Tyre condition monitoring system

• US 20020044050A1
• Filed: 08/06/2001
• Published: 04/18/2002
• Est. Priority Date: 08/31/1994
• Status: Active Grant

• Current Assignee: Andrew John Derbyshire, Edward Charles Gibson, Jeremy Francis Siddons, John Kitto Richards, Sean Patrick Davies
• Original Assignee: Andrew John Derbyshire, Edward Charles Gibson, Jeremy Francis Siddons, John Kitto Richards, Sean Patrick Davies
• Inventors: Siddons, Jeremy Francis, Gibson, Edward Charles, Derbyshire, Andrew John, Richards, John Kitto, Davies, Sean Patrick
• Granted Patent: US 6,545,599 B2
• Time in Patent Office: Days
• US Class Current: 340/442
• CPC Class Codes: B60C 23/0401 characterised by the type of alarm
• 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
• CPC Class Codes: B60C 23/0454 Means for changing operation mode, e.g. sleep mode, factory mode or energy save mode
• CPC Class Codes: B60C 23/0457 self triggered by timer
• CPC Class Codes: B60C 23/0459 self triggered by motion sensor
• CPC Class Codes: B60C 23/0462 Structure of transmission protocol
• CPC Class Codes: H04L 7/06 the synchronisation signals differing from the information signals in amplitude, polarity or frequency or length

Abstract

A tire condition monitoring system (1) comprises a wheel transmitter unit (2) for each wheel of a vehicle. The transmitter unit is mountable in the wheel and has sensors (9, 10) for sensing pressure and temperature in and rotation of the wheel. Signals from the sensors are processed by a processor (9) to produce data which is transmitted via a radio frequency transmitter (23). The data is transmitted with data representing a unit identity code. Transmitted data is received by a receiver unit (5, 6, 7) where it is analysed to determine the condition of the tire. The receiver unit includes a user operable input for setting threshold limits for the temperature and/or pressure such that if a threshold is passed an alarm is sounded. Each wheel transmitter unit includes a power supply and is arranged so that power is only applied during the sensing and transmission of data. Intervals between transmissions of data can be varied depending on whether rotation of the wheel has been sensed.

Claims

1. A sensor device for sensing parameters associated with a pressurised unit, the sensor device comprising a sensor for sending one or more parameters associated with said pressurised unit, a processor for processing signals from the sensor, and a transmitter for transmitting data, the processor being operable in plural different modes including a calibration mode in which data is recorded for known conditions and in a normal operating mode in which data representing the one or more sensed parameters is transmitted by the transmitter.

2. A sensor device as claimed in claim 1, wherein, in the calibration mode, pressure data is recorded for two different pressure conditions under the same temperature condition.

3. A sensor device as claimed in claim 2, wherein data representing the temperature condition is also recorded.

4. A sensor device as claimed in claim 1, 2 or 3, wherein the processor is operable in an installation mode in which the recorded data is transmitted by the transmitter.

5. A sensor device as claimed in claim 1, wherein, in the calibration mode, pressure data is recorded for two different pressure conditions each under two different temperature conditions.

6. A sensor device as claimed in any preceding claim, wherein, in the normal operating mode, the processor is arranged to process data representing the signals from the sensor with the recorded data to produce calibrated data representing the one or more sensed parameters for transmission by the transmitter.

7. A sensor device as claimed in any preceding claim, wherein, in the normal operating mode, data representing the temperature of and pressure in the pressurised unit is transmitted by the transmitter.

8. A sensor device as claimed in any preceding claim, wherein the processor is arranged to output identity data identifying the device for transmission with the data representing the one or more sensed parameters.

9. A sensor device as claimed in any preceding claim, wherein the processor is arranged to enter the calibration mode when power is installed in the device, and further comprising indicator means for indicating that the device is in the calibration mode.

10. A sensor device as claimed in any preceding claim adapted for use as a wheel transmitter unit for a tire condition monitoring system.

