METHODS AND SYSTEMS FOR IMPROVING CHARGING RESPONSE BEHAVIOR

Abstract

Method for a turbocharged engine (10) comprising the following: in response to determining, with an engine control, a deceleration event, and with the engine control: deactivating fuel injectors (50) to all cylinders of the engine (10), while the airflow through a turbine (62) of a turbocharger is increased in response to the determination that a temperature of an exhaust catalyst downstream of the turbine (62) is between an upper threshold and a lower threshold, characterized in that the deceleration event is triggered following a tip-in event.

Description

Field of invention

[0001] The present description generally relates to methods and systems for controlling a vehicle engine to reduce turbocharger response delay in internal combustion engines having at least one turbocharger. State of the art / brief description

[0002] A method according to the preamble of claim 1 or claim 10 is already known from DE 10 2014 210 642 A1. Further methods are known from DE 10 2014 218 409 A1 and DE 35 44 247 A1.

[0003] Turbocharging an engine allows the engine to produce similar power to a larger displacement engine while keeping the engine pumping work close to that of a non-turbocharged engine of similar displacement. Thus, turbocharging can expand an engine's operating range. Turbocharged engines use a turbocharger to compress intake air and increase the engine's power output. A turbocharger may use an exhaust-driven turbine to drive a compressor, which compresses the intake air. As the compressor speed increases, more boost pressure is provided to the engine. However, under certain vehicle start-up conditions, such as accelerating from idle, it may take some time for the turbine and compressor to accelerate and provide the required boost pressure due to minimal exhaust flow combined with increased load on the compressor.This delay in turbocharger response, known as turbocharger response lag, can result in a delay in delivering the requested engine power.

[0004] An exemplary approach to reducing turbocharger response delay is shown by Pallett et al. in US Pat. No. 8,355,858 B2. This approach utilizes a first and second fuel injection amount during deceleration and / or idle conditions when the driver's tip-in is imminent, with the first amount producing lean combustion and sufficient torque to maintain engine speed, while the second injection, injected after lean combustion, provides additional exhaust reductant to match the excess combustion air and generate sufficient exhaust energy to maintain the turbocharger speed at a target speed.

[0005] However, the inventors have identified potential problems with such approaches. For example, because such operations to reduce turbocharger response delay are only performed when the driver's tip-in is imminent, the turbine speed is allowed to decrease significantly during deceleration, and thus the energy required to increase the turbine speed is greater. Thus, fuel injection is required to provide the additional exhaust energy to spin the turbine, increasing fuel consumption and deteriorating fuel economy. While the second injection may maintain the overall air-fuel ratio at stoichiometry, unburned fuel in the exhaust gas can still react with the exhaust catalyst and raise the temperature of the exhaust catalyst, increasing the risk of thermal damage to the exhaust catalyst.In order to control engine speed when increasing turbine speed, it may still be necessary to limit the power generated during combustion, for example, by airflow adjustments and / or by ignition retardation, which, in addition to deteriorating fuel economy, degrades engine efficiency.

[0006] According to the invention, methods according to claim 1 and claim 10 as well as a turbocharged engine system according to claim 16 are proposed. Advantageous embodiments of the invention are specified in the dependent claims and the following description.

[0007] Thus, in one example, some of the above-noted problems may be addressed, at least in part, by a method for a boosted engine according to claim 1. By thus increasing airflow to the turbine under selected conditions, boost response during subsequent tip-in may be improved.

[0008] As an example, if tip-out conditions favor fuel cutoff upon deceleration and the exhaust catalyst temperature is within a threshold range, the fuel injectors for all engine cylinders may be deactivated in response to a tip-out that occurs after a long and large tip-in. At the same time, airflow through a turbine may be increased (e.g., by opening an air intake throttle, closing a wastegate, etc.), resulting in increased turbine speed. Furthermore, airflow through the turbine may be adjusted to maintain turbine speed above a threshold speed. Thus, during tip-out, the turbine speed is not allowed to drop below a threshold due to the increased airflow to the turbine.By keeping the turbine speed above the threshold, the time it takes to ramp up the turbine to a required speed during a subsequent tip-in is reduced. Consequently, the turbocharger response delay is reduced and boost response is improved.

[0009] Furthermore, airflow through the turbine can only be increased if tip-out occurs after a long and / or large tip-in. Thus, the turbine speed at the onset of deceleration fuel cut-off is sufficient to allow a more rapid increase in turbine speed above the threshold with reduced actuator settings. By further increasing airflow only when the fuel injectors are deactivated, measures to limit the power produced during combustion (e.g., spark retard) may not be utilized, thereby increasing fuel economy and engine braking efficiency. By further increasing airflow during deceleration fuel cut-off conditions only when the exhaust catalyst temperature is within a threshold range, exhaust catalyst efficiency can be improved and thermal damage due to excessive exhaust heat can be reduced.

[0010] It should be understood that the Summary above 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 this disclosure. Short description of the drawings Fig. 1 is a block diagram of a vehicle powertrain. Fig. Figure 2 is a schematic diagram showing aspects of the engine from Fig. 1 shows. Fig. 3 shows a flowchart illustrating an example method for adjusting airflow through a turbine of a turbocharger under selected deceleration conditions. Fig. 4 shows a flowchart illustrating an example method for adjusting one or more actuators to increase airflow through the turbine. Fig. 5 shows an example adjustment of airflow through the turbine based on vehicle operating conditions according to the present disclosure. Detailed description

[0011] The following description relates to systems and methods for improving boost response in a turbocharged engine system, such as the engine system of Fig. 2, which feeds a vehicle drive train, such as the drive train from Fig. 1. A controller may be designed to execute a control routine, such as the routine in Fig. 3, to increase airflow through an exhaust turbine of the turbocharged engine to increase and maintain turbine speed at or above a threshold speed under selected deceleration conditions. The selected deceleration conditions may include deceleration fuel cut-off conditions where deceleration occurs following a strong throttle input condition (tip-in above a threshold), and when an exhaust catalyst temperature is within a threshold range. The airflow through the turbine may be increased according to the example routine of Fig. 4 by adjusting one or more actuators of the engine system. An exemplary adjustment of the air flow through the turbine according to the present disclosure during vehicle operation is shown in Fig. 5 shown.

[0012] Fig. 1 is a block diagram of a vehicle powertrain 20. The powertrain 20 may be powered by the engine 10. The engine 10 may be started, for example, with an engine starting system 19 including a motor-driven starter. The starter motor may be operated, for example, using power from the battery 46. Furthermore, the engine 10 may generate or adjust torque via the torque actuator 26, such as a fuel injector, a throttle, etc.

[0013] Engine output torque may be transferred to torque converter 28 to drive an automatic transmission 30. Further, one or more clutches 31 may be engaged, including forward clutch 32, to propel the automobile. In one example, torque converter 28 may be referred to as a component of transmission 30. Transmission 30 may include a plurality of gear clutches 33 that may be engaged as needed to activate a plurality of fixed transmission gear ratios. In particular, by adjusting the engagement of the plurality of gear clutches 33, the transmission may be shifted between a higher gear (i.e., a gear with a lower gear ratio) and a lower gear (i.e., a gear with a higher gear ratio).As such, the gear ratio differential allows for a lower torque gain through the transmission when the higher gear is engaged, while allowing for a higher torque gain through the transmission when the lower gear is engaged. A controller may adjust the transmission gear (e.g., shift the transmission gear up or down) to adjust a torque transmitted through the transmission and torque converter to the vehicle wheels 36 (i.e., an engine shaft output torque).

