System and method for reducing engine overheating using liquid fuel

Abstract

The present disclosure provides a system and method for reducing engine overheating using liquid fuel. Systems and methods are provided for cooling an overheating engine using a combination of variable displacement engine (VDE) technology and direct injection technology. In one example, a method may include deactivating a subset of engine cylinders based on engine temperature and injecting liquid fuel directly into the deactivated cylinders. In this way, the increased thermal conductivity of liquid fuel compared to air reduces engine temperature at a faster rate than using air-based engine cooling methods, thereby preventing overheat-related engine degradation.

Description

Technical Field

[0001] The present description generally relates to methods and systems for increasing the cooling rate of an overheated variable displacement engine.

[0002] Background Art / Summary of the Invention

[0003] The vehicle may include a coolant system configured to reduce engine overheating by transferring heat to the ambient air. The coolant is circulated through the engine (e.g., through the engine block), where heat is transferred from the hot engine to the coolant, and then circulated through a radiator near the front of the vehicle, where heat is transferred from the coolant to the ambient air. The heated coolant may also be circulated through a heat exchanger to heat the passenger compartment. The coolant system may include various components, such as various valves, a pump, and one or more thermostats.

[0004] Various methods have been developed to address engine overheating in the event of coolant system degradation. Willard et al. present an exemplary method in US Pat. No. 9,217,379. Disclosed therein is a method for addressing engine overheating by alternately shutting off fuel to one or more cylinders while maintaining vehicle torque demand with fueled cylinders. In yet other examples, the engine can be cooled bank-wise, shutting off fuel to each cylinder of a first bank to cool the first bank while delivering fuel to each cylinder of a second bank to continue generating torque for vehicle propulsion.

[0005] However, the inventors herein have recognized potential problems with such systems. As an example, while heat can be transferred from a hot engine to the cool air flowing through unfueled cylinders, air is a poor conductor of heat. Additionally, high engine compartment temperatures can be exacerbated on hot days, which can increase the temperature of the air pumped through the engine.

[0006] In addition, the inventors herein have recognized that a combination of variable displacement engine (VDE) technology and direct injection technology can be used to cool the engine. A variable displacement engine is configured to operate with a variable number of active or deactivated cylinders to improve fuel economy. For example, a portion of the cylinders can be deactivated during selected conditions (such as during periods of low engine torque demand). The control system can selectively deactivate the cylinders via multiple cylinder valve deactivators, thereby sealing the deactivated cylinders by keeping the intake and exhaust valves of the deactivated cylinders closed. Typically, the deactivated cylinders are not refueled. However, the inventors herein have recognized that liquid fuel has a higher thermal conductivity than air, which can increase the engine cooling rate compared to air. Additionally, the change in state of the liquid fuel as it vaporizes in the deactivated cylinders can further improve engine cooling.

[0007] In one example, this problem can be addressed by a method that includes deactivating a subset of cylinders in a multi-cylinder engine based on the engine's temperature and injecting fuel directly into each subset of cylinders during the deactivation period. In this way, an overheated engine can be cooled with liquid fuel, thereby increasing the cooling rate compared to when the engine is cooled with air.

[0008] As an example, deactivating a subset of engine cylinders includes maintaining closed the intake and exhaust valves coupled to each subset of engine cylinders. In this way, each subset of engine cylinders is sealed. By injecting fuel directly into the sealed cylinders, the fuel will remain in the sealed cylinders until the corresponding intake and exhaust valves are reactivated and opened. In addition, the spark plugs coupled to each subset of engine cylinders can be disabled so that no spark is provided and combustion does not occur in each subset of engine cylinders. Liquid fuel can be injected into the sealed cylinders at multiple piston positions to coat various cylinder surfaces (e.g., top, bottom, and walls) and stirred within the sealed cylinders by the pistons, thereby absorbing heat from the hot cylinder surfaces. After the liquid fuel vaporizes (e.g., after stirring for a period of time), the intake and exhaust valves of each subset of engine cylinders can be opened to expel the vaporized unburned fuel. The process of deactivating a subset of engine cylinders and injecting fuel directly into each subset of engine cylinders during deactivation can be repeated until the engine is sufficiently cooled (e.g., the engine temperature is below a threshold temperature). Furthermore, cooling the engine with liquid fuel can be combined with an air cooling method, where the cooling method is selected based on operating conditions for greater flexibility. By utilizing VDE technology to deactivate and seal a subset of engine cylinders and injecting liquid fuel directly into them, the engine can be cooled at a faster rate than using airflow through the engine, thereby preventing engine overheating-related degradation.

[0009] It should be understood that the foregoing summary is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is uniquely defined by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 A schematic diagram of an exemplary vehicle system is shown.

[0011] Figure 2 An example of a compound supercharging engine system with a multi-stage intake air compression device and an engine cooling system is shown.

[0012] Figure 3 A high-level flow chart is shown of an exemplary method for cooling an overheated engine via intake airflow or liquid fuel injection based on operating conditions.

[0013] Figure 4 An exemplary method for cooling an overheated engine by electrically spinning the engine and providing airflow via an electric supercharger while the engine is shut down is shown.

[0014] Figure 5 An exemplary method for using intake airflow to cool an overheated engine while selectively inhibiting cylinder fueling is shown.

[0015] Figure 6 An exemplary method for cooling an overheated engine by selectively deactivating a subset of cylinders and injecting liquid fuel into the subset of cylinders is shown.

[0016] Figure 7 An exemplary timeline for predicting cooling an overheated engine using a combination of intake airflow and liquid fuel injection based on operating conditions is shown. DETAILED DESCRIPTION

[0017] The following description relates to a method for cooling an overheated engine in a vehicle system such as Figure 1 and Figure 2 Specifically, the engine controller may be configured to execute a control program (such as Figure 3 ) to select between using intake airflow to cool the engine while operating in VDE mode and using liquid fuel to cool the engine while operating in VDE mode based on, for example, operating conditions and cooling needs. When the engine is off, such as when the vehicle is turned off or during an idle stop, such as based on Figure 4 An exemplary method of the invention can use intake airflow to cool the engine by electrically spinning the engine and providing airflow via an electric supercharger. Figure 5 An exemplary method of may cool the engine with intake airflow while disabling fueling of one or more cylinders in a distributed manner. If the intake airflow is insufficient to cool the engine, such as when the engine temperature continues to increase (e.g., at a rate greater than a threshold rate) or when the engine is severely overheated (e.g., the engine temperature is greater than a higher threshold), then a method such as based on Figure 6 An exemplary method may use liquid fuel to cool the engine while operating in VDE mode. Figure 7 An exemplary overheat engine cooling operation is shown.

[0018] Turning now to the accompanying drawings, Figure 1An example of cylinder 14 of internal combustion engine 10 is depicted, which may be included in vehicle 5 . Engine 10 may be a variable displacement engine (VDE), as described further below. Engine 10 may be controlled at least partially by a control system including controller 12 and input from a vehicle operator 130 via an input device 132 . In this example, input device 132 includes an accelerator pedal and a pedal position sensor 134 for generating a proportional pedal position signal PP. Cylinder 14 of engine 10 (also referred to herein as a "combustion chamber") may include combustion chamber walls 136 with a piston 138 positioned therein. Piston 138 may be coupled to a crankshaft 140 such that reciprocating motion of the piston is translated into rotational motion of the crankshaft. Crankshaft 140 may be coupled to at least one wheel 55 of the vehicle via a transmission 54, as described further below. Furthermore, a starter motor (not shown) may be coupled to crankshaft 140 via a flywheel to enable starting of engine 10.

[0019] In some examples, vehicle 5 may be a hybrid vehicle having multiple torque sources available to one or more wheels 55. In other examples, vehicle 5 is a conventional vehicle having only an engine or an electric vehicle having only one or more electric motors. In the illustrated example, vehicle 5 includes engine 10 and electric motor 52. Electric motor 52 may be a motor or a motor / generator. When one or more clutches 56 are engaged, crankshaft 140 of engine 10 and electric motor 52 are connected to wheels 55 via transmission 54. In the depicted example, a first clutch 56 is disposed between crankshaft 140 and electric motor 52, while a second clutch 56 is disposed between electric motor 52 and transmission 54. Controller 12 may send signals to the actuator of each clutch 56 to engage or disengage the clutch, thereby connecting or disconnecting crankshaft 140 from electric motor 52 and components connected thereto, and / or connecting or disconnecting electric motor 52 from transmission 54 and components connected thereto. Transmission 54 may be a gearbox, a planetary gear system, or another type of transmission.

[0020] The powertrain system can be configured in various ways, including parallel, series, or series-coupled hybrid vehicles. In an electric vehicle embodiment, the system battery 58 can be a traction battery that delivers power to the motor 52 to provide torque to the wheels 55. In some embodiments, the motor 52 can also be used as a generator to provide power to charge the system battery 58, such as during braking operations. It should be understood that in other embodiments, including non-electric vehicle embodiments, the system battery 58 can be a typical starting, lighting, and ignition (SLI) battery coupled to the alternator 46.

[0021] The alternator 46 can be configured to charge the system battery 58 using engine torque via the crankshaft 140 during engine operation. Additionally, the alternator 46 can power one or more electrical systems of the engine, such as one or more auxiliary systems (including a heating, ventilation, and air conditioning (HVAC) system, lights, an in-vehicle entertainment system, and other auxiliary systems) based on their corresponding electrical demands. In one example, the current drawn on the alternator can be continuously varied based on each of cabin cooling requirements, battery charging requirements, other auxiliary vehicle system demands, and motor torque. A voltage regulator can be coupled to the alternator 46 to adjust the alternator's electrical output based on system usage requirements, including auxiliary system demands.

[0022] Cylinder 14 of engine 10 can receive intake air via a series of intake passages 142 and 144 and an intake manifold 146. Intake manifold 146 can also communicate with other cylinders of engine 10 in addition to cylinder 14. One or more intake passages may include one or more boosting devices, such as a turbocharger or supercharger. For example, Figure 1 Engine 10 is shown configured with a turbocharger including a compressor 174 disposed between intake passages 142 and 144 and an exhaust turbine 176 disposed along exhaust passage 135. When the boosting device is configured as a turbocharger, compressor 174 may be at least partially powered by exhaust turbine 176 via shaft 180. However, in other examples, such as when engine 10 is provided with a supercharger, compressor 174 may be powered by a mechanical input from a motor or the engine, and exhaust turbine 176 may optionally be omitted. In still other examples, engine 10 may be provided with an electric supercharger (e.g., an "eBooster"), and compressor 174 may be driven by an electric motor. As will be seen in FIG. Figure 2 As described, engine 10 may be configured with a dual-stage compound charging system (including a turbocharger and an electric supercharger) to overcome lag time while the turbocharger rotates in response to driver torque demand. As further described herein, the electric supercharger may also operate to cool an overheated engine.

[0023] A throttle 162 including a throttle plate 164 may be positioned in the engine intake passage to vary the flow rate and / or pressure of intake air provided to the engine cylinders. For example, throttle 162 may be positioned downstream of compressor 174, such as Figure 1 As shown in , or alternatively may be located upstream of compressor 174 .

[0024] Exhaust manifold 148 may receive exhaust gases from other cylinders of engine 10 in addition to cylinder 14. Exhaust gas sensor 126 is shown coupled to exhaust manifold 148 upstream of emission control device 178. Exhaust gas sensor 126 may be selected from a variety of suitable sensors for providing an indication of exhaust air-fuel ratio (AFR), such as, for example, a linear oxygen sensor or UEGO (universal or wide-range exhaust gas oxygen sensor), a two-state oxygen sensor or EGO, a HEGO (heated EGO), nitrogen oxides (NOx), hydrocarbons (HC), or carbon monoxide (CO) sensors. Figure 1 In the example shown, exhaust gas sensor 126 is a UEGO sensor. Emission control device 178 may be a three-way catalyst, a NOx trap, various other emission control devices, or a combination thereof. Figure 1 In the example shown, emission control device 178 is a three-way catalyst.

[0025] Each cylinder of engine 10 may include one or more intake valves and one or more exhaust valves. For example, cylinder 14 is shown as including at least one intake poppet valve 150 and at least one exhaust poppet valve 156 located at an upper region of cylinder 14. In some examples, each cylinder of engine 10, including cylinder 14, may include at least two intake poppet valves and at least two exhaust poppet valves located at an upper region of the cylinder. Intake valve 150 may be controlled by controller 12 via actuator 152. Similarly, exhaust valve 156 may be controlled by controller 12 via actuator 154. The positions of intake valve 150 and exhaust valve 156 may be determined by respective valve position sensors (not shown).

[0026] During certain conditions, controller 12 may vary the signals provided to actuators 152 and 154 to control the opening and closing of the corresponding intake and exhaust valves. The valve actuators may be electric valve actuation, cam actuation, or a combination thereof. Both intake and exhaust valve timing may be controlled simultaneously, or any of variable intake cam timing, variable exhaust cam timing, dual independent variable cam timing, or fixed cam timing may be employed. Each cam actuation system may include one or more cams and may utilize one or more of a variable displacement engine (VDE), a cam profile switching system (CPS), variable cam timing (VCT), variable valve timing (VVT), and / or variable valve lift (VVL) system, which may be operated by controller 12 to vary valve operation. For example, cylinder 14 may alternatively include an intake valve controlled via electric valve actuation and an exhaust valve controlled via cam actuation (including CPS and / or VCT). In other examples, 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).

