JP3885399B2 - Spindle motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention mainly relates to a spindle motor used in information-related equipment such as a magnetic disk device, and more particularly to a bearing structure thereof.
[0002]
[Prior art]
In recent years, magnetic disk devices tend to be smaller, lighter, and higher in capacity. The spindle motor used in this magnetic disk apparatus is also inevitably adapted to miniaturization and thinning, and there is a demand for improved impact resistance, higher accuracy, and longer life. As a bearing used for a conventional spindle motor, a small ball bearing is often used. However, if a small ball bearing is used, sufficient rotational accuracy cannot be obtained, it is difficult to realize a high capacity, and the impact resistance performance is extremely reduced, causing the ball bearing to deteriorate and causing noise problems. . As a countermeasure, recently, a spindle motor using a hydrodynamic bearing filled with a lubricating fluid has been developed.
[0003]
Conventionally, as a spindle motor employing a hydrodynamic bearing, one described in Japanese Patent Laid-Open No. 9-17110 is known. FIG. 6 shows the structure of a conventional spindle motor. In FIG. 6, a substantially ring-shaped flange 16 is fixed in the vicinity of the upper end side of the fixed shaft 15, and this flange 16 is accommodated in a recess of the sleeve 17. Further, the thrust plate 18 is fixed to the sleeve 17 together with the O-ring 20 by the reinforcing ring 19 in contact with the flange 16.
[0004]
This structure has a sufficiently high mechanical strength because the thrust plate 18 is firmly fixed to the sleeve 17 by the reinforcing ring 19.
[0005]
[Problems to be solved by the invention]
However, from the viewpoint of further miniaturization and high reliability, the thickness of the reinforcing ring increases in order to maintain sufficient mechanical strength, which causes a problem with miniaturization.
[0006]
Conventionally, a method has been used in which the reinforcement ring is eliminated for miniaturization and the thrust plate is press-fitted directly into the sleeve, but the fixing method by press-fitting only is simple, but an attempt is made to obtain a large holding force. As a result, the press-fitting allowance increased, and excessive distortion occurred in the sleeve in the vicinity of the flange constituting the thrust dynamic pressure bearing, resulting in a reliability problem that the roundness of the inner diameter of the sleeve was deteriorated and the life of the bearing was reduced.
[0007]
In addition to the above conventional example, there is a method of fastening a thrust plate to a sleeve using a plurality of screws. Although this is mentioned as a conventional example in the above publication, it is not suitable for miniaturization because it requires a space for forming a plurality of screws.
[0008]
Furthermore, a method of applying electroless nickel plating to a sleeve for the purpose of long life is known. This method has the effect of increasing the surface hardness of the sleeve and increasing the bearing life. However, the conventional press-fitting of the reinforcing ring or thrust plate has a problem that the electroless nickel plating layer is cut and the original mechanical strength cannot be obtained.
[0009]
The present invention solves such a conventional problem, is small in size, has good productivity, and has sufficient thrust plate holding strength while maintaining good roundness of the sleeve of the thrust dynamic pressure bearing portion. Can be obtained. In addition, electroless nickel plating can be applied to the sleeve. Accordingly, an object is to provide a long-life brushless motor.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, the brushless motor of the present invention is such that an introduction portion longer than the thickness of the thrust plate is provided in the thrust plate press-fitting portion of the sleeve, and the end portion of the sleeve introduction portion is crimped after press-fitting the outer peripheral portion of the thrust plate. did.
[0011]
Further, the sleeve was plated with electroless nickel, and the thrust plate was pressed into the sleeve with a press-fitting allowance equal to or less than the thickness of the electroless nickel plated layer.
[0012]
Further, the sleeve is hard-coated, an introduction portion longer than the thickness of the thrust plate is provided on a hub that has not been subjected to the hard coating treatment, and the hub introduction portion end is crimped after press-fitting the outer periphery of the thrust plate. I did it.
[0013]
Furthermore, the thrust plate was press-fitted by minute vibration.
Accordingly, it is possible to obtain a sufficient thrust plate holding strength while maintaining good roundness of the sleeve of the thrust dynamic pressure bearing portion in a small size and high productivity. In addition, electroless nickel plating can be applied to the sleeve. Thereby, a long-life brushless motor can be realized.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
According to the first aspect of the present invention , an electroless nickel plating is applied to the sleeve, and an introduction portion for inserting the thrust plate and a press-fit portion for press-fitting and fixing are provided on the inner peripheral portion of the upper end, and the outer peripheral portion of the thrust plate And the sleeve are fixed by press-fitting with a press-fitting margin equal to or less than the thickness of the electroless nickel plating layer of the sleeve, and caulking the introduction portion of the sleeve. It is expressed by features.
In this way, by pressing the thrust plate with a press-fitting allowance that is less than the thickness of the electroless nickel plating layer of the sleeve, the press-fitting is suppressed in the plating layer with a high hardness on the sleeve surface. Stable press-fitting is possible without being mixed in.
