Seal for a joint or juncture – Seal between relatively movable parts – Piston ring or piston ring expander or seat therefor
Reexamination Certificate
1999-03-17
2001-04-10
Knight, Anthony (Department: 3626)
Seal for a joint or juncture
Seal between relatively movable parts
Piston ring or piston ring expander or seat therefor
C277S443000, C277S444000, C277S447000, C420S104000, C420S105000, C420S110000
Reexamination Certificate
active
06213474
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to piston rings for use in internal combustion engines, and more particularly to piston rings, including compression rings and side rails of combined type oil rings, made of steel material suitable for gasoline engines and diesel engines, and to a combination of first and second compression rings made of steel material suitable for large diesel engines.
BACKGROUND OF THE INVENTION
Conventional piston rings, including compression rings and side rails of combined type oil rings, of gasoline and diesel engines, are made of martensite-based stainless steel with the surface thereof applied with nitriding treatment, to improve abrasion resistance. As for conventional first compression rings of large diesel engines, rings made of cast iron have been used with the external circumference thereof applied with chromium plating. When the EGR (exhaust gas recycling) system is employed in accordance with the exhaust gas regulations, however, the cast iron applied with chromium plating, comes to lack in sufficient abrasion resistance, whereby the first compression rings are required to improve the abrasion resistance thereof by having the rings made of martensite-based stainless steel, with the external circumference thereof applied with nitriding treatment.
As for second compression rings of large diesel engines, the operational environment in cylinders of the engines, is not so severe as the first compression rings. Nevertheless, a problem of insufficient abrasion resistance occurs in case of conventional rings using cast iron applied with chromium plating, when the EGR system is employed. Besides, when implementing axially thinner second compression rings to improve the engine fuel consumption, the cast iron rings come to lack in sufficient strength. The second compression rings are, therefore, also desired to be made of steel.
Compression rings made of steel are disclosed in Japanese Patent Publications No. 58-25863 (1983) and No. 61-54103 (1986), wherein the first and second compression rings are both provided to be made of an identical steel material.
In case of manufacturing piston rings, including compression rings and side rails of combined type oil rings, for use in internal combustion engines, including gasoline and diesel engines, made of steel material, a problem exists in that the bending work during the ring forming process, is not easy, and occasionally causes a broken ring.
As for compression rings used in large diesel engines, the compression rings, particularly, first compression rings, require a significantly high abrasion resistance, the rings are manufactured using relatively expensive high-Cr steel material. Thus, there has been another problem in that the total manufacturing cost of compression rings is caused expensive when the second compression rings are made of the same steel material as that of the first compression rings.
Moreover, there has existed a further problem in that, when the first and second compression rings are made of an identical steel material, and are applied with chromium plating of an identical hardness, then, the difference between the first and second compression rings, in the abutting gap thereof, grows abnormally great after a long time use, thereby resulting in the compression rings having their sealing capability decreased and causing the blow-by gas volume to increase.
Furthermore, an additional problem exists in that, since the second compression rings, used in large diesel engines, have a larger cross-sectional area than those used in in gasoline engines, the rings exhibit poor cold workability during the ring forming process.
SUMMARY OF THE INVENTION
The present invention has been made to solve the problems described above. Therefore, an object of the present invention is to provide piston rings, including compression rings and side rails of combined type oil rings, for internal combustion engines, including gasoline and diesel engines, made of steel material, such that, in manufacturing the rings, the bending work during the ring forming process, is made easy, whereby the rings are prevented from breakage at that time.
Another object of the present invention is to provide a combination of first and second compression rings, for large diesel engines, where the material and surface treatment of the second compression rings are degraded, considering the severeness of working conditions, and the difference therebetween, of the first and second compression rings, so that the total manufacturing cost of a combination of first and second compression rings is reduced, and their sealing capability is maintained for a long time, while also keeping an excellent abrasion resistance.
An additional object of the present invention is to provide second compression rings used in large diesel engines, exhibiting excellent cold workability during the ring forming process.
In order to accomplish the objects described above, piston rings, including compression rings and side rails of combined type oil rings, for use in internal combustion engines, including gasoline and diesel engines, are provided, according to one aspect of the present invention, where the piston ring is made of steel material advantageously containing C of not less than 0.4 and not more than 0.8 weight percent, Si of not less than 0.16 and not more than 0.4 weight percent, Mn of not less than 0.1 and not more than 0.4 weight percent, and Cr of not less than 2.0 and not more than 11.0 weight percent. Advantageously, the steel material has mainly chromium carbide precipitated in the base texture thereof, and then has a hardened layer formed thereon by means of surface treatment.
According to another aspect of the present invention, a combination of a first compression ring and a second compression ring, for use in internal combustion engines, including large diesel engines, is provided, where the first compression ring is advantageously made of steel material containing C of not less than 0.16 and not more than 1.4 weight percent, and Cr of not less than 12 and not more than 23.0 weight percent. Advantageously, the steel material of the first compression ring has mainly chromium carbide precipitated in the base texture thereof, and, then, has a hardened layer of hardness of not less than Hv1050 formed thereon by means of surface treatment.
The second compression ring is advantageously made of steel material containing C of not less than 0.4 and not more than 0.8 weight percent, Si of not less than 0.16 and not more than 0.4 weight percent, Mn of not less than 0.1 and not more than 0.4 weight percent, and Cr of not less than 2.0 and not more than 11.0 weight percent. Advantageously, the steel material of the second compression ring has mainly chromium carbide precipitated in the base texture thereof, and, then, has a hardened layer of hardness of less than Hv1050 formed thereon by means of surface treatment.
According to a further aspect of the present invention, the surface treatment described above, may be advantageously nitriding treatment, particularly, one nitriding treatment selected from the group consisting of gas nitriding treatment, gas soft-nitriding treatment, acid nitriding treatment, salting-in nitriding treatment, and ionitriding treatment.
According to a still further aspect of the present invention, advantageously, the surface treatment described above, may be a combination of a first treatment of nitriding treatment and a second treatment of either PVD plating treatment or composite plating treatment applied on the surface hardened with first treatment, of the piston ring, for gasoline and diesel engines, as described above, and the combination of the first and second compression rings, for large diesel engines.
According to another aspect of the present invention, as surface treatment for the piston ring of steel material, for gasoline and diesel engines, chromium plating may be applied to obtain an excellent abrasion resistance.
According to a still further aspect of the present invention, preferably, the first com
Sameshima Shuji
Takeuchi Koji
Birch & Stewart Kolasch & Birch, LLP
Knight Anthony
Nippon Piston Ring Co. Ltd.
Peavey Enoch
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