FIG. 2. 3
Working principle of external gear oil pump
The working principle diagram of the external meshing pump is shown. There is an external meshing gear in the shell of the pump, which is covered by end covers on both sides (not shown in the figure). The housing, the end cover and the intertooth grooves of the gear form a number of sealed working cavities. When the gear inside the gear pump rotates in the direction shown, the right oil suction chamber is gradually separated due to the gear teeth meshing with each other, and the volume of the sealing working chamber gradually increases, forming a partial vacuum, and the oil is sucked in, filling the groove between the teeth, and with the gear rotation, the oil is brought to the left pressure oil chamber. On the side of the oil pressure area, the oil is extruded because the gear teeth are gradually engaged here and the volume of the sealing working chamber is constantly reduced. The oil suction zone and the oil pressure zone are separated by meshing gear and pump body.
The advantages of external gear oil pump are simple structure, small size, light weight, convenient manufacturing, low price, reliable work, strong self-priming ability (allow oil suction vacuum degree is large, its representative is external mesh centrifugal pump), not sensitive to oil pollution, easy maintenance. Its disadvantages are that some parts bear unbalanced radial force, serious wear, large leakage, the increase of working pressure is limited. In addition, its flow pulsation is large, so the pressure pulsation and noise are large. In order to improve the pressure of gear oil pump, it is necessary to reduce the leakage of the end face.
Working principle of internal gear oil pump
Internal meshing gear oil pump has involute tooth shape and cycloid tooth shape (also known as high viscosity pump) two types. Their working principle and main characteristics are exactly the same with the external gear oil pump. FIG. 2.4 shows the working principle diagram of internal involute gear oil pump.
The sealing volume enclosed by the meshing pinion 1 and inner gear 2 and the side plate is separated into two parts by the meshing line of the crescent plate 3 and the gear, forming the oil suction cavity and the oil pressure cavity. When the drive shaft drives the pinion to rotate in the direction shown in the figure, the inner gear rotates in the same direction. In the figure, the teeth of the upper part of the gear are disengaged and meshed, and the volume of the sealing oil cavity increases gradually, forming a vacuum locally, and the oil is absorbed. The lower half of the gear teeth into the meshing, so that the volume of the sealing oil chamber is gradually reduced, the oil is extruded.
The internal involute gear oil pump has the advantages of small flow pulsation, compact structure, small volume, light weight, low noise and high efficiency compared with the external gear oil pump.
图2. 5所示
Is the working principle diagram of internal cycloid gear oil pump. In the internal meshing cycloid gear oil pump, there is only one tooth difference between the outer rotor 1 and the inner rotor 2, there is no middle crescent plate, and the axis line of the inner and outer rotor has an eccentricity. The inner rotor is the main driving wheel, and the sealing volume is formed between the inner and outer rotor and the oil distribution plate on both sides. The meshing line of the inner and outer rotor divides the sealing volume into oil suction chamber and oil pressure chamber. When the inner rotor rotates in the direction shown in the figure, the sealing volume on the left gradually increases, which is the oil suction cavity; The decreasing sealing volume on the right side is the pressure oil chamber. The advantages of internal cycloid gear oil pump are compact structure, few parts, large working volume, high speed, smooth movement and low noise. Due to the small number of teeth, the flow pulsation is relatively large, and the gap leakage at the meshing is large. It is usually used as an auxiliary pump for lubrication and oil replenishment.
