Wiper Arm Retainer Geometry to Prevent Held-Part Interference
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Solution Overview
Problem
In wiper arms, increasing the radius of curvature of bent portions in the retainer's holding part can lead to interference with the arm piece, causing improper connection and reduced holding force, which degrades the wiper's performance.
Innovation Solution
The wiper arm design includes a retainer with a bent portion and an arm piece with a chamfered portion, allowing for proper gap formation between the bent and chamfered surfaces, preventing interference and ensuring correct posture of the arm piece.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the radius of curvature of the bent portions is increased to reduce protrusions, then the curvature is smoothed, but the inner surfaces of the bent portions enter the accommodating portion and interfere with the held part
Solution Approach 1:
The held part is divided into multiple surfaces: an upper surface that contacts the top wall, side surfaces that are chamfered to avoid contact with bent portions, and a lower surface. This segmentation allows the held part to maintain proper orientation while accommodating larger radius bent portions without interference.
Solution Approach 2:
The chamfered side surfaces act as intermediaries between the bent portions and the held part, preventing direct contact and interference. The chamfered surfaces provide a transition zone that eliminates the harmful interaction while maintaining the structural integrity of both components.
2Shape
If the held part contacts the inner surfaces of the bent portions, then a gap is generated between the top wall and held part, but the held part tilts relative to the holding part
Solution Approach 1:
The held part is segmented into distinct functional surfaces: a flat upper surface for stable contact with the top wall, chamfered side surfaces to prevent contact with bent portions, and a lower surface. This segmentation ensures that the held part maintains proper orientation and stability while allowing gap formation where needed.
Solution Approach 2:
Different surfaces of the held part have different geometric qualities tailored to their specific functions: the upper surface is flat for stable contact, the side surfaces are chamfered to avoid interference, and the lower surface provides the connection interface. This local differentiation of surface qualities resolves the contradiction between gap formation and posture stability.
3Ease of manufacture
If caulking is performed when the held part is tilted, then the arm piece is connected in a twisted state, but the holding force decreases
Solution Approach 1:
The chamfered side surfaces are formed in advance on the held part to prevent contact with the bent portions during assembly. This preliminary geometric modification ensures that the held part automatically assumes the correct orientation during the caulking process, eliminating the need for complex alignment procedures and ensuring proper connection without twisting.
Solution Approach 2:
The geometric parameters of the held part are modified by adding chamfered surfaces with specific angles and dimensions. This parameter change transforms the held part from a simple rectangular shape to one with built-in orientation guidance, ensuring that during caulking the held part maintains the correct posture and achieves maximum holding force without twisting.
Data Source
AI summary
A wiper arm properly connects a retainer and an arm piece, even if a radius of curvature in a bent portion of a holding part of the retainer is set large, in the wiper arm including the arm piece connected to the retainer by accommodating and holding a held part of the arm piece within the holding part of the retainer. An arm piece includes a held part including chamfered portions disposed opposite to bent portions of a holding part of a retainer. A held part has a flat upper surface between the chamfered portions and is held within an accommodating portion of the holding part so that the upper surface abuts on a lower surface of a flat top wall of the holding part. The chamfered portions are formed so that a width of the upper surface is not larger than a width of the lower surface.