外文翻译--Fuller双中间轴变速器结构特点分析

附 录 A The Analysis of Fuller Twin Countershafts Transmission Structure Sharacteristics Fulham (Fuller) because American Eaton is twin countershafts transmission Eaton company of the 60s original products, in 1965 patent application, and then put into production, supply market. It is aimed at the condition of design: when the U.S. has gradually built highway system, in order to improve the economic benefit to freight cars, trucks, and fast pace to large, specialty direction. In the United States more prevalent mode of transportation is by the saddle type tractor trailer and car pulled the tractor is the train, the main road with heavy car models, its characteristic is short wheelbase, in addition to the U.S. highway law caps the car before hanging must not be more than 800mm , and consequently make twin countershafts transmission shaft to size is very limited. The needs of the development of surface but repeated requests to improve the car engine power, and corresponding enlarges the bearing capacity of the transmission, this to the traditional single axis twin countershafts transmission for, its axial dimensions must increase thus had a contradiction, double the axis is that the twin countershafts transmission in such a situation of The Times looks unfamiliar. It greatly improve the twin countershafts transmission torque capacity (Fuller products has reached 2240Nm ), largest and decreases the axial dimensions. It supply market in the United States, after the heavy car gradually replaced the traditional single axis transmission. Eighty s it almost exclusive American heavy vehicle twin countershafts transmission market (including Eaton company products accounted for about 75%). Since the mid seventy s, Eaton products in reducing noise and improve life and reliability have increased significantly. And in the twin countershafts transmission basic structure under the condition of invariable, and has successfully developed series presentation of a new generation transmission. At the same time, adjusted the original, redesign the product series and realize standardization. Eighty s has the new series production. This paper is based on the original 900 series (namely the new series 11600, both the same basic structure of RT-915) type group structure of the desktop twin countershafts transmission for an example cent fold. Figure A1 Fuller Twin Countershafts Transmission -The first shaft -Lord box box axial -The second Lord box in the axis R-Lord box in reverse Thaft axis -vice Box-vice box output shaft -Bhift joints set -Vice box high low synchronizer joints sets -Vice box super cheap synchronizer joints set of ZR2-Lord box in reverse presence wheel Attached A1 RT-915 type the basic structure of transmission Figure A1 shows is the RT-915 type twin countershafts transmission structure diagram, it consists of a main five gear box and a rear times of three gear shift combination to vice box, it has 15 forward gears and three in reverse. The Lord box and vice gearbox which is 148.43mm center distance they each have two sets of intermediate bearing assembly, all the gear for spur gear, often meshing type transmission , both on the output shaft gear are floating, Lord box output shaft also float. The box without the file synchronizer, vice box with high cheap locking pin type synchronizer, ultra low inertia by outer profile of mating type shift device. The box for each file mechanical hand manipulation, vice box every file adopted the pneumatic control shift. When vice box synchronizer joints set with mating set of ( ) are moved to the mating position when the left and the twin countershafts transmission were at high speed area, low speed area, super-low speed area, equipped