Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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SHOCK ABSORBER
BACKGROUND OF THIE: INVE:NTION
Field of the Invention
The present invention relates to a shock
absorber for an automotive suspension system. More
specifically, -the invention relates to a seal structure
for a shock absorber for preventing a yaseous state
working fluid in a fluid reservoir from leaking into a
working chamber.
Description of the Background Art
Japanese Patent First (unexamined~ Publication
(Tokkai) Showa 58-156739 discloses a shock absorber
which has coaxially defined inner and outer cylinders
defining a fluid reservoir chamber in which hydraulic :-
working fluid and pneumatic working fluid are filled,
which fluid reservoir chamber is defined between the ~-
inner and outer cylinders. The disclosed shock absorber
has a path for establishing a working chamber filled
with a hydraulic working fluid and a the fluid reservoir
chamber. A seal structure is provided in the path for
permitting the hydraulic fluid from the working chamber
to the fluid reservoir and blocking pneumatic fluid flow
from the fluid reservoir to the working chamber.
In the conventional construction oE the seal
structure for such a type of the shock absorber, a seal
member is provided for permitting and blocking fluid
communication. Namely, in yenera3, the hydraulic fluid
pressure in the working chamber is hi~her than the
pneuma-tic fluid pressure in the fluid reservoir chamber,
and, alternatively, in the piston rebounding stroke, the
pneumatic pressure in the fluid reservoir becomés higher
than the hydraulic fluid pressure in the workiny
chamber. Therefore, in the usual construction of the
seal structure as disclosed in the Japanese Patent First
Publication 5B-156739, one or more grooves are formed on
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the seal member so that part of hydraulic working fluid
in the working chamber can flow i~to the fluid reservoir
only in the piston bounding stroke.
In such conventional seal structure, various
drawback have been encountered. For example, when the
seal member establishes the gas tight seal by
face-to-face contact with a constructional seat member
to seat there~f. Substantially high surface accuracy of
the mating surfaces o~ the seal member and the seat
member are required. On the other hand, when the seal
member is formed of d resin material, wearing of the
resin seal member will cause leakage of the pneumatic
working fluid i.nto the working chamber to cause
aeration.
SL~ARY OF_TIIE IN~ENTION
Therefore, it is an object of the present
invention to provide a shock absorber which can
successfully prevent a pneumatic working fluid from
leaking into working chamber at any mode of shock
.absorber operation.
In order to accomplish aforementioned and
other objects, a shock ab~orber, according to the
present invention, includeg a cylinder assembly
defining a working chamber filled with a hydraulic
working Eluid and disposed therein a piston, and a fluid
reservoir chamber fil-led with the hydraulic working
fluid and a pneumatic working fluid, a communication
path for connecting the working chamb~r and the fluid
reservoir chamber for fluid communication therebetween,
a check an5 flow restriction assembly disposed :~
within the communication path for selectively
establishing and blocking ~luid communication between
the working chamber and the fluid reservoir chamber, the
check and flow restriction assembly including a check neans and a
flow restriction means arranged in series, the flow
restriction means permitting pneumatic and hydraulic
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fluid flow directed to the fluid reservoir chamber during a
piston bounding stroke and providing ~low reskriction for
the hydraulic fluid flow, and khe check means blocking fluid
communication between the fluid reservoir chamber and the
working chamber during a piston rebounding stroke and
permitting hydraulic fluid flow during the piston bounding
stroke;
the check means including an elastic seal; and
the flow restriction means including a seal ring having
an orifice which extends in an axial direction between the
outer periph~ry of a piston rod connected to the piston and
an inner periphery of the seal ring. .:
Preferably, the check and flow restriction
a~sembly may further include a retainar, and the flow
restriction mea~s may include a radially extending groove in
the retainer :Eor forming a flow restriction orifice. The
check and ~low restriction assembly may also further include
a retainer, and the flow restrictit)n means may include a
plurality of ring members disposed between the seal ring and
the retainer ~or de~ining a flow re~tricting orifice.
According to the present i.nvention, there is also
provided a shock absorber including:
a cylinder assembly defining a working chamber filled
with a hydraulic wor~ing fluid and disposed therein a
piston, and a fluid reservoir chamber filled with the ..
hydraulic working fluid and a pneumatic working fluid;
a communication path for connecting the working chamber
and the fluid reservoir chamber for fluid communication
therebetween; -.
a check and flow restriction a~sembly disposed within .:.
the communication path for selectively establishing and
blocking fluid communication between the working chamber and
the fluid reservoir chamber, the check and flow restriction .
a~sembly including a check means and a flow restriction
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means arrangad in series, the flow restriction means
providing ~low restriction against fluid flow therethrough,
and the check means being respon~ive to pressure difference
betw~en the working chamber and the fluid reservoir chamber
5 and responsive to higher pressure in the fluid reservoir
chamber than that in the working cham'oer for elastically ..
establishing a flow blocking seal for blocking fluid
communic~tion between the fluid reservoir chamber and the
working chamber and responsive to higher pxessure in the
working chamber than in the fluid reservoir chamber for
permitting hydraulic fluid flow; and
ths flow xestriction means including an orifice ~ormed
in a ring member, the orifice extending in an axial
direction between the outer periphery of a piston rod
connecked to the piston and in inner periphery o~ the ring
member; and
the check means comprises an ~lastic seal alastically
contacting an inner periphery of the communication p~th, the
elastic seal being designed so that the pressux~ in the
working chamber is exerted onto the elastic seal in a
direction for releasing ~ealing contclct between the elastic
seal and tha inner periphery of the communication path, and
the pressure in the fluid reservoir chamber i~ exerted onto
the ~lastic seal in a direction for urging the elastic seal
2~ unto the inner periphery of the communication path.
