Internal combustion engine

Abstract

To provide an internal combustion engine that enables generation of a strong tumble flow, improvement of combustion efficiency by further enhancing efficiency of flame propagation in a combustion chamber and reduction of emissions of carbon dioxide in the internal combustion engine having a plurality of intake valves.SOLUTION: An internal combustion engine includes: a plurality of intake valve ports 40 each opened / closed by an intake valve 46; and a plurality of intake flow passages 80 coupled to the plurality of intake valve ports 40, respectively. One of the intake flow passages 80 has a partitioning part 81 that partitions the intake flow passage 80 in an intake flowing direction. The partitioning part 81 partitions the intake flow passage 80 into a main flow passage 80B and a tumble flow passage 80A. A downstream side end of the tumble flow passage 80A is directed to the intake valve port 40 located downstream of the intake flow passage 80, so as to enable generation of a stronger tumble flow.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to an intake structure for an internal combustion engine having a plurality of intake valves and an intake passage 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. Various structures have been proposed for generating a tumble flow in a 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, the intake structure of an internal combustion engine disclosed in Patent Document 1 is an internal combustion engine having one intake valve and one exhaust valve, and 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 upper and lower lower auxiliary passages and an upper main passage, with the lower auxiliary passage serving as a tumble flow path. Note that although the internal combustion engine disclosed in the above Patent Document is not provided with a tumble valve, there is a case where a tumble valve that essentially opens and closes the upper main passage is provided.

[0004] The internal combustion engine of Patent Document 1 employs a so-called two-valve system with one intake valve and one exhaust valve, and the tumble flow entering the combustion chamber is concentrated at one intake valve port, which tends to generate a strong tumble flow. However, in internal combustion engines equipped with multiple intake valves, such as four-valve or five-valve engines, multiple intake valves are opened when generating tumble flow, which reduces the flow velocity in each tumble flow path and makes it difficult to generate a strong tumble flow. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] WO2022 / 210121A1 publication Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above, the present invention provides an internal combustion engine equipped with multiple intake valves that enables the generation of a strong 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: a plurality of intake valve ports that are opened and closed by intake valves; a plurality of intake flow paths respectively connected to the plurality of intake valve ports; one of the intake air passages includes a partition portion that divides the intake air passage in the intake air flow direction; The partition divides the intake passage into a main passage and a tumble passage, An internal combustion engine, characterized in that the downstream side of the tumble flow passage is directed toward an intake valve port located downstream of the intake flow passage.

[0008] According to the above configuration, even in an internal combustion engine having multiple exhaust valve ports, one of the intake passages is equipped with a partition that divides the intake passage in the intake flow direction, and the partition 81 divides the intake passage into a main passage and a tumble passage, and the downstream side of the tumble passage is directed toward the intake valve port located downstream of the intake passage.This makes it possible to concentrate the intake air flowing through the tumble passage and generate a stronger tumble flow, which increases the efficiency of flame propagation in the combustion chamber, improves combustion efficiency, and enables reduction of carbon dioxide emissions.

[0009] In the above configuration, the internal combustion engine includes an ignition means in the combustion chamber, The tumble passage may be directed towards the ignition means projecting into the combustion chamber.

[0010] According to the above configuration, the tumble flow passage is provided so as to be directed toward the ignition means. When the intake flow that passes through the tumble flow passage comes into contact with the ignition means that protrudes into the combustion chamber, the flow direction of the tumble flow is changed toward the cylinder axis, and a stronger tumble flow is generated in the combustion chamber.

[0011] In the above configuration, the ignition means may be oriented toward the cylinder axis of the combustion chamber and disposed at an angle with respect to the cylinder axis.

[0012] According to the above configuration, the ignition means is arranged in the combustion chamber at an angle toward the cylinder axis with respect to the cylinder axis, so that the tumble flow flowing in the combustion chamber is more likely to come into contact with the ignition means, making it possible to generate a more powerful tumble flow.

