Patent attributes
In a belt drive system 20 for transmitting torque at a crankshaft 11 of an automotive engine 10 to a supercharger (engine accessory) 130a, an output pulley unit 40 formed of a first flat pulley 50 and a second flat pulley 60 is coupled to the rotational shaft 131a of the supercharger 130a. A flat belt 70 entrained between the output pulley unit 40 and the crank pulley 30 of the crankshaft 11 is shifted from the first flat pulley 50 to the second flat pulley 60 or vice versa by a speed ratio selector 80. The rotational shaft 131a can thereby be driven into rotation with the switching between a high speed ratio during acceleration and a low speed ratio during constant speed cruise. As a result, the supercharger 130a can bring out its capability into full play without using parts involving increases in weight, cost and power consumption, such as a solenoid-operated clutch, and concurrently suppress the deterioration of fuel economy.