[0014] The output of the torque converter may be controlled by the torque converter lock-up clutch 34. For example, when the torque converter lock-up clutch 34 is fully disengaged, the torque converter 28 transfers engine torque to the automatic transmission 30 via fluid communication between the torque converter turbine and the torque converter impeller, enabling torque amplification. In contrast, when the torque converter lock-up clutch 34 is fully engaged, the engine output torque is transferred directly via the torque converter clutch to an input shaft (not shown) of the transmission 30. Alternatively, the torque converter lock-up clutch 34 may be partially engaged, allowing the torque sent to the transmission to be adjusted.

[0015] A controller 12 may be configured to adjust the torque transmitted by the torque converter 28 by adjusting the torque converter lock-up clutch in response to various engine operating conditions or based on a driver-based engine operation request. In one example, an engine operation request may be received from the vehicle user via an accelerator pedal and / or a brake pedal (in Fig. 2). The torque output from the automatic transmission 30 may, in turn, be transmitted to wheels 36 to propel the vehicle. Specifically, the automatic transmission 30 may transmit input drive torque at the input shaft (not shown) in response to a vehicle driving condition before transmitting output drive torque to the wheels.

[0016] Furthermore, a frictional force may be applied to the wheels 36 by engaging the wheel brakes 38. In one example, the wheel brakes 38 may be engaged in response to the driver pressing their foot on a brake pedal. In the same way, a frictional force on the wheels 36 may be reduced by disengaging the wheel brakes 38 in response to the driver removing their foot from the brake pedal. Furthermore, the vehicle brakes may apply a frictional force to the wheels 36 as part of an automated engine stop procedure. In some examples, the transmission may be connected to a transmission case to assist the vehicle brakes in holding the vehicle stationary.

[0017] A mechanical oil pump 40 may be in fluid communication with the automatic transmission 30 to provide hydraulic pressure to engage the various clutches 31, such as the forward clutch 32, the gear clutches 33, and / or the torque converter lock-up clutch 34. The mechanical oil pump 40 may operate in conjunction with the torque converter 28 and may be driven, for example, by the rotation of the engine or the transmission input shaft. Thus, the hydraulic pressure generated in the mechanical oil pump 40 may increase as the engine speed increases and may decrease as the engine speed decreases. An electric oil pump 41, also in fluid communication with the automatic transmission but operating independently of the drive power of the engine 10 or the transmission 30, may be provided to supplement the hydraulic pressure of the mechanical oil pump 40.The electric oil pump 41 can be driven by an electric motor (not shown) to which electrical power can be supplied, for example, from the battery 46.

[0018] The controller 12 may be configured to receive inputs from the engine 10, as shown in Fig. 2, and accordingly control engine torque output and / or operation of the torque converter, transmission, clutches, and / or brakes. As an example, torque output may be controlled by adjusting a combination of spark timing, fuel pulse width, fuel pulse timing, and / or air charge by controlling throttle opening and / or valve timing, valve lift, and boost pressure for turbocharged or mechanically boosted engines. For a diesel engine, controller 12 may control engine torque output by controlling a combination of fuel pulse width, fuel pulse timing, and air charge. Engine control may be performed on a cylinder-by-cylinder basis to control engine torque output (e.g., in all cases).The controller 12 may request a shift and set the transmission shift request flag based on various engine and vehicle operating parameters, including, but not limited to, the current transmission gear, engine speed, and accelerator pedal position - for example, threshold changes in accelerator pedal position for an appropriate duration may trigger a shift.

[0019] Fig. Figure 2 is a schematic diagram illustrating aspects of the engine 10 of Fig. 1. The engine 10 is shown with four cylinders 29. However, other numbers of cylinders may be used in accordance with the present disclosure. The engine 10 may be controlled at least in part by a control system including a controller 12 and by input from a vehicle user 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. Each combustion chamber (e.g., cylinder) 29 of the engine 10 may include combustion chamber walls with a piston (not shown) positioned therein. The pistons may be coupled to a crankshaft 39 such that reciprocating motion of the piston is translated into rotational motion of the crankshaft. The crankshaft 39 may be coupled, for example, via the transmission 30, to at least one drive wheel of a vehicle.Furthermore, a starter motor can be coupled to the crankshaft 39 via a flywheel to enable starting of the engine 10.

[0020] Combustion chambers 29 may receive intake air from an intake manifold 44 via intake passage 42 and may expel combustion exhaust gases via exhaust passage 48. Intake manifold 44 and exhaust manifold 45 may be selectively connected to combustion chamber 29 via respective intake valves and exhaust valves (not shown). In some embodiments, combustion chamber 29 may include two or more intake valves and / or two or more exhaust valves.

[0021] The fuel injectors 50 are shown coupled directly to the combustion chamber 29 so that fuel is injected directly into them in proportion to the pulse width of the FPW signal received from the controller 12. In this manner, the fuel injector 50 provides what is known as direct fuel injection into the combustion chamber 29. 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 50 by a fuel system (not shown) including a fuel tank, a fuel pump, and a fuel rail.In some embodiments, the combustion chambers 29 may alternatively or additionally include a fuel injector disposed in the intake manifold 44 in a configuration that provides what is known as port injection of fuel into the intake port upstream of each combustion chamber 29.

[0022] The intake passage 42 may include throttles 21 and 23 with throttle bodies 22 and 24, respectively. In this particular example, the positions of throttle bodies 22 and 24 may be adjusted by the controller 12 via signals provided to an actuator included in the throttles 21 and 23. In one example, the actuators may be electric actuators (e.g., electric motors), a configuration commonly referred to as electronic throttle control (ETC). In this manner, the throttles 21 and 23 may be operated to adjust the intake air provided to the combustion chamber 29, among other engine cylinders. The position of the throttle bodies 22 and 24 may be provided to the controller 12 by the throttle position signal TP.The intake passage 42 may further include a mass air flow sensor 120, a manifold pressure sensor 122, and a throttle inlet pressure sensor 123 to provide respective MAF (mass air flow) and MAP (manifold pressure) signals to the controller 12.

[0023] In one example, as described below, under tip-out conditions, airflow to turbine 48 may be increased by opening throttle 21 and 23 instead of maintaining closed throttle conditions. By increasing airflow to the turbine, turbine speed may be maintained at or above a threshold during deceleration conditions so that during a subsequent tip-in, a duration to increase turbine speed to a requested speed is reduced, thereby improving boost response. Furthermore, airflow to the turbine may only be increased when deceleration conditions favor a power cut event. Consequently, measures to reduce combustion power (e.g., spark retard) may not be required.Further, airflow to the turbine may only be increased while the exhaust catalyst temperature is within a threshold range to reduce emissions and reduce thermal damage to the catalyst. Details of increasing airflow to the turbine according to the present disclosure are discussed with respect to FIG. Fig. 3 - 5 further elaborated.

