Patent Publication Number: US-2011067395-A1

Title: Method of controlling an engine during transient operating conditions

Description:
TECHNICAL FIELD 
     The subject invention generally relates to a method of controlling an internal combustion engine, and more specifically to a method of minimizing soot emissions from a diesel engine during operation of the diesel engine in a transient operating condition. 
     BACKGROUND OF THE INVENTION 
     Internal combustion engines, and diesel engines in particular, are designed to operate efficiently with low emissions during a steady state operating condition, and tend to produce a large volume of soot emissions, i.e., smoke, during transient operating conditions of the engine. Transient operating conditions occur when the engine operates outside of the steady state operating condition, and may include, but are not limited too, initial engine start-up, accelerating from a low engine speed, a load increase on the engine while the engine maintains a constant engine speed, and an engine speed decrease while the load on the engine remains constant. 
     The transient operating conditions are generally associated with a lack of combustion air flowing into the engine for a given amount of fuel injected into the engine, causing a rich combustion that produces a large volume of soot emissions in the exhaust. In order to meet Federal emissions guidelines and requirements, the engine may include a particulate filter that filters the soot emissions from the exhaust. However, the particulate filters currently available must be regenerated on a regular basis to maintain proper operation. 
     SUMMARY OF THE INVENTION 
     A method of controlling an internal combustion engine coupled to a mechanically driven supercharger controlling a flow of air to the engine is disclosed. The method includes defining a steady state operating condition of the engine; monitoring an operating parameter of the engine to determine if the engine is operating outside of the steady state operating condition in a transient operating condition; and adjusting the flow of air from the supercharger during operation of the engine in the transient operating condition. The flow of air supplied from the supercharger maintains a fuel/air mixture of the engine to within a pre-determined ratio to minimize emissions from the engine during operation of the engine in the transient operating condition. 
     A method of minimizing emissions from a diesel engine coupled to a mechanically driven supercharger controlling a flow of air to the diesel engine is also disclosed. The method includes defining a steady state operating condition of the engine; defining a transient operating condition of the engine as operation of the engine outside of the steady state operating condition; associating a range of values of an operating parameter of the engine with the steady state operating condition; measuring a value of the operating parameter during operation of the engine; comparing the measured value of the operating parameter with the associated range of values of the operating parameter to determine if the measured value of the operating parameter is in the transient operating condition; and adjusting the flow of air from the supercharger during operation of the diesel engine in the transient operating condition. The flow of air supplied from the supercharger maintains a fuel/air mixture of the diesel engine to within a pre-determined ratio to minimize emissions from the diesel engine during operation of the diesel engine in the transient operating condition. 
     Accordingly, the method supplies a flow of combustion air to the engine during transient operating conditions independently of a flow rate of the exhaust gas to maintain a proper fuel/air ratio by increasing the flow rate of air supplied to the engine from the supercharger prior to increasing the fuel injection rate to the engine. Maintaining the proper fuel/air ratio minimizes soot emissions during operation of the engine in the transient operating conditions. The reduced soot emissions allow the engine to operate for extended periods of time without the need to regenerate a particulate filter. 
     The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross sectional view of a first embodiment of an internal combustion engine. 
         FIG. 2  is a schematic cross sectional view of a second embodiment of an internal combustion engine. 
         FIG. 3  is a flow chart showing a method of controlling the internal combustion engine. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, a first embodiment of an internal combustion engine is shown generally at  20  in  FIG. 1 . The engine  20  includes a conventional engine, such as a diesel engine or a gasoline engine. As shown in  FIG. 1 , the engine  20  is coupled to a “superturbo” boosting system, which includes both a turbocharger  22  and a supercharger  24  disposed in-line with each other to increase the boost, i.e., pressure, of combustion air of the engine  20 . 
     The turbocharger  22  is powered by exhaust gas provided by the engine  20  as is well known. The supercharger  24  is mechanically linked to the engine  20  and is powered by the engine  20 . The supercharger  24  may include a clutch  26 , as shown in  FIG. 1 , interconnecting the engine  20  and the supercharger  24 . Alternatively, as shown in  FIG. 2 , the supercharger  124  may be directly coupled to the engine  120  for continuous operation of the supercharger  124  with the engine  120 . The clutch  26  is configured for selectively engaging and disengaging the supercharger  24 . It should be understood by those skilled in the art that the clutch  26  may, within the scope of the present invention, comprise any type of clutch  26  (e.g., engageable friction discs, electromagnetic, etc.) which is effective in transmitting mechanical drive from the vehicle engine  20  (typically, but not necessarily, from the crankshaft) to the input shaft of the supercharger  24 . Also, as is also now well known to those skilled in the art, there may be some sort of “step-up gear” speed increasing arrangement between the clutch  26  and the input shaft, with a typical ratio for such a speed increasing arrangement being in the range of about 2:1 to about 4:1. 
