The ZF AS Tronic Family Automotive Transmissions for All Commercial Vehicle Classes 1 Requirements for Commercial Vehicle Transmissions Customers demand high efficiency along with increasing vehicle comfort and safety. As an independent transmission manufacturer, ZF customer needs include the needs of drivers, forwarding companies, and vehicle manufacturers. Therefore, ZF considers the many requirements that a new transmission concept must fulfill when developing a transmission, Figure 1 . 圖1商用車輛的需求 Fig. 1 Requirements for commercial vehicles Keeping costs low is a considerable challenge, initially in terms of acquisition and later during operation. That is why fuel consumption is increasingly one of the decisive vehicle features that separate the competition. A modern transmission can make an important contribution here: On the one hand by improving efficiency and on the other hand in automatic transmissions by the optimal selection of the gear ratio dependent on the driving situation. Reducing the transmission, s weight also leads to reduced costs: Using less material reduces acquisition costs and enabling a higher payload reduces operating costs. On the one hand, decreased oil consumption contributes to environmental protection; additionally, it has an immediate influence on the costs, however, that accrue throughout the vehicle ’ s service life. The demand for system comfort increasingly approaches the standard set by car technology, whereas in this case limits are set by mass ratios and cost constraints. Low noise emissions are a result of legal regulations on the one hand but also contribute to more comfortable driver workplaces when met. Furthermore, electronic systems increasingly support the driver and relieve him/her from routine tasks. This benefits safety in traffic. 2 Advances with Automatic Transmissions Automatic transmissions can satisfy many of the demands that customers make on commercial vehicles considerably better than manual transmissions. Despite the fact that automatic transmissions are generally more expensive, if one takes the complete installed manual transmission system including the gearshift system into account, the difference in acquisition costs is no longer as great. Moreover, the goal of future developments is to further reduce the costs for automatic transmissions. Even today the higher acquisition costs are already paying for themselves relatively quickly due to lower operating costs so that automatic transmissions are economically advantageous in the long run. The efficiency of the AS Tronic family of transmissions is comparable to a manual transition; however, as a rule, the shifting point selection is better due to the application of an automatic driving strategy, which positively affects fuel consumption. A long term study conducted by ZF and DEKRA found that the automatic shifting point selection represents the consumption performance of a very good, concentrated driver. Thus, averaging all drivers and driving situations in a commercial fleet, consumption is reduced on the order of 3 percent since the engine operates reliably in the optimum speed range with regard to fuel consumption; a process that is controlled independently of the driver, s qualification. An additional advantage in terms of operating costs is reduced clutch wear. Reduced differential speeds during starting and shifting operations lengthen