JPH05163906A - Combustion chamber structure of two-cycle internal combustion engine - Google Patents

Abstract

PURPOSE:To scavenge already burnt gas in good condition by providing a pair of intake valves on one side in a cylinder head, providing at least three exhaust valves on the other side thereof, in symmetric positions respectively, providing a mask wall at the opening port of one side intake valve opposing to the exhaust valve on one side of symmetric surfaces, also providing a mask on the other side thereof in the same way, so as to make new air flow in a loop shape. CONSTITUTION:Intake valves 9 to 11 are provided on one side of a cylinder head inner wall surface, exhaust valves 12 to 14 are provided on the other side, and the valves 9 to 14 are provided symmetrically in relation to a symmetric surface K-K. For example, the opening port of the intake valve 9 is covered with a cylindrical inner circumferencial wall part so as to form mask wall 16. The mask wall 16 covers a range within straight lines L1a, L1b which hold inward the whole of the umbrella parts of the exhaust valves 12, 14 from the umbrella part center of the intake valve 9, and a mask angle alpha1 becomes a minimum value. Thus new air flows in a loop shape so as to scavenge already burnt gas in the circumferential rim part of a combustion chamber in good condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion chamber structure for a two-cycle internal combustion engine.

[0002]

2. Description of the Related Art A pair of air supply valves are arranged symmetrically with respect to a plane of symmetry including a cylinder axis on one side of an inner wall surface of a cylinder head, and an exhaust valve is arranged on the other side of the inner wall surface of the cylinder head, and is located on the exhaust valve side. There is known a combustion chamber structure of a two-cycle internal combustion engine in which the opening of each intake valve is covered with a mask wall over the entire opening period of the intake valve (JP-A-2-
153222). In the combustion chamber structure of this two-cycle internal combustion engine, since the openings of the intake valves located on the exhaust valve side are covered by the mask wall, fresh air is introduced from the openings of the intake valves on the opposite side of the mask wall to the combustion chamber. This fresh air flows down to the inner wall surface of the cylinder bore below the intake valve, then advances to the top surface of the piston and rises along the inner wall surface of the cylinder bore below the exhaust valve, so that loop scavenging can be performed.

[0003]

[Problems to be Solved by the Invention] However, the above-mentioned 2
In the combustion chamber structure of the cycle internal combustion engine, the range of the mask wall extending along the peripheral portion of the intake valve, that is, the length and position of the mask wall along the peripheral direction of the intake valve have not been sufficiently studied. That is, if the range of the mask wall along the peripheral direction of the air supply valve is made too small, new air flows into the combustion chamber from the opening of the air supply valve which is not covered by the mask wall and is located on the exhaust valve side. Air travels along the inner wall surface of the cylinder head and then blows through the opening of the exhaust valve into the exhaust port. In this case, since the fresh air that blows through does not contribute to the scavenging action of the burnt gas in the combustion chamber, it becomes useless air, resulting in a problem that the scavenging efficiency decreases.

On the other hand, if the area of the mask wall along the peripheral direction of the air supply valve is made too large in order to surely prevent fresh air from blowing through into the exhaust port along the inner wall surface of the cylinder head, then the air supply will be performed. Since the opening area of the air valve decreases, the flow resistance, that is, the air supply resistance, that the fresh air receives when passing through the air supply valve opening increases, and thus it is difficult for fresh air to flow from the air supply port into the combustion chamber. Become. As a result, the discharge work performed by the mechanical supercharger arranged upstream of the air supply port to send the fresh air into the combustion chamber is increased, and thus the thermal efficiency of the engine is reduced.

Therefore, in order to perform good loop scavenging,
Optimum length and position of the mask wall along the peripheral edge of the air supply valve so that the amount of new air that blows along the inner wall surface of the cylinder head can be reduced as much as possible while keeping the air supply resistance as small as possible. And it is important to form in an optimal position. However, in the above-described combustion chamber structure of the two-cycle internal combustion engine, the optimum range of the mask wall for ensuring such good loop scavenging has not been sufficiently studied.

[0006]

In order to solve the above problems, according to the present invention, a pair of air supply valves are arranged symmetrically with respect to a plane of symmetry including a cylinder axis on one side of an inner wall surface of a cylinder head. A combustion chamber structure of a two-cycle internal combustion engine, in which at least three exhaust valves are arranged on the other side of the inner wall surface of the cylinder head, and the openings of the intake valves located on the exhaust valve side are covered with a mask wall. Of all the first exhaust valves for at least one of the three exhaust valves of the first exhaust valve in which part or all of the exhaust valve bulk is arranged on the side of one intake valve with respect to the plane of symmetry. It is located in a region sandwiched by a pair of straight lines that minimizes the sandwiching angle formed between a pair of straight lines extending from the center of the bulge portion of one air supply valve so as to sandwich the whole. Open the opening of one air supply valve to the mask wall. All the second exhausts for the second exhaust valve which is located on the side of the other intake valve with respect to the plane of symmetry with respect to the plane of symmetry, of the at least three exhaust valves described above. A region sandwiched by a pair of straight lines that extends from the center of the bulk portion of the other air supply valve so as to sandwich the entire bulk portion of the valve and has a minimum sandwich angle formed between the pair of straight lines. The opening of the other air supply valve located inside is covered with the mask wall.

Further, in order to solve the above problems, according to the present invention, a pair of air supply valves are arranged symmetrically with respect to a plane of symmetry including the cylinder axis on one side of the inner wall surface of the cylinder head and the inner wall surface of the cylinder head. In the combustion chamber structure of the two-cycle internal combustion engine, in which at least three exhaust valves are arranged on the other side and the openings of the intake valves located on the exhaust valve side are covered by the mask wall, The air valve is arranged on one side peripheral portion of the cylinder head inner wall surface, and at least three exhaust valves described above are arranged on the other side peripheral portion of the cylinder head inner wall surface. A part of or the entire exhaust valve bulkhead is arranged on the side of one intake valve with respect to the plane of symmetry. Regarding the first exhaust valves, one of the intake valves is placed so as to sandwich the entire bulkhead of all the first exhaust valves. A pair of straights extending from the center of the Covered by the mask wall openings of one of the air supply valve included angle formed between the pair of straight lines positioned sandwiched by the regions in the pair of linear such that minimum of,
Of all at least three exhaust valves, a part or all of the exhaust valve bulk is arranged on the other charge valve side with respect to the plane of symmetry For the second exhaust valve All of the bulk of the second exhaust valve The other of which is located in a region sandwiched by a pair of straight lines that minimizes the sandwiching angle formed between the pair of straight lines that extend from the center of the bulge portion of the other air supply valve The opening of the air supply valve is covered with a mask wall, and an additional air supply valve is placed in the center of the inner wall of the cylinder head so that fresh air is supplied from the additional air supply valve toward the center of the combustion chamber. I have to.

