JP2013072390A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress reduction of an effective opening area at early stages of opening an intake valve while enhancing an air flow from a region on the opposite side of a region adjacent to an exhaust port toward into a combustion chamber in an intake port.SOLUTION: An intake port 18a and an exhaust port are provided adjacently. An aperture part on the exhaust side of the intake port 18a is formed with a projecting wall part 52 extending to a valve opening direction so as to cover the side of an umbrella part 34a at a position on the exhaust side. The projecting wall part 52 is set lower than a maximum lift amount of an intake valve 34. On an inner face of the projecting wall part 52, an air flow guide groove 54 extending in a direction perpendicular to a center axis of the intake valve 34 is formed along the inner face at a position opposing the side of the umbrella part 34a when in a valve opening state. A width of the air flow guide groove 54 is formed narrower than a width of a portion opposing the air flow guide groove 54 in the side of the umbrella part 34a. Both ends of the air flow guide groove 54 are opened towards the intake side.

Description

  The present invention relates to an internal combustion engine, and more particularly to an internal combustion engine suitable for scavenging residual exhaust gas by using blow-through of fresh air from an intake port to an exhaust port during an overlap period of intake and exhaust valves.

  In order to improve the output of the internal combustion engine and suppress the occurrence of abnormal combustion, it is effective to reduce the amount of exhaust gas remaining in the combustion chamber. In order to reduce the amount of residual exhaust gas in the combustion chamber, in the internal combustion engine with a supercharger, by increasing the overlap period of the intake and exhaust valves during high load operation when the intake pressure is higher than the exhaust pressure, There is a method of blowing fresh air through the exhaust port. However, if the amount of fresh air to be blown through is too large, problems such as deterioration in fuel consumption and deterioration in air-fuel ratio deviation from the target value occur.

  A combustion chamber structure of an engine as one countermeasure for solving the above problem is disclosed in, for example, Patent Document 1. In this conventional combustion chamber structure, a partition wall is provided between an intake port and an exhaust port arranged close to each other. More specifically, a protruding wall (the partition wall) extending in the lift direction of the intake valve is formed at a portion closer to the combustion chamber than the valve seat along the peripheral edge of the intake port valve seat on the exhaust port side. ing. In addition, the following detailed settings are made. That is, the protrusion margin of the protruding wall is obtained by multiplying the lift amount of the intake valve at the top dead center and the crank angle between the top dead center and the exhaust valve substantially closing after the top dead center by 0.15. The gap between the protruding wall and the large-diameter peripheral edge of the intake valve umbrella is set smaller than the protruding margin, and the large diameter of the intake valve umbrella is set. The clearance between the peripheral edge of the portion and the combustion chamber wall on the peripheral side of the bore is set to be larger than the clearance between the peripheral edge of the large-diameter portion of the intake valve umbrella and the protruding wall.

  By adopting the configuration as described above, in Patent Document 1, it is possible to effectively prevent the blow-through of fresh air while minimizing an increase in intake resistance due to the provision of the protruding wall. Further, in Patent Document 1, fresh air flowing into the combustion chamber from the bore peripheral side forms a longitudinal swirling flow (reverse tumble flow) that flows from the cylinder wall on the intake side to the exhaust side along the piston top surface in the cylinder. As a result, the scavenging action of pushing the residual exhaust gas in the cylinder at the time of overlap to the exhaust port can be obtained, and the scavenging efficiency can be improved.

Japanese Patent Laid-Open No. 5-1554 Japanese Patent Laid-Open No. 5-98972 JP 2010-112227 A Japanese Utility Model Publication No. 61-91045

  In the combustion chamber structure of the engine described in Patent Document 1, the above consideration is given to the protruding margin of the protruding wall. However, at the initial stage of opening of the intake valve, the effective opening area of the intake valve becomes small due to the presence of the protruding wall, and this causes a decrease in charging efficiency. In this respect, the technique of Patent Document 1 still leaves room for improvement.

  The present invention has been made to solve the above-described problems. By providing the protruding wall portion, the effective opening area at the initial opening of the intake valve is prevented from decreasing, and the intake valve is opened and closed by the intake valve. It is an object of the present invention to provide an internal combustion engine that can reinforce an air flow from a portion on the opposite side of the intake port to a portion close to the exhaust port into the combustion chamber.

