JP3077403B2 - Uniflow type 2-stroke engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a uniflow type two-stroke engine in which a scavenging port is formed below a cylinder and an exhaust port is formed in a cylinder head.

[0002]

2. Description of the Related Art In general, the operation of an engine is such that the operation of an explosion stroke, that is, an expansion stroke, an exhaust stroke, a suction stroke, and a compression stroke is sequentially repeated, and two types of a four-stroke engine and a two-stroke engine are available. is there. Some two-stroke engines, i.e., two-stroke engines, have a uniflow type in which an exhaust port is formed in a cylinder head and a scavenging port is provided in a lower portion of the cylinder. This uniflow type two-stroke engine is also called uniflow scavenging, and is of a single flow scavenging type, in which the scavenging action is performed by airflow in a certain direction with respect to the cylinder center line. In the uniflow type two-stroke engine, the intake stroke and the exhaust stroke are performed in a part of the combustion stroke and the compression stroke, and one cycle is completed by two strokes of the piston. Can be obtained.

[0003] A two-cycle adiabatic engine is disclosed in Japanese Patent Application Laid-Open No. HEI 3-50363. The two-stroke insulated engine is configured such that a lower surface of a cylinder head and an upper portion of a cylinder liner are insulated, and an exhaust valve is disposed in an exhaust port formed in a lower portion of the cylinder head. A heat insulating gasket is disposed at the boundary, a number of intake ports are formed below the cylinder liner, and the intake ports are opened to intake ports formed on the outer periphery of the lower portion of the cylinder liner. The supercharger is connected to the intake port.

[0004] As a sub-combustion chamber type insulated engine, there is one disclosed in Japanese Patent Application Laid-Open No. 4-132821.
In the sub-combustion chamber type insulated engine, at least the ceramic inner wall surface of the sub-combustion chamber is formed of a heat insulating material, and the ceramic outer wall surface of the sub-combustion chamber is exposed in an exhaust pipe. Effectively recovers the amount of heat released from the sub-combustion chamber,
Reducing the emissions of O _X, to improve the efficiency of the entire engine, it is obtained by improving the durability of the material.

[0005] In the above-described heat-insulated engine, the combustion chamber composed of a cylinder formed in a cylinder head and a cylinder block has a heat-insulating structure made of a heat-insulating material, a ceramic material, or the like. Efficiency is reduced, resulting in reduced output. The reason is that the intake valve and the exhaust valve are arranged on the cylinder head and are arranged close to each other, and in the case of an insulated engine, the cylinder head and the upper part of the cylinder are insulated, so
The upper part of the combustion chamber and the wall surface are hot, and the temperatures of the exhaust gas and the upper part of the combustion chamber are considerably high. Therefore,
The intake port and the intake air are easily affected by the exhaust port, the upper wall of the combustion chamber and the exhaust gas, and the fresh air sucked into the cylinder receives heat from the cylinder or the wall and expands by heating, so that the intake air is thermally heated. Due to the influence, the air is expanded and the amount of intake air is extremely reduced, for example, to 20% or more, and the intake efficiency is reduced.

[0006]

However, in a two-stroke operation engine, the intake port is provided below the cylinder liner, and air is exchanged when the exhaust valve is opened and exhausted through the exhaust port. A pressure wave, that is, a pulse wave is generated in the inside, and the exhaust gas is pushed out. As a result, fresh air flows into the negative pressure zone generated downstream of the exhaust gas from the lower part of the cylinder, but since the lower part of the cylinder is not so hot compared to the cylinder head, the fresh air is Insensitive to wall temperature. This has the merit that the scavenged air amount or the intake air amount does not decrease particularly if the adiabatic engine performs two-cycle operation and sucks fresh air from the lower part of the cylinder.

In a two-stroke engine in which a scavenging port is formed in a lower portion of a cylinder and an exhaust port is formed in a cylinder head, when a sub-chamber is formed in a cylinder head, a single exhaust port has a short passage area. Problem arises. Also, in the sub-chamber insulated engine, when the sub-chamber is provided in the cylinder head, heat radiation from the wall of the sub-chamber through the cylinder head increases, and the exhaust gas energy can be effectively recovered by the turbocharger or the energy recovery turbine. It also has the problem of disappearing.

