System and method for evaporative emissions system and fuel system with single delta pressure sensor

Abstract

Methods and systems are provided for including a single pressure sensor in an evaporative emission system and a fuel system. In one example, a method may include venting a fuel tank of a fuel system in response to a decompression condition determined based on a differential pressure measured by a delta pressure sensor coupled across a fuel tank isolation valve (FTIV), the fuel tank being isolated from the evaporative emission system by the FTIV. The venting may include opening and closing the FTIV in a pulsating manner, and may also include adjusting the pulsation in response to the differential pressure measured when the FTIV is closed and independent of the differential pressure measured when the FTIV is open.

Description

Technical Field

[0001] The present description generally relates to methods and systems for a non-integrated controlled refueling-only emissions canister system.

[0002] Background technology / invention content

[0003] The vehicle fuel system may include an evaporative emission system designed to reduce the release of fuel vapor to the atmosphere. For example, vaporized hydrocarbons (HC) from the fuel tank may be stored in a fuel vapor storage canister filled with an adsorbent that adsorbs and stores vapor. Subsequently, when the engine is in operation, the fuel vapor may be purged from the evaporative emission system into the engine intake manifold for use as fuel. In some examples, the evaporative emission system may be configured to store refueling vapor, operating loss vapor, and day and night vapor. However, in other examples, the evaporative emission system and the fuel system may be configured as a non-integrated refueling canister only system (NIRCOS). In such a system, during a refueling event, the fuel tank is sealed and fuel vapor is directed only to the fuel vapor storage canister. For example, due to limited engine operating time, a plug-in hybrid electric vehicle (PHEV) may include a NIRCOS. If the fuel tank is vented, prolonged electric mode driving (where the engine is off and the vehicle is propelled by torque from the electric motor) may cause the fuel vapor storage canister to overload and vent fuel vapors to the atmosphere.

[0004] In order to seal the fuel tank from the fuel vapor storage canister, the NIRCOS may include a fuel tank isolation valve (FTIV) between the fuel tank and the fuel vapor storage canister. For example, the FTIV may be a solenoid valve controlled by a pulse width modulated signal. Typically, a pressure sensor is coupled to the fuel system (such as a fuel tank pressure transducer coupled to the fuel tank) to measure the fuel tank pressure. The fuel vapor storage canister side of the FTIV may include an additional pressure sensor to monitor degradation of the evaporative emissions system. Based on the fuel tank pressure, the FTIV may be at least partially opened to ventilate the fuel tank during an engine-on state and to prepare the fuel tank for refueling (e.g., during an engine-off state).

[0005] However, the inventors herein have recognized that including two pressure sensors in a NIRCOS may increase the cost of the system and result in multiple degradation points because each sensor may degrade independently, and have further recognized that vehicle cost and complexity may be reduced by including a single Δ pressure sensor coupled across the FTIV. The Δ pressure sensor may output a signal corresponding to the pressure difference (e.g., differential pressure) between the evaporative emissions system and the fuel system, which may be used to detect both evaporative emissions system degradation and fuel system degradation. In addition, the differential pressure may be used to determine the relative fuel tank pressure. However, when the FTIV is open, the differential pressure approaches zero and is therefore not useful for determining the relative fuel tank pressure. When there is no feedback regarding the relative fuel tank pressure when ventilating the fuel tank, the relative fuel tank pressure may be overestimated. Therefore, the FTIV may remain open for an extended duration, which may delay refueling and / or increase the load on the fuel vapor storage canister compared to when the duration is not extended.

[0006] In one example, the above described problems may be solved by a method including: in response to a decompression condition determined based on a differential pressure measured by a delta pressure sensor coupled across a fuel tank isolation valve (FTIV), venting a fuel tank by opening and closing the FTIV in a pulsating manner; and during the pulsation, adjusting the pulsation in response to the differential pressure measured when the FTIV is closed and independently of the differential pressure measured when the FTIV is open. In this way, a single delta pressure sensor may be used to determine whether to vent the fuel tank by pulsating the FTIV and whether to adjust the pulsation.

[0007] As an example, a first pressure port of the delta pressure sensor may be fluidly coupled to a conduit between the FTIV and the fuel tank, and a second pressure port of the delta pressure sensor may be fluidly coupled to a conduit between the FTIV and a fuel vapor storage canister of an evaporative emission system. In the absence of a restrictive component (such as a valve) between the fuel tank and the first pressure port and / or between the fuel vapor storage canister and the second pressure port, the differential pressure measured by the delta pressure sensor indicates the relative pressure (or vacuum) of the evaporative emission system and the relative pressure (or vacuum) of the fuel tank. In the case where the evaporative emission system is normally open to the atmosphere, the differential pressure may indicate the pressure of the fuel tank relative to atmospheric pressure. Thus, a decompression condition may be determined when the fuel tank relative pressure is greater than or equal to a threshold relative pressure, which may be a predetermined relative pressure value above atmospheric pressure. In addition, the pulsation rate may be adjusted based on the fuel tank relative pressure, such as by reducing the rate when the fuel tank relative pressure approaches the threshold relative pressure. By opening and closing the FTIV in a pulsed manner and determining the relative pressure of the fuel tank only when the FTIV is closed, feedback regarding the fuel tank pressure may be maintained when venting the fuel tank, resulting in efficient tank venting.

[0008] It should be understood that the above summary is provided to introduce a series of concepts in a simplified form, which are further described in the detailed description. This is not meant to identify key or essential features of the claimed subject matter, the scope of which is uniquely defined by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that address any disadvantages noted above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 An exemplary vehicle system is schematically illustrated.

[0010] Figure 2 A schematic depiction of a fuel system and an evaporative emissions system coupled to an engine system is shown.

[0011] Figure 3 A high level flow chart is shown of an exemplary method for diagnosing components of a fuel system and an evaporative emissions system using output from a delta pressure sensor coupled across a fuel tank isolation valve (FTIV).

[0012] Figure 4 An example method for determining whether degradation exists on the FTIV or the fuel tank side of the FTIV based on delta pressure sensor measurements is shown.

[0013] Figure 5 An exemplary method for performing a fuel vapor storage canister side diagnostic test using delta pressure sensor measurements is depicted.

[0014] Figure 6 An exemplary method for evaluating a purge path of an evaporative emissions system using output from a delta pressure sensor is shown.

[0015] Figure 7 An exemplary method for evaluating a ventilation path of an evaporative emissions system using output from a delta pressure sensor is shown.

[0016] Figure 8 An exemplary method for regulating fuel tank pressure based on output from a delta pressure sensor during engine operation and a refueling event is shown.

[0017] Fig. 9 is a predictive exemplary timeline for determining if degradation exists on the FTIV or the fuel tank side of the FTIV using the output from a single delta pressure sensor coupled across the FTIV.

[0018] Fig.10is a predictive exemplary timeline for performing a diagnostic test on the fuel vapor storage canister side of the FTIV using output from a single delta pressure sensor coupled across the FTIV.

[0019] Fig.11 is a predictive exemplary timeline for determining if a purge path obstruction exists in an evaporative emissions system based on output from a single delta pressure sensor.

[0020] Fig.12 is a predictive exemplary timeline for determining if a vent path blockage exists in an evaporative emissions system based on output from a single delta pressure sensor.

[0021] Fig.13 is a prospective exemplary timeline for regulating pressure on the fuel tank side of the FTIV based on measurements from a delta pressure sensor coupled across the FTIV.

[0022] Fig.14 is a predictive exemplary timeline for depressurizing a fuel tank for a refueling event using output from a delta pressure sensor. DETAILED DESCRIPTION

[0023] The following description relates to a method for measuring the pressure of a fuel system and an evaporative emissions system (such as a Figure 2 The fuel system and evaporative emission system may include a vehicle system such as a Figure 1 For example, the fuel system and the evaporative emission system may be a non-integrated controlled refueling only emission canister system (NIRCOS) included in a plug-in hybrid electric vehicle (PHEV), wherein the fuel tank of the fuel system is sealed and isolated from the fuel vapor storage canister of the evaporative emission system by a fuel tank isolation valve (FTIV). Figure 3 A high level flow chart is shown for identifying degradation of the fuel system and evaporative emissions system based on the output of the dP sensor and depending on whether the vehicle's engine is on or off. More specifically, Figure 4 An exemplary method of detecting degradation of the FTIV and the fuel tank side of the FTIV is provided, and an example of the exemplary method is provided in Fig. 9 The timeline is shown in Figure 5 An exemplary method of detecting degradation of the fuel vapor storage canister side of the FTIV, and an example of the exemplary method is Fig.10 In addition, Figure 6 and Figure 7 An exemplary method of inspecting the fuel vapor storage canister side of the FTIV for blockage is also described in Fig.11 and Fig.12The pressure of the fuel tank may be determined based on Figure 8 An exemplary method of using the output from the dP sensor to make adjustments to maintain the pressure of the fuel tank below a threshold pressure and to depressurize the tank during a refueling event. Fig.13 An exemplary timeline for fuel tank depressurization while the engine is running is shown in FIG. Fig.14 An exemplary timeline for fuel tank depressurization for a refueling event at engine shutoff is shown in FIG.

[0024] As used herein, the term "vacuum" refers to a negative pressure relative to a reference pressure, such as atmospheric pressure, and the term "pressure" may refer to both negative and positive pressures relative to a reference pressure.

[0025] Figure 1 An exemplary vehicle system 100 is shown. The vehicle 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. As such, a vehicle having the propulsion system 100 may be referred to as a hybrid electric vehicle (HEV).

[0026] The vehicle 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 (e.g., set to a deactivated state), wherein 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.

[0027] During other operating conditions, the engine 110 may be set to a deactivated 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, and 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 vehicle regenerative braking. Thus, in some examples, the motor 120 may act as a generator. However, in other examples, alternatively, the generator 160 may receive wheel torque from the drive wheel 130, and may convert the kinetic energy of the wheel into electrical energy for storage at the energy storage device 150, as indicated by arrow 162. As another example, in a starting operation, the motor 120 may use the energy stored at the energy storage device 150 to crank the engine 110, as indicated by arrow 186.

[0028] 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, the engine 110 may be operated to propel the vehicle via the drive wheels 130, as indicated by arrow 112, while the motor 120 is deactivated. 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.

[0029] In other examples, the vehicle system 100 may be configured as a series vehicle propulsion system, in which the engine does not directly propel the drive wheels. Instead, the engine 110 may be operated to provide power to the motor 120, which in turn may propel the vehicle via the drive wheels 130, as indicated by arrow 122. For example, during selected operating conditions, the engine 110 may drive the generator 160, as indicated by arrow 116, which in turn may supply electrical energy to one or more of 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 may be operated to drive the motor 120, which in turn may act as a generator to convert the engine output into electrical energy. The electrical energy may be stored at the energy storage device 150 for later use, for example, by the motor.

[0030] 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 fuel. 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 (such as E10, E85, etc.) or a mixture of gasoline and methanol (such as M10, M85, etc.), wherein these fuels or fuel mixtures may be delivered to the engine 110, as indicated by arrow 142. Some other suitable fuels or fuel mixtures may be supplied to the engine 110, where the fuel or fuel mixture may be burned to produce an engine output (e.g., torque). The engine output may be used to propel the vehicle (as indicated by arrow 112) or to recharge the energy storage device 150 via the motor 120 or the generator 160.

[0031] 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, headlights, cabin audio and video systems, etc. As non-limiting examples, energy storage device 150 may include one or more batteries and / or capacitors.

[0032] Control system 190 may communicate with one or more of engine 110, motor 120, fuel system 140, energy storage device 150, and generator 160. Control system 190 may receive sensory feedback information from one or more of engine 110, motor 120, fuel system 140, energy storage device 150, and generator 160. Control system 190 may send command signals to one or more of engine 110, motor 120, fuel system 140, energy storage device 150, and generator 160 in response to the sensory feedback.

[0033] The control system 190 may receive an indication of a driver-requested output of a vehicle propulsion system from a vehicle driver 102. For example, the control system 190 may receive sensory feedback regarding the position of a pedal 192 from a pedal position sensor 194. The pedal 192 may illustratively be a brake pedal and / or an accelerator pedal that may be depressed by the vehicle driver 102. Additionally, 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), the remote engine start may be initiated via a cellular phone or smartphone-based system, where the user's phone sends data to a server and the server communicates with the vehicle to start the engine.

[0034] The energy storage device 150 may periodically receive electrical energy from a power source 180 residing outside the vehicle (e.g., an external fixed power grid that is not part of the vehicle), as indicated by arrow 184. As a non-limiting example, the vehicle system 100 may be configured as a plug-in HEV, where electrical energy may be supplied to the energy storage device 150 from the power source 180 via an electrical energy transmission cable 182. During operation to recharge the energy storage device 150 from the power source 180, the electrical transmission cable 182 may 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 may be disconnected between the power source 180 and the energy storage device 150. The control system 190 may identify and / or control the amount of electrical energy stored at the energy storage device, which may be referred to as a state of charge (SOC).

[0035] In other examples, the electrical transmission cable 182 may be omitted, where electrical energy may be wirelessly received at the energy storage device 150 from the power source 180. For example, the energy storage device 150 may 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 approach may be used to recharge the energy storage device 150 from a power source that is not part of the vehicle. In this way, the motor 120 may propel the vehicle by utilizing an energy source other than the fuel utilized by the engine 110.

[0036] In still other examples, the vehicle system 100 may include one or more solar cells 108 that operate to convert incident solar radiation into electrical energy. The solar cell 108 is electrically coupled to the solar battery 30 via the charge controller 32. The solar cell 108 and the charge controller 32 operate to supply current for charging the solar battery 30. In this example, the solar battery 30 is housed within and electrically coupled to the energy storage device 150, but in other configurations, the solar battery 30 may be electrically coupled to the energy storage device 150 while being separately housed. Thus, the solar battery 30 may be configured to provide charge or receive charge from the energy storage device 150 based on engine operating conditions, state of charge, and one or more battery requirements. In still other configurations, the solar battery 30 may be physically and electrically isolated from the energy storage device 150. In some examples, the solar battery 30 may be configured to independently supply charge directly to vehicle actuators and devices. In still other examples, charge controller 32 may be used to supply charge directly to vehicle actuators and devices without first storing the charge in solar battery 30 .

[0037] The solar cell 108 may be mounted on any convenient exterior surface of the vehicle, such as the roof, hood, trunk, etc. However, additionally or alternatively, the solar cell 108 may be mounted on the interior of the vehicle, such as on the dashboard or other passenger compartment surface adjacent to a window or interior light bulb. In general, the solar cell operates to convert solar radiation incident thereon into electrical energy. In some embodiments, the solar cell 108 may include a series of photovoltaic cells formed of an amorphous semiconductor material, such as silicon. Additionally, the individual photovoltaic cells may be interconnected to provide a constant flow of electrical energy to a common output cable 188, which electrically couples the solar cell 108 to the charge controller 32 and the solar battery 30. In this way, the solar cell 108 may generate electrical energy to propel the vehicle or to power one or more additional vehicle actuators or devices, and the motor 120 may propel the vehicle by utilizing an energy source other than the fuel utilized by the engine 110.

[0038] The fuel system 140 may periodically receive fuel from a fuel source residing outside the vehicle. As a non-limiting example, the vehicle system 100 may be refueled by receiving fuel via the fuel dispensing device 170, as indicated by arrow 172. In some examples, the fuel tank 144 may be configured to store the fuel received from the fuel dispensing device 170 until the fuel is supplied to the engine 110 for combustion. The control system 190 may receive an indication of the level of fuel stored in the fuel tank 144 via a fuel level sensor. The level of fuel stored in the fuel tank 144 (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 dashboard (e.g., a message center) 196.

[0039] The vehicle system 100 may also include an ambient temperature / humidity sensor 198, and roll stability control sensors, such as one or more lateral and / or longitudinal and / or yaw rate sensors 199. The vehicle dashboard 196 may include one or more indicator lights, and / or a text-based display in which messages are displayed to the driver. The vehicle dashboard 196 may also include various input devices for receiving driver input, such as buttons, touch screens, voice input / recognition, etc. For example, the vehicle dashboard 196 may include a refueling button 197, which may be manually actuated or pressed by the vehicle driver to initiate refueling. For example, as described in more detail below, in response to the vehicle driver actuating the refueling button 197, a fuel tank in the vehicle (e.g., fuel tank 144) may be depressurized so that refueling can be performed.

[0040] The control system 190 can be communicatively connected to other vehicles or infrastructure using various appropriate communication technologies. For example, the control system 190 can be connected to other vehicles or infrastructure via a wireless network 131, which may include Wi-Fi, Bluetooth, a cellular service, a wireless data transmission protocol, etc. The control system 190 can 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 or V2X) technologies. The information exchanged between vehicles can be transmitted directly between vehicles, or can be transmitted in multiple hops. In some examples, longer range communications (e.g., WiMax) can be used in conjunction with V2V or V2I2V to extend the coverage area by several miles. In some other examples, the vehicle control system 190 can be communicatively connected to other vehicles or infrastructure via a wireless network 131 and the Internet (e.g., the cloud).

[0041] The vehicle system 100 may also include an onboard navigation system 132, such as a Global Positioning System (GPS), with which the vehicle driver may interact. The navigation system 132 may include one or more position sensors to help estimate vehicle speed, vehicle altitude, vehicle orientation / position, etc. This information may also be used to infer engine operating parameters, such as local barometric pressure. As discussed above, the control system 190 may be further configured to receive information via the Internet or other communication network. Information received from the GPS may be cross-referenced with information available via the Internet to determine local weather conditions, local vehicle regulations, etc.

[0042] Figure 2 FIG. 2 is a schematic diagram of a vehicle system 206. It is understood that the vehicle system 206 may include Figure 1 The vehicle system 206 may be the same vehicle system as the vehicle system 100 depicted. The vehicle system 206 may be powered by an engine system 208 and / or an onboard energy storage device such as Figure 1 The energy storage device 150 shown is used to obtain propulsion. An energy conversion device (such as a generator (e.g., Figure 1 The generator 160)) is operable to absorb energy from vehicle movement and / or engine operation and convert the absorbed energy into an energy form suitable for storage by the energy storage device.

[0043] The engine system 208 may include an engine 210 having a plurality of cylinders 230. The engine 210 may be, for example, Figure 1 The engine 110 shown. The engine 210 may include an engine intake system 223 and an engine exhaust system 225. The engine intake system 223 may include an intake throttle valve 262, which is fluidly coupled to an engine intake manifold 244 via an intake passage 242. Air may be directed to the intake throttle valve 262 after passing through an air filter 252, which is coupled to the intake passage 242 upstream of the intake throttle valve 262. The engine exhaust system 225 includes an exhaust manifold 248, which leads to an exhaust passage 235 that directs exhaust gas to the atmosphere. The engine exhaust system 225 may include an emission control device 270 installed in a close-coupled position. The emission control device may include one or more of the following: a three-way catalyst, a lean NOx trap, a particulate filter (e.g., a diesel particulate filter or a gasoline particulate filter), an oxidation catalyst, etc. It should be appreciated that the engine may include other components, such as various valves and sensors, as further detailed herein. In some embodiments where the engine system 208 is a boosted engine system, the engine system may also include a boosting device, such as a turbocharger (not shown).

[0044] The engine system 208 is coupled to a fuel system 218 and an evaporative emissions system 219. The fuel system 218 includes a fuel tank 220 coupled to a fuel pump 234 that supplies fuel to an engine 210 that propels the vehicle system 206. The evaporative emissions system 219 includes a fuel vapor storage canister 222. During a fuel tank refueling event, fuel may be pumped into the vehicle from an external source through a refueling port 284, and fuel vapors may be directed to the fuel vapor storage canister 222, as further described below. When in a closed position, the fuel port 286 may prevent access to the refueling port 284. The fuel port 286 may be normally lockable in a closed position such that the fuel port 286 may not be opened. The fuel port 286 may be unlocked during a fuel tank refueling event in response to determining that the fuel tank 220 is depressurized, such as by being opened relative to the fuel tank 220. Figure 8 When unlocked, fuel port 286 may be opened to allow access to refueling port 284. Fuel tank 220 may hold a variety of fuel mixtures, including fuels having a range of alcohol concentrations, such as various gasoline-ethanol blends, including E10, E85, gasoline, etc., and combinations thereof. A fuel level sensor 282 located in fuel tank 220 may provide a control system 290 (which may be, for example, Figure 1 The controller 12 of the control system 190 of the fuel level sensor 182 provides an indication of the fuel level ("fuel level input"). As shown, the fuel level sensor 282 may include a float connected to a variable resistor. Alternatively, other types of fuel level sensors may be used.

