TEMPERATURE CONTROL OF A PETROL PARTICULATE FILTER

Abstract

Method for an internal combustion engine (10) comprising the following: as a reaction to a particle filter temperature above a threshold temperature and during operation of the machine (10) with deceleration fuel shutdown (DFSO), complete closing of a throttle valve configured to regulate the flow of intake air to the machine (10), and In response to the intake manifold pressure falling below a threshold pressure while the throttle valve is fully closed, adjusting the position of the throttle valve based on the particulate filter temperature.

Description

Area

[0001] The present description generally relates to methods and systems for reducing airflow to a gasoline particulate filter while increasing the deceleration of the fuel shutoff time of an engine. State of the art / brief description

[0002] Automotive engine fuel consumption can be improved by shutting off the fuel supply to an engine when a vehicle decelerates. This is known as deceleration fuel shut-off (DFSO). However, during DFSO, the supply of oxygen to a vehicle's emissions control device increases. In vehicles equipped with a particulate filter, this increased oxygen supply can result in filter degradation due to filter overheating.

[0003] Document US 8,407,988 B2 proposes a method for reducing the flow of oxygen to the particulate filter during non-combustion conditions by closing an intake throttle valve. However, the inventors identified a problem with the above approach. As the engine continues to rotate with the intake throttle valve closed, the manifold air pressure (MAP) begins to decrease. If the MAP becomes too low, engine degradation can occur, for example, lubricants can be sucked into the combustion chamber.

[0004] A method for an internal combustion engine in which a throttle valve is adjusted based on a pressure signal is known from WO 86 / 04641 A1. Further methods are known from US 2015 / 0 275 773 A1, DE 10 2010 046 762 A1, and US 2017 / 0 044 998 A1.

[0005] The inventors therefore provide an approach to at least partially mitigate these problems. In one example, a method includes, in response to determining that a particulate filter has reached a temperature above a threshold while an engine is operating in deceleration fuel shutoff (DFSO), fully closing the throttle valve configured to regulate the flow of intake air to the engine, and, in response to the intake manifold pressure falling below a threshold pressure while the throttle valve is fully closed, adjusting a position of the throttle valve based on the particulate filter temperature.

[0006] In this way, the particulate filter temperature may be maintained below a temperature threshold during DFSO, preventing filter degradation and extending the duration of DFSO operation. If the MAP drops below a threshold pressure while the throttle valve is closed, the throttle valve position may be adjusted based on the filter temperature. For example, if the filter temperature is above the threshold temperature but below an upper limit threshold, the throttle valve may be open by a small, preset amount. However, if the particulate filter temperature rises above the upper limit threshold, the throttle valve may be maintained fully closed, and MAP may be controlled by adjusting the intake and / or exhaust valve timing to increase the overlap between the intake and exhaust valves of an engine's cylinders to increase manifold pressure.This allows the MAP to be increased while maintaining a restricted air flow into the particulate filter, and in this way helps to reduce the temperature of the particulate filter while the engine remains in DFSO mode.

[0007] It should be understood that the above summary is provided to introduce, in simplified form, a selection of concepts further described in the detailed description. It is not intended to identify key or essential features of the claimed subject matter, the scope of which is defined solely by the claims following the detailed description. Furthermore, the claimed subject matter is not limited to implementations that address any disadvantages noted above or in any part of the present disclosure. Short description of the drawings Fig. 1 shows a schematic representation of a combustion chamber of an internal combustion engine. Fig. 2 shows a flowchart illustrating a method for controlling the deceleration fuel cut-off parameters of an engine. Fig. 3 shows a flowchart illustrating a method for preventing a gasoline particulate filter from overheating while an engine is in deceleration shutdown mode. Fig. 4 shows an exemplary time frame for controlling the temperature of a gasoline particulate filter according to the methods of Fig. 2 and Fig. 3. Detailed description

[0008] The following description relates to systems and methods for maintaining an engine in deceleration shutdown (DFSO) mode while preventing a gasoline particulate filter from overheating. Some internal combustion engines use a particulate filter in an exhaust system to capture particulate matter flowing through the exhaust system and thereby meet emissions standards. For example, a direct-injection spark-ignition engine may include a particulate filter to capture soot. As particulate matter accumulates in a particulate filter, exhaust back pressure increases, which can negatively impact fuel economy. A particulate filter may thus be regenerated periodically by oxidizing deposited particulate matter. A regeneration reaction typically involves elevated oxygen concentration at the filter and appropriate temperature conditions.As more oxygen is supplied to the filter, the heat generated by the combustion of the soot particles trapped by the filter can increase the temperature of the filter. Eventually, the filter can overheat.

