A DEEPER UNDERSTANDING OF THE MECHANISMS BEHIND BRAKE PULSATION

摘要

Pulsation is often written about, often talked about and frequently found on vehicles. In the last few years, vehicle manufacturers have attempted to cure pulsation by reducing lateral runout (LRO) specifications on bearings, rotors and corners; they have reduced caliper slide forces; they have greatly increased the size of brakes while simultaneously reducing the coefficients of friction in linings to reduce wear rates. These and other changes have not worked entirely as planned and, in fact, have added a tremendous cost. One of the reasons for the lack of success has been the lack of a clear understanding of the mechanism behind pulsation. Using a cam and follower analogy, the author was able to derive a mathematical expression for pulsation. The rotor is analogous to the cam and the piston is analogous to the follower. Also, Harmonic Lateral Runout (HLRO) is defined. By integrating the two methods the author suggests that in many cases, only certain harmonics of LRO need to be controlled to prevent pulsation. With the mathematical expression, pulsation can be studied before making expensive changes.