WO2008015849A1

WO2008015849A1 - Bearing device, and turbo-molecular pump

Info

Publication number: WO2008015849A1
Application number: PCT/JP2007/062236
Authority: WO
Inventors: Takashi Kabasawa; Satoshi Okudera
Original assignee: Edwards Japan Limited
Priority date: 2006-08-01
Filing date: 2007-06-18
Publication date: 2008-02-07
Also published as: JP2008038935A

Abstract

A protective bearing equipped with rolling elements of nonmagnetic body in which corotation of a magnetized inner ring is suppressed. An inner ring and an outer ring are formed of a member of magnetic body, respectively, and rolling elements are formed of nonmagnetic body. A magnetism inductor is a member formed of a magnetic material and has a function for inducing magnetism of a magnetized inner ring to a closed magnetic path passing the inner ring and the outer ring. A magnetism inducing portion is constituted of a part stretching out in the extending direction and the axial direction of a bearing fixing portion from the inner circumferential edge thereof, and touches the outer ring in order to reduce reluctance. The interval β of the clearance between the inner ring of the protective bearing and the magnetism inducting portion is set sufficiently smaller than the interval α of the clearance between the inner circumferential surface of the inner ring and the outer circumferential wall face of a shaft. Since the magnetism inductor is provided such that the interval β becomes smaller than the interval α, more magnetic fluxes can be picked up and induced to the closed magnetic path passing the inner ring and the outer ring.

Description

Specification

Bearing device and turbomolecular pump

Technical field

TECHNICAL FIELD [0001] The present invention relates to a bearing device that supports a rotating shaft in a non-contact manner and a turbo molecular pump, and more particularly to a bearing device that includes a protective bearing (auxiliary bearing) that backs up when touched down, and a turbo molecular pump.

Background art

In a bearing device that supports a rotating shaft in a non-contact manner, such as a hydrodynamic bearing device and a magnetic bearing device, it is structurally difficult to obtain a high (high) rigidity of the device.

For this reason, these non-contact bearing devices are used for emergency (protective) protective bearings (touch-down and non-contact) when a disturbance such as an earthquake impact is applied or when the control system is abnormal. If the rotating shaft cannot be held, it is configured to back up with this protective bearing.

The protective bearing is constituted by a rolling bearing such as a ball bearing or a roller bearing.

[0003] While the rotating shaft is supported in a non-contact manner, no load is applied to the protective bearing (auxiliary bearing), so the inner ring (contact wheel with the rotating shaft) of the protective bearing is stopped.

However, when the bearing device is in a non-contact state and cannot hold the rotating shaft, that is, when the protective bearing functions, the inner ring of the protective bearing contacts the rotating shaft and is close to the rated speed (rotor speed). It is accelerated rapidly.

For this reason, the rolling elements (balls, rollers) of the protective bearing are made of a ceramic member that is lightweight and has a small rotational torque.

[0004] Incidentally, a turbo molecular pump that uses such a non-contact bearing to exhaust gas by the action of a fixed blade and a rotating blade rotating at high speed is available.

The turbo molecular pump uses a high-frequency motor to rotate the rotor blades at high speed. Therefore, the permanent magnet which comprises a high frequency motor is embed | buried in the rotating shaft. When assembling such a turbo-molecular pump, generally, a protective bearing is disposed at the end, and a rotating shaft is inserted through a cylindrical fixed portion.

Therefore, the raceway rings (inner ring, outer ring) of the protection bearing are magnetized when passing through the inside of the permanent magnet force protection bearing carried on the rotating shaft.

FIG. 9 is a diagram showing a state where the raceway ring is magnetized in a conventional protective bearing. 9A shows a cross section in the radial direction (radial direction) of the protective bearing, and FIG. 9B shows a cross section in the axial direction (axial direction).

When the bearing ring of the protective bearing is magnetized, as shown in FIG. 9, a closed magnetic circuit (thick line) passing through the inner ring 101 and the rotating shaft 104, and a closed magnetic circuit (broken line) passing through the inner ring 101 and the outer ring 102, ie, magnetic A circuit is formed.

However, since the rolling element 103 is made of a non-magnetic member (for example, a ceramic member), it functions as an air gap between the inner ring 101 and the outer ring 102, as between the inner ring 101 and the rotating shaft 104. To do.

Therefore, the magnetic flux density in the magnetic circuit is larger (higher) in the closed magnetic path (thick line) passing through the inner ring 101 and the rotating shaft 104 than in the closed magnetic path (broken line) passing through the inner ring 101 and the outer ring 102.

[0006] When the bearing ring of the protective bearing is magnetized, the interaction with the rotary shaft 104 causes the inner ring of the protective bearing 10 3 even while the rotary shaft 104 is supported in a non-contact manner. However, the rotation shaft 104 rotates with the rotation shaft 104.

Specifically, an induced current is generated in the rotating shaft 104 due to the magnetism of the race (inner ring 101). As a result, the inner ring 101 of the protective bearing rotates by attracting the magnetic force generated by the rotating shaft 104.

[0007] If the accompanying rotation of the inner ring 101 occurs, the life of the protective bearing may be reduced. Further, when the inner ring 101 is rotated, noise and vibration due to the rotation of the inner ring 101 may be a problem.

Therefore, conventionally, a method for preventing the rotation of the bearing ring in a protective bearing using such a non-magnetic rolling element has been proposed in the following patent documents.

Patent Document 1: Japanese Patent Laid-Open No. 2002-54593

[0008] Patent Document 1 describes that an inner ring of a touchdown bearing (protective bearing) has a low residual magnetic flux density. A technique has been proposed in which the inner ring is formed of a different material and is suppressed from being magnetized. Specifically, a technology has been proposed in which the inner ring of the touchdown bearing is formed of a non-magnetic member such as austenitic stainless steel formed in a solid state, thereby suppressing the inner ring of the touchdown bearing from being magnetized. Yes.

Disclosure of the invention

Problems to be solved by the invention

However, as proposed in Patent Document 1, when the inner ring is made of a non-magnetic member, the non-magnetic member has low rigidity, so the strength (rigidity of the protective bearing (touch down bearing)) ) Was difficult to hold sufficiently.