By the way, the in-cylinder pressure immediately before the exhaust stroke is several kg / cm ² or more. If the high in-cylinder pressure is used, the exhaust gas can be effectively recovered by the exhaust turbine. However, in reality,
It once expands to the pressure before the exhaust turbine, and the pressure expands to atmospheric pressure. Only the pressure difference can be recovered by the exhaust turbine. Also, when considering increasing the pressure in front of the exhaust turbine to increase the amount recovered,
In a stroke engine, it is necessary to increase the scavenging pressure to a pressure higher than the pressure before the exhaust turbine, and the energy required for the scavenging pressure increases, and the total recovery efficiency does not improve.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems, and a sub-chamber and a plurality of exhaust ports are formed in a hole formed in a cylinder head so as to surround an outer wall of the sub-chamber. A headliner is arranged, these exhaust ports are gathered into one collective exhaust port formed in the cylinder head, and the exhaust port communicates with a turbocharger or an energy recovery turbine provided downstream, and the sub-chamber is covered with exhaust gas. By keeping the wall temperature of the sub-chamber high,
Improving the degree of heat insulation, the heat energy radiated from the sub-chamber is absorbed by the exhaust gas, and the exhaust gas energy is sent to the turbocharger to increase the exhaust pressure, effectively recovering the exhaust energy, and increasing the recovered energy. A uniflow type two-stroke engine that reduces piston compression work in the exhaust stroke by increasing the passage area by a plurality of exhaust ports, reduces residual gas remaining in the cylinder, improves suction efficiency, and prevents a decrease in engine output. It is to provide.

[0010]

The present invention is configured as follows to achieve the above object. That is,
The present invention provides a uniflow type two-stroke engine in which a scavenging port is formed in a lower portion of a cylinder and an exhaust port is formed in a cylinder head, and a headliner made of ceramics constituting a main chamber fitted in a hole formed in the cylinder head. A sub-chamber provided corresponding to the center of the cylinder of the headliner, a plurality of exhaust ports formed in the headliner in a state surrounding the wall of the sub-chamber, and the exhaust ports being combined into one. The present invention relates to a uniflow type two-stroke engine having a collective exhaust port formed in a cylinder head.

In the uniflow type two-stroke engine, a fuel injection nozzle for injecting fuel is provided in the sub chamber.

[0012]

The uniflow type two-stroke engine according to the present invention is configured as described above and operates as follows. That is, in this uniflow type two-stroke engine, a head liner made of ceramics is fitted into a hole formed in a cylinder head, and a sub-chamber is provided corresponding to the center of the cylinder of the head liner, and a wall of the sub-chamber is provided. A plurality of exhaust ports are formed in the headliner in an enclosed state, and the respective exhaust ports are gathered into one collective exhaust port formed in the cylinder head, so that the exhaust ports are located around the wall of the sub chamber. The sub-chamber is covered with exhaust gas, the degree of heat shielding of the sub-chamber is improved, the heat radiation from the sub-chamber is absorbed by the exhaust gas, and the heat energy radiated from the sub-chamber is supplied by the turbocharger and the energy recovery turbine. Collected effectively.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a uniflow type two-stroke engine according to the present invention will be described below with reference to the drawings.
FIG. 1 is a sectional view showing an embodiment of a uniflow type two-stroke engine according to the present invention, FIG. 2 is an explanatory view of a schematic cross section taken along line AA of FIG. 1, and FIG. It is sectional drawing which shows another Example.

As shown, the uniflow type two-stroke engine has a scavenging port 4
And a head liner 3 made of ceramics constituting a main chamber 16 fitted in a hole 20 formed in the cylinder head 1 and formed in the cylinder head 1. Sub-chamber 5 formed corresponding to the center of the formed cylinder 14, a plurality of exhaust ports 8 formed in the headliner 3 in a state surrounding the wall 15 of the sub-chamber 5, and each of the exhaust ports 8 are integrated into one. It has a collective exhaust port 7 that is assembled and formed in the cylinder head 1.

A collective exhaust port 7 formed in the cylinder head 1 is provided with an aluminum titanate A for preventing exhaust gas energy from being radiated through the cylinder head 1.
The exhaust port liner 10 is made of a heat insulating material such as l ₂ TiO ₅ . Wall body 15 forming sub-chamber 5
Are silicon nitride Si ₃ N ₄ , sialon Si—Al—O
-N, made of ceramics having excellent high-temperature strength such as silicon carbide SiC. The headliner 3 is made of a ceramic such as silicon nitride.

