JPH06307242A - Auxiliary chamber type engine - Google Patents

Abstract

PURPOSE:To provide an auxiliary chamber type engine which reduces the generation of smoke by activating unburned mixture at its auxiliary combustion chamber. CONSTITUTION:In the case of this auxiliary chamber type engine, the top surface of a projecting portion 5 projecting to the upper part of a piston 8 is formed into a flat surface. Liquidlike fuel through the single nozzle hole 11 of a fuel injection nozzle 4 is injected to the flat surface and made to collide with it, and at a connection hole 10 territory, fuel spray is scattered uniformly in a disk shape. The formation of mixture is promoted by making filmlike scattering fuel intersect with a strong squish current to an auxiliary combustion chamber 2, and by means of the projecting portion 5, the flow passage area of the connection hole 10 is reduced, and by means of the auxiliary combustion chamber 2, a combustion period is extended by conducting burning in the state of fuel being rich, and gas in the auxiliary combustion chamber 2 is activated, and is jetted into a main combustion chamber 1 at a high speed, and by means of the main combustion chamber 1, the combustion period is shortened, and secondary combustion is carried out excellently, and the generation of smoke and NOx is thus reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an auxiliary chamber type engine having an auxiliary combustion chamber formed in a cylinder head and a fuel injection nozzle for injecting fuel into the auxiliary combustion chamber.

[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 combustion chamber achieves mixing of fuel and air by the injection energy of the fuel injected from the fuel injection nozzle and the swirl formed in the combustion chamber to form a combustible mixture. The sub-chamber combustion chamber achieves mixing of fuel oil droplets and air by the high swirl formed in the sub-chamber, and forms a combustible mixture.

However, the direct injection type combustion chamber has a problem that the intake efficiency is lowered due to the generation of swirl, and the fuel injection nozzle has a high pressure in order to improve atomization and penetration of fuel. However, there is a problem that the structure becomes complicated.

Further, the sub-chamber combustion chamber has a problem that a high swirl is formed in the sub-chamber, the total heat transfer area of the main chamber and the sub-chamber is increased, and heat loss is increased. There is a problem that the throttling loss due to the communication hole that connects the chamber and the sub chamber increases.

In order to solve the above problems, therefore, an engine having a direct injection type collision diffusion stratified charge type utilizing a collision jet of fuel, a so-called OSKA type combustion chamber is disclosed. This OSKA engine is provided with a collision part projecting from the center of the bottom of the concave part, that is, the cavity formed in the piston, and a concave combustion chamber is formed around the collision part.
The liquid fuel injected from the fuel injection nozzle collides with the collision part, and the collision action of the fuel jet on the collision part achieves diffusion and atomization of the fuel starting from the collision surface, and good mixing of fuel and air Is achieved. In the engine having the combustion chamber as described above, the fuel injected from the single hole nozzle of the fuel injection nozzle collides with the flat collision surface of the collision portion of the piston head to diffuse into a disk shape, and then is generated by the ascent of the piston. The squish flow pushes the fuel below the cavity while mixing the fuel and air to form an air-fuel mixture.

Further, Japanese Patent Laid-Open No. 3-115721 discloses a sub-chamber type alcohol engine. The sub-chamber alcohol engine includes a sub-chamber having a heat insulating structure formed in a cylinder head, a main combustion chamber formed by a lower surface of the cylinder head and a cylinder liner, and a communication hole having a heat insulating structure for communicating the main combustion chamber with the sub chamber. And a fuel injection nozzle having a nozzle main body penetrating the central portion of the sub chamber and a multi-injection nozzle opening facing the wall surface of the communication hole. The fuel injection timing of the fuel injection nozzle is set before the top dead center of the compression stroke.

[0007]

By the way, the above OSK
In an engine using a piston equipped with an A-type combustion chamber, the collision surface for colliding the fuel injected from the single-hole nozzle is the flat collision surface of the piston head, and the fuel collides with the collision surface to form a disc shape. However, the squish flow into the combustion chamber is generated by the upward stroke of the piston, and the squish flow generates a thin film disk-shaped fuel and air and a good mixture to try to improve the combustion state. is there. However, with the above-described method for forming the air-fuel mixture, the generation or combustion of the air-fuel mixture is insufficient, and the generation of smoke cannot be sufficiently suppressed.

