Brake squeal is an elusive problem which has been the subject of
investigation for many decades, but there is still a lack of
knowledge regarding the excitation mechanisms. New vehicle
solutions, for instance the electrical vehicle, will have a lower
general noise level. Thus, silent brake systems will gain in
importance. To obtain such systems, in-depth investigations of the
brake disc/pad contact are required.
For these investigations a new sensor has been developed. The
guide pins of the caliper are replaced by modified ones which
measure the friction force. Additionally, eddy current sensors are
installed for contact-free measurement of the pad movement.
Furthermore, triaxial acceleration sensors are mounted in the disc
vents. Thus, it is possible to evaluate the operational deflection
shapes of the disc.
Next, an extensive sensibility analysis is performed. Parameters
such as environmental conditions, friction coefficient and many
others are thereby changed. For example shown is the root mean
square (RMS) value of the out-of-plane vibration of one
acceleration sensor mounted in the brake disc vents. Five
revolutions are depicted in the polar axis plot. The sensor passes
the contact area at an angle of ± 18 degrees. The significant
higher value at running-in occurs only when squealing is
present.
The innovative design of the guide pin sensors allows
measurements with a very high resolution. Thus, the friction force
and even the superposed vibration of this force can be measured.
The results lead to further insights regarding brake squeal
triggering mechanisms.
