System And Method For Controlling Regeneration Of An Exhaust After-treatment Device

Abstract

A method for controlling regeneration of an exhaust after-treatment device for an internal combustion engine in a vehicle includes establishing a baseline value for a mass of soot collected in the exhaust after-treatment device. The baseline value is a threshold mass of soot to be reached for regenerating the filter, and is determined as a function of a speed of the engine and a quantity of fuel entering the engine. The method also includes modifying the baseline value in response to an engine operating parameter that alters a fuel-air ratio of a combustible mixture entering the engine to generate a modified baseline value. The method additionally includes regenerating the exhaust after-treatment device using the modified baseline value. A system for controlling regeneration of an exhaust after-treatment device for an internal combustion engine is also provided.

Description

TECHNICAL FIELD

[0001] The present invention is drawn to a method for controlling regeneration of an exhaust after-treatment device for an internal combustion engine in a vehicle.

BACKGROUND

[0002] Various exhaust after-treatment devices, such as diesel particulate filters and other devices, have been developed to effectively limit exhaust emissions from internal combustion engines. In the case of diesel engines, a great deal of effort continues to be expended to develop practical and efficient devices and methods for reducing emissions of largely carbonaceous particulates in exhaust gases.

[0003] One method for reducing such particulate emissions is to provide suitable particulate filters or traps in engine or vehicle exhaust systems. Such particulate filters are typically adapted to collect and dispose of the sooty particulate matter emitted from diesel engines prior to discharge of the exhaust gases to atmosphere. Additionally, such filters may be regenerated or cleaned using high temperature exhaust, which burns particles that may otherwise accumulate and clog the system.

SUMMARY

[0004] A method for controlling regeneration of an exhaust after-treatment device for an internal combustion engine in a vehicle includes establishing a baseline value for a mass of soot collected in the exhaust after-treatment device. The baseline value is a threshold mass of soot to be reached for regenerating the filter, and is determined as a function of a speed of the engine and a quantity of fuel entering the engine. The method also includes modifying the baseline value in response to an engine operating parameter that alters a fuel-air ratio of a combustible mixture entering the engine to generate a modified baseline value. The method additionally includes regenerating the exhaust after-treatment device using the modified baseline value.

[0005] According to the method, the modification of the baseline value may be executed in response to an engine operating parameter that alters the fuel-air ratio by varying the mass of air entering the engine.

[0006] The modification of the baseline value may also be executed in response to an engine operating parameter that alters the fuel-air ratio by varying a mass of fuel entering the engine.

[0007] The mass of fuel entering the engine may be varied in one manner when the engine is operating in a steady state and in another manner when the engine is operating in a transient state. Additionally, the mass of fuel entering the engine may be varied by turning on exhaust gas recirculation in the engine.

[0008] Furthermore, according to the method, the modification of the baseline value may be executed via a controller. The controller may be programmed with a look-up table that may include a range for the engine operating parameter.

[0009] A system for controlling regeneration of an exhaust after-treatment device for an internal combustion engine and a vehicle employing such a system are also provided.

[0010] 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

[0011] FIG. 1 is a schematic illustration of vehicle with an engine connected to an exhaust system having an exhaust after-treatment device; and

[0012] FIG. 2 is a flow diagram of a method for controlling regeneration of the exhaust after-treatment device of FIG. 1.

DETAILED DESCRIPTION

[0013] Referring to the drawings, wherein like reference numbers refer to like components throughout the several views, FIG. 1 schematically depicts a vehicle 2. Vehicle 2 includes a system 8 configured to control regeneration of an exhaust after-treatment device 24. System 8 includes an internal combustion engine 10 connected to an air intake system 12. Air intake system 12 is configured for delivering an ambient air flow 14 to the engine for subsequent combining with an appropriate amount of fuel into a combustible mixture entering the engine 10. The temperature of the air flow 14 entering engine 10 is monitored by a sensor 13.