The first invention is an internal combustion engine,
An intake port formed in the cylinder head and opening into the combustion chamber;
An exhaust port formed in the cylinder head at a position close to the intake port and opening into the combustion chamber;
An intake valve for opening and closing an opening on the combustion chamber side in the intake port;
An exhaust valve that opens and closes an opening on the combustion chamber side in the exhaust port,
The opening portion of the intake port in the cylinder head has a valve seat portion that closes the opening portion of the intake port when contacting the umbrella portion of the intake valve,
The opening portion of the intake port in the cylinder head covers the side surface of the umbrella portion of the intake valve at a position closer to the combustion chamber than the valve seat portion and to the exhaust port side. A protruding wall extending in the valve opening direction of the intake valve is formed,
The height of the protruding wall portion is set lower than the maximum lift amount of the intake valve with reference to the position where the umbrella portion of the intake valve is in contact with the valve seat portion when the valve is closed,
The inner peripheral surface of the protruding wall portion is orthogonal to the central axis of the intake valve along the inner peripheral surface at a position facing the side surface of the umbrella portion of the intake valve when the valve is closed. An airflow guide groove extending in the direction is formed,
The width of the airflow guide groove is formed narrower than the width of the portion facing the airflow guide groove on the side surface of the umbrella portion of the intake valve,
Both ends of the airflow guide groove are open toward a portion on the opposite side of the opening portion of the intake port that is close to the exhaust port.

The second invention is the first invention, wherein
The contact length between the intake valve and the valve seat portion is a portion closer to the exhaust port at a portion closer to the exhaust port in an arbitrary longitudinal section including the central axis of the intake valve. It is set so that it may become longer than this.

The third invention is the first or second invention, wherein
The internal combustion engine is an internal combustion engine with a supercharger,
A variable valve mechanism capable of changing a valve overlap period in which the valve opening period of the exhaust valve and the valve opening period of the intake valve overlap;
An overlap period setting means for controlling the variable valve mechanism so that the valve overlap period is set during a high load operation in which the intake pressure is higher than the exhaust pressure;
Is further provided.

Moreover, 4th invention is set in 3rd invention,
The height of the projecting wall portion is set to be substantially equal to the lift amount of the intake valve at the end of the valve overlap period set by the overlap period setting means.

  According to the first invention, the projecting wall portion in which the airflow guide groove is formed is provided at a position close to the exhaust port in the opening portion of the intake port in the cylinder head, thereby providing the following effects. be able to. That is, while blocking the flow of intake air from the portion close to the exhaust port in the opening of the intake port to the combustion chamber using the protruding wall portion, the air flow guide groove is used to stop the flow from the portion close to the exhaust port. The flow of the intake air can be guided toward the site opposite to the site. Therefore, according to the present invention, by providing the projecting wall portion, the effective opening area of the intake valve at the initial stage of opening of the intake valve is suppressed, and combustion from a portion on the opposite side to the portion close to the exhaust port is performed. It becomes possible to strengthen the airflow toward the room.

  According to the second invention, the portion closer to the exhaust port is set to have a longer contact length between the intake valve and the valve seat portion than the portion farther from the exhaust port. In the initial stage of opening of the intake valve, the inflow resistance at the part near the exhaust port is larger than the inflow resistance at the part far from the exhaust port. As a result, due to the effect of the above setting, the flow of intake air into the combustion chamber is mainly in the portion far from the exhaust port. For this reason, in addition to the action by the setting of the first invention, the action by the setting can more effectively enhance the air flow from the part opposite to the part close to the exhaust port into the combustion chamber. It becomes.

  According to the third aspect of the present invention, by providing the valve overlap period during the high load operation, it is possible to reduce the amount of residual exhaust gas in the cylinder using the scavenging action. In addition, by providing the protruding wall portion having the airflow guide groove in the first or second invention, when using the scavenging action during the high load operation, the intake air that has passed through the airflow guide groove is used. The reverse tumble flow in the cylinder can be strengthened by strengthening the airflow in the above-described direction using the flow. As a result, the amount of residual exhaust gas can be effectively reduced. As a result, it is possible to improve the output of the internal combustion engine and suppress abnormal combustion.

  According to the fourth aspect of the invention, the height of the protruding wall portion is set substantially equal to the lift amount of the intake valve at the end of the valve overlap period set during the high load operation. The strengthening of the reverse tumble flow by damming the intake flow near the exhaust port near the exhaust port and strengthening the air flow using the air flow guide groove during the valve overlap period of the initial opening of the intake valve It will be done only. Therefore, an effective reverse tumble flow can be generated while suppressing fuel adhesion to the cylinder liner as compared with the case where a configuration in which a reverse tumble flow is always generated during the intake stroke is used.

