Rigidity and lubrication of crossed roller bearings

Rigidity Because there are more cylindrical rollers, the bearing has higher axial and radial load carrying capacity. The line contact between the roller and the raceway ensures that the bearing has a higher rigidity. After the installation and fit, the rigidity of the bearing will also increase due to the increase of the preload. The axial offset a of the crossed roller bearing can be obtained by the following formula under the action of the axial force Ka passing through the shaft center. Axial offset when Ka 2.114 · FV: Axial offset when K 2.114 · FV: a mm Axial offset between shaft washer and seat washer Ka kN Internal axial force FV kN Bearing preload Cs kN0.926 /mm Axial rigidity parameter. The calculation can only give the deflection of the bearing and must also consider the deflection of the surrounding structural parts. Sealed bearings are open. Some seals can be designed on the surrounding structural parts. Lubricated cross roller bearings can be lubricated with oil or grease. Grease lubrication For grease lubrication, high-quality lithium-based greases KP2N20 to DIN 51825 are suitable, such as Arcanol MULTITOP. For low speeds, especially horizontal shafts, simple grease lubrication is sufficient. For vertical shaft grease lubrication, a baffle must be installed under the bearing to prevent grease leakage. It is recommended to use lithium-based grease with EP additives. When adding grease for initial installation, add some grease in the gap between the rollers. The amount of regrease is 20% to 30% of the initial grease amount. Oil lubrication For oil lubrication, oil CLP conforming to DIN 51517 or HLP conforming to DIN 51524 Viscosity ISO VG 46 to ISO VG 68 are suitable. Circulating oil lubrication Generally speaking, the circulating oil of the cross roller can be shared with the drive system. If it is only used for bearing lubrication, only a small amount of lubricating oil is needed. For high speed, oil cooling is required, and a large amount of lubricating oil is required, as shown in Figure 5. For each working condition, the actual amount of oil required in the end is determined by the bearing temperature. V u003d Oil quantity Du003d Bearing outer diameter a u003d Sufficient oil quantity required for lubrication b u003d Oil quantity required for cooling and lubrication Lubrication and cooling Only used for lubricating the oil quantity shown in Figure 5. The reference viscosity of mineral oil is determined by the reference viscosity 1 in order to ensure adequate lubrication of NTN bearings. In this case, ensure that the lubricant's working viscosity (viscosity at working temperature) is at least equal to the reference viscosity 1. Ratio u003d / 1 u003d 2, Figure 6. The reference viscosity is determined by the average bearing diameter dM u003d (D + d)/2 and the speed. The working viscosity can be queried through the viscosity/temperature table, the reference temperature and the viscosity at +40 °C are required. Lubricants with an operating viscosity greater than 1 at operating temperature have a positive effect on bearing fatigue life. In addition, bearings with EP additives can ensure adequate lubrication at low speeds. EP additives are also required at lower levels. Operating temperature The suitable operating temperature range for crossed roller bearings is 30 °C to +80 °C. n u003d Working speed 1 u003d Reference viscosity dM u003d Bearing diameter (d +D)/2 u003d Working temperature Viscosity mm2s1 at +40 °C Figure 6 Reference viscosity and V/T of mineral oil.