JP2500395B2 - Sub-chamber insulation 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 subchamber type adiabatic engine in which a main chamber is formed in a piston head and a subchamber is formed in a cylinder head.

[0002]

2. Description of the Related Art Conventionally, a combustion chamber of an engine is represented by a direct injection type or a sub chamber type. The direct injection type combustion chamber achieves mixing of fuel and air by the injection energy of the fuel injected from the fuel injection nozzle and the swirl and squish flow formed in the combustion chamber to form a combustible mixture. In the sub-chamber combustion chamber, the fuel oil droplets and air are mixed by the high swirl formed in the sub-chamber, and a combustible mixture is formed, but a high swirl is formed in the sub-chamber and heat transfer is performed. There is a problem that the heat loss increases due to the increase of the area, and further there is a problem that the throttle loss due to the communication hole increases when the air flows into the sub chamber.

Conventionally, an adiabatic engine having a sub chamber has been developed for the purpose of improving combustion of the adiabatic engine. For example, Japanese Patent Application No. 1-252277 related to the applicant's application discloses a sub-chamber engine. The sub-chamber type adiabatic engine includes a sub-chamber having a heat-insulating structure formed in a cylinder head, a communication hole having a heat-insulating structure that communicates the sub-chamber with the main chamber, a fuel injection nozzle having multiple injection holes arranged in the sub-chamber, and a piston. The piston head has a protrusion that protrudes into the communication hole near the top dead center.

Further, the Japanese Patent Application No.
No. 173888 discloses a sub-chamber engine as described above. In the sub-chamber engine, the piston head does not have a main chamber with a narrowed opening, but the piston head is provided with a protrusion that projects into the communication hole at the piston top dead center.

[0005]

By the way, normally, in a sub-chamber engine, the blowing of combustion gas, that is, flame, from the sub-chamber to the main chamber is limited to one direction. The outflow velocity in the initial stage of the flame blowout is such that the pressure difference between the sub chamber and the main chamber is large, and the flame is blown out at a high velocity in the first half of the flame blowout, but the outflow velocity decreases in the latter half of the flame blowout. , It takes time to mix with the air existing in the main chamber, the combustion period becomes long, the fuel consumption deteriorates, and the hydrocarbon H
It is a cause of the occurrence of C.

An object of the present invention is to solve the above-mentioned problems. An auxiliary chamber having a heat insulating structure in which a fuel injection nozzle for radially injecting fuel is arranged is formed in a cylinder head, and an opening formed by a lip portion is formed. Forming a main chamber having a piston head with a conical surface projecting into the communication hole at the piston top dead center, the combustion gas that has undergone primary combustion in the sub chamber from the sub chamber It flows into the main chamber along the conical surface, promotes the mixing of combustion gas and air in the main chamber, achieves the mixture of flame and air in a short period of time to achieve good secondary combustion, and then from the main chamber lip is tertiary combustion air mixture by flowing out into the cylinder chamber formed between the cylinder head lower surface and the piston head upper surface by the reverse squish by then completely combusted, HC, suppressing generation of the NO _X pre-combustion chamber Insulation It is to provide an engine.

[0007]

In order to achieve the above object, the present invention is configured as follows. That is,
The present invention provides a sub-chamber of a heat insulating structure formed in a cylinder head and provided with a fuel injection nozzle for spraying fuel radially.
A cavity having an opening formed in the piston head facing the sub chamber and formed with a tapered lip portion, a communication hole formed in the cylinder head that communicates the sub chamber with the cavity side, and the piston head A protrusion having a conical surface extending from the bottom surface of the formed cavity, protruding from the center of the opening, protruding into the communication hole in the vicinity of the piston top dead center, and forming a flow area variable passage with the communication hole; The present invention relates to a sub-chamber type adiabatic engine including a main chamber formed by the conical surface of the protrusion and the cavity wall surface.

Further, in this sub-chamber type adiabatic engine, the lower portion of the projecting portion is undercut, and the main chamber is formed in an annular shape opening to the cylinder head side through an annular opening.

[0009]

