided by the partition portion; a tumble flow path in which the intake flow path is divided by the partition portion, The throttle valve has a valve stem rotatably supported by a throttle body, and a valve element rotated integrally with the valve stem, the valve body is divided into two parts with the valve stem in between, and comprises a half body on one end side of the tumble flow path and a half body on the other end side of the main flow path, The intake structure for an internal combustion engine is characterized in that, when the throttle valve is at a low opening, the first opening on the one end half opens 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 larger than the second opening on the other end half, so that the amount of intake air flowing toward the tumble flow passage increases, the flow velocity within the tumble flow passage increases, a stronger tumble flow is generated, the efficiency of flame propagation in the combustion chamber increases, combustion efficiency improves, and carbon dioxide emissions can be reduced.

[0009] In the above configuration, the valve body has a valve body main body portion offset downstream with respect to the axial center of the valve stem, and a margin portion that provides a thickness to the valve body main body portion, When the throttle valve starts to open, the one end half of the valve body may be rotated so as to approach the tumble flow passage side.

[0010] According to the above configuration, the valve body has a valve body main body portion that is offset downstream from the axial center of the valve stem, and a margin portion that adds thickness to the valve body main body portion, and when the throttle valve begins to open, one end half of the valve body is rotated so that it approaches the tumble flow path side, so that the first opening on the tumble flow path side opens larger than the second opening on the main flow path side, increasing the amount of intake air heading toward the tumble flow path, increasing the flow velocity within the tumble flow path, 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 main body in the intake air flow direction.

[0012] According to the above configuration, the margin portion is provided upstream of the valve body main body in the intake flow direction, so that when the throttle valve is fully open, the projected area of ​​the valve body is small when viewed in the intake flow direction, which makes it possible to reduce the obstruction of the intake flow by the valve body in the intake passage and improve intake efficiency.

[0013] In the above configuration, the margin portion may be provided downstream of the valve body main body in the intake air flow direction.

[0014] According to the above configuration, when the throttle valve begins to open, the valve body rotates to approach the tumble flow path, and since the margin portion is located downstream of the valve body main body in the intake flow direction, the end of the margin portion can be moved closer to the tumble flow path, ensuring that intake air is sent to the tumble flow path 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, the chamfered portion on the margin of one end half, i.e., the chamfered margin on the tumble flow path side, increases the flow velocity in the tumble flow path when the throttle valve is at a low opening, thereby generating a stronger tumble flow.

[0017] In the above-described configuration, the margin portion of the other end half may have a relief portion for preventing interference with the throttle body when the throttle valve is opened or closed.

[0018] According to the above configuration, a relief portion is provided on the main flow path side, far from the tumble flow path, to prevent interference with the throttle body when the throttle valve is opened and closed. Therefore, when the throttle valve is at a small opening, it is possible to reduce the opening on the main flow path side of the throttle valve, allowing the intake air to flow through the opening on the tumble flow path side, and generating a stronger tumble flow.

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

[0020] According to this configuration, when the throttle valve is in a low opening range, the flow of intake air is changed by the chamfered portion, so that the flow velocity on the tumble flow passage side increases, and a stronger tumble flow is generated.

[0021] In the above configuration, the valve body may have a chamfered portion extending from the upstream side to the downstream side so that, when the throttle valve is closed, the upstream edge of the other end half abuts against the inner wall surface of the throttle body and closes, and the downstream edge of the other end half is separated from the inner wall surface of the throttle body.

[0022] According to this configuration, when the throttle valve is at a small opening, the intake air flowing from the opening in the other half of the throttle valve is guided along the chamfered portion toward the tumble flow passage, generating an even stronger tumble flow.

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

[0024] According to the above configuration, when the throttle valve is at a low opening, the opening on the main flow path side is blocked by the other end half that is farther from the tumble flow path, and the flow velocity is increased by the throttling effect on the tumble flow path side of the one end half that is closer to the tumble flow path, and 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 may be formed as an integral member.

[0026] According to the above-described configuration, the margin portion and the main body portion are integrally molded, which reduces the number of processing steps and allows for inexpensive manufacturing.

