阅读说明：本技术 用于在燃料切断模式下操作发动机的系统和方法 (System and method for operating an engine in a fuel cut-off mode ) 是由 兰尼·基万 戈皮钱德拉·苏尼拉 克里斯·保罗·格鲁格拉 于 2021-04-02 设计创作，主要内容包括：本公开提供了“用于在燃料切断模式下操作发动机的系统和方法”。描述了用于操作包括可调整提升阀正时和排气再循环阀的发动机的方法和系统。在一个示例中,所述排气再循环阀打开并且所述提升阀的正时延迟,使得可以减少由所述发动机泵送到后处理装置的新鲜空气的量。(The present disclosure provides "systems and methods for operating an engine in a fuel cut-off mode". Methods and systems for operating an engine including adjustable poppet valve timing and an exhaust gas recirculation valve are described. In one example, the exhaust gas recirculation valve is opened and the timing of the poppet valve is retarded so that the amount of fresh air pumped by the engine to an aftertreatment device may be reduced.)

1. An engine operating method, comprising:

adjusting, via a controller, an intake valve closing timing and opening an exhaust gas recirculation valve in response to the engine entering a fuel cut mode.

2. The engine method of claim 1, wherein adjusting intake valve closing timing comprises retarding intake valve closing timing, and further comprising:

operating a first cylinder group in a cylinder cut-off mode while the exhaust gas recirculation valve is open and valve timing of a second cylinder group is retarded, and wherein the exhaust gas recirculation valve selectively enables and disables communication between an intake manifold of the engine and an exhaust manifold of the second cylinder group.

3. The engine method of claim 1, further comprising: the engine is placed into the fuel cut-off mode in response to releasing an accelerator pedal.

4. The engine method of claim 1, wherein said exhaust gas recirculation valve is a high pressure exhaust gas recirculation valve.

5. The engine method of claim 1, further comprising: closing the exhaust gas recirculation valve prior to exiting the engine from the fuel cut-off mode.

6. The engine method of claim 1, further comprising: adjusting intake valve timing in response to at least one of accelerator pedal position, engine speed, or vehicle speed prior to exiting the engine from the fuel cut mode.

7. The engine method of claim 1, further comprising: opening an engine throttle prior to exiting the engine from the fuel cut-off mode.

8. The engine method of claim 1, further comprising: closing a vane of a variable geometry turbocharger in response to the engine entering the fuel cut-off mode.

9. An engine system, comprising:

an engine including a high pressure Exhaust Gas Recirculation (EGR) valve and a poppet valve; and

a controller comprising executable instructions stored in non-transitory memory that cause the controller to open the high pressure EGR valve and adjust timing of the poppet valve in response to a request to stop engine rotation.

10. The engine system of claim 9, wherein said adjusting the timing of said poppet valve comprises retarding intake valve closing timing.

11. The engine system of claim 9, further comprising: additional instructions for fully closing the high-pressure EGR valve in response to the engine not rotating.

12. The engine system of claim 9, further comprising: additional instructions for fully closing the high pressure EGR valve in response to an operator change of mind.

13. The engine system of claim 9, further comprising: additional instructions for fully opening the high pressure EGR valve and adjusting timing of the poppet valve in response to releasing an accelerator pedal.

14. The engine system of claim 13, further comprising: additional instructions for fully opening the high pressure EGR valve and adjusting timing of the poppet valve in response to vehicle speed.

15. The engine system of claim 9, further comprising: additional instructions for discontinuing flow of fuel to the engine in response to the request to stop engine rotation.

Technical Field

The present disclosure relates generally to vehicle engines.

Background

The engine of the vehicle may be operated in a fuel cut-off mode when the vehicle speed is greater than a threshold speed and when the driver demand torque is less than a threshold torque. The fuel cut-off mode may include rotating the engine without supplying fuel to the engine. The engine may continue to rotate via the transfer of torque from the wheels of the vehicle to the engine. The kinetic energy of the vehicle may supply torque to rotate the wheels and engine of the vehicle. Operating the engine in the fuel cut-off mode may reduce fuel consumption since the engine does not consume fuel to maintain engine rotation. However, the reduction in fuel consumption may not be cost-free. In particular, rotating the engine without supplying fuel to the engine may cause the engine to pump fresh air to an exhaust aftertreatment device (e.g., a catalyst). Excess air introduced into the aftertreatment device may upset the balance of the oxidant and reductant in the aftertreatment device such that if the engine is restarted, NOx generated by the engine may break through the aftertreatment device without being reduced to N₂And O₂. The balance of the oxidant and reductant may be reestablished after exiting the fuel cut mode via combustion of a rich air-fuel ratio in the engine cylinder or by injection of fuel during the exhaust stroke of the cylinder. Thus, saving at least a portion of the fuel by operating the engine in a fuel cut-off mode may be used to ensure that engine emission standards are met. Therefore, operating the engine in a fuel cut mode may not be as beneficial as desired. Accordingly, it may be desirable to provide a way to operate the engine in a fuel cut-off mode so that less fuel may be applied to restart the aftertreatment device to a desired operating state.

