ENGINE BRAKING APPARATUS WITH TWO-LEVEL PRESSURE CONTROL VALVES

摘要

Apparatus and method are disclosed for converting an internal combustion engine from a normal engine operation (20) to an engine braking (or retarding) operation (10). The apparatus has an actuation means (100) containing two braking pistons (160) slidably disposed in the valve bridge (400) between an inoperative position (0) and an operative position (1). The apparatus also has a flow control valve (50) for supplying control fluid to the actuation means (100) with two levels of pressure. At the first level or lower pressure, the braking pistons (160) will stay in the inoperative position (0), and a gap (234) is formed between the valve bridge (400) and the exhaust valves (300) to skip the motion from the lower portion of the cam (230) for the normal engine operation (20). At the second level or higher pressure, the braking pistons (160) will be moved to the operative position (1), and a linkage is formed between the valve bridge (400) and the exhaust valves (300) so that the motion from the whole cam (230) can be transmitted to the valves (300) for the engine braking operation (10). The apparatus also includes a supporting means (250) for preventing any no-follow of the valve train components and a resetting means (150) for modifying the valve lift profile (220v) generated by the cam (230). The supporting means (250) does not impose any force on the braking pistons (160), while the resetting means (150) stays at the off or draining position during the normal engine operation (20).