Method and system for engine temperature control

Abstract

Methods for an engine, including: selecting a cylinder for deactivation; and in an engine cycle immediately preceding deactivation, the keeping closed of an exhaust valve of the selected cylinder during an exhaust stroke of the cylinder, wherein the selected cylinder is a first cylinder, the method further comprising selecting a second, different cylinder for deactivation and operating the second cylinder with one or more consisting of a deactivated intake valve, a deactivated exhaust valve, a deactivated fuel injector, a deactivated ignition spark and a delayed ignition spark, which includes operation: Operating the second cylinder in a first mode, wherein the intake valve opens during an intake stroke, the fuel injector is deactivated, the ignition spark is deactivated, and the exhaust valve opens during an exhaust stroke; operating the second cylinder in a second mode, in which the intake valve opens during the intake stroke and the fuel injector is activated, the ignition spark is deactivated and the exhaust valve opens during the exhaust stroke; the operation of the second cylinder in a third mode, wherein the intake valve opens during an intake or compression stroke, the fuel injector is activated and fuel is supplied during the compression stroke, the ignition spark is deactivated and the exhaust valve opens during the exhaust stroke; Operating the second cylinder in a fourth mode, wherein the intake valve opens during the intake stroke, the fuel injector is activated, the ignition spark is delayed until the exhaust stroke, and the exhaust valve opens during the exhaust stroke; and selecting a mode based on the exhaust catalyst temperature, furthermore including: deactivating a cylinder pattern of individual cylinder mechanisms, wherein the cylinder pattern comprises a first deactivated cylinder and a second active cylinder, wherein, in response to a command to deactivate the first cylinder and further based on an engine temperature, an exhaust valve of the first cylinder is kept closed during an exhaust stroke of an engine cycle immediately preceding the deactivation of the first cylinder. where, in response to an expected engine temperature being below a threshold, further comprising operating a third cylinder with a rich fuel injection provided during a compression stroke and with the ignition spark deactivated, while a fourth cylinder is operated with a lean fuel injection during an intake stroke and with the ignition spark deactivated, and wherein the engine temperature is an estimated engine temperature or the expected engine temperature, the expected engine temperature comprising a temperature of the engine or an engine component that is expected upon reactivation.

Description

Area

[0001] The present application relates to methods and systems for maintaining an engine temperature and / or an exhaust catalyst temperature in order to control particulate matter emissions from an engine system configured to perform skip-fire combustion. Background and Summary

[0002] After a cold engine start, exhaust emissions and fuel consumption tend to be higher. This is because cold combustion surfaces result in poor fuel vaporization, which means that fuel films remain on the combustion surfaces even after combustion has occurred. The fuel-rich area above the film, and the fuel that evaporates from the film after the flame has passed, can lead to increased carbon and particulate matter (PM) emissions. Additionally, cold engine oil results in increased friction losses.

[0003] In recent years, spark-ignition internal combustion engines have been configured to operate with a variable number of active or deactivated cylinders to improve fuel economy while maintaining an approximately stoichiometric air-fuel ratio in the overall exhaust mixture. Such engines can vary the effective displacement by skipping fuel delivery to certain cylinders in an indicated cylinder firing pattern, also known as a "skip-fire" pattern. For example, as demonstrated by Tripathi et al. in US 8,651,091 B2, an engine fuel control system can continuously rotate which cylinders receive fuel, which cylinders are skipped, and for how many cylinder events the pattern continues. Additionally, individual valve mechanisms of each cylinder can be selectively deactivated.By omitting the fuel supply to selected cylinders, the active cylinders can be operated close to their optimal efficiency, thereby increasing the overall operating efficiency of the engine.

[0004] From US patent 2014 / 0053803 A1, a system for deactivating the cylinders of an internal combustion engine is known, in which, immediately before deactivation, an exhaust valve of a cylinder to be deactivated is kept closed during the push-out stroke, wherein gas enclosed in the cylinder provides a spring effect for moving the cylinder between its two end positions.

[0005] The inventors recognized that the individually controllable valves of the selectively deactivated cylinders could be used to improve the rate of cylinder heating in a driving cycle. Specifically, the valve operation of a cylinder that will not fire in the next cycle due to engine load can be controlled to retain hot exhaust gases in the cylinder, thereby heating the combustion chamber surfaces more quickly. In one example, some of the problems mentioned above can be addressed by a method that increases the rate of engine heating during cylinder deactivation, comprising: selecting a cylinder for deactivation; and, immediately preceding deactivation in a combustion cycle, keeping an exhaust valve of the selected cylinder closed during an exhaust stroke of that cylinder.In this way, the fast-responding individual cylinder valve mechanisms can be supported to increase combustion surface temperatures.

[0006] As an example, in response to a drop in engine load, an engine control unit (ECU) can select a cylinder pattern on individual cylinders from selective deactivation mechanisms. Within this pattern, the ECU can choose a number and identity of cylinders to be deactivated. A cylinder selected for deactivation, which will not fire in the next engine cycle, can keep its exhaust valve closed during an exhaust stroke of the firing cycle immediately before deactivation. Specifically, instead of expelling the exhaust gases, the hot gases are retained in the cylinder by keeping the exhaust valve closed. The exhaust gases are then held in the cylinder while the cylinder is deactivated in the next cycle.

[0007] By retaining the hot exhaust gases in the cylinder for the next cycle, the combustion chamber surface heats up much faster. Consequently, the entire engine also heats up more quickly. Furthermore, retaining the burnt gases in the deactivated cylinder for a longer period improves the further oxidation of the hydrocarbons remaining in the combustion chamber, resulting in improved emissions for that cycle. Overall, engine performance is enhanced.

[0008] Other valve operations can be used in various combinations to improve engine warm-up and accelerate catalyst warm-up. For example, a cylinder to be deactivated in the engine cycle preceding deactivation can be fired and exhausted normally. Alternatively, the cylinder can be configured to inlet but not supply fuel and exhaust fresh charge. In yet another example, the cylinder can inlet and fire but not exhaust. By choosing to inlet and allow air to flow, the exhausted air can be combined with exhaust from other cylinders running slightly rich to provide fuel and air at the exhaust catalyst. The reaction of the fuel and air at the exhaust catalyst generates heat, resulting in rapid catalyst warm-up.Other alternatives include introducing air and supplying fuel during the intake and compression strokes without ignition, to provide a fuel-air mixture for the catalytic converter. Furthermore, air can be introduced into a cylinder, compressed, but not fueled until the exhaust stroke, i.e., as a post-injection. This latter approach can also include ignition close to the exhaust stroke and combustion during the exhaust phase to provide heat flow to the exhaust catalyst. In this way, various combinations of ignition, non-ignition, ignition during post-injection, rich running in some cylinders while air is pumped to other cylinders, etc., can be used in various ways, all while applying known torque pulses within the engine system to provide acceptable NVH characteristics.Additionally, cylinders that have undergone normal combustion (active cylinders) can be operated under higher loads, making them more stable and tolerant of additional ignition delay. This additional ignition delay can be advantageous under these conditions, adding more heat to the engine and the catalytic converter.

