The motor 1 includes a static portion 2 as a stator assembly and a rotor portion 3. The rotor portion 3 is supported by the static portion 2 via a bearing assembly utilizing fluid dynamic pressure of lubricant so as to rotate around the central axis J1. It is noted that, in the description of the present invention, positional relations and directions of respective members described as up, down, left, and right simply indicate positional relations and directions in the drawings, and do not indicate positional relations and directions when actually incorporated in equipment.
The rotor portion 3 includes a rotor hub 31 and a rotor magnet 32. A center of the rotor hub 31 is connected with a shaft 311 extending downwards from the rotor hub 31. The rotor magnet 32 is attached to the rotor hub 31 and arranged around the central axis J1. The rotor hub 31 and the shaft 311 are formed as a single member made of stainless steel and the like.
The rotor hub 31 includes a discoid portion 312 in a substantially circular disk shape and a cylindrical portion 313 in a substantially cylindrical shape. The discoid portion 312 extends perpendicularly to the central axis J1 from an upper end part of the shaft 311. The cylindrical portion 313 projects downwards from an outer edge of the discoid portion 312. A thrust plate 33 in a substantially circular disk shape is attached to a lower distal end of the shaft 311. A data storage disk 9 is set on an upper surface of the rotor hub 31 as indicated with chain double-dashed line.
The static portion 2 includes a base plate 21 serving as a base portion for supporting each part of the static portion 2, a sleeve unit 22 in a substantially cylindrical shape, and an armature 24. The shaft 311 is inserted into the sleeve unit 22. The armature 24 is attached to the base plate 21 around the sleeve unit 22.
The armature 24 is attached to the base plate 21 from an upper side by press fitting or adhesive joining, and torque around the central axis J1 is generated between the armature 24 and the rotor magnet 32 arranged around the shaft 311. In other words, the armature 24 and the rotor magnet 32 function as a drive mechanism for rotating the rotor portion 3 with respect to the static portion 2.
At a center of the base plate 21, there is provided a sleeve attaching portion 211 having a substantially cylindrical shape and projecting upwards around the central axis J1. The sleeve unit 22 includes a sleeve 221, a sleeve housing 222 in a substantially cylindrical shape as a sleeve supporting member, and a seal cap 223 in a substantially circular disk shape, and is inserted into the sleeve attaching portion 211 and fixed with adhesive to the base plate 21. The sleeve 221 is formed into a substantially cylindrical shape around the central axis J1. The sleeve housing 222 is attached to an outer surface of the sleeve 221. The seal cap 223 seals an opening at a lower side of the sleeve housing 222. Alternatively, the sleeve housing 222 and the seal cap 223 may be formed as a single member. In this case, the sleeve housing is formed into a cylindrical shape having a bottom surface.
At an upper part of the sleeve housing 222, there is formed a flange portion 2221 projecting radially outwards along an outer periphery of the sleeve unit 22. When the sleeve unit 22 is attached to the base plate 21, a lower part of the flange portion 2221 and an upper end part of the sleeve attaching portion 211 come in contact to each other.
The motor 1 is formed with microscopic spaces including an upper space 41, a side space 42, a first lower space 43, a second lower space 44, and an outer space 45.
The upper space 41 is formed between a lower surface of the discoid portion 312 of the rotor hub 31 and an upper end surface of the sleeve 221. The side space 42 is formed between an inner surface of the sleeve 221 and an outer surface of the shaft 311. The first lower space 43 is formed between a lower surface of the sleeve 221 and an upper surface of the thrust plate 33. The second lower space 44 is formed between a lower surface of the thrust plate 33 and an upper surface of the seal cap 223. The outer space 45 is formed between an outer surface of the flange portion 2221 of the sleeve housing 222 and an inner surface of the cylindrical portion 313 of the rotor hub 31.
The outer surface of the flange portion 2221 is inclined such that an outer diameter thereof is gradually decreased toward a lower side. An interface of lubricant in the outer space 45 is formed into a meniscus shape due to capillarity and surface tensity, defining a taper seal in the outer space 45. According to such a configuration, the outer space 45 functions as an oil buffer to prevent the lubricant from flowing outwards.