     The boosting system includes a plurality of air ducts configured for communicating the combustion air to the engine  20 . The air ducts communicate the combustion air to and from the engine  20 . The air ducts include an intake  28 , through which the combustion air enters the boosting system in a direction indicated by arrow  30 . A first air duct  32  includes a filter  34 , and is in fluid communication with an inlet of the supercharger  24 . The combustion air enters the boosting system through the intake  28 , and flows through the filter  34  toward the supercharger  24 . 
     A second air duct  38  connects an outlet of the supercharger  24  with a pumping portion, i.e., a compressor  42 , of the turbocharger  22 . A third air duct  44  interconnects an outlet of the compressor  42  with an inlet of an intercooler  46 . The function of the intercooler  46  is well known, and outside the scope of this invention. Accordingly, the function of the intercooler  46  is not described in detail herein. A fourth air duct  48  interconnects an outlet of the intercooler  46  with a combustion chamber  50  of the engine  20 . 
     Disposed within the fourth air duct  48  is an engine throttle  52 , which is shown in  FIG. 1  in a fully open position. It should be appreciated that the engine throttle  52  may be controlled to be in any position between the fully open position shown in  FIG. 1 , and a fully closed position, which substantially blocks all air flow through the fourth air duct  48 , thereby limiting air flow into the combustion chamber  50  of the engine  20 . 
     The turbocharger  22  also includes a turbine portion  54 , which is mechanically coupled to and configured to drive the compressor  42 . A fifth air duct  56  interconnects the combustion chamber  50  of the engine  20  with an inlet of the turbine portion  54  of the turbocharger  22  to provide the turbine portion  54  with the exhaust gas. A sixth air duct  58  interconnects an outlet of the turbine portion  54  of the turbocharger  22  with exhaust exit  60 . The exhaust gas flows out of the boosting system through the exhaust exit  60  in a direction indicated by arrow  62 . 
     A combustion air bypass duct  64  is disposed between the first air duct  32  and the outlet of the supercharger  24 . A combustion air bypass valve  66  is disposed within the combustion air bypass duct. The combustion air bypass valve  66  is normally in a closed position when the supercharger  24  is operating to direct the combustion air through the first air duct  32  to the supercharger  24 . However, when reduced levels of boost are sufficient, the combustion air bypass valve  66  may be moved from the closed position of the combustion air bypass valve  66  toward an open position of the combustion air bypass valve  66  to decrease the flow of combustion air through the supercharger  24 , and allow a portion of the combustion air to flow through the combustion air bypass duct  64 , into the second air duct  38 . 
     One result of moving the combustion air bypass valve  66  toward a more open position is that the boost pressure of the combustion air in the second air duct  38  lower than the normal boost pressure present when the combustion air bypass valve  66  is fully closed. As the vehicle engine  20  reaches relatively higher engine  20  speeds, the clutch  26  may be disengaged, so that the supercharger  24  is not being driven. At the same time, the turbocharger  22  is being driven by the flow of exhaust gas through the fifth air duct  56 . During this mode of operation, the combustion air bypass valve  66  is in the fully opened position and should be large enough not to present any undesirable flow restriction to the combustion air, which flows from the intake  28 , through the first air duct  32 , through the combustion air bypass valve  66 , through the combustion air bypass duct  64 , through the second air duct  38  and into the compressor  42  of the turbocharger  22 . 
     An exhaust gas bypass duct  68  interconnects the fifth air duct  56  with the sixth air duct  58 . An exhaust gas bypass valve, i.e., a wastegate  70 , is disposed within the exhaust gas bypass duct  68 . The wastegate  70  may be made and function as is well known in the turbocharger  22  art. 
