Patent Publication Number: US-8978370-B2

Title: Engine off particulate filter (“PF”) regeneration using a single secondary energy storage device

Description:
FIELD OF THE INVENTION 
     Exemplary embodiments of the invention relate to exhaust gas treatment systems for internal combustion engines and, more particularly, to an exhaust gas treatment system that includes a single secondary energy storage device selectively connected to a primary energy storage device. 
     BACKGROUND 
     The exhaust gas emitted from an internal combustion engine is a heterogeneous mixture that contains gaseous emissions such as carbon monoxide (“CO”), unburned hydrocarbons (“HC”) and oxides of nitrogen (“NO x ”) as well as condensed phase materials (liquids and solids) that constitute particulate matter (“PM”). An exhaust treatment technology in use for high levels of particulate matter reduction may include a particulate filter (“PF”) device including a filter that traps particulate matter. Regeneration is the process of removing the accumulated particulate matter from the PF device. 
     During regeneration, a front surface of the filter is heated to a specified temperature that allows for the trapped particulate matter to oxidize, thereby creating a flame front that generally burns longitudinally along the filter. In one approach, the exhaust gas temperature may be raised through operation of the engine during regeneration. Specifically, the exhaust gas temperature is elevated to a level sufficient to reduce the probability that the flame front may be extinguished by relatively high airflow created by accelerating the engine. However, raising the exhaust gas temperature generally requires increased amounts of fuel, which in turn will decrease fuel economy. Moreover, exhaust emissions are increased during the regeneration process. 
     Active regeneration refers to the process of oxidizing the accumulated diesel particulate matter in the PF device without relying on the temperature of the exhaust gas emitted by the engine, which in turn improves fuel economy. This approach may involve heating the PF device by an electrical heater until the PF device reaches the point at which the particular matter trapped in the PF device oxidizes. The electrical heater is energized if the engine is turned off, and generally receives electrical power from a vehicle battery. However, the use of an electrical heater while the engine is turned off will, over time, diminish the vehicle battery. Accordingly, it is desirable to provide an exhaust gas treatment system that provides heat needed for regeneration when the engine is turned off, while at the same time reducing or substantially eliminating battery drainage. 
     SUMMARY OF THE INVENTION 
     In one exemplary embodiment of the invention, an exhaust gas treatment system for an internal combustion engine is provided. The internal combustion engine has an engine off condition. The exhaust gas treatment system includes a particulate filter (“PF”) device in fluid communication with an exhaust gas conduit, an electric heater, a primary energy storage device, a single secondary energy storage device, and a control module. The PF device has a filter structure for removal of particulates in the exhaust gas. The PF device is selectively regenerated based on an amount of particulates trapped within the filter structure. The electric heater is disposed upstream of the filter structure and is selectively energized to provide heat for regeneration of the PF device. The single secondary energy storage device is selectively connected to the primary energy storage device. The single secondary energy storage device selectively energizes the electric heater. The control module is in communication with the electric heater, the primary storage device, the single secondary energy storage device, and the internal combustion engine. The control module receives a regeneration signal indicating the amount of particulates trapped within the filter structure of the PF device. The control module includes control logic for disconnecting the single secondary energy storage device from the primary storage device if the internal combustion engine is in the engine off condition. The control module includes control logic for connecting the single secondary energy storage device to the electric heater if the regeneration signal is received. 
     The above features and advantages and other features and advantages of the invention are readily apparent from the following detailed description of the invention when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features, advantages and details appear, by way of example only, in the following detailed description of embodiments, the detailed description referring to the drawings in which: 
         FIG. 1  is a schematic diagram of an exemplary exhaust gas treatment system; 
         FIG. 2  is a schematic diagram of the circuit illustrated in  FIG. 1 ; and 
         FIG. 3  is a process flow diagram illustrating a method of operating the exhaust gas treatment system shown in  FIG. 1 . 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 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 executes one or more software or firmware programs, and/or a combinational logic circuit. 