[0045] Fuel pump 234 is configured to deliver pressurized fuel to fuel injectors of engine 210, such as exemplary fuel injector 266. Although only a single fuel injector 266 is shown, additional fuel injectors may be provided for each cylinder. It should be appreciated that fuel system 218 may be a returnless fuel system, a return fuel system, or various other types of fuel systems. Vapors generated in fuel tank 220 may be directed to fuel vapor storage canister 222 via conduit 231 for storage before being purged into engine intake system 223. Thus, fuel system 218 may be in fluid communication with evaporative emission system 219.

[0046] Fuel vapor storage canister 222 is filled with a suitable adsorbent 280 for temporarily capturing fuel vapors (including vaporized hydrocarbons) generated during a fuel tank refueling operation. In one example, adsorbent 280 is activated carbon (e.g., carbon). Although a single fuel vapor storage canister 222 is shown, it should be understood that fuel system 218 and evaporative emissions system 219 may include any number of fuel vapor storage canisters. When a purge condition is met, such as when the fuel vapor storage canister is saturated, vapors stored in the fuel vapor storage canister 222 may be purged to the engine intake system 223 via purge line 228 by opening canister purge valve (CPV) 212, which may be a normally closed valve. In one example, canister purge valve 212 may be a solenoid valve, wherein the opening or closing of the valve is performed via actuation of a canister purge solenoid.

[0047] The fuel vapor storage canister 222 may include a buffer zone 222a (or buffer area), each of which includes an adsorbent. For example, the buffer zone 222a is shown as being filled with an adsorbent 280a. As shown, the volume of the buffer zone 222a may be smaller than the volume of the fuel vapor storage canister 222 (e.g., be a portion thereof). The adsorbent 280a in the buffer zone 222a may be the same as or different from the adsorbent 280 in the fuel vapor storage canister (e.g., both may include carbon). The buffer zone 222a may be positioned within the fuel vapor storage canister 222 so that during loading of the fuel vapor storage canister, the fuel tank vapor is first adsorbed within the buffer zone, and then when the buffer zone is saturated, additional fuel tank vapor is adsorbed in the fuel vapor storage canister. In contrast, during cleaning of the fuel vapor storage canister, the fuel vapor is first desorbed from the fuel vapor storage canister (e.g., to a threshold amount) and then desorbed from the buffer zone. In other words, the loading and unloading of the buffer zone is not consistent with the loading and unloading of the fuel vapor storage canister. Thus, the fuel vapor storage canister buffer zone functions to attenuate any fuel vapor spikes flowing from the fuel tank to the fuel vapor storage canister, thereby reducing the likelihood of any fuel vapor spikes entering the engine.

[0048] The fuel vapor storage canister 222 includes a vent 227 for conveying gas from the fuel vapor storage canister 222 to the atmosphere when storing fuel vapor from the fuel tank 220. The vent 227 may also allow fresh air to be drawn into the fuel vapor storage canister 222 when the stored fuel vapor is purged to the engine air intake 223 via the purge line 228 and the canister purge valve 212. Although this example shows that the vent 227 is connected to fresh, unheated air, various modifications may also be used. In some examples, an air filter may be coupled to the vent 227. The vent 227 may include a canister vent valve (CVV) 214 to adjust the flow of air and vapor between the fuel vapor storage canister 222 and the atmosphere. When a vent valve is included, the vent valve may be a normally open valve so that air stripped of fuel vapor after passing through the fuel vapor storage canister can be pushed out to the atmosphere (e.g., during refueling when the engine is off). Similarly, during a purge operation (e.g., during fuel vapor storage canister regeneration and while the engine is running), the fuel vapor storage canister ventilation valve may be opened to allow fresh air flow to strip fuel vapor stored in the fuel vapor storage canister. In one example, canister ventilation valve 214 may be a solenoid valve, wherein the opening or closing of the valve is performed via actuation of a canister ventilation solenoid. Specifically, canister ventilation valve 214 may be a normally open valve that is closed upon actuation of a canister ventilation passage solenoid.

[0049] The evaporative emission system 219 may also include a hybrid fuel vapor storage canister 211. Hydrocarbons desorbed from a fuel vapor storage canister 222 (hereinafter also referred to as a "primary fuel vapor storage canister") may be adsorbed in the hybrid fuel vapor storage canister. The hybrid fuel vapor storage canister 211 may include an adsorbent material 280b that is different from the adsorbent material included in the primary fuel vapor storage canister 222. Alternatively, the adsorbent material in the hybrid fuel vapor storage canister 211 may be the same as the adsorbent material included in the primary fuel vapor storage canister 222 (e.g., the adsorbent 280 may be the same as the adsorbent material 280b).

[0050] A hydrocarbon (HC) sensor 213 may be present in the evaporative emission system 219 to indicate the hydrocarbon concentration in the ventilation passage 227. As shown, the hydrocarbon sensor 213 is positioned between the main fuel vapor storage canister 222 and the mixed fuel vapor storage canister 211. A probe (e.g., a sensing element) of the hydrocarbon sensor 213 is exposed to the fluid flow in the ventilation passage 227 and senses the hydrocarbon concentration of the fluid flow. In one example, the hydrocarbon sensor 213 may be used by the control system 290 to determine the breakthrough of hydrocarbon vapors from the main fuel vapor storage canister 222.

[0051] One or more temperature sensors 215 may be coupled to and / or within the fuel vapor storage canister 222. When the adsorbent in the fuel vapor storage canister adsorbs fuel vapor, heat (adsorption heat) is generated. Similarly, when the adsorbent in the fuel vapor storage canister adsorbs fuel vapor, heat is consumed. In this way, the adsorption and desorption of fuel vapor by the fuel vapor storage canister can be monitored and estimated based on the temperature changes within the fuel vapor storage canister. In addition, one or more canister heating elements 216 may be coupled to and / or within the fuel vapor storage canister 222. The canister heating element 216 may be used to selectively heat the fuel vapor storage canister (and the adsorbent contained therein) before performing a cleaning operation, so as to, for example, enhance the desorption of fuel vapor. As described above, heating the fuel vapor storage canister may be particularly beneficial for cleaning heavy hydrocarbon fractions (e.g., higher molecular weight hydrocarbons). The canister heating element 216 may include an electrical heating element, such as an electrically heatable conductive metal, ceramic, or carbon element. In some embodiments, the canister heating element 216 may include a microwave energy source, or may include a fuel vapor storage canister jacket coupled to a hot air source or hot water source. The canister heating element 216 may be coupled to one or more heat exchangers, which may facilitate the transfer of heat (e.g., from hot exhaust) to the fuel vapor storage canister 222. The canister heating element 216 may be configured to heat the air within the fuel vapor storage canister 222 and / or directly heat the adsorbent located within the fuel vapor storage canister 222. In some embodiments, the canister heating element 216 may be included in a heater compartment coupled to the interior or exterior of the fuel vapor storage canister 222. In some embodiments, the fuel vapor storage canister 222 may be coupled to one or more cooling circuits and / or cooling fans. In this way, the fuel vapor storage canister 222 may be selectively cooled to enhance adsorption of fuel vapor (e.g., before a refueling event). In some examples, the canister heating element 216 may include one or more Peltier elements, which may be configured to selectively heat or cool the fuel vapor storage canister 222.

[0052] Since the vehicle is driven by the engine system 208 during some conditions and by the energy storage device under other conditions, the hybrid vehicle system 206 may have a reduced engine operating time. Although the reduced engine operating time reduces carbon emissions from the vehicle, they may also result in insufficient fuel vapor cleaning from the evaporative emission system 219. In addition, due to the reduced engine operating time, the consumption of fuel may be slow. For example, without any refueling events, the fuel contained in the fuel tank 220 may last for a relatively long duration (e.g., several months to a year). If the fuel tank 220 is ventilated regularly, such as via a conduit 231 that communicates with the evaporative emission system 219, the fuel in the fuel tank 220 may age and lose its volatility, such as by escaping to the fuel vapor storage canister. Lower molecular weight hydrocarbons (e.g., light fractions). Therefore, the fuel vapor storage canister 222 may be overloaded, and when the aged fuel is used for combustion in the engine, engine performance may deteriorate. For example, a reduction in fuel volatility may result in a long and polluting start.

[0053] To address this issue, a fuel tank isolation valve (FTIV) 236 may be included in conduit 231 such that fuel tank 220 is connected to canister 222 via a valve. In some examples, the FTIV may also be a tank pressure control (TPC) valve. When closed, FTIV 236 may seal fuel tank 220 from evaporative emissions system 219 and the atmosphere. Thus, fuel tank 220 may be constructed of a suitable material (e.g., steel) to withstand pressure changes, such as 5 psi pressure or vacuum (relative to atmospheric pressure). FTIV 236 may be a normally closed valve to prevent diurnal vapors or "loss of operation" vapors from being directed from fuel tank 220 to canister 222. During a refueling operation, FTIV 236 may be temporarily opened to direct fuel vapors from fuel tank 220 to fuel vapor storage canister 222, as will be discussed below with respect to FIG. Figure 8 Additionally, when the fuel tank pressure is above a threshold (eg, above the mechanical pressure limit of the fuel tank), the FTIV 236 may also be temporarily opened so that fuel vapors may be released to the fuel vapor storage canister and the fuel tank pressure may be maintained below the threshold, as also described with respect to Figure 8 Further, the FTIV 236 may be opened at a predetermined duty cycle to detect FTIV degradation and / or degradation in the fuel system 218 (eg, the fuel tank side of the FTIV), as will be described below with respect to Figure 4 In some examples, a vacuum pump 238 may be included in the vent passage 227 to evacuate the evaporative emission system and facilitate testing, as described in more detail below.

[0054] A delta (e.g., differential) pressure sensor (e.g., dP sensor) 221 may be coupled to the fuel system 218 and the evaporative emission system 219 across the FTIV 236. In one example, the dP sensor 221 is the only pressure sensor included in the fuel system 218 and the evaporative emission system 219, and no absolute pressure sensor is included. A first conduit 231a may fluidly couple a first pressure port of the dP sensor 221 to the conduit 231 on the fuel tank side of the FTIV, and a second conduit 231b may fluidly couple a second pressure port of the dP sensor 221 to the conduit 231 on the fuel vapor storage canister side of the FTIV. The dP sensor 221 may be, for example, a media-isolated pressure sensor. A pressure-sensitive diaphragm (such as a stainless steel diaphragm, a titanium diaphragm, or a nickel alloy diaphragm) may be included within the dP sensor 221 between the first pressure port and the second pressure port to separate two media (e.g., fuel vapor at the first pressure port and fresh air at the second pressure port). The dP sensor 221 may generate a voltage that is proportional to a delta pressure (e.g., a pressure differential) between a first pressure port corresponding to the pressure of the fuel system 218 (and the fuel tank 220) and a second pressure port corresponding to the pressure of the evaporative emissions system 219 (e.g., the pressure on the fuel vapor storage canister side of the FTIV 236). When the FTIV 236 is open, the pressure at the first pressure port of the dP sensor 221 is the same as the pressure at the second pressure port. In the absence of a pressure differential, the dP sensor 221 may output a small voltage (e.g., 0.45-1.0 V) that is equivalent to a pressure differential of 0 inches H2O. When the FTIV 236 is closed, the pressure at the first port may be determined relative to the pressure at the second port (and vice versa). As an example, when the CVV 214 is open and the CPV 212 is closed, the fuel vapor storage canister side (also referred to herein as the canister side) may be at atmospheric pressure, and therefore, the dP sensor 221 may provide an indication of the pressure of the fuel tank 220 relative to atmospheric pressure. As another example, during purging of fuel vapor storage canister 222 when CVV 214 is open and CPV 212 is open, vacuum from engine intake manifold 244 may reduce pressure on the canister side of FTIV 236, and this pressure reduction may be indicated by dP sensor 221 relative to pressure in fuel tank 220 (e.g., pressure on the fuel tank side of FTIV 236). In still other examples, control system 290 may diagnose components of the fuel system and evaporative emissions system based on the differential pressure measured by dP sensor 221, as described below with reference to Figures 3 to 7 described.

[0055] One or more temperature sensors 217 may also be coupled to the fuel system 218 for providing an estimate of the fuel system temperature. In one example, the fuel system temperature is a fuel tank temperature, where the temperature sensor 217 is a fuel tank temperature sensor coupled to the fuel tank 220. While the depicted example shows the temperature sensor 217 coupled directly to the fuel tank 220, in alternative embodiments, the temperature sensor may be coupled between the fuel tank 220 and the FTIV 236.

[0056] Fuel vapor released from the fuel vapor storage canister 222 during, for example, a purge operation, may be directed into the engine intake manifold 244 via a purge line 228. The flow of vapor along the purge line 228 may be regulated by a canister purge valve 212 coupled between the fuel vapor storage canister and the engine intake. The mass and rate of vapor released by the CPV 212 may be determined by the duty cycle of an associated canister purge valve solenoid (not shown). As such, the duty cycle of the canister purge valve solenoid may be determined by the controller 12 in response to engine operating conditions, such as engine speed-load conditions, air-fuel ratio, fuel vapor storage canister load, etc. By commanding the canister purge valve to close, the controller may seal off the evaporative emission system 219 from the engine intake. An optional canister check valve (not shown) may be included in the purge line 228 to prevent intake manifold pressure from causing gas to flow in the opposite direction of the purge flow. Thus, if the canister purge valve control is not timed accurately or the canister purge valve itself may be forced open due to high intake manifold pressure, the check valve may be beneficial. An estimate of manifold absolute pressure (MAP) or manifold vacuum (ManVac) may be obtained by controller 12 from a MAP sensor 240 coupled to the engine intake manifold 244. Alternatively, MAP may be inferred from alternative engine operating conditions such as mass air flow (MAF) as measured by a MAF sensor (not shown) coupled to the intake manifold.

[0057] Fuel system 218 and evaporative emission system 219 may be operated in a variety of modes by controller 12 by selectively adjusting various valves and solenoids. For example, fuel system and evaporative emission system may be operated in a fuel vapor storage mode (e.g., when the engine is not running), wherein controller 12 may maintain CVV 214 open while maintaining CPV 212 and FTIV 236 closed. In this way, fuel vapor may be prevented from flowing from fuel tank 220 to fuel vapor storage canister 222 and from fuel vapor storage canister 222 to engine intake manifold 244. As another example, fuel system and evaporative emission system may be operated in a refueling mode (e.g., when the vehicle operator requests refueling of the fuel tank), wherein controller 12 may open FTIV 236 while maintaining CVV 214 open and maintaining CPV 212 closed in order to depressurize the fuel tank and thereafter enable fuel to be added thereto. In this way, FTIV 236 may remain open during a refueling operation to allow refueling vapors to be stored in the fuel vapor storage canister. After refueling is complete, FTIV 236 may be closed. As yet another example, the fuel system and evaporative emissions system may be operated in a canister purge mode (e.g., after the emission control device light-off temperature has been reached and the engine is running), where controller 12 may open CPV 212 while maintaining CVV 214 open and maintaining FTIV 236 closed. Vacuum generated by engine intake manifold 244 may be used to draw fresh air through vent 227 and through fuel vapor storage canister 222 to purge stored fuel vapor into engine intake manifold 244. In this mode, fuel vapor purged from the canister is combusted in the engine. Purge may continue until the amount of fuel vapor in the canister is below a threshold.

[0058] During the purge, the learned vapor amount / concentration may be used to determine the fuel vapor stored in the fuel vapor storage canister, and then during a later portion of the purge operation (when the fuel vapor storage canister is sufficiently purged or empty), the learned vapor amount / concentration may be used to estimate the load state of the fuel vapor storage canister. For example, one or more oxygen sensors (not shown) may be coupled to the fuel vapor storage canister 222 (e.g., downstream of the fuel vapor storage canister) or positioned in the engine intake passage and / or the engine exhaust passage to provide an estimate of the fuel vapor storage canister load (i.e., the amount of fuel vapor stored in the fuel vapor storage canister). Based on the fuel vapor storage canister load and further based on engine operating conditions (such as engine speed-load conditions), a purge flow rate may be determined.

[0059] Control system 290 is shown receiving information from a plurality of sensors 16 (various examples of which are described herein) and sending control signals to a plurality of actuators 81 (various examples of which are also described herein). As one example, sensors 16 may include: exhaust gas sensor 226 located upstream of emission control device 270, temperature sensor 232 coupled to exhaust passage 235, MAP sensor 240, temperature sensor 217, hydrocarbon sensor 213, dP sensor 221, and pressure sensor 229 located downstream of emission control device 270. Other sensors (such as additional pressure, temperature, air-fuel ratio, and composition sensors) may be coupled to various locations in vehicle system 206. As another example, actuators 81 may include fuel injector 266, FTIV 236, CPV 212, CVV 214, fuel pump 234, vacuum pump 238, and intake throttle valve 262.

[0060] The control system 290 may further receive information about the location of the vehicle from an onboard global positioning system (GPS). The information received from the GPS may include vehicle speed, vehicle altitude, vehicle location, etc. This information may be used to infer engine operating parameters, such as local air pressure (e.g., barometric pressure). The control system 290 may further be configured to receive information via the Internet or other communication network. The information received from the GPS may be cross-referenced with information available via the Internet to determine local weather conditions, local vehicle regulations, etc. The control system 290 may use the Internet to obtain updated software modules, which may be stored in the non-transitory memory.

[0061] The controller 12 of the control system 290 may be configured as a conventional microcomputer, including a microprocessor unit, input / output ports, read-only memory, random access memory, keep-alive memory, a controller area network (CAN) bus, etc. The controller 12 may be configured as a powertrain control module (PCM). The controller may switch between a sleep mode and a wake-up mode to obtain additional energy efficiency. The controller may receive input data from various sensors, process the input data, and trigger actuators in response to the processed input data based on instructions or codes corresponding to one or more routines programmed therein, examples of which are referenced Figures 3 to 8 Give a description.

[0062] As mentioned above, to reduce vehicle cost, a single delta pressure sensor (eg, dP sensor 221) may be included to measure the pressure of a fuel system (eg, Figure 2 fuel system 218) and evaporative emission systems (e.g., Figure 2More specifically, the dP sensor may be across a fuel tank isolation valve (e.g., Figure 2 The output of the dP sensor (i.e., the pressure difference between the fuel tank side of the FTIV and the carbon canister side of the FTIV) can be, for example, based on Figures 3 to 8 Exemplary methods are provided for detecting FTIV degradation, detecting fuel tank side degradation, detecting canister side degradation and blockage, regulating fuel tank pressure during engine operation (eg, when the engine is on), and depressurizing the fuel tank for a refueling event.

[0063] First go to Figure 3 , a high-level flow chart of an exemplary method 300 for diagnosing components of an evaporative emissions system and a fuel system based on the output of a dP sensor is provided. As will be described below and with respect to Figures 4 to 7 As further elaborated, different components of the fuel system and the evaporative emissions system may be diagnosed based on whether the engine is on or off. Figures 3 to 7 approach, although it should be understood that Figures 3 to 7 The methods may also be performed independently of each other. Instructions for performing method 300 and the remaining methods included herein may be provided by a controller (e.g., Figure 2 The controller 12 is executed based on instructions stored in the memory of the controller and in conjunction with signals received from sensors of the engine, such as those described above with reference to Figure 1 to Figure 2 The sensors described (e.g. Figure 2 The controller may employ an actuator of the engine system (e.g., Figure 2 FTIV 236 and vacuum pump 238) to adjust engine operation. For example, Figure 3 Method 300 includes "passive" diagnostics of the FTIV and the fuel tank side of the FTIV using only the output of the dP sensor without making additional adjustments to the actuators of the fuel system and the evaporative emissions system. Therefore, portions of method 300 may be performed each time the engine is shut down and the controller receives output from the dP sensor.

