JP2010053947A - Bearing arrangement of rotating portion and pump using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing arrangement performing bearing in thrust direction by applying a force balancing with a thrust load of rotation driven portions without the need for control current, and also to provide a pump using the bearing arrangement. <P>SOLUTION: The bearing arrangement includes: a shaft 50; a cylindrical member 60 which is inserted through the shaft; and a rotary driving portion 94 which forms the rotary driven portions 60, 80, 92 with one of the shaft and the cylindrical member as a fixed guide member and the other of the shaft and the cylindrical member and drives them. The bearing arrangement also includes: radial bearings 100A, 100B which support the shaft and the cylindrical member in non-contact manner to them in radial direction by generating a gas pressure in a clearance between the shaft and the cylindrical member during rotation; a first member 113 which contains a plurality of permanent magnet rings the separate poles of N and S of which are set adjacently while placing spacing in thrust direction at one of the shaft and the cylindrical member; and at least one thrust bearing 110 which contains a second members 118 with a magnetism opposed to the first member and maintains the free rotary driven portion in the thrust direction in a predetermined position of the thrust direction balancing with the thrust directional load of the rotary driven portion. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a bearing device for a rotating part including a radial bearing and a thrust bearing, and a pump using the same.

  As radial bearings and thrust bearings, non-contact bearings such as fluid bearings, gas bearings, and magnetic bearings are known in addition to bearings that depend on mechanical contact such as bearings.

For example, Patent Document 1 discloses that a radial direction and a bearing of a shaft and a sleeve inserted into the shaft are formed by a fluid bearing. A dynamic pressure bearing using gas is disclosed in Patent Document 2. As magnetic bearings, bearings in the thrust direction are disclosed in Patent Documents 3-5.
JP 2007-139199 A JP 2007-170578 A Japanese Patent Laid-Open No. 11-230086 Japanese Patent Publication No. 7-85638 JP 2003-97555 A

  In the technique of Patent Document 1, as shown in FIG. 1 of Patent Document 1, circulating fluid (62) such as circulating oil is pumped into the gap between the shaft (28) and the sleeve (26). Contamination is inevitable.

  In the technique of Patent Document 2, as shown in FIG. 1 of Patent Document 2, the radial bearing (R) has dynamic pressure grooves (Ra, Rb) formed on the shaft (61), and the shaft (61) and the cylindrical portion. The dynamic pressure by air is generated in the gap between (50). This radial bearing is a non-contact bearing using a dynamic pressure bearing by gas. However, the thrust bearing (S) is a pivot type bearing in which a hemispherical convex portion is provided on the bottom portion (52) of the cylindrical portion (50) and the shaft end portion is brought into point contact with the convex portion, and is not a non-contact bearing. .

  In Patent Documents 3-5, magnetic bearings are employed in the thrust direction, thereby bearings in a non-contact manner in the thrust direction. As shown in FIG. 1 of Patent Document 3, the thrust bearing (11) shown in Patent Document 3 is provided with a target disk (9) having a diameter larger than that of the main shaft (4) at one end of the main shaft (4). The electromagnets (10a, 10b) are arranged at predetermined intervals. In this case, electrical control of the electromagnets (10a, 10b) is necessary, and the large-diameter target disk (9) hinders downsizing of the apparatus. Moreover, in patent document 3, since it is necessary to arrange | position the emergency bearing (21, 22), a perfect non-contact bearing cannot be implement | achieved.

  As shown in FIG. 1, FIG. 3, or FIG. 4 of Patent Document 4, the thrust bearing (5) shown in Patent Document 4 is provided with a magnetic body or permanent magnet (51) on the shaft (1), and around the periphery thereof. A plurality of magnetic portions (52, 52a, 52b) such as a coil with a core or a solenoid are provided in a ring shape or a spiral shape. A plurality of magnetic parts (52, 52a, 52b) are independently magnetized or demagnetized, or excited or demagnetized, thereby realizing a non-contact bearing while driving the shaft (4) in the thrust direction. ing. The thrust bearing shown in Patent Document 5 is the same as that of Patent Document 4. As shown in FIG. 1 of Patent Document 5, a permanent magnet (1a) is arranged on the rotating shaft (3), and a yoke (6 A plurality of voice coils (5a, 5b) magnetically coupled with each other in FIG. Then, by controlling the current flowing through the voice coils (5a, 5b), it is possible to control the position of the rotating shaft (3) in the thrust direction with high accuracy.

  However, in both Patent Documents 4 and 5, the rotating shaft is horizontal, the load of the rotating shaft does not act in the thrust direction, and current control to flow through the coil or the like is essential.

  An object of the present invention is to provide a bearing for a rotating part that does not require current control and can perform a bearing in a thrust direction while applying a force suspended from a thrust load of a driven part to be rotated that is free in the thrust direction. It is providing a device and a pump using the same.

A bearing device for a rotating part according to an aspect of the present invention is provided.
The axis,
A cylindrical member inserted through the shaft;
One of the shaft and the cylindrical member is a fixed guide member, a rotation drive unit is formed including the other of the shaft and the cylindrical member, and a rotation drive unit that rotationally drives the rotation drive unit;
At least one radial bearing that generates a gas pressure in a gap between the shaft and the cylindrical member during rotation of the rotation drive unit and maintains the shaft and the cylindrical member in a non-contact manner in a radial direction;
One of the shaft and the cylindrical member includes a plurality of permanent magnet rings arranged at intervals along the thrust direction and arranged such that the N poles and the S poles are adjacent to each other in the thrust direction. Including the first member and a second member that is magnetized by being opposed to the first member on the other side of the shaft and the cylindrical member, and the rotated drive unit that is free in the thrust direction, At least one thrust bearing that maintains a predetermined position in a thrust direction suspended from a load in a thrust direction of the driven part;
It is characterized by having.

