Control system for a fuel shut-off system of a motor vehicle and fuel shut-off system for a motor vehicle

Abstract

Control system (28) for a fuel shut-off system (10) of a motor vehicle, the control system (28) comprising: a fuel shutoff module (30) that determines a delay fuel shutoff event and generates a fuel shutoff signal for shutting off fuel supply to an internal combustion engine (12) in response to the fuel shutoff module (30) detecting the delay fuel shutoff event; an oxygen storage module (32) that determines an amount of oxygen accumulated in a catalyst (36) located downstream of the internal combustion engine (12), and wherein the oxygen storage module (32) compares the amount of oxygen to an oxygen storage capacity of the catalyst (36) in response to the fuel shutoff module (30) determining the delay fuel shutoff event; and an intake valve timing module (52) that generates a phase signal to actuate a plurality of cam phasers (50) to move into one of a plurality of activated states to modify a valve timing to reduce a flow rate of oxygen to the catalyst (36) in response to the fuel cut-off module (30) determining the retard fuel cut-off event and in further response to the oxygen storage module (32) determining that the amount of oxygen stored in the catalyst (36) is less than the oxygen storage capacity; wherein the oxygen storage module (32) is configured to receive a first oxygen signal from a first oxygen sensor (46) located upstream of the catalyst (36) and determine an amount of oxygen entering the catalyst (36) in response to the first oxygen signal and an air mass flow of oxygen into the catalyst (36); wherein the oxygen storage module (32) is configured to receive a second oxygen signal from a second oxygen sensor (46) located downstream of the catalyst (36), and the oxygen storage module (32) is configured to determine the amount of oxygen downstream of the catalyst (36) in response to the second oxygen signal; wherein the fuel shutoff module (30) is configured to receive an engine speed signal from an engine speed sensor (38) coupled to the internal combustion engine (12), and the fuel shutoff module (30) is configured to determine an engine speed of the internal combustion engine (12) in response to the engine speed signal; wherein the oxygen storage module (32) is configured to receive a pressure signal from a pressure sensor (48) coupled to an intake manifold (18), the pressure signal indicative of a manifold pressure, and the oxygen storage module (32) is further configured to receive a temperature signal from a temperature sensor (49) coupled to the intake manifold (18), the temperature signal indicative of a manifold temperature; in response to the oxygen storage module (32) receiving the pressure signal and the temperature signal, the oxygen storage module (32) is configured to measure the pressure of the airflow through the intake manifold (18) and the temperature of the airflow through the intake manifold (18); and in response to the measured engine speed, the measured manifold pressure and the measured manifold temperature, the oxygen storage module (32) determines the air mass flow into the catalyst (36); wherein the oxygen storage module (32) is configured to determine the amount of oxygen stored in the catalyst (36) in response to the first oxygen signal and an estimated air mass flow rate into the catalyst (36).

Description

[0001] The present description relates to internal combustion engine control systems for motor vehicles, and more particularly to a system and method for reducing the amount of oxygen flow to a catalyst during a deceleration fuel cut-off event and improving the fuel efficiency of a motor vehicle.

[0002] Engines emit exhaust gases containing carbon dioxide, water, carbon monoxide (CO), nitrogen oxides (NOx), unburned hydrocarbons (HC), and other compounds. Exhaust systems typically contain a catalyst that reduces the levels of CO, NOx, and HC in the exhaust by chemically converting these gases into carbon dioxide, nitrogen, and water. The catalyst reduces the levels of the gases by catalyzing a reaction between the gases and oxygen. The catalyst stores oxygen when operating under lean fuel conditions and consumes the stored oxygen when operating under rich fuel conditions.

[0003] A vehicle may be operating in a fuel cut-off mode where fuel supply to the cylinders is disabled. Fuel cut-off mode can occur when the vehicle is decelerated with no power demand from the driver and the engine acts as a brake. During fuel cut-off mode, the engine pumps air through the exhaust system rather than exhaust gas, delivering excess oxygen to the catalyst. The catalyst stores the oxygen until an oxygen storage capacity (OSC) is reached. When OSC is reached and fuel supply to the engine cylinders is restored, the catalyst's ability to convert NOx emissions can be significantly reduced, leading to NOx breakthrough. Therefore, when fuel supply resumes, an increased amount of fuel is delivered to the engine to create rich fuel conditions and release oxygen from the catalyst.While rich fuel conditions reduce the amount of oxygen in the catalyst to improve NOx conversion, rich fuel conditions can reduce the fuel efficiency improvements achieved by fuel shutoff systems.

