Resistive ceramic bushings for brake lining wear sensor

摘要

A brake lining wear sensor includes a metal contact secured to a grounded brake lining support plate through a semiconductive ceramic bushing containing silicon carbide and silicon nitride which establishes an electrical resistance between the contact and the support plate so that the contact has a resistance to ground when the brake lining is not worn, but when the brake lining is worn and the contact touches a grounded brake rotor or drum, a short to ground occurs. The sensor is coupled by a lead wire to an indicator circuit which senses the resistance value in the circuit path to ground to determine whether the contact is connected to the indicator circuit and whether it is electrically grounded to the rotor. An indicator lamp comprises a tri-color LED to emit different colors signifying a normal condition, an open circuit, or a worn brake lining condition.