Intake system for internal combustion engine

Abstract

The present disclosure is directed to a configuration that can improve suction of air intake when the degree of opening of a throttle valve is relatively small in an internal combustion engine having a partition part provided in an air intake passage on the downstream side of the throttle valve. An air intake device S for an internal combustion engine 10 according to one embodiment comprises: a partition part 70 extending in an air intake flow direction so as to divide an air intake passage on the downstream side of a throttle valve 62c into a plurality of flow paths; and a resonator 77 provided to communicate with the air intake passage on the downstream side of an intermediate part 70m of the partition part in the air intake flow direction.

Description

[Technical field]

[0001] The present invention relates to an intake system for an internal combustion engine that is provided with a partition in an intake passage communicating with a combustion chamber and that is also provided with a resonator. [Background technology]

[0002] 2. Description of the Related Art Conventionally, various configurations have been proposed for generating vortex flows, such as tumble flows and swirl flows, within a combustion chamber in order to promote the combustion of an air-fuel mixture in the combustion chamber and improve combustion efficiency.

[0003] For example, Patent Document 1 discloses a structure in which an intake passage of an internal combustion engine is divided into a main passage and a sub-passage by a partition to generate a tumble flow. In this intake structure for an internal combustion engine, a tumble control valve is provided downstream of a throttle valve, and a partition plate portion, which is a partition portion, is provided downstream of the tumble control valve from an inlet pipe to an intake port, and the partition plate portion divides the intake passage into an upper main passage and a lower sub-passage. The lower sub-passage becomes a tumble passage, and the tumble control valve essentially opens and closes the upper main passage. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent No. 6714764 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the internal combustion engine is operating in a low load region, the tumble control valve is closed and the opening of the throttle valve provided upstream of the tumble control valve is also relatively small. Therefore, during the intake stroke from when the intake valve opens to when it closes, the volume of the intake port increases as the piston descends, but the intake air from the opening of the throttle valve cannot keep up with the increase in volume, so the pressure inside the intake port suddenly becomes negative and the flow inside the intake passage becomes weak.

[0006] An object of the present invention is to provide a configuration that makes it possible to improve the intake of intake air when the opening degree of the throttle valve is relatively small in an internal combustion engine in which a partition portion is provided in the intake passage downstream of the throttle valve. [Means for solving the problem]

[0007] In order to achieve the above object, one aspect of the present invention is to a partition portion extending in an intake air flow direction so as to divide an intake passage downstream of the throttle valve into a plurality of flow paths; a resonator provided downstream of an intermediate portion of the partition portion in the intake air flow direction so as to communicate with the intake passage; Equipped with An intake system for an internal combustion engine, comprising: to provide.

[0008] According to the above configuration, the resonator is provided so as to communicate with the intake passage downstream of the middle part of the partition in the intake flow direction, so that when the throttle valve is throttled, i.e., its opening is relatively small, for example, when the internal combustion engine is operating in a low load range, the intake air can flow from the resonator side into the intake passage downstream of the partition, thereby improving the flow of intake air from the intake passage into the combustion chamber.

[0009] Preferably, the axis of the downstream outlet of the communication passage connecting the resonator to the intake passage is designed to face the combustion chamber. With this configuration, the air flowing in from the resonator can be easily guided to the combustion chamber, thereby improving the combustion efficiency in the combustion chamber.

[0010] Preferably, the resonator is directly connected to a cylinder head of the internal combustion engine that defines a ceiling surface of the combustion chamber through a communication passage, whereby air flowing in from the resonator can be more easily guided directly to the combustion chamber.

[0011] Preferably, when a direction from a crankshaft side to a cylinder head side in a direction of a cylinder axis of the internal combustion engine is defined as a first direction, the partition portion is provided so as to divide the intake passage into a first intake passage and a second intake passage which are arranged in sequence in the first direction, whereby, for example, a tumble flow can be generated in the intake air flowing from the first intake passage into the combustion chamber.

[0012] Preferably, a communication passage connecting the resonator to the intake passage communicates with a downstream portion of the second intake passage or a downstream junction of the first intake passage and the second intake passage, thereby making it possible to introduce intake air from the resonator into the combustion chamber from the second intake passage side or the downstream junction.

[0013] Preferably, when a virtual plane is defined that passes through a center of an intake valve port facing the combustion chamber and opened and closed by an intake valve and a center of an exhaust valve port facing the combustion chamber and that is opened and closed by an exhaust valve, and that extends parallel to the cylinder axis, a deflection portion is further provided that is configured to deflect the intake air from the first intake passage to the combustion chamber to one side of the virtual plane. With this configuration, the intake air from the first intake passage can be biased to one side of the virtual plane and guided thereto, thereby further strengthening the vortex flow in the combustion chamber.

[0014] Preferably, the second intake passage has a larger cross-sectional area than the first intake passage, and the fuel injection valve is provided on the second intake passage side. This makes it possible to strongly introduce intake air from the first intake passage into the combustion chamber, and also makes it possible to suitably guide sprayed fuel from the fuel injection valve into the combustion chamber while maintaining a suitable flow of intake air in the first intake passage.

[0015] Preferably, the fuel injection direction of the fuel injection valve is approximately parallel to the axis of the downstream outlet of the communication passage that connects the resonator to the intake passage. With this configuration, the air flow from the resonator can be made substantially the same as the fuel injection direction, and therefore the sprayed fuel can be more effectively diffused in the combustion chamber.

[0016] Preferably, a tumble control valve for opening and closing the second intake passage is further provided at the upstream end of the partition portion or upstream of the upstream end. With this configuration, the intake air from the first intake passage can more suitably generate a tumble flow in the combustion chamber.

[0017] Preferably, a notch is further provided at a downstream outlet of a communication passage connecting the resonator to the intake passage. With this configuration, it is possible to further prevent injected fuel from accumulating in the communication hole, thereby preventing a deterioration in fuel efficiency. Effect of the Invention

[0018] According to the above aspect of the present invention, since the above configuration is provided, in an internal combustion engine in which a partition is provided in the intake passage downstream of the throttle valve, it is possible to improve the intake of intake air when the opening degree of the throttle valve is relatively small. [Brief description of the drawings]

[0019] [Figure 1] 1 is a cross-sectional view of an internal combustion engine and its surroundings according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a right side view of the cylinder head and its vicinity of the internal combustion engine of FIG. [Diagram 3]3 is a cross-sectional view of the internal combustion engine of FIG. 1 taken along line III-III of FIG. 2. [Figure 4] FIG. 2 is a bottom view of the cylinder head of the internal combustion engine of FIG. [Diagram 5] FIG. 2 is a front view of a three-dimensional model of an intake system and an exhaust system in the vicinity of a combustion chamber of the internal combustion engine of FIG. [Figure 6] FIG. 6 is a plan view of the three-dimensional model of FIG. 5. [Figure 7] 7 is a cross-sectional view of the three-dimensional model of FIG. 5 taken along line VII-VII of FIG. 6. [Figure 8] 8 is a cross-sectional view of the three-dimensional model of FIG. 5, mainly of the intake system, taken along line VIII-VIII in FIG. 6. [Figure 9] 6, mainly showing the intake system of the three-dimensional model of FIG. 5; FIG. [Figure 10] 5, mainly showing the intake system, and is a cross-sectional view taken along line XX in FIG. 6, which diagrammatically illustrates sprayed fuel. [Figure 11] FIG. 9 is a perspective view of the three-dimensional model of FIG. 8. [Figure 12] 8 is a cross-sectional view of the three-dimensional model of FIG. 5 taken along line XII-XII of FIG. 7. [Figure 13A] FIG. 7 is a perspective view of the three-dimensional model in FIG. 6, and is a diagram showing a schematic diagram of sprayed fuel. [Figure 13B] FIG. 6 is a perspective view of the three-dimensional model in FIG. 5, and is a diagram illustrating a schematic diagram of sprayed fuel. [Figure 14] 2 is a schematic diagram of a combustion chamber of the internal combustion engine of FIG. 1 and its surroundings as viewed from the cylinder axial direction. [Figure 15] 2 is a schematic diagram showing the direction of a communication passage that connects a resonator to an intake passage in the internal combustion engine of FIG. 1. FIG. [Figure 16] 2 is a schematic diagram of the internal combustion engine of FIG. 1, looking at the intake valve port side from the upstream side in the intake air flow direction. [Figure 17] FIG. 2 is a schematic diagram of an intake passage showing a region downstream of a throttle valve. [Figure 18] FIG. 18 is a diagram showing pressure fluctuations at the points shown in FIG. 17 in the cycle of an internal combustion engine. [Figure 19] 4 is an operation map of a throttle valve and a tumble control valve. [Figure 20A] 4 is a graph showing the relationship between the throttle opening and the intake air flow rate. [Figure 20B] 1 is a graph showing the correlation between the throttle opening and the strength of the vortex flow. [Figure 21] 13 is a diagram showing a joining portion of a resonator to an intake passage in an intake device of a modified example. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0021] An intake device S for an internal combustion engine according to one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of an internal combustion engine 10 to which the intake device S according to one embodiment of the present invention is applied, and its surroundings. FIG. 2 is a right side view of the cylinder head of the internal combustion engine of FIG. 1 and its vicinity. FIG. 3 is a cross-sectional view of the internal combustion engine of FIG. 1 taken along line III-III in FIG. 2. FIG. 4 is a bottom view of the cylinder head of the internal combustion engine of FIG. 1. In the description of this specification, the directions of front, rear, left and right are based on the usual standard that the straight-ahead direction of a motorcycle (not shown) on which the internal combustion engine 10 according to the embodiment is mounted is the front, and in the drawings, FR indicates the front, RR indicates the rear, LH indicates the left, and RH indicates the right.

