Method and system for evaporative emission system

Abstract

Methods and systems are provided for an evaporative emission system. In one example, a method includes fluidly coupling the evaporative emission system to an interior volume of a fuel tank in response to a canister load and a fuel tank pressure. The method also includes sealing off the evaporative emission system from the atmosphere and an intake manifold.

Description

TECHNICAL FIELD

[0001] This specification generally relates to methods and systems for an evaporative emissions system for a vehicle. BACKGROUND OF THE INVENTION

[0002] Due to including an electric motor in a hybrid vehicle, the vehicle may experience shorter engine run times. Shorter engine run times may limit purge events and other events that clean an evaporative emissions system canister and / or relieve fuel tank pressure.

[0003] Some examples include forcing the engine on to consume vapors. However, this reduces customer satisfaction and increases emissions relative to all-electric drive. Some other examples include actively increasing the load on the engine so that the engine can effectively consume vapors while charging an energy storage device of the vehicle or a power assist component of the vehicle. These solutions may all be unsatisfactory because they all result in increased fuel consumption beyond that requested by the vehicle operator. Different methods and systems from those already in existence may be needed.

[0004] In one example, the above problem can be solved by a method that includes fluidly coupling a fuel tank to an evaporative emissions system (evap system) and isolating the evap system from an intake manifold and the atmosphere. In this way, the volume of the fuel tank and the evap system is increased.

[0005] As an example, when the fuel tank pressure is greater than a threshold fuel tank pressure and the engine load is less than a threshold engine load, the fuel tank is fluidly coupled to the evap system. The engine load may not be operating at a load that can consume vapors at a rate that can mitigate vapor breakthrough.

[0006] As another example, when there is no manifold vacuum, the fuel tank is fluidly coupled to the evap system. A fuel tank vacuum can be supplied to the canister to fulfill a purge request. In this way, when the fuel tank pressure is greater than an upper threshold fuel tank pressure, the evap system volume can be used, and when there is no manifold vacuum, the fuel tank volume can be used to purge the canister. These routines can be performed without actively modifying engine operating parameters other than those that occur in response to drive demands.

[0007] It should be understood that the above Summary of the Invention is provided to introduce in a simplified form a series of concepts that 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 solve any disadvantages noted above or in any part of this disclosure. SUMMARY OF THE INVENTION

[0008] According to the present invention, a method includes: fluidly coupling a fuel tank to an evaporative emissions system (evap system) and isolating the evap system from an intake manifold and the atmosphere in response to fuel tank pressure.

[0009] In one aspect of the present invention, the fuel tank pressure is greater than an upper threshold fuel tank pressure.

[0010] In one aspect of the present invention, fluidly coupling the fuel tank to the evap system further includes a canister load being greater than a threshold canister load.

[0011] In one aspect of the present invention, fluidly coupling the fuel tank to the evap system further includes a manifold pressure being greater than a threshold manifold pressure.

[0012] In one aspect of the present invention, fluidly coupling the fuel tank to the evap system further includes an engine load being less than a threshold engine load.

[0013] In one aspect of the present invention, the fuel tank pressure is less than a lower threshold fuel tank pressure.

[0014] According to the present invention, a system is provided that has: an engine; an evaporative emissions system (evap system) including a canister, a switching valve (COV), and a purge valve (PV); a fuel system including a fuel tank and a fuel tank isolation valve (FTIV); and a controller including computer-readable instructions stored in a memory, the computer-readable instructions when executed causing the controller to: close the COV, open the FTIV, and close the PV in response to fuel tank pressure and the load of the canister.

[0015] According to an embodiment, the instructions further cause the controller to monitor the fuel tank pressure via a fuel tank pressure sensor (FTPT) and open the PV in response to the fuel tank pressure stabilizing.

[0016] According to an embodiment, the fuel tank pressure is greater than an upper threshold fuel tank pressure or less than a lower threshold fuel tank pressure, and the load of the canister is greater than a threshold canister load.

[0017] According to an embodiment, the instructions further cause the controller to open the PV in response to the manifold pressure of the intake manifold of the engine being less than a threshold manifold pressure.

[0018] According to an embodiment, the instructions further cause the controller to open the COV in response to the pressure of the canister being less than a threshold canister pressure.

[0019] According to an embodiment, the instruction further causes the controller to close the COV, open the FTIV, and close the PV in response to the engine being turned off or the engine load being less than a threshold engine load.

[0020] According to an embodiment, the instruction further causes the controller to open the PV and close the FTIV in response to the engine being turned on and the engine load being greater than the threshold engine load.

[0021] According to an embodiment, the instruction further causes the controller to open the COV in response to the canister load being less than a threshold canister load.

[0022] According to an embodiment, the instruction further causes the controller to balance the pressure of the fuel tank with the pressure of the evap system.

[0023] According to the present invention, a method includes: opening a fuel tank isolation valve (FTIV), closing a switching valve (COV), and closing a purge valve (PV) in response to one of a canister load, a fuel tank pressure, and a manifold pressure or an engine load.

[0024] In one aspect of the present invention, the canister load is greater than a threshold canister load, the fuel tank pressure is greater than an upper threshold fuel tank pressure, and the engine load is greater than a threshold engine load.

[0025] In one aspect of the present invention, the canister load is greater than a threshold canister load, the fuel tank pressure is less than a lower threshold fuel tank pressure, and the manifold pressure is greater than a threshold manifold pressure.

[0026] In one aspect of the present invention, the method includes opening the PV, opening the COV, and closing the FTIV in response to the fuel tank pressure being stable.

[0027] In one aspect of the present invention, the method includes opening the switching valve and opening the purge valve in response to the canister load being less than a threshold canister load and the engine being turned on. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Advantages described herein will be more fully understood when read in conjunction with the examples of embodiments referred to herein as the Detailed Description, when taken alone or in reference to the accompanying drawings, in which:

[0029] Figure 1 A high-level block diagram illustrating an example vehicle propulsion system is shown;

[0030] Figure 2 Shows Figure 1 An example engine system, fuel system, and evaporative emissions control (EVAP) system included in an example vehicle system of

[0031] Figure 3A and Figure 3B Shows different positions of the switching valve (COV) of the evaporative leak check module (ELCM);

[0032] Figure 4A and Figure 4B A method for opening a fuel tank to an evap system when fuel tank pressure is high and engine load is low is shown;

[0033] Figure 5A and Figure 5B A method for purging a canister using a fuel tank vacuum is shown;

[0034] Figure 6 Graphically shows the Figure 4A and Figure 4B The sequence of operations of the method; and

[0035] Figure 7 Graphically shows the Figure 5A and Figure 5B The sequence of operations of the method. DETAILED DESCRIPTION

[0036] The following description relates to systems and methods for an evaporative emissions system (evap system) and a fuel system for a vehicle. The vehicle may be an at least partially electric vehicle including an electric-only mode. Figure 1 A high-level block diagram illustrating an exemplary vehicle propulsion system is shown. Figure 2 Shown included in Figure 1 An exemplary engine system, fuel system, and evap system in an exemplary vehicle system. Figure 3A and Figure 3B Different positions of the switching valve (COV) of the evaporative leak check module (ELCM) are shown. Figure 4A and Figure 4B A method is shown for opening a fuel tank to an evap system when fuel tank pressure is high and engine load is low. Figure 5A and Figure 5B A method for purging a canister using fuel tank vacuum is shown. Figure 6 Graphically shows the Figure 4A and Figure 4B The sequence of operations of the method. Figure 7 Graphically shows the Figure 5A and Figure 5B The sequence of operations of the method.

