Hollow Engine Valve Drilling Geometry for Lower Tool Wear
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Solution Overview
Problem
Conventional manufacturing methods for hollow engine valves, particularly those using high heat-resistant materials, face increased costs and reduced tool life due to difficult cutting processes, and stress concentration issues arise from the formation of hollow holes with flat bottoms, leading to durability concerns.
Innovation Solution
A manufacturing method involving forging and cutting processes to form hollow engine valves with inverted cone-shaped hollow holes, using a drill bit with an inclined tip end to reduce tool costs and stress concentration, while maintaining high durability and weight reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a punching process is used to form a hollow hole with a bottom on the upper surface of the intermediate member made of heat-resistant material, then the hollow engine valve can be manufactured, but the manufacturing cost increases because the tool (punch) has to be changed frequently due to short tool life
Solution Approach 1:
The patent changes the geometric parameters of the hollow hole bottom from a flat surface (conventional) to an inverted cone shape with a specific apex angle (140° to 178°). This parameter change allows the use of a drill bit with an inclined tip end instead of a punching tool, significantly extending tool life and reducing manufacturing costs while working with difficult-to-cut heat-resistant materials
Solution Approach 2:
Instead of forming the hollow hole bottom by punching from the upper surface (conventional method), the patent inverts the approach by forming the hollow hole with a bottom through a cutting process using a drill bit with an inclined tip end. This inversion of the forming method resolves the tool life issue associated with punching heat-resistant materials
2Ease of manufacture
If a narrow, long hollow hole is formed by drilling through the stem portion of the semifinished product, then the hollow hole can be created, but the process becomes difficult and tool life becomes very short
Solution Approach 1:
The patent performs preliminary action by forming the hollow hole with a bottom (including the inverted cone-shaped bottom surface) before the final drawing process. This preliminary formation of the hollow hole structure, using a drill bit with an inclined tip end, avoids the difficulty of drilling narrow, long holes through the finished stem portion and extends tool life
3Ease of manufacture
If the bottom surface of the hollow hole is flat with a 90° angle formed by the bottom surface and the inner circumference surface, then the hollow hole can be formed easily, but stress concentration occurs at the corner during use, decreasing durability
Solution Approach 1:
The patent replaces the flat bottom surface with a curved inverted cone shape having an apex angle of 140° to 178°. This curvature eliminates the sharp 90° corner between the bottom surface and inner circumference surface, preventing stress concentration and improving durability while maintaining ease of formation through the inclined tip end drill bit process
Solution Approach 2:
The patent changes the geometric parameters of the hollow hole bottom from a flat surface with 90° angles to an inverted cone shape with a specific apex angle (140° to 178°). This parameter change simultaneously improves durability by eliminating stress concentration points and maintains ease of manufacture through the corresponding drill bit design
Data Source
AI summary
A manufacturing method for a hollow engine valve comprises: a step of forming, by forging, a solid round bar as a material of a valve main body into a valve main body intermediate member provided with a semifinished product valve head portion corresponding to a valve head portion and a solid stem portion corresponding to a valve stem portion; a step of performing cutting process with respect to the valve main body intermediate member across the solid stem portion and the semifinished product valve head portion for forming a semifinished product hollow hole with a bottom corresponding to a hollow hole; and a step of performing necking process with respect to the valve main body semifinished product for squeezing the semifinished product valve stem portion step by step, to form the valve main body semifinished product into the valve main body.