System and method for reducing saddle fuel tank decompression time

Abstract

The present disclosure provides a system and method for reducing saddle fuel tank depressurization time. Methods and systems are provided for diagnosing a valve of a fuel system. In one example, the fuel system is configured to reduce a depressurization time of one or more fuel tanks disposed therein. A method for diagnosing the valve includes monitoring a number of premature closing events during a fueling event to determine whether the valve is degraded.

Description

Technical Field

[0001] The present description generally relates to methods and systems for reducing the time frame in which a saddle tank is depressurized to enable the initiation of a refueling event. Background Art

[0002] A vehicle system may be equipped with a fuel system that includes a bifurcated fuel tank for storing fuel and delivering the fuel to an internal combustion engine. For example, the fuel tank may include a reserve tank, or the fuel tank may be configured as a saddle box to enable compact packaging without compromising fuel storage. For example, a saddle box may be used in an all-wheel drive (AWD) vehicle, where the AWD hardware occupies a large amount of underbody space required to package a single box. In addition, saddle boxes may be designed to store more fuel than a standard fuel tank, making them more desirable in vehicle systems that require more fuel storage, such as AWD vehicles.

[0003] A bifurcated or otherwise separated fuel tank may have two or more compartments fluidly coupled, including a first "active" compartment and a second "passive" compartment. A fuel pump may be coupled directly to the active compartment (and not to the passive compartment), the active compartment being maintained with fuel via a jet pump that draws fuel from the second compartment to replenish the fuel drawn by the fuel pump.

[0004] For certain hybrid electric vehicles (HEVs), including but not limited to plug-in hybrid electric vehicles (PHEVs), such saddle-shaped fuel tanks may include sealed tanks. Specifically, such tanks may be sealed via a fuel tank isolation valve and may be made of steel to withstand pressure and vacuum growth due to diurnal temperature cycles. Vehicles with sealed fuel tanks may also include a locked fuel door to prevent the fuel door from being opened to allow refueling when the fuel tank is under pressure. Therefore, for such tanks, in response to a refueling request, the fuel tank isolation valve is commanded to open, and the fuel tank pressure sensor is relied upon to infer whether the fuel tank pressure is below a threshold, at which time the fuel door may be unlocked.

[0005] However, certain conditions, including but not limited to high ambient temperatures, aggressive driving, significant fuel slosh events, variable loading levels of the fuel vapor storage canister coupled to the fuel tank, etc., may result in a fuel tank depressurization procedure that takes longer than necessary, which may lead to customer dissatisfaction. Such problems may be exacerbated for vehicles that include saddle-type fuel tanks. Specifically, the primary factors associated with fuel tank depressurization include the size of the vapor space and the size of the pressure. The larger the vapor space, the more time it may take for the pressure to reach atmospheric pressure when vented. In the event that one tank of the saddle tank is empty, the empty tank becomes a vapor reservoir, which may therefore result in a longer than desired depressurization time in response to a refueling request.

[0006] Some methods may include depressurizing the primary side to the secondary side, and may include commanding opening of a first refueling valve included in a conduit coupling the primary side to the secondary side. Such methods may also include selectively coupling the secondary side to a fuel vapor storage canister via a second refueling valve, wherein the refueling request may also include maintaining the second refueling valve in an open configuration during depressurizing the primary side to the secondary side.

[0007] While these routines may reduce decompression time, vehicle manufacturers include diagnostic routines for components included in the powertrain.Thus, a robust method and system for accurately determining the condition of the first and second refueling valves may be desired. Summary of the invention

[0008] In one example, the above problems can be at least partially addressed by a method for diagnosing a valve disposed in a conduit fluidly coupling a primary fuel tank and a secondary fuel tank during or after a refueling event. In this way, the valve can be diagnosed without changing engine operating parameters.

[0009] The above advantages and other advantages and features of the present specification will be readily apparent from the following detailed description when read alone or in conjunction with the accompanying drawings.

[0010] It should be understood that the above summary is provided to introduce a series of concepts further described in the detailed description in a simplified form. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is uniquely defined by the claims following the detailed description. Furthermore, the claimed subject matter is not limited to embodiments that address any disadvantages mentioned above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 An example vehicle propulsion system is schematically illustrated.

[0012] Figure 2 An example engine system having a fuel system including a saddle-type fuel tank and an evaporative emissions system is schematically illustrated.

[0013] Figure 3 A method for diagnosing a first condition of a first fueling valve of a fuel system is shown.

[0014] Figure 4 A method for diagnosing a second condition of a first fueling valve of a fuel system is shown.

[0015] Figure 5 A method for diagnosing a first condition of a second fueling valve of a fuel system is shown.

[0016] Figure 6 A method for diagnosing a second condition of a second refueling valve of a fuel system is shown.

[0017] Figure 7 Shows Figure 5 A graphic illustration of the method. DETAILED DESCRIPTION

[0018] The following description relates to systems and methods for reducing fuel tank depressurization time in response to a request to initiate a refueling event via a vehicle operator. The systems and methods are particularly relevant to AWD hybrid electric vehicles with limited engine operating time, such as Figure 1 The hybrid vehicle depicted. The reduction in fuel tank decompression time disclosed herein relates to a method for use in a vehicle such as Figure 2 Specifically, by incorporating a first refueling valve for sealing the primary and secondary sides of the saddle fuel tank, and extending a load conduit including a second refueling valve from the secondary fuel tank (the load conduit fluidly coupling the secondary fuel tank to a fuel vapor storage canister), the method discussed herein can be used to prevent the secondary fuel tank from acting as a vapor storage tank, which can thereby change the conditions such as Figure 2 The decompression rate of the saddle tank as depicted. The diagnostic method for determining a first condition or a second condition of the first refueling valve (RV1) and / or the second refueling valve (RV2) is Figures 3 to 6 Shown in. Figure 7 Shows Figure 5 A graphic illustration of the method.

[0019] Figure 1 An example vehicle propulsion system 100 is shown. The vehicle propulsion system 100 includes a fuel combustion engine 110 and a motor 120. As a non-limiting example, the engine 110 includes an internal combustion engine and the motor 120 includes an electric motor. The motor 120 can be configured to utilize or consume a different energy source than the engine 110. For example, the engine 110 may consume a liquid fuel (e.g., gasoline) to produce an engine output, while the motor 120 may consume electrical energy to produce a motor output. Therefore, a vehicle having the propulsion system 100 may be referred to as a hybrid electric vehicle (HEV).

[0020] The vehicle propulsion system 100 may utilize a variety of different operating modes depending on the operating conditions encountered by the vehicle propulsion system. Some of these modes may enable the engine 110 to be maintained in an off state (i.e., set to a deactivated state) in which fuel combustion at the engine is stopped. For example, under selected operating conditions, the motor 120 may propel the vehicle via the drive wheels 130 as indicated by arrow 122, while the engine 110 is deactivated.

[0021] During other operating conditions, the engine 110 may be set to an inactive state (as described above), and the motor 120 may be operated to charge the energy storage device 150. For example, the motor 120 may receive wheel torque from the drive wheel 130, as indicated by arrow 122, wherein the motor may convert the kinetic energy of the vehicle into electrical energy for storage at the energy storage device 150, as indicated by arrow 124. This operation may be referred to as a regenerative energy recovery operation of the vehicle. Thus, in some examples, the motor 120 may provide a generator function. However, in other examples, the generator 160 may alternatively receive wheel torque from the drive wheel 130, wherein the generator may convert the kinetic energy of the vehicle into electrical energy for storage at the energy storage device 150, as indicated by arrow 162. In some examples, the motor 120 and / or the generator 160 may include the same motor / generator.