The wall 15 constituting the sub-chamber 5 may be divided into upper and lower parts to constitute a part of the head liner 3. In this case, the wall 15 of the sub-chamber 5 has The lower wall 25 formed by a part of the liner 3 and the upper wall 24 in which the upper part is joined to the lower wall 25 by the joint surface 26 can be constituted. Alternatively, the wall 15 constituting the sub chamber 5 is
As shown in FIG. 3, the head liner 3 may be arranged on a wall 27 located at the center of the head liner 3.

Although not shown, a turbocharger and an energy recovery device driven by the exhaust energy of the engine are provided downstream of the collective exhaust port 7. The two-stroke engine having the cylinder head structure includes a cylinder block 2,
, A cylinder liner 12 fitted in a hole formed in the cylinder block 2, a cylinder 14 formed by the cylinder liner 12, a piston (not shown) reciprocating in the cylinder 14, And a connecting rod and a crankshaft for converting a reciprocating motion of the piston into a rotary motion. A collective exhaust port 7 and a sub chamber 5 are formed in the cylinder head 1, and a fuel injection nozzle 6 for injecting fuel into the sub chamber 5 is arranged.

The head liner 3 includes a liner upper portion 21 and a head lower surface portion 22. The main chamber 16 is formed in a space surrounded by the liner upper portion 21 and the head lower surface portion 22, and a plurality of head chambers are formed in the head lower surface portion 22. Two (four in FIG. 2) exhaust ports 8 are formed, and an exhaust valve 9 is disposed in each of the exhaust ports 8. A part of the head lower surface 22 of the head liner 3 constitutes a wall body 15 constituting the sub-chamber 2, and the head lower surface 22 includes the main chamber 16 and the sub-chamber 5.
A communication hole 11 is formed to communicate with.

The upper wall 24 of the sub-chamber 5 has a heat insulating plate 23
A hole 1 through which the fuel injection nozzle 6 penetrates is fixed to the cylinder head 1
3 are formed. The headliner 3 is disposed in the hole 20 of the cylinder head 1 with a heat insulating gasket 17 and a positioning ring 18 interposed. In the figure, a heat insulating air layer 19 is formed between the outer peripheral surface of the head liner 3 and the inner wall surface of the hole of the cylinder head 1.

The cylinder 14 of the cylinder liner 12
A scavenging port 4 is formed at the lower part. The collective exhaust port 7 formed in the cylinder head 1 is connected to an exhaust manifold via a manifold gasket, for example, and then the exhaust manifold is connected to a turbocharger or an energy turbine.

Since this uniflow type two-stroke engine is constructed as described above, the wall 1 of the sub-chamber 5
5 is configured to be exposed to a plurality of exhaust ports 8 formed in the headliner 3, and the wall 15 of the sub-chamber 5 is configured to be surrounded by, or exposed to, exhaust gas. Therefore, the wall 15 of the sub-chamber 5 is surrounded by the exhaust port 8, the wall temperature is maintained at a high temperature, and the degree of heat insulation can be improved. In the sub-chamber insulated engine, since the heat radiation from the sub-chamber 5 increases, it is necessary to maintain the sub-chamber 5 at a high temperature.

In order to maintain the sub-chamber 5 at a high temperature, the sub-chamber 5
It is more effective to shield the outer periphery of the device with the exhaust gas than to block the heat with the heat insulating layer. The heat radiated from the sub-chamber 5 is absorbed by the exhaust gas and can be recovered by a turbocharger or an energy recovery turbine disposed downstream. In the case of a two-stroke engine, in particular, since the heat radiation ratio increases, a further heat shielding structure is required. In the uniflow engine, when the sub chamber 5 is formed in the cylinder head 1, the passage area of the exhaust port 8 cannot be formed so large. Therefore, if a plurality of exhaust ports 8 are formed as in this two-stroke engine, and these exhaust ports 8 surround the wall 15 of the sub-chamber 5, an ideal heat shielding structure for the sub-chamber 5 is constituted. be able to.

