JPH04330397A - Turbo molecular pump - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbo-molecular pump, and more particularly to an axial-flow type turbo-molecular pump equipped with rotary vanes and stationary vanes.

[0002] Turbomolecular pumps, which create a vacuum state by discharging gas molecules using high-speed rotary blades and stationary blades, are commonly used in sputtering equipment, vapor deposition equipment, etc. for thin film formation technology due to their high efficiency. used in And in recent years,
Research and practical application are being made in various fields of technology that operates in an ultra-high vacuum (10-10 torr or less) environment, which has a higher degree of vacuum than the sputtering equipment and vapor deposition equipment mentioned above. There is a strong desire to adopt the above-mentioned efficient turbomolecular pump in place of the conventional ion pump, which has poor performance.

0003

2. Description of the Related Art FIG. 6 is a sectional view of an example of a conventional turbo-molecular pump.

In the figure, a turbo molecular pump (hereinafter simply referred to as pump) 1 generally includes a casing 2 provided with a gas inlet 2a and a gas outlet 2b, and blades 3a radially extending from a rotating shaft 3b. , consists of a rotary blade 3 formed in multiple stages along the axial direction of the rotary shaft 3b, and a stationary blade 4 fixed within the casing 2 so as to be disposed between the blades 3a of each stage of the rotary blade 3. ing.

The rotary blade 3 is rotated at a high speed of about several thousand rpm/min by a prime mover 5 fixed to the lid 2c of the casing 2. For this reason, the rotor blade 3 needs to be strong enough to withstand centrifugal force and collisions with gas molecules during high-speed rotation, and therefore, the rotor blade 3 is manufactured using a manufacturing method in which the blades 3a and the rotating shaft 3b are carved out of one member. It is removed and formed into a high-strength material.

As shown in a plan view and a side view in FIG.
d is an extended shape, and in order to arrange it around the rotary blade 3 integrally formed as described above, the two stationary blade halves 4a and 4b are butted together at the abutting surface 4c to form a circular shape. The structure is such that a stationary wing 4 is formed. stationary wing 4
The blades 4d of the stationary blade halves 4a and 4b are connected to the rotary blade 3.
It is installed around the rotor blade 3 by inserting it from both sides between the upper and lower blades 3a and bringing the respective abutment surfaces 4c into contact with each other.

As shown in FIG. 6, the stationary blade 4 having the above configuration has a circumferential portion 4e having a flat upper and lower surface.
It is fixed within the casing 2 by being sandwiched by a ring-shaped spacer 6 having the same outer diameter as . At this time, the axial position of the stationary blade 4 is also determined by the spacer 6 at the same time.

[0008] In the assembly process of the pump 1, first, the lid part 2 is assembled.
The rotary blade 3 is installed together with the prime mover 5 on c, and around it,
Spacers 6-1, 6-2, 6-3..., stationary wings 4-1, 4
By assembling -2, 4-3... from the bottom alternately,
A stack 7 having rotary blades 3 and stationary blades 4 is formed on the lid portion 2c. Then, the stack 7 is fitted into the main body 2d of the casing 2 from below, and the lid 2c is fixed to the main body 2d with bolts 8. At this time, by tightening the bolt 8, the spacer 6 holding the stationary blade 4 is compressed in the axial direction, so that the stationary blade 4 is firmly fixed within the casing 2.

The blades 3a and 4d each have a pitch, and when the rotor blade 3 rotates at high speed as described above, gas molecules are discharged from the gas suction part 2a to the gas discharge part 2b, and the gas molecules are discharged from the gas suction part 2a to the gas discharge part 2b. Make a vacuum on the side.

0010

[Problems to be Solved by the Invention] The pump 1 having the above-mentioned structure has the rotor blade 3 having ten or more stages (seven stages are omitted in FIG. 6), and when the rotor vane 3 is rotated at a predetermined rotation speed, Theoretically, compression of 10,000 to 1,000,000 times can be achieved, and an ultra-high vacuum of about 10-10 torr can be created in the gas suction section 2a. However, pump 1
The ultimate vacuum degree in actual operation is 10-10to
It is much lower than rr, and it is impossible to form a theoretical ultra-high vacuum.

[0011] It is believed that the reason why the ultimate vacuum degree is far lower than the theoretical value is that there is a problem in the structure of the pump 1. FIG. 8 is a diagram illustrating problems with the conventional pump 1.

