The main function of the gearbox is supporting the drive shaft to ensure that the center distance between the axis and parallel, and to ensure tractor gearbox components connected with other parts of the correct installation.
As the gray cast iron has good casting and machinability, and good wear resistance and vibration damping, and low prices, it's rough cabinet usually cast iron. China 75 tractor box material selection HT150. Plane before and after the taper angle is very small. Margin on the plane for the 5mm, flat margin around 3.2 to 3.6mm, the maximum margin is 4.5mm, 80mm diameter bearings except margin to 10mm diameter, all bearing bore diameter of the margin for the 9mm. Hole and splash gear fork shaft 30mm diameter holes are not casting out the following. Not specify the fillet radius of 3 - 5mm, non-specified taper angle of 1 degree to 1.3 degrees. Sub-surface fault movement allowed to 1mm, casting wall thickness tolerance of 2mm. Casting non-processed surface, deep hole to allow a single 2mm, the maximum size to 5mm, the total number of not more than 10. All the ribs on the deep hole of not more than 3mm. Casting process allowed the surface within a depth of allowances of two-thirds of casting defects. Beyond the scope of casting defects can cast iron welding repair welding repair the technological procedure.
Technological features from the structure point of view, it is a thin-walled shell cavity-shaped parts, complex shapes, casting difficulties, poor stiffness, deformation, high precision machining. It joins the outer surface of the plane needs more processing, supporting distribution of holes in front, back surface, in order to better meet the processing requirements, particularly in processing the orientation plane for the four auxiliary reference, in addition to supporting hole outside, in the a series of threaded holes connected surface.
Tractor gearbox main technical requirements are as follows: bearing bore size and geometry precision accuracy. It is used to install bearings, and its size and geometry of the error caused by errors and holes with bad bearings, so bearing raceway deformation, rotary precision bearing down and working temperature. The diameter tolerance level for the IT7, does not make special provisions for the shape of tolerance, its value should be in the hole tolerance range. Bearing hole pitch tolerance. It consists of the standard deviation of gear center distance requirements. It affects Gears backlash, caused by excessive drive when the impact of non-face, over an hour can not guarantee the normal lubrication of gears and even put away transmission stuck. Tractor Transmission pore center distance tolerance of 0.12mm about IT9 level.
This article is from our Dandong Foundry's Tractor Gearbox made in China.
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