JP3387185B2 - Combustion chamber with subchamber - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion chamber having a sub chamber on the piston side.

[0002]

2. Description of the Related Art Conventionally, a swirl chamber type engine having a swirl chamber has been developed for the purpose of improving combustion of the engine. Such a swirl chamber engine has a swirl chamber formed in a cylinder head or a piston head, a communication hole for communicating the swirl chamber with a main chamber formed on the cylinder side, and a fuel injection nozzle for spraying fuel into the swirl chamber. Have. In the above swirl chamber type engine, an air-fuel mixture is formed by a swirl flow flowing into the swirl chamber through a communication hole and a fuel injected into the swirl chamber, the air-fuel mixture is primarily burned, and then the swirl chamber is passed through the communication hole to a main chamber. Gas such as flame and unburned mixture is ejected for secondary combustion. As an example of such a swirl chamber type engine, the structure of the auxiliary combustion chamber disclosed in Japanese Patent Laid-Open No. 2-112613 is known.

Further, Japanese Utility Model Publication No. 62-93141 discloses a piston having a ceramic crown and an aluminum skirt. In this piston, the outer periphery of a ceramic crown having a cavity is fitted with the head portion of a cylindrical aluminum skirt, and a cast iron ring is made to coexist with a plastic fluid material in the gap between the outer periphery of the combustion chamber and the head portion. It is fixed.

Further, in Japanese Patent Laid-Open No. 5-26111,
Adiabatic pistons are disclosed. The heat insulating piston secures heat insulation between the piston head and the piston skirt, prevents cracks and the like of the heat insulating member arranged at the joint between the two, and prevents scattering of the heat insulating member.

[0005]

To the 0005] Generally, the combustion temperature in the secondary chamber are the high temperature, as a measure to reduce the production of NO _X, it is effective to combust the fuel-rich. Also, in order to burn fuel-rich when the combustion temperature is high, it is effective to use a sub-chamber engine as the type of engine structure. When the conventional engine uses a sub-chamber combustion chamber, in order to increase the combustion speed of the sub-chamber combustion chamber, the passage cross-sectional area of the communication hole that connects the sub-chamber with the main chamber is reduced to reduce the vortex flow. It is necessary to speed up and increase the jet velocity to the main chamber. However, in the sub-chamber type combustion chamber, when the passage cross-sectional area of the communication hole is made small, the jet speed flowing out from the sub-chamber to the main chamber becomes large, but the throttling loss becomes large and the combustion in the main chamber becomes sufficient. There is a problem that it is not done.

In the case of a conventional engine in which a communication hole that connects the main combustion chamber and the sub chamber is provided in the peripheral portion of the cylinder, if the passage area of the communication hole is increased in order to reduce the throttling loss, the main combustion from the sub chamber will occur. The penetrating force of flames, unburned air-fuel mixture, and other gases ejected into the chamber becomes small, and the state where the central part of the cylinder cannot be reached occurs. In order to improve the thermal efficiency of the engine, it is important to improve the air utilization rate in the main combustion chamber to complete combustion in a short time and prevent the generation of white smoke.

Further, in the conventional swirl chamber type engine, in order to solve the above-mentioned problems, the communication hole that communicates the sub chamber and the main chamber is small, so throttling loss occurs due to the communication port and the engine output is reduced. Cause. Generally, the direct injection type has a communication hole that connects the main chamber and the sub-chamber to the reentrant type, and one is provided in the center of the cylinder on the outer periphery of the sub-chamber type, so the jet flow must reach. The distance that has to be extended becomes longer, the mixing with the air in the main room becomes insufficient,
It causes HC and smoke.

An object of the present invention is to solve the above-mentioned problems. A sub-chamber is formed in a piston head fixed to a piston skirt, a cavity is formed in the lower surface of the cylinder head, and the shape of the main combustion chamber is By constructing the communication hole that connects the main combustion chamber and the sub chamber with an optimum structure, the penetration force of the flame from the sub chamber to the main combustion chamber and the gas such as unburned mixture in the main combustion chamber is improved. , The intake air swirl existing in the main combustion chamber is used to improve the air utilization rate in the main combustion chamber of gases such as flames from the sub chamber to the main combustion chamber and unburned air-fuel mixture. Promotes mixing with air, increases combustion speed, shortens combustion period, and completes combustion in a short period of time.
Improve thermal efficiency is to provide a combustion chamber with a sub-chamber to reduce NO _X, carbon, generation of smoke and the like.

