JP7600426B2 - Intake system for internal combustion engine - Google Patents

Description

The present invention relates to an intake device for an internal combustion engine that has a partition in an intake passage connected to a combustion chamber and is also equipped with a resonator.

Various configurations have been proposed to generate vortex flows, such as tumble flow and swirl flow, within the combustion chamber in order to promote the combustion of the air-fuel mixture in the combustion chamber and improve combustion efficiency.

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

Japanese Patent No. 6714764

When the internal combustion engine is operating in a low load range, the tumble control valve is closed and the throttle valve, which is located upstream of the tumble control valve, is also relatively small in opening. 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 throttle valve opening cannot keep up with the increase in volume, so the intake port suddenly becomes negative pressure and the flow in the intake passage weakens.

The object of the present invention is to provide a configuration in an internal combustion engine in which a partition is provided in the intake passage downstream of the throttle valve, which makes it possible to improve the intake of intake air when the opening of the throttle valve is relatively small.

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 in communication with the intake passage downstream of a middle portion of the partition in the intake air flow direction.

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. Therefore, 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, improving the flow of intake air from the intake passage into the combustion chamber.

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. This configuration makes it easier to guide the air flowing in from the resonator to the combustion chamber, thereby improving the combustion efficiency in the combustion chamber.

Preferably, the resonator is directly connected to the cylinder head of the internal combustion engine, which defines the ceiling surface of the combustion chamber, via a communication passage. This makes it easier to guide the air flowing in from the resonator more directly into the combustion chamber.

Preferably, when the direction from the crankshaft side to the cylinder head side in the direction of the 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 arranged in sequence in the first direction. This makes it possible to generate a tumble flow in the intake air flowing from the first intake passage into the combustion chamber, for example.

Preferably, the communication passage connecting the resonator to the intake passage is connected to the downstream portion of the second intake passage or to the downstream junction of the first intake passage and the second intake passage. This allows the intake air from the resonator to be introduced into the combustion chamber from the second intake passage side or the downstream junction.

Preferably, when a virtual plane is defined that passes through the center of the intake valve port facing the combustion chamber and opened and closed by the intake valve and the center of the exhaust valve port facing the combustion chamber and opened and closed by the exhaust valve, and extends parallel to the cylinder axis, a deflection section 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.

Preferably, the cross-sectional area of the second intake passage is larger than the cross-sectional area of 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 appropriately guide sprayed fuel from the fuel injection valve into the combustion chamber while maintaining an optimal flow of intake air in the first intake passage.

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. This configuration allows the air flow from the resonator to be substantially the same as the fuel injection direction, thereby allowing the sprayed fuel to be more effectively diffused in the combustion chamber.

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

Preferably, a notch is further provided at the downstream outlet of the communication passage connecting the resonator to the intake passage. This configuration can further prevent injected fuel from accumulating in the communication hole, thereby preventing a deterioration in fuel efficiency.

According to the above aspect of the present invention, the above configuration makes it possible to improve the intake of intake air when the opening of the throttle valve is relatively small in an internal combustion engine in which a partition is provided in the intake passage downstream of the throttle valve.

