METHODS AND SYSTEMS FOR EXHAUST CATALYSATOR DIAGNOSTIC

Abstract

Procedure, comprehensive: Indication of the absence of an exhaust catalyst (170) in response to a detected temperature profile downstream of the exhaust catalyst (170) deviating from an expected temperature profile, wherein the expected temperature profile is based on water absorption and an associated exothermic temperature increase through the exhaust catalyst (170), where the display includes displays in response to the detected temperature profile recorded during a cold engine start, wherein the expected temperature profile includes an increase in the exhaust gas temperature detected downstream of the exhaust gas catalyst (170) with respect to an exhaust gas temperature detected upstream of the exhaust gas catalyst (170) for a threshold duration directly after the engine cold start, characterized in that The threshold duration is based on both ambient humidity and engine temperature, with the threshold duration increasing as ambient humidity increases and / or engine temperature decreases.

Description

Area

[0001] The present invention generally relates to methods and systems for detecting a missing exhaust catalyst from an exhaust system of an internal combustion engine. General state of the art / Summary

[0002] Vehicles can be equipped with various exhaust aftertreatment devices to reduce the release of exhaust emissions into the environment. For example, three-way catalytic converters can reduce the levels of various emissions, including carbon monoxide and unburned hydrocarbons, while selective catalyst reduction (SCR) devices can be used to reduce NOx emissions. To ensure that the aftertreatment devices are functioning optimally and meeting emission control standards, SCR device diagnostics can be performed regularly or opportunistically. Feedback from one or more exhaust system sensors can be used to determine if an SCR device is missing due to manufacturing defects or loosening during vehicle operation.

[0003] German patent application DE 10 2015 223 686 A1 discloses a method for calculating and using a monitoring criterion that serves as an indicator for the presence of a zeolite-containing SCR catalyst in the exhaust system of a motor vehicle. The monitoring criterion is determined by calculating the enthalpy difference of an exhaust stream at the SCR catalyst.

[0004] German patent application DE 10 2014 209 794 A1 discloses a method and a device for diagnosing the removal of a component of an exhaust gas purification system. In this method, a first temporal profile of a state variable of the exhaust gas in the exhaust stream upstream of the exhaust gas purification component and a second temporal profile of the state variable of the exhaust gas downstream of the exhaust gas purification component are determined using a second sensor.

[0005] Document DE 10 2009 007 763 A1 discloses a method for determining the effectiveness of an SCR catalyst.

[0006] Document US 2015 / 0204228A1 discloses a control unit for an internal combustion engine in which an SCR catalyst is arranged.

[0007] Several approaches are provided for diagnosing an SCR system. One example, as shown in US 8,186,146 B2, Jayachandran et al., involves measuring the exhaust gas temperature upstream and downstream of an exhaust aftertreatment device using exhaust gas temperature sensors. The rate of temperature change upstream of the exhaust aftertreatment device can be compared to the rate of temperature change downstream. Due to the thermal mass of the exhaust aftertreatment device, the rate of temperature change downstream of the device may be substantially lower than the rate upstream. Therefore, impairment of the exhaust aftertreatment device may be indicated if the upstream and downstream rates of temperature change differ by less than a predetermined amount.

[0008] However, the inventors of the present invention have recognized potential disadvantages associated with the aforementioned approach. For example, the operation of an exhaust aftertreatment device, such as the SCR device, can lead to temperature exothermicity during certain engine operating conditions, causing the exhaust gas temperature to increase downstream of the SCR device. In the approach demonstrated by Jayachandran et al., during conditions where an exothermic reaction is present in the SCR device, erroneous indications of the SCR device's absence may occur because the temperature downstream of the catalyst is higher than the temperature upstream of the catalyst. In another approach, for SCR device diagnostics, urea can be injected upstream of the SCR device, and the NOx levels upstream of the SCR device can be compared with the NOx levels downstream of the SCR catalyst.However, to provide a reliable assessment of the SCR system's status, it may be necessary to collect a significant number of measurements over an extended period of engine operation. During periods of low NOx load on the SCR system, urea injection can negatively impact emission quality if carried out for the required extended duration.

[0009] In one example, the problems described above can be addressed by a method that includes: indicating the absence of an exhaust catalyst in response to a detected temperature profile downstream of the catalyst deviating from an expected temperature profile, where the expected temperature profile is based on water absorption and the associated exothermic temperature increase by the exhaust catalyst. In this way, a missing catalyst can be reliably indicated by comparing the exhaust gas temperature downstream of the catalyst with an expected temperature profile during a cold start condition, using the differences in catalyst water absorption.

[0010] As an example, exhaust aftertreatment devices, such as an SCR system, can use a zeolite-based catalyst. During cold start conditions, water from the exhaust gas can be absorbed by the zeolite layer of the SCR system. Water absorption by zeolite is an exothermic process that releases heat. Due to the exothermic nature of water absorption at the SCR system, the exhaust gas temperature measured downstream of the SCR system can be significantly higher than the exhaust gas temperature measured upstream of the catalyst. By utilizing this attribute, the presence of an SCR system can be confirmed immediately after a cold engine start if the exhaust gas temperature downstream of the SCR system is higher than the exhaust gas temperature upstream of the SCR system.If the SCR device is missing, the zeolite may not be able to absorb water from the exhaust gas, and the temperature downstream of the SCR device may be substantially the same as, or lower than, the exhaust gas temperature upstream of the SCR device. Furthermore, after the engine has warmed up, once water has been removed from the exhaust gas due to evaporation, or once the zeolite in the SCR device is saturated with water, the exhaust gas temperature upstream of the SCR device may become substantially the same as, or lower than, the exhaust gas temperature. If the missing SCR device is confirmed, a diagnostic code may be set, and one or more engine operating parameters, such as fuel delivery schedule, boost pressure, torque output, etc., may be adjusted in subsequent engine cycles.

