METHOD AND SYSTEM FOR FUEL VAPOR LIMITATION

Abstract

Method for an internal combustion engine (10) comprising the following: during a first key-on state, the rotation of the internal combustion engine (10) with fuel and storage of fuel tank vapors in a first, larger container (60); and during a second key-off state, the internal combustion engine (10) is turned without fuel and fuel tank vapors are stored in a second, smaller container (62).

Description

Field of invention

[0001] The present application concerns fuel vapor purging in vehicles such as hybrid vehicles. General state of the art and brief description of the invention

[0002] Vehicle exhaust aftertreatment systems may be configured to store fuel vapors from fuel tank refueling operations and daily combustion engine operation, and then purge the stored vapors during a subsequent combustion engine run. In an effort to meet stringent federal emissions guidelines, aftertreatment systems may need to be intermittently diagnosed for leaks that could release fuel vapors into the atmosphere. Evaporation leaks can be identified by sealing the aftertreatment system after creating a vacuum within it and then monitoring the vacuum venting. In hybrid vehicles, leak detection routines may be designed to account for reduced combustion engine operating times, which can result in insufficient vacuum for leak detection and purge routines.

[0003] An exemplary approach for detecting evaporative leaks in a hybrid vehicle is presented by Chung et al. in US 7,562,559 B2. This approach involves disabling fuel injection and throttle valve operation to the engine when the vehicle's internal combustion engine is not running or during an electric driving mode. Meanwhile, an electric motor or generator is engaged to rotate the internal combustion engine and create a vacuum for leak detection. After generating sufficient vacuum, the exhaust aftertreatment system is sealed, and evaporative leaks are diagnosed.

[0004] However, the inventors of the present invention have identified potential problems with such an approach. For example, if the internal combustion engine is rotated to create a vacuum, fuel vapors from the fuel tank may be drawn into the internal combustion engine's intake manifold. The drawn-in fuel vapors can lead to variations in the air-fuel ratio during subsequent engine operation. The situation can be exacerbated if the internal combustion engine is rotated during hot ambient conditions, which result in the generation of more fuel vapors daily. As another example, if the internal combustion engine is rotated to create a vacuum while the vehicle is stationary during refueling or while the operator is inspecting the vehicle, the operator may be startled.

[0005] DE 10 2010 040 880 A1 discloses a generic method for operating a fuel vapor control system.

[0006] The objective, technical problem to be solved can be seen as eliminating or at least reducing the disadvantages of the prior art. According to the invention, this problem is solved by the subject matter of the independent claims.

[0007] According to the invention, some of the above problems can thus be at least partially addressed by a method for operating an exhaust gas purification system, comprising the following: during a first key-on state, rotating the internal combustion engine with fuel and storing fuel tank vapors in a first, larger container; and during a second key-off state, rotating the internal combustion engine without fuel and storing fuel tank vapors in a second, smaller container. In this way, fuel vapors drawn from the fuel tank during vacuum generation can be stored in an auxiliary inline container that is separate from the main fuel vapor container.

[0008] For example, during specified conditions, such as when the internal combustion engine has not been running for a specified duration, the engine can be turned over by a starter motor without any air or fuel injection into the cylinders to create a vacuum for a subsequent leak detection routine. After the vacuum is created, it can be applied to the engine's fuel system to identify fuel system leaks (e.g., from the fuel tank and / or the larger main fuel vapor reservoir). The vacuum creation can be deactivated if the fuel tank is being refueled, if the ambient temperature exceeds a specified threshold, and / or if the vehicle operator is inside the vehicle.Fuel vapors drawn from the fuel tank during vacuum generation can be stored in the smaller auxiliary reservoir, which is connected in-line between the fuel tank and the intake manifold. Purging the fuel vapors stored in the auxiliary reservoir can be coordinated with purging fuel vapors from the main reservoir during subsequent engine operation.

[0009] In this way, an internal combustion engine can be rotated without fuel injection to generate a vacuum for evaporative leak diagnosis, while fuel tank vapors are separated from the rotating engine by an auxiliary container. By reducing the amount of fuel vapors drawn into the intake manifold during vacuum generation, variations in the air-fuel ratio during subsequent engine operation can be minimized. Disabling vacuum generation under specified engine-off conditions may also prevent the vehicle operator from being alerted.

[0010] It is understood that the above brief description is presented to introduce, in simplified form, a selection of concepts that are described in more detail in the full description. It is not intended to identify any important or essential features of the claimed subject matter, the scope of which is defined exclusively by the claims following the full description. Furthermore, the claimed subject matter is not limited to implementations that resolve any disadvantages mentioned above or in any part of this disclosure. Brief description of the drawings Fig. Figure 1 shows a schematic representation of an internal combustion engine and an associated fuel vapor retention system. Fig. Figure 2 shows a high-level flowchart illustrating a routine for operating the fuel vapor retention system of Fig. 1 represents. Fig. Figure 3 shows a high-level flowchart illustrating an example of a rinsing routine. Detailed description

[0011] The following description concerns systems and methods for controlling an internal combustion engine system coupled to a fuel system, such as the system of Fig. 1. An internal combustion engine without fuel is rotated during selected vehicle key-off states to create a vacuum for a subsequent leak detection routine. An engine controller can be configured to execute a control routine such as the routine of Fig. 2. To operate an internal combustion engine starter motor, rotate the engine without fuel, and generate a vacuum. Fuel vapors drawn from the fuel tank during rotation are retained in a smaller inline reservoir. Once a vacuum threshold has been generated, the engine rotation is stopped, and the fuel system is sealed to perform a leak detection routine. Any fuel vapors retained in the smaller reservoir are purged in coordination with the purging of a larger main reservoir of the fuel system during purging conditions, as described in Fig. 3. By performing leak detection during static conditions, where noise factors are mitigated, the signal-to-noise ratio of the detection is improved while reducing the required calibration effort. By storing fuel vapors in the smaller container during vacuum generation, the fuel vapors are not drawn into the intake manifold, and variations in the air-fuel ratio during subsequent internal combustion engine operation can be reduced.