It is a figure for demonstrating the whole structure of the internal combustion engine in Embodiment 1 of this invention. FIG. 2 is a diagram for explaining a configuration around an opening on a combustion chamber side in an intake port shown in FIG. 1. It is a figure for demonstrating the positional relationship with respect to the exhaust port (exhaust valve) of the airflow guide groove formed in the periphery of an intake port. It is a figure showing the flow of the intake toward the combustion chamber from the intake port when the intake valve is in the initial valve opening state. It is a figure for demonstrating the effect by having employ | adopted the structure around the intake port in Embodiment 1 of this invention. It is a figure for demonstrating the effect by having employ | adopted the structure around the intake port in Embodiment 1 of this invention. It is a figure for demonstrating the bad effect which arises by the production | generation of the reverse tumble flow in the past. It is a figure for demonstrating the structure around the opening part by the side of the combustion chamber in the intake port with which the internal combustion engine in the modification of Embodiment 1 of this invention is provided. It is a figure showing the flow of the intake air at the time of valve opening of the intake valve in the case of having the configuration shown in FIG.

Embodiment 1 FIG.
[Description of overall configuration of internal combustion engine]
FIG. 1 is a diagram for explaining the overall configuration of an internal combustion engine 10 according to Embodiment 1 of the present invention. The system shown in FIG. 1 includes an internal combustion engine 10. Here, as an example, the internal combustion engine 10 is a gasoline engine with a supercharger including a supercharger (not shown) (such as a turbocharger).

  A piston 14 is provided in each cylinder of the cylinder block 12 of the internal combustion engine 10. In each cylinder, a combustion chamber 16 is formed on the top side of the piston 14. An intake passage 18 and an exhaust passage 20 communicate with the combustion chamber 16. In addition, the intake port 18a of the intake passage 18 is formed in such a shape as to promote the generation of a tumble flow of intake air that is a longitudinal swirling flow in a direction indicated by “tumble direction” in FIG. Although not shown in FIG. 1, an air flow control valve for effectively generating a tumble flow may be provided in the intake passage 18.

  An air flow meter 22 that outputs a signal corresponding to the flow rate of air sucked into the intake passage 18 is provided in the vicinity of the inlet of the intake passage 18. An electronically controlled throttle valve 24 for controlling the intake air amount is provided in the intake passage 18. The cylinder head 26 disposed above the cylinder block 12 is provided with a fuel injection valve 28 for directly injecting fuel into the combustion chamber 16 (inside the cylinder) for each cylinder. The cylinder head 26 is provided with an ignition plug (ignition plug) 30 for igniting the air-fuel mixture in the combustion chamber 16 for each cylinder. The spark plug 30 is connected to the ignition coil 32.

  Further, each cylinder is provided with an intake valve 34 and an exhaust valve 36 for opening and closing the intake port 18a of the intake passage 18 and the exhaust port 20a of the exhaust passage 20, respectively. As an example, the internal combustion engine 10 of this embodiment is a four-valve internal combustion engine in which two intake valves 34 and two exhaust valves 36 are provided in the same cylinder.

  The intake valve 34 and the exhaust valve 36 are driven by an intake variable valve mechanism 38 and an exhaust variable valve mechanism 40, respectively. These variable valve mechanisms 38, 40 change the opening / closing timing of the intake valve 34 or the exhaust valve 36 within a predetermined range by changing the rotation phase of each camshaft (not shown) relative to the rotation phase of the crankshaft (not shown). It includes a variable valve timing mechanism that can be changed by the above. According to such variable valve mechanisms 38 and 40, the valve overlap period in which the valve opening period of the exhaust valve 36 and the valve opening period of the intake valve 34 overlap can be adjusted. The intake variable valve mechanism 38 and the exhaust variable valve mechanism 40 include an intake cam angle sensor 42 and an exhaust cam angle sensor for detecting the rotation angles of the respective cam shafts, that is, the intake cam angle and the exhaust cam angle. 44 is attached. Further, a crank angle sensor 46 for detecting a crank angle is disposed in the vicinity of the crankshaft.

  The system shown in FIG. 1 includes an ECU (Electronic Control Unit) 48. Various sensors for detecting the operation state of the internal combustion engine 10 such as the air flow meter 22, the cam angle sensors 42 and 44, and the crank angle sensor 46 described above are connected to the input portion of the ECU 48. Also, various actuators for controlling the operation of the internal combustion engine 10 such as the throttle valve 24, the fuel injection valve 28, the ignition coil 32, and the variable valve mechanisms 38 and 40 are connected to the output portion of the ECU 48. Yes. The ECU 48 controls the operating state of the internal combustion engine 10 by operating various actuators according to a predetermined program based on the outputs of the various sensors described above. Further, the ECU 48 calculates the engine speed Ne based on the change rate of the crank angle detected by the crank angle sensor 46, and determines the internal combustion engine based on the intake air amount detected by the air flow meter 22 and the engine speed Ne. The charging efficiency (load factor) KL of the engine 10 is calculated. Further, the ECU 48 calculates the advance amount of the opening / closing timing of the intake valve 34 and the exhaust valve 36 based on the outputs of the crank angle sensor and the cam angle sensors 42, 44.

