JP7575615B2 - Intake structure of an internal combustion engine - Google Patents

Description

The present invention relates to an intake structure for an internal combustion engine in which a partition is provided to divide the intake passage into multiple sections.

Various intake structures for internal combustion engines have been proposed in which the intake passage downstream of the throttle valve is divided into multiple passages by a partition. For example, in the intake structure for an internal combustion engine disclosed in Patent Document 1, a tumble valve is provided downstream of the throttle valve, and a partition plate portion, which is a partition portion, is provided downstream of the tumble valve from the inlet pipe to the intake port, and this partition plate portion divides the intake passage into an upper and lower lower auxiliary passage and an upper main passage. The lower auxiliary passage becomes the tumble passage, and the tumble valve essentially opens and closes the upper main passage.

In addition, in the internal combustion engine disclosed in Patent Document 2, an intake control valve is provided downstream of the throttle valve, and a horizontal plate-shaped member is arranged in the intake passage further downstream of that, along the flow direction of the intake air. Internal combustion engines with one horizontal plate-shaped member and two or more horizontal plate-shaped members are disclosed. According to the description in Patent Document 2, by forming multiple horizontal plate-shaped members and determining the opening degree of the intake control valve according to the operating conditions of the internal combustion engine, the flow of intake air is not disturbed even at an intermediate opening degree of the intake control valve, and a stable gas flow is generated.

Japanese Patent No. 6714764 Japanese Patent Application Publication No. 2006-77590

In order to operate an internal combustion engine optimally, it is desirable to ensure both an intake air volume appropriate to the operating state of the engine and optimally generate vortex flows such as tumble flow in the combustion chamber to improve combustion efficiency. However, for example, in the configuration of Patent Document 2, it is essential to provide an intake control valve in addition to a throttle valve, and it is essential to precisely adjust the intake control valve to various angles when generating a tumble flow. This leads to a more complex structure of the intake control valve, which poses problems.

The object of the present invention is to provide a configuration in an internal combustion engine in which the intake passage is divided by a partition, which makes it possible to ensure both the amount of intake air according to the operating conditions and tumble performance without requiring an intake control valve with a complex structure in addition to the throttle valve.

In order to achieve the above object, one aspect of the present invention is to
a main partition portion that partitions an intake passage downstream of the throttle valve into a first intake passage that serves as a tumble flow passage for generating a tumble flow and a second intake passage located on a first direction side of the first intake passage;
a sub-partition portion provided in the first intake passage to define a third intake passage and a fourth intake passage on the first direction side of the third intake passage;
Equipped with
a valve axis of the throttle valve intersects the first direction and the intake air flow direction of the intake passage,
an upstream end of the sub-partition portion extends upstream of an upstream end of the main partition portion in the intake air flow direction;
The present invention provides an intake structure for an internal combustion engine, wherein the throttle valve is configured to be capable of opening to a plurality of opening degrees including a predetermined small opening degree.

According to the above configuration, the intake passage downstream of the throttle valve is provided with a main partition that partitions the first intake passage into a tumble flow passage for generating a tumble flow and a second intake passage, and a sub-partition that is provided in the first intake passage to form a third intake passage and a fourth intake passage. Therefore, by using one, more than one, or all of them depending on the operating state of the internal combustion engine, it is possible to ensure the amount of intake air according to the operating state. In addition, the valve shaft of the throttle valve intersects with the first direction and the intake flow direction of the intake passage, the upstream end of the sub-partition extends upstream of the upstream end of the main partition in the intake flow direction, and the throttle valve is configured to be able to open to a plurality of openings including a predetermined small opening. Therefore, when the throttle valve opens to a predetermined small opening, it is possible to promote the flow of intake air to the third intake passage, and tumble performance can be ensured. And, in the above configuration, since the tumble flow can be realized by operating the throttle valve, an intake control valve with a complex structure is not necessarily required.

Preferably, when the throttle valve is open to the predetermined small opening, a first gap and a second gap are formed between the valve body of the throttle valve and the wall surface of the intake passage, and the first gap is located on the opposite side of the second gap across the valve shaft of the throttle valve. With this configuration, when the throttle valve is open to the predetermined small opening, the flow of intake air can be favorably promoted to the third intake passage.

Preferably, each of the first gap and the second gap has a gap width equal to or less than the thickness of the main partition. With this configuration, when the throttle valve is opened to a predetermined small opening, the flow of intake air into the third intake passage can be more effectively promoted.

Preferably, the valve axis of the throttle valve is perpendicular to the first direction and the intake air flow direction of the intake passage. With this configuration, when the throttle valve is open to a predetermined small opening, the flow of intake air can be more suitably urged into the third intake passage.

Preferably, the sum of the cross-sectional areas of the second intake passage and the fourth intake passage is larger than the cross-sectional area of the third intake passage, and an intake control valve capable of opening and closing the second intake passage is further provided. By making the sum of the cross-sectional areas of the second intake passage and the fourth intake passage larger than the cross-sectional area of the third intake passage, when the throttle valve is opened to a predetermined small opening, the flow of intake air that once flowed to the second intake passage and the fourth intake passage side can be more suitably promoted to the third intake passage. In addition, by providing an intake control valve, for example, the second intake passage can be closed when the throttle valve is opened to a predetermined small opening, and the flow of intake air to the third intake passage can be further promoted.

Preferably, the cross section of the second intake passage at the installation position of the intake control valve is substantially circular. This configuration makes it easier to increase the degree of occlusion of the second intake passage by the intake control valve when the valve is closed.

Preferably, a tapered portion having a cross-sectional area that decreases toward the downstream side in the intake flow direction is provided in the second intake passage between the upstream end of the main partition and the installation position of the intake control valve. This configuration makes it possible to more suitably smooth the flow of intake air into the second intake passage.

It is preferable that a resonator is connected to the first intake passage. This configuration increases the flow of intake air from the first intake passage, thereby strengthening the tumble flow.

Preferably, the intake structure further includes a junction where the third intake passage and the fourth intake passage join, and the first intake passage joins the second intake passage through the junction. This configuration allows the intake from the first intake passage, which includes the third intake passage and the fourth intake passage, to have a strong directivity, and further ensures tumble performance.

Preferably, the junction is partitioned so that the area of a cross section perpendicular to the flow direction downstream of the upstream end of the junction is smaller than the sum of the cross-sectional areas of the third and fourth intake passages. With this configuration, when the intake air from the third intake passage and the intake air from the fourth intake passage join at the junction and flow into the second intake passage, it is possible to maintain a high flow rate of the intake air.

Preferably, the confluence is partitioned so that the intake air from the first intake passage through the confluence flows into the combustion chamber at a smaller angle of approach than the intake air from the second intake passage. This configuration allows the intake air that has passed through the first intake passage to be introduced into the combustion chamber with strong directionality, thereby generating a strong tumble flow in the combustion chamber.

According to the above aspect of the present invention, since the above configuration is provided, in an internal combustion engine in which the intake passage is divided by a partition, it is possible to ensure both the intake air volume according to the operating conditions and the tumble performance without requiring an intake control valve with a complex structure in addition to the throttle valve.

