XZ25-50变速箱加工工艺及镗床夹具设计-组合机床含9张CAD图
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XZ25-50变速箱加工工艺及镗床夹具设计-组合机床含9张CAD图,文本
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附录附录1Sand CastingThe first stage in the production of sand castings must be the design and manufacture of a suitable pattern. Casting patterns are generally made from hard word and the pattern has to be made larger than the finished casting size to allow for the shrinkage that takes place during solidification and cooling. The extent of this shrinkage varies with the type of metal or alloy to be cast. For all but the simplest shapes the pattern will be made in two or more pieces to facilitate moulding. If a hollow casting is to be made the pattern design will include extension pieces so that spaces to accept the sand core are moulded into sand. These additional spaces in the mould are termed core prints. Sand moulds for the production of small and medium-sized castings are made in a moulding box. The mould is made in two or more parts in order that the pattern may be removed. The drag half of the mould box is placed on a flat firm board and the drag half of the pattern placed in position. Facing sand is sprinkled over the pattern and then the mould box is filled with moulding sand. The sand is rammed firmly around the pattern. This process of filling and ramming may be done by hand but mould production is automated in a large foundry with the mould boxes moving along a conveyor, firstly to be filled with sand from hoppers and then to pass under mechanical hammers for ramming. When ramming of the sand is complete, excess sand is removed to leave a smooth surface flush with the edges of the moulding box. The completed drag is now turned over and the upper, or cope, portion of the moulding box positioned over it. The cope half of the pattern is placed in position, correct alignment being ensured by means of small dowel pins. Patterns for the necessary feeder, runner and risers are also placed so as to give an even distribution of metal into the mould cavity. The risers should coincide with the highest readily escape from the mould. The sizes of risers should be such that the metal in them does not freeze too rapidly. An important function of a riser is to act as reservoir of liquid metal to feed solidification within the mould. A thin coating of dry parting sand is sprinkled into mould at this stage. This is to prevent the cope and drag sticking together when the cope half is moulded. The cope is now filled with moulding sand and this is rammed firmly into shape in the same manner as in the making of the drag. After the ramming of sand in the cope is completed the two halves of the moulding box are carefully separated. At this stage venting of the moulding box are carefully separated. At this stage venting of the mould can be done, if necessary, to increase the permeability of the mould. After venting the patterns are carefully removed from both cope and drag, and a gate or gates are carefully cut to connect the runner channel with the main cavity. Gates should be sited to allow for entry into mould with a minimum of turbulence. Any loose sand is gently blown away and if a core is to be used it the cope upon the drag and it is then ready for use. Liquid metal is poured smoothly into the mould via the feeder. Pouring ceases when liquid metal appears at the top of the risers and the feeder channel is also full. When the metal that has been poured into a sand mould has fully solidified the mould is broken and casting is removed. The casting still has the runner and risers attached to it and there will be sand adhering to portions of the surface. Runners and risers are cut off and returned to the melting furnace. Sand cores are broken and adherent sand is cleaned from the surface by vibration or by sand blasting with dry sand. Any fins or metal flash formed at mould parting lines are removed by grinding and the castings are then ready for inspection.EngineAn engine is a device that uses the energy in a fuel to do work. The energy in the chemicals of the fuel is turned into heat energy. The heat is then used to move the metal parts of a machine. There are many kinds of fuel. Most engines use gasoline, oil, kerosene, coal, or coke. The heat that comes from burning the fuel makes a gas expand. This expand gas drives pistons or turbine blades. The pistons or turbines turn shafts. The turning shafts move gears and other wheels. We use these rotating wheels