[0022] During still other operating conditions, the engine 110 may be operated by combusting fuel received from the fuel system 140, as indicated by arrow 142. For example, when the motor 120 is deactivated, the engine 110 may 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 may 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 may selectively propel the vehicle may be referred to as a parallel-type vehicle propulsion system. It should be noted that in some examples, the motor 120 may propel the vehicle via a first set of drive wheels, and the engine 110 may propel the vehicle via a second set of drive wheels.

[0023] 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 selected operating conditions, the engine 110 can drive the generator 160 as indicated by arrow 116, which in turn can supply electrical energy to one or more of the following: the motor 120 as indicated by arrow 114 or 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 at the energy storage device 150 for subsequent use by the motor.

[0024] Fuel system 140 may include one or more fuel tanks for storing fuel on board the vehicle (see Figure 2). For example, one or more fuel tanks 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 blend of two or more different fuels. For example, the fuel system may be configured to store a blend of gasoline and ethanol (e.g., E10, E85, etc.) or a blend of gasoline and methanol (e.g., M10, M85, etc.), whereby these fuels or fuel blends may be delivered to the engine 110, as indicated by arrow 142. Yet other suitable fuels or fuel blends may 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 arrow 112, or the energy storage device 150 may be recharged via the motor 120 or the generator 160.

[0025] In some examples, energy storage device 150 may be configured to store electrical energy that may be supplied to other electrical loads resident on the vehicle (in addition to the motor), including cabin heating and air conditioning systems, engine starting systems, headlight systems, cabin audio and video systems, etc. As non-limiting examples, 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 sensory feedback information from one or more of the engine 110, the motor 120, the fuel system 140, the energy storage device 150, and the generator 160. In addition, the control system 190 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 this sensory feedback. The control system 190 may receive an indication of an operator-requested output of the vehicle propulsion system from the vehicle operator 102. For example, the control system 190 may receive sensory feedback from a pedal position sensor 194 in communication with a pedal 192. The pedal 192 may schematically refer to a foot pedal to increase or decrease the powertrain output.

[0027] As indicated by arrow 184, energy storage device 150 may periodically receive electrical energy from a power source 180 that resides external to the vehicle (e.g., not part of the vehicle). As a non-limiting example, vehicle propulsion system 100 may be configured as a plug-in hybrid electric vehicle (PHEV), whereby electrical energy may be supplied to energy storage device 150 from power source 180 via power transmission cable 182. During operation to recharge energy storage device 150 from power source 180, power transmission cable 182 may electrically couple energy storage device 150 and power source 180. When the vehicle propulsion system is operating to propel the vehicle, power transmission cable 182 may be disconnected between power source 180 and energy storage device 150. Control system 190 may identify and / or control the amount of electrical energy stored at the energy storage device, which amount of electrical energy may be referred to as a state of charge (SOC).

[0028] In other examples, power transmission cable 182 may be omitted, where electrical energy may be received wirelessly at energy storage device 150 from power source 180. For example, energy storage device 150 may receive electrical energy from power source 180 via one or more of electromagnetic induction, radio waves, and electromagnetic resonance. As such, it should be understood that any suitable method may be used to recharge energy storage device 150 from a power source that is not part of the vehicle. In this manner, motor 120 may propel the vehicle by utilizing an energy source other than the fuel utilized by engine 110.

[0029] Fuel system 140 may periodically receive fuel from a fuel source residing external to the vehicle. As a non-limiting example, vehicle propulsion system 100 may be refueled by receiving fuel via fuel dispensing device 170, as indicated by arrow 172. In some examples, fuel system 140 may be configured to store fuel received from fuel dispensing device 170 until the fuel is supplied to engine 110 for combustion. In some examples, control system 190 may receive an indication of the level of fuel stored at fuel system 140 via a fuel level sensor. The level of fuel stored at fuel system 140 (e.g., as identified by the fuel level sensor) may be communicated to the vehicle driver, for example, via a fuel gauge or indication in a vehicle instrument panel 196.

[0030] The vehicle propulsion system 100 may also include vehicle stability control sensors, such as inertial sensors 199. The inertial sensors 199 may include one or more of the following: a longitudinal sensor, a lateral sensor, a vertical sensor, a yaw sensor, and a pitch sensor.

[0031] The vehicle dashboard 196 may include indicator lights and / or a text-based display in which messages are displayed to the operator. The vehicle dashboard 196 may also include various input portions for receiving operator input, such as buttons, touch screens, voice input / recognition, etc. In other words, the vehicle dashboard may include a human-machine interface (HMI) with which a user may interact. As an example, the vehicle dashboard 196 may include a refueling button 197, which may be manually actuated or pressed by the vehicle operator to initiate refueling. For example, in response to the vehicle operator actuating the refueling button 197, the fuel system in the vehicle may be decompressed so that refueling may be performed. In an example where the vehicle includes an autonomous vehicle, refueling may be initiated under the control of the control system 190, wherein refueling may be initiated without manual actuation of the refueling button 197.

[0032] The control system 190 may be communicatively coupled to other vehicles or infrastructure using appropriate communication technologies, as known in the art. 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, a type of cellular service, a wireless data transmission protocol, etc. The control system 190 may broadcast (and receive) information about 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) technologies. The communication between vehicles and the information exchanged between vehicles may be direct between vehicles, or may be multi-hop. In some examples, longer-range communications (e.g., WiMax) may be used instead of V2V or V2I2V or in combination with V2V or V2I2V to extend the coverage area by several miles. In yet other examples, the vehicle control system 190 may be communicatively coupled to other vehicles or infrastructure via a wireless network 131 and the Internet (e.g., cloud), as known in the art. Specifically, the control system 190 may be coupled to a wireless communication device ( Figure 1 Not shown, but see Figure 2 284 at 134) so ​​that the vehicle system 100 can communicate directly with the wireless network 131. Using wireless communication, in some examples, the vehicle system 100 can retrieve data about current and / or upcoming environmental conditions (such as ambient humidity, temperature, pressure, precipitation, wind, etc.), current traffic conditions, etc. from a server, infrastructure, other vehicles, etc.

[0033] The vehicle system 100 may also include an onboard navigation system 132 (e.g., a global positioning system) with which the operator of the vehicle 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 available via the Internet to determine local weather conditions, traffic information, etc. In one example, the information received from the GPS may be used in conjunction with a route learning method so that the vehicle control system 190 may learn the routes that the vehicle typically travels, or the routes that a particular vehicle operator typically travels, or the routes that passengers typically travel (in the case of an autonomous vehicle). In some examples, other sensors 133 such as lasers, radars, sonars, acoustic sensors, etc. may be used in addition or alternatively in conjunction with the onboard navigation system to perform route learning on the routes that the vehicle typically travels. In some examples, the GPS may also provide a suggested route for the vehicle to take based on the current vehicle operating conditions, current traffic conditions, etc.

[0034] Figure 2 A schematic depiction of a vehicle system 200 that can derive propulsion power from an engine system 208 is shown. The vehicle system 200 can be a conventional vehicle that is powered solely by combustion, or it can be a hybrid vehicle system that can derive propulsion power from the engine system 208 and / or an onboard energy storage device (e.g., 150) such as a battery system. An energy conversion device such as a generator (e.g., 160) can be operated to absorb energy from vehicle motion and / or engine operation, and then convert the absorbed energy into an energy form suitable for storage by the energy storage device.

[0035] The engine system 208 may include an engine 110 having a plurality of cylinders 230. The engine 110 includes an engine intake 223 and an engine exhaust 225. The engine intake 223 includes an intake throttle 262 fluidly coupled to an engine intake manifold 244 via an intake passage 242. Air may enter the intake passage 242 via an air filter 252. The engine exhaust 225 includes an exhaust manifold 248 leading to an exhaust passage 235, which directs exhaust gas to the atmosphere. The engine exhaust 225 may include one or more emission control devices 270 mounted in a close-coupled position. The one or more emission control devices may include a three-way catalyst, a lean NOx trap, a diesel particulate filter, an oxidation catalyst, etc. It should be understood that other components (such as various valves and sensors) may be included in the engine, as further described in detail herein. In some embodiments in which the engine system 208 is a supercharged engine system, the engine system may also include a supercharging device, such as a turbocharger (not shown).