Further, the sub-chamber type alcohol engine disclosed in Japanese Patent Laid-Open No. 3-115721 mentioned above is formed in a film shape by injecting fuel from the fuel injection nozzle in the communication hole region, and is provided on the piston top surface. The protruding portion causes squish to be generated in the inflowing air in the sub chamber, and the squish is applied to the fuel spray at a right angle to promote mixing, and does not cause the fuel jet flow from the fuel injection nozzle to collide with the protruding portion.

Therefore, an object of the present invention is to solve the above-mentioned problems. A sub-combustion chamber formed in the cylinder head and a protrusion protruding upward from the piston top surface are provided, and the planar top of the protrusion is provided. The surface is a collision surface, that is, a flat surface, and a fuel injection nozzle for injecting liquid fuel to the flat surface is arranged in the auxiliary combustion chamber, fuel is injected from the fuel injection nozzle to the flat surface, and the injected liquid Fuel is made to collide and spread uniformly in a disk shape, promoting the formation of air-fuel mixture, and reducing the flow passage area by closing the communication hole to the almost closed state by the protrusion provided on the piston top surface. Combustion in a fuel-rich state prolongs the combustion period, activates the unburned air-fuel mixture in the sub-combustion chamber, and then the protrusion opens the communication hole to transfer the flame and air-fuel mixture in the sub-combustion chamber to the main combustion chamber. It blows out at once and the combustion period in the main combustion chamber Condensation and improves the thermal efficiency,
Smoke is to provide a pre-combustion chamber engine to reduce the occurrence of NO _X.

[0010]

In order to achieve the above object, the present invention is configured as follows. That is,
The present invention is directed to a sub combustion chamber formed in a cylinder head, a fuel injection nozzle for spraying fuel into the sub combustion chamber, a main combustion chamber formed on the cylinder side, a piston reciprocating in the cylinder, the sub combustion chamber and the main combustion chamber. In a sub-chamber engine having a communication hole that communicates with a combustion chamber, a protrusion provided with a flat surface that protrudes into the communication hole near the top dead center to reduce the flow passage area of the communication hole is provided with a top surface of the piston. And the fuel injected from the fuel injection nozzle is made to collide with the flat surface of the projecting portion and diffused in a film shape in the region near the communication hole.

Further, in this sub-chamber engine, the sub-chamber volume is configured to be 65% or less of the total combustion chamber volume at the compression end.

Further, in this sub-chamber engine, the passage area of the communication hole is set to 3 to 8%, and a plurality of vertical grooves are formed circumferentially spaced around the protrusion. is there.

[0013]

The subchamber engine according to the present invention is constructed as described above and operates as follows. That is, in this sub-chamber engine, a protrusion having a flat surface that reduces the flow passage area of the communication hole near the top dead center and projects into the communication hole is provided on the top surface of the piston, and the fuel is injected from the fuel injection nozzle. Since the fuel to be collided with the flat surface of the protruding portion, the liquid fuel injected from the fuel injection nozzle collides with the flat surface and uniformly diffuses in a film shape in the region near the communication hole,
Moreover, the flow passage area is reduced by the protruding portion of the communication hole, and a strong squish flow is generated and flows from the main combustion chamber to the sub combustion chamber.

Therefore, since the film-shaped fuel spray diffuses at a right angle to the strong squish flow formed in the sub-combustion chamber, the formation of a mixture of the film-diffused fuel and the inflowing air is promoted. To be done. Furthermore, the flow passage area of the communication hole is reduced to a closed state near the top dead center by the protrusion provided on the top surface of the piston, prolonging the combustion period in the auxiliary combustion chamber, and in the auxiliary combustion chamber. since burning the fuel-rich state, generation of the NO _X is reduced, moreover activates unburned mixture. Then, in the combustion process, gas such as flame and unburned air-fuel mixture is ejected into the main combustion chamber through the vertical groove provided in the protruding portion, and the passage area of the communication hole is rapidly expanded as the piston descends. Gases such as flames, unburned air-fuel mixture, etc. are blown out at a stretch along the vertical grooves from the combustion chamber to the main combustion chamber and along the vertical groove, which enhances the penetration and extends to a long distance and exists in the main combustion chamber. It promotes mixing with fresh air, shortens the combustion speed, improves thermal efficiency, and reduces the generation of HC, smoke, etc.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a subchamber engine according to the present invention will be described below with reference to the drawings. 1 is a schematic cross-sectional view showing an embodiment of a sub-chamber engine according to the present invention, FIG. 2 is a plan view showing a lower surface of a cylinder head of the sub-chamber engine of FIG. 1, and FIG. 3 is a sub-chamber engine of FIG. Sectional drawing which shows an example of the fuel injection nozzle arrange | positioned in a sub combustion chamber, FIG. 4 is explanatory drawing which shows the fuel spray state of the sub combustion chamber of FIG. 1, and FIG. 5 shows one Example of the protrusion part formed in the piston. It is a perspective view.