[0009]

The present invention comprises a fuel injection nozzle arranged so as to project from the lower surface of a cylinder head, and a plurality of cavities formed in the lower surface of the cylinder head around the fuel injection nozzle. The main combustion chamber, the sub-chamber provided almost at the center of the piston head,
A main communication hole, which is formed substantially in the center of the piston head and which is closed by the thrust of the fuel injection nozzle near the top dead center, connects the main combustion chamber and the sub chamber, and the cavity around the main communication hole. A plurality of sub-communication holes that are formed in the piston head and incline inward from the cylinder outer side to the inner side and that communicate the main combustion chamber and the sub chamber with each other,
And a multi-injection hole for injecting fuel into the sub-chamber provided in the fuel injection nozzle.
It is formed eccentrically from the center of the sub chamber,
Flames ejected toward the cavity through the communication hole
The swirl flow is combined with the intake swirl existing in the main combustion chamber.
And a combustion chamber provided with a sub chamber.

Further, the cavity is formed in the valve relief portion arranged in the cylinder head or in an area other than the valve relief portion.

Further, the present invention is not limited to the bottom surface of the cylinder head.
Fuel injection nozzle arranged so as to project from the
Formed on the lower surface of the cylinder head around the injection nozzle
The main combustion chamber composed of multiple cavities
Sub-chamber provided almost at the center of the stone head, the piston
The fuel is formed near the center of the head and near the top dead center.
In front of the main combustion chamber closed by the injection of the injection nozzle
Main communication hole that communicates with the auxiliary chamber, around the main communication hole
Tilt toward the cavity and from the outside to the inside of the cylinder
The main combustion chamber is formed obliquely on the piston head and
And a plurality of sub-communication holes communicating between the sub-chamber and the fuel, and the fuel.
Multi for injecting fuel into the auxiliary combustion chamber provided in the injection nozzle
Has a nozzle hole, the cavity, especially in that the flame relief portion which is enlarged in the circumferential direction of the flame swirl flow ejected into the main combustion chamber from the sub-chamber through the sub communication holes are formed
The present invention relates to a combustion chamber provided with a sub chamber for collection.

Since the combustion chamber provided with this sub-chamber is configured as described above, flames, unburned air-fuel mixture, and other gases ejected from the sub-chamber to the main combustion chamber through the sub-communication holes are jetted to the cavity. It becomes a swirling flow and is mixed with the intake swirl existing in the main combustion chamber to promote mixed combustion.

The sub chamber is located at the center of the piston,
Since the sub-communication holes extend around the cylinder, the sub-communication holes are radially formed at equal intervals around the main communication hole so as to extend from the sub-chamber to the main combustion chamber. The flame, the unburned air-fuel mixture, and other gases are injected into the cavity toward the cylinder periphery. Moreover, by providing the sub-communication hole around the main communication hole, the reaching distance of the flame, unburned air-fuel mixture, and other gases ejected from the sub-chamber to the main combustion chamber to the cylinder periphery is evenly shortened. As a result, the time to reach the cylinder periphery is shortened, and the velocity can be converted into pressure to reach the cylinder periphery in a short period of time, and the fresh air existing in the main combustion chamber is mixed in a short period of time to promote combustion. And can be completed in a short time. Further, since a plurality of the sub-communication holes can be formed and the passage area of the communication holes can be made large as a whole, squeezing loss can be reduced.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a combustion chamber having a sub chamber according to the present invention will be described below with reference to FIG. FIG. 1 is a sectional view showing an embodiment of a combustion chamber having a sub chamber according to the present invention, and FIG. 2 is an explanatory view showing a lower surface of a cylinder head.

The combustion chamber including the sub chamber includes a cylinder block 20 having a cylinder 8, a cylinder head 15 fixed to the cylinder block 20 via a gasket 29, a fuel injection nozzle 10 attached to the cylinder head 15, and It is composed of a piston 3 which reciprocates in a cylinder 8. The combustion chamber with this sub-chamber is the piston 3
The sub chamber 2 is formed on the side. The cylinder block 20 is formed with holes 24 corresponding to the number of cylinders of the engine, and the cylinder liner 21 having the cylinders 8 formed therein may be fitted into the holes 24. The cylinder 24 may be configured by the hole 24. An intake / exhaust port 14 is formed in the cylinder head 15, and an intake / exhaust valve 13 is arranged in the intake / exhaust port 14.

