JP2000048472A - Exchange medium drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a motor a thin film and to suppress inexpensively rust and magnetic powder caused from a broken surface of a gate part at the time of injection molding by constituting a chucking magnet with an injection molded magnet and coating or plating this magnet surface. SOLUTION: The chucking magnet 52 is obtained by injection molding an Nd-Fe-B system magnet. Individual magnet 52 is separated from the gate part a whole surface of which is coating processed, and a coating layer 62 is formed. Since the broken surface 60 is placed on the axial direction one surface (upper surface) of the magnet 52, it is covered perfectly by the coating. Particularly, when the broken surface 60 is placed on a recessed part 58 provided on the magnet upper surface, since the matter that a projection part caused on the broken surface 60 is projected from the magnet surface is eliminated, the concern causing the projection from the magnet surface is eliminated even after the coating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exchange medium driving apparatus for driving a disk-shaped exchange medium which is a recording disk such as a floppy disk drive (FDD), a high-capacity FDD, a magneto-optical disk, and a removable HDD.

[0002]

2. Description of the Related Art Conventionally, an exchange medium drive for rotating a disk-shaped exchange medium such as a magnetic disk has been used, for example, with a high capacity FD.
In the case of D, the structure shown in FIG. 6 is known. FIG.
Is a spindle motor A of the high capacity FDD. The motor A has a housing 2 and a rotor 4 rotated with respect to the housing 2.
The housing 2 has a bottom wall portion 6 and a cylindrical portion 8 protruding from the bottom wall portion 6, and is supported by the apparatus main body. The shaft member 1 is provided inside the cylindrical portion 8 via a pair of bearings 10 and 12.
The shaft 4 is rotatably supported, and the rotor 4 is fixed to the tip of the shaft member 14 via a sleeve member 16. The rotor 4 has a cup-shaped rotor main body 18, a rotor magnet 20 is mounted on the inner peripheral surface of a cylindrical portion of the rotor main body 18, and an annular chucking magnet 22 is mounted on an upper wall of the rotor main body 18. I have. A stator 24 is fixed to the outer peripheral surface of the cylindrical portion 8 of the housing 2 so as to face the rotor magnet 20.

[0003] A magnetic disk as a disc-shaped exchange medium on which information is recorded has a center hole and a magnetic body portion on an inner peripheral portion. At the same time, the magnetic body portion is magnetically attracted to the chucking magnet 22, the magnetic disk is held on the ring body 26 on the upper wall of the rotor 4, and rotates integrally with the rotor body 18.

As the chucking magnet 22 of the spindle motor A, a ferrite plastic magnet or a rubber magnet formed by injection molding is used. Usually, a plurality of such magnets are molded simultaneously. For example, a plurality of magnet cavities are formed in a fixed arrangement in a molding die, and a plurality of gate paths branching from a molding material supply path running in the mold in a branch shape communicate with the magnet cavities, respectively. A plurality of chucking magnets 22 are simultaneously molded by injecting a molding material for magnet into each cavity from the supply path through each gate path and solidifying the molding material.

FIG. 7 shows a chucking molded magnet immediately after injection molding formed in this manner.
The plurality of chucking magnets 22 are connected by a stem 28 made of a molding material filled in a supply path and a gate 30 made of a molding material filled in a gate path. FIG. 8A is an enlarged view of a connecting portion between the chucking magnet 22 and the gate unit 30 described above, and each chucking magnet 22 is broken from the gate unit 30 by a manual operation or the like. FIG. 8B shows a fractured surface 23 of the chucking magnet 22 that has been broken from the gate portion 30. The ferrite-based plastic magnet or the rubber-based magnet itself does not generate rust, and there is no problem of rust even in the fracture surface 23. Also, the particle size of the magnet magnetic powder in the molding material is small, and burrs at the fracture surface with the gate portion 30 are small.

[0006]

With the recent demand for smaller and thinner exchange medium driving devices, thinner motors incorporated in the devices have also been required to be thinner. Needs to be thinner. However, the above-mentioned conventional ferrite-based magnet has a fatal drawback that a sufficient magnetic force cannot be obtained as the magnet becomes thinner.

