Internal combustion engine piston

Abstract

Internal combustion engine piston, particularly for diesel engines, with a bottom part and a top part which is connected separately thereto by means of an intermediate ring having a forked cross-section.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an internal combustion engine piston, particularly for diesel engines, with a bottom part consisting preferably of light metal providing the piston skirt and the gudgeon pin mounting, and, connected separably thereto, a preferably steel upper part comprising the piston crown and the ring zone, the upper part being supported by two concentric annular ribs standing out from the inside of the piston crown.

2. Description of the Prior Art

Such a piston is illustrated in the Motortechnische Zeitung, 31st Year, No. 10, October 1970, on p.415 (FIG. 3). With this construction, connection of the bottom part to the top part is effected by a centrally disposed screw bolt and by expanding bolts which pass through the outer annular ribs and are anchored in the lower part. The inner annular rib is braced on the lower part but is not bolted thereto. Therefore it is capable of additionally supporting the piston crown which is loaded by the gas forces and of transmitting these forces to the lower part. However, the inner annular rib can contribute nothing towards preventing the outwards arching of the piston crown which is observed under heavy loading and which originates from the uneven temperature and wall thickness conditions.

It would be obvious, then, also to bolt the inner annular rib to the lower part. On the other hand, it must be remembered that the preferably light metal lower part would then be weakened by additional bores. In fact, a high-strength screw connection between a light metal member and a steel part already presents so many problems that it becomes desirable to minimise the number of connecting elements although spreading the stresses over a plurality of connecting elements is acknowledged to be very favourable.

SUMMARY OF THE INVENTION

The invention is based on the problem of finding a construction in which both the annular ribs projecting from the inside face of the piston crown are rigidly bolted, but in which the lower part nevertheless has to accommodate but few screwed anchorings.

According to the invention, this problem is resolved in that between the lower part and the upper part there is an intermediate ring consisting preferably of cast-iron and of bifurcated cross-section, the base part of which is bolted to the lower part of the piston while its two form parts are bolted to the annular ribs projecting from the inside face of the piston crown.

By reason of the construction according to the invention, the bolting of both annular ribs is made possible by a plurality of favourably distributed screw elements without the lower parts becoming weakened by additional bores. Furthermore, for connection of the upper part to the intermediate ring, it is possible to use short slender screws so that the two annular ribs can remain narrow.

BRIEF DESCRIPTION OF THE DRAWING

An example of the embodiment of the object of the invention is illustrated in the attached drawings, in which:

FIG. 1 is a partial longitudinal section on the line I--I in FIG. 2 through a piston according to the invention, and

FIG. 2 is a partial cross-section through the piston, on the line II--II in FIG. 1

DESCRIPTION OF THE PREFERRED EMBODIMENT

The lower part, consisting of an aluminium alloy, is generally designated 1 while the upper parts, made from steel, is identified by reference numeral 2. It consists of the ring zone 3 and a piston crown 4, from the inside face of which projects two concentric annular ribs 5, 6. Through the lower part 1 pass strong screws 7, the ends 8 of which are screwed into the base part 9 of a cross-sectionally bifurcated intermediate ring 10 made from cast-iron. The fork parts 11, 12 of the bifurcated intermediate ring 10 are bolted to the annular ribs 5, 6 which project from the piston crown 4 by means of expanding screws 13, 14 which pass through tubes 15, 16 formed on the fork parts 11, 12. The cavity 17 formed by the bifurcated intermediate ring 10 and the annular ribs 5, 6 is connected to the coolant circuit by transfer ports 18, 19.

Claims

I claim:

1. An internal combustion engine piston including a lightweight metal lower part comprising the piston skirt, a piston crown connected with the piston skirt and comprising the upper part of the piston, which piston crown is formed from steel, two concentric integral annular ribs projecting from the inside face of the piston crown, a piston ring zone surrounding the piston crown, a cross-sectionally Y-shaped bifurcated annular intermediate ring of cast iron located between the upper and lower piston part, said ring including fork parts mating with said annular ribs respectively and a base part mating with said lower piston part, at least one tube formed on each fork part of the ring, an expanding screw provided in each tube for bolting the two fork parts of said intermediate ring to the annular ribs, and further screws in a single circular arrangement located in the piston skirt and connected to said base part for bolting the base part of the intermediate ring to the lower part of the piston.