Steering Column End Stop Mechanism for Steer-by-Wire Systems
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Solution Overview
Problem
In steer-by-wire systems, the lack of a mechanical connection between the steering wheel and the vehicle wheels necessitates a mechanism to limit the steering wheel's rotation to match the maximum pivoting range of the vehicle wheels, preventing indefinite rotation at maximum steering angles.
Innovation Solution
A steering column assembly with a housing, a rotatable shaft, and an engagement portion with end stop means, where the engagement portion is a Woodruff key seated in a recess on the shaft, interacting with a T-shaped end stop insert mounted on the housing, allowing the steering wheel to rotate nearly a full turn before being stopped, and featuring a resilient design for a 'soft-stop' effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the steering wheel is allowed to rotate freely in a steer-by-wire system, then the driver can operate the steering wheel without restriction, but the steering wheel can rotate indefinitely beyond the maximum steering angle of the vehicle wheels
Solution Approach 1:
The end stop means is pre-positioned in the housing to engage with the engagement portion on the shaft at predetermined angles before the steering wheel can rotate beyond the maximum steering angle. This preliminary positioning prevents excessive rotation by establishing mechanical limits in advance, resolving the contradiction between free operability and angle control reliability.
2Reliability
If a rigid end stop mechanism is used to limit steering wheel rotation, then the maximum steering angle is precisely controlled, but the driver experiences harsh feedback and potential damage upon engagement
Solution Approach 1:
The end stop means incorporates a resilient element that deforms elastically upon engagement with the engagement portion. This cushioning effect absorbs the impact energy when the steering wheel reaches its rotation limit, providing soft stopping that prevents harsh feedback to the driver while maintaining reliable angle control. The resilient deformation occurs in advance of any potential damage or harsh impact.
3Reliability
If the end stop means is designed to engage precisely at maximum steering angle, then the steering wheel rotation is accurately limited, but the mechanism becomes complex and difficult to manufacture
Solution Approach 1:
The end stop means utilizes the elastic deformation parameter of a resilient element to achieve precise angular positioning. By selecting appropriate material properties and geometric dimensions for the resilient element, the engagement angle can be precisely controlled through parameter optimization rather than complex mechanical linkages. This approach maintains manufacturing simplicity while achieving reliable steering angle precision.
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
Effectively limits steering wheel rotation to match the vehicle's maximum steering angle in both directions, providing a safe and controlled steering experience by preventing excessive rotation, while the resilient design cushions the stop, enhancing driver feedback.
Implementation Method 1
the end stop means is resiliently deformable to provide a 'soft-stop' effect upon engagement of the engagement portion with the end stop means
Data Source
AI summary
A steering column assembly for a vehicle includes a housing, a shaft and an end stop means. The shaft is rotatably mounted with respect to the housing and is configured for attachment of a steering wheel at one end with an engagement portion connected to and configured to rotate with the shaft. The end stop means is located in the path of the engagement portion and engageable with the engagement portion upon rotation of the shaft through a predetermined angle. The engagement portion engages with the end stop means upon rotation of the shaft through predetermined angles in both directions. The engagement portion includes a member projecting outwardly from the shaft. The end stop means is mounted on the housing and the end stop means comprises a strip of material bent into a generally T-shape.