| The main vibration sources of combine come from four aspects:engine,header, conveying and separation divice,road random excitation.The main cause of engine vibration is the periodic movement of the engine center of gravity,the inertia force of the vertical motion of reciprocating parts along the inside wall of cylinder,the centrifugal inertial force of rotational motion parts,the periodic motion of crankshaft.The main cause of header vibration is the constantly changeable inertial force of the reciprocating and rotary motion of the unbalance mass and variable-speed motion of header transmission system.The reciprocating parts are moving blade and its accessory,the rotary parts are crank and crank pin as well as triangle swing part. The structure of conveying and separation divice is very complex,devices such as conveyors and threshing cylinder and straw walker have a strong vibration due to unbalance mass.Road random excitation is also a main cause of the vibration of combine,the influence of road environment to the vibration of combine is more complex than other vehicle owing to the work place of combine is farm field.In view of the above issues,a combined method of theoretical analysis and experimental study for the vibration characteristics of Xin Jiang-2A wheat combine harvester is put forward,the main instrument used in the experiment is DH-5922 test and analysis system.the conclusions abtained in this paper as follows:(1) Based on the theoretical analysis of the vibration of Xingjiang-2A wheat combine driver base,a analytic modal of transverse vibration law of driver base is obtained and the relationship between the transverse vibration amplitude and the parameters that influenced the vibration is This research method can also used in the vibration analysis of other parts.(2)The vibration strength and frequencies of the testing points on the engine bracket is measured and analysed under the working condition of low-speed of engine.The research shows that the main vibration frequency of the engine bracket is 49.4Hz and the maximum transverse acceleration under this frequency is 11.1m/s2.(3)The vibration strength and frequencies of the testing points on the diver base are measured under four working conditions:low-speed of engine,high-speed of engine, low-speed of whole machine,high-speed of whole machine.The main vibration frequencies are around 40.9Hz is obtained by analysing the signals of four working conditions,The modal parameters and modal shapes of the driver base are obtained by using modal analysis system.The relatively accurate modal frequencies are 23.49Hz,41.99Hz,49.66Hz, 101.29Hz, 116.34Hz150.57Hz178.70Hz,199.17Hz,and the damping ratio under frequencies above are respectively 2.19%,4.07%,13.31%,5.06%,3.28%5.93%,4.24%,3.15%(4) The vibration strength and frequencies of testing points on the header are measured under two working conditions:low-speed of engine and low-speed of whole machine. The main vibration frequencies are also around 40.9Hz is obtained by analysing the signals of two working conditions.The modal parameters and modal shapes of the header are obtained by using modal analysis system.The relatively accurate modal frequencies are 25.50Hz,86.26Hz,120.75Hz,144.95Hz,191.67Hz,214.99Hz.and the damping ratio under frequencies above are respectively 7.77%,2.87%,1.17%,5.21%,3.38%,2.23%.(5) The vibration strength and frequencies of testing points on the combine frame are measured under the working condition of low-speed of engine.The main vibration frequencies are around 48.8Hz is obtained by analysing the signals of the working condition.The modal parameters and modal shapes of the combine frame are obtained by using modal analysis system.The modal frequencies are 33.59Hz,64.35Hz,122.11Hz,179.40 Hz.and the damping ratio under frequencies above are respectively12.79%,0.62%,1.24%, 2.67%. |
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