PARTICLE FILTER AND METHOD FOR THE PURIFICATION OF AN EXHAUST-GAS FLOW

RELATED APPLICATIONS

The present application claims priority to German Patent Application No. 102011003019.0 filed on Jan. 24, 2011, the entire contents of which are hereby incorporated by reference for all purposes.

FIELD

The description relates to a particle filter and to a method for the purification of an exhaust-gas flow. In particular, the description relates to the purification or filtering of exhaust gases of an internal combustion engine of a motor vehicle.

BACKGROUND AND SUMMARY

Particles, such as for example carbonaceous soot, generated during the combustion of fuels may be retained by a filter in order to reduce the exhaust-gas emissions. For this purpose, the exhaust-gas flow passes through a filter in which the particles accumulate. A periodic regeneration of the filter is necessary in order to reduce the particle loading and to ensure a controlled level of the exhaust-gas counterpressure.

In the event of the filter approaching a storage capacity, the increased exhaust-gas counterpressure may have an adverse effect on the performance of the engine. Furthermore, in the case of a high soot loading, the exothermic heat generated during particulate filter regeneration may degrade parts of the exhaust system.

DE 102 06 805 A1 presents a soot filter for the purification of exhaust gases, in which the soot filter has a predetermined breaking point for reducing an exhaust-gas counterpressure prevailing in the soot filter. The predetermined breaking point may be arranged in a filter body of the filter and/or in a bypass line of the filter. The description is based on the object of improving the purification of exhaust gases. The object is achieved by way of the features of the claims included herein. The dependent claims included herein define advantageous refinements of the description.

In one example, the inventors herein have developed an exhaust system of a motor vehicle, comprising: a first particulate filter; a second particulate filter; and a exhaust gas routing system including a first exhaust passage through the first particulate filter and a second exhaust passage through the second particulate filter, an inlet valve biased in a closed position and located upstream of the first and second particulate filters.

The possibility of increasing vehicle emissions may be reduced by providing a secondary exhaust path around a first particulate filter during conditions in which particulate matter stored in a first particulate filter approaches a storage capacity of the first particulate filter. Specifically, during conditions where particulate matter stored in the particulate filter is less than a threshold amount, exhaust gases may be directed substantially solely to the first particulate filter to save or maintain particulate matter storage capacity in a second particulate filter. However, when particulate matter stored in the first particulate filter exceeds the threshold level, a second exhaust path may be enabled, the second exhaust path directing exhaust gases to the second particulate filter. In this way, engine exhaust back pressure may be reduced until the first particulate filter is regenerated or replaced.

The present description may provide several advantages. In particular, the approach may improve engine emissions by increasing the exhaust filtering capacity of the vehicle exhaust system. In addition, the approach may extend the time between vehicle service intervals and or particulate filter regeneration. Further, in some examples, the approach may be implemented in a cost effective configuration which may not include an electrically controlled exhaust gas routing system.

The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.

It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages described herein will be more fully understood by reading an example of an example, referred to herein as the Detailed Description, when taken alone or with reference to the drawings, where:

FIG. 1 is a schematic diagram of an engine;

FIG. 2 shows a particulate filter and exhaust gas routing system according to the description during normal operation of the particulate filter;

FIG. 3 shows the particulate filter and exhaust gas routing system according to the description during a condition where particulate matter stored in the first particulate filter is greater than a threshold; and

FIG. 4 is a flowchart for operating an engine including an exhaust system that can direct engine exhaust into first and second particulate filters.

The drawings serve merely for the explanation of the description, and are not intended to restrict the description. The drawings and the individual parts are not necessarily drawn to scale. The same reference numerals are used to denote identical or similar parts.

DETAILED DESCRIPTION

The present description is related to operating an engine that directs exhaust gas to a particulate filter. In one non-limiting example, the engine may be configured as illustrated in FIG. 1. FIGS. 2 and 3 provide a detailed view of two particulate filters and an exhaust gas routing system that directs exhaust gas through the two particulate filters. Exhaust gases may flow substantially solely through the first particulate filter as is shown in FIG. 2 when particulate matter stored in the first particulate filter is less than a threshold amount. Exhaust gases may flow through the second particulate filter as is shown in FIG. 3 when particulate matter stored in the first particulate filter is greater than the threshold amount. FIG. 4 provides a method for operating an engine and purifying engine exhaust gases via first and second particulate filters.

