JPH07299537A - Manufacture of roll die for manufacturing kinetic pressure bearing device - Google Patents

Abstract

PURPOSE:To facilitate the working of the form rolling part of a roll die. CONSTITUTION:Two disk-shaped roll dies 31a and 31b are put one upon another, they are put between supporting disks 42 and 43, and are freely rotatably supported by a shaft 41. Grooves 46 are cut at specific intervals by a wheel cutter 45 from an oblique direction on the peripheral surfaces of both roll dies 31a and 31b, and after cutting them, the roll die 31b on one side is turned over to place it upon another. Consequently, form rolling parts by continuous V-type grooves can be formed on the peripheral surface of the roll die 31. Therefore, the form rolling part of the roll die 31 can easily be worked, moreover, the form rolling part can inexpensively be worked differently from the conventional method, and a die can easily be repaired.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a roll die for manufacturing a dynamic pressure bearing device used for a hard disk drive (HHD), a polygon mirror or the like.

[0002]

2. Description of the Related Art Since the basic structure of a hydrodynamic bearing device is the same in the conventional example and the embodiment, the structure of the hydrodynamic bearing device will be schematically described with reference to FIG. Will be described in detail in Examples). In FIG. 4 showing an embodiment, a shaft 1 on the fixed side is provided at a portion serving as an axis of the hole 10 of the motor hub 9 on the rotating side. The shaft 1 is composed of a magnet 4 and two shafts 2 and 3 provided on both sides in the axial direction of the magnet 4, and a non-magnetic sleeve 5 is press-fitted onto the outer circumference of the shaft 1. is doing. A pair of pole pieces 11a, 11b corresponding to the upper surface and the lower surface of the sleeve 5 are also provided.
Is provided on the motor hub 9 side.

Gaps 12, 13a, 13b formed between the inner peripheral surface of the motor hub 9 and the outer peripheral surface of the sleeve 5,
A magnetic fluid 15 is enclosed in 14a and 14b. The outer peripheral surface of the sleeve 5, the lower surface of the upper pole piece 11a, and the upper surface of the lower pole piece 11b are surface-treated to generate dynamic pressure in the magnetic fluid 15 by the rotation of the motor hub 9. . That is, the sleeve 5
The outer peripheral portion and the inner peripheral wall of the hole 10 of the motor hub 9 form a journal bearing, and the upper and lower outer end surfaces of the sleeve 5 and the inner side surfaces of the pole pieces 11a and 11b form a thrust bearing.

Here, the upper and lower peripheral surfaces of the substantially cylindrical sleeve 5 are subjected to the surface treatment for generating the dynamic pressure in the magnetic fluid 15 as described above. This portion is used for generating the dynamic pressure. The surface processed portion 20 is used. FIG. 2 shows the dynamic pressure generating surface processing portion 2 formed on the upper and lower circumferential surfaces of the sleeve 5.
This is a plan view in which the 0 portion is developed, and W ₁ indicates the width of the dynamic pressure generating surface processed portion 20. By forming V-shaped concave portions 21 and convex portions 22 alternately and continuously on the upper and lower peripheral surfaces of the sleeve 5, the surface processing portion 2 for generating dynamic pressure is formed.
Forming 0. The shaded portion in the figure is the recess 21.
And the white portion is the convex portion 22. W ₂ represents the groove width of the groove-shaped recess 21.

The most common pressure generating group for journal (radial) bearings is the herringbone group shown in FIG. 2. However, when a dynamic pressure bearing is used in an HDD motor, the size of the ball bearing is large. It becomes a very small one that exceeds the limit of rotation accuracy. For example, the shafts 2 and 3 constituting the shaft 1 have a diameter of about 2 mm and a journal bearing diameter of about 3 to 4 mm. Therefore, in FIG. 2 of the group development view, W ₁ is about 0.7 mm, W ₂
Is about 0.2 mm, and the groove depth of the concave portion 21 is a minute pattern of about 0.02 mm.

