Abstract:
An engine system and method for operating an internal combustion engine includes a turbocharger that generates a boost to the engine. A coolant temperature of the engine is determined along with other based engine inputs and calculated values. A normal boost based on operating conditions of the engine is determined. A supplemental boost is determined based on the coolant temperature. An offset boost based on the normal boost and the supplemental boost is determined. An air output of the turbocharger is modified based on the offset boost. The supplemental boost increases combustion efficiency, which reduces white smoke exhaust.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to vehicle control systems and more particularly to vehicle control systems for minimizing white smoke exhaust.  
       BACKGROUND OF THE INVENTION  
       [0002]     Diesel engines typically have higher thermal efficiency and lower fuel consumption rates than gasoline engines due to the increased compression ratio of the diesel combustion process and the higher energy density of diesel fuel. Consequently, diesel engines have a higher thermal burn efficiency which leads to improved fuel economy as compared to gasoline engines with similar output.  
         [0003]     Internal combustion engines combust an air and fuel mixture within cylinders of the engine to produce drive torque. Engines can include a turbocharger that increases torque output by delivering additional air into the cylinders. One traditional turbocharger includes a variable nozzle turbo (VNT). VNT&#39;s include vanes that can be adjusted to regulate the amount of air delivered through the VNT. The vane position ranges from a fully-open position to a fully-closed position. In the fully-open position, the VNT delivers a minimum amount of air to the engine. In the fully-closed position, the VNT delivers a maximum amount of air to the engine. The vanes can be positioned between the fully-open and fully-closed positions to provide an intermediate amount of air to the engine. A vane solenoid adjusts the vane position based on a vane control signal and a vane control sensor generates a vane position signal indicating the actual vane position.  
         [0004]     Diesel engines often include a turbocharger for increased air flow to meet emission requirements and performance standards. Boost (increased air flow) is typically calibrated based on sensed parameters. Typical indicators for engine running conditions are intake manifold temperature, coolant temperature, engine rpm, fuel quantity and injection timing. In diesel engines with waste-gate turbochargers, the boost map is typically set up for normal (warm) engine running conditions. In instances where normal conditions do not apply such as cold/hot ambient conditions, certain engine controls such as injection timing would be adjusted with minimal impact.  
         [0005]     In some instances, diesel engines may exhaust white smoke. Typically white smoke is generated when the engine temperature and charge air temperatures in the cylinders is cooler, thus causing inefficient combustion and fuel not to completely burn. The unburned fuel is then exhausted and may produce a rich fuel smell. In cold weather it is common to exhaust white smoke until the engine temperature reaches normal operating temperature.  
       SUMMARY OF THE INVENTION  
       [0006]     An engine system and method for operating an internal combustion engine includes a turbocharger that generates a boost to the engine. A coolant temperature of the engine is determined. A normal boost based on operating conditions of the engine is determined. A supplemental boost is determined based on the coolant temperature. An offset boost based on the normal boost and the supplemental boost is determined. An air output of the turbocharger is modified based on the offset boost.  
         [0007]     According to other features, the supplemental boost is further based on an RPM of the engine. In addition, the supplemental boost is further based on an intake air temperature and a manifold air flow through an intake manifold on the engine, and an injector timing of a fuel injection system associated with the engine.  
         [0008]     According to still other features, a position of a plurality of vanes arranged on the turbocharger is determined. An actual boost supplied to the engine is determined. The supplemental boost is modified based on the actual boost and the offset boost.  
         [0009]     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0011]      FIG. 1  is a functional block diagram of a VNT control system that reduces white smoke exhaust according to some implementations of the present invention;  
         [0012]      FIG. 2A  is a logic diagram illustrating VNT control;  
         [0013]      FIG. 2B  is a logic diagram illustrating boost control according to some implementations of the present invention; and  
         [0014]      FIG. 3  is a flowchart showing steps for reducing white smoke exhaust according to some implementations of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0015]     The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. As used herein, the term module refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. As used herein, the term boost refers to an amount of compressed air introduced into an engine by a supplemental forced induction system such as a turbocharger.  
         [0016]     Referring now to  FIG. 1 , an exemplary engine control system  10  is schematically illustrated in accordance with the present invention. The engine control system  10  includes an engine  12  and a control module  14 . The engine  12  further includes an intake manifold  15 , a fuel injection system  16 , an exhaust system  17  and a turbocharger  18 . The exemplary engine  12  includes six cylinders  20  configured in adjacent cylinder banks  22 , 24  in a V-type layout. Although  FIG. 1  depicts six cylinders (N=6), it can be appreciated that the engine  12  may include additional or fewer cylinders  20 . For example, engines having 2, 4, 5, 8, 10, 12 and 16 cylinders are contemplated. It is also anticipated that the engine  12  can have an inline-type cylinder configuration.  
         [0017]     Air is drawn into the intake manifold  15  by the inlet vacuum created by the engine intake stroke. Air is drawn into the individual cylinders  20  from the intake manifold  15  and is compressed therein. Fuel is injected by the injection system  16  and is mixed with air. The air/fuel mixture is compressed and the heat of compression and/or electrical energy ignites the air/fuel mixture. Exhaust gas is exhausted from the cylinders  20  through exhaust conduits  26 . The exhaust gas drives the turbocharger&#39;s turbine blades which in turn drives the turbocharger&#39;s compressor blades  18 . The blades  18  deliver additional air (boost) to the intake manifold  15  and into the cylinders  20  for combustion.  
