Electrically heated particulate filter with zoned exhaust flow control

A system includes a particulate matter (PM) filter that includes X zones. An electrical heater includes Y heater segments that are associated with respective ones of the X zones. The electrical heater is arranged upstream from and proximate with the PM filter. A valve assembly includes Z sections that are associated with respective ones of the X zones. A control module adjusts flow through each of the Z sections during regeneration of the PM filter via control of the valve assembly. X, Y and Z are integers.

FIELD

The present disclosure relates to engine control systems for internal combustion engines, and more particularly to particulate filter regeneration systems.

BACKGROUND

Engines such as diesel engines produce particulate matter (PM) that is filtered from exhaust gas by a PM filter. The PM filter is disposed in an exhaust system of the engine. The PM filter reduces emission of PM that is generated during combustion.

Over time, the PM filter becomes full. During regeneration, the PM may be burned within the PM filter. Regeneration may involve heating the PM filter to a combustion temperature of the PM. There are various ways to perform regeneration including modifying engine management, using a fuel burner, using a catalytic oxidizer to increase the exhaust temperature with after injection of fuel, using resistive heating coils, and/or using microwave energy. The resistive heating coils are typically arranged in contact with the PM filter to allow heating by both conduction and convection.

PM reduction systems that use fuel tend to decrease fuel economy. For example, many fuel-based PM reduction systems decrease fuel economy by 5%. Electrically heated PM reduction systems reduce fuel economy by a negligible amount, but are operation limited based on exhaust flow. As exhaust flow increases, for example, above a particular flow rate (kg/s), the facilitation and ability to initiate regeneration by an electrically heated element decreases.

SUMMARY

In one embodiment, a system is provided that includes a particulate matter (PM) filter that includes X zones. An electrical heater includes Y heater segments that are associated with respective ones of the X zones. The electrical heater is arranged upstream from and proximate with the PM filter. A valve assembly includes Z sections that are associated with respective ones of the X zones. A control module adjusts flow through each of the Z sections during regeneration of the PM filter via control of the valve assembly. X, Y and Z are integers.

In other features, a method is provided that includes providing a particulate matter (PM) filter that includes X zones. An electrical heater is provided that includes Y heater segments that are associated with respective ones of the X zones. The electrical heater is arranged upstream from and proximate with the PM filter. Exhaust flow through a selected one of the X zones is restricted during regeneration of the PM filter. X and Y are integers.

DETAILED DESCRIPTION

In addition, although the following embodiments are described primarily with respect to example internal combustion engines, the embodiments of the present disclosure may apply to other engines. For example, the present invention may apply to compression ignition, spark ignition, spark ignition direct injection, homogenous spark ignition, homogeneous charge compression ignition, stratified spark ignition, diesel, and spark assisted compression ignition engines.

In addition, in the following description terms, such as “first”, “second”, and “third” are used. These terms are not specific to any one device or element. More than one of the terms may be used to refer to the same device depending upon the context. For example, the terms first and second may be used to refer to the same module.

Furthermore, various sensors and parameters are disclosed herein. The parameters may be directly determined based on signals from the corresponding sensors or may be indirectly determined. When indirectly determined, the parameters may be based on signals from non-corresponding sensors, based on determined engine and/or exhaust system operating conditions, and/or based on predetermined values. For example, air flow across an external area of an exhaust system may be directly determined via an air flow sensor or may be estimated based on information from a vehicle speed sensor and/or other sensors.

Referring now toFIG. 1, a functional block diagram of an engine system100that incorporates a regeneration system102with a valve assembly104is shown. Although the following embodiment is directed to a hybrid vehicle, the embodiments disclosed herein may be applied to non-hybrid vehicles. The engine system100includes an exhaust system101with the regeneration system102. The regeneration system102is used to remove particles in a particulate filter (PF)103of the exhaust system101. The regeneration system102incorporates the valve assembly104, which adjusts flow of exhaust into selected portions of the PF103.

The engine system100includes an engine105that combusts an air/fuel mixture to produce drive torque for a vehicle based on a driver input module106. Air is drawn into an intake manifold110through a throttle valve112. A control module114, which may be referred to as an engine control module, commands a throttle actuator module116to regulate opening of the throttle valve112to control the amount of air drawn into the intake manifold110.

