Abstract:
A method for monitoring at least one part of an internal combustion engine based on a variable whose values characterize the operation of the part of the internal combustion engine during different states of the internal combustion engine, including: determining an actual pattern with the actual values of the variable during different states of the internal combustion engine which describe the actual operation of the internal combustion engine; providing a reference pattern for a known operation of the internal combustion engine, the reference pattern including reference values of the variable for different states of the internal combustion engine; and comparing the actual pattern to the reference pattern to determine a similarity between the actual operation and the known operation.

Description:
RELATED APPLICATION INFORMATION 
       [0001]    The present application claims priority to and the benefit of German patent application no. 10 2011 083 587.3, which was filed in Germany on Sep. 28, 2011, the disclosure of which is incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to error detection in internal combustion engines. 
       BACKGROUND INFORMATION 
       [0003]    On board diagnostic systems are known from the automotive technology. These systems are vehicle diagnostic systems which monitor all emission-influencing systems during the operation and store possibly arising errors in a memory so that they may be queried and, if necessary, eliminated. 
         [0004]    Common monitoring functions in the air system for internal combustion engines are in most cases configured in such a way that a characteristic (for example, system deviation) is determined from inputs (sensors, model values, . . . ) under certain release conditions used to establish an operating range. For this purpose, the air system must either be transferred into the established operating range or the monitoring functions must wait until the air system is transferred on its own into the established operating range. As soon as the air system is transferred into this established operating range, the characteristic is compared to the boundaries and an error is detected in the case of (permanent) exceedance of the boundaries. 
         [0005]    Such common monitoring functions, however, monitor the air system only for their correct function and detect a malfunction per se. If a malfunction of the air system is determined, such common monitoring functions are presently not capable of qualifying this error. This makes the error diagnosis and the error cause investigation more difficult. Furthermore, it is possible that such common monitoring functions do not detect some of the errors at all. These are, in particular, those errors which do not result in any malfunctions of the internal combustion engine in the established operating range. This may be a soot clot, for example, which has settled in a valve and holds the valve open permanently. If the established operating range for the error diagnosis includes the valve in an open position, it is not possible to detect this error. 
         [0006]    One possibility would be to monitor the air system over time. This is, however, complicated since a large amount of memory space is needed to store and evaluate the monitored signals. The evaluation itself is only marginally efficient since the air system greatly changes over time, resulting in errors being detectable only with great difficulties or not at all. 
       SUMMARY OF THE INVENTION 
       [0007]    It is therefore an object of the exemplary embodiments and/or exemplary methods of the present invention to provide a method for monitoring at least one part of an internal combustion engine with the aid of an efficient error monitoring which makes an error cause investigation possible and uses only few resources. 
         [0008]    The object may be achieved by the features of the systems and/or methods described herein. 
         [0009]    Additional advantageous embodiments are described in the further descriptions herein. 
         [0010]    According to a first aspect of the exemplary embodiments and/or exemplary methods of the present invention, a method for monitoring at least one part of an internal combustion engine based on a variable whose values characterize the operation of the part of the internal combustion engine during different states of the internal combustion engine includes the following steps:
       determining an actual pattern with the aid of actual values of the variable during different states of the internal combustion engine which describe the actual operation of the internal combustion engine;   providing a reference pattern for a known operation of the internal combustion engine, the reference pattern including reference values of the variable for different states of the internal combustion engine; and   comparing the actual pattern to the reference pattern to determine a similarity between the actual operation and the known operation.       
 
         [0014]    The above-mentioned method has the advantage that, compared to the conventional methods for error monitoring in an internal combustion engine, it makes it possible to determine an error cause or at least to narrow it down, while keeping additional technical complexity for the implementation of the method according to the present invention within limits. The method according to the present invention is based on the idea that conventional monitoring functions check a characteristic only one-dimensionally within a certain operating range, e.g., with regard to its amplitude, thus making it almost impossible to qualify the error. With the aid of the above-mentioned method, the characteristic to be monitored is detected two-dimensionally as a pattern via its amplitude as well as as a function of the operating state, and may thus be compared to different reference patterns for different error causes. 
         [0015]    Even if it is not possible to exactly assign the measured pattern to a reference pattern and thus to a known error cause, due to a similarity between the measured pattern and the known error pattern, a statement may be made with regard to what errors may be considered as causes for the malfunction of the internal combustion engine. This narrowing down of error causes saves the technician time during the repair of the internal combustion engine. The method according to the present invention is implementable with little memory space since, in contrast to recording the operating behavior of the internal combustion engine over time during a certain operating state, characteristic measurements which were carried out twice do not have to be stored twice. This reduces the number of the necessary measurements to be stored and processed and reduces the technical complexity to a minimum with regard to practical implementation of the method according to the present invention. 
