JPH04303117A - Structure of combustion chamber for subchamber type engine - Google Patents

Abstract

PURPOSE:To provide a structure of the combustion chamber of a subchamber type engine to make flames and a mixture which have burnt primarily in a subchamber smoothly flow into a main chamber. CONSTITUTION:The combustion chamber of this subchamber type engine is constructed so as to introduce flames and a mixture blown out through a connecting hole 9 formed in a subchamber 2 into a main chamber 1 having a combustion chamber opening 18 formed of a sharp tip-shaped lip part 20 through a gap passage 8 formed in a piston head 4. Combustion gas blown out of the subchamber 2 can therefore be prevented from interfering with combustion gas flowing out on account of an inverse squish flow from the main chamber 1. Thus primary combustion is finely carried out in the subchamber 2, and the secondary mixing of the combustion gas and fresh air can be accomplished in a short time in the main chamber 1 for excellent secondary combustion, and the combustion gas and the fresh air then flow from the main chamber 1 into a cylinder chamber 12 on account of the inverse squish flow, and finely accomplish the third mixing for their third combustion and finish the combustion. Thus the combustion is improved for controlling the occurrence of HC, NOX and moreover improving the performance of the engine.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion chamber structure for a sub-chamber engine in which a main chamber is formed in a piston head and a sub-chamber is formed in a cylinder head.

0002

[Prior Art] Conventionally, the structure of the sub-combustion chamber was
There is one disclosed in Japanese Patent No.-112613. The structure of the sub-combustion chamber is such that the sub-combustion chamber wall, which forms the sub-combustion chamber that communicates with the main combustion chamber through the nozzle holes, is made of a heat insulating material, and the inner wall surface of the sub-combustion chamber wall is made of a thin film made of a ceramic material. In addition to arranging the members, a metal protection cylinder is fitted onto the outer circumferential surface of the auxiliary combustion chamber wall.

[0003] Furthermore, an adiabatic engine having a pre-chamber has been developed for the purpose of improving combustion in the adiabatic engine. For example, Japanese Patent Application No. 1-252277 filed by the present applicant discloses a subchamber type engine. The pre-chamber type adiabatic engine includes a pre-chamber with a heat-insulating structure formed in the cylinder head;
A communication hole with an insulating structure that communicates the sub-chamber and the main chamber, a fuel injection nozzle with multiple injection holes arranged in the sub-chamber, and a protrusion provided on the piston head that protrudes into the communication hole near the top dead center of the piston. have.

[0004] Furthermore, the applicant previously filed a patent application No. 2-
No. 173888 discloses a subchamber type engine as described above. In the sub-chamber type engine, the piston head does not have a main chamber with a narrowed opening, but the piston head has a protrusion that projects into the communication hole at the top dead center of the piston.

[0005]

By the way, as a prior art, a pre-chamber type engine as shown in FIG. 3 has been disclosed. The sub-chamber type engine has a structure in which a sub-chamber 32 and a reentrant piston 36 are combined, and the sub-chamber 32 is formed by a sub-chamber wall 34 disposed on a cylinder head 33, The main combustion chamber 31 formed in the main combustion chamber 36 is opened through a communication hole 37 . Further, a fuel injection nozzle 40 is arranged on the sub-chamber wall 34 to inject fuel into the sub-chamber 32. Further, a cavity 39 constituting the main combustion chamber 31 is formed in the piston head 38 of the piston 36, and a protrusion 35 extending upward from the center portion of the bottom surface 29 of the cavity 39 is provided. This protrusion 35 is formed so as to be able to enter into a communication hole 37 formed in a sub-chamber wall 34 disposed in the cylinder head 33 near the top dead center.

