Power steering is a system for reducing the steering effort on vehicles by using an external power source to assist in turning the wheels. Steering is the term applied to the collection of components linkages etc It is said that power steering was invented in the 1920s by Klara Gailis and George Jessup in Waltham, Massachusetts, USA. The 1920s is sometimes referred to as the " Jazz Age " or the " Roaring Twenties " when speaking about the United States and Canada One of the early centers of the Industrial Revolution in northern America Waltham is a city in Middlesex County, Massachusetts, United States The United States of America —commonly referred to as the However, the earliest known patent related to power steering was filed (as recorded by the US Patent Office) on Aug. 30, 1932, by Francis W. Davis [1] 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) on Feb. 16, 1954 [2]. Chrysler Corporation introduced the first commercially available power steering system on the 1951 Chrysler Imperial under the name Hydraguide. Chrysler LLC is an American Automobile manufacturer that has been producing Automobiles since 1925 For Imperial models sold under its own marque (1955-1975 1981-83 see Imperial (automobile For the type of rose see Chrysler Imperial Rose 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 steering effort needed. Front-wheel drive (or FF layout) is a form of engine / transmission layout used in Motor vehicles where the engine drives the front Wheels This article is about tires used on road Vehicles including pneumatic tires and solid tires. Modern vehicles would be extremely difficult to maneuver at low speeds (e. g. , when parking) without assistance.
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Hydraulic systems
Most power steering systems work by using a hydraulic system to turn the vehicle's wheels. A hydraulic or hydrostatic drive system or hydraulic power transmission is a drive- or transmission system that makes use of a hydraulic fluid under pressure to drive The hydraulic pressure is usually provided by a gerotor or rotary vane pump driven by the vehicle's engine. A gerotor is a Positive displacement pumping unit The name gerotor is derived from "Generated Rotor " A rotary vane pump is a positive-displacement Pump that consists of vanes mounted to a rotor that rotates inside of a cavity A double-acting hydraulic cylinder applies a force to the steering mechanism, which in turn applies a torque to the wheels. A Hydraulic cylinder (also called a linear Hydraulic motor) is a mechanical Actuator that is used to give a linear Force through a linear stroke In Physics, a force is whatever can cause an object with Mass to Accelerate. A torque (τ in Physics, also called a moment (of force is a pseudo- vector that measures the tendency of a force to rotate an object about The flow to the cylinder is controlled by valves operated by the steering wheel. For other uses see Valve (disambiguation. For the electronic component see Thermionic valve. There are several common valve systems of varying complexity, but they all allow the steering wheel to turn further than is necessary to simply open a valve. This is done so that the position of the steering wheel corresponds to the position of the vehicle's wheels. As the pumps employed are of the positive displacement type, the flow rate they deliver is directly proportional to the speed of the engine. This means that at high engine speeds the steering would naturally operate faster than at low engine speeds. Because this would be undesirable, a restricting orifice and flow control valve are used to direct some of the pump's output back to the hydraulic reservoir at high engine speeds. A pressure relief valve is also used to prevent a dangerous build-up of pressure when the hydraulic cylinder's piston reaches the end of the cylinder.
Some modern implementations also include an electronic pressure relief valve which can reduce the hydraulic pressure in the power steering lines as the vehicle's speed increases (this is known as variable assist power steering).
DIRAVI
In the DIRAVI system invented by Citroën, the force turning the wheels comes from the car's high pressure hydraulic system and is always the same no matter what the road speed is. DIRAVI is the name given by Citroën to its proprietary Power steering system first seen in 1970 DIRAVI is the name given by Citroën to its proprietary Power steering system first seen in 1970 Citroën (pronounced See-Troh-Enn is a French Automobile manufacturer, founded in 1919 by André Citroën. As the steering wheel is turned, the wheels are turned simultaneously to a corresponding angle by a hydraulic piston. A piston is a component of Reciprocating engines Pumps and Gas compressors It is located in a cylinder and is made gas-tight by Piston In order to give some artificial steering feel, there is a separate hydraulically operated system that tries to turn the steering wheel back to center position. The amount of pressure applied is proportional to road speed, so that at low speeds the steering is very light, and at high speeds it is very difficult to move more than a small amount from the centre position.
As long as there is pressure in the car's hydraulic system, there is no mechanical connection between the steering wheel and the road wheels. This system was first introduced in the Citroën SM in 1970, and was known as 'VariPower' in the UK and 'SpeedFeel' in the U. The Citroën SM was a high performance Coupé produced by the French manufacturer Citroën between 1970 and 1975 S.
While DIRAVI is not the mechanical template for all modern power steering arrangements, it did innovate the now common benefit of speed adjustable steering. Steering is the term applied to the collection of components linkages etc The force of the centering device increases as the car's road speed increases.
