Abstract:
A Diesel particulate filter cartridge system for filtering particulate matter and nitrogen oxide from a flow of air containing particular matter includes a filter support plate with a plurality of cylindrical electrically regenerable filter media members connected thereto. A NOx trap is also provided that is either incorporated directly into the filter media members or provided as a separate structure in close proximity to the filter media members. A valve assembly includes a number of independently actuatable damper valves that correspond to a number of through holes in the filter support plate. When actuated, the damper valves limiting flow of air through a corresponding through hole and filter media member connected thereto. An outer housing is disposed about the valve assembly and filter media members to contain them in a compact package. A programmable computer control module shuts off the flow of air through a filter media member and selectively electrically regenerates it. Such electrical regeneration is accomplished through heat which also, either directly or indirectly, regenerates the NOx trap.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to an electrically regenerable filter cartridge system. More specifically, the present invention relates to the regenerable self-cleaning filter cartridge system for removing carbon, lube oil and unburned fuel particulates from the exhaust of internal combustion engines. In addition, the present invention relates to a regenerable filter cartridge system for removing particulates from Diesel engine exhaust gases. Further, the present invention also relates to a trap or filter for nitrogen oxide (NOx) to convert such gases to more desirable gases and to purge the exhaust of sulfur. 
     In the automotive industry, there has been a tremendous concern over the introduction of harmful pollutants into the air which have been generated by vehicle exhaust. Due to the negative health effects of such emissions, the Environmental Protection Agency of the United States has expressed a desire to reduce particle emissions from internal combustion engines. In the United States, the majority of particulate emissions come from Diesel engines on trucks and buses, which have not been regulated as closely as vehicles with gasoline engines. 
     Various attempts have been made to decrease the particulate emissions from Diesel engines. Unlike with gasoline engine vehicles, existing catalytic converters do not work well with Diesel engines since particulates typically clog these devices since the temperatures within them are too low to effectively burn carbon, lube oil and unburned fuel particles. Other efforts have been made to specifically address the Diesel particulate emissions problem. For example, fired burner systems have been employed to heat a combustion chamber, which receives Diesel exhaust for the purpose of burning the particulates within the chamber at very high temperatures. Such combustion chambers suffer from the drawbacks of high initial cost, high complexity, large size, high-energy consumption and high maintenance cost. 
     Another prior art attempt is the employment of passive particle filters and configurations to trap the particulates associated with Diesel emissions. These passive particle filters are commonly made from ceramic and metal, for example. These passive particulate filters are inadequate because when the filter fills up with carbon particles, the back pressure within the exhaust increases to such a level which necessitates that the filter be either regenerated in some fashion or replaced entirely. Since replacing the filter is not practical, many types of regeneration have been attempted, including the raising of the temperature of the filter above the combustion point of the carbon particulates in similar fashion to a self-cleaning oven. These prior art methods of filter regeneration include using a fired burner assembly using some type of fuel; raising the exhaust gas temperature by turbo charging the engine or other means; reducing the ignition temperature of carbon particles by adding a suitable catalyst to the fuel or filter material; and electrical heating. The foregoing methods of filter regeneration are not typically used in vehicles today due to their associated cost and practicality. 
     Further, there have been prior art attempts to employ electrically regenerable filter media instead of the passive filters that need to be replaced and fired burner systems which burn off the collected particulate matter. While the prior electrically regenerable filter media is suitable for burning off collected particulate matter, there is no known complete filter media cartridge system that can accommodate selective regeneration of multiple cartridges in a single system to achieve continuous operation. Further the prior art systems are not compact and, as a result, not suitable for many vehicle applications. Moreover, existing filter media systems cannot be precisely controlled to provide customized continuous filtration. The energy consumption is very high in these prior systems. 
     Specifically, there are a number of products that address the problem of reducing diesel engine emissions through the use of Diesel Oxidation Catalysts (DOC). DOCs are usually constructed of a ceramic or metal substrate coated with a catalytic material. Although a DOC can reduce the Soluble Organic Fraction of the Particulate Matter, it has no effect on the carbon particles. Most systems based on catalytic oxidation achieve only in the order of 20-25% reduction in PM, the level presently approved by the EPA and which will soon be inadequate as new tougher standards are applied. Furthermore, as soot covers the surface of the catalytic converter, the catalyst quickly becomes ineffective which shortens the service life and degrades the performance of the system. Most of the systems rely on high exhaust temperature to initiate and maintain the regeneration, a factor that limits the useful range of these systems. 
