Patent Document

BACKGROUND OF THE INVENTION 
   The present invention relates to a method of operating an internal combustion engine, in particular in a motor vehicle. 
   More particularly, it relates to a method of operating an internal combustion engine, in accordance with which, from the signals of two detecting devices, angular positions of a crankshaft and a camshaft are determined, and in which a relative angular position of one shaft relative to another shaft is monitored. 
   The invention also relates to a computer program, to an electrical storage medium for a control and/regulating device of an internal combustion engine, to a control and/regulating device for an internal combustion engine, and to an internal combustion engine. 
   A method of the above mentioned general type is disclosed for example in the German patent document DE 100 32 332 A1. In this document it is described that for monitoring and diagnosis an association of the angular position of the camshaft of an internal combustion engine to a crankshaft must be tested, whether the signals of a detecting device for detecting the camshaft angle and a detecting device for detecting the crankshaft angle are plausible relative to one another. 
   Here and later a relative angular position is identified as the angular position of a reference mark on one shaft relative to a reference mark on another shaft. Since the camshaft and the crankshaft are conventionally coupled with one another through a transmission device, the angular positions of the both shafts relative to one another are equal at least in predetermined operational conditions of the internal combustion engine, if the internal combustion engine operates correctly. When a difference between an actual angular position of the camshaft with respect to a nominal angular position exceeds a predetermined threshold, then an action is released. Such a difference can be for example obtained when the detecting devices are positioned erroneously or when an error occurs during the signal processing. 
   SUMMARY OF THE INVENTION 
   Accordingly, it is an object of the present invention to provide a method of the above mentioned general type, which avoids the disadvantages of the prior art. 
   More particularly, it is an object of the present invention to provide a method of the above mentioned general type, which is performed so that the internal combustion engine can operate reliably. 
   In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated in a method of the above mentioned type, in which, depending on whether a change of the detected actual relative angular position is located outside a tolerance region, an action is released. 
   In a computer program, this objective is achieved in that it is programmed for the use in a method in accordance with the present invention. In an electrical storage medium this objective is achieved in that a computer program for the use in the inventive method is stored in the storage medium. A control and/regulating device achieves this objective in that it is programmed for the use of the inventive method. In the internal combustion engine, the above mentioned objective is achieved when it includes a control and/or regulating device which is programmed for the use of the inventive method. 
   When the method is performed in accordance with the present invention, the change of the coupling of one shaft to the other shaft, or in other words a change in the transmission device which couples the camshaft with the crankshaft can be recognized. Thereby the reliability to the operation of the internal combustion engine is increased and damaged of the internal combustion engine in the case of errors can be eliminated. With the inventive method a complete malfunction of the transmission device which couples the both shafts is detectable. 
   The basis for this is that conventionally the camshaft and the crankshaft of an internal combustion engine are coupled with one another through a mechanical transmission. Such a transmission includes conventionally a control chain or a toothed belt, which is tensioned between corresponding transmission wheels. In the inventive method it is possible to recognize when during the operation of the internal combustion engine the control chain or the toothed belt slips on one of the drive wheels, when the coupling of both shafts changes. This recognition is based on the fact that a tolerance region is provided around the actual relative angular position of the both shafts determined by the detecting devices. It is measured so that when the coupling is clearly changed, for example a control chain or a toothed belt slips by at least one pitch on a corresponding transmission wheel, the relative angular position leaves the tolerance region. 
   In accordance with another embodiment of the present invention, it is proposed that the release of the action depends on whether the change is performed within a predetermined time period and/or within a predetermined number of revolutions of one of the shafts. The basic consideration is that a sliding of a control chain or a toothed belt or a complete failure of the transmission device which couples the shafts with one another is performed suddenly or at least very fast. Due to this additional feature, such error can be distinguished from slowly occurring errors, for example a drift of a detection device. 
   It is also proposed that a determined relative angular position the latest at the end of an operational cycle of the internal combustion engine is stored in a non-volatile storage. During a subsequent operational circle of the internal combustion engine, comparison values are available, so that for example also an error during maintenance works on the transmission device, which couples the both shafts, can be recognized. Also, mounting errors of one of the detecting devices must not be taken into consideration with this further feature during the determination of the tolerance region, so that the tolerance region can be relatively narrow. This increases the reliability of the inventive method. 
   A further advantageous embodiment of the inventive method resides in that a desired relative angular position of the both shafts relative to one another can be changed, and for monitoring an actual relative angular position can be used, which in a specified position, for example in one of the both end positions of the possible adjusting region, is determined. Thereby the application region of the inventive method can be expanded also to such internal combustion engines in which a camshaft adjustment is available. 
   With such a camshaft adjustment, the relative angular position of the both shafts can be influenced as desired. For determining a relatively narrow tolerance region, only those signals for the above explained monitoring are used, which in a reproducible operational condition, namely in an exactly known position of the adjusting device, are contained in one of the end positions of the adjusting region of the camshaft adjustment. 