         [0016]    According to another aspect of the exemplary embodiments and/or exemplary methods of the present invention, a device for monitoring at least one part of an internal combustion engine based on a variable whose values characterize the operation of the part of the internal combustion engine during different states of the internal combustion engine includes the following characteristics:
       an observation device for outputting an actual pattern with the aid of actual values, detected by the observation device, of the variable during different states of the internal combustion engine which describe the actual operation of the internal combustion engine;   a memory which is designed to store a reference pattern for a known operation of the internal combustion engine, the reference pattern including reference values of the variable for different states of the internal combustion engine; and   an evaluation device which is designed to compare the actual pattern to the reference pattern in order to determine a similarity between the actual operation and the known operation.       
 
         [0020]    In one embodiment of the present invention, the observation device may include the following characteristics in the method according to the present invention or in the device according to the present invention:
       a sensor for detecting a measured variable as a function of the state of the internal combustion engine;   a modeling unit for outputting a model variable of the internal combustion engine; and   an arithmetic unit for calculating the actual values of the variable based on the model variable and the measured variable.       
 
         [0024]    By calculating the variable from model variables and measured variables, it is possible to select, for the characteristic to be monitored, an easily understandable and comprehensible variable whose values are easily interpretable and understandable to a technician during the repair of the internal combustion engine so that these values may provide other important information regarding a quick narrowing down of the error cause. 
         [0025]    In one refinement of the exemplary embodiments and/or exemplary methods of the present invention, the observation device for assigning the actual values to the corresponding operating states in the actual pattern and the evaluation device for comparing the actual pattern to the reference pattern may be provided in the method according to the present invention or in the device according to the present invention when the actual values present in the actual pattern exceed a minimum. By taking into consideration the actual pattern starting from a certain number of measured actual values, it is possible to significantly increase the information content of the actual pattern, since the detected pattern only contains enough information for a reliable error diagnosis starting from a certain size. If the individual actual values of the actual pattern are additionally stored in a table, it is not only possible to avoid storing actual values for one single operating state twice, thus delimiting the memory space needed to establish the actual pattern to a minimum, but also to determine in a simple manner which operating state has not yet been assigned an actual value. 
         [0026]    In another embodiment of the present invention, the reference pattern in the method according to the present invention or in the device according to the present invention may be a standard pattern whose reference values indicate the error-free operation of the internal combustion engine. In this way, the error-free operation of the internal combustion engine may be incorporated into the error cause detection. 
         [0027]    In an additional refinement of the exemplary embodiments and/or exemplary methods of the present invention, the reference pattern in the method according to the present invention or in the device according to the present invention may be an error pattern whose reference values indicate the operation of the internal combustion engine at a known error. 
         [0028]    In another embodiment of the exemplary embodiments and/or exemplary methods of the present invention, in the method according to the present invention or in the device according to the present invention, a standard pattern having reference values during the error-free operation of the internal combustion engine may be stored in the memory as a reference pattern and at least one reference pattern having reference values during the operation of the internal combustion engine at a known error may be stored in the memory, and the evaluation device may be provided for determining the distances between the actual pattern and the individual reference patterns and for outputting an error when the distance is smaller to the error pattern than to the standard pattern. By comparing the distances to the standard pattern and to the error pattern, tolerances in the monitoring function may be considered which do not allow an error to be output until a certain degree is reached. 
         [0029]    In another refinement of the exemplary embodiments and/or exemplary methods of the present invention, in the method according to the present invention or in the device according to the present invention the comparison unit may be provided for transferring the internal combustion engine into the operating states for which actual values for the actual pattern are not yet available. In this way, the detected pattern may be expanded until a reliable error measurement may be ensured with the aid of the monitoring function according to the present invention. 
         [0030]    According to another aspect of the exemplary embodiments and/or exemplary methods of the present invention, an air system for supplying a combustion engine of an internal combustion engine with gas for a combustion cycle of the combustion engine includes a device according to the present invention for monitoring the air system based on a variable whose values characterize the operation of the air system during different states of the internal combustion engine. The gas may be fresh air to which exhaust gas has additionally been added. 
         [0031]    In one refinement of the exemplary embodiments and/or exemplary methods of the present invention, the variable may be a volumetric efficiency factor which indicates how much gas is taken in by a combustion engine of the internal combustion engine during a combustion cycle in relation to a theoretically possible gas intake volume. Since the volumetric efficiency factor is already made available by the filling control in the internal combustion engine, the time constant at which the volumetric efficiency factor is present essentially corresponds to the time constant of the filling control. Therefore, the monitoring function is particularly fast. 
         [0032]    In the following, specific embodiments of the present invention are elucidated in greater detail with reference to the appended drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0033]      FIG. 1  shows a block diagram of a monitoring function in a device according to the present invention. 
