JPH1150846A - Auxiliary-chamber type engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce discharge of NOx, particulates and soot and improve fuel consumption by making thick air-fuel mixture jetted from an auxiliary-chamber collide with air in a main chamber, mixing it with air into the interior of the flame inside the main chamber within a short time, leaning it at a stretch, and making a quick diffusion combustion. SOLUTION: This auxiliary-chamber type engine is constructed by forming the opening 21 of a first connection hole 13 in the position where atomized fuel from a fuel injection nozzle 9 reaches and the opening 22 of a second connecting hole 14 in the position where atomized fuel from a fuel injection nozzle 9 does not reach, while axes 18, 19 of the first and the second connecting holes 13, 14 are formed to cross a main chamber 1. Thick air-fuel mixture jetted from the first connecting hole 13 into the main chamber 1 collides with air jetted from the second connecting hole 14 into the main chamber 1 inside the main chamber 1 and the air-fuel mixture is leaned at a stretch.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention 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. About the engine.

[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, NO _X emissions many years, under stricter NO _X regulations, fuel economy benefits has become relatively small. 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. In order to meet the stringent NO _X regulations, NO _X emissions less pre-combustion chamber engine has come to attract attention. And
It has been studied to improve the fuel efficiency of the sub-chamber engine and to meet the exhaust gas regulations without EGR.

[0003] As a sub-chamber engine, for example, there is one disclosed in Japanese Patent Application Laid-Open No. Hei 6-241048 (first conventional example). This sub-chamber type engine is also called a swirl chamber type diesel engine and has a sub-combustion chamber (sub-chamber) provided in the cylinder head. Two sub-chamber injection holes are provided in the sub-chamber mouthpiece. Each sub-chamber nozzle is arranged such that an extension of the axis of the sub-chamber nozzle intersects the sub-chamber center line at a point on the cylinder center line side on a plane including the sub-chamber center line and the cylinder center line. It is a thing. With such a configuration, the two gas jets flowing into the main chamber are collided and synthesized, and the jet penetration is improved and the turbulence is increased, so that the mixing and combustion of the unburned gas and the air are promoted. .

There is another sub-chamber type engine disclosed in, for example, Japanese Utility Model Laid-Open No. 57-103327 (second conventional example). This sub-chamber engine also
Similar to the first conventional example, it is also called a vortex chamber type diesel engine, and has a sub-combustion chamber (sub-chamber) provided in a cylinder head. This sub-chamber type engine has a main communication hole for communicating the swirl chamber (sub-chamber) with the main chamber, and a sub-communication connecting the sub-chamber and the main chamber on or near the center line of the fuel injection valve. A hole is formed, and the passage cross-sectional area of the sub-communication hole is formed in a tapered shape gradually increasing from the sub-chamber-side opening toward the main chamber-side opening. Is directly injected into the main chamber. In this sub-chamber engine, part of the fuel in the atomized state is directly supplied to the main chamber through the sub communication hole, so that combustion can be generated not only in the sub-chamber but also in the main chamber. It will be done slowly. Further, since the sub communication hole is formed in a tapered shape, the amount of air flowing from the main chamber to the sub chamber is reduced, and the strength of the vortex in the sub chamber can be maintained. Further, since the fuel spray spreads in accordance with the tapered cross section of the passage, it is possible to prevent carbon from adhering to the wall surface of the sub communication hole.

[0005] In these sub-chamber engines, the communication hole communicating the main chamber and the sub-chamber is provided in one portion of the outer peripheral portion of the cylinder and has a small diameter, so that a throttle loss due to the communication hole occurs. , Therefore lowering the engine output,
In addition, the distance that the jet must reach in the main chamber becomes longer, mixing with air in the main chamber becomes insufficient, and HC,
May cause smoke. Further, if the area of the passage of the communication hole is reduced in order to promote mixing in the main chamber, the vortex in the sub-chamber becomes too strong, and the combustion in the sub-chamber deteriorates.

[0006] The cause of the deterioration of the fuel efficiency of the conventional sub-chamber type engine (vortex chamber type diesel engine) is as follows. First, fuel is injected into the sub-chamber and ignited and burned in the sub-chamber. And then diffuses throughout the main chamber, resulting in a long combustion period, secondly, a large throttle loss in the communication hole, and thirdly, heat dissipation due to the large air flow and surface area in the sub-chamber. It is big. 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. Is reduced to 1/2, and the contact area ratio is increased.

