JP2007170182A - Vacuum pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively increase an exhaust speed by a radial flow system vacuum pump. <P>SOLUTION: Fixed grooved plates 30 having ribs 32 formed at least on the one surfaces and rotary plates 10 are alternately disposed on each other in three stages. Namely, five stages of radial flow elements are installed in the vacuum pump. The gas flow passage formed between the rib 32-forming surface of the fixed plate 31 and the upper surface of the rotary plate 10 facing the rib molding surface is formed in a one-stage radial flow element. Gas molecules introduced from an intake port 3 are taken from the outer peripheral edge of the rotary plate 10 into the gas intake area of the radial flow element on each stage. The gas intake area of the radial flow element on each stage is communicated with a fixed side communication hole 33. The gas molecules introduced from a suction port 3 are directed to any of the multiple stages of radial flow elements. The gas molecules directed to each stage of radial flow element are fed in the inner peripheral direction by the interaction between the rotary plate 10 and the rib 32 and discharged to a discharge area. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vacuum pump for discharging a gas from a container and obtaining a high vacuum.

Examples of the apparatus using a vacuum apparatus that performs exhaust processing using a vacuum pump and keeps the inside in a vacuum include a semiconductor manufacturing apparatus, a liquid crystal manufacturing apparatus, an electron microscope, a surface analysis apparatus, and a fine processing apparatus. .
Among various types of vacuum pumps, turbo molecular pumps are frequently used when realizing a high vacuum state.
The turbo-molecular pump includes a fixed portion fixed to the casing and a rotating portion that rotates by the action of the motor. The fixed blade and the rotating blade are arranged in multiple stages in the fixed portion and the rotating portion, respectively, and when the rotating portion rotates at high speed, the gas introduced from the intake port by the action of these blades is exhausted from the exhaust port. ing.

In addition, the vacuum pump includes a thread groove type molecular pump and a radial flow type molecular pump, which are different in gas exhaust method from the turbo molecular pump.
The thread groove type molecular pump evacuates by relative movement between a thread groove provided on the outer peripheral wall surface of the uniaxial rotating cylinder and a sleeve surface disposed on the outer side through a gap. It should be noted that the screw groove is provided on the inner peripheral wall surface of the fixed sleeve, and the exhaust is performed by relative movement between the outer peripheral wall surface of the uniaxial rotating cylinder and the screw groove provided on the inner peripheral wall surface of the sleeve. You can also.

The radial flow type molecular pump exhausts air by relative movement between a uniaxial rotating disk and a groove provided on the surface of the fixed plate fixed via the plate surface and a gap.
As described above, the thread groove type molecular pump and the radial flow type molecular pump have a gas flow direction (diffusion of gas molecules) caused by relative movement between the plane and the flow channel groove, and the direction of the exhaust direction by the flow channel groove. The gas is exhausted by imparting the property.
In the thread groove type molecular pump, axial directionality is given, and in the radial flow type molecular pump, radial directionality is given.
The thread groove of the thread groove type molecular pump and the groove provided on the fixed plate of the radial flow type molecular pump all have a spiral shape.

By the way, if the depth of the channel groove provided in the thread groove type molecular pump and the radial flow type molecular pump is increased, the gas exhaust efficiency is lowered in the intermediate flow rate region of the gas molecules.
Therefore, it is difficult to increase the exhaust speed even if the gas suction area is increased.
In addition, when the depth of the channel groove is set deeper than the average flight distance (average free path) from one gas molecule to another gas molecule after one collision, At the bottom (part away from the relatively moving plane), the probability of incidence of gas molecules that are given directionality in the exhaust direction decreases.
As a result, diffusion of gas molecules in the exhaust direction does not occur at the bottom of the flow channel groove, and the exhaust action hardly occurs (is difficult to occur), resulting in a decrease in exhaust efficiency.

Conventionally, in order to suppress such a decrease in exhaust efficiency, that is, in order to improve the exhaust speed, a technology for expanding the gas suction area with a restriction on the depth of the channel groove is disclosed in the following patent. Proposed in the literature.
Japanese Utility Model Publication No. 5-38389

In Patent Document 1, by providing screw groove portions on both the outer and inner peripheral walls of the rotating cylindrical member of the thread groove type molecular pump, that is, providing gas flow paths on both the inner and outer sides of the rotating cylindrical member. Thus, a technique for increasing the flow rate of gas molecules to be exhausted has been proposed.
By using this technique, the flow rate of gas molecules can be increased without increasing the size of the pump.

When the technique described in Patent Document 1 described above is used, the flow rate of gas molecules can be increased as compared with a pump in which a thread groove is provided only on either the outer side or the inner side of the rotating cylindrical member.
However, since the distance from the center of the rotating shaft is different between the inner side and the outer side of the rotating cylindrical member, the peripheral speed is not equal between the inner screw groove and the outer screw groove. Specifically, the peripheral speed of the inner thread groove is smaller than the peripheral speed of the outer thread groove.
For this reason, it is difficult to increase the gas exhaust speed by a factor of two even if the gas flow path is provided in two paths on the inner and outer sides of the rotating cylindrical member.
Then, an object of this invention is to provide the vacuum pump which can improve an exhaust speed more effectively.