[0014] The air intake system 12 includes a turbocharger 16 for pressurizing the incoming air flow 14, and a charge air cooler 18 for reducing the temperature of the pressurized air flow in order to improve the operating efficiency of engine 10. The temperature of the air flow 14 following the charge air cooler 18 is monitored by a sensor 19. Turbocharger 16 is energized by an exhaust gas flow 20 that is released by engine 10 following each combustion event. The turbocharger 16 is connected to an exhaust system 22, which includes the exhaust after-treatment device 24. As shown, the engine 10 is a compression ignition, i.e., a diesel, engine, and the exhaust after-treatment device 24 is a particulate filter adapted to collect and dispose of the sooty particulate matter emitted from the engine prior to discharge of an exhaust gas flow 20 to atmosphere.

[0015] The exhaust system 22 includes a diesel oxidation catalyst 26 that is adapted to oxidize and burn hydrocarbon emissions present in the exhaust flow 20. Following the diesel oxidation catalyst 26, the exhaust flow 20 passes through a selective catalytic reduction catalyst 28, which reduces at least some of the nitrogen oxides present in the exhaust flow into water and nitrogen. After the reduction catalyst 28, the exhaust flow 20 passes into the exhaust after-treatment device 24 through an entrance 30, and then exits the after-treatment device through an outlet 32 and continues on to the atmosphere sans the majority of soot particulates. Although, as shown, the reduction catalyst 28 is positioned upstream of the exhaust after-treatment device 24, the after-treatment device may also be positioned downstream of the reduction catalyst without affecting the after-treatment of the exhaust flow 20.

[0016] System 8 also includes a controller 34 that is operatively connected to engine 10. Controller 34 is programmed to predict a baseline value for the mass of soot that collects in the after-treatment device 24 during operation of engine 10. The baseline value for the mass of soot is a threshold amount of soot that is allowed to be reached or collected in the after-treatment device 24 before maintenance or regeneration of exhaust system 22 is performed. The baseline value in one embodiment may be established as a function of an operating speed of engine 10 and a quantity of fuel that has entered the engine for combustion. Speed of engine 10 may be sensed by a sensor 36, while the amount of fuel that has entered the engine may be sensed by a sensor 38.

[0017] The baseline value may be an amount of soot that has been empirically determined to be the level at which maintenance of exhaust system 22 should be performed. Maintenance of exhaust system 22 may be achieved either by active regeneration or by replacing the after-treatment device 24. Active regeneration of the after-treatment device 24 may be performed by changing operating parameters of engine 10 to increase temperature of exhaust flow 20 to burn the soot that has collected in the after-treatment device. Accordingly, controller 34 may be programmed to command or trigger the engine 10 to actively regenerate the after-treatment device 24. Additionally, active regeneration of the after-treatment device 24 may be performed by a direct injection and igniting of fuel in the exhaust gas flow 20. In such a case, controller 34 may be programmed to command the fuel to be injected into the exhaust system 22 at an appropriate time.

[0018] Controller 34 is additionally programmed to modify by a mathematical calculation the baseline value in response to engine operating parameters that alter a fuel-air ratio of the combustible mixture entering engine 10. In general, when the fuel-air ratio is increased, the mass of soot collecting in the after-treatment device 24 is increased. The operating parameters that alter or influence a fuel-air ratio of the combustible mixture entering engine 10 may include a change in density of the incoming air flow 14, i.e., an increase or a decrease in the mass of the air entering the engine. A signal indicating a change in density of the incoming air flow 14 may be provided to the controller 34 by a sensor 40. Sensor 40 is adapted to detect the ambient air pressure, which may then be correlated to the altitude at which engine 10 is operating. Additionally, a signal from a sensor 42 that is adapted to sense ambient air temperature may be employed to further modify the baseline value.

[0019] The operating parameters that influence a fuel-air ratio of the combustible mixture entering engine 10 may also include a signal indicating whether the engine 10 is operating in a transient or in a steady state. When engine 10 is operating in the transient state, an additional amount of fuel may be used for combustion, as compared to the amount of fuel being injected into the engine during the steady state operation. The baseline value may be modified to indicate that a larger mass of soot is being collected when the engine 10 is operating in a transient state, and modified to indicate that a lower mass of soot is being collected when the engine is operating in a steady state. Whether the engine 10 is operating in a transient or in a steady state is regulated by the controller 34. A signal indicating the current operating state of engine 10 may, therefore, also be provided by the controller 34.