     In the world market, many producers have emerged as key players, especially in Europe, taking advantage of the significant support from governments and diesel engine manufacturers. Currently, the European market is dominated by a few technologies, mainly variations of the ceramic substrates. The most prevalent mode of regeneration, unlike the USA market, is fuel additives. It is important to mention that the effect of such additives has not been thoroughly studied, but there are indications that perceived harmful side effects will impede their introduction to the USA market and might lead to limiting their wide spread use in Europe. 
     Diesel particulate filters available in today&#39;s market are typically built on a ceramic substrate that traps soot by forcing the exhaust to flow through porous walls in a monolith. A catalyst is coated on the inside surface of the monolith. This lowers the soot combustion temperature, allowing the filter to regenerate at lower temperature than the ignition temperature of soot. An inherent limitation of such systems is that they rely on high exhaust temperatures and are practically inoperable at lower temperatures. For optimal performance, these systems require that the hot duty cycle of the engine be at least 20% of its operation, some system producers specify a hot duty cycle as high as 40-50% of the engine&#39;s operation. In some driving conditions, it is difficult to maintain the necessary exhaust temperature required to regenerate this type of filter. Such a situation can cause excessive accumulation of particulate matter (soot overloading) and clogging of the filter and may later lead to uncontrolled combustion resulting in the destruction of the filter. To overcome this problem, some filters have installed electric heaters to maintain the necessary temperature for regeneration. Two regeneration strategies have developed in the market: 
     a. Regeneration while the engine is running, usually requiring large electric currents. 
     b. Regeneration while the engine is off. This is usually done after 8 engine hours, and requires plugging into an external power source, and is not convenient for normal driving conditions. 
     Another inherent limitation of the catalyzed ceramic filters is the fact that sulfur compounds in the Diesel fuel poison the catalysts needed to reduce the particulate matter emitted by Diesel engines. 
     In the prior art, it is also desirable to employ a nitrogen oxide (NOx) trap in addition to a particulate filter to improve the overall operation of the engine. Lean NO.sub.x traps operate cyclically. During the lean portion of the cycle (fill duration), NO.sub.x is adsorbed. After running lean for a period of time, the trapping efficiency becomes low and the trap must be regenerated. This is done by operating rich of stoichiometric. The hydrocarbons and CO emitted during rich operation causes the NO.sub.x to reduce to N.sub.2 and O.sub.2. The lean part of the cycle may typically last for one minute followed by the regeneration or purge part of the cycle for one second. 
     It is desirable that the transition between the fill and purge portions of the cycle be imperceptible to the driver. Accordingly, the prior art strategies provide for a relatively slow transition between the fill and purge portions of the cycle. Of the transitions that must occur, including fuel flow and spark changes, the most difficult transition is the manifold pressure change. The throttle (or other valve) must be closed rapidly to accomplish the lean to rich and rich to lean transition. Even after the throttle has attained the appropriate position, it takes a few cycles for the intake manifold to fill or to purge, depending on the transition. Thus, the transition occurs over a number of engine cycles. Because of the number of parameters which must be changed, it is a challenge to do this robustly and with no torque fluctuation. Furthermore, the ramping of the conditions which are required to get to and from the purge condition negatively impacts fuel economy. Alternatively, fuel may be separately injected into the NOx trap to supply the needed hydrocarbons for regeneration. 
     In view of the above, there is a demand for a low energy regenerable Diesel exhaust filter system which can successfully remove carbon, lube oil and unburned fuel particulates from the exhaust of a Diesel engine. It is also desirable for a filter system to be able to remove nitrogen oxide from the exhaust. It is also desirable that the regenerable filter system be compact and inexpensive to manufacture and use while being efficient in the field. It is desirable for a filter system to not impact the fuel economy of the engine while still providing an efficient filter system. Further, it is desirable that the filter system is reliable over long periods of time without maintenance while improving the overall performance and particle holding capacity, even at low differential pressure. 
     SUMMARY OF THE INVENTION 
     The present invention preserves the advantages of prior art electrically regenerated diesel particulate filter systems. In addition, it provides new advantages not found in currently available filter systems, and overcomes many disadvantages of such currently available filter systems. 
