JP3411344B2 - Spindle motor for recording medium drive - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor for driving a recording medium used for driving a recording medium such as a hard disk. 2. Description of the Related Art Among spindle motors for driving a recording medium such as a hard disk or the like, among small spindle motors used for driving a small disk of, for example, 2.5 inches or less, FIG. 2, a rotary shaft body a2 is integrally formed at the center of the disc-shaped base a1 of the rotor hub a, and the rotary shaft body a2 rotates with respect to the motor frame d via upper and lower ball bearings c. Those freely supported are often used. Since the rotor has the rotating shaft body a2, a screw hole b for attaching a disk fixing clamp is formed in the rotating shaft body a2.
This is because the disk base a1 of the rotor hub a can be made sufficiently thin in the axial direction to reduce the size of the motor. [0003] However, such a shaft-rotating type has a so-called rotatable support of the rotor hub on the outer peripheral side of the fixed shaft via a bearing in terms of the rotational accuracy of the rotor hub including the deflection of the rotation axis. It is disadvantageous compared to a spindle motor having a fixed shaft structure. Therefore, in order to increase the capacity of the recording medium drive, the shaft fixing structure is more advantageous, but since the rotor does not have a rotating shaft, a screw hole for attaching a disk fixing clamp is provided in the rotor hub. It must be provided at the base. Therefore, in order to provide a screw hole having a sufficient axial length, the axial thickness of the base of the rotor hub must be increased, which is a factor that makes it difficult to reduce the size (particularly, the thickness) of the motor. The present invention has been made in view of the above-mentioned problems in the prior art, and has as its object to rotatably support a rotor hub on the outer peripheral side of a fixed shaft body. By this, the rotation accuracy of the rotor hub can be improved, and a clamp mounting hole having a sufficient axial length for mounting the clamp for fixing the recording medium can be provided.
It is another object of the present invention to provide a recording medium driving spindle motor which is highly effective in reducing the size and thickness of the motor. In order to achieve the above object, a recording medium driving spindle motor according to the present invention is provided with an annular recess at an outer peripheral side of a fixed shaft protruding toward the front end in the axial direction. For a fixed shaft in a stator frame having an annular peripheral wall,
Between the fixed shaft and the annular peripheral wall, the cylindrical portion of the rotor hub is
It is rotatably supported via a bearing portion, and the sealing member is fixed to an opening at the tip end in the axial direction of the rotor hub, so that the opening is sealed, and from the inner periphery of the bearing portion in the central portion of the sealing member. The inner part is also formed in a protrusion projecting toward the base end in the axial direction, and the position of the tip of the protrusion in the axial direction is substantially the same as the position of the end of the bearing portion facing the sealing member. It is closer to the base end in the axial direction than it is, and the projection is in a non-contact state with respect to the fixed portion of the bearing portion and the fixed shaft body.
It has an opening in the axial direction toward the front end and a hole for mounting a clamp in the axial direction reaching at least the inside of the projection. The protrusion of the sealing member fixed to the opening at the tip end in the axial direction of the rotor hub does not hinder the rotation of the rotor hub because it is not in contact with the fixed part of the bearing and the fixed shaft. . The position of the tip of the projection in the axial direction is substantially the same as the position of the end of the bearing facing the sealing member or is closer to the base in the axial direction than the position of the end of the bearing. It is possible to provide a clamp mounting hole having a sufficient axial length for mounting the clamp. Since the opening at the tip end in the axial direction of the rotor hub is sealed by a sealing member, the lubricant and the like of the bearing located between the cylindrical portion of the rotor hub and the fixed shaft are removed from the tip end in the axial direction by the motor. Leakage to the outside is prevented. Also, in order for lubricant or the like of the bearing to reach the outside of the motor from the base end of the bearing in the axial direction, the lubricant must pass through the gap between the cylindrical portion of the rotor hub and the annular peripheral wall of the stator frame. Leakage of the lubricant and the like from the base end side can also be prevented with high effectiveness. An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a half sectional view of a spindle motor for driving a hard disk as one embodiment of the present invention. It goes without saying that the recording medium in the present invention is not limited to a hard disk. The case member 10 has a substantially bowl shape, a lower bottom plate 10a having an open central portion, a small-diameter cylindrical portion 10b raised from an outer peripheral portion thereof, and a radially outwardly extending upper end portion. It comprises a bottom plate 10c, a large-diameter cylindrical portion 10d raised from the outer periphery thereof, and a flange portion 10e projecting radially outward from the upper end thereof. The fixed shaft member 12 is axially directed from the central portion of the substantially disk-shaped bottom plate portion 12a to the distal end in the axial direction,
That is, the fixed shaft body 12b projects upward in FIG. A cylindrical member 14 is coaxially fitted in the small-diameter cylindrical portion 10b of the case member 10, and a lower small-diameter portion of the bottom plate portion 12a of the fixed shaft member 12 is fitted to the lower bottom plate 10a of the case member 10. The upper large-diameter portion 12a2 of the bottom plate portion 12a is fitted inside the lower end of the cylindrical member 14 at the lower end of the cylindrical member 14, so that the case member 10, the cylindrical member 14, and the fixed shaft member 12 are integrally fixed. ing. The cylindrical member 14 and the fixed shaft 12b are coaxial and form an annular recess 16 between them. A stator core 20 around which the stator coil 18 is wound is fixedly fitted to the upper portion of the cylindrical member 14, and the stator core 20 is provided on an upper surface of an annular outer protrusion 14 a provided at an upper and lower intermediate position of the cylindrical member 14. The lower surface of the base is supported on the lower surface of the stator coil 18 on the upper bottom plate portion 12a of the case member 10, respectively. The rotor hub 22 has a substantially cylindrical shape as a whole, and includes a lower cylindrical portion 22a and an upper enlarged diameter portion 22b. A rotor hub 22 is rotatably supported at its cylindrical portion 22a on the outer peripheral side of the fixed shaft body 12b via a first ball bearing 24 and a second ball bearing 26 (bearing portion). The upper end surface of the first ball bearing 24 located on the upper side is fixed to the fixed shaft body 12b.
