What should I do if the roller bearings are running off track?

When the roller bearing is in operation, the wooden stick performs a pure turning movement on the inner and outer ring raceways, so the support frame that drives the roller must have sufficient drag force to overcome frictional resistance. If the drag force is not enough to overcome the friction resistance, the roller will roll on the dovetail guide rail, causing a speed difference, that is, deviation. So what should you do if your roller bearings are misaligned?

Roller bearing

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

The roller is held by the rotating ring. When the strength allows, its weight can be reduced to achieve the purpose of reducing inertial resistance. It becomes very important to avoid and reduce scrolling. This strategy is relatively simple, just reduce its number and diameter. In airline turbines, due to the small external load, contact fatigue is no longer the main damage factor of the rollers. According to the basic standard, the bearing size margin may be large. It is generally believed that the number of rollers is reduced by 50%, and after the diameter is reduced by 25%, its contact fatigue life will not be affected. Many automobile engines have adopted this strategy. For example, the Spey engine main bearing is of this type, which not only has significantly fewer rollers, but also has a small size.

2. Choose an effective structure and reduce cage weight

In addition to minimizing its weight when the strength allows, the cage should also consider its own characteristics, such as resonance, high-speed running resistance, etc. should be avoided.

The correct guide method of the cage is also a very critical factor in fast bearings. If the unevenness of the cage is considered to be stable, changing the cage from the outer guide to the inner guide is also very beneficial for reducing deviation. Due to the relative velocity between the outer guide, the guide surface of the cage and the bearing, the sliding oil produces a viscous friction resistance, while the inner guide is reversed, the viscosity of the sliding oil between the cage and the guide surface The force becomes the drag force. In this way, the viscous frictional resistance becomes a force dragging the cage to rotate. The difference between the two cannot be ignored.

3. Oil provided under the ring

The advantage of using the oil provided under the ring is that it takes away the heat of the bearing and at the same time minimizes the additional damage caused by mixing. Another example is changing the outer ring with ribs to the inner ring with ribs, which will undoubtedly reduce the frictional resistance of mixing, as shown in Figure 4.

4. Use hollow roller preload bearings

Hollow roller preload bearings can add preload to all rollers so that there is no rolling in all areas. Because the speed ratio and temperature range of the rotor bearing of the turbine motor are relatively wide, it is reasonable to choose the appropriate preload carefully. Even at very low additional loads, excessive preload can cause premature roller failure. A common form of destruction is bending and fatigue. For a typical hollow roller, the ratio of the diameter to the inner diameter is 2, and the hole stress should be less than 25,000 lbs/ft; the coaxiality of the inner and outer diameters should be maintained at 0.005mm.

5. Choose elliptical bearings

The use of elliptical bearings is the most common ground anti-skid method, and generally has two structures: double-lobe and three-lobe. Taking the double-lobe elliptical bearing as an example, talk about its structure and ground anti-skid principle. The diameter of the outer ring of this type of bearing is generally elliptical, and the inner diameter (raceway) of the outer ring and the bearing seat are both ring-shaped. After installation, the outer ring raceway becomes an ellipse, which adds preload to the rollers. In other words, the axial backlash between the roller and the dovetail guideway at the short drive shaft of the elliptical dovetail guideway is cleared (creating clearance fit), and the rollers are reduced. Therefore, in addition to the fact that several rollers at the bottom are subjected to the force load of the motor rotor, the rollers at 90° to the left and right are also subjected to a certain amount of preload, so that the number of rollers bearing the load Increase to about 60% of the number of rollers (roller bearings generally bear the load on the number of rollers accounting for about 20% of the number of rollers). Therefore, increasing the drag force is helpful to prevent the rollers and cage from misalignment. However, the way to obtain the ovality will reduce the fatigue life of the bearing, so the selection of ovality must be considered in the application.