Method and system for particulate filter with bypass

Abstract

The present application discloses a method and system for an emission control device including a particulate filter with a bypass. In one example, the method includes bypassing the particulate filter when the exhaust gas has a reduced soot load and when the particulate filter has a reduced soot storage. The method further includes reducing the filter bypass flow and terminating or adjusting a deceleration fuel cut-off operation due to an exhaust gas temperature near the particulate filter being above a threshold.

Description

Technical Field

[0001] The present invention generally relates to methods and systems for controlling particulate emissions from a vehicle engine including a particulate filter having an adjustable bypass around the particulate filter. Background Art

[0002] An exhaust aftertreatment device or emission control device (ECD) may be used to treat the exhaust gas of an internal combustion engine in order to reduce the amount of particulate emissions into the atmosphere. In particular, the emission control device may include a particulate filter (PF), an oxidation catalyst, and a nitrogen oxide (NOx) catalyst. Particulate matter, which is primarily composed of carbon particles (e.g., soot) from incomplete combustion, may be collected in the particulate filter, resulting in a gradual increase in the restriction of exhaust gas flow and reduced fuel economy as the particulate matter accumulates in the particulate filter. It should be understood that there are a variety of types of particulate filters, including diesel particulate filters and gasoline particulate filters. In order to periodically clean or regenerate particulate filters that accumulate soot to reduce exhaust back pressure, measures may be taken to increase the exhaust gas temperature above a predetermined level to a regeneration temperature (e.g., for example, above 450° C.) in order to incinerate the carbon particles accumulated in the filter to form gaseous products. However, in addition to soot, the exhaust gas also carries non-combustible solid materials that remain after regeneration, referred to as ash, and may remain trapped in the PF for the remaining service life of the PF. Ashes are primarily derived from lubricating oil that enters the combustion chamber or exhaust duct. Other sources include corrosion from the exhaust manifold and debris from the upstream catalytic converter. As particulate matter (e.g., ash and soot) accumulates in the PF, exhaust backpressure can increase, adversely affecting fuel economy. Since stored ash can remain within the PF after regeneration, the exhaust backpressure generated by the PF can be partially reduced due to regeneration, but not completely eliminated. As a result, ash can continue to contribute to exhaust backpressure on the engine, thereby reducing engine torque output and / or engine fuel economy.

[0003] In some operating conditions, the vehicle may be operated with the exhaust reaching a sufficiently high temperature to passively perform particulate filter regeneration without selectively or intrusively controlling engine parameters to achieve an increase in exhaust temperature for the purpose of particulate filter regeneration. However, in some cases, active regeneration may be performed, in which the engine control is adjusted to selectively increase the exhaust temperature to facilitate particulate filter regeneration. In addition, particulate filter regeneration may occur during a deceleration fuel cut-off (DFSO) condition. During DFSO operation, in order to reduce fuel consumption and increase fuel economy, fuel injection to one or more cylinders is disabled during select conditions (such as gently releasing the throttle when the vehicle is coasting down a hill). The engine continues to rotate during DFSO operation, and therefore air may still flow through the engine to the exhaust during DFSO operation, thereby increasing the oxygen concentration of the gas flowing to the particulate filter. The increased oxygen concentration in the exhaust gas may promote particulate filter regeneration of the particulate filter at the regeneration temperature.

[0004] Attempting to manage particulate filter regeneration conditions (including the temperature of the particulate filter) during DFSO includes adjusting the length of the deceleration fuel cut-off event during DFSO and the total number of activated and deactivated cylinders based on the change in particulate filter temperature during particulate filter regeneration. In addition, fuel may be injected into one or more cylinders during DFSO to reduce the oxygen concentration of the exhaust gas flowing to the particulate filter (e.g., stoichiometrically igniting one or more cylinders). In addition, the ignited cylinders may be operated at a variable air / fuel ratio (e.g., λ greater than, less than, or equal to 1). By burning the air mixture, oxygen is consumed and the relative oxygen percentage of the exhaust gas is significantly reduced, ultimately reducing the rate of increase in the particulate filter temperature. Ulrey et al. show an example method in U.S. application 2016 / 0222898. Therein, Ulrey determines whether the particulate matter reaction length (e.g., particulate filter regeneration) is greater than the length of DFSO, and then one or more cylinders of the engine may be activated during DFSO to reduce the oxygen flow and extend the length of DFSO to match the reaction rate of the soot. In this way, the oxygen flow rate is reduced during DFSO while still performing particulate filter regeneration. By doing so, the filter may not exceed a maximum allowable particulate filter temperature, thereby reducing the likelihood of particulate filter degradation while completing particulate filter regeneration. Summary of the invention

[0005] However, the inventors herein have recognized potential problems with such systems. As one example, indiscriminately routing exhaust gas through a particulate filter even under operating conditions when no net gain in emissions reduction or fuel economy is achieved unnecessarily shortens the life of the particulate filter. Furthermore, because DFSO may be controlled based on the temperature of the particulate filter as exhaust gas is routed through the particulate filter, this may undesirably limit the use of DFSO, thereby limiting the potential for further increases in fuel economy and emissions reductions by operating in a DFSO mode.

[0006] In one example, the above problem can be solved by a method for an engine, the method comprising: in response to reduced soot generation or reduced soot storage, flowing gasoline combustion exhaust gas to a particulate filter with increased filter bypass flow even when exhaust temperature is above a first threshold; and in response to increased soot generation or increased soot storage, reducing the filter bypass flow and terminating a deceleration fuel cut-off operation after a threshold duration due to exhaust temperature being above the first threshold. In some examples, the threshold duration may be based on one or more of soot generation, soot storage, and exhaust temperature relative to a corresponding threshold. When the filter bypass flow is increased, the engine may be operated with DFSO for a first duration based on an operator demanded torque, rather than operating with DFSO for a second duration based on the temperature of the particulate filter.

[0007] In this way, under operating conditions when the particulate matter load in the exhaust gas is low, a portion of the exhaust gas may bypass the particulate filter, thereby reducing exhaust back pressure and thereby improving fuel economy. In addition, by not allowing the exhaust gas to flow through the particulate filter during all driving conditions, soot and ash accumulation in the particulate filter may be reduced, thereby increasing the life of the particulate filter. In addition, by allowing the exhaust gas to bypass the particulate filter, the possibility of excessive heat release on the particulate filter during the DFSO mode is reduced, and DFSO may be performed without regard to the temperature of the particulate filter. When particulate filter regeneration is desired, or when the exhaust gas contains an increased amount of soot, the flow through the bypass may be reduced by reducing the opening of the bypass valve disposed in the bypass. If the particulate filter is at an elevated temperature when DFSO is initiated, engine operating parameters and / or the DFSO operation itself may be adjusted to control the flow of oxygen-carrying exhaust gas through the particulate filter. By controlling the oxygen concentration in the exhaust gas entering the particulate filter, the temperature of the particulate filter may be maintained below an upper threshold (e.g., a maximum allowed particulate filter temperature to reduce filter degradation), and thus, degradation of the particulate filter may be reduced while still performing regeneration and DFSO. As a result, the filter may not exceed a maximum allowable particulate filter temperature, thereby reducing the likelihood of particulate filter degradation.

[0008] It should be understood that the above summary of the invention is provided to introduce some concepts that are further described in the detailed description in a simplified form. This is not meant to identify key or essential features of the claimed subject matter, the scope of which is uniquely determined by the appended claims. Furthermore, the claimed subject matter is not limited to embodiments that address any disadvantages mentioned above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 A schematic diagram of a vehicle system having an emission control device including a particulate filter with a bypass is shown.

[0010] Figure 2 Shows such as Figure 1 Schematic diagram of an emission control device.

[0011] Figure 3 A flow chart illustrating an example method for controlling flow through a bypass of an emissions control device of a vehicle and adjusting a deceleration fuel shutoff (DFSO) operation based on the flow through the bypass and a temperature of the emissions control device is shown.

[0012] Figure 4 A flow chart illustrating an example method for performing DFSO after increasing flow through a bypass of an emissions control device is shown.

[0013] Figure 5 Prognostic operation of the engine is shown, including controlling flow through a bypass around an emissions control device and adjusting DFSO operation in response to flow through the bypass and temperature of the emissions control device. DETAILED DESCRIPTION

[0014] The following description relates to an emission control device (such as a Figure 1 A system and method for determining a flow rate of an emission control device and a temperature of the emission control device of a vehicle engine including an exhaust system having an emission control device and a bypass around a portion of the emission control device, such as Figure 2 In the depicted example, the emission control device includes a catalyst and a particulate filter that can capture soot (e.g., particulate matter) from the exhaust gas of the engine, and the bypass includes a bypass passage disposed around the particulate filter and a bypass valve disposed in the bypass passage. Adjusting the position of the bypass valve can control the amount of exhaust gas that bypasses the particulate filter, and can be based on the soot load of the exhaust gas entering the particulate filter and the soot load of the particulate filter, such as Figure 3The method presented is shown. When the amount of exhaust gas flowing through the particulate filter bypass passage decreases and deceleration fuel cutoff (DFSO) conditions are met, the particulate filter can be regenerated during DFSO. However, when the temperature of the particulate filter is above a threshold, the DFSO operation can be adjusted to maintain the exhaust gas closer to stoichiometry and / or maintain the temperature of the particulate filter below an upper threshold level, above which particulate filter degradation can occur, such as Figure 3 When the exhaust gas volume bypassing the particulate filter increases and satisfies the DFSO entry conditions, DFSO can be implemented without considering the temperature of the particulate filter, as shown in Figure 4 In this manner, the controller may adjust engine parameters during engine operation, including the position of the particulate filter bypass valve and engine operating parameters that control DFSO, such as based on the exhaust and / or particulate filter soot loading and the temperature of the particulate filter. Figure 5 By controlling flow through a bypass around the particulate filter based on engine exhaust and particulate filter soot levels, and by controlling DFSO based on bypass flow and particulate filter temperature, the engine can be operated with DFSO to increase fuel economy while also reducing particulate filter degradation during DFSO and increasing overall life of the particulate filter.

[0015] Now go to Figure 1 , Figure 1 One cylinder of a multi-cylinder engine 10 that may be included in a propulsion system of a vehicle system 5 is schematically shown. In some examples, the vehicle system 5 may be a hybrid vehicle having multiple torque sources that may be used for one or more wheels 55. In other examples, the vehicle system 5 is a conventional vehicle having only an engine, or an electric vehicle having only one or more motors. In the example shown, the vehicle system 5 includes an engine 10 and a motor 52. The motor 52 may be a motor or a motor / generator. When one or more clutches 56 are engaged, the crankshaft 140 of the engine 10 and the motor 52 are connected to the wheels 55 via a transmission 54. In the depicted example, a first clutch 56 is disposed between the crankshaft 140 and the motor 52, and a second clutch 56 is disposed between the motor 52 and the transmission 54. The controller 12 may send a signal to the actuator of each clutch 56 to engage or disengage the clutch so as to connect or disconnect the crankshaft 140 with the motor 52 and components connected to the motor 52, and / or to connect or disconnect the motor 52 with the transmission 54 and components connected to the transmission 54. The transmission 54 may be a gearbox, a planetary gear system, or other types of transmissions. The powertrain may be configured in a variety of ways, including as a parallel, series, or series-parallel hybrid vehicle.

[0016] The electric machine 52 receives power from the traction battery 58 to provide torque to the wheels 55. The electric machine 52 may also operate as a generator to provide power to the rechargeable battery 58, for example, during a braking operation.

