WO2009139276A1

WO2009139276A1 - Bearing for swing arm and method of manufacturing bearing for swing arm

Info

Publication number: WO2009139276A1
Application number: PCT/JP2009/057963
Authority: WO
Inventors: 中関　嗣人
Original assignee: Ntn株式会社
Priority date: 2008-05-16
Filing date: 2009-04-22
Publication date: 2009-11-19

Abstract

A support point bearing unit (100, 200, 300, 400) stabilizes torque of a swing arm by reducing a variation in a rolling body load to facilitate control of the load. Either an inner raceway surface (141, 142, 120, 121, 110, 111) or an outer raceway surface (122) with which balls (109) make contact is constructed from two contact surfaces (circular conical raceway surfaces (120, 121) (141, 142)) having a circular conical surface shape and crossing each other. A ball (109) is in contact with contact surfaces, which have a circular conical surface shape, at three points.

Description

Swing arm bearing and manufacturing method of swing arm bearing

The present invention relates to a swing arm bearing (fulcrum bearing unit) used in a hard disk drive, and more specifically to a fulcrum bearing unit that stabilizes the torque of the swing arm. The present invention also relates to a method for manufacturing the swing arm bearing.

A swing arm used for a hard disk used as an external storage device of a computer reads and writes information using a magnetic head on an aluminum or glass disk coated with a magnetic material. This magnetic head is attached to one end of a driving body called a swing arm. Then, when the swing arm is driven to swing around the fulcrum bearing unit by the voice coil motor, the magnetic head attached to one end of the swing arm is moved to an arbitrary position on the hard disk, and information is stored in the hard disk. Enables reading and writing.

The conventional fulcrum bearing unit incorporated in the center of gravity of the swing arm for swinging the swing arm has the following configuration. FIG. 30 is a schematic cross-sectional view showing the structure of a fulcrum bearing unit incorporated in a swing arm conventionally used. The swing arm 1 shown in FIG. 30 has a magnetic head 2 attached to one end, a voice coil motor (not shown) at the other end, and a fulcrum bearing unit 500 incorporated at the center of gravity.

In order for the magnetic head 2 to accurately read and write information on the hard disk, the swing arm 1 must be driven to swing so that the magnetic head 2 can move to an accurate position. For this reason, the fulcrum bearing unit 500 that supports the swing arm 1 is required to have high rigidity. In order to ensure rigidity, the parts constituting the fulcrum bearing unit 500 shown in FIG. 30 need to be incorporated with an appropriate preload. Specifically, first, two outer rings 104 in FIG. 30 and a spacer 105 provided between the two outer rings 104 are directly connected to the swing arm 1 so that the two outer rings 104 do not contact each other. The sleeve 102 is fixed. Subsequently, one of the two inner rings 103 in FIG. 30 is fixed to the shaft 101 existing in the center portion of the fulcrum bearing unit 500. This is the inner ring 103 installed on the lower side in FIG. Here, a ball 109 is interposed between the outer ring 104 and the inner ring 103. Then, as shown in FIG. 1, a preload F is applied in the axial direction, that is, the vertical direction of the paper surface, and the other inner ring 103 is fixed to the shaft 101. As a result, a preload F is applied to each component constituting the fulcrum bearing unit 500, and fixing for ensuring rigidity is possible.

With the recent expansion of hard disk capacity, the magnetic head 2 is required to have higher positional accuracy. For this reason, the fulcrum bearing unit 500 is required to have higher rigidity. For hard disk drives of 1.8 inches or less, the fulcrum bearing unit 500 is also required to be thin as the disk is thinned. Further, the fulcrum bearing unit 500 having a large number of components is required to reduce the cost by reducing the number of components.

FIG. 31 is a schematic cross-sectional view showing the structure of a conventional fulcrum bearing unit in which the number of parts is reduced. In FIG. 31, the hatched portion represents a cross section. A fulcrum bearing unit 600 shown in FIG. 31 does not have an equivalent to the outer ring 104 shown in the fulcrum bearing unit 500 shown in FIG. 30, and a ball 109 as a rolling element is formed on the surface of the sleeve 102 facing the inner ring 103. A bearing groove 110 is formed as a raceway surface for rolling. Therefore, the number of parts is reduced by the amount that the outer ring 104 is not provided, and the cost can be reduced. Furthermore, the rotational accuracy of the swing arm 1 can also be improved by eliminating the portion where the sleeve 102 and the outer ring 104 shown in FIG. 30 are fitted. Similarly, a hard disk swing arm having a structure in which a bearing groove as a raceway surface for rolling balls is formed directly on the outer peripheral surface of the shaft and on the sleeve of the swing arm without providing an outer ring or an inner ring. This is disclosed in Japanese Utility Model Laid-Open No. 7-6969 (Patent Document 1).

On the other hand, as a measure for reducing the thickness of the fulcrum bearing unit, for example, as disclosed in Japanese Patent Laid-Open No. 10-318255 (Patent Document 2), the inner ring is made thinner than the outer ring. There is a method of eliminating the spacer that is designed and arranged between the two outer rings by making the two outer rings contact each other. By using such a method, the thickness of the entire fulcrum bearing unit can be reduced by an amount corresponding to the thickness of the spacer being eliminated.

Also, in order to increase the rigidity, the contact stress applied to the balls interposed between the outer ring and the inner ring is increased by increasing the preload as described above. As a result, the rigidity of the entire fulcrum bearing unit can be increased. However, as the contact stress increases, the friction torque applied to the ball increases. Accordingly, there is a possibility that plastic deformation occurs in the region including the ball or the raceway surface in contact with the ball due to a large friction torque. For this reason, an idea has been made to increase the number of balls to be incorporated as a countermeasure. Or, for example, in the fulcrum bearing unit disclosed in Japanese Patent Application Laid-Open No. 2006-316915 (Patent Document 3), the outer ring or the inner ring is divided into two in the axial direction, that is, the vertical direction, and each of the divided outer rings or inner rings is divided. The member and the ball can be brought into contact with each other. A fulcrum bearing unit designed to increase rigidity by increasing the number of contact points in this way has also been devised.

Japanese Utility Model Publication No. 7-6969 Japanese Patent Laid-Open No. 10-318255 JP 2006-316915 A

However, all of the swing arm bearings disclosed in Patent Document 1, Patent Document 2, and Patent Document 3 have a bearing groove formed in an R-surface shape as a raceway surface for rolling the ball on the inner ring side. Used on both the outer ring side and the outer ring side. However, in such a configuration, the position of the ball can be determined at one place, but the contact point can freely move on the raceway surface of the bearing groove surface. As a result, the contact angle is not fixed. For example, in Patent Document 3, there are four contact points between balls (rolling elements) and bearing grooves (track grooves). When the contact is made at four points as in Patent Document 3, the processing becomes troublesome.

If the contact angle is not fixed, it is difficult to control the rolling element load, which is the force applied to the ball, to be substantially constant. A fulcrum bearing unit for a hard disk is generally required to have a low torque during operation and a small fluctuation in torque, but if the fluctuation in rolling element load becomes large, it is difficult to stabilize the torque of the fulcrum bearing unit. Become.

Also, due to the recent demand for cost reduction of hard disk drives, there is also a demand for cost reduction of swing arm bearings. In addition, the conventional swing arm bearings including the swing arm bearings described in Patent Documents 1 to 3 cannot be said to sufficiently meet the demand for cost reduction.

The present invention has been made in view of the above-described problems. The first object is to provide a fulcrum bearing unit that stabilizes the torque of the swing arm by reducing fluctuations in the rolling element load and facilitating the control thereof. The second object is to provide a low-cost swing arm bearing and a manufacturing method thereof.

A swing arm bearing as a fulcrum bearing unit used for a swing arm in the present invention is an inner member in which an annular inner raceway surface is formed on the outer peripheral surface, and is disposed so as to surround the inner member. And an outer member to which a swing arm of a hard disk drive is to be connected, and a plurality of balls arranged in contact with the inner raceway surface and the outer raceway surface. In addition, one of the inner raceway surface and the outer raceway surface has a first contact surface and a second contact surface that contact the ball, and the first contact surface and the second contact surface are Cross each other. Further, the other raceway surface has a third contact surface that contacts the ball. The ball is in contact with the inner raceway surface and the outer raceway surface with the first, second, and third contact surfaces at a total of three points.

As described above, any one of the inner raceway surface of the inner member and the outer raceway surface of the outer member has two contacts with the first contact surface and the second contact surface intersecting each other. A structure having a surface (a surface in contact with the ball) is used. In addition, the other raceway surface different from the one raceway surface has a structure having a third contact surface in contact with the ball. The balls are brought into contact with the inner raceway surface and the outer raceway surface at a total of three points. In this way, the contact angle of the ball is stabilized and the rolling element load can be easily controlled, so that torque fluctuations can be suppressed.

Further, it is more preferable that at least one of the first contact surface and the second contact surface has a conical surface shape. Further, it is more preferable that the third contact surface has a conical surface shape.

Therefore, the first contact surface, the second contact surface, and the third contact surface may all have an arcuate surface shape in a cross section including the bearing groove of the R surface, that is, the rotation axis of the swing arm bearing. All of the three contact surfaces may have a conical shape, that is, a linear shape in a cross section including the rotation axis of the swing arm bearing. However, for example, both the first contact surface and the second contact surface may have a conical surface shape, and the third contact surface may be a R-side bearing groove. As another example, for example, the second contact surface may have a conical surface shape, and the first contact surface and the third contact surface may be R-side bearing grooves. As yet another example, for example, the second contact surface and the third contact surface may be conical, and the first contact surface may be a R-side bearing groove. Furthermore, both the first contact surface and the second contact surface are R-surface bearing grooves, and only the third contact surface can be conical.

If the conical surface shape is used as described above, the rigidity of the swing arm bearing is improved, and the rotation accuracy and positioning accuracy of the swing arm bearing are improved. Further, since the conical surface shape is easier than the processing of the bearing groove, the processing cost may be reduced.

In the swing arm bearing according to the present invention, the surface roughness Ra (centerline average roughness) of the first region in contact with the ball on the inner raceway surface and the outer raceway surface is adjacent to the first region. The surface roughness Ra of the area 2 may be smaller.

The torque fluctuation of the fulcrum bearing unit for hard disk drive can be suppressed by reducing the surface roughness Ra of the raceway surface so as to reduce the unevenness of the surface of the raceway surface. At this time, not the entire inner raceway surface and outer raceway surface, but only the first region in contact with the ball is processed to reduce the surface roughness Ra, and is adjacent to the first region, that is, not in contact with the ball. The second region is not processed to reduce the surface roughness Ra. As a result, the tact time of processing for reducing the surface roughness Ra can be shortened, and low-cost processing can be realized.

In the swing arm bearing according to the present invention, it is preferable that the ball is in contact with the inner raceway surface at one point and in contact with the outer raceway surface at two points.

In the manufacturing process of the swing arm bearing, the processing amount of the outer member tends to be larger than that of the inner member. In the bearing for a swing arm of the present invention, the ball contacts the inner raceway surface at one point and adopts a configuration in which the ball contacts the outer raceway surface at two points, thereby suppressing the hardness of the outer member having a large machining amount. It is possible to do. Therefore, it is possible to reduce manufacturing costs. As described above, according to the swing arm bearing of the present invention, a low cost swing arm bearing can be provided.

In the swing arm bearing according to the present invention, the hardness of the inner raceway surface is preferably HRC40 or more and HRC50 or less, and the hardness of the outer raceway surface is preferably HRC25 or more and HRC35 or less.

When the swing arm bearing is used, for example, if an external impact load is applied to the swing arm bearing as an unexpected external force, the rolling element applies an impact load to the raceway surface. As a result, indentations may occur on the raceway surface. In order to suppress the generation of such indentations, it is preferable to increase the hardness of the raceway surface to such an extent that the indentations do not occur. In order to sufficiently suppress the occurrence of the indentation, the inner raceway surface that contacts the rolling element at one point must have a hardness of HRC 40 or higher for the outer raceway surface that contacts at two points, and a hardness of HRC25 or higher. However, it became clear by examination of this inventor.

On the other hand, if the hardness of the inner raceway surface and the outer raceway surface is increased, the cost required for processing increases. In order to suppress this, as described above, for example, the hardness of the inner raceway surface of the inner member is preferably HRC50 or less, and the hardness of the outer raceway surface of the outer member is preferably HRC35 or less. From the above, it is preferable that the hardness of the inner raceway surface is HRC40 or more and HRC50 or less, and the hardness of the outer raceway surface is HRC25 or more and HRC35 or less. In consideration of the balance between suppression of generation of indentation and reduction of processing cost, it is more preferable that the hardness of the inner raceway surface is HRC43 or more and HRC47 or less, and the hardness of the outer raceway surface is HRC28 or more and HRC32 or less.

In the bearing for a swing arm according to the present invention, a hole is formed in the inner member in a region including the central axis of the inner raceway surface, and the hardness of the inner raceway surface is HRC40 or more, and the surface layer portion of the hole The hardness is preferably HRC25 or less.

As described above, for the inner raceway surface, for example, the rolling element gives an impact force to the inner raceway surface due to an impact load from the outside, and the hardness is increased in order to suppress the occurrence of indentation on the inner raceway surface. (HRC 40 or more) is preferable. On the other hand, a hole may be formed in the central portion of the inner member, that is, in a region including the central axis extending in the long axis direction of the inner member for the purpose of fixing the inner member to another member. is there. In this case, it is preferable that the hardness of the surface layer portion of the hole is HRC25 or less in order to suppress the processing cost of the hole. Here, the surface layer portion of the hole refers to a region having a depth of 0.1 mm or less from the surface of the hole, for example. And the hardness of the said surface layer part can be investigated, for example by cut | disconnecting an inner member in a cross section perpendicular | vertical to the surface of a hole, and measuring the hardness of the area | region 0.1 mm or less from the surface using a hardness meter. .

In the swing arm bearing according to the present invention, the region including the inner raceway surface is preferably induction hardened. By using induction hardening, as described above, the hardness of the outer peripheral portion of the inner member, that is, the region including the inner raceway surface is increased, while the center portion of the inner member, that is, the surface layer portion of the hole is suppressed. The structure can be easily achieved.

In the swing arm bearing according to the present invention, the hardness of the first contact surface and the second contact surface is preferably lower than the hardness of the third contact surface. As will be described later, a load is applied to the inner raceway surface and the outer raceway surface using a plurality of balls arranged in contact with the inner raceway surface and the outer raceway surface, and the pressure applied to the raceway surface at that time Thus, a process called burnishing can be performed in which the surface of the raceway surface is plastically processed to reduce the surface roughness Ra. At this time, the force applied to the track surface on the side where the two surfaces of the inner track surface and the outer track surface, the first contact surface and the second contact surface exist, is applied to two locations by two contact points. Distributed. Since the contact surfaces need to be processed with a distributed force, the hardness of the first contact surface and the second contact surface is preferably smaller than the hardness of the third contact surface.

Further, in the swing arm bearing according to the present invention, a plurality of balls are arranged in two rows, and the inner member and the outer member have a pair of inner raceway surface and outer raceway surface corresponding to the two rows described above. You may do it. In that case, in the cross section including the rotation axis of the swing arm bearing, the center of the ball included in one of the two rows and the contact where the ball included in the one row contacts the above-described third contact surface. A second straight line connecting the first straight line connecting the points, the center of the ball included in the other of the two columns, and the contact point at which the ball included in the other column contacts the third contact surface. It is preferable that the straight line intersects on the radially outer side when viewed from the contact point between the ball and the third contact surface. By determining the shapes of the inner member and the outer member so as to satisfy the above-described conditions, the rigidity when a moment force acts on the fulcrum bearing unit is improved.

In order to assemble the swing arm bearing having the above-described structures, the inner member includes a first inner member having an inner raceway surface in contact with the ball, and a first inner member, which are included in one row. And a second inner member having an inner raceway surface that comes into contact with the ball and is included in the other row.

