Control system for determining exhaust gas temperature

Abstract

Control system for an engine (22), comprising: a temperature determination module (72) that determines the temperature of exhaust gas based on the resistance of a heating element (60) of an oxygen sensor (56) associated with a catalyst (54), wherein the oxygen sensor (56) comprises an upstream oxygen sensor (56-1) and a downstream oxygen sensor (56-2) with respect to the catalyst (54), wherein the upstream oxygen sensor (56-1) comprises an upstream heating element (60-1) and the downstream oxygen sensor (56-2) comprises a downstream heating element (60-2); and a catalyst protection module (74) that adjusts an operating parameter of the engine (22) to reduce the exhaust gas temperature when the exhaust gas temperature is greater than a catalyst threshold temperature, wherein the catalyst threshold temperature is based on a temperature that damages a catalyst in an exhaust system, wherein the catalyst protection module (74) determines, based on the resistance of the upstream heating element (60-1) and the downstream heating element (60-2), that the temperature of the catalyst (54) approaches the catalyst threshold temperature, where: If the upstream heating element (60-1) does not indicate that the temperature of the catalyst (54) is approaching the catalyst threshold temperature, while the downstream heating element (60-2) indicates that the temperature of the catalyst (54) is approaching the catalyst threshold temperature, the catalyst protection module (74) determines that the catalyst (54) is heating up due to a misfire; If the upstream heating element (60-1) indicates that the temperature of the catalyst (54) is approaching the catalyst threshold temperature, while the downstream heating element (60-2) does not indicate that the temperature of the catalyst (54) is approaching the catalyst threshold temperature, the catalyst protection module (74) determines that the catalyst (54) is heating up due to a misfire causing combustion near the upstream side of the catalyst (54); and When an increase in the temperature of the exhaust gas due to an increased load on the engine (22) is detected by each of the upstream heating element (60-1) and the downstream heating element (60-2), the catalyst protection module (74) determines, based on the resistance of each of the heating elements (60), that the temperature of the catalyst (54) is approaching the catalyst threshold temperature due to the increased load on the engine (22).

Description

[0001] The present disclosure relates to a control system for determining the exhaust gas temperature and in particular a control system for determining the exhaust gas temperature using a heating element of an oxygen sensor.

[0002] A vehicle with an internal combustion engine can produce exhaust gas containing varying oxygen concentrations. The vehicle may have one or more oxygen sensors to monitor the oxygen concentration in the exhaust gas. Oxygen sensors typically consist of a sensing element and a heating element. The sensing element operates effectively once it reaches an operating temperature (for example, 650°C).

[0003] An engine control module (ECM) can apply a voltage and / or current to the heating element to heat the sensor element to its operating temperature. The ECM determines that the heating element has reached operating temperature based on its resistance.

[0004] GB 2 277 594 A discloses an internal combustion engine with a catalytic converter and a first heated exhaust gas oxygen sensor downstream of the catalytic converter. By monitoring the resistance of the sensor's heating element, a temperature reading of the catalytic converter is provided during and shortly after engine start. A second sensor upstream of the catalytic converter can be used for mixture control, and the first sensor can also be used to detect a fault in the second sensor.

[0005] Further control systems for determining exhaust gas temperature are described in US 2004 / 0 050 693 A1, DE 43 44 137 A1, DE 102 12 428 A1, DE 10 2006 009 241 A1 and DE 10 2007 034 251 A1.

[0006] The object of the invention is to provide a control system that is able to protect an exhaust gas catalyst from overheating in a simple and reliable manner.

[0007] The problem is solved by the subject matter of claim 1. Advantageous embodiments of the invention are described in the dependent claims.

[0008] The present revelation is better understood from the detailed description and accompanying drawings, in which: Fig. 1 a functional block diagram of a vehicle system according to the present disclosure; Fig. 2 a functional block diagram of an engine control module according to the present disclosure; and Fig. 3 is a flowchart illustrating a method for protecting a catalyst according to the present disclosure.

[0009] The term "module" as used here refers to an application-specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated or group) and memory that executes one or more software or firmware programs, a combinational logic circuit and / or other suitable components that provide the described functionality.

