Patent ID: 7455239

Claim:
A cooling system for an internal combustion engine comprising: a small cooling circuit without a radiator, a large cooling circuit with a radiator and a motor driven fan which is associated with the radiator; both said cooling circuits are interconnected by a thermostatic valve, said thermostatic valve regulating the flow of coolant through both said small and large cooling circuits, control means for controlling operation of said thermostatic valve and for controlling operation of the motor of said fan so as to achieve an objective temperature of said coolant, which is set by a temperature setting means, said temperature setting means selecting the objective temperature out of several objective temperatures depending on the actual demand of said internal combustion engine; and, wherein said control means, for different objective temperatures, use different motor characteristic curves (K high , K low ) for control of power to the motor of the fan according to the characteristic curve (K high , K low ), if said objective temperature is changed from a higher to a lower objective temperature, the actual operation of the fan motor is maintained at a constant power level for an adjustable minimum waiting time (Δt 1 ) so as to avoid howling up of the fan, and, in the event of a change in the objective temperature, the control means changes the characteristic curve (K high , K low ), and a damping filter is switched into a power control line for activation of the fan motor.