Method for detecting a wear-relevant load on a vehicle wheel

1 . A method for detecting a wear-relevant load on a vehicle wheel of a vehicle by means of a tire pressure monitoring unit optimized for low energy consumption that is mounted on the vehicle wheel and comprises at least one acceleration sensor, the method comprising the steps of:

providing the tire pressure monitoring unit with the at least one acceleration sensor;

providing a central unit of the vehicle in data communication with the tire pressure monitoring unit;

mounting the tire pressure monitoring unit on the vehicle wheel;

rotating the vehicle wheel;

measuring, via the tire pressure monitoring unit, a first set of centrifugal acceleration values at first time intervals by the at least one acceleration sensor;

determining, via the tire pressure monitoring unit and/or the central unit, a first rotational frequency of the vehicle wheel for an overall first time interval from a series of measured values of the at least one acceleration sensor at the first time intervals;

determining, via the tire pressure monitoring unit and/or the central unit, a centrifugal acceleration value for the overall first time interval;

determining, via the tire pressure monitoring unit and/or the central unit, a proportionality factor from the first rotational frequency and the centrifugal acceleration value, linking the square of the rotational frequency with the centrifugal acceleration;

measuring, via the tire pressure monitoring unit, a second set of centrifugal acceleration values at second time intervals by the at least one acceleration sensor;

successively calculating, via the tire pressure monitoring unit and/or the central unit, a second rotational frequency of the vehicle wheel from measured values of the centrifugal acceleration, which have been determined at the second time intervals that are greater than the first time intervals, and from the proportionality factor;

calculating, via the tire pressure monitoring unit and/or the central unit, a load value from the rotational frequency and the corresponding second time interval; and

via the tire pressure monitoring unit and/or the central unit, successively adding these load values up to an overall load;

wherein energy consumption of the at least one acceleration sensor over time is greater during a defined time period when the at least one acceleration sensor measures in the first time intervals than during the defined time period when the at least one acceleration sensor measures in the second time intervals.

2 . The method according to claim 1 , wherein the second time intervals are at least 100 times as large as the first time intervals.

3 . The method according to claim 1 , wherein the rotational frequency is determined for the time interval from 4 to 100 measured values of the acceleration sensor.

4 . The method according to claim 1 , wherein the first time intervals are less than 30 milliseconds.

5 . The method according to claim 1 , wherein the second time intervals are at least 2 seconds.

6 . The method according to claim 1 , wherein the rotational frequency is determined for the time interval from measured values of tangential acceleration.

7 . The method according to claim 1 , wherein the proportionality factor is statistically calculated from several series of measured values of the acceleration sensor for different time intervals and centrifugal acceleration values determined in each case for these time intervals.

8 . The method according to claim 1 , wherein the load value corresponds to the number of wheel revolutions made in the second time interval.

9 . The method according to claim 1 , wherein the load value is calculated from the number of wheel revolutions made in the second time interval and from the tire pressure.

10 . The method according to claim 1 , wherein the overall load is set to zero if the tire pressure falls below a predetermined threshold.

11 . The method according to claim 10 , wherein the overall load, before it is set to zero, is stored as the load value.

12 . The method according to claim 1 , wherein the first time intervals are less than 30 milliseconds and wherein the second time intervals are at least 2 seconds.

13 . A tire pressure monitoring device optimized for low energy consumption comprising a pressure sensor, at least one acceleration sensor and a control unit, wherein the control unit is designed to carry out in operation a method comprising the following steps:

determining a first rotational frequency of the vehicle wheel for an overall first time interval from a series of measured values of the at least one acceleration sensor at first time intervals;

determining a centrifugal acceleration value for the overall first time interval;

determining a proportionality factor from the rotational frequency and centrifugal acceleration value, linking the square of the rotational frequency with the centrifugal acceleration

measuring a second set of centrifugal acceleration values by the at least one acceleration sensor;

successively calculating a second rotational frequency of the vehicle wheel from measured values of the centrifugal acceleration, which have been determined at second time intervals that are greater than the first time intervals, and from the proportionality factor;

calculating a load value from the rotational frequency and the corresponding second time interval; and

successively adding these load values up to an overall load;

wherein a first energy consumption of the at least one acceleration sensor of the tire pressure monitoring device during the first time intervals is greater than a second energy consumption of the at least one acceleration sensor of the tire pressure monitoring device during the second time intervals when the first and second time intervals are compared over a same elapsed time period.

14 . The tire pressure monitoring device according to claim 13 , wherein the first time intervals are less than 30 milliseconds and wherein the second time intervals are at least 2 seconds.

15 . A tire pressure monitoring system comprising:

a tire pressure monitoring device and a central vehicle unit in data communication with the tire pressure monitoring unit, said tire pressure monitoring device comprising a pressure sensor, at least one acceleration sensor and a control unit;

wherein the tire pressure monitoring system is designed to carry out a method comprising the following steps:

measuring, via the tire pressure monitoring unit, a first set of centrifugal acceleration values by the at least one acceleration sensor;

determining, via the tire pressure monitoring unit and/or the central unit, a first rotational frequency of the vehicle wheel for an overall first time interval from a series of measured values of the at least one acceleration sensor at first time intervals;

determining, via the tire pressure monitoring unit and/or the central unit, a centrifugal acceleration value for the overall first time interval;

determining, via the tire pressure monitoring unit and/or the central unit, a proportionality factor from the rotational frequency and centrifugal acceleration value, linking the square of the rotational frequency with the centrifugal acceleration;

measuring, via the tire pressure monitoring unit, a second set of centrifugal acceleration values by the at least one acceleration sensor;

successively calculating, via the tire pressure monitoring unit and/or the central unit, a second rotational frequency of the vehicle wheel from measured values of the centrifugal acceleration, which have been determined at second time intervals that are greater than the first time intervals, and from the proportionality factor;

calculating, via the tire pressure monitoring unit and/or the central unit, a load value from the rotational frequency and the corresponding second time interval; and

via the tire pressure monitoring unit and/or the central unit, successively adding these load values up to an overall load.

16 . The tire pressure monitoring system according to claim 15 , wherein the first time intervals are less than 30 milliseconds and wherein the second time intervals are at least 2 seconds.

17 . The tire pressure monitoring system according to claim 15 , wherein the tire pressure monitoring system is optimized for low energy consumption.