JP2001167538A - Pivot mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pivot mechanism with high bearing rigidity at low cost which has superior assembling performance and can suppress the production of contaminative substances. SOLUTION: To support a sleeve member 64 with respect to a shaft member 61 rotatably around an axis PA of circular movement without using any bearing, the tip surface 612 of the shaft member 61 is made projected, the recessed internal bottom surface 642 of the sleeve member 64 is so made recessed to engage a projecting surface 612, and those projecting surface 612 and recessed surface 642 are made to abut against each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pivot mechanism for supporting an arm for holding at least a head for reproducing information on a storage medium so as to be rotatable about a predetermined rotation axis.

[0002]

2. Description of the Related Art Conventionally, in a magnetic disk drive, one or more magnetic disks (recording media) are driven to rotate by a motor, and a magnetic head is arranged on both sides or one side of each magnetic disk. Plays information recorded on a disk or writes information on a magnetic disk. The magnetic head is held by an arm of a head actuator, and when the arm is driven to rotate about a predetermined rotation axis, the magnetic head is moved and positioned in the radial direction of the magnetic disk by this arm rotation operation. You.

In order to move the magnetic head as described above, the head actuator is provided with a pivot mechanism for rotating the arm about a rotation axis. For example, in a pivot mechanism described in Japanese Patent Application Laid-Open No. 5-205413, a pivot shaft is provided along a rotation axis, and an inner ring of a ball bearing is provided on an outer surface thereof in two stages by an adhesive or the like by a fastening member. At the same time, the actuator body is rotatable about the pivot shaft with respect to the pivot shaft by these two-stage ball bearings. The arm is attached to the rotatable actuator body as described above, and is rotatable about a rotation axis.

[0004]

Incidentally, among the components constituting the pivot mechanism, the bearings are more expensive than other components, and occupy most of the member cost of the pivot mechanism. In particular, the conventional pivot mechanism uses two bearings, which is one of the main factors that increase the product cost. Further, when the number of bearings increases, the following problems occur in addition to the cost.

First, as the number of bearings increases, the number of assembling steps also increases, and there is a problem that the manufacturing steps become complicated.

In addition, oil mist is generated from the bearings, and outgas is generated from the adhesive for fixing the bearings, which becomes a substance that contaminates a clean space formed in the magnetic disk device, and is generated in the magnetic disk device. May have adverse effects. Such contaminants increase with the number of bearings, and it is desired that the number of bearings be reduced. And information cannot be reproduced / written on the magnetic disk accurately.

The present invention has been made in view of the above problems, and has as its object to provide a pivot mechanism which is excellent in assemblability, can suppress generation of pollutants, and has high bearing rigidity at low cost. .

[0008]

According to one aspect of the pivot mechanism according to the present invention, an arm for holding at least a head for reproducing information from a storage medium is supported rotatably about a predetermined rotation axis. A pivot mechanism, which is fixedly arranged on the rotation axis to achieve the above object,
A shaft member having a distal end extending along the rotation axis, a sleeve member attached to the arm and having a concave portion opened toward the shaft member, an inner surface of the concave portion, and an outer surface of the shaft member. A bearing provided between the shaft member and the shaft member for supporting the sleeve member rotatably around the rotation axis with respect to the shaft member,
One of the inner bottom surface of the concave portion and the distal end surface of the shaft member is formed as a substantially hemispherical or substantially conical convex surface, and the other surface is formed as a concave surface engageable with the convex surface, These convex and concave surfaces are in contact with each other.

In the invention configured as described above, two configurations are employed to support the sleeve member rotatably around the rotation axis with respect to the shaft member. That is, 1
The third configuration is a bearing provided between the inner surface of the concave portion of the sleeve member and the outer surface of the shaft member. In the other configuration (rotation support configuration), one of the concave inner bottom surface of the sleeve member and the distal end surface of the shaft member is formed as a substantially hemispherical or substantially conical convex surface, and the other surface is formed as a convex surface. It is formed in a concave surface that can be engaged, and the convex surface and the concave surface are in contact with each other. As described above, by adopting the latter rotation support configuration instead of the bearing, the pivot mechanism which conventionally required two bearings is configured by one bearing.

Here, it is desirable that the convex surface and the concave surface are made of materials different from each other in strength or coefficient of thermal expansion, and such a configuration can prevent problems such as adhesion and seizure of the convex surface and the concave surface. Generation can be suppressed. In this configuration, each of the sleeve member and the shaft member is configured so as to satisfy the above conditions (the convex surface and the concave surface are made of materials different in strength or thermal expansion coefficient from each other). Alternatively, while assuming that the whole is configured by combining a plurality of parts, the above condition may be satisfied for parts corresponding to the convex or concave portions.