[0064] Method 300 begins at 302 and includes evaluating operating parameters. The operating parameters may include, for example, a vehicle state, an engine state, an evaporative emissions system state, and a fuel system state. The vehicle state may refer to whether the vehicle is on or off, which may be determined based on, for example, the position of an ignition switch. The engine state may refer to whether the engine is on or off, and if the engine is on, the engine state may further refer to engine operating parameters such as engine speed, engine load, etc. If the engine is stationary (e.g., the engine speed is zero) and no combustion is occurring within the engine cylinders (e.g., no fuel is being supplied to the engine cylinders), then the engine may be off. The evaporative emissions system state may refer to an operating mode of the evaporative emissions system (such as a fuel vapor storage mode, a refueling mode, and a canister cleaning mode, as described above with respect to the evaporative emissions system). Figure 2 ), and / or various actuators of the evaporative emission system (such as a canister vent valve (e.g., Figure 2 CVV 214) and canister purge valve (e.g. Figure 2 The fuel system status may refer to whether the fuel system is sealed with the FTIV closed. In addition, the differential pressure between the evaporative emission system and the fuel system may be measured by a dP sensor. For example, if the CVV is kept open, thereby connecting the evaporative emission system to the atmosphere, the pressure of the evaporative emission system may be equal to the atmospheric pressure. Therefore, the fuel tank pressure may be determined relative to the atmospheric pressure based on the output from the dP sensor.

[0065] At 304, it is determined whether the engine is off. For example, when the vehicle is on and in a mode where only power is being supplied from the electric motor (e.g., Figure 1 The engine may be off when the vehicle is operating in an electric mode using torque from the motor 120 to propel the vehicle. In another example, the engine may be off when the vehicle is off (e.g., the vehicle's ignition switch is in the off position), but the controller may be operating in a wake-up mode, such as to perform diagnostic routines, transmit data, etc.

[0066] If the engine is not off, method 300 proceeds to 306 and includes checking the canister side for blockage. Blockage (e.g., obstruction) in the purge path or in the vent path of the evaporative emission system may degrade evaporative emission system performance, such as when a purge event is requested. Thus, when the engine is running, the purge path and the vent path may be evaluated for blockage to ensure that purge is performed optimally, such as by comparing the purge path and the vent path with respect to the evaporative emission system. Figure 6 to Figure 7 After 306 , method 300 ends.

[0067] In contrast, if the engine is off at 304, method 300 proceeds to 308 and includes maintaining the FTIV closed. Maintaining the FTIV closed prevents fuel vapor from flowing from the fuel tank to the evaporative emissions system, such as to the fuel vapor storage canister. In addition, maintaining the FTIV closed isolates the fuel tank side (also referred to herein as the tank side) from the canister side of the FTIV and seals the fuel tank. This can create a pressure differential between the sealed fuel tank and the canister side, which is vented to the atmosphere (e.g., through a vent line (such as a Figure 2 ventilation duct 227) and an open canister ventilation valve).

[0068] At 310, it is determined whether the dP sensor pressure measurement is greater than a first threshold or less than a second threshold, which are non-zero. As mentioned above, in the case where the canister side is open to the atmosphere, the dP sensor reading indicates the relative pressure of the fuel tank relative to the atmospheric pressure. Due to the volatility of the fuel, the fuel tank pressure is not expected to be equal to the atmospheric pressure. In addition, the pressure inside the fuel tank changes with temperature. For example, when the temperature increases and more fuel evaporates, the fuel tank pressure increases. As another example, when the temperature decreases and the fuel vapor condenses, the fuel tank pressure may decrease, thereby creating a vacuum (e.g., a negative pressure relative to the atmospheric pressure) inside the fuel tank. Therefore, the tank side pressure may fluctuate with diurnal temperature fluctuations. If the FTIV is open, thereby fluidly connecting the first pressure port of the dP sensor and the second pressure port of the dP sensor, the dP sensor will indicate a differential pressure of zero (e.g., no pressure difference). In addition, if there is degradation on the tank side of the FTIV, so that the fuel tank is connected to the atmosphere (e.g., the fuel tank is not completely sealed), the dP sensor will read a relative pressure of zero or close to zero. Thus, the first threshold may correspond to a threshold amount of non-zero positive pressure relative to atmospheric pressure (e.g., a positive pass threshold), above which a threshold amount indicates no degradation on the tank side of the FTIV or the FTIV itself. Similarly, the second threshold may correspond to a threshold amount of non-zero negative pressure (e.g., vacuum) relative to atmospheric pressure (e.g., a negative pass threshold), below which a threshold amount indicates no degradation on the tank side of the FTIV or the FTIV itself. In one non-limiting example, the first threshold is a differential pressure of 3 inches of H2O, and the second threshold is a differential pressure of -3 inches of H2O (e.g., a vacuum of 3 inches of H2O on the tank side relative to the canister side).

[0069] If the differential pressure measurement output by the dP sensor is greater than the first threshold or less than the second threshold (e.g., the relative pressure of the tank side versus the canister side is not between the first threshold and the second threshold), method 300 proceeds to 312 and includes indicating that tank-side degradation and FTIV degradation are not detected. In the event that the differential pressure measurement output by the dP sensor indicates that the fuel tank pressure is not approximately equal to the canister-side pressure (e.g., atmospheric pressure), it can be assumed that the fuel tank is sufficiently sealed from both the evaporative emission system and the atmosphere. Indicating that tank-side degradation and FTIV degradation are not detected may also include storing the indication at the controller (e.g., in a memory of the controller).

[0070] At 314, method 300 includes performing a canister side engine shutdown diagnostic, as will be described with reference to Figure 5 The canister side of the FTIV may be conclusively diagnosed without deterioration of the tank side and the FTIV. For example, if the FTIV has deteriorated and is stuck in the open position, the dP sensor may measure a differential pressure substantially equal to zero, which may result in an incorrect indication of degradation of the canister side of the FTIV. After 314, method 300 ends.

[0071] Conversely, if the differential pressure reading output by the dP sensor at 310 is not greater than the first threshold or less than the second threshold (e.g., the pressure difference between the tank side and the canister side is between the first threshold and the second threshold), method 300 proceeds to 316 and includes determining whether tank side degradation or FTIV degradation exists, as described below with respect to Figure 4 After 316, method 300 ends.

[0072] Continue to Figure 4 , shows an exemplary method 400 for detecting degradation of the fuel tank side of the FTIV and the FTIV itself and distinguishing between the two. The method 400 may be performed when the engine is off, for example as Figure 3 A portion of method 300 (eg, at 316) is performed. Figure 3 Method 300 includes a “passive” check of the fuel system and FTIV, while method 400 includes actively varying fuel system and evaporative emission system pressures, as described below.

[0073] Method 400 begins at 402 and includes closing the evaporative emission system's CVV and actuating the evaporative emission system's vacuum pump (eg, Figure 2 By actuating the CVV closed (and maintaining the evaporative emission system's canister purge valve and FTIV closed), the canister side of the FTIV may be sealed. For example, the vacuum pump may evacuate the evaporative emission system to a predetermined vacuum amount.

[0074] At 404, it is determined whether the dP sensor detects a canister side vacuum. When the FTIV is closed, the pressure on the canister side may decrease while the pressure on the canister side may remain constant, resulting in an increase in the differential pressure measured by the dP sensor. Specifically, the dP sensor measurement may indicate a canister side vacuum relative to the tank side. Therefore, detecting a canister side vacuum may refer to a differential pressure measured by the dP sensor being greater than or equal to a threshold, wherein the threshold corresponds to a non-zero differential pressure indicating that the canister side is under vacuum relative to the fuel tank side. In some examples, the threshold may be set based on a predetermined amount of vacuum applied by a vacuum pump, wherein the threshold increases as the predetermined amount of vacuum increases. For example, a controller may input the predetermined amount of vacuum applied by the vacuum pump into a lookup table or equation and output a corresponding threshold. In other examples, the threshold may be a constant predetermined value that is independent of the amount of vacuum applied by the vacuum pump.

[0075] If the FTIV is, such as when the FTIV is stuck in an open position (e.g., stuck and not degraded fully closed), the differential pressure measured by the dP sensor may be zero or near zero. Therefore, if the dP sensor does not detect a canister side vacuum (e.g., the differential pressure measured by the dP sensor is less than a threshold), method 400 proceeds to 406 and includes indicating that the FTIV is degraded. For example, in the event that the FTIV is degraded and stuck in an at least partially open position, the pressure at the first pressure port of the dP sensor (which is coupled to the tank side of the FTIV) and the pressure at the second pressure port (which is coupled to the canister side of the FTIV) may be the same, resulting in a differential pressure of zero. Indicating that the FTIV is degraded may include setting a diagnostic trouble code (DTC) at the controller, and may also include illuminating a malfunction indicator lamp (MIL) to alert the vehicle operator to service the vehicle. In addition, fuel vapor storage canister cleaning may be adjusted in response to an indication of FTIV degradation. For example, vacuum drawn from the fuel vapor storage canister during purging may be transmitted to the fuel tank through the degraded and at least partially open FTIV, resulting in additional fuel vapor being drawn through the open FTIV to the fuel vapor storage canister and ultimately to the engine intake. In the case of purging two fuel vapor sources (e.g., fuel vapor desorbed from the fuel vapor storage canister and fuel vapor from the fuel tank), the purge flow rate may be reduced to prevent engine stall. For example, the CPV may be adjusted to an open position that is further closed than when FTIV degradation is not indicated to reduce the purge flow rate.

[0076] At 408, method 400 includes deactivating the vacuum pump and opening the CVV. In this way, the evaporative emission system can be re-equilibrated to atmospheric pressure. By returning the evaporative emission system and the fuel system (via the degraded FTIV) to atmospheric pressure, less fuel can be evaporated than if the evaporative emission system and the fuel system were maintained under vacuum. After 408, method 400 ends.

[0077] However, if the dP sensor does not detect a canister side vacuum (e.g., a differential pressure greater than or equal to a threshold) at 404, indicating that the canister side and the box side are isolated from each other by the fully closed FTIV, the method 400 proceeds to 410 and includes opening and closing the FTIV at a predetermined duty cycle until the box side relative pressure decreases by a threshold amount. Each time the FTIV is opened, the evaporative emission system will evacuate the fuel system, thereby generating a reduced differential pressure after each opening of the FTIV (e.g., the box side pressure becomes more similar to the canister side pressure). In addition, each time the FTIV is opened, the dP sensor will read a differential pressure of zero or near zero because the pressure at the first pressure port of the dP sensor may be approximately equal to the pressure at the second pressure port of the dP sensor when the FTIV is open. Therefore, the differential pressure may be evaluated when the FTIV is closed. The threshold amount may be a non-zero differential pressure amount and may be determined based on a starting differential pressure before opening and closing the FTIV at a certain duty cycle. For example, the controller may input the starting differential pressure into a lookup table or equation and output the threshold amount.

[0078] Once the tank side relative pressure decreases by a threshold amount, at 412, method 400 includes maintaining the FTIV closed to isolate the tank side of the FTIV from the canister side of the FTIV. At 414, method 400 includes deactivating the vacuum pump and opening the CVV. In this way, the canister side can be re-equilibrated to atmospheric pressure while the tank side will remain under vacuum. By coupling the canister side of the FTIV to atmosphere, any degradation of the canister side that would prevent the canister side from maintaining vacuum will not affect the dP sensor reading.

[0079] At 416, method 400 includes determining a bleed-up threshold based on the relative tank side pressure after the canister side is balanced to atmosphere. In the case where the tank side is under vacuum and the canister side is at atmospheric pressure, the pressure at the first pressure port of the dP sensor (which is coupled to the tank side of the FTIV) is less than the pressure at the second pressure port (which is coupled to the canister side of the FTIV). When the dP sensor reading remains substantially constant (e.g., the rate of increase or decrease in differential pressure is approximately zero), it can be determined that the canister side is balanced to atmospheric pressure. The bleed-up threshold can refer to an increase in tank side pressure (e.g., a decrease in vacuum) that may occur over a certain duration, at or above which it can be inferred that the fuel tank side of the FTIV is not maintaining a vacuum, such as when air from the atmosphere is introduced into the fuel tank through an orifice or a disconnect. Therefore, the bleed-up threshold can be set for a predetermined amount of tank side pressure increase starting from a starting differential pressure (corresponding to the differential pressure after the canister side is balanced to atmosphere). Alternatively, a threshold rate of pressure relief may be determined, which may be a non-zero rate corresponding to a rate at which tank-side pressure would increase (eg, vacuum loss) if the fuel tank side of the FTIV were not fully sealed.

[0080] At 418, method 400 includes monitoring the differential pressure for the duration. The duration may be a predetermined duration, such as 30 seconds. With the canister side coupled to the atmosphere, the canister side pressure is not expected to change significantly. Therefore, changes in the differential pressure measured by the dP sensor may be attributed to changes in the tank side pressure, and the tank side pressure relative to atmospheric pressure may be inferred from the differential pressure measurement. In the illustrative example, if the differential pressure measured by the dP sensor is -10 inches H2O, then it may be inferred that the tank side pressure is -10 inches H2O relative to atmospheric pressure.

[0081] At 420, it is determined whether the tank side relative pressure is less than the bleed threshold after the duration has elapsed. If the tank side relative pressure remains less than the bleed threshold (or if the rate of pressure bleed is less than the threshold rate), method 400 proceeds to 422 and includes indicating that tank side degradation and FTIV degradation are not detected. Additionally, the results of the test may be stored at the controller, such as on a memory of the controller.

[0082] At 426, method 400 includes performing a canister side engine shutdown diagnostic, such as Figure 5 In the event that the FTIV is determined to be nominally functional (eg, not degraded), the dP sensor readings may be used to detect canister side degradation without potential FTIV degradation confounding their interpretation. After 426 , method 400 ends.

[0083] On the contrary, if the relative tank side pressure is greater than or equal to the discharge threshold (or the rate of pressure discharge is greater than or equal to the threshold rate) at 420, the method 400 proceeds to 424 and includes indicating tank side degradation. As mentioned above, in the case where the tank side relative pressure reaches the discharge threshold within the duration, it can be inferred that the fuel tank side of the FTIV is not completely sealed, so that air from the atmosphere enters the tank side through, for example, an orifice, thereby increasing the tank side pressure. Indicating tank side degradation may include setting a corresponding DTC at the controller, and may also include lighting up the MIL to alert the vehicle driver to come to service the vehicle. The method may then proceed to 426, because as long as the degradation of the FTIV is not indicated, the charcoal canister side may still be checked for degradation, even if the tank side is degraded. In addition, during the diurnal cycle, the FTIV may remain open in response to an indication of tank side degradation. For example, the fuel tank temperature that increases due to diurnal temperature and sun loading may increase fuel evaporation, thereby increasing the fuel tank pressure. In the presence of tank-side degradation, increased pressure may cause fuel vapor to escape to the atmosphere to relieve pressure. By keeping the FTIV open, less pressure may build up in the fuel tank and at least a portion of the fuel vapor will be directed to the fuel vapor storage canister rather than the atmosphere, thereby reducing vehicle emissions.

[0084] Next turn Figure 5 , shows an exemplary method 500 for a canister-side engine shutdown diagnostic test. Since degradation of the fuel vapor storage canister side of the FTIV can result in undesirable evaporative emissions, checking the canister side for degradation can help ensure that vehicle emissions remain within emission requirements. In some examples, method 500 can be used as Figure 3 Executed as part of method 300 (e.g., at 314) Figure 4 However, in other examples, whenever the conditions for the canister-side engine shutdown diagnostic test are met, the method 400 may be executed as a portion of the method 400 (eg, at 426). Figure 5 Method 500, as will be described below.

[0085] Method 500 begins at 502 and includes evaluating operating parameters. The operating parameters may include, for example, a vehicle state, an engine state, an evaporative emissions system state, and a fuel system state. The vehicle state may refer to whether the vehicle is on or off, which may be determined based on, for example, the position of an ignition switch. The engine state may refer to whether the engine is on (e.g., the engine has a non-zero speed and combustion is occurring in the engine cylinders) or off (e.g., the engine speed is zero and combustion is not occurring in the engine cylinders). The evaporative emissions system state may refer to an operating mode of the evaporative emissions system (such as a fuel vapor storage mode, a refueling mode, and a canister cleaning mode, as described above with respect to FIG. 1 ). Figure 2The status of the fuel system may refer to whether the fuel system is sealed with the FTIV closed, and / or whether any degradation is indicated in the fuel system. In addition, the differential pressure between the evaporative emission system and the fuel system may be measured by a dP sensor.

[0086] At 504, it is determined whether conditions for a canister side engine shutdown diagnostic test are met. Entry conditions for the canister side engine shutdown diagnostic test may include: the engine is off and there is no indication of FTIV degradation. Conditions may also include: no indication of other canister side degradation, such as an electrical short, vacuum pump degradation, and / or CVV degradation (such as a CVV stuck in an open position). In some examples, conditions may also include: the canister has recently (e.g., within a first predetermined duration) been degraded, such as according to Figure 3 and / or Figure 4 The exemplary method evaluates the FTIV and a second predetermined duration has elapsed since a previous canister side engine shutoff diagnostic test was initiated.

[0087] If the conditions for the canister side engine shutdown diagnostic test are not met, method 500 proceeds to 506 and includes maintaining current operating parameters. Maintaining current operating parameters may include not changing the control of evaporative emission system actuators (such as CVV, CPV, and vacuum pump). For example, if the CVV is currently open, it will not be commanded to close and will remain open. After 506, method 500 ends.

[0088] If the conditions for the canister side engine shutdown diagnostic test are met, method 500 proceeds to 508 and includes maintaining the FTIV and CPV closed and closing the CVV. For example, the FTIV will not be actuated to open. With the FTIV closed, the dP sensor output corresponds to the pressure difference between the fuel vapor storage canister side of the FTIV and the fuel tank side of the FTIV. In addition, the CPV will not be actuated to open, thereby isolating the evaporative emissions system from the intake manifold of the engine. Further, with the CVV commanded to close, the evaporative emissions system will be sealed off from the atmosphere. Therefore, the evaporative emissions system will be sealed off from the fuel system, the engine, and the atmosphere.

[0089] At 510, method 500 includes actuating the vacuum pump until the relative pressure on the canister side decreases by a threshold amount. For example, the pressure at the first pressure port of the dP sensor coupled to the fuel system may be higher than the pressure at the second pressure port of the dP sensor coupled to the evaporative emission system. As the vacuum pump evacuates the evaporative emission system, the pressure difference between the first pressure port and the second pressure port may increase. Thus, the threshold amount may correspond to a predetermined vacuum target (e.g., -10 inches H2O) to be applied to the canister side starting from a starting differential pressure. In an illustrative example, if the starting relative pressure is 5 inches H2O (e.g., the pressure on the tank side is 5 inches H2O higher than the pressure on the canister side) and the predetermined vacuum target is -10 inches H2O, the vacuum pump may be actuated until the dP sensor reads a relative pressure of 15 inches H2O (which means that the canister side pressure has decreased by 10 inches H2O relative to the tank side pressure).

[0090] At 512 , method 500 includes deactivating the vacuum pump. In the event that a target vacuum amount is achieved within the canister side, the vacuum pump may be deactivated in order to maintain the canister side at the target vacuum.