[0027] In one example, intake valve 150 and exhaust valve 156 can be deactivated during VDE mode via hydraulically actuated tappets coupled to valve pushrods or via a CPS mechanism in which cam lobes without lift are used for the deactivated valves. Other valve deactivation mechanisms may also be used, such as, for example, mechanisms for electrically actuated valves. In one embodiment, deactivation of intake valve 150 may be controlled by a first VDE actuator, while deactivation of exhaust valve 156 may be controlled by a second VDE actuator. In alternative embodiments, a single VDE actuator may control deactivation of both the intake and exhaust valves of a cylinder. In yet other embodiments, a single cylinder valve actuator deactivates multiple cylinders (both intake and exhaust valves), such as all cylinders in an engine bank, or different actuators may control deactivation of all intake valves while another different actuator controls deactivation of all exhaust valves of the deactivated cylinders. It should be understood that if the cylinder is a non-deactivatable cylinder of a VDE engine, the cylinder may not have any valve deactivation actuator.

[0028] Cylinder 14 can have a compression ratio, which is the ratio of volumes when piston 138 is at bottom dead center (BDC) to top dead center (TDC). In one example, the compression ratio is in the range of 9:1 to 10:1. However, in some examples using different fuels, the compression ratio can be increased. This can occur, for example, when using a higher octane fuel or a fuel with a higher latent enthalpy of vaporization. The compression ratio can also be increased if direct injection is used due to its effect on engine knock.

[0029] Each cylinder of engine 10 may include a spark plug 192 for initiating combustion. In a selected operating mode, ignition system 190 may provide an ignition spark to combustion chamber 14 via spark plug 192 in response to a spark advance signal SA from controller 12. The timing of signal SA may be adjusted based on engine operating conditions and driver torque demand. For example, the spark may be provided at maximum brake torque (MBT) timing to maximize engine power and efficiency. Controller 12 may input engine operating conditions (including engine speed, engine load, and exhaust gas AFR) into a lookup table and output a corresponding MBT timing for the input engine operating conditions. In other examples, the spark may be retarded from MBT, such as to accelerate catalyst warm-up or reduce the occurrence of engine knock during engine startup.

[0030] In some examples, each cylinder of engine 10 may be configured with one or more fuel injectors for providing fuel thereto. As a non-limiting example, cylinder 14 is shown as including fuel injector 166. Fuel injector 166 may be configured to deliver fuel received from fuel system 8. Fuel system 8 may include one or more fuel tanks, fuel pumps, and a fuel rail. Fuel injector 166 is shown directly coupled to cylinder 14 for injecting fuel directly therein in proportion to the pulse width of signal FPW received from controller 12 via electronic driver 168. In this manner, fuel injector 166 provides what is known as direct injection of fuel (hereinafter also referred to as "DI") into cylinder 14. Although Figure 1 Fuel injector 166 is shown located on the side of cylinder 14, but may alternatively be located on top of the piston, such as near spark plug 192. Due to the lower volatility of some alcohol-based fuels, such a location may improve mixing and combustion when the engine is operated on alcohol-based fuels. Alternatively, the injector may be located on top and near the intake valve to improve mixing. Fuel may be delivered to fuel injector 166 from a fuel tank of fuel system 8 via a high-pressure fuel pump and a fuel rail. The fuel tank may also have a pressure sensor that provides a signal to controller 12.

[0031] In an alternative example, fuel injector 166 may be configured to be located in an intake port rather than being directly coupled to cylinder 14, providing so-called port injection (hereinafter also referred to as "PFI") of fuel into the intake port upstream of cylinder 14. In other examples, cylinder 14 may include multiple injectors, which may be configured as direct fuel injectors, port fuel injectors, or a combination thereof. Thus, it should be understood that the fuel system described herein should not be limited to the specific fuel injector configurations described herein by way of example.

[0032] Fuel injector 166 can be configured to receive different fuels from fuel system 8 as a fuel mixture in different relative quantities and further configured to inject the fuel mixture directly into the cylinder. In addition, fuel can be delivered to cylinder 14 during different strokes of a single cycle of the cylinder. For example, the directly injected fuel can be delivered at least partially during the previous exhaust stroke, during the intake stroke, and / or during the compression stroke. Thus, for a single combustion event, one or more fuel injections can be performed per cycle. Multiple injections can be performed during the compression stroke, the intake stroke, or any suitable combination thereof, which is referred to as split fuel injection. In addition, liquid fuel can be injected into the deactivated cylinder at multiple piston positions while operating in VDE mode to cool the cylinder, as will be described with reference to FIG. Figure 6 described.

[0033] The fuel tank in the fuel system 8 can accommodate fuels of different fuel types, such as fuels with different fuel qualities and different fuel compositions. The differences can include different alcohol contents, different water contents, different octane numbers, different heats of vaporization, different fuel mixtures and / or combinations thereof. An example of fuels with different heats of vaporization includes gasoline as a first fuel type with a lower heat of vaporization, and includes ethanol as a second fuel type with a larger heat of vaporization. In another example, the engine can use gasoline as the first fuel type and use an alcohol-containing fuel mixture (such as E85 (approximately 85% ethanol and 15% gasoline) or M85 (approximately 85% methanol and 15% gasoline)) as the second fuel type. Other feasible substances include water, methanol, a mixture of alcohol and water, a mixture of water and methanol, a mixture of alcohol, etc. In another example, both fuels can be alcohol mixtures with different alcohol compositions, wherein the first fuel type can be a gasoline alcohol mixture with a lower alcohol concentration, such as E10 (approximately 10% ethanol), and the second fuel type can be a gasoline alcohol mixture with a higher alcohol concentration, such as E85 (approximately 85% ethanol). Additionally, the first and second fuels may also differ in other fuel qualities, such as differences in temperature, viscosity, octane rating, etc. Furthermore, the fuel characteristics of one or both fuel tanks may vary frequently, for example due to daily variations in fuel tank refilling.

[0034] The controller 12 Figure 11 is shown as a microcomputer that includes a microprocessor unit 106, input / output ports 108, an electronic storage medium for executable programs (e.g., executable instructions) and calibration values ​​(shown in this particular example as a non-transitory read-only memory chip 110), random access memory 112, keep alive memory 114, and a data bus. Controller 12 may receive various signals from sensors coupled to engine 10, including the previously discussed signals and additionally including a measurement of intake mass air flow (MAF) from mass air flow sensor 122; engine coolant temperature (ECT) from temperature sensor 116 coupled to cooling jacket 118; exhaust temperature from temperature sensor 158 coupled to exhaust passage 135; a surface ignition probe (PIP) signal from Hall effect sensor 120 (or other type of sensor) coupled to crankshaft 140; throttle position (TP) from a throttle position sensor; signal UEGO from exhaust gas sensor 126, which may be used by controller 12 to determine exhaust gas AFR; and manifold pressure absolute signal (MAP) from MAP sensor 124. Controller 12 may generate engine speed signal RPM from signal PIP. Manifold pressure signal MAP from MAP sensor 124 may be used to provide an indication of vacuum, or pressure, in the intake manifold. Controller 12 may infer engine temperature based on engine coolant temperature and the temperature of emission control device 178 based on signals received from temperature sensor 158 .

[0035] The controller 12 Figure 1 Various sensors receive signals and use Figure 1 The controller may control various actuators to adjust engine operation based on the received signals and instructions stored in the controller's memory. For example, the controller may switch the engine to VDE mode by actuating valve actuators 152 and 154 to deactivate selected cylinders and inject liquid fuel into selected cylinders (e.g., via fuel injector 166) based on signal ECT measured by engine coolant temperature sensor 116, as will be described with reference to FIG. Figure 6 Further description.

[0036] As mentioned above, Figure 1 Only one cylinder of a multi-cylinder engine is shown. Thus, each cylinder may similarly include its own set of intake / exhaust valves, one or more fuel injectors, spark plugs, etc. It should be appreciated that engine 10 may include any suitable number of cylinders, including 2, 3, 4, 5, 6, 8, 10, 12, or more cylinders. Furthermore, each of these cylinders may include a Figure 1 Some or all of the various components described and depicted with reference to cylinder 14 .

[0037] During selected conditions, such as when the full torque capability of engine 10 is not requested, controller 12 can select one of the first or second cylinder groups for deactivation (also referred to herein as a VDE operating mode). During VDE mode, cylinders of the selected cylinder group can be deactivated by shutting off the corresponding fuel injectors 166 and deactivating the corresponding intake valves 150 and exhaust valves 156. When the fuel injectors of the disabled cylinders are turned off, the remaining enabled cylinders continue to combust, with the corresponding fuel injectors and intake and exhaust valves active and operating. To meet the torque demand, the engine produces the same amount of torque in the remaining active cylinders as it would if all cylinders were combusting. This requires a higher manifold pressure, resulting in reduced pumping losses and improved engine efficiency. Additionally, the lower effective surface area exposed to combustion (from only the active cylinders) reduces engine heat losses, thereby improving the thermal efficiency of the engine.

[0038] Next, Figure 2 Aspects of an exemplary engine system 100 that may be coupled to a vehicle 5 and includes an engine 10 are schematically shown. Figure 2 described and has reference to Figure 1 Parts with the same identification labels as those described above are the same parts and can function as previously described. In addition, some parts may not be reintroduced. In addition, Figure 1 and Figure 2 Some or all of the components depicted in may be included in vehicle 5 .

[0039] In the depicted example, engine 10 is a compound boosted engine configured with multiple stages of boosting. Specifically, engine 10 includes an electric supercharger 13 staged upstream of a turbocharger 15, although other configurations are possible (such as a turbocharger 15 staged upstream of the electric supercharger 13) without departing from the scope of this disclosure. The depicted configuration results in a first compressor 111 (of the electric supercharger 13) being positioned in the intake duct 142 upstream of a second compressor 174 (of the turbocharger 15). As shown, the electric supercharger 13 includes an electric motor 107. In alternative examples, the turbocharger 15 can be an electric turbocharger having an electric motor coupled to the compressor 174, the turbine 176, or the shaft 180, while the supercharger 13 is configured as either an electric or mechanical supercharger. In other examples, both the first and second boosting devices can be electric superchargers or electric turbochargers. In still other examples, only a single boosting device, such as an electric supercharger or an electric turbocharger, may be included in engine system 100 .

[0040] In the depicted example, the first compressor 111 is driven by the electric motor 107. Specifically, the fan of the first compressor 111 can be driven by power received from the electric motor 107 along the supercharger compressor shaft 80. In some examples, the first compressor 111 of the supercharger 13 can be additionally driven by the engine crankshaft via a clutch and gear mechanism. The electric motor 107 can be powered by an onboard energy storage device (such as the system battery 58). The electric motor 107 can additionally or alternatively be powered by the alternator 46 ( Figure 1 The amount of power delivered to the electric motor 107 can be varied to adjust the duty cycle of the electric supercharger 13. In one example, the amount of power delivered to the electric motor 107 can be increased to increase the speed of the first compressor 111, while correspondingly increasing the electrical load applied to the alternator and reducing the alternator current. As a result, the electric supercharger 13 can rotate faster, providing fast-acting or high-frequency boost actuation.

[0041] The turbocharger 15 includes a second compressor 174 that is driven by a turbine 176 via a shaft 180. The turbine 176 is driven by expanding engine exhaust. In one example, the turbocharger 15 can be a twin scroll device. In another example, the turbocharger 15 can be a variable geometry turbocharger (VGT), in which the turbine geometry is actively varied based on engine operating conditions.

[0042] During selected conditions, when the opening of electric supercharger bypass valve (ESBV) 72 is reduced, air can enter first compressor 111, thereby directing intake air from air filter 113 through first compressor bypass passage 70 and through first compressor 111, where it is pressurized for delivery to second compressor 174. Fresh air received at the inlet of second compressor 174 is then compressed and introduced into engine 10. As the opening of ESBV 72 increases, the amount of air that enters second compressor 174 without passing through first compressor bypass passage 70 and first compressor 111 increases. During conditions in which ESBV 72 is fully open, pressurized air can be delivered to engine 10 via second compressor 174 of turbocharger 15 without passing through first compressor 111 of electric supercharger 13.

[0043] During selected conditions, air compressed by the turbocharger 15 can be recirculated from the outlet of the second compressor 174 to the inlet through the second compressor bypass passage 60 by adjusting the opening of the compressor recirculation valve (CRV) 62. The CRV 62 can be a continuously variable valve, and increasing the opening of the CRV 62 can include actuating (or energizing) a solenoid of the valve. One or both of the CRV 62 and the ESBV 72 can be continuously variable valves, wherein the position of the valve is continuously variable from a fully closed position to a fully open position. Alternatively, the CRV 62 can be a continuously variable valve and the ESBV 72 is an on-off valve. In some embodiments, the CRV 62 can be partially opened during boosted engine operation to provide surge margin. In this context, the partially open position can be a default valve position. Then, in response to an indication of surge, the opening of the CRV 62 can be increased. For example, CRV 62 may be adjusted from a default partially open position to a fully open position, where the degree of opening is based on a surge indicator (e.g., compressor ratio, compressor flow rate, pressure differential across the compressor, etc.) In an alternative example, CRV 62 may remain closed during boosted engine operation (e.g., peak performance conditions) to reduce boost response time and increase peak performance.

[0044] like Figure 2 As shown in FIG, air flows from the second compressor 174 through the charge air cooler (CAC) 18 and the throttle 162 to the intake manifold 146. For example, the CAC 18 may be an air-to-air or water-to-air heat exchanger. The MAP sensor 124 may be used to determine the intake manifold pressure (e.g., the pressure of the air charge within the intake manifold).

