JPH051554A - Combustion chamber structure of engine - Google Patents

Abstract

PURPOSE:To improve those of emission performance and engine power plus fuel consumption by preventing any blow-by of fresh air so effectively without entailing any increment of intake air resistance, and expediting a scavenging action. CONSTITUTION:Each opening of an independent intake port 23 and an independent exhaust port 27 opening to a combustion chamber 6 is set up in getting closer to each other. A projecting wall 33, extending in the lift direction, of an intake valve 8 is formed at the more combustion chamber side than a valve seat 31 along a peripheral edge at the exhaust port side of this valve seat 31 of the independent intake port 23. A projecting allowance in this projecting wall 33 should be set to less than either of a larger value out of a lift value of the intake valve 8 at a top dead center and another value made up of multiplying 0.15 to a crank angle at an interval till an exhaust valve 18 is substantially closed after the top dead center. A clearance between the projecting wall 33 and a large diametral part peripheral edge of an intake valve cap part is set to be smaller than the projecting allowance, and another clearance between the large diametral part peripheral edge of the intake valve cap part and the combustion chamber wall at the side of a bore peripheral edge is set to be larger than that between the large diametral part peripheral edge of the intake valve cap part the projecting wall 33.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a combustion chamber of an engine, and more particularly to a structure for improving blow-through of air-fuel mixture.

[0002]

2. Description of the Related Art Conventionally, in an engine, the opening area of intake and exhaust valves is maximized to improve intake efficiency and scavenging efficiency, and a compact combustion chamber is adopted to improve combustibility. Therefore, there are some that are designed to improve the engine output. With such an engine,
Multiple valves are used to efficiently secure the opening area of the valve,
The intake port openings and the exhaust port openings of the combustion chamber are arranged close to each other. Therefore, the valve overlap (hereinafter, both intake and exhaust valves are open)
During a period of overlap, the fresh air (mixture) that has flowed into the combustion chamber from the intake port flows out to the exhaust port as it is, so-called blow-through of fresh air easily occurs,
Problems such as deterioration of emission performance, output, and fuel consumption occur. On the other hand, there is an idea that a wall is provided around the intake port or the exhaust port. For example, as disclosed in Japanese Patent Laid-Open No. 55-104519,
It is known that a wall portion that forms a wall surface that extends toward the combustion chamber is provided around the intake port opening to determine the directionality of the air-fuel mixture that flows into the combustion chamber from the intake port.

[0003]

However, in the case where a wall is provided around the intake port as described in the above publication,
If the gap between the large-diameter peripheral edge of the intake valve umbrella portion and the wall is too large, the effect of restricting the fresh air flow passage to the exhaust side by the wall is lost, and it is impossible to effectively prevent the fresh air from passing through. . On the other hand, if the above-mentioned gap is made small, the intake resistance becomes large, the filling efficiency is lowered, and the output is lowered. Also,
Even if the projection of the wall is too large, the throttle period of the flow passage becomes long, intake resistance becomes large, the charging efficiency decreases, the output decreases, and the air-fuel mixture in the cylinder is disturbed. It becomes difficult to generate a vertical swirling flow of the air-fuel mixture, which causes a problem that the combustibility is deteriorated.

Further, as one of the actions at the time of overlap, there is a scavenging action for pushing the exhaust gas in the combustion chamber to the exhaust port by the fresh air and scavenging the exhaust gas. There is a demand for Particularly, in an engine equipped with a supercharger, during supercharging operation, the scavenging action is improved by the pressurized intake air (fresh air), and the temperature of the air-fuel mixture in the cylinder is reduced by reducing the residual gas to prevent knocking. There is also a demand to improve the quality.

The present invention has been made in view of the above points, and an object thereof is to effectively prevent blow-through of fresh air and promote the scavenging action without increasing the intake resistance. To improve the emission performance, output, and fuel efficiency.

