System and method for operating an engine including a fuel vapor canister

Abstract

The present application discloses a system and method for operating an engine including a canister for storing fuel vapors. In one example, when a deceleration fuel cutoff condition is met, one or more engine cylinders are deactivated in response to the level of fuel vapor stored in the fuel vapor storage canister. By deactivating one or more engine cylinders with closed intake and exhaust valves, it is possible to reduce the inhalation of fuel vapor into the engine cylinders, thereby reducing the likelihood of cylinder misfire.

Description

Background Art

[0001] The internal combustion engine can be supplied with fuel from a fuel tank. The fuel tank can contain fuel vapor, which increases the pressure in the fuel tank to above atmospheric pressure. The pressure in the fuel tank can be the power to drive the fuel vapor from the fuel tank into the fuel vapor storage tank. One side of the fuel vapor storage tank can be vented to the atmosphere so that the fuel vapor can flow into the fuel vapor storage tank. Once the fuel vapor enters the fuel vapor storage tank, they can be adsorbed in the activated carbon. The activated carbon separates the fuel from the gaseous mixture entering the fuel vapor storage tank and allows the air to be released into the atmosphere, thereby reducing the pressure in the fuel tank and the fuel vapor storage tank. The tank purge valve located along the line or conduit leading from the fuel vapor tank to the engine intake manifold can be opened from time to time to purge the fuel vapor from the fuel vapor storage tank. The lower pressure in the engine intake manifold draws air from the atmosphere through the fuel vapor tank, which combines with the stored fuel vapor at the fuel vapor tank before entering the engine. The fuel concentration in the air-fuel mixture drawn from the fuel vapor storage tank can vary from mostly air to mostly fuel. If the fuel concentration in the vapor drawn into the engine is high, the engine cylinders will be exposed to an amount of fuel that may be sufficient to cause the engine cylinders to misfire.

[0002] During lower driver demand torque conditions, the internal combustion engine may also enter a mode known as deceleration fuel shutoff (DFSO) or deceleration fuel stop. During DFSO, fuel supply to the engine cylinders is stopped while the engine continues to rotate with the aid of the vehicle's kinetic energy, which is transferred to the engine through the vehicle's wheels and powertrain. By stopping the delivery of fuel to the engine during periods of lower driver demand, engine fuel consumption may be reduced. However, if fuel vapors are drawn from the fuel vapor canister into the engine cylinders when the canister purge valve is closed due to low engine intake manifold pressure, the engine cylinders may misfire when the engine cylinders are reactivated. Therefore, it may be desirable to provide a way to reduce the likelihood of engine misfire when the engine cylinders are reactivated after the engine exits DFSO. Summary of the invention

[0003] The inventors have recognized that engine stalling during cylinder reactivation is undesirable and have developed an engine operating method that includes: in response to a deceleration fuel cutoff condition existing and an amount of fuel vapor stored in a canister being greater than a threshold, a controller maintaining the intake and exhaust valves of a cylinder closed during one or more engine cycles.

[0004] By closing the intake and exhaust valves of a cylinder and keeping them closed when a deceleration fuel cutoff condition exists, the following technical effects can be provided: reducing the likelihood of cylinder misfire when the cylinder resumes burning air and fuel after exiting DFSO. In one example, as the engine enters DFSO, air can be trapped in the engine cylinder so that the cylinder can be restarted without over-fueling due to fuel vapor entering the cylinder during DFSO. In this way, at least one cylinder of the engine can be reactivated with a higher degree of confidence after exiting DFSO.

[0005] The present description may provide several advantages. In particular, the scheme may provide improved engine reactivation after the engine enters DFSO. In addition, the scheme may reduce engine air flow to a catalyst in an exhaust system of the engine when the engine is in a deceleration fuel cutoff so that less fuel may be injected into the engine cylinders to balance the catalytic oxidant and reductant. Additionally, the scheme may reduce intake manifold vacuum during DFSO, thereby reducing the likelihood of fuel vapor being absorbed from a fuel vapor storage canister into the engine during DFSO.

[0006] It should be understood that the above summary is provided to briefly introduce the invention summary, which will be further described in the detailed description. It is not intended to identify key or essential features of the claimed subject matter, and the scope of protection is solely defined by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages mentioned above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 A schematic diagram showing one cylinder of an exemplary engine system;

[0008] Figure 2 An exemplary cylinder valve activation / deactivation arrangement is shown;

[0009] Figure 3 An exemplary fuel vapor management system is shown;

[0010] Figure 4A and Figure 4B An exemplary cylindrical configuration is shown;

[0011] Figure 5 An exemplary DFSO sequence is shown; and

[0012] Figure 6 An example method for operating an engine is shown. DETAILED DESCRIPTION

[0013] The present description relates to operating an engine in a vehicle including a fuel vapor storage canister for storing vapors from a fuel tank. Figure 1 An exemplary engine that may combust fuel vapors from a fuel vapor storage canister is shown. Figure 2 An exemplary actuation mechanism for activating and deactivating cylinder valves is shown. Figure 3 Shown including Figure 1 Fuel vapor control system for engines. Figure 4A and Figure 4B An exemplary engine cylinder configuration is shown, and Figure 5 The sequence of entering and exiting DFSO is shown. Figure 6 A method is described for entering and exiting DFSO to reduce the likelihood of engine flameout associated with fuel stored in a fuel vapor storage canister.

[0014] refer to Figure 1 The internal combustion engine 10 includes a plurality of cylinders, one of which is Figure 1 , which is controlled by electronic engine controller 12. Engine 10 includes cylinder head 35 and cylinder block 33, which includes combustion chamber 30 and cylinder wall 32. Piston 36 is positioned therein and reciprocates through connection with crankshaft 40. Flywheel 97 and ring gear 99 are coupled to crankshaft 40. Starter 96 (e.g., a low voltage (operated with a voltage less than 30 volts) motor) includes pinion shaft 98 and pinion 95. Pinion shaft 98 can selectively advance pinion 95 to engage with ring gear 99. Starter 96 can be mounted directly to the front or rear of the engine. In some examples, starter 96 can selectively supply torque to crankshaft 40 via a belt or chain. In one example, starter 96 is in a basic state when not engaged to the engine crankshaft.