[0017] Engine 10 may be controlled at least in part by a control system including controller 12 and by input from a vehicle operator 130 via input device 32. In this example, input device 132 includes an accelerator pedal and a pedal position sensor 134 for generating a proportional pedal position signal PP. Combustion chamber (e.g., cylinder) 14 of engine 10 may include combustion chamber walls 136 having a piston 138 positioned therein. In some embodiments, the face of piston 138 inside cylinder 14 may have a bowl. Piston 138 may be coupled to a crankshaft 140 so that reciprocating motion of the piston is converted into rotational motion of the crankshaft. Crankshaft 140 may be coupled to at least one drive wheel of the vehicle via an intermediate transmission system. In addition, a starter motor (not shown) may be coupled to crankshaft 140 via a flywheel to enable a starting operation of engine 10.

[0018] Combustion chamber 14 may receive intake air from intake manifold 146 via intake passages 142 and 144, and may exhaust combustion gases via exhaust manifold 148. In this manner, intake passages 142 and 144 are fluidly coupled to intake manifold 146. Intake manifold 146 and exhaust manifold 148 can selectively communicate with combustion chamber 14 via respective intake valve 150 and exhaust valve 156. In some embodiments, combustion chamber 14 may include two or more intake valves and / or two or more exhaust valves.

[0019] The intake valve 150 and the exhaust valve 156 may be controlled by the controller 12 via respective electric variable valve actuators 152 and 154. Alternatively, the variable valve actuators 152 and 154 may be electro-hydraulic or any other possible mechanism to enable valve actuation. Under some conditions, the controller 12 may change the signal provided to the variable valve actuator to control the opening and closing of the respective intake valve and exhaust valve. The positions of the intake valve 150 and the exhaust valve 156 may be determined by respective valve position sensors (not shown). In alternative embodiments, one or more of the intake valve and the exhaust valve may be actuated by one or more cams, and one or more of the cam profile switching (CPS), variable cam timing (VCT), variable valve timing (VVT) and / or variable valve lift (VVL) systems may be used to change the valve operation. For example, the cylinder 14 may alternatively include an intake valve controlled via electric valve actuation and an exhaust valve controlled via cam actuation including CPS and / or VCT.

[0020] Fuel injector 166 is shown coupled directly to combustion chamber 14 for injecting fuel directly into combustion chamber 14 in proportion to the pulse width of signal FPW received from controller 12 via electronic driver 168. In this manner, fuel injector 166 provides what is known as direct injection of fuel into combustion chamber 14. It will be appreciated that the fuel injector could be mounted on the side of the combustion chamber or on the top of the combustion chamber, for example.

[0021] Fuel injector 170 is shown coupled directly to intake manifold 146 for injecting fuel directly into intake manifold 146 in proportion to the pulse width of signal FPW-2 received from controller 12 via electronic driver 171. In this manner, fuel injector 170 provides what is known as port injection of fuel into intake manifold 146. Fuel may be delivered to fuel injectors 166 and 170 by fuel system 8, which may include fuel tanks, fuel pumps, and a fuel rail. It will be appreciated that engine 10 may include one or more of port injection and direct injection.

[0022] As previously mentioned, some engine embodiments may include operating the engine in a deceleration fuel cut-off (DFSO) mode to increase fuel economy and reduce brake wear. When the engine is operated in a DFSO mode, the engine operates without fuel injection while the engine rotates and pumps air through the cylinders. Specifically, fuel injection to one or more cylinders 14 via fuel injectors 166 and / or fuel injectors 170 is disabled, while intake air can continue to be pumped from the intake to the exhaust through the cylinders via operating the intake and exhaust valves. DFSO entry conditions may be based on multiple vehicle and engine operating conditions. Specifically, a combination of one or more of vehicle speed, vehicle acceleration, engine speed, engine load, throttle position, pedal position, transmission gear position, and various other parameters may be used to determine whether the engine will enter DFSO. In one example, the DFSO entry condition may be met when the vehicle decelerates (e.g., the vehicle speed is decreasing). In another example, the DFSO entry condition may be based on the engine speed being below a threshold. In yet another example, the DFSO entry condition may be based on the engine load being below a threshold and / or reducing the engine load. In yet another example, DFSO conditions may be based on an accelerator pedal position indicating that no torque is being requested. For example, during a light throttle release with the operator releasing the accelerator pedal (e.g., input device 132), DFSO entry conditions may be met and DFSO may be requested. Additionally or alternatively, entering DFSO may be determined based on a command signal to stop fuel injection.

[0023] Ignition system 188 can provide an ignition spark to combustion chamber 14 via spark plug 192 in response to spark advance signal SA from controller 12, under select operating modes. Although spark ignition components are shown, in some embodiments, combustion chamber 14 or one or more other combustion chambers of engine 10 may be operated in a compression ignition mode, with or without an ignition spark.

[0024] Intake passage 144 or intake manifold 146 may include a throttle 162 having a throttle plate 164. In this particular example, the position of throttle plate 164, or throttle opening, may be varied by controller 12 via a signal provided to an electric motor or actuator included with throttle 162, a configuration commonly referred to as electronic throttle control (ETC). In this manner, throttle 162 may be operated to vary the intake air provided to combustion chamber 14 as well as other engine cylinders. The position of throttle plate 164 may be provided to controller 12 via throttle position signal TP. Intake passage 142 may include a mass air flow sensor 122 and a manifold air pressure sensor 124 for providing respective signals MAF and MAP to controller 12.

[0025] Engine 10 may further include a compression device such as a turbocharger or supercharger including at least one compressor 174 arranged along intake passage 144. For a turbocharger, compressor 174 may be at least partially driven by a turbine 176 arranged along exhaust passage 158 (e.g., via shaft 180). For a supercharger, compressor 174 may be at least partially driven by engine 10 and / or an electric machine, and may not include a turbine. Thus, the amount of compression provided to one or more cylinders of the engine via a turbocharger or supercharger may be varied by controller 12.

[0026] In some embodiments, engine 10 may include an exhaust gas recirculation (EGR) system including a low pressure (LP) EGR passage and / or a high pressure (HP) EGR passage for recirculating exhaust gas (not shown). One example of an EGR system includes a low pressure EGR system, in which EGR may be delivered from downstream of a turbine 176 of a turbocharger to upstream of a compressor 174 of a turbocharger. In a high pressure (HP) EGR system, EGR may be delivered from upstream of a turbine 176 of a turbocharger to downstream of a compressor 174 passage of a turbocharger. In both the LP EGR system and the HP EGR system, the amount of EGR provided to intake manifold 146 may be varied by controller 12 via corresponding LP EGR valves and HP EGR valves (not shown). In addition, an EGR sensor (not shown) may be disposed in the corresponding LP EGR passage and / or HP EGR passage and may provide an indication of one or more of a pressure, temperature, and concentration of the exhaust gas. Alternatively, the EGR flow may be controlled by a calculated value based on signals from a MAF sensor (upstream), MAP (intake manifold), MAT (manifold gas temperature), and a crankshaft speed sensor. In addition, the EGR flow may be controlled based on an exhaust oxygen sensor and / or an intake oxygen sensor (not shown). Under some conditions, the EGR system may be used to regulate the temperature of the air and fuel mixture within the combustion chamber and / or the temperature near the particulate filter 72.

[0027] It should be understood that in several embodiments, the exhaust passage 158 may include a bypass passage 173 positioned upstream of the turbine 176. A flow control valve, referred to as a wastegate valve 172, may be included between the exhaust passage 158 and the bypass passage. Depending on the position of the wastegate valve 172, the amount of exhaust gas passing through the turbine 176 may be controlled. In response to a signal from the controller 12, the position of the wastegate valve may be controlled via a wastegate actuator (not shown, and the wastegate actuator may be hydraulic, pneumatic, electrical, or mechanical in nature). For example, the controller 12 may want to increase torque, and may do so by increasing boost pressure. One way to increase boost pressure is to increase the amount of energy going to the turbine 176. In order to allow more energy to go to the turbine 176, the controller may send a signal to the wastegate actuator to change the wastegate valve to a first position or maintain the first position (e.g., fully closed), i.e., so that no exhaust gas can travel through the bypass passage 173, and all exhaust gas passes through the turbine 176. Conversely, to reduce boost pressure, controller 12 may send a signal to the wastegate actuator to cause the wastegate valve to assume or maintain a second position (e.g., fully open) to allow a percentage of exhaust gas traveling from exhaust passage 158 to flow through the wastegate valve, through the bypass passage, and thereby bypass turbine 176, until the bypass passage is reconnected to exhaust passage 158 downstream of turbine 176. It should be appreciated that the wastegate valve may assume a plurality of intermediate positions (in response to controller 12 sending a signal to the wastegate actuator to change the position of the wastegate valve) that reside between the first (e.g., fully closed) position and the second (e.g., fully open) position, such that a variable amount of exhaust gas may travel through the bypass passage, thereby bypassing turbine 176.

[0028] Similarly, it should be understood that the compressor 174 may include a recirculation passage (not shown) connected to both ends of the compressor. The recirculation passage can be used to recirculate (warm) compressed air from the compressor outlet back to the compressor inlet. In some embodiments, the compressor recirculation system may alternatively or in addition include a recirculation passage for recirculating (cooled) compressed air from the compressor outlet downstream of the charge air cooler (not shown) to the compressor inlet or compressor bypass for dissipating the compressed air to the atmosphere. A flow control valve referred to as a compression recirculation valve (not shown) may be included between the intake passage 142 and the recirculation passage. Depending on the position of the wastegate valve, the amount of recirculated intake air can be controlled. In response to a signal from the controller 12, the position of the compression recirculation valve (CRV) can be controlled via a CRV actuator (not shown, and the CRV actuator can be hydraulic, pneumatic, electric or mechanical in nature). The CRV can be a continuously variable valve, wherein the position of the valve is continuously variable from a fully closed position to a fully open position. In some embodiments, the compressor recirculation valve may be normally partially opened during boosted engine operation to provide some surge margin. Here, the partially open position may be a default valve position. Increasing the opening of the compressor recirculation valve may include actuating (or energizing) a solenoid of the valve.

[0029] Emission control device (ECD) 70 is shown arranged along exhaust passage 158 downstream of exhaust manifold 148 and downstream of exhaust gas sensor 128. Exhaust gas sensor 128 is shown coupled to exhaust passage 158 upstream of emission control device (ECD) 70. Exhaust gas sensor 128 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 sensor), a two-state oxygen sensor or EGO, HEGO (heated EGO), NOx, HC, or CO sensor.

[0030] In this example, ECD 70 includes a catalyst, which may be a three-way catalytic converter (TWC) 71, a particulate filter (PF) 72, a catalyst monitoring sensor 13, a pressure sensor 15, and a temperature sensor 16. It should be understood that Figure 1One or more of the sensors shown in the drawings may be omitted and / or relocated. In some embodiments, in addition to being configured to filter components of the exhaust, PF 72 may include one or more catalyst materials. For example, PF 72 may be coated with a washcoat layer including one or more catalyst materials. This configuration may be employed, for example, for embodiments in which engine 10 is spark ignited. In some embodiments, TWC 71 and PF 72 may be separate components including separate housings positioned away from each other (e.g., TWC upstream of PF as shown). Bypass passage 19 may be coupled to exhaust passage 158 immediately upstream and downstream of PF 72, and therefore disposed about PF 72. Exhaust control valve (e.g., bypass valve) 17 is positioned within bypass passage 19. Details regarding an exemplary ECD are described below with reference to Figure 2 However, it should be understood that ECD 70 is provided as a non-limiting example, and in other embodiments, the ECD may include other components in addition to or in place of TWC 71 and / or PF 72, including but not limited to a lean NOx trap, an SCR catalyst, an oxidation catalyst, or an alternative gas treatment device. For example, in some embodiments, an alternative catalyst or exhaust aftertreatment device may be positioned upstream of PF 72, instead of TWC 71.

