JP2023116194A - Vacuum pump - Google Patents

Abstract

To provide a vacuum pump that can favorably discharge powder contained in gas from a rotor chamber.SOLUTION: A vacuum pump 1 includes: a pump casing 6 having a rotor chamber 5 therein; a pair of Roots rotors 8 disposed in the rotor chamber 5; and a pair of rotary shafts 9 supporting the pair of Roots rotors 8. The pump casing 6 has a gas inlet 12 and a gas outlet 13 communicating with the rotor chamber 5. A connection 25 between the inner wall 22 forming the rotor chamber 5 and an inner wall 23 forming the gas outlet 13 is located on or outside a rotor centerline CL, which extends through a center of rotation RC and a bottom dead point LP of each Roots rotor 8.SELECTED DRAWING: Figure 2

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum pump, and more particularly to a vacuum pump suitable for exhausting process gases used in manufacturing semiconductor devices, liquid crystal panels, LEDs, solar cells, and the like.

2. Description of the Related Art In manufacturing processes for manufacturing semiconductor devices, liquid crystal panels, LEDs, solar cells, etc., a process gas is introduced into a process chamber to perform various treatments such as etching and CVD. A process gas introduced into the process chamber is evacuated by a vacuum pump. In general, the vacuum pumps used in these manufacturing processes that require high cleanliness are so-called dry vacuum pumps that do not use oil in gas flow paths. A representative example of such a dry vacuum pump is a positive displacement vacuum pump that rotates a pair of roots rotors arranged in a rotor chamber in opposite directions to transfer gas.

JP 2010-101321 A

The process gas may contain powders that are by-products. Such powder flows into the vacuum pump along with the process gas. Most of the powder is exhausted from the vacuum pump with the process gas, but some of the powder stays in the rotor chamber and gradually builds up in the rotor chamber. The powder may accumulate on the inner wall of the rotor chamber and the outer surface of the roots rotor, resulting in impeding the rotation of the roots rotor.

Accordingly, the present invention provides a vacuum pump capable of satisfactorily discharging powder contained in gas from a rotor chamber.

In one aspect, a pump casing having at least one rotor chamber therein, at least a pair of roots rotors arranged in the rotor chamber, and at least a pair of rotating shafts supporting the pair of roots rotors, the pump casing comprising: It has a gas inlet and a gas outlet that communicate with the rotor chamber, and the connecting portion between the inner wall that forms the rotor chamber and the inner wall that forms the gas outlet passes through the rotation center and bottom dead center of each roots rotor. A vacuum pump is provided located on or outboard of the rotor centerline extending along the rotor centerline.

In one aspect, the width of the gas outlet is greater than the width of the gas inlet.
In one aspect, the pair of roots rotors are a pair of two-leaf roots rotors, and the angle of the straight line from the center of rotation to the connecting portion with respect to the rotor centerline is in the range of 0 degrees to 35 degrees.
In one aspect, the pair of roots rotors are a pair of three-lobe roots rotors, and the angle of a straight line from the center of rotation to the connecting portion with respect to the rotor centerline is in the range of 0 degrees to 45 degrees.
In one aspect, the at least one pair of roots rotors includes a pair of first roots rotors and a pair of second roots rotors arranged downstream of the pair of first roots rotors in a gas transfer direction, and the at least one rotor chamber includes a first rotor chamber in which the pair of first roots rotors are arranged and a second rotor chamber in which the pair of second roots rotors are arranged, and the pump casing communicates with the first rotor chambers. It has a gas inlet and a first gas outlet, and a second gas inlet and a second gas outlet communicating with the second rotor chamber, forming an inner wall forming the first rotor chamber and the first gas outlet. the inner wall forming the second rotor chamber; The second connection with the inner wall forming the second gas outlet is located on a second rotor centerline extending through the center of rotation and bottom dead center of each second roots rotor, or and the width of the first gas outlet is greater than the width of the second gas outlet.