Therefore, an object of the present invention is to provide a bearing device and a turbo molecular pump including a protective bearing capable of appropriately suppressing the rotation of the inner ring while maintaining sufficient rigidity.

Means for solving the problem

[0010] The invention according to claim 1 is a bearing device that supports a rotating shaft on which a permanent magnet constituting a motor is disposed in a non-contact manner, the rolling element made of a non-magnetic material, and the rolling element. A protective bearing for supporting the rotating shaft at the time of a stop and abnormal condition, the inner ring and the outer ring made of a magnetic material forming a raceway, wherein the protective bearing has a rotational torque of the inner ring smaller than a friction torque; The above object is achieved by having a magnetic induction structure.

Note that the rotational torque of the inner ring indicates, for example, traction torque that rotates with the rotation of the rotation shaft.

In claim 1, for example, it is preferable that a magnetic resistance between the inner ring and the outer ring is smaller than a magnetic resistance between the inner ring and the rotating shaft.

According to a second aspect of the present invention, in the bearing device according to the first aspect, the magnetic induction structure is a magnetic induction member force composed of a magnetic member for guiding the magnetism of the inner ring to the outer ring. .

According to a third aspect of the present invention, in the bearing device according to the second aspect, the magnetic induction member is disposed at a predetermined distance / 3 from the inner ring, and the distance / 3 is defined by the rotation shaft and the inner ring. It is characterized by being smaller than the distance between and. According to a fourth aspect of the present invention, in the bearing device according to the first, second, or third aspect, the magnetic induction structure includes a distance γ between the inner ring and the outer ring, and the rotation shaft and the inner ring. It is characterized in that it is smaller than the interval α.

The invention according to claim 5 is the bearing device according to claim 1, claim 2, claim 3 or claim 4, wherein the rolling element is made of a ceramic member.

The invention according to claim 6 is characterized in that in the bearing device according to any one of claims 1 to 5, the rotating shaft is supported by a magnetic force or a dynamic pressure.

The invention according to claim 7 is a turbomolecular pump comprising the bearing device according to any one of claims 1 to 6.

The invention's effect

[0011] According to the present invention, the rotation of the inner ring in the protective bearing is provided with the magnetic induction structure that makes the rotation torque of the inner ring smaller than the friction torque, so that the accompanying rotation of the inner ring can be suppressed.

Brief Description of Drawings

FIG. 1 is a diagram showing a schematic configuration of a turbo molecular pump according to the present embodiment.

[FIG. 2] (a) is a diagram showing a configuration of a magnetic induction structure, and (b) is an enlarged view of a region indicated by a broken line part in (a).

FIG. 3 is a diagram showing a state in which the protective bearing according to the present embodiment is magnetized.

FIG. 4 is a diagram showing a configuration of a first modification of the magnetic induction structure.

FIG. 5 is a diagram showing a configuration of a second modification of the magnetic induction structure.

FIG. 6 is a diagram showing a configuration of a third modification of the magnetic induction structure.

FIG. 7 is a view showing a configuration of a fourth modification of the magnetic induction structure.

FIG. 8 is a view showing a configuration of a fifth modification of the magnetic induction structure.

FIG. 9 is a view showing a state in which a race is magnetized in a conventional protective bearing. Explanation of symbols

[0013] 1 turbo molecular pump

2 Casing

3 base 4 Air intake

5 Flange

6 Exhaust vent

7 Shaft

8 Rotor body

9 Rotor blade

10 Cylindrical member

11 Motor section

12 ~: 14 Magnetic bearing

15 ~: 17 Displacement sensor

18 Metal disc

19, 20 electromagnet

23 volts

25 Vol

30 fixed wing

31 Thread groove spacer

32 Spiral groove

33 Spacer

34 Stator column

40, 50 Protective bearing

41 inner ring

42 Outer ring

43 Rolling elements

44 Magnetic derivatives

70 Control unit

111 Permanent magnet

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to FIGS. The

In this embodiment, a turbo molecular pump provided with a magnetic bearing device will be described as a device using a non-contact bearing device having a protective bearing.

In this embodiment, a description will be given using a composite turbo molecular pump having a turbo molecular pump part T and a thread groove pump part S as an example of a turbo molecular pump.

FIG. 1 is a diagram showing a schematic configuration of a turbo molecular pump 1 according to the present embodiment. FIG. 1 shows a cross section in the axial direction of the turbo molecular pump 1. The turbo molecular pump 1 is installed, for example, in a semiconductor manufacturing apparatus, and is used when exhausting process gas from a vacuum chamber.

The casing 2 constituting the exterior body of the turbo molecular pump 1 has a substantially cylindrical shape, and constitutes the casing of the turbo molecular pump 1 together with the base 3 provided at the lower part of the casing 2 (exhaust port 6 side). ing. A structure for allowing the turbo molecular pump 1 to perform an exhaust function, that is, a gas transfer mechanism is disposed inside the housing.

[0016] This gas transfer mechanism is mainly composed of a rotating part that is rotatably supported by a shaft and a fixed part that is fixed to the casing.

An inlet 4 for introducing gas into the turbo molecular pump 1 is formed at the end of the casing 2. In addition, a flange portion 5 is formed on the end surface of the casing 2 on the intake port 4 side so as to project to the outer peripheral side.

Further, the base 3 is formed with an exhaust port 6 for exhausting gas from the turbo molecular pump 1, that is, exhausting process gas from the semiconductor manufacturing apparatus.

[0017] The rotating part includes a shaft 7 that is a rotating shaft, a substantially inverted U-shaped port body 8 disposed on the shaft 7, a rotor blade 9 provided on the rotor body 8, and an exhaust port 6 side. It is composed of a cylindrical member 10 provided in the (thread groove pump part S).

The rotor body 8 is fixed to the upper part of the shaft 7 with bolts 23. The cylindrical member 10 is formed on the extension of the rotor body 8 and is a cylindrical member that is concentric with the rotation axis of the rotor body 8.

A rotor blade 9 is disposed on the outer periphery of the rotor body 8, and the rotor blade 9 is inclined by a predetermined angle from a plane perpendicular to the axis of the shaft 7 and extends radially from the shaft 7 (blade blades). Root).