[0004] WO 2019 / 244675 A1 describes a valve opening / closing timing control device provided with: a drive-side rotor that rotates synchronously with a crankshaft of an internal combustion engine E; a driven-side rotor that is rotatable relative to the drive-side rotor and rotates together with a camshaft that opens and closes an intake valve; and a phase adjustment mechanism that adjusts a relative rotational phase of the drive-side rotor and the driven-side rotor using a driving force of an electric motor. The phase adjustment mechanism is configured to be capable of performing retardation control to adjust the relative rotational phase to the retardation side when the internal combustion engine E can no longer be started until a phase is reached where autonomous operation becomes impossible, even when fuel injection and ignition are performed in the internal combustion engine E.

[0005] DE 10 2016 004 820 A1 describes a method for controlling a, in particular a supercharged, internal combustion engine, in particular of a motor vehicle, comprising the steps of: - determining an oxygen loading of a catalyst of the internal combustion engine; and - increasing a valve overlap of the internal combustion engine from a lower valve overlap value to an upper valve overlap value, wherein the increase in the valve overlap and / or, for at least one phase of increasing the valve overlap, a control value for increasing an air-fuel ratio in at least one cylinder of the internal combustion engine is reduced as a function of the determined oxygen loading.

[0006] DE 199 52 037 A1 describes that in a reciprocating piston internal combustion engine with poppet valves, valve timing, and fuel injection, the fuel supply is shut off during engine overrun, and the valve timing is controlled to retain charge in the engine cylinders during the fuel shutoff. As such, catalytic aftertreatment devices are neither cooled nor saturated with oxygen, and fuel economy is improved.

[0007] JP 2009 - 19 611 A describes a control unit with a turbocharger having variable valve timing that allows valve overlap timing to be adjusted. When reducing valve overlap during engine speed reduction from a boosted state, if a signal from an oxygen sensor located downstream of an upstream catalyst indicates rich output, after controlling an intake VVT ​​advance amount until its target value is reached, an exhaust VVT retard amount is controlled until its target value is reached. If the oxygen sensor signal indicates lean output, after controlling the exhaust VVT retard amount until its target value is reached, the intake VVT ​​advance amount is controlled until its target value is reached.

[0008] DE 10 2013 202 196 A1 describes a method for operating an internal combustion engine with an exhaust system downstream of the internal combustion engine, which exhaust system has at least one catalytic converter device and at least one gas exchange device for controlling the intake side and the exhaust side of the internal combustion engine. It is provided that, in an operating mode in which the internal combustion engine is not supplied with fuel, the exhaust side of the internal combustion engine is closed and the opening of the intake side is advanced compared to a regular operating mode.

[0009] DE 601 17 483 T2 describes an internal combustion engine and a method for operating the same which allows overrun fuel cut-off.

[0010] DE 198 58 468 A1 describes a feed control method for a motor.

[0011] DE 10 2014 001 672 A1 describes a method for operating an internal combustion engine with at least one exhaust gas turbocharger, at least one catalytic converter and a variable valve train.

[0012] While existing automotive fuel shutoff systems serve their purpose, the object of the invention is to provide a system for reducing the oxygen pumped through the catalytic converter in order to improve emissions and optimize fuel consumption.

[0013] The object of the invention is achieved by means of a control system for a fuel shutoff system of a motor vehicle, comprising a fuel shutoff module that determines a delayed fuel shutoff event. The fuel shutoff module generates a fuel shutoff signal for shutting off the fuel supply to an internal combustion engine in response to the fuel shutoff module detecting the delayed fuel shutoff event. The control system further comprises an oxygen storage module that determines an amount of oxygen accumulated in a catalyst arranged downstream of the internal combustion engine. The oxygen storage module compares the amount of oxygen with an oxygen storage capacity of the catalyst in response to the fuel shutoff module determining the delayed fuel shutoff event.The control system further includes an intake valve timing module that generates a phase signal to actuate a plurality of cam phasers to move in one of a plurality of activated states, to modify a valve timing to reduce an amount of oxygen flow to the catalyst in response to the fuel cutoff module determining the retard fuel cutoff event and in further response to the oxygen storage module determining that the amount of oxygen stored in the catalyst is less than the oxygen storage capacity. The oxygen storage module is configured to receive a first oxygen signal from a first oxygen sensor disposed upstream of the catalyst. The oxygen storage module is configured to determine an amount of oxygen entering the catalyst in response to the first oxygen signal and a mass air flow of oxygen into the catalyst.The oxygen storage module is configured to receive a second oxygen signal from a second oxygen sensor located downstream of the catalyst. The oxygen storage module is configured to determine the amount of oxygen in the exhaust gas downstream of the catalyst in response to the second oxygen signal. The fuel shutoff module is configured to receive an engine speed signal from a speed sensor coupled to the engine. The fuel shutoff module is configured to determine an engine speed of the internal combustion engine in response to the engine speed signal. The oxygen storage module is configured to receive a pressure signal from a pressure sensor coupled to an intake manifold, the pressure signal indicative of a manifold pressure.The oxygen storage module is further configured to receive a temperature signal from a temperature sensor coupled to the intake manifold, the temperature signal indicative of a manifold temperature. In response to the oxygen storage module receiving the pressure signal and the temperature signal, the oxygen storage module is configured to measure the pressure of the airflow through the intake manifold and the temperature of the airflow through the intake manifold. In response to the measured engine speed, the measured manifold pressure, and the measured manifold temperature, the oxygen storage module determines a mass air flow into the catalyst. The oxygen storage module is configured to determine the amount of oxygen stored in the catalyst in response to the first oxygen signal and an estimated mass air flow rate into the catalyst.

