Download Power Steering PDF

TitlePower Steering
TagsAutomobiles Motor Vehicle Automotive Technologies Wheeled Vehicles Steering
File Size373.2 KB
Total Pages13
Table of Contents
                            Power Steering
Turning the Car
Rack-and-pinion Steering
Recirculating-ball Steering
The Future of Power Steering
                        
Document Text Contents
Page 1

Power steering (or more correctly for most road vehicles power assisted steering), assists the driver of
an automobile in steering by directing a portion of the vehicle's power to traverse the axis of one or more
of the roadwheels. On most road going vehicles there has to be a mechanical linkage as a fail safe.
Originally invented in the early 20th century, automotive engineers have implemented this now standard
feature with a variety of technologies.

History

The earliest known patent related to power steering was that by Frederick W. Lanchester in the UK,in

February 1902. His invention was to "cause the steering mechanism to be actuated by hydraulic power".

The next design was filed as recorded by the US Patent Office on August 30, 1932, by Klara Gailis, from

Belmont, Massachusetts. There is another inventor credited with the invention of power steering by the

name of Charles F. Hammond an American, born in Detroit, who filed similar patents, the first of which

was filed as recorded by the Canadian Intellectual Property Office.

Chrysler Corporation introduced the first commercially available power steering system on the

1951 Chrysler Imperial under the name Hydraguide. Most new vehicles now have power steering, owing

to the trends toward front wheel drive, greater vehicle mass, and wider tires, which all increase the

required steering effort. Modern vehicles would be extremely difficult to maneuver at low speeds.

[edit]Hydraulic systems

Main article: Hydraulic power steering

A power steering fluid reservoir and pulley driven pump

Most power steering systems work by using a hydraulic system to turn the vehicle's wheels. The hydraulic

pressure is usually provided by a gerotor orrotary vane pump driven by the vehicle's engine. A double-

acting hydraulic cylinder applies a force to the steering gear, which in turn applies a torque to the steering

axis of the roadwheels. The flow to the cylinder is controlled by valves operated by the steering wheel; the

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Page 7

Animation showing what happens inside the rotary valve when you first start to turn the steering

wheel

When the steering wheel is 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 appropriate line.

It turns out that this type of power-steering system is pretty inefficient. Let's take a look at some advances

we'll see in coming years that will help improve efficiency.

You know that when you turn the steering wheel in your car, the wheels turn. Cause and effect, right? But

a lot of interesting stuff goes on between the steering wheel and the tires to make this happen.

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In this article, we'll see how the two most common types of c ar steering systems work: rack-and-pinion

and recirculating-ball steering. Then we'll examine power steering and find out about some interesting

future developments in steering systems, driven mostly by the need to increase the fuel efficiency of cars.

But first, let's see what you have to do turn a car. It's not quite as simple as you might think!

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Page 12

Instead of the bolt directly engaging the threads in the block, all of the threads are filled with ball

bearingsthat recirculate through the gear as it turns. The balls actually serve two purposes: First, they

reduce friction and wear in the gear; second, they reduce slop in the gear. Slop would be felt when you

change the direction of the steering wheel -- without the balls in the steering gear, the teeth would come

out of contact with each other for a moment, making the steering wheel feel loose.

Power steering in a recirculating-ball system works similarly to a rack-and-pinion system. Assist is

provided by supplying higher-pressure fluid to one side of the block.

Now let's take a look at the other components that make up a power-steering system.

The Future of Power Steering

Take the Quiz

Do you know what steering systems are used in cars? Test your knowledge with this quiz fromTurbo:

Car Steering Quiz

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 steering, replacing it with a purely

electronic control system. Essentially, the steering wheel would work like the one you can buy for your

home computer to play games. 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 driver with feedback on what 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.

General Motors has introduced a concept car, the Hy-wire, that features this type of driving system. One

of the most exciting things about the drive-by-wire system in the GM Hy-wire is that you can fine-tune

vehicle handling without changing anything in the car's mechanical components -- all it takes to adjust the

steering is some new computer software. In future drive-by-wire vehicles, you will most likely be able to

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