The subchamber type adiabatic engine according to the present invention is constructed as described above and operates as follows. That is, in this sub-chamber type adiabatic engine, a sub-chamber having a heat insulating structure in which a fuel injection nozzle for radially injecting fuel is arranged is formed in a cylinder head, and a main chamber having an opening formed by a lip is formed in a piston head. In addition, since the protrusion having the conical surface that projects into the communication hole at the top dead center of the piston is formed in the piston head, the communication area and the conical surface of the protrusion form the variable passage area passage. Then, the air flow in the sub-chamber and the fuel injected radially are promoted to be mixed, and the combustion gas primarily combusted in the sub-chamber is passed from the sub-chamber through the flow area variable passage along the conical surface and It flows into the main room. Therefore, it is possible to promote the mixing of the combustion gas and the air in the main chamber, achieve the mixing of the flame and the air in a short period of time, and favorably perform the secondary combustion. Then, by reverse squishing by the lip portion from the main chamber, it can flow into the cylinder chamber between the lower surface of the cylinder head and the upper surface of the piston head, and the air-fuel mixture can be tertiary-combusted for complete combustion.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a subchamber type adiabatic engine according to the present invention will be described below with reference to the drawings. First, FIG. 1 and FIG.
An embodiment of the sub-chamber type adiabatic engine according to the present invention will be described with reference to FIGS. 1 is a cross-sectional view showing an embodiment of a sub-chamber type adiabatic engine according to the present invention, and FIG. 2 is a cross-sectional view showing the state of the sub-chamber type adiabatic engine of FIG. 1 in the first half of an expansion stroke.
3 and 4 are sectional views showing a state following the first half of the expansion stroke of FIG.

As shown in the figure, this sub-chamber type adiabatic engine is formed on a cylinder block 7, a cylinder head 7 having an intake / exhaust port 25 (only one of which is shown) fixed to the cylinder block 14, and a cylinder head 7. In the sub chamber 2 of the heat insulating structure, the piston 17 that reciprocates in the cylinder 18 formed in the cylinder block 14, the fuel injection nozzle 6 in which the injection holes are arranged in the sub chamber 2, and the cavity 22 formed in the piston head 4 of the piston 17. It has a main chamber 1 of a heat insulating structure configured. Regarding the heat insulating structure of the sub chamber 2, for example, the sub chamber wall body 3 made of ceramics, heat resistant metal or the like having a high heat resistance and a high heat insulating property, which is disposed in the recess 19 formed in the cylinder head 7, is configured. The sub chamber wall body 3 is fixed to the cylinder head 7 with a mounting bracket 27. A heat insulating air layer 28 is formed between the outer surface of the sub chamber wall 3 and the inner surface of the recess 19 of the cylinder head 7 to improve the heat insulation of the sub chamber 2. Further, the lower surface of the sub chamber wall body 3 constitutes a part of the cylinder head lower surface 13, and the sub chamber 2 formed in the cylinder head 7 is formed in the piston head 4 in the central portion of the lower surface of the sub chamber wall body 3. A communication hole 9 is formed so as to face the chamber 1. The sub-chamber wall body 3 around the communication hole 9 is formed of a wall body 11 thinner than other portions. Further, regarding the heat insulation structure of the main chamber 1, for example,
The cavity 22 of the piston head 4 is made of ceramics or the like in a heat insulating structure. The intake / exhaust port 25
An intake / exhaust valve 26 is arranged in the.

In this sub-chamber type adiabatic engine, the sub-chamber 2
The fuel injection nozzle 6 arranged at is provided with multiple injection holes 16 formed in the circumferential direction of the nozzle body so that the fuel can be sprayed radially into the sub chamber 2. The fuel injection nozzle 6 is provided in the sub chamber 2
The nozzles 16 are arranged downward from the center, and the multiple injection holes 16 open toward the peripheral wall of the sub chamber 2. In other words, the inside of the sub chamber 2 is formed in a shape that is substantially symmetrical with respect to the nozzle axis of the fuel injection nozzle 6. Further, the cavity 22 formed in the piston head 4 of the piston 17 is provided with the opening 10 formed by the pointed lip portion 20, so that the main chamber 1 constitutes a reentrant combustion chamber. . Moreover, the diameter of the opening 10 of the main chamber 1 is formed larger than the diameter of the communication hole 9. That is, the communication hole 9
The structure of the portion is formed by a thin wall body 11 extending from the sub chamber wall body 3 around the communication hole 9, and the sub chamber wall body portion 11 forms the same surface as the cylinder head lower surface 13 and a cylinder head lower surface. Make up the department. Moreover, the communication hole 9 itself faces the opening 10 of the main chamber 1 formed in the piston head 4.

Further, a protrusion 5 which protrudes from the piston head upper surface 12 and penetrates the center of the communication hole 9 in the vicinity of the piston top dead center and can enter the sub chamber 2 at the center of the cavity 22 formed in the piston head 4. Are formed. The protrusion 5 has a bottom surface 21 at the center of the cavity of the piston head 4.
It has a conical surface 8 such as a conical surface that extends upward from and protrudes. Since the protruding portion 5 is a portion that is exposed to high-temperature combustion gas and has a high heat load, it is preferable that the protruding portion 5 be made of ceramics that has high heat resistance and high-temperature strength. Further, in the drawing, the projecting portion 5 is formed as a truncated cone whose upper surface is a flat surface, but it is not limited to the truncated cone and the upper portion may be formed as a rounded cone. .
That is, the protruding portion 5 is configured such that the combustion gas blown out from the sub chamber 2 flows into the main chamber 1 at a high speed along the conical surface 8. Therefore, the opening 10 of the main chamber 1 has an annular shape because the projecting portion 5 is arranged at the center,
Further, the main chamber 1 is formed into an annular chamber by the conical surface 8 of the protrusion 5 and the wall surface of the cavity 22. An annular passage 23 is formed by the peripheral surface of the communication hole 9 and the conical surface 8 of the protrusion 5 near the top dead center of the piston.
Since the projecting portion 5 is formed from the conical surface 8, the flow passage area variable passage whose flow passage area changes according to the reciprocating motion of the piston 17 near the piston top dead center is formed.

