Steering Support Shaft Reinforcement for Collision Safety
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Solution Overview
Problem
The existing steering apparatuses face issues with deformation of the support shaft under load, making it difficult to operate the operating lever due to increased operation force and peak values, especially in scenarios where the support shaft is prone to breakage during secondary collisions.
Innovation Solution
Incorporating a tubular reinforcing member on the support shaft to enhance its structural integrity, coupled with a strength difference between the reinforced area and the to-be-broken portions, which allows the support shaft to break reliably at the designated points during secondary collisions, thereby preventing deformation and maintaining smooth operation of the engaging tooth formation member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the support shaft is made from a resin member or similar material to achieve light weight and cost-effectiveness, then manufacturing cost and weight are reduced, but the shaft deforms under load during normal operation, increasing operation force and making the operating lever difficult to operate
Solution Approach 1:
The support shaft is constructed as a composite structure combining a resin member with a reinforcing member. The resin member provides light weight and cost-effectiveness, while the reinforcing member (made of metal or other rigid material) is fitted into a fitted hole within the resin member to provide structural strength and prevent deformation under load. This composite construction resolves the contradiction by integrating materials with complementary properties.
Solution Approach 2:
The reinforcing member is strategically positioned within the support shaft at locations where strength is most needed to prevent deformation during operating lever operation. The fitted hole for the reinforcing member is specifically located to provide local reinforcement without requiring the entire shaft to be made of heavy material, thus maintaining light weight while improving operational ease at critical locations.
2Reliability
If the support shaft is designed to break during secondary collision to protect the driver, then safety is improved, but the shaft may deform under normal operating loads before breaking, affecting operational reliability
Solution Approach 1:
The composite structure of the resin member and reinforcing member creates a controlled strength differential. The reinforcing member provides sufficient strength for normal operation, while the resin member's inherent lower strength ensures that during secondary collision, the support shaft breaks in a controlled manner to protect the driver. This resolves the contradiction by using material properties to achieve both operational stability and collision safety.
Solution Approach 2:
The design incorporates a predetermined failure mode where the support shaft is engineered to break during secondary collision. The reinforcing member is designed with specific strength characteristics that allow it to maintain structural stability during normal use but fail in a controlled manner during severe collisions, providing beforehand protection without affecting normal operational reliability.
3Ease of operation
If the support shaft is reinforced to prevent deformation during normal operation, then operational smoothness is improved, but the shaft becomes too strong to break reliably during secondary collisions
Solution Approach 1:
The reinforcing member is fitted into a specifically positioned fitted hole within the resin member, providing localized reinforcement only where needed to prevent deformation during operating lever rotation. This local reinforcement is sufficient to ensure smooth operation but is strategically limited in scope to maintain the overall controlled strength of the support shaft, allowing it to break reliably during secondary collisions when and where designed.
Data Source
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AI summary
A steering apparatus includes a steering shaft (3); a column jacket (8) including an outer jacket (12) including a slit (26) and a pair of fastened portions (19), and an inner jacket (11); a fastening mechanism (18); an engaged tooth formation member (40) including at least one engaged tooth (41) and fixed to the inner jacket (11); a support shaft (50) including end portions (50a, 50b) supported by support holes (38) of the fastened portions (19); a tubular reinforcing member (60) fitted to an outer peripheral surface (50c) of the support shaft (50) at a prescribed area between the pair of end portions (50a, 50b); and an engaging tooth formation member (70) including an engaging tooth (72a) that engages with the engaged tooth (41).