[0011] In this way, the absence of the SCR device can be indicated by opportunistically comparing the exhaust gas temperature measured upstream of an exhaust catalyst, such as an SCR device, with the exhaust gas temperature measured downstream of the SCR device. The technical benefit of utilizing the exothermic process of water absorption by a zeolite layer present in the SCR device during cold-start conditions is that the presence of zeolite in the SCR device can be successfully used for in-vehicle detection of a missing SCR device. By adjusting the engine operating parameters in response to the detection of a missing catalyst, compliance with emission standards can be maintained until the SCR device is reinstalled.Overall, by detecting a missing exhaust aftertreatment device and subsequently adjusting engine operating conditions, emission quality and fuel efficiency can be improved.

[0012] It is understood that the foregoing summary is provided to present, in simplified form, a selection of concepts that are described in more detail in the detailed description. It is not intended to identify important or essential features of the claimed subject matter, the scope of which is defined solely by the claims following the detailed description. Furthermore, the claimed subject matter is not limited to implementations that address the disadvantages mentioned above or in any part of this disclosure. Brief description of the drawings Fig. Figure 1 shows an exemplary embodiment of an engine system that includes a selective catalyst reduction (SCR) device coupled to the exhaust gas channel. Fig. Figure 2 shows a flowchart illustrating an exemplary procedure that can be implemented to detect a missing SCR device. Fig. Figure 3 shows example exhaust gas temperature curves upstream and downstream of the SCR device based on a saturation level of the SCR device. Fig. Figure 4 shows an example diagnosis of the SCR device during cold start conditions. DETAILED DESCRIPTION

[0013] The following description concerns systems and methods for detecting a missing exhaust catalyst during cold start conditions. An exemplary engine system that includes an SCR device is described in Fig. 1 shown. A motor control unit can be designed to execute a control routine, such as the example routine from Fig. 2. To detect a missing SCR device based on thermal changes occurring during water absorption by a zeolite layer of the SCR device. Exemplary exhaust gas temperature profiles based on water absorption, recorded upstream and downstream of the SCR device, are shown in Fig. Figure 3 shows an example diagnosis of the SCR device in connection with Fig. 4 discussed.

[0014] Fig. Figure 1 schematically shows aspects of an exemplary engine system 100, which includes an engine 10. In the illustrated embodiment, the engine 10 is a turbocharged engine coupled to a turbocharger 13, which includes a compressor 114 driven by a turbine 116. In particular, fresh air is fed into the engine 10 along the intake duct 42 via the air cleaner 112 and flows to the compressor 114. The compressor can be any suitable intake air compressor, such as a turbocharger compressor driven by an engine or a drive shaft. In the engine system 10, the compressor is a turbocharger compressor mechanically coupled to the turbine 116 via a shaft 19, with the turbine 116 being driven by expanding engine exhaust gases.

[0015] As in Fig. As shown in Figure 1, the compressor 114 is coupled to the throttle valve 20 via the charge-air cooler (CAC) 17. The throttle valve 20 is coupled to the engine intake manifold 22. The compressed air flows from the compressor through the charge-air cooler 17 and the throttle valve to the intake manifold. In the Fig. In the embodiment shown in Figure 1, the pressure of the air filling inside the intake manifold is detected by the manifold air pressure (MAP) sensor 124.

[0016] One or more sensors can be coupled to an inlet of the compressor 114. For example, a temperature sensor 55 can be coupled to the inlet to estimate a compressor inlet temperature, and a pressure sensor 56 can be coupled to the inlet to estimate a compressor inlet pressure. As another example, a humidity sensor 57 can be coupled to the inlet to estimate the humidity of an air charge entering the compressor. Other sensors, such as air-fuel ratio sensors, etc., may be used. In other examples, one or more of the compressor inlet conditions (such as humidity, temperature, pressure, etc.) can be derived from engine operating conditions.Furthermore, when exhaust gas recirculation (EGR) is activated, the sensors can estimate the temperature, pressure, humidity, and air-fuel ratio of the air charge mixture, including fresh air and residual exhaust gases, that were taken in at the compressor inlet.

[0017] A wastegate actuator 92 can be opened to release at least a portion of the exhaust pressure from upstream of the turbine via the wastegate 90 to a point downstream of the turbine. By reducing the exhaust pressure upstream of the turbine, the turbine speed can be reduced for boost control and / or to reduce compressor pump operation.

[0018] The intake manifold 22 is coupled to a series of combustion chambers 30 via a series of intake valves (not shown). The combustion chambers are further coupled to the exhaust manifold 36 via a series of exhaust valves (not shown). In the illustrated embodiment, a single exhaust manifold 36 is shown. In other embodiments, however, the exhaust manifold can include a plurality of exhaust manifold sections. Configurations featuring a plurality of exhaust manifold sections can allow wastewater from different combustion chambers to be routed to different locations in the engine system.

[0019] In one embodiment, each of the exhaust and intake valves can be electronically actuated or controlled. In another embodiment, each of the exhaust and intake valves can be actuated or controlled by cams. Regardless of whether actuation is electronic or cam-operated, the timing of the opening and closing of the exhaust and intake valves can be adjusted as required for the desired combustion and emission control performance.

[0020] The combustion chambers 30 can be supplied with one or more fuels, such as gasoline, alcohol-fuel mixtures, diesel, biodiesel, compressed natural gas, etc., via the injection system 66. The fuel can be supplied to the combustion chambers via direct injection, port injection, throttle body injection, or a combination thereof. Combustion in the combustion chambers can be initiated by spark ignition and / or compression ignition.

[0021] As in Fig. As shown in Figure 1, exhaust gas is directed from one or more exhaust manifold sections to the turbine 116 to drive it. The combined flow from the turbine and the wastegate then flows through an exhaust aftertreatment catalyst 170. One or more exhaust aftertreatment catalysts 170 can be designed to catalytically treat the exhaust gas stream and thereby reduce the amount of one or more substances in the exhaust gas stream. For example, the catalyst 170 can be a selective catalyst reduction (SCR) device designed to reduce the NOₓ. x -ratio to change or NO xThe SCR device selectively reduces the emissions by means of a reducing agent, such as ammonia or urea, which is added to the exhaust gas via the injection device 135. The SCR device can include a substrate, such as zeolite, to absorb water from the exhaust gas flowing through it. A first exhaust gas temperature sensor 128 can be coupled to the exhaust gas channel 104 upstream of the SCR device 170. A second exhaust gas temperature sensor 129 can be coupled to the exhaust gas channel 104 downstream of the SCR device 170. Furthermore, a first coaxial radio frequency (RF) feed probe 175 can be coupled to a first end of the SCR device 170 proximal to the turbine 116, and a second coaxial RF feed probe 176 can be coupled to a second end of the SCR device 170 proximal to the tailpipe 105. The RF feed probes can be designed to measure an ammonia level stored in the SCR device 170.