[0006]

In order to achieve the above-mentioned object, a solution means provided by the invention of claim 1 is such that a plurality of intake port openings and exhaust port openings which are open to the combustion chamber are close to each other. It is premised on the combustion chamber structure of the engine in which the projecting wall extending in the lift direction of the intake valve is formed on the combustion chamber side from the valve seat in each intake port opening. The projecting wall is provided along the periphery of each intake port opening on the exhaust port side, and the projecting margin of the projecting wall is set above the valve lift amount of the intake valve at the top dead center and the top dead center. A value obtained by multiplying the crank angle obtained by multiplying 0.15 by the crank angle until the exhaust valve is closed after the dead point, whichever is larger, is set to the larger value, and the protruding wall and the large diameter portion of the intake valve umbrella portion are set. The clearance between the intake valve umbrella portion and the large-diameter portion of the intake valve umbrella portion is set to be smaller than the projection margin, and the clearance between the large-diameter portion peripheral edge of the intake valve umbrella portion and the combustion chamber wall on the bore peripheral edge side is defined by It is configured to be set to be larger than the gap with the protruding wall.

According to a second aspect of the invention, in the first aspect of the invention, the engine is provided with a supercharger, and a large valve overlap period is set in which the opening periods of the intake and exhaust valves overlap before and after top dead center. I am trying.

According to a third aspect of the present invention, in the first aspect of the present invention, the intake valve umbrella extends from the valve seat to the combustion chamber side along the peripheral edge of the intake port opening on the peripheral side of the bore. A large diameter part of the intake valve head is provided with a tumble generating wall having a predetermined gap with a peripheral edge of the large diameter part, and a large diameter of the intake valve umbrella part is provided between a valve seat of the tumble generating wall and a portion corresponding to a protrusion of the protruding wall. The configuration is such that a concave portion is formed to increase the gap with the peripheral edge of the portion.

According to a fourth aspect of the present invention, in the first aspect of the present invention, an exhaust side protruding wall extending in the lift direction of the exhaust valve from the valve seat to the combustion chamber side is provided along the periphery of each exhaust port opening on the intake side. The exhaust margin of the exhaust side protruding wall is set to 0. Crank angle between the valve lift amount of the exhaust valve at the top dead center and the valve opening time of the intake valve opened before the top dead center to the top dead center.
The value is multiplied by 15 or less, whichever is greater, and the gap between the large-diameter peripheral edge of the exhaust valve umbrella portion and the projecting wall is set to be smaller than the projection margin, and the exhaust valve umbrella portion is set. The gap between the peripheral portion of the large diameter portion and the combustion chamber wall on the peripheral side of the bore is set to be larger than the gap between the peripheral portion of the large diameter portion of the exhaust valve umbrella portion and the exhaust side protruding wall.

[0010]

With the above construction, in the first aspect of the invention, the amount of protrusion of the protruding wall is determined by the valve lift amount of the intake valve at the top dead center and from the top dead center until the exhaust valve is substantially closed after the top dead center. Since the crank angle is multiplied by 0.15 or the larger value, whichever is greater, the protrusion amount of the protruding wall is determined by the intake valve at the time when the overlap period of the intake and exhaust valves ends. The valve lift amount of 1 does not greatly exceed and does not unnecessarily increase. Therefore, the increase in intake resistance due to the provision of the protruding wall is suppressed to the minimum. Further, since the gap between the projecting wall and the peripheral portion of the large diameter portion of the intake valve umbrella is set to be smaller than the projecting margin,
The throttling effect of the fresh air flow passage on the protruding wall portion is effectively exerted, and the fresh air blow-through is effectively prevented. At this time,
Since the gap between the large-diameter peripheral edge of the intake valve umbrella and the combustion chamber wall on the bore peripheral side is set larger than the gap between the large-diameter peripheral edge of the intake valve umbrella and the protruding wall, Will flow into the combustion chamber from the periphery of the intake port bore. And
The fresh air that has flowed in from the peripheral edge of the bore forms a vertical swirl flow (reverse tumble flow) that flows from the cylinder wall on the intake side to the exhaust side along the top surface of the piston in the cylinder. Exhaust gas remaining in the vehicle (residual gas)
The scavenging action of pushing the air to the exhaust port is obtained, and the scavenging efficiency is improved.

According to the second aspect of the present invention, when the supercharger is provided and the valve overlap period is set to a large value, among the actions of the first aspect of the present invention, particularly in the scavenging action, the supercharger is added. The compressed intake air (fresh air) effectively pushes out the residual gas, further promoting the scavenging action.

