JPH03222661A - Spindle motor - Google Patents

Abstract

PURPOSE:To improve accuracy of rotation by a disposing plurality of spherical members, respectively, in a pair of ball containing spaces defined respectively by a pair of inner and outer annular grooves rotatably and movably along corresponding ball containing space. CONSTITUTION:A pair of outer annular grooves 12a, 12b corresponding to a pair of inner annular grooves 8a, 8b in a shaft member 4 are made, with an interval in the axial direction, in the inner circumferential face of a rotary member 6. The outer annular grooves 12a, 12b define a pair of ball containing spaces having approximately elliptical cross section together with the inner annular grooves 8a, 8b in the shaft member 4 and a plurality of spherical members 14 are arranged, respectively, in the ball containing spaces rotatably and movably along the corresponding ball containing space. When normal current is fed to an armature coil 21, the rotary member 6 is rotated in predetermined direction.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a spindle motor for rotationally driving a recording disk.

[Prior art and its drawbacks]

Generally, a spindle motor includes a mounting member attached to a device frame, a rotating member rotatably supported by the mounting member via a bearing member, and a rotor magnet attached to the inner peripheral surface of the rotating member. The rotor includes a stator mounted on a mounting member facing the rotor magnet, and a recording disk such as a magnetic disk is mounted on the rotating member. In a fixed shaft type motor, a shaft member is fixed to a mounting member, and a rotating member is rotatably mounted on the shaft member via a bearing member. Further, in a shaft-rotating type motor, a hollow cylindrical portion is provided in the mounting member, a shaft member is rotatably supported within this hollow cylindrical portion via a bearing member, and a rotating member is fixed to the shaft member. .

However, this type of spindle motor has the following problems to be solved. That is, the bearing member is composed of an inner ring member, an outer ring member, and a spherical member interposed between the two members, and due to the structure of the bearing member, it is difficult to miniaturize the motor, and it is difficult to maintain sufficient rotational accuracy. is difficult to obtain.

Further, in this type of spindle motor, a magnetic seal mechanism or a halabyrinth seal mechanism is employed in order to prevent grease and the like scattered from the bearing member from adhering to the surface of the recording disk. However, in connection with the magnetic seal mechanism or the labyrinth seal mechanism, the structure of the motor itself becomes complicated and the manufacturing cost increases.

[Purpose of the invention]

An object of the present invention is to provide a spindle motor that can obtain sufficient rotational accuracy with a simple configuration and is particularly effective in reducing the size of the motor.

[Summary of the invention]

According to the present invention, a mounting member, a shaft member fixed to the mounting member, a rotating member disposed outside the shaft member and rotatable relative to the shaft member; The rotating member includes a rotor magnet attached to the rotating member, and a stator disposed opposite to the rotor magnet, a pair of inner annular grooves are provided on the outer peripheral surface of the shaft member, and the rotating member A pair of outer annular grooves are provided on the inner circumferential surface of the inner circumferential surface thereof in correspondence with the pair of inner annular grooves, and the pair of inner annular grooves and the pair of outer annular grooves cooperate with each other, A pair of ball accommodation spaces are defined that are spaced apart in the axial direction of the shaft member, and a plurality of spherical members are rotatably arranged in each of the pair of ball accommodation spaces and along the corresponding ball accommodation spaces. A spindle motor is provided, which is characterized in that it is movably disposed.

Further, according to the present invention, there is provided a mounting member having a mounting body and a hollow cylindrical portion extending substantially perpendicularly from the mounting body; a shaft member, a rotating member fixed to the shaft member, and a rotor magnet attached to the rotating member;
a stator disposed opposite to the rotor magnet;
A pair of inner annular grooves are provided on the outer circumferential surface of the shaft member, and a pair of outer annular grooves are provided on the inner circumferential surface of the hollow cylindrical portion, corresponding to each of the pair of inner annular grooves. are provided, the pair of inner annular grooves and the pair of outer annular grooves respectively cooperate with each other to define a pair of ball accommodation spaces spaced apart in the axial direction of the shaft member, There is provided a spindle motor characterized in that a plurality of spherical members are rotatably disposed in each of the pair of ball accommodating spaces and movable along the corresponding ball accommodating spaces.

[Specific examples of the invention]

Hereinafter, specific examples of the spindle motor according to the present invention will be described with reference to the accompanying drawings.

Figures 1 and 2 show a first specific example of a spindle motor according to the present invention. In Figures 1 and 2,
The illustrated spindle motor includes a mounting member 2, a shaft member 4, and a rotating member 6.