In addition, since the thrust plate is fixed by caulking with the sleeve, it has an effect that it can be firmly fixed in a small space without detaching the thrust plate due to excessive thrust force caused by dropping or impact.
[0016]
According to the second aspect of the present invention, a thrust plate is press-fitted and fixed to the sleeve by minute vibration. This is a description of a press-fitting method suitable for maintaining the reliability of the press-fitting portion of the thrust plate.
Since the thrust plate is press-fitted and fixed by minute vibrations, there is no excessive force applied to the sleeve at a time, and it has the effect that highly reliable work that does not affect the hydrodynamic fluid bearing part is affected. .
[0020]
【Example】
Embodiments of the spindle motor of the present invention will be described below with reference to the drawings.
[0021]
Example 1
1 and 2 are cross-sectional views of the spindle motor in the first embodiment of the present invention. In FIG. 1, 1 is a fixed shaft. A hub 2 for mounting a magnetic disk has an outer peripheral surface for mounting the magnetic disk, and a rotor magnet 4 is attached to the inner peripheral surface via a cylindrical rotor frame 3. Reference numeral 5 denotes a lower case. A fixed shaft 1 is fixed at the center, and a stator core 6 having a winding is attached to the outer peripheral portion thereof at a position facing the rotor magnet 4. Reference numeral 7 denotes a sleeve. A dynamic pressure generating groove is provided in the sleeve 7, and is supported rotatably on the fixed shaft 1 as a radial dynamic pressure fluid bearing via a lubricating fluid, and is formed on the inner peripheral surface of the hub 2. Fixed. A flange 8 having dynamic pressure generating grooves on both sides is fixed near the upper end of the fixed shaft 1. A thrust plate 9 is disposed in the recess above the sleeve 7 so as to face the flange 8. Reference numeral 7 a denotes an introduction portion at the inner peripheral portion of the upper stage of the sleeve, and has an inner diameter slightly larger than the outer diameter of the thrust plate 9. 7b is a press-fitting portion of the inner peripheral portion of the upper stage of the sleeve, and the thrust plate 9 is press-fitted and fixed therein.
[0022]
Next, the structure of the hydrodynamic bearing assembly, which is the main part of the present invention, will be described together with the assembly procedure. First, the lubricating fluid is injected into the sleeve 7 and then inserted into the fixed shaft 1. Thereafter, the lubricating fluid is again lubricated on the upper surface of the flange 8. Next, the thrust plate 9 is inserted from the introduction portion 7a at the inner peripheral portion of the upper end of the sleeve 7, and press-fitted by micro-vibration at the press-fitting portion 7b. Further, the upper end 7c of the introduction portion of the sleeve 7 is firmly fixed by caulking, and the bearing assembly is completed.
[0023]
The operation of the spindle motor configured as described above will be described. When a current is passed through the stator winding, a magnetic field is generated in the stator core 6, and a rotational torque is generated between the stator magnet 6 and the rotor magnet 4 facing the stator core 6, and the hub 2, sleeve 7, thrust plate 9 together with the rotor magnet 4. Begins to rotate. At this time, the radial dynamic pressure bearing collects the lubricating fluid and generates a pressure by the pumping action. The lower dynamic pressure generating groove and the upper dynamic pressure generating groove of the flange 8 also collect the lubricating fluid. The rotor of the thrust plate 9 is in a completely non-contact state with the fixed shaft 1 and the flange 8.
[0024]
As described above, according to the present embodiment, since the thrust plate 9 is fixed by press-fitting the outer peripheral portion and caulking the end surface of the introduction portion of the sleeve 7, the allowance for press-fitting the outer peripheral portion can be reduced. A long-life brushless motor can be realized without distortion in the hydrodynamic bearing.
[0025]
Further, since the thrust plate 9 is fixed to the sleeve 7 by caulking, the thrust plate 9 can be firmly fixed in a small space without the thrust plate 9 being detached even by excessive thrust force caused by dropping or impact.
[0026]
Further, since the thrust plate 9 is press-fitted and fixed by minute vibration, an excessive force is not applied to the sleeve 7 at a time, and a highly reliable operation that does not affect the hydrodynamic fluid bearing portion is possible. .
[0027]
(Example 2)
Next, a second embodiment of the present invention will be described with reference to FIGS. In the following description of the embodiment, the same components as those in the first embodiment shown in FIG. 1 are denoted by the same reference numerals, description thereof is omitted, and only differences are described.
[0028]
In FIG. 3, electroless nickel plating is applied to the surface of the sleeve 10 of this embodiment. By applying electroless nickel plating to the sleeve 10, the surface hardness of the sleeve 10 is increased, and the bearing life is increased. An inlet portion 10 a having an inner diameter slightly larger than the outer diameter of the thrust plate 11 and a press-fit portion 10 b for press-fitting and fixing the thrust plate 11 are provided on the inner periphery of the upper end of the sleeve 10. Then, the outer peripheral portion of the thrust plate 11 and the sleeve 10 are press-fitted with a press-fitting margin less than the thickness t of the electroless nickel plating layer of the sleeve 10 and fixed by caulking the upper end 10c of the introduction portion of the sleeve 10 It is.