Air from the intake manifold110is drawn into the cylinder118through an intake valve122. The control module114controls the amount, timing, and number of fuel injections into each cylinder of the engine105and during a combustion cycle via a fuel injection system124that includes one or more fuel injectors125. A combustion cycle may refer to an intake stroke, a compression stroke, an ignition stroke and an exhaust stroke of a cylinder. The fuel injection system124may inject fuel into the intake manifold110at a central location or may inject fuel into the intake manifold110at multiple locations, such as near the intake valve of each of the cylinders. Alternatively, the fuel injection system124may inject fuel directly into the cylinders, as shown.

The fuel that is injected prior to an ignition stroke with the air and creates the air/fuel mixture in the cylinder118. A piston (not shown) within the cylinder118compresses the air/fuel mixture. Based upon a signal from the control module114, a spark actuator module126energizes a spark plug128in the cylinder118, which ignites the air/fuel mixture. The timing of the spark may be specified relative to the time when the piston is at its topmost position, referred to as to top dead center (TDC), the point at which the air/fuel mixture is most compressed.

The combustion of the air/fuel mixture drives the piston down, thereby driving a rotating crankshaft (not shown). The piston then begins moving up again and expels the byproducts of combustion through an exhaust valve130of the cylinder118. The byproducts of combustion are exhausted from the vehicle via an exhaust system101. Exhaust passes through an oxidation catalyst135and the PF103. The embodiments disclosed herein may be applied to an aftertreatment system that includes an oxidation catalyst, a particulate filter, and/or other catalyst and aftertreament components. The oxidation catalyst135promotes oxidation of unburned fuel and raises the temperature of the exhaust gas using heat generated by an oxidation reaction.

The intake valve122may be controlled by an intake camshaft140, while the exhaust valve130may be controlled by an exhaust camshaft142. In various implementations, multiple intake camshafts may control multiple intake valves per cylinder and/or may control the intake valves of multiple banks of cylinders. Similarly, multiple exhaust camshafts may control multiple exhaust valves per cylinder and/or may control exhaust valves for multiple banks of cylinders. The cylinder actuator module120may deactivate cylinders by halting provision of fuel and spark and/or disabling their exhaust and/or intake valves.

A control module114may regulate the position of the intake valve122and/or the exhaust valve130to increase the quantity of fuel ingested into the cylinder(s)118. The control module114may also adjust operation of the fuel injector(s)125, such as ON time or size of injector openings, to increase the amount of fuel injected into the cylinder(s)118. The control module114may also adjust the timing of the exhaust camshaft(s) corresponding to the change in the A/F mixture.

The time at which the intake valve122is opened may be varied with respect to piston TDC by an intake cam phasor148. The time at which the exhaust valve130is opened may be varied with respect to piston TDC by an exhaust cam phasor150. A phasor actuator module158controls the intake cam phasor148and the exhaust cam phasor150based on signals from the control module114.

The control system100may include a boost device that provides pressurized air to the intake manifold110. For example,FIG. 1depicts a turbocharger160. The turbocharger160is powered by exhaust gases flowing through the exhaust system101, and provides a compressed air charge to the intake manifold110. The turbocharger160may compress air before the air reaches the intake manifold110.

A wastegate164may allow exhaust gas to bypass the turbocharger160, thereby reducing the turbocharger's output (or boost). The control module114controls the turbocharger160via a boost actuator module162. The boost actuator module162may modulate the boost of the turbocharger160by controlling the position of the wastegate164. The compressed air charge is provided to the intake manifold110by the turbocharger160. An intercooler (not shown) may dissipate some of the compressed air charge's heat, which is generated when air is compressed and may also be increased by proximity to the exhaust system101. Alternate engine systems may include a supercharger that provides compressed air to the intake manifold110and is driven by the crankshaft.

The engine system100may include an exhaust gas recirculation (EGR) valve170, which selectively redirects exhaust gas back to the intake manifold110. In various implementations, the EGR valve170may be located after the turbocharger160. The engine system100may measure the speed of the crankshaft in revolutions per minute (RPM) using an engine speed sensor180. The temperature of the engine coolant may be measured using an engine coolant temperature (ECT) sensor182. The ECT sensor182may be located within the engine105or at other locations where the coolant is circulated, such as a radiator (not shown).