The mounting member 2 can be formed from aluminum or the like,
Although not shown, it is attached to the device frame of the drive device. The shaft member 4 is composed of an elongated cylindrical rod, and one end (lower end) of the shaft member 4 is fixed to the mounting member 2 by press fitting or the like. This shaft member 4 extends substantially vertically upward from the mounting member 4, and a rotating member 6 is rotatably supported at the other end.

In the first specific example, a pair of inner annular grooves 8a and 8b are formed on the outer peripheral surface of the other end of the shaft member 4 at intervals in the axial direction. The inner annular grooves 8a and 8b have a substantially semicircular cross-sectional shape and extend in parallel to each other around the entire circumference of the shaft member 4. The rotating member 6 has a substantially cylindrical shape, and is provided with a flange portion 10 projecting radially outward at one end thereof. The inner diameter of one end (lower end) of the rotating member 6 is the same as that of the other end (
It is larger than the inner diameter of the upper end). A pair of inner annular grooves 8 of the shaft member 4 are provided on the inner peripheral surface of the other end of the rotating member 6.
A pair of outer annular grooves 12a and 12b are formed at intervals in the axial direction corresponding to the grooves a and 8b. The outer annular grooves 12a and 12b also have a substantially semicircular cross-sectional shape, and extend in parallel to each other all around the inner peripheral surface of the rotating member 6. Such a pair of outer annular grooves 12. 1 and 12b cooperate with the inner annular grooves 8a and 8b of the shaft member 4 to define a pair of ball accommodating spaces with a substantially circular cross section, and a plurality of spherical members 14 are rotated in each of the pair of ball accommodating spaces. The rotating member 6 is freely and movably arranged along the corresponding ball accommodation space, and therefore, the rotating member 6 is rotatably supported via these spherical members 14. In a specific example, the rotating member 6 is made of a magnetic material such as steel, and functions as a hub member to which a recording disk such as a magnetic disk is mounted on the outer circumferential surface.

In the first embodiment, the stator 16 and the rotor magnet 1 are placed in a relatively large space defined at one end of the rotating member 6.
8 is placed. The stator 16 includes a stator core 20 formed by laminating plate-like members, and the stator core 20 is fixed to the outer peripheral surface of one end of the shaft member 4 by means such as press fitting. Stator core 2
0 has an amateur coil 21 wound as required.

The rotor magnet 18 is composed of an annular permanent magnet,
It is fixed to the inner circumferential surface of one end of the rotating member 6 facing the stator 16 with an adhesive or the like. With this configuration, by supplying current to the armature coil 21 as required, the rotating member 6 is rotated in a predetermined direction.

In the first embodiment, the outside of the pair of ball accommodation spaces, that is, the outside (lower side in FIGS. 1 and 2) of one of the ball accommodation spaces defined by the inner annular groove 88 and the outer annular groove 12a. A sealing member 22 is disposed outside (on the upper side in FIGS. 1 and 2) the other ball accommodating space defined by the inner annular groove 8b and the outer annular groove 12b. The sealing member 22 is annular and can be made of synthetic rubber, for example. The outer periphery of the seal member 22 is somewhat thickened, and this outer periphery is fitted into an annular groove formed in the inner periphery of the rotating member 6. The inner circumferential edge of the seal member 22 is close to the outer circumferential surface of the shaft member 4, and prevents grease or the like filled in the ball accommodation space from scattering to the outside. This seal member 22
The inner circumferential edge of the shaft member 4 may be brought into relatively weak contact with the outer circumferential surface of the shaft member 4. Note that if scattering of grease or the like is not a problem, this sealing member 22 can be omitted.

The shaft member 4 and the rotating member 6 can be assembled, for example, as follows. That is, the rotary member 6 is heated with a high-frequency heater (not shown) or the like to expand its inner diameter, and in this state, the rotary member 6 is attached to the shaft member 4 through the plurality of spherical members 14 to a required degree. Assemble as expected. By slightly shifting the interval between the inner annular grooves 8a and 8b and the interval between the outer annular grooves 12a and 12b, when combined as described above,
A predetermined preload can be applied between the shaft member 4 and the rotating member 6. Moreover, by holding the plurality of spherical members 14 accommodated in each ball accommodating space by the ball holding member 24 at substantially equal intervals, assembly of the spherical members 14 is facilitated, and the rotating member 6 The rotation will also be smooth.

