Research On The Precision Design Of The Knotter Of Square Baler

One of the key technologies for the collection of crop straw and forage is the automatic tying technique of Square Baler.The knotter is the core component of the square baling machine,which directly affects the performance index of the baling machine.Because of the complexity of the spatial structure of the knotter,the high precision of the curved surface and the difficulty of the manufacturing of the key parts,the knotters in our country are generally dependent on the import.Therefore,it is of important theoretical and engineering application value to study the working principle of the knotter and to carry out the precision design.The main contents of this paper are as follows:(1)The reverse engineering technology is used to reconstruct the key parts of the Dknotter and establish the assembly model of the knotter.The ADAMS virtual prototyping technology is applied to analyze the motion characteristics and motion timing of each part of the knotting machine,revealing the working process and working principle of the Dknotter.(2)The analysis of the space structure is carried out on the complex structure of the knotter cam gear and knotter frame.And the reference coordinate system is set up to determine the spatial angle relationship between the 5 different axial holes of the frame in the same coordinate system.A mathematical model of cam contour surface is established,which makes the roller rotate with sine acceleration rule,so as to reduce the impact action of knotter tongue.Through the oil injection pressure test,the tightness of the matching of 5 shaft holes on the knotter is determined.The precision design of 5 shaft holes and key working faces on the knotter is also carried out.(3)According to impact dynamic load theory,and the characteristics of the knotter gear pair transmission accuracy and stability of the transmission requirements are relatively high,application the probability theory for equal effect accuracy synthesis,the outer gear of knotter cam gear and pinion of knotter hook select from 8 grade precision,and modification of teeth top along the normal direction of the measurement of 50.04 μm for pinion of knotter hook.And the inner gear of knotter cam gear and pinion of knotter hook select from 8 grade precision,and modification of teeth top along the normal direction of the measurement of 73.88 μm for pinion of knotter hook.This way can control the additional impact dynamic load less than 0.085 times of the calculated load.It is effective to reduce the impact load and reduce the vibration,so that the transmission is more stable and the transmission precision is improved.(4)The traditional calculation of fatigue strength and finite element analysis of two methods of calculation,strength analysis of the design of “the outer gear of knotter cam gear and pinion of knotter hook” and “the inner gear of knotter cam gear and pinion of knotter hook”.Finally,the fatigue strength of two pairs of bevel gears is all qualified.