Fluid Dynamic Bearing Adhesive Pool Design
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Solution Overview
Problem
Fluid dynamic bearing devices face challenges in maintaining sufficient adhesive between the housing and bearing sleeve to enhance fixation strength, leading to potential adhesive flow into thrust bearing gaps and compromised performance.
Innovation Solution
A fluid dynamic bearing device design featuring an adhesive pool between the housing and bearing sleeve, with an inner peripheral chamfer and sealed gap, reduces adhesive extrusion and ensures adequate adhesive interposition for increased bonding strength, while maintaining lubricant flow paths and preventing contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If more adhesive is applied to increase fixation strength between the bearing sleeve and housing, then the bonding strength is improved, but the adhesive is extruded forward during insertion and flows around the bearing sleeve onto the housing closed side, causing insufficient adhesive interposition and potential intrusion into thrust bearing gaps
Solution Approach 1:
The patent applies preliminary action by providing an adhesive pool in advance between the bearing sleeve and housing before the bearing sleeve is inserted. This pre-positioned adhesive pool ensures that sufficient adhesive is available for bonding without requiring excessive adhesive application that would cause extrusion and flow into thrust bearing gaps during insertion.
2Strength
If the bearing sleeve is inserted through press-fitting to increase fixation strength, then the bonding strength is improved, but the adhesive becomes more liable to occur and flow around the bearing sleeve
Solution Approach 1:
The adhesive pool acts as an intermediary element between the bearing sleeve and housing. By providing this intermediate adhesive layer in advance, the patent mediates the interaction during press-fitting insertion, allowing the bearing sleeve to be securely fixed while preventing adhesive extrusion and flow into thrust bearing gaps that would otherwise occur during the press-fitting process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively increases the fixation strength of the bearing sleeve to the housing, reduces adhesive flow into thrust bearing gaps, and maintains bearing performance by ensuring sufficient adhesive interposition and lubricant circulation.
Implementation Method 1
Bonding fixation of the bearing sleeve with respect to the housing is performed, for example, by inserting the bearing sleeve along the inner periphery of the housing while an adhesive is applied to the inner peripheral surface of the housing, and the adhesive is cured thereafter.
Implementation Method 2
an inner peripheral chamfer continuous with the adhesive pool is provided on an inner peripheral portion of the housing; a gap between the inner peripheral chamfer and the bearing sleeve is sealed with an adhesive
Implementation Method 3
a shaft member inserted along an inner periphery of the bearing sleeve, the shaft member being supported in a radial direction by oil films formed in radial bearing gaps between an inner peripheral surface of the bearing sleeve and an outer peripheral surface of the shaft member, the oil films being formed in accordance with a relative rotation of the bearing sleeve and the shaft member
Data Source
AI summary
To increase fixation strength of a bearing sleeve with respect to a bottomed cylindrical housing, a fluid dynamic bearing device (1) is provided with a bottomed cylindrical housing (7), a bearing sleeve (8) fixed to an inner periphery thereof, and a shaft member (2) inserted along an inner periphery of the bearing sleeve (8). An adhesive pool (11) is provided between an inner peripheral surface (7a2) of a smaller diameter portion (7a) of the housing (7) and an outer peripheral surface (8d) of the bearing sleeve (8), which are opposed to each other. Further, an inner peripheral chamfer (7f) continuous with the adhesive pool (11) is provided on an inner peripheral portion of the housing (7), and a first tapered space (12) formed between the inner peripheral chamfer (7f) and the bearing sleeve (8) is sealed with an adhesive (13).