Steering Device Rack Housing Stroke Restricting Portion
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Solution Overview
Problem
The existing steering device design can cause damage to the stroke restricting portion due to tensile stress applied to its outer peripheral edge when the rack bar deflects radially, leading to potential cracks.
Innovation Solution
The stroke restricting portion of the rack housing is designed with an inner diameter greater than the minimum value of the tubular body portion, and an offset inner peripheral surface to distribute loads effectively, reducing contact pressure and preventing excessive tensile stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the stroke restricting portion has the same inner diameter as the tubular body portion, then the structure is simple and manufacturing is easy, but the outer peripheral edge portion of the stroke restricting portion is damaged due to tensile stress when the rack bar deflects radially
Solution Approach 1:
The stroke restricting portion is designed with a different inner diameter than the tubular body portion, creating a step-like structure where the inner peripheral surface is offset radially inward. This local structural modification concentrates the tensile stress away from the vulnerable outer peripheral edge, preventing damage while maintaining overall manufacturing feasibility through standard casting or machining processes.
2Strength
If the stroke restricting portion has a larger inner diameter than the minimum value of the tubular body portion, then the outer peripheral edge portion is protected from damage, but the structure becomes more complex
Solution Approach 1:
The inner diameter parameter of the stroke restricting portion is specifically changed to be larger than the minimum inner diameter of the tubular body portion. This parameter modification creates the protective effect by offsetting the inner peripheral surface radially inward, thereby protecting the outer peripheral edge from tensile stress damage while maintaining reasonable structural simplicity.
Data Source
AI summary
A rack housing (9) is provided with: a cylindrical main body (19) for movably accommodating a rack bar (8); and a stroke limiting section (25) annularly protruding from the cylindrical main body (19) toward a first end (9a). The inner peripheral surface (25b) of the stroke limiting section (25) is located offset radially outward from a support surface (19a), i.e. the inner peripheral surface of the cylindrical main body (19). The inner peripheral surface (25b) and the support surface (19a) are connected to each other by a sloped section (26) which is sloped circular conically. The sloped section (26) is provided at a position overlapping the cylindrical main body (19) when viewed radially. The sloped section (26) is sloped so that the inner diameter of the cylindrical main body (19) of the rack housing (9) increases toward a first contact section (25a).