Patent ID: 8590497

Claim:
A split-cycle air-hybrid engine comprising: a crankshaft rotatable about a crankshaft axis; a compression piston slidably received within a compression cylinder and operatively connected to the crankshaft such that the compression piston reciprocates through an intake stroke and a compression stroke during a single rotation of the crankshaft; an expansion piston slidably received within an expansion cylinder and operatively connected to the crankshaft such that the expansion piston reciprocates through an expansion stroke and an exhaust stroke during a single rotation of the crankshaft; an exhaust valve selectively controlling gas flow out of the expansion cylinder; a crossover passage interconnecting the compression and expansion cylinders, the crossover passage including a crossover compression (XovrC) valve and a crossover expansion (XovrE) valve defining a pressure chamber therebetween; an air reservoir operatively connected to the crossover passage and selectively operable to store compressed air from the compression cylinder and to deliver compressed air to the expansion cylinder; and an air reservoir valve selectively controlling air flow into and out of the air reservoir; the engine being operable in an Air Compressor (AC) mode, wherein, in the AC mode, the XovrE valve is kept closed during an entire rotation of the crankshaft, and the exhaust valve is kept open for at least 240 CA degrees of said entire rotation of the crankshaft; and wherein, in the AC mode, the exhaust valve closing position and the exhaust valve opening position are symmetrical, within plus or minus 10 CA degrees, about the top dead center position of the expansion piston.