Chassis part consisting of fibre-reinforced plastics, equipped with an integrated sensor

Abstract

The present invention pertains to a chassis part for connection and force transmission between a vehicle chassis of at least one wheel, consisting of fiber-reinforced plastics or plastic composite systems, preferably for a passenger car or utility vehicle.

Description

[0001] The present invention pertains to chassis parts for connection and force transmission between a vehicle chassis and at least one wheel, consisting of fiber-reinforced plastics or plastic composite systems, preferably for a passenger car or utility vehicle.

[0002] Such chassis parts for connection and force transmission between the vehicle chassis and the wheel, also called control arms, are known, in principle. Furthermore, it has been known, e.g., from DE 38 39 855 A1 that lightweight components comprising a connection between structural parts made of metal and plastic can be manufactured. It is problematic in such composite materials that the plastic portions, especially fiber-reinforced plastic components, may undergo brittle fracture under excessively high loads. This means that such parts may abruptly lose their strength and stability under an excessively high load. The use of such composite materials in chassis control arms therefore represents a certain safety hazard, because, on the one hand, extremely high safety requirements are imposed here, but enormous forces may briefly act on the chassis control arms because of unpredictable driving situations or accident situations. However, such composite materials make possible an extremely low-weight and consequently energy-saving design, so that it is desirable for reasons of the efficient manufacture of vehicles to use such composite materials in chassis control arms as well.

[0003] The object of the present invention is therefore to design the above-mentioned chassis parts such that a hazard-free and risk-free use in vehicles is possible.

[0004] This object is accomplished by the features of the independent patent claims. Advantageous variants of the present invention are the subject of subclaims.

[0005] The inventors have recognized that it is possible to recognize symptoms of fatigue in time by the continuous monitoring of the forces occurring in these chassis parts and thus to guarantee sufficient safety during the use of composite materials for such chassis parts. Since plastics have a substantially greater elongation than metals at equal strength, these materials are especially suitable for determining the load actually acting on them simply and accurately by means of wire strain gauges or piezo elements. Since integration over time is also possible, it is also possible to detect symptoms of material fatigue that are generated not only by peak loads but also by permanent loads. Moreover, it proved to be especially advantageous that not only are force measurements possible as a result for monitoring the service life of these chassis parts, but the measured force values can also be utilized in electronic control devices, preferably for stabilizing the driving or position of vehicles.

[0006] Corresponding to the idea of the present invention, the inventors consequently propose to improve chassis parts for connection and force transmission between a vehicle chassis and at least one wheel, consisting of fiber-reinforced plastics or plastic composite systems, preferably for a passenger car or a utility vehicle, in such a way that at least one means for measuring forces acting on the chassis parts is integrated in the plastic portions of the chassis parts.

[0007] Chassis parts are basically lever constructions, which are also subject to higher loads and especially accelerations than the rest of the vehicle in a jerky and shock-like manner, especially if they are so-called control arms. These accelerations occurring can be measured with an acceleration sensor. If we now assume that certain accelerations over a defined period of time describe a path traveled, abuse of the control arm, e.g., high-speed travel over a curb, can be inferred. Even though this is not a direct force measurement, it is nevertheless sufficient for identifying states of abuse.

[0008] As was mentioned above, wire strain gauges or piezo elements, by means of which the forces occurring and acting on the chassis parts can be determined in an electronic manner, may be mentioned here especially advantageously.

[0009] In a special design of the chassis parts according to the present invention, the means for measuring the acting forces are arranged such that they can record forces along at least two and preferably three independent axes. As a result, it is possible to define the acting forces either in one plane or even in space.

[0010] Another manner of measuring the load acting on a force connection strut may be to embed a fiber-optic light guide in a plastic, in which case the transmission changes in individual modes as soon as the plastic is bent under load. Thus, the bending stress in the control arm can be inferred from the measurement of frequency band shifts, e.g., the extinction of individual modes.

[0011] Corresponding to the basic idea of the present invention, the inventors also propose a vehicle with the above-mentioned chassis parts, wherein at least one means for measuring the acting forces is coupled with an electronic control device for stabilizing the travel and/or the position of the vehicle, especially by acting on driving or braking elements. Such control devices may be, e.g., the prior-art ESP (Electronic Stability Program) or even a simple headlight leveling control of the vehicle headlights.

