JP2008208942A - Turbo-molecular pump and touchdown bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a touchdown bearing device capable of surely supporting a shaft by predetermined times even if the shaft has a long lifetime and rotation speed of the shaft is high, and a turbo-molecular pump of which touchdown bearing device has a long lifetime. <P>SOLUTION: The touchdown bearing device 10 comprises a first inner ring 31 externally fitted and fixed on a rotary shaft 3, a first outer ring 32 radially opposed to the first inner ring 31, a first ball 33 interposed between the first inner ring 31 and the first outer ring 32, a second inner ring 51 radially opposed to the first outer ring 32, a second outer ring 52 internally fitted and fixed in an inner circumference surface of the housing 2, and a second ball 53 interposed between the second inner ring 51 and the second outer ring 52. The touchdown bearing device 10 is configured so that when a magnetic bearing normally operate, the first outer ring 32 and the second inner ring 51 are in a non-contact state, and that meanwhile, when the magnetic bearing does not normally operate, the rotary shaft 3 is supported by the second inner ring 51 so as to support the first outer ring 32 against the housing 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a turbo molecular pump. The present invention also relates to a touchdown bearing device used for a turbo molecular pump, a vacuum pump, or the like.

  Conventional turbomolecular pumps include those described in Japanese Patent Application Laid-Open No. 2004-116558 (Patent Document 1).

  The turbo molecular pump includes a rotating shaft, a housing, a magnetic bearing, and a ball bearing as a touchdown bearing. The magnetic bearing has an electromagnet and supports the rotating shaft magnetically in a non-contact manner during normal operation.

  On the other hand, the ball bearing has an inner ring, an outer ring, and a ball. The outer ring is disposed so as to be fitted inside the inner peripheral surface of the housing, while the inner ring is in a non-contact state with respect to the rotating shaft when the magnetic bearing is operating normally. .

  When the magnetic bearing does not operate normally due to an operation error (human error) of the magnetic bearing or a power failure, the outer surface of the rotating shaft is the inner surface of the inner ring. In response, the rotating shaft is mechanically supported with respect to the housing.

In the turbo molecular pump, when the magnetic bearing is uncontrollable, the rotating shaft is shaken, so the rotating shaft hits the inner ring of the ball bearing. Also. During the touchdown, the rotation speed of the inner ring of the ball bearing is suddenly and rapidly accelerated from the stopped state to near the high rotation speed of the rotor due to friction with the rotation shaft. For this reason, at the time of touchdown, a large frictional force is generated between the bearing ring and the ball, the ball is easily locked to the bearing ring, and the ball and the bearing ring are easily seized. There is a problem that it is unavoidable that the lifetime is shortened. Further, the raceway may be worn by the balls, and the adjacent portion between the rotating shaft and the housing may come into contact. In addition, there is a demand for a touchdown bearing device that can perform touchdown at a rotational speed higher than that of a turbo molecular pump.
JP 2004-116558 A

  Accordingly, an object of the present invention is to provide a turbo molecular pump having a long life of a touchdown bearing device. Another object of the present invention is to provide a touch-down bearing device that can reliably support a shaft a predetermined number of times even when the shaft has a long life and a high rotational speed.

In order to solve the above problems, the turbo molecular pump of the present invention is
The axis,
A housing facing the shaft at a radial interval,
A magnetic bearing for supporting the shaft magnetically in a non-contact manner with respect to the housing;
A touchdown bearing device disposed between the housing and the shaft and mechanically supporting the shaft when the magnetic bearing is not operating normally;
A motor for rotating the shaft relative to the housing;
The touchdown bearing device is
A first track member fixed to the shaft;
A second race member facing the first race member, a first rolling element disposed between the first race member and the second race member,
A third track member fixed to the housing;
A fourth track member facing the third track member; a second rolling element disposed between the third track member and the fourth track member;
When the magnetic bearing is operating normally, the second track member and the fourth track member are not in contact with each other, whereas when the magnetic bearing is not operating normally, the second track member is Is supported by the fourth track member so that the shaft is supported with respect to the housing.

  The housing is defined as a case and a member that does not move relative to the case. The shaft may be a rotor of a motor, and the shaft may constitute a part of the motor. The shaft and the rotor of the motor may be separate members. For example, the motor rotor may be a ring-shaped member, and the ring-shaped rotor may be fixed to the outer peripheral surface of the shaft.

  The first, second, third, and fourth track members described above and below may be track rings themselves, or may be a member in which another member is attached to the track rings.