[0024] The exhaust passage 48 may receive exhaust gases from the cylinders 29. The exhaust gas sensor 128 is shown coupled to the exhaust passage 48, upstream of the turbine 62 and to the emission control device 78. The sensor 128 may be selected from various suitable sensors for providing an indication of the air-fuel ratio in the exhaust gas, such as a linear oxygen sensor or UEGO (Universal Exhaust Gas Oxygen), a two-point oxygen sensor or EGO (Exhaust Gas Oxygen), a NOx, HC, or CO sensor. The emission control device 78 may be a three-way catalyst (TWC), a NOx trap, various other emission control devices, or combinations thereof. Although Fig. 2, it is understood that a similarly configured intake air sensor may be included in engine 10 (e.g., coupled to intake passage 42) to enable sensing of intake gas AFR (Air-Fuel Ratio). As with exhaust gas sensor 128, the intake air sensor may be any suitable sensor for providing an indication of intake air AFR, such as a linear oxygen sensor or UEGO, a two-point oxygen sensor or EGO, a HEGO (Heated EGO), a NO x- , HC or CO sensor.

[0025] The exhaust gas temperature may be measured by one or more temperature sensors (not shown) located in the exhaust passage 48. Alternatively, the exhaust gas temperature may be derived based on engine operating conditions, such as speed, load, AFR, spark retard, etc.

[0026] In Fig. 2, the controller 12 is shown as a microcomputer including the microprocessor unit 102, the input / output ports 104, an electronic storage medium for executable programs and calibration values, shown in this particular example as a read-only memory chip 106, the random access memory 108, the keep alive memory 110, and a data bus.The controller 12 may receive various signals from sensors coupled to the engine 10, in addition to the signals previously discussed, including measurements of the inducted mass air flow (MAF) from the mass air flow sensor 120, the engine coolant temperature (ECT) from the temperature sensor 112, which is schematically shown at a location within the engine 10, a crankshaft position signal (PIP) from the Hall sensor 118 (or other type) coupled to the crankshaft 39, the throttle position (TP) from a throttle position sensor, as discussed, and an absolute manifold air pressure (MAP) signal from the sensor 122, as discussed. The engine speed signal RPM may be generated by the controller 12 based on the PIP signal.The manifold pressure signal MAP from a manifold pressure sensor may be used to provide an indication of vacuum or pressure within the intake manifold 44. 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. Furthermore, 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 39.In some examples, the read-only memory storage medium 106 may be programmed with computer-readable data representing instructions executable by the processor 102 to perform the methods described below, as well as other variations anticipated but not specifically listed. The controller 12 receives signals from the various sensors in . Fig. 1 and Fig. 2 and exposes the various actuators Fig. 1 and Fig. 2 to adjust the motor operation based on the received signals and the instructions stored in a memory of the controller.

[0027] The engine 10 may further include a compression device, such as a turbocharger or a supercharger including at least one compressor 60 disposed along the intake manifold 44. For a turbocharger, the compressor 60 may be driven at least in part by a turbine 62, for example, via a shaft or other coupling arrangement. The turbine 62 may be disposed along the exhaust passage 48 and in communication with the exhaust gases flowing therethrough. Various arrangements may be provided to control the compressor. For a supercharger, the compressor 60 may be driven at least in part by the engine 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 adjusted by the controller 12.In some cases, for example, the turbine 62 may drive an electric generator 64 to provide power to a battery 66 via a turbo driver 68. The power from the battery 66 may then be used to drive the compressor 60 via a motor 70. Furthermore, a sensor 123 may be disposed in the intake manifold 44 to provide a BOOST signal to the controller 12.

[0028] Furthermore, the exhaust passage 48 may include a wastegate 25 for directing exhaust gas away from the turbine 62. In some embodiments, the wastegate 25 may be a multi-stage wastegate, such as a two-stage wastegate having a first stage configured to control boost pressure and a second stage configured to increase heat flow to the emission control device 78. The wastegate 25 may be actuated with an actuator 150, which may be an electric actuator, such as an electric motor, although pneumatic actuators are also contemplated. The intake passage 42 may include a compressor bypass valve 27 configured to bypass intake air around the compressor 60. The wastegate 25 and / or the compressor bypass valve 27 may be controlled by the controller 12, for example, via actuators (e.g.,the actuator 150) so that they are opened, for example, when a lower boost pressure is required.

[0029] Intake passage 42 may further include charge air cooler (CAC) 80 (e.g., an intercooler) to reduce the temperature of intake gases boosted by the turbocharger or supercharger. In some embodiments, charge air cooler 80 may be an air-to-air heat exchanger. In other embodiments, charge air cooler 80 may be an air-to-liquid heat exchanger.

[0030] Furthermore, in the disclosed embodiments, an exhaust gas recirculation (EGR) system may direct a requested portion of exhaust gas from the exhaust passage 48 via the EGR passage 140 to the intake passage 42. The amount of EGR provided to the intake passage 42 may be adjusted by the controller 12 via the EGR valve 142. Further, an EGR sensor (not shown) may be disposed within the EGR passage and may provide an indication of one or more of the pressure, temperature, or concentration of the exhaust gas. Alternatively, the EGR may be controlled by a calculated value based on signals from the MAF sensor (upstream), the MAP (intake manifold), the MAT (manifold gas temperature), and the crankshaft speed sensor. Further, the EGR may be controlled based on an exhaust O2 sensor and / or an intake manifold oxygen sensor.Under some conditions, the EGR system can be used to regulate the temperature of the air and fuel mixture within the combustion chamber. Fig. Figure 2 shows a high-pressure EGR system in which the EGR is routed from upstream of a turbocharger turbine to downstream of a turbocharger compressor. In other embodiments, the engine may additionally or alternatively include a low-pressure EGR system in which the EGR is routed from downstream of a turbocharger turbine to upstream of a turbocharger compressor.

[0031] In one example, the systems of Fig. 1 and Fig. 2 enable a system for a turbocharged engine system, comprising: an engine including an intake manifold and an exhaust manifold; a compressor coupled to the intake manifold and driven by a turbine coupled to the exhaust manifold; an air intake throttle positioned within an intake passage upstream of a compressor, the intake passage coupling the compressor to ambient air; an exhaust catalyst coupled within an exhaust passage downstream of the turbine, the exhaust passage coupling the catalyst to ambient air; one or more fuel injectors supplying fuel to the engine; an accelerator pedal for receiving a user torque request;and a controller having executable instructions stored in non-volatile memory to: deactivate all fuel injectors in response to an accelerator pedal tip-out event initiated subsequent to a tip-in event; and, under a first condition, flow ambient air to the turbine and engine via the compressor while maintaining deactivation of the fuel injectors; under a second condition, flow ambient air to the turbine via the engine by passing through the compressor while maintaining deactivation of the fuel injectors; and, under a third condition, cease flowing air to the turbine while maintaining deactivation of the fuel injectors;and wherein the first condition includes an exhaust catalyst temperature being between a lower threshold and a first upper threshold; wherein the second condition includes the exhaust catalyst temperature being at or above the first upper threshold and below a second upper threshold, the second upper threshold being greater than the first upper threshold;and wherein the third condition includes the exhaust catalyst temperature being at or above the second upper threshold. The system further includes where flowing air to the turbine includes increasing an opening of the air intake throttle based on a requested turbine speed. The system further includes where the controller further includes instructions to: in response to application of the accelerator pedal following the tip-out, activate one or more fuel injectors and adjust flow through the turbine based on a user torque request;

[0032] Fig. 3 shows a flowchart illustrating an example method 300 for reducing turbocharger response delay in a boosted engine. Specifically, method 300 includes increasing airflow through an exhaust turbine of the boosted engine under selected deceleration fuel shutoff conditions to improve boost response. Method 300 is described herein with reference to the Fig. 1 and Fig. 2, although it is understood that the method may be applied to other systems without departing from the scope of this disclosure. Instructions for carrying out method 300 and the other methods included herein may be executed by a controller, such as controller 12 in the Fig. 1 - 2, 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 respect to the Fig. 1 - 2. The controller may use motor actuators of the engine system to adjust engine operation according to the procedures described below.

