Patent ID: 6106250
Filing Date: 2000-08-22
Classification: F04C

Abstract:
A lobed-rotor-type pump for pumping an incompressible fluid, having a communication passage between working-fluid chambers, said lobed-rotor-type pump comprising:a drive shaft;a housing defining therein an internal space and having a circumferentially-extending peri-trochoidal curved surface in an inner periphery of said housing;an eccentric rotor journal fixedly connected to said drive shaft for co-rotation, an axis of said eccentric rotor journal being eccentric to a center line of said drive shaft;a rotor slidably fitted to said eccentric rotor journal and having a plurality of circumferentially equi-distant spaced lobes on an outer periphery of said rotor so that said rotor rotates eccentrically in said housing, keeping said lobes in sliding-contact with said peri-trochoidal curved surface;plurality of working-fluid chambers defined between respective two adjacent lobes by said peri-trochoidal curved surface and the outer periphery of said rotor, said working-fluid chambers rotating in synchronism with said rotor;an intake port communicating the internal space of said housing;a discharge port communicating the internal space of said housing; anda communication passage for intercommunicating a first chamber of said working-fluid chambers, said first chamber decreasing in volume during compression state, and a second chamber of said working-fluid chambers, said second chamber increasing in volume during expansion stage,wherein a total volumetric capacity of said communication passage is set at a value equal to or greater than a predetermined volumetric capacity, which is obtained by subtracting a minimum volumetric capacity of said first chamber from a maximum volumetric capacity of said first chamber to permit decrease in the volumetric capacity of said first chamber during the compression stage.