Gearbox trends
    Posted byadmin  date2009-9-29  click3241

    Heavy vehicle transmission refers to large passenger heavy commercial vehicles and the matching transmission, although in the industry on the transmission capacity of the division no clear boundaries, but we usually calibrated input torque at 900Nm more auto transmission called heavy vehicle transmissions.
    1 foreign heavy vehicle transmissions structural features
    abroad, transmissions specialized manufacturers are focusing on product series for OEMs to select the most satisfactory transmission offers great convenience and flexibility. Such as Germany ZF (ZF) company with a central base from 8.0,95,105,115,120,143,154 mm7 kind type transmission, to adapt the input torque of 130-1900Nm, the number of stalls from 3-17 months, there are various The transmission control method of a vehicle to adapt to different matching requirements. Toyota Motor Corporation Aisin Seiki with center distance 72,78,88,98,135 mm5 kind of base-type combinations, 286 kinds of transmission for users to choose. In China, a large number of automotive transmission manufacturers, there is no transmission of the enterprise formed series products.
    1.1 Germany ZF9S109
    structural features multi-speed transmission produced by German ZF 9S109 synchronizer file 9 file type compound transmission times, the main transmission has five forward gears, auxiliary transmission planetary gear transmission structure. When the auxiliary transmission synchronizer clutch engagement with the fixed ring gear, planetary gear ring gear is fixed and can not rotate, then splitter into the low hanging, The main transmission were linked into 5 different stalls available Combined Transmission 5 large transmission ratio. When the clutch engagement with the ring gear auxiliary transmission end, the planetary gear shaft, the output shaft, the ring gear and the planetary gear auxiliary transmission gear fixed to the input shaft rotates in synchronization, the auxiliary link into the high (direct drive), the main The five gear transmission ratio is equal to compound transmissions are five smaller transmission ratio. Since there are two values ​​very close to the transmission ratio, the dispense a transmission ratio, composition 9-speed transmission. Maximum transmission input torque 1250Nm, the total mass of 310kg, with the engine directly connected or stand-alone installation, horizontal left or right horizontal. Transmission control system or remotely operated by a rotary shaft direct manipulation, double-XH type shift arrangement, auxiliary transmission automatic transmission by compressed air, crawling gear and reverse gear meshing sets of gear with the other files with synchronizer gear.
    2 U.S. Eaton Fuller family structure features twin countershaft transmission
    U.S. Eaton produced BT-11509C twin countershaft times file 9 files modular mechanical transmission, both the main and auxiliary transmission with dual intermediate shaft structure. There are five main transmission forward gears. 2 auxiliary files (high and low) gear, because of two transmission ratio is very close, so save one, composed of 9-speed transmission. X file
    twin countershaft compound transmission has the following advantages:
    (1) as a shaft and two gear shafts with both of the intermediate shaft corresponding to the two meshed gears, power split, theoretically speaking, each of the torque transmitted to the gear is 1/2, which makes each of the torque transmitted to the gear reduction of 50% of the center distance of the transmission, the gear module and the width can be reduced, thereby reducing the quality and size of the transmission , in particular length dimensions.
    (2) due to the shaft driven gear is radially floating state, the axis of the intermediate shaft two uniformly distributed on the center axis of the biaxial theory to center distance of the radius of the cylindrical surface of the Therefore, two of the gear shaft and a shaft with two gears corresponding to the intermediate shaft gear meshed to balance the radial forces, which cancel each other. Two-axis radial force not only transfer torque, so that two-axis can be designed carefully, the structure can be simpler and subsequently bearings can select a smaller size, which also helps to reduce the transmission quality and size.
    (3) due to the radial axis of the gear and the two axes of the articulated float floating
    result, when the gear automatic cancellation of the engagement part manufacture and assembly errors, the engagement quality is better than a single countershaft. Mating area is easy to meet the design requirements, the actual usage also confirmed this point. This engagement helps reduce noise and increase durability.
    (4) times the twin countershaft type compound transmission file can be significantly reduced and the axial dimension of the transmission quality, the use of this advantage, the transmission can increase the maximum transmission power and torque, expand the scope. This is the short wheelbase
    power heavy vehicles and special vehicles optimal transmission. RT-11509C type transmission maximum input torque 1500Nm, the maximum input power of 265kW, the total length of 735mm, XXH or single H control, you can also right-left manipulation manipulation, the total mass of 270kg.
