Systems and methods for determining fuel release from a fuel injector

Abstract

The present disclosure provides "systems and methods for determining fuel release from a fuel injector". Methods and systems are presented for evaluating whether, when commanding a fuel injector to close, a fuel quantity greater than a threshold is released into the engine via the fuel injector. In one example, an oxygen sensor is activated and engine cranking is blocked until the pumping current of the oxygen sensor is proportional to the oxygen concentration sensed via the oxygen sensor, such that fuel released can be observed during engine startup.

Description

Technical Field

[0001] This specification generally relates to methods and systems for diagnosing the presence of fuel release from a fuel injector of an internal combustion engine. Background Art

[0002] During operation, an internal combustion engine may emit hydrocarbons, carbon monoxide, and nitrogen oxides. These emissions can be processed via a post-treatment system such that they can be converted to carbon dioxide and water. However, the post-treatment system may have to reach an elevated temperature before it can begin to convert a high percentage of the engine emissions. If the engine is operated at stoichiometric or lean combustion before the post-treatment system reaches its operating temperature, then hydrocarbon and carbon monoxide tailpipe emissions can be reduced compared to when the engine is operated at rich combustion. Thus, before the post-treatment system reaches its operating temperature, the engine can be started and operated with a lean or stoichiometric air-fuel mixture. However, during engine start-up, it can sometimes be difficult to operate the engine at a stoichiometric or slightly lean air-fuel ratio.

[0003] The inventors have recognized herein that a potential cause for the engine not being able to operate at a stoichiometric or lean air-fuel ratio during engine start-up and tip-in acceleration is that, without the fuel injector being commanded to open, a small amount of fuel can be released into the engine cylinders or the engine intake manifold. The amount of fuel released can depend on the fuel pressure, the characteristics of the individual fuel injectors, the time the fuel injectors are closed and exposed to pressurized fuel, and other factors. If fuel is released from the fuel injectors without the fuel injectors being commanded to open when the engine is stopped, the released fuel can increase engine hydrocarbon emissions and cause the vehicle to exceed desired emission levels. Summary of the Invention

[0004] In one example, the above problem can be solved by an engine operating method that includes: identifying a fuel injector of the engine that releases fuel when commanded to close via a controller, and identifying the fuel-air ratio indicated by an oxygen sensor during engine cranking start-up and tip-in acceleration; and adjusting an actuator based on the fuel injector via the controller.

[0005] By monitoring the output of an oxygen sensor that has reached its operating temperature before engine rotation startup and during initial acceleration, the engine fuel-air ratio Φ can be sensed, enabling the technical result of determining whether there is fuel released from a fuel injector that has never been commanded to open (i.e., injector leakage during engine shutdown). Specifically, a large fuel-air ratio during engine startup can indicate that fuel has been released into the engine cylinders after the engine has stopped. It is possible to determine into which specific cylinders fuel has been released via the fuel injectors by starting the engine with one cylinder deactivated and re-evaluating the engine fuel-air ratio. If the engine fuel-air ratio remains large, a different cylinder can be deactivated for the next engine startup, and the previously deactivated cylinder can be activated during the next startup. This process can be repeated until all cylinders in the cylinder bank have been deactivated once during startup or until the engine fuel-air ratio decreases. If the engine fuel-air ratio decreases, the cylinders deactivated during engine startup can be identified as the cylinders with deteriorated fuel injectors.

[0006] This specification can provide several advantages. For example, the method can reduce engine emissions by determining whether there is fuel that may have been released into the engine cylinders. Additionally, the method can allow for specific cylinder identification, enabling a reduction in the time required to service the engine. Further, the method can reduce engine fuel consumption.

[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 will be further described in the Detailed Description section. This is not meant to identify the key or essential features of the claimed subject matter, the scope of which is uniquely defined by the claims that follow the Detailed Description. Additionally, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 A schematic diagram of an engine system of a vehicle is shown;

[0009] Figure 2A and Figure 2B Signals of interest during an exemplary engine startup are shown;

[0010] Figure 3 Shows according to Figure 4 and Figure 5 An exemplary engine operation sequence of the method; and

[0011] Figure 4 and Figure 5 An exemplary method for operating an engine and determining whether there is fuel released from a fuel injector is shown. Detailed Implementation Manner

[0012] The following description relates to systems and methods for detecting the presence of fuel that may have been released from one or more fuel injectors of an engine. As Figure 1 shown, the engine system may include an exhaust oxygen sensor upstream of an emissions control device. The upstream exhaust oxygen sensor may be a UEGO sensor, such as an exemplary UEGO sensor configured to measure the amount of oxygen in the exhaust. The fuel-air ratio of the engine may be determined by the oxygen sensor, and its output during engine cranking and initial acceleration (e.g., the engine accelerating from cranking speed to idle speed) may indicate that fuel is being released into the engine, as Figure 2A shown. If no fuel is released into the engine when the engine is stopped (e.g., not rotating), the fuel-air ratio of the engine during engine cranking and initial acceleration may be as Figure 2B shown. Since the oxygen sensor may be located in an exhaust manifold that communicates with multiple engine cylinders, it may be difficult to determine which fuel injector, if any, has released fuel into the engine when the fuel injectors are commanded to close. By deactivating engine cylinders and operating the engine as Figure 3 shown, the engine cylinders that may include fuel injectors that are releasing fuel can be isolated. Methods for determining the presence of fuel released into an engine cylinder are shown in Figure 4 and Figure 5 .

[0013] Figure 1 An example of a cylinder 14 of an internal combustion engine 10 included in an engine system 100 that may be included in a vehicle 5 is depicted. The engine 10 may be controlled at least in part by a control system including a controller 12 and an input from a vehicle human operator 130 via an input device 132. In this example, the input device 132 includes an accelerator pedal and a pedal position sensor 134 for generating a proportional pedal position signal. Alternatively, the controller 12 may receive input from an autonomous driver 135. The cylinder (also referred to herein as a "combustion chamber") 14 of the engine 10 may include a combustion chamber wall 136 within which a piston 138 is located. The piston 138 may be coupled to a crankshaft 140 such that the reciprocating motion of the piston is converted into rotational motion of the crankshaft. The crankshaft 140 may be coupled to at least one wheel 55 of the vehicle via a transmission 54, as further described below. Additionally, a starter motor (not shown) may be coupled to the crankshaft 140 via a flywheel to effect starting operation of the engine 10.

[0014] In some examples, the vehicle 5 may be a hybrid vehicle having multiple torque sources available for one or more wheels 55. In other examples, the vehicle 5 is a conventional vehicle having only an engine. In Figure 1In the example shown, vehicle 5 includes engine 10 and electric machine 52. Electrification allows flexibility in engine starting, including starting on fewer cylinders than are allowed for subject diagnostics. Electric machine 52 can be a motor or a motor / generator (M / G). When clutch 56 is engaged, crankshaft 140 of engine 10 and electric machine 52 are connected to wheels 55 via transmission 54. In the depicted example, clutch 56 is disposed between crankshaft 140 and electric machine 52, and electric machine 52 is coupled to transmission 54. Controller 12 can send a signal to the actuator of clutch 56 to engage or disengage the clutch to connect or disconnect crankshaft 140 from electric machine 52 and the components connected thereto. Transmission 54 can be a gearbox, a planetary gear system, or another type of transmission.

[0015] The powertrain can be configured in various ways, including in a parallel, series, or series-parallel hybrid vehicle. In an electric vehicle embodiment, system battery 58 can be a traction battery that delivers electrical power to electric machine 52 to provide torque to wheels 55. In some embodiments, electric machine 52 can also operate as a generator to provide electrical power to charge system battery 58, such as during a braking operation. It should be understood that in other embodiments including non-electric vehicle embodiments, system battery 58 can be a typical starting, lighting, ignition (SLI) battery coupled to an alternator (ALT) 46.

[0016] Alternator 46 can be configured to charge system battery 58 using engine torque via crankshaft 140 during engine operation. Additionally, alternator 46 can power one or more electrical systems of the engine based on their respective electrical demands, such as one or more accessory systems including a heating, ventilation, and air conditioning (HVAC) system, vehicle lights, an in-vehicle entertainment system, and other accessory systems. In one example, the current drawn on the alternator can vary continuously based on each of cab cooling requirements, battery charging requirements, other accessory vehicle system requirements, and motor torque. A voltage regulator can be coupled to alternator 46 to regulate the power output of the alternator based on system usage requirements, including accessory system demands.