  According to the present invention, the second track member comes into contact with the fourth track member, so that the load from the shaft is applied to the first track member, the first rolling element, the second track member, the fourth track member, and the second track member. It can be received by the housing via the rolling element and the third track member, and at the time of touchdown, the rotation speed (relative rotation speed) of the first track member with respect to the second track member and the first speed with respect to the third track member The rotational speed (relative rotational speed) of the four track members can be rapidly reduced to a rotational speed that is about half the rotational speed of the shaft at the time of touchdown as compared with the conventional case.

  Therefore, at the time of touchdown, it can suppress that the 1st rolling element locks with respect to at least one of the 1st track member and the 2nd track member, and the 2nd rolling element is the 3rd track member and Locking to at least one of the fourth track members can be suppressed. Therefore, the life of the touch-down bearing device can be remarkably increased compared to the conventional case.

  In addition, the relative rotational speed between the first track member and the second track member and between the third track member and the fourth track member is approximately half that of the conventional one. Therefore, the upper limit of the rotational speed of the shaft that can be touched down by the touchdown bearing device can be significantly increased. Therefore, compared with the prior art, the possibility of contact between two different members such as contact between the magnetic bearing and the shaft and contact between the rotor constituting the motor and the stator can be significantly reduced.

  Further, according to the present invention, at least one of the first track member, the second track member, and the first rolling element is seized, and the first track member does not normally rotate with respect to the second track member. Even so, the third track member, the fourth track member, and the second rolling element can rotatably support the shaft with respect to the housing. On the other hand, even if at least one member of the third track member, the fourth track member, and the second rolling element is seized and the fourth track member does not rotate normally with respect to the third track member. The shaft can be rotatably supported with respect to the housing by the first track member, the second track member, and the first rolling element. Therefore, it can suppress that the axis | shaft which contacts a touchdown bearing apparatus wears out or damages compared with the past.

Moreover, the touchdown bearing device of the present invention includes:
A first track member fixed to the shaft;
A second race member facing the first race member, a first rolling element disposed between the first race member and the second race member,
A third track member fixed to the housing;
The second raceway member is disposed between the fourth raceway member, the fourth raceway member facing the third raceway member, the fourth raceway member facing the third raceway member, and the second raceway member. Rolling elements,
By changing the relative position between the shaft and the housing, when the second track member and the fourth track member are in contact, the second track member is supported by the fourth track member, The shaft is supported with respect to the housing.

  According to the present invention, it is possible to significantly increase the service life as compared with the prior art. Moreover, the upper limit of the rotational speed of the shaft that can be touched down can be significantly increased as compared with the conventional case.

  According to the turbo molecular pump of the present invention, the life of the touch-down bearing device can be significantly increased compared to the conventional one. In addition, compared to the prior art, the upper limit of the rotational speed of the shaft that can be touched down by the touchdown bearing device can be significantly increased.

  In addition, according to the touchdown bearing device of the present invention, the life can be remarkably increased as compared with the conventional case. Moreover, the upper limit of the rotational speed of the shaft that can be touched down can be significantly increased as compared with the conventional case.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

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

  This turbo molecular pump includes a turbo molecular pump main body 1 and a controller (not shown), and communicates with a vacuum device (not shown).

  The turbo molecular pump body 1 includes a housing 2, a rotating shaft 3 as a shaft, a motor 4 that drives the rotating shaft 3, an axial position detection sensor 16, radial position detection sensors 14 and 15, and an axial magnetic bearing 6. And first and second radial magnetic bearings 7, 8, a first touchdown bearing device 10 according to the first embodiment of the present invention, and a second touchdown bearing device 11.

  The axial position detection sensor 16 detects the axial position of the rotary shaft 3 and outputs a signal representing the axial position of the rotary shaft 3 to the controller. Further, the radial position detection sensors 14 and 15 are arranged at intervals in the axial direction of the rotary shaft 3. The radial position detection sensors 14 and 15 detect the radial position of the rotary shaft 3 and output a signal representing the radial position of the rotary shaft 3 to the controller. The controller outputs a control signal to the axial magnetic bearing 6 based on the signal from the axial position detection sensor 16 and also the first and second radial magnetic bearings 7 based on the signals from the radial position detection sensors 14 and 15. , 8 output a control signal.

  The motor 4 includes a rotor 20 and a stator 21. The rotor 20 is composed of a ring-shaped two-pole permanent magnet, and is fixed to the outer peripheral surface of the rotating shaft 3. The stator 21 has an armature coil (not shown). By appropriately supplying an electric current to the armature coil, the rotor 20 is rotated at a high speed with respect to the stator 21, and the rotary shaft 3 to which the rotor 20 is fixed is rotated at a high speed.