    2 domestic mechanical structural characteristics of heavy vehicle transmission
    domestic heavy truck transmission products, technology and more from the United States, Germany, Japan and several countries, the introduction of technology, mostly abroad last century, 80 - 90's products. As the field of automotive advanced technology in the domestic heavy-duty automotive transmissions lengthy introduction and assimilation process, now has made great progress, it is possible on the basis of the original introduction of technology, developed through modifications to meet the matching requirements of new products, heavy vehicles per year transmission industry can have more than a dozen new products to market. However, the development of today's heavy-duty truck transmission situation, in new product development is still on the domestic heavy-duty truck transmission is taking the general development process, there is no real core technology products; heavy vehicle transmissions from the domestic market capacity point of view, there are three One of two products from imports, while the other two-thirds of products in more than 80% from foreign technology and domestic self-developed heavy-duty auto transmission product sales is very small, thus indicating that domestic manufacturers of heavy-duty vehicle transmission capacity of independent development is still very weak, and respond to new vehicle models supporting products, the ability is not enough. Will focus on the development of urban vehicles used on the 13.8m bus transmission, ZF one can currently only supply to domestic enterprises, it is sufficient to explain the domestic heavy-duty truck transmission companies are still very small in terms of technology still has a long way to go.
    Domestic heavy vehicle transmissions almost by Shaanxi Fast Gear Co., Ltd., Qijiang Gear Transmission Co., Ltd., Shanxi Datong Gear Group Co., Ltd., FAW Harbin transmission plant, such as several people swept. These companies manufacture products for the transmission of the market have focused on more than 8t like Shaanxi Fast heavy vehicles in more than 40% market share, and in the heavy-duty truck market share of more than 15t absolute advantage, with a market share of more than 85% ; Qijiang Gear Transmission Co., Ltd. is Kai, Sivori, Yaxing Benz, Guilin Daewoo and Xiamen Golden Dragon and other enterprises 7 ~ 12m grade large and medium-sized passenger cars as well as the total mass of 14 ~ 50t heavy-duty trucks, tractor saddle , dump trucks and all kinds of special vehicles, special vehicles matching; Shanxi Datong Gear Group is supporting the market, mainly in 8 ~ 10t-grade, low tonnage of heavy-duty trucks.
    3 mechanical characteristics of heavy vehicle transmission technology
    large mass loading of heavy vehicles, the use of complex conditions. To ensure that heavy vehicles with good power, economy and acceleration, gear ratios must expand the scope and increase the number of stalls. To avoid transmission structure is too complex and easy to series production, the use of modular mechanical transmission. That is, twelve kinds of 4 to 6-speed transmission as the main body, by replacing the series of gears and configure different sub-transmission, the number of stalls to get a different set, different gear ratio range of transmission line. Currently, the combined mechanical transmission has become the main type of heavy vehicle use. Combined mechanical transmission times are generally divided into files (files with segmented) and semi-modular mechanical transmission files (files with plug-in) modular mechanical transmission.
    3.1 times the speed compound mechanical transmission
    times the speed compound mechanical transmission is in the rear of the main gearbox installed in series a 2 files (high and low) auxiliary transmission, the main transmission doubling the number of stalls, the gear transmission ratio increased transmission ratio value equal to the main and sub-transmission ratio of the product, and gear for less than the number of stalls, so box size shortened, shortening the length of the shaft, stiffness increases, so increases the transmission capacity. For example, in a five-speed main transmission rear, mounted in series one with high and low two auxiliary files, can be composed of 10 files (or 9 files) times the speed compound mechanical transmission. Fold increase in the maximum speed compound transmission input torque and the most low technical difficulty of the transmission ratio is low gear strength auxiliary transmission capacity is insufficient, beyond the carrying capacity of the gear teeth. The solution is to bear the load will be a split tooth to several teeth to bear. As a result, the input gear torque constant, the load of each tooth is equal to the average values ​​of both the number of teeth in contact.