[0037] Figures 1 to 3BExample configurations with relative positioning of various components are shown. In at least one example, if elements are shown as being in direct contact or directly coupled to each other, such elements may be referred to as being in direct contact or directly coupled, respectively. Similarly, in at least one example, elements that are shown as being adjacent or adjacent to each other may be adjacent or adjacent to each other, respectively. As an example, components that are in coplanar contact with each other may be referred to as being in coplanar contact. As another example, in at least one example, elements that are positioned apart from each other with only space between them and no other components may be referred to as being so. As yet another example, elements that are shown as being above / below each other, on opposite sides of each other, or on the left / right side of each other may be referred to as being so relative to each other. In addition, as shown in the accompanying drawings, in at least one example, the topmost element or the vertex of an element may be referred to as the "top" of a component, and the bottommost element or the lowest point of an element may be referred to as the "bottom" of a component. As used herein, top / bottom, upper / lower, and above / below may be relative to the vertical axis of the accompanying drawings and are used to describe the positioning of elements of the accompanying drawings relative to each other. Thus, in one example, an element that is shown above other elements is directly above the other elements. As yet another example, the shapes of elements depicted in the accompanying drawings may be referred to as having these shapes (e.g., such as being round, straight, planar, curved, rounded, chamfered, angled, etc.). Additionally, in at least one example, elements shown as intersecting each other may be referred to as intersecting elements or intersecting each other. Still further, in one example, elements shown as being within another element or shown as being outside another element may be referred to as such. It should be understood that one or more components referred to as being "substantially similar and / or identical" may differ from one another according to manufacturing tolerances (e.g., within a deviation of 1% to 5%).

[0038] Figure 1 An example vehicle propulsion system 100 is shown. Vehicle propulsion system 100 includes a fuel-burning engine 110 and a motor 120. As a non-limiting example, engine 110 includes an internal combustion engine and motor 120 includes an electric motor. Motor 120 can be configured to utilize or consume a different energy source than engine 110. For example, engine 110 can consume a liquid fuel (e.g., gasoline) to produce an engine output, while motor 120 can consume electrical energy to produce a motor output. Therefore, a vehicle having propulsion system 100 can be referred to as a hybrid electric vehicle (HEV).

[0039] Vehicle propulsion system 100 can utilize a variety of different operating modes depending on the operating conditions encountered by the vehicle propulsion system. Some of these modes can enable engine 110 to remain in a shut-down state (e.g., set to a deactivated state), where fuel combustion at the engine stops. For example, under selected operating conditions, when engine 110 is deactivated, motor 120 can propel the vehicle via drive wheels 130 as indicated by arrow 122.

[0040] During other operating conditions, engine 110 can be set to a deactivated state (as described above), while motor 120 can be operated to charge energy storage device 150. For example, motor 120 can receive wheel torque from drive wheels 130 as indicated by arrow 122, where the motor can convert the vehicle's kinetic energy into electrical energy for storage at energy storage device 150 as indicated by arrow 124. This operation can be referred to as regenerative energy recovery of the vehicle to reduce speed. Thus, in some embodiments, motor 120 can provide a generator function. However, in other embodiments, generator 160 can alternatively receive wheel torque from drive wheels 130, where the generator can convert the vehicle's kinetic energy into electrical energy for storage at energy storage device 150 as indicated by arrow 162.

[0041] During yet some other operating conditions, engine 110 can be operated by burning fuel received from fuel system 140 as indicated by arrow 142. For example, when motor 120 is deactivated, engine 110 can be operated to propel the vehicle via drive wheels 130 as indicated by arrow 112. During other operating conditions, both engine 110 and motor 120 can each be operated to propel the vehicle via drive wheels 130 as indicated by arrows 112 and 122, respectively. A configuration where both the engine and the motor can selectively propel the vehicle can be referred to as a parallel-type vehicle propulsion system. It should be noted that in some embodiments, motor 120 can propel the vehicle via a first set of drive wheels, while engine 110 can propel the vehicle via a second set of drive wheels.

[0042] In other embodiments, vehicle propulsion system 100 can be configured as a series-type vehicle propulsion system, where the engine does not directly propel the drive wheels. Instead, engine 110 can be operated to power motor 120, which in turn can propel the vehicle via drive wheels 130 as indicated by arrow 122. For example, during selected operating conditions, engine 110 can drive generator 160 as indicated by arrow 116, and the generator can in turn do one or more of the following: supply electrical energy to motor 120 as indicated by arrow 114 or to energy storage device 150 as indicated by arrow 162. As another example, engine 110 can be operated to drive motor 120, which in turn can provide a generator function to convert the engine output into electrical energy, where the electrical energy can be stored in energy storage device 150 for subsequent use by the motor.

[0043] The fuel system 140 may include one or more fuel tanks 144 for storing fuel on the vehicle. For example, the fuel tank 144 may store one or more liquid fuels, including but not limited to: gasoline, diesel, and alcohol fuels. In some examples, the fuel may be stored on the vehicle as a blend of two or more different fuels. For example, the fuel tank 144 may be configured to store a blend of gasoline and ethanol (e.g., E10, E85, etc.) or a blend of gasoline and methanol (e.g., M10, M85, etc.), whereby these fuels or fuel blends may be delivered to the engine 110, as indicated by arrow 142. Yet other suitable fuels or fuel blends may be supplied to the engine 110, where they may be burned at the engine to produce an engine output. The engine output may be utilized 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.

[0044] In some embodiments, the energy storage device 150 may be configured to store electrical energy, which may be supplied to other electrical loads (other than the motor) residing on the vehicle, including cabin heating and air conditioning, engine starting, headlights, cabin audio and video systems, etc. As a non-limiting example, the energy storage device 150 may include one or more batteries and / or capacitors.

[0045] The control system 190 may communicate with one or more of the engine 110, the motor 120, the fuel system 140, the energy storage device 150, and the generator 160. The control system 190 may receive sensed feedback information from one or more of the engine 110, the motor 120, the fuel system 140, the energy storage device 150, and the generator 160. Additionally, the control system 190 may send control signals to one or more of the engine 110, the motor 120, the fuel system 140, the energy storage device 150, and the generator 160 in response to this sensed feedback. The control system 190 may receive an indication of an operator request for an output of the vehicle propulsion system from the vehicle operator 102. For example, the control system 190 may receive sensed feedback from a pedal position sensor 194 that communicates with a pedal 192. The pedal 192 may schematically refer to a friction pedal and / or a foot pedal.