In the invention of claim 1, a guide groove that is provided from the suction part to the exhaust part and guides the incident gas molecules in the radial direction, and a guide surface that is disposed to face the guide groove via the gap, A rotational flow is applied to one of the guide groove and the guide surface, the guide groove and the guide surface are moved relative to each other, and the gas molecules incident on the radial flow element are moved in the radial direction. A vacuum pump that employs a radial flow system that exhausts gas in the radial direction, and a drive unit that provides directionality, wherein the radial flow elements are arranged in parallel in at least two stages in the axial direction. The object is achieved by including an element group and communication means for communicating all of the suction portions of the radial flow element constituting the radial flow element group.
According to a second aspect of the present invention, in the first aspect of the present invention, the driving means applies a rotational motion to the guide surface, causes the guide groove and the guide surface to move relative to each other, and enters the radial flow element. Radial directionality is given to gas molecules, and the guide surface is constituted by a member having high specific strength.
According to a third aspect of the present invention, in the second aspect of the present invention, the member having a high specific strength is a carbon fiber reinforced plastic material (CFRP material).
According to a fourth aspect of the present invention, in the second or third aspect of the present invention, the guide groove is formed on a fixed plate fixed to a housing of the vacuum pump, and the communication means is the guide. It is comprised by the communicating hole which penetrates the rotation board in which the surface was formed, or the said fixed board in the thickness direction.
The invention according to claim 5 is the invention according to claim 2, claim 3 or claim 4, wherein the radial flow element groups having different gas molecule guiding directions are alternately arranged in parallel in the axial direction.

  According to the present invention, all the intake portions in the radial flow element group in which the radial flow elements are arranged in parallel in at least two stages in the axial direction are communicated with each other, thereby exhausting gas molecules simultaneously in all the radial flow elements. Therefore, the exhaust speed can be effectively improved according to the number of stages of the radial flow elements.

Hereinafter, preferred embodiments of the vacuum pump of the present invention will be described in detail with reference to FIGS. 1 to 10.
FIG. 1 is a diagram showing a schematic configuration in the axial direction of the vacuum pump of the present embodiment. In addition, FIG. 1 has shown the cross section of the axial direction in a vacuum pump. This vacuum pump is installed in, for example, a semiconductor manufacturing apparatus, and is used when the process gas is discharged from the vacuum chamber.
In the present embodiment, a composite vacuum pump having a radial flow type molecular pump portion α and a thread groove pump portion S will be described as an example of a vacuum pump.

A casing 1 constituting an exterior body of the vacuum pump has a substantially cylindrical shape, and constitutes a casing of the vacuum pump together with a base 2 provided at a lower portion (exhaust port 5 side) of the casing 1. A structure that allows the vacuum pump to perform an exhaust function, that is, a gas transfer mechanism is disposed inside the housing.
This gas transfer mechanism is roughly composed of a rotating part that is rotatably supported and a fixed part fixed to the casing.
An intake port 3 for introducing gas into the vacuum pump is formed at the end of the casing 1. A flange portion 4 is formed on the end surface of the casing 1 on the intake port 3 side so as to project to the outer peripheral side. The vacuum pump is fixed to the vacuum chamber via the flange portion 4 by a fastening member.

Further, an exhaust port 5 for exhausting gas from the vacuum pump, that is, exhausting process gas from the semiconductor manufacturing apparatus, is formed at the end of the base 2.
The rotating portion includes a shaft 6 that is a rotating shaft, a rotor body 7 disposed on the shaft 6, a lower cylindrical portion 8 formed so as to extend from the outer peripheral edge of the rotor body 7 toward the exhaust port 5, and the rotor body 7. The upper cylindrical portion 9 is formed so as to extend from the outer peripheral edge portion in the direction of the intake port 3, and the annular rotating plate 10 is provided to project from the outer peripheral wall surface of the upper cylindrical portion 9.

A rotating side communication hole 60 is formed on the rotating plate 10 provided in the upper cylindrical portion 9 except for the one disposed closest to the intake port 3 side.
By not providing the rotation side communication hole 60 in the rotary plate 10 disposed on the most inlet side 3, the compressed and exhausted gas can be prevented from returning to the suction side (upstream side).
The rotation-side communication hole 60 is a hole that penetrates the rotation plate 10 in the thickness direction, and is formed in a portion on the inner side (closer to the shaft 6) than the inner peripheral edge of the fixed groove plate 30 described later, that is, in the vicinity of the upper cylindrical portion 9. ing. The rotation side communication hole 60 is formed in an arbitrary shape such as a circular shape or an elliptical shape extending in the radial direction.
In addition, the rotation plate 10 is provided with a plurality of rotation side communication holes 60 at equal intervals along the radial direction.
The rotor body 7 is fixed to the upper part of the shaft 6 with bolts 11. The lower cylindrical portion 8 is formed on the extension of the rotor body 7 and has a cylindrical shape concentric with the rotation axis of the rotor body 7.