Disclosure of Invention

The inventors herein have recognized the above disadvantages and have developed a method of operating an engine, the method comprising: an intake valve closing timing is adjusted and an Exhaust Gas Recirculation (EGR) valve is opened via a controller in response to the engine entering a fuel cut mode.

By adjusting the intake valve closing timing and opening the EGR valve in response to the engine entering a fuel cut mode, the amount of fresh air and oxygen that may be pumped by the engine to the exhaust aftertreatment device may be reduced. Therefore, it is possible to restart the aftertreatment device using less fuel than without adjusting the intake valve closing timing and without opening the EGR valve. Restarting the aftertreatment device may allow the aftertreatment device to reduce exhaust emissions (e.g., NOx) with greater efficiency.

The present description may provide several advantages. In particular, the method may reduce fuel consumption of the engine. In addition, the method may reduce cooling of the aftertreatment device such that the aftertreatment device may operate more efficiently. Further, the method may increase aftertreatment device efficiency after entering an engine fuel cut mode or after rotation of the engine is stopped.

The above advantages and other advantages and features of the present description will be readily apparent from the following detailed description when taken alone or in connection with the accompanying drawings.

It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.

Drawings

FIG. 1 shows a detailed schematic of an exemplary engine;

FIGS. 2 and 3 illustrate exemplary engine configurations;

FIG. 4 illustrates an exemplary engine operating sequence according to the method of FIG. 5; and is

FIG. 5 illustrates an exemplary method for operating an engine to improve aftertreatment efficiency and reduce fuel consumption.

Detailed Description

This description relates to operating an engine that may enter a fuel cut mode. Additionally, the present description applies to engines that may be commanded to stop automatically or via dedicated operator input. FIG. 1 shows one example of an internal combustion engine that may be operated according to the method of FIG. 5. The engine includes variable valve timing and a high pressure EGR valve and passage. Variable valve timing and high pressure EGR valves may be operated to reduce the amount of air and oxygen that may be pumped through the engine to the aftertreatment device. The engine may be configured with a single set of cylinders as shown in FIG. 2 or two sets of cylinders as shown in FIG. 3. An exemplary engine operating sequence according to the method of FIG. 5 is shown in FIG. 4. A method for operating an engine and reducing the amount of air and oxygen pumped to an aftertreatment device of an exhaust system is shown in fig. 5.

Referring to FIG. 1, an internal combustion engine 10 (including a plurality of cylinders, one of which is shown in FIG. 1) is controlled by an electronic engine controller 12. The controller 12 receives signals from the various sensors of FIG. 1 and employs the various actuators of FIG. 1 to adjust engine operation based on the received signals and instructions stored on a memory of the controller.

Engine 10 includes a combustion chamber 30 and a cylinder wall 32 with a piston 36 positioned therein and connected to a crankshaft 40. The cylinder head 13 is fastened to the engine block 14. Combustion chamber 30 is shown communicating with intake manifold 44 and exhaust manifold 48 via respective intake valve 52 and exhaust valve 54. Each intake and exhaust valve may be operated by an intake cam 51 and an exhaust cam 53. In other examples, however, the engine may operate the valves via a single camshaft or pushrod. The position of the intake cam 51 may be determined by an intake cam sensor 55. The position of exhaust cam 53 may be determined by exhaust cam sensor 57. The intake poppet valve 52 may be operated by a variable valve activation/deactivation actuator 59, which variable valve activation/deactivation actuator 59 may be a cam-driven valve operator (e.g., as shown in U.S. patent nos. 9,605,603; 7,404,383 and 7,159,551, all of which are hereby fully incorporated by reference for all purposes). Likewise, the exhaust poppet valve 54 may be operated by a variable valve activation/deactivation actuator 58, which variable valve activation/deactivation actuator 58 may be a cam-driven valve operator (e.g., as shown in U.S. Pat. Nos. 9,605,603; 7,404,383 and 7,159,551, all of which are hereby fully incorporated by reference for all purposes). For one or more complete engine cycles (e.g., two-wheel engine revolutions), intake poppet valve 52 and exhaust poppet valve 54 may be deactivated and held in a closed position via activation/deactivation actuators 58 and 59 to prevent flow into and out of cylinder 30, thereby deactivating cylinder 30. When the cylinders 30 are deactivated, the fuel flow supplied to the cylinders 30 may also be stopped. The phase of the exhaust valve timing relative to the crankshaft timing may be adjusted via a phase actuator 84. Similarly, the phase of the intake valve timing relative to the crankshaft timing may be adjusted via phase actuator 85.

