System and method for operating deactivated cylinders

Abstract

Systems and methods for operating an engine including cylinders that can be deactivated are presented. In one example, intake and exhaust valves of a cylinder may be operated according to the valve operation for a conventional four-stroke cycle. The same valves may be operated differently during one four-stroke cycle to provide air charge and exhaust charge to active cylinders during a different four-stroke cycle.

Description

Area

[0001] The present description relates to a system and method for operating a variable displacement engine. The system and methods can provide useful work from deactivated cylinders. Background and brief presentation

[0002] A variable displacement engine includes engine cylinders that can be deactivated from time to time to save fuel. By deactivating a portion of the engine cylinders, active cylinders can operate at higher efficiency. Pistons of deactivated cylinders can reciprocate within the deactivated cylinders while the cylinders' intake and exhaust valves remain closed. The deactivated cylinders can contain fresh air or exhaust gas to reduce negative pressure within the cylinders, but engine power may be lost due to compression and expansion of the air. The compression and expansion of air provides minimal useful work. For this reason, it would be desirable to increase the amount of useful work provided by one or more deactivated cylinders.

[0003] The inventor of the present invention has recognized the above-mentioned problems and developed an engine control method comprising: deactivating a cylinder of an engine via a controller that interrupts the supply of fuel to the cylinder, the engine being a four-stroke engine; and drawing air during a first stroke of four strokes in a cycle of the deactivated cylinder from a vacuum reservoir into the deactivated cylinder, the air being drawn into the deactivated cylinder without having traversed a passage of an intake manifold leading to other cylinders of the engine.

[0004] By adjusting the valve timing of a deactivated cylinder, the deactivated cylinder can be used in a manner that increases engine efficiency while the cylinder is deactivated. In particular, a second intake valve can be opened to provide negative pressure to a vacuum accumulator during an intake stroke of the deactivated cylinder. The air drawn to the cylinder can then be expelled to the engine's intake manifold to increase intake manifold pressure and provide air to other engine cylinders. The exhaust valves of the deactivated cylinder can be opened during an expansion stroke of the deactivated cylinder to draw exhaust gas into the deactivated cylinder. The first intake valve can be opened during an exhaust stroke of the cylinder to recirculate exhaust gas to other engine cylinders.

[0005] The present description may provide several advantages. In particular, the approach may improve engine efficiency when an engine is operating with one or more cylinders deactivated. Additionally, the approach may provide vacuum when vacuum generation may be difficult. Furthermore, the approach may provide higher exhaust gas recirculation (EGR) flow rates under conditions where intake manifold pressure may be higher.

[0006] The above advantages as well as other advantages and features of the present description will be readily apparent from the following detailed description when read alone or in conjunction with the accompanying drawings.

[0007] It should be understood that the foregoing summary is provided to introduce, in a simplified form, a selection of concepts that are further described in the detailed description. It is not intended to identify important or essential features of the claimed subject matter, the scope of which is defined solely in the claims following the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve disadvantages mentioned above or in any part of this disclosure. Brief description of the drawings

[0008] The advantages described herein will become more fully apparent from reading an example of an embodiment, referred to herein as the detailed description, whether read in isolation or with reference to the drawings, in which: Fig. 1 is a schematic diagram of an engine; Fig. Figure 2A is a schematic diagram of an eight-cylinder engine with two cylinder banks; Fig. Figure 2B is a schematic diagram of a four-cylinder engine with a single cylinder bank; Fig. 3 is a detailed diagram of passages leading to a cylinder; Fig. 4 is an operating sequence of a cylinder of an engine; and Fig. 5 is a flow diagram of a method for operating a cylinder of an engine. Detailed description

[0009] This description relates to the operation of an engine with one or more cylinders that can be deactivated from time to time. The engine may be a supercharged engine, as in Fig. 1, or a naturally aspirated engine. The engine may contain one or two cylinder banks, as shown in the Fig. 2A and Fig. 2B. Air can be supplied to the engine cylinders via passages as shown in Fig. 3. One or more engine cylinders can be operated as shown in the operating sequence Fig. 4. The engine cylinders can be operated according to the procedure in Fig. 5 are operated.

[0010] With reference to Fig. 1, an internal combustion engine 10 comprising a plurality of cylinders, one of which is in Fig. 1, is controlled by the electronic engine control unit 12. The engine 10 includes the combustion chamber 30 and cylinder walls 32 with the piston 36 disposed therein and connected to the crankshaft 40. The crankcase 135 encloses the crankshaft 40 and provides a barrier to atmospheric conditions.

