Method and system for a particulate filter

Abstract

The present application relates to methods and systems for particulate filters and provides methods and systems for regenerating and purging a particulate filter for an exhaust gas treatment system for a combustion engine. In one example, a method may include flowing exhaust gas through a particulate filter in a reverse direction to purge particulate matter to an intake manifold of the engine for combustion. The duration of the purge may be based on the regeneration achieved during a previous regeneration of the particulate filter during a deceleration fuel cut-off event.

Description

Technical Field

[0001] The present description generally relates to methods and systems for removing soot from a particulate filter of an exhaust treatment system of a combustion engine. Background Art

[0002] The engine exhaust system utilizes an emission control device to treat the exhaust of an internal combustion engine, thereby reducing the amount of particulate emissions released into the atmosphere. The emission control device typically includes a particulate filter and a catalytic converter. For example, a three-way catalytic converter (TWC) capable of reducing NOx can be included in the emission control device. In addition, a particulate filter (PF) can typically be located downstream of the TWC to collect particulate matter, which includes carbon particles (such as smoke and ash) from incomplete combustion. As particulate matter accumulates in the filter, the restriction on exhaust flow gradually increases. When the particulate filter is full of smoke particles, an unfavorable exhaust back pressure may be generated, which can have an adverse effect on combustion, emissions and engine performance.

[0003] In order to reduce the problems associated with exhaust back pressure, the particulate filter can be regenerated periodically. For example, the filter can be regenerated in time during vehicle driving. For example, during the condition that the engine is operated in a deceleration fuel cut-off (DFSO) mode, the exhaust gas can passively reach the regeneration temperature (for example, above 450°C). The flow of the hot exhaust gas through the particulate filter can incinerate at least some of the carbon particles accumulated in the filter, and the combustion products can be discharged into the atmosphere. However, passive regeneration opportunities may be rare because they rely on the occurrence of DFSO. In one example, if the DFSO event does not occur frequently due to the extended duration of the vehicle running at high load, the filter regeneration may be impaired. In another example, the particulate filter can be actively regenerated, wherein the engine operation can be invasively adjusted to increase the exhaust temperature and promote the burning of soot particles. For example, the engine can be operated in sequence rich and lean (relative to stoichiometric) to actively burn soot particles. In a further example, fuel can be injected into the exhaust gas near the filter when the engine is operated lean so as to locally burn soot particles at the filter. However, the reliance on rich / lean engine operation during active regeneration may lead to a decrease in fuel economy.

[0004] Another attempt to manage soot loading of a particulate filter includes routing exhaust gas through an exhaust treatment system to an engine intake via exhaust gas recirculation (EGR system), as shown in Lupescu et al., US 8,635,852. Therein, Lupescu discloses an exhaust treatment system configured to purge stored hydrocarbons and particulate matter from a trap assembly including a particulate filter to an engine intake via an EGR passage of the EGR system.

[0005] However, the inventors herein have recognized potential problems with such systems. As an example, it may be difficult to coordinate the purge flow required to regenerate the filter with the EGR flow requirements. Specifically, based on engine operating conditions, the EGR valve may frequently and rapidly switch between a high flow setting (e.g., a setting that provides 7-20% of the mass flow) and a low flow setting (e.g., a setting that provides 2% of the mass flow). Rapid and significant changes in the EGR flow setting allow for reduced pumping losses, thereby improving fuel economy associated with EGR use. However, the same change in the flow setting of the purged HC may cause combustion instability. As another example, in Lupescu's method, if there are intermittent torque transients, filter regeneration may not be completed. For example, if there is a tip-out to idle condition when purging the filter into the intake, the EGR valve may be closed because the engine's EGR tolerance is low under idle conditions, and also due to the disturbance of the EGR valve opening to the manifold vacuum. Therefore, even if the engine's purge tolerance is higher than the EGR tolerance under idle conditions, further purging of the filter may be terminated. Summary of the invention

[0006] In one example, the above problem can be solved by a method comprising: using a reverse exhaust flow through the filter to purge soot from a loaded particulate filter to an engine intake when the engine is rotating with fuel, and using a forward air flow through the filter to regenerate soot from the loaded particulate filter and flow to the tailpipe when the engine is rotating without fuel. In this way, the purge and regeneration can be performed in coordination with each other so that the soot load of the particulate filter can be reduced as effectively as possible.

[0007] As an example, an exhaust system may include an emission control device having a three-way catalyst (TWC) upstream of a gasoline particulate filter (GPF). The exhaust system may include an exhaust manifold leading to a branch exhaust channel system, the branch exhaust channel system including a plurality of exhaust valves for controlling the direction of the exhaust flow through the emission control device. For example, a first exhaust channel may guide exhaust from an exhaust manifold to an emission control device via an exhaust turbine and / or via a wastegate channel that bypasses the turbine. The exhaust may flow to a tail pipe after flowing through the emission control device (i.e., from the inlet to the outlet of the GPF and passing through the TWC thereon) in a forward direction. Another bypass exhaust channel may be coupled to the first exhaust channel downstream of the turbine for guiding the exhaust to the tail pipe while bypassing the emission control device. A bypass valve coupled to the junction of the first exhaust channel and the bypass channel may be used to guide the exhaust through the first exhaust channel or the bypass channel. A second exhaust channel may couple the exhaust manifold to the first exhaust channel at a position downstream of the TWC. A flow selector valve coupled at the junction of the second exhaust passage and the first exhaust passage can be used to direct exhaust gas to the tailpipe or into the outlet of the GPF through the first exhaust passage (when bypassing the emission control device) to enable reverse exhaust flow through the GPF. The third exhaust passage can couple the inlet of the GPF to the intake manifold at a location downstream of the intake compressor. The third exhaust passage may include a recirculation valve for directing exhaust gas drawn from the inlet of the GPF into the intake manifold. At any given time, a larger portion of the total exhaust flow from the exhaust manifold can be directed into the first exhaust passage relative to the second exhaust passage.

[0008] Based on the engine operating conditions, the position of each valve can be adjusted to achieve one of the forward flow, reverse flow or bypass flow through the emission control device. For example, during conditions where soot loading or unloading is not required at the GPF, the valve position can be adjusted so that the exhaust can be directed to the bypass channel while bypassing the GPF. As another example, during conditions where soot loading is required at the GPF, the valve position can be adjusted so that all exhaust can be directed into the first exhaust channel and flow from the first exhaust channel through the GPF in a first forward direction (from the inlet to the outlet of the GPF and from the outlet into the TWC), wherein the exhaust PM is stored on the GPF. At this time, no exhaust is directed to the second exhaust channel. Moreover, during conditions where soot unloading is required at the GPF and a DFSO opportunity is available, the valve position can be adjusted so that the flow in the first forward direction passes through the GPF via the first exhaust channel, so that passive regeneration can be advantageously used to burn soot at the filter. During conditions where soot unloading is required at the GPF and DFSO opportunities are not available, such as when the engine is operating on supply fuel, the valve position can be adjusted so that a portion of the total exhaust flow (e.g., 10-20% of the total flow) is directed into the second exhaust passage and flows out of the second exhaust passage to flow through the GPF in a second direction opposite to the first direction (from the outlet to the inlet of the GPF) before the exhaust is flowed to the intake manifold. In this article, exhaust PM is drawn out of the grid structure of the GPF during exhaust flow and directed into the engine intake manifold where it is incinerated with the injected fuel during cylinder combustion.

[0009] In this way, particulate filter cleaning can be improved. By causing at least a portion of the exhaust gas to flow through the filter in the reverse direction (in the direction of filter loading), the smoke particles collected on the filter can be gradually removed from the filter and purged to the engine intake manifold. By adjusting the exhaust system valve so that reverse flow occurs when the engine is operated with fuel supply, the filter can be cleaned in a larger part of the drive cycle, although at a slower rate. By providing reverse flow via a dedicated GPF recirculation channel and a GPF recirculation valve, the engine's higher tolerance for low purge flow can be used to slowly but more completely purge the filter without affecting combustion stability or manifold vacuum generation, especially under idle conditions. Also by achieving forward flow through the filter during the engine's operation without fuel supply (such as DFSO), the filter can also be cleaned timely at a higher rate. By coordinating the use of reverse flow through the filter to remove smoke particles and the use of forward flow through the filter to remove smoke particles for different drive cycle conditions, a more complete filter cleaning can be achieved, thereby reducing the need for active regeneration of the filter and reducing associated fuel losses. By also regulating recirculation of exhaust gas to the engine intake based on ingestion of soot from the GPF at the engine, interruptions to filter regeneration due to sudden torque transients may be reduced.

[0010] It should be understood that the above summary is provided to introduce a selection of concepts further described in the detailed description in a simplified form. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is solely defined by the appended claims. Furthermore, the claimed subject matter is not limited to implementations that address any deficiencies mentioned above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 A schematic diagram of an internal combustion engine including an emissions control device including a gasoline particulate filter (GPF) is shown.

[0012] Figure 2A Shows Figure 1 The emission control device operates in the GPF bypass mode.

[0013] Figure 2B Shows Figure 1 The emission control device operates in the GPF in forward flow mode.

[0014] Figure 2C Shows Figure 1 The emission control device operates in the GPF in reverse flow mode.

[0015] Figure 3 Shows Figure 2A-2CSummary table of the different exhaust system valve configurations for each operating mode.

[0016] Figure 4 A high level flow chart of an example method for coordinating regeneration of a GPF during DFSO with purging of the GPF during fueled engine operation is shown.

[0017] Figure 5 A method for adjusting multiple GPF valves in response to engine operating conditions is shown. Figure 2A-2C A high level flow chart of an example method of operating a GPF in one of multiple modes.

[0018] Figure 6 Prophetic examples of engine operation are shown to provide either forward exhaust flow or reverse exhaust flow through the exhaust GPF. DETAILED DESCRIPTION

[0019] The following description relates to systems and methods for operating an exhaust gas treatment system of an internal combustion engine including a particulate filter. An engine controller may be configured to execute a control routine (e.g. Figure 5 ) to operate in one of several operating modes ( Figure 2A-2C and Figure 3 ) to operate the engine exhaust system to provide a forward exhaust flow or a reverse exhaust flow through the GPF. The engine controller may be further configured to perform Figure 4 An exemplary routine is provided for coordinating regeneration of the GPF during DFSO with purging the GPF into the engine intake during fueled engine operation. Figure 6 Examples of engine operation and filter soot removal are shown.

[0020] Now turn to Figure 1, which shows a schematic diagram of a vehicle 100 including one cylinder of a multi-cylinder engine 10, which can be included in the propulsion system of the vehicle 100. In some examples, the vehicle 100 can be a hybrid vehicle with multiple torque sources that can be used for one or more wheels 59. In other examples, the vehicle 100 is a conventional vehicle with only an engine or an electric vehicle with only (multiple) motors. In the example shown, the vehicle 100 includes an engine 10 and a motor 61. The motor 61 can be a motor or a motor / generator. When one or more clutches 56 are engaged, the crankshaft 40 of the engine 10 and the motor 61 are connected to the wheels 59 via the transmission 50. In the depicted example, the first clutch 56 is disposed between the crankshaft 40 and the motor 61, and the second clutch 56 is disposed between the motor 61 and the transmission 50. The controller 12 can send a signal to the actuator of each clutch 56 to engage or disengage the clutch to connect the crankshaft 40 to the motor 61 and its connected components or disconnect the crankshaft 140 from the motor 61 and its connected components, and / or connect the motor 61 to the transmission 50 and its connected components or disconnect the motor 61 from the transmission 50 and its connected components. The transmission 50 can be a gearbox, a planetary gear system, or other types of transmissions. The powertrain can be configured in various ways, including parallel, series, or series-parallel hybrid vehicles.

[0021] The electric machine 61 receives power from the traction battery 58 to provide torque to the wheels 59. The electric machine 61 may also operate as a generator to provide power to charge the battery 58, such as during braking operations.

[0022] Engine 10 may be controlled at least partially by a control system including controller 12 and by input from a vehicle operator 132 via an input device 130. In this example, input device 130 includes an accelerator pedal and a pedal position sensor 134 for generating a proportional pedal position signal PP. Combustion chamber (e.g., cylinder) 30 of engine 10 may include combustion chamber walls 32 with piston 36 disposed therein. In some embodiments, piston 36 may have a bowl on one side within cylinder 30. Piston 36 may be coupled to crankshaft 40 so that reciprocating motion of the piston is converted into rotational motion of the crankshaft. Crankshaft 40 may be coupled to at least one drive wheel of a vehicle via an intermediate transmission system. Additionally, a starter motor may be coupled to crankshaft 40 via a flywheel (not shown) to enable a starting operation of engine 10.

[0023] Combustion chamber 30 may receive intake air from intake manifold 44 via intake passage 42 and may exhaust combustion gases via exhaust manifold 48. Intake manifold 44 and exhaust manifold 48 may selectively communicate with combustion chamber 30 via respective intake valve 52 and exhaust valve 54. In some embodiments, combustion chamber 30 may include two or more intake valves and / or two or more exhaust valves.