1 is a cross-sectional view of an internal combustion engine and its surroundings according to an embodiment of the present invention. FIG. 2 is a right side view of the cylinder head and its vicinity of the internal combustion engine of FIG. 1 . 3 is a cross-sectional view of the internal combustion engine of FIG. 1 taken along line III-III of FIG. 2. FIG. 2 is a bottom view of the cylinder head of the internal combustion engine of FIG. 1 . 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. 1 . FIG. 6 is a plan view of the three-dimensional model of FIG. 5 . 7 is a cross-sectional view of the three-dimensional model of FIG. 5 taken along line VII-VII of FIG. 6. 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. 9 is a cross-sectional view of the three-dimensional model of FIG. 5, mainly of the intake system, taken along line IX-IX in FIG. 6. 7 is a cross-sectional view of the three-dimensional model of FIG. 5, mainly of the intake system, taken along line XX in FIG. 6, and is a diagram showing a schematic diagram of sprayed fuel. FIG. 9 is a perspective view of the three-dimensional model of FIG. 8 . 8 is a cross-sectional view of the three-dimensional model of FIG. 5 taken along line XII-XII of FIG. 7. FIG. 7 is a perspective view of the three-dimensional model of FIG. 6, and is a diagram illustrating a schematic diagram of sprayed fuel. FIG. 6 is a perspective view of the three-dimensional model of FIG. 5, and is a diagram illustrating a schematic diagram of sprayed fuel. 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. FIG. 2 is a schematic diagram showing the direction of a communication passage connecting a resonator to an intake passage in the internal combustion engine of FIG. 1 . FIG. 2 is a schematic diagram of the internal combustion engine of FIG. 1 , as viewed from the upstream side in the intake air flow direction toward the intake valve port side. FIG. 2 is a schematic diagram of an intake passage showing a region downstream of a throttle valve. FIG. 18 is a diagram showing pressure fluctuations at the points shown in FIG. 17 during the cycle of an internal combustion engine. 4 is an operation map of a throttle valve and a tumble control valve. 4 is a graph showing the relationship between the throttle opening and the intake air flow rate. 1 is a graph showing the correlation between the throttle opening and the strength of the vortex flow. 13 is a diagram showing a joining portion of a resonator to an intake passage in an intake device of a modified example. FIG.

Hereinafter, an embodiment of the present invention will be described with reference to the attached drawings. Identical parts (or configurations) are given the same reference numerals, and their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated.

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 an 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 forward direction, and in the drawings, FR indicates the forward direction, RR indicates the rearward direction, LH indicates the leftward direction, and RH indicates the rightward direction.

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 the crankshaft 12 oriented in the vehicle body width direction and the cylinders tilted slightly forward relative to the vehicle body. In the crankcase 14 that rotatably supports the crankshaft 12 of the internal combustion engine 10, a speed change gear mechanism 20 is configured between the main shaft 16 disposed behind the crankshaft 12 and the countershaft 18, which is the output shaft.

A cylinder block 22 with a single cylinder liner 22L cast in 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 configuration, and may be an internal combustion engine configured in various forms.

The crankcase 14 is split into left and right halves, and the lower end of the 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 that it can slide back and forth. A connecting rod 30 connects the piston pin 28p of the piston 28 and the crank pin 12p of the crankshaft 12 to form the crank mechanism.

A combustion chamber 32 is formed between the top surface 28t of the piston 28 sliding in the cylinder bore 22b of the cylinder block 22 and the combustion chamber ceiling surface (hereinafter, simply referred to as the "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 opposite positions with respect to the 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 by extending from the intake valve port 34 and the exhaust valve port 36, respectively, 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.

The intake valve 44 and the exhaust valve 46, which are slidably supported by the valve guides 42i and 42e, respectively, which are integrally fitted to the cylinder head 24, are driven by a valve mechanism 48 provided on the cylinder head 24 to open and close the intake valve opening 34 of the intake port 38 and the exhaust valve opening 36 of the exhaust port 40 in synchronization with the rotation of the crankshaft 12. That is, the 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 facing the combustion chamber 32 of the intake port 38. In addition, 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 opening 36 facing the combustion chamber 32 of the exhaust port 40.

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

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

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) fitted to the crankshaft 12. The camshaft 48a rotates in the same direction as the crankshaft 12 at half the rotation speed as the crankshaft 12.

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 Figure 3, a spark plug 54, which serves as ignition means, is fitted into the right wall of the cylinder head 24 toward the combustion chamber 32. It is preferable that an internal cylinder pressure sensor (not shown) be fitted into the vicinity of the spark plug 54 toward the combustion chamber 32.

Figure 4 is a bottom view of the cylinder head 24 that is superimposed on the cylinder block 22, with the cylinder axis C of the internal combustion engine 10 indicated by a dot. Referring to Figure 4, the mating surface 24f of the cylinder head 24 that faces the mating surface of the cylinder block 22 is recessed to form a ceiling surface 24t of the combustion chamber 32 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 into the mating surface 24f on the left side of the combustion chamber 32.

