A Case Study of Reaction Time Reduction of Vehicle Brake System

There has to be a good co-relation/relationship between the pedal effort applied, pedal travel, deceleration level achieved and stopping distance for "good brake feel". Brake feel also depend upon the time lag between the force applied on brake pedal and the response of braking system. Hence "brake feel" can be improved by reducing the response time of the brake system. Many vehicles are having "poor brake feel" complaints, pertaining to the above mentioned reasons. This paper relates to an improved brake system for automobile in which reduction in reaction time was done by artificially increasing differential pressure head across vacuum booster diaphragm. Brake booster is given an input of compressed air to the valve body during actuation, thereby increasing the differential pressure across the diaphragm. The compressed air is bled from turbocharger-intercooler of the vehicle which is stored in a reservoir, with one way valve, while cruising. However, same compressed air is utilized by the brake booster during brake application. Additionally, the compressed air reservoir acts as a cooler for stored air. By virtue of this mechanism, the overall reaction time of the brake booster reduces significantly for the same testing conditions. The whole circuit is provided with a pressure switch which detects any failure in the compressed air circuit and opens it up to the atmosphere, making booster work to its conventional capability. Using this concept on vehicle, marked reduction in stopping distance with improvement in "brake feel" was observed.