Abstract:
The present disclosure relates to internal combustion engines and the teachings thereof may be embodied in methods for controlling an internal combustion engine. The method may include: measuring the actual camshaft position using a camshaft sensor, measuring the actual rail pressure using a rail pressure sensor, calculating, for each of the plurality of cylinders, a phase correction value depending at least in part on the measured actual rail pressure and a mass of fuel to be injected, calculating, for each cylinder, a corrected actual camshaft position based at least in part on the measured actual camshaft position and the respective phase correction value, and adjusting the camshaft position using a camshaft adjuster based on one or more of the corrected actual camshaft positions.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a U.S. National Stage Application of International Application No. PCT/EP2015/068341 filed Aug. 10, 2015, which designates the United States of America, and claims priority to DE Application No. 10 2014 217 563.1 filed Sep. 3, 2014, the contents of which are hereby incorporated by reference in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure relates to internal combustion engines and the teachings thereof may be embodied in methods and/or devices for improving the combustion processes taking place in the cylinders of an internal combustion engine by controlling camshaft adjustment. 
       BACKGROUND 
       [0003]    Fuel injection systems may include a plurality of cylinders, in each of which a fuel-air mixture is introduced and then ignited. The cylinders may include inlet and outlet valves driven with cams on an inlet valve camshaft or an outlet valve camshaft. The opening and closing times may be set by a control unit in dependence on the camshaft position signal provided by a camshaft sensor. 
         [0004]    To determine the mass of air required in each case for the fuel-air mixture, it is typical to use the camshaft position signal provided by the camshaft sensor as an actual position signal for each of the cylinders of the fuel injection system. Furthermore, a setpoint phase shift of the inlet valve camshaft may be calculated on the basis of the setpoint air mass and the engine speed. The phase shift may then be controlled using the camshaft position signal and the setpoint phase shift. 
         [0005]    A method for controlling the quantity of air and/or the fuel-air ratio for individual cylinders of an internal combustion engine is taught in DE 10 2005 057 974 A1. In that document, the amplitude and frequency of a signal, which is not cylinder-specific and is influenced by an actuator which is not cylinder-specific, is determined and is used to identify cylinder-specific signal components, and the cylinder-specific signal components are used as the basis for actuating the actuator, which is not cylinder-specific. 
         [0006]    Furthermore, some systems drive the high-pressure pump of a fuel injection system using the cams of a camshaft. In such a fuel injection system, if the pressure in the rail and/or the delivery volume of the high-pressure pump increases, then the torque to be provided therefor by the camshaft also increases. This increased increases torsion of the camshaft. In turn, this leads to undesired deviation in the control times of the inlet valves, which is greater the greater the distance of the respective cam from the camshaft sensor. The undesired deviation in the control times in turn affects the quantity of air with which the respective cylinder is filled, and thus also the associated quantity of fuel. 
       SUMMARY 
       [0007]    The teachings of the present disclosure may be embodied in methods and/or devices for improving the combustion processes taking place in the cylinders of an internal combustion engine, which reduce the undesired influences, of pressure changes in the rail and/or of a change in the delivery volume of the high-pressure pump of the internal combustion engine, on the combustion processes taking place in the cylinders. 
         [0008]    Some embodiments may include a method for improving the combustion processes taking place in the cylinders of an internal combustion engine having a camshaft, a high-pressure pump driven by the camshaft, a rail and a control unit, having the following steps: measuring the actual camshaft position using a camshaft sensor, measuring the actual rail pressure using a rail pressure sensor, determining, for each cylinder, a phase correction value in dependence on the measured actual rail pressure and the mass of fuel to be injected, determining, for each cylinder, corrected actual camshaft positions by evaluating the measured actual camshaft position and the respective phase correction value, and adjusting the camshaft position using a camshaft adjuster in dependence on one or more corrected actual camshaft positions. 
         [0009]    In some embodiments, the adjustment of the camshaft position takes place in dependence on the corrected actual camshaft position of a cam arranged in the central region of the longitudinal direction of the camshaft. 
         [0010]    In some embodiments, the adjustment of the camshaft position takes place in dependence on the average value of the corrected actual camshaft positions. 
         [0011]    Some embodiments may include measuring the actual intake pipe pressure using a pressure sensor arranged in the intake pipe of the internal combustion engine, and adapting the corrected actual camshaft positions using the measured actual intake pipe pressure. 
         [0012]    Some embodiments may include measuring the actual pressure in the cylinders using a pressure sensor arranged in the respective cylinder, and adapting the corrected actual camshaft positions using the actual pressure values measured in the cylinders. 
         [0013]    Some embodiments may include a device for improving the combustion processes taking place in the cylinders of an internal combustion engine, which has: a camshaft, a high-pressure pump driven by the camshaft, a rail and a control unit, characterized in that the control unit ( 10 ) is designed to carry out the following steps: receiving output signals from a camshaft sensor, describing the actual camshaft position, receiving the output signals from a rail pressure sensor, describing the actual rail pressure, determining, for each cylinder, a phase correction value in dependence on the measured actual rail pressure and the mass of fuel to be injected, determining, for each cylinder, corrected actual camshaft positions by evaluating the measured actual camshaft position and the respective phase correction value, and adjusting the camshaft position using a camshaft adjuster in dependence on one or more corrected actual camshaft positions. 