[0022] The internal combustion engine 10 is a SOHC type two-valve single-cylinder four-stroke internal combustion engine, and is suspended in an upright position with a crankshaft 12 oriented in the vehicle body width direction and the cylinders tilted slightly forward relative to the vehicle body. In a crankcase 14 that rotatably supports the crankshaft 12 of the internal combustion engine 10, a speed change gear mechanism 20 is configured between a main shaft 16 disposed behind the crankshaft 12 and a countershaft 18 that is an output shaft.

[0023] A cylinder block 22 into which a single cylinder liner 22L is cast is placed on top of the crankcase 14, and a cylinder head 24 is placed on top of the cylinder block 22 via a gasket and fastened together with stud bolts, with a cylinder head cover 26 covering the top of the cylinder head 24. The cylinder block 22, cylinder head 24, and cylinder head cover 26 placed on top of the crankcase 14 extend upward from the crankcase 14 in a slightly forward-inclined position. Note that the internal combustion engine 10 is not limited to being a single-cylinder internal combustion engine with the above-described configuration, and may be an internal combustion engine configured in various types.

[0024] The crankcase 14 is split into left and right halves, and the lower end of a cylinder liner 22L is fitted into an opening formed in the mating surface of the left and right crankcases. The cylinder block 22 is tilted slightly forward and protrudes upward from the crankcase 14. A piston 28 is fitted into a cylinder bore 22b inside the cylinder liner 22L so as to be able to slide back and forth. A connecting rod 30 connects a piston pin 28p of the piston 28 and a crank pin 12p of the crankshaft 12 to form a crank mechanism.

[0025] A combustion chamber 32 is defined between a top surface 28t of a piston 28 sliding in a cylinder bore 22b of the cylinder block 22 and a combustion chamber ceiling surface (hereinafter, may be simply referred to as a "ceiling surface") 24t of the cylinder head 24, which faces the top surface 28t. The combustion chamber 32 is generally defined by the cylinder bore 22b of the cylinder block 22, the top surface 28t of the piston 28, and the ceiling surface 24t of the cylinder head 24. In the cylinder head 24, an intake valve port 34 and an exhaust valve port 36 are opened on the ceiling surface 24t at positions opposite to each other with respect to a cylinder axis C, which is the central axis of the cylinder bore 22b, facing the combustion chamber 32, and an intake port 38 and an exhaust port 40 are formed from the intake valve port 34 and the exhaust valve port 36, respectively, and extend while curving in a direction away from each other. In this way, a single intake port 38 and a single exhaust port 40 are defined in the cylinder head 24.

[0026] The intake valve 44 and the exhaust valve 46, which are slidably supported by valve guides 42i and 42e, respectively, which are integrally fitted to the cylinder head 24, are driven by a valve operating mechanism 48 provided on the cylinder head 24 to open and close the intake valve orifice 34 of the intake port 38 and the exhaust valve orifice 36 of the exhaust port 40 in synchronization with the rotation of the crankshaft 12. That is, a cylindrical intake valve guide 42i is integrally fitted to the curved outer wall portion 38a of the intake port 38 in the cylinder head 24. The intake valve 44 slidably supported by the intake valve guide 42i opens and closes the intake valve 44 of the intake port 38 facing the combustion chamber 32. Also, the exhaust valve 46 slidably supported by the exhaust valve guide 42e, which is integrally fitted to the curved outer wall portion 40a of the exhaust port 40 in the cylinder head 24, opens and closes the exhaust valve orifice 36 of the exhaust port 40 facing the combustion chamber 32.

[0027] 1 and 3, the valve mechanism 48 is a valve mechanism for an SOHC type internal combustion engine in which one camshaft 48a is journaled on the cylinder head 24 so as to be oriented in the left-right direction, and rocker arm shafts 47i, 47e are supported diagonally above the front and rear of the camshaft 48a, with an intake rocker arm 48i journaled at its center so as to be freely swingable on the rear rocker arm shaft 47i, and an exhaust rocker arm 48e journaled at its center so as to be freely swingable on the front rocker arm shaft 47e.

[0028] One end of the intake rocker arm 48i contacts the intake cam lobe of the camshaft 48a, and the other end contacts via an adjustment screw the upper end of the valve stem 44s of the spring-biased intake valve 44. One end of the exhaust rocker arm 48e contacts the exhaust cam lobe of the camshaft 48a, and the other end contacts via an adjustment screw the upper end of the valve stem 46s of the spring-biased exhaust valve 46. The intake rocker arm 48i and the exhaust rocker arm 48e swing with the rotation of the camshaft 48a, thereby driving the intake valve 44 and the exhaust valve 46 to open and close.

[0029] The camshaft 48a protrudes to the left from the bearing, and a cam chain sprocket 50 is supported on its left end. A cam chain 52 is wound around the cam chain sprocket 50 and faces the crankshaft 12, and is wound around a cam chain sprocket (not shown) that is fitted onto the crankshaft 12. The camshaft 48a rotates in the same direction as the crankshaft 12 at half the rotation speed as the crankshaft 12.

[0030] Cam chain chambers 22c, 24c, which are rectangular holes through which a cam chain 52 passes, are formed on the left side of the cylinder bore 22b of the cylinder block 22 and on the left side of the combustion chamber 32. As shown in Fig. 3, an ignition plug 54, which serves as ignition means, is fitted into the right side wall of the cylinder head 24 toward the combustion chamber 32. It is preferable that an internal cylinder pressure sensor (not shown) is fitted into the vicinity of the spark plug 54 toward the combustion chamber 32.

[0031] 4 is a bottom view of the cylinder head 24 that is to be fitted to the cylinder block 22, and the cylinder axis C of the internal combustion engine 10 is indicated by a dot. Referring to FIG. 4, a ceiling surface 24t of the combustion chamber 32 is recessed in a mating surface 24f of the cylinder head 24 that faces the mating surface of the cylinder block 22, corresponding to the cylinder bore 22b. The combustion chamber 32 does not have the shape of a so-called pent roof type combustion chamber, and the ceiling surface 24t is formed as a concave curved surface and is formed in a roughly hemispherical shape. In addition, a cam chain chamber 24c that corresponds to and communicates with the cam chain chamber 22c is drilled on the left side of the combustion chamber 32 in the mating surface 24f.

[0032] A circular opening edge 24e of a ceiling surface 24t of the combustion chamber 32 at a mating surface 24f of the cylinder head 24 coincides with a circular hole of the cylindrical cylinder bore 22b. A large-diameter intake valve port 34 opens into the ceiling surface 24t rearward of the cylinder axis C, and an exhaust valve port 36, somewhat smaller in diameter than the intake valve port 34, opens into the ceiling surface 24t forward of the cylinder axis C.