[0013] In the above configuration, the ignition means is inserted into the combustion chamber from the opposite side to the cam chain chamber with respect to an imaginary plane that passes through the cylinder axis of the combustion chamber and is perpendicular to the crank axis, The tumble flow passage may be connected to one of the plurality of intake valve ports that is located on the opposite side of the imaginary plane from the cam chain chamber.

[0014] According to the above configuration, the ignition means is inserted into the combustion chamber from the opposite side to the cam chain chamber with respect to an imaginary plane that passes through the cylinder axis of the combustion chamber and is perpendicular to the crank axis, so that the ignition means can be easily removed. Furthermore, by arranging the tumble flow passage on the same side as the ignition means, the tumble flow can be redirected downward by the ignition means, thereby promoting the generation of a stronger tumble flow.

[0015] In the above configuration, the intake flow path includes an inlet pipe and an intake port connected to the inlet pipe, a downstream side of the tumble flow passage of the inlet pipe is opened to one side, which is the ignition means side, with respect to an imaginary plane that passes through the cylinder axis of the combustion chamber and is perpendicular to the crank axis, The downstream side of the tumble flow passage of the intake port may be in communication with an intake valve port disposed on the one side.

[0016] According to the above configuration, the downstream side of the tumble flow passage of the inlet pipe opens to one side opposite the ignition means with respect to an imaginary plane that passes through the cylinder axis of the combustion chamber and is perpendicular to the crank axis, and the downstream side of the tumble flow passage of the intake port is connected to the intake valve port located on the above-mentioned one side.As a result, the tumble flow passage in the intake port is arranged in a straight line, and a stronger tumble flow is generated.

[0017] In the above configuration, the intake flow path includes an inlet pipe and an intake port connected to the inlet pipe, a downstream side of the tumble flow passage in the inlet pipe opens to one side opposite to the ignition means side with respect to an imaginary plane that passes through a cylinder axis of the combustion chamber and is perpendicular to a crank axis, The downstream side of the tumble flow passage of the intake port may be connected to an intake valve port disposed on the other side of the imaginary plane.

[0018] According to the above configuration, the downstream side of the tumble flow passage in the inlet pipe opens to the side opposite the ignition means with respect to an imaginary plane that passes through the cylinder axis of the combustion chamber and is perpendicular to the crank axis, and the downstream side of the tumble flow passage in the intake port is connected to the intake valve port that is arranged on the other side of the imaginary plane. Therefore, the tumble flow passage is arranged at an angle to the imaginary plane, and the tumble flow passage in the intake port can be set long, making it possible for the tumble flow to hit the cylinder wall surface of the combustion chamber directly and reducing attenuation of the tumble flow.

[0019] In the above configuration, the tumble flow passage may have a cross-sectional area that gradually decreases from upstream to downstream.

[0020] According to the above configuration, the cross-sectional area of ​​the tumble flow passage is narrowed to increase the flow velocity, thereby efficiently generating a stronger tumble flow. [Effects of the Invention]