[0022] The SCR device 170 can be opportunistically diagnosed during engine cold-start conditions to determine if the device is missing. The SCR device 170 may be missing due to a manufacturing defect during vehicle assembly or due to the device becoming detached during operation or handling. An SCR device 170 may be indicated as missing if an estimated exhaust gas temperature profile downstream of the SCR device 170 (estimated via a second exhaust gas temperature sensor 129) differs from an expected exhaust gas temperature profile downstream of the SCR device 170.The expected temperature profile during a cold start includes an increase in the exhaust gas temperature measured downstream of the SCR device 170, relative to the exhaust gas temperature measured upstream of the SCR device 170 for a threshold period (time), immediately after engine start, and then, after the threshold period, a decrease in the exhaust gas temperature downstream of the SCR device relative to the exhaust gas temperature upstream of the SCR device. If an SCR device is present (not absent), the exhaust gas temperature downstream of the SCR device is expected to increase relative to the exhaust gas temperature upstream of the SCR device due to an exothermic effect of water absorption by the zeolite present in the vehicle. After the threshold period, the zeolite in the SCR device may be saturated with moisture and may no longer be able to absorb water, thus reducing the exothermic process.Furthermore, the water in the exhaust duct can evaporate as the engine temperature increases, and the exothermic water absorption process can no longer occur. The threshold duration can be based on either ambient humidity or engine temperature, with the threshold duration increasing when ambient humidity increases and engine temperature decreases, or decreasing when ambient temperature decreases and engine temperature increases, or decreasing. Alternatively, the threshold duration can be based on the water content of the zeolite layer relative to a saturation level, with the threshold duration decreasing as the water content of the zeolite layer increases.Therefore, the detection of a missing SCR device can be performed within each of the following driving cycles, from a threshold distance immediately after a cold start to a threshold number of engine cycles following that initial cycle. Upon confirmation of a missing SCR device, a diagnostic code can be set, and one or more engine operating parameters can be adjusted based on power reduction measures, as required by regulatory authorities to improve emissions. For example, an engine load can be limited below a threshold load by reducing the opening of an intake throttle.In another example, which is not part of the present invention, the fuel supply schedule for subsequent engine cycles (after detection of the missing SCR device) can be adjusted by reducing the pulse width of the fuel supplied during each subsequent engine cycle for a number of engine cycles. Furthermore, upon detection of a missing SCR device, the supply of reducing agent to the SCR device can be stopped.

[0023] Furthermore, the RF probes 175 and 176 can be used to measure the electromagnetic resonance in the tube containing the SCR device 170. An RF signal can include one or more of the amplitude of the energy exceeding the resonance frequency, the frequency at which the electromagnetic resonance occurs, the width (frequency) of the resonance peak, and the ratio of the resonance frequency to the resonance frequency width. For example, a change (such as a decrease) in the RF signal can be observed in response to water absorption by the zeolite layer in the SCR device 170, thus confirming the presence of an SCR device 170.

[0024] Furthermore, an oxidation catalyst or a three-way catalyst for oxidizing hydrocarbon and / or carbon monoxide residues in the exhaust gas stream can be coupled to the exhaust gas channel 104. Different exhaust aftertreatment catalysts, exhibiting any of the discussed functionalities, can be arranged separately or together in washcoats or elsewhere in the exhaust aftertreatment stages. In some embodiments, a regenerable soot filter can be included in the exhaust aftertreatment stages, designed to capture and oxidize soot particles in the exhaust gas stream.

[0025] Lambda sensors suitable for providing an indication of an exhaust air-fuel ratio, such as linear lambda sensors or UEGO sensors (Universal Exhaust Gas Oxygen Sensor, wideband or wide-range lambda sensors), dual-state lambda sensors or EGO, HEGO sensors (heated EGO sensors), NOx, HC or CO sensors may also be coupled to the exhaust channel 104.

[0026] The treated exhaust gas from the catalyst 170 can be discharged into the environment, in whole or in part, via a main exhaust duct 104 after passing through a silencer 172. A low-pressure exhaust gas recirculation (LP-EGR) system duct 180 can direct exhaust gas from the exhaust duct 104 (downstream of the turbine 116) to the intake duct 42 (upstream of the compressor 114). The EGR valve 52 can be opened to allow a controlled amount of exhaust gas to enter the compressor inlet for desired combustion and emission control performance. The EGR valve 52 can be configured as a continuously variable valve. Alternatively, the EGR valve 52 can be configured as an on / off valve. In further embodiments, the engine system can include a high-pressure EGR flow path, wherein exhaust gas is drawn in upstream from the turbine 116 and returned downstream from the compressor 114 to the engine intake manifold.

[0027] One or more sensors can be coupled to the EGR channel 180 to provide details regarding the composition and conditions of the EGR. For example, a temperature sensor can be provided to determine the EGR temperature, a pressure sensor can be provided to determine the EGR pressure, a humidity sensor can be provided to determine the moisture or water content of the EGR, and an air-fuel ratio sensor can be provided to estimate the air-fuel ratio of the EGR. Alternatively, EGR conditions can be derived from the one or more temperature, pressure, humidity, and air-fuel ratio sensors 55-57 coupled to the compressor inlet. In one example, the air-fuel ratio sensor 57 is a lambda sensor.

