Tire inflation pressure monitoring and location determining method and apparatus

• US 6,463,798 B2
• Filed: 01/17/2001
• Issued: 10/15/2002
• Est. Priority Date: 01/17/2001
• Status: Active Grant

• Current Assignee: Microchip Technology Incorporated
• Original Assignee: Microchip Technology Incorporated
• Inventors: Niekerk, Jan Van, Katz, Paul N., Uradnik, Joseph A., St. Amand, Roger
• Primary Examiner(s): Fuller, Benjamin R.
• Assistant Examiner(s): ALLEN, ANDRE J
• Application Number:
  US09/765,094
• Publication Number:
  US 20020092346A1
• Time in Patent Office: 636 Days
• Field of Search: 731/46, 731/462, 731/463, 731/464, 731/465, 731/468, 340/447, 340/442, 340/445
• US Class Current: 73/146.2
• CPC Class Codes: B60C 23/0416 allocating a corresponding wheel position on vehicle, e.g. front/left or rear/right
• CPC Class Codes: B60C 23/0425 Means comprising permanent magnets, e.g. Hall-effect or Reed-switches

Abstract

A wireless tire inflation pressure measurement device is used to obtain inflation pressure information for a tire of a vehicle and a signal therefrom may be used for determining the location of the tire. An identifier may be associated with the inflation pressure information for each wheel of the vehicle. Tire rotation speed may be determined by amplitude fluctuations of a radio frequency carrier from a radio frequency transmitter rotating with the wheel. Differences in wheel rotation speeds during a turn may be used in determining the location of each tire of the vehicle. An antenna may be placed on each wheel toward the outer perimeter of the wheel and connected to the radio frequency transmitter. A radio frequency identification (RFID) tag and pressure sensor may be used as the wireless tire inflation pressure measurement device and a RFID pickup coil may be provided in each wheel well for pickup of the inflation pressure signals from each RFID tag on a wheel.

Claims

1. A method for determining inflation pressures of tires and locations thereof on wheels of a vehicle, said method comprising the steps of:

providing a wireless inflation pressure measuring device for each wheel of a vehicle, each of the wireless inflation pressure measuring devices has an antenna located toward an outer perimeter of a respective one of the wheels, wherein each of the wireless inflation pressure measuring devices transmits from its respective antenna a radio frequency signal comprising inflation pressure information of a tire mounted on the respective one of the wheels;

providing an inflation pressure monitor having a radio frequency receiver adapted for receiving the radio frequency signals from each of the inflation pressure measuring devices, whereby an amplitude of each of the received radio frequency signals varies periodically with each rotation of the respective one of the wheels;

determining a rotation speed of each of the wheels by detecting the periodic amplitude variations of each of the radio frequency signals as the respective ones of the wheels rotate;

detecting when the vehicle turns and the relative direction thereof,

determining relative wheel rotation speeds; and

assigning a location to each of the wheels based on the relative wheel rotation speeds and vehicle turning direction.

2. The method of claim 1, wherein the step of assigning a location to each of the wheels when the vehicle is making a right turn and going forward, comprises the steps of:

assigning a left front wheel location to the wheel having the fastest relative wheel rotation speed;

assigning a left rear wheel location to the wheel having the second fastest relative wheel rotation speed;

assigning a right front wheel location to the wheel having the third fastest relative wheel rotation speed; and

assigning a right rear wheel location to the wheel having the slowest relative wheel rotation speed.

3. The method of claim 1, wherein the step of assigning a location to each of the wheels when the vehicle is making a left turn and going forward, comprises the steps of:

assigning a right front wheel location to the wheel having the fastest relative wheel rotation speed;

assigning a right rear wheel location to the wheel having the second fastest relative wheel rotation speed;

assigning a left front wheel location to the wheel having the third fastest relative wheel rotation speed; and

assigning a left rear wheel location to the wheel having the slowest relative wheel rotation speed.

4. The method of claim 1, wherein the step of assigning a location to each of the wheels when the vehicle is making a left turn and going backward, comprises the steps of:

assigning a left front wheel location to the wheel having the fastest relative wheel rotation speed;

assigning a left rear wheel location to the wheel having the second fastest relative wheel rotation speed;

assigning a right front wheel location to the wheel having the third fastest relative wheel rotation speed; and

assigning a right rear wheel location to the wheel having the slowest relative wheel rotation speed.

5. The method of claim 1, wherein the step of assigning a location to each of the wheels when the vehicle is making a right turn and going backward, comprises the steps of:

assigning a right front wheel location to the wheel having the fastest relative wheel rotation speed;

assigning a right rear wheel location to the wheel having the second fastest relative wheel rotation speed;

assigning a left front wheel location to the wheel having the third fastest relative wheel rotation speed; and

assigning a left rear wheel location to the wheel having the slowest relative wheel rotation speed.

