System and method for cylinder exhaust valve diagnostics

Abstract

The present disclosure provides a system and method for cylinder exhaust valve diagnostics. Methods and systems are provided for diagnosing degradation of an exhaust valve coupled to an engine cylinder. In one example, a method may include directing compressed air from an electric booster into a cylinder with the intake valve of the cylinder open and the exhaust valve closed; and indicating exhaust valve degradation based on exhaust air flow relative to a baseline air flow.

Description

Technical Field

[0001] The present description generally relates to methods and systems for performing diagnostics on exhaust valves coupled to cylinders during a vehicle key-off state. Background Art

[0002] In a four-stroke cycle engine, power is recovered from the combustion process during the four independent piston motions (strokes) of a single piston: intake, compression, power, and exhaust. During the intake stroke, the intake valve opens to admit air into the combustion chamber. Similarly, during the exhaust stroke, the exhaust valve opens to allow exhaust gas to escape from the combustion chamber. During the compression and power strokes, the intake and exhaust valves remain closed, sealing the combustion chamber and maximizing compression during the compression stroke, effectively transferring the energy generated by combustion to the piston motion during the power stroke. Exhaust gas flowing out of the cylinder via the exhaust valve includes combustion byproducts. Consequently, over time, soot and other carbonaceous materials may accumulate in the exhaust valve. For example, the exhaust valve may gradually fill with soot, which in some examples may cause the exhaust valve to exhibit degradation (e.g., become stuck in an at least partially open position). For example, if the combustion chamber is not sealed during the compression stroke, the cylinder may lose most of its air / fuel mixture before ignition, leading to combustion instability and misfires.

[0003] Sellers, in U.S. Patent No. 7,581,433, discloses an exemplary method for conducting an off-vehicle cylinder leak test. Sellers describes an apparatus comprising a hose, one end of which is configured to communicate with a spark plug hole coupled to a cylinder to be tested, and the other end of which is configured to attach to a pressurized gas source. The pressurized gas is introduced into the cylinder, and the pressure in the cylinder is monitored to detect whether the cylinder is leaking.

[0004] However, the present inventors have recognized potential issues with such a system. For example, off-board diagnostic methods require expert personnel to perform, and such methods are also invasive, difficult, and time-consuming. The method described by Sellers may not be able to distinguish between a leaking intake valve and a leaking exhaust valve of a cylinder. Exhaust valve leakage can adversely affect engine operation by causing misfires, backfires, rough idle, lower power output, and reduced fuel economy. If a cylinder is operated for an extended period with a leaking exhaust valve, the significant heat released during combustion can further erode the valve. Summary of the Invention

[0005] In one example, the aforementioned problem can be addressed by an engine method comprising: testing exhaust valve degradation coupled to a cylinder of a multi-cylinder engine driving a vehicle by sealing the exhaust valve during an on-vehicle test; directing pressurized air into the cylinder during the test; and indicating the presence or absence of exhaust valve degradation during the test based on air flow through an exhaust device coupled to the cylinder relative to a baseline air flow through the exhaust device. In this manner, by directing pressurized air through the engine cylinder during a vehicle key-off state, degradation of the exhaust valve coupled to the cylinder can be detected.

[0006] In one example, a diagnostic routine for cylinder exhaust valves can be performed in a timely manner during a vehicle key-off state when the engine is not running. The vehicle can be an autonomous vehicle and / or a hybrid vehicle. The engine can be a supercharged engine comprising a turbine-driven intake compressor and an electrically driven intake compressor (also referred to herein as a battery-operated electric booster) that selectively operates to provide additional boost during periods of increased torque demand. During on-board power distribution analysis, a cylinder can be identified as providing power below a threshold. During a subsequent vehicle key-off state, the cylinder can be positioned with the intake valve open and the exhaust valve closed. The diagnostic routine for the exhaust valve includes operating the electric booster to direct pressurized air from the intake manifold via the cylinder to the exhaust manifold. The air flow leaving the cylinder can be compared to a threshold air flow, and exhaust valve degradation can be diagnosed based on the exhaust air flow above the threshold. Subsequent engine cylinders of a multi-cylinder engine can be similarly diagnosed to detect degradation of individual exhaust valves.

[0007] In this way, by making timely use of existing engine components, such as the electric boost and differential pressure sensor, the need for off-board intervention and the use of additional sensors and / or equipment for exhaust valve diagnostics can be reduced. The technical benefit of performing exhaust valve diagnostics during the vehicle's key-off state is that exhaust valve diagnostics can be performed while maintaining the engine valves in a static position and without impacting engine performance. By identifying the cause of below-threshold power output in a specific cylinder, appropriate mitigating measures can be taken, reducing the potential for engine system degradation. Overall, by regularly monitoring exhaust valve health, combustion stability, engine performance, and fuel efficiency can be improved.

[0008] It should be understood that the above Summary is provided to introduce in simplified form a series of concepts that will be further described in the Detailed Description. It is not intended to identify key or essential features of the claimed subject matter, the scope of which is uniquely defined by the Examples that follow the Detailed Description. Furthermore, the claimed subject matter is not limited to implementations that address any shortcomings noted above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 An example hybrid vehicle system having a multi-cylinder engine is schematically illustrated.

[0010] Figure 2 A schematic diagram showing one cylinder of a multi-cylinder engine is shown.

[0011] Figure 3 A block diagram of an exemplary autonomous driving system is schematically shown.

[0012] Figure 4 A flow chart is shown illustrating an exemplary method that may be implemented to diagnose exhaust valve degradation.

[0013] Figure 5 An example graph of cylinder power is shown.

[0014] Figure 6 An exemplary timeline of engine position during an exhaust valve diagnostic routine is shown.

[0015] Figure 7 Exemplary operation of an electric booster for exhaust valve diagnostics according to the present disclosure is shown. DETAILED DESCRIPTION

[0016] The following description relates to systems and methods for diagnosing exhaust valves coupled to engine cylinders during a vehicle shut-off state. Such methods may include flowing compressed air through an engine cylinder, such as a valve coupled to an engine cylinder. Figure 1 The cylinders of the hybrid vehicle system are depicted in Figure 2. Figure 2 An example cylinder including an exhaust valve is shown in FIG. In some examples, exhaust valve diagnostics may be performed in an autonomous vehicle, where Figure 3 An exemplary autonomous vehicle control system is depicted. The engine controller may be configured to execute a control program such as Figure 4 An exemplary procedure of the invention is provided for diagnosing exhaust valve degradation. An engine cylinder may be identified for performing exhaust valve diagnostics based on the power delivered by the cylinder, such as Figure 5 As shown in the curve. Figures 6 and 7 Example electric booster operation and engine positions for implementing exhaust valve diagnostics are shown in FIG.

[0017] Figure 1 A schematic diagram 101 of a vehicle system 102 is shown having an example engine system 100 including an engine 10. In one example, the engine system 100 can be a diesel engine system. In another example, the engine system 100 can be a gasoline engine system. In the depicted embodiment, the engine 10 is a supercharged engine coupled to a turbocharger 15, which includes a compressor 114 driven by a turbine 116. Specifically, fresh air is introduced into the engine 10 via an air cleaner 112 along an intake passage 42 and flows to the compressor 114. The compressor can be any suitable intake air compressor, such as a supercharger compressor driven by a motor or a drive shaft. In the engine system 10, the compressor is a turbocharger compressor, which is mechanically coupled to a turbine 116 via a shaft 19, and the turbine 116 is driven by expanding engine exhaust gas.

[0018] like Figure 1 As shown, compressor 114 is coupled to throttle valve 20 via charge air cooler (CAC) 118. Throttle valve 20 is coupled to engine intake manifold 22. Compressed air charge flows from the compressor through charge air cooler 118 and throttle valve 20 to intake manifold 22. Figure 1 In the illustrated embodiment, the pressure of the air charge within intake manifold 22 is sensed by manifold air pressure (MAP) sensor 124. The temperature of the ambient air entering intake passage 42 may be estimated via intake air temperature (IAT) sensor 51.

[0019] One or more sensors may be coupled to the inlet of compressor 114. For example, a temperature sensor 55 may be coupled to the inlet to estimate the compressor inlet temperature, and a pressure sensor 56 may be coupled to the inlet to estimate the compressor inlet pressure. As another example, an ambient humidity sensor 57 may be coupled to the inlet to estimate the humidity of the air charge entering the intake manifold. Other sensors may include, for example, an air-fuel ratio sensor, etc. In other examples, one or more of the compressor inlet conditions (such as humidity, temperature, pressure, etc.) may be inferred based on engine operating conditions. Additionally, when exhaust gas recirculation (EGR) is enabled, sensors may estimate the temperature, pressure, humidity, and air-fuel ratio of the air charge mixture (which includes fresh air, recirculated compressed air, and exhaust gas residuals received at the compressor inlet).

[0020] Wastegate actuator 91 may be actuated open to vent at least some exhaust pressure from upstream of the turbine outwardly to a location downstream of the turbine via wastegate 90. By reducing the exhaust pressure upstream of the turbine, turbine speed may be reduced, which in turn helps reduce compressor surge.