1 is a cross-sectional view showing a schematic configuration of an internal combustion engine according to an embodiment of the present invention. FIG. 2 is a diagram showing a three-dimensional model of an intake system in the internal combustion engine of FIG. 1 . 2 is a cross-sectional view of a part of a main flow passage and an upstream end side part of a main partition portion in the internal combustion engine of FIG. 1 . 4 is a view of a part of the main flow path shown in FIG. 3 as viewed from the upstream side. FIG. 2 is a three-dimensional model of the intake system in the internal combustion engine of FIG. 1 when a tumble valve, which is an intake control valve, is closed and a throttle valve is opened to a predetermined small opening degree. FIG. 2 is a three-dimensional model of the intake system in the internal combustion engine of FIG. 1 when the tumble valve is closed and the throttle valve is opened to an opening degree larger than a predetermined small opening degree. FIG. 2 is a three-dimensional model of the intake system in the internal combustion engine of FIG. 1 when a tumble valve and a throttle valve are both fully open. 2 is a view of a three-dimensional model including a portion of an intake passage downstream of a throttle valve and a tumble valve and an exhaust port in the internal combustion engine of FIG. 1, viewed in a direction perpendicular to the cylinder axis and perpendicular to the intake air flow direction. 9 is a cross-sectional view of the three-dimensional model of FIG. 8 taken along line IXA-IXA. 9 is a cross-sectional view of the three-dimensional model of FIG. 8 taken along line IXB-IXB. 9 is a cross-sectional view of the three-dimensional model of FIG. 8 taken along line IXC-IXC. FIG. 4 is a diagram for explaining the flow of intake air through a butterfly valve. FIG. 13 is a further diagram for explaining the flow of intake air through the butterfly valve. 2 is a diagram for explaining the flow of intake air around a throttle valve in the internal combustion engine of FIG. 1 . FIG. FIG. 2 is a diagram showing the results of a simulation of the flow of intake air around a throttle valve in the internal combustion engine of FIG. 1 . 14 is a cross-sectional view of the intake passage at a position along line XIVA-XIVA in the simulation model of FIG. 13. 14 is a cross-sectional view of the intake passage at a position along line XIVB-XIVB in the simulation model of FIG. 13. FIG. 2 is a diagram showing a modified example of the intake structure of the internal combustion engine of FIG. 1 .

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.

The schematic configuration of an internal combustion engine 10 according to one embodiment of the present invention is shown in Figure 1. Figure 1 is a cross-sectional view of the internal combustion engine 10 taken along the axis C of the cylinder bore 12b of the cylinder block 12 of the internal combustion engine 10 (cylinder axis).

A piston 15 that reciprocates within a cylinder bore 12b of the cylinder block 12 is connected to a crank pin of a crankshaft 17 of a crankcase portion 16 by a connecting rod 18. A combustion chamber 20 is formed between a top surface 15a of the piston 15 that is slidably fitted within the cylinder bore 12b of the cylinder block 12 and a combustion chamber ceiling surface 14a of the cylinder head 14 that faces the top surface 15a.

The internal combustion engine 10 employs a two-valve system of the SOHC type, and the cylinder head 14 is provided with a valve train 22. A cylinder head cover 24 is placed over the cylinder head 14 to cover the valve train 22. To transmit power to the valve train 22 in the cylinder head cover 24, an endless cam chain (not shown) is installed between the camshaft 26 and the crankshaft 17, passing through a cam chain chamber (not shown) provided on one side of the crankshaft direction of the crankcase 16, the cylinder block 12, and the cylinder head 14, and the camshaft 26 rotates at half the rotational speed of the crankshaft 17 in synchronization with the crankshaft 17. An ignition plug (not shown) is inserted into the combustion chamber 20 from the opposite side of the cam chain chamber (the other side of the crankshaft direction) in the cylinder head 14.

In the cylinder head 14, an intake port 32 and an exhaust port 34 are formed by extending from the intake valve port 28 and exhaust valve port 30, which open into the combustion chamber ceiling surface 14a, while curving upward and downward away from each other. The upstream end of the intake port 32 opens toward the top of the cylinder head 14 and connects to an inlet pipe 36 to form a continuous intake passage 38, and a throttle body 40 is connected to the upstream side of the inlet pipe 36.

The downstream end of the exhaust port 34 opens downwardly into the cylinder head 14 and is connected to an exhaust pipe 42. An exhaust purification device and a silencer may be provided downstream of the exhaust pipe 42.

A cylindrical intake valve guide 44 is fitted integrally to the curved outer wall portion 32a of the intake port 32 in the cylinder head 14. An intake valve 46 slidably supported by the intake valve guide 44 opens and closes the intake valve opening 28 of the intake port 32 facing the combustion chamber 20.

In addition, an exhaust valve 50 slidably supported on an exhaust valve guide 48 integrally fitted to the curved outer wall portion 34a of the exhaust port 34 in the cylinder head 14 opens and closes the exhaust valve opening 30 of the exhaust port 34 facing the combustion chamber 20.

The intake valve 46 and the exhaust valve 50 are biased upward by a valve spring so that their umbrella portions 46a, 50a close the intake valve port 28 and the exhaust valve port 30 that face the combustion chamber 20. The stem ends 46b, 50b of the intake valve 46 and the exhaust valve 50 are pushed down by the intake rocker arm 56 and the exhaust rocker arm 58, which swing against the intake cam and the exhaust cam of the camshaft 26, respectively, and the intake valve 46 and the exhaust valve 50 open at a predetermined timing, connecting the intake port 32 and the combustion chamber 20, and the exhaust port 34 and the combustion chamber 20, and allowing intake and exhaust to occur at a predetermined timing.

An inlet pipe 36 is connected to the upstream end of the intake port 32 of the internal combustion engine 10 via an insulator 60 to form a continuous intake passage 38, and a throttle body 40 is connected to the upstream side of the inlet pipe 36. The throttle body 40 has an intake passage 40a with a roughly circular cross section that forms part of the intake passage 38 leading to the combustion chamber 20 of the internal combustion engine 10, and its upstream side is connected to an air cleaner device (not shown).

The throttle body 40 is provided with a throttle valve 40c that is rotatably supported within the throttle body 40 by a valve shaft, i.e., a throttle valve shaft 40b, that intersects perpendicularly with the flow direction of the intake air in the intake passage 40a, i.e., at a right angle with the central axis of the intake passage 40a, and that can variably control the flow area of the intake passage 40a and open and close the intake passage 40a. The throttle valve 40c is of the butterfly type and has the throttle valve shaft 40b and a disk-shaped valve body 40d that is fixed to the throttle valve shaft 40b and rotates integrally therewith.

Throttle valve 40c can be rotated in the opening direction clockwise in Fig. 1 by the driver's operation, etc., and a return spring (not shown) urges valve body 40d counterclockwise in the closing direction so that the edge of valve body 40d is in the fully closed position where it abuts on the inner wall surface of intake passage 40a. Note that the opening and closing directions of throttle valve 40c may be opposite to each other.