The pressure within the intake manifold110may be measured using a manifold absolute pressure (MAP) sensor184. In various implementations, engine vacuum may be measured, where engine vacuum is the difference between ambient air pressure and the pressure within the intake manifold110. The mass of air flowing into the intake manifold110may be measured using a mass air flow (MAF) sensor186. The MAF sensor186may be located in a housing that includes the throttle valve112.

The throttle actuator module116may monitor the position of the throttle valve112using one or more throttle position sensors (TPS)190. The ambient temperature of air being drawn into the engine system100may be measured using an intake air temperature (IAT) sensor192. The control module114may use signals from the sensors to make control decisions for the engine system100.

The control module114may communicate with a transmission control module194to coordinate shifting gears in a transmission (not shown). For example, the control module114may reduce torque during a gear shift. The control module114may communicate with a hybrid control module196to coordinate operation of the engine105and an electric motor198. The electric motor198may also function as a generator, and may be used to produce electrical energy for use by vehicle electrical systems and/or for storage in a battery. In various implementations, the control module114, the transmission control module194, and the hybrid control module196may be integrated into one or more modules.

The combined torque of engine105and electric motor198is applied to an input of transmission202. Transmission202may be an automatic transmission that switches gears in accordance with a gear change command from the control module114. An output shaft of transmission202is coupled to an input of a differential gear204. Differential gear204drives axles and wheels200. Wheel speed sensors206generate signals that indicate a rotation speed of their respective wheels200.

The control module114estimates an engine output torque to provide based on received sensor signals and other parameters described herein. The control module114may adjust a position of the throttle, air-fuel ratio, valve timing, fuel injection, etc. to provide the estimated engine output torque. Based on a desired engine output torque, a desired air flow, a desired fuel injection, and/or a desired spark timing is achieved. The desired engine output torque may be based on a vehicle operator (driver) request and/or may be controller based, such as a torque output request from a cruise control system. In particular, the control module114controls the torque output of the engine based on the coordinated torque control methods and systems of the present disclosure.

The sensor signals that are received by the control module114may include sensor signals from: the MAP sensor184, the MAF sensor186, the throttle position sensor190, the IAT sensor192, an accelerator pedal position sensor195, or other sensors, such as the engine coolant temperature sensor182, the engine speed sensor180, an ambient temperature sensor197, an oil temperature sensor199, and a vehicle speed sensor201.

The control module114communicates with the throttle actuator module116. The control module114receives a throttle position signal from the throttle position sensor190and adjusts throttle position based on the throttle position signal. The control module114may control the throttle112using a throttle actuator based on a position of an accelerator pedal193.

Air mass, volume, and pressure per cylinder may be determined and/or estimated based on signals from the sensors184,186. The control module114may adjust engine and exhaust system devices based on a desired MAP and a desired MAF. The desired MAP and MAF may be determined based on engine speed and torque request signals.

The engine system100may further include other sensors218, such as exhaust flow sensors220, an EGR sensor222, environmental sensors224, an oxygen sensor226, and engine sensors230not mentioned above. The environmental sensors224may include an altitude sensor, the ambient temperature sensor197, a barometric pressure sensor, and an air flow sensor. The sensors218-230may be used to determine engine and environmental conditions, which may be further used to adjust the valves of the valve assembly104, to adjust current and/or voltage of a heater assembly251, and/or to determine a desired throttle area. The desired throttle area may correspond to a specific throttle position.

The engine system100may also include memory240, which may be used when adjusting the valve assembly104and/or when performing various functions associated with the control module114. The memory240may include various tables242, which may include predetermined exhaust temperature values, predetermined environmental condition values, correction factors, coefficient values, etc. for regeneration of the PF103. The contents of the memory240may be associated with one or more of the steps described with respect to the methods described below.

