Optimization Design and Simulation for Pricking Mechanism of Off-Centre Embedded Seed Metering Device

In order to improve the quality of pricking hole and reduce throwing soil as merering the field, this paper presents a method of off-centre embedded pricking mechanism operation. Established a mathematical model of pricking hole mechanism, preparation of computer aided analysis platform by using VB software, and the simulation effects are buried and the effects of the eccentricity, rocker arm length, pricking hole connected with the handle, the swing rod length, length the pricking hole angle and swing arm and the connecting rod handle parameters related to the initial position. One group of optimization parameters: radial eccentricity 50mm, pricking hole arm length 220 mm, connecting handle length 135 mm, pendulum length 120 mm, pricking hole arm and the connecting handle 55 degree angle, pendulum hinge rotation center end and rocker wire length 130 mm, connecting with the horizontal angle of 5 degrees. Through the verification, pricking hole mechanism after optimization has been a significant improvement in reducing throwed soil problems and improve the pricking quality.


Introduction
At present, no-tillage planter was parted into mechanical and pneumatic according to the operation mode.Because ditching devices are assembled in the front of metering device in traditional tools.High resistance operation that sources from the interaction between ditching devices and soil will increase the traction energy consumption and equipment vibration (Yuexia, 2003), moreover, the metering pipeline of seed-outlet often clogs up with soil.These problems always affect the seeding quality, thus impediment the development of seed metering mechanism and the improvement of operation mode.This paper aimed at above problems and based on the principle of crank-rocker mechanism, put forward a type of pricking mechanism with off-centre embedded seed metering device operation mode (Fei et al., 2016;Hongxin, 2017;Jinwu et al., 2015).Optimize the pricking motion trace by using VB programming software.Furthermore, improve structure parameters and installation angle of pricking mechanism, and verify its applicability to overcome the main disadvantages of the traditional seed metering device, that within high resistance and large power, and solve the phenomenon of soil plugging.

Mechanism Composition
Its working principle is: when it works, the power output connecting hole on the off-centre concave hole wheel is a power input, and the off-centre concave hole wheel driven by rotating principal axis eccentricity.Inside the off-centre concave hole wheel, embed a non-circular concave slideway.The return spring loaded in the piston chamber of pricking arm shell.Slideway and spring both drives the piston whose end loads in bearing to take linear recipro-cating motion in the piston chamber, which is in the pricking arm shell.At the same time, the off-centre concave hole wheel drives the pricking arm shell to take reciprocating rotation; when the pricking arm shell is rotated close to the ground, the piston out from the piston chamber into the soil and prick a hole under the function of the non-circular concave slideway.When the piston moves upward under the function of return spring which is compressed, seeds are thrown out from the seed metering chamber of the pricking arm to the

Establish vector equation of mechanism
OA + OB = OC + CB Transform as analytic form: Simplify Equations ( 2): For formula: Set the intersection angle between the AC line and the x axis as β, then.
OA rod centroid coordinate: x 1 = L 10 cosα 1 y 1 = L 10 sinα 1 (5) The coordinate of AB rod centroid: From the formula above: The coordinate of BC rod centroid: For formula: L 10 : The distance from OA centroid to O, mm; L 2A : The distance from AB centroid to A, mm; L 3C : The distance from BC centroid to C, mm.

The Displacement Equation of Pricking Cusp
Relative motion displacement of pricking cusp D: For formula: L AD : The length of pricking limb AD, mm; α 2 : The angle between connecting handle AB and x axis, ( o ); α AD : The angle between pricking limb AD and x axis, ( o ).

L 1 :
The length of Rocker OA, mm; L 2 : The length of connecting handle AB, mm; L 3 : The length of oscillationg bar BC, mm; α 1 : The rotation angle of Rocker OA, ( o ); α 2 : The intersection angle of connecting handle AB and x axis, ( o ); α 3 : The intersection angle of oscillationg bar BC and level, ( o ); α 1 : The palstance of Rocker AB, rad/s.