JPH05340252A - Combustion chamber of two-cycle engine - Google Patents

Abstract

PURPOSE:To scavenge the whole space inside a combustion chamber in a two-cycle engine. CONSTITUTION:Three exhaust valves 9, 10, 11 are arranged on one side of the inner wall face 3a of a cylinder head, and two intake valves 12, 13 are arranged on the other side of the inner face 3a of the cylinder head. Additionally, one intake valve 14 is arranged in the central area of the inner wall face 3a of the cylinder head. Openings of the respective intake valves 12, 13, 14 formed on the exhaust valves 9, 10, 11 side are covered by mask walls 16, 19, 22. The valve opening timing of the intake valve 14 is delayed the valve opening timings of the intake valves 12, 13. The peripheral part of the combustion chamber is scavenged by the fresh air which flows in from the intake valves 12, 13, and the central are of the combustion chamber is scavenged by the fresh air which flows in from the intake valve 14.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a combustion chamber of a two-stroke engine.

[0002]

2. Description of the Related Art A pair of exhaust valves are arranged on one side peripheral portion of a cylinder head inner wall surface, and a pair of air supply valves are arranged on the other side peripheral portion of a cylinder head inner wall surface. By covering the air valve opening with a mask wall, fresh air that has flowed in from the air supply valve opening formed on the exhaust valve side is blocked, and fresh air that has flowed in from each air supply valve opening formed on the side opposite to the exhaust valve is blocked. Lower along the inner wall of the cylinder bore below the air supply valve,
Next, after advancing along the top surface of the piston, the piston is raised along the inner wall surface of the cylinder bore below the exhaust valve.
A cycle engine is known (see Japanese Patent Application Laid-Open No. 1-2777619). In this two-cycle engine, burnt gas is scavenged as much as possible by flowing fresh air flowing in from the air supply valve in a loop shape along the periphery of the combustion chamber.

[0003]

However, when fresh air is flowed in a loop shape along the periphery of the combustion chamber in this way, the burnt gas existing in the peripheral portion of the combustion chamber is scavenged well by the fresh air, but the center of the combustion chamber is scavenged. The burnt gas existing in the part remains as it is without being scavenged, thus causing a problem that the burnt gas in the entire combustion chamber cannot be scavenged well.

[0004]

In order to solve the above problems, according to the present invention, at least one exhaust valve is arranged at one peripheral portion on one side of the inner wall surface of the cylinder head, and at the same time other than the inner wall surface of the cylinder head. At least one air supply valve is arranged in the peripheral portion of the side, and inflow of fresh air from the opening of the air supply valve opening located on the exhaust valve side is blocked to prevent the air supply valve on the side opposite to the exhaust valve. A two-cycle engine in which fresh air flowing in from the opening is lowered along the inner wall surface of the cylinder bore below the air supply valve, then advanced along the top surface of the piston, and then raised along the inner wall surface of the cylinder bore below the exhaust valve. In this case, an additional air supply valve is placed in the center of the inner wall surface of the cylinder head to supply fresh air from this additional air supply valve toward the center of the combustion chamber, and the opening timing of the additional air supply valve Is placed around the inner wall surface of the cylinder head It has been slower than the opening timing of the intake valve that was.

[0005]

The burned gas existing in the peripheral portion of the combustion chamber is scavenged by the new airflow flowing from the air supply valve arranged in the peripheral portion of the inner wall surface of the cylinder head and flowing in the combustion chamber in a loop shape. Further, the burned gas existing in the central portion of the combustion chamber is scavenged by the fresh air supplied from the additional air supply valve without disturbing the new air flow flowing in the loop shape.

[0006]