Fuel injector 68 is shown positioned in cylinder head 13 to inject fuel directly into combustion chamber 30, which is referred to by those skilled in the art as direct injection. Fuel is delivered to fuel injectors 68 by a fuel system including a fuel tank 26, a fuel pump 21, a fuel pump control valve 25, and a fuel rail (not shown). The pressure of the fuel delivered by the fuel system may be adjusted by changing a position valve that regulates flow to a fuel pump (not shown). Additionally, metering valves may be located in or near the fuel rail for closed loop fuel control.

Engine intake system 9 may include an intake manifold 44, a central throttle 62, a turbocharger compressor 162, and an air filter 42. Intake manifold 44 is shown communicating with an optional central throttle 62 that adjusts a position of throttle plate 64 to control airflow from intake plenum 46. Turbocharger compressor 162 draws air from air filter 42 to supply plenum 46. The turbocharger turbine 164 rotates the turbocharger compressor 162 via a shaft 161. The exhaust gas may apply a force to the variable geometry vanes 163 to rotate the shaft 161. The vane actuator 165 may adjust the position of the vanes 163 to increase or decrease the efficiency of the vanes 163. Thus, the compressor speed may be adjusted via adjusting the position of the vanes 163. Compressor recirculation valve 158 allows compressed air at outlet 15 of compressor 162 to return to inlet 17 of compressor 162. In this manner, the efficiency of the compressor 162 may be increased or decreased in order to affect the flow of the compressor 162 and reduce the likelihood of compressor surge. Arrow 5 shows the direction of airflow through the engine when the engine is operating in a fuel cut mode or after a request to stop engine rotation.

A flywheel 97 and a ring gear 99 are coupled to crankshaft 40. The starter 96 (e.g., a low voltage (operating at less than 30 volts) motor) includes a pinion shaft 98 and a pinion gear 95. Pinion shaft 98 may selectively advance pinion gear 95 to engage ring gear 99 such that starter 96 may rotate crankshaft 40 during an engine cranking. The starter 96 may be mounted directly to the front of the engine or to the rear of the engine. In some examples, starter 96 may selectively supply torque to crankshaft 40 via a belt or chain. In one example, starter 96 is in a base state when not engaged to the engine crankshaft. The driver or vehicle occupant may request engine start or engine stop rotation via a dedicated human/machine interface 69 (e.g., key switches, buttons, remote radio frequency transmission devices, etc.) having the sole function of starting and stopping the engine. Alternatively, a stop engine rotation request or an engine start request may be automatically generated via controller 12 in response to vehicle operating conditions (e.g., brake pedal position, propulsion pedal position, battery SOC, etc.). The low-voltage battery 8 can supply electric power to the starter 96. The controller 12 may monitor the battery state of charge.

Combustion is initiated in combustion chamber 30 via spark plug 66. The ignition system 88 may include a coil and circuitry to provide electrical energy to the spark plug 66. In some examples, a Universal Exhaust Gas Oxygen (UEGO) sensor 126 may be coupled to Exhaust manifold 48 upstream of Exhaust device 70. In other examples, the UEGO sensor may be positioned downstream of one or more exhaust aftertreatment devices. Further, in some examples, the UEGO sensor may be replaced by a NOx sensor having both NOx and oxygen sensing elements.

Engine exhaust may be processed via an exhaust system 11 including an exhaust manifold and an aftertreatment device 70 (e.g., a three-way catalyst, a particulate filter, etc.). EGR may be provided to the engine via a high pressure Exhaust Gas Recirculation (EGR) system 83. The high-pressure EGR system 83 includes a valve 80 and an EGR passage 81. EGR valve 80 is a valve that blocks or allows exhaust gas to flow from upstream of exhaust device 70 to a location in the engine intake system downstream of compressor 162. The EGR may be cooled via passage through an EGR cooler (not shown). EGR may also be provided via a low pressure EGR system 75. The low-pressure EGR system 75 includes an EGR passage 77 and an EGR valve 76. Low pressure EGR may flow from downstream of exhaust 70 to a location upstream of compressor 162. Low-pressure EGR system 75 may include EGR cooler 74, cooler bypass passage 77a, and low-pressure cooler bypass valve 78. The low pressure cooler bypass valve 78 may be opened to bypass the gas around the cooler 74.