[0021] To assist the turbocharger 15, an additional intake air compressor (also referred to herein as an electric booster 155) can be incorporated into the vehicle propulsion system. The electric booster 155 can be powered via an onboard energy storage device 250, which can include a battery, a capacitor, an ultracapacitor, or the like. The electric booster can include a compressor driven by an electric motor. The operating speed of the electric booster can include regulating the operating speed of the electric motor, which is operated via the onboard energy storage device 250.

[0022] In one example, the electric boost 155 can be activated in response to a demand for increased wheel torque to quickly provide the desired boost air to the engine as the turbocharger turbine accelerates. Thus, the increased torque can be met without causing turbo lag, which might otherwise occur without assistance from the electric boost. In this example, the electric boost 155 can be activated to shut off or deactivate in response to the turbocharger accelerating to a threshold speed (e.g., 70,000 rpm). More specifically, operational control of the electric boost 155 can be implemented based on a command signal (e.g., a duty cycle or pulse width signal) received from a vehicle controller (e.g., controller 12). For example, the controller can send a signal to the electric boost actuator 155b that can activate the electric boost. In another example, the controller can send a signal to the electric boost actuator 155b that can activate the electric boost. In one example, the electric boost actuator can include an electric motor that drives air compression.

[0023] The electric booster 155 can be located between a first electric booster conduit 159a and a second electric booster conduit 159b. The first electric booster conduit 159a can fluidly couple the intake passage 42 to the electric booster 155 upstream of the electric booster bypass valve 161. The second electric booster conduit 159b can fluidly couple the electric booster 155 to the intake passage 42 downstream of the electric booster bypass valve 161. As an example, air can be drawn into the electric booster 155 via the first electric booster conduit 159a upstream of the electric booster bypass valve 161, and compressed air can exit the electric booster 155 and be directed to the intake passage 42 downstream of the electric booster bypass valve 161 via the second electric booster conduit. In this manner, compressed air can be directed to the engine intake manifold 22.

[0024] In the event that the electric boost 155 is activated to provide boost faster than relying solely on the turbocharger 15, it will be appreciated that the electric boost bypass valve 161 can be commanded to close when the electric boost 155 is activated. In this way, intake air can flow through the turbocharger 15 and through the electric boost 155. Once the turbocharger reaches a threshold speed, the electric boost 155 can be turned off and the electric boost bypass valve 161 can be commanded to open.

[0025] Intake manifold 22 is coupled to a series of combustion chambers 30 via a series of intake valves (not shown). The combustion chambers are also coupled to exhaust manifold 36 via a series of exhaust valves (not shown). Figure 2 An exemplary combustion chamber (cylinder) is described in detail. In the illustrated embodiment, a single exhaust manifold 36 is shown. However, in other embodiments, the exhaust manifold may include multiple exhaust manifold sections. A configuration with multiple exhaust manifold sections can enable the outflow from different combustion chambers to be directed to different locations in the engine system.

[0026] In one embodiment, each of the exhaust valve and the intake valve can be electronically actuated or electronically controlled. In another embodiment, each of the exhaust valve and the intake valve can be cam-actuated or cam-controlled. Whether electronically actuated or cam-actuated, the timing of the opening and closing of the exhaust and intake valves can be adjusted as needed to achieve desired combustion and emissions control performance.

[0027] As combustion progresses in an engine cylinder, the exhaust valve may gradually fill with carbon deposits, which may cause the exhaust valve to become stuck in a partially or fully open position. In one example, upon indicating that the power output of a first cylinder is below a threshold power output, a diagnostic may be performed on the exhaust valve coupled to the first cylinder during a subsequent engine non-combustion state. In one example, the power output of the first cylinder may be estimated by selectively disabling spark for the first cylinder while maintaining spark for each remaining cylinder of the multi-cylinder engine, estimating a change in engine speed via a crankshaft position sensor, and estimating the power output of the first cylinder based on the estimated change in engine speed after disabling spark. During the diagnostic period, the cylinder may be parked in a first position in which the intake valve coupled to the cylinder is in an open position and the exhaust valve is in a closed position. Compressed air from the engine intake manifold 22 may be forced into the cylinder by operating the electric booster 155 via the electric booster actuator 155b. Exhaust air flow may be estimated via the differential pressure sensor 127 and compared to a baseline air flow. In response to the estimated exhaust air flow being greater than a baseline air flow, the exhaust valve may be indicated as degraded. In response to the estimated exhaust air flow being substantially equal to the baseline air flow (such as within 5% of the baseline air flow), the exhaust valve may be indicated as non-degraded. During subsequent engine operation, in response to the indication of a degraded exhaust valve, fuel and spark may be suspended to the cylinder having the degraded exhaust valve.

[0028] Combustion chamber 30 may be supplied with one or more fuels such as gasoline, an alcohol fuel blend, diesel, biodiesel, compressed natural gas, or the like via injector 66. Fuel may be supplied to the combustion chamber via direct injection, port injection, throttle body injection, or any combination thereof. Combustion may be initiated in the combustion chamber via spark ignition and / or compression ignition.

[0029] like Figure 1 As shown, exhaust gas from one or more exhaust manifold sections may be directed to turbine 116 to drive the turbine. The combined flow from the turbine and the wastegate then flows through emission control device 170. In one example, emission control device 170 may be a light-off catalyst. Typically, exhaust aftertreatment device 170 is configured to catalytically treat the exhaust flow, thereby reducing the amount of one or more substances in the exhaust flow. For example, exhaust aftertreatment device 170 may be configured to capture NO from the exhaust flow when the exhaust flow is lean. x , and reduces the trapped NO when the exhaust stream is rich x In other examples, the exhaust aftertreatment device 170 may be configured to x Disproportionate or selective reduction of NO with the aid of reducing agents xIn other examples, exhaust aftertreatment device 170 may be configured to oxidize residual hydrocarbons and / or carbon monoxide in the exhaust flow. Different exhaust aftertreatment catalysts having any such functionality may be disposed individually or together in the washcoat or elsewhere in the exhaust aftertreatment stage.

[0030] Gasoline particulate filter (GPF) 172 may be coupled to exhaust passage 104 downstream of exhaust aftertreatment device 170. GPF 172 may include a particulate filter, a hydrocarbon trap, a catalytic washcoat, or a combination thereof. In some examples, during engine operation, GPF 172 may be periodically regenerated by operating at least one cylinder of the engine within a particular air-fuel ratio to increase the temperature of GPF 172 so that residual hydrocarbons and soot particulates may be oxidized.

[0031] The pressure in the exhaust system may be assessed by pressure sensor 127. For example, pressure sensor 127 may be a differential pressure sensor coupled across GPF 172. Pressure sensor 127 may be used to determine the airflow at the inlet of GPF 172 to assess the conditions under which air is introduced into the inlet of GPF 172 for regeneration.

[0032] Exhaust gas recirculation (EGR) delivery passage 180 can be coupled to exhaust passage 104 upstream of turbine 116 to provide high-pressure EGR (HP-EGR) to the engine intake manifold downstream of compressor 114. EGR valve 152 can be coupled to EGR passage 180 at the junction of EGR passage 180 and intake passage 42. EGR valve 152 can be opened to allow a controlled amount of exhaust gas to enter the compressor outlet to achieve desired combustion and emissions control performance. EGR valve 152 can be configured as a continuously variable valve or an on / off valve. In further embodiments, the engine system may include a low-pressure EGR (LP-EGR) flow path in which exhaust gas is extracted downstream of turbine 116 and recirculated to the engine intake manifold upstream of compressor 114.

[0033] One or more sensors may be coupled to EGR passage 180 to provide details regarding the composition and condition of the EGR. For example, a temperature sensor may be provided to determine the temperature of the EGR, a pressure sensor may be provided to determine the pressure of the EGR, a humidity sensor may be provided to determine the humidity or water content of the EGR, and an air-fuel ratio sensor may be provided to estimate the air-fuel ratio of the EGR. Alternatively, EGR conditions may be inferred from one or more temperature, pressure, humidity, and air-fuel ratio sensors coupled to the compressor inlet.

[0034] A plurality of sensors, including an exhaust temperature sensor 128, an exhaust oxygen sensor, and an exhaust flow sensor, may be coupled to the main exhaust passage 104. The oxygen sensor may be a linear oxygen sensor or UEGO (Universal or Wide Range Exhaust Gas Oxygen), a two-state oxygen sensor or EGO, a HEGO (Heated EGO), a NOx, HC, or CO sensor.

[0035] The engine system 100 may also include a control system 14. The control system 14 is shown receiving information from a plurality of sensors 16 (various examples of which are described herein) and sending control signals to a plurality of actuators 18 (various examples of which are described herein). As an example, the sensors 16 may include an exhaust gas sensor 126 located upstream of the turbine 116, a MAP sensor 124, an exhaust gas temperature sensor 128, an exhaust gas pressure sensor 127, a compressor inlet temperature sensor 55, a compressor inlet pressure sensor 56, an ambient humidity sensor 57, an IAT sensor 51, an engine coolant temperature sensor, and an EGR sensor, among others. Other sensors (such as additional pressure sensors, temperature sensors, air-fuel ratio sensors, and composition sensors) may be coupled to various locations within the engine system 100. Additionally, sensors coupled to the exterior of the vehicle system, such as a rain sensor (windshield sensor) 130, may be used to estimate ambient humidity.