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, three exhaust valves 9, 10, 11 are arranged on one side peripheral portion of the cylinder head inner wall surface 3a. Two air supply valves 12 and 13 are arranged on the other side peripheral portion of the cylinder head inner wall surface 3a. Further, a third or additional air supply valve 14 is arranged at the center of the cylinder head inner wall surface 3a. As shown in FIG. 1, the exhaust valve 9 and the exhaust valve 1
0 is arranged symmetrically with respect to the plane of symmetry KK including the cylinder axis, and the air supply valve 12 and the air supply valve 13 are also planes of symmetry KK.
Are arranged symmetrically with respect to. Also, three air supply valves 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 2, 13, 14 and the exhaust valve 11, the air supply valve 14 and the injection port 6 are arranged on the plane of symmetry KK. It Therefore, in the embodiment shown in FIGS. 1 to 4, three exhaust valves 9, 10 are provided in the peripheral portion of the cylinder head inner wall surface 3a.
The one and two air supply valves 12 and 13 and the injection port 6 are arranged at substantially equal angular intervals, and the additional air supply valve 14 is arranged substantially at 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 12 is arranged at the deepest portion of the concave portion 15. Exhaust valve 9,1
An inner peripheral wall surface portion 16 of the concave portion 15 located on the 0, 11 side has a cylindrical shape extending 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 on the exhaust valve 9, 10, 11 side. A mask wall is formed to cover the opening of the air supply valve 12 formed in. In the embodiment shown in FIGS. 1 to 4, the mask wall 16 extends below the air supply valve 12 in the maximum lift position, and thus the exhaust valves 9,1.
The opening of the air supply valve 12 formed on the 0, 11 side is the air supply valve 12
Will be covered by the mask wall 16 for the full valve opening period. However, the height of the mask wall 16 may be slightly lowered so that the opening of the air supply valve 12 is covered with the mask wall 16 only when the lift amount of the air supply valve 12 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. Exhaust valve 9,1
The inner peripheral wall surface portion 19 of the recess 18 located on the 0, 11 side has a cylindrical shape extending 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 therefore the cylindrical inner peripheral wall surface portion 19 is on the exhaust valve 9, 10, 11 side. A mask wall is formed to cover the opening of the air supply valve 13 formed in the above. In the embodiment shown in FIGS. 1 to 4, the mask wall 19 extends below the air supply valve 13 in the maximum lift position, like the mask wall 16.
Therefore, the air supply valve 13 formed on the exhaust valve 9, 10, 11 side
Of the mask wall 19 during the full opening period of the air supply valve 13.
Will be covered by. 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, as shown in FIGS. 1 and 4, a concave portion 21 is formed on the inner wall surface 3a of the cylinder head, and the air supply valve 14 is arranged at the deepest portion of the concave portion 21. Inner peripheral wall surface portion 2 of the concave portion 21 located on the exhaust valve 9, 10, 11 side
2 has a cylindrical shape extending along the outer peripheral edge of the air supply valve 14, and the inner peripheral wall surface portion 23 of the recess 15 excluding the cylindrical inner peripheral wall surface portion 22 is a cone that expands toward the inside of the main chamber 4. It is formed into a shape. Therefore, the opening of the air supply valve 14 facing the cylindrical inner peripheral wall surface portion 22 is covered by the cylindrical inner peripheral wall surface portion 2, and thus the cylindrical inner peripheral wall surface portion 2 is formed.
Reference numeral 2 forms a mask wall that covers the opening of the air supply valve 14 formed on the exhaust valve 9, 10, 11 side. In the embodiment shown in FIGS. 1 to 4, this mask wall 22 extends below the air supply valve 14 in the maximum lift position, like the mask walls 16 and 19, and therefore on the exhaust valve 9, 10, 11 side. The opening of the air supply valve 14 that is formed is covered with the mask wall 22 during the full opening period of the air supply valve 14. However, also with respect to the mask wall 22, the height of the mask wall 22 may be slightly lowered so that the opening of the air supply valve 14 is covered with the mask wall 22 only when the lift amount of the air supply valve 14 is small.

On the other hand, no mask wall is provided for each of the exhaust valves 9, 10 and 11, so that the exhaust valves 9, 10 and 11 are not provided.
When the valves 10, 11 are opened, the exhaust valves 9, 10, 11 are opened in the main chamber 4 over the entire circumference. In the embodiment shown in FIGS. 1 to 4, all exhaust valves 9, 10, 11 are driven by a common camshaft 25 via corresponding valve lifters 24 slidably inserted into the cylinder head 3 to provide full air supply. Valve 1
2, 13, 14 are driven by a common cam shaft 27 via corresponding valve lifters 26 slidably inserted in the cylinder head 3. That is, all exhaust valves 9, 1
0, 11 are directly driven by a common cam shaft 25 located on the axis of each exhaust valve 9, 10, 11 without passing through a rocker arm, and all intake valves 12, 13, 14 are driven.
Does not use the rocker arm to supply each intake valve 12, 1
It is directly driven by a common camshaft 27 located on the axis of 3,14.

