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汽车起重机
总体
机构
设计
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汽车起重机总体及支腿机构设计,汽车起重机,总体,机构,设计
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河北建筑工程学院毕业设计（论文）外文资料翻译 系别： 机械工程系 专业： 机械设计制造及其自动化 班级： 机063 姓名： 江 超 学号： 2006307319 外文出处：English in Mechanical and ElectricalEngineering 附 件：1、外文原文；2、外文资料翻译译文。指导教师评语：签字： 年 月 日The Automobile ComponentsEngine The engine is a power plant, which provides power to drive the automobile. In most automobile engines, the explosive power of the mixture of air and gasoline drives the pistons. The pistons turn a crankshaft to which they are attached. The rotating force of the crankshaft makes the automobiles wheels turn. Some automobiles are powered by another kind of engine, known as the rotary valve, rotating combustion engine or Wankel engine. The rotary valve engine also draws in a mixture of air and fuel, which is then compressed and burnt. A motor revolving in an elliptical chamber is connected to a shaft, which finally drives the rear wheels. In most automobiles, the engine is mounted at the front end of the car, with the clutch and gearbox immediately behind it; the engine, clutch and gearbox are assembled into a single unit. A number of systems are necessary to make an engine work. A lubrication system is needed to reduce friction and prevent engine wear. A cooling system is required to keep the engines temperature within safe limits. The engine must be provided with the correct amount of air and fuel by a fuel system. The mixture of air and fuel must be ignited inside the cylinder at just the right time by an ignition system. Finally, an electrical system is required to operate the cranking motor that starts the engine and to provide electrical energy to power engine accessories.Lubrication System An engine has many moving parts which eventually develop wear, as they move against each other. The engine circulates oil between these moving parts to prevent the metal-to-metal contact that results in wear. Parts that are oiled can move more easily with less friction and hence power loss due to friction is minimized. The secondary function of lubricant is to act as a coolant and also as a sealing medium to prevent leakages. Finally, a film of lubricant on the cylinder walls helps the rings in sealing and thus improves the engines compressions.Cooling System Due to the combustion of fuel with air inside the cylinder, the temperature of the engine parts increases. This increase of temperature directly affects the engine performance and the life of the engine parts. The cooling system keeps the engine operating at the efficient temperature. Whatever the driving conditions, the system is designed to prevent both overheating and overcooling.Fuel System The main function of the fuel supply system is to provide fuel to the carburetor or injection system at a rate and pressure sufficient to meet engine demands under all conditions of load, speed and gradients encountered by the vehicle. The fuel system must also have enough reserve fuel for several miles of vehicle operation.Ignition System The purpose of the ignition system is to provide assistance for the combustion of fuel either by a high voltage spark or self-ignition in each of the engines cylinder at the right time so that the air-fuel mixture can burn completely. The fuel supplied to the combustion chamber must be ignited to deliver power. In a spark-ignition engine an electric spark is used for this purpose. The compression-ignition engine does not require a separate ignition system because the ignition is affected by compression of the mixture to a high pressure.Electrical System The engines electrical system provides energy to operate a starting motor and to power all the accessories. The main components of the electrical system are a battery, an alternator, a starting motor, ignition coil and heater.Frame The frame provides a foundation for the