In-wheel Motor with Cycloid Decelerator for Compact Packaging
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Solution Overview
Problem
Conventional in-wheel motor systems compromise spatial efficiency and increase unsprung mass, leading to reduced vehicle performance and vulnerability to external impacts due to the need for a decelerator and brake components within the wheel.
Innovation Solution
The in-wheel motor system incorporates a cycloid decelerator with a pair of eccentric bearings, cycloid discs, and a ring gear housing, allowing for a compact design that positions the motor and decelerator inside the wheel, reducing protrusion and enhancing protection from external impacts while minimizing unsprung mass.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the in-wheel motor system includes a decelerator and brake components installed inside the wheel, then the motor can be protected from external impacts, but the spatial efficiency is reduced and unsprung mass is increased
Solution Approach 1:
The cycloid decelerator is nested within the in-wheel motor structure, with the input shaft passing through the motor and the decelerator components arranged concentrically around the motor shaft. This nesting allows both the motor and decelerator to occupy the same spatial envelope, maximizing the use of available space inside the wheel while maintaining motor protection.
Solution Approach 2:
The input shaft is designed to pass through the motor in the axial direction, allowing the decelerator to be arranged in a different spatial dimension (radially around the shaft) rather than requiring additional axial space. This dimensional arrangement optimizes the use of three-dimensional space within the wheel assembly.
2Reliability
If the in-wheel motor system includes a decelerator and brake components installed inside the wheel, then the motor can be protected from external impacts, but the unsprung mass is increased
Solution Approach 1:
The decelerator and brake components are merged into a single integrated assembly with the in-wheel motor, sharing common structural elements such as the housing and mounting points. This consolidation reduces the total weight compared to separate components while maintaining the protective function and deceleration capability.
Solution Approach 2:
The input shaft serves multiple functions: it transmits rotational force from the motor, acts as the input to the decelerator, and provides the mounting axis for the brake disc. This multi-functionality reduces the number of separate components needed, thereby reducing unsprung mass while maintaining motor protection and braking capability.
3Volume of stationary object
If the in-wheel motor protrudes toward the outer side of the wheel to accommodate decelerator and brake components, then the spatial limitation inside the wheel is addressed, but the motor becomes vulnerable to impact with external objects
Solution Approach 1:
The decelerator and brake components are nested within the motor housing and wheel assembly, with all components contained inside the wheel's outer perimeter. This nesting eliminates the need for the motor to protrude outward while providing sufficient space for all necessary components through efficient three-dimensional arrangement.
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 improves spatial efficiency, reduces unsprung mass, enhances vehicle performance by preventing motor damage from external impacts, and simplifies installation, thereby improving design flexibility and safety.
Implementation Method 1
The cycloid decelerator may include a pair of eccentric bearings, a pair of cycloid discs, a ring gear housing, and the output shaft. The pair of eccentric bearings is connected to the input shaft rotating together with the rotor to eccentrically transmit a rotation.
Implementation Method 2
The disc brake may be configured to provide a braking force by pressing the disc.
Data Source
AI summary
An in-wheel motor system capable of maximizing the efficiency in using a wheel space by improving a mounting structure thereof, the in-wheel motor system installed at a wheel of a vehicle to transmit a rotational force including an axle installed at the wheel of the wheel and rotating together with the wheel, an in-wheel motor mounted inside the wheel and provided with a rotor and a stator that are used to generate a rotational force to drive the wheel, the rotor, and the stator disposed to face each other while having an accommodation space thereinbetween, a cycloid decelerator installed at a center of the in-wheel motor, and provided with an output shaft to transmit a rotational force at a reduced speed from the in-wheel motor to the axle and an input shaft that passes through the in-wheel motor and rotates together with the rotor, a disc installed at one end portion of the input shaft that protrudes by passing through the in-wheel motor, and a disc brake configured to provide a braking force by pressing the disc, wherein the in-wheel motor and the cycloid decelerator are disposed in a space formed inside the wheel.