[0036] Engine system 208 is coupled to fuel system 140 and evaporative emissions system 255. Fuel system 140 includes a fuel tank 250 coupled to fuel pump 221, and evaporative emissions system 255 includes a fuel vapor canister 222. During a fuel tank refueling event, fuel may be pumped into the vehicle from an external source through a refueling port 251 as part of refueling system 246. Fuel tank 250 may store a variety of fuel blends, including fuels having a range of alcohol contents, such as various gasoline-ethanol blends (including E10, E85, gasoline, etc.), and combinations thereof.

[0037] In addition, the refueling system 246 may include a refueling lock 245. In some embodiments, the refueling lock 245 may be a fuel tank cap locking mechanism. The fuel tank cap locking mechanism may be configured to automatically lock the fuel tank cap in a closed position so that the fuel tank cap cannot be opened. For example, when the pressure or vacuum in the fuel tank is greater than a threshold value, the fuel tank cap 205 may remain locked via the refueling lock 245. In response to a refueling request, such as a request initiated by a vehicle driver, the fuel tank may be decompressed, and the fuel tank cap may be unlocked after the pressure or vacuum in the fuel tank drops below a threshold value. The fuel tank cap locking mechanism may be a clutch that prevents the removal of the fuel tank cap when engaged. The clutch may be electrically locked, for example, by a solenoid, or may be mechanically locked, for example, by a pressure diaphragm.

[0038] In some embodiments, refuel lock 245 may be a filler pipe valve. In such embodiments, refuel lock 245 may not prevent removal of tank cap 205. Instead, refuel lock 245 may prevent insertion of a refuel pump into refuel port 251. In such an example, refuel lock may be locked electrically, such as by a solenoid, or mechanically, such as by a pressure diaphragm.

[0039] In some embodiments, refuel lock 245 may be a refuel door lock, such as a clutch that locks a refuel door located in a body panel of the vehicle. The refuel door lock may be electrically locked, such as by a solenoid, or mechanically locked, such as by a pressure diaphragm.

[0040] In embodiments where an electrical mechanism is used to lock refuel lock 245, for example, when the fuel tank pressure drops below a pressure threshold, refuel lock 245 may be unlocked by a command from controller 212. In embodiments where a mechanical mechanism is used to lock refuel lock 245, for example, when the fuel tank pressure drops to atmospheric pressure, refuel lock 245 may be unlocked via a pressure gradient.

[0041] The fuel tank 250 may be configured as a bifurcated fuel tank, or a fuel tank having two or more separate chambers, each of which is fluidly coupled to at least one other chamber via a conduit. In this example, the auxiliary fuel tank 240 is shown as being coupled to the main fuel tank 253. As discussed herein, the auxiliary fuel tank 240 may be referred to as a passive fuel tank 240, and the main fuel tank 253 may be referred to as an active fuel tank 253. As discussed herein, the main fuel tank 253 may also be referred to as the "active side" 253, and the auxiliary fuel tank 240 may also be referred to as the "passive side" 240. The main fuel tank 253 and the auxiliary fuel tank 240 may be considered as a single saddle fuel tank, which may be configured to be placed above the engine drive train 241. The auxiliary fuel tank 240 may store additional fuel that is metered to the main fuel tank 253 via the jet pump 224. For example, the jet pump 224 may deliver fuel from the auxiliary fuel tank 240 to the main fuel tank 253 based on a signal received from the controller 212. In some examples, the jet pump 224 may be configured to continuously replenish the fuel drawn from the main fuel tank 253 by the fuel pump 221. The jet pump 224 may deliver fuel between the auxiliary fuel tank 240 and the main fuel tank 253 via a conduit or hose 293 coupled to the jet pump 224. The jet pump 224 may have an inlet 291 positioned in the auxiliary fuel tank 240 and an outlet 292 positioned in the main fuel tank 253. A check valve 294 may be included in the conduit 293 of the jet pump 224 to enable fuel to be drawn from the auxiliary fuel tank 240 into the main fuel tank 253 when the jet pump 224 is enabled, but this prevents fuel and / or fuel vapor from traveling from the main fuel tank 253 to the auxiliary fuel tank 240 when the jet pump 224 is turned off. Furthermore, in some embodiments, the jet pump 224 and the fuel pump 221 may be combined into a single pump unit.

[0042] A first fuel level sensor 206 located in the main fuel tank 253 may provide an indication of the fuel level (“fuel level input”) to the controller 212 . As depicted, the fuel level sensor 206 may include a float connected to a variable resistor. Alternatively, other types of fuel level sensors may be used.

[0043] The conduit 239 can couple the main fuel tank 253 to the auxiliary fuel tank 240 to allow vapor (and in some examples, fuel) to flow between the main fuel tank 253 and the auxiliary fuel tank 240. In some examples, the jet pump 224 can transfer fuel between the main fuel tank 253 and the auxiliary fuel tank 240 via a hose or conduit passing through the conduit 239. The conduit 239 may include a first refueling valve (RV1) 261. The RV1 261 may include a valve that can be actuated to open or close under the control of the controller 212. Therefore, the RV1 may include a solenoid valve, a butterfly valve, a flapper valve, etc. During certain vehicle maneuvers or other conditions that may cause fuel sloshing, assuming that the RV1 is open, the fuel from the main fuel tank 253 may flow into the auxiliary fuel tank 240 via the conduit 239, or vice versa. In some examples, when the vehicle passes through a steep gradient, the fuel may also flow between the main fuel tank 253 and the auxiliary tank 240 (or vice versa) via the conduit 239 when the RV1 is commanded to open. In some examples, during refueling, when the main fuel tank 253 reaches full capacity and with RV1 open, fuel may flow from the main fuel tank 253 into the auxiliary fuel tank 240 via conduit 239. In some examples, the jet pump 224 may adjust the fuel transfer between the main fuel tank 253 and the auxiliary fuel tank 240 during the refueling event. The second fuel level sensor 209 located in the auxiliary fuel tank 240 may provide an indication of the fuel level in the auxiliary fuel tank 240 ("fuel level input") to the controller 212. As depicted, the fuel level sensor 209 may include a float connected to a variable resistor. Alternatively, other types of fuel level sensors may be used. In addition, the vehicle system 200 may include an overall fuel level indicator (not shown) indicating the average value of the outputs of the first fuel level indicator 206 and the second fuel level indicator 209.

[0044] Fuel pump 221 is configured to pressurize fuel for delivery to injectors (such as exemplary injector 266) of engine 110. Although only a single injector 266 is shown, additional injectors are provided for each cylinder. It should be understood that fuel system 140 may be a returnless fuel system, a return fuel system, or various other types of fuel systems. Vapors generated in fuel tanks 253 and / or 240 may be directed to fuel vapor canister 222 via load conduit 231 and then purged to engine intake 223. Figure 2 As depicted, it will be appreciated that load conduit 231 extends from auxiliary fuel tank 240 rather than from main fuel tank 253 .

[0045] The fuel vapor canister 222 may be filled with a suitable adsorbent for temporarily capturing fuel vapor (including vaporized hydrocarbons) and daytime vapor generated during the fuel tank refueling operation. In one example, the adsorbent used is activated carbon. When the extraction conditions are met, such as when the canister is saturated, the vapor stored in the fuel vapor canister 222 may be extracted to the engine intake 223 via the extraction line 228 by opening the canister extraction valve 260. Although a single canister 222 is shown, it should be understood that the fuel system 140 may include any number of canisters. One or more temperature sensors 297 may be coupled to the canister 222 and / or in the canister. When the adsorbent in the canister adsorbs fuel vapor, heat (adsorption heat) is generated. Similarly, when the adsorbent in the canister desorbs fuel vapor, heat is consumed. In this way, the adsorption and desorption of fuel vapor by the canister can be monitored and the canister load can be estimated based on the temperature change in the canister.