Is located above the upper end surface of the. In this embodiment, the difference between them is about one third of the axial length of the first ball bearing 24. Thereby, the upper surface of the fixed shaft body 12b and the first ball bearing 2
A circular concave portion 28 is formed by the inner peripheral surface of 4. A cylindrical radial gap 29 formed between the outer peripheral surface of the cylindrical portion 22a and the inner peripheral surface of the cylindrical member 14.
Is set as small as possible. As a result, a labyrinth seal structure is formed, and the unclean air containing the bearing lubricant is prevented from leaking out of the motor from the second ball bearing 26 side. The annular inward projection 22a1 at the upper and lower intermediate position of the cylindrical portion 22a functions as a spacer separating the first ball bearing 24 and the second ball bearing 26. Since the cylindrical portion 22a of the rotor hub 22 is rotatably supported on the outer peripheral side of the fixed shaft body 12b via the first ball bearing 24 and the second ball bearing 26, the rotation accuracy of the rotor hub 22 is improved. Thus, when this motor is used in a hard disk drive, it is highly effective in reducing the size, thickness, and capacity of the device. The rotor hub 22 has an annular projection 22c at an intermediate position between the enlarged diameter portion 22b and the cylindrical portion 22a. An annular plate portion 30a is provided on the lower surface of the overhang portion 22c.
The inner peripheral portion of a magnet support member 30 made of a ferromagnetic material and having an annular hanging portion 30b on the outer peripheral portion is fixed.
A rotor magnet 32 is provided on the inner peripheral side of the annular hanging portion 30b.
Are fixed, and are opposed to the stator core 20 with a radial gap therebetween. A ferromagnetic ring 34 for magnetic leakage is fixed to the outer peripheral side of the annular hanging portion 30b.
That is, the ferromagnetic ring 34 may be made of pure stainless steel, non-magnetized magnet, magnetic stainless steel, or the like. Thus, the magnetic flux leaking from the rotor magnet 32 to the hard disk 46 can be effectively suppressed. A sealing member 36 is fitted and fixed to the enlarged diameter portion 22b of the rotor hub 22. The sealing member 36 has a substantially disk shape having a large thickness in the axial direction, and a portion of the center of the sealing member 36 inside the inner periphery of the first ball bearing 24 projects downward (toward the base end in the axial direction). Formed on the projection 36a. The position of the lower end surface of the protrusion 36a (the tip of the protrusion 36a in the axial direction) is lower than the position of the upper end surface of the first ball bearing 24 (the end facing the sealing member 36) (closer to the base in the axial direction). Located in. That is, the protrusion 36a
Is inserted into the circular recess 28 in a non-contact state. At the center of the sealing member 36, a projection 36a is provided.
Screw holes 4 for attaching clamps penetrating up and down including
Has zero. By using the protrusion 36a inserted in the circular recess 28, the screw hole 40 having an axial length sufficient for attaching the hard disk fixing clamp can be provided. The thickness can be made relatively thin, which is highly effective in reducing the size and thickness of the motor. The lower end surface of the screw hole 40 is
4 sealed. Seal member 44 and fixed shaft 1
2b and the protrusion 36a of the sealing member 36
And the upper end surface of the first ball bearing 24 are separated from each other by a small axial distance. The protrusion 36a of the sealing member 36 and the seal member 44 are in a non-contact state with the inner ring 24a and the fixed shaft body 12b, which are fixed portions of the first ball bearing 24, and therefore do not hinder the rotation of the rotor hub 22. Two hard disks 46 are externally fitted to the enlarged diameter portion 22b of the rotor hub 22 with a spacer 48 interposed therebetween.