In order to make the distal end surface of the shaft member convex, for example, a ball member may be pressed into the distal end surface, and the surface of the ball member may be the convex surface. Further, in order to make the inner bottom surface of the concave portion of the sleeve member a convex surface, similarly to the case of the shaft member, for example, a ball member may be press-fitted to the front end surface and the surface of the ball member may be the convex surface.

Another aspect of the pivot mechanism according to the present invention is a pivot mechanism which supports an arm for holding at least a head for reproducing information from a storage medium so as to be rotatable about a predetermined rotation axis. In order to achieve the above object, a shaft member fixedly disposed on the rotation axis, and a tip end thereof is attached to the arm, and is open toward the shaft member. A sleeve member having a recessed portion, an inner surface of the recessed portion,
A bearing provided between the outer surface of the shaft member and the shaft member for rotatably supporting the sleeve member around the rotation axis with respect to the shaft member; and an inner bottom surface of the recess on the rotation axis. And a ball member rotatably arranged between a tip surface of the shaft member and a tip surface of the shaft member, wherein an inner bottom surface of the concave portion and a tip surface of the shaft member are formed into a concave surface engageable with the ball member. The two concave surfaces are in contact with the ball member.

In the invention having the above-described structure, the sleeve member is provided between the inner surface of the concave portion of the sleeve member and the outer surface of the shaft member so as to rotatably support the sleeve member around the rotation axis with respect to the shaft member. In addition to the bearings, a rotation support structure configured as described below is provided to reduce the number of bearings by one. That is, in this rotation support configuration, the ball member is rotatably arranged on the rotation axis and between the inner bottom surface of the concave portion of the sleeve member and the distal end surface of the shaft member, and the inner bottom surface of the concave portion of the sleeve member The shaft and the distal end surface of the shaft member are formed as concave surfaces engageable with the ball member, and both concave surfaces are in contact with the ball member.

Another aspect of the pivot mechanism according to the present invention is a pivot mechanism which supports an arm for holding at least a head for reproducing information on a storage medium so as to be rotatable about a predetermined rotation axis. In order to achieve the above object, a shaft member fixedly disposed on the rotation axis, and a tip end thereof is attached to the arm, and is open toward the shaft member. A supporting member movably arranged along the rotation axis in a guide groove dug down along the rotation axis direction from the inner bottom surface of the recess, A bearing provided between an inner surface and an outer surface of the shaft member for supporting the sleeve member rotatably around the rotation axis with respect to the shaft member; A ball member rotatably disposed on a shaft and between the surface of the support block and the tip end surface of the shaft member, and attaching the support block provided in the guide groove toward the ball member. A biasing member for biasing, wherein a surface of the support block and a distal end surface of the shaft member are formed as concave surfaces engageable with the ball member, and both concave surfaces are in contact with the ball member.

In the present invention, the sleeve member is provided between the inner surface of the recess of the sleeve member and the outer surface of the shaft member so as to rotatably support the sleeve member around the rotation axis with respect to the shaft member. In addition to the bearings, a rotation support structure configured as described below is provided to reduce the number of bearings by one. That is, in this rotation support configuration, the ball member is rotatably disposed on the rotation axis and between the inner bottom surface of the concave portion of the sleeve member and the distal end surface of the shaft member. In addition, the surface of the support block movably arranged in the guide groove provided in the sleeve member and the tip end surface of the shaft member are formed as concave surfaces engageable with the ball member, and the support block is biased by the urging member. By being urged toward the ball member, both concave surfaces are in contact with each other so as to sandwich the ball member.

Here, as the ball member, for example, a steel ball or a ceramic ball can be used.

Further, it is desirable that the ball member and the concave surface are made of materials different in strength or coefficient of thermal expansion from each other. With such a structure, the ball member and the concave surface may have adhesion or seizure. The occurrence of defects can be suppressed. In this configuration, each of the sleeve member, the shaft member, and the support block satisfies the above conditions (the ball member and the concave surface are made of materials different from each other in strength or coefficient of thermal expansion). Alternatively, it may be configured such that a plurality of parts are combined to form the whole, but the parts corresponding to the concave portions may satisfy the above condition.

