| Machinery industry is one of four pillar industries of the national economy, the engineering machinery industry is an important component of China's modernization construction, it is one of the major equipment industry and an extremely important position in the national economy, Wheel loader construction machinery industry is the development of our country first, the pace of the fastest-growing sectors. Wheel loader is a wider use of construction machinery. Widely used in construction, railways, highways, docks, mines and other projects to accelerate construction speed, reduce labor intensity and so play a crucial role. Wheel loader is a wide range of its operation, the operating conditions is complex and changeable, the operating environment is very hard. The reliability of wheel loaders transmission parts, as well as comfortable operation of the loader totally dependent on the quality of their own power train. As a core component of power shift transmission gear shift smooth performance, depending on the speed of the shift hydraulic system performance, namely, buffer and variable shift control valve performance.Domestic manufacturers are at a revolution of the wheel loader transmission, gearbox is the core component of the wheel loader drive system; variable-speed hydraulic transmission control system performance, depending on the speed of the technical performance of the hydraulic system. Shift hydraulic transmission control system of the wheel loader has been through research, development and trial stage in foreign countries, switch to mass production stage, but Domestic the system is still in the research stage of development, this article based on using for reference from abroad in the field of shift hydraulic system of the latest achievements, to analysis and research shift hydraulic system of SDLG ZL50 wheel loader with depth and through the establishment of simulation studies have proved the correctness of the mathematical model. In this paper, the research results and research content are mainly embodied in the following areas:This article discusses the characteristic, the main types, research and development, development foreground of the wheel loader variable-speed hydraulic system, for the completion of this article has been paving the way to do a good job:In this paper, it introduced working principle and the selection part characteristics of the ZL50 gearbox and variable speed hydraulic system, in which key components of shift hydraulic system including the shift control valve, the buffer valve, clutch cylinder and so on. Of the power shift transmission, it relies on pressure control to achieve a reasonable shift buffer control. Shift comfort depends on the instantaneous acceleration generated by the whole process of transmission force, the instantaneous force of the wheel loader shifting process decided to engine and torque converter input and output characteristics together and step-up features the work pressure.Power Bond Graph Method is a system dynamics modeling method, which provides a graphic to show that describes the dynamic structure of the system is a dynamic engineering system in effect at the time of digital simulation modeling tools, is an engineering system used to describe energy Picture shows the structure of representation. Based on the power bond graph theory based on research, theory with practice, be used in variable speed loader ZL50 hydraulic shift control system of mathematical modeling. Use power bond graph theory ZL50 loader hydraulic transmission system for mathematical modeling file.MATLAB language with two of the most prominent characteristics of (a powerful matrix calculation ability and perfect graphics visualization function) makes it an international control of the most widely used computer tools. Simulink is a system used for dynamic modeling, simulation and analysis software package, it supports continuous, discrete or a mixture of both linear and nonlinear systems. It provides users with a block diagram model using the graphical interface, with the traditional use of simulation software modeling differential equations and differential equations, compared with a more intuitive, more convenient, more flexible advantages. In this paper, the use of power based on bond graph modeling of variable-speed hydraulic loader ZL50 system modeling, the use of bond graph and block diagram between the transformation, the establishment of the file subsystem block diagram in Matlab / Simulink platform to build simulation models for the simulation of characteristics of response curves obtained in response to pressure-shift transmission and power transfer curve of the corresponding curve. Loader operating on the working conditions of the analysis of shifting patterns, the use of loaders calculated movement and traction characteristics of the file loader ZL50 the time shift buffer for analysis and research to determine the time shift buffer calculation and adjustment method.
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