Coiled Spring End Turn Design for Press-Fit Durability
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Solution Overview
Problem
Existing coiled spring assemblies face issues with proper engagement between the seat member and the coiled spring, leading to forced interference, reduced durability, and potential breakage of the end turn during press-fit engagement, which complicates manufacturing and increases costs.
Innovation Solution
A coiled spring assembly design featuring an end turn with a reduced diameter transitioning to a body portion, a surface-hardened layer of 50µm depth, and a white layer of 3µm or less, along with a seat member with a mounting shaft and enlarged diameter portion, ensuring secure press-fit interference without excessive stress on the end turn.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the seat member is simply engaged with the end portion of the coiled spring, then the manufacturing process is simplified, but forced interference occurs between the end turn and the seat member, deteriorating durability
Solution Approach 1:
The end turn is segmented into multiple regions (first end turn region with reduced diameter, second end turn region with intermediate diameter, third end turn region with body portion diameter) that progressively engage with the seat member's mounting shaft portion. This segmentation allows controlled deformation and engagement without forced interference, resolving the contradiction between simplified manufacturing and improved durability
Solution Approach 2:
The end turn is pre-formed with a reduced diameter at the first end turn region before assembly. This preliminary shaping creates a tapered structure that guides the engagement process, allowing the end turn to gradually deform and fit onto the mounting shaft portion without sudden forced interference, thereby maintaining durability while simplifying the assembly process
2Reliability
If press-fit interference is sufficiently secured between the seat member and the end turn, then attachment stability is improved, but the end turn is broken by large radial deformation
Solution Approach 1:
Different regions of the end turn are given different diameters (reduced, intermediate, and body portion diameters) to create localized engagement zones. The first end turn region with reduced diameter provides the primary press-fit interference for stable attachment, while the gradual diameter increase in subsequent regions prevents excessive radial deformation and breakage, resolving the contradiction between attachment stability and end turn integrity
Solution Approach 2:
The diameter parameter of the end turn is changed progressively across different regions (from reduced diameter at the first end turn region to body portion diameter at the third end turn region). This parameter variation creates a controlled interference fit that provides sufficient attachment stability while preventing the large radial deformation that would cause breakage
3Ease of operation
If a spring attachment member with elastically-locking parts is used, then workability for attaching to the coiled spring is improved, but the number of parts increases, complicating manufacturing and part management
Solution Approach 1:
The spring attachment member is merged with the seat member to form a single integrated component. The mounting shaft portion of the seat member directly provides the engagement structure that would otherwise require a separate spring attachment member, eliminating the need for elastically-locking parts while maintaining improved workability for attaching to the coiled spring, thus resolving the contradiction between ease of operation and device complexity
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
This design enhances durability by preventing breakage and stabilizing attachment, while maintaining a secure press-fit interference, thus improving the coiled spring assembly's overall performance and reducing manufacturing complexity.
Implementation Method 1
the coiled spring with a surface hardened layer of a depth being 50μm and a white layer of a depth from a surface being 3μm or less in order to prevent the end turn from being broken
Data Source
Figure 1~3
Figure 4(A)~4(B)
Figure 5(A)~5(B)
AI summary
Provided is a coiled spring assembly, capable of properly engaging a seat for a coiled spring as a seat member with a coiled spring to prevent forced interference between an end turn of the coiled spring and the seat for the coiled spring and increase durability. The coiled spring (3) has an end turn (9) (11) formed up to a first turn with a reduced diameter and a transition portion (13) (15) with a diameter gradually increasing from the end turn (9) (11) to a body portion (7), the seat (5) for the coiled spring has a seat portion (17), a mounting shaft portion (19), and an enlarged diameter portion (21), the mounting shaft portion (19) has an axial length defining a gap or a zero-gap between the enlarged diameter portion (21) of the seat (5) for the coiled spring and the end turn in a free state in which the end turn (9) (11) is fitted to the mounting shaft portion and the bearing surface (9a) (11a) of the end turn (9) (11) is in contact with the receiving surface (17a) of the seat portion (17), and the transition portion (13) (15) circumvents the enlarged diameter portion (21) while the bearing surface (9a) (11a) of the end turn (9) (11) is in contact with the receiving surface (17a) of the seat portion (17).