Abstract:
A particulate filter regeneration system for an internal combustion engine includes a plurality of combustion cylinders, an intake manifold and an exhaust manifold. The particulate filter regeneration system includes a particulate filter adapted for communication with the exhaust manifold, a flame heater adapted for communication with the intake manifold, and a temperature indicator for providing an indication of a temperature associated with the exhaust manifold. A controller is coupled with the temperature indicator and the flame heater. The controller actuates the flame heater dependent upon a particulate filter regeneration indicator and a signal from the temperature indicator indicating a temperature of less than approximately 300° C.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to internal combustion engines, and, more particularly, to a system and method for regenerating particulate filters used for filtering particulates from an exhaust stream in such an internal combustion engine. 
       BACKGROUND OF THE INVENTION 
       [0002]    In order to meet existing and future particulate emission standards for internal combustion (IC) engines, in particular diesel engines, manufacturers of diesel engines are using particulate filters (PF, also referred to as particulate traps). Such particulate filters are typically placed downstream of the turbocharger turbine and remove solid particulate matter before it exits the exhaust system to the ambient environment. After a particulate filter collects particulates for a period of time, increasing the exhaust temperature to a suitable level (e.g., above a minimum of 600° C.) cleans the filter (also known as regenerating) since the oxygen in the exhaust burns the accumulated carbon in the filter. 
         [0003]    Particulate filters for diesel engines are typically relatively large and expensive, and regeneration under light load conditions is problematic because attaining the necessary exhaust temperature is difficult. This high exhaust temperature is typically accomplished by adding fuel to the exhaust of the diesel engine and flowing this mixture through a diesel oxidation catalyst (DOC). However, the mixture temperature entering the DOC has to be a minimum of about 300° C. to ensure good oxidation of the added fuel. Various means of obtaining the necessary 300° C. exhaust temperature at light loads and low ambient temperatures have been proposed and put into production. Methods of increasing exhaust temperature include adding additional load on the engine, retarding injection timing, injecting additional fuel very late in the combustion process, and reducing engine air flow by air system changes such as turbocharger compressor bypass and changing vane settings on variable geometry turbochargers. 
         [0004]    What is needed in the art is a system and method of easily increasing the exhaust temperature entering a DOC for effective regeneration of the PF under light loads. 
       SUMMARY OF THE INVENTION 
       [0005]    The invention in one form is directed to an internal combustion engine, including a plurality of combustion cylinders, an intake manifold in communication with at least one of the combustion cylinders, and an exhaust manifold in communication with at least one of the combustion cylinders. A particulate filter is in communication with the exhaust manifold, and a flame heater is in communication with the intake manifold. A controller is coupled with one or more temperature indicators and the flame heater. The controller actuates the flame heater dependent upon a particulate filter regeneration indicator and a signal from at least one temperature indicator. 
         [0006]    The invention in another form is directed to a particulate filter regeneration system for an internal combustion engine including a plurality of combustion cylinders, an intake manifold and an exhaust manifold. The particulate filter regeneration system includes a particulate filter adapted for communication with the exhaust manifold, a flame heater adapted for communication with the intake manifold, and a temperature indicator for providing an indication of a temperature associated with the exhaust manifold. A controller is coupled with the temperature indicator and the flame heater. The controller actuates the flame heater dependent upon a particulate filter regeneration indicator and a signal from the temperature indicator indicating a temperature of less than approximately 300° C. 
         [0007]    The invention in yet another form is directed to a method of regenerating a particulate filter in an internal combustion engine, including the steps of: providing a particulate filter regeneration indicator; determining that an exhaust temperature is below a predetermined threshold value; and actuating a flame heater to heat intake air associated with an intake manifold, dependent upon each of the particulate filter regeneration indicator and the determined exhaust temperature above the predetermined threshold value. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a schematic view of an IC engine including an embodiment of a particulate filter regeneration system of the present invention; and 
           [0009]      FIG. 2  is a flowchart illustrating an embodiment of the control logic for the particulate filter regeneration system shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0010]    Referring now to the drawings, and more particularly to  FIG. 1 , there is shown an embodiment of an IC engine  10  which includes an embodiment of a particulate filter regeneration system  12  of the present invention for regenerating a particulate filter  14  at selected points in time. IC engine  10  also generally includes an engine block  16 , turbocharger  18 , DOC  20 , EGR system  22  and air-to-air aftercooler (ATAAC)  24 . 
