Offset Steering Actuator Layout for Reduced Unsprung Mass
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Solution Overview
Problem
Existing automotive steer-by-wire systems face challenges in compactifying the steering actuator while maintaining adequate torque and avoiding interference with vehicle components, leading to reduced layout flexibility and compromised driving stability and comfort.
Innovation Solution
The steering apparatus features an electric motor and speed reducer arranged on a lower arm, with the motor's rotation axis offset from the pivot of the axle housing, allowing for a compact design that avoids interference with vehicle body components and reduces unsprung mass, thereby enhancing layout flexibility and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the steering actuator is installed on the outside end of the lower arm coaxially with the kingpin axis, then the torque output is maximized, but the actuator size and weight increase, causing interference with road-wheel side component parts
Solution Approach 1:
The patent transitions from a coaxial arrangement (one-dimensional alignment) to an offset arrangement where the motor rotation axis is positioned at a distance from the kingpin axis. This dimensional change allows the speed reducer to be integrated between the motor and kingpin, achieving high torque output without increasing the overall actuator footprint, thus avoiding interference with road-wheel side components.
2Force
If the steering actuator is installed on the outside end of the lower arm, then the torque output is maximized, but the unsprung mass increases, deteriorating driving stability and riding comfort
Solution Approach 1:
The patent merges the motor and speed reducer into a compact integrated unit mounted on the lower arm. By combining these components and positioning them with offset axes, the design achieves high torque output while minimizing the overall mass of the steering actuator assembly, thereby reducing unsprung mass and maintaining driving stability and riding comfort.
3Adaptability or versatility
If the steering actuator is mounted on the vehicle body, then the layout flexibility is enhanced, but the tie rod linkage becomes complex and toe changes occur during suspension stroke
Solution Approach 1:
The patent segments the steering system by mounting the actuator directly on the lower arm rather than on the vehicle body. This segmentation allows the steering function to be localized at the wheel end, eliminating the need for complex tie rod linkages and preventing toe changes during suspension stroke, while simultaneously maintaining layout flexibility.
Data Source
AI summary
A steering apparatus includes an axle housing rotatably supporting a wheel hub on which a steered road wheel is installed, and a lower suspension-system control arm adapted to be oscillatingly supported at one end on a vehicle body and having a turning portion provided at the other end for pivotably supporting the axle housing by the turning portion. An electric motor is installed on the lower arm for turning the axle housing by a driving force produced by the motor. A rotation axis of the motor and a pivot of the axle housing are arranged to be offset from each other.