and shafts to move automobiles, airplanes, and other transport. We can also use them for pumping, drilling, digging, and other such activities.Early engines burned coal or wood to heat water. The steam was used to drive steam engine. Until the middle of this century, most locomotives were powered by steam. At the beginning of the century, even some automobiles were run on steam. We still use steam engines, but most of them are being replaced by more efficient engines. Today we have powerful gasoline and diesel engines to work for us. The steam engine is an external combustion engine. This means that fuel is combustion, or burned, outside the cylinder that produces power. Since the invention of the steam engine by James Watt in 1769s, steam engines had a great effect on the industrial revolution in the eighteenth century. Until the middle of the twentieth century, most locomotives were powered by steam. At the end of the century, even some automobiles were run on steam. Today most of the functions of steam engine have been taken over by internal combustion engines fueled by gasoline and diesel oil. However, there are many steam engines in use at sea. Steam is also used to generate electricity. The kind of steam engine that is used today does not have cylinders. It is generally a steam turbine. The steam turbine was invented by Sir Charles Parsons. Steam turbines can handle steam at higher pressures than piston engines can, and they are more compact than piston engines of similar power.The gasoline engine The engine of most automobiles and small vehicle use gasoline as fuel. The gasoline engine is a combustion engine. The fuel is burned in combustion (burning) chambers inside the engine. The combustion chambers are placed at one end of the cylinders. Pistons move up and down in the cylinders. They are pushed by the hot gases from the burning fuel. When the fuel is mixed with air it burns so quickly that it explodes. The combustion chambers and cylinder apart like a bomb, the explosion simply kicks hand against the head of the piston. It pushes it as far as it can.Each movement of a piston up or down in its cylinder is called a stroke. Most gasoline engines work on a four-stroke cycle. This means that each piston goes up and down twice for each explosion. That makes four movement or strokes. This cycle of events is repeated over and over again. On the first down stroke, the piston moves to the lowest part of the cylinder. A mixture of gasoline droplets and air is drawn into the cylinder above it. Now the piston moves up again. This is its second stroke. It squeezes the mixture into a small space. An electric lights the mixture, and it explodes. The piston is force down again for its third stroke. This is called the power stroke. For the fourth stroke, the piston moves to the top again. This time it pushes the burnt gases out of the cylinder. The gases leave the engine as exhaust fumes.The first engine that used the four-stroke cycle was made in about 1876. It was designed by a German engineer, August Otto. He used coal gas, not gasoline. The first engines to burn gasoline were developed by Karl Benz and Gottlieb. These two men were famous as automobile pioneers.A piston simply going up and down cannot push an automobile along. Its movement must be changed to a turning movement. To do this, a crankshaft is used. Each piston of the engine is linked to part of the crankshaft. Each push it gives makes the shaft turn. The spinning shaft passes the power on to the automobiles transmission system. It usually does this through a heavy flywheel. The transmission system transmits power to the clutch and to the propeller shaft, through a gearbox. The propeller shaft drives the road wheels by means of axles.To keep an automobile engine going, there need to be several systems. There must be a fuel system. This has to supply gasoline to the engine cylinders in the right amounts. It has also to mix it with the right amount of air, so that it will explode properly. There must be an ignition system. This has to provide sparks to ignite the explosive mixture fat exactly the right time. There has to be a cooling system, otherwise the engine would overheat. The lubrication system must keep all the moving parts oiled and moving freely. Too much friction causes wear of the metal and makes the engine overheat. The engine unit Gasoline engine has two basic parts. They are called the cylinder head and the cylinder block. The cylinder block is