Tire pressure indicator including pressure gauges that have a self-generating power capability

Claim 1

A tire pressure indicator for the pneumatic tires of a vehicle, said tire pressure indicator comprising a plurality of pressure gauges, at least one receiver circuit adapted to be installed in the vehicle to receive output signal from said pressure gauges wirelessly, and a controller, said pressure gauges each comprising a casing, a power supplying device, a pressure sensing unit, and a transmitter circuit, wherein: said power supplying device comprising a self-generating voltage unit, said self-generating voltage unit comprising a spring element having a first end secured to said casing and a second end, a weight securely mounted on the second end of said spring element, and a piezoelectric unit securely mounted on said spring element, said spring element being vibrated upon motion of the respective pneumatic tire, thereby causing said piezoelectric unit to generate a voltage output to said pressure sensing unit and said transmitter circuit; said pressure sensing unit comprising a capacitor means, said capacitor means comprising a motion member, a conductive member, and a converting circuit, said motion member being made of electrically conductive material and spaced from said conductive member at a distance, said distance being changed subject to the air pressure of respective pneumatic tire, thereby causing the capacity of said capacitor means to be changed relatively, said converting circuit comprising an oscillator connected to said capacitor means such that said converting circuit detects the number of RC oscillating waves from said oscillator and converts detected signal into a first signal indication of the pressure of the respective pneumatic tire; said transmitter circuit receiving said first signal from said pressure sensing unit and outputing a second signal by radio; said receiver circuit outputing a third signal upon receipt of said second signal; said controller comprising a control circuit and an indicator circuit, said control circuit receiving said third signal from said pressure gauges and processing said third signal into an indication signal through a processor thereof for output through said indicator circuit.