Electric Axle Coolant Valve Control for Lower Idling Drag
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Solution Overview
Problem
Existing electric axle arrangements in motor vehicles experience significant drag losses due to the delivery of liquid coolant, which affects the vehicle's range in electric mode.
Innovation Solution
An electric axle arrangement with a drivable axle, an electric machine, a coolant sump, and an elevated tank, where a switchable valve controls coolant delivery to minimize drag losses by preventing coolant return flow during idling, using either a switching unit or a magnetically controlled valve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If liquid coolant is continuously delivered from the coolant sump into the elevated tank, then the electric machine can be cooled effectively, but drag losses increase significantly
Solution Approach 1:
The valve is switched dynamically based on the operating state of the electric machine. When the electric machine is drivingly connected to the axle and requires cooling, the valve opens to allow coolant flow. When the electric machine is not drivingly connected (idling), the valve closes to prevent coolant return flow and eliminate drag losses. This dynamic control resolves the contradiction by providing cooling only when necessary.
Solution Approach 2:
The cooling system uses the existing motion of the axle and electric machine components to deliver coolant from the sump to the elevated tank without requiring additional pumping energy. The system leverages the natural movement already present in the drive train to achieve coolant circulation, reducing energy consumption while maintaining cooling effectiveness.
2Loss of energy
If a switching unit is used to control the valve, then coolant delivery can be optimized to reduce drag losses, but the device complexity increases
Solution Approach 1:
The switching unit serves multiple functions: it controls the driving connection between the electric machine and the axle, and simultaneously controls the coolant valve. By integrating these control functions into a single unit, the patent reduces overall system complexity while achieving the goal of minimizing drag losses through optimized coolant delivery.
3Temperature
If the valve is opened continuously to ensure cooling, then the electric machine remains cooled, but the vehicle range in electric mode is reduced
Solution Approach 1:
The valve operation follows a periodic pattern based on the operating cycles of the electric machine. The valve opens during periods when the electric machine is actively drivingly connected and requires cooling, and closes during periods when the electric machine is idling. This periodic action ensures cooling reliability when needed while minimizing energy consumption to extend vehicle range.
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
Reduces drag losses and enhances vehicle range by optimizing coolant management, achieving improved efficiency and reduced component count with lower costs.
Implementation Method 1
a switchable valve controls coolant delivery to minimize drag losses by preventing coolant return flow during idling
Implementation Method 2
the valve is designed such that it can be switched magnetically
Implementation Method 3
the elevated tank can be fluidically connected to a cooling system for cooling the electric machine
Implementation Method 4
an electric machine, wherein the axle is or can be drivingly connected to the electric machine
Data Source
AI summary
An electric axle arrangement for a drive train of a motor vehicle includes a drivable axle that is or can be drivingly connected to an electric machine, a coolant sump with liquid coolant, and an elevated tank, wherein the liquid coolant is delivered from the coolant sump into the elevated tank via a gearwheel attached to the axle. The elevated tank is connected to a cooling system for cooling the electric machine via a switchable valve. When the valve is closed during an idling operation, the return flow of the coolant into the coolant sump via the cooling system is prevented, and drag losses in the idling operation of the electric machine are reduced, because more coolant collects in the elevated tank and the gearwheel therefore encounters a reduced quantity of coolant in the sump.