A motor portion 12 for rotating the shaft 6 at a high speed is provided in the middle of the shaft 6 in the axial direction. Here, it is assumed that the motor unit 12 is a DC brushless motor configured as follows.
The motor unit 12 includes a permanent magnet fixed around the shaft 6. For example, the permanent magnet is fixed so that the N pole and the S pole are arranged around the shaft 6 every 180 °. The motor unit 12 includes an electromagnet disposed around the permanent magnet with a predetermined clearance from the shaft 6. Here, six electromagnets are arranged so as to be symmetrically opposed to the axis of the shaft 6 every 60 °.

  The vacuum pump is connected to a control device (not shown) via a connector and a cable. And the electric current of an electromagnet is switched one after another so that rotation of shaft 6 may be continued by this control device. That is, the control device generates a rotating magnetic field around the permanent magnet fixed to the shaft 6 by switching the excitation current of the six electromagnets, and rotates the shaft 6 by causing the permanent magnet to follow the rotating magnetic field. .

Magnetic bearing portions 13 and 14 for supporting the shaft 6 in the radial direction (radial direction) are provided on the intake port 3 side and the exhaust port 5 side with respect to the motor portion 12 of the shaft 6. In addition, a magnetic bearing portion 15 for supporting the shaft 6 in the thrust direction (axial direction) is provided at the lower end (end on the exhaust port 5 side) of the shaft 6.
These magnetic bearing portions 13 to 15 constitute a so-called 5-axis control type magnetic bearing.
The shaft 6 is supported by the magnetic bearing portions 13 and 14 in a non-contact manner in the radial direction (the radial direction of the shaft 6), and is supported by the magnetic bearing portion 15 in a non-contact manner in the thrust direction (the axial direction of the shaft 6).
Displacement sensors 16 to 18 that detect the displacement of the shaft 6 are provided in the vicinity of the magnetic bearing portions 13 to 15, respectively.

In the magnetic bearing portion 13, four electromagnets are arranged so as to face the periphery of the shaft 6 every 90 °. The shaft 6 is formed of a high permeability material (iron or the like) and is attracted by the magnetic force of these electromagnets.
The displacement sensor 16 detects the displacement of the shaft 6 in the radial direction by sampling at predetermined time intervals.

When the control device (not shown) detects that the shaft 6 is displaced from the predetermined position in the radial direction by the displacement signal from the displacement sensor 16, the controller 6 adjusts the magnetic force of each electromagnet so as to return the shaft 6 to the predetermined position. Operate. The adjustment of the magnetic force of the electromagnet is performed by feedback controlling the excitation current of each electromagnet.
The control device feedback-controls the magnetic bearing portion 13 based on the signal of the displacement sensor 16, whereby the shaft 6 magnetically levitates in the radial direction with a predetermined clearance from the electromagnet in the magnetic bearing portion 13, and enters the space. It is held without contact.

The configuration and operation of the magnetic bearing portion 14 are the same as those of the magnetic bearing portion 13. The control device feedback-controls the magnetic bearing portion 13 based on the signal from the displacement sensor 17, whereby the shaft 6 is magnetically levitated in the radial direction by the magnetic bearing portion 14 and is held in a non-contact manner in the space.
Thus, the shaft 6 is held at a predetermined position in the radial direction by the action of the magnetic bearing portions 13 and 14.

The magnetic bearing portion 15 includes a disk-shaped metal disk 19 and electromagnets 20 and 21, and holds the shaft 6 in the thrust direction.
The metal disk 19 is made of a high permeability material such as iron, and is fixed perpendicularly to the shaft 6 at the center thereof. Electromagnets 20 and 21 are disposed so as to sandwich and face the metal disk 19. The electromagnet 20 attracts the metal disk 19 upward by magnetic force, and the electromagnet 21 attracts the metal disk 19 downward.
The control device appropriately adjusts the magnetic force exerted on the metal disk 19 by the electromagnets 20 and 21 so that the shaft 6 is magnetically levitated in the thrust direction and held in the space without contact.

Further, a displacement sensor 18 is disposed so as to face the lower end portion of the shaft 6. This displacement sensor 18 samples and detects the displacement of the shaft 6 in the thrust direction, and transmits this to the control device. The control device detects the displacement of the shaft 6 in the thrust direction based on the displacement detection signal received from the displacement sensor 18.
When the shaft 6 moves in one of the thrust directions and is displaced from a predetermined position, the controller adjusts the magnetic force by feedback controlling the exciting currents of the electromagnets 20 and 21 so as to correct this displacement. Is moved back to a predetermined position. The control device performs this feedback control continuously. Thereby, the shaft 6 is magnetically levitated and held at a predetermined position in the thrust direction.
As described above, since the shaft 6 is held in the radial direction by the magnetic bearing portions 13 and 14 and is held in the thrust direction by the magnetic bearing portion 15, the shaft 6 rotates around the axis of the shaft 6. .

Further, protective bearings 22 and 23 are disposed on the upper and lower sides of the shaft 6. Normally, the shaft 6 and the rotating part attached thereto are pivotally supported by the magnetic bearing parts 13 and 14 in a non-contact state while being rotated by the motor part 12. The protective bearings 22 and 23 are bearings for protecting the entire apparatus by pivotally supporting the rotating portion instead of the magnetic bearing portions 13 and 14 when touchdown occurs. Therefore, the protective bearings 22 and 23 are arranged so that the inner ring is in a non-contact state with respect to the shaft 6.
A fixing portion is formed on the inner peripheral side of the housing. This fixed portion is composed of a fixed groove plate 30 provided on the intake port 3 side (radial flow type molecular pump portion α), a thread groove spacer 40, and the like. A thread groove 41 is formed on the inner wall surface of the thread groove spacer 40.
The details of the fixed groove plate 30 will be described later.

