Device for controlling an internal combustion engine

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.

RELATED APPLICATION INFORMATION

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

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

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.

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

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.

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.

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.

Exemplary embodiments of the present invention are depicted in the drawings and explained in greater detail in the following description.

DETAILED DESCRIPTION

FIG. 1shows a schematic representation of a device1for controlling an internal combustion engine which is connected to sensors3and4via connecting leads2. Only crankshaft11and camshaft12of the internal combustion engine itself are shown schematically inFIG. 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 inFIG. 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 wheel21, having a plurality of teeth22is connected to crankshaft11.

These teeth are equally spaced around the entire circumference of sensor wheel21, a tooth22not being present at one point so that a gap23is formed there. Teeth22of sensor wheel21move past sensor3. Each time a tooth22passes sensor3, a pulse is generated in sensor3which is emitted to control device1via line2. By evaluating these pulses, control unit1is able to infer the movement of crankshaft11. Camshaft12has a camshaft sensor disc25to which a mark26is affixed. When mark26brushes past sensor4, a pulse is generated which is fed to control device1via lead2. This pulse enables control device1to infer the rotation of camshaft12.

Customarily, teeth23or mark26are made of soft magnetic material and they move past sensors3,4, which are designed either as inductive sensors or Hall effect sensors. Corresponding pulses which are supplied to control device1via leads2are thus generated. Sensor discs21and25are fixedly joined to the particular shafts, i.e., crankshaft11and camshaft12. The position of gap23and mark26indicates a fixedly set angle of crankshaft11and camshaft12, respectively. This information therefore informs control device1of the position assumed by the cylinders of the internal combustion engine when brushing past gap23or mark26.

The signal of sensor3, i.e., of the crankshaft angle sensor, is plotted against time t on curve A inFIG. 2. The signal of sensor4, 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 sensor3is made up of a sequence of pulses having identical spacing from one another inFIG. 2a. This is the case when the internal combustion engine rotates at a constant speed. The absence of a signal caused by gap23is clearly evident. This gap is also denoted by reference numeral23and the pulses of teeth22are denoted by reference symbol22in curve A. Crankshaft11rotates twice as fast as camshaft12so that it can be seen in curve B that the pulse of mark26occurs only at the time each second gap23occurs. Camshaft sensor discs21and25are designed and affixed to the corresponding shafts in such a way that the signal of mark26in camshaft angle sensor4occurs exactly at the time a signal is absent in crankshaft angle sensor3due to gap23.

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 gap23occurs, a check is performed to determine whether the signal of mark26is present. However, it is of no significance for the detection of the relevant working cycle of the internal combustion engine whether mark26coincides exactly with gap23or whether this signal appears offset by one or two teeth relative to gap23. Such an alternative signal curve, which is based on correspondingly changed positioning of mark26on sensor disc25, is shown inFIG. 2c. As can be readily seen, the appearance of mark26relative to gap23is offset by two teeth22inFIG. 2c. This is irrelevant for the purpose of control, since only the information concerning the working cycle to which gap23must be assigned in the crankshaft signal of curve A is needed. In the case of curve C, it is not checked during gap23if mark26has appeared in gap23or instead two teeth22after gap23.

The information as to whether mark26appears during gap23or 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.

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 crankshaft11and camshaft12. It is only possible to exchange these sensor discs with great effort, making it particularly difficult to overcome this form of assignment of control unit1to the internal combustion engine.

FIGS. 2dand2eshow additional alternative embodiments of marks26on a camshaft sensor wheel25which may also be used to verify whether the control unit is used for a correspondingly provided internal combustion engine.FIG. 2dshows a signal sequence in a sensor wheel having a mark26as in the curve according toFIG. 2b. However, an additional mark33which is positioned after mark26on the camshaft is provided. A sensor wheel that generates a signal sequence according toFIG. 2bwould thus be used for engines of type A. A sensor wheel that generates a signal sequence according toFIG. 2dwould 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 mark26if a signal corresponding to mark33also occurs would be provided. If this signal of mark33does 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.

FIG. 2eshows another signal sequence of a camshaft sensor wheel25, mark26in this case simply being significantly wider than in the signal curve according toFIG. 2b. Again, the same software could be used as for evaluating the signal sequence according toFIG. 2b, i.e., when gap23occurs 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 signal26or 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 gap23to 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.

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 toFIG. 2b, generates a signal curve as inFIGS. 2c,2dor2e. To prevent this, an additional measure may be provided and will now be explained with reference toFIG. 3.FIG. 3ashows rotational speed n plotted against time t. The state shown inFIG. 3acorresponds 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 inFIG. 3b. 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 n1and a high value n2. Minimums101through104of the rotational speed as shown inFIG. 3athus 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 mark26on the camshaft or gap23on 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 inFIGS. 3band3cas used already inFIGS. 2band2c. The evaluation of the rotational speed signal and comparison with the corresponding camshaft signal thus makes it possible to determine if mark26occurs precisely at a minimum of rotational speed or even at a specific offset relative to a rotational speed minimum100through104. Therefore, this evaluation may also be used to verify how mark26and camshaft12are assigned relative to the cylinders. Control unit1is thus able to determine if it is being used for an appropriately provided engine type or another engine type.

The signal curves of the crankshaft signals as described inFIGS. 2band2care shown inFIG. 3. However, it is just as possible to evaluate the signal curves of curves2dand2eor even the relative position of gap23relative to the rotational speed minimums of curve3a.

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.