Theoretical Substantiation of the Design of a Working Depth Adjustment Mechanism for the Opener of a Seeding Unit

Abstract

The aim of the study is the theoretical substantiation of the design of a mechanism for adjusting the working depth of the opener of a seeding unit, which ensures increased accuracy and reproducibility of the preset seeding depth under various soil conditions. The research is focused on eliminating the shortcomings of traditional adjustment mechanisms associated with high labor intensity of settings, the presence of clearances in joints, and the dependence of the result on the operator’s subjective actions. Particular attention is paid to reducing the influence of soil surface microrelief irregularities on the stability of the opener working depth.

The article considers a seeding unit design with a gauge skid and an eccentric cam with indexed fixed positions, which provides discrete and rigidly fixed adjustment of the opener working depth. A kinematic model of the adjustment mechanism is proposed, on the basis of which analytical relationships between the working depth of the opener and the geometric parameters of the eccentric cam are obtained. It is shown that each indexed position of the cam corresponds to a unique value of the working depth, which ensures its reproducibility on all seeding units of the machine. To evaluate the influence of soil surface irregularities, a simplified dynamic model of the vertical motion of the opener with a gauge skid is developed in the form of a single-mass system with elastic and damping properties. On the basis of this model, a frequency analysis is performed and the amplitude–frequency characteristic of the system is obtained, allowing the assessment of the influence of stiffness and damping parameters on the stability of the working depth.

The results of the theoretical study have shown that the use of an eccentric indexed mechanism significantly reduces the time and labor required for adjusting seeding units and ensures high repeatability of setting the opener working depth. It is established that the stability of seeding depth is determined not only by the geometry of the adjustment mechanism but also by the dynamic characteristics of the “opener – gauge skid – soil” system. A rational selection of the gauge skid parameters and the damping properties of the system makes it possible to reduce the amplitude of vertical oscillations of the opener and to improve the uniformity of seed placement. The obtained results can be used in the design of new and modernization of existing seeding units of various types and serve as a basis for further experimental research.