  According to one aspect of the present invention, it is possible to support the rotational drive unit with respect to the guide member in a non-contact manner in the radial direction or in the thrust direction. That is, in the radial bearing, the bearing can be generated by generating a gas pressure in the gap between the shaft and the cylindrical member during rotation. In the thrust bearing, the rotationally driven portion that is free in the thrust direction can be maintained at a predetermined position in the thrust direction that is suspended from the load in the thrust direction of the rotationally driven portion by the magnetic bearing. In other words, non-contact bearings are possible by generating a force that suspends the load in the thrust direction against the driven part that receives a load in the vertical direction (self-weight if the shaft is vertical). It was. In addition, since the thrust bearing uses a permanent magnet instead of an electromagnet, current control is also unnecessary. As described above, since the bearing is non-contact in the radial direction and the thrust direction, the heat generated in the bearing can be radiated by natural air cooling.

  In one aspect of the present invention, the rotation driving unit can use the shaft as a guide member and rotationally drive the cylindrical member that is the rotation driven unit around the shaft. When the shaft is used as a guide member, it is only necessary to insert the rotational drive portion through the shaft, and positioning in the thrust direction can be performed by a thrust bearing using a permanent magnet. Therefore, the assembly becomes extremely simple.

  In one aspect of the present invention, the second member can be a magnetic material, and a permanent magnet can also be used when it is desired to increase the magnetic attractive force.

In one aspect of the present invention, the first member is formed in a ring shape inclined with respect to the thrust direction so that each of the permanent magnets has different thrust positions continuously at each position in the circumferential direction,
The second member is opposed to a plurality of permanent magnets arranged in the thrust direction over a part of the circumferential direction at one position opposed to the diameter direction of the shaft in the diameter direction of the shaft. And a magnetic body disposed over another part in the circumferential direction at the other position. In this way, according to the drive of the rotation drive unit, the rotation drive unit can be reciprocated according to the predetermined position changing in the thrust direction.

  In one aspect of the present invention, the at least one thrust bearing can be disposed between two radial bearings adjacent in the thrust direction. In this way, radial bearings can be arranged on both sides of at least one thrust bearing, and the bearing operation becomes more stable.

  In one aspect of the present invention, the plurality of permanent magnets provided in the first member can be arranged in an arrangement relationship in which two adjacent magnets in the thrust direction repeat different poles and poles alternately. . If it carries out like this, compared with the case where two adjacent in a thrust direction are only different poles, it will become easy to form a closed magnetic circuit, and the force which generate | occur | produces in a thrust direction can be increased. Further, the leakage magnetic field in the thrust direction can also be reduced.

In one aspect of the present invention, the at least one radial bearing generates a dynamic pressure in a gap between the shaft and the cylindrical member during rotation of the rotary drive unit, thereby causing the shaft and the cylindrical member to move in the radial direction. And keep it non-contact
The bearing device further includes
A tank,
A first flow path for guiding the dynamic pressure generated by the at least one radial bearing to the tank;
A second flow path for supplying dynamic pressure in the tank back to the at least one radial bearing;
A valve for communicating the tank with the second flow path at least when the rotation drive unit stops rotating;
Can have.

  In this way, the radial bearing can be switched from the dynamic pressure bearing to the static pressure bearing in the vicinity of the rotation stop where the dynamic pressure is reduced or when the rotation is stopped where no dynamic pressure is generated.

  Another aspect of the present invention defines a pump including the bearing device of the rotating part described above.

  Hereinafter, preferred embodiments of the present invention will be described in detail. The present embodiment described below does not unduly limit the contents of the present invention described in the claims, and all the configurations described in the present embodiment are indispensable as means for solving the present invention. Not necessarily.

(Composite pump)
FIG. 1 is a cross-sectional view of a vacuum pump, such as a composite pump, including a bearing device for a rotating unit according to the present embodiment. The composite pump 10 has an external shape in which a first casing 20 and a second casing 30 are connected by bolts 40. The first casing 20 is a hollow cylinder having a first hollow portion 26 that communicates from the intake port 22 to the connection port, with one end being the intake port 22 and the other end having the first flange 24 being a connection port. The second casing 30 is a hollow cylinder having an exhaust port 32 connected to one end, the other end having the second flange 34 as a connection port, and cooling fins 38 on the outer periphery. The first and second casings 20 and 30 are hermetically connected by fastening the first and second flanges 24 and 34 with bolts 40 via an O-ring 42.

  A shaft 50 and a cylindrical member 60 inserted through the shaft 50 are disposed in the first and second hollow portions 26 and 36. A flange 52 is provided at the end of the shaft 50. The flange 52 is airtightly fastened to the bearing wall portion 37 of the second casing 30 by an bolt 70 via an O-ring 72.