The combustion chamber provided with this sub-chamber includes a piston skirt 9 made of a metal such as aluminum alloy or FC,
Heat-resistant Si ₃ fixed to the piston skirt 9
The piston head 7 is made of high-strength ceramics such as N ₄ , and the sub-chamber wall portion 11 is integrally formed with the piston head 7. A piston ring groove for mounting the piston ring 25 is formed in the piston skirt 9, and a mounting hole 16 is formed in the center of the upper wall body 19 of the piston skirt 9. The piston head 7 is
The sub-chamber wall portion 11 serving as an annular boss portion is provided in the lower center portion. The piston head 7 has an annular ring portion 18 extending downward in the peripheral portion thereof, and a sub chamber wall portion 11 forming the sub chamber 2 and extending downward in the center thereof.

The piston head 7 and the piston skirt 9 are formed by fitting the sub chamber wall portion 11 of the piston head 7 into the mounting hole 16 of the piston skirt 9 and embedding the fixed metal ring 23 between them by metal flow. Both can be fixed to each other. At this time, a heat shield gasket (not shown) is interposed between the lower surface of the annular ring portion 18 of the piston head 7 and the outer peripheral upper surface of the upper wall body 19 of the piston skirt 9 in order to seal and heat the both. Let The lower end surface of the annular ring portion 18 of the piston head 7 is brought into contact with the outer peripheral upper surface of the upper wall body 19 of the piston skirt 9 to fix them to each other, whereby the lower surface of the piston head 7 and the upper wall body 19 of the piston skirt 3 are fixed.
The heat-shielding air layer 17 between the upper surface of the
Are formed.

The combustion chamber with the auxiliary chamber, the fuel injection nozzle 10 arranged in the cylinder head 15 to protrude from the sheet cylinder head lower surface 26, around the fuel injection nozzle 10 is formed on the lower surface of the cylinder head 15 Main combustion chamber 1 formed by a plurality of cavities 4 that are formed in the main chamber, sub chamber 2 that is provided in the substantially central portion of piston head 7, and substantially the center of piston head 7, and fuel injection nozzle 1 near the top dead center
Formed in the piston head 7 toward the cavity 4 around the main communication hole 5 and the main communication hole 5 that connect the main combustion chamber 1 and the sub chamber 2 that are closed by the inrush of 0 toward the cavity 4 and inward from the outside of the cylinder And has a plurality of sub-communication holes 6 that connect the main combustion chamber 1 and the sub-chamber 2 and multiple injection holes 22 that inject fuel into the sub-chamber 2 provided in the fuel injection nozzle 10. is there.

The piston head 7 has a piston skirt 9
The sub-chamber wall portion 11 forming the sub-chamber 2 is fitted and fixed in the central mounting hole 16 formed in the sub chamber 2. The formation direction of the sub communication hole 6 is eccentric from the center of the sub chamber 2. The flame jet swirling flow IS ejected from the sub chamber 2 toward the cavity 4 through the sub communication hole 6 is combined with the intake swirl S existing in the main combustion chamber 1.

A plurality of cavities 4 (four locations in FIG. 4) are formed in the cylinder head 15, and the cavities 4 are formed in the valve escape portion of the intake / exhaust valve 13 arranged in the cylinder head 15 or in an area other than the valve escape portion. There is. In the cavity 4, the lower surface of the cylinder head 15 may be formed as a recess to serve also as a valve relief portion, or the concave portion may be formed in the lower surface of the cylinder head 15 where the valve relief portion of the intake / exhaust valve 13 is not formed. Alternatively, the cavity 4 can be formed. Further, in the cavity 4, a flame escape portion 28 is formed which is enlarged in the circumferential direction of the flame swirling flow ejected from the sub chamber 2 to the main combustion chamber 1 through the sub communication hole 6. The ejection energy of the flame jet swirling flow IS ejected from the sub chamber 2 to the main combustion chamber 1 is amplified by the flame escape portion 28, and the intake swirl S remaining in the main combustion chamber 1, that is, between the fresh air and the flame. Mixing is promoted, the air utilization rate is improved, the combustion speed is increased, the combustion period is shortened to complete the combustion in a short time, and the thermal efficiency is increased to suppress the generation of NO _x , HC and the like.

