JP3423345B2 - Spindle motor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor, and more particularly, to a technique for improving a fixing structure between constituent members of the spindle motor.

[0002]

2. Description of the Related Art Conventionally, a brushless polyphase DC motor has been used as a motor for rotating a magnetic disk drive. This kind of motor is also called a spindle motor, and for example, a stator including a stator coil that generates a magnetic field in an excited state, and a rotor including a rotor magnet that obtains a rotational force by electromagnetic interaction with the magnetic field of the stator coil. , A structure having a sensor for detecting the rotational position of the rotor magnet is well known,
In the spindle motor with such a structure, in many cases,
Rotation control is performed by an electronic circuit formed into a semiconductor chip.

By the way, in such a spindle motor, recently, for example, a small-sized personal computer equipped with a magnetic disk device as a storage medium,
Due to the reduction in thickness, the motor itself is required to be smaller and thinner. The spindle motor shown in FIG. 5 shows an example of one developed to meet such a demand. The spindle motor shown in the figure is a shaft rotating type having a stationary member 1 and a rotating member 2.

The stationary member 1 includes a bracket 3 having a flange portion 3a formed on the outer periphery thereof and an outer peripheral annular wall portion 3b formed inside the flange portion 3a, and the bracket 3
A hollow cylindrical portion 4 fitted and fixed to a hole 3c formed at the center of the outer peripheral annular wall portion 3b and the hollow cylindrical portion 4
An annular concave portion 5 is formed between and. Further, a step portion 4a is formed on the outer periphery of the hollow tubular portion 4, and the annular stator core 6 is fitted and fixed to the hollow tubular portion 4 such that the lower surface on the inner circumferential side abuts on the step portion 4a. ing.

A stator coil 7 is wound around the stator core 6. On the other hand, the rotating member 2 is rotatably supported by vertically arranging a rotating shaft portion 8a at its center and interposing a bearing 9 in a step-like manner between the rotating shaft portion 8a and the hollow cylindrical portion 4. It has a hub 8. An annular outer wall portion 8b is vertically provided on the outer circumference of the hub 8, and an annular wall portion 8c is provided on the outer circumference of the outer wall portion 8b.

The outer peripheral surface of the outer wall portion 8b and the annular wall portion 8
The ring-shaped rotor yoke 10 is externally fitted and fixed so as to come into contact with the lower end surface of c, and the annular rotor magnet 11 is fixedly provided on the inner peripheral surface of the vertically extending portion 10 a provided on the outer periphery of the rotor yoke 10. There is. In the spindle motor configured as described above, the magnetic disk is mounted on the upper surface of the annular wall portion 8c of the hub 8, and the stator coil 7 is inserted through the flexible printed board 12 that is adhesively fixed in the annular recess 5.
By supplying a predetermined exciting current to the hub 8, the hub 8 is driven to rotate.

However, the conventional spindle motor having such a structure has the technical problems described below.

[0008]

That is, in the above-described conventional spindle motor, since the rotor yoke 10 of the rotating member 2 serves as the magnetic path of the rotor magnet 11, a magnetic material is adopted and the hub 8 is made of a non-magnetic material. Was used, and these members were fixed by press fitting, or by using both press fitting and an adhesive. However, as described above, when the motor is made smaller and thinner, the thickness of the hub 8 and the yoke 10 becomes very thin, and accordingly, the contact area between the hub 8 and the rotor yoke 10 becomes smaller, so that the press-fitting or the adhesive is not performed. This makes it difficult to secure strength.

In this case, an annular wall portion 8c is provided on the outer circumference of the hub 8 to increase the mutual contact area. Even if such a structure is adopted, the hub 8 and the rotor yoke 10 are also provided.
Since a sufficient adhesion strength between the above members and the hub 8 and the rotor yoke 10 is exerted on the hub 8 and the rotor yoke 10 by centrifugal force, it is particularly desired to increase the adhesion strength between these members. .

The present invention has been made in view of the above problems, and an object of the present invention is to provide a spindle motor in which a sufficient fixing strength can be ensured even if it is made small and thin. is there.

[0011]

To achieve the above object, the present invention comprises a stationary member to which a stator core wound with a stator coil is attached, and a rotating member to which a rotor magnet is attached. In a spindle motor that rotates the rotating member by electromagnetic interaction between a current magnetic field generated in the rotor and the rotor magnet, the rotating member is mounted with a hub rotatably supported by the stationary member and the rotor magnet. A rotor to be welded, and the hub and the rotor are
Protrusions are integrally formed on either side during press working
And at the joint surface between the hub and the rotor,
Insert a thermosetting sheet that is welded by the heat generated during welding.
It was characterized by being more fixed to performing projection welding.

