Rotary Electric Machine Waterproof Sealing via Segmented Casing
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Solution Overview
Problem
Conventional waterproof structures for motors in refrigerating showcases are inadequate, particularly in environments prone to dew condensation, as they fail to reliably prevent moisture infiltration due to complex sealing mechanisms and potential dimensional errors or degradation of sealing components.
Innovation Solution
A rotary electric machine design featuring a tubular motor case divided into two casings with semi-tubular tap portions and a lead bush with annular bulging portions, providing a simple and effective sealing mechanism that maintains sealing even with dimensional errors or degradation, through the use of grooves and annular bulging portions to grip and compress the lead bush, ensuring double and triple sealing actions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional waterproof structure with O-ring sealing and grommet is used, then the motor can be made waterproof, but the mating surfaces become structurally complex and sufficient waterproof measure is hard to achieve
Solution Approach 1:
The motor case is divided into two separate casings (first casing and second casing) that are assembled together. This segmentation allows for simplified individual casing designs while achieving waterproof sealing through the assembly interface, avoiding the complexity of trying to seal a single-piece case with multiple penetrations.
Solution Approach 2:
A resin layer is introduced as an intermediary sealing element between the first and second casings. This resin layer fills the groove formed by the protruding portions of the casings, creating a reliable waterproof seal without requiring complex mating surfaces or additional sealing components like O-rings or grommets.
2Reliability
If a groove-shaped mounting portion with grommet is used for lead wire outlet, then sealing can be achieved, but dimensional errors or grommet degradation cause gap formation and reduced waterproof effect
Solution Approach 1:
The resin layer is pre-formed in the groove between the first and second casings before final assembly. This preliminary sealing structure ensures that even if dimensional variations occur during manufacturing or if components degrade over time, the resin maintains continuous contact and sealing effectiveness, preventing gap formation.
Solution Approach 2:
The sealing mechanism transitions from relying on rigid dimensional precision and component integrity (grommet) to utilizing the viscoelastic properties of resin that can deform and adapt. The resin's ability to flow and conform to surface variations compensates for dimensional errors and degradation, maintaining sealing performance over extended periods.
3Object-affected harmful factors
If drain hole and cutoff wall structure is used in motor case, then some moisture prevention is attempted, but reliable moisture infiltration prevention cannot be achieved
Solution Approach 1:
The drainage function is completely eliminated by removing drain holes and cutoff walls from the motor case design. Instead, the entire case assembly is made inherently waterproof through the resin-sealed joint between the two casings, preventing moisture infiltration at the source rather than attempting to manage or drain it.
Data Source
AI summary
A rotary electric machine includes a rotor, a stator, a circuit substrate, a tubular closed-top and closed-bottom motor case arranged to accommodate the rotor, and bearings. The motor case is axially divided into a first casing and a second casing. Each of a first and a second tap portion of the first and the second casings includes an inner circumferential surface and at least one groove arranged on the inner circumferential surface. A lead bush includes a through-hole arranged to guide a lead wire and at least three annular bulging portions arranged at a specified interval along an outer circumferential surface of the lead bush. A middle annular bulging portion of the three annular bulging portions is fitted to the groove of each of the first tap portion and the second tap portion so that the lead bush is gripped between the first tap portion and the second tap portion.