[0015] 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. The position of intake cam 51 may be determined by intake cam sensor 55. The position of exhaust cam 53 may be determined by exhaust cam sensor 57. Intake valve 52 may be selectively activated and deactivated by valve actuator device 59. Exhaust valve 54 may be selectively activated and deactivated by valve actuator device 58. Valve actuator devices 58 and 59 may be as shown. Figure 2 As shown or other known configurations.

[0016] Fuel injector 66 is positioned to inject fuel directly into cylinder 30, which is known to those skilled in the art as direct injection. Fuel injector 66 delivers liquid fuel in proportion to the pulse width from controller 12. Fuel is delivered to fuel injector 66 by a fuel system (not shown) including a fuel tank, a fuel pump, and a fuel rail (not shown). In one example, a high pressure dual stage fuel system may be used to generate higher fuel pressures.

[0017] In addition, intake manifold 44 is shown to be in communication with turbocharger compressor 162 and engine intake passage 42. In other examples, compressor 162 may be a supercharger compressor. Shaft 161 mechanically couples turbocharger turbine 164 to turbocharger compressor 162. Optional electronic throttle 62 adjusts the position of throttle plate 64 to control the air flow from compressor 162 to intake manifold 44. The pressure in boost chamber 45 may be referred to as throttle inlet pressure because the inlet of throttle 62 is located in boost chamber 45. The throttle outlet is located in intake manifold 44. In some examples, throttle 62 and throttle plate 64 may be positioned between intake valve 52 and intake manifold 44 so that throttle 62 is an intake port throttle. Wastegate 163 may be adjusted by controller 12 to allow exhaust to selectively bypass turbine 164 to control the speed of compressor 162. The air filter 43 purifies the air entering the engine intake passage 42. The throttle valve 62 is positioned downstream of the compressor 162 in the direction in which air flows into the engine 10.

[0018] Distributorless ignition system 88 provides an ignition spark to combustion chamber 30 via spark plug 92 in response to controller 12. Universal Exhaust Gas Oxygen (UEGO) sensor 126 is shown coupled to exhaust manifold 48 upstream of catalytic converter 70. Alternatively, a two-state exhaust gas oxygen sensor may be substituted for UEGO sensor 126.

[0019] In one example, converter 70 may include multiple catalyst bricks. In another example, multiple emission control devices may be used, each with multiple bricks. In one example, converter 70 may be a three-way catalyst.

[0020] The controller 12 Figure 11 is shown as a conventional microcomputer, including: a microprocessor unit 102, input / output ports 104, read-only memory 106 (e.g., non-volatile memory), random access memory 108, non-failure memory 110, and a conventional data bus. The controller 12 shown receives various signals from sensors coupled to the engine 10, including, in addition to those previously discussed, engine coolant temperature (ECT) from a temperature sensor 112 coupled to a cooling sleeve 114; a position sensor 134 coupled to an accelerator pedal 130 for sensing the force applied by a human foot 132; a position sensor 154 coupled to a brake pedal 150 for sensing the force applied by a human foot 132; a measurement of the engine manifold pressure (MAP) from a pressure sensor 122 coupled to the intake manifold 44; an engine position sensor from a Hall effect sensor 118 sensing the position of the crankshaft 40; a measurement of the air mass entering the engine from a sensor 120 (e.g., a mass air flow sensor); and a measurement of the throttle position from sensor 68. Barometric pressure may also be sensed (sensor not shown) for processing by controller 12. In a preferred aspect of the present description, engine position sensor 118 produces a predetermined number of equally spaced pulses every revolution of the crankshaft from which engine speed (RPM) can be determined.

[0021] During operation, each cylinder within engine 10 typically undergoes a four stroke cycle: including an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. Typically during the intake stroke, 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 so as 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).

[0022] During the compression stroke, intake valve 52 and exhaust valve 54 are closed. Piston 36 moves toward the cylinder head to compress the air within combustion chamber 30. The position 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 typically referred to by those of skill in the art as top dead center (TDC). In a process hereinafter referred to as injection, fuel is introduced into the combustion chamber. In a process hereinafter referred to as ignition, the injected fuel is ignited by known ignition means, such as spark plug 92, causing combustion.

[0023] During the expansion stroke, the expanding gases push piston 36 back to BDC. Crankshaft 40 converts the piston motion into rotational torque of the rotating shaft. Finally, during the exhaust stroke, exhaust valve 54 opens to release the combusted air-fuel mixture to exhaust manifold 48, and the piston returns to TDC. It should be noted that the above is shown only as an example, and the intake and exhaust valve opening and / or closing timings can be varied to achieve, for example, positive or negative valve overlap, delayed intake valve closing, or various other examples.

[0024] Figure 2 Shown in application Figure 1 An exemplary cylinder valve actuator 58 in the engine 10 is shown. The cylinder valve actuator 58 adjusts the lift and / or valve opening duration of the cylinder exhaust valve 54 in response to engine operating conditions. The cylinder valve actuator 58 can provide zero valve lift for one or more engine cycles to deactivate the cylinder exhaust valve 54. The exhaust camshaft 53 is shown positioned above the cylinder head 35 of the engine cylinder bank. The exhaust valve 54 is configured to open and close the cylinder (e.g. Figure 1 For example, the exhaust valve 54 can be actuated between an open position that allows gas to exchange into and out of the cylinder and a closed position that substantially prevents gas from exchanging into and out of the cylinder. It should be understood that although Figure 2 Only one valve is shown, but Figure 1 The engine 10 shown may include any number of cylinder valves. In addition, a cylinder valve actuator similar to the cylinder valve actuator 58 may be applied to the engine intake valve. In addition, Figure 1 Engine 10 may include any number of cylinders with associated valves, and may use a variety of different cylinder and valve configurations, such as V-6, I-4, I-6, V-12, opposed 4, and other engine types.

