JP2002285989A - Vacuum pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a safe vacuum pump preventing damage of a pump case, peripheral apparatuses and the like by reducing broken parts in rotor breakage accident and weakening instant breaking torque. SOLUTION: The rotor 2 is divided into an upper part rotor 21, made of a light alloy in a turbine side and a lower part rotor 22, made of high toughness material in a skirt side, to stop the rotor breakage accident only by the upper part rotor 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum pump used for a semiconductor manufacturing apparatus, an electron microscope, a surface analyzer, a mass analyzer, a particle accelerator, a nuclear fusion experiment apparatus, and the like.

[0002]

2. Description of the Related Art Processes such as dry etching and CVD in a semiconductor manufacturing process must be performed in a vacuum, and a vacuum pump having a high-speed rotating rotor such as a turbo molecular pump is used to obtain the vacuum.

In a conventional vacuum pump of this type, as shown in FIG. 4, a rotor 2 having a plurality of blade-shaped rotor blades 1, 1,.
The rotor shaft 3 integrally mounted on the rotation center axis of the rotor 2 is housed inside the pump case 4 to form a high-speed rotating part, and protrudes from a lower part of a pump base 13 supporting the pump case 4. Bearings 6 provided on the stator column 5 rotatably support the rotor shaft 3. A drive motor 7 is incorporated between the stator column 5 and the rotor shaft 3 between the upper and lower bearings 6, 6.
The drive motor 7 rotates the high-speed rotating section at a high speed of about 400 m / s at the peripheral speed of the rotor blades.

[0004] By this high-speed rotation, gas is taken in from the gas intake port 8 above the rotor, and the gas exhaust port 9 below the rotor is taken.
To a high vacuum in the semiconductor manufacturing process chamber connected to the gas inlet 8.

The above-described vacuum pump action is generated by a turbo molecular pump mechanism A in the upper half of the vacuum pump and a thread groove pump mechanism B in the lower half.

That is, the turbo molecular pump mechanism A
Are arranged alternately between the rotor blades 1, 1,... And the plurality of blade-shaped stator blades 10, 10, fixed to the pump case 4 side.
The exhaust operation is performed by sending high-vacuum gas molecules on the gas inlet port 8 side downward by interaction between the rotor blade 1 rotating at high speed and the fixed stator blade 10.

[0007] The thread groove pump mechanism B has a rotating cylindrical surface 2b on the outer periphery of the lower half skirt 2a of the rotor 2,
The turbo-molecular pump is formed by a screw stator 11 fixed to the inside of the pump case 4 by approaching and surrounding the rotary cylindrical surface 2b. The gas molecules sent from the mechanism part A are sent to the gas exhaust port 9 side along the screw groove 12 by the rotating cylindrical surface 2b of the rotor skirt part rotating at a high speed, and the gas in a state where the degree of vacuum is slightly lowered is reduced. Exhaust operation is performed.

The chambers connected to the rotor blade 1, the rotor 2, the pump case 4, the stator blade 10, and the gas inlet 3 are usually made of a light alloy, especially an aluminum alloy. Aluminum alloy has excellent machinability and is easy to process precisely. However, aluminum alloys have relatively low strength and may cause creep rupture depending on the use conditions.

[0009] Of these components, the rotor blades 1 and the rotor 2 integrally formed therewith are subjected to dynamic balancing in the process of assembly so as to withstand high-speed rotation. Normally, dynamic balancing is performed by shaving a small amount of the upper and lower end surfaces of the rotor 2 with a drill or the like. If the dynamic balance is maintained, high-speed rotation of the high-speed rotating unit becomes possible, and vibration is small and quiet operation can be performed.
During high-speed rotation, centrifugal force causes stress concentration around the micro-drilled holes for dynamic balancing on the upper and lower end surfaces of the rotor 2, and if a process gas corrodes, cracks occur around it. All of these trigger brittle fracture of the high-speed rotating part.

[0010] Since the rotor destruction accident starting from the stress concentration point of the rotor 2 occurs while the rotor 2 and the rotor blade 1 are rotating at high speed, the destruction energy thereof is very strong, and the entire rotor 2 and the rotor blade 1 are instantaneously damaged. Since the spills and destroys them, these fragments are scattered by the centrifugal force and the rotation of the motor is forcibly stopped. As a reaction force, a large torque is generated in the motor case (stator column) 5 and the pump is turned into a vacuum chamber The pump flange bolt 14 attached to the apparatus may be destroyed, and a drop of the pump may cause a part of the manufacturing apparatus to be destroyed, which may lead to a serious accident to humans. It should be noted that this type of destruction accident is not always triggered by the hole for balancing, and can occur during rotation if there is any defect in other parts.

