System and method for heating a vehicle intake manifold during a stop / start event

Abstract

The present disclosure provides "systems and methods for heating a vehicle intake manifold during stop / start events". Methods and systems are provided for improving combustion events during cold starts of a vehicle engine, where the cold start event includes a start / stop event. In one example, a method includes rotating the engine in a reverse direction in response to an engine pull-down event where the temperature of the intake manifold of the engine is below a threshold to heat the intake manifold by thermally pumping exhaust gas into the intake manifold. In this way, combustion can be improved in response to a request to start the engine, which can reduce undesirable emissions and can improve fuel economy.

Description

Technical Field

[0001] The present specification generally relates to methods and systems for controlling a vehicle engine to thermally direct an exhaust system to an intake manifold under cold start conditions of a vehicle having stop / start capabilities.

[0002] Background Art / Contents of the Invention

[0003] When an internal combustion engine is started, if the intake manifold and / or the intake air is cold, then the low temperature may make it difficult for fuel to vaporize in the engine cylinders. Any fuel that is not completely evaporated may not burn completely. The portion of the fuel that does not burn completely during startup and shortly after startup may result in a fuel-rich exhaust mixture. Such a fuel-rich exhaust mixture may increase undesirable hydrocarbon (HC) emissions in the exhaust and / or increase carbon monoxide levels.

[0004] For a gasoline engine, heat generation in the engine after startup may cause the incoming air to acquire engine heat before entering the engine cylinders. In other examples where the engine includes a diesel engine, glow plugs may be employed to heat the engine cylinders when initiating a cold start event. However, for any vehicle having stop / start (S / S) capabilities, in a situation where the engine can be pulled down (e.g., disabled to stop burning air and fuel) when the vehicle speed drops below a threshold speed, the engine heat may not continue to rise monotonically, and thus, at the next startup event, the incoming air may not be warmed sufficiently. In conditions where the ambient temperature is below a predetermined threshold (such as below freezing (e.g., <32°F)), this problem may worsen. Thus, in such an example, during a subsequent engine pull-up (e.g., the engine is activated to burn air and fuel), the cold incoming air may cause incomplete combustion events, resulting in increased exhaust tailpipe emissions.

[0005] Various prior art devices have been employed to achieve heat transfer to the intake air of an engine. For example, a manifold air heater system may help raise the temperature of the combustion air when the intake manifold air is conveyed through the engine's intake manifold by means of an electric heating element or a burner using liquid or gaseous fuel. However, the inventors have recognized problems with such methods herein. For example, a manifold air heater system may increase the cost and complexity of the vehicle system. Additionally, if the heater does not operate as desired, it may cause undesirable emissions when initiating a cold start.

[0006] Accordingly, the inventors have developed herein systems and methods that at least partially address the above problems. In one example, a method includes rotating an engine of a vehicle in a reverse direction without fueling in response to an engine pull-down event until a temperature of an intake manifold of the engine rises to or above a threshold intake manifold temperature due to an airflow from an exhaust manifold of the engine flowing through the engine and into the intake manifold. As an example, the threshold intake manifold temperature may result in a desired efficiency level of fuel combustion in response to a subsequent request to start the engine. In this way, fuel economy can be improved and undesired emissions can be reduced.

[0007] In an example of the method, the engine pull-down event may include an S / S event, which involves shutting down the engine to reduce the amount of time the engine idles. In some examples, rotating the engine in the reverse direction in response to the engine pull-down event may occur in response to a scheduled intake manifold heating operation. For example, scheduling the intake manifold heating operation may involve monitoring a color of exhaust from an exhaust system of the engine at an engine start event, and in response to an indication that the color of the exhaust is white, the intake manifold heating operation may be scheduled. In this way, based on an indication of poor fuel combustion at the engine start event, the intake manifold heating operation may be scheduled for a subsequent engine pull-down event to improve fuel combustion in response to an engine start request, which can improve fuel economy and reduce undesired emissions.

[0008] The above and other advantages and features of this specification will be apparent from the following detailed description when taken alone or in conjunction with the drawings.

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

[0010] Figure 1 An exemplary vehicle propulsion system is schematically illustrated.

[0011] Figure 2 An exemplary vehicle system having a fuel system and an evaporative emissions system is schematically illustrated.

[0012] Figures 3A to 3B An exemplary H-bridge circuit is schematically illustrated, which may be used to rotate a vehicle engine in a forward or reverse direction.

[0013] Figure 4 A high - level flowchart of an exemplary method for determining whether to schedule an intake manifold heating method for a subsequent S / S event is shown.

[0014] Figure 5 A high - level flowchart of an exemplary method for performing an intake manifold heating operation during a start / stop event in which intake manifold heating is scheduled is shown.

[0015] Figure 6 An exemplary timeline for scheduling and performing Figures 4 to 5 the intake manifold heating method shown in DETAILED DESCRIPTION

[0016] The following description relates to systems and methods for improving combustion during cold start events, particularly with respect to S / S events. Specifically, during cold ambient conditions and after a long vehicle soak (e.g., > 6 hours), an engine start event may result in less - than - ideal combustion. More specifically, the combustion efficiency level may be below a threshold efficiency combustion level. For example, the threshold efficiency level may include the level at which a desired percentage of the fuel is burned. For vehicles with S / S features that enable the engine to be pulled down when the vehicle speed drops below a threshold speed and then restarted when the wheel torque is above a threshold wheel torque, these problems may be exacerbated. In particular, the intake manifold may not be heated sufficiently before an S / S event, or the intake manifold may cool to an undesirable level when the engine is pulled down during an S / S event. To address this situation, it may be desirable to heat the intake manifold during an S / S event in which the intake manifold temperature is below a threshold intake manifold temperature. Such heating may include delivering hot air from the vehicle's exhaust system to the intake manifold. It may be desirable to perform such heating of the intake manifold after the engine has rotated to rest at an S / S event to ensure that the intake manifold temperature reaches the threshold intake manifold temperature before an engine restart request. Delivering exhaust system heat to the intake manifold may include rotating the engine in reverse without fueling. Rotating the engine in reverse without fueling may be performed via a motor, such as Figure 1 the motor shown in the hybrid vehicle propulsion system shown at Figure 2 the engine system shown at Figures 3A to 3B In this way, exhaust system heat can be effectively delivered to the intake manifold of an engine system (such as Figure 4 A high - level exemplary method for determining whether to schedule intake manifold heating during an S / S event during a particular driving cycle is shown. In response to such scheduling, Figure 5The method shown heats the intake manifold at an S / S event when conditions for doing so are met. Figure 6 An exemplary timeline 600 of a method according to Figures 5 to 6 is shown, showing intake manifold heating scheduled and carried out for an S / S event.

[0017] Figure 1 An exemplary vehicle propulsion system 100 is shown. Vehicle propulsion system 100 includes a fuel combustion engine 110 and a motor 120. As a non-limiting example, engine 110 includes an internal combustion engine, and motor 120 includes an electric motor. Motor 120 can be configured to utilize or consume an energy source different from that of engine 110. For example, engine 110 can consume liquid fuel (e.g., gasoline) to produce an engine output, while motor 120 can consume electrical energy to produce a motor output. Thus, a vehicle having propulsion system 100 can be referred to as a hybrid electric vehicle (HEV).

[0018] 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 engine 110 to remain in an off state (i.e., set to a deactivated state), where fuel combustion at the engine is interrupted. For example, under selected operating conditions, when engine 110 is deactivated, motor 120 can propel the vehicle via drive wheels 130 as indicated by arrow 122.

[0019] In another example, the engine can have an S / S feature 193, where engine 110 can automatically shut down during times when the vehicle is not moving, or when the vehicle speed is below a threshold speed, when the engine speed is below a threshold engine speed, etc. Control system 190 can be connected to engine 110 and S / S feature 193 to perform a start-stop function. Advantages of the S / S function can include improved fuel economy compared to other vehicles that do not employ such technology.

[0020] During other operating conditions, engine 110 can be set to a deactivated state (as described above), while motor 120 can be operated to charge energy storage device 150. For example, motor 120 can receive wheel torque from drive wheels 130, as indicated by arrow 122, where the motor can convert the vehicle's kinetic energy into electrical energy to be stored at energy storage device 150, as indicated by arrow 124. This operation can be referred to as regenerative braking of the vehicle. Thus, in some examples, motor 120 can provide a generator function. However, in other examples, generator 160 can alternatively receive wheel torque from drive wheels 130, where the generator can convert the vehicle's kinetic energy into electrical energy to be stored at energy storage device 150, as indicated by arrow 162.

[0021] During other operating conditions, the engine 110 can be operated by burning fuel received from the fuel system 140 (as indicated by arrow 142). For example, when the motor 120 is disabled, the engine 110 can be operated to propel the vehicle via the drive wheels 130, as indicated by arrow 112. During other operating conditions, both the engine 110 and the motor 120 can each be operated to propel the vehicle via the drive wheels 130 as indicated by arrows 112 and 122, respectively. A configuration in which both the engine and the motor can selectively propel the vehicle can be referred to as a parallel-type vehicle propulsion system. Note that in some examples, the motor 120 can propel the vehicle via a first set of drive wheels, and the engine 110 can propel the vehicle via a second set of drive wheels.

[0022] In other examples, the vehicle propulsion system 100 can be configured as a series-type vehicle propulsion system, whereby the engine does not directly propel the drive wheels. Instead, the engine 110 can be operated 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 a selected operating condition, the engine 110 can drive the generator 160 as indicated by arrow 116, and the generator 160 can in turn supply electrical energy to one or more of the motors 120 as indicated by arrow 114, or supply electrical energy to the energy storage device 150 as indicated by arrow 162. As another example, the engine 110 can be operated to drive the motor 120, which in turn can provide a generator function to convert the engine output into electrical energy, where the electrical energy can be stored in the energy storage device 150 for later use by the motor.

[0023] In other examples, to be discussed further below, the motor 120 can be configured to use energy provided via the energy storage device 150 to rotate the un-fueled engine in a forward (e.g., default direction) or reverse orientation, as illustrated by arrow 186.

[0024] The fuel system 140 may include one or more fuel storage tanks 144 for storing fuel on the vehicle. For example, the fuel tank 144 may store one or more liquid fuels, including but not limited to: gasoline, diesel, and alcohol fuels. In some examples, the fuel may be stored on the vehicle as a mixture of two or more different fuels. For example, the fuel tank 144 may be configured to store a mixture 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 mixtures may be delivered to the engine 110 as indicated by the arrow 142. Other suitable fuels or fuel mixtures may also be supplied to the engine 110, where they may be burned at the engine to produce an engine output. The engine output may be used to propel the vehicle as indicated by the arrow 112 or to recharge the energy storage device 150 via the motor 120 or the generator 160.

[0025] In some examples, the energy storage device 150 may be configured to store electrical energy, which may be supplied to other electrical loads (other than the motor) residing on the vehicle, including cabin heating and air conditioning, engine starting, headlights, cabin audio and video systems, etc. As a non-limiting example, the energy storage device 150 may include one or more batteries and / or capacitors.

[0026] The control system 190 may communicate 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 may receive sensed 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 may 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 the sensed feedback. The control system 190 may receive an indication of a driver request for an output of the vehicle propulsion system from the vehicle driver 102. For example, the control system 190 may receive sensed feedback from a pedal position sensor 194 that communicates with a pedal 192. The pedal 192 may schematically refer to a brake pedal and / or an accelerator pedal. In addition, in some examples, the control system 190 may communicate with a remote engine start receiver 195 (or transceiver) that receives a wireless signal 106 from a key fob 104 having a remote start button 105. In other examples (not shown), remote engine start may be initiated via a cellular phone or a smartphone-based system, where the user's cellular phone sends data to a server, and the server communicates with the vehicle to start the engine.