[0011] As shown, the combustion chamber 30 communicates with the intake manifold 44 and the exhaust manifold 48 via the corresponding intake valve 52 and exhaust valve 54. Each intake and exhaust valve may be operated by an intake valve actuator 51 and an exhaust valve actuator 53. The intake valve position may be determined by sensor 55. The exhaust valve position may be determined by sensor 57. The intake valve actuator 51 and the exhaust valve actuator 53 may be mechanically, electrically, or hydraulically operated. Furthermore, the intake valve actuator 51 and the exhaust valve actuator 53 may operate synchronously or asynchronously with the crankshaft 40.

[0012] The fuel injector 66 is shown positioned to inject fuel directly into the cylinder 30, known to those skilled in the art as direct injection. Alternatively, fuel may be injected into an intake port, known to those skilled in the art as port fuel injection. The fuel injector 66 delivers liquid fuel proportional to the pulse width of the signal from the controller 12. Fuel is delivered to the fuel injector 66 through a fuel system 175. Additionally, the intake manifold 44 is shown communicating with the optional electronic throttle 62 (e.g., a butterfly valve), which adjusts a position of the throttle plate 64 to control airflow from the air cleaner 43 and air intake 42 to the intake manifold 44. The throttle 62 regulates airflow from the compressor 77 and the air cleaner 43 in the engine air intake 42 to the intake manifold 44.In some examples, throttle 62 and throttle body 64 may be positioned between intake valve 52 and intake manifold 44 such that throttle 62 is a port throttle. Compressor 77 may be driven via exhaust gases or via a belt (not shown) driven via crankshaft 40.

[0013] A distributorless ignition system 88 provides an ignition spark to the combustion chamber 30 in response to the controller 12 via the spark plug 92. A wideband oxygen sensor (UEGO) 126 is shown coupled to the exhaust manifold 48, which is located upstream of the catalytic converter 70. Alternatively, the UEGO sensor 126 may be replaced with a binary oxygen sensor.

[0014] In one example, the catalyst 70 may include multiple catalyst modules. In another example, multiple emission control devices, each including multiple modules, may be used. In one example, the catalyst 70 may be a three-way catalyst.

[0015] In Fig. 1, the controller 12 is illustrated as a conventional microcomputer including: microprocessor unit 102, input / output ports 104, read-only memory 106 (e.g., non-volatile memory), random access memory 108, keep-alive memory 110, and a conventional data bus.The controller 12 is shown receiving various signals from sensors coupled to the engine 10 in addition to the signals previously discussed, including: engine coolant temperature (ECT) from temperature sensor 112 coupled to cooling sleeve 114; a position sensor 134 coupled to an accelerator pedal 130 for sensing the force applied by the human driver 132; a measurement of the engine's manifold pressure (MAP) from pressure sensor 122 coupled to the intake manifold 44; an engine position sensor from a Hall effect sensor 118 that senses the position of the crankshaft 40; a measurement of the mass of air entering the engine from sensor 120; a brake pedal position from brake pedal position sensor 154 when the human driver 132 applies a brake pedal 150; and a measurement of the throttle position from sensor 63.Atmospheric pressure may also be sensed for processing by controller 12 (sensor not shown). In a preferred aspect of the present description, engine position sensor 118 generates a predetermined number of evenly spaced pulses with each revolution of the crankshaft, from which engine speed (RPM) can be determined.

[0016] In some examples, the engine may be coupled to an electric motor / battery system in a hybrid vehicle. Furthermore, in some examples, other engine configurations may be employed, for example, a diesel engine.

[0017] During operation, each cylinder in the engine 10 typically undergoes a four-stroke cycle: the cycle includes the intake stroke, the compression stroke, the power stroke, and the exhaust stroke. During the intake stroke, the exhaust valve 54 generally closes and the intake valve 52 opens. Air is introduced into the combustion chamber 30 via the intake manifold 44, and the piston 36 moves toward the bottom of the cylinder, increasing the volume within the combustion chamber 30. The position where the piston 36 is near the bottom of the cylinder and at the end of its stroke (e.g., when the combustion chamber 30 is at its largest volume) is commonly referred to by those skilled in the art as bottom dead center (BDC). During the compression stroke, the intake valve 52 and the exhaust valve 54 are closed. The piston 36 moves toward the cylinder head to compress the air within the 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 typically referred to by those skilled in the art as top dead center (TDC). In a process referred to herein as injection, fuel is introduced into the combustion chamber. In a process referred to herein as ignition, the injected fuel is ignited by known ignition means, such as spark plug 92, resulting in combustion. During the power stroke, expanding gases force piston 36 back to BDC. Crankshaft 40 converts piston motion into rotating shaft torque. 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 merely an example and that the timing for opening and / or closing the intake and exhaust valves may vary, such as to provide positive or negative valve overlap, late intake valve closing, or various other examples.

