Needle bearings are slightly different
2020年3月27日Needle bearings are slightly different in design and use from the ball, cylindrical, and spherical roller bearings discussed earlier. A typical needle roller is at least 3 to 4 times its diameter. Unlike other types of bearings, slightly longer or slightly inclined rollers relative to the raceway will cause greater sliding friction on the roller end face. This situation is even more true for thrust needle roller bearings. At this time, the speed of the liquid channel surface depends on the contact diameter, while the speed of the needle surface is constant along the length, forcing a slip at the contact point between the needle end surface and the roller track. Furthermore, needle roller bearings are often mounted directly on the shaft or bearing housing processed by the user, which results in the roughness and texture of these mounting surfaces being slightly inferior to the inner and outer rings processed by the bearing manufacturer.
These two conditions make the frictional force of needle roller bearings different from other types of bearings. In the following chapters, it will involve the method of directly calculating the contact friction to estimate the bearing frictional torque. However, here we first introduce the empirical formulas for the friction torque of radial and thrust needle roller bearings proposed by Chiu and Myer. Based on Tippett’s work, Chiu and Me’s formula for radial needle roller bearings with cages is M = d (4.5 × 10-v.n + 0.12F ") (10.29) Chiu and Myers’ experiments show that The friction torque of a radial full needle roller bearing is 1.5-2 times that calculated by formula (10.29). Similarly, the friction torque of a thrust needle roller bearing can be given by the following formula: M = 4.5x10-.nd. + 0.016F1 (10.30 Obviously, it can be seen from the formula (10.30) that the running friction torque of the thrust needle roller bearing is related to the contact length of the needle roller raceway. As discussed earlier, this is related to the sliding of the needle end surface. In Myer’s test, it was proved that formula (10.29) and formula (10.30) are the test results of the bearing under the condition of circulating oil lubrication.
For grease lubrication, in the short time after cyclic lubrication and when the roller pushes the grease in the cavity When the instantaneous moment of the plateau stabilizes, the viscosity of the base oil can be used to calculate the running friction moment of the bearing. Finally, equations (10.29) and (10.30) can also be used to calculate the torque caused by oil bath lubrication, but as Trippett’s test found , The oil supply temperature has a greater effect on the frictional torque than the oil supply rate, because it affects To the viscosity of the lubricating oil. See Example 10.4 and Example 10.5. 10.5.5 Tapered roller bearings Unlike other types of bearings, the large end face of the neutron is in sliding contact with the ribs during the working process. Wie "studied the tapered The friction moment of a liquid bearing under radial load and axial load is obtained as follows: FM = 3.35 × 10’G (mp) K (10.31) M = 3.35 × x10G (10.32) Radial in formula (10.31) The load factor / can be found in Figure 10.2. Similar to the equations (10.22) and (10.23) for estimating the viscous friction moment, the equations (10.31) and (10.32) are effective for lubricating oil having a specific gravity of approximately 0.9.
Wite discusses the treatment of lubricants with different specific gravity. The geometric coefficient G based on the internal structure of the bearing is determined by the following formula: G = dDt (z · D) f (so) wite "is based on experience. He considers the large flanges of the ferrule and The friction of the roller end surface is defined as: F / C, or F, / C, ≤ 0.519nP ≥ 2700 (10.34) 2.4 To ensure the establishment of the above conditions, it is necessary to prevent the friction between the roller end surface and the ribs from becoming too large. In order to avoid the bearing friction torque being underestimated. 2.0We and Hi "further discussed when the condition 1 of formula (10.34) cannot be satisfied, the friction between the roller end face and the rib is calculated by formula (10.2) and (10.23) Influence of bearing frictional torque. 1.2 In the derivation formula (10.22) and formula (10.23), Wite uses 0.8 if: KF / F> 25 and the oil bath lubrication and circulating oil lubrication system. Wite also found that the use of lubrication: F (e 이) = F system type has the least effect on friction torque; while the viscosity of lubricant 4KFaF, 0.52 has a greater effect. The more likely explanation is that the drag force of 0108 to pure radial load when the roller rolls through the lubricant depends more on the viscosity of the lubricant than the amount of lubricant in the bearing’s 0.40.81.21.62.024KFF cavity. For grease lubrication, the viscosity of the base oil should be used to calculate the friction torque.