the service life of the clutch, which has al so been proven in long term tests. Many vehicle manufacturers take this into account and offer a significantly longer warranty cover on the clutch in AS Tronic transmissions. By automating the clutch, the clutch pedal is no longer needed, which clearly simplifies operation for the driver, particularly in stop and go traffic or when maneuvering. The automatic gear selection relieves the driver from shifting as well, whereby he/she can concentrate better on road traffic. However, at the same time, the driver can engage manually at any time, for instance in driving situations where the driver's forward field of vision is in question. This takes place according to Shift by Wire via an electromechanical control switch so that only very little actuating forces are applied when manually selecting gears. The rapid automatic shifting and the protection against operating error also contribute to the increase in driver comfort while at the same time protecting the transmission and driveline. In addition, the absence of a mechanical link between shift lever and transmission reduces cabin noise. Using an automatic transmission also has advantages for vehicle manufacturers. Like the clutch control, the complete shift linkage is no longer needed, which makes both left and right hand steering vehicles easy to manufacture. When designing the driver workplace, anything is possible in terms of operating the transmission. 3 The ZF AS Tronic Family ZF began developing automated manual transmissions for commercial vehicles early. The first product was a partially automated transmission with automatic pre selection, which was introduced into the market in 1984. Ten years later, an automated transmission followed with the introduction of the first AS Tronic; however, the driver still had to select gears. Its successor model was first equipped with an intelligent shift program, which has been in production since 1998. Thus, a fully automatic solution was offered in a heavy commercial vehicle for the first time. The chosen transmission concept for AS Tronic resulted in the most efficient solution possible for larger volumes. Extensive integration and removal of unnecessary components opened up potential cost savings. As a group drive, AS Tronic is designed with an unsynchronized basic transmission and synchronized splitter and range change group, Figure 2. 圖2 ZF AS Tronic的3D剖示圖 Fig. 2 ZF AS Tronic: 3D section cut In order to reduce the weight of the transmission, a design with two countershafts was chosen, which is optimal in this performance class in terms of weight. Due to a modular design and a basic transmission with 3 or 4 speeds, l6 peed, 12 speed, and 10 speed variants could be represented. In the basic transmission, the synchronizations were replaced with shift dogs, because the synchronization can take place by controlling the internal combustion engine in modern EDC engines. An additional transmission brake is then required for up shifts, which is located on one of the two counter shafts. A standard dry clutch is used. It is fully automatic so that a clutch pedal is no longer necessary. All automated components are pneumatically operated and are combined within modules that are integrated into the transmission housing. The coordinated operation of transmission, clutch, and engine takes place by electronic control, which