[0008]

In the invention described in claim 1, all the fresh air flows into the combustion chamber through the opening of the air supply valve on the side opposite to the mask wall,
The fresh air flowing into the combustion chamber descends along the inner wall surface of the cylinder bore below the intake valve, then advances along the top surface of the piston and rises along the inner wall surface of the cylinder bore below the exhaust valve. At this time, the mask wall is sufficiently prevented from blowing the fresh air flowing into the combustion chamber into the exhaust port along the inner wall surface of the cylinder head, and the flow resistance received when the fresh air passes through the air supply valve opening, That is, the air supply resistance can be suppressed small. Thus, the fresh air satisfactorily flows in a loop in the combustion chamber, and the burned gas is scavenged satisfactorily by the loop fresh air.

According to the second aspect of the present invention, fresh air flows into the combustion chamber from the opening of the air supply valve located on the side opposite to the mask wall from the air supply valve arranged in the peripheral portion of the inner wall surface of the cylinder head. The fresh air flowing into the combustion chamber descends along the inner wall surface of the cylinder bore below the intake valve, then advances along the top surface of the piston, and rises along the inner wall surface of the cylinder bore below the exhaust valve. At this time, the mask wall sufficiently prevents fresh air from blowing into the exhaust port along the inner wall surface of the cylinder head, and the air supply resistance is suppressed to be small. Thus, the fresh air flows in a good loop shape along the peripheral edge of the combustion chamber, and the burned gas existing in the peripheral edge portion of the combustion chamber is scavenged well by the fresh air flowing in the loop shape. Further, the burned gas existing in the central portion of the combustion chamber is scavenged well by the fresh air supplied from the additional air supply valve.

[0010]

1 to 4 show a case where the present invention is applied to a two-cycle diesel engine. However, the present invention
It can also be applied to a cycle spark ignition type engine. Figure 1
4, reference numeral 1 is a cylinder block, 2 is a piston that reciprocates in the cylinder block 1, 3 is a cylinder head fixed on the cylinder block 1, and 4 is the top surface of the piston 2 and the cylinder head inner wall surface. A main chamber formed between 3a, 5 is a sub chamber formed in the cylinder head 3 above the peripheral edge of the cylinder head inner wall surface 3a, 6 is a nozzle of the sub chamber 5 opening in the main chamber 4, and 7 is a sub chamber. Reference numeral 8 denotes a fuel injection valve for injecting fuel into the chamber 5, and reference numeral 8 denotes a glow plug arranged in the sub chamber 5.

In the embodiment shown in FIGS. 1 to 4, as shown in FIGS. 1 and 2, two air supply valves 9 and 10 are arranged in the peripheral portion of one side of the cylinder head inner wall surface 3a to form a cylinder. Three exhaust valves 1 are provided around the other side of the head inner wall surface 3a.
2, 13, 14 are arranged. Further, a third or additional air supply valve 11 is arranged at the center of the cylinder head inner wall surface 3a. As shown in FIG. 1, the air supply valve 9 and the air supply valve 10
Are arranged symmetrically with respect to a plane of symmetry KK including the cylinder axis, and the exhaust valves 12 and 13 are also arranged symmetrically with respect to the plane of symmetry KK. Also, three air supply valves 9,1
The injection port 6 of the sub chamber 5 is arranged in the peripheral portion of the cylinder head inner wall surface 3a surrounded by 0 and 11, and the exhaust valve 14,
The air supply valve 11 and the injection port 6 are arranged on the plane of symmetry KK. Therefore, in the embodiment shown in FIGS. 1 to 4, three exhaust valves 12, 13, 1 are provided around the inner wall surface 3a of the cylinder head.
Four or two air supply valves 9 and 10 and the injection port 6 are arranged at substantially equal angular intervals, and an additional air supply valve 11 is arranged substantially in the center of the cylinder head inner wall surface 3a.

As shown in FIGS. 1 and 3, a concave portion 15 is formed on the cylinder head inner wall surface 3a, and the air supply valve 9 is arranged at the deepest portion of the concave portion 15. Exhaust valve 12,1
The inner peripheral wall surface portion 16 of the concave portion 15 located on the 4 side is the air supply valve 9
Has a cylindrical shape that is disposed very close to the outer peripheral edge of the air supply valve 9 and extends along the outer peripheral edge of the air supply valve 9. The inner peripheral wall surface portion 17 of the recess 15 excluding the cylindrical inner peripheral wall surface portion 16 is inside the main chamber 4. It is formed in a conical shape that widens toward. Therefore, the opening of the air supply valve 9 facing the cylindrical inner peripheral wall surface portion 16 is covered by the cylindrical inner peripheral wall surface portion 16, and thus the cylindrical inner peripheral wall surface portion 16 is formed on the exhaust valve 12, 14 side. A mask wall that covers the opening of the air supply valve 9 is formed. As shown in FIG. 1, the exhaust valve 12 has a plane of symmetry KK.
Is arranged on the air supply valve 9 side, and the exhaust valve 14 is arranged on the plane of symmetry KK. That is, the entire bulkhead portion of the exhaust valve 12 is located on the intake valve 9 side with respect to the plane of symmetry KK, and half the bulkhead portion of the exhaust valve 14 is located on the intake valve 9 side with respect to the plane of symmetry KK. .. Considering a pair of straight lines extending from the center of the bulk portion of the air supply valve 9 so as to sandwich the entire bulk portions of the exhaust valves 12 and 14, a sandwiching angle α ₁ formed between the pair of straight lines, that is, a mask The mask wall 16 covers the opening of the air supply valve 9 located in the region sandwiched by the pair of straight lines L _1a and L _1b such that the angle α ₁ is minimized. That is, the mask wall 16 extends in an arc shape along the outer peripheral edge of the bulkhead portion of the air supply valve 9 over the range of the mask angle α ₁ .
In the embodiment shown in FIGS. 1 to 4, the mask wall 16 extends below the air supply valve 9 in the maximum lift position,
Therefore, the opening of the air supply valve 9 formed on the side of the exhaust valves 12 and 14 is covered with the mask wall 16 over the entire opening period of the air supply valve 9. However, the height of the mask wall may be slightly lowered so that the opening of the air supply valve 9 is covered with the mask wall 16 only when the lift amount of the air supply valve 9 is small.