[0009] When the temperature of the particulate filter approaches a point where the filter is at risk of damage, the filter can be cooled by inhibiting the combustion reaction. This reaction can be inhibited by interrupting the oxygen supply to the particulate filter. Normally, an engine uses a significant amount of oxygen during the combustion of fuel at the engine's cylinders. However, when an engine is in DFSO mode, the fuel supply to the engine is temporarily shut off so that no oxygen is consumed at the cylinders and ultimately directed to the particulate filter. Under these circumstances, it is more difficult to control the filter's temperature.In some examples, DFSO may be temporarily interrupted and fuel delivery to the engine may be resumed, resulting in a reduction in oxygen supply to the particulate filter and a subsequent reduction in the filter's temperature. However, premature temporary interruption of DFSO may reduce fuel efficiency.

[0010] The disclosed method attempts to extend the time an engine operates in DFSO mode while preventing the particulate filter from overheating. In one embodiment, once an engine controller determines that the gasoline particulate filter may have reached a threshold temperature, the intake throttle may be adjusted to a minimum position, which in one example may be fully closed. The effect of fully closing the throttle is to temporarily eliminate the flow of additional oxygen into the particulate filter to inhibit the soot combustion reaction, which may then result in reducing the temperature of the filter. Further, if the manifold air pressure drops below a threshold while the throttle valve is at its minimum position, the timing of the intake and exhaust valves of the engine's cylinders may be adjusted to increase valve overlap.In this way, the intake manifold pressure can be increased while maintaining engine operation under DFSO conditions.

[0011] Fig. Figure 1 is a schematic diagram showing a cylinder of a multi-cylinder engine equipped with an emission control device including a gasoline particulate filter. The flowchart shown in Fig. 2 illustrates a method for controlling deceleration fuel shutoff (DFSO) operation of an engine. A flowchart illustrating a method for controlling the temperature of the gasoline particulate filter is shown in Fig. 3, which describes the throttle valve setting and the intake and exhaust valve overlap while an engine is operating in deceleration fuel cut mode. Fig. 4 shows an example timeframe for several engine operating parameters under a variety of engine conditions, including intermittent operation under normal conditions and intermittent operation under DFSO conditions. While the engine is under DFSO conditions, in one example, the engine throttle valve is adjusted in response to particulate filter overheating, and in a second example, both the throttle valve and cam timing valve overlap are adjusted to control the particulate filter temperature.

[0012] The schematic representation of the Fig. 1 illustrates a cylinder of a multi-cylinder engine 10, which may be included in a propulsion system of a motor vehicle. The engine 10 may be controlled at least in part by a control system including a controller 12 and by input from a vehicle operator 132 via an input device 130. In this example, the input device 130 includes an accelerator pedal and a pedal position sensor 134 for generating a proportional pedal position signal PP. The combustion chamber (i.e., cylinder) 30 of the engine 10 may include combustion chamber walls 32 with a piston 36 positioned therein. In some embodiments, the front of the piston 36 may include a bowl within the cylinder 30. The piston 36 may be coupled to the crankshaft 40 such that reciprocating motion of the piston is translated into rotational motion of the crankshaft.The crankshaft 40 may be coupled to at least one drive wheel of a vehicle via an intermediate gear system. Furthermore, a starter motor may be coupled to the crankshaft 40 via a flywheel to enable starting operation of the engine 10.

[0013] Combustion chamber 30 may receive intake air from intake manifold 44 via intake passage 42 and may exhaust combustion gases via exhaust passage 48. Intake manifold 44 and exhaust passage 48 may selectively communicate with combustion chamber 30 via an intake valve 52 and an exhaust valve 54, respectively. In some embodiments, combustion chamber 30 may include two or more intake valves and / or two or more exhaust valves.

[0014] In this example, intake valve 52 and exhaust valves 54 may be controlled by cam actuation via respective cam actuation systems 51 and 53, respectively. Cam actuation systems 51 and 53 may each include one or more cams and may utilize one or more cam profile switching (CPS), variable cam timing (VCT), variable valve timing (VVS), and / or variable valve lift (VVL) systems, which may be actuated by controller 12 to vary valve operation. The position of intake valve 52 and exhaust valve 54 may be determined by position sensors 55 and 57, respectively. In alternative embodiments, intake valve 52 and / or exhaust valve 54 may be controlled by electrical valve actuation.For example, cylinder 30 may alternatively include an intake valve controlled via electric valve actuation and an exhaust valve controlled via cam actuation including CPS and / or VCT systems.

[0015] The fuel injector 66 is shown coupled directly to the combustion chamber 30 so that fuel is injected directly into it in proportion to the pulse width of the FPW signal received from the controller 12. In this manner, the fuel injector 66 provides what is known as direct fuel injection into the combustion chamber 30. The fuel injector may be mounted, for example, in the side of the combustion chamber or in the top of the combustion chamber. Fuel may be delivered to the fuel injector 66 by a fuel system (not shown) including a fuel tank, a fuel pump, and a fuel rail.

[0016] The ignition system 88 may provide an ignition spark to the combustion chamber 30 via the spark plug 92 in response to the spark advance signal SA from the controller 12 during selected operating modes. Although spark ignition components are shown, in some embodiments, the combustion chamber 30 or one or more other combustion chambers of the engine 10 may be operated in a compression ignition mode with or without an ignition spark.