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

In addition, a plug hole 56 is drilled on the right side of the cylinder axis C of the ceiling surface 24t, which allows the electrode of the spark plug 54 to protrude into the combustion chamber 32. That is, the spark plug 54 is not positioned at the center of the ceiling surface 24t, but is 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.

3, the spark plug 54 has 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.

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 connected to the combustion chamber 32 of the internal combustion engine 10, and its upstream side is connected to an air cleaner device (not shown).

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

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

The downstream end of the exhaust port 40 opens downwardly into 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.

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 more favorable 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, and 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 along 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 excluding the tumble passage 72. The intake passage portion 72 that can serve as 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.

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 extending substantially parallel to the axis extending in the intake flow direction. In this embodiment, the flow cross-sectional area of the tumble flow passage 72 is smaller than the flow cross-sectional area of the main flow passage 74, that is, the flow cross-sectional area of the main flow passage 74 is larger than the flow cross-sectional area of the tumble flow passage 72. However, the partition 70 may be provided so that the flow cross-sectional area of the tumble flow passage 72 is larger than the flow cross-sectional area of the main flow passage 74, and it is also possible to make them substantially the same.

As shown in Figure 1, the lower part of the intake passage 60 separated by the partition 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" for 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 "up" 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 "down" direction, and do not mean absolute "up" and "down" in space. This "up" or "up" direction corresponds to the first direction, and the "down" or "down" direction corresponds to the second direction.

A tumble control valve 75 is further provided upstream of the partition 70 and downstream of the throttle valve 62c. As shown in FIG. 1, the tumble control valve 75 is disposed at the upstream end 70u 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-shaped semidisk that blocks 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.

The tumble control valve 75 may also be referred to as an intake control valve, a tumble valve, or a TCV. The tumble control valve 75 and the throttle valve 62c are each electronically controlled as described below, but are not limited to being electronically controlled. For example, at least one of them may be a valve that is mechanically controlled by a cable.

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 the 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 path 74 side. The second fuel injection valve 78 is provided so as to face the main flow path 74, and is provided in the inlet pipe 58 here. In this way, the second fuel injection valve 78 is provided so as to inject fuel from the main flow path 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 the upper wall of the member that defines the intake passage 60. Note 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.

In the internal combustion engine 10 having the above configuration, the resonator 77 is connected to the intake passage 60 via a communication pipe 77a. The communication pipe 77a is provided so as to connect the resonator 77 to 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 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 by the cylinder head 24. Here, the communication passage 77b is defined by the communication pipe 77a connecting the resonator 77 and the cylinder head 24, but is not limited to this and may be configured as part of the resonator 77 or 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.

The ECU (electronic control unit) 80 that controls the internal combustion engine 10 has a so-called computer configuration 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 output from various sensors such as an engine 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 the fuel injection valves 76 and 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.

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

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 described later. Therefore, to facilitate understanding, the parts 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. In addition, the portion where the second fuel injection valve 78 is attached and its injection port faces the intake passage 60 (hereinafter, the mounting portion) is given the reference numeral "78s". Furthermore, in the direction of the cylinder axis C, the above-mentioned "upper" side is designated by the letter "U" and the "lower" side is designated by the letter "D".

As already mentioned, and as is clear from Figure 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 Figure 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 Figure 9.

1, 8 to 10 and 12, the partition 70 has a deviation portion 90 provided downstream of the partition 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 70. The deviation portion 90 is a narrow portion of the partition 70 in the width direction that can be defined as the direction extending from one side of the valve axis of the intake valve 44 to the other side when the intake air flows from the upstream side to the downstream side in the intake passage 60, i.e., in the intake flow direction, toward the intake valve 44. As shown in FIG. 12, in the tumble flow passage 72, the width W2 in the downstream end portion 72d in the width direction is clearly narrower than the width W1 in the upstream end portion located on the upstream end 70u side of the partition 70 among the portions partitioned and formed by the cylinder head 24.

