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履带拖拉机变速器的改进设计【优秀含2张CAD图纸+Word全套机械毕业设计】

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履带拖拉机变速器的改进设计

摘要

本篇文章详细介绍了本次的设计内容和设计思想，这次设计主要是在东方红拖拉机原型1302R变速器的基础上进行的分析改进，重点介绍了原型的设计不足和存在的问题，在分析履带拖拉机的工作环境和农业作业要求的基础上重新布置了传动比的分配，操纵机构的优化，啮合方式的改进，比如增加了传动比的范围，增加了低速作业挡，有利于拖拉机在复杂的环境工作，换挡方式由原来的直接拨动齿轮换挡变为啮合套换挡，使换挡更加方便、可靠，防止打齿。为了改善拖拉机的原地起步性能，该为双作用离合器的结构形式，使动力输出和传递轴在不同的时刻进行结合，这种按先、后依次结合的特点在农业生产中是很必要的。

对于结构设计采用结构紧凑的三轴式，在满足强度的基础上使结构紧凑，节省材料，对于齿轮的布置，尽量节省空间，布置合理。外形轮廓采用大量圆形弧线过渡，使铸造性能提高，结构合理，外形美观。在农业机械化的今天这种多挡位，随着农业的发展振兴，大功率的拖拉机还具有广阔的市场前景。

关键词：啮合套, 双作用离合器，拖拉机，变速器

IMPROVED DESIGN OF THE TRACKED

TRACTOR TRANSMISSION

ABSTRACT

This article describes in detail the design of this content and design ideas. The design is mainly in the DFH 1302R prototype on the basis of the analysis improvements, focus on the prototype design deficiencies and the problems. Analysis of crawler tractor in the work environment and agriculture operations on the basis of a re-arrangement of the distribution of transmission ratio, manipulation of the optimization, and improving the mode of engagement are done, such as increasing the scope of the transmission ratio, increasing a low-speed operation block, and the favorable environment for the complex, shifting the original style of direct pull shift into gear meshing sets shift, shifting more convenient and reliable. In order to prevent tooth playing with greater impact and improve the tractor started in suit performance of the dual role of the structure of the clutch, the output power and transmission shaft in different light moment, and combining the features were in agricultural production is very necessary.

For structural design using compact three-axis, it can meet the compact structure, material savings. For gear settings, as far as possible to save space, a reasonable layout is done. Using contour shape of a large number of circular arc transitions so that the casting performance enhancement, reasonable structure, pleasing in appearance. Agricultural mechanization in the number of such gear today, with the development and revitalization of agriculture, high-power tractor, they have broad market prospects.