[0009] The aforementioned problems are solved by the features of the independent patent claims; advantageous further developments of the invention are the subject of the dependent claims. Brief description of the drawings Fig. Figure 1 shows an exemplary embodiment of an engine system layout. Fig. Figure 2 shows a partial view of an engine. Fig. Figure 3 shows an overview flowchart for adjusting cylinder valve operation during and before cylinder deactivation to accelerate engine warm-up. Fig. Figure 4 shows an example cylinder valve setting during a transition to a skip-fire operating mode to reduce PM emissions. Detailed description

[0010] Procedures and systems are provided for setting a cylinder valve profile when operating an engine configured for selective cylinder deactivation (also referred to herein as skip-fire operation), such as the engine system of the Fig. 1-2. A controller can adjust the operation of an exhaust valve of a cylinder selected for selective deactivation. For example, the controller can run a program such as the example program from Fig. 3. Execute to keep the exhaust valve of a cylinder to be deactivated closed in a subsequent engine cycle. By retaining hot exhaust gases in the cylinder during deactivation, the compression surface temperature can be increased, thereby accelerating engine warm-up. An example setting is given in relation to Fig. Figure 4 shows that fine particulate emissions from cold cylinders can be reduced in this way.

[0011] Fig. Figure 1 shows an exemplary engine 10, which has a first cylinder bank 15a and a second cylinder bank 15b. In the example shown, the engine 10 is a V8 engine, with the first and second cylinder banks each having four cylinders. The engine 10 has an intake manifold 16 with a throttle 20 and an exhaust manifold 18 coupled to an emission control system 30. The emission control system 30 includes one or more catalysts and air-fuel ratio sensors, such as those related to Fig. 2 described. As a non-restrictive example, the motor 10 can be included as part of a drive system for a passenger car.

[0012] The engine system 10 can have cylinders 14 with selectively deactivatable intake valves 50 and selectively deactivatable exhaust valves 56. In one example, the intake valves 50 and the exhaust valves 56 are configured for electric valve actuation (EVA) via individual electric cylinder valve actuators. Although the illustrated example shows each cylinder with a single intake valve and a single exhaust valve, alternative examples such as the one described below may be used. Fig. 2. Each cylinder is designed to have a plurality of selectively deactivatable intake valves and / or a plurality of selectively deactivatable exhaust valves.

[0013] Under selected conditions, such as when the engine's full torque capacity is not required, one or more cylinders of the engine 10 can be selected for selective deactivation (also referred to herein as individual cylinder deactivation). This can include the selective deactivation of one or more cylinders only on the first cylinder bank 15a, of one or more cylinders only on the second cylinder bank 15b, or of one or more cylinders from both the first and second cylinder banks. The number and identity of the cylinders deactivated on each cylinder bank can be symmetrical or asymmetrical.

[0014] During deactivation, selected cylinders can be deactivated by closing the individual cylinder valve mechanisms, such as intake valve mechanisms, exhaust valve mechanisms, or a combination of both. Cylinder valves can be selectively deactivated by hydraulically actuated tappets (e.g., tappets coupled to a valve linkage), via a cam profile switching mechanism in which a distributor cam without lift is used for deactivated valves, or by the electromagnetically actuated cylinder valve mechanisms coupled to each cylinder. Additionally, fuel flow and ignition spark to the deactivated cylinders can be stopped, for example, by disabling cylinder fuel injectors.

[0015] In some examples, the engine system may have 10 selectively deactivatable (direct) fuel injectors, and the selected cylinders can be deactivated by shutting off the respective fuel injector, while maintaining the operation of the intake and exhaust valves so that air can continue to be pumped through the cylinders.

[0016] While the selected cylinders are deactivated, the remaining activated or active cylinders continue combustion with fuel injectors and active, running cylinder valve mechanisms. To meet torque demands, the engine generates the same amount of torque on the active cylinders. This requires higher manifold pressure, resulting in lower pumping losses and increased engine efficiency. The lower effective surface area (from the activated cylinders only) exposed to combustion reduces engine heat losses, improving the engine's thermal efficiency.

[0017] Cylinders can be deactivated to provide a specific ignition pattern (or skip-firing pattern) based on a particular control algorithm. More specifically, selected "skipped" combustion cycles are not fired, while other "active" combustion cycles are fired. If desired, the ignition spark control associated with a selected ignition of a selected combustion chamber can also be set based on a firing order or ignition history of the selected combustion chamber. The engine control unit 12 can be configured with suitable logic, as described below, to determine a cylinder deactivation pattern (or skip-firing pattern) based on engine operating conditions.

[0018] The engine 10 can run on a variety of substances that can be supplied via a fuel system 8. The engine 10 can be controlled, at least partially, by a control system that includes the control unit 12. The control unit 12 can receive various signals from sensors 17 that are coupled to the engine 10 (and related to Fig. 2 described) are, receive and send control signals to various actuators 81 connected to the engine and / or the vehicle (as described in relation to Fig. 2 described) are coupled and transmit data. The various sensors can include, for example, different temperature, pressure, and air-fuel ratio sensors.

[0019] The engine control system can include a drive pulse generator and a sequence control system to determine a cylinder firing pattern based on the desired engine output under current engine operating conditions. For example, the drive pulse generator can use adaptive predictive control to dynamically calculate a drive pulse signal indicating which cylinders should fire and at what intervals to achieve the desired output (that is, the firing / skip-firing pattern of the cylinder). The cylinder firing pattern can be set to provide the desired output without generating excessive or undesirable vibrations within the engine. Thus, the cylinder firing pattern can be selected based on the engine configuration, such as whether the engine is a V-engine, an inline engine, or based on the number of engine cylinders.Based on the selected cylinder pattern, the valve mechanisms of each selected cylinder can be closed, while fuel flow and ignition sparks to the cylinders are stopped.

[0020] Since the optimal efficiency for a given cylinder is near-full power output, a lower firing frequency can be chosen to reduce power output. For example, skipping every other cylinder would, on average, produce half the power. A distribution that is as even as possible tends to minimize oscillations due to varying torque output. Whether all cylinders are included in the skip-firing pattern may depend on the fraction of output desired and other considerations, including cylinder temperature.

[0021] In this way, by adjusting the cylinder pattern of valve mechanisms and fuel injectors of individual cylinders, a desired engine output can be provided by operating fewer cylinders more efficiently, thereby improving fuel economy.

[0022] Fig. Figure 2 represents an exemplary embodiment of a combustion chamber or cylinder of the internal combustion engine 10. The engine 10 can receive control parameters from a control system comprising the controller 12 and input from a vehicle operator 130 via an input device 132. In this example, the input device 132 comprises an accelerator pedal and a pedal position sensor 134 for generating a proportional pedal position signal PP. The cylinder (hereinafter also referred to as the "combustion chamber") 14 of the engine 10 can comprise combustion chamber walls 136 with a piston 138 positioned therein. The piston 138 can be coupled to a crankshaft 140, such that a reciprocating motion of the piston is transmitted as rotary motion of the crankshaft. The crankshaft 140 can be coupled to at least one drive wheel of the passenger car via a transmission system.Furthermore, a starter motor can be coupled to the crankshaft 140 via a flywheel to enable the engine 10 to start up.

[0023] Cylinder 14 can receive intake air via a series of intake air channels 142, 144, and 146. Intake air channel 146 can communicate with other cylinders of engine 10 in addition to cylinder 14. In some embodiments, one or more of the intake channels can include a charging device such as a turbocharger or a supercharger. For example, Figure 1 shows... Fig. 2. An engine 10 configured with a turbocharger comprising a compressor 174 located between the intake ports 142 and 144 and an exhaust turbine 176 located along the exhaust port 148. The compressor 174 may be driven, at least partially, by an exhaust turbine 176 via a shaft 180, with the charging device configured as a turbocharger. In other examples, such as when the engine 10 is provided with a supercharger, the exhaust turbine 176 may be optionally omitted, with the compressor 174 being driven by mechanical input from an engine or by the engine itself. A throttle 20, comprising a throttle plate 164, may be provided along an intake port of the engine to vary the flow rate and / or pressure of the intake air supplied to the engine cylinders. For example, the throttle 20 may be located downstream of the compressor 174, as shown in Fig. 1 is shown, or alternatively it can be arranged upstream of compressor 174.