  The cylindrical member 60 has a rotating body 80 having a thread groove 81 fixed by a bolt 82 so as to be positioned in the first hollow portion 26 of the first casing 20. The rotating body 80 having the thread groove 81 functions as a turbo molecular pump. The cylindrical member 60 has a rotor 92 fixed thereto so as to be positioned in the second hollow portion 36 of the second casing 30. A stator 94 fixed to the second casing 30 is provided around the rotor 92. The rotor 90 and the stator 94 constitute a motor 90. The motor 90 rotates the rotor 92 by the mutual magnetic action between the stator 94 and the rotor 92 when electric current is supplied to the coils of the stator 94. The rotating body 80 is rotated together with the cylindrical member 60 by the rotation of the rotor 92, and the gas can be compressed by the screw groove 81 to suck the gas from the intake port 22.

  In addition, the cylindrical member 60, the rotating body 80, and the rotor 92, which are rotation driven parts, are free in the thrust direction, and are maintained at predetermined positions in the thrust direction by a thrust bearing 110 described later.

  The combined pump 10 has another pump on the exhaust stage side in addition to the above-described turbo molecular pump, which will be described later.

(Outline of bearing device of rotating part)
In the embodiment shown in FIG. 1, the shaft 50 is a fixed guide member, and a rotational drive unit is formed by the cylindrical member 60 and the rotating body 80 and the rotor 92 which are the accessories thereof. A rotational drive unit that rotationally drives 80 and 92 is a stator 94.

  At least one, for example, two first and second radial bearings 100A and 100B, and at least one thrust bearing 110 are provided as bearing devices for the shaft 50 and the cylindrical member 60 rotating around the shaft 50. In the present embodiment, both the first and second radial bearings 100A and 100B are formed by gas bearings.

  Further, as shown in FIG. 1, a thrust bearing 110 is disposed between two first and second radial bearings 100A and 100B adjacent in the thrust direction. In this embodiment, the thrust bearing 110 is formed by a magnetic bearing.

(Radial bearing)
Each of the first and second radial bearings 100A and 100B generates a fluid pressure in the gap between the shaft 50 and the cylindrical member 60 when the driven parts 60, 80, and 92 are rotated. Is kept non-contact in the radial direction. A groove bearing is known as this type of bearing. The groove bearing is provided with a large number of grooves on the surface of a shaft or a bearing, and supports the driven part by the fluid pressure generated in the large number of grooves during rotation. There are roughly two types of groove bearings, one is a static pressure gas bearing, and the other is a dynamic pressure gas bearing. Each of the first and second radial bearings 100A and 100B of the present embodiment employs one of the two, but in this embodiment, a dynamic pressure gas bearing is employed. Therefore, each of the first and second radial bearings 100A and 100B is configured by forming a number of herringbone type dynamic pressure grooves 102 on the outer peripheral surface of the shaft 50 as shown in FIG. .

  The shaft 50 is formed with a center hole 104 that opens to the flange 52, and the center hole 104 reaches the first radial bearing 100A via the second radial bearing 100B. As shown in FIG. 4, which is the IV-IV cross section (two locations of the first and second radial bearings 100A and 100B) shown in FIG. 2, a plurality of, for example, five central holes 104 are provided in the circumferential direction. Communicates with the first lateral hole 105 that extends in the radial direction and opens on the outer peripheral surface of the shaft 50.

  Furthermore, the shaft 50 is formed with a first eccentric hole 107A that opens at the end surface 52A on the flange 52 side so as to reach a position above the second radial bearing 100B. A second eccentric hole 107B opened at an end surface 50A opposite to the flange 52 of the shaft 50 is formed so as to reach a position below the first radial bearing 100A. The first and second eccentric holes 107A and 107B are second lateral holes that open to the outer peripheral surface of the shaft 50 at a total of three locations: a lower position of the first radial bearing 100A, an upper position and a lower position of the second radial bearing 100B. It communicates with the hole 106. Note that the lower end side of the first eccentric hole 107A is closed by an airtight seal member 107C (see FIG. 2).

  A bypass hole 108 communicating with the first eccentric hole 107A is formed in the flange 52, and the bi-pay hole 108 opens at the end face 52A. As shown in FIG. 3 which is a bottom view of FIG. 2, the flange 52 has a plurality of screw holes 109 for fastening the shaft 50 to the bearing wall portion 37 of the second casing 30 by the bolt 70 shown in FIG. Individually formed.

(Operation of radial bearing)
First, the operation of the first and second radial bearings 100A and 100B will be described. When the coil of the stator 94 of the motor 90 is energized, the rotor 92 is rotationally driven by the mutual magnetic action between the rotor 92 and the stator 94. The rotating body 80 is rotated together with the cylindrical member 60 by the rotation of the rotor 92, and gas is sucked from the intake port 22 by the screw groove 81 formed on the outer surface of the rotating body 80, so that the turbo molecular pump of the composite pump 10 is Operate.

  In the first and second radials 100 </ b> A and 100 </ b> B, a large number of herringbone type dynamic pressure grooves 102 formed on the shaft 50 are formed in a slight gap (for example, 5 to 10 μm) between the shaft 50 and the cylindrical member 60. It will be exposed and rotated. In this way, air is drawn into the slight gap between the shaft 50 and the cylindrical member 60 from the center hole 104 through the first lateral hole 105 by a shearing force based on the viscosity of the air, thereby generating dynamic pressure. . This dynamic pressure serves as a supporting force for supporting the cylindrical member 60 as the driven portion to be driven in a non-contact manner in the radial direction with respect to the shaft 50 that is a guide member. Thus, the first and second radial bearings 100A and 100B function as radial bearings at two locations separated in the thrust direction, and stably support the cylindrical member 60 as the rotationally driven portion in the radial direction. Can do. Moreover, since it is a non-contact bearing, noise and wear can be reduced, and there is no fear of contamination with oil. Note that the air that has been drawn into the slight gap between the shaft 50 and the cylindrical member 60 to generate the dynamic pressure can be exhausted through the second lateral hole 106 and the eccentric holes 107A and 107B.