[0021] According to the intake structure for an internal combustion engine of the present invention, even in an internal combustion engine having multiple exhaust valve ports, the tumble flow passage is closed for at least one intake valve port and open for the other intake valve ports, so that the intake air flowing through the tumble flow passage can be concentrated to generate a stronger tumble flow, which increases the efficiency of flame propagation in the combustion chamber, improves combustion efficiency, and enables a reduction in carbon dioxide emissions. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a right side view of a motorcycle equipped with a power unit equipped with an intake structure for an internal combustion engine according to the first or second embodiment of 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 of Example 1A equipped with an intake structure for an internal combustion engine according to Embodiment 1, with the power unit in FIG. 2 removed 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. 2 is a view of the inlet pipe as seen from the side where it is attached to the cylinder head. [Figure 6] FIG. 5 is an enlarged view of the vicinity of the combustion chamber of the cylinder head of FIG. [Figure 7] FIG. 2 is a schematic diagram of the vicinity of the combustion chamber as viewed from above in the cylinder axial direction. [Figure 8] FIG. 8 is a view taken along arrow VIII in FIG. 7. [Figure 9] 6 is a schematic diagram of the vicinity of a combustion chamber of an internal combustion engine according to a second embodiment, viewed from above in the cylinder axial direction. FIG. [Figure 10] FIG. 10 is a view taken along the arrow X in FIG. 9. [Figure 11]6 is a schematic diagram of the vicinity of a combustion chamber of an internal combustion engine according to a second embodiment, viewed from above in the cylinder axial direction. FIG. [Figure 12] FIG. 12 is a view taken along the arrow XII in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0023] An internal combustion engine 30 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 of the throttle body 7 and the intake flow path 80, the upper side of the partition portion 81 that divides them along the intake flow direction will be referred to as the "upper" side, and the lower side will be referred to as the "lower" side. (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 shown in FIGS.

[0024] FIG. 1 shows a right side view of a motorcycle 1 equipped with a power unit 3 equipped with an internal combustion engine 30 according to a first embodiment of the present invention. 2 shows the rear right side of the motorcycle 1 of FIG. 1 with the body cover 10 removed.

[0025] The motorcycle 1 in this first embodiment is a so-called scooter-type motorcycle, in which a front body 1A and a rear body 1B are connected via a low floor portion 1C, and a body frame 2 that forms the skeleton of the body is generally composed 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.

[0026] 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.

[0027] 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 a crankcase section 50a, with the cylinder axis C 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 up and down freely. 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.

[0028] 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.

[0029] 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 .

[0030] 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.

[0031] 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 the reduction gear mechanism 57 in the power transmission case 55 .

[0032] 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.

[0033] In the first embodiment, the internal combustion engine 30 employs an SOHC four-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 also be a DOHC internal combustion engine. Furthermore, the internal combustion engine 30 of this embodiment employs a four-valve internal combustion engine having two intake valves 46 and two exhaust valves 47, but it is sufficient if there are multiple intake valves 46, and there may be one or multiple 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 37 (see FIG. 7) 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. The camshaft 91 rotates in synchronization with the crankshaft 51 at half the rotational speed. 7 and 8, in the cylinder head 32, an ignition plug 49 serving as ignition means is inserted from the opposite side to the cam chain chamber 37 (the other side in the direction of the crankshaft 51) toward the inside of the combustion chamber 36, facing the cylinder axis C of the combustion chamber 36 and tilted relative to the cylinder axis C. In other words, the ignition plug 49 is inserted into the combustion chamber 36 from the opposite side to the cam chain chamber 37 with respect to an imaginary plane P that passes through the cylinder axis C of the combustion chamber 36 and is perpendicular to the crank axis L.

[0034] 3 and 4, which is an enlarged view of a main portion of Fig. 3, in a cylinder head 32 in which the cylinder axis C is tilted forward significantly and nearly horizontal, an intake valve port 40 and an exhaust valve port 41 open to a combustion chamber ceiling surface 32a, from which an intake port 42 and an exhaust port 43 respectively extend while curving in directions that move away from each other in the vertical direction. As shown in Fig. 7, the intake valve port 40 is provided with a first intake valve port 40a located on the opposite side of an imaginary plane P that passes through the cylinder axis C and is perpendicular to the crank axis L from the cam chain chamber 37, and a second intake valve port 40b located on the same side of the imaginary plane P as the cam chain chamber 37, on either side of the imaginary plane P.

[0035] The upstream end of the intake port 42 opens toward the top of the cylinder head 32 and connects to the inlet pipe 6 to form a continuous intake flow path 80. The throttle body 7 is connected to the upstream side of the inlet pipe 6. The intake port 42 branches into two paths, one connected to the first intake valve port 40a and the other connected to the second intake valve port 40b. That is, the intake flow path 80 branches into two paths, one connected to the first intake valve port 40a and the other connected to the second intake valve port 40b (see FIG. 7). 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.