[0027] The energy storage device 150 can periodically receive electrical energy from a power source 180 (e.g., not part of the vehicle) residing external to 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 (HEV), whereby electrical energy can be supplied from the power source 180 to the energy storage device 150 via an electrical power transmission cable 182. During a recharge operation of the energy storage device 150 from the power source 180, the electrical transmission cable 182 can electrically couple the energy storage device 150 and the power source 180. When the vehicle propulsion system is operated to propel the vehicle, the electrical transmission cable 182 can be disconnected between the power source 180 and the energy storage device 150. The control system 190 can identify and / or control the electrical energy stored at the energy storage device, which can be referred to as the state of charge (SOC).

[0028] In other examples, the electrical power transmission cable 182 can be omitted, where electrical energy received from the power source 180 can be received wirelessly at the energy storage device 150. 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. Thus, 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 the fuel utilized by the engine 110.

[0029] The fuel system 140 can periodically receive fuel from a fuel source residing external to the vehicle. As a non-limiting example, the vehicle propulsion system 100 can be fueled by receiving fuel via a fuel dispensing device 170 as indicated by arrow 172. In some examples, 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 examples, the control system 190 can receive an indication of the 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 instrument panel 196.

[0030] The vehicle propulsion system 100 may also include an ambient temperature / humidity sensor 198, as well as roll stability control sensors, such as lateral and / or longitudinal and / or yaw rate sensors 199. The vehicle instrument panel 196 may include indicator lights and / or a text-based display, in which messages are displayed to the driver. The vehicle instrument panel 196 may also include various input portions for receiving driver input, such as buttons, touchscreens, voice input / recognition, etc. For example, the vehicle instrument panel 196 may include a fueling button 197 that can be manually actuated or pressed by the vehicle driver to initiate fueling. For example, as described in more detail below, in response to the vehicle driver actuating the fueling button 197, the fuel tank in the vehicle can be depressurized so that fueling can be performed.

[0031] As is known in the art, the control system 190 may be communicatively coupled to other vehicles or infrastructure using appropriate communication technologies. For example, the control system 190 may be coupled to other vehicles or infrastructure via a wireless network 131, which may include Wi-Fi, Bluetooth, some type of cellular service, wireless data transfer protocol, etc. The control system 190 may broadcast (and receive) information regarding vehicle data, vehicle diagnostics, traffic conditions, vehicle location information, vehicle operating procedures, etc. via vehicle-to-vehicle (V2V), vehicle-to-infrastructure-to-vehicle (V2I2V), and / or vehicle-to-infrastructure (V2I or V2X) technologies. The communications and information exchanged between vehicles may be directly between vehicles or may be multi-hop. In some examples, longer range communications (e.g., WiMax) may be used instead of or in combination with V2V or V2I2V to extend the coverage area for several miles. In other examples, the vehicle control system 190 may be communicatively coupled to other vehicles or infrastructure via the wireless network 131 and the Internet (e.g., cloud), as is known in the art.

[0032] The vehicle system 100 may also include an in-vehicle navigation system 132 (e.g., global positioning system) with which the vehicle driver can interact. The navigation system 132 may include one or more position sensors for assisting in estimating vehicle speed, vehicle height, vehicle position / location, etc. This information may be used to infer engine operating parameters, such as local atmospheric pressure. As discussed above, the control system 190 may also be configured to receive information via the Internet or other communication networks. The information received from the GPS may be cross-referenced with information obtained via the Internet to determine local weather conditions, local vehicle regulations, etc.

[0033] In some examples, the vehicle propulsion system 100 can include one or more on-vehicle cameras 135. For example, the on-vehicle cameras 135 can communicate photos and / or video images to the control system 190. For example, in some examples, the on-vehicle cameras can be used to record images within a predetermined radius of the vehicle.

[0034] In one example, one or more on-vehicle cameras 135 can be included in the vehicle exhaust emission identification system 136. In some examples, the vehicle exhaust emission identification system 136 can include a video processing data unit. In one example, the video processing unit can include the controller 190, but in other examples, the video processing unit can include a control computing device that is separate from the controller 190 but can be selectively electrically coupled to the controller 190 (or wirelessly coupled to the controller 190). In one example, the vehicle exhaust emission identification system 136 can include a method for color identification. In other words, the vehicle exhaust emission identification system can include a computer vision system. In one example, the color identification method can include storing a set of predefined colors in a memory and determining whether the exhaust emission includes a specific color. For example, the color identification method can include indicating that the exhaust emission is white, gray, black, blue-black, etc. In some examples, a confidence value can be associated with the color determination. For example, the exhaust emission identified as white can include a high confidence value, a medium confidence value, or a low confidence value. Alternatively, a digital system can be used to assign a confidence value to a specific color determination. For example, the digital system can include the numbers 1 to 10 or 1 to 100. As the confidence in a specific color determination increases, the confidence value can increase, and as the confidence in a specific color determination decreases, the confidence value can decrease. In some examples, determining that the exhaust emission is "white" can include that the smoke is substantially white or within a threshold for determining that the smoke is white. More specifically, substantially white can include determining that the smoke is within a predetermined threshold of white (e.g., within a 5% margin of error or within a 10% margin of error). In this way, the color of the exhaust leaving the vehicle can be accurately determined, as will be discussed in further detail below.

[0035] Figure 2 A schematic diagram of the vehicle system 206 is shown. It can be understood that the vehicle system 206 can include the same vehicle system as the vehicle system 100 shown Figure 1 at. The vehicle system 206 includes an engine system 208 coupled to an emissions control system 251 and a fuel system 218. It can be understood that the fuel system 218 can include the same as Figure 1The same fuel system as the fuel system 140 shown. The emissions control system 251 includes a fuel vapor container or canister 222, which can be used to capture and store fuel vapor. The engine system 208 can include an engine 110 having a plurality of cylinders 230. The engine 110 includes an engine intake system 223 and an engine exhaust system 225. The engine intake port 223 includes a throttle 262 that is fluidly connected to the engine intake manifold 244 via an intake passage 242. In some examples, the throttle 262 can include an electronic throttle. Additionally, the engine intake port 223 can include an airbox and filter (not shown) positioned upstream of the throttle 262. The engine exhaust system 225 includes an exhaust manifold 248 that leads to an exhaust passage 235, and the exhaust passage 235 conveys the exhaust to the atmosphere. In the situation where the vehicle includes an engine that burns diesel, the exhaust passage can lead to one or more exhaust aftertreatment devices (e.g., 226, 229, 236), as well as a reductant delivery and storage system, such as a diesel exhaust fluid (DEF) system 238.

[0036] The exhaust aftertreatment devices can be arranged in various orders and / or combinations along the exhaust passage 235. For example, a diesel oxidation catalyst (DOC) 226 can be downstream followed by a selective catalytic reduction (SCR) catalyst 229. The SCR catalyst 229 can be downstream followed by a diesel particulate filter (DPF) 236. It should be understood that Figure 2 the emissions control devices of the exhaust system 225 shown are exemplary in nature. Various other emissions control devices and configurations can be included in the engine exhaust system 225. For example, the exhaust system 225 can include an SCR catalyst, followed only by a DPF downstream. In another example, the exhaust system 225 can include only an SCR catalyst. In yet another example, the DPF can be located upstream of the SCR catalyst, or a combined DPF / SCR catalyst can be used.

[0037] The engine exhaust system 225 can also include a reductant delivery and / or storage system, such as a DEF system 238. DEF can be a liquid reductant, such as a mixture of urea and water, which is stored in a storage container (e.g., a storage tank). In one example, the DEF system 238 can include a DEF tank 239 for on-vehicle DEF storage, a DEF delivery line 240 that connects the DEF tank 239 to the exhaust passage 235 via an injector at or upstream of the SCR catalyst 229. The DEF tank 239 can be in various forms and can include a fueling neck 241 and a corresponding cap and / or hatch door in the vehicle body. The fueling neck 241 can be configured to receive a nozzle for refilling DEF.

[0038] The DEF system 238 may also include a DEF injector 243 in the line 240 that injects DEF into the exhaust gas upstream of the SCR catalyst 229. The DEF injector 243 may be used to control the timing and amount of DEF injection via the control system 214. The DEF system 238 may also include a DEF pump 246. The DEF pump 246 may be used to pressurize the DEF and deliver it into the line 240. The DEF system 238 may also include a DEF line heater 247 that heats the DEF line 240. For example, the DEF line heater 247 may heat the DEF fluid on its way to the DEF pump at low temperatures in order to maintain the DEF fluid viscosity. The DEF line heater 247 may be a resistive heater, or various other configurations. The DEF line heater 247 may be coupled to the energy storage device 150, which may include a battery and may be enabled and controlled, for example, via the control system 214.

[0039] It will be appreciated that other components may be included in the engine, such as various valves and sensors. For example, an atmospheric pressure sensor 213 may be included in the engine intake. In one example, the atmospheric pressure sensor 213 may be a manifold air pressure (MAP) sensor and may be coupled to the engine intake downstream of the throttle 262. The atmospheric pressure sensor 213 may rely on a partially open throttle or a fully open or wide open throttle condition (e.g., when the opening amount of the throttle 262 is greater than a threshold) in order to accurately determine the BP. In another example, an intake air temperature sensor 260 may be located in the intake. In yet another example, a humidity sensor 258 may be located in the intake.

[0040] The engine system 208 may also include an exhaust gas recirculation (EGR) system 249 that receives a portion of the exhaust gas stream leaving the engine 110 and returns the exhaust gas to the engine intake manifold 244 downstream of the throttle 262. In some conditions, the EGR system 249 may be used to regulate the temperature and / or dilution of the air and fuel mixture in the combustion chamber, thereby providing a method for controlling the ignition timing during some combustion modes. Additionally, in some conditions, a portion of the combustion gases may be retained or trapped in the combustion chamber by controlling the exhaust valve timing. The EGR system 249 is shown forming a common EGR passage 250 from the exhaust passage 235 to the intake passage 242.

[0041] In some examples, the exhaust system 225 may further include a turbocharger (not shown) that includes a turbine and a compressor coupled on a common shaft. The turbine may be coupled within the exhaust passage 235, and the compressor may be coupled within the intake passage 242. The blades of the turbine may rotate about the common shaft when a portion of the exhaust gas flow exiting the engine 110 impinges on the blades of the turbine. The compressor may be coupled to the turbine such that the compressor can be actuated when the blades of the turbine rotate. When actuated, the compressor can then direct pressurized fresh air to the intake manifold 244, where it can then be directed to the engine 110. In a system where the EGR passage 250 is coupled to the engine exhaust 225 upstream of the turbine and to the intake passage 242 downstream of the compressor, the EGR system can be considered a high-pressure EGR system. The EGR passage may alternatively be coupled downstream of the turbine and upstream of the compressor (low-pressure EGR system).

[0042] An EGR valve 253 may be coupled within the EGR passage 250. The EGR valve 253 may be configured as an active solenoid valve that can be actuated to allow exhaust gas to flow into the intake manifold 244. The portion of the exhaust gas flow exiting the engine 110 that is allowed to pass through the EGR system 249 and return to the engine 110 can be metered by the measured actuation of the EGR valve 253, and the measured actuation of the EGR valve 253 can be adjusted by the controller 212. The actuation of the EGR valve 253 can be based on various vehicle operating parameters and the calculated total EGR flow rate.

[0043] One or more EGR coolers 254 may be coupled within the EGR passage 250. The EGR cooler 254 can be used to reduce the total temperature of the EGR flow before delivering the flow to the intake manifold 244, where it can be combined with fresh air and directed to the engine 110. The EGR passage 250 may include one or more flow restriction regions 255. One or more pressure sensors 256 may be coupled at or near the flow restriction regions 255. Thus, the diameter of the flow restriction region can be used to determine the overall volume flow rate through the EGR passage 250.