  The axial magnetic bearing 6 supports the rotary shaft 3 in a magnetic non-contact manner in the axial direction. Specifically, the axial magnetic bearing 6 has a pair of electromagnets (two in number) arranged so as to sandwich both end faces of the rotating shaft 3 in the axial direction from both sides in the axial direction. The magnetic force of the electromagnet of the axial magnetic bearing 6 is appropriately controlled by a control signal from the controller. The axial magnetic bearing 6 precisely controls the position of the rotating shaft 3 rotating at several tens of thousands of revolutions per minute in the axial direction to suppress the wobbling of the rotating shaft 3 in the axial direction so that the rotating shaft 3 is moved in the axial direction. It is positioned precisely at a predetermined position.

  On the other hand, the first and second radial magnetic bearings 7 and 8 support the rotary shaft 3 in a non-contact manner in the radial direction. More specifically, each of the first and second radial magnetic bearings 7 and 8 includes two pairs of electromagnets that are arranged so as to sandwich the rotary shaft 3 from both sides in the radial direction (in each radial magnetic bearing, The number is 4). The magnetic forces of the electromagnets of the first and second radial magnetic bearings 7 and 8 are appropriately controlled by a control signal from the controller. The first and second radial magnetic bearings 7 and 8 precisely control the position of the rotating shaft 3 rotating at several tens of thousands of revolutions per minute in the radial direction to suppress the wobbling of the rotating shaft 3 in the radial direction, The rotary shaft 3 is precisely positioned at a predetermined position in the radial direction.

  The first touchdown bearing device 10 is configured to mechanically support the rotary shaft 3 in the radial direction when the first and second radial magnetic bearings 7 and 8 become uncontrollable. Further, the second touchdown bearing device 11 moves the rotary shaft 3 in the axial direction and the radial direction when the axial magnetic bearing 6 or the first and second radial magnetic bearings 7 and 8 become uncontrollable. It is designed to be mechanically supported.

  The first touchdown bearing device 10 and the second touchdown bearing device 11 support the rotary shaft 3 when the first and second radial magnetic bearings 7 and 8 become uncontrollable. Contact between the first and second radial magnetic bearings 7 and 8 and the rotating shaft 3, contact between the rotor 20 and the stator 21 and the like are reliably prevented.

  FIG. 2 is a schematic cross-sectional view of the vicinity of the first touchdown bearing device 10 in FIG.

  The first touchdown bearing device 10 includes a deep groove type first total ball bearing 30 and a deep groove type second total ball bearing 50. The first total ball bearing 30 has a first inner ring 31 as a first race member, a first outer ring 32 as a second race member, and a plurality of first balls 33 as first rolling elements, The two total ball bearings 50 include a second inner ring 51 as a fourth race member, a second outer ring 52 as a third race member, and a plurality of second balls 53 as second rolling elements.

  The first inner ring 31, the first outer ring 32, the second inner ring 51, and the second outer ring 52 are made of, for example, bearing steel (SUJ2 or the like), stainless steel (SUS440C or the like), tool steel (SKH4 or the like), or the like. Made of ferromagnetic material. The first ball 33 and the second ball 53 are made of a ferromagnetic material such as bearing steel (SUJ2 or the like) or tool steel (SKH4 or M50 (AISI standard) having excellent heat resistance). Thus, the ferromagnetic material refers to a material that has the property of being magnetized in the same direction as the magnetic field when placed in a magnetic field, and leaving the magnetism even when the magnetic field is removed.

  If the race rings 31, 32, 51, 52 and the balls 33, 53 made of a ferromagnetic material are used as the race rings and balls of the first touchdown bearing device 10 as in the first embodiment, the first The magnetic flux generated by the magnetic fields of the first and second radial magnetic bearings 7 and 8 disposed close to the touchdown bearing device 10 may be passed through the first inner ring 31, the first ball 33, and the first outer ring 32. it can. Further, the magnetic flux generated by the magnetic field of the second radial magnetic bearings 7 and 8 can be passed through the second inner ring 51, the second ball 53, and the second outer ring 52.

  Accordingly, the first ball 33 and the first outer ring 32 can be attracted to the inner ring 31 by the magnetic force during the operation of the turbo molecular pump and when the radial magnetic bearings 7 and 8 are normally driven. In addition, when the radial magnetic bearings 7 and 8 are normally driven, the first outer ring 32 does not rotate relative to the first inner ring 31 and the first outer ring 32 rotates relative to the first inner ring 31 that rotates at a high speed. If so, it is possible to reliably prevent the generation of loud noise (abnormal noise) that will occur (actually, it does not rotate relative).