[0033] At 302, method 300 includes estimating and / or measuring engine operating conditions. These may include, for example, exhaust catalyst temperature, engine speed and load, driver-requested torque (based on throttle position), MAP, MAF, BP, engine temperature, EGR amount, air-fuel ratio, boost pressure, etc. Based on the engine operating conditions and the torque request, the vehicle controller may adjust one or more engine actuator settings. The adjusted actuator settings may include, for example, variable cam timing (VCT), AFR, throttle opening, spark advance, etc.

[0034] At 304, method 300 may include determining whether the engine is operating under defueled conditions. Defueled conditions may include engine operating conditions where fueling is interrupted, but the engine continues to rotate and at least one intake valve and one exhaust valve are operating; thus, air flows through one or more cylinders, but no fuel is injected into the cylinders. During defueled conditions, no combustion is performed, and ambient air is allowed to move from the intake port through the cylinder to the exhaust port. Defueled conditions may include, for example, deceleration fuel shut-off (DFSO). DFSO may occur in response to an accelerator pedal and may occur repeatedly during a drive cycle.Accordingly, in one example, the method may include determining whether engine operating conditions are suitable for triggering DFSO. During DFSO, the engine may operate without fuel injection while rotating and pumping air through the cylinders. In some examples, 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 to trigger DFSO. In one example, DFSO may be triggered if the engine speed is below a speed threshold. In another example, DFSO may be triggered if the engine load is below a threshold. In yet another example, DFSO may be triggered based on an accelerator pedal position and / or a change in the accelerator pedal position for an appropriate duration—e.g.,DFSO may be triggered if a threshold change in accelerator pedal position indicates that a driver tip-out has occurred. Additionally or alternatively, DFSO may be triggered if the vehicle has remained in tip-out conditions (e.g., accelerator pedal is released) for a threshold duration. Additionally or alternatively, entry into DFSO may continue to be determined based on a command signal to stop fuel injection.

[0035] If the fuel-off conditions are not confirmed (i.e., if the answer at 304 is NO), method 300 proceeds to 306. At 306, method 300 includes operating the engine based on current operating conditions. For example, one or more engine actuator settings, such as VCT, AFR, throttle opening, spark timing, etc., may be adjusted based on current engine operating conditions and the torque request. The method may then end.

[0036] If the conditions for fuel-free operation are confirmed (i.e., if the answer at 304 is YES), method 300 proceeds to 308. At 308, method 300 includes initiating fuel shutoff. For example, fuel shutoff may be initiated by stopping fuel injection to the engine. That is, fuel injection may be stopped for all cylinders. For example, control may stop operation of one or more fuel injectors (such as the one shown in Fig. 2) via one or more fuel injector actuators. To deactivate one or more fuel injectors, the controller may remove voltage to the one or more fuel injector actuators. Additionally, in some examples, spark ignition may be terminated in spark-ignition engines.

[0037] After initiating the fuel shutoff, method 300 proceeds to 310. At 310, method 300 includes determining whether a tip-out from closed throttle conditions occurred, and further includes determining whether the tip-out occurred after a tip-in, where a duration of the tip-in is greater than a threshold duration and / or an accelerator pedal deflection (i.e., a depression of the accelerator pedal) during the tip-in is greater than a threshold deflection. In other words, it may be determined whether the vehicle user operated with a high accelerator pedal input (the accelerator pedal input proportional to the depression of the accelerator pedal to on) that was above a threshold input and then transitioned to a zero accelerator pedal input (tip-out).Additionally or alternatively, it may be determined whether the vehicle user operated with an accelerator pedal input greater than zero for a duration longer than the threshold duration and then transitioned to an accelerator pedal input of zero.

[0038] If the answer at 310 is NO, method 300 proceeds to 314. At 314, method 300 includes maintaining fuel shutoff without increasing airflow to the turbine. That is, under tip-out conditions (throttle pedal is released), an air intake throttle may be closed.

[0039] If the answer at 310 is YES, method 300 proceeds to 312. At 312, method 300 includes determining whether an exhaust catalyst temperature (T_cat) is within a threshold range. For example, it may be determined whether the exhaust catalyst temperature is above a lower temperature threshold (T_lower) and below an upper temperature threshold (T_upper). In one example, the lower catalyst temperature may be a catalyst light-off temperature, and the upper catalyst temperature may be a maximum temperature above which catalyst damage may occur. In another example, the lower catalyst temperature may be higher than the catalyst light-off temperature, and the upper catalyst temperature may be lower than the maximum catalyst temperature, where the lower temperature is less than the upper catalyst temperature.

[0040] If it is confirmed at 312 that the exhaust catalyst temperature is not within the threshold range (the answer at 312 is NO), the method continues to 314 to maintain fuel shutoff without increasing airflow to the turbine.

[0041] If it is confirmed at 312 that the exhaust catalyst temperature is within the threshold range (the answer at 312 is YES), method 300 proceeds to 316. At 316, method 300 includes adjusting one or more actuators to increase airflow through an exhaust turbine while maintaining fuel cutoff. For example, the controller may command a throttle actuator to increase an opening of the air intake throttle to increase airflow through the turbine while maintaining deactivation of the fuel injectors. By increasing airflow through the turbine, turbine speed may be increased and maintained above a threshold speed such that a duration for increasing turbine speed during a subsequent tip-in is reduced. Consequently, turbocharger response delay is reduced, and boost response is improved.Details of adjusting the one or more actuators to increase airflow to the turbine are described with respect to . Fig. 4. For example, airflow through the engine may be increased by performing one or more operations including adjusting a throttle position via a throttle actuator, adjusting a turbocharger wastegate position via a wastegate actuator, and adjusting adjustable camshaft timing via an adjustable camshaft timing actuator. While the present example illustrates increasing airflow after fuel shutoff is triggered, in some examples after confirming fuel shutoff conditions (as discussed at 304), tip-out conditions (as discussed at 310), and catalyst temperature conditions (as discussed at 312), the fuel shutoff operation and increasing airflow through the turbine may be performed concurrently.

