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transmission technology international 变速器技术2011.pdf

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TRANSMISSION TECHNOLOGY INTERNATIONAL 变速器 技术 2011
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Accelerating into the future 24 OEM intErviEw: Fiat Transmission Technology International | September 2010Fiat may be steeped in the tradition of manual transmissions but that does not mean the Italian car maker’s sole focus is on conventional gearbox technology n Being the dedicated R&D engine and transmission division to one of Europe’s largest car making groups is no easy task, but that’s exactly the role Fiat Powertrain Technologies (FPT) fulfills for Fiat Group. First, a few numbers to put everything into context: FPT delivers 2.9 million engines a year, makes 2.4 million transmissions, employs 20,000 people, and has a footprint across 10 countries – all of which makes the Italian company a highly significant player in the global powertrain marketplace. And this does not include the development of new engine ideas, notions and concepts taking place on a daily basis. “Fiat’s transmission market is 50% European and 40% Latin American, with the remaining 10% in India and China,” outlines Sergio Cairola, FPT transmission platforms vice president and a Fiat veteran who has been developing engines and transmissions there for nearly 25 years. “Today we produce transmissions not only for our vehicles but also for the likes of the Ford Ka, and Peugeot in Argentina.” As for the types of transmissions on the agenda, Cairola settles this argument very quickly: “Fiat transmissions were born manual,” he says. “Manual is the dominant technology and will remain dominant in our portfolio.” But that’s not to say that FPT is focused exclusively on manual transmissions – far from it, in fact. Not only has Fiat been manufacturing automatics for over a decade, the company also has a portfolio in the A, B and C class segments for AMTs. However, most noteworthy within Fiat’s recent transmission ventures has been its entry into the DCT marketplace. “Even though it is likely automatic transmissions will remain dominant worldwide for now, we believe that the dual clutch has the highest potential growth,” confirms Cairola. “We had long and passionate discussions on the subject and made a thorough comparison analysis. Our view is that the DCT offers the optimal balance between fuel economy , comfort, sportiness and cost.” Fiat’s DCT is part of the new C635 family of transmissions being constructed at the FPT facility in Verrone, Italy . Available in a six-gear layout, the dry DCT can handle torque inputs of 350Nm, making it the highest-torque dry- clutch application in the world. Known as the Alfa TCT transmission, it weighs just 81kg complete with oil and transmission control unit, and is being debuted in the new Alfa Romeo MiTo. “The TCT consists of two gearboxes, each with its own clutch, which allows for the selection and engagement of the next gear, while the previous one is still engaged,” explains Cairola. “This kind of gear change OEM intErviEw: Fiat words: Saul wordsworth 25 September 2010 | Transmission Technology International “Our view is that the DCT offers the optimal balance between fuel economy , comfort, sportiness and cost” Above: t ipping the scales at just 81kg, the Alfa tCt consists of two gearboxes, each with its own clutch Left: Sergio Cairola, FPt transmission platforms vP, says manuals will remain the dominant transmission for Fiat Below: t Ct made its debut in the Alfa Mito earlier this yearmeans continuous torque delivery and traction, the outcome of which is a greater level of comfort than a conventional automatic transmission, as well as a sportier feel. “The speed of the gear change and the ability to switch between manual and automatic, plus the near-zero power loss during gear change, make it the most efficient automatic transmission in terms of fuel consumption levels.” The brand new TCT transmission boasts the largest number of interactions with a vehicle’s systems available today . These include the brake and accelerator controls, steering wheel and Alfa’s stop/start system, all of which means the DCT contains 23 patents in the areas of gearbox control, mechanics and actuator. But despite Fiat, and a host of other car makers and suppliers championing the DCT’s cause, Cairola believes that over the next ten years the manual transmission within Fiat will still remain predominant. “Of course we are interested in other kinds of transmissions, particularly DCTs which are planned to reach 25% of total FPT volumes,” he says. “However our focus will remain in our traditional market. This approach makes sense.” Unlike some of its competitors, FTP also intends to keep things simple. “Although a few manufacturers continue to look at seven- and eight-speed transmissions, we see this as too many operations