Therefore, it has become necessary to use an Nd-Fe-B-based (hereinafter referred to as Nd-based) magnet having a higher energy product than a ferrite-based magnet. Nd-based magnets themselves need to be coated or plated because they are easily rusted. However, when chucking magnets are molded by injection molding of Nd-based magnets, Nd-based magnets usually have a ferrite-based particle size.
Since the magnetic powder is used in an amount of 0 times or more, burrs are generated on the fractured surface that is broken from the gate portion, and it is very difficult to completely cover this portion with coating or plating.

That is, FIG. 9A shows a connecting portion of the chucking magnet 22 connected to the gate 30 by a ferrite magnet. in this case,
Since the particle size of the magnetic powder is as small as 1 μm, the dimension g in the thickness direction of the gate opening of the gate portion 30 can be made relatively small, and the ratio of the fracture allowance of the fractured surface 23 to the magnet thickness t can be reduced, so that the fracture force is concentrated on this portion. As a result, the fracture position is stabilized, and the fracture surface is likely to be relatively flat due to the small particle size of the magnetic powder.

On the other hand, as shown in FIG.
Chucking magnet 2 with Nd magnet
In the portion connected to the gate portion 30 'of 2', the thickness t 'of the magnet is small, and the size g' of the gate opening of the gate portion 30 'in the thickness direction is large due to the large particle size of the magnetic powder. Therefore, the ratio of the fracture allowance of the fractured surface 23 'to the magnet thickness t' becomes very large, the fracture force is easily dispersed, the fracture position becomes unstable, and the fracture surface 2
Burrs and dents easily occur as in 3 ′ and 23 ″. In addition, the large particle size of the magnetic powder causes the fractured surface to be rough, so that even if the magnet surface is coated, it is not completely covered, and there is a serious problem that rust is generated and the magnetic powder flows out. The generation of such rust and the outflow of the magnetic particles substantially hinder reading and writing of information from and to the exchange medium. It is conceivable to cover the burrs and dents by increasing the thickness of the coating on the magnet surface. However, not only is it difficult to obtain dimensional accuracy, but also the cost increases.

The present invention has been made in consideration of the above-mentioned problems of the prior art, and an object of the present invention is to use a chucking magnet formed by injection molding of an Nd-based magnet and to provide a motor. Media drive device capable of contributing to a reduction in the thickness of the device, reducing the rust and magnetic powder generated from the fractured surface of the gate portion during the injection molding at a low cost, and enabling the use of the media in a stable and secure manner. It is in.

[0011]

In order to achieve the above object, according to the present invention, a chucking magnet is arranged on a disk mounting surface of a rotor, and an inner circumference of an exchange medium which is a disk-shaped recording disk is provided. The magnetic medium part of the part is magnetically attracted by the magnet, the exchange medium is chucked to the rotor, and the rotor is rotated integrally with the rotor, and the chucking magnet is formed by injection molding. -Fe-B based magnet, provided with a fracture surface of the magnet and the injection molding gate on the surface facing the magnetic part or the rotor of the exchange medium,
Further, the surface of the magnet is coated or plated (claim 1).

Nd-Fe-B molded by injection molding
The chucking magnet composed of a system magnet is broken from the gate for injection molding, and the surface of the magnet is coated or plated for the purpose of preventing generation of rust and outflow of magnetic powder. However, thin Nd-Fe-B magnets molded by injection molding have conventionally been provided with an injection molding gate on the inner or outer diameter side surface which is orthogonal to the exchange medium or the rotor. In many cases, the broken surface with the gate is shaded and cannot be completely covered. Also, it was very difficult to inspect for defects in the coating or plating process. However, according to the present invention, by providing the fracture surface of the magnet and the injection molding gate on the surface facing the magnetic portion or the rotor of the exchange medium, when performing coating or plating treatment, the surface can be completely covered without being shaded. it can.

That is, as shown in FIG. 10 (a), a disk-shaped chucking magnet B whose fracture surface C with the injection molding gate is provided on the surface of the exchange medium facing the magnetic portion or the rotor. When performing spray coating, which is generally widely used, a fracture surface C having the largest burrs and dents and being difficult to completely cover is present on the upper surface which receives the spray of the spray indicated by the arrow. It is easy to completely cover with a coating. However, as shown in FIG. 10B, in the chucking magnet b in which the fracture surface c is provided on the inner and outer diameter side surfaces as described in the related art, the position of the fracture surface c is orthogonal to the spray injection direction indicated by the arrow. When coating, it is extremely difficult to completely coat the surface due to burrs or dents in the fractured surface c when coating. Although complete coverage can be achieved by increasing the coating film thickness, it is difficult to obtain a dimensional accuracy, which is disadvantageous in terms of cost.