[0045] The intake manifold 146 is opened through a series of intake valves (e.g., Figure 1 ) are coupled to a plurality of cylinders 14 of engine 10. Cylinders 14 are also supplied with air via a series of exhaust valves (e.g., Figure 1 The exhaust manifold 148 is coupled to an exhaust valve 156 (shown in FIG. 1 ). In the depicted embodiment, a single exhaust manifold 148 is shown. However, in other embodiments, the exhaust manifold may include multiple exhaust manifold sections. A configuration with multiple exhaust manifold sections may allow effluent from different combustion chambers to be directed to different locations in the engine system.

[0046] like Figure 2As shown in FIG, exhaust gas from exhaust manifold 148 is directed to turbine 176 to drive the turbine. When it is desired to reduce turbine torque, a portion of the exhaust gas may instead be directed through wastegate 90, thereby bypassing the turbine. Wastegate actuator 92 (e.g., a wastegate valve) may be actuated open to release at least some exhaust pressure from upstream of turbine 176 to a location downstream of turbine 176 via wastegate 90. By reducing exhaust pressure upstream of turbine 176, turbine speed may be reduced.

[0047] The combined flow from turbine 176 and wastegate 90 flows through emission control device 178. All or a portion of the treated exhaust gas from emission control device 178 can be released into the atmosphere via exhaust passage 135. However, depending on operating conditions, some exhaust gas can be diverted to intake passage 142 via an exhaust gas recirculation (EGR) passage (not shown), which includes an EGR cooler and an EGR valve. The EGR can be recirculated to the inlet of first compressor 111, the inlet of second compressor 174, or both.

[0048] One or more sensors may be coupled to the inlet of second compressor 174 (as shown) and / or first compressor 111 (not shown). For example, temperature sensor 255 may be coupled to the inlet of second compressor 174 for estimating the compressor inlet temperature. As another example, pressure sensor 256 may be coupled to the inlet of second compressor 174 for estimating the pressure of the air entering the second compressor. Other sensors may include, for example, an air-fuel ratio sensor, a humidity sensor, and the like. In other examples, one or more second compressor inlet conditions (such as humidity, temperature, and the like) may be inferred based on engine operating conditions. Sensors may estimate the conditions of the intake air received from the intake duct at the second compressor inlet and the air charge recirculated from upstream of CAC 18. One or more sensors may also be coupled to intake duct 142 upstream of first compressor 111 for determining the composition and condition of the charge entering the first compressor. These sensors may include, for example, humidity sensor 257 and pressure sensor 259. Humidity sensor 257 may be any type of humidity sensor, such as a relative humidity sensor or an absolute humidity sensor, and may provide an indication of ambient humidity. Pressure sensor 259 may provide an indication of ambient (e.g., atmospheric) pressure. Additionally, throttle inlet pressure (TIP) sensor 59 may be coupled downstream of CAC 18 and upstream of throttle valve 162 for estimating boost pressure delivered to the engine.

[0049] Engine 10 may have an associated cooling system 290 for maintaining the temperature of engine 10 within a desired range. Cooling system 290 may operate to reduce the temperature of engine 10 by activating coolant pump 293 to flow liquid coolant drawn from a coolant tank or reservoir 294 around engine 10 and through passages within engine 10 via coolant line 282. In some examples, coolant pump 293 may be an engine-driven water pump that is coupled to the engine via a front-end accessory drive and rotates in proportion to engine speed via a belt, chain, etc. The coolant temperature may be regulated by a thermostatic valve 238 located in coolant line 282, which may remain closed until the coolant reaches a threshold temperature.

[0050] After passing through the engine and absorbing engine heat, the heated coolant passes through narrow passages within the radiator 291 where it can transfer heat to the ambient air before returning to the coolant reservoir 294. A cooling fan 292 can be coupled to the radiator 291 for blowing ambient air across the radiator 291, thereby increasing the rate of heat transfer between the heated coolant and the air, particularly when the vehicle 5 is stationary. In other examples, the heated coolant can be circulated through a heater core (not shown) where the heat can be rejected to components requiring heating (such as for cabin heating). The operation of the cooling system 290, including pump output and cooling fan speed, can be controlled by the controller 12 based on one or more temperature sensors, such as Figure 1 The control is based on the output of the engine coolant temperature sensor 116 shown in FIG.

[0051] The controller 12 may be included in the control system 141. The controller 12 is shown receiving information from a plurality of sensors 16 (various examples of which are described herein) and sending control signals to a plurality of actuators 81 (various examples of which are described herein). As an example, the sensors 16 may include the exhaust gas sensor 126, the MAP sensor 124, the exhaust gas temperature sensor 158, the exhaust gas pressure sensor 129 coupled to the exhaust passage 135, the compressor inlet temperature sensor 255, the compressor inlet pressure sensor 256, the MAF sensor 122, the pressure sensor 259, the TIP sensor 59, and the engine coolant temperature sensor 116 (e.g., Figure 1 ). Other sensors (such as additional pressure, temperature, air / fuel ratio, humidity, and composition sensors) may be coupled to various locations in the engine system 100. The actuators 81 may include, for example, the throttle 162, the CRV 62, the ESBV 72, the electric motor 107, the wastegate actuator 92, the fuel injectors 166, the coolant pump 293, the cooling fan 292, the intake valve actuator 152 (e.g., Figure 1 ) and the exhaust valve actuator 154 (as shown in Figure 1). Controller 12 may receive input data from various sensors, process the input data, and employ various actuators to adjust engine operation based on the received signals and instructions stored on the controller's memory. The controller may employ the actuators in response to the processed input data based on instructions or code programmed therein, the instructions or code corresponding to one or more routines, such as those described herein with respect to Figures 3 to 6 For example, the controller 12 may determine an engine overheat condition based on the signal ECT received from the engine coolant temperature sensor 116 and, in response thereto, determine an engine overheat condition based on operating conditions (e.g., regarding Figure 3 As an example, based on the "on" state of engine 10 and signal ECT, controller 12 may determine that liquid fuel is used to cool the engine while operating in VDE mode, and in response thereto, deactivate cylinder 14 (via intake valve actuator 152 and exhaust valve actuator 154) and actuate fuel injector 166 to inject liquid fuel into the deactivated cylinder 14, as described with respect to FIG. Figure 6 Further description.

[0052] When the engine is running, heat is generated. As mentioned above, a cooling system (e.g., Figure 2 The cooling system 290 of the embodiment of the present invention is used to maintain the temperature of the engine within the nominal operating temperature range, thereby preventing the engine from degrading due to overheating. However, degradation of cooling system components or improper maintenance may cause the engine to overheat (e.g., operate above its nominal operating temperature range). As a non-limiting example, even after operating the coolant system (such as by activating the cooling fan and the coolant pump), the engine may overheat due to loss of coolant in the cooling system (e.g., due to degradation of the cooling system or due to the coolant reservoir not being refilled), the cooling fan (e.g., Figure 2 Deterioration of the cooling fan 292), the coolant pump (e.g., Figure 2 Insufficient cooling can also occur due to degradation of the coolant pump 293 and / or the presence of a blockage in the coolant jacket / passage within the cylinder head. Therefore, when the engine becomes overheated, while the cooling system is operating, the controller can employ additional cooling strategies to reduce the engine temperature and prevent engine degradation until the cooling system can be repaired.

[0053] Figure 3 A method for cooling a superheated supercharged VDE engine such as Figure 1 and Figure 2 As described above, due to degradation of the engine cooling system included in the vehicle, the engine may overheat. Therefore, a system may be employed to facilitate engine cooling. For example, an electric supercharger (e.g., Figure 2A supercharger 13) can be used to reduce "turbo lag" as the turbocharger's turbine spins up. An electric boost device can also be used to increase the flow of cold air through the engine, thereby increasing the cooling rate. In addition, due to the higher thermal conductivity of liquid fuel relative to air, a VDE mode can be used to seal the deactivated cylinder and trap the liquid fuel in the deactivated cylinder to increase cooling. However, since injecting liquid fuel into the deactivated cylinder increases fuel consumption, VDE mode cooling can be implemented when air cooling is insufficient. Figure 1 and Figure 2 The method 300 and the remaining methods included herein are described with reference to the system described and illustrated in FIG. 1 , although it should be understood that similar methods may be applied to other systems without departing from the scope of the present disclosure. Figure 1 and Figure 2 The controller may use engine actuators of the engine system (e.g., Figure 1 and Figure 2 fuel injectors 166) to adjust engine operation according to the following method.

[0054] Method 300 begins at 302 and includes estimating and / or measuring operating conditions. Operating conditions may include, but are not limited to, vehicle status (e.g., on or off), engine status (e.g., on or off), engine operating mode (e.g., VDE mode or non-VDE mode), engine speed, engine load, manifold pressure, engine temperature, driver-requested torque, and catalyst (e.g., Figure 1 and Figure 2 For example, the engine speed may be determined based on the temperature of the emission control device 178. Figure 1 The engine load can be determined based on the signal PIP output by the MAF sensor (e.g., Figure 1 and Figure 2 The manifold pressure can be determined based on the signal MAF output by the MAF sensor 122 of the MAF sensor 122, and the manifold pressure can be determined based on the signal MAF output by the MAP sensor (e.g., Figure 1 and Figure 2 The torque required by the driver can be determined based on the signal MAP output by the MAP sensor 124, and the torque required by the driver can be determined based on the signal MAP output by the pedal position sensor (e.g., Figure 1 As an example, the signal PP may be determined based on the output of the engine coolant temperature sensor (e.g., from the pedal position sensor 134). Figure 1As another example, the engine temperature may be determined directly based on the output of a cylinder head temperature sensor. As yet another example, the engine temperature may be determined based on an exhaust manifold coupled to the engine (e.g., Figure 1 and Figure 2 The controller may determine the engine temperature directly based on the output of a temperature sensor located on the exhaust manifold 148. In addition to determining the engine temperature, the controller may also determine the actual and / or predicted (e.g., expected) rate of increase in engine temperature based on operating conditions (e.g., engine speed, engine load, boost pressure, and torque demand).

[0055] At 304, it is determined whether the engine temperature is greater than a first threshold temperature. The first threshold temperature is a non-zero positive temperature value that defines the highest temperature of the engine's nominal operating temperature range. Thus, an engine temperature greater than the first threshold temperature indicates an engine overheat condition, meaning that the engine cooling system is unable to adequately cool the engine (such as due to cooling system degradation). For example, the first threshold temperature may be in the range of 220°F to 250°F.

[0056] If the engine temperature is not above the first threshold temperature, method 300 proceeds to 306 and includes maintaining current operating parameters. For example, because the engine temperature is below the first threshold temperature, it can be assumed that the engine cooling system is nominally functioning, such as not degrading one or more cooling system components, and maintaining the engine adequately cooled and within its normal operating range. As another example, the engine may be shut down and not generating heat from combustion. Thus, maintaining current operating parameters may include not activating the electric supercharger, not selectively disabling cylinder fueling, and not injecting liquid fuel into sealed, deactivated cylinders for engine cooling while operating in VDE mode. After 306, method 300 ends.

[0057] If the engine temperature is above the first threshold temperature, method 300 proceeds to 308 and includes determining whether the engine is on. "On" refers to a state in which the engine is running at a non-zero speed and combusting a mixture of air and fuel in the engine cylinders. "Off" refers to a state in which the engine is at rest and no combustion is occurring in the engine cylinders. The engine state may be independent of the vehicle state, such as when the engine is included in an HEV or a stop / start vehicle. For example, an electric mode of vehicle operation may be selected in an HEV when torque demand is low (e.g., below a torque threshold), when the fuel level in the fuel tank is low (e.g., below a fuel level threshold), and / or when the battery state of charge (SOC) is high (e.g., above a threshold SOC). In electric mode, the vehicle operates via power from an energy storage device (e.g., Figure 1 The system battery 58) powers an electric motor (e.g., Figure 1 The HEV is propelled by torque from the electric motor 52 (e.g., the electric motor 52), rather than by engine torque. Thus, when operating in electric mode, the vehicle is on (e.g., powered on, with the ignition switch in the "on" position), but the engine may also be off. As another example, in an HEV, an engine operating mode may be selected when torque demand is high, when the fuel level in the fuel tank is high, and / or when the battery state of charge is low. In engine mode, the vehicle is propelled by torque from the engine, rather than from torque from the electric motor, so the engine is on and running. As another example, if the torque demand is higher than that which can be provided by engine torque alone, an assist mode may be selected in which the HEV is propelled by a combination of electric motor torque and engine torque, so the engine is on and running in assist mode. As another example, when the engine is included in a stop / start vehicle (such as when the vehicle speed is less than a threshold speed, the battery SOC is above a threshold SOC, etc.), the engine may be turned off, while the vehicle remains on during an idle stop. In other examples, the engine is turned off while the vehicle is off (e.g., powered off, with the ignition switch in the "off" position).

[0058] If the engine is not on (eg, engine off), method 300 proceeds to 310 and includes cooling the engine using the electric supercharger while the engine is spinning electrically, as described with respect to FIG. Figure 4 In this way, the low-temperature intake air can flow through the engine, transferring heat from the engine to the air to increase the cooling rate. After 310, method 300 ends.

[0059] If the engine is on, method 300 proceeds to 312 and includes determining whether the engine temperature is greater than a second threshold temperature. The second threshold temperature is a non-zero positive temperature that is greater than the first threshold temperature and indicates a temperature above which the engine may be considered severely overheated. When the engine is severely overheated, engine degradation may occur. For example, the second threshold temperature may be in the range of 250°F to 280°F. Additionally or alternatively, at 312, method 300 may include determining whether the rate of temperature increase is greater than a threshold rate. The threshold rate is a non-zero positive rate that indicates that the current cooling strategy is unable to prevent the engine temperature from increasing further.