Further, it is preferable that a preload is applied to the swing arm bearing in the present invention. This facilitates maintaining the contact between the inner member and the outer member constituting the swing arm bearing and the ball during operation of the swing arm bearing. As a result, the rigidity of the swing arm bearing is improved, and the rotation accuracy and positioning accuracy of the swing arm bearing are improved. The application of the preload to the swing arm bearing is performed by, for example, fitting the second inner member into the first inner member in a state where the outer member, the first inner member and the ball are combined. Can be implemented. More specifically, the second inner member is fitted and fixed to the first inner member so that appropriate pressure is mutually applied between the outer member and the inner member and the ball. The preload can be applied by pushing in and fixing along the axial direction.

The swing arm bearing according to the present invention has an annular shape, is disposed between the inner member and the outer member, and a plurality of balls are arranged on the annular track with a predetermined pitch. And a retainer that can be freely rolled.

In the swing arm bearing of the present invention, the inner member functioning as a fixed shaft and the outer member to which the swing arm is to be connected are formed with raceway surfaces facing each other, and a cage between the raceway surfaces. The ball is held so that it can roll freely. Thereby, the assembly process can be simplified and the manufacturing cost can be reduced as compared with the conventional configuration in which the rolling bearing having the inner ring and the outer ring is fitted between the outer member and the inner member. As a result, according to the swing arm bearing of the present invention, a low cost swing arm bearing can be provided.

In the above swing arm bearing, the cage is preferably made of a resin molded body. As a result, steps such as caulking of the cage can be omitted as compared with the case where a metal cage is used, and the manufacturing cost of the swing arm bearing can be further reduced.

In the swing arm bearing, preferably, the cage includes a holding portion for holding a ball and a thick portion having a larger radial thickness than the holding portion.

The present inventor conducted a detailed study on cost reduction of the swing arm bearing from the following viewpoints and derived the above configuration. That is, as described above, in the conventional swing arm bearing unit described with reference to FIG. 30, a ball bearing is incorporated. A seal plate protruding toward the inner ring is fixed to the inner peripheral surface of the outer ring of the ball bearing by a clasp for the purpose of suppressing leakage of grease from the inside of the bearing and intrusion of solid foreign matters into the bearing. ing. As a result, the cost of the clasp and the seal plate parts and the cost for carrying out these attachment processes are required, which causes an increase in cost.

Here, since a reduction in bearing torque is strongly demanded for the bearing supporting the swing arm, the amount of grease enclosed in the bearing is smaller than that of a general rolling bearing. Therefore, in the bearing that supports the swing arm, the risk of grease leakage is smaller than that of a general rolling bearing.

Also, since hard disk drives (HDD) are extremely reluctant to generate dust, HDD assembly is usually performed in a clean room. Rolling bearings (ball bearings) used in the conventional swing arm bearing unit unitize the finished bearing, and in the process until the bearing is transported to the clean room, solid foreign substances are present inside the bearing. There is a risk of intrusion. However, the inner member functioning as a fixed shaft and the outer member to which the swing arm is to be connected are directly formed with the raceway surfaces facing each other, and the swing arm of the present invention does not need to carry out the process of incorporating the rolling bearing. In the bearing, it is not necessary that the finished bearing is transported in a state where there is a risk of intrusion of solid foreign matter, and the assembly of the swing arm bearing itself is performed in a clean room. Therefore, in the swing arm bearing of the present invention, it can be said that there is little risk of solid foreign matter entering the bearing. As described above, in the swing arm bearing of the present invention, there is not necessarily a great risk of leakage of grease or intrusion of solid foreign matters, and it is considered that a simple sealing mechanism is sufficient.

On the other hand, as described above, the thick portion is formed in the cage, and the distance between the thick portion and the inner member and the outer member is reduced, so that a conventional sealing plate can be obtained. The present inventors have found that sufficient sealing performance can be obtained even if omitted. Therefore, according to the above configuration, it is possible to omit the seal plate while ensuring sufficient sealing performance, so that the manufacturing cost of the swing arm bearing can be further suppressed.

In addition, it is preferable that the said thick part is formed in the area | region containing one end surface of a holder | retainer. Thereby, more sufficient sealing performance can be obtained.

In the swing arm bearing, the plurality of balls may be arranged on a pair of annular tracks. In this case, the ball arranged on one of the pair of tracks is held by the first cage, and the ball arranged on the other track of the pair of tracks is held second. Can be held by a vessel. In this case, each of the first cage and the second cage has a thick portion formed in a region including an end surface opposite to the other cage as viewed from one cage. Preferably it is.

In this way, when the swing arm bearing is a double row bearing and the cages for holding the balls included in each row are arranged, the end surface on the side opposite to the other cage is viewed from one cage. By forming the thick portion in the region to include, the thick portion that functions as a seal is disposed on both sides in the axial direction inside the bearing. As a result, it is possible to satisfactorily suppress solid foreign matter from entering the bearing.

In the above-mentioned swing arm bearing, the distance between the thick part of the cage and the outer member and the inner member is preferably 0.05 mm or more and 0.2 mm or less.

If the distance exceeds 0.2 mm, the intrusion of solid foreign matters that have a great influence on the durability of the bearing due to intrusion into the bearing may not be sufficiently suppressed. On the other hand, if the distance is less than 0.05 mm, the cage and the inner member or the outer member may come into contact with each other during the operation of the swing arm bearing, which may cause torque fluctuation. Therefore, the interval is preferably 0.05 mm or more and 0.2 mm or less.

Next, the swing arm bearing manufacturing method according to the present invention includes an inner member having an annular inner raceway surface formed on an outer peripheral surface, an annular outer raceway surface, and a swing arm of a hard disk drive. A step of preparing an outer member to be connected and a plurality of balls; the inner raceway surface and the outer raceway surface face each other; and the ball contacts the inner raceway surface at one point, and Assembling the inner member, the outer member and the ball so as to contact the outer raceway surface at two points, and rotating the outer member relative to the inner member relative to the axis. Thus, the manufacturing method includes a step of performing plastic working on a region in contact with the ball on the inner raceway surface and a region in contact with the ball on the outer raceway surface.

In the swing arm bearing according to the present invention, after assembling the inner member, the outer member, and the ball, by rotating the outer member with respect to the inner member, the region in contact with the ball on the inner raceway surface, And the plastic working (burnishing) of the area | region which contacts a ball in an outer raceway surface is implemented. As described above, sufficient durability can be obtained if the processing for reducing the surface roughness Ra is performed on the region of the inner raceway surface and the outer raceway surface that contacts the ball. Then, by adopting the process as described above, before assembling the inner member, outer member, ball and other members constituting the swing arm bearing as the swing arm bearing, the inner race surface and the outer race surface in advance. It is possible to easily perform plastic working to reduce the surface roughness Ra of a necessary region without performing processing such as grinding to reduce the surface roughness Ra. As a result, according to the swing arm bearing manufacturing method of the present invention, the manufacturing cost of the swing arm bearing can be reduced.

Further, in the swing arm bearing manufacturing method according to the present invention, in the step of carrying out the plastic working, the outer member and the inner member are rotated around the axis, whereby the outer member is moved with respect to the inner member. It is preferable that the axial force and the radial force are applied between the inner member and the outer member while rotating around the axis.

¡When the outer member is rotated relative to the inner member while applying only the axial force, the ball applies a load only in the direction perpendicular to the inner raceway surface with respect to the inner raceway surface. As a result, the inner raceway surface is plastically deformed into a shape along the shape of the surface of the ball. In this case, when the swing arm bearing is used, the balls may protrude from the plastically deformed region of the inner raceway surface, and torque fluctuation may occur.

On the other hand, if an axial force and a radial force are applied to the inner member and the outer member, the ball also extends in the direction of expanding the width of the plastic deformation region on the inner raceway surface with respect to the inner raceway surface. Apply load. As a result, the inner raceway surface is plastically deformed so as to have a shape closer to a plane (a smaller curvature) than the shape (curvature) of the surface of the ball. Thereby, the said torque fluctuation | variation can be suppressed. In order to efficiently perform the plastic working to reduce the surface roughness Ra of the raceway surface, it is preferable to apply the axial force and the radial force simultaneously.

Further, when the outer member is rotated relative to the inner member, for example, the outer member only rotates with respect to the central axis while the inner member does not rotate with respect to the central axis and remains stationary. If this is the case, plastic working proceeds favorably on the side of the inner raceway on which the outer member is pressed, but plastic working does not proceed sufficiently on the side opposite to the side on which the outer member is pressed. Therefore, it is preferable to rotate both the outer member and the inner member around the axis in order to plastically process the raceway surface over the entire circumference.

In the swing arm bearing manufacturing method according to the present invention, it is preferable that in the step of plastically processing the region in contact with the ball, the inner raceway surface and the outer raceway surface having a surface roughness Ra of 0.3 or less are plastically processed. . If the surface roughness Ra of the inner raceway surface and the outer raceway surface before plastic working is 0.3 or less, the surface roughness Ra of the inner raceway surface and the outer raceway surface is sufficiently reduced by using the method described above. The swing arm bearing can be manufactured. The surface roughness Ra is more preferably 0.14 or less.

A swing arm fulcrum bearing (swing arm bearing) according to another aspect of the present invention includes an inner member having an annular inner raceway surface formed on an outer peripheral surface, and an inner race that is disposed so as to surround the inner member. An annular outer raceway surface facing the surface is formed, and includes an outer member to which a swing arm of a hard disk drive is to be connected, and a plurality of rolling elements arranged in contact with the inner raceway surface and the outer raceway surface. ing. The rolling element is in contact with the inner raceway surface at one point and in contact with the outer raceway surface at two points. In the inner raceway surface and the outer raceway surface, the surface roughness Ra of the first region in contact with the rolling element is greater than the surface roughness Ra of the second region adjacent to the first region. It is a small swing arm fulcrum bearing.

When the surface roughness Ra is large, the oil film parameter is lowered, and the durability of the bearing may be lowered. For this reason, it is common to perform surface finishing to reduce the surface roughness Ra of the raceway surface by grinding the entire raceway surface using a grindstone or the like.

However, the area where the rolling elements actually roll (contact) is a part of the raceway surface, and the rolling elements do not contact in other areas other than the area. And this inventor secures sufficient oil film parameter by making surface roughness Ra of the area | region where a rolling element actually contacts among surface surfaces smaller than surface roughness Ra of the other area | region adjacent to the said area | region. Thus, it has been found that sufficient durability can be imparted to the swing arm fulcrum bearing.

In the swing arm fulcrum bearing according to another aspect of the present invention, of the raceway surface, the first region that the rolling element contacts when using the swing arm fulcrum bearing is adjacent to the first region. Specifically, when the swing arm fulcrum bearing is used, the surface roughness Ra is smaller than the second region where the rolling elements do not contact. As a result, according to the swing arm fulcrum bearing of the present invention, the area to be processed is reduced as compared with the conventional swing arm fulcrum bearing in which the surface finishing process is performed to reduce the surface roughness Ra with respect to the entire raceway surface. Manufacturing costs can be reduced.

In the manufacturing process of the swing arm fulcrum bearing, the processing amount of the outer member tends to be larger than that of the inner member. In the swing arm fulcrum bearing of the present invention, by adopting a configuration in which the rolling element is in contact with the inner raceway surface at one point and is in contact with the outer raceway surface at two points, the hardness of the outer member having a large amount of processing is increased. It is possible to suppress. Therefore, it is possible to reduce manufacturing costs. As described above, according to the swing arm fulcrum bearing of the present invention, a low-cost swing arm fulcrum bearing can be provided.

In a swing arm fulcrum bearing according to another aspect of the present invention, the hardness of the inner raceway surface is preferably HRC40 or more and HRC50 or less, and the hardness of the outer raceway surface is preferably HRC25 or more and HRC35 or less.

When the swing arm fulcrum bearing is used, for example, if an external impact load is applied to the swing arm fulcrum bearing as an unexpected external force, the rolling element applies an impact load to the raceway surface. As a result, indentations may occur on the raceway surface. In order to suppress the generation of such indentations, it is preferable to increase the hardness of the raceway surface to such an extent that the indentations do not occur. In order to sufficiently suppress the occurrence of the indentation, the inner raceway surface that contacts the rolling element at one point must have a hardness of HRC 40 or higher for the outer raceway surface that contacts at two points, and a hardness of HRC25 or higher. However, it became clear by examination of this inventor.

In the swing arm fulcrum bearing according to another aspect of the present invention, the inner member has a hole formed in a region including the central axis of the inner raceway surface, and the hardness of the inner raceway surface is HRC40 or more, The hardness of the surface layer portion of the hole is preferably HRC25 or less.

In the swing arm fulcrum bearing according to another aspect of the present invention, the region including the inner raceway surface is preferably induction hardened. By using induction hardening, as described above, the hardness of the outer peripheral portion of the inner member, that is, the region including the inner raceway surface is increased, while the center portion of the inner member, that is, the surface layer portion of the hole is suppressed. The structure can be easily achieved.

Next, a method for manufacturing a swing arm fulcrum bearing according to another aspect of the present invention includes an inner member having an annular inner raceway surface formed on an outer peripheral surface, an annular outer raceway surface, and a hard disk drive. A step of preparing an outer member to be connected to the swing arm and a plurality of rolling elements, the inner raceway surface and the outer raceway surface are opposed to each other, and the rolling element is at one point with the inner raceway surface. And assembling the inner member, the outer member, and the rolling element so as to make contact with the outer raceway surface at two points, and the outer member around the axis with respect to the inner member. And a step of performing plastic working on a region in contact with the rolling element on the inner raceway surface and a region in contact with the rolling element on the outer raceway surface. It is.

In the swing arm fulcrum bearing according to another aspect of the present invention, after the inner member, the outer member, and the rolling element are assembled, the outer member is rotated with respect to the inner member, thereby rolling on the inner raceway surface. Plastic working (burnishing) is performed on the area that contacts the moving body and the area that contacts the rolling element on the outer raceway surface. As described above, sufficient durability can be obtained if processing for reducing the surface roughness Ra is performed on the inner raceway surface and the outer raceway surface in the region in contact with the rolling elements. By adopting the process as described above, before assembling the members such as the inner member, the outer member, and the rolling element constituting the swing arm fulcrum bearing as the swing arm fulcrum bearing, the inner raceway surface and the outer raceway are preliminarily assembled. Plastic processing for easily reducing the surface roughness Ra of a necessary region can be performed without performing processing such as grinding to reduce the surface roughness Ra of the surface. As a result, according to the method for manufacturing a swing arm fulcrum bearing of the present invention, the manufacturing cost of the swing arm fulcrum bearing can be reduced.

In the method of manufacturing a swing arm fulcrum bearing according to another aspect of the present invention, in the step of carrying out the plastic working, the outer member is moved inward by rotating the outer member and the inner member around the axis. It is preferable that the axial rotation and the radial force are applied between the inner member and the outer member while rotating relative to the member around the axis.

¡When the outer member is rotated relative to the inner member while applying only the axial force, the rolling element applies a load only in the direction perpendicular to the inner raceway surface with respect to the inner raceway surface. As a result, the inner raceway surface is plastically deformed into a shape along the shape of the surface of the rolling element. In this case, when the swing arm fulcrum bearing is used, the rolling element may protrude from the plastically deformed region of the inner raceway surface, and torque fluctuation may occur.

On the other hand, if an axial force and a radial force are applied to the inner member and the outer member, the rolling element expands the width of the plastic deformation region on the inner raceway surface with respect to the inner raceway surface. Also apply a load. As a result, the inner raceway surface is plastically deformed so as to have a shape closer to a plane (a smaller curvature) than the shape (curvature) of the surface of the rolling element. Thereby, the said torque fluctuation | variation can be suppressed. In order to efficiently perform the plastic working to reduce the surface roughness Ra of the raceway surface, it is preferable to apply the axial force and the radial force simultaneously.

