ПРЕДПОСЕВНАЯ СЕМЯН PRESOWING TREATMENT OF SEEDS Design and Experimental Study on Seed Metering Device of Peanut Plot Seeder

. The seed metering device is the key working part of the peanut planter and is placed above the bottom of the seed box or above the opener. The essence of the seed metering process is the eﬀ ect of the seed meter on the seed, converting the seed from the population into an individual, and converting it into a uniform seed stream or a continuous single seed. The seeding method and quality of the seeding machine depend mainly on the seed metering device. Aiming at the shortage of re-broadcasting rate and missed-out rate during sowing, the diﬀ erent parameters of the air-suction metering device were analyzed, and the seeding performance of the seeding device was tested to obtain the primary and secondary factors aﬀ ecting the performance of the seeding device, and the quality of seeding was improved.

Sowing and harvesting is the most time-consuming part of the peanut production process. The outstanding problem at this stage is that the variety of peanut seeding machinery, performance and quality can not fully meet the requirements [4]. The development of planters has accelerated the pace of mechanized agricultural production, liberated the labor force and promoted economic devel- ПРЕДПОСЕВНАЯ ОБРАБОТКА СЕМЯН PRESOWING TREATMENT OF SEEDS opment. At present, the mechanization level of peanut planters in China is still different from that in developed countries. Therefore, the development of efficient peanut seeding machinery is becoming more and more important. Seeding largely determines the quality of the sowing, and the key component of the planter is the design of the seed meter. As an important form of pneumatic precision seed metering device, the air suction type metering device mainly includes horizontal disc type, vertical disc type and combined suction type. At present, the use of peanut seeding devices in China is less used for air suction type seeding devices, and foreign countries have made great progress. The air suction type metering device has strict requirements on seed size, good versatility, high seeding precision, and is suitable for high speed operation. In China, for high-speed operation, the influence of the vacuum degree of the suction chamber of the metering device, the diameter of the suction hole, the rotation speed of the seeding tray, etc., cannot be well designed to design an effective air suction metering device for Precision seeding. Therefore, this paper focuses on the problem and conducts experimental research on the technical parameters of its key components.
1 Theoretical analysis of the seed meter

Establishment of vacuum degree of air suction type metering device
The performance of the metering device depends on the suction vacuum degree. The greater the degree of vacuum, the stronger the ability of the suction hole to adsorb the seed, and it is not easy to cause leakage. However, if the degree of vacuum is too large, the possibility of adsorbing multiple seeds by one suction hole is increased, and replay is generated. In the actual seeding process, the seed meter is affected by the external factors of the seed and the stability coefficient of the work. The maximum value of the vacuum required for the vacuum chamber of the air suction meter is calculated [5].
, (1) where: H cmax -the maximum vacuum of the suction chamber, kPa; d -row of seed hole diameter, cm; c -the distance between the center of gravity of the seed and the suction tray, cm; m -the quality of a seed, kg; v -the linear velocity at the center of the suction hole of the seed disc, m/s; R -the radius of rotation of the suction hole of the seed disc, m; g -gravity acceleration, m/s 2 ; λ -a comprehensive friction coefficient of friction, λ = (6~10) tanα, α is the natural angle of repose of the seed; k 1 -a species reliability coefficient, taking 1.8~2.0, when the seed 1000-grain weight is small and the shape is approximately spherical, take a small value; k 2 -the external condition coefficient, which is 1.6~2.0. When the seed dry grain is large, take a large value.
It can be known from formula (1) that the maximum vacuum degree required for the air suction type seed meter and the diameter of the suction hole and the line speed level at the center of the suction hole are physically special.
For different seeds, there is an optimum vacuum range. When the vacuum is reduced, the leak rate will increase, and when the vacuum is too large, the reciprocity will increase. In actual work, due to the influence of pipeline pressure loss and mechanical vibration between the fan and the metering device, the maximum degree of vacuum is taken during design.

