| 摘要 |
A viscous fan clutch (10) is typically employed in a fan drive mechanism within a truck or automobile. A shaft (12) driven by the engine, rotates a clutch member (24) within the fan drive. The clutch member is arranged for fluid engagement with a cover assembly (38) for the transmission of torque thereto when the fluid is disposed in an operating chamber (70) defined by complementary shear surfaces (30, 31, 56, and 57) in the clutch and cover. During the relative rotation between the clutch and cover, fluid is pumped from the operating chamber to primary (76) and secondary (77) fluid storage chambers. A fluid temperature responsive control valve (190) provides for selective communication between the storage chambers and the operating chamber to effect modulation of the total fluid flow whereby quasi dual speed operation of the clutch is achieved. Upon receipt of a signal from a control circuit (146), a first measure of viscous fluid (from the primary storage chamber) flows rapidly into the operating chamber to effect a step speed increase. Subsequently, a second measure of viscous fluid (from the secondary storage chamber) flows slowly into the operating chamber to effect a second, gradual speed increase. In the preferred embodiment the valve operates in response to sensed engine liquid coolant temperature. |
