Electric Drive Assembly Cooling with Labyrinth Oil Reservoir
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Solution Overview
Problem
Existing drive arrangements for motor vehicles face challenges with thermal coupling between water-based and oil-based cooling systems, leading to inefficient heat dissipation, risk of air gap oiling between the rotor and stator, and potential gearbox compartment drying due to complex cable routing and space-intensive heat exchangers.
Innovation Solution
A labyrinth space is introduced below the engine compartment to act as part of the oil reservoir, allowing oil to interact thermally with the cooling water jacket and ambient air, eliminating the need for an engine oil sump and reducing the risk of air gap oiling, while using cooling fins for enhanced heat dissipation without a heat exchanger.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a heat exchanger is used to thermally couple the water-based and oil-based cooling systems, then heat dissipation is achieved, but the device complexity increases and space is consumed
Solution Approach 1:
The patent merges the water-based cooling system and oil-based cooling system into a single integrated thermal management system. The oil reservoir serves dual purposes: as lubrication reservoir and as heat exchange medium that thermally couples with the water cooling system through the housing wall, eliminating the need for a separate heat exchanger component.
Solution Approach 2:
The oil reservoir is designed to perform multiple functions simultaneously: storing lubrication oil, acting as a heat sink for the electric machine, and serving as part of the thermal coupling system between water-based and oil-based cooling. This multi-functionality reduces overall system complexity and component count.
2Temperature
If a heat exchanger is used to thermally couple the water-based and oil-based cooling systems, then heat dissipation is achieved, but the area occupied increases
Solution Approach 1:
The housing structure is merged with the thermal coupling function. The housing wall acts as the thermal interface between the water cooling jacket and the oil reservoir, eliminating the need for a separate heat exchanger component that would occupy additional space.
Solution Approach 2:
The oil reservoir is positioned to nest within the available space in the drive assembly, with the thermal coupling interface integrated into the housing structure. This nested arrangement allows the oil reservoir to occupy space that would otherwise be unused, rather than adding to the overall footprint.
3Temperature
If oil is supplied to the electric machine for cooling, then cooling efficiency is improved, but the risk of air gap oiling increases
Solution Approach 1:
The system incorporates feedback control through the thermal coupling mechanism. The oil temperature in the reservoir is passively regulated through thermal exchange with the water cooling system, preventing overheating that could lead to oil vaporization and air gap contamination. The drain opening provides a safety mechanism to remove excess oil that may have entered the air gap.
Solution Approach 2:
The housing wall acts as an intermediary thermal interface between the water cooling system and the oil reservoir. This indirect thermal coupling allows heat transfer without direct fluid contact, and the drain opening serves as an intermediary escape route for any oil that might contaminate the air gap, preventing it from reaching the electric machine.
4Object-affected harmful factors
If the oil reservoir is designed as an oil chamber below the engine compartment, then the risk of air gap oiling is reduced, but thermal coupling efficiency must be improved
Solution Approach 1:
The housing wall at the thermal coupling interface is designed with local quality enhancements - specifically, it serves as a dedicated heat transfer path between the water cooling jacket and the oil reservoir. The drain opening is strategically positioned at a specific location to effectively remove oil while maintaining thermal coupling efficiency at the interface.
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 configuration improves thermal coupling efficiency, reduces the risk of air gap oiling, and provides effective heat dissipation without the need for a space-intensive heat exchanger or complex cable routing, ensuring reliable cooling and lubrication of the electrical machine.
Implementation Method 1
the casing wall of the engine compartment has a cooling water jacket surrounding the stator along its circumference for additional cooling of the electric machine
Implementation Method 2
the upper side of which is thermally coupled to the cooling water jacket
Implementation Method 3
allowing oil to interact thermally with the cooling water jacket and ambient air
Implementation Method 4
using cooling fins for enhanced heat dissipation
Data Source
Figure 1
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Figure 3
AI summary
Motor vehicle drive, comprising: - a housing (12) with an engine compartment (14) and an adjacent transmission compartment (16) delimited by an inner end wall (18), each delimited by the inner end wall (18), an associated outer end wall (20, 22) and a shell wall (24, 26) extending axially between the inner and the associated outer end wall (18; 20, 22); - an electric machine (28) arranged in the engine compartment (14) with a stator (30) fixed to the housing and a rotor (32) with a rotor shaft (34) passing through the inner end wall (18) and rotatably mounted in the engine compartment (14); and - a transmission (38) arranged in the transmission compartment (16) with an input pinion (40) fixed on the rotor shaft (34), which here acts as a drive shaft (36), and an output gear (42) connectable to or connected with an output; and - a oil reservoir,Oil can be conveyed from the oil via an oil supply system to the rotor shaft (34) for cooling the electric machine (28) and via an oil discharge system from the rotor shaft back into the oil reservoir, wherein the shell wall (24) of the motor compartment (14) has a cooling water jacket (56) surrounding the stator (30) along its circumference for additional cooling of the electric machine (28), wherein at least part of the oil reservoir is designed as a labyrinth chamber (58) arranged below the motor compartment (14), the upper side of which is thermally coupled to the cooling water jacket (56).