Spring travel limiter for overrunning alternator decoupler

A decoupler assembly for transferring torque between a drive shaft and an endless drive element of an automotive engine, the decoupler assembly comprising:

• a hub adapted to be fixedly secured to the shaft, the hub extending axially between a first hub end and a second hub end;
• a pulley disposed concentrically about the hub and adapted to be drivingly engaged with the endless drive element;
• a bearing between the hub and the pulley, the bearing supporting the pulley for rotation about a rotational axis of the hub;
• a carrier rotatably mounted about the second hub end;
• a torsion spring extending axially between the hub and the carrier, a first end of the torsion spring being engaged to the carrier, a second end of the torsion spring opposite the first end of the torsion spring being coupled to the hub such that the torsion spring is configured to transfer torque from the carrier to the hub;
• and
• a thrust plate fixedly mounted on the second end of the hub;
• wherein one of the carrier and the thrust plate includes an anti-ramp up feature, wherein the other one of the carrier and the thrust plate includes a circumferentially extending slot into which the anti-ramp up feature is received, the slot having a first slot end and a second slot end, the anti-ramp up feature traveling within the slot between the first slot end and the second slot end for limiting rotation between the carrier and the thrust plate;
• and
• wherein a clutch element is disposed between the hub and the pulley for selectively transmitting rotary power from the pulley to the carrier and enabling overrunning of the hub relative to the pulley.

A decoupler assembly for transferring torque between a drive shaft and an endless drive element of an automotive engine, the decoupler assembly comprising:

• a hub adapted to be fixedly secured to the shaft, the hub extending axially between a first hub end and a second hub end;
• a pulley disposed concentrically about the hub and adapted to be drivingly engaged with the endless drive element;
• a bearing between the hub and the pulley, the bearing supporting the pulley for rotation about a rotational axis of the hub;
• a carrier rotatably mounted about the second hub end;
• a torsion spring extending axially between the hub and the carrier, a first end of the torsion spring being engaged to the carrier, a second end of the torsion spring opposite the first end of the torsion spring being coupled to the hub such that the torsion spring is configured to transfer torque from the carrier to the hub;
• and
• a thrust plate fixedly mounted on the second end of the hub;
• wherein one of the carrier and the thrust plate includes an anti-ramp up feature, wherein the other one of the carrier and the thrust plate includes a circumferentially extending slot into which the anti-ramp up feature is received, the slot having a first slot end and a second slot end, the anti-ramp up feature traveling within the slot between the first slot end and the second slot end for limiting rotation between the carrier and the thrust plate;
• wherein the torsion spring is compressed axially between the hub and the carrier;
• wherein the carrier includes a helical first slot formed on an axial face thereof, the helical first slot defining a ramped first locating surface terminating at a first abutment wall and wherein the first end of the torsion spring abuts the first abutment wall;
• herein the hub includes a helical second slot formed therein concentric about the rotational axis of the hub, the helical second slot defining a ramped second locating surface terminating at a second abutment wall and wherein the second end of the torsion spring abuts the second abutment wall;
• wherein a clutch element is disposed between the hub and the pulley for selectively transmitting rotary power from the pulley to the carrier and enabling overrunning of the hub relative to the pulley;
• wherein the clutch element is in a first condition that inhibits transmission of rotary power from the pulley to the carrier when the anti-ramp up feature is positioned at the first slot end and wherein the clutch element is in a second condition that facilitates transmission of rotary power from the pulley to the carrier when the anti-ramp up feature is positioned at the second slot end;
• wherein the clutch element is a wrap spring that directly engages the pulley when the anti-ramp up feature is positioned at the second slot end;
• and
• wherein a first end of the wrap spring is fixedly coupled to the carrier.