ES345101A1 - Pump - Google Patents

Abstract

A rotary pump includes in its outlet duct a flow control valve including a valve member movable in response to changes in pressure drop across the valve to control a by-pass orifice in a sense to open the by-pass when the pump speed reaches a predetermined value, to increase the orifice opening to reduce flow to the outlet duct as pump speed increases beyond said value and to close the by-pass orifice in response to an increase in fluid pressure in the outlet duct downstream of the flow control valve. As shown, the pump is of the roller vane type for supplying liquid to a power steering system in an automotive vehicle and comprises a rotor 12, Fig. 1, sandwiched between an end cover 15 and a pressure plate 30 subjected to pump discharge pressure. The valve member 33 having a conical end 40 is loaded by a spring 50 and seats upon a seat 51. Liquid from a reservoir 21 flows through a port 23 in end cover 15 into pump suction chamber 14a and from there through inlet ports 15a directly and inlet ports 30a indirectly via an axial passageway 25 and radial ports 26 in the power input shaft 13 into the pumping chamber and is discharged from the pumping chamber through ports 15b, 30b to a discharge chamber 14. The valve 33 is formed with a reduced diameter portion 41 to provide a restricted flow passage 52 leading to an annular chamber 43 communicating with an outlet 17 connected to the system being supplied and a land 42 whose opposite faces communicate with each other via valve member ducts 56, 55, 57. As pump speed reaches a predetermined value the valve member 33 is unseated. With increasing pump speed above this value the valve is progressively moved rightwardly whence liquid at high pressure and speed passes from the discharge chamber 14 into the inlet chamber 14a and into the axial passageway 25 to reduce the supply to the system and also induce liquid from the reservoir 21 into the inlet chamber 14a. When the speed increases still further such that the valve portion 41 overlies the outlet 17, the resulting increment in flow through the by pass exceeds the increment in delivery into the outlet 17 at the same pump speed, so a reduction of flow to the system takesplacedespite increased pump speed resulting in flow "droop." On increase in pressure in the system, the pressure downstream of the restricted flow passage 52 increases relative to that upstream thereof to move the valve member 33 towards closure to reduce the amount of liquid being by-passed and increase flow to the system. In the event of pressure in the system exceeding a predetermined value a spring-loaded loose ball valve 62 is unseated to connect the system to the reservoir 21. This results in a reduction in pressure in the chamber 43 and behind the land 42 to permit further rightward movement of the valve member 33 to reduce further flow to the system. Various modifications of the valve member 33 are described. The loose ball pressure relief valve instead of being housed within the valve member 33 may be a separate valve.