[Description of the configuration around the intake port]
FIG. 2 is a view for explaining the configuration around the opening on the combustion chamber 16 side in the intake port 18a shown in FIG. More specifically, FIG. 2 (A) is a cross-sectional view (FIG. 3 (A) or FIG. 3 (B)) showing the configuration around the intake port 18a in a plane passing through the central axis of the intake valve 34. 2 (B) is a view of the configuration around the opening of the intake port 18a from the combustion chamber 16 side, and FIG. 2 (C) is a view taken along the line A-A in FIG. It is the figure which abbreviate | omitted illustration of the intake valve 34 from FIG. 2 (A). FIG. 3 is a view for explaining the positional relationship of the airflow guide groove 54 formed at the periphery of the intake port 18a with respect to the exhaust port 20a (exhaust valve 36). More specifically, FIG. 3A is an example of the combustion chamber 16 in the four-valve internal combustion engine 10 in which two intake valves 34 and two exhaust valves 36 are provided in the same cylinder. (B) is a figure shown for reference, and is an example of a combustion chamber in a two-valve internal combustion engine in which one intake valve and one exhaust valve are provided in the same cylinder.

  As shown in FIG. 3A, in the internal combustion engine 10 of the present embodiment, a spark plug 30 is disposed at the center of the combustion chamber 16. Two exhaust valves 36 arranged adjacent to each other are arranged at positions close to the two intake valves 34 arranged adjacent to each other. Accordingly, although not shown in FIG. 3A, each of the two intake ports 18a arranged side by side is arranged side by side on the opposite side of the combustion chamber 16 via the spark plug 30. Adjacent to one of the two exhaust ports 20a. In the case of the two-valve internal combustion engine shown in FIG. 3B, one intake valve and one exhaust valve are arranged close to each other. As a result, one corresponding intake port and one exhaust valve are arranged. The two exhaust ports are arranged close to each other.

  As shown in FIG. 2, the valve seat 50 that closes the opening portion of the intake port 18 a when being in contact with the umbrella portion 34 a of the intake valve 34 is fixed to the opening portion of the intake port 18 a in the cylinder head 26. ing. Unlike the configuration shown in FIG. 8 to be described later, in the configuration shown in FIG. 2, the center of the disk-shaped umbrella portion 34 a of the intake valve 34 and the center of the opening of the ring-shaped valve seat 50 coincide.

  Further, as shown in FIGS. 2A and 2C, a protruding wall 52 is formed in the opening of the intake port 18 a in the cylinder head 26. The protruding wall 52 is located at the periphery of the opening of the intake port 18a at the position closer to the combustion chamber 16 than the valve seat 50 and closer to the exhaust port 20a than the umbrella port 18a. It is formed so as to cover the side surface of 34 a and to extend in the valve opening direction of the intake valve 34.

  More specifically, in the example shown in FIG. 2, the protruding wall portion 52 is a side surface of the umbrella portion 34 a of the intake valve 34, mainly in the region on the exhaust side from the vicinity of the center position of the intake valve 34 in FIG. It is formed so as to cover. Further, as shown in FIGS. 2A and 2C, the protruding wall portion 52 is formed so as to gradually increase from the intake side toward the exhaust side. That is, as can be seen from a comparison between FIG. 2 and FIG. 3, the height of the projecting wall 52 is the portion closest to the exhaust port 20a adjacent to the intake port 18a at the periphery of the opening of the intake port 18a. Is formed to have the highest height. Note that the shape of the protruding wall 52 is not limited to the above as long as the height of the portion near the adjacent exhaust port 20a is higher than the height of the portion far from the exhaust port 20a. For example, it may be a stepped shape as viewed from the direction shown in FIG. 2 (A).

  Further, in order to prevent the side surface of the umbrella portion 34a of the intake valve 34 from being covered (not hidden) by the protruding wall portion 52 on the exhaust side when the lift amount of the intake valve 34 exceeds a predetermined amount when the valve is opened, The height of the protruding wall 52 is set lower than the maximum lift amount of the intake valve 34 with reference to the position where the umbrella portion 34a of the intake valve 34 contacts the valve seat 50 when the valve is closed.