Since this sub-chamber type adiabatic engine is constructed as described above, it operates as follows. That is, in the combustion cycle of this sub-chamber type adiabatic engine, the projecting portion 5 of the piston 17 projects into the sub-chamber 2 through the communication hole 9 in the latter half of the compression stroke near the top dead center of the piston, and the annular passage 23 is formed. It Next, the piston 17 rises toward the end of the compression stroke, but since the peripheral side surface of the protrusion 5 is formed as the conical surface 8, the flow passage area of the annular passage 23 becomes small, and in the vicinity of the end of the compression stroke, the auxiliary passage is formed. The air flowing into the chamber 2 is pushed in and forms a swirl in the sub chamber 2. In this state, as shown by the arrow in FIG. 1, the fuel spray injected from the fuel injection nozzle 6 into the sub chamber 2 achieves good mixing with the flowing air in the sub chamber 2 and is fuel rich in primary combustion. Will be done.

Next, the combustion cycle of this sub-chamber type adiabatic engine shifts to the expansion stroke, and the combustion gas consisting of the air-fuel mixture and flame from the sub-chamber 2 at the beginning of the expansion stroke is as shown by the arrow in FIG. It is possible to smoothly and smoothly flow into the main chamber 1 formed in the piston head 4 at a high speed along the conical surface 8 of the protruding portion 6, and most of the combustion gas blown out from the sub chamber 2 is introduced into the main chamber 1. It Therefore, the combustion gas in the main chamber 1 and the fresh air existing in the main chamber 1 are promoted to be mixed with each other, so that the flame and the air are mixed in a short period of time and the secondary combustion is satisfactorily performed.

Subsequently, the combustion cycle of this auxiliary chamber type adiabatic engine shifts to the latter half of the expansion stroke, and as shown by the arrow in FIG. 3, the combustion gas secondarily burned in the main chamber 1 is the lip portion of the main chamber 1. By the action of 20, reverse squish is generated and vigorously flows out into the cylinder chamber 15 formed by the piston head upper surface 12 and the cylinder head lower surface 13, and the air-fuel mixture is tertiary-combusted and completely burned in the cylinder chamber 15. Complete the combustion. Therefore, the fuel injected from the fuel injection nozzle 6 is
It is possible to perform three combustions of primary combustion in the sub chamber 2, secondary combustion in the main chamber 1, and then tertiary combustion in the cylinder chamber 15. Moreover, the main chamber and the sub chamber are separated from each other like a conventional sub chamber engine. It is not necessary to form the communication hole that communicates with each other, and the communication hole 9 in the subchamber type adiabatic engine according to the present invention has the protrusion 6
Since it is configured to rush into the communication hole 9, the diameter of the communication hole 9 can be configured to be large, and the mixing of the fuel or the air-fuel mixture with the air can be promoted. burning, it is possible to suppress HC, and occurrence of NO _X. Therefore, according to this sub-chamber type adiabatic engine, the combustion period is shortened in the combustion cycle, the fuel consumption is improved,
HC, it is possible to suppress the generation of NO _X.

Next, another embodiment of the sub-chamber type adiabatic engine according to the present invention will be described with reference to FIG. The sub-chamber type adiabatic engine of this embodiment has the same configuration as that of the above embodiment except that the shape of the protruding portion is different. Therefore, the same components are designated by the same reference numerals, and duplicated description will be omitted. The protruding portion 5 is formed on the side surface 24 having an arc-shaped cross section that is undercut. Therefore, the piston head 4 is formed with a donut-shaped annular main chamber 1 having a circular cross section. Therefore, FIG.
As indicated by the arrow, the mixture gas and the flame combustion gas flowing from the sub chamber 2 along the conical surface 8 of the protrusion 6 form a good turbulence in the main chamber 1 and are present in the main chamber 1. Mixing with the fresh air is promoted to achieve rapid mixing, and the mixing is promoted, so that the combustion period is shortened, that is, combustion is accelerated, the efficiency is improved, the fuel efficiency is improved, and the generation of hydrocarbons such as hydrocarbon HC is generated. Can be suppressed.