[0033] Further, a plug hole 56 is drilled on the right side of the cylinder axis C of the ceiling surface 24t, through which the electrode of the spark plug 54 projects into the combustion chamber 32. That is, the spark plug 54 is not positioned at the center of the ceiling surface 24t, but is provided offset from the center. When an imaginary plane IS is defined that extends from the intake valve port 34 side to the exhaust valve port 36 side and extends parallel to the cylinder axis C, the spark plug 54 is positioned on one side of the imaginary plane IS. In particular, the spark plug 54 is disposed on one side of the imaginary plane IS opposite the cam chain chamber 24c. In addition, in FIG. 4, the imaginary plane IS is defined so as to pass through the center 34a of the intake valve port 34 and the center 36a of the exhaust valve port 36. That is, the imaginary plane IS is defined so as to pass through the center 34a of the intake valve port 34 and the center 36a of the exhaust valve port 36 and extend parallel to the cylinder axis C. The center 34a of the intake valve port 34 may be the center of the intake valve port 34, and the center 36a of the exhaust valve port 36 may be the center of the exhaust valve port 36. Here, both the intake valve port 34 and the exhaust valve port 36 are substantially circular, and their respective centers are the centers 34a, 36a. Each of the intake valve port 34 and the exhaust valve port 36 may be, for example, a perfect circle or an ellipse.

[0034] 3, the spark plug 54 includes a center electrode 54e and a side electrode (or ground electrode) 54f. The side electrode 54f has a base end 54g on the plug body 54b side of the spark plug 54 and a curved portion 54h that curves and extends from the base end 54g to cover the tip end of the center electrode 54e. The base end 54g of the side electrode 54f extends generally parallel to the axis of the plug body 54b of the spark plug 54.

[0035] The upstream end of the intake port 38 opens toward the top of the cylinder head 24 and is connected to an inlet pipe 58 via an insulator 63 to form a continuous intake passage 60, and a throttle body 62 is connected to the upstream side of the inlet pipe 58. The throttle body 62 has an intake passage 62a with a substantially circular cross section that forms part of the intake passage 60 leading to the combustion chamber 32 of the internal combustion engine 10, and its upstream side is connected to an air cleaner device (not shown).

[0036] The throttle body 62 is provided with a throttle valve 62c that is rotatably supported within the throttle body 62 by a throttle valve shaft 62b that is perpendicular to the flow direction of the intake air in the intake passage 62a, i.e., that intersects at a right angle with the central axis of the intake passage 62a, and that variably controls the flow area of ​​the intake passage 62a to open and close the intake passage 62a. The throttle valve 62c is of a butterfly type and has a throttle valve shaft 62b and a disk-shaped valve element 62d that is fixed to the throttle valve shaft 62b and rotates integrally therewith.

[0037] The throttle valve 62c can be rotated in the opening direction (clockwise in FIG. 1) by operation by the driver, etc., and a return spring (not shown) urges the valve body 62d counterclockwise in the closing direction so that the valve body 62d is positioned in a fully closed position where its edge abuts against the inner wall surface of the intake passage 62a.

[0038] The downstream end of the exhaust port 40 opens downward in the cylinder head 24 and is connected to an exhaust pipe (not shown) to form a continuous exhaust passage 64. An exhaust purification device and a silencer may be provided downstream of the exhaust passage 64.

[0039] In the above internal combustion engine 10, an intake device S is configured to provide a tumble vortex, i.e., tumble flow, i.e., vertical rotation, of the fuel-air mixture in the combustion chamber 32 in order to obtain a more preferable combustion of the fuel, i.e., the mixture, in the combustion chamber 32. The intake device S includes a partition 70 provided in the intake passage 60 so as to divide the intake passage 60 into a plurality of intake passages 72, 74 by the partition 70. Here, the intake passage 60 is divided into a plurality of intake passages 72, 74 in the direction of the cylinder axis C. That is, the intake passage 60d downstream of the throttle valve 62c is divided in the intake flow direction by the partition 70 continuing from the inlet pipe 58 to the intake port 38, and is divided into a tumble passage 72, which is an intake passage portion configured so that the intake air passing through can generate a tumble flow in the combustion chamber 32, and a main passage 74, which is an intake passage portion other than the tumble passage 72. The intake passage portion 72 that can be a tumble passage for generating a tumble flow in the combustion chamber 32 is called a tumble passage, which corresponds to the first intake passage, and the main passage 74 corresponds to the second intake passage. In other words, the tumble passage 72 is an intake passage for generating a tumble flow in the combustion chamber 32 when the throttle valve 62c is at a low opening, for example, when the internal combustion engine 10 is operating at a low load. The tumble passage 72 may be called a sub-passage.

[0040] The partition 70 extending in the intake flow direction like a plate is provided so as to substantially divide the downstream side of the intake passage 60 in the vertical direction, that is, to substantially divide the downstream side of the intake passage 60 in the direction of the cylinder axis C, here, so as to substantially extend parallel to the axis extending in the intake flow direction. In this embodiment, the flow path cross-sectional area of ​​the tumble flow path 72 is smaller than the flow path cross-sectional area of ​​the main flow path 74, that is, the flow path cross-sectional area of ​​the main flow path 74 is larger than the flow path cross-sectional area of ​​the tumble flow path 72. However, the partition 70 may be provided so that the flow path cross-sectional area of ​​the tumble flow path 72 is larger than the flow path cross-sectional area of ​​the main flow path 74, and it is also possible to make them substantially the same.

[0041] As shown in Fig. 1, the lower part of the intake passage 60 partitioned by the partition part 70 is the tumble passage 72, and the upper part is the main passage 74, but in this specification they are not limited to being arranged up and down. In this specification, "up" and "down" of the intake passages 60, 60d, etc. refer to the direction from the crankshaft 12 side to the cylinder head 24 or cylinder head cover 26 side in the direction of the cylinder axis C as the "up" or "upward" direction, and the direction opposite to this "up" direction, that is, the direction from the cylinder head 24 side to the crankshaft 12 side as the "down" or "downward" direction, and do not mean absolute "up" and "down" in space. The "up" or "upward" direction corresponds to the first direction, and the "down" or "downward" direction corresponds to the second direction.

[0042] A tumble control valve 75 is further provided on the upstream side of the partition 70 and downstream side of the throttle valve 62c. As shown in FIG. 1, the tumble control valve 75 is disposed at an upstream end 70u on the upstream side of the partition 70 formed in the inlet pipe 58. The tumble control valve 75 has a tumble valve shaft 75a and a tumble valve body 75b fixed to the tumble valve shaft 75a and rotating integrally therewith. The tumble valve body 75b is formed as a plate-like semicircular disk that closes the opening of the main flow passage 74 near the upstream end 70u of the partition 70 in the inlet pipe 58. The tumble valve shaft 75a is attached to one straight end of the tumble valve body 75b. The tumble valve shaft 75a is rotatably supported by the inlet pipe 58 so as to be parallel to the widthwise surface of the partition portion 70 of the intake passage 60, more specifically, parallel to the throttle valve shaft 62b, and is appropriately rotated by an actuator (not shown). The tumble valve body 75b also rotates with the rotation of the tumble valve shaft 75a, changing the opening degree of the main flow passage 74, and as the amount of intake air flowing through the main flow passage 74 is adjusted, the amount of intake air in the tumble flow passage 72 is also adjusted. In this embodiment, the tumble control valve 75 is provided so as to be continuous with the upstream end portion 70u of the partition portion 70, but may be disposed at a distance from the upstream end portion 70u of the partition portion 70.

[0043] The tumble control valve 75 may also be called an intake control valve, a tumble valve, a TCV, etc. Although the tumble control valve 75 and the throttle valve 62c are each electronically controlled as described below, they are not limited to being electronically controlled, and for example, at least one of them may be a valve that is mechanically controlled by a cable.

