Abstract:
A device for controlling an internal combustion engine has sensors That measure the operating states of the internal combustion engine. The sensor signals are used for determining control signals for the internal combustion engine. Furthermore, testing means are provided which verify the sensor signals and if implausible sensor signals are detected, control of the internal combustion engine is prevented.

Description:
RELATED APPLICATION INFORMATION 
       [0001]    The present application is a United States national phase patent application and claims the benefit of and priority to International Application No. PCT/EP2006/066067, which was filed Sep. 6, 2006, and which claims the benefit of and priority to German Patent Application No. 10 2005 046656.7, which was filed in Germany on Sep. 29, 2005, both of which are incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention is directed to a device for controlling an internal combustion engine according to the definition of the species in the independent patent claim. 
       BACKGROUND INFORMATION 
       [0003]    Devices for controlling internal combustion engines are already known, in which sensor signals that measure the operating states of the internal combustion engine are analyzed. The sensor signals measured in this manner are used to determine control signals for controlling the internal combustion engine. 
         [0004]    Control units in which theft protection is provided for preventing theft of a motor vehicle by exchanging an engine control unit are also already known. However, control units of identical design are used in various vehicles, some of which have no theft protection. 
       SUMMARY OF THE INVENTION 
       [0005]    The device of the present invention having the features of the independent patent claim has the advantage that the control unit and sensors of the relevant internal combustion engine are interlinked via simple means. This makes it possible to prevent an engine control unit from a vehicle without theft protection from being exchanged for an engine control unit of a vehicle with theft protection. 
         [0006]    Additional advantageous embodiments result from the features of the dependent patent claims. The control device may be designed in a particularly simple manner if the verification is based on properties of the sensor signals that are of no significance for determining the control signals. The same software for determining the control signals may be used for different types of devices for controlling an internal combustion engine. It is particularly appropriate to evaluate signals of the crankshaft angle sensors or camshaft angle sensors, since these sensors contain signals of corresponding sensor discs that are connected to the corresponding shafts. These sensor discs in an internal combustion engine are only able to be replaced with considerable effort. 
         [0007]    A simple possibility for ensuring the verifiability of the sensor signals between different control units is a specified angular distance between the signals of the crankshaft and camshaft. Another simple possibility for verifying the plausibility of the sensor signals is to mark a second position on the sensor wheel for the camshaft angle sensor, which is then verified. The thus measured signals of the crankshaft angle sensors and/or the camshaft angle sensors may be verified even further by detecting a compression event in the cylinders of the internal combustion engine and evaluating the relative position of the compression event and signals of the crankshaft angle sensor or camshaft angle sensor. In particular in a starting phase of the internal combustion engine, it is thus possible to detect if an attempt is made to simulate these signals by an external intervention. 
         [0008]    Exemplary embodiments of the present invention are depicted in the drawings and explained in greater detail in the following description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0009]      FIG. 1  shows a device for controlling an internal combustion engine which evaluates the signals of a crankshaft angle sensor and a camshaft angle sensor. 
           [0010]      FIG. 2  shows signals of the crankshaft angle sensor and camshaft angle sensor. 
           [0011]      FIG. 3  shows a rotational speed curve and signals of a camshaft angle sensor of an internal combustion engine. 
       
    
    
     DETAILED DESCRIPTION  
       [0012]      FIG. 1  shows a schematic representation of a device  1  for controlling an internal combustion engine which is connected to sensors  3  and  4  via connecting leads  2 . Only crankshaft  11  and camshaft  12  of the internal combustion engine itself are shown schematically in  FIG. 1 . The additional components of the internal combustion engine are immaterial for the description of the exemplary embodiments and/or exemplary methods of the present invention and are therefore not shown in greater detail in  FIG. 1 . The engines are conventional gasoline or diesel four-cycle engines such as those adequately known to those skilled in the art. A crankshaft sensor wheel  21 , having a plurality of teeth  22  is connected to crankshaft  11 . 
         [0013]    These teeth are equally spaced around the entire circumference of sensor wheel  21 , a tooth  22  not being present at one point so that a gap  23  is formed there. Teeth  22  of sensor wheel  21  move past sensor  3 . Each time a tooth  22  passes sensor  3 , a pulse is generated in sensor  3  which is emitted to control device  1  via line  2 . By evaluating these pulses, control unit  1  is able to infer the movement of crankshaft  11 . Camshaft  12  has a camshaft sensor disc  25  to which a mark  26  is affixed. When mark  26  brushes past sensor  4 , a pulse is generated which is fed to control device  1  via lead  2 . This pulse enables control device  1  to infer the rotation of camshaft  12 . 
