ZF touts new chassis gadgets

GIANT German car parts group ZF Friedrichshafen could be about to become the best friend of boat owners, campers and grey nomads everywhere – it is working on a steering system to take the pain out of reversing a car-trailer combination.

ZF is best known for its transmissions, but the company is also one of the industry’s leading chassis components suppliers.

Last Friday, ZF Australia OEM business manager for passenger cars, Glenn Paine, highlighted some of the company’s newest work at the national conference of the Federation of Automotive Products Manufacturers (FAPM).

Mr Paine said much of the work is driven by the need to reduce weight so that car-makers can reduce the exhaust emissions of their vehicles, but the rapid expansion of electronics and computer control is also driving developments.

The trailer parking assist system is in the latter category, and is based on a ball-joint sensor that was not such a great success when it was first released.

“A few years ago, we had the ‘Lemforder’ sensor module, a sensor integrated into the ball joint,” said Mr Paine, whose company makes around 150 million ball-joints a year.

“An application for that might have been to mount it into the front upper control arm and you could use it in conjunction with your stability system,” he said.

It didn’t take off as ZF had hoped and now the company has applied the sensor to a problem that many Australians have to grapple with regularly.

“We have developed the sensor again and it is now integrated into the towing feature of the car. It connects to and communicates with the power steering system.

“When you are reversing the vehicle with a caravan or a trailer attached, this will actually help you to control that parking maneouvre.”

However, ZF will not have it ready until 2015.

With the accent on emissions reduction, ZF has come up with its own hybrids, a term the company uses to describe components made of two or more materials.

The company has developed a range of control arms and other chassis components that have plastic or carbon-fibre inserts in metal parts to reduce weight.

“We call these hybrids, meaning plastics and metals, and we are also working with fibre-reinforced composites,” said Mr Paine.

“With plastic, parts are fairly uniform in their properties, but some of the composites have different properties in different directions. This means you may be able to twist it in one direction, but you won’t be able to bend it in another because of the way the carbon-fibre is oriented in the component.”

While weight and cost were still major drivers of development, Mr Paine said ZF had not abandoned the quest for improved dynamic performance of vehicles.

He said the company was running five separate projects on rear-wheel steering, a function that was common on a number of Japanese vehicles in the late 1980s.

“Rear steering is not so new – Nissan GTRs and some of the high-end sportscars have had this over the last couple of decades – but the way it is integrated into the vehicle now is new.”

ZF calls it Active Kinematics Control, which gives a less offensive acronym that GM’s system, called Active Rear Steer.

The system replaces passive tie-rods with variable control arms, giving active control of toe-in and toe-out.

“This product is not obviously a cost-saver or weight-saver, this is for performance,” said Mr Paine.

“The benefits of this product at speed are improved directional stability, better comfort, turning radius improvement, even parking assistance.”

It can also be integrated into the electronic stability control system to provide counter-steering when a car starts sliding.

The company is also working on a new system of damper control that will make damper variation available to cars in the B or small-car segment, the fastest-growing sector in the world market.

The systems currently available, like the magnetorheological dampers seen on HSV models, Cadillacs and the Ferrari 458 Italia, are too expensive to be considered for B-segment cars.

Mr Paine said the problem with small cars was that the difference between having just a driver on board and carrying a full load required major compromises in ride and handling.

“B-segment vehicles are typically a challenge in terms of hydraulically tuning the vehicle because they’re typically short-wheelbase, have a lower kerb weight and they have a higher ratio of payload to kerb weight.

“So, as you load, the compromise between safety and performance and ride comfort becomes greater.

“With this system, as you load the vehicle, you can maintain the level of comfort and also the driving performance that you need.

“From a cost point of view, it fits for the sector of the market and from an installation point of view – because it is quite simple, just two dampers and one sensor – there is minimal wiring, no external sensors.

“It reads the velocity of the vehicle, steering wheel sensor angle and brake pressures to adapt the damping to the load of the vehicle and the actual driving characteristics.”