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© 200324 3-5 Description of components PE ENGINE COOLING SYSTEM CF65/75/85 series 2 6 3.4 VISCOUS FAN CLUTCH The fan is connected to the engine by means of a viscous fan clutch. If, under certain circumstances, the heat is not sufficiently dissipated by the air flow passing through the radiator, the fan will have to draw in extra cooling air through the radiator. In a viscous fan clutch, the drive torque is transmitted by a silicone fluid. The fan clutch is divided into two chambers. In the working area (1) is the rotor (2), which is connected to the drive flange (7). The supply chamber (3) rotates freely round the drive flange (7) and is connected to the fan. There is silicone fluid in the supply chamber (3). The opening (4) in the supply chamber (3) is closed by a valve (5). The valve (5) is operated by a bimetallic strip (6). If the opening (4) in the supply chamber (3) is closed by the valve (5), no silicone fluid can enter the working area (1). The silicone fluid still present in the working area (1) will flow back to the supply chamber (3) through the bores (8). As only very little fluid will be left in the working area (1), there will be a great difference in rotating speed (slip) between the drive flange (7) and the supply chamber (3) with the fan. When the air temperature increases, the bimetallic strip (6) will bend and the valve (5) will partially release the opening (4) in the supply chamber (3). Through this opening, a limited amount of silicone fluid can enter the working area (1) and flow past the rotor (2). This will cause friction, so that the difference in rotating speed (slip) between the drive flange (7) and the supply chamber (3) with the fan will decrease. M201039 6 8 7 5 2 3 4 |