Spindle Motor Thrust Bearing Stiffness
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Solution Overview
Problem
Conventional spindle motor designs for HDDs in mobile applications face challenges in maintaining bearing stiffness at high temperatures while minimizing current consumption, leading to noise generation and reduced service life due to metal contact sliding wear, especially when subjected to sudden orientation changes.
Innovation Solution
The spindle motor incorporates a shaft with a thrust flange, a sleeve, radial and thrust hydrodynamic grooves, and a lubricant, where the thrust hydrodynamic groove's outside diameter is at least 10% larger than the disk, and the groove width ratio is adjusted to prioritize angular stiffness in the thrust bearing, reducing interference with the radial bearing and minimizing viscous frictional torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bearing stiffness is increased to suppress vibration and noise, then reliability improves, but viscous frictional torque increases leading to higher current consumption
Solution Approach 1:
The bearing system is segmented into two distinct functional zones: radial bearing for supporting disk weight and suppressing eccentricity, and thrust bearing for absorbing gyro moments. This segmentation allows each bearing to be optimized for its specific function, preventing the need to over-stiffen both bearings simultaneously, thus reducing overall viscous frictional torque while maintaining necessary stiffness where required.
Solution Approach 2:
Different bearing characteristics are applied to different locations and functions: the radial bearing is designed with lower angular stiffness to minimize friction, while the thrust bearing is designed with higher angular stiffness to handle gyro moments. This local differentiation of bearing properties allows the system to achieve necessary reliability without excessive current consumption.
2Reliability
If bearing stiffness is increased to maintain stability at high temperatures, then reliability improves, but metal contact sliding wear occurs causing noise and reduced service life
Solution Approach 1:
The bearing system is divided into radial and thrust functional zones, allowing the thrust bearing to specialize in absorbing gyro moments that cause metal contact wear and noise during rapid panning. This segmentation protects the radial bearing from excessive wear while maintaining overall system stability at high temperatures.
Solution Approach 2:
The thrust bearing acts as an intermediary element that absorbs gyro moments before they can cause metal contact sliding wear in the radial bearing. By introducing this intermediate thrust bearing structure, the harmful wear and noise are prevented while maintaining necessary bearing stiffness.
3Reliability
If both radial and thrust bearings are used to handle gyro moments, then reliability improves, but the bearings interfere with each other producing abnormal vibration noise
Solution Approach 1:
The bearing system is functionally segmented with the radial bearing handling only radial loads and eccentricity suppression, while the thrust bearing handles axial loads and gyro moments. This clear functional segmentation prevents interference between the two bearing types, eliminating abnormal vibration noise while maintaining disturbance resistance.
Solution Approach 2:
Instead of having both bearings share the gyro moment load (which causes interference), the design inverts the approach by assigning gyro moment absorption exclusively to the thrust bearing. This inverted functional assignment eliminates bearing interference and abnormal noise.
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
This design effectively suppresses noise and extends service life by ensuring the thrust bearing handles gyro moments, reducing abnormal vibrations and power consumption, while maintaining adequate bearing stiffness and low power usage.
Implementation Method 1
a radial hydrodynamic groove, a thrust hydrodynamic groove, and a lubricant. The radial hydrodynamic groove is provided to the inner peripheral surface of the bearing hole and/or to the outer peripheral surface of the shaft. The thrust hydrodynamic groove is provided to the surface of the thrust plate and/or the surface of the thrust flange portion
Implementation Method 2
The lubricant fills the microscopic gap in the radial direction and the microscopic gap in the axial direction
Data Source
AI summary
A spindle motor can suppress the generation of noise during swinging and the extend service life, and also suppress the increase in current consumption. The outside diameter of a thrust hydrodynamic groove is at least 10% of the outside diameter of a disk-shaped medium, and the depth of the radial hydrodynamic groove is greater than the depth of the thrust hydrodynamic groove. By adjusting to specific numbers, the angular stiffness in the thrust bearing is raised, and even if a disturbance torque should be applied, wear or noise caused by metal contact inside the bearing can be suppressed.