Deep rolling split-pin fillets of crankshafts

A method of deep rolling fenced fillets of split pairs of cylindrical crank pins of crankshaft for internal combustion engines with each pin of each pair having an axis of revolution offset from the axis of revolution of the other pin of said each pair and having a fence separating the interior fillets of each pair of pins comprising the steps of:

• (1) mounting said crankshaft in a fillet rolling machine;
• (2) employing fillet rolling tools to engage the innermost fillets of at least one of said split pair of crank pins with said fence separating said innermost fillets;
• (3) relatively rotating said crankshaft and the fillet rolling tools;
• (4) deep rolling said innermost fillets of said one of said split pairs of crank pins so that the arcuately fenced segments of said fillet of said first pin and the arcuate fenced segments of said second pins that overlap one another are deep rolled at loads sufficiently higher than the arcuate segments of said fillets which are free from overlapping so that the fillets of the connecting portion of said pins have high residual stresses to strengthen the physical connection between the pins from while eliminating distortions of said fence by rolling.

A method of deep rolling pairs of annular fillets of split and arcuately offset crank pins of a metallic crankshaft for an internal combustion engine separated by a fence at the split of the pins and wherein said fillets lie in separate planes and are offset so that said circular fillets overlap to define an overlap area bounded on one side by limb of one of said fillets and on the other side by a limb of another of said fillets, said limbs intersecting one another at opposite ends thereof to define first and second points of intersection and defining the extent of said areas of overlap comprising the steps of:

• (1) installing the crankshaft in a fillet rolling machine so that a first fillet roller operatively contacts a first of said fillets and a second of said fillet rollers operatively contacts a second of said fillets,
• (2) rotating said crankshaft so that said pins and fillets are rotated,
• (3) deep rolling the limb of a first of said fillets a high load while rolling the arcuate portion of a second of said fillets outside of the limb thereof with a low load, and
• (4) deep rolling the limb of a second of said fillets with a high load while rolling the arcuate portion of said first fillet outside of the limb thereof at a low load,
• (5) removing said crankshaft from said fillet rolling machine.

A method of deep rolling pairs of fillets of split pins of a crankshaft for an internal combustion engine which are adjacent to one another and are on opposite sides of a divider fence separating the pins at the split thereof, said fillets being circular and arcuately offset from one another to describe an overlap area compassed by first and second opposed arcuate limbs which intersect one another at first and second intersect points comprising the steps of:

• (1) loading the crankshaft into a fillet rolling machine,
• (2) engaging a first of said fillets of said pair of fillets with a first fillet rolling tool of said machine and a second of said fillets with a second fillet rolling tool,
• (3) turning said crankshaft relative to said rolling tools,
• (4) deep rolling said first and second limbs of said fillets defining said overlap area with a high pressure to cold-work localized arcs of said fillets which define said limbs to thereby strengthen and optimize the bending yield strength thereof,
• (5) rolling the arcuate segments of said fillets outside of said limbs with rolling loads that are substantially lower than said loads applied to said limbs to strengthen said segments while ensuring that said fence separating said pins is not distorted by said rolling loads.