[0060] If the engine temperature is not greater than the second threshold temperature (e.g., the engine temperature is greater than the first threshold temperature and less than or equal to the second threshold temperature, or if the rate of temperature increase is not greater than the threshold rate), method 300 proceeds to 314 and includes using intake air to cool the engine while selectively disabling fueling, as described with respect to Figure 5By selectively disabling fueling in one or more engine cylinders, intake air may flow through the one or more engine cylinders, thereby cooling them. After 314 , method 300 ends.

[0061] Returning to 312, if the engine temperature is above the second threshold temperature (or the rate of temperature increase is greater than the threshold rate), method 300 proceeds to 316 and includes using liquid fuel to cool the engine while operating in the VDE mode, as described with respect to Figure 6 As described. For example, the engine can be switched to VDE mode by deactivating selected cylinders. The deactivated cylinders are sealed, and the corresponding cylinder intake and exhaust valves are fully closed. Due to the higher thermal conductivity of liquid fuel relative to air, liquid fuel is injected into the sealed, deactivated cylinders for faster cooling. For example, the thermal conductivity of gasoline is more than six times that of air. In addition, as the liquid fuel evaporates, the phase change from liquid to vapor causes a secondary cooling effect. In this way, when other cooling methods cannot reduce or maintain the engine temperature, the liquid fuel is used to cool the engine while operating in VDE mode. After 316, method 300 ends.

[0062] Next, Figure 4 A method for using an electric supercharger (e.g., Figure 2 An exemplary method 400 for cooling an overheated engine in a vehicle is provided by using a supercharger 13 and electrically rotating the engine. Figure 3 As described, the engine may be shut down (e.g., not fueled, no combustion occurring in the engine cylinders) while the vehicle is off (e.g., the vehicle's ignition switch is in the "off" position), while the vehicle is on during an idle stop, and while the engine is operating in electric mode. A controller (e.g., Figure 1 and Figure 2 The controller 12) can operate the electric supercharger to provide on-demand air flow in response to an indication of engine overheating, such as with respect to Figure 3 Additionally, the engine may be spun without fuel by the electric motor to pump cooling air through the overheated engine. Figure 3 Alternatively, method 400 may be performed while the engine is off in response to any indication of engine overheating.

[0063] Method 400 begins at 402 and includes spinning the engine without fuel via an electric motor. For example, the engine may be started using a starter motor (if the engine is included in a conventional vehicle where the engine is the only source of torque) or an electric motor (if the engine is included in a hybrid vehicle, such as a Figure 1In some examples, the controller may be configured to continuously rotate the motor 52 based on operating conditions (as indicated at 404, such as Figure 3 The engine speed is determined based on the operating conditions (measured at 302 of ). The operating conditions may include, but are not limited to, engine temperature, ambient temperature, and ambient humidity. For example, the controller may input the operating conditions (e.g., one or more of engine temperature, ambient temperature, and ambient humidity) into a lookup table, a mapping, or an algorithm, and output the corresponding engine speed under the given operating conditions to cool the overheated engine, and then determine the motor speed of the starter motor or electric motor that will provide the determined engine speed, such as via a lookup table, a mapping, or an algorithm. In another example, the engine speed is independent of the operating conditions. For example, the controller may adjust the duty cycle of the non-zero voltage supplied to the starter motor or electric motor to operate the starter motor or electric motor at a determined motor speed that will provide the determined engine speed.

[0064] At 406, method 400 includes operating the electric supercharger to flow cooled air through the engine. Figure 2 As described, the electrically powered supercharger may be an electrically powered supercharger, although any electrically powered assisted supercharger may be used, such as an electrically powered assisted turbocharger. The electrically powered supercharger may include a compressor (e.g., Figure 2 a first compressor 111) and an electric motor (e.g., Figure 2 ) that drives the compressor via a compressor shaft (e.g., supercharger compressor shaft 80). As an example, activating the electric supercharger may include determining a compressor speed that will provide a desired amount of engine cooling and then determining a motor speed that will provide the determined compressor speed. In some examples, as indicated at 408, the compressor speed may be determined based on operating conditions (such as one or more of engine temperature, ambient temperature, and ambient humidity). For example, the controller may input the operating conditions (e.g., engine temperature, ambient temperature, and ambient humidity) into a lookup table, map, or algorithm and output the desired amount of engine cooling at the given operating conditions and then determine the compressor speed that will provide the desired amount of engine cooling, such as via a lookup table, map, or algorithm. Additionally or alternatively, the compressor speed may be determined based on a difference between the current engine temperature and a first threshold temperature (e.g., at Figure 3) and one or more of the rates of increase of engine temperature, and determine a desired amount of engine cooling and / or compressor speed. For example, as the difference and / or rate increases, the determined compressor speed may increase. In one example, the controller may use a lookup table, mapping table, or algorithm that uses the current engine temperature and the target engine temperature as inputs and outputs a corresponding compressor speed to reduce the current engine temperature to the target engine temperature. In another example, the compressor speed is a predetermined value and is independent of the operating conditions. The controller may adjust the duty cycle of the non-zero voltage supplied to the electric motor of the electric supercharger to operate the motor at a determined motor speed that will provide the determined compressor speed. For example, the voltage may be supplied by the vehicle's system battery (e.g., Figure 1 and Figure 2 In some examples, activating the electric boost device may also include fully closing the bypass valve (e.g., Figure 2 ESBV 72), so that all intake air such as through the bypass passage (eg, Figure 2 The first compressor bypass passage 70 of the electric supercharger is directed through the compressor of the electric supercharger. In addition, as described above, the intake air can be passed through the CAC (e.g., Figure 2 CAC18), where the air is cooled before being delivered to the engine cylinders.

[0065] At 410, method 400 includes determining whether the engine temperature is above a first threshold temperature, as defined above. If the engine temperature is above the first threshold temperature, the engine is still overheated and has not yet cooled sufficiently (e.g., the desired amount of engine cooling has not yet been achieved). Therefore, method 400 returns to 402 to continue rotating the engine via the electric motor without fuel. In some examples, the engine speed may continue to be adjusted (e.g., at 404), and the compressor speed may continue to be adjusted (e.g., at 408) as operating conditions such as engine temperature change. For example, as the engine temperature decreases (e.g., the difference between the current engine temperature and the first threshold temperature decreases), one or more of the engine speed and the compressor speed may be decreased.

[0066] If the engine temperature is not greater than the first threshold temperature (e.g., the engine temperature is less than or equal to the first threshold temperature), the engine may be deemed sufficiently cooled and no longer overheated (e.g., a desired amount of engine cooling has been achieved), and method 400 proceeds to 412. At 412, method 400 includes deactivating the electric supercharger. For example, deactivating the electric supercharger may include deactivating power to the electric motor of the electric supercharger. In some examples, deactivating the electric supercharger may also include at least partially opening a bypass valve such that intake air may bypass the electric supercharger and flow to the engine intake without flowing through the compressor of the electric supercharger.

[0067] At 414, method 400 includes decelerating the engine to a standstill. For example, the starter motor or electric motor may be deactivated, such as by stopping the supply of voltage to the starter motor or electric motor so that the motor speed and the engine speed decrease to zero. As another example, when the electric motor is used to electrically rotate the engine, decelerating the engine to a standstill may include, for example, disengaging a clutch connecting the electric motor to the crankshaft of the engine (e.g., Figure 1 The first clutch 56 of the motor decouples the engine from the electric motor so that the electric motor no longer rotates the crankshaft. After 414, method 400 ends. In this way, the electric supercharger can be used to actively cool the engine while the engine is off, where the degree of active engine cooling can be based on the degree of engine overheating, as indicated by the engine temperature or the rate of increase in engine temperature.

[0068] Next, Figure 5 An exemplary method 500 is shown for using intake air to cool an overheated engine while the engine is on (eg, refueling, combustion occurring in engine cylinders) while refueling is selectively disabled. For example, a controller (eg, Figure 1 and Figure 2 The controller 12 of the embodiment of the present invention can cut off the fuel to one or more engine cylinders in a distributed manner, pumping the intake air through the unfueled cylinders to cool them. Additionally, in some examples, the fuel can be supplied by an electric supercharger (e.g., Figure 2 The supercharger 13) provides additional airflow. The method 500 can be used as Figure 3 as part of method 300 (e.g., at 314) and / or as Figure 6 Alternatively, method 500 may be performed while the engine is on in response to any indication of engine overheating.

[0069] Method 500 begins at 502 and includes determining the number of cylinders to be operated without fuel. This may be based on operating conditions (such as Figure 3) is measured at 302 of . For example, as the engine speed increases and / or as the engine temperature rises, a greater number of cylinders can be operated without fuel. Conversely, as the engine speed decreases and / or the engine temperature decreases, a smaller number of cylinders can be operated without fuel. As another example, when the rate of increase in engine temperature is greater (e.g., greater than a threshold rate), a greater number of cylinders can be operated without fuel, while when the rate of increase in engine temperature is lower, a smaller number of cylinders can be operated without fuel. The number of cylinders can also be based on torque demand to maintain vehicle maneuverability and drivability, as the remaining fueled cylinders provide all engine torque. In addition, the number of unfueled cylinders can be limited to reduce engine noise, vibration, and harshness (NVH) based on the engine configuration (e.g., the layout and total number of cylinders). The engine can determine the number of cylinders to operate without fuel by inputting operating conditions (such as one or more of engine speed, engine temperature (or temperature increase rate), and engine torque demand) into one or more lookup tables, maps, or algorithms, and output the number of cylinders to operate without fuel in a given state.

[0070] At 504, method 500 includes disabling fuel injection to a determined number of cylinders in a distributed manner. As an example, fuel injection to the determined number of cylinders may be disabled in a cyclical manner, wherein the disablement is evenly circulated or distributed among the engine cylinders. Using a four-cylinder engine as an example, when the determined number of cylinders is two, fuel injection to a first group of two cylinders may be disabled during a first engine cycle (or multiple engine cycles), and fuel injection to a second group of two cylinders may be disabled during a second engine cycle (or multiple engine cycles). Fuel injection to the first group of two cylinders may then be disabled again during a third engine cycle (or multiple engine cycles), and so on. The specific cylinders included in each group may be selected, such as based on the engine configuration, in order to reduce engine NVH. As another example, due to hardware limitations, the disablement may be evenly circulated or distributed among the engine cylinders that cannot be deactivated while operating in VDE mode, thereby increasing cooling of engine cylinders that cannot be cooled using liquid fuel (as discussed with respect to FIG. 1 ). Figure 6 As described above, due to the prohibition of fueling, spark can also be disabled in the corresponding cylinders because no combustion will occur in the unfueled cylinders. In addition, while prohibiting fuel injection to a certain number of cylinders, engine operating parameters can be adjusted to maintain engine torque demand using the remaining combustion cylinders. Figure 6 Further describing (eg, at 614 ), one or more of air flow, spark timing, and cylinder valve timing may be adjusted to maintain engine torque demand and minimize torque disturbances.

[0071] At 506, it is determined whether the exhaust temperature is above a third threshold temperature. The third threshold temperature may correspond to a non-zero positive temperature above which, if the exhaust temperature increases further, exhaust system components (such as a catalyst (e.g., Figure 1 and Figure 2 For example, by operating the engine in a lean fueling state or at a high engine load, the exhaust temperature can be further increased. For example, the exhaust temperature can be measured by an exhaust temperature sensor (e.g., Figure 1 and Figure 2 The exhaust temperature is measured by a temperature sensor 158. It should be understood that an exhaust overtemperature condition, in which the exhaust temperature is greater than the third threshold temperature, is different from an overheated engine condition. For example, an exhaust overtemperature condition may exist when an overheated engine condition does not exist, and vice versa.

[0072] If the exhaust temperature is above the third threshold temperature, method 500 proceeds to 508 and includes not operating the electric supercharger. By not operating the electric supercharger, exhaust system degradation due to overheating can be prevented. Additionally, in some examples, engine operating parameters can be adjusted to reduce exhaust temperature. For example, rich fueling can be used in the combustion cylinders, where more fuel is supplied to a given air charge than is required for a chemically complete combustion event to occur (e.g., stoichiometric). The unburned fuel absorbs a portion of the heat from the combustion event, thereby reducing the exhaust temperature.

[0073] If the exhaust temperature is not greater than the third threshold temperature (eg, the exhaust temperature is less than or equal to the third threshold temperature), method 500 proceeds to 510 and includes operating the electric supercharger to increase airflow through the engine. Figure 4 In some examples, as indicated at 512 and as described above with respect to Figure 4 As described in 408 of FIG. , the compressor speed of the electric supercharger can be determined based on operating conditions (such as one or more of engine temperature, ambient temperature, and ambient humidity). Additionally, the compressor speed can be adjusted based on exhaust gas temperature. For example, as exhaust gas temperature increases, the compressor speed can be decreased. In some examples, if the exhaust gas temperature rises above a third threshold temperature at any time while the electric supercharger is operating, the electric supercharger can be deactivated.

[0074] At 514, it is determined whether the engine temperature is above a second threshold temperature. Figure 3As defined (e.g., at 312), the second threshold temperature may refer to a temperature above which the engine is considered severely overheated and may be degraded. Alternatively, it may be determined whether the rate of temperature increase is greater than a threshold rate, also as described above in Figure 3 If the engine temperature is above the second threshold temperature (or if the rate of temperature increase is greater than the threshold rate), the intake air may not be sufficient to cool the overheated engine. Therefore, a more aggressive engine cooling strategy may be used, and method 500 proceeds to 516 to use liquid fuel to cool the engine while operating in VDE mode, as described with respect to FIG. Figure 6 After 516, method 500 ends.