In the subchamber type engine shown in FIG. 3, the upper end of the protrusion 35 functions to narrow the communication hole 37 near the top dead center, thereby making the inside of the subchamber 32 a sealed space. Therefore, the fuel injected from the fuel injection nozzle 40 into the auxiliary chamber 32 at the end of the compression stroke remains in the auxiliary chamber 32, and mixes the fuel with air, decomposes it, and undergoes primary combustion to form a uniform air-fuel mixture. At the same time, the pressure inside the subchamber 32 is increased. Next, when the piston 36 descends during the expansion stroke, the protrusion 35 comes out of the communication hole 37, and the communication hole 37 becomes completely open. Therefore, the air-fuel mixture and flame in the auxiliary chamber 32 flow into the main combustion chamber 31 all at once due to the pressure difference between the auxiliary chamber 32 and the main combustion chamber 31, and undergo secondary mixing in the main combustion chamber 31 to perform secondary combustion. . Next, the piston 36 further descends and is blown out from the main combustion chamber 31 toward the cylinder chamber formed by the cylinder head 33 and the upper surface of the piston head 38 by reverse squish, performing tertiary combustion and ideal combustion.

However, from the auxiliary chamber 32 to the main combustion chamber 31
The flow of the air-fuel mixture and flame blown to the main combustion chamber 31
Since the flow direction is opposite to the reverse squish blown out from the auxiliary chamber 32 to the cylinder chamber, depending on the timing of blowing the flame and air-fuel mixture from the auxiliary chamber 32 to the main combustion chamber 31, The flow into the main combustion chamber 31 is obstructed, and a phenomenon occurs in which the flow does not reliably flow into the main combustion chamber 31 and flows out to the cylinder chamber 41 side. Good tertiary mixing and tertiary combustion may not occur, which may worsen combustion.

[0008] Therefore, an object of the present invention is to solve the above-mentioned problems by forming a sub-chamber in the cylinder head,
A fuel injection nozzle for injecting fuel into the subchamber is disposed in the subchamber, a main combustion chamber having an opening formed by a lip is formed in the piston head, and a protrusion that enters the communication hole at the top dead center of the piston is provided. The piston head is formed with a communication hole that communicates with the main chamber through the gas passage to ensure that the combustion gas and air-fuel mixture that is primarily combusted in the sub-chamber flows from the sub-chamber through the gas passage into the main chamber, thereby allowing combustion in the main chamber. The secondary mixing of gas and air is promoted to achieve mixing of flame and air in a short period of time to achieve good secondary combustion, and then from the main chamber to the lower surface of the cylinder head and the upper surface of the piston head by reverse squishing by the lip part. The H
An object of the present invention is to provide a combustion chamber structure for a pre-chamber engine that suppresses the generation of carbon dioxide and NOx.

[0009]

[Means for Solving the Problems] In order to achieve the above object, the present invention is constructed as follows. That is,
This invention comprises a sub-chamber formed in a cylinder head, a main chamber comprising a cavity formed in a piston head and having a combustion chamber opening consisting of a pointed lip, a communication hole opening the sub-chamber toward the cylinder side, A gas passage formed in the piston head leading from an inlet formed on the upper surface of the piston head facing the communication hole to the lower part of the main chamber, and a gas passage provided in the piston head that can be inserted into the communication hole near the top dead center of the piston. The present invention relates to a combustion chamber structure of a pre-chamber type engine which includes a protruding portion.

Further, in the combustion chamber structure of this pre-chamber type engine, the communication hole is formed to protrude downward from the lower surface of the cylinder head in order to guide the flame and air-fuel mixture blown out from the pre-chamber into the gas passage. The annular protrusion is configured to be able to enter the inlet of the gas passage near the top dead center of the piston.

[0011]

[Operation] The combustion chamber structure of the pre-chamber type engine according to the present invention is constructed as described above, and operates as follows. That is, in the combustion chamber structure of this sub-chamber type engine, a gas passage is formed in the piston head leading from an inlet portion formed on the upper surface of the piston head opposite to the communication hole to the lower part of the main chamber, so that the above-mentioned gas flows through the gas passage. The flame and air-fuel mixture that have undergone primary combustion in the auxiliary chamber are reliably guided and flow into the main chamber of the reentrant combustion chamber. Therefore, the reverse squish flow from the main chamber to the cylinder chamber formed between the lower surface of the cylinder head and the upper surface of the piston head is not hindered by the flame and air-fuel mixture blown out from the sub-chamber.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the combustion chamber structure of a pre-chamber type engine according to the present invention will be described with reference to the drawings. First, with reference to FIGS. 1 and 2, an embodiment of a combustion chamber structure of a pre-chamber type engine according to the present invention will be described. FIG. 1 is a sectional view showing an embodiment of the combustion chamber structure of the pre-chamber type engine according to the present invention, and FIG. 2 is a plan view showing a piston in the combustion chamber structure of the pre-chamber type adiabatic engine of FIG.

