Engine cooling using electrically driven intake compressor

Abstract

Methods and systems are provided for cooling an engine by operating an electrically driven air intake compressor. In one example, in response to determining, based on a measured or inferred engine temperature, that the engine temperature is greater than a threshold temperature, an electrically driven air intake compressor of the vehicle is employed to direct air through a charge air cooler and engine cylinders while the engine is rotating without fueling. In this way, the engine temperature can be reduced even in conditions that would not normally be suitable for engine cooling, such as at idle-stop or when the engine coolant system is degraded.

Description

Field of the Invention

[0001] The present specification generally relates to methods and systems for controlling an electrically driven air intake compressor of a vehicle to cool an overheating vehicle engine.

[0002] BACKGROUND / SUMMARY

[0003] A vehicle can include a coolant system configured to reduce overheating of an engine by transferring heat to ambient air. Therein, coolant is circulated through an engine block to remove heat from a hot engine and then the heated coolant is circulated through a radiator near the front of the vehicle. The heated coolant can also be circulated through a heat exchanger to heat a passenger cabin. The coolant system can include various components, such as various valves, pumps, and one or more thermostats. In the event of a degradation of the coolant system due to a failure of a component (e.g., water pump degradation) or due to a loss of coolant of the coolant system (e.g., due to a coolant leak), the engine can overheat. Engine overheating can be exacerbated in turbocharged direct injection engines due to the supercharging and higher loads.

[0004] Various methods have been developed to address engine overheating in the event of a degradation of the coolant system. One exemplary method, shown by Willard et al. in U.S. Patent No. 9,217,379, addresses engine overheating by alternately shutting off fuel to one or more cylinders while using the fueled cylinders to maintain vehicle torque demand. Cylinder cooling is achieved when cool, unburned air flows through the unfueled cylinders. By cutting fuel to individual cylinders, flexibility in cooling and torque control is provided. In still other methods, cylinder fueling is cut in banks to cool the deactivated bank, while the active bank continues to produce torque for vehicle propulsion.

[0005] The present inventors have recognized potential problems with the above methods. As one example, in an engine configured with start-stop capability, underhood temperatures can continue to climb even with all cylinders deactivated. With the vehicle stationary and not moving, an idle-stop engine can continue to overheat even with an additional cooling fan activated. If the engine is restarted to increase cooling air flow, the fuel economy benefits associated with start-stop operation can be lost. Likewise, in a hybrid electric vehicle, pulling a closed engine (by transitioning out of pure electric mode) to flow cool air over the hot engine can result in a net fuel loss.

[0006] The present inventors have developed systems and methods that address at least some of the above problems. In one example, a method for cooling an overheated engine includes rotating the engine without fueling and operating an electric air intake compressor to direct air to the engine cylinders via a charge air cooler when an engine temperature is greater than a threshold temperature and when an engine idle-stop condition is satisfied. In this way, engine cooling can be accelerated without restarting the engine.

[0007] As one example, a boosted engine can be configured with an air intake compressor coupled to an electric motor. The electric air intake compressor can be included in an electric turbocharger, or can be coupled to a mechanical turbocharger downstream of a turbo-driven air intake compressor. In response to an engine idle-stop condition being satisfied, engine fueling can be disabled. Further, an engine temperature can be evaluated. In response to being above a threshold engine temperature or an engine temperature rise rate above a threshold, an engine controller can rotate the engine without fueling, such as via a starter motor or hybrid powertrain electric motor, while also enabling the electric air intake compressor. Therein, a pulse width commanded to the electric motor driving the electric air intake compressor can be increased as the degree of engine cooling needed increases. Due to compressor operation, intake air drawn via the rotating engine can be delivered to the engine cylinders after being cooled via the charge air cooler. Once the engine is sufficiently cooled, the electric air intake compressor can be disabled and the engine can be rotated to and maintained at a stop until an engine restart condition is satisfied. In one example, electric air intake compressor operation can be performed while an existing coolant system fan is operating to accelerate cooling. In still further examples, in response to engine overheating when a hybrid electric vehicle is operating in a pure engine or assist mode, the vehicle can temporarily transition to a pure electric mode, and operation of the electric air intake compressor can cooperate with the non-fueled rotation of the engine to reduce engine temperature. Thereafter, engine operation can resume.

[0008] In this way, engine overheating can be addressed quickly without stopping the engine for cooling. By rotating the engine without fueling, air can be drawn into the engine cylinders. By simultaneously rotating the air intake compressor via the electric motor, the compressed air can be cooled as it passes through the charge air cooler before being delivered to the cylinders. The technical effect of flowing cooled compressed air through the cylinders is that heat loss from the cylinder walls and pistons can be accelerated, reducing engine and under-hood temperature rise. By operating the electric air intake compressor alongside a cooling fan, engine temperature can be maintained within a target range even with the engine off. By accelerating engine cooling with the engine off, such as during idle-stop, engine overheating can be reduced in response, the engine restarted, extending the duration of engine idle-stop and fuel economy benefits.

[0009] The foregoing advantages and other features of the present description will become apparent to those skilled in the art upon reading the following detailed description with reference to the accompanying drawings, when considered in conjunction with the appended claims.

[0010] It is understood that the foregoing overview is provided as a simplistic introduction to the select concepts further described in the detailed description. It is not intended to identify key or essential features of the claimed subject matter, nor is it intended to limit the scope of what the claimed subject matter is to patents exclusively to implementations described in the foregoing overview. Furthermore, the claimed subject matter is not limited to implementations that solve any or all of the disadvantages recorded in the above background.

[0011] BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 An exemplary vehicle propulsion system is shown.

[0013] Figure 2 An exemplary engine system is shown including an electrically driven air compressor coupled in Figure 1 a vehicle propulsion system.

[0014] Figures 3A-3C An exemplary embodiment of an electrically driven air compressor is shown. Figure 1 and Figure 2 An exemplary embodiment of an electrically driven air compressor is shown.

[0015] Figure 4 A high level flowchart of an exemplary method for cooling an overheated vehicle engine during idle-stop is shown.

[0016] Figure 5 A high level flowchart of an exemplary method for cooling an engine of a hybrid electric vehicle is shown.

[0017] Figure 6 A prophetic example of cooling an overheated engine during idle-stop is shown.

[0018] Figure 7 A prophetic example of cooling an overheated engine of a hybrid electric vehicle is shown. DETAILED DESCRIPTION

[0019] The following description relates to systems and methods for cooling an overheated engine in a vehicle propulsion system, such as a hybrid electric vehicle system shown in Figure 1 Particularly, the description relates to cooling an overheated vehicle engine using an electrically driven air compressor (EDIAC) included in a supercharged engine system of a system, such as Figure 2 An exemplary embodiment of an EDIAC is shown in Figures 3A-3C An engine controller can be configured to perform functions such as Figure 4control routine of an exemplary routine to operate the EDIAC to accelerate engine cooling during idle-stop. Further, an intake compressor can be operable for engine temperature control in a hybrid electric vehicle, as Figure 5 is given. Referring to Figures 6-7 exemplary cooling operation is shown.

[0020] Figure 1 An exemplary vehicle propulsion system 100 is shown. The vehicle propulsion system 100 includes a fuel-burning engine 110 and can include a motor 120. As a non-limiting example, the engine 110 includes an internal combustion engine, and the motor 120 includes an electric motor. The motor 120 can be configured to utilize or consume a different energy source than the engine 110. For example, the engine 110 can consume a liquid fuel (e.g., gasoline) to produce an engine output, while the motor 120 can consume electrical energy to produce a motor output. As such, a vehicle having a propulsion system 100 that includes a motor can be referred to as a hybrid electric vehicle (HEV).

[0021] The vehicle propulsion system 100 can utilize a variety of different operating modes depending on the operating conditions encountered by the vehicle propulsion system. Some of these modes can enable the engine 110 to be maintained in an off state (e.g., set to an inactive state) in which fuel combustion at the engine is stopped. For example, during selected operating conditions, when the engine 110 is inactive, the motor 120 can propel the vehicle via the drive wheels 130 as shown by arrow 122 (also referred to herein as a pure electric mode). During other operating conditions, the engine 110 can be set to an inactive state (as described above), while the motor 120 can operate to charge the energy storage device 150. For example, the motor 120 can receive wheel torque from the drive wheels 130 as shown by arrow 122, where the motor can convert the vehicle’s kinetic energy into electrical energy for storage at the energy storage device 150 as shown by arrow 124. This operation can be referred to as regenerative braking of the vehicle. Thus, in some embodiments, the motor 120 can provide a generator function. However, in other embodiments, a generator 160 can alternatively receive wheel torque from the drive wheels 130, where the generator can convert the vehicle’s kinetic energy into electrical energy for storage at the energy storage device 150 as shown by arrow 162.

[0022] During still other operating conditions, the engine 110 can operate by combusting fuel received from the fuel system 140, as indicated by arrow 142. For example, when the motor 120 is deactivated, the engine 110 can operate to propel the vehicle via the drive wheels 130, as indicated by arrow 112 (also referred to herein as a pure engine mode). During other operating conditions, both the engine 110 and the motor 120 can operate to propel the vehicle via the drive wheels 130, as indicated by arrows 112 and 122, respectively (also referred to herein as an assist mode). Configurations in which both the engine and the motor can selectively propel the vehicle can be referred to as parallel vehicle propulsion systems. It should be noted that, in some embodiments, the motor 120 can propel the vehicle via a first set of drive wheels, while the engine 110 can propel the vehicle via a second set of drive wheels.

[0023] In other embodiments, the vehicle propulsion system 100 can be configured as a series vehicle propulsion system, whereby the engine does not directly propel the drive wheels. Rather, the engine 110 can operate to power the motor 120, which in turn can propel the vehicle via the drive wheels 130, as indicated by arrow 122. For example, during selected operating conditions, the engine 110 can drive the generator 160, as indicated by arrow 116, which in turn can supply electrical energy to one or more of the motors 120, as indicated by arrow 114, or to the energy storage device 150, as indicated by arrow 162. As another example, the engine 110 can operate to drive the motor 120, which in turn can provide a generator function to convert engine output to electrical energy, which can be stored in the energy storage device 150 for later use by the motor.

[0024] The engine 110 can be configured with a start / stop capability, in which the control system 190 can automatically shut down (idle-stop) the internal combustion engine 110 without receiving a driver input to shut down the engine, if selected idle-stop conditions are met. These can include, for example, torque demand less than a threshold, on-board battery sufficiently charged, no request for air conditioning received, etc. In one example, the engine can be shut off in response to engine idling when the vehicle is stopped at a traffic signal. Likewise, the engine can be automatically restarted in response to torque demand greater than a threshold, battery requesting charge, air conditioning compressor requesting operation, etc. In one example, the engine can be restarted in response to the driver applying the accelerator pedal after being stopped at a traffic signal for a period of time. The engine can be cranked via a motor, such as a starter motor coupled to the crankshaft of the engine, without fueling until a threshold engine speed is reached, after which the motor can be disabled and engine fueling resumed. Thereafter, engine combustion can be able to support engine rotation. As a result of automatic start / stop, fuel consumption and exhaust emissions can be reduced.