[0017] The intake passage 42 or intake manifold 44 may include a throttle 62 with a throttle plate 64. In this particular example, the position of the throttle plate 64 or a throttle opening may be varied by the controller 12 via a signal provided to an electric motor or actuator included in the throttle 62, a configuration commonly called Electronic Throttle Control (ETC). Thus, the throttle 62 may be operated to vary the intake air provided to the combustion chamber 30, among other engine cylinders. The position of the throttle plate 64 may be provided to the controller 12 by a throttle position signal TP. The intake passage 42 may include a mass air flow sensor 120 and a manifold air pressure sensor 122 for providing respective MAF and MAP signals to the controller 12.

[0018] Further, in the disclosed embodiments, an exhaust gas recirculation (EGR) system may direct a desired portion of exhaust gas from the exhaust passage 48 to the intake manifold 44. In this example, the high-pressure (HP) EGR passage 140 is illustrated. The amount of EGR provided to the intake manifold 44 may be varied by the controller 12 via the HP EGR valve 142. Further, an EGR sensor 144 may be disposed in the HP EGR line and may provide an indication of pressure, temperature, and / or exhaust gas concentration. Alternatively, the EGR may be controlled by a calculated value based on signals from the MAF (upstream), MAP (intake manifold), MAT (manifold gas temperature), and crankshaft speed sensor. Furthermore, the EGR can be controlled based on an exhaust gas O2 sensor and / or an intake oxygen sensor (intake manifold).Under some conditions, the EGR system can be used to control the temperature of the air and fuel mixture within the combustion chamber and / or the temperature near PF 72. Although . Fig. While Figure 1 shows a high-pressure EGR system, a low-pressure EGR system may be used additionally or alternatively. In a low-pressure EGR system, EGR may be routed from downstream of a turbocharger turbine to upstream of a turbocharger compressor.

[0019] The engine 10 may therefore further include a compression device, such as a turbocharger or a supercharger, including at least one compressor 162 disposed along the intake manifold 44. For a turbocharger, the compressor 162 may be driven at least partially by a turbine 164 (e.g., via a shaft) disposed along the exhaust passage 48. For a supercharger, the compressor 162 may be driven at least partially by the engine 10 and / or an electric machine and may not include a turbine. Therefore, the amount of compression provided to one or more cylinders of the engine via a turbocharger or a supercharger may be varied by the controller 12.

[0020] The exhaust gas sensor 126 is shown coupled to the exhaust passage 48 upstream of the emission control device (ECD) 70. The exhaust gas sensor 126 may be any suitable sensor for providing an indication of an exhaust gas air / fuel ratio, such as a linear oxygen sensor or UEGO (Universal or Wide-Range Exhaust Gas Oxygen), a two-point oxygen sensor or EGO (Oxygen Sensor), a HEGO (Heated Oxygen Sensor), a NOx, HC, or CO sensor. Although the oxygen sensor 14 and the temperature sensor 16 are shown in addition to the exhaust gas sensor 126 in Fig. 1, one or more of these sensors may be omitted and / or relocated.

[0021] The ECD 70 is shown disposed along the exhaust passage 48 downstream of the exhaust gas sensor 126. In this example, the ECD 70 includes a three-way catalyst (TWC) 71 and a particulate filter (PF) 72. In some embodiments, the PF 72 may be located downstream of the TWC 71 (as shown in Fig. 1), while in other embodiments the PF 72 may be positioned upstream of the catalyst (not shown in Fig. 1). Furthermore, the PF 72 may be arranged between two or more three-way catalysts or other emission control devices (e.g., selective catalytic reduction system, NOx trap), or combinations thereof. In other embodiments, the TWC 71 and the PF 72 may be integrated into a single housing. Furthermore, while the PF 72 in Fig. 1 as being positioned downstream of the turbine 164 and the HP EGR passage inlet, in some examples, the PF 72 may be positioned upstream of one or both of the turbine EGR passage inlets. In still other examples, the engine may not include a turbocharger or EGR system.

[0022] The control device 12 is in Fig. 1 as a microcomputer, including a microprocessor 102, input / output ports 104, an electronic storage medium (e.g., computer-readable) for executable programs and calibration values, shown as read-only memory 106 in this particular example, a random access memory 108, a keep-alive memory 110, and a data bus.Controller 12 may receive various signals from sensors coupled to engine 10 in addition to those previously analyzed, including measurements of induced mass air flow (MAF) from mass air flow sensor 120, engine coolant temperature (ECT) from temperature sensor 112 coupled to cooling sleeve 114, a profile ignition pickup (PIP) signal from a Hall effect sensor 118 (or other type) coupled to crankshaft 40, throttle position (TP) or throttle opening from a throttle position sensor, and a manifold absolute pressure (MAP) signal from sensor 122. Engine speed signal RPM may be generated by controller 12 from PIP signal. Manifold pressure signal MAP from the manifold pressure sensor may be used to provide an indication of intake manifold vacuum or pressure.It should be noted that various combinations of the above sensors may be used, such as a MAF sensor without a MAP sensor, or vice versa. During stoichiometric operation, the MAP sensor may provide an indication of engine torque. Further, this sensor, along with the detected engine speed, may provide an estimate of the charge (including air) being introduced into the cylinder. In one example, sensor 118, which is also used as an engine speed sensor, may generate a predetermined number of evenly spaced pulses during each revolution of the crankshaft.