[0036] Actuators 18 may include, for example, electric boost bypass valve 161, throttle valve 20, electric boost actuator 155b, EGR valve 152, wastegate actuator 92, and fuel injector 66. Control system 14 may include controller 12. Controller 12 may receive input data from various sensors, process the input data, and trigger various actuators in response to the processed input data based on instructions or code programmed therein corresponding to one or more routines. In one example, in response to a power output from a cylinder below a threshold, in anticipation of a vehicle key-off state, controller 12 may position the cylinder with an intake valve open and an exhaust valve closed, and may send signals to electric boost bypass valve 161 to actuate the valve to a closed position and to boost actuator 155b to actuate electric boost 155 to direct compressed air through the cylinder. Degradation of an exhaust valve coupled to the cylinder may be diagnosed based on changes in exhaust pressure estimated via pressure sensor 127 during the routing of compressed air through the cylinder.

[0037] In some examples, vehicle 102 may be a hybrid vehicle having multiple torque sources available to one or more wheels 157. In other examples, vehicle 102 may be a conventional vehicle having only an engine, or an electric vehicle having only an electric motor. In the illustrated example, vehicle 102 includes engine 10 and electric motor 52. Electric motor 52 may be a motor or a motor / generator (M / G). When one or more clutches 156 are engaged, the crankshaft of engine 10 and electric motor 52 are connected to wheels 157 via transmission 54. In the depicted example, a first clutch 156 is disposed between the crankshaft and electric motor 52, and a second clutch 156 is disposed between electric motor 52 and transmission 54. Controller 12 may send signals to the actuator of each clutch 156 to engage or disengage the clutch, thereby connecting or disconnecting the crankshaft from electric motor 52 and components connected thereto, and / or connecting or disconnecting electric motor 52 from transmission 54 and components connected thereto. Transmission 54 may be a gearbox, a planetary gear system, or another type of transmission. The powertrain may be configured in various ways, including parallel, series, or series-parallel hybrid vehicles.

[0038] The electric motor 52 receives power from the power battery 58 to provide torque to the wheels 55. The electric motor 52 can also operate as a generator to provide power to charge the power battery 58, such as during braking operations.

[0039] Figure 2 An exemplary embodiment 200 of a combustion chamber or cylinder that may be included in an engine 210 is depicted, which may be used in conjunction with the combustion chamber as described herein and in Figure 1 is configured similarly to the engine 10 depicted in . Cylinder (i.e., combustion chamber) 214 may include combustion chamber walls 236, with piston 238 located therein. Piston 238 may include one or more piston rings 268. For example, one or more piston rings 268 may be used to seal cylinder 214, assist in piston heat transfer, and regulate fuel consumption. Piston 238 may be coupled to crankshaft 240 so that the reciprocating motion of the piston is converted into rotational motion of the crankshaft. Crankshaft 240 may be coupled to at least one drive wheel of a passenger vehicle via a transmission system. In addition, starter motor 212 may be coupled to crankshaft 240 via a flywheel to enable a starting operation of engine 210 and / or to rotate the engine in a non-fueled mode. Crankshaft position sensor 214 may be coupled to crankshaft 240 to estimate engine speed.

[0040] Cylinder 214 can receive intake air via intake passage 244, which can be one of a plurality of intake passages coupled to cylinder 214. In addition to cylinder 214, intake passage 244 can also communicate with other cylinders of engine 210. In some embodiments, one or more of the intake passages can include a boosting device, such as a turbocharger or a supercharger. Exhaust passage 248 can receive exhaust gas from cylinder 214 and from other cylinders of engine 210.

[0041] Each cylinder of engine 210 may include one or more intake valves and one or more exhaust valves. For example, cylinder 214 is shown as including at least one intake poppet valve 256 and at least one exhaust poppet valve 250 located at an upper region of cylinder 214. In some embodiments, each cylinder of engine 210 (including cylinder 214) may include at least two intake poppet valves and at least two exhaust poppet valves located at an upper region of the cylinder.

[0042] Intake valve 256 can be controlled by a controller via actuator 252. Similarly, exhaust valve 250 can be controlled by a controller via actuator 254. During some conditions, the controller can change the signals provided to actuators 252 and 254 to control the opening and closing of the respective intake and exhaust valves. The positions of intake valve 256 and exhaust valve 250 can be determined by respective valve position sensors (not shown). The valve actuators can be electric valve actuation type or cam actuation type or a combination thereof, as described with reference to FIG. Figure 1 As described. The intake and exhaust valve timing can be controlled simultaneously, or any of the possible configurations of variable intake cam timing, variable exhaust cam timing, dual independent variable cam timing, or fixed cam timing can be used. Each cam actuation system can include one or more cams and can utilize one or more of a cam profile switching system (CPS), variable cam timing (VCT), variable valve timing (VVT), and / or a variable valve lift (VVL) system, which can be operated by a controller to change valve operation. For example, cylinder 214 may alternatively include an intake valve controlled by electric valve actuation and an exhaust valve controlled by cam actuation including CPS and / or VCT. In other embodiments, the intake and exhaust valves can be controlled by a common valve actuator or actuation system or a variable valve timing actuator or actuation system.

[0043] Cylinder 214 can have a certain compression ratio, which is the ratio of the volume within the cylinder when piston 238 is at bottom dead center to top dead center. Conventionally, the compression ratio is in the range of 9:1 to 10:1. However, in some examples using different fuels, the compression ratio can be increased. This can occur, for example, when using a higher octane fuel or a fuel with a higher latent enthalpy of vaporization. The compression ratio can also be increased if direct injection is used due to its effect on engine knock.

[0044] In some embodiments, each cylinder of engine 210 may include a spark plug 292 for initiating combustion. In selected operating modes, an ignition system (not shown) may provide an ignition spark or sparks to cylinder 214 via spark plug 292 in response to a spark advance signal from a controller. However, in some embodiments, spark plug 292 may be omitted, such as where engine 210 may initiate combustion via auto-ignition (as in some diesel engines).

[0045] In some embodiments, each cylinder of engine 210 may be configured with one or more fuel injectors for providing fuel thereto. As a non-limiting example, cylinder 214 may include two fuel injectors (e.g., a port fuel injector and a direct fuel injector). Fuel injector 266 is shown as being directly coupled to cylinder 214 for injecting fuel directly therein in proportion to the pulse width of a signal received from a controller via an electronic driver. In this manner, fuel injector 266 provides what is known as direct injection of fuel (hereinafter referred to as "DI") into cylinder 214. Although Figure 2 Injector 266 is shown as a side injector, but the injector may also be located on top of the piston, such as near spark plug 292. Due to the lower volatility of some alcohol-based fuels, such a location may facilitate mixing and combustion when the engine is operated on alcohol-based fuels. Alternatively, the injector may be located on top and close to the intake valve to facilitate mixing. Fuel may be delivered to fuel injector 266 from a high-pressure fuel system including a fuel tank, fuel pump, fuel rail, etc. Alternatively, at lower pressures, the fuel may be delivered by a single-stage fuel pump, in which case the timing of the direct fuel injection during the compression stroke may be more restricted than when using a high-pressure fuel system.

[0046] Fuel can be delivered to the cylinder during a single cycle of the cylinder. Directly injected fuel can be delivered during the intake stroke and partially during the preceding exhaust stroke. Furthermore, directly injected fuel can be delivered as a single injection or as multiple injections. These may include multiple injections during the compression stroke, multiple injections during the intake stroke, or a combination of some direct injections during the compression stroke and some direct injections during the intake stroke. When multiple direct injections are performed, the relative allocation of the total directly injected fuel between the intake stroke (direct) injection and the compression stroke (direct) injection can be referred to as a second injection ratio. For example, injecting a greater amount of directly injected fuel for a combustion event during the intake stroke can be an example of a higher second ratio for intake stroke direct injection, while injecting a greater amount of fuel for a combustion event during the compression stroke can be an example of a lower second ratio for intake stroke direct injection. Note that these are merely examples of different injection ratios, and a variety of other injection ratios can be used.

[0047] A positive crankcase ventilation (PCV) system may be coupled to the engine intake so that gases in the crankcase 262 may be vented from the crankcase in a controlled manner. Figure 1 As described with respect to PCV system 16, engine 210 may include crankcase vent tube 258 and PCV line 260 to vent gases from crankcase 262 and into the intake manifold. In some examples, PCV line 260 may include PCV valve 264, which may be an electronically controlled valve (e.g., a powertrain control module (PCM) controlled valve) where a controller may command a signal to change the valve's position from an open position (or high flow position) to a closed position (or low flow position), or vice versa, or any position in between.

[0048] As mentioned above, Figure 2 Only one cylinder of a multi-cylinder engine is shown. Therefore, each cylinder may similarly include its own set of intake / exhaust valves, fuel injectors, spark plugs, piston rings, etc.