[0042] After increasing airflow through the turbine, the method proceeds to 318. At 318, method 300 includes determining whether the accelerator pedal is applied. For example, it may be determined whether an accelerator pedal input is received by the controller in response to the vehicle user depressing the accelerator pedal. If it is confirmed that the accelerator pedal is applied, method 300 proceeds to 322. At 322, method 300 includes ending fuel cutoff in response to the accelerator pedal input being confirmed. For example, the vehicle user may request torque by applying the accelerator pedal; in response, fuel injection may be activated (e.g., by applying voltage to the fuel injector actuator) to trigger combustion to provide the requested torque.

[0043] Next, method 300 proceeds to 325. At 325, method 300 includes adjusting one or more actuators based on current operating conditions to adjust airflow through the engine to provide the driver-requested torque. For example, an intake throttle opening may be adjusted based on the current throttle pedal position. Adjusting one or more actuators may further include adjusting a wastegate position, adjustable camshaft timing, a transmission gear position, a compressor bypass valve position, and an EGR valve position based on current operating conditions, including engine speed, load, torque request (based on the current throttle pedal position, etc.).

[0044] Referring again to 318, if the accelerator pedal is not applied, the method proceeds to 320. That is, if the vehicle user has not requested torque (tip-out conditions), method 300 proceeds to 320. At 320, method 300 includes determining whether the exhaust catalyst temperature has increased above the upper threshold. For example, under tip-out conditions, air pumped through the turbine flows into the exhaust, which may increase the exhaust catalyst temperature. If the exhaust catalyst temperature increases above the upper threshold, airflow through the turbine may be terminated to reduce thermal damage to the exhaust catalyst. Accordingly, if it is confirmed that the exhaust catalyst temperature has increased above the upper threshold (the answer at 320 is YES), method 300 proceeds to 324.At 324, method 300 includes stopping airflow to the turbine while maintaining fuel shutoff. By stopping airflow to the turbine, airflow to the exhaust catalyst may be reduced, preventing excessive increases in exhaust catalyst temperature. Airflow to the turbine may be stopped by setting the air intake throttle to a closed position (i.e., the intake throttle may be adjusted based on accelerator pedal position). In some examples, stopping airflow to the turbine may further include opening a wastegate to bypass the turbine. In other examples, stopping airflow to the turbine may additionally include opening a low-pressure EGR valve coupled in a low-pressure EGR passage upstream of the catalyst so that a portion of the exhaust passage air is diverted away from the exhaust catalyst.

[0045] Referring again to 320, if the exhaust temperature is not at or above the upper threshold (i.e., the answer at 320 is NO), method 300 proceeds to 326. At 326, method 300 includes continuing airflow through the turbine. For example, the one or more actuators may be adjusted as shown in Fig. 4 to maintain the increased airflow through the turbine. The amount of airflow may be based on a turbine speed threshold. In particular, the amount of airflow is based on a flow required to maintain the turbine speed above the speed threshold. In one example, one or more of the following may be adjusted: a throttle position, a wastegate position, an adjustable camshaft timing, a transmission gear position, a compressor bypass valve position, and an EGR valve position to maintain a turbine speed above a threshold.

[0046] In this way, in response to a tip-out following a tip-in lasting longer than a threshold duration and / or greater than a threshold excursion, and when operating under fuel cut-off conditions with the exhaust catalyst temperature within a threshold range, airflow through an exhaust turbine may be increased for a duration of the tip-out until the accelerator pedal is applied or until the exhaust catalyst temperature increases above an upper threshold. By increasing airflow through the turbine, the turbine speed may be maintained above a threshold speed during the tip-out conditions. As a result, the required boost response with reduced turbocharger response lag may be achieved during a subsequent tip-in.

[0047] Fig. 4 is a flowchart illustrating an exemplary method 400 for increasing airflow through the turbine. The method 400 may be used in conjunction with the method 300 of Fig. 3. As discussed above, the airflow through the turbine can be increased to increase the turbine speed and maintain the turbine speed above a threshold under tip-out conditions, thereby improving boost response during a subsequent tip-in and reducing turbocharger response delay.

[0048] At 402, method 400 includes increasing the airflow through the turbine. Increasing the airflow through the turbine may include, at 404, opening an air intake throttle (e.g., throttle plate 21 in Fig. 2) via a throttle actuator. For example, a position of a throttle valve of the throttle may be adjusted by the controller via a signal provided to an electric motor or actuator included in the throttle. In one example, the air intake throttle may be opened from a fully closed position to an open position, where a degree of opening may be adjusted based on turbine speed. For example, the intake throttle may be opened to a position so as to maintain turbine speed above a threshold speed. That is, the intake throttle may be opened to a first degree until turbine speed increases above a threshold and maintained at the first degree as long as turbine speed is at or above the threshold.If the turbine speed decreases below the threshold, the intake throttle opening may be further increased to a second degree, where the second degree is greater than the first degree, to further increase airflow to the turbine and thus increase the turbine speed. In this way, the intake throttle opening may be dynamically adjusted based on the turbine speed to maintain the turbine speed at or above the threshold speed during deceleration. In other examples, the intake throttle may be opened to a fully open position (wide-open setting) to increase airflow through the turbine.

[0049] In some example systems that include a second intake throttle valve (such as throttle valve 23 in Fig. 2), in addition to increasing the air intake throttle opening, the second intake throttle may be opened via a second throttle actuator coupled to the second throttle. In another example, the second intake throttle may be set to a fully open position. In other examples, the second intake throttle may be adjusted based on the air intake throttle opening.

[0050] Increasing the airflow through the turbine may further include, at 406, closing a turbocharger wastegate (such as wastegate 25 in Fig. 2). The position of the wastegate may be set, for example, to a closed position via a signal provided to a wastegate actuator coupled to the wastegate (such as actuator 150 in Fig. 2). By closing the turbocharger wastegate, a large portion of the airflow from the cylinder can be directed to the turbine. In one example, increasing the intake throttle opening and closing the wastegate can be performed simultaneously.

[0051] Increasing airflow through the turbine may further include, at 408, closing an HP (high pressure) EGR valve. For example, an HP EGR actuator responsive to a control signal from a controller and coupled to the HP EGR valve may command the HP EGR valve to a commanded valve position (e.g., closed). By closing the HP EGR valve, the air mass from the cylinders to the turbine may be increased. In one example, increasing the intake throttle opening, closing the wastegate, and closing the HP EGR valve may be performed concurrently.

[0052] Increasing the air flow through the turbine may further include, at 410, adjusting a compressor bypass valve (CBV), such as CBV 27 in Fig. 2. For example, the position of the CBV may be adjusted via a signal provided to a CBV actuator coupled to the CBV. In one example, the CBV may be adjusted based on the exhaust catalyst temperature. For example, if the exhaust catalyst temperature is between a lower threshold and a first upper threshold, the CBV may remain closed. Consequently, air may flow via the compressor and the engine to the turbine. However, if the exhaust catalyst temperature reaches the first upper threshold, the CBV may be opened, and air may flow via the engine to the turbine, bypassing the compressor. The first upper threshold may be based on the maximum exhaust catalyst temperature before thermal deterioration occurs and may be lower than the Fig. 3. By bypassing the compressor, the temperature of the air supplied to the turbine can be reduced, which can prevent excessive increases in the exhaust catalyst temperature.

