NOx excursion diagnosis during engine wet-milling

Abstract

The present disclosure provides for "NOx offset diagnosis during engine wetup." Methods and systems are provided for waking up a powertrain control module of an engine-driven vehicle during engine wetup to perform an offset test on an exhaust NOx sensor. In one example, a method includes determining a duration to delay waking up the powertrain control module based on an exhaust temperature at a time of parking, waking up the powertrain control module after the duration has elapsed, and then initiating heating of the NOx sensor. After the NOx sensor lights off, the heating is continued for an additional duration before performing an offset test on the NOx sensor.

Description

Technical Field

[0001] This specification generally relates to methods and systems for controlling emissions in vehicle exhaust systems. Background Technology

[0002] Selective catalytic reduction (SCR) catalysts can be used in engine exhaust systems (e.g., diesel engines or other lean-burn engines) to reduce nitrogen oxide (NOx) emissions. A reducing agent, such as urea, can be injected into the exhaust system upstream of the SCR catalyst, and together with the SCR catalyst, the reducing agent chemically reduces NOx molecules to nitrogen and water, thereby limiting NOx emissions. However, if components of the NOx emission control system (such as the SCR catalyst) deteriorate, NOx emissions may increase. Therefore, NOx sensors configured to measure NOx levels in the exhaust system can be located within the exhaust system to detect malfunctions in the NOx emission control system. Specifically, an increase in NOx levels can be detected by the NOx sensor, which may indicate deterioration of one or more components of the NOx emission control system. Thus, the efficiency of the SCR catalyst and other components of the NOx emission control system can be monitored by one or more NOx sensors located within the exhaust system.

[0003] Current OBD (On-Board Diagnostics) regulations require monitoring of exhaust NOx sensors to determine if the NOx sensor has deteriorated (e.g., if gain skew has formed), and to determine if the NOx sensor has developed an offset that could affect exhaust emissions. These two types of determinations are performed independently; typically, gain skew deterioration is determined via a NOx sensor self-diagnostic (SD) test, while a separate test can be performed to determine if the NOx sensor has developed an offset.

[0004] One method for determining whether a NOx sensor has become offset includes performing a NOx offset diagnostic procedure during an engine overrun (e.g., deceleration fuel cut-off) state in which no engine combustion occurs. This diagnostic procedure operates under the assumption that a normally functioning NOx sensor would output a reading close to the ambient NOx value once the overrun state persists for a sufficiently long duration.

[0005] However, the inventors of this application have recognized the potential problems with the aforementioned solution. SCR catalysts store ammonia (NH3) and release it downstream when excessive reductant is injected or when the exhaust temperature rises to a certain level. Once NH3 release from the SCR catalyst begins, it tends to continue for a longer period than the usual overrun. This is problematic because currently available NOx sensors tend to confuse NH3 and NOx, reading NH3 as NOx. Therefore, the output of a NOx sensor located downstream of the SCR catalyst may have an erroneous high NOx offset during NH3 release from the SCR catalyst. This erroneous high NOx offset can cause the vehicle's malfunction indicator lamp (MIL) to illuminate unnecessarily, leading to warranty issues. In the future, as NOx emission regulations become more stringent, NH3 release from the SCR catalyst may occur more frequently due to increased urea injection, thus unintentionally increasing the likelihood of such warranty problems. Summary of the Invention

[0006] In one example, the aforementioned problem can be addressed by a method that involves waking up the powertrain control module and heating the exhaust NOx sensor during a wet engine period after the engine-driven vehicle has stopped. When the NOx sensor ignites, the powertrain control module detects the NOx sensor output, determines the duration for which heating of the NOx sensor should continue based on the detected output, and continues heating the NOx sensor until that duration ends. At the end of the duration, a NOx sensor offset test is performed. The inventors have recognized herein that by waiting a certain duration (e.g., approximately 4 hours) after stopping and before waking up the powertrain control module, and then heating the NOx sensor for an additional duration after the NOx sensor ignites but before performing the NOx sensor offset test, the encapsulated NOx, NH3, and moisture within the sensor protection tube can dissipate, thereby avoiding erroneous high NOx offset readings.

[0007] It should be understood that the foregoing description of the invention is intended to introduce, in a simplified form, a selection of concepts further described in the detailed description. This does not imply representation of key or essential features of the claimed subject matter, the scope of which is uniquely defined by the claims following the detailed description. Furthermore, the claimed subject matter is not limited to implementations that address any shortcomings mentioned above or in any part of this disclosure. Attached Figure Description

[0008] Figure 1A A schematic diagram of an engine including an exhaust system with an exhaust treatment system is shown.

[0009] Figure 1B A schematic diagram of an exhaust system for receiving engine exhaust is shown.

[0010] Figure 2 A high-level flowchart of an exemplary method for performing SD and / or offset tests during engine wet testing is shown.

[0011] Figure 3 A high-level flowchart of an exemplary method for performing offset testing is shown.

[0012] Figure 4 A high-level flowchart of an exemplary method for performing actions in response to the results of SD and / or offset tests performed during engine wet testing is shown.

[0013] Figure 5 It shows according to Figures 3 to 5 An exemplary timeline of the method for performing SD and offset tests during engine wet testing. Detailed Implementation

[0014] The following description relates to a system and method for waking up the powertrain control module (PCM) during engine wet operation to perform NOx sensor offset testing. This applies to diesel engine exhaust systems (such as...). Figure 1A The engine system shown and Figure 1B The exhaust system shown may include a selective catalytic reduction (SCR) catalyst for reducing NOx emissions. The efficiency of the SCR catalyst can be monitored by one or more NOx sensors located upstream and / or downstream of the SCR catalyst. OBD regulations require monitoring of NOx sensor operation to ensure proper functioning, including monitoring gain skew and offset. Gain skew can be monitored via a SD test performed at the NOx sensor, where the PCM determines pass / fail using a threshold switching method and compensation. Conversely, NOx sensor offset is performed by reading the NOx sensor output value directly from the NOx sensor via the PCM and determining the offset without the NOx sensor performing its own test.

[0015] exist Figure 2This document describes an exemplary method for performing SD and / or offset tests on a NOx sensor during engine wet operation. The test involves waking the PCM via an alarm after a certain delay (e.g., 4 hours) following parking, initiating heating of the NOx sensor via a NOx sensor heater, and then continuing heating of the NOx sensor for a calibrable duration after the NOx sensor reaches its ignition temperature before performing the offset test. Parking is the situation where the vehicle's power is cut off, which in vehicles using a physical key will be referred to as key off. However, the vehicle may be operated via FOB and have a button device, or it may also have other vehicle on / off controls, such as remote on / off operation or others. Therefore, wherever a key off event is mentioned herein, even if not separately listed in the specification, the explicitly included optional options will be other parking states such as those described above. Similarly, a vehicle start event can include a key on event when the vehicle is operated with a physical key. Alternatively, a vehicle start event can include a situation where the FOB is used in conjunction with a button device as described above. Furthermore, other options such as remote vehicle start systems are possible.

[0016] If an SD test is to be performed, it can be performed at or after ignition but before the offset test. The additional NOx sensor heating before the offset test advantageously dissipates the NOx and / or ammonia encapsulated within the sensor's protective tube, allowing for a NOx offset value that is closer to the "true" offset value. Figure 3 An exemplary offset test procedure is described.

[0017] like Figure 4 As shown, actions can be performed in response to the results of SD and / or offset tests, such as adjusting vehicle operation, updating stored offset values, and warning the vehicle driver.

[0018] Now for reference Figure 1A The diagram illustrates a schematic of one cylinder of a multi-cylinder engine 10, which may be included in the propulsion system of a vehicle (e.g., an automobile) 5. The vehicle 5, including the engine 10, may be controlled at least in part by a control system including a controller 8 and input from a vehicle driver 72 via an input device 70. The controller 8 may be configured as a PCM. In this example, the input device 70 includes an accelerator pedal and a pedal position sensor 74 for generating a proportional pedal position signal PP. The combustion chamber 30 (e.g., a cylinder) of the engine 10 may include a combustion chamber wall 32 in which a piston 36 is located. The piston 36 may be connected to a crankshaft 40 such that the reciprocating motion of the piston is converted into rotational motion of the crankshaft. The crankshaft 40 may be connected to at least one drive wheel of the vehicle via an intermediate transmission system. Furthermore, a starter motor may be connected to the crankshaft 40 via a flywheel to enable starting operation of the engine 10.

[0019] Combustion chamber 30 receives intake air from intake manifold 44 via intake duct 42 and exhausts combustion gases via exhaust duct 48. Intake manifold 44 and exhaust duct 48 may be selectively connected to combustion chamber 30 via intake valve 52 and exhaust valve 54. In some embodiments, combustion chamber 30 may include two or more intake valves and / or two or more exhaust valves.