In the radial flow type molecular pump portion α, the fixed groove plate 30 is formed in three stages alternately with the rotary plate 10 in the axial direction. The number of stages of the fixed groove plate 30 and the rotating plate 10 is not limited to three, and may be more than that.
The fixed groove plates 30 of each step are separated from each other by a cylindrical spacer ring 50 and are held at predetermined positions.
The spacer ring 50 is a ring-shaped member having a step portion, and is made of a metal such as aluminum, iron, or stainless steel.

The thread groove 41 is formed by a spiral groove formed along a surface facing the lower cylindrical portion 8. The thread groove 41 is provided so as to face the outer peripheral surface of the lower cylindrical portion 8 with a predetermined clearance (gap) therebetween.
The direction of the spiral groove formed in the thread groove 41 is the direction of the exhaust port 5 when gas is transported in the direction of rotation of the shaft 6 in the spiral groove.
Further, the depth of the spiral groove becomes shallower as it approaches the exhaust port 5, and the gas transported through the spiral groove is configured to be compressed as it approaches the exhaust port 5.

Here, the fixed groove plate 30 will be described in detail.
FIG. 2A shows a relationship between the direction of the spiral of the rib 32 formed on the fixed groove plate 30 and the rotational direction of the rotor.
FIG. 2B shows a perspective cross-sectional view of the fixed groove plate 30 along AA ′ shown in FIG.
As shown in FIGS. 2A and 2B, the fixed groove plate 30 includes a fixed plate 31, a rib (spiral wall portion) 32, and a fixed side communication hole 33.
The fixed plate 31 is formed of an annular plate member, and the inner diameter thereof is set larger than the outer diameter of the upper cylindrical portion 9 (FIG. 1).
In addition, it is preferable that the fixed plate 31 is disposed outside the formation site of the rotation side communication hole 60 whose inner peripheral edge is provided in the rotation plate 10.

The rib 32 is provided so as to protrude from both surfaces or one surface of the fixing plate 31 in the axial direction.
The rib 32 is formed such that a protruding portion protruding in the axial direction from both surfaces or one surface of the fixing plate 31 extends along a helical arc extending in the outer peripheral direction from the inner peripheral end of the fixing plate 31.
In other words, the rib 32 functions as a guide means for guiding gas molecules given directionality in the rotation direction (tangential direction) of the rotating plate 10 indicated by white arrows in the drawing to the rotation axis center side (black arrows). To do.
The rib 32 is configured to vortex in the center direction in the same direction as the rotation direction of the rotating plate 10.
As shown in FIG. 2A, a plurality of ribs 32 are provided on the surface of the fixed plate 31 at equal intervals in the circumferential direction.
A flow path (transfer path) for the exhausted gas is formed by a spiral groove (space) formed between adjacent ribs 32.
The helical groove formed between the adjacent ribs 32 is provided from the gas suction region (introduction region) to the discharge region (exhaust part) and functions as a guide groove. It functions as a guide surface.

The depth of the spiral groove, that is, the protruding height of the rib 32 is set to be smaller than the average flight distance (average free path) from one collision of gas molecules to another gas molecule until the next collision. It is configured.
Thus, by setting the depth of the spiral groove to a value that takes into account the mean free path of the exhaust gas, the direction of the exhaust direction at the bottom of the spiral groove (part away from the plane in which the spiral moves) is reduced. It is possible to suppress a decrease in the probability that a given gas molecule is incident.

The fixed-side communication hole 33 is a hole that penetrates the fixed plate 31 in the thickness direction, and is formed on the outer side (near the casing 1) of the rib 32 formation region, that is, in the vicinity of the outer peripheral edge of the fixed plate 31. .
A fixed-side communication hole 33 is formed in the fixed plate 31 except for the one arranged closest to the exhaust port 5.
By not providing the fixed-side communication hole 33 in the fixed plate 31 arranged on the most exhaust side 5 side, it is possible to prevent the compressed and exhausted gas from returning to the suction side (upstream side).
The fixed plate 31 is provided with a plurality of fixed side communication holes 33 at regular intervals along the radial direction.
In the present embodiment, the fixed-side communication hole 33 is configured by a long hole extending in the radial direction. However, the shape of the fixed-side communication hole 33 is not limited to this, and is a circle or an ellipse extending in the radial direction. For example, it may be formed in an arbitrary shape.

Further, the fixed groove plate 30 of each step is divided into two in the circumferential direction so as to be arranged between the rotary plates 10 of each step.
The fixed groove plate 30 formed in this way is assembled by inserting from the outside between the rotating plates 10 of each stage. The fixed groove plate 30 is held (fixed) between the rotating plates 10 in a state where a part of the outer peripheral side is sandwiched in the circumferential direction by the spacer ring 50.

