Steering and torsion rod innovations launched by TRW 08 October 2014

TRW Automotive launched two new commercial steering technologies and a lightweight radius rod for trucks at last week's Hanover IAA Commercial Vehicles show (25 September to 5 October 2014).

On the steering side, the first offering, dubbed ReAX, merges two of TRW's existing systems – hydraulic power steering (HPS) for commercial vehicles and electrically powered steering (EPS) belt drive for passenger cars, with a goal of improving driver control and stability.

The second is the ActivMode energy efficient hydraulic power steering pump, claimed to deliver up to 50% reduction in energy consumption, compared with traditional pumps.

"Our commercial steering efforts are very much focused on making the driving task as safe and comfortable as possible, while minimising the impact of our technologies on the environment," states Andreas Weller, vice president and general manager for global commercial steering systems at TRW.

"With ReAX, hydraulic power steering provides the torque to steer larger commercial vehicles while EPS belt drive offers precision and control. Uniting these two technologies reduces steering efforts at low speeds and yields increased stability at higher speeds," he continues.

TRW has used a similar combination for over a decade on column drives, mostly for bus and motor home applications, but this is the first time the company has redesigned the system for trucks.

Weller says ReAX is also key to enabling semi-automated driving and driver assist systems such as lane departure warning and lane keeping assist.

As for TRW's ActivMode pump, Weller explains that its fuel savings and temperature reduction derive from new dual mode flow logic, which matches steering demand at engine idle and also cruising speed.

At low engine speed, both sides of the circuit are used to provide full flow, while when cruising, one side is hydraulically disengaged to reduce pump action and hence power consumption.

"ActivMode is designed for minimum complexity, requiring no electronics or sensors to achieve its unique flow logic," insists Weller.

"This also helps it to be smaller and lighter than other energy-efficient power steering pumps and fit within current vehicle architectures," he continues.

"Additionally, its ability to operate at lower temperatures provides [OEMs] with the opportunity to eliminate steering system coolers in many applications."

As for the new radius rod, Dr Cengiz Erdogan, head of engineering for CV linkage and suspension at TRW, says is up to 30% lighter than traditional units.

"The key ... was the functional integration of cardanic elements from the rubber bushing into the connecting elements between the two housings," explains Erdogan.

"We re-designed the tube component which now uses two inverted, C-shaped pieces of metal welded to the housings," he continues, adding that the new torsion rod is interchangeable because the connecting geometry precisely matches the existing design.

ReAX is scheduled for production in 2017 for 2018 applications and TRW says it is currently working with "a major vehicle manufacturer to research and develop semi-autonomous vehicle functions" using the technology.

ActivMode is due for production in 2016 for 2017 applications.

Finally, the new torsion rod is the subject of a TRW development contract with another unnamed European truck manufacturer and TRW expects first production "near the end of 2016".

Author
Brian Tinham

Related Companies
ZF TRW

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