JPH03179128A - Manufacture of piston combustion chamber for direct injection type diesel engine - Google Patents

Abstract

PURPOSE:To form a combustion chamber into the desired volumetric capacity and thereby manufacture the combustion chamber simply and inexpensively by forming the combustion chamber equipped with both recess and projection parts, on a surface with a fuel injection nozzle in a piston, and machining this projection properly. CONSTITUTION:A geometrical combustion chamber 7 equipped with a recess 3 and a volume regulating projection 6 installed in a spot where the effect of combustion in this recess 3 is little, is precisely casted on a face-to-face plane 2a with a fuel injection nozzle 5 in a piston 2 housed in a cylinder 1 free of slide motion by means of a lost wax process, by way of example. Then, machining such as metalcutting or the like is applied to this volume regulating projection 6, thereby securing the desired combustion chamber volume. With this constitution, the geometrical combustion chamber 7 is manufactured so simply and inexpensively with applying almost nothing of the metalcutting and so on.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a piston combustion chamber for a direct injection diesel engine.

[Prior Art] In general, a diesel engine burns atomized injected fuel by mixing it with L [compressed air]. Therefore, the combustion chamber formed in the piston is designed to mix the injected fuel and compressed air well. It is necessary to be able to burn the fuel, and to be able to achieve the ignition temperature of the fuel by increasing the compression pressure. As a conventional piston combustion chamber, there is one shown in FIG. 2, for example.

That is, on the facing surface 2a of the piston 2 that faces the lower head surface 1a of the cylinder head 1, a combustion chamber 4 having recesses 3 of various shapes is provided by machining such as cutting.
A fuel injection nozzle 5 is provided in the cylinder head 1 corresponding to the center of the combustion chamber 4, and fuel is injected radially from the fuel injection nozzle 5 and combusted.

In recent diesel engines, fuel is injected at high pressure into the combustion chamber 4 in order to improve fuel efficiency and exhaust gas, and with this high pressure injection, droplets of fuel droplets on the wall 4a of the combustion chamber 4. The rate of adhesion increases, which causes problems such as poor mixing of fuel and compressed air.

Therefore, a combustion chamber with a complicated shape is required in order to make the fuel droplet adhesion rate to the wall 4a of the combustion chamber 4 appropriate as fuel is injected at a higher pressure.

[Problems to be Solved by the Invention] However, since the combustion chamber 4 has conventionally been manufactured entirely by machining such as cutting, the shape is naturally limited, and it is difficult to obtain a combustion chamber with a desired complex shape. I couldn't do it.

In view of the above circumstances, an object of the present invention is to provide a method for manufacturing a piston combustion chamber for a direct injection diesel engine, which can manufacture a combustion chamber with a desired complicated shape almost without machining such as cutting. The purpose is to

[Means for Solving the Problems] The present invention provides a recessed portion by precision casting on the surface facing the fuel injection nozzle of a piston that slides in a cylinder equipped with a fuel injection nozzle, and a volume adjustment at required locations of the recessed portion. A direct injection diesel engine, characterized in that the combustion chamber is formed with a combustion chamber each having a target volume, and the volume adjustment projections are appropriately machined such as cutting to form the combustion chamber to a target volume. The present invention relates to a piston combustion chamber manufacturing method.

[Function] Since the combustion chamber is formed by precision casting, it is possible to form the combustion chamber into a complex shape that provides an appropriate fuel droplet adhesion rate, and the convex portion for volume adjustment can be machined such as cutting. By applying this, the volume of the combustion chamber can be set to the target volume, and the desired compression ratio can be obtained.

[Example] Embodiments of the present invention will be described based on the drawings.

FIG. 1 is a sectional view of a combustion chamber of a piston according to the method of manufacturing a piston combustion chamber of a direct injection diesel engine according to the present invention. However, the same reference numerals as in FIG. 2 indicate the same parts.

A recess 3 is formed on the surface 2a of the piston 2 facing the fuel injection nozzle 5.
A combustion chamber 7 having a complicated shape and having a volume adjusting protrusion 6 at a location where the influence of combustion is relatively small in the recess 3 is precision cast by a lost wax method. Thereafter, the volume adjusting convex portion 6 is subjected to machining such as cutting to obtain a desired combustion chamber volume.

Since the combustion chamber 7 is manufactured by precision casting without machining such as cutting, it can be formed into a complex shape that allows the fuel droplet adhesion rate to the wall portion 7a to be appropriate, thereby ensuring good mixing of fuel and compressed air. As a result, it is possible to cope with high-pressure fuel injection. Also, a volume adjustment convex portion 6 provided in the combustion chamber 7
By performing machining such as cutting, a desired combustion chamber volume can be obtained, and as a result, a desired compression ratio can be obtained and combustion efficiency can be improved.

The present invention is not limited to the illustrated and described embodiments; for example, a plurality of volume adjustment convex portions may be provided in the recessed portion of the surface of the piston that faces the fuel injection nozzle, and methods other than the lost wax method may be used. Precision casting of the concave portion and the volume adjusting convex portion is optional, and it goes without saying that various changes may be made without departing from the gist of the present invention.

[Effects of the Invention] According to the method for manufacturing a piston combustion chamber for a direct injection diesel engine of the present invention, various excellent effects as described below are exhibited.

(1) The combustion chamber is manufactured by precision casting without using machining such as cutting, and only machining such as cutting is performed on the convex part for adjusting the volume of the combustion chamber, so machining such as cutting is significantly reduced. It is possible and economical.

(ii) With O), it is possible to obtain a combustion chamber with a complicated shape with an appropriate fuel droplet adhesion rate, which could not be manufactured conventionally, and it is possible to cope with high-pressure fuel injection.

0 By performing machining such as cutting on the volume adjusting convex portion, a desired combustion chamber volume can be easily obtained and a desired compression ratio can be easily obtained.

By (f)G), it is possible to perform a good combination of fuel and compressed air, improving combustion and exhaust gas, and improving the performance of the diesel engine.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a piston combustion chamber of a piston combustion chamber produced by the method of manufacturing a piston combustion chamber for a direct injection diesel engine according to the present invention, and FIG. 2 is a longitudinal sectional view of a piston combustion chamber of a conventional direct injection diesel engine. l is the cylinder head, 2 is the piston, 2a is the inner surface,
3 is a concave portion, 5 is a fuel injection nozzle, 6 is a volume adjustment convex portion,
7 indicates a combustion chamber.

Claims (1)

[Claims] 1) On the surface of a piston sliding in a cylinder equipped with a fuel injection nozzle that faces the fuel injection nozzle, a combustion chamber is formed by precision casting, and the combustion chamber is provided with a concave portion and volume adjustment convex portions at required locations in the concave portion. A method for manufacturing a piston combustion chamber for a direct injection diesel engine, characterized in that the volume adjustment convex portion is suitably machined such as cutting to form the combustion chamber to a target volume.