    Times the speed compound transmission auxiliary power split in two ways: one is the use of planetary gear transmission method, this structure is very compact, small and large torque capacity, until now still widely used; another kind of power split method is to use twin countershaft transmission structure. Twin countershaft transmission biggest difficulty is to ensure that technology can and the main drive gear meshing twin countershaft gear teeth simultaneously contact problem, the solution is to use a floating main drive gear pinion way to eliminate manufacturing errors on the bit to ensure that teeth simultaneously contact, reach power diversion. Adapt to this shift synchronizer also have some amount of floating.
    half speed compound mechanical transmission gear ratio of the sub-transmission gear ratio spacing evenly into the large main transmission between each gear ratio, the transmission of doubling the number of stalls. Semi file auxiliary front of the main section connected in series, it is only one pair of shift gears and synchronizers. Early semi-auxiliary file a box by a separate component, in recent years to develop into the semi-gear pair directly into the main transmission within the transmission length shortening and simplifying both semi-structured files. Semi auxiliary file a shaft by a pair of similar composition constant mesh gears, gear trap free rotation of the power input shaft, a ring gear when the power input shaft and the main transmission with a shaft, the respective gear ratios are the main transmission a shaft gear components. When the ring gear and the power input shaft engagement tooth connection, constant mesh gear and intermediate shaft on the main transmission connection, so the main gearbox intermediate shaft also rotates, the resulting composition of each gear ratio evenly inserted to take charge of the transmission of the file between transmission ratio. GV80 model ZFAK/6-80 ten semi-file combined mechanical transmission, 6-speed AS6-80 from the main transmission gearbox series semi-file deputy components. The maximum input torque of 750Nm, the transmission ratio ranges from 0.83 to 9.0, reverse gear ratio is 7.05/8.46. This gearbox has been widely used in Europe, such as MAN, Iveco, Steyr, Volvo and so on. ZF developed ECOSPLIT-16S 16-speed compound mechanical transmission, four-speed main gearbox in front of the installation of a pair of half gear pair and other institutions, and then in the back-end series planetary gear drive auxiliary transmission. Biaxial stretching has been the main transmission gear pair of half-power input shaft hole, a shaft in the middle of the main transmission shaft to rotate freely. Maximum transmission input torque 1600Nm, gear ratios range from 1.00 to 13.63 or 0.85-11.46, or reverse gear ratio is 9.41/11.06 8.64/10.15, a length of about 950mm, total mass of about 300kg.
    Half speed compound transmission is widely used in foreign countries, especially in Europe, medium and heavy-duty vehicles in the extensive use of this transmission, including coach (including buses) applications have some more. Car engine power from 85 ~ 200kW various multi-purpose vehicles increased half-file auxiliary gear, because a half-speed compound transmission is shorter than the combined times of file transmission, and its simple structure, low cost, easy maintenance, by users. Foreign medium and heavy-duty vehicle engine power in 200kWl) l under the combination basically semi-file transmission, engine power at times to use more than 200kW file (or files plus a half times the file) modular transmission.
    4 Automatic Transmission Application and Development Trend
    automatic transmission vehicles to meet the frequent start, frequent acceleration requirements, and can accelerate to maximum speed continuously improve vehicle starting acceleration performance, thereby increasing especially in urban passenger vehicle the overall speed. And because the effect of the torque converter, the automatic transmission of the vehicle to increase torque infancy, is conducive to the full use of engine power.
    Foreign city bus has generally equipped with automatic transmission, the penetration rate in the U.S. is essentially 100%, Western Europe 95%, and our only Shenzhen, Shanghai and a few cities in use. Behalf of the international advanced level of technology as ZF, Voith, Allison3 kind of automatic transmission. Learn from foreign experience in developed and advanced transmission technology, you can play a multiplier effect. The following describes two kinds of transmission structure principle and technical characteristics.
    4.1 Automatic Transmission (referred AT)
    compared with a manual transmission, automatic transmission fluid in the structure and use of the manual transmission are very different. Manual transmission mainly composed of gears and shafts through different gear combinations produce variable speed torque; while AT is determined by the torque converter, a planetary gear and hydraulic control system components through a combination of hydraulic transmission and gear means to achieve variable speed moments. Wherein the torque converter is the most characteristic parts of AT. The torque converter pump wheel and turbine is like the relative placement of two fans, a fan blowing wind will drive the other fan blade rotation, the kinetic energy of wind into transmission medium. A liquid instead of air as the energy transfer medium, a liquid pump driven by the turbine wheel will rotate, and then between the pump wheel and turbine wheel with guide through the reaction between the pump wheel and the turbine rotational speed difference is real
    you can achieve a variable speed torque. Since the torque variable speed automatic torque range is not large enough, so the turbine back again several Rank planetary gear series to improve efficiency, the hydraulic control system will change with engine operating planetary gears themselves, in order to achieve variable speed automatic torque.
