JP6508972B2 - Bearing device and magnetic recording device - Google Patents

Description

The present invention relates to a bearing device and a magnetic recording device.

  2. Description of the Related Art In recent years, with high density recording and high capacity of a hard disk (magnetic recording device), high cleanliness is required for components used for the hard disk. In a hard disk, when the magnetic head is moved by the rolling bearing on the disk, the grease inside the rolling bearing scatters and oil droplets adhere to the disk or magnetic head, causing a problem of data read / write failure. there were.

  Therefore, conventionally, an annular plate member that spreads radially outward toward the outer ring of the rolling bearing is fixed to the outer surface of the shaft member that supports the rolling bearing in the fitted state, thereby suppressing air flow inside the rolling bearing. There is known a bearing device that suppresses the spread of grease on rolling bearings (see, for example, Patent Document 1). In the bearing device described in Patent Document 1, in order to enhance the effect of suppressing the scattering of grease, the plate member is formed into a stepped shape to narrow the gap between the plate member and the seal member of the rolling bearing and the outer ring respectively. By forming a long labyrinth (narrow gap), the air flow inside the rolling bearing is further reduced.

JP, 2013-48005, A

  However, if the plate member has a stepped shape as in the bearing device described in Patent Document 1, there is a problem that the shape of the plate member is complicated and difficult to process, and the cost becomes high.

  The present invention has been made in view of the above-described circumstances, and it is an object of the present invention to provide a rolling bearing, a bearing device and a magnetic recording device capable of suppressing the scattering of grease by suppressing the cost.

In order to achieve the above object, the present invention provides the following means.
According to the present invention, an inner ring and an outer ring coaxially disposed, a plurality of rolling elements contained in an annular space between the inner ring and the outer ring, and a plurality of rolling elements are provided along the periphery of the annular space. And a cage for holding the roller so as to be able to roll in a state of being equally spaced in a direction, wherein the inner ring and the outer ring have rolling surfaces formed of curved surfaces in contact with the rolling elements, and the rolling of the inner ring Two of the rolling bearings whose dimension from the surface to one end in the axial direction is longer than the dimension from the rolling surface in the outer ring to one end on the same side in the axial direction ; The end portions are axially spaced from one another such that the ends are axially close to one another,
A shaft member which is fitted to each of the inner rings of the two rolling bearings and is adhered to the inner surface of the inner ring at a position shifted to the one end side with respect to the back side of the rolling surface by an adhesive;
A spacer which is axially interposed between the outer rings and which forms an axial gap between the inner rings;
The other end of the outer ring protrudes in the axial direction more than the other end of the inner ring in a state where each inner ring is pressed in a direction to relatively approach in the axial direction and the preload is applied to the rolling bearing To provide a bearing device .

  According to the present invention, with the rotation of the inner ring or the outer ring about the axis, the plurality of rolling elements are individually rolled between the respective rolling contact surfaces while being spaced apart in the circumferential direction by the cage. The inner and outer rings rotate relative to each other about the axis. Therefore, if the two rolling bearings are arranged at intervals in the axial direction, and the shaft member is fixed in the fitting state to each inner ring and each outer ring is fixed in the fitting state to the outer fitting member, these two rolling The shaft member and the outer fitting member can be relatively rotated about the axis by the bearing.

  Here, while forming a gap in the axial direction between the inner rings by sandwiching a spacer in the axial direction between the outer rings of the two rolling bearings, the inner rings are mutually close to the outer surface of the shaft member fitted in each inner ring. If it fixes by an adhesive agent in the state which pressed in the direction to be made, a bearing apparatus which improved rotational accuracy by pre-loading two rolling bearings can be comprised.

