Energy efficient power steering pump control system

A power steering pump flow and pressure control system for providing hydraulic power to a vehicle steering assist module, the system comprising:

• a hydraulic fluid pump;
• an electronic control, in electronic communication with the vehicle, including the steering assist module and the pressure control system, for regulating pressure and flow within the system;
• and
• a flow control device, having a bore formed therein, in fluid communication with a pump output at a pump-side inlet via an output line, and with a pump input at a supply side inlet via a pressure-relief line, the pump-side inlet and supply-side inlet being located at longitudinally opposite ends of the bore, the flow control device including:
• an electro-hydraulic valve, located in the pressure-relief line and operatively connected to the electronic control;
• an outlet line, in fluid communication between the flow control device and the steering assist module via a pump-side outlet located adjacent the pump-side inlet;
• a feedback line in fluid communication between the outlet line and the supply-side inlet;
• the second pressure relief channel is a bypass line in fluid communication with a bypass orifice formed in the bore;
• a spool element, slidably received within the bore and configured to prevent longitudinal fluid flow past the spool element, the spool element:
• having a longitudinal length less than that of the bore, thereby defining within the bore a pump side chamber between the spool element and the pump inlet, and a supply side chamber between the supply inlet and the spool element;
• and
• being variably movable between a first position wherein the pump-side outlet is not blocked by the spool element and the bypass orifice is blocked by the spool element, and a second position wherein neither the pump-side outlet nor the bypass orifice is blocked by the spool element;
• and
• biasing means for urging the spool element toward the first position;
• wherein the electronic control varies the electro-hydraulic valve, responsive to communication from the vehicle and the system, to control the position of the spool element, providing maximum fluid flow to the steering assist module when required by the steering assist module, and otherwise diverting fluid flow to the pump input, the diverting of the fluid flow being at least partially through the pressure relief line at the supply side inlet, based on an input received from the electronic control, and partially through a channel connecting the pump side chamber to the pump inlet, based on the position of the spool element within the bore.

A method for reducing parasitic losses in a power steering system of an automotive vehicle, the system including a hydraulic fluid pump, a steering assist module, a flow control device, and an electronic control, comprising the steps of:

• receiving an output flow from the pump at the flow control device;
• dividing the output flow into a steering assist flow and a return flow at the flow control device, based on the position of a slidable spool element carried in a bore within the flow control device, and routing the return flow partially through a first pressure relief line fluidly communicating with a pump side chamber of the flow control device, and partially through a second pressure relief line communicating with a supply side chamber of the flow control device;
• sensing fluid flow requirements of the steering assist module at the electronic control;
• altering the position of the spool element by changing the pressure balance within the flow control device, responsive to the sensed requirements;
• and
• controlling the return flow routed through the second pressure relief line based on the sensed requirements.