The exhaust system101includes the PF103, the oxidation catalyst135, an exhaust manifold250, and the heater assembly251with one or more heater elements. Optionally, an EGR valve (not shown) re-circulates a portion of the exhaust back into the intake manifold110. The remainder of the exhaust is directed into the turbocharger160to drive a turbine. The turbine facilitates the compression of the fresh intake air. Exhaust flows from the turbocharger160through the oxidation catalyst135and into the PF103. The oxidation catalyst135oxidizes the exhaust based on a post combustion air/fuel ratio. The amount of oxidation increases the temperature of the exhaust. The PF103receives exhaust from the oxidation catalyst135and filters any soot particulates present in the exhaust. The valve assembly104is used to adjust exhaust flow in areas of the PF103during regeneration of the PF103. Example valve assemblies are shown inFIGS. 3A-4E. The heater assembly251is used to heat the soot to a regeneration temperature. Example heater elements and heater assemblies are shown inFIGS. 5-7.

The control module114controls the engine and regeneration of the PF103based on various sensed information and soot loading. More specifically, the control module114estimates loading of the PF103. When the estimated loading is at a predetermined level and/or the exhaust flow rate is within a desired range, regeneration may be enabled. The duration of the regeneration process may be varied based upon the estimated amount of particulate matter within the PF103.

During regeneration soot in the PF103is ignited. The ignited soot may be partially or fully extinguished due to high exhaust flow rates. The valve assembly104is used to restrict the flow of exhaust in selected areas of the PF103. This allows a regeneration process to occur in the selected areas without extinguishing the ignited soot. The heater assembly251is used to ignite the soot. Heat generated by the heater assembly251causes soot in selected areas of the PF103to reach a point of ignition (light-off) and thus start regeneration. The ignition of the soot creates an exotherm that propagates along the PF103and heats soot downstream, continuing the regeneration process.

The engine system100may include exhaust system sensors, such as the exhaust flow sensors220, exhaust pressure sensors252,254, an exhaust temperature sensor256, etc. for determining exhaust flow levels, exhaust temperature levels, exhaust pressure levels, etc. The control module114may adjust valves of the valve assembly104and/or current and voltage of the heater assembly251based on signals from the sensors220,252,254,256.

The PF103may have an associated predetermined regeneration temperature operating range, a predetermined regeneration operating temperature, and/or a predetermined peak operating temperature. The peak operating temperature may be associated with a point of potential degradation. For example, a PF may begin to breakdown at operating temperatures greater than 800° C. The peak operating temperature may vary for different PFs. The peak operating temperature may be associated with an average temperature of a portion of a PF or an average temperature of the PF as a whole.

To prevent damage to a PM filter, and increase the operating life of the PM filter, the embodiments of the present disclosure may adjust PM filter regeneration based on soot loading. A target maximum operating temperature is set for a PM filter. Regeneration is performed when soot loading is less than or equal to a soot loading level associated with the maximum operating temperature. The regeneration may be performed when soot loading levels are low or within a predetermined range. The predetermined range has an upper soot loading threshold Sutthat is associated with the maximum operating temperature. Limiting peak operating temperatures of a PM filter minimizes pressures in and expansion of the PM filter. In one embodiment, soot loading is estimated and regeneration is performed based thereon. In another embodiment, when soot loading is greater than desired for regeneration, mitigation strategies are performed to reduce PM filter peak temperatures during regeneration.

Soot loading may be estimated and/or predicted from parameters, such as mileage, exhaust pressure, exhaust drop off pressure across a PM filter, etc. Mileage refers to vehicle mileage, which can be used to estimate vehicle engine operating time and/or the amount of exhaust gas generated. For example only, regeneration may be performed when a vehicle has traveled approximately 200-300 miles. The amount of soot generated typically depends upon the amount of vehicle loading and use over time. At idle speeds, less soot is generated than when operating at higher speeds. The amount of exhaust gas generated is related to the state of soot loading in the PM filter.

Exhaust pressure can be used to estimate the amount of exhaust generated over a period of time. Regeneration may be performed when an exhaust pressure exceeds a predetermined level. For example when exhaust pressure entering a PM filter exceeds a predetermined level, regeneration may be performed. As another example when exhaust pressure exiting a PM filter is below a predetermined level, regeneration may be performed.

Exhaust drop off pressure may be used to estimate the amount of soot in a PM filter. For example, as the drop off pressure increases the amount of soot loading increases. The exhaust drop off pressure may be determined by determining pressure of exhaust entering a PM filter minus pressure of exhaust exiting the PM filter. Exhaust system pressure sensors may be used to provide these pressures.