[0018]

FIG. 1 is an internal plan view of a magnetic disk drive provided with a pivot mechanism according to the present invention.
FIG. 2 is a sectional view of the magnetic disk drive of FIG. In this magnetic disk device, as shown in FIG. 1, a plurality of magnetic disks (recording media) 3 are mounted on a spindle mechanism 2 in a housing 1 and a rotating shaft RA is provided.
Is driven to rotate. Although a plurality of magnetic disks 3 are provided here, the same applies to a single disk.

On the other hand, a head actuator 4 is provided in the vicinity of the magnetic disk 3 so as to be rotatable about a rotation axis PA. In the head actuator 4, a predetermined number of magnetic heads 5 are provided according to the number of magnetic disks 3 and corresponding to both surfaces or one surface of the magnetic disks, and are rotatable about a rotation axis PA by a pivot mechanism 6. It is attached to one end of the arm 7. Voice coil motor 1 for rotating head actuator 4 having arm 7 supporting magnetic head 5
0 denotes a lower yoke 9a fixed to the bottom wall of the housing 1.
An upper yoke 9b opposed to the lower yoke 9a with a predetermined gap; a magnet 9c fixed to the inner surface of the lower yoke 9a and facing the upper yoke 9b;
Support frame 8a extended from the sleeve member as in
Is provided with a voice coil 8b. The support frame 8a and the voice coil 8b are located between the upper yoke 9b and the magnet 9c. When a current is applied to the boil coil 8b, a magnetic field is generated, and by interaction with the magnetic field generated from the magnet 9c, The head actuator 4 is rotated in the circumferential direction, and the magnetic head 5 supported by the arm 7 moves in the radial direction of the magnetic disk 3 and is positioned.

Next, the structure of the pivot mechanism 6 will be described with reference to FIG.
This will be described in detail with reference to FIG. In the pivot mechanism 6, as shown in FIG. 2, the shaft member 61 is fixed to the housing 1 on the rotation axis PA by a fastener 62 such as a bolt. The shaft member 61
The tip portion 611 of the pair extends along the rotation axis PA.

The tip 6 of the shaft member 61
11 through a ball bearing 63 to the arm 7
Is provided rotatably about a rotation axis PA. This sleeve member 6
4 has a concave portion 641 opened toward the shaft member 61.
Are provided, and the concave portion 641 is disposed so as to completely cover the distal end portion 611 of the shaft member 61. Specifically, it is assembled as follows. That is, after the inner ring of the ball bearing 63 is attached to the tip 611 of the shaft member 61 and fixed with an adhesive, the concave portion 641 of the sleeve member 64 is removed while the adhesive applied to the outer ring of the ball bearing 63 is not cured. The ball is pressed into the outer ring of the ball bearing 63 to apply a preload to the outer ring.

In the pivot mechanism 6 assembled in this way, the sleeve member 64 is not only rotatably supported by the ball member 63 but also rotatably with respect to the shaft member 61.
4 is in contact with the inner bottom surface of the concave portion, thereby enabling the rotation of the sleeve member 64 with respect to the shaft member 61. In this embodiment, as shown in FIG. 3, the distal end surface 612 of the shaft member 61 is formed as a substantially conical convex surface, whereas the inner bottom surface 642 of the concave portion of the sleeve member 64 is formed as a convex surface 612.
Has a radius of curvature larger than the radius of curvature of
12 is formed on a concave surface that can be engaged with the same. The convex surface 612 and the concave surface 642 abut on each other, so that the sleeve member 64 can rotate with respect to the shaft member 61. The tip surface 6 of the shaft member 61
The shape of the convex surface of 12 is not limited to a substantially conical shape, and may be formed in a substantially spherical shape.

As described above, in the pivot mechanism 6 according to this embodiment, the inner surface of the concave portion 641 of the sleeve member 64 is supported so as to rotatably support the sleeve member 64 around the rotation axis PA with respect to the shaft member 61. And shaft member 61
In addition to the ball bearing 63 provided between the shaft member 61 and the outer surface of the shaft member 61, the distal end surface 612 of the shaft member 61 is formed as a convex surface, and the concave inner bottom surface 642 of the sleeve member 64 is formed as a concave surface engageable with the convex surface 612. Since the convex surface 612 and the concave surface 642 are in contact with each other, the number of bearings can be reduced as compared with the conventional example.
The cost can be reduced and the assemblability is excellent.
Generation of pollutants can be suppressed.

