Title of Invention	"THERMAL SPRAY COATED PISTON RING"
Abstract	A thermal spray coated piston ring having improved initial running in propery, and having scuffing resistance and wear resistance is provided. The spray coating film (3) of the piston ring (1) contains from 2 to 40 mass% of Sn and from 5 to 50 mass% of graphite, and if necessary, P, Sb, Co, Be, Cr, Mn, Si, Cd, Zn, Fe, Ni and/or Pb, the balance essentially consisting of Cu.

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disadvantageously wears off before the initial running-in is completed. Disclosure of Invention It is an object of the present invention to solve the problems of the thermal spray coating of Japanese Published Patent Application (kokai) No. 11-80921 and Japanese Translation of PCT International Application No.2000-507679 and to provide a thermal spray coated piston ring, which has improved initial running-in property, scuffing resistance and wear resistance. The present inventors made energetic researches in view of the object mentioned above and then discovered that the initial running-in property, wear resistance and scuffing resistance of a piston ring are improved by means of mixing Cu, Sn and graphite in a predetermined proportion and thermal spray coating of the mixture on the sliding surface of a piston ring. As a result, the present invention is completed. Accordingly the invention provides a thermal spray coated piston ring comprising at least on the outer peripheral surface thereof, a thermal spray coating film which contains from 2 to 40 mass % of Sn and from 5 to 50 mass % of graphite, the balance essentially consisting of Cu. The thermal spray coating film essentially consists of Cu, Sn and graphite. The graphite particles contained in the thermal spray coating film are dispersed therein and enhance the self-lubricating property of the coating. The particles of graphite prevent the coating film from wearing off until the formation of the running-in surface, which is formed by wearing the copper-based alloy by the opposed material. When the content of graphite particles is less than 5 mass % with the proviso that the entire thermal spray coating film is 100 mass %, the self-lubricating property is poor. On the other hand, when the content of graphite particles exceeds 50 mass %, the coating film becomes soft so that the coating film wears off before the initial running-in is completed. The content of graphite particles is, therefore, from 5 to 50 mass %, and is preferably from 5 to 20 mass %. The Sn, which is plasma-sprayed and included in the coating film, neither forms nor essentially forms hard matter such as oxide. Essential non-formation of hard matter such as oxide herein means that the microscopic observation of FIG. 4 described hereinbelow detects pores formed by thermal spraying but not any hard matter. When Cu, in which Sn is preliminarily alloyed, is thermal-sprayed, Sn is again dissolved in the Cu and hardens the Cu in appropriate level. Namely, although a Cu-Sn intermetallic compound, which has poor initial running-in property, dissolved in the solid solution and perform the solid-solution hardening. In a case where, these elements, particularly Cr, Mn, Fe and Ni, are thermal-sprayed in the form of a single element, they are dispersed in the coated film in the form of a single element and enhance the wear resistance. However, at more than 5% of Sb, more than 5% of Co, more than 5% of Be, more than 5% of Cr, more than 15% of Mn, more than 15% of Si, more than 15% of Cd, more than 15% of Zn, more than 5% of Fe, or more than 20% of Ni in terms of mass percentage, the hardness of the alloy as a whole increases. It becomes difficult to maintain a preferable average hardness of 300HV0.1 or less. The total content of these elements is preferably 25 mass % or less. BRIEF DESCRIPTION OF DRAWINGS Figure 1 is a schematic cross-sectional view of a piston ring according to an example of the present invention. Figure 2 is a schematic cross-sectional view of a piston ring according to another example of the present invention. Figure 3 is a schematic cross-sectional view of a piston ring according to a further example