[0031] The catalyst monitoring sensor 13 may be a HEGO (heated EGO) sensor, but it should be understood that other suitable types of exhaust gas sensors may be used to monitor the catalyst. The pressure sensor 15 may be positioned upstream of the PF 72. In this way, the output of the pressure sensor 15 may provide an indication of the exhaust back pressure level from the PF 72 to the vehicle controller 12, which may be a further indication of the soot load on the filter. For example, if the PF 72 has a higher soot load, there may be an increased back pressure upstream of the PF 72. The temperature sensor 16 may be positioned downstream of the PF 72 to monitor the temperature of the particulate filter. Specifically, the output from the temperature sensor 16 may provide an indication of the exhaust temperature to the controller 12. In some examples, the exhaust temperature may be a temperature close to the outlet of the PF 72, or the exhaust temperature may be the temperature of the particulate filter itself. It should be understood that the temperature sensor may be additionally or optionally placed upstream of the particulate filter to monitor the temperature gradient of the exothermic reaction occurring in the particulate filter, for example, during regeneration. In another example, the temperature sensor 16 may be positioned within the PF 72.

[0032] exist Figure 1In the example, the controller 12 is shown as a microcomputer including a microprocessor (CPU) 106, input / output ports 108, an electronic storage medium (e.g., computer readable) for executable programs and calibration values ​​(shown in this particular example as read-only memory (ROM) 110), a random access memory (RAM) 112, a keep alive memory (KAM) 114, and a data bus. The storage medium read-only memory 110 can be programmed with computer readable data representing instructions executable by the microprocessor 102 for performing the methods described herein as well as other variants that are anticipated but not specifically listed. As described above, Figure 1 One cylinder of a multi-cylinder engine is shown, and it should be understood that each cylinder may similarly include its own set of intake / exhaust valves, fuel injectors, spark plugs, etc.

[0033] In addition to those signals discussed above, controller 12 may receive various signals from sensors coupled to engine 10, including measurements of exhaust and / or PF 72 temperature from temperature sensor 16, measurements of pressure near the inlet of PF 72 (e.g., exhaust back pressure) from pressure sensor 15, the degree of operator-demanded torque from pedal position sensor 134, and the condition of TWC 71 from catalyst monitor sensor 13. Controller 12 may also receive signals including measurements of inlet mass air flow (MAF) from mass air flow sensor 122; engine coolant temperature (ECT) from temperature sensor 116 coupled to cooling sleeve 118; a surface ignition probe signal (PIP) from a Hall effect sensor 120 (or other type) coupled to crankshaft 140; throttle position (TP) or throttle opening from a throttle position sensor; and an absolute manifold pressure signal, MAP, from pressure sensor 124. Engine speed signal, RPM, may be generated by controller 12 from signal PIP. Manifold pressure signal MAP from the manifold pressure sensor may 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, and vice versa. During stoichiometric operation, the MAP sensor may give an indication of engine torque. Additionally, the sensor, along with the detected engine speed, may provide an estimate of charge (including air) introduced into the cylinder. In one example, Hall effect sensor 120, which is also used as an engine speed sensor, may produce a predetermined number of equally spaced pulses every revolution of the crankshaft. Controller 12 receives a pulse from Figure 1 The signals of various sensors (e.g., catalyst monitoring sensor 13, pressure sensor 15, temperature sensor 16, pedal position sensor 134, etc.) are used Figure 1The controller may control various actuators (e.g., valve actuators such as bypass valve 17, throttle plate 164, spark plug 192, etc.) to adjust engine operation based on received signals and instructions stored in the memory of the controller.

[0034] In one example, the controller may reference a raw gas soot model (stored in the controller's memory and according to instructions stored on the memory) to estimate the amount of soot entrained in the exhaust gas leaving the engine cylinder and entering the particulate filter. The raw gas soot model may use multiple sensor inputs to estimate the entrained soot. In one example, the output of the engine coolant temperature sensor 116 may provide an indication of the engine temperature, and the output of the exhaust gas sensor 128 may provide an indication of the air-fuel ratio. Based on these sensor inputs, the raw gas soot model may be used by the controller to estimate the amount of soot entrained in the exhaust gas. For example, when the engine is operating near a stoichiometric air-fuel ratio and the engine coolant temperature is above an "engine warm-up" threshold temperature, the controller may determine that the amount of soot entrained in the exhaust gas is reduced. In response to data from the raw gas soot model, the controller may determine that the raw gas soot level (e.g., the soot level in the exhaust gas) is below a first soot threshold, and therefore an increased amount of exhaust gas can bypass the particulate filter. In addition, the controller may receive a sensor output from a pressure sensor 15 near the inlet of the particulate filter, indicating that there is a low exhaust back pressure upstream of the particulate filter. The controller may associate low exhaust back pressure with a low soot storage load in the particulate filter (e.g., a particulate filter soot load that is less than a second soot threshold). In response to both the raw gas soot load being less than the first soot threshold and the particulate filter soot load being less than the second soot threshold, the controller may send a command signal to the actuator of the particulate filter bypass valve 17 to increase the opening of the bypass valve 17. As a result, an increased amount of exhaust gas may flow through the bypass passage 19 around the particulate filter 72. In this way, a greater portion of the exhaust gas from the engine may bypass the particulate filter, and a smaller portion of the exhaust gas may pass through the particulate filter. It should be understood that the particulate filter bypass valve 17 may be adjustable to a plurality of positions (e.g., between and including a plurality of positions of fully open and fully closed positions) via the controller 12. Alternatively, when the controller determines, based on the sensor signals and stored soot model(s), that the exhaust has an increasing soot level (above a first soot threshold) and / or the particulate filter soot level increases (to above a second soot threshold), the controller may send a signal to the actuator of the bypass valve 17 to reduce the opening of the bypass valve 17 and thereby reduce the amount of exhaust gas flowing through the bypass passage 19 and increase the amount of exhaust gas flowing through the particulate filter.

[0035] Furthermore, in response to the indication of an increase in exhaust mass bypassing the particulate filter 72 via the bypass passage 19, the controller cannot infer the duration of the DFSO event based on the temperature of the particulate filter as indicated by the temperature sensor 16. In this way, the engine can be operated in the DFSO mode for an increased duration based on an operator demand torque demand (e.g., a torque required by a vehicle operator as indicated by the accelerator pedal position) to improve fuel economy, rather than being terminated prematurely (e.g., before the engine speed, engine load, and accelerator position would otherwise terminate the DFSO operation). Additionally, by not flowing exhaust gas through the particulate filter during all operating conditions, fuel economy can be increased during these conditions due to reduced exhaust back pressure, and the life of the particulate filter can be extended.

[0036] Now go to Figure 2 , shows an example vehicle exhaust system 200 including an emission control device (ECD) 202. In some examples, the ECD 202 may be Figure 1 Thus, the ECD 202 may include Figure 1 The exhaust system 200 includes an exhaust manifold 148 having a plurality of exhaust runners or passages from the engine cylinders (e.g., Figure 1 The exhaust flow passage is coupled to a collection area 206 upstream of the ECD 202. In this manner, the ECD 202 is configured to receive exhaust gas from an engine such as a Figure 1 of the engine 10).

[0037] Exhaust manifold 148 may include runners 210, 212, and 214 that converge to form a short, narrow exhaust runner converging duct 216. Converging duct 216 may be connected to Figure 1 The runners 210, 212, and 214 may be identical or similar to the exhaust passages 158. The runners 210, 212, and 214 may have equal or unequal lengths and widths, where the length of the runner may be considered to be the measurement along the central axis of the runner from the exhaust manifold 148 to the center of the exhaust runner converging duct 216, and the width of the runner may be considered to be the diameter of the runner at any given cross-section perpendicular to the central axis of the runner.

[0038] exist Figure 2In the depicted example, the ECD 202 includes a catalyst 71 positioned upstream of a particulate filter 72. The catalyst 71 may include a catalyst canister 218 positioned within an ECD body 219. The catalyst canister 218 is specifically positioned downstream of an exhaust runner conduit 216 and upstream of and proximate to a particulate filter described below. The catalyst canister 218 may include a catalyst block 220 between mounting pads 222 positioned between the catalyst block and an upper wall 224 of the ECD body 219 and between the catalyst block and a lower wall 226 of the ECD body. Figure 2 As shown, the catalyst block 220 is positioned in close proximity to the exhaust manifold 148. This close coupled configuration may cause the temperature of the catalyst block 220 to rise quickly to its light-off temperature. Upon reaching the light-off temperature, exhaust species in the exhaust gas may be effectively converted into desirable inert gases.

[0039] It should be understood that ECD 202 is provided as a non-limiting example, and many additions and modifications may be made to ECD without departing from the scope of the present disclosure. For example, in other embodiments, ECD 202 may include two or more catalyst blocks. In this example, one or more of the multiple catalyst blocks may include two or more different pore densities. The variation in pore density between multiple catalyst blocks may be the same, or may be different between at least two of the catalyst blocks. In addition, the average pore density in multiple catalyst blocks may be the same, or may be different between at least two of the catalyst blocks. Other features may be shared or not shared between multiple catalyst blocks, including but not limited to length, catalyst block substrate material, catalyst material, and oxygen storage material (if included).

[0040] ECD 202 also includes an exhaust gas sensor 128 positioned at an upper region of the ECD proximate exhaust runner conduit 216. Exhaust gas sensor 128 may be, but is not limited to, a linear oxygen sensor or a universal or wide-range exhaust gas oxygen (UEGO), a two-state oxygen sensor (EGO), a heated EGO (HEGO), a NOx, HC, or CO sensor. Figure 2 In the depicted example, the exhaust gas sensor 128 includes an internal electrode (not shown) enclosed within a metal shield 246. Exhaust flow originating from the exhaust runners 210, 212, and 214 flows through the exhaust runner converging conduit 216 and is detected by the electrodes of the exhaust gas sensor 128. The exhaust gas flow is detected by the electrodes after flowing into the metal shield 246 through openings 248 arranged longitudinally along the bottom of the metal shield 246. The sensor housing 250 allows the exhaust gas sensor 128 to be located within the ECD body 219 and couples the electrodes to a control system (e.g., Figure 1 Controller 12 of the ECD 202). Readings from the exhaust gas sensor 128 may be used to control operational aspects of the ECD 202, as described below.

[0041] ECD 202 also includes a catalyst monitoring sensor 13, which may be configured similarly to exhaust gas sensor 128. Figure 2 As shown, catalyst monitoring sensor 13 is positioned downstream of catalyst 71. As described in further detail below, readings from both exhaust gas sensors 128 and 13 may be used to control aspects of the operation of ECD 202. For example, the difference between the readings from each sensor may indicate the amount of oxygen stored in catalyst 71. It should be understood that the relative positioning of exhaust gas sensor 128 and catalyst 71 is non-limiting, and the sensor and / or catalyst may be placed elsewhere. In other embodiments, three or more exhaust gas sensors may be included in ECD 202, for example, in addition to exhaust gas sensors 128 and 13, a third exhaust gas sensor positioned downstream of the particulate filter described below.