and too challenging for the operator,” he adds. “The challenge for us is therefore to achieve a continuous evolution and optimization of the six-speed manufacturing footprint.” In the longer term Cairola predicts a steady rise in the volume of hybrid technology , particularly for customers with significant coast and stop time – in other words, small, compact cars designed for congested, inner- city driving environments. “The challenge is to offer this technology at a fair market price,” he explains. “FPT is developing a new small DCCT to be the basis for a compact, low-weight and low-cost hybrid powertrain, in combination with the T winAir turbo engine. The design concept will allow for an add-on option of the baseline powertrain, minimizing specific investments and R&D costs.” The transmission world waits with baited breath. TTi Home improvements FTP’s plant in Verrone, near Turin, might date back to 1974, but in every other way, this facility is very modern. Not only has it been showered with awards, including those for quality and cost control, its grounds also encompass part of a local nature reserve called Le Baragge. So, when it came to selecting a new production line for the creation of the C635 family of transmissions, there was little debate as to where it was to be built. The new facility at Verrone cost the best part of US$650 million, most of which was spent on equipment and R&D. Boasting a floor space of 35,000m 2 , the area is divided between processing and assembly units and houses nearly 200 cutting-edge machine tools. “All the equipment has been selected from the world’s best suppliers to ensure optimal performance,” says Cairola. “To guarantee every transmission is of the quality we expect, we carry out final inspections on all the products we manufacture.” The investment to date in technology should ensure a production of 400,000 transmissions per year. In the longer term this number is expected rise to 800,000 and will require the engagement of over 1,000 staff. The new division in Verrone’s facility, dedicated to the C635 transmissions, has also enjoyed the benefit of local subsidies from the Piedmont Region. This investment has contributed to providing training for all employees. In addition, both the Verrone municipality and the Biella province have promised to carry out transportation and urban-planning infrastructure improvements. 26 OEM intErviEw: Fiat FtP has worked hard to bring to market the MultiAir engine, which is mated to Alfa’s tCt . the unit uses Borgw arner’s Dualtronic control system and can handle torque levels up to 350nm transmission technology international | September 2010 FtP’s v errone base has a new division that’s dedicated to the C635 transmissionsGet the specs at WAMetl.com ? Unsurpassed stability in material strength, elasticity and sealing properties ? Dynamic property retention over a wide range of temperatures ? Custom formulations to exceed your end of life requirements ? Resistance to aggressive lubrication  uids Our Extended Transmission Life (ETL) materials are engineered to last up to 3X longer against the next generation of automatic transmission  uids at high temperatures. n Functional features and performance of automatic transmissions offer designs that fully emulate manual shift modes of driving to eight-speed concepts approaching the smoothness of CVT’s. They have kept pace with powertrain technology advancements in meeting the demands for horsepower and torque management while providing significant benefits with respect to fuel economy . Automatic transmissions comprise 55% of the market today and are estimated to reach 70% during the next decade. Significant reliability and extended life gains have been achieved through improved efficiency within fluid power transfer (torque converter assembly), power flow control logic (servo based and electro-hydraulic modules), planetary gear design (tandem based gear ratio systems) and automatic transmission fluid (ATF) formulation changes. Prior to the early 1970’s, ATF’s relied on whale oil as the primary friction modifier and lubricant used in automatic transmissions. As engine operating temperatures were increased to improve fuel economy and emissions, this lubricant was unable to maintain acceptable fluid service life. General Motors introduced the first advancements in lubricant chemistry with Dexron I (T ype A and B) and Dexron II (T ype C and D) as a replacement solution to retain viscosity and minimize lubricant breakdown at higher temperatures. The synthetic blends existing today (ATF+4, Mercon V , Dexron VI, ATF-Z1) support the Chrysler, Ford, GM and Honda automatic transmission system applications today . Dexron VI, as the next-generation lubricant to Dexron III, significantly improves friction clutch wear (120%), oil film thickness Lifecycle optimization (20%), fluid oxidation (100%), shear stability (200%) and foam aeration (150%). These