     Referring now to  FIG. 1 , an exemplary embodiment is directed to an exhaust gas treatment system  10 , for the reduction of regulated exhaust gas constituents of an internal combustion (“IC”) engine  12 . The exhaust gas treatment system described herein can be implemented in various engine systems that may include, but are not limited to, diesel engine systems, engine systems, and homogeneous charge compression ignition engine systems. 
     The exhaust gas treatment system  10  generally includes one or more exhaust gas conduits  14 , and one or more exhaust treatment devices. In the embodiment as illustrated, the exhaust gas treatment system devices include an oxidation catalyst device (“OC”)  20 , a selective catalytic reduction device (“SCR”)  22 , and a particulate filter (“PF”) device  24 . As can be appreciated, the exhaust gas treatment system of the present disclosure may include various combinations of one or more of the exhaust treatment devices shown in  FIG. 1 , and/or other exhaust treatment devices (not shown), and is not limited to the present example. 
     In  FIG. 1 , the exhaust gas conduit  14 , which may comprise several segments, transports exhaust gas  15  from the IC engine  12  to the various exhaust treatment devices of the exhaust gas treatment system  10 . The OC device  20  includes, for example, a flow-through metal or ceramic monolith substrate that may be packaged in a stainless steel shell or canister having an inlet and an outlet in fluid communication with exhaust gas conduit  14 . The substrate can include an oxidation catalyst compound disposed thereon. The oxidation catalyst compound may be applied as a wash coat and may contain platinum group metals such as platinum (Pt), palladium (Pd), rhodium (Rh) or other suitable oxidizing catalysts, or combination thereof. The OC  20  is useful in treating unburned gaseous and non-volatile HC and CO, which are oxidized to form carbon dioxide and water. 
     The SCR device  22  may be disposed downstream of the OC device  20 . In a manner similar to the OC device  20 , the SCR device  22  may include, for example, a flow-through ceramic or metal monolith substrate that may be packaged in a stainless steel shell or canister having an inlet and an outlet in fluid communication with the exhaust gas conduit  14 . The substrate may include an SCR catalyst composition applied thereto. The SCR catalyst composition may contain a zeolite and one or more base metal components such as iron (“Fe”), cobalt (“Co”), copper (“Cu”) or vanadium (“V”) which can operate efficiently to convert NO x  constituents in the exhaust gas  15  in the presence of a reductant such as ammonia (“NH 3 ”). 
     A reductant  30  may be supplied from a reductant supply source (not shown) and may be injected into the exhaust gas conduit  14  at a location upstream of the SCR device  22  using an injector  32 , or other suitable method of delivery of the reductant  30  to the exhaust gas  15 . In one embodiment, the reductant  30  reductant may be an aqueous urea solution that decomposes to ammonia (“NH 3 ”) in the hot exhaust gases and is absorbed by the SCR device  22 . The ammonia then reduces the NO x  to nitrogen in the presence of the SCR catalyst. A mixer or turbulator  34  may also be disposed within the exhaust conduit  14  in close proximity to the injector  32  to further assist in thorough mixing of the reductant  30  with the exhaust gas  15 . 
     The PF device  24  may be disposed downstream of the OC device  20  and the SCR device  22 . The PF device  24  operates to filter the exhaust gas  15  of carbon and other particulates. In various embodiments, the PF device  24  may be constructed using a ceramic wall flow monolith filter  40  that is wrapped in an insulation mat or other suitable support that expands when heated, securing and insulating the filter  40 . The filter  40  may be packaged in a shell or canister that is, for example, stainless steel, and that has an inlet and an outlet in fluid communication with exhaust gas conduit  14 . 