[0010] An oxygen sensor comprises a sensing element and a heating element. The sensing element generates a signal indicating the amount of oxygen in the exhaust gas. The sensing element operates effectively at a specific temperature. An engine control module (ECM) can electrically heat the heating element to bring the sensing element up to its operating temperature. Additionally, the exhaust gas can also contribute to heating the sensing element to its operating temperature.

[0011] The ECM determines the temperature of the heating element based on its resistance. The temperature of the heating element can be the same as the temperature of the sensor element. Therefore, the ECM can determine when the sensor element reaches its operating temperature based on the resistance of the heating element.

[0012] The heating element can be heated either electrically or by the exhaust gas, provided the ECM heats the element to its operating temperature. Therefore, if the heating element is electrically heated, the ECM does not need to determine the exhaust gas temperature based on the heating element's temperature. The heating element can be deactivated (for example, by the ECM not heating it electrically) if its temperature exceeds the operating temperature.

[0013] A temperature determination control system according to the present disclosure determines the temperature of the heating element when the heating element is deactivated. The heating element can be heated by the exhaust gas, but not electrically, when the heating element is deactivated. Accordingly, the temperature determination system can determine the temperature of the exhaust gas based on the temperature of the heating element when the heating element is deactivated. In other words, the temperature determination system can determine the temperature of the exhaust gas based on the temperature of the heating element when the exhaust gas temperature is higher than the operating temperature.

[0014] The exhaust gas temperature can be higher than the operating temperature if engine misfires result in fuel combustion at the catalytic converter. Additionally, the exhaust gas temperature can be higher than the operating temperature when the engine is operating under high loads.

[0015] The catalyst temperature can exceed a catalyst temperature threshold (for example, 900–950°C) when fuel burns on the catalyst and / or when the engine is operating under high load. The catalyst can be damaged if its temperature exceeds the catalyst temperature threshold.

[0016] The temperature monitoring system can determine, based on the exhaust gas temperature (i.e., the temperature of the heating element), when the catalyst temperature approaches the catalyst temperature threshold. Accordingly, the temperature monitoring system can determine when the catalyst may be damaged due to misfires and / or high load. The temperature monitoring system can operate the engine (for example, modulating air intake and fuel injection) to protect the catalyst from damage when the exhaust gas temperature indicates that the catalyst may be at risk.

[0017] The temperature monitoring system can determine that the catalyst temperature is approaching its threshold based on the exhaust gas temperature, as indicated by a heating element located upstream and / or downstream of the catalyst. The system can also determine that the catalyst is approaching its threshold based on heating of the heating element upstream of the catalyst due to fuel combustion. Furthermore, the system can detect that the catalyst is approaching its threshold based on heating of the heating element downstream of the catalyst, resulting from heating of the exhaust gas passing through the catalyst.Additionally, the temperature determination system can detect, based on a heating of the heating element upstream and / or downstream of the catalyst under a high load, that the catalyst is approaching the catalyst temperature threshold.

[0018] Now, referring to Fig. Figure 1 shows an exemplary vehicle system 20 comprising an engine 22 that drives a transmission 24. While a spark-ignition engine is shown, compression-ignition engines are also conceivable. An ECM 32 communicates with components of the vehicle system 20. The components of the vehicle system 20 include the engine 22, sensors, and actuators, as discussed here. The ECM 32 can implement the temperature determination control system of this disclosure.

[0019] A throttle 26 can regulate the airflow into an intake manifold 28. Air in the intake manifold 28 is distributed to cylinder 30. Each cylinder 30 can have a fuel injector 34 for injecting fuel into the cylinder 30. Each cylinder 30 can have a spark plug 36 for igniting the air / fuel mixture. Alternatively, the air / fuel mixture can be ignited by compression in a compression-ignition engine. Although Fig. If 1 shows four cylinders 30, the engine can have 22 additional or fewer cylinders 30.

