TRW Supplies Electrically Powered Hydraulic Steering (EPHS) for New Opel Astra
18 August 1998
TRW Supplies Electrically Powered Hydraulic Steering (EPHS) for New Opel Astra
STERLING HEIGHTS, Mich., Aug. 18 -- The recent launch of
the new Opel Astra marks TRW's first mass production of an electro-hydraulic
steering system for passenger cars. The Electrically Powered Hydraulic
Steering (EPHS) system was developed by TRW Steering and Suspension Systems in
Dusseldorf, Germany, in cooperation with Adam Opel's International
Technical Development Center in Russelsheim, Germany.
The EPHS system also incorporates the electronic and mechanical knowledge
gained from TRW's activities in the aerospace industry.
The TRW EPHS system used in the Opel Astra combines an electrically driven
hydraulic pump with conventional rack-and-pinion steering to give the most
precise handling and steering assistance with minimal energy consumption.
In a conventional hydraulic steering system, power is provided by a
hydraulic pump driven directly by the car engine. The pump must be designed
to deliver maximum flow at low engine speeds to provide high power assistance
during parking maneuvers. At normal highway speeds, little power assistance
is actually required, yet the engine-driven pump continues to deliver a
heavy flow of oil which has to be pumped back to the reservoir via a bypass
valve. So energy and fuel are wasted during most of the vehicle driving time.
In the TRW EPHS steering system, a 12-volt brushless DC motor is used to
drive the hydraulic pump and only delivers a high flow rate when the steering
maneuver requires it. In more than 85 percent of driving conditions, the
power pack is running at standby speed and consumes less than 4 amps current,
yet can accelerate to full speed for an emergency steering maneuver.
The motor is commutated electronically, so there are no brushes to wear
out, and the whole system is designed to be maintenance-free. By designing
the complete steering system, TRW has been able to provide optimized steering
assistance with improved steering feel and vehicle driving characteristics.
It also provides power assistance if the engine stalls, for greater comfort
and increased safety.
The TRW EPHS system used on the Astra is manufactured at TRW Automotive's
Gelsenkirchen-Schalke plant in Germany and is delivered on a just-in-time
basis to Opel assembly plants in Germany, Belgium and the United Kingdom. The
EPHS is delivered to the car assembly plants as a single module, filled with
hydraulic fluid and fully tested for function and performance. The module
simply has to be installed and connected to the car's electrical system.
In a conventional hydraulic system, the oil pump and belt must be
assembled to the engine, the steering gear assembled to the suspension or body
and the whole system connected via hoses and pipes before filling with oil and
testing. TRW's EPHS module approach can eliminate approximately 93 percent of
this assembly time, as well as improve quality, avoid the risk of
contamination and eliminate the handling of hydraulic fluid.
In addition to the two-speed EPHS system supplied for the Astra, TRW
offers a range of EPHS products -- from a single-speed version for less
demanding steering applications, up to a fully variable-speed system for even
greater fuel economy.
The variable-speed version uses an electronic sensor to monitor the
steering wheel turn rate and automatically adjusts the motor speed and oil
flow to precisely match it. This ultimate in energy-efficient hydraulic
steering enables fuel consumption savings up to 0.2 liter/100km.
In addition to Opel, TRW has been awarded a major European platform
beginning production in the year 2000 for its rack-drive Electrically Powered
Steering (EPS) system, and also has been awarded a major European platform for
the column-drive EPS system beginning production in 2002. TRW is currently
showing its pinion-drive EPS system to many major automotive OEMs worldwide.
Providing steering systems for one in four cars worldwide, TRW is the
world's leading supplier of automotive power rack-and-pinion steering and
suspension systems. The company's Passenger Car Steering Systems business
annually produces more than 10 million power rack-and-pinion steering gears
worldwide and about 400,000 integral power steering systems for commercial
vehicles.
TRW Inc. is headquartered in Cleveland, Ohio, and has sales of
nearly $12 billion. The company, which employs approximately 80,000 people in
30 countries, is one of the largest independent automotive components
suppliers in the world with $7 billion in worldwide automotive sales. The
company also provides advanced technology products and services for the
space, defense and information technology markets.
For more information about TRW, visit its web site at http://www.trw.com.