JPH05163905A - Combustion chamber structure of two-cycle internal combustion engine - Google Patents

Abstract

PURPOSE:To make new air flow in a loop shape so as to make scavenging in good condition by providing a mask wall opposing to the umbrella part of each exhaust valve on each intake valve which is nearest to the exhaust valve among a plurality of intake valves in a combustion chamber provided with a plurality of exhaust valve. CONSTITUTION:Exhaust valves 9, 10 are provided on the one side of a cylinder head inner wall surface, intake valves 12, 13 are provided on the other side respectively, and also the injection port 6 of an auxiliary chamber is provided on a symmetric position thereof. for example, the distance between the centers of umbrella parts of the intake valve 12 and the exhaust valve 9 is set smaller as compared with that concerning the exhaust valve 10 and the intake valve 12. A mask wall for covering the intake valve 12 is formed by the cylindrical inner wall part 16 of the intake valve 12, and extended along the range of an angle alpha1 (mask wall formed between straight lines L1a, L1b in contact with an outer peripheral edge of the umbrella part of the exhaust valve 9 opposing to the intake valve 12 from the center part on the umbrella part of the intake valve 12. Since new air flows in from the opening port opposite to the mask wall 16 in a loop shape, already burnt gas is scavenged by new air 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 plurality of exhaust valves are arranged on one side of an inner wall surface of a cylinder head, and at least one air supply valve is arranged on the other side of the inner wall surface of the cylinder head. There is a known combustion chamber structure of a two-cycle internal combustion engine in which the opening of the valve is covered with a mask wall over the entire opening period of the air supply valve (see Japanese Patent Laid-Open No. 2-153222). In the combustion chamber structure of this two-cycle internal combustion engine, since the opening of the intake valve located on the exhaust valve side is covered by the mask wall, fresh air flows into the combustion chamber through the opening of the intake valve on the opposite side of the mask wall. However, this fresh air 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, 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 area 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 with 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 plurality of exhaust valves are arranged on one side of the inner wall surface of the cylinder head, and at least on the other side of the inner wall surface of the cylinder head. One air supply valve is arranged, and the opening of the air supply valve located on the exhaust valve side is covered by the mask wall 2
In the structure of the combustion chamber of a cycle internal combustion engine, the air intake valves having the closest distance between the center of the air intake valve and the exhaust valve and the corresponding exhaust valve are The mask wall covers the opening of the air supply valve located in a region sandwiched by a pair of straight lines extending from the center so as to contact the outer peripheral edge of the corresponding exhaust valve.

Further, in order to solve the above problems, according to the present invention, a plurality of exhaust valves are arranged on one side of the inner wall surface of the cylinder head, and at least one supply valve is provided 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 an air valve is arranged and an opening of an intake valve located on the exhaust valve side is covered with a mask wall, the plurality of exhaust valves described above are connected to one side of an inner wall surface of a cylinder head. And the at least one air supply valve described above is arranged on the other side peripheral part of the inner wall surface of the cylinder head, and the distance between the center of the air supply valve and the center of the exhaust valve. Is located within a region sandwiched by a pair of straight lines extending from the center of the air supply valve's bulge to the outer peripheral edge of the corresponding exhaust valve's bulge for the closest air supply valves and the corresponding exhaust valves. Cover the opening of the air supply valve In the center of the inner wall surface cylinder head is adapted to supply fresh air toward a central portion of the combustion chamber Achieved adding of the air supply valve located additional air supply valve.

[0008]

According to the first aspect of the present invention, the air supply valve is the same as the air supply valve having the closest distance between the center of the air supply valve and the center of the exhaust valve. By covering the opening of the air supply valve located in the area sandwiched by a pair of straight lines extending from the center of the hood with the outer peripheral edge of the bulge of the corresponding exhaust valve with the mask wall, all fresh air is removed. The fresh air that has flowed into the combustion chamber through the opening of the air supply valve on the side opposite to the mask wall descends along the inner wall of the cylinder bore below the air supply valve, and then proceeds along the top surface of the piston to the exhaust valve. Ascend along the inner wall of the lower cylinder bore. Thus, the fresh air flows in a loop in the combustion chamber. At this time, by forming the range of the mask wall in the above range, it is possible to sufficiently prevent the fresh air that has flowed into the combustion chamber from blowing through the exhaust port along the inner wall surface of the cylinder head, and to supply the fresh air to the intake valve. The flow resistance received when passing through the opening, that is, the air supply resistance is suppressed to be small. Thus, the burned gas is scavenged well by the fresh air flowing in a loop in the combustion chamber.

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. Thus, this fresh air flows in a loop along the periphery of the combustion chamber. At this time, the fresh air is sufficiently blocked by the mask wall from blowing into the exhaust port along the inner wall surface of the cylinder head, and the air supply resistance is suppressed small. Thus, the burned gas existing in the peripheral portion of the combustion chamber is scavenged well by the fresh air flowing in a loop along the peripheral edge of the combustion chamber.
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 3 show the 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
3, reference numeral 1 is a cylinder block, 2 is a reciprocating piston in the cylinder block 1, 3 is a cylinder head fixed on the cylinder block 1, 4 is the top surface of the piston 2 and the inner wall surface of the cylinder head. 3a, a main chamber, 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 3, a pair of exhaust valves 9 and 10 are arranged on one side of the cylinder head inner wall surface 3a as shown in FIG. 1, and a pair of exhaust valves 9 and 10 are arranged on the other side of the cylinder head inner wall surface 3a. The air supply valves 12 and 13 are arranged. Exhaust valve 9
And the exhaust valve 10 are arranged symmetrically with respect to a plane of symmetry KK including the cylinder axis, and the intake valves 12 and 13 are also arranged symmetrically with respect to the plane of symmetry KK. In addition, between the pair of air supply valves 12 and 13, and the peripheral portion of the cylinder head inner wall surface 3a farthest from the pair of air supply valves 9 and 10, the injection port 6 of the sub chamber 5 is arranged. It is arranged on the plane of symmetry KK.

