Metal working – Method of mechanical manufacture – Prime mover or fluid pump making
Patent
1997-04-07
1999-05-18
Solis, Erick R.
Metal working
Method of mechanical manufacture
Prime mover or fluid pump making
29888073, 29566, 29 33R, 72 71, B23P15/08;15/10
Patent
active
059039744
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD TO WHICH THE INVENTION BELONGS
The present invention relates to a method of and apparatus for producing a hollow ring groove insert for an engine piston. More particularly, the present invention relates to a method of and apparatus for efficiently and highly accurately producing a hollow ring groove insert which is integrally inserted in a piston for a small-sized diesel engine by casting to form a top-ring groove and an annular cooling path for cooling the groove.
CONVENTIONAL TECHNIQUE
A cylinder and a piston which constitute a combustion chamber of a diesel engine are, mechanical parts which are required to exhibit long-term durability under severe conditions where they are subjected to high loads due to combustion impact pressure, heat and so forth. To meet the requirement, a piston has recently been developed in which a ring-shaped cooling path is provided near a top-ring groove of the piston, and a coolant (engine oil) is circulated through the ring-shaped cooling path to cool the piston.
It is necessary in order to cool the piston efficiently to provide the ring-shaped cooling path as close to the ring groove as possible. As shown in FIGS. 15 and 16, it has been proposed to insert a hollow ring groove insert 85 in the outer periphery of the top portion of a piston 80 made of aluminum alloy by casting process (for example, JP-A-5-231539 (Japanese Patent Application Unexamined Publication, KOKAI).
In FIGS. 15 and 16, the hollow ring groove insert 85 has a structure comprising a formed sheet ring 10 with a U-shaped cross-section, and a cast ring (a ring body) 82, which are integrated by welding together the outer peripheral portion of the ring 10 and the inner peripheral surface 83 of the ring 82. The formed sheet ring 10 is produced by roll-forming a sheet of a metal having the same coefficient of thermal expansion as that of an aluminum alloy used to form the piston body. The cast ring 82 is produced from a material having high wear resistance and the same coefficient of thermal expansion as that of the piston body, for example, a Niresist material. A cooling path 86 is defined by the formed sheet ring 10 and the inner peripheral surface 83 of the cast ring. The cast ring 82 has a piston ring groove 81 for accommodating a top ring.
The formed sheet ring 10, which is a metal sheet with a U-shaped cross-section, has heretofore been produced as follows: A stainless steel sheet having a width of 18 mm, a length of 290 mm and a thickness of 0.6 mm, by way of example, is formed into an arcuate shape by a roll forming machine. Then, the metal sheet formed in an arcuate shape is fitted on a jig with a circular cross-section of a welding apparatus and butt-welded at both ends thereof to form a ring (sheet ring), and the ring is roll-formed into a piece with a U-shaped cross-section.
The cast ring is produced from a cast Niresist material such that the inner diameter thereof is slightly smaller than the outer diameter of the sheet ring having a U-shaped cross-section. The cast ring is heated so that its inner diameter expands, and in this state, the formed sheet ring is warm-fitted into the cast ring. Thereafter, the joint surfaces of the formed sheet ring and cast ring are welded to each other by a welding apparatus.
The above-described formed sheet ring with a U-shaped cross-section has heretofore been produced by carrying out the following steps: A sheet ring formed by welding the butted ends of a sheet is roll-formed by a roll forming apparatus to form a circular collar on each end thereof, as described, for example, in JP-A-6-210383 (Japanese Patent Application Unexamined Publication, KOKAI), and JP-A-6-269882. Then, the formed sheet ring is removed from the roll forming apparatus and set on a turning apparatus to turn the outer peripheral portion of each circular collar, thereby finishing the outer diameter to a predetermined dimension conforming to the inner diameter of the cast ring. Further, the formed sheet ring is set on a deburring apparatus to remove burrs from the end portions
REFERENCES:
patent: 3805532 (1974-04-01), De Montremy
patent: 4085490 (1978-04-01), McCormick et al.
patent: 4485656 (1984-12-01), Nilson et al.
patent: 4494294 (1985-01-01), Sims
patent: 5301599 (1994-04-01), Dearnley et al.
patent: 5396787 (1995-03-01), Kanemitsu et al.
Hino Motors Ltd.
Solis Erick R.
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