[0012] Fig. Figure 1 shows a hybrid drive system 100 for a vehicle. The hybrid drive system 100 includes an internal combustion engine 10 with an intake manifold 11. The internal combustion engine 10 is coupled to a transmission 44. The transmission 44 can be a manual transmission, an automatic transmission, or a combination thereof. Furthermore, it can include various additional components, such as a torque converter, a gear set, a wheel drive unit, etc. The transmission 44 is coupled to drive wheels 52 that can contact a road surface.

[0013] The transmission 44 can alternatively be driven by an electric motor 50. The electric motor 50 is driven by energy stored in an energy storage device, in this case a battery 46. Other energy storage devices can include a capacitor, a flywheel, a pressure vessel, etc. An energy conversion device, in this case an inverter 48, can be configured to convert the direct current output of the battery 46 into an alternating current output for use by the electric motor 50. The electric motor 50 can also be operated in a regenerative mode, that is, as a generator, to absorb energy from vehicle movement and / or the internal combustion engine and convert the absorbed energy into a form of energy suitable for storage in the battery 46.Furthermore, the electric motor 50 can be operated as a motor or generator as required to increase or absorb torque during a transition of the internal combustion engine 10 between different combustion modes (e.g. during transitions between a spark ignition mode and a self-ignition mode).

[0014] The internal combustion engine 10 can be started by an internal combustion engine starting system 54, which includes a starter motor. In one example, a battery-powered starter motor can be coupled to the internal combustion engine, with the starter motor being driven by energy from the battery 46. In another example, the starter can be a powertrain drive motor, such as a hybrid drive, which is coupled to the internal combustion engine via a coupling device. The coupling device can be a gearbox, one or more gears, and / or any other suitable coupling device. The starter can be configured to restart the internal combustion engine at or below a predetermined threshold speed to zero (e.g., below 50 or 100 rpm). -1) to assist. In other words, the internal combustion engine 10 can be turned by operating the starter motor of the starting system 54. During some conditions, such as during a key-on state when internal combustion engine operation is desired for vehicle movement, the internal combustion engine can be started (e.g., using starter motor assistance) and turned with fuel (i.e., with fuel and air injected into the internal combustion engine cylinders) to allow cylinder combustion. During other conditions, such as in Fig. 2. When performed, such as during selected key-off states, the engine can be started with starter motor assistance and turned without fuel (i.e., without air or fuel injected into the internal combustion engine cylinders) to generate an intake vacuum. The engine can be turned until a threshold vacuum is generated, after which turning can be stopped. The generated vacuum can then be applied to the internal combustion engine fuel system 30 for leak detection diagnostics.

[0015] The hybrid drive system 100 can be operated in various configurations, including a full hybrid system, where the vehicle is powered solely by the internal combustion engine, solely by the electric motor, or by a combination of both. Alternatively, assist or mild hybrid configurations can be used, where the internal combustion engine is the primary source of torque and the electric motor selectively adds torque under specific conditions, such as during a tip-in event. Accordingly, the hybrid drive system 100 can be operated in different operating modes. For example, during an "internal combustion engine on" mode, the internal combustion engine 10 can be operated and used as the primary source of torque for driving the wheels 52. During the "internal combustion engine on" mode, fuel can be supplied to the internal combustion engine 10 from the fuel system 30, which includes a fuel tank 20.In another example, the electric motor 50 can be operated during a "combustion engine off" mode to drive the wheels. The "combustion engine off" mode can be used during braking, at low speeds, when stopping at traffic signs, etc. In yet another example, during an "assist" mode, an alternative torque source can supplement and work in cooperation with the torque supplied by the combustion engine 10.

[0016] The fuel system 30 includes a fuel tank 20 coupled to the combustion engine intake manifold 11. The fuel tank 20 can hold several fuels, such as gasoline or fuel mixtures, such as fuel with a range of alcohol concentrations (e.g., ethanol), including E10, E85, etc., and combinations thereof. The fuel tank can include a fuel level sensor 22 for sending a signal regarding the fuel level in the tank to the controller 12. The fuel level sensor 22 can include a float connected to a variable resistance, as shown. Alternatively, other types of fuel level sensors can be used. In response to a drop in the fuel level below a threshold, a fuel tank refueling request can be issued, and the vehicle operator can stop the vehicle for refueling.Fuel can be pumped into the vehicle from an external source during the refueling event via a refueling line 25, which forms a passage from a refueling door 24 located on the vehicle's exterior body. A refueling door sensor 26, coupled to the refueling door 24, can be a position sensor that sends input signals to the controller 12 indicating whether the refueling door is open or closed.

[0017] The fuel system 30 can include one or more fuel vapor retention devices, such as one or more containers filled with a suitable adsorbent to temporarily capture fuel vapors (including vaporized hydrocarbons) generated in the fuel tank. In one example, the adsorbent used is activated carbon. The one or more containers can communicate with an upper internal volume of the fuel tank 20 via a vapor line 80. As such, fuel vapors can be generated in the fuel tank during fuel tank refueling events (refueling fuel vapors) as well as during vehicle operation (daily fuel vapors). When purging conditions are met ( Fig. 3) For example, when the canisters are saturated, the stored fuel vapors can be purged to the combustion engine intake manifold 11 by actuating a canister purge valve (CPV) 64. By storing the fuel vapors in the canister and purging them at a later time during combustion engine operation, vehicle emissions can be reduced while improving fuel economy.