is located in the shift module. The interfaces to the out side were minimized. AS Tronic was initially limited to torques of 2, 300 Nm (12 speed) and 2, 600 Nm (16 speed). Afterward, variants were introduced in a two step development, which expand the torque ranges of 12 speed transmissions upwards. AS Tronic is offered in direct drive and overdrive designs and is generally available with an integrated secondary retarder “Intarder. ’’ Automatic transmissions have found increasing acceptance in heavy commercial vehicles in the past few years and enjoy enormous popularity among customers. However, the advantages of these transmissions are also demonstrated especially in light and medium duty commercial vehicles. Vehicles in these classes are primarily used in city and regional traffic. Relief from operating the transmission and the clutch is especially important in this case because the traffic environment requires the driver’s full attention. Furthermore, this sector is marked by a high number of untrained drivers and frequent driver turnover. Therefore, reducing the driver's influence on fuel consumption and clutch wear is an unmistakable advantage, not to mention safeguarding against transmission and clutch damage caused by the driver. For these reasons ZF decided to expand the product portfolio for automatic transmissions systematically into the area of low torques, Figure 3. 圖3變速器型譜:ZF AS Tronic的轉(zhuǎn)矩范圍 Fig. 3 Transmission portfolio： the ZF AS Tronic products with torque ranges Starting from the technical fundamental principle- two pedal solutions with automatic shifting and a customer benefit that is commensurate with the AS Tronic- smaller AS Tronic transmission will be developed as well. They receive additional coding to their genuine designation in order to mark their association to the respective vehicle applications. AS Tronic mid will be used for applications from 800 Nm to 1, 600 Nm； AS Tronic lite will cover trucks in the lower torque range up to 1, 050 Nm with 6 speed transmissions. 4 ZF AS Tronic mid The vehicle sector where the AS Tronic mid series will be used is very sensitive to price and highly differentiated in terms of application types. Thus, midrange vehicles will service both distributor and long distance transport as well as construction sites. Therefore, one of the focal points of development lies in a cost effective design that will fulfill the many and diverse customer requirements easily and also cover the wide torque range. Consistent product planning led to the development of an uncompromising midrange transmission series designed for automation. It encompasses seven transmission types combined into one modular design. With 840 mm short and 900 mm long transmission variants, the modular design concept is primarily based on the variation of the wheel widths in order to cover the torque ranges up to 1, 200 Nm and 1，600 Nm respectively. Both transmission lengths will be offered in direct and overdrive de signs. Compared to the AS Tronic, the AS Tronic mid transmissions are approx. 