Coaxial Electric Drive Cooling Cavity for Shaft Lubrication
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Solution Overview
Problem
Existing electric drives with coaxial arrangements face challenges in smoothly introducing lubricating or cooling fluids into the small gap between the rotor shaft and the output shaft, affecting efficient cooling and lubrication.
Innovation Solution
The electric drive design includes a support element surrounding the rotor and output shafts, with sealing elements forming a cavity that fluidically communicates with the flow space between the shafts, and a through-hole connecting this cavity to the environment, allowing for efficient fluid introduction and circulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If sealing elements are arranged to form a cavity between rotor shaft and output shaft, then cooling efficiency is improved, but device complexity increases
Solution Approach 1:
The cavity is formed by nesting sealing elements between the rotor shaft and output shaft, utilizing the existing coaxial arrangement to create a cooling chamber without adding external structures. The first and second sealing elements are positioned at different axial locations to define the cavity space, effectively using the gap between concentric shafts for cooling purposes.
Solution Approach 2:
The support element serves multiple functions: it provides structural support for the sealing elements, defines the cavity geometry, and acts as a mounting structure for the bearings. This multi-functionality reduces the need for separate components, thereby improving cooling efficiency without proportionally increasing device complexity.
2Ease of operation
If a through-hole is formed in the support element to connect cavity to environment, then fluid introduction is improved, but manufacturing precision requirements increase
Solution Approach 1:
The through-hole is extracted directly from the support element as an integrated feature, allowing cooling fluid to be introduced from the external environment through the support element into the cavity. This extraction approach simplifies fluid introduction by providing a direct pathway, while the hole can be manufactured using standard drilling or machining operations on the support element.
3Loss of time
If sealing elements are positioned between bearings axially, then cooling circuit establishment is accelerated, but pressure on sealing elements increases
Solution Approach 1:
The sealing elements are pre-positioned between the bearings in the axial direction, establishing the cooling circuit pathway before the system operates. This preliminary positioning ensures that the cooling fluid can immediately flow through the cavity when introduced, reducing the time to establish the cooling circuit. The bearings provide natural support points for the sealing elements, distributing the pressure loads.
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 design enables quick establishment of a lubrication/cooling circuit, reduces pressure on shaft sealing elements, minimizes air mixing and cavitation erosion risks, and improves noise, vibration, and harshness (NVH) behavior.
Implementation Method 1
Cooling a rotor typically involves inducing a lubricating fluid/cooling fluid into a gap between the rotor shaft and the output shaft
Implementation Method 2
a first sealing element is provided between the support element and the rotor shaft, and a second sealing element is provided between the support element and the part of the output shaft extending beyond the rotor shaft
Data Source
Figure 1
AI summary
The present invention provides an electric drive. It comprises an electric motor module and a gear mechanism module connected to the electric motor module. The electric motor module includes a hollow rotor shaft attached to a rotor, which transmits power to the gear mechanism module. The gear mechanism module includes an output shaft arranged coaxially within the rotor shaft. The rotor shaft and the output shaft extend along an axial direction within the electric motor module, and a flow space is defined between the rotor shaft and the output shaft. At an end of the electric motor module facing away from the gear mechanism module in the axial direction, the output shaft extends beyond the rotor shaft, and a support element is provided that surrounds the rotor shaft and the output shaft.A first sealing element is provided between the support element and the rotor shaft, and a second sealing element is provided between the support element and the portion of the output shaft extending beyond the rotor shaft, such that a cavity communicating fluidically with the flow chamber is formed between the rotor shaft, the output shaft, and the support element. A through-hole is formed in the support element, connecting the cavity to the surrounding environment.