JPS59160061A - Piston for internal-combustion engine - Google Patents

Abstract

PURPOSE:To reduce a dead space as well as the smoke of exhaust gas by a method wherein a porous layer is provided on the top of the main body of the piston for the direct-injection type diesel engine by a material having elastic power and excellent in heat resistant property. CONSTITUTION:The top 4a of the piston 4 is formed with the recess 7 of a combustion chamber 6 while the porous layer 8 of elastic foamed metal is provided integrally on the top of the piston around the recess in such a manner that it is abutted against the lower surface 3a of a cylinder head 3. When the piston 4 is risen and arrives at the position of the upper dead point thereof, the porous layer 8 at the top of the piston collides against or contacts with the lower surface 3a of the cylinder head 3, however, the porous layer 8 is pressed and deformed. In this case, the voids of the porous layer 8 are filled with carbon in combustion gas and the layer reduces dead volume since the material thereof becomes dense. According to this method, the smoke of the exhaust gas of the engine may be reduced and the output of the engine may be increased.

Description

[Detailed Description of the Invention] More specifically, at the top dead center position of a piston in an internal combustion engine such as a direct injection diesel engine, the top clearance between the cylinder head and the top of the piston is reduced as much as possible to reduce incomplete combustion volume (so-called dead volume). This invention relates to an improvement to a piston that aims to reduce engine volume (volume) as much as possible, reduce engine exhaust smoke, and improve engine output.

Conventionally, in internal combustion engines such as direct-sounding diesel engines,
When taking into account the variation in the thickness of the hend gasket installed between the top of the piston and the bottom of the cylinder head when tightening, and the accumulated error in the dimensional tolerances of the piston, piston pin, connecting rod, crankshaft, etc. , top clearance is 0.6 to 1. It is normal to take it to about 01111.

FIG. 1 shows a cross-sectional view of the combustion chamber of a conventional internal combustion engine, in which a cylinder head 3 is stacked on the upper surface of a cylinder 1 (cylinder body) with a hend gasket 2 interposed therebetween.
These were all tied together with bolts (not shown).

A piston 4 is inserted into the bore 1a of the cylinder 1, and a fuel injection valve 5 is provided in the cylinder head 3 to inject fuel into a combustion chamber 6.

As mentioned above, if a top clearance h inevitably occurs between the lower surface of the ring head 3 and the upper surface of the piston 4, the part indicated by D in the figure becomes an incomplete combustion part (so-called dead volume). , this dead volume D
There is a problem in that the compression ratio decreases depending on the size of the fuel, and as a result, the improvement in combustion efficiency is hindered, resulting in incomplete combustion and deterioration of exhaust gas.

Therefore, in order to improve the combustion efficiency of the engine, it is clear that it is desirable to reduce the dead volume portion as much as possible.

In particular, in a small displacement direct-injection diesel engine, the presence of the above-mentioned dead volume has a significant adverse effect, causing an increase in exhaust smoke and a decrease in engine output.

In addition, in order to reduce the gap between the piston and the cylinder head at the top dead center position of the piston, a heat insulating layer is formed on the top of the piston using a heat-resistant material (for example, Utility Model No. 57-52. -178148. Jitsukaisho 5
7-21/169), but in such conventional methods, the piston top is simply a heat insulating layer, or the piston top is made of a hard material, so the piston top does not easily deform. Because of this structure, there was a risk that the piston would collide with the underside of the cylinder head when the engine was operating, causing damage to the engine.

This invention was devised by focusing on the conventional problems, and its purpose is to reduce the dead volume between the piston body and the cylinder head at the top dead center position of the piston body of an internal combustion engine. To provide a piston for an internal combustion engine that can reduce engine smoke as much as possible and improve engine output.

In order to achieve the above object, the present invention provides a piston that slides in the cylinder of an internal combustion engine and defines a combustion chamber of the engine. The porous layer is formed of a material containing a porous material, and the porous layer contacts the lower surface of the cylinder head during operation of the engine to reduce the gap in the combustion chamber.