[0046] As indicated by arrow 184, the energy storage device 150 may periodically receive electrical energy from a power source 180 (e.g., not part of the vehicle) residing external to the vehicle. As a non-limiting example, the vehicle propulsion system 100 may be configured as a plug-in hybrid electric vehicle (HEV), such that electrical energy may be supplied from the power source 180 to the energy storage device 150 via an electrical power transmission cable 182. During an operation of recharging the energy storage device 150 from the power source 180, the electrical power transmission cable 182 may electrically couple the energy storage device 150 and the power source 180. When the vehicle propulsion system operates to propel the vehicle, the electrical power 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 amount of electrical energy may be referred to as the state of charge (SOC).

[0047] In other embodiments, the electrical power transmission cable 182 may be omitted, where electrical energy may be received wirelessly 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. To this end, it should be appreciated that any suitable method may be used to recharge the energy storage device 150 from a power source (such as from solar or wind energy) that does not form part of the vehicle. In this way, the motor 120 may propel the vehicle by utilizing an energy source different from the fuel utilized by the engine 110.

[0048] The fuel system 140 may periodically receive fuel from a fuel source residing external to the vehicle. As a non-limiting example, the vehicle propulsion system 100 may be refueled by receiving fuel via a fuel dispensing device 170, as indicated by arrow 172. In some embodiments, the fuel tank 144 may be configured to store the fuel received from the fuel dispensing device 170 until it is supplied to the engine 110 for combustion. In some embodiments, the control system 190 may receive an indication of the level of fuel stored at the fuel tank 144 via a fuel level sensor. The fuel level stored at the fuel tank 144 (e.g., as identified by the fuel level sensor) may be communicated to the vehicle operator, for example, via a fuel gauge or an indication in the vehicle instrument panel 196.

[0049] The vehicle propulsion system 100 may also include an ambient temperature / humidity sensor 198 and stability control sensors such as lateral and / or longitudinal and / or yaw rate sensors 199. The vehicle instrument panel 196 may include indicator lights and / or a text-based display in which messages are displayed to the operator. The vehicle instrument panel 196 may also include various input portions for receiving operator input such as buttons, touchscreens, voice input / recognition, etc. For example, the vehicle instrument panel 196 may include a fuel fill button 197 that the vehicle operator can manually actuate or press to initiate a fuel fill. For example, as described in more detail below, in response to the vehicle operator actuating the fuel fill button 197, the fuel tank in the vehicle can be depressurized so that a fuel fill can be performed.

[0050] In an alternative embodiment, the vehicle instrument panel 196 may communicate an audio message to the operator without displaying it. Additionally, the sensor 199 may include a vertical accelerometer for indicating road roughness. These devices may be connected to the control system 190.

[0051] Figure 2 A schematic diagram of a vehicle system 206 is shown. The vehicle system 206 includes an engine system 208 coupled to an evaporative emissions control system 251 and a fuel system 218. The emissions control system 251 includes a fuel vapor container such as a fuel vapor canister 222 that can be used to capture and store fuel vapors. In some examples, the vehicle system 206 may be a hybrid electric vehicle system such as Figure 1 the vehicle propulsion system 100.

[0052] The engine system 208 may include an engine 210 having a plurality of cylinders 230. In one example, the engine 210 is an Figure 1 embodiment of the engine 110. The engine 210 includes an engine intake 223 and an engine exhaust 225. The engine intake 223 includes a throttle 262 that is fluidly coupled to an engine intake manifold 244 via an intake passage 242. The engine exhaust 225 includes an exhaust manifold 248 that leads to an exhaust passage 235 that directs exhaust to the atmosphere. The engine exhaust 225 may include one or more emissions control devices 270 that may be mounted in a close-coupled position in the exhaust. The one or more emissions control devices may include a three-way catalyst, a lean NOx trap, a diesel particulate filter, an oxidation catalyst, etc. It should be understood that other components may be included in the engine such as various valves and sensors.

[0053] The fuel system 218 may include a fuel tank 220 that is coupled to a fuel pump system 221. In one example, the fuel tank 220 includes Figure 1Fuel tank 144. The fuel pump system 221 may include one or more pumps for pressurizing fuel delivered to an injector (such as the exemplary injector 266 shown) of the engine 210. Although a single injector 266 is shown, additional injectors are provided for each cylinder. It should be understood that the fuel system 218 may be a returnless fuel system, a return fuel system, or various other types of fuel systems.

[0054] Vapors generated in the fuel system 218 may be directed via a vapor line 231 to an evaporative emissions control system 251 before being drawn into the engine intake 223. The evaporative emissions control system includes a fuel vapor canister 222. The vapor line 231 may be coupled to the fuel tank 220 via one or more conduits and may include one or more valves for isolating the fuel tank during certain conditions. For example, the vapor recovery line 231 may be coupled to the fuel tank 220 via one or more of the conduits 271, 275, and 276 or a combination thereof.

[0055] Additionally, in some examples, one or more fuel tank vent valves may be located in the conduits 271, 275, or 276. Among other functions, the fuel tank vent valves may also allow the fuel vapor canister of the emissions control system to remain at a low pressure or vacuum without increasing the fuel evaporation rate of the fuel tank (which would otherwise occur in the case of a reduced fuel tank pressure). For example, the conduit 271 may include a fuel tank isolation valve (FTIV) 252. The conduit 275 may include a relief valve (RV) 285. In one example, the conduit 275 is a bypass conduit, where the RV 285 is configured to allow vapor flow to the canister 222 when the FTIV 252 is closed. Additionally, in some examples, the vapor line 231 may be coupled to a fuel fill system 219. In some examples, the fuel fill system 219 may include a fuel tank cap 205 for sealing the fuel fill system from the atmosphere. The fuel fill system 219 is coupled to the fuel tank 220 via a fuel fill tube 211.

[0056] Additionally, the fuel fill system 219 may include a fuel fill lock 245. In some embodiments, the fuel fill lock 245 may be a fuel tank cap locking mechanism. The fuel tank cap locking mechanism may be configured to automatically lock the fuel tank cap 205 in a closed position such that the fuel tank cap cannot be opened. For example, when the pressure or vacuum in the fuel tank 220 is greater than a threshold, the fuel tank cap 205 may be held locked via the fuel fill lock 245. In response to a fuel fill request, such as when a vehicle operator actuates a fuel fill button on the vehicle dashboard (such as Figure 1Upon a request initiated by the fueling button 197 on the vehicle instrument panel 196, the fuel tank can be depressurized, and the fuel tank cap can be unlocked after the pressure or vacuum in the fuel tank drops below a threshold. In this document, unlocking the fueling lock 245 can include unlocking the fuel tank cap 205.

[0057] In some embodiments, the fueling lock 245 can be a fill - tube valve located at the mouth of the fuel fill tube 211. In such embodiments, the fueling lock 245 may not prevent the removal of the fuel tank cap 205. Instead, the fueling lock 245 can prevent a fueling pump from being inserted into the fuel fill tube 211. The fill - tube valve can be electrically locked, for example, by a solenoid, or mechanically locked, for example, by a pressure diaphragm.

[0058] In some embodiments, the fueling lock 245 can be a fueling door lock, such as a clutch that locks a fueling door located in a body panel of the vehicle. The fueling door lock can be electrically locked, for example, by a solenoid, or mechanically locked, for example, by a pressure diaphragm.