Furthermore, the deviation portion 90 is biased in one direction in the left-right direction, i.e., in the width direction. Here, as described above, the downstream end portion 72d of the tumble flow passage 72 is partitioned so as to be biased toward the right RH side (see Figures 10 and 12). Therefore, the deviation portion 90 downstream of the partition portion 70 that at least partially partitions the biased downstream end portion 72d of the tumble flow passage 72 is biased toward the right RH side here. Therefore, in Figure 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 partitioned so as to be biased to the same side in the width direction.

Here, the relationship between the partition section 70 and the downstream deviation section 90, and the tumble flow path 72 and main flow path 74 will be further explained with reference to Figures 8 to 10.

At the cut location in Figure 8 (VIII-VIII in Figure 6), the tumble flow path 72 and the main flow path 74 are completely separated. The width of the tumble flow path 72 and the width of the main flow path 74 are approximately the same. 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 path 72 and the main flow path 74, and the partition body portion 92 that connects to the upstream side of the deviation portion 90 extends. Note that in Figure 8, the portions corresponding to the surface 70s of the partition portion 70 and the surface 92s of the partition body portion 92 therein are given the same reference numerals.

At the cut location in Figure 9 (line IX-IX in Figure 6), the tumble flow path 72 and the main flow path 74 are completely separated, but the width of the tumble flow path 72 is narrower than the width of the main flow path 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 path 72 and the main flow path 74, and is in the process of transitioning from the partition main body portion 92 to the offset portion 90. Note that in Figure 9, the locations corresponding to the surface 70s of the partition portion 70 are labeled with their corresponding reference numerals.

At the cut portion of FIG. 10 (line X-X of 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 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 70 transitions from the partition main body portion 92 to the offset portion 90, and that the offset portion 90 extends leftward from the right side of the inner wall surface 24s of the cylinder head 24 to the intake port 38, to the extent that it 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 are connected 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 Figure 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.

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 section 90 in the region where the deviation section 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 section 90 is biased, and in this case, it is performed on the left LH side of the deviation section 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 section 90.

9 and 10, as the partition portion 70 transitions from the partition body portion 92 to the offset portion 90, a wall surface 24w appears that biases the tumble flow passage 72 in the width direction. The wall surface 24w is a part of the inner wall surface 24s of the cylinder head 24, located directly below the second direction side of the main flow passage 74, and extends in the direction of the cylinder axis C as shown in Figs. 9 and 10, has a vertical length, 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 flow passage 74. The wall surface 24w extends to the left LH side of the downstream end portion 72d of the tumble flow passage 72 to define it, biasing the tumble flow 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 flow passage 72 to one side of the above-mentioned imaginary plane IS, that is, to the right RH side.

The mounting portion 78s of the second fuel injection valve 78 is positioned on the left LH side of the intake passage 60, as is clear from Figures 6, 8, and 11. In this way, 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, i.e., on the main flow path 74 side, and injects fuel from the main flow path 74 side.

Here, perspective views of the three-dimensional model M shown in Figures 6 and 5 are shown in Figures 13A and 13B. In Figures 13A and 13B, the sprayed fuel SF injected from the second fuel injection valve 78, which is provided at a position biased toward the left LH side, is shown typically. Also, in Figure 10, a part of the sprayed fuel SF injected from the second fuel injection valve 78 is shown typically. From Figures 10, 13A, and 13B, it can be understood that the fuel SF injected from the second fuel injection valve 78 is not blocked by the partition portion 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 portion 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 offset 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 offset portion 90, preferably without touching the offset portion 90 (see, for example, Figure 10).

Furthermore, the second fuel injection valve 78, which is arranged to inject fuel SF from the main flow passage 74 side toward the combustion chamber 32, is arranged to inject fuel in the direction opposite to the biased direction of the deviation portion 90. Therefore, the partition portion 70, and 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 that it is biased downstream in the biased direction of the deviation portion 90. Therefore, the deviation portion 90 of the partition portion 70, which is extended further downstream in the intake flow direction, can impart stronger directionality to the intake air from the tumble flow passage 72.