As shown in FIG. 1, this sub-chamber engine has a cylinder block 9 constituting a cylinder 6, a cylinder head 3 fixed to the cylinder block 9, an intake port 16 and an exhaust port formed in the cylinder head 3. 1
7, a sub-combustion chamber 2 formed in the cylinder head 3 and formed in the center on the central axis of the cylinder 6, a piston 8 reciprocating in the cylinder 6, a main combustion chamber 1 formed on the cylinder 6 side, and a sub-combustion It has a communication hole 10 which connects the chamber 2 and the main combustion chamber 1 and is formed in the cylinder head 3.
An intake valve is arranged in the intake port 16, and an exhaust valve is arranged in the exhaust port 17. Cylinder block 9
A cylinder liner having a cylinder 6 may be fitted into the hole formed in the cylinder block 9. At that time, in the cylinder block 9,
The cylinder 6 constitutes the cylinder 6.

In this sub-chamber engine, in particular, the piston 8 is made of, for example, a metal material such as aluminum or ceramics such as silicon nitride, and the piston top surface 15 of the piston 8 is located near the piston top dead center. Communication hole 10
A projecting portion 5 is formed so as to project into. This protrusion 5
The piston top surface 1 so that the flat surface 12 of the top surface is located at the boundary region between the communication hole 10 and the auxiliary combustion chamber 2 at the top dead center.
A slight protrusion from 5 is sufficient. The region of the piston top surface 15 that forms the protrusion 5 is preferably made of a material such as ceramics having a high heat resistance. It is preferable that the outer diameter of the projecting portion 5 is formed to a size that almost closes the passage area of the communication hole 10 in order to temporarily restrain the combustion in the auxiliary combustion chamber 2, that is, to extend the combustion period. Further, the flat surface 12 of the protruding portion 5 may be formed in a dish shape.

A fuel injection nozzle 4 having a single injection port 11 for injecting fuel in the direction of the communication hole 10 is arranged at the upper center of the auxiliary combustion chamber 2 formed in the cylinder head 3. The top surface of the protrusion 5 formed on the piston top surface 15 is formed as a flat surface 12, and the flat surface 12 forms a collision surface for colliding the liquid fuel injected from the fuel injection nozzle 4. Further, a plurality of grooves 18 are formed around the protrusion 5 so as to be spaced apart in the circumferential direction, and the sub combustion chamber 2 to the main combustion chamber 1 are formed.
Directs the ejection of gas such as flames and unburned air-fuel mixture to increase the ejection energy. The fuel injection nozzle 4
It is composed of an injection nozzle such as a pintle nozzle, and is attached to the sub combustion chamber 2 of the piston head 3 with the injection port 11 opened. Moreover, the fuel injected from the injection port 11 of the fuel injection nozzle 4 is in a liquid state. It is configured to collide with the center of the collision surface, that is, the flat surface 12.

Further, in this sub-chamber engine, a block, for example, a block in which a portion forming the communication hole 10 for communicating the main combustion chamber 1 and the sub-combustion chamber 2 is arranged in a hole portion 14 formed in the cylinder head 3, for example, Silicon nitride (Si ₃
It is preferable to form the connection hole forming block 7 made of a ceramic material such as N ₄ ) or a refractory metal material.
By forming the corner of the communication hole 10 sharp,
The intake air flowing into the auxiliary combustion chamber 2 from the main combustion chamber 1 through the communication hole 10 by the rise of the piston 8 in the compression stroke can form a strong squish flow.

Further, in this sub-chamber engine, the volume of the sub-combustion chamber 2 is 65% or less of the total volume of the sub-combustion chamber 2 and the main combustion chamber 1 at the compression end in terms of equivalence ratio control. Is preferred.