The plurality of sub-communication holes 6 are opened in the inclined direction toward the cylinder peripheral side with respect to the lower surface 26 of the cylinder head, are spaced at equal intervals around the main communication hole 5, and are plural in the radial direction, for example. , 4 to 6 are formed, and from the sub chamber 2 to the main combustion chamber 1
Gas such as flame to the cylinder, unburned air-fuel mixture and the like is injected into the cavity 4 toward the peripheral direction of the cylinder 8. Further, by providing the sub communication hole 6 around the main communication hole 5, gases such as flames and unburned gas mixture ejected from the sub chamber 2 to the main combustion chamber 1 can reach the cylinder periphery uniformly. This shortens the time required to reach the area around the cylinder.

Further, the fuel injection nozzle 10 has an outer peripheral portion covered with a heat shield cover 12 to protect it from heat in the main combustion chamber 1, the sub chamber 2 and the main communication hole 5. The fuel injection nozzle 10 is located in the center of the sub chamber 2 by penetrating into the main communication hole 5 in the vicinity of the top dead center of the piston. Multiple injection holes 22 are provided to inject fuel into the chamber 1. Further, the piston head 7 is formed so that the clearance between the piston upper surface 27 and the cylinder head lower surface 26 at the piston top dead center is small, and is formed in a flat surface so as to be large in the formation region of the cavity 4. .

Sub chamber wall portion 11 of the cylinder head 7.
Is configured such that the sub chamber 2 is formed in the center of the piston by the thin wall body. The piston head 7 and the piston skirt 9 are in contact with each other except that the annular ring portion 18 and the upper surface of the upper wall body 19 are in contact with each other and the sub chamber wall portion 11 and the inner wall surface of the mounting hole 16 are in contact with each other. Separated by layers 17. Further, the fuel injection nozzle 10 extends downward from the cylinder head lower surface 26, projects into the sub chamber 2 from the main communication hole 5 in the vicinity of the piston top dead center, and from the multiple injection holes 22 provided in the fuel injection nozzle 10 to the sub chamber. 2 is set to inject fuel. In addition, the sub chamber 2 formed in the sub chamber wall portion 11
Is located substantially at the center of the cylinder 8, and the auxiliary communication hole 6 that connects the auxiliary chamber 2 and the main combustion chamber 1 is formed so as to be positioned on the outer peripheral portion of the auxiliary chamber 2.

Since the combustion chamber provided with this sub-chamber is constructed as described above, it operates as follows. In the combustion chamber equipped with this sub chamber, the intake port 14 is used in the intake stroke.
The intake air introduced into the cylinder 8 through is compressed in the compression stroke and is introduced into the sub chamber 2 through the main communication hole 5 and the sub communication hole 6. When the fuel injection nozzle 10 closes the main communication hole 5 in the vicinity of the compression top dead center, highly compressed compressed air is further introduced into the sub chamber 2 through the sub communication hole 6.
In this state, the fuel is injected from the multiple injection holes 22 of the fuel injection nozzle 10 into the sub chamber 2, the fuel and the air are mixed in the sub chamber 2 and ignited and burned in a fuel rich state, and the combustion in the sub chamber 2 is performed. state is combusted in the fuel-rich, it is possible to suppress the generation of NO _X. Next, since the fuel injection nozzle 10 closes the main communication hole 5 at the beginning of the expansion stroke after shifting to the expansion stroke, gas such as flame and unburned air-fuel mixture in the sub-chamber 2 is discharged from the sub-chamber 2 to the sub-communication hole. It is jetted to the main combustion chamber 1 constituted by the cavity 4 through 6.

At this time, since a plurality of sub-communication holes 6 that connect the main combustion chamber 1 and the sub-chamber 2 are formed in the circumferential direction of the sub-chamber 2, the total passage area is the total of the sub-communications holes 6. As a result, a large size can be formed, and the squeezing loss can be reduced. Further, the sub-chamber 2 is formed in the center of the piston, that is, in the center of the cylinder. 4. That is, the flame jet swirl flow IS is guided by the valve escape portion to be combined with the intake swirl S existing in the main combustion chamber 1, and the fresh air existing in the main combustion chamber 1 is entrained, and further into the flame escape portion 28. The existing air is entrained to improve the air utilization rate, the mixed combustion is promoted, then the piston 3 descends, the fuel injection nozzle 10 comes out from the main communication hole 5, the main communication hole 5 opens, and the sub chamber Gas such as flame and unburned air-fuel mixture is ejected from the main combustion chamber 1 through the main communication hole 5 from the main combustion chamber 1
Of promoting mixing of the air present in the center to increase the combustion speed can reduce the combustion period, NO _X, HC, it is possible to perform combustion while suppressing generation of smoke.

