Abstract:
An operating time is determined by an approximation method within the scope of the method for determining the actual operating time of a hydraulic, electrohydraulic or electric component of a motor vehicle or of a working machine within a reference time or a monitoring period.

Description:
This application es a national stage completion of PCT/EP02/13978 filed Dec. 10, 2002 which claims priority from German Application Serial No. 101 61 742.9 filed Dec. 15, 2001. 
   FIELD OF THE INVENTION 
   This invention relates to a method for calculating the operating time of hydraulic, electrohydraulic or electric components of a motor vehicle or of a working machine. 
   Certain hydraulic, electrohydraulic or electric components of a motor vehicle or of a working machine, such as valves or pumps, usually are not laid out with fatigue limit so that a maximum admissible operating time (ED) is indicated within a reference period. To make possible the elimination of damage of said components due to permanent control, the control devices or control software concerned must know the actual operating time (ED) at the moment at which a control signal is generated. 
   For determining the actual operating time, it is required that one component be controlled beginning from the present moment up to the moment lying back by the reference period. If the control device generates a control signal, for example, every 5 ms, the operating time in a reference period of 60 seconds, for example, 12000 individual values, has to be taken into account for calculating. Therefore, to exactly determine the operating time, the values have to be separately stored for each component. The storage place, as a rule, is not available in a control device for reasons of cost. 
   The problem on which this invention is based is to outline a method for determining the actual operating time of a hydraulic, electrohydraulic or electric component of a motor vehicle or of a working machine, which makes determining the actual operating time as precisely as possible in case of storage place need clearly smaller than the method according to the prior art. 
   It is accordingly proposed that an approximation method is used for calculating the actual operating time. 
   SUMMARY OF THE INVENTION 
   In particular, the monitoring period or the reference period is divided into separate intervals or time windows which correspond to a certain number of program or control runnings; there is coordinated with each time window one value which is increased by the momentary control period. The operating time then results as sum of the values of the individual time windows; it is possible to provide one or more windows with weighting factors. 
   The inventive method considerably reduces the number of values to be stored; it corresponds to the number of time windows and the stored meter. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     invention will now be described, by way of example, with reference to the accompanying drawings in which: 
       FIG. 1  shows a time/signal diagram with the corresponding time windows for a general case; and 
       FIG. 2  is a time/signal diagram with the inventive time windows for a concrete embodiment explained herebelow. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   As shown in  FIG. 1 , according to the invention, the monitoring or reference period is divided into individual time windows, each time window having the length of k control or program runnings. The number k can be defined based on the precision of calculation desired to be achieved. The higher k is, the lower the precision obtainable, since several values are combined. 
   The operating time of the component concerned during one of said time windows is stored as one value, the value of the actual time window being increased with each program running by the momentary control time of the component. After k program runnings, which are detected by a meter n, the time window just expired moves to the second place, the meter is reset and the value of the time window lying farthest back is deleted whereby the storage place that has become free is available for recording the operating time in the new actual time window. The number of time windows does not change all together. 
   According to the invention, the operating time within the monitoring period is calculated by summing up all values of the individual time windows. One variant of the invention provides weighting of the individual window by means of an appertaining weighting factor. 
   According to a special advantageous variant of the invention, the time window lying farthest back loses influence as the level (meter n) of the actual time window increases. The time window lying farthest back is weighted with the factor (1−n/k), n representing the meter of the actual time window. 
   The determination of the number of time windows needed for storing the total operating time in the monitoring period results from the following formula: 
           Number   ⁢           ⁢   of   ⁢           ⁢   time   ⁢           ⁢   windows     =       (         T   u     /     T   p       k     )     +   1       ,       
     T u =monitoring period   T p =program running time   k=number of values per time window   

   There results, for example, for a program running time of 5 milliseconds, a monitoring period of 60 seconds and the value 1000 for the factor k 13 time windows with a length of 5 seconds each. The diagram corresponding to these values is object of  FIG. 2   
   As already explained, the precision of the calculation of the operating time is mainly determined by the factor k. Besides, the maximum possible divergence of the calculated value from the real value occurs precisely at the moment of the program running when the condition n=k/2 has been met. The typical maximum values for the errors occurring in such a situation are in the order of ±2.0% and can only be reached by a quite specific control signal for k=1000 and 13 time windows; for the normal case, on the other hand, an error of about ±1.0% is to be expected, a compromise having to be reached between precision and storage need. 
   REFERENCE NUMERALS 
   
       
       T u  monitoring period 
       t p  program running time 
       k number of values per time window 
       n meter