In this way, the partition 70 is designed to completely separate the main flow path 74 and the tumble flow path 72 with the partition body 92 on the upstream side, and to have the offset portion 90 on the downstream side, so that the flow from the tumble flow path 72 is characterized further downstream while realizing the connection between the main flow path 74 and the tumble flow path 72. In addition, the second fuel injection valve 78 is arranged in a biased position opposite to the biased direction of the offset portion 90, and is arranged on the opposite side in the width direction here, so that fuel can be injected in a direction different from the offset portion 90, and fuel can be introduced into the combustion chamber 32 almost directly through the intake valve port 34. In other words, the supply of fuel to the combustion chamber can be well ensured. Therefore, the offset portion 90, which is the downstream portion of the partition 70, can be extended further downstream. Therefore, a stronger directivity can be given to the flow from the tumble flow path 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 .

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 section 70, i.e., the downstream edge 90d of the offset section 90, and forms a single intake passage leading to the combustion chamber 32. This allows the intake air from the tumble flow passage 72 to be introduced into the combustion chamber 32 together with the 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 the intake air from the single intake port 38, which is a single intake passage. This configuration also makes it possible to suppress an increase in the number of parts, and is also excellent in terms of cost.

In the above internal combustion engine 10, as described above, the wall surface 24w can bias the intake air from the tumble flow passage 72 to one side of the imaginary plane IS, i.e., the right RH side, and allow it to flow into the combustion chamber 32. The intake air from the tumble flow 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 ceiling surface 24t or the cylinder bore 22b, which extend toward the exhaust side, among the walls 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, in addition to the vertical force component of the tumble flow, the intake air from the tumble flow passage 72 can also have the lateral force component of the swirl flow, i.e., the force component in the cylinder circumferential direction.

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 preferably ignite the fuel contained in the intake air from the tumble passage 72, that is, the air-fuel mixture.

Figure 14 shows 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. Figure 14 also shows the outline of the circular opening edge 24e of the cylinder bore 22b or the ceiling surface 24t of 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 34a of the intake valve port 34 and the center 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 Figure 14.

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 passes mainly on 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, where it can collide. At this time, the wall surface 32W against which the flow of the arrow T collides 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.

The wall surface 32W against which the intake air from the tumble flow passage 72 collides is, as described above, the wall surface that defines the combustion chamber 32 and extends toward the exhaust side, such as the portion of the ceiling surface 24t or the portion of the cylinder bore 22b. As described above, the ceiling surface 24t is formed as a concave curved surface. Therefore, the ceiling surface 24t can favorably generate a force of the tangential component Fb by the intake air from the tumble flow passage 72. In particular, since the ceiling surface 24t is formed in an approximately hemispherical shape and is a smooth concave curved surface, such a force can be generated in the intake air from the tumble flow passage 72, contributing to more favorably generating a swirl-like flow.

In addition, the flow when the intake air is directed more to the right and flows into the combustion chamber 32 is shown by the arrow T1 in FIG. 14. In this case, compared to the flow of the arrow T, the flow of the arrow T1 collides with the wall surface 32W at an angle (θ1 < θ2). Therefore, 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 swirl flow component becomes larger, and flame propagation from one side of the imaginary plane IS to the other side becomes easier. It is advisable to design the bias of the tumble flow passage 72, the inclination of the tumble flow passage 72 with respect to the combustion chamber 32, etc., for example, the wall surface 24w, taking into account the degree of the force of the tangential component that is generated.

Furthermore, in the internal combustion engine 10, the spark plug 54 is positioned on the side of the imaginary plane IS to which the intake air from the tumble passage 72 is biasedly directed. Therefore, the intake air from the tumble passage 72 contains fuel and essentially forms an air-fuel mixture, and the mixture introduced into the combustion chamber 32 is suitably ignited by the spark plug 54. And, because a flow from the right RH side, which is one side of the imaginary plane IS, to the left LH side is formed as described above, flame propagation in the combustion chamber 32 can be suitably generated.

