Pneumatic tire having transponder and method of measuring pressure within a pneumatic tire

• US 6,543,279 B1
• Filed: 08/18/2000
• Issued: 04/08/2003
• Est. Priority Date: 04/14/1998
• Status: Expired due to Fees

• Current Assignee: Goodyear Tire & Rubber Company
• Original Assignee: Goodyear Tire & Rubber Company
• Inventors: Black, Donald Lee, Pollack, Richard Stephen, Yones, Dale Lee, Brown, Robert Walter
• Primary Examiner(s): MCCALL, ERIC SCOTT
• Application Number:
  US09/622,688
• Time in Patent Office: 963 Days
• Field of Search: 731/464, 731/465, 731/463, 731/46, 731/462, 731/468, 340/442-448
• US Class Current: 73/146.5
• CPC Class Codes: B60C 23/0408 transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver

Abstract

A transponder measures temperatures and pressure within a pneumatic tire. A temperature count is transmitted, which is a function of temperature. A pressure count is transmitted, which is a function of both temperature and pressure. The pressure is determined by dividing the temperature count by the pressure count. Within the transponder, a timing generator generates a first timing window during which temperature is measured and a second timing window during which pressure is measured; a temperature register captures first data indicative of the temperature within the tire; a pressure register captures second data indicative of the pressure within the tire; and a modulator circuit impresses the first data as a first portion of a data stream on a signal output by the transponder, and impresses the second data as a second portion of the data stream on the signal output by the transponder. An oscillator outputs a signal having a first frequency which is indicative of the temperature within the tire during the first timing window, and having a second frequency which is indicative of the pressure within the tire during the second timing window. A register/counter circuit counts the oscillations of the oscillator signal during the first timing window to capture the first data in the first register, and counts the oscillations of the oscillator signal during the second timing window to capture the second data in the second register.

Claims

1. In combination with a pneumatic tire, a passive transponder disposed within the pneumatic tire, the transponder including:

an antenna;

a rectifier circuit connected to the antenna to provide electrical power from an RF signal received by the antenna to other components of the transponder;

a modulator circuit, operatively connected to the antenna to form an RF signal output for the transponder by modulation of the RF signal received by the antenna;

a temperature sensor for sensing temperature within the tire;

a pressure sensor for sensing pressure within the tire;

a timing generator for generating a first timing window during which temperature is measured and a second timing window during which pressure is measured;

a temperature register for capturing first data indicative of the temperature within the tire;

a pressure register for capturing second data indicative of the pressure within the tire; and

the modulator circuit impressing the first data as a first portion of a data stream on a signal output by the transponder, and impressing the second data as a second portion of the data stream on the signal output by the transponder;

characterized by;

an oscillator outputting a signal having a first frequency which is indicative of the temperature within the tire during the first timing window, and having a second frequency which is indicative of the pressure within the tire during the second timing window; and

a register/counter circuit which counts the oscillations of the oscillator signal during the first timing window to capture the first data in the first register, and which counts the oscillations of the oscillator signal during the second timing window to capture the second data in the second register.

2. In combination with a pneumatic tire, a passive transponder according to claim 1, wherein:

the first data is a function of temperature; and

the second data is a function of both temperature and pressure;

characterized in that;

a ratio of the first data divided by the second data is a function of pressure only.

3. In combination with a pneumatic tire, a passive transponder according to claim 1, characterized in that:

the first frequency and the second frequency are both proportional to the temperature.

4. In combination with a pneumatic tire, a passive transponder, according to claim 1, characterized in that:

the signal output by the transponder is an RF signal and is transmitted by the antenna.

5. In combination with a pneumatic tire, a passive transponder, according to claim 1, characterized in that:

the antenna is selected from the group consisting of coil, loop and dipole.

6. In combination with a pneumatic tire, a passive transponder according to claim 1, characterized by:

an excessive temperature sensor providing third data indicative of an excessively high temperature condition;

wherein;

the modulator circuit impresses the third data on a third portion of the data stream on the signal output by the transponder.

7. In combination with a pneumatic tire, a passive transponder, according to claim 1, characterized in that:

the time period of the first timing window and the time period of the second timing window are adjusted to different durations, thereby adjusting the resolution of the counts of one of the first and second data relative to the resolution of the counts of the other one of the first and second data.

8. In combination with a pneumatic tire, a passive transponder according to claim 1, characterized in that:

a base-emitter voltage-to-current converter circuit includes the temperature sensor and outputs a current to the oscillator, wherein the current is proportional to temperature; and

a frequency of the oscillator output signal is proportional to the current output by the temperature sensor.

9. In combination with a pneumatic tire, a passive transponder according to claim 1, characterized by:

a current-scaling circuit, disposed between the temperature sensor and the oscillator, for scaling a current output by the temperature sensor by a factor of 1/N, and providing a scaled current to the oscillator.

10. In combination with a pneumatic tire, a passive transponder according to claim 9, wherein the current-scaling circuit is characterized by:

a current-mirror including two transistors having dissimilar areas, a one of the two transistors being “

N”

times larger in area than an other of the two transistors.

11. In combination with a pneumatic tire, a passive transponder according to claim 1, wherein the oscillator is characterized by

a relaxation oscillator having a first phase path and a second phase path.

12. In combination with a pneumatic tire, a passive transponder according to claim 11, further characterized by:

a first fixed-value capacitor disposed in the first phase path; and

a second fixed-value capacitor disposed in the second phase path.

13. In combination with a pneumatic tire, a passive transponder according to claim 11, further characterized in that:

the relaxation oscillator has a 50% duty cycle.

14. In combination with a pneumatic tire, a passive transponder according to claim 11, further characterized in that:

the pressure sensor is a variable-value capacitor which is switched into a one of the first and second phase paths, across a respective one of the first and second fixed value capacitors, during the second timing window.

15. In combination with a pneumatic tire, a passive transponder according to claim 1, characterized in that:

the temperature sensor, the oscillator, the timing generator, the temperature register, the pressure register, and the modulator circuit, are resident on a single integrated circuit chip.

16. In combination with a pneumatic tire, a passive transponder according to claim 15, characterized in that:

the pressure sensor is external to the IC chip.