As a central sub-chamber type engine, for example, there is one disclosed in Japanese Patent Application Laid-Open No. 7-127456 (third conventional example). In this central sub-chamber engine, the fuel injection nozzle is suspended from the center of the cylinder head, and a large chamber, which is a rich mixture chamber, and a small chamber, which is an ignition chamber, are arranged in two stages in the upper center of the piston. The combustion chamber (subchamber) is composed of a large chamber with a communication hole communicating with the main combustion chamber (main chamber) in the upper wall. The spray is controlled so as to be 1 or less, and is ignited first in the small chamber, and the combustion gas that has become a flame blows out the unburned rich air-fuel mixture in the large chamber into the main chamber through the communication hole. The aim is to reduce fuel consumption and thereby improve fuel efficiency.

[0008]

By the way, in order to improve the fuel efficiency of a diesel engine, as can be seen from the third conventional example, the fuel is quickly injected into the main chamber where a large amount of air is present to shorten the combustion period. Need to be done. on the other hand,
In order to suppress the generation of the NO _X forms a mixture of homogenous and rich, is burned, by diffusing in a short time,
It is necessary to perform secondary combustion in a lean state. In the sub-chamber type engine, how to realize it in order to satisfy these demands has become an issue.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems, and a flame containing a rich air-fuel mixture and a lean fuel air collide in a main chamber to form a fuel inside the flame. short period of time is mixed with air to, causes rapid spread by once diluted, the fuel component by quickly ejected into the main chamber and providing a good pre-combustion chamber engine of small fuel-NO _X emissions is there.

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 sub-chamber engine having a main chamber, a sub-chamber formed at the center of the piston, a communication hole communicating the main chamber with the sub-chamber, and a fuel injection nozzle for spraying fuel into the sub-chamber. , The communication hole is a first communication hole and a second communication hole.
The sub-chamber side opening of the first communication hole is formed at a position where the fuel sprayed from the fuel injection nozzle reaches, and the sub-chamber side opening of the second communication hole is formed from the fuel injection nozzle. Formed at locations where the sprayed fuel does not reach,
The present invention relates to a sub-chamber engine, wherein an axis of the first communication hole and an axis of the second communication hole cross each other in the main chamber.

In this sub-chamber engine, as described above, the sub-chamber side opening of the first communication hole is formed at a position where the fuel sprayed from the fuel injection nozzle reaches.
The fuel sprayed into the sub-chamber collides with the wall near the sub-chamber side opening of the first communication hole, and becomes a rich mixture (an extremely rich mixture with a large fuel density). Therefore,
The vicinity of the sub-chamber side opening of the first communication hole is an area where fuel is rich. On the other hand, since the sub-chamber-side opening of the second communication hole is formed at a position where the fuel sprayed from the fuel injection nozzle does not reach, the vicinity of the sub-chamber-side opening of the second communication hole is extremely low in fuel density. This results in a thin mixture or air region.

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 is sprayed in the vicinity of the opening of the first communication hole on the side of the sub-chamber, and becomes an air-fuel mixture. Next, when the mixture is ignited, the engine shifts to an expansion stroke. In the expansion stroke, the flame containing the rich mixture passes through the first communication hole and blows out to the main chamber, while the air passes through the second communication hole and blows out to the main chamber. Since the first communication hole and the second communication hole are formed so that their respective axes intersect each other in the main chamber, the flame containing the rich air-fuel mixture ejected from the first communication hole and the second communication hole are formed. The air ejected from the holes collide in the main chamber, and the mixing of the two due to turbulence is promoted. Then, the flame is mixed with air in a short period of time and burns rapidly after being diluted and burned in the main chamber, and the combustion period is shortened by rapid diffusion combustion in the main chamber.
The emission of NO _X is small, the generation of particulates and soot is reduced, and an engine with good fuel efficiency is provided.

According to a second aspect of the present invention, in the sub-chamber engine, the first communication hole has a recess formed in or near the sub-chamber side opening, and the fuel injection is formed in the recess. The fuel sprayed from the nozzle collides. The recesses serve to promote the formation of a rich mixture and to facilitate the flow of the mixture into the first communication hole.

