JP2931073B2 - Spindle motor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a spindle motor suitable for use in a magnetic disk drive or the like.

[Prior Art] Generally, a spindle motor includes a bracket main body, a hub member rotated relatively to the bracket main body, and a pair of bearing members interposed between the bracket main body and the hub member. I have. However, such a spindle motor is not easy to assemble, and it is difficult to reduce the size of the motor.

Therefore, the present application has proposed a spindle motor using bearing means having the following configuration instead of a pair of bearing members. The bearing means includes a bearing sleeve, a bearing shaft disposed in the bearing sleeve, and a plurality of rows of spherical members interposed between the bearing sleeve and the bearing shaft. The bearing shaft is fixed to the bracket body,
The bearing sleeve is fixed to the hub member. Conversely, there is a form in which the bearing sleeve is fixed to the bracket body and the bearing shaft is fixed to the hub member.

[Problems to be Solved by the Invention] By the way, in such a spindle motor, the hub member rotates while slightly swinging (vibrating) due to the processing tolerance of the bearing sleeve, the bearing shaft and the spherical member between them. I do.

Therefore, if the machining tolerance of the parts of the bearing means is large,
The hub member also has a strong tendency to rotate while swinging in a different trajectory for each rotation.

When such a spindle motor is applied to a magnetic disk device, a magnetic disk as a recording member for writing or reading data is fixed to a hub member. for that reason,
Depending on how the hub member oscillates, the relative positional relationship between the head and the disk when the head of the magnetic disk device writes or reads data on the magnetic disk cannot be accurately reproduced, and the data can be written and read accurately. It may not be possible.

On the other hand, if the machining accuracy of each part of the bearing means is excellent,
To some extent, the fluctuation of the runout of the hub member can be suppressed. However, such a bearing means used in a spindle motor has a plurality of rows (mostly two rows) of spherical members, and the natural frequencies of the components in each row match each other. And may swing with a larger amplitude. In such a case, writing and reading of data may not be performed correctly.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems in the conventional example, and has as its object to provide a spindle motor capable of suppressing fluctuation of the runout of a hub member and accurately writing and reading data using a disk device, for example. I do.

Means for Solving the Problems In order to achieve the above object, the present invention provides a bracket main body, a hub member which is relatively rotated with respect to the bracket main body, and a bracket main body and the hub member. Bearing means interposed therebetween, wherein the bearing means comprises two rows of spherical members spaced apart in the axial direction, and a bearing sleeve forming the outer rolling surface of the two rows of spherical members. And a bearing shaft disposed in the bearing sleeve and forming an inner rolling surface of the two rows of spherical members, one of the bearing shaft and the bearing sleeve is fixed to the bracket, and the other is fixed to the bracket. In the spindle motor fixed to the hub member, characteristics of each row of the two rows of spherical members are different.

For example, the characteristics of each row of the spherical members in two rows can be made different by changing the diameter and the number of orbits of the orbits of the spherical members in each row, or the number or the contact angle with the bearing sleeve and the bearing shaft.

[Operation] According to the motor having the above-described configuration, the diameter and the number of orbits of the spherical members in each row of the two rows of spherical members of the bearing means or the contact angles with the bearing sleeve and the bearing shaft are made different. By changing the characteristic of each row and changing the natural frequency, occurrence of resonance can be prevented.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a spindle motor according to a first embodiment of the present invention.

The spindle motor shown in this figure includes a substantially disk-shaped bracket body 2 and a substantially cylindrical hub member 4.

A circular hole is formed substantially at the center of the bracket main body 2, and a hollow cylindrical wall 6 protruding upward is integrally provided at a peripheral edge defining the hole, that is, at an inner peripheral edge. . A stator 8 is mounted on the outer peripheral surface of the hollow cylindrical wall 6. The stator 8 has a stator core 10 fixed to the hollow cylindrical wall 6 and a coil 12 wound around the stator core 10. A circuit board 14 is provided on the inner surface (the upper surface in FIG. 1) of the bracket body 2. The circuit board 14 is provided with a drive circuit (not shown) including a Hall element for controlling the rotation of the hub member 4.

