System and method for extending the operating time of valve actuators of an internal combustion engine

Abstract

Engine control procedures, comprehensive: Engine cylinder deactivation via a control system according to a first cylinder deactivation strategy in response to the fact that the actual total number of valve actuator state changes is less than a first threshold; and Engine cylinders are deactivated via the control system according to a second cylinder deactivation strategy in response to the fact that the actual total number of valve actuator state changes is greater than a second threshold.

Description

Area

[0001] The present description relates to a system and method for selectively activating and deactivating cylinders of an engine to conserve fuel while meeting engine torque demands. The system and methods vary which cylinders of an engine fire from one engine cycle to the next. Background and brief presentation

[0002] An engine may include a plurality of variable valve actuators that allow one or more engine cylinders to be turned on or off between engine cycles. In some engines, the engine cylinders that are deactivated may vary each engine cycle, so that each engine cylinder is deactivated as often as other cylinders in the engine over a plurality of engine cycles. By deactivating engine cylinders in this manner, engine pumping losses can be reduced and operating conditions of engine cylinders can be more uniform. However, over the course of engine operation over a significant amount of time and distance, the engine valve actuators may change state so frequently that they degrade, making engine cylinder deactivation less reliable.This can be especially true for engines that alternate deactivated engine cylinders during each engine cycle or engine event, since each valve actuator of each engine cylinder can be repeatedly switched from actuating a valve to deactuating the valve, even when the engine load is constant.

[0003] US 2014 / 0 041 382 A1 describes a turbocharged internal combustion engine with cylinder deactivation. The internal combustion engine has a first and a second cylinder group, each with intake and exhaust valves that can be deactivated via valve actuators. In an operating range with low load or engine speed, the second cylinder group is deactivated by deactivating the fuel supply and the intake and exhaust valves. To ensure even wear of the cylinder groups, the deactivated cylinder group is periodically replaced.

[0004] US 2016 / 0 108 798 A1 teaches a method and system for improving the efficiency of a turbocharger. The underlying internal combustion engine has selectively deactivatable intake and exhaust valves. The selection of a deactivation pattern or strategy for the cylinders at low load depends on various criteria. In one embodiment, the deactivation pattern is selected such that the number of activations and deactivations of each cylinder is reduced.

[0005] The inventor of the present invention has recognized the above-mentioned problems and, to solve them, has developed an engine control method having the features of the independent patent claims. Advantageous developments of the invention are the subject of the dependent claims.

[0006] Accordingly, the engine control method includes deactivating engine cylinders via a controller according to a first cylinder deactivation strategy in response to an actual total number of valve actuator state changes being less than a first threshold; and deactivating the engine cylinders via the controller according to a second cylinder deactivation strategy in response to an actual total number of valve actuator state changes being greater than a second threshold.

[0007] By switching between two or more cylinder deactivation strategies in response to an actual total number of valve actuator state changes, it may be possible to provide the technical result of extending the operating time of engine valve actuators. In particular, valve actuators may have a limited number of state changes and are expected to operate with a low probability of degradation. If the valve actuators continue to change states at a constant rate after the limited number of state changes, the possibility of valve actuator degradation may increase. Nevertheless, the rate at which valve actuators change states can be reduced by deactivating fixed groups of cylinders rather than rotating or varying which cylinders are deactivated in each engine cycle.The rate at which a valve actuator changes state can be reduced when cylinders are deactivated in fixed groups, as valve actuators do not need to change state every engine cycle, compared to strategies where valve actuators can change state every engine cycle. Therefore, a second valve strategy where cylinders are deactivated in a fixed group can be replaced by, or combined with, a first strategy where cylinders are deactivated on a rotating basis (e.g.,In a first engine cycle, engine cylinder number one may be deactivated while engine cylinders two, three, and four are active; in a second engine cycle immediately following the first engine cycle, engine cylinder number two may be deactivated while engine cylinders one, three, and four are active; in a third engine cycle immediately following the second engine cycle, engine cylinder number three may be deactivated while engine cylinders one, two, and four are active, and so on) to reduce valve actuator state changes, thereby increasing valve actuator operating time.

[0008] The present description may provide several advantages. In particular, the approach may increase the amount of time a valve actuator can operate without degradation. Furthermore, the approach provides progressive operations that act to extend valve actuator benefit while still enabling cylinder deactivation. Furthermore, the approach may deactivate cylinder deactivation, allowing cylinder operation to be maintained even as a valve actuator approaches conditions where valve actuator degradation is expected.

[0009] 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. Short description of the drawings

[0010] The advantages described herein will become more fully apparent upon 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. Figure 1 is a schematic diagram of an internal combustion engine; Fig. Figure 2A is a schematic representation of an eight-cylinder engine with two cylinder banks; Fig. Figure 2B is a schematic representation of a four-cylinder engine with a single cylinder bank; Fig. 3A is a flow chart of a first exemplary operating sequence; Fig. 3B is a graph of a second exemplary operating sequence; Fig. 4A and Fig. 4B are traces of exemplary engine cylinder deactivation ranges; and Fig. 5 shows a flowchart of an exemplary method for operating an engine. Detailed description

[0011] This description concerns the extension of the operating time of engine cylinder valve actuators. The valve actuator can be used in an engine such as Fig. 1-2B. The motor can be controlled according to the instructions in Fig. 3A and Fig. 3B. The engine cylinder valve actuators can be operated based on the sequences shown in Fig. 4A and Fig. 4B shown engine operating ranges. A method for operating the engine of Fig. 1-2B to provide extended operating time will be Fig. 5 shown.

[0012] 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 the cylinder walls 32 with the piston 36 disposed therein and connected to the crankshaft 40.

[0013] As shown, the combustion chamber 30 communicates with the intake manifold 44 and the exhaust manifold 48 via the respective intake valve 52 and exhaust valve 54. Each intake and exhaust valve may be actuated by a variable intake valve actuator 51 and a variable exhaust valve actuator 53, which may be actuated mechanically, electrically, hydraulically, pneumatically, or by a combination thereof. For example, the valve actuators may be of the type described in US 2014 / 0 303 873 A1 and US patents US 6 321 704 B1, US 6 273 039 B1, and US 7 458 345 B2, which are hereby incorporated in their entirety for all intents and purposes. The intake valve actuator 51 and an exhaust valve actuator can open the intake valve 52 and exhaust valve 54 synchronously or asynchronously with the crankshaft 40. The position of the intake valve 52 can be determined by the intake valve position sensor 55.The position of the exhaust valve 54 can be determined by the exhaust valve position sensor 57.