When the projection welding is performed
, Said the point of the projection welding, the gap to electrically isolate between the welding object member, the insulating ring, the insulating coating,
Ru can be interposed an insulation means selected from any of the insulating tape.

[0013]

According to the spindle motor having the above structure, the hub rotatably supported by the stationary member and the rotor on which the rotor magnet is mounted are fixed to each other by welding. Therefore, it is sufficient to make the motor small and thin. Secures a high level of adhesion.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. 1 to 3 show a first embodiment of a spindle motor according to the present invention. The spindle motor shown in the figure shows a shaft fixed type motor having a stationary member 20 and a rotating member 21 to which the present invention is applied.

The stationary member 20 has a bracket 22 and a central shaft portion 23 which is the center of rotation of the motor. The bracket 22 includes an annular base portion 22a, a circular hole portion 22b provided at the center of the base portion 22a, an outer peripheral wall portion 22c provided upright on the outer periphery of the base portion 22a, and a flange provided on the upper end of the outer peripheral wall portion 22c. And a portion 22d. Central shaft portion 23
Is a ring-shaped base portion 23a, a cylindrical shaft portion 23b erected on the central axis of the base portion 23a, an annular wall portion 23c provided around the outer periphery of the shaft portion 23b, and an annular wall portion 23c. It has an annular flange portion 23d provided on the outer periphery of the lower end, and the base portion 23a is fitted and fixed in the circular hole portion 22b of the bracket 22.

An annular wall portion 23c is provided on the outer periphery of the central shaft portion 23.
The annular stator core 25 is supported in a fitted and fixed state so as to abut the annular flange portion 23d, and the stator coil 25 is wound around the stator core 25. On the other hand, the rotating member 21 has a hub 27 and a rotor yoke 30. The hub 27 is made of, for example, non-magnetic stainless steel, and has an annular base portion 27a, a hollow cylindrical portion 27b integrally formed on the inner peripheral surface of the base portion 27a so that both ends thereof project in the vertical direction, and a base portion. It has an annular outer wall portion 27c protrudingly provided on the outer periphery of 27a.

Then, with the hollow cylinder portion 27b facing the outer periphery of the shaft portion 23b of the central shaft portion 23, the bearings 29 are interposed between these members in a two-step manner so that the hub 27 is centered. The part 23 is rotatably supported. In addition, the base portion 27 a of the hub 27 and the annular outer wall portion 2
A rotor yoke 30 having a through hole 30a formed in the center thereof is fixed to the lower surface side of 7c.

The rotor yoke 30 is made of, for example, a magnetic stainless material, and the annular wall 3 is provided on the outer peripheral side thereof.
0b is provided vertically, and the starter core 25 is provided on the inner surface thereof.
A rotor magnet 31 that faces is fixed. In addition, in FIG. 1, a member indicated by reference numeral 32 is a dustproof cap of the bearing 29. In the spindle motor configured as described above, the magnetic disk is mounted on the outer periphery of the base portion 27a of the hub 27, that is, on the upper side of the annular outer wall portion 27c, and the flexible printed board 33 adhesively fixed to the inner surface of the bracket 22 is used. The hub 27 is rotationally driven by supplying a predetermined exciting current to the stator coil 26.

The basic structure of the spindle motor as described above is the same as that of the conventional motor of this type,
The spindle motor according to the present embodiment has the salient features described below. That is, in the spindle motor of this embodiment, the hub 27 and the rotor yoke 28 are fixed to each other by welding, and projection welding is used for this welding.

FIG. 2 shows details of the projection welding when fixing the hub 27 and the rotor yoke 30. In the projection welding shown in the figure, first, the protrusion 34 is formed on the upper surface side of the rotor yoke 30. Although the protrusion 34 varies depending on the material such as the rotor yoke 30 and the thickness thereof, the protrusion 34 has a diameter of 0.2 mm, for example.
It is formed at the same time when the rotor yoke 30 is pressed to a height of about 1 mm.

Further, three or more protrusions 34 are formed on the same circumference at equal angular intervals. When performing the projection welding, first, the hub 27 is placed upside down, and the upper surface of the annular outer wall portion 27c is placed so as to abut the annular lower electrode 35. Then, next, the rotor yoke 30 is placed on the bottom surface side of the base portion 27a of the hub 27 and the annular outer wall portion 27c, and then the annular upper electrode 36 is lowered, and the tip thereof is brought into contact with the bracket 22 (FIG. 2).
(See (A)).