[0046] Canister 222 includes a vent 227 for directing gas from canister 222 to the atmosphere when storing or capturing fuel vapor from fuel tank 250. Vent 227 can also allow fresh air to be drawn into fuel vapor canister 222 when the stored fuel vapor is drawn to engine air intake 223 via purge line 228 and purge valve 260. Although this example shows vent 227 in communication with fresh, unheated air, various modifications can also be used. Vent 227 can include canister ventilation valve 214 to adjust the flow of air and vapor between canister 222 and the atmosphere. The canister ventilation valve can also be used for diagnostic procedures. The ventilation valve (when included) can be opened during fuel vapor storage operations (e.g., during fuel tank refueling and when the engine is not running) so that air stripped of fuel vapor after passing through the canister can be discharged to the atmosphere. Similarly, during purge operations (e.g., during canister regeneration and when the engine is running), the ventilation valve can be opened to allow fresh air flow to strip fuel vapor stored in the canister.

[0047] If vehicle system 200 is a hybrid vehicle, it may have reduced engine operating time due to the vehicle being powered by engine system 208 during some conditions and by energy storage device (e.g., 150) during other conditions. While reduced engine operating time reduces overall carbon emissions from the vehicle, they may also result in inadequate extraction of fuel vapors from the vehicle's emission control system. To address this issue, a fuel tank isolation valve 210 may optionally be included in load conduit 231 so that fuel tank 250 is coupled to canister 222 via the fuel tank isolation valve. As discussed herein, fuel tank isolation valve 210 may also be referred to as a second refueling valve 210 (RV2). Under certain conditions, which will be further detailed below, RV2 210 may remain closed to limit the amount of diurnal or "running loss" vapors directed from fuel tank 250 to canister 222. During other conditions, isolation valve 210 may be commanded to open. As an example, during a refueling operation and a selected purge condition, the isolation valve 210 may be temporarily opened, for example, for a certain duration, to direct fuel vapors from the fuel tank 250 to the canister 222. By opening the valve during a purge condition when the fuel tank pressure is above a threshold (e.g., above the mechanical pressure limit of the fuel tank, which may cause mechanical degradation of the fuel tank and other fuel system components when above the mechanical pressure limit), the fuel tank vapors may be released into the canister and the fuel tank pressure may be maintained below the pressure limit. Although the depicted example shows the isolation valve 210 positioned along the load conduit 231, in an alternative embodiment, the isolation valve may be mounted on the auxiliary fuel tank 240. As will be discussed in more detail below, RV2 210 may be controlled together with RV1 261 according to the fuel level in the auxiliary fuel tank 240. It is understood that RV2 may include a catchable valve, such as RV2 may catch open and / or catch closed. Similarly, RV1 may include a catchable valve, such as RV1 may catch open and / or catch closed. In this way, the amount of battery power required to maintain RV1 and / or RV2 may be reduced.

[0048] Pressure sensor 220 may be coupled to fuel system 140 for providing an estimate of fuel system pressure. In one example, the fuel system pressure is a fuel tank pressure, where pressure sensor 220 is a fuel tank pressure sensor (FTPT) coupled to fuel tank 253 for estimating a fuel tank pressure or vacuum level. In some examples, a second pressure sensor (not shown) may be coupled to auxiliary fuel tank 240 for estimating a fuel tank pressure or vacuum level.

[0049] For example, fuel vapor released from canister 222 during a purge operation may be directed into engine intake manifold 244 via purge line 228. The flow of vapor along purge line 228 may be controlled by canister purge valve (CPV) 260, which is coupled between the fuel vapor canister and the engine intake. The amount and rate of vapor released by CPV 260 may be determined by the duty cycle of an associated CPV solenoid (not shown). Thus, the duty cycle of the CPV solenoid may be determined by a powertrain control module (PCM) of the vehicle (such as controller 212) in response to engine operating conditions (including, for example, engine speed-load conditions, air-fuel ratio, canister load, etc.). By commanding the CPV 260 to be closed, the controller may seal the fuel vapor recovery system from the engine intake. An optional canister check valve (not shown) may be included in purge line 228 to prevent intake manifold pressure from causing gas to flow in the opposite direction of the purge flow. Thus, a check valve may be necessary if canister purge valve control is not accurately timed or the CPV itself may be forced open by high intake manifold pressure. An estimate of manifold absolute pressure (MAP) or manifold vacuum (ManVac) may be obtained from a MAP sensor 218 coupled to intake manifold 244 and in communication with controller 212. Alternatively, MAP may be inferred from alternative engine operating conditions such as mass air flow (MAF) measured by a MAF sensor (not shown) coupled to the intake manifold.

[0050] Fuel system 140 may be operated in a number of modes by selectively adjusting various valves and solenoids by controller 212. For example, fuel system 140 may be operated in a fuel vapor storage mode (e.g., during a fuel tank refueling operation and with the engine not running) in which controller 212 may open RV1 261 and RV2 210 while closing CPV 260 to direct refueling vapors into canister 222 while preventing fuel vapors from being directed into the intake manifold.

[0051] As another example, the fuel system may be operated in a refueling mode (e.g., when a vehicle operator requests a refueling of the fuel tank), wherein the controller 212 may open RV1 261 and RV2 210 while maintaining CPV 260 closed to depressurize the fuel tank before allowing fuel to be added to the fuel tank. In this way, RV1 261 and RV2 210 may remain open during the refueling operation to allow refueling vapors to be stored in the canister. After refueling is complete, RV2 210 may be closed.

[0052] Returning to the discussion regarding the operating modes of the fuel system, as yet another example, the fuel system may be operated in a canister purge mode (e.g., after the emission control device light-off temperature has been reached and with the engine running), wherein controller 212 may open CPV 260 while closing RV2 210. Herein, vacuum generated by the intake manifold of the operating engine may be used to draw fresh air through vent 227 and through fuel vapor canister 222 to purge stored fuel vapors into intake manifold 244. In this mode, fuel vapors purged from the canister are combusted in the engine.

[0053] The controller 212 may also be configured to intermittently perform diagnostic routines for the presence or absence of evaporative emissions on the fuel system 140 to confirm that the fuel system has not degraded. To this end, such diagnostic routines may be performed while the vehicle is operating with the engine on (e.g., during an engine mode of operation of a hybrid vehicle) or with the engine off (e.g., during a battery mode of operation of a hybrid vehicle). Specifically, with the engine running, the engine intake manifold vacuum may be used to apply vacuum to the fuel system (by commanding the CPV to open) and / or the evaporative emissions system that is sealed from the atmosphere (by closing the CVV), and when the desired vacuum is achieved, the fuel system and / or the evaporative emissions system may be sealed from the engine intake (by commanding the CPV to close), and the pressure relief may be monitored. A pressure relief that remains below a preset pressure threshold and / or a pressure relief that is relieved at a rate below a threshold relief rate may indicate that there is no source of evaporative emissions originating from the fuel system.