[0025] The fuel system 140 can include one or more fuel tanks 144 for storing fuel on the vehicle. For example, the fuel tanks 144 can store one or more liquid fuels, including but not limited to gasoline, diesel, and alcohol fuels. In some examples, fuel can be stored on the vehicle as a blend of two or more different fuels. For example, the fuel tanks 144 can be configured to store a blend of gasoline and ethanol (e.g., E10, E85, etc.) or a mixture of gasoline and methanol (e.g., M10, M85, etc.), whereby these fuels or fuel blends can be delivered to the engine 110 as indicated by arrows 142. Other suitable fuels or fuel blends can also be supplied to the engine 110, where they can be combusted at the engine to produce an engine output. The engine output can be utilized to propel the vehicle as indicated by arrows 112 or to recharge the energy storage device 150 via the motor 120 or generator 160.

[0026] In some embodiments, the energy storage device 150 can be configured to store electrical energy that can be supplied to other electrical loads resident on the vehicle (in addition to the motor), including cabin heating and air conditioning systems, engine starting systems, headlamps, cabin audio and video systems, etc. In still other examples, as detailed with reference to Figure 2 Figures 4-5 The EDIAC can be operable for boost pressure control during fueled engine operation, and can also be used for engine temperature control during unfueled engine rotation, as detailed at

[0027] The control system 190 can be in communication with one or more of the engine 110, the motor 120, the fuel system 140, the energy storage device 150, and the generator 160. The control system 190 can receive sensory feedback information from one or more of the engine 110, the motor 120, the fuel system 140, the energy storage device 150, and the generator 160. In addition, the control system 190 can send control signals to one or more of the engine 110, the motor 120, the fuel system 140, the energy storage device 150, and the generator 160 in response to this sensory feedback. The control system 190 can receive an indication of a driver requested output of the vehicle propulsion system from the vehicle driver 102. For example, the control system 190 can receive sensory feedback from a pedal position (PP) sensor 194 in communication with a pedal 192. The pedal 192 can illustratively refer to a brake pedal and / or an accelerator pedal.

[0028] ​The energy storage device 150 can periodically receive electrical energy from a power source 180 that resides outside of the vehicle (e.g., not part of the vehicle), as indicated by arrow 184. As a non-limiting example, the vehicle propulsion system 100 can be configured as a plug-in hybrid electric vehicle (PEV), whereby electrical energy can be supplied from the power source 180 to the energy storage device 150 via an electrical energy transfer cable 182. The electrical power transfer cable 182 can electrically couple the energy storage device 150 and the power source 180 during recharging operations of the energy storage device 150 from the power source 180. The electrical power transfer cable 182 can be disconnected from the power source 180 and the energy storage device 150 when the vehicle propulsion system is operating to propel the vehicle. The control system 190 can identify and / or control the amount of electrical energy stored at the energy storage device, which can be referred to as the state of charge (SOC).

[0029] In other embodiments, the electrical power transfer cable 182 can be omitted, where electrical energy can be received wirelessly at the energy storage device 150 from the power source 180. For example, the energy storage device 150 can receive electrical energy from the power source 180 via one or more of electromagnetic induction, radio waves, and electromagnetic resonance. As such, it should be understood that any suitable method can be used to recharge the energy storage device 150 from a power source that does not form part of the vehicle. In this manner, the motor 120 can propel the vehicle by utilizing an energy source other than fuel utilized by the engine 110.

[0030] The fuel system 140 can periodically receive fuel from a fuel source that resides outside of the vehicle. As a non-limiting example, the vehicle propulsion system 100 can be refueled by receiving fuel via a fuel dispensing device 170, as indicated by arrow 172. In some embodiments, the fuel tank 144 can be configured to store fuel received from the fuel dispensing device 170 until it is supplied to the engine 110 for combustion. In some embodiments, the control system 190 can receive an indication of a fuel level stored at the fuel tank 144 via a fuel level sensor. The fuel level stored at the fuel tank 144 (e.g., as identified by the fuel level sensor) can be communicated to the vehicle driver, for example, via a fuel gauge or indication in the vehicle dashboard 196. The vehicle dashboard 196 can include one or more indicator lights and / or text-based displays, where messages are displayed to the driver. The vehicle dashboard 196 can also include various input portions for receiving driver input, such as buttons, touchscreens, voice input / recognition, etc. For example, the vehicle dashboard 196 can include a refueling button 197 that can be manually actuated or pressed by the vehicle driver to initiate refueling. For example, in response to the vehicle driver actuating the refueling button 197, the fuel tank in the vehicle can be depressurized so that refueling can be performed.

[0031] The vehicle propulsion system 100 can also include an ambient temperature sensor 198, a humidity sensor 185, and an engine temperature sensor 115. In one example, the engine temperature sensor 115 is an engine coolant temperature (ECT) sensor, where the engine temperature is inferred from the engine coolant temperature. In another example, the engine temperature sensor 115 is a cylinder head temperature (CHT) sensor, where the engine temperature is inferred from the cylinder head temperature. Further, the engine 110 can include an engine coolant system 117 for engine temperature control, which can include various components such as a radiator, additional cooling fans, a coolant pump, a water pump, and a coolant reservoir (or sump). As will be discussed in greater detail below, in the event of engine idle-stop and engine over-temperature, the EDIAC 113 can be used to speed up engine cooling. Briefly, when the engine is rotating without fueling, the EDIAC 113 operates to drive air through a charge air cooler (CAC) and then drive the cooled air into the engine cylinders, cooling the cylinder walls and pistons.

[0032] Reference is now made to Figure 2 , showing a schematic diagram of an engine system 200. The engine system 200 is comprised of a multi-cylinder engine 211 that can be included in a propulsion system of an automobile, such as the propulsion system shown in Figure 1 . In one example, the engine 211 can be an embodiment of the engine 110 of Figure 1 .

[0033] The engine 211 can be configured as a supercharged engine that receives intake air compressed via an electrically driven intake compressor (EDIAC) 113. There can be various configurations of EDIACs. As non-limiting examples, the EDIAC 113 can include an electrically driven compressor that is also coupled to a turbine in an electrically driven turbocharger, an electrically driven compressor of a mechanical supercharger, and an electrically driven auxiliary compressor (also referred to herein as an electrically driven supercharger) coupled in bypass upstream or downstream of a main intake compressor, as shown in Figures 3A-3C .

[0034] Briefly, an electrically driven turbocharger refers to a turbocharger system in which the intake compressor can receive electrical power directly from an electric motor and / or from a turbine (such as the turbine 216), an electrically driven mechanical supercharger refers to an intake compressor that is driven solely by an electric motor, and an electrically driven supercharger refers to a system that includes a conventional turbocharging system with an additional electrically driven compressor downstream of a first mechanically driven compressor. Further details regarding EDIAC embodiments will be given in Figures 3A-3C .

[0035] Fresh air is introduced along intake tract 242, flowing to EDIAC 113 where it is compressed before continuing to flow to the engine cylinders. EDIAC 113 includes a compressor 214 for compressing the intake air, a motor 213 for rotating the compressor 214, and an electrical energy storage device 258 for supplying electrical energy to the electric motor 213. In one example, the electrical energy storage device 258 is a battery. In one example, the electrical energy storage device 258 is a capacitor. In the case where EDIAC 113 is an electrically driven turbocharger, as depicted, the compressor can also be mechanically coupled to and driven by the turbine 216 via shaft 219. Thus, when EDIAC 113 is embodied as an electrically driven turbocharger, the compressor 214 can be driven by electrical power from electric motor 213 and turbine 216. Rotation of turbine 216 can be induced by the flow of exhaust gas passing therethrough. However, in some EDIAC 113 embodiments, electric motor 213 can instead be coupled to shaft 219 or turbine 216, where the output of the turbine can be adjusted via motor output adjustment. Although the depicted EDIAC 113 is in the form of an electrically driven turbocharger, it should be understood that other EDIAC 113 embodiments are possible, such as those shown. Figure 2 Figures 3A-3C

[0036] As the air charge is heated due to the pressurization upon passing through the compressor, a charge air cooler 218 can be coupled to EDIAC 113 downstream for cooling the pressurized air before it is delivered to the engine cylinders. The CAC can be, for example, an air-to-air or air-to-water heat exchanger. In one example, the CAC can be coupled to the engine coolant system 290, where coolant from the engine coolant system 290 can also be circulated through the CAC 218. A throttle valve 220 is coupled to the engine intake manifold 222 downstream of the CAC 218.

[0037] ​​The pressure of the charge air within the intake manifold 222 can be sensed by a manifold air pressure (MAP) sensor 225 and the boost pressure at the outlet of the EDIAC can be sensed by a boost pressure sensor 224. A compressor recirculation valve (CRV) 272 can be coupled between the inlet and outlet of the EDIAC 113 in a bypass passage 270. By adjusting the opening of the CRV 272, at least a portion of the boosted charge air can be recirculated around the compressor. The compressor recirculation valve 272 can be a normally closed valve configured to open to release excess boost pressure under selected operating conditions. For example, the CRV 272 can open under conditions of engine speed reduction to avoid compressor surge. Specifically, to reduce compressor surge, such as when the driver releases the accelerator pedal, the boost pressure can be dumped from the intake manifold 222 (downstream of the CAC 218 and upstream of the intake throttle 220) to the intake tract 242 by increasing the opening of the CRV 272. By flowing the boosted air from upstream of the intake throttle inlet to upstream of the EDIAC 113 inlet, the boost pressure can be rapidly reduced, thereby speeding up the boost control. The CRV 272 can be a continuously variable valve that can be adjusted to a fully open position, a fully closed position, or any position therebetween.

[0038] The intake manifold 222 can be coupled to a series of combustion chambers 231 of the engine 211 by a series of intake valves (not shown). The combustion chambers 231 can be supplied with one or more fuels, such as gasoline, an alcohol fuel blend, diesel, biodiesel, compressed natural gas, etc. The fuel can be supplied to the combustion chambers via fuel injectors 266. In the depicted example, the fuel injectors 266 are configured for direct injection, but in other embodiments, the fuel injectors 266 can be configured for intake port injection or throttle body injection. Further, each combustion chamber can include one or more fuel injectors of different configurations to enable each cylinder to receive fuel via direct injection, intake port injection, throttle body injection, or a combination thereof. In the combustion chambers, combustion can be initiated via spark ignition and / or compression ignition. The engine temperature can be measured or estimated via one or more temperature sensors, such as an engine temperature sensor 240.