     The ceramic wall flow monolith filter  40  may have a plurality of longitudinally extending passages that are defined by longitudinally extending walls. The passages include a subset of inlet passages that have and open inlet end and a closed outlet end, and a subset of outlet passages that have a closed inlet end and an open outlet end. Exhaust gas  15  entering the filter  40  through the inlet ends of the inlet passages is forced to migrate through adjacent longitudinally extending walls to the outlet passages. It is through this wall flow mechanism that the exhaust gas  15  is filtered of carbon and other particulates. The filtered particulates are deposited on the longitudinally extending walls of the inlet passages and, over time, will have the effect of increasing the exhaust gas backpressure experienced by the IC engine  12 . It is appreciated that the ceramic wall flow monolith filter is merely exemplary in nature and that the PF device  24  may include other filter devices such as wound or packed fiber filters, open cell foams, sintered metal fibers, etc. The increase in exhaust backpressure caused by the accumulation of particulate matter in the monolith filter  40  typically requires that the PF device  24  is periodically cleaned, or regenerated. Regeneration involves the oxidation or burning of the accumulated carbon and other particulates in what is typically a high temperature environment (&gt;600° C.). 
     The electric heater  52  is included to selectively provide heat to the PF device  24 . In the embodiment as shown, the electric heater  52  is positioned proximate to a front face  54  of the monolith filter  40  of the PF device  24 . Specifically, the electric heater  52  is mounted to an upstream end  56  of the monolith filter  40 . The electric heater  52  may include a resistive heating element (not shown) such as, for example, a resistive wire. When energized, electric current flows to the electric heater  52  through the resistive wire to generate heat. The electric heater  52  allows for the exhaust gas  15  and particulate matter to flow through to the PF device  24 . In one exemplary embodiment, a zoned electric heater may be employed that heats zoned sections to the monolith filter  40 , however, it is to be understood that other types of electric heaters may be used as well. 
     The exhaust gas treatment system  10  also includes various energy storage devices. In the embodiment as illustrated, a primary energy storage device  42  and a single secondary energy storage device  44  are provided. The primary energy storage device  42  is a vehicle battery such as, for example, a 12 volt lead acid type battery. Although a lead acid battery is discussed, it is to be understood that other types of energy storage devices may be used as well. The secondary energy storage device  44  is generally any type of rechargeable energy storage device such as, for example, a lithium-ion battery or an ultracapacitor. 
     The primary energy storage device  42  is electrically connected to a vehicle generator  46 . The generator  46  is part of the engine  12 . The generator  46  converts mechanical power and energy received from the engine  12  into electrical power and energy needed for vehicle electrical loads of various electrical components and systems of a vehicle (not shown). The generator  46  may convert additional mechanical power and energy into electrical power and energy beyond what is needed for the vehicle electrical loads (not shown). This additional electrical power and energy is referred to as the excess power or energy. In this case, an electrical system voltage is generally raised, and the excess power or energy from the generator  46  is stored in the primary energy storage device  42 , in the secondary energy storage device  44 , or in both the primary and secondary energy storage devices  42  and  44 . Likewise, if the generator  46  does not convert the mechanical power and energy into electrical power and energy required for vehicle electrical loads (not shown), then the electrical system voltage is generally lowered. Power or energy may be removed from the primary energy storage device  42 , the secondary energy storage device  44 , or from both the primary and secondary energy storage devices. The secondary energy storage device  44  is selectively connected to the primary energy storage device  42  and the vehicle generator  46  through a circuit  50 . One embodiment of the circuit  50  is illustrated in  FIG. 2 , and the operation of the circuit  50  is described in subsequent paragraphs. 
     During operation of the engine  12  (e.g., during an engine on condition), the primary energy storage device  42  may charge the secondary energy device  44 . Specifically, in one embodiment, the state of charge (“SOC”) of the primary energy storage device  42  and the secondary energy storage device  44  may be monitored to determine if the primary energy storage device  42  should charge the secondary energy device  44 . After starting the engine  12  (e.g., to the engine on condition), the SOC of the primary energy storage device  42  and the secondary energy storage device  44  are both monitored to determine if a threshold SOC is maintained. Specifically, the SOC of the primary energy storage device  42  is monitored to determine if the SOC is above a primary threshold level (e.g., in one embodiment to 85% SOC). Alternatively, the charging current of the primary energy storage device  42  may drop to a threshold current (e.g., 2 Amps). If either condition is met, the vehicle electrical system voltage is maintained such that the primary energy storage device  42  may not be charged or discharge (e.g., once the primary energy storage device  42  reaches 85% SOC, the secondary energy storage device  44  may not be charged by the primary energy storage device  42 ). 