[0024] The exhaust port 148 can receive exhaust gases from other cylinders of the engine 10 in addition to cylinder 14. The exhaust gas sensor 128 is coupled to the exhaust port 148 and is shown upstream of an emission control device 178. The sensor 128 can be selected from various suitable sensors to provide an indication of the air-fuel ratio, such as a linear oxygen sensor or UEGO (universal or wideband oxygen sensor), a dual-state oxygen sensor or EGO (as shown), a HEGO (heated EGO), a NOx, HC, or CO sensor. The emission control device 178 can be a three-way catalytic converter (TWC), NOx trap, various other emission control devices, or combinations thereof.

[0025] The exhaust gas temperature can be measured by one or more temperature sensors (not shown) arranged in the exhaust duct 148. Alternatively, the exhaust gas temperature can be derived based on engine operating conditions such as speed, load, air-fuel ratio (AFR), ignition timing, etc. Furthermore, the exhaust gas temperature can be calculated by one or more exhaust gas sensors 128. It is clear that the exhaust gas temperature can alternatively be determined by any combination of the temperature measurement methods listed here.

[0026] Each cylinder of the engine 10 can comprise one or more intake valves and one or more exhaust valves. For example, cylinder 14 is shown to comprise at least one intake poppet valve 150 and at least one exhaust poppet valve 156, which is arranged in an upper region of cylinder 14. In some embodiments, each cylinder of the engine 10, including cylinder 14, can comprise at least two intake poppet valves and at least two exhaust poppet valves, which are arranged in an upper region of the cylinder.

[0027] The intake valve 150 can be controlled by the control unit 12 via a cam actuation system 151. Likewise, the exhaust valve 156 can be controlled by the control unit 12 via a cam actuation valve 153. The cam actuation systems 151 and 153 can each comprise one or more cams and can employ one or more cam profile switching (CPS), variable cam timing (VCT), variable valve timing (VVT), and / or variable valve lifter (VVL) systems, which can be operated by the control unit 12 to vary the valve operation. The operation of the intake valve 150 and the exhaust valve 156 can be determined by (not shown) valve position sensors and / or camshaft position sensors 155 and 157, respectively. In alternative embodiments, the intake and / or exhaust valve can be controlled by means of electric valve actuation. For example, cylinder 14 can be...Alternatively, the system may comprise an intake valve controlled by electrical valve actuation and an exhaust valve controlled by cam actuation, which includes CPS and / or VCT systems. In other embodiments, the intake and exhaust valves may be controlled by a common valve actuator or a common valve actuation system, or by a variable valve timing actuator or a variable valve timing actuation system.

[0028] Cylinder 14 can have a compression ratio that is the volume ratio when piston 138 is in its lower to upper midpoint. Conventionally, the compression ratio is in the range of 9:1 to 13:1. However, in some cases where different fuels are used, the compression ratio can be increased. This can occur, for example, when using fuels with a higher octane rating or fuels with a higher latent enthalpy of evaporation. The compression ratio can also be increased when direct injection is used due to its effect on engine knock.

[0029] In some embodiments, each cylinder of the engine 10 may include a spark plug 192 for initiating combustion. Under selected operating modes, the ignition system 190 can provide a spark to the combustion chamber 14 via the spark plug 192 in response to the pre-ignition signal (SA signal) from the control unit 12.

[0030] In some embodiments, each cylinder of the engine 10 can be configured with one or more injectors to supply fuel to the cylinder. As a non-limiting example, cylinder 14 is shown, which includes two fuel injectors 166 and 170. The fuel injectors 166 and 170 can be configured to supply fuel received from the fuel system 8 via a high-pressure fuel pump and fuel distributor. Alternatively, fuel can be supplied by a single-stage fuel pump at a lower pressure, in which case the timing of direct fuel injection during the compression stroke may be more restricted than when a high-pressure fuel system is used. Furthermore, the fuel tank can include a pressure transducer that provides a signal to the control unit 12.

[0031] The fuel injector 166 is shown directly coupled to the cylinder 14 to inject fuel into it proportionally to the pulse width signal FPW-1, which is received by the control unit 12 via the electronic actuator 168. In this way, the fuel injector 166 provides what is known as direct injection (hereinafter also referred to as "DI") of fuel into the combustion cylinder 14. Fig. Figure 1 shows the injector 166 positioned on one side of cylinder 14. However, it can also be located above the piston head, for example, near the spark plug 192. Such a position can improve mixing and combustion when the engine is running on an alcohol-based fuel due to the lower volatility of some alcohol-based fuels. Alternatively, the injector can be located above the cylinder head and near the intake valve to improve the mixture.

[0032] The fuel injector 170 is shown in the intake port 146 instead of in the cylinder 14 in a configuration that provides what is known as intake injection (hereinafter referred to as "PFI") into the intake port upstream of cylinder 14. The fuel injector 170 can inject fuel received from the fuel system 8 proportionally to the pulse width modulation (FPW-2) signal received by the controller 12 via the electronic actuator 171. It should be noted that a single controller 168 or 171 can be used for both fuel injection systems, or that multiple controllers can be used, for example, controller 168 for fuel injector 166 and controller 171 for fuel injector 170 as shown.

[0033] Fuel injectors 166 and 170 can have different characteristics. These include differences in size; for example, one injector may have a larger injection orifice than the other. Other differences include, but are not limited to, different spray angles, different operating temperatures, different objectives, different injection timing, different spray characteristics, different locations, etc. Furthermore, different effects can be achieved depending on the distribution ratio of the injected fuel between the 166 and 170 injectors.

[0034] Fuel can be delivered to the cylinders by both injectors during a single cylinder cycle. For example, each injector can provide a portion of the total fuel injection that is burned in cylinder 14. Even during a single combustion event, the injected fuel can be delivered by the intake and direct injectors at different times. Furthermore, multiple injections of the provided fuel can be performed per cycle during a single combustion event. These multiple injections can occur during the compression stroke, the intake stroke, or any suitable combination thereof.

[0035] As described above, Fig. 2 only one cylinder of a multi-cylinder engine. Thus, each cylinder can equally include its own set of intake / exhaust valves, fuel injectors, spark plugs, etc. It is clear that the engine 10 can include any suitable number of cylinders, including 2, 3, 4, 5, 6, 8, 10, 12 or more. Furthermore, each of these cylinders can have some or all of the different functions provided by Fig. The components described and illustrated in relation to cylinder 14 are included.

[0036] The engine may further include one or more exhaust gas recirculation channels to recirculate a portion of the exhaust gas from the engine exhaust system to the engine intake. Recirculating exhaust gas can induce engine dilution, which can improve engine performance by reducing engine NOx, maximum cylinder combustion temperatures and pressures, throttling losses, and NOx emissions. In the illustrated embodiment, exhaust gas can be recirculated from the exhaust port 148 into the intake port 144 via an EGR channel 141. The amount of EGR supplied to the intake port 144 can be varied by the controller 12 via an EGR valve 143. Furthermore, an EGR sensor 145 can be arranged within the EGR channel and provide a reading of one or more values ​​for the pressure, temperature, and concentration of the exhaust gas.

