Internal-combustion engines – Particular piston and enclosing cylinder construction – Piston
Patent
1995-08-04
1996-09-03
McMahon, Marguerite
Internal-combustion engines
Particular piston and enclosing cylinder construction
Piston
29888047, B22D 1900
Patent
active
055513883
DESCRIPTION:
BRIEF SUMMARY
This invention is concerned with a method of manufacturing a piston having a cavity therein and with such a piston.
In some cases, it is necessary to provide pistons for internal combustion engines, or other purposes, with cavities. The term "cavity" is used herein to denote a substantially enclosed space having only restricted openings whereas the term "recess" is used to denote a space having a relatively large opening. For example, pistons have been proposed which have cavities in the crown thereof having one or more restricted openings which communicate with a combustion .recess in the crown. The combustion recess co-operates with the space above the crown of the piston in the cylinder in which it reciprocates to form a combustion chamber in which the fuel charge is burnt. These cavities (see U.S. Pat. No. 4,898,135) are intended to provide reaction chambers to shelter radical species of the fuel from being exhausted from the cylinder so that they can return to the cylinder to seed subsequent fuel charges. Such seeding improves the completeness of the combustion of the fuel.
The cavities to provide the aforementioned reaction chambers have hitherto been provided by manufacturing the piston in two halves, viz a lower half and an upper half which is subsequently secured to the top of the lower half. The lower half defines a lower potion of the combustion recess and also a lower portion of the reaction cheer, including the lower part of the restricted opening or openings of the reaction chamber. The upper half defines upper side portions of the combustion recess and an upper portion of the reaction chamber, including an upper part of the restricted opening or openings. The upper and lower halves of the piston can be secured together by bolts or electron beam welding. Thus, the manufacture of such pistons is complex and the possibility exists that the two halves of the piston may become detached in service. An alternative way of providing the restricted openings is to form bores through the material of the piston after the two halves thereof have been secured together. Where such bores are used, a slow process is involved because the bores are usually of small diameter and relatively long.
It is an object of the present invention to provide a method of manufacturing a piston having a cavity therein which is less complex and produces a more reliable piston.
The invention provides a method of manufacturing a piston having a cavity therein, wherein the method comprises forming a box, the box having an interior which is the size and shape of the required cavity, providing the box with at least one external projection by which the box can be supported, mounting the box in a die cavity bounded by a wall having the shape of the required piston, introducing molten metal into the die cavity so that the metal envelopes the box without entering the interior thereof, allowing the metal to solidify, and removing the piston from the die cavity, characterised in that said box is mounted in the die cavity with said external projection extending into a recess in the wall of the die cavity and resting on an abutment in said recess so that said projection serves to support and orientate the box in the cavity, machining off the portion of the projection which extends beyond the cast metal after the piston has been removed form the die cavity, and forming an opening of said cavity in a combustion recess in a crown of the piston.
In a method in accordance with the invention, the piston is essentially in one piece which is cast around the box, the piston is thus, unlikely to come apart in service, and is relatively simple to manufacture. The method can be used to provide a piston with the aforementioned reaction chambers.
Preferably, the box is formed with at least one tube projecting therefrom, the tube forming at least part of an opening of the cavity. This avoids the necessity of forming a bore to provide a restricted opening of the cavity. If desired, the tube can be used to allow air to vent from the interior of the box dur
REFERENCES:
patent: 4559685 (1985-12-01), Hara
patent: 4712600 (1987-12-01), Hamajima
patent: 4776075 (1988-10-01), Kawabata et al.
patent: 4898135 (1990-02-01), Failla
patent: 5121722 (1992-06-01), Horiuchi
patent: 5224449 (1993-07-01), Fukano
patent: 5273009 (1993-12-01), Ozawa
Patent Abstracts of Japan, vol. 10, No. 88 (M-467) [2145], 5 Apr. 1986 "Production of Piston".
Patent Abstracts of Japan, vol. 9, No. 282 (M-428) [2005], 9 Nov. 1985 "Combustion Chamber for Direct-Injection Diesel Engine and Manufacturing Thereof".
McMahon Marguerite
T&N Technology Limited
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