[0053] In some examples, in addition to adjusting the air intake throttle, closing the wastegate, and closing the high-pressure EGR valve, the engine may be operated with adjustable camshaft phasing. For example, intake camshaft timing may be set to an optimal position for volumetric efficiency (e.g., advanced) so that during a subsequent vehicle start-up (e.g., tip-in), the camshaft timing is already at an optimal position, reducing the response delay associated with adjusting camshaft timing during tip-in.

[0054] After increasing airflow through the turbine, method 400 may proceed to 412. At 412, method 400 includes adjusting one or more actuators (e.g., to increase wheel braking efficiency, increase alternator load, etc.) to compensate for the reduced braking efficiency when the air intake throttle is open. For example, if the air intake throttle is opened to increase airflow and fuel injection is turned off, the vehicle may not receive sufficient engine braking, and therefore, a braking effort may need to be applied to obtain the requested deceleration rate, which is typically present with closed-throttle engine braking. Therefore, a vehicle control system may coordinate and adjust the braking efforts of alternative vehicle brakes (e.g., the wheel brakes) to maintain a requested deceleration rate.In some examples, in embodiments where the engine or drivetrain is coupled to an electric machine (e.g., in a hybrid electric vehicle) or in any other hybrid-like device (hydraulic or pneumatic), the throttle opening may be coordinated with such devices (e.g., the devices could be operated in an energy or torque absorbing mode) to maintain the requested deceleration rate while maintaining engine speed and airflow through the turbine.

[0055] It is understood that the increased airflow during the deceleration event is determined based on vehicle operating conditions in response to resuming fuel supply to the engine cylinder, as described in Fig. 3. For example, in response to a sudden increase in torque demand (e.g., upon a tip-in or the vehicle entering a hill section), fueling to the cylinder may be resumed, and the air intake throttle may be adjusted based on the throttle pedal position. Alternatively, if the turbine speed drops below a threshold speed during deceleration (e.g., if the turbine speed was below a threshold during previous operation prior to the tip-out), such that even by opening the throttle to wide open throttle conditions and adjusting the wastegate and HP-EGR valve, airflow to the turbine may not be sufficient to increase and maintain the turbine speed at the threshold speed, airflow to the turbine may be stopped.In some examples, an airflow amount to maintain the turbine speed at or above the threshold may be estimated based on a current turbine speed and a commanded turbine speed under the deceleration fuel cutoff condition. If it is determined that the estimated airflow through the turbine, and thus the commanded turbine speed, cannot be achieved, airflow through the turbine may be terminated under the deceleration fuel cutoff condition. However, the fuel cutoff may be maintained until the accelerator pedal is applied by the vehicle user.

[0056] With reference to Fig. 5: An example map 500 is shown illustrating example settings of the airflow through the turbine in response to the throttle pedal position, the catalyst temperature, and the fuel injection. The sequence in Fig. 5 can be executed by executing instructions in the system from the Fig. 1 - 2 according to the procedure Fig. 3 in conjunction with the procedure from Fig. 4. The vertical markers at times t0 - t5 represent times of interest during the process.

[0057] In particular, the first curve from the top in Fig. 5 Accelerator pedal position over time, and the accelerator pedal is further depressed in the direction of the Y-axis arrow. Line 502 shows the change in accelerator pedal position, and horizontal line 504 shows the accelerator pedal depression threshold.

[0058] The second curve from the top in Fig. Figure 5 shows the exhaust catalyst temperature over time, and the catalyst temperature increases in the direction of the Y-axis arrow. Line 508 shows the change in catalyst temperature, horizontal line 506 shows the upper catalyst temperature threshold, and horizontal line 507 shows the lower catalyst temperature threshold.

[0059] The third curve from the top in Fig. Figure 5 shows the intake throttle opening over time, and the throttle opening increases in the direction of the Y-axis arrow. Line 510 shows the actual change in throttle opening to increase airflow through the turbine under deceleration conditions according to the present disclosure, and line 510 shows the change in throttle opening when airflow through the turbine is not increased under deceleration conditions.

[0060] The fourth graph from the top in Fig. Figure 5 shows deceleration fuel cutoff conditions over time. Line 514 shows an on or off deceleration fuel cutoff condition.

[0061] The fifth curve from the top in Fig. Figure 5 shows the flow through the turbine over time, and the flow through the turbine increases in the direction of the Y-axis arrow. Line 516 shows the actual flow through the turbine when the airflow through the turbine is increased under deceleration conditions according to the present disclosure, and line 518 shows the flow through the turbine when the airflow through the turbine is not increased.

[0062] The sixth curve from the top in Fig. Figure 5 shows the turbine speed over time, and the turbine speed increases in the direction of the Y-axis arrow. Line 524 shows the turbine speed when the airflow is increased under deceleration conditions, line 520 shows the turbine speed when the airflow is not increased under deceleration conditions, line 526 shows the demanded turbine speed, and the horizontal line 522 shows the threshold turbine speed.

[0063] In all curves, the x-axis represents time, and time increases from the left side of the curve to the right side of the curve.

[0064] At t0, the vehicle may be operating under boost, and the exhaust catalyst temperature may be within the range of the upper (506) and lower (507) thresholds. Furthermore, the throttle position (510), and thus the flow through the turbine (516), may be adjusted based on the accelerator pedal position (502) to provide the torque requested by the driver.

[0065] Shortly before t1, the vehicle user may request more torque by further pressing the accelerator pedal (tip-in). In response to the tip-in, the intake throttle opening may be increased based on the accelerator pedal position, and flow through the turbine may increase (516). Consequently, turbine speed may increase (524). The vehicle user may maintain tip-in operation for a duration longer than a threshold duration until shortly before t2, when the user may release the accelerator pedal (502). In response to releasing the accelerator pedal, the intake throttle opening may decrease (510), and at t2, the intake throttle opening may be closed. Consequently, flow through the turbine may decrease (516), and turbine speed (524) may decrease.Further, at t2, in response to the vehicle operating under tip-out conditions for a threshold duration, a fuel cut-off on deceleration event (514) may be triggered. Further, at t2, the exhaust catalyst temperature (506) may be within the threshold range. Thus, at t2, in response to the tip-out following the vehicle operating under tip-in conditions for the threshold duration, the fuel cut-off conditions, and the exhaust catalyst temperature remaining within the threshold range, airflow through the turbine may be increased to increase turbine speed and maintain turbine speed at or above the threshold speed (522). Airflow through the turbine may be increased by increasing the intake throttle opening. Additionally, in some examples, a wastegate may be closed to increase flow through the turbine.In some other examples, a compressor bypass valve may additionally or alternatively be closed. In still other examples, increasing flow through the turbine may be accomplished by adjusting one or more actuators, including adjustable camshaft timing. In yet another example, in systems including a HP EGR valve, the HP EGR valve may be closed. Details regarding increasing airflow through the turbine under deceleration conditions are provided above at . Fig. 4 described.