In the internal combustion engine 10 as described above, an intake structure 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 20 in order to obtain more favorable combustion in the combustion chamber 20. That is, the intake passage 38 is divided along the intake flow direction by a partition 62 continuing from the inlet pipe 36 to the intake port 32, and is divided into a tumble flow passage 64 configured so that the intake air that passes through generates a tumble flow in the combustion chamber 20, and a main flow passage 66 excluding the tumble flow passage 64. The tumble flow passage 64 corresponds to the first intake passage, and the main flow passage 66 corresponds to the second intake passage. The tumble flow passage 64 may also be called a secondary passage.

Furthermore, a partition 72 is provided in the tumble passage 64 so as to continue mainly from the inlet pipe 36 to the intake port 32. By providing the partition 72, two intake passages 68, 70 are partitioned in the tumble passage 64. One of the two intake passages 68, 70 is the first tumble passage 68, and the other is the second tumble passage 70. The first tumble passage 68 corresponds to the third intake passage, and the second tumble passage 70 corresponds to the fourth intake passage.

Here, the partition 62 separating the tumble flow passage 64 and the main flow passage 66 is referred to as the main partition, and the partition 72 separating the first tumble flow passage 68 and the second tumble flow passage 70 of the tumble flow passage 64 is referred to as the sub-partition. The main partition 62 extends in a plate-like manner in the flow direction of the intake air, and the sub-partition 72 also extends in a plate-like manner in the flow direction of the intake air, for example, approximately parallel to the main partition 62. The main partition 62 is provided so as to substantially bisect the intake passage 38 in the vertical direction, here substantially extending on the central axis extending in the flow direction. The sub-partition 72 is provided so as to substantially bisect the tumble flow passage 64 in the vertical direction, here substantially extending on the central axis of the tumble flow passage 64 extending in the flow direction. As a result, the intake passage 38 is formed with a tumble passage 64 and a main passage 66 separated by the main partition portion 62, and the tumble passage 64 is formed with a first tumble passage 68 and a second tumble passage 70 located closer to the main passage 66 than the first tumble passage 68, that is, between the first tumble passage 68 and the main passage 66, by the sub-partition portion 72. As described above, the main partition portion 62 extends so as to substantially divide the intake passage 38 in half in the vertical direction, and the sub-partition portion 72 extends so as to substantially divide the tumble passage 64 in half in the vertical direction, so that the cross-sectional area of the main passage 66 is obviously larger than the cross-sectional area of the first tumble passage 68 and is also obviously larger than the cross-sectional area of the second tumble passage 70. Therefore, the sum of the cross-sectional areas of the main passage 66 and the second tumble passage 70 is obviously larger than the cross-sectional area of the first tumble passage 68. In addition, each of the main partition 62 and the sub-partition 72 may be provided so as to be biased toward either the top or bottom direction.

The ratio (SA1:SA2) of the sum SA1 of the cross-sectional area of the main flow path 66 and the cross-sectional area of the second tumble flow path 70 to the cross-sectional area SA2 of the first tumble flow path 68 is preferably set to 8:2 to 7:3. However, the ratio is not limited to this range.

The lower part of the intake passage 38 separated by the main partition 62 becomes the tumble passage 64, the upper part becomes the main passage 66, the lower part of the tumble passage 64 separated by the sub-partition 72 becomes the first tumble passage 68, and the upper part becomes the second tumble passage 70, but in this specification they are not limited to the up-down arrangement. In this specification, "up" and "down" for the intake passage 38, etc. refer to the direction from the crankshaft 17 side to the cylinder head 14 or cylinder head cover 24 side in the cylinder axis C direction as the "up" or "up" direction, and the direction opposite to this "up" direction, that is, the direction from the cylinder head 14 side to the crankshaft 17 side as the "down" or "down" direction, and do not mean absolute "up" and "down" in space. In this specification, this "up" or "up" direction corresponds to the first direction, and the "down" or "down" direction corresponds to the second direction. However, it is possible for this relationship to be reversed, with the "up" or "up" direction corresponding to the second direction and the "down" or "down" direction corresponding to the first direction.

The main partition 62 extends continuously from a position spaced apart from the throttle valve 40c by a first predetermined distance in the intake flow direction F to the intake port 32. Similarly, the sub-partition 72 extends continuously from a position spaced apart from the throttle valve 40c by a second predetermined distance in the intake flow direction F to the intake port 32. As is clear from FIG. 1, the upstream end 72a of the sub-partition 72 extends upstream of the upstream end 62a of the main partition 62 in the intake flow direction F. In other words, the upstream end 72a of the sub-partition 72, i.e., its edge 72at, is located upstream of the upstream end 62a of the main partition 62, i.e., its edge 62at, in the intake flow direction F. Here, the upstream side of the sub-partition 72 extends to the connecting pipe 77 between the inlet pipe 36 and the throttle body 40. Similarly, the upstream side of the main partition portion 62 extends to a connecting pipe 77 between the inlet pipe 36 and the throttle body 40. It is noted that the main partition portion 62 and the sub-partition portion 72 may be formed without providing the connecting pipe 77. It is noted that the downstream end 62b of the main partition portion 62 extends downstream of the downstream end 72b of the sub-partition portion 72, and the downstream edge 62bt of the downstream end 62b is located downstream of the downstream edge 72bt of the downstream end 72b in the intake flow direction F.

As mentioned above, the valve shaft 40b of the throttle valve 40c is perpendicular to the intake flow direction F of the intake passage 40a of the intake passage 38. In FIG. 1, the up-down direction is parallel to the paper, and the valve shaft 40b of the throttle valve 40c is perpendicular to the paper. Therefore, the valve shaft 40b of the throttle valve 40c intersects with the intake flow direction F and also intersects with the up-down direction, e.g., the first direction. In particular, here, the valve shaft 40b of the throttle valve 40c is perpendicular to the up-down direction, e.g., the first direction, and the intake flow direction F of the intake passage 38.

A tumble valve 76 is provided in the main flow passage 66. Here, the tumble valve 76 is provided in the inlet pipe 36, but it may be provided in the connecting pipe 77. The tumble valve 76 is supported rotatably in the inlet pipe 36 by a valve shaft 76b that intersects perpendicularly with the intake flow direction of the main flow passage 66, i.e., at a right angle with the central axis of the main flow passage 66, so that it can open and close the main flow passage 66. The tumble valve 76 is of a butterfly type, and has a valve shaft 76b and a substantially disk-shaped valve body 76c that is fixed to the valve shaft 76b and rotates integrally therewith. In this way, the tumble valve 76 is configured with a valve body 76c that is a single valve member that rotates integrally with the valve shaft 76b. However, here, the valve shaft 76b of the tumble valve 76 is parallel to the throttle valve shaft 40b, but it does not have to be parallel. The tumble valve 76 may also be called a tumble control valve, TCV, etc., and corresponds to the intake control valve of the present invention.