As shown in FIGS. 1 and 2, a recess 15 is formed on the inner wall surface 3a of the cylinder head, and the air supply valve 12 is arranged at the innermost portion of the recess 15. As shown in FIG. 1, the distance between the center of the bulge portion of the intake valve 12 and the center of the bulge portion of the exhaust valve 9 is the center of the bulge portion of the air supply valve 12 and the center of the bulge portion of the exhaust valve 10. Closer than the distance between. Thus, the inner peripheral wall surface portion 16 of the recess 15 located on the exhaust valve 9 side closer to the air supply valve 12 is arranged very close to the outer peripheral edge of the air supply valve 12 and along the outer peripheral edge of the air supply valve 12. The inner peripheral wall surface portion 17 of the recess 15 excluding the cylindrical inner peripheral wall surface portion 16 is formed in a conical shape that expands toward the inside of the main chamber 4. Therefore, the opening of the air supply valve 12 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 9 side. A mask wall that covers the opening of the air supply valve 12 is formed. As shown in FIG. 1, a pair of straight lines L _1a extending from the center of the bulge portion of the intake valve 12 so as to contact the outer peripheral edge of the bulge portion of the corresponding exhaust valve 9,
The opening of the air supply valve 12 located in the region sandwiched by L _1b is covered with the mask wall 16. That is,
The mask wall 16 extends in an arc shape along the outer peripheral edge of the cap portion of the air supply valve 12 over an angle α ₁ formed by the pair of straight lines L _1a and L _1b , that is, a range of the mask angle α ₁ . In the embodiment shown in FIGS. 1 to 3, the mask wall 16 extends below the air supply valve 12 in the maximum lift position, so that the opening of the air supply valve 12 formed on the exhaust valve 9 side is the air supply. It will be covered by the mask wall 16 for the entire opening period of the valve 12. However, the height of the mask wall 16 is lowered a little and the air supply valve 1
It is also possible to cover the opening of the air supply valve 12 with the mask wall 16 only when the lift amount of 2 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.
An air supply valve 13 is arranged at the innermost portion of 8. As shown in FIG. 1, the distance between the center of the air intake valve 13 and the center of the exhaust valve 10 is determined by the distance between the center of the air intake valve 13 and the center of the exhaust valve 9. Closer than the distance between. Thus, the inner peripheral wall surface portion 19 of the concave portion 18 located on the exhaust valve 10 side closer to the air supply valve 13 is arranged very close to the outer peripheral edge of the air supply valve 13 and along the outer peripheral edge of the air supply valve 13. The inner peripheral wall surface portion 20 of the recess 18 excluding the cylindrical inner peripheral wall surface portion 19 is formed in a conical shape that expands toward the inside of the main chamber 4. Therefore, the opening of the air supply valve 13 facing the cylindrical inner peripheral wall surface portion 19 is covered by the cylindrical inner peripheral wall surface portion 19, and thus the cylindrical inner peripheral wall surface portion 19 is formed on the exhaust valve 10 side. Air supply valve 13
Forming a mask wall covering the opening. As shown in FIG. 1, the corresponding exhaust valve 1 from the center of the bulk of the air supply valve 13
A pair of straight lines L extending so as to contact the outer peripheral edge of the 0-bulb
_2a, the valve opening of the intake valve 13 positioned sandwiched within the area L _2b is adapted to be covered by the mask walls 19. That is, the mask walls 19 extend in an arc shape along the umbrella outer periphery of the pair of linear L _2a, the angle alpha ₂ L _2b, ie air-supply valve 13 over a range of mask angle alpha _2. As described above, the exhaust valve 9 and the exhaust valve 10 are arranged symmetrically with respect to the plane of symmetry KK, and the air supply valve 12 and the air supply valve 13 are arranged symmetrically with respect to the plane of symmetry KK. because there are formed equal to the mask angle alpha ₂ of the mask angle alpha ₁ and an air supply valve 13 of the air supply valve 12. In the embodiment shown in FIGS. 1 to 3, the mask wall 19 extends below the air supply valve 13 in the maximum lift position like the mask wall 16, and therefore the air supply valve formed on the exhaust valve 10 side. The opening of 13 is covered with the mask wall 19 over the entire opening period of the air supply valve 13. 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 13 is covered by the mask wall 19 only when the lift amount of the air supply valve 13 is small.

On the other hand, no mask wall is provided for each of the exhaust valves 9 and 10. Therefore, when the exhaust valves 9 and 10 are opened, the exhaust valves 9 and 10 are provided with the main chamber 4 over the entire circumference. Open inside. In the embodiment shown in FIGS. 1 to 3, a pair of exhaust valves 9 and 10 are driven by a common camshaft 25 via corresponding valve lifters 24 slidably inserted into the cylinder head 3 to provide a pair of air supplies. The valves 12, 13 are driven by a common camshaft 27 via corresponding bubble lifters 26 slidably inserted in the cylinder head 3. That is, all the exhaust valves 9 and 10 are directly driven by the common camshaft 25 located on the axis of each exhaust valve 9 and 10 without passing through the rocker arm, and all the intake valves 1
2 and 13 are air supply valves 1 without a rocker arm
It is directly driven by a common cam shaft 27 located on the axis of 2, 13.

As shown in FIGS. 1 and 2, the exhaust port 2 is provided for each exhaust valve 9 and 10 in the cylinder head 3.
8 and 29 are formed respectively, and air supply ports 30 and 31 are formed to the air supply valves 12 and 13, respectively. FIG. 4 shows the opening timing of the exhaust valves 9 and 10 and the air supply valves 12 and 13. As shown in FIG. 4, the exhaust valves 9 and 10 are opened prior to the air supply valves 12 and 13 and closed prior to the intake valves 12 and 13.

Next, the operation of the two-stroke diesel engine shown in FIGS. 1 to 3 will be described with reference to FIG. As described above, the exhaust valves 9 and 10 are opened before the air supply valves 12 and 13. When the exhaust valves 9 and 10 are opened, the burned gas in the main chamber 4 is rapidly discharged into the exhaust ports 28 and 29, that is, blowdown occurs, and as a result, the pressure in the main chamber 4 sharply decreases. .. When the pressure in the main chamber 4 decreases, the burnt gas in the sub chamber 5 flows into the main chamber 4 via the injection port 6.

Next, when the air supply valves 12 and 13 are opened, a mechanical supercharger (not shown) driven by the engine causes each air supply port 3 to be opened.
The fresh air sent into the chambers 0 and 31 is supplied into the main chamber 4 through the air supply valves 12 and 13. Intake valve 1 in this case the range of mask angle alpha ₁ is located in the exhaust valve 9 side as described above
The opening 2 is covered by the mask wall 16 and is located on the side of the exhaust valve 10 within the range of the mask angle α ₂
Since the opening 3 is covered by the mask wall 19, the fresh air passes through the opening of the air supply valve 12 on the side opposite to the mask wall 16 and the opening of the air supply valve 13 on the side opposite to the mask wall 19 to the main chamber 4.
Flows in. The fresh air flowing in from these air supply valves 12 and 13 descends along the corresponding cylinder bore inner wall surface 1a below the corresponding air supply valves 12 and 13, as indicated by arrow W in FIG. 5, and then to the top surface of the piston 2. And then rises along the cylinder bore inner wall surface 1a below the exhaust valves 9 and 10. That is, the fresh air flowing in from the air supply valves 12 and 13 flows in a loop in the main chamber 4, and the burned gas in the main chamber 4 is discharged from the exhaust valves 9 and 10 by the fresh air W flowing in the loop. To be done.