[0049] A common failure mode in internal combustion engines is misfire. Typical causes of misfire include leaking or clogged fuel injectors, fouled spark plugs, degraded ignition coils, and poor cylinder compression. Misfires due to poor cylinder compression can be indicated by an onboard power balance test, which is run with the engine burning and uses crankshaft position sensor 215 as input to calculate the RPM contribution of each cylinder's power stroke. Another test that indicates poor cylinder compression is a relative compression test. Prior art methods for relative compression testing use a high-ampere current probe to measure battery current during the starting event, as a cylinder with poor compression will not draw as much current as a healthy cylinder. However, diagnosis of the cause of poor cylinder compression (e.g., a leaking cylinder valve) is typically performed using an off-board cylinder leak test, which involves disabling fuel flow to the cylinder, removing the spark plug, installing a pressure gauge, and introducing air into the cylinder. For example, a misfiring cylinder may be placed at top dead center (TDC) with both the intake and exhaust valves closed, allowing the inducted air to escape indicating a leaking intake or exhaust valve, or a leaking piston ring. Because such off-vehicle cylinder leak testing is intrusive, difficult, and time-consuming, on-vehicle cylinder leak testing is required to diagnose the cause of cylinder misfires due to poor compression. Figure 4 A non-intrusive on-vehicle test is described for detecting exhaust valve degradation, which can result in reduced power output from the cylinders or cause misfire.

[0050] The exhaust valve diagnostic procedure can be performed in a vehicle configured as an autonomous vehicle, as will be referred to below. Figure 3 Discuss an exemplary autonomous drive system. Figure 3 It is possible to operate above Figure 1 1. A block diagram of an exemplary autonomous driving system 300 of the vehicle system 100 described herein. The vehicle system 100 will be referred to herein as simply a "vehicle." As shown, the autonomous driving system 300 includes a user interface device 310, a navigation system 315, at least one autonomous driving sensor 320, and an autonomous mode controller 325. It is understood that the vehicle navigation system 315 can be used with Figure 1 The in-vehicle navigation system 132 is the same as that depicted in FIG, and the user interface device 310 may be the same as that depicted in FIG. Figure 1 The same as the HMI 133 depicted in FIG.

[0051] The user interface device 310 may be configured to present information to a vehicle occupant in the presence of a vehicle occupant. However, it will be appreciated that under certain conditions, the vehicle may operate autonomously without the presence of a vehicle occupant. The information presented may include audible or visual information. Additionally, the user interface device 310 may be configured to receive user input. Thus, the user interface device 310 may be located in a passenger compartment (not shown) of the vehicle. In some possible implementations, the user interface device 310 may include a touch-sensitive display screen.

[0052] The navigation system 315 may be configured to determine the vehicle's current location using, for example, a global positioning system (GPS) receiver configured to triangulate the vehicle's location relative to satellites or ground-based transmission towers. The navigation system 315 may also be configured to develop a route from the current location to a selected destination and display a map and present the driving route to the selected destination via, for example, the user interface device 310.

[0053] Autonomous driving sensors 320 may include any number of devices configured to generate signals to assist in navigating the vehicle. Examples of autonomous driving sensors 320 may include radar sensors, lidar sensors, vision sensors (e.g., cameras), vehicle-to-vehicle infrastructure networks, and the like. When the vehicle 100 is operating in autonomous mode, autonomous driving sensors 320 may enable the vehicle to "see" the road and vehicle surroundings, and / or navigate various obstacles. Autonomous driving sensors 320 may be configured to output sensor signals to, for example, an autonomous mode controller 325.

[0054] The autonomous mode controller 325 may be configured to control one or more subsystems 330 when the vehicle is operating in autonomous mode. Examples of subsystems 330 controllable by the autonomous mode controller 325 may include a braking subsystem, a suspension subsystem, a steering subsystem, and a powertrain subsystem. The autonomous mode controller 325 may control any one or more of these subsystems 330 by outputting signals to control units associated with the subsystems 330. In one example, the braking subsystem may include an anti-lock braking subsystem configured to apply a braking force to one or more of the vehicle's wheels. As discussed herein, applying a braking force to one or more of the vehicle's wheels may be referred to as activating the brakes. To autonomously control the vehicle, the autonomous mode controller 325 may output appropriate commands to the subsystems 330. These commands may cause the subsystems to operate according to driving characteristics associated with the selected driving mode. For example, driving characteristics may include how aggressively the vehicle accelerates and decelerates, how much space the vehicle leaves behind the vehicle ahead, how often the autonomous vehicle changes lanes, and so on.

[0055] In this way, Figures 1 to 3The assembly is capable of implementing a system for a vehicle, comprising: a vehicle, including an autonomous vehicle and / or a hybrid vehicle; an engine that propels the vehicle, the engine including a first cylinder, an intake passage, and an exhaust passage, the first cylinder including an intake valve and an exhaust valve, the intake valve being actuated via an intake cam actuation system and the exhaust valve being actuated via an exhaust cam actuation system; a conduit coupled to the intake passage downstream of a compressor and upstream of a CAC, the conduit including a motor-driven electric booster; a particulate filter coupled to the exhaust passage; a differential pressure sensor coupled across the particulate filter; and a controller having computer-readable instructions stored on a non-volatile memory for: during operation of the electric booster when the vehicle is in a key-off state, commanding the intake cam actuation system and the exhaust cam actuation system to park the first cylinder in a first position in which the intake valve is open and the exhaust valve is closed; sensing exhaust air flow in the exhaust passage via the differential pressure sensor after commanding the first cylinder to be parked; and indicating exhaust valve leakage in response to the sensed exhaust air flow being above a threshold air flow.

[0056] Figure 4 shows a method that can be implemented to detect a motor coupled to an engine cylinder such as Figure 2 The exhaust valve of the cylinder 214 in the Figure 2 Instructions for executing method 400 and the remaining methods included herein may be provided by a controller based on instructions stored on a memory of the controller and in conjunction with sensors from the engine system (such as those described above with reference to FIG. Figure 1 and Figure 2 The controller may use the engine actuators of the engine system to adjust engine operation according to the method described below.

[0057] At 401, current engine and vehicle operating conditions may be estimated, measured, and / or inferred. The operating conditions may include one or more vehicle conditions (such as vehicle speed, vehicle location), various engine conditions (such as engine state, engine load, engine speed, air-fuel ratio, fuel economy), various fuel system conditions (such as fuel level, fuel type, fuel temperature), various evaporative emission system conditions, and various ambient conditions (such as ambient temperature, humidity, barometric pressure, etc.).

[0058] At 402, the routine includes determining whether conditions are met for performing exhaust valve diagnostics on one or more engine cylinders. In one example, the conditions may include an on-board cylinder power balance test that identifies one or more cylinders contributing less than a threshold engine power. The power balance test may be performed in response to detecting certain engine operating conditions, such as misfire, backfire, rough idle, reduced fuel economy, etc. A cylinder misfire event may be detected based on one or more of crankshaft acceleration, exhaust air-fuel ratio, exhaust gas oxygen sensor output, and spark plug ionization (e.g., ionization current determined by an ionization sensor coupled to the spark plug). As another example, the controller may monitor the engine misfire ratio over a predetermined duration of engine operation (e.g., time or number of engine cycles) or a predetermined distance of vehicle travel, such that the misfire ratio may be compared to a threshold ratio. For example, the threshold ratio may be determined based on the engine's misfire history. In some embodiments, the cylinder indicating the cause of the misfire event may be determined based on the cylinder firing order.

[0059] In a power balance test, while the engine is running, the controller can selectively disable spark for a first engine cylinder to temporarily stop combustion in that cylinder while maintaining fuel and spark supply in each of the remaining engine cylinders. When combustion stops in the first cylinder, the engine speed estimated by the crankshaft position sensor drops accordingly. The controller can then restore the spark in the first cylinder and disable the spark in the next cylinder to estimate the corresponding change in engine speed. After temporarily stopping combustion in each cylinder (one at a time), the controller can monitor the change in engine speed. If the drop in engine speed corresponding to each engine cylinder is substantially equal (such as within 5% of each other), it can be inferred that each cylinder contributes equally to the total engine power. In one example, the percentage of power delivered by a cylinder can be estimated using Equation 1.

[0060]

[0061] Where P is the percentage power delivered by the cylinder, T is the threshold drop in engine speed when combustion is suspended in the cylinder, and y is the estimated drop in engine speed when combustion is suspended in the cylinder. The threshold drop in engine speed when combustion is suspended in the cylinder can be calibrated immediately after an engine installation or repair event at a manufacturing plant or repair center.

[0062] Figure 5An example graph 500 shows the power delivered by each cylinder of a four-cylinder engine, as estimated by performing a cylinder power balance test. The y-axis shows the percentage of power delivered by each cylinder of the four-cylinder engine (as estimated using Equation 1). Bar graph 502 shows the percentage power delivered by the first cylinder in the cylinder bank. Similarly, bar graphs 504, 506, and 508 show the corresponding percentage power delivered by the second, third, and fourth cylinders in the cylinder bank. Dashed line 510 shows a threshold percentage power below which it can be inferred that carbon deposits on the exhaust valve of the cylinder may be present, causing exhaust valve leakage, and an exhaust valve diagnostic routine can be performed on the cylinder. Threshold percentage 510 can be a predetermined non-zero threshold.

