Steering Lock Mechanism Arc Guide Hole Load Distribution
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Solution Overview
Problem
The existing steering device with a tilt function experiences abnormal noise and user discomfort due to manufacturing variability, which causes the engagement protrusion to get caught in impressions formed on the tilt guide hole, leading to inconsistent operational feelings.
Innovation Solution
The steering device incorporates a lock mechanism with a cam portion and cam follower portion that includes a lock position restriction surface and a release position restriction surface, where the angle of the release position restriction surface is larger than the lock position restriction surface, allowing for line contact and reducing the load component in the circumferential direction, thereby minimizing the formation of impressions on the tilt guide hole.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the engagement surface and restriction surface are caused to come into surface contact with each other, then the relative movement of drive cam and driven cam is restricted, but the contact area is small due to manufacturing variability, causing large load concentration and impression formation on the tilt guide hole
Solution Approach 1:
The invention applies curvature by forming an arc-shaped tilt guide hole instead of a straight guide hole. This curved geometry allows the engagement protrusion to follow a smooth arc path, distributing the load more evenly along the contact surface and preventing concentration of stress at specific points, thereby eliminating impression formation while maintaining reliable restriction of relative movement.
Solution Approach 2:
The invention changes the geometric parameters of the tilt guide hole from a straight linear path to an arc-shaped path with specific radius. This parameter change transforms the contact mechanics, allowing for larger and more consistent contact area between the engagement protrusion and the guide hole wall, reducing load concentration despite manufacturing variability.
2Ease of operation
If the driven cam rotates due to frictional force during lock mechanism operation, then the lock mechanism switches between locked and unlocked states, but the engagement protrusion collides with the tilt guide hole edge causing impression formation and abnormal noise
Solution Approach 1:
The arc-shaped tilt guide hole provides a smooth curved path for the engagement protrusion to follow during rotation. This eliminates sharp edges and corners that cause collision and impact, allowing the driven cam to rotate smoothly between locked and unlocked states without generating abnormal noise or forming impressions on the guide hole.
3Force
If the angle of the release position restriction surface is larger than the lock position restriction surface, then line contact is achieved reducing circumferential load, but the geometry becomes more complex
Solution Approach 1:
The arc-shaped tilt guide hole inherently provides the necessary geometric complexity in a simple and elegant manner. The curved geometry naturally creates the appropriate contact angles and load distribution without requiring additional complex cam surface features, achieving line contact and reduced circumferential load while maintaining design simplicity.
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
This configuration stabilizes the load and surface pressure, reducing abnormal noise and user discomfort, and providing a consistent operational feeling regardless of manufacturing variability.
Implementation Method 1
the driven cam is caused to rotate by an amount corresponding to a gap between an inner peripheral edge of the tilt guide hole and an outer peripheral surface of the engagement protrusion portion at the lime of a switch between the locked state and the unlocked state of the lock mechanism due to a frictional force or the like acting between the drive cam and the driven cam
Data Source
AI summary
In a steering device according to an aspect of the present disclosure, a driven cam includes a lock position restriction surface with which a cam portion of a drive cam engages in a locked state and a release position restriction surface that is provided to be separated front the lock position restriction surface in a bolt circumferential direction and that engages with the drive cam in the bolt circumferential direction in an unlocked state. The cam portion includes a sliding surface that faces the driven cam in the unlocked state and a flank surface that faces the release position restriction surface in the bolt circumferential direction. The angle of the flank surface with respect to the bolt circumferential direction is smaller than the angle of the release position restriction surface with respect to the bolt circumferential direction.