Particulate filter assembly and associated method

A particulate filter assembly includes an electrode assembly, a particulate filter positioned in an electrode gap defined between two electrodes of the electrode assembly, a power supply electrically coupled to the electrode assembly, and a controller for controlling operation of the power supply to apply a regenerate-filter signal to the electrode assembly to oxidize particulates collected by the particulate filter. An associated method of regenerating the particulate filter is disclosed.

FIELD OF THE DISCLOSURE

The present disclosure relates to a particulate filter assembly and a method of regenerating a particulate filter thereof.

BACKGROUND OF THE DISCLOSURE

A particulate filter is used to collect particulates such as, for example, particulates that may be present in air, exhaust gas, and a wide variety of other media that may contain particulates. From time to time, the collected particulates may be removed from the particulate filter to thereby “regenerate” the filter for further filtering activity.

SUMMARY OF THE DISCLOSURE

According to an aspect of the present disclosure, a particulate filter assembly comprises an electrode assembly, a particulate filter positioned in an electrode gap defined between first and second electrodes of the electrode assembly, and a power supply electrically coupled to the electrode assembly. A controller is electrically coupled to the power supply and comprises a processor and a memory device electrically coupled to the processor.

The memory device has stored therein a plurality of instructions which, when executed by the processor, cause the processor to operate the power supply according to predetermined signal-application criteria to cause the power supply to intermittently apply a regenerate-filter signal to the electrode assembly so as to intermittently generate at least one of (1) an arc between the first and second electrodes to oxidize particulates collected by the particulate filter if generation of the arc is initiated as a result of reduction of electrical resistance in the electrode gap due to creation of an arc-conductive path by particulates collected by the particulate filter and (2) a corona discharge between the first and second electrodes to oxidize particulates collected by the particulate filter. An associated method of regenerating the particulate filter is disclosed.

DETAILED DESCRIPTION OF THE DRAWINGS

A particulate filter assembly10comprises a particulate filter12for filtering particulates provided by a particulate source14and a filter regenerator16for regenerating the filter12by removing from the filter12particulates collected by the filter12, as shown, for example, inFIG. 1. The filter12may be configured to filter air, exhaust gas, or a wide variety of other substances containing particulates. As such, the particulate source14may be a room or other air-containing space, an internal combustion engine or other exhaust gas producer, or a wide variety of other sources that generate, produce, discharge, or otherwise provide particulates.

The particulate filter12may be any type of commercially available particulate filter. For example, the particulate filter12may be embodied as any known exhaust particulate filter such as a “wall flow” filter or a “deep bed” filter. Wall flow filters may be embodied as a cordierite or silicon carbide ceramic filter with alternating channels plugged at the front and rear of the filter thereby forcing the gas advancing therethrough into one channel, through the walls, and out another channel. Deep bed filters, on the other hand, may be embodied as metallic mesh filters, metallic or ceramic foam filters, ceramic fiber mesh filters, and the like. Moreover, the particulate filter12may also be impregnated with a catalytic material such as, for example, a precious metal catalytic material. The filter12may be electrically non-conductive or may include electrically conductive material. Illustratively, the filter12is made of a ceramic.

The particulate filter12is mounted in a passageway18of a fluid conductor20which is fluidly coupled to the particulate source14. A mount22is used to mount the filter12in the passageway18. The mount22is configured, for example, as a sleeve surrounding the filter12and secured to the conductor20.

The filter regenerator16comprises an electrode assembly24, a power supply26for supplying power to the electrode assembly24, and a controller28for controlling operation of the power supply26.

The electrode assembly24comprises first and second electrodes30,32which are spaced apart from one another to define an electrode gap34therebetween. The filter12is positioned in the electrode gap34between the electrodes30,32so that the electrode30is positioned next to an inlet face36of the filter12and the electrode32is positioned next to an outlet face38of the filter12. Electrodes30,32are configured, for example, as wire screen electrodes to maximize surface area coverage of faces36,38.

The power supply26is electrically coupled to the electrode assembly24and the controller28. The power supply26is electrically coupled to the first electrode30via a signal line40, the second electrode32via a signal line42, and the controller28via a signal line44. A suitable power supply is disclosed in U.S. patent application Ser. No. 10/737,333 which was filed on Dec. 16, 2003 and is hereby incorporated by reference herein.

