DYNAMIC MEASUREMENT OF THE FORCES IN THE FRICTION ...

All these methods have, beside their limited accuracy (e.g. Tekscan fault indication >10%
(18)) the disadvantage that they can be only applied by a stationary brake disc. According to
Fig. 3, however, it appears that during the braking process other distributions lead to the
clamping force by the support of the tangential force. By these methods the effect of the
caliper expansion can be primarily examined, which, however, will not behave in the same
way during the braking process as one by a stationary disc. Measuring methods for
determination of the clamping force during a braking process do not exist until now.
The focus of this work lays on the determination of the point of application of the clamping
force of the finger and piston side during the braking process correspondingly to Fig. 8.
FC,piston
Fig. 8: Shifting of the point of application of the clamping force
DESIGN OF THE MEASURING SYSTEM
In order to measure the desired forces, an analysis of the force lines in a disc brake is
necessary. For this analysis and the following measurements a two-piston finger framework
caliper of the company Continental Teves (type 2 FNR-Al42, fig. 1) was chosen. This caliper
is currently used in many upper class vehicles.
In Fig.9 the force lines of the clamping and the tangential force are qualitatively presented.
force lines
p
FT,piston
brake disc
FT,finger
FC,finger
f
Fig. 9: Force Lines in a caliper
- 5 -
FC,piston
rC,p
rC,f
FC,finger
caliper