Vehicle HVAC Air Mix Door Control for Cold-Weather Under-Heating
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Solution Overview
Problem
Modern vehicle HVAC systems often result in under-heating of the cabin during cold outside temperatures due to inaccuracies in calculating the air mix door position, which affects occupant comfort.
Innovation Solution
The HVAC system employs a controller with ambient, evaporator, and coolant temperature sensors to substitute an alternate heater core outlet temperature when outside temperatures are low and engine coolant is warm, ensuring a more accurate air mix door position for proper heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the standard calculation method using predicted heater core outlet temperature is used, then the air mix door position can be controlled, but the cabin becomes under-heated during cold outside temperatures
Solution Approach 1:
The patent changes the temperature parameter used in the calculation from the predicted heater core outlet temperature to the actual measured heater core outlet temperature. This parameter change resolves the contradiction by using real measured data instead of predicted values, ensuring accurate air mix door positioning that prevents cabin under-heating during cold outside temperatures.
2Extent of automation
If the air mix door position is calculated using predicted temperature, then the control system operates automatically, but insufficient heated air is provided to the cabin
Solution Approach 1:
The patent implements feedback by measuring the actual heater core outlet temperature and using this measured value to adjust the air mix door position calculation. This feedback mechanism ensures that the automatic control system receives accurate temperature information, enabling it to position the air mix door correctly and provide sufficient heated air flow to the cabin during cold conditions.
3Ease of operation
If the standard calculation is used for air mix door position, then the system maintains simple operation, but occupant comfort is reduced due to under-heating
Solution Approach 1:
The patent enables the HVAC system to self-adjust by automatically measuring the heater core outlet temperature and using this information to control the air mix door position. This self-service approach maintains operational simplicity for the user while significantly improving heating reliability, as the system automatically compensates for cold outside temperature conditions without requiring manual intervention.
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 solution ensures that the cabin is adequately heated, maintaining occupant comfort by accurately adjusting the air mix door position, even in cold conditions, by using an alternate heater core outlet temperature derived from outside and coolant temperatures.
Implementation Method 1
The conditioned air that is heated is typically provided to the cabin by passing outside air through a heater core
Implementation Method 2
The conditioned air that is cooled is typically provided to the cabin by passing outside air through an evaporator
Data Source
AI summary
A method of controlling a vehicle heating, ventilation, and air conditioning (HVAC) system. Outside or ambient temperature, evaporator temperature, and coolant temperature are measured with sensors. These values, along with a TAO, which is a calculated value of outlet temperature in the vehicle, are sent to a controller. The controller determines a predicted heater core outlet temperature based upon the coolant temperature. Based upon the outside air temperature and coolant temperature, the controller will decide whether to use the previously determined estimated heater core outlet temperature or to substitute an alternate value for the heater core outlet temperature to determine a position for the air mix door. After calculating the air mix door position, the controller signals an air mix door movement device to adjust the air mix door to the required position. Position of the air mix door affects the air temperature inside of the vehicle.