The controller28comprises a processor46and a memory device48electrically coupled to the processor46via a signal line50. The memory device48has stored therein a plurality of instructions which, when executed by the processor46, cause the processor46to operate the power supply26according to predetermined signal-application criteria to cause the power supply26to intermittently apply a regenerate-filter signal52to the electrode assembly24. Such intermittent application of the regenerate-filter signal52to the electrode assembly is used to intermittently generate at least one of (1) an arc between the first and second electrodes30,32to oxidize particulates collected by the particulate filter12if generation of the arc is initiated (or if initiation of generation of the arc is enabled) as a result of reduction of electrical resistance in the electrode gap34from an arc-prevention level to an arc-enabling level due to creation of an arc-conductive path by particulates collected by the particulate filter12and (2) a corona discharge between the first and second electrodes30,32to oxidize particulates collected by the particulate filter12.

Such intermittent application of the regenerate-filter signal52to the electrodes30,32helps to avoid overheating of, and thus potential damage to, the filter12. It also allows ions generated by the arc and/or the corona discharge to evacuate the electrode gap34to facilitate subsequent initiation of an arc in an area of filter12that needs regeneration.

The regenerate-filter signal52is an alternating current (AC) signal. It is within the scope of this disclosure for the regenerate-filter signal to be a direct current (DC) signal.

According to a first embodiment of the filter regenerator16, the processor46cycles a control signal54between a first control state56and a second control state58to control cycling of the power supply26between an arc-generation mode and a signal non-generation mode, as shown, for example, inFIG. 2. In the first control state of the control signal54, the processor46generates the control signal54on line44to cause the power supply26to assume the arc-generation mode in which the power supply26generates the regenerate-filter signal52and applies the regenerate-filter signal52to the first and second electrodes30,32so as to generate an arc between the first and second electrodes30,32to oxidize particulates collected by the particulate filter12if generation of the arc is initiated (or if generation of the arc is enabled) as a result of reduction of electrical resistance in the electrode gap34from the arc-prevention level to the arc-enabling level due to creation of an arc-conductive path by particulates collected by the particulate filter12. As such, the power supply26causes the regenerate-filter signal52to assume an arc-generation state60in response to the first state56of the control signal54.

In the second control state of the control signal54, the processor46ceases generation of the control signal54on line44to cause the power supply26to assume the signal non-generation mode in which the power supply26ceases generation of the regenerate-filter signal52and thus ceases application of the regenerate-filter signal52to the first and second electrodes30,32. The regenerate-filter signal52thus assumes an off state62when the power supply26is in the signal non-generation mode. The filter12is allowed to cool somewhat during the signal non-generation mode to prevent overheating of the filter12. Further, ions generated by the arc during the arc-generation mode of the power supply26are allowed to evacuate the electrode gap34during the signal non-generation mode of the power supply26to promote initiation of the arc in an area of the filter12that needs to be regenerated upon subsequent operation of the power supply26in the arc-generation mode.

The control signal54remains in the first control state for a predetermined period of time (Δt) before it changes to the second control state unless the electrical current applied to the electrodes30,32by the regenerate-filter signal52reaches a predetermined current level, as shown, for example, inFIG. 3. If the processor46detects that the current has reached the predetermined current level, the processor46switches the control signal54to its second control state before expiration of the predetermined period of time (i.e., at some t1<Δt) to cause the power supply26to cease generation of the regenerate-filter signal52and thus application of the regenerate-filter signal52to the electrodes30,32to prevent overheating of and potential damage to the filter12.

The average power applied to the electrodes30,32may be varied during application of the regenerate-filter signal52to the electrodes30,32. To do so, the average voltage and/or the average current applied to electrodes30,32is increased or decreased.

With respect to voltage variation, exemplarily, the average voltage is decreased after initiation of an arc because the voltage needed to sustain an arc may be less than the voltage needed to initiate an arc due to creation of electrically conductive ions in the electrode gap34by the arc, as shown, for example, inFIG. 4. Initiation of the arc may be detected by an increase in the average current applied to electrodes30,32or may be assumed to occur within a predetermined period of time after application of the signal52to the electrodes30,32.

With respect to current variation, exemplarily, the average current may increase and/or decrease in response to an arc encountering different levels of electrical resistance in the electrode gap24. Such variation in the electrical resistance may be due to, for example, areas of filter12having collected different amounts of particulates.

According to a second embodiment of the filter regenerator16, the processor46cycles the control signal54between the first and second control states56,58to control cycling of the power supply26between a corona-generation mode, the arc-generation mode, and the signal non-generation mode, as shown, for example, inFIG. 5. The corona-generation mode is initiated in response to initiation of the first control state56of the control signal54. In the corona-generation mode, the power supply26generates the regenerate-filter signal52at a lower average voltage level so as to generate a corona discharge between the first and second electrodes30,32without generation of an arc therebetween. The corona causes creation of ozone when oxygen is present. The ozone reacts with carbon in the particulates to thereby oxidize the particulates. The regenerate-filter signal52assumes a corona-generation state64when the power supply26is in the corona-discharge mode.