On the other hand, as shown in FIG. 1, a recess 18 having a shape symmetrical to the recess 15 with respect to the plane of symmetry KK is formed on the inner wall surface 3a of the cylinder head.
The air supply valve 10 is arranged at the innermost portion of the position 8. Exhaust valve 13,1
The inner peripheral wall surface portion 19 of the recess 18 located on the fourth side is the air supply valve 1
0 is arranged very close to the outer peripheral edge of 0 and has a cylindrical shape extending along the outer peripheral edge of the air supply valve 10. The inner peripheral wall surface portion 20 of the recess 18 excluding the cylindrical inner peripheral wall surface portion 19 is the main chamber 4 It is formed in a conical shape that expands inward. Therefore, the opening of the air supply valve 10 facing the cylindrical inner peripheral wall surface portion 19 is covered by the cylindrical inner peripheral wall surface portion 19,
Therefore, the cylindrical inner peripheral wall surface portion 19 is provided with the exhaust valves 13, 14
A mask wall that covers the opening of the air supply valve 10 formed on the side is formed. As shown in FIG. 1, the exhaust valve 13 is arranged on the side of the intake valve 10 with respect to the plane of symmetry KK, and the exhaust valve 14 is arranged on the plane of symmetry KK. That is, the entire bulkhead portion of the exhaust valve 13 is provided with respect to the plane of symmetry KK.
The exhaust valve 14 is located on the 0 side, and half of the cap portion of the exhaust valve 14 is a symmetry plane K.
It is located on the air supply valve 10 side with respect to −K. Air supply valve 10
Considering a pair of straight lines extending from the center of the bulge portion so as to sandwich the entire bulge portions of the exhaust valves 13 and 14, the holding angle α ₂ formed between the pair of straight lines, that is, the mask angle α.
_The mask wall 19 covers the opening of the air supply valve 10 located in the region sandwiched by the pair of straight lines L _2a and L _2b such that ₂ is minimized. That is, the mask wall 19 has a mask angle α ₂
The arc shape extends along the outer peripheral edge of the cap portion of the air supply valve 10 over the range. In the embodiment shown in FIGS. 1 to 4, the mask wall 19 extends below the air supply valve 10 in the maximum lift position, like the mask wall 16, and thus the air supply valves formed on the exhaust valves 13 and 14 side. The opening of the air valve 10 is the air supply valve 1
The mask wall 19 covers the entire zero valve opening period. However, with respect to the mask wall 19 as well, the height of the mask wall 19 may be slightly lowered so that the opening of the air supply valve 10 is covered with the mask wall 19 only when the lift amount of the air supply valve 10 is small.

On the other hand, as shown in FIGS. 1 and 4, a recess 21 is formed on the inner wall surface 3a of the cylinder head, and the air supply valve 11 is arranged at the innermost portion of the recess 21. The inner peripheral wall surface portion 22 of the concave portion 21 located on the exhaust valve 12, 13, 14 side is arranged in the vicinity of the outer peripheral edge of the air supply valve 11 and has a cylindrical shape extending along the outer peripheral edge of the air supply valve 11. ,
The inner peripheral wall surface portion 23 of the recess 21 excluding the cylindrical inner peripheral wall surface portion 22 is formed in a conical shape that widens toward the inside of the main chamber 4. Therefore, the opening of the air supply valve 11 facing the cylindrical inner peripheral wall surface portion 22 is covered by the cylindrical inner peripheral wall surface portion 22, and thus the cylindrical inner peripheral wall surface portion 22 is on the exhaust valve 12, 13, 14 side. A mask wall is formed to cover the opening of the air supply valve 11 formed in. As shown in FIG. 1, the exhaust valves 12, 13,
14 included angle β formed between the pair of straight line when considering a pair of straight line extending so as to sandwich the entire bulk portion, i.e. the pair, such as the mask angle β is minimum straight M _a, M _b
The opening of the air supply valve 11 located in the region sandwiched by is covered with the mask wall 22. That is, the mask wall 22 extends in an arc shape along the outer peripheral edge of the bulkhead portion of the air supply valve 11 over the range of the mask angle β. In the embodiment shown in FIGS. 1 to 4, the mask wall 22 extends below the air supply valve 11 in the maximum lift position, like the mask walls 16 and 19, and therefore, on the exhaust valve 12, 13 and 14 side. The formed opening of the air supply valve 11 is covered with the mask wall 22 over the entire opening period of the air supply valve 11. However, with respect to the mask wall 22 as well, the height of the mask wall 22 is made slightly lower, and the air supply valve 11 is provided only when the lift amount of the air supply valve 11 is small.
It is also possible to cover the openings of the above with the mask wall 22.

On the other hand, no mask wall is provided for each of the exhaust valves 12, 13, 14 and therefore the exhaust valve 1
When the valves 2, 13, 14 are opened, the exhaust valves 12, 13, 14 are opened in the main chamber 4 over the entire circumference. In the embodiment shown in FIGS. 1 to 4, all the intake valves 9, 10, 11 are the cylinder head 3
A corresponding valve lifter 26, driven by a common camshaft 25 via a corresponding valve lifter 24 slidably inserted therein, with all exhaust valves 12, 13, 14 slidably inserted in the cylinder head 3. It is driven by a common cam shaft 27 via. That is, the full charge valve 9,
10 and 11 are directly driven by a common cam shaft 25 located on the axis of each air supply valve 9, 10, 11 without using a rocker arm, and all exhaust valves 12, 13, 14 are driven.
Each exhaust valve 12, 1 without going through a rocker arm
It is directly driven by a common camshaft 27 located on the axis of 3,14.

Inside the cylinder head 3, exhaust valves 12, 1 are provided.
A common exhaust port 28 is formed for all the exhaust valves 12, 13, 14 extending to 3, 3 and 14, and a pair of supply valves extending to each supply valve 9, 10 on both sides of the sub chamber 5 in the cylinder head 3. Air ports 29, 30 are formed. Also,
In the cylinder head 3, a pair of air supply branch passages 31 and 32 are formed to branch from the air supply ports 29 and 30 to extend to the air supply valve 11 and join each other in the vicinity of the air supply valve 11. Therefore, fresh air is supplied from the air supply valves 9 and 10 through the corresponding air supply ports 29 and 30, respectively.
1 to each air supply port 29, 30 to each air supply branch passage 3
The fresh air that has been diverted into the inside of 1, 32 is supplied.

FIG. 5 shows the opening timing of the intake valves 9, 10, 11 and the exhaust valves 12, 13, 14. As shown in FIG. 5, each exhaust valve 12, 13, 14 is connected to each intake valve 9, 1
It opens before 0 and 11, and closes before it. Next, the operation of the two-stroke diesel engine shown in FIGS. 1 to 4 will be described with reference to FIGS. 6 to 8.

As described above, each exhaust valve 12, 13, 14
Is opened before the air supply valves 9, 10, 11 are opened. When the exhaust valves 12, 13, 14 are opened, the burned gas in the main chamber 4 is rapidly discharged into the exhaust port 28, that is, blowdown occurs, and as a result, the pressure in the main chamber 4 is rapidly reduced. .. When the pressure in the main chamber 4 drops, the burnt gas in the sub chamber 5 is discharged from the injection port 6
Through the main chamber 4.