[0014] According to one embodiment, the fuel cutoff module determines the deceleration fuel cutoff event in response to the fuel cutoff module determining that a vehicle speed is greater than a vehicle speed threshold and in further response to an accelerator pedal position being less than a position threshold.

[0015] According to one embodiment, the deceleration fuel cut-off event occurs in response to the internal combustion engine delivering negative engine torque.

[0016] According to the invention, a fuel shutoff system for a motor vehicle comprises an internal combustion engine. The internal combustion engine includes a plurality of engine cylinders and a plurality of intake valves operatively engaged with the engine cylinders, each of the intake valves being movable between an open and a closed position. The internal combustion engine further includes a plurality of exhaust valves operatively engaged with the engine cylinders, each of the exhaust valves being movable between an open and a closed position. The internal combustion engine further includes a throttle body movable from a closed position to an open position to allow air to flow to the engine cylinders.The internal combustion engine further includes a plurality of pistons movable between an upper and a lower position within a respective engine cylinder, and a position of the pistons when the respective intake valves and exhaust valves are arranged in the closed position defines a valve timing. The fuel cutoff system further includes a control system having a fuel cutoff module, an oxygen storage module, and an intake valve timing module. The fuel cutoff module generates a fuel cutoff signal to cut off fuel supply to the engine cylinders and moves the throttle body to the closed position in response to the fuel cutoff module detecting that a retard fuel cutoff event has occurred.The oxygen storage module determines an amount of oxygen accumulated in a catalyst and compares the amount of oxygen to an oxygen storage capacity of the catalyst in response to the fuel cutoff module determining the retard fuel cutoff event. The intake valve timing module generates a phase signal to actuate the cam phasers to move to one of the activated states in response to the fuel cutoff module determining that the retard fuel cutoff event has occurred and in further response to the oxygen storage module determining that the amount of oxygen stored in the catalyst is less than the oxygen storage capacity. The fuel cutoff system further includes a plurality of cam phasers operatively engaged with the intake valves and exhaust valves.The cam phasers are movable into a plurality of activated states in which the cam phaser modifies the valve timing to reduce the flow rate of oxygen to the catalyst. The cam phaser is movable into a first activated phaser state in which the pistons are arranged in a predetermined standard position when the associated intake valves are in the closed position such that oxygen flows to the catalyst at a first flow rate. The cam phaser is further movable into a second activated phaser state in which the valve timing is modified such that the closing of the intake valves is advanced or retarded by a cam angle that reduces the oxygen flow rate from the first flow rate to a second flow rate.The engine cylinders remain in a fixed activated state where the intake valves and the exhaust valves continuously reciprocate between open and closed positions while each of the pistons moves between the upper and lower positions. The cam phaser is movable to the second activated phaser state in response to the intake valve timing module determining that the amount of oxygen accumulated in the catalyst is less than the oxygen storage capacity. The oxygen storage module is configured to receive a first oxygen signal from a first oxygen sensor located upstream of the catalyst and to determine an amount of oxygen entering the catalyst in response to the first oxygen signal and a mass air flow into the catalyst.The oxygen storage module is configured to receive a second oxygen signal from a second oxygen sensor disposed downstream of the catalyst, and the oxygen storage module is configured to determine the amount of oxygen in the exhaust gas downstream of the catalyst in response to the second oxygen signal. The fuel cut-off module is configured to receive an engine speed signal from an engine speed sensor coupled to the engine, and the fuel cut-off module is configured to determine an engine speed of the internal combustion engine in response to the engine speed signal. The oxygen storage module is further configured to receive a temperature signal from a temperature sensor coupled to the intake manifold, the temperature signal indicative of a manifold temperature.In response to the oxygen storage module receiving the pressure signal and the temperature signal, the oxygen storage module is configured to measure the pressure of the airflow through the intake manifold and the temperature of the airflow through the intake manifold. In response to the measured engine speed, the measured manifold pressure, and the measured manifold temperature, the oxygen storage module determines a mass air flow into the catalyst. The oxygen storage module is configured to determine the amount of oxygen stored in the catalyst in response to the first oxygen signal and an estimated mass air flow into the catalyst.