According to the third aspect of the invention, in the portion having the protruding wall, the tumble generating wall is formed with a concave portion for increasing the clearance between the tumble generating wall and the peripheral portion of the large diameter portion of the intake valve umbrella portion. With the action and effect obtained, from the point where the protruding wall disappears, that is, from the time when the valve overlap substantially ends, the tumble generating wall restricts the fresh air flow passage on the bore peripheral side of the intake port, Fresh air mainly flows into the combustion chamber from the exhaust side of the intake port.
The fresh air flowing in from the exhaust side promotes the generation of a vertical swirl flow (tumble flow) that flows in the cylinder from the cylinder wall on the exhaust side to the intake side along the top surface of the piston to improve combustibility. To be

According to the fourth aspect of the present invention, since the exhaust side protruding wall is provided in the peripheral portion of the exhaust port opening on the intake port side similarly to the protruding wall provided in the intake port opening, the exhaust resistance is required to be the minimum required. While restraining to the limit, the blow-through of fresh air (air mixture) is prevented, and the scavenging action by the vertical swirling flow (reverse tumble flow) of the air-fuel mixture in the cylinder is easily received. The function and effect can be further improved.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an overall schematic structure of an engine according to a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes an engine, which includes a cylinder block 3 forming a cylinder 2, a cylinder head 4 joined to the upper surface of the cylinder block 3, and a piston 5 reciprocating in the cylinder 2. And a combustion chamber 6 defined by the lower surface of the cylinder head 4 and the top surface of the piston 5 in the cylinder 2.
Are formed.

An intake passage 7 is connected to the combustion chamber 6,
Intake valves 8, 8 are provided at the opening to the combustion chamber 6,
The intake air is introduced into the combustion chamber 6 at a predetermined timing. In the intake passage 7, an air cleaner 9 and an air flow meter 1 for detecting the intake air amount are sequentially provided from the upstream side.
0, a supercharger 11 as a mechanical supercharger driven by an output shaft of the engine 1, an intercooler 12 for cooling intake air, a surge tank 13 for absorbing intake pulsation, and an injector for injecting and supplying fuel. 1
4 are provided. Further, the intake passage 7 is provided with a bypass passage 15 that bypasses the supercharger 11 and the intercooler 12. In the middle of the bypass passage 15, a supercharger for supercharging pressure adjustment by the supercharger 11 is provided. A bypass valve 16 is arranged.

An exhaust passage 17 is connected to the combustion chamber 6, and exhaust valves 18, 18 are provided at the opening of the combustion chamber 6.
Is provided and the exhaust gas is discharged from the combustion chamber 6 at a predetermined timing. The exhaust cam shaft 21 that drives the exhaust valves 18, 18 to open and close at a predetermined timing includes
A variable valve timing mechanism 20 for changing the opening / closing timing of the exhaust valves 18, 18 according to the operating state is provided, and as shown in FIG. 2, during low engine speed (low load) and high engine speed (high). (At load) and change the opening and closing timing to delay the closing timing of the exhaust valves 18, 18 at high engine speed (from 5 ° after top dead center to 25 ° after top dead center)
The overlap period is set to be large. That is, in the present embodiment, during the overlap period in which both the intake valve 8 and the exhaust valve 18 are open, the top dead center at which the intake valve 8 opens when the engine speed is low (low load). From 15 ° before to 5 ° after top dead center when the exhaust valve 18 closes,
When the engine is running at high speed (high load), the intake valve 8 is set to 15 ° before the top dead center before opening and the exhaust valve 18 closes to 25 ° after the top dead center. Reference numeral 19 is a catalyst provided in the exhaust passage 17 for purifying exhaust gas.

