Auxiliary Bearing Misalignment for Starting Torque
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Solution Overview
Problem
Auxiliary ball-bearing systems in magnetically suspended rotor systems face challenges in maintaining sufficient starting torque, especially under high-speed conditions and severe process gas cooling flows, leading to uncontrolled rotation and accelerated wear due to insufficient resistive torque.
Innovation Solution
The introduction of a misalignment between coaxially arranged annular surfaces in the auxiliary bearing, achieved through geometrical offset, differential loading, or the use of annular wavy spring washers with varying stiffness, to create radial or angular misalignment, thereby increasing the starting torque without altering the bearing's behavior during landing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional auxiliary bearings with coaxially aligned ball bearings are used, then the structure is simple and easy to manufacture, but the starting torque is insufficient under high-speed conditions and severe cooling flows
Solution Approach 1:
The patent applies asymmetry by intentionally misaligning the axes of the first and second ball bearings relative to each other. This misalignment creates an asymmetric load distribution that generates higher starting torque. The asymmetric configuration is achieved through geometric offset between the bearing seats or by applying differential axial loads, transforming the symmetric coaxial arrangement into an asymmetric one that better resists high-speed cooling flows.
Solution Approach 2:
The patent changes the geometric parameters of the bearing arrangement by introducing an offset between the first and second ball bearing axes. This parameter change (from zero offset to non-zero offset) directly increases the starting torque. The offset can be implemented through geometric design of the bearing seats or by applying differential preloading forces, thereby modifying the operational characteristics of the auxiliary bearing system.
2Speed
If ball bearings are used to increase load carrying capacity and handle high sliding speeds, then the bearing can support high speeds and loads, but the starting torque becomes insufficient under severe cooling conditions
Solution Approach 1:
The patent resolves this contradiction by introducing asymmetric misalignment between the first and second ball bearings. While both bearings remain capable of handling high speeds and loads, their misaligned configuration creates a mechanical advantage that significantly increases the starting torque. This asymmetric arrangement allows the bearing system to simultaneously maintain high-speed capability and generate sufficient starting torque even under severe process gas cooling flows.
3Ease of operation
If the auxiliary bearing is softly preloaded in axial and radial directions, then the bearing operates smoothly during normal operation, but the starting torque is reduced due to the soft preload
Solution Approach 1:
The patent overcomes this contradiction by introducing asymmetric misalignment between the ball bearings. The soft preload maintains smooth operation during normal running conditions, while the misaligned configuration generates higher starting torque. The misalignment creates a mechanical leverage effect that compensates for the reduced torque from soft preloading, allowing the bearing to start reliably even with minimal preload forces.
Solution Approach 2:
The patent addresses the torque deficiency by transitioning from a single-dimension preload approach to a multi-dimensional solution. By misaligning the ball bearings, the system utilizes both radial and axial force components in combination, creating a resultant force vector that provides higher starting torque while maintaining the benefits of soft preload for smooth operation.
Data Source
AI summary
An assembly includes a rotating shaft supported with respect to a stationary housing by at least one active magnetic bearing presenting a mean radial air gap and at least one auxiliary bearing having first and second coaxially arranged annular surfaces is provided. One of the first and second coaxially arranged annular surfaces defines a clearance (E2) with one of the stationary housing and the rotating shaft, the clearance (E2) being less than the mean radial air gap and the other of the first and second coaxially arranged annular surfaces being integral with the other one of the stationary housing and the rotating shaft. The auxiliary bearing provides a first ball bearing and a second ball bearing having a misalignment with respect to each other in order to increase the starting torque.