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    Structure and principle of main components of lubrication system

    Release time:2019-12-20

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      ► External gear oil pump

      The external gear oil pump housing is equipped with a driving gear and a driven gear. The gap between the gear and the inner wall of the casing is small, and there is an oil inlet on the casing. When the engine is running, the gear rotates in the direction of the arrow shown in the figure. The volume of the oil inlet chamber increases due to the gear teeth moving in the disengagement direction. A certain degree of vacuum is generated in the cavity. Into the oil cavity. When the gear rotates, the oil stored between the teeth is brought into the oil outlet cavity. Because the gear teeth on one side of the oil outlet cavity enter into mesh, the volume of the oil outlet cavity decreases and the oil pressure rises, and the oil is sent to the engine oil passage through the oil outlet. The oil pump is usually driven by a helical gear on the camshaft or the front gear of the crankshaft. When the engine is working, the oil pump is constantly working, so as to ensure the continuous circulation of the oil in the lubricating oil circuit.

      When the gears are in mesh, the oil between the meshing teeth will generate a large thrust between the gears due to the reduced volume. To this end, a pressure relief groove is milled on the pump cover, so that the oil extruded between the teeth when the gear teeth mesh can flow to the oil outlet cavity through the pressure relief groove. A limit pressure valve is installed on the oil pump cover, which can control the oil pressure of the main oil passage within a normal range (0.15 ~ 0.9MPa). A radial ring groove is formed at the end of the plunger of the pressure limiting valve to store abrasive debris and impurities entering the mating surface to ensure the plunger's flexible movement.

      Gear oil pumps are widely used because of their simple structure, easy manufacture, and reliable operation.

      ► Internal gear oil pump

      The working principle of internal gear oil pump is basically the same as that of external gear oil pump. The internal gear of the internal gear pump is a driving gear, which is sleeved on the front end of the crankshaft and is directly driven by the crankshaft through a spline. The outer ring gear is a driven gear, which is installed in the oil pump body, and the pump body is fixed at the front end of the body.

      ► Rotary Oil Pump

      The inner rotor of the -rotor oil pump is fixed on the driving shaft, and the outer rotor is inside the oil pump housing, which can rotate freely with a certain eccentricity between the two. When the inner rotor rotates, it drives the outer rotor to rotate. The tooth profile of the rotor is designed so that when the rotor is turned to any angle, the tooth profile of each tooth of the inner and outer rotor can always make point contact with each other. In this way, four working chambers are formed between the inner and outer rotors. When a working chamber is turned from the oil inlet, the volume increases and a vacuum is generated, and the oil is sucked in through the oil inlet. The rotor continues to rotate. When the working cavity communicates with the oil outlet, the inner volume of the cavity decreases, the oil pressure rises, and the oil is pressed out through the oil outlet.

      The rotor oil pump has a compact structure, a high suction vacuum, a large pump oil volume, and an even oil supply. This kind of oil pump is more suitable when the oil pump is installed outside the crankcase and its position is high.

      ►Safety valve

      The oil pump must be able to supply a sufficient amount of oil at various engine speeds to maintain sufficient oil pressure and ensure engine lubrication. The oil pump's oil supply is related to its speed, and the speed of the oil pump is proportional to the engine speed.

      Therefore, when designing the oil pump, it is necessary to have a sufficient oil supply at low speeds. However, at high speeds, the oil supply of the oil pump is significantly larger, and the oil pressure is significantly higher. In addition, when the engine is cold-started, the viscosity of the oil is large, the fluidity is poor, and the oil pressure will increase significantly.

      In order to prevent the oil pressure from being too high, a safety valve or a pressure limiting valve is installed in the lubricating oil circuit. Generally, the safety valve is installed on the oil pump or the main oil passage of the body. When the oil pressure rises to the specified value, the safety valve opens, and the excess oil returns to the oil pump inlet or directly back to the oil pan.

      ►Oil filter

      The function of the oil filter is to remove metal wear debris, mechanical impurities and oil oxides from the oil. If these impurities enter the lubrication system with the oil, they will increase the wear of the engine parts and may block the oil pipes or oil passages.

      Oil filters are installed before the oil pump and after the oil pump. The oil filter is installed before the oil pump. Installed after the oil pump and according to its arrangement, there are two types: full flow and split flow.