         [0014]    Customarily, teeth  23  or mark  26  are made of soft magnetic material and they move past sensors  3 ,  4 , which are designed either as inductive sensors or Hall effect sensors. Corresponding pulses which are supplied to control device  1  via leads  2  are thus generated. Sensor discs  21  and  25  are fixedly joined to the particular shafts, i.e., crankshaft  11  and camshaft  12 . The position of gap  23  and mark  26  indicates a fixedly set angle of crankshaft  11  and camshaft  12 , respectively. This information therefore informs control device  1  of the position assumed by the cylinders of the internal combustion engine when brushing past gap  23  or mark  26 . 
         [0015]    The signal of sensor  3 , i.e., of the crankshaft angle sensor, is plotted against time t on curve A in  FIG. 2 . The signal of sensor  4 , i.e., of the camshaft angle sensor, is plotted against time on curve B. In a similar manner, the curves may also be plotted against the angle of rotation of the internal combustion engine. As can be seen in curve A, the signal of sensor  3  is made up of a sequence of pulses having identical spacing from one another in  FIG. 2   a.  This is the case when the internal combustion engine rotates at a constant speed. The absence of a signal caused by gap  23  is clearly evident. This gap is also denoted by reference numeral  23  and the pulses of teeth  22  are denoted by reference symbol  22  in curve A. Crankshaft  11  rotates twice as fast as camshaft  12  so that it can be seen in curve B that the pulse of mark  26  occurs only at the time each second gap  23  occurs. Camshaft sensor discs  21  and  25  are designed and affixed to the corresponding shafts in such a way that the signal of mark  26  in camshaft angle sensor  4  occurs exactly at the time a signal is absent in crankshaft angle sensor  3  due to gap  23 . 
         [0016]    The control of the internal combustion engine is now essentially based on the signal of curve A, since very exact rotational speed information is present there. Due to the doubled rotational speed of the crankshaft, however, it is not possible to judge from the signal of curve A which working cycle the particular cylinder is in. For this purpose, when gap  23  occurs, a check is performed to determine whether the signal of mark  26  is present. However, it is of no significance for the detection of the relevant working cycle of the internal combustion engine whether mark  26  coincides exactly with gap  23  or whether this signal appears offset by one or two teeth relative to gap  23 . Such an alternative signal curve, which is based on correspondingly changed positioning of mark  26  on sensor disc  25 , is shown in  FIG. 2   c.  As can be readily seen, the appearance of mark  26  relative to gap  23  is offset by two teeth  22  in  FIG. 2   c.  This is irrelevant for the purpose of control, since only the information concerning the working cycle to which gap  23  must be assigned in the crankshaft signal of curve A is needed. In the case of curve C, it is not checked during gap  23  if mark  26  has appeared in gap  23  or instead two teeth  22  after gap  23 . 
         [0017]    The information as to whether mark  26  appears during gap  23  or is offset to an earlier or later point in time may, however, be used to differentiate between internal combustion engines of different manufacturers and in particular to prevent an exchange of control units between combustion engines of different types or vehicle manufacturers. This is useful in particular when control units having identical functionality are sold for the control of internal combustion engines having varying complexity of theft protection. A control unit which is equipped with a relatively high level of theft protection complexity is used in vehicle type A. In such a vehicle, it is particularly difficult for a thief to start the engine. In vehicle type B, a control unit having the same range of functions is used and it also uses the same sensor signals. However, no theft protection is used in vehicle type B. The theft protection of vehicle A could be overcome by removing the control unit with theft protection and replacing it with the control unit of vehicle B without theft protection. The exemplary embodiments and/or exemplary methods of the present invention eliminates this problem by using somewhat modified sensor signals in vehicle type B and having the control unit of vehicle B perform an additional verification of the sensor signals. If implausible sensor signals which do not correspond to the modification of the sensor signals compared to vehicle type A are detected during this verification, the control unit prevents the control of the internal combustion engine in that the corresponding control signals are not determined for controlling the internal combustion engine. 
         [0018]    In principle, the device of the present invention is capable of working with any type of sensor signals to perform a verification to determine whether the sensor signals match the corresponding control unit for the relevant internal combustion engine. Sensors, however, may be used that are not easily exchangeable. The sensors for the crankshaft angle and the camshaft angle are therefore suitable in particular, since these sensors require a corresponding sensor wheel disc which is fixedly joined to crankshaft  11  and camshaft  12 . It is only possible to exchange these sensor discs with great effort, making it particularly difficult to overcome this form of assignment of control unit  1  to the internal combustion engine. 
