Abstract:
A control system for an internal combustion engine comprises pressure sensing means, memory means, processing means, and fuel injection control means. Pressure sensing means generate in-cylinder pressure data used to calculate total heat generated during combustion cycle. Memory means store predetermined crank angle data, such as CA50 crank angle data, for variety of engine operating conditions. A CA50 crank angle is a crank angle position where fifty percent of total heat is generated. Memory means  38  additionally stores allowable start of injection crank angle data. Processing means determine an observed CA50 crank angle. Processing means conducts comparison of at least one of the predetermined CA50 crank angle data against the observed CA50 crank angle to generate a start of fuel injection crank angle which impacts the observed CA50 crank angle during subsequent combustion cycle. Fuel injection control means controls start of fuel injection crank angle generated by the processing means.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to a system and method of controlling combustion within an internal combustion engine having an in-cylinder pressure sensor for monitoring combustion occurring within a cylinder, such that adjustments may be made to operating parameters of the internal combustion engine. The adjustments of the operating parameters allow combustion to function properly, i.e. without an usually high number of misfires, while allowing a very high rate of exhaust gas recirculation (“EGR”) to be used in combustion, and allowing fuel injection to begin after a cylinder has passed top dead center. 
       BACKGROUND 
       [0002]    Many modern diesel engines have an exhaust system that features an exhaust gas recirculation (“EGR”) system that routes a portion of engine exhaust gas into an air intake system, such that a mixture of fresh air and engine exhaust is supplied to a combustion chamber during engine operation. In order to reduce certain pollutants found in exhaust gas of an internal combustion engine, such as NOx and particulate matter, several approaches have been tried, including using an after-treatment chemical in conjunction with a catalytic converter, a system often referred to as a selective catalyst reduction system or an “SCR system.” An SCR system adds complexity to an engine, and requires a catalyst that must be periodically replenished, which increases operating costs. If the catalyst is not replenished, the engine exhaust typically will not meet emissions standards, and the engine may be required to cease operations. 
         [0003]    Therefore, a need exists for an engine capable of meeting emissions standards without the use of an after-treatment system to control parameters useful in reducing emissions of the engine. 
       SUMMARY 
       [0004]    According to one embodiment, a control system for an internal combustion engine comprises pressure sensing means, memory means, processing means, and fuel injection control means. The pressure sensing means generate in-cylinder pressure data used to calculate the total heat generated during a combustion cycle. The memory means stores predetermined CA50 crank angle data for a variety of engine operating conditions. A CA50 crank angle is a crank angle position where fifty percent of the total heat during a combustion cycle is generated. The memory means additionally stores allowable start of injection crank angle data. The processing means determines an observed CA50 crank angle. The processing means conducts a comparison of at least one of the predetermined CA50 crank angle data against the observed CA50 crank angle to generate a start of fuel injection crank angle which impacts the observed CA50 crank angle during a subsequent combustion cycle. The fuel injection control means controls the start of fuel injection crank angle generated by the processing means. 
         [0005]    According to one process, a method of controlling operation of an internal combustion engine is provided. An angular position of a crankshaft of the engine is monitored using a crank position sensor. A pressure reading is generated with a first in-cylinder pressure sensor for a first cylinder. An electronic control module is utilized to calculate the heat generated during the combustion cycle within the first cylinder based upon the pressure reading. An observed crank angle within the first cylinder is determined with the electronic control module based upon output of the crank position sensor and the first in-cylinder pressure sensor, wherein the observed crank angle is a crank angle position where a predetermined percent of the total heat is generated. The observed crank angle is compared against a predetermined crank angle stored in the electronic control module. A provisional start of injection crank angle is generated for the first cylinder in response to the comparison of the observed crank angle and the predetermined crank angle. A difference between the provisional start of injection crank angle of the first cylinder is compared to an average start of injection crank angle for a remainder of a plurality of cylinders to a preset phasing limit value. The fuel injector is utilized to match an actual start of fuel injection crank angle in the first cylinder to the provisional start of injection crank angle when the difference between the provisional start of injection crank angle and the average start of injection crank angle for the remainder of the plurality of cylinders is less than the preset phasing limit value. 
