Oil-free screw compressor

Abstract

Provided is an oil-free screw compressor capable of minimizing pressure loss in an annular space connecting an air opening hole and a communication hole and preventing the inflow of lubricating oil during an unloading operation. Equipped with a shell (12), a bearing (22), a shaft seal device (20), an air opening hole (24a), an annular space (25), and at least one communication hole (31a), the aforementioned shell (12) has a rotor chamber (150 ), the aforementioned bearing (22) supports the rotating shaft (21) of the screw rotor, the aforementioned shaft sealing device (20) has an oil seal part (31) and an air sealing part (60), and the aforementioned atmospheric opening hole (24a) is formed in the shaft sealing device , the aforementioned at least one communication hole (31a) is formed on the rotating shaft, the aforementioned annular space (25) communicates the atmospheric opening hole with the at least one communication hole, and the annular space has an inner peripheral annular ring formed on the inner peripheral side of the shell. space (24g), set the opening cross-sectional area of ​​the inner peripheral annular space as S1, set the total opening cross-sectional area of ​​the communicating holes as S2, set the opening cross-sectional area of ​​the i-th communicating hole as S2i, and set the aforementioned communicating holes When the number of is set to n (n is a natural number greater than or equal to 1), it is configured to satisfy the following relationship.

Description

technical field [0001] The invention relates to an oil-free screw compressor. Background technique [0002] In an oil-free screw compressor, air is compressed by a pair of male and female screw rotors that can rotate without oil supply and in a non-contact manner. In oil-free screw compressors, compressed air generated in the rotor chamber may leak while being transmitted along the rotating shaft, or lubricating oil supplied to gears driving the rotating shaft and bearings supporting the rotating shaft may flow into the rotor chamber. In order to prevent this, a shaft seal is provided between the rotor chamber and the bearing. The shaft seal device includes an air seal portion that seals compressed air from the rotor chamber, and an oil seal portion that seals lubricating oil from the bearing. [0003] During the unloading operation, when the rotor chamber has a negative pressure, lubricating oil supplied to the bearing and the like may pass through the oil seal and flow i...

AI Technical Summary

Problems solved by technology

Therefore, in Patent Document 2, a large pressure loss occurs not at the plurality of communicating holes but at the annular space.

[0010] In this way, in both Patent Document 1 and Patent Document 2, there is a possibility that a large pressure loss occurs at the annular space connecting the atmospheric opening hole and the communication hole, so that the prevention of lubricating oil from flowing into the air cannot be fully exerted during the unloading operation. Effect of rotor chamber inflow

However, neither Patent Document 1 nor Patent Document 2 takes this point into special consideration.

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