  As shown in FIGS. 2A and 2C, an airflow guide groove formed as a partial ring-shaped groove (substantially a semi-ring shape in the example shown in FIG. 2) on the inner peripheral surface of the protruding wall portion 52. 54 is provided. The airflow guide groove 54 is formed in a substantially semi-ring shape along the inner peripheral surface of the protruding wall portion 52 at a position facing the side surface of the umbrella portion 34a of the intake valve 34 when the valve is closed. More specifically, the airflow guide groove 54 is formed as a groove extending in a direction orthogonal to the valve opening direction of the intake valve 34. As described above, the protruding wall portion 52 is formed so as to gradually increase from the vicinity of the center position of the intake valve 34 toward the exhaust side, so that both ends of the airflow guide groove 54 are shown in FIG. Thus, it opens toward the intake side (cylinder bore side).

  The airflow guide groove 54 is formed immediately below the contact position of the valve seat 50 with the umbrella portion 34a. As shown in FIG. 2A, the width of the airflow guide groove 54 is set smaller than the width of the portion facing the airflow guide groove 54 on the side surface of the umbrella portion 34a. Further, the diameter of the tip 52a closer to the combustion chamber 16 than the airflow guide groove 54 in the protruding wall 52 is slightly larger than the diameter (intake valve diameter) of the portion where the diameter is maximum in the umbrella portion 34a of the intake valve 34. It is supposed to be.

  In addition, the height of the protruding wall portion 52 defined as described above is substantially equal to the lift amount of the intake valve 34 at the end of the valve overlap period set during high-load operation for obtaining the scavenging action described later. It is set equally. This is because an effective opening area is ensured between the intake valve 34 and the tip end portion 52a of the protruding wall portion 52 at the timing when the end point of the valve overlap period of the intake / exhaust valves 34, 36 is reached or immediately after. This is to get you started.

[Description of Operation and Effect of Configuration around Intake Port of Embodiment 1]
FIG. 4 is a diagram showing the flow of intake air from the intake port 18a toward the combustion chamber 16 when the intake valve 34 is in the initial valve opening state. 4A and 4B are views seen from the same direction as FIGS. 2A and 2B, respectively.

  The internal combustion engine 10 of the present embodiment includes the protruding wall portion 52 in which the airflow guide groove 54 described above is formed at the opening of the intake port 18a on the exhaust side in the cylinder head 26. According to such a configuration, out of the flow of intake air from the intake port 18 a toward the combustion chamber 16, it passes through the intake side portion of the valve seat 50 (the portion where the projecting wall portion 52 is not provided) and blows out. As for the flow, there is nothing that hinders the flow of intake air after the lift of the intake valve 34 is started, and therefore the flow is along the wall surface of the cylinder head 26 as shown in FIG.

  On the other hand, the flow of the intake air toward the exhaust side in the valve seat 50 is blocked between the tip end portion 52a of the protruding wall portion 52 and the umbrella portion 34a of the intake valve 34, and thus this portion is directly interposed. Therefore, it does not flow into the combustion chamber 16. Then, the flow of the intake air toward the exhaust side once flows into the air flow guide groove 54 formed in the protruding wall portion 52 as shown in FIG. As shown in FIG. 4B, the flow flowing into the airflow guide groove 54 is guided by the airflow guide groove 54 and guided to the intake side, and then blows out toward the intake side.

  Unlike the configuration of the present embodiment, when the airflow guide groove 54 is not provided in the protruding wall portion 52, the flow of intake air from the exhaust side of the intake port 18a toward the combustion chamber 16 is only blocked. On the other hand, according to the configuration of the present embodiment, the air flow guide groove 54 is provided, so that the intake valve 34 is opened while the flow of the intake air from the exhaust side of the intake port 18a toward the combustion chamber 16 is blocked. This means that the effective opening area at the initial stage of the valve can be increased. More specifically, as described above, the width of the airflow guide groove 54 is set to be smaller than the width of the umbrella portion 34a facing the airflow guide groove 54. Therefore, when the intake valve 34 is in the small lift state, FIG. The state shown in A) is obtained, and the flow of intake air can be guided to the intake side while inhibiting the flow of intake air from the exhaust side into the combustion chamber 16.

  Further, by adding the flow of intake air that is guided to the intake side through the air flow guide groove 54, the air flow from the intake side of the intake port 18a toward the combustion chamber 16 can be strengthened. As a result, a reverse tumble flow (flow opposite to the tumble flow shown in FIG. 1) that is a longitudinal swirling flow that flows from the cylinder wall side on the intake side to the exhaust side along the top surface of the piston 14 in the cylinder is effective. Can be generated automatically.

