Hydrodynamic Bearing Bubble Suppression via Recessed Flange
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Solution Overview
Problem
Conventional hydrodynamic bearing devices in spindle motors are prone to generating negative pressure and fluid leakage due to vibrations or impacts, which affects their durability and reliability.
Innovation Solution
The hydrodynamic bearing device incorporates a bubble suppression portion and communicating portions to manage fluid flow and pressure, preventing negative pressure formation by ensuring smoother fluid movement and increased volume capacity, thus enhancing durability and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the flange portion and flange cover are made with flat faces and a narrow gap (about 0.1 mm), then the structure is simple and compact, but vibration or impact generates negative pressure at the center, causing bubbles to form and lubricating fluid to leak
Solution Approach 1:
The flange portion is divided into a center portion and an outer peripheral portion with different functions. The center portion has a recessed bottom surface to prevent negative pressure, while the outer peripheral portion maintains the narrow gap for bearing function. This segmentation allows each part to optimize its performance without compromising the other.
Solution Approach 2:
The bottom surface of the flange portion is made non-flat (recessed) specifically at the center portion where negative pressure tends to occur, while other areas maintain their original flat structure. This local modification targets the specific problem area without changing the overall simple structure.
2Speed
If the shaft rises suddenly during impact, then the space between the sleeve and flange cover increases, but the oil cannot move quickly enough through the narrow gap due to viscosity, generating negative pressure and bubbles
Solution Approach 1:
The bottom surface of the flange portion is recessed in the axial direction, creating an additional volume dimension. This allows the oil to be stored in advance in the recessed portion, so when the shaft rises suddenly, the oil can be supplied from this reservoir without needing to move quickly through the narrow radial gap.
Solution Approach 2:
The recessed bottom surface pre-positions the lubricating fluid in the center portion of the flange portion before impact occurs. This preliminary arrangement ensures that when sudden impact causes the shaft to rise, the oil is already in position to fill the expanding space, preventing negative pressure and bubble formation.
3Stress or pressure
If communicating holes are provided in the inner periphery of the flange portion, then pressure imbalance is eliminated, but bubbles can enter through the holes and cause lubricating fluid to leak
Solution Approach 1:
The recessed bottom surface is specifically located in the center portion of the flange portion, away from the inner periphery where communicating holes would be. This local modification addresses the negative pressure problem at the center without creating openings at the periphery that could allow bubble entry.
Solution Approach 2:
Instead of using communicating holes that could allow bubble entry, the invention uses the recessed bottom surface to create a positive pressure zone that actively prevents bubble formation. The recessed portion acts as a buffer that maintains positive pressure, converting the potential harm of pressure imbalance into a beneficial pressure stabilization mechanism.
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 prevents fluid leakage and improves the durability and reliability of the hydrodynamic bearing device even under conditions of impact or vibration, ensuring stable operation.
Implementation Method 1
the fluid pressure of oil or another such lubricating fluid interposed between a shaft and a sleeve is utilized to support the shaft and the sleeve so that they can rotate relative to one another
Implementation Method 2
the oil is drawn into the radial and thrust bearing portions by the pumping pressure generated by the hydrodynamic grooves
Implementation Method 3
Oil is held as a lubricating fluid in these tiny gaps
Data Source
AI summary
A hydrodynamic bearing device includes a sleeve having a bearing hole, a shaft, and a flange cover. The shaft is disposed in the bearing hole of the sleeve in a state of being capable of relative rotation, and has a large diameter flange portion. The flange cover is disposed opposite the bottom surface of the flange portion. A bubble suppression portion, which is formed as a recess on the bottom surface of the shaft, communicates with the upper surface of the flange portion through a communicating hole in the flange portion. This provides a hydrodynamic bearing device with which negative pressure is prevented from being generated in the bearing even when it is subjected to impact or vibration, and durability and reliability can be enhanced, as well as a spindle motor and a recording and reproducing apparatus equipped with this hydrodynamic bearing device.