[0024] In the present example, each cylinder 30 includes a corresponding intake valve 52 and exhaust valve 54. Each intake valve 52 and exhaust valve 54 may be held in a desired position via a corresponding spring. The engine 10 further includes one or more camshafts (not shown) for operating the intake valve 52 and / or for operating the exhaust valve 54. In one example, the intake camshaft may be coupled to the intake valve 52 and may be actuated to operate the intake valve 52. In another example, the exhaust camshaft may be coupled to the exhaust valve 54 and may be actuated to operate the exhaust valve 54. In some embodiments, where the intake valves of multiple cylinders 30 are coupled to a common camshaft, the intake camshaft may be actuated to operate the intake valves of all coupled cylinders.

[0025] Intake valve 52 may be actuated between an open position that allows intake air to enter the corresponding cylinder and a closed position that substantially blocks intake air from the cylinder. An intake camshaft (not shown) may be included in an intake valve actuation system that communicates with controller 12. The intake camshaft may include an intake cam having a cam lobe profile for opening intake valve 52 for a defined intake duration. In some embodiments (not shown), the camshaft may include an additional intake cam having an alternating cam lobe profile that allows intake valve 52 to be opened for alternating durations (also referred to herein as a cam profile switching system). Based on the lobe profile of the additional cam, the alternating duration may be longer or shorter than the defined intake duration of the intake cam.

[0026] In the same manner, each exhaust valve 54 can be actuated between an open position that allows exhaust gas to be discharged from the corresponding cylinder and a closed position that substantially retains the gas in the cylinder and prevents exhaust gas from being discharged from the cylinder. The intake valve 52 can be controlled by the controller 12 via an electric valve actuator (EVA) 51. Similarly, the exhaust valve 54 can be controlled by the controller 12 via EVA 53. Alternatively, the variable valve actuator can be an electro-hydraulic or any other conceivable mechanism for achieving valve actuation. During some conditions, the controller 12 can change the signals provided to the actuators 51 and 53 to control the opening and closing of the corresponding intake and exhaust valves. The positions of the intake valve 52 and the exhaust valve 54 can be determined by valve position sensors 55 and 57, respectively. In alternative embodiments, one or more of the intake valve and the exhaust valve may be actuated by one or more cams, and valve operation may be varied using one or more of a cam profile switching (CPS) system, a variable cam timing (VCT) system, a variable valve timing (VVT) system, and / or a variable valve lift (VVL) system. For example, cylinder 30 may alternatively include an intake valve controlled via electric valve actuation and an exhaust valve controlled via cam actuation including CPS and / or VCT.

[0027] Fuel injector 66 is shown coupled directly to combustion chamber 30 for injecting fuel directly into combustion chamber 30 in proportion to the pulse width of signal FPW received from controller 12 via electronic driver 68. In this manner, fuel injector 66 provides what is known as direct injection of fuel into combustion chamber 30. For example, the fuel injector may be mounted to the side of the combustion chamber or to the top of the combustion chamber. Fuel may be delivered to fuel injector 66 by a fuel system (not shown) including a fuel tank, a fuel pump, and a fuel rail. In some embodiments, combustion chamber 30 may alternatively or additionally include a fuel injector arranged in intake manifold 44 in a configuration that provides what is known as port injection of fuel into the intake port upstream of combustion chamber 30.

[0028] Ignition system 88 can provide an ignition spark to combustion chamber 30 via spark plug 192, under select operating modes, in response to spark advance signal SA from controller 12. Though spark ignition components are shown, in some embodiments, combustion chamber 30 or one or more other combustion chambers of engine 10 may be operated in a compression ignition mode, with or without an ignition spark.

[0029] In addition to the intake system throttle 63, the intake passage 42 may also include an intake throttle 62, and the throttles 62 and 63 have throttle plates 64 and 65, respectively. The intake throttle 62 is located downstream of the intake compressor and changes the amount of air directed from the intake manifold to the engine cylinders. The intake system throttle 63 is located upstream of the intake compressor and changes the amount of air directed into the intake manifold and into the compressor. In this particular example, the positions of the throttle plates 64 and 65 can be changed by the controller 12 via a signal provided to an electric motor or actuator included in the throttles 62 and 63, and this configuration is generally referred to as electronic throttle control (ETC). In this manner, the throttles 62 and 63 can be operated to change the intake air provided to the combustion chamber 30 and other engine cylinders. The positions of the throttle plates 64 and 65 can be provided to the controller 12 by throttle position signals TP1 and TP2, respectively. Pressure, temperature, and mass air flow can be measured at various points along the intake passage 42 and the intake manifold 44. For example, intake passage 42 may include a mass air flow sensor 120 for measuring clean air mass flow entering through throttle 63. The clean air mass flow measurement may be communicated to controller 12 via a MAF signal. Additionally, the pressure of the air charge within intake manifold 44 may be sensed via a manifold absolute pressure sensor 122 and a MAP signal may be communicated to controller 12. The temperature of the air charge within intake manifold 44 may be measured by a manifold air temperature sensor 147 and the measurement may be provided to controller 12 as a MAT signal.

[0030] The engine 10 may further include an intake air compression device, such as a turbocharger or a supercharger, which includes at least a compressor 162 arranged upstream of the intake manifold 44. For a turbocharger (as shown), the compressor 162 may be at least partially driven by a turbine 164 (e.g., via a shaft) arranged along the exhaust passage 49. For a supercharger (not shown), the compressor 162 may be at least partially driven by an engine and / or an electric machine, and may not include a turbine. A charge air cooler 154 may be included downstream of the compressor 162 and upstream of the intake valve 52. For example, the charge air cooler 154 may be configured to cool the charge air heated by compression via the compressor 162. The charge air cooler 154 may be located upstream of the throttle 62. In addition, the pressure of the compressed air upstream of the intake throttle 63 and downstream of the compressor 162 may be sensed by a throttle inlet pressure (TIP) sensor 145. Specifically, TIP represents the boost level or boost pressure in the engine system.

[0031] Exhaust gas exiting combustion chamber 30 and exhaust manifold 48 rotates exhaust turbine 164, which is coupled to compressor 162 along shaft 163. The amount of compression provided to one or more cylinders of the engine via the turbocharger can be varied by controller 12 by adjusting the amount of exhaust gas directed through turbine 164. When reduced turbine torque is desired, some exhaust flow can be directed through wastegate passage 83 by adjusting the position of wastegate valve 82 to bypass the turbine. By adjusting the position of wastegate valve 82 via controller 12, the amount of boost provided by the turbocharger can be controlled. Thus, wastegate valve 82 can be a boost actuator. For example, controller 12 can provide a signal in response to a demand for increased boost pressure that reduces the opening of the wastegate valve. The combined flow from turbine 164 and wastegate valve 82 can then flow through emission control device 70.

[0032] Engine system 100 may further include an EGR system for routing a desired portion of exhaust gas from exhaust manifold 48 and / or exhaust passage 49 to intake manifold 44 . Figure 1 A high pressure exhaust gas recirculation system (HP-EGR system) and a low pressure EGR system (LP-EGR system) are shown. The HP-EGR is routed from the upstream of the turbine 164 to the downstream of the compressor 162 through the HP-EGR passage 140. The amount of HP-EGR provided to the intake manifold 44 can be changed by the controller 12 via adjusting the opening of the HP-EGR valve 142. For example, the HP-EGR system may include an HP-EGR cooler 146 to discharge heat from the HP-EGR gas to the engine coolant. In some cases, the EGR system may be used to regulate the temperature of the air and fuel mixture in the combustion chamber 30. Therefore, it may be necessary to measure or estimate the EGR mass flow. The EGR sensor may be arranged in the EGR passage and may provide an indication of one or more of mass flow, pressure, temperature, O2 concentration (or engine dilution), and exhaust concentration. For example, the HP-EGR sensor 144 may be arranged in the HP-EGR passage 140. As described in detail herein, at least some amount of HP-EGR may also be adjusted during torque transients to increase boosted engine response.

[0033] LP-EGR is routed through LP-EGR passage 150 from downstream of turbine 164 to upstream of compressor 162. The amount of LP-EGR provided to intake passage 42 may be varied by controller 12 via LP-EGR valve 152. Similar to the HP-EGR system, the LP-EGR system may include an LP-EGR cooler 158 that rejects heat from the LP-EGR gases to the engine coolant, and an LP-EGR sensor 153 disposed within LP-EGR passage 150.

[0034] Depending on operating conditions, LP-EGR valve 152 and HP-EGR valve 142 may be opened (e.g., the opening of the EGR valve may be increased) to allow a controlled amount of cooled exhaust gas to enter the intake passage for desired combustion and emissions control performance. Thus, LP-EGR valve 152 and HP-EGR valve 142 may be actuated by actuators (e.g., electric, mechanical, hydraulic, etc.) based on commands received from controller 12.

[0035] Emission control device (ECD) 70 is shown arranged along exhaust passage 49 downstream of exhaust manifold 48 and downstream of compressor 162. Exhaust passage 49 is connected to a tailpipe. Exhaust gas sensor 126 is shown coupled to exhaust passage 49 upstream of emission control device (ECD) 70. Exhaust gas sensor 126 may be any suitable sensor for providing an indication of exhaust air-fuel ratio, such as a linear oxygen sensor or UEGO (universal or wide range exhaust gas oxygen), a two-state oxygen sensor or EGO, HEGO (heated EGO), a NOx, HC, or CO sensor.

[0036] In this example, ECD 70 includes a catalyst, which may be a three-way catalytic converter (TWC) 71, and further includes a gas particulate filter (GPF) 72. One or more sensors may be coupled to the upstream, downstream, or body of ECD 70. For example, catalyst monitoring sensor 13, pressure sensor 15, and temperature sensor 16 may be coupled to ECD 70. It should be understood that the sensors may be omitted and / or relocated. Figure 1 One or more sensors shown in .

[0037] In addition to being configured to filter particulate matter from the exhaust gas, GPF 72 may also include one or more catalyst materials. For example, GPF 72 may be coated with a washcoat layer including one or more catalyst materials. For example, this configuration may be used in embodiments where engine 10 is spark-ignited. In some embodiments, TWC 71 and GPF 72 may be separate components that include separate housings positioned away from each other (e.g., as shown, TWC is upstream of GPF). TWC 71 and GPF 72 are shown as being arranged downstream of exhaust gas sensor 126 along exhaust passage 49. It should be understood that TWC 71 and GPF 72 may alternatively be any one of a three-way catalyst (TWC), a NOx trap, an SCR catalyst, an oxidation catalyst, or an alternative gas treatment device, or a combination thereof. In addition, it should be understood that GPF 72 may be a gasoline particulate filter or any other type of particulate filter, including a diesel particulate filter (DPF). In some embodiments, GPF 72 may be located downstream of TWC 71 (e.g., Figure 1 ), while in other embodiments, the GPF 72 may be located upstream of the TWC 71 ( Figure 1 However, it should be understood that the ECD 70 is provided as a non-limiting example and that in other embodiments, the ECD may include other components without departing from the scope of the present disclosure.

[0038] One or more exhaust treatment system valves (or GPF valves) may be included to regulate the direction of exhaust gas flow through ECD 70. Figure 2A-2C and Figure 5 As described in detail, by adjusting the positions of various valves, the operating mode of the ECD can be changed so that particulate matter stored on the GPF can be locally burned before being released into the tail pipe, or for particulate matter to be drawn into the engine intake and burned in the cylinder. For example, as described below, one or more exhaust treatment system valves may include a GPF bypass valve 17, a GPF flow direction selector valve 191, and a GPF recirculation valve 189.

[0039] GPF bypass valve 17 (e.g., bypass valve) can be positioned in bypass passage 19 coupled to exhaust passage 49, the bypass coupling a location upstream of GPF 72 with a location immediately downstream of the GPF (e.g., at the GPF outlet, as shown). In this manner, bypass 19 is disposed around GPF 72. However, in other examples, bypass passage 19 can be coupled to a tailpipe instead of being coupled to the GPF outlet. GPF bypass valve 17 can be a continuously variable valve whose position can be adjusted to a fully open position, a fully closed position, or any position therebetween. Referring below to Figure 2A-2C and Figure 3 Further details are provided regarding GPF valve positioning.

[0040] GPF flow direction selector valve 191 is coupled to exhaust passage 49 downstream of GPF 72. Selector valve 191 is also coupled to reverse flow passage 178. Figure 2A-2CAs shown, the reverse flow passage 178 is configured to receive exhaust gas from the exhaust manifold 48 and flow it through the GPF 72 in a reverse direction, which is defined herein as from the outlet to the inlet of the particulate filter. The flow direction selector valve 191 can be configured to control the exhaust gas flow from the reverse flow passage 178 into the GPF 72 in the exhaust passage 49. Specifically, when the GPF flow direction selector valve 191 is actuated to a first position that allows reverse exhaust flow, the exhaust passage 49 can be fluidly coupled to the reverse flow passage 178 via the selector valve 191, and the exhaust gas can flow from the exhaust manifold 48 to the reverse flow passage 178, from which it enters the exhaust passage 49 and then enters the outlet of the GPF 72. The exhaust gas then flows out of the outlet of the GPF 72 and then flows to the engine intake manifold via the GPF recirculation passage 188. In contrast, when the GPF flow direction selector valve 191 is actuated to a second position that disables reverse exhaust flow, the exhaust passage 49 can be separated from the reverse flow passage 178. During this condition, there can only be forward flow through the GPF or bypass flow around the GPF. GPF recirculation valve 189 is depicted along GPF recirculation passage 188, which couples the exhaust treatment system to intake manifold 44. Specifically, recirculation passage 188 couples exhaust passage 49 at a location upstream of the inlet of GPF 72 to intake manifold 44 downstream of compressor 162. When GPF recirculation valve 189 is open, exhaust gas received at the inlet of GPF 72 via reverse flow through GPF 72 can flow through recirculation passage 188 and enter intake manifold 44. In this way, reversing the exhaust flow can purge particulate matter from GPF 72 into the combustion chamber of the engine. GPF recirculation valve 189 can be a fully variable valve that can be adjusted to a fully open position, a fully closed position, or any position therebetween. In this way, GPF recirculation valve 189 can throttle the purge flow from the particulate filter into intake manifold 44.

