1.Reduce the number of rollers and reduce the diameter of rollers

Roller is carried by rotating ring, in the case of strength allows, reduce its weight, to reduce the purpose of inertia resistance. It becomes very important to prevent and reduce slippage. Using this measure is relatively simple, just reduce its number and diameter can be achieved. Contact fatigue is not the main failure factor of roller in aero-turbine engine because of the small external load. According to the conventional standard bearing size redundancy is still large, it is generally believed that the number of rollers is reduced by 50%, and the diameter is reduced by 25%, still does not affect its contact fatigue life. Many engines have adopted this measure, for example, spebe engine main bearing is this type, not only the roller is sparse, but also small size.

2. Choose reasonable structure and reduce cage weight

In addition to reducing its weight as far as strength allows, the cage should also consider its own characteristics, for example, should avoid its resonance, high-speed rotation resistance and so on.

Cage guiding mode is also a very important factor in high-speed bearings. If the unbalance of the cage is properly controlled, the cage is changed from outside guide to inside guide, which is also very beneficial to reduce skid. Because of the relative movement between the outer guide cage and the guide surface of the bearing, the oil film forms a viscous resistance, while the inner guide is on the contrary. The viscous force between the cage and the guide surface of the oil film becomes a drag force. In this way, viscous resistance becomes a force that drags the cage around. The difference between the two can not be ignored.

3. Oil supply under the ring

Underring oil supply has the advantage of removing heat from the bearing while minimizing additional losses caused by agitation. And such as the outer ring of the rim to the inner ring of the rim, no doubt also can reduce the resistance of stirring.

4. using hollow roller preload bearing

Hollow roller preload bearing can apply preload to all rollers, so that no slip in all areas. Because turbine engine rotor bearing operating speed and temperature range is wide, so the selection of appropriate preload should be careful. Even at very low applied load, excessive preload will still cause premature roller failure. A common form of failure is bending fatigue. A typical hollow roller with an outer diameter to inner diameter ratio of 2 should have a maximum hole bending stress of less than 25,000 LBS/in. The concentricity of the inner and outer diameters should be kept at 0.005 mm.

5. the use of elliptical bearings

Elliptical bearing is the most common form of anti-skid, and generally has two types of structures, double and triple, as shown in Figure 6. Taking double disc elliptic bearing as an example, its structure and anti-skid mechanism are discussed. The outer diameter of the outer ring of this kind of bearing is oval, and the inner diameter of the outer ring (raceway) and the bearing seat are round. After assembly, the outer ring raceway becomes elliptical, that is, the roller is preloaded. That is to say, the radial clearance between the roller and the raceway at the short half axis of the elliptical raceway is eliminated (forming interference), so that the roller is compressed. Therefore, in addition to the bottom of a few roller by the rotor outside the effect of gravity load, on the left, right, 90 ° roller, also the load by a certain amount of additive, so the load of the roller number increased to about 60% of the total number of roller (roller bearing the load of the roller number commonly accounted for about 20% of the total number of roller), as shown in figure 7. Therefore, the added towing power helps prevent the roller and cage from slipping. However, the method of ellipticity can reduce the fatigue life of bearings, so it is necessary to consider the selection of optimal ellipticity in use.

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