    Voith automatic transmission designed for city buses, is fully automatic hydraulic mechanical transmission, the torque converter for acceleration and deceleration. Since input power is a differential gear unit into two, its efficiency is higher than normal hydraulic drive transmission.
    Hydraulic automatic transmission The main advantages are as follows:
    (1) in the mechanical transmission, the planetary gear mechanism than conventional gear drive mechanism with a compact, quality, small size, large transmission ratio and high efficiency.
    (2) AT shift without the clutch, gear few changes, connecting smooth, so easy to operate, not only bring convenience to the driver, but also bring comfort to the passengers. Disadvantage is a complex mechanism, manufacture and repair are more difficult. Currently used in the car, not to be optimistic about the future more and more.
    4.2 electro-mechanical automatic transmission (referred AMT)
    electro-mechanical automatic transmission, Captive in the traditional dry clutch transmission and, based on the application of electronic technology, fuzzy control theory and variable theory, the core of the electronic control unit ECU, via the hydraulic control system in conjunction with the separation of the clutch, and a selector, a shift operation, by adjusting the engine throttle, by the electronic control unit ECU to achieve the car started, the shift of the automatic operation.
    AMT control of the basic principle: based on intention of the driver (accelerator pedal, brake pedal, etc.) and the status of the vehicle (engine speed, output shaft speed, vehicle speed, gear, etc.), based on certain rules (shift schedule , clutch engagement rules, etc.), by means of the appropriate actuator (oil executive body, the election shift actuator, and the engaging clutch actuator), the vehicle powertrain (engine, clutch, transmission) to conduct joint manipulation, implementation started shifting automatic manipulation.
    Electronically controlled automatic transmission machinery main features are as follows:
    (1) convenient and flexible, able to reduce pilot labor intensity and improve traffic safety. This is from the manual gear after the automatic transmission into one of the most important features.
    (2) fuel economy, extend the life of the vehicle. Compared with AT, AMT mechanical transmission efficiency is almost the same, so it than the current car automatic transmissions used on other more economical energy, improve environmental pollution levels.
    (3) simple structure, easy to install, easy maintenance. Its main drawback with two points, one car is not CVT, there is a class in the presence of shifting power interruption; two is in the loading and debugging have a professional staff debugging.
    4.3 development trend of automatic transmission automatic transmission
    main hydraulic automatic transmission (AT), electronically controlled automatic mechanical transmission (AMT), stepless automatic transmission (CVT). Its key technology is electronics, electro-hydraulic control and sensor technology. China is currently difficult to meet the basic industries AT-tech, high investment requirements, coupled with these products matching engine displacement differences, production AT difficult series. For CVT, must develop its key components - the torque converter, it is excellent, but also with AMT form a new hydraulic mechanical transmission, automatic transmission is the "soul." China's current situation should be the main direction of the AMT, it cost-effective, the price of AT 1/4 to 1/3, died after which it still competitive; produce good inheritance, transforming less capital investment; production volume flexibility, small volume, small benefit, high-volume, high benefit; relative to the various models, the hardware development and software development in the structure, in theory, is the same, the results can be generalized to all types of vehicles.
    5 Conclusion
    With the development of the domestic car market growth, the transmission spectrum gradually refined products, products targeted getting stronger, and therefore ensure that the existing transmission manufacturing and improved at the same time, to fully understand After joining the WTO to develop a good opportunity to learn from each other, but also should recognize suppliers, buyers, substitutes, products, competitors, the enormous pressure. To keep heavy commercial vehicle industry to high-end, high-tech and intelligent direction of the trend, to be followed by low-floor buses, green environmental protection, urban public transport development direction of large-scale development and production with independent intellectual property rights for China's national conditions of heavy vehicle transmission.

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