Working principle of ion nitriding roots pump

Ion nitriding is carried out in a vacuum environment, so understanding the working principle of vacuum pump is conducive to daily work.


The structure of roots pump used in plasma nitriding is shown in Figure 1. In the pump cavity, there are two "8" shaped you do rotor vertically installed on a pair of parallel axles, driven by a pair of gears with transmission ratio of 1 to do the opposite synchronous rotation. Between the rotors, there is a certain gap between the rotor and the inner wall of the pump housing. Roots pump is a kind of vacuum pump without internal compression, usually the compression ratio is very low, so the middle and high vacuum roots pump needs the front pump. Therefore, the limit vacuum of Roots pump depends not only on the pump structure and manufacturing accuracy, but also on the limit vacuum of the front pump.

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The working principle of Roots pump used in plasma nitriding has not only the working principle of volumetric pump, but also the pumping effect of molecular pump. The following is a diagram of the roots pump.

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Because of the continuous rotation of the rotor, the air is sucked from the inlet of the pump into the space V0 between the lower rotor and the pump shell. After suction, the space V0 is completely closed. As the rotor rotates, the closed V0 space is connected with the exhaust port. Because of the high gas pressure on the exhaust side, a part of the gas backlash occurs, resulting in the sudden increase of gas pressure in the V0 space. As the rotor continues to rotate, the original sealed gas in the V0 space, together with the recoil gas, is discharged out of the pump. At this time, the upper rotor seals the V0 volume gas from the pump inlet. Because of the continuous operation of the pump, the two rotors continuously form a closed space V0 and continuously discharge the gas from the closed space, thus achieving the purpose of pumping.


Understanding the working principle of ion nitriding roots pump is helpful to find out the problems in the field production, and can be solved in time.