On the other hand, upper and lower end surfaces of the sleeve 221 are respectively formed with upper and lower thrust dynamic pressure groove arrays for generating fluid dynamic pressure in the lubricant due to rotation of the rotor portion 3, so that thrust dynamic pressure bearing portions are formed in the first lower space 43 and the upper space 41. Alternatively, the lower surface of the thrust plate or the upper surface of the seal cap may be provided with the dynamic pressure groove array to form the thrust dynamic pressure bearing portion in the second lower space. Further, the inner surface of the sleeve 221 is formed with a radial dynamic pressure groove array for generating fluid dynamic pressure in the lubricant in the side space 42, so that a radial dynamic pressure bearing portion is formed in the side space 42.
As described above, in the motor 1, the sleeve unit 22, the seal cap 223, the shaft 311, the discoid portion 312 and the thrust plate 33 (as well as the lubricant) form the bearing assembly utilizing fluid dynamic pressure. Since the bearing assembly contactlessly supports the rotor portion 3 via the lubricant, the rotor portion 3 and the data storage disk 9 can be rotated highly accurately and quietly. Particularly, the bearing assembly in which the upper space 41, the side space 42, the first lower space 43, the second lower space 44, and the outer space 45 are continuously filled with lubricant can further suppress unusual contact between the shaft 311 and the sleeve 221 due to bubbles generated in the lubricant, leakage of the lubricant due to expansion of air in the bearing assembly.
After the sleeve 221 is inserted into the sleeve housing 222, the sleeve 221 is fixed to the sleeve housing 222 with adhesive 220 interposing between the inner surface 2222 of the sleeve housing 222 and an outer surface 2211 of the sleeve 221.
An outer peripheral edge at a lower end part of the sleeve 221 is chamfered to form an adhesive holding portion 56 to be described later. Adhesive 220a is held between the adhesive holding portion 56 and the inner surface 2222 of the sleeve housing 222 continuously from between the sleeve housing 222 and the sleeve 221. On the other hand, the adhesive 220 is merely held between an upper end part of the sleeve 221 and the sleeve housing 222.
The adhesive 220a functions as a wedge and prevents the sleeve 221 from being displaced with respect to the sleeve housing 222 even when heavy downward load is applied to the sleeve 221 via the rotor hub 31. That is, the adhesive 220a prevents destruction of adhesive joining between the sleeve 221 and the sleeve housing 222.
Each of the outer surface 2211 and the inner surface 2212 of the sleeve 221 has a substantially cylindrical shape. On an upper end surface 2213 connecting an upper end of the outer surface 2211 and an upper end of the inner surface 2212 of the sleeve 221, and on a lower end surface 2214 connecting a lower end of the outer surface 2211 and a lower end of the inner surface 2212, dynamic pressure grooves as a group of grooves are respectively formed. Dynamic pressure grooves 511 on the upper end surface 2213 are formed into a herringbone shape, and dynamic pressure grooves 512 on the lower end surface 2214 are formed into a spiral shape.
Further, dynamic pressure grooves 513 in a herringbone shape are formed at upper and lower parts on the inner surface 2212 of the sleeve 221, and three communicating grooves 52 extending along the central axis J1 are formed on the outer surface 2211 while equiangularly spaced apart from one another. The communicating grooves 52 reduce difference in pressure between the upper space 41 and the first lower space 43 illustrated in
As illustrated in
As illustrated in
It is alternatively possible to adopt a different adhesive holding portion in a so called stepped shape formed by a combination of a circular surface extending inwards from and perpendicularly to the outer surface 2211 and a cylindrical surface connecting an inner side of the circular surface and the lower end surface 2214.
The adhesive holding portion such as those illustrated in
As described above, the adhesive holding portion may have various shapes as far as the outer peripheral edge of the second end portion 2216 has a surface connecting the outer surface 2211 and the end surface (lower end surface) 2214 having a diameter smaller than that of the outer surface 2211.
Below the sleeve 221, a first biasing portion 612 is attached to a lower supporting portion (not illustrated) via a first coil spring 613. Above the sleeve housing 222, a second biasing portion 622 radially surrounding the sleeve holding portion 611 is attached to an upper supporting portion 64 via a second coil spring 623. A downward pin 631 is indirectly fixed to the upper supporting portion 64 via a block, and a pin contacting portion 632 facing the pin 631 is fixed onto the housing holding portion 621.
After the sleeve 221 and the sleeve housing 222 are arranged to the sleeve holding portion 611 and the housing holding portion 621, the upper supporting portion 64 then descends such that the sleeve holding portion 611 is brought closer to the housing holding portion 621, and the sleeve 221 is inserted into the sleeve housing 222 from the second end portion 2216 (step S14).
