WO2022270295A1

WO2022270295A1 - Bearing device and electric motor

Info

Publication number: WO2022270295A1
Application number: PCT/JP2022/022950
Authority: WO
Inventors: 正典上野
Original assignee: Ntn株式会社
Priority date: 2021-06-22
Filing date: 2022-06-07
Publication date: 2022-12-29
Also published as: CN117480327A; JP2023002235A

Abstract

In the present invention, a free-side bearing is a rolling bearing that comprises: a pair of race rings; and a plurality of rolling elements that are interposed between raceway surfaces of the pair of race rings. The rolling elements are constituted by ceramic rollers which do not have a crown section on the rolling surfaces thereof. In at least one of the race rings, a surface thereof opposing the other race ring is formed by a straight section between a crown section and a crown section at both ends in the axial direction.

Description

Bearing gear and electric motor

The present invention relates to bearing devices and electric motors.

For the bearings (rolling bearings) in bearing devices used in electric motors such as traction motors for railway vehicles, conventionally anti-electrical corrosion rolling bearings have been used in order to prevent electrolytic corrosion. In addition, there are anti-electrical corrosion rolling bearings that use ceramics (Patent Document 1) and resins (Patent Documents 2 and 3) for insulating coatings (insulating coatings).

The one that uses ceramic (the one in Patent Document 1) forms an insulating coating on the outer ring or the like by plasma spraying. However, when the insulating coating is formed by plasma spraying, it is difficult to increase the thickness of the insulating coating due to manufacturing costs. From the viewpoint of preventing electrolytic corrosion of the bearing, it is desirable that the electrostatic capacity of the bearing is small. Therefore, the technique described in Patent Document 1 aims to solve this problem by optimizing the material and film thickness of the insulating coating.

In addition, when resin is used, there are problems of deformation of the resin film and problems of bearing temperature rise due to the heat insulating effect of the resin. Therefore, in Patent Document 2, by limiting the resin material of the insulating coating, the creep resistance of the insulating coating is improved, and the interference of the bearing is stable over time even under high temperature and high load conditions. offers. Further, in Patent Document 3, the insulating coating is made of a resin composition containing a synthetic resin, glass fiber, and a heat conductive substance, and the diameter of the glass fiber is specified, and the heat conductive substance is used. Rolling bearings with highly reliable anti-electrolytic corrosion function by specifying the specific resistance and thermal conductivity and forming an insulating coating with excellent mechanical strength in addition to creep resistance and heat dissipation. offers.

In addition, there is a conventional bearing that uses ceramic spheres as rolling elements (Patent Document 4). In this way, when ceramic balls are used, the electrostatic capacity of the bearing is 1/100 or less of that of the ceramic sprayed insulating bearing described in the aforementioned Patent Document 1. In addition, when ceramic balls are used, an insulating coating is not provided on the outer ring of the bearing or the like, so the problem of increase in bearing temperature due to deformation of the coating and heat insulating effect can be solved.

By the way, bearing devices for medium-sized and large-sized electric motors usually have deep-groove ball bearings, NH-type cylindrical roller bearings, and NUP-type cylindrical roller bearings on one side of the rotating shaft as fixed-side bearings, and on the other side as free-side bearings. NU-type cylindrical roller bearings and N-type cylindrical roller bearings are generally used. Here, the NU type cylindrical roller bearing is a cylindrical roller bearing that has no ribs on the inner ring and has ribs on both sides of the outer ring, and the N type cylindrical roller bearing has ribs on both sides of the inner ring and has ribs on the outer ring. The NUP type cylindrical roller bearing is a cylindrical roller bearing that has a flange on one side of the inner ring, flanges on both sides of the outer ring, and a flange ring on the inner ring side. The NH-type cylindrical roller bearing is a cylindrical roller bearing in which an L-shaped flange ring is combined with the inner ring side of the NJ-type cylindrical roller bearing (having a flange on one side of the inner ring and flanges on both sides of the outer ring). .

In a cylindrical roller bearing, since the raceway surface of the inner or outer ring and the roller rolling surface (surface formed by the outer diameter surface of the cylindrical roller) are in line contact, so-called edge stress is generated at the axial end of the contact area. In order to alleviate this edge stress, it is common to provide a crowning portion on either or both of the raceway surface (the raceway surface of the inner ring and the outer ring) or the roller rolling surface (see Patent Documents 5 and 6). That is, if such a crowning portion is not provided, the generated edge stress may cause peeling or the like at the relevant portion, leading to premature failure of the bearing.