[0025] One or more cam towers or camshaft mounting areas may be coupled to the cylinder head 35 to support the exhaust camshaft 53. For example, cam tower 216 is shown coupled to the cylinder head 35 adjacent to the exhaust valve 54. Although Figure 2 The cam tower is shown coupled to the cylinder head, but in other examples, the cam tower can be coupled to other components of the engine, such as a camshaft support or a cam cover. The cam tower can support an overhead camshaft and can separate the lifting mechanism on the camshaft located above each cylinder.

[0026] The exhaust valve 54 can be operated in a plurality of lift and duration modes, such as high valve lift, low or partial valve lift, short opening duration, long opening duration, and zero valve lift. For example, as described in more detail below, by adjusting the cylinder cam mechanism, the valves on one or more cylinders (e.g., the exhaust valve 54) can be operated in different lift modes based on engine operating conditions.

[0027] The exhaust camshaft 53 may include a plurality of cams configured to control the opening and closing of the exhaust valves. Figure 2 A first cam lobe 212 and a second cam lobe 214 are shown positioned above valve 54. The cam lobes may have different shapes and sizes to form lift profiles for adjusting the lift amount and lift timing of valve 54 as exhaust camshaft 53 rotates. For example, exhaust cam 212 may be a full lift cam lobe, while cam 214 may be a zero lift cam lobe. Although Figure 2 Two lift profiles are shown associated with the first cam 212 and the second cam 214 , but it will be appreciated that there may be any number of lift profile cams, such as three different cam lobes.

[0028] The exhaust camshaft 53 includes a mechanism 218 coupled to the camshaft above the exhaust valve 54, which adjusts the valve lift amount of the exhaust valve 54 and / or deactivates the exhaust valve by changing the position of the cam lobe along the camshaft relative to the exhaust valve 54. For example, the cam lobes 212 and 214 can be slidably attached to the camshaft so that the cam lobes can slide along the camshaft in an axial direction based on each cylinder. For example, multiple cam lobes (e.g., cam lobes 212 and 214) positioned above each cylinder valve (e.g., exhaust valve 54) can slide across the camshaft in the direction indicated by arrow 245 to change the cam lobe profile coupled to the valve follower (e.g., follower 220 coupled to the exhaust valve 54), thereby changing the exhaust valve opening and closing duration and lift amount. The valve cam follower 220 may include a roller finger follower (RFF) 222 that engages a cam lobe positioned above the valve 202. Figure 2 , roller 222 is shown engaged with the full lift cam lobe 212 .

[0029] Not present Figure 2The additional driven elements shown in the figure may also include push rods, rocker arms, tappets, etc. These devices and features can control the actuation of the intake and exhaust valves by converting the rotational motion of the cam into the translational motion of the valve. In other examples, the valves can be actuated by additional cam lobe profiles on the camshaft, wherein the cam lobe profiles between different valves can provide variable cam lift heights, cam durations, and / or cam timings. However, if necessary, alternative camshaft (overhead and / or pushrod) devices can be used. In addition, in some examples, the cylinders may each have only one exhaust valve and / or intake valve, or more than one intake valve and / or exhaust valve. In other examples, the exhaust valve and the intake valve may be actuated by a common camshaft. However, in alternative embodiments, at least one of the intake and / or exhaust valves may be actuated by its own independent camshaft or other device.

[0030] The outer sleeve 224 can be coupled to cam lobes 212 and 214, which are splined to the exhaust camshaft 53. The camshaft position relative to the engine crankshaft is determined by the rotation sensing camshaft position sensor 295 and the exhaust camshaft position indicator 290. The exhaust camshaft 53 can be coupled to a cam phaser, which is used to change the valve timing relative to the crankshaft position. By engaging a pin (e.g., one of pins 230 or 232) into a grooved hub in the outer sleeve, the axial position of the sleeve can be repositioned so that different cam lobes engage with the cam follower coupled to the exhaust valve 54, thereby changing the lift of the exhaust valve 54. For example, the sleeve 224 may include one or more shift grooves extending around the outer periphery of the sleeve, such as grooves 226 and 228. The displacement groove may have a spiral configuration around the outer sleeve, and in some examples, a Y-shaped or V-shaped groove may be formed in the outer sleeve, wherein the Y-shaped or V-shaped groove is configured to engage with two different actuator pins (e.g., first pin 230 and second pin 232) at different times to move the outer sleeve to change the lift profile of the exhaust valve 54. The sleeve 224 is shown in a first position, and the pin 232 displaces the sleeve 224 to Figure 2 When the profile is switched, the sleeve 224 follows the spline 225 in the axial direction along the exhaust camshaft 53. In addition, the depth of each groove in the sleeve 224 can be reduced along the length of the groove, so that after the pin is arranged in the groove from the initial position, as the sleeve and the camshaft rotate, the depth of the groove becomes smaller, thereby returning the pin to the initial position.

[0031] For example, Figure 2As shown, when the first pin 230 is arranged in the groove 226, the outer sleeve 224 will be displaced in the direction toward the cam tower 216 while the exhaust camshaft 53 rotates, thereby positioning the cam lobe 212 above the valve 202 and changing the lift profile. To switch back to the cam lobe 214, the second pin 232 can be arranged in the groove 228, which will displace the outer sleeve 224 away from the cam tower 216 to position the cam lobe 214 above the valve 202. In some examples, multiple outer sleeves containing lobes can be splined to the exhaust camshaft 53. For example, the outer sleeve can be coupled to the cam lobe above each valve in the engine 10, or a selected number of lobes above the valve.