According to the pr0sent invention, there is also
provided a shock absorber including: :
a cylinder assembly definin~ a working chamber filled
with a hydraulic working fluid and disposed therein a
piston, and a fluid reservoir chamber filled with the
hydraulic working fluid and a pneumatic working fluid; ~ -
~a communication path for connecting th~ working chamber
and the ~luid reservoir chamber for fluid communication ~. :
therebatween;
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a check an~ flow restriction assembly disposed wi.thin
the communication path for selectively establishing and
blocking fluid communication between the working chamber and
the fluid reservoir chamber, the check and flow restriction
assembly including a check means and a flow restriction
means arranged in series, the flow restriction means
yermitting pneumatic and hydraulic fluid flow directed to
the fluid reservoir chamber during a piston bounding stroke
and providing flow restriction for the hydraulic fluid flow,
lo and the check means blocking fl.uid communication bet~een the
fluid reservoir chamber and the working chamber during a
piston rebounding stroke and permitting hydraulic fluid flow
during the piston bounding stroke; and
the check means including a seal ring; and
the Elow restriction means including an orifice ring,
and a spacer ring, the orifice ring being axially arranged
on the seal ring and having a radially ex-tending cut-out
portion, the spacer ring being axial:Ly placed on the orifice
ring to define an orifice for providing the flow
restriction.
According to the present invention, there is also
provided a shock absorber including:
a cylinder assembly defining a working chamber fillad
with a hydraulic working fluid and disposed therein a
piston, and a fluid reservoix chamber filled with the
hydraulic working fluid and a pneumatic working fluid;
a communicativn path for connecting the working chamber
and the fluid reservoir chamber for fluid communication
therebetween;
a check and flow restriction assembly disposed within
the communication path for selectively establishing and
blocking fluid communication between the working chamber and
the fluid reservoir chamber, the check and flow assem~ly
including a check means and a flow restriction means
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arranged in series, the f1QW restriction means permitting
pneumatic and hydraulic fluid flow directed to the fluid
reservoir chamber durin~ a piston boundi.ng stroke and
providing flow.restriction for the hydraulic fluid flow, and
the check means blocking fluid communication between the
fluid reservoir chamber and the working chamber during a
piston rebounding stroke and permitting hydraulic fluid flow
during the piston bounding stroke; and
the check means including a seal ring; and
. the flow restriction means including an orifice ring
and a retainer which defines a seal ring receptacle cham~er
along with a groove formed in a rod guide member for .-
receiving the seal ring, the orifice ring being axially
arranged on the seal ring and having a cut-out portion, the .:
retainer having a groove therein which communicates between
the reservoir chamber and the cut-out portion of the orifice ~-
ring. .~;
~RIEF DESC~IPTION OF THE DRA~INGS
The present invention will be understood more -
fully from the detailed description given herebelow and from
the accompanying drawings of the preferred embodiment of the
invention, which, however, should not be taken to limit the :
invention to t~e specific --~
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embodiment but are for explanation and und~rstanding
only.
In -the drawings:
Fig. 1 is a section of the first embodiment of
a major section of a shock absorber according to the
present invention,
Fig. 2 is an enlarged perspective illustration
of a sealing member;
Fig. 3 is a section of the second embodiment
of a major section of a shock a~sorber accordin~ to the
invention;
Fig~ 4 is a section of the third embodiment of
a major section of a shock absorber according to the :~
invention, :::
Fig. 5 is a plan view of a sealing member
employed in the third embodiment of the shock absorber
of Fig. 4,
Fig~ 6 is a section of the fo~rth embodiment -:
of a shock absorber according to the invention; ;:.
F.ig. 7 is an enlarged section of the major ~::
par~ o~ the fourth embodiment of the shock absorber of
~'ig. 6;
Fig. 8 is a bottom view of a fixing member
employed in the fourth embodiment of the shock absorber .
of Fig. 6; and -
: Fig. 9 is a plan view of a sealing member
employed in the fourth embodiment of the ishock absorber
of Fig. 6.
DESCRIPTION OF T~IE PREFERRED EMBODIMENT
: 30 Refering now to the drawings, particularly to
Fig. 1, the first embodiment of a shock absorber,
according to the present invention, has coaxially
arranged inner and outer cylinders 10 and 12. The inner
cylinder 10 defines therein an internal space 14 filled
: 35 with a hydraulic working fluid. The internal space 14 ~ .
o~ the inner cylinder 10 serves as a working chamber.
