Two-speed planetary friction accessory drive

A multiple ratio planetary friction drive adapted to establish plural torque flow paths between a torque input shaft (10) and a torque output shaft (12) comprising a planetary roller assembly with a sun roller element (30), a ring roller element (26), inner and outer groups of planet rollers (84, 66) and a carrier element (50) rotatably supporting said planet rollers;

• said ring roller element having an annular friction surface, said planet rollers having friction surfaces, the friction surfaces of said outer group of planet rollers being in frictional driving engagement with the friction surface of said ring roller element;
• said sun roller element having a friction surface in frictional driving engagement with the friction surface of said inner group of planet rollers;
• means (134, 128) for applying a tangential force to one of said groups of planet rollers, thereby establishing normal forces at the planet roller engagement locations on the frictional surfaces of said sun roller element and said ring roller element;
• clutch and brake means (104, 136) for selectively and alternately anchoring said carrier element to establish a torque reaction point and for clutching together said carrier element and said sun roller element thereby establishing two driving speed ratios between said input and output shafts, said clutch and brake means including an overrunning coupling disposed between said carrier element and said sun roller element whereby said carrier element, said sun roller element and said ring roller element rotate in unison when said carrier element is not anchored.