Outer Rotor Planetary Gear Layout for Compact High-Torque Drives
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Solution Overview
Problem
Existing electromechanical devices face limitations in achieving high torque while maintaining a compact size due to constraints on magnetic flux density and electric current, leading to inefficiencies and heat management issues, necessitating a combination with gear systems that compromise radial space and mechanical strength.
Innovation Solution
An electromechanical device featuring an outer rotor electric machine with a planetary gear system where the gear ring is attached to the stator, allowing for a shorter axial length and increased radial diameter, enabling greater design freedom and mechanical strength while facilitating various gear ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the electric current is increased to produce higher torque, then the torque output is improved, but the resistive losses and heat generation are worsened
Solution Approach 1:
The planetary gear system acts as an intermediary mechanical transmission mechanism between the electric machine and the output load. By introducing this gear mediation, the electric machine can operate at optimal current levels while the gear system provides the necessary torque multiplication, avoiding the need to excessively increase armature current and thereby reducing resistive losses.
2Force
If the magnetic flux density is increased to produce higher torque, then the torque output is improved, but the efficiency is worsened due to iron saturation
Solution Approach 1:
The planetary gear system serves as a mechanical mediator that enables torque amplification without requiring excessive magnetic flux density. This allows the electric machine to operate within its efficient magnetic operating range while still achieving high output torque through gear multiplication.
3Length of moving object
If the planetary gear is placed inside the rotor cavity to reduce axial length, then the axial compactness is improved, but the radial space for the planetary gear is reduced
Solution Approach 1:
The patent transitions the planetary gear system from an internal arrangement within the rotor cavity to an external arrangement on the rotor periphery. This dimensional repositioning allows the gear components to utilize the radial space outside the rotor, thereby resolving the spatial conflict between axial compactness and radial gear space requirements.
4Area of stationary object
If the radial diameter of the wheel motor unit is increased to accommodate the planetary gear, then the space for gear components is improved, but the overall compactness is worsened
Solution Approach 1:
By relocating the planetary gear system to the external periphery of the rotor rather than embedding it within the rotor cavity, the design utilizes otherwise underutilized radial space. This external positioning strategy allows adequate gear component dimensions without significantly increasing the overall motor volume, as the gear train occupies space that would otherwise be empty peripheral volume.
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 enables the creation of a compact, high-torque electromechanical device with improved mechanical strength and flexibility in gear ratio design, addressing the inefficiencies and space constraints of traditional designs.
Implementation Method 1
an outer rotor electric machine comprising a stator and a rotor
Implementation Method 2
a planetary gear configured to transfer torque between the rotor and the connection shaft, the planetary gear comprising a gear ring, a sun wheel, planet wheels meshing with the gear ring and with the sun wheel
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An electromechanical device (100) comprises a connection shaft (101) for connecting to an external rotating element, an outer rotor electric machine, and a planetary gear configured to transfer torque between a rotor (103) of the outer rotor electric machine and the connection shaft. The planetary gear comprises a gear ring (104), a sun wheel (105), planet wheels (106a, 106b), and a planet carrier (107). The planet wheels are configured to mesh with the gear ring and with the sun wheel, and the planet carrier is configured to support the planet wheels. The gear ring of the planetary gear is attached to a stator (102) of the outer rotor electric machine so that the stator surrounds the gear ring. Thus, the electromechanical device can be short in its axial direction.