[0018] In the example shown, the fuel system 30 includes a first, larger reservoir 60 coupled to the combustion engine intake manifold 11 upstream of the fuel tank 20, and a second, smaller reservoir 62 coupled to the intake manifold downstream of the fuel tank 20. The vapor line 80 can be branched into a first branch line 82 and a second branch line 84, with the first reservoir 60 being coupled to the fuel tank 20 via the first branch line 82 and the second reservoir 62 being coupled to the fuel tank 20 via the second branch line 84. As explained herein, the first, larger reservoir 60 can be configured as a primary or main reservoir of the fuel system 30, configured to retain and store refueling and daily fuel vapors generated in the fuel tank during vehicle operation (e.g., during a key-on state).In comparison, the second, smaller inline reservoir 62 can be configured as an auxiliary reservoir for retaining and storing fuel vapors that are drawn into the intake manifold during selected key-off conditions when the engine is running without fuel, in order to create a vacuum for a leak detection routine. In other words, the amount of fuel vapors drawn into reservoir 62 during the selected key-off conditions can be less than the amount of fuel vapors drawn into reservoir 60 during the selected key-on conditions. While the example shown depicts the primary reservoir (first reservoir 60) as a single container, it is understood that in alternative embodiments, several such reservoirs may be connected together.

[0019] The first reservoir 60 may contain a vent 27 to direct gases flowing through it to the atmosphere when fuel vapors are stored or captured from the fuel system 30. The vent 27 may also allow fresh air to be drawn into the fuel system 30 when stored fuel vapors from the fuel system 30 are purged to the combustion engine intake manifold 11 via a purge line 68 and the purge valve 64. The vent 27 may contain an optional canister vent valve (CVV) 66 to regulate the flow of air and vapors between the reservoir 60 and the atmosphere. The canister vent valve 66 may also be used for diagnostic routines.When included, the vent valve can be opened during fuel vapor storage operations (for example, during fuel tank refueling and while the engine is not running) so that air containing removed fuel vapors can be expelled to the atmosphere after passing through the tank. Similarly, during purging operations (for example, during tank regeneration and while the engine is running), the tank vent valve 66 can be opened to allow a flow of fresh air to separate the fuel vapors stored in the tank, and the regeneration valve 64 can be opened to allow the purged vapors to flow into the intake manifold 11. While this example shows that the vent port 27 communicates with unheated fresh air, various modifications can also be used. For example, fresh air heated by a heat exchanger can be used to purge the tank.The controller can seal the fuel system from the atmosphere by commanding the tank vent valve to close. Similarly, the controller can seal the fuel system from the combustion engine intake manifold by commanding the purge valve to close.

[0020] An optional reservoir check valve (not shown) may be included in the purge line 68 to prevent intake manifold pressure from forcing gases in the opposite direction to the purge flow. In an example where the internal combustion engine 10 is a turbocharged internal combustion engine with a boosting device such as a turbocharger, the check valve may be included to prevent the boosted intake manifold pressure from forcing gases in the opposite direction into the purge line. The check valve may be positioned between the purge valve and the intake manifold or upstream of the purge valve. As such, the check valve may be necessary if the purge valve control is not precisely timed or if the purge valve itself can be forced open by high intake manifold pressure.An estimate of the manifold absolute pressure (MAP) can be obtained from a MAP sensor (not shown) coupled to the intake manifold 11 and communicating with the controller 12. Alternatively, the MAP can be inferred from alternative combustion engine operating conditions, such as mass air flow (MAF), after measurement by a MAF sensor (not shown) coupled to the intake manifold.

[0021] The hybrid drive system 100 can exhibit reduced combustion engine operating times because the vehicle is powered by the internal combustion engine 10 during some conditions and by the electric motor 50 during others. While the reduced combustion engine operating times reduce the overall carbon emissions of a vehicle, they can also lead to insufficient purging of the fuel vapors stored in the one or more reservoirs of the vehicle's fuel system. To address this, the fuel tank 20 can be designed to withstand high fuel tank pressures. For example, the fuel tank 20 can be constructed of a material that structurally withstands high fuel tank pressures, such as pressures above a threshold and below atmospheric pressure.

[0022] Furthermore, a fuel tank isolation valve (FTIV) 70 can be positioned in vapor line 80 upstream of (or at) a branch point where branch lines 52 and 54 exit. Alternatively, the FTIV 70 can be contained within branch line 82. The FTIV 70 can normally be kept closed to limit the amount of fuel vapors directed from fuel tank 20 to reservoir 60. In particular, the normally closed FTIV separates the storage of refueling vapors from the storage of everyday vapors. The FTIV may be opened only during refueling and purging operations to allow refueling vapors to be directed to reservoir 60. In one example, the normally closed FTIV is opened only during refueling and purging (if, for example, the fuel tank pressure exceeds a threshold) to allow refueling vapors to be directed to reservoir 60.

[0023] One or more pressure sensors 72 can be coupled to the fuel tank 20 to provide an estimate of the fuel tank pressure. Alternatively, the pressure sensors can be positioned upstream and / or downstream of the FTIV 70 to provide an estimate of the fuel tank pressure. One or more oxygen sensors 74 can be provided downstream of the tanks, in the engine inlet (as shown), and / or in the outlet to provide an estimate of the hydrocarbon load (HC) or capacity of the tanks.

[0024] As such, one or more of the FTIV 70, the regeneration valve 64, and the reservoir vent valve 66 can be solenoid valves, the operation of which can be controlled by setting a control signal to the respective solenoids (not shown). For example, during a purge operation, the quantity and rate of vapors released from the regeneration valve 64 to the intake manifold 11 along the purge line 68 can be determined by the duty cycle of an associated regeneration valve solenoid. As such, the duty cycle of the regeneration valve solenoid can be determined by the vehicle's powertrain control module (PCM), such as the controller 12, in response to internal combustion engine operating conditions, including, for example, an air-fuel ratio.