Electro-hydraulic systems
Electro-hydraulic power steering systems, sometimes abbreviated EHPS, and also sometimes called "hybrid" systems, use the same hydraulic assist technology as standard systems, but the hydraulic pressure is provided by a pump driven by an electric motor instead of being belt-driven by the engine. An electric motor uses Electrical energy to produce Mechanical energy. These systems can be found in some cars by Ford, Volkswagen, Audi, Peugeot, Citroen, SEAT, Skoda, Suzuki, Opel, MINI, Toyota, and Mazda. Ford Motor Company is an American Multinational corporation and the world's fourth largest automaker based on Worldwide vehicle sales, following AUDI AG, ( Xetra: NSU commonly known as Audi (aˈʊdi is a German Automobile manufacturer which produces Audi branded cars with headquarters For the article about the bicycle manufacturer see Cycles Peugeot. Citroën (pronounced See-Troh-Enn is a French Automobile manufacturer, founded in 1919 by André Citroën. SEAT SA ( English pronunciation:, "say-at" Spanish pronunciation:) is a Spanish automobile Škoda Auto ( is an automobile manufacturer in the Czech Republic. is a Multinational corporation headquartered in Hamamatsu Japan that specializes in manufacturing compact automobiles a full range of Motorcycles All-Terrain Adam Opel GmbH (commonly known as Opel) is a German automaker part of General Motors. Mini (styled as MINI) is a British automotive brand owned by the German BMW Group that has produced a redesign of the traditional Mini (pronounced) is a Multinational corporation headquartered in Japan, and is currently the world's largest Automaker. ( is a Japanese automotive manufacturer based in Hiroshima, Japan.
Electric systems
Electric Power Steering systems, such as those found on the Honda NSX, Chevrolet Cobalt, Honda S2000, Saturn Vue V6, 2009 Toyota Corolla, Toyota RAV 4, Toyota Prius, Suzuki Swift and on most Fiat Lancia and Peugeot as also the Peugeot 307 model, use electric components with no hydraulic systems at all. Electric power steering ( EPS or EPAS) is designed to use an Electric motor to reduce effort by providing assist to the driver of a Vehicle Electric power steering ( EPS or EPAS) is designed to use an Electric motor to reduce effort by providing assist to the driver of a Vehicle Development In 1984 Honda commissioned Pininfarina to design the HP-X ( H onda P ininfarina X perimental which had a mid-mounted 2 The Chevrolet Cobalt is a Compact car introduced by Chevrolet in 2004 for the 2005 model year The Honda S2000 is a Roadster manufactured by the Japanese automaker Honda Motor Company. The Saturn Vue is a compact Crossover SUV from General Motors ' Saturn Marque, and was Saturn's top-selling model in the United The Toyota Prius is a hybrid electric Mid-size car developed and manufactured by the Toyota Motor Corporation Fiat SpA (an Acronym for Fabbrica Italiana Automobili Torino (Italian Automobile Factory of Turin) is an Italian automobile manufacturer Lancia Automobiles SpA is an Italian Automobile manufacturer founded in 1906 by Vincenzo Lancia and which became part of the Fiat Group in For the article about the bicycle manufacturer see Cycles Peugeot. The Peugeot 307 is a Family car produced by the French Peugeot manufacturer since 2001 Sensors detect the motion and torque of the steering column and a computer module applies assistive power via an electric motor coupled directly to either the steering gear or steering column. A torque (τ in Physics, also called a moment (of force is a pseudo- vector that measures the tendency of a force to rotate an object about This allows varying amounts of assistance to be applied depending on driving conditions. Most notably on Fiat group cars the amount of assistance can be regulated using a button named "CITY" that switches between two different assist curves (boost curve), while on Volkswagen/Audi group cars, the amount of assistance is automatically regulated depending on vehicle speed.
In the event of component failure, a mechanical linkage such as a rack and pinion serves as a back-up in a manner similar to that of hydraulic systems. A rack and pinion is a pair of Gears which convert rotational motion into linear motion The software in the computer module enables the flexibility of "tuning" the characteristics of the electric power steering system to suit the preference of the vehicle designers. The "feel" is often set a bit on the light side so a criticism commonly expressed is a lack of steering "feel".
Electric power steering is limited to smaller vehicles. This is because the 12 volt electrical system is limited to 80 amps of current which, in turn, limits the size of the motor to less than 1 kilowatt. (12. 5 volts times 80 amps equals 1000 watts. The watt (symbol W) is the SI derived unit of power, equal to one Joule of energy per Second. ) Vehicles such as trucks and SUVs require a more powerful motor. An upcoming new 42 volt electrical system standard may enable use of electric power steering on larger vehicles.
Electric systems have a slight advantage in fuel efficiency (almost 1 MPG) because there is no hydraulic pump constantly running, whether assistance is required or not, and this is the main reason for their introduction. Fuel efficiency, in its basic sense is the same as Thermal efficiency, meaning the efficiency of a process that converts chemical potential energy contained in a carrier Their other big advantage is the elimination of a belt-driven engine accessory, and several high-pressure hydraulic hoses between the hydraulic pump, mounted on the engine, and the steering gear, mounted on the chassis. This greatly simplifies manufacturing.
Servotronic
Servotronic offers speed-dependent power steering, in which the amount of servo assist depends on road speed and thus provides even more comfort and convenience for the driver. Speed is the rate of motion, or equivalently the rate of change in position often expressed as Distance d traveled per unit of A servomechanism, or servo is an automatic device which uses error-sensing Feedback to correct the performance of a mechanism The amount of power assist is greatest at low speeds, for example when parking the car. The greater assist makes it easier to maneuver the car. At higher speeds, an electronic sensing system gradually reduces the level of power assist. In this way, the driver can control the car even more precisely than with conventional power steering. Servotronic is used by a number of automakers including Audi, BMW, Volvo and Porsche. Servotronic is a trademark of AM General. [3]
References
See also
External links
- EPC Working In Detail
- Power steering using FAQ
- Power steering rack and Gear box
- Ways to protect Power steering and Gear box
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