[0039] The combustion chambers 231 can be further coupled to an exhaust manifold 236 via a series of exhaust valves (not shown). In the depicted embodiment, a single exhaust manifold 236 is shown. However, in other embodiments, the exhaust manifold can include multiple exhaust manifold segments. Configurations with multiple exhaust manifold segments can enable outflow from different combustion chambers to be directed to different locations in the engine system. A wide-range exhaust gas oxygen content (UEGO) sensor 226 is shown coupled to the exhaust manifold 236 upstream of the turbine 216. Alternatively, a two-state exhaust gas oxygen content sensor can replace the UEGO sensor 226. It will be appreciated that the UEGO sensor 226 can also be any other suitable sensor for providing an indication of the exhaust gas air-fuel ratio in the exhaust system.

[0040] The engine 211 can have an associated coolant system 290 for maintaining the engine temperature within a desired range. The coolant system 290 can operate to reduce the engine 211 temperature by actuating a coolant pump 293 to flow liquid coolant, drawn from a coolant reservoir or sump 294, around and through passages within the engine 211. After passing through the engine and absorbing engine heat, the heated coolant passes through narrow passages within a radiator 291, where it can release heat to ambient air. A radiator fan 292 can be coupled to the radiator 291 for blowing ambient air through the radiator 291, thereby increasing the rate of heat transfer between the coolant and the air, especially in situations where the vehicle is stationary. In other examples, the heated coolant can be circulated through a heater core (not shown), where heat can be rejected to components that need heating, such as for cabin heating. Finally, the coolant returns to the coolant reservoir (or sump) 294. Coolant system 290 operation, including pump output and cooling fan speed, can be controlled by the vehicle control system 217 based on the output of one or more temperature sensors, such as the engine temperature sensor 240.

[0041] The engine 211 can also include an exhaust gas recirculation (EGR) system for recirculating exhaust gas from the exhaust manifold to the intake manifold to help reduce NOx and other exhaust emissions. For example, the engine 211 can include a low-pressure EGR system, as depicted, in which exhaust gas is recirculated from the exhaust manifold at a location downstream of the exhaust turbine 216 to the intake manifold 222 at a location upstream of the intake compressor 113 via a low-pressure EGR passage 251. The amount of exhaust gas recirculated to the engine intake can be controlled via adjustment of the opening of an EGR valve 252. The heated exhaust gas can be cooled as it passes through an EGR cooler 250 before being recirculated to the intake.

[0042] Exhaust gas from one or more exhaust manifold segments is directed to turbine 216 to drive the turbine. When turbine torque reduction is desired, some exhaust gas is alternatively directed through wastegate 230 that bypasses the turbine. In some embodiments, turbine 216 can be coupled to electric motor 213, which can operate in motor mode to provide electric assist. Specifically, the electric motor can be operable to provide additional torque to turbine 216 to meet an increase in torque demand. When coupled to turbine 216, the electric motor can also operate in generator mode to generate electrical energy when turbine torque exceeds torque demand. Excess electrical energy can be stored in energy battery 258.

[0043] The combined flow from turbine 216 and wastegate 230 then flows through emission control device 280. Emission control device 280 can be configured to treat the exhaust stream in a catalytic manner to reduce the amount of one or more substances in the exhaust stream. Emission control device 280 can include a three-way catalyst (TWC), an oxidation catalyst, a reduction catalyst, or a combination thereof. After passing through emission control device 280, the treated exhaust can be released to the atmosphere via exhaust conduit 235.

[0044] Engine system 200 can also include control system 217. Control system 217 is shown receiving information from a plurality of sensors 282 and sending control signals to a plurality of actuators 281. Sensors 282 can include a UEGO sensor 226 for estimating exhaust air-fuel ratio, a boost pressure sensor 224 for estimating boost manifold pressure downstream of EDIAC 113, an engine temperature sensor 240, and other sensors such as additional pressure sensors, temperature sensors, air-fuel ratio sensors, and flow sensors coupled to various locations of vehicle system 200. As another example, actuators can include fuel injectors 266, throttle valve 220, coolant pump 293, radiator fan 292, electric motor 213, etc. Control system 217 can receive input data from the various sensors, process the input data, and in response to the processed input data, trigger various vehicle actuators based on instructions or code corresponding to one or more routines programmed therein. For example, in response to engine temperature being above a threshold, as inferred based on output of engine temperature sensor, control system can send a command signal to the radiator fan to increase fan speed, and to the coolant pump to increase coolant pump output. Reference is made herein to Figures 4-5 An example control routine is described.

[0045] As referenced above Figure 4As detailed, at least based on engine temperature (as indicated by temperature sensor 240) and when the engine is in an idle-stop condition, control system 217 can operate EDIAC 113 in conjunction with engine rotation without fuel to reduce engine temperature. Specifically, when the engine temperature is above a threshold temperature, and when an idle-stop condition is performed (e.g., when engine refueling has been stopped), intake air can be compressed by EDIAC 113 and blown through CAC 218 while the engine is rotated by a motor without fuel. As the intake air travels through CAC 218, it will be cooled before entering engine cylinders (such as engine cylinder 231). With the cooled intake air passing through the engine cylinders, the engine temperature can be reduced, thereby preventing engine overheating. EDIAC operation can supplement the operation of the coolant system fan and pump. In this way, engine cooling assisted by EDIAC 113 can continue until engine restart conditions are met, or until the engine temperature 211 is sufficiently reduced.

[0046] Similarly, as referenced Figure 5 As detailed, based at least on engine temperature, control system 217 can switch the hybrid vehicle to pure electric mode (where only motor torque from the electric motor is used to propel the vehicle), then operate EDIAC 113 in conjunction with unfueled engine rotation to reduce engine 211 temperature. As an example, the vehicle, propelled using at least some engine torque, can be switched to pure electric mode in response to engine 211 temperature exceeding a threshold or anticipated engine overheating based on the current rate of engine temperature rise. Following the switch to pure electric mode, control system 217 can rotate engine 211 via starter motor while simultaneously rotating EDIAC 113 via electric motor to guide intake air through CAC 218. After passing through CAC 218 and being cooled, the intake air is pumped into and exhausted from the engine cylinders by the pumping action of the rotating engine cylinder pistons. Therefore, heat can be dissipated from the engine cylinders and engine 211 temperature can be reduced.

[0047] Figures 1-2 The EDIAC can have various embodiments. Figures 3A-3C Three exemplary EDIAC embodiments are shown. EDIAC 113 includes an intake compressor driven by an electric motor, wherein the motor operation is controlled by a vehicle control system (such as...). Figure 2 Vehicle control system 217 or Figure 1 The compressor is controlled by a control system 190. The compressor is positioned upstream of the CAC. This arrangement allows the compressor to rotate due to torque provided by the motor, thereby increasing the airflow through the engine cylinders.

[0048] Figure 3AA first exemplary embodiment 310 of an EDIAC included in an electric turbocharger is shown, and thus is Figure 2 depicted embodiment of a supercharged engine system. Figure 3A The electric turbocharger 300 includes an intake compressor 214 mechanically coupled to a turbine along a turbocharger shaft 219. The turbine 216 is rotated by an expanding exhaust stream expelled from the engine. In one example, the compressor 214 and turbine 216 can be coupled within a twin-scroll turbocharger. The turbine geometry can be actively varied according to engine speed, torque demand, and other operating conditions. By adjusting the speed of the turbine 216, the speed of the compressor 214 can be adjusted.

[0049] The compressor 214 is also coupled to an electric motor 213. In the depicted example, the electric motor 213 is coupled to the turbocharger shaft, enabling it to provide electric assist to each of the compressor 214 and turbine 216. In other examples, the electric motor 213 can be selectively coupled to the compressor 214, such that the speed of the compressor 214 can be adjusted independent of the speed of the turbine 216. The motor 213 can be selectively coupled to the compressor 214 via a shaft, a belt, a gear drive, or any other mechanical coupler that enables the torque generated by the electric motor 213 to be used to rotate the compressor 214. The motor 213 can be built-in with the compressor in a common housing, such that the compressor 214 and motor 213 are housed within the same structure. The motor 213 can be powered by an energy storage device, such as a battery 258.

[0050] In the depicted configuration, torque can be provided to the compressor 214 by the motor 213, the turbine 216, or both the motor 213 and turbine 216 simultaneously in response to an increase in torque demand. Alternatively, excess engine torque can be absorbed at the motor 213 in response to a decrease in torque demand. In this way, the motor 213 can operate as a generator to generate electrical energy for immediate consumption by the vehicle system or storage in an electrical storage device, such as the battery 258.

[0051] Referring to Figure 3B , a second exemplary embodiment 320 of an EDIAC in an electric supercharger is shown. Figure 3B The electric supercharger 300 includes a compressor 304 that can be mechanically coupled to an electric motor 213 via a shaft 310. In other examples, the motor 213 can be mechanically coupled to the compressor 304 via a belt, a gear drive, or other mechanical coupler that enables the torque generated by the electric motor 213 to be transmitted to the compressor 304 and operate the compressor 304. The motor 213 can be built-in with the compressor 304 in a common housing. The motor 213 can be powered by an energy storage device, such as a battery 258. Torque can be provided from the motor 213 to the compressor 304. The output of the motor 213 can be adjusted by a control system based on operating conditions, including torque demand.

[0052] In some examples, where the engine system is a split turbocharger engine system, the supercharger can be coupled along the intake tract upstream or downstream of the turbocharger compressor, such that the supercharger compressor can operate to provide supercharging while the turbine is spooling up.

[0053] Figure 3C A third exemplary embodiment 330 of an EDIAC included in an electrically supercharged engine is shown. Figure 3C An electrically supercharged engine is shown in FIG. 3. An electrically supercharged engine 300 includes an engine 301, a turbocharger compressor 305, an electrically operated compressor 306, and an electric motor 213. The electrically supercharged engine 300 is coupled downstream of the turbocharger compressor 305, which is mechanically coupled to a turbine 216 via a shaft 219. The turbine 216 is rotated by an expanding exhaust stream expelled from the engine. In one example, the compressor 305 and turbine 216 can be coupled within a twin-scroll turbocharger. The turbine 216 geometry can be actively varied according to engine speed and other operating conditions. Located downstream of the compressor 305 is an electrically operated compressor 306 that is electrically actuated via the electric motor 213. The electrically operated compressor can be used to supplement the supercharging output provided by the turbocharger compressor 305 and / or provide supercharging in the event of turbine spool-up. In one example, the electrically operated compressor 306 can be housed within the same body or structure as the electric motor 213. The electric motor 213 can be powered by an energy storage device such as a battery 258. The electrically operated compressor 306 can be rotated in proportion to the supply current from the battery 258. Airflow from the compressor 305 can flow along an intake tract 309 to an intake manifold and / or through a bypass duct 307 that houses the electrically operated compressor 306. A bypass valve 308 located downstream of the turbocharger compressor 305 can control the proportion of compressed air flowing along the intake tract 309 versus the bypass duct 307. Specifically, when the valve 308 is fully open, airflow from the turbocharger compressor 305 can bypass the electrically operated compressor 306 and when the bypass valve 308 is fully closed, all air from the turbocharger compressor can flow through the bypass duct 307. The bypass valve 308 can be a normally open valve, such that in most operating conditions, airflow bypasses the electrically operated compressor 306. The bypass valve 308 can be closed during engine operating conditions when the turbocharger compressor is spooling up and during idle-stop conditions when engine cooling is requested. The bypass valve 308 can be a proportional valve, such that the amount of airflow through the duct 307 can be proportional to the position of the bypass valve 308.

