In-Wheel Motor Drive Device with Planetary Reduction Gear
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Solution Overview
Problem
Current drive devices for electric vehicles lack sufficient space for battery installation due to the large size of variable-speed motors and differential gears, making it difficult to implement battery-powered systems without overhead wiring.
Innovation Solution
A drive device featuring an in-wheel motor with a reduction gear system that includes a sun gear, planetary gears, and a transmission member, which reduces the rotational speed and transmits it to the drive wheel, allowing for a compact design that omits large motors and differential gears, thereby creating space for battery installation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a large variable-speed motor and differential gear are used to distribute power to left and right axles, then the power transmission capability is improved, but the space occupied on the carriage increases, leaving insufficient space for battery installation
Solution Approach 1:
The patent divides the single large motor into multiple small in-wheel motors, with each motor independently driving one wheel. This segmentation allows the drive system to be distributed across multiple locations, significantly reducing the centralized space requirement on the carriage while maintaining adequate power transmission capability through parallel operation of multiple motors
Solution Approach 2:
The patent transitions from a centralized drive system (large motor + differential gear at one location) to a distributed drive system (multiple in-wheel motors at different wheel locations). This spatial redistribution across multiple dimensions of the vehicle structure reduces the peak space occupation at any single location, creating sufficient battery installation space on the carriage
2Ease of operation
If a large hypoid gear is used to convert rotation direction between the variable-speed motor and the differential gear, then the rotation direction conversion is achieved, but the overall size of the drive device increases
Solution Approach 1:
The patent extracts and eliminates the large hypoid gear and differential gear from the drive system by adopting in-wheel motors that directly drive the wheels. This removal of unnecessary intermediate components significantly reduces the overall size of the drive device while the rotation direction is naturally handled by the motor's direct connection to the wheel, simplifying the power transmission path
Solution Approach 2:
The patent replaces the complex mechanical gear system (hypoid gear + differential gear) with a direct electromagnetic drive system where in-wheel motors directly couple to the wheels. This substitution eliminates the need for mechanical rotation direction conversion components, reducing drive device size while maintaining effective power transmission
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 secure installation of batteries within the vehicle, allowing for battery-powered electric vehicles to operate without overhead wiring, improving space efficiency and extending cruising range.
Implementation Method 1
a first planetary gear that is arranged to be meshed with the sun gear and has a first number of teeth; a fixed ring gear that is meshed with the first planetary gear; a second planetary gear that is coupled to the first planetary gear and has a second number of teeth that is smaller than the first number of teeth; a movable ring gear that is meshed with the second planetary gear
Data Source
AI summary
A drive device for an electric vehicle includes: a motor configured to be in a drive wheel of the electric wheel; and a reduction gear configured to reduce rotational speed of the motor and transmit resultant rotation to the drive wheel; the reduction gear including a sun gear configured to be driven by the motor, a first planetary gear that is configured to mesh with the sun gear and has a first number of teeth, a fixed ring gear that is meshed with the first planetary gear and arranged non-rotatably, a second planetary gear that is coupled to the first planetary gear and has a second number of teeth that is smaller than the first number of teeth, a movable ring gear that is meshed with the second planetary gear and arranged rotatably, and a transmission member configured to transmit rotation of the movable ring gear to the drive wheel.