Now, in the internal combustion engine 10 configured as described above, as mentioned above, the resonator 77 is connected to the intake passage 60, particularly to the intake passage 60d downstream of the throttle valve 62c. As shown in Figures 1, 5 to 9, 11, 13A and 13B, the resonator 77 is provided so as to communicate with the intake passage 60d at an angle, rather than perpendicular to the intake flow direction. The communication pipe 77a is connected to the cylinder head 24 so as to be inserted obliquely from the top to the bottom. Therefore, the axis 77d (Figures 7 and 9) of the downstream outlet portion 77c of the communication pipe 77a, i.e., the communication passage 77b, intersects obliquely with the intake flow direction at the connection point of the intake passages 60, 60d, and here faces particularly toward the combustion chamber 32.

The communication passage 77b connecting the resonator 77 to the intake passage 60 is provided in a position biased toward the left LH side, like the second fuel injection valve 78. The communication passage 77b is directly connected to the main flow passage 74 and the downstream junction 72f. Furthermore, as is clear from Figures 1 and 6, the communication point of the communication passage 77b to 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 approximately 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.

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

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 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.

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 side (the side facing the combustion chamber) of the umbrella portion 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 portion 44a.

Because 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 greater than the bias of the intake air from the tumble passage 72 because the axis 77d of the downstream outlet portion 77c in the communication passage 77b diagonally 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 to it.

Here, the experimental results will be explained. 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 explained with reference to Figures 17 and 18, in comparison with the case of an intake system without a resonator. As shown in Figure 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. Figure 17 shows the positions of various points representing the change in pressure in the intake system shown in Figure 18, with 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 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.

Figure 18 shows pressure data for each crank angle in one cycle when the throttle valve 62c is slowly 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. These definitions also include the area and volume within the resonator 77 when it is connected.

The following describes 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. When the resonator 77 is not connected downstream of the throttle valve 62c, this refers to when the intake system does not have a resonator 77, or when the intake system has a resonator 77 but is connected upstream of the throttle valve 62c.

In an intake system where 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 charge of the amount of air that increases with the descent of the piston 28 is not in time, and the pressure inside the intake port suddenly becomes negative (between the crank angles of approximately 380 degrees and 540 degrees in Figure 18). When the pressure inside 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.

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 within the resonator 77 than when the resonator 77 is not connected, so the mass of the accumulated air is larger.

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.

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 Figure 18). Because 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 as the piston descends is relatively small, the flow does not decrease, and the flow of vortex flows such as tumble flows formed in the cylinder can be enhanced.

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

Figure 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 the line when the throttle valve 62c is fully open and the opening range of the tumble control valve 75. Both the region α1 and the region α2 are regions in which the tumble control valve 75 is closed as shown by the dashed lines in Figure 1, and the region β is a region in which the tumble control valve 75 is opened as shown by the solid lines in Figure 1. The region α1 is a region in which the throttle valve 62c is gradually opened and corresponds to a low load region, and the region α2 is a region in which the throttle valve 62c is opened to a predetermined opening degree or more that is larger than the opening degree in the region α1 and corresponds to a medium load region. 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 Figure 19 is stored in the memory unit of the ECU 80.

The graph in Figure 20A has the opening of the throttle valve 62c, i.e., the throttle opening TH, on the horizontal axis and the intake air flow rate into the combustion chamber 32 on the vertical axis, 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 in Figure 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.

20B shows the correlation between the strength of vortexes such as tumble flow caused by intake from the tumble passage 72 and swirl flow caused by intake 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 vortexes. 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).

When the tumble control valve 75 is closed and the throttle opening TH is relatively small, such as gradually opening, that is, when the internal combustion engine is operating in the low load region, i.e., region α1, there is little intake air in the tumble flow passage 72, which is the intake flow passage downstream from the throttle valve 62c, as described above. At this time, during the intake stroke, in addition to the intake air flowing in through the tumble flow passage 72, the intake air in the resonator 77 is also drawn into the combustion chamber 32 as described above.