Next, the gas exhaust (compression) operation in the radial flow type molecular pump part α will be described.
FIG. 3 shows an enlarged view of the radial flow type molecular pump portion α of the vacuum pump according to the present embodiment. In FIG. 3, the flow of gas molecules to be exhausted is indicated by black arrows.
In the radial flow type molecular pump part α, when the rotating plate 10 rotates, the surface of the rotating plate 10 facing the fixed groove plate 30 and the helical groove formed by the ribs 32 in the fixed groove plate 30 are moved relative to each other. Exhaust is performed.
The gas flow path formed between the rib 32 forming surface of the fixed plate 31 and the surface on the rotating plate 10 facing this surface is defined as a one-stage radial flow element (radial flow exhaust path).
As shown in FIG. 3, the radial flow type molecular pump portion α of the vacuum pump according to the present embodiment includes five stages of radial flow elements.

The gas molecules introduced from the intake port 3 are taken in (introduced) from the outer peripheral edge of the rotating plate 10 arranged closest to the intake port 3 into the gas intake region (introduction region) in the radial flow element of each stage. )
The gas suction region in each stage of the radial flow element is communicated with the fixed side communication hole 33. This gas suction region indicates a space (gap) between the inner peripheral wall surface of the spacer ring 50 and the formation region of the rib 32.
That is, the gas molecules introduced (incident) from the intake port 3 are incident on the radial flow element of any one of the radial flow elements provided in a plurality of stages.

As described above, the gas molecules incident on the radial flow element of each stage are exhausted (transferred) in the inner circumferential direction by the interaction between the rotating plate 10 and the ribs 32, and are discharged to the gas discharge region.
The gas discharge area in the radial flow element of each stage is communicated via the rotation side communication hole 60. In addition, this gas discharge | emission area | region shows the space (gap) between the outer peripheral wall surface of the upper cylindrical part 9, and the formation area of the rib 32. FIG.
The gas molecules discharged from the radial flow elements at each stage are discharged to the thread groove pump portion S and enter the thread groove 41 of the thread groove spacer 40.

In the present embodiment, in the radial flow type molecular pump portion α, five stages of radial flow elements are provided in parallel in the axial direction. In this way, by providing the radial flow elements in parallel in the axial direction, the peripheral speeds of the rotary plates 10 in each stage can be made equal, so that the five-stage (multiple stages) radial flow elements (in a plurality of stages) arranged in parallel ( Gas molecules can be exhausted simultaneously from the circumferential groove).
Therefore, the exhaust speed of the n-stage radial flow elements arranged in parallel with respect to the exhaust speed s of one stage can be obtained as n × s, that is, an exhaust speed that is multiple times the number of stages.

In the present embodiment described above, the rotor body 7, the lower cylindrical portion 8, the upper cylindrical portion 9, and the rotating plate 10 are integrally formed of aluminum alloy or the like. However, these parts are not limited to integral formation, and each part may be formed using members of different materials in consideration of strength and the like.
For example, since centrifugal force acts on the rotating plate 10 during rotation, the size (outer diameter) is restricted by the strength of the members constituting the rotating plate 10.

Therefore, in order to improve durability against centrifugal force at a higher rotational speed or centrifugal force with a larger outer diameter, the rotating plate 10 ′ (hatched portion in the figure) is compared with its own mass as shown in FIG. And you may make it comprise with a high intensity | strength material, ie, a member with a high specific strength.
As a member having a high specific strength, for example, a carbon fiber reinforced plastic material (CFRP material) is desirable.
In this way, by configuring the rotating plate 10 ′ using a member having a high specific strength, the diameter of the rotating plate 10 ′ can be configured to be larger. Thereby, since the suction area in the radial flow element of each stage can be increased, the exhaust speed can be further improved.

(Modification 1)
Next, a modified example of the structure of the rotating part in the above-described vacuum pump will be described.
FIG. 5 is a diagram showing a schematic configuration in the axial direction of the vacuum pump shown in the first modification.
In addition, the same code | symbol is attached | subjected to the location which overlaps with the vacuum pump shown in FIG. 1, and detailed description is abbreviate | omitted.
In the first modified example, a part of the rotating part integrally formed in the vacuum pump shown in FIG. 1 is configured by combining a plurality of parts.
Specifically, the rotor main body 7, the upper cylindrical portion 9, and the rotating plate 10 that are integrally formed in the vacuum pump shown in FIG. 1 are configured by combining the rotor main body 107, the rotating plate 110, and the spacer 109 with these components.

The rotor body 107 has a disk shape with a flat end surface on at least the intake port 3 side, and a lower cylindrical portion 8 is formed on the outer peripheral edge portion so as to extend in the direction of the exhaust port 5.
The rotor body 107 is configured such that the end surface on the intake port 3 side is disposed at the same height (on the same plane) as the end surface on the intake port 3 side of the thread groove spacer 40 when assembled to the shaft 106. Has been.
The rotating plate 110 is a disk (disk) for exhausting air by relative movement with the fixed groove plate 30. The rotation plate 110 is formed with a rotation side communication hole 60 except for the one arranged closest to the intake port 3 as in the rotation plate 10 described above.
The spacer 109 is a distance piece for positioning to maintain a necessary interval between assembly parts, that is, between adjacent rotating plates 110 or between the rotating plates 110 and the rotor body 107.