[0054] However, because the engine running time may be limited, especially for hybrid vehicles, the vacuum pump 289 is configured to apply a negative pressure to the fuel system relative to atmospheric pressure and / or may include an evaporative emission system. Specifically, the vacuum pump 289 may be configured to be in a vacuum pump conduit 298. The vacuum pump may include a rotary vane pump, a diaphragm pump, a liquid ring pump, a piston pump, a vortex pump, a screw pump, a Wankel pump, etc., and may be understood to be connected in parallel with the CVV 214. The vacuum pump conduit 298 may be configured to guide the fluid flow (e.g., air and fuel vapor) from the ventilation line 227 to around the filter canister ventilation valve 214. The vacuum pump conduit 298 may include a first check valve (CV1) 295 and a second check valve (CV2) 296. When the vacuum pump 289 is activated in vacuum mode, air may be drawn from the ventilation line 227 between the filter canister 222 and the CVV 214 through the vacuum pump conduit 298, and returned to the ventilation line 227 at a position between the filter canister ventilation valve 214 and the atmosphere. In other words, depending on the state of RV2 210 and RV1 261, the vacuum pump may be enabled to evacuate the evaporative emission system 255, and may further evacuate the fuel system 140, as will be discussed in more detail below. CV1 295 may include a pressure / vacuum actuated valve that may open in response to enabling the vacuum pump to evacuate the fuel system and / or the evaporative emission system, and may close in response to the vacuum pump 289 being deactivated or shut down. Similarly, CV2 296 may include a pressure / vacuum actuated valve. When the vacuum pump 289 is enabled to evacuate the fuel system and / or the evaporative emission system, CV2 296 may open to allow fluid flow to be directed from the vacuum pump conduit 298 to the atmosphere, and may close in response to the vacuum pump 289 being shut down. It is understood that the CVV 214 may be commanded to close in order to evacuate the fuel system and / or the evaporative emission system via the vacuum pump 289.

[0055] In vehicle systems 200 including vacuum pump 289, calibration may be utilized to determine a vacuum threshold for indicating the presence or absence of evaporative emissions. For example, there may be a 3D lookup table stored at the controller that may support determining a threshold based on ambient temperature and / or fuel level.

[0056] In the example vehicle system 200, a pressure sensor 232 may be included positioned in the load conduit 231. Thus, it can be appreciated that when the RV2 210 is closed, the vacuum pump 289 or the engine may be used to evacuate the evaporative emission system, and the pressure sensor 232 may be relied upon to monitor the pressure relief to indicate the presence or absence of evaporative emissions from the evaporative emission system.

[0057] In another example, RV2 210 may be commanded to open or maintained open, while RV1 261 may be commanded to close or maintained closed. In this way, vacuum pump 289 or an engine may be used to evacuate auxiliary fuel tank 240 to a desired vacuum, at which point RV2 210 may be commanded to close and pressure relief in auxiliary fuel tank 240 may be monitored via pressure sensor 233. In this way, auxiliary fuel tank 240 may be analyzed for the presence or absence of evaporative emissions independently of main fuel tank 253 and evaporative emissions system 255.

[0058] In yet another example, RV2 210 may be commanded to open along with RV1 261, and vacuum pump 289 or an engine may be used to evacuate the primary fuel tank 253 (along with the secondary fuel tank 240) to a desired vacuum. Then, if RV1 261 is closed, the pressure relief in the primary fuel tank 253 may be monitored via pressure sensor 220 to indicate the presence or absence of evaporative emissions. In this way, the primary fuel tank 253 may be analyzed for the presence or absence of evaporative emissions independently of the secondary fuel tank 240 and the evaporative emissions system 255.

[0059] In another example, each of the primary fuel tank 253, the secondary fuel tank 240, and the evaporative emission system 255 may be simultaneously and individually monitored for the presence or absence of a source of evaporative emissions. Specifically, with RV2 210 and RV1 261 open and CVV 214 closed, the vacuum pump 289 may be used to evacuate the evaporative emission system and both the primary and secondary fuel tanks to a desired vacuum. When the desired vacuum is reached, RV1 and RV2 may be commanded to close, and the vacuum pump 289 may be deactivated. Pressure relief may then be independently monitored for each of the primary fuel tank 253 (via pressure sensor 220), the secondary fuel tank 240 (via pressure sensor 233), and the evaporative emission system (via pressure sensor 232). While the above examples rely on a vacuum pump to evacuate the fuel system and the evaporative emissions system, it will be appreciated that in other examples, the engine may be configured to evacuate by commanding the CPV to open to apply engine intake vacuum to the fuel system and / or the evaporative emissions system, and commanding the CPV to close in response to achieving a desired vacuum to seal the evaporative emissions system and the fuel system from the engine intake.

[0060] The controller 212 may be coupled to the wireless communication device 284 for controlling the system 190 and the vehicle system 200 to communicate directly with the wireless network 131 , as mentioned above.

[0061] The vehicle system 200 may also include a control system 190. The control system 190 is shown as 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 an example, the sensors 216 may include an exhaust gas sensor 226 located upstream of an emission control device, a temperature sensor 299, a MAP sensor 218, a pressure sensor 229, a first fuel level sensor 206, a second fuel level sensor 209, and a fuel tank pressure sensor 220. Other sensors such as additional pressure sensors, temperature sensors, air-fuel ratio sensors, and composition sensors may be coupled to various locations in the vehicle system 200. As another example, the actuators may include a fuel injector 266, an RV1 261, an RV2 210, a purge valve 260, a vent valve 214, a fuel pump 221, a jet pump 224, a vacuum pump 289, and a throttle 262. The control system 190 may include a controller 212. The controller may receive input data from various sensors, process the input data, and trigger the actuators in response to the processed input data based on instructions or codes corresponding to one or more programs programmed in the processed input data. Figure 2 The various sensors receive signals and based on the received signals and the instructions stored in the memory of the controller, use Figure 2 A variety of actuators are used to adjust engine operation.

[0062] Thus, as discussed herein, secondary fuel tank 240 includes a load conduit 231 originating therefrom, wherein secondary fuel tank 240 is selectively coupled to fuel vapor storage canister 222 via RV2 210, and selectively coupled to primary fuel tank 253 via RV1 261. As will be described in greater detail below, such a configuration may enable a faster depressurization procedure of a saddle tank (e.g., 250) in response to a refueling request as compared to other configurations in which a primary fuel tank (e.g., 253) is selectively coupled to a canister (e.g., 222) via a load conduit (e.g., 231) originating from a primary fuel tank (e.g., 253).

[0063] Now turn to Figure 3 , which shows a method 300 for diagnosing a condition of RV1 of a fuel tank system. In one example, the condition is a first condition in which RV1 is stuck in a closed position. Instructions for implementing method 300 and the remaining methods included herein may be provided by a controller based on instructions stored on a memory of the controller and in conjunction with sensors from the engine system (such as those referenced above). Figure 1 and Figure 2 According to the method described below, the controller can use the engine actuator of the engine system to adjust the engine operation.

[0064] Method 300 begins at 302 and includes determining whether a fuel tank depressurization is occurring. Tank depressurization may include a passive fuel tank (e.g., Figure 2 The auxiliary tank 240) is used as an expansion chamber to allow the active tank (e.g. Figure 2 During tank depressurization, which may be initiated in response to a refueling request, fuel in the primary tank may be transferred to the auxiliary tank. For example, a jet pump (such as Figure 2 Pump 224 of the vehicle may be activated to cause fuel to flow from the primary tank to the auxiliary tank. In one example, RV1 and RV2 may be open during the transfer period. Additionally or alternatively, RV1 may be open and RV2 may be closed. Once decompression has occurred, RV2 may be commanded to open and RV1 may be commanded to close to seal the fuel tanks from each other. A refueling request may occur in response to a user of the vehicle pressing a button to indicate a desire to refuel the saddle tanks.

[0065] If tank depressurization has not occurred, method 300 may proceed to 304 , which includes not initiating diagnostics on RV1 .

[0066] If tank depressurization occurs, such as due to the presence of a refueling request, at 306 , method 300 may include signaling RV1 and RV2 to open.

[0067] At 308 , method 300 may include monitoring FTPT pressure.