In course of insertion, the second end portion 2216 of the sleeve 221 is brought into contact with the first biasing portion 612, and the first coil spring 613 is elastically deformed so that the sleeve 221 is biased by the first biasing portion 612 toward the sleeve holding portion 611. After the sleeve 221 has contacted the first biasing portion 612, adsorption of the sleeve 221 by the sleeve holding portion 611 may be halted.
At the same time, in course of inserting the sleeve 221, the upper part of the sleeve housing 222 is brought into contact with the second biasing portion 622, so that the second coil spring 623 is elastically deformed and the sleeve housing 222 is biased toward the housing holding portion 621.
Then, as illustrated in
During insertion, the adhesive 220 is spread by the second end portion 2216 of the sleeve 221 such that the adhesive is held between the outer surface of the sleeve 221 and the inner surface of the sleeve housing 222. As illustrated in
Thereafter, the sleeve 221 and the sleeve housing 222 are held for a predetermined period of time (such as for two minutes), and the anaerobic adhesive 220 not in contact with atmosphere is cured between the outer surface of the sleeve 221 and the inner surface of the sleeve housing 222, so that the sleeve 221 is fixed to the sleeve housing 222.
On completion of fixation, the sleeve holding portion 611 and the housing holding portion 621 are separated from each other, and the sleeve 221 and the sleeve housing 222 are taken out. The adhesive 220a held in the adhesive holding portion 56, that is, exposed, is irradiated with ultraviolet and cured, completing manufacture of the essential part of the sleeve unit 22 (step S15).
First, the anaerobic and ultraviolet curing adhesive 220 is applied to the outer surface 2211 of the sleeve 221 (step S21), and as illustrated in
Subsequently, in a state where the center of the sleeve 221 and the center of the sleeve housing 222 are aligned with the central axis J2 of the sleeve unit assembly device 6a, the sleeve contacting portion 611 is brought closer to the housing contacting portion 621, and the sleeve 221 is inserted from the first end portion 2215 into the sleeve housing 222 (step S24).
When the sleeve contacting portion 611 is brought closer to the housing contacting portion 621 and the pin 631 contacts the pin contacting portion 632, as illustrated in
In course of insertion, while the adhesive 220 is held between the outer surface of the sleeve 221 and the inner surface of the sleeve housing 222 and spread by a thinner part (upper part in
Thereafter, the sleeve 221 and the sleeve housing 222 are held for a predetermined period of time, and the adhesive 220 not in contact with atmosphere is cured while the adhesive 220a exposed on the adhesive holding portion 56 is cured by irradiation of ultraviolet (step S25).
In the two methods for manufacturing the sleeve unit 22 described above, the adhesive 220a is held by the adhesive holding portion 56, and the position of the adhesive 220 to be applied and the direction of the sleeve 221 to be inserted are determined such that the adhesive 220 is not pushed out to the side of the first end portion 2215, thereby preventing deterioration in performance of the thrust bearing portion in the upper space 41 illustrated in
Since the space between the thrust plate 33 and the inner peripheral surface of the sleeve housing 222 is relatively made large, the adhesive merely affects the thrust bearing portions in the first lower space 43 and the second lower space 44 even if the adhesive 220a is spread from the adhesive holding portion 56 toward the sleeve housing 222.
As the chamfered shape at the outer peripheral edge of the first end portion 2215 can be made small, an area of the upper end surface 2213 of the sleeve 221 can be made large and the dynamic pressure can be maintained to be high. Further, the dynamic pressure grooves can be formed into the herringbone shape due to a large dynamic pressure surface, realizing further increased performance of the thrust bearing portion (in the upper space 41).
As already described, because the partial adhesive 220a held by the adhesive holding portion 56 functions as the wedge, joint strength between the sleeve 221 and the sleeve housing 222 can be increased against force such as impact from the thrust direction applied from the rotor portion 3 to the sleeve 221. As a result, length of fastening the sleeve 221 and the sleeve housing 222 in the direction of the central axis J1 can be made shorter, thereby realizing a thinner motor 1.
As the anaerobic and ultraviolet curing adhesive 220 is used in manufacture of the sleeve unit 22, it is possible to easily cure the adhesive held in the space between the sleeve 221 and the sleeve housing 222 as well as the adhesive pushed out of the space, thereby simplifying the manufacture of the sleeve unit 22. Alternatively, the adhesive 220 may be used which has thermosetting property, ultraviolet curing and thermosetting properties, or anaerobic, ultraviolet curing and thermosetting properties. Even if the adhesive 220 with ultraviolet curing property does not have anaerobic property, the adhesive 220 can be tentatively cured by ultraviolet and then further cured in course of time, realizing manufacture without deterioration in tact. In addition, use of the adhesive including a large amount of epoxy further increases adhesive strength.