[0036] 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.

[0037] 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.

[0038] In the internal combustion engine 30 of the first embodiment 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.

[0039] The throttle body 7 is provided with a throttle valve 75 that is rotatably supported within the throttle body 7 by a throttle valve shaft 76 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. The throttle valve 75 is a butterfly type and has a throttle valve shaft 76 and a disk-shaped valve body 77 fixed to the throttle valve shaft 76 and rotating integrally therewith. The valve body 77 is divided into two equal parts across the throttle valve shaft 76, consisting of a semi-disk-shaped one-end half 77A on one side and a semi-disk-shaped other-end half 77B on the other side.

[0040] The throttle valve 75 can be rotated in the clockwise direction in Figures 3 and 4 in the valve opening direction by operation by the driver, etc., and a return spring (not shown) urges the valve body 77 counterclockwise in the valve closing direction so that the rotating one end half 77A abuts against the inner surface 70a of the intake passage 70 and the rotating other end half 77B abuts against the inner surface 70a of the intake passage 70, thereby positioning the valve body 77 in the fully closed position. In the first embodiment, the intake passage 70 of the throttle body 7 is oriented substantially horizontally, with the lower end valve body being one end half 77A and the upper end valve body being the other end half 77B.

[0041] 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 path" refers to a flow path of intake air for generating a tumble vortex T in the combustion chamber 36 when the throttle valve 75 is at a low opening, that is, when the internal combustion engine 30 is under low load. Furthermore, although the internal combustion engine 30 of the first embodiment is not provided with a tumble control valve for controlling the flow of the tumble flow, the internal combustion engine may be provided with a tumble control valve.

[0042] 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 75 refer to the direction of the cylinder head 32 or the cylinder head cover 33 in the direction of the cylinder axis C as "upper," and the direction of the crankshaft 51 as "lower," and do not refer to absolute "upper" and "lower" in space.

[0043] 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 75 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 throttle valve shaft 76 are parallel to each other.

[0044] 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 77A of the throttle valve 75, and the inlet opening 80Ba of the main flow passage 80B is located downstream of the other end 71B of the throttle valve 75. 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.

[0045] 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.

[0046] Fig. 5 is a view of the inlet pipe 6 as seen from the side where it is attached to the cylinder head 32. Fig. 6 is an enlarged view of the vicinity of the combustion chamber of the cylinder head, showing the flow of tumble flow. Fig. 7 is a schematic view of the vicinity of the combustion chamber as seen from above in the cylinder axial direction, and Fig. 8 is a view as seen from the arrow VIII in Fig. 7. In Figs. 6 to 8, the flow of tumble flow is indicated by hatching.

[0047] As shown in FIG. 5, an intake passage 80 in the inlet pipe 6 connected to the intake port 42 is divided by a partition 81 into a tumble passage 80A and a main passage 80B.

[0048] The downstream end of the main flow passage 80B of the inlet pipe 6 on the cylinder head 32 side is formed in a horizontally elongated shape that opens on both sides relative to the imaginary plane P.

[0049] The tumble flow passage 80A in the inlet pipe 6 is formed so that its width gradually narrows from the end connected to the throttle body 7 toward the downstream, and its cross-sectional area A is narrowed. The downstream end of the tumble flow passage 80A in the inlet pipe 6 opens to one side with respect to the imaginary plane P. In this embodiment, the opening of the downstream end of the tumble flow passage 80A in the inlet pipe 6 is formed on the side of the imaginary plane P where the spark plug 49 is fitted, i.e., on the opposite side from the cam chain chamber 37. In this embodiment, the opening at the downstream end of the tumble flow passage 80A in the inlet pipe 6 is entirely included on the side where the spark plug is fitted with respect to the imaginary plane P, but it is sufficient that it is positioned closer to the spark plug side with respect to the imaginary plane P, and a portion of it may be positioned on the opposite side of the imaginary plane P from the spark plug side.