In this case, if the back surface of the rolling surface on the inner surface of the inner ring is made an adhesive surface with the shaft member, the rolling surface of the inner ring is distorted when the adhesive cures, the rotational load torque increases, and heat is generated inside the rolling bearing. The grease becomes hot and easily scattered. On the other hand, in the present invention, by increasing the dimension from the rolling surface of the inner ring to one end in the axial direction, the bonding surface with the shaft member is one more than the rear surface of the rolling surface on the inner surface of the inner ring. It can be secured at a position shifted to the end side of the Therefore, it is possible to reduce the distortion of the rolling surface of the inner ring due to the curing of the adhesive fixing the inner ring and the shaft member, and to suppress the scattering of grease due to the increase of the rotational load torque. Moreover, the length of the outer ring can be shortened, and the cost of the outer ring can be reduced.
According to the present invention, the inner ring and the outer ring of the two rolling bearings are coaxially rotatably supported by the shaft member. Further, the spacer can form a gap between the inner rings without increasing the axial length of the outer rings. As a result, it is possible to apply a preload without lengthening the dimension of the outer ring which requires accuracy as compared with the spacer, and it is possible to suppress the cost of the outer ring and to improve the rotational accuracy of each rolling bearing. The spacer may be a single annular member, or may be a projection formed to project radially inward on the inner surface of the outer fitting member into which the outer ring is fitted.
In this case, the annular hub cap forms a labyrinth between the other end of the outer ring and the shaft member by the amount by which the other end of the outer ring projects in the axial direction more than the other end of the inner ring. It can be made easy to attach to a shaft member.
In the above-mentioned invention, an annular hub cap may be provided, which is fixed to the outer surface of the shaft member and extends radially outward toward the inner surface of the other axial end of the outer ring.
With such a configuration, a long labyrinth can be formed between the shaft member and the inner surface of the outer ring by the hub cap, air flow inside the rolling bearing can be suppressed, and scattering of grease can be reduced.

In the above invention, the dimension from the rolling surface to the one end in the axial direction in the inner ring may be the same as the dimension from the other end.
With this configuration, when assembling the rolling bearing, it is not necessary to care about the front and back of the inner ring. Therefore, the assembly can be facilitated and the cost can be reduced.

  In the above invention, the dimension from the rolling contact surface to the other end in the axial direction in the outer ring may be longer than the dimension to the one end.

  By this configuration, the other end in the axial direction from the rolling contact surface in the outer ring is the rolling contact surface in the inner ring, as compared with the case where the dimensions from the rolling contact surface of the outer ring to both axial ends are the same. Can project axially longer than the other end in the axial direction. Thus, when the shaft member is fitted to the inner ring and the annular hub cap is disposed between the shaft member and the other axial end of the outer ring, the outer surface of the hub cap and the inner surface of the outer ring A narrow gap (labyrinth) can be easily formed.

  The present invention is any one of the above two rolling bearings, wherein the one end of the outer ring is arranged axially spaced from each other in the direction in which the one ends of the outer ring are axially close to each other; A shaft member which is fitted to each inner ring and shifted to the one end side with respect to the back of the rolling surface on the inner surface of the inner ring is axially stuck between the outer ring and a shaft member adhered by an adhesive And a spacer for forming a gap in the axial direction between the inner rings, each inner ring being pressed in a direction relatively close in the axial direction, and in a state where a preload is applied to the rolling bearing, A bearing device is provided, the other end of which projects more axially than the other end of the inner ring.

The present invention provides a bearing device according to claim 3 or 4 , a base member to which the shaft member of the bearing device is fixed, a magnetic recording medium capable of recording magnetic information, and the outer ring of the rolling bearing. A magnetic recording apparatus comprising: a swing arm mounted on the magnetic recording medium for recording magnetic information on the magnetic recording medium; and a drive unit for driving the swing arm.

  According to the present invention, the cost can be suppressed and the scattering of grease can be prevented by the bearing device, and the swing arm can be stably oscillated around the shaft member with respect to the base member. Therefore, the swing arm can be stably reciprocated with respect to the magnetic recording medium by the drive unit, and magnetic information can be accurately recorded.

  ADVANTAGE OF THE INVENTION According to this invention, it is effective in the ability to hold down cost and to prevent scattering of grease.

It is a schematic block diagram of a hard disk drive provided with a bearing device concerning one embodiment of the present invention. It is a longitudinal cross-sectional view of the bearing apparatus of FIG. It is the elements on larger scale of the 2nd rolling bearing and shaft in the bearing apparatus of FIG. It is a figure which shows the relationship of the rotation angle of a rolling bearing and torque which made the back of the rolling contact surface in the inner surface of an inner ring | wheel the adhesion surface with a shaft as a reference example of one Embodiment of this invention. It is a longitudinal cross-sectional view of the bearing apparatus as a 1st modification of one embodiment of one embodiment of the present invention. It is a longitudinal cross-sectional view of the bearing apparatus as a 2nd modification of one embodiment of one embodiment of the present invention.

Hereinafter, a rolling bearing, a bearing device, and a magnetic recording device according to an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the hard disk drive (magnetic recording device) 100 according to the present embodiment includes a substantially rectangular box-shaped base housing (base member) 1, a bearing device 3 fixed to the base housing 1, and bearings. The apparatus includes a swing arm 5 supported so as to be movable relative to the base housing 1 by the device 3, a drive unit 7 such as a voice coil motor for swinging the swing arm 5, and a magnetic recording medium 9 capable of recording magnetic information. ing.

