Power steering pump with balanced porting

Abstract

A balanced vane hydraulic pump designed for automotive power steering applications employs a multi-vane rotor and cam ring. The pump has a three-piece aluminum housing construction, with the flow regulating valve located in the rear housing section, the cam ring and rotor located in the center housing section, and a two bearing sets located in the front housing section for supporting the pump drive shaft from one end only. The rear housing section also preferably includes a semi-flexible inner wall which under high pressure conditions bows inwardly toward the cam ring, rotor and vanes, thereby helping to maintain operating clearances so as to relatively help control leakage under varying pump output pressures, even though separate pressure and thrust plates are not used. An important feature of the pump is the use of hydraulically balanced low pressure and high pressure passageways which are contoured to efficiently direct the moving fluid and to minimize energy loss within the pump passageways, which enhances speed capabilities. The low pressure fluid passageways are in particular balanced through the use of a generally symmetrical wishbone gallery in the center housing section which feeds low pressure hydraulic fluid to two pairs of two diametrically opposed inlet windows adjacent to the low pressure inlet sectors of the cam ring.