[0042] Figure 2 The embodiment of the invention also includes a pressure sensor 15 configured to measure the pressure of the exhaust gas flowing through the ECD. As shown therein, the pressure sensor 15 is positioned along the lower wall 226 and between the catalyst 71 and the particulate filter described below. It should be understood that this positioning is non-limiting and that the pressure sensor 15 may be located elsewhere in the ECD 202. For example, one or more pressure sensors may be positioned upstream of the catalyst block 220 or downstream of the particulate filter. In other embodiments, the pressure sensor 15 may be omitted from the ECD 202, where the exhaust pressure is inferred based on one or more engine operating parameters.

[0043] Figure 2 Embodiments also include a temperature sensor 16 configured to measure the temperature of exhaust gas flowing through the ECD. As shown herein, the temperature sensor 16 is positioned along the lower wall 226 and is positioned after (immediately downstream of) the particulate filter described below. It should be understood that this positioning is non-limiting and that the temperature sensor 16 may be located elsewhere in the ECD 202. For example, one or more temperature sensors 16 may be positioned upstream of the catalyst block 220 or upstream of the particulate filter in order to measure the temperature gradient across the particulate filter. In this way, heat release across the particulate filter may be characterized and monitored, such as during a filter regeneration process. Alternatively, the temperature sensor 16 may be omitted from the ECD 202 where the exhaust temperature is inferred based on one or more engine operating parameters.

[0044] The ECD 202 also includes a particulate filter (PF) 72 positioned downstream of the catalyst 71 within the ECD body 219. The PF 72 may be located between the mounting pads 222 positioned between the particulate filter and the upper wall 224 and between the particulate filter and the lower wall 226 of the ECD body. The PF 72 may be configured to capture particulate matter, such as soot mixed with the exhaust gas flowing through the particulate filter 72. As soot and / or other particulate matter accumulates in the PF 72, back pressure in the particulate filter may accumulate, which may interfere with engine operation and reduce fuel economy. Thus, for example, in response to the soot level stored in the filter exceeding a threshold soot level, the PF 72 may be periodically regenerated and the soot stored therein burned. For embodiments in which the ECD 202 is used with a spark-ignition engine and the PF 72 is a gasoline particulate filter, and the exhaust gas from the spark-ignition engine may be hot enough to burn the soot stored in the filter. However, in some cases, the spark-ignition engine may be operated primarily under stoichiometric conditions, in which case there is not a sufficient amount of gaseous oxygen to combust soot stored in PF 72, and active regeneration may be initiated. It should be appreciated that embodiments of PF 72 may include any type of particulate filter, including but not limited to a gasoline particulate filter (GPF) or a diesel particulate filter (DPF).

[0045] ECD 202 includes bypass valve 17 disposed in bypass passage 19 coupled around particulate filter 72, wherein filter bypass flow (e.g., exhaust gas) bypasses only particulate filter 72 and does not bypass an additional emission control device or catalyst 71 positioned upstream of particulate filter 72. In this manner, bypass passage 19 may be coupled to exhaust passage 217 immediately upstream and downstream of PF 72. In one example, in response to a request to increase the amount of gasoline-burned exhaust gas that bypasses particulate filter 72, ( Figure 1 Controller 12 may send a control signal to an actuator of bypass valve 17 to increase the opening of the valve so that an increased flow of burned exhaust gas may enter bypass passage 19. In this way, as a greater proportion of the total amount of burned exhaust gas passes through bypass passage 19 and travels around particulate filter 72, the amount of burned exhaust gas flow through particulate filter 72 may be reduced. Conversely, reducing the flow of exhaust gas through particulate filter bypass passage 19 may include the controller sending a control signal to an actuator of bypass valve 17 to reduce the amount of opening of bypass valve 17, which will result in an increase in the flow of burned exhaust gas through particulate filter 72. After the exhaust passes through particulate filter 72 or bypass passage 19, the exhaust continues to be discharged to the atmosphere through exhaust passage 208, or is further downstream for exhaust treatment.

[0046] In this way, during various engine operating conditions that may generate exhaust gas with reduced particulate matter loading, exhaust gas may bypass the particulate filter and reduce exhaust back pressure, thereby increasing fuel economy. Additionally, DFSO may not be limited, prematurely terminated, or both avoided in order to avoid exceeding a particulate filter temperature threshold during particulate filter regeneration when the bypass passage around the particulate filter is open, thereby increasing the amount of time the engine may be operated in DFSO mode.

[0047] It should be understood that various aspects of the vehicle exhaust system 200 and ECD202 may be modified without departing from the scope of the present disclosure. For example, the relative positioning, geometry, and dimensions (e.g., length, width, height) of the various components of the system 200 (e.g., catalyst 71, PF 72, exhaust gas sensor 128, catalyst monitoring sensor 13, pressure sensor 15, and temperature sensor 16) may be adjusted. In some embodiments, two or more exhaust gas sensors, two or more pressure sensors, and / or two or more temperature sensors may be provided, while in other embodiments, the temperature sensor 16 may be omitted from the system 200. In some embodiments, two or more ECDs may be provided in a cascaded manner, so that a first ECD (e.g., including a catalyst and / or a particulate filter) may be followed by a second ECD positioned downstream of the first ECD, wherein the second ECD may or may not include the same components as the first ECD. In addition, alternatively or in addition to the catalyst 71 and / or PF 72, the ECD 202 may be modified to include other emission control devices, such as a NOx trap, an SCR catalyst, and the like.

[0048] Now go to Figure 3 , a flow chart showing an exemplary method 300 for adjusting an emission control device (e.g., Figure 1 ECD 70, Figure 2 ECD 202) of a particle filter (e.g., Figure 1 to Figure 2 A bypass passage (e.g., Figure 1 to Figure 2 The bypass passage 19) is used to adjust the flow rate through the bypass passage and the temperature of the emission control device, and adjust the deceleration fuel cut-off (DFSO) operation based on the flow rate through the bypass passage and the temperature of the emission control device. In one example, adjusting the flow rate through the bypass passage may include adjusting the position of a valve disposed in the bypass passage (e.g., Figure 1 to Figure 2The exhaust bypass valve 17 is shown. In one example, the method includes increasing the exhaust flow through the exhaust bypass passage in response to the exhaust soot load being at a first threshold soot load and the soot load stored in the particulate filter being at a second threshold soot load. In this way, when both conditions are met, exhaust from the engine can bypass the particulate filter, reducing exhaust back pressure over a wide range of driving conditions and thereby increasing fuel economy. In addition, when the exhaust bypasses the particulate filter when operating in the DFSO mode, the DFSO operation may not end in response to the temperature of the particulate filter because the exhaust with increased oxygen levels caused by the DFSO is bypassing the particulate filter. In this way, the risk of autoignition of the particulate filter is reduced under a variety of driving conditions, and the DFSO can be controlled based on engine operating conditions (such as operator torque demand) to increase fuel economy without the need to limit the duration of the DFSO based on the temperature of the particulate filter. In addition, since the particulate filter is bypassed when regeneration is not desired and exhaust emissions are below a threshold, soot and ash accumulation in the particulate filter can be reduced, thereby extending the service life of the particulate filter and the exhaust system. Alternatively, the method may include reducing the exhaust gas flow through the exhaust bypass passage in response to the exhaust gas soot load being higher than a first threshold soot load or the soot load stored in the particulate filter being higher than a second threshold soot load. In this way, when one of these conditions is met, the exhaust gas from the engine may pass through the particulate filter for the purpose of reducing particulate emissions from the engine and / or regenerating the particulate filter. When the exhaust gas passes through the particulate filter when operating in DFSO mode, the engine parameters (including DFSO operation) may be adjusted in response to the temperature of the particulate filter to reduce the possibility of degradation of the particulate filter. In this way, by adjusting the amount of oxygen-carrying exhaust gas passing through the filter and / or adjusting the air-fuel ratio of the engine toward stoichiometry, the possibility of autoignition of the particulate filter may be reduced.

[0049] In this manner, a method for an engine includes: in response to meeting an entry condition for a deceleration fuel cutoff (DFSO) operation: in response to a bypass around a particulate filter disposed in an exhaust passage of the engine being opened, operating the engine with DFSO for a first duration based on an operator-requested torque; and in response to the bypass being closed and a temperature being above a first threshold, operating the engine with DFSO for a second duration based on a temperature of the particulate filter. Additionally, when the bypass is closed and the temperature of the particulate filter is below the first threshold, the engine may be operated with DFSO for the first duration based on the operator-requested torque. In other words, if the temperature of the particulate filter does not rise to a temperature that increases the likelihood of filter degradation, DFSO may be performed based on the operator-requested torque, rather than based on the temperature of the particulate filter.

[0050] Instructions for carrying out method 300 and the remaining methods included herein may be provided by a controller (e.g., Figure 1 The controller 12) is based on instructions stored in the controller's memory and in conjunction with information from the vehicle system (e.g., Figure 1 The vehicle system 5) is combined with the signal received by the sensor to perform, such as the above reference Figure 1 to Figure 2 Sensors described. A controller may employ engine actuators of an engine system to regulate engine operation according to the methods described below.

[0051] Method 300 begins at 302, where the routine includes estimating and / or measuring current vehicle conditions. Current vehicle conditions may include, but are not limited to, air-fuel ratio (e.g., the air-fuel ratio of combusted exhaust gas leaving engine cylinders), the position of a particulate filter bypass valve (e.g., Figure 1 and Figure 2 The present vehicle conditions may also include a current particulate filter soot load which may be modeled based on the level of raw gas soot. The raw gas soot level may be modeled based on one or more of the engine coolant temperature, torque, air-fuel ratio, and engine speed.

[0052] In one example, the combustion air-fuel ratio may be determined by an exhaust gas sensor (e.g., Figure 1 to Figure 2 In this way, the controller (e.g., Figure 1 The controller 12 of FIG. 1 may determine whether the engine is operating leaner than stoichiometry (λ greater than 1) or richer than stoichiometry (λ less than 1). The controller may also determine the particulate filter bypass valve ( Figure 1 and 2 In one example, the controller may monitor the duty cycle of the actuator of the bypass valve to estimate the degree of opening of the bypass valve. The controller may also record the duration of time that has passed since the last regeneration of the particulate filter. In one example, this may include a timer that records the time that has passed since the last time the particulate filter reached the regeneration temperature and maintained the regeneration temperature for a specified regeneration duration, such as may be measured by a temperature sensor (e.g., a temperature sensor) proximate to the particulate filter. Figure 1 and Figure 2 The controller may also receive temperature information from a Hall effect sensor (e.g., Figure 1 The Hall Effect sensor 120 of FIG. 1 may be used to measure engine speed and engine load, which may be determined by the engine speed, the degree of accelerator pedal actuation (eg, Figure 1 The controller may receive an indication from an engine coolant temperature sensor (e.g., Figure 1 The controller 12 may receive an indication of the engine temperature from an engine coolant temperature sensor 116 (e.g., an engine coolant temperature sensor 116). An engine temperature above an engine temperature threshold may indicate that the engine temperature is warm, rather than in a cold start state. The controller 12 may receive an indication of the engine temperature from a pressure sensor at the particulate filter (e.g., Figure 1 to Figure 2 The output of a pressure sensor 15) may be indicative of the degree of soot load on the particulate filter as will be further described below. An empirical model may be used to estimate the current particulate filter soot load and may be used as a basis for controlling particulate filter regeneration. In one example, PF soot load modeling updates the PF 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 may include the level of engine feed gas soot, which may be determined primarily based on one or more of engine speed, engine coolant temperature, air-fuel ratio, and torque. Control of particulate filter regeneration may also be based on an alternative PF soot load model. In some examples, particulate filter regeneration may be controlled based on a determined flow restriction that may be related to the soot load. In one example, the flow restriction may be indicated by the output of a pressure sensor proximate to the particulate filter. In one example, the pressure sensor may be positioned upstream of the particulate filter, such as Figure 2 shown.

