Tire pressure sensor and air supply to maintain desired tire pressure

Tire pressure control apparatus for regulating tire pressure on a rotating wheel, the apparatus comprising:

• housing means disposed to be attached to the wheel and having a chamber therein connected to the tire and having an aperture;
• magnet means disposed to slide within the aperture;
• resilient bellows means attached about one end thereof to the magnet means and about the other end thereof to the housing means to form a wall of the chamber exposed on one side thereof to air pressure in the tire and on the other side thereof to atmospheric pressure for positioning the magnet means within the aperture in response to air pressure in the tire;
• first valve means disposed in said housing means to be actuated by the magnet means at a selected position thereof;
• a source of air under pressure carried by the wheel and connected to the first valve means to supply air under pressure to the chamber in response to actuation of the first valve means by the magnet means;
• transducer means for mounting in fixed location relative to the rotating wheel in close proximity to the housing means rotating therewith, said transducer means producing an output indicative of the position of the magnet means in the aperture in response to the rotation thereof relative to the transducer means;
• and
• control means coupled to the transducer means for producing a control signal in response to the output attaining a selected value, said control means supplying the control signal to the transducer means for positioning the magnet means to said selected position for actuating the first valve means to supply air under pressure to the tire.