   It is especially advantageous when the determined actual relative angular position is adapted with respect to a nominal value, wherein the adaptation is performed in a time-delayed fashion, for example by means of a low pass filter. The determined actual relative angular position is basically connected with a certain fuzziness, since during their determination tolerances of the transmission which couples the both shafts, the detecting devices and the evaluating devices are mutually influenced. These tolerances include for example a clearance of a control chain or a toothed belt, a mounting error of one of the detecting devices, tolerances of the detecting devices, temperature influences to which the detection devices are subjected, and the like. At least a part of these tolerance influences, namely the static influences are separated in accordance with a further embodiment of the method, by adapting the detected actual relative angular position generally to the nominal value. With this adaptation however there is a danger that the change of the relative angular position no more can be detected correctly. For this reason the adaptation is performed in a time-delayed fashion. 
   It is first of all proposed that, depending on whether the detected actual angular position is located outside of a tolerance region, an action is released. In this way also a static error of the angular position of the both shafts can be recognized. 
   It is further advantages when the action or the actions include an inputting in an error storage and/or detected in a rest position of the internal combustion engine. Thereby the maintenance is facilitated and/or a damage to the internal combustion engine is reliably avoided. 
   The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a view schematically showing an internal combustion engine with a detecting device for an angular position of a crankshaft and a detecting device for an angular position of a camshaft; 
       FIG. 2  is a diagram showing the signals of the detecting devices of  FIG. 1  as well as the corresponding operational conditions of components of the internal combustion engine of  FIG. 1  in operation; 
       FIG. 3   a  is an enlarged section of the signal of the detecting device for the angular position of the crankshaft; 
       FIG. 3   b  is a corresponding enlarged cross-section of the signal of the detecting device of the angular position of a camshaft in a first operational case; 
       FIG. 3   c  is a view substantially similar to the view of  FIG. 3   b  for a second operational case; 
       FIG. 3   d  is a view substantially corresponding to the view of  FIG. 3   b  of a third operational case; and 
       FIG. 4  is a flow diagram for illustration of a method of operation of the internal combustion engine of  FIG. 1 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   An internal combustion engine is shown in  FIG. 1  and identified as a whole with reference numeral  10 . It serves for driving a motor vehicle which is not shown in the drawing. 
   The illustrated internal combustion engine is a four cylinder internal combustion engine. In  FIG. 1  only the components of one cylinder are shown, which cylinder is identified with reference numeral  12 . The cylinder  12  includes a combustion chamber  14  with an inlet passage  16  and an inlet valve  18  for introducing a combustion air. The hot combustion exhaust gasses are discharged from the combustion chamber  14  through an outlet valve  20  and an outlet passage  22 . Fuel is supplied into the combustion chamber  14  directly through an injection device  24 , and ignites fuel-air mixture located in the combustion chamber  12  by a spark plug  26 . The shown internal combustion engine is a gasoline-direct injection engine. The embodiments of the invention presented herein below are analogously applicable to diesel internal combustion engines as well as to internal combustion engines with a suction pipe injection. 
   A piston  28  is connected through a connecting rod  30  with a crankshaft  32 . The crankshaft  32  is coupled with a camshaft  36  through to a transmission device  34 . The transmission device  34  includes several components which are not shown in the drawings, for example a toothed belt and a crankshaft-side as well as a camshaft-side belt wheel, between which the toothed belt is tensioned. 
   The crankshaft  32  is connected with a pickup disc  38  which rotates angularly synchronously with the crankshaft  32 . The pickup disc  38  includes  58  identical angle marks  40  and one gap  42  which corresponds to the angular region between two angle marks  40 . The position of the pickup disc  38  is detected by a sensor  44 . Its signal is submitted through an input circuit  46  to a control and regulating device  48 . The pickup disc  38  and the sensor  44  are parts of a crank angle detecting device  49 . 
   Similarly the camshaft  36  is connected with a pickup disc  50  which rotates angularly synchronously with a camshaft  36 . Also angle marks  52  are provided on the pickup disc  50  and separated by gaps  54 . The pickup disc  50  is sensed by a sensor  56 . Its signal is supplied to an input circuit  58  and finally also to the control and regulating device  48 . The pickup disc  50  and the sensor  56  are parts of a cam angle detecting device  59 . The control and regulating device  48  controls indirectly (through a not shown ignition device) the spark plugs  26  and the injection device  24 . 
     FIG. 2  shows signals which are supplied from the sensors  44  and  56  to the control and regulating device  48 . The signal of the sensor  44 , with which the pickup disc  38  senses the crankshaft  32  is identified with reference numeral  60 , while the signal supplied by the sensor  56  with which the pickup disc  50  senses the camshaft  36  is identified with reference numeral  62 . The rotary speed of the crankshaft  32  is determined from the time intervals in this embodiment between the falling signal flanks  63  of the signal  60 . A further evaluation is possible for determination of the gaps  42 , whose position is represented for a selected position of the crankshaft  32 . 
