附 錄 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 錄 B Fuller雙中間軸變速器結(jié)構(gòu)特點(diǎn)分析 富勒（ Fuller）雙中間軸變速器是美國伊頓 Eaton 公司六十年代的獨(dú)創(chuàng)產(chǎn)品，于 1965年申請專利，隨即投入生產(chǎn)、供應(yīng)市場。它是針對以下情況設(shè)計(jì)的：當(dāng)時(shí)美國已逐漸建成高速公路網(wǎng)，為了提高汽車貨運(yùn)經(jīng)濟(jì)效益，促使貨車向著大型 化、高速化、專用化的方向發(fā)展。在美國較為盛行 的一種運(yùn)輸方式是由鞍式牽引車牽引的半掛車和汽車列車，此種牽引車是美國公路用重型汽車中的主要車型，其特征是軸距短，加之美國公路法規(guī)限定該類車的前懸不得大于 800mm ，因之使變速器軸向尺寸受到很大限制。面發(fā)展的需要卻一再要求提高汽車發(fā)動(dòng)機(jī)功率，并相應(yīng)加大變速器的承載能力，這對傳統(tǒng)的單中間軸變速器來說，其軸向尺寸必然要加大因而產(chǎn)生了矛盾，雙中間軸變速器即是在此種情況下應(yīng)運(yùn)面生的。它大大提高了變速器的扭矩容量（ Fuller 產(chǎn)品最大已達(dá)到 2240Nm ），并減小了軸向尺寸。它供應(yīng)市場以后，在美國的重型車上逐漸取代了傳統(tǒng)的單中間軸變速器。八十年代以來它幾乎獨(dú)占了美國重型車用變速器的市場（其中 Eaton 公司產(chǎn)品約占 75%)。七十年代中期以后，伊頓公司產(chǎn)品在降低噪音、提高壽命和可靠性方面又有顯著提高。且在變速器基本結(jié)構(gòu)不變的情況下，又研制成功細(xì)齒系列新一代變速器。同時(shí)，調(diào)整了原產(chǎn)品，重新編制了產(chǎn)品系列并實(shí)現(xiàn)標(biāo)準(zhǔn)化。八十年代初已經(jīng)按新系列生產(chǎn)。本文是以原 900 系列（即新系列 11600，二者基本結(jié)構(gòu)相同）的 RT 915 型組臺(tái)式變速器的結(jié) 構(gòu)為例進(jìn)行分折。 附 B1RT 915 型變速器的基本結(jié)構(gòu) 圖 B1 所示為 RT 915 型變速器結(jié)構(gòu)簡圖，它由一個(gè)五檔主箱與一個(gè)三檔位的后置倍檔副箱組合而成，它有 15 個(gè)前進(jìn)檔和三個(gè)倒檔。主箱和副箱齒輪中心距均為 148.43mm 它們各有兩套中間軸總成，全部齒輪為直齒圓柱齒輪，常嚙合式傳動(dòng)，二者輸出軸上齒輪均為浮動(dòng)，主箱輸出軸亦浮動(dòng)。主箱各檔無同步器，副箱高低檔裝有鎖銷式慣性同步器，超低檔采用外齒接合套式換檔裝置。主箱各檔為機(jī)械式手操縱，副箱各檔采用全氣動(dòng)式操縱換檔。當(dāng) 副箱同步器接合套 與接合套 均左移至接合位置時(shí)，組合式變速器分別處于高速區(qū)、低速區(qū)、超低速區(qū)，備有五種速比供選用。 圖 B1 Fuller 雙中間軸變速器 主箱第一軸 主箱第二軸 主箱中間軸 R 主箱倒檔軸 副箱中間軸 副箱輸出軸 換檔接合套 副箱高低檔同步器接合套 副箱超低檔同步器接合套 ZR2 主箱倒檔惰輪 附 B2 結(jié)構(gòu)特點(diǎn)分析 附 B2.1 雙中間軸功率分流 圖 B1 所示變速器主箱和副箱各有兩套中間軸總成，輸入的動(dòng)力分兩路傳給二中間軸總成，再 由輸出軸總成將兩路動(dòng)力合流后輸出。