[0063] In example map 500, the first, second, and third cylinders deliver engine power above a threshold, indicating that the exhaust valves corresponding to each of these cylinders are likely leak-free. However, the fourth cylinder exhibits power output below a threshold. Therefore, an exhaust valve diagnostic may be performed on the fourth cylinder to detect whether the fourth cylinder is leaking.

[0064] The conditions met for performing an exhaust valve diagnostic on a particular engine cylinder may additionally or alternatively include an indication that a threshold duration (e.g., 1 day, 2 days, 5 days, 10 days, 15 days, greater than 20 days but less than 30 days, etc.) has passed since the last diagnostic was performed on the exhaust valve of the cylinder.

[0065] In another example, exhaust valve diagnostics can be performed during autonomous vehicle mode when the vehicle is not being operated by a human driver and when the vehicle is not being propelled by engine torque. Vehicle operation can be controlled from a remote location or pre-programmed in the controller memory. During vehicle operation in autonomous mode, diagnostics can be performed opportunely upon completion of a drive cycle.

[0066] If it is determined that the conditions for performing exhaust valve diagnostics on any engine cylinder are not met, then at 404, current vehicle operation may be maintained. In one example, an electric boost (such as Figure 1 The electric booster 155 in the engine compartment can be coupled to a conduit in parallel with the intake passage, the conduit being coupled to the intake passage downstream of the intake compressor and upstream of the charge air cooler. Figure 1 When the boost pressure provided by the intake compressor 114 and the exhaust turbine 116 in the vehicle is lower than the desired boost pressure, the energy from the on-board energy storage device (such as Figure 1The electric boost is operated using energy from energy storage device 250 (in an energy storage device 250) to provide the desired boost. The operating speed and duration of the electric boost can be adjusted based on the turbocharger speed and the torque demand estimated via the pedal position sensor. In one example, the operating speed and duration of the electric boost can increase as the torque demand increases and the turbocharger speed decreases. In another example, the operating speed and duration of the electric boost can decrease as the torque demand decreases and the turbocharger speed increases.

[0067] If it is determined that the conditions for performing exhaust valve diagnostics on at least one engine cylinder are met, then at 406, the routine may include determining whether a vehicle key-off state is anticipated. In one example, the anticipated key-off state may include an accelerator pedal release event followed by application of the brakes to stop vehicle propulsion (reducing vehicle speed to zero). Additionally, in anticipation of a vehicle key-off, the transmission may be shifted into park. Furthermore, the ignition may be turned off.

[0068] If it is determined that a vehicle key-off state is not expected, the exhaust valve diagnosis can be postponed until the next vehicle key-off state. The current vehicle operating condition can continue. If it is determined that a vehicle key-off state is expected, it can be inferred that the engine can be shut down. The controller can send signals to the fuel injectors and spark plugs coupled to the engine cylinders to suspend the fuel and spark supply, respectively. At 408, during the engine shutdown, the controller can send signals to the cam actuators coupled to the intake and exhaust valves of the cylinders to park the first cylinder accommodating the exhaust valve, which will be diagnosed at a predetermined first position. In the first position, the intake valve of the first cylinder can be in a fully open position, and the exhaust valve of the first cylinder (to be diagnosed) can be in a fully closed position. In one example, the first position can include parking the first cylinder in the intake stroke between the top dead center (TDC) position and the bottom dead center (BDC) position. In a four cylinder engine, if the first cylinder is parked in the first position (in the intake stroke), the second cylinder immediately following the first cylinder may be in the compression stroke with each of the intake and exhaust valves closed, the next (third) cylinder may be in the power stroke with each of the intake and exhaust valves closed, and the last (fourth) cylinder may be in the exhaust stroke with the intake valve closed and the exhaust valve open. In this way, by parking the first cylinder in the first position, the engine only has the intake valve of one cylinder open during the diagnostic routine. In one example, after the supply of fuel and spark has been suspended, the controller may provide a starter motor (such as a starter motor) coupled to the crankshaft with the starter valve closed. Figure 2The controller may send a signal to the starter motor 212 in the engine control panel to crank the engine until the first cylinder reaches the first position, and then may pause operation of the starter motor (when the first cylinder is parked in the first position). At 410, the controller may send a signal to an actuator coupled to the intake throttle plate to open the intake throttle to a wide open position to allow as much ambient air as possible to enter the engine intake manifold.

[0069] Once the engine is shut down, at 414, the electric booster may be operated to direct compressed air from the intake manifold to the exhaust manifold via the first engine cylinder. As an example, with the cylinders parked in the first position, only the intake valve of the first cylinder may be open while the intake valves of the remaining three cylinders may be closed. The EGR valve may be closed to reduce airflow through the EGR passage. The controller may provide a signal to the electric booster actuator (such as Figure 1 The actuator 155b in the intake manifold sends a signal to actuate the electric boost using energy from an energy storage device coupled to the electric boost. As ambient air entering the intake manifold flows through the electric boost, the air is pressurized (compressed). The rotational speed of the electric boost predetermined during the diagnostic procedure can be lower than the rotational speed of the electric boost when operating to compensate for the lag of the mechanical turbocharger. In one example, the rotational speed of the electric boost during the diagnostic procedure can be 2500 RPM. By operating the electric boost at a lower speed, power consumption can be reduced and noise generation during operation of the electric boost can also be reduced. Compressed air can flow into the first intake cylinder via the open intake valve.

[0070] At 414, the controller may retrieve the baseline air flow from an onboard database in the controller memory. In one example, immediately after the engine cylinders are installed or serviced at a manufacturing facility or service station, during a vehicle key-off state, when the first cylinder is parked in a first position (intake valve open and exhaust valve closed), the first cylinder is measured by flowing pressurized air through the first cylinder via a differential pressure sensor (such as a differential pressure sensor) coupled across the exhaust particulate filter. Figure 1 The baseline air flow is estimated using the pressure sensor 127 in the exhaust pressure sensor 127. During the establishment of the baseline air flow, the electric booster can be rotated at 2500 RPM. When the engine cylinder is newly installed or repaired, the exhaust valve may not be degraded. Compressed air can enter the cylinder through the open intake valve, but will not flow out of the cylinder through the closed exhaust valve, resulting in a lower exhaust air flow recorded at the exhaust pressure sensor (the intake valves of the other cylinders are closed, so there is no airflow through any cylinder). In one example, the baseline air flow can be zero. In another example, the intake valves and exhaust valves of the other cylinders can be in an overlapping position (partially open), resulting in a non-zero baseline (exhaust) air flow.

[0071] The baseline air flow rate can be estimated within a threshold duration since the installation or repair of the cylinder. In one example, the threshold duration can be one day since the cylinder was installed or repaired. Alternatively, the baseline air flow rate can be estimated within a first threshold distance of the distance traveled since the installation or repair of the cylinder. In one example, the threshold distance since the installation or repair of the cylinder can be 30 miles.

[0072] At 416 , air flow through the exhaust passage may be estimated via a differential pressure sensor coupled across the exhaust particulate filter. At 418 , the estimated exhaust air flow may be compared to a baseline air flow. At 420 , the routine includes determining whether the estimated exhaust air flow is greater than the baseline air flow. Since only the intake valve of the first cylinder is open, compressed air from the electric booster may enter the first cylinder but may not exit the cylinder due to the closed exhaust valve. Therefore, if the exhaust valve is not degraded, there may not be any substantial airflow through the exhaust passage, and the exhaust air flow may be substantially equal to the baseline air flow (e.g., within 5% of the baseline air flow).

[0073] If the exhaust air flow rate is determined to be higher than the baseline air flow rate, it can be inferred that the exhaust valve is leaking and that pressurized air entering the cylinder is escaping through the exhaust valve even when actuated to a closed position. Therefore, at 422 , a diagnostic code (flag) can be set indicating exhaust valve degradation, such as leakage. The exhaust valve may be filled with carbon deposits, which in some examples may cause the exhaust valve to become stuck in an at least partially open position, causing compressed air to flow through the cylinder to the exhaust passage.

[0074] If it is determined that the exhaust air flow is not above the baseline air flow, it can be inferred that the exhaust air flow is substantially equal to the baseline air flow (such as within 5% of the baseline air flow) and compressed air may not be able to flow through the closed exhaust passage. Therefore, at 424, it can be indicated that the exhaust valve is not degraded (such as not leaking) and can be actuated to a fully closed position.

[0075] In one example, even if one cylinder (a first cylinder) is identified as delivering power below a threshold (such as in a cylinder power balancing test) and a diagnostic routine is performed on the exhaust valve coupled to the first cylinder, the controller may selectively perform exhaust valve diagnostics on the remaining engine cylinders to detect whether any other exhaust valves are degraded. In another example, the engine may not be equipped to perform on-board diagnostics (such as a cylinder power balancing test), and in response to an indication of combustion instability (such as misfire), the controller may perform diagnostics on each cylinder in a bank of cylinders that is misfiring or on each engine cylinder individually. Thus, if degradation of the exhaust valve coupled to the first cylinder is detected or if no degradation of the exhaust valve coupled to the first cylinder is detected, the controller may proceed to diagnose the exhaust valves coupled to cylinders immediately adjacent to the first cylinder.