[0014] 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 by 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 the air intake 42 to the intake manifold 44. The throttle 62 regulates airflow from the air cleaner 43 into the engine air intake 42 to the intake manifold 44.In one example, a two-stage high-pressure fuel system may be used to generate higher fuel pressure. In some examples, throttle 62 and throttle plate 64 may be positioned between intake valve 52 and intake manifold 44 such that throttle 62 is a port throttle.

[0015] 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.

[0016] 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.

[0017] The control 12 is in Fig. 1 as a conventional microcomputer including: a microprocessor unit 102, input / output channels 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 illustrated as receiving various signals from sensors coupled to the engine 10, in addition to those signals previously discussed, including: engine coolant temperature (ECT) from temperature sensor 112 coupled to a cooling sleeve 114; a position sensor 134 connected to an accelerator pedal 130 for detecting the force applied by a human operator 132; a measurement of engine manifold pressure (MAP) from pressure sensor 122 connected to the intake manifold 44; an engine position sensor from a Hall effect sensor 118 detecting the position of the crankshaft 40; a measurement of the mass of air entering the engine from sensor 120; brake pedal position from brake pedal position sensor 154 when the human operator 132 applies the brake pedal 150; and a measurement of throttle position from sensor 58.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 every revolution of the crankshaft, from which engine speed (RPM) can be determined.

[0018] In some examples, the engine may be connected 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.

[0019] 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.

[0020] With reference to Fig. 2A, an exemplary 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 in the cylinders. The fuel injectors 66 selectively supply fuel to each of the cylinders that is activated (e.g., combusting fuel during one cycle of the internal combustion engine). Cylinders 1-8 may be selectively 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., a fixed pattern of deactivated cylinders) may be deactivated during one engine cycle (e.g., two revolutions for a four-stroke engine) and may be deactivated for a plurality of engine cycles while engine speed and load are constant or vary slightly. During another engine cycle, a second fixed pattern of cylinders 1, 4, 6, and 7 may be deactivated.Furthermore, other patterns of cylinders may be selectively deactivated based on vehicle operating conditions. Additionally, engine cylinders may be deactivated so that a fixed pattern of cylinders is not deactivated across a plurality of engine cycles. Instead, deactivated cylinders may change from one engine cycle to the next. Each cylinder includes variable intake valve actuators 51 and variable exhaust valve actuators 53. An engine cylinder may be deactivated by its variable intake valve actuators 51 and variable exhaust valve actuators, which keep the cylinder's intake and exhaust valves closed throughout an entire cylinder cycle while the fuel injector 66 does not inject fuel into the cylinder throughout the cylinder cycle.An engine cylinder can be activated by its variable intake valve actuators 51 and variable exhaust valve actuators 53, which open and close the cylinder's intake and exhaust valves during a cylinder cycle, while the fuel injector 66 injects fuel into the cylinder during a cylinder cycle. 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.

[0021] With reference to Fig. 2B, an exemplary 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 in the cylinders. The fuel injectors 66 selectively supply fuel to each of the cylinders that are activated (e.g., combusting fuel during an engine cycle in which intake and exhaust valves open and close during a cycle of the cylinder that is active). Cylinders 1-4 may be selectively deactivated (e.g., not combusting fuel during an engine cycle in which intake and exhaust valves are held closed for an entire cycle of the deactivated cylinder) to improve engine fuel economy when less than the full torque capacity of the engine is demanded. For example, cylinders 2 and 3 (e.g., a fixed pattern of deactivated cylinders) may be deactivated during a plurality of engine cycles (e.g.,two revolutions for a four-stroke engine). During another engine cycle, a second fixed pattern of cylinders 1 and 4 may be deactivated over a plurality of engine cycles. Further, other patterns of cylinders may be selectively deactivated based on vehicle operating conditions. Additionally, engine cylinders may be deactivated such that a fixed pattern of cylinders is not deactivated over a plurality of engine cycles. Instead, cylinders that are deactivated may change from one engine cycle to the next. In this way, the deactivated engine cylinders may rotate or change from one engine cycle to the next.

[0022] The engine 10 includes a single cylinder bank 250 containing four cylinders 1-4. The cylinders of the individual bank can be active or deactivated during an engine cycle. Each cylinder includes variable intake valve actuators 51 and variable exhaust valve actuators 53. An engine cylinder can be deactivated by its variable intake valve actuators 51 and variable exhaust valve actuators, which keep the cylinder's intake and exhaust valves closed during a cylinder cycle while the fuel injector 66 does not inject fuel into the cylinder during a cylinder cycle.An engine cylinder may be activated by its variable intake valve actuators 51 and variable exhaust valve actuators 53, which open and close the cylinder's intake and exhaust valves during a cycle of the cylinder, while the fuel injector 66 injects fuel into the cylinder during a cycle of the cylinder.

[0023] The system from Fig. 1-2B provides an engine system comprising: an engine having one or more cylinder deactivation mechanisms; a controller having executable instructions stored in non-volatile memory to adjust an engine operating range that defines when engine cylinders may be deactivated in response to an actual total number of valve actuator state changes being greater than a first threshold, and to deactivate engine cylinders according to the engine operating range. The engine system includes where the engine operating range is an engine speed and load range. The engine system includes where adjusting the engine operating range includes dividing the engine operating range into two operating ranges. The engine system includes where, in the first operating range of the two operating ranges, an engine load is less than in a second operating range of the two operating ranges.

[0024] In some examples, the engine system further includes additional instructions to operate the engine with a fixed group of deactivated cylinders over a plurality of engine cycles in the second operating range. The engine system further includes additional instructions to change which engine cylinders are in the fixed group of deactivated cylinders in response to the actual total number of valve actuator state changes.