         [0014]    In some embodiments, the control unit ( 10 ) is designed to control the adjustment of the camshaft position in dependence on the corrected actual camshaft position of a cam arranged in the central region of the longitudinal direction of the camshaft. 
         [0015]    In some embodiments, the control unit ( 10 ) is designed to control the adjustment of the camshaft position in dependence on the average value of the corrected actual camshaft positions. 
         [0016]    In some embodiments, the control unit ( 10 ) is designed to carry out the following further steps: receiving the output signals, describing the actual intake pipe pressure, of a pressure sensor arranged in the intake pipe of the internal combustion engine, and adapting the corrected actual camshaft positions using the measured actual intake pipe pressure. 
         [0017]    In some embodiments, the control unit ( 10 ) is designed to carry out the following further steps: receiving the output signals, describing the actual pressure in the cylinders, of pressure sensors arranged in the cylinders, and adapting the corrected actual camshaft positions using the actual pressure values measured in the cylinders. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    There follows a description of an exemplary embodiment of the invention with reference to the figures, in which: 
           [0019]      FIG. 1  is a block diagram of a device illustrating an internal combustion engine, according to teachings of the present disclosure, and 
           [0020]      FIG. 2  is a more detailed illustration of parts of the device shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    The teachings of the present disclosure may be used to reduce, in spite of using just one camshaft sensor, the undesired influences, of torsion of the camshaft as a reaction to pressure changes in the rail and/or of a change in the delivery volume of the high-pressure pump, on the combustion processes in the cylinders. Adjusting the camshaft position in dependence on one or more corrected actual camshaft positions may balance the cylinder-specific component of the torque to be provided by the individual cylinders. 
         [0022]    This balancing may be conducted such that a cylinder positioned in the central region of the longitudinal direction of the camshaft provides a value, predefined by the control unit, for the cylinder-specific components of the torque to be provided, and the cylinders positioned “left and right” next to this cylinder provide cylinder-specific components that deviate only slightly from the predefined value. 
         [0023]    In some embodiments, the adjustment of the camshaft position is adapted by additionally taking into account the measured actual intake pipe pressure and/or by additionally taking into account the actual pressure values measured in the cylinders. 
         [0024]      FIG. 1  shows a block diagram of a device illustrating an internal combustion engine, according to teachings of the present disclosure. The device shown in  FIG. 1  has a fresh air inlet duct  9  in which are contained a fresh air inlet  11 , an air purification device  12 , and an inlet flap  13 . 
         [0025]    The device shown also has an exhaust gas duct  5  which is connected to the outlet  2   b  of the turbine  2  of an exhaust-gas turbocharger  1 . The exhaust gas duct  5  contains a catalytic converter  17 , a branching point  18 , and a silencer  19 . An exhaust gas recirculation duct  6  branches off at the branching point  18 . This duct  6  has an exhaust gas cooler  20  and an exhaust gas recirculation valve  8 . 
         [0026]    The outlet of the exhaust gas recirculation valve  8  is connected to a first inlet  7   a  of a mixer  7 . The outlet of the inlet flap  13  of the fresh air inlet duct  9  is connected to the second inlet  7   b  of the mixer  7 . 
         [0027]    The outlet  7   c  of the mixer  7  is connected to the inlet  4   a  of a compressor  4  of the exhaust-gas turbocharger. The compressor  4  has a compressor rotor which is secured in rotation with a shaft  3  which is also secured in rotation with a turbine rotor of the turbine  2 . 
         [0028]    The exhaust gases of an internal combustion engine  16 , in the form of an exhaust gas stream, enter at the inlet  2   a  of the turbine. This exhaust gas stream drives the turbine rotor. This also rotates the shaft  3  of the exhaust-gas turbocharger  1 . This rotation of the shaft is transmitted to the compressor rotor. 
         [0029]    The compressor draws in and compresses the fresh air/exhaust gas mixture created in the mixer  7  and supplied to the inlet  4   a  of the compressor. The compressed fresh air/exhaust gas mixture is expelled at the outlet  4   b  of the compressor and is supplied, via a charge air cooler  14  and a throttle flap  15 , to the internal combustion engine  16 . As already explained above, the exhaust gas created in the internal combustion engine is expelled at the inlet  2   a  of the turbine  2 . 
         [0030]    The device shown in  FIG. 1  also has a control unit  10  which contains a processing unit and multiple memory units in which tables and characteristic diagrams may be stored. The output signals from a multiplicity of sensors, which supply the control unit with actual values of a multiplicity of parameters, may be supplied to the control unit  10  as input signals. These include, inter alia, a sensor which detects actuation of the accelerator pedal. The output signals from this sensor tell the control unit  10  that there is a desire for acceleration. Also included is a sensor which provides the control unit  10  with information relating to the actual intake pipe pressure. This sensor may be positioned between the outlet of the throttle flap  15  and the internal combustion engine  16 . Additional sensors may provide information relating to the actual pressure in the cylinders of the internal combustion engine  16 . 