[0059] In embodiments where an electrical mechanism is used to lock the fueling lock 245, the fueling lock 245 can be unlocked by a command from the controller 212, for example, when the fuel tank pressure drops below a pressure threshold. In embodiments where a mechanical mechanism is used to lock the fueling lock 245, the fueling lock 245 can be unlocked via a pressure gradient, for example, when the fuel tank pressure drops to atmospheric pressure.

[0060] The emission control system 251 can include one or more fuel vapor canisters 222 (also simply referred to herein as canisters) filled with a suitable adsorbent, which are configured to temporarily trap fuel vapors (including vaporized hydrocarbons) generated during fuel tank refueling operations and "running loss" vapors (i.e., fuel vaporized during vehicle operation). In one example, the adsorbent used is activated carbon. The emission control system 251 can be referred to interchangeably herein as an evaporative emission control system and / or an evap system. The emission control system 251 can also include a canister vent path or vent line 227 that can direct gas from the fuel vapor canister 222 to the atmosphere when storing or trapping fuel vapors from the fuel system 218. When the emission control system 251 includes more than one canister 222, the canisters can be arranged in series or in parallel. When the canisters are arranged in series, gas can be directed to a first canister of more than one canister, then from the first canister to a second canister of more than one canister, and so on for additional canisters of one or more canisters. When the canisters are arranged in parallel, the total volume of gas directed through more than one canister can be directed to a first canister or a second canister, or the total volume of gas can be divided into two volumes, where a first volume of the two volumes is directed through the first canister and a second volume of the two volumes is directed through the second canister.

[0061] When stored fuel vapors are drawn from the fuel system 218 to the engine intake 223 via the draw line 228 and the draw valve 261, the vent line 227 can also allow fresh air to be drawn into the canister 222 via the vent valve 229. For example, the draw valve 261 can be normally closed, but can be opened during certain conditions (such as certain engine operating conditions) such that a vacuum from the engine intake manifold 244 is applied to the fuel vapor canister for drawing. In some examples, the vent line 227 can include an optional air filter 259 disposed therein upstream of the canister 222. The flow of air and vapors between the canister 222 and the atmosphere can be controlled by the canister vent valve 229.

[0062] An evaporative emissions detection routine can be intermittently executed by the controller 212 on the fuel system 218 to confirm that the fuel system has not deteriorated. Thus, the evaporative emissions detection routine can be performed using engine-off natural vacuum (EONV) generated due to changes in temperature and pressure at the fuel tank after engine shutdown and / or vacuum supplemented from a vacuum pump when the engine is off (engine-off leak test). Alternatively, the evaporative emissions detection routine can be performed while the engine is running by operating a vacuum pump and / or using engine intake manifold vacuum. The testing of evaporative emissions can be performed by an evaporative leak check module (ELCM) 295 communicatively coupled to the controller 212. The ELCM 295 can be coupled between the canister 222 and the vent valve 229 in the vent line 227. The ELCM 295 can include a vacuum pump configured to apply a negative pressure to the fuel system when in a first configuration (such as when performing a leak test). The ELCM 295 can also include a reference orifice and a pressure sensor 296. After applying a vacuum to the fuel system, the pressure change (e.g., absolute change or rate of change) at the reference orifice can be monitored and compared to a threshold. Based on the comparison, evaporative emissions from the fuel system can be identified. The ELCM vacuum pump can be a reversible vacuum pump and is thus configured to apply a positive pressure to the fuel system when the bridging circuit is reversed to place the pump in a second configuration.

[0063] The canister 222 can include a first buffer zone 224 surrounding the load port 213. Like the canister 222, the buffer zone 224 can also include an adsorbent. The volume of the buffer zone 224 can be less than the volume of the canister 222 (e.g., a portion thereof). The adsorbent in the buffer zone 224 can be the same or different from the adsorbent in the canister (e.g., both can include charcoal). The buffer zone 224 can be located within the canister 222 such that during canister loading through the load port 213, fuel tank vapor is first adsorbed within the buffer zone and then, when the buffer zone is saturated, additional fuel tank vapor is adsorbed within the body of the canister. In contrast, when evacuating the canister 222 (where air is drawn in through the vent line 227), fuel vapor is first desorbed from the canister (e.g., to a threshold amount) and then from the buffer zone. In other words, the loading and unloading of the buffer zone 224 is not coincident with the loading and unloading of the canister. Thus, the effect of the canister buffer is to dampen any fuel vapor spikes flowing from the fuel tank to the canister, thereby reducing the likelihood of any fuel vapor spikes entering the engine or being released through the exhaust tailpipe.

[0064] The fuel tank 220 is fluidly coupled to the filter canister 222 via an outlet conduit 276 that branches from a fuel tank isolation valve (FTIV) 252 that controls the flow of fuel tank vapor from the fuel tank 220 and through an inlet conduit 271 into the filter canister 222. By adjusting the position of the FTIV 252, the fuel vapor flow from the fuel tank 220 to the filter canister 222 can be varied. The FTIV 252 can be actuated to a first open position that couples the fuel tank 220 to the filter canister 222 via the conduit 276. In an example where the emissions control system 251 includes more than one filter canister 222 arranged in parallel, adjusting the position of the FTIV 252 to a first position can direct the fuel vapor flow from the fuel tank 220 to a first filter canister, to a second position can direct the fuel vapor flow from the fuel tank 220 to a second filter canister, and to a third position can direct the fuel vapor flow from the fuel tank 220 to both the first and second filter canisters. The FTIV 252 can also be actuated to a fourth closed position.

[0065] For example, when the emissions control system 251 includes one filter canister 222, the FTIV 252 can be actuated to a closed position that isolates the fuel tank 220 from the filter canister 222, where no fuel vapor flows through the conduit 276. The controller 212 can command the FTIV position based on fuel system conditions that include an operator's request for fuel refueling, fuel tank pressure, and filter canister loading. In a second example, the position of the FTIV 252 includes a 0.03” orifice to limit the vapor flow to the filter canister.

[0066] In a configuration where the vehicle system 206 is a hybrid electric vehicle (HEV), the fuel tank 220 can be configured as a sealed fuel tank that can withstand the pressure fluctuations typically encountered during normal vehicle operation and daily temperature cycling (e.g., a steel fuel tank). Additionally, the size of the filter canister 222 can be reduced to account for the reduced engine operation time in a hybrid vehicle. However, for the same reason, the HEV may also have limited opportunities for fuel vapor canister purge operations. Thus, using a sealed fuel tank with a closed FTIV (also known as a NIRCOS or non-integrated refueling canister only system) prevents daytime and running loss vapor from loading the fuel vapor canister 222 and limits fuel vapor canister loading to only refueling vapor. The FTIV 252 can be selectively opened in response to a fuel refueling request to depressurize the fuel tank 220 before fuel can be received into the fuel tank via the fill tube 211. Specifically, when the emissions control system 251 includes one filter canister 222, the FTIV 252 can be actuated to a first open position to depressurize the fuel tank to the filter canister via the first conduit 276 and the filter canister load port 213.

