U.S. patent application number 10/531443 was filed with the patent office on 2006-06-29 for reciprocating seal.
Invention is credited to Hidenori Arai, Shinobu Munekata, Kazuki Takeno, Ichiro Yamane, Katsumi Yamashina.
Application Number | 20060138729 10/531443 |
Document ID | / |
Family ID | 32104990 |
Filed Date | 2006-06-29 |
United States Patent
Application |
20060138729 |
Kind Code |
A1 |
Arai; Hidenori ; et
al. |
June 29, 2006 |
Reciprocating seal
Abstract
The present invention relates to a reciprocating seal used, for
example, for a shock absorber. A main seal lip 32 has a two-step
lip structure including a first lip 32a and a second lip 32b and a
plurality of protrusions 34 extending in the direction of the shaft
are formed on sliding contact surface of the second lip 32b,
thereby improving frictional force characteristics and, at the same
time, improving sealing performance.
Inventors: |
Arai; Hidenori;
(Fukushima-shi, JP) ; Takeno; Kazuki;
(Fukushima-shi, JP) ; Yamane; Ichiro;
(Fukushima-shi, JP) ; Munekata; Shinobu;
(Fukushima-shi, JP) ; Yamashina; Katsumi;
(Fukushima-shi, JP) |
Correspondence
Address: |
JACOBSON HOLMAN PLLC
400 SEVENTH STREET N.W.
SUITE 600
WASHINGTON
DC
20004
US
|
Family ID: |
32104990 |
Appl. No.: |
10/531443 |
Filed: |
September 19, 2003 |
PCT Filed: |
September 19, 2003 |
PCT NO: |
PCT/JP03/11995 |
371 Date: |
November 15, 2005 |
Current U.S.
Class: |
277/559 |
Current CPC
Class: |
F16J 15/56 20130101;
F16J 15/3232 20130101; F16F 9/36 20130101; F16J 15/3236
20130101 |
Class at
Publication: |
277/559 |
International
Class: |
F16J 15/32 20060101
F16J015/32 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 15, 2002 |
JP |
2002-300650 |
Claims
1. A reciprocating seal that is provided in an annular space formed
between a shaft and a housing, which move relatively to each other
in a direction of the shaft, and has a seal lip brought into
sliding contact with a surface of the shaft, wherein the seal lip
has a two-step lip structure in which a plurality of protrusions
extending in the direction in which a main seal lip relatively
moves with respect to the surface of the shaft are formed on a
surface of the lip of a second step.
Description
TECHNICAL FIELD
[0001] The present invention relates to a reciprocating seal used,
for example, for a shock absorber.
BACKGROUND ART
[0002] A reciprocating seal of this kind has been conventionally
known that is used for a shock absorber mounted in an automobile
and the like.
[0003] Among reciprocating seals according to a conventional art
like this is, for example, a seal shown in FIG. 3.
[0004] FIG. 3 is a schematic sectional view of a reciprocating seal
according to a conventional art.
[0005] The reciprocating seal is arranged in an annular space
between a shaft (not shown) and the inner periphery of a housing
(in more detail, shaft hole made in the housing), which move
relatively in the direction of the shaft, to form a sealed
space.
[0006] A reciprocating seal 100 according to the conventional art,
as shown in the drawing, is mainly provided with a metal ring 200
and a rubber seal 300 baked on the metal ring 200.
[0007] The rubber seal 300 has an outer peripheral seal portion 301
mounted on the inner periphery of the housing, a main seal lip 302
brought into sliding contact with the outer peripheral surface of
the shaft, and a sub-seal lip 303 similarly brought into sliding
contact with the outer peripheral surface of the shaft.
[0008] The reciprocating seal constructed in this manner is
required to improve frictional force characteristics.
[0009] That is, it is required to reduce fine vibrations caused
when the reciprocating seal is brought into sliding contact with
the surface of the shaft to a minimum.
[0010] This is because, for example, when the reciprocating seal is
used for the shock absorber of an automobile, as the frictional
force characteristics are more excellent, vibrations are reduced to
improve the riding comfort of the automobile.
[0011] Then, to improve frictional force characteristics, as shown
in FIG. 3, the main seal lip 302 has a two-step lip structure
including the first lip 302a of the first step and the second lip
302b of the second step.
[0012] In this manner, both of the first lip 302a and the second
lip 302b are brought into sliding contact with the surface of the
shaft to stabilize the position of the main seal lip 302.
[0013] With this, the frictional force can be made uniform to
improve frictional force characteristics.
[0014] However, even if the second lip 302b of the second step is
brought into sliding contact with the surface of the shaft to make
the frictional force uniform, the sliding contact of the second lip
302b increases the frictional force.
[0015] Hence, this prevents the smooth sliding contact of the main
seal lip 302, and the frictional force characteristics can not be
improved sufficiently.
[0016] Therefore, a technology of roughening the surface of the
second lip of the second step to reduce frictional force by the
second lip 302b has been developed (for example, see Japanese
Unexamined Patent Publication No. 2001-355740).