[0017] Cylinders 14 of engine 10 can receive intake air via intake passage 142 and intake manifold 146. In addition to cylinders 14, intake manifold 146 can also communicate with other cylinders of engine 10. In some examples, when the engine system is a supercharged engine system, intake passage 142 can include one or more supercharging devices, such as a turbocharger or a supercharger, coupled therein. Throttle 162 including throttle plate 164 can be disposed in the intake passage to vary the flow rate and / or pressure of the intake air provided to the engine cylinders. Exhaust manifold 148 can receive exhaust from cylinders 14 and other cylinders of engine 10.

[0018] Each cylinder of the engine 10 may include one or more intake valves and one or more exhaust valves. For example, cylinder 14 is shown as including at least one intake poppet valve 150 and at least one exhaust poppet valve 156 located in the cylinder head 15. In some examples, each cylinder of the engine 10 (including cylinder 14) may include at least two intake poppet valves and at least two exhaust poppet valves located in the upper region of the cylinder. The intake valve 150 may be controlled by the controller 12 via the actuator 152. Similarly, the exhaust valve 156 may be controlled by the controller 12 via the actuator 154. The positions of the intake valve 150 and the exhaust valve 156 may be determined by respective valve position sensors (not shown).

[0019] During some conditions, the controller 12 may change the signals provided to the actuators 152 and 154 to control the opening and closing of the respective intake and exhaust valves. The valve actuators may be of the electric valve actuation type, cam actuation type, or a combination thereof. The intake and exhaust valve timing may be controlled simultaneously, or any one of the possible configurations of variable intake cam timing, variable exhaust cam timing, dual independent variable cam timing, or fixed cam timing may be used. Each cam actuation system may include one or more cams and may utilize one or more of a cam profile switching system (CPS), variable cam timing (VCT), variable valve timing (VVT), and / or variable valve lift (VVL) systems, which may be operated by the controller 12 to change valve operation. For example, cylinder 14 alternatively may include an intake valve controlled by electric valve actuation and an exhaust valve controlled by cam actuation including CPS and / or VCT. In other examples, the intake and exhaust valves may be controlled by a common valve actuator (or actuation system) or a variable valve timing actuator (or actuation system).

[0020] Cylinder 14 may have a compression ratio that is the ratio of the volume when the piston 138 is at bottom dead center (BDC) to the volume when at top dead center (TDC). In one example, the compression ratio is in the range of 9:1 to 10:1. However, in some examples using different fuels, the compression ratio may be increased. For example, this may occur when using a fuel with a higher octane rating or a fuel with a higher latent heat of vaporization. If direct injection is used due to its effect on engine knock, the compression ratio may also be increased.

[0021] Each cylinder of the engine 10 may include a spark plug 192 for initiating combustion. In a selected operating mode, the ignition system 190 may provide an ignition spark to the combustion chamber 14 via the spark plug 192 in response to a spark advance signal from the controller 12. The timing of the signal may be adjusted based on engine operating conditions and driver torque demand. For example, the spark may be provided at the maximum brake torque (MBT) timing to maximize engine power and efficiency. The controller 12 may input engine operating conditions (including engine speed, engine load, and exhaust AFR) into a look-up table and output the corresponding MBT timing for the input engine operating conditions. In other examples, the spark may be retarded relative to MBT, such as to accelerate catalyst warm-up during engine start or to reduce the occurrence of engine knock.

[0022] In some examples, each cylinder of the engine 10 may be configured with one or more fuel injectors for supplying fuel thereto. As a non-limiting example, cylinder 14 is shown as including one fuel injector 166. The fuel injector 166 may be configured to deliver fuel received from the fuel system 8. The fuel system 8 may include one or more fuel tanks, fuel pumps, and a fuel rail. The fuel injector 166 is shown as being directly coupled to the cylinder 14 for directly injecting fuel into the cylinder in proportion to the pulse width of a signal received from the controller 12. In this manner, the fuel injector 166 provides so-called fuel direct injection (also hereinafter referred to as "DI") into the cylinder 14. Although Figure 1 the fuel injector 166 is shown located on one side of the cylinder 14, the fuel injector 166 may alternatively be located at the top of the piston, such as in a position close to the spark plug 192. Such a position may facilitate mixing and combustion when operating the engine with some alcohol-based fuels due to their lower volatility. Alternatively, the injector may be located at the top and close to the intake valve to increase mixing. The fuel may be delivered from a fuel tank of the fuel system 8 to the fuel injector 166 via a high-pressure fuel pump and a fuel rail. Additionally, the fuel tank may have a pressure sensor that provides a signal to the controller 12.

[0023] In an alternative example, the fuel injector 166 may be arranged in the intake passage rather than being directly coupled to the cylinder 14, in which configuration the fuel injector provides so-called fuel port injection (also hereinafter referred to as "PFI") into the intake port upstream of the cylinder 14. In further other examples, the cylinder 14 may include multiple injectors, which may be configured as direct fuel injectors, port fuel injectors, or a combination thereof. Thus, it should be understood that the fuel systems described herein should not be limited to the particular fuel injector configurations described herein by way of example.

[0024] The fuel injector 166 may be configured to receive different fuels from the fuel system 8 as a fuel mixture in different relative amounts and further configured to directly inject this fuel mixture into the cylinder. Additionally, fuel may be delivered to the cylinder 14 during different strokes of a single cycle of the cylinder. For example, the directly injected fuel may be delivered at least partially during a previous exhaust stroke, during an intake stroke, and / or during a compression stroke. Thus, for a single combustion event, one or more fuel injections may be performed per cycle. Multiple injections may be performed in a so-called split fuel injection manner during the compression stroke, the intake stroke, or any suitable combination thereof.

[0025] The fuel tank in the fuel system 8 may contain fuels of different fuel types, such as fuels having different fuel qualities and different fuel compositions. These differences may include different alcohol contents, different water contents, different octane ratings, different heat of vaporizations, different fuel mixtures, and / or combinations thereof, etc. An example of fuels having different heats of vaporization includes gasoline as a first fuel type having a lower heat of vaporization and ethanol as a second fuel type having a greater heat of vaporization. In another example, the engine may use gasoline as the first fuel type and an alcohol fuel mixture (such as E85 (about 85% ethanol and 15% gasoline) or M85 (about 85% methanol and 15% gasoline)) as the second fuel type. Other viable substances include water, methanol, mixtures of alcohol and water, mixtures of water and methanol, mixtures of alcohol, etc. In yet another example, both fuels may be alcohol mixtures having different alcohol compositions, where the first fuel type may be a gasohol mixture having a lower alcohol concentration, such as E10 (about 10% ethanol), while the second fuel type may be a gasohol mixture having a higher alcohol concentration, such as E85 (about 85% ethanol). Additionally, the first and second fuels may also differ in other fuel qualities, such as differences in temperature, viscosity, octane rating, etc. Further, the fuel characteristics of one or both fuel tanks may change frequently, for example, due to daily variations in fuel tank filling.

[0026] The exhaust sensor 126 is shown as being coupled to the exhaust manifold 148 and located upstream of the emission control device 178 coupled within the exhaust passage 158. The exhaust sensor 126 may be selected from various suitable sensors to provide an indication of the exhaust air-fuel ratio (AFR), for example, such as a linear oxygen sensor or UEGO (universal or wide-range exhaust oxygen), a two-state oxygen sensor or EGO, a HEGO (heated EGO), a NOx, HC, or CO sensor. In Figure 1 an example, the exhaust sensor 126 is a UEGO sensor configured to provide an output (such as a voltage signal) proportional to the amount of oxygen present in the exhaust. The emission control device 178 may be a three-way catalytic converter, a NOx trap, various other emission control devices, or a combination thereof. In Figure 1In the example, the emission control device 178 is a three-way catalytic converter configured to reduce NOx and oxidize CO and unburned hydrocarbons.

[0027] The output current of the UEGO sensor 126 can be used to adjust engine operation. For example, a feedforward (e.g., based on desired engine torque, engine air flow, etc.) and / or feedback (e.g., using the oxygen sensor output) method can be used to vary the amount of fuel delivered to cylinder 14. In this way, the controller 12 can precisely control the AFR of the engine 10 based on feedback from the UEGO sensor 126 and adaptively learn fuel injector and / or air metering errors, which it can then compensate for by adjusting the fuel command until the actual AFR reaches the desired AFR. For example, if the UEGO sensor 126 measures a rich operating condition, the amount of fuel delivered will be reduced (e.g., by decreasing the pulse width of the signal provided via the controller 12). Conversely, if the UEGO sensor 126 measures a lean operating condition, the amount of fuel delivered will be increased (e.g., by increasing the pulse width of the signal provided via the controller 12). However, the closed-loop fuel control of the control architecture 200 may not be utilized until the UEGO sensor 126 reaches its light-off temperature because oxygen measurements made before the UEGO sensor 126 reaches its light-off temperature may not be accurate. For example, the UEGO sensor 126 may not have reached its light-off temperature during engine cold start, as described further below.