According to the present invention, the width of the gas outlet that communicates with the rotor chamber is increased, making it difficult for powder contained in the gas to remain in the rotor chamber. As a result, the powder is discharged from the rotor chamber along with the gas, reducing the amount of powder deposited in the rotor chamber.

1 is a cross-sectional view of one embodiment of a vacuum pumping device; FIG. FIG. 2 is a cross-sectional view taken along the line AA of FIG. 1; FIG. 10 is a cross-sectional view showing another embodiment of a connecting portion between an inner wall forming a rotor chamber and an inner wall forming a gas outlet; FIG. 10 is a cross-sectional view showing still another embodiment of a connecting portion between an inner wall forming a rotor chamber and an inner wall forming a gas outlet; FIG. 10 is a cross-sectional view showing another embodiment of a gas outlet; 1 is a cross-sectional view showing one embodiment of a three-lobe roots rotor; FIG. FIG. 4 is a cross-sectional view showing another embodiment of a vacuum pump device; FIG. 8 is a cross-sectional view taken along line BB of FIG. 7; FIG. 8 is a cross-sectional view taken along line CC of FIG. 7;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing one embodiment of a vacuum pumping device. The vacuum pumping device of the embodiments described below is a positive displacement vacuum pumping device. In particular, the vacuum pump device shown in FIG. 1 is a so-called dry vacuum pump device that does not use oil in gas flow paths. Since the dry vacuum pump device does not allow vaporized oil to flow upstream, it can be suitably used in semiconductor device manufacturing equipment that requires high cleanliness.

As shown in FIG. 1 , the vacuum pump device includes a vacuum pump 1 and an electric motor 2 that drives the vacuum pump 1 . The vacuum pump 1 includes a pump casing 6 having a rotor chamber 5 inside, a pair of roots rotors 8 arranged in the rotor chamber 5 , and a pair of rotary shafts 9 supporting the pair of roots rotors 8 . Each roots rotor 8 and each rotating shaft 9 may be an integral structure. Although only one roots rotor 8 and one rotation shaft 9 are depicted in FIG. 1, a pair of roots rotors 8 are arranged in the rotor chamber 5 and supported by the pair of rotation shafts 9, respectively. The electric motor 2 is connected to one of the pair of rotating shafts 9 . In one embodiment, a pair of electric motors 2 may be coupled to a pair of rotating shafts 9, respectively.

Although the roots rotor 8 in this embodiment is a single stage pump rotor, in one embodiment the roots rotor 8 may be a multi-stage pump rotor.

The pump casing 6 has a gas inlet 12 and a gas outlet 13 communicating with the rotor chamber 5 . Gas inlet 12 is connected to a chamber (not shown) filled with the gas to be transferred. In one example, the gas inlet 12 is connected to a process chamber of a semiconductor device manufacturing apparatus, and the vacuum pump 1 is used to exhaust process gas introduced into the process chamber.

The vacuum pump 1 further comprises a gear housing 16 located outside the sidewall 6A of the pump casing 6. As shown in FIG. A pair of gears 20 that mesh with each other are arranged inside the gear housing 16 . Note that only one gear 20 is depicted in FIG. These gears 20 are fixed to the rotating shaft 9 respectively. The electric motor 2 is rotated by a motor driver (not shown), and one rotating shaft 9 to which the electric motor 2 is connected rotates the other rotating shaft 9 to which the electric motor 2 is not connected via a gear 20 in the opposite direction.

The rotating shaft 9 is rotatably supported by a bearing 17 held on one side wall 6A of the pump casing 6 and a bearing 18 held on the other side wall 6B of the pump casing 6 . The electric motor 2 has a motor housing 14 located outside the side wall 6B of the pump casing 6, and a motor rotor 2A and a motor stator 2B arranged within the motor housing 14. As shown in FIG.

In one embodiment, a pair of electric motors 2 coupled to a pair of rotating shafts 9 may be provided. The pair of electric motors 2 are synchronously rotated in opposite directions by a motor driver (not shown) to synchronously rotate the pair of rotating shafts 9 and the pair of roots rotors 8 in opposite directions. In this case, the role of the gear 20 is to prevent the synchronous rotation of the roots rotor 8 from being out of step due to sudden external factors.