Bearing means 16 is mounted on the bracket body 2. The bearing means 16 includes a hollow cylindrical bearing sleeve 18 (constituting an outer ring) and a bearing shaft 20 disposed inside the bearing sleeve 18. On the inner peripheral surface of the bearing sleeve 18, an annular groove 21 is formed on the upper side, and an annular groove 22 is formed on the lower side. On the outer peripheral surface of the bearing shaft 20, an annular groove 23 is formed on the upper side, and an annular groove 24 is formed on the lower side. Between the upper annular groove 21 of the bearing sleeve 18 and the upper annular groove 23 of the bearing shaft 20, a plurality of spherical members 25 are rotatably and movably interposed along these annular grooves 21 and 23. . Similarly, the lower annular groove 22 of the bearing sleeve 18
A plurality of spherical members 26 are rotatably and movably disposed along the annular grooves 22 and 24 between the bearing and the lower annular groove 24 of the bearing shaft 20. Therefore, the bearing sleeve 18 and the bearing shaft 20 are formed of two rows of a plurality of spherical members arranged at intervals in the axial direction of the bearing shaft 20.
It is relatively rotatable via 25 and 26.

In the bearing member of this embodiment, the spherical member 25 and the spherical member 26
Have different dimensions and numbers. Here, the upper row of spherical members 25 uses eight spherical members having a diameter of 2 mm, and the lower row of spherical members 26 uses seven spherical members having a diameter of 2.778 mm. The orbit diameter of the spherical member is 9.5m in the upper row
m, 10.5 mm in the lower row. Since the orbit diameter of the spherical member is different between the upper row and the lower row,
The inner diameter of the bearing sleeve 18 is small on the upper side and large on the lower side.

The hub member 4 has a cylindrical main body 30, a flange 32 provided at one end (lower end) of the main body 30, and an end wall 34 provided at the other end (upper end) of the main body 30. . The end wall 34 is fixed to the other end (upper end) of the bearing sleeve 18 by press fitting or the like. The main body 30 of the hub member 4 covers the stator 8 mounted on the cylindrical wall 6 of the bracket main body 2. A rotor magnet 38 is attached to the inner peripheral surface of the main body 30 via a yoke member 36. Then, a recording member (not shown) such as a magnetic disk is mounted on the main body 30 of the hub member 4 as required.

Reference numeral 40 denotes an annular seal member provided on the inner peripheral surface of one end of the bearing sleeve 18. The seal member 40 is made of, for example, synthetic rubber, and its free end is brought close to or in contact with the bearing shaft 20 to prevent particles such as grease from flowing out. Reference numeral 42 denotes a cap member attached to the end wall portion 34 of the hub member 4.

FIG. 2 is a sectional view of a spindle motor according to a second embodiment of the present invention. The same or corresponding members as those in FIG. 1 are denoted by the same reference numerals and description thereof will be omitted.

The spindle motor shown in FIG.
In FIG. 6, the diameter, the number, and the orbit of the orbit of the spherical members are made different, whereas the spindle motor shown in FIG. 2 differs only in the number of the spherical members. The number of upper spherical members 25 is 8
The number of the spherical members 26 on the lower side is seven. The diameter of the spherical member and the diameter of the orbit of the orbit are the same in the upper row and the lower row.

FIG. 3 is a sectional view of a spindle motor according to a third embodiment of the present invention. FIG. 4 is an enlarged view of the bearing part of FIG. The same or corresponding members as those in FIG. 1 are denoted by the same reference numerals and description thereof will be omitted.

