The hydraulic cylinder, as the actuator in the hydraulic system, can easily achieve reciprocating linear motion. Therefore, it is widely used in agricultural machinery to realize the action of the mechanism. Due to the harsh working environment of agricultural machinery, it often leads to the failure of the hydraulic system, and for the hydraulic cylinder, the leakage of oil is the most common failure.
1 External leakage of hydraulic cylinder
External leakage refers to the oil leakage from the seal is not strict to the atmosphere outside the hydraulic cylinder, the most common external leakage has the following 3 places:
1.1 The sealing parts of the hydraulic cylinder liner and cylinder head (or guide sleeve) leak oil. The cylinder liner and the cylinder head of the hydraulic cylinder of agricultural machinery are mostly connected by threads, and then the type 0 sealing ring is added at the thread port. When oil leakage occurs here, the type 0 ring is mostly damaged, and the problem can be solved by replacing the appropriate new type 0 ring.
1.2 The relative movement of the piston rod and the guide sleeve is leaking outwards. Usually the piston rod seal here uses 0 ring or Y ring, because the piston rod and the seal is dry friction, friction resistance is large, often aggravate the wear of the seal; In addition, the extended surface of the piston rod is in contact with various impurities, which often causes scars, grooves, pitting or rust stains on the surface of the piston rod, aggravating the wear of the seal ring, and even cutting the seal ring. Therefore, when oil leakage occurs, in addition to replacing the sealing ring, the piston rod should also be checked for damage. If the piston rod is damaged, it can be cleaned with gasoline, and after drying, apply metal glue to the damage, and then move the piston rod oil seal back and forth on the piston rod to scrape off the excess glue, and then put into use after the glue is completely cured. If the guide sleeve is worn, it can be replaced with a slightly smaller guide sleeve. Experience shows that after the installation of the new guide sleeve, if the oil seal can be used for about 1 month, the inner diameter of the new guide sleeve should be reduced by 0.15mm than the original, so that the new guide sleeve can correctly install the seal ring to make up for the wear gap, so as to better seal the role.
2 Internal leakage of hydraulic cylinder
Hydraulic cylinder leakage refers to the leakage of oil from the high pressure chamber to the low pressure chamber through various gaps in the hydraulic cylinder. Internal leakage is more difficult to detect, and can only be judged by system operation conditions, such as insufficient thrust, reduced speed, unstable operation, or high oil temperature rise. It is better if it can be judged by regular measurement procedures. Hydraulic cylinder leakage generally has the following two places:
2.1 Static seal between piston rod and piston. The fixed connection between the hydraulic cylinder piston and the piston rod of agricultural machinery is mostly in the form of locking nut, and the sealing surface of both is equipped with 0-shaped rings. Usually, if the installation is correct and reliable, oil leakage can be effectively avoided here.
2.2 The dynamic sealing part between the inner wall of the cylinder liner and the piston, which is the main way of internal leakage. The cause of leakage here is:
① The wear of the inner wall of the cylinder liner and the piston causes the gap to increase, resulting in high and low pressure cavity interworking.
② The sealing ring on the piston (Y-type sealing ring is more) is worn, scratched and aging, resulting in a loose seal.
③ When the piston rod is improperly forced or the gap between the guide sleeve and the piston rod is large, the piston is biased to a certain side of the cylinder wall, and the tilt or partial wear of the piston causes internal leakage.