| 1 Purpose and significance(including analysis of research status at home and abroad) 1.1 Research Background For more than a century since the advent ofautomobiles, especially since the mass production of automobiles and thegreat development of the automobile industry, automobiles have entered themodern life for the development of the world economy and for mankind. He madeindelible contributions and set off an epoch-making revolution. As an important part of the automotive transmissionsystem, the transmission has a direct impact on the vehicle's power andeconomy, reliability and portability of handling, and smoothness andefficiency of the transmission. Although traditional manual transmissionshave many shortcomings, such as large gear shift impact, large volume, andtroublesome operation, they are still widely used in modern automobiles dueto their high transmission efficiency, mature manufacturing technology, andlow cost [1]. Automobile is an important means of transportation.Its design and manufacturing level is an important indicator of the level ofscientific and technological development in various countries. The automobileindustry is an industry that is capital-intensive, technology-intensive,talent-intensive, comprehensive, and highly economical. The industrializedcountries in the world have almost without exception made the automobileindustry a pillar industry of the national economy [2]. Thedevelopment, production, sales, and operation of automobiles are closelyrelated to many sectors of the national economy and play an important role inpromoting socio-economic construction and the development of science andtechnology. The automobile is also a sign of the development level of socialmaterial life. The number of cars held has increased with the increase innational per capita income. In many developed countries, the number of carsis huge and has spread to millions of households, which has led tosignificant changes in people's social lifestyles [3]. In 1886, the first car born in the world was notequipped with a transmission. It was not until 1902 that the first car with atransmission was manufactured by France. At present, most cars still usemechanical transmissions, transfer cases, and main reducers to form the drivetrain of the entire car. Its simple structure, convenient operation, and lowcost are still the main assembly commonly used in automotive drive trains [4].Because piston-type internal combustion engines are widely used inautomobiles, the range of torque and speed changes is small, and complex useconditions require that the traction and speed of the car can be changedwithin a relatively large range [5]. A transmission is provided inthe drive train for this purpose. Mechanical manual automobile transmissionsare widely used in different forms of automobiles due to their simplestructure, high transmission efficiency, low manufacturing cost, and reliableoperation. The mechanical manual transmission will still occupy a dominantposition in the transmission system of light and medium trucks in China for along time to come [6]. 1.2 Research purpose andsignificance The transmission is used to change the torque andspeed transmitted by the engine to the driving wheels. The purpose is to makethe car obtain different traction and speed under various conditions such asstarting, climbing, turning, and accelerating. Work within the workingconditions. The transmission is set to neutral, which can stop the transmissionof engine power to the drive wheels when the engine is started, the car iscoasting, or the vehicle is stopped. The transmission is equipped withreverse gears, which enables the car to get reverse driving ability. Whenrequired, the mechanical transmission also has a power output function.Therefore, the requirements for the transmission design are: (1) to ensurethat the car has the necessary power and economy. (2) Set neutral to cut offthe transmission of engine power to the drive wheels. (3) Set reverse gear sothat the car can drive backwards. (4) A power output device is provided,which can perform power output when needed. (5) Shifting quickly,labor-saving and convenient. (6) Reliable work. During the driving of thecar, the transmission must not have any phenomena such as jump gears,disorder gears, and shift shocks. (7) The transmission should have highworking efficiency. (8) The working noise of the transmission is low. Inaddition, the transmission should also meet the requirements of small profilesize and mass, low manufacturing cost, easy disassembly and assembly, andconvenient maintenance. Meet the necessary power and economic indicators ofthe car, which are related to the number of transmissions, the range oftransmission ratios, and the ratio of each transmission. The more complicatedthe working conditions of a car and the smaller the specific power, thelarger the transmission ratio range of the transmission. The research objectives of this subject are:designing a transmission that meets the requirements of Chevrolet Mai Ruibao;consolidating the theoretical knowledge learned, and cultivating our abilityto apply the professional theoretical knowledge learned; at the same time,deepening the understanding of the working principle and structure ofautomotive transmissions and Improved ability to apply drawing software. Soit is a good opportunity to combine theory and practiceThe researchsignificance of this subject is: in the research and design process, we havea deeper understanding of the structural characteristics and workingconditions of the transmission; provide a certain method for thedetermination of each part of the transmission parameters; improve theunderstanding of CAD; the design of virtual reality Explore ways to injectdifferent insights into existing transmission design methods and ideas;understand the advantages and processes of modern design methods; and providereference meanings for manufacturers. 