[0037] Control 12 is in Fig. Figure 1 is shown as a microcomputer comprising a microprocessor unit 106, input / output ports 108, an electronic storage medium for executable programs and, as a read-only memory chip 110, calibration values ​​shown in this particular example, a direct-access memory 112, a keep-alive memory 114, and a data bus. The controller 12 can receive various signals from sensors coupled to the engine 10 in addition to those previously executed, including the measurement of the introduced mass airflow (MAF) from the mass airflow sensor 122; an engine coolant temperature (ECT) from the temperature sensor 116 coupled to the cooling jacket 118; a profile ignition tappet signal (PIP) from the Hall effect sensor 120 (or another type) coupled to the crankshaft 140; and the throttle position (TP) from a throttle position sensor. of the absolute manifold pressure (MAP) signal from sensor 124.The engine speed signal (RPM) can be generated by control unit 12 from the PIP signal. The exhaust manifold pressure signal (MAP) from an exhaust manifold pressure sensor can be used to provide an indication of vacuum or pressure in the intake manifold. Other sensors may include fuel level sensors and fuel composition sensors, which are connected to one or more fuel tanks in the fuel system.

[0038] The read-only storage medium 110 can be programmed with computer-readable data that represents instructions executable by a processor 106 to carry out the procedures described below, as well as other variants that are anticipated but not specifically listed. The controller 12 receives signals from the various sensors of the Fig. 1-2 and sets the various actuators of the Fig. 1-2 to adjust the motor operation based on the received signals and the commands stored in a memory of the controller.

[0039] In this way, the system enables the Fig. 1-2 A method for an engine, comprising: selecting a cylinder for deactivation; and, in a combustion cycle immediately preceding the deactivation, holding an exhaust valve of the selected cylinder closed during an exhaust stroke of the cylinder. In an example, the selected cylinder is a first cylinder, the method further comprising selecting a second, distinct cylinder for deactivation and, in the combustion cycle immediately preceding the deactivation, opening an exhaust valve of the second cylinder during an exhaust stroke of the second cylinder. The deactivation can respond to a drop in engine load. The valve closure is performed after an exhaust temperature exceeds a temperature threshold.

[0040] In another example, a method for an engine comprises: deactivating a cylinder pattern on individual cylinder mechanisms, wherein the cylinder pattern comprises a first deactivated cylinder and a second active cylinder, wherein, in response to a command to deactivate the first cylinder, an exhaust valve of the first cylinder is held closed during an exhaust stroke of an ignition cycle immediately preceding the deactivation of the first cylinder.

[0041] Fig. Figure 3 shows an example of a program 300 for adjusting individual cylinder valve mechanisms during cylinder deactivation in response to engine temperature, exhaust gas temperature and / or the temperature of an exhaust catalyst.

[0042] The process allows exhaust gas to be trapped in a deactivated cylinder, keeping the cylinder's combustion surface hot during deactivation. By reducing the cooling of a deactivated cylinder, the frequency of cylinder reactivation is reduced, while PM emissions from a reactivated cylinder are also reduced. Commands to execute process 300 can be issued by a controller based on commands stored in a controller memory and in conjunction with signals from engine system sensors, such as those mentioned above in relation to the Fig. 1-2 described, received, and executed. The control can be used to adjust the motor operation of motor actuators of the motor system, such as the actuators that relate to the Fig. As described in 1-2, use them according to the procedures described below.

[0043] In program 302, the program involves estimating and / or measuring engine operating conditions. The estimated conditions might include, for example, engine speed, drive torque demand, engine temperature, environmental conditions such as ambient temperature, humidity, and barometric pressure, load level, etc. In program 304, based on the estimated conditions, it can be determined whether cylinder deactivation conditions have been met. For example, the cylinder deactivation conditions might be considered met if the engine load is below a threshold or the drive torque demand is below a threshold. If the cylinder deactivation conditions are not met, program 305 involves keeping all engine cylinders active.

[0044] If the cylinder deactivation conditions are met, the control unit at 306 can select a cylinder pattern based on the engine load. The cylinder deactivation pattern can further be selected based on one or more of the following: engine speed, vehicle speed, engine temperature, engine NVH, and a gear ratio selection (e.g., whether the engine is currently in a first gear with a lower gear ratio or in a second gear with a higher gear ratio). Determining the cylinder pattern involves determining the number and identity of the cylinders to be deactivated and also determining the duration of the deactivation. For example, the control unit can determine a number of combustion events or engine cycles during which the selected cylinders should remain deactivated.The total number of deactivated / active cylinders can depend on the actual total number of engine cylinders and the drive torque demand. As a non-restrictive example, two cylinders can be deactivated for a four-cylinder engine, three cylinders for a six-cylinder engine, and four cylinders for an eight-cylinder engine. In some examples, the same group of cylinders can be selected for deactivation each time cylinder deactivation conditions are met, while in other examples, the identity of the deactivated cylinders can vary each time cylinder deactivation conditions are met.

[0045] As an example, the controller can retrieve a pattern from a lookup table stored in the controller's memory. Cylinder patterns can be stored in the lookup table as a function of the engine load for a specific engine configuration. For example, at lower engine loads, the cylinder pattern might involve firing every second or third cylinder. For instance, in a 4-cylinder inline engine, with cylinders labeled 1 through 4 and a cylinder firing pattern of 1-3-4-2, during regular operating conditions, when no cylinder is off and all cylinders are active, the cylinders might fire as 134213421342 and so on.In response to the cylinder deactivation conditions being met, the control unit may, in order to provide fuel-saving benefits, switch the engine operation to a cylinder pattern in which every third cylinder is fired, resulting in the pattern 1xx2xx4xx3xx1xx, where x represents a skipped cylinder.

[0046] In the 308 parameter, it can be determined whether cylinder cooling or engine cooling is expected. For example, engine cooling might be expected if the engine operates for an extended period under low to very light loads (e.g., longer than a threshold duration at less than a threshold load, or with cylinder deactivation longer than a threshold duration). In another example, engine cooling might be expected if the vehicle is traveling on a road with a negative gradient (i.e., downhill). In yet another example, engine cooling might be expected if the ambient temperature is low. As a further example, engine cooling might occur if the engine temperature is relatively low and a tip-out event occurs. Engine cylinder cooling can thus lead to worsened exhaust emissions when the cylinders are subsequently reactivated.Additionally, fuel consumption may be higher when operating with cooler cylinders. If no cylinder cooling is expected, the program for 310 involves switching to engine operation with the cylinder pattern determined for 306.

[0047] If cylinder cooling is anticipated, program 312 can first determine whether the exhaust gas temperature is hot enough. Specifically, it can confirm that the exhaust gas temperature is higher than a threshold to enable the catalytic converter to activate. If the exhaust gas temperature is not hot enough, program 313 involves delaying cylinder deactivation until the exhaust gas temperature is sufficiently hot. This delay allows for a reduction in particulate emissions due to the cooling of the combustion surface.

[0048] However, it is clear that in some examples, even if the exhaust gas temperature is lower than the threshold, the control will proceed to 314 to deactivate one or more engine cylinders, while relying on additional cylinder valve settings described herein in 318 to increase exhaust gas temperatures and accelerate catalyst start-up. This allows cylinder deactivation benefits to be achieved over a longer period of engine operation.