[0041] The catalyst monitoring sensor 13 may be a HEGO (heated exhaust gas oxygen) sensor, but it should be understood that another suitable type of exhaust gas sensor may be used to monitor the catalyst. The pressure sensor 15 may be located upstream of the GPF 72. In this way, the output of the pressure sensor 15 may provide an indication of the exhaust gas back pressure level from the GPF 72 to the vehicle controller 12, which may be a further indication of the soot load on the filter. For example, if the GPF 72 has a higher soot load, there may be an increased back pressure upstream of the GPF 72. The temperature sensor 16 may be coupled to the PF 72 (e.g., downstream, upstream, or both ends) to monitor the temperature of the particulate filter. Specifically, the output from the temperature sensor 16 may provide an indication of the exhaust gas temperature to the controller 12. If the measured exhaust gas temperature is higher than a threshold temperature, it may be determined that the exhaust gas is hot enough to achieve passive regeneration of the filter. In some examples, the exhaust gas temperature may be a temperature close to the outlet of the GPF 72, or it may be the temperature of the particulate filter medium itself. It should be understood that the temperature sensor may be additionally or alternatively placed upstream of the particulate filter to monitor, for example, the temperature gradient of an exothermic reaction occurring in the particulate filter during regeneration. In yet another example, temperature sensor 16 may be located within GPF 72 .

[0042] The controller 12 Figure 110 is shown as a microcomputer, which includes a microprocessor unit 102, input / output ports 104, electronic storage media for executable programs and calibration values ​​(in this particular example, the electronic storage media is shown as a read-only memory chip 106, a random access memory 108, and a non-fail memory 110) and a data bus. In addition to those signals previously discussed, controller 12 may also receive various signals from sensors coupled to engine 10, including a measurement of intake mass air flow (MAF) from a mass air flow sensor 120; an engine coolant temperature (ECT) from a temperature sensor 112 coupled to a cooling jacket 114; a surface ignition sensing signal (PIP) from a Hall effect sensor 118 (or other type) coupled to crankshaft 40; a throttle position (TP1 and TP2) from a throttle position sensor; a boost pressure from a throttle inlet pressure (TIP) sensor 145; and a manifold absolute pressure signal MAP from a manifold absolute pressure sensor 122. An engine speed signal RPM may be generated by controller 12 based on signal PIP. The manifold pressure signal MAP from the manifold pressure sensor can be used to provide an indication of vacuum or pressure in the intake manifold. Note that various combinations of the above sensors may be used, such as a MAF sensor without a MAP sensor, or vice versa. During stoichiometric operation, the MAP sensor can give an indication of engine torque. Additionally, this sensor, along with the detected engine speed, can provide an estimate of the charge (including air) being inducted into the cylinder. In one example, Hall effect sensor 118, which is also used as an engine speed sensor, produces a predetermined number of equally spaced pulses every and every revolution of the crankshaft.

[0043] Based on Figure 1 The controller 12 uses the signals received by various sensors and the instructions stored in the memory of the controller. Figure 1 Controller 12 may be configured to control the engine operation by various actuators. As an example, in response to temperature input from an exhaust temperature sensor and / or pressure input from a pressure sensor coupled to PF 72, controller 12 may send signals to adjust the opening of various exhaust system valves to change the direction of exhaust gas flow through the PF. Similarly, controller 12 may send signals to actuate GPF bypass valve 17, GPF flow direction selector valve 191, GPF recirculation valve 189, throttle plates 64 and 65, LP-EGR valve 152, HP-EGR valve 142, VCT actuator, respective intake valve 52 and exhaust valve 54, wastegate valve 82, etc.

[0044] In response to an indication that the engine temperature and the engine exhaust temperature are above their respective thresholds and in response to an indication that the raw gas soot level is below its threshold, the controller may send a command signal to adjust the opening of the GPF valve to allow reverse flow through the GPF in order to purge particulate matter to the engine. In one example, adjusting the opening of the GPF valve may include the controller sending a control signal to the GPF bypass valve 17 to increase the amount of forward-flowing exhaust gas that bypasses the GPF 72. As another example, adjusting the opening of the GPF valve may include the controller sending a control signal to increase the opening of the GPF recirculation valve 189 to allow exhaust gas from the GPF 72 to enter the intake manifold 44, and sending a command signal to actuate the GPF flow direction selector valve 191 to a position that allows exhaust gas to flow through the GPF 72 in the reverse direction. The GPF valves may be actuated simultaneously or sequentially in a predetermined order. Thus, the amount of exhaust gas flowing through GPF 72 in the reverse direction may be increased, thereby purging particulate matter from GPF 72 to intake manifold 44 of engine 10 for subsequent combustion when the engine is fueled. In this way, the particulate matter load of the particulate filter may be reduced in a timely manner in response to engine operating conditions to extend its service life.

[0045] As another example, the controller may make a logic determination (eg, regarding the position of the GPF valve) based on a logic rule that is a function of the exhaust back pressure proximate the GPF. Figure 2C As described, in response to an indication of exhaust backpressure at or upstream of the GPF (which may be indicated by the output of pressure sensor 15) relative to an exhaust backpressure threshold after a DFSO event, the controller may then generate a control signal to be sent to an actuator of the GPF valve to actuate the GPF valve to a position that facilitates bypassing the GPF.

[0046] In this way, Figure 1The components enable the engine system to include: an engine having an intake manifold and an exhaust manifold; a turbocharger having a turbine coupled to the exhaust manifold, a compressor coupled to the intake manifold, a shaft mechanically coupling the turbine to the compressor, and an electric motor coupled to the shaft; an exhaust particulate filter; a first exhaust passage coupling the exhaust manifold to a tail pipe via the turbine, the first exhaust passage including a first valve coupled to an inlet upstream of the filter; a wastegate including a wastegate valve coupled to the turbine; a second exhaust passage coupling the exhaust manifold to the tail pipe while bypassing the turbine, the second passage including a second valve coupled to an outlet downstream of the filter; a third exhaust passage coupling the inlet of the filter to the engine intake manifold downstream of the compressor, the third passage including a third valve. The engine system may further include a controller having computer readable instructions stored on the non-volatile memory for: in response to each of an operator torque demand and a filter soot load, adjusting a position of each of the first valve, the second valve, and the third valve to change the direction of flow through the filter between a first flow and a second flow, the first flow being from the exhaust manifold to an inlet of the filter and then from an outlet of the filter to the tailpipe, and the second flow being from the exhaust manifold to the outlet of the filter and then from the inlet of the filter to the intake manifold.

[0047] The controller may include further instructions for wherein the adjustment includes: when the operator torque demand is above a threshold demand and the filter soot load is below a threshold load, or when the operator torque demand is below a threshold demand and the filter soot load is above a threshold load, actuating each of the first valve and the second valve to a corresponding first position and closing the third valve to provide a first flow through the filter; and when the operator torque demand is above the threshold demand and the filter soot load is above the threshold load, actuating each of the first valve and the second valve to a corresponding second position and opening the third valve to provide a second flow through the filter.

[0048] Now turn to Figure 2A-2C , schematic diagrams 200, 220 and 240 include Figure 1 Various combinations of GPF valves for engine 10 are described in the previous section. Figure 1 The components introduced in Figure 2A-2C are numbered similarly in , and are not reintroduced. For clarity, Figure 1 Some parts (including TWC 71) are not included in Figure 2A-2C. Engine 10 is shown with four cylinders 30, but it is understood that engine 10 may include more or fewer cylinders. Engine 10 also includes intake manifold 44, which receives intake air from upstream compressor 162 and directs the air charge to cylinder 30. Exhaust manifold 48 is configured to receive exhaust from cylinder 30 and direct the exhaust to turbine 164, which may be bypassed via control of wastegate valve 82 disposed in wastegate passage 83. LP-EGR passage 150 (with LP-EGR valve 152) and HP-EGR passage 140 (with HP-EGR valve 142) may be coupled between intake manifold 44 and exhaust manifold 48 at different locations relative to the compressor. Pressure sensor 15 located upstream of GPF 72 may be used to determine exhaust back pressure at the particulate filter, and thereby infer the soot load of GPF 72. The GPF valves described above include the GPF bypass valve 17 , the GPF flow direction selector valve 191 , and the GPF recirculation valve 189 . Figure 2A A GPF valve configured in a GPF bypass mode is shown; Figure 2B shows a GPF valve configured for forward flow mode through the GPF; Figure 2C A GPF valve configured for reverse flow mode through the GPF is shown.

[0049] Now turn to Figure 2A , view 200 includes an engine 10 having a GPF valve configured to operate the exhaust system in a GPF bypass mode. In the GPF bypass mode, the GPF bypass valve 17 is adjusted to a first position that allows exhaust flow 202 from the exhaust passage downstream of the turbine to bypass the GPF 72 through the bypass passage 19. In the depicted example, the first position of the GPF bypass valve 17 directs all of the exhaust flow 202 through the bypass passage 19 and around the GPF 72. In one example, the GPF valve 17 can be actuated from a default position to the first position. However, it should be understood that in alternative embodiments, such as where the GPF bypass valve 17 is a continuously variable valve, the GPF valve 17 can be actuated to a first opening. In the GPF bypass mode, the GPF flow direction selector valve 191 can be adjusted to a first position that allows exhaust to flow to the atmosphere in a forward direction and does not allow exhaust to flow to the GPF 72 or flow into the reverse flow passage 178 along the exhaust passage 49 in a reverse direction. Furthermore, in the GPF bypass mode, GPF recirculation valve 189 may be adjusted to a first position that does not allow any exhaust gas flow from GPF 72 to enter intake manifold 44 via recirculation passage 188. In this way, exhaust gas may flow from exhaust manifold 48 through turbine 164 and / or wastegate passage 83 through GPF bypass passage 19 to atmosphere.

[0050] Now turn to Figure 2B , view 220 includes an engine 10 having a GPF valve configured to operate the exhaust system in a GPF forward flow mode. In the GPF forward flow mode, the GPF bypass valve 17 is adjusted to a second position that directs a forward-flowing exhaust gas stream 204 through the GPF 72 and then to the atmosphere without flowing through the GPF bypass passage 19. In the depicted example, the second position of the GPF bypass valve 17 directs the entire forward-flowing exhaust gas stream 204 to enter the GPF 72 at an upstream side 205 of the GPF 72 (also referred to herein as the inlet 205 of the GPF) and to exit at a downstream side 203 (also referred to herein as the outlet 203 of the GPF 72). In the GPF forward flow mode, the GPF flow direction selector valve 191 may be adjusted to a first position that allows exhaust gas to flow to the atmosphere in a forward direction and does not allow exhaust gas to flow through the GPF 72 or into the reverse flow passage 178 in a reverse direction. Furthermore, in the GPF forward flow mode, GPF recirculation valve 189 may be adjusted to a first position that does not allow exhaust gas flow from GPF 72 to enter the intake manifold via recirculation passage 188. In this way, exhaust gas may flow from exhaust manifold 48, through turbine 164 and / or wastegate passage 83, through GPF 72, and then to the atmosphere.

[0051] Now turn to Figure 2C , view 240 includes an engine 10 having a GPF valve configured to operate the exhaust system in a GPF reverse flow mode. In the GPF reverse flow mode, the GPF bypass valve 17 is adjusted to a first position that directs the forward flow exhaust gas 206 to flow to the atmosphere through the bypass passage 19 bypassing the GPF 72. In addition, in the GPF reverse flow mode, the GPF flow direction selector valve 191 can be adjusted to a second position that allows the reverse flow exhaust gas 208 to flow from the exhaust manifold 48 through the reverse flow passage 178 and then in a reverse direction through the exhaust passage 49, where the exhaust gas 208 then enters the downstream side 203 of the GPF 72. Since the reverse flow exhaust gas 208 is closer to the exhaust pressure source (i.e., closer to the exhaust manifold) than the forward flow exhaust gas stream 206, the reverse flow exhaust gas 208 can be at a higher pressure than the pressure of the forward flow exhaust gas stream 206. As the forward flowing exhaust gas stream 206 flows through the turbine 164 , the temperature and pressure of the forward flowing exhaust gas stream 206 decreases.