[0044] The Air Intake System Hydrocarbon Trap (AIS HC) 257 can be placed in the intake manifold of the engine 110 to adsorb fuel vapors emitted from unburned fuel in the intake manifold, agitated fuel from degraded fuel injectors, and / or fuel vapors in the crankcase ventilation emissions during engine-off periods. The AIS HC can include a stack of continuously laminated polymer sheets impregnated with an HC vapor adsorption / desorption material. Alternatively, the adsorption / desorption material can be filled in the regions between the polymer sheets. The adsorption / desorption material can include one or more of carbon, activated carbon, zeolite, or any other HC adsorption / desorption material. When the engine operates to create an intake manifold vacuum and thereby generate an air flow through the AIS HC 257, the trapped vapors can be passively desorbed from the AIS HC and burned in the engine 110. Thus, during engine operation, intake fuel vapors are stored and desorbed from the AIS HC 257. Additionally, the fuel vapors stored during engine-off periods can also be desorbed from the AIS HC during engine operation. In this way, the AIS HC 257 can be continuously loaded and drawn down, and the trap can reduce evaporative emissions from the intake tract even when the engine 110 is off.

[0045] The fuel system 218 can include a fuel tank 220 coupled to a fuel pump system 221. It will be appreciated that the fuel tank 220 can include the same fuel tank as the fuel tank 144 shown above in Figure 1 The fuel pump system 221 can include one or more pumps for pressurizing the fuel delivered to the injectors (such as the exemplary injector 266 shown) of the engine 110. Although only a single injector 266 is shown, additional injectors are provided for each cylinder. Additionally, in the case where the vehicle system 206 includes a vehicle that uses diesel fuel, glow plugs 276 can be included for each cylinder 266. The glow plugs 276 can include heating devices that can assist in starting the diesel engine. Alternatively, in an example where the vehicle system 206 includes a vehicle that operates on a fuel other than diesel, spark plugs 277 can be included for each cylinder 266 only. It will be understood that the fuel system 218 can be a returnless fuel system, a return fuel system, or various other types of fuel systems. The fuel tank 220 can hold a variety of fuel mixtures, including fuels having a range of alcohol concentrations, such as various gasoline-ethanol mixtures, including E10, E85, gasoline, etc., and combinations thereof. A fuel level sensor 234 located in the fuel tank 220 can provide an indication of the fuel level ("fuel level input") to the controller 212. As shown, the fuel level sensor 234 can include a float connected to a variable resistor. Alternatively, other types of fuel level sensors can be used.

[0046] Before being drawn into the engine intake port 223, the vapor generated in the fuel system 218 can be delivered to an evaporative emissions control system 251 that includes a fuel vapor canister 222 via a vapor recovery line 231. The vapor recovery line 231 can be coupled to the fuel tank 220 via one or more conduits and can include one or more valves for isolating the fuel tank during certain conditions. For example, the vapor recovery line 231 can be coupled to the fuel tank 220 via one or more or a combination of conduits 271, 273, and 275.

[0047] In addition, in some examples, one or more fuel tank vent valves can be located in conduits 271, 273, or 275. Among other functions, the fuel tank vent valves can allow the fuel vapor canister of the emissions control system to remain at a low pressure or vacuum without increasing the fuel evaporation rate from the canister (which would otherwise occur when the fuel tank pressure decreases). For example, conduit 271 can include a grade vent valve (GVV) 287, conduit 273 can include a fill limit vent valve (FLVV) 285, and conduit 275 can include a grade vent valve (GVV) 283. In addition, in some examples, the recovery line 231 can be coupled to a fuel fill system 219. In some examples, the fuel fill system can include a fuel cap 205 for sealing the fuel fill system from the atmosphere. The fueling system 219 is coupled to the fuel tank 220 via a fuel fill tube or neck 211.

[0048] In addition, the fueling system 219 can include a fuel fill lock 245. In some examples, the fuel fill lock 245 can be a fuel cap locking mechanism. The fuel cap locking mechanism can be configured to automatically lock the fuel cap in a closed position such that the fuel cap cannot be opened. For example, when the pressure or vacuum in the fuel tank is greater than a threshold, the fuel cap 205 can be held locked by the fuel fill lock 245. In response to a fueling request, such as a request initiated by a vehicle driver, the fuel tank can be depressurized, and the fuel cap can be unlocked after the pressure or vacuum in the fuel tank drops below the threshold. The fuel cap locking mechanism can be a latch or clutch that prevents removal of the fuel cap when engaged. The latch or clutch can be electrically locked, for example, by a solenoid, or mechanically locked, for example, by a pressure diaphragm.

[0049] In some examples, the fuel fill lock 245 can be a fill tube valve located at the mouth of the fuel fill tube 211. In such examples, the fuel fill lock 245 can not prevent removal of the fuel cap 205. Instead, the fuel fill lock 245 can prevent a fueling pump from being inserted into the fuel fill tube 211. The fill tube valve can be electrically locked, for example, by a solenoid, or mechanically locked, for example, by a pressure diaphragm.

[0050] In some examples, the fueling lock 245 can be a fuel filler door lock, such as a latch or a clutch, that locks a fuel filler door located in a body panel of the vehicle. The fuel filler door lock can be electrically locked, for example, by a solenoid, or mechanically locked, for example, by a pressure diaphragm.

[0051] In an example where an electric mechanism is used to lock the fueling lock 245, the fueling lock 245 can be unlocked by a command from the controller 212, for example, when the fuel tank pressure drops below a pressure threshold. In an example where a mechanical mechanism is used to lock the fueling lock 245, the fueling lock 245 can be unlocked via a pressure gradient, for example, when the fuel tank pressure drops below atmospheric pressure.

[0052] The emissions control system 251 can include one or more emissions control devices, such as one or more fuel vapor canisters 222 filled with a suitable adsorbent 286b, which are configured to temporarily trap fuel vapors (including vaporized hydrocarbons) during fuel tank fueling operations and "running losses" (i.e., fuel evaporated during vehicle operation). In one example, the adsorbent 286b used is activated carbon. The emissions control system 251 can also include a canister vent path or vent line 227, which can convey gases from the canister 222 to the atmosphere when storing or trapping fuel vapors from the fuel system 218.

[0053] The canister 222 can include a buffer 222a (or buffer region), and each of the canister and the buffer contains an adsorbent. As shown, the volume of the buffer 222a can be less than the volume of the canister 222 (e.g., a fraction of the volume of the canister 222). The adsorbent 286a in the buffer 222a can be the same as or different from the adsorbent in the canister (e.g., both can include charcoal). The buffer 222a can be positioned within the canister 222 such that during canister loading, fuel tank vapors are first adsorbed within the buffer, and then when the buffer is saturated, additional fuel tank vapors are adsorbed in the canister. In contrast, during canister drawdown, fuel vapors are first desorbed from the canister (e.g., to a threshold amount), and then from the buffer. In other words, the loading and unloading of the buffer are not linear with the loading and unloading of the canister. Thus, the role of the canister buffer is to dampen any fuel vapor spikes flowing from the fuel tank to the canister, thereby reducing the likelihood of any fuel vapor spikes entering the engine. One or more temperature sensors 232 can be coupled to the canister 222 and / or incorporated within the canister 222. Heat (adsorption) is generated when fuel vapors are adsorbed by the adsorbent in the canister. Similarly, heat is consumed when fuel vapors are desorbed by the adsorbent in the canister. In this way, the adsorption and desorption of fuel vapors by the canister can be monitored and estimated based on temperature changes within the canister.

[0054] Vent line 227 may also allow fresh air to be drawn into canister 222 as stored fuel vapors are purged from fuel system 218 to engine air intake 223 via purge line 228 and purge valve 261. For example, purge valve 261 may be normally closed, but may be opened under certain conditions so that vacuum from engine intake manifold 244 is provided to fuel vapor canister for purging. In some examples, vent line 227 may include an air filter 259 disposed upstream of canister 222.

[0055] In some examples, the flow of air and vapors between canister 222 and the atmosphere can be regulated by a canister vent valve 297 coupled within exhaust line 227. When included, canister vent valve 297 can be a normally open valve so that a fuel tank isolation valve 252 (FTIV) can control ventilation of fuel tank 220 to the atmosphere. FTIV 252 can be positioned within conduit 278 between the fuel tank and fuel vapor canister 222. FTIV 252 can be a normally closed valve that, when open, allows fuel vapors to be vented from fuel tank 220 to fuel vapor canister 222. Fuel vapors can then be vented to the atmosphere or purged to engine intake system 223 via canister purge valve 261. As will be discussed in detail below, in some examples, a FTIV may not be included, while in other examples, a FTIV may be included. Therefore, where relevant, the use of a FTIV will be discussed with respect to the methods described below.

[0056] By selectively adjusting various valves and solenoids, the fuel system 218 can be operated in a variety of modes by the controller 212. It will be appreciated that the control system 214 may include the same control systems as described above. Figure 1 For example, the fuel system may be operated in a fuel vapor storage mode (e.g., during fuel tank refueling operation and without the engine combusting air and fuel) where controller 212 may open isolation valve 252 (when included) while closing canister purge valve (CPV) 261 to direct refueled vapors into canister 222 while preventing fuel vapors from being directed into the intake manifold.

[0057] As another example, the fuel system may be operated in a refueling mode (e.g., when a vehicle operator requests refueling of the fuel tank), wherein controller 212 may open isolation valve 252 (when included) while maintaining canister purge valve 261 closed to depressurize the fuel tank prior to enabling fuel to be added thereto. Thus, isolation valve 252 (when included) may remain open during the refueling operation to allow refueled vapors to be stored in the canister. After refueling is complete, the isolation valve may be closed.

[0058] As yet another example, the fuel system can operate in a canister purge mode (e.g., after the emissions control device light-off temperature has been reached and while the engine is combusting air and fuel), where the controller 212 can open the canister purge valve 261 when the isolation valve 252 (when included) is closed. Herein, the vacuum generated by the intake manifold of the operating engine can be used to draw fresh air through the vent 227 and through the fuel vapor canister 222 to purge the stored fuel vapor into the intake manifold 244. In this mode, the purged fuel vapor from the canister is combusted in the engine. The purge can continue until the amount of fuel vapor stored in the canister is below a threshold.

[0059] The controller 212 can form part of a control system 214. In some examples, the control system 214 can be the same as the control system 190 shown in Figure 1 The control system 214 is shown receiving information from a plurality of sensors 216 (various examples of which are described herein) and sending control signals to a plurality of actuators 281 (various examples of which are described herein). As one example, the sensors 216 can include an exhaust gas sensor 237 upstream of the emissions control device 270, a temperature sensor 233, a temperature sensor 260, a pressure sensor 291, a pressure sensor 282, and a canister temperature sensor 232. The exhaust gas sensor 237 can be any suitable sensor for providing an indication of the exhaust air-fuel ratio, such as a linear oxygen sensor or UEGO (universal or wide-range exhaust gas oxygen), a two-state oxygen sensor or EGO, a HEGO (heated EGO), a NOx, HC, or CO sensor. The exhaust gas sensor 237 can be connected to the controller 212. It can be appreciated that the exhaust gas sensor 237 can operate effectively when heated to about 600°F. Thus, in some examples, the exhaust gas sensor can include a heating element 279 to enable the exhaust gas sensor to warm up quickly.