A predictive method may include the determination of one or more engine operating conditions, such as engine load, fueling schemes, fuel injection timing, and exhaust gas recirculation (EGR). A cumulative weighting factor may be used based on the engine conditions. The cumulative weighting factor is related to soot loading. When the cumulative weighting factor exceeds a threshold, regeneration may be performed.

Based on the estimated soot loading and a predetermined peak operating temperature for a PM filter, regeneration is performed to prevent the PM filter from operating at temperatures above the peak operating temperature.

Designing a control system to target a selected soot loading allows PM filter regenerations without intrusive controls. A robust regeneration strategy as provided herein, removes soot from a PM filter while limiting peak operating temperatures. Limiting of peak operating temperatures reduces thermal stresses on a substrate of a PM filter and thus prevents damage to the PM filter, which can be caused by high soot exotherms. As a result, durability of the PM filter is increased.

When soot loading is greater than a threshold level associated with a set peak regeneration temperature, mitigation strategies may be performed to reduce PM filter peak temperatures during regeneration. For example, when a maximum soot loading threshold is set at approximately 2 g/l and current soot loading is 4 g/l, to minimize temperatures within a PM filter during regeneration, engine operation is adjusted. The adjustment may include oxygen control and exhaust flow control.

Soot loading may be greater than an upper threshold level, for example, when an engine is operated to receive a high intake air flow rate for an extended period of time. Such operation may occur on a long freeway entrance ramp or during acceleration on a freeway. As another example, a soot loading upper threshold may be exceeded when a throttle valve of an engine is continuously actuated between full ON and full OFF for an extended period of time. High air flow rates can prevent or limit regeneration of a PM filter.

A large increase in exhaust flow can aid in distinguishing or minimizing an exothermic reaction in a PM filter. Exhaust flow control may include an increase in exhaust flow by a downshift in a transmission or by an increase in idle speed. The increase in engine speed increases the amount of exhaust flow.

Referring now toFIG. 2, a regeneration system300is shown. The regeneration system300may replace the regeneration system102and/or may be included in and/or combined with the regeneration system102. The regeneration system300includes a control module302, and a PF assembly304.

The PF assembly304includes a valve assembly306, a heating element assembly308, and a PF310. The valve assembly306is used to adjust exhaust flow in selected areas of the PF310. Example valve assemblies are shown inFIGS. 3A-4E. The heating element assembly308is used to heat selected areas of the PF310. Example heating elements and heating element assemblies are shown inFIGS. 5-7.

The control module302controls the valve assembly306and the heating element assembly308based on, for example, signals received from sensors disclosed herein. For example, the regeneration system300may include one or more sensors, such as an inlet pressure sensor312, an inlet temperature sensor314, an outlet pressure sensor316, and an outlet temperature sensor318. Additional sensors are disclosed inFIG. 1.

The control module302may adjust valves of the valve assembly via magnetic drivers320. The magnetic drivers320may receive power from a power supply322. The magnetic drivers320may be part of the control module302or may be stand alone drivers, as shown.

Referring now toFIGS. 3A and 3B, side and front views of a valve and heater element assembly330in accordance with an embodiment of the present disclosure is shown. The valve and heater element assembly330includes a valve assembly331, a spacer332, and a heater element assembly333. The spacer332separates the valve assembly331from the heater element assembly333. The width W of the spacer332may be adjusted based on the configurations of the valve and heater element assemblies331,333, and current and voltages applied to the valve and heater element assemblies331,333.

The valve assembly331includes valves or louvers334that each rotate about a respective valve rod335. The louvers334may be formed of or coated with a material that reflects heat energy. For example, a reflective coating may be applied on the downstream side, for example side336, of the louvers334that faces a PF339. This facilitates ignition and aids in maintaining the temperature of the soot. The louvers334enable robust regeneration over a wide range of exhaust flows. The valve assembly331may include any number of louvers, which may be arranged in rows and/or columns. The louvers334may be each opened, closed, and/or position adjusted via one or more magnets. In the example embodiment shown, each louver334has an associated upper electromagnet337and a lower permanent magnet stop338. The louvers334may be divided into sections or zones that correspond with zones and/or areas of the heater assembly333and the PF.