In this sub-chamber engine, the piston 8
The squish flow to the sub-combustion chamber 2 caused by the rise of the piston 8 rises when the piston 8 rises and the protrusion 5 rushes into the communication hole 10 and fuel is injected from the fuel injection nozzle 4 near the top dead center. The liquid fuel injected from the single injection port 11 of the fuel injection nozzle 4 has a flat surface 12 which is a collision surface of the protrusion 5.
Collide with and form a disc-shaped fuel thin film along the flat surface 12 and diffuse into the passage of the communication hole 10. Therefore, the squish flow of air to the sub-combustion chamber 2 and the disc-shaped fuel thin film intersect in an orthogonal state, the mixing of the air and the fuel is promoted, and then the sub-combustion chamber 2 is ignited and burned. The communication hole passage area of the communication hole 10 is set to 3 to 8%. A plurality of vertical grooves 18 are formed in the communication hole 10 around the protrusion 5 so as to be circumferentially spaced from each other.

When the protrusion 5 is inserted into the communication hole 10,
Although the communication hole 10 is slightly communicated with the groove 18 formed in the protrusion 5, the communication hole 10 is almost closed and the passage area of the communication hole 10 is reduced. Therefore, the combustion is temporarily restrained in the auxiliary combustion chamber 2. State, that is, the combustion period in the auxiliary combustion chamber 2 is lengthened, primary combustion is performed in a fuel rich state, and the generation of NO _X is suppressed,
By extending the combustion period in the sub combustion chamber 2, the unburned air-fuel mixture in the sub combustion chamber 2 is activated.

Therefore, when the piston 8 starts descending, the gases such as flames and unburned mixture activated in the sub combustion chamber 2 are first projected to the projecting portion 5 between the sub combustion chamber 2 and the main combustion chamber 1. The formed vertical grooves 18 communicate with each other, and gases such as flames and unburned air-fuel mixture are ejected into the main combustion chamber 1 through the vertical grooves 18, and as the piston 8 descends, the projecting portion 5 of the piston 8 comes out from the communication hole 10. As a result, the passage area of the communication hole 10 is suddenly expanded, and gas such as flame, unburned air-fuel mixture, etc., which has been activated along the vertical groove 18 while passing through the communication hole 10 from the auxiliary combustion chamber 2 to the main combustion chamber 1. It is ejected all at once to the main combustion chamber 1, and the penetration is enhanced to eject far. Gases such as flames and unburned air-fuel mixture, which are ejected from the sub-combustion chamber 2 through the communication holes 10 to the main combustion chamber 1 at high speed, promote rapid mixing with the fresh air in the main combustion chamber 1 and also burn. By lowering the temperature, the combustion speed is shortened, the secondary combustion is completed, the thermal efficiency is improved, and the generation of smoke is greatly reduced.

In particular, in this sub-chamber engine, the fuel injected at a low pressure from the nozzle 11 of the fuel injection nozzle 4 attached to the sub-combustion chamber 2 of the cylinder head 3 is a rod-shaped liquid fuel and is opposed to the piston 11 by a piston. It collides with the collision surface, that is, the flat surface 12 formed on the protrusion 5 of the top surface 15, and becomes a thin film-shaped disc in the region of the communication hole 10 and diffuses outward in the radial direction. On the other hand, as the piston 8 rises, the passage area of the communication hole 10 is narrowed by the projecting portion 5, and when the intake air is pushed into the sub combustion chamber 2, a strong annular pushing flow, that is, a squish flow is generated in the sub combustion chamber 2. , Into the auxiliary combustion chamber 2. Therefore, good mixing can be realized by intersecting the squish flow and the disk-shaped thin film fuel in an orthogonal state, and a good combustion state can be secured and combustion efficiency can be improved. That is, the liquid fuel injected from the injection port 11 of the fuel injection nozzle 4 collides with the flat surface 12 of the protrusion 5 and immediately spreads radially along the flat surface 12 to form a disk-shaped film. Spread to. Therefore, the fuel of the disc-shaped film intersects with the squish flow to the sub-combustion chamber 2 which is generated along with the ascending stroke of the piston 8 in a state orthogonal to each other, the mixing is promoted, and the ignition and combustion can be immediately performed.

