Speed Proportional Steering Gear

Available as an option or as standard equipment on certain vehicles is electronically controlled, variable-assist speed-proportional power steering. Variable-assist speed-proportional power steering, provides additional steering assist while the vehicle is stationary and at slow driving speeds. This additional power steering assist reduces the steering effort required by the driver for low speed driving and parking maneuvers. Variable-assist speed-proportional power steering, then provides less power steering assist at highway speeds, to maintain the firm, responsive feel of the existing non variable assist speed proportional power steering system.

The operational range of the variable-assist speed proportional power steering system, is from zero to approximately 60 mph. Maximum available power steering assist is provided at zero miles per hour. The power steering assist is then gradually reduced from vehicle speeds of greater then zero to a maximum speed of approximately 60mph. The minimum power steering assist available, is reached at a vehicle speed of approximately 60 mph.

Variable-assist power steering, is provided by controlling power steering fluid pressure at the power steering gear. The pressure is controlled, by regulating power steering fluid flow from the steering gear back to the power steering pump. A solenoid valve located on the steering gear, is used to control power steering pressure, by varying the size of an orifice which the power steering fluid must flow through, from the steering gear back to the power steering pump.

The variable-assist speed-proportional solenoid control valve is controlled by the steering gear mounted electronic Solenoid Control Module (SCM). The SCM receives the vehicle speed signal sent from the Transmission Control Module (TCM). Upon receiving the vehicle speed signal from the TCM, the SCM converts that speed signal into an electrical current usable by the solenoid control valve for controlling the variable assist of the power steering system.