Here, a three-dimensional model M1 of the intake system of the internal combustion engine 10, particularly the downstream side of the intake system, is shown in FIG. 2. FIG. 2 is a view of the three-dimensional model M1 from the left-right direction (perpendicular to the up-down direction), and is a view from the back side of the paper surface of FIG. 1. FIG. 2 is a view of the three-dimensional model M1 from a direction perpendicular to the valve axis 46c of the intake valve 46 and perpendicular to the extension direction of the main partition section 62 and the extension direction of the sub-partition section 72. The three-dimensional model M1 shows the throttle valve 40c and the tumble valve 76. FIG. 3 shows a cross-sectional view along the intake flow direction of a part of the main flow passage 66 and a part on the upstream end 62a side of the main partition section 62. Furthermore, FIG. 4 shows a view of a part of the main flow passage 66 shown in FIG. 3 from the upstream side.

3 and 4, the upstream end of the main flow passage 66 has a tapered portion 66a that tapers from the upstream side to the downstream side in the intake flow direction. The tapered portion 66a is located in the main flow passage 66 between the upstream end 62a of the main partition portion 62 and the installation position of the tumble valve 76, and is a portion in which the cross-sectional area becomes smaller toward the downstream side in the intake flow direction. In order to form this tapered portion 66a, the upstream end 62a of the main partition portion 62 is formed so that it is thinnest at its end edge 62at side and the thickness increases toward the downstream side (see FIG. 3). The upstream side of the tapered portion 66a is approximately D-shaped as shown in FIG. 4. The downstream side of the tapered portion 66a is directly connected to a circular passage portion 66b with a cross section of approximately circular. The installation position of the tumble valve 76, which is an intake control valve that can open and close the main flow passage 66, is determined in this circular passage portion 66b. Thus, like the throttle valve 40c, the tumble valve 76 has a disk-shaped valve body 76c fixed to a valve shaft 76b and rotating therewith. The tumble valve 76 is selectively controlled to either a fully open or fully closed position by an ECU 80 (described below), and has a simple structure or configuration. Although the tapered portion 66a and the circular passage portion 66b are formed in the connecting pipe 77, they may also be formed in the inlet pipe 36.

As can be seen from FIG. 1, when the throttle valve 40c is in the fully closed position, the one-end half 40f located below the valve body 40d of the throttle valve 40c is located on the upstream side in the intake flow direction F around the valve shaft 40b, and forms an acute angle with the corresponding part of the inner wall surface 38a of the intake passage 38 on the downstream side of the one-end half 76f. Also, at this time, the other-end half 40g located above the valve body 40d of the throttle valve 40c is located on the downstream side in the intake flow direction F around the valve shaft 40b, and forms an obtuse angle with the corresponding part of the inner wall surface 38a on the downstream side of the other-end half 40g. This angular relationship is also established when the throttle valve 40c is at a predetermined small opening angle where it is slightly open.

The internal combustion engine 10 is provided with fuel injection valves 78, 79. The fuel injection valve 78 is provided downstream of the throttle valve 40c and the tumble valve 76. Here, the fuel injection valve 78 is provided in the inlet pipe 36 so as to face the main flow passage 66, and is provided to inject fuel toward the intake port 32. More specifically, the fuel injection valve 78 is provided to inject fuel toward the intake valve 46 via the main flow passage 66. The amount of fuel injected from this fuel injection valve 78 and its injection timing are controlled in association with the control of the throttle valve 40c and the tumble valve 76, respectively.

Another fuel injection valve 79 is provided to inject fuel into the intake passage downstream of the throttle valve 40c and upstream of the sub-partition 72. The fuel injection amount and injection timing from this fuel injection valve 79 can be controlled in the same way as the fuel injection amount and injection timing from the fuel injection valve 78, or in association with the fuel injection amount and injection timing from the fuel injection valve 78.

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 and a fuel injection control unit 84. The ECU 80 analyzes the operating state of the internal combustion engine 10 based on the output from various sensors such as an engine rotation speed sensor and an engine load sensor, and controls the operation of the throttle valve 40c and the tumble valve 76 using the intake control unit 82. The throttle valve 40c can be opened to any opening degree by the ECU 80, and can be controlled to the opening degrees shown in Figures 5 to 7. The ECU 80 also controls the operation of the fuel injection valves 78, 79 using the fuel injection control unit 84 based on the analyzed operating state of the internal combustion engine 10. The ECU 80 stores programs and various data for these controls.

Here, the control of the throttle valve 40c and the tumble valve 76 will be explained with reference to Figures 5 to 7. Note that Figures 5 to 7 show the three-dimensional model M1 shown in Figure 2 with the throttle valve 40c and the tumble valve 76 adjusted in opening degree.

For example, when the internal combustion engine 10 is in a low load region, the ECU 80 closes the tumble valve 76 and controls the throttle valve 40c to a predetermined small opening so that the intake air is substantially drawn from the tumble passage 64, particularly from the first tumble passage 68, and more preferably only from the first tumble passage 68 (see FIG. 5). This promotes the flow of intake air as shown diagrammatically by the arrows in FIG. 5, ensuring the amount of intake air appropriate for the low load region, and forming a tumble flow in the combustion chamber 20 with the intake air from the first tumble passage 68. Since the first tumble passage 68 has a relatively small cross-sectional area, the flow rate can be increased even with the amount of intake air appropriate for the low load region, and a strong tumble flow can be formed. Here, when the internal combustion engine 10 is in a low load region, the fuel injection from the fuel injection valves 78, 79 is controlled so that the air-fuel ratio is lean, but by forming a tumble flow, combustion can be effectively generated. In addition, when shown in FIG. 5, the flow of intake air is promoted as diagrammatically shown by arrows in FIG. 5, and this flow will be described later.

For example, when the internal combustion engine 10 is in a medium load region, the ECU 80 closes the tumble valve 76 and controls the throttle valve 40c to an opening larger than a predetermined small opening so that intake air is drawn from the first tumble passage 68 and the second tumble passage 70, i.e., the tumble passage 64 (see FIG. 6). The throttle valve 40c at this time is controlled to an opening smaller than the full opening, but may be controlled to the full opening. This promotes the flow of intake air as shown diagrammatically by the arrows in FIG. 6, ensuring an intake air volume appropriate for the medium load region, and forming a tumble flow in the combustion chamber 20 with the intake air from the first and second tumble passages 68, 70. Since the tumble flow is formed with the intake air from the first and second tumble passages 68, 70, a strong tumble flow can be formed while ensuring the necessary intake air volume even in the medium load region where a larger intake air volume is required than in the low load region. Here, when the operating state of the internal combustion engine 10 is in the medium load region, the fuel injection from the fuel injection valves 78, 79 is controlled so that the air-fuel ratio is lean, but combustion can be effectively caused by forming a tumble flow.

