JP2003172290A - Vacuum pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a torque transmitted to a casing in case of damage of the inside of a pump. <P>SOLUTION: The vacuum pump is provided with a casing 1a having a suction port 2 and an exhaust port 4; a turbo-molecular pump part disposed at the suction port 2 side and having a rotatable rotor blade 12 and a fixed stator blade 16; a screw groove type pump part, disposed at the exhaust port 4 side and having a rotor part 11a and a stator part 15a fixed to an outer periphery side of the rotor part and comprising a material having strength lower than that of the material for the rotor part 11a, in which a helical groove 17 is formed on an outer periphery surface of the rotor part 11a or an inner periphery surface of the stator part 15. In the case where a damage or the like of the blade is generated at the inside, an impact is relaxed by a stator part having lower strength to efficiently reduce an impact transmitting torque to the casing without requiring a large-sized vacuum pump and an outstanding increase of a cost. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a semiconductor manufacturing apparatus,
The present invention relates to a vacuum pump used in a liquid crystal device or the like.

[0002]

2. Description of the Related Art Conventionally, as one of vacuum pumps, there is known a vacuum pump having a turbo molecular pump section and a thread groove type pump section in a casing having an intake port and an exhaust port. This vacuum pump is also called a turbo-molecular pump, and is widely used in various fields of industry and academic research such as exhaust of semiconductor manufacturing equipment and liquid crystal devices.

The turbo molecular pump has a rotor shaft for rotating the rotor portion, and is provided with a motor composed of, for example, a DC brushless motor, and the motor rotates the rotor portion at a high speed. In the turbo molecular pump section, rotor blades and stator blades are arranged alternately, and when the rotor section rotates at a high speed by a motor, gas is sucked from the intake port by the action of the rotor blades and the stator blades. The sucked gas is sent to the screw groove type pump section, and is discharged from the exhaust port while being guided by the groove formed in the stator section or the rotor section.

[0004]

However, the rotor part is
It rotates at high speed at tens of thousands of revolutions per minute, and large stress acts on the rotor blades and the stator blades during rotation. If the rotor blades or stator blades are damaged in this state, the damaged pieces move to the thread groove type pump while rotating inside the casing,
It is in a state of being strongly sandwiched between the rotor part and the stator part in the spiral groove. In particular, since the spiral groove is usually formed so that the depth becomes gradually smaller, the above-mentioned pinching force rapidly increases due to the rotation of the rotor portion, and the rotor portion is rapidly decelerated and stopped. Therefore, the stator receives a large torque due to the collision, and a large torque is applied to the bolts that fix the turbo molecular pump and the pipes that are connected to the intake port and the exhaust port of the turbo molecular pump. In some cases, a large load was applied to cause a problem.

A means for preventing such a sudden load generation has been proposed in the past, and a method of enlarging the stator portion or inserting other members in order to prevent the energy when the rotor portion is broken from being transmitted to the casing. However, there is a problem that the vacuum pump becomes large and the cost also increases.
Further, Japanese Patent Laid-Open No. 11-280689 proposes a turbo-molecular pump in which a structure is provided in a part of the stator to release the constraint with the casing when an abnormal torque occurs in the stator. However, even with this method, there is a problem that the structure becomes complicated and the cost is increased.

The present invention has been made in view of the above circumstances, and even if the rotor portion or the like is damaged during operation,
An object of the present invention is to provide a vacuum pump that stops the molecular pump so that the impact on the stator portion is reduced, and has a small influence on the members connected to the molecular pump without increasing the cost.

[0007]

In order to solve the above problems, among the vacuum pumps according to the present invention, the invention according to claim 1 has a casing having an intake port and an exhaust port, and an intake port side in the casing. A turbo-molecular pump portion, which is arranged and has a rotatable rotor blade and a fixed stator blade, a rotor portion arranged on the exhaust port side in the casing and rotating integrally with the rotor blade, and an outer periphery of the rotor portion. Fixed to the side, and at least the surface layer portion of which is formed of a material having a lower strength than the material of the rotor portion, and a spiral groove is formed on the outer peripheral surface of the rotor portion or the inner peripheral surface of the stator portion. And a thread groove type pump section.

According to a second aspect of the present invention, in the first aspect of the present invention, the material of the rotor portion is an aluminum alloy, and at least the surface layer portion of the stator portion is
It is characterized by being made of epoxy resin or carbon.

A third aspect of the present invention is the vacuum pump according to the first or second aspect, wherein the surface of the surface layer portion is coated with a corrosion resistant coating.

A fourth aspect of the present invention is the vacuum pump according to the second aspect, wherein the surface of the epoxy resin is plated with Ni.

According to a fifth aspect of the present invention, the vacuum pump according to the second aspect is characterized in that the surface of the carbon is coated with carbon whose porous formation is suppressed.