[0018] In the middle of the shaft 7 in the axial direction, a motor unit 11 for rotating the shaft 7 at a high speed is provided. The motor unit 11 is a DC brushless motor (high frequency motor), and is configured as follows.

The motor unit 11 includes a permanent magnet 111 embedded in the shaft 7. For example, the permanent magnet 111 is fixed so that the N pole and the S pole are arranged around the shaft 7 every 180 °.

In addition, the motor unit 11 includes an electromagnet 112 disposed around the permanent magnet with a predetermined clearance from the shaft 7. Here, six electromagnets are arranged so as to face each other symmetrically with respect to the axis of the shaft 7 every 60 °.

The turbo molecular pump 1 is connected to the control device 70 via a connector and a cable. Then, the current of the electromagnet 112 is switched one after another so that the rotation of the shaft 7 is continued by the control device 70.

That is, the control device 70 generates a rotating magnetic field around the permanent magnet 111 fixed to the shaft 7 by switching the exciting currents of the six electromagnets 112, and causes the shaft to move by causing the permanent magnet 111 to follow the rotating magnetic field. Rotate 7

[0020] Magnetic bearings 12 and 13 for pivotally supporting the shaft 7 in the radial direction (radial direction) are provided on the intake port 4 side and the exhaust port 6 side with respect to the motor portion 11 of the shaft 7. Yes.

In addition, a magnetic bearing 14 for pivotally supporting the shaft 7 in the thrust direction (axial direction) is provided at the lower end (exhaust port 6 side end) of the shaft 7.

These magnetic bearings 12 to 14 constitute so-called five-axis control type magnetic bearings. The shaft 7 is supported by the magnetic bearings 12 and 13 in a non-contact manner in the radial direction (the radial direction of the shaft 7), and is supported by the magnetic bearing 14 in a non-contact manner in the thrust direction (the axial direction of the shaft 7).

Displacement sensors 15 to 17 for detecting the displacement of the shaft 7 are provided in the vicinity of the magnetic bearings 12 to 14, respectively.

On the magnetic bearing 12, four electromagnets are arranged around the shaft 7 so as to face each other at 90 °. The shaft 7 is formed of a high magnetic permeability material (such as iron), and these electromagnets It is attracted by magnetic force.

The displacement sensor 15 detects the displacement of the shaft 7 in the radial direction by sampling at predetermined time intervals.

[0022] When the control device 70 detects that the shaft 7 is displaced from the predetermined position in the radial direction by the displacement signal from the displacement sensor 15, the control device 70 adjusts the magnetic force of each electromagnet in the magnetic bearing 12 to determine the shaft 7 in advance. It operates to return to the position of. The adjustment of the magnetic force of the electromagnet is performed by feedback controlling the excitation current of each electromagnet.

The control device 70 performs feedback control of the magnetic bearing 12 based on the signal of the displacement sensor 15, and as a result, the shaft 7 is magnetically levitated in the radial direction with a predetermined clearance from the electromagnet in the magnetic bearing 12, and the space 7 It is held in a non-contact manner.

The configuration and action of the magnetic bearing 13 are the same as those of the magnetic bearing 12. The control device 70 performs feedback control of the magnetic bearing 13 based on the signal of the displacement sensor 16, whereby the shaft 7 is magnetically levitated in the radial direction by the magnetic bearing 13 and is held in a non-contact manner in the space. . Thus, the shaft 7 is held at a predetermined position in the radial direction by the action of the magnetic bearings 12 and 13.

[0024] The magnetic bearing 14 includes a disk-shaped metal disk 18 and electromagnets 19 and 20, and holds the shaft 7 in the thrust direction.

The metal disk 18 is made of a high permeability material such as iron, and is fixed perpendicularly to the shaft 7 at the center thereof. Magnets 19 and 20 are arranged so as to sandwich the metal disk 18 and face each other. The electromagnet 19 attracts the metal disk 18 upward by magnetic force, and the electromagnet 20 attracts the metal disk 18 downward.

The control device 70 appropriately adjusts the magnetic force exerted by the electromagnets 19 and 20 on the metal disk 18 so that the shaft 7 is magnetically levitated in the thrust direction and held in a non-contact manner in the space.

Further, a displacement sensor 17 is disposed so as to face the lower end portion of the shaft 7. The displacement sensor 17 samples and detects the displacement of the shaft 7 in the thrust direction, and transmits this to the control device 70. The control device 70 detects the displacement of the shaft 7 in the thrust direction based on the displacement detection signal received from the displacement sensor 17. When the shaft 7 moves in one of the thrust directions and is displaced from a predetermined position, the control device 70 adjusts the magnetic force by feedback controlling the exciting currents of the electromagnets 19 and 20 so as to correct this displacement. It operates to return the shaft 7 to a predetermined position. The control device 70 continuously performs this feedback control. As a result, the shaft 7 is magnetically levitated and held at a predetermined position in the thrust direction.

As described above, the shaft 7 is held in the radial direction by the magnetic bearings 12 and 13, and is held in the thrust direction by the magnetic bearing 14, so that it rotates around the axis of the shaft 7. .

[0026] Next, a description will be given of the fixing portion constituting the gas transfer mechanism.

The fixed part is fixed blade 30 provided on the intake port 4 side (turbomolecular pump part T), thread groove spacer 31 provided on the exhaust port 6 side (thread groove type pump part S), stator column 34, etc. Consists of.

The fixed wing 30 is configured with a blade force that is inclined from the plane perpendicular to the axis of the shaft 7 by a predetermined angle and extends from the inner peripheral surface of the casing 2 toward the shaft 7.

In the turbo molecular pump section T, the fixed blades 30 are formed in a plurality of stages alternately with the rotor blades 9 in the axial direction. The fixed wings 30 of each stage are separated from each other by a spacer 33 having a cylindrical shape.

[0027] The thread groove spacer 31 is a cylindrical member in which a spiral groove 32 is formed on the inner peripheral surface. The inner peripheral surface of the thread groove spacer 31 faces the outer peripheral surface of the cylindrical member 10 with a predetermined gap therebetween.