[0049] Returning to step 312, the program, if the exhaust gas temperature is hot enough, includes at step 314 the identification of one or more cylinders to be deactivated in the next engine cycle (e.g., based on the cylinder pattern selected at step 306). That is, a first cylinder that fires in the current cycle but will not fire in the next cycle based on the engine load can be identified. This first cylinder may differ from a second cylinder that fires in both the current and next cycles (active engine cylinder). At step 316, the one or more identified cylinders are operated in the current cycle, while the exhaust valve remains closed during the exhaust stroke.This means that instead of the exhaust gases being extracted and the cylinder engine remaining with low charge or fresh air for the next cycle, the exhaust gases stay in the cylinder because the exhaust valves are not opened after combustion in the cylinder and until the cylinder is reactivated. By keeping the hot exhaust gases in the cylinder for the next cycle (when the cylinder is deactivated), the combustion chamber surface of that particular cylinder can retain heat for a longer period. By performing exhaust valve deactivation similarly for one or more other cylinders that are to be deactivated, cylinder heating is enabled even while the cylinder is deactivated. This allows the engine to gradually warm up.By keeping the burnt gases in the cylinder for a longer period of time, continued oxidation of hydrocarbons remaining in the chamber and of exhaust gas is also improved, resulting in improved emissions for this cycle.

[0050] In one example, determining the selected cylinder pattern involves specifying that one or more selected cylinders must be deactivated for a certain number of engine cycles. In this scenario, keeping the exhaust valve of the selected cylinder closed triggers the deactivation after a certain number of engine cycles exceeds a threshold number. If the number of engine cycles exceeds the threshold number, deactivation might result in significant cylinder cooling, potentially requiring more fuel during subsequent reactivation. The threshold number could be based on one or more of the following temperatures: engine coolant temperature, ambient temperature, and cylinder temperature. The threshold number decreases as any of these temperatures decreases.This allows more heat to be retained in the cylinder to be deactivated by keeping the exhaust valve closed, thus reducing the cylinder cooling effect of the deactivation in the long term.

[0051] It is clear that if the specific cylinders are subsequently reactivated, the exhaust valve of the reactivated cylinder can be opened before the one or more intake valves open, allowing any residual gases remaining trapped in the cylinder to be expelled before a fresh charge is introduced. This reduces the occurrence of misfires during reactivation. For example, the exhaust valve of the reactivated cylinder can be opened during an exhaust stroke of an engine cycle immediately preceding the reactivation. In one example, the exhaust valve can be opened near the beginning of the exhaust stroke. The exhaust valve can then be opened later in the exhaust stroke, such as when necessary for a later decision.However, the exhaust gas may have been compressed during the exhaust stroke, resulting in a loss of work when the exhaust valve is subsequently opened.

[0052] If necessary, at 318, in conjunction with the deactivation of the exhaust valve of a cylinder selected for deactivation in the next cycle, the valve operation of one or more other cylinders to be deactivated or remain active can be adjusted. Consequently, various skip-firing combinations can be generated. While a first cylinder fires and exhausts normally, for example, a second cylinder can be configured to draw in air but not supply it with fuel and to exhaust the fresh charge. In yet another example, the air from such a cylinder can be combined with exhaust from other cylinders running slightly richer than stoichiometric to provide air and fuel for the catalyst to react and generate heat, resulting in rapid catalyst start-up.Other alternatives include introducing air and supplying it with fuel during an intake or compression stroke, but without providing a spark, to create an air-fuel mixture with a desired ratio at the exhaust catalyst. Furthermore, the introduced air can be compressed but not fueled until an exhaust stroke to provide post-injection. This can be coupled with spark timing close to the exhaust event to provide combustion during the exhaust phase. This allows for additional heat flow to the exhaust catalyst.

[0053] The choice between the different options can be based on NVH considerations as well as the excitation pulses. For example, a rich combustion can add torque and / or a torque pulse to the system. However, post-injection during the exhaust stroke can only provide heat without a torque pulse to the system, resulting in different NVH characteristics.

[0054] By using the various combinations discussed in 318, all while applying known torque impulses to the engine system, the engine and exhaust catalyst temperature can be better controlled while providing acceptable NVH characteristics. Furthermore, the active cylinders can also be operated with additional spark delay to add more heat flux to the exhaust catalyst. Since the active cylinders operate at a higher mean cylinder load during selective cylinder deactivation, they can be more tolerant of the additional spark delay.

[0055] As an example, a first cylinder can be selected for deactivation in the cylinder pattern. This first cylinder can have an intake and / or exhaust valve operation that is deactivated for a specific number of engine cycles. Additionally, a second, different cylinder can be selected for deactivation, with the second cylinder operating with one or more of the following components deactivated for at least some of the specified number of engine cycles: an intake valve, an exhaust valve, a fuel injector, and a delayed ignition spark.

[0056] As a non-restrictive example, an engine control unit (ECU) can operate the second cylinder in a first mode, in which the intake valve opens during an intake stroke, the fuel injector is deactivated, the ignition spark is deactivated, and the exhaust valve opens for an exhaust stroke. Alternatively, the ECU can operate the second cylinder in a second mode, in which the intake valve opens during the intake stroke, the fuel injector is activated, the ignition spark is deactivated, and the exhaust valve opens during the exhaust stroke. Alternatively, the ECU can operate the second cylinder in a third mode, in which the intake valve opens during either an intake or compression stroke, the fuel injector is activated and fuel is supplied during the compression stroke, the ignition spark is deactivated, and the exhaust valve opens during the exhaust stroke.Alternatively, the engine control unit can operate the second cylinder in a fourth mode, in which the intake valve opens during the intake stroke, the fuel injector is activated, the ignition spark is delayed until the exhaust stroke, and the exhaust valve opens during the exhaust stroke. The various combinations of valve, fuel, and ignition timing settings thus allow for varying amounts of heat transfer to engine components. Clearly, other modes besides those listed above are possible to provide a combination of valve, fuel, and ignition timing settings that delivers a desired amount of heat to the engine (e.g., the cylinder, the catalytic converter, etc.). The control unit can also select an operating mode for the second cylinder based on the engine temperature.

[0057] The control system can thus aim to either heat the catalyst or the engine / engine cylinders. For example, the control system might select a mode different from the first mode (such as one from the second, third, or fourth mode) in response to the second cylinder requiring more heat than the first (such as if no combustion has occurred in the second cylinder for a period of time or if the cooling system is unbalanced) or in response to the second cylinder being connected to a different catalyst than the first cylinder (such as in a V-engine configuration), with the catalyst connected to the second cylinder requiring additional heat to be sufficiently activated.

[0058] As another example, while the engine cylinders are operating with the selected cylinder pattern on deactivated / active cylinders, the control unit can operate at least one of the remaining cylinders with active ignition and fuel enrichment (e.g., via a rich fuel injection relative to stoichiometry, supplied during a compression stroke), while at least one other of the remaining cylinders operates with active ignition and fuel depletion (e.g., via a lean fuel injection relative to stoichiometry, supplied during an intake stroke) to raise the engine temperature above the threshold. In this case, the rich cylinder provides CO and hydrocarbons to the catalytic converter, which would react with the oxygen supplied to the catalytic converter by the lean cylinder.In this way, a rich air-fuel mixture from the enriched cylinder can mix with the lean air-fuel mixture from the depleted cylinder at the engine exhaust, such as at the catalytic converter, creating an exothermic reaction at the converter. This accelerates the heating of the catalytic converter.