[0060] Other sensors, such as pressure, temperature, air-fuel ratio, and composition sensors, can be coupled to various locations in the vehicle system 206. As another example, the actuators can include a throttle 262, a fuel tank isolation valve 252, a canister purge valve 261, and a canister vent valve 297. The control system 214 can include the controller 212. The controller can receive input data from the various sensors, process the input data, and trigger the actuators in response to the processed input data based on instructions or code programmed therein corresponding to one or more programs. Exemplary control programs are described herein with respect to Figures 4 to 5 describing exemplary control programs.

[0061] In some examples, the control can be placed in a reduced power mode or a sleep mode, where the controller only maintains basic functions and operates with lower battery consumption than the corresponding wake-up mode. For example, the controller can be placed in a sleep mode after a vehicle stop event to perform diagnostic procedures over a duration following the vehicle stop event. The controller can have a wake-up input that allows the controller to return to the wake-up mode based on inputs received from one or more sensors. For example, the opening of a vehicle door can trigger a return to the wake-up mode. In other examples, the controller may need to be awakened to perform such methods. In such examples, the controller can remain awake for a duration, which is referred to as the period during which the controller remains awake to perform an extended shutdown function, such that the controller can be awakened to perform diagnostic procedures. In another example, the wake-up capability can enable the circuit to wake up the controller when a diagnostic is requested.

[0062] An undesired evaporative emissions detection procedure may be intermittently performed by a controller 212 on a fuel system 218 and / or an evaporative emissions system 251 to confirm the absence of undesired evaporative emissions in the fuel system and / or the evaporative emissions system. Thus, an engine-off natural vacuum (EONV) created by changes in temperature and pressure at the fuel tank after engine shutdown and / or a supplementary vacuum from a vacuum pump may be used to perform the evaporative emissions detection procedure while the engine is off (engine-off test). Alternatively, the evaporative emissions detection procedure may be performed while the engine is running by operating a vacuum pump and / or using engine intake manifold vacuum. In some configurations, a canister vent valve (CVV) 297 may be coupled within a vent line 227. The CVV 297 may be used to regulate the flow of air and vapor between the canister 222 and the atmosphere. The CVV may also be used in diagnostic procedures. When included, the CVV may be opened during fuel vapor storage operations (e.g., during fuel tank refueling and when the engine is not running) such that air stripped from fuel vapor after passing through the canister may be vented to the atmosphere. Similarly, during purge operations (e.g., during canister regeneration and when the engine is running), the CVV may be opened to allow a fresh air stream to strip fuel vapor stored in the canister. In some examples, the CVV 297 may be a solenoid valve, where actuation of a canister vent solenoid performs opening or closing of the valve. Specifically, the canister vent valve may be open and closes when the canister vent solenoid is actuated. In some examples, the CVV 297 may be configured as a latching solenoid valve. In other words, when the valve is placed in a closed configuration, it latches closed without the need for additional current or voltage. For example, the valve may be closed with a 100 ms pulse and then opened at a later time point with another 100 ms pulse. In this way, the battery power required to keep the CVV closed is reduced. Specifically, the CVV may be closed when the vehicle is stopped, thereby conserving battery power while keeping the fuel emissions control system sealed off from the atmosphere.

[0063] When the engine rotates in a default direction, a vacuum is created in the intake manifold while a pressure is created in the exhaust system. However, if the engine rotates in reverse, then a vacuum is created in the exhaust system while a pressure is created in the intake manifold. More specifically, when the engine rotates in reverse, the opening of the cylinder exhaust valves (not shown) brings fresh air (and exhaust, if any) into the cylinder, and the subsequent opening of the cylinder intake valves (not shown) evacuates the cylinder into the intake manifold.

[0064] Vehicles such as the vehicle propulsion system 100 described above include hybrid electric vehicles, and thus, a vehicle motor (e.g., 120) can be used to rotate or spin the engine without fuel using power supplied via an on-board energy storage device (e.g., 150) such as a battery. In some examples, further discussed in detail below, it may be desirable to rotate the engine in a reverse direction (opposite to the direction of the default direction). For example, in the case of cold start conditions, if the temperature in the exhaust system exceeds a threshold exhaust system temperature, the engine can be rotated in a reverse orientation to draw exhaust heat through the engine and into the intake manifold. In this way, the intake system can be kept warm so that combustion can be improved for cold start conditions. One such example can include a situation where an S / S event occurs in cold (e.g., below 32°F) ambient temperature conditions. In the case of an engine stop, the intake may cool to a point where incomplete combustion may occur during the next engine start. However, the exhaust system can remain hot (e.g., may take a long time to cool), such that the exhaust heat can be effectively used to heat the intake manifold. Heating the intake manifold in this way can reduce or avoid undesirable emissions during a cold start event. The inventors have also recognized herein that cold air in the intake manifold can reduce the intake manifold pressure and correspondingly increase engine pumping losses under throttle conditions during a subsequent engine start. By heating the intake manifold before engine start and subsequent idle, the intake manifold pressure is increased, thereby reducing pumping losses at idle and improving fuel economy.

[0065] Turning now to Figures 3A to 3B , which illustrate an exemplary circuit 300 that can be used to reverse the rotational orientation of an electric motor. Circuit 300 schematically illustrates an H-bridge circuit that can be used to operate motor 310 in a first (forward) direction and alternately in a second (reverse) direction. Circuit 300 includes a first (LO) side 320 and a second (HI) side 330. Side 320 includes transistors 321 and 322, while side 330 includes transistors 331 and 332. Circuit 300 also includes a power source 340.

[0066] In Figure 3AIn this case, transistors 321 and 332 are activated (energized), while transistors 322 and 331 are turned off. In this configuration, the left lead 351 of motor 310 is connected to power supply 340, and the right lead 352 of motor 310 is connected to ground. In this way, motor 310 can operate in the forward direction. When the engine is operated in the forward direction via the motor, the engine can be in the cranking mode to initiate initial combustion. Additionally and / or optionally, when the engine is operated in the forward direction via the motor, the engine (and the motor or another motor) can be in the drive mode to drive the vehicle. It will be appreciated that in some examples, the engine can rotate in the forward (e.g., default) direction in a condition where the vehicle is stationary, and it is only desired for the engine to rotate or spin in the forward direction without combustion.

[0067] In Figure 3B this case, transistors 322 and 331 are activated (energized), while transistors 321 and 332 are turned off. In this configuration, the right lead 352 of motor 310 is connected to power supply 340, and the left lead 351 of motor 310 is connected to ground. In this way, motor 310 can operate in the reverse direction.

[0068] Accordingly, Figures 1 to 3B A system for a hybrid vehicle can be implemented, the system including: an engine having an intake manifold and an exhaust system; a motor configured to operate via energy supplied from an on-vehicle energy storage device; an S / S system; and a controller that stores instructions in a non-transitory memory, the instructions when executed causing the controller to: schedule an intake manifold heating operation for an engine pull-down event corresponding to an S / S event in response to an indication of poor combustion at an engine start event initiated after a predetermined duration in which the engine has been deactivated, where the engine start event initiated after the predetermined duration does not include the start / stop event. The system can include a controller that stores instructions for performing: in response to an engine pull-down event in which an intake manifold heating operation is scheduled, perform the intake manifold heating operation by rotating the engine in reverse without fuel via the motor to direct hot air from the exhaust system to the intake manifold.

[0069] In one example, such a system can further include an on-vehicle camera, a vehicle exhaust plume recognition system, and an ambient temperature sensor. In such an example, the controller can store other instructions for performing: in response to the on-vehicle camera indicating that the color of the exhaust leaving the exhaust system during an engine start event is white and also in response to an indication that the ambient temperature is below a threshold ambient temperature, indicate poor combustion at the engine start event.

[0070] In another example, such a system can additionally or optionally include an intake manifold temperature sensor, an exhaust system temperature sensor, and a throttle. In such an example, the controller can store other instructions for performing the following operations: performing an intake manifold heating operation in response to the intake manifold temperature monitored via the intake manifold temperature sensor being lower than a threshold intake manifold temperature during an engine pull-down event or during a period when the engine is pulled down before restarting. Performing the intake manifold heating operation can also include controlling the throttle to reach a substantially closed position to perform the intake manifold heating operation, and during the intake manifold heating operation, if the exhaust system temperature drops below a threshold exhaust system temperature, then abort the intake manifold heating operation.

[0071] Turning now to Figure 4 , a flowchart of a high-level exemplary method 400 for determining whether to schedule an intake heating operation for a subsequent S / S event in a driving cycle is shown. More specifically, in response to a request to start the engine after the engine has been turned off and the vehicle has been stationary for a predetermined time (e.g., a shutdown duration greater than a threshold shutdown duration), based on the ambient conditions and the exhaust color during startup, manifold heating can be scheduled for subsequent S / S events during the driving cycle starting at the request to start the engine. Method 400 will be described with reference to Figures 1 to 3B the system described in Figures 1 to 2 , but it should be understood that without departing from the scope of the present disclosure, method 400 can be applied to other systems. Method 400 can be executed by a controller (such as controller 212) and can be stored as executable instructions in a non-transitory memory. The instructions for executing method 400 and the remainder of the methods included herein can be executed by the controller based on the instructions stored on the controller's memory and in combination with signals received from sensors of the vehicle system (such as the sensors described above with reference to Figures 1 to 2 ). According to the methods described below, the controller can employ engine system actuators, such as spark plugs (e.g., 277), fuel injectors (e.g., 266), glow plugs (e.g., 276), motors (e.g., 120), throttles (e.g., 262), CPVs (e.g., 261), EGR valves (e.g., 253), etc.

[0072] Method 400 begins at 405 and may include estimating and / or measuring engine operating conditions. These may include, for example, engine speed, desired torque (e.g., from a pedal position sensor), manifold pressure (MAP), manifold air flow (MAF), BP, engine temperature, catalyst temperature, intake temperature, air temperature, knock limit, etc. Proceeding to 410, method 400 may include indicating whether an engine start event is in progress. More specifically, at 410, method 400 may include indicating whether an engine start event is in progress, where the engine start event includes a request to start the engine after a predetermined shutdown duration has elapsed. For example, "shutdown" may refer to a period during which the engine has been deactivated (e.g., turned off or not combusting air and fuel). Engine start may include a remote engine start request, a key-on event, pressing a start button on the vehicle's dashboard, etc. If no engine start event is indicated at 410, then method 400 may proceed to 415. At 415, method 400 may include maintaining current vehicle operating parameters. For example, if the vehicle is in operation, where the engine is at least partially operating to propel the vehicle, then the engine may remain in operation. Another example may include a situation where the engine is off but the vehicle is propelled via a pure electric operation mode. In such an example, the pure electric operation mode may be maintained. In other examples, the vehicle may be in a stationary state, where the engine and / or motor are off. In such an example, at 415, the current operating conditions may be maintained. Method 400 may then end.

[0073] Returning to 410, in response to an indication of an engine start event, method 400 may proceed to 420. At 420, method 400 may include indicating whether the ambient temperature is below a threshold ambient temperature. As discussed above, in one example, the threshold ambient temperature includes 32°F. In other examples, the threshold may be 40°F. In another example, the threshold may be 25°F. In other examples, the threshold may be 20°F. These examples are intended to be illustrative, and other threshold temperatures are also within the scope of the present disclosure. The ambient temperature may be monitored, for example, via an ambient temperature sensor (e.g., 198). If at 420 it is indicated that the ambient temperature is above the threshold ambient temperature, then method 400 may proceed to 425 and may include starting the engine during engine start without monitoring the exhaust leaving the exhaust passage (e.g., 235). In other words, since the ambient temperature is indicated to be above the threshold ambient temperature, it can be expected that the fuel provided to the engine during an engine start event can be combusted as needed. In other words, fuel combustion may be complete or nearly complete. Thus, starting the engine may include providing fuel and spark to the engine cylinders (in the case of a vehicle including an engine having spark plugs), or may include providing fuel and activating glow plugs (in the case of a diesel vehicle where the engine cylinders include glow plugs). Method 400 may then end.