with five ratio for selection. Attached A2 Structure analysis Attached A2.1 Dual axis power diversion Figure A1 shows twin countershafts transmission box and vice box the Lord had two sets of the axis assembly, input power points to two road axis assembly, again by the output shaft assembly will be two road after mixing power output. Input and output shaft of the gear has at the same time two teeth on the axis of the two respectively with gear, work by load per tooth structure is concerned, because the relative single reduced 1/2, in fact, in theory, the tooth shape error, the tooth thickness error, the center distance, the error on the axis gear and corresponding mesh loading not even, make the actual reduce the value of less than 1/2. This situation than single axis transmission double the axis has obvious advantages. Attached A2.1.1 Dual axis gears life In view of the fatigue life of gear with its load of three times about square of inverse ratio, the formula is as follows: 3P N C? (constant) type (A1) Type: P-Gear load； N-Fatigue damage of gear tooth cycles. The type that a single tooth, A1 power twin countershafts transmission cases, gear load1P, the corresponding fatigue damage cycle times1N. When double teeth power transmission, every single tooth load2P, a former theory, that is21/2PP=, the lower half of the corresponding fatigue damage at this time 3212NN=?, that same cyclic number transfer torque, double teeth power transmission , the fatigue life of gear can be increased greatly. If keep gear fatigue life, that is21NN=, the constant21PP=, this shows that the fatigue life of gear equal, double teeth power transmission , every single tooth can be increased by1/2P the load to1P, can improve a times. If the worst of the actual situation, according to consider, two teeth load distribution non-uniform coefficient for 0.6, by calculating know that the torque capacity still can be increased by 67%. This is double the axis on the basis of which the design principle of the twin countershafts transmission facts. Attached A2.1.2 Double the axis center distance transmission The axis of gear twin countershafts transmission of center distance to the following formula 3 m a x 1A e g gA K B T i h= Type (A2) Type: B-the load distribution non-uniform coefficient (for 0.52 0.60)； By typeA2, it is known that the center distance gear is single axis structure reduce 15 to 20%, this to improve the twin countershafts transmission efficiency and lightweight has the important meaning, we know that gear center distance is reduced, quality can reduce a lot. Therefore, the center distance gear is gear twin countershafts transmission in the design the most basic parameters, it affects the twin countershafts transmission many of the important performance index, and direct and gear twin countershafts transmission and structure design of carrying capacity has close relationship. For a long time, to reduce the twin countershafts transmission of the domestic and foreign traditional gear from center made unremitting efforts, eventually because of bearing, material by technological level and shift the design and manufacture of synchronizer into the technical level of the check and little progress. The axis of the structure of the double appear, because power diversion has greatly improved the gears, bearings and the axis, the loading condition, and may reduce the processing accuracy requirement, and can therefore do not only ensure the twin countershafts transmission performance, and reduced the gear from the center. Due to the stress of gear twin countershafts transmission gear with a more traditional nearly half, it can be reduced to about 40% of the reduced width, already reduced the twin countershafts