Engine Valve Boss Forming for Localized Strength and Neck Toughness
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Solution Overview
Problem
Existing methods for manufacturing engine valves with piston or vane portions struggle to achieve high strength in these components while maintaining toughness in the neck portion, as heat treatment often increases strength uniformly across the valve, potentially leading to fracture. Additionally, forming the boss portion at a location separated from the valve head is challenging due to instability in retaining the outer circumferential surface and limited grippable length.
Innovation Solution
A method involving a stem retaining operation using removably installed intermediate jigs and a base end jig to apply alternating stresses, allowing the boss portion to be formed at a desired location with higher hardness than other areas, thus achieving high strength for the piston or vane portion without compromising the neck portion's toughness. This method includes using precipitation hardenable Ni-based alloys and friction welding with martensite steel for specific regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If heat treatment is applied to the entire engine valve to increase strength of the piston portion or vane portion, then the strength of the piston portion or vane portion is improved, but the toughness of the neck portion decreases and fracture may occur
Solution Approach 1:
The patent applies selective heat treatment only to the boss portion (piston portion or vane portion) rather than the entire engine valve. This localized heat treatment approach increases the strength of the specific area requiring high strength while preserving the toughness and impact resistance of other critical areas like the neck portion that require toughness for absorbing impact during valve operation.
2Adaptability or versatility
If the boss portion is formed at a location separated from the valve head, then the design flexibility is improved, but the stability of retaining the outer circumferential surface deteriorates due to limited grippable length
Solution Approach 1:
The patent introduces a stem-enlarged portion as an intermediary feature that provides a dedicated gripping area for retaining the outer circumferential surface during manufacturing processes. This stem-enlarged portion acts as a mediator between the valve head and the boss portion, enabling stable retention and processing even when the boss portion is located at a distance from the valve head, thus maintaining both design flexibility and manufacturing stability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method allows for high-precision formation of the boss portion at any desired location, maintaining neck portion toughness and reducing manufacturing costs by selectively hardening only the required areas, enhancing the engine valve's strength and durability without heat treating the entire product.
Implementation Method 1
alternating stresses that cause compressive forces and tensile forces to act in alternating and repeated fashion in a direction parallel to the axis of the stem are made to occur at the bent portion
Implementation Method 2
compression of the bent portion, the yield stress of which has been lowered as a result of said alternating stresses, is made to occur from either side of the stem portion
Implementation Method 3
the intermediate product is made to rotate and alternating loads that cause tensile forces and compressive forces to act in repeated and alternating fashion in a direction parallel to a central axis of the stem at the outer circumferential surface of the stem forming portion are applied thereto
Implementation Method 4
using precipitation hardenable Ni-based alloys
Implementation Method 5
friction welding with martensite steel for specific regions
Data Source
Figure 1(a)~1(f)
Figure 1A
Figure 2(a)~2(b)
AI summary
Provided is a method of manufacturing an engine valve intermediate product such as will cause only a boss portion for formation of a piston portion and/or vane portion to be imparted with the required high strength, and such as will permit the boss portion to be formed at any desired location separated by some distance from a valve head forming portion at a stem forming portion. A method of manufacturing an engine valve intermediate product (2) with a boss portion (11) at which a valve head forming portion (4), a maximum outside diameter of which is greater than that of a stem forming portion (3), is present in integral fashion, and at which the boss portion (11), an outside diameter of which is greater than that of the stem forming portion (3), is formed in integral fashion at an outer circumferential surface at an intermediate location on the stem forming portion, comprising a stem retaining operation in which an intermediate location of the stem forming portion (3) is retained by a plurality of intermediate jigs (6a through 6c) capable of being removably installed radially with respect to a center of the stem forming portion (3), and a base end portion (3b) is retained by a base end jig (5); and a stem enlarging operation in which compressive forces are applied from both ends of the intermediate product (2) and the boss portion (11) is formed as the intermediate product (2) is made to rotate and alternating loads that cause tensile forces and compressive forces to act in repeated and alternating fashion at the outer circumferential surface of the stem forming portion (3) are applied thereto.