[0028] The engine system 100 may further include the control system 14. It is shown that the control system 14 receives information from a variety of sensors 16 (various examples of which are described herein) and sends control signals to a variety of actuators 18 (various examples of which are described herein). As an example, the sensors 16 may include the exhaust gas temperature sensors 128 and 129, the radio frequency (RF) supply probes 175 and 176, the MAP sensor 124, the exhaust gas temperature sensor, the exhaust gas pressure sensor, the compressor inlet temperature sensor 55, the compressor inlet pressure sensor 56, the compressor inlet humidity sensor 57, and the EGR sensor. Other sensors, such as additional pressure, temperature, air-fuel ratio, and composition sensors, may be coupled at various points in the engine system 100.The actuating elements 81 can, for example, include a throttle 20, an EGR valve 52, a wastegate 92, and a fuel injection device 66. The control system 14 can include a controller 12. The controller 12 can receive input data from the various sensors, process the input data, and trigger various actuators in response to the processed input data based on an instruction or code programmed therein, according to one or more sequences.

[0029] For example, the absence of the SCR device 170 can be determined during cold-start conditions based on the exhaust gas temperature upstream of the SCR device, as estimated by a first exhaust gas temperature sensor 128, and the exhaust gas temperature downstream of the SCR device 170, as estimated by the second exhaust gas temperature sensor 129. A variety of engine actuators (e.g., the fuel injection device 66) can be adjusted based on an indication of the absence of the SCR device 170. In another example, the controller 12 can regulate the opening of the EGR valve 52 based on engine operating conditions and EGR requirements to draw a desired amount of EGR from the exhaust bypass channel into the engine intake manifold.

[0030] In this way, the system enables Fig. 1. A system for an engine comprising: an intake system; an exhaust system comprising a selective catalyst reduction (SCR) device comprising a zeolite material coupled to an exhaust duct, a first exhaust gas temperature sensor coupled to the exhaust duct upstream of the SCR device, a second exhaust gas temperature sensor coupled to the exhaust duct downstream of the SCR device, a turbocharger comprising a turbine coupled to the exhaust duct, a turbine-driven compressor coupled to the intake system, a wastegate bypassing the turbine, and a controller with computer-readable instructions stored in non-volatile memory for the following: during a cold start condition, in response to a second exhaust gas temperature estimated via the second exhaust gas temperature sensor,If the second exhaust gas temperature is equal to or lower than the first exhaust gas temperature estimated by the first exhaust gas temperature sensor, this indicates that the SCR device is missing from the exhaust duct; and conversely, if the second exhaust gas temperature is higher than the first exhaust gas temperature, this indicates that the SCR device is not missing.

[0031] Fig. Figure 2 illustrates an exemplary method 200 for detecting a missing selective catalyst reduction (SCR) device, as described in Fig. 1 shown, which is coupled to the exhaust duct, can be implemented. Instructions for executing procedure 200 and the other procedures included herein can be implemented by a controller based on instructions stored in a memory of the controller and in conjunction with sensors of the engine system, such as those referred to above. Fig. The control system can execute the signals received from the sensors described in section 1. The control system can use motor actuators of the motor system to adjust the motor operation according to the procedures described below.

[0032] At 202, the routine involves estimating and / or measuring engine operating conditions. Conditions assessed may include, for example, engine temperature, engine load, driver torque demand, engine speed, throttle position, exhaust pressure, exhaust air-fuel ratio, environmental conditions including ambient temperature, pressure, and humidity, MAP, MAF, boost pressure, etc.

[0033] At 204, the routine includes determining whether the vehicle engine is operating under cold-start conditions. A cold-start condition can be confirmed if the engine is started after a prolonged period of inactivity, when the engine temperature is below a threshold (such as below the activation temperature of the exhaust gas SCR device), and while ambient temperatures are below a threshold. SCR device diagnostics can be performed during cold-start conditions based on water absorption by a zeolite material present in the SCR device.

[0034] If cold start conditions are not confirmed, the routine proceeds to 206, and engine operation can continue without initiating SCR device diagnostics. If the engine is not operated under cold start conditions, water in the exhaust gas may evaporate, and SCR device diagnostics based on its water absorption properties cannot be effectively performed. In one example, SCR device diagnostics can be initiated even after confirmation that cold start conditions are not present, in response to ambient humidity exceeding a threshold. If the ambient humidity is higher than a threshold, water may be present in the exhaust duct even at high engine temperatures, and SCR device diagnostics can be performed based on the effects of water absorption by the zeolite present in the SCR device.During such humidity conditions above a threshold, even if a cold start condition is not confirmed, the routine may proceed to step 208 to detect whether the SCR device is missing.

[0035] If engine cold start conditions are confirmed, a first exhaust gas temperature (T1) upstream of the SCR device can be determined at 208 based on inputs from a first exhaust gas temperature sensor (such as sensor 128 in Fig. 1), which is coupled to the exhaust duct upstream of the SCR device, can be estimated, and a second exhaust gas temperature (T2) downstream of the SCR device can be determined based on inputs from a second exhaust gas temperature sensor (such as sensor 129 in Fig. 1), which is coupled to the exhaust gas duct downstream of the SCR device. The first exhaust gas temperature, T1, represents the temperature of exhaust gas containing water before it enters the SCR device. The second exhaust gas temperature, T2, represents the temperature of exhaust gas after water has been absorbed by the zeolite of the SCR device. The absorption of water by the zeolite is an exothermic process and can lead to a significant increase in the exhaust gas temperature downstream of the SCR device. During operation of the SCR device, a reducing agent, such as urea, can be injected into the exhaust gas upstream of the SCR device to facilitate NOx conversion. However, during cold start conditions, when the exhaust gas temperature is measured both upstream and downstream of the SCR device, the injection of the reducing agent may be suspended.Therefore, the addition of the reducing agent can be stopped during the generation of the exothermic reaction caused by water absorption.