[0017] According to one embodiment, the fuel cutoff module determines the deceleration fuel cutoff event in response to the fuel cutoff module determining that a vehicle speed is greater than a vehicle speed threshold and in further response to an accelerator pedal position being less than a position threshold.

[0018] According to another embodiment, the deceleration fuel cut-off event occurs in response to the engine outputting negative engine torque.

[0019] To understand the functions of the claimed control system, a method is described below that includes the steps corresponding to the functions of the claimed control system. The method of operating a fuel shutoff system is provided for a motor vehicle having an internal combustion engine, a fuel shutoff module, and an oxygen storage module. The method includes moving a plurality of intake valves between open and closed positions. A plurality of engine cylinders move between upper and lower positions, and a position of the pistons when the associated intake valves are arranged in the closed position defines a valve timing. The fuel shutoff module generates a fuel shutoff signal in response to the fuel shutoff module determining that a delay fuel shutoff event has occurred.Fuel supply to the engine cylinders is shut off in response to the fuel shutoff signal, and the oxygen storage module determines an amount of oxygen stored in a catalyst. A plurality of cam phasers move into a plurality of activated states, where the cam phaser modifies valve timing to reduce the flow rate of oxygen to the catalyst, in response to the fuel shutoff module determining the retard fuel shutoff event and in further response to the oxygen storage module determining that the amount of oxygen stored in the catalyst is less than the oxygen storage capacity.

[0020] In one example of the method, the fuel shutoff module generates the fuel shutoff signal in response to a vehicle speed sensor detecting that a speed of the motor vehicle is greater than a speed threshold.

[0021] In another example of the method, the fuel shutoff module generates the fuel shutoff signal in response to an accelerator pedal sensor detecting that the displacement of an accelerator pedal from a rest position is less than a displacement threshold.

[0022] In another example of the method, the engine cylinders are arranged in a first activated phaser state in which the intake valves move between an open and a closed position at a preset cam angle while the pistons move between an upper and a lower position in response to the cam phasers being arranged in the first activated phaser state.

[0023] In another example of the method, the engine cylinders are arranged in a second activated cylinder state in which the intake valves move between an open and a closed position at an advanced or retarded cam angle while the pistons move between a top and a bottom position in response to the cam phasers being arranged in the second activated phaser state.

[0024] Further areas of applicability will become apparent from the description provided herein. It is to be understood that the description and specific examples are for illustrative purposes only and are not intended to limit the scope of this description. Fig. 1 is a schematic diagram of a fuel shutoff system for a motor vehicle. Fig. 2 is a flowchart for a method of operating the system of Fig. 1.

[0025] For clarity, the same reference numbers are used throughout the drawings to identify similar elements. As used herein, the phrase "at least one of A, B, and C" should be construed to mean a logical combination (A or B or C), using a non-exclusive logical "or." It should be understood that steps within a method may be performed in different orders without altering the principles of the present description.

[0026] As used herein, the term module refers to an application-specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or grouped), and memory executing one or more software or firmware programs, a combinational logic circuit, and / or other suitable components that provide the described functionality. As described in detail below, a fuel cutoff system and method reduces the oxygen flow rate to a catalyst during a deceleration fuel cutoff (DFCO) event and reduces fuel enrichment to improve the fuel efficiency of a motor vehicle.

[0027] With reference to Fig. 1, a fuel shutoff system 10 for a motor vehicle includes an internal combustion engine 12 having a plurality of engine cylinders 14. While the engine 12 includes two representative cylinders 14, it is contemplated that the engine may include any number of cylinders. In other examples, the engine may include one, three, four, five, six, eight, ten, eleven, twelve, or any other number of cylinders.

[0028] The engine 12 also includes a plurality of intake valves 16 operatively connected to the associated cylinders 14. Each intake valve 16 is movable between an open and a closed position. The intake valve 16 regulates the flow of air from the intake manifold 18 into the cylinder 14, as described below. It is contemplated that the engine may include any number of intake valves for each cylinder. In other examples, the engine may include two, three, or any other number of intake valves for each cylinder.