[0006]

In the hydrodynamic bearing device as shown in FIG. 4, the groove pattern of the journal bearing is as shown in FIG.
In the case of herringbone as shown in Fig. 1, rolling is attempted for its processing, but the rolling surface of the rolling die for rolling is processed by photoetching or electric discharge machining. Is not only expensive,
There was a problem that it was difficult to repair the mold.

The present invention has been made to solve the above-mentioned conventional drawbacks, and an object thereof is a roll for manufacturing a dynamic pressure bearing device capable of facilitating the processing of a rolling portion of a roll die. It is to provide a method for manufacturing a die.

[0008]

Therefore, in the method of manufacturing a roll die for manufacturing a dynamic pressure bearing device according to a first aspect of the invention, a V-shaped groove is continuously formed along the circumferential direction on the peripheral surface of the roll die 31. A dynamic pressure bearing device for performing surface processing for generating dynamic pressure on the peripheral surface of the workpiece 37 by rolling the roll die 31 on the peripheral surface of the workpiece 37 by the rolling unit 32. In the method of manufacturing a roll die for manufacturing, the roll die 31 is composed of two disk-shaped first roll dies 31a and second roll dies 31b, and the roll dies 31 are provided on the circumferential surfaces of the roll dies 31a, 31b. Grooves 46 are formed in the diagonal direction at predetermined intervals, and one roll die 31 is formed.
It is characterized in that the rolling portion 32 formed by a continuous V-shaped groove is formed on the peripheral surface of the roll die 31 by superimposing b on the opposite side.

According to a second aspect of the present invention, there is provided a method of manufacturing a roll die for manufacturing a dynamic pressure bearing device, wherein a rolling portion 32 having a V-shaped groove formed continuously on the peripheral surface of the roll die 31 along the circumferential direction. Of a roll die for manufacturing a dynamic pressure bearing device for performing surface processing for generating dynamic pressure on the peripheral surface of the workpiece 37 by rolling the roll die 31 on the peripheral surface of the workpiece 37. In the manufacturing method, the roll die 31 is composed of two disk-shaped first roll dies 31a and second roll dies 31b.
The roll dies 31a and 31b are rotatably supported, and grooves 46 are formed obliquely at predetermined intervals on the circumferential surfaces of the roll dies 31a and 31b.
It is characterized in that the rolling portion 32 formed by a continuous V-shaped groove is formed on the peripheral surface of the roll die 31 by superimposing b on the opposite side.

Further, the method for manufacturing a roll die for manufacturing a dynamic pressure bearing device according to a third aspect is characterized in that the groove 46 is formed by cutting with a cutter 45 using a diamond or a grindstone.

[0011]

In the method of manufacturing a roll die for manufacturing a dynamic pressure bearing device according to the first aspect, a pair of roll dies 31a and 31b having grooves 46 formed at predetermined intervals in an oblique direction are separately formed. After that, by combining these, the rolling portion 32 composed of a continuous V-shaped groove can be formed, so that the forming process of the rolling portion 32 can be simplified,
Therefore, the manufacturing cost of the roll die 31 can be reduced, and the die can be easily repaired.

In the method of manufacturing a roll die for manufacturing a dynamic pressure bearing device according to a second aspect of the present invention, the two disk-shaped roll dies 31a and 31b are superposed and pivotally supported. Grooves 46 are formed on the peripheral surfaces of both roll dies 31a and 31b at predetermined intervals in the oblique direction, and then one roll die 31b is reversed and overlapped. As a result, the rolling portion 32 having a continuous V-shaped groove can be formed on the peripheral surface of the roll die 31. Therefore, similarly to claim 1, the rolling portion 3 of the roll die 31
No. 2 can be easily and inexpensively processed, and the mold can be easily repaired. In addition, since the lap processing is performed, the accuracy of the roll die outer shape, groove width, groove depth and groove interval can be improved. It will be.

Further, in the method of manufacturing a roll die for manufacturing a dynamic pressure bearing device according to a third aspect of the present invention, a catch line of the cutter 45 is formed in the formed rolling portion 32, and this catch line of the workpiece 37 is formed. It will be transferred to the peripheral surface, but since this crease is in the direction along the flow of the bearing working fluid,
The flow resistance of the fluid at the time of rotation on the surface of the rolled work piece 37 can be reduced, so that the loss torque can be suppressed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A concrete embodiment of a method for manufacturing a roll die for manufacturing a dynamic pressure bearing device according to the present invention will be described in detail with reference to the drawings. First, the overall structure of the dynamic pressure bearing device will be described. FIG. 4 shows a sectional view of a dynamic pressure bearing device according to an embodiment of the present invention. In FIG. 4, 1
Is a shaft, and is composed of a first shaft 2, a second shaft 3, and a magnet 4. Cylindrical magnet 4
Are magnetized in the axial direction as shown in the drawing, and the cylindrical first shaft 2 and second shaft 3 are magnetic bodies. A magnet 4 is sandwiched between the shafts 2 and 3. Here, the outer diameter of the magnet 4 is smaller than the outer diameters of the shafts 2 and 3. Further, the outer diameter of the magnet 4 may be a magnetically sufficient area, and high precision machining is unnecessary. As the material of the magnet 4, a strong magnet such as samarium / cobalt magnet, neodymium magnet, and alnico magnet is used, and if these strong magnets are used, it is magnetically sufficient and the area (the area of the end face in the axial direction) can be reduced. . Therefore, the outer diameter of the magnet 4 can be made smaller than the outer diameter of the shafts 2 and 3.

Reference numeral 5 denotes a sleeve, which is made of a non-magnetic material. The sleeve 5 is formed in a substantially cylindrical shape, and the shaft 1 is press-fitted and fitted into an insertion hole 6 which is an axis of the sleeve 5. The shaft 1 including the shafts 2 and 3 and the magnet 4 and the sleeve 5 are integrated with each other to have mechanical strength as a central axis. The lower portion of the shaft 1 in which the sleeve 5 is integrated is fixed to the base 7. Reference numeral 8 is a motor coil.

The motor hub 9 on the rotating side is formed in a substantially cylindrical shape and is made of a magnetic material. This motor hub 9
A hole 10 having a diameter larger than the outer diameter of the sleeve 5 is formed in the shaft center of the shaft 5, and a pair of cylindrical pole pieces 11a and 11b made of a magnetic material are fixed to the upper end and the lower end of the hole 10. .

Here, the outer peripheral surface of the sleeve 5 and the motor hub 9
A gap 12 is formed between the inner peripheral surface of the hole 10 and the lower and upper surfaces of the pole pieces 11a and 11b and the sleeve 5.
Gaps 13a and 13b are also formed between the upper surface and the lower surface. Further, gaps 14a and 14b are also formed between the inner peripheral surfaces of the pole pieces 11a and 11b and the upper and lower portions of the shaft 1, and these gaps 12, 13a, 13b, 14a and 1 are formed.
A magnetic fluid 15 as hydraulic oil is enclosed in 4b.

The surfaces forming the gaps 12 and 13a, 13b, that is, the inner peripheral surface of the hole 10 or the outer peripheral surface of the sleeve 5, the lower surface of the upper pole piece 11a, the upper surface of the lower pole piece 11b or the sleeve 5. Both upper and lower surfaces are surface-treated to generate dynamic pressure in the magnetic fluid 15 by the rotation of the motor hub 9. That is, the outer peripheral portion of the sleeve 5 and the inner peripheral wall of the hole 10 of the motor hub 9 form a journal bearing, and the upper and lower outer end surfaces of the sleeve 5 and the inner side surfaces of the pole pieces 11a and 11b form a thrust bearing. Is there.

