Terminal Fitting Hook Engagement Cap Retention

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Solution Overview

Problem

Conventional terminal fittings face issues with decreased engagement force between the cap member and the electric contact portion due to downsizing, leading to potential cap member detachment, increased worker burden from adhesive application, skill-dependent retention variability, and elevated costs from adhesive use.

Innovation Solution

A terminal fitting design featuring a hook-like first engagement portion at the electric contact portion and a corresponding hook-like second engagement portion on the cap member, allowing reliable retention without adhesives, reducing worker burden, and eliminating adhesive costs, with the cap member fitted perpendicular to the electric contact portion to prevent pull-out.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the cap member is downsized to reduce overall terminal fitting size, then the terminal fitting becomes more compact, but the engagement force between the electric contact portion and the cap member decreases

Engineering Contradiction:

Improveterminal fitting sizeVSAvoidengagement force

Core Design Contradiction:

Volume of moving objectVSForce

Solution Approach 1:

The engagement structure is segmented into multiple interaction points: the outer peripheral surface of the electric contact portion and the inner peripheral surface of the cap member create circumferential engagement, while the distal end engagement portion provides additional axial retention. This multi-point segmentation distributes and enhances engagement force despite reduced overall size.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The distal end engagement portion features an asymmetric design where the outer peripheral surface of the electric contact portion engages with the inner peripheral surface of the cap member at a position offset from the central axis. This asymmetric engagement creates a mechanical interlock that enhances retention force while maintaining compact dimensions.

Inventive Principle:

Principle #4Asymmetry

2Reliability

If adhesive agent is applied to retain the cap member on the electric contact portion, then the cap member can be reliably retained, but the worker burden and manufacturing complexity increase

Engineering Contradiction:

Improvecap member retentionVSAvoidmanufacturing process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The terminal fitting structure provides self-retention through its geometric design. The distal end engagement portion creates a mechanical interlock where the cap member is retained by the shape complementarity between its outer peripheral surface and the electric contact portion's inner peripheral surface, eliminating the need for external adhesive agents or additional retention mechanisms.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The chemical bonding mechanism of adhesive agents is replaced with a purely mechanical engagement system. The distal end engagement portion utilizes geometric interlocking and frictional forces between the cap member and electric contact portion surfaces to achieve reliable retention without any chemical substances.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If adhesive agent is used to fix the cap member, then the cap member can be retained, but the cost increases due to material and processing requirements

Engineering Contradiction:

Improvecap member retentionVSAvoidadhesive agent consumption

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The design eliminates the need for expendable adhesive agents by using a permanent geometric engagement structure. The distal end engagement portion provides enduring retention through its mechanical interlock design, removing the ongoing cost and waste associated with adhesive consumption.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

4Strength

If the terminal fitting edge is sharp to maintain structural integrity, then the terminal fitting is structurally sound, but the connector inner side may be cut and damaged during insertion

Engineering Contradiction:

Improveterminal fitting structural integrityVSAvoidconnector damage risk

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The terminal fitting exhibits local quality differentiation: the main body maintains sharp edges for structural integrity and electrical performance, while the distal end of the electric contact portion features a specifically modified geometry with a reduced radius of curvature. This localized geometric adjustment prevents connector damage during insertion while preserving the overall structural strength of the terminal fitting.

Inventive Principle:

Principle #3Local quality

Data Source

PatentEP2717388B1Terminal fitting

Publication Date: 2018.01.17 YAZAKI CORP

Figure 1~2
Figure 3A~3B
Figure 4A~4B

AI summary

Provided is a terminal fitting capable of making an electric contact portion and a cap member retained at the electric contact portion to be reliably engaged together. A terminal fitting (1) includes an electric contact portion (6) provided at one end side and formed into a tube-like shape such that a mating terminal is fitted thereto, an electric wire connection portion (9) provided at the other end side and arranged to fasten an electric wire, and a cap member (3) fitted to a distal end of the electric contact portion (6) and retained at the distal end. A first engagement portion (28) arranged to engage with the cap member (3) is provided at the distal end of the electric contact portion (6), and the cap member (3) is provided with a second engagement portion (41) arranged to engage with the first engagement portion (28).