[0067] In some embodiments (not shown), a pressure control valve (PCV) (e.g., RV 285) may be configured in a conduit that couples the fuel tank 220 to the charcoal canister 222 in parallel with conduit 276. When included, the RV may be controlled by the powertrain control module (e.g., controller 212) using a pulse width modulation cycle to relieve any excessive pressure generated in the fuel tank, such as during engine operation. Additionally or optionally, for example, in the case of a hybrid electric vehicle, the RV may be pulse width modulated to vent excessive pressure in the fuel tank when the vehicle is operating in electric vehicle mode.

[0068] When transitioning to the second (open) position for the emissions control system 251 with one charcoal canister 222, the FTIV 252 allows fuel vapor to be vented from the fuel tank 220 to the charcoal canister 222. The second open position may be a fully open position, and the first open position may be a partially open position, such as a half-open position.

[0069] For an emissions control system 251 having at least one charcoal canister 222 (including more than one charcoal canister 222 arranged in parallel), fuel vapor may be stored in the charcoal canister 222, and air stripped from the fuel vapor exits into the atmosphere via the canister vent valve 229. When engine conditions permit, the fuel vapor stored in the charcoal canister 222 may be purged to the engine intake 223 via the purge valve 261. After the fuel tank is sufficiently depressurized (such as below a second threshold pressure), the fuel fill lock 245 may be unlocked to open the fuel tank cap.

[0070] In the absence of an input from the controller 212, the RV 285 may open during a condition where the fuel tank pressure exceeds a threshold fuel tank pressure. This may occur during a condition where the controller 212 is dormant, which may occur when the engine is off and / or when the vehicle is off. In other examples, a venting event while the controller 212 is dormant may not be tracked, resulting in insufficient canister cleaning, which may cause vapor to be released to the atmosphere. This may be exacerbated in a hybrid vehicle where the engine may be off for an extended period of vehicle operation.

[0071] The vehicle system 206 may also include a control system 214 (such as Figure 1Control system 214 is shown as receiving information from a plurality of sensors 216 (various examples of which are described herein) and sending control signals to a plurality of actuators 281 (various examples of which are described herein). As one example, sensors 216 may include exhaust gas sensor 237 located upstream of an emission control device, exhaust gas temperature or pressure sensor 233, fuel tank pressure sensor (FTPT) or pressure sensor 291, canister load sensor 243, and ELCM pressure sensor 296. Thus, pressure sensor 291 provides an estimate of fuel system pressure. In one example, fuel system pressure is fuel tank pressure, such as the pressure within fuel tank 220. Other sensors, such as pressure, temperature, air-fuel ratio, and composition sensors, may be coupled to various locations within vehicle system 206. As another example, actuators may include fuel injector 266, throttle 262, FTIV 252, refuel lock 245, canister vent valve 229, and purge valve 261. Control system 214 may include controller 212. The controller may receive input data from various sensors, process the input data, and trigger the actuators in response to the processed input data based on computer readable instructions or code programmed into the input data corresponding to one or more routines. Figures 1 to 2 Various sensors receive signals and use Figures 1 to 2 Various actuators are controlled to adjust engine operation based on received signals and instructions stored in the controller's memory.

[0072] Figure 3A A fuel vapor canister (such as Figure 2 A first schematic diagram 300 of the evaporative leak check module (ELCM) 295 in a first configuration with the canister 222 vented to atmosphere. Figure 3B A second schematic diagram 350 is shown of the ELCM 295 in a second configuration in which the evap system is sealed from the atmosphere.

[0073] ELCM 295 includes a switching valve (COV) 396, a vacuum pump 360, and a pressure sensor 397. Vacuum pump 360 can be a reversible pump, such as an impeller pump. COV 396 can move between a first position and a second position. In the first position, as shown in FIG. Figure 3A As shown, air can flow through the ELCM 295 via the first flow path 320. In the second position, as shown Figure 3B As shown, air can flow through the ELCM 295 via the second flow path 323. As shown, the ELCM 295 is sealed from the atmosphere in the second position. In this way, Figure 3A The first position is the open position, and Figure 3BThe second position of [COV 396] is the closed position. The position of COV 396 can be controlled by solenoid 310 via compression spring 303. ELCM 295 can also include reference orifice 340. The diameter of reference orifice 340 can correspond to the magnitude of a threshold leak to be tested, such as 0.02". In the first or second position, pressure sensor 397 can generate a pressure signal reflective of the pressure within ELCM 295. The operation of pump 360 and solenoid 310 can be controlled via signals received from Figure 2 controller 212.

[0074] As Figure 3A shown, in the first configuration, COV 396 is in the first position and pump 360 is deactivated. This configuration allows air to flow freely between the atmosphere and the charcoal canister via first flow path 320. This configuration can be used, for example, during charcoal canister draw operations, or during other conditions in which the fuel vapor charcoal canister will vent to the atmosphere. Upon receiving a request for fuel refueling, COV 396 can be actuated to the first position (the first position of the ELCM) to facilitate air flow through the charcoal canister and vent fuel refueling vapors from the fuel tank to the charcoal canister.

[0075] As Figure 3B shown, COV 396 is in the second position and pump 360 is deactivated. This configuration allows the evap system to be sealed off from the atmosphere. During this condition, the fuel tank can be fluidly coupled to the evap system to equalize the pressures of the fuel tank and the evap system. By doing so, the pressure in the fuel tank can be relieved, or if desired, the fuel tank vacuum can be used to draw on the charcoal canister.

[0076] Turning now to Figure 4A and Figure 4B , which illustrate method 400 for fluidly coupling a fuel tank to an evap system in response to fuel tank pressure. The instructions for implementing method 400 and the remaining methods included herein can be executed by a controller based on instructions stored on the controller's memory and in conjunction with signals received from sensors of the engine system, such as the sensors described above with reference to Figure 1 . According to the methods described below, the controller can employ engine actuators of the engine system to adjust engine operation.

[0077] Method 400 begins at 402, which includes determining an operating condition. The operating condition can include, but is not limited to, one or more of engine speed, manifold pressure, vehicle speed, and air-fuel ratio.

[0078] At 404, method 400 may include determining whether the fuel tank pressure is greater than or equal to an upper threshold fuel tank pressure. In one example, the fuel tank pressure may be sensed via FTPT. The upper threshold fuel tank pressure may be based on a non-zero positive number. The upper threshold fuel tank pressure may correspond to the pressure at which vapor can be released from the fuel tank. If the operating conditions are not adjusted, depending on the canister load, the released vapor may be vented to the atmosphere.

[0079] If the fuel tank pressure is not greater than or equal to the upper threshold fuel tank pressure, then at 406, method 400 may include maintaining the fuel tank sealed off from the evap system. Accordingly, the FTIV may remain in the closed position.

[0080] If the fuel tank pressure is greater than or equal to the upper threshold fuel tank pressure, then at 408, method 400 may include determining whether the engine load is greater than a threshold engine load. The threshold engine load may be based on a non-zero positive number. In one example, the threshold engine load is equal to the lower end of a medium load range, such as 20% engine load. If the engine load is greater than the threshold engine load, the canister and thus the extraction rate of fuel tank vapor may be relatively high, and canister overload can be avoided. In other words, extraction may be metered at idle or low loads below the threshold engine load, and canister overload may occur due to excessive radiant heat and / or solar heat.

