Power steering
Power steering in a recirculating-ball system works similarly to a rack-and-pinion system.A power steering system should assist the driver only when he is exerting force on the steering wheel(such as when you starting a turn ),When the driver is not exerting force(such as when driving in a strsight line), the system shouldn’t provide any assist.
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 fro the steering is provideed by a rotary-vane pump.This pump is driven by the car’s engine via a belt and pully. It contains a set of retractable vanes that spin inside a oval chamber.
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 amount of flow provided by the pump depends on the car’s engine speed. The pump must provide adequate flow when the engine is idling. As a result, the pump moves much more fluid than necessary when the engine is running at faster speeds.
The pump contains a pressure-relief valve to make sure thet the pressure does not get too high, especially at high engine speeds when so much fluid is being pumped.
Rotary Valve
The device that sense the force on the steering wheel is called the rotary valve. The key to the rotary valve is a torsion bar. The tortion bar is a thin rod of metal that twist when torque is applied to it. The top of the bar is connected to the steering wheel, and the bottom of the bar is connected to the piston or worm gear(which turns the wheels), so the amount of torque in the torsion bar is equal to the amount of torque the driver is using to turn the wheels.The more torque the driver uses to turn thw wheels, the more the bar twists.
The input from the steering shaft froms the inner part of a spool-valve assembly.It also connects to the top end of the torsion bar. The bottom of the torsion bar connects to the outer part of the spool valve. The torsion bar also turns the output of the steering gear, connecting to either the pinion gear or the worm gear depending on which type of steeering the car has.
When the steering wheel is not not being turned, both hydraulic lines provide the same amount of pressure to the steering gear. But if the spool valve is turned one way or the other, ports open up to provide high-pressure fluid to the approprite line.
The future of power steering
Since the power-steering pump on most cars today runs constantly, pumping fluid all the time, it wastes horsepower. This wasted power translates into wasted fuel.
You can expect to see several innovations that will improve fuel economy. One of the coolest ideas on the drawing board is the “steer-by-wire” or “drive-by-wire” system. These systems would completely eliminate the mechanical connection between the steering wheel and the steeering, replacing it with a purely electronoc control system. It would contain sensors that tell the car what the driver is doing with the wheel. And have some motors in it to provide the driner with feedback on whant the car is doing. The output of these sensors would be used to control a motorized steering system. This would free up space in the engine compartment by eliminating the steering shaft. It would also reduce vibration inside the car.
In the past fifty years, car steering system haven’t changede much. But in the next decade, we’ll see advances in car steering that will result in more efficient cars and a more comfortable ride.
auther:Candywww.sinodiesel.com