[0066] In this way, by increasing the flow through the turbine, the turbine speed can be maintained above a threshold so that during a subsequent demand for boost pressure (i.e., during a subsequent tip-in following a tip-out), the boost response can be improved. In other words, during a subsequent tip-in following the tip-out, a duration to reach a requested turbine speed can be reduced, thereby reducing turbocharger response delay. By increasing the flow during fuel cut-off conditions, undesirable acceleration can be further reduced. Consequently, additional measures to increase engine braking (e.g., spark retard) can be reduced. Furthermore, by increasing the flow only when the exhaust catalyst is within the threshold range, thermal damage to the exhaust catalyst can be reduced.

[0067] As such, airflow through the turbine may continue until the accelerator pedal is depressed and / or until the exhaust catalyst temperature reaches the upper threshold. Thus, airflow through the turbine may continue during fuel cutoff upon deceleration from t2 until just before t3, when a high throttle tip-in may be initiated by the vehicle user pressing the accelerator pedal. In response to the tip-in, just before t3, fuel injection may resume, and throttle opening may be adjusted based on the accelerator pedal input. Furthermore, one or more actuators used to increase airflow through the turbine during tip-out may be adjusted based on current operating conditions.For example, one or more actuators, including the wastegate actuator, the CBV actuator, the HP-EGR valve actuator, and the adjustable camshaft timing actuator, can be adjusted based on current operating conditions to provide the torque requested by the driver. Furthermore, by increasing airflow through the turbine during deceleration conditions (between t2 and just before t3) prior to tip-in, the time required to reach a requested turbine speed in response to tip-in is reduced, thereby reducing turbocharger response delay. Thus, boost response is improved.In other words, an actual rate of change of turbine speed is closer to the required rate of change of turbine speed when the air flow through the turbine is increased than a rate of change of turbine speed when the air flow through the turbine is not increased.

[0068] Between t3 and t4, the vehicle user may maintain the high input to the accelerator pedal (502). Shortly before t4, the vehicle user may initiate a tip-out operation under closed throttle conditions. In response to the tip-out shortly before t4, at t4, fuel to the engine may be shut off (514). Further, the exhaust catalyst temperature may be within the threshold range (508). In response to the tip-out following the tip-in for a high throttle input (that is, a tip-out following a tip-in where the accelerator pedal depression is greater than a threshold), the exhaust catalyst temperature remaining within the threshold range, and the fuel shutoff to the engine, flow to the turbine may be increased (516). As shown in this example, flow to the turbine may be increased by opening the intake throttle when the accelerator pedal is released (tip-out).The throttle position when the airflow through the turbine is not increased is shown at 512. Additionally or alternatively, one or more actuators may be adjusted to increase the flow through the turbine, as described above with respect to . Fig. 4. The one or more actuators that can be adjusted include the wastegate actuator for adjusting the wastegate position, the CBV actuator for adjusting the CBV position, the HP EGR valve actuator for adjusting the HP EGR valve position, and the camshaft timing actuator. For example, to increase flow through the turbine, the wastegate actuator can be closed.

[0069] In some examples, if the turbine speed decreases below the threshold, flow through the turbine may be terminated under deceleration fuel shutoff conditions.

[0070] Airflow to the turbine may continue until just before t5 when the driver triggers a tip-in event (502). In response to the tip-in event, fuel injection to the engine may resume (514). Airflow to the turbine may be adjusted based on current vehicle operating conditions to provide the driver-requested torque. For example, the intake throttle opening may be adjusted in response to accelerator pedal input to provide the driver-requested torque. Because airflow to the turbine has been increased during tip-out (between t4 and t5) to maintain turbine speed at or above the pre-tip-in threshold (just before t5), the duration to reach a requested turbine speed may be reduced. Thus, boost response is improved, and turbocharger response lag is reduced.Furthermore, the tip-in event triggered shortly before t5 may result in a sub-threshold accelerator pedal input (i.e., the accelerator pedal depression may be below the threshold), and the tip-in event may occur for a duration shorter than the threshold shortly before t6 if the vehicle user may initiate a tip-out under closed throttle conditions. In response to the tip-out, a deceleration fuel cutoff event may be triggered at t6. Furthermore, at t6, the exhaust catalyst temperature may continue to be within the threshold range. However, at t6, due to the preceding tip-in event (between t5 and t6 before the tip-out) being shorter than a threshold duration and below a threshold input, the turbine speed may be below the threshold.Consequently, any increase in turbine airflow during deceleration may not be sufficient to maintain turbine speed above a threshold. Accordingly, no increase in turbine airflow may be triggered at t6 (i.e., the air intake throttle may not be opened), and the engine may operate with fuel cutoff and without increasing turbine airflow (516).

[0071] Next, shortly before t7, the vehicle user may initiate a tip-in, where the tip-in excursion is greater than a threshold excursion (i.e., the amount of accelerator pedal input is greater than a threshold). In response to the tip-in, fuel injection may resume, and turbine speed may begin to increase. However, the vehicle may experience a turbocharger response delay, i.e., a delay in boost response (524). At a time shortly before t8, the vehicle user may initiate a tip-out. In response to the tip-out at t8, the throttle opening decreases to a closed position. Furthermore, a duration of the tip-out may be shorter than a threshold. Therefore, DFSO may not be performed. Consequently, operations to increase airflow through the engine may not be performed. Thus, airflow to the turbine may not be increased.Immediately after t8, the vehicle user can initiate another tip-in. Furthermore, between t8 and t9, the exhaust catalyst temperature may increase above the threshold. If the exhaust catalyst temperature is higher than the threshold, operations to increase airflow through the turbine during deceleration may not be performed. Therefore, in response to a tip-out, the airflow through the turbine may not be increased at t9 due to the catalyst temperature being higher than the threshold.

[0072] By increasing airflow through the turbine during deceleration conditions that occur following vehicle operation with prolonged and / or high throttle input, when the fuel is shut off and when the exhaust catalyst temperature is within a threshold range, the turbine speed can be increased and maintained at or above a threshold speed. Consequently, the engineering impact of reducing the duration required to increase the turbine speed to a required speed during a subsequent tip-in is reduced. As a result, boost response and fuel consumption are improved without causing thermal damage to the exhaust catalyst.

[0073] In an example, the procedures from the Fig. 3 and Fig. 4 and the process from Fig. 5 enable a method for a turbocharged engine, comprising: in response to a deceleration event, deactivating fuel injectors for all cylinders of the engine while increasing airflow through a turbine of a turbocharger when a temperature of an exhaust catalyst downstream of the turbine is between an upper threshold and a lower threshold. The method includes where the deceleration event is triggered following a tip-in event. The method further includes where, during the tip-in event, a degree of throttle depression is greater than a threshold degree and where increasing airflow through the turbine includes increasing an opening of an air intake throttle positioned in the engine's air intake passage upstream of a compressor of the turbocharger.The method includes where a degree of opening of the air intake throttle is based on a requested turbine speed, and where increasing airflow through the turbine further includes closing a turbine wastegate and closing a high pressure EGR valve. The method further includes: during the deceleration event, stopping airflow through the turbine in response to the temperature increasing above an upper threshold while maintaining deactivation of the fuel injectors, wherein stopping airflow through the turbine includes closing the air intake throttle. The method further includes: in response to detecting an accelerator pedal application, adjusting airflow through the turbine and activating one or more of the deactivated fuel injectors, wherein the adjusting and activation are based on a current engine load request.The method further includes the deceleration event being a tip-out to a closed throttle condition.