[0081] If the engine load is greater than or equal to the threshold engine load, then at 410, method 400 may include opening the FTIV and the PV. Accordingly, the fuel tank may be fluidly coupled to the canister, and the canister may be fluidly coupled to the intake manifold.

[0082] At 412, method 400 may include flowing vapor to the engine. In one example, vapor from the fuel tank may flow to the canister. Canister vapor may flow to the intake manifold for combustion in the engine.

[0083] At 414, method 400 may include determining whether the fuel tank pressure is less than the upper threshold fuel tank pressure. If the fuel tank pressure is not less than the upper threshold fuel tank pressure, method 400 may continue to flow vapor to the engine with the FTIV and the PV open. If the fuel tank pressure is less than the upper threshold fuel tank pressure, extraction may no longer be requested, and at 416, method 400 may include closing the FTIV and the PV similar to 406 above.

[0084] Returning to 408, if the engine load is not greater than the threshold engine load, then at 418, method 400 may include determining the canister load. The canister load may be measured directly via a sensor or estimated based on previous loading and extraction events.

[0085] At 420, method 400 may include determining whether the breakthrough likelihood is greater than a threshold likelihood. Breakthrough may include a situation where the canister becomes overloaded, such as when the canister load is greater than a threshold canister load, and the stored vapor is released. If the engine cannot receive the vapor, the vapor may be released to the atmosphere.

[0086] If the breakthrough likelihood is not greater than the threshold likelihood, method 400 may proceed to 410 and utilize a slower draw rate of the engine at a low load or idle load. If the breakthrough likelihood is greater than the threshold likelihood, at 422, method 400 may include closing the COV in the ELCM module. Thus, the evap system may be sealed off from the atmosphere.

[0087] At 424, method 400 may include closing the PV and opening the FTIV. Thus, the evap system may be sealed off from the intake manifold. Additionally, the fuel tank may be fluidly coupled to the evap system. In this way, a certain volume of the fuel tank may be fluidly coupled to the conduits and components of the evap system. By doing so, the effective volume of the fuel tank may be increased.

[0088] At 426, method 400 may include allowing fuel tank vapor to flow into the sealed evap system. The pressure of the fuel tank may decrease while the load on the canister may increase. Although at a high load (e.g., a load greater than the threshold canister load), the increased pressure presented by the fuel tank vapor may force the hydrocarbons (HCs) stored in the canister deeper into the catalyst bed. The fuel tank vapor may be stored in the canister and reside in the conduits of the evap system. Thus, the canister may be configured to store more vapor at a higher pressure. By doing so, the fuel tank pressure may be relieved via the canister without the chance of breakthrough.

[0089] At 428, method 400 may monitor the engine load to determine whether the engine load is greater than a threshold engine load. If the engine load is not greater than the threshold engine load, the fuel tank may remain fluidly coupled to the evap system. If the engine load is greater than the threshold engine load, at 430, method 400 may include closing the FTIV and sealing off the fuel tank from the evap system.

[0090] At 432, method 400 may include opening the PV. The intake manifold may be fluidly coupled to the canister, and the vapor from the canister may flow to the intake manifold. The vapor in the manifold may flow to the engine for combustion.

[0091] At 434, method 400 may include determining whether the canister pressure is equal to a threshold canister pressure. In one example, the threshold canister pressure is based on a non-zero positive number. The threshold canister pressure may be based on atmospheric pressure (e.g., 1 atm). If the canister pressure is not equal to the threshold canister pressure, then at 436, method 400 may include maintaining the COV closed. If the canister pressure is equal to the threshold canister pressure, then at 438, method 400 may include opening the COV. The evap system is fluidly coupled to atmosphere.

[0092] Now turn Figure 5A and Figure 5B , which shows method 500 for purging a canister via manifold vacuum or fuel tank vacuum based on conditions. At 502 , method 500 may include determining canister loading.

[0093] At 504, method 500 may include determining whether the canister load is greater than a threshold canister load. The threshold canister load may be based on an upper limit load of the canister (e.g., 90% full) at which a purge may be requested. If the canister load is not greater than or equal to the threshold canister load, then at 506, method 500 does not purge the canister due to the absence (e.g., lack) of a purge request.

[0094] If the canister load is greater than or equal to the threshold canister load, a purge request is present, and method 500 may include determining manifold pressure at 508. Manifold pressure may be sensed via a pressure sensor (eg, MAP) or estimated based on one or more of throttle position, vehicle speed, and engine speed.

[0095] At 510 , method 500 may include determining whether the manifold pressure is less than or equal to a threshold manifold pressure. In one example, the threshold manifold pressure is based on manifold vacuum. The threshold manifold pressure may be equal to 0 or -0.5 inches of mercury. If the manifold pressure is less than the threshold manifold pressure, at 512 , method 500 may include purging the canister using manifold vacuum.

[0096] At 514 , method 500 may include opening the PV. The manifold and canister may be fluidly coupled.

[0097] At 516 , method 500 may include maintaining the FTIV closed. Thus, the fuel tank is isolated from the evap system. Additionally or alternatively, the COV may be maintained open.

[0098] At 518 , method 500 may include flowing canister vapors to the intake manifold. Positive pressure from the atmosphere and vacuum from the manifold may facilitate the flow of vapors from the canister to the intake manifold, where the vapors may be directed to the engine for combustion.

[0099] At 520, method 500 may include determining whether the canister load is less than a threshold canister load. If the canister load is not less than the threshold canister load, the method may continue to direct the vapor flow to the intake manifold.

[0100] If the canister load is less than the threshold canister load, the purge request may be satisfied, and at 522, method 500 may include closing the PV. The canister may be sealed off from the manifold, and purging may be blocked.

[0101] Returning to 510, if the manifold pressure is not less than or equal to the threshold manifold pressure, the engine load may be relatively low, and the manifold pressure may be insufficient to purge the canister. In other words, the manifold may not include a vacuum.

[0102] After method 500 is "No" at 510, it proceeds to 524, which includes determining whether the fuel tank pressure is less than a lower threshold fuel tank pressure. The lower threshold fuel tank pressure may be equal to the threshold manifold pressure or based on the current manifold pressure. For example, the lower threshold fuel tank pressure may be a dynamic value set to be less than the current manifold pressure.

[0103] If the fuel tank pressure is not less than the lower threshold fuel tank pressure, method 500 proceeds to 506 as described above. If the fuel tank pressure is less than the lower threshold fuel tank pressure, at 526, method 500 may include using the fuel tank vacuum to purge the canister.

[0104] At 528, method 500 may include closing the COV to seal the evap system from the atmosphere.

[0105] At 530, method 500 may include closing the PV to seal the evap system from the intake manifold.

[0106] At 532, method 500 may include opening the FTIV to fluidly couple the fuel tank to the canister.

[0107] At 534, method 500 may include directing the fuel tank vacuum flow to the canister. The fuel tank vacuum may flow into the evap system. Accordingly, the evap system pressure and the canister pressure may decrease, and the fuel tank pressure may increase.

