| Motor graders are kind of traction machinery with relatively high speed. Theworking productivity and quality can be directly affected by the performance ofdriving system. Currently, there is a driving system technology gap between domesticproducts and foreign products. Three main driving systems, mechanical transmission,hydrodynamic transmission and hydraulic transmission, have respectively advantagesand disadvantages. Hydraulic and mechanical hybrid transmission, which combinestwo transmission merits, may be a reasonable method to deal with the scarce of keytechnology in processing of multi-position gearbox. Hydraulic transmission used intraction machinery belongs to frontier subject, and was once successfully realized insmall and medium-sized bulldozers. Hydraulic and mechanical hybrid transmissionhas lots of critical technical problems including design of driving system, systemstatic parameters matching design, infinite speed control method, automatictransmission offering a large speed ratio, system dynamic parameters control in orderto achieve a better power and economy performance. By conducting a research ofhydraulic and mechanical hybrid transmission in motor graders, the main results ofthis article are fivefold.1.A new transmission system of motor grader is provided as following: engine,hydraulic pump, hydraulic motor, transaxle and driving tires. By using the simulationand experiment methods, the analysis of two different hydraulic systems is conductedfor the typical working conditions such as quick start and natural parking. The resultof simulation and experiment shows that the closed-circuit hydraulic driving systemhas a fast response speed, short stopping time and distance, relatively large systempressure impact in stopping and a reverse dragging which is more prone to happen inparking. The open-circuit hydraulic system has long parking time and distance, noreverse dragging and an air suction which is easily to yield in parking process. Thesimulation results are the foundation of control system design.2.According to the research of kinetics, dynamics and mass parameters of foreignproducts, the driving system is determined. Then the parameters matching areresearched for example pump displacement, motor displacement and ratio of gear axle.The theoretical and experimental analyses reveal that the static parameters matchingare reasonable. Comparing with the hydraulic driving system without gear axle, thedesign has advantages including wide range of speed, good synchronization, low pressure of hydraulic system and high transmission efficiency under high speedtraveling.3.Owing to study on the dynamic procedure of clutch engagement, the simulationmode is established in ADAMS. By using the software, the research of the effects ofshift time, friction moment, shift shock and work of clutch slipping caused by thevelocity of clutch pressure increase, the accurate increase realization method and theamount of pressure. The mechanic and hydraulic control method is provided, whichmoderates the rotation speed of clutch driving disc and designs the curve of clutchpressure. The experimental results show that the control method can meet therequirement of shifting comforts.4.The dynamic parameters matching and control are discussed. According to theworking conditions and load characteristics, gear speed range and the staticparameters matching in different gears are determined. The control methods ofhydraulic pump and motor under limit load condition are given. The experimentalresult shows that the main performance and technology indexes meet the demands,and also are superior to hydraulic motor grader.5.The principle of variable engine power control is elaborated, and its realizationmethods are given. In order to meet the requirements of actual working condition, themulti-power curves of engine are designed. The experimental results reveal that thevariable engine power technology can significantly improve the fuel economy ofmotor graders. |
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