[0074] In another example, the procedures from the Fig. 3 and Fig. 4 and the process in Fig.5 enable a method for an engine comprising: maintaining a turbine speed of a turbocharger above a threshold speed in response to a deceleration fuel cut-off event when a temperature of an exhaust catalyst is between an upper threshold and a lower threshold; wherein the deceleration fuel cut-off event occurs in response to a tip-out following a tip-in to a wide-open throttle setting condition; wherein maintaining the turbine speed includes increasing airflow through the turbine during the deceleration fuel cut-off event;and wherein increasing airflow through the turbine includes closing a wastegate coupled above the turbine, closing a high-pressure EGR valve, and increasing an opening of an air intake throttle positioned in the engine's air intake passage upstream of the turbocharger's compressor. The method further includes: during the deceleration fuel cut-off event, stopping airflow through the turbine in response to the exhaust catalyst temperature increasing above an upper threshold temperature, wherein stopping includes closing the air intake throttle. The method further includes: in response to detecting application of an accelerator pedal, terminating the deceleration fuel cut-off event and adjusting airflow through the turbine based on a current engine load demand;and that terminating the deceleration fuel cutoff event includes activating one or more fuel injectors based on the current engine load demand. The method further comprises: opening a compressor bypass valve coupled across the compressor in response to the exhaust catalyst temperature reaching a second threshold, wherein the second threshold is less than the upper threshold and greater than the lower threshold;

[0075] It should be noted that the control and estimation routines contained 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-volatile memory and may be executed by the control system, including 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 illustrated 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-volatile 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 controller.

[0076] It is understood that the configurations and routines disclosed herein are exemplary in nature, and that these specific embodiments are not to be construed in a limiting sense, 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.

[0077] The following claims particularly point out certain combinations and sub-combinations 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 sub-combinations 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 included within the subject matter of the present disclosure.

Claims

[1] A method for a supercharged engine (10) comprising: in response to determining, with an engine controller, a deceleration event, and with the engine controller: deactivating fuel injectors (50) to all cylinders of the engine (10) while increasing airflow through a turbine (62) of a turbocharger in response to determining that a temperature of an exhaust catalyst downstream of the turbine (62) is between an upper threshold and a lower threshold, characterized by that the slowdown event is triggered following a tip-in event. [2] The method of claim 1, wherein during the tip-in event, a degree of depression of the accelerator pedal is greater than a threshold degree. [3] The method of claim 1, wherein increasing the air flow through the turbine (62) includes increasing an opening of an air intake throttle positioned in an air intake passage of the engine (10) upstream of a compressor (60) of the turbocharger. [4] The method of claim 3, wherein a degree of opening of the air intake throttle is based on a turbine speed. [5] The method of claim 4, wherein increasing airflow through the turbine (62) further includes closing a turbine boost control valve and closing a high pressure exhaust gas recirculation valve. [6] The method of claim 1, further comprising, during the deceleration event, stopping airflow through the turbine (62) in response to the temperature increasing above the upper threshold while maintaining deactivation of the fuel injectors (50). [7] The method of claim 6, wherein stopping the air flow through the turbine (62) includes closing the air inlet throttle. [8] The method of claim 1, further comprising, in response to detecting an accelerator pedal application, adjusting airflow through the turbine (62) and activating one or more of the deactivated fuel injectors (50), wherein the adjusting and activation are based on a current engine load request. [9] The method of claim 1, wherein the deceleration event is a tip-out to a closed air intake throttle condition. [10] A method for an engine (10) comprising: In response to determining, with an engine control, a deceleration fuel cutoff event when a temperature of an exhaust catalyst determined with the engine control is between an upper threshold and a lower threshold, maintaining a turbine speed of a turbocharger above a threshold speed, characterized by that the deceleration fuel cutoff event occurs in response to a tip-out following a tip-in to a wide-open throttle setting condition. [11] The method of claim 10, wherein maintaining turbine speed includes increasing airflow through the turbine (62) during the deceleration fuel cutoff event. [12] The method of claim 11, wherein increasing the air flow through the turbine (62) includes closing a wastegate (25) coupled across the turbine (62), closing a high pressure exhaust gas recirculation valve, and increasing an opening of an air intake throttle positioned in an air intake passage of the engine (10) upstream of the compressor (60) of the turbocharger. [13] The method of claim 12, further comprising, during the deceleration fuel cutoff event, stopping airflow through the turbine (62) in response to the exhaust catalyst temperature increasing above the upper threshold, wherein stopping includes closing the air intake throttle. [14] The method of claim 13, further comprising, in response to detecting actuation of an accelerator pedal, terminating the deceleration fuel cut-off event and adjusting airflow through the turbine (62) based on a current engine load request, and wherein terminating the deceleration fuel cut-off event includes activating one or more fuel injectors (50) based on the current engine load request. [15] The method of claim 12, further comprising opening a compressor bypass valve coupled across the compressor (60) in response to the exhaust catalyst temperature reaching a second threshold, the second threshold being less than the upper threshold and greater than the lower threshold. [16] Turbocharged engine system comprising: an engine (10) including a plurality of cylinders, an intake manifold (44) and an exhaust manifold (45); a compressor (60) coupled to the intake manifold (44) and driven by a turbine (62) coupled to the exhaust manifold (45); an air inlet throttle positioned within an inlet duct (42) upstream of a compressor (60), the inlet duct (42) coupling the compressor (60) to ambient air; an exhaust gas catalyst coupled downstream within an exhaust passage (48) of the turbine (62), the exhaust passage (48) coupling the catalyst to ambient air; wherein each of the plurality of cylinders has a fuel injection valve (50) for injecting fuel into the cylinder; an accelerator pedal for receiving a torque request from the user; and a controller (12) having executable instructions stored in a non-volatile memory to: deactivate all fuel injectors (50) in response to an accelerator pedal tip-out event triggered subsequent to a tip-in event; and under a first condition, allowing ambient air to flow via the compressor (60) to the turbine (62) and the engine (10) while maintaining deactivation of the fuel injectors (50); under a second condition, to allow ambient air to flow via the engine (10) to the turbine (62) by passing through the compressor (60) while maintaining deactivation of the fuel injectors (50); and under a third condition, to stop the flow of air to the turbine (62) while maintaining the deactivation of the fuel injectors (50); and wherein the first condition includes an exhaust catalyst temperature being between a lower threshold and a first upper threshold; wherein the second condition includes the exhaust catalyst temperature being at or above the first upper threshold and below a second upper threshold, the second upper threshold being greater than the first upper threshold; and wherein the third condition includes the exhaust catalyst temperature being at or above the second upper threshold. [17] The turbocharged engine system of claim 16, wherein flowing air to the turbine (62) includes increasing an opening of the air intake throttle based on a requested turbine speed. [18] The turbocharged engine system of claim 17, wherein the controller (12) includes further instructions to: in response to application of the accelerator pedal subsequent to the tip-out, activate one or more fuel injectors (50) and adjust flow through the turbine (62) based on a user torque request.

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