Japanese Patent Application Laid-Open No. 2007-333031 Japanese Patent Laid-Open No. 2002-168253 Japanese Patent Application Laid-Open No. 2005-140168 JP 2013-139842 A Japanese Patent Application Laid-Open No. 2007-146941 JP 2016-089954 A

When crowning is provided on the rolling surface of the roller, there are cut crowning provided only at both ends in the roller axial direction and full crowning over the entire length of the roller. Further, the formation of the crowning portion is generally performed by polishing, barrel processing, or the like.

However, ceramic rollers have higher hardness than steel rollers such as ordinary bearing steel, making crowning difficult and requiring a long time to process. Therefore, crowned ceramic rollers are expensive to manufacture. However, compared to the ceramic sprayed insulation bearing and the resin film insulation bearing, the insulation performance is superior, and unlike the resin film insulation bearing, the deformation of the film and the heat insulating effect do not affect the bearing. For this reason, ceramic rollers have not been widely used as insulating bearings for electric motors, although they are excellent in performance.

Therefore, in view of such circumstances, it is an object of the present invention to provide a bearing device that is superior in performance to ceramic sprayed insulation bearings and resin film insulation bearings conventionally used for electric motors.

A bearing device according to the present invention includes a fixed-side bearing structure having a fixed-side bearing and a free-side bearing structure having a free-side bearing, wherein the free-side bearing comprises a pair of bearing rings and a pair of bearing rings. and a plurality of rolling elements interposed between the raceway surfaces of the bearing ring, wherein the rolling elements are ceramic rollers having no crowning on their rolling surfaces, and at least one of The other bearing ring facing surface of the bearing ring is formed by the crowning portions at both ends in the axial direction and the straight portion between the crowning portions, the total length of the roller of the free side bearing is L _R , and the roller of the free side bearing is The length in the axial direction of the chamfer is L _CH , the straight length of the raceway surface of the free side bearing is L _ST , the axial clearance of the fixed side bearing is δ _FXA , and the axial clearance of the free side bearing ring and roller is δ _FLA . It is set so that the following formula 1 is satisfied when

In the bearing device of the present invention, if it is set so as to satisfy the numerical formula shown in Equation 1, even if axial relative movement occurs between the raceway ring and the rollers having the crowning portion, the straight portion of the raceway surface and the rollers will not roll. It is possible to effectively prevent the contact of the face ends. Therefore, it is possible to suppress the edge stress due to the contact between the straight portion of the raceway surface and the end of the roller rolling surface.

The free-side bearing is a single-row cylindrical roller bearing in which one bearing ring constituting the inner ring has no flange and the other bearing ring constituting the outer ring has flanges on both sides in the axial direction, and at least constitutes the inner ring. The outer diameter surface of one of the bearing rings may be formed by crowning portions at both ends in the axial direction and straight portions between the crowning portions.

With this setting, even if relative axial movement occurs between the inner ring and the cylindrical rollers, it is possible to effectively prevent contact between the inner ring raceway surface straight portion and the roller rolling surface ends. Edge stress due to contact with the end of the roller rolling surface can be suppressed.

Further, the free-side bearing is a single-row cylindrical roller bearing in which the other bearing ring constituting the outer ring has no flange and one bearing ring constituting the inner ring has flanges on both sides in the axial direction, and at least the outer ring is The inner diameter surface of the other bearing ring can be formed by the crowning portions at both ends in the axial direction and the straight portion between the crowning portions.

With this setting, even if relative axial movement occurs between the outer ring and the cylindrical rollers, it is possible to effectively prevent contact between the outer ring raceway surface straight portion and the roller rolling surface ends. Edge stress due to contact with the end of the roller rolling surface can be suppressed.

It is preferable that the ceramic rollers contain silicon nitride as the main component. Silicon nitride exhibits excellent properties such as high-temperature mechanical strength, thermal shock resistance, wear resistance, corrosion resistance, electrical insulation, and high toughness. Therefore, ceramic rollers containing silicon nitride as a main component exhibit excellent performance as rollers and can provide stable bearings over a long period of time.

An electric motor according to the present invention includes at least a rotor, a stator, and a rotating shaft for transmitting rotation of the rotor to the outside, wherein the bearing device rotatably supports the rotating shaft. is.