Furthermore, for example, when the operating state of the internal combustion engine 10 is in the high load region, the ECU 80 opens the tumble valve 76, fully opening here, and controls the throttle valve 40c to an opening degree larger than a predetermined small opening degree, such as fully opening, so that intake air is drawn in from the tumble passage 64 including the first tumble passage 68 and the second tumble passage 70 and the main passage 66 (see FIG. 7). As a result, an intake air flow is generated as shown diagrammatically by the arrows in FIG. 7, and the intake air volume according to the high load region is secured, and the intake air from the first and second tumble passages 68, 70 preferably creates a tumble flow in the combustion chamber 20, or otherwise realizes a suitable in-cylinder flow velocity. Here, when the operating state of the internal combustion engine 10 is in the high load region, the fuel injection from the fuel injection valves 78, 79 is controlled so that the air-fuel ratio becomes stoichiometric, and furthermore, by realizing a suitable in-cylinder flow velocity, more effective combustion can be generated.

For example, when the operating state of the internal combustion engine 10 is in the high load region, as described above, the tumble valve 76 is opened and the throttle valve 40c is opened to draw in intake air from the tumble passage 64 and the main passage 66. At this time, the intake structure S of the internal combustion engine 10 has a further configuration and shape so that the intake air volume is increased by the intake from the main passage 66 and the tumble performance by the intake from the tumble passage 64 can be more suitably ensured. This will be explained further below. Note that the effect of the following configuration, for example the junction section 86, which makes it possible to more suitably ensure the tumble performance by the intake from the tumble passage 64, is achieved even when the tumble valve 76 is closed.

A junction section 86 is defined and formed downstream of the tumble flow passage 64. The junction section 86 is provided at the point where the first tumble flow passage 68 and the second tumble flow passage 70 join downstream. The tumble flow passage 64 then joins the main flow passage 66 via the junction section 86. The junction section 86 is formed in the cylinder head 14. Here, the junction section 86 is formed as part of the intake port 32.

8 shows a three-dimensional model M2 including the portion of the intake passage 38 downstream of the throttle valve 40c and the tumble valve 76 and the exhaust passage of the exhaust port 34. FIG. 8 shows the three-dimensional model M2 from a direction perpendicular to the cylinder axis C and perpendicular to the intake flow direction F. FIG. 9A shows a cross-sectional view of the three-dimensional model M2 at a position along IXA-IXA in FIG. 8, FIG. 9B shows a cross-sectional view of the three-dimensional model M2 at a position along line IXB-IXB in FIG. 8, and FIG. 9C shows a cross-sectional view of the three-dimensional model M2 at a position along line IXC-IXC in FIG. 8. Line IXA-IXA in FIG. 8 passes near the upstream end of the intake port 32, line IXB-IXB in FIG. 8 passes near the downstream edge of the sub-partition 72, and line IXC-IXC in FIG. 8 passes near the downstream edge of the main partition 62. All of these lines IXA-IXA to IXC-IXC are parallel to the cylinder axis C in FIG.

9A and 9B, the first tumble flow passage 68 and the second tumble flow passage 70 have approximately the same shape and size. In this way, the first tumble flow passage 68 and the second tumble flow passage 70 smoothly reach from the upstream side to the downstream side without changing their shape or size significantly in the intake flow direction. The first tumble flow passage 68 and the second tumble flow passage 70 are connected to the junction 86. The junction 86 is connected to the main flow passage 66 downstream of the edge of the downstream end 62b of the main partition 62, i.e., the downstream edge 62bt (see Figs. 1 and 8). With this configuration, the first tumble flow passage 68 and the second tumble flow passage 70 are connected to the main flow passage 66 via the junction 86 downstream of the edge of the downstream end 72b of the sub-partition 72, i.e., the downstream edge 72bt. Therefore, the intake air that has passed through the first tumble passage 68 and the second tumble passage 70 of the tumble passage 64 can be given strong directionality.

8, a line L1 that is determined to extend in the intake flow direction at the confluence 86 intersects with the cylinder axis C at an angle θ1 close to a right angle, while a line L2 that is determined to extend in the flow direction at the downstream end of the main flow path 66 intersects with the cylinder axis C at an angle θ2 smaller than the angle θ1. In this way, the confluence 86 is partitioned so that the intake air from the tumble flow path 64 via the confluence 86 flows into the combustion chamber 20 at a smaller approach angle than the intake air from the main flow path 66. With this configuration, the intake air that has passed through the tumble flow path 64 can be introduced into the combustion chamber 20 while maintaining a strong directivity, and for example, a strong tumble flow can be generated in the combustion chamber 20. The approach angle here refers to the angle of the intake air flowing toward the combustion chamber 20 into the combustion chamber 20. For example, the larger the angle between the intake air and the cylinder axis C in FIG. 8 viewed from a direction perpendicular to the cylinder axis C and perpendicular to the intake flow direction, the smaller the approach angle.

1 and 8, the tumble flow passage 64 is defined to have a curved shape that is convex downward, and the main flow passage 66 is defined to have a curved shape that is convex upward. With this configuration, as described above, it becomes possible to guide the intake air from the tumble flow passage 64 to the combustion chamber 20 at a smaller approach angle, and it becomes possible to guide the intake air from the main flow passage 66 to the combustion chamber 20 more effectively.

9B shows the first tumble flow path 68 and the second tumble flow path 70 communicating with the upstream end of the junction 86. For reference, FIG. 9B shows the cross section 68A of the first tumble flow path 68, the cross section 70A of the second tumble flow path 70, and an imaginary plane defined at the upstream end 86u of the junction 86, i.e., one side TA1 of the cross section on this imaginary plane. The side TA1 of the upstream end 86u of the junction 86 is clearly longer than the vertical length of the cross section 68A of the first tumble flow path 68 and the vertical length of the cross section 70A of the second tumble flow path 70. In this manner, the junction 86 is partitioned so that the cross-sectional areas (areas S1, S2 in FIG. 9B) of the first tumble passage 68 and the second tumble passage 70 are smaller than the cross-sectional area S3 (area of a cross section partially partitioned by side TA1) of the upstream end 86u of the junction 86 (S1<S3, S2<S3). With this configuration, the intake air from the first tumble passage 68 and the intake air from the second tumble passage 70 can suitably flow into the junction 86. More specifically, when the intake air flows through the first tumble passage 68 and the second tumble passage 70, the cross-sectional area of the junction 86 is larger than the cross-sectional areas of the first tumble passage 68 and the second tumble passage 70, so that the intake air amount is less likely to be restricted at the junction 86, and it is possible to ensure the intake air amount appropriate for an operating range, for example, a medium load range.