[0020] exist Figure 1A In the example depicted, intake valve 52 and exhaust valve 54 are controlled by cam actuation via corresponding cam actuation systems 51 and 53. Cam actuation systems 51 and 53 each include one or more cams and can utilize one or more of a cam profile changing system (CPS), variable cam timing (VCT), variable valve timing (VVT), and / or variable valve lift (VVL) systems, which can be operated by controller 8 to change valve operation. The positions of intake valve 52 and exhaust valve 54 are determined by position sensors 55 and 57, respectively. In an alternative embodiment, intake valve 52 and / or exhaust valve 54 can be controlled by electric valve actuation. For example, a cylinder may optionally include an intake valve controlled by electric valve actuation and an exhaust valve controlled by cam actuation (including CPS and / or VCT systems).

[0021] In some embodiments, each cylinder of engine 10 may be configured with one or more fuel injectors for supplying fuel thereto. As a non-limiting example, a cylinder is shown to include a fuel injector 66. The fuel injector 66 is shown to be directly connected to the cylinder for injecting fuel therein in proportion to the pulse width of the signal FPW received from controller 8 via electronic actuator 68. In this way, fuel injector 66 provides so-called direct fuel injection (hereinafter also referred to as "DI") into the combustion cylinder.

[0022] It should be understood that, in an alternative embodiment, injector 66 may be an intake port injector that supplies fuel to the intake port upstream of the cylinder. It should also be understood that the cylinder may receive fuel from multiple injectors (such as multiple intake port injectors, multiple direct injectors, or a combination thereof).

[0023] In one example, engine 10 is a diesel engine that burns air and diesel fuel via compression ignition. In other non-limiting embodiments, engine 10 may burn different fuels, including gasoline, biodiesel, or alcohol-containing fuel mixtures (e.g., gasoline and ethanol or gasoline and methanol), via compression ignition and / or spark ignition.

[0024] In the depicted example, intake manifold 42 includes a throttle valve 62 with a throttle plate 64. In this particular example, the position of the throttle plate 64 is changed by controller 8 via a signal provided to an electric motor or actuator included in the throttle valve 62, a configuration commonly referred to as electronic throttle control (ETC). In this way, throttle valve 62 can be operated to change the intake air supplied to combustion chamber 30 and other engine cylinders. The position of throttle plate 64 is provided to controller 8 via a throttle position signal TP. In the depicted example, intake manifold 42 also includes a mass airflow (MAF) sensor 50 and a manifold air pressure (MAP) sensor 56, which are used to provide signals MAF and MAP to controller 8, respectively.

[0025] Furthermore, in the depicted example, the exhaust gas recirculation (EGR) system is configured to guide a desired portion of the exhaust gas from the exhaust manifold 48 to the intake manifold 42 via the EGR passage 47. The amount of EGR supplied to the intake manifold 44 can be varied by the controller 8 via the EGR valve 49. By introducing exhaust gas into the engine 10, the amount of oxygen available for combustion is reduced, thereby lowering the combustion flame temperature and reducing the formation of, for example, NOx. As depicted, the EGR system also includes an EGR sensor 46 disposed within the EGR passage 47, which provides indications of one or more of the pressure, temperature, and concentration of the exhaust gas within the EGR passage.

[0026] In the depicted example, engine 10 includes an exhaust system 2. The exhaust system 2 includes an exhaust sensor 26 connected upstream of exhaust treatment system 80 to exhaust passage 48, and an exhaust temperature sensor 27 connected upstream of exhaust treatment system 80 to exhaust passage 48. An exemplary embodiment of exhaust treatment system 80 is described below. Figure 1B The sensor 26 is shown and described below. Sensor 26 can be any suitable sensor used to provide an indication of the exhaust air-fuel ratio, such as a linear oxygen sensor or UEGO (universal or wide-range exhaust oxygen) sensor, a dual-state oxygen sensor or EGO sensor, HEGO (heated EGO) sensor, a NOx sensor, a hydrocarbon (HC) sensor, or a carbon monoxide (CO) sensor. Sensor 26 is... Figure 1A The example shown provides an EGO signal to controller 8.

[0027] Controller 8 in Figure 1AThe controller 8, shown as a microcomputer, includes a microprocessor (e.g., CPU) 16, an input / output port 4, an electronic storage medium for executable programs and calibration values ​​(shown in this particular example as a read-only memory (ROM) chip), a random access memory (RAM) 18, a keep-alive memory (KAM) 20, and a data bus. The controller 8 communicates with and therefore receives various signals from sensors connected to the engine 10 in addition to those previously discussed, including a signal representing the MAF value from the MAF sensor 50; the engine coolant temperature (ECT) from the temperature sensor 58 connected to the cooling sleeve 61; the surface ignition sensing signal (PIP) from the Hall effect sensor 59 (or other type of sensor) connected to the crankshaft 40; the throttle position (TP) from the throttle position sensor; the MAP from the MAP sensor 56; the exhaust gas composition concentration (EGO) from the exhaust gas sensor 26; and the exhaust gas temperature from the exhaust gas temperature sensor 27. The controller 8 can generate an engine speed signal (RPM) from the PIP signal. (See below for reference.) Figure 1B Other sensors that communicate with controller 8 are described. Based on signals received from the sensors and further based on instructions stored in memory, controller 8 employs... Figure 1A Various actuators are used to adjust engine operation.

[0028] The storage medium, read-only memory 14, can be programmed with non-transitory computer-readable data representing instructions executable by processor 16 for performing the methods described below, as well as other anticipated but not specifically listed variations. (References to...) Figures 2 to 4 Describe an exemplary method.

[0029] As mentioned above, Figure 1A Only one cylinder of a multi-cylinder engine is shown. Each cylinder may similarly include its own set of intake / exhaust valves, fuel injectors, spark plugs, etc.

[0030] In the illustrated example, vehicle 5 may be a hybrid vehicle having multiple torque sources available for one or more wheels 71. However, in other examples, vehicle 5 is a conventional vehicle with only an engine or an electric vehicle with only one or more electric motors. In the illustrated example, vehicle 5 includes an engine 10 and an electric motor 73. The electric motor 73 may be a motor or an electric motor / generator. When one or more clutches are engaged, crankshaft 40 and electric motor 73 are connected to wheels 71 via transmission 75. In the illustrated example, a first clutch 77a is disposed between crankshaft 40 and electric motor 73, while a second clutch 77b is disposed between electric motor 73 and transmission 75. Controller 8 may be configured to send signals to the actuators of each clutch to engage or disengage the clutch, thereby connecting or disconnecting crankshaft 40 from electric motor 73 and components connected thereto, and / or connecting or disconnecting electric motor 73 from transmission 75 and components connected thereto. Transmission 75 may be a gearbox, planetary gear system, or other type of transmission. The powertrain may be configured in various ways such that the vehicle is a parallel, series, or series-parallel hybrid vehicle.

[0031] The motor 73 receives power from the traction battery 79 to provide torque to the wheel 71. Optionally, during braking operations, the motor 73 can also be used as a generator to provide power to charge the battery 79.

[0032] Figure 1B A schematic diagram of an exemplary exhaust system 102 for conveying exhaust gas produced by the internal combustion engine 110 of vehicle 5 is shown. The exhaust system 102 may correspond to... Figure 1A The exhaust system 2, while the engine 110 can correspond to Figure 1A Engine 10. In a non-limiting example, engine 110 is a diesel engine that produces mechanical output by burning a mixture of air and diesel fuel. Alternatively, engine 110 can be another type of engine, such as a gasoline combustion engine.

[0033] exist Figure 1B In the non-limiting example shown, the exhaust system 102 includes an exhaust manifold 120 for receiving exhaust gas produced by one or more cylinders of the engine 110, an oxidation catalyst 124, a mixing zone 130, a selective catalytic reduction (SCR) catalyst 140, an emission control device 142, and a noise suppression device 150. Additionally, the exhaust system 102 includes multiple exhaust pipes or passages for fluid connection of various exhaust system components. However, one or more of the oxidation catalyst 124, mixing zone 130, SCR catalyst 140, emission control device 142, and noise suppression device 150 can be arranged in any order or combination within the exhaust system 102.

[0034] The exhaust system 102 may be located on the underside of the vehicle chassis. Additionally, the exhaust system 102 may include one or more bends or curves to adapt to a specific vehicle configuration. Furthermore, in some embodiments, the exhaust system 102 may include... Figure 1B Additional components not shown and / or components described herein may be omitted.

[0035] The flow of gas and / or fluid in exhaust system 102 occurs in a direction away from exhaust manifold 120, toward the surrounding environment 195, through exhaust system 102, and out of exhaust system 102 through exhaust duct 168 (optionally referred to below as fourth exhaust duct 168). Therefore, in Figure 1B In the example shown, the flow of gas and / or fluid in exhaust system 102 is generally from left to right, as indicated by flow direction arrow 180. Therefore, in this description, the term "downstream" refers to the relative positioning of a component in exhaust system 102 with respect to the flow direction in exhaust system 102. Thus, if a first component is described as downstream of a second component in exhaust system 102, the gas and / or fluid flowing in exhaust system 102 flows past the second component before flowing past the first component.