[0018] With reference to Fig. 2A, an exemplary top view schematic of a multi-cylinder engine including two cylinder banks is shown. The engine includes cylinders and associated components as shown in Fig. 1. The engine 10 includes eight cylinders 210. Each of the eight cylinders is numbered, and the cylinder numbers are included with the cylinders. Cylinders 1-8 may be selectively deactivated by interrupting the supply of fuel and / or spark to the deactivated cylinders. One or more cylinders may be deactivated to improve engine fuel efficiency when less than the engine's full torque capacity is demanded. For example, cylinders 2, 3, 5, and 8 (e.g., one deactivated cylinder pattern) may be deactivated during one engine cycle (e.g., two revolutions for a four-stroke engine). During another engine cycle, cylinders 1, 4, 6, and 7 may be deactivated. Further, other patterns of cylinders may be selectively deactivated based on vehicle operating conditions.

[0019] The engine 10 includes a first cylinder bank 204 including four cylinders, 1, 2, 3, and 4. The engine 10 also includes a second cylinder bank 202 including four cylinders, 5, 6, 7, and 8. The cylinders of each bank can be active or deactivated during an engine cycle. The intake manifold 44 supplies air to each cylinder that is activated (e.g., burning fuel during an engine cycle) via passages 52a and intake valves 52. Thus, the intake manifold 44 supplies air to a plurality of engine cylinders via passages 52a. Each of the eight cylinders also includes a second intake valve 299 and a second passage 230. The passage 230 may be integrated into a cylinder head and / or intake manifold, however, the passage 230 does not pneumatically communicate with the intake manifold 44 unless the intake valves 52 and 299 are open simultaneously.The passage 230 does not lead directly to the plenum 44a, which distributes air passing through the engine throttle (not shown) to all engine cylinders. The passage 230 may communicate with the intake manifold 44 through the cylinder 210 when the intake valves 52 and 299 are open simultaneously. Thus, the passage 230 is pneumatically isolated from a portion of the intake manifold 44 that communicates with other cylinders of the engine 10 when the intake valve 299 is closed. The passage 230 is a closed, sealed volume, except that access to the passage 230 may be provided by opening the intake valve 299. Further, the passage 230 may be pneumatically coupled to a vacuum reservoir or the crankcase 135, as shown in FIG. Fig. 3 shown.

[0020] With reference to Fig. 2B, an exemplary top view schematic of a multi-cylinder engine including a cylinder bank is shown. The engine includes cylinders and associated components as shown in Fig. 1. The engine 10 includes four cylinders 210. Each of the four cylinders is numbered, and the cylinder numbers are included with the cylinders. Cylinders 1-4 may be selectively deactivated to improve engine fuel efficiency when less than the engine's full torque capacity is demanded. For example, cylinders 2 and 3 (e.g., one deactivated cylinder pattern) may be deactivated during one engine cycle (e.g., two revolutions for a four-stroke engine). During another engine cycle, cylinders 1 and 4 may be deactivated. Further, other patterns of cylinders may be selectively deactivated based on vehicle operating conditions.

[0021] The engine 10 includes a single cylinder bank 250 that includes four cylinders 1-4. The cylinders of the individual bank can be active or deactivated during an engine cycle. The engine 10 includes a first cylinder bank 204 that includes four cylinders 1, 2, 3, and 4. The intake manifold 44 supplies air to each cylinder that is activated (e.g., burning fuel during an engine cycle) via passages 52a and intake valves 52. Thus, the intake manifold 44 supplies air to a plurality of engine cylinders via passages 52a. Each of the four cylinders also includes a second intake valve 299 and a second passage 230. The passage 230 may be integrated into a cylinder head and / or intake manifold, however, the passage 230 does not pneumatically communicate with the intake manifold 44 unless the intake valves 52 and 299 are open simultaneously.The passage 230 does not lead directly to the plenum 44a, which distributes air passing through the engine throttle (not shown) to all engine cylinders. The passage 230 may communicate with the intake manifold 44 through the cylinders 210 when the intake valves 52 and 299 are open simultaneously. Thus, the passage 230 is pneumatically isolated from a portion of the intake manifold 44 that communicates with other cylinders of the engine 10 when the intake valve 299 is closed. The passage 230 is a closed, sealed volume, except that access to the passage 230 may be provided by opening the intake valve 299. Further, the passage 230 may be pneumatically coupled to a vacuum reservoir or the crankcase 135, as shown in FIG. Fig. 3 shown.

