Rotation-Limiting Device for Steering Shaft Multi-Turn Control

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Solution Overview

Problem

Existing rotation limiting devices for steering systems, such as those described in Patent Literatures 1 to 5, limit the rotatable amount of the steering shaft to less than ±360 degrees, resulting in a limited number of lock-to-lock turns of the steering wheel, which is insufficient for typical passenger cars that require more than two turns.

Innovation Solution

A rotation limiting device comprising a first member, a second member, and at least one intermediate member, where the first member has a first protrusion, the second member has a second protrusion, and the intermediate member includes side plate portions with intermediate protrusions. This configuration allows for a high degree of freedom in setting the rotatable amount of the steering shaft by adjusting the number and arrangement of intermediate members.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the steering shaft rotation is limited to less than ±360 degrees using conventional stopper mechanisms, then the mechanical connection between steering unit and steered unit is simplified, but the number of lock-to-lock turns of the steering wheel becomes insufficient for typical passenger cars

Engineering Contradiction:

Improvemechanical connection complexityVSAvoidnumber of lock-to-lock turns

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The rotation limiting device is divided into multiple independent rotation members (first rotation member, second rotation member, third rotation member) that can rotate relative to each other. Each rotation member has protrusions that engage with adjacent members at different rotation angles, allowing the steering shaft to rotate more than 360 degrees while still providing mechanical stopping force at the extreme positions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second rotation member acts as an intermediary between the first and third rotation members. It transmits rotation from the steering shaft while being constrained by the first rotation member, and simultaneously constrains the third rotation member. This intermediary structure enables multi-turn rotation while maintaining mechanical connection simplicity.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If the number of rotation members and protrusions is increased to achieve more than two lock-to-lock turns, then the rotatable amount of the steering shaft increases, but the device complexity and structural complexity increase

Engineering Contradiction:

Improverotatable amount of steering shaftVSAvoidnumber of rotation members and protrusions

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

Each rotation member serves multiple functions: it acts as a rotating element that transmits steering input, provides mechanical constraints through its protrusions, and limits the rotation of adjacent members. The protrusions on each member simultaneously engage with multiple adjacent members, allowing a single component to perform multiple constraint functions.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The rotation members are arranged concentrically around the steering shaft, with each member nested within the structure formed by the others. The first rotation member is coupled to the steering shaft, the second rotation member is supported by the first, and the third rotation member is supported by the second, creating a nested configuration that maximizes rotational capability within a compact structure.

Inventive Principle:

Principle #7Nested doll (Nesting)

Data Source

PatentUS20250121879A1Rotation-limiting device and steering device

Publication Date: 2025.04.17 NSK STEERING & CONTROL INC

AI summary

A rotation limiting device including: a first member having a first protrusion; a second member having a second protrusion disposed on an axial one side with respect to the first protrusion, the second member being disposed coaxially with the first member and configured to rotate relative to the first member; and at least one intermediate member supported in a relatively rotatable manner with respect to the first member and the second member, the intermediate member including a side plate portion disposed between the first protrusion and the second protrusion in an axial direction, an intermediate side first protrusion protruding toward an axial other side from an axial other side surface of the side plate portion, and an intermediate side second protrusion protruding toward the axial one side from an axial one side surface of the side plate portion.