Decoupler with concentric clutching members

Abstract

In an aspect, a decoupler includes a hub, a pulley, a torsion spring having a plurality of coils including first and second end coils, a first spring driver fixed to the pulley, and having a first spring driver surface and a first end coil support surface; a second spring driver not fixed to the pulley, and having a second spring driver surface and a second end coil support surface, a driving clutch member mounted connected to the second spring driver, a driven clutch member mounted concentrically with the driving clutch member and drivingly connected to the hub, a one-way wrap spring clutch mounted about the hub and disposed to interconnect the driving and driven clutchmembers, and configured to transfer torque in a first direction between the driving and driven clutchmembers. A first overrun limit surface connected to the first spring driver engages a second overrun limit surface connected to the second spring driver when an angular displacement of the second spring driver relative to the first spring driver reaches a first selected angular displacement so as to prevent an increase in the angular displacement. At the selected angular displacement any axial compression of the torsion spring resulting from rotation of the second end coil support surface relative to the first end coil support surface is sufficiently small to prevent the coils from binding to one another.