By the way, if the air supply valves 12 and 13 are not provided with the mask walls 16 and 19 and the air supply valves 12 and 13 are opened in the main chamber 4 over the entire circumference, The fresh air that has flowed into the main chamber 4 through the openings of the air supply valves 12 and 13 formed in the exhaust valves 9 and 10 is the cylinder head inner wall surface 3a.
And then blows through the openings of the exhaust valves 9 and 10 into the exhaust ports 28 and 29. in this case,
Most of the fresh air that blows through in this way out of the fresh air that flows in from the respective air supply valves 12 and 13.
The distance from the center of the bulge portion to the center of the exhaust valve bulge portion is the shortest and blows through the corresponding openings of the exhaust valves 9 and 10. That is, the fresh air flowing in from the air supply valve 12 is the air supply valve 1
2 is easily blown through the exhaust valve 9 that is closest to the air supply valve 2, while fresh air that flows in from the air supply valve 13 is easily blown through the exhaust valve 10 that is closest to the air supply valve 13. When the fresh air blows through in this way, the fresh air that blows through does not contribute to the scavenging action in the main chamber 4, so that it becomes useless air, and as a result, good scavenging efficiency cannot be obtained. However, in the embodiment shown in FIG. 1 to FIG. 3, as described above, regarding the supply / exhaust valves whose distances between the supply / exhaust valves are the shortest, the corresponding exhaust valves 9, 13 from the center of the bulk part of the intake valves 12, 13
The openings of the air supply valves 12 and 13 located in the region sandwiched by the pair of straight lines (L _1a, L _1b ), (L _2a , L _2b ) extending so as to contact the outer peripheral edge of the bulkhead 10 are respectively masks. Wall 16,1
Since it is covered with 9, fresh air is almost completely prevented from blowing through the exhaust ports 28, 29 along the cylinder head inner wall surface 3a. Therefore, the intake valves 12, 13
Almost all the fresh air flowing in from can be effectively contributed to the generation of the loop scavenging airflow W.

On the other hand, if the mask angles α ₁ and α ₂ of each air supply valve are made too large, blow-through of fresh air can be prevented, but the opening area of the air supply valves 12 and 13 is reduced, so that fresh air is supplied. The flow resistance received when passing through the openings of the air valves 12 and 13, that is, the air supply resistance increases. When the air supply resistance increases in this way, the discharge work performed by the mechanical supercharger for sending fresh air into the main chamber 4 increases, and as a result, the thermal efficiency of the engine decreases. However, in the embodiment shown in FIGS. 1 to 3, since the mask angles α ₁ and α ₂ are formed to be the minimum necessary angles capable of satisfactorily preventing the fresh air from passing through, the air supply resistance can be suppressed to a small level, and therefore the new Qi each air supply valve 12,
It is allowed to smoothly flow into the main chamber 4 through the opening of 13. In this way, the blow-through of fresh air is satisfactorily prevented and the air supply resistance is suppressed to a small value, so that a strong new air flow W flowing in a loop in the main chamber 4 is formed. The inside of 4 is scavenged well.

Next, the exhaust valves 9 and 10 are closed, and the air supply valve 1
When valves 2 and 13 are closed, the gas in the main chamber 4 is sent into the sub chamber 5 through the injection port 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 air supply valves 12 and 13 are opened, the burnt gas in the main chamber 4 flows back into the air supply ports 30 and 31. However, when such 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 ports 28, 29. Therefore, the output loss of the engine will increase accordingly. Therefore, in order to prevent such a backflow of burnt gas, the intake valves 12, 13
When the valve is opened, the pressure in the main chamber 4 must be lowered, and therefore, when the exhaust valves 9 and 10 are opened, burned gas is discharged into the exhaust ports 28 and 29 as quickly as possible. Will be required.

However, the period from the opening of the exhaust valves 9 and 10 to the opening of the air supply valves 12 and 13 is extremely short,
In order to promptly discharge the burnt gas during this short period, the exhaust valves 9 and 10 must be opened at high speed. In this case, the exhaust valves 9, 10 are connected via the rocker arm.
When is driven, the valve opening speed at the time of opening the exhaust valves 9 and 10 becomes slow due to elastic deformation of the rocker arm and the like. Therefore, in the embodiment according to the present invention, in order to increase the valve opening speed when the exhaust valves 9 and 10 are opened, the exhaust valves 9 and 10 are directly driven by the cam shaft 25 without the rocker arm.

FIG. 6 shows a second embodiment. The same reference numerals are used for components as in the embodiment shown in FIGS. 1 to 3. In the embodiment shown in FIG. 6, three exhaust valves 40, 4 are provided in the peripheral portion on one side of the cylinder head inner wall surface 3a.
1, 42 are arranged, and a pair of air supply valves 12, 13 are arranged on the other side of the cylinder head inner wall surface 3a. 1 to 3
Similar to the embodiment shown in FIG. 5, each air supply valve 12, 13 has a corresponding recess 15, 18 formed on the inner wall surface 3a of the cylinder head.
Located inside each. As shown in FIG. 6, the air supply valve 12
Of all the exhaust valves 40, 41, 42, the bulge portion of the exhaust valve 40 is arranged closest to the center of the bulge portion. A pair of straight lines L _1a extending from the center of the cap portion of the air supply valve 12 so as to contact the outer peripheral edge of the cap portion of the corresponding exhaust valve 40,
The opening of the air supply valve 12 located in the region sandwiched by L _1b is covered with the mask wall 16. On the other hand, of the exhaust valves 40, 41, 42, the cap portion of the exhaust valve 41 is disposed closest to the center of the cap portion of the air supply valve 13. A pair of straight lines L _2a , L extending from the center of the cap portion of the air supply valve 13 to contact the outer peripheral edge of the cap portion of the corresponding exhaust valve 41.
The opening of the air supply valve 13 located in the area sandwiched by _2b is covered by the mask wall 19.

FIG. 7 shows a third embodiment. In the embodiment shown in FIG. 7, the cylinder head inner wall surface 3a is provided with 4
Individual exhaust valves 44, 45, 46, 47 are arranged, and a pair of air supply valves 12, 13 are arranged on the other side of the cylinder head inner wall surface 3a. As shown in FIG. 7, among the exhaust valves 44, 45, 46, 47, the exhaust valve 44 is located closest to the center of the intake valve 12. A pair of straight lines L _1a, L extending from the center of the cap portion of the air supply valve 12 to contact the outer peripheral edge of the corresponding cap portion of the exhaust valve 44.
The opening of the air supply valve 12 located in the region sandwiched by _1b is covered with the mask wall 16. On the other hand, of the all exhaust valves 44, 45, 46, 47, the bulk part of the exhaust valve 45 is arranged closest to the center of the bulk part of the air supply valve 13.
From the center of the cap portion of the air supply valve 13, the corresponding exhaust valve 45
The mask wall 19 covers the opening of the air supply valve 13 located in the region sandwiched by the pair of straight lines L _2a and L _2b extending so as to contact the outer peripheral edge of the bulge portion.

FIG. 8 shows a fourth embodiment. In the embodiment shown in FIG. 8, four exhaust valves 44, 45, 46, 47 are arranged on one side peripheral portion of the cylinder head inner wall surface 3a, and three air supply valves are provided on the other side peripheral portion of the cylinder head inner wall surface 3a. Valves 56,5
7,58 are arranged. The exhaust valve 44 and the exhaust valve 45 are arranged symmetrically with respect to the plane of symmetry KK including the cylinder axis, the exhaust valve 46 and the exhaust valve 47 are also arranged symmetrically with respect to the plane of symmetry KK, and the supply valve 56 and the supply valve 56 are provided. The air valve 57 is also arranged symmetrically with respect to the plane of symmetry KK. Further, the air supply valve 58 is arranged on the plane of symmetry KK. Also in the embodiment shown in FIG. 8, each air supply valve 5 is similar to the embodiment shown in FIGS.
6, 57 and 58 are arranged in corresponding recesses 59, 62 and 65 formed on the cylinder head inner wall surface 3a. Cylindrical inner peripheral wall surface portion 6 of each recess 59, 62, 65
0, 63, 66 are each air supply valve 56 formed on the exhaust valve side,
Mask walls are formed to cover the openings 57 and 58, respectively.
Further, the inner peripheral wall surface portions 61, 64, 67 of the respective concave portions 59, 62, 65 excluding the cylindrical inner peripheral wall surface portions 60, 63, 66 have a conical shape that expands toward the main chamber 4 or the combustion chamber, respectively. Has been formed.