[0059] In yet another example, while the engine cylinders are operated with the selected cylinder pattern of deactivated / active cylinders, the control system can operate at least one of the remaining cylinders with the ignition spark deactivated, supplying the cylinder stoichiometrically with fuel to accelerate catalyst heating.

[0060] Now Fig. 4 facing the Fig. An example exhaust valve setting for a 4-cylinder in-line engine, having cylinders 1-4 arranged sequentially along an engine block (not shown). Cylinders 1-4 are configured to fire in the sequence 1-3-4-2. Fig. represents intake valve timing (solid line) and exhaust valve timing (dashed line) in relation to the engine piston position during an intake stroke (I), exhaust stroke (E), power stroke (P), or compression stroke (C). Fig. Furthermore, cylinder spark ignition events are represented by stars 403a-b, 413b, 423a-b, 433a-b and cylinder fuel injection events by rectangles 402a-b, 412b, 422a-b, 432b.

[0061] In the example shown, the engine fires in the first cycle (Cycle_1) in the firing order 1-3-4-2, with each cylinder firing once. In the next cycle (Cycle_2), the engine switches to a skip-fire mode and fires according to the cylinder pattern 1-x-4-x, where x represents the skipped cylinder. In this pattern, every other cylinder fires while the others are skipped, resulting in a 1 / 2 firing pattern. Specifically, cylinder 3 is skipped after cylinder 1, and then cylinder 2 is skipped after cylinder 4.

[0062] The first curve from the top of the figure represents the position of cylinder number 1 (cylinder 1) and, in particular, the stroke of cylinder number 1 as the engine crankshaft rotates. The stroke of cylinder 1 is marked according to the engine position. For example, cylinder 1 is first shown in an intake stroke (I). As the engine rotates, cylinder number 1 enters the compression stroke (C), followed by the power stroke (P) and exhaust stroke (E). The cylinder cycle for cylinder 1 then repeats. For a four-stroke engine, one cylinder cycle can be 720°, the same crankshaft interval for a complete engine cycle.

[0063] The second curve from the top of the figure represents the position of cylinder number 3, specifically the stroke of cylinder number 3 as the engine crankshaft rotates. The stroke of cylinder 3 is marked according to the engine position. For example, cylinder 3 is first shown in an exhaust stroke (E). The engine rotates, and cylinder number 3 enters the intake stroke (I), followed by the compression stroke (C) and power stroke (P). The cylinder is then deactivated for the next combustion cycle (which would begin with the next intake stroke). The third curve from the top of the figure represents the position of cylinder number 4, specifically the stroke of cylinder number 4 as the engine crankshaft rotates. The stroke of cylinder 4 is marked according to the engine position.For example, cylinder 4 is first shown in a power stroke (P), the engine rotates, and cylinder 4 enters the exhaust stroke (E), followed by the intake stroke (I) and compression stroke (C). The cylinder cycle for cylinder 4 then repeats. Similarly, the fourth curve from the top of the figure represents the position of cylinder 2, specifically the stroke of cylinder 2 as the engine crankshaft rotates. The stroke of cylinder 2 is marked according to the engine position. For example, cylinder 2 is first shown in a compression stroke (C), the engine rotates, and cylinder 2 enters the power stroke (P), followed by the exhaust stroke (E) and intake stroke (I). The cylinder is then deactivated for the next combustion cycle (Cycle_2).

[0064] With respect to the first cylinder, a first cylinder event is shown at 401a-404a, and a subsequent cylinder event in cylinder 1 is shown at 401b-404b. During each of the first and second cylinder events, the intake valve opens during the intake stroke (401a, 401b) to provide air to the cylinder. Fuel is then injected into the engine cylinders through the intake manifold or direct injection valve (402a, 402b). The fuel-air mixture is compressed and ignited during the compression stroke (403a, 403b). Maximum cylinder pressure may occur at top dead center of the compression stroke or during the expansion stroke. Exhaust gases are then released by opening the exhaust valve during the exhaust stroke (404a, 404b). Since cylinder 1 must remain active after the first cylinder event, the exhaust valve operation continues as expected at 404a.

[0065] With respect to the fourth cylinder, the completion of the first cylinder event is shown at 423a-424a, and a subsequent cylinder event in cylinder 4 is shown at 421b-424b. During each of the first and second cylinder events, the intake valve opens during the intake stroke (421b, shown) to provide air to the cylinder. Fuel is then injected into the engine cylinders through the intake manifold or direct injection valve (422b, shown). The fuel-air mixture is compressed and ignited during the compression stroke (423a, 423b). Maximum cylinder pressure may occur at top dead center of the compression stroke or during the expansion stroke. Exhaust gases are then released by opening the exhaust valve during the exhaust stroke (424a, 424b). Since cylinder 4, like cylinder 1, must remain active after the first cylinder event, the exhaust valve operation continues as expected at 424a.Similarly, the exhaust valve operation continues as expected at 424b, since cylinder 4 must remain active after the second cylinder event; this is followed by another intake valve and fuel event at 421c and 422c, respectively.

[0066] Regarding the third cylinder, a first cylinder event is shown at 411b-413b, and during the subsequent cylinder event (that is, during Cycle_2), cylinder 3 is deactivated. Specifically, fuel, ignition, and valve operation of cylinder 3 are deactivated during the cylinder event following 411b-413b. During the first cylinder event (i.e., during Cycle_1), the intake valve opens during the intake stroke (411b) to provide air to the cylinder. Subsequently, fuel is injected into the engine cylinders through the intake manifold or direct injection valve (412b). The fuel-air mixture is compressed and ignited during the compression stroke (413b). Maximum cylinder pressure can occur at top dead center of the compression stroke or during the expansion stroke.Since cylinder 3 is to be deactivated after the first cylinder event, exhaust gases are not released but instead retained in the cylinder by keeping the exhaust valve closed during the exhaust stroke. In contrast, during the cylinder event preceding the first cylinder event shown at 411b-413b, exhaust valve operation can continue at 414a, with the exhaust valve opening during the exhaust stroke to release exhaust gases. By closing the exhaust valve during the cylinder event in cylinder 3 (in cycle_1) immediately before cylinder 3 is deactivated (in cycle_2), heat is retained in the combustion chamber, allowing for warming of the cylinder combustion surface and reducing PM emissions when cylinder 3 is subsequently reactivated. Additionally, the coolant temperature for the rest of the engine (e.g., slowly) can be increased, improving passenger comfort.

[0067] Similarly, with respect to the second cylinder, a first cylinder event is shown at 431b-433b, and in the subsequent cylinder event, cylinder 2 is deactivated. Specifically, fuel, ignition, and valve operation of cylinder 2 are deactivated in the cylinder event following 431b-433b. During the first cylinder event, the intake valve opens during the intake stroke (431b) to provide air to the cylinder. Subsequently, fuel is injected into the engine cylinders through the intake manifold or direct injection valve (432b). The fuel-air mixture is compressed and ignited during the compression stroke (433b). Maximum cylinder pressure may occur at top dead center of the compression stroke or during the expansion stroke. However, since cylinder 2 is to be deactivated after the first cylinder event, exhaust gases are not released but instead retained in the cylinder by keeping the exhaust valve closed during the exhaust stroke.In contrast, during the cylinder event preceding the first cylinder event shown at 431b-433b, the exhaust valve operation can continue at 434a, with the exhaust valve opening during the exhaust stroke to release exhaust gases. By closing the exhaust valve during the cylinder event in cylinder 2 immediately before cylinder 2 is deactivated, heat is retained in the combustion chamber, allowing the cylinder combustion surface to warm up and reducing PM emissions when cylinder 2 is subsequently reactivated.

