Bearings – Rotary bearing – Fluid bearing
Reexamination Certificate
1999-12-07
2002-04-16
Fenstermacher, David (Department: 3682)
Bearings
Rotary bearing
Fluid bearing
C384S110000
Reexamination Certificate
active
06371651
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a thrust dynamic pressure bearing.
Conventionally, as shown in
FIG. 2
, a thrust dynamic pressure bearing is configured so that a flanged shaft
102
is inserted into a sleeve
101
, and a flange-like plate
105
fixed to an end of the sleeve
101
and a step portion
101
A of the sleeve
101
are opposed to a flange
103
of the shaft
102
with forming a predetermined dynamic pressure space S therebetween. The sleeve
101
and the plate
105
constitute a housing
100
.
Dynamic pressure generating grooves
106
and
107
are formed in end faces of the flange
103
, respectively. The space between the housing
101
and the flanged shaft
102
is filled with a dynamic pressure generating lubricant (not shown).
In the thrust dynamic pressure bearing, when the flanged shaft
102
relatively rotates with respect to the sleeve
101
, the dynamic pressure generating grooves
106
and
107
formed in the flange
103
cause the dynamic pressure generating lubricant to generate a dynamic pressure, so as to support the shaft
102
with respect to the sleeve
101
in the thrust direction.
The prior art thrust dynamic pressure bearing involves the following problem. When the flange
103
is tilted with respect to the direction perpendicular to the axial center of the shaft
102
, or when a force of tilting the shaft
102
with respect to the sleeve
101
is produced, an outer circumference portion
103
A of the flange
103
comes into contact with the sleeve
101
and the plate
105
, so as to cause some deficiency such as abrasion.
The thrust dynamic pressure bearing has another problem as follows. Even if the flange
103
is precisely perpendicular to the axial center of the shaft, the flange
103
unavoidably comes into contact with the sleeve
101
at starting and stopping. The dynamic pressure space S is easily clogged with abrasion powder generated by the contact.
SUMMARY OF THE INVENTION
Consequently, it is an object of the invention to provide a thrust dynamic pressure bearing in which an unsymmetrical contact during rotation is prevented from occurring, and a dynamic pressure space is prevented from being clogged with abrasion powder generated by a contact at starting and stopping.
In order to attain the object, the thrust dynamic pressure bearing of the invention of claim
1
is a thrust dynamic pressure bearing in which a thrust bearing face disposed on a housing is opposed to a thrust receiving face of a flange-like thrust receiving portion disposed on a shaft, at least one of the thrust bearing face and the thrust receiving face has dynamic pressure generating grooves for generating a dynamic pressure, and
a space between the thrust bearing face and the thrust receiving face is filled with a lubricant, and is characterized in that
the thrust receiving portion has a substantially tapered shape in section, a thickness of the thrust receiving portion becoming smaller as moving toward an outer circumference.
In the invention of claim
1
, since the flange-like thrust receiving portion disposed on the shaft is tapered as moving toward the outer circumference thereof, the dynamic pressure space between the thrust bearing face of the housing and the thrust receiving face of the shaft during rotation becomes wider as moving toward the outer circumference thereof. According to the invention, even if the shaft is tilted with respect to the housing during rotation, therefore, it is possible to prevent an unsymmetrical contact of the thrust receiving face of the shaft in the vicinity of the outer circumference against the thrust bearing face of the housing, from occurring. In addition, since the dynamic pressure space becomes wider as moving toward the outer circumference, the abrasion powder generated by the contact at starting and stopping can be easily discharged from a radially inward portion toward a radially outward portion of the dynamic pressure space.
According to the invention, therefore, an unsymmetrical contact during rotation can be prevented from occurring, and the dynamic pressure space can be prevented from being clogged with the abrasion powder generated by the contact at starting and stopping. Consequently, a stable operation can be realized.
The thrust dynamic pressure bearing of the present invention is characterized in that a level difference between an innermost circumference end and an outermost circumference end of the thrust receiving portion is set in the range of 1 to 5 &mgr;m.
In the present invention, since the level difference between the innermost circumference end and the outermost circumference end of the thrust receiving portion of the shaft is set in the range from 1 to 5 &mgr;m, it is possible to prevent an unsymmetrical contact and the clog with the abrasion powder from occurring, while the dynamic pressure generating performance is sufficiently maintained.
If the level difference between the innermost circumference end and the outermost circumference end is set to be smaller than 1 &mgr;m, it is difficult to prevent an unsymmetrical contact and the clog with the abrasion powder from occurring. If the level difference exceeds 5 &mgr;m, the dynamic pressure generating performance is insufficient.
REFERENCES:
patent: 2966381 (1960-12-01), Menzel
patent: 3174809 (1965-03-01), Mackie
patent: 3749456 (1973-07-01), Whitaker
patent: 4575264 (1986-03-01), Mizobunchi et al.
patent: 5518319 (1996-05-01), Selby
patent: 5789839 (1998-08-01), Langenbeck
patent: 5795073 (1998-08-01), Arvidsson et al.
patent: 5855436 (1999-01-01), Eum et al.
patent: 5952752 (1999-09-01), Kim
patent: 6020664 (2000-02-01), Liu et al.
patent: 6127756 (2000-10-01), Iwaki et al.
patent: 0411696 (1991-02-01), None
patent: 55-109822 (1980-08-01), None
patent: 7-52419 (1991-10-01), None
Fujii Yoshiki
Takahashi Takeshi
Fenstermacher David
Hansen Colby
Jacobson & Holman PLLC
Koyo Seiko Co. Ltd.
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