1.3 Research Status atDomestic and Abroad From the perspective of the global passenger carmarket, passenger cars using hydraulic automatic transmissions occupy a highproportion. Almost all passenger models provide optional configurations ofautomatic transmissions and manual transmissions, but only on most high-endluxury models. Automatic Transmission. Passenger cars using automatictransmissions have become mainstream in some automotive developed countries.The market share of passenger cars using automatic transmissions in differentcountries and regions around the world varies widely. This has a lot to dowith the natural geographical conditions, road conditions, trafficregulations, per capita income levels, and user purchasing psychology ofvarious countries [7]. In recent years, automatic transmission ATis in the North American market, AT and CVT continuously variabletransmissions are in the Japanese market, and manual transmissions havedominated the European market respectively. A few years ago, the dual clutchtransmission DCT began to appear, which will change the existing marketstructure to a certain extent. In the next few years, the global passengercar transmission market will compete fiercely between AT and CVT Hunan DCT [8]. At present, there are ten automatic vehiclemanufacturers in the world. Generally, there are ten vehicle manufacturersthat select relevant products from the ten automatic transmissionmanufacturers that are designed for their vehicles. The transmissions on themarket are currently divided into five categories: manual transmission (MT),manual automatic transmission (AMT), continuously variable transmission(CVT), dual clutch transmission (DCT) and automatic transmission (AT) eachwith different advantages. Domestic and foreign automobile manufacturing andsales data show that people are paying more and more attention to the comfortof driving. It can be foreseen that cars with automatic transmissions will bethe leading products in the future market. The development and mastery ofautomatic transmission manufacturing technology is the direction to catch upwith the world's transmission manufacturing trend [9]. From the research and production point of view,nearly 2,000 CA770 hydraulic automatic transmissions have been produced. Inaddition, construction machinery and military vehicles have usedpower-shifting planetary gear transmissions for more than 10 years. Theelectronically controlled automatic transmission has been successfullydeveloped, so it can be said that there is a fixed foundation in the research,production and repair of hydraulic automatic transmissions. But all thehydraulic automatic transmissions used in domestic cars are imported.However, GM ’s joint venture in Shanghai has begun trial production of the4T65E four-speed electronically-controlled automatic transaxle. Of course,there is still a long way to go for full domestication [10]. The performance and quality of China's auto andvarious vehicle parts and components have certain gaps with developedcountries. One of the important reasons is that the design methods arebackward, and developed countries are in the design of mechanical products.They use computer-aided design technology to apply modern design methods,such as finite element analysis, optimization design, and reliability design,to product design. They use mechanical CAD systems to perform modeling,analysis, simulation, and interference inspection on the computer to achievethree-dimensional Design greatly improves the success rate of product design,reduces test costs, and shortens product update cycles. However, our designmethod is still in the 2D design stage based on empirical design. After thedesign is completed, it is often necessary to make large changes inproduction, which makes the product development cycle very long and theperformance and quality low. In order to change the backward state ofproduction and design methods of vehicle parts in China, shorten thedevelopment cycle of new products, and improve market competitiveness, it isnecessary to develop some CAD systems for automobiles and parts that aresuitable for China's national conditions. The CAD system needs to be furtherimproved and improved [11]. With the development and application of CADtechnology, many countries and departments have carried out a lot of researchand experiments on it, and subsequently developed and formed some completehardware and software systems. In the United States, Japan and Europeandeveloped countries, CAD technology is used to solve many tedious design andanalysis calculations. An integrated system based on a graphics system, adatabase as a core, a tool system as a support, and analysis and calculationas an application has been formed. The CAD technology in the United States has been ina leading position, and its main goal is to establish a complete CAD / CAMintegrated system. The American automotive industry first applied CADsystems. General Motors Corporation, Ford Motor Company, etc. have widelyused CAD technology. They apply calculations such as structure, strength,stiffness, and three-dimensional solid modeling to the design and developmentof automobiles. They integrate CAD, CAPR, CAM, and CAE to improve productionefficiency, ensure product quality, and increase market response speed,thereby greatly improving Not only their competitiveness, but also broughtthem huge economic benefits. The CAD software they applied mainly includesPR0 / E, UG, CATIA, IGES, etc. These foreign automobile companies already have CADprograms, but the standards and technical specifications and tests involvingeach company are very confidential. Compared with foreign countries, China'sautomotive industry started late in CAD and developed more slowly. Atpresent, some universities and large and medium-sized enterprises have begunto carry out CAD research, and have achieved some results in terms of productimprovement design, computer drawing after design and finite elementanalysis. But in general, most domestic factories rely on the traditionaldesign method-the empirical analogy. The introduction of products is mainlybased on surveying and mapping, which is difficult to meet the objectiverequirements of the modern automotive industry. Adopting modern designmethods is an extremely important means to improve self-design, digestion andlocalization. |