[0025] With reference to Fig. 3A shows traces of an engine operating sequence. The two traces are aligned in time and occur simultaneously. The vertical dashed lines identified by the markers T0-T4 separate engine cycles. The sequence can be determined by the system from Fig. 1 and Fig. 2A with the procedure from Fig. 5, stored as executable instructions in non-volatile memory. The sequence of Fig. 3A is based on an eight-cylinder four-stroke engine with a firing order or sequence of combustion of 1, 3, 7, 2, 6, 5, 4 and 8. The engine cylinder firing fraction for this sequence is 0.333.

[0026] The first course at the top of the Fig. 3A is a history of the cylinder activation decision (e.g., firing with intake and exhaust valves opening and closing and fuel injection during one cylinder cycle) or deactivation (e.g., no firing with intake and exhaust valves held closed and no fuel injection during one cylinder cycle) for engine cylinders versus the engine event count. An engine event can be an occurring stroke of a cylinder (e.g., intake stroke, compression stroke, power stroke, exhaust stroke), an opening or closing timing of an intake or exhaust valve, the injection of fuel, the timing of ignition of an air-fuel mixture in the cylinder, a position of a piston in the cylinder relative to the crankshaft position, or another engine-related event. The engine event count corresponds to a specific cylinder.For example, engine event number one may correspond to a compression stroke of cylinder number one. Engine event number two may correspond to a compression stroke of cylinder number three.

[0027] The decision to turn on or off a cylinder and open and close the cylinder's intake and exhaust valves and inject fuel may be made a predetermined number of cylinder events (e.g., one cylinder event, or alternatively, one cylinder cycle, or eight cylinder events) before the cylinder is to be turned on or off, to allow evaluation of the time to begin the process of opening and closing the cylinder's intake and exhaust valves. For example, for an eight-cylinder engine with a firing order of 1, 3, 7, 2, 6, 5, 4, 8, the decision to turn on or off cylinder number seven during an intake or compression stroke of cylinder number seven may be made one engine cycle before cylinder number seven is deactivated.Alternatively, the decision to turn a cylinder on or off may be made a predetermined number of engine events or cylinder events before the selected cylinder is turned on or off. The cylinder that is on its compression stroke at the time corresponding to the event number will be turned on if the firing decision value indicated by the circle is a value of one. The cylinder that is on its compression stroke at the time corresponding to the event number will not be turned on if the firing decision value indicated by the circle is zero. The vertical axis represents the firing decision, and the horizontal axis represents the cylinder event number or the actual total number of cylinder events.

[0028] The second course at the top of the Fig. 3A is a graph of the cylinder numbers that correspond to the first graph at the top of the Fig. 3A. The vertical axis represents the cylinder count for the currently evaluated cylinder. The horizontal axis represents the engine event count or actual total number of engine events. The solid filled circles represent an active cylinder with combustion during the cylinder's cycle. The unfilled circles represent deactivated cylinders with no combustion during the engine's cycle.

[0029] In this example, the first engine cycle shown begins at time T0. The first engine event corresponds to cylinder number one, as indicated at 302. Cylinder number one is not firing, as indicated by the unfilled circle at 302 and the firing decision at 304, which is zero. The second engine event corresponds to cylinder number three, as indicated at 310. Cylinder number three is active and is firing, as indicated by the filled circle at 310 and the firing decision at 312, which is one. Firing decisions for the remaining cylinders follow a similar convention.

[0030] It can be observed that the engine's cylinders are energized and fired three times for every nine compression strokes, so that the engine follows the desired engine cylinder firing fraction of 0.333. Furthermore, engine cycles begin and end at the vertical markers T0, T1, T2, T3, and T4. For example, the first engine cycle is between time T0 and time T1. The second engine cycle is between time T1 and time T2. Different engine cylinders are deactivated from one engine cycle to the next, so there is no fixed pattern of deactivated cylinders during adjacent engine cycles. The engine cylinder firing fraction of 0.333 is a non-steady-state or non-fixed pattern because the cylinders that are energized and deactivated change from engine cycle to engine cycle. All engine cylinders can fire over the course of one or more cylinder cycles for a non-steady-state pattern when cylinders are deactivated.

[0031] Now, with reference to Fig. 3B shows the traces of a second engine operating sequence. The two traces are aligned in time and occur simultaneously. The sequence can be determined by the system from Fig. 1 and Fig. 2A with the procedure from Fig. 5, stored as executable instructions in non-volatile memory. The sequence of Fig. 3B is based on an eight-cylinder four-stroke engine with a firing order or combustion sequence of 1, 3, 7, 2, 6, 5, 4, 8. The engine cylinder firing fraction for this sequence is 0.5.

[0032] The first course at the top of the Fig. Figure 3B is a graph of the cylinder activation or deactivation decision for engine cylinders versus engine event count. The vertical axis represents the ignition decision, and the horizontal axis represents the engine event count, or the actual total number of engine events.

[0033] The second one at the top of the Fig. 3B is a graph of the cylinder numbers that correspond to the first graph at the top of the Fig. 3B shown ignition decisions.

[0034] The vertical axis represents the cylinder count for the evaluated engine event. The horizontal axis represents the engine event count or actual total number of engine events. The solid filled circles represent an active cylinder with combustion during the engine cycle. The open circles represent deactivated cylinders with no combustion during the engine cycle.

[0035] In this example, the first engine event corresponds to cylinder number one, as indicated at 352. Cylinder number one is firing, as indicated by the filled circle at 352 and the firing decision at 354, which is one. The second engine event corresponds to cylinder number three, as indicated at 360. Cylinder number three is deactivated and does not fire, as indicated by the unfilled circle at 360 and the firing decision at 362, which is zero. Firing decisions for the remaining cylinders follow a similar convention.

[0036] It can be observed that the engine's cylinders are turned on and fired five times for every ten compression strokes, so that the engine follows the desired engine cylinder firing fraction of 0.5. The engine cylinder firing fraction of 0.5 is a fixed or steady-state pattern because the cylinders that are turned on and off do not change from engine cycle to engine cycle. For example, cylinders 1, 6, 7, and 4 always fire in an engine cycle, while cylinders 2, 3, 5, and 8 do not fire at any time during the sequence. The vertical markers at time T10-T14 represent the beginning and end of engine cycles. For example, the first engine cycle is between time T10 and time T11. The second engine cycle is between time T11 and time T12.