[0018]

The subchamber type adiabatic engine according to the present invention is
It is configured as described above and has the following effects. That is, this sub-chamber type adiabatic engine includes a sub-chamber having a heat insulating structure formed in a cylinder head, a cavity having an opening formed in a piston head facing the sub-chamber and formed with a pointed lip portion, A communication hole formed in the cylinder head that communicates the sub chamber to the cavity side, extending from the cavity bottom formed in the piston head and protruding from the center of the opening, and protruding into the communication hole near the piston top dead center. Since it is composed of a projecting portion having a conical surface that forms a passage area variable passage between the communicating hole and the main chamber formed by the conical surface of the projecting portion and the cavity wall surface, it is close to the piston top dead center. With the reciprocating movement of the piston, the passage formed between the inner peripheral surface of the communication hole and the side surface of the protrusion has a variable flow area.

Then, the sprayed fuel from the fuel injection nozzle disposed in the sub chamber is injected into the strong air flow, that is, the swirl generated in the sub chamber, a good air-fuel mixture is formed, and the primary fuel is ignited. Burn. That is, at the top dead center of the piston, the flow area variable passage has a reduced flow area and is in a throttled state, and the air introduced into the sub chamber generates a strong swirl in the sub chamber. Moreover, since the fuel injection nozzle is composed of multiple injection holes, the fuel is sprayed radially with high injection, so that the sprayed fuel forms a good mixture with the swirl and the fuel rich in the sub chamber. generation of the NO _X is suppressed by burning in a state.

Next, the flame and the combustion gas of the air-fuel mixture, which are primarily burned in the sub chamber, flow into the main chamber at high speed from the sub chamber along the conical surface of the projecting portion, and swirl vertically in the main chamber. Becomes fluid. Therefore, the mixing of the combustion gas and the fresh air in the main chamber is promoted in the main chamber, and the mixing of the combustion gas and the air is achieved in a short period of time to promote the mixing,
The combustion period is shortened, good secondary combustion is performed, fuel efficiency is improved, and generation of hydrocarbons HC can be suppressed.

Further, the combustion gas that has been secondarily burned in the main chamber flows from the main chamber through the lip portion to the cylinder chamber formed between the lower surface of the cylinder head and the upper surface of the piston head. The reverse squish causes the mixed gas to mix with the fresh air existing in the cylinder chamber, and the mixed gas is subjected to tertiary combustion to complete combustion.

Therefore, in this auxiliary chamber type adiabatic engine, in the combustion cycle, primary combustion is performed in the auxiliary chamber, secondary combustion is performed in the main chamber, and finally tertiary combustion is performed in the cylinder chamber. HC, it is possible to suppress the generation of NO _X. Moreover, since the protruding portion projects into the communication hole, the communication hole itself does not need to be narrowed as in a conventional subchamber engine, and can be formed to have a large diameter. There is no aperture loss when introducing
It is possible to provide a highly efficient engine without degrading the engine performance.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a sub-chamber type adiabatic engine according to the present invention and showing a state in the latter half of a compression stroke during a combustion cycle.

FIG. 2 is a cross-sectional view showing a state in an early stage of an expansion stroke during a combustion cycle in the sub-chamber adiabatic engine of FIG.

FIG. 3 is a cross-sectional view showing a state in the first half of the expansion stroke following the state of FIG. 2 during the combustion cycle in the auxiliary chamber adiabatic engine of FIG.

FIG. 4 is a sectional view showing another embodiment of the adiabatic chamber adiabatic engine according to the present invention and showing a state at the beginning of the expansion stroke during the combustion cycle.

[Explanation of symbols]

 1 Main Chamber 2 Sub Chamber 4 Piston Head 5 Projection 6 Fuel Injection Nozzle 7 Cylinder Head 8 Conical Surface 9 Communication Hole 10 Opening 12 Piston Head Upper Surface 13 Cylinder Head Lower Surface 15 Cylinder Chamber 16 Multiple Injection Holes 17 Piston 20 Lip Part 21 Cavity Bottom 22 Cavity 23 Flow area variable passage 24 Side with arcuate section (undercut)

Claims (2)

(57) [Claims] 1. A sub-chamber having a heat insulating structure formed in a cylinder head and provided with a fuel injection nozzle for spraying fuel radially, formed in a piston head facing the sub-chamber and formed with a pointed lip portion. A cavity with an opening,
A communication hole formed in the cylinder head that communicates the sub chamber with the cavity side, extending from the bottom surface of the cavity formed in the piston head and projecting from the center of the opening to project into the communication hole near the piston top dead center. A sub-chamber type adiabatic engine including a protrusion having a conical surface that forms a passage area variable passage between the communication hole and a main chamber formed by the conical surface of the protrusion and a cavity wall surface. 2. The sub-chamber type according to claim 1, wherein a lower portion of the protrusion is undercut in an arc shape in cross section, and the main chamber is formed in an annular shape that opens to the cylinder head side at an annular opening. Adiabatic engine.