[0020] Air is drawn from an inlet 42 through a mass airflow (MAF) sensor 44. The MAF sensor 44 generates a MAF signal that indicates the mass of air flowing into the intake manifold 28. A manifold pressure (MAP) sensor 46 is positioned in the intake manifold 28 between the throttle 26 and the engine 22. The MAP sensor 46 generates a MAP signal that indicates the manifold absolute pressure. An intake air temperature (IAT) sensor 48, located in the intake manifold 28, generates an IAT signal that indicates the intake air temperature. An engine crankshaft (not shown) rotates at an engine speed or a rate proportional to the engine speed. A crankshaft position sensor 50 generates a crankshaft position (CSP) signal that indicates the speed and position of the crankshaft.

[0021] An intake valve 38 opens and closes selectively to allow air to enter cylinder 30. An intake camshaft (not shown) regulates the position of the intake valve 38. A piston (not shown) compresses the air / fuel mixture in cylinder 30. The ECM 32 actuates a fuel injector 34 to inject fuel into cylinder 30. The ECM 32 can actuate a spark plug 36 to initiate combustion of the air / fuel mixture, thereby driving the piston in cylinder 30. The piston drives the crankshaft to generate torque. Exhaust gases from cylinder 30 are expelled through an exhaust manifold 52 when an exhaust valve 40 is in an open position. An exhaust camshaft (not shown) regulates the position of the exhaust valve 40.Although individual intake and exhaust valves 38, 40 are shown, the engine 22 can have multiple intake and exhaust valves 38, 40 per cylinder 30. The engine 22 can also provide an active fuel management system (not shown) that deactivates intake and exhaust valves 38.

[0022] The vehicle system 20 includes a catalyst 54 (for example, a three-way catalyst housed in a catalytic converter) that treats exhaust gas. The vehicle system 20 may have one or more oxygen sensors 56-1, 56-2 (collectively oxygen sensors 56) mounted in the exhaust manifold 52. Oxygen sensor 56-1 is located upstream of the catalyst 54. Oxygen sensor 56-2 is located downstream of the catalyst 54. The oxygen sensors 56 generate oxygen level signals that indicate the amount of oxygen in the exhaust gas. The ECM 32 can determine the efficiency of the catalyst 54 and control the vehicle system 20 based on the oxygen level signals.

[0023] The oxygen sensors 56 comprise sensor elements 58-1, 58-2 (collectively, sensor elements 58). The oxygen sensors 56-1, 56-2 each have heating elements 60-1, 60-2. Heating element 60-1 can be referred to as an upstream heating element 60-1. Heating element 60-2 can be referred to as a downstream heating element 60-2. The heating elements 60-1, 60-2 can be referred to collectively as heating elements 60. The heating elements 60-1, 60-2 can have similar functionality. Accordingly, either the upstream heating element 60-1 or the downstream heating element 60-2 can be generally referred to as "the heating element 60".

[0024] The heating elements 60 heat the corresponding sensor elements 58 to the operating temperature. The operating temperature can be a temperature at which the sensor elements 58 function effectively (for example, 650°C). The heating elements 60 can be located close to the sensor elements 58 so that the sensor elements 58 and the heating elements 60 are at approximately the same temperature. The heating elements 60 can be electrically heated wires. Accordingly, the ECM 32 can supply a voltage and / or current to the heating elements 60 to heat them to the operating temperature.

[0025] The catalyst 54 can be damaged due to fuel combustion on the catalyst 54 if the engine 22 misfires. The engine 22 can misfire, for example, if the spark plug 36 malfunctions, if the fuel injector 34 malfunctions, and / or if there is a loss of compression in cylinder 30 due to a leak in the exhaust valve 40.

[0026] The ECM 32 can detect misfires based on CSP signals, for example, based on a deceleration of the engine 22. However, the ECM 32 cannot detect the fuel mixture entering the catalyst due to misfires based on CSP signals. Accordingly, the ECM 32 cannot determine whether the catalyst 54 may be damaged due to fuel combustion on the catalyst 54 when misfires are detected.

[0027] The temperature of the catalyst 54 can rise above the catalyst temperature threshold if the exhaust gas entering the catalyst 54 contains unburned hydrocarbons that combust on the catalyst 54. For example, the catalyst 54 can be damaged (e.g., melt) if it absorbs the unburned hydrocarbons. The temperature control system of this disclosure can determine when the temperature of the catalyst 54 approaches the catalyst temperature threshold. Accordingly, the temperature control system can determine when the catalyst overheats due to misfires and / or high load.