[0036] Exhaust manifold 120 is fluidly connected to oxidation catalyst 124 via first exhaust passage 162 and second exhaust passage 164. In this example, oxidation catalyst 124 is disposed downstream of exhaust manifold 120, wherein no component other than exhaust passages 162 and 164 separates oxidation catalyst 124 from exhaust manifold 120. First exhaust passage 162 and second exhaust passage 164 provide fluid communication between exhaust manifold 120 and oxidation catalyst 124. In some examples, oxidation catalyst 124 is a diesel oxidation catalyst (DOC), such as an exhaust flow-through device, which includes a substrate with a honeycomb structure and a large surface area coated with a catalyst layer. The catalyst layer may include precious metals, including but not limited to platinum and palladium. When exhaust flows through the catalyst layer, CO, gaseous HC, and liquid HC particles can be oxidized to reduce emissions.

[0037] A mixing region 130 is disposed immediately downstream of the oxidation catalyst 124 for receiving a liquid reducing agent, wherein no additional components separate the mixing region 130 from the oxidation catalyst 124. The mixing region 130 includes a first mixing region 132 and a second mixing region 134, the second mixing region 134 being disposed downstream of the first mixing region 132. The first mixing region 132 includes an injector 136 for injecting liquid into the mixing region 130. In some examples, the liquid injected by the injector 136 is a liquid reducing agent, such as ammonia or urea. In some examples, the liquid reducing agent can be supplied from a storage tank to the injector 136. In this example, the injector 136 is electronically actuated and communicates electrically and / or electronically with a controller 112, which may correspond to... Figure 1A Controller 8. Similar to Figure 1A Controller 8 and controller 112 can be configured as PCM. Controller 112 from Figure 1B Various sensors receive signals and employ Figure 1B Various actuators adjust engine operation based on received signals and instructions stored in the controller's memory. For example, controller 112 is configured to send signals to the actuators of injector 136 for adjusting injector operation. In response to signals received from controller 112, the actuators of injector 136 can adjust the amount of liquid reducing agent injected into mixing zone 130 and / or injection timing.

[0038] An intake NOx sensor (optionally referred to herein as a first NOx sensor) and an intake air temperature sensor (optionally referred to herein as a first temperature sensor) are disposed in the first mixing region 132. Therefore, in this example, the first NOx sensor and the first temperature sensor are disposed downstream of the oxidation catalyst 124, wherein no other exhaust treatment device is inserted between the oxidation catalyst and the sensor 191. The positioning of the first NOx sensor 190 and the first temperature sensor 191 in the exhaust system 102 may allow the first NOx sensor 190 and the first temperature sensor 191 to overlap. For example, the first NOx sensor 190 and the intake air temperature sensor 191 may be substantially aligned with each other and may overlap each other in the exhaust system 102. In other words, the first NOx sensor 190 and the first temperature sensor 191 may be longitudinally aligned in the first mixing region 132. In some examples, the first NOx sensor 190 and the first temperature sensor 191 are perpendicular to the gas flow and / or fluid arrangement in the exhaust system 102, and in such examples, they may be positioned such that they are parallel to each other. In other examples, the first temperature sensor 191 is positioned adjacent to the first NOx sensor 190, such that the first temperature sensor 191 and the first NOx sensor 190 are in coplanar contact and thermally connected. In this way, gas and / or fluid flowing through the exhaust system 102, and more specifically through the first mixing region 132, can flow past the first NOx sensor 190 and the first temperature sensor 191 almost simultaneously. Therefore, the first temperature sensor 191 can be positioned within the first mixing region 132 to measure the temperature of gas and / or fluid flowing through the first NOx sensor 190 and / or sampled at that first NOx sensor. However, in other examples, the first temperature sensor 191 may not be aligned with the first NOx sensor 190, but rather spaced apart from it in the longitudinal direction.

[0039] The first temperature sensor 191 is electrically connected to the controller 112, and its output, corresponding to the temperature of the gas and / or fluid flowing through the first NOx sensor 190, is sent to the controller 112. Similarly, the first NOx sensor 190 is electronically connected to the controller 112, and its output, corresponding to the NOx level (e.g., the concentration of NOx and / or O2) of the gas and / or fluid flowing through it, is sent to the controller 112.

[0040] Although the first NOx sensor 190 and the first temperature sensor 191 are located in Figure 1BThe first NOx sensor 190 and the first temperature sensor 191 may be located downstream of the injector 136, but they may optionally be positioned substantially in line with the injector 136. In a further example, the first NOx sensor 190 and the first temperature sensor 191 may be located upstream of the injector 136 or upstream of the oxidation catalyst 124.

[0041] The second mixing region 134 is configured to accommodate changes in the cross-sectional area or flow area between the first mixing region 132 and the SCR catalyst 140, which in the depicted example is positioned immediately downstream of the second mixing region 134. Specifically, the cross-sectional flow area generated by the second mixing region 134 can be increased in the downstream direction as shown. Therefore, the first NOx sensor 190 and the first temperature sensor 191 are positioned upstream of the SCR catalyst 140. In some examples, no additional components separate the second mixing region 134 from the SCR catalyst 140.

[0042] A mixing device 138 is disposed downstream of the injector 136. The mixing device 138 is configured to receive engine exhaust and / or injected fluid reducing agent from the injector 136, and to direct the engine exhaust and / or fluid reducing agent downstream of the mixing device 138 toward the SCR catalyst 140. Figure 1B As shown, the mixing device 138 may include a disc with vane portions. Each vane portion may have straight edges and curved edges. In some examples, the mixing device 138 is positioned in a first mixing region 132 downstream of the injector 136, the first temperature sensor 191, and the first NOx sensor 190. In other examples, the mixing device 138 is positioned in a second mixing region 134. The mixing device 138 is configured to increase the mixing of the exhaust gas and fluid reducing agent mixture in the second mixing region 134 before it reaches the SCR catalyst 140, and thus increase the homogeneity of the mixture.

[0043] SCR catalyst 140 is configured to convert NOx into water and nitrogen as inert combustion byproducts using a fluid reducing agent (e.g., ammonia (NH3) or urea injected by injector 136) and an active catalyst. The SCR catalyst, optionally referred to as a DeNOx catalyst, may be composed of titanium dioxide containing oxides of transition metals (such as, for example, vanadium, molybdenum, and tungsten) as the catalytically active component. SCR catalyst 140 may be configured as a ceramic brick or ceramic honeycomb structure, a plate structure, or any other suitable design. SCR catalyst 140 may include any suitable catalyst for reducing NOx or other combustion products generated by the combustion of fuel in engine 110.

[0044] Emission control device 142 is located downstream of SCR catalyst 140. In some examples, emission control device 142 is a diesel particulate filter (DPF). A DPF can operate actively or passively, and the filter media can have various types of materials and geometries. One exemplary configuration includes a wall-flow ceramic monolith comprising alternating channels inserted at opposite ends, thus forcing exhaust flow through the common wall of adjacent channels to deposit particulate matter.

[0045] Optionally, the emission control device 142 and the SCR catalyst 140 can be combined on a single substrate (e.g., a wall-flow ceramic DPF element coated with NOx storage agent and platinum group metals).

[0046] After passing through the emission control device 142, exhaust gas and / or fluid flow through the aftertreatment region 144. The aftertreatment region 144 is configured to accommodate changes in cross-sectional area or flow area between the emission control device 142 and a third exhaust duct 166 located immediately downstream of the emission control device 142. Specifically, the cross-sectional flow area generated by the aftertreatment region 144 decreases in the downstream direction. The aftertreatment region 144 fluidly connects the emission control device 142 to the third exhaust duct 166. However, in other examples, the exhaust system 102 does not include an aftertreatment region, and the emission control device 142 is directly and / or physically connected to the third exhaust duct 166, wherein no additional components separate the emission control device 142 from the third exhaust duct 166.

[0047] The exhaust tailpipe temperature sensor (optionally referred to herein as the second temperature sensor) 193 and the exhaust NOx sensor (optionally referred to herein as the second NOx sensor) are located in the third exhaust duct 166. However, in other examples, the second temperature sensor 193 and the second NOx sensor 192 may be located in the aftertreatment zone 144. However, in all examples, the second temperature sensor 193 and the second NOx sensor 192 are located downstream of the SCR catalyst 140 and the emission control device 142. The positioning of the second temperature sensor 193 and the second NOx sensor 192 relative to each other and relative to the aftertreatment zone 144 can be similar to the positioning of the first temperature sensor 191 and the first NOx sensor 190 relative to each other and relative to the first mixing zone 132 as described above.

[0048] The second temperature sensor 193 is electrically connected to the controller 112, and its output, corresponding to the temperature of the gas and / or fluid flowing through the second NOx sensor 192, is sent to the controller 112. Similarly, the second NOx sensor 192 is electrically connected to the controller 112, and its output, corresponding to the NOx level in the gas and / or fluid flowing through the second NOx sensor 192, is sent to the controller 112.

[0049] The first NOx sensor 190 and the second NOx sensor 192 can have similar structures and functions. In a non-limiting example, each NOx sensor includes a sensing element disposed within a protective tube; a heater disposed within the protective tube, which is in thermal communication with the sensing element and optionally in direct physical contact with the sensing element; and a gas exchange port configured to draw in the gas to be tested and to expel the gas after testing. The sensing element may include multiple layers of one or more ceramic materials arranged in a stacked configuration. These layers may include one or more solid electrolytes capable of conducting ionic oxygen. Examples of suitable solid electrolytes include, but are not limited to, zirconia-based materials. In each NOx sensor, a heater is disposed between the layers (or otherwise in thermal communication with the layers) to increase the ionic conductivity of the layers. The heater is configured to include a heater from a battery (e.g., ...) during a key-off state. Figure 1B The battery 184 or another power source receives power to heat the NOx sensor to its ignition temperature and optionally above its ignition temperature, as discussed below. For example, as further described below, an alarm clock can “wake up” the controller after a certain delay following a key-off event, and the controller can then send a signal to the battery 184 to power the heaters of one or both NOx sensors to heat one or more sensors.