[0050] The main flow path 80B of the inlet pipe 6 is connected to the main flow path 80B of the intake port 42, and within the intake port 42, it branches into two branches: a first main flow path 80B1 located on the spark plug 49 side of the imaginary plane P, and a second main flow path 80B2 located on the opposite side of the spark plug 49.

[0051] The tumble flow passage 80A of the inlet pipe is connected to the tumble flow passage 80A of the intake port 42. As shown in Fig. 7, the tumble flow passage 80A of the intake port 42 is disposed only on the spark plug 49 side with respect to the imaginary plane P, and as shown in Fig. 6, the tumble flow passage 80A merges with the first main flow passage 80B1 on the downstream side and is connected to the first intake valve port 40a. The tumble flow passage 80A is not connected to the second intake valve port 40b and is closed to the second intake valve port 40b.

[0052] The tumble flow passage 80A opens downstream in the inlet pipe 6 toward the spark plug 49 with respect to the imaginary plane P. Thereafter, the tumble flow passage 80A of the intake port 42 is connected only to the first intake valve port 40a side and is closed to the second intake valve port 40b side. Therefore, the intake air flowing through the tumble flow passage 80A is concentrated only at the first intake valve port 40a, increasing the flow velocity and generating a stronger tumble flow.

[0053] The air-fuel mixture that passes through the tumble flow passage 80A and flows into the combustion chamber 36 flows toward the first intake valve port 40a on the spark plug 49 side with respect to the imaginary plane P. As a result, as shown in Figures 6 and 8, the flow of the air-fuel mixture is changed vertically by the spark plug 49 so as to face the piston 34 side, generating a stronger tumble flow.

[0054] The internal combustion engine 30 of the first embodiment is configured as described above, and therefore provides the following effects.

[0055] The internal combustion engine 30 of the first embodiment has a plurality of intake valve ports 40 that are opened and closed by intake valves 46, and a plurality of intake flow paths 80 that are respectively connected to the plurality of intake valve ports 40, one of the intake flow paths 80 having a partition section 81 that divides the intake flow path 80 in the intake flow direction, the partition section 81 dividing the intake flow path 80 into a main flow path 80B and a tumble flow path 80A, and the downstream side of the tumble flow path 80A is oriented toward the intake valve port 40 located downstream of the intake flow path 80.

[0056] With the above configuration, even in an internal combustion engine 30 having multiple exhaust valve ports 40, one of the intake passages 80 is provided with a partition 81 that divides the intake passage 80 in the intake flow direction. The partition 81 divides the intake passage 80 into a main passage 80B and a tumble passage 80A, and the downstream side of the tumble passage 80A is directed toward the intake valve port 40 located downstream of the intake passage 80. This allows the intake air flowing through the tumble passage to be concentrated, generating a stronger tumble flow, which increases the efficiency of flame propagation in the combustion chamber, improves combustion efficiency, and enables a reduction in carbon dioxide emissions.

[0057] Furthermore, the internal combustion engine 30 is provided with an ignition means 49 in the combustion chamber 36, and the tumble flow path 80A is directed toward the ignition means 49 protruding into the combustion chamber 36. When the intake air flow that passes through the tumble flow path 80A comes into contact with the ignition means 49 protruding into the combustion chamber 36, the flow direction of the tumble flow is changed toward the cylinder axis C, and a more powerful tumble flow is generated in the combustion chamber 36.

[0058] Furthermore, since the spark plug 49 is oriented toward the cylinder axis C of the combustion chamber 36 and is positioned at an angle relative to the cylinder axis C, the tumble flow flowing within the combustion chamber 36 is more likely to come into contact with the spark plug 49, making it possible to generate a more powerful tumble flow.