As shown in FIG. 8, among the exhaust valves 44, 45, 46, 47, the exhaust valve 44 is located closest to the center of the intake valve 56. A pair of straight lines L _1a , L extending from the center of the cap portion of the air supply valve 56 to contact the outer peripheral edge of the corresponding cap portion of the exhaust valve 44.
The opening of the air supply valve 56 located in the region sandwiched by _1b is covered with the mask wall 60. On the other hand, with respect to the center of the air intake valve 57, the air exhaust valve 45 has the air outlet closest to the air outlet of all the exhaust valves 44, 45, 46, 47.
From the center of the bulk of the air supply valve 57 to the corresponding exhaust valve 45
The mask wall 63 covers the opening of the air supply valve 57 located in the region sandwiched by the pair of straight lines L _2a and L _2b extending so as to contact the outer peripheral edge of the bulge portion. On the other hand, with respect to the mask wall 66 of the air supply valve 58, the center of the air supply valve 58 is located so as to sandwich the entire air exhaust valve 46, 47 located near the plane of symmetry KK. included angle alpha ₃ is formed between this pair of straight line when considering a pair of straight line extending from, i.e. a pair of straight lines L _3a as masks angle alpha ₃ is minimized, sandwiched by the area L _3b The opening of the located air supply valve 58 is covered by the mask wall 66.

It should be noted that in the embodiment shown in FIG. 8, the mask wall 66 is not provided for the air supply valve 58 which is far away from all the exhaust valves 44, 45, 46, 47, but the air supply valve is not provided. When the valve 58 is opened, the opening of the air supply valve 58 may be opened in the main chamber 4 or the combustion chamber over the entire circumference of the air supply valve 58. By not providing the mask wall 66 for the air supply valve 58 in this manner, the air supply resistance received by the fresh air flowing from the opening of the air supply valve 58 is reduced. On the other hand, if the mask wall 66 is not provided for the air supply valve 58 in this way, the fresh air that has flowed in through the opening of the air supply valve 58 advances along the cylinder head inner wall surface 3a and blows into the exhaust port. The amount of fresh air increases. In this case, since the fresh air that blows through does not contribute to the scavenging action of the burned gas, it becomes useless fresh air, but the air supply valve 58 has all the exhaust valves 44, 45, 46, 47.
Since it is far away from, the amount of fresh air blown through does not increase so much.

A fifth embodiment is shown in FIGS. 9 to 15. In this embodiment, as shown in FIGS. 9 and 10, three exhaust valves 9 are provided in the peripheral portion on one side of the cylinder head inner wall surface 3a.
0, 91, 92 are arranged, and the cylinder head inner wall surface 3a
Two air supply valves 93 and 94 are arranged on the other side peripheral portion. Further, a third part is provided at the center of the cylinder head inner wall surface 3a.
, I.e. an additional air supply valve 95 is arranged. As shown in FIG. 9, the exhaust valve 90 and the exhaust valve 91 are arranged symmetrically with respect to a plane of symmetry KK including the cylinder axis, and the intake valve 93 is provided.
And the air supply valve 94 are also arranged symmetrically with respect to the plane of symmetry KK. Further, 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 the three supply valves 93, 94, 95, and the exhaust valve 92, the supply valve 95 and the injection port 6 are symmetrical. It is arranged on the plane KK. Therefore, in the embodiment shown in FIGS. 9 to 12, three exhaust valves 90, 91, 92 and two air supply valves 9 are provided around the inner wall surface 3a of the cylinder head.
3, 94 and the injection port 6 are arranged at substantially equal angular intervals, and an additional air supply valve 9 is provided at approximately the center of the cylinder head inner wall surface 3a.
5 is arranged.

As shown in FIGS. 9 and 11, a recess 97 is formed on the inner wall surface 3a of the cylinder head, and the air supply valve 93 is disposed at the innermost part of the recess 97. As shown in FIG. 9, of all the exhaust valves 90, 91, 92, the cap portion of the exhaust valve 90 is disposed closest to the center of the cap portion of the air supply valve 93. The recess 9 located on the exhaust valve 90 side
The inner peripheral wall surface portion 98 of 7 has a cylindrical shape that is arranged very close to the outer peripheral edge of the air supply valve 93 and extends along the outer peripheral edge of the air supply valve 93. The inner peripheral wall surface portion 99 of 97 is formed in a conical shape that expands toward the inside of the main chamber 4. Therefore, the cylindrical inner peripheral wall surface portion 9
The opening of the air supply valve 93 facing 8 is a cylindrical inner peripheral wall surface portion 9
Therefore, the cylindrical inner peripheral wall surface portion 98 forms a mask wall that covers the opening of the air supply valve 93 formed on the exhaust valve 90 side. As shown in FIG. 9, a corresponding exhaust valve 90 is provided from the center of the cap portion of the air supply valve 93.
A pair of straight lines L extending so as to contact the outer peripheral edge of the
_1a, the valve opening of the intake valve 93 located at the sandwiched within the area L _1b is covered by the mask walls 98. That is, the mask walls 98 extend a pair of straight lines L _1a, the angle alpha ₁ is L _1b, i.e. the shape of a circular arc along the umbrella outer periphery of the air supply valve 93 over a range of mask angle alpha _1. In the embodiment shown in FIGS. 9 to 12, the mask wall 98 is located at the maximum lift position of the air supply valve 93.
Therefore, the opening of the air supply valve 93 formed on the exhaust valve 90 side is covered by the mask wall 98 over the entire opening period of the air supply valve 93. However, the height of the mask wall 98 may be slightly lowered so that the opening of the air supply valve 93 is covered with the mask wall 98 only when the lift amount of the air supply valve 93 is small.