[0037] Now, with reference to Fig. 4A shows an example engine cylinder deactivation operating range. The vertical axis represents engine load, and engine load increases in the direction of the vertical axis arrow. The horizontal axis represents engine speed, and engine speed increases in the direction of the horizontal axis arrow.

[0038] The area bounded by solid line 400 is a range of engine operation in which one or more engine cylinders may be deactivated to conserve fuel. The engine cylinders may be deactivated (e.g., by adjusting fuel to deactivated cylinders and keeping intake and exhaust valves of deactivated cylinders closed throughout an entire engine cycle) within the area enclosed by solid line 400 by deactivating the cylinders such that different engine cylinders are deactivated for each engine cycle and such that cylinders deactivated during one engine cycle are not the same cylinders deactivated during a next or adjacent engine cycle. For example, for a four-cylinder, four-cycle engine with a firing order of 1, 3, 4, 2, cylinders 1 and 4 may be deactivated during a first engine cycle, and only cylinder number 1 may be deactivated during a subsequent engine cycle. Fig. 3A also shows a cylinder deactivation example for this engine operating range. Thus, the group of deactivated cylinders changes from one engine cycle to the next. In the area surrounding solid line 400, all engine cylinders are active (e.g., fuel flows to active cylinders and combusts air and fuel in the active cylinders while intake and exhaust valves open and close during an engine cycle).

[0039] In this example, the solid line 400 shows that the engine cylinder deactivation operating range has a trapezoidal shape, but the engine cylinder deactivation range may be shaped differently in other examples. The engine cylinder deactivation range is defined by the engine load (e.g., the vertical axis) and engine speed (e.g., the horizontal axis). The engine cylinder deactivation range extends from an engine load at 402 to an engine load at 404 and from an engine speed at 410 to an engine speed at 412.

[0040] Now, with reference to Fig. 4B shows a second example of an engine cylinder deactivation operating range. The vertical axis represents the engine load, and the engine load increases in the direction of the vertical axis arrow. The horizontal axis represents the engine speed, and the engine speed increases in the direction of the horizontal axis arrow. Fig. 4B has the same size as that shown in Fig. 4A, but the cylinder deactivation range shown in Fig. The span shown in Figure 4B is divided into two parts or sections.

[0041] The area or range bounded by solid line 462 and dot-dashed line 465 is an engine operating range in which one or more engine cylinders may be deactivated to save fuel. The engine cylinders may be deactivated in the area surrounded by solid line 462 and dot-dashed line 465 by deactivating the cylinders such that different engine cylinders are deactivated for each engine cycle and such that cylinders deactivated during one engine cycle are not the same cylinders deactivated during a next or adjacent engine cycle when engine speed, load, and temperature are substantially constant (e.g., change by less than ± 3%). Thus, the engine cylinders may be deactivated in the same ways as for range 400 of Fig. 4A. Consequently, the group of deactivated cylinders may change from one engine cycle to the next engine cycle if engine cylinders are deactivated within that engine operating range. Fig. 3A shows an example cylinder deactivation sequence for this engine operating range.

[0042] The area or range bounded by dashed line 460 and dot-dashed line 465 is an engine operating range in which one or more engine cylinders may also be deactivated to save fuel. The engine cylinders may be deactivated in the area surrounded by dashed line 460 and dot-dashed line 465 by deactivating the cylinders such that the same engine cylinders are deactivated for each engine cycle and such that cylinders deactivated during one engine cycle are the same cylinders that are deactivated during a next or adjacent engine cycle when engine speed, load, and temperature are substantially constant (e.g., change by less than ± 3%). The cylinder deactivation pattern is fixed, as in the example from Fig. 3B shown.

[0043] Thus, engine cylinders (e.g., different engine cylinders are deactivated for each engine cycle, such that engine cylinders deactivated during one engine cycle are not the same cylinders deactivated during a next or adjacent engine cycle when the engine is operated at constant speed, engine load, and engine temperature) may be deactivated via a first engine cylinder deactivation strategy in a first engine operating range, surrounded by solid line 462 and dotted-dashed line 465. The engine cylinders may be deactivated via a second strategy (e.g., the same engine cylinders are deactivated for each engine cycle, such that cylinders deactivated during one engine cycle are the same cylinders deactivated during a next or adjacent engine cycle) in the second engine operating range, surrounded by dashed line 460 and dotted-dashed line 465.

[0044] If the actual number of valve actuator state changes exceeds a threshold, the second span can be extended to include the range of the first span, and the first span can be omitted so that the engine cylinders can only be deactivated via the second strategy.

[0045] In the area surrounding solid line 462 and dashed line 460, all engine cylinders are active (e.g., fuel flows to active cylinders and combusts air and fuel in the active cylinders as intake and exhaust valves open and close during one cycle of the engine).

[0046] In this example, solid line 462 and dashed line 460 show that the engine cylinder deactivation operating range has a trapezoidal shape, but the engine cylinder deactivation range may be shaped differently in other examples. The engine cylinder deactivation range is defined by engine load (e.g., the vertical axis) and engine speed (e.g., the horizontal axis). The engine cylinder deactivation range extends from an engine load at 402 to an engine load at 404 and from an engine speed at 410 to an engine speed at 412. The engine cylinder deactivation range bounded by solid line 400 may be the basis for cylinder deactivation when the actual total number of valve actuator state changes is less than a first threshold amount.

[0047] It should be noted that the engine operating range enclosed by dashed line 460 and dot-dashed line 465 may be increased by extending the range in the direction of lower engine loads, as shown by arrow 470 (e.g., moving dot-dashed line 465) in response to the actual total number of valve actuator state changes increasing. At the same time, the range enclosed by solid line 462 and dot-dashed line 465 may be reduced so that the area enclosed by solid line 462 and dashed line 460 remains the same size.By increasing the range bounded by dashed line 460 and dot-dashed line 465, the rate at which the actual total number of valve actuator state changes occurs can be reduced because cylinders are deactivated according to a fixed pattern during a plurality of engine cycles in the range bounded by dashed line 460 and dot-dashed line 465. When cylinders are deactivated according to a fixed pattern, where deactivated cylinders do not change in each engine cycle, the rate of change of the actual total number of valve actuator state changes can be reduced.