           [0034]      FIG. 2  shows a first diagram to illustrate the monitoring function according to the present invention from  FIG. 1 . 
           [0035]      FIG. 3  shows a second diagram to illustrate the monitoring function according to the present invention from  FIG. 1 . 
           [0036]      FIG. 4  shows a block diagram to illustrate the air system in an internal combustion engine. 
           [0037]      FIG. 5  shows a block diagram to illustrate the calculation of the volumetric efficiency factor in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0038]      FIG. 1  shows the block diagram of a monitoring function  2  of a device according to the present invention. Monitoring function  2  is implementable in an arithmetic unit (not shown). In a vehicle, such an arithmetic unit is provided by the engine control unit, for example, which may thus also execute monitoring function  2 . 
         [0039]    Monitoring function  2  includes a model  4  and an evaluation device  8 . Based on the values of different measured variables  10  and model variables  12 , model  4  calculates a monitoring variable  6  which is made available to the comparison section. The values of measured variables  10  are delivered by sensors (not shown) in an internal combustion engine (not shown). Model variables  12  describe boundary conditions using which the at least one part of the internal combustion engine, such as air system  46  of the internal combustion engine which is explained later with reference to  FIG. 4 , may be simulated. 
         [0040]    The exemplary embodiments and/or exemplary methods of the present invention are described below in a non-limiting manner based on a monitoring of air system  46  of the internal combustion engine. To clearly illustrate the exemplary embodiments and/or exemplary methods of the present invention, volumetric efficiency factor  6 , which indicates how much gas is taken in by a combustion engine of the internal combustion engine during a combustion cycle in relation to a theoretically possible gas intake volume, is chosen as monitoring variable  6 , as an example. 
         [0041]    In evaluation device  8 , volumetric efficiency factor  6  is supplied to an assignment unit  14 . Assignment unit  14  assigns an operating state  16  of the air system of the internal combustion engine to received volumetric efficiency factor  6  and stores this assignment in a table (not shown). Operating state  16  may be deduced from different characteristics of the air system. For example, the air system may be transferred into a spatial illustration of the state known to those skilled in the art from which operating state  16  needed for the assignment may be obtained. Alternatively, operating state  16  may be deduced from certain elements of the air system. For example, the opening degree of the throttle valve for the gas supply may be used as operating state  16 . 
         [0042]    From the assignment of volumetric efficiency factor  6  to operating state  16  during different operating states  16 , a pattern  18  results in assignment unit  14 , the pattern representing the actual behavior of air system  46  of the internal combustion engine. Therefore, this pattern is referred to in the following as actual pattern  18 . Actual pattern  18 , thus represents a characteristics line from which a volumetric efficiency factor  6  may be unambiguously obtained for each operating state  16  of air system  46 . 
         [0043]    Actual pattern  18  is output to a comparison unit  20  which compares actual pattern  18  to at least one reference pattern  22  and determines the degree of similarity between this reference pattern  22  and actual pattern  18 . Reference pattern  22  may show the behavior of air system  46  during error-free operation or the behavior of air system  46  during the operation at a known error. The exact determination of the similarity between reference pattern  22  and actual pattern  18  will be discussed later in this application. 
         [0044]    In the following, it is assumed that reference pattern  22  represents the behavior of air system  46  during error-free operation, and is thus referred to as standard pattern  22 . Furthermore, two additional reference patterns  24 ,  26  which identify the behavior of air system  46  at a first known error and a second known error, respectively, are supplied to comparison unit  20 . Accordingly, the two additional reference patterns  24 ,  26  are referred to as first error pattern  24  and second error pattern  26 . 
         [0045]    Standard pattern  22  as well as first and second error patterns  24 ,  26  are accordingly stored in a first, second, and third memory area  28 ,  30 ,  32  in evaluation device  8 . 
         [0046]    The result of the comparison, and thus the specification of whether and due to what error the air system malfunctions, may eventually be made available in an output signal  29 . 
         [0047]    Comparison unit  20  may also output a control signal  34  to air system  46 , using which air system  46  may be forced into a predetermined operating state in order to complete actual pattern  18 , if necessary. This will be discussed in detail later in this application. 
         [0048]    Reference is made to  FIG. 2  which shows a first diagram  36  to illustrate monitoring function  2  according to the present invention. 
         [0049]    In the diagram, volumetric efficiency factor  6  is plotted qualitatively against operating state  16 . In first diagram  36 , actual pattern  18  is illustrated qualitatively using a solid line. First error pattern  24  and second error pattern  26  are each identified by dashed lines in first diagram  36 . 