Also, for example, side TA2 in FIG. 9C is shorter than side TA1 in FIG. 9B. That is, the cross-sectional area of the junction 86 of the tumble flow passage 64 tends to become smaller at the cross-sectional location in FIG. 9C than at the cross-sectional location in FIG. 9B, for example, at the side TA1 in FIG. 9B, as it approaches the downstream side. In this way, in the internal combustion engine 10, the junction 86 is partitioned so as to taper from the upstream end of the junction 86 toward the downstream side. With this configuration, the area (cross-sectional area) of the cross section perpendicular to the flow direction downstream of the upstream end 86u of the junction 86 is smaller than the sum of the cross-sectional areas of the first tumble flow passage 68 and the second tumble flow passage 70 (for example, the sum of the area S1 of the cross section 68A and the area S2 of the cross section 70A). This makes it possible to maintain the flow velocity of the intake air high when the intake air from the first tumble flow passage 68 and the intake air from the second tumble flow passage 70 join at the junction 86 and flow into the main flow passage 66. Therefore, the intake air from the tumble passage 64 flows into the combustion chamber 20 at a high flow velocity, and preferably forms a tumble flow. Note that making the area of the cross section perpendicular to the flow direction downstream of the upstream end of the junction 86 smaller than the sum of the cross-sectional areas of the first tumble passage 68 and the second tumble passage 70 may be achieved by means other than tapering.

Now, as mentioned above, the case where the throttle valve 40c is opened to a predetermined small opening will be described. As shown in FIG. 5, when the throttle valve 40c is opened to a predetermined small opening, two gaps G1 and G2 are formed between the valve body 40d of the throttle valve 40c and the intake passage wall surface 38a. The lower gap (first gap) G1 in FIG. 5 is formed between the one end half 40f located below the valve body 40d of the throttle valve 40c and the corresponding part of the inner wall surface 38a of the intake passage 38. At this time, the one end half 40f is located upstream in the intake flow direction F with the valve shaft 40b as the center, and forms an acute angle α with the corresponding part of the inner wall surface 38a of the intake passage 38 downstream of the one end half 76f. The upper gap (second gap) G2 in Fig. 5 is formed between the other end half 40g located above the valve body 40d of the throttle valve 40c and the corresponding part of the inner wall surface 38a of the intake passage 38, and is located on the opposite side of the first gap G1 with the valve shaft 40b of the throttle valve 40c in between. At this time, the other end half 40g is located downstream in the intake flow direction F with the valve shaft 40b as the center, and forms an obtuse angle β with the corresponding part of the inner wall surface 38a downstream of the other end half 40g. Note that when the throttle valve 40c is at the predetermined small opening shown in Fig. 5, the valve body 40d of the throttle valve 40c is inclined, so that the first gap G1 is located upstream of the second gap G2 in the intake flow direction F.

Each of the first gap G1 and the second gap G2 has a gap width equal to or less than the thickness of the main partition 62. The thickness of the main partition 62 is preferably the average thickness of the main partition 62 extending in the intake flow direction. Specifically, each of the first gap G1 and the second gap G2 has a gap width equal to or less than 3 mm (0 < gap width ≦ 3 mm), more preferably equal to or less than 2 mm (0 < gap width ≦ 2 mm). Here, the sub-partition 72 is also formed to have approximately the same thickness as the main partition 62. In other words, in this embodiment, each of the first gap G1 and the second gap G2 has a gap width equal to or less than the thickness of the sub-partition 72. The first gap G1 has the maximum width in FIG. 1 and FIG. 3, and the gap width is preferably formed so that it becomes smaller as it moves to the left and right (in the direction perpendicular to the paper surface in FIG. 1 and FIG. 3). 1 and 3, the second gap G2 may be formed so as to have a maximum width and to have a smaller width toward the left and right. Note that the first gap G1 and the second gap G2 are not limited to these widths, and may be designed and formed so as to achieve the effects described below.

Before describing the effects of providing the gaps G1 and G2, the related phenomenon will be described below with reference to Figures 10 and 11. Note that a similar explanation to the following explanation with reference to Figures 10 and 11 is described in detail in JP 2019-23459 A.

Figure 10 is a diagram showing the intake air flow when a butterfly valve 108 is gradually opened (slightly open) when a partition 106 is provided in the intake passage 100 to separate the tumble flow path 102 and the main flow path 104, and a butterfly valve 108 is provided upstream of the partition 106. Figure 11 is a diagram showing the pressure mainly downstream of the butterfly valve 108 shown in Figure 10 when it is gradually opened.

The butterfly valve 108 can rotate in the clockwise direction R in FIG. 10 in the valve opening direction, and is biased counterclockwise in the valve closing direction by a return spring (not shown) so that the rotating one end half 108b of the valve body 108a abuts against the inner wall surface 110 that defines the intake passage 100, and the rotating other end half 108c abuts against the same inner wall surface 110 in the fully closed position.

In the fully closed state, one end half 108b of the butterfly valve 108 forms an acute contact angle with the inner wall surface 110 of the intake passage 100 downstream of the intake flow direction F, and the other end half 108c forms an obtuse contact angle with the inner wall surface 110 of the intake passage 100 downstream of the intake flow direction F. In other words, the butterfly valve 108 is inclined, with one end half 108b located upstream of the intake passage 100 around the valve shaft 108d, and the other end half 108c of the butterfly valve 108 located downstream of the intake passage 100. 10 and 11, when the butterfly valve 108 moves from the fully closed position to the gradually opened position, the intake air flows from the upstream side of the intake passage 100 to the downstream side through a gap (hereinafter, obtuse angle gap) 110a formed between the one end half 108b and the inner wall surface 110 that defines the intake passage 100, and a gap (hereinafter, acute angle gap) 110b formed between the other end half 108c and the inner wall surface 110. At this time, as shown in FIG. 11, the angle α1 between the one end half 108b of the butterfly valve 108 and the inner wall surface 110 of the intake passage 100 is an acute angle, and the angle β1 between the other end half 108c and the inner wall surface 110 of the intake passage 100 is an obtuse angle.

At this time, as shown in Figure 11, a strong negative pressure is generated in the area 112 immediately downstream of the obtuse angle side gap 110a and the acute angle side gap 110b (black area in Figure 11), and a wide negative pressure area 114 (dotted hatched area in Figure 11) is generated in the downstream range of the butterfly valve 108, including the valve stem 108d of the butterfly valve 108. That is, as shown in FIG. 11, the portion of the intake flow passage 100 downstream of the butterfly valve 108 is partitioned into two flow passages 102, 104 of large and small cross-sectional area by a partition 106 having a surface that is approximately parallel to the valve axis 108d of the butterfly valve 108 along the intake flow direction F, and the flow passage 104 with the larger cross-sectional area is located downstream of the other end half 108c, and the flow passage 102 with the smaller cross-sectional area is located downstream of the one end half 108b. When the butterfly valve 108 is slowly opened, the momentum of the intake air that passes through the butterfly valve 108 and flows into the flow passage 104 with the larger cross-sectional area tends to weaken, and the intake air that has lost momentum and flowed into the flow passage 104 with the larger cross-sectional area is attracted to the negative pressure generated in the portions 112 (black portions in FIG. 11) immediately downstream of each end of the one end half 108b and the other end half 108c of the butterfly valve 108, and flows back upstream. The backflowing intake air is attracted to the negative pressure generated in the immediate downstream portion 112 of the one end half 108b on the side of the flow path 102 with the smaller cross-sectional area, and then flows into the flow path 102 with the smaller cross-sectional area together with the intake air that has passed through the butterfly valve 108, and the amount of intake air flowing through the flow path 102 increases.