[0036] In procedure 210, the routine involves determining whether the difference between the second exhaust gas temperature T2 and the first exhaust gas temperature T1 is greater than or equal to a threshold temperature difference. The threshold temperature difference can correspond to the temperature difference of the exhaust gas upstream and downstream of the SCR device, caused by the exothermic process of water absorption at the SCR device. In addition to comparing the difference between the second exhaust gas temperature T2 and the first exhaust gas temperature T1 with the threshold temperature difference, one example involves comparing the rate of change of the second exhaust gas temperature T2 with a threshold rate. Another example involves comparing the profile of the second exhaust gas temperature T2 with an expected (stored) temperature profile.In yet another example, the ratio of the second exhaust gas temperature T2 to the first exhaust gas temperature T1 can be compared to a threshold ratio. If it is determined that the difference between the second exhaust gas temperature T2 and the first exhaust gas temperature T1 is greater than or equal to the threshold value, it can be confirmed at 212 that the catalytic converter is not missing. Furthermore, if the rate of change of the second exhaust gas temperature T2 is higher than the threshold rate, the profile of the second exhaust gas temperature T2 is essentially the same as an expected (stored) temperature profile, and the ratio of the second exhaust gas temperature T2 to the first exhaust gas temperature T1 is higher than the threshold ratio, it can be confirmed that the catalytic converter is not missing.In this way, during a cold start condition, the presence of the exhaust catalyst can be indicated in response to each of the differences between the first detected exhaust gas temperature upstream of the catalyst and the second detected exhaust gas temperature downstream of the catalyst being lower than the threshold temperature difference. The presence of the exhaust catalyst can also be indicated when the engine coolant temperature is below a threshold and / or when the ambient humidity is below a threshold.

[0037] As the water content of the zeolite increases, its capacity for further water absorption decreases, and the temperature difference between the first exhaust gas temperature T1 and the second exhaust gas temperature T2 may decrease. When the zeolite is saturated with water, or when the water in the exhaust gas has evaporated due to engine warm-up, the first exhaust gas temperature T1 may become essentially the same as the second exhaust gas temperature T2. In one example, if no further water absorption occurs, the second exhaust gas temperature T2 may be lower than the first exhaust gas temperature T1 because the exhaust gas temperature can drop downstream of the SCR device due to the thermal mass of the SCR device. The first and second exhaust gas temperatures can be selectively measured during an initial number of engine cycles immediately after the engine is started from idle.Furthermore, the detection of a missing SCR device can be performed during a threshold period immediately following a cold engine start or during the first number of engine cycles after a cold start, ensuring that the zeolite material is not saturated with moisture or that the moisture in the exhaust duct has not evaporated due to the increased engine temperature. In this way, the detection of the missing catalyst can be carried out under predetermined conditions, including one or more of the following: catalyst temperature, time since the start of the engine from which the exhaust gas is generated, engine coolant temperature, or ambient humidity.

[0038] If code 210 indicates that the difference between the second exhaust gas temperature T2 and the first exhaust gas temperature T1 is lower than the threshold value, even during cold start conditions, code 214 may indicate that the SCR device is missing. Furthermore, if the rate of change of the second exhaust gas temperature T2 is lower than the threshold rate, the profile of the second exhaust gas temperature T2 deviates substantially from the expected (stored) temperature profile, and the ratio of the second exhaust gas temperature T2 to the first exhaust gas temperature T1 is lower than the threshold ratio, it may be confirmed that the catalytic converter is missing. The SCR device may be missing due to a manufacturing defect during vehicle assembly or because the device was disconnected and detached from its intended position in the exhaust duct before operation or handling of the engine.In one example, a damaged catalyst, such as an SCR unit that has ruptured due to external influence, can be detected by monitoring the exothermic process of water absorption by the zeolite layer of the SCR unit. The absence of the SCR unit can be indicated by setting a warning light or diagnostic code, or by activating a malfunction indicator lamp, to inform the driver that the catalyst is missing and needs to be replaced.

[0039] The following section is not part of the present invention. In response to an indication of a missing SCR device, the control unit at 216 can suspend the operation of one or more engine actuators based on power-reduction measures, as required by regulatory authorities, in order to stop engine operation. As an example, in response to an indication of a missing SCR device for a second number of engine cycles following the first number of engine cycles, the control unit can: adjust the fuel delivery schedule, limit an engine load (e.g., by reducing the opening of an intake throttle), limit engine torque output, and / or reduce boost pressure (e.g., by opening a wastegate coupled to the exhaust turbine or a bypass valve coupled to an intake compressor). Furthermore, the introduction of a reducing agent, such as urea, into the SCR catalyst should be suspended.

[0040] In this way, during an engine start from idle, the absence of an exhaust catalyst can be indicated in response to a difference between a first detected exhaust gas temperature upstream of the exhaust catalyst and a second detected exhaust gas temperature downstream of the exhaust catalyst exceeding a threshold temperature difference.

[0041] Fig. Figure 3 shows example 300 exhaust gas temperature profiles detected upstream and downstream of the SCR device, where the profiles are based on the water saturation level of a zeolite layer of the SCR device. In each of the profiles 301, 305 and 307, the x-axis represents time (in seconds) while the y-axis represents temperature (in °C).

[0042] The first curve 301 shows exhaust gas temperatures upstream and downstream of the SCR device when the SCR device is dry immediately after a cold start. In the first curve 301, line 302 shows the exhaust gas temperature upstream of the exhaust SCR device, as estimated by a first exhaust gas temperature sensor coupled to the exhaust duct upstream of the SCR device, and line 304 shows the exhaust gas temperature downstream of the exhaust SCR device, as estimated by a second exhaust gas temperature sensor coupled to the exhaust duct downstream of the SCR device. During a cold start, if the SCR device is dry, it can initially absorb all the water from the exhaust gas flowing through it. Since water absorption by zeolite is an exothermic process, this water absorption can lead to an increase in the exhaust gas temperature downstream of the SCR.As can be seen from lines 302 and 304, in a dry SCR device, the temperature downstream of the device is significantly higher than the temperature upstream. Furthermore, a rapid increase in temperature downstream of the device is observed. The temperature profile illustrated by line 304 rises rapidly and indicates the exothermic reaction generated by water absorption.

[0043] If water absorption continues, the zeolite can become saturated and will no longer be able to absorb the entire volume of water flowing through the device. The second graph 305 shows exhaust gas temperatures upstream and downstream of the SCR device when the SCR device is partially saturated with water. In the second graph 305, line 306 shows the exhaust gas temperature upstream of the exhaust SCR device, and line 308 shows the exhaust gas temperature downstream of the exhaust SCR device. When the zeolite is partially saturated with water, a smaller amount of water can still be absorbed by the SCR device.Accordingly, the difference between the exhaust gas temperature downstream of the SCR device and the exhaust gas temperature upstream of the SCR device can decrease due to a smaller amount of heat released from the exothermic process of absorbing a smaller amount of water, compared to the temperature difference during the operation of a dry SCR device.