[0028] Return Figure 1 , the controller 12 at Figure 1is shown as a microcomputer and includes a microprocessor unit 106, an input / output port 108, an electronic storage medium for executable programs (e.g., executable instructions) and calibration values shown as a non-transitory read-only memory chip 110 in this particular example, a random access memory 112, a keep-alive memory 114, and a data bus. The controller 12 can receive various signals from sensors coupled to the engine 10, the signals including those previously discussed and additionally including: a measurement of the intake mass air flow (MAF) from a mass air flow sensor 122; an engine coolant temperature (ECT) from a temperature sensor 116 coupled to the coolant jacket 118; an ambient temperature from a temperature sensor 123 coupled to the intake passage 142; an exhaust temperature from a temperature sensor 128 coupled to the exhaust passage 158; a surface ignition sensing signal from a Hall effect sensor 120 (or other type of sensor) coupled to the crankshaft 140; a throttle position from a throttle position sensor; a signal UEGO from an exhaust sensor 126, which can be used by the controller 12 to determine the AFR of the exhaust; and a manifold absolute pressure signal from a MAP sensor 124. The engine speed signal RPM can be generated by the controller 12 based on the position sensor 120. The manifold pressure signal MAP from the MAP sensor 124 can be used to provide an indication of the vacuum or pressure in the intake manifold. The controller 12 can infer the engine temperature based on the engine coolant temperature. Additionally, the controller 12 is shown to have a current sensor 113, which can be used to detect the current output of sensors such as the UEGO sensor 126, as further described below. Additional sensors such as various temperature, pressure, and humidity sensors can be coupled at various locations in the vehicle 5.

[0029] The controller 12 receives signals from Figure 1 various sensors and, based on the received signals and instructions stored in the controller's memory, utilizes Figure 1 various actuators to adjust the engine operation. For example, the controller can determine the amount of power (and corresponding voltage) to supply to the heater of the UEGO sensor 126 to quickly raise the UEGO sensor 126 to its operating temperature.

[0030] As described above, Figure 1 only one cylinder of a multi-cylinder engine is shown. Thus, each cylinder can similarly include its own set of intake / exhaust valves, one or more fuel injectors, spark plugs, etc. It should be understood that the engine 10 can include any suitable number of cylinders, including 2, 3, 4, 5, 6, 8, 10, 12, or more cylinders. Additionally, each of these cylinders can include some or all of the various components described and depicted with reference to cylinder 14. Figure 1

[0031] Figure 1 A system is provided that includes: an engine including at least one fuel injector and an oxygen sensor located in an exhaust manifold; a controller storing executable instructions in a non-transitory memory, the executable instructions when executed causing the controller to: adjust an engine start-up procedure after identifying that the at least one fuel injector has released a fuel quantity greater than a threshold quantity into the engine when the engine is stopped and the at least one fuel injector is commanded to close, the identification being performed during a cranking start and a launch acceleration of the engine during engine start-up. The system further includes additional instructions for determining a maximum fuel-air ratio during the cranking start and the launch acceleration. The system includes where the identification is based on the maximum fuel-air ratio exceeding a threshold. The system includes where adjusting the engine start-up procedure includes deactivating engine cylinders.

[0032] Now referring Figure 2A to, an exemplary engine start-up sequence is shown. Figure 2A Three graphs are shown and the three graphs are aligned in time. Vertical lines at times t0 to t1 represent times of interest in the sequence. The controller 12 may include non-transitory executable instructions for operating the engine under the conditions shown and discussed in Figure 2A the description.

[0033] From Figure 2A the top, the first graph is a graph of engine lambda (λ) (e.g., actual air-fuel ratio divided by stoichiometric air-fuel ratio) versus time. The vertical axis represents engine λ and the horizontal axis represents time. Time increases from the left side of the drawing to the right side of the drawing. The solid line 202 represents engine λ values. The horizontal line 201 represents the stoichiometric air-fuel ratio.

[0034] From Figure 2A the top, the second graph is a graph of engine speed versus time. The vertical axis represents engine speed and engine speed increases in the direction of the vertical axis arrow. The horizontal axis represents time and time increases from the left side of the drawing to the right side of the drawing. The dashed line 204 represents engine speed values.

[0035] From Figure 2A the top, the third graph is a graph of the concentration of hydrocarbons exhausted from the engine versus time. The vertical axis represents the concentration of hydrocarbons exhausted from the engine and the concentration of hydrocarbons exhausted from the engine increases in the direction of the vertical axis arrow. The horizontal axis represents time and time increases from the left side of the drawing to the right side of the drawing. The dotted line 206 represents the concentration of hydrocarbons exhausted from the engine.

[0036] In this example, one or more fuel injectors have released fuel into one or more engine cylinders before the engine starts to crank (e.g., rotate under the power of a starter before torque from combustion is sufficient to rotate the engine at a cranking speed (250 RPM) or higher than the cranking speed (250 RPM)). The fuel released into the engine cylinders does not count towards the amount of fuel injected into the engine during engine startup. The amount of fuel injected into the engine is based on engine temperature, barometric pressure, and the number of fuel injections since the engine last stopped. For example, as the engine temperature increases, the amount of fuel injected can decrease. Additionally, the amount of fuel injected into the engine can decrease as the number of fuel injections since the last engine stop increases, which can compensate for fuel that may enter the engine crankcase after fuel injection. The amount of fuel injected can decrease as barometric pressure decreases to compensate for the lower amount of air in the engine cylinders during engine cranking. The engine stops at time t0 and it has been stopped for more than a threshold amount of time (e.g., 25 minutes), such that when the fuel injectors are commanded to close (e.g., no voltage is applied to the fuel injectors), the pressure in the fuel system can be used to release fuel from one or more fuel injectors.

[0037] Shortly before time t1, the engine is cranked, and then combustion within the engine accelerates the engine to idle at time t1. The engine lambda value starts at a high level and it rapidly decreases as the exhaust leaves the engine cylinders. The engine lambda value decreases to a minimum of approximately 0.7 and then starts to slowly increase. For example, an engine lambda value of 0.7 corresponds to releasing more than a threshold amount of fuel from the fuel injectors during the engine stop period. An engine lambda value of 0.7 corresponds to an engine phi (e.g., fuel air ratio divided by the stoichiometric fuel air ratio) value of 1.43 (e.g., a maximum phi of 1.43). For example, during engine cranking and initial acceleration, a maximum engine phi value greater than 1.3 can correspond to releasing more than a threshold amount of fuel from the fuel injectors during the engine stop period. For example, during engine cranking and initial acceleration, a maximum engine phi value less than 1.3 can correspond to releasing less than a threshold amount of fuel from the fuel injectors during the engine stop period. Due to fuel being released into the engine cylinders when the engine stops, the rich mixture leaving the engine results in a higher concentration of hydrocarbons being discharged from the engine.

[0038] Accordingly, by monitoring the engine Φ during engine cranking start-up, initial acceleration, and for several seconds after the engine reaches idle speed, it can be determined whether more than a threshold amount of fuel has been released into the engine via the fuel injectors during a period when the engine is not rotating and the fuel injectors are commanded to be closed. For example, if more than a threshold amount (e.g., 1.3) of engine Φ has been observed during the time period between engine cranking start-up and several seconds after the engine reaches idle speed, it can be determined that more than a threshold amount of fuel has been released into the engine cylinders during an engine stop period in which the fuel injectors have been commanded to be closed.

[0039] Additionally, if one of the cylinders that is first fueled and ignited misfires, it can also be an indication of fuel being released by the injectors during engine shutdown. Misfiring can be indicated by a deceleration of the crankshaft speed.

[0040] Now referring to Figure 2B , an exemplary engine start-up sequence is shown. Figure 2B Three graphs are shown and the three graphs are aligned in time. The vertical lines at times t10 to t11 represent times of interest in the sequence. The controller 12 can include non-transitory executable instructions for operating the engine in the conditions shown and discussed in the Figure 2B description.

[0041] From Figure 2B the top, the first graph is a graph of engine lambda (λ) (e.g., the actual air-fuel ratio divided by the stoichiometric air-fuel ratio) versus time. The vertical axis represents engine λ and the horizontal axis represents time. Time increases from the left side of the drawing to the right side of the drawing. The solid line 210 represents the engine λ value. The horizontal line 211 represents the stoichiometric air-fuel ratio.