[0053] It should be understood that raw gas soot or exhaust soot can be the amount of soot entrained in the exhaust gas leaving the engine and entering the exhaust system. Ambient and other engine operating conditions may also be included as affecting the raw gas soot. An example of a typical operating condition that can generate a raw gas with a soot level below the first soot level threshold is when the engine coolant temperature is above the threshold engine temperature (e.g., when the engine is warm), when the air-fuel ratio is close to the stoichiometric air-fuel ratio, and when the engine is not operating in the compression injection mode. Conversely, an example of an operating condition that can generate a raw gas with a soot level above the first soot level threshold is when the engine coolant temperature is below the threshold engine temperature (e.g., during a cold start) and / or when the air-fuel ratio is rich.

[0054] In one example, a PF soot model may estimate soot every 100 ms, while a slower calibrable timer determines the frequency of soot accumulation estimated by the model and added to the measured soot load value. The timer may be executed when the engine is running and the PF (such as a gasoline particulate filter) is not in regeneration mode. For example, the timer may be calibrated to execute as slowly as once every 6 minutes, and thus an additional accumulator may be used to capture soot generated under transient conditions. The transient accumulator may also be reset at the same frequency as the above timer, but with a delay. Soot from the soot model may be accumulated separately and added to the last measured soot load value. When the measured soot load value is available, the accumulated soot load from the model is cleared (e.g., set to zero).

[0055] Under certain engine operating conditions, the PF soot load may not be accurately determined based on the differential pressure measured across the PF. For example, the PF soot load measurement may be less accurate at low exhaust flow rates due to reduced accuracy of the pressure sensor under low exhaust flow conditions. Additionally, the PF soot load may be inaccurate during transients due to higher time constants of the sensor and / or unstable fluid dynamics in the exhaust system. Therefore, during these conditions, the estimate of the PF soot load is independent of the soot load based on the differential pressure measured across the PF. Instead, a PF soot model is used to estimate the soot load based on engine speed and load, and then the PF soot model is calibrated for engine / ambient operating conditions. The corrected PF soot model output is then added to the latest soot load measurement from the differential pressure occurring under conditions other than those described above.

[0056] At 304, the routine includes determining whether the raw gas soot level is less than a threshold soot level (e.g., a first soot threshold) and determining whether the particle filter soot load is less than a threshold soot load (e.g., a second soot threshold). In other words, the controller determines whether the operating conditions of the engine result in a reduction in soot generation (in the form of soot entrained in the exhaust gas leaving the engine and entering the exhaust system) and whether the current soot load stored in the particle filter (e.g., soot storage at the particle filter) is less than the threshold soot load. As previously described, the engine raw gas soot level or soot amount can be modeled and can be determined primarily based on one or more of the engine speed, engine coolant temperature, air-fuel ratio, and torque. The environment and other engine operating conditions can also affect the raw gas soot level. It should be understood that the raw gas soot or exhaust soot can be the amount of soot entrained in the exhaust gas leaving the engine and entering the exhaust system. An example of a typical operating condition that may generate a feed gas having a soot level below a threshold soot level (e.g., a first soot threshold) is when the engine coolant temperature is above a threshold engine temperature (e.g., when the engine is warm), when the air-to-fuel ratio is close to the stoichiometric ratio, and when the engine is not operating in a compression injection mode.

[0057] In one example, the routine determines the engine feed gas soot level using an engine feed gas soot model based on one or more of engine speed, engine coolant temperature, torque, and air-fuel ratio. For example, the controller may estimate the current feed gas soot level based on a feed gas soot model stored in a memory of the controller. Figure 1 output of a Hall effect sensor 120), engine coolant temperature (such as from Figure 1 engine coolant temperature sensor 116) and air-fuel ratio (such as from Figure 1 to Figure 2 The controller may determine an estimated current raw gas soot level based on an indication of the output of the exhaust gas sensor 128. The controller may then compare the estimated current raw gas soot level with a first soot threshold to determine whether the estimated current raw gas soot level exceeds the first soot threshold.

[0058] This routine may similarly be based on the current feed gas soot level estimated as described above, engine speed and load, and an indication of exhaust back pressure near the inlet of the PF (such as from Figure 1 to Figure 2 The controller may determine the PF soot load PF using one or more of the pressure sensors 15 of the controller. For example, the controller may estimate the current PF soot load (e.g., the amount of soot stored in the PF) based on the PF soot model stored in the memory of the controller. Based on the indication of the above engine parameters, the controller may determine the current PF soot load and compare the current PF soot load to a second soot threshold. The soot load may accumulate until the time for the PF to regenerate, and the PF soot model may be updated accordingly. It should be understood that the controller may maintain a similar PF ash model for monitoring the level of ash stored in the PF.

[0059] In response to the controller determining that one or both of the raw gas soot level and the PF soot load are higher than the first soot threshold or the second soot threshold, respectively, the controller may send a command signal to the actuator of the bypass valve to reduce the opening of the bypass channel. As a result, the increased exhaust mass can pass through the particulate filter instead of bypassing the particulate filter. As another example, the controller may make a logical determination (e.g., about the position of the bypass valve 17) based on a logic rule, which is a function of one or more engine parameters including engine speed and load, engine coolant temperature, and pressure close to the upstream side of the particulate filter. In response to each engine parameter being higher or lower than the corresponding threshold, the controller may then generate a control signal that is sent to the actuator of the bypass valve to adjust the position of the bypass valve and control the amount of exhaust gas that bypasses the particulate filter.

[0060] In one example, determining when to adjust the exhaust flow through the bypass passage may be empirically determined and stored in a predetermined lookup table or function. For example, one table may correspond to determining the raw gas soot level and one table may correspond to determining the particulate filter soot load. Both tables may be indexed to engine operating conditions, such as engine speed and engine load, engine coolant temperature and air-fuel ratio, and other engine operating conditions. In addition, the table may output the position of the bypass valve to allow a desired amount of exhaust gas to pass through the bypass passage around the particulate filter.

[0061] As previously described, the controller may also estimate and / or measure the PF soot load (e.g., the amount of soot stored in the PF). The PF soot load may be determined based on the output of one or more pressure sensors proximate to the particulate filter and / or by a particulate filter soot model. A threshold soot load (e.g., a second soot threshold) in the particulate filter may be defined as an upper threshold of carbon particles from incomplete combustion (e.g., soot) that may be collected in the particulate filter before causing a prohibitive restriction of exhaust flow through the particulate filter (which may result in reduced fuel economy and engine performance degradation). In one example, the threshold soot load may be defined based on an upper threshold of exhaust back pressure upstream of the particulate filter. When the exhaust back pressure is indicated by the pressure sensor to be above the exhaust back pressure upper threshold, the controller may infer that the soot load in the particulate filter is above the second soot threshold.

[0062] In this manner, the controller may determine if one or more of the soot load of the PF is greater than a first threshold load and if soot generation at the cylinder is greater than a second threshold amount. If only one or neither of the conditions are met at 304, the routine proceeds to 306 where the routine includes reducing the particulate filter bypass (e.g., Figure 1 and Figure 2The controller may determine a control signal to be sent to a bypass valve actuator, such as a duty cycle of a solenoid of a bypass valve, based on determining a soot load of the particulate filter and / or a soot level of the particulate filter entering the exhaust system (e.g., raw gas soot). In one example, in response to an indication of an engine coolant temperature from an engine coolant temperature sensor and an indication of an engine speed from a Hall effect sensor, the controller may determine that the soot level of the exhaust gas from the engine is above a first soot threshold. An estimate of the soot level of the exhaust gas may be based on a model of the exhaust soot level, the model of the exhaust soot level being based on the engine coolant temperature, the engine operating conditions, and the air-fuel ratio. In this way, the exhaust gas contains enough soot (e.g., particulate matter) to pass through the particulate filter. Because the soot level of the exhaust gas is higher than the threshold soot level, even if the soot load of the particulate filter is lower than the second soot threshold, the controller may send a control signal to the actuator of the bypass valve to reduce the opening of the bypass valve, thereby increasing the amount of exhaust gas passing through the particulate filter and reducing the amount of exhaust gas passing through the bypass passage.

[0063] As another example, the controller may make a logical determination (e.g., regarding the position of an actuator of a bypass valve) based on a logic rule as a function of exhaust back pressure, as may be indicated by the output of a pressure sensor proximate to the particulate filter. The controller may then generate a control signal that is sent to the actuator of the bypass valve to adjust the degree of opening of the bypass valve. In this manner, in response to the exhaust back pressure being above a threshold back pressure (which may indicate that the soot load on the particulate filter is above a second soot threshold), the opening of the particulate filter bypass may be reduced. As previously described, reducing the opening of the particulate filter bypass may include fully closing a bypass valve that is disposed in a bypass passage that is disposed only around the particulate filter and not around an additional device or catalyst that is positioned upstream of the particulate filter. As previously described, the bypass valve may be fully adjustable between a fully open position (e.g., a maximum opening of 100%) and a fully closed position (e.g., a minimum opening of 0%). Thus, in some examples, method at 306 may include partially closing the bypass valve, wherein the closing amount is based on the determined feedgas soot level and the determined particulate filter soot loading, wherein the closing amount increases as the feedgas soot level and / or the particulate filter soot loading increases.

[0064] The routine then proceeds to 308, where the routine includes determining whether deceleration fuel shutoff (DFSO) entry conditions have been met. DFSO entry conditions may include, but are not limited to: the accelerator pedal is not depressed (such as during a light release of the throttle) (e.g., Figure 1The throttle position sensor signal (e.g., the input device 132), a decrease in vehicle speed (e.g., the vehicle speed decreases over a period of time, causing the vehicle to slow down), and / or the brake pedal is depressed. Figure 1 The TP of the throttle valve (e.g., the throttle position) may be used to determine the accelerator pedal position (e.g., the pedal position). As the pedal position tilts (e.g., becomes less depressed), the throttle position may be less open. Alternatively or in addition, a pedal position sensor (e.g., Figure 1 A pedal position sensor 134 of the embodiment of the present invention determines the pedal position and sends a signal to a controller (e.g., Figure 1 The controller 12 of the vehicle sends a pedal position (PP) signal. Vehicle deceleration may be determined via a second vehicle speed sensor reading that is less than the first vehicle speed sensor reading. The first vehicle speed sensor reading is measured before (e.g., five seconds before) the second vehicle speed sensor reading, and no other vehicle speed sensor reading is measured between the first vehicle speed sensor reading and the second vehicle speed sensor reading. It may be determined via a brake pedal sensor that the brake pedal is depressed. In some embodiments, there may be other suitable occurrence conditions for DFSO.

[0065] In some embodiments, a GPS / navigation system may be used to predict when a DFSO condition will be met. The information that the GPS uses to predict that a DFSO condition is met may include, but is not limited to, route directions, geographic data including road slope, traffic information, and / or weather information. As an example, the GPS may be able to detect traffic conditions downstream of the driver's current path and predict the occurrence of one or more of the DFSO conditions (one or more). By predicting one or more DFSO conditions being met, the controller may be able to plan when to initiate DFSO.