Referring to FIG. 1, internal combustion engine 10, comprising a plurality of cylinders, one cylinder of which is shown in FIG. 1, is controlled by electronic engine controller 12. Engine 10 includes combustion chamber 30 and cylinder walls 32 with piston 36 positioned therein and connected to crankshaft 40. Combustion chamber 30 is shown communicating with intake manifold 44 and exhaust manifold 48 via respective intake valve 52 and exhaust valve 54. Each intake and exhaust valve may be operated by an intake cam 51 and an exhaust cam 53. The position of intake cam 51 may be determined by intake cam sensor 55. The position of exhaust cam 53 may be determined by exhaust cam sensor 57.

Fuel injector 66 is shown positioned to inject fuel directly into cylinder 30, which is known to those skilled in the art as direct injection. Fuel injector 66 delivers liquid fuel in proportion to the pulse width of signal FPW from controller 12. Fuel is delivered to fuel injector 66 by a fuel system (not shown) including a fuel tank, fuel pump, fuel rail (not shown). Fuel pressure delivered by the fuel system may be adjusted by varying a position valve regulating flow to a fuel pump (not shown). In addition, a metering valve may be located in or near the fuel rail for closed loop fuel control. Fuel injector 66 is supplied operating current from driver 68 which responds to controller 12.

Intake manifold 44 is shown communicating with optional electronic throttle 62 which adjusts a position of throttle plate 64 to control air flow from intake boost chamber 46. Compressor 162 draws air from air intake 42 to supply boost chamber 46. Exhaust gases spin turbine 164 which is coupled to compressor 162.

Combustion is initiated in combustion chamber 30 when fuel automatically ignites as piston approaches top-dead-center compression stroke. In some examples, a universal Exhaust Gas Oxygen (UEGO) sensor (not shown) may be coupled to exhaust manifold 48 upstream of emissions device 70. In other examples, the UEGO sensor may be located downstream of one or more exhaust after treatment devices. Further, in some examples, the UEGO sensor may be replaced by a NOx sensor.

Exhaust aftertreatment device 70 can include a particulate filter, in one example. In another example, multiple emission control devices such as catalysts and particulate filters, each with multiple bricks, can be used. Emissions aftertreatment device 70 can include a particulate filter and an oxidation catalyst in one example.

Controller 12 is shown in FIG. 1 as a conventional microcomputer including: microprocessor unit 102, input/output ports 104, read-only memory 106, random access memory 108, keep alive memory 110, and a conventional data bus. Controller 12 is shown receiving various signals from sensors coupled to engine 10, in addition to those signals previously discussed, including: engine coolant temperature (ECT) from temperature sensor 112 coupled to cooling sleeve 114; a position sensor 134 coupled to an accelerator pedal 130 for sensing accelerator position adjusted by foot 132; a pressure sensor 80 for sensing exhaust pressure upstream of turbine 164; a pressure sensor 82 for sensing exhaust pressure downstream of turbine 164; a measurement of engine manifold pressure (MAP) from pressure sensor 122 coupled to intake manifold 44; an engine position sensor from a Hall effect sensor 118 sensing crankshaft 40 position; a measurement of air mass entering the engine from sensor 120 (e.g., a hot wire air flow meter); and a measurement of throttle position from sensor 58. Barometric pressure may also be sensed (sensor not shown) for processing by controller 12. In a preferred aspect of the present description, engine position sensor 118 produces a predetermined number of equally spaced pulses every revolution of the crankshaft from which engine speed (RPM) can be determined.

In some embodiments, the engine may be coupled to an electric motor/battery system in a hybrid vehicle. The hybrid vehicle may have a parallel configuration, series configuration, or variation or combinations thereof.