  Similarly, the second ball 53 and the second inner ring 51 are attracted to the second outer ring 52 fixed to the housing 2 by a magnetic force when the turbo molecular pump is operated and the radial magnetic bearings 7 and 8 are normally driven. Therefore, when the turbo molecular pump is operated and the radial magnetic bearings 7 and 8 are normally driven, the second inner ring 51 does not rotate relative to the second outer ring 52 (the second rotation shaft 3 has a second rotation). If the second inner ring 51 rotates relative to the second outer ring 52 (without actually rotating), noise (abnormal noise) is surely generated. Can be prevented.

  The first inner ring 31 is fitted and fixed to the outer peripheral cylindrical surface 45 of the rotating shaft 3. The first outer ring 32 is disposed radially outward of the first inner ring 31 so as to face the first inner ring 31 in the radial direction. The plurality of first balls 33 are disposed between the raceway groove of the first inner ring 31 and the raceway groove of the first outer ring 32.

  On the other hand, the second inner ring 51 is disposed outward in the radial direction of the first outer ring 32 so as to face the first outer ring 32 in the radial direction. Further, the second outer ring 52 is fitted and fixed to the inner peripheral cylindrical surface 46 of the housing 2. The plurality of second balls 53 are disposed between the raceway groove of the second inner ring 51 and the raceway groove of the second outer ring 52.

  When the radial magnetic bearings 7 and 8 normally magnetically control the rotating shaft 3, the second inner ring 51 is located radially outward of the first outer ring 32 and is spaced from the first outer ring 32. In this case, they face each other in a non-contact manner in the radial direction.

  In the turbo molecular pump having the above configuration, when the supply of power from the power supply side is stopped due to a power supply abnormality or a power failure, and the power supply voltage decreases, the motor 4 outputs a voltage as a generator. Specifically, when the power supply voltage is lowered, the motor 4 has position detection sensors 14, 15, 16, a magnetic bearing drive circuit (not shown) for each of the magnetic bearings 6, 7, 8 and a motor driver (not shown). ) To supply regenerative power. While the regenerative power supplied from the motor 4 can drive the magnetic bearings 6, 7, 8, the magnetic bearings 6, 7, 8 are controlled to be magnetically levitated by the regenerative power.

  When the rotational speed of the motor 4 is reduced and the regenerative power from the motor 4 is lower than the power required for driving the radial magnetic bearings 7 and 8, the magnetic levitation control of the radial magnetic bearings 7 and 8 is stopped. Yes. When the magnetic levitation control of the radial magnetic bearings 7 and 8 is stopped, the first touchdown bearing device 10 mechanically supports the rotating shaft 3 in the radial direction instead of the radial magnetic bearings 7 and 8, and The touch-down bearing device 11 mechanically supports the rotary shaft 3 in the radial direction instead of the radial magnetic bearings 7 and 8. When the magnetic levitation control of the magnetic bearing 6 is stopped, the second touchdown bearing device 11 also plays a role of mechanically supporting the rotary shaft 3 in the axial direction.

  Specifically, the first touchdown bearing device 10 operates as follows. When the magnetic levitation control of the magnetic bearings 7 and 8 is stopped, the outer peripheral surface of the first outer ring 32 comes into contact with the inner peripheral surface of the second inner ring 51. The moment when the outer peripheral surface of the first outer ring 32 comes into contact with the inner peripheral surface of the second inner ring 51, that is, the moment when the first touchdown bearing device 10 is touched down, the first outer ring 32 and the second outer ring 32 are caused by friction. The rotation speed of the inner ring 51 is rapidly accelerated to about half the rotation speed of the rotation shaft 3 of the rotation shaft at the time of touchdown by friction.

  That is, since the first inner ring 31 is fixed to the rotary shaft 3 and the second outer ring 52 is fixed to the housing 2 that is a stationary member, the moment when the first touchdown bearing device 10 is touched down. Both the rotation speed of the first inner ring 31 with respect to the first outer ring 32 and the rotation speed of the second inner ring 51 with respect to the second outer ring 52 are approximately half the rotation speed of the rotation shaft 3 of the rotation shaft at the time of touchdown. Become. As described above, in the first touchdown bearing device 10, the inner rings 31, 51 with respect to the outer rings 32, 52 that are instantaneously generated at the time of touchdown in each of the first total ball bearing 30 and the second total ball bearing 50. The relative rotational speed can be greatly suppressed.

  According to the turbo molecular pump of the first embodiment, when the first outer ring 32 of the first touchdown bearing device 10 contacts the second inner ring 51, the load from the rotating shaft 3 is applied to the first inner ring 31. The first ball 33, the first outer ring 32, the second inner ring 51, the second ball 53, and the first outer ring 52 can be received by the housing 2 and are instantly generated at the time of touchdown. The rotational speed of the first inner ring 31 with respect to the first outer ring 32 and the rotational speed of the second inner ring 51 with respect to the second outer ring 52 are both about half the rotational speed of the rotary shaft 3 at the time of touchdown as compared with the conventional case. It can be reduced rapidly to the rotational speed.