[0068] It is clear that if cylinders 2 and 3 are reactivated sequentially, the exhaust valve of the reactivated cylinder can be opened before the intake valve(s) open to allow any residual gas trapped in the cylinder to be expelled before a fresh charge is introduced. This reduces misfires during reactivation. For example, in response to a cylinder reactivation indicator, the exhaust valve of the deactivated cylinder can be opened during an exhaust stroke of an engine cycle immediately before reactivation to expel the residue. The cylinder can then be reactivated, and the intake and exhaust valves can operate as intended during the intake and exhaust strokes, respectively.In other words, the exhaust valve of the deactivated cylinder is opened during an exhaust stroke immediately preceding the reactivation, and subsequently during an exhaust stroke upon reactivation.

[0069] An exemplary procedure for an engine comprises: selecting a cylinder for deactivation; and, in an engine cycle immediately preceding the deactivation, holding an exhaust valve of the selected cylinder closed during an exhaust stroke of that cylinder. In the preceding example, selecting a cylinder for deactivation additionally or optionally responds to a drop in engine load. In any or all of the preceding examples, during selection, an exhaust temperature is additionally or optionally higher than a threshold temperature. Any or all of the preceding examples may additionally or optionally, during reactivation of the selected cylinder, further comprise opening the exhaust valve before opening the intake valve to release trapped exhaust gases.before air is introduced. In any or all of the preceding examples, opening the exhaust valve may additionally or optionally include opening the exhaust valve during an exhaust stroke of the engine cycle immediately prior to reactivation. In any or all of the preceding examples, the selected cylinder is a first cylinder, and the method may additionally or optionally further include selecting a second, distinct cylinder for deactivation and operating the second cylinder with one or more of a deactivated intake valve, a deactivated exhaust valve, a deactivated fuel injector, a deactivated spark plug, and a delayed spark plug. In any or all of the preceding examples, operation may additionally or optionally include operating the second cylinder in a first mode,wherein the intake valve opens during an intake stroke, the fuel injector is deactivated, the ignition spark is deactivated, and the exhaust valve opens during an exhaust stroke; operating the second cylinder in a second mode wherein the intake valve opens during the intake stroke, the fuel injector is activated, the ignition spark is deactivated, and the exhaust valve opens during the exhaust stroke; operating the second cylinder in a third mode wherein the intake valve opens during an intake or compression stroke, the fuel injector is activated, fuel is supplied during the compression stroke, the ignition spark is deactivated, and the exhaust valve opens during the exhaust stroke; operating the second cylinder in a fourth mode wherein the intake valve opens during the intake stroke, the fuel injector is activated,the ignition spark is delayed until the exhaust stroke and the exhaust valve opens during the exhaust stroke; and the selection of a mode based on the exhaust catalyst temperature. Any or all of the preceding examples may additionally or optionally further include deactivating the selected cylinder for a number of engine cycles, wherein holding an exhaust valve of the selected cylinder closed responds to the number of engine cycles greater than a threshold number. In any or all of the preceding examples, the threshold number is additionally or optionally based on one or more of an engine coolant temperature, an ambient temperature, and a cylinder temperature, wherein the threshold number decreases as any one of the engine coolant temperature, the ambient temperature, and the cylinder temperature decreases.

[0070] Another exemplary procedure for an engine comprises: deactivating a cylinder pattern of individual cylinder mechanisms, wherein the cylinder pattern includes a first deactivated cylinder and a second active cylinder, wherein, in response to a command to deactivate the first cylinder and further based on an engine temperature, an exhaust valve of the first cylinder is held closed during an exhaust stroke of an engine cycle immediately prior to the deactivation of the first cylinder. In the preceding example, the exhaust valve of the first cylinder may additionally or optionally be held closed in response to the engine temperature being below a threshold.In any or all of the preceding examples, the cylinder pattern may additionally or optionally include a number of engine cycles during which the first cylinder remains deactivated, and the method may additionally or optionally include reactivating the first cylinder after the specified number of engine cycles. In any or all of the preceding examples, the engine temperature may additionally or optionally be an estimated engine temperature or an expected engine temperature, the expected engine temperature being a temperature of the engine or an engine component that is anticipated upon reactivation. Any or all of the preceding examples may additionally or optionally include, during reactivation, opening the exhaust valve of the first cylinder before opening the intake valve of the first cylinder to release trapped exhaust gases before air is introduced into the first cylinder.Any or all of the preceding examples may additionally or optionally include, in response to the expected engine temperature being below a threshold, the operation of a third cylinder with a rich fuel injection provided during a compression stroke and with the ignition spark deactivated, while a fourth cylinder is operated with a lean fuel injection during an intake stroke and with the ignition spark deactivated.

[0071] Another exemplary engine system comprises: an engine having a plurality of cylinders, each cylinder comprising an intake and an exhaust valve; a deactivation mechanism for disabling at least one of the intake valve and the exhaust valve from one of the plurality of cylinders; a temperature sensor for estimating an engine temperature; and a control system.The control system can be configured with computer-readable commands stored in non-transient memory to: select one of the multitude of cylinders for deactivation based on engine load; and, during a first engine cycle, open the intake valve of each of the multitude of engine cylinders during respective intake strokes, keep the exhaust valve of that one of the multitude of cylinders closed during an exhaust stroke, while opening the exhaust valve of the remaining cylinders during respective exhaust strokes; and, during a second engine cycle immediately following the first, deactivate the intake valve and the exhaust valve of that one of the multitude of cylinders, while the remaining cylinders remain active.In the preceding example, keeping the exhaust valve closed by one of the plurality of cylinders during the exhaust stroke can additionally or optionally respond to the fact that the engine temperature is below a threshold. Any or all of the preceding examples can additionally or optionally further include operating one or more of the remaining cylinders with ignition timing delayed until an exhaust stroke in order to raise the engine temperature above the threshold. Any or all of the preceding examples can additionally or optionally further include operating at least one of the remaining cylinders with active ignition and fuel enrichment, while at least one other of the remaining cylinders is operated with active ignition and fuel depletion in order to raise the engine temperature above the threshold.Any or all of the preceding examples may additionally or optionally include, in a third engine cycle, the reactivation of the exhaust valve of one of the plurality of cylinders and the opening of the exhaust valve during an exhaust stroke, and in a fourth engine cycle immediately following the third engine cycle, the reactivation of the intake valve of one of the plurality of cylinders and the opening of the intake valve during an intake stroke.

[0072] In another curve, a method for an engine comprises deactivating a cylinder pattern of individual cylinder mechanisms, wherein the cylinder pattern comprises a first deactivated cylinder and a second active cylinder, wherein, in response to a command to deactivate the first cylinder, an exhaust valve of the first cylinder is held closed during an exhaust stroke of an ignition cycle immediately prior to the deactivation of the first cylinder.