  The swing arm 5 has a magnetic head 6 at its front end for writing magnetic information to the magnetic recording medium 9 and reading the magnetic information recorded on the magnetic recording medium 9. Further, the swing arm 5 has a bearing fitting hole (not shown) for fitting the bearing device 3 at its base end.

  As shown in FIG. 2, the bearing device 3 includes a shaft (shaft member) 31 and a first rolling bearing (rolling bearing) 10 and a first rolling bearing (a rolling bearing) arranged coaxially with a shaft 31 spaced apart in the axial direction. A rolling bearing (rolling bearing) 20, a spacer 33 axially interposed between the rolling bearings 10 and 20, and an annular hub cap 35 fixed to the shaft 31 are provided.

  The shaft 31 is formed in a hollow substantially cylindrical shape, and has a flange-shaped flange portion 31 a protruding radially outward over the entire circumference at one end in the axial direction. The flange portion 31 a is fixed to the base housing 1 and the shaft 31 is disposed on the central axis C. The first rolling bearing 10, the spacer 33, the second rolling bearing 20, and the hub cap 35 are fitted in the shaft 31 in order from the flange portion 31a side.

  The first rolling bearing 10 includes an annular inner ring 11 and an outer ring 13 coaxially disposed, a plurality of rolling elements 15 contained in an annular space between the inner ring 11 and the outer ring 13, and A retainer (a cage) 17 which holds the movable body 15 so as to be capable of rolling in the circumferential direction of the annular space at equal intervals, and both axial ends of the annular space between the inner and outer rings are closed. And shield plates 19A and 19B.

The inner ring 11 and the outer ring 13 respectively have rolling surfaces 11 a and 13 a formed of curved surfaces in contact with the rolling element 15.
A rolling surface 11a is formed circumferentially at a position slightly closer to the end 11c than the axial center of the outer ring 11 in the outer surface, and the dimension from the rolling surface 11a to one end 11b in the axial direction Is longer than the dimension from the rolling surface 11a to the other end 11c in the axial direction. The dimension from the rolling surface 11a to the end 11b of the inner ring 11 is such that the bonding surface with the adhesive 31 with the adhesive is limited to the end 11b side of the inner surface of the inner ring 11 rather than the back of the rolling surface 11a. The shaft 31 has such a length that the inner ring 11 can be sufficiently fixed.

  The outer ring 13 has a stepped shape including thin portions at both end portions in the axial direction and a thick portion at the central portion in the axial direction where the inner surface protrudes radially inward of the thin portions. In the outer ring 13, a rolling surface 13a is formed on the inner surface of the thick portion in the circumferential direction, and the dimension from the rolling surface 13a to one end 13b in the axial direction is from the rolling surface 13a to the axial direction It is shorter than the dimension up to the other end 13c of.

  The inner ring 11 and the outer ring 13 are formed so that the dimension from the rolling surface 11 a to the end 11 b of the inner ring 11 is longer than the dimension from the rolling surface 13 a to the end 13 b of the outer ring 13. Further, the dimension from the rolling surface 13 a to the end 13 c of the outer ring 13 is formed longer than the dimension from the rolling surface 11 a to the end 11 c of the inner ring 11. Accordingly, in the first rolling bearing 10, the end 11b of the inner ring 11 protrudes axially longer than the end 13b of the outer ring 13, and the end 13c of the outer ring 13 is longer in the axial direction than the end 11c of the inner ring 11. It protrudes.

The respective rolling elements 15 are arranged at equal intervals in the circumferential direction by the retainers 17 and are respectively held rollably between the rolling surface 11 a of the inner ring 11 and the rolling surface 13 a of the outer ring 13.
The shield plates 19A and 19B are, for example, ring-shaped plate-like members made of metal or plastic, and can be manufactured by press molding, resin molding, or the like. The shield plates 19A and 19B are respectively butted against the thick portion of the outer ring 13 and held in a fitted state by the thin portion. The inner edge portion has a slight gap in the radial direction with the inner ring 11 ing.

  The second rolling bearing 20 has the same configuration as the first rolling bearing 10. That is, the second rolling bearing 20 includes the inner ring 21 and the outer ring 23, a plurality of rolling elements 25, a retainer 27 and shield plates 29A and 29B.