On the other hand, as shown in FIG. 9, a recess 100 having a shape symmetrical to the recess 97 with respect to the plane of symmetry KK is formed on the inner wall surface 3a of the cylinder head. An air valve 94 is arranged. As shown in FIG. 9, among the exhaust valves 90, 91, 92, the cap portion of the exhaust valve 91 is disposed closest to the center of the cap portion of the air supply valve 94. The concave portion 1 located on the exhaust valve 91 side
The inner peripheral wall surface portion 101 of 00 has a cylindrical shape which is arranged very close to the outer peripheral edge of the air supply valve 94 and extends along the outer peripheral edge of the air supply valve 94. An inner peripheral wall surface portion 102 of 100 is formed in a conical shape that expands toward the inside of the main chamber 4. Therefore, the opening of the air supply valve 94 facing the cylindrical inner peripheral wall surface portion 101 is covered by the cylindrical inner peripheral wall surface portion 101, and thus the cylindrical inner peripheral wall surface portion 101 is formed on the exhaust valve 91 side. A mask wall that covers the opening of the air supply valve 94 is formed.
As shown in FIG. 9, it is located in a region sandwiched by a pair of straight lines L _{2a and} L _2b extending from the center of the air supply valve 94 to the outer peripheral edge of the corresponding exhaust valve 91. The opening of the air supply valve 94 is covered by the mask wall 101. That is, the air supply valve 94 mask wall 101 a pair of straight lines L _2a, the angle alpha ₂ L _2b, ie over a range of mask angle alpha ₂
It extends in an arc shape along the outer peripheral edge of the bulge portion. In addition, as described above, the exhaust valve 90 and the exhaust valve 91 have the symmetrical plane KK.
They are symmetrically arranged with respect, since the intake valve 93 and the air supply valve 94 are symmetrically arranged with respect to the symmetry plane K-K, the mask angle of mask angle alpha ₁ and an air supply valve 94 of the air supply valve 93 It is formed equal to α ₂ . In the embodiment shown in FIGS. 9 to 12, the mask wall 101 extends below the air supply valve 94 in the maximum lift position like the mask wall 98, and thus the air supply valve formed on the exhaust valve 91 side. The opening of 94 is covered with the mask wall 101 over the entire opening period of the air supply valve 94. However, this mask wall 1
Also for 01, the height of the mask wall 101 may be slightly lowered so that the opening of the air supply valve 94 is covered with the mask wall 101 only when the lift amount of the air supply valve 94 is small.

On the other hand, as shown in FIGS. 9 and 12, a recess 103 is formed on the inner wall surface 3a of the cylinder head, and the air supply valve 95 is arranged at the innermost portion of the recess 103. The inner peripheral wall surface portion 104 of the recess 103 located on the exhaust valve 90, 91, 92 side is arranged in the vicinity of the outer peripheral edge of the air supply valve 95 and has a cylindrical shape extending along the outer peripheral edge of the air supply valve 95. The inner peripheral wall surface portion 105 of the recess 103 excluding the cylindrical inner peripheral wall surface portion 104 is formed in a conical shape that expands toward the inside of the main chamber 4. Therefore, the opening of the air supply valve 95 facing the cylindrical inner peripheral wall surface portion 104 is covered by the cylindrical inner peripheral wall surface portion 104. Therefore, the cylindrical inner peripheral wall surface portion 104 is on the exhaust valve 90, 91, 92 side. A mask wall is formed so as to cover the opening of the air supply valve 95 formed in the above. In FIG. 9, _a straight line Ma connecting the center of the bulge portion of the exhaust valve 90 and the bulge portion of the intake valve 95, which is arranged below the plane of symmetry KK, and above the plane of symmetry KK. The mask wall 104 covers the opening of the air supply valve 95 located in a region sandwiched by a straight line M _b connecting the center of the air valve of the exhaust valve 91 and the center of the air valve of the air supply valve 95. .. That is, the mask wall 104 extends in an arc shape along the umbrella outer periphery of the pair of straight M _a, M _b is the angle beta, ie air supply valve 95 over a range of mask angle beta. 9 to 1
In the embodiment shown in FIG. 2, the mask wall 104 is the mask wall 9
As with Nos. 8 and 101, it extends below the intake valve 95 at the maximum lift position, and therefore the exhaust valves 90, 91, 9
The opening of the air supply valve 95 formed on the second side is covered with the mask wall 104 over the entire opening period of the air supply valve 95. However, also with respect to the mask wall 104, the height of the mask wall 104 may be slightly lowered so that the opening of the air supply valve 95 is covered with the mask wall 104 only when the lift amount of the air supply valve 95 is small.

On the other hand, no mask wall is provided for each of the exhaust valves 90, 91, 92, and therefore the exhaust valve 9
When the valves 0, 91, 92 are opened, the exhaust valves 90, 91, 92 are opened in the main chamber 4 over the entire circumference. In the embodiment shown in FIGS. 9 to 12, all the exhaust valves 90, 91, 92 corresponding to the valve lifter 2 slidably inserted in the cylinder head 3.
4 is driven by a common camshaft 25, and all air supply valves 93, 94, 95 are driven by a common camshaft 27 via corresponding valve lifters 26 slidably inserted in the cylinder head 3. It That is, all the exhaust valves 90, 91, 92 are directly driven by the common camshaft 25 located on the axis of each exhaust valve 90, 91, 92 without the rocker arm, and all the intake valves 93, 9 are provided.
4 and 95 are each air supply valve 9 without a rocker arm.
It is directly driven by a common camshaft 27 located on the axis of 3,94,95.

In the cylinder head 3, exhaust valves 90, 9 are provided.
A common exhaust port 107 is formed for all the exhaust valves 90, 91, 92 extending to 1, 92, and a pair of air supply valves 93, 94 extending on both sides of the sub chamber 5 in the cylinder head 3 are provided. Air ports 108 and 109 are formed. In addition, each air supply valve port 10 is provided in the cylinder head 3.
A pair of air supply branch passages 110 and 111, which branch from 8 and 109 respectively, extend to the air supply valve 95 and merge with each other in the vicinity of the air supply valve 95, are formed. Therefore, the air supply valves 93, 9
4, fresh air is supplied via the corresponding air supply ports 108 and 109, and from the air supply valve 95, each air supply port 10 is supplied.
The fresh air that has been branched is supplied from each of the air supply branch passages 110 and 111 from 8,109.

Next, the operation of the two-stroke diesel engine shown in FIGS. 9 to 12 will be described with reference to FIGS. 13 to 15. The opening timings of the exhaust valves 90, 91, 92 and the air supply valves 93, 94, 95 are the same as those in the embodiment shown in FIGS. 1 to 3, and as shown in FIG. 90, 91, and 92 are opened before the air supply valves 93, 94, and 95, and closed first.

When the exhaust valves 90, 91, 92 are opened, the burnt gas in the main chamber 4 is rapidly discharged into the exhaust port 107, that is, blowdown occurs, and as a result, the pressure in the main chamber 4 is sharply increased. Fall to. When the pressure in the main chamber 4 drops, the sub chamber 5
The burnt gas inside flows out into the main chamber 4 through the injection port 6. Next, when the air supply valves 93, 94, 95 are opened, the engine-driven mechanical supercharger (not shown) causes the air supply ports 108, 1 to open.
The fresh air sent to the inside of 09 is each supply valve 93,94,95.
Is supplied into the main chamber 4 via. At this time, as described above, the opening of the air supply valve 93 within the range of the mask angle α ₁ located on the exhaust valve 90 side is covered by the mask wall 98, and the range of the mask angle α ₂ located on the exhaust valve 91 side. Air supply valve 9 inside
4 is covered by the mask wall 101, and the opening of the air supply valve 95 located on the exhaust valve 90, 91, 92 side within the range of the mask angle β is covered by the mask wall 104. Into the main chamber 4 through the opening of the air supply valve 93 opposite to the mask wall 98, the opening of the air supply valve 94 opposite to the mask wall 101, and the opening of the air supply valve 95 opposite to the mask wall 104. Inflow. In this case, since the air supply valves 93, 94 are arranged in the peripheral portion of the cylinder head inner wall surface 3a, the fresh air flowing in from these air supply valves 93, 94 is respectively indicated by the arrow X in FIGS. 13 and 15. It descends along the cylinder bore inner wall surface 1a below the corresponding air supply valves 93, 94, then advances along the top surface of the piston 2, and then rises along the cylinder bore inner wall surface 1a below the exhaust valves 90, 91. That is, the fresh air that has flowed in from the air supply valves 93, 94 flows in a loop along the peripheral edge of the main chamber 4, and the burned gas in the main chamber 4 is exhausted by the fresh air X that flows in the loop. It is discharged from the valves 90, 91 and 92. Therefore, the peripheral portion of the main chamber 4 is scavenged by the fresh air X flowing from the air supply valves 93, 94.