[0075] If the engine temperature is not above the second threshold temperature at 514 (or if the rate of temperature increase is not greater than the threshold rate), method 500 proceeds to 518 and includes determining whether the engine temperature is above the first threshold temperature. Figure 3 As defined (e.g., at 304), the first threshold temperature is lower than the second threshold temperature and may refer to a temperature above which the engine is considered overheated, but not severely overheated. If the engine temperature is above the first threshold temperature, method 500 returns to 502 to determine the number of cylinders operating without fueling. In this way, the engine will continue to utilize charge air cooling while selectively disabling fueling, and the number of cylinders operating without fueling may be continuously adjusted based on current operating conditions.

[0076] Returning to 518, if the engine temperature is not greater than the first threshold temperature (e.g., the engine temperature is less than or equal to the first threshold temperature), method 500 proceeds to 520 and includes resuming fueling to all cylinders. With the resumption of fueling, spark may also be resumed so that combustion may occur in all cylinders. Additionally, with the resumption of combustion in all cylinders, engine operating parameters may be adjusted. Figure 6 Further describing (eg, at 630 ), one or more of air flow, spark timing, and cylinder valve timing may be adjusted to maintain engine torque demand and minimize torque disturbances while resuming combustion in all engine cylinders.

[0077] At 522, method 500 optionally includes deactivating the electric supercharger. For example, if the electric supercharger is operating to provide additional airflow for cooling the engine (e.g., as at 510), the electric supercharger will be deactivated, such as described above. Figure 4As described at 412 of FIG. However, if the electric supercharger is not operating to provide additional airflow for cooling the engine (as at 508 ), 522 may be omitted. Method 500 then ends. In this way, while providing engine torque via active cylinders, the engine can be cooled via intake airflow through unfueled and non-firing cylinders. Furthermore, the electric supercharger can be used to provide additional airflow, thereby increasing the engine cooling rate.

[0078] Next, Figure 6 An exemplary method 600 for cooling an overheated engine using liquid fuel while operating in VDE mode is shown. For example, the method 600 may be performed to cool an overheated engine in a condition such as due to an engine cooling system (e.g., Figure 2 The degradation of the cooling system 290) of the direct injection variable displacement engine (e.g., Figure 1 and Figure 2 Cooling the engine 10) when it is severely overheated. Figure 6 can be controlled by a controller (e.g. Figures 1 to 2 The controller 12) is for example as Figure 3 a portion of method 300 (e.g., at 316) or Figure 5 Alternatively, method 600 may be performed in response to any indication of an overheating direct injection variable displacement engine, particularly when air cooling methods are not sufficient to cool the engine.

[0079] Method 600 begins at 602 and includes determining whether the torque demand is less than a threshold torque. For example, the torque demand may be determined based on the position of the accelerator pedal, such as determined by a pedal position sensor (e.g., Figure 1 The torque demand is determined using a pedal position sensor 134 (measured by a pedal position sensor 134). The threshold torque may refer to a positive, non-zero amount of torque that cannot be satisfied by the deactivated cylinders while operating in the VDE mode. For example, when the torque demand is less than the threshold torque, the torque demand may be satisfied by the remaining active cylinders while deactivating one or more cylinders, as further described below.

[0080] If the torque demand is not less than the threshold torque, method 600 proceeds to 604 and includes entering a low torque mode to enable a transition to operating in the VDE mode. Entering the low torque mode may include reducing the engine load. For example, the controller may determine the reduced engine load by inputting the desired lower torque (less than the threshold torque) and the engine speed into one or more lookup tables, algorithms, and / or maps and outputting the corresponding engine load. In some examples, the transmission (e.g., Figure 1The transmission 54 can be upshifted to a higher gear to provide a desired lower torque while reducing engine speed and load. As another example, upshifting to a higher gear can be used to increase torque while maintaining engine speed and load. By entering low torque mode, vehicle drivability and maneuverability can be maintained while transitioning to VDE mode for engine cooling.

[0081] If the torque demand is less than the threshold torque at 602 (or if the vehicle enters a low torque mode at 604), method 600 proceeds to 606 and includes selecting cylinders to deactivate. The controller may select a cylinder to deactivate based on engine operating conditions (e.g., Figure 3 The controller may select a group of cylinders and / or engine banks to deactivate based on the engine's current VDE mode (as estimated and / or measured at 302 of FIG). The selection may be based on, for example, which group of cylinders was deactivated during a previous VDE mode operation. For example, if a first group of cylinders was deactivated during a previous VDE mode operation, the controller may select a second group of cylinders (e.g., the remaining cylinders) to deactivate during a current VDE mode operation. In another example, cylinders of a first engine bank may be selected for deactivation, while cylinders of a second engine bank may remain active. In yet another example, hardware may limit the deactivation of selected cylinders. Using a V-8 engine as an example, hardware may limit the deactivation of two specific cylinders in each engine bank. In such an example, the controller may select cylinders to deactivate based on hardware limitations.

[0082] At 608, method 600 includes transitioning to VDE mode by deactivating the selected cylinders. Deactivating the selected cylinders may include closing the cylinder intake and exhaust valves (as indicated at 610), disabling spark (as indicated at 612), and adjusting engine operating parameters to maintain torque demand (as indicated at 614). For example, the intake and exhaust valves coupled to the selected cylinders may be fully closed and maintained closed via a cam profile switching mechanism using a cam with no lift, or by actuating a valve deactivator (e.g., a VDE actuator), as described with respect to FIG. Figure 1 Further described. In one example, exhaust gas from a previous charge combustion can be trapped within selected cylinders during deactivation. In another example, fresh air can be trapped within selected cylinders to provide lower torque pulses during deactivation by drawing air into the selected cylinders before closing the intake and exhaust valves. For example, disabling spark can include not actuating a spark plug coupled to each selected cylinder (e.g., Figure 1 Adjusting engine operating parameters to maintain torque demand may include, for example, increasing the intake throttle (e.g., Figure 1 and Figure 2The opening of the throttle valve 162) is increased to increase airflow into the active cylinder, thereby maintaining torque during VDE mode. In addition, the spark timing can be adjusted in the active cylinder. For example, the spark can be initially retarded to minimize torque disturbances during the transition to VDE mode and then restored. In addition, the intake and exhaust valve timing can be adjusted for the active cylinder. For example, the cam timing in the active cylinder can be modified, where the camshaft is positioned to achieve the desired cylinder air charge to deliver the desired torque. Depending on the desired torque, in one example, the exhaust cam can be retarded to allow exhaust residuals in the active cylinder. In another example, the intake cam can be advanced to increase volumetric efficiency in the active cylinder. Therefore, the above adjustments can enable the desired airflow to maintain the desired engine torque.

[0083] At 616, method 600 includes injecting liquid fuel into the deactivated cylinders at multiple piston positions. For example, once the intake and exhaust valves are fully closed, fuel may be injected while the piston in each deactivated cylinder is at TDC (e.g., to cool the top of the cylinder), while at BDC (e.g., to cool the bottom of the cylinder), and at a position intermediate between TDC and BDC (e.g., 90 crank angle degrees after TDC). Injecting liquid fuel into the deactivated cylinders may include reducing the injection pressure compared to the injection pressure used to provide fuel to the active cylinders. For example, at higher injection pressures, the fuel is finely atomized by the fuel injector upon injection, and the fine fuel droplets rapidly vaporize within the cylinder. Therefore, reducing the injection pressure may include injecting the fuel at a pressure that substantially does not atomize the fuel during injection, so that the fuel does not rapidly vaporize within the cylinder and instead remains liquid, as liquid fuel has a greater cooling capacity than vaporized fuel. For example, the reduced injection pressure can be a predetermined pressure within the range of 40 psi to 60 psi (e.g., fuel rail pressure) for deactivated cylinders (compared to greater than 2000 psi for active cylinders), with the injection pressure further adjusted based on the specific fuel injectors used. In some examples, the reduced injection pressure can be a pressure just above a threshold for triggering a low fuel pressure diagnostic trouble code. For example, by opening a fuel injector at 100% duty cycle, liquid fuel can be injected at the reduced injection pressure.

[0084] In addition, the total amount of fuel injected into each deactivated cylinder can be greater than the amount of fuel injected into each active cylinder during the engine cycle. For example, the amount of fuel injected into each deactivated cylinder can be a pre-calibrated value stored in the memory of the controller. In some examples, the pre-calibrated value can be further adjusted based on engine temperature and / or fuel volatility, with the amount of fuel injected increasing as the engine temperature and / or fuel volatility increases until an upper threshold is reached, and the upper threshold defines the maximum injection amount to prevent water lock. The total amount of fuel injected into each deactivated cylinder can be distributed between injections at multiple piston positions. In one example, the total amount of fuel can be evenly distributed between each injection. In another example, a larger proportion of the total fuel amount can be injected during a single injection or a subset of injections (such as while the piston is at TDC).

[0085] The controller may send a series of control signals to the fuel injector of each deactivated cylinder to inject the appropriate amount of fuel at the appropriate piston position, each control signal having a pulse width corresponding to the amount of fuel to be injected. The controller may determine the pulse width of each signal based on the total amount of fuel to be injected, the number of injections, the fuel allocation per injection (e.g., the proportion of the total amount of fuel to be injected), and the injection pressure. For example, the controller may input the total amount of fuel to be injected, the number of injections, the fuel allocation per injection, and the injection pressure into one or more lookup tables, mappings, or algorithms stored in the controller's memory and output the pulse width and / or timing of each control signal to be sent to the fuel injector of each deactivated cylinder. As an example, to prevent rapid vaporization of the injected fuel, method 600 may include injecting fuel during the downward motion of the piston (such as during the power stroke). Similarly, fuel injection may not be performed during the upward motion of the piston because the heat generated by compression may quickly vaporize the liquid fuel, thereby preventing the cooling effect of the liquid fuel. For example, when the piston is at TDC of the power stroke, the fuel injector can be actuated at a 30% duty cycle, when the piston is between TDC and BDC, the fuel injector can be actuated at a 60% duty cycle, and when the piston is at BDC of the power stroke, the fuel injector can be actuated at a 100% duty cycle, thereby increasing the amount of fuel injected as the piston moves downward.

[0086] At 618, method 600 includes stirring fuel in the deactivated cylinders. Because the intake and exhaust valves of each deactivated cylinder are (fully) closed, the deactivated cylinders are sealed, and the piston in each deactivated cylinder continues to move up and down as the engine rotates. Thus, the fuel remains in the sealed cylinders and moves across the surfaces of the cylinders and piston heads due to the piston motion. Stirring the fuel in the deactivated cylinders may also include monitoring the deactivated cylinders for unexpected combustion. For example, unexpected combustion may occur due to compression ignition in the hot, deactivated cylinders. In one example, the fuel may be detected based on a signal output by an engine speed sensor (e.g., from a Figure 1 Unintended combustion may be determined based on a signal PIP from Hall effect sensor 120. For example, if the engine speed accelerates without a command to increase the engine speed, the controller may determine that unintended combustion has occurred. In another example, unintended combustion may be determined based on a signal indicative of autoignition output by an engine knock sensor. As yet another example, unintended combustion may be determined by combining the output of an engine speed sensor with the output of a knock sensor. If unintended combustion is detected, the intake and exhaust valves of the corresponding cylinder may be opened to exhaust the burned gases and reduce the pressure of the corresponding cylinder.

[0087] At 620 , a determination is made as to whether a threshold duration has been met. The threshold duration may refer to the amount of time expected to be required for the liquid fuel to fully vaporize when agitated within the deactivated cylinder. The threshold duration may also correspond to a number of engine cycles expected to be required for the liquid fuel to fully vaporize. After vaporization, the fuel's cooling capacity is significantly reduced, so continued agitation of the vaporized fuel within the deactivated cylinder may be disadvantageous. In one example, the threshold duration may be a predetermined duration. Additionally or alternatively, the threshold duration may be adjusted based on one or more of engine temperature, engine speed, injected fuel amount, and fuel volatility. For example, the controller may input engine temperature, engine speed, injected fuel amount, and / or fuel volatility into one or more lookup tables, algorithms, or maps and output the threshold duration. As an example, the threshold duration may decrease as engine temperature increases. As another example, the threshold duration may increase as the injected fuel amount increases. As another example, the threshold duration may decrease as engine speed increases. As yet another example, the threshold duration may decrease as fuel volatility increases.

[0088] If the threshold duration has not been met, method 600 returns to 618 to continue stirring the fuel in the deactivated cylinder. In this way, the liquid fuel will continue to absorb heat from the overheated cylinder and the engine until the fuel is vaporized. If the threshold duration has been met, method 600 proceeds to 622 and includes activating the cylinder intake and exhaust valves of the deactivated cylinder to expel unburned fuel vapor. For example, the cylinder intake and exhaust valves of the deactivated cylinder can be activated via a cam profile switching mechanism (such as by switching to a cam with lift or by deactivating a valve deactivator). By activating the cylinder intake and exhaust valves of the deactivated cylinder, fresh charge air can enter the cylinder and vaporized unburned fuel can leave the cylinder. The vaporized fuel can be directed to a catalyst (e.g., Figure 1 and Figure 2 The catalyst temperature may be monitored based on the exhaust gas temperature (e.g., an exhaust gas temperature sensor coupled to the exhaust gas passage at the inlet of the catalyst). Figures 1 to 2 As another example, the temperature sensor can be directly coupled to the catalyst. If the catalyst temperature exceeds a threshold temperature (e.g., as described with respect to Figure 5 If the third threshold temperature described in 506 of FIG5 is exceeded, the controller can adjust the fueling in the active cylinder. For example, the exhaust temperature (and therefore the catalyst temperature) can be reduced via a rich fueling state, in which more fuel is delivered to the active cylinder than is required for complete combustion to occur with a given cylinder air charge. Furthermore, if the VDE engine is included in an engine system that also includes an external exhaust gas recirculation (EGR) system, a maximum amount of EGR can be used, such as by fully opening an EGR valve located in an EGR passage that couples the exhaust tract to the engine's intake. In this way, a portion of the vaporized fuel can be recirculated and combusted in the active cylinder compared to when external EGR is not used, thereby improving fuel economy and reducing catalyst temperature.