During operation, each cylinder within engine 10 typically undergoes a four stroke cycle: the cycle includes the intake stroke, compression stroke, expansion stroke, and exhaust stroke. During the intake stroke, generally, the exhaust valve 54 closes and intake valve 52 opens. Air is introduced into combustion chamber 30 via intake manifold 44, and piston 36 moves to the bottom of the cylinder so as to increase the volume within combustion chamber 30. The position at which piston 36 is near the bottom of the cylinder and at the end of its stroke (e.g. when combustion chamber 30 is at its largest volume) is typically referred to by those of skill in the art as bottom dead center (BDC). During the compression stroke, intake valve 52 and exhaust valve 54 are closed. Piston 36 moves toward the cylinder head so as to compress the air within combustion chamber 30. The point at which piston 36 is at the end of its stroke and closest to the cylinder head (e.g. when combustion chamber 30 is at its smallest volume) is typically referred to by those of skill in the art as top dead center (TDC). In a process hereinafter referred to as injection, fuel is introduced into the combustion chamber. In some examples, fuel may be injected to a cylinder a plurality of times during a single cylinder cycle. In a process hereinafter referred to as ignition, the injected fuel is ignited by compression ignition or by known ignition means such as spark plug (not shown), resulting in combustion. During the expansion stroke, the expanding gases push piston 36 back to BDC. Crankshaft 40 converts piston movement into a rotational torque of the rotary shaft. Finally, during the exhaust stroke, the exhaust valve 54 opens to release the combusted air-fuel mixture to exhaust manifold 48 and the piston returns to TDC. Note that the above is described merely as an example, and that intake and exhaust valve opening and/or closing timings may vary, such as to provide positive or negative valve overlap, late intake valve closing, or various other examples. Further, in some examples a two-stroke cycle may be used rather than a four-stroke cycle.

According to a first aspect of the description, a particle filter for an exhaust system of a motor vehicle with an exhaust-gas path comprises a filter and comprises a secondary filter, wherein in normal operation, the exhaust-gas path runs through the filter, and wherein in the event of an overloading or approaching storage capacity of the filter, the exhaust-gas path runs through the secondary filter. In the event of an overloading or approaching storage capacity of the filter (e.g., storing a predetermined threshold amount of particulate matter), which may also be referred to here as primary filter or main filter, the secondary filter is activated. The secondary filter then filters the exhaust-gas flow. According to the description, in the event of an overloading or approaching a soot filter storage capacity, the exhaust-gas flow continues to be filtered.

Thus, emissions regulations are still adhered to and degradation in the exhaust-gas aftertreatment system may be mitigated. In the event of overloading or approaching storage capacity of the soot filter, the exhaust-gas flow can run substantially only through the secondary filter, or through the secondary and to a certain extent through the (primary) filter. Aside from the overloading or approaching storage capacity, it is also possible in this way for the severity of effects of degradation states of the filter in which the exhaust-gas counterpressure is increased to be reduced. Correspondingly, the mode in which the one or more secondary filters are activated may also be referred to as a secondary operating mode. In said secondary operating mode, the soot filter can be regenerated and/or a filter exchange can be initiated.

The secondary filter may surround the filter. This is desirable arrangement from a flow aspect, which is furthermore space-saving and compatible with the established installation dimensions. The particle filter may be of cylindrical form, which harmonizes well with the tubular exhaust system.

The secondary filter may have an inlet valve and an outlet valve. By way of the valves, or a similar means such as a flap or some other variable opening, the secondary filter can be activated. That is to say, the exhaust gas routing system can be switched from the normal mode, in which the exhaust-gas flow runs through the filter, into the secondary mode, in which the exhaust-gas flow runs through the secondary filter. In some example, the exhaust gas routing system may only include a single inlet valve and no outlet valve.

The inlet valve and/or the outlet valve may be preloaded by means of a spring. The switching may be realized in a simple manner by way of the one or more springs. The spring on the inlet valve may be dimensioned so as to open up the exhaust path for the exhaust gas into the secondary filter when a certain exhaust-gas counterpressure is reached. The spring on the outlet valve may be dimensioned so as to open up the path for the exhaust gas out of the secondary filter when the pressure in the secondary filter is higher than the pressure in the outlet region of the filter or of the particle filter. Thus, in some examples, the exhaust gas routing system may be passively operated without being electrically controlled.

A pressure sensor may be arranged in the region of the secondary filter in order to detect the loading of the secondary filter. It is thereby possible to initiate a regeneration of the secondary filter, and exchange of the particle filter and/or one or more status messages for example to the exhaust-gas aftertreatment system and/or the engine management controller, in order thereby to improve the integration into the overall system.

A sensor may be provided for detecting the position of the inlet valve and/or of the outlet valve. By way of said sensor, the operating mode of the particle filter can be detected and transmitted, for information, to further systems. A temperature sensor may be arranged in the region of the secondary filter. A temperature measurement in the region of the secondary filter may be used, together with a measurement of the exhaust-gas temperature for example at the inlet of the exhaust system, to detect the operating mode. The filter and/or the secondary filter may be designed as a wall-flow filter or as a throughflow filter. Said established filter types are highly suitable for the particle filter.