[0066] If the DFSO entry conditions are not met, the routine continues to 310, where the routine includes maintaining the current engine operation and regenerating the particulate filter based on the engine operating conditions. In one example, this may include passively regenerating the particulate filter when the engine operating conditions naturally increase the exhaust temperature to a level above the regeneration temperature of the particulate filter. In other examples, this may include the controller intrusively adjusting engine operating parameters to increase the exhaust temperature to reach the regeneration temperature and actively regenerate the particulate filter. In some examples, active regeneration may include the controller sending an ignition system (e.g., Figure 1 The ignition system 188 of the embodiment sends a command signal to delay the ignition of the ignition via the spark plug (e.g., Figure 1 spark plug 192) to one of more cylinders of the engine (e.g., Figure 1 The routine then ends and exits.

[0067] If the DFSO entry conditions are met at 308, the routine continues to 312, where the routine includes determining whether the particulate filter temperature is greater than a first upper threshold temperature. In some examples, the particulate filter temperature may be based on the exhaust gas temperature proximate the particulate filter (e.g., as may be determined by Figure 1 to Figure 2 16). For example, the controller may determine the particle filter temperature based on a measured exhaust temperature proximate to the particle filter (e.g., immediately upstream or downstream of the particle filter) and a correction factor that relates the exhaust temperature to the particle filter. In another example, the controller may determine the particle filter temperature using a lookup table stored in a memory of the controller that uses the exhaust temperature as an input and the particle filter as an output. In yet another example, the method of 312 may alternatively include determining whether the exhaust temperature of the exhaust gas flowing through the particle filter (as determined by an exhaust temperature sensor positioned in the exhaust passage proximate to the particle filter) is greater than a first upper threshold temperature. In one example, the first upper threshold temperature may be a temperature above which, during DFSO, the increased oxygen level in the exhaust gas may increase the likelihood that the temperature of the particle filter increases to a level that causes degradation of the particle filter. Because the exhaust gas flow bypassing the particle filter is reduced at 312, a majority of the exhaust gas (and the increased oxygen level due to DFSO operation, where air may still be pumped to the exhaust by the engine cylinders) may pass through the particle filter rather than through the bypass passage. Therefore, the temperature of the particle filter may be monitored during this period. If the particulate filter temperature is less than the first upper threshold, the likelihood that the temperature of the particulate filter reaches a level at which particulate filter degradation occurs during a DFSO event may be reduced. Therefore, the routine then continues to 314, where the routine includes allowing DFSO and regenerating the particulate filter. In one example, this may include operating the engine with DFSO for a first duration based on an operator-requested torque in response to the bypass being closed and the temperature of the particulate filter being below the first upper threshold. For example, the DFSO operation may terminate at 314 only in response to an operator-requested torque (e.g., an operator pressing an accelerator pedal) rather than based on an increase in the temperature of the particulate filter. It should be understood that passive or active regeneration of the particulate filter may occur at 314 due to the soot load of the particulate filter described at 304 exceeding the second threshold soot level.

[0068] The routine then proceeds to 316, where the routine includes determining whether the DFSO operation has been terminated. In some examples, terminating DFSO may include no longer satisfying DFSO conditions. This may include injecting fuel to each cylinder of the engine (e.g., firing all cylinders of the engine), the throttle is no longer in an idle state, the accelerator pedal is depressed, and / or the brake is no longer depressed. In other examples, the DFSO operation may be terminated in response to an increase in torque required by the operator, including an increase in torque demand indicated by an increase in the pedal position of the accelerator pedal. If the DFSO is not terminated, the routine proceeds to 318, where the routine includes waiting and maintaining engine operating conditions until the DFSO is terminated. In one example, this may include continuing to operate the engine in DFSO mode (e.g., no fuel is delivered to any cylinder of the engine). When DFSO is terminated, the routine continues to 320, where the routine includes starting stoichiometric combustion. In an example where the engine may operate in a lean range (e.g., λ is greater than 1.0) due to an increase in oxygen entrained in the exhaust gas due to operation in the DFSO mode, this may include increasing the air-fuel ratio toward a λ value of 1.0. In two non-limiting examples, decreasing the air-fuel ratio toward a lambda value of 1.0 may be achieved by increasing fuel delivery to the engine cylinders and / or decreasing air flow to the engine cylinders by decreasing the opening of the intake throttle. In this way, stoichiometric combustion may begin at the cylinders of the engine during increased soot generation and increased soot storage when DFSO is terminated. The routine then ends.

[0069] At 312, if the particulate filter temperature is greater than the first upper threshold, the routine continues to 322, where the routine includes adjusting engine operating parameters based on the temperature of the particulate filter during the DFSO event. In one example, adjusting the engine operating parameters may include adjusting the DFSO operation. In this way, the engine operating parameters may be adjusted to reduce the amount of oxygen flowing to the particulate filter in response to the exhaust temperature being above the first threshold before terminating the deceleration fuel cut-off condition while reducing the particulate filter bypass flow. In this way, the controller may adjust the engine parameters to maintain a combustion air-fuel ratio close to stoichiometric combustion, wherein stoichiometric combustion includes a condition in which the fuel delivered to the cylinder is completely combusted (e.g., burned) and there is no excess fuel or air remaining after combustion. In this way, the controller may adjust the engine parameters to control the amount of oxygen entering the exhaust, and thereby also entering the particulate filter.

[0070] In one example, adjusting the engine operating parameters to reduce the amount of oxygen flowing to the particulate filter may include one or more of the following: activating one or more cylinders of the engine (e.g., increasing the number of cylinders of the engine that are active and burning fuel) at 324, adjusting the throttle upstream of the engine cylinder at 326 (e.g., reducing the amount of opening of the throttle located upstream of the cylinder to reduce airflow and thus reduce the amount of oxygen flowing to the exhaust), and disabling one or more exhaust valves of the cylinder at 328. By disabling one or more exhaust valves of the cylinder, the exhaust valve may remain closed during the exhaust stroke, preventing and / or reducing the amount of oxygen-carrying exhaust gas from entering the emission control device and passing through the particulate filter. In one example, in response to the PF temperature further increasing above the first upper threshold temperature, the controller may send a command signal to increase the number of activated cylinders, increase the amount of throttle closure, and / or increase the number of disabled throttles. As a result, the reduced exhaust oxygen flow may travel downstream to the particulate filter, and thus may maintain the temperature of the particulate filter below a second upper threshold (the temperature of the particulate filter may be greater than the first upper threshold at 312, and may be a temperature at which the particulate filter may degrade above this temperature). In this way, adjustments to engine parameters may actively manage exhaust gas from the engine to the particulate filter during DFSO operation such that the likelihood of uncontrolled oxidation of soot in the particulate filter and potential degradation of the particulate filter may be reduced.

[0071] In addition, at 330, the controller may further include the controller terminating the DFSO operation after a threshold duration due to the exhaust temperature being above a first upper threshold temperature. In one example, the threshold duration may be based on the exhaust temperature (e.g., the particle filter temperature), wherein the threshold duration may decrease when the exhaust temperature further increases above the first upper threshold temperature. Thus, in one example, if the temperature of the particle filter increases above a second upper threshold temperature (which is greater than the first upper threshold temperature and may be a temperature at which the particle filter may degrade above this temperature), the controller may terminate the DFSO operation. In other words, if the particle filter temperature increases toward a temperature at which particle filter degradation may occur, the DFSO operation may run for a shorter duration in order to avoid the risk of particle filter degradation. In other embodiments, the threshold duration may alternatively or optionally be based on one or more of the soot generation (e.g., raw gas soot level) and the soot storage load in the particle filter relative to a corresponding threshold. Thus, the threshold duration before terminating the DFSO may decrease as the raw gas soot level and / or the soot storage level in the particle filter increase toward their corresponding soot thresholds. In one example, as described with reference to 304 , these respective soot thresholds may be the same as the first soot threshold and the second soot threshold, respectively.

[0072] The routine then continues to 332, where the routine includes determining whether DFSO operation has terminated. In some examples, terminating DFSO may include no longer satisfying DFSO conditions. This may include one or more of fuel injection to each cylinder of the engine (e.g., all cylinders of the firing engine), the throttle is no longer in an idle state, and the brake is no longer depressed. Termination of DFSO may also be a result of the controller terminating DFSO after a threshold duration due to exhaust temperature being above a first upper threshold temperature. In this way, DFSO may have been operated for a shorter duration in order to avoid the risk of particulate filter degradation. In other examples, termination of DFSO may be in response to an increase in torque requested by the operator.

[0073] If DFSO has not been terminated, the routine proceeds to 334, where the routine includes waiting and maintaining engine operating conditions until DFSO terminates. In one example, this may include continuing to operate the engine in DFSO mode (e.g., no fuel is delivered to any cylinder of the engine). When DFSO terminates, the routine continues to 320, where the routine includes starting stoichiometric combustion. In an example where the engine is operated in a lean range (e.g., λ is greater than 1.0) due to increased oxygen entrained in the exhaust gas due to operation in DFSO mode, this may include increasing the air-fuel ratio toward a λ value of 1.0. In two non-limiting examples, reducing the air-fuel ratio toward a λ value of 1.0 may be achieved by increasing fuel delivery to the engine cylinders and / or by reducing the opening of the intake throttle to reduce the air flow to the engine cylinders. When DFSO terminates, stoichiometric combustion may be started at the cylinders of the engine during increased soot generation and increased soot storage in the particulate filter. The routine then ends.

[0074] If at 304, the routine determines that the raw gas soot level is less than a threshold soot level (e.g., a first soot threshold), and determines that the particulate filter soot load is less than a threshold soot load (e.g., a second soot threshold), the routine proceeds to Figure 4 , as described below.

[0075] Now go to Figure 4, which shows a flowchart illustrating an example method 400 for performing DFSO after increasing the flow through the bypass of the emission control device. Method 400 may be performed as part of method 300. For example, in response to the raw gas soot level being less than the first soot threshold and the particulate filter soot load being less than the second soot threshold, method 400 may be performed. In response to the raw gas soot level being less than the first soot threshold and the particulate filter soot load being less than the second soot threshold, at 402, the flow of exhaust gas bypassed by the particulate filter is increased. Specifically, the controller may send a command signal to the actuator of the particulate filter bypass valve to increase the opening of the particulate filter bypass valve, thereby allowing the increased amount of exhaust gas to bypass the particulate filter instead of passing through the particulate filter. In some examples, increasing the opening of the particulate filter bypass valve may include fully opening the filter bypass valve to a maximum degree of opening (e.g., 100%). In this way, the maximum amount of exhaust gas flow may bypass the particulate filter. It should be understood that even when the bypass valve is fully open, in some examples, some exhaust gas may continue to flow through the particulate filter.

[0076] The routine then continues to 404, where the routine includes determining whether DFSO entry conditions are met, as described above with reference to Figure 3 If the DFSO entry conditions are not met, such as may occur during cold start conditions, when the engine is under high load, or when the operator requests torque to accelerate the vehicle, the routine continues to 406, where the routine includes maintaining engine operation. In one example, this may include continuing to deliver fuel to the cylinders of the engine for combustion and operating the engine to meet the operator's torque request. The routine then ends.