     The invention is generally directed to a novel and unique self-cleaning particle filter system with particular application in removing carbon, lube oil, unburned fuel particulates as well as nitrogen oxide from the exhaust of Diesel engines. The self-cleaning particle filter system of the present invention enables the inexpensive assembly, use and maintenance of a compact self-cleaning particle filter system for Diesel engines without detracting from the overall performance of the engine or the fuel economy thereof. 
     The preferred embodiment of the present invention includes a filter support plate with a plurality of cylindrical electrically regenerable filter media members connected thereto. A valve assembly includes a number of independently actuatable damper valves that correspond to a number of through holes in the filter support plate. When actuated, the damper valves limiting or reducing flow of air through a corresponding through hole and filter media member connected thereto. An outer housing is disposed about the valve assembly and filter media members to contain them in a compact package. A programmable computer control module shuts off the flow of air through a filter media member and selectively electrically regenerates it. 
     The filter system also preferably includes a NOx trap as well that takes advantage of the electrically regenerable particulate filter employed in the system. The NOx trap portion of the present invention may be in the form of a wash coat of the appropriate chemical composition, such as barium oxide) on the downstream side of the electrically regenerable filter media. As a result, the NOx trap is directly heated simulataneously while the filter media is being regenerated for removal of particulate matter trapped thereon. Also, hydrocarbons, in the form of unburned fuel, are supplied to the NOx trap layer on the filter media since it is in line with the exhaust which inherently traps excess hydrocarbons. Thus, the regeneration of the NOx layer and the removal of sulfur is facilitated without the need for the separate injection of hydrocarbons or separate heating source for the NOx trap. 
     In accordance with the method of the present invention, a filter support plate is provided with a plurality of through holes along with a number of cylindrical filter media members, each having a bottom closed end and a top open end. The cylindrical configuration has an outer surface defining an upstream side and an inner surface defining a downstream side with the top open end of each of the filter media members being connected to the filter support plate with the top open end of each of the filter media members in respective fluid communication with the through holes. A NOx trap chemical layer, such as barium oxide, is coated on the downstream side of the filter media. Alternatively, a separate NOx filter member, infused with barium oxide or the like, may be provide in communication with the downstream side of the filter media member. A valve assembly is provided with a number of damper valves connected thereto. Air, containing particulate matter therein, is passed through the filter media members so that particulate matter is collected in the filter media members. One of the damper valves is actuated into communication with its corresponding through hole thereby reducing flow of air through a corresponding filter media member connected thereto. Electricity is passed through the filter media member with reduced airflow therethrough. The filter media member, with reduced airflow therethrough, is regenerated. The NOx trap material, either directly coated to the filter media or in a separate filter member, is also regenerated with the assistance of the electrically generated heat as well as the hydrocarbons from the unburned fuel trapped by the filter media. To allow for resumed use of the now regenerated filter media member, its corresponding damper valve is actuated out of communication with its corresponding through hole thereby allowing full flow of air through the corresponding filter media member connected thereto. 
     It is therefore an object of the present invention to provide an improved Diesel exhaust filter system. 
     Another object of the present invention is to provide a Diesel exhaust filter cartridge with is electrically regenerated with a minimum amount of energy. 
     A further object of the present invention is to provide a Diesel exhaust filter system that also includes an integrated NOx trap that does not require the injection of additional hydrocarbons or separate heating supply. 
     It is a further object of the present invention to provide an exhaust filter, which is reliable over long periods of time without maintenance. 
     It is yet a further object of the present invention to provide a Diesel exhaust filter, which has improved overall performance and increased particle-holding capacity at low differential pressure. 
     It is another object of the present invention to provide a Diesel exhaust filter, which efficiently removes carbon, lube oil and unburned fuel particles from the exhaust of internal combustion engines. 
     It is yet a further object of the present invention to provide a low cost Diesel exhaust filter with improved manufacturability. 
     It is another object of the present invention to provide a filter cartridge system that achieves continuous operation. 
     A further object of the invention is to provide a filter cartridge system that is compact. 
