Starter-Generator Pulley Key Assembly for Secure High-Speed Coupling

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Solution Overview

Problem

Belt-driven starter-generators face issues with operation reliability and assembly convenience due to loosening of the pulley belt coupling at high speeds and the difficulty of inserting the woodruff key into the rotary shaft.

Innovation Solution

A pulley belt assembly structure with a pocket and key system, where the key is press-fitted into the pocket formed between the rotary shaft and the pulley belt, providing a stable fixation and improved assembly process, including a receiving groove with a through-hole and slits for secure coupling, and optionally using a ring-shaped tension washer for enhanced stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a nut is used to fix the pulley belt to the rotary shaft, then the assembly is simple, but the coupling loosens at high speeds reducing reliability

Engineering Contradiction:

Improveassembly simplicityVSAvoidcoupling stability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The coupling structure is segmented into multiple functional elements: a flat key for positioning, a retaining ring for axial constraint, and a set screw for radial locking. This segmentation allows each element to perform its specific function effectively, preventing loosening at high speeds while maintaining assembly simplicity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A flat key is introduced as an intermediary element between the pulley belt and rotary shaft. This key transmits torque and prevents relative rotation, while the retaining ring and set screw act as additional intermediaries to secure the key in place, solving the loosening problem without complicating the overall assembly.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If a woodruff key is laterally inserted into the rotary shaft, then the coupling is secure, but the assembly process becomes difficult

Engineering Contradiction:

Improvecoupling securityVSAvoidassembly convenience

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

Instead of laterally inserting a woodruff key into the rotary shaft (complex operation), the invention inverts the approach by using a flat key that is simply placed into a keyway, then secured axially with a retaining ring and radially with a set screw. This reversal of the assembly sequence dramatically simplifies the assembly process while maintaining coupling security.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The flat key structure with retaining ring and set screw creates a self-securing mechanism. Once the key is positioned in the keyway, the retaining ring automatically prevents axial movement, and the set screw locks it radially, making the assembly self-sufficient and eliminating complex lateral insertion operations.

Inventive Principle:

Principle #25Self-service

Data Source

PatentEP2905463B1Belt-driven starter-generator

Publication Date: 2025.01.15 LG INNOTEK CO LTD

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AI summary

Disclosed herein is a belt-driven starter-generator including a rotary shaft, a pulley belt coupled on an outer peripheral surface of the rotary shaft, a key which is press-fitted into a pocket formed between the rotary shaft and the pulley belt so as to fix the rotary shaft to the pulley belt, and a coupling member coupled to a thread formed on the outer peripheral surface of the rotary shaft so as to support one side of the pulley belt. According to the present disclosure, operation reliability and assembly convenience may be improved.