These two conditions make the frictional force of needle roller bearings different from other types of bearings. In the following chapters, it will involve the method of directly calculating the contact friction to estimate the bearing frictional torque. However, here we first introduce the empirical formulas for the friction torque of radial and thrust needle roller bearings proposed by Chiu and Myer. Based on Tippett’s work, Chiu and Me’s formula for radial needle roller bearings with cages is M = d (4.5 × 10-v.n + 0.12F ") (10.29) Chiu and Myers’ experiments show that The friction torque of a radial full needle roller bearing is 1.5-2 times that calculated by formula (10.29). Similarly, the friction torque of a thrust needle roller bearing can be given by the following formula: M = 4.5x10-.nd. + 0.016F1 (10.30 Obviously, it can be seen from the formula (10.30) that the running friction torque of the thrust needle roller bearing is related to the contact length of the needle roller raceway. As discussed earlier, this is related to the sliding of the needle end surface. In Myer’s test, it was proved that formula (10.29) and formula (10.30) are the test results of the bearing under the condition of circulating oil lubrication.
For grease lubrication, in the short time after cyclic lubrication and when the roller pushes the grease in the cavity When the instantaneous moment of the plateau stabilizes, the viscosity of the base oil can be used to calculate the running friction moment of the bearing. Finally, equations (10.29) and (10.30) can also be used to calculate the torque caused by oil bath lubrication, but as Trippett’s test found , The oil supply temperature has a greater effect on the frictional torque than the oil supply rate, because it affects To the viscosity of the lubricating oil. See Example 10.4 and Example 10.5. 10.5.5 Tapered roller bearings Unlike other types of bearings, the large end face of the neutron is in sliding contact with the ribs during the working process. Wie "studied the tapered The friction moment of a liquid bearing under radial load and axial load is obtained as follows: FM = 3.35 × 10’G (mp) K (10.31) M = 3.35 × x10G (10.32) Radial in formula (10.31) The load factor / can be found in Figure 10.2. Similar to the equations (10.22) and (10.23) for estimating the viscous friction moment, the equations (10.31) and (10.32) are effective for lubricating oil having a specific gravity of approximately 0.9.
Wite discusses the treatment of lubricants with different specific gravity. The geometric coefficient G based on the internal structure of the bearing is determined by the following formula: G = dDt (z · D) f (so) wite "is based on experience. He considers the large flanges of the ferrule and The friction of the roller end surface is defined as: F / C, or F, / C, ≤ 0.519nP ≥ 2700 (10.34) 2.4 To ensure the establishment of the above conditions, it is necessary to prevent the friction between the roller end surface and the ribs from becoming too large. In order to avoid the bearing friction torque being underestimated. 2.0We and Hi "further discussed when the condition 1 of formula (10.34) cannot be satisfied, the friction between the roller end face and the rib is calculated by formula (10.2) and (10.23) Influence of bearing frictional torque. 1.2 In the derivation formula (10.22) and formula (10.23), Wite uses 0.8 if: KF / F> 25 and the oil bath lubrication and circulating oil lubrication system. Wite also found that the use of lubrication: F (e 이) = F system type has the least effect on friction torque; while the viscosity of lubricant 4KFaF, 0.52 has a greater effect. The more likely explanation is that the drag force of 0108 to pure radial load when the roller rolls through the lubricant depends more on the viscosity of the lubricant than the amount of lubricant in the bearing’s 0.40.81.21.62.024KFF cavity. For grease lubrication, the viscosity of the base oil should be used to calculate the friction torque.
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