In the electric motor of the present invention, even if relative axial movement occurs between the raceway ring having the crowning portion and the cylindrical roller, contact between the straight portion of the raceway surface and the end of the rolling contact surface of the roller can be effectively prevented. It is possible to suppress edge stress due to contact between the straight portion and the end of the roller rolling surface. For this reason, an optimal bearing device is used for electric motors, particularly traction motors for railway vehicles.

By suppressing edge stress, early bearing failure can be avoided. Therefore, it is possible to inexpensively provide a ceramic rolling element insulated cylindrical roller bearing that is superior in performance to conventionally proposed ceramic sprayed bearings and resin film insulated bearings.

1 is an enlarged cross-sectional view of a free side bearing of the present invention; FIG. FIG. 4 is an enlarged cross-sectional view of the inner ring of the free-side bearing of the present invention; 1 is an enlarged cross-sectional view of a main part of a free-side bearing according to the present invention; FIG. It is sectional drawing which shows a free side bearing and shows an inner ring|wheel roller and axial direction relative motion amount. 4 is an enlarged cross-sectional view of a fixed-side bearing; FIG. FIG. 2 is a cross-sectional view of a main part of a traction motor for railway vehicles; FIG. 5 is an enlarged cross-sectional view of a main part showing another embodiment of a free-side bearing;

An embodiment of the present invention will be described below with reference to FIGS. 1 to 7. FIG. FIG. 6 shows a traction motor for railway vehicles, which is an electric motor. A frame 11 arranged to surround the child 13 is mainly provided. A main shaft (rotating shaft) 15 is fixed to a portion including the central portion of the rotor 13 so as to pass therethrough. Further, the main motor 10 is supported by a bearing device according to the present invention so that the main shaft 15 can rotate about the axis with respect to a member disposed facing the outer peripheral surface 15a of the main shaft 15 . This bearing device includes a fixed side bearing structure M1 having a fixed side bearing 21 and a free side bearing structure M2 having a free side bearing 22 .

　The operation of the main motor 10 will be described. First, a three-phase alternating current is supplied to the coils 12a of the stator 12. At this time, a rotating magnetic field is formed around the rotor 13, and an induced current is generated in the rotor 13 by this rotating magnetic field. In this manner, a rotating magnetic field is formed around the rotor 13 and an induced current is generated in the rotor 13, thereby generating an electromagnetic force that acts to rotate the rotor 13 around the rotation axis. 13 rotates. Then, the rotation of the rotor 13 is extracted outside through the main shaft 15 .

The fixed-side bearing structure M1 of the bearing device includes a fixed-side bearing 21, a housing 25 as a fixed member,

annular parts

26, 27, and the like. The fixed side bearing 21 is a rolling bearing including a pair of bearing rings and a plurality of rolling elements interposed between the raceway surfaces of the pair of bearing rings. In this case, as shown in FIG. and a cylindrical roller 33 as a rolling element to be mounted.

Also, in this embodiment, the stationary side bearing 21 is a single-row NH-shaped cylindrical roller bearing. The NH-type cylindrical roller bearing is a cylindrical roller bearing in which an L-shaped collar ring is combined with the inner ring 31 side of the NJ-type cylindrical roller bearing. Here, the NJ-type cylindrical roller bearing has a flange on one side of the inner ring and flanges on both sides of the outer ring. Therefore, as shown in FIG. 5, the fixed-side bearing 21 has an inner ring 31 with a flange 31b on one side, an outer ring 32 with

flanges

32b, 32b on both sides, and an L-shaped flange ring 34 on the inner ring 31. combined. Cylindrical rollers 33 are held in pockets 30 a of retainer 30 interposed between inner ring 31 and outer ring 32 .

By the way, in the fixed side bearing 21, the inner ring 31, the outer ring 32, and the collar ring 34 are made of, for example, high-carbon chromium bearing steel such as JIS standard SUJ2, machine structural alloy such as SCM420, or machine structural carbon steel such as S53C. etc. The cylindrical rollers 33 as rolling elements may be made of an iron-based metal material, ceramics, or the like. Examples of iron-based metal materials include bearing steel used for rolling bearings, carburized steel, carbon steel for machine structural use, cold-rolled steel, hot-rolled steel, and the like. Ceramics are based on silicon nitride (Si ₃ N ₄ ). The ceramic material is not limited to silicon nitride, and may be zirconia (Zr), alumina (Al ₂ O ₃ ), or the like. The retainer material may be a metal material or a resin material. Metal materials include cold-rolled or hot-rolled steel, and resin materials preferably include engineering plastics (engineering plastics). engineering plastics) are included.

