BEV Thermal Management Valve Control for Heat Switching Stress
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Solution Overview
Problem
Existing thermal management systems for battery electric vehicles face frequent switching between heat absorption and release operations, leading to severe temperature changes and potential damage when using a single outside air heat exchanger for both heating and cooling the motor.
Innovation Solution
A thermal management system with a switching valve that controls the flow of a heat medium between an outside air heat exchanger, a motor cooler, and a heater, allowing the system to hold the valve in a second position during high motor loads to prevent frequent switching, thereby reducing thermal stress on components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single outside air heat exchanger is used for both heating (absorption of heat from outside air) and cooling of the motor (release of heat to outside air), then system efficiency is improved and device complexity is reduced, but frequent switching between operations causes severe temperature changes that may damage the system
Solution Approach 1:
The controller predicts future motor load based on current operating conditions and proactively switches the three-way valve to the cooling position (second position) in advance when high load is anticipated. This preliminary action prevents frequent switching by maintaining the valve in the cooling position during predicted high-load periods, even if the motor temperature temporarily drops below the switching threshold.
Solution Approach 2:
The control system continuously monitors motor temperature, motor load, and valve position, and uses this feedback to make intelligent switching decisions. The controller compares actual motor temperature with threshold values and adjusts valve position accordingly, while also incorporating load prediction to optimize switching timing and reduce frequency of operations.
2Measurement precision
If the switching valve frequently switches between first position (heating mode) and second position (cooling mode), then motor temperature control precision is improved, but the frequency of switching increases causing thermal stress and potential damage
Solution Approach 1:
The controller predicts future motor load based on current operating conditions and proactively switches the three-way valve to the cooling position (second position) in advance when high load is anticipated. This preliminary action prevents frequent switching by maintaining the valve in the cooling position during predicted high-load periods, even if the motor temperature temporarily drops below the switching threshold.
Solution Approach 2:
The controller uses motor load prediction to occasionally maintain the valve in the cooling position even when motor temperature is already below the lower threshold, applying excessive cooling action preemptively. This approach trades slight over-cooling for preventing frequent switching cycles and reducing thermal stress on the heat exchanger.
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 reduces the frequency of switching between heat release and absorption operations, maintaining motor temperatures within safe ranges and extending the lifespan of system components by managing heat transfer effectively.
Implementation Method 1
an outside air heat exchanger configured to exchange heat between the heat medium and an outside air
Implementation Method 2
a motor cooler configured to cool the motor with a heat medium
Implementation Method 3
a heater configured to warm a vehicle cabin using heat of the heat medium
Data Source
AI summary
A thermal management system includes a circulation channel that connects a motor cooler, outside air heat exchanger, and a heater, a switching valve, and a controller. In a heating mode of operating the heater, the controller sets the switching valve in the first valve position when the motor temperature is lower than a motor temperature threshold value, and sets the switching valve in the second valve position when the motor temperature is higher than the motor temperature threshold value. When a load or a load predicted value of the motor exceeds a load threshold value, the controller holds the switching valve in the second valve position during a predetermined holding time.