Tire sensor and method

• US 6,637,276 B2
• Filed: 04/27/2001
• Issued: 10/28/2003
• Est. Priority Date: 11/28/2000
• Status: Expired due to Term

• Current Assignee: Michelin Recherche et Technique SA (Compagnie Generale DES Etablissements Michelin SCA)
• Original Assignee: Michelin Recherche et Technique SA (Compagnie Generale DES Etablissements Michelin SCA)
• Inventors: Adderton, Dennis M., Minne, Stephen C.
• Primary Examiner(s): Lefkowitz, Edward
• Assistant Examiner(s): Dickens, Charlene
• Application Number:
  US09/844,193
• Publication Number:
  US 20020092364A1
• Time in Patent Office: 914 Days
• Field of Search: 738/620.41, 738/620.43, 738/620.44, 738/620.45, 738/623.38, 738/624.24, 738/626.27
• US Class Current: 73/862.41
• CPC Class Codes: B60C 11/00 Tyre tread bands; Tread patterns; Anti-skid inserts
• CPC Class Codes: B60C 2019/004 Tyre sensors other than for detecting tyre pressure
• CPC Class Codes: G01L 5/162 of piezoresistors
• CPC Class Codes: G01L 5/1627 of strain gauges using piezoresistors G01L5/162

Abstract

A tire sensor assembly that is embedded in an elastomeric tire at a particular radial depth inwardly from a contact patch of the tire includes a flexible generally pyramid-shaped body and a pair of first strain sensors disposed on first opposed faces of the pyramid-shaped body, the first strain sensors detecting a force in a first direction. In addition, the assembly includes a pair of second strain sensors disposed on second opposed faces of the pyramid-shaped body, the second strain sensors detecting a force in a second direction. Moreover, each face of the first and second opposed faces is non-planar. Preferably, the first and second opposed faces of the pyramid-shaped body are curved and generally symmetrical about an axis extending longitudinally through the apex of the body so as to allow adjustment of the sensitivity of the sensor assembly generally independent of the radial depth. In one example, the first and second opposed faces are concave such that the sensor assembly is more sensitive to a tensile strain and less sensitive to a shear strain.

Claims

1. A plurality of sensor assemblies embedded in an elastomeric material of a tire, each said sensor assembly comprising:

a pair of first strain sensors disposed on first opposed faces of a flexible pyramid-shaped body, said first strain sensors detecting a force in a first direction, wherein said first strain sensors generate corresponding output signals in response to strain in the first sensors generated by the force in the first direction, and wherein the force in the first direction is generally equal to the difference between the output signals of said first strain sensors;

a pair of second strain sensors disposed on second opposed faces of said body, said second opposed faces adjacent to said first opposed faces, and said second strain sensors detecting a force in a second direction orthogonal to said first direction, wherein said second strain sensors generate corresponding output signals in response to strain in the second sensors generated by the force in the second direction, and wherein the force in the second direction is generally equal to the difference between the output signals of said second strain sensors;

wherein a sum of the first output signals and the second output signals is indicative of a force in a third direction, and wherein the plurality of sensor assemblies are embedded in a tire in mutually spaced relationship.

2. The sensor assembly of claim 1, further including a bus to communicate signals generated by the plurality of sensor assemblies.

3. The sensor assembly of claim 2, wherein said bus is a five-wire bus.

4. The sensor assembly of claim 1, wherein a contact region is defined at a position where the tire contacts a surface, and wherein the plurality of sensor assemblies are mutually spaced about a circumference of the tire so that each sensor assembly of the plurality of sensor assemblies passes the contact region at a different time.

5. A process of producing a sensor assembly embedded in an elastomeric material of a tire, the process comprising:

providing a pyramid-shaped body and first and second pairs of strain sensors;

disposing the first pair on first opposed faces of the pyramid-shaped body;

disposing the second pair on second opposed faces of the pyramid-shaped body; and

,

placing the sensor assembly having the pyramid-shaped body with sensors on the first and second opposed faces in an uncured elastomeric material of a tire.

6. The process of claim 5, further comprising the step of embedding a plurality of said sensor assemblies around a circumference of the tire.

7. The process of claim 6, wherein the sensor assemblies are positioned in mutually spaced relationship.

8. The process of claim 7, wherein the sensor assemblies are positioned such that only one of the sensor assemblies passes through the contact patch of the tire during operation at a particular time.

9. The process of claim 6, further comprising the step of providing a sensing system including a sensor bus.

10. The process of claim 9, wherein the sensor bus includes a plurality of conductors, each of the conductors corresponding to one strain axis to be monitored.