[0068] At 310, method 300 may include determining if the FTPT pressure is equal to a lower threshold. In one example, the lower threshold is equal to 0. In another example, the lower threshold is based on a pressure less than the average pressure in the load pipe when RV1 and RV2 are open. If the FTPT pressure is not equal to the lower threshold, then at 312, method 300 includes determining that RV1 is not in a normally closed fault. To this end, steam can flow from the main tank to the auxiliary tank and to the FTPT. The diagnostic passed and RV1 is not degraded.

[0069] If FTPT is equal to the lower threshold, RV1 may be in a normally closed fault or FTPT may be unreasonable (e.g., degraded). Method 300 can diagnose RV1 and FTPT by monitoring the fueling nozzle condition during the refueling event at 314. At 316, method 300 may include determining whether the refueling nozzle has been closed prematurely. In one example, if RV1 is in a normally closed fault, the refueling nozzle may be closed prematurely at an upper threshold fuel level. In one example, the upper threshold level may be based on the 100% fuel limit of the main fuel tank. Vapors in the main fuel tank may not be discharged to the auxiliary fuel tank, and feedback to FLVV may close the refueling nozzle before filling the auxiliary fuel tank. Additionally or alternatively, if the volume of the main fuel tank is equal to the auxiliary fuel tank, the upper threshold level may be equal to half of the total fuel volume limit of the main fuel tank and the auxiliary fuel tank. If the refueling nozzle is not closed at the upper threshold level, RV1 is not in a normally closed fault, and at 318, method 300 may determine that FTPT is degraded. That is, RV1 is open and vapors from the primary tank can flow to the secondary tank, allowing refueling without premature closing.

[0070] In one example, if the vehicle operator selects a fuel fill volume that is less than an upper threshold volume, the diagnostic may not be completed. In some examples, method 300 may include monitoring whether the refueling nozzle is re-initiated after shutdown and more fuel is dispensed. If the refueling nozzle is re-initiated after shutdown, RV2 may be in a normally closed fault. If the refueling nozzle is not re-initiated, the desired amount of fuel is dispensed and the diagnostic may be performed during a different refueling event. Figure 5 The diagnostics used to determine if RV2 is in a normally closed fault are described in .

[0071] If the refueling nozzle is closed at the upper threshold level, the vapor from the main fuel tank may not migrate to the auxiliary fuel tank. At 320, the method 300 determines that RV1 is sticky. The indicator light can be activated to indicate to the user that RV1 is in a normally closed fault. In some examples, in addition or alternatively, the fuel filling limit of the main fuel tank and / or the two fuel tanks can be adjusted to take into account the ventilation restriction of the main fuel tank. For example, in order to alleviate the vapor pressure accumulation in the main fuel tank, the fuel can be transferred from the main fuel tank to the auxiliary fuel tank. To alleviate the vapor pressure exceeding the threshold pressure, the fuel level in the main fuel tank can be maintained below the determined fuel level. The determined fuel level can be less than the upper threshold level. In one example, the determined fuel level can be based on the head volume of the tank in which the engine can be supported and used to receive the vapor to maintain the vapor pressure below the threshold pressure. In addition or alternatively, the determined fuel level can be adjusted based on environmental conditions such as temperature, sunlight, etc., which may change the vapor generation in the main fuel tank. In some examples, in addition or alternatively, when RV1 is in a normally closed fault, the engine fueling can be adjusted. For example, engine fueling may be increased such that the air-fuel ratio of the engine is lower (eg, richer).The determined fuel level may also be based on driver behavior, length of time of electric-only operation, and an estimated duration of engine run time.

[0072] In one example, when the vehicle is off and RV1 is in a normally closed fault, fuel from the main tank can be pumped to the auxiliary tank. By doing so, vapors from the main tank can flow to the auxiliary tank via the pump, which can then be directed to the canister. Prior to a subsequent vehicle start, the pump can return a portion of the fuel in the auxiliary tank to the main tank for engine fueling.

[0073] Now turn to Figure 4 , which shows a method 400 for diagnosing a second condition of RV1. In one example, the second condition is a normally open fault condition. In one example, Figure 3 Method 400 is performed after a pass diagnosis of method 300. To this end, it may be determined that RV1 is not in a normally closed fault before performing method 400. Additionally or alternatively, method 400 may be performed at a time independent of the results of method 300.

[0074] Method 400 begins at 402, which includes cleaning the canister after a refueling event. Cleaning the canister may include opening a purge valve and allowing vapor to flow from the canister to the engine. During the canister cleaning, the engine may be refueled and the vehicle may be turned on. To this end, when the canister cleaning is performed and the canister load is reduced, the refueling event is complete.

[0075] Additionally or alternatively, a canister load may be determined. The canister load may be determined via a hydrocarbon sensor disposed at the canister inlet port in combination with the duration of the purge event, ambient weather, an oxygen sensor, and canister temperature. In one example, the canister load may be determined when RV1 is open and RV2 is closed. To this end, the canister load may be determined when the canister is sealed from the fuel tank. To this end, the canister may not be cleaned or may be completely cleaned in order to perform the diagnosis of method 400. In some examples, the canister may be at least partially cleaned such that the canister load is less than a full load of the canister.

[0076] At 404, method 400 may include determining whether the fuel volume of the auxiliary fuel tank is less than or equal to a threshold volume. The threshold volume may be a dynamic value based on the current fuel volume of the primary fuel tank, wherein the threshold volume increases as the current fuel volume in the primary fuel tank decreases. If the fuel volume of the auxiliary fuel tank is greater than the threshold volume, the auxiliary fuel tank may not be emptied by directing fuel therein to the primary fuel tank, and at 406, method 400 may include not diagnosing RV1. Additionally or alternatively, the method may continue to monitor the fuel level, and once the fuel level is less than or equal to the threshold volume, a diagnostic for determining whether RV1 is in a normally open fault may be performed.

[0077] If the fuel volume is less than or equal to the threshold volume, then at 407, method 400 may include moving all of the fuel in the auxiliary fuel tank to the main fuel tank. In one example, a pump may be activated to draw fuel from the auxiliary fuel tank to the main fuel tank. To this end, liquid fuel and vapors in the auxiliary fuel tank may be emptied.

[0078] At 408 , method 400 may include commanding RV1 to close and commanding RV2 to open. To this end, the primary fuel tank may be sealed from the secondary fuel tank, and the secondary fuel tank may be open to the canister.

[0079] At 410 , method 400 may include starting the engine. Starting the engine may include fueling the engine and performing combustion in cylinders of the engine.

[0080] At 412, method 400 may include initiating purge control and monitoring canister loading. Initiating purge control may include opening a purge valve to fluidly couple the canister to an intake of the engine. Monitoring canister loading may include sensing vapor flow from the canister to the engine. Additionally or alternatively, feedback from the FTPT may be monitored.

[0081] At 414, method 400 may include determining whether the canister load is greater than the starting load. The starting load may be equal to the clean canister load or equal to a load less than full load due to partial cleaning. For example, if canister vapors flow to the engine, vapors from the primary fuel tank may still flow to the secondary fuel tank due to the RV1 normally open fault. If the canister load is not greater than the starting load, the canister may still be clean and vapors may not flow from the auxiliary tank to the canister, and at 416, method 400 may include determining that RV1 is not in a normally open fault. To this end, vapors from the primary fuel tank may be prevented from flowing to the auxiliary fuel tank, and the auxiliary fuel tank may remain free of fuel vapor and liquid fuel when RV2 is open.

[0082] If the canister load is greater than the starting load and vapors are flowing to the canister during the purge control, then at 418, method 400 may include determining that RV1 is in a normally open fault. Vapors from the primary tank may flow through the open RV1, into the auxiliary tank, through the open RV2, into the canister, and to the engine. This may increase the load on the canister for a period of time, indicating that the first tank is not sealed by RV1.

