Abstract:
The invention concerns a method and a device for determining an internal combustion engine phase. Said device comprises an intake zone, an exhaust zone, at least one camshaft which acts on the gas exchanging valves and whereof the phase can be adjusted relative to that of a crankshaft by means of a phase adjusting device, and at least one sensor whereof the measurement signal enables a specific phase to be determined. The phase adjusting device is controlled in accordance with phase adjustment of the camshaft until detection of a gas reflux from the exhaust zone to the intake zone. A correction value is determined based on the associated specific phase and on a specific allocated phase. In the next operating mode, the respectively specific phase is corrected based on the correction value.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is the US National Stage of International Application No. PCT/EP2005/056284, filed Nov. 28, 2005 and claims the benefit thereof. The International Application claims the benefits of German Patent application No. 10 2004 062 406.2 filed Dec. 23, 2004. All of the applications are incorporated by reference herein in their entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     Method and device for determining a phase of an internal combustion engine with an intake zone, an exhaust gas zone and at least one camshaft, which acts on gas exchange valves and whose phase in respect of a crankshaft can be adjusted by means of a phase adjusting device.  
       BACKGROUND OF THE INVENTION  
       [0003]     The requirements relating to the output and efficiency of internal combustion engines are becoming increasingly stringent. At the same time strict legal provisions require pollutant emissions to be kept at low levels. To this end it is known that internal combustion engines can be fitted with a phase adjusting device, which can be used to modify a phase between a crankshaft and a camshaft of the internal combustion engine during operation. The respective start and end of the opening or closing of the gas inlet and/or gas outlet valve can thus be modified in relation to a reference point on the crankshaft. This allows the level of gas in a cylinder to be modified; in particular it is possible for exhaust gas to be fed back internally into the respective cylinder.  
       SUMMARY OF THE INVENTION  
       [0004]     The object of the invention is to create a method and device for determining a phase of an internal combustion engine, allowing precise determination of the phase.  
         [0005]     The object is achieved by the features of the independent claims. Advantageous embodiments of the invention are characterized in the subclaims.  
         [0006]     The invention is characterized by a method and a corresponding device for determining a phase of an internal combustion engine with an intake zone, an exhaust gas zone and at least one camshaft, which acts on gas exchange valves and whose phase in respect of a crankshaft can be adjusted by means of a phase adjusting device, with at least one sensor, as a function of whose measurement signal a determined phase is determined. The phase adjusting device is activated to adjust the phase of the camshaft, until a reflux of gas from the outlet zone into the intake zone is identified. A correction value is then determined as a function of the determined phase then assigned and a predetermined default phase. The respectively determined phase is then corrected as a function of the correction value during subsequent operation.  
         [0007]     The phase is representative of an angle between a reference mark on both the respective camshaft and the crankshaft in a predetermined angle position of the crankshaft for example, which can for example be a top dead center during ignition of a piston of a cylinder but can also be any other predetermined angle position of the crankshaft. The sensor(s), as a function of whose measurement signal the determined phase is determined, is/are frequently incremental sensors, such as Hall sensors, with a toothed wheel as the primary element. Tolerances in the arrangement of the sensor(s), wear and/or aging of the adjusting devices result in an inaccurate or modified assignment of the measurement signal(s) of the sensor(s) and thus in errors in the determined phase.  
         [0008]     By adjusting the phase adjusting device in an appropriate manner, it is possible to achieve an operating point of the internal combustion engine, at which there is a reflux of gas from the outlet zone into the intake zone. Reflux of gas means that gas in the outlet zone flows back from the outlet zone into the intake zone during the operating cycle of the internal combustion engine.  
         [0009]     The invention hereby utilizes the knowledge that the phase, during which said reflux starts to occur, is known for the respective internal combustion engine or internal combustion engine type. It is thus possible to assign a correct phase, the default phase, on identification of the reflux. A correction value can then be determined as a function of the default phase and the phase determined when the reflux of gas from the outlet zone into the intake zone is identified and it is thus possible in subsequent operation, during optionally different activation of the phase adjusting device, to correct the phase then determined in each instance as a function of the correction value. This then allows very precise control of the internal combustion engine.  
         [0010]     According to one advantageous embodiment of the invention, the reflux of gas from the outlet zone into the intake zone is identified as a function of an intake pipe pressure. This has the advantage that an intake pipe pressure sensor, which is frequently present in any case, can easily be used to identify the reflux of gas from the outlet zone into the intake zone.  