The controller 12 is shown in fig. 1 as a conventional microcomputer including: microprocessor unit 102, input/output ports 104, read only memory (e.g., non-transitory memory) 106, random access memory 108, keep alive memory 110, and a conventional data bus. Controller 12 is shown receiving various signals from sensors coupled to engine 10 in addition to those signals previously discussed, including: engine Coolant Temperature (ECT) from temperature sensor 112 coupled to cooling sleeve 114; a position sensor 134 coupled to the propulsion pedal 130 for sensing a propulsion position adjusted by the human foot 132; a measurement of engine manifold pressure (MAP) from a pressure sensor 121 coupled to intake manifold 44 (alternatively or additionally, sensor 121 may sense intake manifold temperature); boost pressure from pressure sensor 122; exhaust oxygen concentration from oxygen sensor 126; an engine position sensor from a Hall effect sensor 118 sensing crankshaft 40 position; a measurement of air mass entering the engine from a sensor 120 (e.g., a hot wire air flow meter); and a measurement of throttle position from sensor 58. Atmospheric pressure may also be sensed (sensor not shown) for processing by controller 12. In a preferred aspect of the present description, the engine position sensor 118 generates a predetermined number of equally spaced pulses every revolution of the crankshaft from which the engine speed (RPM) can be determined.

During operation, each cylinder within engine 10 typically undergoes a four-stroke cycle: the cycle includes an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. During the intake stroke, generally, exhaust valve 54 closes and intake valve 52 opens. Air is introduced into combustion chamber 30 via intake manifold 44 and piston 36 moves to the bottom of the cylinder to increase the volume within combustion chamber 30. The position at which piston 36 is near the bottom of the cylinder and at the end of its stroke (e.g., when combustion chamber 30 is at its largest volume) is typically referred to by those of skill in the art as Bottom Dead Center (BDC). During the compression stroke, intake valve 52 and exhaust valve 54 are closed. Piston 36 moves toward the cylinder head to compress air within combustion chamber 30. The point at which piston 36 is at the end of its stroke and closest to the cylinder head (e.g., when combustion chamber 30 is at its smallest volume) is commonly referred to by those skilled in the art as Top Dead Center (TDC). In a process hereinafter referred to as injection, fuel is introduced into the combustion chamber. In some examples, fuel may be injected into a cylinder multiple times during a single cylinder cycle.

In a process hereinafter referred to as ignition, the injected fuel is ignited via compression ignition by a spark generated at spark plug 66, or alternatively in a diesel engine, resulting in combustion. During the expansion stroke, the expanding gases push piston 36 back to BDC. Crankshaft 40 converts piston movement into rotational torque of the rotary shaft. Finally, during the exhaust stroke, the exhaust valve 54 opens to release the combusted air-fuel mixture to exhaust manifold 48 and the piston returns to TDC. Note that the above is described merely as an example, and that intake and exhaust valve opening and/or closing timings may vary, such as to provide positive or negative valve overlap, late intake valve closing, or various other examples. Further, in some examples, a two-stroke cycle may be used instead of a four-stroke cycle.

Referring now to FIG. 2, a first exemplary configuration of engine 10 is shown. In this example, engine 10 includes a single cylinder bank 200, which single cylinder bank 200 includes four cylinders. The four cylinders are numbered 1-4. During the fuel cut mode, throttle 62 may be fully closed and air may be pumped from intake manifold 44 through cylinders 1-4 and into exhaust manifold 48. At least a portion of the air in the exhaust manifold may be returned to intake manifold 44 via high-pressure EGR passage 81, as indicated by arrow 202. Air that is not returned to intake manifold 44 may exit engine 10 as indicated by arrow 204.

Referring now to FIG. 3, a second exemplary configuration of engine 10 is shown. In this example, engine 10 includes two cylinder banks 300 and 302, where two cylinder banks 300 and 302 include eight cylinders. Eight cylinders are numbered 1-8. During the fuel cut mode, throttle 62 may be fully closed and air may be pumped from intake manifold 44 through cylinders 5-8 and into exhaust manifold 48 b. At least a portion of the air in the exhaust manifold may be returned to intake manifold 44 via high-pressure EGR passage 81, as indicated by arrow 304. Air that is not returned to intake manifold 44 may exit engine 10 and aftertreatment device 70b, as indicated by arrow 306. The intake and exhaust valves of cylinders 1-4 may remain closed during a complete cycle of engine 10 so that air and oxygen are not pumped to aftertreatment device 70 a. In examples where the poppet valves in cylinders 1-4 may not remain closed for a complete engine cycle, a portion of the air and oxygen in intake manifold 44 may exit engine 10 as indicated by arrow 308.

The system of fig. 1-3 provides an engine system comprising: an engine including a high pressure Exhaust Gas Recirculation (EGR) valve and a poppet valve; and a controller comprising executable instructions stored in non-transitory memory that cause the controller to open the high pressure EGR valve and adjust timing of the poppet valve in response to a request to stop engine rotation. The engine system includes: wherein adjusting the timing of the poppet valve includes retarding an intake valve closing timing. The engine system further includes: additional instructions for fully closing the high-pressure EGR valve in response to the engine not rotating. The engine system further includes: additional instructions for fully closing the high-pressure EGR valve in response to an operator change of mind. The engine system further includes: additional instructions for fully opening the high pressure EGR valve and adjusting the timing of the poppet valve in response to releasing the propulsion pedal. The engine system further includes: additional instructions for fully opening the high pressure EGR valve and adjusting the timing of the poppet valve in response to vehicle speed. The engine system further includes: additional instructions for discontinuing the flow of fuel to the engine in response to a request to stop engine rotation.