         [0050]    In this first diagram  36 , comparison unit  20  may determine a first difference area  38  which is determined from the areas below actual pattern  18  minus the area below first error pattern  24 . In the same manner, comparison unit  20  may determine a second difference area  40  which is determined from the areas below actual pattern  18  minus the area below second error pattern  26 . Difference area  38 ,  40  having the smallest absolute value indicates that its corresponding reference pattern  24 ,  26  is most similar to actual pattern  18 . In output signal  29 , corresponding reference pattern  24 ,  26  or corresponding information may be output regarding reference pattern  24 ,  26  which has been assigned as being most similar to actual pattern  18 . 
         [0051]    Reference is made to  FIG. 3  which shows a second diagram  42  to illustrate monitoring function  2  according to the present invention. Similarly to first diagram  36 , volumetric efficiency  6  is plotted against operating state  16 . 
         [0052]    Second diagram  42  additionally shows standard pattern  22  and a third error pattern  44  (not shown in  FIG. 1 ). Moreover, second diagram  42  shows an incomplete actual pattern  18 . As is easily apparent in second diagram  42 , it is not clearly attributable from incomplete actual pattern  18  whether actual pattern  18  is more similar to standard pattern  22  or second error pattern  26 . 
         [0053]    The dotted lines between the solid lines of actual pattern  18  indicate what the shape of actual pattern  18  which has not yet been measured might look like. For completion, the shape could be interpolated in comparison unit  20 , whereby the missing information is available in real-time and without further interventions into air system  46 . If, however, the missing areas in actual pattern  18  are too large, there is the risk of the interpolation result being too inaccurate and inconclusive. To avoid this, it is possible, as shown in  FIG. 1 , to transfer air system  46  into missing operating states  16  with the aid of a control signal  34  from monitoring function  2  in order to complete actual pattern  18  insofar that a reliable statement with regard to the behavior of air system  46  may be made based on a comparison to standard pattern  22  and error patterns  24 ,  26 ,  44 . 
         [0054]    Similarly to  FIG. 2 , the difference areas with regard to individual reference patterns  22 ,  24 ,  26 ,  44  may also be determined for actual pattern  18  in  FIG. 3 . In one embodiment, a threshold value, which determines starting from which size a difference area is interpreted as an error in air system  46 , may also be stored in comparison unit  20 . In this case, comparison unit  20  may output in output signal  29  all error patterns  24 ,  26 ,  44  whose difference areas with actual pattern  18  fall below the threshold value. Thus, in the case of an erroneous operation of the air system, more likely error causes may be separated from the less likely error causes to narrow down the error cause. 
         [0055]    Subsequently, the determination of volumetric efficiency factor  6  is described with reference to  FIGS. 4 and 5 . Volumetric efficiency factor  6  is measured in air system  46  which is illustrated in  FIG. 4  as a block diagram. It supplies a combustion engine  48  with an engine intake gas mass flow  50  and outputs the combusted engine intake gas mass flow in the form of exhaust gas  52 . Engine intake gas mass flow  50  is composed of fresh air  54  and a recirculated portion  56  of exhaust gas  52 , supplied fresh air  54  being controlled via a throttle valve  58  and recirculated exhaust gas  56  via an exhaust gas recirculation valve  60 . Fresh air  54  and recirculated exhaust gas  56  are mixed in a junction  62 . 
         [0056]    To determine volumetric efficiency factor  6 , various sensors are available in air system  46 . They allow at least some measured variables to be determined redundantly, thus increasing the information content of the volumetric efficiency factor. 
         [0057]      FIG. 5  shows calculation function  64  which calculates the volumetric efficiency factor in model  4  of  FIG. 1 . As shown in  FIG. 5 , the mass flow through exhaust gas recirculation valve  60 , referred to as an EGR mass flow in the following, is initially determined in two different ways. A first EGR mass flow  66  is determined directly at exhaust gas recirculation valve  60 . A second EGR mass flow  68  is determined via balancing the mass flow of fresh air  54  and engine intake gas mass flow  50 . Theoretically, both EGR mass flows  66 ,  68  are the same. Practically, however, they deviate from one another due to measuring errors and other inaccuracies in the measuring system. An estimation function  70 , which is not described in greater detail in the following, is used to select EGR mass flows  66 ,  68  having the highest information content. Estimated EGR mass flow  72  is subsequently converted via a thermodynamic approach using measured temperature  74  of EGR mass flow  72  into an enthalpy flow  76  through exhaust gas recirculation valve  60 , and it is balanced with enthalpy flow  78  of fresh air  54 , thus resulting in an estimated enthalpy flow  80  through combustion engine  48 . 
         [0058]    Using pressure  82  of fresh air  54 , volumetric efficiency factor  6  may finally be determined via another thermodynamic approach. 
         [0059]    The exemplary embodiments and/or exemplary methods of the present invention provide for ascertaining errors in a part of an internal combustion engine by the operating state-dependent evaluation of a variable in the part of the internal combustion engine.