In this sub-chamber type engine, the sub-chamber is composed of two chambers which are arranged vertically and communicate with each other, the first communication hole is opened in the upper chamber, and the lower chamber is opened. Has the second communication hole opened. Fuel is sprayed from the fuel injection nozzle into the upper chamber,
The upper chamber is an area rich in fuel and the lower chamber is not fuel-sprayed from the fuel injection nozzle, so the lower chamber is an area rich in fuel and low in air. Further, by providing a throttle between the upper chamber and the lower chamber, a fuel-rich mixture and a combustion gas are formed in the upper chamber, and a fuel-lean mixture and a combustion gas are formed in the lower chamber. Combustion gas is surely formed.

The sub-chamber is composed of two chambers which are arranged vertically and communicate with each other, the first communication hole is opened in the upper chamber, and the second communication hole is opened in the lower chamber. Is opened, a fuel-rich mixture and a combustion gas are ejected from the first communication hole, and a fuel-lean mixture and a combustion gas are ejected from the second communication hole. By colliding in the main chamber, the secondary combustion can be completed in a short period of time by rapid mixing in the main chamber, and fuel efficiency can be improved.

Further, in this sub-chamber engine, the diameter of the first communication hole is different from the diameter of the second communication hole. Since the lengths of the first communication hole and the second communication hole are different, the means of making the diameters different is optimal for the time required for mixing an air-rich mixture with air and for the time required for dilution. This is particularly effective as a means for adjusting the adjustment.

[0017]

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.
1 is a sectional view showing an embodiment of a sub-chamber engine according to the present invention, and FIG. 2 is a plan view of a piston of the sub-chamber engine shown in FIG. In this sub-chamber engine, the intake and exhaust ports and intake and exhaust valves are not shown in order to explain only the main parts, but they are provided similarly to a normal diesel engine.

This sub-chamber engine 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 fitted with a cylinder liner 7 constituting the cylinder 3. 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. The piston 4 is formed with a cavity 8 constituting the sub-chamber 2.
The sub chamber 2 is formed substantially at the center of the cylinder center axis 15. The fuel injection nozzle 9 is disposed on the cylinder head 5 so as to inject fuel into the sub-chamber 2.

The piston 4 has communication holes 13 and 14 for communicating the main chamber 1 and the sub-chamber 2 with the piston top 16 and the fuel injection nozzle 9 to protrude into the sub-chamber 2 near the piston top dead center. Nozzle insertion hole 10 is formed. The fuel injection nozzle 9 has an injection hole 23 for injecting fuel in a substantially horizontal direction.
And six injection holes 23 are provided at equal angles.

A communication hole 13 for communicating between the main chamber 1 and the sub-chamber 2;
14 is a pair of first communication holes 1 as shown in FIG.
3 and the second communication hole 14 for a total of six pairs of communication holes 1
3 and 14 are formed radially toward the outer peripheral direction of the piston 4 at intervals around the cylinder center axis 15. The first communication holes 13 and the second communication holes 14 are provided by the number of injection holes 23 of the fuel injection nozzle 9 respectively. The sub-chamber-side opening 21 of the first communication hole 13 is formed at a position where the fuel sprayed from the fuel injection nozzle 9 reaches, and the sub-chamber-side opening 22 of the second communication hole 14 is formed by the fuel sprayed from the fuel injection nozzle 9. Is formed at a position where it does not reach. A recess 20 is formed near the sub-chamber-side opening 21 of the first communication hole 13. The fuel injection nozzle 9 injects fuel toward a recess 20 formed near the sub-chamber-side opening 21 of the first communication hole 13, and the fuel collides with the recess 20 to form an rich mixture. You. Therefore, in the vicinity of the sub-chamber-side opening 21 of the first communication hole 13, an area where fuel is excessively rich, that is, an area where an extremely rich air-fuel mixture is high in fuel density is formed. On the other hand, in the vicinity of the sub-chamber-side opening 22 of the second communication hole 14, a region of air, that is, a region of a large amount of air with a relatively small amount of fuel, or a mixture with a small fuel density and almost almost only air. A region of qi is formed.

This sub-chamber engine has six sets of communication holes 1
3 and 14 are provided, and each pair of the first communication hole 13 and the second communication hole 14 is provided with a respective one of the axes 18 and 19.
Are formed so as to cross each other in the main chamber 1. For this reason, the rich air-fuel mixture ejected into the main chamber 1 through the first communication hole 13 and the rich air-fuel mixture passing through the second communication hole 14
And air has been ejected into the inner can may collide with the main chamber within 1, is promoted mixed in the main chamber 1, the combustion is completed in short, it can be reduced NO _X, particulate, the generation of soot, Fuel efficiency can be improved.