[0025] The hybrid drive system 100 may further include a control system 14. The control system 14 is shown to receive information from several sensors 16 (various examples of which are described herein) and to send control signals to several actuators 81 (various examples of which are described herein). As an example, the sensors 16 may include a pressure sensor 72, a fuel door position sensor 26, a fuel level sensor 22, an oxygen sensor 74 coupled to the intake manifold, various exhaust gas sensors arranged upstream of an internal combustion engine exhaust aftertreatment device, etc. Other sensors, such as additional pressure, temperature, air-fuel ratio, and composition sensors, may be coupled at various points in the drive system 100.As another example, the actuators can include the regeneration valve 64, the vent valve 66, the FTIV 70, cylinder fuel injectors (not shown), an air intake throttle valve coupled to the engine intake manifold (not shown), etc. The control system 14 can include a controller 12. The controller can receive input data from the various sensors, process the input data, and trigger the actuators in response to the processed input data based on an instruction or code programmed therein according to one or more routines. Examples of control routines are shown herein. Fig. 2-3 described.

[0026] The fuel system 30 can be operated by the controller 12 in several modes by selectively adjusting the various valves (and their associated solenoids). For example, the fuel system can be operated in a primary fuel vapor storage mode (e.g., during a fuel tank refueling operation and with the engine not running), whereby the controller 12 can open the FTIV 70 and the tank vent valve 66, while closing the purge valve (CPV) 64 to direct refueling vapors into the first tank 60, while preventing fuel vapors from being directed into the intake manifold.

[0027] In another example, the fuel system 30 can be operated in a vacuum generation mode (e.g., during a selected key-off state with the combustion engine running without fuel and the starter motor assisted to generate an inlet vacuum for a leak detection routine), whereby the controller 12 can open the CPV 64 and the FTIV 70 while the CVV 66 is closed to store any fuel vapors drawn from the fuel tank during the rotation of the combustion engine in the second reservoir 62. Specifically, any fuel tank vapors drawn to the combustion engine due to the vacuum generated in the intake manifold of the rotating combustion engine can be stored in the smaller inline reservoir 62, thereby reducing disturbances in the air-fuel ratio that occur during subsequent combustion engine operation with fuel.

[0028] As another example, the fuel system can be operated in a tank purge mode (e.g., after an exhaust aftertreatment system activation temperature has been reached and with the combustion engine running), during which the controller 12 can open the regeneration valve 64 and the tank vent valve 66 while closing the FTIV 70. In this mode, the vacuum generated by the intake manifold of the running combustion engine can be used to draw in fresh air through the vent opening 27 and through the tanks 60 and 62 to purge the stored fuel vapors into the intake manifold 11. The purged fuel vapors are then combusted from the tank in the combustion engine. Purging can continue until the amount of stored fuel vapor in the tanks falls below a threshold.In an alternative embodiment, instead of fresh air at atmospheric pressure, compressed air that has been passed through a charging device (such as a turbocharger or supercharger) can be used for a supercharged purge operation. As such, the fuel system 30 may require additional channels and valves to enable a supercharged purge operation. During purging, the learned vapor quantity / concentration can be used to determine the amount of fuel vapor stored in each reservoir, and then, during a later stage of the purge operation (when the reservoir is sufficiently purged or empty), the learned vapor quantity / concentration can be used to estimate the loading state of each reservoir.In one example, a certain amount of daily fuel vapors might only be purged from the fuel tank to the buffer by opening the FTIV once a threshold quantity of fuel vapors has been purged from the first reservoir. In another example, a vacuum generation operation of the internal combustion engine (where the engine is turned over by the starter motor without fuel) is only activated after a threshold quantity of fuel vapors has been purged from the second reservoir.

[0029] As yet another example, the fuel system can be operated in a fuel tank purge mode (e.g., after the first container 60 has been purged long enough to reduce the container's loading state below a threshold amount of stored fuel vapors), whereby the controller 12 can open the FTIV 70 for a duration to purge an amount of fuel vapors from the fuel tank to the container.

[0030] As a further example, the fuel system can be operated in a refueling mode (e.g., when a vehicle operator requests refueling), in which the controller 12 can open the FTIV 70 and the regeneration valve 66, while the regeneration valve 64 remains closed to relieve the pressure in the fuel tank before allowing fuel to be added. As such, the FTIV 70 can be kept open during the refueling operation to allow refueling vapors to be stored in the first reservoir. After refueling is complete, the FTIV can be closed.

[0031] As another example, the fuel system can be operated in a leak detection mode (e.g., when the engine is in a selected key-off state and a threshold amount of intake vacuum is present), whereby the controller 12 can close the tank vent valve 66 while opening the purge valve and the FTIV to seal the fuel system. The controller can then apply the vacuum generated in the combustion engine intake manifold to the vehicle fuel system, specifically to the fuel tank and / or reservoirs, to detect a leak in the fuel system. Based on a vacuum vent (e.g., vent rate), the controller 12 can identify the presence and diameter of leaks in the fuel tank and / or reservoirs.By performing leak detection when the combustion engine is off and the vehicle is stationary, noise factors such as sloshing fuel, high temperatures, fuel vaporization, and vehicle dynamics can be significantly reduced, thereby improving the signal-to-noise ratio. Consequently, leaks as small as 0.02 inches (i.e., hole diameter) can be reliably detected.

[0032] Now with reference to Fig. Section 2 describes an exemplary routine 200 for operating a vehicle internal combustion engine and an associated fuel system. The routine enables the turning of an internal combustion engine without fuel under selected key-off states using a starter motor to generate sufficient intake vacuum for a leak detection routine.