[0089] At 624, method 600 includes determining whether the engine temperature is below a second threshold temperature. Figure 3As described (e.g., at 312), when the engine temperature is above a second threshold temperature, the engine may be considered severely overheated and cooling via airflow may be insufficient. Therefore, if the engine temperature is above the second threshold temperature, liquid fuel may continue to be used to cool the engine while operating in VDE mode, and method 600 returns to 606 and includes selecting cylinders to be deactivated. Depending on the configuration of the variable displacement engine, the selected cylinders may be the same or different than the cylinders selected during the previous VDE mode operation. For example, if the hardware does not restrict the deactivation of specific cylinders, the cylinders that remained active during the previous VDE mode operation may be selected to distribute the liquid fuel cooling process across the cylinders. However, if only specific cylinders are deactivatable, the same cylinders may be selected, while the remaining cylinders benefit from the peripheral cooling effect from the deactivatable cylinders due to heat diffusion.

[0090] However, when the engine temperature is less than or equal to a second threshold temperature, cooling via airflow may be preferred while operating in VDE mode due to the reduced fuel economy of cooling the engine. Therefore, if the engine temperature is not greater than the second threshold temperature at 624, method 600 proceeds to 626 and includes reactivating the deactivated cylinders. Reactivating the deactivated cylinders may include, for example, enabling spark and nominal fueling as indicated at 628, and adjusting engine operating parameters to maintain torque demand as indicated at 630. With the intake and exhaust valves of the deactivated cylinders activated (e.g., at 622), nominal fueling may be initiated, such as by signaling the fuel injectors with pulse widths determined based on operating conditions (e.g., engine speed, engine load, and desired AFR). For example, the controller may input operating conditions into one or more lookup tables, algorithms, and / or maps and output nominal fuel injection amounts and / or fuel injection timings for the input operating conditions. By enabling spark, combustion may be restored in the cylinders deactivated during VDE mode. Additionally, engine operating parameters can be adjusted to compensate for the reactivated cylinders to maintain engine torque. For example, the intake throttle opening can be reduced to allow for reduced airflow when the cylinders are reactivated, thereby reducing the air charge and, therefore, the load on each cylinder, as more cylinders are available for combustion. In one example, the intake throttle can be adjusted to a closed position. In another example, the throttle opening can be reduced to allow sufficient airflow to the increased number of active cylinders while maintaining torque demand. Simultaneously, spark timing can be retarded to maintain constant torque across all cylinders, thereby reducing cylinder torque disturbances. When sufficient airflow is reestablished, spark timing can be restored. In addition to throttle and spark timing adjustments, valve timing can be adjusted at 630 to compensate for torque disturbances. Cam timing can be modified to deliver the desired air charge to one or more cylinders to provide the required torque. In one example, if cylinder air charge is low, exhaust cam timing can be advanced to reduce residuals and ensure complete combustion. In another example, if higher torque is desired, the intake cam may be fully advanced and the exhaust cam may be retarded to provide lower dilution and increased power.

[0091] At 632, method 600 includes determining whether the engine temperature is above a first threshold temperature. Figure 3As defined (e.g., at 304), the first threshold temperature may correspond to a temperature above which the engine is considered overheated and below a second threshold temperature. If the engine temperature is not above the first threshold temperature (e.g., the engine temperature is below or equal to the first threshold temperature), method 600 proceeds to 634 and includes maintaining the current operating parameters. For example, because the engine temperature is below the first threshold temperature, the engine may be considered to be operating within its nominal temperature range. Therefore, no indication is given for use of an additional cooling strategy. Maintaining the current operating parameters may include, for example, not switching to VDE mode to facilitate engine cooling (e.g., although the engine may switch to VDE mode in response to a low torque demand) and not using intake air to cool the engine while selectively disabling refueling. After 634, method 600 ends.

[0092] Returning to 632, if the engine temperature is above the first threshold temperature (e.g., between a first lower threshold temperature and a second higher threshold temperature), method 600 proceeds to 636 and includes using intake air to cool the engine while selectively disabling fueling, as described above with respect to Figure 5 Compared to cooling the engine with liquid fuel while operating in VDE mode, fuel economy may be improved by using intake air to cool the engine while selectively disabling refueling when the engine is not severely overheated. After 636, method 600 ends.

[0093] So, in conclusion, Figures 3 to 6The method described in provides a method for cooling an overheated engine under various operating conditions and modes. In one example, the method may include: determining a first engine overheat condition and, in response thereto, cooling the engine with intake airflow while selectively disabling cylinder fueling; determining a second engine overheat condition and, in response thereto, cooling the engine with liquid fuel injected into deactivated cylinders; and determining a third engine overheat condition and, in response thereto, cooling the engine with intake airflow provided by an electric supercharger while the engine is rotating without fueling via an electric motor. For example, during the first engine overheat condition, the engine temperature may be greater than a first, lower threshold engine temperature and less than or equal to a second, higher threshold engine temperature, while during the second engine overheat condition, the engine temperature may be greater than the second, higher threshold engine temperature. As another example, additionally or alternatively, the rate of increase in engine temperature may be less than or equal to a threshold rate during the first engine overheat condition, and greater than a threshold rate during the second engine overheat condition. Furthermore, the first and second engine overheat conditions may occur while the engine is on, with combustion occurring within the engine, and the third engine overheat condition may occur while the engine is off. Thus, during the third engine overheat condition, the engine temperature may be above the first lower threshold engine temperature while combustion is not occurring within the engine. Accordingly, the controller may determine whether the first engine overheat condition, the second engine overheat condition, or the third engine overheat condition exists based on the engine temperature and / or the rate of increase in engine temperature and the engine state (e.g., on or off).

[0094] Furthermore, the instructions stored in the memory may include instructions for determining a first engine overheat condition from an engine coolant temperature sensor while combustion occurs in the engine, and in response, cooling the engine with intake airflow while selectively disabling cylinder fueling by sending a signal to a fuel injector coupled to each cylinder. Furthermore, in some examples, the instructions stored in the memory may also include instructions for sending a signal to an electric supercharger to increase intake airflow in response to determining the first engine overheat condition. As another example, the instructions stored in the memory may include instructions for determining a second engine overheat condition from an engine coolant temperature sensor while combustion occurs in the engine, and in response, cooling the engine with liquid fuel injected into the deactivated cylinders by sending a signal to a cylinder valve deactivator of each deactivated cylinder and sending a different signal to a fuel injector coupled to each deactivated cylinder. In yet another example, the instructions stored in the memory may include instructions for determining a third engine overheat condition from an engine coolant temperature sensor while combustion is not occurring in the engine, and in response, cooling the engine with intake airflow while selectively disabling cylinder fueling by instructions for sending a signal to an electric motor coupled to a crankshaft of the engine to rotate the engine at a desired speed without fueling and sending a different signal to an electric supercharger to operate the electric supercharger at a desired speed to provide a desired airflow.

[0095] Furthermore, in some examples, the method may include instructions for selecting between cooling the engine with intake airflow while selectively disabling cylinder fueling and cooling the engine with liquid fuel injected into deactivated cylinders based on determining whether a first engine overheat condition exists and determining whether a second engine overheat condition exists. As an example, the controller may distinguish between the first engine overheat condition and the second engine overheat condition based on output of an engine coolant temperature sensor when the engine is on. As another example, the controller may distinguish between the first engine overheat condition, the second engine overheat condition, and the third engine overheat condition based on output of an engine coolant temperature sensor and an indication of whether the engine is on or off.

[0096] Figure 7 A method for cooling an overheated variable displacement engine such as Figures 1 to 2 For example, in response to an engine overheat condition, a controller (e.g., Figures 1 to 2 The controller 12) can be based on the operating conditions such as Figures 3 to 6The method for selecting an appropriate cooling strategy is shown in curve 702. Torque demand is shown in curve 704, engine state is shown in curve 706, exhaust temperature is shown in curve 708, valve deactivation in VDE mode is shown in curve 710, cylinder fueling is shown in curve 712, cylinder spark is shown in curve 714, compressor speed is shown in curve 716, and electric motor state is shown in curve 718. For all of the above, the horizontal axis represents time, with time increasing from left to right along the horizontal axis. The vertical axis represents each labeled parameter. For curves 702, 706, 708, and 716, the labeled parameters increase from bottom to top along the vertical axis. For curves 704, 710, and 718, the vertical axis indicates whether the labeled parameter is on or off, as labeled. For curves 712 and 714, the vertical axis indicates the number of cylinders receiving fuel and spark, respectively (labeled 0, 2, or 4). A four-cylinder engine is used in the example of timeline 700, although other examples may include engines with different numbers of cylinders. Additionally, a threshold torque is indicated by dashed line 720, a first threshold engine temperature is indicated by dashed line 722, a second threshold engine temperature is indicated by dashed line 724, and a threshold exhaust temperature is indicated by dashed line 726.

[0097] Prior to time t1, as shown by curve 704, the engine is on and running (e.g., combustion is occurring in the engine cylinders) to meet the torque demand from the vehicle operator (curve 702). For example, the torque demand may be determined based on the position of the accelerator pedal as described above. As the engine is on and providing the required torque, an electric motor (e.g., a starter motor or an electric motor, such as a starter motor) configured to electrically rotate the engine is turned on. Figure 1 The motor 52) is turned off (curve 718). The engine temperature (curve 706) is lower than the first threshold engine temperature (dashed line 722). Figure 3 As described, the engine temperature can be determined by, for example, the engine coolant temperature (e.g., measured by an engine coolant temperature sensor) or the cylinder head temperature (e.g., measured by a cylinder head temperature sensor). The first threshold engine temperature is lower than the second threshold engine temperature (dashed line 724) defining an upper limit of the nominal engine operating temperature range, above which the engine is considered to be overheated. Therefore, before time t1, the engine will not overheat. In addition, the exhaust temperature (curve 708) is lower than the threshold exhaust temperature (dashed line 726), indicating that there is no exhaust overtemperature condition. The VDE mode valve deactivation is closed (curve 710), indicating that the engine is operating in a non-VDE mode, in which fueling (curve 712) and spark (curve 712) are enabled for all cylinders. In addition, the electric supercharger (e.g., Figure 2The supercharger 13 of FIG. 1 is not activated and the compressor speed is zero (curve 716). For example, the engine may be operated in a non-boosted mode or by another boosting device (e.g., Figure 2 The turbocharger 15) provides the boost to operate.

[0098] At time t1, the engine temperature (curve 706) exceeds a first threshold engine temperature (dashed line 722), and the engine becomes overheated. For example, the engine may become overheated due to cooling system degradation, causing the cooling system (e.g., Figure 2 In response to the engine temperature exceeding the first threshold engine temperature, and further in response to the engine temperature remaining below the second threshold engine temperature (dashed line 724), the controller executes a cooling routine using intake airflow by disabling fuel injection to a determined number of cylinders in a distributed manner, as described with respect to Figure 5 As described above. In the example of timeline 700, fueling of two cylinders is disabled (curve 712). Since no fuel is provided, spark is also disabled for the corresponding two cylinders (curve 714). However, the cylinder intake and exhaust valves remain active (e.g., closed VDE mode valve deactivation, as shown in curve 710), with intake air being pumped through the disabled cylinders to cool the engine. Because the exhaust temperature (curve 708) is below the threshold exhaust temperature (dashed line 726), the electric supercharger is operated at a compressor speed (curve 716) determined based on operating conditions to provide, for example, a desired amount of engine cooling.

[0099] Between time t1 and time t2, the intake air cooling strategy stabilizes engine temperature (e.g., the rate of temperature increase is approximately zero), but exhaust temperature (plot 708) increases due to increased airflow through the engine caused by operation of the electric supercharger. At time t2, the exhaust temperature exceeds a threshold exhaust temperature (dashed line 726), above which exhaust component degradation may occur. Therefore, at time t2, the electric supercharger is deactivated, and the compressor speed is reduced to zero (plot 716) as the compressor spins down. Due to the reduced cooling airflow, engine cooling becomes insufficient, and engine temperature (plot 706) begins to increase.

[0100] At time t3, the engine temperature (curve 706) exceeds the second threshold engine temperature (dashed line 724), indicating that the engine is severely overheated. As a result, the controller performs a more aggressive cooling program using liquid fuel while operating in VDE mode, as described with respect to Figure 6As described, and VDE mode valve deactivation is turned on (curve 710). In the example of timeline 700, two cylinders are deactivated and the intake and exhaust valves are fully closed by VDE mode valve deactivation. No spark is provided to the deactivated cylinders, so the number of spark-enabled cylinders remains at 2 (curve 714), although the two spark-enabled cylinders may be the same or different than the two spark-enabled cylinders before the transition to VDE mode at time t3. After the intake and exhaust valves of the deactivated cylinders are fully closed, liquid fuel is injected into the deactivated cylinders at multiple piston positions until the desired total amount of fuel is injected. Thus, fueling is enabled in all four cylinders while liquid fuel is injected into the deactivated cylinders (curve 712), and then fueling is enabled in only two cylinders (e.g., the cylinders that remain active) after the desired total amount of fuel is injected. Additionally, after the desired total amount of fuel is injected, the liquid fuel is stirred within the deactivated cylinders for a duration d1. Heat is transferred from the hot deactivated cylinders to the liquid fuel, which increases the cooling effect due to the higher thermal conductivity of the liquid fuel compared to air or vaporized fuel. Figure 6 As described, duration d1 can be the amount of time it is expected that the liquid fuel will be fully vaporized within the deactivated cylinder. After duration d1 elapses, the VDE mode valve deactivation is briefly closed (curve 710), allowing the intake and exhaust valves of the deactivated cylinder to open to expel the vaporized fuel. Spark remains disabled (graph 714). Since the engine temperature (curve 706) remains above the second threshold engine temperature (dashed line 724), the VDE mode valve deactivation is reopened (curve 710) and the liquid fuel cooling process is repeated. As shown in timeline 700, the process of cooling the engine using liquid fuel while operating in VDE mode continues to repeat while the engine temperature remains above the second threshold engine temperature.