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 pressure-fed to the sub-chamber 2 through the plurality of communication holes 13 and 14. At the end of the compression stroke, the fuel injection nozzle 9 is
The fuel enters the sub chamber 2 from 0, and the fuel is sprayed into the sub chamber 2 from the fuel injection nozzle 9. The fuel injected from the fuel injection nozzle 9 is sprayed toward a recess 20 formed in the vicinity of the sub-chamber-side opening 21 of the first communication hole 13, and collides with the recess 20 to become a rich mixture. . Then, when the mixture is ignited, the engine transitions to an expansion stroke. In the expansion stroke, the flame containing the rich air-fuel mixture smoothly flows into the first communication hole 13 due to the presence of the recess 20, and the first communication hole 13
, And blows out to the main chamber 1 while air blows out to the main chamber 1 through the second communication hole 14. Since the first communication hole 13 and the second communication hole 14 are formed so that their respective axes 18 and 19 intersect each other in the main chamber 1, the first communication hole 13 and the second communication hole 14 contain a rich air-fuel mixture ejected from the first communication hole 13. The air flame and the air ejected from the second communication hole 14 collide in the main chamber 1, and the mixing of the two due to turbulence is promoted. Then, the flame mixes with the air to the inside in a short period of time, rapidly dilutes, and can rapidly diffuse in the main chamber 1. Therefore, NO _X
Emissions are reduced. Further, the fuel component passes through the plurality of first communication holes 13 and the second communication holes 14 and is quickly ejected into the main chamber 1, so that fuel efficiency is also improved.

As described above, this sub-chamber engine burns in the state of a fuel-rich mixture at the beginning of combustion,
Thereafter, the air-fuel mixture in this state was rapidly dilute state rapidly spreading, since once burned, as well as NO _X,
Diesel particulates and soot can be reduced at the same time.

Next, another embodiment of the sub-chamber engine according to the present invention will be described with reference to FIG. This embodiment is
Compared with the embodiment shown in FIG. 1, the sub-chamber has the same configuration except that the shape of the sub-chamber is different and the arrangement of the first communication hole and the second communication hole is accordingly different. Are denoted by the same reference numerals, and redundant description is omitted.

In the sub-chamber type engine of this embodiment, the sub-chamber 2 formed in the piston 4 is composed of a large chamber 24 and a small chamber 25 which are arranged vertically and communicate with each other. At the boundary between the large chamber 24 and the small chamber 25, a throttle part 26 projecting inward is formed. The upper large chamber 24 communicates with the main chamber 1 via the first communication hole 13. Small room 25 on the lower side
Communicates with the main chamber 1 through the second communication hole 14. The fuel injection nozzle 9 sprays fuel on a wall surface near the lower side of the sub-chamber-side opening 21 of the first communication hole 13. Then, the sprayed fuel collides with the wall surface of the large chamber 24 and becomes an rich mixture. Therefore, the large chamber 24 is an area where fuel is rich. On the other hand, since the sub-chamber-side opening 22 of the second communication hole 14 is formed in a position where the fuel sprayed from the fuel injection nozzle 9 does not reach, that is, in the small chamber 25, the small chamber 25 has relatively little fuel. This is an area with a lot of air. Since the throttle portion 26 is formed at the boundary between the large chamber 24 and the small chamber 25, the fuel sprayed into the large chamber 24 is supplied to the second communication hole 14 formed in the small chamber 25.
Does not flow toward the sub-chamber side opening 22.

The first communication hole 13 and the second communication hole 14 are formed so that their respective axes 18 and 19 intersect in the main chamber 1 and, as shown in FIG.
The angles of the respective axes 18 and 19 with respect to are different. Therefore, the air sprayed from the second communication hole 14 collides obliquely from below with the flow of the rich air-fuel mixture sprayed from the first communication hole 13. A strong vortex is generated to further promote mixing due to turbulence.