[0032] The actuator pins 230 and 232 are included in a cam lobe switching actuator 234 that adjusts the position of the pins 230 and 232 so as to switch the cam lobe positioned above the valve 202. The exhaust cam lobe switching actuator 234 includes an actuating mechanism 236, which can be hydraulically driven or electrically driven or a combination thereof. The activation mechanism 236 changes the position of the pin to change the lift profile of the valve. For example, the activation mechanism 236 can be a coil coupled to the pins 230 and 232, so that when the coil is energized, for example by an electric current provided thereto from a control system, a force is applied to the two pins to arrange the two pins toward the sleeve.

[0033] Now refer to Figure 3 , which shows an exemplary fuel vapor management system. Figure 3 The fuel management system includes Figure 1 The engine 10 of FIG. 1 is shown in FIG. 1 and a fuel tank 306 , a fuel vapor storage canister 304 , a canister purge valve 302 , and a canister vent valve 308 . The fuel 312 may be gasoline, alcohol, or a combination of gasoline and alcohol, and is stored in the fuel tank 306 .

[0034] When the fuel 312 is agitated or exposed to higher temperatures, the fuel 312 may generate fuel vapor. When the canister vent valve 302 and the canister purge valve 308 are closed, the fuel vapor may cause the pressure in the fuel tank 306 to increase. The pressure in the fuel tank 306 may be released by opening the canister vent valve 308 so that the fuel vapor may travel to the fuel vapor storage canister 304 through the conduit 303. The activated carbon 305 stores the fuel vapor and allows air to be exhausted from the fuel vapor storage canister 304 to the atmosphere via the conduit 310 and the canister purge valve 308. The fuel vapor stored in the fuel vapor storage canister 304 may be drawn into the engine 10 via the opened canister vent valve 308 and the opened canister purge valve 302. Air is drawn onto the activated carbon 305 by the vacuum generated in the intake manifold of the engine 10 to release the fuel vapor from the fuel vapor storage canister 304. The hydrocarbon concentration of the fuel vapor drawn into the engine 10 may vary depending on the load of the fuel vapor storage canister 304. For example, if fuel vapor storage canister 304 is storing a large amount of fuel vapor, then when canister purge valve 302 is open, the concentration of fuel vapor drawn into engine 10 may be high. On the other hand, if fuel vapor storage canister 304 is storing a small amount of fuel vapor, then when canister purge valve 302 is open, the concentration of fuel vapor drawn into engine 10 may be low.

[0035] In this manner, fuel vapors from fuel tank 306 may be temporarily stored in fuel vapor storage canister 304. The stored fuel vapors may subsequently be combusted by engine 10 such that the fuel vapors do not reach the atmosphere.

[0036] Now refer to Figure 4A , which shows a first configuration of the engine 10. The engine 10 includes two cylinder groups 402 and 404. The first cylinder group 404 includes cylinders 410 numbered 1-4. The second cylinder group 402 includes cylinders 410 numbered 5-8. Therefore, the first configuration is a V8 engine including two cylinder groups. All cylinders in operation can be in the first cylinder operating mode. The front 405 of the engine 10 includes an accessory drive 407, which may include a pump, a fan, etc. The transmission 406 is shown as being coupled to the rear side of the engine 10.

[0037] During the selected condition, one or more cylinders 410 can be deactivated by stopping the flow of fuel to the deactivated cylinder. In addition, by closing the intake valve and exhaust valve of the deactivated cylinder and keeping it closed, the air flow to the deactivated cylinder can be stopped, thereby deactivating the intake valve and exhaust valve. The engine cylinder can be deactivated in various modes to provide the actual desired total number of activated or deactivated cylinders. For example, cylinders 2, 3, 5 and 8 can be deactivated to form the first deactivated cylinder mode and the second cylinder operating mode. Alternatively, cylinders 1, 4, 6 and 7 can be deactivated to form the second deactivated cylinder mode and the third cylinder operating mode. In another example, cylinders 2 and 8 can be deactivated to form the third deactivated cylinder mode and the fourth cylinder operating mode. In another example, cylinders 3 and 5 can be deactivated to form the fourth deactivated cylinder mode and the fifth cylinder operating mode. In this example, five cylinder operating modes are provided; however, additional or fewer cylinder operating modes can be provided. If the engine conditions are such that the engine can be operated in any of the five described cylinder modes, the engine can be described as having five available cylinder operating modes. In this example, if two of the five operating modes of the engine are unavailable, the engine can be described as having three available operating modes. The engine always has one available cylinder operating mode (e.g., all cylinders are active and burning air and fuel). Of course, depending on the engine configuration, the actual total number of available operating modes may be greater or less than five.

[0038] Now refer to Figure 4B , which shows a second configuration of engine 10. Engine 10 includes one cylinder bank 422. Cylinder bank 406 includes cylinders 410 numbered 1-4. Therefore, the first configuration is an I4 engine including one cylinder bank. For this engine configuration, all cylinders in operation can be in the first cylinder operating mode. Cylinder number one is closest to the front of engine 420.

[0039] Similar to the first configuration, one or more cylinders 410 can be deactivated by stopping the flow of fuel to the deactivated cylinders. In addition, by closing the intake valve and exhaust valve of the deactivated cylinder and keeping it closed, the air flow to the deactivated cylinder can be stopped. The engine cylinders can be deactivated in various modes to provide the actual desired total number of activated or deactivated cylinders. For example, cylinders 2 and 3 can be deactivated to form the first deactivated cylinder mode and the second cylinder operating mode. Alternatively, cylinders 1 and 4 can be deactivated to form the second deactivated cylinder mode and the third cylinder operating mode. In another example, cylinder 2 can be deactivated to form the third deactivated cylinder mode and the fourth cylinder operating mode. In another example, cylinder 3 can be deactivated to form the fourth deactivated cylinder mode and the fifth cylinder operating mode. In this example, if the engine condition makes the engine operate in any of the five cylinder modes described, the engine can be described as having five available cylinder operating modes. If two of the five operating modes of the engine are unavailable, the engine can be described as having three available operating modes. The engine always has one available cylinder operating mode (eg, all cylinders are active and burning air and fuel). Of course, depending on the engine configuration, the actual total number of available operating modes may be greater or less than five.