     In one embodiment, an unfueled vehicle braking event may be used to charge the primary energy storage device  42  and the secondary energy device  44  during the engine on condition. Specifically, in the event a brake pedal (not illustrated) is pressed by a driver, fueling to the engine  12  is temporarily ceased. During the unfueled vehicle braking event, the vehicle generator  46  converts mechanical power and energy into electrical power and energy beyond what is required for vehicle electrical loads (e.g., the excess power or energy). Thus, the electrical system voltage is generally raised, and the excess power or energy is stored in the primary energy storage device  42  and in the secondary energy storage device  44  through the circuit  50 . Once the secondary energy storage device  44  is charged to above a SOC level that supports heating of the electrical heater  52  during regeneration, the secondary energy storage device  44  may no longer be charged through the circuit  50  during the unfueled vehicle braking event. 
     The electric heater  52  is energized during regeneration of the PF device  24  to provide heat to the monolith filter  40 . In one embodiment, the electrical heater  52  is energized during regeneration of the PF device  24  if the IC engine  12  is in an engine off condition. The electrical heater  52  is selectively connected to the secondary energy storage device  44  by the circuit  50 , where the secondary energy storage device  44  provides electrical power to the electrical heater  52 . 
     An air pump  60  is disposed upstream of the electric heater  52  and provides airflow to the PF device  24  during regeneration if the engine  12  is in the engine off condition. The air pump  60  is selectively connected to and energized by the circuit  50 , where the secondary energy storage device  44  provides power to the air pump  60 . A check valve (not illustrated) is included as well to generally prevent backflow through the air pump  60  when the air pump  60  is not in use (e.g., when the engine  12  is in the engine on condition and operating). 
     A control module  70  is operably connected to and monitors the engine  12 , the injector  32 , the circuit  50 , and the exhaust gas treatment system  10  through a number of sensors. Specifically,  FIG. 1  illustrates the control module  70  in communication with a temperature sensor  72  located in the exhaust gas conduit  14  as well as a backpressure sensor  76 . The temperature sensor  72  is situated downstream of the PF device  24 , and sends electrical signals to the control module  70  indicating the temperature in the exhaust gas conduit  14  at a specific location. That is, the temperature sensor  52  indicates the temperature of the PF device  24 . 
     The backpressure sensor  76  is located upstream of the PF device  24  and generates a signal indicative of the carbon loading and particulate loading in the monolith filter  40 . It should be noted that while  FIG. 1  illustrates a backpressure sensor  76  for determining carbon loading in the monolith filter  40 , other approaches may be used as well for determining carbon loading. For example, in an alternative embodiment, a delta pressure sensor may be used instead to measure the differential pressure across the PF device  24 . The control module  70  includes control logic for continuously monitoring the backpressure sensor  76  and the temperature sensor  72 . Specifically, the control module  70  includes control logic for monitoring the backpressure sensor  76  for the amount of particulates trapped within the monolith filter  40  of the PF device  24 . For example, in one embodiment, the amount of particulates trapped within the monolith filter  40  may be the minimum amount of particulate matter that allows for self-combustion. For example, in one embodiment, the minimum amount of particulate matter needed for self-combustion is about 2 g/l. The control module  70  further includes control logic for continuously monitoring the temperature sensor  72  for a temperature reading of the PF device  24 . 
     In the embodiment as shown, the control module  70  is also in communication with an ignition switch  80 . The ignition switch  80  sends a signal to the control module  70  that is indicative of the engine off condition. Specifically, the ignition switch  80  includes a key-on state and a key-off state, where the key-off state coincides with the engine off condition. It should be noted that while the terms key-on and key-off are used, a key may not be employed with the ignition switch  80  in some embodiments. For example, in one embodiment the ignition switch  80  may be activated by proximity to a fob (not shown) that is carried by a user instead of a key. Thus, the key-off state exists when power is supplied to the engine  12  and the key-off state exists when power is not supplied to the engine  12 , regardless of whether an actual key is employed. It should also be noted that while an ignition switch  80  is illustrated, other approaches may be used as well to determine the engine off condition. 