[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-described configuration, the margin portion can be made of a lighter metal or resin, which reduces the weight of the valve body and improves the responsiveness when the throttle valve is opened and closed. [Effects 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, the first opening on one end half opens larger than the second opening on the other end half, thereby increasing the amount of intake air flowing toward the tumble flow passage, increasing the flow velocity within the tumble flow passage, generating a stronger tumble flow, increasing the efficiency of flame propagation in the combustion chamber, improving combustion efficiency, and enabling a reduction in carbon dioxide emissions. [Brief explanation of the drawings]

[0030] [Figure 1] 1 is a right side view of a motorcycle equipped with a power unit having an intake structure for an internal combustion engine according to the present invention. [Figure 2] This is a rear right side view of the motorcycle in Figure 1 with the body cover removed. [Figure 3] 3 is a side cross-sectional view of a power unit provided with an intake structure for an internal combustion engine according to the first embodiment, with the power unit removed from FIG. 2 and shown in substantially the same orientation as that shown in FIG. 2. FIG. [Figure 4] FIG. 4 is an enlarged view of a main part of FIG. 3. [Figure 5] FIG. 5 is an enlarged view of a main part of FIG. 4, showing a state in which the throttle valve is at a low opening. [Figure 6] 1 is a view of the opening of the throttle valve in a small opening state as viewed from the upstream side of the intake air flow. [Figure 7] FIG. 2 is a view of the throttle valve in a small opening state as viewed from the downstream side of the intake air flow. [Figure 8] FIG. 2 is a view of the throttle valve in a medium opening state as viewed from the downstream side of the intake air flow. [Figure 9] FIG. 2 is a view of the throttle valve in a small opening state as viewed from the upstream side of the intake air flow. [Figure 10] FIG. 2 is a perspective view of a main part of the throttle valve as viewed from the downstream side of the intake air flow. [Figure 11] FIG. 2 is a perspective view of a main part of the throttle valve as viewed from the upstream side of the intake air flow. [Figure 12] FIG. 4 is a diagram showing a closed state of the throttle valve. [Figure 13] FIG. 4 is a cross-sectional view showing a first modified example of the first embodiment. [Figure 14] FIG. 10 is a cross-sectional view showing a second modified example of the first embodiment. [Figure 15] FIG. 10 is a perspective view of a main part of a throttle valve according to a second modified example of the first embodiment, as viewed from the downstream side of the intake air flow. [Figure 16] FIG. 10 is a perspective view of a main part of a throttle valve according to a second modified example of the first embodiment, as viewed from the upstream side of the intake air flow. [Figure 17]FIG. 6 is a cross-sectional view showing a throttle valve of a second embodiment. [Figure 18] FIG. 10 is a cross-sectional view showing a throttle valve according to a modified example of the second embodiment. [Figure 19] FIG. 10 is a cross-sectional view showing a throttle valve of a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0031] An intake structure for an internal combustion engine according to a first embodiment of the present invention will be described with reference to FIGS. In the description of this specification and the claims, the directions of front, rear, left, right, up, down, etc. are determined to correspond to the directions of the vehicle when the power unit equipped with the intake structure for an 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 regard to the intake passage 70 and the intake flow path 80 of the throttle body 7, the upper side and the lower side of the partition 81 that divides them along the intake air flow direction will be referred to as the "upper" side and the "lower" side, respectively (see Figures 3 and 4). In addition, in the figure, the arrow FR indicates 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 above also applies to the second and third embodiments.

[0032] Fig. 1 shows a 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 a first embodiment of the present invention. Fig. 2 shows a rear right side view of the motorcycle 1 of Fig. 1 with a body cover 10 removed.

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

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

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

[0036] The power unit 3 has a power unit case 50 that forms a crankcase section 50a, and the cylinder block 31, cylinder head 32, and cylinder head cover 33 that form the internal combustion engine 30 are fastened to the front of the power unit case 50 so that they are stacked one on top of the other, with the cylinder block 31, cylinder head 32, and cylinder head cover 33 being tilted forward substantially horizontally and fastened to the front of the power unit case 50a. In addition, a power transmission case section 55 that is equipped with a belt-type continuously variable transmission and the like extends integrally from the crankcase section 50a to the rear left side, and a rear axle 56 that is the output shaft of the power unit 3 is provided at the rear of the power unit 3, and the rear wheel 17 is attached to it. That is, the power unit 3 is a so-called swing unit, and a rear cushion (not shown) is interposed between the power transmission case portion 55 at the rear of the power unit 3 and the rear portion of the main pipe 22.