Therefore, by making the flow passage 104 with the larger cross-sectional area the main flow passage and the flow passage 102 with the smaller cross-sectional area the tumble flow passage, i.e., by setting the cross-sectional area of the main flow passage 104 larger than the cross-sectional area of the tumble flow passage 102, the intake air that once flows into the main flow passage 104 can be guided to the tumble flow passage 102. In other words, by setting the cross-sectional area of the main flow passage 104 larger than the cross-sectional area of the tumble flow passage 102, the intake air flowing through the tumble flow passage 102 can be strengthened.

Now, we return to the description of the above embodiment of the present invention. As described above, when the throttle valve 40c is at a predetermined small opening shown in FIG. 5, the valve shaft 40b of the throttle valve 40c is perpendicular to the vertical direction and the intake flow direction F of the intake passage 38, so that the first tumble flow passage 68 is located immediately downstream of the one end half 40f of the valve body 40d of the throttle valve 40c. The upstream end 72a of the sub-partition 72 extends upstream of the upstream end 62a of the main partition 62. Focusing on this sub-partition 72, the sum of the cross-sectional area of the main flow passage 66 above the sub-partition 72 and the cross-sectional area of the second tumble flow passage 70 is clearly larger than the cross-sectional area of the first tumble flow passage 68 of the sub-partition 72. In this embodiment, the throttle valve 40c is inclined when it is at a predetermined small opening, and the one end half 40f located below the valve body 40d of the throttle valve 40c is located on the upstream side in the intake flow direction F with the valve shaft 40b as the center, and forms an acute angle α with the corresponding wall surface on the downstream side, and the other end half 76g located above the valve body 40d of the throttle valve 40c is located on the downstream side, and forms an obtuse angle β with the corresponding wall portion on the downstream side. Therefore, the butterfly valve 108, the tumble passage 102, and the main passage 104 in FIG. 10 can be respectively associated with the throttle valve 40c, the first tumble passage 68, the main passage 66, and the second tumble passage 70 in this embodiment. Therefore, by opening the throttle valve 40c to the predetermined small opening as described above, the intake structure S for an internal combustion engine of this embodiment can realize the intake flow described based on FIG. 5 (see the arrows in FIG. 5).

That is, as shown in FIG. 12, according to the intake structure S of the internal combustion engine 10 of FIG. 1, when the throttle valve 40c is at the same predetermined small opening as shown in FIG. 5, the first gap G1 and the second gap G2 are formed as described above. The intake air that passes through the second gap G2 can mainly flow to the main flow passage 66 side, but a part of it, preferably all of it, returns to the tumble flow passage 64 side and flows through the first tumble flow passage 68 together with the intake air that passed through the first gap G1. In this way, the intake air that flows downstream of the throttle valve 40c at the predetermined small opening enters the first tumble flow passage 68 and eventually flows into the tumble flow passage 64 (see the arrow in FIG. 12).

The results of a simulation of the flow through the intake structure S of this internal combustion engine 10 are shown in Figure 13. The cross-sectional shape of the passage along line XIVA-XIVA in Figure 13 is shown in Figure 14A, and the cross-sectional shape of the passage along line XIVB-XIVB in Figure 13 is shown in Figure 14B. The position in Figure 14A roughly corresponds to the position immediately upstream of the tapered portion 66a, and the position in Figure 14B corresponds to the position of the circular passage portion 66b.

In this simulation, a model was used in which the throttle valve 40c was opened to a predetermined small opening and the tumble valve 76 was completely closed. In Figure 13, the black parts are the parts with the lowest pressure, and they occurred downstream of the first gap G1 and downstream of the second gap G2. In this simulation, the intake air that passed through the second gap G2 may initially head toward the main passage 66 and the second tumble passage 70 above the sub-partition 72, as shown by arrow FA, but then flows into the first tumble passage 68.

In the intake structure S of the internal combustion engine 10 described above, a tumble passage 64 including a first tumble passage 68 and a second tumble passage 70 and a main passage 66 are formed. Therefore, by using one, more than one or all of them depending on the operating state of the internal combustion engine, it is possible to ensure the amount of intake air according to the operating state.

The valve shaft 40b of the throttle valve 40c crosses the vertical direction and the intake flow direction F of the intake passage 38, and the throttle valve 40c can be opened to a plurality of openings including a predetermined small opening. Therefore, when the throttle valve 40c is opened to a predetermined small opening, the first gap G1 formed between the throttle valve 40c and the intake passage wall surface 38c is located on the first tumble flow path 68 side, and the second gap G2 formed between the throttle valve 40c and the intake passage wall surface 38c is located on the main flow path 66 side. Furthermore, the upstream end 72a of the sub-partition 72 extends upstream of the upstream end 62a of the main partition 62 in the intake flow direction F. Therefore, the intake air that has passed through the second gap G2 is urged toward the first tumble flow path 68 side and can flow there. Therefore, the tumble performance can be ensured.

Such a backflow phenomenon when the throttle valve 40c is opened to a predetermined small opening (see, for example, the above explanation based on Figures 10 to 12) occurs even when the tumble valve 76 is not provided. In addition, the intake structure S of the internal combustion engine 10 is provided with a tumble valve 76, and when the operating state of the internal combustion engine 10 is in the low to medium load operating range, for example, the tumble valve 76 is closed, allowing the intake air to flow more suitably through the tumble flow passage 64. In this way, the intake structure S of the internal combustion engine 10 configured as described above is provided with a tumble valve 76 that opens and closes the main flow passage 66, but it is only opened fully open and fully closed, and its structure or configuration is not complicated.

In addition, in the above-mentioned intake structure S, the valve shaft 40b of the throttle valve 40c is perpendicular to the vertical direction and the intake flow direction F of the intake passage 38. Therefore, when the throttle valve 40c is opened to a predetermined small opening, the first gap G1 can be suitably positioned on the first tumble passage 68 side, and the second gap G2 can be suitably positioned on the main passage 66 side. Therefore, at that time, it is possible to more suitably promote the flow of intake air through the second gap G2 to the first tumble passage 68.

Furthermore, the cross section of the circular passage portion 66b of the main flow path 66 at the installation position of the tumble valve 76 is approximately circular. This makes it easier to increase the degree of blockage of the main flow path 66 by the tumble valve 76 when the valve is closed. Also, a tapered region, or tapered portion 66a, whose cross-sectional area decreases toward the downstream side in the intake flow direction F, is provided in the main flow path 66 between the upstream end 62a of the main partition portion 62 and the installation position of the tumble valve 76. This configuration makes it possible to more suitably smooth the flow of intake air into the main flow path 66.