         [0011]     In this context it is advantageous, if the reflux from the outlet zone into the intake zone is identified, when the intake pipe pressure exceeds a predeterminable intake pipe threshold value under predetermined operating conditions. This allows the reflux to be identified particularly easily. The predetermined operating conditions are preferably predetermined such that the intake pipe pressure before and during the reflux of gas can be determined sufficiently precisely and preferably does not change significantly without reflux. It can thus be advantageous, if the predetermined operating conditions for example include a stationary operating state of the internal combustion engine.  
         [0012]     According to a further advantageous embodiment of the invention, the reflux from the outlet zone into the intake zone is identified, when an amplitude of a pulsation of the intake pipe pressure exceeds a predeterminable pulsation threshold value. The pulsation is an oscillation of the intake pipe pressure with a frequency, which is a function of the rotational speed and number of the cylinders. This procedure is based on the knowledge that such a pulsation occurs during reflux and the reflux can thus be identified particularly precisely in this manner.  
         [0013]     According to a further advantageous embodiment of the invention, the reflux of gas from the outlet zone into the intake zone is identified as a function of a temperature of the gas in the intake zone. This is based on the knowledge that the temperature of the gas in the intake zone increases due to hot reflux gases. It is thus possible to use a temperature sensor that is optionally present in any case for other purposes in the intake zone to identify the reflux of gas from the outlet zone into the intake zone.  
         [0014]     According to a further advantageous embodiment of the invention, the reflux from the outlet zone into the intake zone is identified, when the temperature of the gas in the intake zone exceeds a predeterminable temperature threshold value. The reflux can thus be determined particularly easily. Particularly early identification is thus possible, without a large quantity of exhaust gas necessarily having to flow back into the intake zone.  
         [0015]     According to a further advantageous embodiment of the invention, the reflux of gas from the outlet zone into the intake zone is identified as a function of a temperature of the gas in the outlet zone. The reflux is identified, when, during an operating state of the internal combustion engine, the detected temperature changes from a value, which is representative of the absence of exhaust gases, to a temperature, which is representative of the presence of exhaust gases, without fuel being fed in.  
         [0016]     According to a further advantageous embodiment of the invention, the reflux of the gas from the outlet zone into the intake zone is identified when the temperature of the gas in the outlet zone exceeds a predeterminable further temperature threshold value.  
         [0017]     According to a further advantageous embodiment of the invention, a gas type sensor is assigned to the internal combustion engine in the outlet zone, whose measurement signal is representative of the absence or presence of exhaust gases in the region of the gas type sensor. The reflux is identified, when, during an operating state of the internal combustion engine, the measurement signal of the gas type sensor changes from a measurement signal value, which is representative of the absence of exhaust gases, to a measurement signal value, which is representative of the presence of exhaust gases, without fuel being fed in. The gas type sensor can for example be a lambda probe, even a two-position or linear lambda probe. Such a gas type sensor, i.e. in particular a lambda probe, is in any case present in internal combustion engines for lambda regulation and can thus easily be used for the purposes of identifying the reflux of gas from the outlet zone into the intake zone. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]     Exemplary embodiments of the invention are described below with reference to the schematic drawings, in which:  
         [0019]      FIG. 1  shows an internal combustion engine with a control device,  
         [0020]      FIG. 2  shows a further view of parts of the internal combustion engine according to  FIG. 1 ,  
         [0021]      FIG. 3  shows a flow diagram of a first program for determining a determined phase,  
         [0022]      FIG. 4  shows a flow diagram of a second program for determining the determined phase and  
         [0023]      FIG. 5  shows a flow diagram of a third program for determining the determined phase. 
     
    
       [0024]     Elements with the same structure or function are shown with the same reference characters in all the figures.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0025]     An internal combustion engine ( FIG. 1 ) comprises an intake zone  1 , an engine block  2 , a cylinder head  3  and an outlet zone  4 . The intake zone  1  preferably comprises a throttle valve  5 , also a manifold  6  and an intake pipe  7 , which leads to a cylinder Z 1  via an inlet channel into the engine block  2 . The engine block  2  also comprises a crankshaft  8 , which is coupled via a connecting rod  10  to the pistons  11  of the cylinder Z 1 .  
         [0026]     The cylinder head  3  comprises a valve drive with gas exchange valves, which are gas inlet valves  12  and gas outlet valves  13 , and valve drives  14 ,  15  assigned thereto.  