[0033] At 202, the routine includes confirming that the internal combustion engine is switched off and not running. Specifically, it can confirm that the engine is in a key-off state. If the engine is indeed in the key-off state, then at 204, it can be determined whether a leak detection diagnostic should be performed. As such, leak detection routines may need to be performed periodically. Thus, in one example, a leak detection diagnostic can be performed after a threshold duration has elapsed since the last leak detection. In another example, a leak detection diagnostic can be performed after the vehicle has been driven a threshold distance (e.g., a threshold number of miles). If no leak detection is to be performed, the routine can end.If leak detection is required, then at 206 it can be determined whether sufficient negative pressure is available to perform the leak detection routine. For example, it can be determined whether sufficient inlet negative pressure is available. Alternatively, if negative pressure has been stored in a pressure storage device such as an accumulator, then it can be determined whether sufficient negative pressure exists in the accumulator to perform the diagnosis.

[0034] If sufficient vacuum is available, a leak detection routine can be activated at 220. The available vacuum can be applied to the fuel system (e.g., the fuel tank and / or containers), and a vacuum vent can be monitored for leaks. In one example, if the vacuum vent rate exceeds a threshold, the presence of a leak can be determined, provided the fuel is not highly vaporous. In another example, the presence of a leak can be confirmed based on the final vent pressure relative to a reference vent pressure. Furthermore, the size of the leak opening can also be determined based on the final vent pressure relative to a reference pressure determined during a calibration step.

[0035] In one example, the leak detection routine might include an initial calibration step. During this step, a vacuum can be applied to a reference port with a reference size (or diameter). For instance, the fuel system might contain a valve with a reference port used to determine a vacuum reading in the presence of a small leak of a reference size, such as the EPA standard of 0.5 mm. Alternatively, the reference port could be located in the fuel system's purge line, for example, between the reservoirs and the purge valve, or in a branched purge line running parallel to the purge valve. Based on this configuration, the pressure applied to the reference port and any vacuum venting are monitored. A final reference vacuum value is then determined.The intake vacuum is then applied to the sealed fuel system, and a vacuum vent is monitored. The final venting vacuum value obtained while the system is closed is compared to the value obtained with the reference port open. If, for example, the final venting vacuum value of the closed system is below the reference value (i.e., even lower than atmospheric pressure), it can be determined that no leak is detected in the fuel system. If, in comparison, the final venting vacuum value is above the reference value (i.e., closer to atmospheric pressure), then it can be determined that a leak is present in the fuel system.

[0036] It is understood that the leak detection routine can identify leaks in response to the vacuum venting rate (or the final venting vacuum value) exceeding a threshold, provided the fuel is not highly vaporous. As such, vaporous fuels, such as winter-grade fuels, can produce higher venting rates due to their greater volatility (compared to summer-grade fuels). That is, in a leak-free fuel system where the fuel tank is filled with winter-grade fuel, a leak detection routine performed when the ambient temperature is above a threshold (e.g., on a hot summer day) may produce a false leak indication. In one example, to reduce the occurrence of false positives (i.e., a detected leak when there is no leak), the leak detection routine can be further modified.If a potential leak is identified, particularly in response to a high vacuum venting rate, the routine can vent the fuel tank to atmosphere and reseal the fuel system. If, after resealing the fuel system, the change in fuel system pressure over time exceeds a threshold (e.g., the pressure changes by more than a predefined amount over a predefined period), the routine can close and indicate that the preceding high vacuum venting rate was due to the fuel being in vapor form and that the identified potential leak was a false positive. Accordingly, the test result can be ignored, and any deterioration indication based on it can be modified.

[0037] By performing leak detection during a vehicle key-on state when the vehicle is stationary (e.g., parked), leak detection can be performed during a static state where the fuel tank temperature is the ambient temperature and the signal-to-noise ratio for the detection routine is improved.

[0038] If insufficient vacuum is available when returning to position 206, then position 208 can be used to determine whether vacuum generation conditions exist. Selected key-on states can be confirmed here.

[0039] In particular, vacuum generation conditions can be confirmed in response to any of the following: the internal combustion engine is in a key-off state for a threshold duration, the vehicle is stationary, no fuel tank refueling is taking place (i.e., no fuel tank refueling is requested), an ambient temperature is lower than a threshold (i.e., cooler temperature conditions), a vehicle operator is not in the vehicle (e.g., the car is parked without the vehicle operator inside), a battery charge level is above a threshold, and a hydrocarbon load in the second, smaller reservoir of the fuel system (reservoir 62) is below a threshold (e.g., reservoir 62 is empty).

[0040] If all vacuum generation conditions are met, then routine 210 involves operating the starter motor and turning the internal combustion engine without fuel, using starter motor assistance, to generate a vacuum in the internal combustion engine's intake manifold. Turning the internal combustion engine without fuel involves turning the engine without air or fuel injection until a threshold intake vacuum is reached. Specifically, the controller may be configured to disable a spark plug and keep an intake air throttle valve closed to turn the internal combustion engine without fuel injection. For example, the intake air throttle valve may be moved from its neutral, partially open position to or into a fully closed position to accelerate vacuum generation while conserving electrical power.The routine further includes, at 212, storing fuel tank vapors drawn from the fuel system in the smaller reservoir of the fuel system, i.e., the small inline reservoir 62, which is coupled between the fuel tank and the combustion engine intake manifold, while the internal combustion engine is running. If no vacuum generation conditions are confirmed at 208, then the routine at 209 can delay the starter motor operation and the internal combustion engine turning until each of the vacuum generation conditions is met.

[0041] At 214, it can be confirmed whether the intake vacuum has reached a threshold value. If the threshold intake vacuum has been reached, then the routine at 218 involves disabling the starter motor and isolating the fuel system. As previously explained, isolating the fuel system involves closing the purge valve and the purge valve while the FTIV is open to isolate the fuel system from the atmosphere. If the threshold intake vacuum has not been reached, then the routine at 216 involves continuing to operate the starter motor and turning the internal combustion engine with starter motor assistance until the threshold intake vacuum is reached, and then, after reaching the threshold intake vacuum, disabling the starter motor.

