Patent ID: 6050796
Filing Date: 2000-04-18
Classification: F04C

Abstract:
In a vane pump includinga housing,a discharge pressure chamber in said housing having a fluid therein at a discharge pressure of said vane pump,a rotating group including a thrust plate seated on said housing and a pressure plate exposed to said discharge chamber and a cam ring clamped between said pressure plate and said thrust plate by a fluid pressure force on said pressure plate attributable to said fluid in said discharge chamber,an oval-shaped wall on said cam ring cooperating with a planar side of said pressure plate and with a planar side of said thrust plate in defining a rotor chamber in said rotating group,a rotor supported in said rotor chamber for rotation about a longitudinal centerline of said vane pump perpendicular to said planar side of said thrust plate and to said planar side of said pressure plate,a plurality of radial vane slots in said rotor each intersecting a first planar end wall of said rotor facing said planar side of said pressure plate and a second planar end wall of said rotor facing said planar side of said thrust plate and an outer cylindrical surface of said rotor facing said oval-shaped wall on said cam ring, anda plurality of flat vanes slidable in said respective ones of said vane slots,the improvement comprising:a first chamber-forming means operative to define a first longitudinal balance chamber exposed to a reaction portion of said first planar end wall of said rotor constituting at least 30% of the area of said first planar end wall and to said planar side of said pressure plate,a second chamber-forming means operative to define a second longitudinal balance chamber exposed to said planar side of said thrust plate and to a reaction portion of said second planar end wall of said rotor equal to said reaction portion of said first planar end wall of said rotor,a first port means operative to port fluid at said discharge pressure of said vane pump to said first balance chamber thereby to balance a fraction of said pressure force on said pressure plate attributable to said fluid in said discharge chamber, anda second port means operative to port fluid at said discharge pressure of said vane pump to said second balance chamber thereby to maintain said rotor in static equilibrium in the direction of said longitudinal centerline of said vane pump.