[0059] Furthermore, the spark plug 49 is inserted into the combustion chamber 36 from the side opposite the cam chain chamber 37 with respect to an imaginary plane P that passes through the cylinder axis C of the combustion chamber 36 and is perpendicular to the crank axis L, and the tumble flow path 80A is connected to the first intake valve port 40a, of the multiple intake valve ports 40, which is located on the opposite side of the imaginary plane P from the cam chain chamber 37, so that the spark plug 49 can be easily removed. Furthermore, by arranging the tumble flow passage 80A on the same side as the spark plug 49, the direction of the tumble flow is changed downward by the spark plug 49, which can promote the generation of a stronger tumble flow.

[0060] Furthermore, the intake passage 80 includes an inlet pipe 6 and an intake port 42 connected to the inlet pipe 6. The downstream side of the tumble passage 80A of the inlet pipe 6 opens to one side, that is, the spark plug 49 side, of an imaginary plane P that passes through the cylinder axis C of the combustion chamber 36 and is perpendicular to the crank axis L. The downstream side of the tumble passage 80A of the intake port 42 is connected to the first intake valve port 40a located on the one side. As a result, the tumble passage in the intake port 42 is arranged in a straight line, and a stronger tumble flow is generated.

[0061] Next, an internal combustion engine 30 according to a second embodiment will be described. The same components as those in the internal combustion engine 30 according to the first embodiment will be described with the same reference numerals. Fig. 9 shows a schematic diagram of the vicinity of the combustion chamber 36 of the internal combustion engine 30 according to the second embodiment, viewed from above in the cylinder axial direction. Fig. 10 shows a view taken along the arrow X in Fig. 9. The flow of the tumble flow is indicated by hatching.

[0062] In the internal combustion engine 30 of the second embodiment, the tumble flow passage 80A in the inlet pipe 6 opens at the downstream end to the cam chain side on the opposite side of the imaginary plane P from the spark plug 49.

[0063] The tumble flow passage 80A of the inlet pipe is connected to the tumble flow passage 80A of the intake port 42. As shown in Figure 9, the tumble flow passage 80A of the intake port 42 is disposed only on the side opposite the spark plug 49 with respect to the imaginary plane P, and merges with the second main flow passage 80B2 on the downstream side and is connected to the second intake valve port 40b. The tumble flow passage 80A is not connected to the first intake valve port 40a and is closed to the first intake valve port 40a, so that the intake air flowing through the tumble flow passage 80A is concentrated only at the second intake valve port 40b, increasing the flow velocity and generating a stronger tumble flow.

[0064] Furthermore, as shown in FIG. 9, the tumble flow passage 80A is formed at an angle with respect to a direction perpendicular to the crank axis L and directed toward the spark plug 49, so that the flow of the mixture is changed by the spark plug 49 to a vertical direction toward the piston 34, generating a stronger tumble flow.

[0065] Next, an internal combustion engine 30 according to a third embodiment will be described. The same components as those in the internal combustion engine 30 according to the first embodiment will be described with the same reference numerals. Fig. 11 shows a schematic diagram of the vicinity of the combustion chamber 36 of the internal combustion engine 30 according to the third embodiment, viewed from above in the cylinder axial direction. Fig. 12 shows a view taken along the arrow XII in Fig. 11. The flow of the tumble flow is indicated by hatching.

[0066] In the internal combustion engine 30 of the third embodiment, a tumble flow passage 80A in the inlet pipe 6 opens at its downstream end to the cam chain chamber side on the opposite side of the imaginary plane P from the spark plug 49.

[0067] The tumble flow passage 80A of the inlet pipe is connected to the tumble flow passage 80A of the intake port 42. As shown in Fig. 11, the tumble flow passage 80A of the intake port 42 is formed from the cam chain chamber side toward the spark plug side so as to straddle the imaginary plane P, and merges with the first main flow passage 80B1 on the downstream side and is connected to the first intake valve port 40a. The tumble flow passage 80A is not connected to the second intake valve port 40b and is closed to the second intake valve port 40b.