When the roots rotor 8 is rotated by the electric motor 2 , gas is sucked into the pump casing 6 through the gas inlet 12 . Gas is transported from the gas inlet 12 to the gas outlet 13 by the rotating roots rotor 8 .

FIG. 2 is a cross-sectional view taken along line AA of FIG. As shown in FIG. 2, each roots rotor 8 of this embodiment is a two-leaf roots rotor. A gas inlet 12 is located on one side of the pump casing 6 and a gas outlet 13 is located on the opposite side of the pump casing 6 . A pair of roots rotors 8 are positioned between a gas inlet 12 and a gas outlet 13 . The roots rotor 8 and the inner wall 22 of the pump casing 6 forming the rotor chamber 5 are not in contact with each other, and the two roots rotors 8 are also in non-contact with each other. These roots rotors 8 rotate in opposite directions within the rotor chamber 5 as indicated by the arrows.

As the roots rotor 8 rotates, a closed space is formed between the outer surface of the roots rotor 8 and the inner wall 22 forming the rotor chamber 5 . The gas flowing from the gas inlet 12 fills this closed space, and the gas is transferred from the gas inlet 12 to the gas outlet 13 by rotating the pair of roots rotors 8 in opposite directions. The gas is evacuated by the vacuum pump 1 by continuously transferring the gas in such a closed space.

The gas inlet 12 and gas outlet 13 communicate with the rotor chamber 5 . The inner wall 23 forming the gas outlet 13 is connected to the inner wall 22 forming the rotor chamber 5 . As shown in FIG. 2, the connecting portion 25 between the inner wall 22 forming the rotor chamber 5 and the inner wall 23 forming the gas outlet 13 is located outside the rotor centerline CL. The rotor centerline CL is a straight line extending through the rotation center RC and the bottom dead center LP of each roots rotor 8 . The bottom dead center LP of the roots rotor 8 corresponds to the lowest point of the rotating roots rotor 8 . Here, "positioned outside the rotor center line CL" means a position across the rotor center line CL from the center point CP of the rotor chamber 5. As shown in FIG.

The width W2 of gas outlet 13 is greater than the width W1 of gas inlet 12 . For example, the width W2 of the gas outlet 13 is 1.1 to 2.0 times the width W1 of the gas inlet 12, preferably 1.7 times.

Examples of gases handled by the vacuum pump 1 of the present embodiment include process gases used in semiconductor device manufacturing apparatuses such as CVD apparatuses and etching apparatuses. This process gas contains powders of by-products. As can be seen from FIG. 2, the width W2 of the gas outlet 13 is larger than the width W1 of the gas inlet 12, so the powder is less likely to remain in the rotor chamber 5, and as a result, the powder accumulates in the rotor chamber 5. Hateful. Therefore, according to the present embodiment, it is possible to prevent rotation failure (for example, rotation stoppage) of the roots rotor 8 due to accumulation of powder in the rotor chamber 5 .

In this embodiment, each roots rotor 8 is a two-leaf roots rotor. A closed space must be formed between the outer surface of the roots rotor 8 and the inner wall 22 forming the rotor chamber 5 in order to transfer the gas from the gas inlet 12 to the gas outlet 13 . From this point of view, the connection 25 between the inner wall 22 forming the rotor chamber 5 and the inner wall 23 forming the gas outlet 13 is closer to the gas outlet 13 than to the gas inlet 12 . The angle α of the straight line NL from the rotation center RC to the connecting portion 25 with respect to the rotor center line CL is within the range of 0 degrees to 35 degrees. In one embodiment, connection 25 may be located on rotor centerline CL.

Although the width W2 of the gas outlet 13 is larger than the width W1 of the gas inlet 12, a closed space is provided between the outer surface of the roots rotor 8 and the inner wall 22 forming the rotor chamber 5, as described above. is formed, the evacuation performance of the vacuum pump 1 does not substantially decrease.

