JP3820036B2 - Exchange medium drive - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exchange medium driving device that drives a disk-like exchange medium that is a recording disk such as a floppy disk drive (FDD), a high-capacity FDD, a magneto-optical disk, and a removable HDD.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an exchange medium driving device that rotationally drives a disk-like exchange medium such as a magnetic disk has a structure shown in FIG. 5 in the case of a high capacity FDD, for example. FIG. 5 shows the spindle motor A as a center of the high capacity FDD. The motor A has a housing 2 and a rotor 4 that is 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. A shaft member 14 is rotatably supported inside the cylindrical portion 8 via a pair of bearings 10 and 12, and the rotor 4 is fixed to the tip end portion of the shaft member 14 via a sleeve member 16. The rotor 4 has a cup-shaped rotor body 18, a rotor magnet 20 is attached to the inner peripheral surface of the cylindrical portion of the rotor body 18, and an annular chucking magnet 22 is attached to the upper wall portion of the rotor body 18. Yes. 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 the inner periphery, and the center hole is fitted into the tip of the shaft member 14 and aligned. 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 in the upper wall portion of the rotor 4, and rotates together with the rotor 4.
[0004]
As the chucking magnet 22 in the spindle motor A described above, a ferrite plastic magnet formed by injection molding or a ferrite rubber magnet formed into a sheet by extrusion molding is generally used.
A plurality of ferrite-based injection-molded plastic magnets are usually 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 passage running in the mold communicate with the magnet cavities, respectively. A plurality of chucking magnets 22 are simultaneously molded by injecting a magnet molding material into each cavity from the supply path through each gate path and solidifying it.
[0005]
The ferrite rubber magnet is formed into a sheet with a predetermined thickness by an extrusion roll or an injection molding machine after the ferrite magnet and the rubber material are blended and mixed by kneading. And it is used by punching into a predetermined shape with a mold or a Thomson blade.
[0006]
These ferrite-based plastic magnets or ferrite-based rubber magnets themselves do not generate rust, and there is no problem of rust even on the fracture surface. Further, the particle size of the ferrite-based magnetic powder used is as small as about 1 μm, and the burr on the injection molded gate portion or the fracture surface generated at the time of punching is small.
[0007]
Therefore, ferrite plastic magnets or ferrite rubber magnets are generally used as they are without coating, or they are simply coated on one or both sides to suppress particles generated during molding, and are usually the cheapest epoxy as the coating material. System paint is used.
[0008]
[Problems to be solved by the invention]
By the way, along with the recent demand for smaller and thinner exchange medium driving devices, motors built in the devices are also required to be thinner, and the chucking magnet described above needs to be thinner. Yes. However, the conventional ferrite magnet described above has a fatal defect that a sufficient magnetic force cannot be obtained as the thickness is reduced.
[0009]
Therefore, it has become necessary to use an Nd—Fe—B (hereinafter referred to as Nd) magnet having a higher energy product than that of a ferrite. Sintering, compression molding, and injection molding magnets are generally well known as Nd magnets. Here, Nd-based sintered and compression-molded magnets are not suitable because their energy product is too high and thinning is difficult. Therefore, Nd-based injection-molded magnets have begun to be used, but it is difficult to make the gate portion thinner due to restrictions on the fluidity of the magnet molding material in the gate portion, and it is difficult to make it 0.8 mm or less.
[0010]
In addition, since the Nd magnet itself rusts easily, it is necessary to coat the magnet surface. However, when a chucking magnet is molded by injection molding of an Nd magnet, the Nd magnet spontaneously ignites when it is finely crushed. The burr generated on the fractured surface is severe, and it is particularly difficult to completely coat this part.
[0011]
That is, FIG. 8A shows a connecting portion with the gate portion 30 of the chucking magnet 22 by the ferrite magnet. In this case, since the particle size of the magnetic powder is as small as 1 μm, the thickness direction dimension g of the gate opening of the gate portion 30 can be made relatively small, and the ratio of the fracture margin of the fracture surface 23 to the magnet thickness t can be made small. The fracture position is stabilized by concentrating on the portion, and the fracture surface is likely to be relatively flat due to the small particle size of the magnetic powder.