  Therefore, at the time of touchdown, the first ball 33 can be prevented from locking to at least one of the first outer ring 32 and the first inner ring 31, and the second ball 53 can be prevented from being locked to the second outer ring. Locking with respect to at least one of 52 and the 2nd inner ring | wheel 51 can be suppressed. Therefore, the lifetime of the first touchdown bearing device 10 can be significantly increased compared to the conventional case.

  In addition, the inner ring 31 with respect to the outer rings 32 and 52 is respectively compared between the first inner ring 31 and the first outer ring 32 and between the second inner ring 51 and the second outer ring 52 as compared with the conventional example. 51, the relative rotational speed of the first total ball bearing 30 and the second total ball bearing 50 can be greatly suppressed, and the first touchdown bearing device 10 can be touched. The upper limit of the rotational speed of the rotating shaft 3 that can be lowered can be significantly increased.

  Further, according to the turbo molecular pump of the first embodiment, at least one member of the first outer ring 32, the first inner ring 31, and the first ball 33 is baked, and the first outer ring 32 is in contact with the first outer ring 32. Even if the inner ring 31 does not normally rotate, the second inner ring 51, the second outer ring 52, and the second ball 53 can support the rotating shaft 3 with respect to the housing 2 in a rotatable manner. Conversely, at least one member of the second outer ring 52, the second inner ring 51, and the second ball 53 is seized and the second inner ring 51 does not normally rotate with respect to the second outer ring 52. In addition, the first inner ring 31, the first outer ring 32, and the first ball 33 can rotatably support the rotating shaft 3 with respect to the housing 2.

  Therefore, the radial magnetic bearings 7 and 8 and the rotary shaft 3 are compared with the conventional configuration, that is, the case where the touch-down bearing is constituted by one inner and outer rings and rolling elements arranged between the inner and outer rings. And the possibility of contact between the rotor 20 constituting the motor 4 and the stator 21 can be significantly reduced.

  Further, according to the first touchdown bearing device 10 of the first embodiment, the rotational speed of the first inner ring 31 with respect to the first outer ring 32 and the rotational speed of the second inner ring 51 with respect to the second outer ring 52 are In a conventional touchdown bearing composed of a ring and a ball, the rotational speed of the inner ring relative to the outer ring can be reduced to about half.

  Further, in the axial load from the rotating shaft 3 generated when the rotating shaft 3 hits the first touchdown bearing device 10 based on the swing of the rotating shaft 3, the first outer ring 32, the first inner ring 31 and the first Both the share loaded by one ball 33 and the share loaded by the second outer ring 52, the first inner ring 51 and the second ball 53 are a conventional touch-down bearing in which rolling bearings are arranged in one stage. In comparison, it is about half as small.

  Therefore, compared with the possibility that seizure occurs in the inner and outer rings or balls in the conventional touchdown bearing, the possibility that seizure occurs in the race rings 31, 32, 51, 52 or the balls 33, 53 is reduced by half. It can be drastically lowered to the extent that the life of the first touchdown bearing device 10 can be significantly reduced. Moreover, the upper limit of the rotational speed of the rotating shaft 3 that can be touched down can be significantly increased as compared with a conventional touchdown bearing.

  The first touchdown bearing device 10 of the first embodiment includes a deep groove type first total ball bearing 30 fixed to the rotary shaft 3 and a deep groove type second total ball bearing fixed to the housing 2. And 50. However, in the present invention, at least one of the two rolling bearings included in the touchdown bearing device may be an angular ball bearing instead of a deep groove type ball bearing, and in this case, a large axial load is applied. It is preferable because it can be loaded.

  In the first touchdown bearing device 10 of the first embodiment, the two rolling bearings are the total ball bearings 30 and 50 that do not have a cage. At least one of the two rolling bearings may be a ball bearing having a cage instead of a full ball bearing having no cage. Further, at least one of the two rolling bearings included in the touchdown bearing device may be a rolling bearing other than a ball bearing such as a cylindrical roller bearing or a tapered roller bearing instead of the ball bearing.

In the first touchdown bearing device 10 of the first embodiment, the first ball 33 and the second 53 made of a ferromagnetic material are used. In the present invention, the first ball and the second ball are used. As at least one of the balls, a ball made of a non-magnetic material made of ceramics such as silicon nitride (Si ₃ N ₄ ) may be used. When ceramic balls are used, the durability of the balls can be improved. In the present invention, the inner and outer rings and the balls may all be made of stainless steel. In this case, the cost of the ball bearing can be significantly reduced.