[0050] Two NOx sensors can be configured to measure and / or estimate the concentration of NOx and / or O2 in the exhaust mixture flowing through exhaust system 102 and transmit this information to a controller. During engine operation, the first NOx sensor measures the NOx level emitted by engine 110, while the second NOx sensor measures the NOx level remaining in exhaust system 102 after treatment by SCR catalyst 140. By comparing the outputs of the first NOx sensor 190 and the second NOx sensor 192, the overall NOx removal efficiency of exhaust system 102 can be estimated.

[0051] However, the first NOx sensor 190 and the second NOx sensor 192 may deteriorate (e.g., gain skew, cracking, contamination, etc.), thus reducing the accuracy of the NOx sensor outputs used to estimate and / or measure NOx levels in the exhaust system 102. Furthermore, NOx sensors may develop offsets that affect exhaust emissions. To detect and diagnose NOx sensor deterioration, an SD test can be performed after a vehicle key-off event, as referenced below. Figure 2 A more detailed description is provided. Conversely, to detect and diagnose NOx sensor offset, an offset test can be performed after the SD test, while the key-off state is still present.

[0052] In addition, the ambient temperature sensor 114 is electrically connected to the controller 112, and the output of the ambient temperature sensor 114 corresponding to the ambient temperature (e.g., the temperature of the air outside the vehicle) is sent to the controller 112. The ambient temperature sensor 114 may be located in the vehicle at a location that is in thermal communication with the outside atmosphere (e.g., at the inlet of the engine intake manifold).

[0053] The described exhaust system also includes an exhaust sensor 126 and an exhaust temperature sensor 127, which can correspond to Figure 1A The exhaust gas sensor 26 and exhaust gas temperature sensor 27 are included. Although sensors 126 and 127 are shown as being located in the second exhaust duct 164 for illustrative purposes, they may optionally be located in any part of the exhaust system upstream of the exhaust treatment system 80 (e.g., in the first exhaust duct 162). Sensors 126 and 127 are each electronically connected to controller 112, and their outputs are sent to controller 112.

[0054] A noise suppression device 150 is disposed downstream of the catalyst 140 and the emission control device 142. The noise suppression device 150 is configured to attenuate the intensity of sound waves traveling away from the exhaust manifold 120 toward the surrounding environment 195. A third exhaust duct 166 provides fluid communication between the aftertreatment zone 144 and the noise suppression device 150. Therefore, exhaust gas flows from the aftertreatment zone 144 through the third exhaust duct 166 to the noise suppression device 150. After passing through the noise suppression device 150, the exhaust gas flows through a fourth exhaust duct 168, reaching the surrounding environment 195 en route.

[0055] The controller 112 can detect a key off event based on a signal received from the input device 170 of the vehicle 5. Figure 1BThe diagram is schematically shown. Input device 170 may include buttons, switches, knobs, ignition devices, touchscreen displays, etc., wherein the position and / or digital state of input device 170 is adjustable to turn engine 110 on or off. In the context of hybrid vehicles, input device 170 may also be adjustable to turn on or off the electric motor providing vehicle drive power. Therefore, in some examples, input device 170 may be a vehicle ignition device with key-controlled engine start and engine stop functions. Optionally, in the case of keyless vehicles, the vehicle's start / stop and / or on / off functions can be controlled via buttons, switches, knobs, touchscreens, etc. Thus, vehicle driver 172 can adjust input device 170 to a first position and / or digital state to initiate a key-on event to start engine 110 and / or the electric motor providing drive power, while vehicle driver 172 can adjust input device 170 to a second position and / or digital state to initiate a key-off event to turn off engine 110 and / or stop the electric motor from providing vehicle drive power. In other words, a key-off event can refer to a state in which the engine 110 is turned off and stationary (e.g., during a vehicle key-off event or an engine stop event in a keyless system with a stop / start button) and, in the context of a hybrid vehicle, the electric motor is prohibited from providing driving force to the vehicle. Therefore, a key-off event can include terminating the combustion cycle in the engine 110 based on input from the vehicle driver 172 via input device 170. Input device 170 is electronically connected to controller 112 and is configured to send signals indicating the position and / or digital status of input device 170 to controller 112 (e.g., intermittently, continuously, or periodically when the position / status changes).

[0056] According to the method disclosed herein, after a certain duration following a key-off event, power is supplied to the NOx sensors to allow for SD testing, followed by an offset test. In the depicted example, during key-off period, power is supplied to the first NOx sensor 190 and the second NOx sensor 192 via battery 184, including supplying power to a heater for each NOx sensor to heat the NOx sensors. In an example where the vehicle is a hybrid vehicle, battery 184 may optionally correspond to... Figure 1A Battery 79. Battery 184 communicates electronically with controller 112 to receive digital signals from the controller. Furthermore, during a key-off event, power can be supplied to controller 112 via battery 184.

[0057] See below for reference. Figures 2 to 3In more detail, controller 112 may include computer-readable instructions stored in non-transitory memory for initiating a NOx sensor SD test and / or offset test after a key-off event, and particularly after a specified duration following key-off. The specified duration may be determined by the controller based on engine operating conditions as described below. In any case, the specified duration is long enough that the NOx sensor SD test and / or offset test will not be initiated while the engine is still in after-run (e.g., when the engine is off after a key-off event but still supplying power to one or more vehicle components via glow plugs or battery). Instead, the test is initiated after auto-ignition operation is completed (e.g., several hours after auto-ignition operation is completed). To wake the controller after the specified duration, the vehicle includes an electronic timer or alarm 111 configured to “wake up” controller 112. Therefore, alarm 111 communicates electronically with controller 112, and specifically with the microprocessor unit of controller 112. Figure 1B In the example shown, alarm clock 111 is powered by battery 184. However, alarm clock 111 may include its own power source, such as a battery, or may be powered by the battery of controller 112 without departing from the scope of this disclosure.

[0058] Figures 1A to 1BExemplary configurations with the relative positioning of various components are shown. If shown as directly contacting or directly connected to each other, such components may be referred to as directly contacting or directly connected, respectively, in at least one example. Similarly, in at least one example, components shown as adjacent or adjacent to each other may be referred to as adjacent or adjacent to each other, respectively. As an example, components that are in coplanar contact with each other may be referred to as coplanar contact. As another example, components positioned spaced apart from each other such that there is only a gap between them without other components may be so referred to in at least one example. As yet another example, components shown as above / below each other, on opposite sides of each other, or on the left / right side of each other may be so referred to relative to each other. Furthermore, as shown in the figures, in at least one example, the topmost component or the topmost point of the component may be referred to as the “top” of the component, while the bottommost component or the bottommost point of the component may be referred to as the “bottom” of the component. As used herein, top / bottom, upper / lower, above / below may be relative to the vertical axis of the figure and used to describe the positioning of the components of the figure relative to each other. Thus, in one example, an component shown above other components is positioned vertically above other components. As yet another example, the shape of the elements depicted in the figure can be described as having those shapes (e.g., such as circular, straight, flat, curved, round, chamfered, inclined, etc.). Furthermore, in at least one example, elements shown as intersecting each other can be described as intersecting elements or intersecting one another. Additionally, in one example, an element shown inside another element or outside another element can be so named.

[0059] Figures 2 to 4 Each section describes a high-level flowchart of an exemplary method. (Refer to...) Figures 1A to 1B The system shown is used to describe Figures 2 to 4 These methods are applicable to other systems without departing from the scope of this disclosure. Figures 2 to 4 The method can be executed by a controller such as controller 112, and can be stored as executable instructions in non-transitory memory. The controller can then execute instructions based on those stored in its memory, combined with data from sensors in the vehicle system (such as those referenced above). Figures 1A to 1B The sensor receives signals to execute instructions for performing the methods included herein. The controller may employ actuators such as heaters for NOx sensors, reducing agent injectors, etc., according to methods further described below.

[0060] Figures 2 to 4The methods generally involve NOx sensors. The NOx sensor can be any NOx sensor disposed in the exhaust system 102, such as a first NOx sensor 190 or a second NOx sensor 192. In some examples, these methods can be performed simultaneously on multiple NOx sensors (e.g., both the first NOx sensor 190 and the second NOx sensor 192). Alternatively, these methods can be performed continuously on multiple NOx sensors to avoid excessive battery drain at any given time.

[0061] First turn Figure 2 It depicts a high-level flowchart of an exemplary method 200 for performing SD and / or offset tests and performing actions in response to test results.

[0062] At 202, the method includes detecting a key off event. As discussed above, the controller can detect the key off event based on signals received from an input device such as input device 170.