     Another object of the present invention is to provide a filter cartridge system that is computer controlled to efficiently use an array of filter media cartridges. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features which are characteristic of the present invention are set forth in the appended claims. However, the invention&#39;s preferred embodiments, together with further objects and attendant advantages, will be best understood by reference to the following detailed description taken in connection with the accompanying drawings in which: 
     FIG. 1 is an exploded perspective view of the filter cartridge system of the present invention; 
     FIG. 2 is the filter cartridge system in an assembled condition; 
     FIG. 3 is a exploded perspective view of the filter cartridge system of FIG. 1 with one damper valve closed to enable regeneration of its corresponding filter media member; 
     FIG. 4 is a close-up perspective view of the valve assembly and filter plate arrangement; 
     FIG. 5 is an exploded perspective views a preferred filter cartridge member with a number discrete sub-cartridges; 
     FIG. 6 is a perspective view of the filter cartridge of FIG. 5; 
     FIG. 7 is an exploded perspective view of a sub-cartridge employed in the filter cartridge of FIG. 5; 
     FIG. 8 is an exploded perspective view of a sub-cartridge employed in the filter cartridge of FIG. 5 with additional wash coat NOx trap; and 
     FIG. 9 is an exploded perspective view of a sub-cartridge employed in the filter cartridge of FIG. 5 with additional NOx trap member. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring first to FIG. 1, the exploded perspective view of the filter cartridge assembly  10  of the present invention is shown to include a filter support plate  12  with a number of apertures  14  therethrough. A number of corresponding filter media members  16  downwardly depend from the filter support plate  12 . In particular, an array of filter media members  16  are, preferably, generally cylindrical in configuration with a closed bottom end  18  and an open top end  20 . Details of the construction of a filter media member  16  is discussed in detail below in connection with FIGS. 5-7. 
     Each of the filter media members  16  are connected to the filter support plate  12  so that the open top ends  20  of each of the filter media members  16  align with their corresponding apertures  14  through the filter support plate  12 . They are affixed in place by welding, or the like. Further, each of the filter media members  16  include an outer upstream surface  22  as well as an inner downstream filter surface  24 , as seen in FIG.  7 . The interior or downstream surface  24  of each of the cylinder configurations of the filter media members  16  are in fluid communication with the apertures  14  through the filter support plate  12 . As will be discussed in detail below, the flow of air, with particulate matter therein, flows in an upward direction in accordance with the orientation of the system  10  shown in FIG.  1 . 
     A valve assembly, generally referenced as  26 , is provided to control the air flow through each of the apertures  14  in the filter support plate  12 , thereby controlling the flow through each of the filter media members  16  respectively connected thereto. In particular, the valve assembly  26  includes a central mounting tube  28  with a main frame  30  having a corresponding number of actuatable piston cylinders  32  attached thereto. Each of these piston cylinders  32  include a rod  34  downwardly depending therefrom with a damper plate  36  disposed at each respective free end. The number of piston cylinders  32  and damper plates  36  are selected to match the number of apertures  14  in the filter support plate  12  and the number of corresponding filter media members  16 . As will be shown below in connection with FIG. 3, the flow of air through a given filter media  16  member may be selectively controlled by actuating a damper plate  36 , otherwise known generally as a damper valve, into communication with an aperture  14  through the filter support plate  12  to permit the corresponding filter media member  16  to be regenerated by the passage of electricity therethrough. 
     A cylindrical base  38  is also provided for supporting electronic computer control circuitry, generally referred to as a computer control module  40 , which can control, through programming, a selective flow control of air through the filter media members  16  as well as the electric regeneration thereof. Details of the computer control module  40  is not discussed in detail herein because such computer control is well known in the art. 
     Referring now to FIGS. 1 and 2, the assembly of the filter cartridge system  10  is illustrated. In particular, the filter support plate  12  and the filter media members  16  connected thereto reside within a main sleeve  42  so that the outer edges  44  of the filter support plate  12  rest on the top edge of the main sleeve  42 . As seen in FIG. 2, the filter media members  16  are housed securely within the main sleeve  42 . The cylindrical base  38 , with electronic computer control module  40 , which may include more than one component as shown, disposed thereon, resides on the outer edges  44  of the filter support plate  12  so that the valve assembly  26  extends through the center of the base  38 . The cylindrical mounting tube  28  of the valve assembly  26  extends upwardly through the support base  38  and is subsequently routed through the exit port  46  of a top cap  48  which seals and protects the valve assembly  26  and electronic computer control module  40  therein. 