The direction of the spiral groove 32 formed in the thread groove spacer 31 is the direction of force toward the exhaust port 6 when gas is transported in the spiral groove 32 in the rotational direction of the rotating part. The depth of the spiral groove 32 becomes shallower as it approaches the exhaust port 6. The gas transported through the spiral groove 32 is compressed as it approaches the exhaust port 6.

The base 3 and the casing 2 constitute an exterior body of the turbo molecular pump 1. At the center of the base 3 in the radial direction, a stator column having a cylindrical shape concentrically with the rotational axis of the rotor is attached in the direction of the 34 force inlet 4.

[0028] The turbo molecular pump 1 is disposed on the intake port 4 side of the displacement sensor 15 inside the casing 2. In addition, a protective bearing (auxiliary bearing) 40 constituted by a full ball type deep groove ball bearing is provided.

Details of the protective bearing 40 will be described later.

Further, on the exhaust port 6 side of the displacement sensor 16, a protective bearing 50 constituted by a pair of angular ball bearings in which oblique contact directions are combined in opposite directions is provided.

These protective bearings 40 and 50 are rolling bearings (touch-down bearings) for protecting the shaft 7 from contact with the magnetic bearings 12, 13, and 14 when the shaft 7 is stopped or abnormally controlled. It is.

[0029] Between the outer peripheral surface of the shaft 7 and the inner peripheral surface of the protective bearings 40, 50, a gap slightly smaller than the gap between the shaft 7 and each of the magnetic bearings 12, 13, 14 is interposed. Yes.

As a result, in a state where the shaft 7 is rotatably supported by the magnetic bearings 12, 13, 14 in a magnetically levitated state, the shaft 7 maintains a non-contact state with respect to the protective bearings 40, 50. On the other hand, when the shaft 7 is stopped or when the control is abnormal due to the action of an external force, the shaft 7 comes into contact with the protective bearings 40 and 50 and is rotatably supported before contacting the magnetic bearings 12, 13 and 14.

[0030] Here, a method for assembling (assembling) the shaft 7 in the turbo molecular pump 1 configured as described above will be briefly described.

In the turbo molecular pump 1 according to the present embodiment, the rotor body 8 is fixed to the shaft 7 using the bolts 23. The shaft 7 is preloaded with a permanent magnet 111 that constitutes a motor unit 11 (high frequency motor).

On the other hand, on the fixed part side, a cylindrical stator column 34 is fixed to the base 3 using bolts 25.

A protective bearing 40 is fixed to the inner peripheral surface of the stator column 34 in the vicinity of the end on the intake port 4 side.

After inserting the shaft 7 to which the rotor body 8 is fixed into the stator column 34 from the direction of the intake port 4, the metal disk 18 (magnetic bearing 14) is attached to the shaft 7 from the direction of the exhaust port 6. (Mounting) Assemble the rotating part to the fixed part.

[0032] When the rotating part is assembled to the fixed part in this way, that is, the shaft 7 is connected to the stator column. When assembled to 34, the protective bearing 40 is magnetized by the magnetic field of the permanent magnet 111 mounted on the shaft 7. That is, a magnetic field remains in the protective bearing 40.

In the present embodiment, even if the protective bearing 40 is magnetized in this way,

Magnetic induction structure that suppresses the accompanying phenomenon in which the protective bearing ₄₀ rotates as the shaft ₇ rotates due to the action of the magnetic circuit formed by the generated residual magnetic field as in the past (magnetic induction mechanism) Is provided.

Here, a magnetic induction structure that suppresses the accompanying phenomenon of the protective bearing 40 will be described.

Fig. 2 (a) is a diagram showing the configuration of the magnetic induction structure, and Fig. 2 (b) is an enlarged view of the region indicated by the broken line in (a). In FIG. 2, the description of the rotor main body 8 and the like fixed to the shaft 7 is omitted to avoid complicating the description.

As shown in FIG. 2, the turbo molecular pump 1 according to the present embodiment includes an inner ring 41, an outer ring 42, a protective bearing 40 including rolling elements 43, and a magnetic derivative 44.

The inner ring 41 and the outer ring 42 constitute a raceway (circular raceway) on which the rolling elements 43 in the protective bearing 40 roll.

The inner ring 41 and the outer ring 42 are formed of a magnetic member (for example, a SUS440C member that is martensitic stainless steel or SUJ2 that is carbon steel).

The rolling elements 43 are balls (balls) disposed between the circular raceways of the inner ring 41 and the outer ring 42, and are formed of a ceramic material that is a nonmagnetic material.

The density of this rolling element 43 made of ceramics (for example, 3.20g / cm3 for Si3N4 ceramics) is lower than the density of bearing steel (7.85g / cm3). Thus, the centrifugal force can be effectively suppressed, and the load on the rolling element 43 can be reduced.

[0035] The magnetic derivative 44 is a member formed of a magnetic material, and has a magnetic induction function for guiding the magnetism of the magnetized inner ring 41 to a closed magnetic path passing through the inner ring 41 and the outer ring 42, and a protective bearing 40 (outer ring 42). ) Is fixed to the stator column 34.

As shown in the figure, the magnetic derivative 44 is composed of a bearing fixing portion 44a and a magnetic induction portion 44b.

[0036] The bearing fixing portion 44a is formed of an annular plate member, and the magnetic derivative 44 is attached to the stator column 34. A plurality of through-holes 47 into which screws 45 for fixing (wearing) are fitted (pressed) are formed.

Further, a screw hole 48 for fixing the screw 45 is provided on the end surface of the stator column 34 on the intake port 4 side.

The protective bearing 40 in which the outer ring 42 is disposed in the fitting groove 46 provided on the end of the intake port 4 of the stator column 34 is fixed to the screw hole 48 with the screw 45 so that It is pressed down from the 4th side and fixed.

[0037] The magnetic induction portion 44b extends from the inner peripheral edge of the bearing fixing portion 44a to the direction in which the bearing fixing portion 44a extends.

(Radial direction) and axially projecting (projecting) parts.