The louvers334may be opened and/or closed by providing current to either the electromagnets337or the permanent magnet stops338. Each of the louvers334may thus have a fully closed position (when the louvers are in contact with the electromagnets), a fully open position (when the louvers are in contact with the permanent magnet stops), or may be variably adjusted to a position between fully closed and fully open. Current may be applied to both the electromagnets337and the permanent magnet stops338to provide partially open or partially closed positions. The louvers334may be adjusted to any position between the fully closed and fully open positions. The louvers334may be opened, closed, or position adjusted individually, in groups, and/or with respect to selected areas and/or zones of the PF. Each louver334may have any number of associated magnets, electromagnets, permanent magnets, etc.

The louvers may have a normally open or a normally closed state. Associated magnets may have normally magnetized or normally demagnetized states that are associated with the normally open or closed states. The term normally refers to a default state or state when the corresponding regeneration system is depowered and/or when regeneration is not being performed.

The heater element assembly333includes one or more heater elements340. The heater elements are located downstream from the valve assembly331and are arranged over a front surface of the PF.

In operation, a front area of the PF may be selected. Louvers associated with the selected front area may be partially or fully closed based on exhaust flow or signals from sensors disclosed herein. Current may be applied to the heater elements associated with the selected area to initiate regeneration. Examples of zoned selection are shown inFIGS. 4A-E.

Although the embodiment ofFIGS. 3A and 3Binclude the use of magnetically adjusted flapper valves or louvers, other valves may be used. The valves may include bimetal devices or other mechanical and electrical actuators and activators.

Referring now toFIG. 4A-E, are front views illustrating zoned operation of the valve assembly331ofFIG. 3A.FIG. 4Aillustrates the closing of an upper left zone of louvers. The heating elements that are located behind or downstream from the louvers in the upper left zone may be activated.FIG. 4Billustrates the closing of an upper right zone of louvers. The heating elements that are located behind or downstream from the louvers in the upper right zone may be activated.FIG. 4Cillustrates the closing of a center zone of louvers. The heating elements that are located behind or downstream from the louvers in the center may be activated.FIG. 4Dillustrates the closing of a lower left zone of louvers. The heating elements that are located behind or downstream from the louvers in the lower left zone may be activated.FIG. 4Eillustrates the closing of a lower right zone of louvers. The heating elements that are located behind or downstream from the louvers in the lower right zone may be activated.

Referring now toFIG. 5, exemplary zoning of a zoned inlet heater assembly350is shown. An exemplary zoned inlet heater assembly350is arranged upstream from a PM filter assembly352. The PM filter assembly352includes multiple spaced heater zones including zone1(with sub-zones1A,1B and1C), zone2(with sub-zones2A,2B and2C) and zone3(with sub-zones3A,3B and3C). The zones1,2and3may be activated during different respective periods.

As exhaust gas flows through the activated zones of the heater, regeneration occurs in the corresponding portions of the PM filter that initially received the heated exhaust gas (e.g. areas downstream from the activated zones) or downstream areas that are ignited by cascading burning soot. The corresponding portions of the PF that are not downstream from an activated zone act as stress mitigation zones. For example inFIG. 5, sub-zones1A,1B and1C are activated and sub-zones2A,2B,2C,3A,3B, and3C act as stress mitigation zones.

The corresponding portions of the PM filter downstream from the active heater sub-zones1A,1B and1C thermally expand and contract during heating and cooling. The stress mitigation sub-zones2A and3A,2B and3B, and2C and3C mitigate stress caused by the expansion and contraction of the heater sub-zones1A,1B and1C. After zone1has completed regeneration, zone2can be activated and zones1and3act as stress mitigation zones. After zone2has completed regeneration, zone3can be activated and zones1and2act as stress mitigation zones.

Referring now toFIG. 6, exemplary zoning of a zoned inlet heater assembly360is shown. A center portion may be surrounded by a middle zone including a first circumferential band of zones. The middle portion may be surrounded by an outer portion including a second circumferential band of zones.

In this example, the center portion includes zone1. The first circumferential band of zones includes zones2and3. The second circumferential band of zones comprises zones1,4and5. As with the embodiment described above, downstream portions from active zones are regenerated while downstream portions from inactive zones provide stress mitigation. As can be appreciated, one of the zones1,2,3,4and5can be activated at a time. Others of the zones remain inactivated.

