JPH11280477A - Sub-chamber type engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To promote mixture of air with fuel and reduce residual combustible fuel by preventing interference between the fuel injected from a fuel injection nozzle and air flow introduced into a sub-chamber through communication holes. SOLUTION: Fuel is injected from a multiple nozzle holes 23 of a fuel injection nozzle 9, substantially perpendicularly against a side wall surface 16 extended between sub-chamber side openings 17 of communication holes 14 radially formed so as to be communicated with a main chamber. The fuel has no interference with air flow introduced into the sub-chamber 2 through the communication holes 14, until it is collided against the side wall surface 16. The fuel is atomized after being collided against the side wall surface, and mixed with air in the vicinity of the openings 17 of the communication holes 14, to form superrich air-fuel mixture. The air flow is regulated by a projection formed on a center of the bottom of the sub-chamber to generate longitudinal vortex.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sub-chamber engine having a main chamber, a sub-chamber, and a fuel injection nozzle for spraying fuel into the sub-chamber.

[0002]

2. Description of the Related Art As a diesel engine, a direct engine and a sub-chamber engine are generally well known. Direct-fire engines have been used more frequently in large vehicles such as trucks and buses because they have better fuel efficiency than sub-chamber engines. However, direct type engine, compared to Fukushitsushiki engine, many NO _X emissions, in recent years, NO _X
Regulations are becoming more stringent. Although NO _X reduction by such an exhaust gas recirculation apparatus that circulates a part of exhaust gas to the intake side (EGR system) is being considered, the occurrence of corrosion problems due to exhaust gas EGR, engine However, there is a problem that the durability and reliability are deteriorated. Therefore, in order to meet the stringent NO _X regulation, N
A sub-chamber engine with low _OX emission has been attracting attention. And improve the fuel efficiency of the sub-chamber engine,
Clearing the exhaust gas regulations without EGR is being considered.

As a diesel engine, for example, there is one disclosed in Japanese Patent Application Laid-Open No. 5-202755 (first conventional example). This diesel engine has a plurality of injection holes arranged in a circumferential direction directly above a combustion chamber of a piston, in which a piston having a combustion chamber with an open upper surface and a concave shape is fitted to a cylinder block so as to be vertically movable. A fuel injection nozzle is provided, and a groove-shaped auxiliary combustion chamber having an open top is formed on the upper surface of the piston, and the auxiliary combustion chamber is radially arranged so as to be located between the injection holes of the fuel injection nozzle in a plan view. In the intake stroke, swirl, which is a horizontal vortex, is given to air taken in from the outside and introduced into the combustion chamber, and intake air passing through the auxiliary combustion chamber is introduced into the combustion chamber as a longitudinal flow. The two airs collide in the combustion chamber to promote air flow in the combustion chamber to promote mixing of intake air and spray, thereby reducing the amount of black smoke generated. This sub-chamber type engine is called a vortex chamber type engine because swirl is given to intake air in a combustion chamber.

[0004] As a diesel engine, there is one disclosed in, for example, Japanese Patent Application Laid-Open No. 7-83055 (second conventional example). This diesel engine includes an injection nozzle provided in a cylinder head and a combustion chamber formed in a recess at the top of a piston, a rotating member rotatably fitted to the inner periphery of the combustion chamber, The rotating member is provided with a protruding wall and a recessed wall formed on the rotating member, and at the time of medium / low load operation, the rotating member is rotated so that the injection of fuel from the injection nozzle collides with the recessed wall, and the air to the spray is sprayed. By suppressing the introduction of NOx, the generation of NOx is reduced, and at the time of high load operation, the rotating member is rotated so that the spray collides with the protruding wall, so that the air introduction into the spray is activated, and NOx over the entire load area. And smoke are reduced.

The first prior art diesel engine forms a longitudinal flow of intake air and places an auxiliary combustion chamber between adjacent injection holes to promote mixing of intake air and spray. Has a large opening, and there is no clear distinction between the main room and the sub room, and no communication hole communicating the two rooms. Moreover, the longitudinal flow is intended for mixing with swirl generated in the combustion chamber, and does not take into account the diffusion of spray into the main chamber at the start of combustion.