[0012] Furthermore, a vehicle according to the present invention may also be designed such that at least one means for measuring the acting forces is coupled with an electronic documentation device for the measured forces. This electronic documentation device, which comprises, e.g., a simple electronic memory, in which the measured values are stored electronically, now also makes it possible to recognize loads that occur later. Another possibility is to also carry out an evaluation of the measured values, e.g., with respect to the maxima read out, or a more complex calculation of an integrated load and consequently of the life expectancy still present, in the electronic documentation device. This may possibly also be performed combined with a temperature sensor, because there likewise are dependences between the strength of the particular chassis part and the current body temperature of the chassis part, which should be taken into account especially in case of the use of plastics. The load-bearing capacity of plastics has a substantially stronger temperature dependence than metals.

[0013] It is especially advantageous in the sense of the idea of the present invention if the electronic documentation device is integrated in the electronic control device for stabilizing the driving and/or the position of the vehicle. This leads to the possibility of having to calculate the currently occurring forces only once and to use them at the same time for the life expectancy, on the one hand, and for stabilizing the driving and/or the position of the vehicle, on the other hand.

[0014] Since information is obtained on the durability of the chassis part based on the knowledge of the loads on the corresponding chassis part, it may, furthermore, be advantageous to provide means for warning when preset maximum loads are exceeded and/or a maximum service life has been reached. The measured data are consequently used for two applications at the same time. This results in a synergistic effect due to the elimination of the need for additional sensors for controlling the overload on the control arm or for the determination of the chassis parameters for an electronic drive or position stabilization.

[0015] In a continuation of this idea of the present invention, the inventors propose, furthermore, that the documentation device also have means for locking the vehicle when the above-mentioned preset maximum loads or the maximum service life of an essential chassis part are exceeded.

[0016] Due to the outfit of chassis parts according to the present invention, it is now also possible to manufacture control arms that are relevant for safety from fiber-reinforced plastics and to use them without safety hazards. If the control arms are manufactured according to an injection molding process or an RTM-like process (RTM=Resin Transfer Molding), the integration of prefabricated sensors as inserts can be accomplished very easily. Control arms from other materials or material composite systems, which have a high local elongation due to their design, are suitable as well. Sensors can be integrated in this case in the control arm in a simple manner in appropriate areas, e.g., where high local loads occur. The sensors may assume two functions, namely, they may be used, on the one hand, for the continuous measurement of the forces and consequently for providing data for an electronic chassis control, and, on the other hand, for monitoring to show whether overloads that could damage the control arm itself occur.

[0017] The information that makes possible the diagnosis of the state of the chassis is thus made available by the process described. In particular, such a diagnosis may be meaningful after accidents, in which, e.g., no visible damage can be recognized on chassis parts, but it may be assumed based on the forces measured that structural damage must have occurred inside such parts.

Claims

1. Chassis part for connection and force transmission between a vehicle chassis and at least one wheel of a motor vehicle, consisting of fiber-reinforced plastics or plastic composite systems, characterized in that at least one means for measuring forces acting on the chassis part is integrated in the plastic portion of the chassis part.

2. Chassis part in accordance with claim 1 above, characterized in that at least one means for measuring the acting forces is a wire strain gauge, a piezo element, an acceleration sensor or a fiber-optic light guide embedded in the plastic of the chassis part.

3. Chassis part in accordance with one of the above claims, characterized in that the means for measuring the acting forces are arranged such that they can record forces along at least two and preferably three independent axes.

4. Vehicle with a chassis part having the features in accordance with one of the above claims, characterized in that at least one means for measuring the acting forces is coupled with an electronic control device for stabilizing the driving and/or the position of the vehicle, especially by action on driving or braking elements (e.g., ESP).

5. Vehicle in accordance with the preamble of claim 4 above or in accordance with claim 4 above, characterized in that at least one means for measuring the acting forces is coupled with an electronic documentation device for the measured forces.

6. Vehicle in accordance with claim 5 above, characterized in that the electronic documentation device is integrated within the electronic control device for stabilizing the driving and/or the position of the vehicle.

7. Vehicle in accordance with one of the claims 5 or 6 above, characterized in that the documentation device has means for warning when preset maximum loads and/or the service life are exceeded.

8. Vehicle in accordance with one of the claims 5 through 7 above, characterized in that the documentation device has means for locking the vehicle when preset maximum loads are exceeded.

9. Use of means integrated in chassis parts made of plastic or composite materials for measuring forces acting on the chassis parts, preferably in accordance with one of the claims 1 through 3 above, for checking the service life of these chassis parts and for collecting measured values for electronic control devices, especially for the headlight leveling control and/or for the stabilization of the driving and the position of a vehicle.