         [0006]    According to another process, a method of controlling operation of an internal combustion engine is provided. An angular position of a crankshaft of the engine is monitored using a crank position sensor. A pressure reading is generated with a first in-cylinder pressure sensor for a first cylinder. An electronic control module is utilized to calculate the heat generated during the combustion cycle within the first cylinder based upon the pressure reading. An observed CA50 crank angle within the first cylinder is determined with the electronic control module based upon output of the crank position sensor and the first in-cylinder pressure sensor. The observed CA50 crank angle is compared against a predetermined CA50 crank angle stored in the electronic control module. A provisional start of injection crank angle is generated for the first cylinder in response to the comparison of the observed CA50 and the predetermined CA50. The provisional start of injection crank angle for the first cylinder is compared to a range of predetermined start of injection crank angles stored in the electronic control module. A difference between the provisional start of injection crank angle of the first cylinder is compared to an average start of injection crank angle for a remainder of a plurality of cylinders to a preset phasing limit value. The fuel injector is utilized to match an actual start of fuel injection crank angle in the first cylinder to the provisional start of injection crank angle when the provisional start of injection crank angle is within the range of predetermined start of injection crank angles, and when the difference between the provisional start of injection crank angle and the average start of injection crank angle for the remainder of the plurality of cylinders is less than the preset phasing limit value. An exhaust gas recirculation valve position is generated for the first cylinder when one of the difference between the provisional start of injection crank angle for the first cylinder and the average start of injection crank angle for the remainder of the plurality of cylinders exceeds the preset phasing limit and the provisional start of injection crank angle is outside of the range of predetermined start of injection crank angles. The fuel injector is utilized to match an actual start of fuel injection crank angle into the first cylinder to an adjusted start of injection crank angle when one of the difference between the provisional start of injection crank angle for the first cylinder and the average start of injection crank angle for the remainder of the plurality of cylinders exceeds the preset phasing limit, and the provisional start of injection crank angle is outside of the range of predetermined start of injection crank angles. A position of the exhaust gas recirculation valve is adjusted to the generated exhaust gas recirculation valve position. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a schematic diagram showing an engine; 
           [0008]      FIG. 2  is a sectional view of an engine showing a cylinder having an in-cylinder pressure sensor; 
           [0009]      FIG. 3  is block diagram showing a control system for an engine having an in-cylinder pressure sensor; 
           [0010]      FIG. 4  is block diagram showing a control system for an engine having an in-cylinder pressure sensor according to another embodiment; 
           [0011]      FIG. 5  is a block diagram showing a control system for an engine having an in-cylinder pressure sensor according to a further embodiment; 
           [0012]      FIGS. 6   a  and  6   b  are a flow chart showing one process of controlling an engine; and 
           [0013]      FIGS. 7   a  and  7   b  are a flow chart showing another process of controlling an engine. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]      FIG. 1  shows an engine  10  having an exhaust system  12 . The exhaust system  12  has an exhaust gas recirculation (“EGR”) portion  13 . The EGR portion  13  has an EGR cooler  14  and an EGR valve  16 . The EGR cooler  14  reduces the temperature of exhaust gas within the EGR portion  13 . The exhaust system  12  additionally is shown as having a first turbocharger turbine  18  and a second turbocharger turbine  20 . The EGR valve  16  controls the flow of exhaust gas within the EGR portion  13 . 
         [0015]    The engine  10  additionally has an air intake system  22 . The air intake system  22  has a first turbocharger compressor  24  and a second turbocharger compressor  26 . A charge air cooler  28  is additionally provided to cool intake air within the air intake system  22 . A first throttle valve  30  and a second throttle valve  32  are also disposed within the air intake system  22 . The first turbocharger turbine  18  and the first turbocharger compressor  24  form a first turbocharger and the second turbocharger turbine  20  and the second turbocharger compressor  26  form a second turbocharger. It is contemplated that the first turbocharger and the second turbocharger may be variable geometry turbochargers. 
