Decoupler with tuned damping and methods associated therewith
In an aspect, the invention relates to a decoupler that is positionable between a shaft (eg. for an alternator) and an endless power transmitting element (eg. a belt) on an engine. The decoupler includes a hub that mounts to the shaft, and a pulley that engages the endless power transmitting element, an isolation spring between the hub and the shaft. The decoupler provides at least a selected damping torque between the hub and the pulley.
1. A decoupler for transferring torque between a shaft and an endless power transmitting element, said decoupler, comprising:
a hub that is adapted to be coupled to the shaft such that the shaft co-rotates with the hub about a rotational axis;
a pulley rotatably coupled to the hub, the pulley having an outer periphery that is adapted to engage the endless power transmitting element;
an isolation spring positioned to transfer rotational force from the pulley to the hub and to accommodate torsional vibration between the pulley and the hub; and
a first friction surface operatively connected with the pulley;
a second friction surface operatively connected with the hub;
a friction surface biasing member positioned for exerting a biasing force to biasing the first and second friction surfaces against each other; and
a retainer that is engaged with the friction surface biasing member and positioned to cause the friction surface biasing member to apply at least a selected biasing force on the first and second friction surfaces thereby generating at least a selected damping torque during relative rotational movement between the pulley and the hub, wherein the first and second friction surfaces are engaged with one another sufficiently to attenuate first order vibrations from an engine that drives the endless drive member, to result in less than a selected peak to peak angular range of movement between the hub and pulley,
wherein the biasing force is selected so that the damping torque is sufficiently high to inhibit angular vibration on the hub from exceeding a selected peak-to-peak angle during use of the decoupler on an engine generating a selected torsional vibration at the pulley over a selected range of frequencies,
wherein the selected range of frequencies is about 5 Hz to about 20 Hz.
2. A decoupler as claimed in claim 1 , wherein the selected peak-to-peak angle is less than about 1 degree.
3. A decoupler as claimed in claim 1 , wherein the selected peak-to-peak angle is selected based on providing a selected fatigue life for the isolation spring.
4. A decoupler as claimed in claim 1 , wherein the shaft is the shaft of an alternator.
5. A decoupler as claimed in claim 4 , wherein the engine is a 4-cylinder engine.
6. An endless drive arrangement for an engine, comprising:
a crankshaft pulley driven by a crankshaft from the engine;
an alternator pulley mounted to an input shaft of an alternator;
an endless drive member that is positioned to transfer power from the crankshaft pulley to the alternator pulley, wherein first order vibrations are produced at the crankshaft; and
a decoupler between the endless drive member and at least one of the alternator pulley and the crankshaft pulley, wherein the decoupler is damped sufficiently to attenuate said first order vibrations to result in less than a selected peak to peak angular range of movement at the input shaft of the alternator, wherein the selected peak-to-peak angle is less than about 1 degree.
7. An endless drive arrangement as claimed in claim 6 , wherein the decoupler includes:
a hub that is adapted to be coupled to the shaft such that the shaft co-rotates with the hub about a rotational axis;
a pulley rotatably coupled to the hub, the pulley having an outer periphery that is adapted to engage the endless power transmitting element;
an isolation spring positioned to transfer rotational force from the pulley to the hub and to accommodate torsional vibration between the pulley and the hub; and
a first friction surface operatively connected with the pulley;
a second friction surface operatively connected with the hub;
a friction surface biasing member positioned for exerting a biasing force to biasing the first and second friction surfaces against each other; and
a retainer that is engaged with the friction surface biasing member and positioned to cause the friction surface biasing member to apply at least a selected biasing force on the first and second friction surfaces thereby generating at least a selected damping torque during relative rotational movement between the pulley and the hub.
8. An endless drive arrangement as claimed in claim 6 , wherein the selected peak-to-peak angular range of movement is selected based on providing a selected fatigue life for the isolation spring.