The intake structure S is provided with the aforementioned junction 86. For example, when the throttle valve 40c is controlled to a predetermined small opening, even if the intake air flows into the second tumble passage 70, the intake air merges with the intake air of the first tumble passage 68, whose main purpose at that time is to flow the intake air, at the junction 86 and is drawn into the combustion chamber 20. Therefore, at this time, the intake air from the tumble passage 64, including the intake air flowing through the second tumble passage 70, can be given strong directionality, the tumble flow in the combustion chamber 20 can be suitably strengthened, and the tumble performance can be further ensured.

The number of sub-partitions is not limited to one, and may be multiple. By providing multiple sub-partitions in the tumble flow passage 64, it becomes possible to divide the tumble flow passage 64 into three or more intake passages, i.e., intake passage portions, including a third intake passage corresponding to the first tumble flow passage 68 and a fourth intake passage corresponding to the second tumble flow passage 70. The divided multiple intake passage portions may be connected to the main flow passage 66 via a junction 86, similar to the first and second tumble flow passages 68, 70, and then to the combustion chamber 20. In this case, multiple sub-partitions may be provided in the tumble flow passage 64 spaced apart in the vertical direction.

In addition, it is preferable that the various components that define the intake passage of the internal combustion engine 10, particularly the intake passage downstream of the throttle valve 40c, are mainly manufactured by casting. This makes it possible to realize various shapes, such as a tumble passage 64 that is convex downward and a main passage 66 that is convex upward. Note that this disclosure does not exclude the manufacture of components that define the intake passage by methods other than casting.

As shown in FIG. 15, the resonator 90 may be provided so as to communicate with the tumble passage 64. In FIG. 15, the resonator 90 is connected to the first tumble passage 68 of the tumble passage 64 through a communication pipe 94 that defines a communication passage 92. However, the resonator 90 may be connected to the second tumble passage 70. By directly connecting the resonator 90 to the tumble passage 64 in this manner, when the amount of intake air remaining in the intake passage downstream of the throttle valve 40c before the intake valve opens during the intake stroke is relatively small, such as when the throttle valve 40c is at a predetermined small opening, the air in the resonator 90 can be used as intake air (see the arrow in FIG. 15), so that the amount of intake air that can be supplied to the combustion chamber 20 via the tumble passage 64 can be increased. Therefore, by connecting the resonator 90 to the tumble passage 64, the flow of the intake air from the tumble passage 64 can be increased, and the tumble flow in the combustion chamber 20 can be strengthened.

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.

In the intake structure of the internal combustion engine of the above embodiment, the second tumble passage is formed above the first tumble passage, i.e., on the first direction side, and the main passage is provided above the tumble passage including these, i.e., on the first direction side. However, as described above, the second tumble passage may be formed below the first tumble passage, and the main passage may be provided below the tumble passage including these. In this case, however, the throttle 40c may be inverted upside down and oriented in the opposite direction in the drawing corresponding to FIG. 1. In addition, the present disclosure allows the inclination of the throttle valve 40c to be reversed upside down in the intake structure S of FIG. 1. In this case, the above-mentioned action and effect described based on FIG. 5, FIG. 10 to FIG. 12 can be similarly produced.

10... internal combustion engine, 12... cylinder block, 14... cylinder head, 15... piston
20... combustion chamber, 28... intake valve port, 30... exhaust valve port, 32... intake port, 34... exhaust port
38...intake passage, 40...throttle body, 40c...throttle valve, 46...intake valve, 50...exhaust valve
62: Partition portion (main partition portion), 64: Tumble flow passage (first intake passage)
66: main passage (second intake passage), 68: first tumble passage (third intake passage)
70: second tumble flow passage (fourth intake passage), 72: partition portion (sub-partition portion)
76: tumble valve (intake control valve), 86: junction portion, 90: resonator S: intake structure, G1: first gap portion, G2: second gap portion

Claims (11)

a main partition section (62) that partitions an intake passage (38) downstream of a throttle valve (40c) into a first intake passage (64) that serves as a tumble flow passage for generating a tumble flow, and a second intake passage (66) located on a first direction side of the first intake passage;
a sub-partition portion (72) provided in the first intake passage (64) so as to form a third intake passage (68) and a fourth intake passage (70) on the first direction side of the third intake passage;
an intake control valve (76) capable of opening and closing the second intake passage (66),
a valve shaft (40b) of the throttle valve (40c) intersects the first direction and the intake air flow direction of the intake passage,
an upstream end (72a) of the sub-partition portion (72) extends upstream of the upstream end of the main partition portion (62) in the intake air flow direction;
The throttle valve (40c) is configured to be able to open to a plurality of opening degrees including a predetermined small opening degree,
An intake structure (S) for an internal combustion engine (10), characterized in that a tapered section (66a) whose cross-sectional area decreases toward the downstream side in the intake flow direction is provided in the second intake passage (66) between the upstream end (62a) of the main partition section (62) and the installation position of the intake control valve (76). When the throttle valve (40c) is opened to the predetermined small opening degree, a first gap (G1) and a second gap (G2) are formed between a valve body (40d) of the throttle valve (40c) and an intake passage wall surface (38a),
The intake structure (S) of an internal combustion engine (10) as described in claim 1, characterized in that the first gap portion (G1) is located on the opposite side of the second gap portion (G2) with the valve shaft (40b) of the throttle valve (40c) sandwiched therebetween. The intake structure (S) of an internal combustion engine (10) according to claim 2, characterized in that each of the first gap portion (G1) and the second gap portion (G2) has a gap width equal to or less than the thickness of the main partition portion (62). 4. The intake structure (S) for an internal combustion engine according to claim 2, wherein the valve shaft (40b) of the throttle valve (40c) is perpendicular to the first direction and the intake air flow direction of the intake passage. The sum of the cross-sectional area of the second intake passage (66) and the cross-sectional area of the fourth intake passage (70) is greater than the cross-sectional area of the third intake passage (68).
An intake structure (S) for an internal combustion engine (10) according to any one of claims 1 to 4. 6. The intake structure (S) of an internal combustion engine (10) according to claim 1, wherein a cross section of the second intake passage (66) at an installation position of the intake control valve (76) is substantially circular. (delete) 7. The intake structure (S) of an internal combustion engine (10) according to claim 1, wherein a resonator (90) is connected to the first intake passage (64). a junction (86) where the third intake passage (68) and the fourth intake passage (70) join, and the first intake passage (64) joins the second intake passage (66) through the junction (86);
The intake structure (S) of an internal combustion engine (10) according to any one of claims 1 to 6 and 8, further comprising: The intake structure (S) of an internal combustion engine (10) as described in claim 9, characterized in that the junction (86) is partitioned so that the area of a cross section perpendicular to the flow direction downstream of the upstream end (86u) of the junction (86) is smaller than the sum of the cross-sectional areas (S1, S2) of the third intake passage (68) and the fourth intake passage (70). The intake structure (S) of an internal combustion engine (10) as described in claim 9 or claim 10, characterized in that the junction portion (86) is partitioned so that the intake air from the first intake passage (64) through the junction portion (86) flows into the combustion chamber (20) at a smaller approach angle than the intake air from the second intake passage (66).

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