Referring now to FIG. 4, an exemplary predictive engine operating sequence for an engine is shown. The operational sequence of fig. 4 may be generated via the systems of fig. 1-3 executing instructions according to the method described in fig. 5. The graphs of fig. 4 are aligned in time and occur simultaneously. the vertical markers at t0-t5 indicate times of particular interest during the sequence.

The first plot from the top of fig. 4 represents engine state versus time. Trace 402 represents engine state, and the engine is off and not rotating when trace 402 is at a low level near the horizontal axis. When trace 402 is at a higher level near the vertical axis arrow, the engine is turned on and receives fuel, burns fuel, or at least attempts to burn fuel. The vertical axis indicates the engine state. The engine is in a fuel cut mode in which the engine rotates without receiving fuel and combusting the fuel when trace 402 is at the mid-level of the vertical axis. The vertical axis indicates the engine state. The horizontal axis represents time, and time increases from the left side to the right side of the figure.

The second plot from the top of FIG. 4 represents EGR valve position versus time. Trace 404 represents EGR valve position. The vertical axis represents the EGR valve position, and the EGR valve is fully open when trace 404 is near label FO along the vertical axis. When trace 404 is near tag FC along the vertical axis, the EGR valve is fully closed. The horizontal axis represents time, and time increases from the left side to the right side of the figure.

The third plot from the top of fig. 4 represents center throttle position versus time. Trace 406 represents the center throttle condition. The vertical axis represents the central throttle state, and the central throttle is fully open when trace 406 is near label FO along the vertical axis. When trace 406 is near tag FC along the vertical axis, the central throttle is fully closed. The horizontal axis represents time, and time increases from the left side to the right side of the figure.

The fourth plot from the top of fig. 4 represents Intake Valve Closing (IVC) position versus time. Trace 408 represents IVC position. The vertical axis represents the IVC position, and the IVC advances when trace 408 is near label adv along the vertical axis. When trace 408 is near tag ret. along the vertical axis, IVC delays. The horizontal axis represents time, and time increases from the left side to the right side of the figure.

The fifth plot from the top of fig. 4 represents propulsion pedal position versus time. Trace 410 represents the propel pedal position, and when trace 401 is near tab FA along the vertical axis, the propel pedal is fully depressed. When trace 410 is near label FR along the vertical axis, the propel pedal is fully returned. The horizontal axis represents time, and time increases from the left side to the right side of the figure.

At time t0, the engine is turned on and fuel is combusted. The EGR valve is partially open and the central throttle valve is partially open. IVC timing is partially advanced and the propulsion pedal is partially depressed. Such conditions may exist when the vehicle is traveling on a road at cruising speeds.

At time t1, the engine enters a fuel cut mode in which the engine rotates without fuel being supplied to the engine. The engine may continue to rotate as the kinetic energy of the vehicle is transferred from the wheels of the vehicle to the engine. When the engine is operating in a fuel cut mode via discontinuing the supply of fuel to the engine cylinders, all of the engine cylinders may be deactivated. The EGR valve is fully opened in response to the engine entering a fuel cut mode, and the central throttle valve is also fully closed in response to the engine entering the fuel cut mode. Closing the central throttle and fully opening the EGR valve may reduce the amount of air and oxygen pumped by the engine to the exhaust aftertreatment device. IVC timing is also retarded so that the amount of air entering the engine cylinders from the intake manifold can be reduced. The propel pedal is shown fully released. The engine may enter a fuel cut mode based on the driver requested torque and the vehicle speed. The driver demand torque may be determined based on the propulsion pedal position and the vehicle speed. For example, a table or function of empirically determined driver demand torque values may be indexed or referenced via vehicle speed and propulsion pedal position. The table or function outputs the driver demand torque. The values in the table or function may be determined via operating the vehicle on a dynamometer and adjusting the values in the table until a desired vehicle performance level is reached that provides the desired vehicle performance level for the particular propulsion pedal position and vehicle speed. Between time t1 and time t2, the engine remains in the fuel cut mode.

At time t2, the vehicle operator (not shown) depresses the propulsion pedal to increase the operator demand torque, causing the engine to exit the fuel cut-off mode and restart. The EGR valve is partially closed so that a desired amount of EGR can be provided to the engine cylinders. The central throttle valve is opened so that air can be supplied to the engine. The increase in airflow to the engine allows the engine to generate the driver requested torque. IVC timing is advanced so that a greater amount of air may enter the engine cylinders so that engine torque output may be increased. Shortly after the EGR valve closes, the engine exits the fuel cut mode and begins to burn fuel.