In the cylinder head 3, each exhaust valve 9, 1 is provided.
A common exhaust port 28 is formed for all the exhaust valves 9, 10, 11 extending to 0, 11 and further for the cylinder head 3
A pair of air supply ports 29 and 30 extending to the air supply valves 12 and 13 on both sides of the sub chamber 5 are formed therein. Also,
In the cylinder head 3, a pair of air supply branch passages 31 and 32, which branch from the air supply ports 29 and 30 to extend to the air supply valve 14 and merge with each other in the vicinity of the air supply valve 14, are formed. Therefore, fresh air is supplied from the air supply valves 12 and 13 through the corresponding air supply ports 29 and 30, respectively, and from the air supply valve 14, from the air supply ports 29 and 30 to the air supply branch passages 3 respectively.
The fresh air that has been diverted into the inside of 1, 32 is supplied.

FIG. 5 shows the opening periods of the exhaust valves 9, 10, 11 and the air supply valves 12, 13, 14. As shown in FIG. 5, all exhaust valves 9, 10 and 11 are connected to respective air supply valves 12 and 1.
3 and 14 are opened at the same time before each of the intake valves 12, 1
The valves are closed at the same time before 3,14. Further, the additional air supply valve 14 arranged at the center of the cylinder head inner wall surface 3a
Is opened later than the opening timing of the pair of air supply valves 12 and 13 arranged in the peripheral portion of the inner wall surface 3a of the cylinder head, and is set near the bottom dead center BDC.
The valve closing timings of 2, 13 and 14 are set to the same timing.

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, all the exhaust valves 9, 10, 11 are opened before the air supply valves 12, 13, 14 are opened. All exhaust valves 9,
When the valves 10 and 11 open, the burnt gas in the main chamber 4 is rapidly discharged into the exhaust port 28, that is, blowdown occurs,
As a result, the pressure in the main chamber 4 drops sharply. 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 pair of air supply valves 12 and 13 arranged on the periphery of the inner wall surface 3a of the cylinder head are opened, a mechanical supercharger (not shown) driven by the engine drives each air supply port 2.
The fresh air sent into the chambers 9 and 30 is supplied into the main chamber 4 through the air supply valves 12 and 13. At this time, as described above, the intake valves 12, 1 formed on the exhaust valves 9, 10, 11 side
Since the openings 3 are covered by the corresponding mask walls 16 and 19, the fresh air passes through the openings of the air supply valves 12 and 13 located on the opposite side of the exhaust valves 9, 10 and 11, and inside the main chamber 4. Flow into. In this case, since the air supply valves 12 and 13 are arranged in the peripheral portion of the cylinder head inner wall surface 3a, the fresh air flowing in from the air supply valves 12 and 13 is respectively indicated by the arrow X in FIGS. 6 and 8. It descends along the inner wall surface 1a of the cylinder bore below the corresponding air supply valve 12, 13 and then proceeds along the top surface of the piston 2, and then the exhaust valves 9, 10
Ascend along the lower cylinder bore inner wall surface 1a. That is, the fresh air that has flowed in from the air supply valves 12 and 13 flows in a loop along the peripheral portion of the main chamber 4, and the burned gas in the main chamber 4 is caused by the fresh air X that flows in the loop. 9, 10,
It is discharged from 11. Therefore, the peripheral portion of the main chamber 4 is scavenged by the fresh air X flowing from the air supply valves 12 and 13.

On the other hand, the pair of air supply valves 12 and 13 arranged in the peripheral portion of the cylinder head inner wall surface 3a are opened and, after a while, an additional air supply valve arranged in the central portion of the cylinder head inner wall surface 3a. 14 opens. When the air supply valve 14 is opened, the fresh air sent from the mechanical supercharger into each intake branch passage 31, 31 is supplied into the main chamber 4 via the air supply valve 14.
At this time, as described above, since the opening of the air supply valve 14 formed on the exhaust valve 9, 10, 11 side is covered with the mask wall 22, the fresh air is located on the opposite side of the exhaust valve 9, 10, 11. It flows into the main chamber 4 through the opening of the air supply valve 14. In this case, since the air supply valve 14 is arranged in the central portion of the cylinder head inner wall surface 3a, the fresh air flowing in from the air supply valve 14 is in the central portion of the main chamber 4 as shown by the arrow Y in FIGS. And then changes direction at the top surface of the piston 2, and then rises along the inner wall surface 1a of the cylinder bore below the exhaust valves 9, 10, 11. Therefore, the burned gas existing in the central portion of the main chamber 4 is exhausted by the new airflow Y to the exhaust port 28.
Therefore, the central portion of the main chamber 4 is scavenged by the fresh air Y flowing from the air supply valve 14. As described above, the fresh air flowing from the air supply valves 12 and 13 scavenges the peripheral portion of the main chamber 4, and the fresh air flowing from the air supply valve 14 scavenges the central portion of the main chamber 4. 12,
The entire inside of the main chamber 4 is satisfactorily scavenged by the fresh air flowing in from the ports 13 and 14.