     In addition, an input port  50 , of a preferably funnel-shape, is affixed to the lower open end of the main sleeve  42  via a spacer sleeve  52 . These components may be secured in place by welding, soldering, riveting, threaded fasteners, or the like. As a result of this configuration, air flow, with particulate matter therein, flows in through the input port  50 , through the spacer sleeve  52 , and into each of the filter media members  16  from their outer upstream surfaces  22  and into the interior of the cylindrical filter media members  16  to exit out their respective apertures  14  in the filter support plate  12  if a damper plate  36  is not engaged with the corresponding aperture  14  in the filter support plate  12 . If the damper plate  36  is open, air will flow freely through the central mounting tube  28  to exit out of the top cap  48  via the exit port  46 . 
     Turning now to FIGS. 3 and 4, details of the operation of the filter cartridge system  10  of the present invention, is shown. As stated above, each of the filter media members  16  are mounted to the filter support plate  12  so that air can flow through the filter media members  16  and through their respective apertures  14  in the filter support plate  12 . The filter cartridge system  10  of the present invention can easily replace known vehicle filtration systems, including mufflers and catalytic converters, In that connection, when the filter cartridge system  10  of the present invention is placed in line with the exhaust of a vehicle, such as the exhaust of a diesel truck, air flows through the input port  50 , through the filter media members  16 , and out through the exit port  46  in the top cap  48 . Typically, diesel exhaust includes various particulate matter, such as soot, and the like. This particulate matter must be filtered to reduce emissions and comply with environmental guidelines and regulations. As a result, the filter cartridge system  10  of the present invention can be employed to comply with such government regulations and guidelines. 
     As can be understood, the passing of air with particulate matter through the filter media members  16  will cause the filtered particulate matter to be collected on the surfaces and within the filtered media members  16  themselves. Further, collection of particulate matter will eventually reduce the air flow and pressure through the exhaust line thus necessitating some type of regeneration and cleaning of the filter medial members. In accordance with the present invention, the filter media members  16  are selectively electrically regenerated and cleaned as desired. For example, in accordance with the present invention, it is preferred that four filter media members  16  be used where a single filter media member  16  is regenerated and cleaned at a time. FIGS. 3 and 4 illustrates the electrical regeneration and cleaning of the left-most filter media member  16 . 
     First, the flow of air and particulate matter through this filter media member  16  is shut off or significantly dampened by the actuation of its corresponding damper plate  20  into communication with the corresponding aperture  14  in the filter support plate  12 . With the damper plate  20  in its closed position, flow through the left-most filter media member  16  will be, essentially, cut off. The complete cut-off of air with a perfect seal is typically unnecessary as long as the rate of regeneration exceeds the rate of accumulation of particulate matter on the filter media member. In certain applications, a complete cut-off of air flow may be desired thus requiring additional seals, and the like, to ensure such a complete cut-off of air flow. Also, while a better seal is desired, it is not always necessary to carry out the present invention. However, as shown in the drawings, a perfect seal is not illustrated. 
     With the damper plate  20  engaged and the air flow through the corresponding filter media member  16  significantly reduced or cut-off, that particular filter media member  16  can now be electrically regenerated and cleaned. The computer control module  40  is electrically interconnected to the filter media member to regenerated. The computer control module  40  is pre-programmed to set a given cycle of damper valve actuations and electrical regeneration of the respective filter media members  16  in accordance with the particulate application at hand, namely, the particular vehicle in which the filter cartridge system  10  is installed. For example, a typical routine that can be easily programmed into the electronic computer control module  40  is for each damper plate  20  to close for a period of 60 seconds while the other damper plates  20  stay open. During this time, the corresponding filter media member  16  is electrically regenerated and cleaned. Then, another damper plate  20  for another filter media member  16  is actuated downwardly while keeping the other damper plates  20  open to repeat the cycle. 
     While it is preferred that a single damper plate or valve  20  be actuated and a single filter media member  16  be electrically regenerated and cleaned at a time, certain applications may require that more than one filter media member  16  be regenerated at a time. Also, the preferred embodiment of the present invention includes four filter media members  16 . However, certain applications may require less or more filter media members  16  to address the particular needs of the vehicle into which the filter cartridge system is installed. As a result, the number of corresponding damper plates  20  and apertures  14  in the filter support plate  12  can be modified accordingly. 
