Universal Drive Gear Layout Without CV Joints for In-Wheel EVs
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Solution Overview
Problem
In-wheel motor driving devices face durability issues and ride comfort problems due to increased unsprung mass, and they require constant velocity joints for power transmission, which limits space utilization and operational stability.
Innovation Solution
A universal driving device with a ring gear, sun gear, and split gear configuration that allows adjustable inter-shaft distance, using multiple links and pinions to split and transmit power, enabling continuous power transmission without constant velocity joints and allowing for a lightweight motor with high gear ratio, thus improving durability and ride comfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an in-wheel motor is installed directly on the driving wheel, then power transmission is simplified, but motor durability decreases and ride comfort deteriorates due to increased unsprung mass
Solution Approach 1:
The power transmission system is segmented into separate components: the motor is mounted on the vehicle body while the drive wheels are connected through a differential mechanism. This separation divides the heavy motor mass from the unsprung mass of the wheel assembly, improving both durability and ride comfort while maintaining functional integration through the differential gear train
Solution Approach 2:
A differential mechanism serves as an intermediary between the motor and the drive wheels. This intermediate transmission system allows the motor to be positioned separately from the wheel while still delivering power, acting as a mediator that resolves the conflict between simplified power transmission and reduced unsprung mass
2Device complexity
If an in-wheel motor is installed directly on the driving wheel, then power transmission is simplified, but ride comfort deteriorates due to increased unsprung mass
Solution Approach 1:
The power transmission system is segmented into separate components: the motor is mounted on the vehicle body while the drive wheels are connected through a differential mechanism. This separation divides the heavy motor mass from the unsprung mass of the wheel assembly, improving both durability and ride comfort while maintaining functional integration through the differential gear train
Solution Approach 2:
The motor is positioned in a different spatial dimension (mounted on the vehicle body rather than on the wheel), transferring mass from the unsprung to sprung portion of the vehicle. This dimensional repositioning reduces unsprung mass without compromising power delivery capability
3Reliability
If a constant velocity joint is used for power transmission, then continuous power transmission is achieved, but space utilization between wheels deteriorates
Solution Approach 1:
Instead of using a constant velocity joint to accommodate angular movement, the patent inverts the approach by using a differential mechanism with a specific gear arrangement that naturally accommodates the motion requirements. The differential case and pinion configuration provides continuous power transmission while occupying less space than conventional CV joint arrangements
4Speed
If a motor with high speed output is used, then power delivery is improved, but torque requirements for vehicle operation are not met
Solution Approach 1:
A differential mechanism serves as an intermediary between the motor and the drive wheels. This intermediate transmission system allows the motor to be positioned separately from the wheel while still delivering power, acting as a mediator that resolves the conflict between simplified power transmission and reduced unsprung mass
Solution Approach 2:
The differential gear train changes the speed-torque parameters through its gear ratio. The high-speed output from the motor is converted to lower speed with higher torque at the drive wheels, transforming the motor's output characteristics to match vehicle operational requirements
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 universal driving device enhances uphill and acceleration performance, improves motor durability, reduces unsprung mass, and optimizes space utilization between wheels by decoupling the power source from the wheel, ensuring stable and efficient power transmission.
Implementation Method 1
a ring gear, a sun gear installed such that the shaft distance between a rotation shaft of the sun gear and a rotation shaft of the ring gear is changeable, and a split gear disposed between the sun gear and the ring gear
Data Source
AI summary
A universal driving device includes a ring gear, a sun gear installed such that the shaft distance between a rotation shaft of the sun gear and a rotation shaft of the ring gear is changeable, and a split gear disposed between the sun gear and the ring gear, and configured to split power, received from the sun gear through one path, into multiple paths and transmit the power to the ring gear.