Electronic stroke sensor for air disc brake

A method of monitoring the stroke of a brake actuator of an air disk braking system having a pneumatic chamber actuating a pushrod for exerting force on a lever arm of the air disk brake, said pushrod including a pushrod shaft and a contact member disposed in a telescoping relationship with said pushrod shaft, said method comprising the steps of:

• detecting pressure generated by actuating a brake pedal;
• detecting a length of extension of said pushrod by sensing variation of a sensible medium disposed upon said pushrod thereby distinguishing between a normal and an overstroke condition of said pushrod;
• and
• detecting contact between said pushrod and said lever arm of said air disk brake by determining the length of telescopic extension of said contact member relative to said pushrod shaft by sensing variation of said sensible medium thereby identifying a hanging brake condition by identifying if separation has occurred between said contact member and said lever arm when the length of telescopic extension of said contact member is inconsistent with the pressure generated by actuating said brake pedal.

A vehicle brake monitor assembly for an air brake, comprising:

• a brake actuator having a pushrod slidably extending from a chamber of said brake actuator, said pushrod actuating a lever arm of the air brake thereby moving the vehicle brake into an actuated position when said pushrod is disposed in an extended position and allowing the brake to move into a retracted position when said pushrod is disposed in a retracted position;
• said pushrod comprising a pushrod shaft and a contact member having a telescoping bias from said pushrod shaft for releasably contacting the lever arm of the air brake;
• a pressures sensor for detecting pressure from actuating a brake pedal;
• an optical sensor transmitting a light signal toward said contact member and detecting a variation in an amount of reflectivity from said contact member with said controller determining which of a plurality of conditions of said brake actuator is present including an overstroke and a hanging brake condition, which is dependent upon telescoping position of said contact member, and the pressure is inconsistent with the amount of reflectivity detected from said contact member.