Hybrid Vehicle SOC Control for PM Emission Reduction
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Solution Overview
Problem
Hybrid vehicles face challenges in suppressing particulate matter (PM) emissions and maintaining drivability, especially during cold starts when the engine is low on temperature, as engine torque suppression control relies on battery state of charge, leading to limited duration and reduced output, which can result in insufficient driving force and increased PM emissions.
Innovation Solution
A control system that raises the state of charge (SOC) of the power storage device before stopping the vehicle, using electric driving devices to extend the duration of engine torque suppression control, by charging the battery and adjusting the SOC range based on particulate matter deposition, outside temperature, and travel conditions to optimize PM emission reduction and drivability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If engine torque suppression control is performed during cold start to reduce PM emissions, then PM emission is reduced, but the duration of suppression is limited due to low battery state of charge
Solution Approach 1:
The system performs preliminary charging of the battery during warm operating conditions before cold start occurs. By raising the SOC control range when the vehicle is warm and the engine is operating normally, sufficient electric power is stored in advance to enable extended duration of torque suppression control during subsequent cold starts, thereby resolving the contradiction between reducing PM emissions and maintaining sufficient suppression duration.
2Ease of operation
If engine output is increased before engine warm-up to secure driving force, then drivability is improved, but PM emission increases
Solution Approach 1:
The system dynamically adjusts the SOC control range based on real-time operating conditions including filter deposition amount, outside temperature, and vehicle speed. When conditions favor low emission operation (sufficient battery charge, moderate driving conditions), the system maintains higher SOC control ranges to enable torque suppression. When driving demand is high, the system flexibly adjusts parameters to balance drivability and emission reduction, resolving the contradiction between maintaining ease of operation and reducing harmful emissions.
3Duration of action of moving object
If SOC control range is raised to extend suppression control duration, then suppression duration is extended, but fuel efficiency deteriorates
Solution Approach 1:
The system changes multiple parameters dynamically including SOC control range, lower limit SOC value, and upper limit SOC value based on operating conditions. The control range is raised selectively based on filter deposition amount, outside temperature, and vehicle speed conditions. By adjusting these parameters adaptively rather than maintaining a constantly high SOC control range, the system extends suppression control duration when needed while minimizing fuel efficiency deterioration during normal operation.
Data Source
AI summary
An ECU is configured to control an SOC control center of a battery and perform an engine torque suppression control. The engine torque suppression control is a control that suppresses output of an engine during a predetermined period of time after starting a system, and causes motor generators to output torque supplementing the suppressed output of the engine. When a deposition amount of PM on a filter exceeds a first specified amount, the ECU raises the SOC control center by controlling the motor generators before stopping the system as compared to when the deposition amount of PM is lower than a specified amount, and performs the engine torque suppression control at a next start after stopping the system.