         [0016]    Turning now to  FIG. 2 , a cross section of a cylinder  34  of the engine  10 . The cylinder  34  has a piston  36  that moves reciprocally within the cylinder  34 . A cylinder head  38  is disposed above the cylinder  34 , such that the movement of the piston  36  within the cylinder  34  increases a pressure within the cylinder  34 . An in-cylinder pressure sensor  40  is additionally provided. The in-cylinder pressure sensor  40  is disposed within the cylinder head  38  and a portion of the in-cylinder pressure sensor  40  is exposed within the cylinder  34 . The in-cylinder pressure sensor  40  monitors the pressure within the cylinder  34 . In a multi-cylinder engine  10 , there are multiple sensors  40  forming a sensor group  41 . 
         [0017]      FIG. 3  depicts a block diagram for a control system  42  for the engine  10 , while  FIGS. 6   a  and  6   b  depict a flow chart of a method of controlling the engine  10 . The control system  42  has a fuel system control component  44  and an air system control component  46 . The fuel system control component  44  has an accelerator position sensor  48  and an engine speed sensor  50 . The accelerator position sensor  48  and the engine speed sensor  50  are in electrical communication with a fuel system controller  52 . The fuel system controller  52  has a memory that stores fuel injection quantity data  54  as well as fuel injection timing data  56 , wherein both data  54 ,  56  are graphically represented with curves. Based upon the input received from the accelerator position sensor  48  and the engine speed sensor  50 , the fuel system controller  52  retrieves a fuel injection quantity output from the fuel injection quantity data  54  (block  602 ,  FIG. 6   a ) and also retrieves a fuel injection timing output from the fuel injection timing data  56  (block  610 ,  FIG. 6   a ). The fuel injection quantity output is communicated to a fuel injection quantity comparator  58 , while the fuel injection timing output is communicated to a fuel injection timing comparator  60 . 
         [0018]    The fuel system control component  44  additionally utilizes the group  41  of in-cylinder pressure sensors  40  that communicate with a combustion monitoring processor  64  that contains a fuel system memory  66  containing fuel injection timing correction data (block  612 ,  FIG. 6   a ) and fuel injection quantity correction data (block  604 ,  FIG. 6   a ) based upon the output of the group  41  of in-cylinder pressure sensors  40 . Outputs of the fuel system memory  66  is electronically communicated to the fuel injection quantity comparator  58  and the fuel injection timing comparator  60  (block  614 ,  FIG. 6   a ). The fuel injection quantity comparator  58  compares the output of the fuel injection quantity data  54  with the output from the fuel system memory  66  of the combustion monitoring processor  64  (block  606 ,  FIG. 6   a ) to generate a corrected fuel injection quantity communicated to a fuel injector  70  (blocks  608 ,  610 ,  FIG. 6   a ). Similarly, the fuel injection timing comparator  60  compares the output of the fuel injection timing data  56  with the output from the fuel system memory  66  of the combustion monitoring processor  64  (block  614 ,  FIG. 6   a ) to generate a corrected fuel injection timing communicated to a fuel injector  70  (blocks  616 ,  618 ,  FIG. 6   a ). 
         [0019]    The air system control component  44  of the control system  42  for the engine  10  additionally utilizes the group  41  of in-cylinder pressure sensors  40  that communicate with the combustion monitoring processor  64  that has an air intake system memory  68  (blocks  620 ,  630 ,  FIG. 6   b ). An air intake system controller  72  has a memory that stores turbocharger data  74  as well as EGR system data  76 . The air intake system controller  72  retrieves a turbocharger setting from the turbocharger data  74  based upon engine operating conditions (block  622 ,  FIG. 6   b ). The air intake system controller  72  additionally retrieves an EGR valve setting from the EGR system data  76  (block  632 ,  FIG. 6   b ). Output of the turbocharger data  74  and the air intake system memory  68  is transmitted to a turbocharger comparator  78  which compares the turbocharger data  74  with the output of the air intake system memory  68  (block  624 ,  FIG. 6   b ) and may adjust the turbocharger setting output using the turbocharger data  74  (block  626 ,  FIG. 6   b ) to generate a corrected turbocharger setting to a turbocharger  82  (block  628 ,  FIG. 6   b ). 