According to the present invention, in the thread groove type pump portion, at least the surface layer portion of the stator portion is lower in strength than the rotor portion, so that a part of the rotor portion such as rotor blades is operated during operation as a vacuum pump. If the broken piece comes into contact with the stator portion, the stator portion side is appropriately deformed and scraped off. This relieves the stress on the stator side, prevents the sudden time stress from being applied to the stator side in a short time by lengthening the time it takes for the pump to stop due to the impact, and by extension, connect devices around the pump. The impact on Although the degree of impact relaxation depends on the strength of the stator side, the time it takes for the pump to stop can be extended several times longer than before, and the impact force per hour can be greatly reduced. It will be possible. As a result, the maximum torque that acts on the casing can be reduced to a fraction.

The vacuum pump of the present invention is provided with the turbo molecular part and the thread groove type pump part as described above, and the pump structure is limited to that extent, but other structures are not particularly limited. The spiral groove may be formed in either the rotor or the stator. In the present invention, the strengths of the materials of the rotor portion and the stator portion are compared, and the strength of the material of the stator portion may be relatively low. This strength is typically shown by an elastic modulus (Young's modulus, rigidity, bending elastic modulus, etc.) and can be compared. That is, the smaller the elastic modulus, the lower the strength. When comparing the strengths with this elastic modulus, the strength of the stator portion is preferably 70% or less as compared with the strength of the rotor portion. As a result, the above-mentioned operation can be surely obtained.

Further, in the stator, it suffices if the surface layer portion in contact with the broken piece satisfies the above strength condition,
The inner side thereof may be made of the same material as the rotor. Of course, the entire stator may satisfy the above strength condition. The depth of the surface layer portion can be appropriately determined in consideration of the magnitude of stress applied by the broken pieces.
Further, the low-strength portion does not need to extend over the entire stator in the surface direction, and may be made of a low-strength material only in an area where the broken pieces are supposed to come into contact with each other.

The low-strength portion provided on at least the surface layer portion of the stator is not limited to a particular material, as long as the strength is low in comparison with the material of the rotor. Considering that the material of the rotor is usually made of a high-strength aluminum alloy, it is preferable to use a non-metallic material. For example, as described in claim 2, epoxy resin and carbon can be used. In the above epoxy resin, a resin before curing may be applied to the surface of the stator to be thermally cured, or may be fixed to the surface of the stator in a thermally cured state. Further, the carbon can be fixed to the surface of the stator after having a predetermined shape.

When a vacuum pump is used for exhausting a semiconductor manufacturing apparatus or the like, since the corrosive gas is used in many cases in the apparatus, the inside of the vacuum pump is also exposed to the corrosive gas. Become. For this reason, conventionally, the surface of a rotor or a stator made of an aluminum alloy is plated with Ni, which has excellent corrosion resistance. Therefore, it is desirable that even the low-strength portion of the stator of the present invention is not easily denatured to corrosive gas, and if the material itself does not have sufficient corrosion resistance, it is desirable to apply a corrosion-resistant coating.
That is, Ni plating can be applied to the surface of the epoxy resin or carbon like the rotor and the like. However, in the case of carbon, due to the problem of the adhesion of the plating, it is possible to coat with carbon that suppresses the formation of porous material, instead of plating. As a result, it is possible to obtain a coating having excellent adhesiveness. The carbon coating in which the porous formation is suppressed can be realized by using a film forming technique using CVD, for example. The no-porous carbon coating satisfies the requirements of ultra-high vacuum and contamination-free.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing a turbo molecular pump 1 according to an embodiment of the present invention, and is a diagram showing a sectional view in the axial direction. 2 and 3 are enlarged views showing the facing portion of the rotor portion and the stator portion of the thread groove type pump portion.

In the vacuum pump (turbo molecular pump) 1 of this embodiment, an intake port 2 is formed at one end of a cylindrical casing 1a, and the intake port 2 is connected to a semiconductor manufacturing apparatus. Inhale corrosive gases from equipment. In addition, the peripheral edge of the intake port 2 is extended outward in the radial direction so that the attachment portion 2a
Has become. A base 3 is connected to the other end of the casing 1a, and the base 3 forms a hollow portion that is continuous with an external device via the intake port 2 and the casing 1a. An exhaust port 4 for discharging the gas in the hollow portion is provided. An auxiliary pump (not shown) or the like is connected to the exhaust port 4.

The rotor shaft 1 is provided at the center of the casing 1a.
0 is arranged, and bearing portions 20 and 21 are provided as magnetic bearings that magnetically support the rotor shaft 10.
The magnetic bearing portion constitutes a three-axis control magnetic bearing, and the rotor shaft 10 is magnetically levitated in the radial direction (radial direction of the rotor shaft 10) by the magnetic bearing portion 20 and is supported in a non-contact manner. The portion 21 magnetically levitates in the thrust direction (axial direction of the rotor shaft 10) and is supported in a non-contact manner. Further, a motor 22 for rotating the rotor shaft 10 supported by these magnetic bearing portions is provided between the magnetic bearing portions 20 and 21.

