Abstract:
The invention relates to a method for correcting the input signal of a function by means of which misfire is detected and for synchronizing the cylinders in an internal combustion engine, especially of a vehicle. According to the invention, a control device for correcting the input signal ( 10 ) and a control device for synchronizing the cylinders ( 11 ) are alternately activated by means of an alternative switching unit ( 12 ).

Description:
[0001]    The invention relates to a method for the input signal correction of a misfire detection function and for the cylinder equalization in an internal combustion engine, especially of a motor vehicle, corresponding to the preamble of claim  1 .  
         STATE OF THE ART  
         [0002]    Methods for detecting combustion misfires by means of determining a rough running are known, if required, while considering filtered rough-running values. Likewise, methods for improving the quality of the combustion misfire detection, for example, by means of transducer wheel adaptations or general adaptations, belong to the state of the art. An optimization of the combustion misfire detection of this kind is known under the designation “fuel-on-adaptation”. The fuel-on-adaptation is based on rough-running values or segment times of the internal combustion engine and learns transducer wheel faults and torque differences between the individual cylinders during operation of the engine. When learning the transducer wheel faults and the torque differences, corrective values are formed by the fuel-on-adaptation with which the instantaneously present segment times or the rough-running values, are corrected. Here, only the input signals of a misfire detection function are changed. A correction utilizing the fuel-on-adaptation has no effect on the engine as can take place, for example, in the form of a torque correction via an injected quantity of fuel increased in a suitable manner.  
           [0003]    In gasoline direct injection systems, a cylinder equalization functions to cancel torque differences of individual cylinders during the operation of the engine. Torque differences of this kind amongst the individual cylinders can, for example, occur because of scattered differences of individual injection valves, which are present (manufacturing inaccuracies which cannot be avoided) or these torque differences can occur because of valve coking. A control for cylinder equalization determines the torque deviations amongst the individual cylinders on the basis of rough-running values during the operation of the engine. The cylinder torques are preferably equalized in a stratified operation by adapting the cylinder-individual injection quantity of fuel in the form of a dynamic control. The cylinder equalization functions to correct for cylinder-individual correction of the injection times in dependence upon the cylinder torques which are adjusted in each case. The corrected injection times have, in turn, an influence on the cylinder torque. Accordingly, an effect of the injection times on the cylinder torque is present so that torque differences amongst the cylinders can be controllable to the value zero via the control for cylinder equalization.  
           [0004]    It is disadvantageous that a trouble-free function of the fuel-on-adaptation and therefore a reliable misfire detection during operation of the engine is not ensured.  
         ADVANTAGES OF THE INVENTION  
         [0005]    The method of the invention is characterized in that a control for input signal correction and a control for cylinder equalization are alternatively activated. In this way, it is ensured that the activated control for input signal correction (fuel-on-adaptation) is not negatively influenced by the simultaneous activation of the control for cylinder equalization. Such a disturbance of the control for fuel-on-adaptation is especially caused by the situation that a correction of the input signals of misfire detection functions takes place also on the basis of the cylinder torques which, in turn, are corrected by means of the cylinder equalization. The cylinder equalization thereby influences the fuel-on-adaptation via the cancellation of torque differences between individual cylinders by means of cylinder-individual correction of the injection times. This is&#39; so, because the fuel-on-adaptation corrects the input signals of misfire detection functions, inter alia, on the basis of the cylinder torques. A reliable misfire detection and simultaneously an effective cylinder equalization is ensured during operation of the engine because of the alternative activation of the control for input signal correction and the control for cylinder equalization. This is so because the control for fuel-on-adaptation can only be activated at a time point at which the control for the cylinder equalization is not activated and vice versa.  
           [0006]    A cylinder torque correction takes place for cylinder equalization and is advantageously considered by the activated input signal correction control. A detection and consideration of a cylinder torque correction is ensured in a reliable manner for an activated input signal control because of the alternative activation of the two controls. The cylinder torque correction was initiated by the previously activated cylinder equalization control for cylinder equalization.  
           [0007]    According to a first embodiment, the cylinder torque correction values of the input signal correction control are incorporated in corresponding input signal correction values. In this way, and by means of a direct and time-proximate computation of the cylinder torque correction values with the input signal correction valves, a continuously adapted input signal correction is maintained during the activation of the corresponding control.  
           [0008]    According to a second embodiment, the particular cylinder torque correction value is maintained constant when the input signal correction control is activated until the difference between a pregiven desired value and an actual value of the cylinder torque correction exceeds a fixable threshold value whereupon a new constant actual value is adjusted to the pregiven desired value and the input signal correction control is reset. Here, the cylinder torque value of the particular poorest cylinder is applied for the actual value. The desired value is adjusted as a new constant actual value for all cylinders. The input signal correction control (fuel-on-adaptation) is reset to neutral start values because of the reset thereof. In this way, the fuel-on-adaptation starts the learning proceeding from neutral start values. After the reset of the fuel-on-adaptation, the thresholds of a misfire detection are increased and are only lowered again after advanced fuel-on-adaptation.  
           [0009]    In an advantageous manner, the cylinder equalization control adjusts the injection time at least for the next combustion for each cylinder in dependence upon the cylinder torque, which adjusts after each combustion. In this way, a reliable and effective cylinder equalization is ensured during the operation of the engine.  
           [0010]    It is advantageous that the input correction forms corrective values for adjusting the input signals of at least one misfire detection function for each cylinder individually in dependence upon the degree of rough running and/or the segment times. In this way, the quality of the combustion misfire detection is improved or optimized in a reliable manner.  
           [0011]    Preferably, the activation of the input signal correction control and the cylinder equalization control takes place via an alternative switching unit. Alternative switching units permit an alternative activation of the control for the input signal correction and the control for cylinder equalization in a reliable, rapid and automatic manner.  
           [0012]    Additional advantageous configurations of the invention become evident from the description. 
       
