JP5229499B2 - Magnetic bearing device and vacuum pump including the same - Google Patents

Description

  The present invention relates to a magnetic bearing device including a magnetic bearing that supports a rotating body in a non-contact state with a magnetic force, and a vacuum pump such as a turbo molecular pump including the magnetic bearing device.

FIG. 5 is a cross-sectional view of a conventional magnetic bearing device. The rotating body 10 is controlled by the radial magnetic bearing 30 and the radial magnetic bearing 40 so as to float in a non-contact manner in the radial direction. The radial magnetic bearing 30 includes a radial electromagnet 31, a radial electromagnet target 32, a radial sensor 33, and a radial sensor target 34. The radial magnetic bearing 40 includes a radial electromagnet 41, a radial electromagnet target 42, a radial sensor 43, and a radial sensor target 44.
The rotating body 10 is controlled by the thrust magnetic bearing 50 to float in a non-contact manner in the axial direction. The thrust magnetic bearing 50 includes a thrust disk 51, thrust electromagnets 52 and 53, and a thrust sensor 54 attached in parallel to the radial direction of the rotating body 10.
Thus, the rotating body 10 that has floated in a non-contact manner in the radial direction and the axial direction is rotated by the motor 60.

  The protective bearings 21 and 22 are disposed at both ends of the rotating body 10. The clearance between the protective bearings 21 and 22 and the rotating body 10 is narrower than the clearance formed in the radial magnetic bearings 30 and 40 and the clearance formed in the thrust magnetic bearing 50. For this reason, when the radial magnetic bearings 30 and 40 and the thrust bearing 50 are not functioning, the rotating body 10 is contact-supported by the protective bearings 21 and 22 in the radial direction and the axial direction. Normally, after the rotation of the rotating body 10 stops or after the number of rotations of the rotating body 10 becomes sufficiently low, the rotating body 10 is supported by contact with the protective bearings 21 and 22.

JP 2002-339970 A

However, when the magnetic bearings 30 and 40 do not function due to a power failure or some failure, the rotating body 10 is contact-supported by the protective bearings 21 and 22 even when the rotating body 10 is in a high rotational speed state. Become. In this case, a large load is applied to the rotating body 10 and the protective bearings 21 and 22. In particular, since the hardness of the protective bearings 21 and 22 is high, wear occurs on the contact surface of the rotating body 10 that contacts the protective bearings 21 and 22. In the prior art, the wear powder generated by this wear was present at the contact portion between the rotating body 10 and the protective bearings 21 and 22, so that there was a problem of increased wear on the contact surface of the rotating body 10. .
In order to prevent the contact surface of the rotating body 10 from being worn, the contact surface of the rotating body 10 is hardened to increase the surface hardness, or a solid lubrication or the like is applied to reduce friction, or the contact portion of the rotating body 10 is reduced. It is also conceivable to take a measure such as to make up a separate part of a material having a high hardness different from that of the rotor shaft. However, in any of these, there is a problem that the manufacturing cost is high and the replacement cost of the parts is also high.
In addition, wear powder is mixed into the protective bearings 21 and 22, and the damage to the protective bearings 21 and 22 increases, resulting in a problem that the life of the protective bearings 21 and 22 is shortened. In particular, since the protective bearings 21 and 22 are expensive, this problem is a serious problem in terms of cost.

  The present invention has been made in view of such a problem, and can suppress an increase in wear of a contact surface of a rotating body while suppressing cost more than the conventional one, and can extend the life of a protective bearing. An object is to provide a device and a vacuum pump including the same.

The invention according to claim 1 relates to a magnetic bearing device, wherein the magnetic bearing device is provided around a rotating body, and a magnetic bearing that supports the rotating body rotatably and in a non-contact manner, A groove provided around the rotating body and supporting the rotating body when the magnetic bearing does not support the rotating body, and a groove extending in the axial direction of the rotating body provided on the inner ring side of the protective bearing facing the rotating body. And a protective member formed on a surface facing the rotating body.
The invention according to claim 2 is the magnetic bearing device according to claim 1, characterized in that the end of the protection member in the axial direction covers at least the end of the inner ring of the protection bearing in the axial direction. is there.
According to a third aspect of the present invention, in the magnetic bearing device according to the second aspect, the end portion of the protective member in the axial direction further covers a gap between the inner and outer rings of the protective bearing formed along the axial direction. It is characterized by.
According to a fourth aspect of the present invention, in the magnetic bearing device according to any one of the first to third aspects, the protective member is further formed with a groove extending in a circumferential direction of the rotating body. Is.
According to a fifth aspect of the present invention, in the magnetic bearing device according to any one of the first to fourth aspects, the shape of the end portion in the axial direction of the contact surface of the protective member that contacts the rotating body is a tapered shape. It is characterized by that.
According to a sixth aspect of the present invention, in the magnetic bearing device according to any one of the first to fifth aspects, the hardness of the contact surface of the protective member that comes into contact with the rotating body is determined by the contact of the rotating body that comes into contact with the protective member. It is characterized by being lower than the hardness of the surface.
According to a seventh aspect of the present invention, in the magnetic bearing device according to any one of the first to sixth aspects, a motor for driving the rotating body is further provided.
The invention according to an eighth aspect is a vacuum pump including the magnetic bearing device according to any one of the first to seventh aspects.

