Patent Application
20230383679
The present application generally relates to a vehicle electrically heated catalyst (EHC) and, more particularly, to techniques for estimating exhaust system temperature(s) using the EHC and thermoelectric effect(s).
Exhaust gas resulting from combustion of an internal combustion engine is expelled from the cylinders and treated by an exhaust system to mitigate/eliminate emissions before release into the atmosphere. This is typically achieved by chemical reactions at one or more catalysts disposed in the exhaust system. Exhaust gas temperature is a critical component for various aspects of engine control. This includes, but is not limited to, engine emissions mitigation because these exhaust system catalysts(s) require a certain exhaust gas temperature range. Conventional techniques for measuring/estimating exhaust gas temperature include using dedicated thermocouples and complex modeling techniques (e.g., resistance-based modeling). These conventional techniques increase engine costs and/or processing requirements. Accordingly, while such conventional techniques do work well for their intended purpose, there exists an opportunity for improvement in the relevant art.
According to one example aspect of the invention, a temperature estimation system for a powertrain of a vehicle, the powertrain comprising an electrically heated catalyst, is presented. In one exemplary implementation, the temperature estimation system comprises an electrical heater disposed proximate to the electrically heated catalyst, the electrical heater comprising a heating element and a controller configured to monitor a voltage of the electrical heater and estimate a temperature of the heating element of the electrical heater based on the monitored voltage of the electrical heater and a set of known thermoelectric effects.
In some implementations, the heating element of the electrical heater comprises two dissimilar metals arranged in parallel between a power terminal and a ground terminal. In some implementations, the controller is configured to temporarily turn off a supply voltage to the electrical heater and monitor the voltage of the electrical heater as a voltage difference between the power and ground terminals. In some implementations, the controller is otherwise configured to turn on the supply voltage to the electrical heater to thereby heat the electrically heated catalyst. In some implementations, the set of known thermoelectric effects includes the Seebeck effect.
In some implementations, the electrical heater is disposed upstream from the electrically heated catalyst. In some implementations, the electrical heater is disposed mid-bed of or between one or more catalysts of the electrically heated catalyst. In some implementations, the electrical heater is disposed downstream of the electrically heated catalyst. In some implementations, the powertrain does not include a dedicated thermocouple for measuring a temperature relative to the electrically heated catalyst. In some implementations, the controller does not utilize a resistance-based temperature modeling technique to model a temperature relative to the electrically heated catalyst.
According to another example aspect of the invention, a temperature estimation method for a powertrain of a vehicle, the powertrain comprising an electrically heated catalyst, is presented. In one exemplary implementation, the temperature estimation method comprises monitoring, by a controller, a voltage of an electrical heater disposed proximate to the electrically heated catalyst, the electrical heater comprising a heating element, and estimating, by the controller, a temperature of the heating element of the electrical heater based on the monitoring of the voltage of the electrical heater and a set of known thermoelectric effects.
In some implementations, the heating element of the electrical heater comprises two dissimilar metals arranged in parallel between a power terminal and a ground terminal. In some implementations, the temperature estimation method further comprises temporarily turning off, by the controller, a supply voltage to the electrical heater and monitoring the voltage of the electrical heater as a voltage difference between the power and ground terminals. In some implementations, the controller is otherwise configured to turn on the supply voltage to the electrical heater to thereby heat the electrically heated catalyst. In some implementations, the set of known thermoelectric effects includes the Seebeck effect.
In some implementations, the electrical heater is disposed upstream from the electrically heated catalyst. In some implementations, the electrical heater is disposed mid-bed of or between one or more catalysts of the electrically heated catalyst. In some implementations, the electrical heater is disposed downstream of the electrically heated catalyst. In some implementations, the powertrain does not include a dedicated thermocouple for measuring a temperature relative to the electrically heated catalyst. In some implementations, the controller does not utilize a resistance-based temperature modeling technique to model a temperature relative to the electrically heated catalyst.
Further areas of applicability of the teachings of the present application will become apparent from the detailed description, claims and the drawings provided hereinafter, wherein like reference numerals refer to like features throughout the several views of the drawings. It should be understood that the detailed description, including disclosed embodiments and drawings referenced therein, are merely exemplary in nature intended for purposes of illustration only and are not intended to limit the scope of the present disclosure, its application or uses. Thus, variations that do not depart from the gist of the present application are intended to be within the scope of the present application.
