Built-up piston

Details Built-up piston Built-up piston

1999-04-09

2001-05-01

McMahon, Marguerite (Department: 3747)

Internal-combustion engines

Particular piston and enclosing cylinder construction

Piston

Reexamination Certificate

active

06223710

ABSTRACT:

The invention relates to a built-up piston as defined in the introductory part of claim
1
.
A corresponding piston with a lower part made from an aluminum material is known from U.S. Pat. No. 4,517,930. The development in connection with such pistons is in the direction of ignition pressures of more than 150 bar. As the ignition pressure load increases, the load acting on the gudgeon pin bosses is found to be excessively high and may lead to initial fissuring of the bosses and cracks in the supporting elements. This problem has been solved heretofore by manufacturing the lower part from an iron material as well, whereby a piston cast in one single piece from grey cast iron is then employed as well, if need be.
The drawback of said solution is that the weight advantage gained by the use of aluminum materials is dispensed with.
The invention, therefore, deals with the problem of increasing in connection with a piston of the type specified above the strength of the bosses and supports as well as the strength within the region of the screwed joint while keeping the weight of the piston low.
Said problem is solved in connection with pistons of said type by the design according to the characterizing features of claim
1
or
2
. Advantageous further developments are the objects of the depending claims.
Since with the solution as defined by the invention only the region of the bosses and, if need be, of the boss supports are made of iron material, said regions being highly stressed in terms of strength, whereas the shaft and the bottom of the lower part absorbing the forces from the head of the piston, however, continue to consist of an aluminum-based material, the piston has, combined with a highly improved loading capacity of the bosses, a lower weight than a comparable piston completely consisting of an iron material. The pressure pieces normally used with pistons of this type for admitting the force into the lower aluminum part can be advantageously omitted if, as shown in the exemplified embodiment, the force admitted by the connection screws is introduced in each case in the iron material of the upper part and the bosses and the boss support or connection plates.
If the gudgeon pin bosses screwed to the lower part consist of steel, preferably forged steel is employed. However, cast steel can satisfy the requirements as well.
Furthermore, as compared to pistons with lower parts made from cast iron, advantages are gained also with respect to the required quality controls and in regard to material and casting defects.


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patent: 38 30 033 (1989-06-01), None
patent: 0 731 268 (1996-09-01), None

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