         [0027]     A camshaft  18  is provided, comprising a cam  16 , which acts on the gas inlet valve  12 . A phase adjusting device  20  ( FIG. 2 ) is provided, which can be used to adjust a phase between the crankshaft  8  and the camshaft  18 . This phase adjustment can for example be effected by increasing a hydraulic pressure in high-pressure chambers of the phase adjusting device  20  or reducing the corresponding pressure, depending on the direction in which the phase is to be adjusted. A possible phase adjustment region is marked with an arrow  21 .  
         [0028]     At least two camshafts  18 ,  18 ′ are preferably provided, a first camshaft  18  being assigned to the respective gas inlet valves  12  and a second camshaft  18 ′ being assigned to the respective gas outlet valves  13 . In a simple embodiment the second camshaft  18 ′ in particular can be coupled mechanically to the crankshaft  8  with a fixed phase in respect of said crankshaft  8 . It can however also be coupled to the crankshaft  8  via a corresponding phase adjusting device. In this instance the phase of the second camshaft  18 ′ can also be modified.  
         [0029]     By varying the phase between the crankshaft  8  and the camshaft  18  it is possible to modify the valve lap of the gas inlet valve  12  and the gas outlet valve  13 , in other words the crankshaft angle range, during which both an inlet and an outlet of the cylinder Z 1  are enabled. The phase adjusting device  20  and also the valve lift adjusting device  19  can also be configured in any other manner known to the person skilled in the art.  
         [0030]     The cylinder head  3  also comprises an injection valve  22  and a spark plug  23 . The injection valve  22  can alternatively also be located in the intake pipe  7 .  
         [0031]     A control device  25  is provided, to which sensors are assigned, which detect different measured variables and determine the value of the measured variable in each instance. The control device  25  determines manipulated variables as a function of at least one of the measured variables and these are then converted to one or more actuating signals to control the final control elements by means of corresponding actuators. The control device  25  can also be referred to as a device for controlling the internal combustion engine or even as a device for determining the phase of the internal combustion engine.  
         [0032]     The sensors are a pedal position sensor  26 , which detects the position of an accelerator pedal  27 , an air mass sensor  28 , which detects an air mass flow upstream of the throttle valve  5 , a throttle valve position sensor  30 , which detects the degree to which a throttle valve is open, a first temperature sensor  32 , which detects a temperature T_IM of the gas in the intake zone  1 , an intake pipe pressure sensor  34 , which detects an intake pipe pressure P_IM in the manifold  6 , a crankshaft angle sensor  36 , which detects a crankshaft angle CRK, to which a rotational speed N is then assigned. A camshaft angle sensor  39  is also provided, which detects a camshaft angle CAM. If two camshafts are present, a camshaft angle sensor  39 ,  40  is preferably assigned to each camshaft. A gas type sensor, in particular a lambda probe  42 , is also provided, which detects the oxygen content of the gas in the outlet zone and whose measurement signal is characteristic of the air/fuel ratio in the cylinder Z 1 , when fuel combustion takes place in the cylinder. A specific sensor can also be provided to detect the determined phase PH_E. The at least one sensor for detecting the determined phase PH_E can however also preferably be provided by the camshaft angle sensor  39 ,  40  and/or the crankshaft angle sensor  36 .  
         [0033]     Depending on the embodiment of the invention, any subset of the sensors mentioned can be present or additional sensors may also be present.  
         [0034]     The final control elements are for example the throttle valve  5 , the gas inlet and gas outlet valves  12 ,  13 , the phase adjusting device  20 , the injection valve  22  or the spark plug  23 .  
         [0035]     As well as the cylinder Z 1 , further cylinders Z 2  to Z 4  are preferably also provided, to which corresponding final control elements and optionally sensors are also assigned.  
         [0036]     A program for determining the phase of the internal combustion engine is stored in a program memory of the control device  25  and can be processed during operation of the internal combustion engine. Such a program is started in a step S 1  ( FIG. 3 ). Variables can optionally be initialized in the step S 1 .  
         [0037]     In a step S 2  the intake pipe pressure P_IM is detected. In a step S 4  an intake pipe pressure threshold value is determined preferably as a function of the intake pipe pressure P_IM and optionally further operating variables of the internal combustion engine. Operating variables of the internal combustion engine include measured variables and also variables derived therefrom. The intake pipe pressure threshold value is preferably determined by means of a corresponding characteristic curve or set of characteristics, determined beforehand by tests on an engine test bed or by simulations. In one simple embodiment, the intake pipe pressure threshold value TDH_P_IM can also be set permanently beforehand.  