         [0020]    The EGR system data  76  from the air intake system controller  72  is transmitted to an EGR system comparator  80  where the EGR system comparator  80  compares it to the output of the air intake system memory  68  (block  634 ,  FIG. 6   b ) and may adjust the EGR setting output using the EGR system data  76  (block  636 ,  FIG. 6   b ) to generate a corrected EGR system setting to an EGR valve  84  (block  638 ,  FIG. 6   b ). 
         [0021]    Turning now to  FIG. 4 , a control system  86  is shown having a processor  88 , an interface  90 , and an ECM  92 . The processor  88  is disposed in electrical communication with both the interface  90  and the ECM  92 . The processor  88  is additionally disposed in electrical communications with an in-cylinder pressure sensor  40 , a cam position sensor  96  and a crank position sensor  98 . The processor  88  utilizes the input from the in-cylinder pressure sensor  40 , the cam position sensor  96 , and the crank position sensor  98  to generate a CA 50  crank angle using a CA50 estimator  100  of the processor  88 . 
         [0022]    The CA50 crank angle is the crank angle where 50% of the heat is generated for a particular combustion cycle. In order to determine when 50% of the heat has been generated, the in-cylinder pressure sensor  40  is utilized to determine a total heat release for the combustion of fuel within the cylinder  34  based upon the pressure within the cylinder  34 . The output of the in-cylinder pressure sensor  40  may also be utilized by a torque estimator  102  of the processor  88 . 
         [0023]    While the CA50 crank angle is described in this disclosure, it is contemplated that a different crank angle may be utilized that corresponds to a specific percentage of heat generated for a particular combustion cycle, and the invention is not limited to the specific crank angles or specific percentages heat generated. For instance, it is additionally contemplated that a range of a CA10 crank angle to a CA90 crank angle may be utilized, wherein the CA10 crank angle is the crank angle where 10% of the heat is generated for a particular combustion cycle, and CA90 is the crank angle where 90% of the heat is generated for a particular combustion cycle. Therefore, it is contemplated that CA50 may be substituted by a crank angle (CA) corresponding to another predetermined percentage amount of heat generated during combustion without altering the principals of this disclosure. 
         [0024]    The in-cylinder pressure sensor  40  is utilized to determine the pressure within the cylinder from combustion by comparing the actual pressure within the cylinder, to the pressure that would be within the cylinder without any combustion occurring. This is done by comparing the output of the in-cylinder pressure sensor  40  at a crank angle after a piston within the cylinder has passed top dead center (“TDC”) with the output of the in-cylinder pressure sensor  40  at a corresponding crank angle before the position within the cylinder has reached TDC. For example, the output of the in-cylinder pressure sensor  40  at a crank angle 25 degrees after TDC is compared to the output of the in-cylinder pressure sensor  40  at a crank angle 25 degrees before TDC, wherein the pressure difference is based upon combustion of fuel within the cylinder  34 . The pressure within the cylinder  34  attributed to combustion from the in-cylinder pressure sensor  40  may be used to generate a heat release amount, such that a crank angle may be determined where various percentages of the total amount of heat released from a particular fuel injection into a particular cylinder may be calculated. Thus, the CA50 estimator  100  may calculate a CA50 crank angle that corresponds to the crank angle where 50% of the heat released during combustion of a particular combustion cycle within a particular cylinder occurs. 
         [0025]    Similarly, the torque estimator  102  may utilize the output of the in-cylinder pressure sensor  40  to calculate a torque output of the engine  10 . The torque estimator  102  utilizes the output of the in-cylinder pressure sensor  40  and a known equation of the relationship between pressure within the cylinder  34  and the geometry the engine  10  to calculate an estimate of torque produced by the engine  10 . The torque can be calculated by the following formula: Torque=BMEP*V/4II, where BMEP is the brake mean effective pressure and V is the volume of the piston. BMEP may be calculated using the formula BMEP=IMEP−FMEP, where IMEP is the indicated mean effective pressure and FMEP is the friction mean effective pressure. IMEP may be generated from the output of the in-cylinder pressure sensor  40  when fuel in injected into a cylinder  34 , and FMEP may be calculated using the in-cylinder pressure sensor  40  when no fuel is injected into a cylinder  34  during a cycle, or may be estimated. 