  Since the internal combustion engine 10 of the present embodiment is an internal combustion engine with a supercharger, a state in which the intake pressure is higher than the exhaust pressure is obtained when the high load region is used. By providing a valve overlap period when using such a high load region, fresh air is blown out from the intake port 18a side to the exhaust port 20a side through the combustion chamber 16 during the valve overlap period. Thus, a scavenging action for scavenging the residual exhaust gas in the cylinder can be obtained.

  According to the configuration around the intake port 18a of the present embodiment, since the projecting wall portion 52 in which the airflow guide groove 54 is formed is provided, the scavenging effect is obtained by providing a valve overlap period when the high load region is used. When used, the following effects can be achieved. That is, in the initial stage of opening of the intake valve 34, it is possible to prevent intake air from flowing into the combustion chamber 16 from the exhaust side at the opening of the intake port 18a while securing an effective opening area of the intake valve 34. Accordingly, it is possible to prevent fresh air from flowing toward the adjacent exhaust port 20a after passing through the combustion chamber 16 through the shortest distance from the exhaust side opening of the intake port 18a. In addition, as described above, the exhaust gas remaining in the combustion chamber 16 can be effectively guided toward the exhaust port 20a by the reverse tumble flow of fresh air strengthened in the initial stage of opening the intake valve 34. For this reason, the scavenging action can be effectively enhanced.

  Further, according to the setting of the height of the protruding wall portion 52 in the present embodiment, the lift amount of the intake valve 34 becomes higher than the height of the protruding wall portion 52 after the valve overlap period ends. As a result, the flow of the intake air flowing into the combustion chamber 16 from the intake port 18a is greatly affected by the flow direction in the intake port 18a (characteristics of the intake port 18a). For this reason, the flow of the intake air in this case is switched to a normal tumble flow main flow. As described above, according to the configuration of the opening portion of the intake port 18a of the present embodiment, the reverse tumble flow can be generated at the initial opening of the intake valve 34, and the lift amount of the intake valve 34 is increased thereafter. Later, a normal tumble flow can be generated.

  FIG. 5 and FIG. 6 are diagrams for explaining the effect of adopting the configuration around the intake port 18a in the first embodiment of the present invention. More specifically, FIG. 5 shows the relationship between the amount of residual exhaust gas remaining in the cylinder for the next cycle and the valve overlap period when only the protruding wall portion 52 is not provided. It is the figure compared between the case where it had, and the case where the protrusion wall part 52 and the airflow guide groove 54 are provided. FIG. 6 is a diagram comparing the filling efficiency in the above three cases.

  When the high load region is used, as shown in FIG. 5, the amount of residual exhaust gas in the cylinder can be reduced using the scavenging action by extending the valve overlap period. In addition, according to the configuration of the present embodiment including the projecting wall portion 52 in which the airflow guide groove 54 is formed, the flow of intake air that has passed through the airflow guide groove 54 is used to enter the combustion chamber 16 from the intake side. It is possible to strengthen the airflow flowing into the air and to strengthen the reverse tumble flow. For this reason, as shown in FIG. 5, the amount of residual exhaust gas can be further effectively reduced as compared with the case where only the protruding wall portion 52 is provided as well as the configuration not including the protruding wall portion 52. It becomes possible. As a result, it is possible to improve the output of the internal combustion engine 10 and suppress abnormal combustion.

  Further, according to the configuration of the present embodiment including the protruding wall portion 52 in which the airflow guide groove 54 is formed, the effective opening area at the initial opening of the intake valve 34 due to the provision of the protruding wall portion 52 is reduced. Can be suppressed. For this reason, as shown in FIG. 6, compared with the case where only the protrusion wall part 52 is provided, filling efficiency can be improved. Furthermore, according to the configuration of the present embodiment, since the airflow guide groove 54 can be used, the reverse tumble flow at the initial opening of the intake valve 34 can be strengthened without depending on the existence of the protruding wall portion 52 itself. As a result, the height of the protruding wall 52 can be reduced as compared with the case where only the protruding wall 52 is provided.

FIG. 7 is a diagram for explaining the adverse effects caused by the generation of the conventional reverse tumble flow.
In the internal combustion engine shown in FIG. 7, the shape of the intake port is set so that the generation of the reverse tumble flow can be promoted. In an internal combustion engine having such a configuration, the airflow direction from the intake port into the combustion chamber during the opening period of the intake valve is always the direction as shown in FIG. 7 in order to facilitate the generation of a reverse tumble flow. Become. As a result, the fuel tends to adhere to the cylinder liner regardless of whether the port fuel injection valve or the direct injection fuel injection valve is used. Such adhesion of fuel to the cylinder liner facilitates the occurrence of problems such as running out of oil or dilution of oil fuel.