transmission shaft to size, and keep the bearing capacity of the gear, with improved load of the tooth, and to improve the distribution of gear life. Attached A2.2 Gear floating The box on the output shaft gear at the same time and the two symmetrically arranged on the axis of gear engagement, it in two gears can be along radial direction between floating, rely on meshing round self-centering, vice box also is such. This is because of the structure of the double Fuller twin countershafts transmission characteristics, its advantage is: (1) to make the output shaft gear and two on the axis gear meshing, and correct evenly distributed load. (2) tell the traditional twin countershafts transmission output shaft in all often mesh in the needle bearing. The needle bearing is the weaknesses in traditional twin countershafts transmission structure, cancel it, to improve the twin countershafts transmission of life and the working reliability have obvious function. (3) on gear precision, accuracy and the shaft bearing hole position precision can reduce requirements. (4) make tooth shape by the error of dynamic load less of an effect. (5) test shows that the meshing can reduce the floating strong resonance noise intensity. Attached A2.3The arrangement of the shaft and stress The second shaft for the box floating structure, two axis back end and vice box drive gear spline connection, and through the bearing can support on the enclosure； Shaft front shaft neck and oil bearing radial clearance of the big (shaanxi automobile wheel factory measurement for the 0.9mm ), the shaft is the fulcrum, front after floating. Therefore, the second shaft gear are floating, shift, in the second shaft of the outer profile of engagement with floating, facilitate change gear shaft. Figure A1 shows, the axis of the centre of the attachment and the Angle a between horizontal, Fuller 19 Angle, this is too small, if will make the width dimension increase, stir oil loss increases, the loss is the main factors of influence twin countershafts transmission efficiency； If too much, is the size, and increase the height above bearing bad lubrication condition. Symmetrical arrangement of the axis make first shaft, double the second shaft gear by radial force balance each other, make this second shaft under bending moment, and are not only bear torque, put can make the first axis, the second shaft diameter. 2 the axis also this by bending moment, can make the shaft decrease 1/2 ensure enough (this is intermediate bearing stiffness design should be the main consideration question), to improve the working conditions of the gear and bearing, this to raises gear and bearing life and reduce the noise is favorable. Attached A2.4 Solve the bearings use life problem By that, input shaft and the output shaft bearings by composition of radial force to zero, twin countershafts transmission gears for straight teeth, no axial force, bearing under gravity only； The axis of the bearing by radial force nearly 1/2, reduce without axial force. All bearing load conditions have been great improvement, this is caused such twin countershafts transmission bearing life long basic factors. In addition, the one end of the intermediate bearing vice box still used bearing capacity of strong roller bearing, already won the benefits of large capacity, but also because of the axis must be adopted to support, and separate swimming type type bearings with convenient fold to. The box is a common type though bearing the rest, but compared with the traditional twin countershafts transmission coefficient of its life, but many high. Deputy box output shaft is made up of two the outfits circular cone roller bearings, according to the analysis of the main support