[0077] If the DFSO entry conditions are met, the routine continues to 408, where the routine includes operating in a DFSO mode (by disabling fuel to the engine cylinders and continuing to pump air through the engine cylinders to the exhaust passages) as required without limiting (or adjusting) the DFSO operation based on the temperature of the particulate filter. Specifically, in response to a particulate filter bypass around the particulate filter, the exhaust passage of the engine is opened, and the engine can be operated in a DFSO mode for a first duration based on the torque requested by the operator. The first duration can be based on the duration that the DFSO entry conditions continue to be met, as described above with reference to 308. In this way, when the bypass valve is open, the DFSO operation can be operated without regard to the temperature of the particulate filter. In one example, in response to an indication that the particulate filter bypass valve is open and combustion exhaust is flowing through the bypass passage around the particulate filter, if the DFSO entry conditions described at 308 are met, the engine can continue to operate in DFSO even when the temperature of the particulate filter may exceed a first threshold temperature (e.g., the first upper threshold temperature of 312). The first threshold temperature may be a temperature above which the particulate filter temperature is closely monitored when the bypass valve opening is reduced (e.g., closed), and subsequent DFSO operation may be limited in response to the temperature of the particulate filter in addition to other engine operating conditions (such as the soot level of the feed gas and the amount of soot stored in the particulate filter). In one example, the first threshold temperature may be a temperature at which regeneration of the particulate filter occurs (e.g., a regeneration temperature).

[0078] The routine then proceeds to 410, where the routine includes determining whether the DFSO operation has terminated. In some examples, terminating the DFSO may include terminating the DFSO conditions no longer being met. This may include one or more of fuel injection to each cylinder of the engine (e.g., all cylinders of the engine are fired), the throttle is no longer in an idle state, the accelerator pedal is depressed, and / or the brake is no longer depressed. In other examples, the DFSO operation may be terminated in response to an increase in operator-demanded torque (e.g., in response to an increase in pedal position of the accelerator pedal). If the DFSO is not terminated, the routine proceeds to 412, where the routine includes waiting and maintaining engine operating conditions until the DFSO is terminated. In one example, this may include continuing to operate the engine in a DFSO mode (e.g., no fuel is delivered to any cylinder of the engine). When the DFSO is terminated, the routine proceeds to 414, where the routine includes as described in reference Figure 3 Stoichiometric combustion begins as described at 320. The routine then ends.

[0079] Now go to Figure 5, chart 500 shows predicted operation of the engine, which includes controlling flow through a bypass around the emission control device and adjusting DFSO operation in response to flow through the bypass and the temperature of the emission control device. In addition, engine parameters including DFSO operation can be adjusted and / or terminated in response to the position of the bypass valve and / or the temperature of the particulate filter. Chart 500 includes various engine parameters along the vertical axis and elapsed time along the horizontal axis. Chart 500 depicts an accelerator pedal position (PP) at curve 502, which indicates an operator torque demand. Chart 500 further depicts an air-fuel ratio at curve 504 relative to a stoichiometric air-fuel ratio at 503, and a raw gas soot level (e.g., exhaust soot level) at curve 506 relative to a first soot threshold at 505. Graph 500 also depicts particulate filter (PF) soot loading at curve 508 relative to a second soot threshold at 507, a position (e.g., degree of opening) of a bypass valve positioned in a bypass passage around the particulate filter at curve 510, and exhaust back pressure at curve 512 relative to a threshold exhaust back pressure at 511. Additionally, DFSO operation is shown at curve 514, and particulate filter temperature relative to a regeneration temperature threshold at 513, a first upper threshold at 515, and a second upper threshold at 517 is shown at curve 516. Finally, particulate filter regeneration is shown at 518.

[0080] Prior to time t1, the operator is requesting torque, as shown by the increased actuation of the accelerator pedal (curve 502). Therefore, the engine is operated at a rich air-fuel ratio (curve 504), where λ is less than the stoichiometric air-fuel ratio at 503. Due to the rich operation of the engine, the raw gas soot may rise (curve 506) above the first soot threshold (curve 505). As soot from the raw gas accumulates in the particulate filter, the soot load of the particulate filter may increase (curve 508) toward the second soot threshold (curve 507). Because the PF soot load is below the second soot threshold 507, but the raw gas soot is above the first soot threshold 505, the PF bypass valve remains closed before time t1 (curve 510). As the PF soot load increases, the exhaust back pressure (curve 512) may increase toward the threshold exhaust back pressure 511. Because there is an operator torque demand, the engine is not operated in DFSO mode (curve 514).

[0081] At time t1, the operator stops requesting acceleration and requests steady torque from the engine as indicated by steady actuation of the accelerator pedal (curve 502). Therefore, the engine is not operated with DFSO (curve 514). The air-fuel ratio may tend toward the stoichiometric ratio (curve 504), and the raw gas soot level (506) may drop below the first soot threshold (dashed curve 505) at time t1. At the same time, the PF soot load (curve 508) remains below the second soot threshold 507, and the opening of the PF bypass valve may therefore be increased (curve 510). In the depicted embodiment, the PF bypass valve is fully opened, but it should be understood that the valve opening may alternatively be increased without being fully opened. Since the exhaust gas is now able to substantially bypass the particulate filter, the soot load of the particulate filter does not continue to increase (curve 508), and the exhaust back pressure does not continue to increase (curve 512). However, due to continued engine operation and exhaust gas flowing through the particulate filter, the temperature of the particulate filter may continue to gradually increase (plot 516 ), but the temperature of the particulate filter remains below the regeneration temperature (plot 518 ), so regeneration does not occur.

[0082] At time t2, the actuation of the accelerator pedal is reduced (curve 502). This may be due to the operator gently releasing the throttle. In response to meeting the DFSO condition at time t2, the engine enters DFSO mode (curve 514), and fuel is no longer delivered to the cylinders of the engine. Therefore, the air-fuel ratio is lean (curve 504) and the raw gas soot level is reduced (curve 506). Also at time t2, the particulate filter bypass is opened (curve 510), and the particulate filter soot load (curve 508) and exhaust back pressure (curve 512) do not continue to increase. The particulate filter temperature (curve 516) continues to remain below the regeneration temperature (dashed curve 513), so regeneration does not occur (518).

[0083] The operating conditions remain stable until time t3, at which time there is an operator torque request, as shown by the accelerator pedal (curve 502). The depression of the accelerator pedal causes the DFSO entry conditions to no longer be met, and therefore the first duration D1 of the DFSO ends at time t3. In this way, the first duration D1 (e.g., t2 to t3) is terminated based on the operator torque demand rather than based on the temperature of the particulate filter. At time t3, the air-fuel ratio decreases toward enrichment (curve 504) and the raw gas soot level increases (curve 506). In response to the raw gas soot level increasing to above the first soot threshold (curve 505), the bypass valve is closed (curve 510). The particulate filter soot load (curve 508) also increases to above the second soot threshold (curve 507). In this way, in response to the bypass opening around the particulate filter disposed in the exhaust passage of the engine, the engine operates the first duration with DFSO based on the torque required by the operator.

[0084] At time t4, the accelerator pedal continues to be depressed (curve 502). Also at t4, the temperature of the particulate filter (curve 516) increases to above the regeneration threshold temperature (dashed curve 513), so regeneration can begin at t4 (curve 518). At the same time, the raw gas soot level (curve 506) is above the first soot threshold (dashed curve 505) and the soot load of the particulate filter (curve 508) is above the second soot threshold (dashed curve 507), so the particulate filter bypass is closed (curve 510). Due to the regeneration of the particulate filter, the amount of soot in the particulate filter is oxidized and removed, and therefore due to the regeneration between t4 and t6, the exhaust back pressure (curve 512) decreases away from the threshold exhaust back pressure (curve 511).

[0085] At time t5, there is another sudden release of the accelerator pedal depression (curve 502). Therefore, the DFSO entry condition is met and the engine begins to operate in DFSO mode (curve 514). The air-fuel ratio is lean (curve 504) and the raw gas soot is reduced (curve 506), but the particulate filter soot load (curve 508) remains above the second soot threshold (dashed curve 507), and therefore the particulate filter bypass valve remains closed (curve 510). As the regeneration operation continues, the temperature of the particulate filter continues to increase, which is partly due to the increased oxygen level in the exhaust gas entering the particulate filter during regeneration. Because the particulate filter temperature at t5 is higher than the first upper threshold temperature (515) when DFSO begins, the controller monitors the temperature of the particulate filter during DFSO. When the temperature of the particulate filter reaches the second upper threshold temperature (517), DFSO terminates. In this way, when the particulate filter bypass valve is closed, in response to the temperature of the particulate filter reaching the second upper threshold temperature 517, DFSO operates for a second duration D2. If the particulate filter bypass valve is opened between t5 and t6, DFSO may continue for a third duration D3 (eg, t5 to t6) before terminating. During D3, DFSO will terminate because DFSO entry conditions are not met, not because the temperature of the particulate filter reaches an upper threshold.

[0086] At time t6, regeneration ends (curve 518), and the bypass valve is reopened (curve 510) because the raw gas soot level (curve 506) caused by regeneration is below the first soot threshold 505 and the soot load of the particle filter (curve 508) returns to below the second soot threshold 507. As a result of opening the bypass valve, the temperature of the particle filter (curve 516) decreases.

[0087] In this way, under operating conditions where the particulate matter load in the exhaust gas is low, a portion of the exhaust gas can bypass the particulate filter, thereby reducing exhaust back pressure and thereby improving fuel economy. In addition, by not passing the exhaust gas through the particulate filter during all driving conditions, soot and ash accumulation in the particulate filter can be reduced, thereby increasing the life of the particulate filter.

[0088] When exhaust gas bypasses the particulate filter, the likelihood of excessive heat release on the particulate filter during DFSO mode is reduced, and DFSO can be performed without regard to the temperature of the particulate filter. When particulate filter regeneration is desired, flow through the bypass is reduced, and DFSO operation during the reduced bypass flow can be adjusted in response to the particulate filter temperature. In this way, the amount of oxygen flowing through the particulate filter can be reduced while still performing particulate filter regeneration during DFSO. As a result, the filter can not exceed the maximum allowable particulate filter temperature, thereby reducing the likelihood of particulate filter degradation, while completing particulate filter regeneration.

[0089] The technical effect of increasing the bypass valve opening in response to reduced soot levels in the feed gas and reduced soot amounts stored in the particulate filter is that filter life can be extended due to more selective use of the particulate filter. In addition, when the bypass valve is open, DFSO may not be limited by the temperature of the particulate filter, and fuel economy may be increased while still meeting reduced emission requirements. The technical effect of reducing the bypass valve opening in response to increased soot levels in the feed gas or increased soot amounts stored in the particulate filter is that emission reduction and / or particulate filter regeneration may be performed as required. In addition, when the bypass valve is closed, DFSO may be adjusted and / or terminated when the exhaust temperature is above a temperature threshold so that the increased oxygen content of the exhaust gas during DFSO does not contribute to degradation of the particulate filter.

