The schematic diagram of the eccentric gear non-circular gear planetary system transplanting mechanism is shown in Figure 1. The relative motion track of the seedling needle tip (i.e. the track when the transplanter is not moving forward) is a “waist shaped” track, also known as a static track.
The transmission part of the eccentric gear noncircular gear planetary system transplanting mechanism is composed of three congruent eccentric gears (1, 4, 6) and two congruent noncircular gears (2, 5). The pitch curve perimeter of the eccentric gear and the non-circular gear is equal, the rotation centers of the two planetary gears (1 and 6) are O1 and O2 respectively, the rotation center of the planet carrier 3 is O, the rotation centers of the two non-circular gears are M1 and M2 respectively, the non-circular gears mesh with the eccentric gear respectively, the initial installation phase angle of the five gears is the same, and the rotation center of the gears is on the same straight line, As shown in Figure 1a. During operation, the eccentric gear 4 (referred to as the central gear or sun gear for short) is fixed, and the planet carrier 3 rotates clockwise around the rotation center O driven by the central shaft. The conjugate non-circular gear 5 meshed with the sun gear 4 and the planet gear 6 rotates with the planet carrier 3 (taking one side gear structure as an example). Because the eccentric gear and the conjugate non-circular gear mesh, Cause the non-uniform change of transmission ratio, so that the planetary gear rotates non-uniform relative to the planetary carrier. The planetary gear makes a circular motion around the rotation center o with the planetary carrier 3, and makes a non-uniform rotation with respect to the planetary carrier 3. The absolute motion of the planetary gear is a composite motion of the two motions. A pair of planting arms and planetary gears consolidated by keys, planetary axles and planetary gears make the same compound motion. Under the action of compound motion, the seedling needle moves according to the required attitude. By selecting appropriate structural parameters, the working track meeting the requirements of seedling transplanting can be obtained.
1. Eccentric gear non-circular gear pitch curve model
The meshing of eccentric gear and its conjugate non-circular gear to realize variable speed transmission is the key to the formation of “waist shaped” static track of seedling needle. In Fig. 2, the pitch radius of eccentric gear 1 is r, the eccentricity is e = lo1o, the eccentricity k = E / R, and the center distance between the two gears is a. R1 = lop, R2 = lpm1, a = lom1, eccentric gear 1 rotates counterclockwise φ The non-circular gear 2 turns clockwise when the angle is φ 21. Set the coordinate system xoy as shown in the figure, and the meshing point P (R1) on the curve of gear 1, φ） Meet:
The pitch curve equation of non-circular gear 2 is obtained as follows:
When φ When it changes from 0 to 2 π, φ 21 varies accordingly with 0 ~ – 2 π.
1. eccentric gear 2. Non-circular gear
1. eccentric gear 2. Non-circular gear
2. Curve closure conditions and center distance
Since the pitch curve of conjugate noncircular gear is closed, the number of teeth of conjugate noncircular gear and eccentric gear is the same, and the circumference of the pitch curve is equal to 2 π R. therefore, the conditions for closing the pitch curve are as follows:
According to the formula, the center distance a depends on the pitch radius R and eccentricity K of the eccentric gear.