[0029] The engine 12 also includes a plurality of exhaust valves 17 operatively connected to the associated cylinders 14. Each exhaust valve 17 is movable between an open and a closed position. The exhaust valve 17 regulates the flow of air from the cylinder 14 into an exhaust system 35. It is contemplated that the engine may include any number of exhaust valves for each cylinder. In other examples, the engine may include two, three, or any other number of exhaust valves for each cylinder.

[0030] The engine 12 draws air from an intake manifold 18 through a throttle valve 19. In this limiting example, the throttle valve 19 may be a butterfly valve with a rotatable vane for controlling the amount of air drawn into the intake manifold 18. Air from the intake manifold 18 flows into the cylinders of the internal combustion engine 12.

[0031] The system 10 also includes a fuel actuator module 20 that regulates fuel injection to achieve a desired air / fuel ratio. Fuel may be injected into the intake manifold 18 at a central location or at multiple locations, for example, near the intake valve 16 of each cylinder 14, and the injected fuel mixes with air to create an air / fuel mixture that is directed into the cylinder 14. In other embodiments, the fuel may be injected directly into the cylinders or into the mixing chambers associated with the cylinders. The fuel actuator module 20 may pause fuel injection into the cylinders during a fuel cut-off mode, as described below.

[0032] The engine 12 further includes a plurality of pistons 22 movable between an upper and a lower position within a respective cylinder 14. A position of the pistons 22 when the respective intake valves 16 are in the closed position defines a valve timing. In the upper position, the piston 22 compresses the air / fuel mixture.

[0033] The system 10 further includes a spark actuator module 24 that can energize a spark plug 26 in the cylinder 14, which ignites the air / fuel mixture. The timing of the spark can be set relative to the time at which the piston is at its uppermost position, known as top dead center (TDC). In diesel engines, the spark actuator module and spark plug can be omitted.

[0034] The combustion of the air / fuel mixture drives piston 22 downward, thereby driving a rotating crankshaft (not shown). Piston 22 then begins to move upward again, expelling the combustion byproducts through exhaust valve 17. The combustion byproducts, including the exhaust gas, are expelled from the vehicle via an exhaust system 35.

[0035] The system 10 further includes a control system 28 with a fuel shutoff module 30, an oxygen storage module 32, and an intake valve timing module 52 that modifies valve timing to reduce the flow rate of oxygen to a catalyst as described below. In this example, the control system 28 is an engine control module (ECM), and the ECM is further electrically coupled to a throttle actuator module 34 that regulates the opening of the throttle valve 19 and controls the fuel actuator module 20.

[0036] The system 10 includes a catalyst 36 located downstream of the internal combustion engine 12 and in fluid communication with the engine cylinders to receive exhaust gases from the engine cylinders 14 and convert NOx emissions. During the fuel cutoff mode, excess oxygen is stored by the catalyst, increasing the oxygen storage capacity of the catalyst 36 and reducing the catalyst's ability to convert NOx emissions. When fueling resumes, the fuel actuator module 20 injects fuel to create a rich air-fuel mixture, reducing oxygen in the catalyst and restoring the catalyst's ability to convert NOx emissions.

[0037] The fuel shutoff module 30 is configured to determine that a DCFO event has occurred. The fuel shutoff module 30 is electrically coupled to the fuel actuator module 20 and configured to generate a fuel shutoff signal to prevent the fuel actuator module 20 from supplying fuel to the engine cylinders 14 when the fuel shutoff module determines that the DCFO event has occurred. In this example, the fuel shutoff module 30 may include an engine speed sensor 38 coupled to the engine 12 and configured to detect an engine speed of the internal combustion engine 12. In response to the engine speed being below a predetermined engine speed threshold, the fuel shutoff module 30 may determine that the DCFO event has occurred.In another example, the fuel cutoff module 30 may further include a vehicle speed sensor 40 for determining a vehicle speed and an accelerator pedal sensor 42 for detecting displacement of the accelerator pedal relative to a rest position. In response to the vehicle speed being above a predetermined speed threshold and the displacement of the accelerator pedal 44 being less than a predetermined displacement threshold, the fuel cutoff module 30 may determine that the DFCO event has occurred. In another example, the fuel cutoff module 30 may be configured to detect engine output torque. In response to the engine being in a coasting or engine braking state where the engine is outputting negative torque, the fuel cutoff module 30 may determine that the DFCO event has occurred.