  On the other hand, according to the configuration of the present embodiment including the protruding wall portion 52 in which the airflow guide groove 54 is formed, the intake side damming of the exhaust side intake flow by the protruding wall portion 52 and the airflow guide groove 54 is used. The strengthening of the reverse tumble flow due to the strengthening of the airflow to the valve is performed only during the valve overlap period at the initial stage of opening of the intake valve 34. For this reason, as shown in FIG. 7, it is possible to generate an effective reverse tumble flow while suppressing fuel adhesion to the cylinder liner as compared with the case where a configuration in which a reverse tumble flow is always generated during the intake stroke is used. Become.

  By the way, in Embodiment 1 mentioned above, the structure around the intake port 18a provided with the protrusion wall part 52 in which the airflow guide groove 54 was formed in the opening part by the side of the exhaust port 18a in the cylinder head 26 is demonstrated. It was. However, the configuration around the intake port applied to the internal combustion engine of the present invention is not limited to the above, and may be described with reference to FIGS. 8 and 9 below, for example. .

  FIG. 8 is a diagram for explaining a configuration around the opening on the combustion chamber 16 side in the intake port 18a provided in the internal combustion engine 60 in the modification of the first embodiment of the present invention. In FIG. 8, the same components as those shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted or simplified. Except for the points described with reference to FIG. 8 and FIG. 9 described later, the internal combustion engine 60 is configured in the same manner as the internal combustion engine 10 shown in FIG.

  The configuration shown in FIG. 8A includes a ring-shaped valve seat 64 at the opening of the intake port 18 a in the cylinder head 62. FIG. 8B is a view of the valve seat 64 as viewed from the combustion chamber 16 side. As shown in FIGS. 8A and 8B, the opening (valve seat hole) of the valve seat 64 is offset to the intake side with respect to the axial center of the intake valve 34.

  And as shown to FIG. 8 (A), the valve seat 64 has the part which the umbrella part 34a of the intake valve 34 covers. More specifically, the length of the portion of the valve seat 64 that covers the umbrella portion 34a (the contact length between the umbrella portion 34a of the intake valve 34 and the valve seat 64 when the valve is closed) is shown in FIG. In the cross section, the length L2 of the portion on the exhaust side is longer than the length L1 of the portion on the intake side. In this way, the contact length between the intake valve 34 and the valve seat 64 is such that the portion closer to the adjacent exhaust port 20a in the arbitrary longitudinal section including the central axis of the intake valve 34 has the exhaust port concerned. It is set so as to be longer than the part far from 20a.

  Although not shown in FIG. 8, also in the configuration shown in FIG. 8, the opening on the exhaust side of the intake port 18 a in the cylinder head 62 protrudes in the same role as the protruding wall 52. A wall portion 66 is formed. Although not shown here, it is assumed that an air flow guide groove similar to the air flow guide groove 54 is formed on the inner peripheral surface of the protruding wall portion 66.

  FIG. 9 is a view showing the flow of intake air when the intake valve 34 is opened when the configuration shown in FIG. 8 is provided. More specifically, FIG. 9A shows the flow of intake air when the intake valve 34 is in the initial valve opening state, and FIG. 9B shows intake air when the intake valve 34 is in the high lift state. Shows the flow.

  In the configuration shown in FIG. 8, as described above, the umbrella portion 34a and the valve seat 64 of the intake valve 34 on the exhaust side are longer than the contact length L1 between the umbrella portion 34a and the valve seat 64 of the intake valve 34 on the intake side. The contact length L2 is set to be larger. According to such a setting, the inflow resistance on the exhaust side becomes larger than the inflow resistance on the intake side when the intake valve 34 is initially opened. As a result, due to the effect of the above setting, the intake air flow into the combustion chamber 16 is mainly on the intake side. For this reason, in addition to the effect of providing the protruding wall portion 66 and the effect of providing the air flow guide groove (not shown in FIGS. 8 and 9) in the protruding wall portion 66 as in the first embodiment, the above setting is used. By the action, the reverse tumble flow can be generated more effectively at the initial opening of the intake valve 34.

  Further, as the lift amount of the intake valve 34 increases, the influence of the throttle portion between the umbrella portion 34a and the valve seat 64 on the flow of intake air from the intake port 18a into the combustion chamber 16 decreases. The influence of the flow direction in the port 18a (characteristics of the intake port 18a) increases. For this reason, as shown in FIG. 9B, the flow of the intake air in this case becomes stronger as the flow of the intake air passing through the exhaust side changes to a normal tumble flow. As described above, even with the configuration shown in FIG. 8, the reverse tumble flow can be generated at the initial stage of opening of the intake valve 34, and after the lift amount of the intake valve 34 becomes high thereafter, the normal tumble flow is generated. Can be generated.