[0012]
On the other hand, as shown in FIG. 8B, the connecting portion of the chucking magnet 22 ′ with the Nd-based magnet 22 ′ and the gate portion 30 ′ has a reduced magnet thickness t ′ and a magnetic particle particle. Since the size g ′ of the gate opening in the gate portion 30 ′ increases due to the large diameter, the ratio of the fracture margin of the fracture surface 23 ′ to the magnet thickness t ′ becomes very large, and the breaking force is dispersed. As a result, the breaking position becomes unstable, and burrs and dents are likely to occur as in the fracture surfaces 23 ′ and 23 ″. In addition, since the particle size of the magnetic powder is large, the fracture surface becomes rough, and even if the surface of the magnet is coated, it is not completely covered, and there is a serious problem that causes rust generation and magnetic powder outflow. Such generation of rust and outflow of magnetic particles substantially impairs reading and writing of information with respect to the exchange medium.
[0013]
Although it is conceivable to cover the burrs and dents by increasing the thickness of the coating on the magnet surface, not only is the dimensional accuracy difficult to obtain, but there is also a problem of increased costs.
[0014]
The present invention has been made in consideration of such problems of the prior art, and the object of the present invention is a chucking that is a thin layer and can obtain a sufficient magnetic force that can be chucked. Another object of the present invention is to provide an exchange medium driving apparatus that can contribute to the reduction in the thickness of a motor by using a magnet, and can suppress the generation of rust and magnetic powder from the magnet.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, a chucking magnet is arranged on the disk mounting surface of the rotor, and the magnetic body part of the inner periphery of the exchange medium, which is a disk-shaped recording disk, is magnetically attracted. In the exchange medium driving device for rotating the exchange medium integrally with the rotor, the chucking magnet is composed of a coated Nd- Fe- B rubber magnet, and the chucking magnet is extruded. The surface in the direction in which the blade enters in the punching of extrusion molding is the adsorption surface side of the magnetic body portion (Claim 1).
[0016]
A chucking magnet made of an Nd—Fe—B rubber magnet formed by extrusion molding is coated on the surface of the magnet for the purpose of preventing the generation of rust and the outflow of magnetic powder. This type of extruded rubber magnet can be thinned, has no fracture surface with the gate like an injection molded magnet, and the magnet surface is coated so that the magnet surface is completely covered without leakage, and rust-free Generation and outflow of magnetic powder are prevented. Nd—Fe—B magnets have a higher energy product than ferrite magnets, and a sufficient magnetic force can be obtained even if they are thin.
[0017]
Nd-Fe-B rubber magnets molded by extrusion can be thinned to 0.2mm by adjusting the gap of the extrusion roll, and this sheet is punched with a Thomson blade or a die. Can be used. This Nd rubber magnet is generally used by mixing Nd magnet powder having an average particle diameter of about 10 μm with rubber such as chlorinated polyethylene, NBR, nitrile rubber, etc., but the rubber material is limited to this. is not. The mixing amount of the Nd-based magnet powder is preferably 70% to 98% by weight (Claim 2). If the weight ratio is 70% or less, sufficient magnetic force cannot be obtained, and if it is 98% or more, it becomes difficult to form a sheet, and the rubber elasticity is remarkably lowered.
[0018]
Nd rubber magnets themselves are easily rusted, and it is necessary to coat the magnet surface for the purpose of preventing the scattering of magnetic powder. However, Nd rubber magnets can be made thinner than injection molded Nd magnets, and there is no complicated fracture surface with the gate part. By coating the magnet surface, the magnet surface is completely covered without leakage. Thus, generation of rust and scattering of magnetic powder can be prevented. Nd magnets have a higher energy product than ferrite magnets, and a sufficient magnetic force can be obtained even if they are thin.
