专业英语第8课全文及翻译 滚动轴承

Lesson 8 Rolling Bearings

Rolling bearings can carry radial, thrust or combination of the two loads. Accordingly, most rolling bearings are categorized in one of the three groups: radial bearings for carrying loads that are primarily radial, thrust bearings for supporting loads that are primarily axial, and angular conta ct bearings or tapered roller bearings for carrying combined radial and axial loads. Figure 8.1a sh ows a common single-row, deep groove ball bearing. The bearing consists of an inner ring, an out er ring, the balls and the separator. To increase the contact area and. hence permit larger loads to b e carried, the balls run in curvilinear grooves in the rings called raceway. The radius of the racewa y is very little larger than the radius of the ball. This type of bearing can stand a radial load as well as some thrust load. Some other types of rolling bearings are shown in Figs. 8. 1b, 8. lc and 8. 1d.

Figure 8.1 Some type: of rolling bearings: (a) deep groove ball bearing; (b) thrust ball bearing;

(c) tapered roller thrust bearing;(d) needle roller bearing.

The concern of a machine designer with ball and roller bearings is fivefold as follows: (a) life in relation to load; (b) stiffness, i. e. deflections under load; (c) friction; (d) wear; (e) noise. For m oderate loads and speeds the correct selection of a standard bearing on the basis of load rating will usually secure satisfactory performance. The deflection of the bearing elements will become impo rtant where loads are high, although this is usually of less magnitude than that of the shafts or othe r components associated with the bearing. Where speeds are high special cooling arrangements be come necessary which may increase frictional drag. Wear is primarily associated with the introdu ction of contaminants, and sealing arrangements must be chosen with regard to the hostility of the environment.

Because the high quality and low price of ball and roller bearings depends on quantity production, the task of the machine designer becomes one of selection rather than design. Rolling bearings are generally made with steel which is through-hardened to about 900 HV. Owing to the high stresses involved, a predominant form of failure should be metal fatigue, and a good deal of work is curren tly in progress intended to improve the reliability of this type of bearing. Design can be based on accepted values of life and it is general practice in the bearing industry to define the load capacity of the bearing as that value below which 90 per cent of a batch will exceed a life of one million re volutions.

Notwithstanding the fact that responsibility for the basic design of ball and roller bearings rests

with the bearing manufacturer, the machine designer must form a correct appreciation of the duty t o be performed by the bearing and be concerned not only with bearing selection but with the condi tions for correct installation.

The fit of the bearing rings onto the shafts or onto the housings is of critical importance beca use of their combined effect on the internal clearance of the bearing as well as preserving the desir ed degree of interference fit. Inadequate interference can induce serious trouble from fretting corr osion. The inner ring is frequently located axially by abutting against a shoulder. A fillet radius at t his point is essential for the avoidance of stress concentration and the inner ring is provided with a corner radius or chamfer to allow space for this.

Where life is not the determining factor in design, it is usual to determine maximum loading by the amount to which a bearing will deflect under load. Thus the concept of "static load- carryin g capacity" is understood to mean the load that can be applied to a bearing, which is either stationa ry or subject to slight swiveling motions, without impairing its running qualities for subsequent rot ational motion. This has been determined by practical experience as the load which when applied t o a bearing results in a total deformation of the rolling element and raceway at any point of contact not exceeding 0.01 per cent of the rolling-element diameter. This would correspond to a permanen t deformation of 0.0025 mm for a ball 25 mm in diameter.

The successful functioning of many bearings depends upon providing them with adequate prote ction against their environment, and in some circumstances the environment must be protected fro m lubricants or products of deterioration of the bearing surfaces. Achievement of the correct functi oning of seals is an essential part of bearing design. Moreover, seals which are applied to moving parts for any purpose are of interest to tribologists because they are components of bearing system s and can only be designed satisfactorily on the basis of the appropriate bearing theory. Notwithsta nding their importance, the amount of research effort that has been devoted to the understanding o

f the behavior of seals has been small when compared with that devoted to other aspects of bearin

g technology.

Words and Expressions

radial bearing向心轴承(主要用于承受径向载荷的滚动轴承)

thrust bearing推力轴承(主要用于承受轴向载荷的滚动轴承) angular contact bearing角接触轴承 tapered roller bearing圆锥滚子轴承 deep groove ball bearing深沟球轴承

thrust ball bearing推力球轴承(滚动体是球的推力滚动轴承)

tapered roller thrust bearing推力圆锥滚子轴承(滚动体是圆锥滚子的推力滚动轴承) needle roller bearing滚针轴承(滚动体是滚针的向心滚动轴承) fivefold a.;ad.五倍(的)，五重的

stiffness ['stifnis} n.刚性，刚度，稳定性 deflection n.偏差，偏移，弯曲，挠度 frictional a.摩擦的，由摩擦产生的