Although the embodiment shown in FIG. 2 describes the arrangement of the connection 25 associated with one of the two roots rotors 8 and the rotor centerline CL, the connection associated with the other roots rotor 8 and the rotor centerline , and so on, redundant description and reference numerals are omitted.

As shown in FIG. 3, the connecting portion 25 between the inner wall 22 forming the rotor chamber 5 and the inner wall 23 forming the gas outlet 13 may have an arc-shaped cross section. Alternatively, as shown in FIG. 4, the connecting portion 25 between the inner wall 22 forming the rotor chamber 5 and the inner wall 23 forming the gas outlet 13 may have a chamfered cross section. According to the shape shown in FIGS. 3 and 4, turbulence of the gas is less likely to occur, and the powder can be sent to the gas outlet 13 smoothly.

In the embodiment shown in FIGS. 2-4, the inner wall 23 forming the gas outlet 13 is parallel to the rotor centerline CL and the width of the gas outlet 13 is constant. In one embodiment, as shown in FIG. 5, the inner wall 23 forming the gas outlet 13 may slope outward with distance from the center point CP of the rotor chamber 5 . That is, the width of the gas outlet 13 may gradually increase with the distance from the center point CP of the rotor chamber 5 . Such a shape allows the gas containing the powder to smoothly pass through the gas outlet 13 .

The roots rotor 8 may be a trilobal roots rotor, as shown in FIG. In the embodiment shown in FIG. 6 as well, the connection 25 between the inner wall 22 forming the rotor chamber 5 and the inner wall 23 forming the gas outlet 13 extends through the center of rotation RC and the bottom dead center LP of each roots rotor 8. It is located on the centerline CL or located outside the rotor centerline CL. The configuration of the embodiment of FIG. 6, which is not particularly described, is the same as that of the embodiment described with reference to FIG. 2, so redundant description thereof will be omitted.

As in the embodiment described with reference to FIG. 2, a closed space must be formed between the outer surface of the roots rotor 8 and the inner wall 22 forming the rotor chamber 5 . From this point of view, in the embodiment shown in FIG. 6, the angle α of the straight line NL from the rotation center RC to the connecting portion 25 with respect to the rotor center line CL is within the range of 0 degrees to 45 degrees.

Although not shown, the roots rotor 8 may be a roots rotor with four or more lobes. Even in that case, the connecting portion 25 between the inner wall 22 forming the rotor chamber 5 and the inner wall 23 forming the gas outlet 13 is on the rotor center line CL extending through the rotation center RC and the bottom dead center LP of each roots rotor 8. or outside the rotor centerline CL. Since the width of the gas outlet 13 is larger than the width of the gas inlet 12 , powder is less likely to remain in the rotor chamber 5 , and as a result, powder is less likely to accumulate in the rotor chamber 5 .

FIG. 7 is a cross-sectional view showing another embodiment of the vacuum pump 1. As shown in FIG. The vacuum pump 1 of this embodiment is a multi-stage vacuum pump. Since the description of the embodiment with reference to FIGS. 1 to 6 can also be applied to the configuration and operation of this embodiment, redundant description thereof will be omitted.

As shown in FIG. 7, the vacuum pump 1 includes a pump casing 6 having a plurality of rotor chambers 5A to 5E therein, a plurality of pairs of roots rotors 8A to 8E arranged in the rotor chambers 5A to 5E, respectively, and a plurality of pairs of rotors 8A to 8E. Roots rotors 8A to 8E are provided. Roots rotors 8A to 8E and rotary shaft 9 may be an integral structure. Although only one set of roots rotors 8A to 8E and rotating shaft 9 are depicted in FIG. It is The electric motor 2 is connected to one of the pair of rotating shafts 9 . In one embodiment, a pair of electric motors 2 may be coupled to a pair of rotating shafts 9, respectively.

