Metal working – Method of mechanical manufacture – Process for making bearing or component thereof
Reexamination Certificate
2003-04-04
2004-10-05
Compton, Eric (Department: 3726)
Metal working
Method of mechanical manufacture
Process for making bearing or component thereof
C029S898041, C451S406000, C082S162000
Reexamination Certificate
active
06799372
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for manufacturing a hydro dynamic bearing device. In particular, the present invention relates to a method for manufacturing a hydro dynamic bearing device to be used in a spindle motor equipped in an information technology device such as a magnetic disk device (e.g., HDD or FDD), an optical disk device (e.g., CD-ROM, CD-R/RW, or DVD-ROM/RAM), and an optical magnetic disk device (e.g., MD or MO), a scanner motor equipped in a copying machine, a laser printer (LBP), a barcode reader, or the like, or a small-sized motor equipped in an electrical equipment such as an axial fan.
2. Description of the Related Art
As is generally known in the art, each kind of the motors listed above have been promoted to be provided at lower cost, driven at higher speed and more quiet, and so on in addition to attain a high rotational accuracy. As one of factors that define these required performances, a bearing supporting spindle of the motor has been increasingly valued. In recent years, therefore, as such a kind of the bearing, the use of a hydro dynamic bearing device having excellent characteristics that serve a request for the above performance has been studied, and such a hydro dynamic bearing device has been developed in a quest to put it to practical use.
For instance, a hydro dynamic bearing device to be built in a spindle motor of a disk device such as a hard disk drive (HDD) comprises a radial bearing part for rotatably retaining an axial member in a non-contact manner in the radial direction and a thrust bearing part rotatably retaining the axial member in a non-contact manner in the thrust direction. As a bearing part of each of them, a hydro dynamic bearing device having a groove (a hydro dynamic pressure generating groove) for the generation of hydro dynamic pressure on its bearing surface is used.
In this case, the hydro dynamic pressure generating groove of the radial bearing part is formed in the inner peripheral surface of the bearing member or the housing, or formed in the outer peripheral surface of the axial member. On the other hand, in the case of using an axial member having a flange part, the hydro dynamic pressure generating groove of the thrust bearing part is formed in each of the opposite end faces of the flange part or the surface (e.g., the end face of the bearing member or the bottom surface of the housing) facing to such an end face.
In such a kind of the spindle motor, furthermore, a higher rotational accuracy has been desired in recent years for attaining an increase in information-recording density and an increase in rotation speed of the motor. For addressing such a request, a higher rotational accuracy of the hydro dynamic bearing device to be built in the spindle motor has also been desired.
To improve the rotational accuracy of the hydro dynamic bearing device, it is important to adjust the radial bearing clearance and the thrust bearing clearance in which hydro dynamic pressures are generated. For properly adjusting the clearance, there is a need to work upon the structural component of the hydro dynamic bearing device related to each bearing clearance, especially the axial member that forms each axial bearing with the axial member. Therefore, the required grinding is performed as a finish machining on the part where each bearing clearance of the axial member is formed at the time of processing or manufacturing the axial member.
More concretely, as shown in
FIG. 10
, the axial member
2
is comprised of an axial part
2
a
and a flange part
2
b
, which are molded in one piece. A bearing member (not shown) is arranged on the outer peripheral side of the axial member
2
. In addition, a radial bearing clearance is formed between the outer peripheral surface of the axial part
2
a
and the bearing member. Furthermore, a thrust bearing clearance is formed between the distal end face
2
b
1
of the flange part
2
b
(the end face on the near side to the axial part
2
a
) and the bearing member, and also another thrust bearing clearance is formed between the proximal end face
2
b
2
of the flange part
2
b
(the end Face on the far side from the axial part
2
a
) and the inner bottom face of the housing (not shown).
In this case, in the process of manufacturing the axial member
2
, the outer peripheral surface of the axial part
2
a
, which forms the radial bearing clearance with the bearing member, is subjected to grinding. For grinding the outer peripheral surface, heretofore, the following exemplified method has been generally applied.
As shown in
FIG. 11
, the conventional method comprises the steps of perforating the center of the distal end face
2
a
4
of the axial part
2
a
formed on the axial member
2
and the center of the proximal end face
2
b
2
of the flange part in the axial member with center holes
2
bc
, respectively, and fitting a pair of tapered centering members
41
into the center holes
2
bc
, respectively, to sandwich the axial member
2
with the centering members
41
.
Under such a condition, the grinding is performed by imparting an axial rotary motion from the centering member
41
to the axial member
2
, while pressing a grindstone
43
on the outer peripheral surface.
However, when the grinding is performed while supporting the axial member from its opposite ends with the respective centering members
41
, there is a possibility of causing a decrease in not only a grinding efficiency but also a work efficiency because of the following reasons. That is, the circumferential speed of the axial member
2
is hardly increased in a sufficient manner at the time of the rotary motion of the axial member
2
(e.g., it is limited to about 100 rpm) due to the facts, for example the contact area between the centering member
41
and the center hole
2
bc
is small.
In the grinding with such a center support, the axial member may cause centrifugal whirling while rotating when the center position is deviated. As a result, the quality of the axial member may decrease as the outer peripheral surface of the axial part of the axial member may be ground in a slanting direction, or the roundness of the axial member may deviate from the desired level.
BRIEF SUMMARY OF THE INVENTION
The present invention has been completed in consideration of the above circumstances. A technical object of the present invention is to provide a method for manufacturing a hydro dynamic bearing device capable of sufficiently increasing a circumferential speed of an axial member in the step of grinding the axial member and capable of preventing the generation of centrifugal whirling of the axial member to increase the grinding efficiency and the working efficiency in addition to improve the quality of the resulting product.
In the present invention, for attaining the above technical object, there is provided a method for manufacturing a hydro dynamic bearing device including an axial member having a flange part on one end of an axial part thereof a radial bearing part that support the axial part in a non-contact manner in a radial direction by a hydro dynamic pressure action of a fluid generated in a radial bearing clearance, and a thrust bearing part that supports the flange part in a non-contact manner in a thrust direction by a hydro dynamic pressure action of a fluid generated in a thrust bearing clearance. The method includes, the steps of: supporting the axial member at both ends of the axial member in an axial direction thereof with a pair of plate members in a face-contact manner, rotating the axial member around its axial center, and grinding an outer peripheral surface of the axial part of the axial member on a grindstone while supporting the outer peripheral surface of the axial part with a supporting member.
Here, the phrase “supporting the axial member at both ends of the axial member with a pair of plate members in a face-contact manner” means that the proximal end face of the flange part of the axial member (i.e., the end face of the flange part on the far
Hirano Hidekazu
Kaimi Masayuki
Kokubu Kuniharu
Marui Norimasa
Compton Eric
J.C. Patents
NTN Corporation
LandOfFree
Method for manufacturing hydro dynamic bearing device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for manufacturing hydro dynamic bearing device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for manufacturing hydro dynamic bearing device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3269733