The distal end surface 612 of the shaft member 61
And the inner bottom surface 642 of the concave portion of the sleeve member 64 abut each other and rub against each other due to the turning operation of the arm 7. Therefore, the shaft member 61 and the sleeve member 64 are made of different materials such as strength and thermal expansion coefficient. By selecting the material in this way, adhesion and seizure between the shaft member 61 and the sleeve member 64 can be suppressed, and the life of the pivot mechanism 6 can be extended. here,
In selecting the material in this way, the sleeve member 6
Each of the shaft member 4 and the shaft member 61 may be configured so as to satisfy the above conditions (the convex surface and the concave surface are made of materials different in strength or coefficient of thermal expansion). While it is assumed that the whole is configured by combining the parts, the above conditions may be satisfied for the parts corresponding to the convex or concave portions.

The present invention is not limited to the above-described embodiment, and various changes other than those described above can be made without departing from the gist of the present invention. For example, in the above embodiment, the distal end surface 612 of the shaft member 61 is finished to a convex surface by molding.
A ball member such as a steel ball or a ceramic ball may be pressed into the tip end surface 612 of the shaft member 61 to form a convex surface by the surface of the ball member.

In the above embodiment, the shaft member 6
1 is formed as a convex surface, and the inner bottom surface 642 of the concave portion of the sleeve member 64 is formed as a concave surface engageable with the convex surface 612. However, the inner bottom surface 642 of the concave portion of the sleeve member 64 is formed as a convex surface. Alternatively, the distal end surface 612 of the shaft member 61 may be formed as a concave surface capable of engaging with the convex surface (the inner bottom surface 642 of the concave portion).

In the above embodiment, the shaft member 6
1 and the inner bottom surface 6 of the recess of the sleeve member 64.
42 is in direct contact with the shaft member 61 to support the sleeve member 64 so as to be rotatable around the rotation axis PA, but indirectly via a ball member or the like as shown in FIGS. May be configured to come into contact with. Hereinafter, a modification of the pivot mechanism according to the present invention will be described with reference to FIGS. 4 and 5.

FIG. 4 is a sectional view showing another embodiment of the pivot mechanism according to the present invention. In this embodiment,
The inner race of the ball bearing 63 is fixedly mounted on the outer surface of the shaft member 61, while the recess 64 of the sleeve member 64 is fixed.
The outer race of the ball bearing 63 is fixed to the inner surface of the shaft member 1 and the sleeve member 64 is rotated with respect to the shaft member 61 by the rotation axis P.
It is common to the previous embodiment in that it is rotatably supported about A, but differs in the following points.

That is, in this embodiment, as shown in FIG. 4, the ball member 65 rotates on the rotation axis PA and between the inner bottom surface 642 of the concave portion of the sleeve member 64 and the tip end surface 612 of the shaft member 61. It is arranged freely. The concave inner bottom surface 642 of the sleeve member 64 and the distal end surface 612 of the shaft member 61 are formed as concave surfaces that can be engaged with the ball member 65. The rotation operation of the sleeve member 64 with respect to 61 is possible.

FIG. 5 is a sectional view showing another embodiment of the pivot mechanism according to the present invention. This embodiment is similar to the embodiment shown in FIG. 4 in that the sleeve member 64 is rotatably supported on the shaft member 61 about the rotation axis PA by the ball bearing 63. And in common. However, this embodiment is significantly different from the embodiments of FIGS. 2 and 3 in the following points.

That is, in this embodiment, as shown in FIG. 5, a guide groove 6 further dug down along the direction of the rotation axis PA is formed on the bottom surface 642 inside the concave portion of the sleeve member 64.
The support block 66 is provided movably along the rotation axis PA in the guide groove 643.
The back surface 661 of the support block 66 and the guide groove 6
A biasing member 6 such as a spring or an elastic sheet
7, which urges the support block 66 toward the distal end surface 612 of the shaft member 61.

The ball member 65 is rotatably disposed on the rotation axis PA and between the surface 662 of the support block 66 and the distal end surface 612 of the shaft member 61. The ball member 65 is sandwiched between the support block 66 and the shaft member 61 by the force. Here, the support block 6 in contact with the ball member 65
6 and the tip end surface 612 of the shaft member 61 are both formed as concave surfaces that can be engaged with the ball member 65, and these two concave surfaces 612 and 662 abut on the ball member 65 and the sleeve member 64 with respect to the shaft member 61. Can be rotated.