[0052] In one example, purging soot using reverse exhaust flow includes causing a smaller first portion of the exhaust gas from exhaust manifold 48 to flow into the outlet of the filter (e.g., downstream side 203 of GPF 72) and then flow from the inlet of the filter (e.g., upstream side 205 of GPF 72) to the engine intake manifold 44. At the same time, a second portion including the remainder of the total exhaust gas can flow from exhaust manifold 48 to the tail pipe (e.g., atmosphere) while bypassing the filter. This is schematically represented by the thickness of the flow arrows, and the forward-flowing exhaust gas 206 can include a larger proportion of the total exhaust gas than the reverse-flowing exhaust gas 208. In one example, the reverse-flowing exhaust gas 208 can include 10%-20% of the total exhaust gas from exhaust manifold 48, wherein the remainder of the total exhaust gas includes the forward-flowing exhaust gas 206. As previously described, the second portion of the exhaust gas can flow to the tail pipe via one or more of the exhaust turbine 164 and the wastegate passage 83 that bypasses the turbine 164. After exiting GPF 72 on upstream side 205 of GPF 72, reverse-flow exhaust gas 208 enters recirculation passage 188 and is directed through GPF recirculation valve 189, which may be adjusted to a second position. In this manner, exhaust gas flow may flow from exhaust manifold 48 through reverse-flow passage 178, through GPF 72 (in a reverse direction), and then through recirculation passage 188 to intake manifold 44 where it may join fresh intake air and be directed to cylinder 30 for combustion.

[0053] In some embodiments, engine operation may be further controlled in response to purge conditions. Specifically, while purging soot from the filter, the amount of motor torque supplied to the exhaust turbine 164 based on the operator torque demand may be adjusted. In one example, as the operator torque demand increases while purging, the motor torque may be increased. In another example, while regenerating soot from the filter, the motor torque supplied to the exhaust turbine 164 may be adjusted based on the soot load of the filter. In one non-limiting example, as the soot load on the filter increases, the motor torque may increase.

[0054] In this way, a system for an engine is provided, the system comprising: an intake manifold and an exhaust manifold; a turbocharger having a turbine coupled to the exhaust manifold, a compressor coupled to the intake manifold, a shaft mechanically coupling the turbine to the compressor, and an electric motor coupled to the shaft; an exhaust particulate filter; a first exhaust passage coupling the exhaust manifold to a tail pipe via the turbine, the first exhaust passage comprising a first valve coupled to an inlet upstream of the filter; a wastegate comprising a wastegate valve coupled to the turbine; a second exhaust passage coupling the exhaust manifold to the tail pipe while bypassing the turbine, the second passage comprising a second valve coupled to an outlet downstream of the filter; a third exhaust passage coupling the inlet of the filter to the engine intake manifold downstream of the compressor, the third passage comprising a third valve; and a controller. The controller may be configured with computer readable instructions stored on a non-volatile memory to: in response to each of an operator torque demand and a filter soot load, adjust a position of each of the first valve, the second valve, and the third valve to change the direction of flow through the filter between a first flow from the exhaust manifold to an inlet of the filter and then from an outlet of the filter to the tailpipe and a second flow from the exhaust manifold to the outlet of the filter and then from the inlet of the filter to the intake manifold.

[0055] In some examples, the adjusting may include: when the operator torque demand is above a threshold demand and the filter soot load is below a threshold load, or when the operator torque demand is below a threshold demand and the filter soot load is above a threshold load, actuating each of the first valve and the second valve to a corresponding first position and closing the third valve to provide a first flow through the filter; and when the operator torque demand is above a threshold demand and the filter soot load is above a threshold load, actuating each of the first valve and the second valve to a corresponding second position and opening the third valve to provide a second flow through the filter. In a further example, an exhaust gas recirculation (EGR) passage couples an exhaust manifold downstream of a filter to an engine intake manifold upstream of a compressor, the EGR passage may include an EGR valve, wherein the controller further includes instructions for: when operating with the second flow through the filter, decreasing the opening of the EGR valve as the opening of the third valve increases; and when operating with the second flow through the filter, decreasing the opening of the EGR valve as the engine dilution demand decreases.

[0056] Now turn to Figure 3 , showing the summary Figure 2A-2C 300 of different combinations of GPF valve configurations are shown in FIG. As previously described, the GPF valve may include a GPF bypass valve (e.g., Figure 1 and Figure 2A-2C GPF bypass valve 17), GPF flow direction selector valve (e.g., Figure 1 and Figure 2A-2C GPF flow direction selector valve 191) and GPF recirculation valve (e.g., Figure 1 and Figure 2A-2C GPF recirculation valve 189). By selectively actuating each valve to a desired position, the amount and direction of exhaust flow through the GPF can be controlled. As previously described, each of the above-mentioned valves can be a variable valve, wherein the variable valve can be adjusted to a fully closed position (e.g., 0% open), a fully open position (e.g., 100% open), or any position therebetween. To simplify the discussion, the example modes below will refer to the fully open or closed position, but it should be understood that the opening of each of the GPF valves can be changed without departing from the scope of the present disclosure.

[0057] The GPF bypass mode is shown at 302 (also shown in FIG. Figure 2A ) and includes a GPF bypass valve (e.g., GPF bypass valve 17) actuated to a first position (e.g., position 1), wherein the first position of the GPF bypass valve includes directing all forward-flowing exhaust gas through a bypass passage (e.g., Figure 1 and Figure 2A-2C bypass passage 19). In this manner, forward-flowing exhaust gas may be delivered to the atmosphere without passing through GPF 72. The GPF bypass mode may also include a GPF flow direction selector valve actuated to a first position (e.g., position 1), wherein the first position of the GPF flow direction selector valve includes directing all exhaust flow downstream toward the tailpipe and into the atmosphere. In this manner, reverse exhaust flow upstream toward the GPF or into a reverse flow passage (e.g., reverse flow passage 178) may be avoided by positioning the GPF flow direction selector valve in the first position. The GPF bypass mode may also include a GPF recirculation valve actuated to a first position (e.g., a closed position), wherein the first position of the GPF recirculation valve does not allow exhaust gas to flow through the recirculation passage (e.g., Figure 1 and Figure 2A-2C Recirculation passage 188 shown) into the intake manifold (eg, Figure 1 and Figure 2A-2CIntake manifold 44 shown). Thus, by actuating the valve to operate the exhaust system in GPF bypass mode, an exhaust flow direction can be provided from the engine through the GPF bypass and then to the tail pipe (e.g., atmosphere). Operating conditions that may be suitable for operating in GPF bypass mode include warm engine temperatures and low particulate emissions. In one non-limiting example, warm engine temperatures may include one or more of an engine coolant temperature greater than 160°F and an exhaust temperature greater than 1200°F. Low particulate emissions can be determined based on mapping data stored in a memory of the vehicle controller and can be based on operating conditions such as engine speed and load and engine temperature. In one example, GPF bypass mode can be selected under warm idle conditions.

[0058] The GPF forward flow mode is shown at 304 (also shown in FIG. Figure 2B The GPF forward flow mode may also include a GPF bypass valve actuated to a second position (e.g., position 2), wherein the second position of the GPF bypass valve includes directing all forward-flowing exhaust gas through the GPF. In this way, the forward-flowing exhaust gas may pass through the GPF before being delivered to the atmosphere. The GPF forward flow mode may also include a GPF flow direction selector valve actuated to a first (closed) position, wherein the first position of the GPF flow direction selector valve includes directing all exhaust gas flows leaving the GPF to continue downstream toward the tail pipe and reach the atmosphere. In this way, the GPF flow direction selector valve in the first position may prevent the exhaust gas flow from moving in a reverse direction upstream toward the GPF or into the reverse flow channel. The GPF forward flow mode may also include a GPF recirculation valve actuated to a first position, wherein the first position of the GPF recirculation valve does not allow exhaust gas to enter the intake manifold via the recirculation channel. Therefore, in the GPF forward mode, an exhaust gas flow direction is provided in a forward direction from the engine through the GPF and then to the tail pipe (e.g., the atmosphere). As previously described, forward flow through a particle filter can be defined as flow from the upstream side of the particle filter (e.g., Figure 2A-2C As shown, the upstream side 205 is close to the particulate filter and on the downstream side of the particulate filter (e.g., as shown Figure 2A-2CAs shown, the incident airflow of the downstream side 203) leaving the particle filter. Specifically, in the forward flow mode, the exhaust gas enters the GPF at the inlet 205 and leaves the GPF at the outlet 203. Exemplary operating conditions suitable for operation in the GPF forward flow mode may include DFSO, peak power demand, rich combustion conditions, cold start and compression injection. In this way, during conditions where the exhaust gas contains a high particulate content, the engine can be operated in the GPF forward flow mode so that particulate matter can be loaded onto the GPF, thereby reducing tail pipe emissions. In addition, during conditions where it is desired or possible to regenerate the GPF (for example, when passive regeneration is possible), the engine can be operated in the GPF forward flow mode so that the exhaust gas at high temperature can pass through the GPF in the forward direction, burn the smoke particles stored in the GPF, and transmit the gaseous products to the tail pipe. In other words, the exhaust gas flows from the exhaust manifold into the inlet of the filter, and then flows from the inlet of the filter to the tail pipe to regenerate the smoke particles and make the regenerated smoke particles flow to the tail pipe. In some examples, operation in the first loading mode may occur when the operator torque demand is above a threshold demand and the filter soot load is below a threshold load. In other examples, operation in the third regeneration mode may occur when the operator torque demand is below a threshold demand and the filter soot load is above a threshold load.

[0059] The GPF reverse flow mode is shown at 306 (also shown in FIG. Figure 2C ), and the mode includes a GPF bypass valve actuated to a first position, wherein the first position of the GPF bypass valve includes directing all forward-flowing exhaust gas through the GPF bypass. In this way, forward-flowing exhaust gas can pass through the GPF bypass instead of the GPF and then be delivered to the atmosphere. The GPF reverse flow mode may also include a GPF flow direction selector valve actuated to a second position (e.g., position 2), wherein the second position of the GPF flow direction selector valve includes allowing exhaust gas from the reverse flow channel to flow through the GPF flow direction selector valve in a reverse direction (e.g., upstream), the reverse direction being toward the GPF instead of downstream to the tailpipe. Specifically, in the reverse flow mode, exhaust gas enters the GPF at outlet 203 and leaves the GPF at inlet 205. The GPF reverse flow mode may also include a GPF recirculation valve actuated to a second position (e.g., position 2), wherein the second (open) position of the GPF recirculation valve allows exhaust gas to pass through the recirculation channel (e.g., Figure 1 and Figure 2A-2C Thus, by actuating the valve to operate the exhaust system in a GPF reverse mode, an exhaust flow direction may be provided from the engine through the GPF in a reverse direction and then to the intake manifold of the engine.

[0060] As previously described, reverse flow through the particulate filter can be defined as an incident airflow approaching the particulate filter from the downstream side of the particulate filter and leaving the particulate filter from the upstream side of the particulate filter. Suitable operating conditions for operating in the GPF reverse flow mode may include warm engine temperatures and low particulate emissions. In a non-limiting example, warm engine temperatures may include engine coolant temperatures greater than 160°F and exhaust temperatures greater than 1200°F. Low particulate emissions may be determined based on mapping data stored in a memory of the vehicle controller and may be based on operating conditions such as engine speed and load and engine temperature. In addition, suitable operating conditions for operating in the GPF reverse flow mode may include low to medium engine speeds and loads, under which it is desirable or possible to purge the GPF. Specifically, when the soot load of the GPF is above a lower threshold (as indicated by the output of a pressure sensor close to the GPF being above a pressure threshold) and when the engine operating conditions allow exhaust gas to be recirculated from the GPF to the intake manifold of the engine for combustion, it may be desirable to purge the GPF. In this way, GPF purging may be performed during conditions where EGR is desired to improve engine performance and reduce filter soot levels. In some examples, the engine may be operated in the second mode when the operator torque demand is above a threshold demand and the filter soot loading is above a threshold soot loading.

[0061] In this manner, operating the engine in a first mode (e.g., loading) or a third mode (e.g., regeneration) includes actuating a first valve (e.g., GPF bypass valve 17) coupling the exhaust manifold to the tailpipe upstream of the filter to a first position of the first valve and actuating a second valve (e.g., GPF flow direction selector valve 191) coupling the exhaust manifold to the tailpipe downstream of the filter to a first position of the second valve, and wherein operating in a second mode (e.g., purging) includes actuating the first valve to a second position of the first valve and actuating the second valve to a second position of the second valve. In addition, operating in the second mode further includes opening a third valve (e.g., GPF recirculation valve 189) in a recirculation passage (e.g., recirculation passage 188) coupling an inlet of the filter to an engine intake downstream of an intake throttle (e.g., throttle 62).

[0062] Now turn to Figure 4 , shows an example method 400 for coordinating GPF regeneration with the GPF. The method can reduce soot load without subjecting the purge to the adverse effects of transients. Instructions for executing method 400 and the remaining methods included herein can be provided by a controller (e.g., Figure 1 The controller 12) is based on instructions stored in the memory of the controller and in conjunction with instructions from the vehicle (e.g., Figure 1 The vehicle 100) has a sensor (such as the one referenced above) Figure 1According to the method described below, the controller can use engine actuators of the engine system to adjust engine operation.

[0063] Routine 400 begins at 402, where the routine includes estimating and / or measuring current engine and vehicle operating conditions. Current engine and vehicle conditions may include, but are not limited to, air-fuel ratio (e.g., the air-fuel ratio of the combusted exhaust gas leaving the engine cylinders), the position of the GPF bypass valve (e.g., Figure 1 and Figure 2A-2C GPF bypass valve 17 shown), GPF flow direction selector valve (e.g., Figure 1 and Figure 2A-2C The position of the GPF flow direction selector valve 191) and the GPF recirculation valve ( Figure 1 and Figure 2A-2C Current engine and vehicle conditions may further include the duration since the last particulate filter regeneration event, engine speed and engine load, boost level, engine coolant temperature, accelerator pedal position (e.g., Figure 1 The operator torque demand inferred from the degree of actuation (or position) of the input device 130 ) and the proximity of the particulate filter (e.g., Figure 1 and Figure 2A-2C The current vehicle operating conditions may also include a current particulate filter soot load, which may be modeled based on the level of raw gas soot and regeneration achieved during a previous DFSO regeneration operation. The raw gas soot level may be modeled based on one or more of engine coolant temperature, torque, air-fuel ratio, and engine speed.