[0101] At time t4, the engine temperature (curve 706) drops below the second threshold engine temperature (dashed line 724). Therefore, after duration d1 has elapsed and unburned vaporized fuel has been exhausted from the deactivated cylinders, the VDE mode valve deactivation (curve 710) remains closed. Instead of using liquid fuel to cool the engine in VDE mode, the engine is again cooled using intake airflow, with fueling and spark disabled in both cylinders (curves 712 and 714, respectively). Because the exhaust temperature (curve 708) remains above the threshold exhaust temperature (dashed line 726), the electric supercharger is deactivated. Using intake airflow for cooling, the engine temperature (curve 706) remains below the second threshold engine temperature (dashed line 724), but remains above the first threshold engine temperature (dashed line 722).

[0102] At time t5, the torque demand (curve 702) decreases to zero and the engine is shut down (curve 704). In one example, the engine is shut down for idle stop. In another example, the vehicle key is in the off position. With the engine shut down, no cylinders are fueled (curve 712) or spark is set (curve 714). Because the engine temperature (curve 706) remains above the first threshold engine temperature (dashed line 722), the controller executes a routine for using intake airflow to cool the engine while the engine is spinning without fuel, as described with respect to FIG. Figure 4 The electric supercharger is operated to provide intake air flow, for example, by determining a non-zero compressor speed based on operating conditions (curve 716). The electric motor is turned on (curve 718) to electrically spin the engine and pump cold intake air through the unfueled engine. Figure 4 As described, the engine speed can be adjusted based on the operating conditions. Heat is transferred from the overheated engine to the intake air, particularly because no combustion occurs in the engine cylinders, resulting in a decrease in engine temperature (curve 706). Due to the lack of heat from combustion, the exhaust temperature (curve 708) also decreases. At time t6, the engine temperature (curve 706) drops below the first threshold engine temperature (dashed line 722). As a result, the electric supercharger is deactivated, the compressor speed decreases to zero (curve 716) as the device decelerates to a standstill, and the electric motor is deactivated (curve 718) to allow the engine to decelerate to a standstill. When the engine temperature is below the first threshold engine temperature, the engine is no longer considered to be in an overheated state.

[0103] In this way, an overheated engine can be cooled with liquid fuel, particularly when air cooling methods are ineffective, thereby increasing the cooling rate compared to when the engine is cooled with air. By selecting between using intake airflow to cool the engine while operating in a non-VDE mode and using liquid fuel to cool the engine while operating in a VDE mode based on operating conditions, the overheated engine cooling strategy can be optimized to balance faster cooling with engine cooling requirements based on fuel consumption. For example, when using intake airflow to cool the engine (such as when the engine cooling requirement is low), fuel economy is improved and the cooling rate is reduced, while when using liquid fuel to cool the engine (such as when the engine cooling requirement is high), fuel economy is reduced and the cooling rate is increased. This flexibility in the cooling strategy enables the controller to more aggressively cool the engine via liquid fuel when the engine is severely overheated (e.g., when the cooling requirement is high), thereby preventing engine degradation due to overheating, and to less aggressively cool the engine via intake airflow when the engine is overheated but not severely overheated (e.g., when the cooling requirement is low), thereby reducing fuel consumption. In summary, an overheated engine can be cooled more efficiently than when the engine is cooled solely via intake airflow while cylinder fueling is selectively disabled.

[0104] The technical effect of cooling an overheated engine by injecting liquid fuel into sealed, deactivated cylinders is that the engine temperature decreases at a rate greater than it would if no liquid fuel were injected.

[0105] As an example, a method includes: deactivating a subset of cylinders of a multi-cylinder engine based on the temperature of the engine; and directly injecting fuel into each subset of cylinders during the deactivation period. In the aforementioned examples, deactivating the subset of cylinders based on engine temperature additionally or alternatively includes: operating at an engine temperature greater than a threshold temperature and deactivating the subset of cylinders in response to the engine temperature being greater than the threshold temperature; and operating at an engine temperature less than or equal to the threshold temperature and not deactivating the subset of cylinders in response to the engine temperature being less than or equal to the threshold temperature. In any or all of the aforementioned examples, the method additionally or alternatively includes: activating an intake valve, an exhaust valve, and a spark plug coupled to each cylinder, and wherein the deactivation includes fully closing the intake and exhaust valves of each subset of cylinders and inhibiting spark plug firing for each subset of cylinders such that the injected fuel is not combusted. In any or all of the aforementioned examples, the method additionally or alternatively includes: activating the intake and exhaust valves coupled to each subset of cylinders after a threshold duration of the deactivation is reached; and exhausting the injected fuel. In any or all of the foregoing examples, the method additionally or alternatively further includes, after exhausting the injected fuel, enabling spark plugs coupled to each subset of cylinders to ignite in response to the engine temperature being less than or equal to the threshold temperature. In any or all of the foregoing examples, additionally or alternatively, injecting the fuel directly into the subset of cylinders during the deactivation period includes injecting fuel via the fuel injectors coupled to each subset of cylinders whenever the pistons of each subset of cylinders are at a plurality of predefined positions. In any or all of the foregoing examples, additionally or alternatively, the plurality of predefined positions includes top dead center, bottom dead center, and positions between top dead center and bottom dead center. In any or all of the foregoing examples, additionally or alternatively, injecting the fuel directly into the subset of cylinders during the deactivation period also includes reducing an injection pressure compared to an injection pressure outside of the deactivation period, and wherein an amount of fuel injected during the deactivation period is greater than an amount of fuel injected outside of the deactivation period.

[0106] As a second example, a method includes, in response to overheating of a multi-cylinder engine and based on operating conditions, selecting between cooling the engine by flowing air through one or more engine cylinders while disabling fueling of the one or more engine cylinders and cooling the engine by fueling the subset of engine cylinders with unburned liquid fuel while deactivating intake and exhaust valves of each subset of engine cylinders. Additionally or alternatively to the foregoing example, the one or more engine cylinders may be the same or different cylinders as the subset of engine cylinders, and the engine overheat condition is determined based on engine temperature and is independent of exhaust temperature. In any or all of the foregoing examples, additionally or alternatively, the operating conditions include engine temperature and engine state (e.g., "on" or "off"), and the selection additionally or alternatively also includes: in response to the engine temperature being above a first lower threshold temperature while the engine is off, cooling the engine by flowing air through one or more engine cylinders while disabling fueling of one or more engine cylinders; in response to the engine temperature being above a first lower threshold temperature and below or equal to a second higher threshold temperature while the engine is on, cooling the engine by flowing air through one or more engine cylinders while disabling fueling of one or more engine cylinders; and in response to the engine temperature being above a second higher threshold temperature while the engine is on, cooling the engine by fueling a subset of engine cylinders with unburned liquid fuel while deactivating intake and exhaust valves of the subset of engine cylinders. In any or all of the foregoing examples, the method additionally or alternatively further comprises an electric supercharger coupled to an air intake of the engine, and wherein cooling the engine by flowing air through one or more engine cylinders while disabling fueling of one or more engine cylinders comprises operating a compressor of the electric supercharger at a desired speed determined based on at least one of the engine state, the engine temperature, and the exhaust gas temperature. In any or all of the foregoing examples, the method additionally or alternatively further comprises an electric motor configured to electrically rotate the engine, and wherein cooling the engine by flowing air through one or more engine cylinders while disabling fueling of one or more engine cylinders when the engine is off comprises disabling fueling of all engine cylinders and rotating the engine electrically. In any or all of the foregoing examples, additionally or alternatively, cooling the engine by flowing air through one or more engine cylinders while disabling fueling of one or more engine cylinders when the engine is on comprises disabling fueling of a determined number of engine cylinders while enabling fueling of a remaining number of engine cylinders, and wherein the engine cylinder selected for the determined number of engine cylinders changes at a predetermined time.In any or all of the foregoing examples, additionally or alternatively, cooling the engine by fueling the subset of engine cylinders with unburned liquid fuel while deactivating the intake and exhaust valves of each subset of engine cylinders includes: completely closing the intake and exhaust valves of each subset of engine cylinders; disabling the spark plugs coupled to each subset of engine cylinders; injecting a desired amount of liquid fuel into each subset of engine cylinders via multiple injections; maintaining the intake and exhaust valves of each subset of engine cylinders completely closed for a period of time after the multiple injections are completed to allow the liquid fuel to vaporize as it absorbs heat from the engine; and opening the intake and exhaust valves of each subset of engine cylinders after the period of time has elapsed to expel the vaporized fuel.

[0107] As a third example, a system includes: an engine including a plurality of cylinders coupled to a crankshaft, each cylinder including a piston, an intake valve, an exhaust valve, a spark plug, and a fuel injector directly coupled thereto; a fuel system configured to deliver pressurized fuel from a fuel tank to the fuel injector; a first electric motor coupled to the crankshaft and receiving power from a system battery; a supercharger compressor coupled to an intake port of the engine and driven by a second electric motor receiving power from the system battery; a temperature sensor for estimating engine temperature; a temperature sensor coupled to an exhaust passage of the engine upstream of an emission control device; and a control A controller storing executable instructions in a non-transitory memory that, when executed, cause the controller to: during an engine overheat condition and when the engine is on, cool the engine using intake airflow while selectively disabling fueling of a plurality of cylinders and cooling each of the engine using liquid fuel injected into each deactivated subset of cylinders while operating in a variable displacement engine (VDE) mode under different operating conditions; and during the engine overheat condition and when the engine is off, cool the engine using airflow from the supercharger compressor while the engine is rotating without fueling via the first electric motor. In the foregoing example, additionally or alternatively, the overheat condition includes the engine temperature being greater than a lower threshold temperature, and the different operating conditions include a first operating condition in which the engine temperature is less than or equal to a higher threshold temperature and a second operating condition in which the engine temperature is greater than the higher threshold temperature. In any or all of the foregoing examples, additionally or alternatively, cooling the engine using the intake airflow while selectively disabling fueling of the plurality of cylinders is performed during the first operating condition, and cooling the engine using liquid fuel injected into each of the deactivated subsets of cylinders while operating in the VDE mode is performed during the second operating condition. In any or all of the foregoing examples, cooling the engine using the intake airflow while selectively disabling fueling of the plurality of cylinders additionally or alternatively further comprises: determining a number of cylinders to operate without fueling based on at least one of engine speed, the engine temperature, a rate of increase of the engine temperature, and a torque demand; disabling fuel injection to the determined number of cylinders in a distributed manner; and operating the supercharger compressor at a speed determined based on at least one of the engine temperature, the rate of increase of the engine temperature, and an exhaust temperature measured by a temperature sensor coupled to the exhaust passage.In any or all of the foregoing examples, cooling the engine while operating in the VDE mode using liquid fuel injected into each subset of cylinders that is deactivated additionally or alternatively includes: deactivating the subset of cylinders by fully closing the intake and exhaust valves coupled to each subset and disabling the spark plugs coupled to each subset; injecting fuel into each subset at multiple piston positions and at an injection pressure that is less than the injection pressure of the cylinders that remain active; and stirring the fuel within the subset of cylinders for a period of time before opening the intake and exhaust valves of each subset to expel the fuel.

[0108] In another representation, a method includes, in response to an engine overheat condition, selecting between cooling the engine via intake airflow while selectively disabling cylinder fueling and cooling the engine via unburned liquid fuel in the engine while selectively deactivating cylinder intake and exhaust valves. In the foregoing examples, additionally or alternatively, the engine overheat condition is based on engine temperature and is independent of exhaust temperature, and the selection is based on operating conditions including one or more of the engine temperature and an operating state of the engine. In any or all of the foregoing examples, additionally or alternatively, the operating state of the engine includes an engine-off condition in which combustion does not occur in the engine cylinders and an engine-on condition in which combustion occurs in at least one engine cylinder. In any or all of the foregoing examples, additionally or alternatively, further comprising: during the engine-off state, in response to the engine temperature being above a first lower threshold temperature, cooling the engine via intake airflow while selectively disabling cylinder fueling; and during the engine-on state, selecting between cooling the engine via intake airflow while selectively disabling cylinder fueling and cooling the engine via unburned liquid fuel in the engine while selectively deactivating cylinder intake and exhaust valves based on the engine temperature. In any or all of the foregoing examples, additionally or alternatively, during the engine-on state, in response to the engine temperature being above the first lower threshold temperature and below or equal to a second higher threshold temperature, selecting cooling the engine via intake airflow while selectively disabling cylinder fueling; and selecting cooling the engine via unburned liquid fuel in the engine while selectively deactivating cylinder intake and exhaust valves based on the engine temperature. In any or all of the foregoing examples, the method additionally or alternatively further includes an electric supercharger coupled to an air intake of the engine, and wherein the electric supercharger generates at least a portion of the intake airflow for cooling the engine. In any or all of the foregoing examples, the method additionally or alternatively further includes an electric motor configured to electrically rotate the engine, and wherein cooling the engine via the intake airflow while selectively disabling cylinder fueling during an engine-off state includes rotating the engine unfueled via the electric motor.