輸入、輸出軸上的齒輪同時(shí)有兩個(gè)齒分別與二中間軸上的齒輪嚙合，工作時(shí)每齒所受載荷相對單中間軸結(jié)構(gòu)而言，理論上降低了 1/2，實(shí)際上則由于齒形誤差、齒厚誤差、中心距誤差等， 使二中間軸上齒輪與相應(yīng)嚙合齒輪受載不均勻，使實(shí)際降低值少于 1/2。 此情況使雙中間軸變速器較之單中間軸變速器具有明顯的優(yōu)勢。 附 B2.1.1 雙中間軸變速器齒輪壽命 鑒于齒輪的疲勞壽命約與其負(fù)荷的 3 次方成反比，關(guān)系式如下 : 3P N C? （常數(shù)） 式 (B1) 式 中： P 齒輪輪齒負(fù)荷； N 輪齒疲勞損壞的循環(huán)次數(shù)； 由式 B1 可知，設(shè)單齒傳力情況下，輪齒負(fù)荷1P ，對應(yīng)的疲勞損壞循環(huán)次數(shù)為1N。當(dāng)雙齒傳力時(shí)，每一單齒負(fù)荷2P，較前者理論上降低了 1/2，即21/2PP=，此時(shí)對應(yīng)的疲勞損壞循環(huán)次數(shù) 3212NN=?,即傳遞相同扭矩 ,雙齒傳力時(shí)，齒輪疲勞壽命可 大幅度提高如果保持齒輪疲勞壽命不變，即，21NN=，則21PP=，這說明了在齒輪疲勞壽命相等的情況下，雙齒傳力時(shí)，每一單齒的負(fù)荷可由1/2P提高到1P，即可提高一倍若按最差的實(shí)際情況，考慮，二齒載荷分布不均勻系數(shù)取為 0.6，由計(jì)算知道此時(shí)扭矩容量仍可提高 67 。這也就是雙中間軸變速器設(shè)計(jì)原理所根據(jù)的事實(shí)。 附 B2.1.2 雙中間軸變 速器中心距 雙中間軸變速器的齒輪中心距按下列公式計(jì)算 3 m a x 1A e g gA K B T i h= 式 (B2) 式中： B 載荷分布不均勻系數(shù) ( 取 0.52 0.60)； 由式 B2 可知，齒輪中心距可較單中間軸結(jié)構(gòu)減小 15 20%，這對改善變速器的經(jīng)濟(jì)性和輕量化有著重要的意義，我們知道齒輪中心距稍許減小，質(zhì)量即可減輕許多。 因此，齒輪中心距是齒輪傳動(dòng)設(shè)計(jì)中最基本的參數(shù)，它影響到變速器的很多重要性能指標(biāo)，并直接和齒輪傳動(dòng)的結(jié)構(gòu)設(shè)計(jì)及承載能力有密切關(guān)系。長期以來，國內(nèi)外對減小傳統(tǒng)變速器的齒 輪中心距進(jìn)行了不懈的努力，終因受到軸承、材料 工藝水平及換檔同步器成的設(shè)計(jì)制造技術(shù)水平的制約而進(jìn)展不大。雙中間軸結(jié)構(gòu)的出現(xiàn)，由于功率分流大大改善了齒輪、軸、軸承和箱體的受載情況，并可降低加工精度要求，因而能做到既保證了變速器的使用性能，又減小了齒輪中心距。 由于齒輪輪齒應(yīng)力較傳統(tǒng)變速器減小近一半，故可減小齒寬約 40%，既減小了變速器軸向尺寸，又保持了齒輪的承載能力，同對還改善了載荷沿齒面的分布狀況，有利于提高齒輪壽命。 附 B2.2 齒輪浮動(dòng) 主箱輸出軸上的齒輪同時(shí)與對稱布置的二中間軸上的齒輪嚙合，它在二 齒輪之間可沿徑向浮動(dòng)，靠嚙合圓自動(dòng)定心，副箱也是如此。