It should be noted that the new air flowing in from each air supply valve 93, 94
Qi is the exhaust gas closest to each air supply valve 93, 94.
Blows into the exhaust port 107 through the air valves 90 and 91
Cheap. However, in the embodiment shown in FIGS.
As described above, the air supply / exhaust with the closest distance between the air supply / exhaust valves
About the valve Corresponding from the center of the air supply valve 93, 94
Extends so as to contact the outer peripheral edges of the exhaust valves 90, 91
A pair of straight lines (L_1a,L _1b), (L_2a,L_2b)
The openings of the air supply valves 93 and 94 located in the area are masks, respectively.
Each air supply valve 9 is covered by the walls 98 and 101.
The fresh air flowing in through the openings of 3,94 is the inner wall of the cylinder head.
It may blow through the exhaust port 107 along the surface 3a.
Almost completely blocked. The conical inner peripheral wall of the recess 97
Conical shape located on the exhaust valve 91, 92 side within the surface portion 99
Inner peripheral wall surface portion 99a (see FIG. 9) and a peripheral portion of the air supply valve 93
Fresh air flowing into the main chamber 4 through the opening formed between
Of the exhaust valve 9 along the inner wall surface 3a of the cylinder head.
Attempts to proceed in the direction of 1,92. However, this
The fresh air trying to progress toward the exhaust valves 91 and 92 of
Conical inner peripheral wall surface 1 of the concave portion 103 located on the exhaust valve 90 side
Opening formed between 05a and the peripheral portion of the air supply valve 95
15 and colliding with the flow of fresh air flowing into the main chamber 4 from FIG.
In the main chamber 4 as indicated by the arrow Xa in FIG.
become. Therefore, from the conical inner peripheral wall surface 99a of the recess 97,
Most of the fresh air that has flowed into the main chamber 4 also enters the exhaust port 107.
It doesn't blow through. Similarly, the conical inner peripheral wall surface of the recess 100
Conical shape located on the exhaust valve 90, 92 side in the portion 102
Between the inner peripheral wall surface portion 102a and the peripheral portion of the air supply valve 94,
Part of the fresh air flowing into the main chamber 4 through the created opening
Are exhaust valves 90, 9 along the inner wall surface 3a of the cylinder head.
Trying to proceed in the direction of 2. However, this exhaust
The fresh air trying to progress toward the valves 90 and 92 is the exhaust valve.
The conical inner peripheral wall surface portion 10 of the concave portion 103 located on the 91 side
5b and an opening formed between the peripheral portion of the air supply valve 95
Figure 15 shows a collision with the flow of fresh air flowing into the main chamber 4 from
Leave arrow X_bAs shown in, descending in the main chamber 4
Become. Therefore, the conical inner peripheral wall surface portion 102 of the recess 100 is
The fresh air flowing into the main chamber 4 from a also enters the exhaust port 107.
It hardly blows through. Thus, the respective air supply valves 93, 94
The fresh air flowing in from the exhaust port flows along the inner wall surface of the cylinder head.
Almost completely prevented from blowing through into the hood 107,
Therefore, almost all the gas that has flowed in through the openings of the air supply valves 93 and 94
Of fresh air flowing in a loop along the peripheral edge of the main chamber 4.
This effectively contributes to the generation of the flow X. Also, the air supply valve 9
Mask angle α of 3₁And mask angle α of the air supply valve 94 ₂Is
Prevents fresh air from passing through along the Linda head inner wall surface 3a
Since it is formed at the minimum necessary angle,
Is kept small, so that fresh air is supplied to each air supply valve 93, 94.
It smoothly flows into the main chamber 4 through the opening. Thus, the Lord
A powerful new air flow X flowing in a loop along the peripheral edge of the chamber 4.
Is formed, and the powerful new air flow X causes the periphery of the main chamber 4 to
The part is scavenged well.

On the other hand, since the air supply valve 95 is arranged at the center of the cylinder head inner wall surface 3a, the fresh air flowing from the air supply valve 95 is supplied to the main chamber as shown by the arrow Y in FIGS. 4 down the center, then piston 2
Exhaust valves 90, 91, 9 after changing direction on the top surface of
2 Ascend along the inner wall surface 1a of the lower cylinder bore. The burnt gas existing in the central portion of the main chamber 4 is discharged into the exhaust port 107 by this fresh air Y, and therefore the central portion in the main chamber 4 is scavenged by the fresh air Y flowing from the air supply valve 95. become. In this case, the straight line M _a connecting the bulk portion center of the bevel portion centered exhaust valve 90 of the intake valve 95 as described above,
Air supply valve 95 located in a region sandwiched by a straight line M _b connecting the center of the air supply valve 95 and the center of the exhaust valve 91.
Since the opening is covered with the mask wall 104, the fresh air flowing in from the opening of the air supply valve 95 is almost completely prevented from blowing through the exhaust port 107 along the cylinder head inner wall surface 3a. Therefore, almost all the fresh air flowing in from the opening of the air supply valve 95 can be effectively contributed to the generation of the scavenging airflow Y that descends in the central portion of the main chamber 4. Further, since the mask angle β is formed at the minimum angle required to satisfactorily prevent the fresh air from passing through along the inner wall surface 3a of the cylinder head, the air supply resistance is suppressed to be small, and thus the fresh air is supplied. It smoothly flows into the main chamber 4 through the opening of the valve 95. Thus, a strong new airflow Y that descends the central portion of the main chamber 4 is formed, and the central portion of the main chamber 4 is scavenged well by the strong new airflow Y.

As described above, the fresh air X flowing in from the air supply valves 93 and 94 scavenges the peripheral portion of the main chamber 4 favorably, and the fresh air Y flowing in from the air supply valve 95 favors the central portion of the main chamber 4. Since the air is scavenged, the entire main chamber 4 is satisfactorily scavenged by the fresh air flowing in from the air supply valves 93, 94, and 95. Next, when the exhaust valves 90, 91, 92 are closed and the air supply valves 93, 94, 95 are closed, the gas in the main chamber 4 is sent into the sub chamber 5 via 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.

