Method of monitoring pressure in a pneumatic tire

• US 6,658,928 B1
• Filed: 06/03/2002
• Issued: 12/09/2003
• Est. Priority Date: 12/14/1999
• Status: Expired due to Fees

• Current Assignee: Goodyear Tire & Rubber Company
• Original Assignee: Goodyear Tire & Rubber Company
• Inventors: Pollack, Richard Stephen, Yones, Dale Lee, Brown, Robert Walter
• Primary Examiner(s): Oen, William
• Application Number:
  US10/148,782
• Time in Patent Office: 554 Days
• Field of Search: 29/254.1, 29/254.2, 296/211, 737/06, 737/44, 737/45, 737/15--27, 737/56, 731/46, 731/462, 731/463, 731/465, 731/468, 737/08, 340/442, 340/443, 340/444, 340/446, 340/447, 340/449
• US Class Current: 73/146
• CPC Class Codes: B60C 23/0408 transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver
• CPC Class Codes: B60C 23/0433 Radio signals

Abstract

A method for monitoring pressure with a transponder (200, 604) capable of measuring temperature data (N_T) and pressure data (N_P) in an object (e.g., a tire, (104)) and transmitting a data stream (FIG. 3C) to an external reader/interrogator (106, 400). The transponder includes a memory (238) for storing measurements, calibration data (662), transponder ID number and the like. Since the transponder combines temperature and pressure information in the “pressure” data, the ratio N_T/N_P is a direct indicator of pressure-only, and is also relatively insensitive to transponder power variations. The calibration method employs a calibration chamber (602) containing reference pressure (614) and temperature (612) sensors. The transducer to be calibrated is placed in the chamber and exposed (652) to a number of predetermined temperatures and pressures (as measured by the reference sensors) at a number of calibration points. At each calibration point, a temperature reading (N_T) and a pressure reading (N_P) sensed by the transponder are recorded along with the reference temperature and pressure. From these readings and reference measurements the calibration constants (N_T25, m_T, N_T/N_P700.25, m_p) are calculated (658).

Claims

1. Method of monitoring pressure in a pneumatic tire, comprising:

sensing ambient temperature within the tire, and generating a first reading which is a linear function of ambient temperature only;

sensing ambient pressure within the pneumatic tire, and generating a second reading which is a hybrid, non-linear function of both ambient pressure and ambient temperature;

characterized by;

generating a reading which is a linear function of only the ambient pressure by dividing the first reading by the second reading.

2. Method, according to claim 1, characterized by:

transmitting the first and second readings from a transponder within the tire to a reader/interrogator external to the tire.

3. Method, according to claim 2, characterized by:

calculating at least one calibration constant for use in an equation which characterizes pressure responsiveness of the transponder;

wherein

the at least one calibration constant is based on a ratio of a calibration temperature reading which is a function of ambient temperature sensed by the transponder, to a calibration pressure reading which is a function of both ambient pressure and ambient temperature sensed by the transponder.

4. Method, according to claim 3, characterized by:

storing the at least one calibration constant in the transponder.

5. Method, according to claim 4, characterized by:

subsequently providing from the transponder the at least one calibration constant along with a real-time ambient pressure reading.

6. Method, according to claim 3, characterized in that:

the equation is expressed in the form of a line equation;

the line equation is in a point-slope form characterized by a defining point and a slope which are the calibration constants; and

the calibration constants comprise;

the defining point of a pressure response line equation; and

the slope of the pressure response line equation.

7. Method of measuring pressure within a pneumatic tire comprising:

in a transponder, storing calibration data related to a ratioed response of a first reading divided by a second reading, as determined during a calibration of the transponder;

characterized in that;

the first reading is a linear function of ambient temperature within the tire only, and the second reading is a hybrid, non-linear function of both ambient pressure and ambient temperature within the tire.

8. Method, according to claim 7, characterized by:

providing a radio frequency transponder within the tire, said RF transponder including a temperature sensor and a pressure sensor; and

transmitting the first reading and the second reading.

9. Method, according to claim 8, further characterized by:

dividing the first reading by the second reading.

10. Method, according to claim 7, characterized by:

transmitting the calibration data related to a ratioed response of the first reading divided by the second reading, as determined during a calibration of the transponder and which is stored in the transponder.

11. Method, according to claim 8, further characterized by:

transmitting the calibration data related to a ratioed response of the first reading divided by the second reading, as determined during a calibration of the transponder and which is stored in the transponder.