[0042] From Figure 2B the top, the second graph is a graph of engine speed versus time. The vertical axis represents engine speed and the engine speed increases in the direction of the vertical axis arrow. The horizontal axis represents time and time increases from the left side of the drawing to the right side of the drawing. The dashed line 212 represents the engine speed value.

[0043] From Figure 2B the top, the third graph is a graph of the concentration of hydrocarbons exiting the engine versus time. The vertical axis represents the concentration of hydrocarbons exiting the engine and the concentration of hydrocarbons exiting the engine increases in the direction of the vertical axis arrow. The horizontal axis represents time and time increases from the left side of the drawing to the right side of the drawing. The dotted line 214 represents the concentration of hydrocarbons exiting the engine.

[0044] In this example, one or more fuel injectors do not release more than a threshold amount of fuel into one or more engine cylinders before the engine starts cranking (e.g., rotates under the power of a starter before torque from combustion is sufficient to rotate the engine at a cranking speed (250 RPM) or higher than the cranking speed (250 RPM)). However, a hybrid vehicle can rotate the engine at a higher speed (e.g., 1000 RPM) via an electric motor. The amount of fuel injected into the engine is based on engine temperature, barometric pressure, and the actual total number of fuel injections since the engine last stopped. These variables are sensed and / or inferred to calculate the cylinder air charge, which is then matched to the corresponding fuel amount. The engine stops at time t10 and it has been stopped for more than a threshold amount of time (e.g., 25 minutes), such that when the fuel injectors are commanded to close (e.g., no voltage is applied to the fuel injectors), the pressure in the fuel system can be used to release fuel from one or more fuel injectors.

[0045] Shortly before time t11, the engine is cranked, and then combustion within the engine accelerates the engine to idle at time t11. The engine lambda value starts at a high level and it rapidly decreases as the exhaust leaves the engine cylinders. The engine lambda value decreases to a minimum of about 0.9 and then starts to slowly increase. For example, an engine lambda value of 0.9 corresponds to less than a threshold amount of fuel being released from the fuel injectors during the engine stop period. An engine lambda value of 0.9 corresponds to an engine phi (e.g., fuel air ratio divided by the stoichiometric fuel air ratio) value of 1.11 (e.g., the maximum phi of 1.11 during this sequence). For example, during engine cranking and initial acceleration, a maximum engine phi value less than a threshold of 1.3 can correspond to less than a threshold amount of fuel being released from the fuel injectors during the engine stop period. For example, during engine cranking and initial acceleration, a maximum engine phi value less than 1.3 can correspond to less than a threshold amount of fuel being released from the fuel injectors during the engine stop period. Since no fuel is released into the engine cylinders when the engine stops, the mixture leaving the engine is much lower in concentration than Figure 2A the mixture shown leaving the engine. The concentration of hydrocarbons leaving the engine is also significantly lower than Figure 2A the concentration of hydrocarbons shown.

[0046] Now referring to Figure 3 , a graph showing a predicted engine start sequence is shown. The sequence can be provided via the system of Figure 1 in cooperation with the method of Figure 4 and Figure 5 . Figure 3 the sequence of Figure 3The graphs are time-aligned and they occur simultaneously. The vertical lines at times t20 to t27 represent times of interest in the sequence. The controller 12 may include non-transitory executable instructions for operating the engine in the conditions shown and discussed in Figure 3 the description. Figure 3 The starting sequence for a four-cylinder four-stroke engine with an ignition order of 1-3-4-2.

[0047] From Figure 3 The first graph from the top is a graph of engine speed versus time. The vertical axis represents engine speed and the engine speed increases in the direction of the vertical axis arrow. The horizontal axis represents time and time increases from the left side of the drawing to the right side of the drawing. Line 302 represents the engine speed.

[0048] From Figure 3 The second graph from the top is a graph of oxygen sensor temperature versus time. The vertical axis represents oxygen sensor temperature and the oxygen sensor temperature increases in the direction of the vertical axis arrow. The horizontal axis represents time and time increases from the left side of the drawing to the right side of the drawing. Line 304 represents the oxygen sensor temperature. Dashed line 303 represents the threshold oxygen sensor temperature. When the oxygen sensor temperature is greater than the threshold 303, the pumping current of the oxygen sensor becomes proportional to the oxygen concentration sensed via the oxygen sensor.

[0049] From Figure 3 The third graph from the top is a graph of the first cylinder to receive fuel after the most recent engine stop. The vertical axis represents the first cylinder to receive fuel after the most recent engine stop. For example, if the engine stops rotating and then turns over for starting, the first cylinder to receive fuel by commanding the fuel injector to turn on after the most recent engine stop is the first cylinder to receive fuel. The engine cylinder numbers are indicated along the vertical axis. The horizontal axis represents time and time increases from the left side of the drawing to the right side of the drawing. Line 306 represents the first engine cylinder to receive fuel after the most recent engine stop.

[0050] From Figure 3 The fourth graph from the top is a graph of engine start request versus time. The vertical axis represents the engine start request and there is an engine start request when the trace 308 is at a high level near the vertical axis arrow. When the trace 308 is near the horizontal axis, there is no engine start request. Even after the engine starts, the engine start request remains at a high level. The horizontal axis represents time and time increases from the left side of the drawing to the right side of the drawing. Line 308 represents the engine start request status.

[0051] From Figure 3The fifth graph from the top is a graph showing the variation of engine lambda over time as determined from the output of an oxygen sensor. The vertical axis represents engine lambda and the engine lambda values are positioned along the vertical axis. The horizontal axis represents time and time increases from the left side of the drawing to the right side of the drawing. Line 310 represents engine lambda. The dashed line 311 represents the stoichiometric air-fuel ratio.

[0052] From Figure 3 The sixth graph from the top is a graph showing the variation of engine fuel injector fuel release indication over time. The vertical axis represents the engine fuel injector fuel release indication status, and when the trace 312 is at a high level near the vertical axis arrow, it indicates that there is fuel injector fuel release. When the trace 312 is close to the horizontal axis, it does not indicate engine fuel injector fuel release.

[0053] From Figure 3 The seventh graph from the top is a graph showing which cylinders (if any) are deactivated during engine startup over time. The vertical axis represents the deactivated engine cylinders and the engine cylinder numbers are listed along the vertical axis. When the trace 314 is close to the horizontal axis, no engine cylinders are deactivated. A cylinder is deactivated by keeping the intake and exhaust valves of the cylinder closed and not injecting fuel into the cylinder. Alternatively, the intake valve of the cylinder can be kept closed while allowing the exhaust valve to operate without injecting fuel into the cylinder. The horizontal axis represents time and time increases from the left side of the drawing to the right side of the drawing. Line 314 represents the engine cylinders deactivated during engine startup.

[0054] At time t20, one or more fuel injectors have released fuel into one or more engine cylinders while the engine was commanded to shut down (not rotating) for a duration exceeding a threshold time amount. The oxygen sensor was at a low temperature, and cylinder number 1 was the first engine cylinder scheduled to fire (e.g., combust air and fuel) since the most recent engine shutdown. Cylinder number 1 was selected as the first engine cylinder to fire since the most recent engine shutdown based on the engine shutdown position. In this example, the engine could have stopped at 340 crankshaft degrees before top dead center compression stroke of cylinder number 1 with the intake valve of cylinder number 1 open. The engine startup request was not asserted and the engine air-fuel did not provide an accurate value. The fuel injector fuel release indication was not asserted and no cylinders were scheduled to be deactivated during subsequent engine startup.