[0044] The internal combustion engine 10 is provided with fuel injection valves 76 and 78. One of the fuel injection valves (hereinafter, the first fuel injection valve) 76 is provided upstream of the upstream end 70u of the partition portion 70 and is provided to inject fuel into a portion of the intake passage 60 upstream of the upstream end 70u. The other fuel injection valve (hereinafter, the second fuel injection valve) 78 is provided to inject fuel into the intake port 38. The second fuel injection valve 78 is provided on the main flow passage 74 side. The second fuel injection valve 78 is provided to face the main flow passage 74, and is provided in the inlet pipe 58 here. In this manner, the second fuel injection valve 78 is provided to inject fuel from the main flow passage 74 side and supply fuel to the combustion chamber 32 through the intake port 38. As is clear from FIG. 1, the second fuel injection valve 78 is attached to an upper wall of a member that defines the intake passage 60. It should be noted that the present disclosure does not limit the number of fuel injection valves to two, but may be, for example, one, and only one of the fuel injection valves 76, 78, for example, only the second fuel injection valve 78, may be provided.

[0045] In the internal combustion engine 10 configured as above, the resonator 77 is connected to the intake passage 60 via a communication pipe 77a. The communication pipe 77a is provided so as to communicate the resonator 77 with the intake passage 60 downstream of the intermediate portion 70m of the partition portion 70 in the intake flow direction. Here, the communication pipe 77a is positioned so as to communicate with the intake port 38 defined and formed in the cylinder head 24, particularly the downstream portion 74d of the main flow passage 74 and its downstream side. Therefore, the downstream outlet portion 77c of the communication passage 77b connecting the resonator 77 of the communication pipe 77a to the intake passage 60 opens to the intake port 38 defined and formed by the cylinder head 24. Here, the communication passage 77b is defined and formed by the communication pipe 77a connecting the resonator 77 and the cylinder head 24, but is not limited thereto, and may be configured as a part of the resonator 77 or a part of the cylinder head 24. The downstream portion 74d of the main flow path 74 is a portion of the main flow path 74 that is downstream of the intermediate portion 70m of the partition portion 70. The intermediate portion 70m of the partition portion 70 is a portion located in the middle of the length of the partition portion 70 in the intake flow direction that extends in the intake flow direction, and in this embodiment, it is a portion located in the middle of the length of the partition portion 70 including the partition main body portion 92 and the deviation portion 90 in the intake flow direction, but for example, when the partition portion 70 is provided with only the partition main body portion 92, it is a portion located in the middle of the length in the intake flow direction.

[0046] An ECU (electronic control unit) 80 that controls the internal combustion engine 10 has a configuration as a so-called computer, and includes an intake control unit 82, a fuel injection control unit 84, and an ignition control unit 85. The ECU 80 analyzes the operating state of the internal combustion engine 10 based on the outputs from various sensors such as an engine rotation speed sensor and an engine load sensor, and controls the operation of the throttle valve 62c and the operation of the tumble control valve 75 using the intake control unit 82. The ECU 80 also controls the operation of each of the fuel injection valves 76, 78 using the fuel injection control unit 84 based on the analyzed operating state of the internal combustion engine 10. The ECU 80 also controls the operation of the spark plug 54 using the ignition control unit 85 based on the analyzed operating state of the internal combustion engine 10. The ECU 80 stores programs and various data for these controls.

[0047] Here, Fig. 5 and Fig. 6 show a three-dimensional model M of the intake system and the exhaust system in the vicinity of the combustion chamber 32. Fig. 7 shows a cross-sectional view of the three-dimensional model M taken along line VII-VII in Fig. 6, Fig. 8 shows a cross-sectional view of mainly the intake system of the three-dimensional model M taken along line VIII-VIII in Fig. 6, Fig. 9 shows a cross-sectional view of mainly the intake system of the three-dimensional model M taken along line IX-IX in Fig. 6, and Fig. 10 shows a cross-sectional view of mainly the intake system of the three-dimensional model M taken along line XX in Fig. 6. Fig. 11 is a perspective view of the three-dimensional model M shown in Fig. 8. Fig. 12 shows a cross-sectional view of the three-dimensional model M taken along line XII-XII in Fig. 7.

[0048] The three-dimensional model M includes the intake port 38 from the downstream end of the inlet pipe 58, and also includes the exhaust port 40. The outer surface 79 of the intake system in the three-dimensional model M has a portion corresponding to the inner surface 58s of the inlet pipe 58, the inner surface 63s of the insulator 63, and the inner wall surface 24s of the cylinder head 24, which are members that define the downstream side of the intake passage 60, and a portion corresponds to the surface 70s of the partition portion 70, and a portion corresponds to the surface 90s of the offset portion 90, which will be described later. Therefore, for ease of understanding, the portions of the three-dimensional model M that correspond to the inner surface 58s of the inlet pipe 58, the inner surface 63s of the insulator 63, the inner wall surface 24s of the cylinder head 24, the surface 70s of the partition portion 70, and the surface 90s of the offset portion 90 are given their respective reference numerals. Also, the portion (hereinafter, the mounting portion) where the second fuel injection valve 78 is attached and its injection port faces the intake passage 60 is given the reference numeral "78s". Furthermore, in the direction of the cylinder axis C, the symbol "U" is used to denote the above-mentioned "upper" side, and the symbol "D" is used to denote the "lower" side.

[0049] As already described and as is clear from Fig. 5, the tumble flow passage 72 and the main flow passage 74 overlap vertically in the direction of the cylinder axis C. Also, as is clear from Fig. 8, the downstream end 72d of the tumble flow passage 72 is narrower in width in the left-right direction than the main flow passage 74 and is biased to the right here. In particular, the portion 72d of the tumble flow passage 72 defined by the inner wall surface 24s of the cylinder head 24 is biased to the right with respect to the intake valve port 34, as shown in Fig. 9.

[0050] As can be understood from Fig. 1, Fig. 8 to Fig. 10 and Fig. 12, the partition portion 70 has a deviation portion 90 provided on the downstream side of the partition portion 70. The deviation portion 90 has a width in the left-right direction (LH-RH direction) intersecting the cylinder axis C, i.e., in the width direction, which is narrower than the upstream end (upstream end) 70u of the partition portion 70. The deviation portion 90 is a narrow portion of the partition portion 70 in the width direction that can be defined as a direction extending from one side of the valve axis of the intake valve 44 to the other side when the deviation portion 90 faces the intake valve 44 in the direction in which the intake air flows from the upstream side to the downstream side in the intake passage 60, i.e., in the intake air flow direction. As shown in Fig. 12, in the tumble flow passage 72, the width W2 in the width direction of the downstream end portion 72d is clearly narrower than the width W1 in the width direction of the upstream end portion located on the upstream end 70u side of the partition portion 70 among the portions partitioned and formed by the cylinder head 24.

[0051] Further, the deviation portion 90 is biased in one direction in the left-right direction, i.e., the width direction. Here, as described above, the downstream end portion 72d of the tumble flow passage 72 is defined so as to be biased toward the right RH side (see Figs. 10 and 12). Therefore, the deviation portion 90 downstream of the partition portion 70 that defines at least partially the biased downstream end portion 72d of the tumble flow passage 72 is biased toward the right RH side here. Therefore, in Fig. 1, the cylinder axis C extends parallel to the paper surface, and the width direction extends approximately perpendicular to the paper surface, so the deviation portion 90 extending downstream of the partition portion 70 does not appear, and is therefore shown by a two-dot dashed line instead of a solid line. In this way, on the downstream side of the intake flow direction, the tumble flow passage 72 is designed to be biased in the width direction, and accordingly, the deviation portion 90 is defined so as to be biased toward the same side in the width direction.

[0052] Here, the relationship between the partition portion 70 and the deviation portion 90 downstream thereof, and the tumble flow passage 72 and main flow passage 74 will be further described with reference to FIGS. 8 to 10. FIG.

[0053] At the cut portion of Fig. 8 (VIII-VIII in Fig. 6), the tumble flow passage 72 and the main flow passage 74 are completely separated. The width of the tumble flow passage 72 and the width of the main flow passage 74 are approximately the same. At this cut portion, the partition portion 70 extends to the inner wall surface 24s of the cylinder head 24 at both ends in the width direction between the tumble flow passage 72 and the main flow passage 74, and a partition body portion 92 connected to the upstream side of the deviation portion 90 extends. Note that in Fig. 8, the surface 70s of the partition portion 70 and the surface 92s of the partition body portion 92 therein are denoted by the same reference numerals.