Nd-Fe-B molded by injection molding
The base magnet is subjected to a base treatment for obtaining conductivity, and can be subjected to cationic electrodeposition coating or electric nickel plating, or can be subjected to electroless nickel plating as it is. In these coating or plating treatments, the magnet is immersed in a treatment liquid, and the whole magnet is uniformly treated by sliding, rotating, stirring or applying ultrasonic waves. Compared to the one provided on the surface facing the exchange medium or the rotor (FIG. 10A), the conventional one provided on the inner and outer diameter side surfaces (FIG. 10B) slides, rotates,
Defects and pinholes are liable to occur in coating or plating processing because effects such as worries and ultrasonic waves are not sufficiently obtained.

Further, in the above-described exchange medium driving device of the present invention, the connecting portion of the chucking magnet to the injection molding gate is provided on a surface of the magnet facing the magnetic body or the rotor. And the broken surface with the gate may be a part of the inner bottom surface of the concave portion (claim 3).

Nd-Fe-B molded by injection molding
The chucking magnet composed of a system magnet has a fracture surface with the injection molding gate provided on the surface facing the exchange medium or the rotor, and can completely cover the fracture surface by coating or plating. However, the fractured surface of the chucking magnet has projections as well as burrs and dents. If coating or plating is performed on these, there is a possibility that projections may be formed on the exchange medium or the magnet surface facing the rotor. Therefore, when the fracture surface of the magnet is provided in the concave portion of the surface facing the exchange medium or the rotor, even if a convex portion is formed, the convex portion does not protrude from the concave portion, and comes into contact with the exchange medium or complete adhesion with the rotor. Is more preferable.

Further, according to the present invention, a chucking magnet is disposed on a disk mounting surface of a rotor, and a magnetic body portion of an inner peripheral portion of an exchange medium which is a disc-shaped recording disk is magnetically attracted to thereby remove the exchange medium. In an exchange medium driving device that rotates an exchange medium integrally with the rotor, a fracture surface of the magnet with an injection molding gate is provided on a surface facing the exchange medium or the rotor, and the magnet is coated or plated. Further, the magnet surface provided with the fracture surface of the magnet is on the side to be bonded to the rotor (claim 2).

Nd-Fe-B molded by injection molding
The chucking magnet made of a system magnet is provided with a fracture surface of the magnet with respect to the injection molding gate on the surface facing the exchange medium or the rotor, and the surface of the magnet can be completely covered by coating or plating. Here, when the magnet has large burrs, dents, and projections in the fracture surface with respect to the injection molding gate, there is a possibility that a small defect may occur during coating or plating. Therefore, it is more preferable that the magnet surface having a fracture surface with the injection molding gate is on the side to be bonded to the rotor. That is, the magnet surface having the fracture surface with the injection molding gate is not exposed by facing the rotor, and the generation of magnetic powder and rust is prevented by covering the fracture surface by applying an adhesive. You.

[0019]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a drive device using a high-capacity FDD as an exchange medium, focusing on a motor portion.
Compared with the motor shown in FIG. 6, the overall thickness of the motor is reduced, and the chucking magnet is also reduced in thickness.

The fixed portion of the motor mainly includes a flat base 32, a sleeve member 34, a thrust receiving portion 36, a stator core 40 around which a stator coil 38 is wound, and a fixed retaining member 42. The fixed retaining member 42, the stator core 40, and the sleeve member 34 are simultaneously fixed to the base 32 with screws (not shown).

The rotating shaft of the motor includes a rotating shaft 44.
An annular body 46 externally fitted and fixed to the upper part of the rotating shaft 44;
A substantially bowl-shaped rotor frame 48 made of a ferromagnetic material having an inner peripheral portion fixed at a radially intermediate position on the lower surface side of the annular body 46;
Rotor magnet 5 fixed to the inner peripheral surface of the outer peripheral wall of rotor frame 48 and radially opposed to stator core 40
0, an annular disk-shaped chucking magnet 52 for holding the recording disk is provided on an outer peripheral portion of a metal annular body 46 used as a turntable when driving an exchange medium as a recording disk. Externally fitted and fixed.