The spindle motor shown in FIGS. 3 and 4 has a contact angle between the upper and lower spherical members 25 and 26 (a line perpendicular to the axis and a straight line connecting the contact between the spherical member and the bearing sleeve, the contact between the spherical member and the bearing shaft). (The angle between the straight line). The contact angle α of the upper spherical member 25 (for example, 11.1)
Degrees), the contact angle β of the lower spherical member 26 (for example, 16.5
Degree) is larger.

The embodiment shown in FIGS. 1 to 3 is an example in which the bearing sleeve 18 of the bearing means 16 is fixed to the bracket body 2 and the bearing shaft 20 is fixed to the hub member 4. As shown in FIG. 5, the bearing sleeve 18 of the bearing means 16 may be fixed to the hub member 4 and the bearing shaft 20 may be fixed to the bracket body 2. In FIG. 5, members common or corresponding to those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

In FIG. 5, a short cylindrical wall 6 'is integrally provided substantially at the center of the bracket body 2', and a stator 8 is mounted on the outer peripheral surface of the short cylindrical wall 6 '. The bearing means 16 has the same configuration as that shown in FIG. A bearing sleeve 18 of the bearing means 16 is fixed to the cylindrical wall 6 'by press fitting or the like.

On the other hand, the hub member 4 'includes a hub body 52 and a hub bush 54. The end wall portion 34 of the hub body 52 is connected to the bearing bush
It is fixed to the protruding end projecting from 18.

In any of the motors described above, the numerical values assigned to the following equations are different between the upper spherical member and the lower spherical member, so that the natural frequencies are different from each other and resonance can be prevented.

Where D: diameter of spherical member (mm) Z: number of spherical members (pieces) dP: orbital diameter of spherical member (mm) F: number of rotations per second of motor (rps) α: contact angle of spherical member (Deg) n: integer Furthermore, it is assumed that the bearing shaft is fixed and the bearing sleeve rotates (in the opposite case, the formula is slightly different).

Revolution frequency of spherical member: Fa (Hz) (frequency generated when spherical member revolves) Fa = [1 + (D · cos α / dP)] · F · 1/2 (Hz) Cage (illustrated) Omitted vibration: Fb (Hz) Fb = Fa Automatic frequency of spherical member: Fc (Hz) (frequency generated by rotation of spherical member) Fc = [(dP / D)-(D / dP) cos2 α ] ・ Fr ・ 1/2 Vibration frequency of spherical member: Fd (Hz) (Vibration frequency generated when spherical member passes through the position in the radial load direction) Fd = Z ・ Fa Contact spherical member of bearing shaft Frequency of undulating part: Fe (Hz) (frequency of spherical member generated when part in contact with spherical member of bearing shaft is undulating (non-circular)) Fe = n · Z ・ Fa The undulation frequency of the part of the bearing sleeve that is in contact with the spherical member: Ff (Hz) (The part of the bearing sleeve that is in contact with the spherical member is undulating (in a perfect circle) F) The frequency of the spherical member generated in the shape) Ff = n · Z · (Fr−Fa) The undulating frequency of the spherical member (thrust direction): FgT (Hz) (When the spherical member has a scratch or true FgT = 2 · n · Fc Swelling frequency (radial direction) of spherical member: FgR (Hz) (frequency generated when spherical member has scratches or is not a true sphere) FgR = FgT ± Fa [Effects of the Invention] As described above, according to the spindle motor of the present invention, each row of the two rows of spherical members interposed between the bearing sleeve and the bearing shaft of the bearing means. The characteristics of each row are varied by varying the diameter of the spherical member and the diameter and number of orbits of the orbit, or the contact angle with the bearing sleeve and the bearing shaft, so that the natural frequency of each row is also different. Can prevent the spherical member from resonating. Wear. Therefore, the fluctuation of the runout of the hub member is suppressed,
For example, there is provided a spindle motor capable of accurately writing and reading data using a disk device or the like.

