Rigid crankshaft cradle and actuator

A variable compression ratio mechanism for a reciprocating piston machine having one or more cylinders, a piston mounted for reciprocating movement in each of said cylinders, a crankshaft defining an axis about which the crankshaft rotates, and a connecting rod connecting each of said pistons to the crankshaft, said connecting rod having a connecting rod crankshaft bearing having a mid span, comprising;

• a crankshaft cradle supporting the crankshaft for rotation of the crankshaft about the rotational axis of the crankshaft, said cradle having an outer cradle bearing diameter for pivotally supporting said cradle in the reciprocating piston machine about a pivot axis, said pivot axis being concentric with said outer cradle bearing diameter, the pivot axis being substantially parallel to and spaced from the rotational axis of the crankshaft,
• wherein said cradle is mounted in said reciprocating piston machine and motion of said outer cradle bearing diameter is restricted by said reciprocating piston machine to pivoting about said pivot axis, thereby substantially preventing reciprocating motion of said cradle in said reciprocating machine,
• an actuator for varying the position of the cradle about the pivot axis for varying the position of the rotational axis of the crankshaft, said cradle comprising a primary eccentric member, a plurality of bearing caps, and a plurality of bearing cap fasteners for removably fastening each bearing cap to the primary eccentric member,
• wherein said primary eccentric member comprises a plurality of disc segments and webbing, said disc segments being rigidly joined together by said webbing,
• wherein a portion of said webbing and at least two of said disc segments are a single cast piece,
• said crankshaft axis and said pivot axis defining a first plane, said bearing caps having a primary contact surface for contact with said primary eccentric member, a portion of said primary contact surface being within 40 degrees of perpendicular to said first plane, and at least one of said fasteners being within 40 degrees of parallel to said first plane for providing space on the far side of the cradle for a large and contiguous webbing,
• said crankshaft having a plurality of main bearings, said main bearings having a working diameter and a main bearing mid span, and said bearing caps having a bridge thickness, said bridge thickness being the distance on said first plane between said outer cradle bearing diameter and said crankshaft main bearing, the bridge thickness of at least one bearing cap being less than 70 percent of the thickness of at least one crankshaft main bearing working diameter, for location of the crankshaft adjacent to the outer diameter of the cradle for providing space for a large web on the far side of the cradle,
• said reciprocating piston machine having a second plane perpendicular to said pivot axis and perpendicular to said first plane and passing through said connecting rod crankshaft bearing mid span,
• wherein said cradle has webbing between at least two adjacent eccentric discs, said webbing being located on said second plane over an arc distance about said pivot axis greater than 120 degrees, thereby providing a crankshaft cradle with a high stiffness.