[0068] With the above configuration, the tumble flow passage 80A is arranged diagonally with respect to the imaginary plane P, which allows the tumble flow passage 80A in the intake port 42 to be set long, making it possible for the tumble flow to directly hit the cylinder wall surface of the combustion chamber 36, thereby reducing the attenuation of the tumble flow.

[0069] The first, second and third embodiments of the present invention have been described above, but 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 the sake of convenience, the illustrated embodiment has been described as being arranged on the left and right, but other arrangements may also be included in the present invention as long as they fall within the scope of the gist of the invention. [Explanation of symbols]

[0070] 6...inlet pipe, 30...internal combustion engine, 36...combustion chamber, 37...cam chain chamber, 40...intake valve port, 40a...intake valve port, 40b...intake valve port, 41...exhaust valve port, 42...intake port, 46...intake valve, 47...exhaust valve, 49...spark plug, 80...intake flow path, 80A...tumble flow path, 80B...main flow path, 81...partition portion, C...cylinder axis, L...crank axis.

Claims

1. a plurality of intake valve ports (40) that are opened and closed by intake valves (46); a plurality of intake flow paths (80) respectively connected to the plurality of intake valve ports (40); one of the intake air passages (80) includes a partition (81) that divides the intake air passage (80) in the intake air flow direction; The partition (81) divides the intake passage (80) into a main passage (80B) and a tumble passage (80A). The internal combustion engine is characterized in that the downstream side of the tumble flow passage (80A) is directed toward an intake valve port (40) located downstream of the intake flow passage (80).

2. The internal combustion engine is provided with an ignition means (49) in a combustion chamber (36), 2. The internal combustion engine according to claim 1, wherein the tumble flow passage (80A) is directed toward the ignition means (49) projecting into the combustion chamber (36).

3. 3. The internal combustion engine according to claim 2, wherein the ignition means (49) is oriented toward the cylinder axis (C) of the combustion chamber (36) and is disposed at an angle relative to the cylinder axis (C).

4. The ignition means (49) is inserted into the combustion chamber (36) from the opposite side to the cam chain chamber (37) with respect to an imaginary plane (P) that passes through the cylinder axis (C) of the combustion chamber (36) and is perpendicular to the crank axis (L), 3. The internal combustion engine according to claim 2, wherein the tumble flow passage (80A) is connected to an intake valve port (40a) of the plurality of intake valve ports (40) that is located on an opposite side of the imaginary plane (P) from the cam chain chamber (37).

5. the intake passage (80) includes an inlet pipe (6) and an intake port (42) connected to the inlet pipe (6); a downstream side of the tumble flow passage (80A) of the inlet pipe (6) opens to one side, which is the ignition means (49) side, with respect to an imaginary plane (P) that passes through a cylinder axis (C) of the combustion chamber (36) and is perpendicular to a crank axis (L); 3. The internal combustion engine according to claim 2, wherein the downstream side of the tumble flow passage (80A) of the intake port (42) is connected to an intake valve port (40a) arranged on the one side.

6. the intake passage (80) includes an inlet pipe (6) and an intake port (42) connected to the inlet pipe (6); a downstream side of the tumble flow passage (80A) in the inlet pipe (6) opens to one side opposite to the ignition means (49) side with respect to an imaginary plane (P) that passes through the cylinder axis (C) of the combustion chamber (36) and is perpendicular to the crank axis (L); 3. The internal combustion engine according to claim 2, wherein a downstream side of the tumble flow passage (80A) of the intake port (42) is connected to an intake valve port (40a) disposed on the other side of the imaginary plane (P).

7. 2. The internal combustion engine according to claim 1, wherein the cross-sectional area (A) of the tumble flow passage (80A) gradually decreases from upstream to downstream.

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