of the present invention. Figure 4 is an optical microphotograph (magnification 100 times) of the metal structure of a specimen, on which a plasma thermal spray coating film is formed in an example of the present invention. Figure 5 is a schematic cross-sectional drawing of the plasma spray coating apparatus (a plasma gun). Figure 6 is a schematic drawing of the ultra-high pressure wear tester. Figure 7 is a cross-sectional view along A-A of FIG. 6.6 Figure 8 is a graph showing the time until scuffing in the wear test of the example and the comparative examples. Figure 9 is a graph showing the wear amount of test pieces at the occurrence of scuffing in the wear test of the examples and comparative examples. EMBODIMENTS OF INVENTION Referring to FIGS. 1 and 2, a schematic cross-sectional view of a piston ring according to examples of the present invention is illustrated. The piston ring 1 comprises a piston ring body 2 of known cast iron, stainless steel or the like and has a flat outer peripheral sliding surface or a groove on the outer peripheral sliding surface. The thermal spray coating film 3 is formed on the flat outer peripheral sliding surface or in a groove on the outer peripheral sliding surface. If necessary, the thermal spray I/We claim: 1. A thermal spray coated piston ring, characterized in that it is provided with a thermal spray coating film which contains from 2 to 40 mass % of Sn and from 5 to 50 mass % of graphite, the balance essentially consisting of Cu. 2. A thermal spray coated piston ring as claimed in claim 1, wherein said thermal spray coating film is formed on the outermost peripheral surface. 3. A thermal spray coated piston ring as claimed in claim 1 or 2, wherein at least 5 % or more of particles of said graphite in volume ratio are dispersed in the thermal spray coating film. 4. A thermal spray coated piston ring as claimed in any one of claim 1 through 3, wherein the thermal spray coating film contains, except for the general impurities of Sn bronze, one or more kinds selected from the group consisting of P, Sb, Co, Be, Cr, Mn, Si, Cd, Zn, Fe, Ni and Pb, and the amount of these components are: 1.0% of P at the highest, 5 % of Sb at the highest, 5% of Co at the highest, 5% of Be at the highest, 5% of Cr at the highest, 15% of Mn at the highest, 15% of Si at the highest, 15% of Cd at the highest, 15% of Zn at the highest, 5% of Fe at the highest, 20% of Ni at the highest, and 20% ofPb at the highest. 5. A piston ring as claimed in claim 4, wherein the total amount of one or more elements selected from the group consisting of P, Sb, Co, Be, Cr, Mn, Si, Cd, Zn, Fe, Ni and Pb, is 25 mass % at the highest. 6. A thermal spray coated piston ring as claimed in any one of claims 1 through 5, wherein the average hardness of the thermal spray coating film is 300Hv0.1 or less. 7. A thermal spray coated piston ring as claimed in any one of claims 1 through 6, wherein said thermal spray coating film consists of multiple layers, an upper coating layer is formed on a lower coating layer which has a surface roughness as thermal spray coated and is not mechanically machined. 8. A thermal spray coated piston ring as claimed in any one of claims 1 through 7, wherein said thermal spray coating film is from 50 to 500 µ m thick. 9. A thermal spray coated piston ring substantially as herein described with reference to the accompanying drawings.

Documents:

1954-DELNP-2004-Claims-(17-02-2011).pdf

1954-delnp-2004-Claims-(23-02-2015).pdf

1954-delnp-2004-Correspondence Others-(11-12-2012).pdf

1954-delnp-2004-Correspondence Others-(23-02-2015).pdf

1954-delnp-2004-Correspondence-others (12-11-2012).pdf

1954-delnp-2004-Correspondence-Others-(12-11-2010).pdf

1954-DELNP-2004-Correspondence-Others-(17-02-2011).pdf

1954-DELNP-2004-Description (Complete)-(17-02-2011).pdf

1954-DELNP-2004-Drawings-(17-02-2011).pdf

1954-delnp-2004-Form-3 (12-11-2012).pdf

1954-delnp-2004-Form-3-(11-12-2012).pdf

1954-delnp-2004-Form-3-(12-11-2010).pdf

1954-delnp-2004-GPA (12-11-2012).pdf

1954-delnp-2004-Marked Claims-(23-02-2015).pdf

1954-delnp-2004-Petition 137-(12-11-2010).pdf

1954-delnp-2004-Petition 138-(12-11-2010).pdf