Second pressure ring for Al cylinders and its producing method

Details Second pressure ring for Al cylinders and its producing method Second pressure ring for Al cylinders and its producing method

1998-03-09

2001-03-27

Knight, Anthony (Department: 3626)

Seal for a joint or juncture

Seal between relatively movable parts

Piston ring or piston ring expander or seat therefor

C277S491000

Reexamination Certificate

active

06206379

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a second pressure ring to be mounted on a piston in internal combustion engines employing A1 cylinders and a method for producing such a second pressure ring.
BACKGROUND OF THE INVENTION
In prior art techniques, as disclosed in Japanese laid-open Patent Gazette Nos. 246087/1996 and 19757/1997, as cylinder liners of reciprocating internal combustion engines, cylinder liners made of hyper-eutectic aluminum-silicon alloy by an aluminum alloy casting method (hereinafter, called A1 cylinders) have been developed. Such liners are excellent in anti-abrasion property, have less consumption of lubricant and less abrasion on the piston, and promote light engine weight, and thus are increasingly being used.
A piston for such an A1 cylinder is normally provided with a set of three piston rings. The three piston rings include a top ring (pressure ring) with a surface which is nitriding-treated, a second pressure ring of which the outer peripheral sliding surface is chromium-plated, and an oil ring forming a third ring (oil scraping ring). Incidentally, as opposed to an A1 cylinder such as, for example, one made of A390 alloy, a pressure ring made of acicular cast iron without plating thereon could be employed as the second pressure ring.
The second pressure ring needs to be airtight for backing up the top ring and to provide a degree of scraping for scraping a little lubricant that the oil ring may possibly leave unscraped.
As for the second pressure ring, therefore, the outer periphery thereof should slant so as to be downwardly divergent or slant with an undercut, and the lowermost portion of its sliding surface should be formed with a sharp edged shape. On the other hand, in order to prevent the cylinder from being scratched, the sliding surface should be chromium-plated and the slant shaped surface should be polished to make the edged portion sharply and smoothly finished. Therefore, it has been hard in practice to satisfy requirements for both providing the scraping property and preventing longitudinal scratching of the bore (cylinder side).
SUMMARY OF THE INVENTION
An object of the invention is to provide a second pressure ring which keeps a scraping property and prevents the cylinder side from being scratched longitudinally, and a method for producing it.
A second pressure ring for A1 cylinders according to the invention is made of iron without plating thereon and has the outer peripheral sliding surface thereof downwardly divergent so as to slant. The second pressure ring includes, at the lower end of the outer peripheral sliding surface, a slanting, upwardly divergently worked portion of less than 0.15 mm in its axial direction. The junction between the outer peripheral sliding surface and the slanting worked portion is lapped for finishing.
A method for producing a second pressure ring for A1 cylinders, in which the outer peripheral sliding surface of the second pressure ring, made of iron without plating thereon is downwardly divergent so as to slant, comprises working upwardly divergently the lower end of the outer peripheral sliding surface of the second pressure ring in a range of less than 0.15 mm in its axial direction, and finishing by lapping cylindrically the junction between the outer peripheral sliding surface and the slanting worked portion.
A second pressure ring for A1 cylinders according to the invention, made of iron without plating thereon and with the outer peripheral sliding surface thereof being downwardly divergent so as to slant, has the outer peripheral sliding surface buffed. The lower end of the outer peripheral sliding surface is lapped for finishing.
A method for producing a second pressure ring for A1 cylinders according to the invention, in which the outer peripheral sliding surface of the second pressure ring made of iron without plating thereon is downwardly divergent so as to slant, comprises buffing the outer peripheral sliding surface, and then lapping cylindrically the lower end of the outer peripheral sliding surface for finishing.
A second pressure ring for A1 cylinders according to the invention, made of iron without plating thereon and with the outer peripheral sliding surface thereof being downwardly divergent and slanting, has a resin coating of a thickness of 3 &mgr;m or more than 3 &mgr;m on the outer peripheral sliding surface.
A method for producing a second pressure ring for A1 cylinders according to the invention, in which the outer peripheral sliding surface of the second pressure ring made of iron without plating thereon is downwardly divergent so as to slant, comprises applying a resin coating of a thickness of 3 &mgr;m or more than 3 &mgr;m on the outer peripheral sliding surface.


REFERENCES:
patent: 3926166 (1975-12-01), Packard
patent: 4432313 (1984-02-01), Matlock
patent: 5598763 (1997-02-01), Rao et al.
patent: 5901963 (1999-05-01), Hite et al.
patent: 8-246087 (1996-09-01), None
patent: 9-19757 (1997-01-01), None

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