[0074] Returning to 420, in response to an indication that the ambient temperature is less than the threshold ambient temperature, method 400 may proceed to 430. At 430, method 400 may include monitoring the color of the exhaust leaving the exhaust passage during engine start. More specifically, one or more on-vehicle cameras (e.g., 135) may be utilized to monitor the color of the exhaust leaving the exhaust passage. As discussed, the on-vehicle camera may be included in a vehicle smoke emission recognition system (e.g., 136), which may include a computer vision system and may be configured to accurately evaluate the color of the smoke emission leaving the vehicle exhaust passage. In some examples, such an on-vehicle camera may include one or more cameras positioned at the rear of the vehicle and may be configured to monitor obstacles, etc. when the vehicle is backing up (e.g., moving in reverse). Alternatively, in other examples, the camera used to monitor the exhaust may be different from the camera configured to monitor obstacles, etc. when the vehicle is being propelled in reverse. In any case, it can be understood that in response to an engine start condition after a long shutdown when the ambient temperature is below the ambient temperature threshold, an on-vehicle camera may be utilized to indicate whether the exhaust leaving the exhaust passage during the start event is white.

[0075] Accordingly, at 435, method 400 can include indicating whether the exhaust leaving the exhaust passage is white. In some examples, in response to a determination that the exhaust is white (including a high-confidence result, or a confidence level greater than a threshold (e.g., greater than 90 out of 100 if a numerical confidence scale is utilized)), the exhaust can be classified as white. If it is indicated at 435 that the exhaust leaving the vehicle during an engine start event is not white, then method 400 can proceed to 440. At 440, method 400 can include starting the engine without scheduling intake manifold heating operation for any subsequent S / S events during the driving cycle that began at the engine start event discussed above at 410. In other words, starting the engine can include providing fuel and spark to the engine cylinders (in the case of a vehicle including an engine with spark plugs), or can include providing fuel and activating glow plugs (in the case of a diesel vehicle where the engine cylinders include glow plugs). Method 400 can then end.

[0076] Alternatively, returning to 435, in response to an indication that white smoke has been emitted from the exhaust passage, method 400 can proceed to 445. At 445, method 400 can include scheduling intake manifold heating for any subsequent S / S events during the driving cycle that began at the engine start event discussed at 410. This method is shown at Figure 5 . For example, scheduling intake manifold heating for subsequent S / S events can include storing an instruction at the controller. Method 400 can then end.

[0077] Accordingly, turning to Figure 5 , a high-level flowchart of an exemplary method 500 for heating an intake manifold in response to an S / S event is shown. More specifically, method 500 can include Figure 4 sub-methods of method 400 as shown in Figure 4 . Method 500 can include transferring exhaust system heat to the intake manifold in response to an S / S event (where the ambient temperature is below an ambient temperature threshold and where the intake manifold temperature is below a threshold intake manifold temperature). Method 500 can be performed at the S / S event in response to this method being scheduled, as discussed above in

[0078] Method 500 will be described with reference to the system described in Figures 1 to 3B , but it should be understood that method 500 can be applied to other systems without departing from the scope of the present disclosure. Method 500 can be executed by a controller (such as controller 212) and can be stored as executable instructions in non-transitory memory. The instructions for executing method 500 and the remainder of the methods included herein can be performed by the controller based on instructions stored on the controller's memory and in combination with data from sensors of the vehicle system (such as those referenced above in Figures 1 to 2The method is implemented based on signals received by the sensors described above. According to the method described below, the controller may employ engine system actuators such as spark plugs (e.g., 277), fuel injectors (e.g., 266), glow plugs (e.g., 276), motors (e.g., 120), throttles (e.g., 262), CPVs (e.g., 261), EGR valves (e.g., 253), etc.

[0079] At 505, method 500 may include indicating whether an S / S event is in progress. In response to an indication that the S / S event is not in progress, method 500 may proceed to 510 and may include maintaining current vehicle operating parameters. More specifically, if the vehicle is at least partially propelled by the engine, engine operation may be maintained. If the engine is at least partially propelled by the motor, motor operation may be maintained. In other examples, if the vehicle is not in operation, the vehicle may remain in a non-operating state. Method 500 may then end.

[0080] Returning to 505, in response to an indication of an S / S event, method 500 may proceed to 515. At 515, method 500 may include indicating whether conditions are met to heat the intake manifold. Conditions that are met to heat the intake manifold may include the intake manifold temperature being lower than a threshold intake manifold temperature, as monitored via, for example, an intake temperature sensor (e.g., 260). The threshold intake manifold temperature may include a temperature at which, above the threshold, it is expected that most of the fuel provided to the engine will combust during the next engine start event. In other words, when the temperature of the intake manifold is greater than the threshold intake manifold temperature, it is expected that the engine start event will be substantially pollution-free. An engine start event in which most of the fuel provided to the engine combusts may include an engine start event in which the exhaust is more gray than white. Meeting the conditions at 515 may additionally or alternatively include the exhaust system temperature being greater than a threshold exhaust system temperature. The exhaust system temperature may be monitored via, for example, an exhaust system temperature sensor (e.g., 233). The threshold exhaust system temperature may include a temperature at which exhaust heat can be transferred to the intake manifold to raise the intake manifold temperature to at least the threshold intake manifold temperature without the exhaust system temperature dropping below, for example, the exhaust catalyst light-off temperature. However, in other examples, the threshold exhaust system temperature may include the light-off temperature. It can be understood that due to the lower thermal mass of the exhaust manifold compared to the intake manifold and additionally due to the flow of hot exhaust to the exhaust system during engine operation, the exhaust system temperature may increase more quickly than the intake manifold temperature during engine operation.

[0081] The condition being satisfied at 515 can additionally or alternatively include an indication that the state of charge (SOC) of an on-vehicle energy storage device (such as 150) is greater than a threshold SOC. The threshold SOC can include an SOC at which the engine can be reversed for a predetermined time duration (e.g., 30 seconds or less, 1 minute or less, 2 minutes or less, 3 minutes or less, 5 minutes or less, etc.) without depleting the on-vehicle energy storage device to an undesirable level. For example, if the SOC is such that by reversing the engine, the SOC could be depleted to a point that could adversely affect subsequent events that utilize the on-vehicle energy storage device, then the condition being satisfied may not be indicated for intake manifold heating.

[0082] The condition being satisfied at 515 can additionally or optionally include an indication that the ambient temperature is below a threshold ambient temperature. For example, the threshold ambient temperature can include the threshold ambient temperature discussed above, e.g., at step 420 of method 400.

[0083] In some examples where the vehicle is equipped with the ability for V2V, V2I2V, and / or V2I or V2X technologies, the condition being satisfied can include an indication that a particular S / S event is expected or inferred to be greater than a first threshold S / S duration but less than a second threshold S / S duration. More specifically, such technologies can be utilized to approximate the duration of the S / S event. If the S / S event is approximated as having a short duration (less than the first threshold S / S duration), e.g., less than 10 seconds, then the condition being satisfied may not be indicated because the intake manifold heating operation can utilize the power stored in the on-vehicle energy storage device without sufficiently heating the intake manifold prior to a request to restart the engine. Or, if the inferred S / S duration is greater than the second threshold S / S duration, then it may not be desirable to transfer exhaust heat back to the intake manifold because the net effect may not provide a gain, as the catalyst must be reignited at the next start when it has been cooled too much. Thus, by enabling the transfer of exhaust to the intake manifold only when the inferred S / S duration is greater than the first threshold S / S duration but less than the second threshold S / S duration, the method for heating the intake manifold can be optimized and method aborts can be reduced.

[0084] If at 515 it is not indicated that the conditions are met to perform the intake manifold heating operation, then method 500 can proceed to 520. At 520, method 500 can include continuing to monitor the intake manifold temperature during the duration of the S / S event. More specifically, it can be understood that immediately in response to the S / S event, the intake manifold temperature can be above the threshold intake manifold temperature due to the engine being in operation and heat being discharged to the intake port. However, in the case where the ambient temperature is below the threshold ambient temperature, the intake manifold can cool rapidly. Additionally, it can be understood that the intake manifold can include a large thermal mass compared to the exhaust manifold. Therefore, the intake manifold may take a long time to heat up to the threshold intake manifold temperature such that it is possible that even after the engine runs following an initial engine start event (see step 410 of method 400), the intake manifold may not reach the threshold intake manifold temperature before the start of the S / S event.

[0085] Accordingly, proceeding to 523, method 500 can again include indicating whether the conditions are met to perform the intake manifold heating. In other words, if at 515 the intake manifold temperature is not below the threshold intake manifold temperature but becomes less than the threshold intake manifold temperature during the S / S event in which the engine is off, then at 523, the conditions can be met to perform the intake manifold heating method.

[0086] If at 523 it is not indicated that the conditions are met to perform the intake manifold heating, then method 500 can proceed to 570. At 570, method 500 can include indicating whether an engine start is requested. For example, a vehicle driver can depress the accelerator pedal to request wheel torque. The requested wheel torque being greater than a threshold wheel torque, or the accelerator pedal position being greater than a threshold accelerator pedal position can indicate a request to start the engine. If at 570 an engine start is not requested, then method 500 can return to 520 and can continue to monitor the intake manifold temperature during the duration of the S / S event. Alternatively, if an engine start event is requested, then method 500 can proceed to 575 and can include starting the engine. As described above, starting the engine can include providing fuel and spark in the case where the engine includes spark plugs, or can include providing fuel and activating glow plugs in the case of a diesel vehicle where the vehicle includes glow plugs for the engine cylinders. In response to starting the engine, method 500 can then end. However, it can be understood that for any subsequent S / S event in the current driving cycle, in response to the conditions being met to perform the intake manifold heating, method 500 can be used again to heat the intake manifold.

[0087] Alternatively, if at 515 or 523, the indication condition is met to perform intake manifold heating, then method 500 can proceed to 525. At 525, method 500 can include closing the throttle (e.g., 262). Closing the throttle can be used to trap heat within the intake manifold for the purpose of heating the intake manifold. In one example, closing the throttle can include fully closing the throttle. In another example, closing the throttle can include closing the throttle to a threshold closed state (e.g., 95% closed).

[0088] In addition, at 525, method 500 can include closing the CPV (e.g., 261), and closing the EGR valve (e.g., 253), if the vehicle is equipped with such a valve. For example, if the CPV and / or EGR valve are not commanded to close, then heat may not be effectively transferred to the intake manifold via reverse rotation of the engine.

[0089] Proceeding to 530, method 500 can include indicating whether the vehicle is a vehicle including a diesel engine. If the vehicle is indicated as including a diesel engine with glow plugs coupled to the engine cylinders, then method 500 can proceed to 535 and can include activating one or more of the glow plugs. In one example, the activation of one or more glow plugs can be based on the SOC of the on-board energy storage device, and can also be based on the intake manifold temperature. For example, the lower the intake manifold temperature is below a threshold, the greater the number of glow plugs that can be activated. In another example, the lower the intake manifold temperature is below a threshold, the greater the amount of energy supplied to the glow plugs, as long as the SOC of the on-board energy storage device remains above a threshold SOC (as discussed above). In other examples, the activation of the glow plugs (the number of glow plugs activated and / or the amount of energy supplied to the glow plugs) can be a function of the exhaust system temperature. For example, the higher the exhaust system temperature, the fewer the number of glow plugs that can be activated and / or the less the amount of energy that can be supplied to the glow plugs.

[0090] To determine how many glow plugs to activate and the energy levels to use, one or more look-up tables can be stored at the controller. For example, such one or more look-up tables can include information regarding how many glow plugs to activate and the energy levels to use as a function of the intake manifold temperature and / or the exhaust system temperature.