engine and the body of the vehicle. The frame is constructed from square or box-shaped steel members strong enough to support the weight of the body and other components. The automobile frame is usually made up of a number of members welded or riveted together to give the final shape. The engine is mounted on the frame with rubber pads which absorb vibrations and also provide damping of these vibrations. Absorption and damping of vibrations protects passengers from discomfort caused by shocks. The frame is supported on wheel axles by means of springs. This whole assembly is called the chassis. Suspension System The function of the suspension system is to absorb vibrations due to the up and down motion of wheels, caused by the irregularities in the road surface. The springs, connecting linkages, and shock absorber comprise the suspension system of a vehicle. The suspension system is of two types：(1) Rigid system(2) Independent system In the rigid system, the road springs are attached to a rigid beam axle. It is mostly used in the front axle of commercial vehicles and in the car axle of all types of vehicles. The independent system does not have a rigid axle. Each wheel is free to move vertically without any reaction on its mating wheel. The independent system is mostly used in small cars.Power Train The power train carries the power that the engine produces to the car wheels. It consists of the clutch (on cars with a manual transmission), transmission (a system of gears that increases the turning effort of the engine to move the automobile), drive shaft, differential and rear axle.Clutch A clutch is required with the manual transmission system to temporarily disconnect the engine from wheels. Such disengagement of the power train from the engine is essential while changing the gear ratio or while stopping the vehicle.Transmission The main function of the transmission is to provide the necessary variation to the torque applied by the engine to the wheels. This is achieved by changing the gearing ratio between the engine output shaft and the drive shaft.Drive Shaft The drive shaft or propeller shaft connects the gearbox and the differential unit. The drive shaft has universal joints at its ends.Differential The function of the differential is to split the power received from the propeller shaft to the rear axle shaft. It allows the rear wheels to be driven at different speeds when the vehicle takes a bend or falls into a ditch.Axles Axles are the shafts on which road wheels are mounted. The road wheels are provided with the required drive through these axles.Wheels The automobile wheels take the load of the vehicle and also produce tractive force to move the vehicle. The wheels are also used for retardation and for stopping the vehicle.Steering System The steering system is used for changing the direction of the vehicle. The major requirements in any steering mechanism are that it should be precise and easy to handle, and that the front wheels should have a tendency to return to the straight-ahead position after a turn. A gear mechanism, which is known as steering gear, is used in this system to increase the steering effort provided by the driver. This system makes the vehicle steering very easy as the driver does not have to put in much effort. Vehicle steering is not only required on a curved road but also while maneuvering on the busy traffic roads. The steering system allows the vehicle to be guided i.e. to be turned left or right.Braking System Brakes are required for slowing down or stopping a moving vehicle. The braking system may be operated mechanically or hydraulically. 