50 to 65 kg lighter. In order to optimize costs, a consistent complexity management system was pursued. Approximately 40% of the components were taken from existing transmissions in production at ZF. In order to offer uniform automation technology for all commercial vehicles in the midrange and heavy duty sectors, the proven AS Tronic components such as transmission/clutch actuators, electronics, and software were used. Due to the inter face equality this achieved, the vehicle manufacturer can offer both AS Tronic and AS Tronic mid series in almost identical vehicles with various drive line variants at minimal expense. In a preliminary concept study, various gear set concepts were considered. Eight gear set formulas were compared using eleven selected evaluation criteria in terms of function, costs, and deadline. In order to provide this complex decision matrix with the necessary transparency, a decision making software tool was used. The choice was made for a 12 speed gear set (2x3x2), which is comparable to a conventional 9 speed gear set in terms of design space and weight and even has advantages compared to a 10 speed gear set, Figure 4. 圖4 ZF AS Tronic mid變速器剖示圖 Fig. 4 ZF AS Tronic mid in complete view It consists of engaging and disengaging input constants ( splitter group), 3 speed main transmission, and an output end planetary drive stage (range change group). Synchronizations are used in the splitter and range change group; the main transmission shifting elements are designed as dogs. The gear steps has a slightly progressive gear interval due to a small increase in the gear ratio. Thus, at a total gear spread of approx. 12. 8, the gear ratio of 23. 8 % from 11th to 12th speed is on par with a comparable 16 speed transmission. For the first time, the gear ratio of the reverse gear was designed 13. 1, i. e. slower than 1st gear on a range change group transmission by an offset engagement over the reverse idler gear. In close cooperation with the customers, high drivability was already emphasized in the specification phase. Upon completion of the rough design, the drivability release criteria of one customer were already proven in simulations. A detailed cost analysis of the gear units in ZF transmissions led to the design of the planetary rear mounted range change group in the AS Tronic mid，in which the most cost effective solutions were adopted in each case. Thus, the design of the new gear unit is marked by the synchronization of the AS Tronic and the gear set design of the Ecosplit Figure 5. 圖5 ZF AS Tronic mid:行星齒輪傳動 Fig. 5 ZF AS Tronic mid： planetary drive detail The bearings of the swing fork in the range change group are realized between the two housing parts, which minimizes seal points to the outside and possible corrosion weak points. The clutch actuating cylinder was turned in driving direction from the 6 o’ clock position for AS Tronic to the 8 o'clock position for AS Tronic mid. This not only increases vehicle road clearance and brings the actuating cylinder out of the danger zone, it al so offers the flexibility to react to potential requirements pushed clutch release under compression. Different from the AS Tronic, the AS Tronic mid gear set will only be designed with one counter shaft. The solution was the best in a parameter study for the torque range considered, which takes into account both the modular design aspects as regards optimal gear set length variation as well as the legally permitted noise requirements. As a result, the developer faced an additional challenge. If the oil pump and transmission brake are each driven by one countershaft in the AS Tronic, then both components now must be combined in a joint, cost effective brake pump module. Maximizing