[0055] The heater of the oxygen sensor is not activated and no power is applied to the oxygen sensor at time t20. When a voltage (e.g., a pumping voltage) is applied to the pumping unit of the oxygen sensor (not shown), the oxygen sensor can operate by electrochemically pumping out the oxygen sensed by the oxygen sensor from the inner cavity. Applying the pumping voltage to the pumping unit pumps oxygen into or out of the inner cavity to maintain the stoichiometric level of oxygen in the inner cavity. When the oxygen sensor is at the operating temperature (e.g., above the light-off temperature), the generated pumping current is proportional to the oxygen concentration in the intake or exhaust gas. The pumping current can be converted into a voltage and output from the oxygen sensor. However, if the oxygen sensor temperature is not higher than the light-off temperature (e.g., a lower threshold temperature), the output of the oxygen sensor may not represent the oxygen concentration sensed by the oxygen sensor. Since the output of the oxygen sensor (e.g., Figure 1 the oxygen sensor 126) can vary significantly with temperature, precise control of the oxygen sensor temperature may be desired. For example, the oxygen sensor can provide desired sensing when the temperature is higher than the lower threshold temperature. The lower threshold temperature can be, for example, the light-off temperature of the oxygen sensor (e.g., between 720 °C and 830 °C). Thus, in a situation where the oxygen sensor temperature is lower than the lower threshold temperature (e.g., during engine cold start), the oxygen sensor temperature can be raised to the lower threshold temperature. For example, during the oxygen sensor heating via the heater of the oxygen sensor, the oxygen sensor temperature can be raised to the lower threshold temperature. Since the output of the oxygen sensor may not represent the oxygen concentration sensed by the oxygen sensor, the inference of the engine air-fuel ratio or fuel-air ratio may be unreliable at a lower oxygen sensor temperature. Therefore, the engine start can be delayed until the oxygen sensor is at or above the lower threshold (e.g., the light-off temperature). To reduce the engine start delay, the oxygen sensor heater can be activated when the vehicle is unlocked or the driver's door is opened. In addition, a large amount of power can be supplied to the oxygen sensor heater for a short period of time so that the oxygen sensor temperature reaches the light-off temperature within a short period of time. In addition, electrified vehicles generally do not start their engines immediately, thus providing time for UEGO preheating. For example, hybrid vehicles usually reverse out of the driveway in front of the garage and do not start the engine until a large amount of driver demand is required. This also provides an opportunity for the electric heating device to heat. The system can also consider factors that cause injector leakage: pressure, time under pressure, and possibly temperature. At the first engine start, the time under pressure can be several days. However, during engine restart, the time may be much shorter. Therefore, if the injector releases fuel, it may be detected that the injector is releasing fuel. However, if the fuel released into the cylinder does not repeatedly produce rich exhaust spikes during restart, the release of fuel may not be finally determined. If the fuel injector cannot consistently release fuel during a short engine stop time, the described algorithm works well. Avoiding false alarms of cylinder leakage may require observing the rich exhaust spike more than once.

[0056] At time t21, in response to an engine start request, or alternatively, when the vehicle door is opened or when the key fob is near the vehicle, the engine start request is asserted and the oxygen sensor heater is activated. Engine rotation startup is delayed until the oxygen sensor reaches the threshold temperature 303, and then shortly after time t21, the engine speed increases as the engine starts. When the engine is started shortly after time t21, the engine lambda value begins to decrease. There is no indication of injector fuel release and no cylinders are deactivated.

[0057] Between time t21 and time t22, the engine lambda decreases to near 0.7, but in this example there is no indication of fuel release because it is desired to determine in which cylinder the fuel was released. However, in other examples, for instance, when the engine phi value exceeds 1.3, injector fuel release may be indicated. No engine cylinders are deactivated and the oxygen sensor temperature is higher than the threshold 303. Since the engine is operating and the final engine stop position is unknown, the first cylinder to be ignited in the planned ignition retains its previous value 1.

[0058] At time t22, the engine start request is withdrawn and the engine is stopped shortly thereafter. The oxygen sensor temperature is greater than the threshold 303, and the engine lambda value increases, indicating that air is being sensed. The first cylinder to be ignited in the next engine start is updated shortly after the engine stops at time t22. Based on the engine stop position and because the fuel release of the fuel injectors has been determined, the value of the first cylinder to be ignited is modified to value 4. There is no indication of fuel injector fuel release, and based on the first cylinder to be ignited during the most recent previous engine start, the cylinders to be deactivated during the next engine start are updated shortly after the engine stops. The engine cylinders to be deactivated for the next engine start are cylinder No. 1 because it was the first cylinder to be ignited during the most recent previous engine start.

[0059] At time t23, an engine start is requested based on a low battery charge state. However, since the oxygen sensor temperature is less than the threshold 303, the engine start is delayed until time t24. The engine start is delayed while the oxygen sensor temperature sensor increases above the level 303. At this time, a lower power level is applied to the oxygen sensor heater because an immediate quick start of the engine is not required at this time. Therefore, the oxygen sensor takes longer to reach the operating temperature, which results in a delay between time t23 and time t24. The time between time t22 and time t24 can be greater than the threshold time amount such that sufficient time is given for the fuel injector fuel release to occur.

[0060] At time t24, the engine is started after the oxygen sensor temperature exceeds the threshold 303. The engine is started with cylinder No. 1 deactivated (e.g., during engine cranking and during engine start-up acceleration, the intake and exhaust valves remain closed), and the first engine cylinder to be ignited since the engine was last stopped is cylinder No. 4. The engine lambda value indicates that the oxygen sensor detected air before engine cranking, and then the lambda value starts to decrease. No fuel injector fuel release is indicated.

[0061] Between time t24 and time t25, the engine lambda value decreases to a minimum value of approximately 0.92. This indicates that the amount of fuel released from the fuel injector is not greater than the threshold fuel amount. No fuel release indication is asserted, and the deactivated cylinder No. 1 is reactivated shortly after engine start so that the engine can provide a greater amount of torque. Additionally, any fuel that may have been released into cylinder No. 1 can be oxidized in the exhaust system and after-treatment device. The oxygen sensor temperature remains above the threshold 303 and the engine speed varies with the operating conditions. The first engine cylinder to be ignited since the most recent engine stop remains cylinder No. 4.

[0062] At time t25, the engine start request is withdrawn and the engine is stopped shortly thereafter. The oxygen sensor temperature is greater than the threshold 303, and the engine lambda value increases, indicating that air is being sensed. The first cylinder to be ignited for the next engine start is updated shortly after the engine stop at time t25. The value of the first cylinder to be ignited is modified to the value 1 so that the fuel release of the fuel injector from cylinder No. 1 can be verified a second time. No fuel injector fuel release is indicated, and the cylinder to be deactivated during the next engine start is updated shortly after the engine stop. Since the previous engine start indicated no fuel release and because the fuel release from cylinder No. 1 will be verified a second time before indicating fuel release from the fuel injector, no cylinders are scheduled to be deactivated.

[0063] At time t26, an engine start is requested a second time based on a low battery charge state. However, since the oxygen sensor temperature is less than the threshold 303, the engine start is delayed until time t27. The engine start is delayed while the oxygen sensor temperature sensor increases to above the level 303. At this time, a lower power level is applied to the oxygen sensor heater because an immediate quick start of the engine is not required at this time. Therefore, the oxygen sensor takes longer to reach the operating temperature, which results in a delay between time t26 and time t27. The time between time t25 and time t27 can be greater than the threshold time amount so that sufficient time is given for the fuel injector fuel release to occur.

[0064] At time t26, the engine is started after the oxygen sensor temperature exceeds threshold 303. The engine is started with all cylinders activated, and the first engine cylinder to fire since the engine was last stopped is cylinder number 1, so that fuel release to cylinder number 1 can be confirmed or denied. The engine lambda value indicates that the oxygen sensor detects air before the engine is cranked, and then the lambda value begins to drop. No fuel injector fuel release is indicated.

[0065] Shortly after time t27, the engine lambda decreases to a minimum value of approximately 0.7. This indicates that the amount of fuel released from the fuel injector is greater than the threshold fuel amount. The fuel release indication is now asserted because when the engine is started, no fuel release is indicated when cylinder No. 1 is deactivated. In this way, cylinder No. 1 can be isolated to determine that fuel has been released via the fuel injector of cylinder No. 1. Other engine cylinders can be isolated to verify or deny that fuel may have been released into those engine cylinders when the engine is stopped and the fuel injectors are commanded to close. An indication of fuel injector fuel release is generated shortly after a lambda value of 0.7 is observed during engine starting. The oxygen sensor temperature remains above threshold 303 and the engine speed varies with operating conditions. The first engine cylinder to ignite since the most recent engine stop is cylinder No. 1.

[0066] Reference now Figure 4 , shows an exemplary method 400 for diagnosing whether there is fuel released from a fuel injector when the fuel injector is commanded to close. The method 400 can diagnose whether there is fuel released from a fuel injector that is commanded to close after the engine has stopped rotating for a predetermined amount of time. The predetermined amount of time allows fuel to be released from the fuel injector when the fuel injector is commanded to close. Based on instructions stored in the non-volatile memory of the controller and in combination with signals received from sensors of the engine system, such as those described above with reference to Figure 1 The sensors described herein (eg, UEGO sensor 126), instructions for executing method 400 (including operating the engine under the conditions described herein) may be provided by a controller (eg, Figure 1 The controller may use the engine actuators of the engine system to adjust the engine operation according to the method described below.

