CONTINUOUSLY VARIABLE FAN DRIVE CLUTCH

摘要

A clutch mechanism (25) is provided for a cooling fan (23) of a size capable of fitting into the limited envelope available in an over-the-road diesel tractor. A compact housing (43) has a belt drive input and an output connected to the fan hub (45). The housing (43) includes a pressure chamber (102) in fluid communication with a pressurized air supply and a controllable valve in the air supply line for regulating the pressure in the pressure chamber (102) when the clutch (20) must be operated. The air pressure actuates an internal piston (86) to translate the clutch (20) in a continuously variable manner between engaged and disengaged conditions. A small envelope clutch, having an outer diameter less than about 9.8 inches in diameter within the fan hub (45) and less than about 6 inches under the belts (27) and 7.3 inches overall so the housing (43) may be positioned between the radiator (22) and the engine (21), is capable of generating 150 foot-pounds of torque, running a 55 horsepower fan at 2100rpm, and dissipating 10 horsepower of heat while in the slip mode. The clutch (20) also has at least 130 inches in clutch area. Fan speed is controlled utilizing a closed loop control system. The control system is capable of monitoring engine conditions and controlling fluid pressure actuating the clutch assembly (91a) to control the fan speed in response to the engine conditions.