Patent ID: 8620550

Claim:
A method of determining disc brake wear in a final drive arrangement including a spindle having a cylindrical section, a wheel hub mounted for rotation about said spindle, a drive shaft extending axially in said spindle and being coupled for driving said wheel hub, an electric motor coupled to said drive shaft, a disc brake arrangement including: a plurality of rotor discs mounted for rotation with said hub and interleaved with a plurality of stator discs mounted to said spindle thereby forming a disc brake pack, a compression spring arrangement mounted in axial alignment with said disc brake pack and normally being compressed for establishing a preload biasing the rotor and stator discs together so as to establish a park brake engaged condition, and a park brake release hydraulic piston being mounted for powered engagement with said spring arrangement, thereby making it possible to selectively apply a force against the spring arrangement so as to establish a park brake-release condition, said method comprising the following steps: a. establishing said park brake engaged condition in said disc brake pack when the brake pack is new; b. sending an increasing drive torque command to said electric motor for causing an increase drive torque to be delivered to said drive shaft until said drive torque reaches an initial break away torque value corresponding to when said disc brake pack is new and said rotor discs slip relative to said stator discs; c. using said initial break away torque value to compute a corresponding initial preload exerted by said compression spring arrangement when said disc brake pack is new; d. repeating step b during the service life of said disc brake pack with said increasing drive torque being delivered to said shaft until said drive torque reaches a subsequent break away torque value corresponding to when said disc brake pack is worn and said rotor discs slip relative to said stator discs; e. using said subsequent break away torque value to compute a corresponding subsequent preload exerted by said compression spring arrangement when said disc brake pack is worn; and f. consulting a load curve pertaining to said compression spring arrangement containing compression spring preloads plotted against compression spring arrangement heights and noting the difference in the heights respectively corresponding to said initial and subsequent preloads, this height difference being equal to an amount of wear of said disc brake pack.