Roots rotors 8A-8E and rotor chambers 5A-5E are arranged along the gas transfer direction. In other words, the roots rotor 8A and the rotor chamber 5A are positioned on the most upstream side in the direction of gas transfer within the pump casing 6 . The roots rotor 8B and the rotor chamber 5B are located downstream of the roots rotor 8A and the rotor chamber 5A, the roots rotor 8C and the rotor chamber 5C are located downstream of the roots rotor 8B and the rotor chamber 5B, and the roots rotor 8D and the rotor chamber 5D are: Roots rotor 8C and rotor chamber 5C are positioned downstream, and roots rotor 8E and rotor chamber 5E are positioned downstream of roots rotor 8D and rotor chamber 5D. The roots rotor 8E and the rotor chamber 5E are positioned on the most downstream side in the direction of gas transfer within the pump casing 6 .

The pump casing 6 includes a gas inlet 12A and a gas outlet 13A communicating with the rotor chamber 5A, a gas inlet 12B and a gas outlet 13B communicating with the rotor chamber 5B, a gas inlet 12C and a gas outlet 13C communicating with the rotor chamber 5C, It has a gas inlet 12D and a gas outlet 13D communicating with the rotor chamber 5D, and a gas inlet 12E and a gas outlet 13E communicating with the rotor chamber 5E. The gas outlet 13A communicates with the gas inlet 12B through a channel (not shown), the gas outlet 13B communicates with the gas inlet 12C through a channel (not shown), and the gas outlet 13C communicates through a channel (not shown). It communicates with the gas inlet 12D, and the gas outlet 13D communicates with the gas inlet 12E via a channel (not shown).

When the electric motor 2 rotates the Roots rotors 8A-8E, gas is sucked into the rotor chamber 5A through the gas inlet 12A. Gas is sequentially compressed by Roots rotors 8A-8E in rotor chambers 5A-5E and discharged from pump casing 6 through gas outlet 13E.

8 is a cross-sectional view taken along the line BB of FIG. 7. FIG. As shown in FIG. 8, the roots rotors 8A to 8E of this embodiment are three-lobe roots rotors. A connecting portion 25A between the inner wall 22A forming the rotor chamber 5A and the inner wall 23A forming the gas outlet 13A is located outside the rotor center line CL1 passing through the rotation center RC1 and the bottom dead center LP1 of the roots rotor 8A. . The angle α1 of the straight line NL1 from the rotation center RC1 of the roots rotor 8A to the connecting portion 25A with respect to the rotor center line CL1 is within the range of 0 to 45 degrees. The width W4 of the gas outlet is greater than the width W3 of the gas inlet 12A.

9 is a cross-sectional view taken along line CC of FIG. 7. FIG. As shown in FIG. 9, the connecting portion 25E between the inner wall 22E forming the rotor chamber 5E and the inner wall 23E forming the gas outlet 13E is located from the rotor center line CL2 passing through the rotation center RC2 and the bottom dead center LP2 of the roots rotor 8E. are also located outside. In one embodiment, connection 25E may be located at rotor centerline CL2. The angle α2 of the straight line NL2 from the rotation center RC2 of the roots rotor 8E to the connecting portion 25E with respect to the rotor center line CL2 is within the range of 0 to 45 degrees and is smaller than the angle α1 shown in FIG. The width W6 of the gas outlet 13E is greater than the width W5 of the gas inlet 12E.

Although not shown, the connecting portion between the inner wall forming the rotor chamber 5B and the inner wall forming the gas outlet 13B, the connecting portion between the inner wall forming the rotor chamber 5C and the inner wall forming the gas outlet 13C, and the rotor chamber 5D are formed. Each connection between the inner wall and the inner wall that forms the gas outlet 13D is also positioned outside or on the corresponding rotor centerline.

According to the embodiments described with reference to FIGS. 7-9, the width of the gas outlets 13A-13E is greater than the width of the gas inlets 12A-12E, respectively, so that the powder is placed in the rotor chambers 5A-5E. As a result, it is difficult for the powder to accumulate in the rotor chambers 5A to 5E.

8 and 9, the width W4 of the gas outlet 13A shown in FIG. 8 is larger than the width W6 of the gas outlet 13E shown in FIG. This is based on the results of powder flow simulations showing that a wider gas outlet width on the low pressure side and a relatively smaller gas outlet width on the atmospheric pressure side facilitates powder discharge. there is According to this embodiment, the powder can be discharged from the pump casing 6 sequentially through the rotor chambers 5A-5E.