[0020] The operating parameters that influence a fuel-air ratio of the combustible mixture entering engine 10 may additionally include whether an exhaust gas recirculation (EGR) valve 44 is on or off As is appreciated by those skilled in the art, when the EGR valve 44 is on, the fuel-air mixture becomes richer because the re-circulated exhaust gas flow 20 includes unburned fuel which is reintroduced for combustion. Therefore, the baseline value is modified to show an increase in the mass of soot collected in the after-treatment device 24 when the EGR valve 44 is on. The controller 34 is additionally programmed to trigger regeneration of the after-treatment device 24 using the baseline value that was modified in response to the sensed variation in the engine operating parameters that alter the amount of air entering the engine 10. In operation, when the current modified baseline value for the mass of soot collected reaches a predetermined level, the controller 34 provides an output signal that indicates a trigger to perform regeneration of the after-treatment device.

[0021] Furthermore, controller 34 may be programmed with a look-up table 46 that includes ranges of values for the previously described operating parameters of engine 10 that influence or alter a fuel-air ratio of the combustible mixture entering the engine. The ranges of values for the operating parameters of engine 10 that influence or alter a fuel-air ratio of the combustible mixture are typically determined empirically during the testing and calibration stages of engine development. Once determined, the variation in such operating parameter values is correlated with a variation in the amount of soot mass that is collected in the after-treatment device 24. Based on the recorded variation in the amount of soot collected, a mathematical factor is derived for each observed data point of each operating parameter, representing the effect that such variation has on the mass of soot collected above the baseline value. Additionally, the observed data points for the operating parameters may be plotted to generate graphical curves and then utilize the curves to interpolate between data points, thus generating continuous ranges of mathematical factors.

[0022] The derived mathematical factors are assembled into a look-up table 46, which is then programmed into the controller 34 for subsequent access during actual operation of engine 10. Thus, generally in order to determine the modified baseline value for the mass of soot collected in the after-treatment device 24, controller 34 multiplies the predetermined baseline value by the derived factor(s) whenever the described variation in the engine operating parameter(s) is sensed. Following such modification of the baseline value for the mass of soot, controller 34 triggers the regeneration of the after-treatment device 24 to burn off the collected particulates prior to the occurrence of any damage to the device.

[0023] FIG. 2 depicts a method 50 for controlling regeneration of the exhaust after-treatment device 24 as described with respect to FIG. 1. Accordingly, the method commences in frame 52, where it includes establishing the baseline value for the mass of soot collected in the exhaust after-treatment device 24 that is to be reached prior to regenerating the filter. As described above, the baseline value for the mass of soot may be based on the speed of engine 10, and on the quantity of fuel entering the engine. Following frame 52, the method proceeds to frame 54, where it includes modifying the baseline value for the mass of soot collected in response to the engine operating parameter that alters the fuel-air ratio of the combustible mixture entering engine 10. The baseline value for the mass of soot collected may be modified by the controller accessing the appropriate derived mathematical factors in the look-up table 46, as described above.

[0024] As described above, the engine operating parameter that alters the fuel-air ratio of the combustible mixture may include a factor that drives a change in the density of air that is used by the engine 10 for combustion. The engine operating parameter that alters the fuel-air ratio of the combustible mixture may also include a factor that accounts for the engine 10 operating either at a steady or at a transient state. Additionally, the engine operating parameter that alters the fuel-air ratio of the combustible mixture may include a factor that accounts for whether the exhaust gas recirculation (EGR) in the engine 10 is on or off. Controller 34 may be programmed to continuously monitor the appropriate time to trigger regeneration of the exhaust after-treatment device 24 based on the modified baseline value of soot collected.

[0025] After the baseline value for the mass of soot collected in the exhaust after-treatment device 24 has been modified in frame 54, the method advances to frame 56. In frame 56, the method includes regenerating the exhaust after-treatment device 24 using the modified baseline value for the mass of soot. Following frame 56, the method may loop back to frame 52. Once the method returns to frame 52, the monitoring of sensors 13, 19, 36, 38, 40, and 42, as well as monitoring of the status of EGR valve 44, may be resumed in order to determine the appropriate time for the next regeneration of the after-treatment device 24.

