1. Oil tank
The function of the oil tank is to store oil, emit heat, precipitate impurities and separate bubbles in the oil. There are three types of oil tanks: open type, isolated type and pressure type. The hydraulic oil in the open oil tank is connected to the atmosphere through the air filter. Yuchai excavator adopts the open oil tank.
Symbol of oil tank:
2. Oil filter
(1) The filtration accuracy of oil filter refers to the diameter of the oil filter (or filter material) that can effectively filter out the largest particles, expressed in microns. For example, an oil filter with a filtration accuracy of 5um can pass through the largest particle with a diameter of 5um.
(2) The oil filter of the oil suction circuit is mainly used to protect the hydraulic pump and prevent large particulate pollutants from being sucked into the pump during oil suction. The pressure difference of the oil suction filter is limited by the oil suction characteristics of the hydraulic pump, and the maximum pressure difference in use is generally not greater than 0.02MPa. If the pressure difference is too large, it is easy to cause the hydraulic pump to empty and cause cavitation damage. Therefore, 100um low-precision filter element is generally used for oil suction filter. The filter element is made of copper wire woven mesh.
(3) Return circuit oil filter: from the installation position, it is ideal to install an oil filter in the system return circuit. Before the system oil flows back to the oil tank, the oil filter filters out the pollutants that invade the system and are generated in the system to provide clean oil for the hydraulic pump. The oil filter of the oil return circuit adopts a high-precision filter element with a filtering accuracy of 10um. The filter element is made of synthetic fiber.
(4) Pilot circuit oil filter: the filtering accuracy is 5um. The filter element is made of synthetic fiber.
The return oil filter and suction oil filter of excavator are generally installed in the oil tank.
3. Accumulator
Function of accumulator: store the energy in the hydraulic system and release it again when necessary. Yuchai excavator uses an air bag accumulator with an inflation pressure of 1.6Mpa, which is installed on the pilot oil circuit. Its functions are as follows:
(1) As an emergency power source, the boom and bulldozer can be put down to ensure safety in case of flameout;
(2) Eliminate pulsation of oil pump.
4. Seals
Common sealing materials are nitrile rubber, polytetrafluoroethylene, etc.
O-type seal ring O-type seal ring can be used for static seal, rotary motion seal and reciprocating motion seal. When it is used for dynamic seal and the working pressure is greater than 7MPa, it must be equipped with retaining ring. Compression ratio and stretching amount of 0-ring: if the compression amount of 0-ring is too small, it will cause leakage of 0-ring after assembly. If the compression amount is too large, it will cause excessive compression and cause relaxation of rubber stress, resulting in leakage of sealing device. Generally, the compression ratio of static seal is 25%, and that of transport seal is 15%. Generally, the tensile strength is 1.04 times for static seal and 1.02 times for transport seal.
Retaining ring: the retaining ring and 0-ring are used to prevent the 0-ring from being embedded into the gap between the sealing coupling parts due to elastic deformation after bearing the pressure. If the 0-ring bears high pressure on one side, the retaining ring shall be installed on the low-pressure side of the 0-ring. If the 0-ring bears high pressure on both sides, the retaining ring shall be installed on both sides. The retaining ring is made of polytetrafluoroethylene.
0-ring installation groove width: 1.5 times of 0-ring section diameter for static sealing, 1.3 times of 0-ring section diameter for reciprocating sealing, and 1.1 times of 0-ring section diameter for rotating dynamic sealing.
Example of 0-ring marking: the 0-ring with inner diameter of 18mm and section diameter of 1.8mm is marked as 18x1.8.
The cross section of the Y-ring is Y-shaped.
Installation of Y-ring: A. when installing various types of Y-ring, the parts passing through, such as the cylinder barrel of the oil cylinder and the end of the piston rod, shall have 15-30 chamfer; b. When installing various types of y-rings, apply lubricating grease or working oil on the surface of the sealing ring and the parts passing through the assembly; c. When installing various types of y-rings, the concave part (lip end face) of the Y-ring shall be facing the pressure medium,; d. When installing various Y-shaped sealing rings, pay attention to the thorough cleaning of sealing couple and hydraulic parts, and prevent sand dust, iron filings and other sundries.