The following FIGS. 3 and 4 show details around the combustion chamber. In these figures, the cylinder head 4 has a left side portion of the cylinder bore which branches from one main intake port 22 on the left side wall of the cylinder head and guides fresh air to the cylinder 2.
Book independent intake ports 23, 24 are provided. The independent intake ports 23 and 24 are provided so that one ends thereof open to the left inclined wall surface of the combustion chamber 6 and the other ends thereof open to the cylinder head left side wall (main intake port 22). Further, one end of 25 opens directly upstream of the combustion chamber side opening of the independent intake port 23, and the independent intake port 23
And an auxiliary intake port that extends closely below the main intake port 22 and has the other end opened immediately below the opening of the main intake port 22 on the left side wall of the cylinder head. The main intake port 22 and the auxiliary intake port 2 on the left side wall of the cylinder head 4
5, the downstream end of the intake manifold 29 is connected to each of the openings of the intake manifold 29, and the downstream end passage corresponding to the opening of the main intake port 22 of the intake manifold 29 has:
A secondary valve 30 is provided. The secondary valve 30 opens during high load operation to allow intake air to flow to the main intake port 22, and closes during low load operation to close the main intake port 22.
The intake air is blocked from flowing, and the intake air is controlled to flow to the auxiliary intake port 25.

On the right side of the cylinder bore of the cylinder head 4, there are provided two independent exhaust ports 27 and 28 for guiding the exhaust gas of the cylinder 2 to the outside. One end of each of the independent exhaust ports 27 and 28 is opened on the inclined wall surface on the right side of the combustion chamber 6, and the independent intake port 2 is provided.
The openings 3 and 24 are arranged to face and close to the respective openings on the combustion chamber side, and the other ends are gathered into one exhaust port 26 on the right side wall side of the cylinder head so as to open on the right side wall of the cylinder head. It is provided.

Valve seats 31, 31 and valve seats 32, 32 are provided at the combustion chamber side openings of the independent intake ports 23, 24 and independent intake ports 23, 24, respectively. Then, as shown in FIGS. 4 and 5, on the exhaust port side peripheral portion of the outer periphery of the valve seats 31, 31 of the independent intake ports 23, 24, a protruding wall 33 extending in the lift direction of the intake valve 8 toward the combustion chamber side. Are formed. Here, in this embodiment,
As shown in FIG. 12, the valve lift amount Lit of the intake valves 8 and 8 at the top dead center is set to 1 mm, and
From FIG. 2, the crank angle between the top dead center and the point at which the exhaust valves 18, 18 are substantially closed after the top dead center is 25 ° (at high engine speed or high load), and this angle is 0.1
The value A multiplied by 5 becomes 3.75 (mm). At this time,
The protrusion H of the protrusion wall 33 from the valve seat 31 is equal to the above A.
Or Lit, whichever is greater, which is 3.7 in this case.
It is set to 5 mm or less, and specifically, the above-mentioned protrusion margin H is set to 2 mm. The valve lift amount Lec of the intake valve 8 when the exhaust valve 18 is closed, that is, when the overlap period ends is set to 3 mm. Further, a gap α between the protruding wall 33 and the peripheral edge of the large diameter portion 8a of the umbrella portion of the intake valve 8
Is set to be smaller than the protruding margin H, and further, a gap β between the peripheral edge of the large diameter portion 8a of the umbrella portion of the intake valve 8 and the combustion chamber wall on the peripheral side of the bore is set larger than the gap α. Has been done.

With the above construction, in the above-described embodiment, the flow passage from the exhaust port side of each opening on the combustion chamber side of the independent intake ports 23, 24 is provided with the intake valve 8, by the projecting wall 33.
8 has started to open, and the valve lift amount is the above-mentioned protruding wall 3
It will be squeezed until it exceeds the protruding margin H of 3,
It is possible to prevent the fresh air that has flowed in from the independent intake ports 23, 24 from passing through the flow passages to the independent exhaust ports 27, 28 as it is. In this case, since the protruding margin H is smaller than the valve lift amount Lec of the intake valve 8 at the end of the overlap period, the flow passage is not throttled beyond the overlap period, and the overlap period is not reduced. The aperture will be finished shortly before the end. This is because the valve lift amount of the exhaust valve 18 is small near the end of the overlap period.
This is because the amount of fresh air blown through in that period becomes small and its influence is small, and rather the influence of the intake resistance becomes large, so that it is suppressed. Therefore, the projecting wall 33 can effectively prevent blow-through of fresh air while suppressing an increase in intake resistance to a minimum.