[0073] In this way, the technical effect of retaining combustion residues in a deactivated cylinder is that the benefits of deactivation can be maintained for a longer period without worsening exhaust emissions. By keeping the exhaust valve of a cylinder scheduled to be deactivated in the next cycle closed during an exhaust stroke, hot exhaust gases can be retained in the cylinder, thereby increasing the temperature of the combustion surface of the deactivated cylinder even while it is inactive. This not only reduces the need to reactivate cooled cylinders, thus improving fuel economy, but also reduces particulate emissions from the reactivated cylinders.By operating the active cylinders with variable valve timing and ignition timing, while other cylinders in the cylinder pattern are deactivated, the heating of the exhaust catalyst is accelerated and the duration of engine operation with cylinder deactivation is extended. This allows the fuel-saving benefits to be expanded, improving both engine performance and fuel economy.

[0074] It should be noted that the exemplary control and estimation programs contained herein can be used with various engine and / or vehicle system configurations. The control methods and programs disclosed herein can 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 engine hardware. The specific programs described herein can represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. As such, various illustrated actions, operations, and / or functions can be performed in parallel in the illustrated sequence or, in some cases, omitted.Likewise, the processing sequence is not strictly necessary to achieve the features and benefits of the exemplary embodiments described herein, but it is provided to simplify illustration and description. One or more of the illustrated actions, operations, and / or functions can be performed repeatedly, depending on the specific strategy employed. Furthermore, the described actions, operations, and / or functions can graphically represent code to be programmed in the non-transitory memory of the computer-readable storage medium in the engine control system, the described actions being executed by carrying out the commands in a system comprising the various engine hardware components in combination with the electronic control unit.

[0075] It is evident that the configurations and programs disclosed herein are exemplary and that these specific embodiments should not be considered restrictive, as numerous variations are possible. For example, the above technology can be applied to V6, I4, I6, and V12 engines, engines with four counter-rotating pistons, or other engine types. The subject matter of this disclosure includes all new and non-obvious combinations and sub-combinations of the various systems and configurations and other features, functions, and / or properties disclosed herein.

[0076] The following claims highlight in particular certain combinations and subcombinations that are considered novel and not obvious. These claims may refer to "one" element or "a first" element or the equivalent thereof. Such claims shall be understood to include one or more such elements, without requiring or excluding two or more such elements.

Claims

[1] A method for an engine, comprising: selecting a cylinder for deactivation; and in an engine cycle immediately preceding deactivation, keeping an exhaust valve of the selected cylinder closed during an exhaust stroke of the cylinder, wherein the selected cylinder is a first cylinder, the method further comprising selecting a second, different cylinder for deactivation and operating the second cylinder with one or more of a deactivated intake valve, a deactivated exhaust valve, a deactivated fuel injector, a deactivated ignition spark, and a retarded ignition spark, in which the operation includes: operating the second cylinder in a first mode wherein the intake valve opens during an intake stroke, the fuel injector is deactivated, the ignition spark is deactivated, and the exhaust valve opens during an exhaust stroke; operating the second cylinder in a second mode, wherein the intake valve opens during the intake stroke, the fuel injection valve is activated, the ignition spark is deactivated and the exhaust valve opens during the exhaust stroke; operating the second cylinder in a third mode, wherein the intake valve opens during an intake or compression stroke, the fuel injector is activated and fuel is delivered during the compression stroke, the ignition spark is deactivated, and the exhaust valve opens during the exhaust stroke; operating the second cylinder in a fourth mode, wherein the intake valve opens during the intake stroke, the fuel injector is activated, the ignition spark is delayed until the exhaust stroke, and the exhaust valve opens during the exhaust stroke; and selecting a mode based on the exhaust catalyst temperature, further comprising: deactivating a cylinder pattern of individual cylinder mechanisms, the cylinder pattern comprising a first deactivated cylinder and a second active cylinder, wherein, in response to a command to deactivate the first cylinder and further based on an engine temperature, an exhaust valve of the first cylinder is held closed during an exhaust stroke of an engine cycle immediately preceding the deactivation of the first cylinder, wherein, in response to an expected engine temperature being below a threshold, further comprising operating a third cylinder with a rich fuel injection provided during a compression stroke and with the ignition spark deactivated while operating a fourth cylinder with a lean fuel injection during an intake stroke and with the ignition spark deactivated, and wherein the engine temperature is an estimated engine temperature or the expected engine temperature, wherein the expected engine temperature comprises a temperature of the engine or an engine component expected upon reactivation. [2] The method of claim 1, wherein selecting a cylinder for deactivation is responsive to a decrease in engine load. [3] The method of claim 1 or 2, wherein during the selecting an exhaust gas temperature is higher than a threshold temperature. [4] The method of any one of claims 1 to 3, wherein during reactivation of the selected cylinder further comprising opening the exhaust valve prior to opening the intake valve to release trapped exhaust gases before introducing air. [5] A method according to any one of claims 1 to 4, wherein opening the exhaust valve comprises opening the exhaust valve during an exhaust stroke of an engine cycle immediately preceding the reactivation. [6] The method of any one of claims 1 to 5, further comprising deactivating the selected cylinder for a number of engine cycles, wherein maintaining an exhaust valve of the selected cylinder closed is responsive to the number of engine cycles being higher than a threshold number. [7] The method of claim 6, wherein the threshold number is based on one or more of an engine coolant temperature, an ambient temperature, and a cylinder temperature, the threshold number decreasing as any of the engine coolant temperature, the ambient temperature, and the cylinder temperature decreases. [8] The method of claim 1, wherein the exhaust valve of the first cylinder held closed based on engine temperature comprises the exhaust valve held closed in response to the engine temperature being lower than a threshold. [9] The method of claim 8, wherein the cylinder pattern further comprises a number of engine cycles during which the first cylinder remains deactivated, the method further comprising reactivating the first cylinder after the number of engine cycles. [10] The method of claim 9, wherein during reactivation further comprising opening the exhaust valve of the first cylinder prior to opening the intake valve of the first cylinder to release trapped exhaust gases before introducing air into the first cylinder. [11] Engine system comprising: an engine having a plurality of cylinders, each cylinder including an intake and an exhaust valve; a deactivation mechanism for deactivating at least one of the intake valve and the exhaust valve of one of the plurality of cylinders; a temperature sensor for estimating an engine temperature; and a controller configured with computer-readable instructions stored in non-transitory memory to: select one of the plurality of cylinders for deactivation based on engine load; and during a first engine cycle, open the intake valve of each of the plurality of engine cylinders during respective intake strokes, keep the exhaust valve of the one of the plurality of cylinders closed during an exhaust stroke, while the exhaust valve of the remaining cylinders is opened during the respective exhaust strokes; and during a second engine cycle immediately following the first engine cycle, deactivating the intake valve and the exhaust valve of one of the plurality of cylinders while the remaining cylinders remain active, wherein maintaining the exhaust valve of the one of the plurality of cylinders closed during the exhaust stroke is responsive to the engine temperature being less than a threshold. further comprising operating one or more of the remaining cylinders with spark timing delayed until an exhaust stroke to raise the engine temperature above the threshold, further comprising operating at least one of the remaining cylinders with active spark and fuel enrichment while operating at least another of the remaining cylinders with active spark and fuel depletion to raise the engine temperature above the threshold. [12] The engine system of claim 11, further comprising operating one or more of the remaining cylinders with spark timing retarded until an exhaust stroke to raise the engine temperature above the threshold. [13] The engine system of claim 11 or 12, further comprising, during a third engine cycle, reactivating the exhaust valve of the one of the plurality of cylinders and opening the exhaust valve during an exhaust stroke, and during a fourth engine cycle immediately following the third engine cycle, reactivating the intake valve of the one of the plurality of cylinders and opening the intake valve during an intake stroke.

Images