[0040] In other examples, different cylinder configurations may be provided. For example, the engine may be a V6 engine or a V10 engine. Different engine configurations may also have different numbers of cylinder operating modes.

[0041] therefore, Figure 1-4B The system provides an engine system, including: an engine including a cylinder having an intake valve, an exhaust valve, and one or more cylinder valve deactivation mechanisms; a fuel vapor storage canister; and a controller, the controller including executable instructions stored in a non-volatile memory to keep the intake valve and the exhaust valve closed by one or more cylinder valve deactivation mechanisms in one or more engine cycles in response to the presence of a deceleration fuel cut-off condition and the amount of fuel vapor stored in the canister being greater than a threshold, and including additional instructions to open and close the intake valve and the exhaust valve in response to the presence of a deceleration fuel cut-off condition. The engine system also includes additional instructions to stop delivering fuel to the cylinder in response to the presence of a deceleration fuel cut-off condition. The engine system includes: wherein the deceleration fuel cut-off condition includes a driver demand torque less than a threshold and a vehicle speed greater than a threshold. The engine system also includes additional instructions to stop delivering spark to the cylinder in response to the presence of a deceleration fuel cut-off condition. The engine system also includes additional instructions to open the intake valve and the exhaust valve in response to an increase in driver demand torque after keeping the intake valve and the exhaust valve of the cylinder closed during one or more engine cycles. The engine system also includes additional instructions to supply fuel to the cylinder after opening the intake and exhaust valves.

[0042] Now refer to Figure 5 , which shows an exemplary engine operating sequence for a four-cylinder four-stroke engine. Figure 1-4B System execution Figure 6 The method described in the instructions to generate Figure 5 sequence of operations. Figure 5 Each of the graphs shown in Figure 5 The other graphs in occur simultaneously, while the vertical labels T0-T9 indicate moments of particular interest during the sequence. Figure 5 is a predictive example of an engine entering and exiting DFSO mode. The vertical markers T0-T2 represent moments of particular interest during the sequence. The engine's firing order is 1-3-4-2.

[0043] from Figure 5 The first graph from the top is a graph of the relationship between the driver's demand torque and the engine position. The horizontal axis represents the engine position, and the engine position can be Figure 5 The position of cylinders number one to four shown in the 2nd to 5th graphs of the present invention is determined. The vertical marks along the horizontal axis represent the top dead center or bottom dead center position of different engine cylinders. The vertical axis represents the driver demand torque, and the driver demand torque increases in the direction of the vertical axis arrow. The driver demand torque can be determined based on the accelerator pedal position and the vehicle speed. In one example, the accelerator pedal position and the vehicle speed reference a table or function of empirically determined values ​​of the driver demand torque. The table or function outputs the driver demand torque.

[0044] from Figure 5 The second graph from the top is a graph of the stroke of cylinder number one. Figure 5 Left to Figure 5 , cylinder No. 1 is on the stroke identified by the second curve. These strokes vary according to the strokes of the four-stroke engine. INT. is an abbreviation for intake stroke, CMP. is an abbreviation for compression stroke, EXP. is an abbreviation for expansion stroke, and EXH. is an abbreviation for exhaust stroke. The intake valve opening time of the intake valve of cylinder No. 1 is indicated by a thick horizontal line under the stroke label of cylinder No. 1. The exhaust valve opening time of the exhaust valve of cylinder No. 1 is indicated by a thinner horizontal line under the stroke label of cylinder No. 1. The spark timing of cylinder No. 1 is indicated by an * under the stroke label. The fuel injection timing is indicated by a slash under the stroke label of cylinder No. 1. The vertical lines separate different cylinder strokes and indicate whether the piston of the cylinder is at the bottom dead center or the top dead center. For example, the vertical line between the intake stroke and the compression stroke is the bottom dead center of the intake or compression stroke.

[0045] from Figure 5The third graph from the top is the graph of the stroke of cylinder number 3. As the engine rotates through Figure 5 Left to Figure 5 , cylinder number three is on the stroke identified by the third curve. The intake valve opening time of the intake valve of cylinder number three is indicated by the thick horizontal line under the stroke label of cylinder number three. The exhaust valve opening time of the exhaust valve of cylinder number three is indicated by the thinner horizontal line under the stroke label of cylinder number three. The spark timing of cylinder number three is indicated by the * under the stroke label of cylinder number three. The fuel injection timing is indicated by the slash under the stroke label. The vertical lines separate the different cylinder strokes and indicate whether the cylinder's piston is at bottom dead center or top dead center.

[0046] from Figure 5 The fourth graph from the top is a graph of the stroke of cylinder number four. Figure 5 Left to Figure 5 , cylinder number four is on the stroke identified by the fourth curve. The intake valve opening time of the intake valve of cylinder number four is indicated by the thick horizontal line under the stroke label of cylinder number four. The exhaust valve opening time of the exhaust valve of cylinder number four is indicated by the thinner horizontal line under the stroke label of cylinder number four. The spark timing of cylinder number four is indicated by the * under the stroke label of cylinder number four. The fuel injection timing is indicated by the slash under the stroke label. The vertical lines separate the different cylinder strokes and indicate whether the cylinder's piston is at bottom dead center or top dead center.

[0047] from Figure 5 The fifth graph from the top is a graph of the stroke of cylinder No. 2. Figure 5 Left to Figure 5 , cylinder number two is on the stroke identified by the fifth curve. The intake valve opening time of the intake valve of cylinder number two is indicated by the thick line under the stroke label of cylinder number two. The exhaust valve opening time of the exhaust valve of cylinder number two is indicated by the thinner horizontal line under the stroke label of cylinder number two. The spark timing of cylinder number two is indicated by the * under the stroke label of cylinder number two. The fuel injection timing is indicated by the slash under the stroke label. The vertical lines separate the different cylinder strokes and indicate whether the cylinder's piston is at the bottom dead center or the top dead center.