(Thrust bearing)
As shown in FIG. 1, the thrust bearing 110 formed on the shaft 50 between the first and second radial bearings 100A and 100B has a smaller diameter than the other portions as shown in FIG. The magnet arrangement part 112 is provided. The first member 113 shown in FIGS. 5 and 6 is disposed in the magnet arrangement portion 112. The first member 113 includes a plurality of permanent magnets 114 and 116 that are spaced along the thrust direction and are arranged so that different polarities are adjacent to each other in the thrust direction. The permanent magnets 114 and 116 have different magnetization directions. The permanent magnet 114 is referred to as an S pole ring, and the permanent magnet 116 is referred to as an N pole ring.

  As shown in FIG. 6, the S-pole ring 114 is a ring-shaped permanent magnet that is magnetized so that its outer peripheral surface is S-pole and its inner peripheral surface is N-pole. The N-pole ring 116 is a ring-shaped permanent magnet that has a different magnetization direction from the S-pole ring 114 and is magnetized so that the outer peripheral surface is N-pole and the inner peripheral surface is S-pole as shown in FIG. is there. Note that the S-pole ring 114 and the N-pole ring 116 are combined as a whole by combining a plurality of arc-shaped pieces divided in the circumferential direction via a gap for convenience in mounting the shaft 50 to the magnet arrangement portion 112. It can be ring-shaped. At this time, the gap between the arc-shaped pieces can be set within a range in which the magnetic field action in the circumferential direction is not adversely affected.

  In the first member 113, a non-magnetic ring 115 can be inserted and disposed in order to isolate the south pole ring 114 or the north pole ring 116 adjacent to each other in the thrust direction. The thickness T of each ring 114-116 is, for example, 1.5 mm, and the width W = (outer diameter-inner diameter) / 2 of the ring portion of each ring 114-116 is, for example, 2 mm.

  Here, in the first member 113, the plurality of S-pole rings 114 and the plurality of N-pole rings 116 are arranged in an arrangement relationship in which two adjacent poles in the thrust direction repeat different poles and same poles alternately. Has been. In other words, in the present embodiment, two S-pole rings 114 are arranged at both ends in the thrust direction, two N-pole rings 116 are arranged inside each of the two S-pole rings 114, and further, Two south pole rings 114 are arranged inside the north pole ring 116. Alternatively, N pole rings 116 may be disposed at both ends in the thrust direction, and the total number of S poles and N pole rings 114 and 116 may be more than eight.

  On the other hand, the cylindrical member 60 is provided with a second member 118 that is magnetized by being opposed to at least a part of the first member 113 attached to the shaft 50 in the circumferential direction. As shown in FIG. 7, the second member 118 has a magnetic body 119 that is disposed on the inner surface side of a cylindrical member 60 formed of, for example, a non-magnetic body and formed in a ring shape. When the second member 118 is viewed in the thrust direction, as shown in FIG. 1, the first member 113 is spaced from the S-pole ring 114 and the N-pole ring 116 in the radial direction at intervals in the thrust direction. A magnetic body 118 is disposed.

  The second member 118 may not be a magnetic material but may be a permanent magnet that is divided in the thrust direction and magnetized so as to be opposed to the first member 113 and magnetically attracted. In this case, in the second member 118, the N pole ring may be disposed at a position facing the S pole ring, and the S pole ring may be disposed at a position facing the N pole ring. Further, the second member 118 is not formed in a ring shape, and is, for example, two locations facing each other on a diametrical line, and a magnetic material or an angle θ (for example, θ = 60 °) at each location. The permanent magnet 119 may be disposed on the cylindrical member 60.

  The shaft 50 and the cylindrical member 60 of the present embodiment have a screw seal portion 120 in a region between the flange 52 of the shaft 50 and the second radial bearing 100B. The screw seal portion 120 functions as an auxiliary pump on the discharge stage side that has a lower exhaust speed than the turbo molecular pump using the thread groove 81. The gas compressed and exhausted by the turbo molecular pump using the thread groove 81 is compressed by the auxiliary pump by the screw seal portion 120, and further to the exhaust port 32 through the first horizontal hole 105 and the center hole 104 of the shaft 50. Exhausted.

(Pump assembly method and thrust bearing action)
The shaft 50 to which the first member 113 is attached is inserted from above the second casing 30 to which the exhaust port 32 and the stator 94 are fixed. A flange 52 at the lower end of the shaft 50 is airtightly fastened to the bearing wall portion 37 of the second casing 30 by an bolt 70 via an O-ring 72.

  Next, the cylindrical member 60 to which the rotating body 80 and the rotor 92 are fixed is inserted into the shaft 50 from above, and finally the first casing 20 is fastened by the second casing 30 and the bolt 40 via the O-ring 42, The composite pump 10 is completed.

  Here, the cylindrical member 60 to which the rotating body 80 and the rotor 92 are fixed only needs to be inserted from above the shaft 50, and the assembly is remarkably easy. At this time, the second member 118 provided on the cylindrical member 60 is opposed to the first member 113 provided on the shaft 50, so that the magnetic body 119 of the second member 118 is magnetized and has opposite polarities. They are magnetically attracted to each other. Due to the action of the thrust bearing 110, the rotationally driven parts 60, 80, 92 that are free in the thrust direction are maintained at predetermined positions in the thrust direction that are suspended from the weights of the rotationally driven parts 60, 80, 92. be able to.

