CS201273B1 - Piston from the alloyed perlitic plastic cast iron for the ignition engines - Google Patents

Abstract

In a piston made of alloyed perlitic modular cast iron the head of which is supported by a concentric circular fin 2 there is provided a cooling annulus 9 defined by the peripheral portion of the piston head 1 and by the piston skirt 4 in the region of the piston ring grooves. The fin 2 projects from a cross wall 3 which extends perpendicularly to the longitudinal piston axis and forms together with said fin a cooling chamber 8 disposed below the central portion of the piston head while merging into the piston skirt in the region of the piston ring grooves. The cooling chamber is connected, via short, rigid ribs 5, with gudgeon pin bosses 6. The concentric circular fin is provided with at least two apertures 7 constituting communication passages between the cooling chamber 8 and the cooling annulus 9. <IMAGE>

Description

The present invention relates to a piston of alloyed pearlitic nodular iron for circulating oil-cooled internal combustion engines.

The prior art single-piece ductile cast iron pistons have a piston base supported by ribs anchored in the piston pin receiving lugs, which are separated from the piston housing, so that the combustion pressures acting on the piston bottom are not transmitted to the piston housing. The support ribs simultaneously form the inner wall of the annular cooling chamber bounded by the circumference of the piston bottom and the piston shell at the location of the piston rings. In this way, a safe low temperature of the piston is achieved at the location of the piston ring grooves. The disadvantage of this construction is that the central part of the piston bottom is cooled and reaches a high temperature which affects the stability of the mechanical values of the piston material. At the same time, a very uneven temperature distribution in the bottom of the piston occurs, with high temperature gradients between the uncooled and intensely cooled piston section causing high temperature stresses, which increases the risk of fatigue failure of the material. The two lugs for receiving the piston pin, separated from the piston housing, must be unsuitable for achieving sufficient rigidity and accuracy of the borehole 1 with respect to stress and casting technology.

The aforementioned drawbacks are eliminated by a circulating oil cooled pearlitic ductile iron alloy, which consists in that the concentric annular rib is anchored in a partition perpendicular to the longitudinal axis of the piston, which forms a concentric annular cooling chamber below the middle of the piston bottom and to the piston housing at the location of the piston rings, being connected by low rigid ribs to the stubs for receiving the piston pins, wherein the concentric circular rib is provided with at least two openings forming a connection between the cooling chamber and the cooling ring.

By forming a cooling chamber below the central part of the piston bottom, connected by openings in a concentric circular rib to the cooling ring bounded by the peripheral part of the piston bottom and the piston housing, intensive cooling of the entire piston bottom has been achieved, its temperature being more uniform and lower. A main element of the rigid joint between the eyes for receiving the piston pin has been formed by a transverse line perpendicular to the longitudinal axis of the piston.

An exemplary embodiment of a piston according to the invention is shown in the attached drawing. On the left half of the drawing, a longitudinal section of the piston is guided by a plane passing through the axis of the piston pin, on the right half of the drawing, a longitudinal section of the piston is guided by a plane perpendicular to the axis of the piston pin. The piston base 1 is supported by a concentric annular rib 2 anchored to a crossbar 3 perpendicular to the longitudinal axis of the piston, passing into the piston housing 4 at the location of the piston ring grooves and connected by the low rigid ribs 5 to the lugs 6 for receiving the piston. The crossbar 3 forms the main element of the rigid connection between the lugs 6 for receiving the piston pin. Zebro 2 is provided at two opposite locations with openings 7 connecting the cooling chamber -8 formed below the central part of the piston bottom 1 with the cooling ring 9 delimited by the circumferential part of the piston bottom 1 and the piston housing 4 at the piston ring grooves. In the middle of the crossbar 3 is an opening 10 into which an insert 11 with a neck 12 is inserted, extending beyond the bottom of the crossbar 3 and ensuring a minimum oil level in the cooling chamber 8. The cooling oil is supplied to the piston via the connecting rod and the piston pin and from there through the bore 13 into the cooling ring 9 and further the holes 7 in the concentric circular rib 2 into the cooling chamber 8 and through the neck 12 in the liner 11 flows into the engine crankcase.

Claims (1)

A piston of alloyed pearlitic nodular cast iron - for internal combustion engines, - cooled by circulating oil, the bottom of which is supported by a concentric circular rib and the cooling ring is delimited by the circumferential part of the piston bottom and the piston housing at the piston rings; the rib (2) is anchored in a partition (3), perpendicular to the longitudinal axis of the piston, which forms with the concentric circular rib (2) a cooling chamber (8) - below the middle part of the piston bottom (1) and - passes. into the piston housing (4) at the location of the piston rings, being connected by low rigid ribs (5) to the lugs (6) for receiving the piston pin, the concentric circular rib (2) having at least two holes (7) forming the connection between the cooling chamber (8) and the cooling ring (9).