[0037] As shown in FIG. 2, at the top of the power unit 3, an inlet pipe 6 extends from the top of the cylinder head 32 of the internal combustion engine 30, which is tilted significantly forward, and curves rearward. 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 disposed above the power transmission case portion 55. On the other hand, an exhaust pipe 38 extending downward from the lower part of the cylinder head 32 bends rearward, leans to the right, extends rearward, and is connected to a muffler 39 on the right side of the rear wheel 17 .

[0038] 3 is a side cross-sectional view of the power unit 3 of FIG. 2, taken out and shown in substantially the same orientation as that shown in FIG. The internal combustion engine 30 in the power unit 3 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 mating surface 50b with the right case half (not shown) toward the front of the illustration.

[0039] The power unit case 50 is formed by combining a left case half 50L that is split into left and right halves and a right case half (not shown). 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 and extends rearward to form a power transmission case section 55 that houses a transmission device including 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 open surface 55R at the rear of the power transmission case 55, and is covered by a reducer case (not shown). The output shaft of the reduction gear mechanism 57 is the rear axle 56 of the rear wheel 17. Thus, the rotational power of the crankshaft 51 of the crankcase 50 a of the internal combustion engine 30 is transmitted to the rear wheel 17 via the belt-type continuously variable transmission and reduction gear mechanism 57 in the power transmission case 55 .

[0040] A piston 34 reciprocates within a cylinder bore 31a of the cylinder block 31 and is connected by a connecting rod 35 to a crank pin 51a of a crankshaft 51 in the crankcase portion 50a. A combustion chamber 36 is defined between a top surface 34a of a piston 34 slidably fitted in a cylinder bore 31a of the cylinder block 31 and a combustion chamber ceiling surface 32a of the cylinder head 32 that faces the top surface 34a.

[0041] In the first embodiment, the internal combustion engine 30 employs an SOHC two-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 to cover the valve train 9. The internal combustion engine 30 of this embodiment is an SOHC internal combustion engine, but may be a DOHC internal combustion engine. Furthermore, the internal combustion engine 30 of this embodiment employs a two-valve internal combustion engine that has one intake valve 46 and one exhaust valve 47, but may have a plurality of intake valves 46 and exhaust valves 47. 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 a cam chain chamber (not shown) provided on one side of the crankcase portion 50a, the cylinder block 31, and the cylinder head 32 in the direction of the crankshaft 51, and the camshaft 91 rotates in synchronization with the crankshaft 51 at half the rotational speed. In the cylinder head 32, an ignition plug 49 serving as ignition means is inserted toward the inside of the combustion chamber .

[0042] As shown in Figure 3 and Figure 4, which is an enlarged view of a main portion of Figure 3, in a cylinder head 32 in which the cylinder axis L is tilted forward significantly to be nearly horizontal, an intake valve port 40 and an exhaust valve port 41 that open to the combustion chamber ceiling surface 32a are formed such that they extend, curving upward and downward, from each other.

[0043] The upstream end of the intake port 42 opens upward in the cylinder head 32 and connects to the inlet pipe 6 to form a continuous intake flow path 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 downward from the cylinder head 32 and is connected to the exhaust pipe 38 (see FIG. 2), and an exhaust flow path 60 extends from the downstream of the exhaust valve port 41.

