Thrust Bearing Sliding Layer With Anisotropic Thermal Expansion
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Solution Overview
Problem
Conventional sliding members in thrust bearings, particularly those with synthetic resin compositions, are prone to surface cracks and shear failures due to thermal expansion and pressure from fluid films, especially at high speeds, leading to reduced durability and performance.
Innovation Solution
A sliding member with a partially annular shape, featuring a back-metal layer and a synthetic resin sliding layer, where the linear expansion coefficients in different directions are carefully controlled to achieve anisotropic thermal expansion, reducing the likelihood of cracks and shear failures. The sliding layer includes specific materials like polyether ether ketone and fibrous particles, and a porous metal portion on the back-metal layer enhances bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the resin composition of the sliding layer is thermally expanded in an almost isotropic manner, then the sliding layer can accommodate thermal expansion uniformly, but damage such as cracks and shear failures is highly likely to occur due to elastic deformation from fluid film pressure
Solution Approach 1:
The patent applies local quality by creating anisotropic thermal expansion characteristics in different regions of the sliding layer. Specifically, the sliding layer is designed with different linear expansion coefficients in the radial direction (parallel to sliding surface) versus the thickness direction (perpendicular to sliding surface). This localized differentiation of thermal expansion properties allows the material to expand differently in different directions, preventing uniform isotropic expansion that leads to cracks while maintaining overall structural integrity under fluid film pressure
Solution Approach 2:
The patent changes the thermal expansion parameters of the sliding layer by specifying that the linear expansion coefficient in the radial direction (αr) should be smaller than the linear expansion coefficient in the thickness direction (αt). This parameter change from isotropic to anisotropic thermal expansion fundamentally alters how the sliding layer responds to thermal and mechanical loads, reducing crack formation while maintaining reliability under operating conditions
2Speed
If the sliding member operates at high speed, then productivity and performance are improved, but centrifugal force has a large influence on the fluid film causing increased thermal expansion and elastic deformation
Solution Approach 1:
The patent addresses high-speed operation effects by changing the thermal expansion parameters of the sliding layer. By designing the sliding layer with anisotropic thermal expansion characteristics (αr < αt), the material can better accommodate the thermal and mechanical stresses generated at high rotational speeds, reducing the harmful effects of centrifugal force on the fluid film while maintaining operational performance
3Stability of the object's composition
If the amount of thermal expansion in the thickness direction is approximately same as in the in-plane direction, then isotropic expansion is achieved, but shear failure is more likely to occur at the interface between the back-metal layer and the sliding layer
Solution Approach 1:
The patent applies local quality by creating different thermal expansion characteristics in different directions of the sliding layer. The sliding layer is designed with a smaller linear expansion coefficient in the radial direction (αr) compared to the thickness direction (αt). This directional differentiation prevents uniform isotropic expansion that causes shear failure at the interface, while maintaining appropriate expansion in the thickness direction to preserve interface bonding strength between the back-metal layer and sliding layer
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 controlled thermal expansion coefficients and material composition significantly reduce the occurrence of cracks and shear failures, enhancing the durability and reliability of the sliding member during high-speed operations.
Implementation Method 1
the sliding layer has a linear expansion coefficient KS in a direction parallel to a circumferential direction of the sliding member, a linear expansion coefficient KJ in a radial direction of the sliding member, and a linear expansion coefficient KT in a direction perpendicular to the sliding surface
Implementation Method 2
KS, KJ, and KT satisfy the following relations (1) and (2): 1.1 ≤ KS/KJ ≤ 2.0 and 1.3 ≤ KT/((KS+KJ)/2) ≤ 2.5
Implementation Method 3
a porous metal portion on the back-metal layer enhances bonding
Implementation Method 4
due to frictional heat generated by sliding
Implementation Method 5
dynamic pressure is generated due to a wedge effect, and the lubricant forms a fluid film. The fluid film supports an axial load of the rotating shaft
Implementation Method 6
when the shaft rotates with a high speed, a centrifugal force has a large influence on the fluid film
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
Provided is a sliding member (1) for a thrust bearing. The sliding member includes a back-metal layer (2) and a sliding layer (3), and has a partially annular shape. In a center line region of the sliding layer, the sliding layer (3) includes a synthetic resin (4) and has a sliding surface (30). The sliding layer (3) has a linear expansion coefficient KS in a direction parallel to a circumferential direction of the sliding member, a linear expansion coefficient KJ in a direction parallel to a radial direction of the sliding member, and a linear expansion coefficient KT in a direction perpendicular to the sliding surface (30), and the linear expansion coefficients KS, KJ, and KT satisfy the following relations (1) and (2): Relation (1): 1.1 ≤ KS/KJ ≤ 2; and Relation (2): 1.3 ≤ KT/{(KS + KJ)/2} ≤ 2.5.