  FIG. 3 is a schematic cross-sectional view of the vicinity of the second touchdown bearing device 11 in FIG.

  The second touchdown bearing device 11 is different from the first touchdown bearing device 10 in that the first touchdown bearing device 10 mainly receives only support in the radial direction. The second touchdown bearing device 11 is configured to receive support in the radial direction and the axial direction. For this reason, the material of the total ball bearing of the second touchdown bearing device 11 is selected from the same materials as those used for the first touchdown bearing device 10, and the operation is the same as that of the first touchdown bearing device 10. However, the structure that receives support in the axial direction differs as follows.

  The second touchdown bearing device 11 includes an axial third angular ball bearing 60 on the one side in the axial direction (upper side in FIG. 3) and the radial inner side, and the other side in the axial direction (lower side in FIG. 3) and the radial direction. Inner angular type fourth total ball bearing 70, axially one side and radially outer angular type fifth total ball bearing 80, and axially other side and radially outer side angular type sixth total ball bearing 90. And have. The third total ball bearing 60 includes a third inner ring 61, a third outer ring 62, and a plurality of third balls 63, and the fourth total ball bearing 70 includes a fourth inner ring 71, a fourth outer ring 72, and a plurality of third balls 63. And a fourth ball 73. The fifth total ball bearing 80 includes a fifth inner ring 81, a fifth outer ring 82, and a plurality of fifth balls 83, and the sixth total ball bearing 90 includes a sixth inner ring 91, a sixth outer ring 92, and A plurality of sixth balls 93.

  The plurality of third balls 63 are arranged between the raceway groove of the third inner ring 61 and the raceway groove of the third outer ring 62. The plurality of fourth balls 73 are disposed between the raceway grooves of the fourth inner ring 71 and the raceway grooves of the fourth outer ring 72. The plurality of fifth balls 83 are disposed between the raceway groove of the fifth inner ring 81 and the raceway groove of the fifth outer ring 82. The plurality of sixth balls 93 are disposed between the raceway grooves of the sixth inner ring 91 and the raceway grooves of the sixth outer ring 92.

  The third inner ring 61 and the fourth inner ring 71 are aligned in the axial direction and are fitted and fixed to the outer peripheral cylindrical surface 47 of the rotating shaft. Thus, the third total ball bearing 60 and the fourth total ball bearing 70 are arranged in parallel in the axial direction. The fifth outer ring 82 and the sixth outer ring 92 are aligned in the axial direction and are fitted and fixed to the inner peripheral cylindrical surface 48 of the housing 2. Thus, the fifth total ball bearing 80 and the sixth total ball bearing 90 are arranged in parallel in the axial direction. Further, the fifth inner ring 81 of the fifth total ball bearing 80 and the sixth inner ring 91 of the sixth total ball bearing 90 are fixed to the contact member 40.

  That is, the second touchdown bearing device 11 includes the third inner ring 61 and the fourth inner ring 71 as the first track member, the third outer ring 62 and the fourth outer ring 72 as the second track member, and the first rolling element. A plurality of third balls 63 and a plurality of fourth balls 73, a fifth inner ring 81 and a sixth inner ring 91 and a contact member 40 as fourth track members, a fifth outer ring 82 and a third member as third track members. 6 outer rings 92.

  The contact member 40 includes a cylindrical portion 41, a diameter-expanded portion 42 that increases in diameter on one axial side of the cylindrical portion 41, and a diameter-reduced portion 43 that decreases in diameter on the other axial side of the cylindrical portion 41. The enlarged diameter portion 42 is in contact with the end surface on one axial side of the fifth inner ring 81, and the outer peripheral surface of the cylindrical portion 41 is in contact with the inner peripheral surface of the fifth inner ring 81 and the inner peripheral surface of the sixth inner ring 91. .

  When the radial magnetic bearings 7 and 8 and the axial magnetic bearing 6 normally magnetically control the rotating shaft 3, the contact member 40 is located radially outward of the third outer ring 62 and the fourth outer ring 72, and The third outer ring 62 and the fourth outer ring 72 are spaced apart from each other in the radial direction and the axial direction.

  When at least one of the magnetic levitation control of the radial magnetic bearings 7 and 8 and the magnetic levitation control of the axial magnetic bearing 6 is stopped, the outer peripheral surface of the third outer ring 62, the inner peripheral surface of the cylindrical portion 41, and the outer periphery of the fourth outer ring 72 At least one of the surface, the inner peripheral surface of the cylindrical portion 41, the end surface on the other axial side of the fourth outer ring 72, and the reduced diameter portion 43 is in contact with the housing 2 in the radial direction and It can be mechanically supported in at least one of the axial directions.