[0023]

The uniflow type two-stroke engine according to the present invention is configured as described above and has the following effects. That is, in this uniflow type two-stroke engine, a head liner made of ceramics constituting a main chamber is fitted into a hole formed in a cylinder head, and a sub chamber is formed corresponding to the center of a cylinder formed in the head liner. A plurality of exhaust ports formed in the head liner are positioned so as to surround the wall surface of the sub-chamber, and the respective exhaust ports are gathered into one collective exhaust port formed in the cylinder head. Is directly exposed to the exhaust gas, the wall temperature can be maintained at a high temperature, and an ideal heat shielding structure for the sub-chamber can be formed. Can be held.
That is, by surrounding the sub chamber with the exhaust port, NO _X
Generation can be reduced, combustion speed can be increased and high efficiency 2
A stroke type engine can be provided. Further, in order to arrange the sub-chamber in the center of the cylinder and surround the sub-chamber with the exhaust port, it is difficult to manufacture a four-stroke type in which a suction / exhaust port is provided in a cylinder head. Can be achieved well.

In particular, if the sub-chamber is of a heat shielding type, it is important to prevent heat radiation from the sub-chamber. However, by arranging the sub-chamber in the exhaust port, the temperature difference can be reduced, and The heat radiation from the room can be reduced. Moreover, the heat radiated from the sub-chamber can be effectively recovered by a turbocharger or an energy recovery turbine provided downstream. Further, since the scavenging port is provided at the lower portion of the cylinder, only a plurality of exhaust ports are formed in the cylinder head, so that a passage area that can cope with the amount of exhaust gas can be secured.

In the uniflow type two-stroke engine, the sub-chamber is arranged at the center of the cylinder.
It has the following advantages: In other words, for mixing and combustion in the main chamber, the injection energy of the air-fuel mixture from the sub-chamber to the main chamber is an important factor. By arranging the sub-chamber in the center of the cylinder, The distance that the jet reaches to the outer periphery is shortened, and as a result, short-time combustion becomes possible.
When the sub-chamber is arranged at the center of the cylinder, the energy of the intake swirl in the cylinder can be effectively utilized in the sub-chamber. Furthermore, since primary combustion can be performed in the sub chamber and secondary combustion can be performed in the main chamber, NO _x , HC
The exhaust gas can be reduced to a clean exhaust gas.
It said be to primary combustion in the sub-chamber, to burn at a high equivalent ratio of Dekii, it is possible to perform the reduced combustion of NO _X, then occur jet into the main chamber, the jet the main the mixture speed of the indoor significantly improve, can reduce to reduce the combustion temperature become lean combustion in the main chamber burning time, can reduce the production of NO _X.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a uniflow type two-stroke engine according to the present invention.

FIG. 2 is an explanatory diagram of a schematic cross section taken along line AA in FIG. 1;

FIG. 3 is a sectional view showing another embodiment of the uniflow type two-stroke engine according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder head 2 Cylinder block 3 Head liner 4 Scavenging port 5 Sub chamber 6 Fuel injection nozzle 7 Collecting exhaust port 8 Exhaust port 9 Exhaust valve 10 Exhaust port liner 11 Communication hole 12 Cylinder liner 14 Cylinder 15 Sub chamber wall 16 Main chamber 20 holes

Continuation of the front page (51) Int.Cl. ⁷ Identification code FI F02F 1/42 F02F 1/42 JN (56) References JP-A-4-58013 (JP, A) JP-A-4-132821 (JP, A) JP-A-4-365930 (JP, A) JP-A-4-314916 (JP, A) JP-A-4-17718 (JP, A) JP-A-3-213641 (JP, A) JP-A-3 -50363 (JP, A) Japanese Utility Model 4-109425 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02F 1/24 F02B 19/16 F02B 25/02 F02F 1/42

Claims (2)

(57) [Claims] 1. A uniflow type two-stroke engine in which a scavenging port is formed in a lower part of a cylinder and an exhaust port is formed in a cylinder head, a headliner made of ceramics constituting a main chamber fitted in a hole formed in the cylinder head. A sub-chamber provided corresponding to the center of the cylinder of the head liner, a plurality of exhaust ports formed in the head liner in a state surrounding the wall of the sub-chamber, and the respective exhaust ports were assembled into one. A uniflow two-stroke engine having a collective exhaust port formed in the cylinder head. 2. The uniflow type two-stroke engine according to claim 1, wherein a fuel injection nozzle for injecting fuel is provided in the sub-chamber.