Next, when the air supply valves 9, 10, 11 are opened, the fresh air sent from the engine-driven mechanical supercharger (not shown) into the air supply ports 29, 30 is supplied to the air supply valves 9. , 1
It is supplied into the main chamber 4 via 0 and 11. At this time, as described above, the opening of the air supply valve 9 located on the exhaust valve 12, 14 side is covered with the mask wall 16, and the exhaust valve 13,
Since the opening of the air supply valve 10 located on the 14 side is covered by the mask wall 19 and the opening of the air supply valve 11 located on the exhaust valve 12, 13, 14 side is covered by the mask wall 22, Air flows into the main chamber 4 through the openings of the air supply valves 9, 10, 11 located on the opposite side of the mask walls 16, 19, 22. In this case, since the air supply valves 9 and 10 are arranged in the peripheral portion of the cylinder head inner wall surface 3a, the fresh air flowing in from the air supply valves 9 and 10 is indicated by arrows _Xa and _Xb in _FIGS . As shown, the corresponding intake valves 9, 1
0 down along the inner wall surface 1a of the cylinder bore, then proceed along the top surface of the piston 2, and then the exhaust valve 1
2, 13 rises along the inner wall surface 1a of the cylinder bore. That is, the fresh air flowing in from each air supply valve 9 and 10 is transferred to the main chamber 4
The burnt gas in the main chamber 4 is discharged from the exhaust valves 12, 13, 14 by the fresh air X _a , X _b flowing in a loop along the peripheral edge of the. Hence the fresh air X _a flowing from the feed valves 9 and 10, the peripheral edge portion of the main chamber 4 by X _b is scavenged. At this time, the fresh air X _a flowing in from the air supply valve 9 serves to scavenge the peripheral portion of the main chamber 4 located on the air supply valve 9 side with respect to the plane of symmetry KK, while fresh air flowing in from the air supply valve 10 is introduced. The air _Xb plays a role of scavenging the peripheral portion of the main chamber 4 located on the air supply valve 10 side with respect to the plane of symmetry KK.

As described above, the entire bulkhead portion of the exhaust valve 12 and half the bulkhead portion of the exhaust valve 14 are located on the air supply valve 9 side with respect to the plane of symmetry KK, and these two exhaust valves 12,
The opening of the air supply valve 9 within the range of the mask angle α ₁ located on the 14th side is covered with the mask wall 16. Therefore, as described above, the fresh air flowing in from the air supply valve 9 serves to scavenge the peripheral portion of the main chamber 4 located on the air supply valve 9 side with respect to the plane of symmetry KK. The fresh air flowing from 9 advances along the inner wall surface 3a of the cylinder head, and the exhaust valve 1
Blowing through the exhaust port 28 through 2, 14 is blocked by the mask wall 16. In addition, from the opening portion of the air supply valve 9 formed between the conical inner peripheral wall surface portion 17 a located on the exhaust valve 13 side of the conical inner peripheral wall surface portion 17 of the recess 15 and the peripheral edge portion of the air supply valve 9. A part of the fresh air that has flowed into the main chamber 4 tends to travel toward the exhaust valve 13 along the inner wall surface 3a of the cylinder head. However, this exhaust valve 13
The fresh air which is going to move in the direction is the concave portion 21 on the air supply valve 9 side.
8 confronts the flow of fresh air flowing into the main chamber 4 through the opening of the air supply valve 11 formed between the conical inner peripheral wall surface portion 23a of the air supply valve 11 and the peripheral portion of the air supply valve 11, and the arrow X _{c in} FIG. As shown by, the inside of the main chamber 4 is lowered. Therefore, the fresh air that has flowed in from the conical inner peripheral wall surface portion 17a of the recess 15 does not blow into the exhaust port 28. Thus, the fresh air flowing from the air supply valve 9 is almost completely prevented from blowing through the exhaust port 28 along the inner wall surface of the cylinder head. 4 of the peripheral edge new stream X _a flowing in a loop along, are effectively caused to contribute to the generation of X _c. Further, since the mask angle α ₁ of the air supply valve 9 is formed at the minimum necessary angle capable of satisfactorily preventing blow-through of fresh air along the inner wall surface 3a of the cylinder head, the fresh air is opened by the air supply valve 9. The flow resistance, that is, the air supply resistance, which is received when the air passes through is suppressed small, so that the fresh air smoothly flows into the main chamber 4 through the opening of the air supply valve 9. Thus, the fresh air flowing in from the intake valve 9 causes the intake valve 9 to move with respect to the plane of symmetry KK.
Strong new airflows _Xa and _Xc flowing in a loop are formed along the peripheral portion of the main chamber 4 located on the side.

On the other hand, the entire bulk of the exhaust valve 13 and the exhaust
Half of the bulb of valve 14 is an air supply valve with respect to plane of symmetry KK
Located on the 10 side, these two exhaust valves 13, 14
Mask angle α located on the side₂Of the intake valve 10 within the range of
Are covered by the mask wall 19. Therefore, the above
As described above, the fresh air flowing in from the air supply valve 10 is on the symmetrical plane KK.
The peripheral portion of the main chamber 4 located on the air supply valve 10 side is scavenged.
Functioning as an exhaust gas, but at this time, the gas entered from the air supply valve 10.
Fresh air travels along the inner wall surface 3a of the cylinder head and the exhaust valve
Blow through the exhaust port 28 through 13, 14
Are blocked by the mask wall 19. In addition,
Same as the case of fresh air flowing in from the conical inner peripheral wall surface portion 17a
Similarly, the conical inner peripheral wall surface portion 20 of the recess 18 on the exhaust valve 12 side
a of the air supply valve 10 formed between a and the peripheral portion of the air supply valve 10.
A part of the fresh air flowing from the mouth into the main chamber 4 is transferred to the cylinder.
Let's move toward the exhaust valve 12 along the inner wall surface 3a of the hood.
However, the fresh air that is going to progress toward the exhaust valve 12
Is a conical inner peripheral wall surface portion 23 of the concave portion 21 on the air supply valve 10 side.
b, the opening of the air supply valve 11 formed between the periphery of the air supply valve 11
Figure colliding with the flow of fresh air flowing into the main chamber 4 from the mouth
Arrow X at 8_dAs shown by, the inside of the main chamber 4 is lowered.
Therefore, it flows in from the conical inner peripheral wall surface portion 20a of the concave portion 18.
Fresh air also does not blow into the exhaust port 28. Thus salary
The fresh air flowing in from the air valve 10 moves along the inner wall surface of the cylinder head.
Therefore, it is almost completely prevented that the air blows into the exhaust port 28.
Almost all new air that has been turned off and therefore flowed in from the intake valve 10.
A new air flow X in which air flows in a loop along the peripheral edge of the main chamber 4.
_b, X_dCan be effectively contributed to the occurrence of. Also air supply
Mask angle α of valve 10₂Along the inner wall surface 3a of the cylinder head
The minimum necessary corners that can prevent the blow of fresh air
Since it is formed every time, the air supply resistance is suppressed to a small
Therefore, fresh air smoothly enters the main chamber 4 through the opening of the air supply valve 10.
Inflow. Thus, by the fresh air flowing from the air supply valve 10,
Main chamber 4 located on the side of the air supply valve 10 with respect to the plane of symmetry KK
Strong new air flow X flowing in a loop along the peripheral edge of the_b，
X_dIs formed. In this way, inflow from the intake valves 9 and 10
By the fresh air to form a loop along the entire periphery of the main chamber 4
A powerful new airflow X_a, X_b, X _c, X_dFormed
This powerful new airflow X_a, X_b, X_c, X_dBy
The peripheral portion of the main chamber 4 is scavenged well.