         [0018]     The turbocharger  18  is preferably a variable nozzle turbocharger (VNT). The turbocharger  18  includes a plurality of variable position vanes  19  that regulate the amount of air delivered from the vehicle exhaust  17  to the engine  12  based on a signal from the control module  14 . More specifically, the vanes  19  are movable between a fully-open position and a fully-closed position. When the vanes  19  are in the fully-closed position, the turbocharger  18  delivers a maximum amount of air into the intake manifold  15  and consequently into the engine  12 . When the vanes  19  are in the fully-open position, the turbocharger  18  delivers a minimum amount of air into the engine  12 . The amount of delivered air is regulated by selectively positioning the vanes  19  between the fully-open and fully-closed positions.  
         [0019]     The turbocharger  18  includes an electronic control vane solenoid  28  that manipulates a flow of hydraulic fluid to a vane actuator (not shown). The vane actuator controls the position of the vanes  19 . A vane position sensor  30  generates a vane position signal based on the physical position of the vanes  19 . A boost sensor  31  generates a boost signal based on the additional air delivered to the intake manifold  15  by the turbocharger  18 . While the turbocharger implemented herein is described as a VNT, it is contemplated that other turbochargers employing electronic control methods may be employed.  
         [0020]     A manifold absolute pressure (MAP) sensor  34  is located on the intake manifold  15  and provides a (MAP) signal based on the pressure in the intake manifold  15 . A mass air flow (MAF) sensor  36  is located within an air inlet and provides a mass air flow (MAF) signal based on the mass of air flowing into the intake manifold  15 . The control module  14  uses the MAF signal to determine the A/F ratio supplied to the engine  12 . An RPM sensor  44  provides an engine speed signal. A coolant temperature sensor  46  provides a coolant temperature signal. An intake manifold temperature sensor  48  generates an intake air temperature signal. The control module  14  communicates an injector timing signal to the injection system  16 . An accelerator pedal sensor  49  generates a pedal position signal that is output to the control module  14 .  
         [0021]     The control module  14  controls overall operation of the engine system  10 . More specifically, the control module  14  controls engine system operation based on various parameters including, but not limited to, driver input, stability control and the like. The control module  14  can be provided as an Engine Control Module (ECM). The control module  14  regulates operation of the turbocharger  18  by regulating current to the vane solenoid  28 . The control module  14  according to an embodiment of the present invention communicates with the vane solenoid  28  to provide an increased flow of air (boost) into the intake manifold  15 . An increased flow of air causes the engine temperature to rise and therefore promote a favorable environment for combustion. As a result, white smoke exiting the vehicle  10  through the exhaust system  17  is reduced.  
         [0022]     With reference now to  FIGS. 2A-3 , a method  50  for reducing white smoke according to an embodiment of the present invention will be described in further detail. As depicted in  FIG. 2A , the control module  14  may include a standalone module or a VNT control module  32 . Control begins in step  60 . In step  62 , control determines if the engine  12  is on. If the engine  12  is not on, control ends in step  64 . If the engine is on, control receives input parameters in step  70 . In step  70 , control determines an intake air temperature based on the signal from the intake air temperature sensor  48 . Control also determines a coolant temperature based on the signal from the coolant temperature sensor  46 . Additionally, control determines a throttle request based on the signal from the pedal position sensor  49  for engine rpm and fuel quantity.  
         [0023]     In step  72 , control determines whether the measurements are within an acceptable range. For example, if at least one of the intake air temperature, the coolant temperature and/or the throttle request is above a calibration, control determines that increased boost with the VNT is unnecessary and control ends in step  64 . In one implementation, control determines that increased boost is unnecessary for at least one of an intake air temperature and a coolant temperature above 25 degrees Celsius. If increased boost is unnecessary, control disables supplemental boost in step  74  and control ends in step  64 . It is appreciated that additional measurements may be performed and included as necessary criteria for proceeding with the control method  50 .  
         [0024]     If the measurements are acceptable, control calculates an offset boost in step  76 . An offset boost control module  78  is illustrated in  FIG. 2B . The offset boost control module  78  generates an offset boost signal based on the sum of a normal boost and a supplemental boost. The supplemental boost is enabled based on an affirmative output in step  72 . The normal boost represents the airflow injected into the intake manifold  15  by the turbocharger  18  based on normal operating conditions of the engine  12 . The normal boost may be estimated based on engine speed (RPM), fuel injector timing, MAF, coolant temperature, intake air temperature and fuel quantity through a lookup table. The supplemental boost is the additional boost that is necessary to reduce white smoke exhausted through the exhaust  17 . The supplemental boost may be estimated based on engine speed (RPM), fuel quantity, fuel injector timing, MAF, coolant temperature and intake air temperature through a lookup table. If control determines that the measurements are not acceptable, supplemental boost is disabled in step  74  and control ends in step  64 .  
         [0025]     In step  80 , control performs the offset boost with the VNT  18 . More specifically, the control module  14  communicates with the vane solenoid  28  to manipulate a flow of hydraulic fluid to the vane actuator based on the calculated offset boost. In step  82 , control determines the offset boost supplied by the VNT  18 . More specifically, control communicates with the position sensor and the boost sensor to determine an actual boost supplied at the intake manifold  15 . In step  84 , control determines if the actual boost supplied at the intake manifold  15  is correct based on the desired offset boost. If not, control modifies the signal communicated to the vane solenoid  28  in step  88 . If the boost supplied at the intake manifold  15  is correct, control loops to step  70 .  
         [0026]     Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims.