US20210332824A1

US20210332824A1 - Turbo-molecular pump and stator

Info

Publication number: US20210332824A1
Application number: US17/217,740
Authority: US
Inventors: Tomoki Yasuda
Original assignee: Shimadzu Corp
Current assignee: Shimadzu Corp
Priority date: 2020-04-28
Filing date: 2021-03-30
Publication date: 2021-10-28
Also published as: CN113565776A; TW202140933A; JP2021173257A; TW202309401A

Abstract

A turbo-molecular pump comprises: multiple stages of rotor blades formed with multiple blades and provided in a pump axial direction; and multiple stages of stator blades provided with multiple blades, the multiple stages of the rotor blades and the multiple stages of the stator blades being alternately arranged in the pump axial direction. Each stage of the stator blade includes multiple divided stator blades, and a clearance is formed at a portion where the multiple divided stator blades face each other, and circumferential phases of the clearances of adjacent ones of the stages of the stator blades in the pump axial direction are shifted from each other.

Description

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a turbo-molecular pump.

2. Background Art

A turbo-molecular pump rotates, at high speed, multiple stages of rotor blades formed with turbine blades relative to multiple stages of stator blades formed with turbine blades, thereby discharging gas molecules having flowed in through a suction port of the pump from an exhaust port of the pump. Each stage of the stator blade includes, due to limitations on assembly, a pair of divided stator blades divided in a semi-circular shape (see, e.g., Patent Literature 1 (JP-A-2014-37808)).

SUMMARY OF THE INVENTION

The stator blade is assembled with the stator blade being sandwiched by a pair of upper and lower spacer rings. In this state, the divided stator blades in a pair are arranged not to overlap with each other, and therefore, slight clearances are formed between the divided stator blades. These clearances allow a gas molecule backflow from an exhaust side to a suction side, and therefore, are one of causes for degradation of exhaust performance.
A turbo-molecular pump comprises: multiple stages of rotor blades formed with multiple blades and provided in a pump axial direction; and multiple stages of stator blades provided with multiple blades, the multiple stages of the rotor blades and the multiple stages of the stator blades being alternately arranged in the pump axial direction. Each stage of the stator blade includes multiple divided stator blades, and a clearance is formed at a portion where the multiple divided stator blades face each other, and circumferential phases of the clearances of adjacent ones of the stages of the stator blades in the pump axial direction are shifted from each other.
Each rotor blade includes the multiple blades arranged at a predetermined interval in a circumferential direction, and in a case where an angle between adjacent ones of the blades of each rotor blade in the circumferential direction is a single-pitch angle, an amount of shift between the circumferential phases of adjacent ones of the stages of the stator blades in the pump axial direction is set greater than the single-pitch angle.
The amount of shift between the circumferential phases of adjacent ones of the stages of the stator blades is set to 90 deg.
The turbo-molecular pump according to claim 1, further comprises: multiple spacer rings provided such that the multiple spacer rings and the multiple stages of the stator blades are alternately stacked on each other in the pump axial direction. Each spacer ring includes a position adjustment member configured to adjust the circumferential phases of adjacent ones of the stator blades in the pump axial direction.
A stator used in a turbo-molecular pump comprises a rotor and the stator. The rotor includes multiple stages of rotor blades formed with multiple blades and provided in a pump axial direction, and the stator includes multiple stages of stator blades provided with multiple blades, the multiple stages of the rotor blades and the multiple stages of the stator blades being alternately arranged in the pump axial direction. Each stage of the stator blade includes multiple divided stator blades, and a clearance is formed at a portion where the multiple divided stator blades face each other, and circumferential phases of the clearances of adjacent ones of the stages of the stator blades in the pump axial direction are shifted from each other.
Each rotor blade includes the multiple blades arranged at a predetermined interval in a circumferential direction, and in a case where an angle between adjacent ones of the blades of each rotor blade in the circumferential direction is a single-pitch angle, an amount of shift between the circumferential phases of adjacent ones of the stages of the stator blades in the pump axial direction is set greater than the single-pitch angle.
The amount of shift between the circumferential phases of adjacent ones of the stages of the stator blades is set to 90 deg.
According to the present invention, degradation of the exhaust performance due to the backflow of the gas molecule can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic sectional view of an outline configuration of a turbo-molecular pump;

FIG. 2 illustrates a plan view of an N-th stage of a stator blade;

FIG. 3 illustrates views of the N-th and N+1-th stages of the stator blades;

FIG. 4 illustrates a view for describing an effect on a backflow molecule;

FIG. 5 illustrates a view of a comparative example where assembly phases are coincident with each other;

FIG. 6 illustrates views of one example of assembly phases of the multiple stator blades;

FIG. 7 illustrates views of another example of the assembly phases of the multiple stator blades;

FIG. 8 illustrates views for describing a position adjustment mechanism; and

FIG. 9 illustrates a view of a section along a C-C line of FIG. 8.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Hereinafter, an embodiment of the present invention will be described with reference to the figures. FIG. 1 illustrates a schematic sectional view of an outline configuration of a turbo-molecular pump 1. Note that a magnetic bearing type turbo-molecular pump will be described as an example in the present embodiment, but the present invention is not limited to the magnetic bearing type and is applicable to various turbo-molecular pumps.
The turbo-molecular pump 1 has a turbo pump stage TP including multiple stages of stator blades 30 and multiple stages of rotor blades 40 and a drag pump stage DP including a stator cylindrical portion 31 and a rotor cylindrical portion 41. In an example illustrated in FIG. 1, the turbo pump stage TP includes eight stages of the stator blades 30 and nine stages of the rotor blades 40, but the number of stages is not limited to above. In the drag pump stage DP, a screw groove is formed at the stator cylindrical portion 31 or the rotor cylindrical portion 41. The rotor blades 40 and the rotor cylindrical portion 41 are formed at a pump rotor 4 a. The pump rotor 4 a is fastened to a shaft 4 b as a rotor shaft with multiple bolts 50. The pump rotor 4 a and the shaft 4 b are integrally fastened with the bolts 50, thereby forming a rotary body 4.
Each of the multiple stages of the stator blades 30 includes a pair of divided stator blades ( reference numerals 30 a, 30 b of FIG. 2) in a half shape. The multiple stages of the stator blades 30 and the multiple stages of the rotor blades 40 provided in an axial direction of the pump rotor 4 a are alternately arranged. The stator blades 30 are stacked in a pump axial direction through multiple spacer rings 33. The shaft 4 b is magnetically levitated and supported by magnetic bearings 34, 35, 36 provided at a base 3. Although not illustrated in detail in the figure, each of the magnetic bearings 34 to 36 includes an electromagnet and a displacement sensor. A levitation position of the shaft 4 b is detected by the displacement sensors.
The rotary body 4 configured such that the pump rotor 4 a and the shaft 4 b are fastened with the bolts is rotatably driven by a motor 10. When the magnetic bearings are not in operation, the shaft 4 b is supported by emergency mechanical bearings 37 a, 37 b. When the rotary body 4 is rotated at high speed by the motor 10, gas on a pump suction port side is sequentially discharged by the turbo pump stage TP and the drag pump stage DP, and is discharged through an exhaust port 38. An auxiliary pump is connected to the exhaust port 38.
FIGS. 2 and 3 illustrate views for describing the stator blade 30. FIG. 2 illustrates a plan view of the N-th stage of the stator blade 30 from the pump suction port side (a suction side) among the eight stages. FIG. 3 illustrates plan views of the N-th and N+1-th stages of the stator blades 30. As illustrated in FIG. 2, the stator blade 30 includes the pair of divided stator blades 30 a, 30 b divided in a semi-circular shape due to limitations on assembly. The divided stator blades 30 a, 30 b divided in the semi-circular shape are arranged in a circular shape with clearances 305. Each of the divided stator blades 30 a, 30 b includes multiple blades 301 formed radially, an arc-shaped inner rib 302 provided on an inner circumferential side of the blade 301, and an arc-shaped outer rib 303 provided on an outer circumferential side of the blade 301. Note that in an example illustrated in FIG. 2, both of the inner rib 302 and the outer rib 303 are provided at the divided stator blade 30 a, 30 b, but it may be configured such that either one of the inner rib 302 or the outer rib 303 is provided.
Upon assembly of the multiple stages of the stator blades 30 as illustrated in FIG. 1, the pair of divided stator blades 30 a, 30 b is placed on the spacer ring 33, and the upper (suction side) spacer ring 33 is placed on the outer ribs 303 of these divided stator blades 30 a, 30 b. The divided stator blades 30 a, 30 b are supported such that the outer ribs 303 thereof are sandwiched by a pair of upper and lower spacer rings. It is required for the divided stator blades 30 a, 30 b that both ends thereof in a circumferential direction do not overlap with each other upon assembly. Thus, the stator blades 30 are, as illustrated in FIG. 2, assembled in a state in which the clearances 305 are formed between the divided stator blades 30 a, 30 b.
FIG. 3 illustrates the views for describing assembly phases of the multiple stages of the stator blades 30, and illustrates the plan views of the N-th and N+1-th stages of the stator blades 30 (the divided stator blades 30 a, 30 b) from the suction side. The assembly phase of the stator blade 30 in the embodiment is an indicator of the direction of assembly of the pair of divided stator blades 30 a, 30 b in the stator blade 30, and is specifically the angle of rotation of the clearance 305 from a reference position. In an example illustrated in FIG. 3, the position of the clearance 305 of the N-th stage of the stator blade 30 is taken as the reference position, and the phase of the position of the clearance 305 of the N+1-th stage of the stator blade 30 is shifted in a counterclockwise direction by a rotation angle (+θ) (hereinafter, a phase shift in the counterclockwise direction will be referred to as a plus). That is, the assembly phase of the N+1-th stage of the stator blade 30 with respect to the N-th stage of the stator blade 30 is +θ.
FIG. 4 illustrates a section along an A-A line of FIG. 2, and illustrates a view for describing an effect on a backflow molecule in a case where the pair (the N-th stage and the N+1-th stage) of stator blades 30 adjacent to each other are shifted from each other by an assembly phase of +θ as illustrated in FIG. 3. As described later, in FIGS. 3 and 4, an assembly phase of +θ is set to about twice as great as the single-pitch angle θ1 of the N+1-th stage of the rotor blade 40.
As illustrated in FIG. 3, the phase of the N-th stage of the stator blade 30 and the phase of the N+1-th stage of the stator blade 30 are shifted from each other by +θ, and therefore, the clearance 305 between the divided stator blade 30 a and the divided stator blade 30 b is shifted in the circumferential direction (a right-left direction of FIG. 4). The clearance 305 of the N+1-th stage of the stator blade 30 is shifted from the clearance 305 of the N-th stage of the stator blade 30 in the rightward direction of FIG. 4.
As illustrated in FIG. 4, a case where gas molecules G on an exhaust side flow back through the clearance 305 of the N+1-th stage of the stator blade 30 will be assumed. Distribution of the gas molecule G, which has passed through the clearance 305 of the stator blade 30, in a movement direction is uneven distribution in the pump axial direction. For this reason, most of the gas molecules G having passed through the clearance 305 of the N+1-th stage of the stator blade 30 move upwardly along a pump axis as viewed in the figure. Some of the gas molecules G moving upwardly as viewed in the figure collide with blades 401 of the rotating rotor blade 40, and other gas molecules G reach the N-th stage of the stator blade 30 through a portion between the blades 401.
In an example illustrated in FIG. 4, the assembly phases of the N-th and N+1-th stages of the stator blades 30 are shifted from each other by +θ, and therefore, the clearance 305 of the N-th stage of the stator blade 30 and the clearance 305 of the N+1-th stage of the stator blade 30 do not face each other. Thus, the gas molecules G having reached the N-th stage of the stator blade 30 collide with the blade 301, and therefore, a backflow to the suction side is prevented. The gas molecules G having collided with the blade 301 are discharged to the exhaust side by exhaust action of the turbo pump stage TP including the stator blades 30 and the rotor blades 40.
As described above, the clearance 305 of the N-th stage of the stator blade 30 and the clearance 305 of the N+1-th stage of the stator blade 30 are shifted from each other by a phase of +θ, and therefore, the N-th stage of the stator blade 30 prevents most of the gas molecules G having flowed back in the clearance 305 of the N+1-th stage of the stator blade 30 from moving to the suction side. As a result, degradation of exhaust performance due to the backflow of the gas molecule G can be reduced. Such an effect of reducing degradation of the exhaust performance is more noticeable as a gas flow rate increases.
FIG. 5 illustrates, as a comparative example, a view in a case where the phases of the clearances 305 are coincident with each other. In this case, the gas molecules G having passed through the clearance 305 of the N+1-th stage of the stator blade 30 in the axial direction are likely to flow back to the suction side through the clearance 305 of the N-th stage of the stator blade 30. That is, when the assembly phases θ of the stages of the stator blades 30 adjacent to each other are coincident with each other (θ=0), influence of the backflow is great, and degradation of the exhaust performance is caused.
The above-described backflow reduction effect is obtained regardless of the degree of shift as long as the phases of the stages of the stator blades 30 adjacent to each other are shifted from each other. In the example illustrated in FIG. 4, the degree of the assembly phase θ (=+θ) is set to about twice as great as the single-pitch angle θ1 of the N+1-th stage of the rotor blade 40, but is preferably set greater than the single-pitch angle θ1 of the N+1-th stage of the rotor blade 40. When the degree of the assembly phase θ is smaller than the single-pitch angle θ1 of the N+1-th stage of the rotor blade 40, a probability that the gas molecules G having passed through the portion between the blades 401 flow back to the exhaust side through the clearance 305 of the N-th stage of the stator blade 30 is high.
For the multiple stages of the stator blades 30, the backflow of the gas molecule can be reduced as long as the phases of the stator blades 30 adjacent to each other in an upper-lower stage direction are shifted from each other. For example, the method for shifting the adjacent stator blades 30 from each other by the phase θ may be any of FIGS. 6 and 7. In an example illustrated in FIG. 6, the assembly phases of the N+1-th to N+3-th stages of the stator blades 30 are +θ, +2θ, and +3θ in this order in the counterclockwise direction with respect to the N-th stage of the stator blade 30, and the phase is shifted in the counterclockwise direction by +θ in every stage. On the other hand, in an example illustrated in FIG. 7, the N-th and N+2-th stages have the same phase (θ=0), and the assembly phases of the N+1-th and N+3-th stages are set to +θ. In any case, a similar reduction effect regarding degradation of the exhaust performance is obtained. When a phase between the stator blades 30 adjacent to each other is set to θ=90 degrees (deg), i.e., θ=90 deg is set in FIG. 7, arrangement is made with excellent workability in assembly.
(Position Adjustment Mechanism)
In a case where each of the multiple stages of the stator blades 30 is shifted by the constant phase θ as in FIGS. 6 and 7, if a position adjustment mechanism as illustrated in FIGS. 8 and 9 is provided, the workability can be improved and an assembly error can be prevented. FIG. 8 illustrates, from the pump suction port side, plan views of the spacer rings 33 (33 a, 33 b, 33 c) on which the N-th, N+1-th, and N+2-th stages of the stator blades 30 (the divided stator blades 30 a, 30 b) are placed. FIG. 9 illustrates a C-C sectional view of the stator blades 30 and the spacer rings 33 a, 33 b alternately stacked on each other. Note that in FIGS. 8 and 9, the assembly phase is −θ and the divided stator blades 30 a, 30 b are indicated by chain double-dashed lines. That is, the phases of the N+1-th and N+2-th stages of the stator blades 30 (the divided stator blades 30 a, 30 b) are shifted from the N-th stage of the stator blade 30 (the divided stator blades 30 a, 30 b) by −θ and −2θ.
Pins P1, P2 for adjusting the positions of the divided stator blades 30 a, 30 b are provided at each spacer ring 33 (33 a to 33 c). As illustrated in FIG. 9, the pin P1 is provided on a suction-side surface of a blade placement portion 331 formed at the spacer ring 33, and the pin P2 is provided on an exhaust-side surface of the blade placement portion 331. The pins P1, P2 are provided to be put into pin holes 332, 333 formed at the blade placement portion 331. The height h of an exposed portion of the pin P1, P2 is set smaller than the thickness dimension of the outer rib 303 of the divided stator blade 30 a, 30 b.
In a case where the N+1-th stage of the stator blade 30 (the divided stator blades 30 a, 30 b) is placed on the spacer ring 33 b, the divided stator blade 30 a is placed on the blade placement portion 331 on the left side of the pin P1 as viewed in FIG. 9, and the divided stator blade 30 b is placed on the blade placement portion 331 on the right side of the pin P1 as viewed in FIG. 9. The assembly phases of the divided stator blades 30 a, 30 b are set by the pin P1. Next, as illustrated in FIG. 9, the spacer ring 33 a is placed on the outer rib 303 of the N+1-th stage of the stator blade 30 (the divided stator blades 30 a, 30 b). At this point, the spacer ring 33 a is placed such that the pin P2 provided on the exhaust-side surface of the blade placement portion 331 of the spacer ring 33 a is put into the clearance 305 of the N+1-th stage of the stator blade 30.
Thereafter, the divided stator blade 30 a of the N-th stage is placed on the blade placement portion 331 on the left side of the pin P1 of the spacer ring 33 a as viewed in the figure, and the divided stator blade 30 b of the N-th stage is placed on the blade placement portion 331 on the right side of the pin P1 as viewed in the figure. As a result, the N+1-th stage of the stator blade 30 is assembled with the N-th stage of the stator blade 30 with the assembly phase (−θ). The pins P1, P2 are provided at the spacer rings 33 with a phase difference (180−θ) deg as described above, and therefore, the stages of the stator blades 30 adjacent to each other can be easily assembled with the phase difference (−θ).
Those skilled in the art understand that the above-described exemplary embodiment is a specific example of the following aspects.
[1] A turbo-molecular pump according to one aspect includes multiple stages of rotor blades formed with multiple blades and provided in a pump axial direction, and multiple stages of stator blades provided with multiple blades, the multiple stages of the rotor blades and the multiple stages of the stator blades being alternately arranged in the pump axial direction. Each stage of the stator blade includes multiple divided stator blades, and a clearance is formed at a portion where the multiple divided stator blades face each other. Circumferential phases of the clearances of adjacent ones of the stages of the stator blades in the pump axial direction are shifted from each other.
For example, as illustrated in FIG. 2, the stator blade 30 has the pair of divided stator blades 30 a, 30 b divided in the semi-circular shape and arranged in the circular shape with the clearances 305. The assembly phase (i.e., the circumferential phase) of the N+1-th stage of the stator blade 30 is shifted in the counterclockwise direction with respect to the assembly phase of the adjacent N-th stage of the stator blade 30 by the angle (+θ). That is, the circumferential phases of the clearances 305 of the N-th and N+1-th stages of the stator blades 30 are shifted from each other by the angle θ. As described above, the assembly phases of the stator blades 30 adjacent to each other are shifted from each other so that the backflow of the gas molecule can be reduced and degradation of the exhaust performance can be reduced.
Note that in the above-described embodiment, the stator blade 30 is divided into two divided stator blades 30 a, 30 b in the semi-circular shape, but may be divided into three or more fan-shaped divided stator blades. In this case, the same number of clearances 305 as the number of divisions are formed at the assembled stator blade 30. The assembly phases of the stages adjacent to each other are shifted from each other as in the case of division into halves so that advantageous effects similar to those in the case of division into halves can be provided.
[2] In the turbo-molecular pump according to [1], each rotor blade includes the multiple blades arranged at a predetermined interval in a circumferential direction. In a case where an angle between adjacent ones of the blades of each rotor blade in the circumferential direction is a single-pitch angle, the amount of shift between the circumferential phases of adjacent ones of the stages of the stator blades in the pump axial direction is set greater than the single-pitch angle.
For example, when the degree of the assembly phase θ is smaller than the single-pitch angle θ1 of the N+1-th stage of the rotor blade 40, the probability that the gas molecules G having passed through the portion between the blades 401 flow back to the exhaust side through the clearance 305 of the N-th stage of the stator blade 30 is high. However, the assembly phase θ is set greater (twice) than the single-pitch angle θ1 as in FIG. 4, and therefore, the probability of the backflow can be decreased. The effect of reducing degradation of the exhaust performance can be more enhanced.
[3] In the turbo-molecular pump according to [1], the amount of shift between the circumferential phases of adjacent ones of the stages of the stator blades is set to 90 deg. In stacking the stator blade 30, it is sufficient to alternately shift the stator blades 30 by 90 deg for each stage, therefore, the assembly workability is excellent.
[4] The turbo-molecular pump according to any one of [1] to [3] further includes multiple spacer rings provided such that the multiple spacer rings and the multiple stages of the stator blades are alternately stacked on each other in the pump axial direction. Each spacer ring includes a position adjustment member configured to adjust the circumferential phases of adjacent ones of the stator blades in the pump axial direction.
The spacer ring 33 includes the pins P1, P2 for position adjustment. Thus, when the divided stator blades 30 a, 30 b of the N+1-th stage are placed on the spacer ring 33 b, the divided stator blades 30 a, 30 b are arranged on both sides of the pin P1. When the spacer ring 33 a is placed on the divided stator blades 30 a, 30 b of the N+1-th stage, the spacer ring 33 a is arranged such that the pin P2 is inserted into the clearance 305 between the divided stator blades 30 a, 30 b of the N-th stage. Thus, the divided stator blades 30 a, 30 b of the N-th and N+1-th stages are automatically set to the phase shift θ. With this configuration, excellent assembly can be provided, and occurrence of an error regarding the assembly phase can be reliably prevented.
Various embodiments and variations have been described above, but the present invention is not limited to the contents of these embodiments and variations. Other aspects conceivable within the scope of the technical idea of the present invention are also included within the scope of the present invention.