Key words : meshing sets, double-clutch, tractor，transmission

第一章前言……………………………………………………1

第二章履带拖拉机变速箱的改进方案的探讨与确定……2

§2.1 变速箱存在的问题………………………………………2

§2.2 变速器的功用………………………………………………2

§2.3 变速器的类型……………………………………………3

§2.4 变速器传动方案的确定…………………………………4

第三章变速器的结构参数的设计及选择…………………………6

§3.1确定变速器的外形尺寸………………………………………6

§3.1.1变速箱齿轮中心距…………………………………………6

§3.1.2 变速箱的轴参数确定…………………………………6

§3.2 传动比的确定…………………………………………………7

§3.2.1 最高档传动比的选择………………………………………7

§3.2.2最低档传动比的确定………………………………………8

§3.3 变速箱齿轮设计计算…………………………………………9

§3.3.1齿轮的设计准则……………………………………………9

§3.3.2变速箱各档齿轮基本参数的选择…………………………10

§3.3.3 齿轮参数的计算………………………………………12

第四章变速器齿轮的校核…………………………………………15

§4.1齿轮的损坏形式……………………………………………15

§4.2 轮齿弯曲强度计算……………………………………………15

§4 .3 齿轮接触应力计算……………………………………………17

第五章变速器轴的强度校核…………………………………………19

§5.1轴的刚度校核……………………………………………19

§5.2 轴的刚度校核……………………………………………20

第六章变速器轴承的校核 ……………………………………………22

第七章变速器操纵机构的设计说明…………………………………23

§7.1 功用和要求…………………………………………………23

§7.2 换档机构…………………………………………………23

§7.3 锁定机构………………………………………………24

第八章结论………………………………………………………27

参考文献…………………………………………………………28

致谢………………………………………………………………29

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内容简介：: CHAPTER 1 AUTOMOTIVE BASICS Principal Components Todays average car contains more than 15,000 separate, individual parts that must work together. These parts can grouped into four major categories: engine, body, chassis and electrical equipment. Engine The engine acts as the power unit. The internal combustion engine is most common: this obtains its power by burning a liquid fuel inside the engine cylinder. There are two types of engine :gasoline(also called a spark-ignition engine) and diesel(also called a compression-ignition engine).Both engines are called heat engines; the burning fuel generates heat which causes the gas inside the cylinder to increase its pressure and supply ntspower to rotate a shaft connected to the transmission. Body An automobile body is a sheet metal shell with windows, doors, a hood, and a trunk deck built into it. It provides a protective covering for the engine, passengers, and cargo. The body is designed to keep passengers safe and comfortable. The body styling provides an attractive, colorful, modern appearance for the vehicle. Chassis The chassis is an assembly of those systems that are the major operating part of a vehicle. The chassis includes the transmission, suspension, steering, and brake systems. Transmission systems conveys the drive to the wheels. The main components are clutch, gearbox, driveshaft, final drive, and differential. Suspension absorbs the road shocks. Steering controls the direction of the movement. Brake slows down the vehicle. Electrical Equipment The electrical system supplies electricity for the ignition, horn, lights, heater, and starter. The electricity level is maintained by a charging circuit. This circuit consists of the battery, alternator (or generator). The battery stores electricity. The alternator changes the engines mechanical energy into electrical energy and recharges the batte Engine and power Engine is used to produce power. The chemical energy in fuel is converted to heat by the burning of the fuel at a controlled rate. This process is called combustion. If engine combustion occurs with the power chamber. ,the engine is called internal combustion engine. If combustion takes place outside the cylinder, the engine is called an external combustion engine. Engine used in automobiles are internal combustion heat engines. Heat energy released in the combustion chamber raises the temperature of the combustion gases with the chamber. The increase in gas temperature causes the pressure of the gases to increase. The pressure developed within the combustion chamber is applied to the head of a piston to produce a usable mechanical force, which is then converted into useful mechanical power. Engine Terms Linking the piston by a connecting rod to a crankshaft causes the gas to rotate the shaft through half a turn. The power stroke “uses up” the gas , so means must be provided to expel the burnt gas and recharge the cylinder with a fresh petrol-air mixture :this control of gas movement is the duty of the valves ;an inlet valve allows the new mixture to enter at the right time and an exhaust valve lets out the burnt gas after the gas has done its job. Engine terms are : TDC(Top Dead Center):the position of the crank and piston when the piston is farther away from the crankshaft. BDC(Bottom Dead Center):the position of the crank and piston when the piston is nearest to the crankshaft. Stroke : the distance between BDC and TDC; stroke is controlled by the crankshaft. Bore : the internal diameter of the cylinder. Swept volume : the volume between TDC and BDC. Engine capacity : this is the swept volume of all the cylinder e.g. a four-stroke having a capacity of two liters(2000cm) has a cylinder swept volume of 50cm. nts Clearance volume: the volume of the space above the piston when it is at TDC. Compression ratio = (swept vol + clearance vol)(clearance vol) Two-stroke : a power stroke every revolution of the crank. Four-stroke : a power stroke every other revolution of the crank. The Four-stroke Spark-ignition Engine Cycle The spark-ignition engine is an internal-combustion engine with externally supplied in ignition , which converts the energy contained in the fuel to kinetic energy. The cycle of operations is spread over four piston strokes. To complete the full cycle it takes two revolutions of the crankshaft. The operating strokes are : This stroke introduces a mixture of atomized gasoline and air into the cylinder. The stroke starts when the piston moves downward from a position