Vehicle Step Unit Assembly via Inverted Insertion
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Solution Overview
Problem
The existing step unit for vehicles with sliding doors has complex assembly processes due to the need for precise alignment of fastening holes and low rigidity around the cutout portion, leading to difficulties in coupling the step member and rail plate member, and requires a complicated structure for the rail plate member.
Innovation Solution
A step unit with a resin step member featuring a lower surface and first and second lower rails, including a cutout portion and an insertion hole, where the rail plate member is inserted through the hole and fixed using a resin fastening member, which simplifies assembly and eliminates the need for high-accuracy manufacturing and reinforcement structures, allowing for a simpler rail plate member design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the rail plate member is coupled to the step member by aligning fastening holes from below the step member, then the coupling can be achieved, but the assembly work becomes difficult due to the need to grope below the step member for alignment
Solution Approach 1:
The patent inverts the assembly direction by providing a through-hole in the step member that allows the rail plate member to be inserted from above rather than requiring alignment from below. This reversal of the assembly approach eliminates the need to grope for alignment and makes the coupling operation straightforward.
Solution Approach 2:
The coupling structure is segmented into distinct components: the step member with its through-hole, the rail plate member with positioning protrusions, and the fastening member. This segmentation allows each component to have its own specific function - the through-hole provides access, the positioning protrusions ensure correct alignment, and the fastening member secures the connection - making assembly easier.
2Strength
If the rail plate member is designed with reinforcement structures and welding to handle large loads from rollers, then the load-bearing capacity is sufficient, but the structure becomes complicated
Solution Approach 1:
The patent merges the reinforcement function directly into the step member by providing extended portions that protrude from the lower surface. These extended portions serve dual purposes: they structurally reinforce the area around the cutout portion to handle roller loads, and they provide mounting surfaces for the rail plate member, eliminating the need for separate reinforcement structures.
Solution Approach 2:
The step member is designed with local quality variations - the extended portions are specifically located at the cutout portion where reinforcement is needed to bear roller loads. This localized reinforcement approach provides strength exactly where required without adding unnecessary complexity to the entire structure.
3Reliability
If press-fitting is used to fix the rail plate member to the insertion hole, then fixation can be achieved, but high manufacturing accuracy is required to avoid looseness or excessive press-fitting force
Solution Approach 1:
The patent introduces a fastening member as an intermediary component between the rail plate member and the step member. Instead of relying on precise press-fitting, the fastening member (such as a bolt or screw) provides reliable fixation while accommodating dimensional variations in the through-hole and rail plate member, eliminating the need for high manufacturing precision.
4Reliability
If the rail plate member is press-fitted and fixed, then it can be secured, but removal for maintenance becomes difficult as the desired press-fitting force cannot be obtained upon reinstallation
Solution Approach 1:
The patent employs a dynamic fastening system using a fastening member that can be easily installed and removed. Unlike permanent press-fitting, the fastening member (bolt or screw) allows the rail plate member to be readily removed for maintenance and reinstalled without requiring the original press-fitting force, providing both secure fixation and ease of repair.
Data Source
AI summary
A step unit that guides a sliding door of a vehicle includes a step member and a rail plate member. The step member includes first and second lower rails. The first lower rail has two ends that face toward each other to form a cutout portion in between. The rail plate member is arranged in the cutout portion. The step member includes an insertion hole and an extended portion. The insertion hole is located at a position corresponding to the cutout portion. The extended portion is extended from at least one of the two ends to support the rail plate member against a load received by the rail plate member from the roller. The rail plate member is inserted through the insertion hole from above the upper side of the step member and fixed by a fastening member to the step member.