According to a second aspect of the description, a method for the purification of an exhaust-gas flow of a combustion plant, in particular of an engine of a motor vehicle, comprises the following steps: purification of the exhaust-gas flow by means of a filter, diverting the exhaust-gas flow through a secondary filter in the event of an overloading of the filter.

The same advantages and modifications as those described above likewise apply here. As a result of the diversion of the exhaust-gas flow, a possibility of impairment of or degradation to the engine as a result of an increase in the exhaust-gas counterpressure may be reduced. Particulate filter overloading or particulate matter accumulation within the first and/or second particulate filter may be detected from an increased exhaust-gas counterpressure. The detection may take place by way of one or more sensors. On the other hand, the overloading may also be detected implicitly using the means for diverting the exhaust-gas flow, for example by means of the switching or activation of the one or more diverting devices.

In the event of an overloading or reaching a threshold soot storage capacity of the secondary filter, the filtering efficiency thereof may fall, and the exhaust-gas counterpressure may remain at a normal level. This has the advantage that the exhaust-gas counterpressure is not increased again by the secondary filter. The primary particulate filter may be regenerated and/or a filter exchange may be initiated when the exhaust-gas flow runs through the secondary filter. It is thus possible for the state of the (primary) filter to be restored during the operating time of the secondary filter. The exhaust-gas flow can directed through the primary filter again when the primary filter has been regenerated and/or exchanged. In this way, the primary particle filter is returned to the normal operating mode. This may be followed by a regeneration of the secondary filter.

Thus, the system of FIG. 1 provides for an exhaust system of a motor vehicle, comprising: a first particulate filter; a second particulate filter; and a exhaust gas routing system including a first exhaust passage through the first particulate filter and a second exhaust passage through the second particulate filter, an inlet valve biased in a closed position and located upstream of the first and second particulate filters. The exhaust system includes where exhaust gases are directed substantially solely to the first particulate filter when particulates stored in the first particulate filter are less than a threshold level, and the exhaust gas routing system supplying exhaust gases to the second particulate filter when particulates stored in the first particulate filter are greater than the threshold level.

The exhaust system also includes where the second particulate filter surrounds the first particulate filter. In some examples, the exhaust system further comprises a preload spring biasing the inlet valve in a closed position. Pressure exerted by the exhaust gases may overcome the spring to open the inlet valve. The exhaust system further comprises an outlet valve positioned downstream of the second particulate filter and the first particulate filter. The exhaust system further comprises a preload spring biasing the outlet valve in a closed position.

The exhaust system further comprises a pressure sensor positioned upstream of the first particulate filter. The pressure sensor may be the basis for determining when to open the inlet valve. Further, the pressure sensor may be the basis for determining when to close the inlet valve. The exhaust system further comprises a pressure sensor located downstream of the second particulate filter. The exhaust system further comprises an inlet valve position sensor, an outlet valve position sensor, and a temperature sensor positioned upstream of the second particulate filter.

Referring now to FIG. 2, an exhaust system or exhaust-gas aftertreatment system 70 for an internal combustion engine, for example of a motor vehicle, is shown. The exhaust-gas flow 203 generated by the internal combustion engine flows through an exhaust line 202 in the direction of an outlet or exhaust tailpipe. Arranged in the exhaust line 202 is a particle filter 204, which may also be a constituent part of the exhaust line 202 or of the exhaust system 70. The particle filter 204 serves for filtering particles out of the exhaust-gas flow 203 in order to reduce emissions. The exhaust-gas flow 203 runs in the particle filter 204 along an exhaust-gas path 203, which is provided with the same reference numeral as the exhaust-gas flow 203.

For the filtering, the particle filter 204 comprises a filter 205, which is designed here as a wall-flow filter. Arranged upstream of the filter 205 is an inlet region 206 of the particle filter 204, which inlet region widens the cross section of the exhaust line 202 to the larger cross section of the filter 205. Arranged downstream of the filter 205 is an outlet region 207 which narrows the cross section again to the cross section of the exhaust line 202. The filter 205 and the particle filter 204 are, overall, of rotationally symmetrical design with respect to an axis of rotation 208. The inner region of the filter 205, in particular flow ducts and/or walls, need not be rotationally symmetrical.