[0091] Regardless of whether the vehicle includes glow plugs, method 500 can proceed to 540 and can include rotating the engine in reverse without fueling at a predetermined engine speed (e.g., 500 RPM). In some examples, rotating the engine in reverse may not include a predetermined engine speed but may include a variable engine speed, where the speed may be a function of the intake manifold temperature. For example, the lower the intake manifold temperature is than a threshold intake manifold temperature, the faster the engine can be rotated to ensure that the intake manifold temperature rises to the threshold intake manifold temperature within a predetermined amount of time.

[0092] As discussed above, rotating the unfueled engine in reverse can include configuring an H-bridge circuit (as shown above at Figures 3A to 3B ) to enable a motor (e.g., 120) to rotate the engine in the reverse direction. It can be understood that the reverse direction is opposite to the direction in which the engine rotates when burning air and fuel. By rotating the engine in reverse, a vacuum can be created in the exhaust system while a pressure can be created in the intake manifold. Operating the engine in this way can thus draw exhaust heat into the intake manifold.

[0093] When rotating the engine in reverse without fueling, method 500 can proceed to 545 and can include indicating whether the exhaust system temperature has dropped below a threshold exhaust system temperature. More specifically, as the exhaust is transferred from the exhaust system to the intake manifold, the exhaust system temperature can correspondingly decrease. For subsequent engine starts, it may be undesirable for the exhaust system temperature to be below the catalyst light-off temperature. Thus, if at 545 it is indicated that the exhaust system temperature has dropped to or below the threshold exhaust system temperature, then method 500 can proceed to 550. Additionally, although not explicitly shown, at 545 method 500 can include indicating whether the temperature of an exhaust sensor (e.g., 237) has dropped below a threshold exhaust sensor temperature. If so, then one or more heaters (e.g., 279) associated with the exhaust sensor can be activated to raise the temperature of the exhaust sensor to the threshold exhaust sensor temperature.

[0094] At 550, in response to the exhaust system temperature being below a threshold exhaust system temperature, method 500 may include aborting the method. Aborting the method may include stopping the un-fueled engine reverse rotation at 555 and returning the throttle to a default position (e.g., the position it was at before being commanded to close at step 525) at step 560. Additionally, if glow plugs are activated during engine reverse rotation, the glow plugs may be deactivated. For example, such steps may be performed by a controller. Proceeding to 565, method 500 may include updating vehicle operating parameters. For example, it may be indicated to proceed with a program to increase the intake manifold temperature during an S / S event, but the program is aborted because the exhaust system has dropped below the threshold exhaust system temperature. For example, such an indication may be stored in the controller. As discussed above, in examples where the vehicle includes V2V or V2X technology, this abort may be reduced or eliminated by only enabling the intake manifold heating method to start in response to a predicted S / S duration within a specified window (e.g., greater than a first threshold S / S duration but less than a second threshold S / S duration).

[0095] Proceeding to 570, method 500 may include indicating whether an engine start is requested. As discussed above, an engine start event may include a requested wheel torque greater than a threshold wheel torque, an accelerator pedal position greater than a threshold position, etc. In response to such a request to start the engine, method 500 may proceed to 575 and may include starting the engine to combust air and fuel. Method 500 may then end.

[0096] Alternatively, returning to 545, in response to the exhaust system temperature remaining above the threshold exhaust system temperature during engine reverse rotation, method 500 may proceed to 570. At 570, method 500 may include indicating whether the intake manifold temperature is greater than a threshold intake manifold temperature. In other words, at 570, method 500 may determine whether the transfer of exhaust heat to the intake manifold is sufficient to raise the intake manifold temperature above the threshold intake manifold temperature. If at 570 the intake manifold temperature is not equal to or higher than the threshold intake manifold temperature, then method 500 may return to 540 and may include continuing to reverse rotate the un-fueled engine to continue transferring exhaust system heat to the intake manifold.

[0097] In response to the intake manifold temperature increasing to or exceeding a threshold intake manifold temperature, method 500 may proceed to 555. Steps 555 through 575 are the same as the steps described above and thus will not be repeated here for brevity. Briefly, the engine can be stopped from turning without fuel, the throttle can be returned to its original position before it was commanded to close, the glow plugs (if included) can be deactivated, and the vehicle operating parameters can be updated. In some examples, the throttle can remain closed until an engine start request is indicated so that heat can be trapped in the intake manifold for as long as possible before the requested engine start. Updating the vehicle operating parameters in response to the intake manifold temperature reaching or exceeding the threshold intake manifold temperature can include storing the result at the controller such that the intake manifold temperature has successfully increased to or above the threshold intake manifold temperature. Additionally, it can be understood that although the intake manifold temperature has increased to or above the threshold intake manifold temperature, if an engine start request is not initiated soon thereafter, the intake manifold temperature can drop below the threshold again. Thus, at 570, if no engine start event is indicated, the method described at Figure 5 can be repeated such that the intake manifold temperature can increase again before an engine start request.

[0098] In response to receiving an engine start request, method 500 can continue to start the engine as discussed above. Method 500 can then end.

[0099] Now turning to Figure 6, an exemplary timeline 600 is shown for determining whether to schedule an intake manifold heating procedure during an S / S event of a driving cycle and, if so, for performing such a heating method in response to the S / S event. Timeline 600 includes curve 605, which indicates the change in engine speed (e.g., RPM) over time. The engine can rotate or spin in a forward direction (forward) or a reverse direction (reverse), or can be off. Timeline 600 also includes curve 610, which indicates whether fuel injection to one or more engine cylinders is on or off over time. Timeline 600 also includes curve 615, which indicates the change in ambient temperature over time. Line 616 shows a threshold ambient temperature at which, if the ambient temperature is below the threshold, heating of the intake manifold can be scheduled and / or performed during an S / S event. Timeline 600 also includes curve 620, which indicates the change in the temperature of the intake manifold over time. Line 621 represents a threshold intake manifold temperature, which can represent the desired intake manifold temperature for performing an engine start event such that most (e.g., the expected or desired amount) of the fuel burns during the engine start event. Timeline 600 also includes curve 625, which indicates the position of the throttle (e.g., 262) over time. The throttle can be open or closed. In this example, it can be understood that throttle open includes the throttle being fully open or wide open, and throttle closed includes the throttle being fully closed or wide closed.

[0100] Timeline 600 also includes curve 630, which indicates the exhaust color over time. The exhaust color can be understood to refer to the color of the exhaust exiting the vehicle's exhaust passage. Timeline 600 also includes curve 635, which indicates whether a stop / start event is encountered (yes) or not encountered (no) during the driving cycle shown by timeline 600. Timeline 600 also includes curve 640, which indicates the state of the glow plugs included in the vehicle engine over time. Thus, it can be understood that in the exemplary timeline 600, the vehicle engine includes a diesel engine. Timeline 600 also includes curve 645, which indicates the temperature of the vehicle exhaust system (e.g., 225). Line 646 represents a threshold exhaust system temperature at which, if the temperature of the exhaust system drops below the threshold during the intake manifold heating method, then this method can be aborted. Timeline 600 also includes curve 650, which indicates whether an engine start event is requested (yes) or not requested (no) over time. Timeline 600 also includes curve 655, which indicates whether intake manifold heating is scheduled (yes) or not scheduled (no) for the current driving cycle over time.

[0101] At time t0, the engine is not operating (curve 605), and fuel injection is turned off (curve 610). The ambient temperature (curve 615) is lower than the threshold ambient temperature (line 616). In this example, it can be understood that the threshold ambient temperature includes 32°F. In the case where the ambient temperature is lower than the threshold, the intake manifold temperature (curve 620) is lower than the threshold intake manifold temperature (line 621). The throttle position (curve 625) includes the position of the throttle at the last engine shutdown event. At time t0, after a long shutdown, the vehicle is not currently in an engine start event, and therefore the exhaust color is not applicable (n / a) because at time t0, there is no exhaust to measure. The engine shutdown state at time t0 can be understood to include an engine shutdown condition, wherein the engine has been shut down for at least a threshold duration (e.g., 6 hours or more), and wherein the vehicle has not been propelled via an electrical energy source during the time when the engine is shut down. In other words, the engine shutdown state does not represent an S / S event (curve 635). When the engine is off and no engine start is requested (plot 650), the glow plugs are off (plot 640). The exhaust system temperature (plot 650) is below the threshold exhaust system temperature (line 646), and intake manifold heating has not been scheduled (plot 655) because no engine start request has been initiated since the last engine off event (e.g., engine start request) (the engine has been in an off condition).

[0102] At time t1, an engine start is requested (curve 650). Because the vehicle includes a diesel engine, and because the ambient temperature is below a threshold ambient temperature (line 616), the glow plugs are activated (curve 640) to provide heat to the engine cylinders. Additionally, fuel is provided to the engine (curve 610) to initiate the requested start event. Between time t1 and t2, the engine speed increases in coordination with the engine start event initiated at time t1.

[0103] Since the engine start request occurs when the ambient temperature is below the threshold ambient temperature, it is understood that the onboard camera (e.g., 135) can be controlled via the controller to record video and / or images of exhaust gas exiting the exhaust duct of the exhaust system during the engine start event initiated at time t1. In addition, the vehicle exhaust recognition system (e.g., 136) can be used for color recognition purposes to indicate to the controller whether the exhaust smoke is white or another color.

[0104] At time t2, it is indicated that the exhaust gas leaving the exhaust passage is actually white. Thus, in the case where the ambient temperature is lower than the threshold ambient temperature, and by indicating the white smoke leaving the exhaust device, intake manifold heating (curve 655) is scheduled for any subsequent S / S event during the current driving cycle initiated at time t1. By time t3, it can be understood that the engine start event has ended, and the engine operates to combust air and fuel. Accordingly, no further engine start is requested (curve 650), and correspondingly, the glow plugs are deactivated (curve 640), and image / video acquisition is stopped (curve 630).

[0105] Between times t3 and t4, the vehicle is propelled at least in part via the engine. As shown between times t3 and t4, the exhaust system temperature (curve 645) rises faster than the intake manifold temperature. The faster rise in the exhaust system temperature is due to the lower thermal mass of the exhaust manifold and the result of hot exhaust being discharged into the exhaust system. More specifically, between times t3 and t4, the exhaust system temperature is higher than the threshold exhaust system temperature, which in this example can be understood to include the exhaust catalyst light-off temperature. However, between times t3 and t4, the intake manifold temperature remains below the threshold intake manifold temperature. Thus, it can be understood that the cold ambient temperature coupled with the large thermal mass of the intake manifold prevents the intake manifold from warming up above the threshold intake manifold temperature.

[0106] At time t4, an S / S event is initiated (curve 635). As discussed above, the S / S event can be initiated when the vehicle speed is below the threshold speed, and thus it can be understood that at time t4, the S / S event is requested via the controller. The S / S event can be a function of vehicle speed, accelerator pedal position, engine speed, etc. By the S / S event initiated at time t4, fuel injection is stopped (curve 610). Additionally, via intake heating scheduled due to the ambient temperature being lower than the threshold ambient temperature, and also in response to the indication of white smoke discharged from the exhaust passage during the engine start event initiated at time t1, one or more glow plugs are activated at time t5 (curve 640) to provide another heat source to the engine system. Additionally, at time t5, the throttle is commanded to the closed position. In this exemplary timeline 600, the throttle is commanded to the fully closed position; however, it can be understood that in other examples, the throttle can be commanded to a substantially closed (e.g., within 95% closed) position. Although not explicitly shown, it can be understood that at time t5, if the CPV or EGR valve is open, then such valves can be commanded to close via the controller.