The inner ring 21 and the outer ring 23 each have rolling surfaces 21 a and 23 a formed of curved surfaces in contact with the rolling elements 25.
A rolling surface 21a is formed in the circumferential direction at a position slightly closer to the end 21c than the axial center of the outer ring 21 in the outer surface, and the dimension from the rolling surface 21a to one axial end 21b Is longer than the dimension from the rolling surface 21a to the other end 21c in the axial direction. Also in the dimension from the rolling surface 21a to the end 21b of the inner ring 21, when the bonding surface with the adhesive 31 with the adhesive is limited to the end 21b side of the inner surface of the inner ring 21 rather than the back of the rolling surface 21a. The shaft 31 has such a length that the inner ring 21 can be sufficiently fixed.

  Similar to the outer ring 13, the outer ring 23 has a stepped shape including thin portions at both end portions in the axial direction and a thick portion at the central portion in the axial direction. The outer race 23 has a rolling surface 23a formed on the inner surface of the thick portion in the circumferential direction, and the dimension from the rolling surface 23a to one end 23b in the axial direction is axial from the rolling surface 23a. It is shorter than the dimension up to the other end 23c.

  The inner ring 21 and the outer ring 23 are formed so that the dimension from the rolling surface 21 a to the end 21 b of the inner ring 21 is longer than the dimension from the rolling surface 23 a to the end 23 b of the outer ring 23. Further, the dimension from the rolling surface 23 a to the end 23 c of the outer ring 23 is formed longer than the dimension from the rolling surface 21 a to the end 21 c of the inner ring 21. Therefore, in the second rolling bearing 20, the end 21b of the inner ring 21 protrudes axially longer than the end 23b of the outer ring 23, and the end 23c of the outer ring 23 is longer in the axial direction than the end 21c of the inner ring 21. It protrudes.

The respective rolling elements 25 are arranged at equal intervals in the circumferential direction by the retainers 27, and are rotatably held between the rolling surface 21a of the inner ring 21 and the rolling surface 23a of the outer ring 23.
The shield plates 29A and 29B are plate-like members similar to the shield plates 19A and 19B, but are abutted against the thick-walled portion of the outer ring 23 and held in a fitted state by the thin-walled portion. There is a slight gap in the radial direction between the two.

  The rolling bearings 10 and 20 configured in this manner are disposed such that the end portions 13 b and 23 b of the outer rings 13 and 23 face each other in the axial direction. In the rolling bearings 10 and 20, the shaft 31 is fitted to the inner rings 11 and 21, respectively, and the outer rings 13 and 23 are fitted to the bearing fitting holes of the swing arm 5, respectively.

  The spacer 33 has, for example, a ring shape having an outer diameter dimension slightly smaller than that of the outer rings 13 and 23 and an inner diameter dimension slightly smaller than that of the outer rings 13 and 23. In the spacer 33, the end 13b of the outer race 13 of the first rolling bearing 10 is butted against one end in the axial direction, and the end 23b of the outer race 23 of the second rolling bearing 20 at the other end in the axial direction. Is hit. By the spacer 33 being sandwiched between the outer rings 21 and 23, a gap is formed in the axial direction between the inner rings 11 and 21.

The bearing device 3 configured in this manner has the inner surface of the inner rings 11 and 21 and the shaft 31 in a state in which the inner rings 21 are pressed in the axial direction such that the inner rings 11 and 21 of the rolling bearings 10 and 20 approach each other. The outer surface is bonded by an adhesive. Specifically, among the inner surfaces of the inner rings 11 and 21, the bonding surface with the adhesive 31 and the bonding surface with the shaft 31 is limited to a position shifted to the end portions 11b and 21b from the back of the rolling surfaces 11a and 21a. ing.
As a result, the rolling bearings 10 and 20 are preloaded, and the inner and outer rings 11 and 21 and the outer rings 13 and 23 and the rolling elements 15 and 25 are kept in contact with each other without a gap.

Further, the outer rings 13 and 23 of the rolling bearings 10 and 20 and the inner surface of the bearing fitting hole of the swing arm 5 are also joined by an adhesive.
As an adhesive agent used for adhesion | attachment of the inner ring | wheels 11 and 21 and the outer ring | wheels 13, 23, an anaerobic adhesive agent, a thermosetting adhesive agent, etc. are mentioned, for example.

  As shown in FIG. 3, the hub cap 35 is fixed to the outer surface on the tip end side of the shaft 31 and is disposed between the shaft 31 and the end 23 c of the outer ring 23 of the second rolling bearing 20. The hub cap 35 has an outer dimension slightly smaller than the inner surface of the end 23 c of the outer ring 23, and a narrow gap (hereinafter referred to as a narrow gap) with the inner surface of the end 23 c of the outer ring 23. "Labyrinth L" is formed.

