Methods and systems for reducing water buildup in engines

Abstract

This application relates to methods and systems for reducing water buildup in an engine, providing methods and systems for reducing condensate buildup in the engine intake port during engine non-combustion conditions. In one example, during engine non-combustion conditions, in response to ambient humidity above a threshold and intake manifold temperature below a threshold, the intake and exhaust valves of a deactivated cylinder can be closed to seal the cylinder, and immediately following engine combustion conditions, the intake and exhaust valves of the deactivated cylinder can be opened, and combustion can be resumed in the deactivated cylinder before combustion begins in the non-deactivated cylinder. Furthermore, during engine non-combustion conditions, residual hot exhaust gas can be recirculated to the intake manifold to evaporate condensate in the intake manifold.

Description

Technical Field

[0001] This specification generally relates to methods and systems for reducing water buildup in engine air intakes. Background Technology

[0002] During engine combustion, condensate that accumulates in the engine intake can be drawn into the engine, potentially causing misfires. For example, moisture from humid air can condense on engine components such as the intake manifold and supercharger air cooler, forming localized puddles. Condensate that accumulates in the intake manifold or in the supercharger air cooler (CAC) coupled to the intake manifold can enter the engine cylinders during engine operation and lead to combustion instability.

[0003] Various methods are provided for reducing engine misfires due to condensate intake. In one exemplary method, as shown by Russ et al. in US 20160169170, a method for increasing airflow through a booster air cooler (CAC) to purge condensate from the CAC is disclosed. Multiple engine cylinders of a variable displacement (VDE) engine are selectively deactivated to momentarily increase airflow via the CAC. During cylinder deactivation, fuel injection into one or more deactivated engine cylinders can be disabled while the intake and exhaust valves remain operational, thereby increasing airflow through the CAC. By adjusting the number of deactivated cylinders based on the increase in airflow required to purge condensate stored in the CAC, condensate intake is reduced.

[0004] However, the inventors of this paper have recognized the potential drawbacks of the above methods. As an example, the methods may not be able to address the condensation that accumulates at one or more engine components during engine-off conditions. The inventors have recognized that moisture can accumulate in the engine during selected conditions, such as during propulsion in a hybrid vehicle using motor torque from the system battery, during engine deceleration fuel cut-off conditions, or during engine idle-stop conditions. In particular, during such engine-off conditions, the engine intake air temperature can drop below the dew point temperature. If the vehicle is traveling through an area of ​​increased ambient humidity when the intake air temperature drops below the dew point temperature, moist air can enter the intake manifold (such as through the substantially closed intake throttle valve and cylinder valves) even when the engine is not running. Because the cylinder valves can remain open based on the position of the relevant cam lobe angle when the engine is stopped during off-state conditions, the moist air entering the engine can condense in the intake manifold. Moisture may even enter the cylinders and condense inside them. When the engine is restarted and fuel is subsequently burned in the engine cylinders, condensate collected in the intake manifold may be drawn into the cylinders, leading to engine misfire and combustion instability. Summary of the Invention

[0005] The inventors of this paper have recognized that the valve mechanism of a selectively deactivated cylinder can be controlled to remain closed when needed. During conditions where the engine is not burning and the vehicle is traveling through the intake manifold where condensation from ambient air may be present, by keeping the valve mechanism actively closed, moisture intake in at least those deactivated cylinders can be reduced. Therefore, in one example, the aforementioned problem can be addressed by an engine method comprising: in response to ambient humidity exceeding a threshold, keeping the deactivated cylinder valve closed during engine non-burning conditions; and, immediately following engine burning conditions, activating the deactivated cylinder valve and initiating combustion in the deactivated cylinders before combustion begins in non-deactivated cylinders. In this way, when ambient humidity is high and the vehicle is operating with the engine not burning fuel, the valve coupled to the deactivated cylinder can be intentionally kept closed to reduce moisture intake into the cylinder.

[0006] As an example, during engine non-combustion conditions (such as vehicle propulsion using motor torque, deceleration fuel cut-off conditions, and engine idle-stop conditions), the engine intake manifold temperature can drop below a threshold temperature (such as dew point temperature). If the vehicle is simultaneously traveling through an area with ambient humidity above the threshold, as estimated based on inputs from engine system sensors and / or from external networks communicatively coupled to the vehicle, humid air may enter the intake manifold and condense there. To reduce this moisture intake from the intake manifold to the engine cylinders, when the engine is not burning fuel, the engine can use motor torque to rotate to engage valve actuators of selectively deactivated cylinders. The amount of applied motor torque is adjusted so that the valve can remain closed, thereby sealing the corresponding cylinder. Since the engine exhaust manifold can retain heat during engine non-combustion conditions, unburned fuel and hot exhaust gas can also be diverted from the exhaust manifold to the intake manifold via the exhaust gas recirculation (EGR) passage in response to exhaust temperatures above the threshold to further reduce intake manifold condensation. When the engine is not burning, the valve can remain closed until the engine restart conditions are met. During the subsequent engine combustion event immediately following restart, the corresponding valve mechanism can be actuated to reactivate the deactivated cylinder, and combustion can be restored first in the deactivated cylinder while the non-deactivated cylinder remains in a non-burning state. After a threshold number of engine cycles have elapsed since combustion was restored in the deactivated cylinder, combustion can be restored in the non-deactivated cylinder while maintaining combustion in the deactivated cylinder.

[0007] In this way, by selectively closing the valves of deactivated engine cylinders during engine non-combustion periods, moisture intake into the deactivated cylinders and moisture buildup within the cylinders can be reduced in response to ambient humidity exceeding a threshold. Therefore, misfires in those cylinders are also reduced during subsequent engine operation. Moisture condensation in the intake manifold is also reduced by simultaneously recirculating hot residual exhaust gas through the intake manifold. The technical effect of reactivating the deactivated cylinders immediately following an engine restart and initiating combustion in the deactivated cylinders (before reactivation in the non-deactivated cylinders) is that it increases intake manifold temperature, allowing accumulated moisture to evaporate. By allowing at least some of the accumulated moisture to evaporate before combustion begins in the non-deactivated cylinders (whose valves remain closed and cannot be activated), condensate intake into the non-deactivated cylinders during cylinder combustion is reduced, thereby increasing combustion stability and reducing misfires in the non-deactivated cylinders. By recirculating hot residual exhaust gas into the intake manifold during engine non-combustion conditions in ambient humidity above a threshold, the residual exhaust heat can be effectively used to increase engine intake air temperature, thereby reducing the likelihood of intake manifold water pooling. In summary, by reducing water buildup in the intake manifold and engine cylinders during engine non-combustion conditions, combustion stability can be increased and misfire tendency can be reduced during the subsequent engine combustion conditions.

[0008] It should be understood that the above description of the invention is provided to introduce, in a simplified form, the conceptual options further described in the detailed embodiments. This is not intended to identify key or essential features of the claimed subject matter, the scope of which is uniquely defined by the appended claims. Furthermore, the claimed subject matter is not limited to solutions to any of the shortcomings pointed out above or in any part of this disclosure. Attached Figure Description

[0009] Figure 1 An exemplary embodiment of an engine equipped with a separate cylinder deactivation mechanism is shown.

[0010] Figure 2 An exemplary variable displacement engine (VDE) system coupled to a hybrid vehicle is shown.

[0011] Figure 3 A flowchart illustrating an exemplary method for reducing water buildup in the engine intake can be implemented during engine non-combustion conditions.

[0012] Figure 4 A flowchart illustrating an exemplary method for shutting off an engine during high humidity conditions is shown.

[0013] Figure 5An exemplary reduction of water buildup in an engine air intake is shown according to this disclosure. Detailed Implementation

[0014] The following description relates to systems and methods for reducing water intake into engine cylinders when the engine is in a non-combustion state during ambient humidity conditions exceeding a threshold. This is as described with reference to an exemplary engine system coupled to a hybrid vehicle system. Figures 1-2 As shown, selective cylinder deactivation in DE allows for the selective sealing of one or more engine cylinders. The engine controller can be configured to execute control routines (such as...) Figure 3 (Exemplary routines) to reduce cylinder water intake that accumulates in the engine intake by keeping the valves of selectively deactivated cylinders closed during engine non-combustion conditions. The controller can also adjust the engine shut-off position (e.g., via...) during ambient humidity conditions above a threshold. Figure 4 The control routine is used to shut down the engine and place it in a position where at least the valves of the selectively deactivated cylinders are closed. Figure 5 An example of an engine tuning technique that can reduce intake water buildup and cylinder water intake is shown.

[0015] Figure 1 An exemplary embodiment 100 of an engine 10 coupled to a vehicle system 102 is shown. The engine 10 may have a first row 15a and a second row 15b. In the depicted example, the engine 10 is a V8 engine with a first row and a second row, each row having four cylinders. The engine 10 has an intake manifold 16, a throttle valve 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... Figure 2 As described. As a non-limiting example, engine 10 may be included as part of a propulsion system for a passenger vehicle.

