Structural Characteristics Of Vacuum Pump

(1) The overall structure of the pump

The arrangement of the pump body of the vacuum pump determines the overall structure of the pump.

The intake and exhaust ports of the vertical structure are set horizontally, which is convenient for assembly and connection of pipelines. However, the center of gravity of the pump is high, and the stability is poor at high speed, so this type is mostly used for small pumps.

The intake port of the horizontal pump is on the top and the exhaust port is on the bottom. Sometimes in order to facilitate the installation and connection of the vacuum system pipeline, the exhaust port can be connected from the horizontal direction, that is, the inlet and exhaust directions are perpendicular to each other. At this time, the exhaust port can be opened from the left or right direction, except for one end of the exhaust pipe, the other end is blocked or connected to the bypass valve. This kind of pump has a low center of gravity and good stability during high-speed operation. Generally, large and medium-sized pumps use this structure.

The two rotor shafts of the pump are mounted perpendicular to the horizontal plane. The assembly gap of this structure is easy to control, the rotor assembly is convenient, and the pump occupies a small area. However, the center of gravity of the pump is high, the disassembly and assembly of the gear is inconvenient, and the lubrication mechanism is relatively complicated.

(2) Transmission mode of the pump

The two rotors of the vacuum pump are operated relatively synchronously through a pair of high-precision gears. The driving shaft is connected with the motor through a coupling. There are two main types of transmission structure layout: one is that the motor and the gear are placed on the same side of the rotor as shown in the figure. The driven rotor is directly driven by the motor end gear, so that the torsional deformation of the driving rotor shaft is small, and the gap between the two rotors will not be changed due to the large torsional deformation of the driving shaft, so the gap between the rotors is running. uniform in the process. The biggest disadvantage of this transmission method is: a. There are three bearings on the driving shaft, which increases the difficulty of processing and assembling the pump, and the disassembly and adjustment of the gear is inconvenient; b. The overall structure is not symmetrical, and the center of gravity of the pump is biased towards the motor and the gear. side of the box.

Features:

(1) Larger pumping speed in a wider pressure range;

(2) The rotor has good geometric symmetry, so the vibration is small and the operation is stable. There are gaps between the rotors and between the rotors and the casing, no lubrication is required, and the friction loss is small, which can greatly reduce the driving power, so that a higher speed can be achieved;

(3) The pump cavity does not need to be sealed and lubricated with oil, which can reduce the pollution of oil vapor to the vacuum system;

(4) There is no compression and no exhaust valve in the pump chamber. Simple and compact structure, insensitive to dust and water vapor in the pumped gas;

(5) The compression ratio is low, and the effect of hydrogen pumping is poor;

(6) The rotor surface is a curved cylinder with a complex shape, which is difficult to process and inspect.