Next, the operation of the bearing device 3 and the hard disk drive device 100 will be described.
In the rolling bearings 10 and 20 according to the present embodiment, the rolling elements 15 and 25 are arranged at intervals in the circumferential direction by the retainers 17 and 27 as the inner rings 11 and 21 or the outer rings 13 and 23 rotate about their axes. The inner races 11 and 21 fixed to the shaft 31 and the outer races 13 and 23 fitted to the swing arm 5 by rolling individually between the rolling faces 11 a and 13 a and between the rolling faces 21 a and 23 a in the state of Relative rotation around the axis.

  Therefore, in the hard disk drive apparatus 100 according to the present embodiment, the swing arm 5 fixed to the outer rings 13 and 23 of the rolling bearings 10 and 20 by the operation of the drive unit 7 is fixed to the base housing 1 to which the shaft 31 is fixed. It is pivoted around the central axis C. Then, the magnetic head 6 is reciprocated on the magnetic recording medium 9 in accordance with the swing of the swing arm 5.

  For example, when the swing arm 5 is operated at high speed by the drive unit 7, the magnetic head 6 is instantaneously moved to data recorded at a predetermined position of the magnetic recording medium 9, and the magnetic head 6 records on the magnetic recording medium 9. It can read and write magnetic information.

  Here, a gap is formed between the inner rings 11 and 21 with the spacer 33 interposed between the outer rings 13 and 23 of the two rolling bearings 10 and 20, and the inner rings 11 and 21 fitted with the shaft 31 are close to each other. By fixing the inner rings 11 and 21 to the shaft 31 with an adhesive in a pressed state, it is possible to maintain the state in which the two rolling bearings 10 and 20 are preloaded and to improve the rotation accuracy.

  In this case, when the back surfaces of the rolling surfaces 11a and 21a on the inner surface of the inner rings 11 and 21 are adhesive surfaces with the shaft 31, the rolling surfaces 11a and 21a of the inner rings 11 and 21 are distorted when the adhesive cures. For example, as indicated by reference numeral B in FIG. 4, the rotational load torque is increased. As a result, due to the heat generation, the grease inside the rolling bearing 20 becomes high temperature and is easily scattered. If oil droplets adhere to the disk or magnetic head, this may cause data read / write failure. FIG. 4 shows the fluctuation of torque when the rolling bearing is rotated 360 °, where A is an example where there is no distortion in the rolling surface of the inner ring, and B is at the rolling surface of the inner ring. This is an example when there is distortion.

  On the other hand, in the bearing device 3 according to the present embodiment, since the dimensions from the rolling surfaces 11a, 21a of the inner rings 11, 21 to the end portions 11b, 21b are elongated, the inner surface of the inner rings 11, 21 The bonding surface with the shaft 31 by the adhesive can be secured in a range limited to the end portions 11 b and 21 b side rather than the back of the running surfaces 11 a and 21 a.

  Therefore, it is not necessary to use the back of the raceway surfaces 11a and 21a on the inner surface of the inner races 11 and 21 as the bonding surface, and the distortion of the raceway surfaces 11a and 21a due to the curing of the adhesive for fixing the It can be reduced. As a result, the rotational load torque can be kept constant as shown by the symbol A in FIG. 4, and the scattering of grease due to the increase in the rotational load torque can be suppressed.

  Further, by using the spacer 33, it is possible to form a gap between the inner rings 11 and 21 while suppressing the length of the outer rings 13 and 23 required to have processing accuracy as compared with the spacer 33. Therefore, pressure can be applied to the rolling bearings 10 and 20 with a simple configuration to improve the rotation accuracy, and the lengths of the outer rings 13 and 23 can be shortened to suppress the cost of the outer rings 13 and 23.

  Further, according to the hard disk drive device 100 according to the present embodiment, the cost is reduced by the bearing device 3 to prevent grease from scattering, and the swing arm 5 is stably rocked around the shaft 31 with respect to the base housing 1 be able to. Therefore, the swing arm 5 can be stably reciprocated with respect to the magnetic recording medium 9 to record magnetic information with high accuracy.