The pole pieces 11a and 11b also form a seal portion. That is, the magnet 4 sequentially forms the magnetic circuit 16 that returns to the magnet 4 via the first shaft 2, the upper pole piece 11a, the motor hub 9, the lower pole piece 11b, and the second shaft 3, so that the gap 1
A magnetic field is formed in 4a and 14b, and these gaps 14a and 1b
The magnetic fluid 15 is sealed at 4b, and the sealing action prevents the fluid from leaking in the gaps 12, 13a, 13b.

In the above structure, when the motor hub 9 and the pole pieces 11a, 11b rotate, the gaps 12,
Dynamic pressure is generated in the magnetic fluid 15 enclosed in 13a and 13b, and this dynamic pressure is generated on the inner peripheral surface of the hole 10 of the motor hub 9,
It acts on the sleeve 5 and the pole pieces 11a and 11b, respectively. At this time, the radial load in the radial direction is supported by the shaft 1, and the axial thrust load is in each pole piece 1.
The shaft 1 will be supported via 1a and 11b.

Next, regarding the rolling process of the bearing portion of the sleeve 5, the groove shape of the dynamic pressure generating surface processed portion 20 formed on the upper and lower circumferential surfaces of the sleeve 5 is as shown in FIG. It is a herringbone group. As described above, the surface-processed portion 20 for generating the dynamic pressure has the V-shaped concave portions 21 and the convex portions 22 alternately and continuously formed.
As shown in FIG. 3, the dynamic pressure generating surface processed portion 20 is rolled by a roll die 31 having a rolling portion 32 having a pattern opposite to that of the dynamic pressure generating surface processed portion 20. The rolling method will be described later. Before that, a method of manufacturing the rolling portion 32 of the roll die 31 will be described.

As shown in FIG. 1, the roll die 31 is composed of two disc-shaped roll dies 31a and 31b. Two roll dies 31a are formed before the rolling portion 32 is processed. , 31b are overlapped. Then, both side surfaces of the roll dies 31a and 31b are sandwiched by support disks 42 and 43 which are rotatable by a shaft 41, and both roll dies 31a and 31b are rotatably supported. Here roll-dies 31a, 31b of the respective thickness of the half of the width _{W 1} of the hydrodynamic surface processing unit 20 thickness Satoshi, dynamic pressure generating as the thickness and _{W 1} when the superimposed roll dies 31a, 31b are The width W ₁ of the surface processing portion 20 is set to be the same.

A wheel cutter 45 is provided on the diagonal side of the roll dies 31a and 31b. The wheel cutter 45 is mounted on a shaft 44 and is movable in the direction of the arrow in FIG. The width W ₂ of the wheel cutter 45 is the same as the groove width of the convex portion 22 of the dynamic pressure generating surface processed portion 20. Note that if the widths of the concave portion 21 and the convex portion 22 are the same, W ₂ = W ₂ in FIGS. 1 and _2.
Becomes

The rotation of the roll dies 31a, 31b is stopped and the wheel cutter 45 is moved to the roll dies 31a, 3b.
By moving the wheel cutter 45 to the 1b side and controlling the movement of the wheel cutter 45 so as to follow the circular arc surfaces of the roll dies 31a and 31b, the circumferential surfaces of the roll dies 31a and 31b are cut obliquely to form the grooves 46. When one groove 46 is formed, the wheel cutter 45 moves the roll die 31.
a, 31b away from the roll die 31a, 31
b is rotated by the width of the concave portion 21 and stopped at that position. Then, the wheel cutter 45 is moved to cut the peripheral surfaces of the roll dies 31a and 31b to form the grooves 46. This operation is repeated for a distance along the desired peripheral surface of the roll dies 31a and 31b, and the grooves 46 are formed in the peripheral surface of the roll dies 31a and 31b in a diagonal direction at predetermined intervals. In the present embodiment, this cutting distance is set to a substantially one circumference of the sleeve 5. Of course roll dice 3
It may be formed on the entire circumference of 1a and 31b.