[0048] Now, with reference to Fig. 5 shows a flowchart describing various strategies for deactivating engine cylinders in response to an actual total number of valve actuator state changes. The method of Fig. 5 can be inserted into the system Fig. 1-2B and cooperate with it. Furthermore, at least sections of the procedure can be Fig. 5 may be integrated as executable instructions stored in a non-volatile memory, while other portions of the method may be performed via a controller that transforms operating states of devices and actuators in the physical world.

[0049] At 502, method 500 counts or infers an actual total number of valve actuator state changes (e.g., changing from a state where the valve actuator actuates a valve such that the valve opens and closes during an engine cycle to a state where the valve actuator does not actuate the valve, so the valve remains closed during a full engine cycle, or vice versa). In one example, the actual total number of valve actuator state changes may be tracked in memory by incrementing a value stored in memory each time a valve actuator state change is commanded. In other examples, a position of the valve actuator may be indicative of a valve actuator state change, and a sensor may indicate such state changes. A value stored in memory may be incremented each time a valve actuator state change is indicated by the sensor.Alternatively, the actual total number of valve actuator state changes may be inferred by tracking an amount of time the engine operates in a specific operating range. The amount of time may be used to index a table or function of empirically determined values ​​representing the actual total number of valve actuator state changes. Output from the table or function may be added to an accumulator that totals the number of valve actuator state changes to determine the total number of valve actuator state changes. After determining the actual total number of valve actuator state changes, method 500 proceeds to 504.

[0050] At 504, method 500 assesses whether the actual total number of valve actuator state changes for one or more valve actuators is greater than a first threshold amount. If so, the answer is yes, and method 500 proceeds to 506. Otherwise, the answer is no, and method 500 proceeds to 520. The first threshold amount may be based on empirically determined valve actuator degradation data. For example, the first threshold may be based on an actual total number of valve actuator state changes corresponding to eighty percent of an actual total number of valve actuator state changes at which valve actuator degradation can be expected.

[0051] At 506, method 500 assesses whether the actual total number of valve actuator state changes for one or more valve actuators is greater than a second threshold amount. If so, the answer is yes, and method 500 proceeds to 508. Otherwise, the answer is no, and method 500 proceeds to 540. The second threshold amount may be based on empirically determined valve actuator degradation data. For example, the second threshold may be based on an actual total number of valve actuator state changes corresponding to ninety percent of an actual total number of valve actuator state changes at which valve actuator degradation can be expected.

[0052] At 508, method 500 assesses whether the actual total number of valve actuator state changes for one or more valve actuators is greater than a third threshold amount. If so, the answer is yes, and method 500 proceeds to 510. Otherwise, the answer is no, and method 500 proceeds to 530. The third threshold amount may be based on empirically determined valve actuator degradation data. For example, the third threshold may be based on an actual total number of valve actuator state changes corresponding to ninety-five percent of an actual total number of valve actuator state changes at which valve actuator degradation can be expected.

[0053] At 510, method 500 disables all engine cylinder deactivation modes so that the engine operates with all engine cylinders when the engine is operating (e.g., combusting air and fuel). The engine cylinder deactivation modes are disabled so that the engine can provide torque at its full capacity and so that the possibility of valve actuator degradation may be reduced. Method 500 proceeds to 512.

[0054] At 512, method 500 actuates the engine so that all of the engine cylinders are active (e.g., combusting air and fuel) when engine torque is requested. If a small amount of engine torque is requested, the engine may be throttled to provide the requested amount of torque. Method 500 proceeds to exit.

[0055] At 520, method 500 enables a first cylinder deactivation strategy that allows different engine cylinders to be deactivated for each engine cycle such that engine cylinders deactivated during one engine cycle are not the same cylinders deactivated during a next or adjacent engine cycle when the engine is operating at substantially constant (e.g., changing less than ± 3 percent over a predetermined period of time) speed, substantially constant engine load, and substantially constant engine temperature. Fig. 3A shows an example of cylinder deactivation according to a first strategy as described. Furthermore, the number of active cylinders (e.g., cylinders combusting air and fuel, with exhaust and intake valves opening and closing during an engine cycle) may change from engine event to engine event as the engine torque demand and / or engine speed changes. The first cylinder deactivation strategy may be applied to deactivate engine cylinders in an engine operating range as indicated by the solid line 400 in Fig. 4A specified to be switched off.

[0056] The first engine cylinder deactivation strategy also selects which particular cylinders are activated and deactivated based on engine speed, engine load, a desired cylinder firing fraction, and other conditions. For example, the first engine cylinder deactivation strategy may select cylinders for deactivation as described in US Pat. No. 7,577,511 B1, which is hereby incorporated by reference in its entirety for all intents and purposes. Alternatively, a different engine cylinder deactivation strategy may be employed to select which engine cylinders are activated and deactivated. Method 500 proceeds to 522.

[0057] At 522, the method 500 operates engine cylinders according to the first strategy when the engine is operating within an engine speed / load range where cylinder deactivation is permitted (e.g., the range within the solid line 400 of Fig. 4A). Cylinders may be deactivated based on the requested engine torque, engine speed, and engine temperature. A cylinder may be deactivated by keeping the cylinder's intake and exhaust valves closed throughout an entire engine cycle and by discontinuing fueling to the deactivated cylinder. If the engine is operating outside the range where engine cylinder deactivation is permitted, the engine is operated with all engine cylinders activated. Method 500 proceeds to exit.

[0058] At 540, method 500 reduces a size of the first engine operating range (e.g., an engine speed and load range defined by the area bounded by dotted-dashed line 465 and solid line 462 in Fig. 4B), wherein the first engine cylinder deactivation strategy is the basis for deactivating cylinders. Further, method 500 provides a second engine operating range, wherein a second engine cylinder deactivation strategy is the basis for deactivating cylinders. The second engine operating range has higher engine loads than the first engine operating range (e.g., the area surrounded by dashed line 460 and dot-dashed line 465 in Fig. 4B).