The filter 205 is surrounded by a secondary filter 209 which, like the (primary) filter 205, contains filter elements 210, for example ducts, walls and/or suitable material. The secondary filter 209 is structurally separate from the filter 205, that is to say there is no communication of the exhaust flow 203 between the two filters 205 and 209. In one example, the secondary filter is adjacent to the primary filter and forms an annulus that surrounds the primary filter. The secondary filter may have a longer length than the primary filter to account for the variation in flow through its annulus as compared to through the oval or circular cross-section of the primary filter. In addition, the cell size, shape, and/or spacing of the secondary filter may differ from that of the primary filter. In one example, the cell area of the secondary filter may be greater than that of the primary filter. Additionally, a single can may form a housing around both the primary and secondary filter so only that a single inlet and outlet may be provided via the can for exhaust flow.

One or more inlet valves 211 are arranged in the inlet region 206, which inlet valve(s) connect the inlet region 206 and therefore the exhaust line 202 to the secondary filter 209. The inlet valves 211 may be distributed over an inner circumference of the secondary filter 209. One or more outlet valves 212 are arranged in the outlet region 207, which outlet valves connect the secondary filter 209 to the outlet region 207 and therefore to the exhaust line 202. The outlet valves 212 may be designed and/or arranged analogously to the inlet valves 211. Further, the exhaust flow may be in a direction to assist in opening the valves into and out of the secondary filter.

A temperature sensor 213 is arranged in the secondary filter 209 in order to detect the temperature in the secondary filter 209. The temperature sensor 213 may also be arranged in the region of the secondary filter 209, for example on an outer wall of the secondary filter 209 or on the outlet valve 212. Also arranged in the secondary filter 209 is a pressure sensor 214 by means of which the loading of the secondary filter 209 can be detected on the basis of rising pressure. The pressure sensor 214, too, need not be arranged directly in the secondary filter 209 but rather may be arranged for example on the inlet valve 211.

One or more sensors 215, of which two sensors are illustrated by way of example, detect the position of the inlet valve 211 and/or of the outlet valve 212. Depending on the number of inlet valves 211 and outlet valves 212, a plurality of sensors 215 may be provided. It is also possible for one or more sensors 215 to detect only the position of the one or more inlet valves 211 or only the position of the one or more outlet valves 212. The particle filter 204 is illustrated with the sensors 213, 214 and 215, but the particle filter 204 may self-evidently be formed entirely without sensors or may be equipped with only some of said sensors.

The operation of the particle filter 204 will be described below on the basis of FIGS. 2 and 3. When the filter 205 is fully functional, that is to say is not degraded, overloaded with particles, or where less than a threshold amount of particulate matter is stored in the primary particulate filter 204, the particle filter 204 is in a normal mode (e.g., FIG. 2). In said normal mode, the exhaust-gas counterpressure generated by the particle filter 204 is in a normal range which does not degrade the engine or the exhaust system or cause a threshold reduction in engine power. The exhaust-gas flow 203 which passes through the exhaust line 202 flows through the filter 205 in order to be purified. During normal operation, therefore, the exhaust-gas path 203 runs through the filter 205.

During ongoing operation of the internal combustion engine, an ever increasing number of particles are accumulated in the filter 205, such that the loading of the filter 205 with particles continuously increases, as a result of which the flow resistance of the filter 205 increases. Consequently, the exhaust-gas counterpressure increases until it reaches a value at which the performance of the internal combustion engine reduced more than a threshold amount or there is a risk of degradation to the internal combustion engine or the exhaust system. The particle filter 204 now switches into a secondary mode illustrated in FIG. 202, in which the exhaust-gas path 203, that is to say the path of the exhaust-gas flow 203, runs through the secondary filter 209.

A trigger or stimulus for the change of the operating mode may be the exhaust-gas counterpressure of the filter 205 and therefore of the particle filter 204. The exhaust-gas counterpressure may be determined either by means of a pressure sensor 240 for example in the inlet region 206 or in the exhaust line 202. If the exhaust-gas counterpressure exceeds a certain threshold, which may be predefined and/or variable, the inlet valves 211 open, such that the exhaust-gas path runs through the secondary filter 209. The inlet valves 211 may be either externally actuated via actuator 250, for example by a motor or a mechanical system, or internally opened and closed by means of a mechanism or actuator 250, such as a spring, arranged on or in the valve. In the example with the spring, the sensor for the exhaust-gas counterpressure may be omitted, because the valve opens automatically above an exhaust-gas counterpressure set by means of the spring force.