At time t3, the vehicle operator (not shown) fully releases the propulsion pedal and the engine continues to burn fuel and spin. When the propulsion pedal is released, the EGR valve is partially open and the central throttle is closed. IVC timing begins to retard in response to the propulsion pedal being fully released.

At time t4, a request to stop engine rotation (not shown) is issued, and the EGR valve is fully opened in response to the request to stop engine rotation. The central throttle remains closed and IVC timing is further retarded. The propel pedal remains released. The fuel supply to the engine (not shown) is also cut off so that the engine speed starts to decrease (not shown).

At time t5, engine speed reaches zero, and the EGR valve is fully closed in response to engine speed reaching zero. IVC timing is also advanced in preparation for a subsequent engine start. The central throttle remains closed and the push pedal remains fully released.

In this way, when it is requested to stop the engine rotation and when the engine enters the fuel cut mode, the flow of air and oxygen to the catalyst may be reduced.

Referring now to FIG. 5, a method for operating an engine is shown. In particular, a flow chart of a method for operating an internal combustion engine is shown. The method of fig. 5 may be stored as executable instructions in a non-transitory memory in a system such as that shown in fig. 1-3. The method of fig. 5 may be incorporated into and cooperate with the systems of fig. 1-3. Further, at least part of the method of fig. 5 may be incorporated as executable instructions stored in a non-transitory memory, while other parts of the method may be performed via a controller transforming the operating states of devices and actuators in the physical world. The controller may employ engine actuators of the engine system to adjust engine operation according to the methods described below. Further, the method 500 may determine the selected control parameter based on the sensor input.

At 502, method 500 determines vehicle operating conditions. Vehicle operating conditions may include, but are not limited to, engine temperature, propulsion pedal position, ambient temperature, engine start request, engine stop rotation request, vehicle speed, ambient pressure, driver demand torque, and engine speed. Vehicle operating conditions may be determined via the vehicle sensors and engine controller described in FIG. 1. The method 500 proceeds to 504.

At 504, method 500 judges whether or not there is a condition for the engine to enter a fuel cut mode. In one example, method 500 may enter a fuel cut mode when the driver demand torque as determined from the propulsion pedal position is less than a threshold and the vehicle speed is greater than a threshold. If method 500 determines that there is a condition for entering a fuel cut mode, the answer is yes and method 500 proceeds to 506. Otherwise, the answer is no and method 500 proceeds to 530.

At 506, method 500 fully closes the engine throttle. Closing the engine throttle reduces the flow of air and oxygen to the aftertreatment device so that the aftertreatment device may not be saturated with oxygen. Additionally, closing the throttle may help maintain the temperature of the aftertreatment device, which may help maintain the efficiency of the aftertreatment device. It should be noted that even if the engine throttle is fully closed, a small amount of air may pass through the engine, as fully closing the throttle may not provide an air-tight seal. The method 500 proceeds to 508.

At 508, method 500 fully opens the high-pressure EGR valve. By fully opening the high pressure EGR valve, at least a portion of the air that may be pumped from the engine intake manifold to the engine exhaust manifold may be returned to the engine intake manifold, thereby reducing the flow of air and oxygen to the aftertreatment devices in the exhaust system. Additionally, in some examples, method 500 may fully close the vanes of the variable geometry turbocharger to limit the flow of air through the aftertreatment device. Method 500 proceeds to 510.

At 510, method 500 adjusts the timing of engine poppet valves to reduce air flow through engine cylinders. In one example, the timing of the intake poppet valves may be retarded so that a portion of the air drawn into the engine cylinders may be injected back into the engine intake manifold. The timing of the cylinder groups may be adjusted in this manner. In addition, if the engine is a V-type engine, the poppet valves of one cylinder group may be deactivated in the closed state, so that one cylinder group may enter a cylinder cut-off mode in which the valves of the cylinders are deactivated. As previously described, the timing of the poppet valves of the second cylinder group may be retarded. The EGR valve may couple the exhaust manifold of the second cylinder group directly to the engine intake manifold, as shown in fig. 3, so that the air flow through the second cylinder group may be reduced. Method 500 proceeds to 512.

At 512, method 500 causes the selected cylinder to enter a fuel cut mode. In one example, if the engine includes a single cylinder bank, all of the engine cylinders may be placed in a fuel cut mode. For example, if the cylinder is a four cylinder engine, four cylinders of the engine may cease to receive fuel while the poppet valves of the selected cylinders continue to operate. Additionally, if the engine includes two cylinder banks, some of the cylinders may enter a cylinder cut-off mode in which the poppet valves of those cylinders remain closed during a complete cycle of the engine (e.g., two revolutions of the engine). Fuel delivery to the cylinder in the cylinder cut-off mode is also suspended. Method 500 proceeds to 514.

