JPH1113473A - Combustion chamber structure of direct injection diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combustion chamber structure of a direct injection diesel engine that is strong in the strength of a turbulent flow of air in a combustion chamber, and generates the turbulent flow for hours, thereby attaining an improvement in low smoke, low NOx, low fuel consumption and so on. SOLUTION: In a direct injection diesel engine whose combustion chamber 1 is formed of a cylinder head 2, cylinder block 3, and a recessed part 5 formed at the top of a piston 4, a cylinder part 6 composed of a small recessed part communicated with the recessed part 5 is provided on the top of the piston 4, while a piston part 7 which can be fitted in the cylinder part 6 through a gap is provided on the cylinder head 2 side so as to protrude therefrom. With such a constitution, the air held between the piston part 7 and the cylinder part 6 is jetted at the upstroke of the piston 4 while the air suction action resulting from the volume change in the space held between the piston part 7 and the cylinder part 6 occurs, thereby allowing a strong turbulent flow to be induced actively in the combustion chamber 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct injection diesel engine, and more particularly to a combustion chamber structure capable of improving low smoke, low NOx, and low fuel consumption.

[0002]

2. Description of the Related Art In a direct-injection diesel engine in which a combustion chamber is formed by a cylinder head, a cylinder block, and a recess formed at the top of a piston, a turbulent flow of air flow in the combustion chamber generated near the top dead center of the compression stroke is: It promotes the mixing of fuel spray and air and contributes to the performance improvement of direct injection diesel engines.

[0003]

However, the prior art relies on a squish flow that generates turbulence due to the reciprocation of the piston, so that the intensity of the turbulence generated in the combustion chamber is weak and sufficient effects can be obtained. The fact is that it has not been done. still,
Conventional direct injection diesel engine combustion chamber improvement technologies include:
A technique is known in which two vortices are generated by a combustion chamber at the top of the piston and a sub-combustion chamber at the bottom of the cylinder head, and the vortices interfere with each other to be disturbed, thereby increasing the energy (Japanese Patent Laid-Open No. 9-32560). However, the structure of the top combustion chamber at the top of the piston is complicated, and the purpose is also limited to smoke reduction.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems. The turbulence of the air flow in the combustion chamber is high, and the turbulence is generated for a long time.
Accordingly, it is an object of the present invention to provide a combustion chamber structure of a direct injection diesel engine capable of improving low smoke, low NOx, and low fuel consumption.

[0005]

According to a first aspect of the present invention, there is provided a direct injection diesel engine in which a combustion chamber is formed by a cylinder head, a cylinder block, and a recess formed at the top of a piston. A cylinder portion formed of a small concave portion communicating with the concave portion, and a piston portion that can be fitted into the cylinder portion through a gap is provided on the cylinder head side.

The invention according to claim 2 is characterized in that the piston is a fixed piston provided on the lower surface of the cylinder head. The invention according to claim 3 is characterized in that the piston portion is a movable piston portion provided on an intake valve or an exhaust valve on the cylinder head side.

According to a fourth aspect of the present invention, the cylinder portion is formed at a position outside the recess at the top of the piston, and a small-diameter communication hole formed in a wall portion separating the cylinder portion and the recess. The concave portion and the cylinder portion are configured to communicate with each other. The operation of the present invention will be described.

According to the first aspect of the present invention, when the piston is lifted, the air interposed between the piston and the cylinder into which the piston is fitted blows out into the combustion chamber, thereby causing strong turbulence in the combustion chamber. Flow is actively induced.
When the piston descends, strong turbulence is positively induced in the combustion chamber by the air suction effect due to the volume change of the space interposed between the piston and the cylinder into which the piston is fitted.

In this case, in the invention according to claim 2, the piston portion is fixed to the cylinder head side,
The cylinder part on the piston side moves with respect to the piston part to perform the above-described operation. In the invention according to claim 3, the piston part is fixed to a movable intake valve or an exhaust valve. The part moves with respect to the cylinder part on the piston side, and the above-described action is achieved.

According to the fourth aspect of the present invention, since the recess and the cylinder communicate with each other through a small-diameter communication hole formed in the wall separating the cylinder and the recess, the fuel is ejected from the communication hole into the combustion chamber. The airflow and the airflow sucked into the cylinder are strong, and a strong turbulence is positively induced in the combustion chamber.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2, the combustion chamber 1 is formed by a cylinder head 2, a cylinder block 3, and a recess 5 formed at the top of a piston 4. Here, at the top of the piston 4, one or more (for example, 4
) Is provided, and a piston portion 7 that can be fitted into the cylinder portion 6 on the cylinder head 2 side via a gap (for example, 0.2 mm) is protrudingly provided.

In this case, in the present embodiment, the piston portion is a fixed piston portion 7 integrally formed on the lower surface of the cylinder head 2 or, as shown in FIG.
The movable piston portion 17 is provided integrally with the intake valve or the exhaust valve 8 on the cylinder head 2 side. The fixed piston portion 7 in FIG. 1 is formed in a cylindrical or prismatic shape, and the cylinder portion 6 is formed in a cylindrical or rectangular tube shape in accordance with this.

The movable piston portion 17 shown in FIG. 3 is preferably formed in a columnar shape.
Is formed in a cylindrical shape. As shown in FIG. 2, when the cylinder portion 6 is cylindrical, its cross section is formed in a shape in which a part of a circular portion is cut off, and the cut portion forms a communication port for communicating the cylinder portion 6 and the concave portion 5. 6a.