[0063] If no key off event is detected, the method returns. Otherwise, if a key off event is detected, the method continues to step 203 to determine if SD and / or offset tests are needed. For example, it might be desirable to perform SD and / or offset tests at regular intervals, such as after a threshold number of driving cycles, a threshold amount of time, a threshold number of engine cycles, etc. In other examples, SD and / or offset tests might be required if certain engine or environmental conditions are met. For example, the intervals between SD tests and / or offset tests could be adjusted based on engine conditions and / or environmental conditions. If neither SD nor offset tests are needed, the method returns. Otherwise, the method proceeds to step 204.

[0064] At 204, the method includes estimating and / or measuring engine operating conditions. Engine operating conditions may include the highest NOx sensor temperature during the driving cycle prior to ignition off (e.g., measured by temperature sensors 191 and / or 193), the exhaust temperature at ignition off (e.g., measured by temperature sensor 127), etc. For example, the controller may monitor the NOx sensor throughout the driving cycle and update the stored highest NOx sensor temperature whenever it is exceeded, such that the highest NOx sensor temperature during the driving cycle prior to ignition off is stored in memory. Similarly, the controller may monitor the exhaust temperature throughout the driving cycle and may store the exhaust temperature at ignition off in memory, such that the controller can disconnect power at ignition off. Optionally, after ignition off, the controller may continue to receive power (e.g., from the vehicle battery) for a certain duration, during which the highest NOx sensor temperature during the driving cycle and the exhaust temperature at ignition off are determined based on other stored data.

[0065] After step 204, the method proceeds to step 206 to determine if the dew point temperature is lower than the highest NOx sensor temperature during the previous driving cycle. As used herein, the dew point temperature is the temperature at which air becomes saturated with water and begins to condense to form dew. At 100% relative humidity, the ambient temperature equals the dew point temperature. The more negative the dew point temperature is relative to the ambient temperature, the lower the risk of condensation, and the drier the air. While the dew point is not temperature-dependent, it is affected by pressure.

[0066] If the dew point temperature is not lower than the highest NOx sensor temperature during the driving cycle prior to ignition off, the method returns to normal and no test is performed during engine wet operation. This reduces the likelihood of NOx sensor element breakage, which could occur if the NOx sensor is heated with dew / water that may have accumulated inside the sensor protection tube during previous driving cycles. It is likely preferable to delay NOx sensor diagnostics, which require heating the NOx sensor during a period when condensation may exist inside the sensor protection tube, to avoid damaging the sensing element.

[0067] Otherwise, if the dew point temperature is lower than the highest NOx sensor temperature during the driving cycle before the key is turned off, the risk of condensation within the sensor protection tube of the NOx sensor is lower, and therefore the risk of thermal breakage of the sensing element during heating of the NOx sensor via the heater is lower. In this case, the answer at 206 is yes, and the method proceeds to 208.

[0068] At 208, the method includes determining whether the exhaust temperature at the time of ignition off is within a predetermined range. For example, the exhaust temperature value at the time of ignition off stored in memory can be compared with upper and lower thresholds stored in memory that define the predetermined range. Exhaust temperature values ​​outside this range may produce unreliable test results. For example, if the exhaust temperature at the time of ignition off is too high, it indicates that DPF regeneration may have occurred not far from the ignition off event, which tends to lead to unreliable SD test results. If the exhaust temperature at the time of ignition off is too low, water condensation may be present near the NOx sensor sensing element, even if the highest NOx sensor temperature is high enough to indicate that the dew point was reached during a previous driving cycle. Therefore, if the answer at 208 is no, the method returns, and no type of test is performed during engine wet operation.

[0069] Otherwise, if the answer at 208 is yes, the method proceeds to 210 to determine the PCM wake-up delay duration based on the exhaust temperature at the time the key is turned off. The exhaust temperature at the time the key is turned off can be used as an indication of the time required for environmental conditions in the exhaust system (e.g., oxygen concentration, pressure, temperature, ammonia concentration, NOx concentration) to stabilize after the key is turned off. In a non-limiting example, the determined PCM wake-up delay duration is proportional to the exhaust temperature at the time the key is turned off, such that a higher exhaust temperature at the time the key is turned off results in a longer PCM wake-up delay duration, while a lower exhaust temperature at the time the key is turned off results in a shorter PCM wake-up delay duration. The controller can send a signal indicating the duration of the PCM wake-up delay to an electronic timer or alarm (e.g., the aforementioned electronic timer), and set the electronic timer to the desired PCM wake-up delay duration before power is turned off. In a non-limiting example, the PCM wake-up delay duration is approximately 4 hours (e.g., greater than 3 hours and less than 5 hours).

[0070] After 210, the method continues to 212 to delay the PCM wake-up delay duration determined at 208, and then wakes up the PCM. In one example, the controller is an electronic timer or alarm clock (e.g., the one mentioned above). Figure 1B The electronic timer described in the text is turned on, and then the controller turns on the various exhaust sensors used in the test to be performed.

[0071] Following step 212, the method proceeds to step 214 to determine whether the test entry conditions are met. Test entry conditions may include, for example, that the exhaust temperature at the NOx sensor, ambient pressure, ambient temperature, and battery voltage are all within their respective calibrable ranges.

[0072] If the answer at 214 is no, the method proceeds to 216 to shut down the PCM, and no test is performed during engine wet operation. However, in other examples, after initially determining whether the test entry condition has not been met and then determining again whether the test entry condition has been met, the PCM can be woken up at a predetermined interval, and if so, the desired test continues to be performed.

[0073] Otherwise, if the answer at 214 is yes, the method proceeds to 218 to activate the NOx sensor heater. This could, for example, involve applying current from the vehicle battery to the NOx sensor heater.

[0074] Following step 218, the method proceeds to step 220. At step 220, the NOx sensor initiates ignition, and its output is detected. Based on the detected NOx sensor output (e.g., as a function of it), the post-ignition heating duration of the NOx sensor for each test to be performed is determined. The post-ignition heating duration for a given test is the length of time the controller will delay before performing the test, starting from the time the NOx sensor initiates ignition. If only the SD test is to be performed, only the post-ignition heating duration for the SD test is determined; if only the offset test is to be performed, only the post-ignition heating duration for the offset test is determined; and if both the SD and offset tests are to be performed, the corresponding post-ignition heating durations for both tests are determined.

[0075] In one example, upon reaching the ignition temperature, the NOx sensor sends a signal to the PCM, indicating that the sensor is ignited and in normal operation. The PCM receives and uses this signal, along with the value of the NOx sensor output at ignition, to determine whether the NOx reading from the sensor is valid. This initial NOx reading provides information about how much NOx and / or ammonia is contained within the NOx sensor's protective tube at ignition. One or more durations of continuous heating of the NOx sensor can be determined based on this initial NOx reading to optimize NOx / ammonia dissipation and also minimize battery current consumption. Optionally, other parameter values ​​may be taken into account the determination of the post-ignition heating duration, or the post-ignition heating duration may be a predetermined value stored in the controller's memory. In some examples, the post-ignition heating duration for the SD test is zero, causing the SD test to begin when the NOx sensor ignites. Furthermore, in examples where both SD and offset tests are performed, the post-ignition heating duration for both tests begins at ignition, and the post-ignition heating duration for the offset test is longer than the heating duration for the SD test.

[0076] After step 220, the method proceeds to step 222 to perform one or more desired tests after delaying one or more corresponding post-ignition heating durations from the start of ignition. If both the SD and offset tests are performed simultaneously, the corresponding post-ignition heating durations both begin when the NOx sensor ignites and end at different times, wherein the post-ignition heating duration for the SD test ends before the post-ignition heating duration for the offset test ends, allowing for further heating of the NOx sensor prior to the offset test. Once the post-ignition heating duration for a given test has elapsed, the test is performed. In a non-limiting example, the SD test can be performed in the manner described in US 2017 / 0240024. An exemplary method for performing the offset test is described in... Figure 3 As shown in the image.

[0077] Following step 222, the method proceeds to step 224 to perform an action in response to the result of the offset test and any SD tests performed. An exemplary method for performing an action in response to test results is described in... Figure 4 As shown in the diagram. After 224, the method returns.

[0078] Figure 3 A high-level flowchart is depicted for an exemplary method 300 for performing offset tests, which is a sub-method of method 200.

[0079] At 302, the method includes selecting the NOx sensor output monitoring duration and further selecting minimum and maximum thresholds for the NOx sensor output. The minimum and maximum thresholds can define a range of NOx sensor output values ​​that indicate appropriate NOx sensor operation, while NOx sensor output values ​​outside this range can indicate that performing an offset test will not produce meaningful results. The minimum and maximum thresholds can be determined based on current operating conditions, such as temperature and pressure sensed in the exhaust system or atmosphere.

[0080] Following step 302, the method continues to step 304 to sample the NOx sensor output throughout the monitoring duration. For example, signals can be continuously sent from the NOx sensor to the controller throughout the monitoring duration, or the NOx sensor can send signals to the controller intermittently at predetermined intervals.

[0081] Following step 304, the method proceeds to step 306. At step 306, the method includes calculating the average value of the NOx sensor output sampled during the monitoring duration, once the monitoring duration has elapsed. This calculation can be performed at the controller.