[0054] At the cut location in Fig. 9 (line IX-IX in Fig. 6), the tumble flow passage 72 and the main flow passage 74 are completely separated, but the width of the tumble flow passage 72 is narrower than the width of the main flow passage 74. At this cut location, the partition portion 70 extends to the inner wall surface 24s of the cylinder head 24 at both ends in the width direction between the tumble flow passage 72 and the main flow passage 74, and is in the middle of transitioning from the partition main body portion 92 to the deviation portion 90. Note that in Fig. 9, the portion corresponding to the surface 70s of the partition portion 70 is denoted by a reference symbol.

[0055] At the cut portion of FIG. 10 (line XX in FIG. 6), the tumble flow passage 72 and the main flow passage 74 are partially connected. Also, at this cut surface, the surface 70s of the partition portion 70 extends in the width direction as well as in the vertical direction, and is biased to the right. From this, it can be seen that the partition portion 70 transitions from the partition body portion 92 to the offset portion 90, and the offset portion 90 extends from the right side of the inner wall surface 24s of the cylinder head 24 to the left direction in the intake port 38 to an extent that does not completely separate the tumble flow passage 72 and the main flow passage 74. In other words, the tumble flow passage 72 and the main flow passage 74 are partitioned so that the main flow passage 74 and the tumble flow passage 72 communicate with each other in the region where the offset portion 90 extends in the intake flow direction. In other words, the deviation portion 90 connected to the partition main body portion 92 is formed to extend downstream of the partition main body portion 92 so that a portion of the partition main body portion 92 of the partition portion 70 is extended in the intake air flow direction downstream of the partition main body portion 92. Note that in Fig. 10, the surface 70s of the partition portion 70 and the surface 90s of the deviation portion 90 thereon are denoted by the same reference numerals.

[0056] The tumble flow passage 72 and the main flow passage 74 are partitioned so that the main flow passage 74 extends downward to the side of the deviation portion 90 in the region where the deviation portion 90 extends in the intake flow direction. This downward expansion of the main flow passage 74 is performed in the direction opposite to the direction in which the deviation portion 90 is biased, and in this case, it is performed on the left LH side of the deviation portion 90. Note that this downward expansion of the main flow passage 74 and the resulting merging of the main flow passage 74 and the tumble flow passage 72 are more noticeable downstream of the deviation portion 90.

[0057] As shown in Figures 9 and 10, as the partition portion 70 moves from the partition body portion 92 to the offset portion 90, a wall surface 24w appears that biases the tumble passage 72 in the width direction. The wall surface 24w is a part of the inner wall surface 24s of the cylinder head 24, and is located directly below the second direction side of the main passage 74. As shown in Figures 9 and 10, the wall surface 24w extends in the direction of the cylinder axis C, has a length in the up-down direction, and extends in the intake flow direction. Therefore, when the inner wall surface 24s is extended in the direction of the cylinder axis, the extended inner wall surface 24s crosses the main passage 74. The wall surface 24w extends to the left LH side of the downstream end portion 72d of the tumble passage 72 to define it, and biases the tumble passage 72 to the right RH side. In other words, the wall surface 24w becomes a deflection portion DP that is configured to bias the intake air from the tumble passage 72 to one side of the above-mentioned imaginary plane IS, that is, to the right RH side.

[0058] 6, 8, and 11, the mounting portion 78s of the second fuel injection valve 78 is positioned on the left LH side of the intake passage 60. In this manner, the second fuel injection valve 78 is provided at a position offset in a direction opposite to the offset direction of the offset portion 90. Therefore, the second fuel injection valve 78 can inject fuel in a direction different from the offset direction of the offset portion 90, more preferably in the opposite direction. The second fuel injection valve 78 is provided on the upper side, that is, on the main flow passage 74 side, and injects fuel from the main flow passage 74 side.

[0059] Here, perspective views of the three-dimensional model M shown in Figs. 6 and 5 are shown in Figs. 13A and 13B. Figs. 13A and 13B show the sprayed fuel SF injected from the second fuel injection valve 78, which is provided at a position biased toward the left LH side. Fig. 10 shows a part of the sprayed fuel SF injected from the second fuel injection valve 78. It can be seen from Figs. 10, 13A and 13B that the fuel SF injected from the second fuel injection valve 78 is not blocked by the partition 70, and at least a part of it, particularly at least a majority of it, and more preferably all of it, first flows through the main flow passage 74, then flows to the junction (downstream junction) 72f of the main flow passage 74 and the tumble flow passage 72, and then directly reaches the intake valve port 34 and is introduced into the combustion chamber 32. The arrangement of the second fuel injection valve 78 and the shape of the partition 70 including the offset portion 90 are designed to enable such fuel injection. In particular, the partition body portion 92 of the partition portion 70 partially terminates on its downstream side to enable the main flow path 74 and the tumble flow path 72 to merge, and the partition body portion 92 of the partition portion 70 and the deviation portion 90 continuing downstream therefrom are designed so that the fuel SF injected from the second fuel injection valve 78 reaches the intake valve port 34 along the surface 90s of the deviation portion 90, preferably without touching the deviation portion 90 (see, for example, Figure 10).

[0060] Furthermore, the second fuel injection valve 78, which is provided to inject fuel SF from the main flow passage 74 side toward the combustion chamber 32, is provided to inject fuel in a direction opposite to the biased direction of the deviation portion 90. Therefore, the partition portion 70, particularly the deviation portion 90, can be extended further downstream in the intake flow direction. The deviation portion DP, which is the wall surface 24w, defines the tumble flow passage 72 so as to be biased downstream in the biased direction of the deviation portion 90. Therefore, the deviation portion 90 of the partition portion 70 extended further downstream in the intake flow direction can impart stronger directionality to the intake air from the tumble flow passage 72.

[0061] In this way, the partition 70 is designed to completely separate the main flow passage 74 and the tumble flow passage 72 with the partition body 92 on the upstream side, and to have the offset portion 90 on the downstream side thereof, so as to realize the connection between the main flow passage 74 and the tumble flow passage 72 while characterizing the flow from the tumble flow passage 72 further downstream. In addition, the second fuel injection valve 78 is arranged offset to the opposite side to the offset direction of the offset portion 90, and here, is arranged on the opposite side in the width direction, so that it can inject fuel in a direction different from the offset portion 90, and can introduce fuel into the combustion chamber 32 almost directly through the intake valve port 34. In other words, it is possible to ensure good supply of fuel to the combustion chamber. Therefore, the offset portion 90, which is the downstream portion of the partition 70, can be extended further downstream. Therefore, it is possible to give a stronger directivity to the flow from the tumble flow passage 72. This directivity is directed between the intake valve port 34 and the umbrella portion of the intake valve 44 when the valve is open so as to form a stronger tumble flow in the combustion chamber 32. Therefore, the intake air from the tumble flow passage 72 can more suitably form a tumble flow in the combustion chamber 32 .

[0062] The tumble flow passage 72 and the main flow passage 74 are partitioned so that the tumble flow passage 72 communicates with the main flow passage 74 downstream of the downstream edge of the partition portion 70, i.e., the downstream edge 90d of the offset portion 90, to form a single intake passage leading to the combustion chamber 32. This allows intake air from the tumble flow passage 72 to be introduced into the combustion chamber 32 together with intake air from the main flow passage 74, making it possible to supply fuel to the combustion chamber 32 and form a tumble flow with intake air from the single intake port 38, which is a single intake passage. This configuration is also excellent in terms of cost, as it can suppress an increase in the number of parts.

[0063] In the above internal combustion engine 10, as described above, the wall surface 24w can bias the intake air from the tumble passage 72 toward one side of the imaginary plane IS, i.e., toward the right RH side, and can flow into the combustion chamber 32. The intake air from the tumble passage 72 flows into the combustion chamber 32 with a strong directivity to form a strong tumble flow as described above, and collides with, for example, the portion of the ceiling surface 24t or the portion of the cylinder bore 22b that extends toward the exhaust side of the wall surfaces that define the combustion chamber 32. This collision can cause the wall surface to generate a lateral force component in the vertical flow of the tumble flow. Therefore, the intake air from the tumble passage 72 can have not only the vertical force component of the tumble flow, but also the lateral force component of the swirl flow, i.e., the force component in the cylinder circumferential direction.

[0064] In addition, the spark plug 54 provided in the combustion chamber 32 is positioned on one side of the imaginary plane IS, that is, on the side to which the intake air from the tumble passage 72 is biasedly led. This makes it possible to suitably ignite the fuel contained in the intake air from the tumble passage 72, that is, the air-fuel mixture.