[0067] At 402, method 400 determines whether the engine is stopped. When the position sensor of the engine indicates that the engine is not rotating, method 400 can determine that the engine is stopped. If method 400 determines that the engine is not stopped, method 400 then exits. If method 400 determines that the engine is stopped, method 400 proceeds to 404.

[0068] At 404, method 400 determines the engine temperature. The controller may determine the engine temperature via an engine temperature sensor. After determining the engine temperature, method 400 proceeds to 406.

[0069] At 406, method 400 determines the first cylinder to be fired after the most recent engine stop. In one example, method 400 determines the first cylinder to be fired based on the engine's stop position. The engine stop position may be determined when the engine stops or in response to an engine start request. In one example, method 400 selects the first cylinder to be fired (e.g., combust air and fuel) as the engine cylinder having an open intake valve and whose piston is closest to top dead center of the compression stroke. In other examples, method 400 may select the cylinder whose piston is closest to top dead center of the compression stroke. In yet another example, method 400 may select the first cylinder to be fired via other selection processes. The method selects the first cylinder to be fired during the subsequent next engine start, then proceeds to 408.

[0070] At 408, method 400 determines whether an engine start has been requested or is scheduled. An engine start may be requested by a human driver or via an automatic process (e.g., based on the vehicle's accelerator pedal and brake pedal positions). An engine start may be scheduled by an automatic driver or via the vehicle's control system in response to road conditions and vehicle conditions. An engine start may be scheduled at a future time from the current time (e.g., within 60 seconds). Method 400 may determine that an engine start has been requested or is scheduled based on the value of a variable stored in memory. For example, an engine start request variable may transition from a value of 0 to a value of 1 to indicate an engine start request. If method 400 determines that an engine start request exists or is scheduled, method 400 proceeds to 412. Otherwise, method 400 returns to 404.

[0071] At 410, method 400 determines whether the engine temperature is greater than a threshold temperature. The threshold temperature may be the engine temperature when only a small amount of fuel concentrate is provided to the engine due to lower fuel volatility. In one example, the engine threshold temperature may be 20 degrees Celsius. If method 400 determines that the engine temperature is greater than the threshold temperature, the answer is yes and method 400 proceeds to 412. Otherwise, the answer is no and method 400 allows the engine to start and then exits.

[0072] In addition, in some examples, method 400 may require the engine to be stopped for a predetermined amount of time (e.g., 25 minutes) to allow the release of fuel from the fuel injectors of the engine. The threshold amount of time may vary depending on the pressure of the fuel supplied to the fuel injectors and the engine temperature. If method 400 determines that the engine has been stopped for the threshold amount of time, the answer is yes and method 400 proceeds to 412. Otherwise, the answer is no and method 400 allows the engine to start and then exits.

[0073] At 412, method 400 supplies power to the oxygen sensor of the vehicle. The power source activates the oxygen sensor heater and provides a voltage to activate the sensing element of the sensor. Method 400 proceeds to 414. The power supplied to the oxygen sensor may be sufficient to activate the oxygen sensor such that the pumping current of the oxygen sensor is proportional to the oxygen concentration sensed via the oxygen sensor within a threshold amount of time (e.g., less than 1 second).

[0074] At 414, method 400 determines whether the pumping current of the oxygen sensor is proportional to the oxygen concentration sensed by the oxygen sensor. In one example, if a predetermined amount of time has elapsed since the most recent power supply to the oxygen sensor after the oxygen sensor was previously deactivated, method 400 determines whether the pumping current of the oxygen sensor is proportional to the oxygen concentration sensed by the oxygen sensor. If method 400 determines that the pumping current of the oxygen sensor is proportional to the oxygen concentration sensed via the oxygen sensor, the answer is yes and method 400 proceeds to 416. Otherwise, the answer is no and method 400 returns to 414.

[0075] At 416, method 400 begins recording the engine fuel-air ratio Φ into the controller's instantaneous memory. The engine fuel-air ratio Φ can be determined based on the output voltage of the oxygen sensor. In particular, the voltage output from the oxygen sensor is referenced to a transfer function that describes the engine fuel-air ratio as a function of the oxygen sensor voltage output. Method 400 proceeds to 418.

[0076] At 418, method 400 causes the engine to be cranked (e.g., using the power of an electric motor such as a starter or a motor / generator to rotate the engine) and starts the engine by supplying fuel to the cylinders of the engine and spark. Method 400 proceeds to 420.

[0077] At 420, method 400 determines that the engine fuel-air ratio Φ is greater than all other engine fuel-air ratios measured during current engine cranking, initial acceleration, and after the engine has reached an idle for a threshold amount of time (e.g., the maximum engine Φ). Alternatively, method 400 may integrate the engine fuel-air ratio Φ for a predetermined amount of time starting from engine cranking until the engine reaches an idle (e.g., 800 RPM) for a threshold amount of time. After determining the maximum engine fuel-air ratio Φ or integrating the engine fuel-air ratio Φ, method 400 proceeds to 422.

[0078] At 422, method 400 determines whether the maximum engine fuel-air ratio Φ is greater than a threshold (e.g., 1.3) or whether the integrated engine fuel-air ratio Φ is greater than a predetermined value. The predetermined value may be stored in the controller memory. If method 400 determines that the maximum engine fuel-air ratio Φ is greater than the threshold or if the integrated engine fuel-air ratio Φ is greater than the predetermined value, the answer is yes and method 400 proceeds to 424. Otherwise, the answer is no and method 400 proceeds to 440.

[0079] At 424, method 400 determines whether to isolate the engine fuel injectors that are considered to be releasing fuel to the engine. In one example, when the engine includes an actuator to deactivate individual engine cylinders, method 400 may determine to isolate the engine fuel injectors. By isolating the fuel injectors of the engine by deactivating the engine cylinders, the fuel injectors that may be releasing fuel into the engine cylinders can be identified. If method 400 determines to isolate the fuel injectors, the answer is yes and method 400 proceeds to 426. Otherwise, the answer is no and method 400 proceeds to 450.

[0080] At 426, when the engine fuel-air ratio Φ is stored in the memory, method 400 determines whether a cylinder was deactivated during the most recent engine start. Method 400 may determine whether an engine cylinder was deactivated during the most recent engine start based on the value of a variable stored in the memory. For example, when the value of the variable is 1, the variable may indicate that cylinder 1 is active. When the value of the variable is 0, the variable may indicate that cylinder 1 is deactivated. If method 400 determines that a cylinder was deactivated during the most recent engine start, the answer is yes and method 400 proceeds to 460. Otherwise, the answer is no and method 400 proceeds to 428.

[0081] At 428, method 400 schedules the first cylinder that fired during the previous engine start to be deactivated during the next subsequent engine start. For example, if cylinder 1 is the first cylinder that fired, then cylinder 1 is deactivated during the next subsequent engine start. By deactivating the first cylinder that fired during the most recent engine start, the fuel injectors that release fuel into the engine can be determined. Method 400 proceeds to 430.

[0082] At 430, method 400 can indicate that one or more fuel injectors may release fuel into the engine when commanded to close. Alternatively, method 400 may not immediately indicate that one or more fuel injectors may be releasing fuel into the engine when method 400 attempts to isolate the fuel injectors that may release fuel.

[0083] The indication can be provided via a human-machine interface, a display light, or other indicating means. Additionally, method 400 can adjust one or more actuators to compensate for the released fuel. For example, the amount of fuel injected via each fuel injector of the engine can be reduced by a small predetermined amount to reduce the engine's fuel-air ratio Φ during the next subsequent engine start. Method 400 then exits.

[0084] At 440, when the engine fuel-air ratio Φ is stored in the memory, method 400 determines whether a cylinder was deactivated during the previous most recent engine start. Method 400 can determine whether an engine cylinder was deactivated during the most recent engine start based on the value of a variable stored in the memory. For example, when the value of the variable is 1, the variable can indicate that cylinder 1 is active. When the value of the variable is 0, the variable can indicate that cylinder 1 is deactivated. If method 400 determines that a cylinder was deactivated during the most recent engine start, the answer is yes and method 400 proceeds to 442. Otherwise, the answer is no and method 400 proceeds to 446.