The shaft 106 is provided with a round bar-like (columnar) protrusion 116 extending in the axial direction from the end surface on the inlet 3 side. A thread groove is provided on the outer peripheral surface of the protruding portion 116.
The rotor body 107, the spacer 109, and the rotating plate 110 are provided with a fixing hole for allowing the protruding portion 116 of the shaft 106 to pass through at the center.
First, the rotor main body 107 is fitted into the protruding portion 116 of the shaft 106, and the rotating plate 110 is fitted with the spacer 109 interposed therebetween.
Then, these parts are pressed and fixed by the nut 111.

Even a rotating part that has a complicated shape by integral formation can be configured by combining simple shaped parts.
By dividing the rotating portion, it is possible to easily configure only the rotating plate 110 with a member having a high specific strength (for example, a CFRP material).
In addition, by dividing the rotating portion, the rotating portion (the spacer 109, the rotating plate 110) and the fixing portion (the fixed groove plate 30, the spacer ring 50) can be assembled at the same time. Can be disposed between the rotating plates 110 without being divided into two in the circumferential direction.

(Modification 2)
Next, a description will be given of a composite type vacuum pump with different pumping methods.
FIG. 6 is a diagram showing a schematic configuration in the axial direction of the vacuum pump shown in the second modified example.
In addition, the same code | symbol is attached | subjected to the location which overlaps with the vacuum pump mentioned above, and detailed description is abbreviate | omitted.
In the second modification, a composite vacuum pump in which the turbo molecular pump unit T and the radial flow type molecular pump unit α are combined will be described.
Specifically, the vacuum pump shown in the second modification is provided with a radial flow type molecular pump part α on the exhaust port 5 side (downstream stage) of the turbo molecular pump part T.

The rotating part includes a shaft 6 as a rotating shaft, a rotor body 207 having a substantially inverted U-shaped cross section disposed on the shaft 6, a rotating blade 209 provided on the rotor body 207, and a cylinder provided on the exhaust port 5 side. It is comprised from the member 208 grade | etc.,.
A rotor blade 209 is disposed on the outer periphery of the rotor body 207. The rotor blade 209 is formed by blades (blades) extending radially from the shaft 6 at a predetermined angle from a plane perpendicular to the axis of the shaft 6. Become.

A fixing portion is formed on the inner peripheral side of the housing. The fixed portion is composed of a fixed blade 211 provided on the intake port 3 side (turbo molecular pump portion T), a fixed groove plate 30 and the like.
The fixed wing 211 has a blade that is inclined by a predetermined angle from a plane perpendicular to the axis of the shaft 6 and extends from the inner peripheral surface of the housing toward the shaft 6.
In the turbo molecular pump part T, the fixed blades 211 are formed in a plurality of stages alternately with the rotary blades 209 in the axial direction.
The fixed wings 211 of each stage are separated from each other by a cylindrical spacer ring 50 and are held at predetermined positions.

In the turbo molecular pump section T, when the rotating section rotates at a high speed, the gas introduced from the intake port 3 is exhausted to the exhaust port 5 side by the action of the rotary blade 209 and the fixed blade 211.
In other words, the turbo molecular pump unit T performs exhaust processing by imparting momentum to gas molecules colliding with the rotating blades 209 that rotate at high speed, and performing gas transport (gas transport).

An annular rotating plate 210 protruding from the outer peripheral wall surface of the cylindrical member 208 is provided in a region of the cylindrical member 208 on the exhaust port 5 side (downstream stage) of the turbo molecular pump portion T.
A rotating side communication hole 60 is formed on the rotating plate 210 provided in the cylindrical member 208 except for the one disposed closest to the intake port 3 side.
In addition, since the effect | action of the radial flow element in the radial flow type molecular pump part (alpha) is the same as that of the vacuum pump shown in FIG. 1 mentioned above, description is abbreviate | omitted.
As described above, according to the vacuum pump shown in the second modification, it is possible to configure a composite vacuum pump in which the function of the radial flow type molecular pump unit α is appropriately mounted.

(Modification 3)
Next, another example of a composite type vacuum pump with different pumping methods will be described.
FIG. 7 is a diagram showing a schematic configuration in the axial direction of the vacuum pump shown in the third modification.
In addition, the same code | symbol is attached | subjected to the location which overlaps with the vacuum pump mentioned above, and detailed description is abbreviate | omitted.
In the third modified example, a composite vacuum pump in which the turbo molecular pump unit T and the radial flow type molecular pump unit α shown in the second modified example are combined, and further, similar to the vacuum pump shown in FIG. A composite type vacuum pump in which the thread groove pump portion S is combined (added) will be described.

Specifically, the rotating member is provided with a cylindrical member 308 obtained by extending the cylindrical member 208 provided in the second modification (FIG. 6) to the exhaust port 5 side. Further, a thread groove spacer 340 constituting a fixed portion is provided on the exhaust port 5 side (downstream stage) of the radial flow type molecular pump portion α.
A thread groove 341 is formed on the inner wall surface of the thread groove spacer 340. Further, a rib (spiral wall portion) 342 similar to that provided in the fixed groove plate 30 is formed on the end surface of the screw groove spacer 340 on the intake port 3 side.
In addition, since the effect | action of the thread groove pump part S is the same as that of the vacuum pump shown in FIG. 1 mentioned above, description is abbreviate | omitted.