[0016] Engine 10 may have cylinder 14 having a selectively deactivated intake valve 50 and a selectively deactivated exhaust valve 56. In one example, the intake valve 50 and exhaust valve 56 are configured for camshaft actuation via separate camshaft-based cylinder valve actuators (e.g., Figure 2(As described in detail in the text). Each engine cylinder bank may include a camshaft that actuates both the intake and exhaust valves. In an alternative example, each engine cylinder bank may include a camshaft-actuated intake valve and separate camshaft-actuated exhaust valves. In an alternative example, the valves may be configured for electric valve actuation (EVA) via electrically operated individual cylinder valve actuators. While the depicted example shows each cylinder with a single intake valve and a single exhaust valve, in alternative examples, each cylinder may have multiple selectively deactivated intake valves and / or multiple selectively deactivated exhaust valves. Engine components actuated during cylinder valve activation / deactivation may be collectively referred to as VDE mechanisms or VDE actuators.

[0017] During selected conditions, such as when the engine's full torque capability is not desired (e.g., when the engine load is less than a threshold load, or when the operator's torque demand is less than a threshold demand), one or more cylinders of engine 10 may be selected for selective deactivation (also referred to herein as individual cylinder deactivation). This may include selectively deactivating one or more cylinders only in the first row 15a, one or more cylinders only in the second row 15b, or one or more cylinders in each of the first and second rows. The number and identification of cylinders deactivated in each group may be symmetrical or asymmetrical.

[0018] During deactivation, selected cylinders can be deactivated by closing individual cylinder valve mechanisms (such as intake valve mechanism, exhaust valve mechanism, or a combination of both). Cylinder valves can be selectively deactivated by: a hydraulically actuated lift (e.g., a lift coupled to a valve pushrod), a deactivation follower mechanism where the cam lift of the follower can be separated from the valve actuation portion of the follower, or an electrically actuated cylinder valve mechanism coupled to each cylinder. The cam-based cylinder valve actuator can be controlled by engine torque. When the engine is not burning, the engine position can be adjusted using motor torque from the starter motor. During the engine non-combustion condition, the engine position can be adjusted to a desired engine off position, where the cam is engaged and the cylinder valves can be actuated to the desired valve position. In this document, the cylinder deactivation mechanism can be collectively referred to as the VDE mechanism. In some examples, such as by deactivating the cylinder fuel injector 66, the fuel flow to the deactivated cylinder can be stopped. In some examples, such as by disabling the current to the spark circuit, the spark supply to the deactivated cylinder can also be stopped.

[0019] When a selected cylinder is disabled, the remaining enabled cylinders continue combustion, with the fuel injectors and cylinder valve mechanism activated and operating. To meet torque requirements, the engine produces the same amount of torque on the enabled cylinders. This requires higher manifold pressure, resulting in reduced pumping losses and improved engine efficiency. Furthermore, the lower effective surface area exposed to combustion (from the enabled cylinders) reduces engine heat losses, thereby improving engine thermal efficiency.

[0020] As described in detail herein, deactivated cylinder valves can be effectively used to reduce water buildup in deactivated cylinders during engine off-state conditions, thereby reducing the tendency for misfires during subsequent engine operating conditions. (See reference...) Figure 3 As described in detail, during the engine's non-combustion phase, the intake manifold temperature and engine temperature (indicating the engine cylinder wall temperature) can decrease below the dew point temperature, and if the ambient humidity increases above a threshold humidity, moisture from the ambient air can condense on the cooler surfaces of the intake manifold. Because engine valves can remain open during the non-combustion phase, moisture can even enter the cylinders and condense inside. During the subsequent engine combustion phase, the condensate collected in the intake manifold may be drawn into the cylinders, leading to engine misfires and combustion instability.

[0021] In this way, in response to ambient humidity exceeding a threshold, during engine shutdown, each intake and exhaust valve coupled to one or more deactivated engine cylinders can be closed to seal the deactivated cylinders, thereby reducing the likelihood of water condensation within these cylinders. During a subsequent engine restart, each intake and exhaust valve coupled to one or more deactivated engine cylinders can be reopened, and refueling of one or more deactivated cylinders can be resumed before refueling of the non-deactivated cylinders.

[0022] By initially resuming combustion in previously sealed, deactivated cylinders during engine restart, misfire occurrence and combustion instability can be reduced because these cylinders actively reduced water intake during the previous engine shutdown (or idle-stop) period. After combustion in deactivated cylinders for several engine cycles, engine and intake manifold temperatures may rise. Any remaining condensate in the intake manifold may evaporate due to this increased temperature. By resuming combustion in non-deactivated cylinders after the intake manifold temperature has risen above a threshold temperature, non-deactivated cylinder operation can be delayed until it can be better ensured that remaining condensate has evaporated, thereby increasing combustion stability.

[0023] Engine 10 can operate on a variety of substances that can be delivered via fuel system 8. The fuel tank in fuel system 8 can hold fuels with different fuel qualities (such as different fuel compositions). These differences can include different alcohol contents, different octane ratings, different heats of vaporization, different fuel mixtures, and / or combinations thereof. Engine 10 can be at least partially controlled by control system 41, which includes controller 12. Controller 12 can receive various signals (and reference) from sensors 82 coupled to engine 10. Figure 2 (as described), and sends control signals to various actuators 81 coupled to the engine and / or vehicle (as referenced). Figure 2 (Description to follow). For example, various sensors may include various temperature sensors, pressure sensors, and air-fuel ratio sensors.

[0024] Figure 2 This is a schematic diagram 200 showing a vehicle system 102 including an engine system 101. The vehicle system may also be a hybrid vehicle system that includes an electric motor for operating the vehicle. Figure 2 A cylinder of a multi-cylinder engine 10 in engine system 101 is shown. Engine 10 can be controlled at least in part by a control system including controller 12 and by input from vehicle operator 132 via input device 130. In this example, input device 130 includes an accelerator pedal and a pedal position sensor 134 for generating a proportional pedal position signal PP. Combustion chamber (cylinder) 30 of engine 10 can include combustion chamber walls 32, in which piston 36 is positioned. Piston 36 can be coupled to crankshaft 40 such that the reciprocating motion of the piston is converted into rotational motion of the crankshaft. Crankshaft 40 can be coupled to at least one drive wheel of the vehicle via an intermediate transmission system. Furthermore, starter motor 171 can be coupled to crankshaft 40 via flywheel 162 to enable starting rotation (e.g., rotation) of engine 10, which is typically used to start an engine. When starting the engine, the actuation of the starter motor stops after combustion occurs, as combustion contributes to the rotation of the engine. In one example, starter motor 171 can be a conventional starter motor. In other examples, the starter motor 171 may be an integrated starter motor, such as those commonly found in hybrid vehicles.

[0025] The combustion chamber 30 receives intake air from the intake manifold 44 via the intake passage 42 and exhausts combustion gases via the exhaust passage 48. The intake manifold 44 and the exhaust passage 48 are selectively connected to the combustion chamber 30 via corresponding intake valves 52 and exhaust valves 54. In some embodiments, the combustion chamber 30 may include two or more intake valves and / or two or more exhaust valves.

[0026] In this example, cam actuation can control the intake valve 52 and exhaust valve 54 via corresponding cam actuation systems 51 and 53. Cam actuation systems 51 and 53 include a variable displacement engine (VDE) mechanism and can be used to selectively deactivate (close) one or more of the intake valve 52 and exhaust valve 54 during cylinder deactivation. Cam actuation systems 51 and 53 may each include one or more cams and can utilize one or more of the following: a cam profile change (CPS) system, a variable cam timing (VCT) system, a variable valve timing (VVT) system, and / or a variable valve lift (VVL) system, which can be operated by controller 12 to change valve operation. Position sensors 55 and 57 can determine the positions of the intake valve 52 and exhaust valve 54, respectively. In an alternative embodiment, the intake valve 52 and / or exhaust valve 54 can be controlled by electric valve actuation. For example, combustion chamber 30 may alternatively include an intake valve controlled by electric valve actuation and an exhaust valve controlled by cam actuation including a CPS system and / or a VCT system. In other embodiments, the intake and exhaust valves may be controlled by a common valve actuator or actuation system, or a variable valve timing actuator or actuation system. One or more engine cylinders may be selectively deactivated by closing individual intake valve mechanisms, exhaust valve mechanisms, or a combination of both via a cylinder deactivation mechanism (referred to herein as a VDE mechanism).

[0027] Fuel injector 66 is shown directly coupled to combustion chamber 30 for injecting fuel into combustion chamber 30 in proportion to the pulse width of the signal FPW received from controller 12 via electronic driver 68. In this manner, fuel injector 66 provides so-called direct injection of fuel into combustion chamber 30. For example, the fuel injector may be mounted in the side or top of combustion chamber (as shown). Fuel can be delivered to fuel injector 66 via a fuel system (not shown) including a fuel tank, fuel pump, and fuel rail. In some embodiments, combustion chamber 30 may alternatively or additionally include a fuel injector arranged in intake manifold 44 to provide so-called intake manifold injection of fuel into intake duct upstream of combustion chamber 30.

[0028] In some embodiments, each cylinder of engine 10 may include a spark plug 192 for initiating combustion. In a selected operating mode, the ignition system may, in response to a spark advance signal SA from controller 12, supply an ignition spark to combustion chamber 30 via spark plug 192. However, in some embodiments, spark plug 192 may be omitted, for example, in which case engine 10 may initiate combustion via automatic ignition or fuel injection, as may be the case in some diesel engines. In one example, during selective deactivation (via a VDE mechanism) of one or more engine cylinders, operation such as disabling spark plug 192 may also stop the supply of spark to the deactivated cylinder.

[0029] The intake passage 42 may include a throttle valve 62 with a throttle plate 64. In this particular example, the controller 12 may change the position of the throttle plate 64 by providing a signal to an electric motor or actuator included in the throttle valve 62, a configuration commonly referred to as electronic throttle control (ETC). In this way, the throttle valve 62 can be operated to change the intake air supplied to the combustion chamber 30 and other engine cylinders. The position of the throttle plate 64 may be provided to the controller 12 by a throttle position signal TP. The intake passage 42 may include an intake air temperature (IAT) sensor 125, an atmospheric pressure (BP) sensor 128, and an ambient humidity sensor 172. The IAT sensor 125 estimates the intake air temperature to be used during engine operation and provides a signal to the controller 12. The BP sensor 128 estimates the ambient pressure for engine operation and provides a signal to the controller 12. Similarly, the ambient humidity sensor 172 estimates the ambient humidity for engine operation and provides a signal to the controller 12. The intake passage 42 may also include a mass airflow sensor 120 and a manifold air pressure sensor 122 for providing corresponding signals MAF and MAP to the controller 12. A rain sensor 176 may be coupled to the windshield of the vehicle 102 to detect increased humidity and rain conditions.

[0030] Exhaust gas sensor 126 is shown coupled to exhaust passage 48 upstream of emission control device 70. Sensor 126 can be any suitable sensor for providing an indication of exhaust air-fuel ratio (AFR), such as a linear oxygen sensor or UEGO (universal or wide-range exhaust oxygen) sensor, dual-state oxygen sensor or EGO sensor, HEGO (heated EGO) sensor, NOx sensor, HC sensor, or CO sensor. Input from exhaust gas sensor 126 can also be used to estimate ambient humidity.

[0031] The emission control device 70 is shown arranged along the exhaust passage 48 downstream of the exhaust sensor 126. The device 70 may be a three-way catalytic converter (TWC), a NOx trap, a particulate filter, various other emission control devices, or combinations thereof. In some embodiments, the emission control system 70 can be periodically reset during engine 10 operation by operating at least one cylinder of the engine within a specific air-fuel ratio.

[0032] Exhaust gas recirculation (EGR) system 140 can guide a desired portion of exhaust gas from exhaust passage 48 to intake manifold 44 via EGR passage 142. Controller 12 can modify the amount of EGR supplied to intake manifold 44 via EGR valve 144. Furthermore, EGR sensor 146 can be arranged within EGR passage 142 and can provide indications of one or more of exhaust gas pressure, temperature, and component concentration. In one example, sensor 146 can be a DPFE (Differential Pressure Feedback EGR) sensor. The amount of EGR recirculated from the exhaust manifold to the intake manifold can be estimated based on input from the DPFE sensor. A DPFE sensor can monitor the pressure difference across a flow control orifice in the EGR passage to measure the EGR flow rate. In some cases, EGR system 140 can be used to regulate the temperature of the air-fuel mixture in the combustion chamber, thereby providing a method for controlling ignition timing during certain combustion modes. Additionally, during certain conditions, a portion of the combustion gases can be retained or trapped in the combustion chamber by controlling exhaust valve timing (e.g., by controlling a variable valve timing mechanism).

[0033] Therefore, hot EGR can be effectively used to evaporate condensate accumulated in the engine intake manifold. During engine shutdown, some residual exhaust gas may remain in the exhaust manifold. In response to below-threshold engine intake air temperature and above-threshold ambient humidity, the opening of the EGR valve can be adjusted to recirculate hot residual exhaust gas into the intake manifold. Hot residual exhaust gas can evaporate at least a portion of the condensate accumulated in the intake manifold, thereby further reducing water intake from the intake manifold to the cylinders. Furthermore, further condensation of moisture in the intake manifold is reduced. Adjusting the EGR valve opening includes: increasing the opening in response to above-threshold residual exhaust temperature, increasing the opening at each of the decrease in intake manifold temperature and increase in ambient humidity, and decreasing the opening at each of the increase in intake manifold temperature and decrease in ambient humidity. In response to below-threshold residual exhaust temperature, the EGR valve can be closed.

[0034] Controller 12 in Figure 2The controller 12 is shown as a microcomputer, which includes a microprocessor unit 102, an input / output port 104, an electronic storage medium for executable programs and calibration values ​​(shown in this particular example as a read-only memory chip 106), a random access memory 108, a non-fail-in-time memory 110, and a data bus. The controller 12 can receive various signals from sensors coupled to the engine 10, including, in addition to those previously discussed, the following measurements: exhaust airflow rate (AFR) from oxygen sensor 126; intake airflow rate (MAF) from mass airflow sensor 120; engine coolant temperature (ECT) from temperature sensor 112 coupled to cooling sleeve 114; surface-sensed ignition signal (PIP) from Hall effect sensor 118 (or other type) coupled to crankshaft 40; throttle position (TP) from throttle position sensor; absolute manifold pressure signal (MAP) from sensor 122; ambient humidity signal from sensor 172; and intake air temperature from IAT sensor 125. The controller 12 can generate an engine speed signal (RPM) based on the PIP signal. The manifold pressure signal (MAP) from the manifold pressure sensor can be used to provide an indication of vacuum or pressure in the intake manifold. It should be noted that various combinations of the above sensors can be used, such as a MAF sensor without a MAP sensor, or vice versa. During stoichiometric operation, the MAP sensor can provide an indication of engine torque. Furthermore, this sensor, along with the detected engine speed, can provide an estimate of the charge (including air) introduced into the cylinders. In one example, sensor 118 (which also functions as an engine speed sensor) can generate a predetermined number of equally spaced pulses per crankshaft rotation. Additionally, sensors coupled external to the vehicle system (such as rain sensor 176) can be used to estimate ambient humidity. Controller 12 can be coupled to wireless communication device 155 for direct communication with vehicle 102 via network cloud 160. When using wireless communication 150 via device 155, vehicle 102 can retrieve data on current and / or upcoming environmental conditions (such as ambient humidity, temperature, pressure, etc.) from network cloud 160.

[0035] The storage medium read-only memory 106 can be programmed by computer-readable data representing non-transitory instructions, as well as other variations contemplated but not specifically listed, which can be executed by processor 102 to perform the methods described below. As described above, Figure 2 The diagram shows one cylinder in a multi-cylinder engine, and each cylinder may similarly include its own set of intake / exhaust valves, fuel injectors, spark plugs, etc.

[0036] Controller 12 from Figure 2 Various sensors receive signals and employ Figure 2Various actuators are used to adjust engine operation based on received signals and instructions stored in the controller's memory 12. In one example, in response to ambient humidity conditions above a threshold (e.g., estimated by input from humidity sensor 172), during engine-off conditions, the controller 12 may signal cam actuation systems 51 and 53 to selectively close intake valve 52 and exhaust valve 54 of deactivated cylinders. In another example, in response to ambient humidity conditions above a threshold, during engine-off conditions, the controller 12 may signal EGR valve 144 to actuate the valve to the open position, thereby recirculating hot residual exhaust gas from the exhaust manifold to the intake manifold.

[0037] In some examples, vehicle 102 may be a hybrid vehicle having multiple torque sources available for one or more vehicle wheels 55. In other examples, vehicle 102 may be a conventional vehicle with only an engine, or an electric vehicle with only an electric motor. In the example shown, vehicle 102 includes an engine 10 and an electric motor 52. The electric motor 52 may be a motor or a motor / generator. When one or more clutches 56 are engaged, the crankshaft 40 of engine 10 and the electric motor 52 are connected to the vehicle wheels 55 via a transmission 46. In the depicted example, a first clutch 56 is disposed between the crankshaft 40 and the electric motor 52, and a second clutch 56 is disposed between the electric motor 52 and the transmission 46. Controller 12 may send signals to the actuators of each clutch 56 to engage or disengage the clutch, thereby connecting or disconnecting the crankshaft 40 from the electric motor 52 and its connected components, and / or connecting or disconnecting the electric motor 52 from the transmission 46 and its connected components. Transmission 46 may be a gearbox, a planetary gear system, or another type of transmission. The powertrain may be configured in various ways, including as a parallel, series, or series-parallel hybrid vehicle.

[0038] The motor 52 receives electrical power from the traction battery 58 to provide torque to the vehicle wheels 55. The motor 52 can also operate as a generator to provide electrical power, for example, during braking operations, to charge the traction battery 58.

[0039] In this way, Figures 1-2The system implements a system for a hybrid vehicle, the system comprising: an electric motor including a battery; an engine having deactivated cylinders and non-deactivated cylinders; each of an intake valve and an exhaust valve coupled to the deactivated cylinders, each of the intake valves and the exhaust valves being selectively actuated by a variable displacement engine (VDE) actuator; each of another intake valve and another exhaust valve coupled to the non-deactivated cylinders; one or more fuel injectors coupled to each of the deactivated cylinders and the non-deactivated cylinders; an ambient humidity sensor and an intake air temperature sensor coupled to the engine intake manifold; an exhaust air temperature sensor coupled to the exhaust manifold; a rain sensor coupled to the vehicle's windshield wipers; and an exhaust gas recirculation (EGR) passage coupled to the engine exhaust manifold to the engine intake manifold, the EGR passage including an EGR valve. The vehicle engine may further include a controller having computer-readable instructions stored in a non-transitory memory, the instructions being configured to: estimate ambient humidity via one or more of the ambient humidity sensor and the rain sensor; in response to a first engine off condition, actuate the VDE actuator to selectively close the intake and exhaust valves of the deactivated cylinders while keeping the other intake and exhaust valves of the non-deactivated cylinders open before disabling fuel in the engine; and in response to a second engine off condition, keep each of the intake and exhaust valves of the deactivated cylinders and the other intake and exhaust valves of the non-deactivated cylinders open before disabling fuel in the engine.