[0029]
In this way, the press-fitting of the thrust plate 11 is performed with a press-fitting allowance that is equal to or less than the thickness t of the electroless nickel plating layer of the sleeve 10, so that the press-fitting is suppressed in the plating layer having a high hardness on the sleeve surface. A stable press-fit is possible without mixing inside the peeling bearing, and a highly reliable bearing can be constructed.
[0030]
Further, since the thrust plate 11 is fixed to the sleeve 10 by caulking, the thrust plate 11 can be firmly fixed in a small space without detaching the thrust plate 11 due to excessive thrust force caused by dropping or impact.
[0031]
In this embodiment, specifically, the electroless nickel plating thickness t is about 6 μm. In fixing the thrust plate 11 only by conventional press-fitting, a press-fitting allowance of about 20 μm is required. This time, the press-fitting allowance is 5 μm, which is equal to or less than the plating thickness, and by using caulking together in the thrust direction, it is possible to fix the thrust plate 11 stronger than before.
[0032]
(Example 3)
Next, a third embodiment of the present invention will be described with reference to FIG. In FIG. 5, the surface of the sleeve 13 is subjected to a hard coat process. As the hard coating process, for example, a fluorine coating process or an electroless nickel plating process is known, which has the effect of increasing the surface hardness of the sleeve 13 and increasing the bearing life. However, fixing such as press-fitting and adhesion becomes unstable. Therefore, in the present embodiment, the hub 12 and the sleeve 13 are firmly fixed by shrink fitting, the thrust plate 14 is inserted from the introduction portion 12a at the inner peripheral portion of the upper end of the hub 12, and press-fitted by minute vibration at the press-fitting portion 12b. The configuration.
[0033]
Accordingly, the thrust plate 14 can be fixed without causing distortion in the sleeve 13 constituting the thrust dynamic pressure fluid bearing, and a long-life brushless motor can be realized.
[0034]
It should be noted that the reliability of the fixing portion between the thrust plate 14 and the hub 12 can be further improved by caulking and fixing the thrust plate 14 at the upper end portion of the hub introduction portion 12a.
[0035]
Furthermore, the thrust plate 14 is press-fitted and fixed to the hub 12 by minute vibrations, so that an excessive force is not applied to the sleeve 7 at a time and the hydrodynamic bearing portion is not affected by stress or the like with high reliability. Work is possible.
[0036]
【The invention's effect】
As described above, in the brushless motor according to the present invention, it is possible to obtain a sufficient holding strength of the flange while maintaining a good roundness of the thrust dynamic pressure fluid bearing portion with a small size, good productivity, and good thrust. it can. In addition, the sleeve can be hard-coated. As a result, a long-life brushless motor can be realized.
[Brief description of the drawings]
FIG. 1 is a structural cross-sectional view showing a spindle motor in Embodiment 1 of the present invention. FIG. 2 is a structural cross-sectional view for detailed description of the spindle motor in Embodiment 1 of the present invention. FIG. 4 is a structural cross-sectional view illustrating a spindle motor in detail according to a second embodiment of the present invention. FIG. 5 is a structural cross-sectional view illustrating a spindle motor according to a third embodiment of the present invention. 6] Cross-sectional view of the structure of a conventional spindle motor [Explanation of symbols]
1, 15 Fixed shafts 2, 12 Hub 3 Rotor frame 4 Rotor magnet 5 Lower case 6 Stator core 7, 10, 13, 17 Sleeve 8, 16 Flange 9, 11, 14, 18 Thrust plate 7a, 10a Introducing portion 7b, 10b Press-fit portion 7c of sleeve upper end inner periphery caulking portion 12a of sleeve upper end introduction portion 12b of hub upper end inner periphery press-fit portion 19 of hub upper end inner periphery portion Reinforcing ring 20 O-ring

Claims (2)

  A fixed shaft fixed to the magnetic disk device side, a hub for attaching and rotating the magnetic disk, a rotor magnet for generating the rotational force of the hub, and a stator core provided facing the rotor magnet and provided with windings A sleeve fixed to the hub and rotationally supported with respect to the fixed shaft via a lubricating fluid to form a radial hydrodynamic bearing, and the fixed shaft facing both one end surface portion of the sleeve and a thrust plate Arranged, having a flange forming a thrust hydrodynamic bearing, the sleeve is electroless nickel plated, and provided with an introduction part for inserting the thrust plate and a press-fitting part for press-fitting and fixing to the inner peripheral part of the upper end, The outer peripheral portion of the thrust plate and the sleeve are press-fitted and fixed with a press-fitting allowance less than the thickness of the electroless nickel plating layer of the sleeve, and the sleeve A spindle motor fixed by the introduction portion is caulked. The spindle motor according to claim 1 , wherein the thrust plate is press-fitted and fixed to the sleeve by minute vibration.

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