Thus, by providing the rib 342 which is a part of the component of the radial flow element on the end surface on the inlet 3 side of the thread groove spacer 340, the thread groove spacer 340 can be used also as the fixed groove plate 30. Thereby, reduction of the number of parts which comprise a pump and improvement in the efficiency of assembly work can be aimed at.
According to the vacuum pump shown in the third modified example, similarly to the vacuum pump shown in the second modified example, it is possible to configure a composite vacuum pump appropriately equipped with the function of the radial flow type molecular pump part α. it can.

(Modification 4)
Next, a modified example of the structure of the radial flow type molecular pump portion α in the above-described vacuum pump will be described.
FIG. 8 is a diagram showing a schematic configuration in the axial direction of the vacuum pump shown in the fourth modification.
In addition, the same code | symbol is attached | subjected to the location which overlaps with the vacuum pump mentioned above, and detailed description is abbreviate | omitted.
In the above-described vacuum pump, a radial flow type molecular pump unit provided with a radial flow element that introduces gas molecules from the outer peripheral side and gives direction to the introduced gas molecules in the inner peripheral direction to exhaust (compress) the gas. α was explained.
However, the directionality given to the gas in the radial flow element is not limited from the outer peripheral side to the inner peripheral side.
That is, the radial flow element may be configured such that gas molecules are introduced from the inner peripheral side, and gas is exhausted (compressed) by giving direction to the introduced gas molecules in the outer peripheral direction.

In the vacuum pump described above, the radial flow molecular pump portion α is provided with five stages of radial flow elements in parallel in the axial direction. A group of adjacent radial flow elements having the same exhaust gas directivity is defined as a radial flow element group.
That is, in the above-described vacuum pump, one radial flow element group is constituted by five stages of radial flow elements.
However, the number of radial flow elements constituting one radial flow element group is not limited to five, and may be more or less than this.

As shown in FIG. 8, the vacuum pump shown in the fourth modified example is a composite type in which a turbo molecular pump part T and a radial flow type molecular pump part α are combined in the same manner as the vacuum pump shown in the second modified example. Vacuum pump.
Further, in the fourth modified example, the radius flow type molecular pump portion α is configured to give a directionality from the outer peripheral side to the inner peripheral side (outside to inside) with respect to the introduced gas molecules. By arranging two types of radial flow element groups alternately in the axial direction, a flow element group and a radial flow element group configured to give directionality from the inner circumference side to the outer circumference side (inside to outside) Constitute.
Note that the operation of the turbo molecular pump unit T is the same as that of the vacuum pump shown in the second modified example, and thus the description thereof is omitted.

As shown in FIG. 8, the radial flow type molecular pump portion α includes a first radial flow element group a, a second radial flow element group b, and a third radial flow element group c.
The first radial flow element group a and the third radial flow element group c give directionality from the outer peripheral side to the inner peripheral side (outer to inner) for each gas molecule introduced (incident). Three stages of radial flow elements configured as described above are provided.
In addition, the second radial flow element group b is configured so as to give directionality from the inner peripheral side to the outer peripheral side (inside to outside) for the introduced (incident) gas molecules. 3 stages.

FIG. 9A shows a relationship diagram between the direction of the spiral of the rib 32 and the rotational direction of the rotor in the radial flow element configured to give directionality from the inner peripheral side to the outer peripheral side.
FIG. 9B shows a relationship between the direction of the spiral of the rib 32 ′ and the rotational direction of the rotor in the radial flow element configured to give directionality from the outer peripheral side to the inner peripheral side.
As shown in FIG. 9A, the fixed groove plate 30 in the radial flow elements constituting the first radial flow element group a and the third radial flow element group c has a rotating plate 410 (cylindrical member 408). Ribs 32 are provided so as to spiral in the center direction in the same direction as the rotation direction.
On the other hand, the fixed groove plate 30 ′ in the radial flow elements constituting the second radial flow element group b is opposite to the rotation direction of the rotary plate 410 (cylindrical member 408) as shown in FIG. 9B. Ribs 32 ′ are provided so as to spiral in the center direction.
The rotation side communication hole 60 and the fixed side communication hole 33 are provided so that one radial flow element group is constituted by three stages of radial flow elements, and the shape thereof is a size corresponding to the degree of compression in each region. And For example, the opening area is formed smaller in order from the upstream to the downstream of the gas flow path.

Next, the gas exhaust (compression) operation in the radial flow type molecular pump section α of the fourth modification will be described.
FIG. 10 shows an enlarged view of the radial flow type molecular pump portion α of the vacuum pump shown in the fourth modification. In FIG. 10, the flow of gas molecules to be exhausted is indicated by black arrows.
The gas molecules introduced from the turbo molecular pump unit T are taken into the gas suction region in the first radial flow element group a from the outer peripheral edge of the rotating plate 10 disposed on the most inlet side 3 side.
The gas molecules taken into the gas suction region in the first radial flow element group a are incident on the radial flow element at any one of the three radial flow elements.