  In this sense, this embodiment is suitable for the case where the thrust direction is the vertical direction rather than the horizontal direction. This is because if the thrust direction is the horizontal direction, the weights of the rotated parts 60, 80 and 92 are received by the radial bearings. In other words, the present embodiment can be applied to the case where the thrust direction is the vertical direction or is inclined with respect to the vertical direction so that the weight of the rotated parts 60, 80, 92 or a part thereof acts in the thrust direction. Is preferred.

  The bearing action in the thrust direction will be described with reference to FIGS. FIG. 8A shows a facing state in which the center line CL1 of the first member 113, for example, the center line CL1 of the S-pole ring 114 completely coincides with the center line of the magnetic body 119 of the second member 118. The opposing surface of the magnetic body 119 has an N pole. When the driven parts 60, 80, and 92 are unloaded, the thrust position is determined at the position shown in FIG. 8A, but in actuality, the load in the thrust direction of the driven parts 60, 80, and 92 (see FIG. 1). This is not the case because of its own weight). In FIG. 8B, the center line CL2 of the magnetic body 119 of the second member 118 is shifted by a displacement amount dy below the fully-facing position with respect to the center line CL1 of the S pole ring 114 of the first member 113. Shows the state. In FIG. 8A, the magnetic flux easily flows from the north pole to the south pole at the fully-facing position. On the other hand, in FIG. 8B, the magnetic flux that is shifted by the displacement amount dy becomes difficult to flow and is restored to the side of FIG. A restoring force Fy to be generated is generated. FIG. 8B shows a state in which the weight of the rotationally driven parts 60, 80, 92 and the restoring force Fy are suspended, whereby the thrust position of the rotationally driven parts 60, 80, 92 in a steady state is predetermined. The position is determined.

  The solid line shown in FIG. 9 shows the simulation result of the relationship between the displacement dy and the restoring force Fy calculated using the thrust bearing 110 (magnet material: Nd42BH) of FIG. As is clear from the solid line in FIG. 9, if the displacement amount dy is within a certain range (in FIG. 9, the maximum value of dy is calculated to 1 mm), the restoring force Fy increases in proportion to the displacement amount dy. .

  However, when the displacement dy further increases in FIG. 8B and, for example, the S-pole ring 114 and the magnetic body 119 are not opposed to each other, the restoring force Fy does not act. The rotationally driven parts 60, 80, and 92 are in a state where the weight of the rotationally driven parts 60, 80, and 92 and the restoring force Fy are suspended in a steady state, whereby the rotationally driven parts 60, 80, and Since it is maintained at a predetermined position suspended from its own weight, the displacement amount dy does not reach 1 mm unless a large external force is applied. However, this embodiment is applied to the composite pump 10, and when the intake port 22 side or the exhaust port 32 side in FIG. May act. Therefore, a lower limit / upper limit stopper for the cylindrical member 60 is provided.

  FIG. 10 shows an example of a pivot type lower limit / upper limit stopper. As shown in FIG. 10, the rotating body 80 shown in FIG. 1 includes a first concave portion 84 formed in a hemispherical shape facing the lower surface, and a second concave portion 86 formed in a hemispherical shape facing the upper surface. Is provided. On the other hand, the upper end of the shaft 50 is provided with a lower limit stopper 54 having a hemispherical tip, and the first casing 20 is provided with an upper limit stopper 28 having a hemispherical lower end. 10, assuming that the position of the rotating body 80 in the thrust direction is the predetermined position shown in FIG. 8B, the allowable clearance CLL between the first recess 84 and the lower limit stopper 54, the second recess 86, and the upper limit. The allowable clearance CLU between the stopper 28 and the stopper 28 is set to 1 mm, for example.

  In the present embodiment, as shown in FIG. 6, a plurality of permanent magnet rings 114, such that an S pole ring 114 and an N pole ring 116, which are permanent magnets having different polarities (SN), are adjacent to each other in the thrust direction. 116 are arranged. In addition, a pair of the S pole ring 114 and the N pole ring 116, which are two permanent magnets having different polarities (S-N) in the thrust direction, and the same polarity (S-S or N-N). The S-pole rings 114 or the sets of N-pole rings 116, which are permanent magnets, are arranged in an arrangement relationship that repeats alternately.

  In FIG. 6, the magnetic circuit is closed by four sets of S-pole rings 114 and N-pole rings 116, which are permanent magnets having different polarities (SN) adjacent to each other in the thrust direction. When the first member 113 of this embodiment is used, the characteristic of the displacement amount dy-restoring force Fy shown by the solid line in FIG. 9 can be obtained.

  On the other hand, unlike the arrangement of FIG. 6, the plurality of permanent magnet rings 114 and 116 can be arranged so that the N poles and S poles 114 and 116 are necessarily adjacent to each other in the thrust direction. For example, the S pole ring 114, the N pole ring 116, the S pole ring 114, the N pole ring 116,. However, in this case, the displacement amount dy-restoring force Fy indicated by the broken line in FIG. 6 is obtained, and it was found that the restoring force Fy is smaller than the solid line property. Moreover, since the magnetic circuit of the S pole ring 114 does not close at both ends in the thrust direction, the leakage magnetic field in the thrust direction also increases. In this respect, the magnet arrangement shown in FIG. 6 is superior.

  According to the embodiment described above, non-contact bearings are possible by generating a force suspended in the thrust direction in the thrust direction for the driven parts 60, 80, and 92 in which the own weight acts in the vertical direction. It becomes. Moreover, since the thrust bearing 110 uses permanent magnets 114 and 116 instead of electromagnets, current control is also unnecessary. Thus, since the radial direction is a gas bearing, the thrust direction is a magnetic bearing, and both directions are non-contact bearings, the heat generated in the bearings 100A, 100B, 110 is naturally generated by the cooling fins 38 shown in FIG. Heat can be dissipated by air cooling.

(Modification of shaft and cylindrical member)
In FIG. 11, for the convenience of assembling the thrust bearing 110, the region of the first radial bearing 100 </ b> A of the shaft 50 is formed in the small diameter portion 51. The shaft 50 shown in FIG. 11 having the small-diameter portion 51 is further different from that in FIG. 2 in that eight permanent magnets 114 and 116 forming the thrust bearing 110 are inserted into the shaft 50 and a retaining C-ring at the upper end thereof. This is the point where 51A is press-fitted. Therefore, as in the case where the shaft 50 shown in FIG. 2 is used, the eight permanent magnets 114 and 116 do not have to be mounted in the shape of a half piece in the circumferential direction. A cylindrical member 60 shown in FIG. 11 has a relief hole 61 for not interfering with the C ring 51 </ b> A, and a thick portion 62 for fitting to the small diameter portion 51 of the shaft 50.

(Pump variation)
FIG. 12 shows a turbo molecular pump 130 different from that in FIG. The turbo molecular pump 130 shown in FIG. 12 is different from FIG. 1 in that the exhaust port 32 communicates with the second hollow portion 36 of the second casing 30 and is attached to the side surface of the second casing 30. In this case, a gap seal portion 132 is formed instead of the screw seal portion 120 shown in FIG. For this reason, on the lower end side of the shaft 50 and the cylindrical member 60, the gap between the shaft 50 and the cylindrical member 60 is hermetically sealed by the gap seal portion 132 and does not function as an exhaust route. That is, the turbo molecular pump 130 of FIG. 12 functions as a turbo molecular pump only by the rotation of the rotating body 80, and does not have the auxiliary pump by the screw seal portion 120 shown in FIG.

(Reciprocating thrust bearing and pump using it)
In the present embodiment, by changing the first and second members 113 and 118 in the thrust bearing 110, the rotational drive units 60, 80, and 92 can be reciprocated while rotating. FIG. 13 is the same as the above-described embodiment in that the shaft 50, the cylindrical member 60, and the first and second radial bearings 100A and 100B are provided. A thrust bearing 140 shown in FIG. 13 is different from the thrust bearing 110 described above.

  A thrust bearing 140 shown in FIG. 13 has, as a first member 142 fixed to the shaft 50, an S pole ring 144 and an N pole ring 146 in which the aforementioned S pole ring 114 and N pole ring 116 are inclined with respect to the thrust direction. It was. That is, the permanent magnets of the S pole ring 144 and the N pole ring 146 are formed so that the thrust positions are continuously different at each position in the circumferential direction.

  In the present embodiment, the second member 150 fixed to the cylindrical member 60 has two types of permanent magnets 152 and 154 having different magnetization directions at one position facing each other in the diameter direction of the shaft 50, and the other. The magnetic body 156 is provided at the position. One permanent magnet 152 is an N-pole piece arranged to face the S-pole ring 144 of the first member 142, and the other permanent magnet 154 is arranged to face the N-pole ring 146 of the first member 142. S pole piece.

  The thrust bearing 140 shown in FIG. 13 can also secure the thrust bearing function described in FIG. In addition, the thrust bearing 140 can reciprocate the cylindrical member 60 in the thrust direction in accordance with the rotational drive of the cylindrical member 60. This is because the S pole ring 144 and the N pole ring 146 are inclined so that the thrust positions are continuously different at each position in the circumferential direction, and the rotated S pole piece 152 and N pole piece 154 are rotated. Is displaced in the thrust direction according to the fixed south pole ring 144 and north pole ring 146. The main function of the magnetic body 156 of the second member 150 is to support the shaft 50 in the radial direction in cooperation with the opposing permanent magnets 152 and 154 rather than to generate a driving force in the thrust direction. It becomes.

  FIG. 14 is a person who has changed the arrangement of the thrust bearing 140 that rotates and reciprocates similarly to FIG. In the above-described embodiment, the thrust bearings 110 and 140 are disposed between the two radial bearings 100A and 100B adjacent in the thrust direction, but the present invention is not limited to this. In FIG. 14, the thrust bearing 140 is disposed at the end of the shaft 50 to improve the assemblability of the thrust bearing.

(Pump using a bearing that rotates and reciprocates)
FIG. 15 shows a pump capable of communicating / blocking a gas passage by reciprocating a rotating piston. This type of pump is disclosed in Japanese Patent Application Laid-Open No. 6-129354. FIG. 15 shows the same function realized by using a thrust bearing 140 according to this embodiment.

  In FIG. 15, a rotating shaft 164 having a central portion disposed in a cylinder chamber 162 having an intake port 162 </ b> A and an exhaust port 162 </ b> B is rotationally driven by energizing the stator 168 with a rotor 166 fixed to one end thereof. The rotating shaft 164 is supported by two radial bearings 100A and 100B that generate dynamic pressure between the two cylinders 170 and 172 fixed to the cylinder chamber 162. A thrust bearing 180 is provided at the other end of the rotating shaft 164.