6. The method of claim 1, further comprising the step of encrypting the tire inflation pressure information.

7. The method of claim 1, further comprising the steps of:

providing a temperature sensor coupled to the wireless inflation pressure measuring device; and

measuring tire temperature with the temperature sensor, wherein the radio frequency signal further comprises tire temperature information.

8. The method of claim 7, further comprising the step of calculating a tire pressure value of each tire of the vehicle based upon the respective tire temperature and pressure.

9. The method of claim 1, wherein the step of determining the relative direction of the vehicle is obtained from the vehicle odometer.

10. The method of claim 1, wherein the step of determining the relative direction of the vehicle is obtained from the vehicle transmission.

11. The method of claim 1, wherein the step of determining the relative direction of the vehicle is obtained from an accelerometer.

12. The method of claim 1, wherein the step of determining when the vehicle turns is obtained from limit switches on the vehicle steering column.

13. The method of claim 1, wherein the step of determining when the vehicle turns is obtained from a gyroscopic device.

14. The method of claim 1, wherein the step of determining when the vehicle turns is obtained from a compass.

15. The method of claim 1, wherein the step of determining when the vehicle turns is obtained from turn signals.

16. The method of claim 1, further comprising the step of transmitting with the radio frequency signal an identifier for each of the wheels.

17. The method of claim 16 further comprising the step of assigning each identifier to a respective wheel location.

18. The method of claim 1, further comprising the step of generating an alert signal when a tire pressure is less than a minimum pressure.

19. The method of claim 1, further comprising the step of generating an alert signal when a tire pressure is greater than a maximum pressure.

20. A method for determining inflation pressures of tires and locations thereof on wheels of a vehicle, said method comprising the steps of:

providing a wireless inflation pressure measuring device for each wheel of a vehicle, each of the wireless inflation pressure measuring devices has an antenna located toward an outer perimeter of a respective one of the wheels, wherein each of the wireless inflation pressure measuring devices transmits from its respective antenna a radio frequency signal comprising inflation pressure information of a tire mounted on the respective one of the wheels;

providing an inflation pressure monitor having a radio frequency receiver adapted for receiving the radio frequency signals from each of the inflation pressure measuring devices, whereby an amplitude of each of the received radio frequency signals varies periodically with each rotation of the respective one of the wheels;

determining rotation speeds of each of the vehicle wheels by detecting the periodic amplitude variations of each of the radio frequency signals as the respective ones of the vehicle wheels rotate;

detecting a position of the vehicle front wheels relative to an axis along the length of the vehicle as viewed facing the front of the vehicle;

determining relative wheel rotation speeds; and

assigning a location to each of the wheels based on the relative wheel rotation speeds and the position of the vehicle front wheels relative to an axis along the length of the vehicle as viewed facing the front of the vehicle.

21. The method of claim 20, wherein the step of assigning a location to each of the wheels when the position of the vehicle front wheels are to the right of the axis as viewed facing the front of the vehicle, comprises the steps of:

assigning a left front wheel location to the wheel having the fastest relative wheel rotation speed;

assigning a left rear wheel location to the wheel having the second fastest relative wheel rotation speed;

assigning a right front wheel location to the wheel having the third fastest relative wheel rotation speed; and

assigning a right rear wheel location to the wheel having the slowest relative wheel rotation speed.

22. The method of claim 20, wherein the step of assigning a location to each of the wheels when the position of the vehicle front wheels are to the left of the axis as viewed facing the front of the vehicle, comprises the steps of:

assigning a right front wheel location to the wheel having the fastest relative wheel rotation speed;

assigning a right rear wheel location to the wheel having the second fastest relative wheel rotation speed;

assigning a left front wheel location to the wheel having the third fastest relative wheel rotation speed; and

assigning a left rear wheel location to the wheel having the slowest relative wheel rotation speed.

23. The method of claim 20, further composing the step of encrypting the inflation pressure information.

24. The method of claim 20, further comprising the steps of:

providing a temperature sensor coupled to the wireless inflation pressure measuring device; and

measuring tire temperature with the temperature sensor, wherein the radio frequency signal further comprises tire temperature information.

25. The method of claim 24, further comprising the step of calculating a tire pressure value of each ire of the vehicle based upon the respective tire temperature and pressure.

26. The method of claim 20, further comprising the step of transmitting with the radio frequency signal an identifier for each of the wheels.

27. The method of claim 26, further comprising the step of assigning each identifier to a respective wheel location.

28. The method of claim 20, further comprising the step of generating an alert signal when a tire pressure is less than a minimum pressure.

29. The method of claim 20, further comprising the step of generating an alert signal when a tire pressure is greater than a maximum pressure.

