Method for adjusting a clock on board a motor vehicle and associated adjusting device

1. A method for adjusting a clock on board a motor vehicle, said clock providing an actual time for functions of the vehicle, said vehicle being connected via wireless communication to a data server, said method comprising:

the server transmitting a sequence of consecutive actual-time values, all separated from one another by a fixed time interval;

the vehicle receiving the actual-time values shifted by an unknown and variable time of flight between transmission and reception;

for each received actual-time value:

calculating a difference between an actual-time value received at a given instant and an actual-time value received at a previous instant,

calculating a discrepancy between said difference thus calculated and the fixed time interval, and

calculating a cumulative disparity, consisting in summing the discrepancy calculated for a time value received at one instant and a time value received at the previous instant, and

determining the actual time for adjusting the on-board clock according to said disparity.

2. The adjusting method as claimed in claim 1 , wherein the sequence includes a predetermined number of consecutive actual-time values.

3. The adjusting method as claimed in claim 1 , wherein the actual time for adjusting the clock is the received actual-time value corresponding to the calculated minimum cumulative disparity.

4. The adjusting method as claimed in claim 1 , wherein the server transmits the sequence of consecutive values repeatedly with a predetermined frequency.

5. The adjusting method as claimed in claim 1 , wherein, when the vehicle comprises a geolocation system, the method further comprises an additional step of receiving an actual-time value from the geolocation system and calculating a disparity between said value and the determined actual time, the actual time chosen for adjusting the clock being the actual-time value from the GPS if said disparity is smaller than a predetermined disparity.

6. A device for adjusting a clock on board a motor vehicle for use with a server having wireless communication capability, said clock providing an actual time to vehicle functions, said device comprising:

a receiver wirelessly receiving actual-time values transmitted consecutively by the server and all separated from one another by a fixed time interval, said received values being shifted by an unknown and variable time of flight between transmission and reception;

an electronic controller adapted to:

calculate a difference between an actual-time value received at a given instant and an actual-time value received at a previous instant;

calculate a discrepancy between said difference thus calculated and the fixed time interval,

calculate a cumulative disparity, consisting in summing the discrepancy calculated for a time value received at one instant and a time value received at the previous instant; and

adjust the on-board clock according to said disparity.

7. The device as claimed in claim 6 , wherein the electronic controller is further adapted to determine a minimum value of the cumulative disparity, which is calculated for each received actual-time value and the corresponding received actual-time value.

8. A data server communicating wirelessly with a motor vehicle, for implementing the method for adjusting a clock on board the motor vehicle as claimed in claim 1 .

9. The data server as claimed in claim 8 , wherein the data server consecutively sends a sequence of actual-time values, all separated by a fixed time interval and said sequence is transmitted repeatedly with a predetermined frequency.

10. A motor vehicle communicating wirelessly with a data server, comprising an adjusting device as claimed in claim 6 .