In this case, as shown in FIG.
It is preferable to adopt a configuration in which one of the walls constituting both sides of the communication port 6a is cut as shown in FIG. The operation of this configuration will be described. When the piston 4 is lifted, the piston parts 7, 17 and the piston parts 7, 1
When the air interposed between the cylinder portion 6 into which the airtight tube 7 is inserted is ejected into the combustion chamber 1, strong turbulence is positively induced in the combustion chamber 1.

When the piston 4 descends, the piston parts 7, 1
A strong turbulence is positively induced in the combustion chamber 1 by the air suction effect due to the volume change of the space sandwiched between the cylinder 7 and the cylinder 6 into which the pistons 7 and 17 are fitted. In this case, in the configuration of the fixed piston section 7, the piston section 7 is fixed to the cylinder head 2 side, and the cylinder section 6 on the piston 4 side moves with respect to the piston section 7, so that In the configuration in which the movable piston portion 17 has an effect, the piston portion 17 is fixed to the movable intake valve or the exhaust valve 8, and the piston portion 17 moves with respect to the cylinder portion 6 on the piston 4 side. Thus, the above operation is achieved.

As shown in FIG. 4, in the case where the communication port 6a is narrowed, the air flow ejected from the communication port 6a into the combustion chamber 1 and the air flow sucked into the cylinder portion 6 are strong. There is an advantage that stronger turbulence is positively induced in the combustion chamber 1. Further, as shown in FIG. 5, in the case of a configuration in which one of the walls constituting both sides of the communication port 6a is cut, the air flow ejected into the combustion chamber 1 from the communication port 6a becomes a swirl flow, There is an advantage that stronger turbulence is positively induced in the chamber 1.

Next, another embodiment is shown in FIGS. This embodiment has one or more (in the present embodiment,
Four) cylinder portions 16 are formed at positions outside the recesses 5 at the tops of the pistons 4, and the recesses 5 are formed through small-diameter communication holes 16 a formed in a wall separating the cylinder portion 6 and the recesses 5.
And the cylinder portion 16 communicate with each other.

In this configuration, a small-diameter communication hole 16a formed in a wall portion separating the cylinder portion 16 and the concave portion 5 is provided.
, The concave portion 5 and the cylinder portion 16 communicate with each other.
The strong air flow ejected into the combustion chamber 1 from the communication hole 16a and the air flow sucked into the cylinder portion 16 strongly induce a stronger turbulent flow in the combustion chamber 1. In particular, when the communication hole 16a is formed to be inclined upward and upward from the cylinder portion 16 toward the concave portion 5 as in the present embodiment, the turbulent flow can be effectively formed by the combustion chamber 1.

Further, it is more effective to provide a plurality of communication holes 16a in each cylinder portion 16, and moreover, as shown in FIG.
If the shape is inclined in the horizontal direction from the side toward the concave portion 5, the swirl flow can be generated, which is more effective.

[0020]

As described above, according to the first aspect of the present invention, a strong turbulent flow can be positively induced in the combustion chamber, so that the mixing of fuel spray and air is promoted and uniformized. Therefore, it is possible to improve low smoke, low NOx, and low fuel consumption. According to the invention according to claim 2, the piston portion is fixed to the cylinder head side,
The cylinder chamber on the piston side moves relative to this piston portion, and the effect of the invention according to claim 1 can be achieved.

According to the third aspect of the present invention, the piston portion is fixed to the movable intake valve or the exhaust valve, and the piston portion moves with respect to the cylinder chamber on the piston side to perform the above operation. Can play. According to the invention according to claim 4, since the recess and the cylinder portion communicate with each other through the small-diameter communication hole formed in the wall portion separating the cylinder portion and the recess, air ejected from the communication hole into the combustion chamber. Flow, the air flow sucked into the cylinder part is strong, and strong turbulence can be positively induced in the combustion chamber, and the mixing of fuel spray and air is further promoted and uniformized, so that low smoke, low NOx,
It is possible to more effectively improve fuel efficiency and the like.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of a combustion chamber structure of a direct injection diesel engine of the present invention.

FIG. 2 is a top view of the piston according to the embodiment.

FIG. 3 is a longitudinal sectional view of another embodiment.

FIG. 4 is a top view of a piston according to still another embodiment.

FIG. 5 is a top view of a piston according to still another embodiment.

FIG. 6 is a top view of a piston according to still another embodiment.

7 is a sectional view taken along the line XX in FIG. 6;

FIG. 8 is a top view of a piston according to still another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Combustion chamber 1 2 Cylinder head 3 Cylinder block 4 Piston 5 Recess 6 Cylinder part 6a Communication port 7 Fixed piston part 8 Intake valve or exhaust valve 16 Cylinder part 16a Communication hole 17 Movable piston part

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02F 3/26 F02F 3/26 A

Claims (4)

[Claims] In a direct injection diesel engine in which a combustion chamber is formed by a cylinder head, a cylinder block, and a recess formed at the top of a piston, a cylinder portion including a small recess communicating with the recess is provided at the top of the piston. A combustion chamber structure for a direct-injection diesel engine, wherein a piston portion that can be fitted into the cylinder portion through a gap is provided on the cylinder head side. 2. A combustion chamber structure for a direct injection diesel engine according to claim 1, wherein said piston portion is a fixed piston portion provided on a lower surface of a cylinder head. 3. The combustion chamber structure of a direct injection diesel engine according to claim 1, wherein said piston portion is a movable piston portion provided on an intake valve or an exhaust valve on a cylinder head side. 4. The cylinder portion is formed at a position outside the recess at the top of the piston, and the recess and the cylinder portion are connected to each other through a small-diameter communication hole formed in a wall separating the cylinder portion and the recess. The combustion chamber structure of a direct injection diesel engine according to any one of claims 1 to 3, wherein the combustion chamber is configured to communicate with each other.