In the embodiment shown in FIGS. 4 and 5, the ball member 65 is provided with the distal end surface 612 of the shaft member 61 and the concave inner bottom surface 642 of the sleeve member 64.
Alternatively, since it is rotatably held between the surface 662 of the support block 66, the friction torque generated in the pivot mechanism 6 when the head actuator 4 rotates can be further reduced, and high efficiency can be realized. it can. In addition, since the ball member 65 is supported by the distal end face 612 and the concave inner bottom surface 642 or the surface 662 in line contact in the circumferential direction around the rotation axis PA, the bearing rigidity in the radian direction can be improved. .

In the embodiment shown in FIGS. 4 and 5, for example, a steel ball or a ceramic ball can be used as the ball member 65. However, the ball member 65 and the concave surfaces 612, 642, 662 have strength. Alternatively, it is desirable to use materials different from each other in terms of thermal expansion coefficient. With such a configuration, it is possible to suppress occurrence of problems such as adhesion and seizure of the ball member 65 and the concave surfaces 612, 642, and 662. it can. In this configuration, the shaft member 61 and the sleeve member 6
4 and the support block 66 may be configured so as to satisfy the above conditions (the ball member and the concave surface are formed of materials different in strength or coefficient of thermal expansion). While assuming that the whole is composed by combining the parts of
The parts corresponding to the concave portions may satisfy the above conditions.

[0035]

As described above, according to the first or third aspect of the present invention, in order to support the sleeve member rotatably around the rotation axis with respect to the shaft member, the inner surface of the concave portion of the sleeve member is provided. In addition to the bearing provided between the outer surface of the shaft member and one of the inner bottom surface of the concave portion of the sleeve member and the distal end surface of the shaft member, one surface is formed into a substantially hemispherical or substantially conical convex surface, and the other is formed. Since the surface is formed as a concave surface that can be engaged with the convex surface, and the convex surface and the concave surface are in contact with each other, the number of bearings can be reduced, cost can be reduced, and assemblability can be improved. It is excellent and can suppress generation of pollutants.

According to the second aspect of the present invention, since the convex surface and the concave surface are made of materials different from each other in strength or coefficient of thermal expansion, problems such as adhesion and seizure of the convex surface and the concave surface are eliminated. Generation can be suppressed.

According to the fourth or sixth aspect of the present invention, the inner surface of the concave portion of the sleeve member and the outer surface of the shaft member are provided so as to rotatably support the sleeve member around the rotation axis with respect to the shaft member. The ball member is rotatably disposed on the rotating shaft and between the inner bottom surface of the concave portion of the sleeve member and the distal end surface of the shaft member. The inner bottom surface and the distal end surface of the shaft member are formed as concave surfaces that can be engaged with the ball member, and these two concave surfaces are brought into contact with the ball member, so that the number of bearings can be reduced and the cost can be reduced. In addition, excellent assemblability can be achieved, and generation of contaminants can be suppressed. Moreover, according to the invention configured as described above, the ball member is rotatably held between the distal end surface of the shaft member and the bottom surface inside the concave portion of the sleeve member, so that the friction torque generated in the pivot mechanism is further reduced. Therefore, the efficiency can be improved. In addition, since the ball member is supported by a line contact in the circumferential direction around the rotation axis by the tip surface of the shaft and the inner bottom surface of the concave portion of the sleeve member, the stiffness of the bearing in the radian direction can be improved.

According to the fifth or sixth aspect of the present invention, the inner surface of the concave portion of the sleeve member and the outer surface of the shaft member are provided so as to rotatably support the sleeve member around the rotation axis with respect to the shaft member. In addition to the bearings provided between the shaft member and the ball member, the ball member is rotatably disposed on the rotating shaft and between the inner bottom surface of the concave portion of the sleeve member and the tip end surface of the shaft member. The surface of the support block movably arranged in the guide groove and the distal end surface of the shaft member are formed as concave surfaces engageable with the ball member, and the biasing member directs the support block toward the ball member from the back side. By biasing, the two concave surfaces abut each other so as to sandwich the ball member, so that the number of bearings can be reduced, and cost can be reduced,
Moreover, it is excellent in assemblability and can suppress generation of contaminants. Moreover, according to the invention configured as described above,
Since the ball member is rotatably held between the tip surface of the shaft member and the surface of the support block, friction torque generated in the pivot mechanism can be further reduced, and high efficiency can be realized. . Further, since the ball member is supported by a line contact in the circumferential direction around the rotation axis by the shaft tip surface and the support block surface,
The bearing rigidity in the radian direction can be improved.

Further, according to the invention described in claim 7,
Since the ball member and the concave surface are made of materials different from each other in strength or coefficient of thermal expansion, it is possible to suppress occurrence of problems such as adhesion and seizure of the ball member and the concave surface.