[0059] The first cylinder deactivation strategy allows different engine cylinders to be deactivated for each engine cycle, so that engine cylinders deactivated during one engine cycle are not the same cylinders deactivated during a next or adjacent engine cycle when the engine is operated at constant speed, engine load, and engine temperature. Fig. The engine cylinder deactivation strategy shown in Figure 3A is an example of the first engine cylinder deactivation strategy. In another example, where the engine is an eight-cylinder, four-stroke engine with a firing order of 1, 3, 7, 2, 6, 5, 4, and 8, the engine may operate by firing cylinders 1, 7, 6, 4, and 8 while deactivating all other remaining cylinders during a first engine cycle; by firing cylinders 1, 3, 7, 6, and 4 while deactivating all other remaining cylinders during a next engine cycle; by firing cylinders 1, 7, 2, 5, and 4 while deactivating all other remaining cylinders during a next engine cycle; by firing cylinders 3, 2, 5, 4, and 8 while deactivating all other remaining cylinders during a next engine cycle; and so on.By reducing the size of the range in which the first engine cylinder deactivation strategy can be applied, the benefit of applying the first engine cylinder deactivation strategy is maintained where the benefit (e.g., reduced fuel consumption) is greatest.

[0060] The second engine cylinder deactivation strategy allows only fixed groups of engine cylinders to be deactivated over a plurality of engine cycles, such that engine cylinders deactivated during one engine cycle are the same cylinders deactivated during a next or adjacent engine cycle when the engine is operated at a substantially constant (e.g., changing by less than ± 3 percent over a predetermined period of time) engine speed, substantially constant (e.g., changing by less than ± 3 percent over a predetermined period of time) engine load, and substantially constant (e.g., changing by less than ± 3 percent over a predetermined period of time) engine temperature. Fig. The engine cylinder deactivation strategy shown in Figure 3B is an example of the second engine cylinder deactivation strategy. In another example, where the engine is an eight-cylinder, four-stroke engine with a firing order of 1, 3, 7, 2, 6, 5, 4, and 8, the engine may operate by firing a fixed group of cylinders (e.g., 2, 3, 5, and 8) while deactivating all other remaining cylinders during a first engine cycle and a plurality of subsequent engine cycles. By providing a range of engine operation in which the second engine cylinder deactivation strategy may be applied, at least some benefit (e.g., reduced fuel consumption) may be maintained while reducing the rate at which engine valve actuators change state, thereby increasing the amount of time that cylinder deactivation may be available. Method 400 proceeds to 541.

[0061] At 541, method 500 judges whether the engine is operating in the second engine operating range, in which the second cylinder deactivation strategy is the basis for deactivating engine cylinders. Method 500 may judge that the engine is in the second engine operating range if the engine speed and engine load are within the second engine operating range. If yes, the answer is yes, and method 500 proceeds to 542. Otherwise, the answer is no, and method 500 proceeds to 546.

[0062] At 542, method 500 assesses whether two or more groups of fixed deactivated cylinders can provide the currently requested engine torque. For example, for an eight-cylinder four-stroke engine with a firing order of 1, 3, 7, 2, 6, 5, 4, and 8, where an engine torque request can be met with four active cylinders while four cylinders of an eight-cylinder engine are deactivated, the answer is yes if engine torque can be provided while deactivating a first fixed group of cylinders 2, 3, 5, and 8 in a first engine cylinder deactivation mode and if engine torque can be provided while deactivating a second fixed group of cylinders 1, 4, 6, and 7 in a second engine cylinder deactivation mode, where the first engine cylinder deactivation mode and the second engine cylinder deactivation mode are not active at the same time.If the requested engine torque can be provided by two or more groups of fixed deactivated cylinders, the answer is yes and method 500 proceeds to 543. If the requested engine torque cannot be provided by two or more groups of fixed deactivated cylinders (e.g., the requested engine torque can be provided by only deactivating cylinders 2, 3, 5, and 8), the answer is no and method 500 proceeds to 546.

[0063] At 543, method 500 judges whether the engine is entering the second engine operating range described at 540. Method 500 may judge that the engine is entering the second engine operating range when engine speed and engine load change from being outside the second engine operating range to being within the range defined by the second engine operating range. If method 500 judges that the engine is entering the second engine operating range, the answer is yes and method 500 proceeds to 544. Otherwise, the answer is no and method 500 proceeds to 545.

[0064] At 544, method 500 selects a new fixed group of engine cylinders to deactivate while providing the requested engine torque. For example, if the engine has the capability to provide the desired engine torque with cylinders 2, 3, 5, and 8 deactivated, or with cylinders 1, 4, 6, and 7 deactivated, and the engine last operated with cylinders 2, 3, 5, and 8 deactivated when the engine operated in the second engine operating range before exiting the second engine operating range, the engine selects to deactivate cylinders 1, 4, 6, and 7. In this way, the actual total number of valve actuator state changes may be distributed among the valve actuators of the various engine cycles.If the engine can provide the requested engine torque across three or more different fixed groups of cylinders, method 500 may select the fixed groups of cylinders that have a lower number of valve actuator state changes as the group of engine cylinders to be deactivated. Thus, the actual total number of valve actuator state changes may be balanced between the different cylinders. Method 500 proceeds to 546 after determining which fixed group of engine cylinders to deactivate.

[0065] At 545, method 500 continues to operate the engine with the fixed group of cylinders that were deactivated when the engine first entered the second operating range. Thus, once the engine enters the second engine operating range and the fixed group of cylinders is deactivated, the engine continues to operate with the same group of deactivated cylinders until the engine exits the second operating range. Method 500 proceeds to 546.

[0066] At 546, method 500 operates engine cylinders according to the first strategy when the engine is operating in the first engine operating range, and operates engine cylinders according to the second strategy when the engine is operating in the second engine operating range, as described at 540. Further, if the engine is operating in the second engine operating range, the fixed group of deactivated cylinders is the group described at 544, or method 500 continues to deactivate cylinders as described at 545. Cylinders may be deactivated based on requested engine torque, engine speed, and engine temperature. If the engine is operating in a range outside the range where engine cylinder deactivation is permitted, the engine is operated with all engine cylinders activated. Method 500 proceeds to exit.

