A new innovation in braking technology is illustrated in a video produced by brake design specialists AirBack Ltd, developers of an innovative drag-free brake design which significantly improves braking efficiency. Reliability is crucial to the success of the braking system, and Lee Products, who supplied their 3-port HDI Solenoid Valve, have played a key role in the 100 per cent reliability being achieved.
Designed as an add-on system, AirBack reduces the friction between brake pads and discs without compromising the performance of the brakes, and consequently improves the overall braking performance. It operates as a retraction and pre-fill system which utilises positive and negative pressure and vacuum to deliver a minute gap (depending on the actual brake calliper design) between the brake and the disc. This is achieved by applying negative pressure to the brake line during acceleration and then supplying positive pressure when applying the brake.
The design incorporates miniature compressors and Lee’s plug-in Lo-Lohm Latching 3-port HDI Solenoid Valve which combine the high-flow capabilities of their Lo-Lohm HDI valve with the power savings of their Latching HDI valve. This 3-port Lo-Lohm latching design excels in applications like the AirBack brake system where high flow capacity, low power and miniature size and 100 per cent reliability are critical. For example, after supplying only a momentary (10ms minimum) voltage pulse, this magnetically latched solenoid valve will hold its flow state until follow-on momentary voltage pulse (with reverse polarity) is applied to switch its flow direction. Aside from the momentary pulse, no power is consumed while maintaining each flow state, an important feature when considering range with electric vehicles.
The AirBack system can be used in conjunction with any type of disc or calliper brake design with equal effect and both designs are failsafe in use with power interruption or removal from mid-cycle, without compromising normal braking performance.
System settings can be optimised for reduced brake pedal travel (safer) or less non-braking drag (economy). During accelerator use, brake drag is removed by adding negative pressure to the MC. With the accelerator linked system, when the accelerator is released the compressor adds positive air pressure to the MC reservoir, pre-filling the fluid system ready for use. When brake actuation occurs the compressor switches off to ensure that the system does not affect any other brake control system during its use. The compressor otherwise continues to be operational because motorsport applications will require its continual use.
With the electronically controlled system, when the accelerator is released, a positive pulse of high-pressure air is added for a few tenths of a second (adjustable) from a small reservoir which causes the calliper pistons to return to their former position and be in firmer contact with their respective brake pad. This means that there are no piston gaps remaining and the brake pedal stroke is much reduced, providing a faster-acting, safer brake system.
The AirBack system is both highly effective and adjustable without detriment to either brake effect or brake feel, as confirmed by extensive road tests. Furthermore, additional testing conducted at elevated temperatures has seen results which far exceeded expectations.
For more information about the plug-in Lo-Lohm Latching 3-port HDI Solenoid Valve and other products visit www.leeproducts.co.uk.