On the other hand, since the air supply valve 11 is arranged at the center of the inner wall surface 3a of the cylinder head, the fresh air flowing from the air supply valve 11 is supplied to the main chamber as shown by an arrow Y in FIGS. 4 descends in the central portion of the piston 4, then changes direction at the top surface of the piston 2, and then ascends along the inner wall surface 1a of the cylinder bore below the exhaust valves 12, 13, 14. Main room 4
The burnt gas existing in the central portion of the air is discharged into the exhaust port 28 by the new airflow Y, and therefore the central portion in the main chamber 4 is scavenged by the fresh air Y flowing from the air supply valve 11. At this time, as described above, all exhaust valves 12, 13,
Since the opening of the air supply valve 11 located on the 14 side within the range of the mask angle β is covered by the mask wall 22, the air supply valve 1
It is almost completely prevented that the fresh air flowing in from No. 1 blows into the exhaust port 28 along the inner wall surface of the cylinder head. Therefore, almost all the fresh air flowing in from the air supply valve 11 can be effectively contributed to the generation of the new air flow Y descending in the central portion of the main chamber 4. Further, since the mask angle β is formed at the minimum necessary angle that can favorably prevent the fresh air from passing through along the inner wall surface 3a of the cylinder head, the air supply resistance can be suppressed to be small. Thus, a strong new air flow Y descending in the central portion of the main chamber 4 is formed, and the strong new air flow Y causes the exit chamber 4 to exit.
The central part of is scavenged well.

As described above, the fresh air flowing from the air supply valves 9 and 10 scavenges the peripheral portion of the main chamber 4 well, and the air supply valve 1
Since the central portion of the main chamber 4 is scavenged by the fresh air flowing in from 1, the whole inside of the main chamber 4 is scavenged well by the fresh air flowing in from each of the air supply valves 9, 10, 11. Next, the exhaust valves 12, 13, 14 are closed, and the air supply valves 9, 10, 1
When the valve 1 is closed, the gas in the main chamber 4 is sent into the sub chamber 5 through the nozzle 6 by the ascending action of the piston 2. As described above, since the entire main chamber 4 is scavenged well, a gas containing a large amount of fresh air is sent into the sub chamber 5 and thus injected from the fuel injection valve 7 into the sub chamber 5. The fuel will be burned well.

If the pressure in the main chamber 4 is high when the intake valves 9, 10, 11 are opened, the burnt gas in the main chamber 4 flows back into the intake ports 29, 30. However, when such a backflow occurs, the mechanical supercharger must do extra work in order to return the backburnt burned gas into the main chamber 4 and discharge it into the exhaust port 28. The output loss of the engine will increase accordingly. Therefore, in order to prevent such a backflow of burnt gas, the pressure in the main chamber 4 when the intake valves 9, 10, 11 are opened must be lowered, and for that purpose, the exhaust valve 12, It is necessary to discharge burnt gas into the exhaust port 28 as soon as possible when the valves 13 and 14 are opened.

However, the period from the opening of the exhaust valves 12, 13, 14 to the opening of the intake valves 9, 10, 11 is extremely short, and the burned gas is promptly released during this short period. In order to discharge, the exhaust valves 12, 13, 14 must be opened at high speed. In this case, when the exhaust valves 12, 13, 14 are driven via the rocker arm, the valve opening speed at the time of opening the exhaust valves 12, 13, 14 becomes slow due to elastic deformation of the rocker arm. Therefore, in the embodiment of the present invention, in order to increase the valve opening speed when the exhaust valves 12, 13, 14 are opened, each exhaust valve 12, 13, 14 is directly driven by the cam shaft 27 without the rocker arm. ing.

As for the cylinder head inner wall surface 3a, the temperature in the sub chamber 5 is considerably high, so that the temperature of the cylinder head inner wall surface 3a around the nozzle hole 6 is considerably higher than that of other portions, and therefore the temperature around the nozzle hole 6 is increased. The crack is most likely to occur on the inner wall surface 3a of the cylinder head. However, in the embodiment according to the present invention, as shown in FIG. 1, the injection port 6 is surrounded by the three air supply valves 9, 10 and 11, so that the cylinder head inner wall surface 3a around the injection port 6 is supplied to each supply port. It is possible to prevent the generation of cracks in the cylinder head inner wall surface 3a around the nozzle 6 by being cooled by the fresh air flowing in from the air valves 9, 10, 11.

FIG. 9 shows a second embodiment. In each embodiment described below, the same reference numerals are used for the same components as those in the embodiment shown in FIGS. The embodiment shown in FIG. 9 has substantially the same structure as the embodiment shown in FIGS. 1 to 4, but the mask angle β of the air supply valve 11 arranged at the center of the cylinder head inner wall surface 3a is different. That is, as shown in FIG. 9, _a straight line Ma connecting the center of the bulge portion of the exhaust valve 12 and the center of the bulge portion of the air supply valve 11 located on the intake valve 9 side with respect to the plane of symmetry KK, and the plane of symmetry K With respect to −K, the opening of the air supply valve 11 located in the region sandwiched by the straight line M _b connecting the center of the exhaust valve 13 located on the air supply valve 10 side and the center of the air supply valve 11 It is covered by the mask wall 22. As described above, in the embodiment shown in FIG. 9, the mask angle β of the air supply valve 11 is formed smaller than that in the embodiment shown in FIGS. 1 to 4, and therefore, the air supply when the air supply valve 11 is opened. The opening area of the valve 11 is increased, and as a result, the air supply resistance is further reduced.