[0040] Figure 3 An exemplary method 300 for reducing water buildup in the engine intake manifold and engine cylinders during engine non-combustion conditions is shown. This method is based on instructions stored in the controller's memory and incorporates data from sensors within the engine system (such as those mentioned above). Figure 1 and Figure 2 The controller can execute instructions for performing method 300 and other methods included herein, based on signals received by the described sensors. According to the methods described below, the controller can employ the engine actuator of the engine system to adjust engine operation.

[0041] At point 302, current vehicle and engine operating conditions can be estimated and / or measured. These conditions may include, for example, operator torque demand, engine speed, vehicle speed, engine temperature, engine load, exhaust temperature, manifold pressure, manifold airflow, battery state of charge, etc. Furthermore, environmental conditions (such as ambient humidity, temperature, and atmospheric pressure) can be estimated. In one example, this could be achieved using an intake air humidity sensor (such as...). Figure 2 Humidity sensor 172) and windshield humidity sensor (such as Figure 2One or more of the rain sensors 176 in the vehicle are used to measure ambient humidity. Ambient humidity at the current vehicle's location can be obtained from weather data, such as via wireless communication (e.g., [missing information]). Figure 2 Wireless communication 150) is coupled from the communication ground to the vehicle's external network (such as... Figure 2 The results were retrieved from the network cloud (160).

[0042] At 304, the routine includes determining whether the engine is in a non-combustion condition. Engine non-combustion conditions can include engine idle-stop conditions, deceleration fuel shut-off (DFSO) conditions, and engine shutdown events. For example, engine combustion can be suspended when one or more idle-stop conditions are met. As an example, engine idle-stop conditions can include: engine idling for a duration longer than a threshold (such as during traffic interruption), a state of charge (SOC) greater than a threshold for the battery coupled to the electric motor (such as at least 30% charge), and the air conditioning not requesting a restart of the engine (which could be requested if desired). Furthermore, if the vehicle speed is below a threshold (e.g., 3 mph), engine idle-stop can be requested even if the vehicle is not stationary. Additionally, prior to engine idle-stop, emission control devices coupled to the exhaust manifold of the engine can be analyzed to determine if a request to restart the engine has been made.

[0043] As another example, during a DFSO condition, fuel injection to the engine cylinders can be suspended and the engine can run without refueling. In one example, a DFSO condition can occur in response to the release of the accelerator pedal (tip-out) (i.e., when the operator releases the accelerator pedal and requests a reduction in torque), allowing the vehicle to coast.

[0044] As yet another example, when using a motor from a hybrid electric vehicle (HEV) (such as...) Figure 2 When the vehicle is propelled by the motor torque of the electric motor (52), the engine may be unburned and remain off. The vehicle can be propelled by motor torque during periods below a threshold engine load and above a threshold SOC of the motor battery. The threshold engine load can be calibrated based on vehicle operating conditions including vehicle speed and battery SOC. The threshold SOC can correspond to the minimum motor power desired for propelling the vehicle. In another example, the unburned engine condition can also include a vehicle key-off condition where the vehicle is stationary and not propelled by either engine torque or motor torque.

[0045] If it is determined that the engine is burning fuel in the engine cylinders, then at point 306, the current engine operation can be maintained. If a subsequent engine shutdown request is received, during ambient humidity conditions above a threshold, fuel supply to each deactivated and non-deactivated cylinder can be disabled, and the engine shutdown speed profile can be adjusted to stop the engine at the engine stop position where the deactivated cylinder valves are closed. (Reference) Figure 4 The method for shutting down the engine during ambient humidity conditions above the threshold is described in detail.

[0046] Returning to 304, if it is determined that the engine is not burning, then at 308, the routine includes determining whether the ambient humidity is above a threshold humidity. The controller can calibrate the threshold ambient humidity based on an estimated dew point temperature. The estimated dew point temperature can be based on the ambient humidity and the engine intake manifold temperature. The controller can determine the dew point temperature based on a calculation using a lookup table, where the inputs are each of the ambient humidity and the engine intake manifold temperature, and where the output is the dew point temperature. The controller can also base the output on data from an intake air temperature sensor (such as...). Figure 2 The engine intake manifold temperature is determined by inputs from the IAT sensor 125 and the engine coolant temperature sensor coupled to the engine coolant system. In one example, a threshold humidity may correspond to a humidity level above which moisture from the air may condense in the engine intake manifold.

[0047] During engine non-combustion conditions, the engine intake air temperature may drop below the dew point. If the ambient humidity is simultaneously above a threshold humidity, moist air can enter the intake manifold through the at least partially open intake throttle valve, and the moisture can condense locally in the engine intake manifold. In one example, due to deterioration of the intake passage and / or throttle valve, an opening (such as a leak) may exist in a portion of the intake manifold, allowing fluid communication between the intake manifold and the atmosphere. Even when the engine is not burning and the throttle valve is commanded to the fully closed position, moist air may still enter the engine system through such an opening. This results in a puddle in the intake manifold. If one or more engine valves are also open at this time (e.g., because the engine stop position during engine shutdown is the position where the intake or exhaust valves of the cylinders are open), moist air may enter the engine cylinders. During engine non-combustion conditions, the temperature of the engine cylinder walls (such as that estimated based on input from an engine coolant temperature sensor) may also decrease, thereby allowing moisture to condense within the engine cylinders. Additionally, condensate that accumulates in the intake manifold can be drawn into the cylinders by opening a valve. During subsequent engine operation, this accumulated moisture in the cylinders and in the intake manifold (when drawn in) can cause engine misfire.

[0048] If the ambient humidity is determined to be below a threshold humidity, then at 310, the engine can be kept in a non-combustion state without selectively deactivating cylinder valves. Specifically, if one or more valves of a deactivatable cylinder remain open, then when the engine is not combusting, the valves can remain in their respective open positions and may not be actuated to close.

[0049] If the ambient humidity is determined to be above a threshold humidity, one or more deactivated engine cylinders can be selectively deactivated at 312 via a VDE mechanism. Because the engine is non-combustible, spark and fuel injection to the engine can be disabled. Therefore, selective cylinder deactivation includes simultaneously deactivating one or more cylinder valves of each deactivated cylinder of the engine. For example, in the case where the VDE mechanism is a cam-actuated mechanism, deactivation also includes actuating a solenoid coupled to the camshaft to close one or more cylinder valves of each deactivated cylinder. In an alternative embodiment, each engine cylinder can be deactivated independently and individually. Specifically, for example, an eight-cylinder engine may operate in a seven-cylinder mode, a six-cylinder mode, a five-cylinder mode, or a four-cylinder mode. In another example, in the case where the VDE mechanism is an electrically actuated mechanism, the engine can be equipped with an electric valve actuation (EVA) mechanism (via electrically operated individual cylinder valve actuators), which can be actuated at any time during the engine's non-combustible state to close the deactivated cylinder valves, regardless of the engine position at the time of closure.

[0050] For engines equipped with camshaft actuation mechanisms including separate camshaft-based cylinder valve actuators (such as...) Figure 2 As described in detail below, selective disengagement of deactivatable engine cylinders includes, at 313, adjusting the engine position to engage one or more camshafts coupled to the deactivatable cylinder valves for disengaging (closing) each deactivatable cylinder valve (intake and exhaust valves). Adjusting the engine position facilitates actuation of the camshafts and closure of each deactivatable cylinder valve as the camshafts are driven by engine rotation. Adjusting the engine position involves rotating the engine via an electric motor (such as a starter motor or electric motor in a hybrid vehicle) to bring the engine to a desired stopping position that achieves camshaft engagement and deactivatable cylinder valve closure.

[0051] In this way, during periods of humidity above a threshold, the deactivated cylinder valves can be selectively closed, while one or more valves coupled to non-deactivated cylinders can remain open or closed based on the position of their corresponding cam lobes. By closing the deactivated cylinder valves, the deactivated cylinders are sealed, thereby reducing the airflow (with high moisture content) to the deactivated cylinders. Because the deactivated cylinders are sealed, even when the cylinder temperature drops below the dew point temperature, puddles (caused by condensation of moisture in the air) cannot form inside these cylinders.

[0052] Once the deactivated cylinder valve is closed, at 314, the routine includes determining whether the temperature of the residual exhaust gas remaining in the engine is above a threshold temperature. When cylinder combustion is not performed, no new exhaust gas is generated in the exhaust passage. However, due to slow purging, some residual exhaust gas from earlier combustion events may remain in the exhaust passage. Because the exhaust system has a larger thermal mass relative to the intake system, the residual exhaust gas can retain exhaust heat for a duration even after combustion is stopped. The controller can measure the temperature of the residual exhaust gas via input from an exhaust temperature sensor coupled to the exhaust passage, and / or infer the temperature based on the last estimated exhaust temperature and a duration of engine non-combustion. In one example, the threshold temperature can be calibrated to correspond to a temperature at which moisture from the intake air cannot condense in the intake manifold (such as a temperature above the dew point). In another example, the controller can calibrate the threshold temperature based on the engine intake air temperature, ambient humidity, and engine temperature. In yet another example, the threshold temperature can correspond to the boiling point of water, such that water condensed in the intake manifold can evaporate at temperatures above the threshold temperature.

