Vehicle Steering Rotation Limiter With Spiral Ball Mechanism
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Solution Overview
Problem
Existing steer-by-wire systems face challenges in managing straightness due to tolerance variations in plastic bushings, increased friction, noise generation, and high assembly costs, particularly in leadscrew mechanisms used for limiting rotational shaft rotation.
Innovation Solution
A steering apparatus with a housing, rotational shaft, moving member, first and second rotation limiters, and a spiral mechanism that uses spherical ball members to limit rotational shaft rotation within set angles, distributing load across multiple moving members and limiters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a leadscrew mechanism with plastic bushings is used to limit rotation, then the rotational shaft rotation can be limited, but friction increases and noise is generated due to clearance between plastic bushing and nuts
Solution Approach 1:
The patent replaces the traditional leadscrew mechanism with a rack-and-pinion mechanism. The rotational shaft engages with a rack through a pinion gear, eliminating the need for plastic bushings and nuts. This substitution maintains the rotation limiting function while significantly reducing friction and noise generation, as gear-to-rack engagement is more efficient and produces less wear than screw-bushing interfaces.
Solution Approach 2:
The patent changes the fundamental mechanical parameters of the limiting mechanism by transitioning from a screw thread geometry to a gear rack geometry. This parameter change allows for better load distribution, reduced contact pressure, and improved lubrication characteristics, thereby reducing friction and noise while maintaining effective rotation control.
2Strength
If steel nuts are used in the leadscrew mechanism, then the structural strength is improved, but noise generation increases
Solution Approach 1:
The patent eliminates steel nuts entirely by replacing the leadscrew mechanism with a rack-and-pinion system. The pinion gear directly engages with the rack, providing structural strength through gear teeth design rather than relying on nut-thread engagement. This substitution maintains or improves strength while dramatically reducing noise generation from metal-to-plastic contact and clearance impacts.
3Reliability
If square-shaped plastic bushings are used, then the rotation limiting function is achieved, but assembly costs and machining complexity increase
Solution Approach 1:
The patent replaces complex square-shaped plastic bushings with a simpler rack-and-pinion gear system. The rack can be manufactured as a standard linear component, and the pinion gear is a conventional rotary component. This substitution eliminates the need for specialized square bushing machining, reduces assembly steps, and lowers overall manufacturing costs while maintaining the rotation limiting function through gear engagement geometry.
4Stability of the object's composition
If plastic bushings are used at extremely low temperatures, then the structure remains intact, but adhesion occurs due to shrinkage leading to increased friction
Solution Approach 1:
The patent replaces temperature-sensitive plastic bushings with a metal-based rack-and-pinion system. The rack and pinion can be manufactured from metals or metal-composite materials that exhibit minimal thermal shrinkage. This substitution eliminates adhesion issues at extremely low temperatures while maintaining structural integrity, as metal components do not undergo the same degree of thermal contraction as plastics.
Solution Approach 2:
The patent may utilize composite materials for the rack or pinion that combine metals with low-friction coatings or polymer overlays optimized for cold-temperature performance. These composite constructions provide both the structural integrity needed for strength and the low-friction surface properties needed to prevent adhesion in extreme cold environments.
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
The solution effectively manages rotational shaft rotation within set angles, reducing friction and noise while minimizing assembly costs, thus enhancing the performance and reliability of steer-by-wire systems.
Implementation Method 1
The rotational shaft may be provided with a spiral onto which the moving member is engaged and configured to move the moving member in response to the rotation of the rotational shaft.
Implementation Method 2
The moving member may include a spherical ball member. The ball member may roll between the spiral and the guide.
Data Source
AI summary
Provided is a steering apparatus for a vehicle including a housing, a rotational shaft rotatably mounted in the housing, a moving member interposed between the rotational shaft and the housing and moved by rotation of the rotational shaft, a first rotation limiter formed inside the housing and configured to limit an amount of a first direction movement of the moving member, thereby limiting an amount of a first direction rotation of the rotational shaft, and a second rotation limiter coupled to the housing and configured to cover an opening of the housing and to limit an amount of a second direction movement of the moving member, thereby limiting an amount of a second direction rotation of the rotational shaft.