Electric Drive Hydraulic Circuit With Bi-Directional Pump Switching
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Solution Overview
Problem
Existing electric drive systems face challenges in efficiently combining cooling and lubrication for electric machines and transmissions, with thermal limitations and churning losses affecting performance, particularly under varying operational conditions.
Innovation Solution
A bi-directional pump in a hydraulic circuit optimizes cooling and lubrication by switching between directions of rotation, supplying fluid to reservoirs or cooling nozzles based on operation conditions, reducing churning losses and enhancing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single hydraulic circuit is used for both cooling and lubrication, then device complexity is reduced, but the ability to optimize cooling and lubrication independently is compromised
Solution Approach 1:
The patent employs a bi-directional pump that can dynamically switch between two rotation directions to serve different functions. When rotating in a first direction, the pump supplies fluid to the reservoir for lubrication; when rotating in a second direction, it supplies fluid to cooling nozzles for cooling. This dynamic reconfiguration allows a single pump to perform multiple functions that would traditionally require separate systems, thereby reducing device complexity while maintaining the ability to optimize cooling and lubrication independently based on operational requirements.
2Temperature
If fluid is supplied to cooling nozzles during high speed operation, then cooling efficiency is improved, but churning losses increase
Solution Approach 1:
The control system dynamically adjusts the pump's rotation direction based on operational conditions. During high speed operation, the pump rotates in the first direction to supply fluid to the reservoir, enabling passive splash lubrication without active cooling, thereby avoiding churning losses. During low speed operation or high thermal load conditions, the pump rotates in the second direction to supply fluid to cooling nozzles for active cooling. This dynamic switching allows the system to optimize cooling efficiency only when necessary, while minimizing energy losses during high speed operation.
3Loss of energy
If fluid level in oil sump is reduced, then churning losses are reduced, but lubrication capability may be compromised
Solution Approach 1:
The patent segments the lubrication function into two parts: a reservoir that stores lubricating fluid and a passive splash lubrication system. The reservoir is positioned to allow gravity-fed lubrication of transmission components, ensuring adequate lubrication capability even when the oil sump fluid level is reduced. This segmentation enables the system to maintain reliable lubrication through the reservoir's controlled fluid supply while minimizing churning losses in the reduced-volume oil sump during high speed operation.
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
The bi-directional pump system effectively manages cooling and lubrication needs, optimizing performance by reducing losses and enhancing torque and cooling efficiency across different speed operations.
Implementation Method 1
a hydraulic circuit for circulating a fluid to cool and lubricate the electric machine and the transmission
Implementation Method 2
supplying fluid to cooling nozzles for cooling the stator end-windings
Implementation Method 3
circulating a fluid to cool and lubricate the electric machine and the transmission
Data Source
AI summary
An electric drive arrangement for a vehicle includes a housing, an electric machine, a transmission, and a hydraulic circuit for circulating a fluid to cool and lubricate the electric machine and the transmission.