[0053] If the temperature of the residual exhaust gas is determined to be above the threshold temperature, then at 318, the controller can activate the EGR valve (such as...). Figure 2 The EGR valve 144 is actuated to the open position to allow unburned fuel and hot exhaust gas to pass through the EGR passage (such as...). Figure 2 The EGR passage 142 in the engine recirculates exhaust gas from the exhaust manifold to the intake manifold. In one example, because the engine is not burning, the EGR valve can be fully open to maximize the residual exhaust flow to the intake manifold. During engine non-burning conditions (such as DFSO), the engine intake manifold remains under vacuum (low pressure), which facilitates exhaust gas recirculation from the exhaust manifold, which is at a higher pressure relative to the intake manifold. When hot exhaust gas enters the intake manifold along with unburned fuel, the intake manifold temperature may increase, thereby reducing the likelihood of moisture condensation within the intake manifold.

[0054] In another example, recirculating hot exhaust gas from the exhaust manifold back to the intake manifold may also include, at 319, adjusting the residual exhaust flow based on the intake manifold temperature, exhaust temperature, and ambient humidity. This can be based on a differential pressure feedback EGR sensor (such as...) coupled to the EGR channel. Figure 2The residual exhaust flow is estimated using the input from the DPFE sensor 146. The intake manifold temperature can be based on inputs from one or more of the intake air temperature sensor and the engine coolant temperature sensor. Adjusting the residual exhaust flow involves adjusting the opening of the EGR valve. In one example, the EGR valve opening may increase as the residual exhaust temperature increases, the ambient humidity increases, or the intake air temperature decreases. In another example, the EGR valve opening may decrease as the residual exhaust temperature decreases, the ambient humidity decreases, or the intake air temperature increases. The controller may determine the EGR valve opening based on calculations using a lookup table, where the inputs are each of the intake manifold temperature, the residual exhaust temperature, and the ambient humidity, and the output is the EGR valve opening.

[0055] If the residual exhaust temperature is determined to be below the threshold temperature, the EGR valve can be kept closed at 316, and residual exhaust can be prevented from being directed from the exhaust manifold to the intake manifold when the engine is not burning. Because the residual exhaust temperature is below the threshold temperature, the heat from the residual exhaust cannot be effectively used to reduce moisture condensation in the intake manifold.

[0056] At 320, the routine includes determining whether an engine combustion condition is met. In one example, the engine combustion condition can be met in response to pressing the accelerator pedal (tip-in). In response to an increased torque demand (such as during accelerator pedal pressing), the engine can stop operating in an idle-stop or DFSO state. Furthermore, the HEV motor cannot meet the increased torque demand, thus requiring the provision of engine torque. In another example, during vehicle operation using motor torque, the engine combustion condition can be met in response to the HEV motor's battery state of charge decreasing to below a threshold SOC, where the vehicle can no longer be propelled by motor torque. Therefore, in response to the below-threshold battery SOC, engine combustion can be initiated to propel the vehicle with engine torque and recharge the battery. In yet another example, the engine combustion condition can be confirmed in response to a request for engine power for operating auxiliary devices (such as the air conditioning system). If the engine combustion condition is not met, at 322, the engine can be kept in a non-combustion state and the deactivation valve can be kept in a deactivated (closed) state.

[0057] If any engine combustion condition is determined to be met, at 324, one or more previously deactivated (in step 312) deactivated engine cylinders can be reactivated by actuating the VDE mechanism. Reactivation of a deactivated cylinder involves opening the previously deactivated intake and exhaust valves of the deactivated cylinder. In one example, where the VDE mechanism is an electric valve actuation (EVA) mechanism, the VDE mechanism can be actuated immediately to open the deactivated cylinder valves once the engine combustion condition is met, regardless of the engine position at startup. In another example, where the VDE mechanism includes camshaft-based cylinder valve actuators, the engine can be started and rotated by a starter motor, and the engine position can be adjusted to engage one or more camshafts coupled to the deactivated cylinder valves, and then each deactivated cylinder valve can be opened.

[0058] At point 326, combustion can be initiated in the reactivated cylinder while the non-disabled cylinder remains unburned. Initiating combustion in the reactivated cylinder involves injecting fuel and providing a spark to the disabled cylinder, while fuel injection and sparking are disabled in the non-disabled cylinder. The controller can signal one or more fuel injectors coupled to the disabled cylinder to resume fuel injection into those cylinders. Furthermore, the controller can signal spark plugs coupled to the disabled cylinder to resume sparking. During the immediate preceding engine non-combustion condition, when ambient humidity increases above a threshold humidity, moisture buildup in the disabled cylinder can be reduced by sealing it. However, due to above-threshold ambient humidity, water may have already condensed inside or been drawn into the potentially unsealed non-disabled cylinder during the engine non-combustion condition. By first reactivating combustion in the non-disabled cylinder and by keeping the non-disabled cylinder unburned, the likelihood of misfire (due to water buildup in the cylinder) can be reduced. Combustion in deactivated cylinders (while non-deactivated cylinders remain in a non-combustion state) can continue for multiple engine cycles immediately after the deactivated cylinders are reactivated.

[0059] At 328, the routine includes determining whether a threshold number of combustion events has occurred in the deactivated cylinder. For example, the controller can determine whether the number of engine cycles since combustion began in the non-deactivated cylinder is higher than a threshold number of engine cycles. In one example, the threshold number of engine cycles can be dynamically calibrated based on the intake manifold temperature. As the engine intake manifold temperature increases, the threshold number can decrease. Once combustion begins in the deactivated cylinder, the engine temperature and intake manifold temperature can increase. Increased engine and intake manifold temperatures may reduce the likelihood of water condensation in the engine intake manifold and engine cylinders. Moreover, increased engine and intake manifold temperatures may cause previously accumulated moisture to evaporate from the intake manifold.

[0060] If it is determined that the number of engine cycles since combustion began in the deactivated cylinders is below a threshold number of engine cycles, then at 330, engine operation can continue without initiating combustion in the non-deactivated cylinders. Therefore, the deactivated cylinders can maintain combustion, while the non-deactivated cylinders can remain in an unburned state. Furthermore, the EGR flow can be maintained based on intake manifold temperature, exhaust temperature, and ambient humidity. Due to combustion in the deactivated cylinders, the exhaust temperature may increase, and the recirculation of unburned fuel and hot exhaust can further contribute to increasing the intake manifold temperature.

[0061] If it is determined that the number of engine cycles since combustion began in the deactivated cylinders is higher than a threshold number of engine cycles, then at point 332, combustion can begin in the non-deactivated cylinders while combustion in the reactivated (deactivated) cylinders can be maintained. As an example, after completing more than the threshold number of engine cycles, it can be inferred that accumulated (condensed) moisture in the intake manifold and inside the non-deactivated cylinders (which were not sealed during engine shutdown) has evaporated, and moisture intake is unlikely during combustion in the non-deactivated cylinders, thereby reducing the likelihood of misfire. The controller can send a signal to one or more fuel injectors coupled to the non-deactivated cylinders to resume fuel injection into these cylinders. Furthermore, the controller can send a signal to the spark plugs coupled to the non-deactivated cylinders to resume sparking. In this way, after the threshold number of engine cycles, fuel can be injected into the non-deactivated cylinders and a spark can be provided to them, while fuel injection and sparking can be maintained in the deactivated cylinders. Once combustion is restored in all engine cylinders, the controller can operate the engine with all cylinders engaged, or selectively deactivate one or more cylinders to improve fuel economy, depending on engine operating conditions (such as engine load).

[0062] In this manner, in response to an engine restart immediately following an engine non-combustion condition, the VDE actuator can be actuated to selectively reactivate the intake and exhaust valves of the deactivated cylinders, and fueling of the deactivated cylinders can be resumed while fueling of the non-deactivated cylinders remains deactivated. After a threshold number of engine cycles following the commencement of fueling of the deactivated cylinders, with the deactivated cylinders operating under fueling and the non-deactivated cylinders operating without fueling, fueling of each engine cylinder (including the non-deactivated cylinders) can be resumed.

[0063] Furthermore, as combustion resumes in all engine cylinders, the intake manifold temperature and engine temperature can continue to increase, and further increase in intake manifold temperature through hot exhaust gas recirculation may no longer be desirable. Therefore, at point 334, the EGR valve opening can be adjusted based on the EGR demand (engine dilution demand) and independently of the intake manifold temperature and ambient humidity. The controller can determine the EGR demand based on engine operating conditions, including engine load, engine speed, and engine temperature. In one example, the controller can determine the desired EGR flow based on calculations using a lookup table, where the inputs are each of engine load, engine speed, and engine temperature, and the output is the EGR flow.

[0064] In this way, in response to ambient humidity levels exceeding a threshold, each intake and exhaust valve coupled to one or more deactivated engine cylinders can be selectively closed during engine-off conditions, and the opening of the exhaust gas recirculation (EGR) valve coupled to the EGR passage can be adjusted based on the temperature of the residual exhaust gas. Furthermore, for engines equipped with glow plugs (such as diesel engines), during engine-off conditions, in response to humidity levels exceeding a threshold, the glow plugs can be activated to heat the engine intake manifold. Heating the engine intake manifold accelerates the evaporation of accumulated condensate and reduces further condensation formation.