         [0011]    Engine block  16  includes a plurality of combustion cylinders  26 , four of which are shown in  FIG. 1  for illustration purposes. The particular number of combustion cylinders  26  can of course vary depending upon the application. Each combustion cylinder  26  is fluidly coupled with an intake manifold  28  and an exhaust manifold  30 . In the embodiment shown, a single intake manifold  28  and exhaust manifold  30  are provided; however, it is also to be understood that split manifolds may also be used for a particular application. 
         [0012]    Exhaust manifold  30  is fluidly coupled with turbocharger  18 , including a turbine  32  which rotatably drives a compressor  34  via a drive shaft  36 . Part of the exhaust which is used to drive turbine  32  may be bled off using EGR system  22  for recirculation back to intake manifold  28 . To that end, an EGR valve  38  is controllably actuated to control the amount of exhaust which is recirculated to intake manifold  28 . 
         [0013]    The majority of the exhaust which is not recirculated using EGR system  22  flows through turbine  32  and is discharged to DOC  20 . DOC  20  may be of known design, and thus is not described further herein. 
         [0014]    Particulate filter  14  is used to filter particulate matter from the exhaust flow prior to being discharged from the ambient environment, and may likewise be of conventional design. Particulate filter  14  may be configured as a single particulate filter or multiple particulate filters, depending upon the application. 
         [0015]    Compressor  34  of turbocharger  18  receives combustion air from the ambient environment and compresses the combustion air which is provided to intake manifold  28 . The work of compression on the combustion air heats the combustion air, which is then cooled using ATAAC  24  upstream from intake manifold  28 . 
         [0016]    Particulate filter regeneration system  12  generally includes a flame heater  40 , one or more temperature indicators  42  and ECU  44 . ECU  44  may take the form of any desired combination of electronic hardware and/or software, depending upon the application. In the embodiment shown, ECU  44  is preferably a microprocessor based ECU for performing the various functionality described hereinafter. 
         [0017]    Temperature indicators  42  provide an indication of a temperature associated with exhaust manifold  30 . Such indicators may be positioned at the upstream or downstream side of exhaust manifold  30 , and can be used to directly or indirectly determine the temperature of the exhaust. For example, in the embodiment shown, one temperature indicator  42 A is provided at the upstream side of intake manifold  28 , another temperature indicator  42 B is provided between exhaust manifold  30  and the inlet to turbine  32 , and yet another temperature indicator  42 C is provided between turbine  32  and the inlet of DOC  20 . Temperature indicators  42  are preferably in the form of temperature sensors which may be used to directly determine the temperature of a passing fluid, such as the combustion air on the upstream side of intake manifold  28  or exhaust on the downstream side of exhaust manifold  30 . Alternatively, temperature indicators  42  may be in the form of another type of sensor which can provide an indirect indication of the temperature at selected points along the flow path of the combustion air and/or exhaust. For example, temperature indicators  42  may also be in the form of pressure sensors from which a corresponding temperature of the fluid may be calculated. Temperature indicators  42  are coupled with and provide input signals to ECU  44  via corresponding electric lines, but could also be wirelessly coupled with ECU  44 . 