In the magnetic bearing portion 20, four radial electromagnets 25 are arranged around the rotor shaft 10 so as to face each other at every 90 degrees (two are shown in the figure). The rotor shaft 10 facing these electromagnets is made of a material having high magnetic permeability, and receives the magnetic force of these electromagnets.

A disc-shaped metal disk 30 made of a magnetic material is fixed to the lower portion of the rotor shaft 10,
Above the metal disk 30, an axial electromagnet 26 is fixedly arranged on the base 3. Then, the rotor shaft 10 is magnetically levitated by supplying exciting currents to the radial electromagnet 25 and the axial electromagnet 26, respectively.

Further, in the turbo molecular pump of this embodiment, protective bearings 27 and 28 are arranged on the upper and lower sides of the rotor shaft 10. Normally, the rotor shaft 10
Is rotatably supported by the magnetic bearing in a non-contact state while rotating. The protective bearings 27, 28 replace the magnetic bearings in the event of a touchdown in place of the rotor shaft 10.
The entire device is protected by pivoting. Although the rotor shaft 10 is axially supported by the magnetic bearing in this embodiment, the present invention is not limited to this, and a dynamic pressure bearing, a static pressure bearing, or another bearing may be used.

On the upper end of the rotor shaft 10, a rotor portion 11 composed of a cylindrical wall portion is attached, and the rotor portion 11 is made of an aluminum alloy. Further, a cylindrical stator portion 15 is provided on the inner surface portion of the casing 1. A large number of rotor blades 12 are provided radially and in multiple stages in the axial direction on the outer peripheral surface of the rotor portion 11 on the intake port 2 side, that is, on the substantially upper half portion in the figure from approximately the middle of the rotor portion 11. ing. This rotor blade 12
Is inclined at a predetermined angle with respect to the axial direction so that the intake port side (upper side in the drawing) is the rotation direction side.

On the other hand, the stator portion 15 has a rotor portion 11
Similarly, the stator blades 16 arranged between the stages of the rotor blades 12 are provided on the intake port 2 side, that is, in the substantially upper half portion in the drawing. The stator blades 16 are inclined at a predetermined angle with respect to the axial direction. As described above, the rotor blades 12 and the stator blades 16 are located alternately. Rotor part 1
When 1 is rotationally driven by the motor 22, the rotor blades 12 rotate accordingly, and the rotor blades 12 and the stator blades 16
By the action of and, gas molecules are knocked down to the exhaust port 4 side. Due to the arrangement of the rotor blades 12 and the stator blades 16, the intake port 2 side in the casing 1 constitutes a turbo molecular part.

The upper half of the stator portion 15 in which the stator blades 16 are provided is made of an aluminum alloy as in the rotor portion 11. Further, the surfaces of the rotor portion 11, the rotor blades 12, the stator portion 15 and the stator blade 16 are electroless Ni plated.

Further, the rotor portion 11 and the stator portion 1
5, there is a slight gap between the cylindrical outer peripheral surface of the rotor lower part 11a and the cylindrical inner peripheral surface of the stator lower part 15a on the exhaust port 4 side, that is, in the lower half of the figure. And a spiral groove 17 is formed on the inner peripheral surface of the stator lower portion 15a. That is,
The exhaust port 4 side of the casing 1 is a thread groove type pump portion. In addition, the spiral direction of the thread groove 17 depends on the rotor portion 1.
When the molecules of the exhaust gas move in the rotation direction 1, the molecules are transferred to the exhaust port 4.

Further, the stator lower portion 15a described above is
The entire surface including the surface layer is made of epoxy resin. This epoxy resin has an elastic modulus (flexural modulus) of 15 to 20.
GPa, elastic modulus of the aluminum alloy forming the rotor portion 11 (rigidity modulus: equivalent to bending elastic modulus of resin) 25 to
The material is smaller than 30 GPa and therefore lower in strength than the rotor portion 11. The surface of the lower portion 15a of the stator portion is electrolessly Ni-plated similarly to the rotor portion 11 and the like.

(Operation) Next, the operation of this embodiment will be described. The turbo molecular pump 1 is fixed to an external semiconductor manufacturing apparatus or the like via the attachment portion 2a of the intake port 2, and the motor 22 is operated via an external power source. The rotor blades 12 together with the rotor shaft 10 and the rotor unit 11 are operated by the motor.
Rotates at high speed. As a result, the exhaust gas from the intake port 2 is sucked into the casing 1a, passes between the rotor blade 12 and the stator blade 16, and is sent from the turbo molecular pump unit to the thread groove pump unit. The exhaust gas sent from the turbo molecular pump section is transferred to the exhaust port 4 while being guided by the spiral groove 17.