[0065] Figure 4 An exemplary method 400 for shutting down an engine during high humidity conditions to reduce cylinder condensate intake is shown. Method 400 may be part of method 300 and may be performed, for example, in step 306 of method 300.

[0066] At position 302, you can search for results such as... Figure 3 Step 302 estimates the current vehicle and engine operating conditions. These conditions may include, for example, operator torque demand, engine speed, vehicle speed, engine temperature, engine load, exhaust temperature, manifold pressure, manifold airflow, battery state of charge, etc. Additionally, environmental conditions (such as ambient humidity, temperature, and atmospheric pressure) may be estimated.

[0067] At 404, the routine includes determining whether to request engine shutdown. In one example, this is done when one or more conditions for idling stop are met (such as in...). Figure 3When the engine is shut down (as discussed in step 304), an engine shutdown request can be made. In another example, in response to the accelerator pedal being released (causing a decrease in torque demand) resulting in a deceleration fuel shut-off (DFSO) condition, refueling and spark plugs can be disabled. In yet another example, when motor torque (from the HEV motor) is available to propel the vehicle and engine torque is no longer desired, an engine shutdown request can be made in response to a below-threshold torque demand. In yet another example, when the vehicle is stationary and neither engine torque nor motor torque is used to propel the vehicle, an engine shutdown request can be made in response to a vehicle cutoff.

[0068] If it is determined that no engine shutdown has been requested, then at 406, the current engine operation can be maintained. If it is determined that an engine shutdown has been requested, then at 408, the routine includes determining whether the ambient humidity is above a threshold humidity. The threshold humidity may be based on dew point temperature. In one example, the threshold humidity may correspond to a humidity level above which moisture from the air may condense in the engine intake manifold and / or inside the engine cylinders. In one example, the controller may retrieve weather conditions for the vehicle's expected driving cycle (travel path) from an external server communicatively coupled to the vehicle. The expected driving cycle may be determined based on input from the onboard GPS device. The routine may also include determining whether the ambient humidity may increase above the threshold humidity during any upcoming portion of the driving cycle.

[0069] If it is determined that the ambient humidity is below a threshold and will remain below the threshold throughout the driving cycle, at 410, the engine can be shut off without disabling (closing) the deactivated cylinder valves. If it is determined that the ambient humidity is above the threshold or is likely to increase above the threshold during the driving cycle, the deactivated exhaust valves can be preemptively closed to reduce the intake of air with high moisture content into the deactivated cylinders. Because the deactivated cylinders are sealed, puddles cannot form inside these cylinders even when the cylinder temperature decreases below the dew point temperature. At 412, the engine shutdown speed distribution can be adjusted to bring the engine to a desired engine stop position where the deactivated cylinder valves are closed, such as by stopping the deactivated cylinder pistons during the power stroke. As an example, the engine speed distribution can be adjusted by providing motor torque via one or more of the starter motor and HEV motor. In one example, if the engine speed is higher than the engine speed at which the desired engine stop position can be reached, negative torque can be applied to the engine to reduce the engine speed, so that the engine reaches the desired engine stop position when it stops.

[0070] The controller can first disable fueling and sparking for the deactivated cylinders, and then use motor torque (from the starter motor or HEV motor) to rotate the engine to bring it to a desired engine stop position. At the desired engine stop position, one or more camshafts coupled to the deactivated cylinder valves can be actuated to close the deactivated cylinder valves.

[0071] At 414, the routine includes determining whether an engine start request has been made. In one example, the engine start request may be made in response to pressing the accelerator pedal. In response to increased torque demand (such as during accelerator pedal depressing), the engine may no longer idle or operate in a DFSO state. Furthermore, the HEV motor may not be able to meet the increased torque demand, thus requesting engine torque. In another example, during vehicle operation using motor torque, the HEV motor's battery state of charge may decrease to below a threshold SOC, and the vehicle may no longer be propelled by motor torque. Therefore, during the period below the threshold battery SOC, engine operation (combustion) may be initiated to propel the vehicle with engine torque and recharge the motor. In yet another example, the engine start request may be in response to a request for engine power for operating auxiliary devices (such as the air conditioning system). In yet another example, when it is desired to operate (propel) the vehicle using engine torque after a period of vehicle stillness, the engine start request may be in response to a vehicle on request. If it is determined that no engine start request has been made, then at 416, the engine can be kept in a non-combustion state and the deactivation valve can be kept in a deactivated (closed) state.

[0072] If it is determined that an engine start (combustion) has been requested, then at 418, one or more previously deactivated (in step 412) deactivated engine cylinders can be reactivated via the VDE mechanism. Reactivation of a deactivated cylinder involves opening the previously deactivated intake and exhaust valves of the deactivated cylinder. The routine can then proceed to step 326 of method 300, as referenced. Figure 3 The subject of discussion.

[0073] In this way, during periods of ambient humidity above a threshold, in response to an engine shutdown request, fuel supply to each of the deactivated and non-deactivated cylinders can be disabled, and the engine shutdown speed distribution can be adjusted to stop the engine at the engine stop position where the deactivated cylinder valves are closed.

[0074] Figure 5 An exemplary operating sequence 500 is shown, illustrating the reduction of water buildup in the engine intake manifold and engine cylinders during an engine non-combustion condition. The horizontal (x-axis) represents time, and the vertical markers t1-t5 identify key times in the routines used to reduce water buildup and subsequent misfire.

[0075] The first curve (line 502) shows the position of the accelerator pedal. The second curve (line 504) shows the operation of the electric motor coupled to the hybrid electric vehicle (HEV). The third curve (line 506) shows the engine speed estimated based on input from a crankshaft acceleration sensor. The fourth curve (line 508) shows the ambient humidity estimated based on input from an ambient humidity sensor coupled to the engine intake manifold. Dashed line 509 shows the threshold humidity, above which water from the air can condense on engine components including the intake manifold and engine cylinders. The fifth curve (line 510) shows the exhaust temperature estimated based on input from an exhaust temperature sensor coupled to the exhaust passage. Dashed line 511 shows the threshold exhaust temperature, above which hot exhaust can be used to evaporate accumulated condensate and further reduce moisture condensation on engine components. The sixth curve (line 514) shows the engine intake manifold temperature estimated based on input from one or more of an intake air temperature sensor and an engine coolant temperature sensor. Dashed line 515 indicates the threshold intake manifold temperature, below which water from the air can condense on engine components including the intake manifold and engine cylinders. Curve 7 (line 516) shows the operation of a deactivated engine cylinder. Curve 8 (line 518) shows the refueling of a deactivated engine cylinder. Dashed line 519 shows the refueling of a non-deactivated cylinder. Curve 9 (line 520) shows the location of the exhaust gas recirculation (EGR) valve coupled to the EGR passage, which supplies exhaust gas from the exhaust port to the intake manifold.

[0076] Before time t1, during the accelerator pedal depressed state, engine torque is used to propel the vehicle, while the HEV motor is not operational. All engine cylinders, including those that can be deactivated, are active (e.g., each cylinder valve coupled to a deactivated cylinder is active), and fuel is delivered to each of the deactivated and non-deactivated cylinders. The EGR valve is open to supply the desired amount of EGR to the intake manifold based on engine dilution requirements. Due to combustion in the engine cylinders, the intake manifold temperature and exhaust manifold temperature remain above the corresponding thresholds 515 and 511. Furthermore, the ambient humidity is below the threshold humidity 509, thereby reducing concerns about moisture condensation on engine components.

[0077] At time t1, in response to the release of the accelerator pedal, a decrease in torque demand is inferred. Due to this reduced torque demand, the engine shuts off and the electric motor is activated to provide motor torque for vehicle propulsion. Between times t1 and t2, the motor torque provided by the electric motor is sufficient to propel the vehicle, where torque demand decreases and engine torque is no longer desired. With the engine off, fueling of each of the deactivated and non-deactivated cylinders is disabled, and the EGR valve is actuated to the fully closed position. Due to the cessation of combustion, no more heat is generated at the engine, and therefore, the intake manifold temperature gradually decreases between times t1 and t2.

[0078] At time t2, the intake manifold temperature decreases below threshold 515. As an example, threshold 515 can be calibrated before time t2 based on one or more of engine temperature and dew point temperature. Because the exhaust manifold has a larger thermal mass relative to the intake manifold, the exhaust manifold temperature remains above threshold 511 even though the intake temperature has decreased below threshold 515. Since combustion is not performed, exhaust gas can no longer be supplied. However, some residual exhaust gas from previous combustion events may remain in the exhaust passage, and during the engine's non-combustion state, the exhaust temperature refers to the temperature of the residual exhaust gas present in the exhaust manifold. As an example, threshold 515 can be calibrated before time t2 based on one or more of intake temperature, ambient humidity, dew point temperature, and engine temperature. Between time t2 and t3, ambient humidity remains below threshold 509, thus reducing the likelihood of moisture condensation on engine components. As an example, threshold 509 can be calibrated before time t2 based on dew point temperature. Between t2 and t3, the vehicle is propelled by motor torque from the HEV electric motor.