As previously discussed, conventional techniques for measuring/estimating exhaust gas temperature include using dedicated thermocouples and complex modeling techniques (e.g., resistance-based modeling). These conventional techniques increase engine costs and/or processing requirements (e.g., large amounts of testing and calibration for complex modeling). Accordingly, improved exhaust gas temperature estimation techniques are presented that leverage known thermoelectric effect(s) (e.g., the Seebeck effect) to simply and accurately estimate exhaust gas temperature based on monitoring of the voltage of an electrical heater in the exhaust system. Many engines already include electrically heated catalysts (EHCs) that comprise one or more catalysts and an electrical heater disposed upstream, mid-bed, or downstream of the catalyst(s). Based on the monitored voltage of the electrical heater and the known thermoelectric effect(s), exhaust gas temperature can be estimated and then used for various engine controls (e.g., fuel/air ratio adjustment for quick/accurate catalyst heating). These techniques could potentially reduce engine/processing costs.
Referring now to
The exhaust system 116 includes an electrically heated catalyst (EHC) 120 comprising one or more catalysts 124 and an electrical heater 128. The electrical heater 128 could be disposed mid-bed relative to the catalyst 124, but it will also be appreciated that the electrical heater 128 could be disposed between two or more catalysts 124 or upstream/downstream from the catalyst(s) 124. A controller 132 controls operation of the engine 104 including monitoring the electrical heater 128 as part of the temperature estimation techniques of the present application. This estimated temperature could then be utilized for various aspects of engine control, including, but not limited to, control by the controller 132 of a fuel/air ratio (FAR) of the engine 104 for optimized emissions. It will be appreciated that in addition to exhaust gas temperature estimation based on the estimated temperature of the heating element, the estimated temperature of the heating element of the electrical heater 128 could be leveraged to estimate temperatures of other components (e.g., other catalysts or components in the exhaust system 116).
Referring now to
As shown, electrical current flows in opposing directions through the two dissimilar metals and generates, via the known thermoelectric effect(s) such as the Seebeck effect, a voltage across positive and negative terminals 228 and 232. The exhaust gas temperature estimation technique of the present application also provides estimation accuracy that is less sensitive to edge cases (e.g., extremely cold temperatures) compared to other complex modeling techniques such as resistance-based modeling. In one exemplary implementation, the temperature estimation technique provides accurate exhaust gas temperature estimation while also still allowing the electrical heater to operate as intended (e.g., to increase the exhaust gas temperature, such as during cold starts of the engine).
In addition to the Seebeck effect, the known Peltier and/or Thomson thermoelectric effects could be taken into account as part of the exhaust gas temperature estimation technique of the present application. The term “thermoelectric effect” generally refers to the direct conversion of temperature differences to electric voltage and vice-versa via a thermocouple. A thermoelectric device (e.g., the electrical heater 128) creates a voltage when there is a different temperature on each side.
Conversely, when a voltage is applied to it, heat is transferred from one side to the other, creating a temperature difference. At the atomic scale, an applied temperature gradient causes charge carriers in the material to diffuse from the hot side to the cold side. This effect can be used to generate electricity, measure temperature, or change the temperature of objects. Because the direction of heating and cooling is affected by the applied voltage, thermoelectric devices can be used as temperature controllers. The thermoelectric effect generally encompasses these three separately identified effects: the Seebeck effect, the Peltier effect, and the Thomson effect. The Seebeck and Peltier effects are different manifestations of the same physical process.
Referring now to
This monitoring and temperature estimation could occur during a period where the controller 132 temporarily turns off supply power to the electrical heater 128 to thereby allow for this voltage monitoring. Otherwise, the controller 132 can turn on the supply voltage to the electrical heater 128 to generate heat to thereby heat the electrically heated catalyst 120. Lastly, at 316, the controller 132 optionally controls at least one operating parameter of the engine (e.g., FAR) based on the estimated exhaust gas temperature. The method 300 then ends or returns to 304 for one or more additional cycles.
It will be appreciated that the term “controller” as used herein refers to any suitable control device or set of multiple control devices that is/are configured to perform at least a portion of the techniques of the present application. Non-limiting examples include an application-specific integrated circuit (ASIC), one or more processors and a non-transitory memory having instructions stored thereon that, when executed by the one or more processors, cause the controller to perform a set of operations corresponding to at least a portion of the techniques of the present application. The one or more processors could be either a single processor or two or more processors operating in a parallel or distributed architecture.
It should also be understood that the mixing and matching of features, elements, methodologies and/or functions between various examples may be expressly contemplated herein so that one skilled in the art would appreciate from the present teachings that features, elements and/or functions of one example may be incorporated into another example as appropriate, unless described otherwise above.