The direct injection diesel engine of the second prior art is designed to promote the introduction of air into the spray by switching the unevenness in the combustion chamber where the injected fuel collides in accordance with the engine operating load. The combustion chamber-like surface in the piston is entirely open to the cylinder head side, and does not have a sub-chamber communicating with the cylinder-side main chamber through the communication hole. Further, it is needless to say that it is extremely difficult to rotate the combustion chamber, and it is not a realistic measure.

[0007] The fuel consumption of the sub-chamber type engine (vortex chamber type diesel engine) is deteriorated by first injecting fuel into the sub-chamber and igniting and burning in the sub-chamber. Since it passes through one communication hole extending in the direction inclined to the radial direction of the gas, and diffuses throughout the main chamber, the combustion period is long. Second, the throttle loss of the communication hole is large. Third, heat loss is large due to the large air flow and surface area in the sub-chamber. In order to solve such disadvantages of the conventional sub-chamber engine, a central sub-chamber engine has been proposed. In the central subchamber engine, the subchamber is located at the center of the cylinder, and a plurality of communication holes are radially arranged toward the outer periphery of the main chamber. Time to expand
/ 2, which is an increase in the contact area ratio.

As a central sub-chamber type engine, for example, there is one disclosed in Japanese Patent Application Laid-Open No. 7-332091 (third conventional example). In this central sub-chamber engine, the fuel injection nozzle is suspended from the center of the cylinder head, and a sub-combustion chamber (sub-chamber) is formed in the upper center of the piston as a rich mixture chamber.
The upper wall has a communication hole communicating with the main combustion chamber (main chamber). The fuel injection nozzle protrudes into the sub chamber near the top dead center of the piston. The fuel is injected toward a region higher than half the height in the axial direction with respect to the wall surface. As described above, a fuel-rich mixture is generated in the upper portion of the sub-chamber, and the rich mixture is quickly injected into the main chamber to shorten combustion feedback.

[0009]

By the way, in the sub-chamber engine, generally, the air flow is large in the sub-chamber, and the interference between the air flowing into the sub-chamber and the injected fuel is likely to occur. When interference occurs between the inflowing air and the injected fuel, the fuel is ignited at that moment, and most of the fuel injected thereafter stays in the sub-chamber, and after the combustion in the main chamber, incomplete combustion from the sub-chamber through the communication hole. Since the fuel gas flows out into the main chamber as it is, there is a problem that combustion gas including soot is discharged. In this way, if the above-mentioned interference between the inflow air and the injected fuel occurs, the spread of the fuel spray is hindered or the mixing area does not increase, so that the formation of the air-fuel mixture in the sub-chamber is not promoted, and the fuel consumption and the fuel consumption are reduced. There is a concern that smoke will worsen. Therefore, in a sub-chamber engine, fuel is injected into the sub-chamber without interfering with the air introduced through the communication hole, and the fuel that has collided with the wall of the sub-chamber to be atomized and diffused is mixed with the introduced air. If it is possible to spread the fuel spray and the mixing area,
It is considered that the formation of the air-fuel mixture in the sub-chamber is promoted.
Therefore, in a sub-chamber engine,
The fuel injected into the sub-chamber does not interfere with the air introduced through the communication hole, but collides with the wall of the sub-chamber to atomize and diffuse the fuel, and then mixes the fuel with the introduced air. There are problems to be solved.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and the fuel injected from a fuel injection nozzle does not interfere with the air introduced through a communication hole, and the sub chamber is not affected. It collides with the side wall surface of the fuel and diffuses it, and promotes mixing with the air introduced in the compression stroke, so that the spread of fuel spray is not hindered and the mixing area is widened, promoting the formation of air-fuel mixture in the sub-chamber. To provide a sub-chamber engine. In addition, by forming a vertical vortex flow in the sub-chamber with the air introduced into the sub-chamber, the mixture of the diffused spray fuel and the vertical vortex flow further promotes the formation of a rich mixture in the sub-chamber. It is an object of the present invention to provide a sub-chamber engine.

