JPH0868358A - Built-up type piston for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a piston from wearing out by providing an inexpensive and highly resistant layer by allowing a piston-upper part made of iron material to abut on a piston-lower part made of light metal or cast iron through a mounting surface to connect them by a screw, and covering at least one mounting surface with a layer made of a cured resin which is mixed with a solid lubricant. SOLUTION: A piston-upper part 1 provided with an inner ring rib 2 is connected to a piston-lower part 4 through a screw 3. For example, a layer 6 made of a cured resin which is mixed with a solid lubricant such as graphite, is welded to a ring-like abutting surface of the piston-lower part 4, for example, by the sputtering method. Contact surfaces 8, 9 can also be additionally laminated. The layer 6 has the thickness of 10 μm to 30 μm, and the proportion of solid lubricant particles is set from 30 wt.% to 60 wt.%. As a binder, polyimide which can be cured, can be used. In this way, the layer for the mounting surface between the piston-upper part and the piston-lower part can be formed inexpensively and without requiring many labors.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a prefabricated piston for an internal combustion engine according to the preamble of claim 1.

[0002]

2. Description of the Prior Art A prefabricated piston of this kind for an internal combustion engine is known from German patent DE 36 33 134. In the case of this prefabricated piston, which comprises a piston body made of light metal and a piston bottom made of ferrous material, the piston is brought above the lower part of the piston by the end face of a ring-shaped support collar arranged inside the piston. It is supported by ring-shaped support ribs arranged and is connected to the piston lower part by means of a plurality of screws arranged parallel to the piston axis in the region of the ring ribs, and the ring rib support surface of the piston lower part is Covered by a smooth, hard, thin layer of wear-resistant material. A layer of this kind made of wear-resistant material effectively protects the soft base material in the lower part of the piston against material erosion by frictional erosion.

Layers of this type are relatively expensive and the procurement of layers, for example by explosive spraying or electroplating, is very expensive.

[0004]

SUMMARY OF THE INVENTION The object of the invention is, in the case of an assembled piston, the mounting surface between the upper part of the piston and the lower part of the piston to be mounted in a particularly simple and environment-free manner. The purpose is to be able to provide a relatively inexpensive and resistant layer which can be manufactured.

[0005]

According to the present invention, the above problems can be solved by the fact that the layer is made of a hardened resin mixed with a solid lubricant.

[0006]

A layer of this kind can be used as a running surface for a piston by itself in German patent application 41 33 54.
No. 6 is known. However, in general, in order to prevent the abrasion phenomenon due to frictional erosion at that position, the known abradable running layer of soft and wear is formed by laminating the abutting surfaces of the piston upper portion and the piston lower portion made of various materials. As for using it, I don't recommend it. Surprisingly, however, a layer of this type made of hardened resin mixed with a solid lubricant has a very high surface pressure and a short sliding distance-the amplitude of the relative movement between the upper piston part and the lower piston part is less than 1 mm. It has been found that even in the case of "small", it can be used and can provide effective wear protection.

[0007]

The invention will now be described in greater detail on the basis of an advantageous embodiment illustrated in the drawing.

The upper piston part 1 with the inner ring ribs 2 is connected to the lower piston part 4 by means of screws 3. The screws 3 are locked in the blind screw holes 5 in the ring ribs 3, respectively. A layer 6 of hardened resin mixed with a solid lubricant, such as graphite for example, is deposited on the ring-rib-shaped abutment surface 7 of the piston lower part 4 by sputtering, for example. In addition, the contact surfaces 8 and 9 can also be laminated.

The layers can be applied either by a simple brush or by the screen printing process known per se.

The layer has a layer thickness of between 10 μm and 30 μm, the solid lubricant particles having a size of between 1 μm and 10 μm, the proportion of solid lubricant particles being 30% by weight.
Between 60 and 60%. A curable polyimide can be used as the binder.

Within the material applied, for example by screen printing, to form the layers, there is a solvent, for example N-methyl-pyrrolidine (NMP). The proportion of solvent in the applied layer starting material is about 50% weight percent.

The temperatures for curing are 150 ° C. and 220
C. and curing takes place for a time of between 10 and 30 minutes.

In the case of a prefabricated piston, an arrangement of this kind makes it possible to form a layer for the mounting surface between the upper piston part and the lower piston part, which layer is relatively inexpensive. And it can be installed without requiring a lot of manpower.

[Brief description of drawings]

FIG. 1 is a side sectional view of a piston of the present invention.

[Explanation of symbols]

 1 piston upper part 2 ring rib 3 screw 4 piston lower part 5 blind screw hole 6 layer 7 mounting surface 8, 9 contact surface

Claims (2)

[Claims] 1. A prefabricated piston for an internal combustion engine, comprising a piston upper part made of ferrous material and a piston lower part made of light metal or cast iron, both parts having a ring-rib-shaped bearing surface. Of the type in which they abut one another and are screwed together in the axial direction and at least one mounting surface is covered by a layer, the layer (6) consists of a hardened resin mixed with a solid lubricant. A prefabricated piston for an internal combustion engine, characterized by being made of: 2. A prefabricated piston according to claim 1, characterized in that graphite is used as solid lubricant.