Control valve for bootstrap hydraulic systems

A hydro-mechanical control system for a motor vehicle power steering system operable to selectively control the flow of hydraulic fluid to first and second input ports of a power output transducer for controlling the positioning of a mechanical device in response to rotational input applied to a steering wheel by a vehicle operator, said hydro-mechanical control system comprising:

• a fluid reservoir;
• pump means in fluid communication with said reservoir, said pump means having means for providing said hydraulic fluid at a regulated fluid pressure;
• an open-centered control valve assembly having receiving means for receiving said rotational inputs, an inlet port, a return port and first and second output ports;
• supply line means for deliverying said pressurized hydraulic fluid from said pump means to said inlet port of said control valve assembly;
• return line means for fluidly interconnecting said control valve return port to said fluid reservoir;
• first and second load lines fluidly interconnecting said first and second output ports of said control valve assembly with said first and second input ports of said power output transducer respectively, said control valve assembly being operable to control the differential output pressure applied to said first and second ports of said power output transducer and the differential fluid flow therebetween in response to said rotational inputs, said differential output pressure defining a load pressure;
• valve means in fluid communication with each of said first and second load lines for fluidically coupling the one of said first and second load lines having the higher valued fluid pressure to control line means;
• said control line means provided for coupling said selected one of said first and second load lines to said means for providing fluid at said regulated fluid pressure as a function of said load pressure;
• and
• wherein said control system is operable for generating tactile feedback as a function of said differential output pressure and said differential fluid flow.

An electro-hydro-mechanical control system for a motor vehicle power steering system operable to selectively control the flow of hydraulic fluid to first and second input ports of a power output transducer for controlling the positioning of a mechanical device, said electro-hydromechanical control system comprising:

• a fluid reservoir;
• pump means in fluid communication with said reservoir, said pump means having electrical means for providing hydraulic fluid at a regulated fluid pressure as a function of load pressure;
• an open-center control valve assembly having an inlet port, a return port and first and second output ports;
• supply lines means for deliverying said pressurized hydraulic fluid from said pump means to said inlet port of said control valve assembly;
• return lines means for fluidly interconnecting said control valve return port to said fluid reservoir;
• first and second load lines fluidly interconnecting said first and second output ports of said control valve assembly with said first and second input ports of said power output transducer respectively, said control valve assembly being operable to control the differential output pressure applied to said first and second ports of said power output transducer and the differential fluid flow therebetween in response to said rotational inputs, said differential output pressure defining said load pressure;
• valve means in fluid communication with each of said first and second load lines for fluidically coupling the one of said first and second load lines having the higher valued fluid pressure to means for generating an electrical signal indicative of said higher valued fluid pressure;
• means for coupling said electrical signal to said electrical means;
• said control valve assembly including a valve sleeve selectively rotatable within a central bore of a valve housing, and wherein said means for receiving rotational inputs is a valve spool selectably rotatable within a central bore of said valve sleeve, said control valve assembly being configured in an open-centered manner;
• and
• wherein said control system is operable for generating tactile feedback as a function of said differential output pressure and said differential fluid flow.