Procedure for determining overloading of a vehicle

0001The invention relates to a method for determining vehicle overloads.

0002Depending on the mode of operation, vehicles are subjected to varying degrees of stress. For example, continuous operation of a vehicle on motorways, even if it is accompanied by high vehicle speed, does not usually lead to excessive stress on the vehicle or its components. First and foremost, the chassis as a whole and its parts, but also spring and damping elements, such as the body and its parts, should be mentioned. On the other hand, operating a vehicle on poor roads, for example with potholes and bumps in the road, is also significantly more stressful for the vehicle if it takes place at speeds which are significantly lower than driving on a motorway. The mileage of a vehicle is therefore not a criterion for recognizing possible overstressing of the vehicle.

0003The invention has for its object to provide a method of the type mentioned, which allows a conclusion on possible vehicle overuse.

0004The invention solves this problem by the characterizing features of patent claim 1.

0005In the context of the invention, the individual event in which the vehicle is overstressed does not play a special role. Rather, it comes down to the sum of such events. The sum here is not to be understood, or at least not exclusively, to mean the mathematical addition of several events in which the vehicle is overstressed. Rather, it is to be understood as the valuation index formed from these events, in which these events are included. This rating index is a good indicator of possible vehicle damage.

0006This damage to the vehicle has the property that it cannot be recognized from the outside or is not readily recognizable. It does not, or at least does not necessarily, go hand in hand with any kind of deformation or macroscopic damage to a vehicle part. On the other hand, if there is a vehicle overload in the sense of the invention, it is necessary to check the vehicle and possibly as a precautionary measure, an exchange of vehicle parts, such as a shock absorber, is given or foreseeable.

0007It has been shown that a check of individual vehicle parts, for example as part of the regular vehicle safety inspections, does not exclude the risk of replacing individual vehicle parts long before such an inspection is due due to extraordinary overstressing. Otherwise, safe continued operation of the vehicle is not guaranteed.

0008The evaluation index can be determined in different ways from the output signals of the acceleration sensor. Examples of this can be found in patent claims 2 to 5. The combination of an evaluation with regard to the amplitude and the duration is particularly advantageous, since the energy input into the vehicle can be determined therefrom. This entry is a particularly good measure for assessing whether and to what extent damage or Hazards to the vehicle or vehicle parts are to be expected.

0009The acceleration sensor itself can be an acceleration sensor that is present in the vehicle anyway and is used in the context of the crash sensor system to trigger a front and / or side airbag. In addition, there is also an acceleration sensor that is used in the context of electronic damping force control systems. Due to its location, this is spatially assigned to the chassis and thus to the part of the vehicle that is most at risk in the event of overstressing.

0010Control systems is used. Due to its location, this is spatially assigned to the chassis and thus to the part of the vehicle that is most at risk in the event of overstressing.

0011The use of a single accelerometer is sufficient for a rough estimate of an overuse of the vehicle. If, on the other hand, several accelerometers are used, the extent of the overloading of the vehicle and the need for a possible check and repair of a vehicle part can be estimated much more accurately by comparing and / or summing their evaluated and summed output signals.

0012A particular aspect of the invention deals with the problem of determining overstressing the chassis. For trolleys made of traditional materials such as B. Steel overstressing of chassis components goes hand in hand with macroscopically recognizable changes. Local defects such as deformations or mechanical abnormalities or changes in the track and camber of the vehicle wheels should be mentioned here. There is also a macroscopically recognizable relationship between the extent of the overload and the occurring defect of the undercarriage or the undercarriage component. With the use of modern materials such as fiber-reinforced plastics, composite materials or high-strength aluminum alloys, damage detection on chassis components is made more difficult. The reason for this is the low ductility of these components. Component damage does not result in any visible component deformation. If the undercarriage is overstressed, for example if an obstacle is run over or if the vehicle is thrown against a curb, it is difficult to assess whether serious overstressing of the undercarriage has actually occurred and whether individual undercarriage components or the complete undercarriage may need to be replaced.

0013A particularly advantageous way of determining overstressing of the undercarriage or individual components is specified in patent claim 7. of an airbag. With these, the damage to the vehicle usually goes hand in hand with considerable damage to the chassis.

0014The acceleration sensor can be a separate sensor, for example arranged on the chassis. However, it is also possible to use an encoder that is already present in the vehicle as the acceleration sensor. In addition to an existing airbag sensor, accelerometers that are used in the context of electronic damping force control systems can also be used here. Due to their location, these are already spatially assigned to the chassis.

0015Irrespective of the choice of the respective acceleration sensor, an essential feature of the invention is the permanent, non-erasable storage of an extreme value of the acceleration that has occurred. An extreme value is to be understood as a multiple. It can be the maximum amplitude of the accelerator output signal. The period of time during which the output signal is above the limit value can also be of interest. Other parameters of the output signal, such as, for example, the rise, the time profile, the frequency response and all information known in the context of the signal evaluation, which can be obtained from the output signal of the acceleration sensor, can also be important in the context of the invention.

0016Of course, the special parameters of the respective output signal to be examined are also dependent on the structure, the spatial position and / or the mode of operation of the accelerometer. The special structure of the chassis, both with regard to the interaction of the individual components and with regard to the elasticities usually present and influencing the output signal of the accelerator, can be of interest. This includes the elasticity of the tire as well as that of rubber bearings and the like.