[0082] Following 306, the method proceeds to 308. At 308, the method includes (e.g., at the controller) determining whether a minimum threshold determined at 302 is less than or equal to an average NOx sensor output determined at 306, and whether the average NOx sensor output determined at 306 is less than or equal to a maximum threshold determined at 302.

[0083] If the answer at 308 is yes, the method proceeds to 310 to indicate that the offset test has passed. For example, indicating that the offset test has passed could include updating the controller's memory with the time and date the offset test was successfully executed. See below for more information. Figure 4 The vehicle operation can be adjusted in response to an indication that the offset test has passed. After step 310, the method returns.

[0084] Otherwise, if the answer at 308 is no, the method proceeds to 312 to indicate that the offset test has failed. Indicating that the offset test has failed could, for example, include updating the controller's memory to indicate that the offset test failed at the current time and date, and / or prompting the controller to warn the vehicle driver of a NOx sensor malfunction when the key is turned on. Warning the vehicle driver could include generating a warning light or indicator via, for example, a vehicle display and / or lights on the vehicle's dashboard, an LED display, a touchscreen display, etc. After 312, method 300 returns.

[0085] Figure 4 A high-level flowchart is depicted for an exemplary method 400 that performs an action in response to the result of a performed test, which is also a sub-method of method 200.

[0086] At 402, the method includes determining whether an SD test was performed (e.g., during the execution of method 200 at 222). If the answer at 402 is yes, the method proceeds to 404 to determine whether the SD test indicates NOx sensor degradation.

[0087] If the answer at 404 is yes, the method proceeds to 416 to instruct the controller to warn the vehicle driver of a NOx sensor malfunction when the key is turned on. In some examples, warning the vehicle driver may include generating a warning light or indicator via, for example, a light on the vehicle display and / or dashboard, an LED display, a touchscreen display, etc. After 416, the method continues to 414 to disable the PCM. After 414, the method returns.

[0088] Returning to 404, if the answer is no and the SD test results do not indicate NOx sensor degradation, the method proceeds to 406. If the answer at 402 is no, the method also proceeds to 406, indicating that the SD test was not performed.

[0089] At 406, the method includes determining whether an offset test was performed (e.g., during the execution of method 200 at 222). If the answer at 406 is no, the method returns. Otherwise, if the answer is yes, the method proceeds to 408.

[0090] At 408, the method includes determining whether the offset test has passed. If the answer at 408 is no, the method proceeds to 416 to instruct the controller to warn the vehicle driver of a NOx sensor malfunction when the key is turned on, and then to 414 to disable the PCM. After 414, the method returns.

[0091] However, if the answer at 408 is yes, the method proceeds to 410. At 410, the method includes replacing the stored offset value of the NOx sensor with the average NOx sensor output (e.g., as determined in method 300 at 306).

[0092] Following step 410, the method proceeds to step 412 to adjust the engine operating parameters for the next driving cycle based on the updated stored offset value. For example, the controller can adjust engine operation during the next driving cycle such that the updated stored offset value is added to the NOx sensor output when the NOx sensor performs a measurement. As an example, the controller can make logical determinations based on logic rules that are functions of the updated stored offset value (e.g., regarding the position of actuators such as urea injectors, fuel injectors, and throttles). The controller can then generate control signals to be sent to the actuators. By adjusting the NOx offset value at the NOx sensor output, the accuracy of SCR NOx conversion efficiency monitoring can be improved. Furthermore, if a downstream SCR NOx sensor is used to implement adaptive control of the NH3 storage within the SCR, the adjusted NOx offset value can provide better urea injection control.

[0093] After step 412, the method proceeds to step 414 to disable PCM. After step 414, the method returns.

[0094] Turn now Figure 5 An exemplary timeline 500 for performing SD and offset tests during engine wet testing is shown. Timeline 500 includes curve 502, which indicates the key state (on or off) over time; curve 504, which indicates the PCM state (on or off) over time; curve 506, which indicates the exhaust temperature over time; curve 512, which indicates the NOx sensor temperature over time; curve 518, which indicates the NOx sensor heater state (on or off) over time; curves 520 and 522, which indicate the test cycle; curve 524, which indicates the NOx sensor output; curve 526, which indicates the stored offset value of the NOx sensor output; and curve 528, which indicates whether a NOx sensor malfunction is indicated.

[0095] Dashed line 508 depicts an exemplary upper threshold of the exhaust temperature range, while dashed line 510 depicts an exemplary lower threshold of the exhaust temperature range. In a non-limiting example, the upper threshold 508 can be a non-zero positive temperature in the range of 450°C to 650°C, while the lower threshold 510 can be a non-zero positive temperature in the range of 30°C to 70°C. During the execution of method 200, if the exhaust temperature at the time of key switching is within this range (e.g., above the lower threshold temperature and below the upper threshold temperature), a test can be performed; otherwise, if the exhaust temperature at the time of key switching is not within this range, the method returns and no test is performed during engine wet operation. In a non-limiting example, it can be based on, for example... Figure 1B The exhaust temperature is determined by the output of sensors such as the exhaust temperature sensor 127.

[0096] Dashed line 514 depicts an exemplary ignition temperature of the NOx sensor (e.g., the temperature at which the NOx sensor becomes fully operational), while dashed line 516 depicts an exemplary dew point temperature. In a non-limiting example, the ignition temperature 514 can be a non-zero positive temperature in the range of 700°C to 800°C, and the dew point temperature 516 can be a non-zero positive temperature in the range of 90°C to 120°C. During execution of method 200, if the highest NOx sensor temperature during the driving cycle prior to ignition is higher than the dew point temperature, a test can be performed if other entry conditions are met; otherwise, if the highest NOx sensor temperature during the driving cycle prior to ignition is not higher than the dew point temperature, the method returns and no test is performed during engine wet operation. This operation reduces the likelihood of breakage of the sensing element of the NOx sensor, which could occur if dew (condensate) accumulated during previous driving cycles is inside the sensor protection tube during NOx sensor heating.

[0097] Dashed line 525 depicts an exemplary upper threshold for the average NOx sensor output, while dashed line 527 depicts an exemplary lower threshold for the average NOx sensor output. In a non-limiting example, the upper threshold 525 can be a non-zero positive value in the range of 40 ppm to 50 ppm, while the lower threshold 527 can be a non-zero negative value in the range of -15 ppm to -30 ppm. During the execution of method 300, if the average value of the NOx sensor output sampled during the duration of the offset test (calculated by the controller) falls within these ranges (e.g., greater than the lower threshold and less than the upper threshold), the offset test passes; otherwise, the offset test fails.

[0098] The interval between time t0 and time t1 represents a portion of a driving cycle (e.g., the previous driving cycle mentioned at 204 in method 200). During this interval, the key is in the ignition state, the PCM is in the ignition state, and the exhaust temperature is within the range mentioned at 208 in method 200 (e.g., greater than threshold 510 and less than threshold 508). Furthermore, when the NOx sensor temperature is above the ignition temperature 514, the NOx sensor provides an output signal indicating the NOx concentration in the engine exhaust. Additionally, the NOx sensor temperature is above the dew point temperature 516; therefore, the highest NOx sensor temperature during this interval exceeds the dew point temperature. Thus, the states at 206 and 208 of method 200 are satisfied.

[0099] At time t1, a key-off event occurs, and the key state and PCM state switch from open to closed. The duration between time t1 and time t2 corresponds to the PCM wake-up delay duration (e.g., the PCM wake-up delay duration determined at 210 via method 200). Therefore, at time t2, the alarm sends a signal to the PCM that turns on (“wakes up”) the PCM. However, in other examples, the PCM may remain open for a certain duration after the key-off event, in which case the PCM wake-up delay duration begins when the PCM is closed, not when the key is off. Upon wake-up, the PCM determines whether test entry conditions are met, such as those described above for method 200 at 214. In the depicted example, the test entry conditions are met, and therefore the NOx sensor heater is activated shortly after time t2.

[0100] During the interval between time t2 and time t3, the NOx sensor temperature rises as the NOx sensor is heated by the heater. At time t3, the NOx sensor reaches its ignition temperature of 514°C, causing it to begin outputting a meaningful result. At this point, if an offset test is desired, the NOx sensor output is detected and the determination of the post-ignition heating duration for the offset test is considered; conversely, if an SD test is desired, the determination of the post-ignition heating duration for the SD test is considered. In the described example, both SD and offset tests are desired; the interval between t3 and t4 represents the determined post-ignition heating duration for the SD test (e.g., the time between NOx sensor ignition and the start of the SD test), while the interval between t3 and t6 represents the determined post-ignition heating duration for the offset test. However, in other examples, the SD test can begin once the NOx sensor ignites.

[0101] At time t4, the post-ignition heating duration for the SD test ends, and the SD test is performed during the test period (curve 520). The test period (curve 520) ends at time t5, at which point the post-ignition heating duration for the offset test has not yet ended. In the depicted example, no NOx sensor fault (e.g., in the form of gain skew) is detected during the SD test, so the PCM is ready to perform the offset test. Therefore, the NOx sensor heater continues to heat the NOx sensor, and the offset test does not begin until time t6, which represents the time when the post-ignition heating duration for the offset test ends (resulting in a delay between the completion of the SD test and the start of the offset test). At this point, the offset test begins and continues for the duration of the test period (curve 522).