Since the pump 1 is assembled by fitting the stack 7 into the main body 2d of the casing 2 as described above, a small gap 9 is formed between the stack 7 and the main body 2d. Furthermore, the degree of vacuum within this gap 9 is considered to be a low degree of vacuum of 10 -3 torr or less due to the manufacturing process.

Therefore, when the pump 1 is operating, a large pressure difference occurs between the gap 9 and the area near the gas suction part 2a, and as shown in FIG. 8, each spacer 6 is not completely vacuum-sealed. and the stationary blade 4, ■ a gap 6b between the uppermost spacer 6A and the casing 2, and ■ a gap 4f between the abutting surfaces 4c of the stationary blade 4 (shown in FIG. 7).
, the gas molecules in the gap 9 flow into the vicinity of the gas suction part 2a with a high degree of vacuum, and thereby,
It is assumed that the degree of vacuum near the gas suction part 2a will be lower than the theoretical value.

SUMMARY OF THE INVENTION The present invention was made in view of the above problems, and an object of the present invention is to provide a turbo-molecular pump that can prevent leakage of gas molecules, improve the degree of vacuum achieved, and create an ultra-high vacuum state. shall be.

[0015]

[Means for Solving the Problem] In order to achieve the above object, the invention of claim 1 provides annular first and second stationary blade support members that sandwich the stationary blade around the rotary blade. In the turbo molecular pump, a vacuum sealing mechanism for blocking gas flow is provided in a first gap interposed between the stationary blade and each of the first and second stationary blade support members. .

[0016] Furthermore, the invention as claimed in claim 2 is such that the stationary blade that can be divided in the circumferential direction is sandwiched between the stationary blade supporting members in a state where the ends of the divided stationary blade segments are abutted against each other to form an annular shape. In the turbo-molecular pump, in which a second gap is interposed between the abutted stationary blade segments,
The stationary blade support member is configured to include a contact surface that comes into contact with an outer circumferential surface of the stationary blade where the second gap is exposed, and the contact surface closes the second gap.

Furthermore, from the viewpoint of further simplifying the vacuum sealing mechanism, the invention of claim 3 provides that the vacuum sealing mechanism includes the stationary blade forming the first gap and the first gap.
and a second stationary wing support member is formed of two types of members having different hardness, and is opposed to the first gap of the stationary wing having higher hardness or the first or second stationary wing support member. a protrusion is formed on a surface of the stationary wing that has a lower hardness, and the protrusion bites into a surface of the stationary wing having a lower hardness or a surface of the first or second stationary wing support member that faces the first gap; This structure blocks the flow of gas.

[0018]

[Operation] In the invention of claim 1, the vacuum sealing mechanism vacuum-seals the first gap interposed between the stationary blade and the first and second stationary blade support members, so that the gas This prevents infiltration from the outside of the stationary blade support member to the inside rotary blade side through the gap.

In the invention of claim 2, the contact surface of the stationary blade support member contacts the outer circumferential surface of the stationary blade, thereby forming the second gap in the portion where the second gap is exposed to the outer circumferential surface. This prevents gas from entering the inner rotating blade side from the outside of the stationary blade.

[0020] In the invention of claim 3, the protrusion having high hardness is simply formed by biting into the opposing stationary blade having low hardness or the surface facing the first gap of the first or second stationary blade support member. The structure completely blocks the flow of gas.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a partial sectional view of an embodiment of a turbomolecular pump according to the present invention.

In the figure, a turbomolecular pump (hereinafter simply referred to as pump) 20 includes a stationary blade 21, spacers 22, 23, 24 supporting the stationary blade 21, and a casing 2.
5 has the same structure as the conventional pump 1, and therefore, the same reference numerals are given to the parts corresponding to those shown in FIG.

The rotor blade 3 has completely the same structure as the conventional one,
Blades 3a are formed radially from a rotating shaft 3b connected to a prime mover (not shown), and multiple stages of blades 3a are provided at regular intervals along the axial direction of the rotating shaft 3b. .

Between the blades 3a of each stage, the stationary blades 21 are provided with spacers 22, 23, 24, which will be described later, so that the blades 3a of the rotary blades 3 and the blades 21a of the stationary blades 21 overlap on a plane in a non-contact state. It is sandwiched between.

