For sowing of corn precision seeders are used, one of the most complex and responsible details of which is a sowing machine. The purpose of this study is to substantiate the rational design and parameters of the dosing elements and the «superfluous» seeds seeder of the vacuum sowing device, which ensure an even increase in the supply of corn seeds to the furrow. A vacuum sowing machine is proposed for use in production, in which elongated suction holes are made on the sowing disk in such a way that their long axes are oriented to a radial direction at α angle. In addition, in the design of the sowing apparatus, the thickness of the first three projections of seeder for «superfluous» seeds is proposed to be made stepwise. Experiments carried out on the matrix of the orthogonal plan of the second order showed that the following parameters and tuning regimes of such a machine are rational for sowing corn seeds: width of suction holes tдэ = 3 mm; the smallest slot width in the vacuum chamber liner t = 3,0...3,5 mm; exhaustion in the vacuum chamber H = 5 kPa; thickness of the input edge of the working part of the “superfluous” seeds seeder h = 1,5 mm; angle of deviation of the longitudinal axes of the suction holes of the sowing disc from the radial direction α = 12...15 deg. Under laboratory conditions the machine provided the frequency of single seed feeds p1 = 99,0...99,5 %, which is close to the technological optimum. At the same time, the quality of seed dosing remained stable even with a significant increase in the angular velocity of the sowing disk.

Introduction. The study of working processes of row crop seeders, their improvement, increase in productivity and (or) quality of work are topical agroengineering tasks. Aim of the Article. The article deals with developing proposals to optimize the design of vacuum mechanisms for row crop seeders based on the analysis of the laws of the process of dosing sunflower and corn seeds by suction holes of the seed discs. Materials and Methods. The operation characteristics of the vacuum seeding mechanism depend on the diameter of the suction holes and the rarefaction in the vacuum chamber. Hypothetically, it can be assumed that with a constant calculated value of the suction force, it is possible to choose a ratio of these characteristics in which the number of skips and group feeding of seeds will not exceed the tolerance of agro-requirements. Verification of this assumption was carried out experimentally in laboratory conditions. Results. There were found polynomials describing with a fair degree of accuracy the dependence of formation of group feedings of sunflower and corn seeds on the diameter of suction holes. Discussion and Conclusion. The frequency of group feeding of the seeds less than 0.05% will be achieved with suction hole diameters of about 0.8 mm for sunflower and about 1.9 mm for corn. In this case, the values of rarefaction in the vacuum chamber must be 31–56 kPa that exceeds the capabilities of the pneumatic systems of existing row seeders. Accordingly, the modernization of the seeding mechanisms of vacuum row seeders by reducing the diameter of the suction holes should be accompanied by additional improvements aimed at increasing their gripping ability.

The aim of the study was to analyze the regularities of the influence of the diameter of the suction holes and the vacuum depth in the vacuum chamber of the precision seeding apparatus on the probability of the formation of group seed feeds. The study was of an experimental nature and was conducted with a specialized stand in laboratory conditions. The results showed that an increase in the diameter of the suction holes (at a constant value of the suction force) led to an increase in the frequency of formation of group seed feeds. Moreover, when the values of this factor varied from 4 to 5 mm (when sowing maize), practically no changes in the seed supply were observed. At the same time, a decrease in the diameter of the holes of the seeding disc to values less than 4 mm led to a sharp decrease in the likelihood of the formation of double feeds, and at d > 5 mm, the frequency of group feeds increased rapidly. This can be explained by two possible reasons: the error of the experiment, which led to a distortion of the result, or the regularity associated with the fact that in this interval (4...5 mm) the change in the parameter d is compensated by the variability of the main sizes of the sown seeds. In the first case, the dependence of the formation of the frequency of group feeds on the diameter of the suction holes is linear; in the second, it is cubic. The analysis of the obtained dependences shows that with a diameter of the suction holes of 1,0...2,9 mm, it is possible to ensure the operation of the vacuum seeding apparatus with a sufficiently high quality (practically without the formation of zero and group seed feeds) by excluding the reflector from the apparatus design. However, in this case, it is necessary to verify the reliability of each of the obtained dependences, since in the first case the required vacuum in the vacuum chamber is about 113 kPa, and in the second “only” 13.5 kPa.

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