[0065] Fig. 14 is a schematic diagram of the combustion chamber 32 of the internal combustion engine 10 and its surroundings as viewed from above in the direction of the cylinder axis C. Fig. 14 shows the outline of the circular opening edge 24e of the ceiling surface 24t of the cylinder bore 22b or the combustion chamber 32, and the relative arrangement of the intake valve port 34, the exhaust valve port 36, and the spark plug 54. The aforementioned imaginary plane IS, which is defined so as to pass through the center portion 34a of the intake valve port 34 and the center portion 36a of the exhaust valve port 36, passes through the cylinder axis C and overlaps with the axis of the valve stem 44s of the intake valve 44 (valve axis) in Fig. 14.

[0066] As shown by the arrow T in FIG. 14, the intake air from the tumble flow passage 72 enters the combustion chamber 32 biased toward the right RH side in the width direction perpendicular to the imaginary plane IS. In FIG. 12, the downstream end portion 72d of the tumble flow passage 72 has a substantially constant width, so the arrow T of the intake air from the tumble flow passage 72 is shown to be substantially parallel to the imaginary plane IS. In the combustion chamber 32, this arrow T mainly passes through the right side, which is one side of the imaginary plane IS, and proceeds toward the wall surface 32W on the exhaust valve port 36 side of the combustion chamber 32, and can collide with it. At this time, the wall surface 32W that the flow of the arrow T collides with is mainly a wall on the right RH side of the imaginary plane IS, and is concavely curved toward the left so as to approach the imaginary plane IS as it approaches the exhaust side, as shown in FIG. 14. Therefore, the collision force F of the flow of the arrow T against the wall surface 32W can be divided into an orthogonal component Fa perpendicular to the wall surface 32W and a tangential component Fb along the wall surface 32W. The orthogonal component Fa is a component that generates a vertical vortex flow in the direction of the cylinder axis C, i.e., a tumble flow. The tangential component Fb is a component that generates a flow that rotates along the cylinder circumferential direction from the right side, which is one side of the imaginary plane IS, to the left side, which is the other side, i.e., a swirl flow. In other words, the flow of the arrow T forms a flow in the combustion chamber 32 so as to generate a tumble flow as well as a swirl flow. As a result, the flow from the tumble flow passage 72 has a vortex center different from that when a tumble flow is simply formed in the combustion chamber 32, and it is possible to generate a tumble flow in the combustion chamber 32 as well as a flow like a swirl flow from the right RH side, which is one side of the imaginary plane IS, to the left LH side.

[0067] The wall surface 32W against which the intake air from the tumble channel 72 collides is, as described above, for example, the portion of the ceiling surface 24t or the portion of the cylinder bore 22b that extends toward the exhaust side among the wall surfaces that define the combustion chamber 32. As described above, the ceiling surface 24t is formed into a concave curved surface. Therefore, the ceiling surface 24t can suitably generate a force of the tangential component Fb by the intake air from the tumble channel 72. In particular, since the ceiling surface 24t is formed into a substantially hemispherical shape and is a smooth concave curved surface, such a force can be generated in the intake air from the tumble channel 72, which can contribute to more suitably generating a flow such as a swirl flow.

[0068] When the intake air is directed to flow into the combustion chamber 32 so as to be more biased toward the right side, the flow is indicated by an arrow T1 in FIG. 14. At this time, compared with the flow of the arrow T, since the flow of the arrow T1 collides at an angle by the wall surface 32W (θ1 < θ2), when the collision force F1 of the flow of the arrow T1 has the same magnitude as the collision force F of the flow of the arrow T (F1 = F), the collision force F1 of the flow of the arrow T1 can generate a relatively small orthogonal component Fa1 (Fa1 < Fa) and a relatively large tangential component Fb1 (Fb1 > Fb). Therefore, the component of the swirl flow becomes larger, and flame propagation from one side to the other side of the virtual surface IS is more likely to occur. Considering the degree of the force of the tangential component generated, for example, the wall surface 24w such as the bias of the tumble flow path 72 and the inclination of the tumble flow path 72 with respect to the combustion chamber 32 may be designed.

[0069] Further, in the internal combustion engine 10, the ignition plug 54 is positioned on the side of the virtual surface IS where the intake air from the tumble flow path 72 is biased and introduced. Therefore, since the intake air from the tumble flow path 72 contains fuel and substantially forms an air-fuel mixture, the air-fuel mixture introduced into the combustion chamber 32 is preferably ignited by the ignition plug 54. And since the flow from the right RH side to the left LH side, which is one side of the virtual surface IS, is formed as described above, flame propagation in the combustion chamber 32 can be preferably generated.

[0070] Now, in the internal combustion engine 10 having the above configuration, as described above, a resonator 77 is connected to the intake passage 60, particularly to the intake passage 60d on the downstream side of the throttle valve 62c. As shown in FIGS. 1, 5 to 9, 11, 13A, and 13B, the resonator 77 is provided so as to communicate with the intake passage 60d obliquely, rather than orthogonally, with respect to the intake air flow direction. And the communication pipe 77a is connected to the cylinder head 24 so as to be inserted obliquely from the upper side to the lower side. Therefore, the axis 77d (FIGS. 7 and 9) of the downstream outlet portion 77c in the communication pipe 77a, that is, the communication passage 77b, intersects obliquely with the intake air flow direction at the connection portion to the intake passages 60 and 60d, and particularly faces the combustion chamber 32 side here.

[0071] The communication passage 77b connecting the resonator 77 to the intake passage 60 is provided at a position offset to the left LH side, similar to the second fuel injection valve 78. The communication passage 77b directly communicates with the main passage 74 and the downstream junction 72f. Furthermore, as is clear from Figs. 1 and 6, the communication point of the communication passage 77b with the intake passage 60 is positioned near the mounting portion 78s of the second fuel injection valve 78, immediately downstream of the mounting portion 78s. As a result, the axis 77d of the downstream outlet portion 77c of the communication passage 77b connecting the resonator 77 to the intake passage 66 is made substantially parallel to the fuel injection direction of the second fuel injection valve 78. That is, just as the second fuel injection valve 78 is oriented so as to be able to introduce fuel almost directly into the combustion chamber 32 via the intake valve port 34, the communication passage 77b of the resonator 77 is provided with respect to the intake passage 60 so as to be able to direct the intake air from the resonator 77 directly into the combustion chamber 32. Particularly here, the directionality of the intake air from the resonator 77 is directed between the intake valve port 34 and the head portion of the intake valve 44 when the valve is open so as to form a stronger swirl flow in the combustion chamber 32.

[0072] Fig. 15 shows the three-dimensional model of Fig. 5, and also shows the intake valve 44 and the flow direction of the intake air from the resonator 77, i.e., the axis 77d. Fig. 16 shows a schematic diagram of the intake valve port 34 from the upstream side in the intake air flow direction, and shows the fuel SF sprayed from the second fuel injection valve 78 to the intake valve 44 with the intake valve port 34 open, and the flow direction of the intake air from the resonator 77, i.e., the axis 77d.

[0073] 15 and 16, the axis 77d of the communication passage 77b passes directly between the umbrella portion 44a of the intake valve 44 when the valve is open and the intake valve port 34 and extends to the combustion chamber 32 so that the intake air from the resonator 77 passes directly between the umbrella portion 44a of the intake valve 44 when the valve is open and the intake valve port 34 toward the combustion chamber 32. Here, as shown in FIG. 16, which shows the umbrella portion 44a of the intake valve 44 when the valve is open from the upstream side in the intake air flow direction, the direction of the axis 77d of the communication passage 77b is determined so that the axis 77d of the communication passage 77b intersects with the valve stem 44s of the intake valve 44 upstream of the valve stem 44s. In addition, the axis 77d of the connecting passage 77b is not limited to intersecting with the valve stem 44s of the intake valve 44 upstream of the valve stem 44s of the intake valve 44, and may be determined to intersect with the valve stem 44s directly or downstream of the valve stem 44s.