[0022] With reference to Fig. 3 is a schematic plan view showing sections of passages leading to or leaving the combustion chamber 30. Fresh air can enter the combustion chamber 30 via the intake manifold 44, the passage 52a, and the intake valve 52. Air can also enter the combustion chamber 30 via the intake valve 299, the passage 230, and the vacuum reservoir 310, or the engine crankcase 135. Conduit 370 pneumatically couples passage 230 to engine crankcase 135 via isolation valve 343. Isolation valve 343 allows gas to flow from crankcase 135 to passage 230, but terminates flow from passage 230 to crankcase 135. Conduit 371 pneumatically couples passage 230 to vacuum reservoir 310 via isolation valve 345. Isolation valve 345 allows air to flow from vacuum reservoir 310 to passage 230, but terminates flow from passage 230 to reservoir 310.Conduit 372 pneumatically couples vacuum reservoir 310 to brake booster 340 via isolation valve 346. Isolation valve 346 allows air to flow from brake booster 340 to vacuum reservoir 310, but terminates flow from vacuum reservoir 310 to brake booster 340. Air can enter brake booster 340 when a human driver 152 presses and releases brake pedal 150. Passages 382 and 322 pneumatically couple exhaust manifold 48 to combustion chamber 30 via exhaust valves 54 and 389.

[0023] During conventional four-stroke operation, when air and fuel are combusted in the cylinder or combustion chamber 30, intake valves 52 and 299 open during an intake stroke, allowing air from the intake manifold, vacuum reservoir 310, and crankcase 135 to be introduced into the combustion chamber or cylinder 30. Exhaust valves 54 and 389 open, allowing exhaust gases to be discharged to the exhaust manifold 48 during an exhaust stroke of the cylinder or combustion chamber 30.

[0024] When the cylinder or combustion chamber 30 is shut down (e.g., not burning air and fuel during a four-stroke cycle), the opening times of the intake valves 52 and 299 on the other side are set to different times, as in the sequence in Fig. 4. Similarly, the opening times of the exhaust valves 54 and 389 are set to different times, as shown in the sequence in Fig. 4 shown.

[0025] For example, during a first stroke of a cylinder cycle, when the combustion chamber or cylinder 30 is deactivated, the intake valve 299 is opened while the intake valve 52 is closed. The exhaust valves 54 and 389 are closed. During the first stroke, the piston of the cylinder or combustion chamber 30 moves in a downward direction, expanding the volume of the cylinder or combustion chamber 30. As a result, air is drawn from the vacuum chamber 310 and the crankcase 135 into the cylinder or combustion chamber 30. During a second stroke of the cylinder cycle, when the combustion chamber or cylinder 30 is deactivated, the intake valve 299 is closed while the intake valve 52 is opened. The exhaust valves 54 and 389 are closed.During the second stroke, the piston of cylinder or combustion chamber 30 moves in an upward direction, reducing the volume of cylinder or combustion chamber 30. Consequently, air from cylinder or combustion chamber 30 is expelled into intake manifold 44. During a third stroke of the cylinder cycle, when combustion chamber or cylinder 30 is deactivated, intake valve 299 and intake valve 52 are closed. During the third stroke, the piston of cylinder or combustion chamber 30 moves in a downward direction, expanding the volume of cylinder or combustion chamber 30. Consequently, exhaust gas from other active cylinders is drawn from exhaust manifold 48 into cylinder or combustion chamber 30. During a fourth stroke of the cylinder cycle, when combustion chamber or cylinder 30 is deactivated, intake valve 299 is closed while intake valve 52 is opened.Exhaust valves 54 and 389 are closed. During the fourth stroke, the piston of cylinder or combustion chamber 30 moves in an upward direction, reducing the volume of cylinder or combustion chamber 30. As a result, exhaust gas is expelled from cylinder or combustion chamber 30 into intake manifold 44, allowing exhaust gas recirculation to other engine cylinders to be increased.

[0026] The system from the Fig. 1-3 provides an engine system comprising: an engine including a plurality of cylinders, wherein one cylinder of the plurality of cylinders includes a passage leading to the one cylinder via a second intake valve, the passage not leading to a portion of an intake manifold that is in pneumatic communication with other engine cylinders of the engine when a second intake valve of the cylinder is closed, the passage being in pneumatic communication with a vacuum accumulator when the second intake valve is closed. The engine system further comprises a controller, the controller including executable instructions stored in non-transitory memory to open the second intake valve of the cylinder during a first stroke of a cycle of the cylinder to draw air from the vacuum accumulator into the cylinder.

