METHOD AND SYSTEM FOR COOLANT TEMPERATURE SENSOR DIAGNOSIS

Abstract

Procedure, comprehensive: during an exhaust gas flow from a vehicle engine (10) through a heat exchanger (54; 176; 402) with an engine coolant flowing therethrough, in response to a difference above a threshold between a measured coolant temperature and a modeled coolant temperature based on the heat transfer between a heat loss source (302) and a vehicle cabin (4), indicating the deterioration of a first and / or second coolant temperature sensor (180; 182), coupled accordingly upstream and downstream of the heat exchanger (54; 176; 402), wherein the heat transfer between the heat loss source (302) and the vehicle cabin (4) is based on one or more of an air mass flow rate between the heat loss source (302) and the vehicle cabin (4) and a temperature of the air entering the vehicle cabin (4) from the heat loss source (302).

Description

Area

[0001] The present description generally concerns methods and systems for on-board diagnostics of engine coolant temperature sensors coupled to an exhaust gas heat recovery system. General state of the art / Summary

[0002] Engines can be configured with an exhaust gas heat recovery (EGHR) system to recover heat from exhaust gases. During lower engine temperatures and / or when vehicle cabin heating is required, exhaust gas can be routed through the EGHR system, and exhaust heat can be recovered by coolant flowing through a heat exchanger within the EGHR system. Coolant with recovered exhaust heat can be circulated through the engine and / or the heater core of an onboard heating, ventilation, and air conditioning (HVAC) system. This exhaust heat can be used to provide heat to the engine and also to warm the vehicle cabin, thereby improving engine and fuel efficiency.A diagnostic procedure may need to be performed periodically or opportunistically to monitor different components of the EGHR system, including the coolant temperature sensors housed in coolant lines fluidly coupled to the EGHR system's heat exchanger.

[0003] Several approaches are available for diagnosing engine coolant temperature sensors. In one example, as shown in US 6,848,434 B2, Li et al. disclose a method for diagnosing a coolant temperature sensor coupled to an engine coolant system. A coolant temperature can be modeled based on any energy flow between the engine and the coolant, an energy flow between the coolant and air, and an energy flow from the coolant to an engine radiator. By specifying the engine warm-up based on the modeled coolant temperature, the coolant sensor diagnosis can be performed by comparing a coolant temperature estimated by the sensor with a predetermined regulated temperature.

[0004] Another method for diagnosing the coolant temperature sensor in a vehicle is described in German patent application DE 10 2010 009 424 A1, in which sensor faults are determined from temperature differences between sensors over time. Estimated exhaust gas temperatures are compared with real-time temperature measurements to assume a sensor fault if the measured value deviates excessively from the modeled value. Typical changes in exhaust gas temperature over predetermined time intervals under specific operating conditions are used to estimate the exhaust gas temperature. Further diagnostic methods for coolant temperature sensors are described in German patent applications DE 10 2013 209 429 A1 and DE 10 2013 209 384 A1.

[0005] However, the inventors of the present invention have recognized potential problems with the above approach. For example, in embodiments with an EGHR system, multiple coolant temperature sensors may be located in the coolant lines coupled to the EGHR system, and the rationality of each coolant temperature sensor must be monitored independently. The coolant temperature at each point in the EGHR system may differ in different operating modes of the EGHR system, and it may be impossible to use a single model to calculate the coolant temperature at every point in the EGHR system during operation in every operating mode.Furthermore, by modeling the coolant temperature solely on the basis of the energy flow between each of the engine, coolant, air and car radiator, it may be impossible to quantify energy loss during heat transfer between the aforementioned components, thus reducing the accuracy of the temperature model.

[0006] The present invention is based on the objective of creating an improved method and an improved vehicle system of the type mentioned above, which mitigate the problems described and enable a precise diagnosis of the coolant temperature sensors under various operating conditions.

[0007] According to the invention, the aforementioned problem is solved by a method according to claim 1 and a vehicle system according to claim 13. Preferred embodiments of the invention are the subject of the dependent claims.

[0008] The method involves indicating the degradation of a first and / or second coolant temperature sensor, coupled upstream and downstream of the heat exchanger, in response to a difference above a threshold between a measured coolant temperature and a modeled coolant temperature (based on heat transfer between a heat loss source and a vehicle cabin) during an exhaust gas flow from a vehicle engine through a heat exchanger containing coolant. In this way, by using separate temperature models to calculate the coolant temperature at different points in the EGHR system and by comparing the measured coolant temperature with the modeled coolant temperature, the degradation of one or more coolant temperature sensors can be detected independently.

[0009] The engine system is configured with an exhaust gas heat recovery (EGHR) system that includes a heat exchanger. The heat exchanger is positioned in an exhaust bypass channel that runs parallel to a main exhaust channel, and a diverter valve coupled to the main exhaust channel is used to allow exhaust gas to be diverted into the bypass channel or routed through the main channel to the tailpipe. Based on engine heating and / or vehicle cabin heating requirements, the EGHR system can operate in a variety of modes by adjusting the position of the diverter valve.As an example, during periods of increased engine and / or cabin heating demand, the bypass valve can be moved to a first position (first operating mode of the EGHR system) to allow exhaust gas to flow to the tailpipe via the heat exchanger. Once the engine temperature has risen above a certain threshold and cabin heating is no longer required, the bypass valve can be moved to a second position (second operating mode of the EGHR system) to allow exhaust gas to flow directly to the tailpipe, bypassing the heat exchanger. During the exhaust gas flow through the heat exchanger, engine coolant can also be routed through it, transferring heat from the exhaust gas to the coolant. This coolant, now carrying the heat from the exhaust gas, can then be directed through the engine and the heater core of the vehicle's HVAC system, utilizing the exhaust gas heat to increase the engine and / or cabin temperature.A first coolant temperature sensor is connected to a first coolant line entering the heat exchanger (upstream of the heat exchanger), and a second coolant temperature sensor is connected to a second coolant line exiting the heat exchanger (downstream of the heat exchanger). During operation of the EGHR system in the first mode, when exhaust gas is passed through the heat exchanger, the coolant temperature upstream of the heat exchanger can be modeled using two different modeling approaches. Each of these approaches can be based on heat loss during heat transfer from the heater core and coolant lines to the vehicle cabin.The modeled coolant temperature upstream of the heat exchanger can be calibrated and optimized over a variety of operating conditions of the HVAC system upstream of the heat exchanger. The coolant temperature downstream of the heat exchanger can also be modeled using two different modeling approaches. Each of these approaches can be based on heat loss during heat transfer from the exhaust gas to the heat exchanger and the modeled coolant temperature upstream of the heat exchanger. The optimized modeled coolant temperature upstream of the heat exchanger can be compared to a measured coolant temperature, and deterioration of the upstream coolant temperature can be detected in response to a difference between the modeled and measured temperatures exceeding a threshold.Similarly, the modeled coolant temperature downstream of the heat exchanger can be compared with a measured coolant temperature, and a deterioration of the second coolant temperature can be detected in response to a difference between the modeled and measured temperatures exceeding a threshold. In addition to diagnosing the coolant temperature sensors, a diagnosis of the bypass valve and the heat exchanger can also be performed during operation of the EGHR system in the exhaust gas heat.

[0010] In this way, by using different mathematical approaches to model the coolant temperature upstream and downstream of a heat exchanger in the EGHR system, the deterioration of a first coolant temperature sensor upstream of the heat exchanger can be distinguished from the deterioration of a second coolant temperature sensor downstream of the heat exchanger, and appropriate mitigation measures can be implemented. By opportunistically performing diagnostics on the coolant temperature sensors, the bypass valve, and the heat exchanger during specific operating modes of the EGHR system, the probability of falsely detecting the deterioration of one or more components of the EGHR system can be reduced.The technical benefit of including heat loss between one or more vehicle components, including the heater core, coolant lines, vehicle cabin, exhaust, and heat exchangers, in the modeled temperature calculation is that the accuracy of the modeled temperature upstream and downstream of the heat exchanger can be improved. By enabling reliable and accurate diagnostics from the coolant temperature sensors, the coolant's tendency to overheat can be reduced, and the robustness of the HVAC system can be improved. Brief description of the drawings Fig. Figure 1A shows an embodiment of an engine system which includes an exhaust gas heat recovery (EGHR) system which is operated in a first mode. Fig. Figure 1B shows an embodiment of a motor system which includes the EGHR system, which is operated in a second mode. Fig. Figure 2 shows an exemplary heating, ventilation and air conditioning (HVAC) system that is connected to the EGHR system from the Fig. 1A-1B is fluid-coupled. Fig. Figure 3 shows an exemplary schematic representation of the modeling technique used for diagnosing the coolant temperature sensor coupled upstream of a heat exchanger of the EGHR system. Fig. Figure 4 shows an exemplary schematic representation of the modeling technique used for diagnosing the coolant temperature sensor coupled downstream of the heat exchanger of the EGHR system. Fig. Figure 5 shows a flowchart illustrating an exemplary procedure that can be implemented for diagnosing the bypass valve and heat exchanger of the EGHR system. Fig. Figure 6 shows a flowchart illustrating an exemplary procedure that can be implemented for the diagnosis of a coolant temperature sensor coupled upstream of a heat exchanger of the EGHR system. Fig. Figure 7 shows a flowchart illustrating an exemplary procedure that can be implemented for the diagnosis of a coolant temperature sensor coupled downstream of the heat exchanger of the EGHR system. Fig. Figure 8 shows an example of diagnosing coolant temperature sensors coupled to the EGHR system, according to the present disclosure. Detailed description

[0011] The following description concerns systems and procedures for the on-board diagnostics of a variety of engine coolant temperature sensors coupled to an exhaust gas heat recovery (EGHR) system. The EGHR system may include a heat exchanger (coupled to a bypass channel) for exhaust gas heat recovery. Different operating modes of the EGHR system are described in the Fig. Figures 1A-1B show an example of a vehicle's HVAC system fluidly coupled to the EGHR system. Fig. 2 shown. Exemplary schematic representations of the modeling techniques used for diagnosing the coolant temperature sensors coupled upstream and downstream of the EGHR system's heat exchanger are shown in the Fig. 3-4 shown. An engine control unit can be configured to run the control routines, such as the example routines from the Fig. 5-8, to perform periodic or opportunistic diagnostics of the components of the EGHR system, including the bypass valve, heat exchanger, and coolant temperature sensors coupled upstream and downstream of the EGHR system. An exemplary diagnostic routine is described with reference to Fig. 8 shown.

[0012] Fig. Figure 1A shows a schematic view 110 of a vehicle system 101 with an exemplary engine system 100, which includes an engine 10. In one example, the engine system 100 can be a diesel engine system. In another example, the engine system 100 can be a gasoline engine system. In the 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 compressor driven by an electric motor or by a drive shaft.In the engine system 10, the compressor is a turbocharged compressor which is mechanically coupled to the turbine 116 via a shaft 19, the turbine 116 being driven by expanding engine exhaust gases.

[0013] As in Fig. As shown in Figure 1A, the compressor 114 is coupled to the throttle valve 20 via the charge-air cooler (CAC) 118. The throttle valve 20 is coupled to the engine intake manifold 22. The compressed air flows from the compressor through the charge-air cooler 118 and the throttle valve 20 to the intake manifold 22. In the Fig. In the embodiment shown in 1A, the pressure of the air filling inside the intake manifold 22 is detected by the manifold air pressure (MAP) sensor 124.

[0014] 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 may include, for example, air-fuel ratio sensors, etc. In other examples, one or more of the compressor inlet conditions (such as humidity, temperature, pressure, etc.) can be derived based on engine operating conditions.Additionally, if exhaust gas recirculation (EGR) is enabled, the sensors can estimate the temperature, pressure, humidity, and air-fuel ratio of the air-fill mixture, including fresh air, recirculated compressed air, and residual exhaust gases captured at the compressor inlet.

[0015] 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 91 to a point downstream of the turbine. By reducing the exhaust pressure upstream of the turbine, the turbine speed can be reduced, which contributes to a reduction in compressor pump operation.

[0016] The intake manifold 22 is connected 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.

[0017] 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.

[0018] 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 device 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.

[0019] As in Fig. As shown in Figure 1A, exhaust gas from one or more exhaust manifold sections can be directed to the turbine 116 to drive the turbine. The combined flow from the turbine and the wastegate then flows through the emission control devices 170 and 171. In one example, the first emission control device 170 can be a start-up catalyst, and the second emission control device 171 can be an underfloor catalyst. In general, the exhaust aftertreatment devices 170 and 171 are configured to catalytically treat the exhaust gas stream, thereby reducing the amount of one or more substances in the exhaust gas stream. For example, the exhaust aftertreatment devices 170 and 171 can be configured to reduce NOₓ. x to capture from the exhaust stream when the exhaust stream is lean, and the stored NO xto reduce when the exhaust gas flow is rich. In further examples, the exhaust aftertreatment devices 170 and 171 can be configured to reduce NO x to disproportionate or NO x to selectively reduce using a reducing agent. In further examples, the exhaust aftertreatment devices 170 and 171 can be configured to oxidize hydrocarbon and / or carbon monoxide residues in the exhaust stream. Different exhaust aftertreatment catalysts with such functionality can be arranged separately or together in washcoats or elsewhere in the exhaust aftertreatment stages. In some embodiments, the exhaust aftertreatment stages can include a regenerable soot filter configured to capture and oxidize soot particles in the exhaust stream.

