The Performance Characteristic Analysis On The Powertrain Of 80 Wheel Loader

The powertrain which has functions as transfering of power, transmission, steering,braking and so on is an important component of the loader and plays an important role in the vehicles'dynamic quality and economy.Therefore,the dynamic characteristics of the powertrain has an important impact in the vehicles dynamic performance.Many developped countries have had mature designing experience but they keep the key technology as top secret,so we must do our best to self-study in theory,method and technology. When we do the performance study of the powertrain, it is easier to get the requested results and data by the test,however, it has many shortcomings: high cost,heavy workload and long cycle.What is worse,there are many complex factors in the actual performance and it is difficult to measure some parameters because of the condition of an actual experiment.With the improvement of computer technology, the application of virtual prototyping technology for the transmission will be a new development trend. In this paper, based on previous studies, analysising the performance characteristic on the powertrain of 80 wheel loader by the ADAMS software.The full dissertation was divided into seven chapters, mainly as follows:1. PrefaceIn recent decades,the powertrain has developed rapidly, especially in its structure,function and performance.Nowadays,the powertrain has integrated mechanism,electricity and liquid into the whole.As the powertrain has created a lot of malfunctions during the usage because of the continuous impact of dynamic load, the study of the dynamic load of vehicles causes wide public concern.So to carry out a research is very important to improve vehicle operating performance and increase of service life of vehicles. At present,the study of the dynamic characteristics of the transmission system is mainly based on MATLAB/Simulink software. MATLAB/Simulink is a generic numerical simulation tool, its strength lies in scientific computation,signal processing and control system simulation,but it is quite difficult to give a detailed description of the mechanical systems and reserchers need to do a lot of simplification and abstraction work. With the improvement of computer technology, the application of virtual prototyping technology for the transmission will be a new development trend. Virtual prototyping technology is comprehensive application of technology,which includes a whole product development process, ranges over many technologies and is suitable for the simulation of mechanical products.2. Introduction and application to ADAMS softwareADAMS is an authoritative software on the dynamic analysis of mechanical systems in the world.Users can easily construct any complex multi-body dynamics virtual prototype model.Lots of books were written to introduce module functions of the ADAMS software so there is no need to give uncecessary details in this paper.This chapter emphasized the reasons for numerical divergence in the process of using the ADAMS software and how to deal with this problem.3.Virtual prototyping for the coordinated work of engine and torque converterThe coordinated work of engine and torque converter can be regarded as a new powerplant,which has new performance characteristics.This chapter constructed the entity models of engine and torque converter,the mathematical models of torque converter ,then constructed dynamics virtual prototyping for the coordinated work of engine and torque converter. According to the principle of proper matching between engine and torque converter, the characteristica of concerted work was determined. By using the MATLAB software, input/output characteristic was obtained for engine and torque converter working together. The dynamic simulation for virtual prototyping for the coordinated work of engine and torque converter verified the validity and effectiveness of the model.4. Virtual prototyping for the gear_box and driving bridgeThe gear_box and driving bridge are very important parts of the powertrain. This chapter constructed many entity models of components including gears,clutches and transmission shafts, then constructed dynamics virtual prototyping for the gear_box. Emphasis was put on the dynamics virtual prototyping for the clutch.The chapter also introduced transmission relations of gears and how to control shifting. A simplified treatment for the model of the driving bridge including final driver and wheel reduction,in this process,the emphasis was put on the wheel reduction.This chapter is very important for the future powertrain model. 5. The performance characteristic analysis on the powertrainThe virtual prototypes of each subsystem included engine,torque converter, gear_box,driving axle,were assembled into a whole virtual prototype. This paper introduced a variety of vehicles shift schedules.The emphasis was put on the shifting of vehicle efficiency and dynamic,and the best dynamic shift were determined.The kinematics simulation based on the virtual prototype of the powertrain verified the feasibility of shifting control by simulation scripts.The starting acceleration performance was analysised on the powertrain of 80 wheel loader,including the research of different gears based on the same road and the same gear based on different roads.By the comparative analysis,the first gear was more advantageous to the vehicle.The wheel loader based on the high_speed operating condition was simulated by two different methods.This process gained the respective advantages and disadvantages of the two methods.A scooping cycle of wheel loader based on two different methods was also studied,which was divided into four phases.By the comparative analysis,we got both of the advantages and disadvantages of different ways. The results showed that the second approach (the function of KD shifting ) could reduce the labor intensity of the operator and improve the efficiency of loader by saving work time around 30 percent and improving the energy efficiency to increase the economic benefits of the loader.6. Dynamic simulation study of transmission gearThe significance of the study of gear meshing was introduced in this chapter.The virtual prototype of gear meshing transmission was established based on ADAMS.This chapter introduced the theory of Hertz embedded,analysed parameters of gear meshing and the methods to determine them.Meanwhile,the causes of the penetrating phenomenon of the gear contact and the methods to deal with this phenomenon were studied.The meshing process of six gears was simulated in three running situations and their dynamic meshing force responses were calculated.The three running situations were as follows:the first one,the stable running of the loader at the first gear,analyzing the changes of speed of the gears and meshing force and proving the correctness of the model by the analysis on the meshing frequency;the second one,the loader started to accelerate at first gear;the third one,the scooping of wheel loader,in this procees,the meshing force is largest. In addition,the effect of the accuracy of manufacturing and assembling of the transmission gear was examined by virtual prototyping model,which provided refernces to research on the strength, fatigue analysis and stiffness of the gear and lay the foundation of the control of gear noise.7. ConclusionIn this part,the main conclusions of the paper were given,the prospects of the research for the powertrain of wheel loader were discussed and the future directions of the research were given.