[0027] In some examples, the engine system includes additional instructions to open a first intake valve of the cylinder while closing the second intake valve of the cylinder during a second stroke of the cylinder's cycle. The engine system includes additional instructions to open the exhaust valves of the deactivated cylinder while closing the first and second intake valves of the cylinder during a third stroke of the cylinder's cycle. The engine system includes additional instructions to open the first intake valve of the cylinder while closing the second intake valve of the cylinder during a fourth stroke of the cylinder's cycle. The engine system includes deactivating the cylinder by interrupting the flow of fuel to the cylinder.

[0028] With reference to Fig. 4 shows an example expected sequence showing the valve operation for a cylinder that is active and then deactivated. The sequence of Fig. 4 may be made in accordance with the procedure Fig. 5 and the system from the Fig. 1-3 are provided. The Fig. 4 shown courses occur simultaneously and are aligned in time.

[0029] The first course from above in Fig. Figure 4 is a plot of a curve indicating cylinder position versus crankshaft position. Crankshaft position is indicated by vertical markers along the horizontal axis. Specifically, the horizontal axis is divided into sections representing strokes of the cylinder, where "I" indicates an intake stroke, "C" indicates a compression stroke, "P" indicates a power stroke, and "E" indicates an exhaust stroke. The cylinder strokes for the cylinder with a position indicated by curve 750 are separated by small vertical markers separated by 180 degrees of crankshaft rotation. Thus, there are 180 degrees of crankshaft rotation between each cylinder cycle. Thus, an intake valve that opens at the beginning of an intake stroke and closes at the end of the intake stroke is open for a crankshaft interval of 180 degrees of crankshaft rotation. A similar procedure occurs for valve timing events that occur during other strokes of the cylinder.Curve 750 indicates the position of a cylinder of the engine. Specifically, a rising edge 702 of curve 750 indicates that the position is at top dead center on the cylinder's compression stroke. As the engine rotates, the cylinder continues through the other engine strokes, and curve 750 transitions to a lower stage before another rising edge 702 indicates that the engine has completed a cycle (e.g., two engine revolutions) and is back at top dead center on the cylinder's compression stroke.

[0030] The second course from the top in Fig. Figure 4 is a graph of cylinder state versus crankshaft position. The vertical axis represents the cylinder state, and the cylinder is active and combusting air and fuel when the curve is at a higher level near the vertical axis arrow. The cylinder is deactivated and not combusting air and fuel when the curve is at a lower level near the horizontal axis. The horizontal axis represents the cylinder stroke and position, as previously discussed.

[0031] The third course from the top in Fig. Figure 4 is a graph of the cylinder's exhaust valve status versus crankshaft position. The vertical axis represents the exhaust valve, and the exhaust valves are open when the curve is at a higher level near the vertical axis arrow. The exhaust valves are closed when the curve is at a lower level near the horizontal axis. The horizontal axis represents the cylinder stroke and position, as previously discussed.

[0032] The fourth course from the top in Fig. Figure 4 is a graph of the state of a cylinder's first intake valve versus crankshaft position. The vertical axis represents the state of the first intake valve, and the first intake valve is open when the curve is at a higher level near the vertical axis arrow. The first intake valve is closed when the curve is at a lower level near the horizontal axis. The horizontal axis represents the cylinder stroke and position, as previously discussed.

[0033] The fifth course from the top in Fig. Figure 4 is a graph of the state of a second intake valve of the cylinder versus crankshaft position. The vertical axis represents the state of the second intake valve, and the second intake valve is open when the curve is at a higher level near the vertical axis arrow. The second intake valve is closed when the curve is at a lower level near the horizontal axis. The horizontal axis represents the cylinder stroke and position, as previously discussed.

[0034] At time T0, the cylinder is active and combusting air and fuel, as indicated by the state of the cylinder curve, which is at a higher stage. The cylinder is starting an intake stroke, and the first and second intake valves are in an open state, as indicated by their corresponding curves, which are at a higher stage.

[0035] At time T1, the engine has rotated through the intake and compression strokes and has reached the cylinder's top dead center. The cylinder state indicates that the cylinder is active and combusting air and fuel.

[0036] Between time T1 and time T2, the engine rotates through several engine and cylinder cycles. The cylinder cycle repeats every four strokes. The intake valves are open during the cylinder's intake stroke, and the exhaust valves are open during the cylinder's exhaust stroke. It should be noted that actual valve timing for intake and exhaust valves in some examples may differ slightly from that in Fig. 4 without departing from the spirit of this disclosure. For example, the exhaust valve may open ten degrees of crankshaft rotation before the exhaust stroke begins.

