【正文】 84.[8] 王伯平 [M].：機械工業(yè)出版社，2009.[9] 殷玉楓 [M]. 武漢：華中科技大學出版社，2006.[10] 劉鴻文 （Ⅰ、Ⅱ）[M].：高等教育出版社，2008.[11] 張福生 [N].太原：太原科技大學，2010.[12] 諸文農 ：機械工業(yè)出版社[M]，1981.[13] [M].北京：高等教育出版社，2007.[14] （下冊）[M].北京：機械工業(yè)出版社，2005.[15] [M].北京：中國建筑工業(yè)出版社，1986.[16] 聞邦椿 [M].北京：機械工業(yè)出版社，2010.[17] 西北工業(yè)大學機械原理及機械零件教研室 [M].北京：，[18] 西北工業(yè)大學機械原理及機械零件教研室 [M].北京：.附錄一：Mechanical parts (The main parts type in gearbox) Transmission is by gear, axle, bearings, fasteners in metal box according to certain request with connection and bee.1. Gear Type Drives Geartrains can be used to increase rotation speed but decrease torque , to keep speed and torque constant, or to reduce rotation speed but increase torque. Mechanisms incorporating gears are mon in the design of machinery. At this point, our objective is simply to explore various types of gears with an emphasis on characteristics. The shape to a gear39。s front wheels, and they also positioned read/write heads above magnetic disks in vintage puter storage drives. Rack and pinion III. Bevel Gears Whereas the teeth of spur gears are arranged on a cylinder, a bevel gear is produced by instead forming teeth on a truncated cone. ( Figure 3 ) is a photograph of a bevel gearset. Bevel gears are appropriate for applications in which two shafts must be connected at right angle and where extensions to the shaft centerlines would intersect.Fig. 3 Two bevel gears in mesh IV. Helical Gears Because the teeth on the spur gears are straight with faces parallel to their shafts, as two teeth approach one another, they make contact along the full width of each tooth. Similarly, the teeth separate and lose contact along the tooth 39。 they offer the advantage of meshing more smoothly. Helical gears are similar to their spur counterparts in the sense that teeth are still formed on a cylinder, but in this case the teeth are not parallel to the gear39。s cylinder in the shape of a shallow helix. A single helical gear is shown in ( Figure 4 ). With the same objective of having teeth mesh gradually, bevel gears can likewise be formed with spiral instead of straight teeth.Helical gear are evidently more plex to analyse and manufacture than spur gear. On the other hand, helical gearsets do have the advantage that they produce less noise and vibration in machinery. Automobile automatic transmissions, for instance, A helical gear and integral shaftare typically constructed using both external and helical helical gears for precisely that reason. In a helical gearset, toothtotooth contact starts at one edge of a tooth and proceeds gradually across its width, thus smoothing out the engagement and disengagement of teeth. Another attribute of helical sized spur gears because the toothtotooth contact forces are spread over more surface area. We have seen how helixshaped teeth can be formed on gears that are mounted on parallel shafts, but gears that are attached to perpendicular shafts can also incorporate helical teeth. The crossed helical gears connect two perpendicular shafts, but unlike the bevel gearset application, the shafts here are offset from one another and extensions to their centerlines do not intersect. V. Worm Gearsets If the helix angle on a pair of crossed helical gears is large enough, the resulting pair is called a worm and worm gear. ( Figure 5 ) illustrates this type of gearset where the worm itself has only one tooth that wraps several times around a cylindrical body, similar to thread of a screw. For each revolution of the worm the worm gear advances by just one tooth in its rotation. A worm gearset Worm gearsets can operate with large speedreduction instance, if the worm gear has 50 teeth, the speed reduction would be 50fold. The ability to package a geartrain with large speed reduction into a small physical space is an attractive feature of worm gearsets. However, the tooth profiles within worm gearsets are not involutes. Significant sliding occurs between teeth during meshing, and that friction results in power loss, heating, and inefficiency pared to other types of gears. It is also possible to design worm gearsets such that they can be driven in only one direction, namely, from the worm to the worm gear. For such a selflocking gearset, It would not be possible to reverse power flow and cause the worm gear to back drive the worm. This oneway drive capability is sometimes exploited in such application as hoists or jacks where it is necessary to mechanically prevent the system from being back driven. Not all worm gearsets are selflocking。 an outer race。 and a separator that prevents the rolling elements from rubbing against one another. They are ubiquitous in machine design, and are found in applications as diverse as bicycle wheels, robotic joints, and automobile transmissions. A sample installation of a rolling contact bearing is illustrated in ( Figure 6 ). The shaft and the bearing 39。s housing are stationary. When a shaft is supported in this way, the bearing 39。s connections to shaft and housing. The separator keeps the balls evenly spaced around the bearing 39。s races. ( Figure 8 ) illustrates the of straight roller bearing. In ( Figure 8 ), the centerlines of the rollers and the race are parallel to one another, and a separator is again used to space rollers around the bearing 39。s shaft ) and the cornering force generated during turns ( which is a thrust force ). Tapered roller bearings are regarded as having an intermediate cost, a high capacity for radial force, and a moderate capacity for thrust forces.IV. Thrust Roller BearingsWhile straight roller bearings are well suited for supporting loads that are directed mostly radically, and tapered roller bearings can support a bination of radial and thrust forces, thrust roller bearings carry loads that are directed primarily along a shaf