Communications: electrical – Land vehicle alarms or indicators – Internal alarm or indicator responsive to a condition of the...
Reexamination Certificate
2000-05-19
2001-04-17
Wu, Daniel J. (Department: 2736)
Communications: electrical
Land vehicle alarms or indicators
Internal alarm or indicator responsive to a condition of the...
C340S449000, C340S539230, C073S146400, C073S146500
Reexamination Certificate
active
06218937
ABSTRACT:
BACKGROUND OF THE INVENTION
A system for monitoring the pressure of a tyre of a vehicle wheel comprises at least - inserted in the wheel rim - a pressure sensor, a transmitter and a battery and a power-supply capacitor for the transmitter.
The system must regularly transmit, to the central computer of the vehicle, bursts of bits of information relating, of course, to the pressure of the tyre but also to, for example, the temperature, the voltage of the power-supply battery and the identity of the wheel.
The system must transmit a specific number Ne, generally five, of identical bursts and a number Nr of these bursts must have been received so that it may be considered that the immediate information has been transmitted and received. The transmission of the bursts can take place, for the sake of providing a basis, every hour if the vehicle is stationary, and every six minutes if the vehicle is moving.
Furthermore, the system is activated at regular intervals, for example, every two seconds, for the transmission of the bursts. Finally, the bursts, each of a duration t
b
, generally of 8 ms, are spaced, again generally by 12 ms. Thus series of five bursts are transmitted, of a duration of 88 ms over an activation period of 2s.
If it is desired that the system be resistant to very low temperatures, of the order of −40° C., it is necessary to use expensive power-supply batteries, costing around 2 Euros.
The Applicant has sought to overcome this constraint by using inexpensive batteries costing less than 1 Euro but which, consequently, are not made for such low temperatures, such as, for example, recyclable lithium batteries.
SUMMARY OF THE INVENTION
To this end the invention relates to a system for monitoring the pressure of a tyre of a vehicle wheel comprising
a pressure sensor
a transmitter for transmitting pressure data,
a power-supply battery,
characterised in that
a temperature sensor and
a processor are also provided, the processor being arranged to control the transmission of the pressure data according to the temperature.
A capacitor is preferably mounted in parallel with the power-supply battery in order to ensure the power supply for the transmitter during the transmission periods and to be recharged outside these transmission periods.
More preferably, the pressure data being transmitted by series of identical bursts and the system being activated at regular intervals, the processor is arranged in order, below a temperature threshold, to spread the transmission of the bursts of a series over a number of activation intervals, advantageously one burst per activation interval.
At low temperatures, the resistance of the battery increases considerably and the spreading of the transmission of the bursts leaves the battery more time between two bursts to recharge the capacitor.
In the preferred embodiment of the system of the invention, the battery, the capacitor, the sensors, the processor and the transmitter are mounted in parallel.
REFERENCES:
patent: 4909074 (1990-03-01), Gerresheim et al.
patent: 4942510 (1990-07-01), Edwards
patent: 5231872 (1993-08-01), Bowler et al.
patent: 5708411 (1998-01-01), Hill
patent: 5837891 (1998-11-01), Bridge
patent: 5900808 (1999-05-01), Lebo
patent: 6034596 (2000-03-01), Smith et al.
patent: 6148888 (2000-11-01), Benimeli
patent: 0 016 991 (1980-10-01), None
Sagem S.A.
Vorys Sater Seymour and Pease LLP
Wu Daniel J.
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