[0037] At time T2, the cylinder changes state from active to deactivated. Fuel injection to the cylinder is interrupted, and exhaust gas from a recent combustion event in the cylinder is expelled to the exhaust manifold when the exhaust valves are open. The cylinder deactivates during its exhaust stroke; however, in some examples, the cylinder may begin deactivation at an earlier crankshaft angle. Valve timing is adjusted in response to the cylinder starting on the next stroke of the cylinder, which would have been an intake stroke had valve timing continued in conventional valve timing mode.

[0038] At time T3, the intake stroke begins, and the second intake valve opens, allowing air to be drawn into the cylinder from the vacuum reservoir and crankcase. The first intake valve and exhaust valves are closed, while the second intake valve is open, allowing the negative pressure in the cylinder, caused by the expansion of the cylinder volume due to the movement of the piston away from the cylinder head, to be used to increase the negative pressure in the vacuum reservoir. The amount of air entering the cylinder can be estimated based on the cylinder pressure and the pressure in the vacuum reservoir.

[0039] At time T4, the first intake valve is open and the second intake valve is closed, while the exhaust valves are closed at the beginning of the cylinder's compression stroke. The piston begins to move toward the cylinder head, reducing cylinder volume and pressurizing air within the cylinder. This expels the air to the engine intake manifold, where it can be introduced by active engine cylinders. Opening the first intake valve allows air to flow into the intake manifold, where intake pressure can be boosted in an attempt to improve engine efficiency.

[0040] At time T5, the first and second intake valves are closed, while the exhaust valves are open at the beginning of the cylinder's power stroke. The piston begins to move away from the cylinder head to increase cylinder volume and reduce cylinder pressure, allowing exhaust gas to be drawn into the cylinder from the exhaust manifold. Closing the intake valves and opening the exhaust valves allows exhaust gas to be drawn into the cylinder without drawing air into the cylinder, allowing the amount of exhaust gas in the cylinder to be increased.

[0041] At time T6, the first intake valve is open and the second intake valve is closed, while the exhaust valves are closed at the beginning of the cylinder's exhaust stroke. The piston begins to move toward the cylinder head, reducing cylinder volume and pressurizing exhaust gas within the cylinder and expelling it to the engine intake manifold, where it can be introduced by active engine cylinders. Opening the first intake valve allows exhaust gas to flow into the intake manifold. It should be noted that the intake valve timing and exhaust valve timing can be adjusted to increase or decrease airflow and exhaust gas flow into the engine intake manifold. The cycle repeats after the exhaust stroke at time T6.

[0042] With reference to Fig. 5 shows a method for operating a cylinder of an engine. The method of Fig. 5 can be imported into the system as executable instructions stored in non-volatile memory from the Fig. 1-3. Furthermore, sections of the procedure from Fig. 5 measures taken in the real world to determine an operating state of the system from the Fig. 1-3. In addition, the procedure can be Fig. 5 which in Fig. 4 provide the operating sequence shown.

[0043] At 502, method 500 judges whether the cylinder is deactivated or requested to be deactivated. Cylinder deactivation may be requested based on engine speed and load or other vehicle conditions. A variable stored in memory may indicate whether the cylinder is deactivated or not. For example, if a bit in memory has a value of zero, the cylinder may be deactivated. If the bit in memory has a value of one, the cylinder may be active. The cylinder is deactivated by discontinuing the flow of fuel to the cylinder. Additionally, spark delivery to the deactivated cylinder may be terminated. If method 500 judges that the cylinder is deactivated, the answer is yes and method 500 proceeds to 504. Otherwise, the answer is no and method 500 proceeds to 520.

[0044] At 504, method 500 closes a first intake valve and opens a second intake valve of the deactivated cylinder while keeping the exhaust valves of the deactivated cylinder closed during a stroke that would be an intake stroke if the cylinder were activated. The cylinder piston moves in a direction that increases the cylinder volume during the cylinder stroke. Closing the first intake valve isolates and seals the cylinder from a portion of the intake manifold that is in pneumatic communication with other engine cylinders. Opening the second intake valve allows air to be drawn into the cylinder from a vacuum reservoir or the engine crankcase. Closing the exhaust valves pneumatically isolates the cylinder from the exhaust manifold, allowing a vacuum to develop as the piston approaches bottom dead center. Method 500 proceeds to 506.

[0045] At 506, method 500 opens the first intake valve and closes the second intake valve of the deactivated cylinder while keeping the exhaust valves of the deactivated cylinder closed during a stroke that would be a compression stroke if the cylinder were activated. The cylinder piston moves in a direction that reduces the cylinder volume during the cylinder's stroke. Opening the first intake valve exposes the cylinder to the intake manifold, allowing air drawn into the cylinder from the vacuum reservoir to be delivered to the intake manifold to increase pressure in the engine intake manifold. Closing the second intake valve pneumatically isolates the cylinder from the vacuum reservoir and the engine crankcase. Method 500 proceeds to 508.