In the method for manufacturing a swing arm fulcrum bearing according to another aspect of the present invention, in the step of plastic working the region in contact with the rolling element, the inner raceway surface and the outer raceway surface having a surface roughness Ra of 0.3 or less are plastic worked. It is preferred that If the surface roughness Ra of the inner raceway surface and the outer raceway surface before plastic working is 0.3 or less, the surface roughness Ra of the inner raceway surface and the outer raceway surface is sufficiently reduced by using the method described above. The swing arm fulcrum bearing thus manufactured can be manufactured. The surface roughness Ra is more preferably 0.14 or less.

A swing arm fulcrum bearing (swing arm bearing) according to still another aspect of the present invention includes an inner member that has an annular inner raceway surface formed on an outer peripheral surface and functions as a fixed shaft of a swing arm of a hard disk drive. An annular outer raceway surface is formed so as to surround the inner member and faces the inner raceway surface, and contacts the outer member to which the swing arm is to be connected, the inner raceway surface and the outer raceway surface. Are arranged between the inner member and the outer member, and the plurality of rolling elements are rolled on the annular raceway at a predetermined pitch. And a cage for holding it movably.

In the swing arm fulcrum bearing according to still another aspect of the present invention, a raceway surface facing each other is formed on the inner member functioning as a fixed shaft and the outer member to which the swing arm is to be connected. In the meantime, the rolling element is movably held by the cage. Thereby, the assembly process can be simplified and the manufacturing cost can be reduced as compared with the conventional configuration in which the rolling bearing having the inner ring and the outer ring is fitted between the outer member and the inner member. As a result, according to the swing arm fulcrum bearing of the present invention, a low-cost swing arm fulcrum bearing can be provided.

In the above swing arm fulcrum bearing, the cage is preferably made of a resin molded body. As a result, steps such as caulking of the cage can be omitted as compared with the case where a metal cage is used, and the manufacturing cost of the swing arm fulcrum bearing can be further reduced.

Preferably, in the above swing arm fulcrum bearing, the cage includes a holding portion for holding the rolling element and a thick portion having a larger radial thickness than the holding portion.

The present inventor conducted a detailed study on cost reduction of the swing arm fulcrum bearing from the following viewpoints and derived the above configuration. That is, as described above, in the conventional swing arm fulcrum bearing unit described with reference to FIG. 2, a ball bearing is incorporated. A seal plate protruding toward the inner ring is fixed to the inner peripheral surface of the outer ring of the ball bearing by a clasp for the purpose of suppressing leakage of grease from the inside of the bearing and intrusion of solid foreign matters into the bearing. ing. As a result, the cost of the clasp and the seal plate parts and the cost for carrying out these attachment processes are required, which causes an increase in cost.

Also, since hard disk drives (HDD) are extremely reluctant to generate dust, HDD assembly is usually performed in a clean room. Since the rolling bearing (ball bearing) used in the conventional swing arm fulcrum bearing unit unitizes the finished bearing, in the process until the bearing is transported to the clean room, solid foreign substances are present inside the bearing. There is a risk of intrusion. However, the inner surface that functions as a fixed shaft and the outer member to which the swing arm is to be connected are directly formed with mutually opposing raceway surfaces, and the swing arm fulcrum of the present invention that does not require the step of incorporating a rolling bearing. In the bearing, it is not necessary that the completed bearing is transported in a state where there is a risk of intrusion of solid foreign matter, and the assembly of the swing arm fulcrum bearing itself is performed in a clean room. Therefore, in the swing arm fulcrum bearing of the present invention, it can be said that there is little risk of solid foreign matter entering the bearing. As described above, in the swing arm fulcrum bearing of the present invention, there is not necessarily a great risk of leakage of grease or intrusion of solid foreign matters, and it is considered that a simple sealing mechanism is sufficient.

On the other hand, as described above, the thick portion is formed in the cage, and the distance between the thick portion and the inner member and the outer member is reduced, so that a conventional sealing plate can be obtained. The present inventors have found that sufficient sealing performance can be obtained even if omitted. Therefore, according to the above configuration, it is possible to omit the seal plate while ensuring sufficient sealing performance, so that the manufacturing cost of the swing arm fulcrum bearing can be further suppressed.

In the swing arm fulcrum bearing, the plurality of rolling elements may be arranged on a pair of annular tracks. In this case, the rolling elements disposed on one of the pair of tracks are held by the first cage, and the rolling elements disposed on the other track of the pair of tracks are the second. Can be held by a cage. In this case, each of the first cage and the second cage has a thick portion formed in a region including an end surface opposite to the other cage as viewed from one cage. Preferably it is.

In this way, when the swing arm fulcrum bearing is a double row bearing and the cage that holds the rolling elements included in each row is arranged, the end surface on the side opposite to the other cage when viewed from one cage By forming the thick part in the region including the thick part, the thick part that functions as a seal is arranged on both sides in the axial direction inside the bearing. As a result, it is possible to satisfactorily suppress solid foreign matter from entering the bearing.

In the above swing arm fulcrum bearing, the distance between the thick part of the cage and the outer member and the inner member is preferably 0.05 mm or more and 0.2 mm or less.

If the distance exceeds 0.2 mm, the intrusion of solid foreign matters that have a great influence on the durability of the bearing due to intrusion into the bearing may not be sufficiently suppressed. On the other hand, if the distance is less than 0.05 mm, the cage and the inner member or the outer member may come into contact with each other during the operation of the swing arm fulcrum bearing, which may cause torque fluctuation. Therefore, the interval is preferably 0.05 mm or more and 0.2 mm or less.

According to the fulcrum bearing unit of the present invention, it becomes easy to control the rolling element load applied to the ball, and the torque of the fulcrum bearing unit can be stabilized.

It is a cross-sectional schematic diagram which shows the structure of the fulcrum bearing unit integrated in the swing arm in Embodiment 1 of this invention. FIG. 2 is an enlarged cross-sectional view of a region “20” surrounded by a round dotted line in FIG. 1. It is an expanded sectional view of the area | region of "30" enclosed with the dotted line in FIG. It is the schematic showing the area | region which performs a surface roughness improvement process with respect to the conical track surface 120 in FIG. FIG. 5 is a schematic cross-sectional view taken along line VV in FIG. 1. It is a table | surface which shows the order of the manufacturing process of the fulcrum bearing unit in this invention, and the member used as object. It is the schematic which shows the jig | tool for arrange | positioning a some ball in ring shape. FIG. 8 is a schematic sectional view taken along line VIII-VIII in FIG. (A) It is the schematic which shows the state arrange | positioned so that a some ball may contact the outer track surface of a sleeve. (B) It is the schematic which shows the state which has arrange | positioned the axis | shaft. (C) It is the schematic which shows the state which has arrange | positioned the adjustment ring further. It is a graph of the data which shows the state which reduced surface roughness Ra of only the area | region which contacts the ball | bowl which is a rolling element among raceway surfaces using burnishing. It is a cross-sectional schematic diagram which shows the aspect which processes the track surface on which a ball rolls in embodiment of this invention. It is a cross-sectional schematic diagram which shows the structure of the fulcrum bearing unit integrated in the swing arm based on Embodiment 2 of this invention. It is an expanded sectional view of the area | region of "20" enclosed with the dotted line in FIG. It is an expanded sectional view of the area | region of "30" enclosed with the dotted line in FIG. It is a flowchart which shows the manufacturing method of the fulcrum bearing unit based on Embodiment 2 of this invention. It is a flowchart which shows the detailed process which concerns on formation of an inward member among the processes (S10) which prepare the member of the flowchart of FIG. (A) It is a schematic sectional drawing which shows the state which performed the process (S11) of induction hardening of FIG. 16 of the process which manufactures an inward member (shaft 101). (B) It is a schematic sectional drawing which shows the state which performed the drilling process (S12) of FIG. 16 of the process which manufactures an inward member (axis | shaft 101). (C) It is a schematic sectional drawing which shows the state which performed the process (S13) of the tapping process of FIG. 16 in the process of manufacturing an inner member (shaft 101). (D) It is a schematic sectional drawing which shows the state which performed the process (S14) of the turning process of FIG. 16 of the process which manufactures an inward member (shaft 101). (E) It is a schematic sectional drawing which shows the state which performed the cutting process (S15) of FIG. 16 of the process which manufactures an inward member (shaft 101). (F) It is a schematic sectional drawing which shows the completed state of an inward member (shaft 101). (A) It is a schematic sectional drawing which shows the state which performed the process (S11) of induction hardening of FIG. 16 of the process which manufactures an inward member (adjustment ring 123). (B) It is a schematic sectional drawing which shows the state which performed the process (S12) of drilling of FIG. 16 of the process which manufactures an inward member (adjustment ring 123). (C) It is a schematic sectional drawing which shows the state which performed the process (S14) of the turning process of FIG. 16 of the process which manufactures an inward member (adjustment ring 123). (D) It is a schematic sectional drawing which shows the completed state of the inward member (adjustment ring 123). It is a schematic sectional drawing which shows the deformation | transformation state of the inner raceway surface of an adjustment ring when burnishing is performed in a state where only an axial force is applied. It is a schematic sectional drawing which shows the deformation | transformation state of the inner raceway surface of an adjustment ring when burnishing is performed in the state where an axial force and a radial force are applied. It is the schematic which shows the structure of the swing arm support mechanism containing the bearing for swing arms in Embodiment 3 of this invention. It is a cross-sectional schematic diagram which shows the structure of the fulcrum bearing unit in Embodiment 4 of this invention. FIG. 2 shows a fulcrum bearing unit “20” in FIG. 2 in which the inner member has two R-surface bearing grooves intersecting each other, the outer member has one bearing groove, and the ball contacts each bearing groove at a total of three points. It is an expanded sectional view of the area | region. The inner member has one R-plane bearing groove and one conical raceway surface, the outer member has one bearing groove, and the ball contacts each bearing groove and conical raceway surface at a total of three points. It is an expanded sectional view of the area | region of "20" in FIG. The inner member is provided with one R-side bearing groove and one conical raceway surface, the outer member is provided with one conical raceway surface, and the ball has three bearing points and a conical raceway surface in total. FIG. 3 is an enlarged cross-sectional view of a fulcrum bearing unit in contact with a region “20” in FIG. 2. FIG. 2 shows a fulcrum bearing unit in which the inner member has two R-surface bearing grooves intersecting each other, the outer member has one conical raceway surface, and the balls contact each of the bearing grooves at a total of three points. It is an expanded sectional view of the area of “20”. It is a graph which shows the contact stress at the time of indentation with respect to the hardness of steel materials. It is a graph which shows the relationship between the magnitude | size of external force, and hardness required in order not to generate an indentation with respect to external force. It is a graph which shows the hardness distribution at the time of performing induction hardening of the round bar which makes a cross section 5 mm in diameter circular. It is a cross-sectional schematic diagram which shows the structure of the fulcrum bearing unit integrated in the swing arm used conventionally. It is a cross-sectional schematic diagram which shows the structure of the fulcrum bearing unit which reduced the number of parts conventionally performed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each embodiment, portions having the same function are denoted by the same reference numerals, and the description thereof will not be repeated unless particularly necessary.

(Embodiment 1)
In FIG. 1, the hatched portion shows a cross section. The swing arm 1 shown in FIG. 1 has a magnetic head 2 attached to one end, and a fulcrum bearing unit 100 as a swing arm bearing (swing arm fulcrum bearing) is incorporated at the center of gravity.

The fulcrum bearing unit 100 includes a shaft 101 as a first inward member at the center. In addition, a sleeve 102 is provided as an outer member connected to the swing arm 1 of the hard disk drive and disposed so as to surround the shaft 101. A plurality of balls 109 as rolling elements for rotating the swing arm 1 are arranged in two rows in the vertical direction in a region sandwiched between the shaft 101 and the sleeve 102. The balls 109 arranged in a plurality are generally steel balls, but ceramic balls may be used instead of the steel balls for the purpose of reducing the weight of the balls.

In the fulcrum bearing unit 100, the adjustment as the second inner member so as to be fitted to the shaft 101 in the upper part of the shaft 101, that is, in the vicinity where the upper balls 109 are present in two rows in the vertical direction. A ring 123 is fixed. The adjustment ring 123 is provided as a second inward member independent of the shaft 101 for convenience when assembling the fulcrum bearing unit 100 described later. The adjustment ring 123 is in contact with the plurality of balls 109 at two locations as will be described later. Further, in the lower part of the shaft 101, that is, in the vicinity where the lower balls 109 are present in two rows in the vertical direction, the conical surface shape, that is, the rotation shaft of the swing arm bearing is directly provided on the outer peripheral surface of the shaft 101. A conical raceway surface 120 and a conical raceway surface 121 having a linear shape in a cross section including the same are provided. The conical raceway surface 120 and the conical raceway surface 121 are in contact with the plurality of balls 109, respectively. Also, the sleeve 102 has a conical shape as a contact surface for contacting the ball 109 in the vicinity of the upper ball 109 and the vicinity of the lower ball 109 in two rows in the vertical direction. A raceway surface 122 is provided.

In the fulcrum bearing unit 100 shown in FIG. 1, there are two contact points between a member on the shaft 101 side as an inward member and a plurality of balls 109. For example, as shown in FIG. 2, the upper ball 109 is an annular inner raceway surface formed on an adjustment ring 123 fitted to the shaft 101, and is a cone that is a first contact surface having a conical shape. Two contact points are provided on the conical raceway surface 141 and on the conical raceway surface 142, which is a second contact surface having a conical shape, which is an annular inner raceway surface that intersects the first contact surface. . Further, as shown in FIG. 3, the lower ball 109 has a conical raceway surface 120 as a first contact surface having a conical surface shape, and a second conical surface shape intersecting the first contact surface. Two conical track surfaces 121 which are contact surfaces are provided with contact points.

The fulcrum bearing unit 100 does not include an inner ring and an outer ring that are used for ordinary bearings. For example, the fulcrum bearing unit 100 is an annular outer raceway surface facing the inner raceway surface on which a ball 109 rolls on a sleeve 102 that is an outer member. The conical track surface 122, which is the third contact surface in contact with the ball, is directly provided. Accordingly, the balls 109 are arranged in contact with the inner raceway surface of the inner member (the shaft 101 and the adjustment ring 123) and the outer raceway surface of the outer member (sleeve 102). As described above, in the fulcrum bearing unit 100 of the present invention, one of the inner raceway surface and the outer raceway surface has the first contact surface and the second contact surface in contact with the ball 109. These contact surfaces intersect each other. In addition, the other raceway surface of the inner raceway surface and the outer raceway surface has a structure that has a third contact surface that contacts the ball 109. Accordingly, the balls 109 are in contact with the inner raceway surface and the outer raceway surface at a total of three points. In this way, as will be described later, the contact angle of the ball 109 is stabilized and the control of the rolling element load is facilitated, so that fluctuations in torque can be suppressed.

In addition, as described above, by adopting a structure that does not include an inner ring or an outer ring that is used for a normal bearing, the vertical thickness of the fulcrum bearing unit 100 can be reduced by the amount that the outer ring or the inner ring is not used. Further, since the outer ring and the inner ring are not provided, the spacer can be abolished, so that the thickness of the fulcrum bearing unit 100 in the vertical direction can be further reduced accordingly.

Further, as shown in FIG. 1, a seal 125 is provided on the sleeve 102 in order to prevent the lubricant such as grease enclosed in the bearing from leaking to the outside and to prevent the entry of foreign matter from the outside. Is provided.