drag v.拖，牵引，摩擦，拖着，阻碍;n，阻力，摩擦力，阻尼 wear v. n.磨损，磨蚀，消耗，耗损

contaminant n.沾染，杂质，污染物质，污染剂 sealing n.密封，封接

hostility n. 敌视，敌意，敌对 through-harden v.整体淬火

HV= Vickers hardness维氏硬度

notwithstanding prep.; ad.; conj. 虽然，尽管……(还是) clearance n.间隙，裕度，空隙，余地，间距

interference n.干涉，干扰，妨碍，过盈，相互影响 fret v.侵蚀，腐蚀，磨损，损坏 fretting n.松散，微振磨损

abut v.邻接，毗连，倚着，支撑;n.端，尽头，支架 chamfer n.;二在……开槽，倒棱，倒角，圆角 swivel n.旋转轴承，转体;v.旋转，用活节连接 raceway n.轴承座圈，滚道

lubricant n.润滑剂，润滑材料;a.润滑的 deterioration n.变质，退化，恶化，变坏 tribology n.摩擦学

Notes

1. through-hardened意为“整体淬火的，，。

2. fretting corrosion意为“微动腐蚀(即由腐蚀和两固体接触面有微小振幅的振动而引起的磨损之联合作用所产生的材料破坏)”。

3. static load-carrying capacity意为“静态承载能力”。

第8课滚动轴承

滚动轴承可以承受径向载荷，轴向载荷或者同时承受这两种载荷。因而，大部分滚动轴承可以被划分为三种类型:向心轴承，主要承受径向载荷；推理轴承，主要承受轴向载荷；角接触轴承货圆锥滚子轴承，能同时承受径向和轴向载荷。一个普通的蛋类深沟球轴承的结构如图8.1a所示，它由内圈、外圈、球和保持架四部分组成。为了增加接触面积以承受更大的载荷，球在内、外圈上的被称为滚到的弧形沟内滚动。滚道的圆弧半径略大于滚动球的半径。这种轴承能够承受径向载荷，也可以承受一定的轴向载荷。其他几种类型的滚动轴承如图8.1b，图8.1c和图8.1d所示。

对于球轴承和滚子轴承，一个机器设计人员应该考虑下面的五个方面：（a）寿命与载荷的关系；（b）刚度，也就是在载荷作用下的变形；（c）摩擦；（d）磨损；（e）噪音。对于中等载荷和转速，根据额定负载选择一个标准轴承，通常都可以保证其具有令人满意的工作性能。当载荷较大时，轴承零件的变形，尽管它通常小于轴和其他与轴承一起工作的零部件的变形，将会变得更重要起来。在转

速高的场合需要有专门的冷却装置，而这可能会增大摩擦阻力。磨损主要是由于污染物的进入引起的，必须选用密封装置以防止周围环境的不良影响。

因为大批量生产这种方式决定了球轴承和滚子轴承不但质量高，而且价格低，因而机器设计人员的任务是选择而不是设计轴承。滚动轴承通常是采用硬度约为900HV，整体淬火的钢来制造的。滚动轴承由于在工作中会产生高的应力，其主要失效形式是金属疲劳。目前人们正在进行大量的研究工作以求提高这种轴承的可靠性。轴承设计是基于能够够被人们所接受的使命值来进行的。在轴承行业中，通常将轴承的承载能力定义为这样的值，即所承担的载荷小于值时，一批轴承中将会有90%的轴承具有超过一百万转的寿命。

尽管球轴承多和滚子轴承的基本设计责任在轴承制造厂家，机器设计人员必须对轴承所要完成的任务作出正确的评价，不仅要考虑轴承的选择，而且还要考虑洲曾的正确安装条件。轴承套圈与轴承或轴承座的配合非常重要，因为它们之间的配合不仅应该保证所需要的过盈量，而且也应该保证轴承的内部间隙。不正确的过盈量会产生微动腐蚀从而导致严重的故障。内圈通常是通过紧靠在轴肩上进行轴向定位的。轴肩根部过渡圆角半径对避免产生应力集中是必要的。轴承内圈上的圆角半径或者倒角提供了容纳轴肩根部过度圆角半径的空间。在使用寿命不是设计中的决定因素的场合，通常根据轴承受载荷时产生的变形量来确定其最大载荷。这个载荷对轴承在随后进行旋转运动时的质量没有不利影响。按照实践经验确定，静态承载能力是这样一个载荷，当它作用在轴承上时，滚动体育滚道在任何一个接触点处的变形量不超过滚动体直径的0.01%。这相当于在直径为25mm的球上产生0.0025永久变形。

只有将轴承与周围环境适当地离开，许多轴承才能成功地实现他们的功用。在某些情况下，必须保护环境，使其不受润滑剂和轴承表面磨损生成物的污染。轴承设计的一个重要组成部分是使密封装置起到应有作用。此外，对摩擦学研究人员来说，为了任何目的而应用与运动零部件上的密封装置都是他们感兴趣的。因为密封装置是轴承系统的一部分，只有根据适当的轴承理论才能设计出令人满意的密封装置。虽然它们很重要，与轴承其他方面的研究工作相比，到目前为止在密封装置的研究方面所做的工作还是比较少的。