As shown in FIG. 1, the stationary blade 21 has a configuration in which the outer circumferential surface 21c does not reach the outer circumferential surfaces of the spacers 22, 23, and 24, so the outer diameter dimension of the stationary blade 21 is as follows.
In FIG. 8, the outer diameter dimension of the conventional stationary blade 4 reaching the outer peripheral surface of the spacer 6 is slightly smaller than that of the conventional stationary blade 4. The stationary blade 21 has the same structure as the conventional stationary blade 4 shown in FIG. 7 except for the above-mentioned difference in outer diameter. It has a shape in which the blade 21a extends toward the center.

2A and 2B show a plan view and a sectional view of the spacer 23, respectively, and FIG. 3 shows a sectional view of the spacer 24. Note that FIG. 2(B) shows a cross section taken along line IIb-IIb in FIG. 2(A).

The spacer 23 is an annular member made of a hard metal such as stainless steel, and has a cross-sectional shape shown in FIG. 2(B). In FIG. 2(B), spacer 2
A step-shaped stationary blade holding part (hereinafter simply referred to as a holding part) 23a for holding the stationary blade 21 is formed on the inner peripheral side of the blade 3 with an open upper part. A convex portion 23b for pressing the lower stationary blade 21 into the lower holding portion is formed at the lower portion of the holding portion 23a. Spacer 23
Contact surfaces 23c, 23d with other stacked spacers are formed on the outer peripheral side of the spacer, and furthermore, these contact surfaces 23c, 2
Sharp-pointed protrusions 23e and 23f are formed in the central portion of 3d, respectively. Note that the holding portion 23a and the convex portion 23b
, the protrusions 23e, 23f are all provided circumferentially along the main body of the spacer 23.

The spacers 24 disposed above and below the spacer 23 are made of a metal with low hardness such as an aluminum alloy, and as shown in FIG.
It has the same shape as the spacer 23 except for the protrusions 23e and 23f. The contact surfaces 24c and 24d are not formed with protrusions and are flat surfaces.

In FIG. 1, the uppermost spacer 22 is made of a metal with low hardness, which is the same material as the spacer 24, and the spacer 22 is the same as the spacer 2 except that the holding portion 24a is not formed on the inner circumferential side.
It has the same configuration as 4.

In the pump 20 of this embodiment, as shown in FIG. 1, spacers 23 and spacers 24 having the above configuration are alternately stacked along the axial direction of the rotor blade 3 with the spacer 22 at the top. has been done.

Furthermore, as shown in FIG. 1, the casing 25 of the pump 20 has a main body portion 25d that contacts the spacer 22.
A protrusion 25f is formed on the surface thereof, and a protrusion is similarly formed on the surface of the lid (not shown) that contacts the lowermost spacer. The casing 25 has the same structure as the conventional casing 2 except for these protrusions.

[0032] Here, the assembly process of the pump 20 of this embodiment will be explained.

First, in the same manner as in the assembly process of the pump 1 described above, the prime mover and the rotor blades 3 are provided on the lid portion constituting the casing 25. Then, spacers 23 and 24 are stacked alternately around the rotary blade 3 from below while sandwiching the stationary blade 21. That is, as shown in an enlarged view of the attached state of the spacers 23 and 24, the outer peripheral part 21b of the stationary blade 21 is fitted into each of the holding parts 23a and 24a of the spacers 23 and 24, and from above Spacers 23 and 24 arranged
Further, the protrusions 23b and 24b are fitted. This convex portion 23b
, 24b and the holding parts 23a, 24b.
The outer peripheral part 21b of the stationary blade 21 is sandwiched between the spacer 23
, 24.

Finally, the uppermost spacer 22 is placed to form a stack 30 in which the prime mover, rotary blades 3, and stationary blades 21 are installed on the lid. In this way, when the spacers 23 and 24 are stacked alternately on the lid of the casing 25, the tips of the protrusions 23e and 23f of the spacers 23 simply contact the contact surfaces 24c and 24d of the opposing spacers 24. The situation is as follows.

Then, as explained in connection with the conventional pump 1, the stack 30 having the above structure is fitted into the main body 25d of the casing 25, and the bolts fixing the lid to the main body 25d are tightened. When the bolts are tightened, the spacers 22 and 23 stacked along the axial direction of the rotor blade 3 as described above
, 24 are compressed along the axial direction between the main body 25d of the casing 25 and the lid, and as shown in FIG.
3f bites into the abutment surfaces 24c and 24d of the spacer 24 made of metal with low hardness. Further, the protrusion 2 provided on the main body 25d of the casing 25
5f, and a protrusion provided on the lid (not shown) of the casing 25, the contact surface 22c of the uppermost spacer 22,
and into the contact surfaces of the lowermost spacer (not shown), respectively. In the pump 20, when the lid of the casing 25 is attached to the main body 25d as described above, the casing 25 is moved such that the projections 23e, 23f, 25f bite into the opposing contact surfaces 24c, 24d, 22c, respectively. The axial dimensions of each of the spacers 22, 23, and 24 are determined in advance.

