| The loader is a typical construction machine,and plays an important role in infrastructure such as earthwork and water conservancy projects.The working condition of the loader is extremely complicated,and the load fluctuates violently.The hydraulic mechanical compound transmission has the characteristics of high efficiency and safety of the mechanical transmission and the characteristics of the hydraulic transmission that can withstand variable load and the variable speed,and can transmit high power,which is very suitable for the loader with complex and changing working conditions.However,the hydraulic mechanical compound transmission system is relatively complex,and the transmission process requires the hydraulic branch and the mechanical branch to participate together.Therefore,it is necessary to conduct in-depth study on the parameter matching,power split,power cycle and transmission efficiency characteristics of the hydraulic mechanical compound transmission.This thesis expounds the working principle of the hydraulic mechanical compound transmission,analyzes the characteristics of the shunt mechanism,single flow mechanism,and confluence mechanism of the hydraulic mechanical composite transmission,and obtains the relationship between the torque and speed of each component.Through the formula derivation and the method of MATLAB software analysis,the three coupling schemes of input-coupling,output-coupling and hybrid coupling are studied in detail,and the speed-adjusting characteristic curves of the three schemes are drawn and analyzed.It is concluded through analysis that the hybrid coupling hydraulic-mechanical compound transmission is more suitable for the wheel loader.Finally,a specific transmission scheme is proposed,a simple transmission diagram of the hydraulic mechanical compound transmission is given,and the power transmission routes of different gears of the wheel loader are analyzed.According to the characteristics of the V-shaped working cycle of the wheel loader,the force analysis of the wheel loader was carried out.With reference to the parameters of the ZL50 wheel loader and the hydraulic-mechanical compound transmission scheme proposed in this paper,through calculation and analysis,the main parameters of the loader werereasonably matched.Finally,the transmission ratio between the gear pairs in the hydraulic mechanical compound transmission,the transmission ratio range of each gear,the characteristic parameters of the front and rear planetary rows and the parameters of the hydraulic motor are provided,which provides a reference design for the design of the hydraulic mechanical composite transmission system.method.The evaluation indexes of the power and economy of the wheel-loader hydraulic mechanical compound transmission are analyzed.Through theoretical analysis and calculation,with the help of MATLAB software,the power shunt bit point,power cycle and transmission efficiency characteristics in the hydraulic mechanical composite transmission system of the loader were analyzed.The factors affecting the power cycle and their influence laws were obtained,and the influence was studied.The factors of transmission efficiency and their influencing laws.The research results show that the power circulation of the compound transmission system can be avoided by controlling the displacement ratio and selecting the smaller planetary row characteristic parameters,thereby improving the efficiency of the hydraulic mechanical compound transmission.Using the simulation software AMESim,simulation modules such as engine,hydraulic speed control system,planetary row,load torque,etc.were built,and the overall simulation model of the hydraulic mechanical compound transmission system was established.According to the model,the transmission characteristics of the hydraulic mechanical compound transmission are simulated and analyzed.The main simulation analysis of the impact of displacement ratio and planetary displacement characteristic parameters on power split ratio and power cycle,and the simulation analysis of displacement ratio and planetary displacement characteristic parameters on transmission efficiency.Through analysis,it is concluded that when the loader is working stably,the displacement ratio should be as small as possible to reduce power circulation and improve compound transmission efficiency.In addition,when designing a hydro-mechanical compound transmission,the planetary row characteristic parameter takes a smaller value within a reasonable range,which can reduce the power cycle of the compound transmission system and achieve the purpose of improving transmission efficiency.The research conclusion can provide a reference for the design and reasonable use of the hydraulic mechanical compound transmission. |
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