[0044] After absorbing a threshold amount of water, the SCR device can become saturated with water, and further water absorption cannot occur. The third graph, 307, shows exhaust gas temperatures upstream and downstream of the SCR device when the SCR device is completely saturated with water. In the third graph, 307, line 310 shows the exhaust gas temperature upstream of the exhaust gas SCR device, and line 312 shows the exhaust gas temperature downstream of the exhaust gas SCR device. When the SCR device is completely saturated with water and no further water absorption occurs at the SCR device, no exothermic heat release takes place. Due to the thermal mass of the SCR device, the exhaust gas temperature can decrease as it flows through the SCR device.Accordingly, in the third run 307 we observed that the exhaust gas temperature downstream of the SCR device is lower than the exhaust gas temperature upstream of the SCR device.

[0045] In this way, the exhaust gas temperature upstream and downstream of the SCR device can vary based on the saturation level of the SCR device, with the difference decreasing as the saturation level increases. Furthermore, the downstream temperature profile and its rate of change can also vary based on the saturation level of the SCR device. All of these approaches, or combinations thereof, can be used to identify a missing or impaired catalyst.

[0046] Fig.Figure 4 shows an exemplary operating sequence 400 illustrating the diagnosis of a selective catalyst reduction (SCR) device coupled to the exhaust manifold of an internal combustion engine during cold start conditions. The horizontal (x-axis) represents time, and the vertical markers t1-t5 represent important time points in the diagnosis of the SCR device.

[0047] The first curve, line 402, shows a change in engine temperature over time, as estimated by an engine coolant temperature sensor. The dashed line 403 represents an engine threshold temperature below which cold-start conditions can be confirmed. The second curve, line 404, shows the exhaust gas temperature upstream of the SCR device (before the catalyst), as estimated by a first exhaust gas temperature sensor connected to the exhaust manifold upstream of the SCR device. The third curve, line 406, shows the exhaust gas temperature downstream of the SCR device (after the catalyst), as estimated by a second exhaust gas temperature sensor connected to the exhaust manifold downstream of the SCR device. The fourth curve, line 410, is a marker indicating the absence of the SCR device.

[0048] Before time t1, the engine is switched off and is not running to power the vehicle. During this time, the engine components, including the SCR unit, are not in operation. The zeolite in the SCR unit is dry from a previous engine operation at a higher temperature. At time t1, the engine starts from rest after a period of inactivity in response to a driver torque demand. At the time of engine start, the engine temperature is lower than the threshold temperature 403, indicating cold start conditions. During a cold start, water from combustion is not vaporized in the exhaust duct due to the lower engine temperature, and exhaust gas flows into the SCR unit along with the water. At the SCR unit, the water is absorbed via an exothermic process.

[0049] Between times t1 and t2, the exhaust gas temperature upstream of the catalyst rises steadily. However, due to the exothermic effect of water absorption by the SCR device, a peak occurs in the exhaust gas temperature downstream of the catalyst. The SCR device has a water absorption threshold capacity and is no longer able to absorb water when saturated. As the amount of water absorbed by the SCR device increases, the further water absorption by the SCR device decreases, and the exothermic effect leading to the peak in the exhaust gas temperature downstream of the catalyst decreases accordingly. In response to the peak in the exhaust gas temperature downstream of the catalyst, caused by water absorption during cold start conditions, it is assumed that the SCR device is not missing, and the indicator can remain in the "off" position.

[0050] At time t2, it is observed that the exhaust gas temperature after the catalyst (as represented by T2) is lower than the exhaust gas temperature before the catalyst (as represented by T1). Based on the decrease in the exhaust gas temperature after the catalyst, it is assumed that the SCR device is saturated with water and no further absorption occurs. At time t2, the engine temperature rises above the threshold temperature of 403°C, and the engine is no longer operating under cold-start conditions. Between times t2 and t3, the exhaust gas temperature after the catalyst remains lower than the exhaust gas temperature before the catalyst due to the thermal mass of the SCR device. Furthermore, the water absorbed in the SCR device evaporates during engine operation between times t2 and t3 due to the higher engine temperature, thus drying the device.

[0051] At time t3, the vehicle is switched off in response to a driver request, and between times t3 and t4, the engine is not running to propel the vehicle. At time t4, the engine restarts from idle in response to a driver torque request. Based on the fact that the engine temperature is lower than the engine threshold temperature, it is assumed that the engine is operating under cold-start conditions. However, between times t4 and t5, it is observed that the exhaust gas temperature downstream of the catalytic converter remains below the exhaust gas temperature upstream of the catalytic converter. Based on each of the exhaust gas temperatures upstream and downstream of the catalytic converter, it is assumed that water absorption by the SCR device, which would have led to an increase in the exhaust gas temperature downstream of the catalytic converter, does not occur.Based on the SCR device's inability to absorb water during cold-start conditions, it is assumed that the device has become dislodged from its intended position and is missing. The indicator can be set to an "On" position to set a diagnostic code indicating the absence of the SCR device in its intended position. Furthermore, after time t5 until the SCR device is engaged, engine operating conditions such as fuel supply are adjusted to account for the compromised SCR device.

[0052] In this way, a method may include: reducing nitrogen oxide emissions in engine exhaust flowing over a substrate of a catalyst containing a catalytic material; generating an exothermic reaction over the substrate by absorption of exhaust water vapor under predetermined conditions; and, during a time when the exothermic reaction would be generated, indicating the absence of the catalyst based on a temperature increase downstream of the catalyst caused by the exothermic reaction, relative to a temperature upstream of the catalyst.