[0091] At 514, method 500 includes determining a bleed threshold based on the canister side relative pressure. The bleed threshold may refer to an increase in canister side relative pressure (e.g., a decrease in relative vacuum) that may occur over a certain duration, at or above which it may be inferred that the fuel vapor storage canister side of the FTIV is not maintaining a vacuum, such as when air from the atmosphere is introduced into the evaporative emission system through an orifice or disconnect. Thus, the bleed threshold may be set for a predetermined amount of canister side relative pressure increase from a starting differential pressure (e.g., the differential pressure when the vacuum pump is disabled). Alternatively, a threshold rate of pressure bleed may be determined, which may be a non-zero rate corresponding to a rate of canister side pressure increase (e.g., vacuum loss) of the FTIV indicating that the canister side of the FTIV is not fully sealed. Detailing the above illustrative example, if the dP sensor reads a differential pressure of 15 inches H2O when the vacuum pump is disabled, then for a canister side relative pressure of -15 inches H2O, the canister side pressure is 15 inches H2O less than the tank side pressure. The bleed threshold may be set to a differential pressure of 13 inches H2O corresponding to a canister-side relative pressure of -13 inches H2O, meaning the canister-side relative pressure may increase by less than 2 inches H2O in order to remain below the threshold.

[0092] At 516, method 500 includes monitoring the differential pressure for the duration. The duration may be a predetermined duration, such as 30 seconds. Although the tank-side pressure may fluctuate, such as due to diurnal temperature, the tank-side pressure is not expected to change significantly during the duration. Therefore, changes in the differential pressure measured by the dP sensor may be attributed to changes in the canister-side pressure.

[0093] At 518, it is determined whether the relative pressure on the canister side is less than a discharge threshold. If the relative pressure on the canister side is not less than the discharge threshold (or if the rate of pressure discharge is not less than a threshold rate), method 500 proceeds to 520 and includes indicating canister side degradation. For example, the canister side may not be sealed, allowing air to enter from the atmosphere through an orifice, a valve stuck in an open position (e.g., CVV or CPV), or a disconnect. Indicating canister side degradation may include setting a corresponding DTC at the controller, and may also include illuminating the MIL to alert the vehicle driver to service the vehicle. Additionally, in some examples, canister cleaning may be prohibited. For example, if the fuel vapor storage canister is cleaned when an orifice is present in the evaporative emissions system, unmetered air may enter through the orifice, causing the engine to operate lean. Therefore, cleaning may be prohibited until the vehicle is serviced and the DTC is cleared. Further, a tank side diagnostic test (such as based on Figure 4 Method 400) may not be performed when canister-side degradation is indicated. For example, canister-side degradation may confound tank-side diagnostic testing.

[0094] If at 518 the canister side relative pressure is less than the bleed threshold after the duration (or if the rate of pressure bleed is less than the threshold rate), method 500 proceeds to 522 and includes indicating that no canister side degradation is detected. Additionally, the results of the test may be stored at the controller, such as on a memory of the controller. The controller may then, for example, schedule a subsequent canister side engine shutdown diagnostic and / or update the purge schedule.

[0095] At 524, method 500 includes opening the CVV. In the event that the canister-side engine-off diagnostic test is completed, the CVV may be opened to couple the evaporative emissions system to atmosphere. In the event that the evaporative emissions system is coupled to atmosphere, the dP sensor reading may correspond to the pressure of the fuel tank relative to atmosphere, which may facilitate fuel tank pressure control, such as coupling relative to atmosphere. Figure 8 After 524, method 500 ends.

[0096] The canister-side engine-off diagnostic test described above can be used to detect degradation that prevents the evaporative emissions system from fully sealing, such as due to an orifice, a valve stuck in an open position, etc. However, the canister-side engine-off diagnostic test does not detect blockages that may exist in the evaporative emissions system that could degrade the fuel vapor storage canister purge operation. In one example, if the fuel vapor storage canister is coupled to a purge line in the engine intake (e.g., Figure 2If there is a blockage in the purge line 228 of the fuel vapor storage canister, fuel vapor may not be purged into the engine intake (or the purge flow rate may be reduced if flow is restricted). In another example, if there is a blockage in the vent passage coupling the fuel vapor storage canister to the atmosphere, fresh air may not be drawn across the fuel vapor storage canister during purge, which may result in incomplete fuel vapor storage canister cleaning.

[0097] Then turn to Figure 6 , an exemplary method 600 for detecting a blockage in a purge path of an evaporative emission system is provided. The purge path may include, for example, a purge line and a CPV. Figure 6 Method 600 may be performed at engine on using vacuum from the intake manifold, as will be described below. For example, method 600 may be performed in response to engine on as Figure 3 However, in other examples, whenever the conditions for evaluating the cleaning path are met, the cleaning path may be executed. Figure 6 Method 600, as will be described below.

[0098] Method 600 begins at 602 and includes evaluating operating parameters. The operating parameters may include, for example, a vehicle state, an engine state, an evaporative emissions system state, and a fuel system state. The vehicle state may refer to whether the vehicle is on or off, which may be determined based on, for example, the position of an ignition switch. The engine state may refer to whether the engine is on (e.g., the engine has a non-zero speed and combustion is occurring in the engine cylinders) or off (e.g., the engine speed is zero and combustion is not occurring in the engine cylinders), and if the engine is on, the engine state may further refer to engine operating parameters such as engine speed, engine load, manifold absolute pressure (MAP), etc. The evaporative emissions system state may refer to an operating mode of the evaporative emissions system (such as a fuel vapor storage mode, a refueling mode, and a canister cleaning mode, as described above with respect to FIG. 1 ). Figure 2 The status of the fuel system may refer to whether the fuel system is sealed with the FTIV closed, and / or whether any degradation is indicated in the fuel system. In addition, the differential pressure between the evaporative emission system and the fuel system may be measured by a dP sensor.

[0099] At 604, it is determined whether the conditions for evaluating the purge path are met. The conditions for evaluating the purge path may include, for example, the engine is on and there is no indication of FTIV degradation. The conditions may also include an indication of no canister side degradation, such as described above with respect to Figure 5Degradation described, electrical short, vacuum pump degradation, degradation of the CVV (such as a CVV stuck in an open position), and / or degradation of the CPV (such as a CPV stuck in a closed position). Conditions for evaluating the purge path may also include MAP being less than a threshold pressure, which refers to an amount of vacuum in the intake manifold sufficient to evaluate the purge path.

[0100] If the conditions for evaluating the purge path are not met, the method 600 proceeds to 606 and includes maintaining the operating parameters. Maintaining the operating parameters may include not changing the control of the evaporative emission system actuators (such as the CVV and CPV). For example, if the CVV is currently open, it will not be commanded to close and will remain open. After 606, the method 600 ends.

[0101] If the conditions for evaluating the purge path are met, method 600 proceeds to 608 and includes closing the CVV and opening the CPV. With the CPV open, the intake manifold may draw vacuum to the evaporative emissions system. Additionally, with the CVV closed, air may not be drawn across the fuel vapor storage canister, which may reduce the amount of fuel vapor that is desorbed from the adsorbent within the fuel vapor storage canister and purged to the intake manifold.

[0102] At 610, it is determined whether the relative vacuum on the canister side is greater than or equal to a threshold. The relative vacuum on the canister side may be determined based on the dP sensor measurement result. For example, the pressure at the first pressure port of the dP sensor connected to the fuel system may be higher than the pressure at the second pressure port of the dP sensor connected to the evaporative emission system. When the intake manifold evacuates the evaporative emission system, the pressure difference between the first pressure port and the second pressure port may increase. Although the tank side pressure may fluctuate, such as due to day and night temperature, the tank side pressure is not expected to change significantly during the cleaning path evaluation. Therefore, the change in the differential pressure measured by the dP sensor can be attributed to the change in the canister side pressure. As an illustrative example, if the dP sensor measures a differential pressure of 10 inches H2O, which indicates that the tank side pressure is 10 inches H2O higher than the canister side pressure, then the relative vacuum (e.g., negative pressure) on the canister side is 10 inches H2O. The threshold value may be a non-zero pressure value that may be determined based on a starting differential pressure (e.g., a differential pressure value just before closing the CVV and opening the CPV at 608) and a minimum amount of vacuum on the canister side that would be achieved without a purge path obstruction. Thus, the threshold value may be further determined based on MAP. For example, the controller may input the starting differential pressure and MAP into a lookup table or equation and output the threshold value. Determining whether the canister side relative vacuum is greater than or equal to the threshold value may also include determining whether the canister side relative vacuum reaches or exceeds the threshold value within a predetermined duration.

[0103] If the canister side relative vacuum is greater than or equal to the threshold (e.g., the canister side relative pressure is less than the threshold), method 600 proceeds to 612 and includes indicating that no purge path blockage is detected. For example, in the case where the purge path is not blocked (such as there is no blockage in the purge line and the CPV is fully open), the vacuum drawn from the intake manifold successfully evacuates the evaporative emission system to at least the threshold vacuum amount within a predetermined duration. Indicating that no purge path blockage is detected may include, for example, storing the result in a memory of the controller.

[0104] If the canister side relative vacuum is not greater than or equal to the threshold (e.g., the canister side relative pressure is greater than the threshold), method 600 proceeds to 614 and includes indicating that a purge path blockage is detected. A purge path blockage (such as a degraded CPV that is not fully open, or a blockage in the purge line) may, for example, prevent the intake manifold from evacuating the evaporative emission system or may reduce the rate at which the evaporative emission system is purged. Indicating a purge path blockage may include setting a corresponding DTC at the controller, and may also include illuminating the MIL to alert the vehicle operator to have the vehicle serviced. Additionally, canister purge may be prohibited until the vehicle is serviced and the DTC is cleared.

[0105] At 616, method 600 includes opening the CVV and closing the CPV. By opening the CVV, the evaporative emissions system can be connected to the atmosphere. In addition, by closing the CPV, the evaporative emissions system is isolated from the intake manifold. Therefore, the evaporative emissions system can be rebalanced to atmospheric pressure. After 616, method 600 ends.

[0106] Continue to Figure 7 , an exemplary method 700 for detecting a blockage in a ventilation path of an evaporative emission system is provided. The ventilation path may include, for example, a ventilation duct and a CVV, and an air filter (if included). Similar to Figure 6 Method 600, Figure 7 Method 700 may be performed using vacuum from the intake manifold when the engine is on. For example, method 700 may be performed in response to the engine being turned on as Figure 3 However, in other examples, whenever the conditions for evaluating the ventilation path are met, the method 300 may be executed as a part of the method 300 (e.g., at 306). Figure 7 Method 700, as will be described below.

[0107] Method 700 begins at 702 and includes evaluating operating parameters. The operating parameters may include, for example, a vehicle state, an engine state, an evaporative emissions system state, and a fuel system state. The vehicle state may refer to whether the vehicle is on or off, which may be determined based on, for example, the position of an ignition switch. The engine state may refer to whether the engine is on (e.g., the engine has a non-zero speed and combustion is occurring in the engine cylinders) or off (e.g., the engine speed is zero and combustion is not occurring in the engine cylinders), and if the engine is on, the engine state may further refer to engine operating parameters such as engine speed, engine load, MAP, etc. The evaporative emissions system state may refer to an operating mode of the evaporative emissions system (such as a fuel vapor storage mode, a refueling mode, and a canister cleaning mode, as described above with respect to FIG. 1 ). Figure 2 The status of the fuel system may refer to whether the fuel system is sealed with the FTIV closed, and / or whether any degradation is indicated in the fuel system. In addition, the differential pressure between the evaporative emission system and the fuel system may be measured by a dP sensor.

[0108] At 704, it is determined whether conditions for evaluating the ventilation path are met. Conditions for evaluating the ventilation path may include, for example, the engine is on and there is no indication of FTIV degradation. Conditions may also include an indication of no canister side degradation, such as described above with respect to Figure 5 Degradation as described, electrical short, vacuum pump degradation, CVV degradation (such as CVV stuck open), CPV degradation (such as CPV stuck closed), and / or purge path obstruction. Conditions for evaluating the ventilation path may also include MAP being less than a threshold pressure, which refers to an amount of vacuum in the intake manifold sufficient to evaluate the ventilation path.

[0109] If the conditions for evaluating the ventilation path are not met, the method 700 proceeds to 706 and includes maintaining the operating parameters. Maintaining the operating parameters may include not changing the control of the evaporative emission system actuators (such as the CVV and CPV). For example, if the CPV is currently closed, it will not be commanded to open and will remain closed. After 706, the method 700 ends.

[0110] If the conditions for evaluating the ventilation path are met, method 700 proceeds to 708 and includes opening the CPV while maintaining the CVV open. With the CPV open, the intake manifold may evacuate the evaporative emissions system. In addition, with the CVV open, fresh air may be drawn through the ventilation passage and across the fuel vapor storage canister, resulting in a smaller canister-side vacuum than the canister-side vacuum that may be generated when the CVV is closed. Thus, a limited amount of vacuum may be accumulated in the evaporative emissions system, which may be less than the vacuum amount before the evaporative emissions system reaches pressure equilibrium and the vacuum amount in the intake manifold remains substantially constant. However, if the ventilation path is blocked, fresh air may not be drawn into the evaporative emissions system, and vacuum may continue to accumulate, as will be described below.

[0111] At 710, method 700 includes monitoring the relative vacuum increase on the canister side. The relative vacuum on the canister side can be determined based on the dP sensor measurement results. For example, the pressure at the first pressure port of the dP sensor connected to the fuel system may be higher than the pressure at the second pressure port of the dP sensor connected to the evaporative emission system. When the intake manifold evacuates the evaporative emission system with the FTIV closed, the pressure difference between the first pressure port and the second pressure port may increase. Although the box side pressure may fluctuate, such as due to day and night temperature, the box side pressure is not expected to change significantly during the ventilation path evaluation. Therefore, the change in the differential pressure measured by the dP sensor can be attributed to the change in the canister side pressure. As an illustrative example, if the dP sensor measures a differential pressure of 10 inches H2O, which indicates that the box side pressure is 10 inches H2O higher than the canister side pressure, then the relative vacuum (e.g., negative pressure) on the canister side is 10 inches H2O. If the subsequent dP sensor output corresponds to a differential pressure of 12 inches H2O, then the relative vacuum on the canister side has increased by 2 inches H2O. If the subsequent dP sensor output corresponds to a differential pressure of 10 inches H2O, then the canister-side relative vacuum has not increased or decreased (e.g., remains stable). For example, monitoring the canister-side relative vacuum for an increase may include comparing a current canister-side relative vacuum measurement to an initial canister-side relative vacuum measurement (such as the canister-side relative vacuum just before opening the CPV) (e.g., at 708).

[0112] At 712 , method 700 includes determining whether canister side relative vacuum continues to increase after a threshold duration. The threshold duration may be a non-zero duration that refers to a maximum amount of time expected for the evaporative emissions system to reach pressure equilibrium if the vent path is not obstructed (e.g., no obstruction and the CVV is fully open).

[0113] If the canister side relative vacuum does not continue to increase after the threshold duration has elapsed (e.g., the canister side relative vacuum reaches a maximum value before the threshold duration and remains substantially constant), method 700 proceeds to 714 and includes indicating that no ventilation path obstruction is detected. For example, in the case of no obstruction in the ventilation path (such as no obstruction in the ventilation passage and the CVV is fully open), the vacuum drawn by the intake manifold may evacuate the evaporative emission system to a limited stable vacuum amount within a predetermined duration. Indicating that no ventilation path obstruction is detected may include, for example, storing the result on a memory of the controller.

[0114] If the relative vacuum on the canister side continues to increase after the threshold duration has elapsed, method 700 proceeds to 716 and includes indicating that a ventilation path blockage is detected. For example, the CVV may be degraded and stuck in an at least partially closed position, there may be a blockage in the ventilation passage, or if an air filter is included, for example, the air filter may be plugged. Such a blockage may prevent the evaporative emission system from reaching pressure equilibrium because the intake manifold may continue to evacuate the evaporative emission system without air (or insufficient air) flowing through the ventilation passage to maintain pressure. Indicating that the ventilation path is blocked may include setting a corresponding DTC at the controller, and may also include illuminating the MIL to alert the vehicle driver to come to service the vehicle. In addition, canister cleaning may be prohibited until the vehicle is serviced and the DTC is cleared. Further, the CPV may be opened during refueling to prevent premature closing of the refueling nozzle. For example, during refueling, refueling vapors may generate pressure in the fuel tank, which may be discharged to the evaporative emission system through the open FTIV. However, in the event that the ventilation path is blocked, the evaporative emission system may not be connected to the atmosphere, resulting in an increase in pressure in the evaporative emission system and the fuel system, which may prematurely close the refueling nozzle. Therefore, by opening the CPV, the evaporative emission system and the fuel system can be connected to the engine. If the vehicle's emission control device is warm (e.g., above its light-off temperature), the engine can be rotated without refueling (e.g., using a starter motor or an electric motor) to direct the refueling vapor toward the emission control device when refueling with the CPV open. If the emission control device is cold (e.g., the temperature of the emission control device is less than its light-off temperature), a spark can be provided while the engine is rotating to combust the refueling vapor. As an example, if the vehicle is an autonomous HEV and it is known a priori that a refueling event will be requested (e.g., within a certain duration), the controller can proactively start the engine so that the emission control device is heated to its light-off temperature before arriving at the refueling station.

[0115] At 718 , method 700 includes closing the CPV. With the CPV closed, the evaporative emissions system will be isolated from the engine intake, and the intake manifold will no longer draw vacuum on the evaporative emissions system. After 718 , method 700 ends.

[0116] In one example, Figures 3 to 7 The method may include: distinguishing degradation between each of a sealed fuel tank, an evaporative emission system, and a FTIV based on a differential pressure measured by a dP sensor coupled across the FTIV, the FTIV being positioned between the sealed fuel tank and a fuel vapor storage charcoal canister of the evaporative emission system. For example, when the engine is off and the FTIV is closed, in response to a differential pressure between a first higher threshold and a second lower threshold, the method may include: distinguishing degradation between the sealed fuel tank and the FTIV instead of the evaporative emission system. Distinguishing degradation between the sealed fuel tank and the FTIV may include: actuating a vacuum pump of the evaporative emission system to evacuate the evaporative emission system, and indicating degradation of the FTIV and non-degradation of the sealed fuel tank in response to the differential pressure remaining between the first higher threshold and the second lower threshold. For example, indicating degradation of the FTIV may include, for example, setting a corresponding DTC at a controller. In response to the differential pressure not remaining between the first higher threshold and the second lower threshold after actuating the vacuum pump, a vacuum may be applied to the sealed fuel tank by opening and closing the FTIV until the relative pressure of the sealed fuel is reduced by a first threshold amount based on the differential pressure measured by the dP sensor when the FTIV is closed. The relative pressure of the sealed fuel tank is then monitored using the dP sensor, and degradation of the sealed fuel tank and non-degradation of the FTIV are indicated in response to the relative pressure of the sealed fuel tank reaching or exceeding a third threshold value within a first predetermined duration. Indicating degradation of the sealed fuel tank may include, for example, setting a corresponding DTC at a controller. In addition, distinguishing degradation between each of the sealed fuel tank, the evaporative emission system, and the FTIV may include: closing a canister vent valve to seal the evaporative emission system from the atmosphere; actuating a vacuum pump until a relative pressure of the evaporative emission system determined based on a differential pressure measured by the dP sensor is reduced by a second threshold amount; and degradation of the evaporative emission system and non-degradation of the FTIV or degradation of the sealed fuel tank are indicated in response to the relative pressure of the evaporative emission system reaching or exceeding a fourth threshold value within a second predetermined duration. Indicating degradation of the evaporative emission system may include, for example, setting a corresponding DTC at a controller.

[0117] In another example, Figures 3 to 7The method may include: determining degradation of the FTIV, and in response thereto, setting a first DTC and not determining degradation of the fuel tank side of the FTIV or the fuel vapor storage canister side of the FTIV; determining degradation of the fuel tank side of the FTIV (which may not be degradation of the FTIV), and in response thereto, setting a second DTC; and determining degradation of the fuel vapor storage canister side of the FTIV (which may not be degradation of the FTIV or degradation of the fuel tank side of the FTIV), and in response thereto, setting a third DTC. In some examples, determining degradation of the fuel vapor storage canister side of the FTIV may occur simultaneously with or during the presence of degradation of the fuel tank side of the FTIV. As illustrated by way of example herein, methods of operating and performing actions in response to determining degradation may include operating in the presence of degradation of the FTIV, the fuel tank side of the FTIV, and / or the fuel vapor storage side of the FTIV (e.g., operating while the vehicle is moving and optionally while the engine is burning fuel), and operating in the absence of degradation of the FTIV, the fuel tank side of the FTIV, and / or the fuel vapor storage side of the FTIV.