According to the present invention, there is provided a cylinder block constituting a cylinder, a cylinder head fixed to the cylinder block, a piston reciprocating in the cylinder, and a cylinder formed between a top surface of the piston and the cylinder head. A main chamber, a sub-chamber formed at the center of the piston, and a plurality of connections formed circumferentially spaced from a center of the sub-chamber to communicate the main chamber with the sub-chamber. In a sub-chamber type engine having a fuel injection nozzle having a hole and a multi-injection hole for injecting fuel into the sub-chamber, the multi-injection hole of the fuel injection nozzle is provided with a fuel injected from the multi-injection hole, respectively. Injects fuel toward the side wall surface of the sub-chamber extending between the adjacent sub-chamber openings of the communication hole in order to avoid interference with the flow of air introduced into the sub-chamber from the communication hole. For the auxiliary chamber type engine, characterized in that it is set to so that.

In this sub-chamber engine, a projection is formed at the center of the bottom of the sub-chamber to generate a vertical vortex in the air introduced from the communication hole during the compression stroke of the engine.

In the sub-chamber engine, the fuel injection nozzle injects fuel toward a projection formed on the side wall surface of the sub-chamber. Further, the end face of the convex portion has a smooth convex curved surface.

Further, in this sub-chamber engine, the communication holes are formed radially with respect to the center of the sub-chamber and at equal intervals in the circumferential direction.

Since the sub-chamber engine is constructed as described above, it operates as follows. That is, in the compression stroke, air contained in the cylinder between the top surface of the piston and the cylinder head is introduced into the sub-chamber through the communication hole. Since the communication hole is formed circumferentially spaced from the center of the sub-chamber, the air introduced into the sub-chamber is
It flows toward the center of the sub chamber. Usually, a plurality of communication holes communicating the main chamber and the sub-chamber are formed, and the sub-chamber is opened to the side wall surface. The multi-injection hole of the fuel injection nozzle is configured so that the fuel injection nozzle injects fuel toward the side wall surface extending between the sub-chamber-side openings in which the adjacent communication holes are opened in the sub-chamber. The fuel injected from each of the multiple injection holes impinges on the side wall between the openings and diffuses without interfering with the flow of air introduced through the communication holes. The diffused spray fuel is mixed with the air flowing in the sub-chamber to form an over-enriched mixture (an extremely rich mixture having a high fuel density).

When a projection is provided at the center of the bottom of the sub-chamber, the air introduced toward the center of the sub-chamber through the communication hole during the compression stroke of the engine is regulated and guided by the projection and is vertically guided. It becomes a vertical vortex swirling in the direction. The flow of air that blows up along the side wall surface of the sub chamber mixes with the spray fuel that has collided and diffused with the side wall surface, and the rich mixture is in the upper part of the sub chamber near the top of the piston, that is, the sub chamber of the communication hole. It is formed near the side opening. A relatively fuel-rich mixture and combustion gas are formed in the upper portion of the sub-chamber, and a relatively fuel-rich mixture and combustion gas are formed in the lower portion of the sub-chamber. The rich mixture mainly formed in the upper part of the sub-chamber is injected into the main chamber early through the communication hole during the expansion stroke, and the fuel combustion efficiency is improved. Therefore, the lower part of the sub-chamber does not accumulate the rich air-fuel mixture, and is an area where the fuel is low and the air is high. When a projection is formed on the side wall surface of the sub chamber where the fuel collides,
The fuel that collides with the projections diffuses around the projections and promotes the formation of a rich mixture. Further, when the end face of the convex portion is formed of a smooth convex curved surface, the colliding fuel spreads sideways and an rich mixture is efficiently formed.

In the compression stroke of the engine, the air in the main chamber compressed by the rise of the piston is introduced from the main chamber into the sub chamber through a plurality of communication holes. Fuel is sprayed from the fuel injection nozzle to the sub chamber near the end of the compression stroke. The fuel injected from the fuel injection nozzle collides with the side wall surface between the sub-chamber-side openings of the communication holes, diffuses in the vicinity thereof, mixes with the flowing air, and becomes a rich mixture. Next, when the mixture is ignited, the engine shifts to an expansion stroke. In the expansion stroke, the flame containing the rich mixture present near the opening of the communication hole on the sub-chamber side passes through the communication hole and blows out to the main chamber. The flame mixes with the air in a short period of time and mixes with the air in a short period of time, rapidly dilutes and burns, and performs rapid diffusion combustion in the main chamber to shorten the combustion period.
O _X emissions is small, the generation of particulates or soot is reduced, so that the suppressed to a low fuel consumption.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a sub-chamber engine according to the present invention will be described below with reference to the drawings. FIG.
2 shows a sub-chamber member used in the first embodiment of the sub-chamber engine according to the present invention, and corresponds to a cross-sectional view taken along a plane indicated by line BB in FIG. FIG. 2 is a sectional view of a sub-chamber type engine using the sub-chamber member shown in FIG.
FIG. 3 is a cross-sectional view taken along a plane corresponding to the plane indicated by line AA in FIG. In the sub-chamber engine of the first embodiment, the intake / exhaust port and the intake / exhaust valve are not shown in order to explain only the main part, but they are provided similarly to a normal diesel engine.