  According to the turbo molecular pump of the first embodiment, the second touchdown bearing device 11 is similar to the first touchdown bearing device 10 in that the third total ball bearing 60, the fourth total ball bearing 70, the fifth It is possible to significantly suppress the relative rotational speed of the inner rings 61, 71, 81, 91 with respect to the outer rings 62, 72, 82, 92 that are instantaneously generated at the time of touchdown in each of the total ball bearing 80 and the sixth total ball bearing 90. It is possible to rapidly reduce the rotational speed to about half the rotational speed of the rotary shaft 3 at the time of touchdown. Thereby, the lifetime of the 2nd touchdown bearing apparatus 11 can be extended markedly.

  In addition, since the rotational speed can be rapidly reduced to about half the rotational speed of the rotary shaft 3 at the time of touchdown, the upper limit of the rotational speed of the rotary shaft 3 that the second touchdown bearing device 11 can touchdown is set. , Can be much larger.

  In addition, according to the turbo molecular pump of the first embodiment, at least one of the third outer ring 62, the third inner ring 61, the third ball 63, the fourth outer ring 72, the fourth inner ring 71, and the fourth ball 73. Even if one member is seized and at least one of the third inner ring 61 and the fourth outer ring 72 does not normally rotate with respect to the third outer ring 62, the fifth inner ring 81, The rotary shaft 3 can be rotatably supported on the housing 2 by the fifth outer ring 82 and the fifth ball 83 and the sixth inner ring 91, the sixth outer ring 92 and the sixth ball 93. Conversely, at least one member of the fifth outer ring 82, the fifth inner ring 81 and the fifth ball 83 and the sixth outer ring 92, the sixth inner ring 91 and the sixth ball 93 is seized, and the fifth outer ring. Even when at least one of the sixth inner ring 91 and the sixth outer ring 92 does not rotate normally with respect to the fifth inner ring 81 and the sixth outer ring 92, the third inner ring 61, the third outer ring 62, the third ball 63, and The rotary shaft 3 can be rotatably supported with respect to the housing 2 by the fourth inner ring 71, the fifth outer ring 72 and the fifth ball 73.

  According to the second touchdown bearing device 11 of the first embodiment, similarly to the first touchdown bearing device 10, the third total ball bearing 60, the fourth total ball bearing 70, and the fifth total ball bearing 80. In addition, the relative rotation speed of the inner rings 61, 71, 81, 91 with respect to the outer rings 62, 72, 82, 92 that occurs instantaneously at the time of touchdown in each of the sixth total ball bearings 90 can be greatly suppressed, and touchdown is performed. The rotational speed can be rapidly reduced to about half the rotational speed of the rotating shaft 3 at the time. Thereby, the lifetime of the 2nd touchdown bearing apparatus 11 can be extended markedly.

  In addition, since the rotational speed can be rapidly reduced to about half the rotational speed of the rotary shaft 3 at the time of touchdown, the upper limit of the rotational speed of the rotary shaft 3 that the second touchdown bearing device 11 can touchdown is set. , Can be much larger.

  Further, in the second touchdown bearing device 11 of the first embodiment, the two rolling bearings are all ball bearings 60, 70, 80, 90 which do not have a cage. At least one of the two rolling bearings included in the down bearing device may be a ball bearing having a cage instead of a full ball bearing having no cage. Further, at least one of the four rolling bearings included in the touchdown bearing device may be a rolling bearing other than a ball bearing such as a cylindrical roller bearing or a tapered roller bearing instead of a ball bearing.

Further, in the second touchdown bearing device 11 of the first embodiment, the balls 63, the balls 73, the balls 83, and the balls 93 made of a ferromagnetic material are used. In the present invention, the third balls, As at least one of the 4 balls, the 5th ball, and the 6th ball, a ball made of a ceramic non-magnetic material such as silicon nitride (Si ₃ N ₄ ) may be used. When ceramic balls are used, the durability of the balls can be improved. In the present invention, the inner and outer rings and the balls may all be made of stainless steel. In this case, the cost of the ball bearing can be significantly reduced.

  FIG. 4 is a partial schematic cross-sectional view of a turbo molecular pump according to a second embodiment of the present invention.

  In the turbo molecular pump of the second embodiment, the description of the operation and effect common to the turbo molecular pump of the first embodiment will be omitted, and the configuration and operation different from the turbo molecular pump of the first embodiment will be omitted. I will only explain.

