Decoupler assembly with sliding interface between hub and pulley

#The present invention relates to decoupling mechanisms for allowing belt driven accessories to operate temporarily at a speed other than the speed of the belt, and more particularly to decoupling mechanisms that incorporate wrap-spring clutches.

#It is known to provide a decoupling mechanism on an accessory, such as an alternator, that is driven by a belt from an engine in a vehicle. Such a decoupling mechanism, which may be referred to as a decoupler, permits the associated accessory to operate temporarily at a speed that is different than the speed of the belt. For example, when there is a sudden stoppage of the belt when the belt was running and driving rotation of the alternator shaft, the decoupler permits the alternator shaft to continue rotating temporarily as a result of inertia until it decelerates to a stop as a result of drag, thereby reducing the stress on the alternator shaft. As another example, the decoupler permits the alternator shaft to rotate at a relatively constant speed even though the crankshaft from the engine undergoes a cycle of decelerations and accelerations associated with the movement of the pistons.

#Such decouplers are valuable additions to the powertrain of the vehicle. However, there is a continuing need to reduce their cost, to improve their operating life, to reduce their complexity and to simplify their manufacture. It would thus be beneficial to provide a decoupler that addresses one or more of these continuing needs.

#The present invention will now be described by way of example only with reference to the attached drawings, in which:

#FIG. 1 is an elevation view of an engine with a plurality of belt driven accessories, one of which has a decoupler assembly in accordance with an embodiment of the present invention;

#FIG. 2 is a magnified sectional view of the decoupler assembly shown in FIG. 1;

#Reference is made to FIG. 1, which shows an engine 10 for a vehicle. The engine 10 includes a crankshaft 12 which drives an endless drive element, which may be, for example, a belt 14. Via the belt 14, the engine 10 drives a plurality of accessories 16 (shown in dashed outlines), such as an alternator and a compressor. Each accessory 16 includes an input drive shaft 15 with a pulley 13 thereon, which is driven by the belt 14. A decoupler assembly 20 is provided instead of a pulley, between the belt 14 and the input shaft 15 of any one or more of the belt driven accessories 16. The decoupler assembly 20 transfers torque between the belt 14 and the shaft 15 but automatically decouples the shaft 15 from the belt 14 when the belt 14 decelerates relative to the shaft 15. Additionally, the decoupler assembly 20 allows the speed of the belt 14 to oscillate relative to the shaft 15. Thus, oscillations in the belt speed that are the result of oscillations in the speed of the crankshaft (an inherent property of internal combustion piston engines), are dampened by the decoupler assembly 20, and as a result, the stresses that would otherwise be incurred by the shaft 15 and the component 16 are reduced.

#Reference is made to FIG. 2, which shows a sectional view of the decoupler assembly 20. The decoupler assembly 20 includes a hub 22, a pulley 24, a bearing 26, a dampening spring 28, a carrier 30, a clutch spring 32 and an end cap 34.

#The hub 22 may be adapted to mount to the shaft 15 in any suitable way. For example, the hub 22 may have a shaft-mounting aperture 36 therethrough that defines a rotational axis A for the decoupler assembly 20. The shaft mounting aperture 36 may be configured to snugly receive the end of the shaft 15. A shaft-mounting fastener (not shown) may be inserted through a distal end 38 of the aperture 36 to fixedly mount the hub 22 to the shaft 15 so that the two co-rotate together about the axis A.