Excavator Hydraulic Cylinder
1.Excavator series of double acting single bucket type hydraulic cylinder is used as reciprocating linear motion actuator in excavator hydraulic system. PC series hydraulic cylinder is a kind of excavator hydraulic cylinder product specially researched and manufactured by Komatsu and Kayaba technology of Japan. It has the characteristics of high working pressure, reliable performance, convenient installation and disassembly, easy maintenance and buffer device. All seals of this series of hydraulic cylinder are imported seals. The surface of piston rod is hardened and plated with hard chromium, and the roughness after polishing can reach Ra0.08, The cylinder head absorption Kayaba technology is specially developed according to the working conditions of excavators. The material is ductile iron, and the two ends are buffered by floating buffer. It has good cushioning performance. It is mainly used for loose PC series hydraulic excavators and other hydraulic excavators produced at home and abroad.
2. Design features of excavator hydraulic cylinder:
A.The piston rod is made of precision ground high-strength alloy steel. The surface of the piston rod is quenched with medium frequency to the maximum hardness of HRC62. The piston rod surface is plated with hard inscription and polished to provide an impact resistant surface to prevent the piston from pulling and bumping, Extended seal life has a safety factor of at least 5 times the tensile strength at rated pressure at the minimum cross section of the piston rod and piston assembly.
B. The guide sleeve is made of ductile iron according to the excavation site. It is made of nodular cast iron and has high wear resistance. It is equipped with sliding bearing imported from Japan. The maximum bearing pressure of the bearing is 270n / mm2, the dynamic load is 140n / mm2, the maximum speed is 5m / s, the friction coefficient is 0.02 ~ 0.07, the working temperature is – 200 ° C to 280 ° C, and the guiding area reduces the stress to the maximum to withstand large lateral load, Extend the life of both cylinder and seal.
C. The piston rod seal is composed of dust ring, piston rod seal ring and hydraulic buffer, which can effectively prevent hydraulic oil leakage of piston rod. The dust ring is a double lip dust-proof ring. Its function is to prevent dust, dirt, sand and metal chips from entering. It greatly prevents scratch, protects the guide element and prolongs the service life of the seal. The medium oriented sealing lip reduces the remaining oil film. The polyurethane material ensures excellent characteristics in dry friction and increases wear resistance, Due to its good resistance to ozone and radiation caused by climatic conditions, the service life is prolonged. The working temperature is from – 35 ° C to 100 ° C, and the surface velocity is less than 2 m / s. The main sealing ring of piston rod is a lip type seal with two sealing lips and a tight fit at the outer diameter. Due to the additional lubricant between the two lips, it greatly prevents dry friction and wear, resists impact and extrusion, and improves the sealing performance under zero pressure. The working pressure is 40MPa, the working temperature is – 35 to 110 ℃, and the surface velocity is less than 0.5m/s. The function of hydraulic buffer is to absorb the impact and fluctuating pressure under high load, isolate high temperature fluid, and improve the durability of seals. The peak pressure can reach 100MPa. Due to the special shape groove on the sliding lip which can release back pressure, it can eliminate the pressure between the sealing ring and the buffer of the movable buttress rod, and transfer the pressure formed between the main seal and the buffer seal back to the system.
D. The cylinder bore is made of alloy steel 27SiMn with high strength, small shape and light weight, honed and rolled to a high surface finish, so as to minimize the internal friction and prolong the service life of the seal.
E. The standard piston is a casting with two concentricity fits with the piston rod. The piston is firmly locked by the screw thread between the nut and the piston nut, so as to ensure the reliable work under high pressure and parts. All piston seals are imported Parker and NOK products. Both ends of the piston are installed with a 4 mm thick dirt ring made of PTFE. As it has the function of impurity immersion, the oil can be prevented from being damaged due to mixing with external substances, so as to ensure that the seal has a long service life and can play a guiding and supporting role. The supporting ring has high pressure bearing capacity, which can eliminate all metal to metal contact between piston and cylinder block, provide high lateral bearing capacity, absorb impact, increase contact area and avoid scratching cylinder block. The piston seal adopts Pak’s open type OK seal, which has the advantages of resistance to impact load, low friction resistance and simple installation. Due to the special material performance of the seal ring, it has strong anti extrusion ability under high pressure and large clearance, and the working pressure is as high as 50MPa.
F.The buffer sleeve with rod cavity is a centering sleeve, which can automatically adjust the concentricity, and because there is a large gap between the buffer sleeve and the piston, the starting pressure can be reduced. The buffer plunger adopts steel ball limit, which can float. The buffer sleeve and buffer plunger have floating characteristics. Therefore, it can have a very small buffer gap, automatically align the center and eliminate the influence of coaxial shaft error. The buffer performance is good, which can reduce the noise and impact load and prolong the service life of the machine.