[0023] The read-only memory storage medium 106 may be programmed with computer-readable data representing instructions executable by the microprocessor 102 to perform the methods described below, as well as other variations that are expected but not specifically listed. The control device 12 receives signals from the various sensors (e.g., an intake manifold air pressure sensor 122, valve position sensors 55 and 57, temperature sensor 16) of the Fig. 1 and uses the various actuators (for example throttle plate 64, cam actuation systems 51 and 53) of the Fig. 1, to adjust the machine operation based on the received signals and instructions stored in a memory of the control device.

[0024] An engine may transition to deceleration fuel shutoff (DFSO) under a variety of conditions, such as when the operator reduces vehicle speed or when the vehicle is coasting. The disclosed method incorporates existing mechanisms that determine the suitability of an engine's transition to DFSO mode. In DFSO mode, the delivery of fuel to the engine is disabled, resulting in increased fuel economy, while the engine continues to rotate while transferring torque to the wheels. The cylinder intake and exhaust valves may continue to be actuated with normal timing (e.g., the same as before entering DFSO). The disclosed method monitors the temperature of the gasoline particulate filter and may adjust the throttle valve to a minimum position if the filter temperature reaches a first threshold.In another example, if manifold air pressure (MAP) falls below a threshold and the temperature of the filter is above a second threshold, the method may adjust intake and / or exhaust valve timing (e.g., the cam timing mechanism may be adjusted) to increase intake and exhaust valve overlap, thereby increasing MAP.

[0025] Fig. 2 illustrates a method 200 for controlling DFSO operation of a machine, such as the machine 10 of the Fig. 1. Instructions for performing method 200 and the remainder of the methods included herein may be executed by a controller (e.g., controller 12) based on instructions stored in a memory of the controller and in conjunction with signals received from sensors of the engine system, such as those described above with reference to Fig. 1 (e.g., sensor 122). The controller may use machine actuators (e.g., throttle 62) of the machine system to adjust machine operation according to the methods described below.

[0026] Method 200 includes, at 202, determining engine operating parameters, including engine speed and load, MAP and MAF, engine and / or manifold temperature, driver requested torque, particulate filter temperature and / or load, etc. At 206, method 200 determines whether conditions for setting the engine to DFSO mode are met. This assessment may include conditions such as an operator-requested deceleration, e.g., reducing speed, or the operator ceasing to press the accelerator pedal to allow the vehicle to coast at the achieved speed. If, at 206, method 200 determines that DFSO conditions have not been met, it may proceed to 210.At 210, the current engine operating parameters are maintained. For example, fuel injection, throttle position, engine torque delivery to the wheels, and valve timing may be maintained at current settings as determined by the engine controller and / or by operator request. Method 200 may return.

[0027] If method 200 determines at 206 that DFSO is appropriate, a DFSO event may be initiated at 214. Fuel injectors (such as fuel injector 66) may be deactivated at 216, and a throttle (e.g., throttle 62) may be set to a preset position at 218. The preset position may be a suitable position to which the throttle is positioned when DFSO is enabled and, in one example, may be at least partially open. In other examples, the preset position of the throttle may be fully closed.At 220, the engine may continue to transfer torque to the wheels while maintaining the overlap timing of an intake valve (e.g., intake valve 52) and a corresponding exhaust valve (e.g., exhaust valve 54) at a first overlap amount, which may be the overlap amount from before the engine entered DFSO mode. While in DFSO mode, an engine may continue to rotate and expel air from the cylinders (e.g., cylinder 30) through an exhaust manifold (such as exhaust manifold 48). This air may flow into a particulate filter (such as particulate filter 72).

[0028] At 224, method 200 maintains the temperature of the particulate filter and the air pressure of an intake manifold (e.g., intake manifold 44) ​​at respective predetermined levels, as described in more detail below with reference to Fig. 3. In short, the particulate filter may be maintained below a threshold temperature by closing the throttle valve during DFSO, and if closing the throttle valve causes the MAP to fall below a threshold pressure, the throttle valve may be adjusted and / or the valve timing may be adjusted.