35. A tire condition monitoring system as claimed in any of claims 30 to 34 in combination with at least one sensor device or wheel transmitter unit or transducer as claimed in any of claims 1 to 29.

11. A wheel transmitter unit for a tire condition monitoring system, the wheel transmitter unit being mountable to a wheel and comprising a sensor for sensing one or more parameters associated with said wheel, a transmitter for transmitting data representing the sensed one or more parameters, a power supply for supplying power to the sensor and the transmitter, and a condition monitor arranged to respond to operating conditions of the wheel transmitter unit to vary the manner in which the transmitter unit transmits data.

12. A wheel transmitter unit as claimed in claim 11, wherein the transmitter unit condition monitor comprises a power supply monitor arranged to respond to a low power condition being sensed by causing the transmitter to transmit data indicative of said condition.

13. A wheel transmitter unit as claimed in claim 12, wherein the condition monitor is arranged to cause the transmitter to transmit said data indicative of said condition in place of said sensed parameter data.

14. A wheel transmitter unit as claimed in any of claims 11 to 13, wherein the power supply is operable to supply power to the sensors and the transmitter from time to time to enable the sensing of said parameters and the transmitting of said data, and the condition monitor comprises a motion sensor for sensing when said wheel is in motion, the condition monitor causing the frequency of the times at which power is supplied to the sensor to increase when the wheel is in motion as compared to the frequency when the wheel is stationary.

15. A wheel transmitter unit as claimed in claim 14, wherein the motion sensor comprises a centrifugal detector for detecting rotation of said wheel.

16. A wheel transmitter unit as claimed in any of claims 11 to 15, wherein the condition monitor is operable to monitor the sensed parameters at closely spaced instances and to apply power to the transmitter for the transmission of data when there has been a significant change in the sensed parameters since the previous transmission of data.

17. A wheel transmitter unit as claimed in any of claims 11 to 16 further comprising a processor for processing signals from the sensor representing the sensed one or more parameters to produce parameter data, the processor being operable in plural different modes including a calibration mode in which parameter data is recorded for known wheel conditions and a normal operating mode in which data representing the one or more sensed parameters is transmitted by the transmitter.

18. A wheel transmitter unit as claimed in claim 17, wherein, in the calibration mode, pressure and temperature data are recorded for two different pressure conditions under the same temperature condition.

19. A wheel transmitter unit as claimed in claim 18, wherein, in the normal operating mode, data representing the temperature of and pressure in the wheel is transmitted together with data identifying the wheel.

20. A wheel transmitter unit as claimed in claim 18 or 19, wherein the processor is operable in an installation mode in which the recorded data representing the pressure and temperature of the wheel is transmitted together with the data recorded in the calibration mode.

21. A wheel transmitter unit as claimed in any of claims 17 to 20, wherein the data produced for transmission is in digital form.

22. A wheel transmitter unit as claimed in any of claims 17 to 20, wherein the processor is arranged to produce data identifying the wheel transmitter unit for transmission with the sensed parameter data.

23. A wheel transmitter unit as claimed in any of claims 17 to 22, wherein the processor is arranged to produce timing information as part of said data for transmission.

24. A wheel transmitter unit as claimed in claim 23, wherein the timing information comprises a mark signal and a space signal which are transmitted prior to the transmission of the data representing the sensed one or more parameters.

25. A wheel transmitter unit as claimed in any of claims 11 to 24, wherein the condition monitor is arranged to apply power to the transmitter such that transmitter.

27. A transducer as claimed in claim 26, wherein the calibration data comprises data representing two different pressure conditions at a known temperature.

28. A transducer as claimed in claim 26, wherein the calibration data comprises data representing two different pressure conditions each at two different temperature conditions.

29. A transducer as claimed in claim 26 or 27 or 28, further comprising a transmitter for transmitting a signal representing the output from the processing means.