[0067] At 530, method 500 allows only the second engine cylinder deactivation strategy to deactivate fixed groups of engine cylinders in the second operating range. The first engine operating range is omitted, and the second engine operating range is expanded to encompass the entire engine operating range in which cylinders can be deactivated (e.g., the area surrounded by solid line 462 and dashed line 460 shown in Fig. 4B).

[0068] The second engine cylinder deactivation strategy allows only fixed groups of engine cylinders to be deactivated over a plurality of engine cycles, such that engine cylinders deactivated during one engine cycle are the same cylinders deactivated during a next or adjacent engine cycle when the engine is operated at a substantially constant (e.g., changing by less than ± 3 percent over a predetermined period of time) engine speed, substantially constant (e.g., changing by less than ± 3 percent over a predetermined period of time) engine load, and substantially constant (e.g., changing by less than ± 3 percent over a predetermined period of time) engine temperature. Fig. The engine cylinder deactivation strategy shown in Figure 3B is an example of the second engine cylinder deactivation strategy. In another example, where the engine is an eight-cylinder, four-stroke engine with a firing order of 1, 3, 7, 2, 6, 5, 4, and 8, the engine may operate by firing a fixed group of cylinders (e.g., 2, 3, 5, and 8) while deactivating all other remaining cylinders during a first engine cycle and a plurality of subsequent engine cycles. By providing a range of engine operation in which the second engine cylinder deactivation strategy may be applied, at least some benefit (e.g., reduced fuel consumption) may be maintained while reducing the rate at which engine valve actuators change state, thereby increasing the amount of time that cylinder deactivation may be available.

[0069] The second engine cylinder deactivation strategy also selects which cylinders are activated and deactivated based on engine speed and engine load. For example, a plurality of engine cylinder modes may be stored in memory, and cylinder modes that provide insufficient torque to meet the requested engine torque are eliminated from the available engine cylinder modes. The engine may operate using the remaining available engine cylinder modes. The engine cylinder modes may include patterns of activated engine cylinders and deactivated engine cylinders that the engine may operate with. For example, the engine operating mode or cylinder pattern for an eight-cylinder engine may include cylinders 1, 4, 6, and 7 active, with cylinders 2, 3, 5, and 8 deactivated.In another example, the engine operating mode or cylinder pattern for the eight-cylinder engine may include cylinders 2, 3, 5, and 8 active, with cylinders 1, 4, 6, and 7 deactivated. Method 500 proceeds to 531.

[0070] At 531, method 500 assesses whether two or more groups of fixed deactivated cylinders can provide the currently requested engine torque. For example, for an eight-cylinder four-stroke engine with a firing order of 1, 3, 7, 2, 6, 5, 4, and 8, where an engine torque request can be met with four active cylinders while four cylinders of an eight-cylinder engine are deactivated, the answer is yes if engine torque can be provided while deactivating a first fixed group of cylinders 2, 3, 5, and 8 in a first engine cylinder deactivation mode and if engine torque can be provided while deactivating a second fixed group of cylinders 1, 4, 6, and 7 in a second engine cylinder deactivation mode, where the first engine cylinder deactivation mode and the second engine cylinder deactivation mode are not active at the same time.If the requested engine torque can be provided by two or more groups of fixed deactivated cylinders, the answer is yes and method 500 proceeds to 532. If the requested engine torque cannot be provided by two or more groups of fixed deactivated cylinders (e.g., the requested engine torque can be provided by only deactivating cylinders 2, 3, 5, and 8), the answer is no and method 500 proceeds to 534.

[0071] At 532, method 500 judges whether the engine is entering the second engine operating range described at 530. Method 500 may judge that the engine is entering the second engine operating range when engine speed and engine load change from being outside the second engine operating range to being within the range defined by the second engine operating range. If method 500 judges that the engine is entering the second engine operating range, the answer is yes and method 500 proceeds to 533. Otherwise, the answer is no and method 500 proceeds to 534.

[0072] At 533, method 500 selects a new fixed group of engine cylinders to deactivate while providing the requested engine torque. For example, if the engine has the capability to provide the desired engine torque with cylinders 2, 3, 5, and 8 deactivated, or with cylinders 1, 4, 6, and 7 deactivated, and the engine last operated with cylinders 2, 3, 5, and 8 deactivated when the engine operated in the second engine operating range before exiting the second engine operating range, the engine selects to deactivate cylinders 1, 4, 6, and 7. In this way, the actual total number of valve actuator state changes may be distributed among the valve actuators of the various engine cycles.If the engine can provide the requested engine torque across three or more different fixed groups of cylinders, method 500 may select the fixed groups of cylinders that have a lower number of valve actuator state changes as the group of engine cylinders to be deactivated. Thus, the actual total number of valve actuator state changes may be balanced between the different cylinders. Method 500 proceeds to 535 after determining which fixed group of engine cylinders to deactivate.

[0073] At 534, method 500 continues to operate the engine with the fixed group of cylinders that were deactivated when the engine first entered the second operating range. Thus, once the engine enters the second engine operating range and the fixed group of cylinders is deactivated, the engine continues to operate with the same group of deactivated cylinders until the engine exits the second operating range. Method 500 proceeds to 546.

[0074] At 535, method 500 operates engine cylinders according to the second strategy if the engine is operating in the second operating range as described at 540. Further, if the engine is operating in the second engine operating range, the fixed group of deactivated cylinders is the group described at 544, or method 500 continues to deactivate cylinders as described at 545. Cylinders may be deactivated based on the requested engine torque, engine speed, and engine temperature. If the engine is operating in a range outside the range where engine cylinder deactivation is permitted, the engine is operated with all engine cylinders activated. Method 500 proceeds to exit.

[0075] Thus, the procedure Fig. 5 provides an engine control method, comprising: deactivating engine cylinders via a controller according to a first cylinder deactivation strategy in response to an actual total number of valve actuator state changes being less than a first threshold; and deactivating the engine cylinders via the controller according to a second cylinder deactivation strategy in response to an actual total number of valve actuator state changes being greater than a second threshold.The method includes the first cylinder deactivation strategy deactivating a first engine cylinder and activating a second engine cylinder during a first engine cycle while the engine is operating at a substantially constant engine speed, a substantially constant load, and a substantially constant temperature, and the first cylinder deactivation strategy deactivating the first cylinder and deactivating a second engine cylinder during a second engine cycle while the engine is operating at the substantially constant engine speed, a substantially constant load, and a substantially constant temperature.