In recent years, there has been an increasing demand for a vacuum pump having a large capacity. However, as the size of the vacuum pump increases, the breaking torque due to the centrifugal force also increases, and the risk of a breaking accident increases.

[0012] Therefore, several measures have been proposed in the past in order to limit the destruction accident to a small-scale destruction in the pump without causing a serious accident.

[0013] Japanese Patent Application Laid-Open No. 11-280689 discloses a structure in which when a destruction torque due to rotor destruction acts on a non-rotating stator blade of a turbo-molecular pump, the constraint between the pump case and the stator blade is released.

In addition, a structure is known in which the rotor is divided and these are joined by press-fitting, screwing, or the like. In addition,
This structure also reduces costs.

However, in the former pump case / stator blade restraint release structure, since the friction reducing structure and the shock absorbing structure are provided between the pump case and the stator blade, the outer shape of the pump becomes large and the price becomes high. Further, in the latter rotor split coupling structure, the coupling portion becomes a portion having a large diameter, and receives a large centrifugal force due to the high-speed rotation of the rotor, so that the rotor is easily broken.

[0016]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to make it difficult for a rotor to be destroyed. An object of the present invention is to provide a vacuum pump capable of preventing a secondary destruction around a pump case or the like by reducing a destruction portion of a rotor.

[0017]

In order to achieve the above object, the present invention has a turbo-molecular pump mechanism and a thread groove pump mechanism, and has a blade-like rotor blade of the turbo-molecular pump mechanism. By rotating the rotor with the rotating cylindrical surface of the thread groove pump mechanism at a high speed while being held by the rotor shaft, the turbo-molecular pump mechanism moves the gas molecules in the high vacuum of the gas inlet port into the thread groove pump mechanism. In a vacuum pump in which the screw groove pump mechanism sends out the gas molecules to the gas outlet along the screw groove,
The rotor includes an upper rotor made of a light alloy on which the rotor blades are formed, and a lower rotor having a skirt portion made of a high toughness material having the rotating cylindrical surface. The upper rotor and the lower rotor are The rotor shaft is configured to be screwed to a flange portion of the rotor shaft in the axial direction of the rotor shaft.

In the present invention, even in the event of high-speed rotation, brittle fracture of the lower rotor does not occur, and only the upper rotor of the high-speed rotating portion breaks.

In the above structure, the upper rotor and the lower rotor are each provided with a fitting hole for fitting to a small diameter portion protruding from a flange portion of the rotor shaft, and the small diameter portion, the fitting hole and The upper rotor and the lower rotor are positioned in the radial direction by the fitting of the upper rotor and the screw fixing part of the upper rotor to the rotor shaft flange and the screw fixing part of the lower rotor to the rotor shaft flange are overlapped, and the common rotor is If the rotor is screwed to the flange of the rotor shaft, the vacuum pump can be more securely assembled and integrated completely, and is stable and hard to break.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a vacuum pump according to the present invention will be described below with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing an embodiment of a vacuum pump according to the present invention, and FIG. 2 is a longitudinal sectional view of a main part of FIG. The point that the vacuum pump shown in FIG. 1 generates a vacuum pump action by the turbo molecular pump mechanism A in the upper half and the thread groove pump mechanism B in the lower half is different from the conventional pump shown in FIG. Similar to a vacuum pump. Therefore, the same portions as those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In the present invention shown in FIG. 1, the rotor 2 is divided into an upper rotor 21 made of aluminum alloy and a lower rotor 22 made of steel. Since the lower rotor 22 was made of high toughness steel, it could be formed thin as shown in the figure.

On the outer periphery of the upper rotor 21, blade-like rotor blades 1, 1,.
The skirt portion 2 having the rotating cylindrical surface 22b of the thread groove pump mechanism B is formed on the lower rotor 22.
2a was provided.