  In the present embodiment, the raceway surfaces 11 a and 21 a are formed at positions slightly closer to the end portions 11 b and 21 b than the axial center of the outer surface of the inner rings 11 and 21. Instead of this, for example, the rolling surfaces 11a, 21a are formed circumferentially at the axial center of the outer surface of the inner rings 11, 21 from the rolling surfaces 11a, 21a to the end portions 11b, 21b. The rolling surfaces 11a and 21a to the end portions 11c and 21c may have the same dimensions.

  In this way, when assembling the rolling bearings 10 and 20, it is not necessary to worry about the front and back of the inner rings 11 and 21, and the assembly can be simplified and the cost can be reduced.

  Further, in the present embodiment, the spacer 33 has been described as an example, but instead, as shown in FIG. 5, the inner surface of the sleeve (outer fitting member) 37 to which the outer rings 13 and 23 are fitted It is good also as adopting a convex part 37a formed so that it might project in the inside as a spacer.

  In this case, the end 13b of the outer ring 13 of the first rolling bearing 10 and the end 23b of the outer ring 23 of the second rolling bearing 20 respectively abut against the projection 37a of the sleeve 37 to form a gap between the inner rings 11 and 21. You should do it. Further, the bearing device 3 may be fitted to the swing arm 5 with the sleeve 37 interposed therebetween.

  Further, in the present embodiment, the ring-shaped spacer 33 having the inner diameter dimension slightly smaller than the inner diameter dimension of the outer rings 13 and 23 has been described as an example. Instead of this, for example, as shown in FIG. 6, a ring-shaped spacer 39 having an inner diameter dimension slightly larger than the outer dimensions of the inner rings 11 and 21 is employed, and the inner surface of the spacer 39 and the outer surface of the inner rings 11 and 21 Labyrinths L may be respectively formed between the two.

  By doing this, air flow between the first rolling bearing 10 and the second rolling bearing 20 can be suppressed, and grease scattering can be further reduced. In this case, the spacer 39 has convex portions 39a and 39b protruding in the axial direction at both end portions in the axial direction, and the convex portions 39a and 39b are fitted to the inner surfaces of the thin portions of the outer rings 13 and 23, respectively. The spacer 39 may be positioned in the radial direction.

1 Base housing (base member)
3 Bearing device 5 Swing arm 7 Drive part 9 Magnetic recording medium 10 1st rolling bearing (rolling bearing)
11, 21 Inner ring 11a, 13a, 21a, 23a Rolling surface 13, 23 Outer ring 15, 25 Rolling element 17, 27 Retainer (retainer)
20 2nd rolling bearing (rolling bearing)
31 shaft (shaft member)
33, 37a, 39 Spacer 35 Hub Cap 100 Hard Disk Drive Device (Magnetic Recording Device)

Claims (5)

Inner and outer rings coaxially arranged,
A plurality of rolling elements contained in an annular space between the inner ring and the outer ring;
And a cage configured to hold the plurality of rolling elements so as to be capable of rolling in a state in which the plurality of rolling elements are arranged at equal intervals in the circumferential direction of the annular space,
The inner ring and the outer ring have rolling surfaces formed of curved surfaces in contact with the rolling elements,
The rolling bearing in which the dimension from the rolling surface to one end in the axial direction in the inner ring is longer than the dimension from the rolling surface to the one end on the same side in the axial direction in the outer ring , The first end portions of the outer ring are arranged axially spaced from each other in such a direction that they are axially close to each other,
A shaft member which is fitted to each of the inner rings of the two rolling bearings and is adhered to the inner surface of the inner ring at a position shifted to the one end side with respect to the back side of the rolling surface by an adhesive;
A spacer which is axially interposed between the outer rings and which forms an axial gap between the inner rings;
The other end of the outer ring protrudes in the axial direction more than the other end of the inner ring in a state where each inner ring is pressed in a direction to relatively approach in the axial direction and the preload is applied to the rolling bearing Bearing device. 2. The bearing device according to claim 1, wherein the dimension from the rolling surface to the one end in the axial direction of the inner ring is the same as the dimension from the other end . 3. The bearing device according to claim 1 or 2, wherein the dimension from the rolling surface to the other end in the axial direction in the outer ring is longer than the dimension from the one end . The bearing device according to claim 3 , further comprising an annular hub cap fixed to the outer surface of the shaft member and radially outwardly extending toward the inner surface of the other axial end of the outer ring. A bearing device according to claim 3 or 4 ;
A base member to which the shaft member of the bearing device is fixed;
A magnetic recording medium capable of recording magnetic information;
A swing arm attached to the outer ring of the rolling bearing and causing the magnetic recording medium to record magnetic information;
And a driving unit for driving the swing arm.

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