The present invention will be described in detail below based on the accompanying drawings.

Components that are the same as those of the conventional example explained in FIG.

FIG. 2 shows a first embodiment of a piston 4 according to the present invention, in which a recess 7 constituting a combustion chamber 6 is formed in the center of the top 4a of the piston 4 (hereinafter referred to as the piston body 4). Furthermore, around the combustion chamber 6, there is integrally formed a porous layer 8 made of a metal material (foamed metal) having an elastic force that comes into contact with the lower surface 3a of the cylinder head 3 during engine operation. is formed.

Examples of methods for forming the porous layer 8 include the conventionally known "differential solubility method" and "powder metallurgy method."

It is molded into a predetermined shape with a constant thickness by a "molten metal direct mixing method" or a "zero gravity mixing method". The porous layer 8 formed in this way is placed inside a mold for manufacturing the piston body 4, and a predetermined molten metal is poured into the mold to form the porous layer 8 and the piston body 4. It is integrally molded.

Further, FIGS. 3 to 6 show other embodiments of the present invention,
In FIG. 3, a porous layer 8a is formed on the top 4a of the piston body 4 by thermal spraying, sintering, or the like. Also the fourth
In the figure, a layered flexible material is fixed to the top 4a of the piston body 40 to form a porous layer 8b.

Further, FIGS. 5 and 6 show an embodiment in which porous layers 8c and 8d made of compressed material are integrally formed on the top 4a of the piston body 4 by welding or adhesive 9, and the embodiment shown in FIG. A recess 10 is formed in the top 4a of the piston body 4, and a compressed porous layer 8c of a predetermined thickness made of foamed metal is fixed to the recess 10 by welding.

FIG. 6 also shows that the compressed material constituting the porous layer 8d is a metal fiber or a heat-resistant material (for example, a woven fabric made of ceramic fiber or felt).
The porous layer 8d thus formed is attached using an adhesive 9.

Next, the operation will be explained based on FIGS. 7 and 8.

First, when the piston body 4 rises from the state shown in FIG. 7 and reaches the top dead center position shown in FIG.
a, but at this time, the upper end of the porous layer 8 is pressed between the piston body 4 and the lower surface 3a of the cylinder head 3 and deforms. At this time, by filling the voids 11 that make up the porous layer 8 with carbon in the combustion gas, the material that makes up the porous layer 8 becomes substantially dense, reducing the dead volume D. It is something that can be done.

As a result, combustion efficiency can be significantly improved.

As described above, in a piston that slides in a cylinder of an internal combustion engine and defines a combustion chamber of the engine, the top of the piston body is made of a material having elastic force and high heat resistance. The porous layer is formed so that it comes into contact with the lower surface of the cylinder head when the engine is operating, reducing the gap in the combustion chamber, thereby reducing the dead volume in the combustion chamber, reducing engine exhaust smoke, and reducing engine exhaust smoke. This has the effect of improving the output.

Moreover, since the structure is simple, it can be manufactured at low cost and maintenance is also easy.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a main part showing a combustion chamber of an internal combustion engine using a conventional piston, Fig. 2 is a cross-sectional view of a piston according to the present invention, and Figs. 3 to 6 are other embodiments of the piston body. FIGS. 7 and 8 are cross-sectional views of main parts showing the operating state of the piston. 1. Cylinder 3... Cylinder head 3a... Bottom surface of cylinder head 4... Piston (piston body) 4a... Top of piston 6... Combustion chamber 8... Porous 'JR, layer agent, patent attorney Shin Ogawa - Patent Attorney Ken Noguchi Teru Patent Attorney Kazuhiko Saishita Figure 1 Figure 3 Figure 2 Figure 4

Claims (1)

[Claims] In a piston that slides in a cylinder of an internal combustion engine and defines a combustion chamber of the engine, a porous layer is formed on the top of the piston body using an abrasive material that has elasticity and is highly heat resistant. A piston for an internal combustion engine, characterized in that the piston is configured to abut against a lower surface of a cylinder head during operation of the engine to reduce a gap within a combustion chamber.