[0019]
The coating can be performed by dissolving a phenol resin, an epoxy resin, an acrylic resin, or the like in an appropriate organic solvent or forming an aqueous emulsion solution, and impregnating the solution by impregnation or reduced pressure. These impregnated coatings have a thin coating thickness, and the flexibility of the rubber magnet is not lost, and can be adhered to the rotor frame 48.
[0020]
The coating of the Nd rubber magnet by the above impregnation is sufficiently useful for preventing the occurrence of rust and scattering of magnetic particles, but it is difficult to increase the film thickness. That is, when the film thickness is increased, the solvent is not easily volatilized, causing adhesion with rubber magnets or work benches, and deformation when exposed to high temperatures.
[0021]
Therefore, in order to prevent the generation of rust and the scattering of magnetic powder, the reliability is improved by coating several μm to several tens of μm by spray coating or the like. Although commonly used coating materials may be used as the coating material, Nd rubber magnets are flexible and easily deformed, so the flexibility is not impaired even after coating and they can be in close contact with the rotor frame. A coating material is preferred (claim 4). When a coating material with poor flexibility is used, if deformation occurs during coating or drying, there is a risk of cracking or cracking when the coating material is adhered to the rotor frame. Examples of the highly flexible coating material include, but are not limited to, urethane-based coating materials such as acrylic urethane and epoxy-urethane, and rubber-based coating materials.
[0022]
Here, when punching as a rubber magnet described above, it is desirable to the surface of the start of the blade and the suction surface side of the magnetic body portion (claim 1). Extruded sheet-like rubber magnets are rich in rubber elasticity, and the surface into which the blade enters when punching is rounded at the edge of the fracture surface, the side receiving the blade is compressed and cut, and the fracture surface is relatively complex It becomes a shape. Therefore, by making the rubber magnet surface on the side where the blade enters into the attracting surface side of the magnetic body portion, the smooth surface of the chucking magnet faces the magnetic body portion, and the relative position between the magnet and the magnetic body portion Can be managed uniformly, which is preferable.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a drive unit using a high-capacity FDD as an exchange medium, centering on the motor portion. Compared with the above-described one shown in FIG. Thinner.
[0024]
The fixed portion of the motor mainly comprises 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 retaining member 42, the stator core 40, and the sleeve member 34 are simultaneously fixed to the base 32 with screws not shown.
[0025]
The rotating portion of the motor includes a rotating shaft 44, an annular body 46 that is externally fitted and fixed to the upper portion of the rotating shaft 44, and a substantially bowl shape in which an inner peripheral portion is fixed at a radially intermediate position on the lower surface side of the annular body 46. And a rotor magnet 50 which is fixed to the inner peripheral surface of the outer peripheral wall portion of the rotor frame 48 and is opposed to the stator core 40 in the radial direction, and drives an exchange medium as a recording disk. An annular thin plate-like chucking magnet 52 for holding a recording disk is externally fitted and fixed to an outer peripheral portion of a metal annular body 46 used as a turntable.
[0026]
A lower projecting portion 48a having a substantially L-shaped cross section is provided by pressing in an appropriate position on the inner peripheral side of the upper plate of the rotor frame 48, and a portion projecting radially inwardly at the lower end portion of the lower projecting portion 48a is provided. The rotation stopper is configured, and the rotation part is prevented from coming off by the engagement with the above-described fixed retaining member 42.
[0027]
The chucking magnet 52 is obtained by extrusion molding of an Nd—Fe—B rubber magnet. As shown in FIG. 2, a coating layer 54 of acrylic urethane paint is provided on the surface of the magnet 52. The entire surface of the magnet 52 is coated.
[0028]
Here, the manufacturing method of the magnet 52 will be described. As shown in FIG. 3, a magnet sheet 56 having a predetermined thickness made of an Nd—Fe—B rubber magnet is formed in advance, and an outer frame as shown in FIG. The extrusion mold 58 provided with the mold 58a and the inner frame mold 58b concentrically is pushed into the magnet sheet 56 from above, and the annular magnet 52 is inserted between the outer frame mold 58a and the inner frame mold 58b. Get. As can be seen from FIG. 2, the magnet 52 obtained in this way is rounded at the upper edge by the elasticity of the magnet material, but the inner and outer peripheries of the magnet 52 are cut by the outer frame mold 58a and inner frame mold 58b. The cut surface is a smooth cylindrical surface, and there are almost no irregularities or burrs. The surface of the magnet 52 is completely covered and prevented from being exposed by coating the surface of the magnet with urethane paint.