The exhaust-gas flow 203 is then filtered by the secondary filter 209. Similarly to the inlet valves 211, the outlet valves 212 open under increasing pressure. If the pressure in the secondary filter 209 exceeds the pressure in the outlet region 207, the spring-preloaded outlet valves 212 open, such that the exhaust-gas flow 203 circulates past the filter 205. Here, it is not ruled out that a small part of the exhaust-gas flow 203 continues to circulate through the filter 205. While the exhaust-gas flow 203 runs through the secondary filter 209, a regeneration of the primary filter 205 can be carried out in order to restore the performance thereof.

Here, the secondary filter 209 is constructed such that, in the event of an overloading of the secondary filter 209, the filtering efficiency thereof falls and the exhaust-gas counterpressure remains at a normal level. In other words, this means that, even in the event of a relatively long period of operation of the secondary filter 209, the exhaust-gas counterpressure is not increased to such an extent that the performance of the internal combustion engine is reduced or the internal combustion engine is damaged.

Furthermore, the pressure sensor 214 may be used to detect the loading of the secondary filter 209. In the event of an overloading, or impending overloading, of the secondary filter 209, an active regeneration of the secondary filter 209 may be initiated. Furthermore, an overloading mode may be indicated, and a regeneration or a filter exchange initiated. What measures are initiated may be made dependent on the required opening pressure for the inlet valves 211 and/or the outlet valves 212. The level of filter loading may be derived from this.

Similarly, the activation of the secondary mode may be detected, and a corresponding reaction initiated, by means of the sensors 215 for detecting the position of the inlet valve 211 and/or of the outlet valve 212. The secondary mode may also be detected by means of the temperature sensor 213. For this purpose, the temperature signal of the temperature sensor 213, for example the dynamic profile of the signal, is compared with the temperature of the exhaust gas at the inlet of the exhaust aftertreatment system 70.

When the filter 205 has been regenerated and/or exchanged, wherein depending on the design of the particle filter 204, the filter 205 or the complete particle filter 204 is exchanged, the exhaust-gas flow runs through the filter 205 again. Since the exhaust-gas counterpressure is at a normal level again when the filter 205 is in a correct state, the inlet valves 211 for the secondary filter 209 are closed. The sensors and the status signals correspondingly indicate normal operation of the particle filter 204 again. The sensors are connected to one or more control units, which are either assigned exclusively to the particle filter 204 or which contain information regarding the state of the particle filter 204, such as for example control units for the exhaust-gas aftertreatment and/or for the engine management.

Referring now to FIG. 4, a method for operating an exhaust system that can direct engine exhaust to first and second particulate filters is shown. The method of FIG. 4 may be stored as executable instructions in non-transitory media such as memory in a system as is shown in FIG. 1. Method 400 may be executed when an engine is combusting an air-fuel mixture.

At 402, method 400 determines operating conditions. Operating conditions may include but are not limited to pressure upstream of the particulate filter, pressure downstream of the particulate filter, engine speed, engine load, and particulate filter temperature. Method 400 proceeds to 404 after operating conditions are determined.

At 404, method 400 directs substantially all engine exhaust to a primary particulate filter. In one example, the primary particulate filter is of the design shown in FIGS. 2 and 3. Thus, the primary particulate filter is the sole particulate filter receiving exhaust gases from the engine. Method 400 proceeds from 404 to 406.

At 406, method 400 determines an amount of particulate matter stored within the primary particulate filter. In one example, the amount of particulate matter is based on an observed pressure upstream of the particulate filter. Specifically, empirically determined soot storage amounts are stored in a table in memory that is indexed via engine speed, engine load or engine air flow, and exhaust pressure upstream. The table outputs an amount of soot stored in the particulate filer or alternatively a percentage of used soot storage capacity of the particulate filter. Method 400 proceeds to 408 after the amount of soot stored in the particulate filter is determined.

At 408, method 400 judges whether or not the amount of particulate matter store in the particulate filter is greater than a threshold amount. In one example, the amount of soot from 406 is compared to a predetermined soot amount. If the amount of soot stored in the particulate filter is greater than the threshold amount, method 400 proceeds to 410. Otherwise, method 400 proceeds to exit.