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 6 is considerably higher than that of the other portions, and therefore the temperature around the nozzle 6 is small. 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. 9, the injection port 6 is surrounded by the three air supply valves 93, 94, 95, so that the cylinder head inner wall surface 3a around the injection port 6 is The cylinder head inner wall surface 3a around the injection port 6 is cooled by the fresh air flowing from the air supply valves 93, 94, 95.
It is possible to prevent cracks from occurring in the.

FIG. 16 shows a sixth embodiment. The embodiment shown in FIG. 16 has substantially the same structure as the embodiment shown in FIGS. 9 to 12, but the mask angle β of the air supply valve 95 arranged at the center of the cylinder head inner wall surface 3a is different. That is, as shown in FIG. 16, _a pair of straight lines M _a and M _b extending from the center of the air intake valve 95 so as to contact the outer peripheral edge of the air exhaust valve 92 disposed on the plane of symmetry KK. The opening of the air supply valve 95 located in the area sandwiched by
Covered by 04. As described above, in the embodiment shown in FIG. 16, the mask angle β is smaller than that in the embodiment shown in FIGS. 9 to 12, so that the opening area of the air supply valve 95 is increased when the air supply valve 95 is opened. As a result, the air supply resistance is further reduced.

FIG. 17 shows a seventh embodiment. The embodiment shown in FIG. 17 has substantially the same structure as the embodiment shown in FIGS. 9 to 12, but the mask angle β of the air supply valve 95 arranged at the center of the cylinder head inner wall surface 3a is different. That is, as shown in FIG. 17, when considering a pair of straight lines extending from the center of the bulk portion of the air supply valve 95 so as to sandwich the entire bulk portion of all the exhaust valves 90, 91, 92, between the pair of straight lines. included angle β formed, i.e. a pair of straight lines M _a as a mask angle β is minimized, the valve opening of the intake valve 95 located in the region between the M _b is covered by the mask wall 104. As described above, in the embodiment shown in FIG. 17, FIG. 9 to FIG.
The mask angle β is larger than that in the embodiment shown in
Therefore, fresh air flowing in from the air supply valve 95 can be better prevented from blowing through the exhaust port 107 along the cylinder head inner wall surface 3a.

The eighth embodiment is shown in FIGS. 18 to 22.
In this embodiment, the exhaust valves 90, 91, 92 and the exhaust port 107 have the same structure as the embodiment shown in FIGS. 9 to 12, and the air supply valves 93, 94 and the air supply ports 108, 109.
The mask walls 98 and 101 also have the same structure as the embodiment shown in FIGS. 9 to 12, and the sub chamber 5 and the injection port 6 also have the same structure as the embodiment shown in FIGS. That is, the recesses 97, 100 formed on the inner wall surface 3a of the cylinder head.
Air supply valves 93 and 94 are respectively arranged therein, and the opening of the air supply valve 93 formed on the exhaust valve 90 side and the opening of the air supply valve 94 formed on the exhaust valve 91 side respectively correspond to the mask wall 9.
It is covered by 8, 101.

On the other hand, in this embodiment, the air supply valve 95a is shown in FIG.
9 to 12 has a valve diameter considerably smaller than that of the air supply valve 95 of the embodiment shown in FIG. 12, and the air supply branch passages 110a and 111a are air supply branch passages 110 and 11 of the embodiment shown in FIGS.
It has a considerably smaller cross-sectional area than unity. Further, in this embodiment, no mask wall is provided for the air supply valve 95a.

Therefore, in this embodiment, a small amount of fresh air is supplied into the main chamber 4 via the air supply valve 95a as compared with the embodiment shown in FIGS. 9 to 12, and this fresh air is then indicated by the arrow Ya in FIG. Flows toward the central portion of the main chamber 4 as shown by. 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 95a, and the other air supply valves 93,
Since the peripheral portion of the main chamber 4 is scavenged by the fresh air flowing from 94, the entire interior of the main chamber 4 is scavenged. In this embodiment, since the mask wall is not provided for the air supply valve 95a, a part of the fresh air flowing from the air supply valve 95a blows into the exhaust port 107. In this case, since the blown-through air does not contribute to the scavenging action of the burnt gas, the amount of air flowing from the air supply valve 95a, which is wasted air, is small, so the amount of wasted air does not increase so much.

FIG. 23 shows a ninth embodiment. Shown in Figure 23
In the illustrated embodiment, around one side of the cylinder head inner wall surface 3a
4 exhaust valves 113, 114, 115, 116 are installed in the
Placed on the other side of the cylinder head inner wall surface 3a.
The air supply valves 93 and 94 are arranged. Further cylinder head
A third or additional air supply valve 95 is provided at the center of the inner wall surface 3a.
Are placed. In addition, the three air supply valves 93, 94, 95
Therefore, in the peripheral portion of the cylinder head inner wall surface 3a surrounded by
The nozzle 6 of the chamber 5 is arranged. As shown in FIG.
All exhaust valves 113, 11 are provided for the center of the air valve 93.
Of 4,115,116, the bulk of the exhaust valve 113 is the most
It is located nearby. From the center of the air supply valve 93
So that it touches the outer peripheral edge of the corresponding exhaust valve 113
A pair of straight lines L extending to_1a, L_1bLocated in the area sandwiched between
The opening of the air supply valve 93 is covered by the mask wall 98.
There is. In addition, the exhaust air is exhausted to the center of the air supply valve 94.
Exhaust valve 114 out of valves 113, 114, 115, 116
The bulge is located closest to it. Is the air supply valve 94
From the center of the bulge to the outer circumference of the corresponding bulge of the exhaust valve 114
A pair of straight lines L extending so as to contact the edges_2a, L_2bSandwiched between
The opening of the air supply valve 94 located in the closed area is the mask wall 101.
Is covered by. The center of the air supply valve 95
To the cap of each exhaust valve 113, 114, 115, 116
Considering the four straight lines extending through the center, the exhaust valve 11
A straight line M extending through the center of the 3 _aAnd exhaust valve 114
A straight line M extending through the center of the nose_bAnd are located on both outer sides
To do. These two straight lines M_a, M_bPlaced in the area sandwiched between
The opening of the supply valve 95 to be placed is covered by the mask wall 104.
Has been.

FIG. 24 shows a tenth embodiment. The embodiment shown in FIG. 24 has substantially the same structure as the embodiment shown in FIG. 23, but the mask angle β of the air supply valve 95 arranged at the center of the cylinder head inner wall surface 3a is different. That is, FIG.
As shown in FIG. 4, a pair of straight lines extending from the center of the bulge portion of the air supply valve 95 is considered so as to sandwich the entire bulge portion of the two exhaust valves 115 and 116 arranged near the plane of symmetry KK. included angle β formed between the pair of straight lines, i.e., a pair of straight lines M _a as a mask angle β is minimized, the valve opening of the intake valve 95 located in the region between the M _b mask when It is covered by a wall 104.