[0054] Such as Figure 2The control system of the control system 217 can determine one or more operating parameters of the electrically actuated intake compressor based on measured or inferred engine operating conditions. As one example, the rotational speed of the electrically operated compressor 306 can be based on the rotational speed of the turbine 216, the driver pedal position, the vehicle speed, the engine torque demand, the intake manifold pressure, etc. As another example, based on the engine rotational speed being greater than a threshold, or based on the intake manifold or boost pressure being greater than a threshold, the control system 217 can operate the electric motor as a generator and generate electrical energy that is stored in the storage device.

[0055] Figure 3C The EDIAC can be operated by the vehicle control system 217 in various modes. As one example, at low vehicle speeds and when the driver requests additional generator torque, the bypass valve 308 can be closed while the electrically operated compressor 306 can be rotated via the motor 213 to quickly provide the required intake air pressure. When the control system 217 determines that the turbine 216 is able to provide sufficient torque to the compressor 305 to meet the desired intake manifold pressure, the electrically operated compressor 307 can be turned off and the bypass valve 308 returns to its open position. By employing the electrically operated compressor 307 to quickly provide increased intake manifold pressure, the "turbine lag" associated with conventional turbochargers is avoided.

[0056] In addition to using the EDIAC for boost pressure control, the EDIAC operation can also be used to cool the engine in response to actual or predicted / anticipated engine overheating. As detailed with reference to Figures 4-5 During vehicle idle-stop or after transitioning the hybrid electric vehicle to pure electric mode to cool the engine, the EDIAC operation with the engine rotating without fuel can be employed.

[0057] Turning to Figure 4 FIG. 4 shows a high-level flowchart of an example method 400 for cooling an engine of a hybrid electric vehicle during idle-stop. The method 400 can be employed by the engine and includes, in response to satisfying idle-stop conditions including the engine temperature being less than a threshold, shutting down the engine until a restart condition is satisfied. The method 400 also includes, in response to satisfying the idle-stop conditions and the engine temperature being greater than the threshold, rotating the engine without fuel and operating the EDIAC to flow air that is cooled by passing through a charge air cooler through the engine until the engine temperature is less than the threshold, and then shutting down the engine until the restart condition is satisfied. The method 400 enables providing engine cooling when other methods of engine cooling are unable to maintain the engine temperature within a desired range. Thus, employing the method 400 can reduce the likelihood and / or extent of engine overheating. Reference will be made to the engine 100, the EDIAC 200, the control system 217, and the hybrid electric vehicle 10 described herein and shown in FIGS. 1-3. Figures 1-2 and Figures 3A-3CThe system illustrated is used to describe method 400, but it should be understood that similar methods can be applied to other systems without departing from the scope of this disclosure. Instructions for performing method 400 and the remaining methods included herein can be provided by, for example... Figure 1 The control system 190 and Figure 2 The control system 217 is based on instructions stored in a non-transitory memory and combined with information from sensors in the engine system (such as temperature sensors, pressure sensors, and...). Figures 1-2 and Figures 3A-3C The controller uses signals received from other sensors described below to perform operations. According to the method described below, the controller can employ engine actuators to regulate engine operation.

[0058] Method 400 begins at 402 and includes estimating the current vehicle and engine operating conditions. Operating conditions can be estimated, measured, and / or inferred, and may include one or more vehicle conditions such as vehicle speed and battery state of charge; various engine conditions such as engine status (started or off), engine load, engine temperature, engine speed, torque demand, and exhaust air-fuel ratio; various fuel system conditions such as fuel level, fuel type, and fuel temperature; various evaporative emission system conditions such as fuel vapor canister load and fuel tank pressure; and various environmental conditions such as ambient temperature, humidity, and atmospheric pressure. Method 400 then proceeds to 404.

[0059] At 404, method 400 includes confirming that idle-stop conditions are met. Idle-stop conditions may include the engine being in operation (e.g., performing combustion), the engine and emission components (e.g., exhaust catalyst, UEGO sensor, etc.) exceeding a threshold temperature, the battery state of charge (SOC) exceeding a threshold (e.g., at least 30%), the vehicle speed being below a threshold speed (e.g., below 30 mph), and the engine starter motor being ready to operate. Additionally, it can be verified that the air conditioner is not requesting a restart of the engine, a request that would be made when air conditioning is desired. The torque requested by the driver can be estimated to indicate that it is less than a predetermined threshold. Confirmation of any or all idle-stop conditions is required to initiate idle-stop. If the idle-stop conditions are met at 404, then at 408, the method includes maintaining engine operation, including continuing to burn fuel in the engine cylinders.

[0060] If the idle-stop condition is met, at 406, the method includes performing an automatic idle-stop, wherein the engine is deactivated and stops rotating. Specifically, in response to the idling-stop condition being met, the vehicle controller can automatically (i.e., without the driver requesting the engine to be turned off) deactivate engine fuel and stop the engine from rotating. By achieving automatic engine shutdown when all idle-stop conditions are met, fuel economy can be improved.

[0061] At 410, while in idle-stop, such as when the engine is being coasted to a stop rotation or when the engine has stopped, the method includes determining whether the engine temperature is greater than a threshold temperature. The engine temperature can be determined based on a cylinder head temperature or an engine coolant temperature. For example, the engine temperature can be determined directly based on a cylinder head or engine coolant temperature sensor (e.g., via a thermocouple mounted in the engine block). Alternatively, the engine temperature can be determined based on a model or algorithm that varies as a function of a measured engine coolant or cylinder head temperature. In addition to estimating the engine temperature, the controller can also determine an actual rate of rise of the engine temperature, and / or a predicted or expected rate of rise of the engine temperature based on engine conditions such as engine speed, engine load, boost pressure, and torque demand.

[0062] In one example, the threshold temperature is a lower threshold temperature (ThrL) such as 240 °F. The threshold temperature can correspond to a temperature above which engine cooling can be desired and which can be determined as a function of engine speed and load. The threshold temperature (ThrL) can also be determined as a function of a desired engine temperature.

[0063] If the engine temperature is below ThrL at 410, the method 400 can proceed to 426 where the vehicle remains in idle-stop until an automatic restart condition is met at 428. The automatic engine restart condition can be considered to be met if the engine is currently experiencing idle-stop (no fuel combustion in the engine), a driver requested torque exceeds a predetermined threshold (such as a driver depressing the accelerator pedal), a request has been made to restart the vehicle air conditioning system, or the battery 258 needs to be charged via engine operation. If any or all of the conditions are met, the restart condition can be confirmed. If the automatic restart condition is not met at 428, the engine can remain in idle-stop until the restart condition is confirmed.

[0064] If it is determined that the engine temperature exceeds ThrL, the method 400 proceeds to step 412 to take a mitigation action. At 412, the method 400 includes actuating one or more cooling fans, such as radiator fans and cooling fans of the engine coolant system, such as Figure 2The controller can also actuate a coolant system pump of the engine 104. The controller can actuate the coolant system pump to increase the circulation of coolant through the engine block. The controller can also actuate one or more coolant system fans, such as radiator fans 292 of the coolant system 290. Operation of the one or more coolant system fans can blow air across the radiator fins, increasing heat loss from the hot engine to ambient air. Optionally, the controller can also enable the coolant system pump (and open any needed valves) to increase circulation of coolant through the engine block. As such, the coolant system pump and fans can be operated for temperature control while the engine is running, and can be disabled when the engine is off. By selectively operating the fans and pump during idle-stop, engine overheating due to the presence of engine residual heat and lower ambient heat loss due to the vehicle being stationary (or nearly stationary) can be avoided.

[0065] Actuating the coolant system fans can include operating the fans at a speed based on the engine temperature being above a threshold, such as based on a difference between the measured engine temperature and a lower threshold temperature (ThrL) or a target engine temperature. As the difference increases, the fan speed can be increased and / or the number of actuated cooling fans in addition to the radiator fans can be increased. Likewise, actuating the coolant system pump can include operating the pump at a speed or flow output based on the engine temperature being above a threshold, such as based on a difference between the measured engine temperature and a lower threshold temperature (ThrL) or a target engine temperature. As the difference increases, the pump speed or output can be increased. Operating one or more coolant system fans and pumps in response to increased engine temperature during idle-stop can represent a first measure taken to reduce engine temperature in response to a condition of engine overheating.

[0066] At 414, it can be determined whether the engine temperature is greater than an upper temperature threshold ThrU, above the lower threshold temperature ThrL. For example, it can be determined whether the measured engine temperature at 402 is above each of the lower threshold temperature and the upper threshold temperature. Alternatively, where a single threshold temperature is applied, it can be determined whether the engine temperature remains above the threshold temperature even after operating the coolant system fans and pump. In one example, the engine temperature can be above the upper threshold temperature due to a higher degree of engine overheating having occurred. This can be due to, for example, a high level of heat generation due to engine operation increases (at high boost pressure), at high load, and a high percentage of fuel directly injected prior to idle-stop. Furthermore, due to the vehicle being stationary or static while performing idle-stop, the under-hood temperature can continue to rise during idle-stop even after the engine is turned off. Due to the higher degree of engine heat generation, operation of the coolant system fans and pump can be insufficient to provide engine cooling.

[0067] In another example, the engine temperature can be above the upper threshold temperature due to degradation of engine coolant system components. As non-limiting examples, insufficient cooling even after operating the coolant system fan and pump can be attributed to loss of coolant from the coolant system (e.g., due to system leaks or due to the coolant reservoir not being refilled), degradation of the coolant system fan (e.g., radiator fan), degradation of the coolant system pump, cylinder over-compression, and / or presence of blockage in the cylinder head inner cooling jacket / channel.