[0026]

The combustion chamber provided with the auxiliary chamber according to the present invention is
With the above-mentioned structure, the sub-communication holes are inclined and opened with respect to the cavities formed in the cylinder head, and the flames and unburned flames ejected from the sub-chamber to the main combustion chamber through the sub-communications holes are opened. Gas such as air-fuel mixture is smoothly ejected toward the main combustion chamber of the cavity at high speed, and is guided by the cavity to form a flame jet swirl flow. These flame jet swirl flows are combined with the intake swirl remaining in the main combustion chamber, mixing is promoted, combustion speed is increased, combustion period is shortened, and combustion can be completed in a short period of time. It is possible to improve the thermal efficiency and suppress the generation of NO _X , HC and smoke.

Further, since the sub chamber is arranged in the center of the piston, and a plurality of the sub communication holes for connecting the main combustion chamber and the sub chamber are formed in the circumferential direction of the sub chamber, the sub chamber is formed. Gases such as flame and unburned air-fuel mixture from the chamber to the periphery of the cylinder of the main combustion chamber are evenly distributed and progress in a short period of time. The reaching distance of the fresh air existing in the main combustion chamber to the wall surface of the cylinder is shortened, the air utilization rate in the main combustion chamber is improved, and mixing is promoted. Moreover, the passage area of the sub-communication holes can be made large as a whole as the total of the sub-communication holes, and the squeezing loss can be reduced.

[Brief description of drawings]

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

FIG. 2 is an explanatory view showing an example of a lower surface of a cylinder head in a combustion chamber including the sub chamber of FIG.

[Explanation of symbols]

1 Main combustion chamber 2 Sub-chamber 3 pistons 4 cavities 5 main communication holes 6 Secondary communication hole 7 piston head 8 cylinders 10 Fuel injection nozzle 13 Intake and exhaust valves 14 intake / exhaust port 15 cylinder head 22 Multiple injection holes 26 Lower surface of cylinder head 28 Flame escape area

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI F02F 3/26 F02F 3/26 C D F02M 61/14 310 F02M 61/14 310D 310P 61/18 320 61/18 320Z (58) Fields investigated (Int.Cl. ⁷ , DB name) F02B 23/06 F02F 3/00 301 F02F 3/00 302 F02F 3/26 F02M 61/14 310 F02M 61/18 320

Claims (3)

(57) [Claims] 1. A fuel injection nozzle arranged so as to project from a lower surface of a cylinder head, a main combustion chamber constituted by a plurality of cavities formed in a lower surface portion of the cylinder head around the fuel injection nozzle, and a piston head. A sub-chamber provided substantially in the center of the piston head, and a main communication hole for communicating the sub-chamber with the main combustion chamber, which is formed approximately in the center of the piston head and is closed by the thrust of the fuel injection nozzle near the top dead center. A plurality of sub-communication holes that are formed in the piston head around the main communication hole toward the cavity and inward from the cylinder outer side to communicate with the main combustion chamber and the sub-chamber; The sub-chamber provided in the injection nozzle has multiple injection holes for injecting fuel ,
The direction of formation of the sub communication hole is eccentric from the center of the sub chamber.
From the sub chamber through the sub communication hole to the cavity
The swirling flow of flame ejected toward the main combustion chamber exists in the main combustion chamber.
Combustion chamber with an auxiliary chamber characterized by being combined with an intake swirl . 2. The combustion chamber having a sub chamber according to claim 1, wherein the cavity is formed in a valve relief portion arranged in the cylinder head or in an area other than the valve relief portion. 3. A cylinder head so as to project from a lower surface thereof.
The fuel injection nozzles arranged, around the fuel injection nozzle
A plurality of cavities formed on the lower surface of the cylinder head
Main combustion chamber composed of tee, piston head
Sub-chamber at the center of the chamber, approximately the center of the piston head
Of the fuel injection nozzle near the top dead center
Connects the main combustion chamber and the sub chamber, which are closed by
Main connection hole, facing the cavity around the main connection hole
Once and tilted inward from the outside of the cylinder
Is formed on the head and connects the main combustion chamber and the sub chamber.
A plurality of sub-communication holes through which the fuel injection nozzle is provided
A plurality of injection holes for injecting fuel into the sub chamber, and a flame escape portion that is enlarged in the circumferential direction of the flame swirl flow ejected from the sub chamber to the main combustion chamber through the sub communication hole in the cavity. a combustion chamber provided with an auxiliary chamber you characterized in that There are formed.