In this first specific example, when the shaft member 4, the plurality of spherical members 14, and the rotating member 6 are made of the same material (for example, steel), the coefficient of expansion is constant, so that even if the temperature changes, the members do not interact with each other. The gap between them does not substantially change, and stable rotation can be obtained even with temperature changes.

In this first specific example, for example, the shaft member 4, the plurality of spherical members 14, and the rotating member 6 can be manufactured as one component. When manufactured in this manner, the rotor magnet 18 is fixed to the inner peripheral surface of the rotating member 6, the stator 16 is fixed to the shaft member 4, and then one end of the shaft member 4 is fixed to the mounting member 2 by press fitting or the like. By doing so, the first
The motor as shown in the figure is completed.

As can be easily understood from FIG. 1, the motor of the first specific example has a smaller number of component parts than the conventional motor, and is easy to assemble, and the motor can be easily miniaturized. Furthermore, since the number of component parts is small, the accumulation of dimensional errors of the parts is also small, and high rotation accuracy can be obtained.

FIGS. 3 and 4 show a second specific example of the spindle motor according to the present invention. In the first specific example, an improvement has been made to the rotating member that functions as a hub member to which a recording disk is mounted. In the second specific example, the same members as those in the first specific example will be described with the same reference numerals.

In FIGS. 3 and 4, the illustrated rotating member 6'' is composed of a substantially hollow cylindrical rotating body 40 and an annular member 42 attached to the rotating body 40. As shown in FIGS.

The inner diameter of one end of the rotating body 40 is larger than the inner diameter of the other end, and the stator 16 and rotor magnet 18 are arranged in the space at this one end, as in the first specific example. A stepped portion 44 (FIG. 4) is formed on the inner peripheral surface of the other end of the rotating body 40, and the inner diameter of the other end is enlarged. In the rotating body 40, one outer annular groove 12a is formed at the inner side of the stepped portion 44, corresponding to the inner annular groove 8a formed in the shaft member 4. The annular grooves 12a cooperate with each other to define a ball accommodating space having a substantially circular cross section. The annular member 42 is attached to the enlarged diameter portion 46 of the rotating body 40 through an opening defined on the other end surface thereof as will be described later. On the inner peripheral surface of this annular member 42,
There are four sections with upper portions extending radially outwardly in an arcuate manner and lower portions extending linearly downward. This recess functions as the other outer annular groove 12b' and cooperates with the inner annular groove 8b of the shaft member 4 to define the other ball accommodating space.

Note that, contrary to the above, one of the ball housing spaces may be defined by the inner annular groove 8a of the shaft member 4 and the outer annular groove 12a of the annular member 42.

Inner annular grooves 8a and 8b and outer annular grooves 12a and 1
The pair of ball accommodation spaces defined by 2b° include the first
Similar to the specific example, a plurality of spherical members 14 are accommodated,
The rotating member 6' is rotatably supported via these spherical members 14. It is desirable that the spherical member 14 be held by the spherical holding member 24 in the same manner as described above.

The rotation member 6° can be assembled, for example, as follows. First, the rotating body 40 is heated with a high-frequency heater (not shown) or the like to expand its inner diameter, and in this state, the rotating body 40 is attached to the shaft member 4 through the plurality of spherical members 14 as required. Assemble as expected. Then, the remaining inner annular groove 8
A plurality of spherical members 14 are positioned within b, and then the annular member 42 is inserted through the opening on the other end surface of the rotating body 40 in the direction shown by the arrow 48, and the inner peripheral surface of the large diameter portion 46 of the rotating body 40 is inserted. Fixed to. This fixation of the annular member 42 can be done, for example, by
It can be fixed with an adhesive or the like under a predetermined load. In place of the adhesive, means such as a shrinkage spring may be used.

The other configurations of the second specific example are substantially the same as those of the first specific example shown in FIGS. 1 and 2. In this second specific example, the structure is somewhat complicated due to the presence of the annular member 42, but the same effect as the first specific example can be achieved in terms of miniaturization of the entire motor.

FIG. 5 shows a modification of the second specific example, in which the preload applying mechanism that applies preload to the spherical member is modified.

In FIG. 5, the annular member 42 is attached to the inner peripheral surface of the enlarged diameter portion 46 of the rotating body 40 so as to be movable in the axial direction (in the vertical direction in FIG. 5). An outer annular groove 12b'' that cooperates with the inner annular groove 8b of the shaft member 4 to define a ball accommodation space is formed on the inner circumferential surface of the annular member 42.
A plurality of spherical members 14 are interposed between the inner annular groove 8b and the inner annular groove 8b.

