EHC Temperature Control via Dual Estimation
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Solution Overview
Problem
In hybrid vehicles, the catalyst device's temperature control is inaccurate due to the absence of exhaust gas when the internal combustion engine is stopped, leading to insufficient purification and increased emissions of pollutants like carbon monoxide and hydrocarbons, and the challenge of ensuring electrical insulation and avoiding damage from thermal stress when placing temperature sensors within the exhaust pipe.
Innovation Solution
A vehicle system that includes a temperature sensor and a control device performing two estimation processes to accurately control the catalyst device's temperature, with the first process using sensor output before engine start and the second process using exhaust gas temperature after engine start, ensuring precise electric power application to maintain the catalyst at a target temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature sensor is disposed in the exhaust pipe near the EHC to measure the EHC's temperature, then the temperature measurement accuracy is improved, but electrical insulation cannot be ensured and the sensor may be damaged by thermal stress
Solution Approach 1:
The patent uses exhaust gas temperature as an intermediary parameter to indirectly estimate the EHC temperature. Instead of directly measuring EHC temperature with a sensor in contact with the catalyst carrier, the system measures the temperature of the exhaust gas passing through the EHC, which correlates with the EHC temperature. This intermediary approach avoids direct contact between the temperature sensor and the EHC, thereby ensuring electrical insulation and avoiding thermal stress damage while maintaining acceptable temperature estimation accuracy.
2Reliability
If the internal combustion engine is frequently started to ensure catalyst temperature control, then the catalyst can maintain purification effectiveness, but pollutant emissions increase due to engine warm-up cycles
Solution Approach 1:
The patent applies preliminary heating action by using the EHC to heat the catalyst before the main catalyst activation is needed. The control device energizes the EHC in advance to raise the catalyst temperature to the activation threshold, ensuring the catalyst is ready for purification when the engine starts. This preliminary action reduces the need for frequent engine starts solely for catalyst warming, thereby reducing pollutant emissions from engine warm-up cycles while maintaining catalyst effectiveness.
3Duration of action of moving object
If electric power is applied to energize the EHC to heat the catalyst, then the catalyst activation time is reduced, but overenergization may occur causing excessive temperature and potential damage
Solution Approach 1:
The patent implements feedback control by continuously monitoring exhaust gas temperature and using it to estimate EHC temperature. The control device adjusts the electric power supplied to the EHC based on this temperature estimation, reducing or stopping power supply when the catalyst approaches the target temperature. This feedback mechanism prevents overenergization and excessive temperature rise while maintaining fast catalyst activation, thereby resolving the contradiction between activation speed and temperature control safety.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for more accurate temperature control of the catalyst device, enhancing its purification efficiency and reducing pollutant emissions by minimizing overenergization and thermal stress risks.
Implementation Method 1
a temperature sensor for sensing a temperature of the catalyst device
Implementation Method 2
a catalyst device electrically heatably configured for purifying exhaust gas
Data Source
AI summary
A vehicle includes: an engine; an EHC (electrically heated catalyst) electrically heated for purifying exhaust gas of the engine; a temperature sensor for sensing the temperature of the EHC; and an ECU that controls the EHC in temperature. The ECU performs a first estimation process and a second estimation process to estimate the temperature of the EHC and accordingly controls electric power applied to energize the EHC, the first estimation process being performed to estimate the temperature of the EHC based on an output of the temperature sensor before the engine starts, the second estimation process being performed to estimate the temperature of the EHC based on the temperature of the exhaust gas emitted by the engine after the engine is started.