As shown in the figure, the combustion chamber structure of this pre-chamber type engine includes a cylinder block 14, a cylinder head 7 having intake and exhaust ports 25 (only one shown) fixed to the cylinder block 14, and a cylinder head 7. A subchamber 2 with a heat insulating structure formed in the cylinder block 14, a piston 17 that reciprocates within a cylinder 23 formed in the cylinder block 14, a fuel injection nozzle 6 with an injection hole arranged in the subchamber 2, and a piston head 4 of the piston 17. It has a main chamber 1 composed of a cavity 22. The heat insulating structure of the subchamber 2 includes, for example, a subchamber wall body 3 made of heat-resistant and heat-insulating ceramics, heat-resistant metal, or the like and placed in a recess 19 formed in the cylinder head 7. Subchamber wall 3
is fixed to the cylinder head 7 with a mounting bracket. Further, the lower part of the sub-chamber wall 3 constitutes a part of the cylinder head lower surface 13. A communication hole 9 is formed in the center of the lower surface of the sub-chamber wall 3 and opens toward the cylinder chamber 12 formed between the cylinder head lower surface 13 and the piston head upper surface 11. Furthermore, a fuel injection nozzle 6 for injecting fuel into the sub-chamber 2 is arranged on the sub-chamber wall 3 . Note that an intake/exhaust valve 26 (one of which is shown) is arranged in the intake/exhaust port 25.

In the combustion chamber structure of this pre-chamber type engine, the main chamber 1 consisting of the cavity 22 formed in the piston head 4 is a reentrant type combustion having a combustion chamber opening 18 consisting of a pointed lip portion 20. It is a room. The piston head 4 has a main chamber lower part 16 from an inlet portion 15 formed on the upper surface 11 of the piston head opposite to the communication hole 9.
A gas passage 8 leading to is formed. The inlet portion 15 is formed in a shape that expands upward. At the center of the inlet portion 15 of the piston head 4, a protrusion 5 protrudes from the bottom surface of the gas passage, and is capable of protruding into the communication hole 9 near the top dead center of the piston. In the figure, the upper surface 21 of the protrusion 5 is located slightly below the piston head upper surface 11. This protrusion 5
Since this is a part exposed to high-temperature combustion gas and subjected to a high heat load, it is preferably made of ceramic such as silicon nitride, which has high heat resistance and high temperature strength.

Furthermore, the wall portion of the sub-chamber wall 3 forming the sub-chamber 2 that forms the communication hole 9 has an annular protrusion 10 extending downward from the lower surface 13 of the cylinder head formed by the sub-chamber wall 3.
It is formed of. This annular protrusion 10 guides the flame and air-fuel mixture blown out from the auxiliary chamber 2 into the gas passage 8 when the piston is located near the top dead center, so that it can protrude into the inlet 15 of the gas passage 8.

Since the combustion chamber structure of this pre-chamber type engine is constructed as described above, it functions as follows. In other words, in the combustion cycle of this pre-chamber engine, the piston 1 in the latter half of the compression stroke near the top dead center of the piston.
The protrusion 5 provided at 7 protrudes into the communication hole 9, and the flow path area of the communication hole 9 is reduced. Next, the piston 17 rises toward the end of the compression stroke, but near the end of the compression stroke, the air flowing into the auxiliary chamber 2 is forced into the auxiliary chamber 2, forming strong turbulence within the auxiliary chamber 2. In this state, the fuel spray injected into the auxiliary chamber 2 from the fuel injection nozzle 6 achieves good primary mixing with the flowing air in the auxiliary chamber 2, resulting in fuel-rich primary combustion. On the other hand, air present in the cylinder chamber 12 is transferred to the main chamber 1, which is a reentrant combustion chamber formed in the piston head 4, by the action of the lip portion 20 forming the combustion chamber opening 18 of the main chamber 1.
2 flows into the main chamber 1 with a strong squish flow, and the main chamber 1
A strong air turbulence is formed inside.