[0074] 15, the axis 77d of the communication passage 77b passes through a virtual wall surface opposite the outlet 77c of the communication passage 77b in a virtual cylinder IC (FIG. 15) that can be defined between the back part (the side facing the combustion chamber) of the umbrella part 44a of the intake valve 44 and the intake valve port 34 when the intake valve 44 is open during the intake stroke. Then, downstream of the intake valve port 34, the axis 77d of the communication passage 77b extends approximately parallel to the surface of the umbrella part 44a.

[0075] Since the resonator 77 is connected to the intake passage 60d via the communication passage 77b as described above, when the air from the resonator 77 flows toward the combustion chamber 32, the air can flow into the combustion chamber 32 biased toward the right side of the intake valve port 34. This bias of the intake air from the resonator 77 is larger than the bias of the intake air from the tumble passage 72 because the axis 77d of the downstream outlet portion 77c of the communication passage 77b obliquely intersects with the intake air flow direction at the connection point to the intake passages 60, 60d as described above. While the intake air from the tumble passage 72 flows into the combustion chamber 32 biased as shown by the arrow T in FIG. 14, the intake air from the resonator 77 can flow into the combustion chamber 32 biased toward the right side or even more biased as shown by the arrow T1 in FIG. 14. Therefore, the intake air from the resonator 77 can generate a swirl flow or a vortex flow similar thereto.

[0076] Here, the experimental results will be described. The effect of strengthening the flow through the tumble flow passage 72 by providing a resonator downstream of the throttle valve 62c in communication with the intake passage 60 will be described with reference to Figs. 17 and 18 in comparison with an intake system without a resonator. As shown in Fig. 17, in these intake systems, a tumble control valve 75 is attached to the upper flow passage of the intake passage, with the upper side being the main flow passage 74 and the lower side being the tumble flow passage 72. In Fig. 17, the positions of the various points showing the change in pressure in the intake system shown in Fig. 18 are indicated by A and B. Point A is located downstream of the throttle valve 62c and upstream of the upstream end, i.e., the upstream end 70u, of the partition portion 70 that separates the tumble flow passage 72 and the main flow passage 74, and point B is located in the tumble flow passage 72.

[0077] 18 shows pressure data for each crank angle in one cycle when the throttle valve 62c is gradually opened for an intake system in which the resonator 77 is connected downstream of the throttle valve 62c and an intake system in which the resonator 77 is not connected downstream of the throttle valve 62c, with the horizontal axis representing the crank angle and the vertical axis representing the pressure. The intake passage area in the intake system from downstream of the throttle valve 62c to the intake valve 44 is defined as the intake area downstream of the throttle valve, and this volume is defined as the intake volume downstream of the throttle valve. In these definitions, the area and volume within the resonator 77 are also included when the resonator 77 is connected.

[0078] The pressure change in the intake passage and the flow of intake air when the resonator 77 is not connected downstream of the throttle valve 62c will be described below. When the resonator 77 is not connected downstream of the throttle valve 62c, this refers to when the intake system does not have the resonator 77, or when the intake system has the resonator 77 but is connected upstream of the throttle valve 62c.

[0079] In an intake system in which the resonator 77 is not connected downstream of the throttle valve 62c, the intake volume downstream of the throttle valve is not large, so the amount of air stored there is small, and air is taken in from the atmosphere upstream of the throttle valve 62c through the opening of the throttle valve 62c during the intake stroke from when the intake valve 44 opens to when it closes. However, because the opening of the throttle valve 62c is small, the amount of air that increases with the downward movement of the piston 28 cannot be charged in time, and the pressure in the intake port suddenly becomes negative (between the crank angles of approximately 380 degrees and 540 degrees in FIG. 18). When the pressure in the intake port suddenly becomes negative in this way, the air in the intake area downstream of the throttle valve expands and is sucked in as the piston 28 descends, weakening the flow and weakening the vortex flow such as the tumble flow formed in the cylinder.

[0080] Next, we will explain the pressure change in the intake passage and the flow of intake air when the resonator 77 is connected downstream of the throttle valve 62c. During the intake stroke from when the intake valve 44 opens to when it closes, the intake volume downstream of the throttle valve is larger by the volume inside the resonator 77 than when the resonator 77 is not connected, so the mass of the accumulated air is larger.

[0081] When the intake valve 44 opens, the amount of air that increases with the downward movement of the piston 28 is charged from the large amount of air that has accumulated in the intake area downstream of the throttle valve, and the amount of air taken in from the atmosphere upstream of the throttle valve 62c through the opening of the throttle valve 62c is relatively small.

[0082] Therefore, even when the opening of the throttle valve 62c is relatively small, such as during gradual opening, the change in the negative pressure in the intake port is relatively small (between crank angles of approximately 380 degrees and 540 degrees in FIG. 18). Since the pressure in the intake port rarely suddenly becomes negative in this way, the expansion of the intake air in the intake area downstream of the throttle valve accompanying the piston descending is relatively small, the flow does not decrease, and the flow of vortexes such as tumble flows formed in the cylinder can be enhanced.

[0083] Returning now to the description of this embodiment, the intake of intake air into the internal combustion engine 10 in the intake system S of this embodiment will be further described with reference to Figures 19, 20A and 20B.

[0084] FIG. 19 is an operation map of the throttle valve 62c and the tumble control valve 75, with the engine speed Ne on the horizontal axis and the output of the internal combustion engine 10 on the vertical axis, and shows a line when the throttle valve 62c is fully open and an opening range of the tumble control valve 75. Both the range α1 and the range α2 are ranges in which the tumble control valve 75 is closed as shown by the dashed lines in FIG. 1, and the range β is a range in which the tumble control valve 75 is opened as shown by the solid lines in FIG. 1. The range α1 is a range in which the throttle valve 62c is gradually opened and corresponds to a low load range, and the range α2 is a range in which the throttle valve 62c is opened to a predetermined opening degree or more that is larger than the opening degree in the range α1 and corresponds to a medium load range. Here, the tumble control valve 75 is set to either a fully open state or a fully closed state. However, the tumble control valve 75 may be controlled to have an opening degree between the fully open state and the fully closed state. The mapped data in FIG. 19 is stored in the storage unit of the ECU 80.

[0085] 20A, the horizontal axis represents the opening of the throttle valve 62c, i.e., the throttle opening TH, and the vertical axis represents the intake air flow rate to the combustion chamber 32, and shows the relationship between the intake air flow rate from the tumble passage 72 and the intake air flow rate from the resonator 77. The thin line represents the intake air flow rate from the resonator 77, and the thick line represents the intake air flow rate from the tumble passage 72. The dashed line in the graph of FIG. 20A represents the sum of the intake air flow rate from the tumble passage 72 and the intake air flow rate from the resonator 77.

[0086] The graph in Fig. 20B shows the correlation between the strength of a vortex flow such as a tumble flow caused by intake air from the tumble flow passage 72 and a vortex flow such as a swirl flow caused by intake air from the resonator 77, with the horizontal axis being the same as that of the graph in Fig. 20A and the vertical axis showing the strength of the vortex flow. However, the horizontal axis in Fig. 20A and Fig. 20B shows the throttle opening when the tumble control valve 75 is closed, and the opening TH1 is the opening at the boundary between the low load region (corresponding to region α1 in Fig. 19) and the medium load region (corresponding to region α2 in Fig. 19).

[0087] When the tumble control valve 75 is in the closed state and the throttle opening TH is relatively small, such as a slow opening, that is, when the operating state of the internal combustion engine is in the low load region, that is, region α1, as described above, the intake air in the tumble flow path 72, which is the intake air flow path portion downstream from the throttle valve 62c, is small. At this time, in the intake stroke, in addition to the intake air flowing in through the tumble flow path 72, the intake air in the resonator 77 is also inhaled into the combustion chamber 32 as described above.

[0088] As described above, when the tumble control valve 75 is in the closed state and the throttle opening TH is relatively small (for example, when TH < TH1), in the intake stroke, in addition to the intake air flowing in through the tumble flow path 72, the intake air in the resonator 77 is also actively inhaled into the combustion chamber 32. At this time, the intake air from the resonator 77 is directed as described above and is strongly directed and inhaled to the right side of the combustion chamber 32. As a result, a strong swirl flow or a tumble flow with a strong swirl component is strongly generated in the combustion chamber 32 (the "swirl" line in Fig. 20B). Therefore, the combustion of the air-fuel mixture in the combustion chamber can be promoted. As described above, with the resonator 77 provided as described above, the intake of intake air when the throttle opening is relatively small can be improved.