[0107] At time t6, the engine is controlled via the controller to rotate in reverse (curve 605) without fueling (curve 610). When rotating in reverse without fueling, the engine speed is controlled to a predetermined speed (e.g., 500 RPM). By rotating the engine in reverse without fueling, heat is directed to the intake manifold when the glow plugs are activated. More specifically, since the engine is operated in reverse without fueling, exhaust system heat can be transferred to the intake manifold. The engine can be rotated in reverse via the motor (e.g., 120) using power provided via the on-vehicle energy storage device (e.g., 150).

[0108] Accordingly, between time t6 and t7, the intake manifold temperature rises (curve 620) while the exhaust system temperature drops (curve 645) due to the transfer of exhaust system heat to the intake manifold. At time t7, the intake manifold temperature reaches the threshold intake manifold temperature. When the intake manifold temperature reaches the threshold intake manifold temperature at time t7, one or more glow plugs are deactivated (curve 640), and the engine is controlled to stop rotating in reverse. Specifically, the controller can send a signal to one or more glow plugs to actuate them to close, and the controller can also send a signal to the motor to actuate the motor to stop the engine from rotating in reverse. Additionally, the throttle remains closed. Keeping the throttle closed can be used to trap heat in the intake manifold until an engine start event is requested.

[0109] Between time t7 and t8, the engine remains off because an engine start has not been requested. The intake manifold temperature remains above the threshold intake manifold temperature. Although not explicitly shown, it can be understood that in response to the intake manifold temperature dropping below the threshold intake manifold temperature after the transfer of exhaust heat to the intake manifold, additional exhaust heat can be transferred to the intake manifold in the same manner as discussed, provided that the temperature of the exhaust system remains above the threshold exhaust system temperature.

[0110] At time t8, an engine start is requested. In other words, it can be understood that the vehicle driver has requested wheel torque in excess of a predetermined threshold, thus requiring an engine start event to provide the requested torque. For example, such a request can be communicated to the controller based on the accelerator pedal position.

[0111] Accordingly, fuel injection is provided to the engine (curve 610). In some examples, the glow plug may be activated, but in other examples, the glow plug may not be activated. In other words, since the intake manifold temperature is higher than the threshold intake manifold temperature, additional heat may not result in improved fuel combustion during an engine start event, and thus battery power may be conserved by not activating the glow plug when the intake manifold temperature is above the threshold. However, in other examples, the glow plug may still be activated due to a low ambient temperature (curve 615) and due to the fact that intake manifold heating is utilized to improve fuel combustion during the next requested engine start event.

[0112] At time t8, the throttle is commanded to the default position, or the position where the throttle was located just prior to commanding the throttle closed at time t5. By the intake manifold heating method performed between times t4 and t8, in some examples, a vehicle camera may not be utilized to monitor the exhaust color during an engine start event after the intake manifold heating method has been performed. However, in other examples, the vehicle camera may be used to confirm that the intake manifold heating method results in no white smoke during the next engine start, which is shown here at time t8. Accordingly, line 631 is shown as a dashed line, which indicates that this action of monitoring the exhaust color during an engine start event may or may not be performed.

[0113] Between times t8 and t9, the engine speed rises in conjunction with the engine start event. At time t9, it is understood that the engine start event has ended such that no further engine start is requested (curve 650). Between times t9 and t10, the engine is operated according to the driver demand (curve 625) (curve 605). Additionally, between times t9 and t10, intake manifold heating remains scheduled (curve 655) when no S / S event is indicated. In other words, for any subsequent S / S event initiated at time t1 during the current driving cycle, the conditions may be evaluated to determine if intake manifold heating is to be performed, and if so, the method may be applied as discussed.

[0114] In this manner, combustion may be improved during an engine start event corresponding to an S / S event in a vehicle equipped with such technology. By improving combustion, undesired emissions caused by incomplete combustion events may be reduced or eliminated. Additionally, fuel economy may be improved, which is particularly desirable for hybrid vehicles equipped with S / S technology.

[0115] The technical effect is to recognize that during or prior to an S / S event, the intake manifold temperature may drop (or fail to rise) to a point where poor combustion may occur, and thus by rotating the engine in reverse, the exhaust system heat can be effectively used to raise the intake manifold temperature to a threshold intake manifold temperature during an S / S event. For vehicles with S / S features, there may be many such stops along a particular driving cycle, where if the above method is not utilized, then many poor internal combustion engine start events may occur during such a driving cycle. Of course, such poor internal combustion engine start events may increase undesirable emissions, reduce fuel economy, and may also reduce engine life. Therefore, it is highly desirable to mitigate such problems.

[0116] Another technical effect is to recognize that when rotating the engine in reverse, if the vehicle engine includes a diesel engine, then one or more glow plugs can be activated to further increase the heat delivered to the intake manifold. The energy supplied to the glow plugs can be a function of the SOC of the on-vehicle energy storage device and can additionally or alternatively be a function of the exhaust system temperature and / or the intake manifold temperature. Further still, a technical effect is to recognize that during reverse rotation, the engine speed can be a function of the exhaust system temperature and / or the intake manifold temperature.

[0117] In this document and with reference to Figures 1 to 3B the system described herein and with reference to Figures 4 to 5The method described can implement one or more systems and one or more methods. In one example, a method includes rotating the engine of a vehicle in a reverse direction without fueling in response to an engine pull-down event until the temperature of the intake manifold of the engine rises to or above a threshold intake manifold temperature due to airflow from the exhaust manifold of the engine flowing through the engine and into the intake manifold. In a first example of the method, the method further includes: wherein the reverse direction includes a direction opposite to the forward direction in which the engine rotates when burning air and fuel to propel the vehicle. A second example of the method optionally includes the first example and further includes: stopping rotating the engine in the reverse direction in response to the temperature of the intake manifold rising to or above the threshold intake manifold temperature. A third example of the method optionally includes any one or more or each of the first example and the second example and further includes: controlling a throttle configured to control the amount of air inhaled into the intake manifold to reach a closed or substantially closed position just before rotating the engine in the reverse direction. A fourth example of the method optionally includes any one or more or each of the first example to the third example and further includes: keeping the throttle closed or substantially closed after rotating the engine in the reverse direction to trap heat in the intake manifold until a request to start the engine is indicated. A fifth example of the method optionally includes any one or more or each of the first example to the fourth example and further includes: sealing the intake manifold to isolate it from the exhaust gas recirculation system and the evaporative emissions system just before rotating the engine in the reverse direction. A sixth example of the method optionally includes any one or more or each of the first example to the fifth example and further includes: wherein the threshold intake manifold temperature results in a desired efficiency level of fuel combustion in response to a request to start the engine. A seventh example of the method optionally includes any one or more or each of the first example to the sixth example and further includes: wherein the engine pull-down event includes a start / stop event, and wherein the start / stop event includes turning off the engine to reduce the amount of time the engine idles. An eighth example of the method optionally includes any one or more or each of the first example to the seventh example and further includes: wherein rotating the engine in the reverse direction in response to the engine pull-down event occurs in response to a scheduled intake manifold heating operation.The ninth example of the method optionally includes any one or more or each of the first example to the eighth example, and further includes: wherein arranging the intake manifold heating operation involves monitoring the color of the exhaust gas leaving the exhaust system of the engine during an engine start event, the engine start event occurring after an engine shutdown condition with an engine shutdown duration exceeding a threshold, wherein the ambient temperature is lower than a threshold ambient temperature; and arranging the intake manifold heating operation in response to an indication that the color of the exhaust gas is white. The tenth example of the method optionally includes any one or more or each of the first example to the ninth example, and further includes: stopping rotating the engine in the reverse direction in response to the exhaust system temperature dropping below a threshold exhaust system temperature during rotating the engine in the reverse direction.

[0118] Another example of a method includes: in response to a request to start the engine after the engine of a vehicle has been deactivated for a predetermined duration and also in response to an ambient temperature being lower than a threshold ambient temperature, monitoring the color of the exhaust exiting the exhaust system of the engine; and in response to the color of the exhaust being substantially white, arranging an intake manifold heating operation to raise the temperature of the intake manifold of the engine to or above a threshold intake manifold temperature during a subsequent engine pull-down event during a driving cycle; the intake manifold heating operation involves rotating the engine without fuel in a reverse direction, and after the engine has been deactivated for the predetermined duration, initiating the driving cycle in response to the request to start the engine. In a first example of the method, the method further includes: wherein rotating the engine without fuel in the reverse direction directs hot air in the exhaust system to the intake manifold until the temperature of the intake manifold rises to or above the threshold intake manifold temperature, and then stopping the engine from rotating in the reverse direction; and wherein the speed at which the engine rotates in reverse can vary according to one or more of the ambient temperature, the intake manifold temperature, and / or the exhaust system temperature. A second example of the method optionally includes the first example and further includes: wherein the intake manifold heating operation involves closing or substantially closing an intake throttle positioned in the intake passage of the engine to trap heat in the intake manifold. A third example of the method optionally includes any one or more or each of the first example and the second example and further includes: wherein the color of the exhaust is monitored at least in part via an on-vehicle camera. A fourth example of the method optionally includes any one or more or each of the first example to the third example and further includes: wherein the pull-down event includes a stop / start event that involves shutting down the engine to reduce the amount of time the engine idles; and wherein arranging the intake manifold heating operation includes arranging the intake manifold heating operation for one or more start / stop events in the driving cycle, provided that the intake manifold temperature is below the threshold intake manifold temperature when the start / stop event is initiated or the intake manifold temperature drops below the threshold intake manifold temperature during the stop / start event. A fifth example of the method optionally includes any one or more or each of the first example to the fourth example and further includes: aborting the intake manifold heating operation in response to the temperature of the exhaust system dropping below a threshold exhaust system temperature during the intake manifold heating operation.

[0119] An example of a system for a hybrid vehicle includes: an engine that includes an intake manifold and an exhaust system; a motor configured to operate via energy supplied from an on-vehicle energy storage device; a start / stop system; and a controller that stores instructions in a non-transitory memory, the instructions, when executed, cause the controller to: schedule an intake manifold heating operation for an engine pull-down event corresponding to a start / stop event in response to an indication of poor combustion upon an engine start event initiated after a predetermined duration in which the engine has been deactivated, wherein the engine start event initiated after the predetermined duration does not include the start / stop event; and in response to the engine pull-down event in which the intake manifold heating operation is scheduled, perform the intake manifold heating operation by causing the engine to rotate in reverse without fuel via the motor to direct hot air from the exhaust system to the intake manifold. In a first example of the system, the system further includes: an on-vehicle camera; a vehicle exhaust recognition system; an ambient temperature sensor; and wherein the controller stores other instructions for performing: indicating poor combustion upon the engine start event in response to the on-vehicle camera indicating that the color of the exhaust leaving the exhaust system during the engine start event is white and further in response to an indication that the ambient temperature is below a threshold ambient temperature. A second example of the system optionally includes the first example and further includes: an intake manifold temperature sensor; an exhaust system temperature sensor; a throttle; and wherein the controller stores other instructions for performing: performing the intake manifold heating operation in response to the intake manifold temperature monitored via the intake manifold temperature sensor being below a threshold intake manifold temperature during the engine pull-down event or during a period in which the engine is pulled down before restarting; and wherein performing the intake manifold heating operation further includes controlling the throttle to a substantially closed position to perform the intake manifold heating operation, and if the exhaust system temperature drops below a threshold exhaust system temperature during the performing of the intake manifold heating operation, then aborting the intake manifold heating operation.