Referring now toFIG. 7, an exemplary resistive heater elements370are shown. The heater elements370may be arranged adjacent to one of the zones (e.g. zone3) from the first circumferential band of zones inFIG. 6. The heater elements370may include one or more coils, heater segments, or conductive elements that cover the respective zone to provide sufficient heating.

Referring now toFIG. 8, an electrically heated PM filter assembly380is shown. The PM filter assembly380includes a housing400, a filter402, a valve assembly404, and a heater assembly406. The heater assembly406is arranged between the valve assembly404and a substrate of the filter402. A diesel oxidization catalyst (DOC) may be incorporated between the Valve assembly404and the heater assembly406. An electrical connector411may provide current to the zones of the valve assembly404and zones of the heater assembly406, as described above.

As can be appreciated, the heater assembly406may be in contact with or spaced from the filter402such that the heating is convection and/or conduction heating. Insulation412may be arranged between the heater assembly406and a housing413. Exhaust gas enters the PM filter assembly380from an upstream inlet414and is heated by one or more zones of the PM filter assembly380. The heated exhaust gas is received by the filter402.

Referring now toFIG. 9, heating within a portion of a PF420is shown. Exhaust gas450passes through a heater452and is heated by one or more zones of the heater452. If spaced from the PF420, the heated exhaust gas travels a distance “d” and is then received by the PF420. For example only, the distance “d” may be ½″ or less. The PF420may have a central inlet454, a channel456, filter material458and an outlet460located radially outside of the inlet. The filter may be catalyzed. The heated exhaust gas causes PM in the filter to burn, which regenerates the PF420. The heater452transfers heat by convection and/or conduction to ignite a front portion of the PF420. When the soot in the front face portions reaches a sufficiently high temperature, the heater is turned off. Combustion of soot then cascades down the filter channel456without requiring power to be maintained to the heater452.

Referring now toFIG. 10, a regeneration method is shown. Although the following steps are primarily described with respect to the embodiments ofFIGS. 1-4E, the steps may be easily modified to apply to other embodiments of the present disclosure.

In step500, control of a control module, such as the control module114ofFIG. 1, begins and proceeds to step501. In step501, sensor signals are generated. The sensor signals may include exhaust flow rate signals, exhaust temperature signals, exhaust pressure signals, an oxygen signal, an intake air flow signal, an intake air pressure signal, an intake air temperature signal, an engine speed signal, an EGR signal, etc., which may be generated by the above-described sensors. The sensor information may be updated throughout this method and the regeneration process and may be detected and/or indirectly estimated.

In step502, control estimates current soot loading Slof the PF. Control may estimate soot loading as described above. The estimation may be based on the sensor information, vehicle mileage, exhaust pressures, exhaust drop off pressures across the PM filter, and/or a predictive method. The predictive method may include estimation based on one or more engine operating parameters, such as engine load, fueling schemes, fuel injection timing, and EGR. In step503, control determines whether the current soot loading Slis greater than a soot loading lower threshold Slt. When the current soot loading Slis greater than the lower threshold Sltcontrol proceeds to step504, otherwise control returns to step502.

In step504, control determines if regeneration is to be performed based on whether current soot loading Slis less than a soot loading upper threshold Sut. When the current soot loading Slis less than the upper threshold Sutthen control proceeds to step508. When the current soot loading Slis greater than or equal to the upper threshold Sutthen control proceeds to step510. A soot loading model may be used when determining when to perform regeneration. In step510, control performs mitigation strategies as described above to limit peak temperatures in the PF during regeneration. Step510is performed while performing regeneration steps512-524.

If control determines that regeneration is needed in step504, control selects one or more zones of the PF in step508. In step512, control determines position of louvers of a valve assembly, such as the valve assemblies104,306and331ofFIGS. 1,2, and3A-4E. Louvers associated with the selected zones may be partially or fully closed by activation or deactivation of respective magnetic drivers associated with the magnets of the louvers. A predetermined number of louvers may be selected to minimize backpressure increase. Selected louvers are at least partially closed to restrict flow in a flow controlled area, not to completely block the flow. In other words, the louvers when fully closed leak. Louvers that are not associated with the selected zones may be partially or fully opened. The louvers may not completely cover respective openings to allow for leakage of exhaust around the louvers and/or may, for example, be perforated to allow for leakage through the louvers.

