Hybrid Vehicle Cold Start Emissions Control via Electric Torque Assist
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Solution Overview
Problem
Hybrid vehicles face challenges in reducing cold start emissions due to catalytic converters not reaching optimal operating temperature during engine startup, leading to inefficient emission control and potential engine stalling from retarding ignition timing.
Innovation Solution
A control module modifies engine combustion parameters to increase exhaust gas temperature and reduce emissions content, supplemented by an electric machine to maintain crankshaft rotation, ensuring the engine power level is insufficient to maintain speed, thereby preventing stalling and enhancing catalytic converter warm-up.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If retarding ignition timing and increasing engine idle speed are used to increase exhaust temperature and mass flow rate, then cold start emissions are reduced, but engine efficiency is lowered and engine stalling may occur
Solution Approach 1:
The electric machine acts as an intermediary to compensate for the power loss caused by retarding ignition timing. It provides supplemental torque to the crankshaft, ensuring the engine does not stall while allowing the combustion parameters to be optimized for emissions reduction. This mediator enables the system to achieve emissions control without sacrificing engine reliability.
Solution Approach 2:
The system changes the ignition timing parameter to a retarded position during cold start conditions, which increases exhaust temperature and promotes catalytic converter warm-up. Simultaneously, the electric machine adjusts its torque output parameter to compensate for the power loss, maintaining stable engine operation despite the suboptimal combustion timing.
2Temperature
If retarding ignition timing is used to increase exhaust temperature, then catalytic converter warm-up is accelerated, but engine efficiency is reduced
Solution Approach 1:
The electric machine serves as a compensatory intermediary that makes up for the energy efficiency loss. By providing electric torque assistance, it allows the engine to operate with retarded ignition timing (which improves exhaust temperature) without suffering the full penalty of reduced thermal efficiency, as the electric machine compensates for the power deficit.
3Object-generated harmful factors
If increasing engine idle speed is used to increase mass flow rate, then cold start emissions are reduced, but engine efficiency is lowered
Solution Approach 1:
The electric machine acts as a compensatory device that allows the engine to run at higher idle speeds for emissions control without proportionally increasing energy consumption. The electric machine can assist in maintaining crankshaft rotation, reducing the burden on the engine to produce all necessary power internally, thereby decoupling the relationship between idle speed and overall energy use.
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 significantly reduces cold start emissions by increasing exhaust gas temperature and decreasing emissions content, while preventing engine stalling through electric machine assistance, thereby improving catalytic converter efficiency and vehicle operation.
Implementation Method 1
an electric machine of the hybrid vehicle supplements the engine power level to maintain crankshaft rotation at a desired speed
Implementation Method 2
modifying combustion parameters of an engine to provide an engine power level insufficient to maintain crankshaft rotation, the modifying including increasing a temperature of an exhaust gas
Data Source
AI summary
A method comprises modifying combustion parameters of an engine of a hybrid vehicle to provide an engine power level insufficient to maintain crankshaft rotation at a desired speed including increasing a temperature of an exhaust gas and reducing an emissions content of the exhaust gas; and supplementing the engine power level with an electric machine of the hybrid vehicle to maintain crankshaft rotation at the desired speed. A control module comprises a cold start combustion control module that modifies combustion parameters of an engine of a hybrid vehicle to provide an engine power level insufficient to maintain crankshaft rotation at a desired speed, wherein the modifying includes increasing a temperature of an exhaust gas, and reducing an emissions content of the exhaust gas; and an electric machine control module that supplements the engine power level using an electric machine of the hybrid vehicle to maintain crankshaft rotation at the desired speed.