Patent ID: 8006656
Filing Date: 2011-08-30
Classification: F02B

Abstract:
1. An engine, comprising: a crankshaft rotatable about a crankshaft axis; an expansion piston slidably received within an expansion cylinder and operatively connected to the crankshaft such that the expansion piston is operable to reciprocate through an expansion stroke and an exhaust stroke of a four stroke cycle during a single rotation of the crankshaft; a compression piston slidably received within a compression cylinder and operatively connected to the crankshaft such that the compression piston is operable to reciprocate through an intake stroke and a compression stroke of said four stroke cycle during a single rotation of the crankshaft; a phase angle that the expansion piston leads the compression piston by, the phase angle defined by the degrees of rotation the crankshaft must rotate after the expansion piston reaches a top dead center (TDC) position of the expansion piston in order for the compression piston to reach a TDC position of the compression piston; a crossover passage interconnecting the compression cylinder and the expansion cylinder, wherein the crossover passage includes a crossover valve proximate the expansion cylinder and an inlet valve proximate the compression cylinder, the crossover valve and inlet valve defining a pressure chamber therebetween; a ratio of expansion cylinder volume from bottom dead center (BDC) to TDC of the expansion piston is 20 to 1 or greater; and means for timing the inlet valve and crossover valve such that, for a period of time during which the expansion piston descends towards its BDC position and the compression piston ascends towards its TDC position, both the inlet valve and the crossover valve are open.