[0028] The oxygen sensors 56 can be located near the catalyst 54. Accordingly, the heating elements 60 can be heated by the catalyst 54. The upstream heating element 60-1 can be heated by the exhaust gas entering the catalyst 54. Additionally, the upstream heating element 60-1 can be heated by the combustion of fuel on the catalyst 54. For example, the combustion of fuel on the catalyst 54 can heat the exhaust gas upstream of the catalyst 54. Furthermore, the combustion of fuel can proceed slightly upstream of the catalyst 54, thereby further heating the heating element 60-1.

[0029] The downstream heating element 60-2 can be heated by exhaust gas and combustion events in the catalyst 54. The exhaust gas flowing through the catalyst 54 can be heated to the temperature of the catalyst 54. Accordingly, the temperature of the heating element 60-2 can indicate the temperature of the catalyst 54.

[0030] Now, referring to Fig. The ECM 32 comprises a heater control module 70, a temperature sensing module 72, and a catalyst protection module 74. The ECM 32 receives input signals from the vehicle system 20. The input signals may include, but are not limited to, the MAF, MAP, IAT, CSP, and oxygen level signals. The ECM 32 processes the input signals and generates timed engine control instructions, which are output to the vehicle system 20. For example, engine control instructions can actuate the throttle 26, the fuel injectors 34, the spark plugs 36, and the heater elements 60.

[0031] The heater control module 70 can heat the heating element 60 to the operating temperature. The heater control module 70 does not need to heat the heating element 60 if its temperature is higher than the operating temperature. The temperature determination module 72 determines the temperature of the heating element 60 if its temperature is higher than the operating temperature. The catalyst protection module 74 determines the exhaust gas temperature based on the temperature of the heating element 60.

[0032] The catalyst protection module 74 determines, based on the temperature of the heating element 60, when the catalyst 54 may be damaged. The catalyst protection module 74 can modify the operation of the vehicle system 20 to protect the catalyst 54 when the temperature of the heating element 60 indicates that the temperature of the catalyst 54 is approaching the catalyst temperature threshold. In other words, the catalyst protection module 74 can modify the operation of the vehicle system 20 when the temperature of the heating element 60 indicates that the catalyst 54 may be damaged.

[0033] The heater control module 70 heats the heating element 60 when the temperature of the heating element 60 is lower than the operating temperature. The heater control module 70 can apply a predetermined voltage and / or current to the heating element 60 to heat it. Accordingly, the heater control module 70 can determine the resistance of the heating element 60 based on the voltage and current applied to it. For example, the heater control module 70 can determine the resistance of the heating element 60 by dividing the voltage applied to it by the current supplied to it.

[0034] In some implementations, the heater control module 70 can apply pulses of voltage and / or current to the heating element 60 to heat it. The heater control module 70 can also vary the duty cycle of these pulses to control the temperature of the heating element 60. For example, increasing the duty cycle of the pulses can increase the temperature of the heating element 60, while decreasing the duty cycle can allow the temperature of the heating element 60 to follow the temperature of the exhaust gas.

[0035] The temperature determination module 72 can determine the temperature of the heating element 60 when the heater control module 70 heats the heating element 60. The temperature determination module 72 can determine the temperature of the heating element 60 based on its resistance. For example, the temperature determination module 72 can use a lookup table to match the resistance of the heating element 60 to the temperature of the heating element 60.

[0036] The temperature control module 72 determines when the heating element 60, and consequently the sensor element 58, have reached their operating temperature. The heating element 60 can be heated by the exhaust gas and the heater control module 70 if its temperature is lower than the operating temperature. Therefore, if the temperature of the heating element 60 is lower than the operating temperature, the temperature control module 72 does not need to determine the exhaust gas temperature, as the heating element 60 is also heated by the heater control module 72. In other words, the temperature control module 72 does not need to distinguish between heating due to electrical heating of the heating element 60 and heating due to the exhaust gas.

