Steering Knuckle Guide Rail Layout for Reduced Scrub Radius
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Solution Overview
Problem
Existing steering devices face challenges in reducing the scrub radius, especially in electric automobiles with in-wheel motors, due to the limitations of ball joints in the joint parts of the upper and lower arms, which hinder the kingpin axis from being closer to the vehicle wheel, affecting steering performance and stability.
Innovation Solution
A steering device with a lower rotation guiding part featuring a guide rail and moving block configuration, allowing the kingpin axis to be embedded within the vehicle wheel, and an imaginary plane perpendicular to the guide rail, enabling adjustment of the kingpin and caster angles for optimal alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ball joints are used for joint parts of upper arm and lower arm, then the structure is simple and easy to manufacture, but the kingpin axis cannot be brought closer to the vehicle wheel, resulting in larger scrub radius
Solution Approach 1:
A guide rail is introduced as an intermediary component between the lower arm and the wheel hub. The guide rail has a specific curved shape that guides the movement of the lower arm, enabling the kingpin axis to be positioned closer to the wheel center while maintaining manufacturability. This intermediary structure resolves the contradiction by providing a mechanical means to achieve precise kingpin axis positioning without requiring complex ball joint modifications.
2Reliability
If the kingpin axis is brought closer to the vehicle wheel to decrease scrub radius, then steering performance is improved, but the kingpin angle and caster angle become difficult to adjust
Solution Approach 1:
The guide rail is designed with adjustable mounting positions and orientations on the lower arm. This dynamic configuration allows the kingpin axis position to be optimized for minimal scrub radius while still permitting adjustment of the kingpin angle and caster angle to suit different suspension types and vehicle requirements. The adjustability is achieved through configurable mounting features on the guide rail structure.
3Reliability
If the kingpin axis is embedded inside the vehicle wheel to minimize scrub radius, then driving stability is improved, but the lower arm connection becomes more complex
Solution Approach 1:
The guide rail is integrated into the lower arm structure in a nested manner, where the guide rail forms part of the lower arm assembly. This nesting approach allows the kingpin axis to be positioned within the wheel hub area while keeping the overall structure compact and manageable. The guide rail's curved path is embedded within the suspension geometry, achieving minimal scrub radius without excessive structural complexity.
Data Source
AI summary
Provided is a steering device (100), which is configured to steer a vehicle wheel about a kingpin axis, the steering device (100) including: a hub (120) configured to rotatably support the vehicle wheel (110); a knuckle arm (130) configured to steer the vehicle wheel (110); and a lower arm (150) configured to connect the vehicle body and the vehicle wheel (110) to each other. A lower rotation guiding part (170) is provided at one end of the lower arm (150), the lower rotation guiding part (170) being rotatable about the kingpin axis. The lower rotation guiding part (170) includes: a guide rail (302) formed in an arc shape having a constant curvature; and a moving block (303) configured to move on the guide rail (302). An imaginary plane including the guide rail (302) is perpendicular to the kingpin axis.