[0102] From time t0 to time t7, the average offset value 526 of the NOx sensor is within the range defined by the upper threshold 525 and the lower threshold 527. However, in the depicted example, the average offset detected by the NOx sensor throughout the entire test period (curve 522) is higher than the previously determined average NOx sensor offset value stored in the memory of the PCM. In the depicted example, the new average offset is still within this range. Therefore, the offset test passes and does not indicate a NOx sensor failure (as shown in curve 528, remains no). Therefore, when the offset test is completed at t7, the stored average offset value (as shown in curve 526) is replaced with the most recently determined higher offset value. When the test is now completed, the NOx sensor heater is turned off because there is no need to further heat the NOx sensor, and the PCM is turned off. Conversely, in the example where the new average offset value is not within this range, a NOx sensor failure is indicated, and the stored offset value is not replaced.

[0103] According to the system and method described above, the PCM is turned on during engine wet operation (e.g., several hours after engine wet operation) to perform a NOx sensor offset test, optionally preceded by a NOx sensor SD test. This test involves waking the PCM via an alarm after a certain delay following key deactivation, initiating heating of the NOx sensor via a NOx sensor heater, and then continuing heating the NOx sensor for a calibrable duration after it reaches its ignition temperature before performing the offset test. The technical effect of performing additional NOx sensor heating after the NOx sensor reaches its ignition temperature and before performing the offset test is the dissipation of encapsulated NOx, NH3, and moisture within the sensor protection tube, which in turn reduces the chance of erroneous high NOx offset readings.

[0104] In one exemplary embodiment of this disclosure, a method for an engine-driven vehicle includes: waiting for a first duration before waking up the PCM and activating the heater of an exhaust NOx sensor when the key to the engine-driven vehicle is turned off; waiting for a second duration after the NOx sensor ignites, and then performing a NOx sensor SD test; and performing a NOx sensor offset test once a third duration has elapsed since the NOx sensor ignites, the third duration being longer than the second duration. A first example of the method also includes measuring the exhaust temperature when the key is turned off and determining the first duration based on the measured exhaust temperature. A second example of the method optionally includes the first example and further includes detecting the NOx sensor output when the NOx sensor ignites and determining the second and third durations based on the detected NOx sensor output. In a third example of the method, which optionally includes one or more of the first and second examples, performing the NOx sensor offset test includes selecting a NOx sensor output monitoring duration, sampling the NOx sensor output throughout the monitoring duration, and calculating an average of the sampled NOx sensor outputs after the monitoring duration. In a fourth example of the method, which optionally includes one or more of the first, second, and third examples, performing the NOx sensor offset test further includes determining whether the calculated average value is greater than or equal to a minimum threshold and less than or equal to a maximum threshold, and if so, indicating that the offset test has passed, and if not, indicating that the offset test has failed. A fifth example of the method, which optionally includes one or more of the first, second, third, and fourth examples, further includes: in response to the indication that the offset test has passed, replacing the stored offset value with the calculated average value and adjusting the engine operation at key turn-on based on the updated stored offset value; and in response to the indication that the offset test has failed, instructing the PCM to warn the vehicle driver of a NOx sensor malfunction at key turn-on. A sixth example of the method, which optionally includes one or more of the first, second, third, fourth, and fifth examples, further includes instructing the PCM to warn the vehicle driver of a NOx sensor malfunction at key turn-on in response to an indication of NOx sensor gain skewness indicated by the SD test.

[0105] In another exemplary embodiment of this disclosure, a method for an engine-driven vehicle includes: waking up a powertrain control module (PCM) during a wet engine period after the engine-driven vehicle key is turned off; heating an exhaust NOx sensor; detecting the NOx sensor output when the NOx sensor ignites; determining a duration for which the NOx sensor should continue to be heated based on the detected output; and continuing to heat the NOx sensor until the duration ends; and performing a NOx sensor offset test at the end of the duration. In a first example of the method, the determined duration for continuously heating the NOx sensor is longer for a higher output of a first NOx sensor, and shorter for a lower output of a second NOx sensor than the first NOx sensor output. In a second example of the method, which optionally includes the first example, performing the NOx sensor offset test includes selecting a NOx sensor output monitoring duration, sampling the NOx sensor output throughout the monitoring duration, and calculating an average of the sampled NOx sensor outputs after the monitoring duration. In a third example of the method, which optionally includes one or more of the first and second examples, performing the NOx sensor offset test further includes determining whether the calculated average value is greater than or equal to a minimum threshold and less than or equal to a maximum threshold, and if so, indicating that the offset test has passed, and if not, indicating that the offset test has failed. A fourth example of the method optionally includes one or more of the first, second, and third examples, and further includes measuring the exhaust temperature when the key is turned off, and determining the duration for which the PCM is delayed after the key is turned off based on the measured exhaust temperature. A fifth example of the method optionally including one or more of the first, second, third, and fourth examples further includes waking the PCM approximately 4 hours after the key is turned off.

[0106] In another exemplary embodiment of this disclosure, a system includes: a NOx sensor located in an engine exhaust system downstream of an SCR catalyst; an electronic timer; and a controller electrically communicating with the electronic timer and the NOx sensor, the controller having computer-readable instructions for: determining, upon a key-off event, a sleep duration after the key-off event before initiating heating of the NOx sensor, a sleep duration sent to the electronic timer and starting the timer, and powering off after the sleep duration is sent to the electronic timer; wherein the electronic timer turns on the controller after the sleep duration has elapsed, and wherein the controller further includes computer-readable instructions for: initiating heating of the NOx sensor in response to power-on; detecting the NOx sensor output and determining a delayed post-ignition heating duration based on the detected NOx sensor output before performing a NOx sensor offset test; and initiating a NOx sensor offset test after the post-ignition heating duration has elapsed. In a first example of the system, the controller also has computer-readable instructions for: measuring the temperature of the exhaust system at the time of key-off and determining the sleep duration based on the measured temperature. In a second example of a system that optionally includes the first example, the instructions for initiating a NOx sensor offset test include instructions for: selecting a NOx sensor output monitoring duration, sampling the NOx sensor output throughout the monitoring duration, and calculating an average value of the sampled NOx sensor output after the monitoring duration. In a third example of a system that optionally includes one or more of the first and second examples, the instructions for initiating a NOx sensor offset test further include instructions for: determining whether the calculated average value is greater than or equal to a minimum threshold and less than or equal to a maximum threshold, and if so, indicating that the offset test has passed, and if not, indicating that the offset test has failed. In a fourth example of a system that optionally includes one or more of the first, second, and third examples, the controller also has computer-readable instructions for: determining a delayed post-ignition heating duration before performing a NOx sensor SD test based on the detected NOx sensor output when the NOx sensor ignites, and initiating the NOx sensor SD test after the post-ignition heating duration has elapsed. In a fifth example of the system, which optionally includes one or more of the first, second, third, and fourth examples, the post-ignition heating duration delayed before performing the NOx sensor SD test is shorter than the post-ignition heating duration delayed before performing the NOx sensor offset test.In a sixth example of the system, which optionally includes one or more of the first, second, third, fourth, and fifth examples, the controller also has computer-readable instructions for: warning the vehicle driver of a NOx sensor malfunction when the key is turned on in response to an indication of a failed offset test.

[0107] Note that the exemplary control and estimation programs included herein can be used in conjunction with various engine and / or vehicle system configurations. The control methods and programs disclosed herein can be stored as executable instructions in non-transitory memory and can be executed by a control system including a controller in conjunction with various sensors, actuators, and other engine hardware. The specific programs 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, or functions shown may be executed sequentially, in parallel, or in some cases omitted. Similarly, the processing order is not necessarily required to achieve the features and advantages of the exemplary embodiments described herein, but is provided for ease of illustration and description. One or more of the actions, operations, and / or functions shown may be repeatedly executed depending on the specific strategy used. Furthermore, the actions, operations, and / or functions can be graphically represented as code programmed into a non-transitory memory of a computer-readable storage medium in an engine control system, wherein the actions are performed by executing instructions in a system including various engine hardware components in conjunction with an electronic controller.

[0108] It should be understood that the configurations and procedures disclosed herein are exemplary in nature, and these specific embodiments should not be considered limiting, as many variations are possible. For example, the above-described techniques can be applied to V-6, I-4, I-6, V-12, opposed 4-cylinder, and other engine types. The subject matter of this disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations disclosed herein, as well as other features, functions, and / or properties.

[0109] The following claims specifically point to certain combinations and sub-combinations considered novel and non-obvious. These claims may refer to a "one" element or a "first" element or its equivalent. Such claims should be understood to include combinations of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and / or properties may be claimed by amendment to these claims or by setting new claims in this application or related applications. Such claims, whether broader, narrower, equivalent, or different in scope from the original claims, are considered to be included within the subject matter of this disclosure.

[0110] According to the present invention, a method is provided in which, when the engine drives the vehicle to a stop, a first duration is waited before waking up the powertrain control module (PCM) and activating the heater of the exhaust NOx sensor; when the NOx sensor ignites, a second duration is waited, and then a NOx sensor self-diagnostic (SD) test is performed; and once a third duration has elapsed since the NOx sensor ignites, the third duration is performed, which is longer than the second duration.

