Pneumatic tire for vehicles, has electrical or electronic sensor in tread to indicate tread height and give warning of unacceptable wear

摘要

Tire tread incorporates an inductive component (1) in a resonant circuit with a condenser (4). The condenser plates are at right angles to the surface of the tread (3) and have wear properties similar to the tread rubber. As the tread wears, the capacitance value reduces while the remainder of the circuit is unaffected so that the resonant frequency decreases and provides a measure of wear. An independent claim is also included for three alternative methods of monitoring the tread height by using a stationary sender to excite the resonant circuit in the tread at a frequency near the resonant frequency. A stationary receiver, preferably in the same housing, can then measure (a) the damping in the resonant circuit, or (b) the current amplitude in the circuit, or (c) the natural frequency of the circuit. Alternative (c) uses a calibration curve in the computation, using several excitation frequencies. Alternative (b) is simpler but requires accurate calibration. Alternative (a) requires a close proximity between transmitter and sensor for sufficient accuracy. Methods are provided to eliminate errors due to wet road surfaces.