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11/02/2020 - 13/02/2020

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Solenoid valve key to brake innovation

A new innovation in braking technology comes from AirBack, the developer of an innovative, drag-free design which significantly improves braking efficiency. Reliability is crucial to the success of the braking system and miniature component specialist Lee Products has play a key role in enabling 100% reliability to be achieved, thanks to its 3-port HDI solenoid valved.

Designed as an add-on system, the AirBack technology 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 the Lo-Lohm HDI valve with the power savings of the company’s 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% 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 appli-cations 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.

Lee Products