Data transmission method for a tire-pressure monitoring system of a vehicle
A data transmission method for a tire-pressure monitoring system ( 10 ) of a vehicle. The data is transmitted by wheel units ( 12 ) to a central computer ( 13 ) located in the vehicle. The method comprises: a data transmission phase in parking mode, over a first period; and a data transmission phase in running mode, over a second period shorter than the first period. The method is characterized in that a natural time lag between various internal clocks with which each wheel unit ( 12 ) is equipped is used to prevent collisions between transmissions from the various wheel units of one and the same vehicle.
1. A data transmission method for a tire-pressure monitoring system ( 10 ) of a vehicle, said data being transmitted by wheel units ( 12 ) to a central computer ( 13 ) located in the vehicle, said method comprising:
a data transmission phase in parking mode, over a first period; and
a data transmission phase in running mode, over a second period shorter than the first period; said method being characterized in that:
a natural time lag between various internal clocks with which each wheel unit ( 12 ) is equipped is used to prevent collisions between transmissions from the various wheel units of one and the same vehicle.
2. The method as claimed in claim 1 , characterized in that the internal time lag between the various clocks of each wheel unit is preferably determined by the precision of an RC-type oscillator mounted in each wheel unit.
3. The method as claimed in claim 2 , characterized in that RC oscillators having a precision of about ±15% are preferably used.
4. The method as claimed in claim 1 , characterized in that each wheel unit transmits several frames for each data item to be transmitted.
5. The method as claimed in claim 4 , characterized in that three frames are transmitted for each data item to be transmitted.
6. The method as claimed in claim 5 , characterized in that the time interval separating the first and second frames is around 60 ms+Δσ ms and the time interval separating the second and third frames is around 80 ms+Δσ ms.
7. The method as claimed in claim 4 , characterized in that the frames transmitting the same data item are transmitted during a single wheel revolution.
8. A tire-pressure monitoring system ( 10 ) of a vehicle, employing the method as claimed in claim 1 , said system being characterized in that it includes, for each wheel unit ( 12 ), an internal clock produced by an RC type circuit whose precision is about ±15%.
9. The method as claimed in claim 2 , characterized in that each wheel unit transmits several frames for each data item to be transmitted.
10. The method as claimed in claim 3 , characterized in that each wheel unit transmits several frames for each data item to be transmitted.
11. The method as claimed in claim 5 , characterized in that the frames transmitting the same data item are transmitted during a single wheel revolution.
12. The method as claimed in claim 6 , characterized in that the frames transmitting the same data item are transmitted during a single wheel revolution.