[0064] In one example, the engine coolant temperature may be determined by an engine coolant temperature sensor (e.g., Figure 1 The exhaust temperature may be indicated by the output of an engine coolant temperature sensor 112, where an engine coolant temperature above an engine temperature threshold may indicate that the engine is warm rather than in a cold start condition. The exhaust temperature may be indicated by an exhaust temperature sensor (e.g., Figure 1 The exhaust gas particulate matter content can be determined based on engine operating conditions (e.g., engine speed, engine load, and air-fuel ratio) using a mapping table stored in the memory of the controller. Figure 1 The output of a Hall Effect sensor 118 of the embodiment of the present invention receives an indication of engine speed. The engine load may be indicated by one or more of engine speed and the degree of actuation of the accelerator pedal. The engine load may be based on an exhaust gas sensor (e.g., Figure 1 The air-fuel ratio is determined based on the output of the exhaust gas sensor 126.

[0065] Controller 12 may receive a pressure sensor at the GPF (eg, Figure 1 - output of the pressure sensor 15 of Figure 2), which output can indicate the degree of soot loading on the particulate filter, which will be further described below. An empirical model can be used to estimate the current particulate filter soot loading and can be used as a basis for controlling GPF regeneration. In one example, GPF soot load modeling updates the GPF soot load under changing operating conditions by adding the soot load estimated by the model (stored in the memory of the controller) to the last measured soot load value. The soot model can include the level of engine raw gas soot, which can be determined based on one or more of engine speed, engine coolant temperature, air-fuel ratio and torque.

[0066] At 404, the routine includes determining whether DFSO entry conditions have been met. In one example, the DFSO entry conditions can be based on multiple vehicle and engine operating conditions. Specifically, the routine can rely on a combination of one or more of vehicle speed, vehicle acceleration, engine speed, engine load, throttle position, pedal position, transmission gear, and various other parameters to determine at 404 whether DFSO entry conditions have been met. In one example, the DFSO entry conditions can be confirmed in response to an engine speed below a threshold speed, an engine load below a threshold load, or an accelerator pedal position indicating a decrease in torque demand (e.g., a tip-out event).

[0067] If DFSO entry conditions are not met at 404, the routine proceeds to 408 where the routine includes maintaining engine operation. In one example, maintaining engine operation may include continuing to deliver fuel to cylinders of the engine and combusting the fuel to meet the torque demand.

[0068] If the DFSO entry conditions are met at 404, the routine proceeds to 406 where the routine includes disabling cylinder fueling to operate the engine in DFSO mode. Specifically, the engine is operated without fuel injection while the engine continues to rotate and move intake air through the cylinders of the engine and the emission control devices. During this time, the emission control devices (e.g., Figure 1 ECD 70) in a catalyst (e.g., Figure 1 The oxygen loading of the TWC 71) is increased because the catalyst can be loaded with oxygen from the fresh air passing through the cylinder when there is no combustion in the cylinder.

[0069] At 410, the routine includes adjusting the position of the GPF valve to operate the exhaust system in a forward flow mode and to cause the exhaust flow to flow through the GPF in a forward direction. As used herein, the forward flow direction refers to exhaust flow from the exhaust manifold through or around the turbine into the inlet 205 of the GPF and then from the outlet 203 of the GPF to the tailpipe. Figure 2B As described, the forward flow mode includes adjusting the GPF bypass valve to a second position that directs forward flow of exhaust gas through the PF (in a first direction from the inlet to the outlet of the PF) and then to the atmosphere. In one example, the second position of the GPF bypass valve directs all exhaust flow received from the exhaust manifold in the exhaust passage through the GPF. In the GPF forward flow mode, the GPF flow direction selector valve can be adjusted to a first position that allows exhaust gas to flow in a forward direction to the atmosphere and does not allow exhaust gas to flow through the GPF in a reverse direction or into a reverse flow passage (e.g., Figure 1 and Figure 2A-2C In addition, in the GPF forward flow mode, the GPF recirculation valve may be adjusted to a first position that does not allow exhaust gas flow from the GPF through the recirculation passage (eg, Figure 1 and Figure 2A-2C recirculation passage 188) into the intake manifold (eg, Figure 1 and Figure 2A-2C In this way, exhaust gas can be removed from the exhaust manifold (e.g., Figure 1 and Figure 2A-2C of the exhaust manifold 48) flows through the turbine (eg, Figure 1 and Figure 2A-2C turbine 164) and / or a wastegate passage (e.g., Figure 1 and Figure 2A-2C The exhaust gas gate passage 83 flows through the GPF and then flows to the atmosphere.

[0070] In the case where the GPF valve is configured to operate the exhaust system in a forward flow mode, if the exhaust temperature is hot enough and the resulting temperature at the GPF exceeds the regeneration temperature, air moving through the engine and the emission control device during DFSO can cause regeneration of the particulate filter. At 412, the routine includes determining whether the GPF temperature (or the exhaust temperature at the GPF) is greater than the regeneration temperature. In one non-limiting example, the regeneration temperature at the particulate filter can be 450°C or higher. If the GPF temperature does not exceed the regeneration temperature, the routine proceeds to 414, where the routine includes continuing DFSO operation as long as DFSO conditions are met.

[0071] If the GPF temperature exceeds the regeneration temperature at 412, the routine proceeds to 416, where the GPF is passively regenerated (e.g., where at least some of the carbon particles accumulated in the particulate filter can be incinerated to form gaseous products that can be discharged into the atmosphere along the tailpipe as exhaust). That is, the soot particles can be incinerated in situ as the hot exhaust flows through the GPF. In addition, the controller can update the GPF soot load, such as a soot load model stored in the memory of the controller, based on the passive GPF regeneration achieved during forward flow. The GPF soot load model can be updated based on each of the exhaust temperature, the duration of the exhaust flow through the GPF, and the exhaust flow rate through the GPF. Updating the GPF soot load model can include reducing the estimated amount of soot stored in the GPF based on the duration of the regeneration operation. In one example, this can include further reducing the estimated soot load of the GPF as the duration of the regeneration (e.g., elapsed time) increases. In other examples, updating the GPF soot load model may include further decreasing the estimated soot load of the GPF load as the GPF temperature (or exhaust temperature) during regeneration increases above a threshold regeneration temperature, and decreasing the estimated soot load as the exhaust flow rate through the GPF increases. The soot load model may also be adjusted based on an indication of exhaust back pressure. In one example, a pressure sensor (e.g., located upstream of the GPF) may be used to determine the soot load. Figure 1 and Figure 2A-2C Exhaust back pressure may be measured using a pressure sensor 15 (eg, a pressure sensor 15). In other examples, a pressure gradient across the GPF obtained using one or more sensors or a differential pressure sensor may be used to determine exhaust back pressure at the GPF (and infer soot storage level). For example, the output of the pressure sensor may decrease after a GPF regeneration because a reduced soot load in the GPF may result in a lower exhaust back pressure upstream of the GPF.

[0072] At 418, the routine includes determining whether DFSO exit conditions have been met. In one example, when a driver demand (such as that detected by a pedal position sensor (e.g., Figure 1The DFSO exit condition may be confirmed when the engine load (indicated by the pedal position sensor 134 and the input device 130) increases above a threshold (e.g., in response to a step-on event). In other examples, the DFSO exit condition may be met if the engine load is greater than a threshold, which may occur when the vehicle is propelled toward high ground or when towing a load. Various other engine and vehicle operating parameters may be monitored, which may indicate the end of a DFSO event. For example, the routine may monitor the temperature of the particulate filter to ensure that the temperature of the particulate filter does not exceed an upper threshold, which is greater than the regeneration temperature, and the upper threshold reflects a temperature above which thermal degradation of the particulate filter may occur. In some examples, DFSO may end in response to the particulate filter temperature reaching an upper threshold. This may include the DFSO ending before the GPF is fully regenerated. In this way, the GPF may be regenerated to any possible extent in a timely manner during the DFSO. As previously described, if the DFSO exit condition is not met, the routine returns to 416 to continue regenerating the GPF and updating the GPF soot load model.

[0073] If DFSO exit conditions are met, the routine continues to 420 where the routine includes reactivating fuel delivery to the engine cylinders and combusting fuel to meet the driver torque demand.

[0074] At 422 , the routine includes adjusting the purging of soot from the GPF to the intake manifold via reverse exhaust flow through the GPF based on the regeneration achieved at 416 , such as Figure 5 As further described in . The inventors have recognized that passive regeneration using forward exhaust flow through the GPF during DFSO conditions can timely reduce a portion of the GPF soot load. However, because DFSO conditions may not be frequent, and further DFSO can be exited in response to torque transients, additional soot load reduction can be achieved by purging the GPF using reverse exhaust flow through the GPF during engine fuel supply conditions. Therein, soot can be purged to the intake manifold, thereby allowing timely soot reduction. Since the engine is operated with supply fuel for a longer portion of the drive cycle, a larger portion of the soot can be purged to the intake device in a timely manner. By coordinating the GPF soot purging to the intake device with the passive regeneration of the GPF during DFSO conditions, the need for active regeneration of the GPF is reduced, thereby providing a fuel economy benefit.

[0075] In one example, regulating the purging of the GPF based on a prior passive regeneration of the GPF may include adjusting a position of a GPF valve to a reverse flow mode and flowing exhaust gas through the GPF in a reverse direction (from an outlet to an inlet of the GPF) so as to purge any remaining GPF soot load to an intake manifold of the engine, where the GPF soot load may be combusted. In this manner, purging uses a reverse flow of exhaust gas (e.g., flowing exhaust gas from an exhaust manifold into a first channel coupled to the filter, the first channel coupled to a downstream outlet of the particulate filter), and regeneration uses a forward flow of exhaust gas (e.g., flowing exhaust gas from the exhaust manifold into a second channel, the second channel being different from the first channel coupled to an upstream inlet of the particulate filter). In some embodiments, the first channel and the second channel are different channels that may overlap at the particulate filter. In one embodiment, the first channel may also be fluidly coupled to an exhaust gas recirculation channel (e.g., Figure 1 HP-EGR system), the exhaust gas recirculation passage recirculates exhaust gas from the exhaust manifold to the engine intake downstream of compressor 162. In other examples, the first passage can also be fluidly coupled to the exhaust gas recirculation passage (e.g., Figure 1 LP-EGR system), the exhaust gas recirculation passage recirculates exhaust gas from the exhaust manifold to the engine intake upstream of compressor 162. The routine then ends.

[0076] Now turn to Figure 5 , shows a flow chart of an exemplary routine 500 for adjusting multiple GPF valves in response to engine operating conditions, including reversing exhaust gas flow through the GPF to purge particulate matter from the GPF to an intake manifold of the engine.

[0077] Routine 500 begins at 502, where the routine includes estimating and / or measuring current engine and vehicle operating conditions. Current engine and vehicle operating conditions may include, for example, operator torque demand, vehicle speed, air-fuel ratio (e.g., the air-fuel ratio of the combusted exhaust gas exiting the engine cylinders), position of the particulate filter bypass valve, position of the GPF flow direction selector valve, and position of the GPF recirculation valve, duration since the last particulate filter regeneration, engine speed and engine load, engine coolant temperature, degree of actuation (or position) of the accelerator pedal, and exhaust gas temperature and pressure proximate the particulate filter. Current engine and vehicle operating conditions may also include current particulate filter soot loading, which may be modeled based on the level of raw gas soot and regeneration achieved during a previous DFSO regeneration operation, for example Figure 4 The DFSO regeneration described in . The feed gas soot level may be modeled based on one or more of engine coolant temperature, torque, air-fuel ratio, and engine speed.

[0078] At 504, the routine includes determining whether GPF positive flow conditions have been met. In one example, GPF positive flow conditions may be met when the engine is operating in a DFSO mode, where passive regeneration of the GPF may or may not occur during DFSO. For example, GPF positive flow conditions may be met when the operator torque demand is below a threshold and the engine may be operating without fuel.

[0079] Alternatively, during conditions where particulate matter emissions are elevated and the GPF needs to be loaded, the GPF forward flow condition may be met. For example, GPF loading using forward flow may be enabled during peak power conditions, during which the torque demanded by the driver is above a threshold load. During peak power conditions, the air-fuel ratio may (or may not) be enriched, and the resulting exhaust may contain elevated levels of particulate matter (e.g., above a threshold level of particulate matter). At this point, the exhaust may pass through the GPF in order to reduce exhaust particulate emissions. Other operating conditions where the GPF forward flow may be enabled include engine cold start conditions, in which the catalyst light-off temperature is not met and the catalyst remains deactivated. Therefore, cold start emissions may not be handled, and instead, particulate matter is trapped at the GPF. Yet another example of a condition where the GPF forward flow may be enabled includes an engine supplying fuel with compression injection, during which at least a portion of the fuel is directly injected during the compression stroke of the engine cycle. For example, based on the engine operating conditions, a cylinder supply fuel curve can be determined, which includes a ratio of fuel to be injected into the intake port to fuel to be directly injected, and further includes a ratio of direct injection fuel to be delivered during the intake stroke to direct injection fuel to be delivered during the compression stroke. Compression stroke direct injection can be used to improve the atomization of the fuel, for example when the fuel has a lower octane number or when the engine temperature is low. However, compression injection is also prone to generating particulate matter. Therefore, by enabling GPF forward flow during compression injection conditions, the generated PM can be captured at the GPF for later discharge.