[0083] At 420, method 400 may include closing RV2. RV2 may be closed to block vapors from the main tank and the secondary tank from flowing to the canister. RV2 may be selectively opened during certain conditions when the canister is conditioned to receive more vapors, such as after cleaning.

[0084] At 422, method 400 may include increasing the depressurization time. By doing so, emissions due to vapors may be mitigated. Increasing the depressurization time may include sending a warning to the vehicle operator that the fuel door may be locked for a longer duration. By doing so, customer satisfaction may be improved and motivation to repair RV1 may be increased.

[0085] Now turn to Figure 5 , which shows a method 500 for diagnosing a first condition of an RV 2. In one example, the first condition is a normally closed fault condition. The method 500 begins at 502 and includes determining whether tank depressurization is occurring.

[0086] If tank depressurization has not occurred, method 500 may proceed to 504 , which includes the situation where diagnostics on RV2 are not initiated.

[0087] If tank depressurization occurs, such as due to the presence of a refueling request, at 506 , method 500 may include signaling RV1 and RV2 to open. A diagnostic may be initiated.

[0088] At 508 , method 500 may include monitoring FTPT pressure.

[0089] At 510, method 500 may include determining if the FTPT pressure is equal to a lower threshold. If the FTPT pressure is not equal to the lower threshold, then at 512, method 500 may include determining that RV2 is not in a normally closed fault. To this end, steam may flow from the auxiliary tank to the FTPT. The diagnostic passes and RV2 is not degraded.

[0090] If the FTPT is equal to the lower threshold, RV2 may be in a normally closed fault or the FTPT may be irrational (e.g., degraded). Method 500 may diagnose RV2 and FTPT by monitoring the fueling nozzle at 514. At 516, method 500 may include determining whether the fueling nozzle is closed multiple times during refueling. In one example, the auxiliary fuel tank may be unable to vent vapors therefrom. This may result in multiple fueling nozzle closures during a single refueling event.

[0091] If multiple shutdowns have not occurred (eg, multiple shutdowns), at 518 , method 500 may include determining that the FTPT is degraded and erroneously sensing vapor pressure. RV2 is not degraded. RV2 is not in a normally closed fault, and diagnostics for RV2 pass.

[0092] If multiple shutoffs do occur, at 520, method 500 may include determining that RV2 is in a normally closed fault. The diagnosis is negative. In one example, additionally or alternatively, operating parameters may be adjusted. For example, the fuel limit of the auxiliary fuel tank may be reduced. Additionally or alternatively, the duration of operation in the electric-only mode of the vehicle may be reduced to limit vapor generation in the auxiliary fuel tank.

[0093] In some examples, methods 300 and 500 may be combined so that RV1 and RV2 may be diagnosed as being in a normally closed fault. For example, if multiple fuel cuts occur, and each of the cuts is at a fuel level different from an upper threshold level, RV2 may be in a normally closed fault. Additionally or alternatively, if only one fuel cut occurs, RV1 may be in a normally closed fault. In one example, if a first premature closing occurs at an upper threshold level during the diagnostic period, followed by multiple fuel cuts at different fuel levels, both RV1 and RV2 may be in a normally closed fault.

[0094] Now turn to Figure 6, which shows a method 600 for diagnosing a second condition of RV2. In one example, method 600 may determine whether RV2 is in a normally open fault. Method 600 begins at 602, which includes determining whether the auxiliary fuel tank level is greater than a lower threshold fuel level. The lower threshold may correspond to an empty fuel tank. If the auxiliary fuel tank is empty and does not include liquid fuel, at 604, method 600 may include not performing diagnostics of RV2. In some examples, additionally or alternatively, if fuel in the main fuel tank is available, fuel from the main fuel tank may be directed to the auxiliary fuel tank and diagnostics may be initiated.

[0095] If the fuel tank level is greater than the lower threshold fuel level, then at 606 , method 600 may include signaling RV1 to open. The primary fuel tank may direct vapors to the secondary fuel tank.

[0096] At 608 , method 600 may include signaling RV2 to close. The auxiliary fuel tank may be sealed off from the canister. Vapors in the auxiliary fuel tank may not flow to the canister.

[0097] At 610, method 600 may include determining whether the canister load is increasing. If the canister load is increasing, then at 612, method 600 may include determining that RV2 is in a normally open fault. The diagnosis fails (e.g., is negative). In one example, operating parameters may be adjusted to account for RV2 being degraded. For example, pure electric operation of the vehicle may be limited in order to increase engine run time to perform additional canister cleaning. Additionally or alternatively, the amount of future refueling events may be limited to reduce vapor generation. For example, the total limit of the fuel tank may be reduced. Once it is determined that RV2 is no longer in a normally open fault, the total limit of the fuel tank may be returned to the starting value.

[0098] If the canister load is not increasing, then at 614 , method 600 may include determining that RV2 is not in a normally open fault. Vapors from the auxiliary fuel tank may flow to the carbon canister when needed. Operating conditions may not be adjusted.

[0099] Additionally or alternatively, the FTPT may be used to diagnose whether the RV2 is in a normally open fault. If the FTPT senses a pressure greater than a lower threshold, the RV2 is in a normally open fault.

[0100] Now turn to Figure 7 , which shows a graph 700 graphically illustrating diagnostics for a valve of a fuel system including a saddle box. Plot 710 shows whether refueling is occurring. Plot 720 shows the position of RV1. Plot 730 shows the commanded position of RV2, and dashed line 735 shows the actual position of RV2. Plot 740 shows the FTPT output. Time increases from the left side to the right side of the figure.

[0101] Prior to t1, no refueling occurs (plot 710). However, there may be a refueling request, and to that end, RV1 and RV2 are commanded to open (plots 720 and 730, respectively). Although RV2 is commanded to open, the FTPT senses no vapor (plot 740). The condition of the refueling nozzle after depressurization is monitored to determine if the FTPT or RV2 is degraded.

[0102] At t1, decompression is complete and refueling begins. Between t1 and t2, refueling starts and stops multiple times. Thus indicating that the shutdown was premature and not requested by the customer.

[0103] At t2, refueling is complete. The diagnostic determines that RV2 is in a normally closed fault and the operating parameters are modified to account for RV2 being in a normally closed fault. In one example, the volume of fuel tank refill may be limited. Additionally or alternatively, the engine may be operated richer to consume more fuel and increase the head space in the fuel tank to hold a larger amount of vapor. Additionally or alternatively, the duration of electric-only operation may be reduced to prioritize consumption of the fuel in the fuel tank. After t2, RV1 remains open. The FTPT senses no pressure because the fuel tank is still sealed off from the FTPT via RV2, which is in a normally closed state.

[0104] It should be noted that the example control and estimation routines included herein can be used with various engine and / or vehicle system configurations. The control methods and routines disclosed herein can be stored as executable instructions in a non-transitory memory and can be executed by a control system including a controller in combination with various sensors, actuators and other engine hardware. The specific routines described herein may represent one or more of any number of processing strategies (such as event-driven, interrupt-driven, multi-tasking, multi-threading, etc.). Therefore, the various actions, operations and / or functions shown may be executed in the sequence shown, executed in parallel, or omitted in some cases. Similarly, the processing order is not necessarily required to achieve the features and advantages of the example embodiments described herein, but is provided for ease of illustration and description. One or more of the actions, operations and / or functions shown may be repeatedly performed according to the specific strategy used. In addition, the actions, operations and / or functions may be graphically represented as codes in a non-transitory memory of a computer-readable storage medium to be programmed into an engine control system, wherein the actions are implemented by executing instructions in a system including various engine hardware components in conjunction with an electronic controller.

[0105] It should be understood that the configurations and routines disclosed herein are exemplary in nature, and these specific embodiments should not be construed in a limiting sense, as many variations are possible. For example, the above techniques may 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.