[0053] In this way, by utilizing the exothermic water absorption property of a zeolite contained in an exhaust catalyst during cold starts and higher ambient humidity conditions, a missing catalyst can be detected. The technical benefit of using an existing component of the exhaust catalyst for in-vehicle diagnostics is that a missing, decoupled, or detached catalyst can be detected without a physical inspection of the engine. By adjusting engine operating parameters in response to the detection of a missing catalyst, emission quality can be improved even with a missing catalyst. By detecting a missing exhaust aftertreatment device in a timely manner, emission problems can be mitigated by implementing appropriate mitigation measures.

[0054] An exemplary procedure comprises the following: Indicating the absence of an exhaust catalyst in response to a detected temperature profile downstream of the exhaust catalyst deviating from an expected temperature profile, where the expected temperature profile is based on water absorption and an associated exothermic temperature increase due to the exhaust catalyst. The indication includes indications in response to the detected temperature profile acquired during an engine cold start. The expected temperature profile includes an increase in exhaust gas temperature detected downstream of the exhaust catalyst, relative to an exhaust gas temperature detected upstream of the exhaust catalyst, for a threshold duration immediately following the engine cold start.In any or all of the preceding examples, the expected temperature profile additionally or optionally includes an increase in the exhaust gas temperature measured downstream of the catalytic converter, relative to an exhaust gas temperature measured upstream of the catalytic converter, for a threshold duration immediately following the engine cold start. In any or all of the preceding examples, the expected temperature profile additionally or optionally further includes an increase in the rate of change of the exhaust gas temperature measured downstream of the catalytic converter, relative to a rate of change of the exhaust gas temperature measured upstream of the catalytic converter, for the threshold duration immediately following the engine cold start.In any or all of the preceding examples, the expected temperature profile additionally or optionally includes, after the threshold period, a decrease in the measured exhaust gas temperature downstream of the catalyst relative to the exhaust gas temperature measured upstream of the catalyst. The threshold period is additionally or optionally based on both ambient humidity and engine temperature, with the threshold period increasing when, alone or together, the ambient humidity increases and the engine temperature decreases.In any or all of the preceding examples, the exhaust gas temperature upstream of the catalytic converter is additionally or optionally measured by a first exhaust gas temperature sensor coupled to an exhaust port upstream of the catalytic converter, and the exhaust gas temperature downstream of the catalytic converter is measured by a second exhaust gas temperature sensor coupled to the exhaust port downstream of the catalytic converter. Any or all of the preceding examples further include, additionally or optionally, in response to the indication that the catalytic converter is absent, adjusting one or more engine operating parameters, including limiting an engine load to below a threshold load by reducing the opening of an intake throttle.In any or all of the preceding examples, the exhaust gas catalyst is additionally or optionally a selective catalytic reduction (SCR) device and is based on water absorption on a zeolite layer within the SCR device which is capable of absorbing water from the exhaust gas flowing over the SCR device.

[0055] Another exemplary procedure includes the following: during an engine start from idle, indicating the absence of an exhaust catalyst in response to a difference between a first detected exhaust gas temperature upstream of the exhaust catalyst and a second detected exhaust gas temperature downstream of the exhaust catalyst exceeding a threshold temperature difference. In any one of the preceding examples, the engine start additionally or optionally includes a cold start at an engine temperature below a threshold. In any or all of the preceding examples, the engine start condition additionally or optionally includes an engine start at an ambient humidity above a threshold.In any or all of the preceding examples, the engine start condition additionally or optionally includes a selective catalytic reduction (SCR) device incorporating a zeolite layer capable of water absorption during the engine condition. Any or all of the preceding examples further include, additionally or optionally, during the engine cold start condition, indications of the presence of the exhaust catalyst in response to each of the differences between the first detected exhaust gas temperature upstream of the exhaust catalyst and the second detected exhaust gas temperature downstream of the exhaust catalyst being less than a threshold temperature difference. In any or all of the preceding examples, the first and second detected exhaust gas temperatures are additionally or optionally measured selectively during an initial number of engine cycles immediately after the engine is started from idle.This part of the section is not part of the present invention. Any or all of the preceding examples further comprise, additionally or optionally, in response to the indication of the absence of the exhaust catalyst, setting a fuel supply schedule for a second number of engine cycles following the first number of engine cycles, wherein the setting involves reducing a pulse width of the fuel supplied by a fuel injection device during each of the second number of engine cycles.

[0056] In yet another example, a process comprises the following: reducing nitrogen oxide emissions in engine exhaust flowing over a substrate of a catalyst containing a catalytic material; generating an exothermic reaction over the substrate by absorption of exhaust water vapor under predetermined conditions; and, during a time when the exothermic reaction would be generated, indicating the absence of the catalyst based on a temperature increase downstream of the catalyst caused by the exothermic reaction, relative to a temperature upstream of the catalyst.In any one of the preceding examples, the change in downstream temperature additionally or optionally includes one or more of the following: a temperature profile that changes over time; a rate of change in the downstream temperature; a difference between the downstream and upstream temperatures; or a change in the ratio of downstream to upstream temperatures. Any one or all of the preceding examples further additionally or optionally include indications of the absence of the catalyst based on a temperature downstream of the catalyst being equal to or lower than a temperature upstream of the catalyst.Any or all of the preceding examples further include, additionally or optionally, the addition of a reducing agent to the catalyst and the cessation of the reducing agent addition during the generation of the exothermic reaction caused by water absorption. In any or all of the preceding examples, the predetermined conditions are additionally or optionally related to one or more of the following: catalyst temperature, time since the starting of an engine from which the exhaust gas is generated, engine coolant temperature, or ambient humidity.

[0057] In another representation, an exemplary engine system comprises the following: an intake system, an exhaust system incorporating a selective catalyst reduction (SCR) device comprising a zeolite layer coupled to an exhaust duct, a first exhaust gas temperature sensor coupled to the exhaust duct upstream of the SCR device, a second exhaust gas temperature sensor coupled to the exhaust duct downstream of the SCR device, a turbocharger incorporating a turbine coupled to the exhaust duct, a turbine-driven compressor coupled to the intake system, a wastegate bypassing the turbine, and a controller with computer-readable instructions stored in non-volatile memory for the following: during a cold start condition, in response to a second exhaust gas temperature estimated via the second exhaust gas temperature sensor,If the first exhaust gas temperature is equal to or lower than the first exhaust gas temperature estimated by the first exhaust gas temperature sensor, the system indicates that the SCR device is missing from the exhaust duct. Conversely, if the second exhaust gas temperature is higher than the first, the system indicates that the SCR device is not missing. In any or all of the preceding examples, the estimation of the first exhaust gas temperature, the second exhaust gas temperature, and the indication of the missing SCR device are additionally or optionally performed within a threshold duration following the cold start condition, the threshold duration being based on a water content of the zeolite layer relative to a saturation level of the zeolite layer.