[0068] If the engine temperature is not above the upper threshold, it can be determined at 416 whether the rate of increase of the engine temperature is greater than a threshold rate ThrR. For example, the controller can measure the actual rate of increase in the engine temperature based on the output of the temperature sensor. Where the engine temperature is currently above ThrL but not currently above ThrU, it can be determined that the engine temperature is approaching ThrU. In another example, the rate of increase in the engine temperature can be predicted or modeled based on the current engine temperature and also based on environmental humidity and environmental wind flow. For example, if the environmental humidity is high (e.g., above a threshold), even if the vehicle is at rest, the engine temperature can be expected not to rise above ThrU due to the heat absorption effects of the environmental humidity. Alternatively, due to the increased environmental humidity, the engine temperature can be expected to rise slowly enough that no further action is needed, such as because the engine is likely to be restarted before reaching ThrU. As another example, if the environmental humidity is low (e.g., below a threshold), the engine temperature can be expected to rise above ThrU due to the vehicle being at rest, the rate of rise increasing as the environmental wind flow decreases. Here the engine temperature can be expected to rise quickly enough that further action is needed, such as because the engine is likely to remain at idle-stop when ThrU is reached.

[0069] If the engine temperature is above the upper threshold (or even exceeds the lower threshold after operating the coolant system fan and pump), or if the rate of increase of the engine temperature is above the threshold rate, the controller continues to operate the electrically actuated air compressor to provide additional cool air for rapid engine cooling. Specifically, at 418, the method includes rotating the engine without fueling. The engine can be rotated without fueling via a starter motor or via an electric motor coupled to the driveline and transmission of the hybrid vehicle. The engine is rotated without fueling at a rate based on the engine temperature and engine operating conditions (e.g., at 500 RPM). The rate of engine rotation without fueling can be based on the state of charge of the battery providing energy to the engine rotation motor, or can be based on the engine temperature or rate of increase of the engine temperature. By rotating the engine without fueling, intake air can be drawn into the engine and circulated through the engine cylinders.

[0070] Next, at 420, the method 400 includes controlling the system to actuate the EDIAC to direct intake air to the engine cylinders via the CAC, where the air is cooled prior to being delivered to the engine cylinders. In this way, by having the engine rotate while also operating the intake compressor, the amount and rate of cooled air flow through the engine cylinders can be increased, thereby increasing the rate of heat loss from the engine and speeding up engine cooling.

[0071] Operating the intake compressor includes actuating an electric motor coupled to the intake compressor to rotate the compressor at a rotational speed based on the engine temperature. In one example, the duty cycle commanded to the electric motor can be based on one or more of a difference between the current engine temperature and a threshold temperature (e.g., based on the current engine temperature and ThrU or ThrL) and a rate of rise of the engine temperature. For example, as the difference increases, or the rate of rise increases, the duty cycle commanded to the motor can increase, causing the motor rotational speed and output to increase, and correspondingly increasing the rotational speed of the intake compressor. In one example, the controller can use a lookup table, model, or algorithm that uses the current engine temperature and a target engine temperature as inputs, calculates a corresponding compressor rotational speed needed to reduce the current engine temperature to the target engine temperature, and outputs a duty cycle to be commanded to the electric motor to achieve a desired level of engine cooling. In another example, the control system can adjust the output of the electric motor of the EDIAC to operate the intake compressor of the EDIAC at a rotational speed based on each of a difference between the engine temperature and a threshold and a rate of rise of the engine temperature, the output and corresponding rotational speed increasing as the difference and the rate of rise increase. In this way, the intake compressor can be used to assist engine cooling, where the degree of EDIAC-assisted engine cooling can be based on the degree of engine overheating indicated by the engine temperature or the engine temperature increase rate. The method 400 can then proceed to 422.

[0072] At 422, the method 400 can include measuring the engine temperature and estimating whether sufficient engine cooling has occurred. For example, it can be determined whether the engine temperature is below a threshold, such as below a lower threshold ThrL. If the engine temperature is not below the threshold even after operating the cooling fan and the intake compressor, the method returns to 412 (or 420, as shown via the dashed line) to continue cooling the engine via operation of the cooling fan and the intake compressor.

[0073] If the engine temperature is below ThrL, it can be inferred that no further engine cooling is needed. Accordingly, at 424, the illustrated method includes stopping coolant system operation. In one example, if only the coolant system fan and pump are operating, stopping coolant system operation can include disabling coolant pump and radiator fan operation. In another example, if the EDIAC is operating to assist engine cooling, the intake air compressor can be disabled by disabling the electric motor coupled to the intake air compressor. In addition to disabling the coolant system fan and intake air compressor, the controller can also stop rotating the engine without fueling. For example, the controller can disable the starter motor, and since the engine is not being fueled, the engine can rotate to a stop and remain in an idle-stop condition. The method 400 can then proceed to 428.

[0074] At 428, the method 400 can include verifying whether an automatic restart condition has been met. The automatic restart condition can include the engine being in an idle-stop condition (no fuel combustion in the engine), a driver requested torque exceeding a predetermined threshold (such as the driver depressing the accelerator pedal), a request to restart the vehicle air conditioning system having been made, and the SOC of the system battery being below a predetermined threshold and thus requiring charging via engine operation. If any of the above listed conditions are met, the automatic restart condition can be confirmed. If the automatic restart condition is not met, at 426, the controller can maintain the engine in the idle-stop condition until the automatic restart condition is met. For example, the engine can be maintained at a stop. If and when the automatic restart condition is met, the method 400 can proceed to 430.

[0075] At 430, the method 400 includes performing an automatic restart. Restarting the engine can include cranking the engine via the starter motor until a threshold engine rotational speed is reached, and then resuming engine fueling. In one example, upon an automatic engine restart, the engine can be fueled to provide a defined engine rotational speed profile and target engine torque. The method 400 can then end.

[0076] It should be appreciated that if the automatic restart condition is met at any time during the performance of the routine 400, such as during engine cooling, the engine cooling is aborted and engine restart can be resumed. For example, if the restart condition is met while the engine is being cooled via an operating cooling fan, the fan can be disabled and the engine restarted. As another example, if the restart condition is met while the engine is being rotated without fueling via the starter motor, and the intake air compressor is rotating, the controller can disable the electric motor to slow the intake air compressor. The controller can continue to rotate the engine via the starter motor until a crank speed is reached, and then resume cylinder fueling.

[0077] In this manner, by rotating the engine without fuel while operating the EDIAC to direct air to the engine cylinders via the charge air cooler in response to an idle-stop event and while the engine temperature is greater than a threshold (ThrU), the vehicle control system can mitigate engine overheating. EDIAC-assisted engine cooling can continue in this manner until the engine temperature is below a threshold temperature (ThrL), at which point the vehicle control system can rotate the engine to rest.

[0078] While Figure 4 The method of resolves engine overheating during vehicle rest conditions, but it should be appreciated that EDIAC-assisted engine cooling can also be used for engine cooling in other situations where the vehicle is being propelled, such as in an HEV or PHEV. Figure 5 A high-level flowchart depicting an example method 500 for using an EDIAC to cool an engine of a hybrid vehicle (e.g., an HEV or PHEV) while only using motor torque to temporarily propel the vehicle. In this manner, an overheated engine can be cooled while the hybrid vehicle is being propelled.

[0079] The method 500 begins at 502 and includes estimating current vehicle and engine conditions. The conditions can be estimated, measured, and / or inferred, and can include one or more vehicle conditions such as vehicle speed, vehicle location, battery state of charge, various engine conditions such as engine state (on or off), engine load, engine temperature, engine speed, exhaust air-fuel ratio, various fuel system conditions such as fuel level, fuel type, fuel temperature, various evaporative emissions system conditions such as fuel vapor canister load, fuel tank pressure, and various environmental conditions such as ambient temperature, humidity, barometric pressure. The method 500 then proceeds to 504.

[0080] At 504, the method 500 includes operating the hybrid vehicle in a propulsion mode based on driver input and vehicle conditions. As one example, the vehicle can be operated in a pure electric mode, in which the vehicle is propelled via motor torque only. The pure electric mode can be selected when the driver torque demand is less than a threshold and the battery state of charge is above a threshold SOC. As another example, the vehicle can be operated in a pure engine mode, in which the vehicle is propelled via engine torque only. The pure engine mode can be selected when the driver torque demand is above a threshold or the battery state of charge is below a threshold SOC. As another example, the vehicle can be operated in an assist mode, in which the vehicle is propelled via each of engine torque and motor torque, the ratio of engine torque to motor torque being adjusted based on various conditions. The assist mode is selected when the driver torque demand is above an upper threshold, in which motor torque alone is insufficient to propel the vehicle. After the operating mode is selected, the method 500 can proceed to 506.

[0081] At 506, the method 500 can include determining whether the engine is operating, that is, whether the engine is combusting fuel. For example, a vehicle engine will be combusting fuel if the vehicle is in a pure engine or assist mode of operation. If the engine is not operating, then at 508, the method includes continuing to propel the vehicle with motor torque only. Here, it is inferred that no engine cooling is needed and the method 500 can end.

[0082] If at 506 it is determined that the vehicle engine is in operation, then the method 500 can proceed to estimate the engine temperature to determine whether the engine is over-temperature, and if so, take appropriate mitigation action.

[0083] In particular, at 510, the method includes determining whether the engine temperature is greater than a threshold temperature. The engine temperature can be determined based on a cylinder head temperature or an engine coolant temperature. For example, the engine temperature can be determined directly based on a cylinder head or engine coolant temperature sensor (e.g., via a thermocouple mounted in the engine block). Alternatively, the engine temperature can be based on a model or algorithm that is a function of the measured engine coolant or cylinder head temperature. In addition to estimating the engine temperature, the controller can also determine an actual rate of rise of the engine temperature, and / or a predicted or expected rate of rise of the engine temperature based on engine conditions such as engine speed, engine load, boost pressure, and torque demand.

[0084] In one example, the threshold temperature is a lower threshold temperature (ThrL) such as 240 °F. The threshold temperature can correspond to a temperature above which engine cooling can be necessary and which can be determined as a function of engine speed and load. The threshold temperature (ThrL) can also be determined as a function of a desired engine temperature.

[0085] If at 510 the engine temperature is below ThrL, then the method 500 can proceed to 512, where the vehicle will continue to operate in the currently selected mode.

[0086] If it is determined that the engine temperature exceeds ThrL, then the method 500 proceeds to take mitigation action by proceeding to step 514. At 514, the method 500 includes actuating one or more cooling fans, such as radiator fans and cooling fans of an engine coolant system, such as the radiator fans 292 of the coolant system 290 of FIG. 3. Figure 2 The operation of the one or more coolant system fans can blow air through the radiator fins, increasing heat loss from the hot engine to the ambient air. Optionally, the controller can also enable the coolant system pump (and open any needed valves) to increase circulation of coolant through the engine block. In this way, the coolant system pump and fans can be operated for temperature control when the engine is running, and can be disabled when the engine is off.

[0087] Actuating the coolant system fans can include operating the fans at a speed based on the engine temperature being above a threshold, such as based on a difference between the measured engine temperature and a lower threshold temperature (ThrL) or a target engine temperature. As the difference increases, the fan speed can be increased and / or the number of actuated cooling fans other than the radiator fan can be increased. Likewise, actuating the coolant system pumps can include operating the pumps at a speed or flow output based on the engine temperature being above a threshold, such as based on a difference between the measured engine temperature and a lower threshold temperature (ThrL) or a target engine temperature. As the difference increases, the pump speed or output can be increased. Operating one or more coolant system fans and pumps in response to increased engine temperature during idle-stop can represent a first measure taken to reduce engine temperature in response to a condition of engine overheating. Method 500 can then proceed to 516.