[0046] At 508, method 500 closes the first and second intake valves and opens the exhaust valves of the deactivated cylinder during a stroke that would be a power stroke if the cylinder were activated. The cylinder piston moves in a direction that increases the cylinder volume during the cylinder's stroke. By closing the first and second intake valves, the cylinder is pneumatically isolated and sealed from the intake manifold and vacuum reservoir. By opening the exhaust valves, exhaust gas can flow into the cylinder from other engine cylinders using vacuum that may develop in the cylinder as the piston approaches bottom dead center. Method 500 proceeds to 510.

[0047] At 510, method 500 opens the first intake valve and closes the second intake valve of the deactivated cylinder while keeping the exhaust valves of the deactivated cylinder closed during a stroke that would be an exhaust stroke if the cylinder were activated. The cylinder piston moves in a direction that reduces the cylinder volume during the cylinder's stroke. Opening the first intake valve allows exhaust gas in the cylinder to be expelled into the intake manifold, allowing exhaust gas to be recirculated to active cylinders. Method 500 proceeds to exit.

[0048] At 520, method 500 delivers spark and fuel to the cylinder so that an air-fuel mixture can be combusted within the cylinder, producing torque for the engine. Method 500 proceeds to 522.

[0049] At 522, method 500 operates intake and exhaust valves according to a conventional four-stroke engine cycle. Specifically, the intake valves are opened during the cylinder's intake stroke, while the exhaust valves are closed. The intake and exhaust valves are closed during the compression and expansion strokes.

[0050] During the exhaust stroke, the exhaust valves are opened and the intake valves are closed. Note that in some examples, during intake cycles, the second intake valve may only be opened in response to a request for additional vacuum in a vacuum reservoir. Method 500 proceeds to exit.

[0051] It should be noted that intake valve timing and exhaust valve timing may overlap slightly in cylinder strokes besides those mentioned in method 500. For example, an intake valve may be open for a few degrees of crankshaft rotation (e.g., less than 25 degrees of crankshaft rotation) of an exhaust stroke or compression stroke when the intake valve is described as open during an intake stroke. The intake valve may then be adjusted in this manner to increase or decrease airflow into or out of the cylinder. The exhaust valves may be operated similarly.

[0052] Thus, the procedure Fig. 5 provides an engine control method comprising: deactivating a cylinder of an engine via a controller that interrupts the supply of fuel to the cylinder, the engine being a four-stroke engine; and drawing air from a vacuum accumulator into the deactivated cylinder during a first stroke of four strokes in a cycle of the deactivated cylinder, wherein the air is drawn into the deactivated cylinder without having traversed a passage of an intake manifold leading to other cylinders of the engine. The method further comprises opening a second intake valve of the deactivated cylinder during a first stroke of a cycle of the deactivated cylinder to draw the air from the vacuum accumulator into the deactivated cylinder.The method further includes opening a first intake valve of the deactivated cylinder while closing the second intake valve of the deactivated cylinder during a second stroke of the deactivated cylinder cycle. The method further includes purging air to an intake manifold of the engine during the second stroke of the deactivated cylinder cycle.

[0053] In some examples, the method further comprises opening exhaust valves of the deactivated cylinder while closing the first and second intake valves of the deactivated cylinder during a third stroke of the deactivated cylinder cycle. The method further comprises drawing exhaust gas into the deactivated cylinder during the third stroke of the deactivated cylinder cycle. The method further comprises opening a first intake valve of the deactivated cylinder while closing the second intake valve of the deactivated cylinder during a fourth stroke of the deactivated cylinder cycle.

[0054] The procedure according to Fig.5 also provides an engine control method comprising: operating a cylinder of an engine with four strokes in a first cycle of the engine, the four strokes including a first stroke defined by a first crankshaft angle interval, the first stroke being an intake stroke, a second stroke defined by a second crankshaft angle interval, the second stroke being a compression stroke, a third stroke defined by a third crankshaft angle interval, the third stroke being a power stroke, and a fourth stroke defined by a fourth crankshaft angle interval, the fourth stroke being an exhaust stroke, deactivating the cylinder of an engine via a controller, interrupting the supply of fuel to the cylinder;and opening the exhaust valves of the cylinder during the third crankshaft interval of a second cycle of the engine while the cycle is off, and drawing exhaust gas from cylinders other than the cylinder into the cylinder.;

[0055] The method includes closing the first and second intake valves of the cylinder during the third crankshaft interval of the second cycle of the engine. The method further includes opening a second intake valve while closing a first intake valve of the cylinder during the first crankshaft interval of the second cycle of the engine. The method further includes opening the first intake valve while closing the second intake valve of the cylinder during the second crankshaft interval of the second cycle of the engine. The method further includes opening the first intake valve while closing the second intake valve of the cylinder during the fourth crankshaft interval of the second cycle of the engine. The method further includes combusting air and fuel in at least one cylinder of the engine while the cylinder is deactivated.The method further includes combusting air and fuel in the cylinder during the first cycle of the engine.

