This application is a National Stage completion of PCT/EP2018/053964 filed Feb. 19, 2018, which claims priority from German patent application serial no. 10 2017 204 729.1 filed Mar. 21, 2017.

FIELD OF THE INVENTION

The invention relates to overload recognition.

BACKGROUND OF THE INVENTION

Modern motor vehicles, especially passenger cars, are increasingly equipped with assistance systems which on the one hand make life easier for the driver, but on the other hand allow less and less feedback about the chassis to the driver. As a result the driver may not be made aware of a defect, such as a bent track-rod or a deformed transverse control arm. From corresponding tests, however, it is known that the residual service life after a plastic deformation of chassis components is sometimes considerably reduced. Thus it could happed that due to the compensating effect of the assistance system prior damage to the track-rod, for example as a result of driving over an obstacle, is not noticed by the driver and later for that reason leads to fracture and to an accident.

Thus, DE 10 2010 043 778 A1 describes a steering element with a mechanical overload protection system which, when it acts, results in a clearly perceptible play of the steering, but which, as already said, would be compensated by an assistance system and would therefore not be noticeable by the driver.

DE 10 2013 018 526 A1 relates to a system for detecting a change of an axle adjustment of a motor vehicle. For this, the system comprises a force-measuring unit or an angle-measuring unit, which sends a signal to an evaluation device. The evaluation device compares the signal at the time with a reference signal, and if the reference signal is exceeded this is interpreted as an overloading of the vehicle axle.

The evaluation of a force signal is often prone to a larger element of vagueness since a force above the calculated load limits does not necessarily also result in damage. Consequently a repair is carried out, which in itself would not be necessary.

Angle measurement is likewise not a clear measurement parameter, since in the event of an overload the theoretical case may arise that although two control arms in the axle have been bent, the angle between the two control arms remains within the tolerance range since the respective deformations, as it were, compensate one another. Then both control arms would have to be replaced, but the system would not detect that situation.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide an overload recognition system which overcomes the problems known from the prior art.

This objective is achieved by designing the sensor system as a deformation detection sensor for an individual chassis component.

In contrast to the prior art, the deformation of the chassis component is detected as the reference variable. Thus, compared with the prior art a value is used which would allow a defect to be recognized directly, which defect also leads to a change of the chassis geometry or even to damage. Furthermore, the load is determined on a single component. No compensation effect can take place within the chassis.

In a further advantageous embodiment of the invention, the sensor system comprises a plurality of individual sensors. On the one hand this makes for a certain redundancy and measurement errors can be recognized.

With regard to determining the deformation direction, the individual sensors are arranged in different planes relative to one another.

To produce a sensor system which is particularly simple to handle, the individual sensors form a cage. The cage only has a low design strength and does not therefore reduce the quality of the measurement signal.

For this it is further provided that the cage is held on one side in the longitudinal direction of the chassis component. Axial stresses could also falsify the measurement signal.

To fix the sensor system, the cage has an annular attachment section. The sensors themselves are not loaded in connection with the attachment function.

According to an advantageous sub-claim, the attachment section is fixed by way of a fastener of the chassis component. The cage can for example consist of a plastic material which is tightened by a screw cap.

For this, the attachment section is made radially elastic, for example in that it has slot-shaped cutouts.

In a further design the chassis component is made in two parts which form between them a parting line where the attachment section is arranged. Consequently no additional fastener are needed for the sensor system.

It can also be provided that the attachment section and the fastener are permanently connected to one another. This considerably simplifies handling during the assembly process.

In order to be able to detect even the slightest deformations, the sensor is arranged at least in the vicinity of the region of the chassis component with the lowest structural strength.

