CN-115875280-B - Vacuum pump

Abstract

The invention provides a vacuum pump with improved back pressure characteristics during high-flow exhaust. The vacuum pump (1) comprises a frame (2), a rotor cylinder (23) and a stator cylinder (6). The housing (2) has an air inlet (14) for sucking air and an air outlet (16) for discharging the sucked air. The rotor cylindrical portion (23) is housed in the housing (2). The stator cylinder part (6) is housed in the housing (2) and is disposed so as to face the rotor cylinder part (23). A screw groove (60) is formed on one of the facing surfaces of the stator cylinder (6) and the rotor cylinder (23). Regarding the groove depth (D) of the screw groove (60), the end (6 b) on the air discharge side is smaller than the end (6 a) on the air suction side. Regarding the reduction ratio of the groove depth (D), the suction side is larger than the discharge side.

Inventors

• True pot Yasi

Assignees

• 株式会社岛津制作所

Dates

Publication Date

20260512

Application Date

20220908

Priority Date

20210929

Claims (6)

1. 1. A vacuum pump, comprising: A housing having an air suction port through which air is sucked and an air discharge port through which the sucked air is discharged; a rotor cylinder part accommodated in the housing, and A stator cylinder portion housed in the housing and disposed opposite to the rotor cylinder portion, A screw groove is formed on one of the facing surfaces of the stator cylinder portion and the rotor cylinder portion, Regarding the groove depth of the thread groove, the end on the air discharge side is smaller than the end on the air suction side, Regarding the reduction ratio of the groove depth, the suction side is larger than the discharge side, The thread groove has: A first portion in which the reduction ratio of the groove depth is constant, and A second portion disposed closer to the exhaust side than the first portion, the reduction ratio of the groove depth being constant, The first portion is reduced more than the second portion, And the first portion is connected to the second portion at a reduced ratio of the varying portion, If the groove depth at the suction side end of the first portion is set to Da, Setting the groove depth at the end of the exhaust side of the second portion to Db, The groove depth at the varying portion is set to Dc, Then Db is less than or equal to Dc is less than or equal to (Da+Db) x 0.5.
2. 2. The vacuum pump of claim 1, wherein If the length from the suction side end of the first portion to the variable portion along the axial direction of the rotor cylindrical portion is La, A length along the axial direction from the suction side end of the first portion to the exhaust side end of the second portion is set to Lb, Then 0< La < Lb×2/3 is satisfied.
3. 3. The vacuum pump according to claim 1 or 2, wherein And also satisfies 1.5≤Da/Db.
4. 4. The vacuum pump of claim 1, wherein The thread groove has a plurality of portions having different reduction ratios of the groove depth, The portion having the greatest reduction ratio of the groove depth is disposed on the intake side than the portion having the smallest reduction ratio of the groove depth.
5. 5. The vacuum pump of claim 4, wherein The portion of the plurality of portions where the reduction ratio of the groove depth is largest is disposed closest to the suction side.
6. 6. The vacuum pump of claim 4 or 5, wherein The portion of the plurality of portions where the reduction ratio of the groove depth is smallest is disposed closest to the exhaust side.

Description

Vacuum pump Technical Field The present invention relates to a vacuum pump. Background In the field of semiconductor manufacturing apparatuses and the like, a vacuum pump is used to form a high vacuum environment (for example, refer to patent document 1). The vacuum pump disclosed in patent document 1 is provided with a turbo pump portion disposed on the intake port side and a drag pump portion disposed on the exhaust port side. The performance index when the turbo molecular pump is used for exhausting gas is the inlet pressure with respect to the flowing gas flow rate, and as the gas flow rate increases, the inlet pressure increases. Further, there is a back pressure characteristic as another performance index when exhaust is performed by a turbo molecular pump. The back pressure characteristic represents a result of measuring a change in the inlet pressure when the pressure of the exhaust port of the turbo molecular pump is increased in a state where a constant amount of gas is introduced. As the exhaust port pressure increases, the number of gas molecules flowing backward from the exhaust port side to the intake port side increases, and thus the pressure on the intake port side increases. The higher the discharge port pressure at which the suction port pressure starts to rise, the more the gas molecules of the reverse flow can be reduced, and the back pressure characteristics are good. [ Prior Art literature ] [ Patent literature ] Patent document 1 Japanese patent laid-open No. 2021-102926 Disclosure of Invention [ Problem to be solved by the invention ] On the other hand, in recent years, the flow rate of the gas flowing into the turbo molecular pump tends to increase, and it is demanded to reduce the suction port pressure at the time of large-flow exhaust. In order to reduce the suction port pressure at the time of large-flow exhaust, it is effective to design to increase the conductance of the drag pump portion. However, in the case of the design, not only the gas molecules moving from the suction side to the discharge side but also the gas molecules flowing back from the discharge side to the suction side increase, and thus the back pressure characteristic is deteriorated. The invention aims to provide a vacuum pump capable of coping with high-flow exhaust and improving back pressure characteristics. [ Means of solving the problems ] The vacuum pump according to an aspect of the present invention includes a housing, a rotor cylinder portion, and a stator cylinder portion. The housing has an air suction port through which air is sucked and an air discharge port through which the sucked air is discharged. The rotor cylindrical portion is accommodated in the housing. The stator cylinder is housed in the case and disposed opposite to the rotor cylinder. A screw groove is formed in one of the facing surfaces of the stator cylinder portion and the rotor cylinder portion. Regarding the groove depth of the screw groove, the end on the air discharge side is smaller than the end on the air suction side. Regarding the reduction ratio of the groove depth, the suction side is larger than the discharge side. [ Effect of the invention ] According to the aspect of the present invention described above, a vacuum pump capable of coping with a large flow rate of exhaust gas and improving the back pressure characteristic can be provided. Drawings Fig. 1 is an external view of a vacuum pump according to embodiment 1. Fig. 2 is a perspective view of a stator cylinder of the vacuum pump according to embodiment 1, as viewed from the suction side. Fig. 3 is a perspective view of the stator cylinder of the vacuum pump according to embodiment 1, as viewed from the side opposite to fig. 2. Fig. 4 (a) is a view of the screw thread near the suction side end of the stator cylindrical portion of the vacuum pump according to embodiment 1, as viewed from the inside, and fig. 4 (b) is a view of the screw thread near the discharge side end of the stator cylindrical portion of the vacuum pump according to embodiment 1, as viewed from the inside. Fig. 5 is a cross-sectional view of the stator cylindrical portion of the vacuum pump according to embodiment 1, taken perpendicularly to the screw angle. Fig. 6 is a diagram showing a change in the screw groove depth of the stator cylindrical portion of the vacuum pump according to embodiment 1. Fig. 7 is a graph showing a change in the thread groove depth in the comparative example. Fig. 8 is a graph showing a change in suction side pressure of the drag pump unit with respect to the discharge side pressure in example 1 and comparative example 1. Fig. 9 is a graph showing a change in suction side pressure of the drag pump unit with respect to the discharge side pressure in example 1 and comparative example 1. Fig. 10 is a graph showing a change in suction side pressure of the drag pump unit with respect to the discharge side pressure in example 2 and comparative example 2. Fig. 11 is a graph s