[0037] The heater control module 70 can deactivate the heating element 60 when the heating element 60 reaches its operating temperature. The heater control module 70 does not need to heat the heating element 60 when it deactivates it. Accordingly, the heating element 60 does not need to be electrically heated when it reaches its operating temperature. The heater control module 70 can deactivate the heating element 60 by limiting the amount of current and voltage supplied to it. For example, the heater control module 70 can supply a small amount of power to the heating element 60 to deactivate it. The heater control module 70 can also deactivate the heating element 60 by supplying no power to it.In some implementations, the heater control module 70 can reduce the duty cycle of pulses used to heat the heating element 60 in order to deactivate the heating element 60. With the reduced duty cycle, the heating element 60 does not need to be heated.

[0038] The temperature determination module 72 determines the temperature of the heating element 60 based on the resistance of the heating element 60 when the heating element 60 is deactivated. For example, the temperature determination module 72 can determine the temperature of the heating element 60 using a lookup table that associates the resistance of the heating element 60 with a range of temperatures greater than the operating temperature.

[0039] The heater control module 70 can determine the resistance of the heating element 60 without significantly heating the heating element 60 when the heating element 60 is deactivated. For example, the heater control module 70 can determine the resistance of the heating element 60 when a low power is supplied to the heating element 60. In some implementations, the heater control module 70 can determine the resistance of the heating element 60 when it applies pulses with a reduced duty cycle to the heating element 60.

[0040] The heating element 60 is heated by the exhaust gas when it is deactivated. The temperature of the heating element 60 can be equal to the temperature of the exhaust gas when it is deactivated. Accordingly, the temperature determination module 72 can determine the temperature of the exhaust gas based on the temperature of the heating element 60 when it is deactivated. For example, the temperature determination module 72 can determine that the temperature of the exhaust gas is equal to the temperature of the heating element 60 when it is deactivated.

[0041] The temperature of the catalyst 54 can approach or exceed the catalyst temperature threshold due to misfire events in the engine 22. The catalyst protection module 74 can determine, based on the temperature of the upstream and / or downstream heating elements 60-1, 60-2, that misfire events are heating the catalyst 54.

[0042] The temperature of the catalyst 54 can also approach or exceed the catalyst temperature threshold based on an increase in the exhaust gas temperature during increased load on the engine 22. The temperature of the catalyst 54 can rise to a temperature greater than or equal to the catalyst temperature threshold if the catalyst 54 is heated due to increased load. The catalyst protection module 74 can determine, based on the temperature of the upstream and / or downstream heating element 60-1, 60-2, that increased load on the engine 22 is heating the catalyst 54.

[0043] The catalyst 54 can be damaged if it reaches the catalyst temperature threshold. For example, sections of the catalyst 54 may melt and break off when it reaches the catalyst temperature threshold. The catalyst protection module 74 can determine, based on the temperature of the upstream and / or downstream heating element 60-1, 60-2, when the catalyst 54 temperature approaches or exceeds the catalyst temperature threshold. Accordingly, the catalyst protection module 74 can modify the operation of the motor 22 to reduce the catalyst 54 temperature when the catalyst temperature approaches or exceeds the catalyst temperature threshold.

[0044] The catalyst protection module 74 can determine, based on the temperature of the heating elements 60, that the temperature of the catalyst 54 is approaching the catalyst temperature threshold. For example, the catalyst protection module 74 can determine that the temperature of the catalyst 54 is approaching the catalyst temperature threshold when the temperature of the upstream and / or downstream heating element 60-1, 60-2 is higher than the operating temperature but lower than the catalyst temperature threshold (for example, higher than 800°C). The catalyst protection module 74 can determine that the temperature of the catalyst 54 exceeds the catalyst temperature threshold when the temperature of the upstream and / or downstream heating element 60-1, 60-2 is higher than the catalyst temperature threshold.

[0045] The catalyst protection module 74 can determine, based on the rate of change of the exhaust gas temperature, that the temperature of the catalyst 54 is approaching the catalyst temperature threshold. For example, if the exhaust gas temperature increases at a rate greater than a predetermined rate, the catalyst protection module 74 can determine that the temperature of the catalyst 54 is approaching the catalyst temperature threshold.