[0118] In yet another example, Figures 3 to 7 The method may include: determining the presence or absence of a blockage in a purge path of the evaporative emission system, and determining the presence or absence of a blockage in a ventilation path of the evaporative emission system. In some examples, determining the presence or absence of a blockage in the purge path occurs when there is no blockage in the ventilation path, and determining the presence or absence of a blockage in the ventilation path occurs when there is no blockage in the purge path. In addition, the instructions stored in the memory may include: when the engine is running, sending a signal to open the canister purge valve, sending a signal to close the canister ventilation valve, and determining the presence or absence of a blockage in the purge path based on the output of the dP sensor. In another example, the instructions stored on the memory may include: when the engine is running, sending a signal to open the canister purge valve, and determining the presence or absence of a blockage in the ventilation path based on the output of the dP sensor.

[0119] Next, Figure 8 Shown is a method for using a single dP sensor (e.g. Figure 2 Example method 800 for regulating fuel tank pressure based on the output of a dP sensor 221 ) that is located across the FTIV (eg, Figure 2 The FTIV 236 of the embodiment of the present invention is coupled to the FTIV, which isolates the fuel system (eg, the fuel tank side of the FTIV) from the evaporative emission system (eg, the fuel vapor storage canister side of the FTIV). Figure 2The fuel tank 220 may be a sealed fuel tank of a NICROS as part of a hybrid vehicle system, for example. In this way, the vehicle's engine is rarely activated, so that the vehicle is more frequently propelled by torque from the electric motor (e.g., operating in an electric-only mode) rather than by torque from the engine. Additionally, when a refueling event is requested, if the fuel tank is pressurized relative to atmospheric pressure, the fuel tank may be placed in communication with an evaporative emissions system such that fuel vapors are directed to a fuel vapor storage canister (e.g., Figure 2 The fuel vapor storage canister 222 is provided to prevent the fuel vapor from being stored in the fuel port (e.g. Figure 2 When the fuel port 286 is opened, fuel mist is ejected from the fuel system.

[0120] Method 800 begins at 802 and includes evaluating operating parameters. The operating parameters may include, for example, a vehicle state, an engine state, an evaporative emissions system state, and a fuel system state. The vehicle state may refer to whether the vehicle is on or off, which may be determined based on, for example, the position of an ignition switch. The engine state may refer to whether the engine is on or off, and if the engine is on, the engine state may further refer to engine operating parameters such as engine speed, engine load, MAP, etc. If the engine is stationary (e.g., the engine speed is zero) and no combustion is occurring within the engine cylinders (e.g., no fuel is being supplied to the engine cylinders), then the engine may be off. The evaporative emissions system state may refer to an operating mode of the evaporative emissions system (such as a fuel vapor storage mode, a refueling mode, and a canister cleaning mode, as described above with respect to FIG. 8 ). Figure 2 ), and / or various actuators of the evaporative emission system (such as a canister vent valve (e.g., Figure 2 CVV 214) and canister purge valve (e.g. Figure 2 The fuel system status may refer to, for example, whether the fuel system is sealed with the FTIV closed, and the fuel level in the fuel tank. In addition, the differential pressure between the evaporative emission system and the fuel system may be measured by a dP sensor. For example, if the CVV is kept open, thereby connecting the evaporative emission system to the atmosphere, the pressure of the evaporative emission system may be equal to the atmospheric pressure. Therefore, the fuel tank pressure may be determined relative to the atmospheric pressure based on the output from the dP sensor.

[0121] At 804, it is determined whether the engine is off (eg, stationary and no combustion is occurring). For example, when the vehicle is on and in a mode where only power is being supplied from the electric motor (eg, Figure 1The engine may be off when the vehicle is operating in an electric mode using torque from the motor 120 to propel the vehicle. In another example, the engine may be off when the vehicle is off (e.g., the vehicle's ignition switch is in the off position), but the controller may be operating in a wake-up mode, such as to perform diagnostic routines, transmit data, etc.

[0122] If the engine is not shut down (e.g., the engine is on, such as combustion is ongoing, speed is above zero), method 800 proceeds to 806 and includes determining whether the tank side relative pressure is less than a first threshold. The first threshold may be a non-zero pressure value, above which the fuel tank pressure may reach the mechanical limit of the fuel tank. Therefore, in order to prevent degradation of the fuel tank, the fuel tank may be reduced to a pressure less than the threshold. In addition, by maintaining the pressure of the fuel tank at a pressure less than the first threshold, the fuel tank decompression during the refueling event may be accelerated, as will be further described below. The tank side relative pressure (e.g., the relative pressure of the fuel tank) may be determined using a dP sensor, wherein the dP sensor outputs a signal corresponding to the pressure difference between the fuel system and the evaporative emission system (e.g., the pressure of the fuel tank relative to the pressure of the evaporative emission system). In the case where the FTIV remains normally closed and the CVV remains normally open, thereby connecting the evaporative emission system to the atmosphere, the dP sensor reading may correspond to the tank side pressure relative to the atmospheric pressure. Therefore, the first threshold may refer to a predetermined threshold relative pressure above the atmospheric pressure.

[0123] If the tank-side relative pressure is less than the first threshold, the method 800 proceeds to 822 and includes maintaining the operating parameters. Maintaining the operating parameters may include not changing the control of the fuel system and the evaporative emission system actuators (such as the CVV, FTIV, and CPV). For example, in the case where the tank-side relative pressure is less than the first threshold, the fuel tank may be within its nominal operating pressure range and the fuel tank may not be in communication with the evaporative emission system. Thus, for example, the FTIV may not be actuated to open and will remain closed. After 822, the method 800 ends.

[0124] If the tank side relative pressure is not less than the first threshold (e.g., the tank side relative pressure is greater than or equal to the first threshold), method 800 proceeds to 808 and includes opening the CPV and adjusting the first threshold based on the new dP sensor measurement. By opening the CPV and maintaining the CVV open, vacuum from the engine's intake manifold due to natural engine aspiration can be directed to the fuel vapor storage canister (e.g., Figure 2 The fuel vapor storage canister 222 is used to draw fresh air from the atmosphere through the ventilation passages in the evaporative emission system (e.g., Figure 2227) and passes through the fuel storage vapor canister. By drawing fresh air across the fuel vapor storage canister, the stored fuel vapor can be desorbed and directed to the engine intake. In addition, when the CPV is open and the intake manifold evacuates the evaporative emission system, the canister side will no longer be at atmospheric pressure, causing the dP sensor measurement to change. For example, as the canister side pressure drops below atmospheric pressure, the pressure difference between the canister side of the FTIV and the fuel tank side of the FTIV can increase. Therefore, the first threshold can be increased by a corresponding amount. As an illustrative example, if the threshold is 10 inches H2O when the canister side is at atmospheric pressure, and the dP sensor reading increases from 15 inches H2O before the CPV is opened to 23 inches H2O after the CPV is opened, that is, a differential pressure increase of 8 inches H2O, then the threshold can be increased to 18 inches H2O. In this way, the first threshold can remain unchanged relative to the canister side pressure. The tank side pressure being greater than or equal to the first threshold is a first example of a fuel tank depressurization condition, which refers to a condition of the fuel tank that makes it necessary to vent the fuel tank to reduce the pressure (eg, depressurize the fuel tank), such as the pressure of the fuel tank.

[0125] In some examples, the first threshold may additionally or alternatively be adjusted based on MAP, which may be determined by a MAP sensor (eg, Figure 2 The controller may adjust the first threshold based on MAP, for example, where the first threshold increases as MAP decreases (e.g., the pressure difference between the canister side and the tank side may increase as manifold vacuum increases).

[0126] At 810, method 800 includes opening and closing the FTIV in a pulsating manner. Each time the FTIV is opened, the evaporative emissions system will evacuate the fuel system, thereby producing a reduced differential pressure (e.g., the tank side pressure becomes more similar to the canister side pressure) after each opening of the FTIV. In this way, the fuel tank pressure can be relieved. With the CPV open, fuel vapors from the fuel tank can be purged into the engine intake for combustion rather than stored in the fuel vapor storage canister (because the fuel vapor storage canister can be configured to store fuel vapor only during a fuel tank refueling event). In some examples, when the CPV is opened, a compensation factor can be determined to adjust the fuel command to correct for the inhalation of fuel vapors to maintain a desired air-fuel ratio (AFR). For this example, the fuel vapor concentration can be determined based on the output from an oxygen sensor, a hydrocarbon sensor, or any sensor that can give an indication of the fuel vapor concentration. In some examples, opening and closing the FTIV in a pulsating manner can include opening and closing the FTIV at a predetermined duty cycle.

[0127] Each time the FTIV is opened, the dP sensor will measure a differential pressure of zero or near zero because the pressure at the first pressure port of the dP sensor may be substantially equal to the pressure at the second pressure port of the dP sensor when the FTIV is open. Therefore, at 812, method 800 includes measuring the tank-side relative pressure when the FTIV is closed. For example, when the FTIV is opened and closed during pulsation, the differential pressure measurement output by the dP sensor each time the FTIV is closed can be used to determine the tank-side pressure relative to the canister-side pressure. Similarly, the differential pressure measurement output by the dP sensor when the FTIV is open cannot be used to determine the relative tank-side pressure. In addition, in some examples, the pulsation rate (or pulsation duty cycle) may be adjusted based on the differential pressure measured when the FTIV is closed (e.g., according to a predetermined duty cycle). Adjusting the FTIV pulsation may include adjusting the duration of each pulse and / or the interval between consecutive pulses. For example, the controller may input the relative pressure of the fuel tank (determined according to the differential pressure) and the first threshold into a lookup table, an algorithm, or an equation and output a corresponding pulsation rate (or pulsation duty cycle). As one example, the FTIV pulsation rate may decrease as the fuel tank relative pressure approaches a first threshold.

[0128] At 814, it is determined whether the tank side relative pressure is less than a first threshold value (as adjusted at 808). As described above, the tank side relative pressure may be measured by a dP sensor coupled across the FTIV when the FTIV is closed. If the tank side relative pressure is not less than the first threshold value, which means that there is still too much pressure on the tank side to be relieved (and the fuel tank decompression condition still exists), the method 800 returns to 810 and includes opening and closing the FTIV in a pulsating manner. Conversely, if the tank side relative pressure is less than the first threshold value, the method 800 proceeds to 816 and includes closing the FTIV (or maintaining it closed). In the event that the tank side relative pressure is less than the first threshold value, the fuel tank may still be within its nominal operating pressure range (and the fuel tank decompression condition no longer exists). By closing the FTIV, the fuel system will be isolated from the evaporative emissions system again, interrupting ventilation of the fuel tank.

[0129] At 818, method 800 includes closing the CPV. With the CPV closed, the evaporative emissions system will be isolated from the intake manifold and no vacuum will be drawn on the evaporative emissions system. The evaporative emissions system can be rebalanced to atmospheric pressure through the vents and the open CVV. After 818, method 800 ends.

[0130] Returning to 804, alternatively, if the engine is off, method 800 proceeds to 820 and includes determining whether a fuel tank refueling event is requested. A refueling event may be initiated by a vehicle operator, such as by depressing a refuel button on a dashboard of the vehicle (e.g., Figure 1Thus, the controller may receive a request for a refueling event from the vehicle driver via the refueling button.

[0131] If a refueling event is not requested, method 800 proceeds to 822 and includes maintaining operating parameters. For example, the fuel tank will not be depressurized for a refueling event. Therefore, the FTIV will not be actuated open and will remain closed. After 822, method 800 ends.

[0132] If a refueling event is requested, method 800 proceeds to 824 and includes determining whether the tank side is pressurized. For example, a dP sensor may be used to measure the tank side pressure relative to the canister side pressure. In the case where the canister side is connected to the atmosphere through an open CVV, the dP sensor measurement may indicate the tank side pressure relative to atmospheric pressure. If the dP sensor measurement indicates that the tank side pressure is greater than the canister side pressure (e.g., atmospheric pressure), it may be determined that the tank side is pressurized. As another example, if the tank side relative pressure is greater than or equal to a second threshold, it may be determined that the tank side is pressurized, and the second threshold may be less than the first threshold. The second threshold may refer to a second (smaller) non-zero predetermined threshold relative pressure above atmospheric pressure, such that if the tank side relative pressure is greater than or equal to the second threshold, the tank side is pressurized relative to atmospheric pressure. A tank side pressure greater than or equal to the second threshold in the case of a refueling event is a second example of a fuel tank decompression condition.

[0133] If the tank side is pressurized (e.g., the tank side relative pressure is greater than or equal to the second threshold), method 800 proceeds to 826 and includes opening and closing the FTIV in a pulsed manner. The FTIV may be opened and closed in a pulsed manner as described at 810, for example, to vent (e.g., depressurize) the fuel tank. Each time the FTIV is opened, fuel vapor may flow from the fuel tank to the fuel vapor storage canister (e.g., via conduit 231, as shown). Figure 2 As shown in FIG. 1 , at the fuel vapor storage canister, the fuel vapor may be adsorbed by the adsorbent in the fuel vapor storage canister. In addition, when the fuel vapor flows from the fuel tank to the fuel vapor storage canister through the open FTIV, the tank side pressure decreases.

[0134] At 828, method 800 includes measuring the tank side relative pressure when the FTIV is closed, as described above at 812. For example, when the FTIV is opened and closed during pulsation, each time the FTIV is closed, the differential pressure measurement result of the dP sensor can be used to determine the tank side pressure relative to the carbon canister side pressure. In addition, the tank side relative pressure measured when the FTIV is closed (rather than when the FTIV is open) can be used to adjust for pulsation, as also described above. The method can then return to 824 to determine whether the tank side is pressurized. Once the tank side is not pressurized (e.g., the tank side relative pressure is less than a second threshold, as measured when the FTIV is closed), method 800 proceeds to 830.

[0135] In the event that the fuel tank is depressurized at 830 (eg, depressurization conditions no longer exist), method 800 includes commanding (or maintaining) the FTIV to open. By opening the FTIV and maintaining it open, refueling vapors may be directed to the fuel vapor storage canister. Additionally, the CPV may remain closed throughout the depressurization and refueling process, thereby preventing fuel vapors from flowing to the intake manifold.

[0136] At 832, method 800 includes unlocking the fuel port to allow refueling. For example, the fuel port may remain locked and closed to prevent access to the refueling port (e.g., Figure 2 The FTIV may be unlocked to prevent refueling until the fuel tank has been depressurized. With the fuel port unlocked, the vehicle operator may open the fuel port and access the refueling port to refill the fuel tank. The FTIV may remain open throughout the refueling operation to allow refueling vapors (such as fuel vapors displaced by liquid fuel) to be vented to the fuel vapor storage canister.

[0137] At 834, it is determined whether the refueling event is complete. In one example, the refueling event may be determined to be complete when the vehicle operator has closed the fuel port (which may be indicated to the controller, for example, by a sensor). If the refueling event is not complete, such as if the fuel port remains open, the method 800 proceeds to 836 and includes continuing the refueling operation. In this way, the fuel port will not be locked and the FTIV will remain open. If the refueling event is complete, the method 800 proceeds to 838 and includes locking the fuel port. In this way, additional fuel tank refills may be prohibited until a subsequent refueling event is requested.

[0138] At 840 , method 800 includes closing the FTIV. With the FTIV closed, the fuel system may again be isolated from the evaporative emissions system. Closing the FTIV seals the fuel tank, thereby preventing additional fuel vapor from flowing to the fuel vapor storage canister. After 840 , method 800 ends.

[0139] So, in one example, Figure 8The method 800 may include: determining a decompression condition of a fuel tank included in an engine system and coupled to an evaporative emission system via a FTIV, and in response thereto, communicating the fuel tank with the evaporative emission system by opening and closing the FTIV in a pulsating manner; and determining when the decompression condition no longer exists, and in response thereto, interrupting the pulsation. In some examples, ventilating the fuel tank occurs when the decompression condition exists, and interrupting the pulsation occurs when the decompression condition does not exist. As a first example, the decompression condition is determined when the engine is turned on and in response to a relative pressure of the fuel tank being greater than or equal to a first higher threshold pressure (as measured by a dP sensor coupled across the FTIV when the FTIV is closed rather than when the FTIV is open). In the first example, interrupting the pulsation includes maintaining the FTIV closed. As a second example, the decompression condition is determined when the engine is turned off, in response to a relative pressure of the fuel tank being greater than or equal to a second lower threshold pressure, and further in response to receiving a request for a refueling event. In the second example, interrupting the pulsation includes maintaining the FTIV open.

[0140] Additionally, the instructions stored in the memory may include determining a depressurization condition based on a dP sensor coupled across the FTIV when the FTIV is closed (and independent of the dP sensor measurement when the FTIV is open), and in response, performing at least one of: opening and closing the FTIV in a pulsed manner via instructions for sending a signal to the FTIV, and opening the CPV via instructions for sending a different signal to the CPV of the evaporative emissions system. In some examples, the method may include determining whether to perform one or more of each of the action of sending a signal to the FTIV and the action of opening the CPV based on a determination of whether the engine is on or off and a determination of whether a fuel tank refueling event is requested.

[0141] As illustrated herein by way of example, a method of operating and performing an action in response to a determination of a fuel tank depressurization condition may include: operating under that condition (e.g., operating while the vehicle is moving and the engine is firing or while the vehicle and / or engine is stationary), determining whether that condition exists (such as based on the output of a dP sensor being greater than a threshold), and performing an action in response thereto; and operating when that condition does not exist, determining that that condition does not exist, and performing a different action in response thereto. For example, in response to the presence of a fuel tank depressurization condition, the fuel tank may be ventilated by opening and closing the FTIV in a pulsating manner, wherein the pulsation is adjusted based on the output of the dP sensor; and in response to the absence of fuel tank depressurization, the FTIV may be maintained closed. In another example, in response to a transition from the presence of a fuel tank depressurization condition to the absence of a fuel tank depressurization, and further in response to a request for a fuel tank refueling event, the FTIV may be maintained open, and the fuel port may be unlocked to enable access to the fuel tank.

[0142] Next, Fig. 9 A method for determining a fuel tank isolation valve in an engine system (e.g., Figure 2 Example timeline 900 of whether the FTIV 236 of the controller or the fuel tank side of the FTIV is degraded. For example, a controller (e.g., Figure 2 The controller 12) may be configured such as according to Figure 3 An exemplary method utilizes a delta pressure sensor (such as Figure 2 The output of the dP sensor 221) is used to "passively" diagnose the FTIV and the tank side of the FTIV. Figure 2 As described, when closed, the FTIV isolates a fuel system including a fuel tank from an evaporative emissions system including a fuel vapor storage canister. A first pressure port of the dP sensor is coupled to the tank side of the FTIV, while a second pressure port of the dP sensor is coupled to the canister side of the FTIV. The signal output by the dP sensor corresponds to a pressure difference between the first pressure port and the second pressure port (e.g., between the tank side and the canister side of the FTIV when closed). Thus, a controller may interpret the dP sensor measurements to determine whether to perform an active diagnostic test (such as Figure 4 An exemplary method of) is used to determine if there is degradation on the FTIV or tank side.