     While a “superturbo” system is shown in  FIG. 1  and described above, in which the supercharger  24  is disposed within the boosting system before the turbocharger  22 , it should be appreciated that the relative positions of the supercharger  24  and the turbocharger  22  may be reversed to define a “turbosuper” boosting system, in which the turbocharger  22  is disposed in the boosting system prior to the supercharger  24 . 
     Referring to  FIG. 2 , a second embodiment of the engine is shown generally at  120 . Features of the second embodiment of the engine  120  that are identical to the first embodiment of the engine  20  include the same reference numeral increased by one hundred. For example, the filter, which is identified in the first embodiment of the engine  20  by the reference numeral  34 , is identified in the second embodiment of the engine  120  by reference numeral  134 . 
     The second embodiment of the engine  120  is similar to the first embodiment of the engine  20  without the turbocharger  22  and associated air ducts. In other words, the boosting system of the second embodiment of the engine  120  only includes the supercharger  124 , and does not include the turbocharger  22 . As such, only the differences between the first embodiment of the engine  20  and the second embodiment of the engine  120  are described below. Accordingly, the features of the second embodiment of the engine  120  shown in  FIG. 2 , including the intake  128 , the arrow  130  indicating air flow into the intake  128 , the fourth air duct  148 , the throttle  152 , the arrow  162  indicating air flow from the exhaust exit  160 , and the combustion air bypass valve  166 , each operate in the same manner as the corresponding features of the first embodiment of the engine  20 , and are not described in detail below. 
     Additionally, the second embodiment of the engine  120  does not include the clutch  26  interconnecting the supercharger  124  and the engine  120 . Accordingly, the supercharger  124  is directly coupled to the engine  120  for continuous operation with the engine  120 . 
     Within the second embodiment of the engine  120 , a seventh air duct  172  interconnects the outlet of the supercharger  124  and the inlet of the intercooler  146  with the combustion air bypass duct  164  interconnecting the first air duct  132  and the seventh air duct  172 , and an eighth air duct  174  interconnects the engine  120  and the exhaust exit  160  to convey the exhaust gas from the combustion chamber  150  of the engine  120  directly to the exhaust exit  160 . 
     Referring to  FIG. 3 , a method of controlling the internal combustion engine  20 ,  120  is shown. Preferably, the engine  20 ,  120  includes a diesel engine. The method includes defining a steady state operating condition of the engine  20 ,  120  (block  76 ). Defining the steady state operating condition of the engine  20 ,  120  may further include defining an operating range within which the engine  20 ,  120  operates without change over time. In other words, the steady state operating condition includes a range of operating conditions that the engine  20 ,  120  normally operates within at a high efficiency over time. 
     Defining the operating range may further include defining an engine operating speed range, such as between 500 and 7000 rpm&#39;s. However, it should be appreciated that the specific operating speed range varies with each specific engine  20 ,  120 , and with different applications of the engine  20 ,  120 . 
     The method further includes defining a transient operating condition of the engine  20 ,  120  (block  78 . The transient operating condition of the engine  20 ,  120  may be defined as operation of the engine  20 ,  120  outside of the steady state operating condition. The transient operating condition of the engine  20 ,  120  corresponds to a change of one or more operating parameters of the engine  20 ,  120  over time. The operating parameters of the engine  20 ,  120  remain substantially constant while the engine  20 ,  120  is operating in the steady state operating condition. However, once outside of the steady state operating condition, the operating parameters of the engine  20 ,  120  vary over time. 
     The operating parameters may include one or more operating parameters of the engine  20 ,  120  chosen from a group of operating parameters including a fuel/air ratio, a speed of the engine  20 ,  120 , an exhaust gas emission level of the engine  20 ,  120 , a fuel flow injection timing of the engine  20 ,  120 , and a flow rate of the combustion air. It should be appreciated that the operating parameters of the engine  20 ,  120  may include other parameters not described herein. 
     The method may further include associating a range of values of one or more of the operating parameters with the steady state operating condition (block  80 ). Accordingly, operation of the engine  20 ,  120  within the range of values for the operating parameter corresponds to operation of the engine  20 ,  120  within the steady state operating condition, whereas operation of the engine  20 ,  120  outside of the range of values for the operating parameter corresponds to operation of the engine  20 ,  120  outside of the steady state operating condition, i.e., operation in the transient operating condition. 