[0029] At 228, method 200 determines whether conditions for exiting DFSO are met. Conditions for exiting DFSO may include the accelerator pedal being depressed and / or other conditions. If conditions for exiting DFSO have not been met, method 200 may return to 224, in which case method 200 may continue to operate in DFSO and maintain the particulate filter temperature and MAP at specified levels until conditions for exiting DFSO are met, for example, the vehicle operator resuming acceleration. If at 228, method 200 determines that exiting DFSO is appropriate, method 200 proceeds to 232.At 232, an event to exit DFSO may be initiated, and the relevant parameters may be reset to normal operating conditions, including activating fuel injection at 234 and adjusting the throttle valve based on requested torque at 236. In one example, the requested torque may comprise operator-requested torque. Additionally or alternatively, the requested torque may comprise vehicle-requested torque, such as an alternator load applied to the engine. At 238, the engine may continue to transmit torque to the wheels, a torque that may be adjusted according to the vehicle operator's request.At 240, while the engine is rotating, intake and exhaust valve timing may be maintained or resumed at the initial overlap amount, for example, the overlap the valves had before entering DFSO mode. Method 200 may return.

[0030] Fig. 3 illustrates a method 300 for maintaining the temperature of a particulate filter (e.g., particulate filter 72) and the air pressure of an intake manifold (e.g., intake manifold 44) ​​while an engine is operating in DFSO mode. Method 300 may be performed as a part of method 200, for example, in response to operation in DFSO. At 302, method 300 determines engine operating parameters, which may include engine speed and load, MAP, particulate filter temperature, throttle valve position, etc. At 306, method 300 determines whether the particulate filter temperature is above a first threshold temperature T1 based on output from a particulate filter temperature sensor, such as sensor 16 of the Fig. 1, or based on an estimated particulate filter temperature. The threshold temperature T1 may be a suitable temperature indicating that particulate filter degradation is likely to occur if relatively high levels of oxygen are provided to the filter. In one example, the threshold T1 may be the temperature at which soot typically burns, such as 500°C. In some examples, the first threshold temperature T1 may vary based on the soot load of the particulate filter; for example, the threshold temperature may increase as the soot load decreases.

[0031] If it is determined that the temperature is lower than T1, method 300 may proceed to 310. At 310, a throttle valve position (e.g., throttle 62) and the overlap amount of an intake valve (such as intake valve 52) and a corresponding exhaust valve (e.g., exhaust valve 54) may be maintained at their current DFSO levels, e.g., those determined 214 of method 200 of the Fig. 2. In such a case, the machine can be used to 228 of the Fig. 2 to continue operation in DFSO mode as described above for method 200.

[0032] If method 300 determines at 306 that the particulate filter temperature has exceeded temperature T1, it may proceed to 314. At 314, method 300 may set the throttle to a minimum position, in one example, a fully closed position. By fully closing the throttle, oxygen flow to the particulate filter may be interrupted, which may result in its temperature decreasing or preventing it from increasing.

[0033] At 318, method 300 determines based on an output from a MAP sensor, such as sensor 122 of the Fig. 1, whether the intake manifold pressure is below a threshold pressure. The threshold pressure may be a pressure below which engine degradation may occur, for example, due to lubricating fluid being drawn into the combustion chambers. In one example, the threshold MAP may be 30 kPa absolute, although other threshold pressures are possible. If the MAP is not below the threshold pressure, method 300 returns to 228 of Fig. 2 to continue operations in DFSO and monitor for conditions to exit DFSO.

[0034] If the MAP is lower than the threshold pressure, method 300 proceeds to 322 to determine if the particulate filter temperature is lower than a second threshold temperature T2. The second threshold temperature may be greater than the first threshold temperature and may represent an upper limit temperature at which particulate filter degradation may occur. In one example, the second threshold temperature may be 600°C. If the particulate filter temperature is not below the second threshold temperature, method 300 proceeds to 326 to adjust intake and / or exhaust valve timing to increase the amount of valve overlap. By increasing the valve overlap, MAP may be increased.To increase valve overlap, the exhaust valve closing timing may be adjusted, the intake valve opening timing may be adjusted, or both the exhaust valve timing and the intake valve timing may be adjusted. Valve timing may be adjusted by adjusting a variable camshaft timing system, variable valve lift system, or other suitable mechanism. Method 300 then returns to 318 to continue assessing MAP and particulate filter temperature.

[0035] If it is determined at 322 that the particulate filter temperature is lower than the second threshold temperature, method 300 proceeds to 330 to open the throttle valve by a predetermined amount. In one example, the predetermined amount may be one degree, although other amounts are possible. By opening the throttle by a relatively small amount, the MAP may be increased without directing too much oxygen to the particulate filter. Method 300 then proceeds back to 318 to continue monitoring the MAP and particulate filter temperature.

[0036] Method 300 therefore monitors the particulate filter temperature during DFSO or other non-combustion operation. If the DFSO temperature is relatively high, the throttle valve is closed to prevent oxygen from flowing to the particulate filter and therefore preventing combustion of the soot in the particulate filter. However, closing the throttle valve during DFSO may cause the intake manifold pressure to fall below a threshold pressure, which may result in engine degradation. To prevent the intake manifold pressure from becoming too low, the temperature of the particulate filter may be assessed. If the particulate filter temperature is lower than an upper limit temperature at which filter degradation may occur, the throttle valve may be opened slightly (e.g., by one degree) to increase the MAP without directing excess oxygen to the particulate filter.However, if the particulate filter is at or above the upper limit temperature, even a small amount of oxygen can cause filter degradation. Therefore, to increase MAP, the intake and / or exhaust valves can be adjusted to increase valve overlap while the throttle valve remains fully closed. Once conditions to exit DFSO are met, the throttle valve can be returned to a position based on operator-requested torque, and valve timing can return to the pre-DFSO valve timing.