[0026] 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.

Claims

1. A method for controlling regeneration of an exhaust after-treatment device for an internal combustion engine in a vehicle, comprising: establishing a baseline value for a mass of soot collected in the exhaust after-treatment device, wherein the baseline value is a threshold mass of soot to be reached before regenerating the after-treatment device, and is determined as function of a speed of the engine and a quantity of fuel entering the engine; modifying the baseline value in response to an engine operating parameter to generate a modified baseline value, the engine operating parameter altering a fuel-air ratio of a combustible mixture entering the engine; and regenerating the exhaust after-treatment device using the modified baseline value.

2. The method according to claim 1, wherein said modifying the baseline value is executed in response to an engine operating parameter that alters the fuel-air ratio by varying a mass of air entering the engine.

3. The method according to claim 2, wherein said modifying the baseline value is executed in response to an engine operating parameter that alters the fuel-air ratio by varying a mass of fuel entering the engine.

4. The method according to claim 3, wherein the mass of fuel entering the engine is varied in one manner when the engine is operating in a steady state and in another manner when the engine is operating in a transient state.

5. The method according to claim 3, wherein the mass of fuel entering the engine is varied by an exhaust gas recirculation in the engine being turned on.

6. The method according to claim 1, wherein said modifying the baseline value is executed via a controller.

7. The method according to claim 6, wherein the controller is programmed with a look-up table that includes a range for the engine operating parameter.

8. A system for controlling regeneration of an exhaust after-treatment device, comprising: an internal combustion engine that generates an exhaust gas as a byproduct of combustion and transfers the exhaust gas to the after-treatment device; and a controller which is: programmed with an established baseline value for a threshold mass of soot collected in the exhaust after-treatment device before regenerating the after-treatment device, wherein the baseline value is determined as a function of a speed of the engine and a quantity of fuel entering the engine; and programmed to modify the baseline value in response to an engine operating parameter that alters a fuel-air ratio of a combustible mixture entering the engine; wherein the controller regenerates the exhaust after-treatment device using the modified baseline value.

9. The system according to claim 8, wherein the baseline value is modified in response to an engine operating parameter that alters the fuel-air ratio by varying a mass of air entering the engine.

10. The system according to claim 9, wherein the baseline value is modified in response to an engine operating parameter that alters the fuel-air ratio by varying a mass of fuel entering the engine.

11. The system according to claim 10, wherein the mass of fuel entering the engine is varied in one manner when the engine is operating in a steady state and in another manner when the engine is operating in a transient state.

12. The system according to claim 10, wherein the mass of fuel entering the engine is varied by an exhaust gas recirculation in the engine being turned on.

13. The system according to claim 8, wherein the controller is additionally programmed with a look-up table that includes a range for the engine operating parameter.

14. A vehicle comprising: an internal combustion engine that generates an exhaust gas as a byproduct of combustion; an exhaust after-treatment device configured to receive the exhaust gas and adapted to be regenerated; and a controller which is: programmed with an established baseline value for a threshold mass of soot collected in the exhaust after-treatment device before regenerating the after-treatment device, wherein the baseline value is determined as a function of a speed of the engine and a quantity of fuel entering the engine; and programmed to modify the baseline value in response to an engine operating parameter that alters a fuel-air ratio of a combustible mixture entering the engine; wherein the controller regenerates the exhaust after-treatment device using the modified baseline value.

15. The vehicle according to claim 14, wherein the baseline value is modified in response to an engine operating parameter that alters the fuel-air ratio by varying a mass of air entering the engine.

16. The vehicle according to claim 15, wherein the baseline value is modified in response to an engine operating parameter that alters the fuel-air ratio by varying a mass of fuel entering the engine.

17. The vehicle according to claim 16, wherein the mass of fuel entering the engine is varied in one manner when the engine is operating in a steady state and in another manner when the engine is operating in a transient state.

18. The vehicle according to claim 16, wherein the mass of fuel entering the engine is varied by an exhaust gas recirculation in the engine being turned on.

19. The vehicle according to claim 14, wherein the controller is additionally programmed with a look-up table that includes a range for the engine operating parameter.