Exhaust Pipe Cover Geometry to Prevent Buckling During Insertion
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Solution Overview
Problem
Existing cover members for exhaust pipes tend to buckle when the tightening allowance exceeds a specified value, reducing the contact area and making it difficult to hold the cover member on the exhaust pipe, which affects heat resistance and durability.
Innovation Solution
The cover member is designed with an inner circumferential portion having a maximum width equal to or greater than the opening radius and a minimum width less than the radius, with an elliptical shape and a chamfered portion to guide insertion, preventing buckling and enhancing heat resistance by contacting heat-sensitive areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the tightening allowance of the inner circumferential portion is increased to facilitate insertion, then the ease of operation is improved, but the cover member is more likely to buckle and the reliability deteriorates
Solution Approach 1:
The inner circumferential portion is designed with an elliptical cross-section where the maximum width direction is oriented at a specific angle relative to the opening circumference. This asymmetric configuration allows the cover member to be inserted by rotating it to align the maximum width with the opening, while preventing buckling once installed because the asymmetric shape creates interference with the circular opening that locks the cover member in place.
Solution Approach 2:
The patent specifies precise parameter relationships: the maximum width equals or exceeds the opening radius, the minimum width is less than the opening radius, and the circumferential length is shorter than the opening circumference. These parameter changes enable the cover member to transition from a state where insertion is difficult (if perfectly circular with tight tolerance) to a state where insertion is easy but buckling is prevented (with elliptical shape and specific dimension ratios).
2Temperature
If the inner circumferential portion is made larger to improve contact area, then the heat resistance is improved, but the device complexity increases due to tighter manufacturing tolerances
Solution Approach 1:
Instead of requiring a perfectly circular inner circumferential portion with tight tolerances to ensure adequate contact area, the patent uses an asymmetric elliptical shape. This allows the maximum width to provide sufficient contact area for heat resistance while the asymmetric geometry itself simplifies the manufacturing process by eliminating the need for high-precision circularity control.
Solution Approach 2:
The patent applies different dimensional characteristics to different parts of the inner circumferential portion: the maximum width provides adequate contact area for heat resistance in critical regions, while the minimum width and overall elliptical shape facilitate insertion and assembly. This local differentiation of dimensional properties optimizes both heat resistance and manufacturability without requiring uniform tight tolerances throughout.
Data Source
AI summary
A method of manufacturing an exhaust pipe includes inserting a cover member into an approximately circular opening provided at a first end of a first exhaust pipe. An inner circumferential portion of the cover member has a ring shape with a central axis. When the cover member is inserted into the opening, its outer circumferential surface faces a first inner circumferential surface of the exhaust pipe. A maximum width of the inner circumferential portion is equal to, or greater than, a radius of a circumference of the opening. A minimum width of the inner circumferential portion is smaller than the radius. A circumferential length of the outer circumferential surface is shorter than the length of the circumference of the opening.