[0106] As used herein, unless otherwise specified, the term "about" is interpreted to mean a range of ±5%.

[0107] The appended claims particularly point out certain combinations and subcombinations regarded as novel and non-obvious. These claims may refer to "an" element or "a first" element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amendment of the present claims or by presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, are also deemed to be included in the subject matter of the present disclosure.

[0108] According to the present invention, a method includes diagnosing a valve disposed in a conduit fluidly coupling a primary fuel tank and a secondary fuel tank during or after a refueling event.

[0109] According to an embodiment, if the refueling event includes a shutoff at an upper threshold fuel level, it is determined that the valve was in a normally closed fault during the refueling event.

[0110] According to an embodiment, the above invention is further characterized by emptying the content of the auxiliary fuel tank into the main fuel tank and closing a second valve disposed between the auxiliary fuel tank and the canister.

[0111] According to an embodiment, the above invention is further characterized by cleaning the canister and commanding the valve to close after the refueling event.

[0112] According to an embodiment, the above invention is further characterized in that if a load of the canister increases after the valve is commanded to close, it is determined that the valve is in a normally open fault after a refueling event.

[0113] According to an embodiment, the above invention is further characterized in that if the load of the canister remains constant after the valve is commanded to close, it is determined that the diagnosis is passed.

[0114] According to the present invention, a system is provided, which has: an engine; a fuel system, the fuel system coupled to the engine, the fuel system including a main fuel tank, an auxiliary fuel tank and a filter canister; wherein the main fuel tank is fluidly coupled to the auxiliary fuel tank via a conduit, and wherein the auxiliary fuel tank is fluidly coupled to the filter canister via a load conduit, the conduit including a first valve, and the load conduit including a second valve; and a controller, the controller having computer-readable instructions stored on a memory, the computer-readable instructions, when executed, causing the controller to: diagnose a first condition of one or more of the first valve and the second valve during a refueling event; and diagnose a second condition of one or more of the first valve and the second valve based on a canister load.

[0115] According to an embodiment, the first condition is a normally closed fault condition, and wherein the instructions further cause the controller to determine that the first valve is in a normally closed fault in response to premature closing occurring during the refueling event.

[0116] According to an embodiment, the instructions further cause the controller to determine that the first valve is not in a normally closed fault and a fuel tank pressure sensor (FTPT) is degraded in response to the premature closing not occurring during the refueling event.

[0117] According to an embodiment, the instructions further cause the controller to determine that the second valve is in a normally closed fault in response to a plurality of premature closings occurring during the refueling event.

[0118] According to an embodiment, the instructions further cause the controller to determine that the second valve is not in a normally closed fault and a fuel tank pressure sensor (FTPT) is degraded in response to a lack of premature closing occurring during the refueling event.

[0119] According to an embodiment, the second condition is a normally open fault condition, and wherein the instructions further cause the controller to determine that the first valve is in a normally open fault in response to an increase in canister load after emptying the contents of the auxiliary fuel tank into the main fuel tank and commanding the first valve to close.

[0120] According to an embodiment, the instructions further cause the controller to determine that the second valve is in a normally open fault in response to the canister load increasing after the second valve is commanded to close and the fuel level in the auxiliary fuel tank is greater than a lower threshold.

[0121] According to an embodiment, the instructions further cause the controller to determine that the second valve is in a normally open fault in response to a pressure read by a fuel tank pressure sensor (FTPT) being greater than a lower limit value.

[0122] According to an embodiment, one or more of the primary fuel tank and the secondary fuel tank is a saddle tank.

[0123] According to the present invention, a method for a fuel system including a first fuel tank and a second fuel tank includes: diagnosing a first condition of one or more of a first valve and a second valve based on a number of premature refueling shut-offs and feedback from a fuel tank pressure sensor (FTPT); and diagnosing a second condition of one or more of the first valve and the second valve based on a load of a filter canister; wherein the first valve is arranged in a conduit that fluidly couples the first fuel tank to the second fuel tank, and wherein the second valve is arranged in a load conduit that fluidly couples the second fuel tank to the filter canister.

[0124] According to an embodiment, diagnosing the first condition of the first valve includes detecting premature closing during the refueling event and the FTPT senses a value equal to a lower threshold.

[0125] According to an embodiment, diagnosing the first condition of the second valve includes detecting a plurality of premature closings during the refueling event and the FTPT senses a value equal to a lower threshold.

[0126] According to an embodiment, diagnosing the second condition of the first valve includes: transferring contents of the second fuel tank to the first fuel tank; commanding the first valve to close; and monitoring the load of the canister.

[0127] According to an embodiment, diagnosing the second condition of the second valve includes monitoring the load of the canister when a fuel level in the second fuel tank is greater than a lower threshold fuel level.

Claims

1. A method comprising: A valve disposed in a conduit fluidly coupling a primary fuel tank and a secondary fuel tank is diagnosed during or after a refueling event. 2 . The method of claim 1 , wherein the valve is determined to be in a normally closed fault during the refueling event if the refueling event includes a shutoff at an upper threshold fuel level. 3 . The method of claim 1 , further comprising emptying the contents of the auxiliary fuel tank into the primary fuel tank and closing a second valve disposed between the auxiliary fuel tank and a canister. 4 . The method of claim 3 , further comprising cleaning the canister and commanding the valve to close after the refueling event. 5 . The method of claim 4 , further comprising determining that the valve is in a normally open fault after the refueling event if a load on the canister increases after the valve is commanded to close. 6 . The method of claim 4 , further comprising determining that the diagnostic passes if a load of the canister remains constant after the valve is commanded to close.

7. A system comprising: engine; a fuel system coupled to the engine, the fuel system comprising a primary fuel tank, a secondary fuel tank, and a canister; in The primary fuel tank is fluidly coupled to the secondary fuel tank via a conduit, and wherein the secondary fuel tank is fluidly coupled to the canister via a load conduit, the conduit including a first valve, and the load conduit including a second valve; and A controller having computer readable instructions stored on a memory, the computer readable instructions, when executed, causing the controller to: diagnosing a first condition of one or more of the first valve and the second valve during a refueling event; and A second condition of one or more of the first valve and the second valve is diagnosed based on canister loading.

8. The system of claim 7, wherein the first condition is a normally closed fault condition, and wherein the instructions further cause the controller to determine that the first valve is in a normally closed fault condition in response to premature closing occurring during the refueling event.

9. The system of claim 8 wherein the instructions further cause the controller to determine that the first valve is not in a normally closed fault and a fuel tank pressure sensor (FTPT) is degraded in response to the premature closing not occurring during the refueling event.

10. The system of claim 7, wherein the instructions further cause the controller to determine that the second valve is in a normally closed fault in response to a plurality of premature closings occurring during the refueling event.

11. The system of claim 10, wherein the instructions further cause the controller to determine that the second valve is not in a normally closed fault and a fuel tank pressure sensor (FTPT) is degraded in response to a lack of premature closing occurring during the refueling event.

12. The system of claim 7 wherein the second condition is a normally open fault condition and wherein the instructions further cause the controller to determine that the first valve is in a normally open fault condition in response to an increase in canister load after emptying the contents of the auxiliary fuel tank into the primary fuel tank and commanding the first valve to close.

13. The system of claim 7 wherein the instructions further cause the controller to determine that the second valve is in a normally open fault in response to the canister load increasing and the fuel level in the auxiliary fuel tank being greater than a lower threshold after the second valve is commanded to close.

14. The system of claim 7, wherein the instructions further cause the controller to determine that the second valve is in a normally open fault in response to a pressure read by a fuel tank pressure sensor (FTPT) being greater than a lower limit.

15. The system of claim 7, wherein one or more of the primary fuel tank and the auxiliary fuel tank is a saddle tank.

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