[Brief description of the drawings]

FIG. 1 is a sectional view of a spindle motor according to a first embodiment of the present invention, FIG. 2 is a sectional view of a spindle motor according to a second embodiment of the present invention, and FIG. FIG. 4 is a sectional view of a spindle motor according to a third embodiment, FIG. 4 is an enlarged view of a bearing part of the spindle motor of FIG. 3, and FIG. 5 is a sectional view of a spindle motor according to a fourth embodiment of the present invention. It is. 2 ... bracket body, 4 ... hub member, 6 ... cylindrical wall, 8 ... stator, 16 ... bearing means, 18 ... bearing sleeve, 20 ... bearing shaft, 21, 22, 23, 24 ... ... circular grooves, 2
5, 26 spherical member, 30 cylindrical part, 34 end wall part, 38
... rotor magnet.

Claims (6)

(57) [Claims] 1. A spindle motor comprising: a bracket main body; a hub member rotated relative to the bracket main body; and bearing means interposed between the bracket main body and the hub member. The bearing means includes two rows of spherical members spaced apart in the axial direction, a bearing sleeve forming an outer rolling surface of the two rows of spherical members, and the two rows of spherical members disposed in the bearing sleeve. A bearing shaft formed with an inner rolling surface of the spherical member, wherein the two rows of spherical members have different spherical member diameters and orbital diameters from each other, and the bearing shaft is fixed to the bracket; The spindle motor, wherein the bearing sleeve is fixed to the hub member. 2. A spindle motor comprising: a bracket body; a hub member rotated relative to the bracket body; and bearing means interposed between the bracket body and the hub member. The bearing means includes two rows of spherical members spaced apart in the axial direction, a bearing sleeve forming an outer rolling surface of the two rows of spherical members, and the two rows of spherical members disposed in the bearing sleeve. A bearing shaft formed with an inner rolling surface of the spherical member, wherein the two rows of spherical members have different spherical member diameters and orbital diameters from each other, and the bearing sleeve is fixed to the bracket; The spindle motor, wherein the bearing shaft is fixed to the hub member. 3. A spindle motor comprising a bracket body, a hub member rotated relative to the bracket body, and bearing means interposed between the bracket body and the hub member. The bearing means includes two rows of spherical members spaced apart in the axial direction, a bearing sleeve forming an outer rolling surface of the two rows of spherical members, and the two rows of spherical members disposed in the bearing sleeve. The two rows of spherical members have different numbers of spherical members, the bearing shaft is fixed to the bracket, and the bearing sleeve is A spindle motor fixed to the hub member. 4. A spindle motor comprising a bracket body, a hub member rotated relative to the bracket body, and bearing means interposed between the bracket body and the hub member. The bearing means includes two rows of spherical members spaced apart in the axial direction, a bearing sleeve forming an outer rolling surface of the two rows of spherical members, and the two rows of spherical members disposed in the bearing sleeve. And the two rows of spherical members have different numbers of spherical members from each other, the bearing sleeve is fixed to the bracket, and the bearing shaft is A spindle motor fixed to the hub member. 5. A spindle motor comprising: a bracket main body; a hub member rotated relative to the bracket main body; and bearing means interposed between the bracket main body and the hub member. The bearing means includes two rows of spherical members spaced apart in the axial direction, a bearing sleeve forming an outer rolling surface of the two rows of spherical members, and the two rows of spherical members disposed in the bearing sleeve. The two rows of spherical members have different contact angles between the spherical member and the bearing sleeve and the bearing shaft. A spindle motor fixed to the bracket, and the bearing sleeve is fixed to the hub member. 6. A spindle motor comprising a bracket body, a hub member rotated relative to the bracket body, and bearing means interposed between the bracket body and the hub member. The bearing means includes two rows of spherical members spaced apart in the axial direction, a bearing sleeve forming an outer rolling surface of the two rows of spherical members, and the two rows of spherical members disposed in the bearing sleeve. The two rows of spherical members have different contact angles with the bearing sleeve and the bearing shaft of the spherical member. A spindle motor fixed to the bracket, and the bearing shaft is fixed to the hub member.