Next, the combustion cycle of this pre-chamber type engine shifts to an expansion stroke, and at the beginning of the expansion stroke, the pre-chamber 2
The air-fuel mixture and flame are blown out from the inlet member 15 formed in the piston head 4 into the gas passage 8, and smoothly flow through the gas passage 8 from the lower part 16 of the main chamber 1 to the main chamber 1 at high speed. There will be an influx. The air-fuel mixture and flame that have flowed into the main chamber 1 undergo secondary mixing within the main chamber 1 with fresh air of strong air turbulence in a short time to achieve secondary combustion. Furthermore, the piston 17 descends, and the flame and the secondary air-fuel mixture that have undergone secondary combustion within the main chamber 1 are blown out into the cylinder chamber 12 in reverse squish from the opening 18 of the main chamber 1 by the action of the lip portion 20. The air is tertiary mixed with fresh air existing in the cylinder chamber 12 to perform tertiary combustion, thereby completing combustion.

Therefore, in the combustion chamber structure of this pre-chamber type engine, the fuel injected from the fuel injection nozzle 6 into the pre-chamber 2 is
In the subchamber 2, the air in the subchamber 2 is mixed with the air in the subchamber 2 for primary combustion, and the flame and mixture blown out from the subchamber 2 smoothly flow into the main chamber 1 through the gas passage 8. The fresh air existing in the main chamber 1 is mixed with the fresh air for secondary combustion, and is then blown out from the main chamber 1 into the cylinder chamber 12 in a reverse squish flow, where the fresh air existing in the cylinder chamber 12 and the tertiary combustion occur. The fuel can be mixed and tertiary-combusted, the fuel can be completely combusted in good conditions, and the generation of HC and NOX can be suppressed. Therefore, according to this subchamber type engine, the combustion period in the combustion cycle is shortened, fuel efficiency is improved, and HC and N
Generation of OX can be suppressed.

[0019]

The combustion chamber structure of the pre-chamber engine according to the present invention is constructed as described above, and has the following effects. In other words, the combustion chamber structure of this pre-chamber engine is as follows:
A sub-chamber is formed in the cylinder head, the sub-chamber is opened to the cylinder side through a communication hole, a main chamber is formed in the piston head, and the main chamber is provided with a combustion chamber opening consisting of a pointed lip part; The gas passage communicates the inlet portion of the upper surface of the piston head opposite to the communication hole with the lower part of the main chamber, and furthermore, the piston head is provided with a protruding portion capable of projecting into the communication hole near the top dead center of the piston. The flame and air-fuel mixture that have undergone primary combustion in the auxiliary chamber are reliably guided and flow into the main chamber of the reentrant combustion chamber through the gas passage. Therefore, the reverse squish flow from the main chamber to the cylinder chamber formed between the lower surface of the cylinder head and the upper surface of the piston head is not hindered by the flame and air-fuel mixture blown out from the sub-chamber.

[0020] Therefore, the combustion gas and the air-fuel mixture that have been primarily combusted in the auxiliary chamber reliably and smoothly flow into the main chamber from the auxiliary chamber through the gas passage, and the flame and the air-fuel mixture are renewed in the main chamber. To promote secondary mixing with air and achieve mixing of flame and air in a short period of time, resulting in good secondary combustion. Next, the flame and air-fuel mixture flowing out from the main chamber flow out into the cylinder chamber by reverse squishing by the lip part, and perform tertiary mixing with the fresh air in the cylinder chamber, resulting in tertiary combustion and complete combustion. Combustion can be completed quickly and the generation of HC and NOX can be suppressed.

