Brushless DC Actuator Bobbin Retainer Clip Design
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Solution Overview
Problem
Existing rotary brushless direct current actuators face issues with bobbin movement due to vibration, leading to loss of electrical contact between bobbin terminals and printed circuit boards, and overmolding methods are costly and potentially damaging.
Innovation Solution
A bobbin retainer clip with a ring plate and alignment fingers is used to secure bobbins on the stator, minimizing movement and maintaining electrical contact, while a housing design with separate cavities and a gear assembly provides structural support and precise control of rotary motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If overmolding of bobbins to stator is used to secure bobbins, then bobbins are firmly secured and movement is prevented, but manufacturing cost increases and damage to bobbin wires may occur
Solution Approach 1:
A retainer plate is introduced as an intermediary component between the bobbins and stator. The retainer plate has fingers that engage with slots in the bobbins and is secured to the stator, providing mechanical restraint without direct contact between the stator and bobbins. This mediator approach prevents bobbin movement while avoiding the costs and risks of overmolding.
2Ease of manufacture
If bobbins are allowed to move on stator due to tolerance stack-ups, then assembly is easier, but vibration causes loss of electrical contact between bobbin terminals and printed circuit board
Solution Approach 1:
The retainer plate is installed beforehand to establish fixed positions for the bobbins on the stator. By pre-positioning the bobbins through the retainer plate mechanism, the system achieves both easy assembly (bobbins can be freely positioned during assembly) and reliable electrical contact (bobbins are subsequently restrained from vibrating).
Solution Approach 2:
The retainer plate acts as an intermediary that decouples the tolerance stack-up issue from the electrical contact reliability. It allows bobbins to accommodate manufacturing tolerances while preventing vibration-induced contact loss.
3Reliability
If retainer plate with fingers engaging bobbin slots is used, then bobbin movement is restrained, but device complexity increases
Solution Approach 1:
The retainer plate is segmented into multiple fingers that can be independently formed or integrated into a single plate. Each finger engages with a slot in a corresponding bobbin, providing distributed restraint. This segmentation allows the complexity to be managed through modular design while achieving reliable bobbin positioning.
Data Source
AI summary
A brushless rotary actuator comprises a housing including a motor housing defining a cavity for a motor assembly and a cover defining a cavity for a gear assembly. The motor assembly includes a rotor and a stator with a plurality of bobbins. A clip in the form of a ring plate is seated against the bobbins for retaining the bobbins on the stator. Fingers formed on the ring plate are fitted into respective slots defined by respective bobbin terminals. A circuit board is seated in the housing against an interior shoulder of the motor housing. A plate is seated in the housing against a peripheral rim of the motor housing in a spaced relationship above the circuit board.