JPS60182341A - Internal-combustion engine covering combustion chamber wall surface with porous heat insulating material - Google Patents

Abstract

PURPOSE:To improve volumetric efficiency every so better, by covering a combustion chamber wall surface of a piston or the like with a porous heat insulating material. CONSTITUTION:A piston 4 is covered with a porous heat insulating member consisting of a porous heat insulating material 2 and a metallic film layer 3. This porous heat insulating material 2 is of ceramic having a minute hole of more than 80% in porosity. A combustion chamber wall surface of a head bottom, a liner, etc., is also covered in addition to the piston. With this constitution, heat in time of combustion will no longer escape owing to a heat insulating effect of the heat insulating layer and what is more, since heating for suction air is reducible, volumetric efficiency is thus improvable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat insulating structure for a combustion chamber in an internal combustion engine.

[Prior art]

In conventional engines, in order to increase thermal efficiency, an adiabatic engine has been proposed and prototyped, in which the cylinder head, piston, cylinder liner, etc. are provided with a heat insulating layer made of a heat insulating material such as ceramic.

However, the idea behind conventional adiabatic engines is to completely prevent the heat of the combustion gas from escaping during the expansion stroke, and therefore, a fairly thick insulating layer of gold film is used.
The heat capacity of the insulation layer increases. If the heat capacity of the heat insulating layer is large, the heat stored in the heat insulating layer during the expansion stroke will heat the air sucked into the cylinder during the intake stroke, and due to the thermal expansion, the intake air will decrease, resulting in a reduction in engine volume. There is a problem that efficiency decreases and fuel consumption worsens.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems in the prior art and provide an internal combustion engine that has excellent volumetric efficiency while maintaining a heat insulating effect.

[Structure of the invention]

The present invention is an internal combustion engine in which the walls of the combustion chamber such as the piston, the lower surface of the head, and the liner are covered with a porous heat insulating material having a porosity of 80% or more and having a heat-resistant metal film layer on the surface.

The present invention will be explained in detail below.

The inventors of the present invention have conducted extensive research in order to solve all of the problems in the prior art. In other words, focusing on the fact that porous insulation materials with high porosity have high insulation properties and low heat capacity, attempts were made to cover the walls of combustion chambers of internal combustion engines with porous insulation materials with high porosity. Since porous η insulation materials with a high ratio usually have a continuous micropore structure, high-temperature gas generated during the combustion process is retained in the micropores, and in the next intake stroke, the high-temperature gas in the micropores is transferred to the intake air. It was found that the volumetric efficiency deteriorates as the intake air temperature increases, and fuel efficiency also deteriorates. Therefore, in order to prevent hot gas from entering and exiting the micropores, a thin metal film layer is provided on the surface of the heat insulating material with a large porosity, which not only improves the heat insulation but also provides an internal combustion engine with excellent volumetric efficiency. I discovered that it is possible.

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

Figure 1 shows a complete cross-sectional view of a porous heat insulating material with a heat-resistant metal film layer on its surface used in the present invention, number 1 is a heat insulating material with a metal film layer on its surface, and number 2 is a porous heat insulating material. ,3
indicates a metal film layer.

FIG. 2 is a complete cross-sectional view of a piston whose upper surface is covered with the heat insulating material of the present invention, where 4 is the piston, 2 is the heat insulating material, 6 is the metal film layer, and 5 is the heat insulating material for joining the heat insulating material to the base material. This shows the metallizing layer provided on the back side of the material.

An example of the porous heat insulating material used in the present invention is ceramic having micropores.

The porosity of the heat insulating material 1 is preferably 80% or more. To explain the reason for this, Fig. 3 is a diagram showing the relationship between the porosity of the heat insulating material and the degree of heat insulation.
When the porosity becomes 80% or more, the degree of insulation rapidly decreases. Therefore, the thickness of the metal film layer should be as thin as possible, preferably less than o, +gut.

The thickness of the heat insulating material 1 is preferably 0.2 to 3111 mm in consideration of ease of manufacture and volumetric efficiency of the engine. To explain the reason for this, Figure 4 is a diagram showing the relationship between the thickness of an insulating material with a porosity of 80%, the degree of insulation, and the volumetric efficiency, and from the perspective of the degree of insulation, it is preferable that the thickness of the insulating material be thicker. When viewed from the volumetric efficiency, a thickness of 3B or less is preferable.

Further, the pore spacing of the porous heat insulating material 2 is preferably 0.11111 or less. To explain the reason for this, Figure 5 shows the relationship between partition wall thickness (hole spacing), volumetric efficiency, and degree of insulation for a 0.7 m thick insulation material. This is because when the thickness is 0.1 mm or less, both volumetric efficiency and heat insulation are excellent.

The metal film layer can be produced by depositing a heat-resistant metal such as titanium or nickel on the surface of the porous insulation material or by laminating a film of the metal. In other words, after metallizing the surface of the insulation material, plating with a heat-resistant metal such as nickel, etc.
Alternatively, a metal film layer can be formed by metallizing the surface of the ceramic bag and then laminating a film of a heat-resistant metal using silver soldering. Next, the method of joining the heat insulating material onto the base material is to metallize the back side of the porous heat insulating material and then braze the PCI.

This may be cast to form parts (or the FC
They can be joined by any method such as providing bolt holes in the material layer or bolting from the back side.

In the above description of a heat insulating material having continuous micropores, 15 parts by volume of silicon nitride with a particle size of around 10 μm and an average diameter of 10 μm are used.
A heat-resistant metal film may be used on the surface of a heat insulating material produced by mixing 85 volume parts of hollow carbon spheres with a wall thickness of 0 μm and 1 to 2 μm, molding the mixture into a predetermined shape, and performing pressureless sintering. The insulation manufactured by this method has many independent micropores, but depending on the manufacturing conditions, the micropores may be exposed on the surface, and in this case, the high temperature gas during the combustion process is retained in these pores. This is because the volume effect is worsened by mixing into the intake air during the intake stroke.

In the present invention, the wall surface of the combustion chamber, that is, the upper surface of the piston, the lower surface of the head, the upper surface of the lychee or the upper surface of the pulp, etc. may be covered with a heat insulating material having a large number of micropores and having a metal film layer on the surface. By doing this, the heat during combustion will not escape due to the heat insulating effect of the heat insulating material layer. Moreover, since high-temperature gas can be prevented from entering and exiting the micropores, heating of the intake air can be reduced, and the volumetric effect can therefore be improved.

[Brief explanation of the drawing]

Figures 1 and 2 are preliminary drawings for explaining one embodiment of the present invention, Figure 6 is a diagram showing the relationship between the porosity of the heat insulating material and the degree of heat insulation, and Figure 4 is the thickness of the heat insulating material. FIG. 5 is a diagram showing the relationship between the thickness of the partition wall of the heat insulating material, the volumetric efficiency, and the degree of heat insulation.

Claims (1)

[Claims] t An internal combustion engine in which the piston, lower head surface, liner, and other combustion chamber walls are covered with a porous heat insulating material having a porosity of 80% or more and having a heat-resistant metal film layer on the surface.