Bearings – Rotary bearing – Antifriction bearing
Reexamination Certificate
2001-11-16
2004-04-06
Graham, Matthew C. (Department: 3683)
Bearings
Rotary bearing
Antifriction bearing
C384S484000
Reexamination Certificate
active
06715922
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a rolling bearing with a sealing device, and more particularly to a rolling bearing with a sealing device having improved characteristics in a seal fitting groove of an outer ring and a mounting portion of the sealing device to be fitted in the seal fitting groove.
With respect to conventional rolling bearings, a lubricant such as a grease or a lubricating oil is applied on raceway surfaces of an inner ring and an outer ring and rolling surfaces of rolling elements such as balls or rollers, for maintaining lubricity for a long period of time. The conventional rolling bearings include a rolling bearing with a sealing device that prevents the lubricant in a space defined by in the raceway surfaces and rolling surfaces from leaking and avoiding adhesion of dusts to these surfaces.
FIG. 5
shows one example of the rolling bearing with the sealing device.
FIG. 5
shows cross sectional view of elemental portions of a single-row deep groove ball bearing with a sealing device
50
(called as “ball bearing” hereafter). As shown in
FIG. 5
, the ball bearing
50
has a plurality of rolling elements
54
that are rotatably held by a retainer
53
and equidistantly arranged between an inner ring
51
and an outer ring
52
in a peripheral direction of the ball bearing
50
.
The inner ring
51
has a protruding portion
55
at a central portion of an outer peripheral surface thereof, that is spaced from both end portions of the outer peripheral surface in an axial direction thereof. The protruding portion
55
protrudes toward the outer ring
52
from the outer peripheral surface of the inner ring
51
. An inner raceway
51
a
is formed into a concave shape for receiving the rolling elements
54
at the outer peripheral surface (an upper surface in the drawing) of the protruding portion
55
.
The outer ring
52
has a protruding portion
56
at a central portion of an inner peripheral surface thereof, that is spaced from both end portions of the inner peripheral surface in an axial direction thereof. The protruding portion
56
protrudes toward the inner ring
51
from the inner peripheral surface of the outer ring
52
. An outer raceway
52
a
is formed into a concave shape for receiving the rolling elements
54
at the inner peripheral surface (a lower surface in the drawing) of the protruding portion
56
. Further, at the inner peripheral surface which is adjacent a side surface
52
b
of the protruding portion
56
, a fitting groove
57
is formed to be hollowed from the both end portion of the inner peripheral surface of the outer ring
52
to outside of the ball bearing
50
in a radius direction of the outer ring
52
.
An annular sealing device
70
is substantially composed of a mounting portion
71
arranged at a outer edge portion of the sealing device
70
, a lip portion
72
arranged at an inner edge portion of the sealing device
70
and a connecting portion
73
connecting the mounting portion
71
with the lip portion
72
. The mounting portion
71
of the sealing device
70
is fitted into the fitting groove
57
of the outer ring
52
. Then the lip portion
72
of the searing device
70
is set on a side surface
51
b
of the protruding portion
55
of the inner ring
51
, so that the sealing device
70
is attached to the side surface of the ball bearing
50
in such manner of being secured to the outer ring
52
. The sealing device
70
may be secured to either of the inner ring or the outer ring. Generally the sealing device is secured to the outer ring.
As a material composing the sealing device
70
, a metal which forms the whole sealing device
70
are known, or others composed of a connecting portion formed with a metal ring, and a mounting portion and a lip portion formed with a soft rubber is also known. A sealing device formed with plastic or elastomer is also known (called as “plastic sealing device” hereafter). For example, Japanese Patent Unexamined Publication No. Hei.6-313436 teaches a plastic sealing device which uses a comparatively hard synthetic-plastic-polymer at a connecting portion and a comparatively soft elastic-synthetic-plastic at a mounting portion and a lip portion, and unifies both of the plastic as one body by insert molding. In Japanese Utility Model Laid-Open No. Hei. 5-96549, another plastic sealing device which is formed by changing kinds of resins for heightening rigidity of a connecting portion and increasing flexibility of a lip portion than that of a mounting portion is described.
A plastic sealing device which is formed with a plastic simplex and has variously designing shapes of a mounting portion is also known. For example, Japanese Utility Model Laid-Open No. Hei. 4-87022 discloses, a plastic sealing device having, at an outside surface of an outer peripheral edge portion, a thin triangular shaped annular protruding portion in cross section. The annular protruding portion almost rectangular contacts with an outside surface of a fitting groove in a bending state. Further, in Japanese Utility Model Laid-Open No. Hei. 6-35662 discloses a plastic sealing device having a trapezoidal shaped protruding portions in cross section and a thin and annular protruding portion is described. An inside surface of an outer peripheral edge portion of the trapezoidal shaped protruding portion contacts an inside surface of a fitting groove of the outer peripheral edge portion. The thin and annular protruding portion contacts with an outside surface of the fitting groove in a bending condition. The trapezoidal shaped protruding portions and the thin and annular protruding portion are divided into a plurality pieces equidistantly following a peripheral edge.
In addition, as the kinds of plastics, engineering-plastic-simplex, or plastic composite materials comprising short fiber of glass fiber and carbon fiber which are mixed to be strengthened is used.
As mentioned above, since the mounting portion of the plastic sealing device is pushed into the fitting groove of the outer ring under the elastically deformed condition, a creep deformation may be caused due to atmospheric temperature or heating with rotation of the rolling bearing. Accordingly, there is a possibility that fixing force of the mounting portion into the fitting groove is reduced.
As coefficient of linear expansion of plastic is larger than that of metal, when the temperature rises, the mounting portion expands in a radial direction of the rolling bearing. Then since the amount of elastic deformation (tightening force) becomes larger than an amount of that at room temperatures, the creep deformation is easier to occur.
When an atmospheric temperature is higher than 80° C., the plastic sealing device causes the creep deformation in almost all cases, then when the atmosphere temperature turns back to the room temperatures, a gap is possibly formed between the fitting groove of the outer ring and the mounting portion of the plastic sealing device. In addition, at that time, the fixing force becomes weak, then play or backlash may be occurred. When the fixing force into the fitting groove is reduced, slipping may be occurred between the outer ring and the plastic sealing device, so that a sealing efficiency of the plastic sealing device is lowered.
If thickness of the mounting portion is made large for heightening rigidity of the plastic sealing device, there is also such a problem that when the plastic sealing device expands in the radial direction, the expanded portion cannot be absorbed with only deformation of the mounting portion, so that the plastic sealing device itself curves outward from the side of the rolling bearing and a portion of the curve projects from the rolling bearing. In an ultra miniaturized rolling bearing having an outer radial of the outer ring being around several mm, a problem is to decrease circularity.
Rolling bearings are often served at atmospheric temperatures of 80 to 120° C., the plastic sealing device cannot fully cope with services for a long period of time, because the plastic sealing device is ea
Asai Hiromitsu
Ogawa Takashi
Takajo Toshimi
Tanaka Yoshinori
Uchiyama Takahiko
Graham Matthew C.
NSK Ltd.
Sughrue & Mion, PLLC
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