The sub-chamber type engine shown in FIGS. 1 and 2 has, for example, a cylinder head 5 fixed to a cylinder block 6, and the cylinder block 6 has a number of cylinder bores (not shown) corresponding to the number of cylinders of the engine. ) Is formed, and a cylinder liner 7 constituting the cylinder 3 is formed in the cylinder bore.
Are fitted. The piston 4 is incorporated in the cylinder 3 formed by the cylinder liner 7 so as to reciprocate. The main chamber 1 is formed between the lower surface 12 of the cylinder head 5 and the top surface 11 of the piston 4. Also,
The piston 4 is formed with a cavity 8 in which a sub-chamber member 13 constituting the sub-chamber 2 is disposed. The fuel injection nozzle 9 is disposed on the cylinder head 5 so as to inject fuel into the sub-chamber 2. The sub-chamber member 13 is made of a heat-resistant material, and its outer periphery has a heat-shielding structure. The sub-chamber 2 has a substantially circular side wall surface 16 when viewed in a cross section.

The sub-chamber member 13 has a communication hole 14 for communicating the main chamber 1 with the sub-chamber 2 and a nozzle insertion hole 10 for allowing the fuel injection nozzle 9 to protrude into the sub-chamber 2 near the top dead center of the piston.
Are formed. Fuel injection nozzle 9 and sub chamber member 13
The sub-chamber 2 is arranged substantially at the center with the cylinder center axis 15 as the center. The fuel injection nozzle 9 is provided with multiple injection holes 23 for injecting fuel in a substantially horizontal direction, and the number of the multiple injection holes 23 is eight provided at equal angles around the cylinder center axis 15. .

A communication hole 14 for communicating the main chamber 1 with the sub-chamber 2
At the upper shoulder of the sub-chamber member 13, around the cylinder center axis 15, preferably at equal intervals.
Are formed radially toward the outer peripheral direction of. That is, the axis of the communication hole 14 is inclined upward from the cylinder center axis 15 toward the lower surface 12 of the cylinder head 5.
The communication holes 14 are provided by the number corresponding to the multiple injection holes 23 of the fuel injection nozzle 9. Further, the communication hole 14 is provided in the sub-chamber 2.
The sub-chamber side opening 17 is formed on the side wall surface 16 of the sub-chamber.

The fuel injection nozzle 9 is connected to the communication hole 14 of the sub-chamber 2.
Fuel is injected toward the side wall surface 16 between them. The fuel sprayed from the fuel injection nozzle 9 collides with the side wall surface 16 substantially perpendicularly. The fuel impinging on the side wall surface 16 is atomized and diffuses in a concave shape as seen in the cross section of FIG. The atomized fuel is diffused particularly near the sub-chamber-side opening 17 in which the communication hole 14 opens on the side wall surface 16 of the sub-chamber 2.