         [0026]    The processor  88  still further has a misfire prevention module  104  adapted to monitor combustion characteristics within the engine  10 . The misfire prevention module  104  is adapted to compare an output of the CA50 estimator  100  with an output from the ECM  92  that contains a target CA50 value retrieved from a memory of the ECM  92 . The misfire prevention module  104  will generate an output signal to adjust at least one of fuel injection timing, EGR valve position, VGT settings, and variable valve timing settings to adjust the actual CA50 value calculated by the CA50 estimator  100  to match the target CA50 value stored in a memory of the ECM  92  as will be explained in further detail below. 
         [0027]    The interface  90  of the control system  86  allows for control of parameters used for the misfire prevention module  104  of the processor  88 . The interface  90  allows limits for the adjustments of the fuel injection timing, and airflow to the engine  10  to be corrected. The interface  90  additionally allows in-cylinder pressure sensor  40  feedback to be turned on and off, depending on expected operating conditions of the engine  10 . 
         [0028]      FIG. 5  shows a schematic of a control system  106  for a diesel engine. The control system  106  is adapted to control combustion phasing, that is the crank angle where CA50 occurs in cylinders within the engine. Combustion phasing may also be controlled between cylinders of a multi-cylinder engine, such that CA50 crank angle for a first cylinder is within a predefined number of degrees from the CA50 crank angle for a second cylinder. Using both a model based portion  108  and an empirical portion  110  of the control system  106 , combustion within the engine is controlled. 
         [0029]    The model based portion  108  has a memory that contains an air flow estimate  112  based upon observed operating conditions of the engine  10 , such as torque output, and engine speed. The output of the air flow estimate  112  is transmitted to an air flow comparator  114 . As explained below, the air flow comparator  114  also receives an input based upon air flow estimated by the in-cylinder pressure sensor  40 . The output of the air flow comparator  114  is transmitted to a throttle controller  116  and an EGR controller  118 . The throttle controller  116  receives input from an engine speed and torque monitor  120 , while the EGR controller  118  further receives input from an engine speed and torque monitor  120 . 
         [0030]    Output from the EGR controller  118  is transmitted to an EGR emission limiter  124 , to ensure that the EGR setting is sufficient to allow the engine to meet emission standards. Output of the throttle controller  116  is transmitted to an intake air comparator  126  where it is compared to a predetermined intake air setting  128 . Output of the intake air comparator  126  is transmitted to an intake manifold air estimator  134 . 
         [0031]    Similarly, output from the EGR emission limiter  124  is transmitted to an EGR comparator  130  where it is compared to a predetermined EGR setting  132 . Output of the EGR comparator  130  is also transmitted to the intake manifold air estimator  134 . Output from the intake manifold air estimator  134  is transmitted to a fuel injector controller  136 , and EGR valve controller  138 , and a variable geometry turbocharger (VGT) controller  140 , to be used in helping to control fuel injection timing, the amount of EGR delivered to the engine, and the VGT setting. 
         [0032]    The intake manifold air estimator  134  also communicates with an in-cylinder pressure sensor based air estimator  142 . The in-cylinder pressure sensor based air estimator  142  also receives input from an in-cylinder pressure sensor  40 , an intake manifold pressure sensor  146 , and an EGR rate estimator  148 . The in-cylinder pressure sensor based air estimator  142  generates an output that is communicated with the airflow comparator  114 , so that the airflow comparator  114  may calculate a correction to the air flow estimate  112  stored in the memory. The correction of the airflow estimate  112  allows for better control of the air/fuel ratio of the engine. 