transmission efficiency in order to reduce fuel consumption attracted much interest during development. By consistently changing splash lubrication to injection lubrication, quasi dry sump lubrication was achieved so that diving losses do not occur. In order to optimize the lubrication system, oil flow calculations were conducted. The oil itself was handled like a structural/ design element. ZF has worked intensively for years with lubricant manufacturers in order to develop synthetic oils such as the ZF Ecofluid M, which is used in these transmissions. This oil has low viscosity and therefore contributes low internal losses; however, at the same time it offers sufficient lubricating film to guarantee the service life of gears, bearings, and synchronizations. An additional advantage of Ecofluid M is high stability, which makes clearly longer oil change intervals possible and greatly reduces oil consumption. Shift dogs in the main transmission and a com pact transmission design with small center distance also contribute to loss reduction. All these measures together increased the efficiency in the direct gear from 99. 2 to 99. 6% under comparable operating conditions. Active heat management enabled additional fuel savings. If the transmission runs at approx. 60℃ oil sump temperature on road, the oil viscosity can be further reduced by additionally heating to 80℃. In this case, AS Tronic mid is optionally available for the addition of a highly integrated heat exchanger. Short payback periods of approx, one year are ensured by cost effectively integrating the heat exchanger cartridge with the integrated bypass valve in the oil circulation on the intake side. ZF AS Tronic系列-適用于各種商用車輛的自動變速器 1 商用車輛變速器的需求 客戶的要求是在提高車輛舒適性和安全性的同 時也提高效率。作為一個獨立的變速器制造商，ZF 公司的客戶還包括駕駛?cè)藛T、運(yùn)輸公司和車輛制造商。 因此，ZF認(rèn)為在開發(fā)變速器時就必須考慮到應(yīng) 滿足各種需求，（圖1)。 圖1商用車輛的需求 Fig. 1 Requirements for commercial vehicles 繼續(xù)降低制造和使用成本是一個很大的挑戰(zhàn)。這就是燃油經(jīng)濟(jì)性為什么正成為車輛競爭的決定性因素之一的緣故。一個現(xiàn)代化的變速器具有以下貢獻(xiàn)：一方面通過優(yōu)化速比改進(jìn)效率、實現(xiàn)自動化、降低變速器重量以減少成本、減少金屬材料用量降低制造成本、提供更大的有效載 荷降低使用成本等。另一方面，減少燃油消耗還有助于環(huán)境保護(hù)，它直接影響到使用成本，因而可提高 車輛的服務(wù)壽命。 對系統(tǒng)舒適性需求的增加已成為車輛技術(shù)的標(biāo)準(zhǔn)配置，盡管這受制于檔位數(shù)量和成本限制。低噪聲一方面是由于法規(guī)要求，同時也提高了駕駛員工作環(huán)境的舒適程度。進(jìn)一步而言，為駕駛員提供支持的電子系統(tǒng)減輕了他們的工作任務(wù)。這有益于交通安全。 2 自動變速器的優(yōu)點 自動變速器比手動變速器更能滿足客戶對商用車輛的需求。除了自動變速器成本較高的事實外，但如果考慮到手動變速器及相應(yīng)的換檔操縱系統(tǒng)的話，兩者成本的差距并不太大。因此進(jìn)一步發(fā)展的目標(biāo)是降低自動變速器的成本。 在今天，較高的制造成本由于更低的使用成本而迅速補(bǔ)償，因此自動變速器最終具有經(jīng)濟(jì)性方面的優(yōu)勢。將ZF AS Tronic系列變速器與手動變速器相比，由于采用了自動駕駛模式其換檔點的選擇更具優(yōu)勢，這有助于燃油經(jīng)濟(jì)性。一項由ZF和 DEKRA公司的長期研究發(fā)現(xiàn)換檔點的自動確定相當(dāng)于一個具有高超技術(shù)駕駛員集中精力的駕駛。因而一個具有平均駕駛水平的車隊燃油消耗可降低 3%，因為發(fā)動機(jī)能可靠地工作在最佳速度區(qū)域，而整個過程與駕駛員的素質(zhì)無關(guān)。 另一個優(yōu)點是可降低離合器的磨損。在起步和換檔過程中減少滑差可增加離合器的使用壽命，這己被長期試驗所證明。許多車輛制造商為配置AS Tronic變速器的車輛提供更長的離合器保修期限。 采用自動離合器后，離合器踏板己不再需要，簡化了駕駛員的工作，特別是在頻繁起步、停車工況下。檔位自動選擇解放了駕駛員的換檔動作，駕駛員的注意力可集中在道路交通上。同時,駕駛員仍可在任何時候切換為手動模式，例如當(dāng)駕駛員視野出現(xiàn)問題時。這些都根據(jù)線控?fù)Q檔系統(tǒng)和機(jī)電一體化的控制開關(guān)完成，因此在手動換檔時僅需很小的操縱力。迅速地自動換檔和防止操縱失誤增加了駕駛舒適性，同時也保護(hù)了變速器和傳動系。另外變速器和換檔操縱桿之間無機(jī)械聯(lián)接可降低駕駛室的噪聲。 使用自動變速器對車輛制造商也有好處。像離合器控制和換檔操縱裝置己不再需要，方便制造轉(zhuǎn)向盤左置和右置的車輛。在設(shè)計駕駛員工作區(qū)域時更能隨心所欲。 3 ZF-AS Tronic 系列 ZF早就開始開發(fā)適用于商用車輛的機(jī)械自動變速器。第一個產(chǎn)品是帶自動預(yù)選檔位的半自動變速器，在1984年投入市場。十年后，推出的是AS Tronic的第一代產(chǎn)品，但是駕駛員仍需要選擇換檔。在1998年，其后續(xù)產(chǎn)品采用了智能化的換檔程序，而全自動化的產(chǎn)品則首先用于重型商用車輛。 