Research On Pre-compression Technology For High-density Large Square Bale Balers

As the basis for the development of animal husbandry,forage is a valuable natural resource.In recent years,with the rapid development of China’s livestock industry,the problem of forage shortage is also increasingly prominent,the main reason for this problem is the low degree of forage harvesting mechanization,because forage has loose physical characteristics,in the transportation and harvesting process to face high costs,occupy a large s Nce and other problems,reducing the profit margin,can not form a large-scale production to supply the development of animal husbandry.The use of large square bale baler to compress forage into high-density bales has become an effective way to solve the current forage harvesting problems.The pre-compression mechanism is one of the core mechanisms of the big square baler,and its operation effect directly affects the performance of the big square baler.Most of the domestic big square balers pre-compression mechanism is to use the small fork with large fork operation,which generally have problems such as complex structure,large power consumption,low operation efficiency and unreasonable movement trajectory of forks.In view of the above problems,this thesis designs a pre-compression mechanism suitable for the larger square baler,which realizes the pre-compression and throwing of forage by using a single shift fork operation.The rationality of the design of the pre-compression mechanism is verified by motion analysis,motion simulation and field experiment.The main research contents are as follows:(1)Because of the problems of the pre-compression mechanism,according to the working principle of the big square baler and the actual operation demand,a compression fork based on the crank rocker mechanism with a single fork and double mode switching operation is developed,which can realize the pre-compression and throwing operation of the forage by cooperating with the mode switching device,simplifying the pre-compression mechanism and providing theoretical support for the design of the pre-compression mechanism of the big square baler.(2)To understand the kinematic relationship between the rods of the compression fork of the pre-compression mechanism,the kinematic analysis was carried out by using the analytical method,and the model of the position,velocity and acceleration changes of the compression fork in the process of grass compression and grass throwing was established,and the coordinate equations of the endpoints of the fork teeth in the process of grass compression and grass throwing were constructed according to the cooperation relationship of the rods of the compression fork.(3)The three-dimensional model of the precompression mechanism was established by UG software,and the interference situation was analyzed after assembly to determine the accuracy of the model.ADAMS simulation software is used to simulate the kinematics of the process of pressing grass and throwing grass with the compression fork,and the movement track,velocity and acceleration curves of the precompression mechanism are obtained.Through the analysis of the motion simulation results,the motion law of the precompression mechanism is obtained,and the rationality of the design of the precompression mechanism is verified.(4)To ensure the safety and stability of the pre-compression mechanism,ANSYS software was used to analyze the static stress of the compression fork and the metering plate of the pre-compression mechanism,to check their strength and explore the maximum stress-strain occurrence point;through the modal analysis,the inherent frequency and vibration Nttern of the compression fork were obtained,and the resonance phenomenon was avoided by calculating the external excitation frequency of the large square baler for com Nrison.(5)The pre-compression mechanism is installed in the prototype for field tests.Taking the bale density and regular bale rate as the response index,selecting the forward speed of the machine,the speed of the driving rod and the preset pressure of the metering plate as the test factors,the box Behnken central combination test method is used to design the three-factor and three-level response surface test,analyze and process the test results,and study the influence law of various factors on the response index.The test results show that the best combination scheme of various factors is:the operation speed is6.65km/h,the driving rod speed is 51.8r/min,the preset pressure value is 1.5k N,and the bale density is 254.8kg/m~3with 98.4%of regular bale rate under this combination.The result of the verification test is close to the predicted value,which is in line with the industry standard of square bale baler and proves that the design of the pre-compression mechanism is reasonable.