Since the sleeve 221 is attached to the sleeve housing 222 by running fitting in manufacture of the sleeve unit 22, it is possible to prevent strong friction between the outer surface 2211 of the sleeve 221 and the inner surface 2222 of the sleeve housing 222 during insertion of the sleeve 221. Therefore, deformation of the dynamic pressure surface of the sleeve 221 is prevented. Thus, the technique of fixing the sleeve 221 and the sleeve housing 222 with adhesive according to the preferred embodiments of the present invention is suited particularly for a case where the sleeve 221 is made of porous material such as a sinter, which is relatively weaker than solid material.
Manufacture of the sleeve 221 is described below.
The forming device 71 includes a upper punch 711 for pressing the powder material from an upper side, a lower punch 712 for pressing the powder material from a lower side, a die 713 for surrounding an outer surface (corresponding to the outer surface 2211 of the sleeve 221) of the powder material, and a core rod 714 to be inserted into an inner surface (corresponding to the inner surface 2212 of the sleeve 221) of the powder material. A cylindrical space 715 is formed by the die 713, the core rod 714 and the lower punch 712.
After the space 715 is filled with the powder material, the upper punch 711 is inserted into the space 715 from the upper side, and the powder material is pressed in a mold and is formed into the sleeve member 8 in a substantially cylindrical shape (step S31).
The sleeve member 8 thus pressed and formed is taken out of the forming device 71 and brought into a heating device, in which the sleeve member 8 is heated at high temperature and is sintered (step S32).
A lower surface of the upper punch 721 is provided with convexes 721a for forming the dynamic pressure grooves on an upper surface of the sleeve member 8, and an upper surface of the lower punch 722 is provided with convexes 722a for forming the dynamic pressure grooves on a lower surface of the sleeve member 8. An outer edge of the upper surface of the lower punch 722 is additionally provided with a circular convex portion 722b for forming the adhesive holding portion 56 (see
As illustrated in
As illustrated in
In a case where the dynamic pressure grooves and the adhesive holding portion 56 are individually formed, it is required, after taking the sleeve member 8 out of a device for forming the dynamic pressure grooves, to load the sleeve member 8 onto a subsequent device for forming the adhesive holding portion 56 while confirming vertical orientation of the sleeve member 8. To the contrary, in the sizing device 72 of
On completion of sizing, the sleeve member 8 is attached to a groove forming device having a structure similar to that of the sizing device 72 illustrated in
The technique of separately performing sizing and formation of the dynamic pressure grooves as illustrated in
While the embodiment of the present invention has been thus described, the present invention is not limited thereto but can be modified in various ways.
For example, while the sleeve 221 and the sleeve housing 222 are held after the adhesive 220 is applied thereto in the above embodiment, application of the adhesive can be performed after the sleeve 221 and the sleeve housing 222 are held. The order of holding the sleeve and holding the sleeve housing may also be appropriately altered.
Moreover, the adhesive holding portion 56 is not limitedly formed as a surface having a cross section including one straight line or a plurality of straight lines continuous with one another, but may be formed as a surface having a cross section including a curved line. In addition, the chamfered shapes at the outer and inner peripheral edges of the first end part and the inner peripheral edge of the second end part may have cross sections including curved lines.
In manufacture of the sleeve 221, formation of the chamfered shapes and the adhesive holding portion 56 of the sleeve 221 (the sleeve member 8 to be precise) may be performed in the forming step. In the forming step, the adhesive holding portion 56 can be easily formed while causing no remaining stress within the sleeve member 8. Alternatively, the adhesive holding portion 56 may be formed in the sizing step (step S33a) not including formation of the dynamic pressure grooves.
The motor according to the above described embodiments is not necessarily of an inner rotor type in which the rotor magnet 32 is arranged radially inside with respect to the armature 24, but may be of an outer rotor type in which the rotor magnet 32 is arranged radially outside the armature 24. Further, the bearing assembly may adopt, for example, so called a gas dynamic pressure bearing in which air is utilized as fluid.
The motor according to the above described embodiments may also be used as a drive source of a device other than a hard disk device (for example, a disk drive device such as a removable disk device).
Number | Date | Country | Kind |
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2006-214335 | Aug 2006 | JP | national |