[0058] It should be noted that the exemplary control and estimation routines contained herein can be used with various engine and / or vehicle system configurations. The control methods and routines disclosed herein can be stored as executable instructions in non-volatile memory and executed by the control system, which includes the control unit in combination with the various sensors, actuators, and other engine hardware. The specific routines described herein can represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Accordingly, various actions, operations, and / or functions shown can be performed in the sequence shown, in parallel, or, in some cases, omitted.Similarly, the processing sequence is not strictly necessary to achieve the features and benefits of the embodiments described here, but is provided for the sake of clarity and description. One or more of the illustrated actions, operations, and / or functions can be performed repeatedly, depending on the specific strategy employed. Furthermore, the described actions, operations, and / or functions can graphically represent code to be programmed in the non-volatile memory of the computer-readable storage medium in the engine control system, with the described actions being executed by carrying out the instructions in a system that includes the various engine hardware devices in combination with the electronic control unit.

[0059] It is understood that the configurations and routines disclosed herein are exemplary and that these specific embodiments are not to be interpreted in a limiting sense, as numerous variations are possible. For example, the aforementioned technology can be applied to V-6, I-4, I-6, V-12, 4-cylinder boxer, 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 and other features, functions, and / or properties disclosed herein.

[0060] The following claims describe, in particular, certain combinations and subcombinations that are considered novel and not obvious. These claims may refer to "one" element, "a first" element, or the equivalent thereof. Such claims should be understood as including one or more such elements and neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amending the present claims or by filing new claims in this or a related application.Such patent claims, whether they have a broader, narrower, the same or different scope compared to the original patent claims, are also considered to be included in the subject matter of the present disclosure.

Claims

[1] Procedure, encompassing: Indication of the absence of an exhaust catalyst (170) in response to a detected temperature profile downstream of the exhaust catalyst (170) deviating from an expected temperature profile, wherein the expected temperature profile is based on water absorption and an associated exothermic temperature increase through the exhaust catalyst (170), where the display includes displays in response to the detected temperature profile recorded during a cold engine start, wherein the expected temperature profile includes an increase in exhaust gas temperature detected downstream of the exhaust gas catalyst (170) relative to an exhaust gas temperature detected upstream of the exhaust gas catalyst (170) for a threshold duration immediately after the engine cold start, characterized by , that The threshold duration is based on both ambient humidity and engine temperature, with the threshold duration increasing as ambient humidity increases and / or engine temperature decreases. [2] Method according to claim 1, wherein the expected temperature profile further includes an increase in a rate of change of exhaust gas temperature detected downstream of the exhaust gas catalyst, in relation to a rate of change of exhaust gas temperature detected upstream of the exhaust gas catalyst, for the threshold duration immediately after the engine cold start. [3] Method according to claim 1, wherein the expected temperature profile further includes a decrease in the detected exhaust gas temperature downstream of the exhaust gas catalyst (170) after the threshold period in relation to the exhaust gas temperature detected upstream of the exhaust gas catalyst. [4] Method according to claim 1, wherein the exhaust gas temperature detected upstream of the exhaust gas catalyst (170) is measured via a first exhaust gas temperature sensor (128) which is coupled to an exhaust gas channel upstream of the exhaust gas catalyst and the exhaust gas temperature detected downstream of the exhaust gas catalyst is measured via a second exhaust gas temperature sensor (129) which is coupled to an exhaust gas channel downstream of the exhaust gas catalyst (170). [5] Method according to claim 1, further comprising, in response to the indication that the exhaust catalyst (170) is absent, adjusting one or more engine operating parameters, including limiting an engine load to below an engine threshold load by reducing the opening of an intake throttle. [6] Method according to claim 1, wherein the exhaust gas catalyst (170) is a selective catalytic reduction (SCR) device and wherein the expected temperature based on water absorption is based on a zeolite layer within the SCR device which is capable of absorbing water from the exhaust gas flowing over the SCR device; and further comprising reducing NOx emissions from engine exhaust gases. [7] Motor system for carrying out a method according to any of the preceding claims, comprising: an engine (10) which includes an intake system; an exhaust system comprising an exhaust catalyst (170) coupled to an exhaust channel (104), a first exhaust temperature sensor (128) coupled to the exhaust channel (104) upstream of the exhaust catalyst (170), a second exhaust temperature sensor (129) coupled to the exhaust channel (104) downstream of the exhaust catalyst (170), a first radio frequency (RF) sensor (175) coupled to a first end of the exhaust catalyst (170) proximal to the first exhaust temperature sensor (128), and a second RF sensor (176) coupled to a second end of the exhaust catalyst (170) proximal to the second exhaust temperature sensor (129); a turbocharger (13) comprising a turbine (116) coupled to the exhaust port (104), a compressor (114) driven by the turbine (116) coupled to the intake system, and a wastegate (90) bypassing the turbine (116); and a controller (14) with computer-readable instructions stored in non-volatile memory for the following: during a start of the engine (10) from standby, indications of the absence of the exhaust catalyst (170) in response to a difference between a first detected exhaust gas temperature upstream of the exhaust catalyst (170) and a second detected exhaust gas temperature downstream of the exhaust catalyst (170) being higher than a threshold temperature difference, Capturing an expected temperature profile including an increase in exhaust gas temperature, which is captured downstream of the exhaust gas catalyst (170), in relation to an exhaust gas temperature, which is captured upstream of the exhaust gas catalyst (170), for a threshold duration directly after the engine cold start, characterized by , that The threshold duration is based on both ambient humidity and engine temperature, with the threshold duration increasing as ambient humidity increases and / or engine temperature decreases.

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