[0038] In response to the fuel shutoff module 30 determining that the DFCO event has occurred, the system 10 is configured to modify the valve timing to reduce the flow rate of oxygen to the catalyst, thereby reducing the likelihood that the catalyst 36 will reach its OSC, which in turn reduces the amount of enriched fuel used to remove oxygen from the catalyst 36 after the DFCO event. Specifically, the oxygen storage module 32 is configured to determine an amount of oxygen accumulated in the catalyst 36 and compare the estimated amount of oxygen to an oxygen storage capacity of the catalyst 36.In particular, the oxygen storage module 32 may include a first oxygen sensor 46 disposed upstream of the catalyst 36 and configured to measure an amount or concentration of oxygen in the air entering the catalyst 36 and generate a corresponding first oxygen signal. The oxygen storage module 32 determines the amount of oxygen stored in the catalyst in response to the first oxygen signal and an estimated mass air flow rate into the catalyst. The oxygen storage module 32 determines the mass air flow rate in response to the measured engine speed, as described above, a manifold pressure, and a manifold temperature. The oxygen storage module 32 further includes a pressure sensor 48 for measuring the pressure of the airflow through the intake manifold 18. The pressure sensor 48 generates a pressure signal associated with the measured pressure and transmits the pressure signal to the oxygen storage module 32.The oxygen storage module 32 further includes a temperature sensor 49 for measuring the temperature of the airflow through the intake manifold 18. The temperature sensor 49 generates a temperature signal associated with the measured temperature and transmits the temperature signal to the oxygen storage module 32. The oxygen storage module 32 may further include a second oxygen sensor 47 located downstream of the catalyst 36 for detecting the amount of oxygen in the exhaust gas downstream of the catalyst, which in turn indicates that the catalyst 36 has reached its oxygen storage capacity. The second oxygen sensor 47 generates a second oxygen signal associated with the detected amount of oxygen and transmits the second oxygen signal to the oxygen storage module 32.

[0039] The system 10 also includes a plurality of cam phasers 50 operatively connected to one of the associated intake valves 16 and exhaust valves 17 for varying valve timing. Each cam phaser 50 is movable into a plurality of activated states in which the cam phaser 50 modifies the valve timing to reduce the flow rate of oxygen to the catalyst 36 during a DFCO event. More specifically, the pistons 22 are arranged in a predetermined default position when the associated intake valves 16 are arranged in the closed position and the cam phaser 50 is arranged in a first activated phaser state such that oxygen flows to the catalyst at a first flow rate.In response to the cam phaser 50 being positioned in a second activated phaser state, the valve timing is modified to either advance or retard intake valve closing through any suitable cam angle that reduces the oxygen flow rate from the first flow rate to a second flow rate. In this non-limiting example, each cam phaser is an electric cam phaser. However, the cam phaser may be any suitable cam phaser that modifies valve timing to reduce oxygen flow to the catalyst.

[0040] The intake valve timing module 52 is configured to generate a phase signal to actuate the cam phaser 50 to move into one of the activated states for modifying valve timing in response to the fuel cutoff module 30 determining that the retard fuel cutoff event has occurred and in further response to the oxygen storage module 32 determining that the amount of oxygen stored in the catalyst 36 is less than the oxygen storage capacity. The cam phaser receives the phase signal to move into one of the activated states.

[0041] In this example, in response to the DFCO event and the catalyst reaching OSC, the fuel shutoff module 30 activates the throttle actuator module 34 to move the throttle body 19 to the closed position to further reduce oxygen flow to the catalyst.

[0042] The engine cylinders 14 remain in a fixed activated state in which the valves 16 continuously move back and forth between the open and closed positions while each of the pistons 22 moves between the upper and lower positions.

[0043] With reference to Fig. 2, a method 100 for operating the fuel shut-off system 10 of Fig. 1 in block 102 with the step of defining a valve timing by arranging the pistons at a predetermined location when the associated intake valves 16 are in the closed positions.

[0044] In block 104, the fuel cutoff module 30 generates a fuel cutoff signal in response to the fuel cutoff module 30 determining that the DCFO event has occurred and in further response to the oxygen storage module determining that the amount of oxygen in the catalyst 36 is less than the oxygen storage capacity of the catalyst 36. The fuel cutoff module 30 may determine that the DFCO event has occurred when the fuel cutoff module 30 determines that the engine speed is below a predetermined engine speed threshold. The fuel cutoff module 30 may further determine that the DFCO event has occurred when the vehicle speed is above a predetermined speed threshold and when the accelerator pedal displacement is less than the predetermined displacement threshold.Additionally, the fuel shutoff module 30 may determine that the DFCO event has occurred when the output engine torque is negative in a coasting or engine braking state.