Then, as shown in FIG.
1 and each disk-shaped screwing portion 21c of the lower rotor 22;
2c were overlapped and fixed to the flange 3a of the rotor shaft 3 by screwing in the axial direction of the rotor shaft with a plurality of bolts 15 and 15.

The positioning of the upper rotor 21 and the lower rotor 22 in the radial direction with respect to the rotor shaft 3 was performed as follows. That is, the lower rotor fitting hole 16 that fits into the small diameter portion 3b protruding from the flange portion 3a of the rotor shaft 3 without gap.
Is formed in the lower rotor 22, and the upper rotor fitting hole 17 is fitted into the small-diameter portion 3 b without any gap.
The small diameter portion 3b and the lower rotor fitting hole 16,
The upper rotor 21 and the lower rotor 22 and the rotor shaft 3 were positioned in the radial direction by fitting into the upper rotor fitting holes 17 respectively. Thereby, the upper rotor 21 and the lower rotor 22 could be integrated without eccentricity.

The bolt 15 fixed to the flange 3a is
It could be arranged adjacent to the small diameter portion 3b and near the center of the rotor shaft. The flange 3a provided with a screw hole has two steps in the drawing. However, the flat end face provided with the screw hole only needs to have a flat end face, so the number of steps is not limited to this. The presence or absence of a step is not particularly relevant to the present invention.

When this vacuum pump was operated, the vicinity of the bolt holes of the screwed portions 21c and 22c through which the bolts 15 were passed was relatively close to the center of rotation of the rotor. No cracks from the holes. This proved that there was no fear that the bolt holes would trigger the destruction.

Further, no trouble occurs in which the bolt 15 is loosened by the high-speed rotation and the upper rotor 21 and the lower rotor 22 rattle.
It was confirmed that as a result, the same stable pump action as that of the related art was obtained. Furthermore, for a destructive test, the rotation was increased more than usual, and the temperatures of the turbo-molecular pump mechanism A and the thread groove pump mechanism B were increased, and the centrifugal force of the high-speed rotating part was also increased, and the operation was performed in a state where breakage was likely to occur. As it continued, the high-speed rotating part was destroyed.

When the pump is disassembled, the upper rotor 21
Had a trace of brittle fracture, and the stator blade 10 was also broken. However, since only the upper rotor 21 is instantaneously broken and the motor stops, the pump flange bolt 14
It was confirmed that the breakage of the inside of the pump was sufficient without breaking of the pump.

The upper rotor 21 and the lower rotor 22 are fixed to the rotor shaft 3 by the bolts 15, as in this embodiment, by screwing portions 21c of the upper rotor and the lower rotor.
It is preferable that the upper rotor 22c and the lower rotor 22 are fixed with different screws, though it is preferable to overlap the upper rotor 22c and fix them with the common screws 15, 15,. You can also. Further, since screw loosening due to centrifugal force or the like during operation is absolutely not allowed, conventionally known screw loosening prevention means, for example, a spring washer,
A screw lock agent or the like which is not affected by the exhaust gas may be used.

FIG. 3 is a partial longitudinal sectional view showing another embodiment of the vacuum pump according to the present invention. This embodiment is
It is intended to more accurately position the upper rotor 21 and the lower rotor 22 in the radial direction with respect to the rotor shaft 3.

First, the first fitting hole 2 is fitted into the first small diameter portion 31b protruding from the flange 3a of the rotor shaft 3 without any gap.
2d is formed on the lower rotor 22, and then the second small-diameter portion 3 concentric with the first small-diameter portion 31b and having a small diameter is connected thereto.
A second fitting hole 21d is formed in the upper rotor 21 so as to fit into the upper rotor 21 with no gap, and the small-diameter portions 31b, 32b and the first,
The second fitting holes 22d and 21d were fitted to each other, and the upper rotor 21, the lower rotor 22, and the rotor shaft 3 were positioned relative to each other in the radial direction. Thereby, the lower rotor 2
When the upper rotor 21 is fitted into the rotor shaft 3, the lower rotor 22 does not come in contact with the small diameter portion and rubs in the middle before being inserted to the predetermined position. The lower rotor 22 and the lower rotor 22 could be integrated and fixed accurately without eccentricity.

Although no destructive test was performed on this vacuum pump, normal operation was normally performed. Since other structures are the same as the embodiment of FIG. 1,
Similarly, in the event of a breakdown, the upper rotor 21 and the stator that is linked to the upper rotor 21 are destroyed, and other parts such as the lower rotor 22 are not destroyed. It seems that it can be stopped.