FIG. 10 shows a third embodiment. The embodiment shown in FIG. 10 has substantially the same structure as the embodiment shown in FIGS. 1 to 4 and the embodiment shown in FIG. 9, but the mask angle of the air supply valve 11 arranged at the center of the cylinder head inner wall surface 3a. β is different. That is, the pair of straight lines M _a which extends from the bevel portion center of the air supply valve 11 so as to be in contact with the bulk outer periphery of the exhaust valve 14 disposed on the plane of symmetry K-K as shown in FIG. 10, in M _b The opening of the air supply valve 11 located in the sandwiched region is covered with the mask wall 22. As described above, in the embodiment shown in FIG. 10, the mask angle β of the air supply valve 11 is formed to be smaller than that in the embodiment shown in FIGS. 1 to 4 and the embodiment shown in FIG. It can be further reduced.

A fourth embodiment is shown in FIGS. 11 to 15.
In this embodiment, the exhaust valves 12, 13, 14 and the exhaust port 28 have the same structure as the embodiment shown in FIGS. 1 to 4, and the air supply valves 9 and 10 and the mask walls 16 and 19 are also shown in FIGS. 1 has the same structure as that of the embodiment shown in FIG. 4, and the sub chamber 5 and the injection port 6 also have the same structure as that of the embodiment shown in FIGS.
That is, the air supply valves 9 and 10 are arranged in the respective recesses 15 and 18 formed on the cylinder head inner wall surface 3a, and the openings of the air supply valve 9 formed on the exhaust valve 12 and 14 side and the exhaust valve are formed. The openings of the air supply valve 10 formed on the 13 and 14 sides are covered with corresponding mask walls 16 and 19, respectively.

On the other hand, in this embodiment, the air supply valve 11a is shown in FIG.
1 to 4 have a considerably smaller valve diameter than the air supply valve 11 of the embodiment shown in FIG. 4, and the air supply branch passages 31a and 32a are provided in the air supply branch passages 31 and 32 of the embodiment shown in FIGS. It has a considerably smaller cross-sectional area. Further, in this embodiment, no mask wall is provided for the air supply valve 11a. Therefore, in this embodiment, a small amount of fresh air is supplied into the main chamber 4 via the air supply valve 11a as compared with the embodiment shown in FIGS. 1 to 4, and this fresh air is then indicated by the arrow Ya in FIG. Flow toward the center of the main chamber 4. Therefore, even in this case, the central portion of the main chamber 4 is scavenged by the fresh air flowing from the air supply valve 11a, and the peripheral portion of the main chamber 4 is scavenged by the fresh air flowing from the other air supply valves 9 and 10. Therefore, the entire main chamber 4 is scavenged. In this embodiment, since the mask wall is not provided for the air supply valve 11a, part of the fresh air flowing in from the air supply valve 11a blows into the exhaust port 28. In this case, the blown air does not contribute to the scavenging action of the burnt gas and is wasted air, but the amount of air flowing in from the air supply valve 11a is small and the amount of wasted air does not increase so much.

FIG. 16 shows a fifth embodiment. In the embodiment shown in FIG. 16 as well, as in the embodiment shown in FIGS. 1 to 4, a symmetry plane K is formed on one peripheral portion of the cylinder head inner wall surface 3a.
A pair of air supply valves 9 and 10 are arranged symmetrically with respect to −K, and an additional air supply valve 11 is arranged in the central portion of the cylinder head inner wall surface 3a, and these three air supply valves 9, 10, 11 are arranged.
The injection port 6 of the sub chamber is arranged in the peripheral portion of the cylinder head inner wall surface 3a surrounded by, and each of the air supply valves 9, 10, 11 has a corresponding recessed portion 15, 18, formed on the cylinder head inner wall surface 3a. It is arranged in 21. On the other hand, in this embodiment, four exhaust valves 40, 41, 42, 43 are arranged on the other side peripheral portion of the cylinder head inner wall surface 3a. FIG.
As shown in, the exhaust valve 40 and the exhaust valve 41 have a symmetry plane K.
The exhaust valve 42 and the exhaust valve 4 are arranged symmetrically with respect to K
3 are also arranged symmetrically with respect to the plane of symmetry KK. Further, the exhaust valves 40 and 42 are arranged on the air supply valve 9 side with respect to the plane of symmetry KK, and the exhaust valve 40 is arranged farther from the plane of symmetry KK than the exhaust valve 42. On the other hand, the exhaust valves 41 and 43 are arranged on the air supply valve 10 side with respect to the plane of symmetry KK, and the exhaust valve 41 is arranged farther from the plane of symmetry KK than the exhaust valve 43.

In this embodiment, as shown in FIG.
The entire bulge of the air valve 40 and the entire bulge of the exhaust valve 42
It is located on the side of the air supply valve 9 with respect to the plane of symmetry KK. Salary
These two exhaust valves 40, 42 from the center of the air valve 9
Considered a pair of straight lines that extend across the entire bulge
Sometimes the included angle α formed between this pair of straight lines₁, Ie
Mask angle α₁A pair of straight lines L such that_1a, L_1b
The opening of the air supply valve 9 located in the area sandwiched by
It is covered by 16. On the other hand, the cap of the exhaust valve 41
The whole and the bulk of the exhaust valve 43 are in the plane of symmetry KK
It is located on the air supply valve 10 side. Bulk of air supply valve 10
From the center of the part, the whole of the bulk part of these two exhaust valves 41, 43
When you think of a pair of straight lines that extend to sandwich the body, this one
The included angle α formed between the pair of straight lines₂, Ie mask angle α₂
A pair of straight lines that minimize_2a, L_2bSandwiched between
The opening of the air supply valve 10 located in the area is defined by the mask wall 19.
Is covered. On the other hand, from the center of the air supply valve 11
Holds the entire bulk of all exhaust valves 40, 41, 42, 43
When you think of a pair of straight lines that extend like
The included angle β formed between them, that is, the mask angle β is minimized.
A pair of straight lines M _a, M_bLocated in the area sandwiched between
The opening of the air supply valve 11 is covered by the mask wall 22.
It

FIG. 17 shows a sixth embodiment. The embodiment shown in FIG. 17 has substantially the same structure as the embodiment shown in FIG. 16, but the mask angle β of the air supply valve 11 arranged at the center of the cylinder head inner wall surface 3a is different. That is, as shown in FIG. 17, _a straight line Ma connecting the center of the exhaust valve 40 and the center of the intake valve 11, the center of the exhaust valve 41 and the center of the intake valve 11. The opening of the air supply valve 11 located in the area sandwiched between the straight line M _b and the mask wall 22.
Is covered by.