[0045] In block 106, the ECM 28 actuates the fuel actuator module 20 to deactivate the supply of fuel to the engine cylinders 14 of the internal combustion engine 12 in response to the fuel shutoff signal.

[0046] In block 108, the oxygen storage module 32 determines the amount of oxygen stored in a catalyst. This step may be accomplished by the first oxygen sensor 46 sensing the amount or concentration of oxygen in the air entering the catalyst 36 and the oxygen storage module determining the mass air flow into the catalyst in response to the measured engine speed, manifold pressure, and manifold temperature.

[0047] In block 110, the ECM 28 compares the amount of oxygen stored in the catalyst with the oxygen storage capacity of the catalyst 36. If the amount of oxygen stored in the catalyst is equal to the oxygen storage capacity, the method continues to block 112. If the amount of oxygen stored in the catalyst is less than the oxygen storage capacity, the method continues to block 114.

[0048] At block 112, the cam phasers 50 are arranged in the first phaser activated state, while the engine cylinders 14 are arranged in a first cylinder activated state, with the pistons 22 moving between the upper and lower positions and the intake valves 16 moving between the open and closed positions. The method returns to block 102.

[0049] In block 114, the intake valve timing module 52 actuates the cam phaser 50 to move from the first activated phaser state to one of the second activated phaser states in which the cam phaser 50 modifies the valve timing to reduce the flow rate of oxygen to the catalyst 36.

[0050] At block 116, the cam phasers 50 are arranged in the second activated phaser state, while the engine cylinders 14 are arranged in a second activated cylinder state, with the pistons moving between the upper and lower positions and the intake valves 16 moving between the open and closed positions.