[0044] A cylindrical intake valve guide 44 is fitted integrally to the curved outer wall portion 42a of the intake port 42 in the cylinder head 32, and an intake valve 46 slidably supported by the intake valve guide 44 opens and closes the intake valve opening 40 of the intake port 42 facing the combustion chamber 36. An exhaust valve 47 is slidably supported by an exhaust valve guide 45 that is integrally fitted to the curved outer wall portion 43a of the exhaust port 43 in the cylinder head 32, and 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 the exhaust valve 47 have their head portions 46a and 47a biased upward by a valve spring 48 so as to close the intake valve port 40 and the exhaust valve port 41 facing the combustion chamber 36. As shown in FIG. 3, the stem ends 46b and 47b of the intake valve 46 and the exhaust valve 47 are pushed down by an intake rocker arm 94 and an exhaust rocker arm 95 which swing against an intake cam 92 and an exhaust cam 93 of a camshaft 91, respectively, opening the intake valve 46 and the exhaust valve 47 at the predetermined timing, connecting the intake port 42 and the combustion chamber 36, and connecting the exhaust port 43 and the combustion chamber 36, allowing intake and exhaust to occur at the predetermined timing.

[0046] In the internal combustion engine 30 as described above, an intake structure is configured to impart a tumble vortex T, i.e., vertical rotation, to the fuel-air mixture in the combustion chamber 36 in order to obtain more favorable combustion in the combustion chamber 36. That is, 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 flow path 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 an intake flow path 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 FIGS. 4 to 12, the throttle body 7 is provided with a throttle valve 72 that is rotatably supported within the throttle body 7 by a valve shaft 73 that is oriented substantially horizontally and perpendicular to the intake air flow direction F of the intake passage 70, i.e., perpendicular to the central axis X of the intake passage 70, and that variably controls the flow area of ​​the intake passage 70 to open and close the intake passage 70.

[0048] 10 and 11, the throttle valve 72 is of a butterfly type. The throttle valve 72 has a valve stem 73 and a disk-shaped valve element 74 that is fixed to the valve stem 73 with a screw 96 and rotates integrally with the valve stem 73. The valve element 74 is divided into two halves across the valve stem 73, consisting of a semi-disk-shaped one-end half 74A on one side and a semi-disk-shaped other-end half 74B on the other side.

[0049] The throttle valve 72 can be rotated counterclockwise in the valve opening direction as shown in Fig. 5 by operation by the driver, and a return spring 97 shown in Fig. 10 and Fig. 11 biases the valve element 74 counterclockwise in the valve closing direction so that, as shown in Fig. 12, 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. In some cases, the other half 74B is set to be kept slightly open to maintain idling speed. The intake passage 70 of the throttle body 7 is oriented substantially 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 extending from the inlet pipe 6 to the intake port 42, and is divided into a tumble passage 80A configured so that the intake air passing through it generates a tumble vortex T in the combustion chamber 36, and a main passage 80B excluding the tumble passage 80A. In the first embodiment, the "tumble flow passage" refers to a flow passage for intake air that generates a tumble vortex 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 at a low load. Furthermore, although the internal combustion engine 30 in the first embodiment is not provided with a tumble control valve that controls the flow of the tumble flow, the internal combustion engine may be provided with a tumble control valve.

[0051] In the first embodiment, the lower portion of the intake air flow path 80 separated by the partition portion 81 is the tumble flow path 80A, and the upper portion is the main flow path 80B, but the present invention is not limited to this upper-lower arrangement. Furthermore, in this specification, the terms "upper" and "lower" used with respect to the intake flow path 80, the intake passage 70, and the throttle valve 72 refer to the direction of the cylinder axis L toward the cylinder head 32 or the cylinder head cover 33 as "upper," and the direction of the crankshaft 51 as "lower," and do not refer to absolute "upper" and "lower" in space.

[0052] The partition section 81 is configured by an inlet pipe side partition section 81A, an insulator side partition section 81B, and an intake port side partition section 81C, which are positioned consecutively from the upstream side to the downstream side of the intake air flow. The main flow path 80B on the upper side in the figure and the tumble flow path 80A on the lower side in the figure are separated by a vertical partition 81 from the inlet pipe 6 to the intake port 42, dividing the intake flow path 80 downstream of the throttle valve 72 into upper and lower parts in the figure. The surface of the partition 81 in the width direction of the intake passage 80 and the valve shaft 73 are parallel to each other.