After operation of the power supply26in the corona-generation mode, the processor46causes the power supply26to assume the arc-generation mode by increasing the average voltage of the signal52from the lower average voltage level to a higher average voltage level. The higher average voltage level is higher than the lower average voltage level and sufficient to generate an arc when initiation of the arc is enabled as a result of reduction of electrical resistance in the electrode gap34from the arc-prevention level to the arc-enabling level due to creation of an arc-conductive path by particulates collected by the filter12. As with the first embodiment of the filter regenerator16, the signal52may be terminated upon expiration of a predetermined period of time or in response to a predetermined current level and the average power may be varied by increasing and/or decreasing the average voltage and/or average current applied to the electrodes30,32.

When the arc-generation mode is completed, the processor46causes the power supply26to assume the signal non-generation mode to cease generation of the signal52and application of the signal52to the electrodes30,32to allow ions to evacuate the electrode gap34.

It is within the scope of this disclosure for the processor46to cause the power supply26to perform in a different mode order. For example, the processor46may cause the power supply26to assume the corona-generation mode immediately after the arc-generation mode so that the power supply26performs the arc-generation mode, then the corona-generation mode, and then the signal non-generation mode, as shown, for example, inFIG. 6.

In an implementation of the particulate filter assembly10, the assembly10is used with an internal combustion engine66(e.g., a diesel engine) to filter exhaust gas discharged therefrom, as shown, for example, inFIG. 7. An engine control unit68(ECU) is electrically coupled to the engine66via a signal line70to control operation of the engine66and is electrically coupled to the processor46via a signal line72and an engine condition sensor74via a signal line76. The sensor74is arranged to sense a condition of the engine66and to provide this engine condition information to ECU68over line76. The processor46is configured to vary the duration of an occurrence of the first state56of the control signal54relative to a predetermined period of time in response to an engine condition signal sent from ECU68over line72to the processor46upon detection of a condition of engine66by sensor74. The duration of an application of the regenerate-filter signal52is thereby varied in response to variation of the duration of the first state56of the control signal54.

Exemplarily, the sensor74is a mass flow sensor coupled to conductor20between engine66and particulate filter assembly10to sense the mass flow rate of exhaust gas discharge from engine66. In such a case, the processor46is configured to increase the duration of the first state56of the control signal54and thereby increase the duration of an application of the regenerate-filter signal52to the electrodes30,32to exceed a predetermined period of time (αt) in response to an increase in the mass flow rate of exhaust gas discharged from engine66, as shown, for example, inFIG. 8. The processor46is further configured to decrease the duration of the first state56of the control signal54and thereby decrease the duration of an application of the regenerate-filter signal52to the electrodes30,32to be less than the predetermined period of time (αt) in response to a decrease in the mass flow rate of exhaust gas discharged from engine66in a manner similar to what is shown inFIG. 3.

Alternatively, exhaust mass flow may be calculated by the ECU68by use of engine operation parameters such as engine RPM, turbo boost pressure, and intake manifold temperature (along with other parameters such as engine displacement).

In some embodiments, controller28is configured to commence cycling of control signal56and thus cycling of power supply26and application of the regenerate-filter signal52to the electrodes30,32in response to a triggering event. In one example, the controller28commences cycling in response to expiration of a predetermined shutdown period. In another example, the controller28commences cycling in response to a commence-cycling signal from ECU68. In yet another example, the controller28commences cycling in response to receipt of a pressure signal representative of a predetermined pressure drop sensed across filter12by a pressure sensor78(FIG. 7) which sends the pressure signal to the processor46over a signal line80.

While the concepts of the present disclosure have been illustrated and described in detail in the drawings and foregoing description, such an illustration and description is to be considered as exemplary and not restrictive in character, it being understood that only the illustrative embodiments have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected.

There are a plurality of advantages of the concepts of the present disclosure arising from the various features of the systems described herein. It will be noted that alternative embodiments of each of the systems of the present disclosure may not include all of the features described yet still benefit from at least some of the advantages of such features. Those of ordinary skill in the art may readily devise their own implementations of a system that incorporate one or more of the features of the present disclosure and fall within the spirit and scope of the invention as defined by the appended claims.