[0048] from Figure 5 The sixth graph from the top is a graph of the relationship between the fuel vapor level of the fuel vapor storage canister and the engine position. The horizontal axis represents the engine position, and the engine position can be determined by Figure 5The position of cylinders 1 to 4 shown in the 2nd to 5th graphs is determined. The vertical marks along the horizontal axis represent the top dead center or bottom dead center position of different engine cylinders. The vertical axis represents the fuel vapor level of the fuel vapor storage canister, and the fuel vapor level of the fuel vapor storage canister increases in the direction of the vertical axis arrow. It should be noted that the time between cylinder strokes can vary as the engine speed increases and decreases; however, the number of engine degrees between strokes is constant and fixed. Horizontal line 502 represents the fuel vapor level threshold of the threshold fuel vapor storage canister. In response to the fuel vapor entering DFSO and stored in the fuel vapor storage canister exceeding the threshold 502, one or more valves of the engine cylinders may remain closed during one or more engine cycles.

[0049] At time T0, the engine is spinning and combusting an air-fuel mixture, and the driver demand torque is at a medium level. The vapor level of the fuel vapor storage canister is at a level greater than threshold 502. Each cylinder of the engine is combusting air and fuel.

[0050] At time T1, in response to the human driver releasing the accelerator pedal or the autonomous driver reducing the torque request (not shown), the driver demand torque is reduced. In addition, the vehicle speed (not shown) is greater than the threshold speed, so there are conditions for entering a deceleration fuel cutoff. Because the fuel vapor level is greater than threshold 502 and because a DFSO condition exists, the intake and exhaust valves of cylinders one and four are commanded to close and remain closed. The intake and exhaust valves of cylinders two and three are allowed to continue to open and close. However, in other examples, in response to DFSO conditions and the vapor storage level exceeds threshold 502, the intake and exhaust valves of all engine cylinders can be commanded to close and remain closed. The engine throttle (not shown) and the tank purge valve are also closed at time T1 in response to the reduction in driver demand torque.

[0051] Between T1 and T2, the engine continues to rotate and driver demand remains at a low level. Just after the driver demand torque is reduced, the final combustion event as shown by the * occurs in cylinder No. 2. Cylinder No. 1 is in the middle of the intake stroke, so fuel is not delivered to the first cylinder, but the air introduced into cylinder No. 1 is captured in cylinder No. 1 by closing the intake and exhaust valves of cylinder No. 1 and keeping them closed. The intake and exhaust valves of cylinders No. 3 and No. 2 continue to open and close. The exhaust and intake valves of cylinder No. 4 are opened once after time T1 and before time T2 to exhaust exhaust from cylinder No. 4 and capture fresh air in cylinder No. 4. Therefore, as the engine rotates, fresh air is captured in cylinders No. 1 and No. 4. The engine throttle remains closed (not shown), causing the engine intake manifold vacuum to increase (not shown), causing fuel vapor to migrate from the fuel vapor tank to the engine intake manifold. Even with the canister purge valve closed, the fuel vapor storage level may decrease, indicating migration of fuel vapor from the fuel vapor storage canister.

[0052] At time T2, in response to the human driver applying the accelerator pedal or the autonomous driver increasing the demand torque (not shown), the driver demand torque increases. Cylinder No. 1 is completing its intake stroke and the intake valve is not open, so fuel is injected into cylinder No. 1 shortly after the driver demand torque increases. Fuel is injected into cylinder No. 1 to mix with the fresh air trapped in the cylinder and then burn. Depending on the duration of the closure of the intake and exhaust valves of cylinder No. 1, the amount of air trapped in cylinder No. 1 may be reduced. The air may be reduced due to the air sliding over the cylinder rings and entering the engine crankcase. The amount of fuel injected to reactivate the combustion in cylinder No. 1 can be based on an estimate of the air trapped in cylinder No. 1. Cylinder No. 1 is the first cylinder to burn air and fuel after the most recent deactivation (e.g., cessation of combustion) of the engine cylinder. Since cylinder No. 1 does not inhale fuel vapor when the engine cylinder is deactivated, the combustion of cylinder No. 1 may be more robust and less likely to cause flameout.

[0053] Combustion in cylinders 2 and 3 also resumes, but the likelihood of misfire in cylinders 2 and 3 increases as fuel vapor migrates from the fuel vapor storage canister to cylinders 2 and 3. If cylinders 2 and 3 misfire, the combustion event in cylinder 1 can help accelerate the engine.

[0054] Fuel is injected into cylinder number four shortly after it is deactivated at time T1 and before the intake and exhaust valves of cylinder number four begin to open and close. After time T1, fresh air trapped in cylinder number four can be combusted with the injected fuel without fuel vapor migrating from the fuel vapor canister to the engine. Therefore, the likelihood of a misfire in the first combustion event in cylinder number four will be reduced after cylinder number four is deactivated at time T1. Cylinder number four can further increase engine acceleration, making it less likely for vehicle occupants to detect a misfire in cylinder number two or three.

[0055] In this way, the engine can enter and exit DFSO with a low probability of engine misfire for all engine cylinders. In this way, the engine can provide torque more quickly so that vehicle occupants are not disturbed.

[0056] Now refer to Figure 6 , which shows a method for operating an engine and reducing the possibility of stalling. Figure 6 The method can be incorporated into Figure 1-4B system and can be used with Figure 1-4B In addition, Figure 6 At least some portions of the method may be incorporated as executable instructions stored in a non-volatile memory, while other portions of the method may be performed by a controller that converts operating states of devices and actuators in the real world.

[0057] At 602, method 600 determines vehicle operating conditions. Vehicle operating conditions may include, but are not limited to, vehicle speed, engine speed, driver demand torque, and a vapor level of the fuel vapor storage canister (eg, the amount of fuel vapor stored in the fuel vapor storage canister). Figure 1-4B The various sensors shown determine various parameters. Method 600 proceeds to 604 .

