VENT STRUCTURE FOR TENSIONER

摘要

A tensioner (24) for tensioning an endless drive member (14) on an accessory drive system or a cam shaft drive system is provided with a vent structure (99) that opens into a cavity (68) of the tensioner (24) to permit reduction of any pressure in the cavity (68) and the ambient environment of the tensioner (24), while inhibiting ingress of contaminants into the cavity (68). In some embodiments the vent structure (99) includes one or more of a mechanical one-way valve (152), a semi-permeable membrane (311) or a passageway with a circuitous path.