Integrated Oil Cooling Circuit for Brake Heat Load Reduction
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Solution Overview
Problem
Existing machine cooling systems in electric machines, particularly those using hydraulic oil circuits, are inefficient and produce excessive heat loads, especially during brake charge events.
Innovation Solution
A cooling system that eliminates the dedicated hydraulic oil cooling pump by using a combined hydraulic oil cooling (HOC) and axle oil cooling (AOC) system, with a flow control device to route oil based on conditions, and a thermal bypass valve to bypass the HOC during cold temperatures to warm the axles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a dedicated hydraulic oil cooling pump is used, then hydraulic oil can be cooled, but excessive heat load is produced and energy efficiency deteriorates
Solution Approach 1:
The patent combines the hydraulic oil cooling function with the axle oil cooling function into a single integrated cooling circuit. The hydraulic oil cooler and axle oil cooler share common components including the cooling pump, heat exchanger, and control valves, allowing both cooling needs to be met while eliminating the separate dedicated cooling pump and reducing overall energy consumption.
Solution Approach 2:
The cooling system is designed to perform multiple functions simultaneously - cooling hydraulic oil and cooling axle oil through a single system. The flow control device enables the system to dynamically allocate cooling capacity between the two functions based on actual thermal demands, making the cooling system universal and adaptable to different operating conditions.
2Temperature
If hydraulic oil is cooled during brake charge events, then oil temperature is reduced, but excessive heat load is generated
Solution Approach 1:
The patent converts the thermal energy that would otherwise be waste heat into a useful resource. During brake charge events, the axle oil cooler absorbs excess heat from the hydraulic oil, and this thermal energy is then transferred to the axle oil that needs heating, particularly during cold temperature operations. This converts harmful heat load into beneficial thermal energy for warming axle oil.
Solution Approach 2:
The system dynamically changes the thermal parameters by using the flow control device to redirect hydraulic oil flow between the hydraulic oil cooler and axle oil cooler based on temperature conditions. When axle oil needs warming, the system allows hot hydraulic oil to pass through the axle oil cooler, reversing the typical cooling function and using it for heating instead.
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 reduces heat load and improves cold temperature performance by strategically routing warm hydraulic fluid to the axle oil cooling system, enhancing the operational efficiency of electric machines.
Implementation Method 1
A cooling circuit can include a hydraulic oil cooling (HOC) element and an axle oil cooling (AOC) element connected in series
Data Source
AI summary
A cooling system can include a hydraulic oil tank. The cooling system can further include a return valve connected to the hydraulic oil tank to supply flow to a cooling circuit. The cooling circuit can include a hydraulic oil cooling (HOC) element and an axle oil cooling (AOC) element connected in series. The cooling system can include a flow control device to route oil away from the HOC and toward the AOC based on an oil condition or a system condition.