Next, when the cutting process by the wheel cutter 45 is completed, then one roll die 31b is reversed and the two roll dies 31a and 31b are superposed. As a result, the roll die 31 is formed, and the groove 46 forms a V-shape in the cut portion, and the pattern is reverse to the pattern of the dynamic pressure generating surface processed portion 20 as shown in FIG. The part 32 will be formed.
The roll die 31 will be very thin,
Since the ratio of the depth to the width of the rolling pattern exceeds 10 times, there will be no problem if the supporting disks 42 and 43 are made sufficiently large and thick. Further, the mating portion of the roll dies 31a and 31b is slightly rolled as a straight line in the center of FIG. 2, but this is not a particular problem. The cutting portion of the wheel cutter 45 is made of diamond or a grindstone.

Next, a method of rolling the dynamic pressure generating surface processing portion 20 on the peripheral surface of the sleeve 5 by the roll die 31 having the rolling portion 32 formed on a part of the peripheral surface as described above will be described. . In FIG. 3, reference numeral 31 denotes the roll die described above, and a rolling surface, that is, a rolling portion 32 is formed only on a part of the peripheral surface of the roll die 31. The peripheral surface of the roll die 31 other than the rolling portion 32 is an escape portion 33 having a diameter one step smaller than that of the rolling portion 32. Further, the length in the circumferential direction of the rolling portion 32, which is the die processing surface of the roll die 31, is set to be substantially the circumferential length of the workpiece (sleeve 5) 37. The roll die 31 is adapted to rotate about a shaft 34. Roll die 3
On the opposite side of 1, a support disk 35 is arranged so as to be rotatable in the reverse direction about a shaft 36, and the support disk 35 only receives the processing pressure.

Here, the rolling portion 32 of the roll die 31 is rotated while pressing the peripheral surface of the workpiece 37 under pressure. The rolling process for the work piece 37 of the roll die 31 is
One rotation of the roll die 31 is performed for one workpiece 37, and the same rolling workpiece 32 is not repeatedly processed by the rolling portion 32. When the rolling portion 32 of the roll die 31 comes off the work piece 37, the peripheral surface of the roll die 31 does not come into contact with the work piece 37 due to the relief portion 33 of the roll die 31. The roll die 31 continues to rotate in one direction at, for example, 30 to 60 RPM, and the workpiece 37 is continuously exchanged for machining. In other words, one rotation of the roll die 31 can be rolled for one workpiece 37. As a result, the surface processing portion 20 for generating dynamic pressure is formed on the peripheral surface of the workpiece 37.
Is rolled to form the sleeve 5.

In the above embodiment, the groove 46 is formed by superposing the two roll dies 31a and 31b, but the groove 46 is formed in each roll die 31a and 31b in a separate process. Good. However, when the overlapping process is performed as in the above-described embodiment, there is an advantage that the accuracy of the outer shape, the groove width, the groove depth, and the groove interval of the roll die 31 can be improved. In addition to the above-described embodiment, the groove machining can be performed by photo etching or electric discharge machining. However, in these machining methods, the machined surface becomes a satin finish, and the surface of the rolled work piece 37 operates for bearings during rotation. The resistance of the fluid may be received, leading to an increase in loss torque. On the other hand, according to the cutting process as described above, the catch line of the cutter 45 is in the flow direction of the fluid, which is advantageous in reducing the resistance of the fluid.
As a result, the loss torque can be suppressed.

[0029]

As described above, in the method for manufacturing a roll die for manufacturing a dynamic pressure bearing device according to the first aspect of the invention, a pair of roll dies having grooves formed at predetermined intervals in the diagonal direction are separately formed. After that, since the rolling portion composed of the continuous V-shaped groove can be formed by combining these, the forming process of the rolling portion can be simplified, and therefore the manufacturing cost of the roll die 31 can be reduced. In addition, the mold can be easily repaired.