[0079] At time t3, the vehicle enters an area with ambient humidity above a threshold 509. In response to the increase in ambient humidity above the threshold 509 and due to the intake air temperature being below the threshold 515, it is deduced that humid air can enter the intake manifold and condense within the intake manifold and engine cylinders, thus initiating a routine to reduce condensate buildup. At time t3, the deactivated cylinders are selectively deactivated via valve actuation mechanisms coupled to them. Selective deactivation of the deactivated engine cylinders involves adjusting the engine position to engage one or more camshafts coupled to the deactivated cylinder valves for deactivating (closing) the deactivated cylinder valves (intake and exhaust valves). The engine rotates by motor torque supplied by the HEV motor until the camshafts are engaged and each valve coupled to the deactivated cylinder is closed. By closing the deactivated cylinder valves, moisture from the high-humidity ambient air entering the deactivated cylinders is reduced, thereby protecting the cylinders from condensate buildup.

[0080] Between times t3 and t4, since the exhaust temperature (the temperature of the residual exhaust) is higher than the threshold 511, it is inferred that the hot exhaust can be used to evaporate any condensate formed in the intake manifold and also to reduce further condensation of moisture in the intake manifold. Therefore, at time t3, the controller actuates the EGR valve to the fully open position to allow the hot exhaust and residue to recirculate from the exhaust manifold to the intake manifold. As the hot exhaust is introduced into the intake manifold, the temperature of the intake manifold steadily increases between times t3 and t4. In this way, by sealing the deactivated cylinders and directing the hot exhaust into the intake manifold, the likelihood of condensate buildup in the intake manifold, and at least inside the deactivated cylinders, is reduced.

[0081] In one example, between times t3 and t4, if the exhaust temperature is below threshold 511 (as shown by dotted line 512), exhaust cannot be recirculated because cold exhaust is not conducive to the evaporation of accumulated condensate from the intake manifold and further reduction of condensation of moist air. Therefore, when the exhaust temperature is below threshold 511 (as shown by dashed line 522), the EGR valve remains closed to reduce exhaust recirculation.

[0082] At time t4, in response to the depressing of the accelerator pedal, it is inferred that the torque demand increases and engine torque is required to meet the desired torque. Therefore, at time t4, the controller selectively activates the deactivated cylinder valve to initiate combustion in the deactivated cylinder. Fueling and sparking are restored for the deactivated cylinder, while fueling and sparking are deactivated for the non-deactivated cylinder, thereby keeping the non-deactivated cylinder in a non-combustion state. Since the deactivated cylinder is sealed between times t3 and t4, moisture accumulation in the deactivated cylinder has decreased during the conditions of ambient humidity above threshold 509 and intake air temperature below threshold 515. However, since the non-deactivated cylinder valve is not closed between times t3 and t4, water may have condensed inside the non-deactivated cylinder. By first restoring combustion in the non-deactivated cylinder and by keeping the non-deactivated cylinder unburned, the tendency for water intake that could cause misfires in the engine cylinders can be reduced. During the restoration of combustion, each of the engine intake and exhaust temperatures gradually increases. The engine operates with combustion in the deactivated cylinders and the non-deactivated cylinders kept unburned until the intake air temperature rises above a threshold of 515°C. Between times t4 and t5, the EGR valve remains fully open to direct hot exhaust gas into the intake manifold, thereby accelerating intake manifold heating. Once engine combustion resumes (in the deactivated cylinders), motor torque is no longer expected to propel the vehicle, and the motor is deactivated.

[0083] At time t5, the intake air temperature increases above the threshold 515, thereby reducing the likelihood of further condensation formation in the intake manifold. Furthermore, an intake air temperature above the threshold 515 may cause any remaining condensation to evaporate from the intake manifold. Because the likelihood of condensation formation in the intake manifold is reduced, at time t5, fuel injection and sparking are resumed to the non-discontinued cylinders, and after time t5, combustion is carried out in each of the discontinued and non-discontinued cylinders. Moreover, since further heating of the intake manifold is not desired, after time t5, the EGR valve position is adjusted based on EGR requirements and independently of exhaust and intake air temperatures.

[0084] In this way, by selectively sealing the deactivated engine cylinders during engine-off conditions when ambient humidity decreases below a threshold, the likelihood of water condensation in the deactivated engine cylinders is reduced. By resuming combustion first in the previously sealed deactivated engine cylinders during subsequent engine combustion events immediately following engine-off conditions, the engine can operate with reduced water ingestion potential and a lower tendency to misfire. The technical effect of recirculating hot exhaust gas to the intake manifold during engine-off conditions is that residual exhaust heat can be effectively used to increase engine intake air temperature and evaporate moisture entering the intake manifold, thereby reducing the likelihood of moisture condensation on engine components. In summary, by reducing water condensation on engine components (including the intake manifold and engine cylinders), combustion stability can be increased and the likelihood of misfire can be reduced during subsequent engine combustion conditions immediately following engine-off conditions.

[0085] An exemplary engine method includes: in response to ambient humidity exceeding a threshold, maintaining a deactivated cylinder valve closed during an engine non-combustion condition; and activating the deactivated cylinder valve during an immediately following engine combustion condition, and initiating combustion in the deactivated cylinder before combustion begins in an undeactivated cylinder. In any of the foregoing examples, additionally or optionally, maintaining the deactivated cylinder valve closed includes rotating the engine via an electric motor to engage one or more camshafts coupled to the deactivated cylinder valve for deactivating the deactivated cylinder valve while keeping the undeactivated cylinder valve in an activated state. In any or all of the foregoing examples, additionally or optionally, initiating combustion in the deactivated cylinder includes injecting fuel and providing a spark to the deactivated cylinder for a threshold number of engine cycles immediately following the activation of the deactivated cylinder valve, while fuel injection and spark ignition are disabled in the undeactivated cylinder. In any or all of the foregoing examples, additionally or optionally, initiating combustion in the non-disposable cylinder includes, after the threshold number of engine cycles, injecting fuel and providing a spark into the non-disposable cylinder while maintaining the ability to fuel and ignite in the disposable cylinder, wherein the threshold number of engine cycles is based on the intake manifold temperature, and the threshold number decreases as the engine intake temperature increases. In any or all of the foregoing examples, the method further includes, additionally or optionally, during the engine non-combustion condition, adjusting an EGR valve coupled to an exhaust gas recirculation (EGR) passage in response to a residual exhaust gas temperature in the engine exceeding a threshold temperature, so that the residual exhaust gas is recirculated from the engine exhaust manifold to the intake manifold through the EGR passage. In any or all of the foregoing examples, additionally or optionally, adjusting the EGR valve includes increasing the opening of the EGR valve as the temperature of the residual exhaust gas increases, the ambient humidity increases, or the intake manifold temperature decreases. In any or all of the foregoing examples, additionally or optionally, the engine is coupled to the vehicle, and the ambient humidity is measured by one or more of an intake air humidity sensor, a windshield humidity sensor, and weather data, the weather data including ambient humidity conditions retrieved wirelessly from an external network communicatively coupled to the vehicle. In any or all of the foregoing examples, additionally or optionally, the vehicle is a hybrid vehicle that also includes an electric motor coupled to a battery, and wherein the subsequent engine combustion conditions respond to a state of charge below a threshold of the battery or an operator torque demand above a threshold.In any or all of the foregoing examples, the method further includes, additionally or optionally, disabling fuel supply to each of the deactivated and non-deactivated cylinders in response to an engine shutdown request during the above-threshold ambient humidity period; and adjusting the engine shutdown speed distribution to stop the engine at an engine stop position where the deactivated cylinder valve is closed. In any or all of the foregoing examples, additionally or optionally, adjusting the engine speed distribution includes rotating the engine via one of the starter motors or electric motors of the hybrid vehicle. In any or all of the foregoing examples, additionally or optionally, the threshold ambient humidity is calibrated based on an estimated dew point temperature.

[0086] Another exemplary engine method includes: selectively closing each intake and exhaust valve coupled to one or more deactivated engine cylinders during an engine-off state in response to ambient humidity above a threshold, and adjusting the opening of an exhaust gas recirculation (EGR) valve coupled to an EGR passage based on the temperature of the residual exhaust gas. In any of the foregoing examples, additionally or optionally, adjusting the opening of the EGR valve includes increasing the opening in response to a residual exhaust gas temperature above a threshold as the intake manifold temperature decreases and the ambient humidity increases, and decreasing the opening in response to an increase in the intake manifold temperature and a decrease in the ambient humidity; and closing the EGR valve in response to a residual exhaust gas temperature below a threshold. In any or all of the foregoing examples, the method further includes, additionally or optionally, enabling each intake and exhaust valve coupled to the one or more deactivated engine cylinders immediately following a subsequent engine restart; and resuming fueling of the one or more deactivated cylinders while keeping the non-deactivated cylinders of the engine unfueled. In any or all of the foregoing examples, the method further includes, additionally or optionally, resuming fueling of the one or more non-disabled cylinders in response to the intake manifold temperature increasing above a threshold temperature, while maintaining the non-disabled cylinders being fueled, and adjusting the opening of the EGR valve based on engine dilution requirements. In any or all of the foregoing examples, additionally or optionally, the engine shutdown condition includes one of an idle-stop condition, a deceleration fuel cut-off condition, and an engine shutdown event.