  Further, according to the configuration shown in FIG. 8, the setting of the contact lengths L <b> 1 and L <b> 2 can cause a bias in the airflow that is already directed into the cylinder, and thus does not rely on the existence of the protruding wall 66 itself. The reverse tumble flow at the initial opening of the intake valve 34 can be enhanced. As a result, the height of the protruding wall portion 66 can be reduced as compared with the case where no consideration is given to the contact flows L1 and L2 as described above. In addition, this leads to securing an effective opening area of the intake valve 34, so that the charging efficiency can be secured higher.

  Moreover, in Embodiment 1 mentioned above, although the example provided with the valve seat 50 separate from the cylinder head 26 as a valve seat part was demonstrated, the valve seat part in this invention is a separate body as mentioned above. It is not limited to the one provided with the valve seat 50, and may be formed integrally with the cylinder head.

In the first embodiment and the modifications thereof described above, the valve seat 50 or 64 corresponds to the “valve seat portion” in the first invention.
In the above-described first embodiment and its modification, the intake variable valve mechanism 38 and the exhaust variable valve mechanism 40 correspond to the “variable valve mechanism” in the third aspect of the invention. Further, the “overlap period setting means” in the third aspect of the present invention is realized by the ECU 48 appropriately controlling the variable valve mechanisms 38 and 40 to adjust the valve overlap period.

10, 60 Internal combustion engine 12 Cylinder block 14 Piston 16 Combustion chamber 18 Intake passage 18a Intake port 20 Exhaust passage 20a Exhaust port 22 Air flow meter 24 Throttle valve 26, 62 Cylinder head 28 Fuel injection valve 30 Spark plug 32 Ignition coil 34 Intake valve 34a Intake valve umbrella 36 Exhaust valve 38 Intake variable valve mechanism 40 Exhaust variable valve mechanism 42 Intake cam angle sensor 44 Exhaust cam angle sensor 46 Crank angle sensor 48 ECU (Electronic Control Unit)
50, 64 Valve seats 52, 66 Protruding wall 52a Protruding wall tip 54

Claims (4)

An intake port formed in the cylinder head and opening into the combustion chamber;
An exhaust port formed in the cylinder head at a position close to the intake port and opening into the combustion chamber;
An intake valve for opening and closing an opening on the combustion chamber side in the intake port;
An exhaust valve that opens and closes an opening on the combustion chamber side in the exhaust port,
The opening portion of the intake port in the cylinder head has a valve seat portion that closes the opening portion of the intake port when contacting the umbrella portion of the intake valve,
The opening portion of the intake port in the cylinder head covers the side surface of the umbrella portion of the intake valve at a position closer to the combustion chamber than the valve seat portion and to the exhaust port side. A protruding wall extending in the valve opening direction of the intake valve is formed,
The height of the protruding wall portion is set lower than the maximum lift amount of the intake valve with reference to the position where the umbrella portion of the intake valve is in contact with the valve seat portion when the valve is closed,
The inner peripheral surface of the protruding wall portion is orthogonal to the central axis of the intake valve along the inner peripheral surface at a position facing the side surface of the umbrella portion of the intake valve when the valve is closed. An airflow guide groove extending in the direction is formed,
The width of the airflow guide groove is formed narrower than the width of the portion facing the airflow guide groove on the side surface of the umbrella portion of the intake valve,
An internal combustion engine characterized in that both ends of the airflow guide groove are opened toward a portion of the opening of the intake port that is opposite to a portion that is close to the exhaust port.   The contact length between the intake valve and the valve seat portion is a portion closer to the exhaust port at a portion closer to the exhaust port in an arbitrary longitudinal section including the central axis of the intake valve. The internal combustion engine according to claim 1, wherein the internal combustion engine is set to be longer. The internal combustion engine is an internal combustion engine with a supercharger,
A variable valve mechanism capable of changing a valve overlap period in which the valve opening period of the exhaust valve and the valve opening period of the intake valve overlap;
An overlap period setting means for controlling the variable valve mechanism so that the valve overlap period is set during a high load operation in which the intake pressure is higher than the exhaust pressure;
The internal combustion engine according to claim 1, further comprising:   The height of the protruding wall portion is set to be substantially equal to the lift amount of the intake valve at the end of the valve overlap period set by the overlap period setting means. The internal combustion engine described.

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