Vehicle Step Unit Rail Plate Rigidity Assembly
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Solution Overview
Problem
The existing step unit for vehicle sliding doors has a complex assembly process due to the need for manual alignment of fastening holes and a low rigidity rail plate member with a discontinuous structure, which complicates assembly and increases the risk of deformation under load.
Innovation Solution
A step unit with a molded plastic step member and a rail plate member that is press-fitted into an insertion slit, featuring support extensions to enhance rigidity and eliminate the need for complex reinforcement, allowing for easier assembly and reduced component count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the step member and rail plate member are assembled together by bolts passed through fastening holes, then the connection strength is improved, but the assembly process becomes complicated due to the need for manual alignment of fastening holes
Solution Approach 1:
The rail plate member integrates both the fastening function and the structural support function into a single component. The rail plate member includes fastening holes that align with the step member, eliminating the need for separate fastening operations. The rail plate member is inserted into the step member and fixed with bolts, combining the alignment and fastening steps into one operation.
2Ease of operation
If the lower rail has a discontinuous structure with cutout portions, then the ease of assembly and disassembly of rollers is improved, but the rigidity of the rail plate member deteriorates
Solution Approach 1:
The rail plate member has varying thickness to provide different levels of rigidity in different areas. The rail plate member is thicker at the ends of the cutout portions to maintain rigidity where needed, while allowing the cutout portions to facilitate roller assembly and disassembly. This local variation in thickness optimizes both the ease of operation and structural stability.
3Strength
If the rail plate member has a complicated shape with welded sheets and reinforcement structures, then the strength and rigidity are improved, but the manufacturing complexity and cost increase
Solution Approach 1:
The rail plate member uses variable thickness as a design parameter to achieve both strength and simplicity. Instead of using multiple welded sheets or additional reinforcement structures, the rail plate member has a uniform shape with controlled thickness variations. This approach simplifies manufacturing while maintaining the required mechanical properties.
Data Source
Figure 1
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Figure 3~4B
AI summary
A step unit comprises: a step member which is provided with a pair of lower rails extending in an opening and closing direction of a slide door of the vehicle; and a rail plate member which is provided to a cutout formed in a part of either of the lower rails and which continuously connects the lower rails in the opening and closing direction. A roller which is connected to the slide door is disposed between the pair of lower rails. The step member is molded using a resin material and is provided with an insertion hole which vertically penetrates through the step member at a position corresponding to the cutout; and a support extension section which is extended from a side end of the cutout of the lower rail so as to support the rail plate member against a load which the rail plate member receives from the roller. The rail plate member is mounted to the step member by being inserted so as to penetrate through the insertion hole from above the step member.