         [0038]     In a step S 6  it is verified whether predetermined operating conditions BB_G are present. The predetermined operating conditions can for example include a largely stationary operating state and/or an operating state BZ_NF without fuel being fed in, e.g. a thrust mode of the internal combustion engine, in which no fuel is fed into the cylinders Z 1  to Z 4  through the injection valves  22 . The predetermined operating conditions BB_G are preferably selected such that any adjustment of the phase of the first camshaft  18  where possible has an insignificant impact on the running of the internal combustion engine and thus in particular on the torque generated by it and optionally the pollutant emissions it produces.  
         [0039]     It can also be advantageous if the predetermined operating conditions BB_G also include temporal conditions or conditions that are a function of drive distance. These can for example comprise the fact that the condition of step S 6  is only satisfied so often that one correction value KOR_E of the phase of the first camshaft is only determined once per engine run or within another time interval or even within a predetermined drive distance of a vehicle, in which the internal combustion engine is disposed.  
         [0040]     If the condition of step S 6  is satisfied, in a step S 8  an actuating signal SG_E is increased by an incrementation value D_SG for the phase adjusting device  20 . Alternatively the actuating signal SG_E can be correspondingly reduced for the phase adjusting device  20 . The phase adjusting device  20  is then activated based on this modified actuating signal SG_E. The intake pipe pressure P_IM is then detected once again in a step S 10 . To this end a number of individual measured values of the intake pipe pressure are preferably detected and averaged.  
         [0041]     In a step S 12  the determined phase PH_E of the first camshaft  18  is then determined as a function of the crankshaft angle CRK and camshaft angle CAM detected after implementation of the step S 8 .  
         [0042]     It is then verified in a step S 14  whether the intake pipe pressure P_IM detected in the step S 10  is greater than the intake pipe pressure threshold value THD_P_IM. It is appropriate for the intake pipe pressure threshold value THD_P_IM to be predetermined such that, if it is exceeded, in step S 14  there is a reflux of gas from the outlet zone into the intake zone. If the condition of step S 14  is not satisfied, processing continues in step S 2 . In an optionally alternative embodiment is can also continue directly in step S 6 .  
         [0043]     If however the condition of step S 14  is satisfied, in a step S 16  the correction value KOR_E of the phase of the first camshaft  18  is determined as a function of the determined phase PH_E of the first camshaft  18  and a default phase PH_G. The default phase is stored in a data memory of the control device  25  and is the essentially correct value of an actual phase of the first camshaft  18 , when the reflux due to the adjustment of the phase just starts to occur or can just be identified based on the procedure of steps S 6  to S 14 . The default phase PH_G is determined beforehand by means of corresponding calculations, simulations or tests on an engine test bed.  
         [0044]     The correction value KOR_E of the phase of the first camshaft  18  is determined in step S 16  by means of a suitable formula. Thus in a particularly simple embodiment it can be determined directly as a function of the difference between the determined phase PH_E and the default phase PH_G. The formula can however also include any weighting of the difference between the determined phase PH_E and the default phase PH_G or can even incorporate a correction value KOR_E of the phase of the first camshaft  18  determined in step S 16  during a previous run through the program. After step S 16  the program preferably continues in step S 2 . Alternatively however it can continue directly in a step S 18 .  
         [0045]     If the condition of step S 6  is not satisfied, in step S 18  the phase PH_E of the first camshaft  18  is determined as a function of the crankshaft angle CRK, the camshaft angle CAM and the correction value KOR_E. In this manner the phase of the first camshaft can thus be determined very accurately in each instance in step S 18  by means of the determined phase PH_E, thus ensuring precise control of the internal combustion engine. Step  18  is preferably processed again during operation of the internal combustion engine at predetermined time intervals or in each instance after the passage of a predeterminable crankshaft angle CRK, at least if the predetermined operating conditions BB_G of step S 6  are not present.  
         [0046]     As an alternative or addition to step S 4 , a step S 4 ′ can be provided, in which a pulsation threshold value THD_PULS is determined, preferably also as a function of the intake pipe pressure P_IM and/or further operating variables of the internal combustion engine. The pulsation threshold value THD_PULS can however also be set permanently beforehand. As an alternative or addition a step S 14 ′ can then be provided, in which it is verified whether an amplitude P_PULS of the pulsation of the intake pipe pressure P_IM is greater than the pulsation threshold value THD_PULS. The pulsation amplitude P_PULS is preferably determined by corresponding evaluation of a number of individual measured values of the intake pipe pressure P_IM detected in step S 10 . The pulsation threshold value THD_PULS is preferably selected in an appropriate manner such that, if it is exceeded, there is a reflux of gas from the outlet zone into the intake zone. According to step S 14 , if the condition of step S 14 ′ is satisfied, step S 16  is processed and, if said condition is not satisfied, step S 2  or S 6  is processed. The conditions of steps S 14  and S 14 ′ can also be verified in an appropriate combination.  