near the top of the cylinder. As the piston moves downward, a vacuum, or low-pressure area, is created. During the intake stroke, one of the ports is opened by moving the inlet valve. The exhaust valve remains tightly closed. Compression stroke As the piston moves upward to compress the fuel mixture trapped in the cylinder, the valves are closed tightly. This compression action heats the air/fuel mixture slightly and confines it ntswithin a small area called the combustion chamber. Power stroke Just before the piston reaches the top of its compression stroke, an electrical spark is introduced from a spark plug screwed into the cylinder head. The spark ignites the compressed, heated mixture of fuel and air in the combustion chamber to cause rapid burning. The burning fuel produces intense heat that causes rapid expansion of the gases compressed within the cylinder. This pressure forces the piston downward. The downward stroke turns the crankshaft with great force. Exhaust stroke Just before the bottom of the power stroke, the exhaust valve opens. This allows the piston, as it moves upward, to push the hot, burned gases out through the open exhaust valve. Then, just before the piston reaches its highest point, the exhaust valve closes and the inlet valve opens. As the piston reaches the highest point in the cylinder, known as TDC, it starts back down again. Thus, one cycle ends and another begins immediately. Engine Overall Mechanics The engine has hundreds of other parts . The major parts of engine are engine block , engine heads, pistons, connecting rods, crankshaft and valves. The other parts are joined to make systems. These systems are the fuel system, intake system, ignition system, cooling system, lubrication system and exhaust system. Each of these systems has a definite function. These systems will discussed in detail later. Engine Block The engine block is the basic frame of the engine. All other engine parts either fit inside it or fasten to it. It holds the cylinders, water jackets, and oil galleries. The engine block also holds the crankshaft, which fastens to the bottom of the block. The camshaft also fits inside the block, except on overhead-cam engines (OHC). In most cars, this block is made of gray iron, or an alloy (mixture) of gray iron and other metals, such as nickel or chromium. Engine blocks are castings. Some engine blocks, especially those in smaller cars, are made of cast aluminum. This metal is much lighter than iron. However, iron wears better than aluminum. Therefore, the cylinders in most aluminum engines are lined with iron or steel sleeves. These sleeves are called cylinder sleeves. Some engine blocks are made entirely of aluminum. nts Cylinder Head The cylinder head fastens to the top of the block, just as a roof fits over a house. The underside forms the combustion chamber with the top of the piston. The most common cylinder head types are the hemi, wedge, and semi-hemi. All three of these terms refer to the shape of the engines combustion chamber. The cylinder head carries the valves, valve springs and the rockers on the rocker shaft, this part of the valve gear being worked by the push-rods. Sometimes the camshaft is fitted directly into the cylinder head and operates on the valves without rockers. This is called an overhead camshaft arrangement. Like the cylinder block, the head is made from either cast iron or aluminum alloy. Gasket The cylinder head is attached to the block with high-tensile steel studs. The joint between the block and the head must be gas-tight so that none of the burning mixture can escape. This is achieved by using cylinder head gasket. This is a sandwich gasket, i.e. a sheet of asbestos between two sheets of copper, both these materials being able to withstand the high temperature and pressures within the engine. Oil Pan or Sump The oil pan is usually formed of pressed steel. The oil pan and the lower part of the cylinder block together are called the crankcase; they enclose, or encase, the crankshaft. The oil pump in the lubricating system draws oil from the oil pan and sends it to all working parts in the engine. The oil drains off and runs down into the pan. Thus, there is constant circulation of oil between the pan and the working parts of the engine. nts Piston Connecting Rod and Crankshaft Piston Assembly The piston is an important part of a four-stroke cycle engine. Most pistons are made from cast aluminum. The piston , through the connecting rod, transfers to the crankshaft the force create by the burning fuel mixture. This force turns the crankshaft .Thin, circular , steel bands fit into grooves around the piston to seal the bottom of the combustion chamber. These bands are called piston rings. The grooves into which they fit are called ring grooves. A piston pin fits into a round hole in the piston . The piston pin joins the piston to the connecting rod . The thick part of the piston that holds the piston is the pin boss. The piston itself , its rings and the piston pin are together called the piston assembly. Piston To withstand the heat of the combustion chamber, the piston must be strong. It also must be light, since it travels at high speeds as it moves up and down inside the cylinder. The piston is hollow. It is thick at the top where it take the brunt of the heat and the expansion force. It is thin at the bottom, where there is less heat. The top part of the piston is the head , or crown . The thin part is the skirt The sections between the ring grooves are called ring lands. The piston crown may be flat , concave ,dome or recessed

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