Putting the brakes on

Citation

(2004), "Putting the brakes on", International Journal of Productivity and Performance Management, Vol. 53 No. 1. https://doi.org/10.1108/ijppm.2004.07953aaf.005

Putting the brakes on

Putting the brakes on

The Delphi Corporation has developed a revolutionary new technology that it believes will help solve many of the challenges currently faced by braking engineers. Based on a twin floating disc architecture with a single piston, the Delphi Maximum Torque Brake provides a high specific torque capability, with substantial improvements in thermal management that can lead to benefits in weight, packaging and NVH (noise vibration and harshness/refinement).

The traditional solution to coping with increasing vehicle weight and performance is to make bigger and better conventional braking systems, including larger discs (often forcing larger wheels) and advanced materials. However, this is a costly solution that often has a negative impact in many other areas of vehicle engineering.

The maximum torque brake (MTB) solves these problems and is the first significant change in base braking technology since the first volume application of disc brakes more than 50 years ago.

The MTB uses two discs floating on the outside diameter of the hub. A hydraulically actuated piston applies braking force via pads that operate on the outside and inside faces of each disc, providing four friction surfaces. The new technology can therefore provide up to 1.7 times the torque output of a conventional single disc system of the same effective diameter, or similar torque from a reduced diameter. Wear and serviceability are equivalent to today's traditional product and the floating disc architecture eliminates problems with lateral run-out.

The twin disc design also provides four cooling surfaces, without the need for vanes or cooling channels, substantially reducing thermal stress on the brake and hub-mounted components.

This improved thermal management provides engineers with many options for enhancing other aspects of the braking system.

By greatly increasing opportunities to optimise the combination of disc size, pedal travel, booster size and friction material, MTB allows the feel, cost and performance of the system to be precisely matched to market requirements. For example, with four pad surfaces, MTB requires approximately half the pressure applied of a conventional disc brake. This could be utilised to significantly reduce the vacuum booster or to reduce the pedal effort and travel. A reduced booster could reduce weight by up to 1kg and provide more premium under-bonnet (hood) space to improve packaging flexibility. Alternatively, disc diameter could be reduced by up to 25mm, allowing smaller wheels (which can generate a substantial cost saving), higher aspect ratio tyres (important for off-road vehicles) and a significant reduction in unsprung weight.

The superior thermal management of MTB, and its minimal generation of disc thickness variation (DTV, caused by the discs wearing unevenly) also provide excellent NVH performance. This helps to solve the potentially significant problem of noise-related warranty claims, which surveys show is a major consumer issue in the USA and the cause of significant warranty costs. Because the discs are floating on the hub, their contact with the pads is always even and MTB does not have the wear issues or the tolerance stack-up that can cause judder and squeal in conventional systems.

Other benefits of the system include reduced brake fade and, due to the reduced pressure required, shorter stopping distances in the event of a vacuum failure.

Delphi's claims for the performance of the system are borne-out by testing to the independent AMS (Auto Motor und Sport) standards using a BMW X5 fitted with the system. In the 12-stop test, which is increasingly seen as a European standard, the vehicle demonstrated an exceptional "no fade" performance.

The system has completed more than 1.5 million test kilometres in 20 vehicles to help ensure that it will continue to perform to specification in any terrain or usage pattern, throughout a vehicle's life. Two fully engineered implementations have been shown to vehicle manufacturers: one fitted to a B-segment small European car, the other on a large high- performance SUV. The former has the piston integrated within the suspension knuckle while the latter demonstrates a stand-alone piston architecture that could be implemented as part of a mid-life model upgrade.

MTB can be manufactured using existing materials and processes and Delphi has taken a hard look at where cost and complexity can be further reduced. An example is the wheel hub on which the discs are mounted, which is neatly designed as a one-piece unit into which the wheel bearing can be press fitted. Future developments will introduce additional lightweight materials, leading to further weight savings.

For more information about Delphi, visit www.delphi.com