At 514, method 500 judges whether or not conditions exist to exit the fuel cut mode and the cylinder cut mode. In one example, if the driver demand torque is greater than a threshold torque, method 500 may determine that conditions exist for exiting the fuel cut mode and the cylinder cut mode. If method 500 determines that there are conditions for exiting the fuel cut mode and the cylinder cut mode, the answer is yes and method 500 proceeds to 516. Otherwise, the answer is no, and method 500 returns to 514.

At 516, method 500 adjusts the position of the throttle to supply air to meet the requested driver demand torque. Additionally, if the vanes of the variable geometry turbocharger have previously been closed, they may be opened to increase the compressor speed in order to meet the driver demand torque. Method 500 proceeds to 518.

At 518, method 500 at least partially closes the high pressure EGR valve. In some examples, the high pressure EGR valve may be fully closed. The high pressure EGR valve is at least partially closed so that the engine cylinder may not receive an amount of EGR that may cause engine misfire when the engine cylinder is restarted. Method 500 proceeds to 520.

At 520, method 500 adjusts poppet timing. In one example, method 500 may advance IVC timing so that engine cylinders may induct a greater amount of air so that the engine may generate torque and have good combustion stability. Method 500 proceeds to 522.

At 522, method 500 exits the cylinders operating in the fuel cut mode by restarting the cylinders. The cylinders may be restarted via injecting fuel into the cylinders and combusting the fuel. Additionally, if any cylinder is currently in the cylinder cut-off mode, method 500 may exit the cylinder from the cylinder cut-off mode. The cylinder may exit the cylinder cut-off mode by opening and closing intake and exhaust valves of the cylinder and injecting fuel into the cylinder. Method 500 proceeds to exit.

At 530, method 500 judges whether or not engine rotation stop is requested. Stopping engine rotation may be requested via a vehicle operator when the vehicle operator intends to leave the vicinity of the vehicle or when the vehicle operator does not intend to move the vehicle for an extended period of time. Alternatively, stopping engine rotation may be requested automatically via an engine controller (e.g., without requiring the vehicle operator to supply input to a dedicated device for the sole purpose of starting and stopping engine rotation) in response to vehicle operating conditions. For example, when the driver demand torque is less than a threshold and the vehicle speed is less than a threshold, it may be requested to stop the engine rotation. If method 500 determines that stopping engine rotation is requested, the answer is yes and method 500 proceeds to 532. Otherwise, the answer is no and method 500 proceeds to 550.

At 532, method 500 aborts fuel injection to the engine to stop engine rotation. Method 500 proceeds to 534.

At 534, method 500 fully opens the high-pressure EGR valve. The high pressure EGR valve opens during engine spin-down so that air entering the engine after fuel injection is discontinued may be recirculated back to the engine intake manifold so that less excess air and oxygen may reach the exhaust system aftertreatment device. By reducing the amount of air reaching the aftertreatment device during engine stop, the engine may be restarted and the aftertreatment device restarted by supplying less fuel to the engine and/or aftertreatment device. Thus, fuel consumption may be reduced and the aftertreatment device may be restarted more quickly so that engine emissions may be converted more quickly and efficiently. Additionally, method 500 may close vanes of a variable geometry turbocharger to further reduce air flow to an aftertreatment device. Method 500 proceeds to 536 after the EGR valve is opened.

At 536, method 500 adjusts the timing of engine poppet valves to reduce the air flow through the engine cylinders as the engine coasts to a stop. In one example, the timing of the intake poppet valves may be retarded so that a portion of the air drawn into the engine cylinders may be injected back into the engine intake manifold. Method 500 proceeds to 538.

At 538, method 500 judges whether the engine has stopped rotating or whether the vehicle operator has instructed to change mind. Changing the mind may include changing the mind from stopping engine rotation to propelling the vehicle. For example, if the vehicle speed reaches zero and the propulsion pedal is not depressed, the engine controller may automatically begin a stop engine rotation sequence. The stopping the engine rotation sequence may include stopping a flow of fuel to the engine. However, the engine may continue to rotate while fuel that has been injected to the engine is being combusted prior to stopping the engine rotation sequence. If the driver of the vehicle depresses the propulsion pedal while the engine is still rotating, then depressing the propulsion pedal may be interpreted as changing mind. The engine may be restarted by starting fuel injection and ignition of the engine in response to changing mind so that the vehicle speed may be increased according to the driver demand. If method 500 determines that the engine has stopped spinning or a change in mind has occurred, the answer is yes and method 500 proceeds to 540. Otherwise, the answer is no and method 500 returns to 538.

At 540, method 500 at least partially closes the high pressure EGR valve. In some examples, method 500 may fully close the high pressure EGR valve. By closing the EGR valve, the engine may be restarted without introducing potentially more EGR than is necessary. Method 500 proceeds to 542.

