Development of externally pressurized small-size conical-shaped gas bearings for micro rotary machines

We have developed externally pressurized small-size conical shaped gas bearings for micro rotary machines such as gas blowers, compressors, and medical devices. The bearings are lightweight and enable machines and devices to be downsized by reducing the number of parts, since the journal and thrust loads can be supported by a pair of bearings. The conical bearings (diameters 8 mm and 10 mm) were designed and the manufacturing techniques were considered. The bearing type is a double-row inherent orifice bearing with four feed holes per row. The shape accuracy of the manufactured bearings is within the design limits, being less than 0.005 mm in both roundness and cylindricity. The surface roughness (arithmetic average roughness) of the parts is 0.0002 mm. The static characteristics were calculated and validated by testing on manufactured bearings. Comparative agreement was obtained between the measured and designed values. The proposed calculation method presents as a relatively simple approach for predicting the bearing characteristics. The test rotor exceeded 350 Hz (21,000 rpm) in the rotational test, and whirl vibration was absent. During testing, the maximum rotor vibration amplitude was 0.0125 mm (corresponding to an eccentricity ratio of 0.89).