Further, at this time, the clearance β between the peripheral edge of the large diameter portion 8a of the cap portion of the intake valve 8 and the combustion chamber wall on the peripheral side of the bore is defined by the protruding wall 33 and the large diameter portion 8a of the cap portion of the intake valve 8. Gap between peripheral edge α
Since it is set larger than that, the fresh air flows into the combustion chamber 6 from the peripheral side of the bore of the combustion chamber side opening of the independent intake ports 23, 24. The fresh air flowing in from the peripheral edge of the bore forms a vertical swirl flow (reverse tumble flow) that flows from the cylinder wall on the intake side to the exhaust side along the top surface of the piston 4 in the cylinder 2. At the time of the overlap, it is possible to obtain a scavenging action of pushing the exhaust gas (residual gas) remaining in the cylinder 2 to the independent exhaust ports 27 and 28, and it is possible to improve the scavenging efficiency. In particular, in the supercharging operation range where supercharging is performed by the supercharger 11, the pressurized intake air (fresh air) effectively pushes out the residual gas, and further promotes the scavenging action. Therefore, the residual gas in the cylinder 2 can be reduced and the temperature of the air-fuel mixture can be lowered. Therefore, the knock resistance in the supercharging operation range can be improved, and the output can be effectively improved. Therefore, in the above embodiment, both prevention of blow-through of fresh air and improvement of scavenging efficiency can be achieved, and emission performance, output, and fuel consumption can be improved.

6 to 8 show the vicinity of the combustion chamber of the engine according to the second embodiment of the present invention, which is different from the first embodiment only in that a tumble generating wall is provided, and other configurations are the same as the above. The same parts as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. That is, in these figures, 34 is the valve seat 31, 3 of the independent intake port 23, 24.
1 is a tumble generating wall that is formed on the periphery of the bore of the outer periphery on the combustion chamber side and extends in the lift direction of the intake valve 8. The tumble generating wall 34 extends to the lower surface of the cylinder head 4 and has a predetermined gap with the periphery of the large diameter portion 8a of the umbrella portion of the intake valve 8 so that the protruding wall 33 projects from the valve seat 31. White H
Corresponds to the large diameter portion 8a of the umbrella portion of the intake valve 8.
The recess 35 is provided so that the gap between the periphery and the protruding wall 33 is larger than the gap α.

With the above structure, in this embodiment, when the valve lift amount of the intake valves 8 and 8 is smaller than the projection margin H of the projecting wall 33, fresh air flows through the recess 35, The same effect as the first embodiment can be obtained. Then, when the valve lift amount of the intake valves 8 and 8 exceeds the protruding margin H of the protruding wall 33, that is, from the time when the overlap period is substantially ended, the tumble generating wall 34 causes the independent intake port 23, The flow passage from the bore peripheral side of each combustion chamber side opening of 24 will be throttled, and the fresh air will mainly flow from the exhaust port side of each combustion chamber side opening of the independent intake ports 23 and 24 to the combustion chamber. It will flow in. Therefore, the fresh air that has flowed in from the flow path on the exhaust port side promotes the generation of a vertical swirl flow (tumble flow) that flows in the cylinder 2 from the cylinder wall on the exhaust side to the intake side along the top surface of the piston 4. Therefore, the combustibility can be improved. Therefore, the output and fuel consumption can be further improved by the improvement of the combustibility.

9 to 11 show the vicinity of a combustion chamber of an engine according to a third embodiment of the present invention, which is different from the first embodiment only in that an exhaust side protruding wall is provided, and other structures are provided. Is the same as that of the first embodiment, and the same portions are denoted by the same reference numerals and detailed description thereof will be omitted. That is, in these figures, 36 is the valve seat 32 of the independent exhaust port 27, 28,
32 is an exhaust-side protruding wall formed to extend in the lift direction of the exhaust valve 18 along the peripheral portion of the outer periphery of the intake port 32. The protruding amount F of the exhaust side protruding wall 36 is determined by the valve lift amount Let of the exhaust valve 18 at the top dead center and the crank angle from the opening time of the intake valve 8 opened before the top dead center to the top dead center. Is multiplied by 0.15, whichever is greater, or less. That is, in the present embodiment, as shown in FIG. 12, the valve lift amount Let of the exhaust valve 18 at the top dead center.
Is set to 2 mm (at high engine speed or high load), and from FIG. 2, the crank angle from the opening of the intake valve 8 to the top dead center is 15 °.
Since the value obtained by multiplying by 15 is 2.25 (mm), the projection amount F of the exhaust side projection wall 36 is set to 2.25 mm or less, and specifically, the projection amount F is 2 mm. It is set. The valve lift amount Li of the exhaust valve 18 when the intake valve 8 is opened, that is, when the overlap period starts
o is set to 3 mm. In addition, a gap γ between the large-diameter portion 18a of the exhaust valve 18 and the exhaust-side protruding wall 36.
Is set to be smaller than the projection margin F, and further, the gap δ between the peripheral edge of the large diameter portion 18a of the umbrella portion of the exhaust valve 18 and the combustion chamber wall on the peripheral side of the bore is set to be larger than the gap γ. Has been done.