At this time, between the outer peripheral surface of the hollow cylindrical portion 27b of the hub 27 and the inner peripheral surface of the through hole 30a of the rotor yoke 30, an annular gap δ (the size of the gap δ is, for example,
It may be 0.03 mm or more. ) Is formed, and the protrusion 3 is provided between the hub 27 and the rotor yoke 30, which are the members to be welded.
It is electrically isolated except for 4 (see FIG. 2 (A)). As a more specific example, the interval when the protrusion 34 provided on the rotor yoke 30 abuts on the annular outer wall portion 27c of the hub 27, that is, substantially equal to 0.1 mm, or somewhat more than this. A large gap δ is set.

When the setting of the upper and lower electrodes 35, 36 is completed, a predetermined DC current is supplied while applying a predetermined pressure between the electrodes 35, 36, and projection welding is performed.
The pressing force at this time is set to, for example, about 44 kgf / cm ² , the direct current is set to about 4000 A, and the current supply time is, for example, 0.003 to 0.008.
It is set to about sec (see FIG. 2B).

When the projection welding is carried out in this way, the members to be welded (the hub 2
7 and the rotor yoke 30) are electrically isolated from each other, the direct current supplied to the electrodes 35 and 36 is concentrated on the protrusion 34, and the protrusion 34 and this protrusion 34 are short-lived. When part of the hub 27 with which 34 is in contact is melted and the power supply to the electrodes 35 and 36 is stopped, the hub 27 is
A weld nugget 37 is formed between the annular outer wall portion 27c and the rotor yoke 30 to firmly fix the two.

In the above embodiment, the rotor yoke 30 is used.
Although the case where the protrusion 34 is formed on the side is illustrated, the protrusion 34 may be formed on the hub 27 side. Now, in the spindle motor configured as described above, since the annular outer wall portion 27c of the hub 27 and the rotor yoke 30 are fixed by projection welding forming the weld nugget 37 at their joint interface, Sufficient bond strength is secured even if the is made smaller and thinner.

FIG. 3 shows the spindle motor shown in FIG.
This is a specific example of the main part, and in the specific example shown in this figure, the hub 2
The magnetic disk 38 is placed on the annular outer wall portion 27c of No. 7,
This magnetic disk 38 is fixed with a clamp 39,
The base 27a of the hub 27 is provided with a screw hole 27d into which a screw 40 for fixing the clamp 39 is screwed.

In such a mounting structure of the magnetic disk 38, the inside of the motor and the upper surface side of the magnetic disk 38 communicate with each other through the screw holes 27d, and the lubricant of the motor leaks to the upper surface side of the magnetic disk 38. There's a problem. Therefore, in this specific example , the thermosetting resin sheet 41 is provided between the lower surface of the base portion 27a of the hub 27 and the upper surface of the rotor yoke 30.
The sheet 41 is melted by the heat generated when the projection 34 is melted by projection welding, and the inside of the motor and the upper surface of the magnetic disk 38 are prevented from communicating with each other through the screw hole 27d. I am trying.

In performing projection welding, the hollow cylindrical portion 27b of the hub 27 is used as in the case described above.
An annular gap δ is formed between the outer peripheral surface of the rotor and the inner peripheral surface of the through hole 30a of the rotor yoke 30. In this case, in order to ensure the welding of the thermosetting resin sheet 41, it is desirable that the plurality of protrusions 34 provided along the circumferential direction be larger than those described above .

Further, instead of providing a plurality of substantially hemispherical projections 34, one annular projection may be provided. In this case, since the inner portions of the screw holes 27d in the hub 27 and the yoke 30 are welded in a ring shape,
The resin sheet 41 can be surely welded to ensure the sealing property. The thermosetting resin sheet 41 is
Although not shown, if it is folded back toward the gap δ side,
It can also function as a means for electrically insulating the welding members.