圖2 ZF AS Tronic的3D剖示圖 Fig. 2 ZF AS Tronic： 3D section cut 選擇ZF AS Tronic變速器將具有更好大批量裝車的可能性。高度集成和省略不必要的元件使得在降低成本方面仍具潛力。作為一組合式變速器，AS Tronic被設(shè)計成由不帶同步器的主變速器、前置同步分流的副變速器和擴(kuò)展速比的后置副變速器組成，圖2。 為減輕主變速器的重量，采用了雙副軸結(jié)構(gòu)。由于主變速器是3或4檔，因此可構(gòu)成16、12和10檔的變速器。在主變速器，同步器被換檔檔塊所替換，因為同步過程可由現(xiàn)代化的EDC發(fā)動機(jī)完成。一個附加的變速器制動裝置用于升檔，它位于兩副軸之一上。采用標(biāo)準(zhǔn)的干式離合器。由于是全自動變速器故無需離合器踏板。所有的換檔元件由氣壓操縱并被以模塊形式集成在變速器殼體上。利用電控系統(tǒng)控制變速器、離合器及發(fā)動機(jī)，該裝置安裝在換檔模塊上。外部界面做成最小。 AS Tronic的輸入轉(zhuǎn)矩為2300Nm(12速）和 2600Nm(16速）。副變速器具有2檔速比，它能擴(kuò)大12速變速器的轉(zhuǎn)矩。AS Tronic提供直接傳動和超速，通常集成一個第二緩速器“Intarder”。 在過去幾年里，自動變速器在商用車輛上的應(yīng)用正在增加并贏得了消費(fèi)者的巨大信任。然而，變速器的優(yōu)點主要體現(xiàn)在輕型和中型商用車輛上。這些車輛主要行駛在城市和近郊交通繁忙的區(qū)域。這時減輕變速器和離合器的操作特別重要，因為交通情況需要駕駛員集中全部精力。另外，車輛是由大量非專業(yè)人員駕駛而且頻繁更換駕駛員。因此減少駕駛員對燃油消耗和離合器磨損的影響是一個顯著的優(yōu)點，同時也減少了駕駛員對變速器和離合器的傷害。 為此ZF決定系統(tǒng)地擴(kuò)展自動變速器的產(chǎn)品型譜，如圖3。 圖3變速器型譜:ZF AS Tronic的轉(zhuǎn)矩范圍 Fig. 3 Transmission portfolio： the ZF AS Tronic products with torque ranges 從技術(shù)基本原則開始，即采用兩個踏板的AS Tronic是解決自動換檔和方便駕駛的方法，因此也將開發(fā)較小的AS Tronic變速器。對應(yīng)于實際產(chǎn)品它們都有附加的代碼以表示其各種的車輛應(yīng)用場合。AS Tronic mid適用于800Nm到 1600Nm; AS Troniclite是適用于卡車的6檔變速器,從低轉(zhuǎn)矩直到1050Nm。 4 ZF AS Tronic mid 適用于AS Tronic mid系列的車輛對價格很敏感，具有廣泛的應(yīng)用場合。中型車輛適用于經(jīng)銷商、長距離運(yùn)輸和建筑等場合。因此，設(shè)計開發(fā)的關(guān)注點之一是效費(fèi)比，它將容易地滿足消費(fèi)者的各種需求和覆蓋廣的轉(zhuǎn)矩范圍。 ZF公司一貫的產(chǎn)品規(guī)劃產(chǎn)生了一個執(zhí)著的中型變速器系列產(chǎn)品的開發(fā)。在一個模塊化設(shè)計中它包含7種變速器。從840mm的短變速器到900mm 的長變速器，模塊化設(shè)計觀念基于不同的車輛寬度以覆蓋1200Nm到1600Nm的轉(zhuǎn)矩范圍。兩種長度的變速器都提供直接和超速設(shè)計。和AS Tronic相比AS Tronic mid輕50 - 65kg。為降低成本，采用了相同的操縱系統(tǒng)。約40%的部件源自ZF現(xiàn)有變速器。 為在中型和重型商用車輛方面提供相同的自動操作技術(shù)，應(yīng)用了經(jīng)檢驗的AS Tronic部件如變速 器/離合器執(zhí)行機(jī)構(gòu)、電子元件和軟件等。由于界面相同，車輛制造商可以最低的代價將AS Tronich和 ASTronic mid系列的各種傳動系統(tǒng)提供給幾乎相同的車輛。 在初步概念階段，考慮了各種齒輪結(jié)構(gòu)。8檔變速是比較了11種評價指標(biāo)，如功能、成本和壽命等。為對該復(fù)雜的決策矩陣提供必要的透明度而采用了決策軟件。12檔變速器則設(shè)計成2X3X2形 式，它與常規(guī)的9檔變速器具有相同的設(shè)計空間和重量，比10檔變速器更先進(jìn)，圖4。 圖4 ZF AS Tronic mid變速器剖示圖 Fig. 4 ZF AS Tronic mid in complete view 它由前置副變速器(分流）、3檔主變速器和后置行星齒輪變速器 (擴(kuò)大速比)組成。同步器用在兩副變速器上，主變速器換檔機(jī)構(gòu)被設(shè)計成擋塊。檔位間隔稍有變化使得速比有所增加。其總速比約為12. 8,和16擋變 速器相比在11和12檔之間速比增加了23. 8%。通過一個附加的倒檔惰輪首次將倒檔速比設(shè)計成低于 1檔速比的13. 1。設(shè)計時與用戶緊密協(xié)作，在規(guī)格中強(qiáng)調(diào)高的傳動性能。完成初步設(shè)計后，對每個用戶的傳動性能都進(jìn)行了相應(yīng)的仿真。 圖5 ZF AS Tronic mid:行星齒輪傳動 Fig. 5 ZF AS Tronic mid： planetary drive detail 對ZF變速器齒輪裝置仔細(xì)地成本分析導(dǎo)致了在AS Tronic mid上采用行星齒輪機(jī)構(gòu)的后置副變速器，這是具有最佳效費(fèi)比的解決方案。因而設(shè)計的新變速裝置用于AS Tronic而常規(guī)變速裝置則是 Ecosplit，圖5。 換檔擺動叉軸承安裝在兩殼體零件上，這使得外部密封點和可能的腐蝕點最少。AS Tronic的離合器執(zhí)行機(jī)構(gòu)活塞沿傳動方向旋轉(zhuǎn)6 點鐘，而AS Tronic mid則旋轉(zhuǎn)8點鐘。這不僅增加了車輛的離地間隙而且使得執(zhí)行機(jī)構(gòu)活塞處于非 危險區(qū)域，同時也提供了將推式離合器改成拉式離合器的靈活性。 與AS Tronic不同，AS Tronic mid的齒輪機(jī)構(gòu)僅有一根副軸。這是在該轉(zhuǎn)矩范圍內(nèi)的最佳解決方案，該方案考慮了模塊化設(shè)計中優(yōu)化齒輪機(jī)構(gòu)長度和噪聲法規(guī)兩方面的問題。其結(jié)果是開發(fā)者面臨著額外的挑戰(zhàn)。例如燃油泵和變速器制動由AS Tronic的同一副軸驅(qū)動，兩部件必須合成為一個制動油泵模塊。 在開發(fā)過程中非常誘人的是將變速器效率最大化以減少油耗。將飛濺潤滑改成噴射潤滑和半干油池潤滑后甩油損失不復(fù)存在。潤滑油被處理成象一個結(jié)構(gòu)/設(shè)計元件。ZF通過多年來和潤滑劑生產(chǎn)商的共同研宄，開發(fā)出適用于這些變速器的合成潤滑油，如ZF Ecofluid M。該潤滑油粘度低，因此內(nèi)部損失低;但是它能提供足夠的潤滑油膜以確保齒輪、軸承和同步器的壽命。另外Ecofluid M的附加優(yōu)點是高穩(wěn)定性，這意味著更長的換油間隔和大大減少潤滑油消耗。 緊湊設(shè)計的主變速器上的換檔擋塊徑向尺寸小，也可減少損失。所有這些努力將直接檔的效率從99. 2%增加至99. 6%。主動溫度管理能節(jié)省燃油。如果變速器工作時油底殼溫度在60 °C左右的話，通過加熱油溫至80 °C潤滑油粘度能進(jìn)一步減少。這時AS Tronic mid可選擇附加的高度集成的熱交換器。約一年左右可確保收回成本，因為在潤滑油回路進(jìn)口處帶旁路閥的集成熱交換器具有高的效費(fèi)比。