     The control module  70  includes control logic for selectively initiating regeneration of the PF device  24  during the engine off condition. Regeneration occurs if the amount of particulates trapped within the monolith filter  40  of the PF device  24  exceeds a threshold pressure value indicative of the need to regenerate, as well as if the temperature reading from the temperature sensor  72  exceeds a threshold temperature value indicative of the ability to regenerate. 
     In the illustration as shown in  FIG. 2 , the electric heater  52  is shown as a resistor. In the example as shown, the secondary energy storage device  44  is an ultracapacitor (which is labeled C 1 ), however, it is to be understood that a battery may be used as well. The circuit  50  also includes a resistive element  90 , voltage measurement devices  92  and  94 , and switching elements  96 ,  98 , and  100 . In the embodiment as shown in  FIG. 2 , the resistive element  90  is an optional element and may be used as a current limiting resistor to limit inrush current to the ultracapacitor C 1  when the switching element  98  is in a closed position. 
     In the exemplary embodiment as shown, the switching elements  96 ,  98  and  100  are illustrated as single-pole single throw switches. In one embodiment, the switching elements  96 ,  98  and  100  are mechanical switches that are actuated by a mechanical element (e.g., a rotating cam, which is not illustrated in  FIG. 2 ). In another approach, the switching elements may be relays. In yet another embodiment, the switch elements may be transistors. For example, in one embodiment, the switching elements may be a metal oxide semiconductor field effect transistors (“MOSFET”) used for switching electronic signals. Although relays and transistor elements are discussed, it is to be understood that a variety of switching elements may be used as well. 
     A motor  110  is included in the circuit diagram as shown in  FIG. 2 , and represents a motor that is part of the air pump  60  (shown in  FIG. 1 ). In one embodiment, the motor  110  is a DC motor with an on/off control. However, other types of motors such as, for example, a DC motor with variable speed control or a brushless DC motor may be used as well. The switching element  96  is provided to selectively apply electrical power to the motor  110 . Specifically, in the event the engine  12  (shown in  FIG. 1 ) is turned off, and if regeneration of the PF device  24  (shown in  FIG. 1 ) is activated, the switching element  96  is switched to an “ON” or closed position to provide electrical power to the motor  110 . 
     The voltage measurement device  92  is provided for diagnostic and control purposes. Specifically, the voltage measurement device  92  measures the voltage available for the motor  110  and for charging the capacitor C 1 . By inference from the voltage measured by the voltage measurement device  92 , it can be determined whether the switch  96  has closed and applied voltage to the motor  110 . The voltage measurement device  94  is also provided for diagnostic and control purposes. Specifically, the voltage measurement device  94  measures the voltage across the capacitor C 1 . By inference from the voltage measured by the voltage measurement device  94 , it can be determined whether the switch  98  has closed and applied voltage to capacitor C 1 . Additionally, the level of charge of the ultracapacitor C 1  can be determined by inference from the voltage measured by the voltage measurement device  94 . The voltages measured by the voltage measurement device  92  and  94  are sent to the control module  70 . The control module  70  includes control logic for determining if the ultracapacitor C 1  has a level of charge sufficient to support heating of an electrical heater  52  during regeneration. 
     The switching element  98  is provided to either apply or remove electrical power supplied from the primary energy storage device  42  to the secondary energy storage device  44 . Specifically, when the switching element  98  is in the closed or “ON” position, electrical power is supplied from the primary energy storage device  42  to the secondary energy storage device  44 . 
     The switching element  100  is provided to allow for the secondary energy storage device  44  to discharge and provide electric power to the electric heater  52  by the switch  98 . Specifically, the switching element  100  provides power to the electric heater  52  when the switching element  100  is in the closed position. When the switching element  100  is in the open position, electric power is not supplied to the electric heater  52 . 