is to enhance the cantilevered shaft stiffness and stability, and increase the bearing capacity. In bearing load is small, as far as possible increase bearing capacity, can rise already bearing life, to that of the twin countershafts transmission adapt to life always； And enhance the stiffness, strengthen the functioning of the shaft rigidity, ensure gear meshing, improve the correct life and reduce noise. The new series of products to reduce noise, and the new design, so as to improve the bearing the bearing quality. The actual application result: Fuller double central axis in the twin countershafts transmission within 480000 kilometers, the life without changing bearing the same level in the value of the worlds best level in transmission. AttachedA2.5 The Lord without synchronizer and the box, type clutch cooperate with shifted gears Fuller double the axis twin countershafts transmission box has not adopted the synchronizer, but the outer profile of mating type shift device. Normally, for large capacity for the twin countershafts transmission torque, due to the large inertia gear, big, shift in entering when the speed of the difference of the larger meshing between gear from the impact is big also, cause shift difficult. Therefore, we should add synchronizer. But the synchronizer, to solve the current problem of its service life. Big torque capacity of the single axis twin countershafts transmission is west Germany government is world famous products, there are still a synchronizer early damage, the problem in the world each production manufacturer also have been solved. Fuller double the axis twin countershafts transmission box has not adopted the synchronizer, but from a device with pull model, with a simultaneous shift. It is in the box on the first shaft installed a friction brake disc, when shift separation clutch, separate fork pulled back bearings, will friction brake disc pressure to the first axis, brake first shaft cover, to speed up the process, according to the gear synchronous this, it can only make the first shaft for, so can only slow movement in place the start up and use, and cant shift in downward shift when used. In the design principle, structure and calculation on the practice of exploratory, from the principle and structure can be done on the up and down when shift all can use. According to the analysis, the device in the simplified operation, shorten the time shift, a simultaneous shift on can be as effective as synchronizer similar role, but for this structure does not have synchronizer is the lock function, to realize no impact shift, but also depends on the driver of the operation of proficiency. Eaton company claimed that the shift in institutions of the engagement of the set, the spline tooth ends and the corresponding spline gears between a big hole are design Angle pouring in shift, it can play a certain process lock up the role. This kind of unique shift agencies from the United States, heavy duty truck generally use the situation, is successful, if via improved. Expected to completely replace the synchronizer function, to cancel synchronizer purpose. So the benefits of the obvious, it avoided the synchronizer this difficult problem, and transmission , improve the life the weaknesses in the work of transmission , simplify the structure reliability transmission , make its axial dimensions cut short, quality, reduce the ease of technology and materials to demand higher parts, make the twin countershafts transmission cost reduced. Attached A2.6 The straight teeth gear transmission Fuller double the axis twin countershafts transmission box and Lord of all gear vice box USES the straight teeth gear meshing twin countershafts transmission at home and