As shown in FIG. 6, the free side bearing structure M2 includes a free side bearing 22, a housing 35 as a fixed member,

annular parts

36 and 37, and the like. The free side bearing 22 is a rolling bearing having a pair of bearing rings and a plurality of rolling elements interposed between the raceway surfaces of the pair of bearing rings. In this case, as shown in FIG. 1, an inner ring 41 constituting one bearing ring, an outer ring 42 constituting the other bearing ring, and a raceway surface 41a of the inner ring 41 and a raceway surface 42a of the outer ring 42 are interposed. and a cylindrical roller 43 as a rolling element to be mounted. Further, it is held in a pocket 40a of the retainer 40 interposed between the raceway surface 41a of the inner ring 41 and the raceway surface 42a of the outer ring 42. As shown in FIG.

By the way, the free side bearing 22 is a single row NU cylindrical roller bearing in this embodiment. Therefore, the inner ring 41 has no flange, and the outer ring 42 has

flanges

42b, 42b on both sides. In addition,

relief portions

39, 39 are provided at axial ends of the raceway surface 42a of the outer ring 42. As shown in FIG.

The outer surface (surface facing the outer ring) of the inner ring 41 of the free side bearing 22 is defined by crowning

portions

50, 50 at both ends in the axial direction and the straight portion 51 between the crowning

portions

50, 50, as shown in FIG. forming. Thus, by having the straight portion 51, so-called cut crowning can be achieved in which the drop amount of the crowning portion can be set large. By using cut crowning in this way, it is possible to reduce the maximum surface pressure and edge stress compared to full crowning, and to stabilize the behavior of the cylindrical rollers 43 during rotation of the bearing.

In this case, no crowning portion is formed on the rolling surface 43a of the roller 43, which is the outer diameter surface of the cylindrical roller 43. The ceramic roller 43 is mainly made of silicon nitride ₍ _Si3N4 ), for example. be a component. The ceramic material is not limited to silicon nitride, and may be zirconia (Zr), alumina (Al ₂ O ₃ ), or the like. The cylindrical roller 43 has a chamfered portion 43b having a convex rounded shape at a corner portion between the end surface and the outer diameter surface (roller rolling surface).

The materials of the inner ring 41, the outer ring 42 and the retainer 40 of the free side bearing 22 are the same as the materials of the inner ring 41, the outer ring 42 and the retainer 40 of the fixed side bearing 21.

In this bearing device, as shown in FIG. 1, the total roller length of the free side bearing 22 is L _R , and the roller chamfered axial length of the free side bearing 22 (the axial length of the chamfered portion 43b) is L _{Let CH} be the length of the straight portion of the inner ring raceway surface of the free side bearing (the axial length of the straight portion 51), and L _ST be the axial clearance of the flange 42b and the roller 43 of the raceway ring (outer ring 42) of the free side bearing 22. With _δFLA and _δFXA (see FIG. 5), the axial clearance of the fixed side bearing 21 is set so as to satisfy the following equation (2).

Specifically, when the fixed-side bearing 21 is an NH-type cylindrical roller bearing with an outer diameter of 190 mm, and the free-side bearing 22 is an NU-type cylindrical roller bearing with an outer diameter of 320 mm, the free-side NU cylindrical roller bearing The total roller length L _R of the bearing 22 is 45 mm, the chamfered axial length L _CH of the free side NU cylindrical roller bearing 22 is 2 mm, and the flange 42b of the outer ring 42 of the free side NU cylindrical roller bearing 22 and the axial direction of the rollers 43 are Assuming that the clearance δ _FLA is 0.1 mm and the axial clearance δ _FXA of the fixed side NH cylindrical roller bearing 21 is 0.5 mm, the straight portion of the inner ring raceway surface of the free side NU cylindrical roller bearing 22 can be obtained from the above-described Equation 2. The length L _ST of 51 is L _ST <40.4 (mm).

In the bearing device of the present invention, if a setting is made so as to satisfy the numerical formula shown in Equation 2, even if axial relative movement occurs between the inner ring 41 having the crowning portions 50 and the cylindrical rollers 43, the inner ring The raceway surface straight portion 51 can effectively prevent contact with the roller rolling surface end, and the edge stress due to the contact between the inner ring raceway surface straight portion 51 and the roller rolling surface end can be suppressed.