[0076] In some examples, the method includes where the second cylinder deactivation strategy deactivates a first group of engine cylinders during a first engine cycle while the engine is operating at a substantially constant engine speed, a substantially constant load, and a substantially constant temperature, and where the second cylinder deactivation strategy deactivates the first group of engine cylinders during a second engine cycle while the engine is operating at the substantially constant engine speed, a substantially constant load, and a substantially constant temperature. The method further includes deactivating the engine cylinders via the controller according to the second cylinder deactivation strategy and the first cylinder deactivation strategy in response to an actual total number of valve actuator state changes being greater than the first threshold and less than the second threshold.The method includes the first group of cylinders being a fixed group of cylinders. The method also includes inferring the actual total number of valve actuator state changes. The method further includes disabling cylinder deactivation in response to the actual total number of valve actuator state changes being greater than a third threshold.

[0077] The procedure from Fig.5 also includes an engine control method comprising: changing which cylinders of an engine are deactivated over a plurality of engine cycles while an engine is operating at a substantially constant temperature and a substantially constant engine speed and load, via a controller in response to an actual total number of valve actuator state changes being less than a first threshold; and deactivating a fixed group of engine cylinders while the engine is operating at the substantially constant temperature and the substantially constant engine speed(s) and loads, via the controller in response to the actual total number of valve actuator state changes being greater than the first threshold.The method includes deactivating engine cylinders by stopping the supply of fuel to deactivated cylinders and keeping intake and exhaust valves of deactivated cylinders closed for at least one cylinder cycle.

[0078] In some examples, the method further comprises changing which engine cylinders are included in the fixed group of engine cylinders in response to the actual total number of valve actuator state changes. The method further comprises disabling cylinder deactivation in response to the actual total number of valve actuator state changes being greater than a third threshold. The method includes where changing which cylinders of the engine are deactivated includes deactivating a first cylinder during a first engine cycle and turning on the first cylinder during a second engine cycle. The method includes where a valve actuator state change includes transitioning from a state where the valve actuator opens and closes a valve during a cylinder cycle to a state where the valve actuator keeps the valve closed over the cylinder cycle.The method includes changing which cylinders of the engine are deactivated over the plurality of engine cycles not including deactivating a fixed group of engine cylinders over the plurality of engine cycles.

[0079] It should be noted that the example control and estimation routines included in this document may be used with various engine and / or vehicle system configurations. The control methods and routines disclosed herein may be stored as executable instructions in non-volatile memory and executed by the control system, including the controller in combination with the various sensors, actuators, and other engine hardware. The specific routines described herein may represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Accordingly, various illustrated acts, operations, and / or functions may be performed in the illustrated order, in parallel, or in some cases, may be 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.

[0080] 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 engine cylinders via a controller according to a first cylinder deactivation strategy in response to an actual total number of valve actuator state changes being less than a first threshold; and Deactivating the engine cylinders via the controller according to a second cylinder deactivation strategy in response to an actual total number of valve actuator state changes being greater than a second threshold. [2] The method of claim 1, wherein the first cylinder deactivation strategy deactivates a first engine cylinder and activates a second engine cylinder during a first engine cycle while the engine is operating at a substantially constant engine speed, a substantially constant load, and a substantially constant temperature, and wherein the first cylinder deactivation strategy deactivates the first cylinder and deactivates a second engine cylinder during a second engine cycle while the engine is operating at the substantially constant engine speed, a substantially constant load, and a substantially constant temperature. [3] The method of claim 2, wherein the second cylinder deactivation strategy deactivates a first group of engine cylinders during a first engine cycle while the engine is operating at a substantially constant engine speed, a substantially constant load, and a substantially constant temperature, and wherein the second cylinder deactivation strategy deactivates the first group of engine cylinders during a second engine cycle while the engine is operating at the substantially constant engine speed, a substantially constant load, and a substantially constant temperature. [4] The method of claim 3, further comprising deactivating the engine cylinders via the controller according to the second cylinder deactivation strategy and the first cylinder deactivation strategy in response to an actual total number of valve actuator state changes being greater than the first threshold and less than the second threshold. [5] The method of claim 3, wherein the first group of cylinders is a fixed group of cylinders. [6] The method of claim 1, wherein the actual total number of valve actuator state changes is inferred. [7] The method of claim 1, further comprising disabling cylinder deactivation in response to the actual total number of valve actuator state changes being greater than a third threshold. [8] The method of claim 1, further comprising: Changing which cylinders of an engine are deactivated over a plurality of engine cycles while an engine is operating at a substantially constant temperature and a substantially constant engine speed and load, via a controller in response to the actual total number of valve actuator state changes being less than a first threshold; and Deactivating, via the controller, a fixed group of engine cylinders while the engine is operating at the substantially constant temperature and the substantially constant engine speed(s) and loads in response to the actual total number of valve actuator state changes being greater than the first threshold. [9] The method of claim 8, wherein engine cylinders are deactivated by stopping the supply of fuel to deactivated cylinders and keeping intake and exhaust valves of deactivated cylinders closed for at least one cylinder cycle. [10] Engine system comprising: an internal combustion engine including one or more cylinder deactivation mechanisms; a controller having executable instructions stored in non-volatile memory to adjust an engine operating range that defines when engine cylinders can be deactivated in response to an actual total number of valve actuator state changes being greater than a first threshold, and to deactivate engine cylinders according to the engine operating range. [11] The engine system of claim 10, wherein the engine operating range is an engine speed and load range. [12] The engine system of claim 10, wherein adjusting the engine operating range includes dividing the engine operating range into two operating ranges. [13] The engine system of claim 12, wherein an engine load is lower in the first operating range of the two operating ranges than in a second operating range of the two operating ranges. [14] The engine system of claim 13, further comprising additional instructions to operate the engine with a fixed group of deactivated cylinders over a plurality of engine cycles in the second operating range. [15] The engine system of claim 10, further comprising additional instructions to change which engine cylinders are in the fixed group of deactivated cylinders in response to the actual total number of valve actuator state changes.

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