[0108] At 536, method 500 may include determining whether the evap system pressure is stable. The pressure may be determined to be stable based on feedback from the FTPT and / or an evap system pressure sensor (e.g., Figure 2 the ELCM pressure sensor 296). Once the fuel tank pressure and the canister pressure are substantially equal, the evap system pressure may be stable. Additionally or alternatively, if the fuel tank pressure remains relatively constant (e.g., within a given value of +If the pressure is not stable (e.g., the fuel tank pressure is not equal to the evap system pressure), method 500 may continue to flow vacuum from the fuel tank to the canister. If the pressure is stable, at 538, method 500 may include closing the FTIV to seal the fuel tank from the canister.

[0109] At 540 , method 500 may include opening the COV to fluidly couple the atmosphere to the evap system.

[0110] At 542 , method 500 may include opening the PV to fluidly couple the canister to the manifold.

[0111] At 544 , method 500 may include flowing fresh air from the atmosphere to the canister.

[0112] At 546 , method 500 may include flowing canister vapors to the manifold. The positive pressure of the fresh air, along with the motive force of the canister vacuum, may force the canister vapors toward the manifold.

[0113] At 548 , method 500 may include combusting the vapor in the engine.

[0114] At 550 , method 500 may include determining if the canister load is less than a threshold canister load. If the canister load is not less than the threshold canister load, canister vapors may continue to flow to the manifold.

[0115] If the canister load is less than the threshold canister load, at 552 , method 500 may include closing the COV and PV. Purging of the canister may be completed.

[0116] In some examples, engine load may be monitored when using fuel tank vacuum to purge the canister. If the engine load is greater than a threshold engine load, the manifold pressure may be relatively low (eg, less than a threshold manifold pressure), and a higher purging rate may be utilized using manifold vacuum.

[0117] Now go to Figure 6 , which shows a graph 600 that graphically illustrates the conditions of the fuel system, evaporation system, and engine system when the fuel tank pressure is high and the engine load is low. Graph 610 illustrates engine load, and dashed line 612 illustrates threshold engine load. Graph 620 illustrates fuel tank pressure, and dashed line 622 illustrates upper threshold fuel tank pressure. Graph 630 illustrates canister load, and dashed line 632 illustrates threshold canister load. Graph 640 illustrates COV position. Graph 650 illustrates PV position. Graph 660 illustrates FTIV position. Time increases from the left side of the figure to the right side.

[0118] Prior to t1, the engine load is less than a threshold engine load. The fuel tank pressure is greater than an upper threshold fuel tank pressure. The canister load is greater than a threshold canister load. Therefore, without a high probability of vapor breakthrough from the canister, the engine may not be operated under load to consume vapors.

[0119] At t1, the COV is closed, the PV is closed, and the FTIV is open. Thus, the evaporation system is isolated from the atmosphere and the manifold while being fluidly coupled to the fuel tank. Between t1 and t2, the fuel tank pressure decreases and the canister load increases. Fuel tank vapors fill the evaporation system and force stored hydrocarbons deeper into the canister's catalyst bed.

[0120] At t2, the fuel tank pressure is less than the upper threshold fuel tank pressure. Between t2 and t3, the fuel tank pressure remains stable and the engine load begins to increase. At t3, the engine load is greater than the threshold engine load. Therefore, the engine can consume vapor at a purge rate sufficient to avoid vapor breakthrough. The PV is actuated to the open position, and the FTIV is actuated to the closed position.

[0121] Between t3 and t4, the canister load begins to decrease as vapors from the canister load are purged to the engine. At t4, the canister load is relatively low and its pressure may be correspondingly low, causing the COV to be actuated open. In one example, once the canister pressure is less than ambient pressure, the COV is commanded to open. After t4, the purging event continues.

[0122] Now go to Figure 7 , which shows a graph 700 that graphically illustrates the conditions of the fuel system, evaporation system, and engine system when the canister load is high and the manifold pressure is low. Graph 710 shows the manifold pressure, and dashed line 712 shows the threshold manifold pressure. Graph 720 shows the fuel tank pressure, and dashed line 722 shows the lower threshold fuel tank pressure. Graph 730 shows the canister load, and dashed line 732 shows the threshold canister load. Graph 740 shows the COV position. Graph 750 shows the PV position. Graph 760 shows the FTIV position. Time increases from the left side to the right side of the figure.

[0123] Prior to t1, manifold pressure is greater than a threshold manifold pressure. Canister load is greater than a threshold canister load and a purge request is present. Tank pressure is less than a threshold tank pressure, indicating that tank vacuum is available. During these conditions, tank vacuum can be used to purge the canister without manifold vacuum.

[0124] At t1, the COV closes and the FTIV opens. The PV remains closed. Thus, the evaporation system is sealed from the atmosphere and fluidly coupled to the fuel tank.

[0125] Between t1 and t2, fuel tank vacuum flows to the canister. Consequently, fuel tank pressure increases as it equalizes with the evaporation system. In this way, the evaporation system and canister pressures decrease, and fuel tank pressure increases.

[0126] At t2, the fuel tank pressure stops increasing. Between t2 and t3, the fuel tank pressure stabilizes and no longer increases or decreases. Therefore, the canister can be primed for purging independent of the manifold pressure.

[0127] At t3, the FTIV is actuated to the closed position, isolating the fuel tank from the evaporation system. The PV is actuated to the open position, and the COV is actuated to the open position. Thus, the evaporation system is coupled to the manifold and atmosphere. Between t3 and t4, the canister load decreases as canister vacuum and atmospheric pressure force vapors to the manifold.

[0128] At t4, the canister load is less than the threshold canister load. As engine load increases, manifold pressure begins to decrease. After t4, the purging event continues via manifold vacuum. Therefore, the purging event can be performed independently via fuel tank vacuum and manifold vacuum.

[0129] In one example, the fuel tank is fluidly coupled to an evaporation system to provide a further condition under which fuel tank pressure may be reduced and / or a condition under which a canister purge may be performed. As an example, when engine load is relatively low, the volume of the evaporation system can be used to reduce the pressure of the fuel tank. One method can wait until engine load increases to open the evaporation system to the engine to purge the canister. As another example, when manifold pressure is too high, fuel tank vacuum can be used to purge the canister. By doing so, an increased purge frequency can occur, which may be beneficial in vehicles with reduced engine run time.

[0130] The present disclosure provides support for a method that includes fluidly coupling a fuel tank to an evaporative emissions system (evap system) and isolating the evap system from the intake manifold and the atmosphere in response to fuel tank pressure. A first example of the method further includes where the fuel tank pressure is greater than an upper threshold fuel tank pressure. A second example of the method optionally including the first example further includes where fluidly coupling the fuel tank to the evap system further includes a canister load being greater than a threshold canister load. A third example of the method optionally including one or more of the previous examples further includes where fluidly coupling the fuel tank to the evap system further includes a manifold pressure being greater than a threshold manifold pressure. A fourth example of the method optionally including one or more of the previous examples further includes where fluidly coupling the fuel tank to the evap system further includes an engine load being less than a threshold engine load. A fifth example of the method optionally including one or more of the previous examples further includes where the fuel tank pressure is less than a lower threshold fuel tank pressure.