  The thrust bearing 180 may be the same as the first member 142 shown in FIGS. 13 and 14, but the first member 142 of the present embodiment includes a total of five permanent magnets 144 and 146, and three S poles. Rings 144 and two N-rings 146 are alternately arranged in the thrust direction. Further, the second member 150 includes three N pole pieces 152 facing the three S pole rings 144 and two S pole pieces 154 facing the N pole ring 146. As shown in FIG. 16, the N-pole and S-pole pieces 152, 154 are formed over a range of an angle θ (for example, θ = 60 °) in the circumferential direction. Further, the magnetic body 156 is opposed to the N pole and S pole pieces 152 and 154 in the diameter direction of the shaft 164 over the range of the same angle θ (for example, θ = 60 °) and along the thrust direction. Is provided. Such an arrangement is the same as in FIGS. 13 and 14. This is because when the driven part is driven to reciprocate, a driving force in the thrust direction is not generated if a permanent magnet is disposed around the entire circumference as the second member 150. Therefore, the permanent magnets 152 and 154 as the second member 150 may be provided only in a part in the circumferential direction. The permanent magnets 152 and 154 and the magnetic body 156 are fixed to the fixed ring member 182.

  A stepped piston 190 is fixed to the shaft 164 so as to be positioned in a space formed between the two cylindrical bodies 170 and 172. The stepped piston 190 is rotated and reciprocated integrally with a rotating shaft 164 that is rotationally driven by the rotor 166 and the stator 168 and reciprocated by the thrust bearing 180.

  Four piston chambers 192, 194, 196, 198 are formed between the end face of the stepped piston 190 and the two cylindrical bodies 170, 172. Further, a gas passage 174 is formed in a part of the circumferential direction in the cylindrical body 172 and the like. In addition, although necessary members are omitted, by rotating and reciprocating the stepped piston 190, the gas from the air inlet 162A is changed to the first in the same manner as the principle disclosed in JP-A-6-129354. The exhaust can be exhausted to the exhaust port 162B through the first to fourth piston chambers 192, 194, 196, 198.

(Switching from dynamic pressure bearing to static pressure bearing when rotation stops)
When dynamic pressure bearings are employed as the radial bearings 100A and 100B, the dynamic pressure generated when the rotation is stopped and in the vicinity thereof is weakened and does not function as a radial bearing. Therefore, at least when the rotation is stopped, the dynamic pressure bearing can be switched to the static pressure bearing. For example, in the embodiment shown in FIG. 1, as shown in FIG. 17, the first pipe 200 connected to the eccentric hole 170A and the bypass hole 108 of the shaft 50, the tank 202 connected to the first pipe 200, and the tank 202 A second pipe 204 connected to the third pipe 206, a third pipe 206 connected to the center hole 104 of the shaft 50, and a valve 208 provided in the middle of the third pipe 206 are further provided. The valve 208 normally exhausts the pump output from the center hole 104, but is switched based on, for example, a signal S in the vicinity of the stop of rotation to close the atmosphere opening of the third pipe 206 and the second pipe 204. And the third pipe 206 are connected.

  During the rotation of the shaft 50, the dynamic pressure generated in the first radial bearing 100A is transferred to the tank 202 via the second lateral hole 106, the eccentric hole 107A, the bypass hole 108, and the first pipe 200 (first flow path). Led to. The dynamic pressure generated in the second radial bearing 100B reaches the second radial bearing 100B through the gap between the shaft 50 and the cylindrical member 60, and is similarly guided to the tank 202.

  When the rotation of the shaft 50 is stopped, a second flow path is established to supply the pressure in the tank 202 back to the radial bearings 100A and 100B. That is, the valve 208 is switched based on the signal S, the air opening of the third pipe 206 is closed, and the second pipe 204 and the third pipe 206 are connected. Thus, the pressure in the tank is supplied to the radial bearings 100A and 100B via the second pipe 204, the valve 208, the third pipe 206, the center hole 104, and the first horizontal hole 105. Therefore, the dynamic pressure at the radial bearings 100A and 100B, which is reduced when the rotation is stopped, is compensated by the pressure from the tank 202, and the radial bearings 100A and 100B can function as static pressure bearings.

  In addition, the switching from the dynamic pressure bearing to the static pressure bearing when the rotation is stopped may be configured to supply separately prepared gas to the radial bearings 100A and 100B in addition to the configuration as shown in FIG.

  Although the present embodiment has been described in detail as described above, those skilled in the art can easily understand that many modifications can be made without departing from the novel matters and effects of the present invention. Accordingly, all such modifications are intended to be included in the scope of the present invention. For example, a term described together with a different term having a broader meaning or the same meaning at least once in the specification or the drawings can be replaced with the different term anywhere in the specification or the drawings.