As described above, in the fulcrum bearing unit 100, the plurality of balls 109 are in contact with the member on the shaft 101 side as an inward member at two points. Further, the sleeve 102 as the outer member contacts at one point on the conical track surface 122. For this reason, the plurality of balls 109 come into contact with the raceway surface at a total of three points. Specifically, as shown in FIG. 2, the upper ball 109 includes an adjustment ring 123 fitted to a shaft 101 as an inward member, and two on the conical raceway surface 141 and the conical raceway surface 142. Contact is made at a point (contact point 143, contact point 144), and contact is made with the sleeve 102 as the outer member at one point (contact point 145) on the conical track surface 122. Further, as shown in FIG. 3, the lower balls 109 are provided on the conical raceway surface 120 having a conical shape and directly on the outer peripheral surface in the longitudinal direction of the shaft 101 as the inner member. Contact at two points (contact point 153, contact point 154) on the cylindrical raceway surface 121, and contact with the sleeve 102 as the outer member at one point (contact point 155) on the conical raceway surface 122. Note that the angles formed by the three contact points between the plurality of balls 109 and the raceway surface and the center O of the balls 109 have a relationship as shown in FIG. 2 or FIG.

With the above configuration, the contact angle is uniquely determined in the fulcrum bearing unit 100 in the present embodiment. As a result, the rolling element load can be stabilized and torque fluctuations can be suppressed. In order to accurately position the magnetic head 2 (see FIG. 1) on the track recorded on the hard disk, the fulcrum bearing unit 100 is required to have a small torque fluctuation. For this reason, the fulcrum bearing unit 100 capable of stabilizing the rolling element load and stabilizing the torque variation by stabilizing the contact angle has excellent characteristics as a swing arm bearing. Further, the processing of the conical surface shape is easier to process than the processing of the arc surface shape in the cross section including the bearing groove of the R surface as the raceway surface, that is, the rotating shaft of the swing arm bearing. Therefore, there is a possibility that the processing cost can be reduced.

Further, for example, as shown in FIG. 2, a straight line connecting the contact point 145 on the conical track surface 122 as the third contact surface with the ball 109 and the center of the ball 109, and the contact with the ball 109, for example, shown in FIG. Attention is paid to a straight line connecting the point 155. Here, the straight line in FIG. 2 is a first straight line, and the straight line in FIG. 3 is a second straight line. At this time, as shown in FIGS. 2 and 3, the first straight line and the second straight line intersect each other in the radial direction as viewed from the contact point 145 and the contact point 155, that is, on the side where the sleeve 102 exists. Preferably it is. By designing each contact surface included in each of the inner member and the outer member so as to satisfy the above-described conditions, rigidity when a moment force acts on the fulcrum bearing unit 100 is improved.

FIG. 4 is a development view of the surface of the conical track surface 120 as the first contact surface having a conical surface shape, which is directly provided on the outer peripheral surface of the shaft 101 as the inner member. For example, only the surface roughness improving region 120A, which is a part of the conical raceway surface 120, for example, a region sandwiched between two dotted lines in FIG. 4, is subjected to surface roughness improving processing. This surface roughness improving processing region 120A is a first region in which the ball 109 is in contact with the swing arm 1 (see FIG. 1) during the rotation operation. In the second region adjacent to the surface roughness improving processing region 120A, which is the first region, the ball 109 does not come into contact with the swing arm 1 (see FIG. 1) during rotation, so the surface roughness Ra is reduced. It is not necessary to perform processing to reduce the unevenness of the surface of the raceway surface.

As described above, for example, by reducing the surface roughness Ra of the conical raceway surface 120 and reducing the surface roughness of the raceway surface, fluctuations in torque of the fulcrum bearing unit 100 for a hard disk drive can be suppressed. Can do. This is convenient for accurately positioning the magnetic head 2 (see FIG. 1) on the track recorded on the hard disk. However, at this time, not the entire surface of the conical raceway surface 120 that is the inner raceway surface, but only the surface roughness improvement machining region 120A (first region) that comes into contact with the ball 109 is processed to reduce the surface roughness Ra. If applied, it is sufficient. As a result, the tact time of processing for reducing the surface roughness Ra can be shortened, and low-cost processing can be realized.

As described above, when processing is performed to reduce the surface roughness Ra only in a region of the raceway surface that contacts the ball 109, the hardness of the ball 109 is a member having a raceway surface such as the adjusting ring 123 and the sleeve 102. It is preferable that the hardness is higher. As will be described later, the processing for reducing the surface roughness Ra is performed by pressing the ball 109 against the surface region to be processed with a force equal to or greater than the yield stress of the surface to be processed and relatively with respect to the surface to be processed. By rotating the surface and plastically deforming the surface irregularities, the surface is smoothed and the surface roughness Ra is reduced (burnishing). For this reason, it is preferable that the hardness of the ball 109 is made higher than the surface desired to be processed by pressing, and the ball 109 is prevented from undergoing plastic deformation due to stress during the burnishing process.

FIG. 5 is a cross-sectional view of a portion where the upper ball 109 is arranged as shown in FIG. As shown in FIG. 5, the fulcrum bearing unit 100 includes an inner shaft 101 as an inner member, and an adjustment ring 123 is fixed to the shaft 101. A plurality of balls 109 are arranged in contact with the adjustment ring 123 and the sleeve 102 as the outer member. How these are in contact is as described above.

Further, a cage may be sandwiched between a plurality of balls 109 so that the balls 109 do not contact each other, but as shown in FIG. Spacer balls 149 may be sandwiched.

The plurality of spacer balls 149 described above are preferably arranged alternately with balls 109 as shown in FIG. However, in order to increase the rigidity of the fulcrum bearing unit 100, the number of balls 109 having a large diameter may be increased and the number of spacer balls 149 may be decreased.

FIG. 6 shows the production order and a table on the right side of the table that summarizes the members to be processed. In the table, A indicates that the member is necessarily processed in the process, and B indicates that the process may be processed in the member (some members may be processed). It shows that. Hereinafter, the fulcrum bearing unit 100 according to the present invention will be described with reference to the fulcrum bearing unit 100 shown in FIG.

First, a step of preparing a member (S10) is performed. Specifically, this is a step of preparing members such as a shaft 101, a sleeve 102, a plurality of balls 109, and an adjustment ring 123 that constitute the fulcrum bearing unit 100 shown in FIG. Here, as the material of the shaft 101, the sleeve 102, and the adjusting ring 123, a material that can be hardened by heat treatment, for example, SUS420J2, is used, but general rolling material such as SUJ2 or SUS440C can also be used.

The adjustment ring 123, the shaft 101, and the sleeve 102, which are members of the fulcrum bearing unit 100, have raceway surfaces on which the balls 109 come into contact and roll. For this reason, as will be described later, in order to maintain the rigidity of the fulcrum bearing unit 100 and stabilize the torque, burnishing is performed on the raceway surface so that the surface roughness Ra of the raceway surface becomes small. Since the fulcrum bearing unit 100 is used for the swing arm 1 for a hard disk drive, the load from the outside is very small at about several grams in this application. Further, the contact stress generated when the balls 109 come into contact with the raceway surface during the rotation of the swing arm 1 is 1.5 GPa or less. Therefore, it is not necessary to increase the hardness of the members and the raceway surface unlike a normal bearing. For example, the hardness of the raceway surface may be HRC45 or less. If the hardness is lowered in this way, it is possible to easily perform a turning process for finishing to a predetermined dimension after adjusting the hardness, to reduce the processing cost and to shorten the processing tact. . In addition, the life of a tool for turning can be extended.

Further, in particular, as in the fulcrum bearing unit 100 shown in FIG. 1, for example, the shaft 101 and the ball 109 formed with the adjusting ring 123, the conical raceway surface 120, and the conical raceway surface 121 provided on the shaft 101 as the inner member. Are contacted at two points, and the sleeve 102 as the outer member and the ball 109 are brought into one point contact, the adjusting ring 123 and the shaft 101 (particularly, the lower side of the inner member) The hardness of the conical raceway surface 120 and the conical raceway surface 121) as the first contact surface and the second contact surface described above formed in the region (member) in which the ball 109 is in contact with the inner member, Hardness of the sleeve 102 having a raceway surface that contacts one point (in particular, the above-described conical raceway surface 122 as the third contact surface formed in the region where the ball 109 contacts the sleeve 102). It is preferable to lower than. This is due to the following reasons. That is, when performing processing (burnishing) to reduce the surface roughness Ra of the raceway surface described later, the ball 109 is pressed against the surface region to be processed with a force equal to or higher than the yield stress of the surface to be processed. Rotate relative to the desired surface to plastically deform the surface irregularities. At this time, the inner member side that comes into contact with the ball 109 at two points has two places where the ball 109 presses the raceway surface at the contact point as compared with the outer member side that comes into contact with the ball 109 at one point. To be distributed. For this reason, it is preferable that the hardness of the raceway surface on the two-point contact side is lower than the altitude of the raceway surface on the one-point contact side.

Therefore, both the inner member side member and the outer member side member do not cause plastic deformation due to the pressure of the ball 109 during the normal swing arm rotation operation, and the respective raceway surfaces on the inner member side and the outer member side. When the processing (burnishing processing) for reducing the surface roughness Ra is preferably performed, the hardness is set such that plastic deformation is caused by pressing of the balls 109.

Conversely, the hardness of the ball 109 is such that it does not cause plastic deformation due to the pressure of the ball 109 not only during the normal swing arm rotation operation but also during the process of reducing the surface roughness Ra (burnishing process). It is preferable to keep it. As described above, when performing the burnishing process, it is necessary that the surface irregularities of the inner member side and the outer member side be plastically deformed by the pressing of the balls 109. It is preferable to make the hardness of the surface of the ball 109 higher than the hardness of each raceway surface on the member side and the outer member side.

Here, as will be described later, a fulcrum bearing is provided in a partial region of the bonding surface 124 shown in FIG. 1 in which the adjustment ring 123 is arranged and bonded at a predetermined position on the axial surface of the shaft 101. For convenience in the process of assembling the unit 100, it is preferable to provide an adhesive pool 133 (see FIG. 9C described later). This is an area for temporarily storing the adhesive having a depth in the radial direction of the shaft 101. Further, as shown in FIG. 1, the sleeve 102 is provided with a seal 125 for preventing the lubricant such as grease enclosed in the bearing from leaking to the outside and for preventing foreign matter from entering from the outside. It has been. In order to adhere this seal 125 stably, the sleeve 102 has a notch 135 (FIGS. 9A and 9B described later) at a position where the seal 125 shown in FIG. B) is preferably provided.

Further, for example, the conical raceway surface 141, the conical raceway surface 142, and the outer member as the inner raceway surface of the inner member in the cross-sectional view of FIG. 2 (the upper ball 109 side of the two rows arranged) described above, for example. A conical raceway surface 122 as the outer raceway surface is defined as a first raceway surface. Further, for example, a conical raceway surface 120, a conical raceway surface 121 and an outer raceway surface (inner side members) as the inner raceway surface (inner member) in the cross-sectional view of FIG. A conical raceway surface 122 as the outer member) is defined as a second raceway surface. Then, in the cross section including the rotation axis of the swing arm bearing, the center of the upper ball 109 out of the two rows and the conical raceway surface in which the ball 109 is the third contact surface of the first raceway surface A straight line connecting a contact point that contacts 122 is defined as a first straight line. Further, a straight line connecting the center of the lower ball 109 out of the two rows and the contact point at which the ball 109 contacts the conical track surface 122 which is the third contact surface of the second track surface. Let it be the second straight line. For example, the straight lines in FIGS. 2 and 3 indicate the straight lines described above. In this case, as shown in FIGS. 2 and 3, the first straight line and the second straight line intersect each other radially outside the contact point 145 and the contact point 155, that is, on the side where the sleeve 102 exists. In addition, it is preferable to design a conical track surface provided on each of the adjustment ring 123, the shaft 101 and the sleeve 102. For example, as shown in FIGS. 2 and 3, when there are two contact surfaces on the inner member side, two straight lines connected to the center of the ball 109 are provided. In this case, considering the bisector of two straight lines, the bisectors of the upper ball 109 and the lower ball 109 intersect each other on the radially outer side (side where the sleeve 102 exists). It is preferable to become.

After performing the step (S10) of preparing the member while paying attention to the material and hardness described above, the step (S20) of performing taper processing is performed. Specifically, for example, in the case of the fulcrum bearing unit 100 shown in FIG. 1, the adjustment ring 123 as an inward member is tapered on the surface facing the upper ball 109, and a conical surface as shown in FIG. A conical track surface 141 which is a first contact surface having a shape and a conical track surface 142 which is a second contact surface having a conical shape intersecting the first contact surface are formed. Further, a region (member) in which the lower ball 109 contacts the inner member among the inner members is also tapered, so that the conical track surface 120 and the first contact surface 120 and the first contact surface as shown in FIG. A conical raceway surface 121 which is the second contact surface is formed. Thus, a conical surface shape for bringing the ball 109 into contact with the inner member at two points is formed. These conical surface raceways are formed by subjecting predetermined portions of the member to forging or turning and taper processing by a combination of these and grinding.

Further, the surface of the sleeve 102 as the outer member facing the upper and lower balls 109 is also tapered to form a conical track surface 122 as the third contact surface. This is for bringing the ball 109 into contact with the sleeve 102 at one point. These conical surface raceways are formed by tapering a predetermined portion by forging or turning and a combination of these and grinding, as in the case of the inner member.

Next, a step of temporarily assembling the members (S30) is performed. Specifically, this is a step of assembling the respective members previously prepared for the fulcrum bearing unit 100 into a predetermined arrangement. Here, the predetermined arrangement means that each member is installed so as to have the arrangement shown in FIG. 1 in order to constitute the fulcrum bearing unit 100 shown in FIG.

In order to install a plurality of balls 109 in an area sandwiched between the shaft 101 and the sleeve 102 so as to have the arrangement shown in FIG. 1, a jig that can arrange the plurality of balls 109 in a ring shape is used. Is preferred.

The jig 210 shown in FIG. 7 and FIG. 8 has a pipe-like shape inside the flange portion 203 at substantially constant angles (approximately 45 ° in FIG. 8) with respect to the center of the main body portion 204 connected to the vacuum pump. The cavity 201 is formed. The cavity 201 is connected to a cavity 202 inside the main body 204, and the cavity 202 is connected to a vacuum pump via an electromagnetic valve. When this electromagnetic valve is operated so as to connect the vacuum pump and the cavity portion 202, air is sucked from the cavity portion 202, so that the ball 109 is moved to the outer diameter surface of the flange portion 203 ( It can be adsorbed to the open end of the cavity 201. Then, as shown in FIG. 8, a plurality of balls 109 can be formed in a ring-like arrangement that is necessary for assembling as the fulcrum bearing unit 100 and that are installed at substantially constant intervals. In addition, by adjusting the size of the flange portion 203 at the stage of preparing the jig 210, the size of the ring formed by the plurality of balls 109 can be adapted to the size of the system to be assembled. When the open ends of all the hollow portions 201 existing on the outer diameter surface of the flange portion 203 are closed by the balls 109, the degree of vacuum inside the hollow portion 202 increases. If this degree of vacuum is detected, it can be confirmed that all the balls 109 are attracted to the jig 210.

As shown in FIG. 5, when the balls 109 and the spacer balls 149 are mixed, only the balls 109 are first adsorbed to the jig 210 and arranged in a system assembled by a method described later. A method in which the spacer ball 149 is attracted to the jig 210 after being released from 210 may be used. Alternatively, a spacer ball 149 is attached to the opening end of the other cavity using a jig in which another cavity connected to an exhaust system different from the cavity 201 that adsorbs the ball 109 is provided in the flange 203. You may use the method of arrange | positioning both the ball | bowl 109 and the spacer ball | bowl 149 to the unit assembled at once by making it adsorb | suck.

The following FIGS. 9A to 9C are schematic diagrams showing a procedure for arranging the members in a system to be assembled.