[0089] On the other hand, when the tumble control valve 75 is in the closed state and the throttle opening TH gradually increases, for example, when the operating state of the internal combustion engine is in the medium load region, that is, region α2, the intake air flowing from the throttle valve 62c to the downstream tumble flow path 72 can supply the intake air in the intake stroke, and the degree to which the intake air in the resonator 77 is inhaled into the combustion chamber 32 decreases.

[0090] In this way, when the tumble control valve 75 is in a closed state and the throttle opening TH is relatively large (for example, when TH>TH1), during the intake stroke, the intake air flowing into the tumble passage 72 is mainly drawn into the combustion chamber 32. This allows the intake air that has passed through the tumble passage 72 to generate a tumble flow in the combustion chamber 32 (the "tumble" line in FIG. 20B). Therefore, even when the tumble control valve 75 is in a closed state and the throttle opening TH is relatively large, intake of the intake air can be performed suitably.

[0091] As described above, the resonator 77 is provided so as to communicate with the intake passage downstream of the intermediate portion 70m of the partition portion 70 in the intake air flow direction. Therefore, when the throttle valve 62c is throttled, that is, its opening is relatively small, for example, when the internal combustion engine is operating in a low load range, the intake air can flow from the resonator side into the intake passage downstream of the partition portion 70. This can improve the inflow of the intake air from the intake passage to the combustion chamber 32.

[0092] As described above, the axis 70d of the downstream outlet 70c of the communication passage 70b that connects the resonator 77 to the intake passage 60 is designed to face the combustion chamber 32. This makes it easier to guide the air flowing in from the resonator to the combustion chamber 32, and therefore makes it possible to more actively generate a vortex flow, such as a swirl flow, in the combustion chamber 32.

[0093] Furthermore, the resonator 77 is directly connected, via a communication passage 77b, to the cylinder head 24 that defines the ceiling surface 24t of the combustion chamber 32. Therefore, the air flowing in from the resonator 77 can be guided more directly to the combustion chamber 32.

[0094] Furthermore, since the fuel from the second fuel injection valve 78 is injected in a direction approximately parallel to the axis 77d of the downstream outlet portion of the connecting passage 77b connecting the resonator 77 to the intake passage 60, when the tumble control valve 75 is in a closed state, the swirl flow and / or tumble flow more effectively promotes mixing of the fuel, thereby promoting its combustion.

[0095] Furthermore, the ignition plug 54 is positioned in the direction of fuel injection, so that the combustion of the fuel in the combustion chamber 32 can be more suitably caused.

[0096] In the intake device S of the internal combustion engine 10, the resonator 77 is provided so as to communicate with the intake passage 60 downstream of the intermediate portion 70m of the partition portion 70 in the intake flow direction, particularly so as to communicate with the downstream portion of the main flow passage 74. This makes it possible to effectively introduce the intake air from the resonator 77 into the combustion chamber 32 when the throttle valve 62c is throttled during operation in the low load range α1 of the internal combustion engine 10. Furthermore, the axis 77d of the downstream outlet portion 77c of the communication passage 77b connecting the intake air of the resonator 77 to the intake passage 60 is designed to face the combustion chamber 32. This makes it possible to direct the intake air from the resonator 77 more directly toward the combustion chamber 32, and actively generate a swirl flow or a tumble flow having a swirl component in the combustion chamber 32. In this way, in order to actively generate a swirl flow or a tumble flow having a swirl component in the combustion chamber 32, the connecting passage 77b may be connected to the main flow passage 74 downstream of its downstream portion, for example, to the downstream junction 72f of the tumble flow passage 72 and the main flow passage 74.

[0097] 21, a notch 77e may be further provided in a downstream outlet 77c of a communication passage 77b that connects the resonator 77 to the intake passage 60. By providing the notch 77e, for example, it is possible to more effectively prevent the fuel from the second fuel injection valve 78 from accumulating in the downstream outlet 77c of the communication passage 77b.

[0098] Although the embodiment and its modified examples according to the present invention have been described above, the present invention is not limited thereto. Various substitutions and modifications are possible without departing from the spirit and scope of the present invention as defined by the claims of this application.

[0099] Although the internal combustion engine 10 is a two-valve internal combustion engine having only one intake valve and only one exhaust valve per cylinder, the internal combustion engine to which the present invention is applied may have three or more valves per cylinder. Also, although the internal combustion engine 10 is provided with the tumble control valve 75, the present invention may be applied to an internal combustion engine that is not provided with the tumble control valve 75. [Explanation of symbols]

[0100] 10... internal combustion engine, 12... crankshaft, 22... cylinder block, 24... cylinder head 24w...wall portion, 32...combustion chamber, 34...intake valve port, 36...exhaust valve port, 38...intake port 40...exhaust port, 44...intake valve, 46...exhaust valve, 54...spark plug, 60...intake passage 62... throttle body, 62c... throttle valve, 70... partition 72... tumble flow passage (first intake flow passage), 74... main flow passage (second intake flow passage) 75... tumble control valve, 76... first fuel injector, 77... resonator, 77b... communication passage 78: second fuel injection valve, 90: offset portion, 92: partition body portion DP: deflection part, M: 3D model, S: intake system

Claims

1. a partition portion (70) extending in an intake flow direction so as to divide an intake passage (60d) downstream of the throttle valve (62c) into a plurality of flow paths; a resonator (77) provided downstream of an intermediate portion (70m) of the partition portion (70) in the intake air flow direction so as to communicate with the intake passage (60d); Equipped with When a direction from a crankshaft (12) side to a cylinder head (24) side in a direction of a cylinder axis (C) of the internal combustion engine is defined as a first direction, the partition portion (70) is provided so as to divide the intake passage (60d) into a first intake flow path (72) and a second intake flow path (74) which are arranged in sequence in the first direction, The fuel injection valve (78) is provided on the second intake passage (74) side, The fuel injection direction of the fuel injection valve (78) is approximately parallel to an axis (77d) of a downstream outlet portion (77c) of a communication passage (77b) connecting the resonator (77) to the intake passage (60d). An intake system (S) for an internal combustion engine, characterized in that

2. The axis (77d) of the downstream outlet portion (77c) of the communication passage (70b) connecting the resonator (77) to the intake passage (60d) is designed to face the combustion chamber (32).

2. An intake system (S) for an internal combustion engine according to claim 1.

3. The resonator (77) is directly connected to the cylinder head (24) of the internal combustion engine, which defines the ceiling surface (24t) of the combustion chamber (32), via the communication passage (77b).

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

4. (delete)

5. The communication passage (77b) connecting the resonator (77) to the intake passage (60d) communicates with a downstream portion (74d) of the second intake flow path (74) or a downstream junction (72f) of the first intake flow path (72) and the second intake flow path (74). An intake system (S) for an internal combustion engine according to any one of claims 1 to 3.

6. When a virtual plane (IS) is defined that passes through a center of an intake valve port (34) facing the combustion chamber (32) and opened and closed by an intake valve (44) and a center of an exhaust valve port (36) facing the combustion chamber (32) and opened and closed by an exhaust valve (46) and extends parallel to the cylinder axis (C), A deflection portion (DP) configured to deflect the intake air from the first intake passage (72) to the combustion chamber (32) to one side of the imaginary plane (IS) is further provided. An intake system (S) for an internal combustion engine according to any one of claims 1 to 3 and claim 5.

7. 7. The intake system (S) for an internal combustion engine according to claim 1, wherein a flow passage cross-sectional area of ​​the second intake passage (74) is larger than a flow passage cross-sectional area of ​​the first intake passage (72).

8. (delete)

9. A tumble control valve (75) for opening and closing the second intake passage (74) is further provided at the upstream end (70u) of the partition portion (70) or upstream of the upstream end (70u). An intake system (S) for an internal combustion engine according to any one of claims 1 to 3 and claims 5 to 7.

10. A notch (77e) is further provided at a downstream outlet (77c) of a communication passage (77b) connecting the resonator (77) to the intake passage (60d). An intake system (S) for an internal combustion engine according to any one of claims 1 to 3, claims 5 to 7 and claims 9.

Images