Claims

What is claimed is:

1. A turbo-molecular pump comprising:

multiple stages of rotor blades formed with multiple blades and provided in a pump axial direction; and

multiple stages of stator blades provided with multiple blades, the multiple stages of the rotor blades and the multiple stages of the stator blades being alternately arranged in the pump axial direction,

wherein each stage of the stator blade includes multiple divided stator blades, and a clearance is formed at a portion where the multiple divided stator blades face each other, and

circumferential phases of the clearances of adjacent ones of the stages of the stator blades in the pump axial direction are shifted from each other.

2. The turbo-molecular pump according to claim 1, wherein

each rotor blade includes the multiple blades arranged at a predetermined interval in a circumferential direction, and

in a case where an angle between adjacent ones of the blades of each rotor blade in the circumferential direction is a single-pitch angle, an amount of shift between the circumferential phases of adjacent ones of the stages of the stator blades in the pump axial direction is set greater than the single-pitch angle.

3. The turbo-molecular pump according to claim 1, wherein

the amount of shift between the circumferential phases of adjacent ones of the stages of the stator blades is set to 90 deg.

4. The turbo-molecular pump according to claim 1, further comprising:

multiple spacer rings provided such that the multiple spacer rings and the multiple stages of the stator blades are alternately stacked on each other in the pump axial direction,

wherein each spacer ring includes a position adjustment member configured to adjust the circumferential phases of adjacent ones of the stator blades in the pump axial direction.

5. A stator used in a turbo-molecular pump comprising a rotor and the stator, wherein the rotor includes multiple stages of rotor blades formed with multiple blades and provided in a pump axial direction, and the stator includes multiple stages of stator blades provided with multiple blades, the multiple stages of the rotor blades and the multiple stages of the stator blades being alternately arranged in the pump axial direction,

6. The stator according to claim 5, wherein

7. The stator according to claim 5, wherein