[0076] At 426, the routine includes determining whether the exhaust valves of each engine cylinder have been tested (diagnosed). If it is detected that the exhaust valves of each cylinder have not been tested, at 428, the controller can send a signal to an actuator connected to the starter motor to rotate the engine without fuel using power from the on-board battery or electric motor. The engine rotates and the cylinder (the second cylinder) that is immediately following the last cylinder (the first cylinder) for which exhaust valve degradation diagnosis was performed is parked in a first position in which the intake valve is open and the exhaust valve is closed. Once the second cylinder is parked in the first position, operation of the starter motor can be suspended.

[0077] The routine can then proceed to step 416 and perform diagnostics on the exhaust valve coupled to the second cylinder. In this manner, the controller can perform diagnostics on each exhaust valve one at a time. Once it is determined in step 426 that the exhaust valves of each cylinder have been tested, the exhaust valve diagnostic routine is complete at 430 and the electric boost can no longer be rotated. The controller can signal the electric boost actuator to stop rotating the engine, and the engine can return to the off state.

[0078] If one or more exhaust valve degradation (such as leakage) is detected during subsequent engine operation, one or more engine operating parameters may be adjusted to account for the degraded exhaust valves at 432. In one example, an exhaust valve degradation flag may be set to disable fuel flow and spark to the cylinders experiencing valve degradation. In another example, if the engine is a variable displacement engine, cylinders may be deactivated during predetermined engine operating conditions, and the variable displacement control method may be adjusted accordingly.

[0079] In this way, during a first state including an engine-off state, compressed air can be forced into a first cylinder of a multi-cylinder engine while maintaining an intake valve of the first cylinder open and an exhaust valve of the first cylinder closed; and in response to an air flow rate through the exhaust device coupled to the first cylinder above a threshold, degradation of the first cylinder can be indicated.

[0080] Figure 6 An exemplary timeline 600 of engine position during an exhaust valve diagnostic routine for a four-cylinder engine is shown. The horizontal axis (x-axis) represents time, and vertical markers t1 through t5 represent significant moments in the exhaust valve diagnostic routine. The various positions of a first engine cylinder throughout the diagnostic routine are shown in row 602. The various positions of a second engine cylinder throughout the diagnostic routine are shown in row 604, with the second cylinder positioned immediately adjacent to the first cylinder in the engine clock. The various positions of a third engine cylinder throughout the diagnostic routine are shown in row 606, with the third cylinder positioned immediately adjacent to the second cylinder in the engine clock. The various positions of a fourth engine cylinder throughout the diagnostic routine are shown in row 608, with the fourth cylinder positioned immediately adjacent to the third cylinder in the engine clock.

[0081] For the first cylinder (cylinder 1), exhaust valve diagnosis can begin at time t1 and be performed between times t1 and t2. During this period (between times t1 and t2), the first cylinder is in the intake stroke, with its intake valve open and its exhaust valve closed. During the diagnosis of the first cylinder, the second cylinder is in the compression stroke, with both its intake and exhaust valves closed. The third cylinder is in the power stroke, with both its intake and exhaust valves closed. The fourth cylinder is in the exhaust stroke, with its intake valve closed and its exhaust valve open.

[0082] At time t2, the exhaust valve coupled to the first cylinder is diagnosed, and the unfueled engine is rotated to park the second cylinder in the intake stroke. Between times t2 and t3, the second cylinder is parked in the intake stroke, with its intake valve open and exhaust valve closed, and exhaust valve diagnosis is performed. During the diagnosis of the second cylinder, the first cylinder is parked in the exhaust stroke, with its intake valve closed and its exhaust valve open. The third cylinder is parked in the compression stroke, with both its intake and exhaust valves closed. The fourth cylinder is parked in the power stroke, with both its intake and exhaust valves closed.

[0083] At time t3, the exhaust valve coupled to the second cylinder is diagnosed, and the unfueled engine is rotated to park the third cylinder in the intake stroke. Between times t3 and t4, the third cylinder is parked in the intake stroke, with its intake valve open and exhaust valve closed, and exhaust valve diagnosis is performed. During the diagnosis of the third cylinder, the second cylinder is parked in the exhaust stroke, with its intake valve closed and its exhaust valve open. The fourth cylinder is parked in the compression stroke, with both its intake and exhaust valves closed. The first cylinder is parked in the power stroke, with both its intake and exhaust valves closed.

[0084] At time t4, the exhaust valve coupled to the third cylinder is diagnosed, and the unfueled engine is rotated to park the fourth cylinder in its intake stroke position. Between times t4 and t5, the fourth cylinder is parked in its intake stroke position, with its intake valve open and its exhaust valve closed, and a diagnosis of the exhaust valve (of the fourth cylinder) is performed. During the diagnosis of the fourth cylinder, the first cylinder is parked in its compression stroke, with both its intake and exhaust valves in the closed position. The second cylinder is parked in its power stroke, with both its intake and exhaust valves in the closed position. The third cylinder is parked in its exhaust stroke, with its intake valve in the closed position and its exhaust valve in the open position. At time t5, the diagnosis of each exhaust valve coupled to the engine cylinder is completed.

[0085] Figure 7 An exemplary timeline 700 is shown illustrating an exhaust valve coupled to a first engine cylinder of a four-cylinder engine (such as Figure 2 The first cylinder also includes an intake valve (such as Figure 2 256 in the exhaust valve diagnostic routine). The exhaust valve is actuated via an exhaust cam actuator coupled to the exhaust valve, and the intake valve is actuated via an intake cam actuator coupled to the intake valve. The horizontal axis (x-axis) represents time, and vertical markers t1 to t4 represent significant moments in the exhaust valve diagnostic routine.

[0086] In the first graph, line 701 shows the position of the accelerator pedal estimated by the pedal position sensor. In the second graph, line 702 shows the change of vehicle speed over time. In the third graph, line 704 shows Figure 1 In the fourth graph, line 706 shows the position of the exhaust valve. In the fifth graph, line 708 shows the position of the intake valve. In the sixth graph, line 710 shows the position of the intake valve via a differential pressure sensor (such as a differential pressure sensor) connected across the exhaust particulate filter. Figure 1The exhaust air flow is estimated by the pressure sensor 127 in FIG. Dashed line 712 shows the baseline exhaust air flow. When the exhaust valves are installed, a baseline air flow is established by directing compressed air through the engine cylinders with the intake valves open and the exhaust valves closed, and the baseline air flow is estimated via a differential pressure sensor. In the seventh graph, dashed line 716 shows an indicator of exhaust valve degradation.

[0087] Prior to time t1, engine torque is used to propel the vehicle. The torque demand, estimated based on pedal position, remains substantially constant, and the electric booster is operated to provide the desired boost pressure. As the engine cycle continues and cylinder position changes from exhaust to intake stroke, the exhaust valve position changes from open to closed. Similarly, the intake valve position changes from closed to open based on cylinder position (stroke). The differential pressure (dP) sensor reading represents exhaust flow through the particulate filter. Since no exhaust valve degradation is detected, the flag remains closed.

[0088] At time t1, in response to releasing the accelerator pedal, it is inferred that the vehicle will stop at time t2 (key-off). As the torque demand decreases, the electric boost is actuated to the closed position. Between times t1 and t2, the intake cam actuator is actuated to open the intake valve coupled to the first cylinder (such as during the intake stroke) and maintain the intake valve in the open position when the engine stops rotating. While the intake valve of the first cylinder is open, the intake valves coupled to each of the remaining cylinders remain in the closed position. The exhaust cam actuator is actuated to close the exhaust valve coupled to the first cylinder (such as during the intake stroke) and maintain the exhaust valve in the closed position when the engine stops rotating.

[0089] At time t2, the vehicle is stopped (key-off). Since engine torque is no longer required for vehicle operation, electric boost operation is also stopped. Between times t2 and t3, no engine torque and / or electric motor torque is used to propel the vehicle. Since the vehicle is not running, the engine is not burning and exhaust gas no longer flows through the exhaust manifold, and the exhaust differential pressure sensor reading decreases to zero.

[0090] After a threshold duration (the duration between times t2 and t3) has elapsed since the vehicle key was turned off, an exhaust valve diagnostic is initiated at time t3. The controller sends a signal to the electric boost actuator to rotate the electric boost. During the diagnostic routine, the electric boost operates at a speed slower than the speed at which the electric boost rotates to provide boost (as before time t1). Between times t3 and t4, compressed air from the electric boost is directed into the first cylinder via the open intake valve, but compressed air cannot flow through the first cylinder due to the closed exhaust valve. Exhaust air flow is substantially equal to baseline air flow 712. Therefore, it is inferred that the exhaust valve of the first cylinder can be actuated to the commanded (closed) position and that the valve is not leaking.

[0091] However, if the exhaust air flow (dP sensor reading) is observed to be above the baseline air flow between t3 and t4, it will indicate that the exhaust valve is leaking, and air is flowing from the engine intake through the cylinder to the exhaust even when the exhaust valve is commanded closed. In response to the air flow being above the baseline 712 between times t3 and t4, a flag 716 indicating that the exhaust valve is stuck open will be raised and a diagnostic code will be set.

[0092] At time t4, the diagnostic routine is completed. The controller sends a signal to the electric boost actuator to stop rotating the electric boost. After time t4, the vehicle remains in the key-off state and the electric motor does not rotate.

[0093] In this way, by diagnosing the exhaust valves during the engine-off state, exhaust valve degradation can be distinguished from any other factors that are detrimental to engine performance. Moreover, by performing the diagnosis during the key-off state, the position of the engine valves can be adjusted to improve the diagnostic procedure. The technical effect of using existing engine components (such as the electric booster and differential pressure sensor) is that the diagnostic procedure can be performed on the vehicle without external intervention. By detecting exhaust valve degradation at an earlier stage, further damage to the exhaust valves caused by prolonged carbon deposits can be prevented. In general, by regularly monitoring the health of the exhaust valves, combustion stability, engine performance and fuel efficiency can be improved.

[0094] An exemplary method includes: testing exhaust valve degradation of a cylinder of a multi-cylinder engine that drives a vehicle by sealing the exhaust valve during an on-vehicle test; directing compressed air into the cylinder during the test; and indicating the presence or absence of exhaust valve degradation during the test based on air flow through an exhaust coupled to the cylinder relative to a baseline air flow through the exhaust. In any of the foregoing examples, additionally or optionally, the test is performed while the engine is not combusting fuel, and wherein the vehicle is an autonomous vehicle and / or a hybrid vehicle. In any or all of the foregoing examples, additionally or optionally, sealing the exhaust valve includes positioning the cylinder in a first position in which an intake valve coupled to the cylinder is in an open position and the exhaust valve is in a closed position. In any or all of the foregoing examples, additionally or optionally, directing the compressed air includes directing compressed air from an engine intake into the cylinder by operating an electric booster via an electric motor. In any or all of the foregoing examples, additionally or optionally, indicating the presence of degradation includes estimating exhaust air flow and indicating exhaust valve degradation in response to the estimated exhaust air flow being greater than the baseline air flow. In any or all of the foregoing examples, additionally or optionally, indicating the absence of degradation includes indicating the exhaust valve is not degraded in response to the estimated exhaust air flow being substantially equal to the baseline air flow. In any or all of the foregoing examples, additionally or optionally, exhaust flow is estimated via a differential pressure sensor coupled across an exhaust particulate filter, the exhaust particulate filter coupled to the engine exhaust downstream of the cylinder. In any or all of the foregoing examples, additionally or optionally, the baseline air flow is established by directing compressed air through the cylinder with the intake valve open and the exhaust valve closed and estimating exhaust air flow via the differential pressure sensor immediately after the exhaust valve is installed in the cylinder. In any or all of the foregoing examples, the method further comprises, additionally or optionally, after indicating the presence or absence of degradation of the exhaust valve coupled to the cylinder, rotating the unfueled engine, positioning another cylinder in the first position, and testing degradation of the exhaust valve coupled to the other cylinder. In any or all of the foregoing examples, additionally or optionally, the electric booster is coupled to a conduit in parallel with the intake passage, the conduit being coupled to the intake passage downstream of an intake compressor and upstream of a charge air cooler. In any or all of the foregoing examples, the method further comprises, additionally or optionally, during subsequent engine operation, responsive to an indication of a degraded exhaust valve, halting fuel and spark to the cylinder having the degraded exhaust valve.

[0095] Another method for an engine includes: during a first state, including an engine-off state, forcing compressed air into a first cylinder while maintaining the intake valve of the first cylinder open and the exhaust valve of the first cylinder closed; and indicating degradation of the first cylinder in response to an air flow through the exhaust coupled to the first cylinder being above a threshold. In any of the foregoing examples, additionally or optionally, the first state includes a power output of the first cylinder being below a threshold power output, and wherein the engine propels a vehicle, including an autonomous vehicle and / or a hybrid vehicle. In any or all of the foregoing examples, additionally or optionally, forcing the compressed air from the engine intake into the first cylinder by operating the electric boost during the engine-off state. In any or all of the foregoing examples, additionally or optionally, estimating air flow through the exhaust via a differential pressure sensor coupled across a particulate filter housed in the exhaust. In any or all of the foregoing examples, additionally or optionally, estimating a power output of the first cylinder by selectively disabling spark for the first cylinder while maintaining spark for each remaining cylinder of the multi-cylinder engine, estimating a change in engine speed via a crankshaft position sensor, and estimating the power output of the first cylinder based on the estimated change in engine speed after disabling spark. In any or all of the foregoing examples, the method further includes, additionally or optionally, establishing the threshold air flow via the differential pressure sensor immediately after installing the first cylinder by operating the electric boost while maintaining the intake valve of the first cylinder open and the exhaust valve of the first cylinder closed.

[0096] In yet another example, a hybrid vehicle system includes: a vehicle, including an autonomous vehicle and / or a hybrid vehicle; an engine that propels the vehicle, the engine including a first cylinder, an intake passage, and an exhaust passage, the first cylinder including an intake valve and an exhaust valve, the intake valve being actuated via an intake cam actuation system and the exhaust valve being actuated via an exhaust cam actuation system; a conduit coupled to the intake passage downstream of a compressor and upstream of a CAC, the conduit including a motor-driven electric booster; a particulate filter coupled to the exhaust passage; a differential pressure sensor coupled across the particulate filter; and a controller having computer-readable instructions stored on a non-volatile memory for: commanding the intake cam actuation system and the exhaust cam actuation system to park the first cylinder in a first position in which the intake valve is open and the exhaust valve is closed during operation of the electric booster when the vehicle is in a key-off state; sensing exhaust air flow in the exhaust passage via the differential pressure sensor after commanding the first cylinder to be parked; and indicating exhaust valve leakage in response to the sensed exhaust air flow being above a threshold air flow. In any of the foregoing examples, additionally or optionally, parking the first cylinder in the first position includes commanding a starter motor coupled to a crankshaft of the first cylinder to rotate the first cylinder until the first cylinder reaches the first position, the starter motor being operated via an electric motor. In any or all of the foregoing examples, additionally or optionally, the controller includes further instructions for, in response to indicating the exhaust valve leak, halting injection of fuel to the first cylinder via one or more fuel injectors coupled to the first cylinder and disabling provision of spark to the first cylinder via a spark plug coupled to the first cylinder during an immediately following engine cycle.

[0097] Note that the exemplary control and estimation routines included herein can be used with various engine and / or vehicle system configurations. The control methods and routines disclosed herein can be stored as executable instructions in a non-volatile memory and can be executed by a control system including a controller in conjunction with various sensors, actuators, and other engine hardware. The specific routines described herein can represent one or more of any number of processing strategies (such as event-driven, interrupt-driven, multi-tasking, multi-threaded processing strategies, etc.). Therefore, the various actions, operations, and / or functions shown can be performed in the order shown, in parallel, or omitted under certain conditions. Similarly, the processing order is not necessarily required to achieve the features and advantages of the exemplary embodiments described herein, but is provided for ease of illustration and description. One or more of the actions, operations, and / or functions shown can be repeatedly performed depending on the specific strategy used. In addition, the described actions, operations, and / or functions can graphically represent code to be programmed into the non-volatile memory of a computer-readable storage medium in an engine control system, where the described actions are implemented by executing the instructions in conjunction with an electronic controller in a system including various engine hardware components.

[0098] It should be understood that the configurations and procedures disclosed herein are exemplary in nature, and these specific embodiments should not be construed in a limiting sense, as many variations are possible. For example, the above technology can be applied to V-6, inline-4, inline-6, V-12, opposed-4, and other engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations and other features, functions, and / or properties disclosed herein.

[0099] The following embodiments specifically point out certain combinations and sub-combinations that are considered to be novel and non-obvious. These embodiments may refer to "an" element or "a first" element or its equivalent. Such embodiments should be understood to include a combination of one or more such elements, and neither require nor exclude two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements and / or properties may be claimed by modifying the embodiments or by proposing new embodiments in this application or related applications. Such embodiments, whether broader, narrower, the same or different in scope than the original embodiments, are also considered to be included in the subject matter of the present disclosure.

[0100] According to the present invention, a method includes: testing exhaust valve degradation by sealing the exhaust valve coupled to a cylinder of a multi-cylinder engine that powers a vehicle during an on-vehicle test; directing compressed air into the cylinder during the test; and indicating the presence or absence of exhaust valve degradation during the test based on air flow through an exhaust device coupled to the cylinder relative to a baseline air flow through the exhaust device.

[0101] According to one embodiment, the test is performed when the engine is not burning fuel, and wherein the vehicle is an autonomous vehicle and / or a hybrid vehicle.