         [0031]    The control unit  10  evaluates the output signals from the sensors, the saved tables, and the saved characteristic diagrams to calculate control signals which are used to actuate components of the device shown. Inter alia, the control unit  10  calculates control signals s 1  for the exhaust gas recirculation valve  8  and transmits these thereto. These control signals s 1  cause the opening state of the exhaust gas recirculation valve  8  to change, depending on the immediate requirement, to supply more or less exhaust gas to the mixer  7 . 
         [0032]    Furthermore, the control unit  10  determines the air mass of the internal combustion engine  16  on an individual cylinder basis, and uses the air mass determined for each cylinder to determine a respective associated fuel injection mass. Furthermore, the control unit  10  is designed such that it controls an adjustment of the camshaft position in dependence on one or more corrected actual camshaft positions. This is explained in greater detail below with reference to  FIG. 2 , which shows a more detailed illustration of parts of the device shown in  FIG. 1 . In particular,  FIG. 2  shows additional components of the fuel injection system of the internal combustion engine  16 . 
         [0033]    These include a high-pressure pump  21 , a rail  22  connected to fuel injectors  23 ,  24 ,  25  and  26 , a camshaft  27  that bears cams  28 - 36 , inlet valves  37 - 44 , a total of four cylinders  45 - 48  in each of which a piston  49 - 52  can be moved up and down, and a crankshaft  53  connected to the pistons by connecting rods  54 - 57 . 
         [0034]    Also included are the control unit  10 , shown in  FIG. 1 , and a camshaft sensor  58 , a camshaft adjuster  59 , a crankshaft sensor  60 , and sensors  61  whose output signals are supplied to the control unit  10 . These sensors may include, inter alia, a rail pressure sensor, an intake pipe pressure sensor, and pressure sensors arranged in the cylinders. 
         [0035]    The high-pressure pump  21  may be engaged to raise the pressure of the supplied fuel, and to forward the high-pressure fuel to the rail  22 . From the rail  22 , the fuel is supplied to the injectors  23 ,  24 ,  25 ,  26  which each inject the fuel into one of the cylinders  45 - 48 . In that context, the control unit  10  controls the quantity of fuel and the injection times. The high-pressure pump  21  may be driven, via the cams  36 , by the rotating camshaft  27 . An increase in the pressure of the fuel in the rail  22  and/or in the delivery volume of the high-pressure pump  21  causes further torsion of the camshaft. 
         [0036]    This increase in the pressure of the fuel in the rail and/or of the delivery volume of the high-pressure pump  21  also means that the cylinder-specific component of the torque that is to be provided varies substantially from cylinder to cylinder. 
         [0037]    To avoid these drawbacks, cylinder-specific phase correction values  601 ,  602 ,  603 , and  604  may be used. These may be determined in dependence on the actual rail pressure measured by a rail pressure sensor, and on the quantity of fuel to be injected, predetermined by the control unit  10 . For each individual cylinder, the determined phase correction values may be added by the control unit  10  to the camshaft position measured by the camshaft sensor  58 . The corrected cylinder-specific actual camshaft positions, determined by this adding step, may be used to adjust the camshaft position by means of the camshaft adjuster  59 . 
         [0038]    One embodiment involves this adjustment of the camshaft position taking place in dependence on the corrected actual camshaft positions of a cam arranged in the central region of the longitudinal direction of the camshaft. In the embodiment shown in  FIG. 2 , the cam arranged in the central region of the longitudinal direction of the camshaft may be cam  31  or cam  32 . The control unit  10  determines, from the corrected actual camshaft position of the cam  31  or  32 , a cylinder-specific component of the torque to be provided by the cylinder  46  or  47  associated with this cam, such that this component corresponds to the average value of the components of all the cylinders  45 - 48 . In the embodiment shown, in which there are provided a total of four cylinders, the component of the torque to be supplied by each of the cylinders  46  and  47  can for example be 25%, the component for cylinder  45  can for example be 26%, and the component for cylinder  48  can for example be 24%. Some embodiments include the adjustment of the camshaft position based on the average value of the corrected actual camshaft positions. 
         [0039]    As described above, there is only a minor difference in the components of the torque to be supplied by the cylinders. This balancing of the torque components to be provided by the cylinders permits exact provision of the required average torque and avoids a larger variation in the torques generated at the cylinders. 
         [0040]    To further adjust of the camshaft position, the actual intake pipe pressure may be measured using a pressure sensor arranged in the intake pipe of the internal combustion engine. The measured actual intake pipe pressure is used to adapt the corrected actual camshaft positions. 
         [0041]    As an alternative or in addition thereto, the camshaft position can be adjusted by measuring the actual pressure in the cylinders using a pressure sensor arranged in the respective cylinder and by adapting the corrected actual camshaft positions using the actual pressure measured in the cylinders. The above-described method may also adapt the quantity of fuel of the respective cylinder to the quantity of air of the respective cylinder, and thus improve the combustion processes taking place in the cylinders.