At an appropriate position on the inner peripheral side of the upper plate of the rotor frame 48, a lower protruding portion 48a having a substantially L-shaped cross section is provided by press working, and a protruding portion is formed radially inward at a lower end portion of the lower protruding portion 48a. The portion thus formed constitutes a rotation stopper, and the engagement with the fixed stopper member 42 described above constitutes a stopper for the rotating portion.

The chucking magnet 52 is made of Nd-
It is obtained by injection molding of a Fe-B based magnet, and is injection molded in a form as shown in FIG. In this case, the plurality of annular magnet cavities formed in a fixed array in the molding die are each connected to a plurality of gate paths branched in a branch shape from the molding material supply path on one axial surface of the magnet cavity. It is set as follows.

FIG. 3 shows a molded magnet for chucking immediately after injection molding thus formed.
The plurality of chucking magnets 52 are connected by a stem 54 made of a molding material filled in the supply path and a gate 56 made of a molding material filled in the gate path. As is clear from FIG. 4 which is an enlarged view of a part of FIG. 3, a circular recess 58 is formed in a part of one surface in the axial direction of the chucking magnet 52, and a gate portion 56 is formed at the center of the inner bottom surface of the recess 58. Are connected. Then, each chucking magnet 52 is broken by a manual operation or the like from the gate section 56.

FIG. 2 is an enlarged view of a broken portion of the magnet 52 from the gate portion 56. The entire surface of each of the individual magnets 52 separated from the gate portion 56 is subjected to coating treatment, that is, spray coating or Cationic electrodeposition coating after conductive undercoating,
A coating layer 62 is formed on the entire surface of the magnet 52 including the fracture surface 60 with the gate portion 56 of the magnet 52. Although the fracture surface 60 is an uneven surface due to burrs and dents as described in the related art, since the fracture surface 60 is located on one surface (upper surface) in the axial direction of the magnet 52, the fracture surface 60 is completely removed by coating. It is possible to cover.

In particular, as in the specific example, if the fracture surface 60 of the chucking magnet 52 with the gate portion 56 is located in the concave portion 58 provided on the upper surface of the magnet, the fracture surface 6
Since the protrusions generated at 0 do not protrude from the magnet surface, there is no fear that the protrusion from the magnet surface occurs even after coating. Therefore, even if the chucking magnet 52 is mounted on the rotor frame 48 such that the fracture surface 60 faces upward, that is, toward the exchange medium, the magnetic material portion of the exchange medium is surely chucked without causing circumferential unevenness. The exchange medium is attracted to the king magnet 52 and the exchange medium can be stably rotated together with the rotor.

FIG. 5 shows another embodiment of the present invention. The chucking magnet 52 formed by injection molding of an Nd-Fe-B magnet is cut from the gate portion and then electrically operated. A plating process such as nickel plating is performed, and a plating layer 64 is formed on the entire surface of the magnet including the fracture surface 60 provided in the concave portion 58 on one surface in the axial direction of the magnet 52. Further, the chucking magnet 52 thus obtained is bonded and fixed to the upper surface of the rotor yoke 48 with the fracture surface 60 facing downward, that is, toward the rotor yoke 48 side.

In this case, the chucking magnet 52
Is provided on the entire surface in the axial direction, so that the magnet 52 is immersed in a plating solution and slid, rotated, stirred, or subjected to plating by applying ultrasonic waves. A uniform plating process is realized without generating defects or pinholes in the layer 64. In particular, since the fracture surface 60 is provided in the concave portion 58 of the magnet 52, the protrusion of the fracture surface 60 can be prevented from protruding from the magnet surface, and the magnet 52 can be completely adhered to the rotor yoke 48.
Since the magnet 52 is bonded to the rotor yoke 48 on the side where the fracture surface 60 is provided, the fracture surface 60 is also covered by the adhesive between the magnet 52 and the rotor yoke 48, and the generation of magnetic powder and rust is ensured. Can be prevented.

Although the specific examples of the present invention have been described above, the present invention is not limited to the above specific examples, and various changes or modifications can be made without departing from the gist of the present invention.