The gas molecules incident on the radial flow element are exhausted (transferred) in the inner circumferential direction by the interaction between the rotating plate 10 and the rib 32, and are discharged to the gas discharge region in the first radial flow element group a.
The gas molecules discharged into the gas discharge region in the first radial flow element group a are subsequently taken into the gas suction region in the second radial flow element group b.
The gas molecules taken into the gas inhalation region in the second radial flow element group b are incident on the radial flow element of any one of the three radial flow elements.
The gas molecules incident on the radial flow element are exhausted (transferred) in the outer peripheral direction by the interaction between the rotating plate 10 and the rib 32 ', and are discharged to the gas discharge region in the second radial flow element group b.

The gas molecules discharged into the gas discharge region in the second radial flow element group b are subsequently taken into the gas suction region in the third radial flow element group c.
The gas molecules taken into the gas suction region in the third radial flow element group c are incident on the radial flow element at any one of the three radial flow elements.
The gas molecules incident on the radial flow element are exhausted (transferred) in the outer circumferential direction by the interaction between the rotating plate 10 and the rib 32, and are discharged to the gas discharge region in the third radial flow element group c.
And the gas molecule discharged | emitted by the discharge area | region of the gas in the 3rd radial flow element group c is discharged | emitted as it is outside the vacuum pump from the exhaust port 5 as it is.
Thus, according to the vacuum pump shown in the 4th modification, a vacuum pump with higher compression performance can be constituted by arranging a plurality of radial flow element groups in parallel in the axial direction.

It is the figure which showed schematic structure of the axial direction of the vacuum pump of this embodiment. (A) shows the relationship figure of the direction of the spiral of the rib formed in a fixed groove plate, and the rotation direction of a rotor, (b) is a section perspective view of a fixed groove plate. It is an enlarged view of the radial flow type molecular pump part of the vacuum pump which concerns on this Embodiment. It is the figure which showed the modification of the rotating plate in a radial flow type molecular pump part. It is the figure which showed schematic structure of the axial direction of the vacuum pump shown in a 1st modification. It is the figure which showed schematic structure of the axial direction of the vacuum pump shown in a 2nd modification. It is the figure which showed schematic structure of the axial direction of the vacuum pump shown in a 3rd modification. It is the figure which showed schematic structure of the axial direction of the vacuum pump shown in a 4th modification. (A) is a relational diagram between the direction of the spiral of the rib in the radial flow element configured to give directionality from the inner peripheral side to the outer peripheral side and the rotational direction of the rotor, and (b) is the outer peripheral side. FIG. 6 is a relationship diagram between the direction of the spiral of the rib and the rotational direction of the rotor in the radial flow element configured to give directionality from the inner circumference to the inner circumference. It is an enlarged view of the radial flow type molecular pump part of the vacuum pump shown in the 4th modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Casing 2 Base 3 Intake port 4 Flange part 5 Exhaust port 6 Shaft 7 Rotor main body 8 Lower cylindrical part 9 Upper cylindrical part 10 Rotating plate 11 Bolt 12 Motor part 13 Magnetic bearing part 14 Magnetic bearing part 15 Magnetic bearing part 16 Displacement sensor 17 Displacement sensor 18 Displacement sensor 19 Metal disk 20 Electromagnet 21 Electromagnet 22 Protective bearing 23 Protective bearing 30 Fixed groove plate 31 Fixed plate 32 Rib 33 Fixed side communication hole 40 Screw groove spacer 41 Screw groove 50 Spacer ring 60 Rotation side communication hole 106 Shaft 107 Rotor body 109 Spacer 110 Rotating plate 111 Nut 116 Protruding portion 207 Rotor body 208 Cylindrical member 209 Rotating blade 210 Rotating plate 211 Fixed wing 308 Cylindrical member 340 Thread groove spacer 341 Thread groove 342 Rib 408 Cylindrical member 410 times Board

Claims (5)

A radial flow element, which is provided from the suction portion to the exhaust portion and which guides incident gas molecules in the radial direction, and a guide surface disposed to face the guide groove via the gap;
Drive means for applying a rotational motion to one of the guide groove or the guide surface to cause the guide groove and the guide surface to move relative to each other and to give a radial direction to gas molecules incident on the radial flow element; ,
A vacuum pump that employs a radial flow system that exhausts gas in the radial direction,
A radial flow element group arranged in parallel in at least two stages in the radial flow element axial direction;
Communicating means for communicating all the suction portions of the radial flow elements constituting the radial flow element group;
A vacuum pump characterized by comprising: The driving means applies a rotational motion to the guide surface, causes the guide groove and the guide surface to move relative to each other, and gives a radial directionality to gas molecules incident on the radial flow element,
The vacuum pump according to claim 1, wherein the guide surface is constituted by a member having a high specific strength.   The vacuum pump according to claim 2, wherein the member having a high specific strength is a carbon fiber reinforced plastic material (CFRP material). The guide groove is formed on a fixed plate fixed to the casing of the vacuum pump,
The vacuum pump according to claim 2 or 3, wherein the communication means includes a communication hole that penetrates the rotating plate or the fixed plate in which the guide surface is formed in the thickness direction.   The vacuum pump according to claim 2, 3 or 4, wherein the radial flow element groups having different gas molecule guiding directions are arranged alternately in parallel in the axial direction.

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