With the above construction, in this embodiment, the independent exhaust ports 27, 2 are formed by the exhaust side protruding wall 36.
The flow passage from the intake port side of each combustion chamber side opening of 8 is
When the exhaust valves 18, 18 are closed and the valve lift amount becomes equal to or less than the projection margin F of the exhaust side projection wall 36, the exhaust valves 18, 18 are throttled. In this period, the independent intake port 2 is closed.
It is possible to prevent the fresh air that has flowed in from 3, 24 from directly flowing out to the independent exhaust ports 27, 28 via the flow passages. In this case, the protrusion F
Is smaller than the valve lift amount of the exhaust valve 18 at the beginning of the overlap period, the flow passage is not throttled at the beginning of the overlap period, and the throttle starts slightly after the overlap period starts. Will be done. This is because the intake valve 8 immediately after the start of the overlap period.
Since the valve lift of is small and the inflow of fresh air is small,
The effect of blow-through is small, and at this time, the flow resistance of the exhaust gas by the throttle, that is, the exhaust resistance is not increased, and the outflow of the exhaust gas is prioritized. As a result, blow-through can be effectively prevented while suppressing an increase in exhaust resistance to a minimum.
Further, since the exhaust gas flows out from the bore peripheral side of each opening on the combustion chamber side of the independent exhaust ports 27 and 28, it becomes easy to be subjected to the scavenging action by the fresh air flowing into the cylinder 2, and the scavenging efficiency is improved. Can be achieved. The above is obtained at the same time as the effect of the projecting wall 33 provided in the opening of the independent intake ports 23 and 24, and the synergistic effect of these can further enhance the effect of the first embodiment.

In addition, in each of the above-described embodiments, the protrusion allowance H of the protrusion wall 33 is set to 2 mm, but it is usually desirable to set the protrusion allowance H to 1.5 to 2.5 mm. Similarly, the projection margin F of the exhaust side projection wall 36 is 1.5
It is desirable to set to ~ 2.5 mm. Further, the same effect can be obtained even in the structure in which only the intake port for generating the tumble flow without the auxiliary intake port 25 and the secondary valve 30 is provided as the intake port.

[0028]

As described above, according to the combustion chamber structure of the engine in the first aspect of the invention, the projecting wall provided in the opening of the intake port suppresses the intake resistance to the minimum and blows the fresh air through. Can be effectively prevented. At the same time, the fresh air can form a vertical swirl flow (reverse tumble flow) in the cylinder to scaveng the residual gas, and the scavenging efficiency can be improved. Therefore, both prevention of blow-through of fresh air and improvement of scavenging efficiency can be achieved, and emission performance, output, and fuel consumption can be improved.

According to a second aspect of the present invention, when the invention is applied to an engine provided with a supercharger and having a large valve overlap period, among the actions of the first aspect of the invention, particularly in the scavenging action, The intake air (fresh air) pressurized by the feeder effectively pushes out the residual gas,
The scavenging action can be further promoted, the residual gas in the cylinder can be reduced, and the temperature of the air-fuel mixture can be lowered. Therefore, the knock resistance in the supercharging operation range can be improved, and the output can be effectively improved.

According to the third aspect of the present invention, the tumble generating wall can promote the generation of the tumble flow of the air-fuel mixture in the cylinder, and can improve the combustibility.

According to the invention of claim 4, the exhaust side protruding wall can further prevent blow-through of fresh air and improve the scavenging action, and the effect of the invention of claim 1 can be further enhanced. .