As shown in FIGS. 7 and 8, the balls 109 are in contact with the conical raceway surface 122 of the sleeve 102 as shown in FIG. 109 is transported for placement. Then, when the ball 109 can be arranged at a predetermined position, the vacuum of the vacuum pump connected to the jig 210 is released, and the ball 109 is released from the jig 210. The spacer ball 149 is also arranged at a predetermined position in the same manner as the ball 109. However, depending on the structure of the jig 210, the spacer ball 149 may be arranged after the ball 109 is arranged, or the ball 109 and the spacer 109 may be arranged. You may arrange | position the ball | bowl 149 simultaneously. Further, the sleeve 102 is turned upside down, and the balls 109 (and the spacer balls 149) in the other row are arranged in the same manner as described above. As described above, the state shown in FIG.

Here, in order to prevent the arranged balls 109 and spacer balls 149 from falling off the conical raceway surface 122 of the sleeve 102, oil or the like used at the time of completion, for example, is applied to the conical raceway surface 122 of the sleeve 102 in advance. It is preferable to apply a paste such as grease for temporarily fixing the arranged balls 109.

Next, the sleeve 102 and ball 109 (and spacer ball 149) of FIG. 9 (A) are fitted to the shaft 101 as the inner member from above, so that the sleeve as shown in FIG. 9 (B). The shaft 101 can be disposed on the inner peripheral side of the ball 102 and the ball 109 (and the spacer ball 149). Further, an adjustment ring 123 provided with a conical raceway surface 141 and a conical raceway surface 142 as inner raceway surfaces is disposed at a predetermined location and temporarily adhered to the adhesion surface 124 of the shaft 101 shown in FIG. Further, the seal 125 shown in FIG. 1 is also arranged in a notch 135 shown in FIG. 9A or 9B, which is a predetermined portion on the surface facing the shaft 101 of the sleeve 102, and is fitted or adhered. Although it may be fixed, the seal 125 may be fixed in the step of assembling a subsequent member (S50).

Here, in the step of preparing the shaft 101, the adjustment ring is filled with the adhesive pool 133 shown in FIG. 9C, which is provided in a partial region of the bonding surface 124. It is preferable that 123 is disposed at a predetermined position and temporarily adhered to the shaft 101. The adhesive pool 133 is preferably filled with an adhesive that does not cure until the assembly of the fulcrum bearing unit 100 is completed. For example, an epoxy adhesive is preferably used. Further, in the step of preparing the sleeve 102, the notch 135 provided on the surface of the sleeve 102 facing the shaft 101 is the same adhesive as the adhesive filled in the adhesive pool 133 inside. It is preferable that the seal 125 is temporarily disposed after a part of is applied.

By the above procedure, as shown in FIG. 9C, when the step of temporarily assembling the members of the fulcrum bearing unit 100 (S30) is completed, the step of burnishing the raceway surface (S40) is performed. Specifically, this is a step of reducing the surface roughness Ra to the inner raceway surface and the outer raceway surface having a conical shape.

As described above, for example, the conical raceway surface 141 as the first contact surface that is the inner raceway surface, and the conical raceway surface 142 that is the second contact surface having a conical surface shape intersecting the first contact surface. Further, it is not necessary to perform processing for reducing the surface roughness Ra on the entire surface of the conical raceway surface 122 as the third contact surface which is the outer raceway surface. As shown in FIG. 4 described above, it is only necessary to perform a process for reducing the surface roughness Ra only in a region where the balls 109 which are rolling elements contact, among these contact surfaces.

For this purpose, after the temporary assembly as shown in FIG. 9C, an inner raceway surface that contacts the ball 109 from the ball 109 with a load several to several tens of times the preload applied to the fulcrum bearing unit 100. And add to the outer raceway. Then, while applying the above-described load, relative rotation is applied several times so that the sleeve 102 is in a state of rotational movement relative to the shaft 101. Then, the contact stress between the ball 109 and the raceway surface exceeds the yield stress of the raceway surface. Therefore, the surface of the raceway surface is plastically deformed by the stress applied by the ball 109, and the surface of the raceway surface in contact with the ball 109 is smoothed to reduce the surface roughness Ra. Burnishing process is performed. At this time, since the ball 109 rotates with the relative rotation of the sleeve 102, the ball 109 is processed to reduce the surface roughness Ra of the entire first region in contact with the ball 109 while rotating. Do. Therefore, the ball 109 does not process the second region of the raceway surface that does not contact the ball 109. As a result, the surface roughness Ra of the first region can be made smaller than the surface roughness Ra of the second region.

In FIG. 10, the horizontal axis indicates the position coordinates of the raceway surface (position coordinates in the direction intersecting with the extending direction of the burnished region), and the vertical axis indicates the unevenness height of the surface. Is. In the region of the position coordinates described as “burnishing position” in FIG. 10, burnishing is performed, and the displacement of the vertical axis is small. In other words, it can be seen that the surface roughness Ra is reduced and the surface is smoothed at the burnished portion. As an actual measurement value, for example, a surface having a 10-point average roughness Rz of 1 μm before burnishing has Rz of 0.02 μm due to burnishing.

By the way, in the embodiment of the present invention, the step of temporarily assembling the members (S30) is completed before the step of burnishing the raceway surface (S40). That is, the step (S40) is performed in a state where the configuration as the fulcrum bearing unit 100 has already been completed. FIG. 11 is a schematic cross-sectional view showing a mode of processing a raceway surface on which a ball rolls in the embodiment of the present invention. In FIG. 11, the hatched portion represents a cross section.

As shown in FIG. 11, the unit that has been temporarily assembled in the step (S 30) is installed on the shaft end support 131. Then, a downward load is applied to the adjustment ring 123 using the holding jig 132. First, F1 which is several times to several tens of times the preload applied to incorporate the fulcrum bearing unit 100 is applied to this load. Then, as shown in FIG. 11, the pressing plate 184 in contact with the outer peripheral surface of the sleeve 102 applies a force to the sleeve 102 in the direction from the sleeve 102 toward the shaft 101 (the direction from right to left in FIG. 11). In addition, the sleeve 102 is driven to rotate along the outer peripheral surface of the sleeve 102 by a frictional force with the sleeve 102.

Note that the sleeve 102 may be driven by a frictional force using a method other than the presser plate 184. For example, there is a method called a capstan drive or a belt drive. In addition, as a method of applying F1 that is several times to several tens of times the preload, a method using a spring, a method using a dead weight, a method using hydraulic pressure or air pressure may be used.

Since the ball 109 performs a rotational movement with the relative rotation of the sleeve 102, the ball 109 is rotated and moved to reduce the surface roughness Ra of the entire first region in contact with the ball 109 in the raceway surface. Therefore, the ball 109 does not process the second region of the raceway surface that does not contact the ball 109. As a result, the surface roughness Ra of the first region can be made smaller than the surface roughness Ra of the second region. In this way, by performing processing for reducing the surface roughness Ra only on a part of the raceway surface, the processing tact time can be shortened and low-cost processing can be realized.

Further, as described above, after all the members are temporarily assembled, the ball 109 as a rolling element is pressed against a predetermined region, whereby both the upper and lower rows of balls 109 roll. All the processes for reducing the surface roughness Ra on both the surface and the outer raceway surface can be performed at once. Thus, the machining tact time can be further shortened and low-cost machining can be realized as compared with the case where the inner raceway surface and the outer raceway surface are burned separately.

The step (S40) may be performed after the temporary assembly in the step (S30) or before the assembly in the parts stage before the temporary assembly in the step (S30). And may be burned separately. However, the positional deviation between the inner raceway surface and the outer raceway surface can be reduced by performing the burnishing process in step (S40) after the temporary assembly in step (S30). Further, the positional deviation between the first region where the surface roughness Ra is reduced by burnishing and the region where the balls 109 are in contact with the raceway surface when actually assembled as the fulcrum bearing unit 100 is used. Can be reduced.

After performing sufficient burnishing on each raceway surface of the balls 109 by the above method, the step of assembling the members (S50) is performed. Specifically, in the step (S30), each member is temporarily fixed to the unit that has been temporarily assembled, and each member is fixed by final fixing to complete the configuration of the fulcrum bearing unit 100. In this step (S50), the load applied by the pressing jig 132 is reduced from F1 to F, which is a preload for fixing the adjustment ring 123, for example. The entire unit shown in FIG. 11 with the press plate 184 removed with the preload set to F is placed in a furnace and heated to the curing temperature of the adhesive. Thus, the adhesive filled in the adhesive pool 133 in the previous step can be cured, and the adjustment ring 123 can be fixed to the shaft 101. Further, the seal 125 is also adhered to the sleeve 102 using the same adhesive while being fitted in the cut 135 shown in FIG. 9A or 9B.

In order to fix the adjustment ring 123 with high rigidity, in order to uniformly apply the preload F so that the load is not biased with respect to the adjustment ring 123, for example, the preload F is applied via an aligning seat. Is preferred. By applying the preload F in this way, the inner member (the shaft 101 and the adjusting ring 123) and the outer member (sleeve 102) constituting the fulcrum bearing unit 100 even when the fulcrum bearing unit 100 is in operation. It becomes easy to maintain contact between the ball 109 and the ball 109. As a result, the rigidity of the swing arm bearing is improved, and the rotation accuracy and positioning accuracy of the swing arm bearing are improved.

As described above, the step (S40) may be performed after the temporary assembly in the step (S30), or before the assembly in the parts stage before the temporary assembly in the step (S30). And the outer raceway surface may be burned separately. When the burnishing process (S40) is performed before the process (S30) is performed, for example, a position shift between the inner raceway surface and the outer raceway surface or a process for reducing the surface roughness Ra by the burnishing process is performed. It is preferable to reduce the influence of the positional shift between the region 1 and the region where the balls 109 are in contact with the raceway surface in actual use on the product performance. For example, by increasing the diameter of the ball 109 used for the burnishing process, if the burnishing process area is widened, the influence of the positional deviation on the product performance can be reduced. Alternatively, by increasing the hardness of the balls 109 used for the burnishing process and increasing the contact stress applied during the burnishing process, the area where the burnishing process is performed can be widened.

(Embodiment 2)
In the swing arm 1 shown in FIG. 12, a fulcrum bearing unit 200 as a swing arm bearing is incorporated at the center of gravity.

The adjusting ring 123 and the shaft 101 constitute an inner member. As will be described later, the adjustment ring 123 is provided as a second inward member independent of the shaft 101 for the convenience of assembling the fulcrum bearing unit 100. The adjustment ring 123 is in contact with each of the balls 109 as a plurality of rolling elements at one point as will be described later. In addition, the width in the direction intersecting the major axis direction of the shaft 101 is widened as shown in FIG. 12 near the lower portion of the shaft 101, that is, in the vicinity where the lower balls 109 are present in two rows in the vertical direction. A conical track surface 120 having a conical surface shape, that is, a linear shape in a cross section including the rotation axis of the swing arm bearing is provided directly on the outer peripheral surface of the region. The conical raceway surface 120 as the inner raceway surface is in contact with each of the plurality of balls 109 at one point. Also, the sleeve 102 has two conical raceway surfaces 122 which are outer raceway surfaces for contacting the balls 109 in the vicinity of the upper balls 109 out of the two rows arranged in the vertical direction, and the lower side. In the vicinity where the balls 109 exist, two conical track surfaces 122 which are outer track surfaces for contacting the balls 109 are provided so as to intersect with each other.

In the fulcrum bearing unit 200 shown in FIG. 12, there are two contact points between the sleeve as the outer member and the plurality of balls 109. For example, as shown in FIG. 13, the upper ball 109 is formed on the conical track surface 122 that is the first contact surface formed on the sleeve 102 and on the second contact surface that intersects the first contact surface. Contact points are provided at two locations on a conical raceway surface 122. Further, as shown in FIG. 14, the lower ball 109 is a conical track surface 122 as a first contact surface formed on the sleeve 102 and a second contact surface intersecting the first contact surface. Contact points are provided at two locations on the conical track surface 122.

The fulcrum bearing unit 200 does not include an inner ring and an outer ring that are used for ordinary bearings. For example, the adjustment ring 123 is directly provided with a conical track surface 141 which is a third contact surface in contact with the ball as the inner track surface. Therefore, the balls 109 are arranged in contact with the inner raceway surface of the inner member (the shaft 101, the adjustment ring 123) and the outer raceway surface of the outer member (sleeve 102). That is, the balls 109 are in contact with the inner raceway surface and the outer raceway surface at a total of three points. Thus, in the fulcrum bearing unit 200, the fulcrum bearing unit 200 according to the second embodiment is in contact with the outer raceway surface at two points and is in contact with the inner raceway surface at one point. Different from the unit 100. Further, the fulcrum bearing unit 200 of the second embodiment has the same aspect as the fulcrum bearing unit 100 of the first embodiment.

Specifically, as shown in FIG. 13, the upper ball 109 is in contact with the adjustment ring 123 fitted to the shaft 101 at one point (contact point 143) on the conical track surface 141, and outward. The sleeve 102 as a member contacts the two conical track surfaces 122 at two points (contact point 144 and contact point 145, respectively). Further, as shown in FIG. 14, the lower ball 109 is a conical shape having a conical shape directly provided on the outer peripheral surface of a region where the width in the direction intersecting the major axis direction of the shaft 101 is widened. Contact is made at one point (contact point 153) on the raceway surface 120, and contact is made with the sleeve 102 as the outer member at two points (contact point 154, contact point 155) on the two conical raceway surfaces 122. Note that the angles formed by the three contact points between the plurality of balls 109 and the raceway surface and the center O of the balls 109 are as shown in FIG. 13 or FIG.

Similarly to the fulcrum bearing unit 100, the fulcrum bearing unit 200 is a part of the surface of the conical raceway surface 120, which is a part of the conical raceway surface 120 and is sandwiched between two dotted lines in FIG. Only a certain surface roughness improving processing region 120A is subjected to processing for improving the surface roughness Ra (decreasing the surface roughness Ra).

During the rotation operation of the swing arm 1, not the entire surface of the conical track surface 120, but a region in the vicinity of the central portion thereof, that is, a surface roughness improving processing region 120 A shown in FIG. The ball 109 rolls in contact with the surface roughness improving processing region 120 A of the conical raceway surface 120. Therefore, when the surface roughness of the surface roughness improving processed region 120A is large, the oil film parameter may be small and the durability of the bearing may be reduced. In order to suppress such a phenomenon, the conical raceway surface 120 is processed to reduce the surface roughness Ra of the surface roughness improving processing region 120A. Thereby, sufficient durability can be imparted to the fulcrum bearing unit 200. Furthermore, at this time, as shown in FIG. 4, not the entire surface of the conical raceway surface 120 that is the inner raceway surface, but only the surface roughness enhancement processing region 120A (first region) that contacts the ball 109. It is sufficient to apply a process for reducing the degree Ra. The manufacturing cost of the fulcrum bearing unit 200 can be reduced by limiting the region to be processed to reduce the surface roughness Ra to only the surface roughness improving processing region 120A.

Further, when the fulcrum bearing unit 200 is used, the balls 109 roll while the balls 109 are in contact with the outer raceway surface and the inner raceway surface. Here, for example, if an external impact load is applied to the fulcrum bearing unit 200 as an unexpected external force, the ball 109 applies an impact load to the raceway surface (outer raceway surface or inner raceway surface) with which the ball 109 is in contact. Therefore, there is a possibility that an indentation is generated on the raceway surface. In order to suppress such indentation during use, it is preferable to increase the hardness of the raceway surface to such an extent that the indentation does not occur. For this purpose, as described above, for example, the hardness of the inner raceway surface of the shaft 101 that is the inner member and the adjustment ring 123 is HRC40 or higher, and the hardness of the outer raceway surface of the sleeve 102 that is the outer member is HRC25 or higher. preferable. As described above, the ball 109 and the outer raceway surface are in contact at two points, and the ball 109 and the inner raceway surface are in contact at one point. Therefore, the outer raceway surface contacting at two points receives less stress when an impact load is applied from the ball 109, for example, than the inner raceway surface contacting at one point. Accordingly, the hardness of the outer raceway surface can be made lower than that of the inner raceway surface.

