TRW Automotive Holdings is unveiling a new electric drum-in-hat (eDIH) park brake concept claimed to free up valuable interior space, allow for easier installation with fewer components, and integrate with other safety systems to bring the safety and comfort benefits of electric park brake technology to a range of larger vehicles. The system is anticipated to be production-ready by 2011.
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The eDIH system eliminates the need for hand levers or foot pedals in the cabin interior to engage the park brake – a switch activates the system, freeing up valuable interior space and allowing for greater freedom of vehicle cockpit design, along with improved crash characteristics in the pedal area (many US markets still have foot-operated park brakes).
Additionally, the TRW eDIH is a fully electric park brake system, not a cable puller, as is the case with a number of competitive systems. The connections are purely electrical and there are no cables, which add significant cost and complexity during the vehicle manufacturer’s assembly process and can cause reliability issues.
Safety is also significantly enhanced by electric park brake systems. These systems better protect against vehicle roll away because the maximum clamp force is always applied. And in emergency stopping situations, rear wheel anti-lock can be applied to prevent spinouts, something not offered by conventional mechanical park brake systems.
Additional functions such as auto hold and hill hold provide drivers a greater degree of safety, comfort and convenience. When activated, auto hold holds the vehicle in a stationary position until the driver presses the accelerator pedal – making it unnecessary to keep the brake pedal depressed in situations such as traffic jams. Hill hold does not allow the vehicle to roll on a hill either from a parked position or in situations such as traffic lights.
The eDIH system is said to be ideal for larger vehicles which require a greater clamp force for parking than is currently available from electric park brake calliper systems. This vehicle segment already uses a high percentage of drum-in-hat style rear brakes that can easily be adapted to the eDIH system which can effectively park vehicles up to the 19,000 lb GVW range.
In addition, a number of high-end performance vehicle manufacturers prefer drum-in-hat rear brake solutions and are currently considering the eDIH system as an alternative to their current park brake solution. A major consideration is the ability to tune the service brakes separately from the park brake with no compromise in the performance of either system.