[0088] At 516, it can be determined whether the engine temperature is greater than an upper temperature threshold ThrU, greater than a lower threshold temperature ThrL. For example, it can be determined whether the measured engine temperature at 502 is higher than each of the lower threshold temperature and the upper threshold temperature. Alternatively, in cases where a single threshold temperature is applied, it can be determined whether the engine temperature remains above the threshold temperature even after operating the coolant system fans and pumps. Due to a higher degree of engine heat generation, operation of the coolant system fans and pumps alone can not be sufficient to provide engine cooling.

[0089] In another example, the engine temperature can be above the upper threshold temperature due to degradation of engine coolant system components. As non-limiting examples, cooling that is insufficient even after operating the coolant system fans and pumps can be due to loss of coolant from the coolant system (e.g., due to system leaks or due to the coolant reservoir not being refilled), degradation of the coolant system fans (e.g., radiator fans), degradation of the coolant system pumps, cylinder over-compression, and / or presence of a blockage in the cylinder head inner cooling jacket / channel.

[0090] If the engine temperature is not above the upper threshold, it can be determined at 518 whether a rate of increase of the engine temperature is greater than a threshold rate ThrR. For example, the controller can measure the actual rate of increase in the engine temperature based on the output of the temperature sensor. Where the engine temperature is currently exceeding ThrL but is not currently exceeding ThrU, it can be determined that the engine temperature is approaching ThrU. In another example, the rate of increase in the engine temperature can be predicted or modeled based on the current engine temperature and also based on such as ambient humidity and ambient wind flow. For example, if the ambient humidity is high (e.g., above a threshold), even if the vehicle is at static, due to the heat absorption effect of the ambient humidity, the engine temperature can not be expected to rise to exceed ThrU.

[0091] If the engine temperature is above the upper threshold (or even exceeds the lower threshold after operating the coolant system fan and pump), or if the rate of increase of the engine temperature is above the threshold rate, then the controller takes mitigating action by proceeding to step 520.

[0092] At 520, the method 500 has determined that the vehicle engine is in operation and additional engine cooling is needed. Accordingly, at 520, the method includes temporarily propelling the hybrid vehicle using motor torque only (i.e., in pure electric mode). This includes forcing the vehicle propulsion system to transition from pure engine mode or assist mode to pure electric mode even if the conditions for propelling the vehicle using engine torque are otherwise met. The transition can include shutting down the engine by disabling fuel and letting the engine rotate idle. By transitioning the vehicle to use motor torque only in response to elevated engine temperature during vehicle propulsion with at least engine torque, the engine can be deactivated without interrupting vehicle propulsion. Subsequent steps of EDIAC assisted engine cooling can be performed in the event that engine fueling is terminated. The method 500 then proceeds to 522.

[0093] At 522, the method includes rotating the engine without fueling. The engine can be rotated without fueling via a starter motor or via motor torque from an electric motor coupled to the driveline and transmission of the hybrid vehicle. The motor torque can be used to both propel the vehicle and rotate the engine without fueling. The engine is rotated without fueling at a rate based on engine temperature and engine operating conditions (e.g., at 500 RPM). The engine rotation rate without fueling can be based on the state of charge of the battery providing energy to the motor, or can be based on engine temperature or engine temperature increase rate. By rotating the engine without fueling, intake air can be drawn into the engine and circulated through the engine cylinders.

[0094] Next, at 524, the method 500 includes controlling the system to actuate the EDIAC to direct intake air to the engine cylinders via the CAC, where the air is cooled before being delivered to the engine cylinders. In this way, by rotating the engine while also operating the intake air compressor, the amount and rate of cooled air flow through the engine cylinders can be increased, increasing the rate of heat loss from the engine and speeding up engine cooling.

[0095] Operating the intake air compressor includes actuating an electric motor coupled to the intake air compressor to rotate the compressor at a speed based on the engine temperature. In one example, the duty cycle commanded to the electric motor can be based on one or more of a difference between the current engine temperature and a threshold temperature (e.g., based on the current engine temperature and ThrU or ThrL) and a rate of rise of the engine temperature. For example, as the difference increases, or the rate of rise increases, the duty cycle commanded to the motor can increase, causing the motor speed and output to increase, and correspondingly increasing the rotational speed of the intake air compressor. In one example, the controller can use a lookup table, model, or algorithm that uses the current engine temperature and a target engine temperature as inputs, calculates a corresponding compressor speed needed to reduce the current engine temperature to the target engine temperature, and outputs a duty cycle to be commanded to the electric motor to achieve a desired level of engine cooling. In another example, the control system can adjust the output of the electric motor of the EDIAC to operate the intake air compressor of the EDIAC at a speed based on each of a difference between the engine temperature and a threshold and a rate of rise of the engine temperature, the output and corresponding speed increasing as the difference and the rate of rise increase. In this way, the intake air compressor can be used to assist engine cooling, where the degree of EDIAC-assisted engine cooling can be based on the degree of engine overheating indicated by the engine temperature or engine temperature increase rate. The method 500 can then proceed to 526.

[0096] At 526, the method 500 can include measuring the engine temperature and estimating whether sufficient engine cooling has occurred. For example, it can be determined whether the engine temperature is below a threshold, such as below a lower threshold ThrL. If the engine temperature is not below the threshold even after operating the cooling fan and intake air compressor, the method returns to 514 (or 524, as shown via the dashed line) to continue cooling the engine via operation of the cooling fan and intake air compressor.

[0097] If the engine temperature is below ThrL, it can be inferred that further engine cooling is not needed. Accordingly, at 528, the illustrated method includes stopping coolant system operation. In one example, if only the coolant system fan and pump are operating, stopping coolant system operation can include disabling coolant pump and radiator fan operation. In another example, if the EDIAC is operating to assist engine cooling, the intake air compressor can be disabled by disabling the electric motor coupled to the intake air compressor. In addition to disabling the coolant system fan and intake air compressor, the controller can also stop the engine from rotating without fueling. For example, the controller can disable the starter motor, and since the engine is not being fueled, the engine can rotate to a stop and remain in an idle-stop state. The method 500 can then proceed to 530.

[0098] At 530, the method 500 can include resuming a previously selected operating mode or alternating nominal mode based on the current vehicle operating conditions. For example, after cooling the engine, the vehicle control system can resume propelling the vehicle with engine torque, such as by transitioning from pure electric mode back to pure engine or assist mode. Therein, the control system can restart the engine and resume cylinder fueling and cylinder combustion. The method 500 can then end.

[0099] Figure 6 An exemplary timeline 600 is shown that cools an overheated engine during idle-stop by operating an electrically actuated intake air compressor. The timeline 600 includes a plot 601 showing the pedal position (PP) of the vehicle over time, which reflects the driver torque demand. The timeline 600 also shows the coolant system fan operation over time at plot 602 and the EDIAC rotational speed (rpm) at plot 603. The coolant system fan is shown as either “on” or “off,” however, the coolant system fan can operate at various rates based on the engine temperature and / or the rate of change of the engine temperature. The timeline 600 also includes a plot 604 showing whether fuel is being delivered to the engine cylinders (on or off). Finally, the timeline 600 includes a plot 607 showing the engine temperature. The plot 607 also includes a lower temperature threshold 606 and an upper temperature threshold 605.

[0100] Prior to tl, the vehicle is stationary and the engine is in idle-stop. At this time, the engine is not fueling (plot 604). The engine temperature (plot 607) is below the lower threshold 606 because the engine has been idle-stopped for some time. Since the engine is idle-stopped and not overheating, the coolant system fan (plot 602) and the intake air compressor (plot 603) are not operating at this time.

[0101] At time tl, in response to the driver pressing the accelerator pedal event (plot 601), the driver is demanding increased torque, causing the engine to restart, and engine fueling begins, as seen at plot 604. Also, as the engine burns fuel, the engine temperature begins to increase. Between times tl and t2, the driver continues to demand torque, as indicated by the change in pedal position (PP), and cylinder fueling continues while the engine temperature continues to rise.

[0102] At time t2, in response to the driver releasing the accelerator pedal event, there is a decrease in torque demand. The engine has satisfied the idle-stop condition at t2, so engine fueling stops. Although engine fueling has stopped, the engine temperature continues to rise between t2 and t3 due to the limited airflow through the vehicle hood as a result of the vehicle being stationary.

[0103] At time t3, in response to the engine temperature being greater than the lower threshold 606, the coolant system is started to cool the engine. Between times t3 and t4, the coolant system fan continues to operate, and thus, the engine temperature decreases. In the depicted example, the coolant system fan is started to a defined speed, however, it should be understood that in other embodiments, the fan speed can be adjusted based on cooling demand.

[0104] At time t4, the coolant system fan operation has decreased the engine temperature below the lower temperature threshold 606. Thus, at t4, the coolant system fan is disabled. Between times t4 and t5, the engine remains at idle-stop with cylinder fueling remaining disabled while the vehicle is stationary.

[0105] At time t5, in response to another driver depressing the accelerator pedal, the engine is automatically restarted, and at t5, engine cylinder fueling is restored. Between times t5 and t6, the engine temperature begins to increase due to fuel combustion within the engine.

[0106] At time t6, the engine temperature has exceeded the lower temperature threshold 606. Thus, the coolant system fan is operated to decrease the engine temperature. However, between times t6 and t7, the coolant system fan operation alone is not able to decrease the engine temperature. This can be due to the engine operating at a higher load. Thus, the engine temperature continues to rise above the upper temperature threshold 605. Since the engine is in operation between t6 and t7, the EDIAC can not be able to operate. However, at time t7, the driver releases the accelerator pedal enabling the engine to perform idle-stop. Thus, engine cylinder fueling is terminated. At t7, engine cylinder fueling is terminated, EDIAC operation begins. The EDIAC rotation rate is based on the status of the coolant system fan (on or off), and also based on the engine temperature and the engine temperature rate of change. As such, at t7, when the coolant system fan is also in operation, the EDIAC operates at a medium rotation rate. Between times t7 and t8, the engine temperature decreases due to the EDIAC and coolant system fan operation. Thus, between times t7 and t8, the EDIAC rotation rate will decrease as the engine temperature meter decreases. By t8, the engine temperature has decreased below the lower temperature threshold 606, thus, the coolant system fan and EDIAC operation are disabled.