FIG. 25 shows the eleventh embodiment. The embodiment shown in FIG. 25 also has substantially the same structure as the embodiment shown in FIG. 23 and the embodiment shown in FIG. 24, but the mask angle β of the air supply valve 95 arranged at the center of the cylinder head inner wall surface 3a is Different. That is, as shown in FIG.
5 exhaust valves 113, 114, 115
When considering a pair of straight lines extending so as to sandwich the entire bulky portion of 116, an included angle β formed between the pair of straight lines,
That is, a pair of straight lines M _a and M that minimizes the mask angle β.
The opening of the air supply valve 95 located in the area sandwiched by _b is covered with the mask wall 104.

FIG. 26 shows a twelfth embodiment. In the embodiment shown in FIG. 26, the exhaust valves 113, 114, 115, 1
16, the air supply valves 93, 94 and the mask walls 98, 101 have the same structure as that of the embodiment shown in FIG. On the other hand, in this embodiment, the air supply valve 95a is the air supply valve 9 of the embodiment shown in FIG.
It has a valve diameter considerably smaller than that of No. 5. Further, the supply branch passages 110a and 111a have a considerably small cross-sectional area as in the case of the embodiment shown in FIGS. Further, in this embodiment, no mask wall is provided for the air supply valve 95a.

FIG. 27 shows a thirteenth embodiment. In Figure 27
In the embodiment shown, one side circumference of the cylinder head inner wall surface 3a
Two exhaust valves 118 and 119 are arranged on the sides to
Two air supply valves 93 on the other side peripheral portion of the inner surface 3a of the da head,
94 is arranged. Furthermore, inside the cylinder head inner wall surface 3a
A third or additional air supply valve 95 is arranged in the central part.
Also, surrounded by three air supply valves 93, 94, 95
The injection port 6 of the sub chamber 5 is provided around the inner wall surface 3a of the cylinder head.
Will be placed. As shown in FIG. 27, the bulk of the air supply valve 93
The two exhaust valves 118 and 119 are exhausted to the center of the part.
The bulk of the air valve 118 is located closer. air supply
From the center of the bulb portion of the valve 93 to the corresponding exhaust valve 118
A pair of straight lines L extending so as to contact the outer peripheral edge of the sash_1a, L
_1bThe opening of the air supply valve 93 located in the area sandwiched by
It is covered by a wall 98. Also, is the air supply valve 94
Of the two exhaust valves 118 and 119,
The bulkhead of the exhaust valve 119 is located closer. Salary
From the center of the bulb portion of the air valve 94 to the corresponding exhaust valve 119
A pair of straight lines L extending so as to contact the outer peripheral edge of the bulkhead _2a，
L_2bThe opening of the air supply valve 94 located in the area sandwiched by
It is covered by the disc wall 101. Also, the air supply valve 95
All exhaust valves 118, 119 from the center of the bulkhead
When you think of a pair of straight lines that extend to sandwich the body, this one
The included angle β formed between the pair of straight lines, that is, the mask angle β is the maximum.
A pair of small straight lines M_a, M_bIn the area sandwiched between
The opening of the air supply valve 95 located at
Is covered.

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.

[0051]

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, it is almost completely prevented that fresh air supplied from the air supply valve arranged in the peripheral portion of the inner wall surface of the cylinder head is 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 side sectional view of the internal combustion engine taken along line II-II 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 diagram showing valve opening timings of an intake valve and an exhaust valve.

5 is a side sectional view of the internal combustion engine for explaining the scavenging action as viewed along the same section as FIG. 2. FIG.

FIG. 6 is a bottom view of an inner wall surface of a cylinder head according to a second embodiment.

FIG. 7 is a bottom view of an inner wall surface of a cylinder head according to a third embodiment.

FIG. 8 is a bottom view of an inner wall surface of a cylinder head according to a fourth embodiment.

FIG. 9 is a bottom view of an inner wall surface of a cylinder head according to a fifth embodiment.

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

11 is a side sectional view of the internal combustion engine taken along the line XI-XI of FIG.

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

13 is a side cross-sectional view of the internal combustion engine for explaining the scavenging action taken along the same cross section as FIG. 11. FIG.

FIG. 14 is a side sectional view of the internal combustion engine for explaining the scavenging action taken along the same section as FIG.

FIG. 15 is a perspective view schematically showing an internal combustion engine of a fifth embodiment.

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

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

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

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

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

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

22 is a side sectional view of the internal combustion engine for explaining the scavenging action taken along the same section as FIG. 21. FIG.

FIG. 23 is a bottom view of the inner wall surface of the cylinder head of the ninth embodiment.

FIG. 24 is a bottom view of the cylinder head inner wall surface of the tenth embodiment.

FIG. 25 is a bottom view of the cylinder head inner wall surface of the eleventh embodiment.

FIG. 26 is a bottom view of the cylinder head inner wall surface of the twelfth embodiment.

FIG. 27 is a bottom view of the inner wall surface of the cylinder head of the thirteenth embodiment.

[Explanation of symbols]

3a ... Cylinder head inner wall surface 5 ... Sub chamber 6 ... Injection port 9,10 ... Exhaust valve 12, 13 ... Air supply valve 16, 19 ... Mask wall 40, 41, 42, 44, 45, 46, 47 ... Exhaust valve 56, 57, 58 ... Air supply valve 60, 63, 66 ... Mask wall 90, 91, 92 ... Exhaust valve 93, 94, 95, 95a ... Air supply valve 98, 101, 104 ... Mask wall 113, 114, 115, 116, 118, 119 ... Exhaust valves α ₁ , α ₂ , α ₃ , β ... Mask angles

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

Claims (2)

[Claims] Claims: 1. A plurality of exhaust valves are arranged on one side of an inner wall surface of a cylinder head, and at least one air supply valve is arranged on the other side of an inner wall surface of the cylinder head. In the combustion chamber structure of a two-cycle internal combustion engine in which the opening of the valve is covered with a mask wall, it corresponds to the air supply valves whose distance between the center of the air supply valve and the center of the exhaust valve is the shortest. And an exhaust valve that is located in a region sandwiched by a pair of straight lines extending from the center of the bulk portion of the air supply valve to the outer peripheral edge of the bulk portion of the corresponding exhaust valve. A combustion chamber structure of a two-cycle internal combustion engine which is covered by the mask wall. 2. A plurality of exhaust valves are arranged on one side of an inner wall surface of the cylinder head, and at least one air supply valve is arranged on the other side of the inner wall surface of the cylinder head, and the air supply is located on the exhaust valve side. In a combustion chamber structure of a two-cycle internal combustion engine in which an opening of the valve is covered with a mask wall, the plurality of exhaust valves are arranged in the peripheral portion on one side of the inner wall surface of the cylinder head and at least one supply valve is provided. The air valve is placed on the other side peripheral part of the inner wall surface of the cylinder head, and the distance between the center of the air intake valve and the center of the exhaust valve is the closest to the air intake valve and the corresponding exhaust valve. The mask wall covers an opening of the air supply valve located in a region sandwiched by a pair of straight lines extending from the center of the air supply valve to the outer peripheral edge of the corresponding exhaust valve cap. , Additional air supply in the center of the inner wall of the cylinder head A combustion chamber structure of a two-cycle internal combustion engine in which a valve is arranged so that fresh air is supplied from the additional air supply valve toward a central portion of the combustion chamber.