1.1 Analysisof the status at home and abroad

Sincethe 1990s, the Chinese economy has developed rapidly and the Chineseconstruction machinery industry has entered a period of rapid development. Withthe development of the urbanization process in China to a depth and breadth,and the increase of the repair and maintenance of roads, municipal facilitiesand urban minor engineering projects, the proportion of such small-scalebusiness projects in total social construction is increasing. Due to theproblem of engineering costs, large and medium-sized excavation machinery isdifficult to perform for such small-volume projects. In the past, these smallbusiness projects were often transported by manual loading. In recent years, asa rising star, small excavation machinery has been widely welcomed by usersbecause of its unique advantages of compactness, flexibility, versatility, andhigh efficiency. It has begun to partially replace medium and large-scalemachinery and labor in small-volume construction. According to calculations,under normal circumstances, a small excavator of 1.5 to 2.0 tons can replaceabout six adults to work, which greatly reduces construction costs andmanagement costs.

Withthe rapid development of small excavators, we are facing some outstandingproblems. Although excavators generally have a self-propelled chassis, theystill require a transport truck between two distant work sites. In general, theexcavator's transportation costs account for a large part of its use cost.Unlike large and medium-sized excavators, which often work long hours at a worksite, the work of small excavators tends to be characterized by a small amountof work and a dispersed operation site. This has led to the fact that smallexcavators are often in the process of transportation and their transportationcosts are greatly increased.

Carexcavator is a kind of construction machine that installs excavation workplatform on car chassis. Becausethis type of machine uses a car as a basic vehicle, it has features such asfast travel speed, high level of basic car tricycle, short development cycle,and the like, making this kind of machine with a wide range of applicationprospects. Car excavators can not only be used for tasks such as municipalconstruction, road repairs and rescue and disaster relief, but also can be usedmilitaryally to provide fast-moving engineering guarantees for modern warfare.In the 1950s, car excavators have been developed abroad. At the beginning, themain military, such as the former Soviet Union, the Czech Republic, Germany,the United States, France, and the United Kingdom, developed and equipped 10different models of car excavators. At the same time, civil-use car excavatorshave achieved certain development. For example, the UDSll4A excavator producedin Czechoslovakia and the XL4100 excavator manufactured by GRADALL in theUnited States belong to the auto excavator. Visible, car excavators occupy animportant position in the category of excavators. There are also some specialcar modification factories in China that place the excavation mechanism on thechassis of the truck, thereby improving its working efficiency.

However,with the acceleration of advanced urbanization, the road conditions arebecoming more and more complicated, so that flexible car excavators aresometimes difficult to use. We all know that when excavators are working, theyoften need to cooperate with trucks to transport slag. In some special venues,the construction site has a small operating space. Even if a small excavator isused, it is difficult to accommodate another truck at the same time, whichseverely limits the efficiency of the project construction.

1.2 Purpose and significance

Solvingthe above problems requires a brand-new machine that combines the functions ofboth a small excavator and a truck. The design product "Self-excavatinglight truck" is a modification of the chassis of the truck so that it cannot only realize the excavating function of the small excavator but also can beused as a truck for transportation. This design product is mainly aimed atspecial sites with small amount of work, scattered work sites or narrowconstruction space. Its unique high mobility design can greatly improve workefficiency.

2. 研究的基本内容与方案

2.1 The basic content and goals of the design

1.Selection ofvehicle structure.

2.System layout,overall layout of the vehicle.