The louver positions may be adjusted between different states during regeneration and may be based on the sensor information obtained in step501and the current soot loading. The positions may be predetermined and stored in a memory, determined via a look-up table, or determined based on engine operating parameters, some of which are stated herein. In step514, control adjusts the positions of the louvers based on the determined positions.

In step516, control selects heating element(s) associated with the selected zones. Control may also select current, voltage and/or frequencies of signals to apply to the heating elements. The current, voltage and frequencies may be predetermined and stored in a memory, determined via a look-up table, or determined based on engine operating parameters, some of which are stated herein. The current, voltage and/or frequencies may be based on the sensor information obtained in step501and the current soot loading.

In step518, control estimates a heating period sufficient to achieve a minimum soot temperature. The minimum soot temperature may be based on at least one of current, voltage, exhaust flow, exhaust temperature and predetermined heating element circuit characteristics, such as heating element length, width, coverage area, heating output, etc. The heating period may also be based on the positions of the louvers, the number and size of the louvers for the selected zone, the reflective characteristics of the louvers, the exhaust leakage associated with each of the louvers. The exhaust leakage referring to the amount of exhaust gas that may pass through and/or around a louver for a particular area when fully closed.

The minimum soot temperature should be sufficient to start the soot burning and to create a cascade effect. For example only, the minimum soot temperature may be set to 700 degrees Celsius or greater. In an alternate step520to step516, control estimates heating element current, voltage and/or frequencies to achieve minimum soot temperatures based on a predetermined heating period, exhaust flows and/or exhaust temperatures.

In step522, the PF is regenerated by selectively heating one or more of the zones and igniting the soot in the portions of the PF associated with the zones. When soot within the selected zones reaches a regeneration temperature, the selected heating elements may be turned off and the burning soot then cascades down the PF, which is similar to a burning fuse on a firework. In other words, the heating elements may be activated long enough to start the soot ignition and may then be deactivated or may be activated throughout the soot burning process. The louvers are cleaned of particulate matter by the radiant heat energy given off by adjacent heating elements.

In one embodiment, radially outer most zones are regenerated first followed by radially inner zones. The zones may be regenerated in a select, predetermined, sequential, independent, or arbitrary manner. Multiple zones may be selected and heated during the same time period.

In step524, control determines whether the heating period is up. If step524is true, control determines whether additional zones need to be regenerated in step526. When regeneration is done for a selected zone, the associated louvers or valves may be opened by a combination of exhaust flow and adjustment in current supplied to associated magnets and/or devices of the valves. Respective magnets may be energized or deenergized to open the valves. If step526is true, control returns to step508.

The burning soot is the fuel that continues the regeneration. This process is continued for each heating zone until the PF is completely regenerated. Control ends in step528.

The above-described steps are meant to be illustrative examples; the steps may be performed sequentially, synchronously, simultaneously, continuously, during overlapping time periods or in a different order depending upon the application.

In use, the control module determines when the PF requires regeneration. The determination is based on soot levels within the PF. Alternately, regeneration can be performed periodically or on an event basis. The control module may estimate when the entire PF needs regeneration or when zones within the PF need regeneration. When the control module determines that the entire PF needs regeneration, the control module sequentially activates one or more of the zones at a time to initiate regeneration within the associated downstream portion of the PF. After the zone or zones are regenerated, one or more other zones are activated while the others are deactivated. This approach continues until all of the zones have been activated. When the control module determines that one of the zones needs regeneration, the control module activates the zone corresponding to the associated downstream portion of the PM filter needing regeneration.

The zoned flow control described-above provides a broader regeneration window using an electrically heated PF. This eliminates the need for post-fuel injected components or fuel heated PF regeneration system components, as an electrically heated PF system may be used during high exhaust flow conditions. The electrically heated PF system may be used over an entire vehicle speed operating range.

The present disclosure provides a low power regeneration technique with short regeneration periods and thus overall regeneration time of a PF. The present disclosure may substantially reduce the fuel economy penalty, decrease tailpipe temperatures, and improve system robustness due to the smaller regeneration time.