11. The process of claim 9, wherein three orthogonal strain axes are monitored.

12. The process of claim 9, wherein the outputs of the sensor bus are electrically coupled to a transmitter.

13. The process of claim 9, wherein the bus is a passive sensor bus.

14. The process of claim 9, wherein the sensing system connects the strain gauges of the sensor assemblies in parallel.

15. A tire sensor assembly embedded in an elastomeric tire at a particular radial depth inward from a road contacting surface of the tire, said sensor assembly comprising:

a flexible generally pyramid-shaped body;

a pair of first strain sensors disposed on first opposed faces of said pyramid-shaped body, said first strain sensors detecting a force in a first direction; and

wherein each face of said first opposed faces is non-planar.

16. The sensor assembly of claim 15, wherein said first opposed faces are curved.

17. The sensor assembly of claim 15, further comprising:

a pair of second strain sensors disposed on second opposed faces of said pyramid-shaped body, said second strain sensors detecting a force in a second direction, wherein each face of said second opposed faces is non-planar.

18. The sensor assembly of claim 17, wherein said first strain sensors generate corresponding output signals in response to strain in said first strain sensors generated by the force in the first direction, and wherein the force in the first direction is generally equal to the difference between the output signals of said first strain sensors, and wherein said second strain sensors generate corresponding output signals in response to strain in said second strain sensors generated by the force in the second direction, and wherein the force in the second direction is generally equal to the difference between the output signals of said second strain sensors.

19. The sensor assembly of claim 17, wherein said first and second opposed faces are generally symmetrical about an axis extending longitudinally through the apex of said pyramid-shaped body.

20. The sensor assembly of claim 17, wherein said first and second opposed faces are curved and which curvature determines the sensitivity of the sensor assembly generally independent of the radial depth.

21. The sensor assembly of claim 17, wherein the sensor assembly is more sensitive to a tensile strain than to a shear strain.

22. The sensor assembly of claim 21, wherein said first and second opposed faces are concave.

23. The sensor assembly of claim 17, wherein said first and second opposed faces are convex.

24. The sensor assembly of claim 17, wherein the forces in the first and second directions are indicative of tire traction.

25. The sensor assembly of claim 15, wherein said first pair of strain sensors are resistive strain sensors.

26. The sensor assembly of claim 15, wherein said first pair of strain sensors generate said first and second output signals differentially.

27. The sensor assembly of claim 15, wherein said first pair of strain sensors are arranged in a Wheatstone bridge circuit to detect said forces in said first direction.

28. The sensor assembly of claim 15, further including a second material that encapsulates said first pair of strain sensors, said second material being different than the material of the elastomeric tire.

29. The sensor assembly of claim 28, wherein a ratio of elastic moduluses between the material of the elastomeric tire and the second material correspondingly scales the strain forces sensed by the strain sensors.

30. The sensor assembly of claim 28, wherein the second material is one of polyimide and epoxy.

31. The sensor assembly of claim 15, further including an adhesive to couple the first pair of strain sensors to the pyramid-shaped body.

32. The sensor assembly of claim 31, further including a potting material disposed on the sensor assembly.

33. The sensor assembly of claim 32, wherein said potting material and said adhesive are the same.

34. The sensor assembly of claim 32, further including a topping layer disposed on said potting material so as to scale strain forces sensed by the first pair of strain sensors.

35. A method of embedding a sensor in a tire, the method comprising:

providing a sensor assembly including a first pair of strain sensors disposed on first opposed faces of a generally pyramid-shaped body; and

shaping the first opposed faces of the pyramid-shaped body so that each face of the first opposed faces is non-planar.

36. The method of claim 35, wherein the sensor assembly is a three-axis sensor assembly including a second pair of strain sensors disposed on second opposed faces of the pyramid-shaped body, and further including the step of shaping the second opposed faces so that each face of the second opposed faces is non-planar.

37. The method of claim 36, wherein the first and second opposed faces of the pyramid-shaped body are curved.

38. The method of claim 35, wherein said shaping step includes shaping the first opposed faces of the pyramid-shaped body so the faces are concave.

39. The method of claim 35, wherein said shaping step includes shaping the first opposed faces of the pyramid-shaped body so the faces are convex.

40. The method of claim 35, wherein said shaping step is based on a desired sensitivity of the sensor.

41. The method of claim 40, wherein the desired sensitivity is greater sensitivity to a tensile strain and less sensitivity to a shear strain.

42. A sensor assembly embedded in an elastomeric material of a vehicle tire at a depth radially inward from a contact surface of the tire, the sensor assembly comprising:

a flexible pyramid-shaped body;

a strain sensing element disposed on said body; and

wherein said body includes curved faces that are shaped so as to determine the sensitivity of the sensor assembly generally independent of the radial depth.

43. The sensor assembly of claim 42, wherein said flexible body is generally pyramid-shaped.