[0143] Graph 902 shows the dP sensor measurement results (eg, differential pressure measured by the dP sensor); Graph 904 shows the evaporative emission system canister purge valve (eg, Figure 2 906 shows the position of the FTIV; 908 shows the evaporative emission system canister ventilation valve (eg, Figure 2 910 shows the position of the evaporative emission system vacuum pump (eg, Figure 2 238); an indication of FTIV degradation is shown in graph 912; and an indication of tank-side degradation is shown in graph 914. For all of the above graphs, the horizontal axis represents time, where time increases from left to right along the horizontal axis. The vertical axis represents each labeled parameter. For graph 902, the dP sensor differential pressure measurement increases from bottom to top along the vertical axis. As noted, positive values ​​(e.g., values ​​above the horizontal axis) indicate tank-side pressure (P 箱 ) is greater than the canister side pressure (P 炭罐), while negative values ​​(e.g., values ​​below the horizontal axis) indicate that the tank side pressure is less than the canister side pressure. For graphs 904, 906, and 908, the vertical axis indicates whether each valve (CPV, FTIV, and CVV, respectively) is open or closed, where in this example, the marked closed position is fully closed and the marked open position is fully open. For graph 910, the vertical axis indicates whether the vacuum pump is on (activated) or off (deactivated). For graphs 912 and 914, the vertical axis indicates whether degradation of the FTIV or tank side is indicated ("yes" or "no"), respectively. In addition, dashed line 916a indicates the positive pass threshold for FTIV and tank side "passive" diagnosis, dashed line 916b indicates the negative pass threshold for FTIV and tank side "passive" diagnosis, dashed line 918 indicates the tank side vacuum threshold, and dashed line 920 indicates the tank side relative pressure relief threshold.

[0144] Throughout Fig. 9 In the exemplary timeline 900 of FIG. 1 , the engine is off (e.g., stationary, with no combustion occurring in the engine cylinders). Prior to time t1, the differential pressure between the tank side and the canister side of the FTIV (graph 902) is greater than the positive pass threshold (dashed line 916a), indicating that the tank side pressure is greater than the canister side pressure. In the event that the differential pressure is above the positive pass threshold, the controller may determine that the fuel tank is isolated from the atmosphere. For example, with the FTIV closed (graph 906) and the CVV open (graph 908), the tank side of the FTIV is isolated from the canister side of the FTIV, which is connected to the atmosphere (and therefore at atmospheric pressure) via the open CVV. Additionally, because the pressure on the tank side is not equal to atmospheric pressure, it may be inferred that the tank side is not degraded and is not connected to the atmosphere via, for example, a disconnect or orifice. Therefore, prior to time t1, the "passive" diagnostic indication does not detect degradation of the FTIV and tank side.

[0145] At time t1, the dP sensor measurement (graph 902) becomes below the positive pass threshold (dashed line 916a). With the tank side pressure approaching the canister side pressure, the "passive" diagnostic can no longer confirm that the FTIV and the tank side of the FTIV are not degraded. Therefore, at time t2, the CVV is commanded to close (graph 908) and the vacuum pump is activated (graph 910), while the CPV remains closed (graph 904). With both the CVV and CPV closed, the vacuum pump evacuates the canister side of the FTIV to the target vacuum amount. As shown in graph 902, as the canister side pressure decreases, the differential pressure increases due to the increase in the difference between the tank side pressure and the canister side pressure. The fact that the pressure differential increases when the canister side is evacuated indicates that the FTIV is closed, as commanded (graph 906). Therefore, the indication of FTIV degradation remains closed (graph 912). However, if, for example, the FTIV is degraded and stuck in the open position, the differential pressure may remain substantially equal to zero, as shown in dashed line segment 902a. Thus, if the differential pressure remains between the positive pass threshold and the negative pass threshold when the canister side is purged, FTIV degradation is indicated (dashed line segment 912a).

[0146] Once the canister side reaches the target vacuum amount, at time t3, the FTIV is opened and closed at a predetermined duty cycle until the relative pressure on the box side decreases by a threshold amount. For example, when the dP sensor measurement is at or below the box side emptying threshold (dashed line 918), the relative pressure on the box side may have decreased by a threshold amount, where the box side emptying threshold refers to a threshold amount of pressure reduction on the box side. Each time the FTIV is opened, the canister side will evacuate the box side, thereby generating a reduced differential pressure after each opening of the FTIV (e.g., the box side pressure becomes more similar to the canister side pressure). In addition, each time the FTIV is opened, the dP sensor reads a differential pressure of zero or near zero because the pressure at the first pressure port of the dP sensor may be approximately equal to the pressure at the second pressure port of the dP sensor when the FTIV is open. Therefore, the differential pressure can be evaluated when the FTIV is closed.

[0147] At time t4, in response to the differential pressure (graph 902) decreasing below the tank side venting threshold (dashed line 918), the FTIV is kept closed (graph 906), the vacuum pump is deactivated (graph 910), and the CVV is opened (graph 908). With the vacuum pump off and the CVV open, the canister side of the FTIV is connected to atmosphere while the tank side of the FTIV remains sealed and under vacuum. The canister side pressure increases above the tank side pressure, so the differential pressure drops below the horizontal axis, as shown in graph 902.

[0148] Once the canister side is rebalanced to atmospheric pressure and the dP sensor measurement is stable, at time t5, the tank side pressure relief threshold (dashed line 920) is set based on the current dP sensor measurement and the increase in the tank side relative pressure that the sealed fuel system can allow. When the canister side is connected to the atmosphere, the canister side pressure remains stable. Therefore, the change in differential pressure can be attributed to the change in tank side pressure. For example, the tank side pressure relief is monitored for a certain duration, where the duration ends at time t7. As shown in the graph 902, the differential pressure (and therefore the tank side relative pressure) remains below the tank side pressure relief threshold (dashed line 920), which indicates that the fuel tank side of the FTIV maintains a vacuum. Therefore, no tank side degradation is indicated (graph 914). On the contrary, if the differential pressure (e.g., the tank side relative pressure) exceeds the tank side pressure relief threshold before the duration has elapsed at time t7, such as shown by the dashed line segment 902b reaching the tank side pressure relief threshold at time t6, then tank side degradation can be indicated, as shown in the dashed line segment 914b.

[0149] Next, Fig.10 A method for determining a fuel tank isolation valve (e.g., Figure 2 Example timeline 1000 of whether the fuel vapor storage canister side of the FTIV 236 of the controller (eg, Figure 2 The controller 12) may be configured such as according to Figure 5 An exemplary method utilizes a delta pressure sensor (such as Figure 2 The output of the dP sensor 221 of the charcoal canister is used to determine whether there is deterioration (e.g., disconnection, orifice, etc.) in the charcoal canister side that may cause undesirable evaporative emissions. Figure 2 As described, when closed, the FTIV connects a fuel system including a fuel tank to an evaporative emissions system including a fuel vapor storage canister (eg, Figure 2 The dP sensor is isolated from the fuel vapor storage canister 222 of the FTIV. A first pressure port of the dP sensor is coupled to the tank side of the FTIV, and a second pressure port of the dP sensor is coupled to the canister side of the FTIV. The signal output by the dP sensor corresponds to the pressure difference at the first pressure port and the second pressure port (e.g., between the tank side and the canister side of the FTIV when closed). Therefore, the controller can use the dP sensor measurement results to determine whether the canister side can maintain a vacuum, as will be described below.

[0150] Graph 1002 shows the dP sensor measurement results (eg, differential pressure measured by the dP sensor); Graph 1004 shows the evaporative emission system canister purge valve (eg, Figure 21006 shows the position of the FTIV; Graph 1008 shows the evaporative emission system canister ventilation valve (eg, Figure 2 1010 shows the position of the CVV 214 of the evaporative emission system vacuum pump (eg, Figure 2 The activation state of the vacuum pump 238 of the dP sensor is shown; and the indication of the canister side degradation is shown in the graph 1012. For all of the above graphs, the horizontal axis represents time, where time increases from left to right along the horizontal axis. The vertical axis represents each labeled parameter. For graph 1002, the dP sensor differential pressure measurement increases from bottom to top along the vertical axis. As noted, positive values ​​(e.g., values ​​above the horizontal axis) indicate that the tank side pressure (P 箱 ) is greater than the canister side pressure (P 炭罐 ), while negative values ​​(e.g., values ​​below the horizontal axis) indicate that the tank side pressure is less than the canister side pressure. For graphs 1004, 1006, and 1008, the vertical axis indicates whether each valve (CPV, FTIV, and CVV, respectively) is open or closed. For graph 1010, the vertical axis indicates whether the vacuum pump is on (activated) or off (deactivated). For graph 1012, the vertical axis indicates whether degradation of the canister side of the FTIV is indicated ("yes" or "no"). In addition, dashed line 1014 indicates a canister side evacuation (e.g., vacuum) threshold, and dashed line 1016 indicates a canister side relative pressure relief threshold.

[0151] Throughout Fig.10 In exemplary timeline 1000 of FIG. 1 , the engine is off (eg, stationary, with no combustion occurring within the engine cylinders). Fig.10 In the example of FIG. 1 , before time t1 , the canister-side pressure is greater than the tank-side pressure because the differential pressure measurement is below the horizontal axis (graph 1002 ).

[0152] At time t1, the conditions for performing the canister side engine shutoff test are met, such as relative to Figure 5 As described, such as an indication of no FTIV degradation. Therefore, the CVV (graph 1008) is closed, thereby isolating the canister side from the atmosphere, while maintaining the CPV (graph 1004) and FTIV (graph 1006) closed. Therefore, at time t1, the canister side of the FTIV (e.g., evaporative emissions system) is sealed. Also at time t1, the vacuum pump (graph 1010) is activated to reduce the canister side relative pressure by a threshold amount, which can be satisfied when the dP sensor measurement reaches the canister side emptying threshold (dashed line 1014). Because the tank side pressure is not expected to change significantly during the canister side engine shutdown diagnostic test, any changes in the dP sensor measurement (graph 1002) can be attributed to changes in the canister side relative pressure.

[0153] Between time t1 and time t2, with the vacuum pump activated and the sealed evaporative emission system evacuated, the canister-side pressure decreases. First, the differential pressure decreases as the canister-side pressure approaches the (lower) tank-side pressure, and then, once the canister-side pressure decreases below the tank-side pressure (e.g., across the horizontal axis), the differential pressure decreases again as the canister-side relative vacuum increases.

[0154] At time t2, the differential pressure (graph 1002) reaches the canister side emptying threshold (dashed line 1014), indicating that the canister side pressure has decreased by a threshold amount. Therefore, the vacuum pump (graph 1010) is disabled, and the canister side pressure relief threshold (dashed line 1016) is set based on the current dP sensor measurement and the increase in the canister side relative pressure that the sealed evaporative emission system can allow. The controller can interpret the positive differential pressure measurement (graph 1002) as a negative canister side pressure (e.g., vacuum) relative to the box side pressure. Therefore, the reduction in differential pressure can be interpreted as an increase in the canister side relative pressure. In the case where the box side pressure is substantially constant, the change in differential pressure can be attributed to the change in the canister side pressure. The canister side pressure relief can be monitored for, for example, a certain duration, where the duration ends at time t4.

[0155] As shown by the differential pressure measurement (graph 1002) remaining above the canister side pressure relief threshold (dashed line 1016), the canister side relative pressure is less than the canister side pressure relief threshold, indicating that the canister side of the FTIV remains vacuum. Therefore, canister side degradation is not indicated (graph 1012). In contrast, if the canister side relative pressure exceeds the canister side pressure relief threshold before the duration has elapsed at time t4, such as indicated by the dashed line segment 1002a reaching the canister side pressure relief threshold at time t3, canister side degradation may be indicated, as shown by the dashed line segment 1012a.

[0156] At time t4, the CVV is opened (graph 1008), thereby connecting the evaporative emission system to the atmosphere. As a result, the canister side re-equilibrates to atmospheric pressure. As the canister side vacuum decreases and the canister side pressure approaches the tank side pressure, the dP sensor measurement (graph 1002) decreases. Then, when the canister side pressure exceeds the tank side pressure, the differential pressure measurement drops below the horizontal axis. For example, the differential pressure measurement may return to approximately the starting differential pressure measurement (e.g., the differential pressure on the canister side before the engine shutdown diagnostic test at time t1).

[0157] However, the canister side engine off test may not detect the presence of a blockage in the evaporative emissions system. Therefore, the controller may perform an engine on test using the vacuum generated by natural engine aspiration to assess for evaporative emissions system blockage, such as relative to Figure 6 to Figure 7 As described.

[0158] For example, Fig.11 A method for evaluating an evaporative emission system (e.g., Figure 2 1100 of a timeline of a purge path for coupling the evaporative emission system 219 to an intake manifold of an engine, the purge path including a purge line (eg, Figure 2 A cleaning pipeline 228) and a canister side cleaning valve (eg, Figure 2 CPV 212). Controller (e.g., Figure 2 The controller 12) may be configured such as according to Figure 6 An exemplary method utilizes a delta pressure sensor (such as Figure 2 The output of the dP sensor 221) is used to detect blockage in the cleaning path. Figure 2 As described, when closed, the FTIV connects a fuel system including a fuel tank to an evaporative emissions system including a fuel vapor storage canister (eg, Figure 2 The dP sensor is isolated from the fuel vapor storage canister 222 of the FTIV. A first pressure port of the dP sensor is coupled to the tank side of the FTIV, and a second pressure port of the dP sensor is coupled to the canister side of the FTIV. The signal output by the dP sensor corresponds to the pressure difference at the first pressure port and the second pressure port (e.g., between the tank side and the canister side of the FTIV when closed). Thus, the controller can use the dP sensor measurements to determine that there is a blockage in the purge path that can degrade the purge from the fuel vapor storage canister to the intake manifold.

[0159] dP sensor measurements (e.g., differential pressure measured by the dP sensor) are shown in graph 1102; the position of the CPV is shown in graph 1104; the position of the FTIV is shown in graph 1106; and the position of the evaporative emission system canister vent valve (e.g., Figure 2 CVV 214); and an indication of a blocked purge path is shown in graph 1110. For all of the above graphs, the horizontal axis represents time, where time increases from left to right along the horizontal axis. The vertical axis represents each labeled parameter. For graph 1102, the dP sensor differential pressure measurement increases from bottom to top along the vertical axis. As noted, positive values ​​(e.g., values ​​above the horizontal axis) indicate that the tank side pressure (P 箱 ) is greater than the canister side pressure (P 炭罐 ), while negative values ​​(e.g., values ​​below the horizontal axis) indicate that the tank side pressure is less than the canister side pressure. For graphs 1104, 1106, and 1108, the vertical axis indicates whether each valve (CPV, FTIV, and CVV, respectively) is open or closed. For graph 1110, the vertical axis indicates whether a purge path blockage is detected ("yes" or "no"). In addition, a dashed line 1112 indicates a canister side relative vacuum threshold.

[0160] Throughout Fig.11 In exemplary timeline 1100 of , the engine is on, the engine speed is above zero and combustion is occurring in the engine cylinders. In addition, the engine is operated with natural aspiration, thereby generating a manifold air pressure (MAP) (e.g., manifold vacuum) that is less than atmospheric pressure. Prior to time t1, the CPV is closed (graph 1104), thereby isolating the evaporative emissions system from the engine intake manifold; and the FTIV is closed (graph 1106), thereby isolating the canister side of the FTIV from the fuel tank side of the FTIV. In addition, the CVV is open (graph 1108), thereby connecting the canister side to the atmosphere. Therefore, the canister side is at atmospheric pressure. As shown in graph 1102, prior to time t1, the dP sensor measurement (graph 1102) indicates that the tank side pressure is greater than the canister side pressure. Therefore, the fuel tank pressure is above atmospheric pressure.

[0161] At time t1, the conditions for evaluating the cleaning path are met, such as relative to Figure 6 As described, such as an indication of no FTIV degradation. Therefore, the CPV is commanded to open (graph 1104), thereby coupling the canister side to the intake manifold; while the CVV is commanded to close (graph 1108), thereby isolating the canister side from the atmosphere. Therefore, the intake manifold evacuates the evaporative emission system, and fresh air is not drawn into the evaporative emission system through the vents and CVV. Also at time t1, a canister side relative vacuum threshold (dashed line 1112) is set based on the differential pressure measurement just before closing the CVV and opening the CPV and the minimum vacuum amount that the canister side will reach in the absence of a purge path obstruction, and the canister side relative vacuum threshold may be further based on MAP.

[0162] After time t1, the relative vacuum on the canister side is monitored. The relative vacuum on the canister side can be determined based on the dP sensor measurement results (graph 1102). For example, when the intake manifold evacuates the evaporative emission system, the pressure difference between the canister side of the FTIV and the tank side of the FTIV can increase. Although the tank side pressure may fluctuate, such as due to day and night temperature, the tank side pressure is not expected to change significantly during the cleaning path evaluation. Therefore, the change in the differential pressure measured by the dP sensor can be attributed to the change in the canister side pressure, and the controller can interpret the increase in the differential pressure as an increase in the relative vacuum on the canister side (e.g., a decrease in the relative pressure on the canister side).

[0163] At time t2, the canister side relative vacuum reaches the canister side relative vacuum threshold (dashed line 1112), as measured by the dP sensor (graph 1102). Therefore, the intake manifold is able to adequately evacuate the evaporative emission system, and no purge path blockage is indicated (graph 1110). With the purge path evaluation complete, the CPV is commanded to close (graph 1104) to isolate the evaporative emission system from the intake manifold, and the CVV is commanded to open (graph 1108) to connect the evaporative emission system to the atmosphere. The canister side pressure is rebalanced to atmospheric pressure, as shown by the dP sensor measurement (graph 1102) decreasing as the canister side vacuum decreases. For example, the differential pressure measurement may return to approximately the starting differential pressure measurement (e.g., the differential pressure before the purge path evaluation at time t1).

[0164] Conversely, if the purge path is blocked, the intake manifold may not sufficiently draw a canister-side vacuum to reach the canister-side relative vacuum threshold (dashed line 1112) within the threshold duration. For example, as shown by dashed line segment 1102a, the differential pressure (and therefore, the canister-side relative vacuum) may remain below the canister-side relative vacuum threshold. The controller may continue to monitor the canister-side relative vacuum until the threshold duration elapses at time t3, at which point a purge path blockage is indicated (dashed line segment 1110a). While the canister-side relative vacuum continues to be monitored prior to time t3, the CPV will remain open (dashed line segment 1104a) and the CVV will remain closed (dashed line segment 1108a).

[0165] Fig.12 A method for evaluating an evaporative emission system (e.g., Figure 2 An exemplary timeline 1200 of a ventilation path for coupling an evaporative emission system 219 to the atmosphere includes a ventilation duct (eg, Figure 2 The ventilation passage 227) and the canister side ventilation valve (for example, Figure 2 CVV 214). For example, a controller (e.g., Figure 2 The controller 12) may be configured such as according to Figure 7 An exemplary method utilizes a delta pressure sensor (such as Figure 2 The output of the dP sensor 221) is used to detect blockage in the ventilation path. Figure 2 As described, when closed, the FTIV connects a fuel system including a fuel tank to an evaporative emissions system including a fuel vapor storage canister (eg, Figure 2The dP sensor is isolated from the fuel vapor storage canister 222 of the intake manifold. A first pressure port of the dP sensor is coupled to the tank side of the FTIV, and a second pressure port of the dP sensor is coupled to the canister side of the FTIV. The signal output by the dP sensor corresponds to the pressure difference at the first pressure port and the second pressure port (e.g., between the tank side and the canister side of the FTIV when closed). Thus, the controller can use the dP sensor measurements to determine that there is a blockage in the ventilation path that can degrade fuel vapor storage canister purging to the intake manifold and fuel vapor storage during a refueling event.

[0166] Graph 1202 shows the dP sensor measurement results (eg, differential pressure measured by the dP sensor); Graph 1204 shows the evaporative emission system canister purge valve (eg, Figure 2 1202 ); the position of the FTIV is shown in graph 1206 ; the position of the CVV is shown in graph 1208 ; and an indication of a blocked ventilation path is shown in graph 1210 . For all of the above graphs, the horizontal axis represents time, where time increases from left to right along the horizontal axis. The vertical axis represents each labeled parameter. For graph 1202 , the dP sensor differential pressure measurements increase from bottom to top along the vertical axis. As noted, positive values ​​(e.g., values ​​above the horizontal axis) indicate a tank side pressure (P 箱 ) is greater than the canister side pressure (P 炭罐 ), while negative values ​​(e.g., values ​​below the horizontal axis) indicate that the tank side pressure is less than the canister side pressure. For graphs 1204, 1206, and 1208, the vertical axis indicates whether each valve (CPV, FTIV, and CVV, respectively) is open or closed. For graph 1210, the vertical axis indicates whether ventilation path blockage is detected ("yes" or "no").

