Hybrid Catalyst Light-Off Control via Electric Motor Speed
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Solution Overview
Problem
In hybrid vehicles, the catalyst in the exhaust gas treatment system often fails to reach the light-off temperature within the first 60 seconds of engine operation, leading to inefficient conversion of emissions, particularly when the engine is started with a 'Silent Start' strategy, which prioritizes drivability over emissions performance.
Innovation Solution
A method that transitions the engine's rotational speed and manifold pressure to specific pre-defined ranges using the electric motor, fuels the engine with retarded spark advance to heat the catalyst efficiently while minimizing emissions, and adjusts torque output to achieve optimal catalyst light-off conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the engine is started with a Silent Start strategy (delayed engine start), then drivability is improved, but the catalyst fails to reach light-off temperature within the first 60 seconds, worsening emissions performance
Solution Approach 1:
The system performs preliminary actions by using the electric motor to transition the engine to a predefined rotational speed range and reducing manifold pressure to a predefined pressure range before fueling the engine. This preparation ensures that when the engine is finally fueled, it can rapidly increase torque and heat the catalyst efficiently, resolving the contradiction between delayed engine start and emissions control.
2Temperature
If the engine is fueled immediately at high torque to heat the catalyst quickly, then catalyst light-off temperature is reached faster, but drivability is compromised due to sudden torque application
Solution Approach 1:
The system performs preliminary actions by using the electric motor to transition the engine to a predefined rotational speed range and reducing manifold pressure to a predefined pressure range before fueling the engine. This preparation ensures that when the engine is finally fueled, it can rapidly increase torque and heat the catalyst efficiently, resolving the contradiction between delayed engine start and emissions control.
Solution Approach 2:
The system dynamically adjusts engine operating parameters including rotational speed, manifold pressure, and torque output. The engine control module continuously monitors catalyst temperature and adjusts fueling and torque delivery to maintain optimal heating rate while ensuring smooth torque transition for drivability, allowing the system to adapt to changing conditions rather than following a fixed sequence.
3Productivity
If the engine operates at high torque from the start to maximize heating rate, then catalyst light-off is achieved faster, but emissions are increased during the transient phase
Solution Approach 1:
The system performs preliminary actions by using the electric motor to transition the engine to a predefined rotational speed range and reducing manifold pressure to a predefined pressure range before fueling the engine. This preparation ensures that when the engine is finally fueled, it can rapidly increase torque and heat the catalyst efficiently, resolving the contradiction between delayed engine start and emissions control.
Solution Approach 2:
The system employs feedback control by continuously monitoring catalyst temperature, engine operating parameters, and emissions. The engine control module uses this feedback to adjust fueling rate, air-fuel ratio, and torque delivery in real-time, optimizing the heating rate while minimizing emissions during the transient phase by preventing overly rich combustion conditions.
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 effectively heats the catalyst to the light-off temperature while maintaining drivability and minimizing emissions, ensuring efficient conversion of emissions to H2O and CO2, even during 'Silent Start' scenarios.
Implementation Method 1
The exhaust gas produced from the operation of the engine within the pre-defined speed range, within the catalyst light-off pressure range, and within the catalyst light-off operating torque range heats the catalyst
Data Source
AI summary
A method of warming a catalyst of an exhaust gas treatment system of a hybrid vehicle includes transitioning a rotational speed of an engine to within a pre-defined speed range with an electric motor, and reducing an engine manifold pressure to within a pre-defined pressure range. The engine is fueled after the rotational speed of the engine is within the pre-defined speed range, and the engine manifold pressure is within the pre-defined pressure range. While the engine is being fueled, the engine manifold pressure is increased to within a catalyst light-off pressure range, and the torque output of the engine is increased to within a catalyst light-off operating torque range. The exhaust gas produced from the operation of the engine within the pre-defined speed range, within the catalyst light-off pressure range, and within the catalyst light-off operating torque range heats the catalyst while minimizing emissions.