[0056] It should be noted that the example control and estimation routines included herein may be used with different engine and / or vehicle system configurations. The control methods and routines disclosed herein may be stored as executable instructions in non-transitory memory and executed by the control system, including the controller in combination with the various sensors, actuators, and other internal combustion engine hardware. The specific routines described herein may represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Accordingly, various illustrated acts, operations, and / or functions may be performed in the illustrated order, in parallel, or in some cases, omitted.Likewise, the processing order is not necessarily required to achieve the features and advantages of the exemplary embodiments described herein, but rather is provided for ease of illustration and description. One or more of the illustrated acts, operations, and / or functions may be performed repeatedly depending on the particular strategy employed. Furthermore, at least a portion of the described acts, operations, and / or functions may graphically represent code to be programmed into non-transitory memory of the computer-readable storage medium in the control system.The control actions may also transform the operating state of one or more sensors or actuators in the physical world when the described actions are performed by executing the instructions in a system that includes the various engine hardware components in combination with one or more controllers.

[0057] This concludes the description. A reading of this description by a person skilled in the art will reveal many changes and modifications without deviating from the spirit and scope of the description. For example, this description can be applied to I3, I4, I5, V6, V8, V10, and V12 engines operating on natural gas, gasoline, diesel, or alternative fuel configurations.

Claims

[1] Engine control method comprising: Deactivating a cylinder of an engine via a control that interrupts the supply of fuel to the cylinder, the engine being a four-stroke engine; and drawing air during a first stroke of four strokes in a cycle of the deactivated cylinder from a vacuum accumulator into the deactivated cylinder, the air being drawn into the deactivated cylinder without having traversed a passage of an intake manifold leading to other cylinders of the engine. [2] The method of claim 1, further comprising opening a second intake valve of the deactivated cylinder during the first stroke of the cycle of the deactivated cylinder to draw the air from the vacuum accumulator into the deactivated cylinder. [3] The method of claim 2, further comprising opening a first intake valve of the deactivated cylinder while closing the second intake valve of the deactivated cylinder during a second stroke of the cycle of the deactivated cylinder. [4] The method of claim 3, further comprising purging air to the intake manifold of the engine during the second stroke of the cycle of the deactivated cylinder. [5] The method of claim 4, further comprising opening exhaust valves of the deactivated cylinder while closing the first and second intake valves of the deactivated cylinder during a third stroke of the cycle of the deactivated cylinder. [6] The method of claim 5, further comprising drawing exhaust gas into the deactivated cylinder during the third stroke of the cycle of the deactivated cylinder. [7] The method of claim 6, further comprising opening a first intake valve of the deactivated cylinder while closing the second intake valve of the deactivated cylinder during a fourth stroke of the cycle of the deactivated cylinder. [8] Engine system comprising: an engine including a plurality of cylinders, one cylinder of the plurality of cylinders including a first intake valve and a passage leading to the one cylinder via a second intake valve, the passage not leading to a portion of an intake manifold that is in pneumatic communication with other engine cylinders of the engine when the second intake valve of the cylinder is closed, the passage being in pneumatic communication with a vacuum accumulator. [9] The engine system of claim 8, further comprising a controller, the controller including executable instructions stored in non-volatile memory to open the second intake valve of the cylinder during a first stroke of a cycle of the cylinder to draw air from the vacuum accumulator into the cylinder. [10] The engine system of claim 9, further comprising additional control instructions to open the first intake valve of the cylinder while closing the second intake valve of the cylinder during a second stroke of the cycle of the cylinder. [11] The engine system of claim 10, further comprising additional control instructions to open exhaust valves of the deactivated cylinder while closing the first and second intake valves of the cylinder during a third stroke of the cylinder's cycle. [12] The engine system of claim 11, further comprising additional control instructions to open the first intake valve of the cylinder while closing the second intake valve of the cylinder during a fourth stroke of the cycle of the cylinder. [13] The engine system of claim 8, wherein the cylinder is deactivated by interrupting the flow of fuel to the cylinder.

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