     The present invention illustrates the use of cylindrical filter media members  16  as a preferred embodiment of the present invention; however, the shape and configuration of the filter media members  16  may be modified to suit the particular application at hand. For example, the filter media members  16  may be plate-like in configuration, or otherwise. 
     FIGS. 5-7 further illustrate the details of the particular construction of the preferred construction for the filter media member  16 . Referring to both FIGS. 5 and 6, a central perforated metal carrier tube  54  is provided with a closed bottom end plate  56 . A top interface cap  58  is provided for engagement with the bottom of the filter support plate  12  at a respective aperture  14  therethrough. The preferred construction of the filter media member  16  of the present invention is modular in construction where a number of different sub-cartridges  60  are provided within a given filter media member  16 . While this is not required to carry out the present invention, it is preferred for additional flexibility and control of the regeneration and cleaning process. In particular, the filter media member  16  has, for example, eight modular sub-cartridges  60  which are illustrated in detail in FIG.  7 . Each of these sub-cartridges  60  include filter media  62  in a corrugated configuration for example, as well as electrical interconnections  64  for interface to the electronic computer control module  40 . It is preferred that each of the separate sub-cartridges  60  within a filter media member  16  are independently connected to the electronic computer control module  40  for independent and separate control. Each of the sub-cartridges  60  also include a top cap  66  and a bottom cap  68  with insulative material  70  adjacent to the corrugated filter media  62 . Spacer washers  72  are also provided between each adjacent sub-cartridge  60 . The bottom end plate  56  is also provided to secure the sub-cartridges  60  in a stack on the perforated metal support tube  54  via a post  74  extending downwardly therefrom. 
     FIG. 6 illustrates a perspective view of an assembled filter media member  16  in accordance with the present invention. As a result, each of the sub-cartridges  60  include their own individual and distinct electrical interconnections  64  for interfacing with the electronic computer control module  40 . Each of the sub-cartridges  60  include two inner connections  64  for providing electric current thereto. Details of the electrical interconnections are shown in FIG.  7 . In FIG. 7, one interface connector  64  is shown connected to one end of the filter media  62  for illustration purposes. A third common line is also provided for grounding purposes and may be connected to the bottom end plate  56  or the top cap portion  58  of the filter media member  16 . In view of the foregoing, each of the individual sub-cartridges  60 , namely the electrical regeneration and cleaning thereof, can be controlled by the programmable electronic computer control module  40 . 
     As shown in FIGS. 8 and 9, an additional nitrogen oxide (NOx) trap may be provided in addition to the particulate filter describe above. In accordance with the present invention, a NOx trap is integrated directly within the existing particulate filter system shown in FIGS. 1-7. The NOx trap takes advantage of various existing features and characteristics of filter system  10  to carry out the NOx trap functionality. 
     As shown in FIG. 8, a filter sub-cartridge  60  is provided with a NOx trap incorporated directly into the filter element. Specifically, the NOx trap is formed by applying a wash coat of the appropriate chemical composition, such as barium oxide, to the downstream surface  24  of the filter media  62 . The wash coat is generally referenced as  80 . During Diesel particulate regeneration, the NOx trap wash coat  80  is exposed to direct heating by electrical current applied to the filter media  62  via electrical interconnections  64 . The electric current raises the temperature of the filter elements to about 800-900 deg. C. To reduce total energy requirements, an exhaust flow control reduces the flow through filter element to be regenerated. The process of heating and burning Diesel particulate on the filter element  64  produces hydrocarbons and carbon monoxide needed to regenerate the NOx trap otherwise known as the wash coat  80 . The temperature reached during the electric regeneration is sufficient to purge the NOx trap of sulfur. 
     A further construction for integrating a NOx trap within the filter media construction  10  of the present is shown in FIG.  9 . Specifically, an additional band  82  of material similar or identical to filter media  64  is provided of, for example, sintered metal fibers to provide a NOx trap member. Configurations other than a band shape can be used to suit the application at hand. The NOx trap band  82  is wash coated or embedded with the appropriate chemicals, such as barium oxide, which are suitable for NOx trap regeneration. This separate NOx trap member  82  is affixed to the downstream surface  24  of the filter media  62 . Thus, the NOx trap  82  is positioned in close proximity to the filter media  62 . As a result, the NOx trap  82  is indirectly exposed to the radiation emitted by the heat electrically generated via interconnections  64 . The NOx trap  82 , similar to the wash coat  80  in FIG. 8, is regenerated to purge sulfur due to the exposure to heat due to the close positioning of the NOx trap  82  close to the heat source, namely, the electrically heated filter media  62 . 