0017In addition to the vehicle-specific parameters mentioned, vehicle-specific parameters such as loading, tire size, speed, direction of travel, ... of the respective vehicle can also be taken into account when an extreme acceleration value occurs and can be used in the analysis to identify the extent of a chassis overload.

0018Additional information that can be important for the events related to the overuse can also be stored. Here are the date and time and / or a z. B. from a navigation system derived location information in connection with the recorded extreme value of the accelerometer. This also allows you to determine the time and place for an accident.

0019The invention is further illustrated by the drawing. It shows<dl id="dl0001"><dt>Fig. 1</dt><dd>schematically a motor vehicle with an accelerometer,</dd><dt>Fig. 2</dt><dd>the output signal of the accelerator when excessive chassis stress occurs.</dd><dt>Fig. 3</dt><dd>the typical course of the output signal of an accelerometer when the vehicle is subjected to extreme stress and</dd><dt>Fig. 4/5</dt><dd>the evaluation and assessment of this signal in the context of the invention</dd></dl>

0020The vehicle shown schematically in FIG. 1 has a central accelerometer, which is, for example, the trigger sensor for an airbag on the driver's side and an airbag on the passenger's side (not shown). A stress occurs in the form of a force on the left rear wheel 3 as seen in the direction of travel, which is greater than the maximum that occurs during normal use of the motor vehicle. This force can be a force F_l act in the longitudinal or vertical direction. Also by an arrow F_s a lateral force is indicated. This can be an abnormal lateral force that occurs, for example, when hurling against a curb.

0021A typical signal curve for the output signal of the acceleration sensor 2 is shown in FIG. 2. After an increase, the output signal a shows a brief settling caused by different component elasticities, in order then to rise again steeply up to a maximum value A. This is followed by a similarly steep drop down to the value 0. For comparison, the output signal a of the accelerator when driving on a rough road and when braking is also shown.

0022The maximum value of the output signal a for case I is significantly higher than the extreme values ​​as they occur in case II with regard to its maximum value. Various characteristics of signal a can be used for evaluation and permanent storage in a non-volatile memory (not shown). For example, it is possible to record whether a limit value has been exceeded and the subsequent period of time before this limit value is undershot. This time period is indicated by Δ. It is also possible to store the maximum value A itself. As already stated, further possibilities are the gradient of rise and the frequency behavior of the signal curve. If a limit value is used, it should generally be selected so that it is above the maximum value that occurs in case II. In principle, the complete recording of the signal curve for a defined period of time, for. B. triggered by a trigger signal if the limit value is exceeded.

0023In addition, further information, for example the time, location, vehicle speed, etc., can be recorded in order to determine the location and cause of the chassis overload.

0024As shown on the basis of a single acceleration sensor 2, it is also possible to also permanently record the output signals of further acceleration sensors and to examine them for themselves and in relation to that of the acceleration sensor 2. Depending on the mode of operation and location of these accelerometers, it is then possible to analyze the direction of impact, determine the acceleration component and, if necessary, to clearly identify damaged chassis components and the extent of their damage.

0025The output signal of another acceleration sensor (not shown), which is shown in its time profile in FIG. 3 and is also used, for example, in the context of airbag electronics, occurs, for example, when braking hard on a roadway which is considered to be <img file="EP0778461A2_D0001.tif" />Washboard ". This is to be understood to mean a course of the road surface in which road surface elevations are present at regular intervals. The acceleration values ​​reach values ​​of almost 6 g, values ​​of about 3 g occurring particularly frequently.

0026On the basis of driving tests, it has been found that acceleration values ​​which, for example for the vehicle shown here, are above 3 g, can permanently damage vehicle parts, for example on the chassis. This is taken into account by evaluating the accelerations in excess of 3 g and the sum of these evaluations. This is explained with reference to FIG. 4.

0027The evaluation of the extreme accelerations made is shown by way of example in FIG. 4. In the simplest case, an evaluation takes place in the sense of a temporal integration. The integrals thus obtained are summed up. The energy input and the sum of these entries is calculated by taking into account the acceleration amplitudes and their duration<img file="EP0778461A2_D0001.tif" />Load index "is formed. With each acceleration value above 3 g, the integration and thus an increase in the load index takes place to an extent which corresponds to the energy input of the respective integral acceleration peak. The course of the load index L is also shown in FIG. 4. The scale from 0 up to 0.1 is only intended to illustrate and be exemplary.

0028For comparison, the result is shown in FIG. 5, which results if +/- 5 g is used as the threshold. Based on the acceleration signal shown in FIG. 3, this results in a load index that is significantly smaller than in FIG. 4. In fact, in FIG. 5, only two events are evaluated over the entire course taken into account, which are above 5 g in amount.

0029The threshold, here 3 or 5 g, depends on the particular circumstances of the vehicle, the position of the acceleration sensor, its response behavior, etc. and can be determined on the basis of driving tests. In addition, the output signals of other accelerometers can also be taken into account. The evaluation and summation of the output signals of the the acceleration sensor (s) can be different from the method shown and / or can be different from one another in the case of several acceleration sensors. In any case, in vehicles with one or more acceleration sensors, only a different evaluation of the output signals of the acceleration sensor gives the possibility of not only recognizing a crash and thus the need to trigger safety devices, but also the possibility of possibly and also detect undetectable damage to the vehicle and its parts.