US 4,363,020 AGranted

Interrogating system for remotely monitoring tire air pressure

AssigneeBorg-Warner Corporation

InventorHarry J. Venema

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Abstract

The air pressure in a tire is monitored by transmitting an electromagnetic interrogating signal (specifically a radio frequency signal) from the vehicle to a passive transponder, affixed to the wheel on which the tire is mounted, in communication with the air pressure within the tire. When the pressure is normal, a semiconductor diode and an antenna in the transponder will be shielded from radiation and therefore no response will be made to the received interrogating signal. On the other hand, abnormal air pressure in the tire causes the antenna to become unshielded and exposed to the interrogating signal radiated from the transmitter, whereupon the diode reacts to the received signal and develops therefrom a response signal which is retransmitted from the antenna and includes, among other signal components, the second harmonic of the interrogating signal. A receiver, tuned to the second harmonic, produces from the response signal an indication (preferably on the vehicle's dashboard) that the sensed tire air pressure is abnormal.

Claims6

Dependent claims

An interrogating system for remotely monitoring the air pressure in a tire mounted on a wheel of a vehicle, comprising:

a passive transponder attached to the wheel and including a semiconductor diode having anode and cathode elements;
a relatively rigid, self-supporting metallic conductor directly connected to and extending from one of the diode's elements to provide an antenna for the diode;
sensing means for sensing the air pressure within the tire;
a movable electromagnetic shield for the antenna;
and means controlled by said sensing means for positioning said shield, with respect to the antenna and in response to the sensed tire air pressure, so that the shield surrounds the antenna when the tire air pressure is within a predetermined desired normal range thereby shielding the antenna from radiation, and so that the antenna extends out of the shield and is exposed to radiation when the sensed tire air pressure is either above or below the desired normal range;
transmitting means in the vehicle for transmitting electromagnetic radiation to said passive transponder to effectively interrogate said transponder, said diode responding to the received radiation, when said antenna is exposed, and generating a response signal which is retransmitted from said antenna;
and receiving means in the vehicle for receiving said response signal and for producing therefrom an output for controlling an indicator to provide an indication to the driver of the vehicle that the tire air pressure is outside of the desired normal range.

4 more elements

Dependencies are inferred from the claim text.