Double torque

A braking system that will be fitted to new cars by 2006 will offer better performance and eliminate some of the wear problems associated with conventional designs, its developer Delphi claimed this week.

The automotive systems specialist has developed a technology based on twin floating brake discs, which it claims will provide greater torque, lower braking temperatures and eliminate the pedal vibration caused by uneven disc wear.

Delphi has been developing the technology, called the Advanced Disc System (ADS) for a number of years, said Yvonne Manning, programme manager for ADS.

Secret project

‘We have kept the technology secret as it is a hydraulic braking system, and we know our competitors have been trying to develop something similar for a number of years and failed.’

The ADS device consists of two discs ‘floating’ on the outside of the brake hub – unlike conventional systems where a single disc is fixed permanently to the hub.

This conventional design can lead to lateral run-out problems, a side-to-side motion caused when the disc is not fitted perfectly to the hub before it is fixed in position. This erratic motion means the disc hits the pads at certain spots even when the brakes are not being applied, leading to uneven wear.

Delphi has developed a gyroscopic effect, without using sensors or electronics, to keep the discs running smoothly in their grooves on either side of the hub. ‘We have two discs, which fully float on the hub. So like a gyroscope they can align themselves to the position of the hub throughout their lifetime.’

A hydraulically-operated piston applies braking force via pads on the outside and inside faces of both discs, providing four braking surfaces. As a result, ADS also has 1.7 times the torque of a single disc braking system, meaning it requires around half the apply pressure of a conventional disc brake.

This could allow manufacturers to reduce the size, and thus decrease the weight, of the brake disc. But most car makers are likely to be interested in using the increased torque to shorten the pedal feel/travel experienced by the driver when applying the brakes, said Manning.

‘A BMW X5 would no longer have long, soft, spongy brakes, all of a sudden it would feel like a Ford Fiesta.’

As the system has four surfaces with which to dissipate the heat produced during braking, it means the discs can be smaller. This will enable manufacturers to fit smaller wheels, which would be particularly beneficial to makers of small volume cars as it could lead to significant cost savings, she said. ‘They [the car makers] would be able to get a 14 in wheel down to 13 in, which has economic value and means they can play games on pricing.’

Conservative launch

Delphi is planning a relatively conservative launch of the system on several thousand vehicles in 2006 to prove the technology in the market, before ramping up production to much higher volumes.

Although Manning would not reveal which car makers the company is working with, she said they were in discussions about fitting the technology to a small car, a sports utility vehicle, a high-performance sports car, and a mid-range vehicle.

On the web