         [0018]    Flame heater  40  is in fluid communication with the compressed combustion air on the upstream side of intake manifold  28 , and is used to selectively heat the intake air to a desired temperature, thereby in turn raising the temperature of exhaust flowing to DOC during a regeneration mode of particulate filter  14 . Flame heater  40  includes a glow plug  46  and a selectively actuated valve  48  which controls a flow of fuel used to generate an open flame for heating the compressed combustion air. Valve  48  is fluidly coupled with and receives fuel from a fuel source  50 , such as an onboard diesel fuel tank on a vehicle. Fuel source  50  may be separate from or the same as the fuel source supplying fuel to combustion cylinders  26 , and also may be the same or a different type of fuel than that supplied to combustion cylinders  26 . Valve  48  is likewise electrically coupled with ECU  44  for controllable actuation during operation. 
         [0019]    Glow plug  46  is typically first turned on for a predetermined period of time prior to opening valve  48  for injection of the fuel for the open flame. Glow plug  46  is electrically coupled with and controllably actuated by ECU  44  as shown. Glow plug  46  may also be controllably actuated to be used as a standard glow plug during engine startup at cold ambient temperatures. Such flame heaters are known for use at engine start-up to increase the intake manifold temperature to allow starting of the diesel engine in cold ambient conditions. For example, Beru Aktiengesellschaft, Ludwigsburg, Germany, and others have made flame heaters for use at engine startup which may be used as a heat source with the particulate filter regeneration system of the present invention. (see, e.g., htt:/www.beru.com/english/produkte/flammstartsystem.php). 
         [0020]    ECU  44  is also coupled with a particulate filter regeneration indicator  52  used as an input for initiating a regeneration cycle for particulate filter  14 . PF regen indicator  52  typically is a separately determined function, such as by using a timed based indicator flag corresponding to the number of hours of engine operation since a last regeneration of particulate filter  14 . Alternatively, PF regen indicator  52  can be integrally incorporated into the logic of ECU  44 . 
         [0021]    Referring now to  FIG. 2 , there is shown a flow chart which will be used to describe the control logic for particulate filter regeneration system  12  of the present invention. At start block  60 , the particulate filter regeneration is initiated using PF regen indicator  52 . At decision block  62 , if the inlet temperature of the exhaust at DOC  20  is greater than 350° C. (NO), then the temperature is already high enough for hydrocarbon dosing for regeneration of PF filter  14  and control logic passes directly to block  64 . Otherwise, if the temperature of the exhaust entering DOC  20  is less than 350° C. (YES), then the glow plug  46  of flame heater  40  is turned on (block  66 ). 
         [0022]    At decision block  68 , the temperature at the inlet to turbine  32  is sensed using sensor  42 B. If the exhaust temperature at the inlet to turbine  32  is greater than 700° C., then a max exhaust temperature already exists and the fuel flow to flame heater  40  is either turned off or maintained off by placing valve  48  in the closed position (block  70 ). Alternatively, if the exhaust temperature at the inlet to turbine  32  is not greater than 700° C. (decision block  68 , NO), then valve  48  is opened to allow fuel to flow to the termination at glow plug  46 , resulting in an open flame for heating the compressed combustion air to intake manifold  28  (block  72 ). Flame heater  40  increases the temperature of the intake air to intake manifold  28  at least 100° C., preferably approximately 200° C. If the exhaust inlet temperature to DOC  20  is greater than 300° C. (decision block  74 , YES), then hydrocarbon dosing within DOC  20  occurs for regeneration of particulate filter  14 . Otherwise, if the exhaust temperature at the inlet to DOC  20  is less than 300° C. (NO), then control loops back to the input side of decision block  68  and the fuel flow to flame heater  40  is maintained in the ON position. 
         [0023]    After hydrocarbon dosing within DOC  20  occurs for regeneration of particulate filter  14 , a decision is made as to whether the regeneration of particulate filter  14  is complete (decision block  76 ). If the regeneration is not complete, then the control logic loops back to the input side of decision block  62  and the process repeats. Otherwise, if the regeneration of particulate filter  14  is complete (YES), then ECU  44  turns off glow plug  46  and closes valve  48  for termination of the regeneration control logic (block  78 ). 
         [0024]    Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.