         [0033]    Turning now to the empirical portion  110  of the control system  106 , as well as the flow chart shown in  FIGS. 7   a  and  7   b,  input from the in-cylinder pressure sensor  40 , a calculated CA50 value  150  (block  702 ,  FIG. 7   a ), and a calculated torque  152  are transmitted to a feedback controller  154 . The feedback controller  154  compares the calculated CA 50  value  150  with a stored CA50 value based on observed engine operating conditions (block  704 ,  FIG. 7   a ) and may adjust the turbocharger setting output using the turbocharger setting data  74  (block  706 ,  FIG. 7   a ). If the calculated CA50 value  150  generally corresponds to the stored CA50 value, very few adjustments, or even no adjustments, are made to operating parameters. However, if the calculated CA50 value  150  does not correspond to the stored CA50 value, the feedback controller  154  generates a provisional start of injection crank angle (block  708 ,  FIG. 7   a ), and compares the provisional start of injection crank angle to a start of injection adjustment limit stored in a memory of the feedback controller  154  (block  710 ,  FIG. 7   a ). If the provisional start of injection crank angle is within the start of injection adjustment limit, the start of injection crank angle is adjusted (block  712 ,  FIG. 7   a ). If the provisional start of injection crank angle is not within the start of injection adjustment limit, the feedback controller  154  generates a provisional EGR valve adjustment (block  716 ,  FIG. 7   a ), and sets the start of injection crank angle at the adjustment limit (block  714 ,  FIG. 7   a ). 
         [0034]    The provisional EGR valve adjustment is also compared to an EGR valve adjustment limit (block  718 ,  FIG. 7   a ). If the provisional EGR valve adjustment is within the EGR valve adjustment limit, the EGR valve is set to the provisional EGR valve adjustment position (block  720 ,  FIG. 7   b ). However, if the provisional EGR valve adjustment is outside of the EGR valve adjustment limit, the feedback controller  154  generates a VGT position setting (block  724 ,  FIG. 7   b ), and sets the EGR valve adjustment position at the adjustment limit (block  722 ,  FIG. 7   b ). The VGT position is set at the generated VGT position setting (block  726 ,  FIG. 7   b ). 
         [0035]    The feedback controller  154  communicates with an instability predictor  156 . The instability predictor  156  is used by an engine having a plurality of cylinders to compare the corrections required by one cylinder to settings for the remaining cylinders. If the instability predictor  156  detects that the setting for the start of injection crank angle for a first cylinder is outside of a range from an average start of injection crank angle for all of the cylinders of the engine, the instability predictor  156  will set an adjusted start of injection crank angle, and will adjust at least one of the EGR valve adjustment and the VGT position setting to compensate for the adjusted start of injection crank angle. The instability predictor  156  therefore generates a final start of injection crank angle  158 , a final EGR valve adjustment position  160 , and a final VGT position setting  162 . The final start of injection crank angle  158  is transmitted to the fuel injector controller  136 , the final EGR valve adjustment position  160  is transmitted to the EGR valve controller  138 , and the final VGT position setting  162  is transmitted to the VGT controller  140 . 
         [0036]    It is additionally contemplated that an intake throttle position setting and a variable valve actuation setting may also be generated as described above with respect to the EGR valve position and the VGT position setting. It is contemplated that the control system  106  may be executed by an ECM, or that separate controllers may be utilized that simply communicate with each other. 
         [0037]    The present disclosure is adapted to allow an engine to operate with high levels of EGR, i.e. above 35%, and with a start of fuel injection occurring after a piston within a cylinder has passed top dead center. These aspects of this disclosure allow combustion to remain stable, even with fuel injection starting after the piston has passed top dead center. Fuel injection occurring after the piston has passed top dead center while utilizing EGR rates above 35% have been found to reduce engine emissions of NOx and particulate matter significantly. However, combustion tends to become unstable with increasing amounts of EGR as less oxygen is present within EGR for use in combustion. Additionally, initiating fuel injection after TDC may lead to unstable combustion as mixing of fuel with air within the cylinder may not sufficiently atomize the fuel for stable combustion to occur, thus, combustion under such conditions must be carefully monitored and controlled. 
         [0038]    As described above, the present disclosure may be applied on a per-cylinder basis, such that fuel injection timing, and EGR valve position setting are adjusted to ensure proper combustion within a single cylinder, or operations of a plurality of cylinders may be controlled by an instability predictor to ensure that proper combustion phasing is maintained between the plurality of cylinders.