[0131] The present disclosure provides additional support for a system that includes: an engine; an evaporative emissions system (evap system) that includes a canister, a canister purge valve (COV), and a purge valve (PV); a fuel system that includes a fuel tank and a fuel tank isolation valve (FTIV); and a controller that includes computer-readable instructions stored in a memory, the computer-readable instructions when executed causing the controller to close the COV, open the FTIV, and close the PV in response to fuel tank pressure and the loading of the canister. A first example of the system further includes where the instructions further cause the controller to monitor the fuel tank pressure via a fuel tank pressure sensor (FTPT) and open the PV in response to the fuel tank pressure stabilizing. Optionally including the first example, a second example of the system further includes where the fuel tank pressure is greater than an upper threshold fuel tank pressure or less than a lower threshold fuel tank pressure, and the loading of the canister is greater than a threshold canister loading. Optionally including one or more of the previous examples, a third example of the system further includes where the instructions further cause the controller to open the PV in response to the manifold pressure of the intake manifold of the engine being less than a threshold manifold pressure. Optionally including one or more of the previous examples, a fourth example of the system further includes where the instructions further cause the controller to open the COV in response to the pressure of the canister being less than a threshold canister pressure. Optionally including one or more of the previous examples, a fifth example of the system further includes where the instructions further cause the controller to close the COV, open the FTIV, and close the PV in response to the engine being off or the engine load being less than a threshold engine load. Optionally including one or more of the previous examples, a sixth example of the system further includes where the instructions further cause the controller to open the PV and close the FTIV in response to the engine being on and the engine load being greater than the threshold engine load. Optionally including one or more of the previous examples, a seventh example of the system further includes where the instructions further cause the controller to open the COV in response to the canister loading being less than a threshold canister loading. Optionally including one or more of the previous examples, an eighth example of the system further includes where the instructions further cause the controller to balance the pressure of the fuel tank with the pressure of the evap system.

[0132] The present disclosure provides additional support for a method that includes opening a fuel tank isolation valve (FTIV), closing a switching valve (COV), and closing a purge valve (PV) in response to one of a canister load, a fuel tank pressure, and a manifold pressure or an engine load. A first example of the method further includes where the canister load is greater than a threshold canister load, the fuel tank pressure is greater than an upper threshold fuel tank pressure, and the engine load is greater than a threshold engine load. A second example of the method optionally including the first example further includes where the canister load is greater than a threshold canister load, the fuel tank pressure is less than a lower threshold fuel tank pressure, and the manifold pressure is greater than a threshold manifold pressure. A third example of the method optionally including one or more of the previous examples further includes opening the PV, opening the COV, and closing the FTIV in response to the fuel tank pressure stabilizing. A fourth example of the method optionally including one or more of the previous examples further includes opening the switching valve and opening the purge valve in response to the canister load being less than a threshold canister load and the engine being on.

[0133] It should be noted that the example control and estimation routines included herein can be used with a variety of engine and / or vehicle system configurations. The control methods and routines disclosed herein can be stored as executable instructions in non-transitory memory and can be executed by a control system including a controller in conjunction with various sensors, actuators, and other engine hardware. The specific routines described herein can represent one or more of any number of processing strategies (such as event-driven, interrupt-driven, multi-tasking, multi-threading, etc.). Accordingly, the various actions, operations, and / or functions shown can be executed in the sequence shown, executed in parallel, or in some cases omitted. Also, the order of processing is not necessarily required to achieve the features and advantages of the example embodiments described herein, but is provided for ease of illustration and description. One or more of the actions, operations, and / or functions shown can be repeatedly executed according to the particular strategy used. Further, the actions, operations, and / or functions can be graphically represented as code to be programmed into the non-transitory memory of a computer-readable storage medium for an engine control system, where the actions are implemented by executing the instructions in a system including various engine hardware components in conjunction with an electronic controller.

[0134] It should be understood that the configurations and routines disclosed herein are exemplary in nature and these specific embodiments should not be considered to have a limiting meaning since many variations are possible. For example, the above techniques can be applied to V-6, I-4, I-6, V-12, opposed 4-cylinder, and other engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations and other features, functions, and / or properties disclosed herein.

[0135] As used herein, unless otherwise specified, the term "about" is interpreted to mean ±5% of a range.

[0136] The appended claims particularly point out certain combinations and sub-combinations regarded as novel and non-obvious. These claims may refer to "an" element or "a first" element or the equivalent thereof. Such claims are to be understood to cover the combination of one or more such elements, neither requiring nor precluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and / or properties may be claimed by amending the claims or by presenting new claims in this application or a related application. Such claims, whether broader, narrower, equivalent, or different in scope from the original claims, are also regarded as included within the subject matter of this disclosure.

Claims

1. A method, comprising: Fluidly coupling a fuel tank to an evaporative emission system (evap system) and isolating the evap system from an intake manifold and the atmosphere in response to a fuel tank pressure.

2. The method of claim 1, wherein the fuel tank pressure is greater than an upper threshold fuel tank pressure.

3. The method of claim 1, wherein fluidly coupling the fuel tank to the evap system further comprises a canister load being greater than a threshold canister load.

4. The method of claim 1, wherein fluidly coupling the fuel tank to the evap system further comprises a manifold pressure being greater than a threshold manifold pressure.

5. The method of claim 1, wherein fluidly coupling the fuel tank to the evap system further comprises an engine load being less than a threshold engine load.

6. The method of claim 1, wherein the fuel tank pressure is less than a lower threshold fuel tank pressure.

7. A system, comprising: An engine; An evaporative emission system (evap system) including a canister, a switching valve (COV), and a purge valve (PV); A fuel system including a fuel tank and a fuel tank isolation valve (FTIV); and A controller including computer-readable instructions stored in a memory, the computer-readable instructions when executed causing the controller to: In response to a fuel tank pressure and a load of the canister, close the COV, open the FTIV, and close the PV.

8. The system of claim 7, wherein the instructions further cause the controller to monitor the fuel tank pressure via a fuel tank pressure sensor (FTPT) and open the PV in response to the fuel tank pressure stabilizing.

9. The system of claim 7, wherein the fuel tank pressure is greater than an upper threshold fuel tank pressure or less than a lower threshold fuel tank pressure, and the load of the canister is greater than a threshold canister load.

10. The system of claim 7, wherein the instructions further cause the controller to open the PV in response to a manifold pressure of an intake manifold of the engine being less than a threshold manifold pressure.

11. The system of claim 10, wherein the instructions further cause the controller to open the COV in response to a pressure of the canister being less than a threshold canister pressure.

12. The system of claim 7, wherein the instructions further cause the controller to close the COV, open the FTIV, and close the PV in response to the engine being off or an engine load being less than a threshold engine load.

13. The system of claim 12, wherein the instructions further cause the controller to open the PV and close the FTIV in response to the engine being on and the engine load being greater than the threshold engine load.

14. The system of claim 7, wherein the instructions further cause the controller to open the COV in response to the canister load being less than a threshold canister load.

15. The system of claim 7, wherein the instructions further cause the controller to equalize a pressure of the fuel tank with a pressure of the evap system.

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