When the turbo molecular pump 1 is broken during operation, the broken pieces easily move to the spiral groove 17, and are sandwiched in the spiral groove 17 between the rotor lower portion 11a and the stator lower portion 15a. Then, the rotor portion 11 further rotating is strongly pushed into the spiral groove 17. Conventionally, in such a state, as shown in FIG.
1 and the stator portion 15, the broken piece 100 is firmly fixed, and the rotational force of the rotor portion 11 causes the broken piece 1 to move.
It is transmitted to the stator part 15 almost as it is through 00,
A large torque is momentarily generated in the rotor unit 11 and the stator unit 15, the rotation of the rotor unit 11 is stopped, and a large amount of torque is shockably transmitted to the casing 1a. A large load is applied to members such as bolts that fix the pump 1, and the casing 1a is damaged, and external devices and auxiliary pumps connected to the casing 1a are affected.

However, in the present invention, the stator lower part 15
Since a is made of a material having a lower strength than that of the rotor portion 11, even when the broken piece 100 is pressed against the spiral groove 17, as shown in FIG.
The contact portion of the broken piece 100 in a is easily deformed or scraped off to relieve the contact stress, and the time required to stop the rotor portion 15 is lengthened to significantly increase the generated torque per unit time. Reduce. According to the repeated breaking test, it is possible to lengthen the time required for the rotor unit 15 to stop to several times. As a result, the maximum torque that acts on the casing 1a can be reduced to a fraction.

In the above embodiment, the entire lower portion of the stator portion is made of low-strength epoxy resin, but as described above, only the surface layer portion may be made of low-strength material, Further, the area of the surface layer portion can be limited to the area where the broken pieces are supposed to come into contact with each other. Further, in the above embodiment, the epoxy resin is used as the material having low strength, but the present invention is not limited to this, and an appropriate material such as carbon may be used. Further, in the present embodiment, the spiral groove 7 is formed on the stator side, and the outer peripheral surface of the rotor lower part 11a has a cylindrical shape, but conversely, the spiral groove is formed on the outer peripheral surface of the rotor part. It can also be a turbomolecular pump.

[0032]

As described above, according to the vacuum pump of the present invention, the casing having the intake port and the exhaust port,
A turbo-molecular pump unit, which is arranged on the intake port side in the casing, has a rotatable rotor blade and a fixed stator blade, and is arranged on the exhaust port side in the casing, and rotates integrally with the rotor blade. A rotor part and a stator part fixed to the outer peripheral side of the rotor part, at least the surface layer part of which is made of a material having a lower strength than the material of the rotor part;
Since the screw groove type pump portion having the spiral groove formed on the outer peripheral surface of the rotor portion or the inner peripheral surface of the stator portion is provided, the pump does not increase in size and the cost is significantly increased. The impact transmission torque to the casing can be effectively reduced when the blades are damaged inside.

[Brief description of drawings]

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

FIG. 2 is likewise an enlarged view showing a portion where a rotor portion and a stator portion of a thread groove type pump portion face each other.

FIG. 3 is likewise an enlarged view showing a portion of the thread groove type pump section where the broken piece is sandwiched and the rotor section and the stator section face each other.

[Explanation of symbols]

1 vacuum pump 1a casing 2 intake 3 base 4 exhaust port 10 rotor shaft 11 rotor part 11a lower part of rotor part 12 rotor blades 15 Stator part 15a Lower part of stator 16 stator blades 17 spiral groove 20 Bearing 21 Bearing 22 motor 100 broken pieces

Claims (5)

[Claims] 1. A turbo molecular pump section having a casing having an intake port and an exhaust port, a rotor blade arranged on the intake port side in the casing, and having a rotatable rotor blade and a fixed stator blade, and the inside of the casing. A rotor portion disposed on the exhaust port side of the rotor and rotating integrally with the rotor blade, and a stator portion fixed to the outer peripheral side of the rotor portion, at least the surface layer portion of which is made of a material having a lower strength than the material of the rotor portion. And a screw groove type pump portion having a spiral groove formed on the outer peripheral surface of the rotor portion or the inner peripheral surface of the stator portion. 2. The vacuum pump according to claim 1, wherein a material of the rotor portion is made of aluminum alloy, and at least a surface layer portion of the stator is made of epoxy resin or carbon. 3. The vacuum pump according to claim 1, wherein the surface of the surface layer portion is coated with a corrosion resistant coating. 4. The vacuum pump according to claim 2, wherein the surface of the epoxy resin is plated with Ni. 5. The vacuum pump according to claim 2, wherein the surface of the carbon is coated with carbon whose porous formation is suppressed.