[0020] An exhaust gas recirculation (EGR) supply channel 181 can be coupled to the exhaust gas channel 102 downstream of the turbine 116 to provide low-pressure EGR (LP-EGR) to the engine intake manifold upstream of the compressor 114. An EGR valve 52 can be coupled to the EGR channel 181 at the junction of the EGR channel 181 and the intake channel 42. The EGR valve 52 can be opened to allow a controlled amount of exhaust gas to the compressor inlet for desired combustion and emission control performance. The EGR valve 52 can be configured as a continuously variable valve or 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 from upstream of the turbine 116 and returned downstream of the compressor 114 to the engine intake manifold.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 of the compressor 114 to the engine intake manifold.

[0021] One or more sensors can be coupled to the EGR channel 181 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.

[0022] A variety of sensors, including an exhaust gas temperature sensor 128, an exhaust gas lambda sensor, an exhaust gas flow sensor, and an exhaust gas pressure sensor 129, can be coupled to the main exhaust gas channel 102. The lambda sensor can be a linear lambda sensor or UEGO sensor (universal or wide-range exhaust gas oxygen sensor), a dual-state lambda sensor, or an EGO, HEGO (heated EGO), NOx, HC, or CO sensor.

[0023] Downstream of the second emission control device 171, exhaust gas can flow to the silencer 172 via one or more main exhaust ducts 102 and bypass ducts 174. For example, the treated exhaust gas from the exhaust aftertreatment devices 170 and 171 can be released to the atmosphere, in whole or in part, via the main exhaust duct 102 after passing through a silencer 172. Alternatively, the treated exhaust gas from the exhaust aftertreatment devices 170 and 171 can be released to the atmosphere, in whole or in part, via an exhaust gas heat recovery (EGHR) system 150 coupled to the main exhaust duct. The EGHR system 150 can be used to recover exhaust gas heat for use in engine heating and vehicle cabin heating.

[0024] The bypass channel 174 of the exhaust gas heat exchange system 150 can be coupled to the main exhaust gas channel 102 downstream of the second emission control device 171 at the junction 106. The bypass channel 174 can extend from downstream of the second emission control device 171 to upstream of the silencer 172. The bypass channel 174 can be arranged parallel to the main exhaust gas channel 102. A heat exchanger 176 can be coupled to the bypass channel 174 to extract heat from the exhaust gas passing through the bypass channel 174. In one example, the heat exchanger 176 is a water-to-gas heat exchanger.

[0025] A bypass valve 175, coupled upstream of the heat exchanger 176 to the junction of the main exhaust duct 102 and an inlet of the bypass duct 174, can be used to regulate the flow of exhaust gas through the bypass duct 174. The position of the bypass valve can be set in response to signals received from an engine control unit to operate the EGHR system in a selected operating mode. For example, the bypass valve can be actuated to a first, fully open position to allow the entire volume of exhaust gas flow from downstream of the catalyst (second emission control device) 171 to flow through the exhaust bypass 174 to the tailpipe 35, thus enabling the EGHR system to operate in a first mode that provides exhaust gas heat recovery.As another example, the bypass valve can be actuated into a second, fully closed position to direct all exhaust gas through the main exhaust channel to the tailpipe, while preventing exhaust gas flow from downstream of the catalyst 171 via the exhaust bypass 174 to the tailpipe 35. This allows the EGHR system to operate in a second mode where exhaust heat recovery is not provided. Therefore, the position of the bypass valve 175 can be adjusted to maintain a desired engine coolant temperature, the desired engine coolant temperature being based on each of the engine heating requirements and vehicle cabin heating needs. A position sensor 32 can be coupled to the bypass valve 175 to detect its position.

[0026] Coolant lines of an onboard heating, ventilation, and air conditioning (HVAC) system 155 of the vehicle can be fluid-coupled to the exhaust gas heat exchanger 176 for exhaust gas heat recovery. Coolant from the HVAC system can flow through the heat exchanger via a coolant inlet line 160, and after circulating through the heat exchanger, the coolant can flow back to the engine via a coolant outlet line 162. An auxiliary pump 81 can be coupled to the coolant inlet line 160 to enable coolant flow through the heat exchanger 176. A first coolant temperature sensor 180 can be coupled to the coolant inlet line 160 upstream of the heat exchanger 176 to measure the temperature of the coolant entering the heat exchanger.A second coolant temperature sensor 182 can be connected downstream of the heat exchanger 176 to the coolant outlet line 162 to measure the temperature of the coolant exiting the heat exchanger. Diagnostics for each of the coolant temperature sensors 180 and 182 can be performed opportunistically to detect any deterioration of the coolant sensors. Exemplary control routines for diagnosing the coolant temperature sensors 180 and 182 are shown in relation to the... Fig. 6-7 described.

[0027] In one example, the deterioration of the bypass valve 175 can be described as a reaction to a difference between the actual position of the bypass valve 175, as estimated based on input from a bypass valve position sensor 32, and an expected position of the bypass valve. The expected position of the bypass valve 175 can include a first position during an engine heating demand and / or a vehicle cabin heating demand above a threshold, which activates exhaust flow through the heat exchanger 176, and a second position during an engine heating demand and a vehicle cabin heating demand below a threshold, which deactivates exhaust flow through the heat exchanger 176.Furthermore, the deterioration of the heat exchanger 176 can be attributed to a difference between the expected temperature difference between the coolant temperature upstream and downstream of the heat exchanger 176 and the actual temperature difference between the coolant temperature upstream and downstream of the heat exchanger. The expected temperature difference is based on the actual position of the bypass valve 175, the coolant mass flow rate through the heat exchanger 176, and the exhaust gas flow rate, while the actual difference is based on inputs from the first coolant temperature sensor 180 and the second coolant temperature sensor 182. Details regarding the diagnosis of the bypass valve 175 and the heat exchanger 176 are given with reference to [reference missing]. Fig. 5 discussed.

[0028] The engine system 100 can 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 can include the first coolant temperature sensor 180, which is coupled to the coolant inlet line 160, the second coolant temperature sensor 182, which is coupled to the coolant outlet line 162, the bypass valve position sensor 32, the exhaust gas sensor 126, which is located upstream of the turbine 116, the MAP sensor 124, the exhaust gas temperature sensor 128, the exhaust gas pressure sensor 129, the compressor inlet temperature sensor 55, the compressor inlet pressure sensor 56, the compressor inlet humidity sensor 57, and the EGR sensor.Additional sensors, such as pressure, temperature, air-fuel ratio, and composition sensors, can be coupled to various points in the engine system 100. Actuators 18 can include, for example, the throttle 20, the EGR valve 52, the bypass valve 175, the wastegate 92, and the 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 instructions or code programmed therein, according to one or more routines. For example, based on the engine temperature, the controller 12 can command a signal to an actuator coupled to the bypass valve 175 to direct exhaust gas through the heat exchanger 176 to the tailpipe.The controller can also periodically or opportunistically diagnose each of the coolant temperature sensors 180 and 182 based on inputs from one and a variety of HVAC system sensors.

[0029] Fig. Figure 1A shows the operation of the EGHR system 150 in a first operating mode. This first operating mode represents an initial setting of the diverter valve 175, which enables exhaust gas flow control. In this first operating mode, the diverter valve 175 can be in its first (fully open) position. Due to the initial position of the diverter valve 175, the entire volume of exhaust gas exiting the second emission control device 171 can be diverted through the open diverter valve 175 into the bypass channel. The exhaust gas can then flow through the heat exchanger 176 and return to the main exhaust channel. After re-entering the main exhaust channel 102, the exhaust gas can flow through the silencer 172 and then be released to the atmosphere via the tailpipe 35. As the exhaust gas passes through the heat exchanger 176, heat can be transferred from the exhaust gas to the coolant circulating through the heat exchanger 176.When heat is transferred from the exhaust gas to the coolant, the heated coolant can be circulated back to and around the engine (such as when engine heating is required) and / or through a heating core via the coolant outlet line 162 to heat a passenger cabin of the vehicle (such as when cabin heating is requested).

[0030] The exhaust gas heat exchanger system can be operated in the first operating mode (as described above) during conditions where exhaust gas heat must be recovered to heat the engine, such as during engine cold starts. By diverting exhaust gas through the heat exchanger 176 during a cold start, heat can be recovered from the exhaust gas at the heat exchanger and transferred to the coolant circulating through the heat exchanger 176. The hot coolant can then be circulated around an engine block, allowing heat extracted from the exhaust gas to be used to warm the engine. For example, engine heating may be desired when the coolant temperature at the coolant inlet, as estimated by the first coolant temperature sensor 180, is below a first threshold temperature.The EGHR system can continue operating in the first mode until the coolant temperature at the coolant inlet rises to a second threshold temperature, which is higher than the first threshold temperature. Once the coolant temperature entering the heat exchanger 176 reaches the second threshold temperature, it can be deduced that the engine temperature has reached an optimal operating temperature, and heat is no longer extracted from the heater core for cabin heating purposes. The EGHR system 150 can then switch from the first mode to the second mode (as described in section 1). Fig. (described in 1B) to the next section.

[0031] By accelerating the engine warm-up during a cold start, cold-start exhaust emissions can be reduced and engine performance improved. Additionally, if the operator requests vehicle heating, such as by adjusting a cabin temperature setting, the hot coolant can be circulated around a heating core of the HVAC system 155 to provide heat to the vehicle's passenger cabin.

[0032] During operation in the first mode, onboard diagnostics can be performed on each of the coolant temperature sensors 180 and 182 using inputs from the exhaust gas temperature sensor 128 and a variety of HVAC system sensors. For example, if at least one of the first coolant temperature sensor 180 and one of the second coolant temperature sensor 182 are malfunctioning, the temperature of the coolant entering and / or exiting the heat exchanger 176 cannot be accurately estimated, and consequently, the amount of heat transferred to the coolant cannot be quantified. This inaccurate coolant temperature estimation can lead to excessive heat transfer from the exhaust gas to the coolant, resulting in coolant overheating.In order to provide a desired mitigation action, each coolant temperature sensor is diagnosed separately to determine which of the coolant temperature sensors is deteriorating.

[0033] During operation of the EGHR system in the first mode, a coolant temperature upstream of the heat exchanger 176 can be measured via the first coolant temperature sensor 180, a coolant temperature upstream of the heat exchanger 176 can be modeled, and the deterioration of the first coolant temperature sensor 180 can be indicated in response to a difference above a threshold value between the modeled coolant temperature upstream of the heat exchanger and the measured coolant temperature upstream of the heat exchanger.Similarly, a coolant temperature downstream of the heat exchanger 176 can be measured via the second coolant temperature sensor 182, a coolant temperature downstream of the heat exchanger can be modeled, and the deterioration of the second coolant temperature sensor 182 in response to a difference above a threshold between the modeled coolant temperature downstream of the heat exchanger and the measured coolant temperature downstream of the heat exchanger 176 can be specified.The modeled coolant temperature upstream of the heat exchanger 176 can be based on one or more of the airflow between the heater core and the vehicle cabin and the coolant flow from the engine to the heater core, and the modeled coolant temperature downstream of the heat exchanger 176 is based on one or more of the modeled coolant temperature upstream of the heat exchanger 176, the airflow between the exhaust gas flowing through the heat exchanger 176 and the coolant flowing through the heat exchanger 176, and the coolant flow from the heater core to the heat exchanger. Details of the diagnostic process for the first coolant temperature sensor 180, which is coupled to the coolant inlet 160, are given with reference to [reference to be added]. Fig. 6 discussed and the details of the diagnostic process for the second coolant temperature sensor 182, which is coupled to the coolant outlet 162, are described with reference to Fig. 7 discussed.

[0034] Fig. Figure 1B shows a schematic view 120 of the operation of the EGHR system 150 in a second operating mode. Previously in Fig. Components presented in section 1A are similarly numbered and will not be presented again.

[0035] Thus, the second operating mode represents a second setting of the diverter valve 175, which enables exhaust gas flow control. In the second operating mode, the diverter valve 175 can be in the second (fully closed) position to deactivate the exhaust gas flow from the main exhaust channel 102 to the bypass channel 174. In this second mode, the exhaust gas can flow directly from the catalyst 171 to the silencer 172, bypassing the heat exchanger 176. Since exhaust gas does not flow through the heat exchanger 176, no exhaust gas heat can be recovered at the heat exchanger.

[0036] The EGHR system 150 can be operated in the second mode (as described above) after the engine and vehicle cabin have warmed up and exhaust heat is no longer required for engine and / or cabin heating. During operation in this mode, when exhaust heat recovery via the coolant is not performed, the coolant temperature upstream of the heat exchanger may be equal to the coolant temperature downstream of the heat exchanger, and therefore diagnostics from either of the coolant temperature sensors 180 and 182 cannot be performed. For example, during operation of the EGHR system 150 in the second mode, the controller can send a signal to the auxiliary pump actuator 81 to stop the pump, thereby shutting off the coolant flow through each of the coolant inlet lines 160, the coolant outlet lines 162, and the heat exchanger.

[0037] In one example, during operation of the EGHR system 150 in the first mode, the bypass valve 175 can be held in a fully open position until the temperature of the coolant entering the heat exchanger 176 reaches a third threshold temperature. The third threshold temperature can be higher than the first threshold temperature but lower than the second threshold temperature (the third threshold temperature lies between the first and second threshold temperatures). As a result of the coolant entering the heat exchanger 176 reaching the third threshold temperature, it can be deduced that a lower rate of heat transfer from the exhaust gas to the coolant is desired.To reduce the rate of heat transfer from the exhaust gas to the coolant, the position of the bypass valve 175 can be adjusted to a third, partially open position. In this position, a first portion of the exhaust gas can enter the bypass channel 174 and flow through the heat exchanger 176, while a second, remaining portion of the exhaust gas can flow directly from the catalyst 171 to the silencer 172 via the exhaust channel 102. In this way, the EGHR system 150 can operate in a third mode, in which the bypass valve is in a third, partially open position. The controller can determine the position of the bypass valve based on the difference between the temperature of the coolant entering the heat exchanger 176 and the second threshold temperature.For example, the control system can refer to a lookup table that takes as its input the difference between the temperature of the coolant entering heat exchanger 176 and the second threshold temperature, and as its output a signal corresponding to the position of the bypass valve 175. As an example, a decrease in the difference between the temperature of the coolant entering heat exchanger 176 and the second threshold temperature can reduce the opening of the bypass valve to reduce the exhaust gas flow through the bypass channel 174 and heat exchanger 176.Once the temperature of the coolant entering the heat exchanger 176 reaches the second threshold temperature, it can be deduced that the engine temperature has reached an optimal operating temperature, and heat is no longer extracted from the heating core for cabin heating purposes, and the operation of the EGHR system 150 can switch from the third mode to the second mode.

[0038] Fig. Figure 2 shows an embodiment 200 of an on-board heating, ventilation, and air conditioning (HVAC) system 5 (also referred to here as the coolant system) in a motor vehicle 6. The coolant system 5 circulates engine coolant and distributes recovered heat from an exhaust gas heat exchanger 54 through an internal combustion engine 10 and the heating core 90. In one example, the coolant system 5 can be the HVAC system 155, and the exhaust gas heat exchanger 54 can be the heat exchanger 176 in the Fig. Be 1A-1B.

[0039] Fig. Figure 2 shows the coolant system 5 coupled to the engine 10 and the circulation of the engine coolant from the engine 10 through the exhaust gas heat exchanger 54, via the heating element 90 and an engine-driven (or electric) water pump 86 to the car radiator 80 and / or the car radiator bypass line 87, and back to the engine 10. The heat exchanger 54 can be part of the exhaust gas heat recovery system 150, and exhaust gas from the main exhaust duct 102 can be routed to the heat exchanger 54 via the bypass duct 174. Coolant from the engine can flow to the heating device 90 via the coolant line 89, and heat from the coolant can be transferred to the heating element 90. An auxiliary pump 75 can be coupled to the coolant inlet line 89 to enable coolant flow via the heating element 90 and the heat exchanger 176. In one example, an evaporator can be coupled to the coolant line 89 upstream of the heating core.In one example, auxiliary pump 75 can be auxiliary pump 81, as in the . Fig. Figures 1A-1B show that the coolant can circulate from the heater core to the heat exchanger 54 via the coolant inlet line 84. In one example, when engine coolant is circulated through the heat exchanger 54, heat from the exhaust gas can be transferred to the engine coolant, and then the heated coolant (heated by the extracted exhaust gas heat) can be circulated through the engine 10. Coolant from the heat exchanger can exit via the coolant outlet line 83 and return to the engine 10. Heat from the engine coolant can be transferred to the engine 10 and / or then to the heater core 90, and the engine 10 (including cylinder walls and pistons) and the vehicle cabin 4 can be heated using the heat extracted from the engine coolant.A first coolant temperature sensor 180 can be coupled to the coolant inlet line 84 to estimate the temperature of the coolant entering the heat exchanger, and a second coolant temperature sensor 182 can be coupled to the coolant outlet line 83 to estimate the temperature of the coolant exiting the heat exchanger.

[0040] The water pump 86 can be coupled to the engine via the front-end accessory drive (FEAD) 37 and rotated proportionally to the engine speed via a belt, chain, etc. Specifically, the water pump 86 circulates coolant through channels in the engine block, cylinder head, etc., to absorb engine heat, which is then transferred to the ambient air via the radiator 80, regulated by the thermostatic valve 38. In an example where the pump 86 is a centrifugal pump, the generated pressure (and resulting flow) can be proportional to the crankshaft speed, which can be directly proportional to the engine speed. The coolant temperature can be regulated by a thermostatic valve 38, which can be kept closed until the coolant reaches a threshold temperature, thereby reducing heat transfer from the radiator 80 to the ambient air when closed.

[0041] After flowing through the engine 10, the coolant can exit the engine via the coolant line 82 and can flow through the car radiator 80 or through the car radiator bypass line 87, as regulated by the thermostat valve 38, whereby the flow is directed through the car radiator bypass line 87 under conditions where the engine temperature (coolant temperature) is below a threshold temperature.

[0042] A fan 93 can be coupled to the car radiator 80 to increase the airflow through the car radiator 80 as needed to keep coolant temperatures below a desired threshold. In some examples, the fan speed can be controlled directly by the engine control unit. Alternatively, the fan 93 can be coupled to the engine and driven directly by it.

[0043] In one example, a climate control system 94 can be coupled to the vehicle cabin 4. The climate control system 94 can be part of the heating core, and heat from the heating core can be used for cabin heating via the climate control system 94. The operator can specify a desired cabin temperature via an input using a dashboard switch coupled to the climate control system 94. The climate control system 94 can have vanes and / or a flap to allow air to circulate between the heating core 90 and the vehicle cabin 4. Based on the temperature and fan settings specified by the operator, one or more vanes and / or flaps can be adjusted to control the fan speed and position.As an example, in response to an increase in the heating demand of cabin 4, the control system can increase the speed of the fan and the opening of the vanes (such as a mixing flap at the heater core inlet) of the climate control system 94 to allow a greater volume of warm air to flow from the heater core 90 into cabin 4. Similarly, in response to a decrease in the heating demand of cabin 4, the control system can decrease the opening of the vanes of the climate control system 94 to reduce the flow of warm air from the heater core 90 into cabin 4.

[0044] In this way, the systems from the Fig. 1A-1B, 2 a system for a vehicle comprising: an engine, a vehicle cabin, an engine intake manifold, an engine exhaust system comprising an exhaust duct and a bypass duct, wherein the exhaust duct includes one or more exhaust catalysts and a silencer, wherein the bypass duct is coupled to the exhaust duct from downstream of the one or more exhaust catalysts to upstream of the silencer, wherein the bypass duct includes a heat exchanger, a bypass valve coupling an inlet of the bypass duct to the exhaust duct, a bypass valve position sensor coupled to the bypass valve, a coolant system comprising an incoming coolant line and an outgoing coolant line for circulating coolant through the heat exchanger, wherein the coolant system is further coupled to each of an engine block and a heater core of a heating, ventilation and air conditioning (HVAC) system,The incoming coolant line includes a first coolant temperature sensor for estimating a coolant temperature upstream of the heat exchanger, and the outgoing coolant line includes a second coolant temperature sensor for estimating a coolant temperature downstream of the heat exchanger. The vehicle system further includes a controller with computer-readable instructions stored on non-volatile memory for performing the following while operating in a first mode: moving the diverter valve to a first position to operate the exhaust system in the first mode, with exhaust gas flowing from downstream of the catalytic converter through the heat exchanger to upstream of the muffler, and measuring a coolant temperature upstream of the heat exchanger via the first coolant temperature sensor.Reporting the deterioration of the first coolant temperature sensor in response to a difference above a threshold between a modeled coolant temperature upstream of the heat exchanger and the measured coolant temperature upstream of the heat exchanger, and, in response to the reported deterioration, using the modeled temperature to estimate the coolant temperature upstream of the heat exchanger.

[0045] Fig. Figure 5 illustrates an exemplary procedure 500, which illustrates an exemplary procedure that can be used for diagnosing the components of an exhaust gas heat recovery (EGHR) system (such as the EGHR system 150 from the Fig. 1A-1B) can be implemented, including a diverter valve (such as diverter valve 175 from the Fig. 1A-1B), which is coupled to a junction of a main exhaust duct and an exhaust bypass duct housing a heat exchanger, and the heat exchanger (such as heat exchanger 176 from the Fig. 1A-1B). Instructions for performing procedure 500 and the other procedures contained herein may be executed by a controller based on instructions stored in a memory of the controller and in conjunction with signals received from sensors of the engine system, such as those referred to above. Fig. The sensors described in 1A-1B. The controller can use motor actuators of the motor system to adjust the motor operation according to the procedures described below.

[0046] In the 502 procedure, the routine involves estimating and / or measuring engine operating conditions. Conditions assessed can include, for example, engine temperature, engine load, driver torque demand, engine speed, throttle position, exhaust pressure, exhaust air-fuel ratio, and ambient conditions, including ambient temperature, pressure, and humidity, MAP, MAF, boost pressure, etc. The control unit can also determine current cabin heating needs, such as whether cabin heating has been requested by the operator, for example, during lower ambient temperature conditions. The operator can request cabin heating via an input from a switch on the vehicle's climate control system, which is coupled to the cabin and the heating core of the heating, ventilation, and air conditioning (HVAC) system.

[0047] In the 504, the controller can select an operating mode for the EGHR system based on specific engine operating conditions and cabin heating requirements. Selecting the operating mode involves determining whether engine heating is required, based on engine temperature, ambient temperature, and / or exhaust catalyst temperature, and / or whether cabin heating has been requested. For example, engine heating is desired during conditions where the engine temperature is low (e.g., below the activation temperature of an exhaust catalyst), such as during a cold start. The heat exchange system can be operated in one of a variety of modes by adjusting the position of the bypass valve, which is located at a junction between the main exhaust duct and a bypass duct (such as bypass duct 174 in the Fig. 1A-1B) is coupled to the heat exchanger. The position of the bypass valve can be adjusted to achieve a desired engine coolant temperature and then maintain that temperature. For example, exhaust gas heat recovery for engine heating might be desired if the temperature of the coolant exiting the heat exchanger is determined by the coolant temperature sensor (such as the second coolant temperature sensor 182 from the Fig. 1A-1B), which is coupled to the coolant outlet downstream of the heat exchanger, is estimated to be below a first threshold temperature. The first threshold can correspond to an engine warm-up temperature, and the first threshold can be calibrated during engine operation based on the catalyst start-up temperature. In another example, exhaust gas heat recovery for vehicle cabin heating may be desired when the temperature of the coolant entering the heat exchanger, as determined by the coolant temperature sensor (such as the first coolant temperature sensor 180 from the Fig. 1A-1B), which is coupled to the coolant inlet upstream of the heat exchanger, is estimated to be below a second threshold coolant temperature. The second threshold coolant temperature can be calibrated based on either an actual cabin temperature, as estimated by a cabin temperature sensor, or a desired cabin temperature, as specified by the operator. In this way, the operating mode of the EGHR system can be selected based on input from at least one of the first coolant temperature sensors, which is coupled upstream of the heat exchanger, and the second coolant temperature sensor, which is coupled downstream of the heat exchanger.As noted here, such procedures, which involve determining whether a certain condition exists and taking action in response to it, can involve working in that condition and determining whether that condition exists and taking action in response to it, as well as working without that existing condition, determining that the condition does not exist, and taking another action in response to it.

[0048] In 506, the routine involves determining whether the exhaust heat recovery mode (1st mode) has been selected. The exhaust heat exchanger system can operate in first mode during cold start conditions if exhaust heat recovery for engine and vehicle cabin heating is desired. Therefore, exhaust heat recovery for engine heating may be desired until the coolant temperature downstream of the heat exchanger reaches the first coolant temperature, and exhaust heat recovery for cabin heating may be desired until the coolant temperature upstream of the heat exchanger reaches the second coolant temperature. To operate the EGHR system in first exhaust heat recovery mode (as described in relation to...) Fig. (Discussed in section 1A), the control unit can send a signal to the bypass valve to actuate it in an initial, open position, allowing the entire exhaust volume to flow from the main exhaust duct through the bypass duct, which houses the heat exchanger, to the tailpipe. In exhaust heat recovery mode, the bypass valve can be partially open based on engine and cabin heating requirements, allowing some exhaust gas to enter the bypass duct and flow through the heat exchanger, while the remaining exhaust gas can be routed directly from the exhaust catalyst to the tailpipe, thus bypassing the heat exchanger.In one example, if the difference between the first threshold coolant temperature and the coolant temperature downstream of the heat exchanger increases, the opening of the bypass valve can be increased to allow a greater volume of exhaust gas to flow through the heat exchanger, thereby increasing exhaust gas heat recovery for engine heating. Conversely, if the difference between the first threshold coolant temperature and the coolant temperature downstream of the heat exchanger decreases, the opening of the bypass valve can be reduced to allow a smaller volume of exhaust gas to flow through the heat exchanger, thereby decreasing exhaust gas heat recovery for engine heating.Similarly, if the difference between the second threshold coolant temperature and the coolant temperature upstream of the heat exchanger increases, the opening of the bypass valve can be increased to allow a greater quantity of exhaust gas to flow through the heat exchanger, thereby increasing exhaust gas heat recovery for cabin heating; and if the difference between the second threshold coolant temperature and the coolant temperature upstream of the heat exchanger decreases, the opening of the bypass valve can be reduced to allow a lesser quantity of exhaust gas to flow through the heat exchanger, thereby decreasing exhaust gas heat recovery for cabin heating.

[0049] When it is determined that the heat recovery mode has been selected for operating the EGHR system, the routine at 510 includes determining whether the bypass valve is in the commanded position. Since the first operating mode for the EGHR system is selected, the commanded position can be the first, open position. The actual position of the bypass valve can be determined based on an input from the bypass valve position sensor (such as position sensor 32 in the Fig. 1A-1B). The actual position of the bypass valve can be compared with the commanded position (such as the first position). For example, during operation in heat recovery mode, the bypass valve can be commanded to a partially open position to allow some of the exhaust gas to enter the bypass channel. Under such conditions, the controller can determine whether the actual position of the bypass valve is the same as the commanded partially open position.

[0050] If it is confirmed that the bypass valve is not in the commanded position, such as if the bypass valve is stuck in a closed position or a partially open position other than the commanded position, a diagnostic code may be set at 512 indicating that the bypass valve is deteriorated. Because the bypass valve is deteriorated, it may be impossible to regulate the bypass valve opening to allow at least some exhaust gas to flow through the heat exchanger. In response to the detection of bypass valve deterioration, the EGHR system may operate in bypass mode at 508, in which the bypass valve is actuated to a second, fully closed position. In the fully closed position, no exhaust gas can enter the bypass channel housing the heat exchanger and can flow directly from downstream of the exhaust catalyst to the tailpipe.In one example, while the EGHR system is operating in the second, bypass mode, the coolant temperature sensor diagnostics cannot be performed because exhaust gas is not flowing through the heat exchanger. In another example, diagnostics of both the first coolant temperature sensor (upstream of the heat exchanger) and the second coolant temperature sensor (downstream of the heat exchanger) can be performed even during EGHR operation in the second, bypass mode. Details of the first coolant temperature sensor diagnostics are provided in reference to [reference missing]. Fig. 6 discussed and the details of the diagnosis of the second coolant temperature sensor are given in relation to Fig. 7 discussed.

[0051] If, at 506, it is determined that the heat recovery mode has not been selected for operation of the EGHR system, it can be inferred that exhaust heat recovery at the heat exchanger is no longer desired due to lower engine heating and / or cabin heating requirements. For example, exhaust heat recovery for engine heating may no longer be desired if the temperature of the coolant exiting the heat exchanger, as estimated by the coolant temperature sensor coupled to the coolant outlet downstream of the heat exchanger, is above the first threshold temperature. In another example, exhaust heat recovery for vehicle cabin heating may no longer be desired if the temperature of the coolant entering the heat exchanger, as estimated by the coolant temperature sensor coupled to the coolant inlet upstream of the heat exchanger, is above the second threshold coolant temperature.Therefore, the routine can switch to 508 to operate the EGHR system in bypass mode.

[0052] If it is determined that the system is not operating in exhaust gas heat recovery mode, it can be deduced from 506 that the EGHR system is operating in bypass mode (2nd mode). The EGHR system can operate in bypass mode when there is no longer any need for engine heating and / or vehicle cabin heating. In the second bypass mode (as in relation to Fig. (Discussed in 1B) the exhaust gas exchange system is operated such that the bypass valve is commanded to a second, closed position to prevent exhaust gas from entering the bypass channel from the main exhaust duct. In bypass mode, since no exhaust gas flows through the heat exchanger, heat cannot be transferred from the exhaust gas to the coolant flowing through the heat exchanger.

[0053] In one example, while the EGHR system is operating in bypass mode, the diverter valve can be diagnosed based on input from the diverter valve position sensor. In bypass mode, the controller can command the diverter valve to move to a fully closed position. If it is determined that the actual position of the diverter valve (determined based on input from the diverter valve position sensor) differs from the commanded fully closed position, it can be inferred that the diverter valve is stuck in a partially open or fully open position, and a diagnostic code can be set indicating the deterioration of the diverter valve.

[0054] If, at 510, it is confirmed that the bypass valve is in the commanded first, open position, then at 514 it can be confirmed that the bypass valve is not deteriorated and the heat exchanger diagnostics can be initiated. At 516, the controller can estimate an expected difference in coolant temperature between upstream and downstream of the heat exchanger. As the coolant flows through the heat exchanger, exhaust heat is transferred to the coolant, causing an increase in coolant temperature. The difference in coolant temperature between upstream and downstream of the heat exchanger can depend on the position of the bypass valve, the coolant flow rate, the exhaust flow rate, and the ambient temperature.When the bypass valve is actuated from a closed position (such as in bypass mode) to an open position (such as in heat recovery mode), the portion of the total exhaust gas flowing through the heat exchanger can be regulated. Since the total exhaust gas volume and the opening of the bypass valve increase, there can be a corresponding increase in the exhaust gas flow rate through the heat exchanger. For example, the controller can determine the exhaust gas flow rate through the heat exchanger based on a calculation using a lookup table, where the total exhaust gas volume (total exhaust gas flow rate through the main exhaust duct) and the position (degree of opening) of the bypass valve are the inputs, and the exhaust gas flow rate through the heat exchanger is the output.The total exhaust gas volume (total exhaust gas flow rate through the main exhaust channel) can be determined based on an input from an exhaust pressure sensor coupled to the main exhaust channel, and the position of the bypass valve can be determined based on a bypass valve position sensor coupled to the bypass valve. The total exhaust gas volume can also be derived from the engine speed, load, ignition timing, and EGR. The coolant flow rate can be determined based on an output from the auxiliary pump (such as auxiliary pump 81 in the...). Fig. 1A-1B) or the motor-driven coolant pump (such as pump 86 in Fig. 2), coupled to the coolant inlet line, can be determined. Since both the exhaust gas flow rate through the heat exchanger and the coolant flow rate increase, there may be an increase in the amount of exhaust gas heat transfer to the coolant, thus increasing the coolant temperature difference between upstream and downstream of the heat exchanger. In one example, the controller can determine the expected coolant temperature difference between upstream and downstream of the heat exchanger based on a calculation using a lookup table, where the ambient temperature, coolant flow rate, exhaust gas temperature at the heat exchanger inlet, and exhaust gas flow rate through the heat exchanger are the inputs, and the coolant temperature difference between upstream and downstream of the heat exchanger is the output.

[0055] At 518, a difference in coolant temperature between upstream and downstream of the heat exchanger can be determined based on inputs from the first coolant temperature sensor, such as the first coolant temperature sensor 180 from the Fig. 1A-1B, which is coupled to the coolant inlet line upstream of the heat exchanger, and the second coolant temperature sensor, such as the second coolant temperature sensor 182 from the Fig. The temperature of sensors 1A-1B, which is connected to the coolant inlet line downstream of the heat exchanger, can be estimated. The controller can retrieve the temperature estimate from each of the first and second coolant temperature sensors and estimate the difference between the coolant temperature downstream of the heat exchanger and the coolant temperature upstream of the heat exchanger.

[0056] At 520, the routine involves determining whether the expected coolant temperature difference upstream and downstream of the heat exchanger is substantially equal to the estimated coolant temperature difference upstream and downstream of the heat exchanger. The control can also determine whether the expected coolant temperature difference is within a specific error range of the estimated coolant temperature difference. For example, if there is deterioration of the heat exchanger, such as a blockage, the exhaust gas flow through the heat exchanger may be adversely affected, resulting in lower-than-expected exhaust gas heat transfer to the coolant.Therefore, due to the deterioration of the heat exchanger, the coolant temperature downstream of the heat exchanger cannot increase as expected, due to the lower amount of exhaust gas heat recovery.

[0057] If it is determined that the expected coolant temperature difference between upstream and downstream of the heat exchanger differs significantly from the measured coolant temperature difference between upstream and downstream of the heat exchanger (outside the fault range), a diagnostic code indicating heat exchanger deterioration can be set at step 524. If the heat exchanger is determined to be deteriorated, exhaust gas heat recovery can no longer operate effectively, and the routine can proceed to step 508 to operate the EGHR system in bypass mode.

[0058] If it is determined that the expected difference in coolant temperature between upstream and downstream of the heat exchanger is substantially equal to (or within the specific error range of) the measured difference in coolant temperature between upstream and downstream of the heat exchanger, it can be confirmed at 522 that the heat exchanger is not deteriorated, and the diagnosis of each of the first coolant temperature sensor upstream of the heat exchanger and the second coolant temperature sensor downstream of the heat exchanger can be initiated. Details of the diagnosis of the first coolant temperature sensor are given in reference to Fig. 6 discussed and the details of the diagnosis of the second coolant temperature sensor are given in relation to Fig. 7 discussed.

[0059] In this way, the deterioration of the heat exchanger can be indicated by the temperature difference of the upstream and downstream coolant temperature sensors and by correlating this with the position of the bypass valve, and the deterioration of the functionality of the bypass valve can be indicated by the difference between the measured and commanded valve position.

[0060] Fig. Figure 6 illustrates an exemplary procedure 600, which is used for diagnosing a first coolant temperature sensor (such as the first coolant temperature sensor 180 from the Fig. 1A-1B), which is coupled to a coolant inlet line upstream of a heat exchanger of the exhaust gas heat recovery (EGHR) system. Method 600 can be a part of Method 500, as described in Fig. 5 described, and can be carried out at 522 of the procedure 500.

[0061] At 602, the diagnosis of the first coolant temperature sensor upstream of the heat exchanger can be initiated. The diagnosis can be initiated upon confirmation that the EGHR system is operating in exhaust gas heat recovery mode, with the bypass valve at least partially open to allow at least some exhaust gas to flow through the heat exchanger. For example, the diagnosis can be triggered in response to a (calibratable) change in the bypass valve position above a threshold when the EGHR system transitions from bypass mode to exhaust gas heat recovery mode. The diagnosis can also be initiated upon confirmation that the engine is operating in a steady state with stabilized engine operating conditions, including engine speed and load.During the transition of engine operation, frequent changes in engine operating conditions may occur, which may affect the diagnostic procedure.

[0062] The diagnosis of the first coolant temperature sensor upstream of a heat exchanger in 603 involves modeling a first coolant temperature (TU1) upstream of the heat exchanger using a first computation method (referred to here as Method 1). The modeled first coolant temperature, as calculated using the first method, can be based on the heat transfer between a heat loss source and a vehicle cabin (such as vehicle cabin 4 in Fig. 2) are based. The heat loss source can include individual heat loss sources, such as the heating core (such as the 90° heating core made of...). Fig. 2) an onboard heating, ventilation and air conditioning (HVAC) system and the coolant lines of the coolant system that transport the coolant from the engine to the heater core and then to the heat exchanger of the EGHR system. By enclosing the individual heat loss sources into a single heat loss source, the exchange characteristics of each individual heat loss source can be compressed into a single time constant that represents the entire system.

[0063] Fig. Figure 3 shows an exemplary schematic representation 300 of the modeling technique used for diagnosing the coolant temperature sensor coupled upstream of a heat exchanger of the EGHR system. The heat loss source 302 can be fluid-coupled to the vehicle cabin 304, allowing airflow between the heat loss source 302 and the cabin 304. Alternatively, the heat loss source 302 can be fluid-coupled to the ambient air, and heat transfer can occur between the heat loss source 302 and the ambient air. Coolant from the engine 10 can enter the heat loss source, and after flowing through it, the coolant can exit the heat loss source and flow towards the heat exchanger of the EGHR system. In the first method, the first coolant temperature upstream of the heat exchanger can be calculated using Equation 1: TU1=Tcoolantin_1−(Tcoolantin1−Tairin1)ekamair1mcoolant1 where TU1 is the first coolant temperature upstream of the heat exchanger, as calculated by the first method, T airin_1 the temperature of the air entering the heat exchanger (which may be ambient air and / or a mixture of ambient air and recirculated air from the climate control system), T coolantin_1 the temperature of the coolant entering the heat loss source 302 from the engine, m air_1 The air mass flow rate between the vehicle cabin 304 and the heat loss source 302 is m coolant_1 where k_a is the coolant mass flow rate through the heat loss source 302 and k_a is the calibratable time constant of the combined heat loss source 302. airin1can be estimated based on input from one or more of a vehicle cabin temperature sensor (when the climate control system is operating), an ambient temperature sensor, and an evaporator outlet temperature sensor (coupled to the evaporator, which is housed in the refrigerant line upstream of the heating core), and T coolantin1 can be estimated based on input from an engine coolant temperature sensor. air_1 can be estimated depending on the position of the mixing flap of the climate control system, which allows airflow between the heat loss source 302 and the vehicle cabin, and m coolant_1 can be based on the operating speed of the motor-driven coolant pump (such as pump 86 in Fig. 2) be estimated, which regulates the coolant flow through the coolant lines of the coolant system. In one example, the control m air_1Determine based on a calculation using a lookup table, where the position of the mixing flap of the climate control system and the total air mass flow from the evaporator are the inputs and m air_1 the output is. In another example, the control m coolant_1 Determine based on a calculation using a lookup table, where the coolant pump speed is the input and m coolant_1 The output is.

[0064] The diagnosis of the first coolant temperature sensor upstream of a heat exchanger involves, at 604, modeling a first coolant temperature (TU2) upstream of the heat exchanger using a second computational method (referred to here as Method 2). The modeled first coolant temperature, as calculated using the second method, can be based on the heat transfer between a heat loss source and a vehicle cabin. The heat loss source can include individual heat loss sources, such as the heater core of the HVAC system and the coolant lines of the cooling system that transport the coolant from the engine to the heater core and then to the heat exchanger of the EGHR system. The individual heat loss sources can be combined into a single heat loss source by calibrating a heat transfer efficiency between the heat loss source 302 and the vehicle cabin 304.

[0065] In the second method, the first coolant temperature upstream of the heat exchanger can be calculated using equation 2: TU2=Tcoolantin_1−ε1.CminC(Tcooantin_1−Tairin_1) where TU2 is the first coolant temperature upstream of the heat exchanger, as calculated by the second method, T airin1 the temperature of the air leaving the vehicle cabin 304 and entering the heat loss source 302, T coolantin_1 The temperature of the coolant entering the heat loss source 302 from the engine is °C. min where is the specific heat of the air, C is the specific heat of the coolant flowing through the heat loss source, and ε1 is the efficiency of heat transfer between the heat loss source 302 and the vehicle cabin 304. In an example, if the specific heat of the coolant (C) is lower than the specific heat of the air (C) min If )) lies, then in equation 2 C mincan be replaced by C. The specific heat of the coolant (C) can depend on the coolant mass flow rate through the heat loss source, as estimated on the basis of the rotational speed of the coolant system pump. The efficiency of the heat transfer (ε1) between the heat loss source 302 and the vehicle cabin 304 can be given by Equation 3: ε1=k1mcoolant_1mair_1+k2mcoolant_12+k3mair_12+k4mcoolant_1+k5mair_1+k6 where ε1 is the efficiency of heat transfer between the heat loss source and the vehicle cabin, k1, k2, k3, k4, k5 and k6 are the calibratable coefficients representing the combined efficiency of the system, including the heat loss source and the vehicle cabin, m air_1 The air mass flow rate between the vehicle cabin 304 and the heat loss source 302 is and m coolant_1 Coolant mass flow rate through heat loss source 302 is.

[0066] In this way, the heat transfer between the heat loss source and the vehicle cabin is a function of one or more of an air mass flow rate between the heat loss source and the vehicle cabin, a temperature of the coolant entering the heat loss source from the engine, a temperature of the air entering the heat loss source from the vehicle cabin, a temperature of the air entering the vehicle cabin from the heat loss source, and an effectiveness of heat transfer between the heat loss source and the vehicle cabin, wherein the effectiveness of heat transfer between the heat loss source and the vehicle cabin is based on each of the air mass flow rate between the heat loss source and the vehicle cabin and a coolant mass flow rate across the heat loss source.

[0067] Once the first coolant temperature upstream of the heat exchanger has been calculated using each of the two calculation models, the modeled coolant temperatures TU1 and TU2 can be optimized over a variety of HVAC system operating conditions to maintain a constant coolant temperature upstream of the heat exchanger. TU1 and TU2 can be calculated for a variety of HVAC system operating conditions, such as different vehicle cabin temperature settings. Based on conditions such as ambient temperature, the operator can request a different temperature in the vehicle cabin. Based on the requested temperature and also the setting of the fan, which is linked to the climate control system, the amount of heat transfer from the heat loss source (including the heater core) to the vehicle cabin can change.The heat loss from the refrigerant flowing through the heat loss source can vary based on the HVAC system operating conditions. For example, during cold weather conditions, the operator might request maximum heat input with an increased fan speed to deliver a greater volume of warm air into the vehicle cabin, thereby increasing the air mass flow rate between the cabin and the heat loss source. Conversely, after the cabin has warmed up, the operator might reduce the fan speed to maintain a lower, constant supply of warm air to the cabin, thus decreasing the air mass flow rate between the cabin and the heat loss source.In yet another example, during warm weather conditions, the operator cannot request arbitrary heat input into the vehicle cabin, further reducing the air mass flow rate between the cabin and the heat loss source. A rolling average time filter can be applied to obtain the optimized constant first coolant temperature upstream of the heat exchanger, where the optimized first coolant temperature is given by Equation 4. TU1(t)=rolledaverage(T01ss(t),T01ss(t−1),tc) where TU1(t) is the modeled first coolant temperature, as calculated using the first method at time t, T01 ss (t) the constant modeled first coolant temperature is, as calculated using the first method at time t, T01 ss(t - 1) the modeled first coolant temperature is, as calculated using the first method at time t - 1, and t c The time constant for a first-order low-pass filter is given for each of the modeled first coolant temperatures at time t and the modeled first coolant temperature at time t - 1. Equation 4 can also be used to obtain an optimized first coolant temperature (TU2), as calculated using the second method.

[0068] At 607, the coolant temperature upstream of the heat exchanger can be measured via the first coolant temperature sensor, which is coupled to the coolant inlet line. At 608, a first residual error between the measured coolant temperature (TU_M) upstream of the heat exchanger and the modeled first coolant temperature upstream of the heat exchanger can be estimated. Estimating the residual error at 609 involves estimating an error (error_TU1) between the measured coolant temperature (TU_M) upstream of the heat exchanger and the modeled coolant temperature (TU1), as calculated using the first method using Equation 5: Error_TU1=TU_M−TU1 where Error_TU1 is the first error between the measured coolant temperature upstream of the heat exchanger and the modeled coolant temperature as calculated using the first method, TU_M is the measured coolant temperature upstream of the heat exchanger, and TU1 is the modeled coolant temperature upstream of the heat exchanger as calculated using the first method.

[0069] Estimating the residual error at 610 also includes estimating an error (error_TU2) between the measured coolant temperature (TU_M) upstream of the heat exchanger and the modeled coolant temperature (TU2), as calculated using the second method using equation 6: Error_TU2=TU_M−TU2 where Error_TU2 is the second error between the measured coolant temperature upstream of the heat exchanger and the modeled coolant temperature as calculated using the second method, TU_M is the measured coolant temperature upstream of the heat exchanger, and TU2 is the modeled coolant temperature upstream of the heat exchanger as calculated using the second method.

[0070] In procedure 612, the routine involves determining whether Error_TU1 and / or Error_TU2 exceed a threshold. The threshold can be a tolerance range with an upper and lower limit. For example, the tolerance range might be ±5 °F; the upper limit could be +5 °F and the lower limit -5 °F relative to zero error.

[0071] If it is determined that Error_TU1 and / or Error_TU2 exceed(s) the upper limit or are below the lower limit of the tolerance range, the deterioration of the first coolant temperature sensor coupled to the coolant inlet line can be specified at 616.

[0072] In one example, each time Error_TU1 and / or Error_TU2 exceed the upper limit or fall below the lower limit of the tolerance range, the error is integrated over time. The integrated error can be compared to a threshold error, and in response to the integrated error for the coolant temperature upstream of the heat exchanger exceeding a threshold error, the degradation of the first coolant temperature sensor coupled to the coolant inlet line can be specified. In another example, the error, Error_TU1, can be accumulated between the output of the first coolant temperature sensor upstream of the heat exchanger and the first modeled coolant temperature over a threshold period.The accumulated error can be compared to a threshold error, and in response to the accumulated error for the coolant temperature upstream of the heat exchanger exceeding a threshold error, the degradation of the first coolant temperature sensor coupled to the coolant inlet line can be specified. In yet another example, each time Error_TU1 and / or Error_TU2 exceeds the upper limit or falls below the lower limit of the tolerance range, an increment is added to a timer. The timer can be compared to a threshold time, and in response to the timer exceeding the threshold time, the degradation of the first coolant temperature sensor coupled to the coolant inlet line can be specified.

[0073] When specifying the deterioration of the first coolant temperature sensor, which is coupled to the coolant inlet line upstream of the heat exchanger, the modeled temperature (TU1 or 2) upstream of the heat exchanger can be used to estimate the temperature of the coolant entering the heat exchanger for engine operations, instead of relying on the output of the deteriorated first coolant temperature sensor upstream of the heat exchanger, until the first coolant temperature sensor at 618 is serviced. For example, based on the modeled temperature of the coolant entering the heat exchanger, a demand for engine heating and / or cabin heating can be estimated, and the position of the bypass valve can be actuated based on the estimated engine heating and / or cabin heating demand.Therefore, if the modeled temperature of the coolant entering the heat exchanger is below a threshold, it can be deduced that engine heating and / or cabin heating is desired, and the diverter valve can be actuated into a fully open (first) position to allow the entire exhaust volume to flow through the heat exchanger.

[0074] If it is determined that the modeled temperature upstream of the heat exchanger is substantially equal to the measured coolant temperature, or if Error_TU1 and / or Error_TU2 are within the threshold tolerance range, it can be deduced at 614 that the first coolant temperature sensor upstream of the heat exchanger is not degraded, and the output of the first coolant temperature sensor can continue to be used to estimate the temperature of the coolant entering the heat exchanger.

[0075] As an example, the two methods for modeling the exhaust gas temperature upstream of the heat exchanger can be compared to determine which method provides a more accurate modeled coolant temperature upstream of the heat exchanger. To compare the first modeling method with the second, the coolant temperature upstream of the heat exchanger (TU1), as modeled using the first method over a period of time, can be used to match the actual (measured) coolant temperature upstream of the heat exchanger over the same period (Match_U_1). Similarly, the coolant temperature upstream of the heat exchanger (TU2), as modeled using the second method over a period of time, can be used to match the actual (measured) coolant temperature upstream of the heat exchanger over the same period (Match_U_2).The quality of the fit (Fit_U_1), including the residual error between the modeled temperature (TU1) and the measured temperature, can be compared with the quality of Fit_U_2, including the residual error between the modeled temperature (TU2) and the measured temperature. If it is deduced that the residual error for Fit_U_1 is lower than the residual error for Fit_U_2, it can be deduced that the coolant temperature upstream of the heat exchanger (TU1), as modeled using the first method, may be more accurate than the coolant temperature upstream of the heat exchanger (TU1), as modeled using the second method.If it is similarly deduced that the residual error for Anpass_U_2 is less than the residual error for Anpass_U_1, it can be deduced that the coolant temperature upstream of the heat exchanger (TU1), as modeled using the second method, may be more accurate than the coolant temperature upstream of the heat exchanger (TU1), as modeled using the first method.

[0076] At 620, the diagnosis of the second coolant temperature sensor, which is coupled to a coolant outlet line downstream of the heat exchanger, can be initiated at least partially based on the first modeled coolant temperature upstream of the heat exchanger. Details of the second temperature sensor diagnosis can be found in [reference to]. Fig. 7 will be discussed.

[0077] Fig. Figure 7 illustrates an exemplary procedure 700, which illustrates an exemplary procedure that can be used for diagnosing a second coolant temperature sensor (such as the second coolant temperature sensor 182 from the Fig. 1A-1B), which is coupled to a coolant outlet line downstream of a heat exchanger of the exhaust gas heat recovery (EGHR) system. Method 700 can be a part of Method 500, as described in Fig. 5 described, and can be carried out at 522 of the procedure 500.

[0078] At 701, the modeled coolant temperature upstream of the heat exchanger (TU) can be retrieved. In an example, as described in procedure 600 from Fig. As described in section 6, the calculation method with the higher accuracy can be determined by comparing the modeled coolant temperature upstream of the heat exchanger, calculated using either the first or second method, with the measured coolant temperature upstream of the heat exchanger. If the accuracy of the modeled coolant temperature upstream of the heat exchanger calculated using the first method is found to be higher than the accuracy of the modeled coolant temperature upstream of the heat exchanger calculated using the second method, the modeled coolant temperature upstream of the heat exchanger calculated using the first method can be retrieved and used for diagnosing the second coolant temperature sensor.If it is determined that the accuracy of the modeled coolant temperature upstream of the heat exchanger, calculated using the second method, is higher than the accuracy of the modeled coolant temperature upstream of the heat exchanger, calculated using the first method, the modeled coolant temperature upstream of the heat exchanger, calculated using the second method, can be retrieved and used for diagnosing the second coolant temperature sensor.

[0079] At 702, the diagnosis of the second coolant temperature sensor downstream of the heat exchanger can be initiated. The diagnosis can be initiated upon confirmation that the EGHR system is operating in exhaust gas heat recovery mode, with the bypass valve at least partially open to allow at least some exhaust gas to flow through the heat exchanger. For example, the diagnosis can be triggered in response to a (calibratable) change in the bypass valve position above a threshold when the EGHR system transitions from bypass mode to exhaust gas heat recovery mode. The diagnosis can also be initiated upon confirmation that the engine is operating in a steady state with stabilized engine operating conditions, including engine speed and load.

[0080] The diagnosis of the second coolant temperature sensor upstream of a heat exchanger in 703 involves modeling a second coolant temperature (TD1) downstream of the heat exchanger using a first calculation method (referred to here as the first method). The modeled second coolant temperature, as calculated using the first method, can be based on the heat transfer between exhaust gas passing through the exhaust gas bypass channel (such as bypass channel 174 in the Fig. 1A-1B) flows, and the heat exchanger (including the coolant lines of the coolant system that carry coolant over the heat exchanger). By including the coolant lines of the coolant system that carry coolant over the heat exchanger and the heat exchanger itself as a single heat exchange source, the exchange characteristics of each individual heat loss source can be compressed into a single time constant representing the entire system.

[0081] Fig. Figure 4 shows an exemplary schematic representation 400 of the modeling technique used for diagnosing the coolant temperature sensor coupled downstream of a heat exchanger of the EGHR system. The heat exchanger 402, together with the coolant lines running through the heat exchanger, can be fluid-coupled to the exhaust bypass duct 404, thereby enabling airflow between the exhaust gas flowing through the exhaust bypass duct 404 and the heat exchanger 402. Coolant from the heating core of the HVAC system (such as the heat loss source 302 from Fig. 3) can enter the heat exchanger via the coolant inlet line and, after flowing through the heat exchanger, can exit via the coolant outlet line and flow towards the engine. In the first method, the second coolant temperature downstream of the heat exchanger can be calculated using Equation 7: TD1=Tcoolantin_2+(Tairin_2−Tcoolantin_2)ek_b.mair_2mcoolant_2 where TD1 is the second coolant temperature downstream of the heat exchanger, as calculated by the first method, T coolantin_2 The temperature of the coolant entering the heat exchanger 402 from the heating core, T airin_2 the temperature of the air leaving the exhaust gas bypass channel 404 and entering the heat exchanger 402, m air_2 The air mass flow rate between the exhaust gas bypass channel 404 and the heat exchanger 402 is m coolant_2 where k_b is the coolant mass flow rate through heat exchanger 402 and k_b is the calibratable time constant of the heat exchanger and the coolant lines running through the heat exchanger. coolantin_2 The modeled first coolant temperature (as retrieved in step 701) can be upstream of the heat exchanger. airin_2can be estimated based on an exhaust gas flow model or on inputs from an exhaust gas flow sensor coupled to the exhaust duct. In one example, T airin_2 estimated based on input from a temperature sensor of an air conditioner (AC) evaporator. air_2 can be estimated depending on the position of the diverter valve and the total amount of exhaust gas flow through the main exhaust duct and m coolant_2 can be based on the operating speed of the motor-driven coolant pump (such as pump 86 in Fig. 2) be estimated, which regulates the coolant flow through the coolant lines of the coolant system. In one example, the control m air_2Determine based on a calculation using a lookup table, where each input is the position of the bypass valve and the total amount of exhaust gas flow through the main exhaust duct, and m air_2 the output is. In another example, the control m coolant_2 Determine based on a calculation using a lookup table, where the coolant pump speed is the input and m coolant_1 the output is. In yet another example, M coolant_2 on an output of an auxiliary pump (such as auxiliary pump 81 in the Fig. 1A-1B) are based on the coolant inlet line, which is coupled to the coolant inlet line, wherein m coolant_2 increases with an increase in the output of the auxiliary pump and m coolant_2 decreases when the output of the auxiliary pump is reduced.

[0082] The diagnosis of the second coolant temperature sensor downstream of a heat exchanger in 704 involves modeling a second coolant temperature (TD2) downstream of the heat exchanger using a second computational method (referred to here as the second method). The modeled second coolant temperature, as calculated using the second method, can be based on the heat transfer between the exhaust gas flowing through the exhaust bypass channel and the coolant flowing through the heat exchanger.

[0083] In the second method, the first coolant temperature downstream of the heat exchanger can be calculated using equation 8: TD2=Tcoolantin_2+ε2.CminC(Tairin_2−Tcoolantin_2) where TD2 is the second coolant temperature downstream of the heat exchanger, as calculated by the second method, T airin_2the temperature of the air leaving the exhaust gas bypass channel 404 and entering the heat exchanger 402, T coolantin_2 the modeled first coolant temperature (as retrieved in step 701) upstream of the heat exchanger is C min where C is the specific heat of the exhaust gas, C is the specific heat of the coolant flowing through the heat exchanger, and ε2 is the efficiency of the heat transfer between the exhaust gas bypass channel 404 and the heat exchanger 402. In an example, if the specific heat of the coolant (C) is less than the specific heat of the exhaust gas (C), then... min If )) is, then in equation 8 C min can be replaced by C. The efficiency of the heat transfer (ε2) between the exhaust gas bypass channel and the heat exchanger can be given by equation 9: ε2=c1mcoolant_2mair_2+c2mcoolant_22+c3mair_22+c4mcoolant_2+c5mair_2+c6 where ε2 is the efficiency of the heat transfer between the exhaust gas bypass channel and the heat exchanger, c1, c2, c3, c4, c5 and c6 are the calibratable coefficients representing the combined efficiency of the EGHR system, including the heat exchanger, the coolant lines through the heat exchanger and the exhaust gas bypass channel, m air_2 The exhaust gas mass flow rate through the heat exchanger 402 is m coolant_2 The coolant mass flow rate through heat exchanger 402 is...

[0084] In this way, the heat transfer between the exhaust gas and the coolant in the heat exchanger is a function of one or more of an exhaust gas mass flow rate through the heat exchanger, a temperature of the coolant entering the heat exchanger, a temperature of the air entering the heat exchanger from the exhaust gas, a temperature of the air entering the exhaust gas from the heat exchanger, and an efficiency of heat transfer between the exhaust gas and the coolant flowing through the heat exchanger, wherein the efficiency of heat transfer between the exhaust gas and the coolant flowing through the heat exchanger is based on each of the air mass flow rates between the exhaust gas and a coolant mass flow rate across the heat exchanger.

[0085] At 705, the coolant temperature downstream of the heat exchanger (TD_M) can be measured via the second coolant temperature sensor, which is coupled to the coolant outlet line. At 706, a first residual error between the measured coolant temperature (TD_M) downstream of the heat exchanger and the modeled second coolant temperature downstream of the heat exchanger can be estimated. Estimating the residual error at 707 involves estimating an error (Error_TD1) between the measured coolant temperature (TD_M) downstream of the heat exchanger and the modeled coolant temperature (TD1), as calculated using the first procedure with Equation 10. Error_TD1=TD_M−TD1 where Error_TU1 is the first error between the measured coolant temperature downstream of the heat exchanger and the modeled coolant temperature as calculated using the first method, TD_M is the measured coolant temperature downstream of the heat exchanger, and TD1 is the modeled coolant temperature downstream of the heat exchanger as calculated using the first method.

[0086] Estimating the residual error at 708 also includes estimating an error (error_TD2) between the measured coolant temperature (TD_M) downstream of the heat exchanger and the modeled coolant temperature (TD2), as calculated using the second method using Equation 11. Error_TD2=TD_M−TD2 where Error_TD2 is the second error between the measured coolant temperature downstream of the heat exchanger and the modeled coolant temperature as calculated using the second method, TD_M is the measured coolant temperature downstream of the heat exchanger, and TD2 is the modeled coolant temperature downstream of the heat exchanger as calculated using the second method.

[0087] In the 710 routine, this involves determining whether Error_TD1 and / or Error_TD2 exceed a threshold. The threshold can be a tolerance range with an upper and lower limit. For example, the tolerance range might be ±5 °F, with the upper limit being +5 °F and the lower limit being -5 °F relative to zero error.

[0088] If it is determined that Error_TD1 and / or Error_TD2 exceed(s) the upper limit or are below the lower limit of the tolerance range, the deterioration of the second coolant temperature sensor coupled to the coolant outlet line can be indicated at 714.

[0089] In one example, each time Error_TD1 and / or Error_TD2 exceed the upper limit or fall below the lower limit of the tolerance range, the error is integrated over time. The integrated error can be compared to a threshold error, and in response to the integrated error for the coolant temperature downstream of the heat exchanger exceeding a threshold error, the degradation of the second coolant temperature sensor, coupled to the coolant outlet line, can be specified. In another example, the error, Error_TD1, can be accumulated between the output of the second coolant temperature sensor downstream of the heat exchanger and the first modeled coolant temperature over a threshold period.The accumulated error can be compared to a threshold error, and in response to the accumulated error for the coolant temperature downstream of the heat exchanger exceeding a threshold error, the degradation of the second coolant temperature sensor, coupled to the coolant outlet line, can be specified. In yet another example, each time Error_TD1 and / or Error_TD2 exceeds the upper or lower limit of the tolerance range, an increment is added to a timer. The timer can be compared to a threshold time, and in response to the timer exceeding the threshold time, the degradation of the second coolant temperature sensor, coupled to the coolant outlet line, can be specified.

[0090] When indicating deterioration of the second coolant temperature sensor, which is coupled to the coolant inlet line upstream of the heat exchanger, the modeled temperature (TD1 or TD2) downstream of the heat exchanger can be used to estimate the coolant exiting the heat exchanger temperature for engine operations, instead of relying on the output of the deteriorated second coolant temperature sensor downstream of the heat exchanger, until the second coolant temperature sensor at 716 is serviced. Therefore, exhaust heat recovery can continue until the coolant temperature downstream of the heat exchanger reaches a desired coolant temperature (such as a coolant temperature corresponding to a warm engine). The position of the bypass valve can be actuated based on the modeled temperature (TD1 or TD2) downstream of the heat exchanger.In one example, if the difference between the desired coolant temperature and the coolant temperature downstream of the heat exchanger increases, the opening of the bypass valve can be increased to allow a greater volume of exhaust gas to flow through the heat exchanger, thereby increasing exhaust gas heat recovery. Conversely, if the difference between the desired coolant temperature and the coolant temperature downstream of the heat exchanger decreases, the opening of the bypass valve can be reduced to allow a smaller volume of exhaust gas to flow through the heat exchanger, thereby decreasing exhaust gas heat recovery.

[0091] If it is determined that the modeled temperature downstream of the heat exchanger is substantially equal to the measured coolant temperature downstream of the heat exchanger, or if Error_TU1 and / or Error_TU2 are within the threshold tolerance range, it can be inferred at 712 that the second coolant temperature sensor downstream of the heat exchanger is not degraded, and the output of the second coolant temperature sensor can continue to be used to estimate the temperature of the coolant exiting the heat exchanger.

[0092] As an example, the two methods for modeling the exhaust gas temperature downstream of the heat exchanger can be compared to determine which provides a more accurate modeled coolant temperature downstream of the heat exchanger. To compare the first and second modeling methods, the coolant temperature downstream of the heat exchanger (TD1), as modeled using the first method over a period of time, can be used to match the actual (measured) coolant temperature downstream of the heat exchanger over the same period (Match_D_1). Similarly, the coolant temperature downstream of the heat exchanger (TD2), as modeled using the second method over a period of time, can be used to match the actual (measured) coolant temperature upstream of the heat exchanger over the same period (Match_D_2).The quality of adaptation_D_1, including the residual error between the modeled temperature (TD1) and the measured temperature, can be compared with the quality of adaptation_D_2, including the residual error between the modeled temperature (TD2) and the measured temperature. If it is deduced that the residual error for adaptation_D_1 is lower than the residual error for adaptation_D_2, it can be deduced that the coolant temperature downstream of the heat exchanger (TD1), as modeled using the first method, may be more accurate than the coolant temperature downstream of the heat exchanger (TD2), as modeled using the second method.If it is similarly deduced that the residual error for Anpass_D_2 is less than the residual error for Anpass_D_1, it can be deduced that the coolant temperature downstream of the heat exchanger (TD2), as modeled using the second method, may be more accurate than the coolant temperature downstream of the heat exchanger (TD1), as modeled using the first method.

[0093] In this way, during an exhaust flow from a vehicle engine to a tailpipe via a heat exchanger with coolant flowing through it, the deterioration of one or more of the first and second coolant temperature sensors can be indicated in response to a difference above a threshold between an output of a first coolant temperature sensor, which is positioned upstream of the heat exchanger, and a first modeled coolant temperature, which is partly based on heat transfer between a heat loss source and a vehicle cabin, and in response to a difference above a threshold between an output of a second coolant temperature sensor, which is positioned downstream of the heat exchanger, and a second modeled coolant temperature, which is partly based on the first modeled coolant temperature.As an example, one or more of the first coolant temperature sensor upstream of the heat exchanger and the second coolant temperature sensor downstream of the heat exchanger can be removed and the coolant temperature measured as based on the values ​​in the... Fig. The approaches discussed in 6-7 can be modeled for engine processes (instead of the recorded temperatures), thereby reducing engine components and associated costs. Fig. Figure 8 shows an example operating sequence 800, illustrating the diagnosis of the coolant temperature sensors coupled to an exhaust gas heat recovery (EGHR) system. The horizontal (x-axis) represents time, and the vertical markers t1-t3 identify significant time points in the diagnosis of the EGHR system's coolant temperature sensors.

[0094] The first trace, line 802, shows a variation in cabin temperature over time. The dashed line 803 shows a threshold cabin temperature below which cabin heating can be requested by the operator. The second trace, line 804, shows the position of the diverter valve, which is coupled to a junction between a main exhaust duct and an exhaust bypass duct and regulates the exhaust flow from the main exhaust duct to the heat exchanger located in the exhaust bypass duct. The third trace, line 806, shows a first modeled temperature upstream of the heat exchanger, as calculated using Equation 1. The dotted line 805 shows a first measured coolant temperature upstream of the heat exchanger, as estimated based on inputs from a first coolant temperature sensor coupled to the coolant inlet line upstream of the heat exchanger.The fourth curve, line 808, shows a difference (error_TU1) between the measured coolant temperature upstream of the heat exchanger (as given by the dotted line 805) and the first modeled temperature upstream of the heat exchanger (as given by line 806). The dotted line 807 shows an upper limit of a threshold error range above which the degradation of the first temperature sensor coupled upstream of the heat exchanger can be derived. The dotted line 809 shows a lower limit of the threshold error range below which the degradation of the first temperature sensor coupled upstream of the heat exchanger can be derived. The fifth curve, line 810, shows a second modeled temperature downstream of the heat exchanger, as calculated using Equation 7.The dotted line 811 shows a second measured coolant temperature downstream of the heat exchanger, as estimated based on inputs from a second coolant temperature sensor coupled to the coolant outlet line upstream of the heat exchanger. The sixth curve, line 812, shows a difference (Error_TD1) between the measured coolant temperature downstream of the heat exchanger (as given by dotted line 811) and the second modeled temperature downstream of the heat exchanger (as given by line 812). The dotted line 813 shows an upper limit of a threshold error range above which the degradation of the second temperature sensor coupled downstream of the heat exchanger can be inferred.The dotted line 814 shows a lower limit of the threshold error range below which the deterioration of the second temperature sensor, coupled downstream of the heat exchanger, can be derived. The seventh curve, line 816, shows the position of a diagnostic marker indicating the condition of the first coolant temperature sensor, coupled upstream of the heat exchanger, and the dotted line 818 shows the position of a diagnostic marker indicating the condition of the second coolant temperature sensor, coupled downstream of the heat exchanger.

[0095] Before time t1, the cabin temperature is higher than the threshold value of 803, and cabin heating is not requested. The bypass valve is held in the second, closed position to prevent exhaust gas flow from the main exhaust duct to the heat exchanger via the bypass valve, thus operating the EGHR system in bypass mode. Because the EGHR system is operating in bypass mode, no exhaust heat is recovered through the heat exchanger, and there is no relevant difference in coolant temperature upstream and downstream of the heat exchanger. Since exhaust heat recovery is not performed during EGHR operation in bypass mode, the coolant temperature sensor diagnostics cannot be performed before time t1.

[0096] At time t1, the cabin temperature drops below the threshold because the vehicle is traveling through a region with a cooler ambient temperature. In response to the decrease in cabin temperature, exhaust gas heat recovery (EGHR) is requested, and the EGHR system switches from bypass mode to exhaust gas heat recovery mode. To operate the EGHR system in exhaust gas heat recovery mode, the bypass valve is actuated from a fully closed position to a fully open, first position, allowing exhaust gas to flow from the main exhaust duct to the heat exchanger via the bypass valve.

[0097] As exhaust gas flows through the heat exchanger, heat from the exhaust gas is transferred to the coolant flowing through the heat exchanger. This coolant, now carrying the heat from the exhaust gas, can then flow through a heating core of the vehicle's heating, ventilation, and air conditioning (HVAC) system, passing over the engine. At the heating core, heat from the exhaust gas is transferred to the vehicle cabin, thus increasing cabin temperature. After flowing through the heating core, the coolant returns to the EGHR system's heat exchanger via the coolant inlet line. During operation of the EGHR system in exhaust heat recovery mode, at time t1, diagnostics are initiated for both the first coolant temperature sensor, connected to the coolant inlet line upstream of the heat exchanger, and the second coolant temperature sensor, connected to the coolant outlet line downstream of the heat exchanger.Between t1 and t2, a modeled coolant temperature (TU1) upstream of the heat exchanger is calculated based on the heat transfer between a heating core and a vehicle cabin. During this time, a modeled coolant temperature (TD1) downstream of the heat exchanger is also calculated based on the heat transfer from exhaust gas flowing through the exhaust bypass channel and the coolant flowing through the heat exchanger.

[0098] Between times t1 and t2, the temperature upstream of the heat exchanger and the temperature downstream of the heat exchanger are each measured via the first and second coolant temperature sensors, respectively. The difference 808 (Error_TU1) between the measured coolant temperature upstream of the heat exchanger and TU1 is compared to each of the upper limit 807 and the lower limit 809 of the threshold error range to detect any deterioration of the first coolant temperature sensor. Between t1 and t2, Error_TU1 remains within the threshold error range, and the marker indicating deterioration of the first coolant temperature sensor remains in the off position.The difference 812 (Error_TD1) between the measured coolant temperature downstream of the heat exchanger and TU1 is compared to each of the upper limit 813 and the lower limit 814 of the threshold error range to detect any deterioration of the second coolant temperature sensor. Between t1 and t2, Error_TD1 remains within the threshold error range, and the marker indicating deterioration of the second coolant temperature sensor remains in the off position. As soon as the exhaust heat is transferred to the vehicle cabin, a constant increase in cabin temperature is observed.

[0099] At time t2, based on the fact that error_TU1 808 has decreased below the lower limit 809 of the threshold error range, it is deduced that there is a difference above a threshold value between the measured coolant temperature upstream of the heat exchanger and the modeled coolant temperature upstream of the heat exchanger. Based on the fact that error_TU1 is above the threshold value, the deterioration of the first coolant temperature sensor is deduced at t2, and the marker (diagnostic code) 816, which indicates the deterioration of the first coolant temperature sensor, is set.In response to the deterioration of the first coolant temperature sensor, after time t2 the coolant temperature upstream of the heat exchanger is derived based on the modeled coolant temperature TU1, and the measurement of the coolant temperature based on an input from the first coolant temperature sensor is suspended until the first coolant temperature sensor is serviced. Between t2 and t3, fault_TD1 remains within the threshold fault range, and the marker indicating the deterioration of the second coolant temperature sensor remains in the off position.

[0100] At time t3, based on the fact that error_TD1 812 has increased above the upper limit 813 of the threshold error range, it is deduced that there is a difference above a threshold value between the measured coolant temperature downstream of the heat exchanger and the modeled coolant temperature downstream of the heat exchanger. Based on the fact that error_TD1 is above the threshold value, the deterioration of the second coolant temperature sensor is deduced at t3, and a marker (diagnostic code) 818, indicating the deterioration of the second coolant temperature sensor, is set.In response to the deterioration of the second coolant temperature sensor, after time t3 the coolant temperature downstream of the heat exchanger is derived based on the modeled coolant temperature TD1 and the measurement of the coolant temperature based on an input from the second coolant temperature sensor is suspended until the second coolant temperature sensor is serviced.

[0101] In this way, the deterioration of individual components can be detected by opportunistically monitoring the condition of the EGHR system components, including the coolant temperature sensors, the bypass valve, and the heat exchanger, during various operating modes of the EGHR system, and appropriate mitigation measures can be taken. The technical benefit of using different mathematical models to calculate the coolant temperature upstream and downstream of a heat exchanger in the EGHR system is that the deterioration of a first coolant temperature sensor upstream of the heat exchanger can be distinguished from the deterioration of a second coolant temperature sensor downstream of the heat exchanger.By optimizing the modeled coolant temperature upstream of the heat exchanger over a variety of HVAC system operating conditions, an accurate constant coolant temperature can be obtained.

[0102] An exemplary procedure comprises: during an exhaust flow from a vehicle engine through a heat exchanger with coolant flowing therethrough, in response to a difference above a threshold between a measured coolant temperature and a modeled coolant temperature, based on the heat transfer between a heat loss source and a vehicle cabin, indicating the deterioration of one or more of a first and a second coolant temperature sensor, coupled accordingly upstream and downstream of the heat exchanger. In a previous example, the heat loss source additionally or optionally includes a heating core and a multitude of coolant lines of an on-board heating system.Ventilation and air conditioning (HVAC) system. In any or all of the preceding examples, the measured coolant temperature additionally or optionally includes a first measured coolant temperature upstream of the heat exchanger based on an input from the first coolant temperature sensor coupled to a coolant line entering the heat exchanger; the modeled coolant temperature includes a first modeled coolant temperature upstream of the heat exchanger and is based on indicating the degradation of the first coolant temperature sensor coupled upstream of the heat exchanger on a difference above a threshold between the first measured coolant temperature upstream of the heat exchanger and the first modeled coolant temperature upstream of the heat exchanger.where the first modeled coolant temperature is calibrated over a variety of vehicle cabin temperature settings. In any or all of the preceding examples, the heat transfer between the heat loss source and the vehicle cabin is additionally or optionally a function of one or more of an air mass flow rate between the heat loss source and the vehicle cabin, a temperature of the coolant entering the heat loss source from the engine, a temperature of the air entering the heat loss source from the vehicle cabin, a temperature of the air entering the vehicle cabin from the heat loss source, and an effectiveness of heat transfer between the heat loss source and the vehicle cabin.where the effectiveness of heat transfer between the heat loss source and the vehicle cabin is based on each of the air mass flow rate between the heat loss source and the vehicle cabin and a coolant mass flow rate across the heat loss source. In any or all of the preceding examples, the air mass flow rate between the heater core and the vehicle cabin is a function of the position of a vent that permits airflow between the heater core and the vehicle cabin. In any or all of the preceding examples, the measured coolant temperature additionally or optionally further includes a second measured coolant temperature downstream of the heat exchanger based on an input from a second coolant temperature sensor coupled to a coolant line exiting the heat exchanger.The modeled coolant temperature further includes a second modeled coolant temperature downstream of the heat exchanger and is based on indicating the degradation of the second coolant temperature sensor coupled downstream of the heat exchanger on a difference above a threshold between the second measured coolant temperature downstream of the heat exchanger and the second modeled coolant temperature of the heat exchanger, wherein the second modeled coolant temperature downstream of the heat exchanger is based on each of the first modeled coolant temperatures upstream of the heat exchanger and the heat transfer between the exhaust gas and the heat exchanger. In any or all of the preceding examples, the heat transfer between the exhaust gas and the coolant flowing through the heat exchanger isadditionally or optionally, a function of one or more of an exhaust gas mass flow rate across the heat exchanger, a temperature of the coolant entering the heat exchanger, a temperature of the air entering the heat exchanger from the exhaust gas, a temperature of the air entering the exhaust gas from the heat exchanger, and an efficiency of heat transfer between the exhaust gas and the coolant flowing through the heat exchanger, wherein the efficiency of heat transfer between the exhaust gas and the coolant flowing through the heat exchanger is based on each of the air mass flow between the exhaust gas and the coolant flowing through the heat exchanger and a coolant mass flow rate across the heat exchanger. In any or all of the preceding examples, the exhaust gas mass flow rate across the heat exchanger is additionally or optionally,wherein the exhaust gas mass flow rate through the heat exchanger is a function of each of the positions of an exhaust bypass valve and the total exhaust gas flow rate through the main exhaust duct. Any or all of the preceding examples additionally or optionally include, in response to a indication of deterioration of the first coolant temperature sensor, further using the first modeled coolant temperature for engine operations, and, in response to a indication of deterioration of the second coolant temperature sensor, using the second modeled coolant temperature for engine operations. In any or all of the preceding examples, the heat exchanger is additionally or optionally coupled to an exhaust bypass, wherein the method further includes adjusting the position of the exhaust bypass valve coupled to a junction of the exhaust bypass and a main exhaust duct to regulate the exhaust gas flow through the heat exchanger.to maintain a desired engine coolant temperature of an engine coolant which is in thermal contact with the coolant of the heat exchanger, wherein the desired engine coolant temperature is based on each of an engine heating demand and a vehicle cabin heating demand. Any or all of the preceding examples additionally or optionally further include specifying a deterioration of the bypass valve in response to an actual position of the bypass valve, as estimated on the basis of an input from a bypass valve position sensor, which differs from an expected position of the bypass valve, wherein the expected position of the bypass valve is one of a first position during an engine heating demand above a threshold and / or a vehicle cabin heating demand above a threshold, which activates exhaust flow through the heat exchanger.and a second position during a below-threshold engine heating demand and a below-threshold vehicle cabin heating demand, which disables exhaust flow through the heat exchanger. Any or all of the preceding examples additionally or optionally further include indicating the deterioration of the heat exchanger in response to an expected temperature difference between the coolant temperature upstream and downstream of the heat exchanger differing from an actual temperature difference between the coolant temperature upstream and downstream of the heat exchanger, wherein the expected temperature difference is based on each of the actual position of the bypass valve, the coolant mass flow rate through the heat exchanger, and the exhaust flow rate, and the actual difference is based on inputs from the first coolant temperature sensor and the second coolant temperature sensor.

[0103] Another exemplary procedure includes: during an exhaust flow from a vehicle engine to a tailpipe via a heat exchanger with coolant flowing therein, in response to a difference above a threshold between an output of a first coolant temperature sensor located upstream of the heat exchanger and a first modeled coolant temperature, which is partly based on heat transfer between a heat loss source and a vehicle cabin, and in response to a difference above a threshold between an output of a second coolant temperature sensor located downstream of the heat exchanger and a second modeled coolant temperature, which is partly based on the first modeled coolant temperature, indicating the deterioration of one or more of the first and second coolant temperature sensors.In any of the preceding examples, the heat transfer between the heat loss source and the vehicle cabin is additionally or optionally based on any of the following: an air mass flow rate between the heat loss source and the ambient air and / or the vehicle cabin, a temperature of the coolant entering the heat loss source from the engine, a temperature of the air entering the heat loss source from the vehicle cabin, and a temperature of the air entering the vehicle cabin from the heat loss source, wherein the heat loss source includes a heating core of an on-board heating, ventilation and air conditioning (HVAC) system that receives coolant from the engine.In any preceding example, the second modeled coolant temperature is additionally or optionally further based on the heat transfer between the exhaust gas flowing over the heat exchanger and the coolant flowing through the heat exchanger, wherein the heat transfer between the exhaust gas and the coolant flowing through the heat exchanger is based on any of an air flow rate between the exhaust gas and the heat exchanger, a temperature of the coolant entering the heat exchanger, a temperature of the air entering the heat exchanger from the exhaust gas, and a temperature entering the exhaust gas from the heat exchanger.Any preceding example additionally or optionally further includes accumulating a first error between an output of the first coolant temperature sensor and the first modeled coolant temperature over a threshold period, accumulating a second error between an output of the second coolant temperature sensor and the second modeled coolant temperature over the threshold period, indicating the degradation of the first sensor in response to the accumulated first error exceeding a threshold error, and indicating the degradation of the second sensor in response to the accumulated second error exceeding the threshold error.In any preceding example, the exhaust flow from the vehicle engine to the tailpipe via the heat exchanger additionally or optionally includes an exhaust flow from a main exhaust duct to the heat exchanger via a diverter valve coupled to a junction of the main exhaust duct and an exhaust bypass housing the heat exchanger, and includes the coolant flow through the heat exchanger, coolant flowing from the vehicle engine to the heat exchanger via the heating core.

[0104] In yet another example, a vehicle system comprises: a vehicle system comprising an engine, a vehicle cabin, an engine intake manifold, an engine exhaust system comprising an exhaust duct and a bypass duct, wherein the exhaust duct includes one or more exhaust catalysts and a muffler, wherein the bypass duct is coupled to the exhaust duct from downstream of the one or more exhaust catalysts to upstream of the muffler, wherein the bypass duct includes a heat exchanger, a bypass valve coupling an inlet of the bypass duct to the exhaust duct, a bypass valve position sensor coupled to the bypass valve, a coolant system comprising an incoming coolant line and an outgoing coolant line for circulating coolant through the heat exchanger, wherein the coolant system is further connected to each of an engine block and a heater core of a heater,a ventilation and air conditioning (HVAC) system coupled, the incoming coolant line includes a first coolant temperature sensor for estimating a coolant temperature upstream of the heat exchanger, the outgoing coolant line includes a second coolant temperature sensor for estimating a coolant temperature downstream of the heat exchanger, and a controller with computer-readable instructions stored on non-volatile memory to perform the following while operating in a first mode: moving the diverter valve to a first position to operate the exhaust system in the first mode, with exhaust gas flowing from downstream of the exhaust catalyst through the heat exchanger to upstream of the muffler, and measuring a coolant temperature upstream of the heat exchanger via the first coolant temperature sensor,Indicates the deterioration of the first coolant temperature sensor in response to a difference above a threshold between a modeled coolant temperature upstream of the heat exchanger and the measured coolant temperature upstream of the heat exchanger, and, in response to the deterioration indication, uses the modeled temperature to estimate the coolant temperature upstream of the heat exchanger. In any preceding example, the controller additionally or optionally includes further instructions during operation in first mode to: measure a position of the bypass valve via the position sensor, measure a coolant temperature downstream of the heat exchanger via the second coolant temperature sensor,Indicating the deterioration of the second coolant temperature sensor in response to a difference above a threshold between a modeled coolant temperature downstream of the heat exchanger and the measured coolant temperature downstream of the heat exchanger; indicating the deterioration of the bypass valve in response to the bypass valve position differing from the first position.Using the modeled temperature to estimate the coolant temperature downstream of the heat exchanger in response to a report of deterioration from the second coolant temperature sensor, and disabling the operation of the exhaust system in the first mode in response to a report of deterioration from the bypass valve. In any or all of the preceding examples, the modeled coolant temperature upstream of the heat exchanger is additionally or optionally based on one or more of the airflow between the heater core and the vehicle cabin and the coolant flow from the engine to the heater core, and the modeled coolant temperature downstream of the heat exchanger is based on one or more of the modeled coolant temperature upstream of the heat exchanger, the airflow between the exhaust gas flowing through the heat exchanger and the coolant flowing through the heat exchanger, and the coolant flow from the heater core to the heat exchanger.

[0105] In another representation, the vehicle is a hybrid vehicle system.

[0106] 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 procedures 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 illustrated actions, operations, and / or functions can be performed in the illustrated sequence or in parallel, or in some cases, omitted.Similarly, the processing sequence is not strictly necessary to achieve the features and advantages 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, processes, and / or functions can graphically represent code to be programmed into 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 components in combination with the electronic control unit.

[0107] 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 new and non-obvious combinations and sub-combinations of the various systems and configurations, as well as other features, functions, and / or properties disclosed herein. Reference symbol list 4 Vehicle cabin 5 Coolant system 6 Motor vehicle 10 Motor 12 Control 13 turbochargers 14 Tax system 16 sensors 18 actuators 19th wave 20 Throttle valve 22 Engine intake manifold 30 combustion chambers 32 Position sensor 35 Tailpipe 36 exhaust manifolds 37 Front end accessory drive (FEAD) 38 Thermostatic valve 42 Intake manifold 52 EGR valve 54 exhaust gas heat exchangers 55 Temperature sensor 56 Pressure sensor 57 Humidity sensor 66 Injection device 75 Auxiliary pump 80 car radiators 81 Auxiliary pump 83 Coolant outlet pipe 84 Coolant inlet line 86 Water pump 87 Car radiator bypass line 89 Coolant line 90 heating core 91 Wastegate 92 Wastegate actuator 93 fans 94 Climate control system 100 motor system 101 Vehicle system 102 Exhaust duct 106 liaison point 112 air purifiers 114 compressors 116 Turbine 118 charge-air cooler (CAC) 124 Manifold air pressure (MAP) sensor 126 Exhaust gas sensor 128 Exhaust gas temperature sensor 129 Exhaust pressure sensor 150 EGHR system 155 Heating, ventilation and air conditioning (HVAC) system 160 Coolant inlet line 162 Coolant outlet pipe 170 first emission control device 171 second emission control device 172 silencers 174 Bypass canal 175 Diversion valve 176 heat exchangers 180 first coolant temperature sensor 181 Exhaust gas recirculation (EGR) feed channel 182 second coolant temperature sensor 302 Heat loss source 304 Cabin 402 Heat exchangers 404 Exhaust bypass channel 800 operating sequence 803 Threshold 807 upper limit 808 difference 809 lower limit 812 difference 813 upper limit 814 lower limit 816 Mark (Diagnostic Code) 818 Mark (Diagnostic Code)

Claims

Method comprising: during an exhaust gas flow from a vehicle engine (10) through a heat exchanger (54; 176; 402) with engine coolant flowing therein, indicating the deterioration of a first and / or second coolant temperature sensor (180; 182), coupled accordingly upstream and downstream of the heat exchanger (54; 176; 402), in response to a difference above a threshold value between a measured coolant temperature and a modeled coolant temperature based on the heat transfer between a heat loss source (302) and a vehicle cabin (4), wherein the heat transfer between the heat loss source (302) and the vehicle cabin (4) is based on one or more of an air mass flow rate between the heat loss source (302) and the vehicle cabin (4) and a temperature of the air entering the vehicle cabin (4) from the heat loss source (302). Method according to claim 1, wherein the heat loss source (302) comprises a heating core (90) and a plurality of engine coolant lines (89) of an on-board heating, ventilation and air conditioning (HVAC) system (155), wherein the engine coolant flows through the coolant lines (89). The method of claim 1, wherein the measured coolant temperature comprises a first measured coolant temperature upstream of the heat exchanger (54; 176; 402) based on an input from the first coolant temperature sensor (180) coupled to an engine coolant line (89) entering the heat exchanger (54; 176; 402), the modeled coolant temperature comprises a first modeled coolant temperature upstream of the heat exchanger (54; 176; 402), and indicates the deterioration of the first coolant temperature sensor (180) coupled upstream of the heat exchanger (54; 176; 402) on a difference above a threshold value between the first measured coolant temperature upstream of the heat exchanger (54; 176; 402) and the first modeled coolant temperature upstream of the heat exchanger (54; 176; 402).402) is based on the first modeled coolant temperature being calibrated over a variety of vehicle cabin temperature settings.; The method according to claim 1, wherein the heat transfer between the heat loss source (302) and the vehicle cabin is further based on one or more of the temperature of the coolant entering the heat loss source (302) from the engine (10), the temperature of the air entering the heat loss source (302) from the ambient air and / or the vehicle cabin (4), and the effectiveness of the heat transfer between the heat loss source (302) and the vehicle cabin (4), wherein the effectiveness of the heat transfer between the heat loss source (302) and the vehicle cabin (4) is based on each of the air mass flow rate between the heat loss source (302) and the vehicle cabin (4) and a coolant mass flow rate across the heat loss source (302). Method according to claim 4, wherein the air mass flow rate between the heating core (90) and the vehicle cabin (4) is a function of a position of a ventilation opening that allows the airflow between the heating core (90) and the vehicle cabin (4). The method of claim 4, wherein the measured coolant temperature further comprises a second measured coolant temperature downstream of the heat exchanger (54; 176; 402) based on an input from the second coolant temperature sensor (182) coupled to an engine coolant line (89) exiting the heat exchanger (54; 176; 402), the modeled coolant temperature further comprises a second modeled coolant temperature downstream of the heat exchanger (54; 176; 402), and indicating the deterioration of the second coolant temperature sensor (182) coupled downstream of the heat exchanger (54; 176; 402) based on a difference above a threshold value between the second measured coolant temperature downstream of the heat exchanger (54; 176; 402) and the second modeled coolant temperature of the heat exchanger (54; 176; 402), wherein the second modeled coolant temperature downstream of the heat exchanger (54; 176;402) is based on each of the first modeled coolant temperatures upstream of the heat exchanger (54; 176; 402) and the heat transfer between the exhaust gas and the engine coolant flowing through the heat exchanger (54; 176; 402). The method of claim 6, wherein the heat transfer between the exhaust gas and the engine coolant flowing through the heat exchanger (54; 176; 402) is a function of one or more of an exhaust gas mass flow rate across the heat exchanger (54; 176; 402), a temperature of the coolant entering the heat exchanger (54; 176; 402), a temperature of the air entering the heat exchanger (54; 176; 402) from the exhaust gas, a temperature of the air entering the exhaust gas from the heat exchanger (54; 176; 402), and an efficiency of the heat transfer between the exhaust gas and the engine coolant flowing through the heat exchanger (54; 176; 402), wherein the efficiency of the heat transfer between the exhaust gas and the engine coolant flowing through the heat exchanger (54; 176; 402) flows, based on each of the exhaust gas mass flow rate through the heat exchanger (54; 176; 402) and the coolant mass flow rate through the heat exchanger (54; 176; 402). Method according to claim 7, wherein the heat exchanger (54; 176; 402) is coupled to an exhaust bypass, the method further comprising adjusting a position of an exhaust bypass valve (175) coupled to a connection point of the exhaust bypass and a main exhaust duct (102) to regulate the exhaust flow via the heat exchanger (54; 176; 402) in order to maintain a desired engine coolant temperature, the desired engine coolant temperature being based on any engine heating requirement and / or vehicle cabin heating requirement. The method of claim 4, further comprising, in response to a notification of deterioration of the first coolant temperature sensor (180), using the first modeled coolant temperature for engine operations and, in response to a notification of deterioration of the second coolant temperature sensor (182), using the second modeled coolant temperature for engine operations. Method according to claim 8, wherein the exhaust gas mass flow rate via the heat exchanger (54; 176; 402) is a function of each of the position of the exhaust gas diversion valve (175) and an overall exhaust gas flow rate via the main exhaust gas duct (102). The method of claim 10, further comprising indicating a deterioration of the exhaust bypass valve (175) in response to an actual position of the exhaust bypass valve (175), as estimated on the basis of an input from a bypass valve position sensor (32), which differs from an expected position of the exhaust bypass valve (175), wherein the expected position of the exhaust bypass valve (175) includes a first position during an engine heating demand above a threshold and / or a vehicle cabin heating demand above a threshold, which activates exhaust flow through the heat exchanger (54; 176; 402), and a second position during an engine heating demand below a threshold and a vehicle cabin heating demand below a threshold, which deactivates exhaust flow through the heat exchanger (54; 176; 402). The method of claim 11, further comprising indicating the deterioration of the heat exchanger (54; 176; 402) in response to an expected temperature difference between the coolant temperature upstream and downstream of the heat exchanger (54; 176; 402) differing from an actual temperature difference between the coolant temperature upstream and downstream of the heat exchanger (54; 176; 402), wherein the expected temperature difference is based on each of the actual position of the exhaust gas bypass valve (175), the coolant mass flow rate through the heat exchanger (54; 176; 402) and the exhaust gas flow rate, and the actual difference is based on inputs from the first coolant temperature sensor (180) and the second coolant temperature sensor (182). Vehicle system comprising: an engine (10); a vehicle cabin (4); an engine intake manifold (22); an engine exhaust system comprising an exhaust duct (102) and a bypass duct (174; 404), wherein the exhaust duct (102) comprises one or more exhaust catalysts and a silencer (172), wherein the bypass duct (174; 404) is coupled to the exhaust duct (102) from downstream of the one or more exhaust catalysts to upstream of the silencer (172), wherein the bypass duct (174; 404) comprises a heat exchanger (54; 176; 402); a bypass valve (175) coupling an inlet of the bypass duct (174; 404) to the exhaust duct (102); a bypass valve position sensor (32) connected to the bypass valve (175) is coupled; a coolant system with an incoming coolant line (89) and an outgoing coolant line (89) for circulating coolant through the heat exchanger (54; 176;402), wherein the coolant system is further coupled to each of an engine block and a heater core (90) of a heating, ventilation and air conditioning (HVAC) system (155), the incoming coolant line (89) includes a first coolant temperature sensor (180) for estimating a coolant temperature upstream of the heat exchanger (54; 176; 402), the outgoing coolant line (89) includes a second coolant temperature sensor (182) for estimating a coolant temperature downstream of the heat exchanger (54; 176; 402); and a control unit (12) with computer-readable instructions stored on non-volatile memory for: moving the diverter valve (175) to a first position for operating the exhaust system in a first mode, wherein exhaust gas flows from downstream of the at least one exhaust catalyst via the heat exchanger (54; 176; 402) to upstream of the silencer (172);and during operation in the first mode, measuring the coolant temperature upstream of the heat exchanger (54; 176; 402) via the first coolant temperature sensor (180); indicating the deterioration of the first coolant temperature sensor (180) in response to a difference above a threshold between a modeled coolant temperature upstream of the heat exchanger (54; 176; 402) and the measured coolant temperature upstream of the heat exchanger (54; 176; 402); and in response to the indication of deterioration, using the modeled coolant temperature to estimate the coolant temperature upstream of the heat exchanger (54; 176; 402).; System according to claim 13, wherein the controller (12) contains further instructions for: during operation in the first mode, measuring a position of the bypass valve (175) via the bypass valve position sensor (32); measuring the coolant temperature downstream of the heat exchanger (54; 176; 402) via the second coolant temperature sensor (182); indicating the degradation of the second coolant temperature sensor (182) in response to a difference above a threshold between a modeled coolant temperature downstream of the heat exchanger (54; 176; 402) and the measured coolant temperature downstream of the heat exchanger (54; 176; 402); indicating the degradation of the bypass valve (175) in response to the position of the bypass valve (175) differing from the first position; using the modeled coolant temperature to estimate the coolant temperature downstream of the heat exchanger (54; 176;402) in response to the indication of deterioration of the second coolant temperature sensor (182); and Disabling the operation of the exhaust system in first mode in response to the indication of deterioration of the bypass valve (175).; System according to claim 13, wherein the modeled coolant temperature upstream of the heat exchanger (54; 176; 402) is based on one or more of the air flow between the heating core (90) and the vehicle cabin (4) and the coolant flow from the engine (10) to the heating core (90), and wherein the modeled coolant temperature downstream of the heat exchanger (54; 176; 402) is based on one or more of the modeled coolant temperature upstream of the heat exchanger (54; 176; 402), the air flow between the exhaust gas flowing through the heat exchanger (54; 176; 402) and the coolant flowing through the heat exchanger (54; 176; 402), and the coolant flow from the heating core (90) to the heat exchanger (54; 176; 402).

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