[0053] Therefore, the inlet opening 80Aa of the tumble flow passage 80A of the intake flow 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 flow passage 80B is located downstream of the other end 71B of the throttle valve 72. The inlet pipe 6 is fitted with a fuel injection valve 87 which penetrates the main flow passage 80B from the upper outside and is arranged to inject and supply fuel towards the intake valve port 40. In this embodiment, the fuel injection valve 87 is disposed in the inlet pipe 6, but the fuel injection valve 87 may be disposed in the cylinder head 32 or the cylinder block 31, and a direct injection structure in which fuel is injected into the combustion chamber 36 may be used.

[0054] As shown in FIG. 4, the downstream end 81b of the partition 81, i.e., the downstream end 81b located within the intake port 42 of the cylinder head 32, is bent toward the cylinder block 31 in the cylinder head 32 and formed integrally therewith, and the terminal end 80Ab of the tumble flow passage 80A is formed so as to face the combustion chamber ceiling surface 32a of the cylinder head 32. 4, the intake air flowing through the tumble flow passage 80A passes above the umbrella portion 46a of the intake valve 46 and then flows into the cylinder bore 31a, which makes it easier for a tumble vortex T to be generated in the combustion chamber 36. In this way, the tumble flow passage 80A is configured so that the intake air that passes through it generates a tumble vortex T.

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

[0056] 5 and 12, the valve element 74 has a substantially disk-shaped valve element main body 75 that is fixed to the valve stem 73 with screws 96, and a margin portion 76 that gives the valve element main body 75 a predetermined thickness t. The valve element main body 75 is disposed so as to be offset downstream from the axial center C of the valve stem 73. The margin portion 76 is formed with a predetermined width t on the surface of the valve element main body 75 facing the valve stem 73; that is, the margin portion 76 is formed on the upstream side in the intake air flow direction. The entire valve element 74, which is the combination of the valve element main body 75 and the margin portion 76, is disposed so as to be offset downstream from the axial center C of the valve stem 73.

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

[0058] 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, 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, i.e., one end half 74A of the valve body 74 begins to rotate toward the tumble flow path 80A, and the other end half 74B begins to rotate away from the main flow path 80B.

[0060] As shown in Figure 12, the valve body 72 is positioned offset downstream from the axial center C of the valve shaft 73, and when the valve is closed, the other end half 74B on the main flow path 80B side is located upstream of the one end half 74A on the tumble flow path 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 when viewed in the valve axis direction.

[0061] Fig. 7 is a view of the throttle valve 72 seen from the downstream side immediately after the throttle valve 72 opens, and Fig. 8 is a view of the throttle valve 72 seen from the downstream side when the throttle valve 72 has further opened. Fig. 9 is a view of the throttle valve 72 in the state shown in Fig. 7 seen from the upstream side. As shown in FIG. 6, the opening area A1 of the first opening 79A on one end side of the throttle valve 72 is larger than the opening area A2 of the second opening 79B on the other end side of the throttle valve 72.

[0062] The intake structure for the internal combustion engine of the first embodiment is configured as described above, and therefore provides the following effects.

[0063] The intake structure of the internal combustion engine of the first embodiment comprises 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 section 81 arranged downstream of the throttle valve 72 and dividing the intake passage 80 in the intake flow direction, a main passage 80B into which the intake passage 80 is divided by the partition section 81, and a tumble passage 80A into which the intake passage 80 is divided by the partition section 81, and the throttle valve 72 has a valve stem 73 rotatably supported by the throttle body 7, and a valve element 74 that rotates integrally with the valve stem 73. The valve body 74 is divided into two halves by the valve stem 73: one end half 74A on the tumble flow passage 80A side, and the other end half 74B on the main flow passage 80B side. 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 in the other end half 74B of the throttle valve 72. This increases the amount of intake air flowing toward the tumble flow passage 80A, increases the flow velocity within the tumble flow passage 80A, and generates a stronger tumble flow. This improves the efficiency of flame propagation in the combustion chamber 36, improves combustion efficiency, and enables carbon dioxide emissions to be reduced.

[0064] In addition, the valve body 74 has a valve body main body 75 that is offset downstream from the axial center C of the valve shaft 73, and a margin portion 76 that adds thickness to the valve body main body 75.When the throttle valve 72 begins to open, the valve body 74 rotates to approach the tumble flow path 80A side, so that the opening area A1 of the first opening 79A on the tumble flow path 80A side of the throttle valve 72 becomes larger than the opening area A2 of the second opening 79B on the main flow path 80B side of the throttle valve 72.As a result, the amount of intake air heading toward the tumble flow path 80A increases, the flow velocity in the tumble flow path 80A increases, and a stronger tumble flow can be generated.

