Vehicle Air Conditioning Evaporator Control for Cooling Capacity Retention
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Solution Overview
Problem
The vehicle air conditioning device experiences a reduction in cooling capacity when the target evaporation temperature is continuously raised, leading to decreased comfort in the vehicle cabin.
Innovation Solution
A control unit that sets a target evaporation temperature in the evaporator, executing a first control to increase the temperature when the coolant temperature is above a certain threshold and a second control to adjust based on cabin cooling load, with the second target evaporation temperature being set only if it exceeds the initial, and reverting to the initial if the coolant temperature drops below another threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the target evaporation temperature is continuously raised to improve radiator heat dissipation, then the condenser load is reduced and driving performance is maintained, but the cooling capacity in the vehicle cabin decreases and comfortability is impaired
Solution Approach 1:
The control unit dynamically switches between first control (raising target evaporation temperature) and second control (maintaining target evaporation temperature) based on real-time comparison between actual evaporation temperature and target evaporation temperature. This dynamic switching prevents continuous raising of the target evaporation temperature while still allowing radiator heat dissipation improvement when conditions are appropriate, thereby resolving the contradiction between temperature management and cooling capacity maintenance.
Solution Approach 2:
The control unit continuously monitors the actual evaporation temperature and compares it with the target evaporation temperature to determine whether to execute first control or second control. This feedback mechanism ensures that the target evaporation temperature is not continuously raised beyond what is necessary for radiator heat dissipation, preventing excessive reduction in cooling capacity while still achieving the heat dissipation benefit.
2Power
If the target evaporation temperature is raised to reduce compressor output, then the condenser load is reduced and heat dissipation capacity is improved, but the cooling capacity in the vehicle cabin is reduced
Solution Approach 1:
The control unit dynamically adjusts the target evaporation temperature strategy based on the difference between actual and target evaporation temperatures. When the actual temperature is sufficiently below the target, first control is executed to raise the target (reducing compressor output). When the actual temperature approaches the target, second control is executed to maintain the target (preserving cooling capacity). This dynamic adjustment resolves the contradiction between compressor output reduction and cooling capacity maintenance.
Solution Approach 2:
The control unit changes the target evaporation temperature parameter based on operating conditions and the relationship between actual and target temperatures. By adjusting this key parameter dynamically rather than continuously raising it, the system achieves compressor output reduction when beneficial while preventing excessive cooling capacity loss, thus resolving the power versus productivity contradiction.
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 prevents a continuous decrease in cooling capacity, maintaining cabin comfort by dynamically managing the target evaporation temperature based on coolant and cabin conditions.
Implementation Method 1
The condenser dissipates heat by condensing a refrigerant
Implementation Method 2
The evaporator absorbs heat by evaporating the refrigerant
Implementation Method 3
a radiator that dissipates heat of a coolant of an engine
Data Source
AI summary
When a temperature of a coolant is a first predetermined temperature or higher, an air conditioner ECU executes a first control that sets a target evaporation temperature higher by a predetermined temperature and the air conditioner ECU executes a second control that changes the target evaporation temperature in accordance with a cooling load inside the vehicle cabin. When the second control is executed after the first control is executed, the air conditioner ECU sets a first target evaporation temperature set by the first control as the target evaporation temperature, and calculates a second target evaporation temperature that is changed by the second control based on the target evaporation temperature immediately before the first control is executed. When the second target evaporation temperature becomes larger than the first target evaporation temperature, the air conditioner ECU sets the second target evaporation temperature as the target evaporation temperature.