[0080] If the GPF forward flow conditions are met, the routine continues to 506 where the routine includes adjusting the GPF valve in response to operating conditions to operate the exhaust system in a forward flow mode and then flowing exhaust gas through the GPF in a forward direction to load particulate matter into the GPF or regenerate the GPF. Figure 2BThis includes adjusting the GPF bypass valve to a second position that directs the forward-flowing exhaust flow through the GPF and then to the atmosphere. In addition, the GPF flow direction selector valve can be adjusted to a first position that allows the exhaust to flow to the atmosphere in a forward direction and does not allow the exhaust to flow through the GPF in a reverse direction or enter the reverse flow channel. In addition, in the GPF forward flow mode, the GPF recirculation valve can be adjusted to a first position that does not allow the exhaust flow from the GPF to enter the intake manifold via the recirculation channel. In this way, the exhaust can flow from the exhaust manifold through the turbine and / or wastegate channel, flow through the GPF in a forward direction (from inlet to outlet) and then flow to the atmosphere. The routine then ends.

[0081] If the GPF forward flow condition is not met, the routine proceeds to 508, where the routine includes determining whether the GPF bypass condition has been met. In one example, the GPF bypass condition may be met when neither GPF loading nor GPF unloading is expected. For example, during a condition where the GPF load is less than a threshold load, neither forward flow through the GPF (to achieve passive regeneration) nor reverse flow through the GPF (to enable purging to the intake device) may be required. As another example, during a condition where the engine is warm idling and no smoke is generated, neither GPF loading nor GPF unloading is required. In one example, the GPF bypass flow condition may be met when the engine temperature is above a threshold temperature (indicating a warm engine condition). In some examples, the GPF bypass condition may also include an engine coolant temperature above a threshold and an exhaust temperature above a threshold. Further GPF bypass conditions may include a particulate matter content of the exhaust below a threshold. In this way, when the particulate matter content of the engine exhaust is low, the exhaust can bypass the particulate filter and still meet emission standards.

[0082] If the GPF bypass conditions have been met, the routine proceeds to 510 where the routine includes adjusting the GPF valve to operate the exhaust system in a GPF bypass mode and flow the exhaust gas to the tailpipe by bypassing around the GPF (without flowing the exhaust gas through the GPF) and then directly to the atmosphere. Figure 2AAs described, in the GPF bypass mode, the GPF bypass valve is adjusted to a first position, which allows the exhaust flow in the forward direction to bypass the GPF through the bypass channel instead of passing through the GPF. In addition, the GPF flow direction selector valve can be adjusted to a first position, which allows the exhaust to flow to the atmosphere in the forward direction and does not allow the exhaust to flow through the GPF in the reverse direction or enter the reverse flow channel. In addition, the GPF recirculation valve can be adjusted to a first position, which does not allow any exhaust flow from the PF to enter the intake manifold via the recirculation channel. In this way, the exhaust can flow from the exhaust manifold through the turbine and / or wastegate channel, through the GPF bypass channel, and to the atmosphere. The routine then ends.

[0083] If the GPF bypass condition is not met, the controller may infer that the GPF reverse flow condition has been met. In one example, the GPF reverse flow mode is the default mode of the exhaust system and is used to slowly purge a portion of the GPF soot load over an extended duration of a drive cycle when the engine is operating with fuel. In response to the inferred GPF reverse flow condition, the routine proceeds to 512 where the routine includes adjusting the GPF valve to operate the exhaust system in reverse flow mode. As previously described with reference to Figure 2C As described, GPF reverse flow mode conditions may include warm engine temperatures and low particulate emissions. In one non-limiting example, warm engine temperatures may include engine coolant temperatures greater than 160°F and exhaust temperatures greater than 1200°F. Low particulate emissions may be determined based on mapping data stored in a memory of the vehicle controller, and may be based on operating conditions such as engine speed and load and engine temperature. In addition, operating conditions suitable for operating in GPF reverse flow mode may include low to medium engine speeds and loads at which it is desired to purge the GPF. Specifically, when the soot load of the GPF is above a lower threshold (which may be indicated by a pressure sensor close to the GPF) and when engine operating conditions allow exhaust gas to be recirculated from the GPF to the intake manifold of the engine for combustion, it may be desired to purge the GPF.

[0084] In the GPF reverse flow mode, the GPF bypass valve is adjusted to a first position, which directs a first forward-flowing exhaust flow from the engine through a bypass passage disposed around the GPF to bypass the GPF to the atmosphere. In addition, the GPF flow direction selector valve can be adjusted to a second position, which directs a second reverse-flowing exhaust flow from the exhaust manifold through the reverse flow passage and then through the GPF in a reverse direction (from outlet to inlet). After leaving the GPF on the upstream / inlet side of the GPF, the exhaust flow enters the recirculation passage and is directed through the GPF recirculation valve, which can be adjusted to a second position. In this way, the exhaust flow can be from the exhaust manifold through the reverse flow passage, through the GPF (in a reverse direction), and then through the recirculation passage to the intake manifold, where the exhaust flow can be connected to fresh intake air and directed to the engine cylinders for combustion. The GPF reverse flow mode is in Figure 2C Shown in.

[0085] The routine then proceeds to 514, where the routine includes flowing exhaust gas through the GPF in a reverse direction so as to purge particulate matter from the GPF to the intake manifold of the engine. This may be referred to as purging, where the reverse exhaust flow through the GPF may release and deliver particulate matter from the GPF from the inlet of the GPF to the intake manifold of the engine for combustion. In some examples, the reverse exhaust flow from the GPF may be connected to one of the existing EGR systems, or it may remain separate. In some embodiments, the routine may include adjusting EGR flow via one or more EGR passages in response to purging GPF soot to the engine intake. For example, in response to the GPF purge, the LP-EGR flow and / or HP-EGR flow may be reduced by reducing the opening of the corresponding EGR valve. In addition, the ratio of HP-EGR flow to LP-EGR flow may vary in response to the purge. For example, since a purged GPF load is received downstream of the compressor, when the GPF recirculation valve is opened, the opening of the HP-EGR valve may be reduced, while the opening of the LP-EGR valve is adjusted (e.g., increased) to maintain a net exhaust gas recirculation amount (exhaust gas recirculation now includes exhaust gas recirculated via the LP EGR passage and the HP EGR passage and exhaust gas received in the intake device via the GPF recirculation passage).

[0086] At 516, the routine includes determining the DFSO event based on the previous DFSO event (eg, Figure 4The duration of the reverse flow (e.g., GPF purge) is adjusted based on the regeneration achieved during a previous DFSO regeneration). In one example, if 80% GPF regeneration is achieved during a previous DFSO, a reverse flow purge can be performed to purge the remaining 20% ​​of the particulate matter load from the GPF within the drive cycle. Alternatively, if 20% GPF regeneration is achieved during a previous DFSO, a reverse flow purge can be performed to purge the remaining 80% of the particulate matter load from the GPF. In this way, purging can be performed for a longer duration in response to a lower regeneration level achieved during a previous DFSO. In addition, the duration of the reverse flow can be based on the exhaust mass flow rate. In one example, exhaust gas can flow through the GPF in a reverse direction until sufficient exhaust mass (or threshold exhaust mass or volume) has flowed through the GPF to achieve the desired reduction in particulate matter from the GPF. In one non-limiting example, the duration can end after ten times the displacement volume of the GPF has flowed to the intake manifold.

[0087] In addition, the controller can adjust the EGR flow to the engine intake manifold based on the GPF recirculation flow. For example, when the GPF recirculation flow is received downstream of the compressor, the controller can reduce the HP-EGR flow. As another example, the controller can adjust the ratio of HP-EGR and LP-EGR delivered to the engine based on the GPF recirculation flow, such as by reducing the HP-EGR flow and increasing the LP-EGR flow. Since the GPF recirculation valve recirculates the exhaust gas back into the intake manifold of the engine downstream of the compressor, the tolerance of the engine combustion process to the recirculated exhaust gas matches its tolerance to the traditional exhaust gas recirculation (EGR) system. Therefore, for an engine with a separate GPF recirculation valve and an EGR valve, the combined exhaust gas flow (from the combination of the GPF recirculation flow and the EGR flow) may not exceed the EGR tolerance of the engine. During large torque transients, it is necessary to mix the recirculated gas to allow more fresh air to meet the torque demand. Therefore, during the accelerator pedal, the EGR valve can be closed to allow more fresh air to be received in the intake manifold. Likewise, during tip-out for low to medium loads, the EGR valve may be opened to increase engine dilution. The EGR valve may be opened until engine idle is reached, and then the EGR valve may be closed to reduce EGR flow due to lower EGR tolerance when the engine is at idle conditions.

[0088] The inventors have recognized that by using different EGR and GPF recirculation passages / valves, filter regeneration requirements can be more easily coordinated with changing EGR flow requirements. Specifically, a higher tolerance for engine purge flow from the GPF relative to EGR flow at engine idle conditions enables a low flow setting of the GPF recirculation valve to be provided whenever a reverse flow condition is met. Furthermore, manifold vacuum generation at engine idle conditions is not affected by the low purge flow setting. Thus, filter regeneration is not affected by sudden and significant changes in EGR demand.

[0089] At 518, the routine includes performing a regeneration based on the regeneration achieved during the previous DFSO event (eg, Figure 4 The controller may also control the position of the GPF recirculation valve in response to a DFSO regeneration (a DFSO regeneration that was not completed) to adjust the position of the GPF recirculation valve. In this way, if a previous DFSO regeneration did not fully regenerate the GPF, the controller may send a control signal to the GPF recirculation valve to increase the opening of the GPF recirculation valve, thereby increasing the reverse exhaust flow from the GPF into the intake manifold, thereby increasing the amount of particulate matter purged from the GPF. In one example, this may occur when a previous DFSO was ended in response to an increase in torque demand before the GPF was fully regenerated (which may be indicated by exhaust back pressure upstream of the GPF not reaching a lower threshold associated with a fully regenerated, "clean" GPF). In other examples, full regeneration of the GPF during DFSO may not occur when the DFSO is abnormally exited prematurely in response to an increase in GPF temperature above an upper threshold that may cause GPF degradation.

[0090] Alternatively, the controller may send a control signal to the GPF recirculation valve to reduce the opening of the GPF recirculation valve to reduce reverse exhaust flow from the GPF into the intake manifold, thereby reducing the amount of particulate matter purged from the GPF. In one example, this may occur when a previous DFSO may have lasted for a duration that would allow the GPF to fully regenerate (which may be indicated by exhaust backpressure upstream of the GPF reaching a lower threshold associated with a fully regenerated, "clean" GPF). In one example, if a previous DFSO fully regenerated the GPF and purging will not achieve further exhaust backpressure reduction, the controller may send a control signal to fully close the GPF recirculation valve to reduce reverse flow through the GPF and purge the GPF.

[0091] The routine then proceeds to 520 where the routine includes determining whether the GPF soot load is below a lower threshold. The lower threshold may be based on a fully regenerated GPF where a sufficient reduction in soot load retained in the GPF has been achieved to reduce exhaust back pressure at the GPF to a lower threshold pressure. If the GPF soot load has not reached the lower soot load threshold, the routine returns to 514 where the routine includes continuing to flow exhaust gas through the GPF in a reverse direction while the engine continues to operate with fuel to purge particulate matter from the GPF to the intake manifold of the engine for combustion.

[0092] If the GPF soot load is below the lower threshold, the routine proceeds to 522, where the routine includes determining whether a tip-in is present. A tip-in can be indicated by actuation of the accelerator pedal and communicates an operator request to increase the torque delivered by the engine. If a tip-in request has been received, the routine continues to 524, where the routine includes adjusting the GPF valve to a forward flow mode to begin loading the GPF. As previously described, adjusting the GPF valve to the forward flow mode includes adjusting the GPF bypass valve to a second position that directs a forward-flowing exhaust flow through the GPF rather than through the GPF bypass and then to the atmosphere. In the GPF forward flow mode, the GPF flow direction selector valve can be adjusted to a first position that allows exhaust to flow in a forward direction to the atmosphere and does not allow exhaust to flow through the GPF in a reverse direction or into a reverse flow passage. Additionally, in the GPF forward flow mode, the GPF recirculation valve may be adjusted to a first position that does not allow exhaust flow from the GPF to enter the intake manifold via the recirculation passage. In this manner, exhaust gas may flow from the exhaust manifold through the turbine and / or wastegate passage, through the GPF, and then to the atmosphere. The routine then ends.