Note that if the hardness of the inner raceway surface and the outer raceway surface is increased, machining becomes difficult, and the cost required for machining increases. In order to suppress this, as described above, for example, the hardness of the inner raceway surface of the shaft 101 that is the inner member and the adjustment ring 123 is HRC50 or less, and the hardness of the outer raceway surface of the sleeve 102 that is the outer member is HRC35. The following is preferable. From the above, the hardness of the inner raceway surface (for example, the conical raceway surface 141 and the conical raceway surface 120) of the shaft 101 and the adjustment ring 123 is HRC40 or more and HRC50 or less, and the outer raceway surface (for example, the conical raceway surface 122) of the sleeve 102. The hardness is preferably HRC25 or more and HRC35 or less. Of these, the inner raceway surface hardness is more preferably HRC43 to HRC47, and the outer raceway hardness is more preferably HRC28 to HRC32. In this way, it is possible to provide the fulcrum bearing unit 100 capable of suppressing the generation of indentation due to an unexpected impact load or the like when using the swing arm 1 without increasing the processing cost.

As described above, the outer raceway surface can be made harder than the inner raceway surface. In other words, it is preferable that the inner raceway surface, for example, the conical raceway surface 120 has a higher hardness than the outer raceway surface, for example, the conical raceway surface 122. However, as shown in FIG. 12, the fulcrum bearing unit 200 has a region in the vicinity of the central axis that extends in the major axis direction of the shaft 101 that is the inner member, that is, a region that includes the central axis of the inner raceway surface of the shaft 101. Are formed with holes 161 and screws 162 used for fixing the fulcrum bearing unit 200 to other members. Therefore, it is preferable that the shaft 101 as the inner member has a conical surface 120 as the inner raceway surface on the outer peripheral portion thereof, so that the hardness is high (preferably HRC 40 or more), but the hole 161 exists. In order to easily perform the process of forming the hole 161, it is preferable that the hardness of the region of the central portion is lower than that of the outer peripheral portion such as the conical raceway surface 120.

That is, the subsequent machining cost can be reduced by increasing the hardness only in the region of the outer peripheral portion forming the conical raceway surface 120 as the inner raceway surface. Specifically, the hardness of the surface layer portion of the hole 161 is preferably HRC25 or less. If the hardness of the central portion of the shaft 101 is lowered to such an extent that the hardness of the surface layer portion of the hole 161 is HRC25 or less, the process of forming the hole 161 and the screw 162 sufficiently reduces the cost of performing the process. It will be as easy as possible.

It is preferable that the outer peripheral portion (the region including the conical raceway surface 120 which is the inner raceway surface) of the shaft 101 which is the inner member is subjected to a treatment for increasing the hardness by induction hardening. When induction hardening is performed, the outer peripheral portion of the member such as the shaft 101 is positively heated to be hardened and hardened, and the central portion of the shaft 101 (for example, the region where the hole 161 is formed) is not hardened. Thus, the desired hardness distribution can be easily imparted to the shaft 101.

Next, a manufacturing method of the swing arm bearing (fulcrum bearing unit 200) according to the second embodiment will be described. FIG. 17 is a diagram for explaining a manufacturing process of the inner member (shaft 101). Further, FIG. 18 is a view for explaining a manufacturing process of the inner member (adjustment ring 123). In each of FIGS. 15 to 18, the hatched portion represents a cross section. Hereinafter, a method for manufacturing the fulcrum bearing unit according to the second embodiment will be described with reference to FIGS. 15 to 18 using the fulcrum bearing unit 200 shown in FIG. 12 as an example.

First, the step (S100) of preparing the member shown in FIG. 15 is performed. This is an inner member in which, for example, an annular inner raceway surface is formed on the outer peripheral surface of the fulcrum bearing unit 200 shown in FIG. This is a step of preparing a member such as a sleeve 102 as an outer member and an adjustment ring 123 as an inner member to be connected to a swing arm of a hard disk drive. .

The step of preparing the member (S100) is basically the same as the step of preparing the member (S10), but will be described in more detail with reference to FIGS. In the step of preparing the shaft 101 in the step of preparing the member (S100), first, the step of induction hardening (S11) shown in FIG. 16 is performed. In this step (S11), as shown in FIG. 17A, the upper side of the dotted line 171 corresponding to the outer peripheral portion of the steel material 99 such as a steel bar or steel wire made of SUS420J2, SUJ2, SUS440C, etc., which is the material of the shaft 101. In addition, the region below the dotted line 172 is subjected to induction heating and then hardened by rapid cooling (induction hardening). The length of the finished product shown in FIG. 17 (F) according to this embodiment (the length in the left-right direction in FIG. 17 (F)) is 6 to 7 mm, and the length of the steel material 99 is 1000 to 2000 mm. . Here, it is preferable to perform induction hardening so that the hardness of the region above the dotted line 171 and below the dotted line 172 is HRC 40 or higher and HRC 50 or lower, which is the preferred hardness of the conical track surface 120 formed on the shaft 101. . In addition, it is more preferable to set it as HRC43 or more and HRC47 or less. In this way, it is possible to suppress the occurrence of indentation on the conical track surface 120 (see FIG. 12) due to an unexpected impact load when using the swing arm 1 without increasing the processing cost.

Also, in the step of preparing the adjustment ring 123 in the step of preparing the member (S100), the step of induction hardening (S11) shown in FIG. 16 is first performed. In this step (S11), as shown in FIG. 18A, in order to set the hardness of the conical track surface 141 (see FIG. 1) to HRC40 or more and HRC50 or less, the outer peripheral portion of the steel material 99, that is, FIG. Induction hardening and tempering are performed so that the hardness of the region above the dotted line 171 and below the dotted line 172 is HRC40 or higher and HRC50 or lower.

Next, in the step of drilling (S12) following the step (S11) in FIG. 16, the central portion of the shaft 101 (the region including the central axis of the inner raceway surface) shown in FIG. A hole 161 that is a cavity is formed in a direction extending in the central axis (long axis direction) with respect to the central portion (region including the central axis of the inner raceway surface) of the adjustment ring 123 shown in B). In this step (S12), the steel material 99 induction-hardened in the step (S11) is rotated around the central axis extending in the major axis direction, for example, by using a center cutting tool, the central portion region. A hole 161 having a predetermined diameter is formed in the substrate. In order to reduce the load required for this step, to facilitate processing, and not to increase the cost of processing, the hardness of the central portion of the steel material 99 in which the hole 161 is formed is HRC 25 or less. Preferably there is.

The subsequent tapping process (S13) shown in FIG. 16 is a process of forming the screw 162 on the wall surface surrounding the hole 161 as shown in FIG. Specifically, a thread (screw 162) can be formed by machining a wall surface surrounding the hole 161 using a tapping tool. This step (S13) is omitted in the step of preparing the adjustment ring 123 that does not require the thread formation.

In order to reduce the load required for this process, to enable easy processing, and not to increase the processing cost, as described above, in particular, the surface layer portion of the wall surface surrounding the hole 161 The hardness is preferably HRC25 or less.

Then, in the turning process (S14) shown in FIG. 16, as shown in FIGS. 17D and 18C, the turning process for forming the outer shapes of the shaft 101 and the adjustment ring 123 is performed. Specifically, turning is performed along an outer shape line 163 showing the outer shape of the shaft 101 shown by a dotted line in FIG. 17D and an outer shape line 165 showing the outer shape of the adjustment ring 123 shown by a dotted line in FIG. Processing to remove the outside of the outline is performed. In this way, an outer shape including the conical track surface 120 of the shaft 101 is formed as shown in FIG. In addition, an outline 165 in FIG. 18C is a conical track surface 141 of the completed adjustment ring 123. The turning process (S14) for forming these conical raceway surfaces is the same as the taper machining process (S20) in FIG.

Referring further to FIG. 16, in the step of preparing shaft 101, a step (S15) that is a step of cutting is performed. In this step (S15), the steel material 99 is cut along the cutting line 164 in FIG. Thereby, as shown in FIG. 17F, the shaft 101 on which the conical track surface 120 is formed is completed. In addition, referring to FIG. 16, also in the step of preparing adjustment ring 123, a step (S15) that is a step of cutting is performed. In this step (S15), referring to FIGS. 18C and 18D, the steel material 99 is cut to adjust the conical track surface 141 as shown in FIG. 18D. The ring 123 is completed. By the above procedure, the shaft 101 and the adjustment ring 123 that constitute the inner member of the fulcrum bearing unit 200 are prepared. In the above description, the step of preparing the shaft 101 and the adjustment ring 123 constituting the inner member has been described. However, the above steps (S11) to (S12) and (S14) also apply to the sleeve 102 which is the outer member. Preparation can be made by performing the same process as in (S15).

When each member constituting the fulcrum bearing unit 100 is prepared, a temporary assembling step (S200) shown in FIG. 15 is performed. This can be explained using FIG. 7, FIG. 8, FIG. 9 (A) and FIG. 9 (B) described above, as in the step of temporarily assembling the members in FIG. 6 (S30). When the step of temporarily assembling the members of the fulcrum bearing unit 100 (S200) is completed, as shown in FIG. 9C, a plurality of balls 109 are arranged on the inner raceway surface (conical raceway surface) of the shaft 101 and the adjustment ring 123. 141, 120) at one point and in contact with the outer raceway surface (conical raceway surface 122) of the sleeve at two points. Next, as shown in FIG. 15, a step of plastic working the raceway surface (S300) is performed. This is basically the same mode as the step of burnishing the raceway surface in FIG. 6 (S40), and this will also be described in more detail than the above-described step of burnishing (S40).

As shown in FIG. 11, the pressing plate 184 in contact with the outer peripheral surface of the sleeve 102 applies a force to the sleeve 102 in the direction from the sleeve 102 toward the shaft 101 (the direction from right to left in FIG. 13). However, the sleeve 102 is rotated along the outer peripheral surface of the sleeve 102 by the frictional force with the sleeve 102. This will be described in more detail below.

The force in the direction applied from the upper side to the lower side with respect to the holding jig 132 shown in FIG. 11 is referred to as an axial force, and the force applied to the sleeve 102 by the pressing plate 184 is referred to as a radial force. As shown in FIG. 11, the presser disc 184 applies a radial force to the sleeve 102 while rotating (spinning) at a rotational speed ω 1 by a motor 181 connected thereto. In addition, in FIG. 11, although the aspect of the fulcrum bearing unit 100 is drawn, the fulcrum bearing unit 200 also takes the same aspect.

Then, the sleeve 102 rotates around the shaft 101. This is because the unit shown in FIG. 11 including the sleeve 102 has already been temporarily assembled as the fulcrum bearing unit 200 (see FIG. 12). As described above, the sleeve 102 which is the outer member is relatively rotated around the shaft 101 which is the inner member. In this way, for example, plastic working can be performed by applying a force to the region where the conical raceway surface 141 contacts the ball 109 and the region where the conical raceway surface 122 contacts the ball 109. The above processing method is burnishing processing according to Embodiment 2 of the present invention.

As described above, the burnishing can be performed in a temporarily assembled state as the fulcrum bearing unit 200 (see FIG. 12). Therefore, there is no need to perform a process of grinding the raceway surface with, for example, a grindstone before performing the temporary assembly step (S20). Further, in a state where provisional assembly has already been performed, the first region in which the balls 109 are in contact with each other by simply rotating the sleeve 102 which is the outer member around the shaft 101 which is the inner member. The surface roughness Ra can be easily made smaller than the surface roughness Ra of the second region adjacent to the first region in the raceway surface. For this reason, by performing the burnishing process, it is possible to omit the process of previously grinding the raceway surface with, for example, a grindstone (the entire raceway surface). For this reason, the labor and cost required for processing can be greatly reduced.

Here, as described above, for example, while the presser plate 184 is rotated by the motor 181, the presser plate 184 rotates the sleeve 102 which is an outer member. Therefore, the conical raceway surface 122 which is the raceway surface of the sleeve 102 is plastically processed over the entire circumference. However, when the inner member (the shaft 101 and the adjustment ring 123) is stationary, the conical track surfaces 141 and 120, which are the track surfaces of the inner member, are partially in the circumferential direction (the shaft 101 in FIG. 11). Only the right side) of the rotating shaft is plastically processed, and there is a possibility that it is not fully processed over the entire circumference. In order to eliminate this problem, it is preferable to rotate the inner member around the axis when performing burnishing. Specifically, as shown in FIG. 11, when performing burnishing, it is preferable to rotate (spin) the shaft 101 at a rotational speed ω2 using, for example, a motor 182.

Also, it is necessary to consider the force that the ball 109 applies to the sleeve 102 that is the outer member, the shaft 101 that is the inner member, and the adjustment ring 123 when performing the burnishing process simultaneously with the rotation described above. The force applied by the ball 109 for burnishing the raceway surface of the sleeve 102 is as described above. Hereinafter, the force that the ball applies to burnishing the raceway surface of the inner member (adjustment ring 123) will be described. In addition, about the force applied in order to burnishing the track surface of the axis | shaft 101, since the same view as the track surface of the adjustment ring 123 can be employ | adopted, description is abbreviate | omitted.

If burnishing is performed with only the axial force applied to the adjustment ring 123, for example, as shown in the cross-sectional view of FIG. 19, the conical track surface 141 follows the shape of the surface of the ball 109 (ball surface 109A). Plastically deforms so as to have a shape. In this case, when the fulcrum bearing unit 200 is operated, there is a possibility that the ball 109 is detached from the region plastically deformed by burnishing and climbs up to the point A in FIG. Such a phenomenon causes a fluctuation in torque of the fulcrum bearing unit 200 and is not preferable from the viewpoint of precise position control of the swing arm 1.

On the other hand, by performing burnishing while applying not only the axial force but also the radial force, the conical track surface 141 is closer to a plane (along the cross section of the conical track surface 141), as shown in FIG. Plastically deformed into a shape that spreads in the opposite direction and the curvature becomes smaller. Thereby, the problem of torque fluctuation as described above can be suppressed.

From the above, when burnishing is performed, it is preferable to apply both axial force and radial force to the temporarily assembled unit. In addition, it is more preferable to apply these axial force and radial force simultaneously.

In the burnishing process described above, the axial force (F1) and radial force (F2) applied to the temporarily assembled unit shown in FIG. This is the force applied to process the raceway surface. Therefore, for example, the above-described F1 is about 3 to 5 times the preload F applied when performing the following assembling step (S40) described below.

Of the raceway surfaces of the fulcrum bearing unit 200 (see FIG. 12) after the burnishing process described above, the surface roughness of the region in contact with the ball 109 is the centerline average roughness Ra. It is preferable that it is 0.02 μm or less. In order to set Ra to 0.02 μm or less after burnishing, the surface roughness Ra of the inner raceway surface and the outer raceway surface before the step of plastic working the raceway surface (S30) is 0.3 μm. The following is preferable. In addition, as for surface roughness Ra of each said track surface before performing the said process (S30), it is more preferable that Ra is 0.14 micrometer or less. In this way, by performing the above-described burnishing, the surface roughness Ra in the region where the balls 109 are in contact with each other is reduced to 0, which is sufficient to suppress fluctuations in the torque of the swing arm bearing. It is easy to make the thickness 0.02 μm or less.

Referring to FIG. 15, after the surface roughness Ra of each raceway surface is reduced by the step of plastically processing the raceway surface (S300), the main assembly step (S400) is performed. This is basically the same as the step of assembling the members in FIG. 6 (S50). In the assembling step (S400), the radial force by the pressing plate 184 is changed from F2 to zero. Among the units shown in FIG. 11, the entire unit excluding the press plate 184 and the motor 181 is placed in a furnace and heated to the curing temperature of the adhesive.