[0085] At 442, method 400 indicates that the fuel injector of the cylinder deactivated during the most recent engine start released fuel into the engine even though the fuel injector was deactivated. Since the engine fuel-air ratio Φ is not greater than a threshold, while the engine fuel-air ratio Φ was greater than the threshold during an earlier engine start, the cylinder suspected of releasing fuel via the fuel injector was deactivated. It can be determined that the deactivated cylinder has a deteriorated fuel injector that releases a fuel amount greater than the threshold amount into the engine when the fuel injector is commanded to close. The closed intake valve and exhaust valve can be used to prevent the fuel that has been released into the cylinder from leaving the cylinder and being discharged into the exhaust system.

[0086] For example, if cylinder 1 is deactivated because the engine fuel air ratio Φ is greater than a threshold and because cylinder 1 is the first cylinder to combust air and fuel after the most recent engine stop, and then the engine is restarted with cylinder 1 deactivated and the engine fuel air ratio Φ less than a threshold amount, it can be determined that when the fuel injector is commanded to close, the fuel injector for cylinder 1 released fuel into cylinder 1. Accordingly, the fuel injector for cylinder 1 can be indicated as degraded via a human machine interface, via a computer network, or via an alternative communication system.

[0087] In addition or alternatively, in some examples such as Figure 3 shown, the cylinder having a fuel injector determined to be degraded may not be immediately indicated. Instead, the cylinder can be reactivated during the next subsequent engine start. If the engine fuel air ratio Φ exceeds the threshold again during engine cranking start, tip-in acceleration, and the idle of the next subsequent engine start, the cylinder fuel injector determined to be degraded can be indicated to the driver of the vehicle and other vehicle systems. Method 400 proceeds to 444.

[0088] At 444, method 400 can operate one or more actuators to compensate for fuel released into the cylinder. In one example, the cylinder having a degraded fuel injector can be deactivated (e.g., for more than one engine cycle) by keeping the exhaust valve and / or intake valve closed during engine start, while other cylinders operate with their intake and exhaust valves opening and closing. The deactivated cylinder can be restarted after engine start and after the catalyst temperature reaches a threshold temperature such that if a rich mixture exits the previously deactivated cylinder, it can be oxidized in the exhaust manifold or catalyst. Spark can be inhibited in the cylinder using the deactivated valve to conserve spark energy. In addition, the degraded fuel injector can be deactivated during engine cranking start, tip-in acceleration, and at least until the engine speed reaches engine idle. After adjusting the engine actuator in response to the degraded fuel injector, method 400 then exits.

[0089] At 446, if no fuel is released from the fuel injectors within a number of actual engine starts greater than a predetermined total while all engine cylinders are activated, method 400 clears the indication that a fuel injector released fuel into an engine cylinder. Accordingly, if the fuel injector is replaced and the new fuel injector does not release fuel into the engine cylinder, the indication of the degraded fuel injector can be cleared from the controller memory and the human / machine interface. Method 400 then exits.

[0090] At 450, method 400 indicates that one or more fuel injectors of the engine may have deteriorated. Since the engine may not be able to isolate the fuel injector that still releases fuel when commanded to close, method 400 may only indicate that one or more fuel injectors may have deteriorated in response to the fuel-air ratio Φ being greater than a threshold. Method 400 proceeds to 452.

[0091] At 452, method 400 may reduce the amount of fuel injected into each engine cylinder in response to an indication that fuel is being released into the engine via a fuel injector that has been commanded to close. Additionally, if the vehicle is a hybrid vehicle, method 400 may prohibit an automatic engine stop (e.g., stopping engine rotation in response to driving conditions without an explicit request from a human driver to stop the engine), such that engine emissions can be kept at a lower level by not restarting the engine that releases fuel into the cylinders via the fuel injector that has been commanded to close. Thus, the fuel injectors can be commanded to open when they can be commanded to close to save fuel. Additionally, the spark and valves can be continuously operated, even when they can be automatically commanded to close via the controller. Method 400 then exits.

[0092] At 460, method 400 determines whether there are four or more consecutive fuel injector fuel release indications after four or more consecutive engine starts. The number 4 may be different for different types of engines. For example, for a six-cylinder engine with two cylinder banks (where each cylinder bank has three cylinders), the number may be three. If method 400 determines that more than a predetermined number of consecutive engine starts exhibit an engine fuel-air ratio Φ that exceeds a threshold fuel amount, the answer is yes and method 400 proceeds to 462. Otherwise, the answer is no and method 400 proceeds to 470.

[0093] At 462, method 400 indicates that when a fuel injector is commanded to be closed for more than a threshold amount of time, one or more fuel injectors may release fuel into an engine cylinder. Since method 400 deactivates each cylinder of a cylinder bank before determining whether there are more than four consecutive fuel release indications, it can be determined that two or more fuel injectors may release fuel into an engine cylinder when the fuel injector is commanded to be closed. For example, if all engine cylinders release more fuel than a threshold amount into an engine cylinder, the engine fuel-air ratio Φ may be greater than a threshold each time the engine restarts. In some examples, method 400 may check fuel injectors of all engine cylinders for releasing fuel into an engine cylinder when commanded to be closed during engine startup by deactivating each engine cylinder (e.g., deactivating only one cylinder each time the engine starts) until each cylinder of the cylinder bank has been deactivated. If the engine fuel-air ratio Φ is less than a threshold when a particular cylinder is deactivated, it can be determined that the particular cylinder may have a fuel injector that releases fuel when the fuel injector is commanded to be closed. On the other hand, if the engine fuel-air ratio Φ is greater than a threshold when each cylinder is deactivated (e.g., deactivated individually during four different engine startups), method 400 may determine that two or more cylinders may have fuel injectors that release fuel when the fuel injector is commanded to be closed. In this way, method 400 can determine which cylinders may have fuel injectors that may release fuel into the cylinders. Method 400 proceeds to 464.

[0094] At 464, method 400 may reduce the amount of fuel injected into each engine cylinder in response to an indication that fuel is released into the engine via a fuel injector commanded to be closed. Additionally, if the vehicle is a hybrid vehicle, method 400 may prohibit automatic engine stop (e.g., stopping engine rotation in response to driving conditions without a human driver explicitly requesting engine stop), such that engine emissions can be kept at a lower level by not restarting an engine that releases fuel into a cylinder via a fuel injector commanded to be closed. Thus, fuel injectors can be commanded to open when they can be commanded to be closed to save fuel. Additionally, spark and valves may be continuously operated even when they can be automatically commanded to be closed via a controller. Method 400 then exits.

[0095] At 470, method 400 schedules the next cylinder in the engine firing order on the same cylinder bank to be deactivated during the next engine start. For example, if the engine is a four-cylinder engine with a firing order of 1-3-4-2, and cylinder number 1 was deactivated during the most recent engine start, method 400 may schedule cylinder number 3 to be deactivated during the next engine start. In this way, method 400 can selectively deactivate engine cylinders until the engine fuel-air ratio Φ is less than a threshold during engine start-up in order to determine which fuel injector may be releasing fuel into the engine cylinder when commanded to close. Method 400 then exits.

[0096] The technical effect of determining whether there is fuel being released into the engine cylinder can reduce engine emissions. Additionally, by selectively deactivating engine cylinders during engine start-up, the cylinders having fuel injectors that release fuel into the engine cylinder when commanded to close can be determined, enabling a service technician to quickly locate a deteriorating fuel injector.

[0097] Accordingly, Figure 4 and Figure 5 An engine operating method is provided that includes: identifying a fuel injector of an engine that releases fuel when commanded to close via a controller, and identifying a fuel-air ratio indicated by an oxygen sensor during engine cranking start-up and initial acceleration; and adjusting an actuator based on the fuel injector via the controller. The method includes where the actuator is a cylinder lift valve operator. The method includes where the actuator is the fuel injector. The method includes where the engine is not rotating when fuel is released into the engine cylinder. The method further includes: identifying the first cylinder to be fired during the engine cranking start-up and initial acceleration, and selectively deactivating engine cylinders in response to an indication that more than a threshold amount of fuel has been released from the fuel injector.

[0098] In some examples, the method further includes: after the engine cranking start-up and initial acceleration, selectively deactivating the engine's cylinders during subsequent engine starts to identify the fuel injector. The method further includes: activating a heater of the oxygen sensor and heating the oxygen sensor to a temperature at which a pumping current of the oxygen sensor is proportional to an oxygen concentration sensed via the oxygen sensor before applying the fuel-air ratio indicated by the oxygen sensor to identify the fuel injector. The method further includes: delaying engine start until the oxygen sensor is heated to a temperature at which the pumping current of the oxygen sensor is proportional to the oxygen concentration sensed via the oxygen sensor.