In other words, by suppressing edge stress, early bearing failure can be avoided. Therefore, it is possible to inexpensively provide a ceramic rolling element insulated cylindrical roller bearing that is superior in performance to conventionally proposed ceramic sprayed bearings and resin film insulated bearings.

By the way, the cylindrical rollers 43 of the free side bearing 22 are made of ceramic rollers mainly composed of silicon nitride, so that the cylindrical rollers 43 of the free side bearing 22 have excellent high-temperature mechanical strength, thermal shock resistance, wear resistance, and corrosion resistance. , showing excellent properties such as electrical insulation and high toughness. Therefore, the ceramic rollers 43 containing silicon nitride as a main component exhibit excellent performance as cylindrical rollers, and can provide stable bearings over a long period of time.

In addition, even if axial relative movement occurs between the bearing ring having the crowning portion 50 and the cylindrical roller 43, contact between the straight portion 51 and roller rolling surface ends can be effectively prevented, Since edge stress due to contact with rolling surface ends can be suppressed, the bearing device is optimal for electric motors, particularly traction motors for railway vehicles. That is, in the bearing device in the electric locomotive main shaft motor, the free side bearing is often arranged on the gear side that mainly supports the gear load. This makes it possible to provide high-quality electric locomotive main shaft motors.

When applying cut crowning to the raceway surfaces 41a and 42a of the inner ring 41 and the outer ring 42, it is desirable to secure a long straight portion 51 of the raceway surface from the viewpoint of suppressing the maximum surface pressure and stabilizing the behavior. The rotor of the electric motor may move axially by the axial clearance of the NH side cylindrical roller bearing 21 on the stationary side during use of the electric motor. Further, the cylindrical rollers 43 of the NU-type cylindrical roller bearing 22 on the free side are axially movable by the clearance between the flange 42b of the outer ring 42 and the cylindrical rollers 43. As shown in FIG. Therefore, the inner ring 41 and the rollers 43 of the NU-type cylindrical roller bearing 22 on the free side can undergo relative axial movement equal to the sum of these (see FIG. 4).

When cut crowning is applied to the inner ring 41 of the NU-type cylindrical roller bearing 22 on the free side, if the straight portion 51 of the raceway surface of the inner ring 41 contacts the roller rolling surface end due to this axial relative movement, edge stress is generated. (see Figure 4). As a result, performance deterioration of the bearing progresses. However, in this bearing device, contact between the straight portion 51 of the raceway surface of the inner ring 41 and the end of the roller rolling surface can be effectively prevented, and progress of bearing deterioration due to edge stress can be suppressed.

If only the roller rolling surface of the free-side bearing is crowned, the axial length of the inner ring raceway surface is sufficiently longer than the straight length of the roller rolling surface, so the above problem does not arise. . When cut crowning is applied to the raceway surfaces of the inner and outer rings of an NH-type cylindrical roller bearing for the fixed side bearing, the amount of relative axial movement between each bearing ring and roller is Determined only by clearance. For this reason, the axial clearance of the fixed side bearing, which is the other bearing used on the same axis, must be considered when determining the crowning dimension of the inner ring raceway surface. It is unique to NU cylindrical roller bearings.

By the way, in the above embodiment, an NU-type cylindrical roller bearing is used as the free-side bearing 22, but an N-type cylindrical roller bearing as shown in FIG. 7 may be used. It is a cylindrical roller bearing with In this case, the N-type cylindrical roller bearing has

flanges

61b, 61b provided at both ends in the axial direction of the raceway surface 61a of the inner ring 61, and crowning portions 70 at both ends in the axial direction. 70 and a straight portion 71 between the crowning

portions

70 , 70 .

Cylindrical rollers 73 as rolling elements are held in pockets 60 a of the retainer 60 interposed between the raceway surface 61 a of the inner ring 61 and the raceway surface 62 a of the outer ring 62 . A raceway surface 61 a of the inner ring 61 is provided with

relief portions

69 , 69 at both ends in the axial direction.

Also in this case, the total length of the rollers of the free side bearing 22 is L _R , the axial length of the chamfered rollers of the free side bearing 22 is L _CH , the straight length of the raceway surface of the free side bearing is L _ST , and the length of the straight portion of the free side bearing is L ST. The axial clearance of the bearing rings and rollers is _δFLA , the axial clearance of the fixed-side bearing is _δFXA , and the relationship of Equation 2 above is established.