Furthermore, due to the compression in the axial direction, the convex portion 23
b, 24b and the holding parts 23a, 24a strongly hold the stationary blade 21, and the stationary blade 21 more firmly holds the spacers 22, 23,
It is fixed between 24 and 24 hours.

As described above, the pump 20 of this embodiment has a structure in which the protrusions 23e, 23f and the protrusions provided on the casing 25 bite into the opposing contact surfaces 22c, 24c, 24d, thereby blocking the gas flow. Vacuum sealing mechanisms are formed in the gaps between the spacers 22, 23, and 24, and in the gaps between the uppermost and lower spacers and the casing 25, respectively.

Therefore, when the pump 20 is in operation, the gap 3 formed between the stack 30 and the casing 25
1 is prevented from flowing out into the vicinity of the gas suction part 25a with a high degree of vacuum through the gaps between the spacers 22, 23, and 24 and the gap between the uppermost and lower spacers and the casing 25. Therefore, the gas suction part 2 of the pump 20
The ultimate degree of vacuum near 5a increases compared to the conventional case.

Furthermore, according to the vacuum sealing mechanism having the above configuration,
Since the gas flow can be reliably sealed with a simple structure, the manufacturing cost of the pump 20 can be reduced and the reliability at the product stage can be improved at the same time.

Furthermore, in the conventional pump 1, gas molecules also pass through the gap 4f between the abutting surfaces 4c of the two divided stationary blades 4, which causes a decrease in the ultimate vacuum. However, the pump 2 of this embodiment
According to 0, as shown in FIG.
is formed into a deep stepped shape, and contact surfaces 23g and 24g that contact the entire outer circumferential surface 21c of the stationary blade 21 fitted in the holding parts 23a and 24a are formed, thereby making it possible to butt the two divided stationary blades 21. The gap between the surfaces is closed at its ends by the abutting surfaces 23g and 24g, thereby blocking the gas molecules present in the gap 31 from entering through the abutting surfaces, which occurred in the past.

FIG. 5 shows a partial sectional view of a modification of the turbomolecular pump according to the invention.

In FIG. 5, the spacer 41 has a holding portion 41 of the stationary blade 21 on the inner circumferential side, similar to the spacer 24 of the above embodiment.
a and a convex portion 41b are formed, and a flat contact surface 41c that contacts the upper spacer 41 is formed at the upper part. A groove 41e is formed along the circumferential direction on the lower contact surface 41d of the spacer 41, and an O-ring 50 is attached thereto. Further, a groove 4 is also provided on the lower surface of the casing 43 that contacts the uppermost spacer 42, similar to the groove 41e.
3a is formed and an O-ring 50 is attached.

In the pump 40 of this modification, as shown in the figure, a stack 44 is formed by stacking spacers 41 having the above structure around the rotary blade 3 while sandwiching the stationary blade 21 therebetween. Then, the stack 44 is fitted into the casing 43, and the lid part (not shown) of the casing 43 is
When fixed to the main body part 43b with bolts, each spacer 41 is compressed along the axial direction of the rotor blade 3 as in the above embodiment, and each O-ring 50 is brought into close contact with the opposing contact surface 41c due to elastic force. Become. Therefore, gas molecules are prevented from passing through the gap between the spacers 41 and the gap between the spacer 41 and the casing 43, and as in the above embodiment, the gas molecules in the gap 45 between the stack 44 and the casing 43 are prevented from passing through the spacer 41 and the gap between the spacer 41 and the casing 43. This prevents the liquid from flowing to the inner peripheral side of 41.

As described above, the vacuum sealing mechanism is not limited to the one using the protrusion in the above embodiment, but even if it is constructed using the O ring 50 as in the above modification, it can be constructed using the same method as in the above embodiment. effect can be obtained. In addition to the O-ring 50 described above, the vacuum sealing mechanism may also include a sealing material such as aluminum foil or gold foil, or an adhesive with low vapor pressure sandwiched between spacers. , it goes without saying that the same effects as the above embodiments and modifications can be obtained.