[0120] Note that the exemplary control and estimation procedures included herein can be used with a variety of engine and / or vehicle system configurations. The control methods and procedures disclosed herein can be stored as executable instructions in a non-transitory memory and executed by a control system including a controller in combination with various sensors, actuators, and other engine hardware. The specific procedures described herein can represent one or more of any number of processing strategies (such as event-driven, interrupt-driven, multi-tasking, multi-threaded, etc.). Accordingly, the various acts, operations, and / or functions illustrated can be executed in the illustrated sequence, executed in parallel, or omitted in some cases. Similarly, the order of processing is not necessarily required to implement the features and advantages of the exemplary embodiments described herein, but is provided for ease of illustration and description. One or more of the illustrated acts, operations, and / or functions can be repeatedly executed according to the particular strategy used. Additionally, the acts, operations, and / or functions described can be graphically represented as code to be programmed into the non-transitory memory of a computer-readable storage medium for an engine control system, where the described acts are executed by executing instructions in a system including various engine hardware components in combination with an electronic controller.

[0121] It will be appreciated that the configurations and procedures disclosed herein are exemplary in nature and these specific embodiments should not be regarded as having a limiting significance since many variations are possible. For example, the above techniques can be applied to V-6, I-4, I-6, V-12, opposed 4, and other engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations and other features, functions, and / or properties disclosed herein.

[0122] The following claims particularly point out certain combinations and sub-combinations regarded as novel and non-obvious. These claims may refer to "an" element or "a first" element or the equivalent thereof. These claims are to be understood to include the combination of one or more such elements, neither requiring nor precluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and / or properties can be claimed by amendment of the present claims or by presentation of new claims in this or a related application. Such claims, whether broader, narrower, the same, or different in scope from the original claims, are regarded as included within the subject matter of the present disclosure.

[0123] According to the present invention, a method includes rotating an engine of a vehicle in a reverse direction without fueling in response to an engine pull-down event until the temperature of an intake manifold of the engine rises to or above a threshold intake manifold temperature due to airflow from an exhaust manifold of the engine flowing through the engine and into the intake manifold.

[0124] According to one embodiment, the reverse direction includes a direction opposite to the forward direction in which the engine rotates when burning air and fuel to propel the vehicle.

[0125] According to one embodiment, the invention is further characterized in that, in response to the temperature of the intake manifold rising to or above the threshold intake manifold temperature, the reverse rotation of the engine is stopped.

[0126] According to one embodiment, the invention is further characterized in that, just before rotating the engine in the reverse direction, the throttle configured to control the amount of air inhaled into the intake manifold is controlled to reach a closed or substantially closed position.

[0127] According to one embodiment, the invention is further characterized in that, after rotating the engine in the reverse direction, the throttle is kept closed or substantially closed to trap heat in the intake manifold until a request to start the engine is indicated.

[0128] According to one embodiment, the invention is further characterized in that, just before rotating the engine in the reverse direction, the intake manifold is sealed to isolate it from the exhaust gas recirculation system and the evaporative emissions system.

[0129] According to one embodiment, the threshold intake manifold temperature results in a desired efficiency level of fuel combustion in response to a request to start the engine.

[0130] According to one embodiment, the engine pull-down event includes a start / stop event, wherein the start / stop event includes shutting down the engine to reduce the amount of time the engine idles.

[0131] According to one embodiment, rotating the engine in the reverse direction in response to the engine pull-down event occurs in response to a scheduled intake manifold heating operation.

[0132] According to one embodiment, scheduling the intake manifold heating operation involves monitoring the color of the exhaust gas leaving the exhaust system of the engine during an engine start event, the engine start event occurring after an engine shutdown condition that exceeds a threshold engine shutdown duration, wherein the ambient temperature is below a threshold ambient temperature; and scheduling the intake manifold heating operation in response to an indication that the color of the exhaust gas is white.

[0133] According to one embodiment, the invention is further characterized in that, in response to the exhaust system temperature dropping below a threshold exhaust system temperature during the reverse rotation of the engine, the reverse rotation of the engine is stopped.

[0134] According to the present invention, a method includes: in response to a request to start the engine after the engine of a vehicle has been deactivated for a predetermined duration and also in response to an ambient temperature being lower than a threshold ambient temperature, monitoring a color of exhaust gas exiting an exhaust system of the engine; and in response to the color of the exhaust gas being substantially white, arranging an intake manifold heating operation to raise a temperature of an intake manifold of the engine to or above a threshold intake manifold temperature during a subsequent engine pull - down event in a driving cycle; the intake manifold heating operation involves rotating the engine without fuel in a reverse direction, and initiating the driving cycle upon the request to start the engine after the engine has been deactivated for the predetermined duration.

[0135] According to one embodiment, rotating the engine without fuel in the reverse direction directs hot air in the exhaust system to the intake manifold until the temperature of the intake manifold rises to or above the threshold intake manifold temperature, and then stopping the engine from rotating in the reverse direction; and wherein a speed at which the engine rotates in reverse can vary according to one or more of the ambient temperature, the intake manifold temperature, and / or the exhaust system temperature.

[0136] According to one embodiment, the intake manifold heating operation involves closing or substantially closing an intake throttle positioned in an intake passage of the engine to trap heat in the intake manifold.

[0137] According to one embodiment, monitoring the color of the exhaust gas is performed at least in part via an on - vehicle camera.

[0138] According to one embodiment, the pull - down event includes a stop / start event that involves shutting down the engine to reduce an amount of time the engine idles; and wherein arranging the intake manifold heating operation includes arranging the intake manifold heating operation for one or more start / stop events in the driving cycle, provided that the intake manifold temperature is below the threshold intake manifold temperature at the initiation of the start / stop event or the intake manifold temperature drops below the threshold intake manifold temperature during the stop / start event.

[0139] According to one embodiment, the above - mentioned invention is further characterized in that the intake manifold heating operation is aborted in response to the temperature of the exhaust system dropping below a threshold exhaust system temperature during the intake manifold heating operation.

[0140] According to the present invention, there is provided a system for a hybrid vehicle, the system having: an engine including an intake manifold and an exhaust system; a motor configured to operate via energy supplied from an on-vehicle energy storage device; a start / stop system; and a controller that stores instructions in a non-transitory memory, the instructions, when executed, causing the controller to: schedule an intake manifold heating operation for an engine pull-down event corresponding to a start / stop event in response to an indication of poor combustion upon an engine start event initiated after a predetermined duration during which the engine has been deactivated, wherein the engine start event initiated after the predetermined duration does not include the start / stop event; and perform the intake manifold heating operation by causing the engine to rotate in reverse without fuel via the motor in response to the engine pull-down event for which the intake manifold heating operation is scheduled, to direct hot air from the exhaust system to the intake manifold.

[0141] According to one embodiment, the above invention is further characterized by: an on-vehicle camera; an automotive exhaust smoke recognition system; an ambient temperature sensor; and wherein the controller stores other instructions for performing the following operations: indicating poor combustion upon the engine start event in response to an indication that the color of the exhaust gas leaving the exhaust system during the engine start event as indicated by the on-vehicle camera is white and further in response to an indication that the ambient temperature is lower than a threshold ambient temperature.

[0142] According to one embodiment, the above invention is further characterized by: an intake manifold temperature sensor; an exhaust system temperature sensor; a throttle valve; and wherein the controller stores other instructions for performing the following operations: perform the intake manifold heating operation in response to the intake manifold temperature monitored via the intake manifold temperature sensor being lower than a threshold intake manifold temperature during the engine pull-down event or during a period when the engine is pulled down before restart; and wherein performing the intake manifold heating operation further includes controlling the throttle valve to reach a substantially closed position to perform the intake manifold heating operation, and aborting the intake manifold heating operation if the exhaust system temperature drops below a threshold exhaust system temperature during the performing of the intake manifold heating operation.

Claims

1. A method for a hybrid vehicle, the method comprising: In response to an engine pull-down event, rotate the vehicle's engine in the reverse direction without fuel until the temperature of the engine's intake manifold rises to or above a threshold intake manifold temperature due to airflow from the engine's exhaust manifold flowing through the engine and into the intake manifold.

2. The method according to claim 1, wherein the reverse direction includes a direction opposite to the forward direction in which the engine rotates when burning air and fuel to propel the vehicle.

3. The method according to claim 1, the method further comprising: Stop rotating the engine in reverse in response to the temperature of the intake manifold rising to or above the threshold intake manifold temperature.

4. The method according to claim 1, the method further comprising: Just before rotating the engine in the reverse direction, control a throttle valve configured to control the amount of air inhaled into the intake manifold to reach a closed or substantially closed position.

5. The method according to claim 4, the method further comprising: Keep the throttle valve closed or substantially closed after rotating the engine in the reverse direction to trap heat in the intake manifold until a request to start the engine is indicated.

6. The method according to claim 1, the method further comprising: Seal the intake manifold to isolate it from the exhaust gas recirculation system and the evaporative emissions system just before rotating the engine in the reverse direction.

7. The method according to claim 1, wherein the threshold intake manifold temperature generates a desired efficiency level of fuel combustion in response to a request to start the engine.

8. The method according to claim 1, wherein the engine pull - down event includes a start / stop event, and the start / stop event includes shutting down the engine to reduce the amount of time the engine idles.

9. The method according to claim 1, wherein causing the engine to rotate in the reverse direction in response to the engine pull - down event occurs in response to a scheduled intake manifold heating operation.

10. The method according to claim 9, wherein scheduling the intake manifold heating operation involves monitoring the color of the exhaust leaving the exhaust system of the engine during an engine start event, the engine start event occurring after an engine shutdown condition that exceeds a threshold engine shutdown duration, wherein the ambient temperature is below a threshold ambient temperature; and scheduling the intake manifold heating operation in response to an indication that the color of the exhaust is white.

11. The method according to claim 10, the method further comprising: Stop rotating the engine in the reverse direction in response to the exhaust system temperature dropping below a threshold exhaust system temperature during rotation of the engine in the reverse direction.

12. The method according to claim 10, wherein the speed at which the engine rotates in the reverse direction without fuel can vary according to one or more of the ambient temperature, the intake manifold temperature, and / or the exhaust system temperature.

13. A system for a hybrid vehicle, the system comprising: An engine, the engine including an intake manifold and an exhaust system; A motor configured to operate via energy supplied from an on-vehicle energy storage device; A start / stop system; and A controller that stores instructions in a non-transitory memory, the instructions causing the controller when executed to: Schedule an intake manifold heating operation for an engine pull-down event corresponding to a start / stop event in response to an indication of poor combustion at an engine start event initiated after a predetermined duration in which the engine has been deactivated, where the engine start event initiated after the predetermined duration does not include the start / stop event; and Perform the intake manifold heating operation by rotating the engine in reverse without fuel via the motor in response to the engine pull-down event in which the intake manifold heating operation is scheduled, to direct hot air from the exhaust system to the intake manifold.

14. The system according to claim 13, wherein the system further comprises: An on-vehicle camera; An automotive exhaust smoke recognition system; An ambient temperature sensor; And Wherein the controller stores other instructions for performing the following: indicating poor combustion at the engine start event in response to the on-vehicle camera indicating that the color of the exhaust exiting the exhaust system during the engine start event is white and further in response to an indication that the ambient temperature is below a threshold ambient temperature.

15. The system according to claim 13, wherein the system further comprises: An intake manifold temperature sensor; An exhaust system temperature sensor; A throttle valve; And Wherein the controller stores other instructions for performing the following: perform the intake manifold heating operation in response to the intake manifold temperature monitored via the intake manifold temperature sensor being below a threshold intake manifold temperature during the engine pull-down event or during a period in which the engine is pulled down before restarting. And Performing the intake manifold heating operation further includes controlling the throttle valve to reach a substantially closed position for performing the intake manifold heating operation, and during the performance of the intake manifold heating operation, if the exhaust system temperature drops below a threshold exhaust system temperature, then the intake manifold heating operation is aborted.

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