[0042] It is understood that the controller may include further instructions to disable the starter motor and stop vacuum generation while the internal combustion engine is running without fuel in response to an ambient temperature exceeding a threshold, a fuel tank refueling request being received, a vehicle operator being seated in the vehicle, a vehicle operator opening a vehicle door, soft top, window, or trunk, and / or a small inline reservoir HC load exceeding a threshold. By stopping vacuum generation if any of the vacuum generation parameters change, a vehicle operator may thus be prevented from being startled by the sudden noise of an internal combustion engine idling.

[0043] At 220, the routine involves applying the generated inlet vacuum to the fuel system, for example, to the fuel tank and / or the larger main reservoir, to detect and identify a leak in the vehicle's fuel system. The controller can then activate a leak detection routine to confirm the presence of a leak in the fuel tank and / or the larger main fuel reservoir (i.e., reservoir 60 of Fig. 1) and to identify the size (e.g., diameter) of the leak opening. During the leak detection routine, a vacuum can be applied to a sealed fuel system (e.g., fuel tank and / or reservoir), and a leak can be identified based on a vacuum venting rate compared to a reference value.

[0044] If the combustion engine off states are not confirmed under 202, then the combustion engine on states can be confirmed under 222. For example, it can be confirmed that the combustion engine is in a key on state. If combustion engine on states are confirmed, then it can be determined under 224 whether purging conditions have been met.As such, purging can be determined based on various internal combustion engine and vehicle operating parameters, including the amount of hydrocarbons stored in each of the containers (such as the amount of hydrocarbons stored in the first, larger container being greater than a first, higher threshold and the amount of hydrocarbons stored in the second, smaller container being greater than a second, lower threshold), the temperature of an exhaust aftertreatment device (such as the temperature being above a threshold), fuel temperature, the number of starts since the last purge (such as the number of starts being above a threshold), fuel properties (such as the amount of alcohol in the fuel burned, increased frequency of purging with a higher alcohol content in the fuel) and various others.In another example, purge conditions can be confirmed if the controller determines that fuel vapors were directed to the first, larger reservoir during a previous combustion engine cycle. If purge conditions are not confirmed, the routine can end. If purge conditions are confirmed, then at 226 a purge routine, as in . Fig. 3. Executed, activated.

[0045] Now with reference to Fig. 3 describes an exemplary routine 300 for coordinating a purging of the first, larger (main) reservoir of the internal combustion engine's fuel system with the purging of the second, smaller (auxiliary) reservoir of the internal combustion engine's fuel system.

[0046] At 302, purging conditions can be confirmed; otherwise, the routine can end. If purging conditions are confirmed, routine 304 includes confirming whether a vacuum generation routine was performed on the immediately preceding engine-off state. If a vacuum generation routine (as in Fig. 2 discussed previously) then the smaller container of the fuel system (i.e. container 62 of Fig. 1) contain at least some fuel vapors stored therein. If a vacuum generation routine was previously performed, then the routine at 306 can accordingly include determining a hydrocarbon (HC) load of the second, smaller container. At 308, an HC load of the first, larger container of the fuel system can be determined. If no vacuum generation routine was previously performed, the routine can then proceed directly to 308 to determine the HC load of only the larger container.

[0047] At 310, the routine involves purging fuel vapors from both the first and second reservoirs to the internal combustion engine intake manifold. Purging fuel vapors from both reservoirs involves closing the fuel tank isolating valve and opening the purge valve. For example, the purge valve may be opened to purge an initial quantity of fuel vapors from the first reservoir and a second quantity from the second reservoir. Reservoir purge data (e.g., reservoir purge rate, duration, purge valve duty cycle, etc.) may be based on engine operating conditions.These can include, for example, mass air flow (MAF), manifold air pressure (MAP), a desired air-fuel ratio, air-fuel ratio feedback from an oxygen sensor and / or a hydrocarbon sensor coupled downstream of the tanks and / or on the engine intake manifold, etc. The tank purge data can also be based on the state of charge of each of the first and second tanks (i.e., the amount / concentration of fuel vapors stored in the tank), as learned during respective tank charging operations immediately prior to the tank purge operations.

[0048] At 312, it can be determined whether the purging operation has been completed. For example, completion of the purging can be based on the elapsed purging time, calculated based on the purging rate and the purging load of each reservoir. Alternatively, it can be confirmed that the amount of stored fuel vapor in at least the first, larger reservoir is below a threshold. Since the HC load of the first, larger reservoir is higher than the HC load of the second, smaller reservoir, a purging time required to adequately purge the first reservoir will also adequately purge the second reservoir.The amount of stored fuel vapor in each container can be estimated based on the container purge rate, the airflow rate through the container, and air-fuel ratio feedback from an oxygen sensor and / or hydrocarbon sensor downstream of the container, feedback from a pressure sensor coupled to the container, etc. Alternatively, the amount of stored fuel vapor can be learned during a previous container loading or purge operation and filtered down as a function of the purge duration or purge volume. In one example, this can confirm that the containers were empty.

[0049] At 314, upon completion of the purge, the regeneration valve can be closed while the FTIV is opened to allow fuel tank vapors to be stored in the freshly purged larger container. The routine further involves setting the internal combustion engine fuel injection based on the amount of fuel vapors purged from the first and second containers. In the example where the regeneration valve was open to purge an initial amount of fuel vapors from the first container and a second amount from the second container, the controller can set the internal combustion engine fuel injection based on the first and second amounts of purged fuel vapors. Specifically, based on the container purge data (e.g., the container purge rates, the amount purged from each container, etc.),Fuel injection into the internal combustion engine cylinders can be adjusted to provide a desired air-fuel ratio. For example, if the (first and second) quantity of fuel vapors directed from the first and second reservoirs to the internal combustion engine intake increases, the amount of fuel injected into the internal combustion engine can be reduced accordingly to maintain the desired air-fuel ratio (for example, at or around stoichiometry). In this way, by adjusting the fuel injection into the internal combustion engine based on the amount of fuel vapors purged from the larger main reservoir and the smaller inline reservoir, variations in the air-fuel ratio can be better compensated for.