[0017] Structures of roughening the surface of the second lip in
this manner include structures of matting the surface of the lip,
forming spiral screw protrusions on the surface of the lip, and
forming parallel protrusions vertical to the shaft on the surface
of the lip (see the above patent publication).
[0018] However, in the case of the structure of matting the surface
of the lip, the surface of the lip is formed in random
asperity.
[0019] For this reason, the amount of leak of sealed-in fluid
(which is usually oil, so descriptions will be provided below,
assuming that the sealed-in fluid is oil) becomes nonuniform in
whole and hence there is a possibility that the amount of leak
might increase in part.
[0020] Further, there is a possibility that also the frictional
force might be nonuniform in whole.
[0021] In other words, in the case of the structure of matting the
surface of the lip, there is presented a problem that it is
difficult to control the amount of leak and the distribution of
frictional force with accuracy.
[0022] Further, in the case of the structure of forming spiral
screw protrusions or the structure of forming parallel protrusions
vertical to the shaft, when the surface of the lip is brought into
sliding contact with the surface of the shaft, these protrusions
scrape off the oil.
[0023] Therefore, there is presented a problem that the thickness
of an oil film is made too thick to increase the amount of leak of
the oil.
DISCLOSURE OF THE INVENTION
[0024] As described above, in the case of a conventional art, it is
difficult to improve frictional force characteristics and, at the
same time, to improve sealing performance.
[0025] The object of the invention is to provide a reciprocating
seal capable of improving frictional force characteristics and at
the same time improving sealing performance.
[0026] To achieve the above object, the invention adopts the
following construction.
[0027] That is, according to the invention, there is provided a
reciprocating seal that is provided in an annular space formed
between a shaft and a housing, which move relatively to each other
in the direction of the shaft, and has a seal lip brought into
sliding contact with the surface of the shaft, wherein the seal lip
has a two-step lip structure in which a plurality of protrusions
extending in the direction of the shaft are formed on the surface
of the lip of the second step.
[0028] According to the construction of the invention, the seal lip
has the two-step lip structure and hence the position of the seal
lip can be stabilized.
[0029] With this, the distribution of frictional force caused
between the seal lip and the shaft can be made uniform.
[0030] Further, since the plurality of protrusions are formed on
the surface of the lip of the second step, they can prevent an
increase in the frictional force.
[0031] Still further, the plurality of these protrusions are so
constructed as to extend in the direction of the shaft and hence
the protrusions do not scrape off sealed-in fluid.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] FIG. 1 is a schematic sectional view of a reciprocating seal
according to an embodiment of the invention.
[0033] FIG. 2 is a sectional view showing conceptually protrusions
formed on the reciprocating seal according to the embodiment of the
invention.
[0034] FIG. 3 is a schematic sectional view of a reciprocating seal
according to a conventional art.
BEST MODE FOR CARRYING OUT THE INVENTION
[0035] Hereafter, the best mode of this invention will be described
as an example in detail with reference to the drawings. However, as
for the size, material, shape, and relative arrangement of
constituent parts described in this embodiment, it is not intended
to limit the scope of this invention only to these unless otherwise
specified.
[0036] A reciprocating seal according to the invention will be
described with reference to FIG. 1.
[0037] FIG. 1 is a schematic sectional view of a reciprocating seal
according to the embodiment of the invention.
[0038] The reciprocating seal 1 according to the embodiment of the
invention can be suitably used for a shock absorber mounted in an
automobile and the like.
[0039] Further, the reciprocating seal 1 according to the
embodiment of the invention is arranged in an annular space between
a shaft (not shown) and the inner periphery of a housing (shaft
hole made in the housing, in more detail), which move relatively to
each other in the direction of the shaft, to form a sealed
space.
[0040] In the case of using the reciprocating seal 1 as a shock
absorber, oil of sealed-in fluid is hermetically sealed in a
hermetically sealed space formed by the reciprocating seal 1.
[0041] With this, when a shaft and a housing reciprocate relatively
to each other, the reciprocating seal 1 exerts a shock-absorbing
function.
[0042] The reciprocating seal 1 according to this embodiment, as
shown in FIG. 1, is roughly provided with a metal ring 2 and a
rubber seal 3 baked on the metal ring 2.
[0043] The rubber seal 3 has an outer peripheral seal portion 31
mounted on the inner periphery of a housing not shown (the inner
periphery of a shaft hole made in the housing), a main seal lip 32
brought into sliding contact with the outer peripheral surface of a
shaft (not shown), and a sub-seal lip 33 similarly brought into
sliding contact with the outer peripheral surface of the shaft.
[0044] Further, a spring 4 for pressing the lip onto the surface of
the shaft is provided on the outer periphery side of the main seal
lip 32.
[0045] Then, the main seal lip 32 has a two-step lip structure.
That is, the main seal lip 32 has the first lip 32a of the first
step located near the sealed-in fluid side and the second lip 32b
of the second step located opposite to the sealed-in fluid
side.
[0046] In this manner, the two-step lip structure is adopted and
both of the first lip 32a and the second lip 32b are brought into
sliding contact with the surface of the shaft to stabilize the
position of the main seal lip 32.