Furthermore, in the above embodiment and the above modification using an O-ring, vacuum sealing mechanisms are provided at all stages of the stationary blade 21, but pressure is not maintained between the inside and outside of the spacer. Even with a configuration in which a vacuum sealing mechanism is provided only on the gas suction side, where the difference is large, it is possible to prevent most of the gas molecules from entering the inside of the spacer, improving the ultimate vacuum compared to conventional methods. be able to. The structure of the pump is simplified compared to the case where vacuum sealing mechanisms are provided in all stages, and the benefits of this simplification can be obtained at the same time.

[0046]

As described above, according to the invention of claim 1, since the vacuum sealing mechanism vacuum-seals the stationary blade and the first gap between the first and second stationary blade support members, the gas is prevented from flowing from the outside to the inside rotary blade side, and the ultimate vacuum degree of the turbomolecular pump can be increased compared to the conventional one.

Further, according to the invention of claim 2, even in a turbo molecular pump having a structure in which the stationary blade is divided and arranged around the rotary blade, the contact surface provided on the stationary blade support member is In order to close the second gap between the abutted stationary wing segments,
Gas is prevented from flowing from the outside of the stationary blade to the inside of the rotary blade, making it possible to increase the ultimate vacuum of the turbomolecular pump compared to the prior art.

Furthermore, according to the third aspect of the invention, it is possible to construct a vacuum sealing mechanism that reliably blocks the flow of gas with a simple structure, thereby reducing the manufacturing cost of the turbomolecular pump.
Also, reliability and durability can be improved.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view of an embodiment of a turbomolecular pump according to the present invention.

FIG. 2 is a plan view and a sectional view of a spacer.

FIG. 3 is a cross-sectional view of a spacer.

FIG. 4 is a diagram illustrating a fixed state of the stationary wing in FIG. 1;

FIG. 5 is a partial sectional view of a modification of the turbomolecular pump of the present invention.

FIG. 6 is a cross-sectional view of the configuration of an example of a conventional turbomolecular pump.

7 is a plan view and a side view of the stationary wing shown in FIG. 6. FIG.

FIG. 8 is a diagram illustrating a problem with the turbomolecular pump shown in FIG. 6.

[Explanation of symbols]

3 Rotary blades 3a, 21a Blades 20, 40 Turbo molecular pump 21 Stationary blade 21b Outer peripheral part 21c Outer peripheral surface 22, 23, 24, 41 Spacer 23a, 24a, 41a Stationary blade holding part 23b, 24
b, 41b Convex portions 23c, 23d, 23g, 24c, 24d, 24g, 4
1c, 41d Contact surfaces 23e, 23f, 25f Projections 25, 43 Casing 25d, 43b Main body 30, 44 Stack 31, 45 Gap 50 O-ring

Claims (3)

[Claims] Claim 1: A stationary blade (21) is provided around the rotary blade (3).
) sandwiching the annular first and second stationary blade support members (2
2, 23, 24), the first stationary blade interposed between the stationary blade (21) and the first and second stationary blade support members (22, 23, 24), respectively. A vacuum sealing mechanism (23
A turbo molecular pump characterized in that it is provided with: e, 23f, 24e, 24d, 50, 41c). Claim 2: A stationary blade (2) that can be divided in the circumferential direction.
1) is attached to the stationary blade support member (22, 23, 2
4) In the turbo-molecular pump in which a second gap is interposed between the abutted stationary blade segments, the stationary blade support member (22, 23, 24)
The second gap of the stationary blade (21) is provided with contact surfaces (23g, 24g) that come into contact with the exposed outer peripheral surface (21c), and the corresponding contact surfaces (23g, 24g) are connected to the second gap. A turbo molecular pump characterized by having a configuration that blocks the. 3. The vacuum sealing mechanism includes the stationary blade (21) forming the first gap, and the first and second gaps.
The stationary blade support members (22, 23, 24) are formed of two types of members having different hardness, and the stationary blade (21), which has higher hardness, or the first or second stationary blade support member ( 23) facing the first gap (23c, 23)
d) is formed with protrusions (23e, 23f), and the protrusions (23e, 23f) are attached to the stationary blade (21), which has a lower hardness, or the first or second stationary blade support member. (2
2, 24) facing the first gap (24c, 2)
4. The turbo-molecular pump according to claim 1, wherein the turbo-molecular pump is configured to cut off gas flow by biting into 4d).