machined from solid metal. The metals usually cast side the cylinder blocks are the cylinders. The walls of the cylinders have to be very accurately made, and are highly polished. The pistons that move up and down in the cylinders must be accurately made, too. They have springy bands of metal around them to press tight against the cylinder walls and stop gases leaking. The bands are called piston rings. They are often made of aluminum alloy for strength and lightness.An engine may have any number of cylinders. They may be arranged in a line, or in opposite pairs. They are often arranged in a “V” shape. In many airplanes with piton engines, the cylinders are arranged in a ring around the crankshaft.The lower part of the cylinder block is called the crankcase. This is where the crankshaft lies. The crank shaft is linked to each piton by a connecting rod. The crankshaft is made in a single piece. It must be tough and accurately machined. It may spin as many as 6000 times a minute. It changes up-and-down motion. It does this by means of cranks, one for each piston. The cranks are set at different angles round the shaft. Each piston gives a push to its crank during its power stroke. During the other three strokes, the crank pushes the piston up ,down and up again. The heavy flywheel is bolted to one end of the crankshaft. It keeps the shaft turning smoothly between the power strokes. Strong main bearings support the crankshaft in its case.The cylinder head is bolted to the cylinder block. Inside it are the combustion chambers. Each combustion chamber is a space above a piston inside a cylinder. This is where the explosion of the mixture of fuel and air takes place. A spark plug is set into the top of the chamber. Each chamber has a pair of valves. There is an inlet valve to allow the fuel and air mixture into the chamber. The other valve is an outlet or exhaust valve. Through this pass the burnt gases after the explosion. The valves are opened and closed by push rods and springs. The push rods are moved up and down by links with the crankshaft. The linkage is through a turning shaft called the camshaft.To carry water to cool the engine, there are passages in the metal of the cylinder head and cylinder block. Oil passes through other passages. Between the cylinder head and block is a gasket. This is a thin plate of metal that acts as a seal. It is put in when the parts of the engine are bolted together. It is often made of copper. The fuel system Fuel system of the engine supplies the gasoline to be burnt. The gasoline is stored in a large tank. In a powerful car, the tank holds many gallons of fuel. The tank is placed well away from the engine, to reduce the risk of fire .The gasoline is pumped through a fuel line. The pump may be driven by links with the engine camshaft. Sometimes it has its own electric motor. Before the gasoline reaches the cylinders, it must be mixed with air. The fuel line leads to the carburetor. In the carburetor the gasoline is forced through a fine nozzle, or jet. It forms a spray of small droplets. The droplets vaporize as they mix with the air. Now the mixture is ready for ignition. The speed of the engine is controlled by a valve. Opening and closing the throttle valve regulates the amount of mixture leaving the carburetor. From the carburetor the mixture passes to the inlet valves of the combustion chambers. The mixture is delivered through a set of tubes called the inlet manifold. A similar set of tubes takes away exhaust gases form the exhaust valves of the combustion chambers. This is called the exhaust manifold. It leads to the outside air through the exhaust pipe. In some automobiles, the fuel is delivered by a different system. Instead of passing through a carburetor, the fuel is sprayed into the air stream just before the inlet valves. It is sprayed in small amounts, which are carefully metered. The system is called fuel injection. The ignition system Mixture inside each cylinder must be made to explode. A spark is used to do this. The spark must jump across the gap in the spark plug at exactly the right times, each of the autombiles cylinders must fire in turn. The ignition system depends upon very accurate timing. If the sparks are a fraction of a second too early or too late, the engine will not run properly. The electricity to make the sparks comes from the automobiles electric storage battery. This battery is kept charged by a dynamo, or generator, run by the engine. The battery supplies