Switchable drive pulley with electrically actuated friction disc torque transfer mechanism
A switchable drive pulley system that allows driving engagement or disengagement of a pulley from the shaft of an accessory drive. The pulley is mounted to the shaft by a bearing having an inner ring that rotates with the shaft and an outer ring that rotates with the pulley. A friction disk is arranged adjacent to the bearing inner and outer ring. When axial pressure is applied to the friction disk, relative motion between the inner and outer bearing rings is stopped, allowing transfer of torque from the pulley to the shaft to drive the accessory drive, with the pulley and shaft rotating at the same speed. When pressure is removed from the friction disk, the pulley and the outer bearing ring can spin independently of the inner ring and shaft. The shaft can therefore remain stationary while the pulley continues to turn driven by the accessory belt drive.
1. A switchable drive pulley system that allows driving engagement or disengagement of a pulley from a shaft, comprising:
a pulley mounted to a shaft by a bearing having an inner ring that rotates with the shaft and an outer ring that rotates with the pulley;
a friction disk arranged axially adjacent to the bearing inner ring and outer ring;
an actuator for applying axial pressure to the friction disk, such that the friction disk engages both the inner and outer bearing rings and relative motion between the inner and outer bearing rings is stopped, allowing transfer of torque from the pulley to the shaft, and upon removal of the axial pressure from the friction disk, the pulley and the outer bearing ring can spin independently of the inner ring and the shaft.
2. The switchable drive pulley system of claim 1 , wherein the actuator comprises an actuator sleeve located about the shaft that is axially moveable, the actuator sleeve has a generally cylindrical body and a flanged end facing the friction disk, and a spring is located between the flanged end and a fixed housing to bias the friction disk against the inner and outer bearing rings.
3. The switchable drive pulley system of claim 2 , further comprising a thrust bearing located between the flanged end of the actuator sleeve and the friction disk.
4. The switchable drive pulley system of claim 3 , wherein the thrust bearing is a needle bearing.
5. The switchable drive pulley system of claim 2 , wherein actuator sleeve is rotatable about the shaft, the generally cylindrical body includes a cam slot and a pin extends from the housing into the cam slot, such that rotation of the actuator sleeve causes the cam slot to slide along the pin to axially displace the actuator sleeve.
6. The switchable drive pulley system of claim 5 , further comprising a control actuator connected to the actuator sleeve to rotate the actuator sleeve in order to axially move the actuator sleeve against a force of the spring to a position to remove axial pressure from the friction disk.
7. The switchable drive pulley system of claim 6 , wherein the control actuator is connected to an ECM, and the shaft is a water pump shaft for a water pump of an internal combustion engine, and the ECM actuates the control actuator to remove axial pressure from the friction disk during engine start-up in order to allow the engine to reach operating temperature more quickly.
8. The switchable drive pulley system of claim 1 , wherein the friction disk engages at least one of the shaft or the inner bearing ring as the actuator applies axial pressure to the friction disk.