[0107] Additionally, at time t8, the driver depresses the accelerator pedal causing the engine to automatically restart. As a result, engine cylinder fueling resumes and the engine temperature begins to slowly increase. Between times t8 and t9, the vehicle is operated with relatively low torque demand, as indicated by the pedal position (PP) of curve 601, which results in a slight increase in engine temperature. Between times t8 and t9, the vehicle control system determines that the engine coolant system has deteriorated, such as based on the output of different cooling fan diagnostic routines. As a result, a flag is set indicating the deteriorated state of the engine coolant system, and the coolant system fan operation is disabled until a mitigation action is taken. As one example, the mitigation action can include repairing the coolant system fan.

[0108] At time t9, the driver releases the accelerator pedal, as indicated by the pedal position in curve 601. As a result, the entry condition for idle-stop is met. When idle-stop is executed, engine cylinder fueling is stopped. When the engine temperature is below the lower temperature threshold 606 during idle-stop, the engine is not assisted by the EDIAC for cooling. As such, between times t9 and tlO, the EDIAC remains disabled.

[0109] At time tlO, the driver depresses the accelerator pedal causing the engine to automatically restart. As a result, at tlO, engine cylinder fueling resumes, and a short high torque demand subsequently occurs between times tlO and tl l. This short high torque demand indicates an increase in engine temperature.

[0110] At time ti 1, the driver releases the accelerator pedal allowing the engine to perform idle-stop. As a result, the engine cylinders are fueling-stop. Between times ti 1 and ti 2, the engine temperature increases despite the engine being in idle-stop due to the high ambient temperature and reduced airflow around the engine (because the vehicle is stationary) through the radiator. At time ti 2, the engine temperature exceeds the lower temperature threshold 606. Additionally, the rate of engine temperature increase at ti 2 is greater than the threshold rate, as indicated by slope 608. Although the engine temperature is greater than the lower temperature threshold 606 at ti 2, the coolant system fan remains disabled due to the vehicle control system determining that the coolant system is degraded. At ti 2, the engine temperature is greater than the lower temperature threshold 606 and increasing at a rate greater than the threshold rate 608. As such, the vehicle control system operates the EDIAC. Because the engine coolant system is degraded, the rotational speed of the EDIAC will be higher in order to provide sufficient cooling to the engine. Between times ti 2 and ti 3, the engine temperature decreases due to the EDIAC operating in conjunction with the engine rotating without fueling. Because the EDIAC rotational speed is based on the engine temperature, the EDIAC rotational speed will decrease as the engine temperature decreases. At time ti 3, the engine temperature has decreased below the lower temperature threshold 606. As a result, the EDIAC is disabled. The timeline 600 then ends. The timeline 600 includes several examples of the engine employing EDIAC-assisted engine cooling during an idle-stop event. Additionally, a hybrid electric vehicle or plug-in hybrid electric vehicle can employ EDIAC-assisted engine cooling during positive propulsion, as previously detailed with respect to Figure 5 and method 500. The timeline 700 includes several exemplary scenarios of a hybrid electric vehicle employing the method 500.

[0111] The timeline 700 shows the torque provided to the vehicle drive wheels by the engine (curve 701) or electric motor (curve 702) over time. The timeline 700 also includes the state (on or off) of the coolant system fan (curve 703) or the rotational speed of the EDIAC compressor (curve 704). The timeline 700 also indicates whether engine cylinder fueling is occurring (curve 705). Finally, the timeline 700 shows the engine temperature (curve 708) over time. The lower temperature threshold 707 and upper temperature threshold 706 are included in the curve 708.

[0112] Prior to ti, the engine and motor are not in operation, and the engine is not fueled. At this time, the coolant system fan and EDIAC are inactive. At time ti, a vehicle start event occurs, as indicated by engine cylinder fueling and initiation of engine torque. Between times ti and t2, the vehicle is operated in pure engine mode, so motor torque is maintained at zero. Between times ti and t2, engine torque increases to meet the increased torque demand of the driver. As the engine burns fuel, the engine temperature increases.

[0113] At time t2, the engine temperature has exceeded the lower temperature threshold 707, so the coolant system fan is enabled. Between times t2 and t3, operation of the coolant system fan causes the engine temperature to decrease below the lower temperature threshold 707. Thus, additional engine cooling is not needed and the coolant system fan is disabled at t3. Between times t3 and t4, the vehicle continues to operate in pure engine mode while the engine temperature increases.

[0114] At time t4, the combustion within the engine has caused the engine temperature to increase above the lower temperature threshold 707. Thus, the coolant system is enabled at this point. However, between times t4 and t5, the engine temperature continues to climb despite the cooling fan operating. By time t5, the engine temperature has risen above the upper temperature threshold 706. Thus, the vehicle transitions from pure engine propulsion to increased pure electric propulsion to propel the wheels. This is shown by the increased engine torque and the increased motor torque between times t5 and t6. By time t6, the engine is no longer providing any torque to the wheels, and fueling of the engine cylinders has stopped. At t6, the vehicle has fully transitioned to pure electric propulsion. Thus, EDIAC assisted engine cooling can now begin. Between times t6 and t7, the EDIAC is spinning at a rate based on the engine temperature and the coolant system state. When the coolant system is in operation between times t6 and t7, the EDIAC will spin at a moderate rate that decreases as the engine temperature decreases. The EDIAC and the coolant system fan operation between t6 and t7 lowers the engine temperature. By t7, the engine temperature has decreased below the lower temperature threshold 707. Thus, at t7, the coolant system fan is disabled and the EDIAC is spun to a standstill. Additionally, at t7, the vehicle control system initiates a transition from pure electric propulsion back to the previously selected pure engine propulsion. Thus, engine cylinder fueling resumes. Between times t7 and t8, the motor torque decreases to zero as the engine torque increases to replace the decreased motor torque. By t8, all propulsion torque is provided by the engine. Between times t8 and t9, the vehicle control system determines that the engine coolant system has degraded. Thus, a flag is set indicating the degraded state of the engine coolant system, and the coolant system fan operation is disabled until a mitigation action is taken. Also between times t8 and t9, the vehicle continues to operate in pure engine mode, which causes the engine temperature to increase.

[0115] At time t9, the engine temperature has increased above the lower temperature threshold 707 and the engine temperature increase rate is greater than the threshold rate, as indicated by the slope 709. Since the coolant system was previously determined to be degraded, the coolant system fan remains disabled at t9. At time t9, the vehicle control system initiates a transition from pure engine propulsion to pure electric propulsion. Between times t9 and tlO, the transition between pure engine propulsion and motor-only propulsion occurs. At time tlO, the vehicle is propelled entirely by motor torque, so engine cylinder fueling can stop. Thus, the EDIAC can operate at a relatively high rotational speed based on the engine temperature increase rate and also based on the degraded state of the coolant system. Between times tlO and tl l, EDIAC-assisted cooling causes the engine temperature to decrease, and as such, the EDIAC rotational speed decreases. By tl l, the engine temperature has decreased below the lower temperature threshold 707. Thus, at tl l, engine cooling is no longer needed and the EDIAC compressor is rotated to rest. Additionally, at tl l, engine fueling can resume, as the vehicle transitions again from pure electric to pure engine propulsion. At tl2, the vehicle is propelled entirely by engine torque, while motor torque has decreased to zero. The timeline 700 then ends.

[0116] the system described herein and with reference to Figures 1-3C and the system described herein and with reference to Figure 4 and Figure 5Methods of the same can implement one or more systems and one or more methods. In one example, a method includes, in response to an engine temperature being greater than a threshold temperature, rotating the engine without fuel and operating an electrically driven air intake compressor to direct air to engine cylinders via a charge air cooler when an engine idle-stop condition is satisfied. In a first example of the method, the operating continues until the engine temperature is below the threshold temperature, and then the engine is rotated to a standstill. A second example of the method optionally includes example one and further includes propelling the hybrid vehicle using motor torque during the operating. A third example of the method optionally includes one or more of examples one through two and further includes wherein the electrically driven air intake compressor includes an air intake compressor driven by an electric motor, the air intake compressor including one of an electrically driven supercharger compressor, a turbocharger compressor coupled to each of the electric motor and an exhaust turbine, and an air intake compressor driven by the electric motor and coupled in a bypass downstream of a turbo-driven air intake compressor. A fourth example optionally includes one or more of examples one through three and further includes a duty cycle commanded to the electric motor is based on each of a difference between the engine temperature and the threshold temperature and a rate of rise of the engine temperature. A fifth example optionally includes one or more of examples one through four and further includes operating an engine coolant system fan in response to the engine temperature being greater than the threshold temperature. A sixth example of the method optionally includes one or more of examples one through five and further includes the operating is further in response to a degradation of an engine coolant system, the degradation including one or more of a cooling fan degradation, a coolant pump degradation, and a coolant level in the engine coolant system below a threshold, the duty cycle commanded to the electric motor is increased in response to the degradation of the engine coolant system. A seventh example of the method optionally includes one or more of examples one through six and further includes the electrically driven air intake compressor is positioned in an air intake tract upstream of the charge air cooler. An eighth example of the method optionally includes one or more of examples one through seven and further includes the engine temperature includes one of an engine coolant temperature and a cylinder head temperature. A ninth example of the method optionally includes one or more of examples one through eight and further includes

[0117] Another example method includes, in response to an idle-stop condition including an engine temperature less than a threshold being satisfied, shutting down the engine until a restart condition is satisfied, and in response to the idle-stop condition being satisfied and the engine temperature greater than the threshold, rotating the engine without fueling and operating an electrically-driven air intake compressor to flow air, cooled while passing through a charge air cooler, through the engine until the engine temperature is less than the threshold, and then shutting down the engine until the restart condition is satisfied. In a first example of the method, the method includes the air intake compressor driven via the electric motor coupled in a bypass passage downstream of another air intake compressor driven via an exhaust turbine. A second example of the method optionally includes the first example and further includes operating the air intake compressor via the electric motor includes adjusting an output of the electric motor to operate the air intake compressor at a rotational speed based on each of a difference between the engine temperature and the threshold and a rate of rise of the engine temperature, the output and the corresponding rotational speed increasing as the difference or the rate of rise increases. A third example of the method optionally includes any one or more of example one and example two and further includes operating an engine coolant system fan in response to the engine temperature being above the threshold. A fourth example of the method optionally includes one or more of examples one through three and further includes the output of the electric motor further increasing in response to a degradation of the engine coolant system fan.