         [0047]     A second program for determining the phase of the internal combustion engine is started in a step S 20  ( FIG. 4 ), in which variables are optionally initialized. The second program and a third program to be described in more detail below with reference to  FIG. 5  can be executed as an alternative to the first program or even as supplements to each other or in combination with each other. The differences compared with the steps of the first program are essentially described below.  
         [0048]     In a step S 22  the temperature T_IM of the gas in the intake zone  1  is determined. In a step S 24  a temperature threshold value THD_T_IM is then determined as in step S 4 . In a step S 26  it is verified according to step S 6  whether the predetermined operating conditions BB_G are present. If the condition of step S 26  is not satisfied, a step S 38  is processed, which corresponds to step S 18 . If however the condition of step S 26  is satisfied, a step S 28  is processed, which corresponds to step S 8 . The temperature T_IM of the gas in the intake zone  1  is then determined in a step S 30 . This can take place as in step S 10 . A step S 32  corresponds to a step S 12 . In a step S 34  it is verified, as in step S 14 , whether the temperature T_IM of the gas in the intake zone is greater than the temperature threshold value THD_T_IM. If the condition of step S 34  is not satisfied, processing continues according to step S 14  either in step S 22  or in step S 26 . If however the condition of step S 34  is satisfied, a step S 36  is processed, which corresponds to step S 16 .  
         [0049]     With the third program ( FIG. 5 ) a start takes place in a step S 40 . In a step S 42  it is verified whether the operating state BZ corresponds to an operating state without fuel being fed in BZ_NF and optionally a redetermination of the correction value KOR_E is required due to the passage of time or drive distance conditions. The condition of step S 42  is preferably verified so frequently that it is satisfied in each instance for the first time an appropriately short time after the start of assumption of the operating state BZ_NF without fuel being fed in. It is preferably then satisfied for the first time, when an oxygen content O 2  determined in the next step S 44  is representative of the absence of exhaust gas in the region of the gas type sensor  42 . After the feeding in of fuel through the injection valves  22  has been deactivated, there is no further combustion in the respective cylinders Z 1  to Z 4  of the internal combustion engine and fresh air is pumped from the intake zone into the outlet zone. Depending on the reaction time of the gas type sensor, an oxygen content O 2 _ 1  is then detected by the gas type sensor  22 , which is representative of the absence of exhaust gases in the region of the gas type sensor  42 . This oxygen content O 2 _ 1  is detected in a step S 44  by the gas type sensor  42 .  
         [0050]     In a step S 46  the actuating signal SG_E for the phase adjusting device  20  is then modified according to step S 8 . In a step S 48  a further oxygen content O 2 _ 2  is again detected by the gas type sensor  42 . In a step S 50  the determined phase is then determined according to step S 12 .  
         [0051]     In a step S 52  it is then verified whether the first oxygen content O 2 _ 1  is representative of the absence of exhaust gases in the region of the gas type sensor  42  and the second oxygen content O 2 _ 2  is representative of the presence of exhaust gases in the region of the gas type sensor. If the condition of step S 52  is not satisfied, processing preferably continues directly again in step S 46 . If however the condition of step S 52  is satisfied, in a step S 54  the correction value KOR_E for the phase of the first crankshaft  18  is determined according to the procedure of step S 16 . With an appropriately short sequence of the repeated processing of steps S 46  to S 52 , it is possible to ensure that, when the reflux of gases or gas from the outlet zone  4  to the intake zone  1  occurs due to the adjustment of the phase, there is still exhaust gas in the outlet zone and this is then taken back into the region, in which the gas type sensor  42  is disposed.  
         [0052]     The default phase PH_G is then determined in an appropriate manner by tests, calculations or simulations, in order to represent the actual phase of the first camshaft  18  when the condition of step S 52  starts to be satisfied.  
         [0053]     To determine the correction value KOR_E, the steps and in particular the conditions of the steps S 14 ; S 34  and S 52  can be combined in any way with each other. If as an alternative the phase adjusting device  20  is assigned only to the second camshaft, corresponding programs can be provided for the second camshaft. If corresponding phase adjusting devices  20  are assigned to both the first and the second camshafts, specific correction values are preferably determined for each of the camshafts  18 ,  18 ′ by means of corresponding programs. To this end the phase adjusting device assigned to the respective other camshaft  18 ,  18 ′ is preferably in a reference position in each instance, for example at a mechanical stop.