JPH0913971A - Structure for nozzle hole of combustion chamber of swirl chamber type diesel engine - Google Patents

Abstract

PURPOSE: To improve combustion performance by accelerating generation of a swirl in a swirl chamber. CONSTITUTION: A combustion chamber 2 is pressed into a cylinder head 1 from below to form a nearly spherical swirl chamber 3, and an inside of the swirl chamber 3 faced with a fuel injection valve 4 is communicated with a main combustion chamber 7 on the cylinder block 6 side via a nozzle hole 5 formed on the combustion chamber 2 in this swirl chamber type Diesel engine. Many recessed guide grooves 9 are spirally provided on an inner peripheral wall of the nozzle hole 5 provided on the combustion chamber 2. When air flows into the swirl chamber 3 during a compression stroke, inflow air is turned by the guide grooves 9, a swirl in the lateral direction is generated in the swirl chamber 3, and combustion performance is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an injection port of a combustion chamber of a swirl chamber type diesel engine, and more particularly to a technique for improving combustion performance.

[0002]

2. Description of the Related Art As a type of diesel engine, in order to improve the fuel consumption rate and the engine output, as shown in FIG. 2, a combustion chamber 2 is press-fitted into a cylinder head 1 from the lower surface thereof to form a substantially spherical swirl chamber ( Sub chamber 3), and the inside of the swirl chamber 3 facing the fuel injection valve 4 is communicated with the main combustion chamber (main chamber) 7 on the cylinder block 6 side through the injection port 5 formed in the combustion chamber 2. Type diesel engines are well known from Japanese Utility Model Laid-Open No. 3-118228 and Japanese Patent Laid-Open No. 3-145515.

[0003]

In such a swirl chamber type diesel engine, a swirl flow of air (pushing swirl flow) is caused in the swirl chamber 3 by the piston 8 during the compression stroke, fuel is injected therein, and the swirling swirl flow causes Combustion is caused by mixing high temperature and high pressure air with fuel. But,
Since the injection port 5 provided in the combustion chamber 2 is formed in a shape that allows air to efficiently flow into the swirl chamber 3 during the compression stroke, only the vertical swirl 10 is generated in the swirl chamber 3. Therefore, unevenness occurs in the mixing of air and fuel in the swirl chamber 3, resulting in incomplete combustion,
There is a risk of increased smoke and reduced output.

In view of the above conventional problems, it is an object of the present invention to improve the combustion performance by promoting the generation of swirl flow generated in the swirl chamber.

[0005]

Therefore, according to the first aspect of the present invention, the subchamber is formed by press-fitting the combustion chamber into the cylinder head from the lower surface thereof, and the subchamber facing the fuel injection valve is used as the combustion chamber. In a swirl chamber type diesel engine configured to communicate with the main chamber on the cylinder block side through the formed injection port, a large number of guide grooves for lateral swirl generation are spirally arranged on the inner peripheral wall of the injection port. .

[0006]

According to the first aspect of the invention, when the air flows into the swirl chamber from the injection port during the compression stroke, the inflowing air is guided by the guide grooves for generating the lateral swirl formed in the inner peripheral wall of the injection port. Swirls and a lateral swirl occurs in the swirl chamber.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 shows the structure of a combustion chamber of a swirl chamber type diesel engine according to an embodiment of the present invention. The basic structure is the same as that of the conventional swirl chamber type diesel engine combustion chamber shown in FIG. 2. Therefore, the common structure is denoted by the same reference numeral as in FIG. 2 and the description thereof is omitted.

As shown in FIGS. 1 (b) and 1 (c), on the inner peripheral wall of the injection port 5 provided in the combustion chamber 2,
A large number of recessed guide grooves 9 are arranged in a spiral. The guide groove 9 is formed to have a narrow groove width and a shallow groove depth in order to prevent the occurrence of cracks. This effect will be described in detail later. Further, the guide groove 9 is integrally formed at the same time when the combustion chamber 2 is manufactured by casting.

The operation of the swirl chamber type diesel engine having the guide groove 9 will be described in detail below. When the piston 8 starts to rise in the compression stroke of the engine, the air in the cylinder (not shown) flows into the swirl chamber (sub chamber) 3 through the injection port 5 provided in the combustion chamber 2. In this inflow process, since the injection port 5 is provided obliquely with respect to the sliding direction of the piston 8, the swirl chamber has a structure shown in FIG.
As shown in (a), a vertical swirl 10 is generated.

Further, in addition to the vertical swirl 10, when the air passes through the nozzle 5 and flows into the swirl chamber 3, the inflowing air is guided by the guide grooves 9 arranged in a row on the inner peripheral wall of the nozzle 5. As shown in (b), the swirl causes a swirl 11 in the lateral direction in the swirl chamber 3. When fuel is injected into the swirl chamber 3 in which the horizontal swirl 11 is generated in addition to the vertical swirl 10 as described above, mixing of air and fuel is promoted as compared with the conventional swirl chamber diesel engine, and combustion performance is improved. Is improved. Therefore, there are effects such as reduction of incomplete combustion, reduction of smoke, and improvement of engine output.

The reason why the guide groove 9 has a narrow groove width and a shallow groove depth will be described in detail. The temperature of the injection port 5 provided in the combustion chamber 2 is such that the air-fuel mixture burns in the expansion (combustion) stroke. This is because the temperature of the guide groove 9 is large and the thermal stress is taken into consideration because the temperature becomes higher (compared to the expansion process) due to the intake of fresh air during the intake process. For example, if the guide groove 9 is a convex blade, cracks may occur due to thermal stress. On the other hand, when the groove width of the guide groove 9 is narrow and the groove depth is shallow, the strength against thermal stress is higher than that of a convex blade or the like, and thus the possibility of cracking is reduced.

[0012]

As described above, according to the first aspect of the present invention, when the air flows into the swirl chamber from the nozzle at the time of the compression stroke, the lateral swirls are formed on the inner peripheral wall of the nozzle. The guide groove swirls the inflowing air and creates a lateral swirl in the swirl chamber, which promotes the mixing of air and fuel in the swirl chamber and improves the combustion efficiency of the mixture, resulting in reduced incomplete combustion. It is possible to reduce smoke and improve engine output.

[Brief description of the drawings]

1A and 1B are views showing an embodiment of a structure of a jetting chamber of a combustion chamber of a swirl chamber type diesel engine of the present invention, in which FIG. 1A is a front sectional view, FIG. 1B is a view seen from an arrow A in FIG. (C) is a cross-sectional perspective view of the conversion chamber.

FIG. 2 is a view showing an example of a structure of a nozzle of a combustion chamber of a conventional swirl chamber type diesel engine,
(A) is a front sectional view, (b) is a view taken in the direction of arrow B in (a)

[Explanation of symbols]

 2 Combustion chamber 3 Vortex chamber (sub chamber) 4 Fuel injection valve 5 Injection port 7 Main combustion chamber (main chamber) 9 Guide groove

Claims (1)

[Claims] 1. A subchamber is formed by press-fitting a combustion chamber into the cylinder head from its lower surface, and an interior of the subchamber facing the fuel injection valve is communicated with a main chamber on the cylinder block side through an injection port formed in the combustion chamber. In the swirl chamber type diesel engine configured to do so, a plurality of guide grooves for lateral swirl generation are helically arranged in a row on the inner peripheral wall of the jet port, and the jet port of the combustion chamber of the swirl chamber type diesel engine is characterized. Structure.