[0087] In yet another example, a hybrid vehicle system includes: an electric motor including a battery; an engine having deactivated cylinders and non-deactivated cylinders; each of an intake valve and an exhaust valve coupled to the deactivated cylinders, each of the intake valves and the exhaust valves being selectively actuated by a variable displacement engine (VDE) actuator; each of another intake valve and another exhaust valve coupled to the non-deactivated cylinders; one or more fuel injectors coupled to each of the deactivated cylinders and the non-deactivated cylinders; an ambient humidity sensor and an intake air temperature sensor coupled to the engine intake manifold; an exhaust air temperature sensor coupled to the exhaust manifold; a rain sensor coupled to the vehicle's windshield wipers; and the engine exhaust manifold coupled to the engine intake manifold. The manifold includes an exhaust gas recirculation (EGR) passage comprising an EGR valve; and a controller having computer-readable instructions stored in a non-transitory memory for: estimating ambient humidity via one or more of the ambient humidity sensor and the rain sensor; in response to a first engine off condition, actuating the VDE actuator to selectively close the intake and exhaust valves of the deactivated cylinders while keeping the other intake and exhaust valves of the non-deactivated cylinders open before disabling fuel in the engine; and in response to a second engine off condition, keeping the intake and exhaust valves of the deactivated cylinders and the other intake and exhaust valves of the non-deactivated cylinders open before disabling fuel in the engine. In any of the foregoing examples, additionally or optionally, the ambient humidity during the first engine off condition is higher than the ambient humidity during the second engine off condition. In any of the foregoing examples, additionally or optionally, the controller includes further instructions for: in response to a subsequent engine restart condition, actuating the VDE actuator to selectively re-enable the intake and exhaust valves of the deactivated cylinders and initiating fuel injection into the deactivated cylinders while keeping fuel injection deactivated for the non-deactivated cylinders; and immediately after initiating fuel injection into the deactivated cylinders, operating the deactivated cylinders with fuel injection and operating the non-deactivated cylinders without fuel injection for a threshold number of engine cycles, resuming fuel injection into each engine cylinder including the non-deactivated cylinders. In any of the foregoing examples, additionally or optionally, the controller includes further instructions for: estimating the temperature of residual exhaust gas via the exhaust gas temperature sensor; actuating the EGR valve to an open position in response to an exhaust gas temperature above a threshold temperature when the vehicle is propelled by the motor, so as to guide the residual exhaust gas from the exhaust manifold to the intake manifold through the EGR passage; and maintaining the EGR valve closed in response to an exhaust gas temperature below a threshold temperature when the vehicle is propelled by the motor.In any of the foregoing examples, additionally or optionally, the controller includes further instructions for adjusting the opening of the EGR valve based on each of the following when the vehicle is propelled by the motor: the exhaust temperature, the ambient humidity, and the engine intake manifold temperature estimated by the intake air temperature sensor.

[0088] It should be noted that the exemplary control and estimation routines included herein can be used with various engine and / or vehicle system configurations. The control methods and routines disclosed herein can be stored as executable instructions in non-transitory memory and can be executed by a control system including controllers combined with various sensors, actuators, and other engine hardware. The specific routines described herein can represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, etc. Therefore, the various actions, operations, and / or functions shown can be executed in the order shown, in parallel, or in some cases omitted. Similarly, the order of processing is not necessary to achieve the features and advantages of the exemplary embodiments described herein, but is provided for ease of illustration and description. Depending on the specific strategy used, one or more of the actions, operations, and / or functions shown can be repeatedly executed. Furthermore, the described actions, operations, and / or functions can be graphically represented as code to be programmed into a non-transitory memory of a computer-readable storage medium in an engine control system, wherein the described actions are executed by executing instructions in a system including various engine hardware components combined with electronic controllers.

[0089] It should be understood that the configurations and routines disclosed herein are exemplary in nature, and these specific embodiments should not be considered limiting, as many variations are possible. For example, the above-described techniques can be applied to V-6, I-4, I-6, V-12, opposed 4-cylinder, and other engine types. The subject matter of this disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations disclosed herein, as well as other features, functions, and / or performance characteristics.

[0090] The appended claims specifically point to certain combinations and sub-combinations that are considered novel and non-obvious. These claims may refer to a "one" element or a "first" element or its equivalent. Such claims should be understood to include combinations of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and / or properties may be claimed by amending these claims or by setting new claims in this application or related applications. Such claims, whether broader, narrower, equal to, or different in scope from the original claims, are considered to be included within the subject matter of this disclosure.

Claims

1. An engine method comprising: In response to humidity levels exceeding the ambient humidity threshold, During engine non-combustion conditions, the cylinder valves of deactivated cylinders are kept closed, said cylinder valves including intake and exhaust valves; and During the subsequent engine combustion conditions, the cylinder valve of the deactivated cylinder is activated, and combustion begins in the deactivated cylinder before combustion begins in the non-deactivated cylinder.

2. The method of claim 1, wherein keeping the cylinder valve of the deactivated cylinder closed comprises rotating the engine by an electric motor to engage one or more camshafts coupled to the cylinder valve of the deactivated cylinder for deactivating the cylinder valve of the deactivated cylinder, while keeping the cylinder valve of the non-deactivated cylinder in the activated state.

3. The method of claim 1, wherein initiating combustion in the deactivated cylinder comprises, for a threshold number of engine cycles of activation of the cylinder valve immediately following the deactivated cylinder, injecting fuel and providing a spark into the deactivated cylinder while maintaining fuel injection and spark disabling in the non-deactivated cylinder.

4. The method of claim 3, wherein initiating combustion in the non-discontinued cylinder comprises, after the threshold number of engine cycles, injecting fuel and providing a spark into the non-discontinued cylinder while maintaining the ability to fuel and ignite in the discontinued cylinder, wherein the threshold number of engine cycles is based on an intake manifold temperature, the threshold number decreasing as the intake manifold temperature increases.

5. The method of claim 4, further comprising, during the engine non-combustion condition, adjusting an EGR valve coupled to the exhaust gas recirculation passage, i.e., the EGR passage, in response to residual exhaust gas in the engine being above a temperature threshold, so that the residual exhaust gas is recirculated from the engine exhaust manifold to the intake manifold through the EGR passage.

6. The method of claim 5, wherein adjusting the EGR valve comprises increasing the opening of the EGR valve as the temperature of the residual exhaust gas increases, the ambient humidity increases, or the intake manifold temperature decreases.

7. The method of claim 1, wherein the engine is coupled to the vehicle, and wherein the ambient humidity is measured by one or more of an intake humidity sensor, a windshield humidity sensor, and weather data, the weather data including ambient humidity conditions retrieved wirelessly from an external network communicatively coupled to the vehicle.

8. The method of claim 7, wherein the vehicle is a hybrid vehicle further comprising an electric motor coupled to the battery, and wherein the subsequent engine combustion condition responds to a state of charge threshold below the battery or a torque demand threshold above the operator's demand threshold.

9. The method of claim 8, further comprising: During the period above the ambient humidity threshold, In response to the engine shutdown request, Disable fueling to each of the deactivated cylinders and the non-deactivated cylinders; as well as Adjust the engine shutdown speed distribution so that the engine stops at the engine stop position where the cylinder valve of the deactivated cylinder is closed.

10. The method of claim 9, wherein adjusting the engine speed distribution comprises rotating the engine via one of the starter motor of the hybrid vehicle or the electric motor.

11. The method of claim 1, wherein the ambient humidity threshold is calibrated based on the estimated dew point temperature.

12. A hybrid vehicle system comprising: Motors including batteries; An engine with both deactivated and non-deactivated cylinders; Each of the intake and exhaust valves coupled to the deactivated cylinder is selectively actuated by a variable displacement engine actuator, i.e., a VDE actuator. Coupled to each of the other intake valve and the other exhaust valve of the said non-disabled cylinder; One or more fuel injectors coupled to each of the deactivated cylinder and the non-deactivated cylinder; An ambient humidity sensor and an intake air temperature sensor are coupled to the engine intake manifold. An exhaust temperature sensor coupled to the exhaust manifold; A rain sensor coupled to the vehicle's windshield wipers; The engine exhaust manifold is coupled to the exhaust gas recirculation (EGR) passage of the engine intake manifold, the EGR passage including an EGR valve; and The controller has computer-readable instructions stored in non-transitory memory, the instructions being used for: The ambient humidity is estimated by one or more of the ambient humidity sensor and the rain sensor; In response to a first engine off condition, before fuel is disabled from the engine, the VDE actuator is actuated to selectively close the intake and exhaust valves of the deactivated cylinder, while keeping the other intake and exhaust valves of the non-deactivated cylinder open; and In response to a second engine off state, the intake and exhaust valves of the deactivated cylinder and the other intake and exhaust valves of the non-deactivated cylinder remain open before fuel is disabled from the engine. The ambient humidity during the first engine off state is higher than the ambient humidity during the second engine off state.

13. The system of claim 12, wherein the controller includes further instructions for: in response to an immediate subsequent engine restart condition, actuating the VDE actuator to selectively re-enable the intake and exhaust valves of the deactivated cylinders and initiating fuel injection into the deactivated cylinders while keeping fuel injection deactivated for the non-deactivated cylinders; and immediately after initiating fuel injection into the deactivated cylinders, after operating the deactivated cylinders with fuel injection and operating the non-deactivated cylinders without fuel injection for a threshold number of engine cycles, resuming fuel injection into each engine cylinder including the non-deactivated cylinders.

14. The system of claim 12, wherein the controller includes further instructions for: The temperature of the residual exhaust gas is estimated using the exhaust gas temperature sensor. When the vehicle is propelled by the motor, in response to an exhaust temperature exceeding a threshold, the EGR valve is actuated to the open position to guide residual exhaust gas from the exhaust manifold to the intake manifold through the EGR passage; and When the vehicle is propelled by the motor, the EGR valve remains closed in response to temperatures below the exhaust temperature threshold.

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