FIG. 18 shows a seventh embodiment. The embodiment shown in FIG. 18 has substantially the same structure as the embodiment shown in FIG. 16 and the embodiment shown in FIG.
The mask angle β of the air supply valve 11 arranged at the center of a is different. That is, as shown in FIG. 18, the plane of symmetry K−
When considering a pair of straight lines extending from the center of the bulk portion of the air supply valve 11 so as to sandwich the entire bulk portion of the two exhaust valves 42, 43 arranged in the vicinity of K, they are formed between the pair of straight lines. that included angle beta, i.e. pair of straight M _a as a mask angle beta is minimized, air supply valve 11 located in the region between the M _b
Is covered with a mask wall 22.

FIG. 19 shows an eighth embodiment. In the embodiment shown in FIG. 19, air supply valves 9 and 10, exhaust valves 40 and 41,
42 and 43 and the mask walls 16 and 19 are shown in FIGS.
It has the same structure as each embodiment shown in FIG. On the other hand, in this embodiment, similarly to the embodiment shown in FIG. 11 to FIG. 15, the air supply valve 11a is the air supply valve 11 of each embodiment shown in FIG. 16 to FIG.
Has a valve diameter considerably smaller than that of the air supply branch passage 31a,
32a (see FIGS. 11 and 12) has a fairly small cross-sectional area, and no mask wall is provided for the intake valve 11a.

FIG. 20 shows a ninth embodiment. In the embodiment shown in FIG. 20, the exhaust valves 12, 13, 14 and the air supply valve 9,
10 and the mask walls 16 and 19 have the same structure as the embodiment shown in FIGS. That is, the air supply valves 9 and 10 are arranged in the recesses 15 and 18 formed on the cylinder head inner wall surface 3a, respectively, and the air supply in the range of the mask angle α ₁ located on the side of the exhaust valves 12 and 14 is performed. The opening of the valve 9 is the mask wall 16
The opening of the air supply valve 10 within the range of the mask angle α ₂ located on the exhaust valve 13 or 14 side is covered by the mask wall 1
Covered by 9. On the other hand, in this embodiment, the air supply valve 11 as shown in FIG. 1 is not arranged at the center of the cylinder head inner wall surface 3a.

In the embodiment shown in FIG. 20, as in the embodiment shown in FIGS. 1 to 4, when the air supply valves 9 and 10 are opened, new air flows into the main chamber 4 through the air supply valves 9 and 10. The air flows in a loop along the peripheral portion of the main chamber 4 as shown by arrows X _a and X _b in FIGS. 6 and 8, and the fresh air X _a and X _b flowing in the loop causes the inside of the main chamber 4 to flow. Burned gas is exhausted from each exhaust valve 12, 13, 14.

At this time, the fresh air flowing from the air supply valve 9 serves to scavenge the inside of the main chamber 4 located on the air supply valve 9 side with respect to the plane of symmetry KK, while the fresh air flowing from the air supply valve 10 flows. Plays a role of scavenging the inside of the main chamber 4 located on the air supply valve 10 side with respect to the plane of symmetry KK. As shown in FIG. 20, the entire bulge portion of the exhaust valve 12 and half of the bulge portion of the exhaust valve 14 are located on the intake valve 9 side with respect to the plane of symmetry KK. Therefore, if the mask wall is not provided for the air supply valve 9, a part of the fresh air flowing from the air supply valve 9 easily travels along the cylinder head inner wall surface 3a and is easily blown out from the exhaust valves 12, 14. However, as shown in FIG. 20, since the opening of the air supply valve 9 located on the exhaust valve 12, 14 side within the range of the mask angle α ₁ is covered with the mask wall 16, the gas flows in from the air supply valve 9. Fresh air is prevented from passing through the exhaust valves 12 and 14 into the exhaust port. Similarly, the mask wall 19 prevents fresh air flowing from the air supply valve 10 from passing through the exhaust valves 13 and 14 into the exhaust port. It should be noted that a part of the fresh air flowing into the main chamber 4 from the opening portion of the air supply valve 9 formed between the conical inner peripheral wall surface portion 17a of the concave portion 15 on the exhaust valve 13 side and the peripheral portion of the air supply valve 9. Advances in the direction of the exhaust valve 13 along the inner wall surface 3a of the cylinder head, while the air supply valve formed between the conical inner peripheral wall surface portion 20a of the recess 18 on the exhaust valve 12 side and the peripheral portion of the air supply valve 10. A part of the fresh air flowing into the main chamber 4 through the opening portion 10 advances toward the exhaust valve 12 along the cylinder head inner wall surface 3a. However, in this way, along the cylinder head inner wall surface 3a from the conical inner peripheral wall surface portion 17a to the exhaust valve 13
To the exhaust valve 1 from the fresh air toward the inner conical wall surface 20a
The fresh air toward 2 collides and interferes with each other in the vicinity of the center of the cylinder head inner wall surface 3a, and then descends in the main chamber 4. Therefore, the fresh air flowing in from the conical inner peripheral wall surface portion 17a of the concave portion 15 and the fresh air flowing in from the conical inner peripheral wall surface portion 20a of the concave portion 18 are not blown into the exhaust port. Thus, the fresh air that has flowed in from the air supply valves 9 and 10 is almost completely prevented from blowing through the exhaust port along the inner wall surface 3a of the cylinder head.
Almost all the fresh air flowing from 0 is effectively contributed to the generation of the new airflows X _a and X _b flowing in the main chamber 4 in a loop shape. Further, since the mask angle α ₁ of the air supply valve 9 and the mask angle α ₂ of the air supply valve 10 are formed at the necessary minimum angles that can favorably prevent the blow-through of fresh air, the air supply resistance can be suppressed to be small. Thus to powerful new stream X _a flowing primary chamber 4 in a loop, X _b is formed, this powerful new stream X _a,
The inside of the main chamber 4 is scavenged well by _Xb .

FIG. 21 shows a tenth embodiment. In Figure 21
In the embodiment shown, the exhaust valves 40, 41, 42, 43,
Air valves 9,10 and mask walls 16,19 are shown in FIG.
It has the same structure as the embodiment. That is, in the cylinder head
The recesses 15 and 18 formed on the wall surface 3a are respectively supplied with
Air valves 9 and 10 are arranged and located on the side of exhaust valves 40 and 42
Mask angle α₁The opening of the air supply valve 9 within the range of the mask wall 1
6 and is located on the side of the air supply valves 41 and 43
Mask angle α₂The opening of the air supply valve 10 within the range is the mask wall
Covered by 19. On the other hand, in this embodiment,
As shown in FIG. 16, the central portion of the inner wall surface 3a
The air supply valve 11 is not arranged. Also in this example
As in the embodiment shown in FIG. 20, the air supply valves 9 and 10 are opened.
And powerful new airflow X flowing in a loop in the main chamber 4_a, X_b
Is formed, this powerful new air flow X _a, X_bMain room 4
The inside is scavenged well.