[0111] According to an embodiment, a method includes: measuring the exhaust temperature at a parking location and determining a first duration based on the measured exhaust temperature.

[0112] According to an embodiment, a method is provided in which the NOx sensor output is detected when the NOx sensor ignites and second and third durations are determined based on the detected NOx sensor output.

[0113] According to an embodiment, a method includes performing a NOx sensor offset test, which includes selecting a NOx sensor output monitoring duration, sampling the NOx sensor output throughout the monitoring duration, and calculating an average value of the sampled NOx sensor output after the monitoring duration.

[0114] According to an embodiment, a method includes performing a NOx sensor offset test, further comprising determining whether a calculated average value is greater than or equal to a minimum threshold and less than or equal to a maximum threshold, and if so, indicating that the offset test has passed, and if not, indicating that the offset test has failed.

[0115] According to an embodiment, in response to an indication that the offset test has passed, the stored offset value is replaced with a calculated average value and the engine operation when the vehicle is started is adjusted based on the updated stored offset value; and in response to an indication that the offset test has failed, the PCM is instructed to warn the vehicle driver of a NOx sensor malfunction when the vehicle is started.

[0116] According to an embodiment, in response to an indication of NOx sensor gain skew in the SD test, the PCM is instructed to warn the vehicle driver of a NOx sensor malfunction when the vehicle is started.

[0117] According to the present invention, during the wet engine period after the engine-driven vehicle stops, the powertrain control module (PCM) is activated; the exhaust NOx sensor is heated; when the NOx sensor ignites, the NOx sensor output is detected, the duration of continuing to heat the NOx sensor is determined based on the detected output, and the NOx sensor is continued to be heated until the duration ends; and a NOx sensor offset test is performed at the end of the duration.

[0118] According to an embodiment, a method is provided in which, for a first higher NOx sensor output, the determined duration of continuous heating of the NOx sensor is longer, while for a second lower NOx sensor output, the determined duration of continuous heating of the NOx sensor is shorter.

[0119] According to an embodiment, a method is provided for performing a NOx sensor offset test, including selecting a NOx sensor output monitoring duration, sampling the NOx sensor output throughout the monitoring duration, and calculating an average value of the sampled NOx sensor output after the monitoring duration.

[0120] According to an embodiment, a method is provided for performing a NOx sensor offset test, which further includes determining whether a calculated average value is greater than or equal to a minimum threshold and less than or equal to a maximum threshold, and if so, indicating that the offset test has passed, and if not, indicating that the offset test has failed.

[0121] According to an embodiment, a method includes measuring the exhaust temperature at the time of parking and determining, based on the measured exhaust temperature, the duration for delaying the wake-up of the PCM after parking.

[0122] According to an embodiment, one method includes waking up the PCM approximately 4 hours after parking.

[0123] According to the present invention, a system is provided comprising: a NOx sensor located downstream of a selective catalytic reduction (SCR) catalyst in an engine exhaust system; an electronic timer; and a controller electrically communicating with the electronic timer and the NOx sensor, the controller having computer-readable instructions for: determining, upon a parking event, a sleep duration after the parking event followed by a power-off of the controller before initiating heating of the NOx sensor, sending the sleep duration to the electronic timer and starting the timer, and turning off the power after sending the sleep duration to the electronic timer; wherein the electronic timer turns on the controller after the sleep duration has elapsed, and wherein the controller further comprises computer-readable instructions for: initiating heating of the NOx sensor in response to power-on; detecting the NOx sensor output and determining a delayed post-ignition heating duration based on the detected NOx sensor output before performing a NOx sensor offset test; and initiating a NOx sensor offset test after the post-ignition heating duration has elapsed.

[0124] According to an embodiment, the controller also has computer-readable instructions for: measuring the temperature of the exhaust system when the vehicle is parked and determining the sleep duration based on the measured temperature.

[0125] According to an embodiment, the instructions for initiating a NOx sensor offset test include instructions for: selecting a NOx sensor output monitoring duration, sampling the NOx sensor output throughout the monitoring duration, and calculating an average value of the sampled NOx sensor output after the monitoring duration.

[0126] According to an embodiment, the instruction for initiating a NOx sensor offset test further includes instructions for: determining whether the calculated average value is greater than or equal to a minimum threshold and less than or equal to a maximum threshold, and if so, indicating that the offset test has passed, and if not, indicating that the offset test has failed.

[0127] According to an embodiment, the controller also has computer-readable instructions for: determining, based on the detected NOx sensor output, a post-ignition heating duration delayed before performing a NOx sensor self-diagnostic (SD) test when the NOx sensor ignites, and initiating a NOx sensor SD test after the post-ignition heating duration has elapsed.

[0128] According to an embodiment, the post-ignition heating duration delayed before performing the NOx sensor SD test is shorter than the post-ignition heating duration delayed before performing the NOx sensor offset test.

[0129] According to an embodiment, the controller also has computer-readable instructions for: warning the vehicle driver of a NOx sensor malfunction when the vehicle is started in response to an indication of a failed offset test.

Claims

1. A method for an engine, comprising: During the wet engine operation after the vehicle has stopped, the powertrain control module (PCM) is activated after a delay period. Heated exhaust NOx sensor; When the NOx sensor ignites, the NOx sensor output is detected, and based on the detected output, the duration for which the NOx sensor continues to be heated is determined, and the NOx sensor continues to be heated until the duration ends; and At the end of the stated duration, a NOx sensor offset test is performed.

2. The method of claim 1, wherein the determined duration of continuous heating of the NOx sensor is longer for a first higher output of the NOx sensor, and the determined duration of continuous heating of the NOx sensor is shorter for a second lower output of the NOx sensor that is lower than the first higher output of the NOx sensor.

3. The method of claim 1, wherein performing the NOx sensor offset test includes selecting a NOx sensor output monitoring duration, sampling the NOx sensor output throughout the monitoring duration, and calculating an average value of the sampled NOx sensor output after the monitoring duration.

4. The method of claim 3, wherein performing the NOx sensor offset test further comprises determining whether the calculated average value is greater than or equal to a minimum threshold and less than or equal to a maximum threshold, and if so, indicating that the offset test has passed, and if not, indicating that the offset test has failed.

5. The method of claim 1, further comprising measuring the exhaust temperature at the time of parking and determining, based on the measured exhaust temperature, the duration for which the PCM is delayed in waking up after parking.

6. The method of claim 1, wherein the delay time is 4 hours.

7. The method of claim 4, further comprising: In response to the indication that the offset test has passed, the stored offset value is replaced with the calculated average value and the engine operation when the vehicle is started is adjusted based on the updated stored offset value.

8. The method of claim 4, further comprising: In response to the indication of the offset test failure, the PCM is instructed to warn the vehicle driver of a NOx sensor malfunction when the vehicle is started.

9. A system for an engine, comprising: The NOx sensor is located downstream of the selective catalytic reduction (SCR) catalyst in the engine exhaust system; Electronic timer; and A controller, which communicates electrically with the electronic timer and the NOx sensor, has computer-readable instructions for the following: In the event of a parking incident, the sleep duration during which the controller power is off after the parking incident but before initiating heating of the NOx sensor is determined, the sleep duration is sent to the electronic timer and the timer is started, and the power is off after the sleep duration is sent to the electronic timer; The electronic timer powers on the controller after the sleep duration has elapsed, and the controller further includes computer-readable instructions for: In response to power-on, heating of the NOx sensor is initiated; When the NOx sensor ignites, the NOx sensor output is detected and the post-ignition heating duration delayed before performing the NOx sensor offset test is determined based on the detected NOx sensor output. as well as The NOx sensor offset test is initiated after the post-ignition heating duration has elapsed.

10. The system of claim 9, wherein the controller further comprises computer-readable instructions for: measuring the temperature of the exhaust system when the vehicle is parked, and determining the sleep duration based on the measured temperature.

11. The system of claim 9, wherein the instructions for initiating the NOx sensor offset test include instructions for: selecting a NOx sensor output monitoring duration, sampling the NOx sensor output throughout the monitoring duration, and calculating an average value of the sampled NOx sensor output after the monitoring duration.

12. The system of claim 11, wherein the instruction for initiating the NOx sensor offset test further includes instructions for: determining whether the calculated average value is greater than or equal to a minimum threshold and less than or equal to a maximum threshold, and if so, indicating that the offset test has passed, and if not, indicating that the offset test has failed.

13. The system of claim 9, wherein the controller further comprises computer-readable instructions for: determining, upon ignition of the NOx sensor, a post-ignition heating duration delayed prior to performing a NOx sensor self-diagnostic (SD) test based on the detected NOx sensor output, and initiating the NOx sensor SD test after the post-ignition heating duration has elapsed.

14. The system of claim 13, wherein the post-ignition heating duration delayed before performing the NOx sensor SD test is shorter than the post-ignition heating duration delayed before performing the NOx sensor offset test.

15. The system of claim 12, wherein the controller further comprises computer-readable instructions for: warning the vehicle driver of a NOx sensor malfunction when the vehicle is started in response to an indication of a failed offset test.

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