abroad, often torque capacity is rare in transmission. In addition to deputy box drive gear is the single diameter temperance gear outside, are more than double diameter temperance short gears, Lord box and vice box of each shift gears are one from each kind of the festival, 6/7 and 5/7 respectively, converted to 4.32/3.63 and 5.08/3.63 module (new series of the products, the modulus gear presentation is less than 1.27 the tooth shape, easy to form more slender gear meshing). The Lord all gear pair of gear box for 22 to 23 of gear teeth, all gear tooth shape by small Angle and deflection is fixed. In order to achieve the new traffic regulations for noise limit, Eaton for new products to take the following measures: (1) improve tooth shape structure； (2) improve the superposition coefficient； vice (3) improve the precision (presentation than thick tooth gear series precision high level, is make series load distribution among gear teeth uniform)； (4) improve bearing quality； (5) improve the rigidity. Good results have been achieved, new series product is old products to reduce noise intensity by 5 7dB . Analysis the characteristics of structure above (1) all adopt the straight teeth gear, to the double integral of the intermediate bear ing structure, easy to assembly assembly and collapse (2) using short teeth gear system can enhance the gear bending strength, but at the same time, they have also made the straight teeth gear coincidence, the defects of small coefficient by small teeth shape Angle and more to the teeth mesh areas, it can make up the defects, new series of products to the superposition coefficient reaches 2.2 (the traditional design superposition coefficient around 1.5) only. Sweden Scania company produces the GR860 main twin countershafts transmission adopts full inclined gear meshing transmission, its often heavy machine, coefficient of 1.45 to 1.68. The improvement of superposition coefficient can improve the gearing mesh performance, test shows that: (1) to reduce the noise； (2) make is the influence of surface fatigue life of gear was obviously improved (for tooth face pressure decrease)； (3) the coincidence degree coefficient of large gear impact resistant ability than superposition coefficient low gear (by the former load distribution is more homogeneous), this ability is heavy auto twin countershafts transmission is required. (3) with small teeth shape Angle will reduce the strength, the root is adopted deflection is modified, in order to enhance strength of tooth root gear. (4) in order to guarantee the box on the axis with the first two gear shaft, the second shaft gear can at the same time, also make the second shaft meshing gears can will load on evenly distributed to two axis, so should guarantee the first axis, the second shaft gear the number of teeth are even on the gear axis all have a tooth is located in the same longitudinal plane inside, and all of the same modulus gear. (7) for gear teeth smaller diameter, wide is narrower, facilitate the pull teeth and shaving teeth and other high efficient processing method production. The road test results show that: the average operation 640000 kilometers of the new series products, the reliability coefficient was 92%, 90% at 800000 km. Not only that such twin countershafts transmission of simple structure, good technology, and reliable work, life index in the advanced world level, durable, easy to make a successful example. Attached A2.7 The Lord box, vice box and the structure characteristics The Fuller double the axis twin countershafts transmission series is two kinds of the center distance (135.128mm and 148.43mm ) of the five gear box for basic, take the Lord box and click unit variant combination princ iple, and different combination, realize after vice box serialization of products standardization many varieties, production figure 1 box in the structure design is very distinctive, the variant is to keep away from the same center in gear and the rest of the parts in addition to the gear basic dont change in the 18 to gear different combinations, to get eight different ratio of combination of Lord box. And as shown in figure A1 shows, in the full set of parts does not change, only change gear1Zgear3Z, gear2Zand4Zassembly and position, and also can get after exchange with the overdrive Lord box, so that the entire series products DuoZhong increase. Variant need to replace parts to take the combination of the spline connection structure； The first axis, the second shaft all gear hole for the same specifications of the spline hole, make gear according to need conversion installation； And so the tooth of the engagement of shift institutions and each file, general. Main box easy to realize the form, also can realize for strength. Because the entire product parts generalization degree is as high as 70% above, great show, where production for high economic performance. The two vice box in the axis axis and the main box two reverse gear axis line, the deputy of the box and the box body as a whole, the body of all zero are installed on the box cover, and to be a assembly, two speed and 3 speed vice box are so, both the box cover general, when when can replace the assembly variant, is very convenient. Integral cabinet tell the Lord box and vice box of between shell and bearing, make whole compact structure, reasonable and shorten the axial dimensions and reduce the quality, simplified the processing. The Fuller products introduced degree is high, the same gear center distance Lord box, it alone the various conversion product can general a cabinet； Combination of the same integral box can also be a cabinet； general The center distance gear were only two but covered the whole series products, the family of the twin countershafts transmission of mass production, meaning for professional is great. In the twin countershafts transmission of production, the production line is the strongest and most personality, keep the cost of production line, not only economic constant is very economical, but also can rapid conveniently to the competitive market needs, make the factory has the very strong capability. Attached A3 Conclusion Because Fuller twin countershafts transmission had taken some unique structure, greatly improving the internal structure of the stress condition, it is not only a performance index advanced, reliable working, and long service life etc advantages, and structure and processing technology is simple, and abroad at present relatively new several with the level in the axis compared single transmission , such as west Germany and Sweden, the government twin countershafts transmission Scania GR860 and VOLVO SR61, method of the kingdom of Berllet BRL3 and NM9-150, the Soviet union and Japans nissan RM3-201 of them THM501, performance index Fuller than double the axis, but the precision requirement, twin countershafts transmission manufacturing difficulty by more than the latter. According to Chinas current technique level, the design and manufacturing of reference technology in quality on more easily pass. This is one more intermediate bearing twin countershafts transmission assembly, only increases the number of parts, quality does not increase, efficient production can make up for the cost, the more work for it good reliability, long life, in use can increase performance, reduce loss, make it has total economic benefit is desirable. Our country is to introduce this twin countershafts transmission manufacturing technology and to promote national auto twin countershafts transmission of design, manufacturing technology quickly reached the advanced world level will play a positive role. In addition, the design concept of transmission , XinQiao Morse, design, test methods for developing ideas, rigorous, this is a long term of meaning. 