The preload applying mechanism of the modified example includes biasing means 52 that acts on the annular member 42. The illustrated biasing means 52 is composed of a pair of disc springs 54, the outer peripheral edge of one disc spring 54 contacts the annular member 42, and the outer peripheral edge of the other disc spring 54 is locked to the rotating body 40. The locking member 56 is in contact with the locking member 56 . Therefore, this biasing means 52 elastically biases the annular member 42 downward in FIG. 5, and applies a predetermined preload between the rotating member 6' and the shaft member 4. The other configurations of the modified example are substantially the same as those of the second specific example shown in FIGS. 3 and 4.

Third Specific Example FIG. 6 shows a third specific example of the spindle motor according to the present invention. The third specific example differs from the first and second specific examples mainly in the locations where the stator and rotor are provided.

In FIG. 6, the spindle motor of the third specific example is also
It includes a mounting member 102, a shaft member 104, and a rotating member 106. The outer peripheral edge of the mounting member 102 protrudes upward,
This projecting end has a flange 108 projecting radially outward.
is provided.

The mounting member 102 is mounted to the device frame (not shown) of the drive device, similar to the first embodiment.

One end (lower end) of the shaft member 104 is fixed to the mounting member 102 by means such as press fitting, and a rotating member 106 is rotatably supported by the shaft member 104 in the same manner as described above. In the third specific example, a pair of inner annular grooves 108a and 108b are formed on the outer peripheral surface of both ends of the shaft member 104, and a pair of inner annular grooves 108b are formed on the inner peripheral surface of both ends of the rotating member 1.
08a and 108b, a pair of outer annular grooves 11
0a and 110b are formed, and these inner annular grooves 108
a and 108b and outer annular grooves 110a and 110b
cooperate with each other to define a sphere accommodating space having a substantially circular cross section.

Each of these ball accommodation spaces includes a plurality of spherical members 112.
are accommodated, and the rotating member 106 is rotatably supported via these spherical members 112.

In the third specific example, a stator 114 is attached to the mounting member 102, and a rotor magnet 116 is attached to the rotating member 106. An annular flange 118 (this flange 11
A recording disk is placed and fixed on the flange 118) is integrally provided, and the lower surface of this flange 118 (lower surface in FIG. 6)
A plate-shaped rotor magnet 116 is fixed to the plate with adhesive or the like. The stator 114 is generally plate-shaped and includes air-core coils spaced apart in the circumferential direction. This stator 114 is connected to the rotor magnet 11
6 is disposed on the inner surface of the main body portion 120 of the mounting member 102. Note that, similarly to the first specific example, it is desirable to arrange the sealing member 122 outside the pair of ball accommodation spaces.

This third specific example can also achieve the same effects as the first specific example. In addition, since the inner annular grooves 108a and 108b are arranged at both ends of the shaft member 104 and the outer annular grooves 110a and 110b are arranged at both ends of the rotating member 106, the rotating member 106 can be made more stable. can be supported.

Fourth Specific Example FIG. 7 shows a fourth specific example of the spindle motor according to the present invention. This fourth specific example is different from the third specific example in the manner in which the shaft member is fixed and the location where the stator is provided. Note that the same members as those in the third specific example will be described with the same numbers.

In FIG. 7, the shaft member 102 is disposed between a base plate 124 of the drive device that functions as a mounting member and a top plate 126 of the drive device, and one end (lower end) of the shaft member 102 is fixed to the base plate 124 by a mounting screw 128.
The other end (upper end) is fixed to the top plate 126 by a mounting screw 130. A rotating member 106 is rotatably supported on this shaft member 102 via a plurality of spherical members 112, similarly to the third specific example.

A circuit board 132 for the motor is disposed on the outside (lower side in FIG. 7) of the base 7"L/-t 124. A stator 114 having an air-core coil is disposed on the circuit board 132. In addition, a plurality of through holes 134 are formed in a predetermined portion of the base plate 1240 to correspond to the air-core coils, and the air-core coils of the stator 114 are positioned in the corresponding through-holes 134. By positioning the air-core coil in this manner, the distance between the stator 114 and the rotor magnet 116 attached to the lower surface of the flange 11B of the rotating member 106 can be reduced, and as a result, the efficiency of the motor can be increased.

