| The Lower-Middle Reaches of the Yangtze River,which are considered as the major winter rape producing area in China,are mainly planted with cropping pattern of rice-rape or rice-rice-rape rotation.In order to solve the problems that high stubble and soil moisture content have great impacts on machine adaptability,sowing quality and efficiency in the whole stubble rice field rape direct seeding operation in this region,while the combined harvester is dedicated to low harvesting efficiency,a full-stubble rice field rapeseed direct seeding process scheme was put forward.The scheme was used as a power platform based on rice and wheat combined harvester,which was equipped with a rape seeder.The floating grass residues was collected by the front harvesting platform,and the rotary tillage and sowing system was realized by the rear tillage and sowing system.The machine was generally utilized as for direct seeding of oilseed rape on the untreated ground after rice harvesting,which could complete the processes of straw return,seedbed rotation,bed furrowing,and seeding and mulching in a single step.The main research contents and conclusions are as follows.(1)The domestic and foreign rapeseed mechanized direct seeding technology and equipment,as well as the research status of agricultural machinery suspension system were systematically analyzed.Based on the characteristics of rice stubble field and the agronomic requirements of rape planting,a full-stubble rice field rapeseed direct seeding process scheme was put forward.The scheme was used as a power platform based on rice and wheat combined harvester,which was equipped with a rape seeder.The floating grass residues was collected by the front harvesting platform,and the rotary tillage and sowing system was realized by the rear tillage and sowing system.Moreover,the design and analysis of the overall scheme of the crawler-type rape direct seeding machine were carried out.The key component structure and main technical parameters of the connection between the harvesting platform and the tillage system were determined.The position of the center of gravity of the whole machine was determined through the longitudinal stability analysis of the crawler-type rape direct seeding machine.The longitudinal stability reserve utilization coefficient was 0.198,which was in line with the quality configuration of each part of the crawler unit.The requirements can meet the basic requirements for field operation and transfer of crawler-type rapeseed direct seeding machine.(2)The structural design and parameter analysis of the key device of the crawler rapeseed direct seeding machine were carried out.The specific contents include:(1)The structure and related parameters of the suspension lifting system were determined through the analysis.Based on the sensitive property of the proximity switch to metal,the positioning control device was designed to realize the safe and controllable lifting of suspension frame.According to the lifting principle,the lateral force of the suspension frame was analyzed.The results showed that three pairs of 6205 bearing outer diameter 67 thickened rail wheels were used as guide wheels,and two pairs of outer diameter 62 unilateral rail wheels were used as limit wheels.It can improve the stability of the lifting process.(2)The power matching and parameter optimization design of the transmission system were carried out,and the structure of each part of the transmission system was analyzed and determined.The power transmission was realized by the combination of belt transmission,chain transmission,and gear transmission.The parameter optimization of two-stage chain transmission was carried out based on the MATLAB optimization toolbox.The results showed that the transmission ratios of the two-stage chain were respectively 1.7and 2.0,and 16 A single-row 86-section roller chain and 16 A single-row 114-section roller chain were respectively selected.(3)The structure and related parameters of the tillage and sowing system and the grass guide device were analyzed and determined.According to the layout of the whole machine,a side-transmission rotary tiller was adopted in the tillage and sowing system,which could achieve stable connection and compact layout through the rear suspension frame and the side seed metering device.The installation height of the seed metering device should be greater than or equal to 800 mm based on the test of the sidemounted seed metering device.The grass guide device adopted the combined structure of the cover,screen,fan,and speed controller to realize the straw covering the function of the side compartment.(3)Based on ANSYS Workbench,the static analysis and modal analysis of the suspension lifting system were carried out.According to the load characteristics of the tracked rapeseed direct seeding machine during transfer between plots and field operations,the loading state of the suspension frame was divided into the transportation state and the working state.Then,the static analysis and modal analysis of the suspension lifting system in different states were carried out to check its stiffness and strength.(1)The static analysis results showed that the maximum deformation under the two states was small,and the maximum stress was located on the guide wheel.The separate analysis of the guide rail and the suspension showed that under the transportation state and the working state,the maximum stress of the guide rail was respectively 147.44 MPa and 145.06 MPa,and was respectively 89.91 MPa and 121.83 MPa for the suspension.All stress values were lower than the allowable stress value,and the rigidity and strength met the request for utilization.(2)The pre-stressed modal analysis results showed that the first six natural frequency ranges of the suspension lifting system under the transportation state and the working state were44.34～216.26 Hz and 83.15～207.07 Hz,respectively.Under the transportation state,the main deformation positions were rod,the top of the guide rail,and the suspension,and the main deformation forms were bending,torsion,and swing.Under the working state,the main deformation positions were the lower hanging plate head,the upper hanging plate,the vertical beam,and the welding place of the vertical beam,and the main deformation forms were bending,swing and torsion.Based on the external excitation analysis of the suspension lifting system,it can be seen that the first six natural frequencies of the suspension lifting system in the transportation and working conditions could avoid the external excitation frequency range,and no resonance would occur.(4)The field experiment was conducted to evaluate the effect of rotary tillage and performance of crawler-type rape direct seeding machine.The actual working performance of the suspension lifting system was tested through the traction resistance test of the tillage and sowing system.(1)The traction resistance test results of the tillage and seeding system showed that the total traction resistance increased with the increase of the operating speed.When the operating speed increased from 0.5m/s to 0.9m/s,the total traction resistance could increase from 1487.23 N to 3267.64 N.During the test,the lifting and lowering of the suspension frame was smooth.The comparison between the test results and the simulation results indicated that the suspension lifting system can ensure stable lifting and traction work within a safe stroke.(2)The rotary tillage performance test results showed that the power of the harvesting platform can be stably transmitted to the tillage and sowing system,which can ensure the stable operation of all functional components of the harvesting platform and meet the power requirements for rotary tillage operation.The rear surface was relatively flat after the rotary tillage operation.The working width was 2400 mm,and the maximum tillage depth was 150 mm.(3)The field test results of the whole machine showed that the crawler-type rapeseed direct seeding machine had stable operation and good machine pass ability under the high stubble and soil moisture working conditions.The whole machine had a flat surface and a stable ditch.There was no ground drag caused by the blockage.The average tillage depth,stability coefficient,soil crushing rate,and qualified rate of the depth of the rotary tillage layer was 125 mm,92.4%,83.7%,and 95%,respectively.All values met the standard operation quality indicators,and can be used for direct rape seeding operations on the untreated surface after the rice harvest in the rice oil rotation area. |
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