(Embodiment 3)
Referring to FIG. 21, a fulcrum bearing unit 300 that is a swing arm bearing in the third embodiment includes an inner member that functions as a fixed shaft, a sleeve 102 that is disposed so as to surround the inner member, and an inner member. A plurality of balls 109 as rolling elements arranged in a double row (two rows) between the side member and the sleeve 102 and an annular shape, and are arranged between the inner member and the sleeve 102. In addition, a first cage 15A and a second cage 15D are provided that hold the balls 109 on an annular track so as to be freely rollable at a predetermined pitch. The inner member includes a shaft 101 and an adjustment ring 123 having an annular shape that is fitted to the outer peripheral surface of the shaft 101.

A conical raceway surface 120 as an annular shaft raceway surface is formed on the outer peripheral surface of the shaft 101. A conical track surface 141 as an annular ring track surface is formed on the outer peripheral surface of the adjustment ring 123. On the other hand, on the inner peripheral surface of the sleeve 102, a conical raceway surface 122 as a first annular raceway surface and a position facing the conical raceway surface 120 and a location facing the conical raceway surface 141, respectively. A conical raceway surface 122 is formed as the second sleeve raceway surface. The conical raceway surface 120, the conical raceway surface 141, and the two conical raceway surfaces 122 have a conical surface shape.

Some of the plurality of balls 109 are included in a first row arranged in contact with the conical raceway surface 120, the conical raceway surface 122, and the conical raceway surface 122. The remainder of the plurality of balls 109 is included in a second row arranged in contact with the conical raceway surface 141, the conical raceway surface 122, and the conical raceway surface 122. The first column and the second column are aligned in the axial direction. The balls 109 included in the first row and the balls 109 included in the second row are held by the first holder 15A and the second holder 15D, respectively. Further, the balls 109 come into contact with the conical raceway surface 122 and the conical raceway surface 122 and one of the conical raceway surface 120 and the conical raceway surface 141, thereby serving as the inner member 21 and the outer member. The sleeve 102 is in contact at three points. With the above configuration, the sleeve 102 is rotatable with respect to the inner member 21.

Furthermore, the swing arm 1 is connected to the outer peripheral surface of the sleeve 102, and the magnetic head 2 is attached to the end of the swing arm 1 opposite to the side connected to the sleeve 102. Then, the swing arm 1 is rotated by a driving device such as a motor (not shown), and the magnetic head 2 is moved to an arbitrary position on a disk (not shown) so that information can be read and written.

That is, the fulcrum bearing unit 300 in the present embodiment is formed with a conical raceway surface 120 and a conical raceway surface 141 as annular inner raceway surfaces on the outer peripheral surface, and functions as a fixed shaft of the swing arm 1 of the hard disk drive. The inner member 21 and the conical raceway surface 120 are disposed so as to surround the inner member 21, and two conical raceway surfaces 122 are formed as an annular outer raceway surface facing the conical raceway surface 120 and the conical raceway surface 141. And a sleeve 102 as an outer member to which the swing arm 1 is to be connected. Further, the fulcrum bearing unit 300 includes a conical raceway surface 120 or a conical raceway surface 141, a conical raceway surface 122, and a plurality of balls 109 as rolling elements arranged in contact with the conical raceway surface 122, A first retainer 15A that has an annular shape, is disposed between the inner member 21 and the sleeve 102, and holds a plurality of balls 109 on an annular track so as to be freely rollable at a predetermined pitch. And a second cage 15D.

In the fulcrum bearing unit 300 in the present embodiment, the inner member 21 functioning as a fixed shaft and the sleeve 102 to be connected to the swing arm 1 are formed with mutually opposing raceway surfaces, and between the raceway surfaces. In addition, the ball 109 as a rolling element is rotatably held by the first cage 15A and the second cage 15D. As a result, the assembly process can be simplified and the manufacturing cost can be reduced as compared with a conventional configuration in which a rolling bearing having an inner ring and an outer ring is fitted between the sleeve 102 and the shaft 101. As a result, the fulcrum bearing unit 300 in the present embodiment is a low-cost swing arm bearing.

Here, in the fulcrum bearing unit 300 in the present embodiment, the first cage 15A and the second cage 15D are made of a resin molded body. As a result, steps such as caulking of the cage can be omitted as compared with the case where a metal cage is used, and the manufacturing cost is further reduced.

Further, in the fulcrum bearing unit 300 in the present embodiment, the first cage 15A and the second cage 15D have a holding portion 15B that holds the ball 109 and a thickness in the radial direction larger than that of the holding portion 15B. And a thick portion 15C. More specifically, each of the first retainer 15A and the second retainer 15D has a thick portion 15C in a region including an end surface opposite to the other retainer when viewed from one retainer. Is formed. And the space | interval (alpha) of the thick part 15C in the 1st holder | retainer 15A and the 2nd holder | retainer 15D, the sleeve 102, and the inner member 21 (shaft 101 or the adjustment ring 123) is 0.05 mm or more and 0.2 mm or less. It has become.

Thereby, the space | interval of the thick part 15C of the 1st holder | retainer 15A and the 2nd holder | retainer 15D, the inner member 21, and the sleeve 102 becomes an appropriate value which can acquire sufficient sealing performance, and is enough It is possible to omit the sealing plate while ensuring a good sealing performance. As a result, in the fulcrum bearing unit 300 in the present embodiment, it is possible to suppress the manufacturing cost. Further, with the above-described configuration, the thick portions 15C that function as a seal are disposed on both sides in the axial direction inside the bearing, so that it is possible to satisfactorily prevent solid foreign matter from entering the bearing.

Further, in the bearing included in the conventional swing arm bearing unit described with reference to FIG. 2, the seal plate is fixed to the outer ring, so that when the seal plate and the inner ring come into contact during the operation of the bearing unit, There is a possibility that the outer ring may not be completely rotatable with respect to the inner ring. On the other hand, in the fulcrum bearing unit 300 in the present embodiment, the first retainer 15A and the second retainer 15D are not fixed with respect to the sleeve 102 and the inner member 21, so Even when the thick portion 15C functioning as a seal and the sleeve 102 or the inner member 21 come into contact with each other, the sleeve 102 does not become completely unrotatable with respect to the inner member 21. Therefore, the interval α can be set to a small value, and excellent sealing performance can be imparted.

Furthermore, the sleeve 102 is formed with a bent portion 13C that bends along the thick portion 15C formed in the first retainer 15A and the second retainer 15D. As a result, of the intrusion path of solid foreign matter from the outside to the inside of the bearing, the area that functions to suppress the intrusion of solid foreign matter by reducing the width of the path, that is, the seal area is bent and becomes a labyrinth shape. Yes. Therefore, intrusion of solid foreign matters is further suppressed, and leakage of grease and the like from the inside of the bearing is further suppressed.

In the present embodiment, the thick portion 15C protrudes radially outward from the holding portion 15B, that is, toward the sleeve 102 that is the outer member, and the bent portion 13C is formed in the sleeve 102. However, the configuration of the bent portion is not limited to this. For example, the thick portion 15C protrudes radially inward with respect to the holding portion 15B, that is, toward the inner member 21 (the shaft 101, the adjustment ring 123), and is bent along the thick portion 15C. May be formed on the inner member 21. Further, the sleeve 102 and the inner member, in which the thick portion 15C protrudes toward both the radially inner side and the outer side with respect to the holding portion 15B, and the bent portion that is bent along the thick portion 15C is the outer member. 21 may be formed on both. That is, the thick portion 15C protrudes toward at least one of the radially inner side and the radially outer side with respect to the holding portion 15B, and the bent portion that bends along the thick portion 15C is the outer member or the inner portion. What is necessary is just to be formed in at least one of the side from which the thick part 15C protrudes among members.

Next, an example of a method for manufacturing a swing arm support mechanism including the fulcrum bearing unit 300 in the present embodiment will be briefly described. First, steel materials (bar steel, steel wire, etc.) that can be hardened by hardening such as JIS standards SUS420J2, SUJ2, and SUS440C are prepared, and the region including the outer peripheral surface is hardened by induction hardening, for example. Next, after the tempering process is performed on the steel material, a cutting process is performed, so that components such as the shaft 101, the adjustment ring 123, and the sleeve 102 are manufactured. At this time, the conical raceway surface 120, the conical raceway surface 141, and the two conical raceway surfaces 122 are included in the hardened and hardened region. As with the fulcrum bearing unit 200 described above, it is preferable that the hardness of the inner raceway surface, for example, the conical raceway surface 120, is higher than the hardness of the outer raceway surface, for example, the conical raceway surface 122. Here, the hardness of the conical raceway surface 120 is preferably HRC40 or more and HRC50 or less, and the hardness of the conical raceway surface 122 is more preferably HRC25 or more and HRC35 or less.

Next, the shaft 101, the adjustment ring 123, and the sleeve 102 are combined with the ball 109, the first cage 15A, and the second cage 15D that are separately prepared, and the fulcrum bearing unit 300 is temporarily assembled. The Specifically, the adjustment ring 123 is fitted into the outer peripheral surface of the shaft 101 in a state where the shaft 101, the sleeve 102, the ball 109, the first retainer 15A, and the second retainer 15D are combined. At this time, the adjustment ring 123 is fitted on the shaft 101 in a state where a thermosetting adhesive is applied to the inner peripheral surface of the adjustment ring 123.

Here, the first cage 15A and the second cage 15D made of a resin molded body can be produced by, for example, resin injection molding. For example, 66 nylon reinforced with glass fiber or the like can be used as the resin used as the raw material for the first cage 15A and the second cage 15D.

Next, on the conical raceway surface 120, the conical raceway surface 141, the conical raceway surface 122, and the conical raceway surface 122, plastic working is performed to reduce the surface roughness of the region in contact with the ball 109. Specifically, for example, an axial force is applied to the fulcrum bearing unit 300 that is temporarily assembled by applying a force that pushes the adjustment ring 123 in the axial direction, and the sleeve 102 is applied to the inner member 21. A radial force is applied by applying a pressing force. At the same time, the inner member 21 and the sleeve 102 are rotated in the circumferential direction, whereby the sleeve 102 is rotated relative to the inner member 21. As a result, in the conical raceway surface 120, the conical raceway surface 141, the conical raceway surface 122, and the conical raceway surface 122, the region that can come into contact with the ball 109 is plastically processed, and the surface roughness is reduced (burnishing process). . Here, similarly to the

fulcrum bearing units

100 and 200 described above, the surface roughness Ra in the first region (surface roughness improving processing region 120A) of the conical raceway surface 120 is, for example, of the conical raceway surface 120. It is preferably smaller than the surface roughness Ra in the region adjacent to the surface roughness improving processing region 120A.

Thereafter, the temporarily assembled fulcrum bearing unit 300 is heated in a state where the adjustment ring 123 is pushed in the axial direction with a force corresponding to a desired preload to be applied to the fulcrum bearing unit 300. Thereby, the above-mentioned adhesive is hardened and the main assembly of the fulcrum bearing unit 300 is completed. Then, the swing arm support mechanism including the fulcrum bearing unit 300 in the present embodiment is completed by attaching the separately prepared swing arm 1 to the outer peripheral surface of the sleeve 102 of the fulcrum bearing unit 300. Through the above process, the swing arm support mechanism including the fulcrum bearing unit 300 in the present embodiment can be easily manufactured. In addition, according to such a process, steps such as fitting of a rolling bearing and attachment of a seal plate by a clasp can be omitted, so that the swing arm bearing and the swing arm support mechanism are manufactured at low cost. be able to.

In addition, in the fulcrum bearing unit 300 described above, the components of the

fulcrum bearing units

100 and 200 may be arbitrarily combined.

(Embodiment 4)
FIG. 22 is a schematic cross-sectional view showing the structure of the fulcrum bearing unit in the fourth embodiment of the present invention. In FIG. 22, the hatched portion represents a cross section. A fulcrum bearing unit 400 in FIG. 22 uses an inner ring 103 as an inward member instead of the adjustment ring 123 and the conical raceway surfaces 120 and 121 in the

fulcrum bearing units

100 and 200. The inner ring 103 is formed with the bearing groove 110 as the above-described third contact surface, and the ball 109 contacts the curved surface of the bearing groove 110 at one point. In addition, the sleeve 102 contacts the ball 109 at two points. Therefore, the sleeve 102 has a conical surface shape, a first contact surface that contacts the ball 109, and a conical surface shape that intersects the first contact surface, and a second contact surface that contacts the ball 109. (Both are conical raceway surfaces 122 in FIG. 22).

As long as the sleeve 102 is in contact with the ball 109 at two points as in the fulcrum bearing unit 400, the inner raceway surface may be the R-side bearing groove 110. The ball 109 comes into contact with the sleeve 102 at two points on the two contact surfaces (both of the conical raceway surfaces 122), and comes into contact with the bearing groove 110 at one point for a total of three points. If two contact points between the ball 109 and the sleeve 102 are determined, the contact point between the ball 109 and the bearing groove 110 is determined at almost one place even if the inner raceway surface is the R-side bearing groove 110. Therefore, the fulcrum bearing unit 300 in which the ball 109 is brought into contact at three points by making contact with the bearing groove 110 of the inner member at one point and contacting at two points with the sleeve 102 as the outer member is described in the first embodiment. This is the same as the fulcrum bearing unit 100 in terms of function and effect. The fourth embodiment of the present invention is different from the first embodiment of the present invention in the above points. That is, in the description of the fourth embodiment of the present invention, all configurations, conditions, processes, effects, and the like not described above are the same as those of the first embodiment of the present invention.

By the way, in the fulcrum bearing unit of the present invention, if the balls 109 are in contact with the inner raceway surface and the outer raceway surface at a total of three points, the contact angle is uniquely determined. As a result, the rolling element load can be stabilized and torque fluctuations can be suppressed. Therefore, in order to make contact at a total of three points, for example, the inner ring of the adjustment ring 123 that is an inner member is provided with two R-plane bearing grooves that intersect each other, and the sleeve 102 that is of the outer member is provided with an outer track. An effect similar to that described above can be obtained by providing one R-surface bearing groove as a surface, and the ball 109 is in contact with each bearing groove at one point, for a total of three points.

As described above, the inner raceway surface and the outer raceway surface are conical raceway surfaces, whereby the rigidity of the swing arm bearing is improved, and the rotation accuracy and positioning accuracy of the swing arm bearing are improved. Further, since the conical surface shape is easier than the R-surface shape processing for forming the bearing groove, the processing cost may be reduced. In order to have the effects as described above, at least one of the configuration in which the balls are in contact at a total of three points and the above-described first contact surface, second contact surface, and third contact surface has a conical surface shape. The following various types of fulcrum bearing units, which are appropriately combined with the configuration described above, are preferable because, for example, the same effects as the fulcrum bearing units in the above-described embodiments can be obtained.

Hereinafter, the configurations of the various types of fulcrum bearing units described above will be described while presenting only enlarged cross-sectional views of the region “20” surrounded by a dotted line in FIG. As shown in FIG. 23, the first contact surface among the three contact surfaces with which the balls 109 are in contact with the track surface, the second contact surface is provided as an inner track surface on the adjustment ring 123 which is an inner member, Both contact surfaces intersect each other. The third contact surface is provided as an outer raceway surface on the sleeve 102 which is an outer member. These contact surfaces are all R-side bearing grooves 111 as raceway surfaces. In this fulcrum bearing unit, the first contact surface, the second contact surface, and the third contact surface described above are all R-side bearing grooves 111, but the balls 109 have a total of three bearing grooves. Since the contact is made at a point, the contact angle is uniquely determined, the rolling element load can be stabilized, and the fluctuation of the torque can be suppressed. For example, the lower ball 109 such as the region “30” in FIG. 2 may be configured to contact the bearing groove at three points. Further, in FIG. 23, the inner member, that is, the inner raceway surface is contacted at two points, and the outer member, that is, the outer raceway surface, is contacted at one point. It may be configured to contact at two points.