At 542, method 500 adjusts poppet timing. In one example, IVC timing may be advanced so that cylinders of the engine may be inducted with sufficient air to support stable combustion in the engine. The IVC timing may be adjusted to the timing required for starting the engine. Method 500 proceeds to exit.

At 550, method 500 adjusts the EGR valve in response to engine operating conditions (e.g., engine speed and engine load). In one example, method 500 references a table of empirically determined EGR flow rates based on engine speed and engine load. The position of the EGR valve is adjusted to provide the EGR rate output by the table. Method 500 proceeds to 552.

At 552, method 500 adjusts poppet valve timing in response to engine operating conditions (e.g., engine speed and engine load). In one example, method 500 refers to a table of empirically determined poppet valve timings based on engine speed and engine load. The timing of the poppet valves may be adjusted to provide the desired volumetric efficiency and internal EGR. The method 500 proceeds to 554.

At 554, method 500 commands the engine to provide the requested driver requested torque. The requested driver demand torque may be provided via adjusting one or more torque actuators of the engine. For example, method 500 may adjust throttle position, spark timing, and fuel injection amount such that the engine may generate the requested driver demand torque. Method 500 proceeds to exit.

In this way, poppet valve timing and EGR valve state may be adjusted to reduce the amount of air and oxygen that may be pumped by the engine to the aftertreatment device. By reducing the amount of air pumped to the aftertreatment device, it is possible to reduce the amount of fuel used to restart the aftertreatment device. Therefore, engine fuel consumption can be reduced.

Accordingly, the method of FIG. 5 provides for an engine operating method comprising: adjusting, via a controller, an intake valve closing timing and opening an exhaust gas recirculation valve in response to the engine entering a fuel cut mode. The engine method includes: wherein adjusting the intake valve closing timing comprises retarding the intake valve closing timing, and the engine method further comprises: operating a first cylinder group in a cylinder cut-off mode while the exhaust gas recirculation valve is open and valve timing of a second cylinder group is retarded, and wherein the exhaust gas recirculation valve selectively enables and disables communication between an intake manifold of the engine and an exhaust manifold of the second cylinder group. The engine method further comprises: the engine is placed into the fuel cut-off mode in response to releasing a propulsion pedal. The engine method includes: wherein the exhaust gas recirculation valve is a high pressure exhaust gas recirculation valve. The engine method further comprises: closing the exhaust gas recirculation valve prior to exiting the engine from the fuel cut-off mode. The engine method further comprises: adjusting intake valve timing in response to at least one of accelerator pedal position, engine speed, or vehicle speed prior to exiting the engine from the fuel cut mode. The engine method further comprises: opening an engine throttle prior to exiting the engine from the fuel cut-off mode. The engine method further comprises: closing a vane of a variable geometry turbocharger in response to the engine entering the fuel cut-off mode.

The method of FIG. 5 also provides for an engine operating method comprising: the intake valve closing timing is adjusted and the exhaust gas recirculation valve is opened via the controller in response to a request to stop engine rotation. The engine method includes: wherein adjusting the intake valve closing timing comprises retarding the intake valve closing timing. The engine method includes: wherein opening the exhaust gas recirculation valve comprises fully opening the exhaust gas recirculation valve. The engine method further comprises: fully closing the exhaust gas recirculation valve in response to changing mind. The engine method includes: wherein the change of mind is indicated via depression of a propel pedal.

It should be noted that the exemplary control and estimation routines included herein may be used with various engine and/or vehicle system configurations. The control methods and programs disclosed herein may be stored as executable instructions in a non-transitory memory and executed by a control system including a controller in conjunction with various sensors, actuators, and other engine hardware. Furthermore, part of the method may be a physical action taken in the real world to change the state of the device. The specific routines described herein may represent one or more of any number of processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. As such, various acts, operations, and/or functions illustrated may be performed in the sequence illustrated, in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily required to achieve the features and advantages of the example embodiments described herein, but is provided for ease of illustration and description. One or more of the illustrated acts, operations, and/or functions may be repeatedly performed depending on the particular strategy being used. Further, the acts, operations, and/or functions may graphically represent code to be programmed into the non-transitory memory of the computer readable storage medium in the engine control system, wherein the acts are performed by execution of the instructions in conjunction with an electronic controller in a system that includes various engine hardware components. One or more of the method steps described herein may be omitted, if desired.

It will be appreciated that the configurations and routines disclosed herein are exemplary in nature, and that these specific examples are not to be considered in a limiting sense, because numerous variations are possible. For example, the above-described techniques may be applied to V-6, I-4, I-6, V-12, opposed 4, and other engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and subcombinations of the various systems and configurations, and other features, functions, and/or properties disclosed herein.

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