附 录 B Fuller双中间轴变速器结构特点分析 富勒（ Fuller）双中间轴变速器是美国伊顿 Eaton 公司六十年代的独创产品，于 1965年申请专利，随即投入生产、供应市场。它是针对以下情况设计的：当时美国已逐渐建成高速公路网，为了提高汽车货运经济效益，促使货车向着大型 化、高速化、专用化的方向发展。在美国较为盛行 的一种运输方式是由鞍式牵引车牵引的半挂车和汽车列车，此种牵引车是美国公路用重型汽车中的主要车型，其特征是轴距短，加之美国公路法规限定该类车的前悬不得大于 800mm ，因之使变速器轴向尺寸受到很大限制。面发展的需要却一再要求提高汽车发动机功率，并相应加大变速器的承载能力，这对传统的单中间轴变速器来说，其轴向尺寸必然要加大因而产生了矛盾，双中间轴变速器即是在此种情况下应运面生的。它大大提高了变速器的扭矩容量（ Fuller 产品最大已达到 2240Nm ），并减小了轴向尺寸。它供应市场以后，在美国的重型车上逐渐取代了传统的单中间轴变速器。八十年代以来它几乎独占了美国重型车用变速器的市场（其中 Eaton 公司产品约占 75%)。七十年代中期以后，伊顿公司产品在降低噪音、提高寿命和可靠性方面又有显著提高。且在变速器基本结构不变的情况下，又研制成功细齿系列新一代变速器。同时，调整了原产品，重新编制了产品系列并实现标准化。八十年代初已经按新系列生产。本文是以原 900 系列（即新系列 11600，二者基本结构相同）的 RT 915 型组台式变速器的结 构为例进行分折。 附 B1RT 915 型变速器的基本结构 图 B1 所示为 RT 915 型变速器结构简图，它由一个五档主箱与一个三档位的后置倍档副箱组合而成，它有 15 个前进档和三个倒档。主箱和副箱齿轮中心距均为 148.43mm 它们各有两套中间轴总成，全部齿轮为直齿圆柱齿轮，常啮合式传动，二者输出轴上齿轮均为浮动，主箱输出轴亦浮动。主箱各档无同步器，副箱高低档装有锁销式惯性同步器，超低档采用外齿接合套式换档装置。主箱各档为机械式手操纵，副箱各档采用全气动式操纵换档。当 副箱同步器接合套 与接合套 均左移至接合位置时，组合式变速器分别处于高速区、低速区、超低速区，备有五种速比供选用。 图 B1 Fuller 双中间轴变速器 主箱第一轴 主箱第二轴 主箱中间轴 R 主箱倒档轴 副箱中间轴 副箱输出轴 换档接合套 副箱高低档同步器接合套 副箱超低档同步器接合套 ZR2 主箱倒档惰轮 附 B2 结构特点分析 附 B2.1 双中间轴功率分流 图 B1 所示变速器主箱和副箱各有两套中间轴总成，输入的动力分两路传给二中间轴总成，再 由输出轴总成将两路动力合流后输出。输入、输出轴上的齿轮同时有两个齿分别与二中间轴上的齿轮啮合，工作时每齿所受载荷相对单中间轴结构而言，理论上降低了 1/2，实际上则由于齿形误差、齿厚误差、中心距误差等， 使二中间轴上齿轮与相应啮合齿轮受载不均匀，使实际降低值少于 1/2。 此情况使双中间轴变速器较之单中间轴变速器具有明显的优势。 附 B2.1.1 双中间轴变速器齿轮寿命 鉴于齿轮的疲劳寿命约与其负荷的 3 次方成反比，关系式如下 : 3P N C? （常数） 式 (B1) 式 中： P 齿轮轮齿负荷； N 轮齿疲劳损坏的循环次数； 由式 B1 可知，设单齿传力情况下，轮齿负荷1P ，对应的疲劳损坏循环次数为1N。当双齿传力时，每一单齿负荷2P，较前者理论上降低了 1/2，即21/2PP=，此时对应的疲劳损坏循环次数 3212NN=?,即传递相同扭矩 ,双齿传力时，齿轮疲劳寿命可 大幅度提高如果保持齿轮疲劳寿命不变，即，21NN=，则21PP=，这说明了在齿轮疲劳寿命相等的情况下，双齿传力时，每一单齿的负荷可由1/2P提高到1P，即可提高一倍若按最差的实际情况，考虑，二齿载荷分布不均匀系数取为 0.6，由计算知道此时扭矩容量仍可提高 67 。这也就是双中间轴变速器设计原理所根据的事实。 附 B2.1.2 双中间轴变 速器中心距 双中间轴变速器的齿轮中心距按下列公式计算 3 m a x 1A e g gA K B T i h= 式 (B2) 式中： B 载荷分布不均匀系数 ( 取 0.52 0.60)； 由式 B2 可知，齿轮中心距可较单中间轴结构减小 15 20%，这对改善变速器的经济性和轻量化有着重要的意义，我们知道齿轮中心距稍许减小，质量即可减轻许多。 因此，齿轮中心距是齿轮传动设计中最基本的参数，它影响到变速器的很多重要性能指标，并直接和齿轮传动的结构设计及承载能力有密切关系。长期以来，国内外对减小传统变速器的齿 轮中心距进行了不懈的努力，终因受到轴承、材料 工艺水平及换档同步器成的设计制造技术水平的制约而进展不大。双中间轴结构的出现，由于功率分流大大改善了齿轮、轴、轴承和箱体的受载情况，并可降低加工精度要求，因而能做到既保证了变速器的使用性能，又减小了齿轮中心距。 由于齿轮轮齿应力较传统变速器减小近一半，故可减小齿宽约 40%，既减小了变速器轴向尺寸，又保持了齿轮的承载能力，同对还改善了载荷沿齿面的分布状况，有利于提高齿轮寿命。 附 B2.2 齿轮浮动 主箱输出轴上的齿轮同时与对称布置的二中间轴上的齿轮啮合，它在二 齿轮之间可沿径向浮动，靠啮合圆自动定心，副箱也是如此。这是 Fuller 双中间轴变速器结构的显著特点，其优点是： （ 1） 使输出轴上齿轮和二中间轴上齿轮正确啮合，并均匀分配载荷。 （ 2） 省去了传统变速器中输出轴上所有常啮合齿轮处的滚针轴承。此滚针轴承是传统变速器结构中的弱点，取消它，对提高变速器寿命和工作可靠性有明显作用。 （ 3） 对齿轮精度、轴的精度以及箱体轴承孔的位置精度可降低要求。 （ 4） 使齿形误差引起的动载荷影响减小。 （ 5） 试验表明，浮动啮合可减小强烈的谐振的噪音强度。 附 B2.3 轴的布置与受力 主箱第二轴为浮动 结构，二轴后端与副箱驱动齿轮花键联接，通过轴承支承在箱体上；轴前端轴颈与含油轴承之径向间隙较大（陕西汽车轮厂测量为 0.9 mm )，全轴以后端为支点，前端浮动。因此，第二轴上齿轮均是浮动的，换档时，在第二轴上的外齿接合套随轴浮动，便于换档。 图 B1 所示，二中间轴之中心连线与水平线之间夹角 a ， Fuller 为 19，此角若过小，将使箱体宽度尺寸加大，搅油损失增加，此损失是影响变速器效率的主要因素；如果过大，则箱体高 度尺寸加大，且使上方轴承润滑条件变坏。 对称布置的双中间轴使第一轴、第二轴上齿轮所受径向力相互平衡，使此二轴均不承受弯矩，而仅承受扭矩，放可使第一 轴、第二轴直径减小。二中间轴亦因此所受弯矩减小1/2，可使轴保证足够刚度（这是设计中间轴应主要考虑的问题 ），以改善齿轮和轴承的工作条件，这对提高齿轮和轴承的寿命和降低噪音甚为有利。 附 B2.4 解决了轴承使用寿命问题 由上可知，输入轴与输出轴轴承所受径向力的合力为零，传动齿轮为直齿，无轴向力，轴承仅承受重力；中间轴的轴承所受径向力减小近 1/2,无轴向力。所有 轴承受载荷情况均获极大改善，这是造成此种变速器轴承寿命长的基本因素。 另外，主副箱中间轴的一端仍采用了承载能力较强的滚柱轴承，既获容量大的好处，也是由于中间轴需采用游动式支承，且分离型轴承使装折方便。主箱其余轴承虽为常见类型，但与传统变速器比较，其寿命系数却高了许多。 副箱输出轴是由两个反装的圆锥滚子轴承支承，按分析主要是为了增强悬臂式轴的支承刚度及稳定性，和增大轴承容量。 在轴承负荷较小的情况下，尽可能增大轴承容量，既可提高轴承寿命，使之与变速器总寿命相适应；又可提高支承刚度，加强轴的运转刚性，保证齿轮正 确啮合，提高齿轮寿命及降低噪音。新系列产品为降低噪音，又新设计了轴承，从而改进了轴承品质。实际使用结果 ： Fuller 双中轴变速器在 48 万公里内无需更换轴承，此寿命值在同等级变速器中居世界最佳水平。 附 B2.5 主箱无同步器，采用拉型离合器配合换挡 Fuller 双中间轴变速器主箱没有采用同步器，而是采用外齿接合套式换档装置。按理，对于扭矩容量大的变速器而言，由于齿轮大，转动惯量大，换档时在将