[0037] With reference to Fig.4 is a chart 400 illustrating operational plotter representations of interest during execution of methods 200 and / or 300 described above. Chart 400 illustrates fuel injection state (as shown by curve 404), throttle position (as shown by curve 410), particulate filter temperature (as shown by curve 416), intake and exhaust valve overlap (as shown by curve 422), manifold pressure (as shown by curve 428), accelerator pedal position (as shown by curve 434), and vehicle speed (as shown by curve 440). For each operational plotter representation, time is plotted along the horizontal axis, and respective values ​​for each parameter are plotted along the vertical axis.

[0038] Prior to time t1, the vehicle operates under standard, non-DFSO conditions. Fuel injection is therefore active, the throttle is controlled and held partially open based on the torque requested by the operator, the particulate filter temperature is relatively low (below the first threshold temperature T1), the valve overlap is at an amount based on operating parameters (as shown, the valve overlap is relatively low), the MAP is above the threshold pressure P1, the accelerator pedal is partially depressed, and the vehicle speed is maintained at a desired speed. At time t1, the operator releases the accelerator pedal, as shown by curve 434, due, for example, to crossing an inclined road surface, and the vehicle speed begins to slowly decrease.Due to the deceleration, combustion is not necessary to maintain the desired vehicle speed and therefore fuel injection is turned off as shown by curve 404.

[0039] Once fuel injection is deactivated, the throttle may initially assume a predetermined position, such as partially open. However, as the particulate filter reaches the first threshold temperature at time t1, the throttle is subsequently fully closed to prevent particulate filter degradation. Because MAP is maintained above the threshold pressure P1, the throttle is maintained fully closed, and valve overlap is not adjusted for the duration of the DFSO event.

[0040] At time t2, the operator presses the accelerator pedal, and the vehicle exits DFSO by resuming fuel injection. The throttle is controlled based on the torque requested by the operator and therefore moves away from the fully closed position. Due to the lack of hot exhaust gas and oxygen delivered to the particulate filter during DFSO, the particulate filter temperature has fallen below the first threshold temperature, although it begins to rise again following time t2.

[0041] At time t3, another DFSO event is initiated where fuel injection is deactivated due to vehicle deceleration / accelerator pedal release. The throttle is moved to the fully closed position because the particulate filter temperature is at the first threshold temperature. However, unlike the first DFSO event, at time t4, MAP drops below the threshold pressure. To increase MAP, since the particulate filter temperature is below the second threshold temperature, the throttle is opened a small amount. However, opening the throttle results in the particulate filter temperature increasing to the second threshold temperature at time t5. Furthermore, while opening the throttle valve at time t4 initially caused an increase in MAP, at time t5, MAP drops below the threshold pressure again.Therefore, to increase the MAP, the valve timing is adjusted to increase the valve overlap amount at time t5.

[0042] At time t6, the operator presses the accelerator pedal again, resulting in the vehicle exiting DFSO by activating fuel injection, opening the throttle, controlling the throttle position based on the requested torque, and reducing the valve overlap amount back to the pre-DFSO overlap amount.

[0043] Thus, fully closing the throttle in DFSO results in a much slower increase in particulate filter temperature, allowing longer DFSO events and therefore increasing fuel economy. MAP can be controlled based on particulate filter temperature such that MAP is increased by slightly opening the throttle if particulate temperature is not too high, or by increasing valve overlap if particulate temperature is too high. Although closing the throttle during DFSO can prevent events with excessive particulate filter temperature, under certain circumstances the particulate filter may still reach the threshold temperature. Under such circumstances, the vehicle may exit DFSO to prevent filter degradation.

[0044] Closing the throttle during DFSO can also improve the consistency of shutdown exhaust flow. The throttle flow may not be affected by other strategy features implemented to increase airflow in anticipation of fuel restoration, such as air conditioning and alternator loads. For example, if the vehicle is predicted to exit DFSO, additional loads can be applied to the engine to increase engine power. If the throttle is closed when the loads are applied, the throttle can be opened to allow an increase in airflow to generate the additional engine power.

[0045] The technical effect of closing the throttle during DFSO and controlling MAP based on particulate filter temperature is to prevent particulate filter degradation during DFSO while increasing the duration of DFSO to improve fuel economy while maintaining MAP above the threshold pressure.