[Brief description of drawings]

FIG. 1 is an overall schematic configuration diagram of an engine according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing valve timing.

FIG. 3 is a sectional view of a combustion chamber according to the first embodiment of the present invention.

FIG. 4 is a bottom view of the combustion chamber according to the first embodiment of the present invention.

5 is an enlarged view of a main part of FIG.

FIG. 6 is a view corresponding to FIG. 3 according to a second embodiment of the present invention.

FIG. 7 is a view corresponding to FIG. 4 according to the second embodiment of the present invention.

FIG. 8 is an enlarged view of a main part of FIG.

FIG. 9 is a view corresponding to FIG. 3 according to the third embodiment of the present invention.

FIG. 10 is a view corresponding to FIG. 4 according to the third embodiment of the present invention.

11 is an enlarged view of a main part of FIG.

FIG. 12 is a characteristic diagram showing a valve lift amount.

[Explanation of symbols]

1 engine 4 cylinder head 6 Combustion chamber 8 intake valve 8a Umbrella part large diameter part 11 Supercharger (supercharger) 18 Exhaust valve 18a Umbrella part large diameter part 23, 24 Independent intake ports 27, 28 Independent exhaust port 31 valve seat (intake port opening) 32 valve seat (exhaust port opening) 33 protruding wall 34 Tumble generation wall 35 recess 36 Exhaust side protruding wall

Claims (4)

[Claims] 1. A plurality of intake port openings and a plurality of exhaust port openings that open into a combustion chamber are arranged close to each other, and an intake valve lift is located closer to the combustion chamber than a valve seat in each intake port opening. In the combustion chamber structure of the engine in which the protruding wall extending in the direction is formed, the protruding wall is provided along the peripheral edge portion of each intake port opening on the exhaust port side, and the protruding margin of the protruding wall is The valve lift amount of the intake valve at the dead center and the crank angle from the top dead center until the exhaust valve is substantially closed after the top dead center are multiplied by 0.15, whichever is larger. The clearance between the projecting wall and the large diameter portion peripheral edge of the intake valve umbrella portion is set smaller than the projection margin, and the large diameter portion peripheral edge of the intake valve umbrella portion and the combustion chamber wall on the bore peripheral side are formed. The gap is formed around the large diameter portion of the intake valve umbrella portion and the protrusion. The combustion chamber structure of the engine is characterized in that it is set to be larger than the gap with the outlet wall. 2. The combustion chamber structure for an engine according to claim 1, wherein the engine is provided with a supercharger, and a valve overlap period in which the opening periods of the intake and exhaust valves overlap near the top dead center is set to be large. 3. The intake valve opening extends in the lift direction of the intake valve toward the combustion chamber side from the valve seat along the peripheral edge portion on the peripheral edge side of the bore of each intake port opening, and has a predetermined gap with the peripheral edge portion of the large diameter portion of the intake valve umbrella portion. A tumble generating wall is provided, and a recessed portion that enlarges a gap between the intake valve umbrella portion and a large-diameter peripheral portion is provided in a portion between the valve seat of the tumble generating wall and a portion corresponding to a protruding margin of the protruding wall. The combustion chamber structure for an engine according to claim 1, wherein the combustion chamber structure is formed. 4. An exhaust side projecting wall extending in the lift direction of the exhaust valve is provided on the combustion chamber side from the valve seat along the peripheral edge of each exhaust port opening on the intake port side, and the projecting margin of the exhaust side projecting wall is provided. Is either the valve lift amount of the exhaust valve at top dead center or the value obtained by multiplying the crank angle between the opening time of the intake valve that opens before top dead center and the top dead center by 0.15. It is set to a large value or less, the gap between the large diameter portion peripheral edge of the exhaust valve umbrella portion and the projecting wall is set smaller than the projection margin, and the large diameter portion peripheral edge of the exhaust valve umbrella portion and the bore peripheral side. The engine combustion chamber structure according to claim 1, wherein a gap between the combustion chamber wall and the combustion chamber wall is set larger than a gap between the large-diameter peripheral portion of the exhaust valve umbrella portion and the exhaust-side protruding wall.