[0046] The catalyst protection module 74 can adjust operating parameters of the engine 22 (for example, actuate the fuel injectors 34 and the throttle 26) to reduce the temperature of the catalyst 54 and / or the exhaust gas when the catalyst 54 temperature approaches the catalyst temperature threshold. For example, the catalyst protection module 74 can actuate the fuel injectors 34 and the throttle 26 to reduce the amount of combustion at the catalyst 54 when the catalyst 54 temperature approaches the catalyst temperature threshold due to misfires in the engine 22. The catalyst protection module 74 can also actuate the fuel injectors 34 and the throttle 26 to reduce the exhaust gas temperature when the catalyst 54 temperature approaches the catalyst temperature threshold due to increased engine load.

[0047] In some implementations, the catalyst protection module 74 can determine, based on the exhaust gas temperature downstream of the catalyst 54, that the catalyst 54 temperature is approaching the catalyst temperature threshold. Similarly, the catalyst protection module 74 can determine, based on the resistance of the heating element 60-2 downstream of the catalyst 54, that the catalyst 54 is approaching the catalyst temperature threshold. If the catalyst 54 is heated due to a misfire in the engine 22, the exhaust gas passing through the catalyst 54 can be heated. Therefore, the catalyst protection module 74 can determine that the catalyst 54 temperature is approaching the catalyst temperature threshold when the exhaust gas temperature downstream of the catalyst 54 approaches the catalyst temperature threshold.For example, the catalyst protection module 74 can determine that the temperature of the catalyst 54 approaches the catalyst temperature threshold when the temperature of the exhaust gas downstream of the catalyst 54 is within a threshold temperature (e.g. 100°C) of the catalyst temperature threshold.

[0048] In other implementations, the catalyst protection module 74 can determine, based on the temperature of the exhaust gas downstream of the catalyst 54, that the temperature of the catalyst 54 is approaching the catalyst temperature threshold. Similarly, the catalyst protection module 74 can determine, based on the resistance of the upstream heating element 60-1, that the temperature of the catalyst 54 is approaching the catalyst temperature threshold.

[0049] If the catalyst 54 is heated due to a misfire in the engine 22, the exhaust gas upstream of the catalyst 54 and / or the upstream heating element 60-1 can be heated. For example, combustion in the catalyst 54 can occur near the upstream side of the catalyst 54, which can heat the upstream heating element 60-1 and / or exhaust gas passing through the upstream heating element 60-1. Additionally, fuel can burn upstream of the catalyst 54 if combustion occurs in the catalyst 54, further heating the upstream heating element 60-1. Accordingly, the catalyst protection module 74 can determine that the temperature of the catalyst 54 approaches the catalyst temperature threshold when the temperature of the heating element 60-1 approaches the catalyst temperature threshold.For example, the catalyst protection module 74 can determine that the temperature of the catalyst 54 approaches the catalyst temperature threshold when the temperature of the heating element 60-1 is within a threshold temperature of the catalyst temperature threshold.

[0050] The catalyst protection module 74 can contain calibration data (for example, a lookup table) that relates the temperature of the upstream heating element 60-1 to the temperature of the catalyst 54, since the temperature of the exhaust gas upstream of the catalyst 54 during a misfire may not be equal to the temperature of the catalyst 54. For example, the temperature of the catalyst 54 may be higher than the temperature of the heating element 60-1, because exhaust gas can bypass the heating element 60-1 and cool it as the temperature of the catalyst 54 approaches the catalyst temperature threshold.

[0051] The catalyst protection module 74 can determine, based on the resistance of both heating elements 60, that the temperature of the catalyst 54 is approaching the catalyst temperature threshold. For example, the upstream heating element 60-1 does not need to indicate that the temperature of the catalyst 54 is approaching the catalyst temperature threshold, while the downstream heating element 60-2 does. In this case, the catalyst protection module 74 can determine that the catalyst 54 is heating up due to a misfire, since the exhaust gas can be heated by the catalyst 54 if it passes through it.

[0052] In one scenario, the upstream heating element 60-1 may indicate that the temperature of catalyst 54 is approaching the catalyst temperature threshold, while the downstream heating element 60-2 does not indicate that the temperature of catalyst 54 is approaching the catalyst temperature threshold. In this scenario, the catalyst protection module 74 may determine that the catalyst 54 is heating up due to a misfire occurring near the upstream side of the catalyst 54.