  The turbo molecular pump includes a housing 102, a rotating shaft 103, and a touchdown bearing device 110 according to the second embodiment of the present invention.

  The rotating shaft 103 has a cylindrical portion 113 at one end portion. Further, the housing 102 has a cylindrical portion 112 that extends in the axial direction of the cylindrical portion 113 inside the cylindrical portion 113. The touch-down bearing device 110 is disposed between the cylindrical portion 113 and the cylindrical portion 112.

  The touchdown bearing device 110 includes a first outer ring 131 as a first bearing ring, a first inner ring 132 as a second bearing ring, a plurality of first balls 133 as first rolling elements, and a third bearing ring. It has the 2nd inner ring | wheel 151, the 2nd outer ring | wheel 152 as a 4th track ring, and the some 2nd ball | bowl 153 as a 2nd rolling element.

  The first outer ring 131 is fixed by being fitted on the inner peripheral cylindrical surface 170 of the cylindrical portion 113 of the rotating shaft 103, and the first inner ring 132 is disposed radially inward of the first outer ring 131. The outer ring 131 is disposed so as to face the outer ring 131 in the radial direction. The plurality of first balls 133 are arranged at intervals in the circumferential direction between the raceway groove of the first outer ring 131 and the raceway groove of the first inner ring 132.

  The second inner ring 151 is externally fitted and fixed to the outer peripheral cylindrical surface 180 of the column portion 112 of the housing 102. The second outer ring 152 is disposed on the outer side in the radial direction of the second inner ring 151 so as to face the second inner ring 151 in the radial direction. The plurality of second balls 153 are arranged at intervals in the circumferential direction between the raceway groove of the second inner ring 151 and the raceway groove of the second outer ring 152.

  According to the turbo molecular pump of the second embodiment, since the touchdown bearing device 110 is positioned radially inward from the outer peripheral surface 190 of the rotating shaft 103, it is possible to reduce the size of the turbo molecular pump. it can.

  In the first and second embodiments, the touchdown bearing devices 10 and 110 of the present invention are mounted on the turbo molecular pump. However, it goes without saying that the touchdown bearing device of the present invention may be mounted on a simple vacuum pump instead of a turbo molecular pump.

It is sectional drawing of the axial direction of the turbo-molecular pump of 1st Embodiment of this invention. FIG. 2 is a schematic cross-sectional view in the vicinity of the touch-down bearing device in FIG. 1. It is a schematic cross section of the 2nd touchdown bearing apparatus vicinity in FIG. It is a partial schematic cross section of the axial direction of the turbo-molecular pump of 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Turbo molecular pump main body 2,102 Housing 3,103 Rotating shaft 4 Motor 6 Axial magnetic bearing 7 1st radial magnetic bearing 8 2nd radial magnetic bearing 10 1st touchdown bearing apparatus 11 2nd touchdown bearing apparatus 30 1st 1 full ball bearing 31,132 first inner ring 32,131 first outer ring 33,133 first ball 50 second full ball bearing 51,151 second inner ring 52,152 second outer ring 53,153 second ball 70 inner Peripheral cylindrical surface 80 outer peripheral cylindrical surface 110 touchdown bearing device 170 inner peripheral cylindrical surface 180 outer peripheral cylindrical surface

Claims (2)

The axis,
A housing facing the shaft at a radial interval,
A magnetic bearing for supporting the shaft magnetically in a non-contact manner with respect to the housing;
A touchdown bearing device disposed between the housing and the shaft and mechanically supporting the shaft when the magnetic bearing is not operating normally;
A motor for rotating the shaft relative to the housing;
The touchdown bearing device is
A first track member fixed to the shaft;
A second race member facing the first race member, a first rolling element disposed between the first race member and the second race member,
A third track member fixed to the housing;
A fourth track member facing the third track member; a second rolling element disposed between the third track member and the fourth track member;
When the magnetic bearing is operating normally, the second track member and the fourth track member are not in contact with each other, whereas when the magnetic bearing is not operating normally, the second track member is A turbo molecular pump characterized in that the shaft is supported with respect to the housing by supporting the shaft with the fourth track member. A first track member fixed to the shaft;
A second race member facing the first race member, a first rolling element disposed between the first race member and the second race member,
A third track member fixed to the housing;
The second raceway member is disposed between the fourth raceway member, the fourth raceway member facing the third raceway member, the fourth raceway member facing the third raceway member, and the second raceway member. Rolling elements,
By changing the relative position between the shaft and the housing, when the second track member and the fourth track member are in contact, the second track member is supported by the fourth track member, A touch-down bearing device, wherein the shaft is supported with respect to the housing.

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