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(2009-10-26 17:49:35)


shafts. For driving the bearings, either the outer ring (Figure 1.52a) or the inner ring may be toothed. The raceways are induction  or flame hardened as well as the highly loaded integrated teeth. The rings (for materials see Table 6.1) are heat-treated in different ways according to the strain on the gear rings and the contact pressure of the area carrying the highest load.
Figure 1.52   Slewing bearings: (a) four-point bearing, (b) cross-roller bearing
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1.1.4  Roller Thrust Bearings
Spherical Roller Thrust Bearings
A spherical roller thrust bearing contains a set of asymmetical barrel rollers inclined to the rotary axis of the bearing so that the bearing accommodates high axial forces in addition to considerable radial forces (Frmax = 0.55Fa), (see Figure 1.53).
The barrel rollers are supported by the high inner-ring lip and can align themselves in the spherical outer raceway. This renders the bearing like other self-aligning bearings, impervious to misalignments and shaft deflections. Spherical roller thrust bearings are provided with machined brass cages or pressed sheet-steel cages. Both cage types retain the roller set and the shaft washer in one unit. Applications include column bearings for cranes, propeller thrust blocks in shipbuilding, slewing column bearings in heavy machinery construction, vertical shafts of air preheaters in power stations and heavy work gears.
Cylindrical Roller Thrust Bearings.
Most cylindrical roller thrust bearings are single-direction bearings. They consist of two plain lipless washers and one or more sets of cylindrical rollers in star formation held together in a solid window-type cage of glass-fibre reinforced polyamide or brass (see Figure 1.54). These bearings can move in the radial direction.
During rotation there is sliding at the roller ends, and this increases with the roller length (Figures 2.31 and 2.32). Therefore, bearings with a large cross-section are provided with several short rollers in a line. The rollers are guided by the cage.
Figure 1.53  Spherical roller thrust bearing
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Figure 1.54  Single-direction cylindrical roller thrust bearing
Needle Roller Thrust Bearings
Needle roller thrust bearings are used where the available mounting height is small (see Figure 1.55). Their design corresponds to that of cylindrical roller thrust bearings. As in radial needle roller bearings, the needle roller thrust bearing with ground and hardened mating surfaces may be installed with a washer or simply as a needle roller and cage assembly. Stamped and hardened 1 mm thick spring-steel washers are frequently used. Since these washers are not ground, they are inexpensive. Where accuracy or interrupted abutment surfaces demand thicker washers, the shaft and housing washers of cylindrical roller thrust bearings may be used
推力滚针轴承应用在有效增加高度很小的地方。这种设计相对于圆柱推力滚子轴承。在径向滚针轴承中,有平坦坚硬平面的滚针推力轴承安装有垫圈或者一个保持架。厚度为1mm的坚硬的碳钢垫圈经常被使用。由于这些垫圈    ,它们不贵。当高精度的表面需要更厚的垫圈时,轴和推力圆柱滚子轴承的垫圈会被使用。
Tapered Roller Thrust Bearings
Several designs are in production. In the most frequently used design (Figure 1.56), the raceway of the shaft washer is tapered and the raceway of the housing washer is flat. To avoid sliding that occurs in cylindrical roller thrust bearings, the taper angle of the rollers is selected so the extended contact lines intersect on the bearing axis. The rollers are guided by the lip of the shaft washer and are generally retained in a machined brass cage. The bearings can align themselves in the radial direction (Figure 1.56a). They are used in rolling mills.
Full-complement bearings are held together by a pressed-steel cap (Figure 1.56b). They are preferably used in motor vehicles as steering knuckle bearings.
Axial-Radial Roller Bearings
The axial-radial roller bearing is a special slewing bearing design. It comprises a double-direction cylindrical roller thrust bearing with two rows of rollers and a single-row full-complement radial cylindrical roller bearing (Figure 1.57). The axial roller rows have machined cages or polyamide separators. Through-holes in the bearing rings make it possible to bolt the bearings to the lower and upper structure. Special designs may feature an external or internal gearing to drive the structures supported by the bearing [14b]. Axial-radial roller bearings are capable
这种轴颈向滚子轴承是一种特殊的回转轴承的设计。它包括一个具有两列滚子的双向推力圆柱滚子轴承和单列径向滚子轴承。轴向滚子具有机制的保持架或者聚酰胺分离器。轴承圈通孔使轴承     特殊的设计可能使传动装置来驱动有轴承支持的结构。轴径向轴承有这种能力的。
Figure 1.55    Needle roller thrust bearing
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Figure 1.56 Tapered roller thrust bearings:
(a) with cage, separable;
(b) full-complement with pressed-steel cap
Figure 1.57  Axial-radial roller bearing of carrying high axial and radial loads and tilting moments. Bearings like the one shown in Figure 1.57 are used on turntables or indexing tables. The number and preload of the rollers for the three rows are selected to achieve the highest possible rigidity.
1.1.5  Special Bearings
The bearings described in the preceding sections are available in a wide variety of special designs. They are tailored to specific applications and may deviate from standard bearings by their dimensions or include additional elements and functions of the bearing location in the rolling bearing unit. Special bearings may have flanges, integrated hubs, special sealing [123a, b, d, e], gearing, integrated pulleys, and encasings; special bearings may be split, both their rings consisting of two semicircular halves [67a, 83f, 14a]. Some examples are shown in Figure 1.58. Economic frame conditions are a criterion for the rolling bearing manufacturer to develop and produce special bearings. More special bearings are shown in Figures 6.26, 8.35, 8.50, 8.51, 8.52 and 8.61.
前章所讲的轴承可在各种各样的特殊设计。它们有特殊的应用,有可能脱离标准轴承尺寸或在滚动轴承单元包含额外的要素和功能的轴承位置。特殊轴承可能法兰、综合中心、独特的密封[123a,b,d,e)、传动装置、综合滑轮;特殊轴承会分离,它们环有两个半圆组成,83f[67a,83f,14a)。一些例子如图1.58所示。使用框架条件是一个标注为了滚动轴承的产品开发和生产特殊轴承。更特别的轴承如图6.26, 8.35,8.50,8.51, 8.52和8.61,。


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