Therefore, even if the free-side bearing 22 is an N-type cylindrical roller bearing shown in FIG. It is possible to achieve the same effects as in the case of using the NU-type cylindrical roller bearing.　

That is, when the N type is used on the free side, the same effect can be obtained by considering the axial clearance of the fixed side bearing 22 when determining the crowning dimension of the outer ring 62.

In this case, even if relative axial movement occurs between the outer ring 62 and the cylindrical rollers 73, contact between the raceway surface straight portion 71 of the outer ring 62 and the roller rolling surface end can be effectively prevented. 71 It is possible to suppress the edge stress due to the contact with the roller rolling surface end.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible. Although used, N-type cylindrical roller bearings, NUP-type cylindrical roller bearings, ball bearings (deep groove ball bearings), and the like may also be used. The NUP type cylindrical roller bearing is a cylindrical roller bearing in which an inner ring has a flange on one side, an outer ring has flanges on both sides, and a flange ring is combined with the inner ring side.

Also, the shape of the crowning portion 50 (70) may be linear (tapered surface), a single arc, or a combination of a plurality of arcs. Applications of the bearing device are not limited to traction motors for electric motors and railway vehicles, but can be used for various devices and structures such as general machinery, electric machinery, and transportation machinery.

The inner ring and outer ring may have a straight portion and a crowning portion on the raceway surface. That is, the outer diameter surface of the inner ring has the straight portion and the crowning portion, and the inner diameter surface of the outer ring has the straight portion and the crowning portion. Further, the drop amount of the crowning portions formed on the inner ring and the outer ring can be arbitrarily set as long as the above-described formula (2) is satisfied for the bearing device.

The bearing device of the present invention can be used for electric motors such as traction motors for railway vehicles. An electric motor, for example, includes a rotor, a stator, and a rotating shaft that transmits the rotation of the rotor to the outside.

10 main motor 12 stator 13 rotor 15 main shaft (rotating shaft)
21 fixed side bearing 22 free side bearing 41 inner ring 41a raceway surface 42 outer ring 42a raceway surface 43 cylindrical roller (ceramic roller)
43a rolling surface 50 crowning portion 51 straight portion 61 inner ring 61a raceway surface 62 outer ring 62b raceway surface 70 crowning portion 71 straight portion M1 fixed side bearing structure M2 free side bearing structure

Claims

A bearing device comprising a fixed-side bearing structure having a fixed-side bearing and a free-side bearing structure having a free-side bearing,
The free-side bearing is a rolling bearing including a pair of bearing rings and a plurality of rolling elements interposed between the raceway surfaces of the pair of bearing rings. At least one of the bearing rings has a bearing ring facing surface of the other bearing ring formed by a crowning portion at both ends in the axial direction and a straight portion between the crowning portions, and the free side L R is the total roller length of the bearing, L CH is the roller chamfer axial length of the free side bearing, L ST is the length of the raceway surface straight part of the free side bearing, δXA is the axial clearance of the fixed side bearing, and δ XA is the free side bearing. A bearing device characterized by being set so as to satisfy the following equation (1), where δFLA is the axial clearance between the bearing rings and rollers of the side bearing.
The free-side bearing is a single-row cylindrical roller bearing in which one bearing ring constituting the inner ring has no flange and the other bearing ring constituting the outer ring has flanges on both sides in the axial direction, and at least constitutes the inner ring. 2. The bearing device according to claim 1, wherein the outer diameter surface of one of the bearing rings is formed by crowning portions at both ends in the axial direction and a straight portion between the crowning portions.
The free side bearing is a single-row cylindrical roller bearing in which the other bearing ring constituting the outer ring has no flange and one bearing ring constituting the inner ring has flanges on both sides in the axial direction, and constitutes at least the outer ring. 2. A bearing device according to claim 1, wherein the inner diameter surface of the other bearing ring is formed by crowning portions at both ends in the axial direction and a straight portion between the crowning portions.
The bearing device according to any one of claims 1 to 3, wherein the ceramic rollers are mainly composed of silicon nitride.
An electric motor comprising at least a rotor, a stator, and a rotating shaft for transmitting the rotation of the rotor to the outside,
An electric motor, wherein the rotating shaft is rotatably supported by the bearing device according to any one of claims 1 to 4.