US Patent 7108493 Variable displacement pump having rotating cam ring

Vane pump (10) mechanical losses are reduced by removing vane friction losses and replacing them with lower magnitude journal bearing fluid film viscous drag losses. A freely rotating cam ring (70) is supported by a journal bearing (80). A relatively low sliding velocity is imposed between the cam ring and the vanes (26). This permits the use of less expensive and less brittle materials in the pump by allowing the pump to operate at much higher speeds without concern for exceeding vane tip velocity limits.