[0109] Note that the exemplary control and estimation routines included herein can be used in conjunction with various engine and / or vehicle system configurations. The control methods and routines disclosed herein can be stored as executable instructions in a non-transitory memory and can be executed by a control system including a controller in conjunction 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, multi-tasking, multi-threaded processing strategies, etc. Therefore, the various actions, operations, or functions shown can be performed in the order shown, in parallel, or in some cases omitted. Likewise, the processing order is not necessarily required to achieve the features and advantages of the exemplary embodiments described herein, but is provided for ease of illustration and description. One or more of the actions, operations, and / or functions shown can be repeatedly performed depending on the specific strategy used. In addition, the actions, operations, and / or functions can graphically represent code programmed into the non-transitory memory of a computer-readable storage medium in the engine control system, where the actions are performed by executing instructions in a system including various engine hardware components in conjunction with an electronic controller.

[0110] It should be understood that the configurations and procedures disclosed herein are exemplary in nature, and these specific embodiments should not be construed in a limiting sense, as many variations are possible. For example, the above technology can be applied to V-6, I-4, I-6, V-12, opposed 4-cylinder, and other engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations and other features, functions, and / or properties disclosed herein.

[0111] The following claims particularly point out certain combinations and subcombinations regarded as novel and non-obvious. These claims may refer to "an" element or "a first" element or the equivalent thereof. These claims should be understood to include reference to one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, are also regarded as included within the subject matter of the present disclosure.

[0112] According to the present invention, a method includes deactivating a subset of cylinders of a multi-cylinder engine based on temperature of the engine; and directly injecting fuel into each of the subset of cylinders during the deactivation period.

[0113] According to an embodiment, deactivating a subset of cylinders based on engine temperature includes: operating at an engine temperature above a threshold temperature and deactivating the subset of cylinders in response to the engine temperature being above the threshold temperature; and operating at an engine temperature below or equal to the threshold temperature and not deactivating the subset of cylinders in response to the engine temperature being below or equal to the threshold temperature.

[0114] According to an embodiment, the above invention is further characterized by an intake valve, an exhaust valve and a spark plug coupled to each cylinder, and wherein the deactivation includes completely closing the intake valve and the exhaust valve of each subset of cylinders and prohibiting the spark plug of each subset of cylinders from igniting so that the injected fuel does not burn.

[0115] According to an embodiment, the above invention is further characterized by activating the intake and exhaust valves coupled to each subset of engine cylinders; and exhausting the injected fuel after reaching a threshold duration of the deactivation.

[0116] According to an embodiment, the above invention is further characterized by enabling spark plugs coupled to each subset of cylinders to fire in response to the engine temperature being less than or equal to the threshold temperature after exhausting the injected fuel.

[0117] According to an embodiment, injecting the fuel directly into the subset of cylinders during the deactivation period includes performing fuel injection via a fuel injector coupled to each subset of cylinders whenever the piston of each subset of cylinders is at a plurality of predefined positions.

[0118] According to an embodiment, the plurality of predefined positions include a top dead center, a bottom dead center, and positions between the top dead center and the bottom dead center.

[0119] According to an embodiment, injecting the fuel directly into the subset of cylinders during the deactivation further comprises reducing an injection pressure compared to an injection pressure outside of the deactivation, and wherein an amount of fuel injected during the deactivation is greater than an amount of fuel injected outside of the deactivation.

[0120] According to the present invention, a method includes, in response to overheating of a multi-cylinder engine and based on operating conditions, selecting between cooling the engine by flowing air through one or more engine cylinders while disabling fueling of the one or more engine cylinders and fueling a subset of the engine cylinders with unburned liquid fuel while deactivating intake and exhaust valves of each subset of the engine cylinders.

[0121] According to an embodiment, the one or more engine cylinders may be the same or different cylinders than the subset of engine cylinders, and the engine overheat condition is determined based on engine temperature and independent of exhaust gas temperature.

[0122] According to an embodiment, the operating conditions include engine temperature and engine state (e.g., "on" or "off"), and the selection additionally or alternatively includes: in response to the engine temperature being above a first lower threshold temperature while the engine is off, cooling the engine by flowing air through one or more engine cylinders while disabling fueling of one or more engine cylinders; in response to the engine temperature being above a first lower threshold temperature and below or equal to a second higher threshold temperature while the engine is on, cooling the engine by flowing air through one or more engine cylinders while disabling fueling of one or more engine cylinders; and in response to the engine temperature being above a second higher threshold temperature while the engine is on, cooling the engine by fueling a subset of engine cylinders with unburned liquid fuel while deactivating intake and exhaust valves of the subset of engine cylinders.

[0123] According to an embodiment, the above invention is also characterized by an electric supercharger device connected to the air intake of the engine, and wherein cooling the engine by flowing air through one or more engine cylinders while prohibiting refueling of one or more engine cylinders includes operating the compressor of the electric supercharger device at a desired speed determined based on at least one of the engine state, the engine temperature and the exhaust temperature.

[0124] According to an embodiment, the above invention is also characterized by an electric motor, which is configured to rotate the engine electrically, and wherein when the engine is shut down, cooling the engine by passing air through one or more engine cylinders while disabling refueling of one or more engine cylinders includes disabling refueling of all engine cylinders and rotating the engine electrically.

[0125] According to an embodiment, cooling the engine by flowing air through one or more engine cylinders while disabling refueling of one or more engine cylinders when the engine is turned on includes disabling refueling of a determined number of engine cylinders while enabling refueling of a remaining number of engine cylinders, and wherein the engine cylinders selected for the determined number of engine cylinders are changed at a predetermined time.

[0126] According to an embodiment, cooling an engine by fueling a subset of engine cylinders with unburned liquid fuel while deactivating the intake and exhaust valves of each subset of engine cylinders includes: fully closing the intake and exhaust valves of each subset of engine cylinders; disabling a spark plug coupled to each subset of engine cylinders; injecting a desired amount of liquid fuel into each subset of engine cylinders via a plurality of injections; maintaining the intake and exhaust valves of each subset of engine cylinders fully closed for a period of time after the plurality of injections are completed to allow the liquid fuel to vaporize as it absorbs heat from the engine; and opening the intake and exhaust valves of each subset of engine cylinders after the period of time has elapsed to expel the vaporized fuel.

[0127] According to the present invention, a system is provided, comprising: an engine including a plurality of cylinders coupled to a crankshaft, each cylinder including a piston, an intake valve, an exhaust valve, a spark plug, and a fuel injector directly coupled thereto; a fuel system configured to deliver pressurized fuel from a fuel tank to the fuel injector; a first electric motor coupled to the crankshaft and receiving power from a system battery; a supercharger compressor coupled to an intake port of the engine and driven by a second electric motor receiving power from the system battery; a temperature sensor for estimating engine temperature; and a temperature sensor coupled to an exhaust port of the engine upstream of an emission control device. and a controller storing executable instructions in a non-transitory memory that, when executed, cause the controller to: during an engine overheat condition and when the engine is on, cool the engine using intake airflow while selectively disabling fueling of a plurality of cylinders and cool each of the engine using liquid fuel injected into each subset of cylinders that is deactivated while operating in a variable displacement engine (VDE) mode under different operating conditions; and during an engine overheat condition and when the engine is off, cool the engine using airflow from the supercharger compressor while the engine is spinning unfueled via the first electric motor.

[0128] According to an embodiment, the overheat condition includes the engine temperature being above a lower threshold temperature, and the different operating conditions include a first operating condition where the engine temperature is below or equal to a higher threshold temperature and a second operating condition where the engine temperature is above the higher threshold temperature.

[0129] According to an embodiment, cooling the engine using the intake airflow while selectively disabling fueling of the plurality of cylinders is performed during the first operating condition, and cooling the engine using liquid fuel injected into each of the deactivated subsets of cylinders while operating in the VDE mode is performed during the second operating condition.

[0130] According to an embodiment, using the intake airflow to cool the engine while selectively disabling fueling of the plurality of cylinders includes: determining a number of cylinders to operate without fueling based on at least one of engine speed, the engine temperature, a rate of increase of the engine temperature, and a torque demand; disabling fuel injection to the determined number of cylinders in a distributed manner; and operating the supercharger compressor at a speed determined based on at least one of the engine temperature, the rate of increase of the engine temperature, and an exhaust temperature measured by a temperature sensor coupled to the exhaust passage.

[0131] According to an embodiment, cooling the engine using liquid fuel injected into each subset of cylinders that is deactivated while operating in the VDE mode includes: deactivating the subset of cylinders by fully closing the intake and exhaust valves coupled to each subset and disabling the spark plug coupled to each subset; injecting fuel into each subset at multiple piston positions and at an injection pressure that is less than the injection pressure of the cylinders that remain active; and stirring the fuel within the subset of cylinders for a period of time before opening the intake and exhaust valves of each subset to expel the fuel.

Claims

1. A method for operating an engine, the method comprising: deactivating a subset of cylinders in a plurality of cylinders of the engine based on a temperature of the engine being greater than a threshold temperature; as well as injecting fuel directly into each cylinder in the subset of cylinders during the deactivation period; Wherein injecting the fuel directly into each cylinder of the subset of cylinders during the deactivation comprises reducing an injection pressure compared to an injection pressure outside of the deactivation.

2. The method of claim 1 , wherein deactivating the subset of cylinders based on the temperature of the engine being greater than the threshold temperature comprises: operating the engine with the temperature of the engine above the threshold temperature, and deactivating the subset of cylinders in response to the temperature of the engine being above the threshold temperature; as well as The engine is operated with the temperature of the engine less than or equal to the threshold temperature, and the subset of cylinders is not deactivated in response to the temperature of the engine being less than or equal to the threshold temperature.

3. The method of claim 2 further comprising an intake valve, an exhaust valve, and a spark plug coupled to each cylinder, and wherein the deactivating comprises completely closing the intake valve and the exhaust valve of each of the subset of cylinders and disabling the spark plug of each of the subset of cylinders from firing such that injected fuel does not combust.

4. The method of claim 3, further comprising: After reaching a threshold duration of said deactivation, activating the intake valve and the exhaust valve coupled to each of the subset of engine cylinders; as well as The injected fuel is exhausted.

5. The method of claim 4, further comprising: After exhausting the injected fuel, the spark plug coupled to each of the subset of cylinders is enabled to fire in response to the temperature of the engine being less than or equal to the threshold temperature.

6. The method of claim 1 , wherein injecting the fuel directly into the subset of cylinders during the deactivation period comprises performing fuel injection via a fuel injector coupled to each subset of cylinders whenever a piston of each subset of cylinders is at a plurality of predefined positions. 7 . The method of claim 6 , wherein the plurality of predefined positions include a top dead center, a bottom dead center, and positions between the top dead center and the bottom dead center. 8 . The method of claim 6 , wherein injecting the fuel directly into the subset of cylinders during the deactivation further comprises injecting a greater amount of fuel into each deactivated cylinder than into each activated cylinder.

9. A system for an engine, comprising: An engine comprising a plurality of cylinders coupled to a crankshaft, each cylinder comprising a piston, an intake valve, an exhaust valve, a spark plug, and a fuel injector directly coupled thereto; a fuel system configured to deliver pressurized fuel from a fuel tank to the fuel injectors; a first electric motor coupled to the crankshaft and receiving power from a system battery; a supercharger compressor coupled to the air intake of the engine and driven by a second electric motor receiving power from the system battery; a temperature sensor for estimating engine temperature; a second temperature sensor coupled to the exhaust passage of the engine upstream of the emission control device; and A controller storing executable instructions in a non-transitory memory that, when executed, cause the controller to: deactivating a subset of cylinders among a plurality of cylinders of the engine based on a temperature of the engine being greater than a threshold temperature; as well as injecting fuel directly into each cylinder in the subset of cylinders during the deactivation period; Wherein injecting the fuel directly into each cylinder of the subset of cylinders during the deactivation comprises reducing an injection pressure compared to an injection pressure outside of the deactivation.

10. The system of claim 9, wherein deactivating the subset of cylinders based on the temperature of the engine being greater than the threshold temperature comprises: operating the engine with the temperature of the engine above the threshold temperature, and deactivating the subset of cylinders in response to the temperature of the engine being above the threshold temperature; as well as The engine is operated with the temperature of the engine less than or equal to the threshold temperature, and the subset of cylinders is not deactivated in response to the temperature of the engine being less than or equal to the threshold temperature.

11. The system of claim 10, wherein deactivating the subset of cylinders comprises fully closing the intake valve and the exhaust valve of each of the subset of cylinders and disabling the spark plug of each of the subset of cylinders from firing such that injected fuel does not combust.

12. The system of claim 9, wherein the executable instructions further cause the controller to: After reaching the threshold duration of deactivation, activating the intake valve and the exhaust valve coupled to each of the subset of engine cylinders; and The injected fuel is exhausted.

13. The system of claim 12, wherein the executable instructions further cause the controller to: After exhausting the injected fuel, the spark plug coupled to each of the subset of cylinders is enabled to fire in response to the temperature of the engine being less than or equal to the threshold temperature.

14. The system of claim 9, wherein injecting the fuel directly into the subset of cylinders during the deactivation period comprises performing fuel injection via a fuel injector coupled to each subset of cylinders whenever a piston of each subset of cylinders is at a plurality of predefined positions.

15. The system of claim 9 wherein injecting the fuel directly into the subset of cylinders during the deactivation further comprises injecting a greater amount of fuel into each deactivated cylinder than into each activated cylinder.

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