[0093] If the accelerator pedal request has not been received, the routine proceeds to 526, where the routine includes adjusting the GPF valve to the GPF bypass mode because there is no need to load soot particles or unload soot particles from the GPF at this time. As previously described, adjusting the GPF valve to the bypass mode includes adjusting the GPF bypass valve to a first position that allows the forward-flowing exhaust flow to pass through the bypass channel to bypass the GPF. In the GPF bypass mode, the GPF flow direction selector valve 191 can be adjusted to a first position that allows the exhaust to flow to the atmosphere in a forward direction and does not allow the exhaust to flow to the GPF along the exhaust channel in a reverse direction or into the reverse flow channel. In addition, in the GPF bypass mode, the GPF recirculation valve can be adjusted to a first position that does not allow any exhaust flow from the GPF to enter the intake manifold via the recirculation channel. In this way, the exhaust can flow from the exhaust manifold through the turbine and / or wastegate channel, through the GPF bypass channel, and to the atmosphere. The routine then ends.

[0094] Now turn to Figure 6 , graph 600 shows a prophetic example operation of an engine, including adjusting a GPF valve in response to engine operating conditions to coordinate GPF purging with GPF regeneration during DFSO. Graph 600 includes various engine parameters along a vertical axis, and elapsed time along a horizontal axis. Graph 600 depicts a graph accelerator pedal position (PP) at 602, which is indicative of an operator torque demand. Graph 600 further depicts engine temperature relative to a warm engine temperature threshold 606 at graph 604, exhaust temperature relative to a warm exhaust temperature threshold 610 at graph 608, and raw gas soot level 612 relative to a raw gas soot threshold at 614. Graph 616 depicts soot load of the GPF relative to an upper soot load threshold at 618 and a lower soot load threshold at 619. Graphs 620, 622, and 624 depict positions of a GPF bypass valve, a GPF recirculation valve, and a GPF flow direction selector valve, respectively. Graph 600 also depicts the DFSO operating mode (on or off) at 626 , and the exhaust system operating mode (forward flow, reverse flow, or bypass flow) at curve 628 .

[0095] Prior to time t1, the operator is requesting torque, which is indicated by increased actuation of the accelerator pedal (curve 602). As a result, the engine temperature (curve 604) increases as does the exhaust temperature (curve 608). As a result of acceleration, the engine may be operated at a rich air-fuel ratio (e.g., a lambda less than the stoichiometric air-fuel ratio), and due to running a rich engine, the raw gas soot may be raised (curve 612) above the raw gas soot threshold (curve 614). As soot from the raw gas accumulates in the particulate filter, the soot load of the particulate filter may increase (curve 616) toward the upper soot threshold 618. Because the GPF soot load is below the upper soot threshold 618, and the raw gas soot is above the raw gas soot threshold 614, the forward flow mode (curve 628) is selected and the GPF valve is actuated to operate the exhaust system in the forward flow mode so that particulate matter in the exhaust gas may be loaded onto the particulate filter. Specifically, the GPF bypass valve is closed (e.g., position 2) at curve 620, the GPF recirculation valve is closed (e.g., position 1) at curve 622, and the GPF flow direction selector valve is closed (e.g., position 1) at curve 624. In this way, exhaust gas flow from the engine can flow through the GPF in a forward direction (from the inlet to the outlet of the GPF) and then to the tailpipe. The engine is not operated in DFSO mode (curve 626) because there is an elevated operator torque demand.

[0096] At time t1, the operator stops accelerating and requests a steady-state torque level from the engine, which is indicated by maintaining the accelerator pedal position (curve 602). The engine temperature (604) has risen above the warm engine temperature threshold 606, and the engine exhaust temperature (608) has risen above the warm exhaust temperature threshold 610. When the vehicle is no longer accelerating, the raw gas soot level drops slightly (curve 612), and therefore may not be operated as rich as before time t1. For example, the engine may be operated at or near stoichiometry at this time. Therefore, it is determined that when the GPF soot load (curve 616) is above the upper GPF soot load threshold 618, the operating conditions are conducive to purging the GPF. In order to operate the exhaust system in the GPF reverse flow mode (curve 628) to purge the GPF, the GPF valve is actuated. Specifically, the GPF bypass valve is opened (e.g., position 1) at curve 620, the GPF recirculation valve is opened (e.g., position 2) at curve 622, and the GPF flow direction selector valve is opened (e.g., position 2) at curve 624. In this manner, exhaust gas flow from the engine may flow through the GPF in a reverse direction (from the outlet to the inlet of the GPF) and to the intake manifold of the engine to purge particulate matter from the GPF for a first duration D1 from t1 to t2 so that the particulate matter may be combusted in the cylinders of the engine. This configuration allows the engine to operate in a first mode (e.g., a "loading" mode in which soot is loaded on the filter) in which the engine is combusting and exhaust gas is directed to the tailpipe while flowing through the particulate filter in a first direction (prior to t2), and then at time t2, the engine is operated in a second mode (e.g., a "purging" mode in which soot is purged from the filter to the intake of the engine) in which the engine continues to combust with exhaust gas directed to the tailpipe while flowing through the particulate filter in a second direction opposite to the first direction.

[0097] A slow drop in GPF soot load may occur between t1 and t2 (616), which may cause the GPF soot load to fall below an upper GPF soot load threshold 618. Because the operator torque demand is still present, the engine is not operated in the DFSO mode (plot 626).

[0098] At time t2, there is a reduction in the actuation of the accelerator pedal (curve 602). This may be the result of the operator releasing the accelerator pedal. In response to the DFSO condition being met at time t2, the engine enters the DFSO mode (curve 626), and fuel is no longer delivered to the cylinders of the engine, but the intake air can continue to be pumped through the engine and through the exhaust system. Therefore, the air-fuel ratio can move toward lean combustion, and the raw gas soot level is reduced (curve 612) to below the raw gas soot threshold 614. At this point, it can be determined that passive regeneration of the GPF can be performed in a timely manner during the current DFSO event. Therefore, at time t2, the GPF valve can be actuated to operate the exhaust system in the GPF forward flow mode, so that regeneration of the GPF can be performed in a timely manner during DFSO. Specifically, the GPF bypass valve is closed at curve 620 (e.g., position 2), the GPF recirculation valve is closed at curve 622 (e.g., position 1), and the GPF flow direction selector valve is closed at curve 624 (e.g., position 1). In this way, the exhaust flow from the engine can flow through the GPF in the forward direction (from the inlet to the outlet of the GPF) and flow to the tail pipe thereon to facilitate the regeneration of the GPF. In the depicted example, the regeneration of the GPF occurs within the duration D2 of the DFSO, and a corresponding reduction in the GPF soot load occurs (616). It should be understood that, as shown in the figure, the soot reduction rate associated with regeneration can be greater than the soot reduction rate associated with purging. This is at least because of the difference in the rate and volume of the exhaust flow through the GPF during forward flow and reverse flow. Specifically, during the forward flow mode, the entire volume of exhaust flows through the GPF (to regenerate the filter during DFSO), but during the reverse flow mode, only a small portion of the entire exhaust flows in reverse through the GPF (to purge the filter) and the remaining exhaust flows to the tail pipe when bypassing the GPF.

[0099] In the depicted embodiment, in response to the operator releasing the accelerator pedal while purging soot from the filter to the engine intake (between t1 and t2), the controller can send a command signal to disable the engine from supplying fuel and switch to regenerating soot from the particulate filter to the tailpipe. Specifically, the engine can be operated in a third mode (e.g., a "regeneration" mode in which soot is regenerated from the filter) in which the engine is not combusted and exhaust flows directly to the tailpipe while flowing in a first direction. The controller can select between the first mode, the second mode, and the third mode described herein based on each of the operator's torque demand and the filter soot load. Thus, bypassing, purging, loading, and regeneration can be achieved between an engine start event and a subsequent engine shutdown (e.g., during a single common drive cycle).

[0100] At time t3, there is a small amount of accelerator pedal push. Because the DFSO between t2 and t3 did not fully regenerate the GPF (e.g., did not reduce the GPF soot load to the lower threshold 619), additional reduction of soot loading in the GPF may be required. Because the feed gas soot level (curve 612) remains below the feed gas soot level threshold 614, purging can be initiated by actuating the GPF valve back into the GPF reverse flow mode as occurred between t1 and t2. In this way, further reduction of the GPF soot load can be achieved by purging particulate matter from the GPF to the intake manifold of the engine. In this way, purging can be performed for another duration D3 in response to the duration of the second duration D2 of the previous DFSO event to further reduce the soot load of the GPF. Therefore, the GPF soot load can continue to decrease within the duration D3 until time t4, at which time the GPF soot load reaches the lower GPF soot load threshold indicating a "clean" GPF.

[0101] Alternatively, at time t3, if there is an aggressive tip-in, as shown in dashed line graph 603, the raw gas soot load may have increased (dashed line graph 613) above the raw gas soot threshold 614, and the controller may have commanded exhaust gas through the GPF in order to load the GPF with particulate matter and reduce particulate matter emissions. Therefore, the controller may have actuated the GPF valve into a forward flow mode (dashed line graph 629), in which the GPF bypass valve is closed (e.g., position 2) at dashed line graph 621, the GPF recirculation valve is closed (e.g., position 1) at curve 623, and the GPF flow direction selector valve is closed (e.g., position 1) at curve 625. In this way, exhaust gas flow from the engine can flow through the GPF and to the tailpipe in a forward direction to load the GPF with particulate matter, thereby increasing the soot load in the GPF (dashed line graph 617) rather than reducing the soot load, as would occur during purge (curve 616). Additionally, in response to the aggressive tip-in at t3, the engine temperature 605 and the exhaust temperature 609 may further increase above the corresponding warm temperature thresholds 606 and 610, respectively. In this manner, in response to a tip-in event occurring while the engine is operating in the third mode (e.g., regeneration), the engine is transitioned to operating in the first mode (e.g., loading) when the tip-in is large, and to operating in the second mode (e.g., purging) when the tip-in is small.

[0102] At time t4, the torque demand level is off and acceleration is no longer required (curve 602), and therefore the raw gas soot level decreases (curve 612). The GPF soot load (616) reaches the lower GPF soot load threshold 619, and therefore the purge (e.g., reverse flow mode) can end and return to the forward flow mode (curve 628). Alternatively, if the torque demand is as shown in the dashed line graph 603, the GPF mode will still change to the forward flow mode (curve 628) due to the higher raw gas soot load (dashed line graph 613). Therefore, as the exhaust gas flows through the GPF in the forward direction, the soot load of the GPF will gradually increase, and particulate matter is deposited in the GPF.

[0103] At time t5, since the engine temperature (604) is above the warm engine temperature threshold (curve 606), the exhaust temperature (curve 608) is above the warm exhaust temperature threshold (curve 610), and the raw gas soot level (612, 613) is below the raw gas soot threshold 614, the GPF valve can be actuated to the GPF bypass mode (curve 628).

[0104] At time t6, another tip-in occurs, similar to the tip-in prior to time t1. In response to the torque demand (curve 602) and the indication that the raw gas soot level (612) is above the raw gas soot threshold 614, the GPF valve is actuated to a forward flow mode (curve 628) so that particulate matter can be deposited onto the GPF. As previously described, the GPF forward flow mode includes reducing the opening of the GPF bypass valve at curve 620 (e.g., position 2), closing the GPF recirculation valve at curve 622 (e.g., position 1), and closing the GPF flow direction selector valve at curve 624 (e.g., position 1). In this manner, exhaust flow from the engine can flow through the GPF in a forward direction so that particulate matter can be loaded onto the GPF.

[0105] In one example, the controller may determine whether a condition for forward flow through the GPF is met (including a condition for reverse flow through the GPF is not met), and in response thereto, the controller may actuate the GPF valve to operate the exhaust system in a forward flow mode. The controller may also determine whether a condition for reverse flow through the GPF is met (including a condition for each of forward flow and bypass flow through the GPF is not met), and in response thereto, the controller may actuate the GPF valve to operate the exhaust system in a reverse flow mode. The controller may also determine whether a condition for reverse flow through the GPF is met (including a condition for forward flow through the GPF is not met), and in response thereto, the controller may actuate the GPF valve to operate the exhaust system in a reverse flow mode. In some examples, actuating the valve to the forward flow mode occurs when the valve is actuated to the reverse flow mode, and actuating the valve to the reverse flow mode occurs when the valve is actuated to the forward flow mode. In this way, particulate filter cleaning may be improved while reducing reliance on fuel-intensive active regeneration of the filter. When the engine is running with fuel, by continuously flowing a smaller portion of the total exhaust flow from the outlet of the filter to the inlet of the filter, soot particles can be removed from the filter at a slower rate and burned in the engine cylinders over a longer duration of the drive cycle. In contrast, when the engine is running without fuel, by intermittently flowing the total exhaust flow from the inlet of the filter to the outlet of the filter, soot particles can be removed from the filter at a higher rate and burned in situ at the filter over a shorter duration of the drive cycle. By coordinating the use of reverse flow through the filter to remove soot particles from the filter during the operation of the engine without fuel and the use of forward flow through the filter to remove soot particles when the engine is operating with fuel, more complete filter cleaning can be achieved within the drive cycle. By reducing the need for active regeneration of the filter, the fuel economy of the engine is improved. In addition, problems related to exhaust back pressure are also solved. By relying on a branch exhaust channel system including multiple valves for controlling the direction and amount of exhaust flow through the filter, filter cleaning can be improved despite the downstream position and packaging of the filter in the under-hood area of ​​the vehicle. By adjusting the ratio of HP-EGR to LP-EGR provided to the engine in response to soot ingestion from the GPF at the engine, engine dilution and combustion stability can be maintained even as torque varies. A technical effect of purging the GPF into the intake manifold of the engine is that soot loading of the GPF can be reduced over a wide range of engine operating conditions while reducing reliance on active regeneration.