     The circuit  50  as shown in  FIG. 2  will disconnect the primary energy storage device  42  (e.g., the vehicle battery) from the electric heater  52 , if the electric heater  52  is energized and the engine  12  is in the engine off condition. Instead, electric power is provided to the electric heater  52  by the secondary energy storage device  44 . This will lengthen the life of the primary energy storage device  42 , as the primary energy storage device  42  is not drained by energizing the electric heater  52  in the engine off condition. 
     Turning back to  FIG. 1 , the exhaust gas treatment system  10  as described may also improve fuel economy of the engine  12 . This is because the exhaust gas treatment system  10  regenerates the PF device  24  during the engine off condition, while using the air pump  60  to provide airflow to the PF device  24 . Specifically, because the engine  12  is in the engine off condition during regeneration, the air pump  60  controls the amount of airflow to the PF device  24 . Thus, because the airflow is controlled, a flame front created by the trapped particulate matter in the PF device  24  during regeneration cannot generally be extinguished by relatively high airflow created by accelerating the engine  12 . As a result, the temperature of the exhaust gas  15  does not need to be elevated by the engine  12  using excess fuel to regenerate the PF device  24 . Moreover, because the electric heater  52  is used to provide heat to the PF device  24 , the time to regenerate may be decreased when compared to regeneration using elevated exhaust gas temperatures. 
     A method of regenerating the PF device  24  will now be explained. Referring to  FIG. 3 , an exemplary process flow diagram illustrating an exemplary process of operating the exhaust gas treatment system  10  is generally indicated by reference number  200 . Referring generally to  FIGS. 1-3 , process  200  begins at step  202 , where a control module  70  includes control logic for receiving a signal indicating an engine off condition. In one exemplary embodiment, an ignition switch  80  is in communication with the control module  70 , and is used to indicate if the engine on or engine off condition has occurred, however it is to be understood that other approaches may be used as well. Process  200  may proceed to step  204  in the event an engine  12  is in the engine on condition. Process  200  may proceed to step  212  if the engine  12  is in the engine off condition. 
     In step  204 , the control module  70  includes control logic for monitoring a backpressure sensor  76  for a signal indicative of the carbon loading and particulate loading in a monolith filter  40  of a PF device  24 . Specifically, if the amount of particulates trapped within the monolith filter  40  is less than the minimum amount of particulate matter that allows for self-combustion (e.g., about 2 g/l in one example), then process  200  may terminate. However, if the amount of particulates trapped within the monolith filter  40  is equal to or above the minimum amount of particulate matter that allows for self-combustion, process  200  may then proceed to step  206 . 
     In step  206 , the control module  70  includes control logic for switching a switching element  98  to a closed position such that a primary energy storage device  42  (shown in  FIGS. 1-2 ) is connected to a secondary energy storage device  44  (shown in  FIGS. 1-2 ). Specifically, referring to  FIG. 2 , the switching element  98  is closed to provide electrical power supplied from the primary energy storage device  42  to the secondary energy storage device  44  (shown as C 1  in  FIG. 2 ). Thus, during the engine on condition, the primary energy storage device  42  may charge the secondary energy storage device  44  if the amount of particulates trapped within the monolith filter  40  is equal to or above the amount needed for self-combustion. 
     In one embodiment, the state of charge of the primary energy storage device  42  may be monitored by a vehicle electrical system (not shown in  FIGS. 1-3 ) to determine if the primary energy storage device  42  charges the secondary energy device  44 . In another embodiment, the unfueled vehicle braking event may be used to charge the primary energy storage device  42  and the secondary energy device  44  by the generator  46 . Process  200  may then proceed to step  208 . 
     In step  208 , the control module  70  includes control logic for continuously monitoring the backpressure sensor  76  for a signal indicative of the carbon loading and particulate loading in a monolith filter  40  of the PF device  24 . Specifically, if the amount of particulates trapped within the monolith filter  40  is at or above a maximum amount allowed before regeneration occurs, then process  200  may proceed to step  210 , where the engine  12  is operated to create elevated exhaust gas temperatures, and the PF device  24  is regenerated. Process  200  may then terminate. However, if the amount of particulates trapped within the monolith filter  40  is less than the maximum amount allowed before regeneration is initiated, process  200  may then terminate, or alternatively, proceed back to step  202 . 