[0065] Furthermore, since the margin portion 76 is provided upstream of the valve body main body 75 in the intake flow direction, the projected area of ​​the throttle valve 72 is small when viewed in the intake flow direction when the throttle valve 72 is fully open, so the intake flow is not obstructed and intake efficiency can be improved.

[0066] Next, a first modified example of the first embodiment is shown in Figure 13. In throttle valve 72 of the first modified example, a chamfered portion 77A is formed to remove the corner on the upstream side of margin portion 76 in one end half 74A. Similarly, a chamfered portion 77B is formed to remove the corner on the upstream side of margin portion 76 in the other end half 74B. Chamfered portion 77A in one end half 74A increases the flow velocity in tumble flow passage 80A when throttle valve 72 is at a low opening, making it possible to generate a stronger tumble flow.

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

[0068] That is, when the throttle valve 72 is closed, the margin portion 76 of the other end half 74B abuts against the inner wall surface 70a, but the chamfered portion 77B is formed so that the valve body main body 75 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 toward the tumble flow path 80A, generating a stronger tumble flow.

[0069] In the first embodiment, the margin portion 76 of the valve body 72 is provided on each of the one end half 74A and the other end half 74B, but the margin portion 76 may be omitted from the one end half 74A and provided only on the other end half 74B. Even if the margin portion 76 is omitted only from the other end half 74B, the second opening 79B can be made smaller in size than the first opening 79A, so that the tumble flow can be strengthened and the weight of the valve body 74 can be reduced, improving the responsiveness of the throttle valve 72.

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

[0071] Since the margin portion 176 is provided on the downstream side of the valve body main body 175 in the intake flow direction, when the throttle valve 172 begins to open, the valve body 174 rotates to approach the tumble flow path 80A side, and since the margin portion 176 is provided on the downstream side of the valve body main body 175 in the intake flow direction, the end of the margin portion 176 can be moved closer to the tumble flow path 80A side, and the intake air is reliably sent to the tumble flow path 80A, making it possible to generate a stronger tumble flow.

[0072] Furthermore, a relief portion 178 is provided in the other end half 174B on the main flow path 80B side, which is farther from the tumble flow path 80A, to prevent interference with the throttle body 7 when the throttle valve 172 is opened or closed. This makes it possible to reduce the opening of the throttle valve 172 on the main flow path 80B side when the throttle valve 172 is at a low opening, allowing intake air to flow through the opening on the tumble flow path 80A side, thereby generating a stronger tumble flow.

[0073] Next, a modified example of the second embodiment will be described with reference to Fig. 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, when the throttle valve 172 is in the low opening range, the flow of intake air passing through the downstream side of the other half 174B and the diffusion of intake air passing through the chamfered portion 177B of the other end half 174B increase the flow velocity on the tumble flow path 80A side, generating a stronger tumble flow.

[0075] An intake structure for an internal combustion engine according to a third embodiment of the present invention is shown in Fig. 19. In the intake structure for an internal combustion engine according to the third embodiment, a valve element 274 has a valve element main body 275 offset upstream from the axial center C of the valve stem 73, and a margin portion 276 that provides thickness to the valve element main body 275. The margin portion 276 is provided upstream of the valve element main body 275 in the intake air flow direction, and when the throttle valve 272 begins to open, the other end half 274B of the valve element 274 rotates to approach the main flow path 80B. 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 opening on the main flow path 80B side is blocked by the other end half 274B on the side farther from the tumble flow path 80A, and the flow velocity is increased by the throttling effect on the tumble flow path side of the one end half on the side closer to the tumble flow path, and as the flow velocity in the tumble flow path increases, a stronger tumble flow is generated.