By the way, a new air flow Y flowing from the exhaust valve 14
When the cylinder collides with the top surface of the piston 2, it actually spreads in all directions, and only a part of the new air flow Y rises along the cylinder bore inner wall surface 1a below the exhaust valves 9, 10, 11. Therefore, if all the intake valves 12, 13, 14 are opened at the same time, the new airflow Y disturbs and decelerates the new airflow X flowing in a loop, and thus the new airflow X flowing in a loop causes the new airflow X to flow. Scavenging action deteriorates. However, in the present invention, after the pair of air supply valves 12 and 13 are opened, the additional air supply valve 14 is set to open with a delay, and therefore, after the new airflow X flowing in a loop is generated, it is delayed. A new air flow Y is generated. That is, the new airflow X reaches the top surface of the piston 2 after the new airflow X starts to rise along the inner wall surface 1a of the cylinder bore below the exhaust valves 9, 10, 11. As a result, the new airflow X is hardly disturbed by the new airflow Y and is not decelerated, so that a good scavenging action by the new airflow X can be secured.

Next, when the exhaust valves 9, 10, 11 are closed and the air supply valves 12, 13, 14 are closed, the gas in the main chamber 4 is introduced into the sub chamber 5 via the nozzle 6 by the ascending action of the piston 2. Sent to. 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 12, 13, 14 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 air supply valves 12, 13, 14 are opened must be lowered,
For that purpose, it is necessary to discharge the burnt gas into the exhaust port 28 as soon as possible when the exhaust valves 9, 10, 11 are opened.

However, the period from the opening of the exhaust valves 9, 10, 11 to the opening of the intake valves 12, 13, 14 is extremely short, and the burned gas is promptly released during this short period. In order to discharge, the exhaust valves 9, 10, 11 must be opened at high speed. In this case, the valve opening speed at the time of opening the exhaust valves 9, 10, 11 becomes slow due to elastic deformation of the rocker arm that drives the exhaust valves 9, 10, 11 via the rocker arm. Therefore, in the embodiment according to the present invention, in order to increase the valve opening speed when the exhaust valves 9, 10, 11 are opened, each exhaust valve 9, 10, 11 is directly driven by the cam shaft 25 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 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. 1, the injection port 6 is surrounded by the three air supply valves 12, 13 and 14, so that the cylinder head inner wall surface 3a around the injection port 6 is provided with each supply port. It is cooled by the fresh air flowing in from the air valves 12, 13, 14, and thus the cylinder head inner wall surface 3a around the injection port 6
It is possible to prevent cracks from occurring in the.

[0022]

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 a cylinder head.

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 period of an intake valve and an exhaust valve.

FIG. 6 is a side sectional view of the internal combustion engine taken along the same section as FIG.

FIG. 7 is a side sectional view of the internal combustion engine taken along the same section as FIG.

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

[Explanation of symbols]

 5 ... Sub chamber 6 ... Injection port 9, 10, 11 ... Exhaust valve 12, 13, 14 ... Air supply valve 16, 19, 22 ... Mask wall

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichi Nakae 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Automobile Co., Ltd.

Claims (1)

[Claims] 1. A cylinder head inner wall surface is provided with at least one exhaust valve on one peripheral portion and at least one air supply valve is arranged on the other peripheral portion of the cylinder head inner wall surface to supply air. The fresh air that has flowed in from the opening of the intake valve on the side opposite to the exhaust valve is blocked along the inner wall surface of the cylinder bore below the intake valve by blocking the inflow of fresh air from the opening located on the exhaust valve side. In a two-cycle engine in which the piston is lowered and then advanced along the top surface of the piston and then raised along the inner wall surface of the cylinder bore below the exhaust valve, an additional air supply valve is arranged at the center of the inner wall surface of the cylinder head. While supplying fresh air from the additional air supply valve toward the center of the combustion chamber,
A combustion chamber of a two-cycle engine, wherein the opening timing of the additional air supply valve is delayed from the opening time of the air supply valve arranged in the peripheral portion of the inner wall surface of the cylinder head.