[0047] With this, the distribution of frictional force can be made
uniform to improve frictional force characteristics. That is, fine
vibrations caused when the main seal lip 32 is brought into sliding
contact with the surface of the shaft can be reduced.
[0048] In this embodiment, a plurality of protrusions 34 extending
in the direction of the shaft are formed on the sliding contact
surface (surface of the lip opposite to the sealed-in fluid side in
this embodiment) of the second lip 32b.
[0049] These protrusions 34 are formed at equal intervals along the
entire periphery.
[0050] The preferable example of these protrusions will be
described.
[0051] FIG. 2 is a sectional view showing conceptually protrusions
formed on the reciprocating seal according to embodiment of the
invention.
[0052] Preferably, the sectional shape of the protrusion is made
triangular.
[0053] Preferably, the height h of the protrusion is made 2 to 500
.mu.m and, when taking elastic contact into consideration, 5 to 100
.mu.m.
[0054] Further, it is preferable that the interval w of the
protrusions (interval of the peaks) is 0.005 to 1.0 mm and, when
taking elastic contact into consideration, 0.01 to 0.2 mm.
[0055] Still further, it is preferable that the vertical angle of
the protrusion is 60 to 120.degree..
[0056] A more specific example of the protrusion has a height H of
0.03 mm, an interval w of 0.15 mm, a vertical angle of 90.degree.,
and a length of 1.2 mm.
[0057] In this manner, in this embodiment, the plurality of
protrusions 34 are formed on the sliding contact surface of the
second lip 32b and hence can prevent an increase in frictional
force.
[0058] This embodiment is so constructed as to prevent an increase
in frictional force by the protrusions 34, so that it is possible
to prevent the surface of the lip from being formed in random
asperity as is the case of matting the surface of the lip.
[0059] That is, it is possible to control the shape and size of the
protrusion 34 with precision.
[0060] Hence, it is possible to make the thickness of an oil film
uniform and to prevent variations in the amount of leak
(distribution of leak) of sealed-in fluid and variations in the
distribution of frictional force.
[0061] Further, the plurality of protrusions 34 are so constructed
as to extent in the direction of the shaft.
[0062] That is, the direction in which the protrusions 34 extend
agrees with the direction in which the shaft and the housing move
relatively to each other, and the direction in which the main seal
lip 32 moves (slides to contact) with respect to the surface of the
shaft.
[0063] Therefore, even when the main seal lip 32 reciprocates in
sliding contact with the surface of the shaft, the protrusions 34
do not scrape off the sealed-in fluid (usually, oil).
[0064] This can prevent the film of the sealed-in fluid (usually,
oil film) from being too thick.
[0065] Further, this can prevent the leak of the sealed-in
fluid.
[0066] Incidentally, two kinds of velocity-ratio leak tests
(Vten/Vcomp=4 (m/s)/1 (m/s), stroke of shaft=.+-.25 mm, the number
of vibrations=300, pressure=0 MPa and 0.5 MPa) were conducted on a
reciprocating seal (conventional seal) having no protrusion and a
reciprocating seal having the protrusions like this embodiment.
[0067] Then, there is little difference in the amount of leak
between the two reciprocating seals.
[0068] Further, the above test was conducted also on a
reciprocating seal having a plurality of spiral screw protrusions
having an angle of 60.degree. inclined with respect to the
direction of the shaft.
[0069] Then, in the case of this reciprocating seal, the amount of
leak increased by a factor of approximately 2 as compared with the
reciprocating seal having no protrusion and the reciprocating seal
according to this embodiment.
[0070] Here, the velocity-ratio leak test is a test of measuring
the amount of leak when a shaft is pushed or pulled in such a way
that a pushing speed is different from a pulling speed.
[0071] In other words, in the case of the reciprocating seal, when
the shaft is pulled out, a thin oil film is formed on the surface
of the shaft.
[0072] The thickness of this oil film tends to be thicker as the
moving speed of the shaft is faster.
[0073] Hence, when the shaft is pulled out at a high speed and
pushed at a low speed, the oil film becomes thicker in a
pulling-out step (taking-out step) and becomes thinner in a pushing
step.
[0074] For this reason, the oil tends to be easily scraped out.
[0075] It is the velocity-ratio leak test that measures the amount
of leak of oil scraped out by pulling or pushing the shaft
repetitively with a difference in speed between the pulling-out
step and the pushing step.
[0076] In the above test, the pulling-out speed in the pulling-out
step was four times the pushing speed in the pushing step.
[0077] As described above, according to the reciprocating seal
according to this embodiment, it is possible to make the
distribution of frictional force of the main seal lip 32 with
respect to the surface of the shaft uniform and to prevent an
increase in the frictional force.
[0078] With this, it is possible to improve frictional force
characteristics, that is, to reduce fine vibrations caused when the
main seal lip 32 is brought into sliding contact with the surface
of the shaft.
[0079] Further, it is possible to prevent the leak of the sealed-in
fluid and hence to improve sealing performance.
INDUSTRIAL APPLICABILITY
[0080] As described above, according to the construction of the
invention, it is possible to improve frictional force
characteristics and, at the same time, to improve sealing
performance.
* * * * *