[0058] At 604, method 600 determines whether a DFSO condition exists. In one example, a DFSO condition exists when the driver demand torque is less than a threshold and the vehicle speed is greater than a threshold. In addition, other conditions such as transmission gear and torque converter clutch state can be used as a basis for determining whether a DFSO condition exists. If method 600 determines that a DFSO condition exists, the answer is "yes" and method 600 advances to 606. Otherwise, the answer is "no" and method 600 advances to 630.

[0059] At 630 , method 600 continues to combust air and fuel in the engine cylinders. Method 600 may also occasionally deactivate selected cylinders while other engine cylinders continue to operate and combust air and fuel. Method 600 proceeds to exit.

[0060] At 606 , method 600 judges whether or not the fuel vapor load or vapor level of the fuel vapor storage canister is greater than a threshold. If so, the answer is yes and method 600 proceeds to 608 . Otherwise, the answer is no and method 600 proceeds to 620 .

[0061] At 608 , method 600 stops delivering fuel to the engine cylinders. For cylinders that are currently delivering fuel, the fuel being delivered is completed and then stopped. Method 600 proceeds to 610 .

[0062] At 610, method 600 deactivates air flow through the selected engine cylinder. The intake valve and exhaust valve of at least one engine cylinder are closed and remain closed to prevent air flow through the cylinder. In one example, when a DFSO condition exists, the intake valve and exhaust valve of half of the engine cylinders are closed and remain closed. However, in some examples, the intake valve and exhaust valve of all engine cylinders are closed and remain closed. The intake valve and exhaust valve of the closed cylinder are closed so that combustion gases are expelled from the cylinder and fresh air is introduced into the cylinder while keeping the intake valve and exhaust valve closed. Figure 5 An example of closing the intake and exhaust valves so that fresh air is trapped in the cylinders with the intake and exhaust valves remaining closed during an entire engine cycle (e.g., two engine revolutions of a four-stroke engine) is shown. By trapping fresh air in the engine cylinders, the engine cylinders can be restarted more reliably, thereby reducing the possibility of engine flameout. In some examples, the intake and exhaust valves of some engine cylinders can be continuously opened and closed during the engine cycle, while the intake and exhaust valves of other cylinders are deactivated. In this way, the number of selectable valve actuators can be reduced. Method 600 advances to 612.

[0063] At 612 , method 600 determines whether DFSO conditions still exist. If so, the answer is “yes” and method 600 returns to 612 . Otherwise, the answer is “no” and method 600 advances to 614 .

[0064] At 614, method 600 resumes combustion in a cylinder having an intake valve and an exhaust valve that were disabled when entering DFSO. Combustion is resumed by injecting fuel into the cylinder having the disabled valve and supplying spark to the cylinder. In one example, a cylinder that is deactivated by closing the intake and exhaust valves is selected to provide the first combustion event since most recently entering DFSO. The air-fuel ratio of the cylinder can be slightly rich or stoichiometric to reduce oxygen stored in the catalyst. This allows a cylinder that did not have fuel vapor introduced during DFSO to be the first cylinder to resume combustion after the most recent DFSO event. Therefore, the reliability of restarting the engine can be improved because the air-fuel mixture in the cylinder will not be too rich. Figure 5 One example of reactivating combustion for a first combustion event in a cylinder that maintained its intake and exhaust valves closed during a DFSO event is shown. Method 600 proceeds to 616 .

[0065] At 616, method 600 begins supplying fuel and spark to all engine cylinders after the DFSO event. In addition, the intake valves and exhaust valves of the cylinders that remained closed during the DFSO event are reactivated to begin opening and closing. If some engine cylinders did inhale fuel vapor from the fuel vapor storage canister during the most recent DFSO event, the amount of fuel injected into these cylinders can be reduced to further reduce the possibility of engine flameout. For example, fuel injected into engine cylinders with valves that were not deactivated during the most recent DFSO event can be injected to provide a lean limit air-fuel ratio for the engine cylinder (e.g., the leanest air-fuel ratio that the cylinder can operate, acting together when the indicated average effective cylinder pressure is less than a threshold) to prevent vapor from the fuel vapor storage canister from migrating to the engine cylinder during the most recent DFSO event. If fuel vapor from the fuel vapor storage canister migrates to the cylinder, the air-fuel mixture in the cylinder can be lean enough to support combustion. Method 600 exits after reactivating the engine cylinder.

[0066] At 620, method 600 stops delivering fuel to all engine cylinders and allows the intake and exhaust valves of all engine cylinders to continue opening and closing during each engine cycle. Therefore, combustion in all engine cylinders is stopped due to the low driver demand torque. The engine throttle may also be fully closed and spark delivery to the engine cylinders may be stopped. Method 600 proceeds to 622.

[0067] At 622 , method 600 determines whether DFSO conditions still exist. If so, the answer is yes and method 600 returns to 622 . Otherwise, the answer is no and method 600 proceeds to 624 .

[0068] At 624, method 600 supplies fuel and spark to all engine cylinders to resume combustion in all engine cylinders. When the fuel vapor level in the fuel vapor storage canister is low, there may be less chance of misfire when the engine cylinders are reactivated due to a richer air-fuel mixture. Therefore, the engine may be reactivated with a full cylinder charge in each cylinder to improve engine torque production. Method 600 proceeds to exit.

[0069] In this way, during conditions that may ingest excess fuel vapor into the engine cylinders during DFSO, the intake and exhaust valves of selected cylinders may be deactivated and maintained in a closed position. Air trapped in the engine cylinders having the deactivated intake and exhaust valves may be mixed with the injected fuel to provide a desired air-fuel ratio, which may reduce the likelihood of engine misfire. However, if the level of fuel vapor stored in the fuel vapor storage canister is lower than if the engine cylinders were reactivated when the intake and exhaust valves had been deactivated, the engine cylinders may be reactivated in a manner that may increase engine output power for the first few combustion events since exiting the most recent DFSO event.