The portion of the magnetic induction portion 44b that protrudes in the axial direction (exhaust port 6 direction) is disposed between the inner ring 41 and the outer ring 42 of the protective bearing 40, and the outer circumferential surface and the inner circumferential surface of the outer ring 42 are arranged. Thus, they are in contact (contacted) so that the magnetic resistance becomes smaller.

Thus, by bringing the magnetic derivative 44 and the outer ring 42 into contact, more magnetic flux can be picked up and guided to the closed magnetic circuit (thick line) passing through the inner ring 41 and the outer ring 42. A closed magnetic path (thick line) passing through the inner ring 41 and the outer ring 42 is an induction magnetic path.

In addition, as shown in FIG. 2 (b), the gap i3 between the inner ring 41 of the protective bearing 40 and the magnetic induction portion 44b is a clearance between the inner peripheral surface of the inner ring 41 and the outer peripheral wall surface of the shaft 7. It is configured to be sufficiently small (narrow) compared to the interval α.

The interval i3 is the distance between the gap between the radially projecting portion of the magnetic guiding portion 44b and the end surface on the inlet 4 side of the inner ring 41, and the portion of the magnetic guiding portion 44b protruding in the axial direction. The distance between the inner ring 41 and the inner peripheral wall surface is shown.

In this way, by providing the magnetic derivatives 44 so as to be spaced at intervals of 3/3, more magnetic flux can be picked up and guided to the closed magnetic circuit (thick line) passing through the inner ring 41 and the outer ring 42.

Next, a description will be given of a state in which the protective bearing 40 configured as described above is magnetized by the permanent magnet 111 when the turbo molecular pump 1 is assembled (assembled).

FIG. 3 is a view showing a state where the protective bearing 40 according to the present embodiment is magnetized. 3A shows a cross section in the radial direction (radial direction) of the protective bearing 40, and FIG. 3B shows a cross section in the axial direction (axial direction). As described above, when the protective bearing 40 is magnetized, as shown in FIG. 3, a closed magnetic circuit passing through the inner ring 41 and the shaft 7 (broken line) and a closed magnetic circuit passing through the inner ring 41 and the outer ring 42 (thick line), that is, Two magnetic circuits are formed.

In the turbo molecular pump 1 according to the present embodiment, as shown in FIG. 2, by providing a magnetic derivative 44 that guides the magnetism of the magnetized inner ring 41 to the outer ring 42, the inner ring 41 and the outer ring 42 are separated. Air gap distance j3 force in the closed magnetic path that passes through It becomes smaller than the conventional air gap distance (the distance between the inner ring 101 and the outer ring 102) (shown in Fig. 9). That is, the magnetic resistivity in the closed magnetic circuit passing through the inner ring 41 and the outer ring 42 is reduced.

Therefore, the magnetic flux density (number of magnetic flux lines per unit area) of the closed magnetic circuit (thick line) passing through the inner ring 41 and the outer ring 42 is larger (higher) than the closed magnetic circuit (broken line) passing through the inner ring 41 and the shaft 7. . Therefore, by providing the magnetic derivative 44, the magnetic flux leaking to the shaft 7 side can be reduced by guiding the magnetic flux to the closed magnetic path (thick line) passing through the inner ring 41 and the outer ring 42.

[0041] Thereby, since the induced current generated in the shaft 7 can be reduced, the turbo molecular pump 1 is supported in steady operation, that is, the shaft 7 is supported by the magnetic bearings 12, 13, and 14 in a non-contact manner. While

The relationship of (rotational torque of the inner ring 41 of the protective bearing 40) <(friction torque of the protective bearing 40) is established. The friction torque of the protective bearing 40 includes a component of the rolling friction force of the rolling element 43.

That is, since the force for braking the inner ring 41 is larger than the force for rotating the inner ring 41 of the protective bearing 40, the accompanying rotation of the inner ring 41 accompanying the rotation of the shaft 7 can be suppressed.

[0042] As described above, according to the present embodiment, by providing the magnetic induction structure that induces the magnetism of the magnetized protective bearing 40, the rotation of the protective bearing 40 during steady operation of the turbo molecular pump 1 is achieved. Therefore, the wear rate (wear rate) of the protective bearing 40 can be reduced. As a result, it is possible to increase the life of the protective bearing 40.

According to the present embodiment, since the accompanying rotation of the protective bearing 40 can be suppressed, noise (abnormal noise) and vibration caused by the rotation of the protective bearing 40 can be reduced. Further, according to the present embodiment, since the magnetic flux leaking to the shaft 7 side is reduced, The temperature rise of the shaft 7 due to heat can be prevented.

In addition, according to the present embodiment, as shown in FIG. 3, a closed magnetic circuit (thick line) passing through the inner ring 41 and the outer ring 42 is formed by inducing magnetic flux through the magnetic derivative 44. In addition, a force (torque) for braking the rotation of the inner ring 41 acts.

Therefore, after the touchdown state (when a disturbance is applied or when the control system is abnormal) is resolved, that is, when rotation support of the shaft 7 in a non-contact manner by the magnetic bearings 12, 13, 14 is resumed, The rotation of the inner ring 41 can be stopped in a shorter time (faster).

Therefore, since the time (period) for idling the inner ring 41 can be shortened, the wear rate (wear speed) of the protective bearing 40 can be reduced. As a result, the life of the protective bearing 40 can be extended.

It should be noted that an AC magnetic field is applied (acts) between the inner ring 41 and the outer ring 42 of the protective bearing 40 when the touch is down (when the shaft 7 is stopped or when the control is abnormal).

Therefore, the magnetic material forming the inner ring 41, the outer ring 42, and the magnetic derivative 44 constituting the protective bearing 40 has a small degree (rectangular ratio) indicating the rectangularity (rectangularity) of the hysteresis curve (B—H curve). It is preferable to select one.

Specifically, magnetic soft iron, 3% silicon iron, free-cutting silicon iron and the like are preferable.

Note that the magnetic induction structure that suppresses the accompanying rotation of the protective bearing 40 described above is not limited to a structure in which the magnetic derivative 44 as shown in FIG. 2 is provided in the protective bearing 40. The structure that can suppress the influence on the shaft 7 of the magnetic circuit formed by the residual magnetic field generated in the magnetized inner ring 41, that is, the inner ring 41 shown by a broken line in FIG. And a structure that can reduce the magnetic flux density in the closed magnetic circuit (magnetic circuit) that passes through the shaft 7.

