Power Steering - How Car Steering Works
There are a couple of key components in power steering in addition to the rack-and-pinion or recirculating-ball mechanism. Pump The hydraulic power for the steering is provided by a rotary-vane pump (see diagram below). As the vanes spin, they pull hydraulic fluid from the return line at low pressure and force it into the outlet at high pressure. The pump contains a pressure-relief valve to make sure that the pressure does not get too high, especially at high engine speeds when so much fluid is being pumped. Rotary Valve A power-steering system should assist the driver only when he is exerting force on the steering wheel (such as when starting a turn). The key to the rotary valve is a torsion bar. The input from the steering shaft forms the inner part of a spool-valve assembly. Animation showing what happens inside the rotary valve when you first start to turn the steering wheel As the bar twists, it rotates the inside of the spool valve relative to the outside.