    
    
     DRAWINGS  
       [0013]    The invention will be explained in greater detail in the following in an embodiment with respect to a corresponding drawing.  
         [0014]    [0014]FIG. 1 is the only figure and shows a block circuit diagram for misfire detection and for cylinder equalization on a cylinder of an internal combustion engine. 
     
    
     DESCRIPTION OF THE INVENTION  
       [0015]    With respect to FIG. 1, an input signal correction control  10  and a cylinder equalization control  11  are shown which are operatively connected to a cylinder  14  of an internal combustion engine (not shown). An alternative switching unit  12  is operatively connected to the input signal correction control  10  and the cylinder equalization control  11  via corresponding control lines shown as double arrows ( 17 ,  18 ) in such a manner that either the control  10  or the control  11  can be activated but not both the controls ( 10 ,  11 ) simultaneously.  
         [0016]    The cylinder equalization control  11  is operatively connected to an injection time control unit  13  by means of a control line shown as arrow  20 . The injection time control unit  13 , in turn, can adjust the injection time at least for the next combustion in the cylinder  14  via a control line shown as arrow  22  or can adapt the injection time to the particular operating situation of the engine. A data transmission line is shown as arrow  23  and leads from cylinder  14  to a torque detecting unit  15 , which is connected to the cylinder equalization control  11  via the data transmission line illustrated as arrow  25 . The injection control unit  13 , the cylinder  14 , and the torque detecting unit  15  are thereby operatively connected to the cylinder equalization control as a closed control loop by means of the lines  20 ,  22 ,  23  and  25 .  
         [0017]    The input signal correction control  10  is also characterized as “fuel-on-adaptation” and is connected to a misfire detection function unit  16  via a data transmission line shown as arrow  19 . The misfire detection function unit  16  is, in turn, in operative effective contact with the cylinder  14  via a connection shown as arrow  21 . A data transmission line shown as arrow  24  leads from the torque detecting unit  15  to the input signal correction control  10  and a data transmission line shown by arrow  26  leads from the cylinder  14  to the input signal correction control  10 .  
         [0018]    In FIG. 1, only a single cylinder  14  of the engine is schematically shown for reasons of clarity. The internal combustion engine (not shown) however normally includes a plurality of cylinders which are in operative effective contact with the input signal correction control  10  and the cylinder equalization control  11  in accordance with FIG. 1. The schematic representation corresponding to FIG. 1 can therefore be transferred to all additional cylinders of an engine (not shown).  
         [0019]    The control of the input signal correction  10  and the control of the cylinder equalization  11  are alternatively activated because of the alternative circuit unit  12 . After a combustion, the cylinder equalization  11  adjusts the injection time at least for the following combustion in cylinder  14  by means of the injection time control unit  13  in dependence upon the particular cylinder torque which adjusts. For each cylinder individually, the input signal correction control  10  forms corrective values for adjusting the input signals for the misfire detection function unit  16  in dependence upon the degree of rough running and/or in dependence upon the segment time. Corresponding data are transmitted to the input signal correction control  10  via the data transmission lines in accordance with arrows  24 ,  26 . Data with respect to the cylinder torque or its changes are transmitted to the input signal correction control  10  as well as to the cylinder equalization control  11  via data transmission lines in accordance with arrows  24 ,  25 . The cylinder torque adjusts in each case after a combustion in cylinder  14 . The cylinder equalization control  11  corrects the cylinder-individual injection times on the basis of the cylinder torques. These injection times, in turn, exercise influence on the cylinder torques of the respective subsequent combustions. Because of the control loop, the cylinder equalization control  11  is suitable to control to the value zero possibly occurring torque differences between the individual cylinders of the engine. The input signal correction control  10  also considers the respective values of the cylinder torques which are transmitted thereto by the torque detection unit  15  via the data transmission line shown as arrow  24 . Additionally or as alternative, the segment times for forming the input signal corrective values can be considered.  
         [0020]    It is possible that a cylinder torque correction, which adjusts for cylinder equalization, is considered by the active input signal correction control  10  in a reliable manner because of the operative inclusion of the alternative circuit unit  12  for alternatively activating the two controls  10 ,  11 . The cylinder torque corrective values can be computed directly into corresponding input signal corrective values by the input signal correction control  19  if the control  10  is activated. In accordance with an alternative embodiment, the particular cylinder torque corrective value can also be held constant for an activated input signal correction control  10  until the difference between a pregiven desired value and an actual value of the cylinder torque correction exceeds a fixable threshold value whereupon a new constant actual value is adjusted to the pregiven desired value and the input signal correction control  10  is reset.  
         [0021]    The input signal correction control  10  and the cylinder equalization control  11  are known per se with respect to their functional and constructive configuration and are therefore not described here in greater detail.