In this way, when the tumble control valve 75 is closed and the throttle opening TH is relatively small (for example, when TH<TH1), during the intake stroke, in addition to the intake air flowing in through the tumble passage 72, the intake air in the resonator 77 is also actively drawn into the combustion chamber 32. At this time, the intake air from the resonator 77 is directed as described above and strongly directed toward the right side of the combustion chamber 32 and drawn in. This causes a strong swirl flow or a tumble flow with a strong swirl component to be generated in the combustion chamber 32 (the "swirl" line in Figure 20B). This promotes the combustion of the mixture in the combustion chamber. In this way, the resonator 77 provided as described above can improve the intake of intake air when the throttle opening is relatively small.

On the other hand, when the tumble control valve 75 is in a closed state and the throttle opening TH gradually increases, for example when the internal combustion engine is operating in the medium load region, i.e., region α2, the intake air flowing from the throttle valve 62c into the tumble flow passage 72 downstream thereof can cover the intake air during the intake stroke, and the degree to which the intake air in the resonator 77 is drawn into the combustion chamber 32 decreases.

In this way, when the tumble control valve 75 is closed 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 Figure 20B). Therefore, even when the tumble control valve 75 is closed and the throttle opening TH is relatively large, intake of the intake air can be performed favorably.

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

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 as described above. 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 vortex flows, such as swirl flows, in the combustion chamber 32.

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

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 of the communicating 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 facilitating its combustion.

Furthermore, the spark plug 54 is positioned in the direction of fuel injection, which allows the fuel to be combusted in the combustion chamber 32 more efficiently.

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 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 that connects the intake air of the resonator 77 to the intake passage 60 is designed to face the combustion chamber 32. This allows the intake air from the resonator 77 to be directed more directly toward the combustion chamber 32, actively generating 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.

21, a notch 77e may be further provided in the downstream outlet 77c of the 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 fuel from the second fuel injection valve 78 from accumulating in the downstream outlet 77c of the communication passage 77b.

Although the embodiments and their modifications 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.

The internal combustion engine 10 described above is a two-valve internal combustion engine with only one intake valve and only one exhaust valve per cylinder, but 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 described above is equipped with a tumble control valve 75, the present invention may also be applied to an internal combustion engine that is not provided with a tumble control valve 75.

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 injection valve, 77... resonator, 77b... communication passage
78: second fuel injection valve; 90: offset portion; 92: partition body portion
DP: Deflection section, M: 3D model, S: Intake system

Claims (10)

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 a middle portion (70m) of the partition portion (70) in the intake air flow direction so as to communicate with the intake passage (60d),
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,
An intake device (S) for an internal combustion engine, characterized in that the fuel injection direction of the fuel injection valve (78) is approximately parallel to an axis (77d) of a downstream outlet portion (77c) in a connecting passage (77b) connecting the resonator (77) to the intake passage (60d). The intake device (S) of an internal combustion engine as described in claim 1, characterized in that the axis (77d) of the downstream outlet portion (77c) of the communicating passage (70b) connecting the resonator (77) to the intake passage (60d) is designed to face the combustion chamber (32). The intake device (S) of an internal combustion engine as described in claim 1 or claim 2, characterized in that the resonator (77) is directly connected to a cylinder head (24) of the internal combustion engine, which defines a ceiling surface (24t) of the combustion chamber (32), via the communicating passage (77b). (delete) An intake device (S) for an internal combustion engine as described in any one of claims 1 to 3, characterized in that the communicating passage (77b) connecting the resonator (77) to the intake passage (60d) is connected to 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). 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),
An intake device (S) for an internal combustion engine as described in any one of claims 1 to 3 and claim 5, further comprising 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). 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). (delete) An intake device (S) for an internal combustion engine as described in any one of claims 1 to 3 and claims 5 to 7, characterized in that a tumble control valve (75) for opening and closing the second intake flow path (74) is further provided at the upstream end (70u) of the partition portion (70) or upstream of the upstream end (70u). An intake device (S) for an internal combustion engine as described in any one of claims 1 to 3, claims 5 to 7 and claim 9, further comprising a notch (77e) provided in a downstream outlet portion (77c) of a communication passage (77b) connecting the resonator (77) to the intake passage (60d).

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