Next, a modification of the magnetic induction structure that suppresses the accompanying rotation of the protective bearing 40 will be described.

(First Modification) FIG. 4 is a diagram showing a configuration of a first modification of the magnetic induction structure.

Here, it has the same configuration as the turbo molecular pump 1 shown in the embodiment described above. The same reference numerals are given to the parts that are omitted, and the description thereof will be omitted.

As shown in FIG. 4, the magnetic induction structure shown in the first modification includes an inner ring 41, an outer ring 42, a protective bearing 40 including a rolling element 43, a bearing fixing member 51, and a magnetic derivative 52. The outer ring 42 constitutes a raceway (circular raceway) on which the rolling elements 43 in the protective bearing 40 roll.

The inner ring 41 and the outer ring 42 are formed of a magnetic member.

The rolling element 43 is a ball disposed between the circular raceways of the inner ring 41 and the outer ring 42, and is formed of a ceramic material that is a non-magnetic substance.

[0047] The bearing fixing member 51 is formed of an annular plate member, and the protective bearing 40 is connected to the stator column.

A plurality of through-holes 47 for fitting (pushing through) screws 45 for fixing (wearing) to 34 are formed.

Then, the protective bearing 40 in which the outer ring 42 is disposed in the fitting groove 46 provided at the end of the intake port 4 of the stator column 34 via the magnetic induction 52 is used to fix the bearing fixing member 51 to the screw hole 48 with the screw 45. By fixing to, it is pressed and fixed from the inlet 4 side.

[0048] The magnetic derivative 52 is a member formed of a magnetic material having a magnetic induction function that guides the magnetism of the magnetized inner ring 41 to a closed magnetic path passing through the inner ring 41 and the outer ring 42, and projects in the axial direction. It has a (protruded) site.

The portion of the magnetic derivative 52 that protrudes in the axial direction (in the direction of the intake port 4) is disposed between the inner ring 41 and the outer ring 42 of the protective bearing 40, and the outer peripheral surface and the inner peripheral surface of the outer ring 42 are more Contact is made so that the magnetic resistance is reduced.

Thus, by bringing the magnetic derivative 52 and the outer ring 42 into contact, more magnetic flux can be picked up and guided to the closed magnetic circuit passing through the inner ring 41 and the outer ring 42.

Further, as shown in FIG. 4, the gap between the inner ring 41 and the magnetic derivative 52 of the protective bearing 40 is equal to the gap j3 between the inner ring 41 and the magnetic guiding portion 44b shown in FIG. In the same way as the gap between the inner peripheral surface of the inner ring 41 and the outer peripheral wall surface of the shaft 7 is sufficiently small (narrow) It is configured to be.

Thus, by providing the magnetic derivative 52, more magnetic flux can be picked up and guided to the closed magnetic circuit passing through the inner ring 41 and the outer ring 42.

Since the magnetic circuit formed when the protective bearing 40 is magnetized is the same as the closed magnetic circuit shown in FIG. 3 described above, detailed description thereof is omitted.

(Second Modification) FIG. 5 is a diagram showing a configuration of a second modification of the magnetic induction structure.

Here, parts having the same configuration as the turbo molecular pump 1 shown in the above-described embodiment (including the modified example) are denoted by the same reference numerals, description thereof will be omitted, and different configurations will be described.

As shown in FIG. 5, the magnetic induction structure shown in the second modification includes an inner ring 41, an outer ring 42, a protective bearing 40 including a rolling element 43, an upper magnetic derivative 53, and a lower magnetic derivative 54.

The inner ring 41 and the outer ring 42 are formed of a magnetic member.

[0051] The upper magnetic derivative 53 is a member made of a magnetic material, and has a magnetic induction function for guiding the magnetism of the magnetized inner ring 41 to a closed magnetic path passing through the inner ring 41 and the outer ring 42, and a protective bearing 40 (outer ring It also has a fixing function for fixing 42) to the stator column 34.

The upper magnetic derivative 53 is made of an annular plate member, and has a plurality of through-holes 47 into which screws 45 for fixing (mounting) the protective bearing 40 to the stator column 34 are fitted (pushed).

Then, the protective bearing 40 disposed in the fitting groove 46 provided at the end of the intake port 4 side of the stator column 34 via the lower magnetic derivative 54 fixes the bearing fixing member 51 to the screw hole 48 with the screw 45. By doing so, it is pressed down and fixed from the inlet 4 side. [0052] The inner peripheral edge portion of the upper magnetic derivative 53 protrudes inward (in the axial center direction) to the vicinity of the inner peripheral wall surface of the inner ring 41 when the protective bearing 40 is fixed to the stator column 34. However, the inner diameter of the upper magnetic derivative 53 is formed larger than the inner diameter of the inner ring 41 so as not to hinder the function as the protective bearing 40.

Further, a part of the surface on the exhaust port 6 side of the upper magnetic derivative 53 comes into contact (contact) with the end surface on the intake port 4 side of the outer ring 42 when the protective bearing 40 is fixed.

The lower magnetic derivative 54 is a member formed of a magnetic material having a magnetic induction function for guiding the magnetism of the magnetized inner ring 41 to a closed magnetic circuit passing through the inner ring 41 and the outer ring 42, and is an annular plate. It consists of members.

The outer peripheral portion of the side surface of the air inlet 4 in the lower magnetic derivative 54 is in contact (contact) with the end surface on the exhaust port 6 side of the outer ring 42 so that the magnetic resistance becomes smaller. In this way, by bringing the upper magnetic derivative 53 and the lower magnetic derivative 54 into contact with the outer ring 42, more magnetic flux can be picked up and guided to the closed magnetic circuit passing through the inner ring 41 and the outer ring 42.

Further, as shown in FIG. 5, the gap between the upper magnetic derivative 53 and the lower magnetic derivative 54 and the inner ring 41 of the protective bearing 40 is equal to the inner ring 41 and the magnetic induction portion shown in FIG. Similar to the gap distance between the inner ring 41 and the outer circumference wall surface of the shaft 7, the gap is sufficiently smaller (narrower) than the gap gap with the 44b.

