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Method of operating an internal combustion engine, in particular in a motor vehicle

Method of operating an internal combustion engine, in particular in a motor vehicle description/claims

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.

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.

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