HVAC Airflow Control to Extend ISG Cooling Stop Time
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Solution Overview
Problem
The Idle Stop and Go (ISG) system's engine stop time is reduced due to rapid temperature rise of the evaporator in HVAC systems during cooling mode, leading to increased fuel consumption and emissions, as the compressor stops when the engine is shut off, causing a short cooling operation time.
Innovation Solution
A method for controlling the HVAC system by allowing only indoor air to flow through the system when the engine is stopped, bypassing the heater core, and maintaining a minimum air flow rate to prevent evaporator temperature rise, using a controller to manage the inlet and bypass passages and air blower operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the engine is stopped by the ISG system during cooling mode, then fuel consumption is reduced, but the evaporator temperature rises rapidly causing the engine to restart prematurely
Solution Approach 1:
The system performs preliminary cooling by operating the compressor at high capacity before the engine stop signal is activated. This pre-cools the evaporator to a lower temperature, creating a thermal buffer that delays temperature rise during the engine stop period, thereby extending the engine stop time while maintaining fuel efficiency
Solution Approach 2:
The system dynamically adjusts the compressor capacity based on the engine stop state. When the engine is stopped, the compressor operates at high capacity to actively counteract temperature rise. When the engine is running, the compressor operates at normal capacity. This dynamic adjustment optimizes evaporator temperature control throughout different operational phases
2Temperature
If the compressor operates at high capacity continuously, then the evaporator temperature is maintained, but energy consumption increases
Solution Approach 1:
The compressor operates at high capacity periodically only during the engine stop period when needed to maintain evaporator temperature. During normal engine operation, the compressor returns to standard capacity operation. This periodic high-capacity operation minimizes energy consumption while achieving the temperature control objective
Solution Approach 2:
The controller continuously monitors evaporator temperature and engine stop state, using this feedback to dynamically adjust compressor capacity. The system activates high-capacity compression only when the engine is stopped and evaporator temperature begins to rise, otherwise maintaining normal operation, thereby optimizing energy efficiency
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 extends the engine stop time, improving fuel efficiency and reducing the need for premature engine restarts, while maintaining indoor cooling performance without increasing system costs.
Implementation Method 1
an evaporator... when the HVAC system operates in a cooling mode
Implementation Method 2
an air blower blowing the air into the housing
Data Source
AI summary
A method for controlling a heating, ventilation, and air conditioning (HVAC) system, may include: allowing, by a controller, only the indoor air to be directed into a housing when the HVAC system operates in a cooling mode and an engine is stopped by an Idle Stop and Go (ISG) system; allowing, by the controller, the indoor air directed into the housing to bypass a heater core; and maintaining, by the controller, a flow rate of the air directed into the housing at a minimum flow rate.