[0030]

Since the exchange medium driving device of the present invention is constructed as described above, the following effects can be obtained. In the exchange medium driving device according to the first aspect, the chucking magnet disposed on the disk mounting surface of the rotor is formed by injection molding of a Nd-Fe-B-based magnet. A sufficient magnetic force can be secured even when the thickness of the chucking magnet is reduced, and the fracture surface of the magnet with the injection molding gate is provided on the surface of the exchange medium facing the magnetic portion or the rotor. Since the magnet surface is coated or plated, the magnet surface can be completely covered and the presence or absence of defects can be easily confirmed by visual inspection, thereby reliably avoiding the generation of rust and the outflow of magnetic powder. be able to. As a result, the influence of the magnet particles on the exchange medium can be avoided, and information can be read and written stably.

According to the second aspect of the present invention, the Nd-Fe-B is disposed on the disk mounting surface of the rotor.
The fracture surface of the chucking magnet molded by injection molding of the system magnet with the injection molding gate is provided in the concave portion of the surface facing the magnetic material portion or the rotor of the exchange medium, and coating or plating is performed. There are no magnets or protrusions due to burrs, so that contact of the protrusions with the exchange medium can be completely prevented, and adhesion to the rotor can be completed.

According to the third aspect of the present invention, the magnet surface having a fracture surface with respect to the injection molding gate of the chucking magnet molded by injection molding is provided at the bonding portion with the rotor. Since the magnet is not exposed to the outside and is covered with the adhesive, the magnet surface including the fractured surface can be completely covered, and the generation of rust and the outflow of magnetic powder can be reliably avoided.

[Brief description of the drawings]

FIG. 1 is a partially cutaway front view of a motor portion showing a first specific example of an exchange medium driving device according to the present invention.

FIG. 2 is a cut-away front view of a main part of the chucking magnet of FIG. 1;

FIG. 3 is a plan view showing the chucking magnet of FIG. 1 immediately after molding.

FIG. 4 is an enlarged cutaway front view showing a part of FIG. 3;

FIG. 5 is a cut-away front view of a bonded portion between a chucking magnet and a rotor yoke, showing a second specific example of the present invention.

FIG. 6 is a cut-away front view of a motor portion of a conventional exchange medium driving device.

FIG. 7 is a plan view showing a state immediately after molding of a general chucking magnet.

8A and 8B show a part of a chucking magnet in a conventional example, wherein FIG. 8A is a cut-away front view of a portion connected to a gate portion, and FIG.

9A and 9B show the relationship between the thickness of the chucking magnet and the gate portion. FIG. 9A is a front view of a ferrite magnet, and FIG. 9B is a front view of an Nd—Fe—B magnet. .

10A and 10B show a state in which the chucking magnet is spray-coated, FIG. 10A is a partially cut front view of the chucking magnet of the present invention, and FIG. 10B is a partially cut front view of the conventional chucking magnet. It is.

[Description of Reference Numerals] 48 Rotor frame 52 Magnet for chucking 58 Depression 60 Breaking surface 62 Coating layer 64 Plating layer

Claims (3)

[Claims] 1. A magnet for chucking is arranged on a disk mounting surface of a rotor, and a magnetic body portion of an inner peripheral portion of an exchange medium which is a disk-shaped recording disk is magnetically attracted by the magnet so as to transfer the exchange medium to the rotor. The chucking magnet is an Nd-Fe-B-based magnet molded by injection molding, and the chucking magnet is broken by the injection molding gate. The cross section is provided on a surface facing the magnetic portion or the rotor of the exchange medium,
An exchange medium driving device, wherein the surface of the magnet is coated or plated. 2. A chucking magnet is arranged on a disk mounting surface of a rotor, and a magnetic body portion of an inner peripheral portion of an exchange medium, which is a disc-shaped recording disk, is magnetically attracted by the magnet to remove the exchange medium from the rotor. The chucking magnet is an Nd-Fe-B-based magnet molded by injection molding, and the chucking magnet is broken by the injection molding gate. A cross section is provided on a surface facing the rotor, and a surface of the magnet is coated or plated, and a surface of the magnet provided with the fractured surface is bonded to the rotor. Exchange media drive. 3. A connecting portion of the chucking magnet with the gate for injection molding is located in a concave portion provided on a surface of the magnet facing the magnetic body portion or the rotor, and a fracture surface with the gate is formed. The exchange medium driving device according to any one of claims 1 to 3, which forms a part of the inner bottom surface of the concave portion.