It is vertically clamped and fixed between the upper surface of the overhang portion 22c and the circular clamp member 48. The clamp member 48 is screwed to the sealing member 36 using the screw hole 40. The upper opening hole 50 provided on the outer peripheral portion of the sealing member 36 is
It is used to prevent the rotation of the rotor hub 22 when the hard disk is fixed. Since the upper opening of the rotor hub 22 is closed by the sealing member 36, the lubricant and the like of the first ball bearing 24 located between the cylindrical portion 22a of the rotor hub 22 and the fixed shaft body 12b move upward. From the motor to the outside of the motor. Also, in order for the lubricant and the like of the second ball bearing 26 to reach the outside of the motor from below, a cylindrical gap 29 between the cylindrical portion 22a of the rotor hub 22 and the cylindrical member 14 is required.
Owing to the labyrinth seal-like effect, the leakage of lubricant and the like from here is also highly effectively prevented. Therefore, it is highly effective in preventing the hard disk from being stained when used in a hard disk drive. Further, since the sealing member 36 is separate from the rotor hub 22, it is easy to form the sealing member 36, and the vertical length including the protrusion 36a is relatively short. It is also easy to make the protrusion 36a penetrate the screw hole 40 in order to ensure the reliability. On the other hand, in the case of a shaft-rotating type rotor hub, in order to ensure the reliability of rust prevention treatment in a screw hole provided in the rotating shaft, a long rotating shaft must be penetrated, or the effective length of the screw must be shorter than the effective length. Although it was necessary to provide an extra deep hole, such a problem is solved. In the above description of the embodiment, the vertical positional relationship, dimensions, number, material, shape,
The relative arrangement and the like are not intended to limit the scope of the present invention only to them, but are merely illustrative examples, unless otherwise specified. According to the spindle motor for driving the recording medium of the present invention, the cylindrical portion of the rotor hub is rotatably supported on the outer peripheral side of the fixed shaft via a bearing portion. The rotation accuracy of the rotor hub can be made better than that of the conventional one, and it is highly effective in reducing the size and thickness and increasing the capacity when used in a recording medium drive. Also, it is possible to provide a clamp mounting hole having an axial length sufficient for mounting the clamp for fixing the recording medium by using the protrusion of the sealing member fixed to the opening on the axial front end side of the rotor hub. Accordingly, the thickness of the other part of the sealing member in the axial direction can be made relatively thin, which is highly effective in reducing the size and thickness of the motor. Also, since the opening at the tip end in the axial direction of the rotor hub is sealed by the sealing member, it is possible to prevent the lubricant and the like of the bearing from leaking from the tip end in the axial direction to the outside of the motor. Leakage of lubricant and the like from the base end side in the axial direction of the rotor frame must pass through the gap between the cylindrical portion of the rotor hub and the annular peripheral wall of the stator frame, so that it can be highly effectively prevented. It is highly effective in preventing the recording medium from being stained in the case where the recording medium is damaged.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a half sectional view of a hard disk drive spindle motor. FIG. 2 is a half sectional view of a conventional spindle motor for driving a hard disk. [Description of Reference Numerals] 12b Fixed shaft body 14 Cylindrical member 22 Rotor hub 22a Cylindrical part 24 First ball bearing 26 Second ball bearing 28 Circular recess 36 Sealing member 36a Projection 40 Screw hole

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02K 21/22 H02K 5/15 H02K 5/173 H02K 29/00

Claims (1)

(57) Claims: 1. A fixed shaft body protruding toward the front end in the axial direction is fixed to a fixed shaft body of a stator frame having an annular peripheral wall with an annular concave portion on an outer peripheral side of the fixed shaft body. The cylindrical portion of the rotor hub is rotatably supported via a bearing portion between the shaft body and the annular peripheral wall, and the sealing member is fixed to the opening at the axial end of the rotor hub, so that the opening is formed. The central portion of the sealing member, a portion inside the inner periphery of the bearing portion is formed as a projection projecting toward the base end in the axial direction, and the position of the tip of the projection in the axial direction is: The position of the end portion of the bearing portion facing the sealing member is substantially the same as or closer to the base end in the axial direction, and the projection is in a non-contact state with the fixed portion of the bearing portion and the fixed shaft body. In the center of the sealing member, Opening in the direction, the recording medium drive spindle motor, characterized in that it comprises an internal reaches the axial direction of the clamp mounting hole of at least the protrusion.