Expansible chamber devices – Piston – With separable means for pivotally mounting connecting rod...
Patent
1995-09-07
1997-08-05
Lopez, F. Daniel
Expansible chamber devices
Piston
With separable means for pivotally mounting connecting rod...
F16J 114
Patent
active
056531567
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a light metal piston for highly stressed internal combustion engines.
In connection with such light metal pistons that are known in practical life, various measures have been implemented--for the purpose of permitting such pistons to be capable of withstanding the stresses caused by the ignition pressure--to reduce, on the one hand, especially bending through of the piston pin, which may lead to cracks in the bosses of the piston pin, and to protect the combustion chamber trough against incipient cracks. For such purpose, such light metal pistons are, for example provided with bushes in the bores of the piston pin bosses, and the trough of the combustion chamber is fitted with an additional reinforcement.
For the purpose of preventing incipient boss cracking, it is known from DE-PS 36 09 019 to provide the boss bores, in each case on both sides, with pocket-like recesses from the inner end of the boss bores, such recesses extending across a certain length in the longitudinal direction of the boss bores. A connection between said recesses and the end of the boss bore on the outer side of the piston is provided by corresponding grooves in the boss bores.
The problem of the present invention is to find in a simple way of engineering a piston in connection with which the stresses on the edge of the combustion chamber trough are kept low without unnecessarily increasing the stresses in the bosses of the piston pin.
Said problem is solved with a light metal piston with the features set forth below.
Advantageous developments of the invention are contained in the dependent claims.
The invention is explained in greater detail in the following on a preferred exemplified embodiment shown in the drawing, in which:
FIG. 1 shows a lateral, partly sectional view of a light metal piston according to the invention;
FIG. 2 shows a top view of the section along line II--II in FIG. 1.
FIG. 3 shows a lateral, partly sectional view of another embodiment of the invention;
FIG. 4 shows a top view of the section along line II--II in FIG. 3; and
FIG. 5 shows a cross-sectional view of the section enclosed by the dotted line in FIG. 4.
A light metal piston 1 for an internal combustion engine, in particular for a highly stressed Diesel engine for a motor vehicle, consists in one piece of a piston head 2 and a piston skirt 3. A unreinforced combustion chamber trough 5 and the annular grooves 6 are shaped by molding in the piston bottom 4 of the piston head 2, whereby the uppermost annular groove 6 is reinforced with an annular support 7. The piston pin bosses 8 are integrated in the piston skirt 3, said bosses having the bores 9 for receiving a piston pin (not shown). Each bore 9 is, at its inner end 10, widened (cambered) in a part zone X toward the inner end, whereby the curvature of such widening may have the form of a polygon as shown in FIG. 5. The transition of said widening into the frontal surface of the boss has a radius of 3 mm, whereby the axial length of the rounding in the longitudinal direction of the piston pin comes to 1 mm in a piston with a diameter of 80 mm. Furthermore, in a part zone Z, the bore 9 is designed as a shaped bore 11 which, in the part zone Z, the latter extending from the outside inwardly and conforming to the supporting zone--which is outwardly limited by the groove for the safety ring of the piston pin--, conically widens from the inside outwardly, for example trumpet-like. The widening (in the drawing shown with an exaggerated size) has an angle alpha of 5 minutes. Such widening, which should have an angle of from 2 to 10 minutes, may be stepped as well, as shown in FIGS. 3 and 4, whereby the widening in the more inwardly disposed part zone Z of the shaped bore 11 should have a smaller angle than in the more outwardly disposed zone of the shaped bore 11.
Between the outwardly conically widening, shaped bore 11 in the part zone Z, and the widening (cambering) provided for at the inner end 10 in the part zone X, the bore 9 has a cylindrically extending zone Y.
Furthermore, in
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Issler Wolfgang
Kollotzek Helmut
Lopez F. Daniel
Mahle GmbH
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