Since the second communication hole 14 is longer than the first communication hole 13, the diameter of the second communication hole 14 is changed to the first communication hole 13.
Smaller than the caliber. Therefore, the second communication hole 1
The speed of the air passing through 4 becomes very high, and the rich air-fuel mixture can be rapidly diluted with high-speed air and rapidly diffused into the main chamber. By appropriately selecting the diameters of the two, it is possible to obtain the optimal effects, that is, the effect of promoting the mixing of the rich mixture and air, and the effect of rapidly diluting and diffusing the rich mixture.

[0028]

As described above, the sub-chamber engine according to the present invention is formed so that the axis of the first communication hole intersects with the axis of the second communication hole. The flame containing the rich air-fuel mixture and the air ejected from the second communication hole collide in the main chamber, and the mixing of the two due to turbulence is promoted. Then, the flame is mixed with air in a short period of time to be diluted with the air, and the flame can be rapidly diffused in the main chamber. Thus, the pre-combustion chamber engine, which fuel can be once combustion is rapidly diffused in a lean state, NO _X, particulate, and emissions of the soot is reduced, it is possible to improve the fuel consumption .

The sub-chamber engine according to the present invention is characterized in that a flame containing an rich air-fuel mixture and a large amount of air containing almost no fuel are simultaneously jetted out to collide in a main chamber. A major feature is that air-fuel mixtures (combustion flames) with different densities are simultaneously ejected and collided. This point, NO _X by the two-stage combustion, particulates, when aimed at the simultaneous reduction of soot, with very important. In the two-stage combustion, it is necessary to burn the fuel in a rich mixture state at the beginning of the combustion, and then it is necessary to rapidly diffuse the fuel in a lean state and burn it at once. A sub-chamber type engine in which the air-fuel mixture ejected from the communication hole is caused to collide in the main chamber is also found in the first conventional example, but the first conventional example uses a jet of the air-fuel mixture having the same fuel density as the main chamber. In this case, the effect of collision is only an effect of promoting mixing. On the other hand, the sub-chamber engine according to the present invention simultaneously mixes fuel (combustion flame) having different fuel densities and causes it to collide. The effect of rapid dilution of the rich mixture can also be obtained. Therefore, the sub-chamber engine according to the present invention has N
Reduction of O _x , particulates, and soot can be achieved at the same time.

Further, in the conventional sub-chamber engine, fuel is directly injected into the main chamber, so that the combustion becomes slow. On the other hand, in the sub-chamber engine according to the present invention, the fuel is ejected into the main chamber after colliding with the wall surface of the opening of the first communication hole at least once, so that the fuel becomes a rich mixture and the main fuel is mixed. It will squirt into the room. Then, the rich Do mixture so rapidly diluted by mixing with air, it is possible to once burned, as compared with the conventional NO _X, particulates, less emissions soot,
Fuel efficiency can be improved.

[Brief description of the drawings]

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

FIG. 2 is a plan view of a piston of the sub-chamber engine shown in FIG.

FIG. 3 is a sectional view showing another embodiment of the sub-chamber engine according to the present invention.

[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 First communication hole 14 Second communication hole 18 Axis 19 Axis 20 Recess 21 Sub chamber opening 22 Sub chamber side Opening 24 Large room (upper room) 25 Small room (lower room)

Claims (4)

[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. In a sub-chamber engine having a sub-chamber, a communication hole for communicating the main chamber with the sub-chamber, and a fuel injection nozzle for spraying fuel into the sub-chamber, the communication hole is a first communication hole and a second communication hole. The sub-chamber-side opening of the first communication hole is formed at a position where the fuel sprayed from the fuel injection nozzle reaches, and the sub-chamber-side opening of the second communication hole is sprayed from the fuel injection nozzle. A sub-chamber engine, wherein the sub-chamber engine is formed at a position where the fuel does not reach, and the axes of the first communication hole and the second communication hole cross each other in the main chamber. 2. The method according to claim 1, wherein the first communication hole has a recess formed at or near the sub-chamber opening, and the fuel sprayed from the fuel injection nozzle collides with the recess. The sub-chamber engine according to claim 1, wherein: 3. The sub-chamber is composed of two chambers which are vertically arranged and communicate with each other, the first communication hole is opened in an upper chamber, and the second communication hole is opened in a lower chamber. The sub-chamber engine according to claim 1 or 2, wherein the opening is open. 4. The sub-chamber engine according to claim 1, wherein a diameter of the first communication hole is different from a diameter of the second communication hole.