The relationship of the widths of the gas outlets 13A to 13E is not particularly limited as long as the width of the gas outlet 13A is greater than the width of the gas outlet 13E. For example, the widths of gas outlets 13A, 13B, 13C may be the same as each other and greater than the width of gas outlets 13D, 13E. Alternatively, the width of the gas outlets 13A, 13B, 13C, 13D, 13E may be gradually reduced according to the direction of gas transport within the pump casing 6.

The vacuum pump 1 shown in FIG. 7 is a five-stage vacuum pump, but the number of stages of the roots rotor 8 is not particularly limited. For example, vacuum pump 1 may be a two-stage vacuum pump with two pairs of roots rotors, or a multi-stage vacuum pump with six or more pairs of roots rotors.

The above-described embodiments are described for the purpose of enabling a person having ordinary knowledge in the technical field to which the present invention belongs to implement the present invention. Various modifications of the above embodiments can be made by those skilled in the art, and the technical idea of the present invention can be applied to other embodiments. Accordingly, the present invention is not limited to the described embodiments, but is to be construed in its broadest scope in accordance with the technical spirit defined by the claims.

1 vacuum pump 2 electric motor 2A motor rotor 2B motor stator 5, 5A to 5E rotor chamber 6 pump casing 8, 8A to 8E roots rotor 9 rotating shaft 12, 12A to 12E gas inlet 13, 13A to 13E gas outlet 14 motor housing 16 gear housing 17 Bearing 18 Bearing 20 Gear 22 Inner wall 23 of pump casing Inner wall 25 of gas outlet Connecting part CL Rotor center line RC Rotation center of root rotor LP Bottom dead center of root rotor CP Center point of rotor chamber

Claims (5)

a pump casing having at least one rotor chamber therein;
at least a pair of roots rotors disposed within the rotor chamber;
At least a pair of rotating shafts supporting the pair of roots rotors,
the pump casing has a gas inlet and a gas outlet communicating with the rotor chamber;
The connecting portion between the inner wall forming the rotor chamber and the inner wall forming the gas outlet is located on the rotor centerline extending through the rotation center and bottom dead center of each roots rotor, or is located on the rotor centerline. The vacuum pump is also located outside. 2. The vacuum pump of claim 1, wherein the width of the gas outlet is greater than the width of the gas inlet. 3. The pair of roots rotors according to claim 1, wherein the pair of roots rotors are a pair of two-leaf roots rotors, and the angle of the straight line from the center of rotation to the connecting portion with respect to the center line of the rotors is within a range of 0 degrees to 35 degrees. vacuum pump. The pair of roots rotors is a pair of three-lobe roots rotors, and the angle of the straight line from the rotation center to the connecting portion with respect to the rotor center line is within a range of 0 degrees to 45 degrees. Vacuum pump as described. The at least one pair of roots rotors includes a pair of first roots rotors and a pair of second roots rotors arranged downstream of the pair of first roots rotors in the gas transfer direction,
the at least one rotor chamber includes a first rotor chamber in which the pair of first roots rotors are arranged and a second rotor chamber in which the pair of second roots rotors are arranged;
The pump casing has a first gas inlet and a first gas outlet communicating with the first rotor chamber, and a second gas inlet and a second gas outlet communicating with the second rotor chamber,
A first connecting portion between the inner wall forming the first rotor chamber and the inner wall forming the first gas outlet is located more than the first rotor centerline extending through the rotation center and bottom dead center of each first roots rotor. is located outside
A second connecting portion between the inner wall forming the second rotor chamber and the inner wall forming the second gas outlet is located on the second rotor centerline extending through the rotation center and bottom dead center of each second roots rotor. or is located outside the second rotor centerline,
5. A vacuum pump as claimed in any preceding claim, wherein the width of the first gas outlet is greater than the width of the second gas outlet.

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