這是 Fuller 雙中間軸變速器結(jié)構(gòu)的顯著特點(diǎn)，其優(yōu)點(diǎn)是： （ 1） 使輸出軸上齒輪和二中間軸上齒輪正確嚙合，并均勻分配載荷。 （ 2） 省去了傳統(tǒng)變速器中輸出軸上所有常嚙合齒輪處的滾針軸承。此滾針軸承是傳統(tǒng)變速器結(jié)構(gòu)中的弱點(diǎn)，取消它，對提高變速器壽命和工作可靠性有明顯作用。 （ 3） 對齒輪精度、軸的精度以及箱體軸承孔的位置精度可降低要求。 （ 4） 使齒形誤差引起的動(dòng)載荷影響減小。 （ 5） 試驗(yàn)表明，浮動(dòng)嚙合可減小強(qiáng)烈的諧振的噪音強(qiáng)度。 附 B2.3 軸的布置與受力 主箱第二軸為浮動(dòng) 結(jié)構(gòu)，二軸后端與副箱驅(qū)動(dòng)齒輪花鍵聯(lián)接，通過軸承支承在箱體上；軸前端軸頸與含油軸承之徑向間隙較大（陜西汽車輪廠測量為 0.9 mm )，全軸以后端為支點(diǎn)，前端浮動(dòng)。因此，第二軸上齒輪均是浮動(dòng)的，換檔時(shí)，在第二軸上的外齒接合套隨軸浮動(dòng)，便于換檔。 圖 B1 所示，二中間軸之中心連線與水平線之間夾角 a ， Fuller 為 19，此角若過小，將使箱體寬度尺寸加大，攪油損失增加，此損失是影響變速器效率的主要因素；如果過大，則箱體高 度尺寸加大，且使上方軸承潤滑條件變壞。 對稱布置的雙中間軸使第一軸、第二軸上齒輪所受徑向力相互平衡，使此二軸均不承受彎矩，而僅承受扭矩，放可使第一 軸、第二軸直徑減小。二中間軸亦因此所受彎矩減小1/2，可使軸保證足夠剛度（這是設(shè)計(jì)中間軸應(yīng)主要考慮的問題 ），以改善齒輪和軸承的工作條件，這對提高齒輪和軸承的壽命和降低噪音甚為有利。 附 B2.4 解決了軸承使用壽命問題 由上可知，輸入軸與輸出軸軸承所受徑向力的合力為零，傳動(dòng)齒輪為直齒，無軸向力，軸承僅承受重力；中間軸的軸承所受徑向力減小近 1/2,無軸向力。所有 軸承受載荷情況均獲極大改善，這是造成此種變速器軸承壽命長的基本因素。 另外，主副箱中間軸的一端仍采用了承載能力較強(qiáng)的滾柱軸承，既獲容量大的好處，也是由于中間軸需采用游動(dòng)式支承，且分離型軸承使裝折方便。主箱其余軸承雖為常見類型，但與傳統(tǒng)變速器比較，其壽命系數(shù)卻高了許多。 副箱輸出軸是由兩個(gè)反裝的圓錐滾子軸承支承，按分析主要是為了增強(qiáng)懸臂式軸的支承剛度及穩(wěn)定性，和增大軸承容量。 在軸承負(fù)荷較小的情況下，盡可能增大軸承容量，既可提高軸承壽命，使之與變速器總壽命相適應(yīng)；又可提高支承剛度，加強(qiáng)軸的運(yùn)轉(zhuǎn)剛性，保證齒輪正 確嚙合，提高齒輪壽命及降低噪音。新系列產(chǎn)品為降低噪音，又新設(shè)計(jì)了軸承，從而改進(jìn)了軸承品質(zhì)。實(shí)際使用結(jié)果 ： Fuller 雙中軸變速器在 48 萬公里內(nèi)無需更換軸承，此壽命值在同等級(jí)變速器中居世界最佳水平。 附 B2.5 主箱無同步器，采用拉型離合器配合換擋 Fuller 雙中間軸變速器主箱沒有采用同步器，而是采用外齒接合套式換檔裝置。按理，對于扭矩容量大的變速器而言，由于齒輪大，轉(zhuǎn)動(dòng)慣量大，換檔時(shí)在將