In the sub-chamber engine, the air introduced through the communication hole 14 during the compression stroke of the engine forms a vertical vortex 22 in the sub-chamber 2 as described below. The sub-chamber member 13 is formed with a protrusion 20 projecting from the bottom surface 21 of the sub-chamber 2 toward the fuel injection nozzle 9. The air that has been sucked into the cylinder 3 between the top surface 11 of the piston 4 and the lower surface 12 of the cylinder head 5 rises during the compression stroke of the engine, causing the combustion nozzle 9 to enter the nozzle insertion hole 10. After that, the communication hole 1
4, is introduced into the sub-chamber 2. The air introduced into the sub-chamber 2 is inclined by the inclination of the communication hole 14 so that
, And is guided and regulated by the projection 20 to form a vertical vortex 22 in the sub chamber 2. After the air flow of the vertical vortex 22 flows outward along the bottom surface 21 of the sub chamber 2,
Sub-chamber side opening 1 of communication hole 14 along side wall surface 16 of sub-chamber 2
It rises to around 7. The fuel that has collided with the side wall surface 16 of the sub-chamber 2 and diffused therein is connected with the air of the vertical vortex 22 rising from below the sub-chamber 2 so as to be caught from the back.
Is promoted in the vicinity of. Therefore, an area rich in fuel, that is, an area of an extremely rich air-fuel mixture having a large fuel density is formed near the sub-chamber side opening 17 as described below. On the other hand, in the vicinity of the bottom surface 21 of the sub-chamber 2 far from the communication hole 14, a region with a relatively large amount of air containing a relatively small amount of fuel and a region of an air-fuel mixture with a small fuel density and almost only air are formed.

Next, the operation of the sub-chamber engine will be described. In the compression stroke of the engine, the air in the main chamber 1 compressed by the rise of the piston 4 is sent to the sub-chamber 2 through a plurality of communication holes 14, and a vertical vortex 22 is formed in the sub-chamber 2 by the projection 20. I do. At the end of the compression stroke, the fuel injection nozzle 9 protrudes from the nozzle insertion hole 10 of the sub-chamber member 13 into the sub-chamber 2, and fuel is injected into the sub-chamber 2 from the injection hole 23 of the fuel injection nozzle 9. The fuel injected from the fuel injection nozzle 9 is supplied to the sub-chamber side opening 17 of the communication hole 14 adjacent to each other.
The fuel is injected substantially perpendicularly to the side wall surface 16 extending therebetween, and diffuses around the side wall surface 16 by colliding with the side wall surface 16. Forming Qi.

Next, when the mixture is ignited, the engine shifts to an expansion stroke. In the expansion stroke, the flame containing the rich air-fuel mixture exists in the upper part of the sub-chamber 2 near the communication hole 14, so that the flame smoothly flows into the communication hole 14, passes through the communication hole 14, and passes through the main chamber 1. Squirt to The air-fuel mixture existing in the area near the bottom surface 21 of the sub-chamber 2 is a fuel-lean air-fuel mixture, and the flame containing the rich air-fuel mixture is injected into the main chamber 1 through the communication hole 14. It works to help you. The flame containing a rich air-fuel mixture ejected from the communication hole 14 flows in the main chamber 1 and mixes with the air in the main chamber 1. Then, the flame is mixed with the air to the inside in a short period of time to be diluted and diffused in the main chamber 1. Thus, fuel is so starts relatively burned at low temperatures in the rich Do mixture state emissions of the NO _X is reduced, also, the fuel component is quickly contact hole 14 main chamber 1 through the The fuel is also improved because the fuel is jetted.

As described above, in this sub-chamber engine, the air introduced into the sub-chamber 2 forms the vertical vortex 22 and the side wall surface 16
In the early stage of combustion, the fuel atomized and diffused and mixed with the fuel diffused and mixed in the vicinity of the communication hole 14 to form an rich mixture.
The fuel is burned in the state of a rich mixture of fuel, and then the mixture is rapidly diffused into the main chamber 1 through the communication hole 14 from this state and burns at once, so that not only NO _X but also diesel particulates and soot are burned. Can also be reduced at the same time. In the above embodiment, the communication hole 14 is formed so as to be directed toward the center of the sub-chamber 2. However, the communication hole 14 is slightly offset toward the center of the sub-chamber 2 so that a slight swirl is formed in the sub-chamber 2. May be formed.

Next, a second embodiment of the sub-chamber engine according to the present invention will be described with reference to FIGS. FIG. 3 is a cross-sectional view showing a sub-chamber member used in a second embodiment of the sub-chamber engine according to the present invention, taken along a plane indicated by line DD in FIG. 4 is a cross-sectional view of a sub-chamber engine using the sub-chamber member shown in FIG. 3, and is a cross-sectional view taken along a plane corresponding to a plane indicated by line CC in FIG. 3 and 4, components and parts having the same functions as in the previous embodiment are denoted by the same reference numerals, and redundant description of those parts and parts will be omitted.