In each of the embodiments described above, the mask wall is formed on the cylinder head, but the mask wall can be formed on a member separate from the cylinder head. In this case, the mask wall may be formed on these valve seats by devising the shape of the air supply valve seat or the exhaust valve seat.

[0041]

According to the first aspect of the present invention, it is possible to almost completely prevent fresh air from blowing through the exhaust port along the inner wall surface of the cylinder head, and to suppress the air supply resistance to a small value. Since good loop scavenging can be ensured, the combustion chamber can be scavenged satisfactorily.

According to the second aspect of the present invention, the fresh air supplied from the air supply valve arranged at the peripheral portion of the inner wall surface of the cylinder head is almost completely prevented from being blown into the exhaust port, and the air is supplied. The resistance is suppressed to a low level, so that a good loop scavenging airflow flowing along the peripheral edge of the combustion chamber is secured, and the peripheral edge portion of the combustion chamber is scavenged well. In addition, the central portion of the combustion chamber is scavenged well by the fresh air supplied from the additional air supply valve. Thus, the entire combustion chamber can be scavenged well.

[Brief description of drawings]

FIG. 1 is a bottom view of an inner wall surface of a cylinder head.

FIG. 2 is a plan sectional view of the cylinder head shown in FIG.

FIG. 3 is a side sectional view of the internal combustion engine taken along line III-III in FIG.

FIG. 4 is a side sectional view of the internal combustion engine taken along line IV-IV in FIG.

FIG. 5 is a diagram showing a valve opening timing of an air supply valve and an exhaust valve.

6 is a side sectional view of the internal combustion engine for explaining the scavenging action as viewed along the same section as FIG.

FIG. 7 is a side sectional view of the internal combustion engine for explaining the scavenging action as viewed along the same section as FIG.

FIG. 8 is a schematic perspective view of an internal combustion engine.

FIG. 9 is a bottom view of the inner wall surface of the cylinder head of the second embodiment.

FIG. 10 is a bottom view of an inner wall surface of a cylinder head according to a third embodiment.

FIG. 11 is a bottom view of the inner wall surface of the cylinder head of the fourth embodiment.

12 is a plan sectional view of the cylinder head shown in FIG.

13 is a side sectional view of the internal combustion engine taken along line XIII-XIII in FIG.

FIG. 14 is a side sectional view of the internal combustion engine taken along line XIV-XIV in FIG.

FIG. 15 is a side sectional view of the internal combustion engine for explaining the scavenging action taken along the same section as FIG.

FIG. 16 is a bottom view of the inner wall surface of the cylinder head of the fifth embodiment.

FIG. 17 is a bottom view of the inner wall surface of the cylinder head of the sixth embodiment.

FIG. 18 is a bottom view of an inner wall surface of a cylinder head according to a seventh embodiment.

FIG. 19 is a bottom view of the inner wall surface of the cylinder head of the eighth embodiment.

FIG. 20 is a bottom view of the inner wall surface of the cylinder head of the ninth embodiment.

FIG. 21 is a bottom view of the inner wall surface of the cylinder head according to the tenth embodiment.

[Explanation of symbols]

3a ... Cylinder head inner wall surface 5 ... Sub chamber 6 ... Injection port 9, 10, 11, 11a ... Air supply valve 12, 13, 14 ... Exhaust valve 16, 19, 22 ... Mask wall 40, 41, 42, 43 ... Exhaust valve α ₁ , α ₂ , β ... Mask angle KK ... Symmetric plane

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaru Fukuyama 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd.

Claims (2)

[Claims] 1. A pair of air supply valves are arranged symmetrically with respect to a plane of symmetry including a cylinder axis on one side of the inner wall surface of the cylinder head, and at least 3 on the other side of the inner wall surface of the cylinder head.
In a combustion chamber structure of a two-cycle internal combustion engine in which a plurality of exhaust valves are arranged and the openings of the intake valves located on the exhaust valve side are covered with a mask wall, the exhaust gas is exhausted from among the at least three exhaust valves. For one of the first exhaust valves, a part or the whole of which is arranged on one side of the air supply valve with respect to the plane of symmetry, the one air supply is provided so as to sandwich the whole of the first exhaust valve. The opening of the one air supply valve located in the region sandwiched by the pair of straight lines that minimizes the sandwiching angle formed between the pair of straight lines extending from the center of the bulb portion of the valve Of the second exhaust valve, which is covered by the mask wall and in which at least three of the exhaust valves have a part or the whole of the exhaust valve bulge arranged on the other intake valve side with respect to the plane of symmetry. Of the other of the second exhaust valves so as to sandwich the entire bulkhead of the second exhaust valve. Of the pair of straight lines extending from the center of the bulge portion of the air valve, the other air supply valve located in the region sandwiched by the pair of straight lines such that the sandwiching angle formed between the pair of straight lines is minimized A combustion chamber structure of a two-cycle internal combustion engine in which an opening is covered by the mask wall. 2. A pair of air supply valves are arranged symmetrically with respect to a plane of symmetry including a cylinder axis on one side of the inner wall surface of the cylinder head, and at least 3 on the other side of the inner wall surface of the cylinder head.
In a combustion chamber structure of a two-cycle internal combustion engine in which a plurality of exhaust valves are arranged and the openings of the intake valves located on the exhaust valve side are covered with a mask wall, the pair of intake valves are connected to the inner wall surface of the cylinder head. The exhaust valve is arranged at the peripheral portion on one side, and the at least three exhaust valves are arranged at the peripheral portion on the other side of the inner wall surface of the cylinder head, and a part of the exhaust valve cap portion is included in the exhaust valve at least three exhaust valves. Alternatively, with respect to the first exhaust valves which are arranged on the side of the one intake valve with respect to the plane of symmetry as a whole, from the center of the bulk of the one exhaust valve so as to sandwich the entire bulk of all the first exhaust valves. The mask wall covers the opening of the one air supply valve located in the region sandwiched by the pair of straight lines that minimizes the sandwiching angle formed between the pair of straight lines. Of the above at least three exhaust valves, the exhaust valve cap A second exhaust valve, which is partially or wholly disposed on the other intake valve side with respect to the plane of symmetry, sandwiches the entire bulk of all the second exhaust valves so as to sandwich the bulk of the other intake valve. Of the pair of straight lines extending from the center, the opening of the other air supply valve located in the region sandwiched by the pair of straight lines such that the sandwiching angle formed between the pair of straight lines is minimized is the mask wall. Combustion chamber of a two-cycle internal combustion engine in which an additional air supply valve is arranged in the center of the inner wall surface of the cylinder head to supply fresh air from the additional air supply valve toward the center of the combustion chamber. Construction.