[0070] therefore, Figure 6 The method provides an engine operation method, including: in response to the presence of a deceleration fuel cut-off condition and the amount of fuel vapor stored in the canister being greater than a threshold, maintaining the intake valve and exhaust valve of the cylinder closed via a controller during one or more engine cycles. The method includes: wherein the deceleration fuel cut-off condition includes a driver demand torque less than a threshold and a vehicle speed greater than a threshold. The method also includes introducing air into the cylinder and trapping the air in the cylinder while maintaining the intake valve and exhaust valve of the cylinder closed. The method also includes stopping the delivery of fuel to the cylinder while maintaining the intake valve and exhaust valve of the cylinder closed within one or more engine cycles. The method also includes stopping the delivery of spark to the cylinder while maintaining the intake valve and exhaust valve of the cylinder closed within one or more engine cycles. The method also includes opening and closing the intake valve and exhaust valve of a second cylinder while maintaining the intake valve and exhaust valve of the cylinder closed. The method includes: wherein the canister is a fuel vapor storage canister containing activated carbon.

[0071] Figure 6The method also provides an engine operation method, including: in response to the existence of a deceleration fuel cut-off condition and the amount of fuel vapor stored in the canister being greater than a threshold, keeping the intake valve and exhaust valve of the cylinder closed via a controller within one or more engine cycles; and in response to an increase in driver demand torque, opening the intake valve and exhaust valve after keeping the intake valve and exhaust valve of the cylinder closed. The method also includes supplying fuel to the cylinder after opening the intake valve and exhaust valve. The method also includes stopping combustion in all cylinders of the engine in response to the existence of a deceleration fuel cut-off condition. The method also includes burning air and fuel in all cylinders of the engine in response to an increase in driver demand torque. The method also includes opening and closing the intake valve and exhaust valve of a second cylinder while keeping the intake valve and exhaust valve of the cylinder closed. The method also includes stopping the supply of spark to all cylinders of the engine in response to the existence of a deceleration fuel cut-off condition. The method also includes opening the intake valve and exhaust valve in response to a vehicle speed less than a threshold after keeping the intake valve and exhaust valve of the cylinder closed.

[0072] It should be understood that the configurations and methods disclosed herein are exemplary in nature, and these specific examples are not to be considered limiting, and many variations are possible. For example, the above technology can be applied to engine types such as V-6, I-4, I-6, V-12, opposed 4 cylinders, etc. The subject matter of the present disclosure includes various systems and configurations, and all novel and non-obvious combinations and sub-combinations of other features, functions and / or characteristics disclosed herein.

[0073] The appended claims particularly illustrate certain combinations and sub-combinations that are considered novel and non-obvious. The claims may refer to "an" element or a "first" element or the equivalent thereof. The claims should be understood to include combinations of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and / or properties may be claimed by amending the present claims or by presenting new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, are deemed to be included in the subject matter of the present disclosure.

Claims

1. A method for operating an engine, comprising: In response to a deceleration fuel cutoff condition being present and an amount of fuel vapor stored in the fuel vapor storage canister being greater than a threshold, deactivating one or more cylinders and maintaining intake and exhaust valves of the one or more cylinders closed via a controller during one or more engine cycles; and After exiting the deceleration fuel cutoff condition and in response to an increase in demanded torque, one of the one or more cylinders that were previously deactivated is activated before activating other cylinders. 2 . The method of claim 1 , wherein the deceleration fuel cutoff condition includes a driver demand torque less than a threshold and a vehicle speed greater than a threshold. 3 . The method of claim 1 , further comprising introducing air into the cylinder and trapping the air in the cylinder while maintaining an intake valve and an exhaust valve of the cylinder closed. 4 . The method of claim 1 , further comprising ceasing to deliver fuel to the cylinder while maintaining an intake valve and an exhaust valve of the cylinder closed during the one or more engine cycles. 5 . The method of claim 1 , further comprising ceasing to deliver spark to the cylinder while maintaining an intake valve and an exhaust valve of the cylinder closed during the one or more engine cycles. 6 . The method of claim 1 , further comprising opening and closing an intake valve and an exhaust valve of a second cylinder while keeping the intake valve and the exhaust valve of the cylinder closed.

7. The method of claim 1, wherein the fuel vapor storage canister comprises activated carbon. 8 . The method of claim 1 , further comprising, in response to an increase in driver demand torque, opening the intake valve and the exhaust valve after maintaining the intake valve and the exhaust valve of the cylinder closed. 9 . The method of claim 8 , further comprising supplying fuel to the cylinder after opening the intake valve and the exhaust valve.

10. The method of claim 8 further comprising ceasing combustion in all cylinders of the engine in response to the presence of a deceleration fuel cutoff condition.

11. An engine system, comprising: An engine including a cylinder having an intake valve, an exhaust valve, and one or more cylinder valve deactivation mechanisms; Fuel vapor storage tanks; as well as A controller including executable instructions stored in a non-volatile memory to, in response to the presence of a deceleration fuel cutoff condition and the amount of fuel vapor stored in the canister being greater than a threshold, deactivate one or more cylinders and maintain intake and exhaust valves of the one or more cylinders closed via the one or more cylinder valve deactivation mechanisms during one or more engine cycles, and including additional instructions to activate one of the one or more cylinders that were previously deactivated before activating other cylinders after exiting the deceleration fuel cutoff condition and in response to an increase in demanded torque.

12. The engine system of claim 11 further comprising additional instructions for ceasing fuel delivery to the cylinder in response to the presence of a deceleration fuel cutoff condition. 13 . The engine system of claim 11 , wherein the deceleration fuel cutoff condition includes a driver demand torque less than a threshold and a vehicle speed greater than a threshold.

14. The engine system of claim 11 further comprising additional instructions for ceasing spark delivery to the cylinder in response to the presence of a deceleration fuel cutoff condition.

15. The engine system of claim 11 further comprising additional instructions to open the intake valve and the exhaust valve of the cylinder in response to an increase in driver demand torque after maintaining the intake valve and the exhaust valve of the cylinder closed during one or more engine cycles.

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