Claims

[1] Control system (28) for a fuel shut-off system (10) of a motor vehicle, the control system (28) comprising: a fuel shutoff module (30) that determines a delay fuel shutoff event and generates a fuel shutoff signal for shutting off fuel supply to an internal combustion engine (12) in response to the fuel shutoff module (30) detecting the delay fuel shutoff event; an oxygen storage module (32) that determines an amount of oxygen accumulated in a catalyst (36) located downstream of the internal combustion engine (12), and wherein the oxygen storage module (32) compares the amount of oxygen to an oxygen storage capacity of the catalyst (36) in response to the fuel shutoff module (30) determining the delay fuel shutoff event; and an intake valve timing module (52) that generates a phase signal to actuate a plurality of cam phasers (50) to move into one of a plurality of activated states to modify a valve timing to reduce a flow rate of oxygen to the catalyst (36) in response to the fuel cut-off module (30) determining the retard fuel cut-off event and in further response to the oxygen storage module (32) determining that the amount of oxygen stored in the catalyst (36) is less than the oxygen storage capacity; wherein the oxygen storage module (32) is configured to receive a first oxygen signal from a first oxygen sensor (46) located upstream of the catalyst (36) and determine an amount of oxygen entering the catalyst (36) in response to the first oxygen signal and an air mass flow of oxygen into the catalyst (36); wherein the oxygen storage module (32) is configured to receive a second oxygen signal from a second oxygen sensor (46) located downstream of the catalyst (36), and the oxygen storage module (32) is configured to determine the amount of oxygen downstream of the catalyst (36) in response to the second oxygen signal; wherein the fuel shutoff module (30) is configured to receive an engine speed signal from an engine speed sensor (38) coupled to the internal combustion engine (12), and the fuel shutoff module (30) is configured to determine an engine speed of the internal combustion engine (12) in response to the engine speed signal; wherein the oxygen storage module (32) is configured to receive a pressure signal from a pressure sensor (48) coupled to an intake manifold (18), the pressure signal indicative of a manifold pressure, and the oxygen storage module (32) is further configured to receive a temperature signal from a temperature sensor (49) coupled to the intake manifold (18), the temperature signal indicative of a manifold temperature; in response to the oxygen storage module (32) receiving the pressure signal and the temperature signal, the oxygen storage module (32) is configured to measure the pressure of the airflow through the intake manifold (18) and the temperature of the airflow through the intake manifold (18); and in response to the measured engine speed, the measured manifold pressure and the measured manifold temperature, the oxygen storage module (32) determines the air mass flow into the catalyst (36); wherein the oxygen storage module (32) is configured to determine the amount of oxygen stored in the catalyst (36) in response to the first oxygen signal and an estimated air mass flow rate into the catalyst (36). [2] The control system (28) of claim 1, wherein the fuel cutoff module (30) determines the deceleration fuel cutoff event in response to the fuel cutoff module (30) determining that a vehicle speed is greater than a vehicle speed threshold and in further response to an accelerator pedal position being less than a position threshold. [3] The control system (28) of claim 2, wherein the deceleration fuel cut-off event occurs in response to the internal combustion engine (12) delivering negative engine torque. [4] A fuel shut-off system (10) for a motor vehicle, the system comprising: an internal combustion engine (12) comprising: a plurality of engine cylinders (14); a plurality of intake valves (16) operatively engaged with the engine cylinders (14), each of the intake valves (16) being movable between an open and a closed position; a plurality of exhaust valves (17) operatively engaged with the engine cylinders (14), each of the exhaust valves (17) being movable between an open and a closed position; a throttle body (19) movable from a closed position to an open position to allow air to flow to the engine cylinders (14); and a plurality of pistons (22) movable between upper and lower positions within a respective one of the engine cylinders (14), and a position of the pistons (22) when the respective intake valves (16) and exhaust valves (17) are arranged in the closed position defines a valve timing; a control system (28) comprising: a fuel shutoff module (30) that generates a fuel shutoff signal for shutting off fuel supply to the engine cylinders (14) and moving the throttle body (19) to the closed position in response to the fuel shutoff module (30) detecting a deceleration fuel shutoff event; an oxygen storage module (32) that determines an amount of oxygen accumulated in a catalyst (36) and compares the amount of oxygen to an oxygen storage capacity of the catalyst (36) in response to the fuel shutoff module (30) determining the delay fuel shutoff event; and an intake valve timing module (52) generating a phase signal to actuate the cam phasers (50) to move to one of the activated states in response to the fuel cutoff module (30) determining the retard fuel cutoff event and in further response to the oxygen storage module (32) determining that the amount of oxygen stored in the catalyst (36) is less than the oxygen storage capacity; and a plurality of cam phasers (50) operatively engaged with the intake valves (16) and the exhaust valves (17), the cam phasers (50) being movable into a plurality of activated states in which the cam phaser (50) modifies the valve timing to reduce the flow rate of oxygen to the catalyst (36). wherein the cam phaser (50) is movable into a first activated phaser state in which the pistons (22) are arranged in a predetermined standard position when the associated intake valves (16) are in the closed position so that oxygen flows to the catalyst (36) at a first flow rate; wherein the cam phaser (50) is further movable to a second activated phaser state in which the valve timing is modified such that the closing of the intake valves (16) is either advanced or retarded by a cam angle that reduces the flow rate of oxygen from the first flow rate to a second flow rate that is less than the first flow rate; wherein the engine cylinders (14) are maintained in a fixed activated state in which the intake valves (16) and the exhaust valves (17) continuously reciprocate between open and closed positions while each of the pistons (22) moves between the upper and lower positions; wherein the cam phaser (50) is movable to the second activated phaser state in response to the intake valve timing module (52) determining that the amount of oxygen accumulated in the catalyst (36) is less than the oxygen storage capacity; wherein the oxygen storage module (32) is configured to receive a first oxygen signal from a first oxygen sensor (46) located upstream of the catalyst (36) and determine an amount of oxygen entering the catalyst (36) in response to the first oxygen signal and a mass air flow into the catalyst (36); wherein the oxygen storage module (32) is configured to receive a second oxygen signal from a second oxygen sensor (46) located downstream of the catalyst (36), and the oxygen storage module (32) is configured to determine the amount of oxygen downstream of the catalyst (36) in response to the second oxygen signal; wherein the fuel shutoff module (30) is configured to receive an engine speed signal from an engine speed sensor (38) coupled to the internal combustion engine (12), and the fuel shutoff module (30) is configured to determine an engine speed of the internal combustion engine (12) in response to the engine speed signal; wherein the oxygen storage module (32) is configured to receive a pressure signal from a pressure sensor (48) coupled to an intake manifold (18), the pressure signal indicative of a manifold pressure, and the oxygen storage module (32) is further configured to receive a temperature signal from a temperature sensor (49) coupled to the intake manifold (18), the temperature signal indicative of a manifold temperature; in response to the oxygen storage module (32) receiving the pressure signal and the temperature signal, the oxygen storage module (32) is configured to measure the pressure of the airflow through the intake manifold (18) and the temperature of the airflow through the intake manifold (18); and in response to the measured engine speed, the measured manifold pressure and the measured manifold temperature, the oxygen storage module (32) determines the air mass flow into the catalyst (36); wherein the oxygen storage module (32) is configured to determine the amount of oxygen stored in the catalyst (36) in response to the first oxygen signal and an estimated air mass flow rate into the catalyst (36).

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