[Brief description of the drawings]

FIG. 1 is an internal plan view of a magnetic disk drive provided with a pivot mechanism according to the present invention.

FIG. 2 is a cross-sectional configuration diagram of the magnetic disk device of FIG.

FIG. 3 is a partially enlarged view of the pivot mechanism shown in FIG.

FIG. 4 is a cross-sectional view showing another embodiment of the pivot mechanism according to the present invention.

FIG. 5 is a cross-sectional view showing another embodiment of the pivot mechanism according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 3 ... Magnetic disk (recording medium) 4 ... Head actuator 5 ... Magnetic head 6 ... Pivot mechanism 7 ... Arm 61 ... Shaft member 63 ... Ball bearing 64 ... Sleeve member 65 ... Ball member 66 ... Support block 67 ... Biasing member 611 Tip portion 612 (of shaft member) Tip surface 641 (of shaft member) Depression 642 (of sleeve member) Bottom surface of recessed portion (of sleeve member) 643 Guide groove 662 surface (of support block) PA rotation axis

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Tadashi Hasegawa, Inventor 1145-4, Iijima-cho, Kamiina-gun, Nagano Prefecture F-term in the Nagano Technology Development Center, Nidec Corporation (reference) 3J011 BA10 BA11 BA11 KA01 5D068 AA01 BB02 CC12 EE06 EE18 GG05 GG07

Claims (7)

[Claims] 1. A pivot mechanism for supporting an arm for holding at least a head for reproducing information on a storage medium so as to be rotatable about a predetermined rotation axis, the pivot mechanism being fixedly arranged on the rotation axis. A shaft member having a distal end portion extending along the rotation axis; a sleeve member attached to the arm and having a concave portion opened toward the shaft member; an inner surface of the concave portion; A bearing provided between the outer side surface and the shaft member to rotatably support the sleeve member around the rotation axis with respect to the shaft member; One surface is formed as a substantially hemispherical or substantially conical convex surface, and the other surface is formed as a concave surface engageable with the convex surface, and the convex surface and the concave surface are in contact with each other. Pivot mechanism, characterized in that. 2. The material forming the convex surface and the concave surface is different from each other in strength or coefficient of thermal expansion.
The pivot mechanism as described. 3. The pivot mechanism according to claim 1, wherein a ball member is press-fitted into a tip end surface of the shaft member or an inner bottom surface of the concave portion, and a surface of the ball member constitutes the convex surface. 4. A pivot mechanism for supporting an arm for holding at least a head for reproducing information on a storage medium so as to be rotatable about a predetermined rotation axis, the pivot mechanism being fixedly arranged on the rotation axis. A shaft member having a distal end portion extending along the rotation axis; a sleeve member attached to the arm and having a concave portion opened toward the shaft member; an inner surface of the concave portion; A bearing provided between the outer surface and the shaft member to rotatably support the sleeve member around the rotation axis with respect to the shaft member; and an inner bottom surface of the recess on the rotation axis and the shaft member. A ball member rotatably arranged between the ball member and the tip surface of the shaft member. The inner bottom surface of the concave portion and the tip surface of the shaft member are formed as concave surfaces engageable with the ball member. Pivot mechanism Luo biconcave is characterized in that in contact with the ball member. 5. A pivot mechanism for supporting an arm for holding at least a head for reproducing information on a storage medium so as to be rotatable about a predetermined rotation axis, the pivot mechanism being fixedly arranged on the rotation axis. A shaft member having a distal end portion extending along the rotation axis; a sleeve member attached to the arm and having a recess opened toward the shaft member; and a rotation axis further from an inner bottom surface of the recess. A support block movably arranged along the rotation axis in a guide groove dug down along a direction; and a shaft provided between an inner surface of the concave portion and an outer surface of the shaft member. A bearing that rotatably supports the sleeve member around the rotation axis with respect to a member; and between the surface of the support block and the tip end surface of the shaft member on the rotation axis. A ball member rotatably arranged; and a biasing member provided in the guide groove to bias the support block toward the ball member, wherein a surface of the support block and a distal end surface of the shaft member are provided. The pivot mechanism is formed in a concave surface capable of engaging with the ball member, and both concave surfaces are in contact with the ball member. 6. The pivot mechanism according to claim 3, wherein the ball member is a steel ball or a ceramic ball. 7. The pivot mechanism according to claim 4, wherein materials forming the ball member and the concave surface are different from each other in strength or coefficient of thermal expansion.