Further, the combustion chamber structure of this pre-chamber type engine has an annular shape forming the communication hole that protrudes downward from the lower surface of the cylinder head in order to guide the flame and air-fuel mixture blown out from the pre-chamber into the gas passage. Since the protrusion is configured to be able to enter the inlet of the gas passage near the top dead center of the piston, the flame and air-fuel mixture blown out from the auxiliary chamber are guided into the gas passage without flowing out into the cylinder chamber. and is smoothly and reliably blown into the main chamber.

In this combustion chamber structure of the pre-chamber type engine, the atomized fuel from the fuel injection nozzle disposed in the pre-chamber is injected into the strong air flow or swirl generated in the pre-chamber, and the fuel spray is The air and the air in the pre-chamber undergo primary mixing to form a good air-fuel mixture, which is ignited to perform primary combustion. That is, at the top dead center of the piston, the communication hole has a reduced flow area and is in a constricted state, thereby making the sub-chamber a sealed space, and the air introduced into the sub-chamber generates a strong swirl within the sub-chamber. do. The atomized fuel injected from the fuel injection nozzle at the end of the compression stroke forms a good mixture with the swirl and burns in a fuel-rich state in the pre-chamber, increasing the pressure in the pre-chamber and generating NOx. Performs combustion that suppresses Next, when the piston descends during the expansion stroke, the protrusion comes out of the communication hole, and the communication hole becomes completely open. Therefore, the air-fuel mixture and flame in the auxiliary chamber flow into the main chamber through the gas passage all at once due to the pressure difference between the auxiliary chamber and the gas passage (therefore, the main chamber), and undergo secondary mixing in the main chamber. to perform secondary combustion. Next, the piston further descends and is blown out from the main chamber into the cylinder chamber formed by the lower surface of the cylinder head and the upper surface of the piston head by reverse squish, performing tertiary combustion and completing ideal combustion.

Therefore, the combustion chamber structure of this pre-chamber type engine performs combustion three times in the combustion cycle: primary combustion in the pre-chamber, then secondary combustion in the main chamber, and finally tertiary combustion in the cylinder chamber. This makes it possible to suppress the generation of HC and NOX. Moreover, since the protruding portion projects into the communication hole, the communication hole itself does not need to be narrowed down unlike in conventional pre-chamber type engines, and can be formed to have a large diameter, allowing air to flow into the pre-chamber. There is no throttling loss when introducing this, and a highly efficient engine can be provided without degrading engine performance.

[Brief explanation of drawings]

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

FIG. 2 is a plan view showing the top surface of a piston in the combustion chamber structure of the pre-chamber engine shown in FIG. 1;

FIG. 3 is a sectional view showing an example of a combustion chamber structure of a pre-chamber type engine.

[Explanation of symbols]

1 Main room 2 Antechamber ３　　　　Subchamber wall body 4 Piston head 5 Protruding part 6 Fuel injection nozzle 7 Cylinder head 8 Gas passage 9 Communication hole 10 Annular protrusion 11 Top surface of piston head 12 Cylinder chamber 13 Lower surface of cylinder head 16 Lower part of main room 17 Piston 18 Combustion chamber opening 20 Lip part 22 Cavity

Claims (2)

[Claims] 1. A main chamber comprising a subchamber formed in a cylinder head, a cavity formed in a piston head, and a combustion chamber opening consisting of a pointed lip, and a communication hole opening the subchamber toward the cylinder side. , a gas passage formed in the piston head leading from an inlet portion formed on the upper surface of the piston head facing the communication hole to the lower part of the main chamber, and a gas passage formed in the piston head that can enter the communication hole near the top dead center of the piston. The combustion chamber structure of a pre-chamber engine consists of a protrusion. 2. In order to guide the flame and air-fuel mixture blown out from the auxiliary chamber into the gas passage, an annular protrusion forming the communication hole protruding downward from the lower surface of the cylinder head is arranged near the top dead center of the piston. The combustion chamber structure for a pre-chamber engine according to claim 1, wherein the combustion chamber structure is configured to be able to enter the inlet portion of the gas passage.