According to the first aspect of the present invention, the groove formed in the protective member causes wear powder generated when the rotating body and the protective member come into contact with each other with a relative speed difference to enter the groove. The wear powder entering the contact portion of the rotating body is reduced. Therefore, it is possible to suppress an increase in wear of the contact surface of the rotating body that contacts the protective member. In addition, since the wear powder enters the groove, scattering of the wear powder is prevented, and contamination of the wear powder into the protective bearing is reduced, and the life of the protective bearing can be extended.
According to the second aspect of the present invention, the rotating body can be supported in the axial direction by the protective member.
According to the invention described in claim 3, it is possible to prevent wear powder generated by the contact between the rotating body and the protective member from entering the protective bearing, and to further extend the life of the protective bearing. Become.
According to the fourth aspect of the present invention, it is possible to further suppress an increase in wear of the contact surface of the rotating body and further extend the life of the protective bearing.
According to the fifth aspect of the present invention, the contact area between the rotating body and the protection member can be increased, and the increase in wear on the contact surface of the rotating body can be further suppressed.
According to invention of Claim 6, it becomes possible to further suppress the increase in wear of the contact surface of a rotary body.

Side sectional view of the magnetic bearing device according to the first embodiment of the present invention. The figure which shows the protection member 72 shown in FIG. The figure which shows the protection member 72 which concerns on Example 2 of this invention. The figure which shows the protection member 72 which concerns on Example 3 of this invention. Side sectional view of a conventional magnetic bearing device

  Embodiments of the present invention will be described below with reference to the drawings.

  1 is a side sectional view of a magnetic bearing device according to a first embodiment of the present invention. In FIG. 1, the magnetic bearing device includes a rotating body 10, protective bearings 21 and 22, radial magnetic bearings 30 and 40, a thrust magnetic bearing 50, a motor 60, and protective members 71 and 72. In FIG. 1, the same components as those shown in FIG. The magnetic bearing device shown in FIG. 1 is mounted on a vacuum pump or the like.

The rotating body 10 is controlled to float in a non-contact manner in the radial direction by a radial magnetic bearing 30 and a radial magnetic bearing 40 provided around the rotor 10. The radial magnetic bearing 30 includes a radial electromagnet 31, a radial electromagnet target 32, a radial sensor 33, and a radial sensor target 34. The radial magnetic bearing 40 includes a radial electromagnet 41, a radial electromagnet target 42, a radial sensor 43, and a radial sensor target 44.
The rotating body 10 is controlled to float in the axial direction by a thrust magnetic bearing 50 provided around the rotor 10. The thrust magnetic bearing 50 includes a thrust disk 51 that is vertically attached to the rotating body 10, thrust electromagnets 52 and 53, and a thrust sensor 54.
Thus, the rotating body 10 that floats in a non-contact manner in the radial direction and the axial direction and is rotatably supported is rotated by the motor 60.

  The protective bearings 21 and 22 are disposed near both ends of the rotating body 10 and support the rotating body 10 when the radial magnetic bearings 30 and 40 and the thrust bearing 50 are not functioning. Here, in this embodiment, protective members 71 and 72 are fitted to the inner rings (rotating body 10 side) of the protective bearings 21 and 22. The clearance between the protection members 71 and 72 and the rotating body 10 is narrower than the clearance formed in the radial magnetic bearings 30 and 40 and the clearance formed in the thrust magnetic bearing 50. For this reason, when the radial magnetic bearings 30 and 40 and the thrust bearing 50 are not functioning, the rotating body 10 is contact-supported by the protective members 71 and 72 in the radial direction and the axial direction.

The shape of the protection member 71 is a cylindrical shape, and the shape of the protection member 72 is a cylindrical shape in which a step is provided on the outer peripheral surface as shown in FIG. 2 is a view showing the protection member 72 shown in FIG. 1, FIG. 2 (a) is a top view of the protection member 72, and FIG. 2 (b) is a side sectional view of the protection member 72. . The material of the protection members 71 and 72 is selected as a material having a lower surface hardness than the contact surface of the rotating body 10 that contacts the protection members 71 and 72. Instead of selecting the material of the protective members 71 and 72 as a material whose surface hardness is lower than the contact surface of the rotating body 10, the protective members 71 and 72 may be subjected to a surface treatment.
Here, grooves extending in the axial direction are provided on the inner peripheral surfaces of the protection members 71 and 72. As shown in FIG. 2A, the protective member 72 is provided with a groove 72a, and the protective member 71 is also provided with the same groove as the groove 72a.
As a result, wear powder generated when the rotating body 10 and the protection members 71 and 72 come into contact with each other with a relative speed difference enters the groove, and wear powder entering the contact portion between the protection members 71 and 72 and the rotation body 10. Is reduced. Therefore, it is possible to suppress an increase in wear of the contact surface of the rotating body 10 that contacts the protection members 71 and 72.
In addition, the wear powder generated upon contact enters the groove, so that the scattering of the wear powder is prevented, the contamination of the wear powder into the protective bearings 21 and 22 is reduced, and the life of the protective bearings 21 and 22 is extended. Is also possible.

  As described above, according to the present embodiment, the protective member provided with the groove extending in the axial direction suppresses the increase in wear of the contact surface of the rotating body while reducing the cost as compared with the conventional one, and extends the life of the protective bearing. It can be extended.

  In addition to the groove 72a, the protective member 72 described above is also provided with a groove 72b extending in the circumferential direction, as shown in FIG. The groove 72b can further suppress an increase in wear of the contact surface of the rotating body 10, and can further extend the life of the protective bearing 22. A groove similar to the groove 72b may also be provided in the protective member 71. By this groove, it is possible to further suppress an increase in wear on the contact surface of the rotating body 10 and further extend the life of the protective bearing 21.

3A and 3B are diagrams showing a protection member 72 according to the second embodiment of the present invention, FIG. 3A is a top view of the protection member 72, and FIG. 3B is a cross-sectional side view of the protection member 72. FIG. The shape of the protection member 72 is a cylindrical shape in which a step is provided on the outer peripheral surface. The outer diameter D2 of the outer peripheral surface of the protective member 72 that does not fit with the protective bearing 22 is larger than the outer diameter D1 of the inner ring of the protective bearing 22. That is, the gap between the inner and outer rings of the protective bearing 22 is covered with the axial end portion of the protective member 72. As a result, it is possible to further prevent wear powder from entering the protective bearing 22 and further extend the life of the protective bearing 22.
The rotating member 10 can be supported in the axial direction by covering at least the end of the inner ring of the protective bearing 22 with the axial end of the protective member 72.
Further, a recess for fitting the protection bearing 21 may be provided on the outer peripheral surface of the protection member 71, and the gap between the inner and outer rings of the protection bearing 21 may be covered by both end portions of the recess in the axial direction. In this case, it is only necessary that the outer diameter of the tip of each end portion in the axial direction is larger than the outer diameter of the inner ring of the protective bearing 21.

4A and 4B are diagrams showing a protection member 72 according to a third embodiment of the present invention, FIG. 4A is a top view of the protection member 72, and FIG. 4B is a side cross-sectional view of the protection member 72. FIG. The axial end of the contact surface of the protection member 72 that contacts the rotating body 10 is tapered. Thereby, the contact area of the rotary body 10 and the protection member 72 can be increased, and the increase in wear of the contact surface of the rotary body 10 can be further suppressed.
In addition, it is good also considering the axial direction edge part of the contact surface of the protection member 71 which contacts the rotary body 10 as a taper shape.

10 Rotating body 21, 22 Protective bearing 30, 40 Radial magnetic bearing 31, 41 Radial electromagnet 32, 42 Radial electromagnet target 33, 43 Radial sensor 34, 44 Radial sensor target 50 Thrust magnetic bearing 51 Thrust disk 52, 53 Thrust electromagnet 54 Thrust Sensor 60 Motor 71, 72 Protection member

Claims (8)

A rotating body,
A magnetic bearing provided around the rotating body and rotatably supporting the rotating body in a non-contact manner;
A protective bearing that is provided around the rotating body and supports the rotating body when the magnetic bearing does not support the rotating body;
A magnetic bearing device comprising: a protective member provided on an inner ring side of the protective bearing facing the rotating body and having a groove extending in an axial direction of the rotating body formed on a surface facing the rotating body. The magnetic bearing device according to claim 1,
The end portion of the protection member in the axial direction covers at least the end portion of the inner ring of the protection bearing in the axial direction. The magnetic bearing device according to claim 2,
An end portion of the protection member in the axial direction further covers a gap between inner and outer rings of the protection bearing formed along the axial direction. The magnetic bearing device according to any one of claims 1 to 3,
The magnetic bearing device, wherein the protective member is further formed with a groove extending in a circumferential direction of the rotating body. In the magnetic bearing device according to any one of claims 1 to 4,
Of the contact surface of the protection member that contacts the rotating body, the end portion in the axial direction has a tapered shape. The magnetic bearing device according to any one of claims 1 to 5,
The magnetic bearing device according to claim 1, wherein a hardness of a contact surface of the protective member that contacts the rotating body is lower than a hardness of a contact surface of the rotating member that contacts the protective member. The magnetic bearing device according to any one of claims 1 to 6,
A magnetic bearing device further comprising a motor for driving the rotating body.   A vacuum pump comprising the magnetic bearing device according to claim 1.

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