[0077] As described above, the intake structures for internal combustion engines of the first embodiment 1, second embodiment and third embodiment of the present invention are applied to an internal combustion engine 30 in which the cylinder axis L is oriented approximately horizontally, but they can also be applied to an internal combustion engine in which the cylinder axis L is oriented approximately vertically. Furthermore, the present invention is not limited to the above-described embodiments, and various design modifications are possible without departing from the spirit of the present invention. It goes without saying that the present invention includes vehicles, internal combustion engines, and the like implemented in various forms within the spirit of the present invention. For convenience of explanation, the illustrated embodiment has been described with a left-right arrangement, but other left-right arrangements are also included in the present invention as long as they fall 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...Other end half, 75...Valve body main body, 76...Margin portion, 77...Chamfered portion, 78...Relief portion, 79A...First opening, 79B...Second opening, 80...Intake flow path, 80A...Tumble flow path, 80B...Main flow path, 81...Partition portion, 172... throttle valve, 174... valve body, 174A... one end side half, 174B... other end side half, 175... valve body main body, 176... margin portion, 177... chamfered portion, 178... relief portion, 272... throttle valve, 274... valve body, 274A... one end side half, 274B... other end side half, 275... valve body main body, 276... margin portion, 277... chamfered portion, 278... relief portion.

Claims

1. an intake air flow path (80) through which intake air flows into the combustion chamber (36); a throttle valve (72, 172, 272) for controlling the flow rate of intake air in the intake passage (80); a partition (81) disposed downstream of the throttle valve (72, 172, 272) and dividing the intake passage (80) into intake air flow directions; a main flow path (80B) in which the intake flow path (80) is divided by the partition portion (81); a tumble flow path (80A) in which the intake flow path (80) is divided by the partition portion (81), The throttle valve (72, 172, 272) includes a valve stem (73) rotatably supported in a throttle body (7), and a valve element (74, 174, 274) rotated integrally with the valve stem (73), The valve body (74, 174, 274) is divided into two halves across the valve stem (73): one end half (74A, 174A, 274A) on the tumble flow path (80A) side, and the other end half (74B, 174B, 274B) on the main flow path (80B) side. an intake structure for an internal combustion engine, characterized in that, when the throttle valve (72, 172, 272) is at a low opening, a first opening (79A) on the one end half (74A, 174A, 174A) side opens larger than a second opening (79B) on the other end half (74B, 174B, 274B) side.

2. The valve body (74, 174) has a valve body main body portion (75, 175) offset downstream with respect to an axial center (C) of the valve stem (73), and a margin portion (76, 176) that provides a thickness to the valve body main body portion (75, 175), 2. The intake structure for an internal combustion engine according to claim 1, wherein, when the throttle valve (72, 172) starts to open, the one end half (74A, 174A) of the valve body (74, 174) rotates so as to approach the tumble flow path (80A).

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

4. 3. The intake structure for an internal combustion engine according to claim 2, wherein the margin portion (176) is provided downstream of the valve body main body (175) in the intake air flow direction.

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

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

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

8. 4. The intake structure for an internal combustion engine according to claim 2, wherein the valve body (74, 174) has a chamfered portion (77B, 177B) extending from the upstream side to the downstream side so that, when the throttle valve (72, 172) is closed, an upstream edge of the other-end half (74B, 174B) abuts against an inner wall surface (70a) of the throttle body (7) to close the throttle valve, and a downstream edge of the other-end half (74B, 174B) is separated from the inner wall surface (70a) of the throttle body (7).

9. The valve body (274) has a valve body main body portion (275) offset upstream with respect to an axial center (C) of the valve stem (73), and a margin portion (276) that provides a thickness to the valve body main body portion (275), the margin portion (276) is provided on the upstream side of the valve body main body (275) in the intake air flow direction, 2. The intake structure for an internal combustion engine according to claim 1, wherein, when the throttle valve starts to open, the other end half (274B) of the valve body (274) rotates so as to approach the main flow path (80B).

10. 10. The intake structure for an internal combustion engine according to claim 2, 3 or 9, wherein the margin portion (76, 176, 276) is an integral member with the valve body main body (75, 175, 275).

11. 10. The intake structure for an internal combustion engine according to claim 2, 3 or 9, wherein the margin portion (76, 176, 276) is a separate member from the valve body main body (75, 175, 275).

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