[0050] In one example, during a first key-on state, the controller can run the internal combustion engine with fuel and store the fuel tank vapors generated during engine operation in a first, larger reservoir of the engine's fuel system. During a second key-off state, the controller can run the engine without fuel and store fuel tank vapors in a second, smaller reservoir of the engine's fuel system, with the smaller reservoir connected to the intake manifold downstream of the fuel tank. The first key-on state can precede the second key-off state (e.g., immediately). Furthermore, scavenging conditions may not be met during the first key-on state, and thus no scavenging operation may occur.Thus, turning the internal combustion engine with fuel during the first key-on state can involve turning the engine with a regeneration valve coupled between the fuel tank and the intake manifold closed. In contrast, turning the internal combustion engine without fuel during the second key-off state can involve turning the engine with the regeneration valve open.

[0051] If, for example, the vehicle has been in a wet state for a threshold duration after the key has been switched off, the internal combustion engine's control system can be reactivated (or woken up), and a starter motor can be engaged to turn the engine without fuel to create an intake vacuum, while any fuel vapors drawn from the fuel tank during turning are absorbed into the smaller reservoir. To accelerate vacuum generation, an air intake throttle valve can be moved from its neutral (or partially open) position to, or towards, a fully closed position while the engine is turning. Once a threshold amount of intake vacuum has been generated, the air intake throttle valve can then be returned to its original neutral (or partially open) position.

[0052] During a third, subsequent key-on state after the second key-off state, the controller can again run the engine with fuel and store fuel vapors drawn from the fuel tank during engine rotation in the larger reservoir connected to the intake manifold upstream of the fuel tank. The third key-on state can be a key-on state where purging conditions are met. Accordingly, the controller can open the purge valve to purge an initial quantity of fuel vapors from the first reservoir and a second quantity of fuel vapors from the second reservoir into the combustion engine's intake manifold, and then adjust fuel injection into the combustion engine based on the first and second quantities of purged fuel vapors.This means the controller can adjust (e.g., reduce) the amount of fuel injected into the combustion engine to a greater extent (compared to if only the first, larger reservoir were purged) in order to provide a desired air-fuel ratio.

[0053] In this way, an engine can be turned over by a starter motor during static conditions without injecting fuel into the combustion engine cylinders, generating sufficient vacuum for a necessary evaporative leak diagnosis. Simultaneously, fuel tank vapors drawn from the rotating combustion engine can be stored in an inline auxiliary reservoir to reduce the amount of fuel vapor drawn into the combustion engine intake manifold, thereby minimizing variations in the air-fuel ratio. Performing leak diagnosis during static conditions reduces factors that can adversely affect the results of a leak detection routine, such as vehicle noise, fuel sloshing, high ambient temperatures, fuel evaporation, and vehicle dynamics. Calibration efforts can also be improved.Improving the signal-to-noise ratio of the leak detection routine can enhance leak detection accuracy, enabling the same components to reliably detect smaller leaks and meet stricter federal emissions regulations. Purging the fuel vapors stored in the smaller reservoir during intake manifold generation can reduce variations in the air-fuel ratio during subsequent engine operation. Disabling vacuum generation under specified engine-off conditions may also prevent the vehicle operator from being startled by a sudden engine idling noise.

[0054] Note that the exemplary control and estimation routines contained herein can be used with various internal combustion engine and / or vehicle system configurations. The specific routines described herein may represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Various actions, operations, or functions shown may be performed as such in the sequence shown, in parallel, or in some cases, omitted. Likewise, the processing order is not necessarily required to achieve the features and benefits of the embodiments described herein but is provided for the convenience of presentation and description. One or more of the actions or functions shown may be performed repeatedly, depending on the specific strategy used.Furthermore, the described actions graphically represent a code programmed into the computer-readable storage medium in the combustion engine control system. Key to symbols Fig. 2 start YES NO end 202 Internal combustion engine off? 204 Leak detection? 206 vacuum available? 208 Are the vacuum generation conditions met? 209 Delay starter motor operation 210 Activate the starter motor and turn the combustion engine without fuel, to create a vacuum 212 Store extracted KT vapors in a smaller inline container 214 Inlet vacuum ≥ threshold value? 216 Further operation of the starter motor 218 Deactivating the starter motor and isolating the fuel system 220 Activating the leak detection routine. Applying a vacuum to the fuel system. 222 Internal combustion engine? 224 Rinsing conditions met? 226 Enable rinsing routine ( Fig. 3) Fig. 3 start YES NO end 302 Rinsing conditions 304 Vacuum generation after prior combustion engine shutdown? 306 Determine the HC load of the smaller inline container 308 Determine the HC load of the main fuel system tank Open 310 CPV while the FTIV is closing. Purge fuel vapors from reservoir(s) to internal combustion engine intake. 312 rinses completed? 314 CPV closes while the FTIV opens. Adjusting the internal combustion engine fuel injection and other operating parameters based on the purged HC load.