electricity at only about 12 volts. To make a spark, volts are required. The voltage from the battery is boosted up to about 30 000 volts by means of a transformer. The transformer is called the ignition coil. The ignition coil supplies high voltage to the distributor. This is a device that distributes in surges, or pulses, to each of the spark plugs in turn. When a surge of electricity at high voltage reaches a plug, a spark leaps across a small gap. The spark is so hot that it makes the mixture of gasoline and air ignite and explode. The cooling system Heat produced by burning the gasoline in the engine is very great. The temperature inside each combustion chamber may reach more than 1 000 over1 800.The engine must be constantly cooled. The cooling system supplies cool water through channels called water jack. The water jackets surround the cylinders. They carry away the excess heat as the water passes through them. The hot water is led away to be cooled in radiator. The radiator is a system of many tubes, linked together, with spaces between them. The hot water loses its heat to the air. The cooled water is then pumped to the engine again. Some automobiles do not have a water-cooled system. They use air cooling. Air from the front Of the automobile is blown over the cylinder block and the cylinder head. The engine is filled with special cooling fins, sticking out into the air stream. These help the head to radiate more quickly. Air-cooled engines tend to be noisier than water-cooled engines. In a water-cooled engine, the water jacket helps to absorb the engine noise. To prevent the water in the cooling system from freezing in cool weather, antifreeze is usually added in water. This is often ethylene glycol or a similar compound.The lubrication system Oil is needed to keep the engines parts from wearing too quickly. A storage tank of oil, called the sump, is attached under the crankcase. The oil is pumped through channels to all the main bearings and the big-end bearings. Eventually it reaches the sump again. It passes through a filter to remove dirt before it is used again. Whenever metal surfaces rub against others, ting particles are worn off. The oil picks them up as it flows between the surfaces .They are trapped by the oil filter. The filter must be changed regularly. The oil itself gradually burns and becomes impure. It must be replaced at intervals.The wankel engine The wankel engine is a gasoline engine that works without pistons. It was invented in Germany by Felix Wankel. He started development of it in 1956. The pistons in an ordinary gasoline engine must move up and down, or backwards and forwards. This kind of motion is called reciprocating motion. It needs to be converted into a turning motion (rotary motion) by a crankshaft. In a Wankel engine, burning the flue produces a rotary motion directly. These is no need for a crank shaft, It is a rotary engine.A Wankel engine has a specially designed combustion chamber. It is roughly an ellipse, , I n shape. Inside is rotor. The rotor is shaped with bulging, rounded sides. Though the center of the rotor passes the driving shaft, it has teeth like a gearwheel that meet teeth inside the rotor. The rotor is shaped so that its corners just touch the walls of the chamber. The rotor can move up and down and also side to side as it turns.The rotor divides the chamber into three parts. As the rotor the shapes of the three parts change. They act like three separate combustion chambers. As in an ordinary engine, there are spark plugs, an inlet port for the gasoline and air mixture, and an outlet port for the exhaust gases.The rotor turns so that each part of chamber in turn meets the inlet. The gasoline and air mixture is drawn in. This is like the first piston down stroke of an ordinary engine. Further turning sweeps the mixture round into a smaller space .The mixture is compressed. This is like the second stroke. Now the spark plugs fires. The explosion drives the rotor further around. This is the power stroke. When the rotor has turned a little further, the exhaust gases are pushed from the chamber through the exhaust port. The process is continuous. It happens as each part of the chamber sweeps round.The Wankel engine has several advantages over an ordinary engine. It has fewer moving parts. There is less vibration. It is lighter, it costs less to produce. However, there are difficulties. The main difficulty is ensuring that the seals, where the corners of the