As described above, by providing the upper magnetic derivative 53 and the lower magnetic derivative 54, more magnetic flux can be picked up and guided to the closed magnetic circuit passing through the inner ring 41 and the outer ring 42.

In the turbo molecular pump 1 having the magnetic induction structure shown in the second modified example, the closed magnetic circuit passing through the inner ring 41 and the outer ring 42 includes a magnetic circuit (closed magnetic circuit) via the upper magnetic derivative 53 and a lower magnetic derivative 54. It is formed from a magnetic circuit (closed magnetic circuit).

(Third Modification) FIG. 6 is a diagram showing a configuration of a third modification of the magnetic induction structure.

Here, parts having the same configuration as the turbo molecular pump 1 (including the modification) shown in the above-described embodiment are denoted by the same reference numerals, description thereof is omitted, and only different configurations are described.

In the third modified example, the above-described protective bearing 40 is a modified protective bearing 80. An example of configuring the magnetic induction structure will be described.

As shown in FIG. 6, the magnetic induction structure shown in the third modification includes an inner ring 55, an outer ring 56, a protective bearing 80 made up of rolling elements 43, and a bearing fixing member 51.

The inner ring 55 and the outer ring 56 constitute a raceway (circular raceway) on which the rolling elements 43 in the protective bearing 80 roll.

[0056] The inner ring 55 and the outer ring 56 are formed of magnetic members.

The rolling element 43 is a ball disposed between the circular raceways of the inner ring 55 and the outer ring 56, and is made of a ceramic material that is a non-magnetic substance.

The depth of the groove of the raceway ring formed on the outer peripheral wall surface of the inner ring 55 and the inner peripheral wall surface of the outer ring 56, that is, the groove into which the rolling element 43 is fitted, is shown in FIG. It is formed deeper than the protective bearing 40 (inner ring 41, outer ring 42).

Then, as shown in FIG. 6, the gap between the opposing wall surfaces of the inner ring 55 and the outer ring 56 excluding the raceway groove region, that is, between the outer peripheral wall surface of the inner ring 55 excluding the raceway groove region and the inner peripheral wall surface of the outer ring 56. The gap interval γ is compared with the gap interval α between the inner peripheral surface of the inner ring 55 and the outer peripheral wall surface of the shaft 7 in the same manner as the gap interval between the inner ring 41 and the magnetic guiding portion 44b shown in FIG. It is configured to be sufficiently small (narrow).

[0057] In this way, by narrowing (decreasing) the gap (gap) between the inner ring 55 and the outer ring 56 in the protective bearing 80, more magnetic flux is picked up and guided to the closed magnetic circuit passing through the inner ring 55 and the outer ring 56. The guiding force can be S.

In the turbo molecular pump 1 having the magnetic induction structure shown in the third modified example, a magnetic circuit (closed magnetic circuit) that passes through the inner ring 55 and the outer ring 56 by passing magnetic flux through the gap between the inner ring 55 and the outer ring 56. Is formed. That is, a magnetic flux (line of magnetic force) is induced to the induction magnetic path.

Further, in the third modified example, as shown in FIG. 6, by increasing the thicknesses of the inner ring 55 and the outer ring 56, the cross-sectional area of the induction magnetic path can be further increased. This increases the allowable limit of the magnetic flux density, which causes magnetic saturation in the protective bearing 80.

(Fourth Modification) FIG. 7 is a diagram showing a configuration of a fourth modification of the magnetic induction structure.

Here, parts having the same configuration as the turbo molecular pump 1 (including the modification) shown in the above-described embodiment are denoted by the same reference numerals, description thereof is omitted, and different configurations are omitted. I will explain only.

In the fourth modification, an example will be described in which a magnetic induction structure is configured by a protection bearing 81 obtained by further modifying the protection bearing 80 shown in the third modification.

As shown in FIG. 7, the magnetic induction structure shown in the fourth modification includes an inner ring 57, an outer ring 58, a protective bearing 81 made up of rolling elements 43, and a bearing fixing member 51.

[0059] The inner ring 57 and the outer ring 58 constitute a raceway (circular raceway) on which the rolling elements 43 in the protective bearing 81 roll.

The inner ring 57 and the outer ring 58 are formed of a magnetic member.

The rolling elements 43 are balls (balls) disposed between the circular raceways of the inner ring 57 and the outer ring 58, and are formed of a ceramic material that is a non-magnetic substance.

As in the third modified example, the depth of the groove of the raceway ring on which the rolling element 43 rolls, that is, the groove into which the rolling element 43 is fitted, is formed on the outer peripheral wall surface of the inner ring 57 and the inner peripheral wall surface of the outer ring 58. It is formed deeper than the protective bearing 40 (inner ring 41, outer ring 42) shown in FIG.

[0060] Furthermore, the outer ring 58 is provided with a magnetic induction part 59 that protrudes (projects) inward (in the axial center direction) from the end of the outer ring 58 on the intake port 4 side. The magnetic induction portion 59 is formed integrally with the outer ring 58 by a magnetic member.

The magnetic induction unit 59 has a magnetic induction function for inducing the magnetism of the magnetized inner ring 57 to a closed magnetic path passing through the inner ring 57 and the outer ring 58.

Thus, by forming the magnetic guiding portion 59 integrally with the outer ring 58, more magnetic flux can be picked up and guided to the closed magnetic path passing through the inner ring 57 and the outer ring 58.

The inner peripheral edge of the magnetic guide portion 59 projects inward (in the axial center direction) to the vicinity of the inner peripheral wall surface of the inner ring 57. However, the inner diameter of the magnetic induction portion 59 is formed larger than the inner diameter of the inner ring 57 so as not to hinder the function as the protective bearing 81.