26. A transducer comprising:

a pressure sensor for producing an output proportional to pressure applied thereto;

a temperature sensor for producing an output representing the temperature thereof;

storing means for storing calibration data representing the behaviour of the pressure sensor in response to both pressure and temperature; and

processing means for processing the pressure and temperature sensor outputs with reference to the stored calibration data to produce a calibrated output representing directly the pressure applied to the transducer.

30. A tire condition monitoring system, comprising at least one sensor device or wheel transmitter unit mountable in the wheel of a vehicle;

and a receiver unit for receiving the data transmitted by the at least one sensor device or wheel transmitter unit and monitoring the received data, the receiver unit comprising user operable means for selecting one or more thresholds and being responsive to the one or more sensed parameters passing a respective user selected threshold by outputting a warning.

31. A tire condition monitoring system as claimed in claim 30, wherein the receiver unit further comprises a display for displaying values of the one or more parameters sensed by the at least one wheel transmitter unit.

32. A tire condition monitoring system as claimed in claim 30 or 31, wherein the user operable means is operable to select for display one of the one or more sensed parameters for one of the at least one transmitter unit.

33. A tire condition monitoring system as claimed in claim 30 or 31 or 32, wherein the display comprises a digital display for displaying values of the one or more sensed parameters and a graphical display for indicating the nature of the displayed value and the wheel unit to which the displayed value relates.

34. A tire condition monitoring system as claimed in any of claim 30 to 33, wherein the user operable input means comprises plural switches.

37. A method as claimed in claim 36, further comprising recording data representing the temperature in the chamber.

38. A method as claimed in claim 36 or 37, further comprising recording predetermined data defining the manner in which the output of the pressure transducer varies with temperature, thereby to enable compensation for the temperature-related changes.

39. A method as claimed in claim 36, 37 or 38, further comprising monitoring the output from the transducer during the varying of the pressure;

and

recording data representing the output from the transducer when the output reaches a steady value.

36. A method of calibrating a pressure transducer for temperature-related changes in the output of the transducer, the method comprising:

placing the transducer in a calibration chamber at a known temperature;

varying the pressure in the chamber to a first pressure;

recording data representing the output of the transducer for the first pressure;

varying the pressure in the chamber to a second pressure; and

recording data representing the output of the transducer for the second pressure.

40. A method as claimed in any of claims 36 to 39, further comprising:

activating an indicator of the transducer before placing the transducer in the chamber; and

deactivating the indicator once the output has been recorded for the second pressure.

41. A method as claimed in any of claims 36 to 40, wherein the first pressure is greater than the second pressure.

42. A method as claimed in any of claims 36 to 41, further comprising varying the temperature in the chamber to a first temperature once the pressure in the chamber has been varied to said first pressure;

and

wherein the data representing the output of the transducer for the first pressure is recorded when the temperature in the chamber reaches said first temperature.

43. A method as claimed in any of claims 36 to 42, further comprising:

varying the temperature in the chamber to a second temperature;

recording data representing the output of the transducer for the second pressure at the second temperature varying the pressure in the chamber to the first pressure; and

recording data representing the output of the transducer for the first pressure at the second temperature.

44. A method as claimed in any of claims 36 to 43, wherein, in the data representing the output of the transducer is recorded automatically within the transducer.

45. A method as claimed in any of claims 36 to 44, wherein the transducer is one of a plurality of transducers which are calibrated concurrently within the chamber.

47. A tire condition monitoring system as claimed in claim 46, wherein the central transceiver unit comprises a processor for determining commands to be transmitted and for processing received data.

48. A tire condition monitoring system as claimed in claim 47, wherein the processor is arranged to monitor the received data for changes in the tire condition and to vary the commands transmitted in dependence thereon.

49. A tire condition monitoring system as claimed in claim 46, 47 or 48, wherein the central transceiver unit comprises means for determining when the vehicle is in use and is operable in a first mode when the vehicle is in use to transmit commands frequency and in a second mode when the vehicle is not in use to transmit commands less frequently.