FIG. 4 shows a second actual施例spindle motor according to the present invention. The embodiment shown in the figure is an application of the present invention to a shaft rotation type spindle motor, and the description will be made by attaching the same reference numerals to the same or corresponding portions as the above-mentioned conventional example. The spindle motor shown in this figure includes a stationary member 1 and a rotating member 2. The stationary member 1 includes a bracket 3 having a flange portion 3a formed on the outer periphery and an outer peripheral annular wall portion 3b formed inside the flange portion 3a, and a hole portion 3c formed at the center of the bracket 3. The hollow cylindrical portion 4 is fitted and fixed, and the annular concave portion 5 is formed between the outer peripheral annular wall portion 3b and the hollow cylindrical portion 4. Further, on the outer periphery of the hollow cylindrical portion 4,
A step portion 4a is formed, and the annular stator core 6 is arranged so that the lower surface on the inner peripheral side abuts on the step portion 4a.
It is fitted and fixed to.

A stator coil 7 is wound around the stator core 6. On the other hand, the rotating member 2 is rotatably supported by vertically arranging a rotating shaft portion 8a at its center and interposing a bearing 9 in a step-like manner between the rotating shaft portion 8a and the hollow cylindrical portion 4. It has a hub 8. An annular outer wall portion 8b is vertically provided on the outer circumference of the hub 8, and an annular wall portion 8c is provided on the outer circumference of the outer wall portion 8b.

The outer peripheral surface of the outer wall portion 8b and the annular wall portion 8
The ring-shaped rotor yoke 10 is externally fitted and fixed so as to come into contact with the lower end surface of c, and the annular rotor magnet 11 is fixedly provided on the inner peripheral surface of the vertically extending portion 10 a provided on the outer periphery of the rotor yoke 10. There is. In the spindle motor configured as described above, the magnetic disk is mounted on the upper surface of the annular wall portion 8c of the hub 8, and the stator coil 7 is inserted through the flexible printed board 12 that is adhesively fixed in the annular recess 5.
The hub 8 is driven to rotate by supplying a predetermined exciting current to the hub 8. The basic construction of such a spindle motor is the same as that of the conventional one.

However, in the motor shown in this embodiment,
The features described below have remarkable features. That is, in this embodiment, projection welding is used to fix the annular wall portion 8c of the hub 8 and the yoke 10 to each other. In this projection welding, with the outer peripheral surface of the outer wall portion 8b,
An annular gap δ is provided between the inner peripheral surface of the hole provided at the center of the yoke 10 and a plurality of welding nuggets 37 are provided along the circumferential direction between the lower surface of the annular wall 8c and the upper surface of the yoke 10. It is performed so that it is formed individually. Also in the shaft rotation type spindle motor configured as described above, the same effects as those of the first embodiment can be obtained.

The electrical insulating means used in the projection welding shown in the above embodiment is not limited to providing a gap, but may be an insulating ring or an insulating sheet made of, for example, polyester synthetic resin, which is the object to be welded. Means for interposing them, or means for providing an insulating coating layer made of a paint composed of epoxy resin, for example, can be adopted.

[0035]

As described above in detail in the embodiments,
According to the spindle motor of the present invention, a larger fixing strength can be obtained as compared with the conventional press-fitting or adhesive fixing means, so that the motor can be further reduced in size and thickness.

[Brief description of drawings]

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

FIG. 2 is a process explanatory diagram when projection welding is performed between a hub and a rotor in the motor of FIG.

3 is a more specific example of the spindle motor shown in FIG .
It is a principal part half cross-sectional view which shows a structure .

It is a sectional view showing a second actual施例of a spindle motor according to the present invention; FIG.

FIG. 5 is a sectional view showing an example of a conventional spindle motor.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-38139 (JP, A) JP-A-4-251554 (JP, A) JP-A 51-71916 (JP, A) JP-A 54- 98914 (JP, A) JP 58-6061 (JP, A) Actually open 2-104779 (JP, U) Actually open 62-57580 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H02K 1/27 502 H02K 1/28 H02K 29/00 H02K 21/00

Claims (2)

(57) [Claims] 1. A stationary member having a stator core wound with a stator coil attached thereto, and a rotating member having a rotor magnet attached thereto, the electromagnetic interaction between the current magnetic field generated in the stator coil and the rotor magnet. In the spindle motor for rotating the rotating member by the action, the rotating member has a hub rotatably supported by the stationary member and a rotor to which the rotor magnet is attached, and the hub and the rotor are provided. , One of the parts to be welded
On the other hand, it is said that the protrusions are integrally formed during press working.
On the joint surface between the hub and the rotor,
With a thermosetting sheet that is welded by generated heat,
Spindle motor, characterized in that a more secured to performing Ekushon welding. 2. The projection welding points include:
Gap that electrically isolates the parts to be welded, insulating ring,
2. The spindle motor according to claim 1, wherein an insulating means selected from either insulating coating or insulating tape is interposed.