Claims

[1] Method for an internal combustion engine (10) comprising the following: during a first key-on state, the rotation of the internal combustion engine (10) with fuel and storage of fuel tank vapors in a first, larger container (60); and during a second key-off state, the internal combustion engine (10) is turned without fuel and fuel tank vapors are stored in a second, smaller container (62). [2] Method according to claim 1, wherein rotating the internal combustion engine (10) without fuel includes rotating the internal combustion engine (10) with starter motor assistance until a threshold intake vacuum is reached, and then deactivating the starter motor. [3] Method according to claim 2, further comprising applying the vacuum to a fuel system (30) during the second key-off state after reaching the threshold inlet vacuum, in order to detect a leak in the fuel system (30). [4] Method according to claim 1, wherein the second key-off state includes each of the following: the internal combustion engine (10) is in a key-off state for a threshold duration, the vehicle is stationary, no fuel tank refueling is taking place, an ambient temperature is lower than a threshold, a vehicle operator is not in the vehicle, a battery charge level is higher than a threshold, and a hydrocarbon load of the second container (62) is lower than a threshold. [5] Method according to claim 1, wherein rotating the internal combustion engine (10) without fuel includes deactivating an ignition spark and keeping an intake air throttle valve closed in order to rotate the internal combustion engine (10) without injecting fuel. [6] Method according to claim 1, wherein an inlet manifold (11) of the internal combustion engine (10) is coupled to the fuel tank (20) and wherein the first larger container (60) is coupled to the inlet manifold (11) upstream of the fuel tank (20) and the second smaller container (62) is coupled to the inlet manifold (11) downstream of the fuel tank (20). [7] Method according to claim 6, wherein the first key-on state precedes the second key-off state and wherein the first key-on state includes the fact that flushing conditions are not met. [8] Method according to claim 7, wherein the internal combustion engine (10) includes a regeneration valve (64) coupled behind the second container (62) between the fuel tank (20) and the intake manifold (11), and wherein rotating the internal combustion engine (10) with fuel during the first key-on state includes rotating the internal combustion engine (10) with the regeneration valve (64) closed, while rotating the internal combustion engine (10) without fuel during the second key-off state includes rotating the internal combustion engine (10) with the regeneration valve (64) open. [9] Method according to claim 8, during a third key-on state after the second key-off state, wherein purging conditions are met, opening the regeneration valve (64) to purge a first quantity of fuel vapors from the first container (60) and a second quantity of fuel vapors from the second container (62) to the inlet manifold (11) and adjusting a fuel injection into the internal combustion engine (10) based on the first and second quantity of purged fuel vapors. [10] Method for an internal combustion engine (10) comprising the following: during a key-off state, Operating a starter motor to turn the internal combustion engine (10) without fuel and Storage of fuel vapors drawn from a fuel tank (20) during rotation in a first container (62) coupled between the fuel tank (20) and an inlet manifold (11). [11] Method according to claim 10, wherein rotating the internal combustion engine (10) without fuel includes rotating the internal combustion engine (10) without air or fuel injection until a threshold inlet vacuum is reached. [12] Method according to claim 11, further comprising deactivating the starter motor after the threshold inlet vacuum has been reached and applying the inlet vacuum to the fuel tank (20) in order to detect a leak in a fuel system (30) of the vehicle. [13] Method according to claim 12, further comprising rotating the internal combustion engine (10) with fuel during a subsequent key-on state and storing fuel vapors drawn from the fuel tank (20) during the internal combustion engine rotation in a second container (60) coupled to the inlet manifold (11) upstream of the first container (62) and upstream of the fuel tank (20), wherein the first container (62) is smaller than the second container (60). [14] Method according to claim 13, further comprising purging fuel vapors from each of the first container (62) and the second container (60) to the inlet manifold (11) during an internal combustion engine purging condition and adjusting a fuel injection based on the amount of fuel vapors purged from each container (60, 62). [15] Method according to claim 10, wherein the key-off state includes the fact that the internal combustion engine (10) is in the key-off state for a threshold duration, no fuel tank refueling is requested, the vehicle is stationary, an ambient temperature is below a threshold, a vehicle operator is not in the vehicle, a battery charge level is above a threshold, and a hydrocarbon load of the first container (62) is below a threshold. [16] Vehicle system comprising the following: an internal combustion engine (10) with an intake manifold (11); a battery-operated starter motor coupled to the internal combustion engine (10); a fuel tank (20); a first, larger container (60) coupled to the inlet manifold (11) in front of the fuel tank (20); a second, smaller container (62) coupled to the inlet manifold (11) behind the fuel tank (20) and a control system (14) with computer-readable instructions to operate during a key-off state to turn the internal combustion engine (10) with starter motor assistance without injecting air or fuel into the internal combustion engine (10) and to store the fuel vapors drawn from the fuel tank (20) during rotation in the second container (62). [17] System according to claim 16, wherein rotating the internal combustion engine (10) without injecting air or fuel includes closing an intake throttle valve and deactivating an internal combustion engine ignition spark while the internal combustion engine (10) is rotated until a threshold intake vacuum is reached, and wherein the control system (14) further includes instructions to deactivate the starter motor and apply the vacuum to the fuel tank (20) to identify a leak after reaching the threshold intake vacuum. [18] System according to claim 17, wherein the control system (14) further includes instructions to deactivate the starter motor and to stop the vacuum generation during rotation in response to the ambient temperature exceeding a threshold, a fuel tank refueling request being received, a vehicle operator being seated in the vehicle, a vehicle operator opening a door, convertible top, window or trunk of the vehicle and / or a hydrocarbon load in the second tank (62) exceeding a threshold. [19] System according to claim 18, wherein the control system (14) further includes instructions to rotate the internal combustion engine (10) with air and fuel injected into the internal combustion engine (10) during a subsequent key-on state and to store fuel vapors drawn from the fuel tank (20) in the first container (60) during rotation. [20] System according to claim 19, wherein the control system (14) further includes instructions to flush a first quantity of fuel vapors from the first container (60) during a flushing condition; to flush a second quantity of fuel vapors from the second container (62) and to adjust an internal combustion engine fuel injection based on the first and second quantity of purged fuel vapors.

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