[0167] Throughout Fig.12 In exemplary timeline 1200 of , the engine is on, the engine speed is above zero and combustion is occurring within the engine cylinders. In addition, the engine is operated with natural aspiration, thereby generating a manifold air pressure (MAP) (e.g., manifold vacuum) that is less than atmospheric pressure. Prior to time t1, the CPV is closed (graph 1204), thereby isolating the evaporative emissions system from the engine intake manifold; and the FTIV is closed (graph 1206), thereby isolating the canister side of the FTIV from the fuel tank side of the FTIV. In addition, the CVV is open (graph 1208), thereby connecting the canister side to the atmosphere. Therefore, the canister side is at atmospheric pressure. As shown in graph 1202, prior to time t1, the dP sensor measurement (graph 1202) indicates that the tank side pressure is greater than the canister side pressure. Therefore, the fuel tank pressure is above atmospheric pressure.

[0168] At time t1, the conditions for evaluating the ventilation path are met, such as relative to Figure 7 As described, there is no indication of FTIV degradation. Therefore, the CPV is commanded to open (graph 1204), thereby coupling the canister side to the intake manifold; while maintaining the CVV open (graph 1208). Therefore, the intake manifold evaporative emission system is evacuated, and fresh air is drawn into the evaporative emission system through the vent passage and the open CVV.

[0169] Starting from time t1, the relative vacuum on the charcoal canister side is monitored. The relative vacuum on the charcoal canister side can be determined based on the dP sensor measurement results (graph 1202). For example, when the intake manifold evacuates the evaporative emission system, the pressure difference between the charcoal canister side of the FTIV and the box side of the FTIV can increase. Although the box side pressure may fluctuate, such as due to day and night temperature, the box side pressure is expected to not change significantly during the ventilation path evaluation. Therefore, the change in the differential pressure measured by the dP sensor can be attributed to the change in the charcoal canister side pressure, and the controller can interpret the increase in the differential pressure as an increase in the relative vacuum on the charcoal canister side (e.g., a decrease in the relative pressure on the charcoal canister side). However, due to the open CVV and the fresh air entering the evaporative emission system through the ventilation path, a limited amount of vacuum can be accumulated in the evaporative emission system, which can be less than the vacuum amount before the evaporative emission system reaches pressure balance and the vacuum amount in the intake manifold remains substantially constant. However, if the ventilation path is blocked, fresh air may not be drawn into the evaporative emission system, and the vacuum may continue to accumulate. Therefore, the controller can monitor the relative vacuum on the charcoal canister side for a threshold duration.

[0170] At time t2, the threshold duration has elapsed. The relative vacuum on the canister side remains constant, as shown by the dP sensor measurement (curve 1202) remaining stable at time t2 and between time t2 and time t3. Therefore, the ventilation path is unobstructed, so that there is enough air flowing through the ventilation path to replace the air and vapor purged to the intake manifold, and there is no indication of ventilation path blockage (curve 1210). With the ventilation path evaluation completed, at time t3, the CPV is commanded to close (curve 1204) to isolate the evaporative emission system from the intake manifold. The canister side pressure is rebalanced to atmospheric pressure, as shown by the dP sensor measurement (curve 1202) decreasing as the canister side vacuum decreases. For example, the differential pressure measurement may return to approximately the starting differential pressure measurement (e.g., the differential pressure before the ventilation path evaluation at time t1).

[0171] Conversely, if the ventilation path is blocked, the canister-side relative vacuum may continue to increase as the intake manifold draws vacuum on the canister side and air is not drawn through the ventilation path. For example, as shown by dashed line segment 1202a, the differential pressure (and therefore, the canister-side relative vacuum) may remain below the canister-side relative vacuum threshold after the threshold duration has elapsed at time t2. Therefore, at time t3, a ventilation path blockage is indicated (dashed line segment 1210a). In addition, in the presence of ventilation path blockage, commanding the CVV to open at time t3 may not connect the evaporative emissions system to the atmosphere. Fig.12 In the example of , the canister side remains under vacuum and does not re-equilibrate to atmospheric pressure (dashed line segment 1202a). However, with the CPV closed, manifold vacuum does not continue to draw vacuum on the evaporative emission system, and therefore, the canister side relative vacuum may remain substantially constant.

[0172] As described herein, a single delta pressure sensor can be used not only to diagnose components of the evaporative emissions system and the fuel system, but also for fuel tank pressure control. Fig.13 , shows an exemplary timeline 1300 for controlling the pressure in the fuel tank during engine operation. For example, a controller (e.g., Figure 2 The controller 12) may be configured such as according to Figure 8 An exemplary method of utilizing a delta pressure sensor (such as a Figure 2 The fuel tank may be, for example, a sealed fuel tank included in a PHEV, such as part of a NIRCOS. Figure 2 As described, when closed, the FTIV isolates a fuel system including a fuel tank from an evaporative emissions system including a fuel vapor storage canister, which may be a "refuel only" fuel vapor storage canister. A first pressure port of the dP sensor is coupled to the tank side of the FTIV, and a second pressure port of the dP sensor is coupled to the canister side of the FTIV. The signal output by the dP sensor corresponds to the pressure difference at the first pressure port and the second pressure port (e.g., between the tank side and the canister side of the FTIV when closed). Thus, the controller may use the dP sensor measurements to determine whether to depressurize the fuel tank.

[0173] Graph 1302 shows the dP sensor measurement results (eg, differential pressure measured by the dP sensor); graph 1304 shows the evaporative emission system canister purge valve (eg, Figure 21304 ); and the position of the FTIV is shown in graph 1306 . For all of the above graphs, the horizontal axis represents time, where time increases from left to right along the horizontal axis. The vertical axis represents each labeled parameter. For graph 1302 , the dP sensor differential pressure measurement increases from bottom to top along the vertical axis. As noted, positive values ​​(e.g., values ​​above the horizontal axis) indicate tank side pressure (P 箱 ) is greater than the canister side pressure (P 炭罐 ), while negative values ​​(e.g., values ​​below the horizontal axis) indicate that the tank side pressure is less than the canister side pressure. For graphs 1304 and 1306, the vertical axis represents whether each valve (CPV and FTIV, respectively) is open or closed. In addition, the tank side relative pressure threshold is indicated by a dashed line 1308.

[0174] Throughout Fig.13 In exemplary timeline 1300 of FIG. 1 , the engine is on, the engine speed is above zero, and combustion is occurring in the engine cylinders. In addition, the engine is operating with natural aspiration, thereby generating a manifold air pressure (MAP) (e.g., manifold vacuum) that is less than atmospheric pressure. Prior to time t1, the CPV is closed (graph 1304), thereby isolating the evaporative emissions system from the engine intake manifold; and the FTIV is closed (graph 1306), thereby isolating the canister side of the FTIV from the fuel tank side of the FTIV. In addition, the canister vent valve (e.g., Figure 2 The CVV 214 of the charcoal tank 1300 remains open (not shown), thereby coupling the canister side to atmosphere. Therefore, the canister side is at atmospheric pressure, and the dP sensor measurement (graph 1302) indicates the tank side pressure relative to atmospheric pressure.

[0175] As shown in graph 1302, prior to time t1, the dP sensor measurements indicate that the tank-side pressure is greater than the canister-side pressure. Thus, the fuel tank pressure is above atmospheric pressure. Additionally, the tank-side relative pressure is greater than the tank-side relative pressure threshold (dashed line 1308), indicating that the fuel tank may be approaching a mechanical pressure threshold, above which fuel tank degradation may occur. Therefore, at time t1, the CPV is commanded to open (graph 1304) so ​​that the fuel tank pressure may be relieved.

[0176] After the CPV is opened at time t1, the dP sensor measurement (graph 1302) increases due to the intake manifold pulling a vacuum on the canister side of the FTIV, thereby reducing the canister side relative pressure. Therefore, the difference between the tank side pressure and the canister side pressure increases. As the canister side pressure (which is the reference pressure for the tank side relative pressure) changes, the tank side relative pressure threshold (dashed line 1308) increases at time t2 to reflect the change in differential pressure. For example, after the CPV is opened, once the dP sensor measurement is stable, the controller can adjust the tank side relative pressure threshold.

[0177] With the adjusted tank-side relative pressure threshold set, the FTIV is opened and closed in a pulsating manner (such as at a predetermined duty cycle) between time t2 and time t3 until the differential pressure (and therefore, the tank-side relative pressure) is less than the tank-side relative pressure threshold. For example, each time the FTIV is opened, the canister side will evacuate the tank side, thereby producing a reduced differential pressure after each opening of the FTIV (e.g., the tank-side pressure becomes more similar to the canister-side pressure). In addition, each time the FTIV is opened, the dP sensor reads a differential pressure of zero or near zero because the pressure at the first pressure port of the dP sensor may be approximately equal to the pressure at the second pressure port of the dP sensor when the FTIV is open. Therefore, the differential pressure may be evaluated when the FTIV is closed.

[0178] At time t3, the dP sensor measurement (graph 1302) is less than the tank side relative pressure threshold (dashed line 1308), indicating that the fuel tank has been sufficiently depressurized. Therefore, the FTIV is maintained closed (graph 1306) and the CPV is commanded to close (graph 1304), thereby isolating the evaporative emission system from the intake manifold. With the CPV closed and the CVV remaining open (not shown), the canister side re-equilibrates to atmospheric pressure, as shown by the decrease in the differential pressure (graph 1302). In addition, with the intake manifold no longer evacuating the canister side, the tank side relative pressure threshold (dashed line 1308) returns to the starting value, which is the canister side pressure threshold relative to atmospheric pressure. As shown in graph 1302, after the canister side is re-equilibrated to atmosphere, the dP sensor measurement is below the tank side relative pressure threshold and remains relatively stable.

[0179] Next, Fig.14 An exemplary timeline 1400 is shown for depressurizing a fuel tank for a refueling event (eg, a second example of a depressurization condition). For example, a controller (eg, Figure 2 The controller 12) may be configured such as according to Figure 8 An exemplary method of utilizing a delta pressure sensor (such as Figure 2The fuel tank may be, for example, a sealed fuel tank included in a PHEV. Figure 2 As described, when closed, the FTIV connects a fuel system including a fuel tank to a fuel vapor storage canister (eg, Figure 2 The dP sensor is configured to isolate the evaporative emissions system of the fuel vapor storage canister 222 of the FTIV, which may be a "refueling only" fuel vapor storage canister. A first pressure port of the dP sensor is coupled to the tank side of the FTIV, and a second pressure port of the dP sensor is coupled to the canister side of the FTIV. The signal output by the dP sensor corresponds to the pressure difference at the first pressure port and the second pressure port (e.g., between the tank side and the canister side of the FTIV when closed). Thus, the controller may use the dP sensor measurements during a refueling event to determine whether to depressurize the fuel tank.

[0180] dP sensor measurements (e.g., differential pressure measured by the dP sensor) are shown in graph 1402; an indication of a refueling request is shown in graph 1404; the position of the FTIV is shown in graph 1406; and the status of the fuel port is shown in graph 1408. For all of the above graphs, the horizontal axis represents time, where time increases from left to right along the horizontal axis. The vertical axis represents each labeled parameter. For graph 1402, the dP sensor differential pressure measurements increase from bottom to top along the vertical axis. As noted, positive values ​​(e.g., values ​​above the horizontal axis) indicate tank side pressure (P 箱 ) is greater than the canister side pressure (P 炭罐 ), while negative values ​​(e.g., values ​​below the horizontal axis) indicate that the tank side pressure is less than the canister side pressure. For graph 1404, the vertical axis indicates whether the fuel tank has been refueled, such as by the vehicle driver pressing the fuel button on the dashboard (e.g., Figure 1 For graph 1406, the vertical axis represents whether the FTIV is open or closed. For graph 1408, the vertical axis represents whether the fuel port is locked (which prevents opening the fuel tank and refueling) or unlocked (which enables opening the fuel tank and refueling).

[0181] Throughout Fig.14 In the exemplary timeline 1400 of FIG. 1400 , the engine is off, the engine is stationary, and no combustion occurs in the engine cylinders. Although not shown, it should be understood that throughout the timeline 1400 , the canister purge valve (e.g., Figure 2 The CPV 212 of the engine is kept closed, thereby isolating the evaporative emission system from the engine's intake manifold; and the canister ventilation valve (e.g., Figure 2 The CVV 214) remains open, thereby connecting the evaporative emissions system to the atmosphere.

[0182] Prior to time t1, the FTIV is closed (graph 1406), thereby isolating the canister side of the FTIV from the fuel tank side of the FTIV; and no refueling event is requested (graph 1404). Figure 2 The fuel port 286 of the fuel tank remains locked, thereby preventing access to the refueling port of the fuel tank (e.g., Figure 2 With the canister side connected to the atmosphere via an open CVV, the dP sensor measurements (graph 1402) indicate tank side pressure relative to atmospheric pressure. As shown in graph 1402, the tank side pressure is greater than the canister side pressure, and therefore, greater than atmospheric pressure.

[0183] At time t1, a refueling event is requested (graph 1404), such as by a vehicle operator. Because the tank-side pressure is greater than atmospheric pressure (e.g., greater than a threshold relative pressure above atmospheric pressure), the fuel port remains locked (graph 1408). To relieve the tank-side pressure, starting at time t2, the fuel tank is ventilated by opening and closing the FTIV in a pulsed manner, such as at a predetermined duty cycle (graph 1406). Each time the FTIV is opened, fuel vapor is directed from the fuel tank to the fuel vapor storage canister, such that a reduced differential pressure is generated after each opening of the FTIV (e.g., the tank-side pressure becomes more similar to the canister-side pressure). The fuel vapor is adsorbed by the adsorbent within the fuel vapor canister, and clean air (e.g., no fuel vapor) leaves through the open vent passage into the atmosphere, thereby maintaining the canister side at atmospheric pressure. In addition, each time the FTIV is opened, the dP sensor reads a differential pressure of zero or near zero because the pressure at the first pressure port of the dP sensor may be approximately equal to the pressure at the second pressure port of the dP sensor when the FTIV is open. Therefore, the differential pressure can be evaluated when the FTIV is closed.

[0184] At time t3, the fuel tank is fully depressurized such that the dP sensor measurement (graph 1402) shows a differential pressure of zero when the FTIV is closed. In response to the tank-side pressure being equal to the canister-side pressure (e.g., atmospheric pressure), at time t4, the FTIV is commanded to open (graph 1406) and the fuel port is unlocked (graph 1408). Thus, the vehicle operator can access the refueling port and refill the fuel tank. As fuel is added to the fuel tank, refueling vapors are directed through the open FTIV to the fuel vapor storage canister, where the refueling vapors are adsorbed by the adsorbent, and clean air is directed from the evaporative emissions system to the atmosphere through the open vent passage.

[0185] At time t5, the refueling event is complete, and therefore, no refueling event is requested (graph 1404). Therefore, the FTIV is commanded to close (graph 1406), thereby isolating the tank side of the FTIV from the canister side of the FTIV. Therefore, fuel vapor will no longer flow from the fuel tank to the fuel vapor storage canister. Additionally, the fuel port is locked (graph 1408), thereby preventing access to the refueling port until a subsequent refueling event is requested.

[0186] In this way, a single Δ pressure sensor is used in the NIRCOS system to determine a differential pressure across a FTIV that isolates a fuel tank of a fuel system from a fuel vapor storage canister of an evaporative emissions system. Specifically, the differential pressure can be measured when the FTIV is closed. The differential pressure can be used to determine the relative pressure or vacuum on the fuel tank side of the FTIV (e.g., of the fuel system), and the relative pressure or vacuum on the fuel vapor storage canister side of the FTIV (e.g., of the evaporative emissions system). In addition, the relative pressure measured by the Δ pressure sensor can be used for evaporative emissions system and fuel system diagnostic testing. The technical effect of a single Δ pressure sensor connected across a fuel tank isolation valve disposed between a fuel vapor storage canister of an evaporative emissions system and a fuel tank of a fuel system is that the differential pressure measured by the Δ pressure sensor can be used to check each of the fuel tank isolation valve, the fuel system, and the evaporative emissions system for degradation. In addition, the relative pressure of the fuel system can be used for fuel tank pressure control, such as by ventilating the fuel tank in response to the presence of a fuel tank decompression condition. By pulsating the opening and closing of the FTIV during ventilation and measuring the differential pressure only when the FTIV is closed, feedback can be maintained regarding the relative pressure on the fuel tank side of the FTIV, thereby allowing controlled and efficient fuel tank depressurization. The technical effect of measuring the differential pressure of the evaporative emission system using a single delta pressure sensor coupled across the fuel tank isolation valve disposed between the fuel vapor storage canister of the evaporative emission system and the fuel tank of the fuel system when the fuel tank isolation valve is closed rather than when the fuel tank isolation valve is open is that the relative fuel tank pressure can be determined from the measured differential pressure. Thus, a single delta pressure sensor can replace two pressure sensors (one coupled to the fuel system and one coupled to the evaporative emission system), thereby reducing vehicle cost.

[0187] As a first example, a method includes: venting a fuel tank by pulsating opening and closing a fuel tank isolation valve (FTIV) in response to a decompression condition determined based on a differential pressure measured by a delta pressure sensor coupled across the FTIV; and during the pulsation, adjusting the pulsation in response to the differential pressure measured when the FTIV is closed and independently of the differential pressure measured when the FTIV is open. In the previous example, additionally or alternatively, the FTIV is positioned in a conduit coupling the fuel tank to an evaporative emissions system, a first pressure port of the delta pressure sensor is fluidly coupled to the conduit between the FTIV and the fuel tank, and a second pressure port of the delta pressure sensor is fluidly coupled to the conduit between the FTIV and a fuel vapor storage canister of the evaporative emissions system. In any or all of the foregoing examples, additionally or alternatively, an unrestricted component is coupled between the fuel tank and the FTIV, and / or an unrestricted component is coupled between the fuel vapor storage canister and the FTIV. In any or all of the foregoing examples, additionally or alternatively, an unrestricted component is coupled between the first pressure port of the Δ pressure sensor and the fuel tank, and / or an unrestricted component is coupled between the second pressure port of the Δ pressure sensor and the fuel vapor storage canister. In any or all of the foregoing examples, additionally or alternatively, the decompression condition includes a relative pressure of the fuel tank being greater than or equal to a threshold relative pressure. In any or all of the foregoing examples, additionally or alternatively, the relative pressure of the fuel tank is determined based on the differential pressure measured when the FTIV is closed and is independent of the differential pressure measured when the FTIV is open, and the relative pressure of the fuel tank is the pressure of the fuel tank relative to the pressure of the evaporative emissions system. In any or all of the foregoing examples, additionally or alternatively, adjusting the pulsation includes reducing the pulsation rate when the relative pressure of the fuel tank approaches the threshold relative pressure. In any or all of the foregoing examples, additionally or alternatively, the evaporative emission system is coupled to the atmosphere via an open canister ventilation valve and isolated from the engine's intake passage by a closed canister purge valve, and the threshold relative pressure is a predetermined pressure value above atmospheric pressure. In any or all of the foregoing examples, the method additionally or alternatively further comprises: in response to the decompression condition and prior to the ventilation, opening the canister purge valve while maintaining the FTIV closed to couple the evaporative emission system to the engine intake passage, and adjusting the threshold relative pressure based on the differential pressure measured by the Δ pressure sensor; in response to the relative pressure of the fuel tank decreasing below the threshold relative pressure, interrupting the ventilation by maintaining the FTIV closed; and in response to the relative pressure of the fuel tank decreasing below the threshold relative pressure, closing the canister purge valve.In any or all of the foregoing examples, additionally or alternatively, the depressurization condition also includes receiving a request to refuel the fuel tank, and the method further includes: in response to the relative pressure of the fuel tank decreasing to below the threshold relative pressure, interrupting the pulsation by maintaining the FTIV open; in response to the relative pressure of the fuel tank decreasing to below the threshold relative pressure, unlocking the fuel port; and in response to completion of the refueling event, locking the fuel port and closing the FTIV.