23, in which all the three contact surfaces are bearing grooves, for example, as shown in FIG. 24, at least one of the first contact surface and the second contact surface intersecting each other has a conical shape. It is good also as a shape. Further, for example, the first contact surface provided in the adjustment ring 123 which is an inward member is a bearing groove 111 and the second contact surface is a conical raceway surface 142. For example, the first contact surface is a conical shape. The raceway surface 142 and the second contact surface may be the bearing groove 111. For example, the lower ball 109, such as the region “30” in FIG. In FIG. 24, the inner member is in contact at two points and the outer member at one point, but conversely, the inner member is in contact at one point and the outer member is in contact at two points. One of the track surfaces may be a conical track surface.

25, the first contact surface is a bearing groove 111, the second contact surface is a conical raceway surface 142, and the third contact surface is a conical raceway surface 122. FIG. 25 shows that the third contact surface may be a conical track surface in addition to the configuration shown in FIG. Also in this case, for example, the first contact surface provided in the adjustment ring 123 which is an inward member is the bearing groove 111, and the second contact surface is a conical raceway surface 142. For example, the first contact surface The conical raceway surface 142 and the second contact surface may be the bearing groove 111. For example, in addition to the configuration shown in FIG. 16, if the second contact surface is also a conical track surface, the configuration in accordance with the configuration of the fulcrum bearing unit 100 shown in the first embodiment of the present invention described above is used. Become. For example, the lower ball 109, such as the region “30” in FIG. In FIG. 25, the inner member is in contact at two points and the outer member at one point, but conversely, the inner member is in contact at one point and the outer member is in contact at two points. One of the track surfaces may be a conical track surface.

26, the third contact surface may be a conical track surface, and the first and second contact surfaces may be bearing grooves 111. For example, the lower ball 109, such as the region “30” in FIG. In FIG. 26, the inner member is in contact at two points and the outer member at one point, but conversely, the inner member is in contact at one point and the outer member is in contact at two points. One of the track surfaces may be a conical track surface.

That is, any one of the first contact surface, the second contact surface, and the third contact surface described above may be a bearing groove, and the other two may be conical track surfaces. Any two of the three contact surfaces may be bearing grooves, and the other one may be a conical track surface.

In Example 1, an attempt was made to calculate the hardness required for the inner raceway surface and the outer raceway surface of the fulcrum bearing unit 200 according to Embodiment 2 of the present invention described above.

27, the horizontal axis indicates the hardness of a steel material such as SUS420J2 used as a material for the sleeve 102 and the shaft 101 of the fulcrum bearing unit 100, for example. In the graph of FIG. 27, the vertical axis indicates the stress that causes indentation in the steel material when the steel ball having the hardness shown on the horizontal axis is brought into contact with the steel ball and stress is applied. It is. For example, as shown in FIG. 27, an indentation is generated in a steel flat plate having a hardness of HRC60 by pressing a steel ball with a stress of 4 GPa.

On the other hand, using SUS420J2 which is the same material as the shaft 101 which is the inner member of the fulcrum bearing unit 200 according to Embodiment 2 of the present invention, a round bar with a hardness of HRC30 having a circular shape with a cross section of 5 mm was prepared. . It rolled, pressing the steel ball of diameter 1mm integrated in the fulcrum bearing unit 100 in the said Embodiment 2 with respect to the outer peripheral surface of this round bar. As a result, a groove having a curvature radius of 0.7 mm was formed on the outer peripheral surface of the round bar. That is, if burnishing is performed under such conditions, a groove having a groove curvature radius of 0.7 mm is processed.

By the way, as described above, the fulcrum bearing unit 200 can suppress the occurrence of indentation or the like on the raceway surface with which the ball 109 contacts due to, for example, an impact load that is an unexpected external force when used as a swing arm bearing. It is preferable to have a design. In general, it is preferable to have a design in which indentation does not occur even when an impact of 1000 G is applied.

The magnitude of the impact load that is an external force is the total mass of the swing arm 1 and the sleeve 102 in the portion to which the impact load is applied to the raceway surface, that is, the system of the fulcrum bearing unit 200 and the swing arm 1 (see FIG. 12). It is obtained by multiplying the acceleration of impact force. For example, for a 2.5 inch hard disk drive, the total mass is 3 grams. Therefore, in this case, a force of 30 N acts on an impact of 1000 G. That is, it is preferable to design so that no indentation is generated on the raceway surface even when a force of 30 N is applied.

Using the radius of the raceway surface in the fulcrum bearing unit 200, the groove radius of curvature, and the radius of the ball 109, the contact stress between the steel ball (the ball 109) and the raceway surface when an impact load is applied. As a result of calculation and using the relationship shown in the graph of FIG. 27, the hardness required for the raceway surface is as shown in FIG.

In FIG. 28, the horizontal axis indicates external force, that is, the unexpected impact load described above in N units, and the vertical axis indicates indentation on the raceway surface when the impact load indicated on the horizontal axis is generated on the raceway surface. The required hardness required for the raceway surface in order to prevent the occurrence of this is shown in HRC (Rockwell C scale). In the graph of FIG. 28, the white circle corresponds to the inner raceway surface that contacts the ball 109 at one point in the raceway surface, for example, in the case of the fulcrum bearing unit 100 in the case of one point contact. Similarly, in the graph of FIG. 28, the black circle corresponds to the outer raceway surface that contacts the ball 109 at two points in the raceway surface in the case of two-point contact, that is, for example, in the case of the fulcrum bearing unit 100.

From the graph of FIG. 28, for example, in order to prevent indentation on the raceway surface even when an impact load of 30 N is generated as described above, the inner raceway surface of the fulcrum bearing unit 100 (cone in FIG. 1) It has been found that the HRC 40, the two-point contact side, that is, the outer race surface of the fulcrum bearing unit 200 (such as the conical race surface 122 in FIG. 1) requires a hardness of HRC 25 or higher. From the above, as described above, in the fulcrum bearing unit of the present invention, it can be said that the hardness of the inner raceway surface is preferably HRC40 or more and the hardness of the outer raceway surface is preferably HRC25 or more.

In Example 2, an experiment was conducted to investigate the hardness distribution when induction hardening was performed on a steel material. In Example 2, first, a round bar having a circular cross section having a diameter of 5 mm is formed using SUS420J2 which is the same material as the shaft 101 which is an inner member of the fulcrum bearing unit 200 according to Embodiment 2 of the present invention. Created.

Then, a high frequency coil was arranged so as to surround the outer peripheral surface of the round bar, and induction hardening using induction heating was performed.

In FIG. 29, the horizontal axis indicates the depth from the surface of the round bar, that is, the distance from the outer peripheral surface of the round bar to the center of the cross section of the round bar in mm units, and the vertical axis indicates each distance from the surface of the round bar. The hardness of the depth after induction hardening is indicated by Hv.

As shown in FIG. 29, in the round bar, the region close to the surface layer portion was hardened by hardening and the hardness was high, while the hardness was low inside. And with reference to FIG. 29, it was confirmed that the area | region within 1 mm from the surface can be hardened. Therefore, in the manufacturing process of the fulcrum bearing unit 100, by subjecting the steel material such as steel bar to induction hardening, for example, the region to be the conical raceway surface 120 of the shaft 101 is sufficiently hardened while the hole 161 is formed. It has been confirmed that it is possible to suppress an increase in hardness in the region where the screw 162 is to be formed.

The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

The present invention is particularly excellent as a technology for stabilizing the torque of the swing arm by reducing fluctuations in the rolling element load of the fulcrum bearing unit and facilitating the control thereof.

1 swing arm, 2 magnetic head, 13C bent part, 15A first holder, 15B holder, 15C thick part, 15D second holder, 21 inner member, 99 steel, 100, 200, 300, 400 , 500, 600 fulcrum bearing unit, 101 shaft, 102 sleeve, 103 inner ring, 104 outer ring, 105 spacer, 109 ball, 109A ball surface, 110, 111 bearing groove, 120, 121, 122, 141, 142 conical raceway surface , 120A surface roughness improvement processing region, 123 adjustment ring, 124 adhesion surface, 125 seal, 131 shaft end support, 132 holding jig, 133 adhesive pool, 135 cut, 143, 144, 145, 153, 154, 155 contact Point, 149 Spacer ball, 161 hole, 162 Flip, 163 and 165 outline 164

cutting line

171 and 172 the dotted line, 181, 182 motor, 184 pressing machine, 201 cavity, 203 flanges, 204 main body, 210 a jig.

Claims

An inner member (101, 103, 123) having an annular inner raceway surface (141, 142, 120, 121, 110, 111) formed on the outer peripheral surface;
An annular outer raceway surface (122) is formed so as to surround the inner members (101, 103, 123) and faces the inner raceway surfaces (141, 142, 120, 121, 110, 111). An outer member (102) to which a swing arm of a hard disk drive is to be connected;
A plurality of balls (109) disposed in contact with the inner raceway surface (141, 142, 120, 121, 110, 111) and the outer raceway surface (122);
One of the inner raceway surfaces (141, 142, 120, 121, 110, 111) and the outer raceway surface (122) has a first contact surface (141, 141) that contacts the ball (109). 142, 120, 121, 111, 122) and a second contact surface (141, 142, 120, 121, 111, 122),
The first contact surface (141, 142, 120, 121, 111, 122) and the second contact surface (141, 142, 120, 121, 111, 122) intersect each other,
The other raceway surface has a third contact surface (120, 122, 141, 110) that contacts the ball (109),
The ball (109) is in contact with the inner raceway surface (141, 142, 120, 121, 110, 111) and the outer raceway surface (122) at a total of three points. , 300, 400).
At least one of the first contact surface (141, 142, 120, 121, 111, 122) and the second contact surface (141, 142, 120, 121, 111, 122) has a conical surface shape (141 , 142, 120, 121, 122), the swing arm bearing (100, 200, 300, 400) according to claim 1.
The swing arm bearing (100, 200, 100) according to claim 1, wherein the third contact surface (120, 122, 141, 110) has a conical shape (120, 122, 141). 300).
In the inner raceway surface (141, 142, 120, 121, 110, 111) and the outer raceway surface (122), the surface roughness Ra (center line average roughness) of the first region in contact with the ball (109). 2. The swing arm bearing (100, 200, 300, 400) according to claim 1, wherein the surface roughness Ra is smaller than a surface roughness Ra of a second region adjacent to the first region.
The swing according to claim 4, wherein the ball (109) contacts the inner raceway surface (141, 120, 110) at one point and contacts the outer raceway surface (122) at two points. Arm bearings (200, 300, 400).
The inner raceway surface (141, 120, 110) has a hardness of HRC40 or more and HRC50 or less,
The swing arm bearing (200, 300, 400) according to claim 5, wherein the outer raceway surface (122) has a hardness of HRC25 or more and HRC35 or less.
The inner member (101) has a hole (161) formed in a region including the central axis of the inner raceway surface (141, 120, 110),
The inner raceway surface (141, 120, 110) has a hardness of HRC40 or higher,
The swing arm bearing (200, 300, 400) according to claim 5, wherein the hardness of the surface layer portion of the hole (161) is HRC25 or less.
The bearing for a swing arm (200, 300, 400) according to claim 5, wherein the region including the inner raceway surface (141, 120, 110) is induction hardened.
The hardness of the first contact surface (141, 142, 120, 121, 111, 122) and the second contact surface (141, 142, 120, 121, 111, 122) is the same as that of the third contact surface ( The bearing for a swing arm (200, 300, 400) according to claim 1, which is lower than the hardness of 120, 122, 141, 110).
The first contact surface (141, 142, 120, 121, 111, 122), the second contact surface (141, 142, 120, 121, 111, 122) and the third contact surface (120, 122). , 141, 110) is a bearing for a swing arm (100, 200, 300, 400) according to claim 1, which is burnished.
The plurality of balls (109) are arranged in two rows,
The inner member (101, 103, 123) and the outer member (102) are a pair of the inner raceway surfaces (141, 142, 120, 121, 110, 111) and the outer side corresponding to the two rows, respectively. A raceway surface (122),
In the cross section including the rotation axis of the swing arm bearing (100, 200, 300, 400), the center of the ball (109) included in one of the two rows and the ball included in the one row (109) is connected to the third contact surface (120, 122, 141, 110) and the first straight line connecting the contact points, and the ball (109) included in the other of the two rows The second straight line connecting the center and the contact point at which the ball (109) included in the other row contacts the third contact surface (120, 122, 141, 110) is the ball (109). The bearing for a swing arm (100, 200, 100) according to claim 1, wherein the bearing (100, 200, 110, 110, 110, 110) intersects at a radially outer side when viewed from a contact point between the third contact surface (120, 122, 141, 110) and 300, 400).
The inner member (101, 103, 123) is a first inner member having the inner raceway surface (120, 121, 110, 111) that contacts the ball (109) included in the one row. (101)
The second inner member (123) having the inner raceway surface (141, 142) that is fitted to the first inner member (101) and contacts the ball (109) included in the other row. And a swing arm bearing (100, 200, 300, 400) according to claim 11.
The swing arm bearing (100, 200, 300, 400) according to claim 12, to which preload is applied.
It has an annular shape and is disposed between the inner member (101, 123) and the outer member (102), and the plurality of balls (109) are arranged in an annular track (141, 142). , 120, 120, 110, 111, 122), further comprising a cage (15 A, 15 D) that can be freely rolled at a predetermined pitch. ).
The bearing for a swing arm (300) according to claim 14, wherein the cage (15A, 15D) is made of a resin molded body.
The cage (15A, 15D)
A holding portion (15B) for holding the ball (109);
The swing arm bearing (300) according to claim 14, including a thick part (15C) having a larger radial thickness than the holding part (15B).
The plurality of balls (109) are arranged on a pair of annular tracks (141, 142, 120, 121, 110, 111, 122),
The ball (109) arranged on one of the pair of tracks (141, 142, 120, 121, 110, 111, 122) on one track (141, 142, 120, 121, 110, 111, 122) is Held by the first cage (15A),
The ball (109) disposed on the other track (141, 142, 120, 121, 110, 111, 122) of the pair of tracks (141, 142, 120, 121, 110, 111, 122) is Held by the second cage (15D),
Each of the first cage (15A) and the second cage (15D) has a side opposite to the other cage (15A, 15D) when viewed from one cage (15A, 15D). The swing arm bearing (300) according to claim 16, wherein the thick part (15C) is formed in a region including the end face.
The distance between the thick part (15C) of the cage (15A, 15D) and the outer member (102) and the inner member (101, 123) is 0.05 mm or more and 0.2 mm or less. The swing arm bearing (300) according to claim 16, wherein the swing arm bearing (300) is provided.
An inner member (101) having an annular inner raceway surface (141, 120, 110) formed on the outer peripheral surface and an annular outer raceway surface (122) are formed, and the swing arm (1) of the hard disk drive is provided. Preparing an outer member (123) to be connected and a plurality of balls (109);
The inner raceway surface (141, 120, 110) and the outer raceway surface (122) face each other, and the ball (109) contacts the inner raceway surface (141, 120, 110) at one point, Assembling the inner member (101), the outer member (102) and the ball (109) so as to contact the outer raceway surface (122) at two points;
A region in contact with the ball (109) on the inner raceway surface (141, 120, 110) by rotating the outer member (102) relative to the inner member (101) about an axis. And a step of performing plastic working on a region in contact with the ball (109) on the outer raceway surface (122), and a manufacturing method of the swing arm bearing (200, 300, 400).
In the step of carrying out the plastic working, the outer member (102) and the inner member (101) are rotated around the axis, whereby the outer member (102) is moved relative to the inner member (101). The swing arm according to claim 19, wherein the swing arm is relatively rotated about an axis and an axial force and a radial force are applied between the inner member (101) and the outer member (102). Of manufacturing bearings (200, 300, 400) for automobiles.
In the step of plastic working the region in contact with the ball (109), the inner raceway surface (141, 120, 110) and the outer raceway surface (122) having a surface roughness Ra of 0.3 or less are plastically processed. A method for manufacturing a swing arm bearing (200, 300, 400) according to claim 19.