This embodiment is different from the first embodiment in that the fuel injected from the fuel injection nozzle 9 collides with the projection on the side wall surface 16 of the sub-chamber 2. That is,
On the side wall surface 16 between the communication holes 14 adjacent to each other, a projection 18 of the sub-chamber member 13 is formed so as to protrude with a step. The end surface 19 of the convex portion 18 is, for example, a part of a cylindrical surface,
It has a smooth convex curved surface like an R surface. The fuel injection nozzle 9 injects fuel toward the projection 18 formed between the communication holes 14. The fuel sprayed from the fuel injection nozzle 9 collides with the end face 19 of the projection 18 substantially perpendicularly. Since the end face 19 flows through the end face 19 with the component of the direction of movement of the colliding fuel, the fuel is further promoted to diffuse around the end face 19, particularly near the sub-chamber-side opening 17 where the communication hole 14 is opened. . Since the adjacent convex portions 18 form a groove-shaped space therebetween, the vertical vortex 22 generated by the projecting portions 20 guides the vertical vortex 22 to rise along the side wall surface 16 between the convex portions 18. Also works. Therefore, the fuel should be
By colliding with the convex portion 18 of the sixth, the diffusion of the fuel atomized by the collision and the mixing with the air rising as the vertical vortex 22 are further promoted.

[0029]

As described above, in the sub-chamber engine according to the present invention, the communication hole connecting the main chamber and the sub-chamber is formed in the circumferential direction with respect to the center of the sub-chamber, and the fuel injection nozzle is provided. Has a structure in which the communication hole is injected toward the side wall surface between the openings that open to the sub-chamber, so that the injected fuel does not interfere with the inflow air introduced through the communication hole, and It collides with the wall and atomizes and diffuses. The atomized fuel is introduced toward the center of the sub-chamber and is quickly mixed with the air flowing in the sub-chamber, so that the rich mixture (extremely rich mixture with a large fuel density) can be mixed with a wide mixing area and a high mixing speed. Can be formed.

When the projection is provided at the center of the bottom of the sub-chamber, the air introduced toward the center of the sub-chamber through the communication hole during the compression stroke of the engine collides with the projection and vertically swirls in the vertical direction. Form a vortex. The flow of air that blows up along the side wall of the sub-chamber impinges on the side wall and atomizes and mixes with the diffused fuel, forming a rich mixture at the top of the sub-chamber near the communication hole. it can. The rich mixture is
During the expansion stroke, the fuel is injected into the main chamber early through the communication hole, and the fuel combustion efficiency is improved. Furthermore, if the side wall surface on which the fuel in the sub-chamber collides is a convex portion, the fuel colliding with the convex portion easily flows around the convex portion and is easily atomized. If the end face of the convex portion is formed of a smooth convex curved surface, the colliding fuel spreads to the side and an rich mixture is efficiently formed.

In the lower part of the sub-chamber, a relatively fuel-lean mixture and combustion gas are formed, so that the fuel components remaining in the sub-chamber can be reduced. When the air-fuel mixture in the vicinity of the communication hole is ignited, the engine shifts to the expansion stroke, and the mixture containing the air-fuel mixture in the lower part of the subchamber and the combustion gas is subjected to the action of the flame, the flame containing the rich air-fuel mixture. Through the main chamber. Flame ejected prematurely main chamber, and the rapid diffusion combustion in the main chamber to shorten the combustion period, emit less NO _X, generation of particulates or soot is reduced, to be suppressed to a low fuel consumption Become. That is, when the fuel injected from the multiple injection nozzles of the combustion injection nozzle interferes with the air introduced through the communication holes, the fuel is ignited there and the injected fuel later flows out into the main chamber. Can be prevented.