[0029]
The chucking magnet 52 described above is mounted on the rotor frame 48 so that the upstream side in the extruding direction, that is, the rounded side faces upward, and the opposing surface of the magnet 52 to the magnetic body portion of the exchange medium is smoothed. Is prevented.
[0030]
As mentioned above, although the specific example of this invention was demonstrated, this invention is not limited to the said specific example, A various change and correction are possible, without deviating from the summary of this invention. For example, the coating of the chucking magnet 52 need not be limited to urethane-based paint, and it is sufficient that the magnet surface can be completely covered without leakage so as to prevent rust and magnetic powder from flowing out. Coating with a paint is preferable because there is no need to worry about cracking of the coating even if there is some deformation due to the elasticity of the rubber magnet.
[0031]
【The invention's effect】
Since the exchange medium driving device of the present invention is configured as described above, the following effects can be obtained.
By using a chucking magnet placed on the disk mounting surface of the rotor that is made into a sheet by extrusion molding of an Nd-Fe-B rubber magnet, it becomes possible to reduce the thickness, which was difficult with conventional injection molding. In addition, a sufficient magnetic force can be secured, and the magnet surface can be kept smooth without causing a fracture surface with the gate as in the case of injection molding. Thus, the entire surface of the magnet can be completely covered, and generation of rust and outflow of magnetic powder can be surely avoided. As a result, the influence of the magnet particles on the exchange medium can be avoided, and information can be read and written stably.
[Brief description of the drawings]
FIG. 1 is a partially cut front view of a motor portion showing a specific example of an exchange medium driving device of the present invention.
FIG. 2 is a cut front view of a main part of the chucking magnet of FIG. 1;
3 is a plan view of a magnet sheet showing a manufacturing method of the chucking magnet of FIG. 1. FIG.
4 is a cut front view showing the manufacturing method of the chucking magnet of FIG. 1 during extrusion molding. FIG.
FIG. 5 is a cut front view of a motor portion of a conventional exchange medium driving device.
FIG. 6 is a plan view showing a state immediately after molding a chucking magnet by conventional injection molding.
7A and 7B show a part of a chucking magnet in a conventional example, in which FIG. 7A is a cut front view of a connecting portion with a gate portion, and FIG.
8A and 8B show the relationship between the thickness of a chucking magnet and a gate portion, where FIG. 8A is a front view in the case of a ferrite magnet, and FIG. 8B is a front view in the case of an Nd—Fe—B magnet. .
[Explanation of symbols]
46 annular body 48 rotor frame 52 magnet 54 for chucking coating layer

Claims (4)

An exchange medium in which a chucking magnet is arranged on the disk mounting surface of the rotor, and the exchange medium is rotated integrally with the rotor by magnetically attracting the magnetic body portion of the inner circumference of the exchange medium that is a disk-shaped recording disk. In the drive device,
The chucking magnet is an Nd- Fe- B rubber magnet whose surface is coated. The chucking magnet is formed by extrusion molding, and the surface in the direction in which the blade enters in the punching of extrusion molding is the magnetic body. An exchange medium driving device characterized by being on the suction surface side of the part.  The exchange medium driving device according to claim 1, wherein the magnet mixing amount in the rubber magnet is 70% to 98% by weight.  2. The exchange medium driving device according to claim 1, wherein the surface of the rubber magnet is coated by impregnation or impregnation under reduced pressure.  2. The exchange medium driving device according to claim 1, wherein the coating on the surface of the rubber magnet is flexible enough to be in close contact with the rotor frame even when the rubber magnet is deformed.

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