Thrust Bearing Tapered Pad Wedge Effect
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Rotary machines, such as superchargers, face challenges in securing high bearing performance against thrust loads due to increased demands for pressure ratio and expansion ratio, which intensify the thrust load on the rotor shaft.
Innovation Solution
A thrust bearing structure utilizing a wedge effect of lubricating oil, where the thrust collar and bearing pads have tapered sections with sloping surfaces that thicken along the trajectory of oil droplets under centrifugal force, enhancing the proportion of oil contributing to the wedge effect and improving load-bearing capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the pressure ratio and expansion ratio are increased to improve supercharger performance, then the thrust load on the rotor shaft increases, but the bearing capacity against thrust load deteriorates
Solution Approach 1:
The bearing pad is divided into different sections with different functions: a tapered section for generating wedge effect and a land section for load bearing. Each section has optimized local properties to maximize the wedge effect and bearing capacity under high thrust loads
Solution Approach 2:
The clearance between the collar pad and bearing pad is designed to vary continuously along the rotating direction, creating a tapered geometry. This parameter change generates the wedge effect that produces hydrodynamic pressure to support the thrust load
2Device complexity
If a conventional thrust bearing structure is used, then the structure is simple, but the bearing performance against increased thrust load is insufficient
Solution Approach 1:
The bearing pad incorporates a tapered section with continuously varying clearance to generate wedge effect, combined with a land section for load support. This localized geometric variation enhances bearing performance without significantly complicating the overall structure
Solution Approach 2:
The thrust bearing utilizes hydrodynamic lubrication where lubricating oil is pressurized through the wedge effect generated by the tapered section. The oil film pressure supports the thrust load, replacing direct metal-to-metal contact with fluid film support
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 enhanced wedge effect allows for efficient and high-performance bearing of thrust loads, ensuring the supercharger maintains optimal operation under increased load conditions.
Implementation Method 1
A surface of the tapered section is inclined in such a manner as to gradually get closer to the collar pad in the rotating direction of the rotor shaft. When the rotor shaft rotates together with the collar pad, the lubricating oil flows in their rotating direction due to the rotation and viscosity of the lubricating oil. The flow of the lubricating oil converges between the land section and the collar pad. As a consequence, a pressure inside the lubricating oil is increased at the land section and at a portion of the tapered section near the land section, thereby drawing the collar pad and the thrust bearing away from each other. This effect is generally referred to as a wedge effect.
Implementation Method 2
the trajectory determined based on a centrifugal force generated by rotation of the rotor shaft and applied to the oil droplet
Data Source
Figure 1
Figure 2
Figure 3(a)~3(b)
AI summary
A thrust bearing structure (39) is equipped with a thrust collar (41) having a collar pad (67), and a thrust bearing (43) having a bearing pad (71) at a position corresponding to the collar pad (67) on a surface facing the thrust collar. The bearing pad (71) has a tapered section (73), and a land section (75) continuously formed on the outer edge of the tapered section (73). Assuming that oil droplets are supplied between the bearing pad (71) and the collar pad (67), and assuming that the rotation speed of a rotor shaft (15) is constant, the tapered section (73) would have a sloping surface formed in such a manner that a wall thickness gradually becomes thicker toward the downstream side along the trajectory (T) of given oil droplets based on the centrifugal forces acting on the droplets due to the rotation of the rotor shaft (15).