[0118] An example of a system for a hybrid electric vehicle includes an electric motor coupled to a wheel, a battery coupled to the electric motor, an engine, a turbocharger including a first air intake compressor driven by an exhaust turbine, a bypass coupled downstream of the first air intake compressor, the bypass including a second air intake compressor driven by the electric motor, a charge air cooler coupled downstream of each of the first and second air intake compressors, a temperature sensor to estimate an engine temperature, and a controller having computer readable instructions stored in a non-transitory memory to, when propelling the hybrid vehicle using at least engine torque, in response to an engine temperature being above a threshold, transition to propelling the vehicle using only motor torque regardless of a state of charge of the battery, disable engine fueling and spin the engine via the electric motor without fueling, operate the second air intake compressor to flow air cooled via the charge air cooler to the spinning engine. In a first example, the system further includes an engine coolant system including a coolant pump, a coolant reservoir, and a cooling fan, where the controller includes further instructions to, in response to the engine temperature above the threshold, enable the engine coolant system. A second example of the system optionally includes the first example and further includes operating the second air intake compressor includes operating the second air intake compressor at a speed based on each of a difference between the engine temperature and the threshold temperature and a rate of rise of the engine temperature. A third example of the system optionally includes any one or more or each of the first and second examples and further includes operating the second air intake compressor further includes increasing the second air intake compressor speed in response to a degradation of the engine coolant system, the degradation including one of a degradation of the coolant pump, a degradation of the cooling fan, and a below threshold coolant level in the coolant reservoir. A fourth example of the system optionally includes any one or more or each of the first through third examples and further includes the controller includes further instructions to, in response to an engine temperature below the threshold, restart the engine and propel the vehicle using at least engine torque. A fifth example of the system optionally includes any one or more or each of the first through fourth examples and further includes when propelling the hybrid vehicle using at least engine torque includes when an engine idle-stop condition is met.

[0119] It should be noted that the example control routines and estimation routines included herein can be used with a variety of engine and / or vehicle system configurations. The control methods and routines disclosed herein can be stored as executable instructions in non-transitory memory and can be executed by a control system including a controller in combination with various sensors, actuators, and other engine hardware. The particular routines described herein can represent one or more of any number of processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and so on. As such, the various acts, operations, and / or functions illustrated can be performed in the manner shown, concurrently, in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily restricted to that shown unless specifically stated. The steps, acts or functions can be repeated, as necessary, to achieve the particular result. Further, the acts, operations and / or functions can be graphically represented as code blocks in non-transitory memory of a computer-readable storage medium programmed to implement the described processes when the computer-readable storage medium is executed by a system including the various engine hardware components in combination with an electronic controller.

[0120] It should be understood that the configurations and routines disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered in a limiting sense, because numerous variations are possible. For example, the above technology can be applied to V-6, inline 4 cylinder, inline 6 cylinder, V-12, opposed 4 cylinder, and other engine types. The subject matter of the present disclosure includes all novel and nonobvious combinations and subcombinations of the various systems and configurations disclosed herein, as well as other features, functions, and / or properties.

[0121] The following claims particularize certain combinations and subcombinations regarded as novel and nonobvious. These claims can refer to "an" element or "a first" element or similar referents. Such claims should be understood as including one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of disclosed features, functions, elements, and / or properties can be claimed through amendment of the following claims or presentation of additional 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.

[0122] According to the present invention, a hybrid vehicle method is provided having: in response to an engine temperature being greater than a threshold temperature, when an engine idle-stop condition is satisfied, rotating the engine without fueling and operating an electrically driven air compressor to direct air to engine cylinders via a charge air cooler.

[0123] According to one embodiment, the above invention is further characterized by continuing the operation until the engine temperature is below the threshold temperature, and then rotating the engine to a standstill.

[0124] According to one embodiment, during the operation, the hybrid vehicle is propelled using motor torque.

[0125] According to one embodiment, the electrically driven air intake compressor comprises an air intake compressor driven by an electric motor, the air intake compressor comprising one of: an electrically driven supercharger compressor driven by the electric motor, a turbocharger compressor coupled to each of the electric motor and an exhaust turbine, and an air intake compressor driven by the electric motor and coupled in a bypass downstream of a turbo-driven air intake compressor.

[0126] According to one embodiment, a duty cycle commanded to the electric motor is based on each of a difference between the engine temperature and the threshold temperature and a rate of rise of the engine temperature.

[0127] According to one embodiment, the above invention is further characterized by operating an engine coolant system fan in response to the engine temperature being greater than the threshold temperature.

[0128] According to one embodiment, the operation is further in response to a degradation of an engine coolant system, the degradation comprising one or more of a cooling fan degradation, a coolant pump degradation, and a coolant level in the engine coolant system below a threshold, the duty cycle commanded to the electric motor being increased in response to the degradation of the engine coolant system.

[0129] According to one embodiment, the electrically driven air intake compressor is positioned in an air intake passage upstream of the charge air cooler.

[0130] According to one embodiment, the engine temperature comprises one of an engine coolant temperature and a cylinder head temperature.

[0131] According to the invention, there is provided a method for an engine having: in response to an idle-stop condition comprising an engine temperature being less than a threshold being satisfied, shutting down the engine until a restart condition is satisfied; and in response to the idle-stop condition being satisfied and the engine temperature being greater than the threshold, rotating the engine without fueling, and operating an electrically driven air intake compressor to flow air cooled by a charge air cooler through the engine until the engine temperature is less than the threshold, and then shutting down the engine until the restart condition is satisfied.

[0132] According to one embodiment, the air intake compressor driven via the electric motor is coupled in a bypass passage downstream of another air intake compressor driven via an exhaust turbine.

[0133] According to one embodiment, the above invention is further characterized in that operating the intake compressor via the electric motor includes adjusting an output of the electric motor to operate the intake compressor at a rotational speed based on each of a difference between the engine temperature and the threshold value and a rate of rise of the engine temperature, the output and the corresponding rotational speed increasing as the difference or the rate of rise increases.

[0134] According to one embodiment, operating an engine coolant system fan in response to the engine temperature being above the threshold value.

[0135] According to one embodiment, the output of the electric motor is further increased in response to degradation of the engine coolant system fan.

[0136] According to the invention, there is provided a hybrid vehicle system having an electric motor coupled to a wheel, a battery coupled to the electric motor, an engine, a turbocharger including a first intake compressor driven by an exhaust turbine, a bypass coupled downstream of the first intake compressor, the bypass including a second intake compressor driven by the electric motor, a charge air cooler coupled downstream of each of the first intake compressor and the second intake compressor, a temperature sensor to estimate an engine temperature, and a controller having computer readable instructions stored in a non-transitory memory to, when the hybrid vehicle is propelled using at least engine torque, transition to propelling the vehicle using only motor torque, independent of a state of charge of the battery, in response to an engine temperature being above a threshold value, disable engine fueling and rotate the engine via the electric motor without fueling, operate the second intake compressor to flow air cooled via the charge air cooler to the rotating engine.

[0137] According to one embodiment, the above invention is further characterized by an engine coolant system including a coolant pump, a coolant reservoir, and a cooling fan, wherein the controller includes further instructions to enable the engine coolant system in response to the engine temperature above the threshold value.

[0138] According to one embodiment, operating the second intake compressor includes operating the second intake compressor at a rotational speed based on each of a difference between the engine temperature and the threshold temperature and a rate of rise of the engine temperature.

[0139] According to one embodiment, operating the second intake air compressor further includes increasing the second intake air compressor speed in response to a degradation of the engine coolant system, the degradation including one of a degradation of the coolant pump, a degradation of the cooling fan, and a below threshold coolant level in the coolant reservoir.

[0140] According to one embodiment, the controller further includes other instructions to restart the engine and propel the vehicle using at least engine torque in response to an engine temperature being below the threshold.

[0141] According to one embodiment, when the hybrid vehicle is propelled using at least engine torque includes when an engine idle-stop condition is met.

Claims

1. A hybrid vehicle method, comprising: The idle-stop operation is performed when the engine idle-stop condition is met, in which the engine is deactivated and stops rotating. During the idle-stop period, in response to the engine temperature exceeding a threshold temperature, To rotate the engine without adding fuel; and The electric intake compressor is operated to direct air into the engine cylinders via a booster air cooler.

2. The method of claim 1, further comprising: Continue the operation until the engine temperature is below the threshold temperature, then bring the engine to a standstill.

3. The method of claim 1, further comprising: During the operation, the hybrid vehicle is propelled by motor torque.

4. The method of claim 1, wherein the electric intake compressor comprises an intake compressor driven by an electric motor, the intake compressor comprising one of: an electromechanical supercharger driven by the electric motor, a turbocharger connected to each of the electric motor and the exhaust turbine, and an intake compressor driven by the electric motor and connected in a bypass downstream of the turbocharger-driven intake compressor.

5. The method of claim 4, wherein the duty cycle commanded to the electric motor is based on each of the difference between the engine temperature and the threshold temperature and the rate of increase of the engine temperature.

6. The method of claim 5, further comprising: The engine coolant system fan is activated in response to the engine temperature exceeding the threshold temperature.

7. The method of claim 5, wherein the operation further responds to degradation of the engine coolant system, the degradation including one or more of coolant fan degradation, coolant pump degradation, and coolant level below a threshold in the engine coolant system, wherein the duty cycle commanded to the electric motor increases in response to the degradation of the engine coolant system.

8. The method of claim 1, wherein the electric intake compressor is positioned in the intake duct upstream of the booster air cooler.

9. The method of claim 1, wherein the engine temperature includes one of the engine coolant temperature and the cylinder head temperature.

10. A hybrid vehicle system comprising: An electric motor, which is connected to a wheel; A battery, which is connected to the electric motor; engine; A turbocharger, the turbocharger including a first intake compressor driven by an exhaust turbine; A bypass, connected downstream of the first intake compressor, the bypass including a second intake compressor driven by the electric motor; A booster air cooler, the booster air cooler being connected downstream of each of the first intake compressor and the second intake compressor; Temperature sensor, the temperature sensor being used to estimate engine temperature; and The controller has computer-readable instructions stored in a non-transitory memory, the computer-readable instructions being used for: When the engine idle-stop condition is met, in response to the engine temperature exceeding a threshold... Independent of the battery's state of charge, the system transitions to using only motor torque to propel the vehicle, the transition including shutting off the engine by disabling fuel and bringing the engine to a standstill; The engine is prohibited from being fueled and is rotated via the electric motor without being fueled; The second intake compressor is operated to allow air cooled by the booster air cooler to flow to the rotating engine.

11. The system of claim 10, further comprising an engine coolant system including a coolant pump, a coolant reservoir, and a cooling fan, wherein the controller includes additional instructions for activating the engine coolant system in response to an engine temperature exceeding a threshold.

12. The system of claim 11, wherein operating the second intake compressor comprises: The second intake compressor is operated at a certain speed, which is based on each of the difference between the engine temperature and the threshold and the rate of increase of the engine temperature.

13. The system of claim 11, wherein operating the second intake compressor further comprises: The second intake compressor speed is increased in response to deterioration of the engine coolant system, the deterioration including one of deterioration of the coolant pump, deterioration of the cooling fan, and coolant level in the coolant reservoir below a threshold.

14. The system of claim 10, wherein the controller includes additional instructions for: In response to the engine temperature falling below the threshold, the engine is restarted and the vehicle is resumed to be propelled using at least the engine torque.

Images