[0099] Figure 4 and Figure 5An engine method is also provided, the method including: positively identifying that one or more fuel injectors of the engine have released a fuel amount greater than a threshold amount when the engine is stopped and when the engine fuel injectors are closed, determining the positive identification by a controller evaluating an engine fuel-air ratio estimate generated during engine cranking and initial acceleration, generating the engine fuel-air ratio via an oxygen sensor, the temperature of the oxygen sensor being greater than or equal to a temperature at which a pumping current of the oxygen sensor is proportional to an oxygen concentration sensed via the oxygen sensor; and in response to the positive identification, adjusting an actuator via the controller. The method also includes negatively identifying that one or more fuel injectors have released a fuel amount greater than a threshold amount when the engine is stopped and when the engine fuel injectors are closed, determining the negative identification by the controller evaluating that the engine fuel-air ratio estimate generated during engine cranking and initial acceleration is greater than a threshold. The method includes where the positive identification is based on the engine fuel-air ratio being greater than a threshold during engine cranking or initial acceleration.

[0100] In some examples, the method further includes: numerically integrating (e.g., by the trapezoidal integration method) the fuel-air ratio estimate generated during engine cranking and initial acceleration. The method includes where the positive identification is based on the integrated engine fuel-air ratio being greater than a threshold. The method also includes: identifying cylinders in which one or more fuel injectors release a fuel amount greater than a threshold amount. The method also includes: when a temperature of the engine is less than a threshold, not identifying that one or more fuel injectors of the engine have released a fuel amount greater than a threshold amount. Additionally, the methods described herein can be repeatedly performed during operation.

[0101] It should be understood that the configurations and procedures disclosed herein are exemplary in nature and these specific embodiments should not be regarded as having a limiting significance since many variations are possible. For example, the above techniques can be applied to V-6, inline 4-cylinder, inline 6-cylinder, 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 characteristics disclosed herein.

[0102] The following claims particularly point out certain combinations and sub - combinations that are considered novel and non - obvious. These claims may refer to "a" element or "a first" element or their equivalents. Such claims are to be understood as covering 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 this claims specification or by presenting new claims in this application or related applications. Such claims, whether broader, narrower, the same, or different in scope compared to the original claims, are equally considered to be included within the subject matter of this disclosure.

[0103] According to the present invention, a method of operating an engine includes: identifying a fuel injector of the engine that releases fuel when commanded to close via a controller, and identifying a fuel - air ratio indicated by an oxygen sensor during engine cranking start - up and initial acceleration; and adjusting an actuator based on the fuel injector via the controller.

[0104] According to one embodiment, a method, wherein the actuator is a cylinder lift valve operator.

[0105] According to one embodiment, a method, wherein the actuator is the fuel injector.

[0106] According to one embodiment, a method, wherein the engine is not rotating when the fuel injector releases fuel into the engine.

[0107] According to one embodiment, a method is further characterized by: identifying a first cylinder to be ignited during engine cranking start - up and initial acceleration, and selectively deactivating engine cylinders in response to an indication that the fuel injector has released more than a threshold amount of fuel.

[0108] According to one embodiment, a method is further characterized by: after engine cranking start - up and initial acceleration, selectively deactivating cylinders of the engine during subsequent engine start - up to identify the fuel injector.

[0109] According to one embodiment, a method is further characterized by: activating a heater of the oxygen sensor and heating the oxygen sensor to a temperature at which a pumping current of the oxygen sensor is proportional to an oxygen concentration sensed via the oxygen sensor before applying the fuel - air ratio indicated by the oxygen sensor to identify the fuel injector.

[0110] According to one embodiment, a method is further characterized by: delaying engine start - up until the oxygen sensor is heated to a temperature at which a pumping current of the oxygen sensor is proportional to the oxygen concentration sensed via the oxygen sensor.

[0111] According to the present invention, a method includes: affirmatively identifying that one or more fuel injectors of an engine have released a fuel amount greater than a threshold amount when the engine is stopped and when the engine fuel injectors are closed, determining the affirmative identification by a controller evaluating an engine fuel-air ratio estimate generated during engine cranking and initial acceleration, generating the engine fuel-air ratio via an oxygen sensor, the temperature of the oxygen sensor being greater than or equal to a temperature at which a pumping current of the oxygen sensor is proportional to an oxygen concentration sensed via the oxygen sensor; and in response to the affirmative identification, adjusting an actuator via the controller.

[0112] According to one embodiment, the method is further characterized by: negatively identifying that one or more fuel injectors have released a fuel amount greater than a threshold amount when the engine is stopped and when the engine fuel injectors are closed, determining the negative identification by the controller evaluating that the engine fuel-air ratio estimate generated during engine cranking and initial acceleration is greater than a threshold.

[0113] According to one embodiment, a method, wherein the affirmative identification is based on the engine fuel-air ratio being greater than a threshold during engine cranking or initial acceleration.

[0114] According to one embodiment, the method is further characterized by: integrating a fuel-air ratio estimate generated during engine cranking and initial acceleration.

[0115] According to one embodiment, a method, wherein the affirmative identification is based on the integrated engine fuel-air ratio being greater than a threshold.

[0116] According to one embodiment, the method is further characterized by: identifying a cylinder in which one or more fuel injectors release a fuel amount greater than a threshold amount.

[0117] According to one embodiment, the method is further characterized by: when a temperature of the engine is less than a threshold, not identifying that one or more fuel injectors of the engine have released a fuel amount greater than a threshold amount.

[0118] According to the present invention, a system includes: an engine including at least one fuel injector and an oxygen sensor located in an exhaust manifold; a controller storing executable instructions in a non-transitory memory, the executable instructions when executed causing the controller to: adjust an engine starting procedure after identifying that the at least one fuel injector has released a fuel amount greater than a threshold amount into the engine when the engine is stopped and a command to close the at least one fuel injector is issued, the identification being performed during engine cranking and initial acceleration of the engine during engine starting.

[0119] According to one embodiment, the system is further characterized by additional instructions for determining a maximum fuel-air ratio during the rotational starting and starting acceleration.

[0120] According to one embodiment, a system wherein the identification is based on the maximum fuel-air ratio exceeding a threshold.

[0121] According to one embodiment, a system wherein adjusting the engine starting procedure includes deactivating engine cylinders.

Claims

1. An engine operating method, which comprises: During engine cranking start and initial acceleration, identifying a fuel injector of the engine that releases fuel when commanded to close via a controller, and identifying the fuel-air ratio indicated by an oxygen sensor, wherein the initial acceleration represents the engine accelerating from the cranking speed to idle speed; and Adjusting an actuator based on the fuel injector via the controller.

2. The method according to claim 1, wherein the actuator is a cylinder lift valve operator.

3. The method according to claim 1, wherein the actuator is the fuel injector.

4. The method according to claim 1, wherein the engine does not rotate when the fuel injector releases fuel into the engine.

5. The method according to claim 1, which further comprises: Identifying the first cylinder to be ignited during engine cranking start and initial acceleration, and selectively deactivating engine cylinders in response to an indication that more than a threshold amount of fuel has been released from the fuel injector.

6. The method according to claim 5, which further comprises: After engine cranking start and initial acceleration, selectively deactivating cylinders of the engine during subsequent engine starts to identify the fuel injector.

7. The method according to claim 1, which further comprises: Before applying the fuel-air ratio indicated by the oxygen sensor to identify the fuel injector, activating a heater of the oxygen sensor and heating the oxygen sensor to a temperature at which the pumping current of the oxygen sensor is proportional to the oxygen concentration sensed via the oxygen sensor.

8. The method according to claim 7, which further comprises: Delaying engine start until the oxygen sensor is heated to a temperature at which the pumping current of the oxygen sensor is proportional to the oxygen concentration sensed via the oxygen sensor.

9. An engine system, which comprises: An engine including at least one fuel injector and an oxygen sensor located in an exhaust manifold; A controller that stores executable instructions in a non-transitory memory, the executable instructions when executed causing the controller to: Adjust the engine start procedure after identifying that the at least one fuel injector has released more than a threshold amount of fuel into the engine when the engine is stopped and the at least one fuel injector is commanded to close, the identification being performed during engine cranking start and initial acceleration of the engine during engine start, wherein the initial acceleration represents the engine accelerating from the cranking speed to idle speed.

10. The engine system according to claim 9, which further includes additional instructions for determining a maximum fuel-air ratio during the cranking start and initial acceleration.

11. The engine system according to claim 10, wherein the identification is based on the maximum fuel-air ratio exceeding a threshold.

12. The engine system according to claim 9, wherein adjusting the engine start procedure includes deactivating engine cylinders.

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