[0061] As shown in FIG. 7, the gap between the outer peripheral wall surface of the inner ring 57 and the inner peripheral wall surface of the outer ring 58, excluding the raceway groove region, and the gap between the magnetic guide portion 59 and the inner ring 57 are as described above. As shown in Fig. 2, the gap spacing between the inner ring 57 and the outer wall surface of the shaft 7 is sufficiently smaller (narrower) than the gap gap / 3 between the inner ring 41 and the magnetic guide 44b shown in Fig. 2. ). As a result, more magnetic flux can be picked up and guided to the closed magnetic circuit passing through the inner ring 55 and the outer ring 56.

Further, in the fourth modified example, by providing the magnetic induction portion 59, the cross-sectional area of the induction magnetic path can be further increased. As a result, the allowable limit of the magnetic flux density further increases, which causes magnetic saturation in the protective bearing ₈₁ .

(Fifth Modification) FIG. 8 is a diagram showing a configuration of a fifth modification of the magnetic induction structure.

Here, parts having the same configuration as the turbo molecular pump 1 (including the modification) shown in the above-described embodiment are denoted by the same reference numerals, description thereof is omitted, and different configurations will be described.

In the fifth modification, an example in which a magnetic induction structure is configured by a protective bearing 82 and a magnetic derivative 63 obtained by further modifying the protective bearing 80 shown in the third modification will be described.

As shown in FIG. 8, the magnetic induction structure shown in the fifth modification includes an inner ring 60, an outer ring 61, a protective bearing 82 composed of rolling elements 43, a magnetic derivative 63, and a bearing fixing member 51.

[0063] The inner ring 60 and the outer ring 61 constitute a raceway (circular raceway) on which the rolling elements 43 in the protective bearing 81 roll.

The inner ring 57 and the outer ring 58 are formed of a magnetic member.

The rolling element 43 is a ball disposed between the circular raceways of the inner ring 60 and the outer ring 61, and is formed of a ceramic material that is a non-magnetic substance.

As in the third modification, the depth of the groove of the raceway ring on which the rolling element 43 rolls, that is, the groove into which the rolling element 43 is fitted, is formed on the outer peripheral wall surface of the inner ring 60 and the inner peripheral wall surface of the outer ring 61. It is formed deeper than the protective bearing 40 (inner ring 41, outer ring 42) shown in FIG.

[0064] The outer ring 61 is provided with a magnetic induction portion 62 that protrudes (projects) inward (in the axial center direction) from the end of the outer ring 61 on the exhaust port 6 side. The magnetic guiding portion 62 is formed integrally with the outer ring 61 by a magnetic member.

The magnetic induction unit 62 has a magnetic induction function for inducing the magnetism of the magnetized inner ring 60 to a closed magnetic path passing through the inner ring 60 and the outer ring 61. Thus, by forming the magnetic induction part 62 integrally with the outer ring 61, more magnetic flux can be picked up and guided to the closed magnetic circuit passing through the inner ring 60 and the outer ring 61.

In addition, a magnetic derivative 63 having an annular plate member force made of a magnetic material is provided on the end surface of the outer ring 61 on the intake port 4 side.

The magnetic derivative 63 also has a magnetic induction function that induces the magnetism of the magnetized inner ring 60 to a closed magnetic circuit passing through the inner ring 60 and the outer ring 61.

Note that the inner peripheral edge portions of the magnetic induction portion 62 and the magnetic derivative 63 project inward (in the axial center direction) to the vicinity of the inner peripheral wall surface of the inner ring 60. However, the inner diameters of the magnetic induction portion 62 and the magnetic derivative 63 are formed larger than the inner diameter of the inner ring 60 so as not to hinder the function as the protective bearing 82.

[0066] The protective bearing 82 in which the outer ring 61 is disposed in the fitting groove 46 can be pressed from the intake port 4 side by fixing the bearing fixing member 51 to the screw hole 48 with the screw 45 via the magnetic derivative 63. Attached and fixed.

By bringing the magnetic derivative 63 and the outer ring 61 into contact, more magnetic flux can be picked up and guided to the closed magnetic circuit passing through the inner ring 60 and the outer ring 61.

[0067] Then, as shown in FIG. 8, the gap between the outer peripheral wall surface of the inner ring 60 and the inner peripheral wall surface of the outer ring 61 excluding the raceway groove region, and the gap between the magnetic induction portion 62 and the magnetic derivative 63 and the inner ring 60 are 2 is sufficiently small compared to the clearance α between the inner peripheral surface of the inner ring 60 and the outer peripheral wall surface of the shaft 7 in the same manner as the clearance of the inner ring 41 and the magnetic induction portion 44b shown in FIG. Narrow).

As a result, more magnetic flux can be picked up and guided to the closed magnetic circuit passing through the inner ring 60 and the outer ring 61.

In the fifth modification, the magnetic induction section 62 and the magnetic derivative 63 are provided, so that the cross-sectional area of the induction magnetic path can be further increased. As a result, the allowable limit of the magnetic flux density is further increased, which causes magnetic saturation in the protective bearing 82.

Claims

The scope of the claims

[1] A bearing device that supports a rotating shaft provided with permanent magnets constituting a motor in a non-contact manner.

The protective bearing includes a rolling element made of a non-magnetic material, and an inner ring and an outer ring made of a magnetic material that form a raceway of the rolling element, and the protective bearing that supports the rotating shaft when stopped and abnormal. A bearing device characterized by having a magnetic induction structure that makes a rotational torque of the inner ring smaller than a friction torque.

2. The bearing device according to claim 1, wherein the magnetic induction structure is a magnetic induction member force made of a magnetic member for guiding the magnetism of the inner ring to the outer ring.

[3] The magnetic induction member is disposed with a predetermined interval β from the inner ring,

3. The bearing device according to claim 2, wherein the distance i3 is smaller than a distance α between the rotating shaft and the inner ring.

[4] The magnetic induction structure according to claim 1, 2, or 3, wherein an interval γ between the inner ring and the outer ring is smaller than an interval α between the rotating shaft and the inner ring. The bearing device described.

[5] The bearing device according to claim 1, 2, 3, or 4, wherein the rolling element is made of a ceramic member.

6. The rotating shaft is supported by magnetic force or dynamic pressure.

The bearing device according to any one of claims 1 to 5, and the bearing device according to claim 1.

[7] A turbomolecular pump comprising the bearing device according to any one of claims 1 to 6.