As a material for the upper rotor in the present invention, other light alloys such as a magnesium alloy can be used in addition to the above-described embodiment. As the material of the lower rotor, a high toughness material such as stainless steel, nickel steel, molybdenum steel, titanium alloy, and molybdenum alloy, which is unlikely to cause brittle fracture, can be used in addition to the above-described embodiment.

[0035]

According to the vacuum pump of the present invention,
As described above, the rotor of the vacuum pump is made of a high-toughness material having a light alloy upper rotor on which the blade-like rotor blades of the turbo molecular pump mechanism are formed, and a rotating cylindrical surface of the thread groove pump mechanism. Divided into a lower rotor with a skirt, and the upper rotor and the lower rotor are screwed to the flange of the rotor shaft in the axial direction of the rotor shaft.
In the event that rotor failure occurs, the rotor remains in the upper rotor, which is apt to be brittle, and its breaking torque is much smaller than the conventional breaking torque when the entire rotor is broken instantaneously. The next destruction remains in the stator blade and its surroundings, at worst, at the vacuum pump alone,
Damage to equipment such as a bolt to which the vacuum pump is attached and a vacuum chamber attached to the pump can be avoided. Further, by dividing the rotor into two parts, the man-hour for manufacturing the rotor and the lead time can be reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of a vacuum pump according to the present invention.

FIG. 2 is a partial longitudinal sectional view of FIG.

FIG. 3 is a partial vertical sectional view showing another embodiment of the vacuum pump according to the present invention.

FIG. 4 is a longitudinal sectional view showing an example of a conventional vacuum pump.

[Explanation of symbols]

 A Turbo molecular pump mechanism B Screw groove pump mechanism 1 Rotor blade 2 Rotor 2a Skirt 2b Rotating cylindrical surface 3 Rotor shaft 3a Flange 3b Small diameter portion 4 Pump case 5 Stator column 6 Bearing 7 Drive motor 8 Gas inlet 9 Gas Exhaust port 10 Stator blade 11 Screw stator 12 Screw groove 13 Base 14 Pump flange bolt 15 Bolt 16 Lower rotor fitting hole 17 Upper rotor fitting hole 21 Upper rotor 21c Screw fixing part 21d Upper rotor fitting hole 22 Lower rotor 22a Skirt part 22b Rotating cylindrical surface 22c Screw fixing portion 22d Lower rotor fitting hole 31b First small diameter portion 32b Second small diameter portion

Continued on the front page (72) Inventor Yuki Sakaguchi 4-3-1 Yashiki, Narashino-shi, Chiba Seiko Seiki Co., Ltd. (72) Inventor Masami Sugiyama 4-3-1 Yashiki, Narashino-shi, Chiba Seiko Seiki Co., Ltd. In-house F-term (reference) 3H031 DA01 DA02 DA07 EA09 FA01 FA39

Claims (3)

[Claims] 1. A rotor having a turbo-molecular pump mechanism and a thread groove pump mechanism, the rotor having a blade-like rotor blade of the turbo-molecular pump mechanism and a rotating cylindrical surface of the thread groove pump mechanism. The high-speed rotation held by the rotor shaft causes the turbo molecular pump mechanism to send gas molecules in a high vacuum at the gas inlet to the screw groove pump mechanism, and the screw groove pump mechanism transfers the gas molecules to the screw groove. Wherein the rotor comprises an upper rotor made of a light alloy on which the rotor blades are formed, and a skirt made of a high toughness material having the rotating cylindrical surface. A vacuum pump comprising a lower rotor, wherein the upper rotor and the lower rotor are screwed to a flange portion of the rotor shaft in a rotor axis direction. 2. The upper rotor and the lower rotor are each provided with a fitting hole that fits into a small diameter portion protruding from a flange of the rotor shaft, and the upper portion is formed by fitting the small diameter portion with the fitting hole. 2. The vacuum pump according to claim 1, wherein the rotor and the lower rotor are positioned radially. 3. The screw fixing portion of the upper rotor to the rotor shaft flange portion and the screw fixing portion of the lower rotor to the rotor shaft flange portion are overlapped and screwed to the flange portion of the rotor shaft by a common screw. The vacuum pump according to claim 1, wherein: