Patent ID: 8118148
Filing Date: 2012-02-21
Classification: F01P,F04D,F16D

Abstract:
1. A control method of an external control system fan clutch comprising: providing on a rotating shaft, a drive disk fixed to the rotating shaft and a housing supported through a bearing on the rotating shaft, the housing having a fan coupled thereto and an interior, a partition plate in the housing and partitioning the interior into an oil reservoir chamber and a torque transmission chamber, said drive disk being in the torque transmission chamber, a torque transmission gap being defined between the drive disk and the housing at locations spaced outward from the rotating shaft, a dam arranged in one portion of an inner circumferential wall face of the housing opposed to an outer circumferential wall portion of the drive disk for collecting and reservoiring oil at a rotating time, an oil circulating flow passage through the partition plate inwardly of the torque transmission gap and a valve member comprising a spring material and having a magnetic property and being arranged within the oil reservoir chamber, the valve member having a fixed end at a radially inner position, a free end at a radially outer position, the free end being aligned for closing the oil circulating flow passage formed in the partition plate between the torque transmission chamber and the oil reservoir chamber; an armature between the fixed and the free end, an electromagnet supported by said rotating shaft through the bearing on the oil reservoir chamber side of said housing, and the electromagnet being aligned with the armature for controlling the opening and closing of the oil circulating flow passage; utilizing a spring characteristic of the spring material of the valve member for biasing the valve member against the partition plate for keeping the oil circulating flow passage in a normally closed condition while keeping the valve member substantially free of magnetic forces acting thereon; selectively operating the electromagnet in response to detected signals indicating a need for an increased rotational speed of the housing for attracting the valve member and deflecting the valve member away from the partition plate for opening the oil circulating flow passage to permit a flow of oil into the torque transmission gap between the drive disk and the housing to increase an effective contact area of the oil in the torque transmission gap; and selectively turning off the electromagnet in response to detected signals indicative of the requirement for a slower rotational speed of the housing so that the valve member is substantially free of magnetic forces and is biased into the normally closed condition by the spring material for controlling rotating torque transmission from a drive side to a driven side by increasing and decreasing an effective contact area of the oil in the torque transmission gap; wherein the operation of the electromagnet, for opening the oil circulating flow passage, and a turning-off of the electromagnet, so that the spring material biases the valve member against the partition plate for closing the oil circulating flow passage, are controlled via a fan rotating speed control signal by setting an upper limit rotating speed lower than a turning-on rotating speed with respect to an optimum fan rotating speed required from an engine, which is coupled to the housing, during normal operation, whereby a response delay with respect to the a subsequent fan rotating speed control signal can be shortened and an associative rotation of the housing at an engine rotation changing time and an engine starting time can be reduced.