Determination of seed force of air suction metering device
When the seed moves on the seed ring, it will exert a force. When the seed meter works, if the friction is neglected, the seed is mainly subjected to the force of gravity G, the adsorption force F, the inertial force J and the support force of the suction hole to the seed. The role. According to the literature [6], the formula of the adsorption force F and the inertial force J is ; (2) were: p a -atmospheric pressure, Pa; p 1 -vacuum chamber pressure, Pa; d -sucking hole diameter, m; m -seed quality, kg; R -the distance from the center of gravity of the seed to the center of the seed tray, m; ω -the angular velocity of the seeding ring, rad/s. In order for the suction hole to suck the seed, the following conditions should be met. h -T to the distance of the suction ring, m.

metering device housing
The seed meter housing is used to closely cooperate with the seeding ring to form a vacuum chamber, and the device has a device such as a friction reducing device, a sealing device and an air suction pipe interface. The casing and the seed ring are sealed with a wear-reducing seal to prevent air leakage. The suction pipe joint is tightly connected to the casing, and is closely connected with the fan by a rubber pipe to provide vacuum pressure to the seed meter. A pulley is arranged in a section of the outer casing, and is driven by a gearbox to provide power to drive the rotation of the seeding ring for seeding.

type of hole movement speed
In order to ensure the quality of the seeding, the re- The seed filling process and the accuracy of seeding are determined by the line speed at the hole. If the line speed is too high, when the seed chamber passes through the hole, the time for the seed to enter the hole is shortened, and the seed is not filled in time. Into the type of hole in the seed ring, it will cause leakage. For the filling condition of the seed, from the kinematic point of view, the seed should be filled into the pore in a limited time, and the excess seed can be removed by the seed cleaning device to ensure the precision of the seeding. Depending on the line speed of the hole, the seed enters the hole by gravity. Therefore, according to the free fall motion equation, the ultimate speed of peanut seeds during the filling process can be obtained.
If there is no device that assists in increasing the filling ability, when the line speed exceeds the limit speed of the hole, the filling ability is lowered. In the actual process, the seed meter is driven by the ground wheel, and the ground wheel is powered by the tractor's traction, so the forward speed of the tractor affects the linear speed of the hole. Through the kinematics formula, the forward speed of the tractor is directly proportional to the linear velocity of the hole. The diameter of the seeding ring and the number of holes in the seeding ring affect the speed of the hole. When the linear velocity of the hole is reduced, the diameter of the seed ring and the number of the hole are reduced, the distance between the holes is shortened, and interference occurs between the seeds when the seed is filled, and the diameter of the larger seed ring can be Increasing the irrigating distance and filling time greatly improves the ability to replenish.
2 Structure design of the seed meter 2.1 Structure and principle of the seed meter The air suction type seed meter is mainly composed of a seeding device, a vacuum chamber, an air suction pipe, a seed cleaning device, a seed room and the like. The seed meter uses a fan to generate a negative pressure for seeding, has a good filling ability, and can operate at a high speed (Fig. 1).
The vacuum chamber of the metering device is connected to the fan suction port to generate a negative pressure in the vacuum chamber.
The seed chamber is connected with the seed ring, relies on the negative pressure generated inside, sucks the seed through the small hole, and uses the transmission system to rotate along with the seed ring. When the seed is transferred out of the vacuum chamber, it is not subjected to negative pressure. The weight or the pusher drops into the seed groove. The seed cleaning device in the upper part of the seed ring removes excess seeds from the suction holes.

Design of the seed ring
The seeding ring is the core component of the air suction type metering device, and determining the reasonable structural parameters of the seeding ring is an important condition for ensuring the quality of the seeding. The size of the seed hole affects the performance of the seed meter. As the area of the pore increases, the pressure required for the adsorption of the seed is reduced, the degree of vacuum is reduced, and the seeding performance is gradually increased. When the suction hole is increased to a certain extent, the gas leakage is generated due to the excessive pore size. Decrease, the seeding performance is reduced. The suction hole is too small, and the adsorption force on the seed is insufficient, which may cause leakage. Therefore, the size of the suction hole should be designed according to the seed size (Fig. 2).
The number of seed holes also affects the performance of the seed meter. In the case that the number of the seeding holes does not affect the seed filling, seeding, and this parameter is increased as much as possible. As the number of seeding holes increases, the rotation speed of the seeding ring decreases, the filling time is longer, and the seeding performance is gradually increased. As the number of seeding holes increases, the distance between the two holes gradually decreases. After the number of seed holes is increased to a certain extent, the two suction holes cause interference when the seeds are sucked, which causes the seeds