[0046] As one embodiment, a method for an engine includes, in response to a particulate filter temperature above a threshold temperature and during deceleration fuel shut-off (DFSO) operation of the engine, fully closing a throttle valve configured to regulate intake air flow to the engine, and, in response to a manifold pressure falling below a threshold pressure while the throttle valve is fully closed, adjusting a position of the throttle valve based on the particulate filter temperature. In a first example of the method, when the particulate filter temperature is above the threshold temperature and below a second, higher threshold temperature, adjusting the position of the throttle valve based on the particulate filter temperature includes opening the throttle valve by a predetermined amount to increase the manifold pressure.A second example of the method optionally includes the first example, and further wherein adjusting the position of the throttle valve based on the particulate filter temperature comprises, when the particulate filter temperature is above the second threshold temperature, maintaining the throttle valve fully closed and adjusting intake and exhaust valve timing to increase manifold pressure. A third example of the method optionally includes one or both of the first and second examples, and further wherein adjusting the intake and exhaust valve timing comprises increasing intake and exhaust valve overlap.A fourth example of the method optionally includes one or more or each of the first through third examples, and further includes that operating the engine with DFSO comprises transmitting engine output to vehicle wheels via a transmission, and disabling fuel injection to the engine during a deceleration condition of a vehicle in which the engine is installed. A fifth example of the method optionally includes one or more or each of the first through fourth examples, and further includes, in response to the particulate filter temperature being below the threshold temperature while the engine is operating in DFSO, maintaining the throttle valve at a fully open or partially open position.A sixth example of the method optionally includes one or more or each of the first through fifth examples, and further includes, in response to a request to exit DFSO operation, enabling fuel injection to the engine and adjusting a position of the throttle valve based on the requested torque. A seventh example of the method optionally includes one or more or each of the first through sixth examples, and further includes adjusting a position of the throttle valve based on the requested torque comprising adjusting a position of the throttle valve based on an operator requested torque.An eighth example of the method optionally includes one or more or each of the first through seventh examples, and further includes that adjusting a position of the throttle valve based on the requested torque comprises adjusting a position of the throttle valve based on torque requested by the vehicle, including one or more auxiliary loads placed on the engine. A ninth example of the method optionally includes one or more or each of the first through eighth examples, and further includes, prior to exiting DFSO operation, increasing one or more auxiliary loads placed on the engine and opening the throttle valve in response to a predicted subsequent exit from DFSO operation.

[0047] One embodiment of a system includes an engine having a plurality of cylinders, each cylinder having at least one intake valve and at least one exhaust valve, a throttle valve controlling the flow of intake air to the engine, a particulate filter coupled to the engine via an exhaust passage, and a controller having computer-readable instructions stored on non-transitory memory to: initiate a deceleration fuel shut-off (DFSO) event during a vehicle deceleration event by disabling fuel supply to the plurality of cylinders of the engine, closing the throttle valve in response to initiating the DFSO event, and, when a manifold pressure of the engine falls below a threshold pressure, adjusting intake and / or exhaust valve timing based on a temperature of the particulate filter.In a first example of the system, adjusting intake and / or exhaust valve timing based on a temperature of the particulate filter includes adjusting intake and / or exhaust valve timing to increase valve overlap when the temperature of the particulate filter is above a threshold temperature. A second example of the system optionally includes the first example and further includes increasing valve overlap compared to an amount of valve overlap prior to initiating the DFSO event. A third example of the system optionally includes one or more or each of the first and second examples and further includes the controller further having instructions to open the throttle valve by a predetermined amount when the intake manifold pressure is below the threshold pressure and the temperature of the particulate filter is below the threshold temperature.A fourth example of the system optionally includes one or more or each of the first through third examples, and further includes the controller having further instructions to, in response to a request to exit DFSO, open the throttle valve and reactivate fueling. A fifth example of the system optionally includes one or more or each of the first through third examples, and further includes the fueling to the plurality of cylinders of the engine comprising a direct injection gasoline fuel supply.

[0048] An embodiment of a method for an engine includes initiating a deceleration fuel shutoff (DFSO) event by disabling fuel injection to the engine and moving a throttle valve coupled upstream of the engine to a preset, at least partially open position, fully closing the throttle valve in response to a particulate filter temperature above a threshold temperature, and maintaining manifold pressure above a threshold pressure by adjusting intake and / or exhaust valve timing. In a first example of the method, the method further includes, prior to initiating the DFSO event, operating with a first amount of intake and exhaust valve overlap, wherein adjusting the intake and / or exhaust valve timing includes adjusting the intake and / or exhaust valve timing to operate with a second amount of intake and exhaust valve overlap.A second example of the method optionally includes the first example and further includes where fully closing the throttle valve comprises fully closing the throttle valve while maintaining operation with the first amount of intake and exhaust valve overlap. A third example of the method optionally includes one or more or both of the first and second examples and further includes, in response to a request to exit the DFSO event, activating fuel injection, adjusting the throttle valve based on the operator requested torque, and adjusting intake and / or exhaust valve timing to operate with the first amount of intake and exhaust valve overlap.