         [0019]      FIGS. 2   d  and  2   e  show additional alternative embodiments of marks  26  on a camshaft sensor wheel  25  which may also be used to verify whether the control unit is used for a correspondingly provided internal combustion engine.  FIG. 2   d  shows a signal sequence in a sensor wheel having a mark  26  as in the curve according to  FIG. 2   b.  However, an additional mark  33  which is positioned after mark  26  on the camshaft is provided. A sensor wheel that generates a signal sequence according to  FIG. 2   b  would thus be used for engines of type A. A sensor wheel that generates a signal sequence according to  FIG. 2   d  would be used for combustion engines of type B. Therefore, the same software could be used in vehicle B in order to generate the control signals for activating the internal combustion engine. However, an additional query routine that verifies after mark  26  if a signal corresponding to mark  33  also occurs would be provided. If this signal of mark  33  does not occur, the control unit determines that although it is intended for an internal combustion engine of type B, it is being used for operating an internal combustion engine of type A and it would accordingly stop generating control signals. 
         [0020]      FIG. 2   e  shows another signal sequence of a camshaft sensor wheel  25 , mark  26  in this case simply being significantly wider than in the signal curve according to  FIG. 2   b.  Again, the same software could be used as for evaluating the signal sequence according to  FIG. 2   b,  i.e., when gap  23  occurs in the crankshaft signal, it would be determined if a corresponding camshaft signal is present. This would be possible either based on the ascending signal flank of signal  26  or even by a simple level query. To determine if the control unit is used for a type B internal combustion engine, a check is simply made after gap  23  to determine whether the signal level of the camshaft signal is still high. The control unit is thus able to evaluate if it is used for a type A or B internal combustion engine and accordingly stop generating control signals in the case of incorrect use. 
         [0021]    An attempt could be made to make it possible to use a control unit for a type B engine in a type A engine by inserting a signal forming circuit between the sensors and the control unit, which based, for example, on the signal curve according to  FIG. 2   b,  generates a signal curve as in  FIGS. 2   c,    2   d  or  2   e.  To prevent this, an additional measure may be provided and will now be explained with reference to  FIG. 3 .  FIG. 3   a  shows rotational speed n plotted against time t. The state shown in  FIG. 3   a  corresponds to a starting event of the internal combustion engine in which the engine is started by operating a starter at a rotational speed in the order of magnitude of several hundreds of revolutions per minute. Corresponding to the rotation of the engine caused by the starter, corresponding sensor signals are also generated, for example, sensor signals of the camshaft sensor shown in  FIG. 3   b.  When the engine is driven by a starter, the rotational speed is subject to fluctuations resulting from the fact that the rotational resistance of the engine is of varying strength. Whenever one of the cylinders compresses the gas mixture contained therein, as is the case before combustion in four-cylinder engines, a very high force must be applied in order to rotate the engine, which is noticed as a reduction of the rotational speed of the engine driven by the starter. The rotational speed thus fluctuates between a low value n 1  and a high value n 2 . Minimums  101  through  104  of the rotational speed as shown in  FIG. 3   a  thus correspond to the operating points at which a compression event occurs in a cylinder. Analyzing the rotational speed thus makes it possible to determine when a compression event occurs in a cylinder. If the sensor discs are designed in such a way that either mark  26  on the camshaft or gap  23  on the crankshaft has a fixed position relative to the compression events in the cylinders, this rotational speed curve may be used to determine if the engine is of type A or B. To that end, the camshaft signals are plotted in  FIGS. 3   b  and  3   c  as used already in  FIGS. 2   b  and  2   c.  The evaluation of the rotational speed signal and comparison with the corresponding camshaft signal thus makes it possible to determine if mark  26  occurs precisely at a minimum of rotational speed or even at a specific offset relative to a rotational speed minimum  100  through  104 . Therefore, this evaluation may also be used to verify how mark  26  and camshaft  12  are assigned relative to the cylinders. Control unit  1  is thus able to determine if it is being used for an appropriately provided engine type or another engine type. 
         [0022]    The signal curves of the crankshaft signals as described in  FIGS. 2   b  and  2   c  are shown in  FIG. 3 . However, it is just as possible to evaluate the signal curves of curves  2   d  and  2   e  or even the relative position of gap  23  relative to the rotational speed minimums of curve  3   a.    
         [0023]    Since the starting phase of the engine is a highly dynamic phase, it is extremely difficult to simulate this signal using a corresponding signal-forming circuit. This method may thus be used as an additional safeguard.