The other configurations of the fourth specific example are substantially the same as those of the third specific example. In this fourth specific example, the same effects as in the third specific example are achieved.

In order to facilitate the assembly of the shaft member 102, the spherical member 112, and the rotating member 106, it is preferable to construct the rotating member 106'' as shown in FIG. and a ring member 142, the rotating body 140
A ring member 142 is fixed to one end of the ring member 142 by means of press fitting or the like. With this configuration, the shaft member 102 and the spherical member 1
12 and the rotating member 106 can be relatively easily manufactured as a bearing unit, and by fixing the ring member 142 functioning as a flange to this unit, it can be used as a spindle motor.

Fifth Specific Example FIG. 9 shows a fifth specific example of the spindle motor according to the present invention. The first to fourth specific examples are applicable to a fixed shaft type motor, but the fifth specific example is applied to a shaft rotating type motor.

In FIG. 9, the illustrated motor also includes a mounting member 202, a shaft member 204, and a rotating member 206. Mounting member 2
02 includes a mounting body 208 that is attached to a frame (not shown) of the drive device, and a hollow cylindrical portion 210 that extends substantially vertically upward from a substantially central portion of the mounting body 208. The hollow cylindrical portion 210 is constructed from a sleeve member (preferably made of steel) separate from the mounting body 208 and is provided as desired by securing one end thereof to the mounting body 208 .

The shaft member 204 is disposed within a hollow cylindrical portion 210 and is rotatably supported via a plurality of spherical members 212 . Outer annular grooves 212a and 212b having a substantially semicircular cross section are formed on the inner peripheral surface of both ends of the hollow cylindrical portion 2100, and the shaft member 2
04, an inner annular groove 214 having a substantially semicircular cross section is provided at both ends of the inner annular groove 214 corresponding to the pair of outer annular grooves 212a and 212b.
a and 214b are formed, and these outer annular grooves 212a
and 212b and the inner annular grooves 214a and 214b cooperate with each other to define a ball accommodating space having a substantially circular cross section.

A plurality of spherical members 216 are accommodated in each of these pair of ball accommodation spaces so as to be rotatable and movable along the corresponding ball accommodation space.

A rotating member 206, which functions as a hub member on which a recording disk is mounted, is fixed to the shaft member 204 by means such as press fitting. In the specific example, the shaft member 204 is attached to the mounting member 20
The end wall portion 217 of the rotating member 206 protrudes upwardly in FIG. 9 beyond the hollow cylindrical portion 210 of
is fixed.

Therefore, the shaft member 204 and the rotating member 206 are rotatable relative to the mounting member 202.

Stator 218 and rotor magnet 220 are arranged in a space covered by rotating member 206. That is, the annular rotor magnet 220 is attached to the inner peripheral surface of the cylindrical main body portion 222 of the rotating member 206 via the yoke member 224. Further, the stator 21B has a stator core 226 formed by laminating plate-like members and an armature coil wound around the stator core 226. It is attached to the outer circumferential surface.

In this fifth specific example, the sealing member 228 is disposed on one side of the pair of ball accommodation spaces, that is, at the free end of the hollow cylindrical portion 210 of the mounting member 202, and grease or the like passes through the free end opening of the hollow cylindrical portion. Prevent leakage.

A motor with such a configuration can be assembled, for example, as follows.

First, the shaft member 204, the spherical member 216, and the hollow cylindrical portion 2
The sleeve member 10 is heated and assembled as required, for example as in the first embodiment.

Next, the stator 218 is attached to the outer peripheral surface of the sleeve member of the assembled unit, and then one end of the sleeve member is fixed to the mounting main body 208.

On the other hand, a yoke member 224 is attached to the inner peripheral surface of the rotating member 206, and a rotor magnet 220 is attached to the inner peripheral surface of this yoke member 224. Thereafter, this rotating member 206 is fixed to the other end of the shaft member 204 supported by the mounting member 208. Thus, as shown in FIG. 9, it can be easily assembled, and the work is significantly easier than in the past.

In this fifth specific example as well, substantially the same improvements as shown in FIGS. 2 to 7 can be made.

That is, for example, the hollow cylindrical portion of the attachment member may be constituted of a cylindrical body portion and an annular member, and the annular member may be fixed to the enlarged inner diameter portion of the cylindrical body portion in a preloaded state. Further, instead of fixing the annular member, it may be elastically biased by a biasing means. In such a case,
One ball accommodation space is defined by the inner annular groove of the shaft member and the outer annular groove of the annular member. Furthermore, the rotor magnet may be attached to the lower surface of the flange of the rotating member, and the stator may be disposed on the inner surface of the attachment member facing the rotor magnet.