A diesel engine that forms a vertical flow in intake air by passing through a portion serving as an auxiliary combustion chamber, positions the auxiliary combustion chamber between adjacent injection holes, and promotes mixing of intake air and spray is a first conventional diesel engine. As seen in the example, the first conventional example is
The combustion chamber is divided into a main chamber and a sub-chamber, and the two chambers are not connected by a communication hole. Instead, the horizontal vortex (swirl) and the vertical vortex in the combustion chamber are mixed. Further, the second prior art discloses a structure in which a wall surface of a combustion chamber to which combustion injection is directed during a high-load operation is convex, but this engine switches the unevenness of the combustion chamber according to the load of the engine. The present invention does not consider the air flowing into the sub chamber or the flow of the combustion gas to the main chamber after ignition as in the present invention. On the other hand, in the sub-chamber engine according to the present invention, the sub-chamber is basically closed by the combustion injection nozzle entering the sub-chamber, and the intake air is introduced into the sub-chamber through the communication hole. In the sub-chamber, a horizontal eddy current hardly occurs. Until the fuel injected into the sub-chamber collides with the wall of the sub-chamber, it is prevented as much as possible from being disturbed by the flow of air introduced into the sub-chamber, and after colliding with the convex wall surface of the sub-chamber. The air diffuses in a concave shape and mixes with the intake air introduced into the through hole for the first time, preferably in the form of a vertical vortex, so that the mixing speed is high, the mixing area is widened and the mixing is promoted. Then, the ignited combustion gas is collected in the vicinity of the communication hole, and is quickly discharged into the main chamber above the piston. Then, the rich mixture is mixed with air and rapidly diluted, so that it can be burned at once, and the emission of NO _X , particulates, and soot is smaller than conventional ones, and the fuel consumption is reduced. Can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a sub-chamber member used in a first embodiment of a sub-chamber engine according to the present invention, which is cut along a plane indicated by line BB in FIG.

FIG. 2 is a cross-sectional view of the sub-chamber engine using the sub-chamber member shown in FIG. 1, taken along a plane corresponding to the plane indicated by line AA in FIG.

FIG. 3 is a sectional view showing a sub-chamber member used in a second embodiment of the sub-chamber engine according to the present invention, which is cut along a plane indicated by line DD in FIG.

FIG. 4 is a cross-sectional view of the sub-chamber engine using the sub-chamber member shown in FIG. 3, taken along a plane corresponding to a plane indicated by line CC in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main chamber 2 Sub chamber 3 Cylinder 4 Piston 5 Cylinder head 6 Cylinder block 9 Fuel injection nozzle 11 Top surface 12 Lower surface 13 Sub chamber member 14 Communication hole 15 Cylinder central axis 16 Side wall surface 17 Sub chamber side opening 18 Convex part 19 Top surface Reference Signs List 20 Projection 21 Bottom surface 22 Vertical vortex 23 Injection hole

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenro Nakajima 8 Tsuchiya, Fujisawa City, Kanagawa Prefecture Isuzu Ceramics Laboratory Co., Ltd.

Claims (5)

[Claims] 1. A cylinder block constituting a cylinder,
A cylinder head fixed to the cylinder block, a piston reciprocating in the cylinder, a main chamber formed in the cylinder between a top surface of the piston and the cylinder head, and a central portion formed in the piston. A sub-chamber, a plurality of communication holes formed circumferentially spaced from a center of the sub-chamber to communicate the main chamber and the sub-chamber, and a multi-injection hole for injecting fuel into the sub-chamber. In the sub-chamber engine provided with the fuel injection nozzle having a fuel injection nozzle, the multi-injection hole of the fuel injection nozzle is provided for controlling a flow of air injected from the multi-injection hole into the sub-chamber through the communication hole. A sub-chamber engine, wherein fuel is injected toward a side wall surface of the sub-chamber extending between sub-chamber side openings of the adjacent communication holes in order to avoid interference. 2. The projection according to claim 1, wherein a vertical vortex is generated in the air introduced from the communication hole in a compression stroke of the engine at a center of a bottom of the sub-chamber. Sub-chamber engine. 3. The sub-chamber engine according to claim 1, wherein the fuel injection nozzle injects fuel toward a convex portion formed on the side wall surface of the sub-chamber. 4. The sub-chamber engine according to claim 3, wherein a top surface of the convex portion has a smooth convex curved surface. 5. The communication device according to claim 1, wherein the communication holes are formed radially at equal intervals in a circumferential direction with respect to a center of the sub-chamber. A sub-chamber engine according to the above.