[0090] A method for an engine includes: in response to reduced soot generation or reduced soot storage, causing gasoline-burned exhaust gas to flow to a particulate filter with increased filter bypass flow even when the exhaust temperature is above a first threshold, and in response to increased soot generation or increased soot storage, reducing the filter bypass flow and terminating a deceleration fuel cut-off operation after a threshold duration due to the exhaust temperature being above the first threshold. In a first example of the method, the method further includes where the exhaust temperature is a temperature of the particulate filter. A second example of the method optionally includes the first example, and further includes during causing gasoline-burned exhaust gas to flow to the particulate filter with increased filter bypass flow, and in response to a request to operate the engine with deceleration fuel cut-off, operating the engine with deceleration fuel cut-off even when the exhaust temperature is above the first threshold. A third example of the method optionally includes one or more of the first example and the second example, and further includes terminating the deceleration fuel cut-off operation in response to an increase in torque requested by an operator. A fourth example of the method optionally includes one or more of the first to third examples, and further includes starting stoichiometric combustion at an engine cylinder of the engine during increased soot generation or increased soot storage when terminating the deceleration fuel cut-off operation. The fifth example of the method optionally includes one or more of the first to fourth examples, and further includes where the threshold duration is based on exhaust temperature, wherein the duration decreases as the exhaust temperature further increases above the first threshold. The sixth example of the method optionally includes one or more of the first to fifth examples, and further includes, during the period of reducing the filter bypass flow in response to increased soot generation or increased soot storage, before terminating the deceleration fuel cut-off condition, in response to the exhaust temperature being above the first threshold, adjusting the engine operating parameters to reduce the amount of oxygen flowing to the particulate filter. The seventh example of the method optionally includes one or more of the first to sixth examples, and further includes where adjusting the engine operating parameters to reduce the amount of oxygen flowing to the particulate filter includes increasing the number of cylinders of the engine that are active and burning fuel, reducing the amount of opening of a throttle located upstream of the cylinder, and disabling one or more cylinder exhaust valves of the cylinder. The eighth example of the method optionally includes one or more of the first to seventh examples, and further includes where causing gasoline combustion exhaust gas to flow to a particulate filter with an increased filter bypass flow includes increasing an opening amount of a bypass valve disposed in a bypass passage coupled around the particulate filter, wherein the filter bypass flow bypasses only the particulate filter and not an additional device or catalyst positioned upstream of the particulate filter. The ninth example of the method optionally includes one or more of the first to eighth examples, and further includes where reducing the filter bypass flow includes reducing an opening amount of the bypass valve.The tenth example of the method optionally includes one or more of the first to ninth examples, and further includes where the gasoline combustion exhaust is generated via spark ignition, and where the engine is a direct injection turbocharged engine. The eleventh example of the method optionally includes one or more of the first to tenth examples, and further includes where the reduced smoke generation includes reduced smoke generation at cylinders of the engine, and the reduced smoke storage includes reduced smoke storage within a particulate filter.

[0091] In another example, a method for an engine includes: in response to meeting entry conditions for a deceleration fuel cutoff (DFSO) operation: in response to a bypass around a gasoline particulate filter (GPF) disposed in an exhaust passage of the engine being opened, operating the engine with DFSO for a first duration based on an operator-requested torque; and in response to the bypass being closed and a temperature being above a first threshold, operating the engine with DFSO for a second duration based on a temperature of the GPF. In the first example of the method, the method further includes operating the engine with DFSO for a first duration based on the operator-requested torque in response to the bypass being closed and the temperature being below the first threshold. The second example of the method optionally includes the first example, and further includes wherein operating the engine with DFSO for a second duration includes terminating the DFSO in response to a temperature increase above a second threshold, wherein the second threshold is greater than the first threshold. The third example of the method optionally includes one or more of the first and second examples, and further includes opening the bypass in response to each of the soot loads of the GPF being less than a first threshold load and soot generation at a cylinder of the engine being less than a second threshold amount, and closing the bypass in response to one or more of the soot loads of the GPF being greater than the first threshold load and soot generation at the cylinder being greater than a second threshold amount. A fourth example of a method optionally includes one or more of the first to third examples, and further includes adjusting an engine operating parameter to reduce a combustion air-fuel ratio of the engine during operation of the engine in DFSO for a second duration.

[0092] A system for an engine includes: an exhaust passage including a turbocharger turbine and a catalyst; a gasoline particulate filter (GPF) disposed in the exhaust passage downstream of the turbocharger turbine and the catalyst; a bypass passage disposed only around the GPF and including a bypass valve disposed therein; and a controller having computer-readable instructions stored in a memory, the computer-readable instructions for: opening the bypass valve in response to a soot level of the exhaust being less than a first threshold and a soot level stored in the GPF being less than a second threshold, and in response to the bypass valve being opened during a deceleration fuel shutoff (DFSO) operation, not limiting a duration of a DFSO operation based on a temperature of the GPF; and closing the bypass valve in response to one or more of the soot levels of the exhaust being greater than a first threshold and a soot level stored in the GPF being greater than a second threshold, and in response to the bypass valve being closed during the DFSO operation and a temperature of the GPF being greater than a first upper threshold, limiting a duration of the DFSO operation based on a temperature of the GPF. In a first example of a system, the system further includes wherein the computer readable instructions further include instructions for: in response to the bypass valve being closed and the temperature of the GPF being below a first upper threshold during the DFSO operation, not limiting the duration of the DFSO operation based on the temperature of the GPF. A second example of a system optionally includes the first example, and further includes wherein the engine is a direct-injection spark-ignited gasoline engine, and wherein the computer readable instructions further include instructions for: during the DFSO operation when the bypass valve is closed and the temperature of the GPF is above a first upper threshold, adjusting a parameter of the engine to maintain a combustion air-fuel ratio within a stoichiometric threshold, and terminating the DFSO operation in response to the temperature of the GPF increasing above a second upper threshold, wherein the second upper threshold is greater than the first upper threshold.

[0093] In another representation, a method for an engine includes: in response to entry conditions for entering deceleration fuel shutoff (DFSO) operation being met: in response to a bypass around a gasoline particulate filter (GPF) disposed in an exhaust passage of the engine being opened, operating the engine with DFSO and allowing a combustion air-fuel ratio that is leaner than within a stoichiometric threshold; and in response to the bypass being closed and a temperature of the GPF being above a first threshold, operating the engine with DFSO and adjusting engine operating parameters to maintain the combustion air-fuel ratio of the engine within a stoichiometric threshold.

[0094] 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-transitory memory and can be implemented by a control system including a controller combined with various sensors, actuators, and other engine hardware. The specific routines described herein may 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 performed in parallel in the sequence shown or omitted in some cases. Similarly, in order to achieve the features and advantages of the exemplary embodiments described herein, the processing sequence is not necessarily required, but the processing sequence is provided for ease of illustration and description. One or more of the actions, operations, and / or functions shown may be repeatedly performed according to the specific strategy used. In addition, the described actions, operations, and / or functions may graphically represent the code in the non-transitory memory of a computer-readable storage medium to be programmed into the engine control system, wherein the described actions are implemented by executing instructions in a system including a combination of various engine hardware components and an electronic controller.

[0095] It will be understood that the configurations and routines disclosed herein are exemplary in nature, and these specific embodiments should not be considered in a limiting sense, as many variations are possible. For example, the above-described technology can be applied to V-6, I-4, I-6, V-12, opposed 4, and other engine types. 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.

[0096] The accompanying claims particularly point out certain combinations and subcombinations deemed novel and non-obvious. These claims may refer to "an" element or "a first" element or their equivalent. 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 deemed to be included in the subject matter of the present disclosure.

Claims

1. A method for an engine, the method comprising: responsive to reduced soot generation or reduced soot storage, flowing gasoline-combusted exhaust gas to a particulate filter at an increased particulate filter bypass flow rate even when exhaust temperature is above a first threshold, wherein the increased particulate filter bypass flow rate reduces exhaust back pressure and increases life of the particulate filter; as well as In response to increased soot generation or increased soot storage, the particulate filter bypass flow is reduced and a deceleration fuel cut operation is terminated after a threshold duration due to exhaust temperature being above the first threshold, wherein reducing the particulate filter bypass flow and terminating the deceleration fuel cut operation regenerates the particulate filter. 2 . The method of claim 1 , wherein the exhaust gas temperature is a temperature of the particulate filter.

3. The method of claim 1 further comprising, during the flow of gasoline-burned exhaust gas to the particulate filter at an increased particulate filter bypass flow and in response to a request to operate the engine with a deceleration fuel cutoff, operating the engine with a deceleration fuel cutoff event even when the exhaust temperature is above the first threshold. 4 . The method of claim 3 , further comprising terminating the deceleration fuel cutoff operation in response to an increase in operator demanded torque. 5 . The method of claim 1 , further comprising initiating stoichiometric combustion at engine cylinders of the engine during the increased soot generation or increased soot storage period upon terminating the deceleration fuel cutoff operation. The method of claim 1 , wherein the threshold duration is based on the exhaust temperature, wherein the threshold duration decreases as the exhaust temperature increases further above the first threshold.

7. The method of claim 1 further comprising, during the decreasing the particulate filter bypass flow in response to increased soot generation or increased soot storage, prior to terminating the deceleration fuel cut operation, adjusting an engine operating parameter to reduce an amount of oxygen flowing to the particulate filter in response to the exhaust temperature being above the first threshold.

8. The method of claim 7, wherein adjusting the engine operating parameters to reduce the amount of oxygen flowing to the particulate filter includes one or more of: increasing the number of cylinders of the engine that are active and burning fuel, reducing the amount of opening of a throttle valve positioned upstream of the cylinder, and disabling one or more cylinder exhaust valves of the cylinder.

9. The method of claim 1 , causing gasoline combustion exhaust gas to flow to the particulate filter with an increased particulate filter bypass flow rate comprises increasing an opening amount of a bypass valve disposed in a bypass passage coupled around the particulate filter, wherein the particulate filter bypass flow rate bypasses only the particulate filter and does not bypass an additional device or catalyst positioned upstream of the particulate filter. 10 . The method of claim 9 , wherein reducing the particulate filter bypass flow comprises reducing the opening amount of the bypass valve.

11. The method of claim 1 , wherein the gasoline combustion exhaust gas is generated via spark ignition, and wherein the engine is a direct injection turbocharged engine. 12 . The method of claim 1 , wherein the reduced soot generation comprises reduced soot generation at cylinders of the engine and the reduced soot storage comprises reduced soot storage within the particulate filter.

13. A system for an engine, comprising: an exhaust passage including a turbocharger turbine and a catalyst; a gasoline particulate filter, or GPF, disposed in the exhaust passage downstream of the turbocharger turbine and the catalyst; a bypass passage disposed only around the GPF and including a bypass valve disposed therein; and A controller having computer readable instructions stored in a memory, the computer readable instructions for: opening the bypass valve in response to a soot level of the exhaust gas being less than a first threshold and a soot level stored in the GPF being less than a second threshold, and in response to the bypass valve being opened during a deceleration fuel shutoff (DFSO) operation, not limiting a duration of the DFSO operation based on a temperature of the GPF; as well as In response to one or more of the soot level of the exhaust gas being above the first threshold and the soot level stored in the GPF being above the second threshold, closing the bypass valve, and in response to the bypass valve being closed and the temperature of the GPF being above a first upper threshold during DFSO operation, limiting the duration of the DFSO operation based on the temperature of the GPF.

14. The system of claim 13, wherein the computer readable instructions further comprise instructions for: in response to the bypass valve being closed during DFSO operation and the temperature of the GPF being below the first upper threshold, not limiting the duration of the DFSO operation based on the temperature of the GPF.

15. The system of claim 13, wherein the engine is a direct injection spark ignition gasoline engine, and wherein the computer readable instructions further include instructions for: during DFSO operation while the bypass valve is closed and the temperature of the GPF is above the first upper threshold, adjusting parameters of the engine to maintain a combustion air-fuel ratio within a stoichiometric threshold, and terminating DFSO operation in response to the temperature of the GPF increasing above a second upper threshold, the second upper threshold being greater than the first upper threshold.

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