Bellows Spring Preload for Centering Tapered Roller Bearings
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing gas turbine engine fan drive gear systems with tapered roller bearings face challenges in accommodating variations due to component tolerances and bearing flexure, leading to excessive wear and instability, particularly in the radial direction.
Innovation Solution
A bellows spring is used to apply preload to both tapered roller bearings in a confined space, acting as a centering spring in the axial direction while accommodating radial flexure, thus maintaining contact and reducing wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a stiff spring load is applied to the tapered roller bearings in the axial direction, then the bearing contact is maintained, but the system cannot easily accommodate variation due to component tolerances
Solution Approach 1:
The spring stiffness parameter is optimized to provide sufficient axial preload while maintaining flexibility. The bellows spring's geometric parameters (convolutes, wire diameter, mean diameter) are specifically designed to achieve the right balance between maintaining bearing contact and accommodating tolerance variations in the bearing compartment assembly.
Solution Approach 2:
The system transitions from a rigid spring connection to a dynamic bellows spring connection that can adapt its response. The bellows structure allows the spring to dynamically adjust to radial displacements and tolerance variations while maintaining axial preload, enabling the system to accommodate component variations without losing bearing contact.
2Reliability
If a traditional spring is used to apply axial preload, then bearing contact is maintained, but the spring does not accommodate bearing flexure in the radial direction leading to excessive wear
Solution Approach 1:
The bellows spring utilizes a flexible corrugated structure with multiple convolutes that can expand and contract radially. This flexible shell design allows the spring to accommodate bearing flexure and radial movements without transmitting excessive forces to the bearing surfaces, thereby preventing wear while maintaining axial preload.
Solution Approach 2:
The bellows spring provides dynamic radial compliance through its convoluted structure. As the bearing flexes radially during operation, the bellows spring can dynamically adjust its radial dimension, absorbing the movement without creating harmful contact stresses that would lead to bearing wear.
3Reliability
If multiple separate springs are used for preload and centering, then both functions are achieved, but the device complexity and space requirements increase
Solution Approach 1:
The bellows spring combines multiple functions into a single integrated component. The corrugated structure simultaneously provides axial stiffness for preload application and radial flexibility for centering and accommodating bearing flexure, eliminating the need for separate springs and reducing overall system complexity.
Solution Approach 2:
The bellows spring is designed as a multi-functional element that performs axial preload, radial centering, and tolerance accommodation all at once. This universal component replaces what would traditionally require multiple specialized springs, simplifying the bearing compartment assembly.
4Stability of the object's composition
If the fan shaft is made longer to increase stability, then shaft stability improves, but the envelope constraints of the bearing compartment are violated
Solution Approach 1:
The bellows spring's geometric parameters are specifically designed to maximize axial stiffness while minimizing radial dimension. By optimizing the number of convolutes, wire diameter, and mean diameter, the spring provides sufficient axial preload to stabilize the short fan shaft without requiring excessive radial space that would violate bearing compartment envelope constraints.
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 bellows spring solution enhances stability and reduces wear on the bearings, allowing for proper operation of the squeeze film damper system while saving space and lowering manufacturing costs.
Implementation Method 1
A spring load must be maintained between the tapered roller bearings to keep the rollers in contact with the raceways
Implementation Method 2
The bellows spring is accommodating of flexing in the radial direction by the first tapered roller bearing and the second tapered roller bearing such that the bellows spring does not wear on the surfaces of bearings
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An assembly includes a first tapered roller bearing (14A) and a second tapered roller bearing (14B) and a bellows spring (20). The bellows spring is disposed adjacent the first tapered roller bearing and the second tapered roller bearing. A method of applying a preload to a first tapered roller bearing and a second tapered roller bearing is also disclosed.