[0049] It should be appreciated that the exemplary control and estimation routines included herein may be used with various engine and / or vehicle system configurations. The control methods and routines disclosed herein may be stored as executable instructions in non-transitory memory and may be executed by the control system comprising the controller combined with the 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, multitasking, multithreading, and the like. Therefore, various actions, operations, and / or functions may be performed in the illustrated order, in parallel, or in some cases, omitted.Likewise, the order of processing is not necessarily required to achieve the features and advantages of the embodiments described herein, but is provided for ease of illustration and description. One or more of the illustrated actions, operations, and / or functions may be performed repeatedly depending on the particular strategy employed. Furthermore, the described actions, operations, and / or functions may graphically represent code to be programmed into non-transitory memory of the computer-readable storage medium in the engine control system, wherein the described actions are performed by executing the instructions in a system including the various engine hardware components in combination with the electronic control device.

[0050] It is understood that the configurations and routines disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered limiting, as numerous variations are possible. For example, the above technology may be applied to V-6, I-4, I-6, V-12, horizontally opposed four, 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 characteristics disclosed herein.

[0051] The following claims particularly point out certain combinations and subcombinations that are considered novel and non-obvious. These claims may refer to "a" element or "a first" element, or the equivalent thereof. Such claims should be understood to encompass the inclusion 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 amending the present claims or by presenting new claims in this or a related application. Such claims, whether broader, narrower, the same, or different in scope from the original claims, are also considered to be encompassed within the subject matter of the present disclosure.

Claims

[1] Method for an internal combustion engine (10), comprising: in response to a particulate filter temperature above a threshold temperature and during operation of the engine (10) with deceleration fuel shutoff (DFSO), fully closing a throttle valve configured to regulate the flow of intake air to the engine (10), and in response to an intake manifold pressure falling below a threshold pressure while the throttle valve is fully closed, adjusting a position of the throttle valve based on the particulate filter temperature. [2] The method of claim 1, wherein adjusting the position of the throttle valve based on the particulate filter temperature comprises, when the particulate filter temperature is above the threshold temperature and below a second, higher threshold temperature, opening the throttle valve by a predetermined amount to increase the intake manifold pressure. [3] The method of claim 2, wherein adjusting the position of the throttle valve based on the particulate filter temperature includes, when the particulate filter temperature is above the second threshold temperature, maintaining the throttle valve fully closed and adjusting intake and exhaust valve timing to increase the intake manifold pressure. [4] The method of claim 3, wherein adjusting intake and exhaust valve timing comprises increasing intake and exhaust valve overlap. [5] The method of claim 1, wherein operating the engine (10) with DFSO comprises transmitting engine output to vehicle wheels via a transmission, and disabling fuel injection to the engine (10) during a deceleration condition of a vehicle in which the engine (10) is installed. [6] The method of claim 1, further comprising, in response to the particulate filter temperature being below the threshold temperature while the engine (10) is operating in DFSO, maintaining the throttle valve in a fully open or partially open position. [7] The method of claim 1, further comprising, in response to a request to exit DFSO operation, enabling fuel injection to the engine (10) and adjusting a position of the throttle valve based on the requested torque. [8] The method of claim 7, wherein adjusting a position of the throttle valve based on requested torque comprises adjusting a position of the throttle valve based on torque requested by the operator. [9] The method of claim 7, wherein adjusting a position of the throttle valve based on the requested torque comprises adjusting a position of the throttle valve based on torque requested by the vehicle including one or more auxiliary loads placed on the machine (10). [10] The method of claim 9, further comprising, prior to exiting DFSO operation, increasing one or more auxiliary loads placed on the engine (10) and opening the throttle valve in response to a predicted subsequent exit from DFSO operation. [11] System comprising: an engine (10) having a plurality of cylinders (30), each cylinder (30) having at least one intake valve and at least one exhaust valve, a throttle valve that controls the flow of intake air to the engine (10), a particulate filter coupled to the engine (10) via an exhaust passage, and a control device (12) having computer-readable instructions stored on the non-volatile memory to: initiate a deceleration fuel shutoff (DFSO) event during a vehicle deceleration event by deactivating fuel supply to the plurality of cylinders (30) of the engine (10), close the throttle valve in response to the DFSO event, and when the intake manifold pressure of the engine (10) falls below a threshold pressure, adjusting the intake manifold and / or exhaust valve timing based on a temperature of the particulate filter. [12] The system of claim 11, wherein adjusting intake and / or exhaust valve timing based on a temperature of the particulate filter comprises adjusting intake and / or exhaust valve timing to increase valve overlap when the temperature of the particulate filter is above a threshold temperature. [13] The system of claim 12, wherein the valve overlap is increased compared to a valve overlap amount prior to initiating the DFSO event. [14] The system of claim 12, wherein the controller (12) further has instructions to open the throttle valve by a predetermined amount when the intake manifold pressure is below the threshold pressure and the temperature of the particulate filter is below the threshold temperature. [15] The system of claim 11, wherein the controller (12) further has instructions to open the throttle valve and re-enable fueling in response to a request to exit DFSO. [16] The system of claim 11, wherein the fuel supply to the plurality of cylinders (30) of the engine (10) comprises a direct injection gasoline fuel supply.

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