46. A tire condition monitoring system comprising at least one wheel transceiver unit mountable in a wheel of a vehicle;

and a central transceiver unit for transmitting commands to the at least one wheel transceiver unit and receiving tire condition data transmitted in reply to said commands from said wheel transceiver unit.

50. A tire condition monitoring system as claimed in any of claims 46 to 49, wherein the transmission of each command is preceded by a preamble, the wheel transceiver unit being arranged to power down after the reception of a command and to power up from time to time to monitor for the transmission of a preamble.

51. A tire condition monitoring system as claimed in claim 50, wherein the preamble comprises a plurality of preamble periods in which time information is transmitted relating to the time until the command will be transmitted and the wheel transceiver unit is arranged to respond to said time information by powering down depending on the time remaining until transmission of the command.

52. A tire condition monitoring system as claimed in claim 51, wherein the time information is transmitted in the form of a digital signal having a frequency related to the remaining time.

53. A tire condition monitoring system as claimed in any of claims 46 to 52, wherein the central transceiver unit is operable to transmit data to the wheel transceiver unit.

54. A tire condition monitoring system as claimed in claim 53, wherein the data from the central transceiver unit comprises identity data uniquely identifying the wheel transceiver unit which is transmittable during installation of the system.

55. A tire condition monitoring system as claimed in claim 54, wherein the commands transmittable from the central transceiver unit comprise a command to transmit the identity data.

56. A tire condition monitoring system as claimed in any of claims 46 to 55, wherein the commands transmittable from the central transceiver unit comprise a command to the wheel transceiver unit to store calibration data.

58. A tire condition monitoring system as claimed in claim 56, wherein the commands transmittable from the central transceiver unit comprise a command to transmit stored calibration data.

59. A tire condition monitoring system as claimed in any of claims 46 to 58, comprising a plurality of wheel transceiver units and wherein the central transceiver unit is operable to transmit commands individually to each wheel unit or globally to all wheel units.

70. A tire condition monitoring system as claimed in any of claims 46 to 59, wherein the wheel transceiver unit and/or the central transceiver unit comprises a circuit as claimed in any of claims 60 to 69.

57. A tire condition monitoring system as claimed in any of claim s 46 to 57 wherein the commands transmittable from the central transceiver unit comprise a command to transmit data pertaining to the condition of the tire.

60. A transceiver circuit comprising an oscillator circuit for providing a reference frequency signal, a modulating circuit for modulating a data signal representing data to be transmitted with the reference signal and outputting the modulated signal for transmission, a receiver circuit for receiving a modulated data signal which receiver circuit is arranged to receive also signals from the modulating circuit derived from the reference signal, and a demodulating circuit for demodulating the received signal to extract the data therefrom.

61. A transceiver circuit as claimed in claim 60, wherein the oscillator circuit comprises a surface acoustic wave resonator.

62. A transceiver circuit as claimed in claim 60 or 61, wherein the modulator circuit comprises a voltage controlled oscillator.

63. A transceiver circuit as claimed in claim 62, wherein the voltage controlled oscillator is arranged to provide a signal which is applied as an in-phase and a quadrature signal to the receiver circuit.

64. A transceiver circuit as claimed in claim 60, wherein the oscillator circuit comprises a frequency synthesizer driven by a crystal.

65. A transceiver circuit as claimed in claim 64, wherein the modulator circuit comprises a voltage controlled oscillator, and a mixer connected to the voltage controlled oscillator and to receive a signal representing data to be transmitted.

66. A transceiver circuit as claimed in claim 65, wherein the signal representing data to be transmitted is generated by a frequency shift keying modulator circuit.

67. A transceiver circuit as claimed in any of claims 60 to 66, wherein the receiver circuit comprises a low noise amplifier.

68. A transceiver circuit as claimed in any of claims 60 to 67, wherein the receiver circuit comprises a mixer connected to receive the signals from the modulating circuit.

69. A transceiver circuit as claimed in any of claims 60 to 68, wherein the receiver circuit comprises a low pass filter and threshold detector for conditioning received signals for input to the demodulating circuit.