PRINCIPLE OF AIR BEARING
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When two surfaces form a wedge, and one surface moves relative to the other surface,
pressure is generated between the surfaces due to the hydrodynamic action of the fluid which carries load.
Eccentricity occurs at the center of the rotor and the bearing by self-load of the rotor, thereby production Con-vering Region.
Hydrodynamic pressure is produced in the conversing region by the rotational force of the rotor.
The airfoil bearing supports the rotor by using that hydro-Dynamic pressure.
The rotor emerges and rotates at 2,000 rpm or higher, and the friction loss that occurs during operation is close to zero.
JOURNAL BEARING
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Even though, the principle of an air bearing is simple, but application is complex.
Usually running radial clearance between the shaft and the bearing is less than 0.012mm
for a 50mm diameter shaft running at 36,000 rpm.
But the shaft growth due to temperature and centrifugal force could be 0.05mm.
Hence a bearing can not be made to work at various speeds and temperatures.
In addition, damping is required to suppress any whirl instability,
and there could be misalignment between various rotating parts and stationary parts.
These problems are resolved by foil bearings.
THRUST BEARINGS
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Thrust bearings withstand axial loads in a rotating machinery.
In a journal bearing the wedge action comes from eccentricity between the center of the rotating shaft
and the center of the bearing itself, whereas in a thrust bearing the wedge is built in taking into account any deflection due the axial load.
There are multiple radial springs which transfer the load to the housing.
Foils between the springs deflect under pressure forming the wedge required for the hydrodynamic action.
Our company developed and applied double layer coating to improve wear resistance and adhesive force while maintaining the unique slippery characteristics of Teflon coating.
FEATURE
- By applying the double bump foil composed of the upper and lower parts, this company prevented the permanent deformations of the upper and lower bump foils caused by abrupt changes of load to improve the deformation of bump bearings due to the external environment.
- To elevate the strength and tensile strength of a bearing, this company has used its own 3 stage heat treatment process with the annealing added and consequently increased the credibility of bearings.
MULTI-LEAF TYPE
- The design is such that pressure occurs even on the upper pad, where the load is not applied, due to the preload formed by the multi-leaf shape, and it increases the sensitivity and attenuation by more than 30% compared with the Single Pad. The purpose was to ensure excellent high-speed stability.
DOUBLE – BUMP STRUCTURE
- A general Foil Bearing uses 1 Bump Foil to support the Top Foil. However, if a large load occurs abruptly due to the external environment, it has the problem that the Bump is not restored, and a permanent deformation occurs.
- Therefore, ACE applied the double Bump Foil composed of the upper and lower parts to prevent the permanent deformations of the upper and lower bump foils even under abrupt load changes. Consequently, ACE improved the credibility of the bearings.
DOUBLE LAYER TEFLON COATING
- When the high-speed motor operates or stops, it contacts bearings because the revolutionary speed of the shaft is low. To prevent the abrasion of bearings at such moments, this company applies Teflon coating, which generally endures high temperature, to strengthen the sliding property.
- To improve the abrasion resistance and adhesion of the Teflon coating while maintaining the sliding property of the coating, this company developed a new coating technology to improve the abrasion resistance and adhesion of the coating.
3 – STEP HEAT TREATMENT
- The heat treatment of the Inconel material is generally carried out in two stages, but the material cannot altogether remove the stress that occurs during heat treatment. In the case of high-speed revolutions or frequent ON/OFFs as in the High-Speed Turbo Blower, bearings may undergo fatigue fracture, cracks, or deformations.
- To enhance the strength and tensile strength of bearings, ACE applied heat treatment to the Inconel material according to its own 3-stage heat treatment process with the annealing added and consequently increased the credibility of the foil bearings.