[0053] An increase in exhaust gas temperature due to an increased load on the engine 22 can be detected by each of the heating elements 60, since the exhaust gas flows past both heating elements 60 at the increased temperature. Accordingly, the catalyst protection module 74 can determine, based on the resistance of each of the heating elements 60, that the temperature of the catalyst 54 is approaching the catalyst temperature threshold due to the increased load on the engine 22.

[0054] Now, referring to Fig. 3 starts a procedure 100 to protect an SCR catalyst at step 101. At step 102, the heater control module 70 heats the heating element 60. At step 104, the temperature determination module 72 determines the temperature of the heating element 60. At step 106, the temperature determination module 72 determines whether the oxygen sensor 56 is at operating temperature. If the result of step 106 is false, the procedure 100 repeats step 102. If the result of step 106 is true, the procedure 100 continues with step 108.

[0055] In step 108, the heater control module 70 deactivates the heating element 60. In step 110, the heater control module 70 determines the resistance of the heating element 60. In step 112, the temperature determination module 72 determines the temperature of the heating element 60 based on its resistance. In step 114, the catalyst protection module 74 determines whether the temperature of the catalyst 54 is greater than the catalyst temperature threshold. If the result of step 114 is false, the procedure 100 repeats step 114. If the result of step 114 is true, the procedure 100 proceeds to step 116. In step 116, the catalyst protection module 74 determines that the catalyst 54 may be damaged. In step 118, the catalyst protection module 74 controls the vehicle system 20 to prevent damage to the catalyst 54. Procedure 100 ends at step 120.

Claims

[1] Control system for an engine (22), comprising: a temperature determination module (72) that determines the temperature of exhaust gas based on the resistance of a heating element (60) of an oxygen sensor (56) associated with a catalyst (54), wherein the oxygen sensor (56) comprises an upstream oxygen sensor (56-1) and a downstream oxygen sensor (56-2) with respect to the catalyst (54), wherein the upstream oxygen sensor (56-1) comprises an upstream heating element (60-1) and the downstream oxygen sensor (56-2) comprises a downstream heating element (60-2); and a catalyst protection module (74) that adjusts an operating parameter of the engine (22) to reduce the exhaust gas temperature when the exhaust gas temperature is greater than a catalyst threshold temperature, wherein the catalyst threshold temperature is based on a temperature that damages a catalyst in an exhaust system, wherein the catalyst protection module (74) determines, based on the resistance of the upstream heating element (60-1) and the downstream heating element (60-2), that the temperature of the catalyst (54) approaches the catalyst threshold temperature, where: If the upstream heating element (60-1) does not indicate that the temperature of the catalyst (54) is approaching the catalyst threshold temperature, while the downstream heating element (60-2) indicates that the temperature of the catalyst (54) is approaching the catalyst threshold temperature, the catalyst protection module (74) determines that the catalyst (54) is heating up due to a misfire; If the upstream heating element (60-1) indicates that the temperature of the catalyst (54) is approaching the catalyst threshold temperature, while the downstream heating element (60-2) does not indicate that the temperature of the catalyst (54) is approaching the catalyst threshold temperature, the catalyst protection module (74) determines that the catalyst (54) is heating up due to a misfire causing combustion near the upstream side of the catalyst (54); and When an increase in the temperature of the exhaust gas due to an increased load on the engine (22) is detected by each of the upstream heating element (60-1) and the downstream heating element (60-2), the catalyst protection module (74) determines, based on the resistance of each of the heating elements (60), that the temperature of the catalyst (54) is approaching the catalyst threshold temperature due to the increased load on the engine (22). [2] Control system according to claim 1, wherein the catalyst threshold temperature is greater than 800°C. [3] Control system according to claim 1, further comprising a heater control module (70) which electrically heats the heating element (60) to an operating temperature of the oxygen sensor (56) and which stops electrical heating of the heating element (60) when the temperature of the heating element (60) is greater than the operating temperature, wherein the operating temperature is less than the catalyst threshold temperature. [4] Control system according to claim 1, wherein the catalyst protection module (74) adjusts a fuel injection and / or a position of the throttle (26) to reduce the temperature of the exhaust gas.

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