     As discussed in step  202 , if the engine  12  is in the engine off condition, process  200  may then proceed to step  212 . In step  212 , the control module  70  includes control logic for determining the carbon loading and particulate loading in the monolith filter  40  (e.g., in one embodiment the control module  50  may monitor the backpressure sensor  76  during the engine on condition and stores the value in a memory of the control module  50 ). In the event that the level of carbon loading indicates that regeneration is not needed in the engine off condition, process  200  may then terminate. In the event that the level of carbon loading indicates that regeneration of the PF device  24  is needed in the engine off condition, process  200  may then proceed to step  214 . 
     In step  214 , the control module  70  includes control logic for monitoring a circuit  50  (shown in  FIG. 1 ) to determine if the secondary energy storage device  44  is at a SOC level that supports heating of an electrical heater  52  during regeneration. Specifically, with reference to  FIG. 2 , a voltage measurement device  94  is provided to measure the level of charge of the secondary energy storage device  44 . In the event that the secondary energy storage device  44  is not at a SOC level that supports heating of the electrical heater  52  during regeneration, then process  200  may terminate. In the event that the secondary energy storage device  44  is at a SOC level that supports heating of the electrical heater  52  during regeneration, then process  200  may proceed to step  216 . 
     In step  216 , the control module  70  includes control logic for switching a switching element  98  to an open position such that the primary energy storage device  42  (shown in  FIGS. 1-2 ) is disconnected from the secondary energy storage device  44  (shown in  FIGS. 1-2 ). Specifically, referring to  FIG. 2 , the switching element  98  is opened to remove electrical power supplied from the primary energy storage device  42  to the secondary energy storage device  44  (shown as C 1  in  FIG. 2 ). Process  200  may then proceed to step  218 . 
     In step  218 , the secondary energy storage device  44  (e.g., C 1  as shown in  FIG. 2 ) is connected to the electrical heater  52 . With reference to  FIG. 2 , the switching element  100  is switched to the closed position to allow for the secondary energy storage device  44  to discharge, and energize the electric heater  52 . Process  200  may then proceed to step  220 . 
     In step  220 , the control module  70  includes control logic for monitoring the temperature of the PF device  24  to determine if the filter  40  is at a temperature needed for regeneration. Referring to  FIG. 1 , the control module  70  monitors the temperature sensor  72  to determine the temperature of the PF device  24 . In the event the temperature of the PF device  24  has not reached a level sufficient for regeneration, process  200  may continue to monitor the temperature of the PF device  24 , or alternatively, process  200  may terminate. In the event the temperature of the PF device  24  has reached a level sufficient for regeneration, and regeneration has begun, process  200  may then proceed to step  222 . 
     In step  222 , the control module  70  includes control logic for activating an air pump  60  (shown in  FIG. 1 ) to provide airflow to the PF device  24  during regeneration. The air pump  60  is selectively connected to and energized by the circuit  50 , where the secondary energy storage device  44  provides power to the air pump  60 . Specifically, referring to  FIG. 2 , the switching element  96  is switched to the closed position to provide power to a motor  110 . The motor  110  represents a motor that is part of the air pump  60  (shown in  FIG. 1 ). Process  200  may then proceed to step  224 . 
     In step  224 , the control module  70  includes control logic for monitoring the backpressure sensor  76  for a signal indicating that regeneration of the PF device  24  is complete. In the event that the level of carbon loading indicates that regeneration is not complete, process  200  may return to step  224 , where the control module  70  continues to monitor the backpressure sensor  76 . In the event that the level of carbon loading indicates that regeneration of the PF device  24  is complete, process  200  may then proceed to step  226 . 
     In step  226 , the circuit  50  will cease to provide electrical power to the electrical heater  52  and the air pump  60  from the secondary energy storage device  44 . Specially, referring to  FIG. 2 , the switching element  96  is switched to the open position to cease providing power to the motor  110 , and the switching element  100  is opened to cease providing power to the electric heater  52 . Process  200  may then terminate. 
     While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the application.