[0025] Therefore, the pre-combustion chamber engine, it is possible to promote mixing of the fuel or mixture and air, the fuel is completely burned in good condition, it is possible to suppress HC, and occurrence of the NO _X runs combustion cycle in an optimum state to engine operating conditions, reduces the combustion period, improved thermal efficiency, fuel economy is improved, HC, and occurrence of NO _X can be suppressed.

[0026]

The subchamber engine according to the present invention is constructed as described above and has the following effects. That is, in this sub-chamber engine, a protrusion having a flat surface that reduces the flow passage area of the communication hole near the top dead center and projects into the communication hole is provided on the top surface of the piston, and the fuel is injected from the fuel injection nozzle. Since the fuel to be injected collides with the flat surface of the projecting portion, the liquid fuel injected from the fuel injection nozzle collides with the flat surface and diffuses into a disc shape in a uniform film shape in the communication hole region. Moreover, since the flow passage area is reduced by the protruding portion of the communication hole, the strong intake air flows from the main combustion chamber into the auxiliary combustion chamber as a squish flow.

Then, since the film-like fuel spray diffuses at a right angle to the squish flow, the fuel spray and the squish flow intersect each other to promote mixing, thereby promoting the formation of a favorable air-fuel mixture. Further, the flow passage area of the communication hole is reduced to an almost closed state in the vicinity of the top dead center by the protrusion provided on the top surface of the piston, the combustion period in the auxiliary combustion chamber is extended, and the auxiliary combustion is performed. since burning the fuel-rich conditions at room, generation of the NO _X is reduced, yet the flame said from the auxiliary combustion chamber unburned mixture activated to subsequent combustion stroke of the auxiliary combustion chamber to the main combustion chamber, Not Gas such as a fuel-air mixture is ejected at high speed through the communication hole, promoting mixing with the fresh air existing in the main combustion chamber, shortening the combustion period, and performing good secondary combustion, and improving thermal efficiency. Complete combustion reduces smoke generation.

Further, by setting the volume of the auxiliary combustion chamber to 65% or less of the total combustion chamber volume at the compression end, it is possible to control the preferable equivalence ratio.

Further, since the passage area of the communication hole is set to 3 to 8% and the vertical grooves are formed circumferentially spaced around the projecting portion, the main combustion chamber to the auxiliary combustion chamber is formed. It is possible to satisfactorily perform inflow of intake air and ejection of flames, unburned air-fuel mixture and the like from the auxiliary combustion chamber to the main combustion chamber.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of a sub-chamber engine according to the present invention.

FIG. 2 is a plan view showing a lower surface of a cylinder head of the sub-chamber engine of FIG.

3 is a cross-sectional view showing an example of a fuel injection nozzle arranged in a sub-combustion chamber of the sub-chamber engine of FIG.

FIG. 4 is an explanatory view showing a fuel spray state of the auxiliary combustion chamber of FIG.

FIG. 5 is a perspective view showing an embodiment of a protruding portion formed on a piston in this sub-chamber engine.

[Explanation of symbols]

 1 Main Combustion Chamber 2 Sub Combustion Chamber 3 Cylinder Head 4 Fuel Injection Nozzle 5 Projection 6 Cylinder 8 Piston 9 Cylinder Block 10 Communication Hole 11 Single Injection Port 12 Flat Surface 15 Piston Top Surface 18 Vertical Groove

Claims (3)

[Claims] 1. A sub combustion chamber formed in a cylinder head, a fuel injection nozzle for spraying fuel into the sub combustion chamber, a main combustion chamber formed on the cylinder side, a piston reciprocating in the cylinder, the sub combustion chamber and the sub combustion chamber. In a sub-chamber engine having a communication hole that communicates with the main combustion chamber, a protrusion provided with a flat surface that protrudes into the communication hole near the top dead center to reduce the flow passage area of the communication hole is provided on the top of the piston. A sub-chamber engine, characterized in that the fuel injected from the fuel injection nozzle is made to collide with the flat surface of the projecting portion and diffused in a film shape in the region near the communication hole. 2. The sub-chamber volume is 65 of the total combustion chamber volume at the compression end.
%, The auxiliary chamber engine according to claim 1, wherein 3. The passage area of the communication hole is set to 3 to 8%, and a plurality of vertical grooves are formed circumferentially spaced around the protrusion. The described sub-chamber engine.