At 410, method 400 directs exhaust gas to the secondary particulate filter. The exhaust gases may be directed via changing a position of a valve. In one example, the valve position is adjusted by overcoming a force of a spring. In other examples, the valve may be opened via a solenoid or a motor. Method 400 proceeds to 412 after exhaust gases are directed to the secondary particulate filter.

At 412, regeneration of the primary particulate filter may begin. Alternatively, an operator of the vehicle may be provided an indication that the primary particulate filter should be replaced. The primary particulate filter may be regenerated by increasing the temperature of the primary filter. In one example, the temperature of the primary particulate filter may be increased by increasing a temperature of exhaust gases. The exhaust gas temperature may be increased via throttling the engine and retarding fuel injection timing. Alternatively, if the engine is a spark ignited engine, spark timing may be retarded to increase exhaust gas temperature. Further, the amount of particulate matter stored in the primary particulate filter may be determined as described at 406. In some examples, the valve that directs exhaust gases to the secondary particulate filter may be periodically closed so that substantially no engine exhaust gases are directed to the secondary particulate filter while the amount of soot stored in the primary particulate filter is determined. Additionally, the inlet valve may be periodically closed when the temperature of the first or second particulate filter exceeds a threshold temperature. Method 400 proceeds to 414 after regeneration or notification is provided.

At 414, method 400 judges whether or not particulate matter stored in the primary particulate filter is less than a threshold amount. The amount of soot determined at 412 is compared to a soot threshold amount. If the amount of soot determined at 412 is less than the soot threshold amount, method 400 proceeds to exit. Otherwise, method 400 returns to 410.

Thus, the method of FIG. 4 provides for an exhaust purification method, comprising: directing exhaust gases from an engine substantially solely to a first particulate filter (PF) when a stored soot amount in the first PF is less than a threshold; and directing exhaust gases from the engine to a second PF when the stored soot amount in the first PF is greater than the threshold, the second PF adjacent to and surrounding the first PF. In this way, exhaust gases may be filtered even after an amount of soot stored in one particulate filter exceeds a threshold amount.

The method further comprises combusting an air-fuel mixture in an engine to produce the exhaust gases, and where the amount of soot stored in the first particulate filter is determined from an increased exhaust-gas counterpressure. The method includes where during a condition where the amount of soot stored in the first particulate filter is greater than a threshold amount, a filtering efficiency of the first particulate filter is decreased from a nominal filtering efficiency and an exhaust-gas counterpressure remains below a threshold level. The method further comprises where the first particulate filter is regenerated when exhaust flow is directed to the second particulate filter, and further comprising opening and closing an inlet valve regulating flow to the second particulate filter during regeneration of the first particulate filter. The method further comprises directing engine exhaust gas solely through the first particulate filter after the first particulate filter is regenerated.

In another example, the method of FIG. 4 provides for purification of engine exhaust, comprising: combusting an air-fuel mixture in an engine; directing exhaust gases from the engine substantially solely to a first particulate filter when an pressure upstream of the first particulate filter is less than a threshold amount; and directing exhaust gases from the engine to a second particulate filter when exhaust pressure upstream of the first particulate filter overcomes a spring force, where the second particulate filter surrounds a portion of the first particulate filter. The method also includes where exhaust gases are directed via an inlet valve and an outlet valve. The method further comprises where the first particulate filter is regenerated when exhaust gases are directed to the second particulate filter.

As will be appreciated by one of ordinary skill in the art, routines described in FIGS. 4 may represent one or more of any number of processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. As such, various steps or functions illustrated may be performed in the sequence illustrated, in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily required to achieve the objects, features, and advantages described herein, but is provided for ease of illustration and description. Although not explicitly illustrated, one of ordinary skill in the art will recognize that one or more of the illustrated steps or functions may be repeatedly performed depending on the particular strategy being used.

This concludes the description. The reading of it by those skilled in the art would bring to mind many alterations and modifications without departing from the spirit and the scope of the description. For example, I3, I4, I5, V6, V8, V10, and V12 engines operating in natural gas, gasoline, diesel, or alternative fuel configurations could use the present description to advantage.

PARTICLE FILTER AND METHOD FOR THE PURIFICATION OF AN EXHAUST-GAS FLOW

Information

Publication Number

Date Filed

Date Published

Inventors

Original Assignees

CPC

US Classifications

International Classifications

Abstract

Description

Claims

Priority Claims (1)