[0106] An exemplary method for an engine includes: when rotating a fueled engine, using a reverse exhaust flow through the filter to purge soot from a loaded particulate filter to an engine intake; and when rotating an unfueled engine, using a forward air flow through the filter to regenerate soot from the loaded particulate filter and flow to a tail pipe. In a first example of the method, the method further includes, wherein purging soot using the reverse exhaust flow includes causing a smaller first portion of the exhaust gas to flow from an exhaust manifold into an outlet of the filter, and then flow from an inlet of the filter to an engine intake, while causing a remaining second portion of the exhaust gas to flow from the exhaust manifold to the tail pipe while bypassing the filter. The second example of the method optionally includes the first example and further includes, wherein the second portion of the exhaust gas flows to the tail pipe via one or more of an exhaust turbine and a wastegate passage that bypasses the turbine. The third example of the method optionally includes one or more of the first and second examples, and further includes, wherein regenerating soot using a forward air flow and flowing to the tail pipe includes causing air to flow from the exhaust manifold into an inlet of the filter, and then flow from the inlet of the filter to the tail pipe. The fourth example of the method optionally includes one or more of the first to third examples, and further includes, wherein the purging using reverse flow includes flowing exhaust gas from the exhaust manifold into a first channel coupled to the filter, wherein the regeneration using forward flow includes flowing air from the exhaust manifold into a different second channel coupled to the filter, wherein the first channel and the second channel are different channels overlapping at the filter. The fifth example of the method optionally includes one or more of the first to fourth examples, and further includes, wherein the first channel is fluidly coupled to an exhaust gas recirculation (EGR) channel that recirculates exhaust gas from the exhaust manifold to an engine intake downstream of an intake compressor. The sixth example of the method optionally includes one or more of the first to fifth examples, and further includes adjusting EGR flow via an EGR channel in response to purging to the engine intake, the adjustment including reducing the EGR flow as the amount of soot purged to the engine intake increases, the EGR flow including one or more of a high pressure EGR flow and a low pressure EGR flow. A seventh example of the method optionally includes one or more of the first to sixth examples, and further includes, in response to an operator tipping out of the accelerator pedal while purging soot from the filter into the engine intake, disabling engine fueling and switching to regenerating soot from the filter and into the tailpipe. An eighth example of the method optionally includes one or more of the first to seventh examples, and further includes, wherein purging soot from the filter and regenerating soot from the filter occur on a common vehicle drive cycle (i.e., between the same engine start and the same engine shutoff event).A ninth example of the method optionally includes one or more of the first to eighth examples, and further includes one or more of the first to eighth examples, and further includes, when purging soot from the filter, adjusting the motor torque supplied to the exhaust turbine based on an operator torque demand, the motor torque increasing as the operator torque demand increases, and when regenerating soot from the filter, adjusting the motor torque supplied to the exhaust turbine based on a soot load on the filter, the motor torque increasing as the soot load on the filter increases.

[0107] In another example, a method for an engine includes operating the engine in a first mode in which the engine burns and exhaust is directed to the tailpipe while flowing through a particulate filter in a first direction; and operating the engine in a second mode in which the engine burns and exhaust is directed to the tailpipe while flowing through the particulate filter in a second direction opposite to the first direction. In the first example of the method, the method further includes operating the engine in a third mode in which the engine does not burn and air is directed to the tailpipe while flowing through the particulate filter in the first direction; and selecting between the first mode, the second mode, and the third mode based on each of an operator torque demand and a filter soot load. The second example of the method optionally includes the first example and further includes, wherein when the engine is operated in the first mode, soot is loaded on the filter, wherein when the engine is operated in the second mode, soot is purged from the filter to the engine intake, and wherein when the engine is operated in the third mode, soot is regenerated from the filter. A third example of the method optionally includes one or more of the first and second examples, and further includes, wherein operating in the first mode or the third mode includes actuating a first valve to a first position of the first valve, the first valve coupling the exhaust manifold to the tail pipe upstream of the filter; and actuating a second valve to a first position of the second valve, the second valve coupling the exhaust manifold to the tail pipe downstream of the filter, and wherein operating in the second mode includes actuating the first valve to a second position of the first valve and actuating the second valve to a second position of the second valve. A fourth example of the method optionally includes one or more of the first to third examples, and further includes, wherein operating in the second mode further includes opening a third valve in a recirculation passage coupling an inlet of the filter to an engine intake downstream of an intake throttle. A fifth example of the method optionally includes one or more of the first to fourth examples, and further includes, wherein the selection includes: selecting the first mode when the operator torque demand is above a threshold demand and the filter soot load is below a threshold load; selecting the second mode when the operator torque demand is above a threshold demand and the filter soot load is above a threshold load; and selecting the third mode when the operator torque demand is below a threshold demand and the filter soot load is above a threshold load. A sixth example of the method optionally includes one or more of the first to fifth examples, and further includes, in response to a tip-out event occurring when the engine is operating in the second mode, switching to operating the engine in the third mode; and in response to a tip-in event occurring when the engine is operating in the third mode, switching to operating the engine in the first mode when the tip-in is large, and switching to operating in the second mode when the tip-in is small.

[0108] A system for an engine includes an intake manifold and an exhaust manifold; a turbocharger having a turbine coupled to the exhaust manifold, a compressor coupled to the intake manifold, a shaft mechanically coupling the turbine to the compressor, and an electric motor coupled to the shaft; an exhaust particulate filter; a first exhaust passage coupling the exhaust manifold to a tail pipe via the turbine, the first exhaust passage including a first valve coupled to an inlet upstream of the filter; a wastegate including a wastegate valve coupled to the turbine; a second exhaust passage coupling the exhaust manifold to the tail pipe while bypassing the turbine, the second passage including a second valve coupled to an outlet downstream of the filter; a third exhaust a passage coupling the inlet of the filter to the engine intake manifold downstream of the compressor, the third passage including a third valve; and a controller having computer readable instructions stored on a non-volatile memory for: in response to each of an operator torque demand and a filter soot load, adjusting a position of each of the first valve, the second valve, and the third valve to change the direction of flow through the filter between a first flow from the exhaust manifold to the inlet of the filter and then from the outlet of the filter to the tailpipe, and a second flow from the exhaust manifold to the outlet of the filter and then from the inlet of the filter to the intake manifold. In a first example of the system, the adjusting includes: when the operator torque demand is above a threshold demand and the filter soot load is below a threshold load, or when the operator torque demand is below the threshold demand and the filter soot load is above the threshold load, actuating each of the first valve and the second valve to a corresponding first position and closing the third valve to provide the first flow through the filter; and when the operator torque demand is above the threshold demand and the filter soot load is above the threshold load, actuating each of the first valve and the second valve to a corresponding second position and opening the third valve to provide the second flow through the filter. A second example of the system optionally includes the first example and further includes an exhaust gas recirculation (EGR) passage that couples the exhaust manifold downstream of the filter to the engine intake manifold upstream of the compressor, the EGR passage including an EGR valve, wherein the controller further includes instructions for: when operating with a second flow through the filter, reducing the opening of the EGR valve as the opening of the third valve increases; and when operating with the second flow through the filter, reducing the opening of the EGR valve as the engine dilution demand decreases.

[0109] In another representation, the vehicle system is a hybrid vehicle system.

[0110] Note that the exemplary control and estimation routines included herein can be used with various engine and / or vehicle system configurations. The control methods and routines disclosed herein can be stored as executable instructions in a non-transient memory and can be executed by a control system including a controller in combination with various sensors, actuators, and other engine hardware. The specific routines described herein can represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multi-tasking, multi-threading, etc. Therefore, the various actions, operations, and / or functions shown can be executed in the sequence shown, executed in parallel, or can be omitted in some cases. Similarly, the processing sequence does not necessarily need to realize the features and advantages of the exemplary embodiments described herein, but is provided for ease of illustration and description. Depending on the specific strategy used, one or more of the actions, operations, and / or functions shown can be repeatedly performed. In addition, the described actions, operations, and / or functions can graphically represent the code in the non-transient memory of a computer-readable storage medium to be programmed into the engine control system, wherein the described actions are executed by executing instructions in a system, and the system includes various engine hardware components combined with an electronic controller.

[0111] It should be understood that the configurations and routines disclosed herein are exemplary in nature, and these specific embodiments should not be considered limiting, as many variations are possible. For example, the above technology can be applied to V-6, I-4, I-6, V-12, opposed 4, or other types of engines. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations and other features, functions, and / or properties disclosed herein.

[0112] The appended claims particularly point out certain combinations and subcombinations regarded as novel and non-obvious. The claims may refer to "an" element or a "first" element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amendment of the present claims or by presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, are also deemed to be included in the subject matter of the present disclosure.

Claims

1. A method for an engine, comprising: while rotating the fueled engine, using reverse exhaust flow through the particulate filter to purge soot from the loaded particulate filter to the engine intake; and while spinning the engine without fuel, regenerating soot from the loaded particulate filter using a positive air flow through the particulate filter and flowing to a tailpipe, Wherein flow through the particulate filter is varied between reverse exhaust flow and forward air flow in response to each of an operator torque demand and a soot load on the particulate filter.

2. The method according to claim 1, wherein: Purging soot using the reverse exhaust flow includes flowing a smaller first portion of the exhaust gas from the exhaust manifold into an outlet of the particulate filter and then from an inlet of the particulate filter to the engine intake, while flowing a remaining second portion of the exhaust gas from the exhaust manifold to the tail pipe while bypassing the particulate filter.

3. The method according to claim 2, wherein: The second portion of the exhaust gas flows to the tail pipe via one or more of an exhaust turbine and a wastegate passage bypassing the turbine.

4. The method according to claim 3, wherein: Regenerating soot using the forward air flow to flow to the tailpipe includes flowing air from the exhaust manifold into the inlet of the particulate filter and then from the inlet of the particulate filter to the tailpipe.

5. The method according to claim 2, wherein: The reverse exhaust flow and the forward air flow flow through different paths that overlap at the particulate filter.

6. The method according to claim 5, wherein: The reverse exhaust gas flow, after leaving the particulate filter, flows into an exhaust gas recirculation passage, or EGR passage, which recirculates exhaust gas from the exhaust manifold to the engine intake device downstream of an intake compressor.

7. The method of claim 1 , further comprising, in response to purging to the engine intake, adjusting EGR flow via an EGR passage, the adjusting comprising reducing the EGR flow as the amount of soot purged to the engine intake increases, the EGR flow comprising one or more of a high pressure EGR flow and a low pressure EGR flow.

8. The method of claim 1 further comprising, in response to an operator tip-out while purging soot from the particulate filter into the engine intake, disabling engine fueling and switching to regenerating soot from the particulate filter and into the tailpipe.

9. The method according to claim 1, wherein: Purging soot from the particulate filter and regenerating soot from the particulate filter occur during a common vehicle drive cycle.

10. The method of claim 3 further comprises, when purging soot from the particulate filter, adjusting the motor torque supplied to the exhaust turbine based on the operator torque demand, the motor torque increasing as the operator torque demand increases, and when regenerating soot from the particulate filter, adjusting the motor torque supplied to the exhaust turbine based on the soot load on the particulate filter, the motor torque increasing as the soot load on the particulate filter increases.

11. An engine system, comprising: an engine having an intake manifold and an exhaust manifold; a turbocharger having a turbine coupled to the exhaust manifold, a compressor coupled to the intake manifold, a shaft mechanically coupling the turbine to the compressor, and an electric motor coupled to the shaft; Exhaust particulate matter filter; a first exhaust passage coupling the exhaust manifold to a tailpipe via the turbine, the first exhaust passage including a first valve coupled upstream of an inlet of the exhaust particulate filter; A wastegate, comprising a wastegate valve coupled to both ends of the turbine; a second exhaust passage coupling the exhaust manifold to the tail pipe while bypassing the turbine, the second exhaust passage including a second valve coupled downstream of an outlet of the exhaust particulate filter; a third exhaust passage coupling the inlet of the exhaust particulate filter to the engine intake manifold downstream of the compressor, the third exhaust passage including a third valve; as well as A controller having computer readable instructions stored on a non-transitory memory, the computer readable instructions for: In response to each of an operator torque demand and a filter soot load, a position of each of the first valve, the second valve, and the third valve is adjusted to change the direction of flow through the exhaust particulate filter between a first flow from the exhaust manifold to the inlet of the exhaust particulate filter and then from the outlet of the exhaust particulate filter to the tailpipe, and a second flow from the exhaust manifold to the outlet of the exhaust particulate filter and then from the inlet of the exhaust particulate filter to the intake manifold.

12. The engine system of claim 11, wherein said adjusting comprises: actuating each of the first valve and the second valve to a corresponding first position and closing the third valve to provide the first flow through the exhaust particulate filter when an operator torque demand is above a threshold demand and a filter soot load is below a threshold load, or when an operator torque demand is below the threshold demand and a filter soot load is above the threshold load; and When the operator torque demand is above the threshold demand and the filter soot load is above the threshold load, each of the first and second valves is actuated to a corresponding second position and the third valve is opened to provide the second flow through the exhaust particulate filter.

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