[0102] According to one embodiment, the invention is further characterized by sealing the exhaust valve including positioning the cylinder in a first position in which an intake valve coupled to the cylinder is in an open position and the exhaust valve is in a closed position.

[0103] According to one embodiment, the invention is further characterized in that directing the compressed air includes directing compressed air from an engine intake into the cylinder by operating an electric booster via an electric motor.

[0104] According to one embodiment, indicating the presence of the degradation includes estimating exhaust air flow and indicating exhaust valve degradation in response to the estimated exhaust air flow being higher than the baseline air flow.

[0105] According to one embodiment, indicating the absence of degradation includes indicating that the exhaust valve is not degraded in response to the estimated exhaust air flow being substantially equal to the baseline air flow.

[0106] According to one embodiment, the exhaust gas flow is estimated via a differential pressure sensor coupled across an exhaust gas particulate filter coupled to the engine exhaust downstream of the cylinder.

[0107] According to one embodiment, the baseline air flow is established by directing compressed air through the cylinder with the intake valve open and the exhaust valve closed and estimating exhaust air flow via the differential pressure sensor immediately after the exhaust valve is installed to the cylinder.

[0108] According to one embodiment, the above invention is further characterized in that, after indicating the presence or absence of degradation of the exhaust valve coupled to the cylinder, the non-fueled engine is rotated, another cylinder is positioned in the first position, and degradation of the exhaust valve coupled to the other cylinder is tested.

[0109] According to one embodiment, the electric booster is coupled to a conduit in parallel with the intake passage, the conduit being coupled to the intake passage downstream of an intake compressor and upstream of a charge air cooler.

[0110] According to one embodiment, the above invention is further characterized by halting the provision of fuel and spark to the cylinder having the degraded exhaust valve in response to an indication of the degraded exhaust valve during subsequent engine operation.

[0111] According to the present invention, an engine method includes: during a first state, including an engine shut-off state, forcing compressed air into a first cylinder while maintaining the intake valve of the first cylinder open and maintaining the exhaust valve of the first cylinder closed; and indicating degradation of the first cylinder in response to an air flow through the exhaust device coupled to the first cylinder above a threshold.

[0112] According to one embodiment, the first state comprises a power output of the first cylinder being below a threshold power output, and wherein the engine is propelling a vehicle, the vehicle comprising an autonomous vehicle and / or a hybrid vehicle.

[0113] According to one embodiment, the compressed air is forced from the engine intake into the first cylinder by operating an electric booster via an electric motor during the engine off state.

[0114] According to one embodiment, the air flow through the exhaust device is estimated via a differential pressure sensor coupled across a particulate filter housed in the exhaust device.

[0115] According to one embodiment, power output of the first cylinder is estimated by selectively disabling spark for the first cylinder while maintaining spark for each remaining cylinder of the multi-cylinder engine, estimating a change in engine speed via a crankshaft position sensor, and estimating the power output of the first cylinder based on the estimated change in engine speed after spark disabling.

[0116] According to one embodiment, the above invention is further characterized in that, immediately after installing the first cylinder, the threshold air flow rate is established via the differential pressure sensor by operating the electric booster while keeping the intake valve of the first cylinder open and keeping the exhaust valve of the first cylinder closed.

[0117] According to the present invention, a system is provided, the system having: a vehicle, including an autonomous vehicle and / or a hybrid vehicle; an engine for propelling the vehicle, the engine including a first cylinder, an intake passage, and an exhaust passage, the first cylinder including an intake valve and an exhaust valve, the intake valve being actuated via an intake cam actuation system and the exhaust valve being actuated via an exhaust cam actuation system; a conduit coupled to the intake passage downstream of a compressor and upstream of a cylinder air conditioning (CAC), the conduit including a motor-driven electric boost; a particulate filter coupled to the exhaust passage; a differential pressure sensor coupled across the particulate filter; and a controller having computer-readable instructions stored on non-volatile memory for: during operation of the electric boost when the vehicle is in a key-off state, commanding the intake cam actuation system and the exhaust cam actuation system to park the first cylinder in a first position in which the intake valve is open and the exhaust valve is closed; sensing exhaust air flow in the exhaust passage via the differential pressure sensor after commanding the parking of the first cylinder; and indicating exhaust valve leakage in response to the sensed exhaust air flow being above a threshold air flow.

[0118] According to one embodiment, parking the first cylinder in the first position comprises commanding a motor coupled to a crankshaft of the first cylinder to rotate the first cylinder until the first cylinder reaches the first position, the motor being operated via an electric machine.

[0119] According to one embodiment, the controller includes further instructions for, in response to indicating the exhaust valve leak, halting injection of fuel to the first cylinder via one or more fuel injectors coupled to the first cylinder and disabling provision of spark to the first cylinder via a spark plug coupled to the first cylinder during a subsequent engine cycle.

Claims

1. A method for an engine, comprising: testing degradation of the exhaust valve by sealing an exhaust valve coupled to one cylinder of a multi-cylinder engine that powers a vehicle during an on-vehicle test, wherein the testing is performed while the engine is not combusting fuel, and wherein sealing the exhaust valve includes positioning the cylinder in a first position in which an intake valve coupled to the cylinder is in an open position and the exhaust valve is in a closed position; directing compressed air into the cylinder during the testing; as well as The presence or absence of degradation of the exhaust valve during the test is indicated based on air flow through an exhaust coupled to the cylinder relative to a baseline air flow through the exhaust.

2. The method of claim 1, wherein the vehicle is an autonomous vehicle and / or a hybrid vehicle.

3. The method of claim 1 , wherein directing the compressed air comprises directing compressed air from an engine intake into the cylinders by operating an electric booster via an electric motor, wherein the electric booster is coupled to a conduit in parallel with an intake passage, the conduit being coupled to the intake passage downstream of an intake compressor and upstream of a charge air cooler.

4. The method of claim 1 , wherein indicating the presence of the degradation comprises estimating exhaust air flow and indicating that the exhaust valve is degraded in response to the estimated exhaust air flow being greater than the baseline air flow, and wherein indicating the absence of the degradation comprises indicating that the exhaust valve is not degraded in response to the estimated exhaust air flow being substantially equal to the baseline air flow. 5 . The method of claim 4 , wherein the exhaust air flow is estimated via a differential pressure sensor coupled across an exhaust particulate filter coupled to the engine exhaust downstream of the cylinder.

6. The method of claim 5 wherein the baseline air flow is established by directing compressed air through the cylinder with the intake valve open and the exhaust valve closed and estimating exhaust air flow via the differential pressure sensor immediately after the exhaust valve is installed to the cylinder.

7. The method of claim 1 further comprising, after indicating the presence or absence of degradation of the exhaust valve coupled to the cylinder, rotating the engine without fuel, positioning another cylinder in the first position, and testing degradation of the exhaust valve coupled to the other cylinder.

8. The method of claim 1, further comprising: During subsequent engine operation, in response to the indication of a degraded exhaust valve, fuel and spark are halted to the cylinder having the degraded exhaust valve.

9. A vehicle system comprising: vehicles, including autonomous and / or hybrid vehicles; a multi-cylinder engine for propelling the vehicle, the engine including a first cylinder, an intake passage, and an exhaust passage, the first cylinder including an intake valve and an exhaust valve, the intake valve being actuated via an intake cam actuation system and the exhaust valve being actuated via an exhaust cam actuation system; a conduit coupled to the intake passage downstream of the compressor and upstream of a charge air cooler, the conduit including a motor-driven electric booster; a particulate filter coupled to the exhaust passage; a differential pressure sensor coupled to both ends of the particulate filter; and a controller having computer-readable instructions stored on a non-transitory memory for: During a first state, including an engine-off state, forcing compressed air into the first cylinder while maintaining the intake valve of the first cylinder open and maintaining the exhaust valve of the first cylinder closed; as well as Responsive to air flow through the exhaust passage coupled to the first cylinder being above a threshold, degradation of the first cylinder is indicated.

10. The vehicle system of claim 9, wherein the first state comprises a power output of the first cylinder being less than a threshold power output, wherein exhaust valve diagnostics are performed on the first cylinder to detect degradation of the first cylinder in response to the power output of the first cylinder being less than the threshold power output, and wherein the engine propels the vehicle, the vehicle comprising an autonomous vehicle and / or a hybrid vehicle.

11. The vehicle system of claim 9, wherein the compressed air is forced from an engine intake into the first cylinder by operating the electric booster during the engine-off state.

12. The vehicle system of claim 9, wherein the air flow through the exhaust passage is estimated via the differential pressure sensor.

13. The vehicle system of claim 10 , wherein the power output of the first cylinder is estimated by selectively disabling spark for the first cylinder while maintaining spark for each remaining cylinder of the multi-cylinder engine, estimating a change in engine speed via a crankshaft position sensor, and estimating the power output of the first cylinder based on the estimated change in engine speed after disabling spark.

14. The vehicle system of claim 9 , wherein the controller includes further instructions for, immediately after installing the first cylinder, establishing a threshold air flow via the differential pressure sensor by operating the electric boost while maintaining the intake valve of the first cylinder open and maintaining the exhaust valve of the first cylinder closed.

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