Vibration measure and analysis of crawler-type rice and wheat combine harvester in field harvesting condition

Abstract: The paper aimed at studying the vibration characteristics of combine harvester in field harvest and the vibration characteristics of combine harvester in different feeding conditions. Taking 4LZ-5.0E crawler-type rice and wheat full-feeding combine harvester manufactured by World Agricultural Machinery Co. Ltd. as study objection, the investigation designed 12 measuring points on the body of the combine harvester to carry out vibration test by DH5902 dynamic signal testing and analysis system. The measuring points were located near the main working components and excitation sources according to the structural characteristics. In the experiment, the combine harvester worked at the speeds of 0, 0.72 and 1.14 m/s respectively. In the paper, only the speed of the combine harvester was changed by hydro static transmission (HST) while other operating parameters were fixed. The aim was to insure the changes in vibration conditions only caused by the changes in feeding quantities. In the research, the spectrum could be gotten from time-domain signal of measuring points by Fourier transform. The physical quantities could be obtained from spectrum diagrams such as vibration frequency of the signal, distribution and peak. In the analysis process, root mean square (RMS) value of vibration acceleration was designated as the assessment standard. And it was calculated by 1/3 octave band of each measurement point in the direction of X, Y and Z, which was obtained from the spectrum received by DH5902 dynamic signal testing and analysis system. The RMS values of vibration acceleration were used as the signs of the intensity of vibration. The analysis indicated that vibrating sieve, threshing cylinder, and engine were the main vibration sources in the forward-backward, left-right, up-down direction, respectively. The vibration caused by the reciprocating motions of cutter and vibrating sieve was an important part of the whole combine harvester vibration. The rotation of the threshing cylinder was the main source of the strong vibration of the front and back support, the drive shaft support. The vibration from vibration sources could be transmitted to each part of the combine harvester through the frame. The engine combustion excitation force was the main source to the vibration in up-down direction, and the cab could effectively reduce the vibration of high frequency (≥150 Hz), but the vibration of combustion excitation frequency (90.33 Hz) was 2.3 times as large as before. In the field experiment of wheat harvest, total vibration of the measuring points on header and the conveying trough respectively decreased by 25% and 39%. The cavity structure composed of header and the conveying trough absorbed some vibration when the crop was fed into it. The feeding of crop caused the magnifying of load on the drive shaft of conveying trough and threshing cylinder. When the feeding quantity was 2.44 kg/s, the total vibration of the measuring points of drive shaft on conveying trough and the threshing cylinder increased by 90% and 149% respectively compared with that when no crop was fed. But the space was filled when feeding quantity was increased to 3.87 kg/s, and the total vibration was decreased by about 15%. The paper suggests that vibration isolation device should be installed between vibrating sieve, threshing cylinder, engine and chassis frame. To reduce vibration, the feeding quantity of threshing cylinder should be constant and vibration isolation device should also be installed on the connection location of the chassis frame. The vibrations of the measuring points on the seat support, engine support and chassis frame are positively correlated with feeding quantity. The result provides a basis for reducing the vibration and improving the driving comfort of the crawler-type rice and wheat combine harvester.