In the method of manufacturing a roll die for manufacturing a dynamic pressure bearing device according to a second aspect of the present invention, two disc-shaped roll dies are superposed on each other and pivotally supported. Grooves are formed on the peripheral surfaces of both roll dies at predetermined intervals in the oblique direction, and then one roll die is reversed to be overlaid. As a result, it is possible to form a rolling portion having a continuous V-shaped groove on the peripheral surface of the roll die.
Therefore, as in the first aspect, the rolled portion of the roll die can be easily and inexpensively processed, and the die can be easily repaired. In addition, since the roll processing is performed, the outer shape and groove width of the roll die can be improved. Therefore, the precision of the groove depth and the groove interval can be improved.

Further, in the method for manufacturing a roll die for manufacturing a dynamic pressure bearing device according to a third aspect of the invention, in the rolling portion to be formed, a catch line of the cutter is formed, and the draw line is formed on the peripheral surface of the workpiece. Although it will be transferred, since this crease is in the direction along the flow of the bearing working fluid, it is possible to reduce the flow resistance of the fluid during rotation on the surface of the rolled work piece, and therefore to reduce the loss torque. It becomes possible to suppress.

[Brief description of drawings]

FIG. 1 is a diagram showing a method for manufacturing a roll die according to an embodiment of the present invention.

FIG. 2 is a development view of a dynamic pressure generating surface processed portion according to the embodiment of the present invention.

FIG. 3 is an explanatory diagram of a case where the sleeve according to the embodiment of the present invention is rolled.

FIG. 4 is a sectional view of a dynamic pressure bearing device according to an embodiment of the present invention.

[Explanation of symbols]

 5 Sleeve 31 Roll Die 31a Roll Die 31b Roll Die 32 Rolling Part 37 Workpiece 45 Wheel Cutter 46 Groove

Claims (3)

[Claims] 1. A roll die (31) having a V-shaped groove formed continuously on the peripheral surface of the roll die (31) continuously in the circumferential direction. In the method for manufacturing a roll die for manufacturing a dynamic pressure bearing device, the peripheral surface of the workpiece (37) is subjected to surface processing for generating a dynamic pressure by rolling the peripheral surface of the roll die. (31) is replaced with two disc-shaped first roll dies (31
a) and a second roll die (31b), and grooves (46) are formed in the peripheral surface of each of the roll dies (31a) (31b) at predetermined intervals in an oblique direction, and one of them is formed. A dynamic pressure characterized in that a rolling portion (32) having a continuous V-shaped groove is formed on the peripheral surface of the roll die (31) by stacking the roll dies (31b) in reverse. A method for manufacturing a roll die for manufacturing a bearing device. 2. A rolling die (32) having a V-shaped groove formed continuously on the circumferential surface of the roll die (31) along the circumferential direction, so that the roll die (31) is machined (37). In the method for manufacturing a roll die for manufacturing a dynamic pressure bearing device, the peripheral surface of the workpiece (37) is subjected to surface processing for generating a dynamic pressure by rolling the peripheral surface of the roll die. (31) is replaced with two disc-shaped first roll dies (31
a) and a second roll die (31b), and the roll dies (31a) and (31b) are superposed on each other and pivotally supported so as to be rotatable.
Grooves (46) are obliquely formed on the peripheral surface of (31b) at predetermined intervals.
To form one roll die (31
Manufacturing of a dynamic pressure bearing device, characterized in that a rolling portion (32) by a continuous V-shaped groove is formed on the peripheral surface of the roll die (31) by superimposing b) in reverse. For manufacturing roll dies for automobiles. 3. The roll for manufacturing a dynamic pressure bearing device according to claim 1, wherein the groove (46) is formed by cutting with a cutter (45) using a diamond or a grindstone. Dice manufacturing method.