Caterpillar Inc.
Hydraulic early engine exhaust valve opening system

Abstract:

An early exhaust valve opening (EEVO) module increases a no-load engine speed so an engine can smoothly transition to driving a load when necessary. The EEVO module includes a drive piston engaging an injector rocker and a driven piston engaging an exhaust rocker. The pistons are fluidly connected by a activation fluid passage so that the drive piston compresses air in the passage when an injector cam rotates the injector rocker and causes movement of the driven gear and the exhaust rocker to open an exhaust valve to release exhaust energy during a piston expansion stroke to limit the energy transferred to a crankshaft. A low pressure timing valve may drain pressurized fluid from the passage during an initial portion of the movement of the drive piston so driven piston does not move to open the exhaust valve until a desired amount of energy has been transferred to the crankshaft.