Self-Steering Axle Knuckle Actuator Positioning
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Solution Overview
Problem
Existing self-steering axle/suspension systems for heavy-duty vehicles face issues with air actuated disc brake systems being prone to damage from road debris and ground contact, having large and heavy king pin mounting bosses, and significant king pin offsets from the axle spindle centerline, which can lead to abnormal load conditions and accelerated tire wear.
Innovation Solution
A new self-steering axle/suspension system with a redesigned knuckle that positions the air disc brake actuator above and forward of the axle, avoiding contact with the ground and vehicle components, and reduces king pin offsets, thereby protecting the actuator from damage and optimizing load distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the air actuated disc brake system is positioned behind and below the axle, then it avoids contact with frame members, but it becomes exposed to damage from road debris and ground contact
Solution Approach 1:
The actuator is repositioned from a vertical arrangement (behind and below the axle) to a horizontal arrangement (inboard of the knuckle between the axle and frame members). This dimensional change allows the actuator to avoid ground contact while maintaining clearance from frame members through the lateral spacing provided by the knuckle structure.
2Ease of operation
If the king pin mounting bosses are made large to accommodate air disc brake actuators, then the actuators can be properly positioned, but the knuckle becomes heavier
Solution Approach 1:
The actuator mounting location is moved from the vertical dimension (requiring large king pin bosses) to the horizontal dimension (inboard area of the knuckle). This allows proper actuator positioning with significantly reduced boss size, thereby reducing knuckle weight while maintaining adequate mounting capability.
3Ease of operation
If the king pin offset from the axle spindle centerline is increased to accommodate actuator mounting, then the actuator can be positioned, but abnormal load conditions and accelerated tire wear occur
Solution Approach 1:
The actuator positioning is relocated from relying on increased king pin offset (lateral dimension) to utilizing the inboard space between the axle and frame members (longitudinal dimension). This maintains proper king pin alignment with the axle spindle centerline, ensuring normal load distribution and preventing accelerated tire wear.
4Object-affected harmful factors
If the actuator is positioned inboard of the knuckle between the axle and frame members, then it avoids contact with ground and vehicle components, but clearance space is reduced
Solution Approach 1:
The design utilizes asymmetric spacing between the axle and frame members, positioning the actuator in the available inboard clearance zone. The knuckle structure is configured to provide adequate lateral and longitudinal clearance for the actuator while maintaining protection from ground contact and vehicle component interference.
Data Source
AI summary
Self-steering axle assembly has an axle with central tube having a longitudinal central axis. A king pin is connected with an end portion of the axle. A knuckle is connected with the king pin. The knuckle includes a torque plate section. A first arm of the knuckle extends from a side of the torque plate section and receives a first end portion of the king pin. A second arm extends from the torque plate section in the same direction as the first arm. The second arm receives a second end portion of the king pin. A spindle is friction welded to the torque plate section and has a longitudinal central axis. The torque plate section has at least one surface on the torque plate section extending substantially perpendicular to the longitudinal central axis of the spindle. A tool engages the surface during friction welding of the spindle to the torque plate section. The relative locations of the axle, spindle and king pin enable an air disc brake actuator to avoid contact with components of the heavy-duty vehicle during steering and with the ground and debris.