rotor meet the chamber walls, are gastight. The Wankel engine is used successfully in several kinds of automobile. The diesel engine The diesel engine is a type of internal combustion engine that is used for heavy-duty work. It uses low-cost oil for fuel, and usually has a long life. Railroad locomotives, trail trucks, buss, tractors, and road building equipment are powered by diesel engine .Ships and electric power generating stations also use diesel engine. Small models are used to power some automobiles. The diesel engine was developed in 1897 by Rudolf Diesel.The diesel engine differs from the gasoline engine in two main ways. The diesel is a compression-ignition engine, whereas the gasoline engine is a spark-ignition engine. In a diesel engine, air is compressed in each cylinder, causing its temperatures to rise. Fuel is then injected into the cylinders. The heat of the air causes the mixture to ignite and to explode. Gasoline engines use electric sparks to ignite the fuel and air mixture in the cylinders. Diesel engines use low grade oils that require less refining than gasoline and are less expensive.Pressure of over 10500 KN per square meter 1500 lbs per square in is built up in the cylinder of a diesel engine by compression and the subsequent explosion, or combustion. This pressure forces the piston downwards, which turns the crankshaft. Cylinder walls and most other parts of diesel engines are thicker and stronger than those parts in gasoline engines so they can stand the extra strains and stresses.There are two main types of diesel engines, the four-stroke engine and the two-stroke engine. In the four-stroke model, which is the larger and more powerful of the two, each moves down, up, down, and up to complete a cycle. The first down stroke draws air into the cylinder. The second down stroke is the power stroke .The second up stoke exhaust the gases produced by combustion.In a two-stroke diesel engine, the exhaust and intake of air occur though openings in the cylinder near the end of the power stroke. The one up stoke is the compression stroke. The down stoke is the power stroke. Two-stroke engines have twice as many power stroke recycle as four-stroke engines. Two-stroke engines are used for applications that require high power in a small engine.附录2砂型铸造砂型铸造生产的第一步是设计并制作一个合适的模型。铸造模型一般由硬木做成,考虑到在金属液凝固及随后的冷却过程中所产生的收缩,模型的尺寸必须大于最终铸件的尺寸。收缩的程度由铸造金属或合金种类的不同而不同。除一些形状极其简单的铸件外,几乎所有的铸件的模型都分成两部分或更多的部分,以便于造型。如果要生产一个空心铸件,那么在模型设计时应加上引伸头,这样在造型时便可留出安放砂芯用的位置,铸型中这些辅助用的空处被称作芯座。 生产中、小型铸件的砂型是在砂箱中做出来的。为了能在造型后取出模型,砂型由两个或更多个部分组成。 将下砂箱放在厚实的平板上,并将下半模型放在适当的位置上,在模型上撒上面纱,然后,往砂箱中填满型砂,并将型砂出社在模型周围。填满和出事可用手工进行,但是在大型铸造车间里,造型过程已自动化。砂箱由传送带输送,首先砂斗往砂箱中填沙,然后,砂箱机械锤下经过,以实现出砂。紧砂作业完成后,除去多余的型砂,使表面平整并与砂箱的周边平齐。 此时可将下箱,翻转过来,将上箱准确地放在下箱上。将上半模型放在准确的位置上。用小暗崤将上、下两半模型对准定位。直浇口、浇道和胃口所用的模型也放置在合适的位置上。直浇口、浇道应被合理的布置使金属流进型腔时能均衡分布。冒口应设在型腔的最高处,以便使浇铸过程中气体能顺畅地从铸型中排出。冒口的尺寸应大到以使冒口部位的金属不致过快的凝固。冒口的一个重要功能是充当液体金属蓄池,对铸型内的凝固起补缩的作用。此时,往铸型内撒上薄薄的一层干燥的分型砂,用来防止在上箱造型时,上、下两砂型粘连在一起。向上箱内填入型砂,并像制作箱一样,将上箱内的型砂出造型。 上箱紧砂后,小心地将两砂箱分开。此时,如有必要,可在铸型上扎通气孔增强铸型的透气性。扎好通气孔后,细心地将模型分别从上、下砂箱中取出并细心地切出一个或更多内浇口使浇道与主型腔接通。内浇口的开设应使液体金属流入型腔时产生的涡流最小。轻轻吹走散砂,如果使用型心的话,将型心安放好。将上箱放到下箱上面,重新装配好铸型以代用。液体金属径直浇口平稳地主入铸型中。当在冒口顶部看到的液体金属以及直浇口也注满十就停止浇铸。 待注入砂型内的金属完全凝固后,将砂型敲碎取出铸件,此时铸件上仍连带着浇道和冒口,铸件表面还黏着砂列。切割下浇道和冒口并将他们重新投入熔化炉中。打碎并去除砂芯,用震动或干砂喷砂法清理表面粘砂。分型面处的翅片和毛边用砂轮清理掉,此时铸件已完成并可对其进行检验了。发动机发动机是一个使用燃料作为能源的工作装置。燃料中化学成分的能源变成了热能源。 然后热能被用到使机器运动的金属部份。 燃料有好多种类型。大部分发动机使用汽油、石油、煤油,煤, 或焦炭。 来自燃料燃烧的热能使气体膨胀。这种膨胀驱动活塞或者涡轮蜗杆。 活塞或涡轮转轴。旋转轴驱动齿轮和其他齿轮。我们使用这些滚动轮和轴到驱动汽车,飞机, 和其他的运输系统。我们能也使用他们在抽泵 ,演练, 挖, 和其他的类似的活动。早期的发动机利用燃烧煤或木材来对水加热。那蒸汽被用到了驱动蒸汽发动机。直到本世纪中期, 大部分火车是用蒸汽来驱动的。在本世纪初, 一些汽车都是通过蒸汽来驱动的。我们仍然使用蒸汽发动机,但是大部份都被效率更高的发动机所代替。今天我们已经使用功能更强的汽油和柴油发动机。蒸汽发动机是一个外部的燃烧发动机。这也就是说燃料是燃烧 , 或燃烧, 外面产生能量的圆筒。自从1769年James Watt发明了蒸汽发动机,蒸汽发动机在18世纪对工业革命产生了深远的影响。直到20世纪中期,大部分火车都是靠蒸汽来提供能量直到世纪末,甚至一些汽车也是靠蒸汽来提供能量。现在,大部分蒸汽发动机的功能已经被以汽油和柴油为燃料的通用发动机所替代。不管怎么样,还有很多蒸汽发动机被使用在海上。蒸汽发动机同样也被用在电力方面。现今,这种蒸汽发动机被用在没有液压缸的情况下。它通常是一个蒸汽涡轮机。这种蒸汽涡轮机是由查尔斯教区牧师发明的。蒸汽涡轮机在高压下比活塞发动机能更好的控制蒸汽,并且,在长生同样能量的情况下蒸汽涡轮机比活 塞发动机结构更简单。汽油发动机 大部分汽车和小的车辆使用汽油做燃料。汽油发动机是一种内燃发动机。燃料是在发动机的内部燃烧室燃烧。燃烧室位于其中一个液压缸的端部。活塞在液压缸里面上下移动。他们是由燃料燃烧长生的热气来驱动。当燃料和空气混合以后燃烧的非常迅速继而发生膨胀。燃烧室和液压缸部分都像一个炸弹,膨胀就是由活塞头的不断来回运动。也是由活塞来获取尽可能大的驱动力。 活塞在液压缸里的每次上下运动称为一个行程。大部分汽油发动机都是以四个行程为一个工作周期。这也就是说每一次膨胀时活塞上下运动两次。也就是四个移动或行程。这种运动周期性的一次次重复。在第一个向下行程时,活塞移动到液压缸最低的那部分。油滴与空气又在液压缸内部开始混合。这时活塞又开始运动。这就是第二个行程。也就是把油滴和空气的混合物挤压在一个狭小的空间里。有一点火花,混合物就会爆炸。活塞再次强力下降做第三次周期性运动。这就叫着能量冲程。在第四个冲程,活塞再次运动到顶端。这一次活塞在液压缸内推动燃烧的汽油。气体以燃料蒸汽的形式从发动机里排出。第一个使用四个冲压行程的发动
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