(1) The overall structure of the pump
The arrangement structure 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 arranged horizontally, making it easier to assemble and connect the pipelines. However, the pump has a high center of gravity and poor stability during high-speed operation, 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 pipes, 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 both left and right directions. Except for one end of the exhaust pipe, the other end is blocked or connected to a 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 installed perpendicular to the horizontal plane. The assembly gap of this structure is easy to control, the rotor is easy to assemble, and the pump has a small footprint. However, the pump has a high center of gravity and inconvenient disassembly and assembly of gears, and the lubrication mechanism is relatively complicated.
(2) The transmission mode of the pump
The two rotors of the vacuum pump realize their relative synchronous operation 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 gear are placed on the same side of the rotor as shown in the figure. The driven rotor is directly driven by the gear at the motor end, so that the torsional deformation of the driving rotor shaft is small, and the gap between the two rotors will not change due to the large torsional deformation of the driving shaft, so the gap between the rotors is running The process is uniform. The biggest disadvantage of this transmission method is: a. There are three bearings on the driving shaft, which increases the difficulty of pump processing and assembly, and it is inconvenient to disassemble and adjust the gear; b. The overall structure is uneven, and the center of gravity of the pump is biased toward the motor and gear. Side of the box.
(1) A 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 rotor and the shell, no lubrication is required, and the friction loss is small, which can greatly reduce the driving power and achieve a higher speed;
(3) There is no need for oil sealing and lubrication in the pump cavity, which can reduce the pollution of oil vapor to the vacuum system;
(4) There is no compression in the pump cavity and no exhaust valve. The structure is simple and compact, and it is not sensitive to dust and water vapor in the exhausted gas;
(5) The compression is relatively low, and the hydrogen pumping effect is poor;
(6) The surface of the rotor is a curved cylindrical surface with a more complicated shape, which is difficult to process and inspect.