[0188] As a second example, a method includes: measuring a differential pressure between a sealed fuel tank and an evaporative emission system using a Δ pressure sensor coupled across a fuel tank isolation valve (FTIV) when the FTIV is closed but not when the FTIV is open, the FTIV being positioned between the sealed fuel tank and a fuel vapor storage charcoal canister of the evaporative emission system; and depressurizing the sealed fuel tank in response to the measured differential pressure being greater than a threshold pressure. In the previous example, additionally or alternatively, the evaporative emission system is coupled to the atmosphere, and the measured differential pressure is a pressure of the sealed fuel tank relative to atmospheric pressure. In any or all of the foregoing examples, additionally or alternatively, the sealed fuel tank and the evaporative emission system are included in an engine system, an engine of the engine system is off, and the depressurizing the sealed fuel tank is further responsive to receiving a request for a refueling event. In any or all of the foregoing examples, additionally or alternatively, depressurizing the sealed fuel tank includes opening and closing the FTIV at a predetermined duty cycle, and the method further includes: in response to the measured differential pressure being less than the threshold pressure, unlocking the fuel port to enable the refueling event; maintaining the FTIV open to direct fuel vapor to the fuel vapor storage canister; and locking the fuel port and closing the FTIV in response to an indication that the refueling event is complete. In any or all of the foregoing examples, additionally or alternatively, the sealed fuel tank and the evaporative emission system are included in an engine system, the engine of the engine system is on, and depressurizing the sealed fuel tank includes: opening a canister purge valve of the evaporative emission system to purge fuel vapor from the fuel vapor storage canister to an intake passage of the engine; adjusting the threshold pressure based on a differential pressure measured after the canister purge valve is opened; opening and closing the FTIV at a predetermined duty cycle after adjusting the threshold pressure; and closing the CPV and maintaining the FTIV closed in response to the measured differential pressure decreasing below the adjusted threshold pressure.

[0189] As a third example, a system for a vehicle includes: an engine system, the engine system including an engine configured to propel the vehicle by burning air and fuel; a fuel system, the fuel system including a fuel tank for storing the fuel and a fuel port that prevents access to the fuel tank when locked; an evaporative emission system, the evaporative emission system is fluidly connected to the fuel system via a pipeline and is fluidly connected to the intake passage of the engine via a purge line, the pipeline including a fuel tank isolation valve (FTIV), the evaporative emission system including a fuel vapor storage canister; a canister ventilation valve, the canister ventilation valve is positioned in the ventilation passage of the evaporative emission system; a canister purge valve, the canister purge valve is positioned in the purge line; a Δ pressure sensor, the Δ pressure sensor is connected across the FTIV, the Δ pressure sensor is included in the fuel tank and the a first pressure port fluidly coupled to the conduit between the FTIV and a second pressure port fluidly coupled to the conduit between the fuel vapor storage canister and the FTIV; and a controller storing instructions in a non-transitory memory that, when executed, cause the controller to: measure a differential pressure between the fuel system and the evaporative emission system via the delta pressure sensor when the FTIV is closed but not when the FTIV is open; determine a relative pressure of the fuel system based on the measured differential pressure; vent the fuel tank when the engine is on in response to the relative pressure of the fuel system being greater than a first, higher threshold; and vent the fuel tank when the engine is off in response to both the relative pressure of the fuel system being greater than a second, lower threshold and receiving a request for a refueling event. In the previous example, additionally or alternatively, the FTIV is a normally closed valve, the canister purge valve is a normally closed valve, the canister vent valve is a normally open valve, and the fuel port is normally locked. In any or all of the foregoing examples, additionally or alternatively, ventilating the fuel tank when the engine is on includes: actuating the canister purge valve to open; adjusting the first higher threshold based on the differential pressure measured after actuating the canister purge valve to open; opening and closing the FTIV in a pulsating manner at a predetermined duty cycle; adjusting the predetermined duty cycle based on the relative pressure of the fuel system; and during the pulsation, maintaining the FTIV closed in response to the relative pressure of the fuel system decreasing to below the adjusted first higher threshold.In any or all of the foregoing examples, additionally or alternatively, venting the fuel tank when the engine is off includes: opening and closing the FTIV in a pulsating manner at a predetermined duty cycle; adjusting the predetermined duty cycle based on the relative pressure of the fuel system during the pulsating; maintaining the FTIV open in response to the relative pressure of the fuel system decreasing below the second lower threshold during the pulsating; and unlocking the fuel port in response to the relative pressure of the fuel system decreasing below the second lower threshold during the pulsating. In any or all of the foregoing examples, additionally or alternatively, the controller stores additional instructions in a non-transitory memory that, when executed, cause the controller to: close the FTIV and lock the fuel port in response to completion of the refueling event.

[0190] In another representation, a method for an engine includes determining a relative pressure of a fuel system based on a differential pressure measured by a delta pressure sensor coupled across a fuel tank isolation valve (FTIV) when the FTIV is closed but not when the FTIV is open; and responsive to the relative pressure of the fuel system indicating a fuel tank depressurization condition, opening and closing the FTIV in a pulsed manner. In a first example, the fuel tank depressurization condition includes the relative pressure of the fuel tank being greater than or equal to a first, higher threshold pressure when the engine is on. In a second example, the fuel tank depressurization condition includes the relative pressure of the fuel tank being greater than or equal to a second, lower threshold pressure when the engine is off and when a fuel tank refueling event is requested.

[0191] It should be noted that the exemplary control and estimation routines included herein can be used with various engine and / or vehicle system configurations. The control methods and routines disclosed herein can be stored as executable instructions in a non-temporary 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, intermittently driven, multi-tasking, multi-threading, etc.). In this way, the various actions, operations and / or functions shown can be performed in the order shown, can be performed in parallel, or in some cases, can be omitted. Similarly, the processing order is not necessarily required to achieve the features and advantages of the exemplary embodiments described herein, but is provided for ease of illustration and description. One or more of the actions, operations and / or functions shown can be repeatedly performed according to the specific strategy used. In addition, the described actions, operations and / or functions can graphically represent the code in the non-temporary memory of the computer-readable storage medium to be programmed into the engine control system, wherein the described actions are implemented by executing the instructions in a system including various engine hardware components in combination with an electronic controller.

[0192] It should be understood that the configurations and routines disclosed herein are exemplary in nature, and these specific embodiments should not be considered in a limiting sense, as many variations are possible. For example, the above technology can be applied to V-6, inline 4, inline 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 characteristics disclosed herein.

[0193] The following claims particularly point out certain combinations and subcombinations that are considered 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 the 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 characteristics may be claimed by amendment of the present claims or by presenting new claims in this or a related application. Such claims are also considered to be included in the subject matter of the present disclosure, whether broader, narrower, the same, or different in scope than the original claims.

[0194] According to the present invention, a method is provided, comprising: ventilating a fuel tank by pulsatingly opening and closing a fuel tank isolation valve (FTIV) in response to a decompression condition determined based on a differential pressure measured by a delta pressure sensor coupled across the FTIV; and during the pulsation, adjusting the pulsation in response to the differential pressure measured when the FTIV is closed and independently of the differential pressure measured when the FTIV is open.

[0195] According to one embodiment, the FTIV is positioned in a conduit coupling the fuel tank to an evaporative emissions system, a first pressure port of the delta pressure sensor is fluidly coupled to the conduit between the FTIV and the fuel tank, and a second pressure port of the delta pressure sensor is fluidly coupled to the conduit between the FTIV and a fuel vapor storage canister of the evaporative emissions system.

[0196] According to one embodiment, an unrestricted component is coupled between the fuel tank and the FTIV and / or an unrestricted component is coupled between the fuel vapor storage canister and the FTIV.

[0197] According to one embodiment, an unrestricted component is coupled between the first pressure port of the delta pressure sensor and the fuel tank and / or an unrestricted component is coupled between the second pressure port of the delta pressure sensor and the fuel vapor storage canister.

[0198] According to one embodiment, the decompression condition comprises a relative pressure of the fuel tank being greater than or equal to a threshold relative pressure.

[0199] According to one embodiment, the relative pressure of the fuel tank is determined based on the differential pressure measured when the FTIV is closed and independently of the differential pressure measured when the FTIV is open, and the relative pressure of the fuel tank is the pressure of the fuel tank relative to the pressure of the evaporative emissions system.

[0200] According to one embodiment, said adjusting said pulsation comprises: reducing the pulsation rate when said relative pressure of said fuel tank approaches said threshold relative pressure.

[0201] According to one embodiment, the evaporative emissions system is coupled to atmosphere via an open canister vent valve and isolated from an intake tract of the engine by a closed canister purge valve, and the threshold relative pressure is a predetermined pressure value above atmospheric pressure.

[0202] According to one embodiment, the above invention is further characterized in that: in response to the decompression condition and before the ventilation, the canister purge valve is opened while maintaining the FTIV closed to connect the evaporative emission system to the engine intake passage, and the threshold relative pressure is adjusted based on the differential pressure measured by the Δ pressure sensor; in response to the relative pressure of the fuel tank decreasing to below the threshold relative pressure, the ventilation is interrupted by maintaining the FTIV closed; and in response to the relative pressure of the fuel tank decreasing to below the threshold relative pressure, the canister purge valve is closed.

[0203] According to one embodiment, the depressurization condition also includes receiving a request to refuel the fuel tank, and the method further includes: in response to the relative pressure of the fuel tank decreasing to below the threshold relative pressure, interrupting the pulsation by maintaining the FTIV open; in response to the relative pressure of the fuel tank decreasing to below the threshold relative pressure, unlocking the fuel port; and in response to completion of the refueling event, locking the fuel port and closing the FTIV.

[0204] According to the present invention, a method is provided, which includes: measuring the differential pressure between a sealed fuel tank and an evaporative emission system using a Δ pressure sensor connected across a fuel tank isolation valve (FTIV) when the FTIV is closed rather than when the FTIV is open, the FTIV being positioned between the sealed fuel tank and a fuel vapor storage charcoal canister of the evaporative emission system; and depressurizing the sealed fuel tank in response to the measured differential pressure being greater than a threshold pressure.

[0205] According to one embodiment, the evaporative emission system is coupled to atmosphere and the measured differential pressure is the pressure of the sealed fuel tank relative to atmospheric pressure.

[0206] According to one embodiment, the sealed fuel tank and the evaporative emissions system are included in an engine system, an engine of the engine system is shut down, and the depressurizing the sealed fuel tank is further responsive to receiving a request for a refueling event.

[0207] According to one embodiment, depressurizing the sealed fuel tank includes opening and closing the FTIV at a predetermined duty cycle, and the method further includes: in response to the measured differential pressure being less than the threshold pressure, unlocking the fuel port to enable the refueling event; maintaining the FTIV open to direct fuel vapor to the fuel vapor storage canister; and locking the fuel port and closing the FTIV in response to an indication that the refueling event is complete.

[0208] According to one embodiment, the sealed fuel tank and the evaporative emission system are included in an engine system, the engine of the engine system is turned on, and the depressurizing of the sealed fuel tank includes: opening a canister purge valve of the evaporative emission system to purge fuel vapor from the fuel vapor storage canister to an intake passage of the engine; adjusting the threshold pressure based on a differential pressure measured after the canister purge valve is opened; opening and closing the FTIV at a predetermined duty cycle after adjusting the threshold pressure; and closing the CPV and maintaining the FTIV closed in response to the measured differential pressure decreasing below the adjusted threshold pressure.

[0209] According to the present invention, a system for a vehicle is provided, which has: an engine system, the engine system including an engine configured to propel the vehicle by burning air and fuel; a fuel system, the fuel system including a fuel tank for storing the fuel and a fuel port that prevents access to the fuel tank when locked; an evaporative emission system, the evaporative emission system is fluidly connected to the fuel system via a pipeline and is fluidly connected to the intake passage of the engine via a purge line, the pipeline including a fuel tank isolation valve (FTIV), the evaporative emission system including a fuel vapor storage canister; a canister ventilation valve, the canister ventilation valve is positioned in the ventilation passage of the evaporative emission system; a canister purge valve, the canister purge valve is positioned in the purge line; a Δ pressure sensor, the Δ pressure sensor is connected across the FTIV, the Δ pressure sensor is included in the fuel tank and the a first pressure port fluidly coupled to the conduit between the FTIV and a second pressure port fluidly coupled to the conduit between the fuel vapor storage canister and the FTIV; and a controller storing instructions in a non-volatile memory that, when executed, cause the controller to: measure a differential pressure between the fuel system and the evaporative emission system via the Δ pressure sensor when the FTIV is closed but not when the FTIV is open; determine a relative pressure of the fuel system based on the measured differential pressure; ventilate the fuel tank in response to the relative pressure of the fuel system being greater than a first, higher threshold when the engine is on; and ventilate the fuel tank in response to both the relative pressure of the fuel system being greater than a second, lower threshold and receiving a request for a refueling event when the engine is off.

[0210] According to one embodiment, the FTIV is a normally closed valve, the canister purge valve is a normally closed valve, the canister vent valve is a normally open valve, and the fuel port is normally locked.

[0211] According to one embodiment, ventilating the fuel tank when the engine is on includes: actuating the canister purge valve to open; adjusting the first higher threshold based on the differential pressure measured after actuating the canister purge valve to open; opening and closing the FTIV in a pulsating manner at a predetermined duty cycle; adjusting the predetermined duty cycle based on the relative pressure of the fuel system; and during the pulsation, maintaining the FTIV closed in response to the relative pressure of the fuel system decreasing to below the adjusted first higher threshold.

[0212] According to one embodiment, venting the fuel tank when the engine is off includes: opening and closing the FTIV in a pulsating manner at a predetermined duty cycle; adjusting the predetermined duty cycle based on the relative pressure of the fuel system during the pulsation; maintaining the FTIV open in response to the relative pressure of the fuel system decreasing below the second lower threshold during the pulsation; and unlocking the fuel port in response to the relative pressure of the fuel system decreasing below the second lower threshold during the pulsation.

[0213] According to one embodiment, the controller stores additional instructions in non-transitory memory that, when executed, cause the controller to: close the FTIV and lock the fuel port in response to completion of the refueling event.

Claims

1. A method comprising: Operate under reduced pressure; venting the fuel tank by opening and closing the FTIV in a pulsed manner multiple times in response to the depressurized condition determined based on a differential pressure measured by a single delta pressure sensor coupled across a fuel tank isolation valve FTIV; as well as During the ventilation, the pulsation is adjusted in response to differential pressures repeatedly measured during multiple closures of the FTIV of the pulsation and independent of differential pressures measured when the FTIV is open during the pulsation.

2. The method of claim 1 , wherein the FTIV is positioned in a conduit coupling the fuel tank to an evaporative emissions system, a first pressure port of the delta pressure sensor is fluidly coupled to the conduit between the FTIV and the fuel tank, and a second pressure port of the delta pressure sensor is fluidly coupled to the conduit between the FTIV and a fuel vapor storage canister of the evaporative emissions system. 3 . The method of claim 2 , wherein an unrestricted component is coupled between the fuel tank and the FTIV and / or an unrestricted component is coupled between the fuel vapor storage canister and the FTIV. 4 . The method of claim 2 , wherein an unrestricted component is coupled between the first pressure port of the delta pressure sensor and the fuel tank and / or an unrestricted component is coupled between the second pressure port of the delta pressure sensor and the fuel vapor storage canister. 5 . The method of claim 2 , wherein the depressurization condition comprises a relative pressure of the fuel tank being greater than or equal to a threshold relative pressure.

6. The method of claim 5, wherein the relative pressure of the fuel tank is determined based on the differential pressure measured when the FTIV is closed and independent of the differential pressure measured when the FTIV is open, and the relative pressure of the fuel tank is the pressure of the fuel tank relative to the pressure of the evaporative emissions system.

7. The method of claim 6, wherein said adjusting said pulsation comprises: A pulsation rate is reduced when the relative pressure of the fuel tank approaches the threshold relative pressure.

8. The method of claim 6, wherein the evaporative emissions system is coupled to atmosphere via an open canister vent valve and isolated from an engine intake by a closed canister purge valve, and the threshold relative pressure is a predetermined pressure value above atmospheric pressure.

9. The method of claim 8, further comprising: in response to the depressurized condition and prior to the venting, opening the canister purge valve to couple the evaporative emissions system to the engine intake while maintaining the FTIV closed, and adjusting the threshold relative pressure based on the differential pressure measured by the delta pressure sensor; in response to the relative pressure of the fuel tank decreasing below the threshold relative pressure, interrupting the venting by maintaining the FTIV closed; as well as In response to the relative pressure of the fuel tank decreasing below the threshold relative pressure, the canister purge valve is closed.

10. The method of claim 8, wherein the depressurization condition further comprises receiving a request to refuel the fuel tank, and the method further comprises: in response to the relative pressure of the fuel tank decreasing below the threshold relative pressure, interrupting the pulsation by maintaining the FTIV open; unlocking a fuel port in response to the relative pressure of the fuel tank decreasing below the threshold relative pressure; as well as In response to completion of the refueling event, the fuel port is locked and the FTIV is closed.

11. A system for a vehicle, comprising: an engine system including an engine configured to propel the vehicle by combusting air and fuel; a fuel system comprising a fuel tank for storing the fuel and a fuel port that prevents access to the fuel tank when locked; an evaporative emission system in fluid communication with the fuel system via a conduit and in fluid communication with an intake passage of the engine via a purge line, the conduit including a fuel tank isolation valve FTIV, the evaporative emission system including a fuel vapor storage canister; a canister vent valve positioned in a vent passage of the evaporative emission system; a canister purge valve, the canister purge valve being positioned in the purge line; a delta pressure sensor coupled across the FTIV, the delta pressure sensor including a first pressure port fluidly coupled to the conduit between the fuel tank and the FTIV and a second pressure port fluidly coupled to the conduit between the fuel vapor storage canister and the FTIV; as well as A controller storing instructions in a non-transitory memory that, when executed, cause the controller to: repeatedly measuring, via the delta pressure sensor, a differential pressure between the fuel system and the evaporative emissions system while the FTIV is closed and not while the FTIV is open during each of a plurality of closed time periods separated by FTIV opening; determining a depressurized condition of the fuel tank based on the measured differential pressure; venting the fuel tank in response to the reduced pressure condition by opening and closing the FTIV in a pulsed manner; as well as The pulsation is adjusted based on differential pressure repeatedly measured at each of the plurality of closed time periods separated by the FTIV opening.

12. The system of claim 11 wherein the FTIV is a normally closed valve, the canister purge valve is a normally closed valve, the canister vent valve is a normally open valve, and the fuel port is normally locked.

13. The system of claim 12, wherein venting the fuel tank when the engine is on comprises: actuating to open the canister purge valve; adjusting a first higher threshold based on the differential pressure measured after actuating opening the canister purge valve; opening and closing the FTIV in a pulsed manner at a predetermined duty cycle; adjusting the predetermined duty cycle based on a relative pressure of the fuel system during the pulsing; In response to the relative pressure of the fuel system decreasing below an adjusted first upper threshold during the pulsation, the FTIV is maintained closed.

14. The system of claim 12, wherein venting the fuel tank when the engine is shut down comprises: opening and closing the FTIV in a pulsed manner at a predetermined duty cycle; adjusting the predetermined duty cycle based on a relative pressure of the fuel system during the pulsing; maintaining the FTIV open in response to the relative pressure of the fuel system decreasing below a second lower threshold during the pulsation; as well as In response to the relative pressure of the fuel system decreasing below the second lower threshold during the pulsation, the fuel port is unlocked.

15. The system of claim 14, wherein the controller stores further instructions in the non-transitory memory, which when executed cause the controller to: In response to completion of a refueling event, the FTIV is closed and the fuel port is locked.

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