EV Powertrain Oil Cooling with Multi-Pump Heat Exchanger Layout
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Solution Overview
Problem
The miniaturization of electric vehicle powertrains and increased rotational speeds lead to higher heat density and reduced cooling effectiveness due to increased flow resistance and decreased flow rate of cooling oil, limiting the cooling performance of existing oil-cooled powertrain systems.
Innovation Solution
A powertrain cooling system incorporating multiple oil pumps, including mechanical and electronic pumps, that work in conjunction with a heat exchanger to ensure a sufficient flow rate of cooling oil, with the mechanical pump driven by the motor or reducer and the electronic pump providing additional cooling when needed, and a dry oil pan design for the reducer to reduce churning losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the powertrain is miniaturized and rotational speed is increased to achieve higher power density, then power output per size is improved, but heat density increases and cooling effectiveness deteriorates due to increased flow resistance and decreased flow rate of cooling oil
Solution Approach 1:
The patent divides the cooling system into multiple independent oil pumps (at least two) that work in parallel to deliver cooling oil to different regions of the powertrain. This segmentation allows each pump to handle a portion of the total cooling demand, enabling sufficient flow rate even with miniaturized oil passages that have high flow resistance.
Solution Approach 2:
The patent combines multiple oil pumps and multiple heat exchangers into an integrated cooling system. The oil pumps are configured to deliver cooling oil to both the motor and reducer through a unified oil passage system, while heat exchangers are positioned to cool the oil at different locations, creating a merged cooling network that efficiently handles heat from multiple sources.
2Volume of moving object
If the oil passage size is reduced due to motor miniaturization, then device size is decreased, but flow resistance increases and flow rate decreases, thereby reducing cooling effect
Solution Approach 1:
The cooling system is segmented into multiple parallel oil delivery paths with multiple oil pumps. This allows the use of smaller, miniaturized oil passages in each path while maintaining adequate total flow rate through the combined output of multiple pumps, effectively resolving the conflict between small passage size and sufficient cooling flow.
Solution Approach 2:
The patent introduces multiple heat exchangers as intermediary cooling devices positioned at different locations in the oil passage system. These heat exchangers provide intermediate cooling of the oil, compensating for the reduced cooling capacity caused by high flow resistance in miniaturized oil passages and maintaining overall cooling effectiveness.
3Device complexity
If a single electric oil pump is used to circulate cooling oil, then device complexity is reduced, but insufficient cooling oil flow rate is delivered to meet cooling demands of miniaturized powertrain
Solution Approach 1:
The single oil pump is segmented into multiple parallel oil pumps (at least two). Each pump delivers cooling oil to the heat exchangers and subsequently to the motor and reducer. This segmentation increases the total cooling oil flow rate capability while keeping each individual pump relatively simple, balancing complexity and performance.
Solution Approach 2:
The multiple oil pumps are configured with multi-functionality to serve different cooling zones. The pumps can deliver cooling oil to both the motor and reducer through the same oil passage system, and work in conjunction with multiple heat exchangers positioned at different locations, providing universal cooling coverage for the entire powertrain system.
4Temperature
If cooling oil flow rate is increased to improve cooling effect, then temperature control is improved, but energy loss due to oil churning increases
Solution Approach 1:
The patent positions heat exchangers at different locations in the oil passage system to provide preliminary cooling of the oil before it reaches certain components. This preliminary action reduces the temperature and viscosity of the cooling oil, thereby reducing oil churning losses while maintaining adequate cooling flow rate for effective temperature control.
Solution Approach 2:
Multiple heat exchangers act as intermediary cooling devices that progressively cool the oil at different stages of circulation. This intermediary cooling reduces the oil temperature and viscosity, decreasing energy loss from churning while ensuring sufficient cooling capacity is delivered to the motor and reducer.
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 enhances the cooling effectiveness of the powertrain by maintaining adequate flow rates and reducing oil churning losses, thereby improving heat dissipation and transmission efficiency, even at high rotational speeds.
Implementation Method 1
The heat exchanger is configured to cool the cooling oil sucked by the at least two oil pumps
Implementation Method 2
The mechanical oil pump is driven by a rotating component of the powertrain... the mechanical oil pump correspondingly increases a flow rate of cooling oil delivered to the powertrain
Data Source
AI summary
A powertrain includes a motor, a reducer, an oil pan, and a cooling system. The cooling system includes at least one heat exchanger and at least two oil pumps. The at least two oil pumps are configured to deliver, to the heat exchanger, cooling oil sucked from the oil pan. The heat exchanger is configured to cool the cooling oil sucked by the at least two oil pumps. An oil outlet port of the heat exchanger is connected to an oil passage in the motor and an oil passage in the reducer, so that a part of the cooling oil cools the motor through the oil passage in the motor, and another part of the cooling oil cools the reducer through the oil passage in the reducer. The embodiments can improve a cooling effect of the cooling system for the powertrain.