荔枝收获切割器果梗锯切功耗影响因素试验

为合理设计荔枝收获装备切割部件,获得理想荔枝果、树分离效果,在确定以回转锯切为切割方式的基础上,搭建果梗锯切功耗测定平台并进行荔枝果梗锯切试验。研究了锯齿前面斜磨角、锯片齿数、进锯速度、锯切转速对果梗锯切实时功耗的影响;以单因素试验结果为依据,选定三因素三水平进行正交试验,得到各因素对锯切实时功耗峰值影响的主次顺序为锯切转速、进锯速度、齿前面斜磨角、锯片齿数;同时得到在给定因素水平下的最佳组合是采用25°齿前面斜磨锯片、进锯速度为60 mm/min、锯切转速为550 r/min,此时电机瞬时功耗峰值最小为0.488 J。该研究为荔枝机械化收获装备切割部件的设计提供了参考。

Experiment on influencing factors of power consumption for sawing stem in cutting device of litchi harvester

Abstract: There are 3 main forms of cutter commonly assembled into agricultural harvesters, which are reciprocating cutter, cutter disks and saw blade. Given the fact that the litchi fruits grow in bunches and hang from the bearing shoots, as well as the bionic principle that the cutting-section of the litchi stem must be smooth and unsplit when litchi is picked, it is more suitable to choose the saw blade when the litchi harvester is designed. However, directly using standardized industrial saw blade could not be best in agronomy. Meanwhile, it is indispensable to focus on the studies on the relationship between structure parameters and power consumption of main motor as well as the relationship between motion parameters and power consumption of main motor. After all, the harvester works in outdoor environment. Applying the principles of wood processing and cutting tool technology, the structure and motion parameters were experimentally studied. The experiment was carried out using an universal testing machine, with a 3-jaw chuck mounted on the upper pressure head and the saw blade - motor system installed at the bottom platform. The motor speed, whose current value was real-time measured during the sawing process by a communication multimeter, was controlled by a speed governor. The samples were taken from the Germplasm Collections of Tropical and Subtropical Fruit Species, South China Agricultural University. It was assured that these samples had a length of about 10 mm and a diameter between 5-6 mm, and the branches were straight, with no divergence and free of diseases. Each group of test was conducted on the same stem so as to lower the impact of the diameter and moisture content between different samples. Experiments were designed by using the single-factor method in the study, and 9 kinds of circular saw blades were trial-manufactured, with the combination of 3 kinds of teeth numbers and 3 kinds of face bevel angles. Besides, 3 rotation speed levels were set respectively. There existed a critical rotation speed in the process of stem sawing. If operating speed was lower than the critical speed, stem fibers would not be cut off thoroughly and even cause stem splitting. Therefore, the critical speed of each saw blade was measured by preliminary tests. Finally, a 250 r/min rotation speed was set as the lowest level over the whole experimental process. After all, the results showed that: 1) The instantaneous power consumption of the sawing motor was significantly affected by the face bevel angle (P<0.05), and the rotation speed (P<0.01), but was not affected by the number of teeth; 2) The instantaneous power consumption of the sawing motor increased with the rise of the feeding speed, while decreased with the rise of the face bevel angle and rotation speed. Based on the single-factor experiment, the L9(34) orthogonal experiment was carried out. The results showed that: 1) The order from high to low for the effect of each factor on instantaneous power consumption peak was rotation speed, feeding speed, face bevel angle and number of teeth; 2) At given levels, the lowest instantaneous power consumption of the cutting motor was 0.488 J, which was detected under the optimal combination of parameters, i.e. the face bevel angle was 25°, the feeding speed was 60 mm/min, and the rotation speed was 550 r/min. The study may provide theoretical basis for the design of cutting device of litchi harvester.