improvements extend transmission life significantly by keeping operating fluid temperatures within the 80°C range with expected fluid service life of 100,000 miles. Heavy towing/grade conditions can bring these temperatures above 150°C, which will destroy lubrication, compromise conventional sealing material thermal resistance, wear/friction properties and require a lubricant change after 1,500 miles under this loading condition. The technical improvements led by ATF formulations to reach vehicle long life targets have posed a new challenge in the area of gasket performance. The ATF developments have not stopped as new lubricants are pushing the envelope. Many sealing elastomer specifications and associated validation key life tests are expecting 3,000 hours of acceptable performance. Achieving this using present ATF formulations combined with sealing materials formulated with less aggressive anti-oxidant and friction modifier additive resistance characteristics is not possible. Seal degradation occurs by either increased cross linking driven by the fluid as a cure catalyst that leads to hardening and embrittlement or softening/plasticizing the elastomer via polar solvent interaction via the ATF immersion at elevated temperatures. Introducing new fluids with incompatible sealing materials was first realized as a major hurdle for long life sealing when gasoline/ alcohol blends became common fuels for petrol vehicles. Pure gasoline is a non-polar fluid. The electron charge distribution is distributed evenly throughout the molecular 28 Case study: Wolverine Adv Anced MA teriAls Transmission Technology International | September 2010 Left and above: the aCM polymer elastomer provides extended life properties for powertrain components Inroads made in extended transmission-life sealing are helping to ensure new automatic gearboxes systems are lasting longerchain. Water is highly polar with a definite positive and negative charge collection at each end of the molecule. They don’t mix because “like dissolves like” is the governing rule. The closer two materials are to equal polarity , the greater their interaction including solubility . In the case of the gasoline/alcohol blends the alcohol component is highly polar and fairly close to acrylonitrile-butadiene. This is the base polymer of NBR and HNBR. At low temperatures or engine startups there is phase separation of the alcohol with the gasoline. In a non-dissolved state, the alcohol is free to cross link with nitrile molecules and form a bridging structure. For both NBR and HNBR this leads to unacceptable high hardness levels and compromises seal over time. Certain fluorine polymers (FKM) also have a highly polar vinylidene fluoride molecule that has greater affinity to the alcohol than its own molecular chain. This type of reaction breaks down the molecular chain, softens the material and leads to elastomer swelling and lower temperature resistance. Higher concentration of tetraflouroethylene monomer within the FKM can reduce this effect. Unfortunately , the cost becomes significantly higher and low temperature sealing function is sacrificed. Engine oils, power steering fluids, long life coolants, A/C refrigerants/lubricants and ATF’s all have the potential for either breaking down via repolymerization or increasing the molecular crosslink structure of the sealing elastomer. Higher thermal conditions accelerate the process. The two major additives to present ATF formulations that effect elastomer resistance and life are incorporating friction modifiers as well as the type and amount of antioxidants. Friction modifiers adhere to metal surfaces and avoid premature wear when lubricating film thickness decreases at lower viscosities and higher pressures. They also assist in maintaining a viscous barrier, increase torque transfer efficiency and have minimal localized heating related to lubricant shear. Antioxidants protect against lubricant viscosity breakdown and oxidation at higher temperatures. These additives have a negative effect in plasticizing (softening) and/or generating increased cross linking via existence of fatty acid derivatives or amines. The amines are highly polar and will easily interact with NBR, HNBR and FKM. Sealing becomes the weak link in achieving extended life of the transmission. In development of an elastomer formulation that would significantly minimize ATF influence on sealing life and performance, a base alkyl acrylate polymer (ACM) was selected as a starting point in development. The application was sealing the valve body channel plate used for guiding hydraulic flow and maintaining proper shift characteristics. Initial screening was performed on the base ACM as compared to peroxide and sulfur The reduction of heat induced breakdown on modified ATF fluids was discussed previously through both antioxidant and friction modifier addit
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