Rotor Field Coil Lead Securing via Insulating Bobbin Hooks
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Solution Overview
Problem
Conventional rotor designs for automotive alternators with Lundell-type pole cores face issues with securing field coil leads, leading to potential loosening and breakage due to centrifugal and tensile forces, and challenges in achieving reliable bonding of insulating tubes.
Innovation Solution
The design incorporates first and second hook portions on the insulating bobbin flanges to securely hold the field coil leads, with specific groove configurations and guiding portions to prevent movement and enhance bonding, and the use of insulating tubes that are deformed to fit within these grooves for secure positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional securing portions are used to hold field coil leads, then the structure is simple, but the leads loosen and break due to centrifugal and tensile forces during operation
Solution Approach 1:
The securing portion is divided into multiple functional elements: a body portion for mounting, a first hook portion for securing the lead, and a second hook portion for additional retention. This segmentation allows each element to perform its specific function effectively, preventing lead loosening and breakage while maintaining structural clarity
Solution Approach 2:
The securing portion acts as an intermediary component between the field coil lead and the insulating bobbin. It provides a dedicated interface that transfers and distributes mechanical stresses, preventing direct stress concentration on the lead itself and thereby preventing lead failure during operation
2Reliability
If insulating tubes are used to protect leads, then lead protection is improved, but bonding reliability between insulating tubes and pole cores is insufficient
Solution Approach 1:
The insulating tubes are pre-positioned on the field coil leads before final assembly. The securing portions are also pre-assembled on the insulating bobbin with hook portions ready to engage. This preliminary positioning ensures correct alignment and facilitates reliable bonding when the insulating tubes are subsequently bonded to the pole cores
Solution Approach 2:
The bonding between insulating tubes and pole cores replaces purely mechanical retention with chemical bonding through adhesive application. This substitution enhances bonding reliability by creating a strong chemical bond in addition to mechanical interlocking, ensuring the insulating tubes remain securely fixed during operation
3Reliability
If leads are allowed to move freely during operation, then assembly is easy, but leads break due to repeated tensile forces from pole core vibrations
Solution Approach 1:
The securing portion provides localized constraint specifically at the lead attachment point, where the first and second hook portions engage the lead. This localized quality ensures the lead is secured only where necessary to prevent breakage from tensile forces, while allowing other portions of the lead to maintain their natural flexibility and movement characteristics
Data Source
AI summary
In a rotor for a rotating electrical machine, a flange of an insulating bobbin is formed with a first hook portion and a second hook portion. The first hook portion directs a lead of a field coil both against the winding direction of the field coil and radially inward. The first hook portion has a first groove in which is hooked a proximal portion of the lead. The second hook portion directs the lead axially outward. The second hook portion has a second groove which has an open end on a radially inner periphery of the second hook portion, a closed end positioned radially outward of the open end, and a neck between the open and closed ends. The second hook portion has an intermediate portion of the lead hooked in the second groove between the neck and closed end of the second groove.