Expansible chamber devices – Piston – With enclosed insulating space in piston part
Patent
1979-11-30
1983-02-08
Cohen, Irwin C.
Expansible chamber devices
Piston
With enclosed insulating space in piston part
92221, 92224, 123193P, F01P 104, F02F 316
Patent
active
043721940
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention, relates to a piston construction for internal combustion engines, particularly for engines which operate at high temperatures and pressures such as Diesel engines.
2. Description of the Prior Art
In such engines, the piston surfaces exposed to the force of the explosion must hold up to said explosion and remain, as soon as possible after starting, at said high operating temperatures and pressures. In contrast, the ring area, and particularly the so-called firing ring, must be protected from the effects of high temperature gas explosions in order to avoid rapid carbon depositing.
A known solution to these problems is to construct composite pistons, of which the upper, steel portion faces the explosion and is maintained at a higher temperature than a lower portion of a light alloy holding the rings and having a classic piston shape, in which the steel upper portion is set, either by assembly or in the form of an insert onto which the lower, light alloy portion is directly cast.
SUMMARY OF THE INVENTION
The object of the present invention is a composite piston of this type, comprising an upper steel surface set onto a lower portion of a light alloy by means of a screw assembly itself known, characterized in that said lower portion comprises a circular cavity, open at the top, concentrically recessed and in proximity to the ring groove beds, said cavity being covered by the steel upper portion.
Said upper portion is advantageously centered on--without contacting--a ledge above the firing ring provided on the upper border of the neck containing the ring grooves and delimiting the aforementioned cavity. Said upper portion advantageously comprises on its lower surface a circular groove covering the circular cavity and forming, within the upper portion, a zone of reduced thickness above said cavity and surrounding the central portion of the piston, which latter may contain, within the steel portion, bossings and threaded assembly holes in said bossings, with corresponding cavities, bossings and screw passage holes in the light alloy lower portion. The contact surfaces of the two assembled portions, in the central portion of the piston, are reduced to the minimum consistent with the mechanical reliability of the light alloy portion.
It follows from this construction that the steel upper portion of the piston, and particularly its central portion, is relatively isolated from the rest of the structure, with a minimum of contact surface. Moreover, the reduced thickness above the circular cavity limits calorific diffusion from center to periphery, and said periphery is only connected to the ring area by the low contact surface on the centering ledge which is itself recessed from the upper surface of the piston, of which the steel portion at its periphery advantageously comprises a circular flange forming a cover rim, receiving the centering ledge on its lower rim and--by its shape--rigidifying the steel upper portion.
BRIEF DESCRIPTION OF THE DRAWINGS
Various other objects, features and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood from the following detailed description when considered in connection with the accompanying drawings in which like reference characters designate like or corresponding parts throughout the several views, and wherein:
The FIGURE is an elecation view, partially cut away, of the piston of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
An example embodiment of a piston according to the invention will be described below, with reference to the attached drawing representing schematically a partial cutaway of a piston of the invention, in which the piston head is constructed of a steel part 1 which--as a result of its high thermic resistance--raises the equilibrium temperature of the piston on compression surface fc to a higher level than it would have been if the compression surface were made of aluminum.
Constriction E prevent
REFERENCES:
patent: 1547737 (1925-07-01), Daiber
patent: 2198771 (1940-04-01), Hazen et al.
patent: 2214891 (1940-09-01), Schrom
patent: 2743143 (1956-04-01), Maybach
patent: 3385175 (1968-05-01), Meier et al.
Cohen Irwin C.
Regie Nationale des Usines Renault
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