Friction resistance distance of slewing ring The slewing ring is a kind of large bearing parts that can bear complex loads. It can support the above part of the slewing ring for slewing motion, and at the same time bear the effects of large axial force, tilting moment and radial force. Slewing ring bearings are divided into four types according to different structures: four-point contact ball bearings, crossed cylindrical roller bearings, crossed tapered roller bearings and three-row cylindrical roller bearings. The three-row cylindrical slewing ring has three seats.
1 Analysis and calculation of friction torque
1.1 The mechanical calculation formula of friction resistance moment of slewing bearing is based on the formula: Tm=(2ωDN)/2. When the slewing bearing’s external dimensions and rollers are clear, the values of ω and D can be directly determined. Therefore, the friction resistance moment of the slewing bearing can be calculated The key step of Tm is to calculate the total pressure ΣN of all rollers.
1.2 Model assumptions As the slewing bearing bears the axial force Fa, radial force Fr and overturning moment T at the same time. The actual rigidity of the inner and outer rings of the slewing ring, the dimensional accuracy of the rolling elements, the processing accuracy of the raceway and the matching tolerances between the components directly affect the force distribution of the rolling elements. When calculating the force of the slewing ring by analysis, the following assumptions are required: Assume that the inner ring and the outer ring of the slewing ring are rigid bodies, and only elastic deformation occurs at the contact point of the rollers. The geometric dimensions of the rolling elements are exactly the same. The roundness of raceways, the concentricity of different raceways, roughness and other factors all meet the ideal requirements. The pressure generated by the rolling elements on the raceway is continuously distributed.
2 Numerical calculation method for frictional resistance moment of three-row roller slewing ring
Three-row roller slewing ring contains three ring gears, two horizontal raceways, and horizontal rollers are installed on the axis. The diameter of the upper horizontal roller is larger than the lower one. Sub diameter; a vertical raceway, the installation axis of the vertical roller. It can resist large axial force, radial force and tipping moment. When analyzing the force of the three-row roller slewing ring, it is assumed that the frictional force of the rollers in the radial direction on the horizontal raceway and the frictional force in the vertical direction on the vertical raceway are zero. The Nm caused by the axial external force Pa of the slewing ring and the tilting moment Pm caused by the ±Nm are borne by the rollers on the horizontal raceway, and the Nr caused by the radial external force Pr is borne by the rollers on the vertical raceway. The vertical force Na and Nm have a pressure angle of 90°, and the horizontal force Nr has a pressure angle of 0°. Therefore, Na=f(Pa) =Pa/sin90°=Pa; Nm=f(Pm)=Pm/sin90°=Pm, Nr=f(Pr)=Pr/cos0°=Pr
The friction resistance distance of the following slewing bearings is relatively low.