   For obtaining however a sufficient information about the actual operating clearance of the internal combustion engine, additionally the signal  62  must be evaluated. Since the pickup disc  50  per operating clearance rotates only once, while to the contrary the pickup disc  38  per operating clearance rotates twice, with a corresponding synchronization of the signal  62  with the signal  60 , the position of the crankshaft  32  can be clearly defined at the corresponding positions of the piston  28  and the operating condition of the cylinder  12  can be correctly detected. For this purpose in the inventive example also the falling flanks  65  of the signal  52  are evaluated. Depending on this, for the single cylinder the injections of fuel by the injection devices  24  (reference numeral  64  in  FIG. 2 ) and in the ignition of the fuel-air mixture by the spark plug  26  (reference numeral  66  in  FIG. 2 ) are performed. The opening time period of the inlet valve  18  in  FIG. 2  is identified with reference numeral  68 . 
   When all tolerance influences are equal to zero and the coupling between the crankshaft  32  and the camshaft  36  is error-free, a predetermined falling flank  65   ref  is located between two short rectangular signals  72  of the signal  62 , which represents the angular position of the camshaft  36 , in this embodiment with a crank angle KW Ref . This situation is shown in form of an increased section in  FIGS. 3   a  and  3   b.    
   A desired angular position between the crankshaft  32  and the camshaft  36  is defined by this crank angle KW Ref , or in other words a predetermined angular position of the camshaft  36  in case of a predetermined angular position of the crankshaft  32 . Because of the manufacturing tolerances, of mounting errors, or because of a malfunction in operation of the internal combustion engine  10 , it is possible that this angular position does not correspond to the desired value. In order to determine this, a method is proposed which is stored as a computer program in a storage  76  of the control and regulating device  48 . This method is illustrated in  FIG. 4 . After a start block  78 , a block  80  is inquired, whether the switching conditions of the internal combustion engine  10  are provided. Thereby it is guaranteed that the method described in  FIG. 4  is efficiently guided to an end when the machine is started and thereby is located in a defined initial condition. This is specifically important in internal combustion engines with an adjustable angular position of the camshaft  36  relative to the crankshaft  32 , to provide defined and reproducible conditions for performance of the method. For this purpose in the block  18  it is inquired whether a bit START_COND=1. 
   If the answer in the block  80  is “yes” then in the block  82  a difference DIF 1  is determined between a relative angular position KW art     —     t1  and a nominal angular position KW REF . The angular position KW act     —     t1  detected during the last operational cycle of the internal combustion  10  and stored in a non-volatile storage. Such an operational situation with DIF 1  not equal to zero is shown in  FIG. 3   c . The difference DIF 1  corresponds finally to the static deviation of the actual relative angular position of the camshaft  36  to the crankshaft  32  from the nominal angular position KW REF . When the amount of the difference DIF 1  exceeds a limiting value G 1  (block  84 ), then in a block  86  an error bit ERROR  1 =1 is set. Otherwise, this error bit is deleted in a block  88 . If the error bit ERROR  1  is set in the block  86 , in the block  90  a return to the start block  78  is performed. 
   If to the contrary in the block  88  the error bit ERROR  1  is deleted, then in the block  92  a difference DIF 2  between the angular position KW act-t1  and the actual relative angular position KW act-t2  is formed (an operational situation with DIF 2  not equal zero is shown in  FIG. 3   d ). The both angular positions KW act     —     t1  and KW act     —     t2  are detected at different time points t 1  and t 2 , so that the difference DIF 2  represents a time (“dynamic”) change of the angular position. In a block  24  it is checked whether the amount of the difference DIF 2  exceeds a limiting value G 2 . If the answer in the block  94  is “YES”, then in the block  96  an error bit ERROR  2 =1 is set. Otherwise, this error bit ERROR  2  in block  98  is set equal 0. 
   With the set error bit ERROR  1  a static error takes place in the coupling between the crankshaft  32  and the camshaft  36 . When the error bit ERROR  2  is set, to the contrary a dynamic error function is generated. For example a sliding of the toothed belt or a tearing off of the toothed belt belongs to the situation. In order to determine moreover whether this dynamic error function is sudden or gradual, it can be detected whether the change of the DIF 2  of the angular position occurs within a predetermined time window. A corresponding inquiry is performed between the blocks  94  and  96  in  FIG. 4 . 
   It should be also pointed out that at least when the difference DIF 1  does not exceed the limiting value G 1 , the difference DIF 1  is made at least approximately to zero by a corresponding adaptation of the angular position KWa act     —     t1  the nominal angular position KW REF . In order to correctly determine the difference DIF 2  the value KWa act     —     t1  as explained hereinabove is stored in a non-volatile storage. Furthermore, the adaptation is performed with a time delay by means of a low pass filter, in order to prevent that the actual relative angular position KWa act     —     t2  is also adapted to the nominal angular position KW REF  which would make impossible the correct determination of the DIF 2 . 
   It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above. 
   While the invention has been illustrated and described as embodied in method of operating an internal combustion engine, in particular in a vehicle, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. 
   Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention. 
   What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

Technology Category: f