A Study on Trigger of Small Friction Noise in Disc Brake Squeal 2018-01-1872
It is well known that brake squeal is caused by flutter of
dynamic unstable system under small disturbance. Therefore the
research of small disturbance is very important technical issues
for disc brake squeal reduction. The experimental set-up for basic
research was developed based on the actual disc brake squeal
vibration mode in experiment and its theoretical analysis, which
replaces cantilever type pad-caliper from actual caliper and pads.
Disc brake squeal depends on the natural frequency of cantilever
type pad-caliper, which were caused at 2.7kHz, 2.0kHz and 5.3kHz
for each cantilever length L=40mm, 50mm and 80mm in each friction
test. In friction test L=40mm and 50mm, cantilever type pad-caliper
vibrates with the 1st order bending vibration mode and disc vibrate
with the 1st or 2nd order bending vibration mode. In friction test
L=80mm, cantilever type pad-caliper vibrates with the 2nd order
bending vibration mode and disc vibrates with the 4th order bending
vibration mode. Theoretical analysis for these experimental results
are shown in this research. The vibration modes in each brake
squeal are not same, then each friction point behaviour per 1 cycle
during brake squeal generation is almost same oval shape not line.
These simulation results mean the same mechanisms of dynamic energy
increase. On the other hand, small friction noise was caused around
1 kHz in this friction test of cantilever length L=80mm, then its
cantilever type pad-type caliper vibrates with the 1st order
bending vibration mode but disc vibration amplitude is so small.
This friction noise 1 kHz is considered to be self-excited
vibration in friction coefficient dm/dv<0, which depends on not
only friction characteristics but also the natural frequencies of
cantilever type pad-caliper and disc. Brake squeal is considered to
be triggered by small friction noise. Accordingly, brake squeal can
be reduced by reduction of small friction noise.
Masaaki Nishiwaki, Yukio Yamamoto
Kanagawa Institute of Technology, Newton Works Corp.