Self-Lubricated Sliding Bearing Groove Layout for Radial Load Control
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Solution Overview
Problem
High-end rotating anode X-Ray tubes face challenges with existing self-lubricated sliding bearings that are insufficient for high gantry and anode rotation speeds, leading to eccentricity and reduced load-bearing capacity due to radial loads and centrifugal forces.
Innovation Solution
A self-lubricated sliding bearing design featuring a first and second bearing member with a lubricant-filled gap, where the second bearing member has a modified pumping pattern with a shallower and narrower groove depth and width around a sector of the circumference, aligned to counteract radial loads and centrifugal forces, reducing eccentricity and enhancing load-bearing capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional self-lubricated sliding bearing with a fixed groove depth and optimised groove angle is used, then the load carrying capacity is optimised for standard conditions, but the bearing cannot effectively resist radial loads at high rotation speeds, leading to increased eccentricity
Solution Approach 1:
The bearing groove geometry is made variable rather than fixed. The groove depth varies continuously around the circumference, being deeper in the load zone and shallower in the opposite zone. This dynamic geometric variation allows the bearing to adapt to different operating conditions and effectively counteract radial loads at high rotation speeds, resolving the contradiction between maintaining load carrying capacity and operating at high speeds
Solution Approach 2:
Different sections of the bearing groove have different depths tailored to local requirements. The groove is deeper in the load-bearing zone to enhance lubricant retention and pressure generation where needed, and shallower in the opposite zone to reduce negative pressure effects. This local differentiation allows the bearing to simultaneously optimize performance for both load carrying and high-speed operation
2Reliability
If the groove depth is increased to enhance lubricant pumping action, then the load bearing characteristic improves, but the eccentricity caused by radial load forces increases
Solution Approach 1:
The bearing groove geometry is made asymmetric with respect to the bearing centerline. The groove depth is intentionally made non-uniform, with deeper sections positioned in the load zone and shallower sections in the opposite zone. This asymmetric design creates a balanced pumping action that generates positive pressure to support loads while simultaneously reducing negative pressure that would otherwise increase eccentricity
Solution Approach 2:
The groove depth parameter is varied continuously around the circumference rather than remaining constant. By changing this geometric parameter spatially, the bearing achieves optimized lubricant pumping characteristics in different zones, balancing load support with eccentricity control through controlled variations in groove depth
3Speed
If a full redesign of the bearing is performed to accommodate higher rotation speeds, then the bearing can effectively handle high-speed operation, but the complexity and cost of the design increases
Solution Approach 1:
The bearing groove is divided into different functional zones with distinct depth characteristics. The groove is segmented into a load zone with deeper grooves and an opposite zone with shallower grooves. This segmentation allows each zone to perform its specific function optimally without requiring a complete redesign of the entire bearing structure, thus managing complexity while enabling high-speed operation
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 modified pumping pattern effectively reduces or cancels the eccentricity caused by radial loads, enhancing the load-bearing capacity and extending the life of the bearing without requiring a full redesign of the X-Ray tube, allowing for faster gantry rotation speeds in X-Ray imaging systems.
Implementation Method 1
a first region (42a, 42b) comprising a pumping pattern (48) configured to pump the lubricant (36)
Implementation Method 2
a bearing force generated by the pumping action of the lubricant opposes a radial load force exerted on the self-lubricated sliding bearing
Data Source
Figure 1
Figure 1A~2A
Figure 3
AI summary
As gantry speeds experienced in CT scanners increase, so too does the radial load force exerted on components attached to the gantry. A self-lubricating sliding bearing used inside a rotary X-Ray source of a CT scanner is particularly susceptible to increasing radial load force, because in operation, a self-lubricating bearing floats on a film of liquid lubricant. Thus, the radial load force will tend to act on the floating portion of the bearing to develop an eccentricity in the longitudinal axis of the floating portion of the bearing as compared to the longitudinal axis of the stationary part of the bearing. The eccentricity will eventually cause the floating portion of the bearing to contact the stationary part of the bearing in operation, thus limiting the load carrying characteristic of the self-lubricating sliding bearing. Accordingly, the present application proposes a modification to the design of a self-lubricating sliding bearing, in which the pumping pattern of the bearing is reduced or removed at special portions within the bearing, to thus compensate for the effect of the radial load force.