95 percent of the braking systems in use today are of the hydraulic type. All brakes consist of two members, one rotating and the other stationary.There are various means by which the two members can be brought in contact, thus reducing the speed of the vehicle. The major components of the braking system are: brake pedal，master cylinder，wheel cylinder，brake drum，brake pipe，brake shoes，brake packing plant and linkages. As the load on the vehicle and the vehicle speed has increased according to recent trends, in modern days, the importance of the braking system has also increased and power brakes are now being preferred. Power brakes utilize vacuum and air pressure to provide most of the brakeapplying effort.Virtual ManufacturingWhat is Virtual Manufacturing Virtual manufacturing (VM) is an integrated, synthetic manufacturing environment exercised to enhance all levels of decision and control in a manufacturing enterprise. VM can be described as a simulated model of the actual manufacturing setup which may or may not exist. It holds all the information relating to the process, the process control and management and product specific data. It is also possible to have part of the manufacturing plant be real and the other part virtual. Virtual manufacturing is the use of computer models and simulations of manufacturing process to aid in design and production of manufactured products. Lawrence Associate 1996, have identified three different types of Virtual Manufacturing paradigms that use Virtual Reality technology to provide the integrated environment.(1) Designcentered VM：provides designers with the tools to design products that meet design criteria such as design for X;(2) Productioncentered VM: provides the means develop and analyze alternative production and process plans;(3) Controlcentered VM：allows the evaluation of product design, production plans, and control strategy and a means to iteratively to iteratively improve all of them through the simulation of the control process.What is the Significance of VM VM aims at providing an integrated environment for a number of isolated manufacturing technologies such as Computer Aided Design, Computer Aided Manufacturing, and Computer Aided Process Planning, thus allowing multiple users to concurrently carry out all or some of these functions without the need for being physically close to each other. For example, a process planning engineer and a manufacturing engineer can evaluate and provide feedback to a product designer, who may be physically located in another state or country, at the same time as the design is being conceived.Another important contribution of VM is Virtual Enterprise (VE). Lin et al .1995 defined a Virtual Enterprise as“rapidly configured multidisciplinary network of small, process specific firms configured to meet a window of opportunity to design and produce a specific product.” Using this technology , a group of people , or corporations can pool their expertise and resources and capitalize a market opportunity, by sharing information in a VM environment. The principal advantage of this technology is its ability to provide a multi-media environment, enhancing communication at all levels in a products life cycle.Applications of VMApplication of VM encompass the entire life cycle of a product. Reported developments include a virtual space decision support system by Imamura and Nomura1994 at the Matsushita company in Japan. This system applied towards the marketing and sales of kitchen furniture, allows customers to experience a kitchen environment and evaluate alternatives and select the best combination according to preferences. Their preferences are stored as drawings and subsequently transferred to the companys production facilities. Owen 1994 presented the work implemented at John Deere Companys production facility, that used Virtual Manufacturing for the installation of an arc welding production system. The project involved using a Virtual 3-D environment for design, evaluation, and testing of the robotic production system. Part of the work was carried out at John Deeres facility while part of it was done by Genesis System and Technomatrix Technologies. The VM approach helped shorten the design-to-manufacturing cycle-time.DuPont 1994 