Although various specific examples of the spindle motor according to the present invention have been described above, the present invention is not limited to these specific examples, and various changes and modifications can be made without departing from the scope of the present invention.

[Brief explanation of drawings]

The first is a simplified sectional view showing a first specific example of a spindle motor according to the present invention. FIG. 2 is a sectional view of essential parts of the spindle motor of FIG. 1. FIG. 3 is a simplified sectional view showing a second specific example of the spindle motor according to the present invention. FIG. 4 is a sectional view of essential parts of the spindle motor of FIG. 3. FIG. 5 is a sectional view of a main part of a partially improved spindle motor of a second specific example. FIG. 6 is a simplified sectional view showing a third specific example of the spindle motor according to the present invention. FIG. 7 is a simplified sectional view showing a fourth specific example of the spindle motor according to the present invention. FIG. 8 is a sectional view of a main part of a spindle motor of a fourth specific example in which a part of the spindle motor has been improved. FIG. 9 is a simplified sectional view showing a fifth specific example of the spindle motor according to the present invention. 2.102 and 202...Mounting member 4.104 and 204...-shaft member 6.6°, 106 and 206...Rotating member 16.11
4 and 218...Stator 1B, 116 and 220...
...Rotor magnets 8a, 8b, 108a, 108b. 214a and 214b--inner annular grooves 12a, 12b
, 12b'12b" 110a, 110b, 212
a and 212b...outer annular groove 14. 112 and 216...spherical member Fig. 2 Fig. 3 Aρ 1 Fig. 4 6' Fig. h Funeral diagram

Claims (1)

[Claims] 1. A mounting member, a shaft member fixed to the mounting member, and a rotating member disposed outside the shaft member and rotatable relative to the shaft member. , a rotor magnet attached to the rotating member, and a stator disposed opposite to the rotor magnet, a pair of inner annular grooves are provided on the outer peripheral surface of the shaft member, A pair of outer annular grooves are provided on the inner peripheral surface of the rotating member in correspondence with the pair of inner annular grooves, and the pair of inner annular grooves and the pair of outer annular grooves cooperate with each other. defines a pair of ball housing spaces spaced apart from each other in the axial direction of the shaft member, and each of the pair of ball housing spaces has a plurality of spherical members rotatably and corresponding thereto. A spindle motor characterized by being disposed so as to be movable along. 2. The stator is attached to one end of the shaft member, and the pair of inner annular grooves are provided at the other end, and the inner diameter of one end of the rotating member is larger than the inner diameter of the other end. , wherein the rotor magnet is attached to the one end of the rotating member facing the stator, and the pair of outer annular grooves are provided at the other end in correspondence with the pair of inner annular grooves. 1. The spindle motor described in 1. 3. A flange protruding radially outward is provided at one end of the rotating member, the rotor magnet is attached to one end surface of the flange, and the stator is disposed opposite to the rotor magnet. 2. The spindle motor according to claim 1. 4. a mounting member having a mounting body and a hollow cylindrical portion extending substantially perpendicularly from the mounting body; a shaft member disposed within the hollow cylindrical portion and rotatable relative to the hollow cylindrical portion; A rotating member fixed to the shaft member, a rotor magnet attached to the rotating member, and a stator disposed opposite to the rotor magnet. , a pair of inner annular grooves are provided, and a pair of outer annular grooves are provided on the inner circumferential surface of the hollow cylindrical portion, corresponding to each of the pair of inner annular grooves, and The pair of outer annular grooves cooperate with each other to define a pair of ball accommodation spaces spaced apart from each other in the axial direction of the shaft member, and each of the pair of outer annular grooves has a plurality of balls in each of the pair of ball accommodation spaces. 1. A spindle motor characterized in that a spherical member is rotatably disposed to be movable along a corresponding ball housing space. 5. The spindle motor according to claim 4, wherein the stator is attached to the outer peripheral surface of the hollow cylindrical portion of the mounting member, and the rotor magnet is attached to the inner peripheral surface of the rotating member. 6. One end of the rotating member is provided with a flange projecting outward in the radial direction, the rotor magnet is attached to one end surface of the flange, and the stator is attached to the mounting body opposite to the rotor magnet. 5. The spindle motor according to claim 4, further comprising: a spindle motor.