It is a schematic sectional drawing of the turbo-molecular pump to which this invention is applied. It is a figure which shows the axis | shaft of the turbo-molecular pump shown in FIG. It is a bottom view of the axis | shaft shown in FIG. It is IV-IV sectional drawing shown in FIG. It is a figure which shows the state which attached the 1st member to the axis | shaft shown in FIG. It is a figure which shows the 1st member shown in FIG. It is a figure which shows the 2nd member shown in FIG. FIG. 8A is a diagram showing a state where the first and second members are completely facing each other, and FIG. 8B is a diagram showing a state where the first and second members are opposed to each other with the center shifted. It is a characteristic view which shows the relationship between the displacement amount of a 1st, 2nd member, and the restoring force which generate | occur | produces according to it. It is a figure which shows the lower limit and upper limit stopper of a to-be-rotated drive part. It is a figure which shows the modification of the axis | shaft which formed the area | region of the 1st radial bearing shown in FIG. 2 in the small diameter part. It is a figure which shows the turbo-molecular pump different from FIG. It is a figure which shows the thrust bearing which reciprocates to an axial direction, rotating the cylindrical member which is a to-be-rotated drive part. It is a figure which shows the modification which changed arrangement | positioning of the 1st, 2nd radial bearing and thrust bearing shown in FIG. It is a figure which shows the pump which can connect / cut off a gas path by reciprocating the rotating piston using the thrust bearing shown in FIG. It is a figure explaining the thrust bearing used for FIG. It is a figure which shows the structure for switching a radial bearing from a dynamic pressure bearing to a static pressure bearing at the time of a rotation stop.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Composite type pump, 20 1st casing, 22 Inlet, 24 1st flange, 26 1st hollow part, 28 Upper limit stopper, 30 2nd casing, 32 Exhaust port, 34 2nd flange, 36 2nd hollow part, 37 Bearing wall, 38 Cooling fin, 40 bolt 42 O-ring, 50 shaft, 51 Small diameter part, 51A C ring, 50A End face, 52 Flange, 52A End face, 54 Lower limit stopper, 60 Cylindrical member, 62 Thick part, 70 bolt, 72 O-ring, 80 rotating body (turbomolecular pump), 81 thread groove, 82 bolt, 84 first recess, 86 second recess, 90 motor, 92 rotor, 94 stator, 100A, 100B first and second radial bearings, 102 Herringbone groove, 104 center hole, 105 first side hole, 106 second side hole, 107 , 107B First and second eccentric holes, 108 Bypass holes, 110 Thrust bearings, 112 Magnet arrangement part, 113 First member, 114 S pole ring, 115 Non-magnetic ring, 116 N pole ring, 118 Second member, 119 Magnetic body, 120 Screw seal part, 130 Turbo molecular pump, 132 Clearance seal part, 140 Thrust bearing, 142 First member, 144 Inclined south pole ring, 146 Inclined north pole ring, 150 Second member, 152,154 Permanent Magnet, 156 Magnetic body, 160 Dry pump, 162 Cylinder chamber, 164 Rotating shaft, 166 Rotor, 168 Stator, 170, 172 Cylindrical body, 174 Gas passage, 180 Thrust bearing, 190 Stepped piston, 192, 194, 196, 198 First to fourth piston chambers 200, 20 , 206 first to the third pipe, 202 tanks, 208 valve

Claims (9)

The axis,
A cylindrical member inserted through the shaft;
One of the shaft and the cylindrical member is a fixed guide member, a rotation drive unit is formed including the other of the shaft and the cylindrical member, and a rotation drive unit that rotationally drives the rotation drive unit;
At least one radial bearing that generates a gas pressure in a gap between the shaft and the cylindrical member during rotation of the rotation drive unit and maintains the shaft and the cylindrical member in a non-contact manner in a radial direction;
One of the shaft and the cylindrical member includes a plurality of permanent magnet rings arranged at intervals along the thrust direction and arranged such that the N poles and the S poles are adjacent to each other in the thrust direction. Including the first member and a second member that is magnetized by being opposed to the first member on the other side of the shaft and the cylindrical member, and the rotated drive unit that is free in the thrust direction, At least one thrust bearing that maintains a predetermined position in a thrust direction suspended from a load in a thrust direction of the driven part;
A bearing device for a rotating part, comprising: In claim 1,
The rotation drive unit is a bearing device for a rotation unit, wherein the shaft serves as a guide member and rotates the cylindrical member as the rotation drive unit around the shaft. In claim 1 or 2,
A bearing device for a rotating part, wherein the second member is a magnetic body. In claim 1 or 2,
A bearing device for a rotating part, wherein the second member is a permanent magnet. In claim 1 or 2,
The first member is formed in a ring shape inclined with respect to the thrust direction so that each of the permanent magnets has different thrust positions continuously at each position in the circumferential direction,
The second member is opposed to a plurality of permanent magnets arranged in the thrust direction over a part of the circumferential direction at one position opposed to the diameter direction of the shaft in the diameter direction of the shaft. A magnetic body disposed over another part in the circumferential direction at the other position
According to the driving of the rotary drive unit, the rotary drive unit is reciprocated according to the predetermined position that changes in the thrust direction. In any one of Claims 1 thru | or 5,
A bearing device for a rotating part, wherein the at least one thrust bearing is disposed between two radial bearings adjacent in the thrust direction. In any of claims 3 to 5,
The plurality of permanent magnets provided in the first member are arranged in an arrangement relationship in which two adjacent magnets in the thrust direction alternately repeat different poles and same poles. Bearing device. In any one of Claims 1 thru | or 7,
The at least one radial bearing generates a dynamic pressure in a gap between the shaft and the cylindrical member when the rotary drive unit rotates, and maintains the shaft and the cylindrical member in a non-contact manner in a radial direction.
The bearing device further includes
A tank,
A first flow path for guiding the dynamic pressure generated by the at least one radial bearing to the tank;
A second flow path for supplying dynamic pressure in the tank back to the at least one radial bearing;
A valve for communicating the tank with the second flow path at least when the rotation drive unit stops rotating;
A bearing device for a rotating part, comprising:   A pump comprising the bearing device for a rotating part according to claim 1.

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