30. An apparatus for determining inflation pressures of tires and locations thereof on wheels of a vehicle, comprising:

a wireless inflation pressure measuring device for each wheel of a vehicle, each of the wireless inflation pressure measuring devices has an antenna located toward an outer perimeter of a respective one of the wheels, wherein each of the wireless inflation pressure measuring devices transmits from its respective antenna a radio frequency signal comprising inflation pressure information of a tire mounted on the respective one of the wheels;

an inflation pressure monitor having a radio frequency receiver adapted for receiving the radio frequency signals from each of the inflation pressure measuring devices, whereby an amplitude of each of the received radio frequency signals varies periodically with each rotation of the respective one of the vehicle wheels;

a vehicle turn sensor for determining in which direction the vehicle is making a turn;

a vehicle relative direction sensor for determining a relative direction in which the vehicle is moving;

an amplitude demodulator circuit connected to the radio frequency receiver and adapted for detecting the periodic amplitude variations of each of the radio frequency signals as the respective ones of the vehicle wheels rotate, whereby rotation speeds of each of the wheels may be determined; and

a logic circuit connected to the vehicle turn and relative direction sensors and the amplitude demodulator circuit, wherein the logic circuit determines wheel locations based on the relative wheel rotation speeds, the relative direction of the vehicle movement, and the direction the vehicle is making the turn;

wherein when the vehicle is making a right turn and going forward

the left front wheel has the fastest rotation speed,

the left rear wheel has the second fastest rotation speed,

the right front wheel has the third fastest rotation speed, and

the right rear wheel has the slowest rotation speed;

wherein when the vehicle is making a left turn and going forward

the right front wheel has the fastest rotation speed,

the right rear wheel has the second fastest rotation speed,

the left front wheel has the third fastest rotation speed, and

the left rear wheel has the slowest rotation speed;

wherein when the vehicle is making a left turn and going backward;

the left front wheel has the fastest rotation speed,

the left rear wheel has the second fastest rotation speed,

the right front wheel has the third fastest rotation speed, and

the right rear wheel has the slowest rotation speed; and

wherein when the vehicle is making a right turn and going backward

the right front wheel has the fastest rotation speed,

the right rear wheel has the second fastest rotation speed,

the left front wheel has the third fastest rotation speed, and

the left rear wheel has the slowest rotation speed.

31. The apparatus of claim 30, further comprising an encryption circuit for encrypting the tire inflation pressure information.

32. The apparatus of claim 30, further comprising:

a tire temperature sensor coupled to the wireless inflation pressure measuring device for measuring tire temperature, wherein the radio frequency signal contains tire temperature information.

33. The apparatus of claim 30, further comprising an alert signal when a tire pressure is less than a minimum pressure.

34. The apparatus of claim 30, further comprising an alert signal when a tire pressure is greater than a maximum pressure.

35. An apparatus for determining inflation pressures of tires and locations thereof on wheels of a vehicle, comprising:

a wireless inflation pressure measuring device for each wheel of a vehicle, each of the wireless inflation pressure measuring devices has an antenna located toward an outer perimeter of a respective one of the wheels, wherein each of the wireless tire inflation pressure measuring devices transmits from its respective antenna a radio frequency signal comprising inflation pressure information of a tire mounted on the respective one of the wheels;

an inflation pressure monitor having a radio frequency receiver adapted for receiving the radio frequency signals from each of the inflation pressure measuring devices, whereby an amplitude of each of the received radio frequency signals varies periodically with each rotation of the respective one of the vehicle wheels;

a vehicle front wheel position sensor for determining a position of the front wheels relative to an axis along the length of the vehicle as viewed facing the front of the vehicle;

an amplitude demodulator circuit connected to the radio frequency receiver and adapted for detecting the periodic amplitude variations of each of the radio frequency signals as the respective ones of the vehicle wheels rotate, whereby wheel rotation speed of each of the wheels may be determined; and

a logic circuit connected to the vehicle front wheel position sensor and the amplitude demodulator circuit, wherein the logic circuit determines relative wheel rotation speeds and assigns a wheel location to each of the wheels based on the relative wheel rotation speeds and the position of the vehicle front wheels determined by the vehicle front wheel position sensor;

wherein when the position of the vehicle front wheels are to the right of the axis as viewed facing the front of the vehicle

the left front wheel has the fastest rotation speed,

the left rear wheel has the second fastest rotation speed,

the right front wheel has the third fastest rotation speed, and

the right rear wheel has the slowest rotation speed; and

wherein when the position of the vehicle front wheels are to the left of the axis as viewed facing the front of the vehicle

the right front wheel has the fastest rotation speed,

the right rear wheel has the second fastest rotation speed,

the left front wheel has the third fastest rotation speed, and

the left rear wheel has the slowest rotation speed.

36. The apparatus of claim 35, further comprising an encryption circuit for encrypting the tire inflation pressure information.

37. The apparatus of claim 35, further comprising a temperature sensor coupled to the wireless inflation pressure measuring device, wherein the radio frequency signal further comprises tire temperature information.

38. The apparatus of claim 35, further comprising an alert signal when a tire pressure is less than a minimum pressure.

39. The apparatus of claim 35, further comprising an alert signal when a tire pressure is greater than a maximum pressure.