Industry news|2022-03-10| admin
Planetary gearbox is a relatively precise gearbox. Different from the worm gear structure, it uses planetary gears and sun gears to decelerate, which can control the precision within a very small range. However, it is a very troublesome thing for the planetary gearbox to leak oil due to improper installation or improper use during use, so today we will tell you how to check the oil leakage of the planetary gearbox.
O-rings are widely used in the static seal design of gearboxs. A static seal is one in which there is no relative motion between two adjacent surfaces. If the size of the O-ring is correct and the material of the O-ring is properly selected, the sealing pressure of the O-ring can reach 100MPa, which can achieve zero leakage.
1. The main reason for static seal oil leakage.
(1) O-ring quality problems: O-rings have poor elasticity and surface defects.
(2) The trimming of the O-ring is caused by assembly; or the tightening torque of the connecting bolt is insufficient.
(3) Parts processing quality problems.
2. Treatment measures.
(1) Select qualified O-rings produced by regular manufacturers.
(2) Make sure that the connecting bolts should have sufficient strength to avoid gaps on the joint surface, causing the O-ring to be squeezed out by pressure and leaking oil.
O-ring seal design:
Guide cone requirements: The guide cone corners must be designed during installation to avoid O-ring surface extrusion and sealing failure. The guide cone should be between 15° and 20°. See standard GB/T3452.1-2005 O-ring seal groove size and tolerance for guide cone width.
Groove design: Groove design includes determining the shape, size, accuracy and surface roughness of the groove.
Design principles: easy to process, reasonable size, easy to guarantee accuracy. A common groove type is a rectangular groove. This groove is easy to machine, and it is convenient to ensure the necessary compression of the O-ring. In addition to rectangular grooves, there are also V-shaped, semicircular, dovetail, triangular and other forms of grooves.
(3) Seal of reciprocating motion.
In hydraulic systems, reciprocating seals are one of the most common sealing requirements. A reciprocating seal should be used between the piston in the gearbox brake and the cylinder block to limit the axial leakage of hydraulic oil. When used for reciprocating sealing, the pre-sealing effect of the O-ring is the same as that of static sealing. Due to the elasticity of the O-ring itself, it has the ability to automatically compensate after wear.
The most common type of failure is O-ring twist. Twist is the phenomenon in which the O-ring twists around its surroundings. There are many reasons for twisting damage, the most important of which are the machining accuracy of the seal (including clearance, coaxiality and roughness), the coaxiality deviation of the sealing groove, the sealing height and the uneven diameter of the O-ring section.