presented an overview of Virtual Reality applications, and reported about Virtual prototyping being carried out at the Coventry School of Art and Design. These virtual prototypes are constructed in a computer at the beginning of the design process and allow the designer to perform tests on the virtual prototype such as a car before hand , by walking around or through the design, examine its performance on a virtual road , sit in the drivers seat , and check view lines, etc. Also reported were VM applications such as the virtual concurrent design and assembly of a landing gear, and simulation of side-impact collision to test vehicle safety.Kim et al. 1994 also reported VR applications including the use of VM by designers at Boeing Aircraft Company for the ergonomic evaluation of their airplane designs for operation as well as maintenance. Another study used a VM environment to train robots. An operators movements were recognized, interpreted and stored in the form of robotic movement commands. Shenai described the Virtual Wafer Fabrication (VWF) infrastructure which provided an framework for the optimization of key process and design variables in the development of application specific semi-conductor devices. Other application areas discussed in Larijani 1994 include machine-vision applications for diagnosis, fault detection, inspection and preventive maintenance, safety and maintenance training, ergonomic analysis For example , new cab or shovel configurations for each Caterpillar moving equipment are tested by real drivers for possible imbalances while handling virtual bulldozers and trucks.5汽车的部件发动机 发动机的作用是为汽车提供动力，人们形象的称之为汽车的动力工厂。 大多数汽车发动机都是利用空气和汽油混合物的爆炸能量推动活塞的。活塞能够转动与它连接在一起的曲柄连杆。从而，曲柄产生牵引力使车轮转动。有些汽车是靠另一种发动机来提供动力的。这种发动机因为它的旋转阀，旋转内燃机或者转子发动机而被人熟知。这种旋转阀式发动机也能够吸入空气和燃料的混合物，然后将它们压缩并燃烧。另外，发动机会在一个椭圆形腔室中旋转，它与驱动汽车后轮的后轴相连接。绝大多数的汽车里，发动机会被安装在汽车的前部末端，离合器和变速箱在它的后面。最后，发动机、离合器和变速箱会被装配成一个整体。想要使一个发动机能够正常工作还需要很多系统的支持。润滑系统可以用来减小摩擦，减轻发动机磨损。冷却系统可以使发动机的工作温度在安全的范围之内。另外，发动机还必须由供油系统提供适量的燃料和空气。在气缸里，空气和燃料的混合物必须由点火系统在适当的情况下点燃。而后，电子系统被用来控制启动发动机用的电动机和为发动机的附属部件提供电能。润滑系统发动机的部件会因为它们之间的相互运动而逐渐导致磨损。在这些部件中间存在着发动机循环油。它可以避免金属间的相互摩擦而导致的磨损。在润滑剂的润滑作用下，各部件会仅受到很小的摩擦力，这可以使它们更容易运动。因此，润滑系统可以将由摩擦引起的能量损失降到最小。润滑剂的第二个作用是可以发挥冷却剂的作用，也可以作为密封介质来防止泄漏。还有在气缸上产生的润滑薄膜也可以有助于活塞环密封，改善发动机的压缩性能。冷却系统在气缸中，燃料会在空气的作用下剧烈燃烧，从而导致发动机各部件的温度升高。温度的上升将直接影响发动机的性能，也会缩短发动机零件的寿命。而冷却系统则可以使发动机在适宜的温度下工作。无论驾驶条件如何，该系统都要被设计用来防止机器过冷或过热。燃料供给燃料供给系统的主要作用是在机动车辆所能遇到的所有条件下（包括负载，速度，温度压力的变化梯度等），提供足够的压力，以一定的速度为化油器或注油系统提供燃料，来满足发动机的燃料要求。另外，燃料系统还必须储备足够的燃料，以便可以支持车辆能够行驶数英里。点火系统点火系统的目的是能在适当的时间里通过高压电火花或自燃，使每个内燃机气缸中的燃料。燃烧以便气缸中的液气混合物得到充分的燃烧。供给到燃烧室的燃料必须经过燃烧才能释放出能量。在火花点火发动机中，点火系统是利用电火花来点燃燃料的。压缩点火发动机则没必要拥有独立的点火系统。因为它其中的混合物是靠压缩产生足够的压力来点燃的。电气系统发动机的电气系统可以提供足够的电力用来启动电动机和操纵其他全部的附属部件。电气系统的主要元件有电池、交流发电机、启动电动机、点火线圈和加热器。车架车架是为发动机和车身提供了一个安装的基础。车架是由数量众多的足够强大的方形和箱形钢构件组成的，这样才能够有效地用来支撑车身和其他构件的重量。汽车车架通常是由大量的钢构件经过焊接或铆接在一起的，从而形成最后的车体形状。一般发动机都将安装在有橡胶垫的车架上，橡胶垫吸收震动的同时也可以减小这些震动的发生。故吸收和减弱这些震动可以有效的帮助乘客减弱因为行驶中的颠簸而感到的不适。这些车架是由车辆轮轴上很多弹簧支撑的。所有这些装配在一起称为车辆底盘。悬挂系统悬挂系统的作用是可以吸收车辆在不平整路面上行驶时，由于车轮上下颠簸而产生的震动。弹簧的连接装置和减震器构成了车辆的悬挂系统。悬挂系统通常有两种类型组成：（1） 刚性系统（2） 独立系统在刚性系统中，弹簧连接在一根刚性横梁轴上。这种系统大多应用于商用车辆的前轴以及各类车辆车轴上。独立系统则不需要拥有刚性横梁轴。每一个车轮可以自由的垂直运动，而相对应的另一侧车轮没有任何反应。独立系统大多应用于小型车辆。动力传动系统动力传动系统的作用是可以用来将发动机产生的能量传递给车轮。它包括离合器（汽车上的手动变速器）、差动器（能提高发动机产生的转矩以催动汽车的齿轮系）、驱动轴、差速器、后桥。离合器离合器是用于手动变速的传动装置，可以用来暂时切断发动机和车轮间的动力传递。在需要换挡或停车时，把传动系统和发动机的连接断开是极其重要的。变速器变速器的主要作用是通过发动机把各种必需的扭矩传递给车轮。通常情况下，这是通过改变发动机输出轴和驱动轴间的齿轮传动比来实现的这些必要的差异的。驱动轴驱动轴或推动轴一般与齿轮变速箱和差速器相连，而在驱动轴的两端也常设计有万向节。差速器差速器的作用是把来自传动轴的能量分给后桥。当汽车转弯时或跌入水沟中，两个后轮可以以不同的速度驱动。车桥车轮被安装在一根轴上，该轴被称为车桥。车桥的各车轮提供必需驱动力。车轮汽车车轮需要支承整辆车，并产生牵引力来驱动车辆行驶。另外，车轮也用来减速和停车。转向系统 转向系统用来改变车辆的行驶方向。在任何转向装置中，一般都要求转向精确和便于操纵，并且在每转一次向后，前轮都应该有一种自动返回到原先直线行驶的位置的趋势。齿轮机构通常以转向齿轮而闻名，通常在转向过程中，能够增大转向的作用力矩。还有这套系统可以让驾驶员不必花费太大的气力就可以轻松地使车辆转向。转向系统极为重要，不仅仅在弯道行驶中需要转向系统，在拥挤的交通道路上汽车行驶时同样也需要它。另外，转向系统能使车辆向左或向右转向。制动系统制动系用来使汽车减速或停车。制动系统分为机械式和液压式两种。目前95%的制动系统都属于液压式的。制动系统包括两部分，转动部分和固定不动的部分。人们都通过各种方式使上述两部分紧密接触，从而可以减小车辆的行驶速度。制
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