Steer-by-Wire Steering Apparatus with Planetary Gear Torque and Rotation Control
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Solution Overview
Problem
The steer by wire system lacks mechanical connection, leading to inadequate feedback of steering information to the driver and requires separate mechanisms for limiting steering wheel rotation and generating reaction torque, compromising space efficiency and increasing costs.
Innovation Solution
A motor-driven power steering apparatus integrates a planetary gear decelerator structure to limit steering wheel rotation and generate reaction torque, using two motors and planetary gear sets to provide torque and variably adjust gear ratios, along with a stopping mechanism to physically limit the steering wheel's rotation angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a steer by wire system is implemented to remove mechanical connection, then fuel efficiency is improved and disturbance reversely input from wheel is removed, but steering information feedback to driver deteriorates and separate mechanisms are required for reaction torque generation and rotation limiting
Solution Approach 1:
The patent combines the reaction torque generation mechanism and the steering wheel rotation limiting mechanism into a single integrated planetary gear system. The planetary gear set simultaneously provides torque multiplication for reaction torque generation and, through its inherent mechanical constraints, limits the rotation range of the steering wheel, thereby reducing device complexity while maintaining the steer-by-wire architecture
Solution Approach 2:
The planetary gear system serves multiple functions: it generates reaction torque through torque multiplication, limits the steering wheel rotation angle through mechanical constraints, and provides steering assistance. This multi-functionality eliminates the need for separate mechanisms, reducing overall system complexity while preserving fuel efficiency benefits
2Reliability
If separate mechanisms are installed for limiting steering wheel rotation and generating reaction torque, then each function is achieved, but space efficiency deteriorates and product costs increase
Solution Approach 1:
The patent merges the rotation limiting function and reaction torque generation function into a single planetary gear assembly. The planetary gears inherently limit rotation through their mechanical constraints while simultaneously providing torque multiplication, achieving both functions within the same spatial envelope and reducing the overall area occupied by the steering system
3Device complexity
If a planetary gear decelerator structure is integrated to limit rotation and generate reaction torque, then space efficiency is improved and device complexity is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The planetary gear system is designed to be self-limiting, where the mechanical constraints of the gear arrangement itself provide the rotation limit without requiring additional external limiting mechanisms. This self-service approach reduces the number of components and interfaces, thereby reducing overall device complexity despite the precision requirements of the gear manufacturing
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 solution enhances steering feel and stability while reducing costs by integrating the MDPS and AFS systems, improving space efficiency and marketability by providing a compact power steering system that effectively limits steering wheel rotation and generates necessary reaction torques.
Implementation Method 1
A first planetary gear set is configured to receive the torque from the first motor and to reduce the torque and output the reduced torque to a steering wheel to generate a reaction torque required for steering. A second planetary gear set is configured to receive the torque from the steering wheel and the second motor, to reduce and output the torque, and to variably output a gear ratio
Data Source
AI summary
A steering apparatus for a steer by wire system includes a first motor and a second motor configured to provide a torque. A first planetary gear set is configured to receive the torque from the first motor and to generate a reaction torque required for steering. A second planetary gear set is configured to receive the torque from the steering wheel and the second motor, and to variably output a gear ratio for an input by the steering wheel depending on a rotation of the second motor. A stopping mechanism is configured to limit a maximum rotation angle of the steering wheel.