Dual Axial-Flow Wheel Drive Transmission for Compact Hub Packaging
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Solution Overview
Problem
Conventional wheel drive units for eco-friendly vehicles are large and protrude outside the wheel hub, causing interference with vehicle parts like suspension and braking systems, and in-wheel motor systems without reducers require large-capacity electric motors, leading to high power consumption and reduced driving distance on a single charge.
Innovation Solution
A power transmission device with a compact structure using two axial flow motor structures to reduce the size of the drive motor assembly and the diameter of the ring gear, and transmitting driving force through two pinion gears to reduce stress on each pinion gear and improve durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a conventional wheel drive unit is used, then the power transmission function is achieved, but the size is large and it protrudes outside the wheel hub causing interference with vehicle parts
Solution Approach 1:
The patent applies nesting by placing the motor, planetary gear set, and wheel bearing in a nested arrangement within the wheel hub. The motor is positioned centrally, with the planetary gear set surrounding it, and the wheel bearing integrated into the outer structure, allowing all components to occupy the limited wheel hub space without protruding outside.
Solution Approach 2:
The patent transitions from a conventional linear/powertrain arrangement to a radial/dimensional arrangement within the wheel hub. The planetary gear set is arranged radially around the motor shaft, utilizing the radial dimension of the wheel hub to accommodate multiple components in a compact configuration rather than extending linearly outward.
2Volume of moving object
If an in-wheel motor system with no reducer is used, then the size is reduced, but a large-capacity electric motor is required leading to high power consumption
Solution Approach 1:
The patent introduces a planetary gear set as an intermediary mechanism between the electric motor and the wheel. This gear set provides mechanical advantage, allowing a smaller-capacity motor to generate the required wheel torque by leveraging the gear ratio, thereby reducing power consumption while maintaining compact size.
Solution Approach 2:
The patent replaces a direct-drive electric motor system with a mechanically-assisted system using a planetary gear set. This substitution allows the system to achieve high torque output with a smaller motor by utilizing mechanical gear multiplication rather than relying solely on electric motor capacity.
3Device complexity
If one pinion gear is used to rotate the ring gear, then the structure is simple, but stress is concentrated on one pinion gear lowering durability
Solution Approach 1:
The patent segments the single pinion gear function into multiple pinion gears (typically three) that are distributed around the ring gear. Each pinion gear engages with the ring gear at different positions, dividing the total load and stress across multiple contact points, thereby reducing stress concentration on any single pinion gear and improving overall durability.
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 compact power transmission device effectively reduces the size and stress on components, improving durability and power transmission efficiency while minimizing interference with vehicle parts.
Implementation Method 1
a first axial flow motor disposed in a front portion of the motor housing and rotating a first pinion gear in a first rotation direction, and a second axial flow motor disposed in a rear portion of the motor housing and operably coupled to a second pinion gear to rotate the second pinion gear in a second rotation direction opposite to the first rotation direction
Data Source
AI summary
The power transmission device includes: a drive motor assembly including a motor housing, a first axial flow motor disposed in a front portion of the motor housing and rotating a first pinion gear in a first rotation direction, and a second axial flow motor disposed in a rear portion of the motor housing and operably coupled to a second pinion gear to rotate the second pinion gear in a second rotation direction opposite to the first rotation direction; a drum surrounding the drive motor assembly by including a drum disk portion disposed on one surface in a wheel axial direction and a cylindrical portion extending from an outer diameter end of the drum disk portion in the wheel axial direction; a drum cover coupled to the other surface of the drum in the wheel axial direction, and having a ring gear disposed on its outer diameter and meshed with the first and second pinion gears; and a wheel hub installed with a tire, and coupled to the drum to be rotated together with the drum, wherein the first and second pinion gears are rotated at the same speed.