     The method may further include monitoring one or more of the operating parameters of the engine  20 ,  120  to determine if the engine  20 ,  120  is operating within the steady state operating condition, or outside of the steady state operating condition in the transient operating condition (block  82 ). Monitoring the operating parameter may further be defined as measuring a value of the operating parameter. Accordingly, the vehicle may include one or more sensors for sensing the value of the operating parameter. 
     The method may further include comparing the measured value of the operating parameter with the associated range of values of the operating parameter to determine if the measured value of the operating parameter is outside of the range of values of the operating parameter (block  84 ). If the measured value of the operating parameter is within the range of values associated with the steady state operating condition, then the engine  20 ,  120  is operating within the steady state operating condition. However, if the measured value of the operating parameter is outside the range of values associated with the steady state operating condition, then the engine  20 ,  120  is operating within the transient operating condition. 
     The method further includes adjusting the flow of air from the supercharger  24 ,  124  during operation of the engine  20 ,  120  in the transient operating condition (block  86 ). Adjusting the supercharger  24 ,  124  provides a continuous flow of air to the combustion chamber  50 ,  150  of the engine  20 ,  120  at a sufficient flow rate to maintain a proper fuel/air mixture to substantially within a pre-determined ratio. The pre-determined ratio corresponds to the efficient operation of the engine  20 ,  120 , in which the engine  20 ,  120  is not operating too richly, i.e., too much fuel to the available amount of combustion air. Maintaining the fuel/air mixture to within the pre-determined ratio minimizes soot emissions from the engine  20 ,  120  during operation of the engine  20 ,  120  in the transient operating condition. Minimization of soot emissions from the engine  20 ,  120  increases the time between regeneration of a particulate filter (not shown) used to filter the soot from the exhaust gas, i.e., the particulate filter lasts longer when the engine  20 ,  120  produces less soot in the exhaust. 
     Adjusting the flow of air from the supercharger  24 ,  124  may further include adjusting the supercharger  24 ,  124  while the engine  20 ,  120  is operating in the transient operating condition to ensure proper combustion air flow to the engine  20 ,  120  during operation of the engine  20 ,  120  in the transient condition. As described above, maintaining the proper air flow to the combustion chamber  50 ,  150  of the engine  20 ,  120  ensures that the proper fuel/air ratio is maintained, which minimizes the soot emissions from the engine  20 ,  120 , particularly in a diesel engine. 
     The method may further include adjusting an input to the engine  20 ,  120  while maintaining the flow of combustion air from the supercharger  24 ,  124  when the engine  20 ,  120  is operating in the transient operating condition, indicated at  88 . Adjusting the input to the engine  20 ,  120  assists in maintaining the fuel/air mixture to within the pre-determined ratio. Adjusting the input to the engine  20 ,  120  may further be defined as adjusting a fuel flow injection timing of the engine  20 ,  120 . Adjusting the fuel flow injection timing may be further defined as adjusting a fuel flow injection rate, i.e. the flow rate of the fuel injected into the engine. It should be appreciated that the input to the engine may include some other input not described herein. 
     The method may further include defining a plurality of intermediate operating conditions within each transient operating condition. In other words, each transient operating condition may be broken up into or include multiple intermediate operating conditions. If the transient operating condition is broken up to define multiple intermediate operating conditions, then adjusting the flow of air from the supercharger  24 ,  124  during operation of the engine  20 ,  120  in the transient operating condition may further be defined as adjusting the flow of air from the supercharger  24 ,  124  to achieve one of the plurality of intermediate operating conditions defined within the transient operating condition. Additionally, the method may further include adjusting a fuel flow injection timing, i.e., fuel flow rate, of the engine  20 ,  120  to achieve one of the plurality of intermediate operating conditions defined within the transient operating condition. The fuel flow injection rate is adjusted after the flow of air from the supercharger  24 ,  124  is adjusted to achieve one of the plurality of intermediate operating conditions defined within the transient operating condition. As such, if multiple intermediate operating conditions are defined, the flow of air is adjusted to achieve a first of the intermediate operating conditions, after which the fuel flow rate is adjusted to achieve the first of the plurality of intermediate operating conditions. After the first of the intermediate operating conditions is achieved, the flow of air from the supercharger is adjusted to meet a second of the intermediate operating conditions, after which the fuel flow rate is adjusted to achieve the second of the plurality of intermediate operating conditions. In this manner, the operation of the engine progresses through each of the intermediate operating conditions until the engine  20 ,  120  is operating within the steady state operating condition. 
     While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.