     The filter system of the present invention provides an Active Diesel Particulate Filter System (ADPFS) that is characterized by high efficiency and very low electric power consumption for regeneration. The regeneration is independent of engine exhaust temperature or fuel sulfur content. The filter material  62  is made of sintered metal fibers and has high porosity, high soot holding capacity, low thermal mass for quick heating and low back pressure. The metal fibers  62  are designed to resist corrosion at high temperatures. This filter material is capable of capturing up to 95% of the soot in diesel exhaust. 
     The operation of the ADPFS is controlled by a microprocessor. The controller monitors the ADPFS and periodically, as required, an electric current is passed through a filter element  62 , which then acts as a heating element. The filter elements are stacked to form a filter cartridge  10 . In a typical system, two or more filter cartridges are used. During regeneration cycle, the exhaust flow is controlled by redirecting the flow away from the filter element that is been heated. This is done to minimize the energy consumption during regeneration. The regeneration strategy is designed to keep the back pressure below a preset level. 
     The ADPFS functions automatically, during normal engine operation. It is scalable from 15 to 1000 HP engines, and can be used in any application, stationary or mobile. In addition, for example, engines up to 2000 HP may be accommodated. The ADPFS can be combined with a Diesel oxidation catalyst to further suppress the carbon monoxide, hydrocarbons and the soluble organic fraction of the particulate matter. 
     A typical 160 HP diesel engine uses  32  filter elements, each of which is regenerated at one time in less than one minute. To regenerate the NOx trap does not require additional energy over the PM regeneration which makes the entire system very energy efficient with an approximate 1.0 to 3.0% total fuel penalty. 
     In operation, further to what is shown in FIGS. 3 and 4, additional customization and control of the electrical regeneration and cleaning of each of the filter media members  16  can be achieved by further control of the sub-cartridges  60  therein. For example, when a given damper plate  20  is closed for a filter media member, it is possible for the electronic computer control module  40  to be programmed so that all of the sub-cartridges  60  within a given filter media member  16  regenerate and are cleaned at the same time. Alternatively, the sub-cartridges  60  may be electrically regenerated and be cleaned one at a time depending on the requirements of the particular vehicle in which the system is installed. 
     The filter cartridge system  10  of the present invention is unique in that there is complete programmable control of every aspect of the electrical regeneration and cleaning of the filter media members  16  and sub-cartridges  16  therein. As a result, the filter cartridge system  10  of the present invention provides filtration efficiency that cannot be achieved in the prior art. The NOx traps  80  and  82 , respectively, may be simultaneously regenerated along with the filter media members  16  to provide a filter system with an integrated NOx trap. The programming of the flow of exhaust can be easily controlled to address the relative needs of the filtration of particulate as well as nitrogen oxide to suit the needs of the application at hand. 
     In accordance with the present invention, it is preferred that the housing components, including the main sleeve  42 , import port  50  and top cap  48  are all made of metal but may be made if other materials such as ceramic, when desired. Further the filter support plate  12  and central mounting tube  28  as well as the support base  38  for the computer control module  40  are also preferably made of metal for resistance to wear. Known electronic computer control modules  40  and other programmable logic arrays (PLAs) are suitable for use in the present invention. Also, solenoid-type pistons  32  are preferably used to drive the damper plates  36  into communication with the apertures  14  on the filter support plate  12 ; however, other types of mechanisms may be employed for actuating the damper plates  36 . 
     Also, the filter media members  16  are preferably made of inorganic filter material and electrically resistive metal filter strips affixed thereto (not shown). Electricity is supplied to the metal filter strips which heat up and burn off the particulate matter collected in the inorganic filter material. Details of such an electrically regenerable filter media construction are well known in the art and need not be discussed in detail herein. 
     It would be appreciated by those skilled in the art that various changes and modifications can be made to the illustrated embodiments without departing from the spirit of the present invention. All such modifications and changes are intended to be covered by the appended claims.