Tyre pressure monitoring apparatus

• US 20060214780A1
• Filed: 02/20/2006
• Published: 09/28/2006
• Est. Priority Date: 08/20/2003
• Status: Active Grant

• Current Assignee: TRW Limited (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Original Assignee: TRW Limited (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Inventors: Mathias, Peter, Rushgrove, Kevin, Rutter, Anthony Lawrence
• Granted Patent: US 7,924,147 B2
• Time in Patent Office: Days
• US Class Current: 340/442
• CPC Class Codes: B60C 23/0416 allocating a corresponding wheel position on vehicle, e.g. front/left or rear/right

Abstract

A tyre pressure monitoring system comprises an initiator which is arranged to transmit an initiation signal, and at least one corresponding transducer associated with a tyre of the vehicle which responds to exposure of the initiation signal from the initiator and is adapted to respond by transmitting a return signal indicating that it has been woken by the initiator, in which the strength of the initiation signal emitted by the initiator is varied across a number of values within a range.

Claims

1. A tyre pressure monitoring system for a vehicle comprising:

an initiator which is arranged to transmit an initiation signal having a strength; and

at least one corresponding transducer associated with a tyre of the vehicle, said transducer responding to exposure from said initiation signal from said initiator, and said transducer being adapted to respond by transmitting a return signal indicating that it has been woken by said initiator, said initiator further adapted to vary the strength of said initiation signal emitted by said initiator across a number of values within a range.

2. A tyre pressure monitoring system according to claim 1 wherein said initiator comprises an antenna which defines a resonant circuit, a carrier signal being applied to said antenna which varies in frequency, said signal transmitted from said antenna being at its greatest the closer said frequency is to a resonant frequency of said resonant circuit.

3. A tyre pressure monitoring system according to claim 2 wherein said initiator is adapted to emit a carrier signal which is swept across a range of frequencies.

4. A tyre pressure monitoring system according to claim 3 wherein said sweep starts higher than said resonant frequency and drops towards said resonant frequency.

5. A tyre pressure monitoring system according to claim 3 wherein said sweep starts at a frequency lower than said resonant frequency and increases towards said resonant frequency.

6. A tyre pressure monitoring system according to claim 1 wherein said signal transmitted by said initiator comprises a number of pulses of differing strength.

7. A tyre pressure monitoring system according to claim 1 wherein said initiator includes an antenna which forms a resonant circuit, and which emits a signal which is pulse width modulated, a duty cycle of said pulse width modulated signal being varied.

8. A tyre pressure monitoring system according to claim 7 wherein said duty cycle of said PWM signal is initially a maximum and is decreased over time to decrease the average power of said signal modulated.

9. A tyre pressure monitoring system according to claim 1 which further includes a carrier signal generating means which generates varying drive signals for said initiator.

10. A tyre pressure monitoring system according to claim 1 wherein said transducer transmits a return signal which comprises a pressure signal whenever said transducer is charged to a predetermined level by said signal from said initiator.

11. A tyre pressure monitoring system according to claim 1 wherein said initiator is adapted to stop sending an initiation signal upon receipt of a return signal.

12. A tyre pressure monitoring system according to claim 8 the wherein said detector monitors return signals and if more than one return signal is received indicating that more than one transducer is responding, said initiator sends a reduced power signal.

13. A control system for a tyre pressure monitoring apparatus for a vehicle comprising:

a carrier signal generator which is adapted to generate at least one carrier signal;

an output through which said carrier signal from said carrier signal generator can be applied to at least one initiator fitted to said vehicle, said initiator transmitting a signal whose strength varies in dependence with properties of said carrier signal;

an input for receiving tyre pressure signals from at least one tyre pressure transducer in response to said signal transmitted by said initiator; and

a processor which is adapted to process said received signals and to vary at least one parameter of said carrier signal according to said signals received at said input.

14. A control system according to claim 13 wherein said processor varies at least one of:

strength of said signal, average power of said signal and frequency of said signal.

15. A control system according to claim 14 further including a computer program for said processor, said computer program operative with said processor to operate the control system.

16. A method of controlling a tyre pressure monitoring apparatus comprising the steps of:

(a) providing a plurality of initiators and associated transducers;

(b) causing one of the initiators to transmit an initiating signal;

(c) monitoring for signals transmitted by the transducers in response to said transmitted signal; and

(d) reducing the strength of the signal transmitted by the initiator if signals are received from more than one transducer.