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An annular chamber 16 is defined bstween the inner and outer
cylinders lo and 12. The annular chamber 16 is filled with
a hydraulic fluid and a pneumatic fluid and serves as a
reservoir chamber. A piston 18 is thrustingly and sealingly
disposed in the working chamber 14 to separate the working
chamber into an upper working chamber 20 and a lower working
chamber 22~ The piston 18 is fixedly secured onto the lower
end section of a piston rod 24. In the shown construction,
the piston rod Z4 is formed with an axi~lly extending
threaded opening 26 to receive a fastening blot 28. The
piston rod extends from the inner and outer cylinders 10 and
12 through the top ends thereof. In order to support the
piston rod 18, an upper end plug 30 which serves as a piston
rod guide, is fitted onto the top ends of the inner and
outer cylinders 10 and 12. The upper end plug 30 has an
upper larger diameter section 32 sealinyly engaginy with the
inner periphery of the top end section of the outer cylinder
12. The upper end plug 30 also has a lower smaller diameter
section 34 sealingly engaging with the top end of the inner
cylinder 10. An upwardly opening recess 36 is formed in the
upper end plug 30. The recess 36 comprises an upper larger
diameter section 38 and a lower smaller diameter section 40.
The upper end plug 30 is formed with a groove 42 having one
end opening to the larger diameter section 38 of the recess
36 and the other end opening to the reservoir chamber 16.
This groove 42 defines a communication path 44 for fluid
communication between the reservoir chamber 16 and the
recess 36.
The shock absorber has a check and seal assembly
including a check means and a flow restriction means
arranged in series.
A seal assembly 46 is provided above the upper end
pluq 30 for establishing liquid-tight and gas-tight seal
between the outer periphery of the piston rod 24. The seal
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assembly 46 comprises an annular rigid reinforcement member
48 and an elastic seal 50. The elastic seal 50 has a
~ection 52 fitted on the upper
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plane of the annular rigid member 48, an inner lip
section 54 sealingly contacting with the piston rod 24,
and an outer lip 56 contacting with the wall section 58
defining the larger diameter section 38 of the recess
36. The outer lip 56 serves as a check lip for
permitting fluid flow from the upper working chamber 20
to the fluid reservoir 16 and blocking fluid flow in
the opposite direction. As will be seen from Fig. 1, in
the shown construction, the contacting point at which
the outer lip 56 contacts with the wall section 58 is
oriented at the lower elevation in r~lation to the
opening end of the communication path in such a manner
that the pressure transmitted through the fluid
reservoir chamber 16 may serve to depress the outer lip
56 on the wall section 58 to enhance sealing contact
therebetween. On -the other hand, the inner lip 54 is
biased toward the piston rod by a spring ring 60. The
elastic seal 50 is made of a rubber material and
vulcanized onto the rigid reinforcement member 48.
A seal housing member or retainer 62 is disposed in the
recess 36. The seal housing member 62 has a lower
portion engaging with the lower smaller diameter section
40 of the recess and extend upwardly to contact to the
elasti~ seal 50 at the upper edge at an orientation
between the inner and outer iips 54 and 56. A plurality
of cut-outs 64 are formed in the upper edge of the seal
housing member 62 for defining through path for the
fluid flowing between the upper working chamber 20 and
the fluid reservoir chamber 16. An annular groove 66 is
~ormed on the inner periphery of the lower section oE
the seal housing member 62. A seal ring 68 is disposed
within the annular groove 66.
As shown in Fig. 2, the seal ring 68 generally
has an internal diameter substantially equal to thP
outer diameter of the piston rod 24 so as to establish
sealing and sliding contact therebetweem. The seal
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ring 68 is formed with a plurality of axia].ly extending
grooves 70. In addition, a bearing sleeve 72 which has
slightly greater internal diameter than the outer
diameter of the piston rod 24 to define therebetween an
annular clearance (though the clearance is not clearly
shown in Fig. 1). Therefore, a space 74 defined between
the seal housing member 62 and the seal assembly 46,
which space is in fluid communication wi~h the fluid
reservoir chamber 16 via the communicati.on path ~4, the
through path 64, is communicated with the ~pper working
chamber 20 via the grooves 70 of the seal ring 68 and
the clearance deFined between the bearing sleeve and the
piston rod 24.
On the other hand, the piston 18 i9 formed
with a bounding communication path 76 and a rebounding
communication path 78. The lower end of the bounding
path 76 is closed by a leaf spring valve 80 which
permits ~low of the working fluid from the upper working
chamber 20 to the lower working chamber 22 during piston
bounding motion and blocks fluid flow in the opposite
direction. On the other hand, the upper end of the
rebounding communication path 78 is closed by a leaf
spring valve 82 which permits fluid flow from the lower
working chamber 22 to the upper working chamber 20
during the piston rebounding motion and blocks fluid
flow in the opposite direction. With flow restriction
provided by the communication path 76 and 78, resistance
against displacement of the piston 18 is generated as
damping force. This damping force serves for
restricting relative displacement between the vehicular
body and a suspension member as employed i.n the
automotive suspension system.
On the other hand, in the piston bounding
stroke, the ~lui.d pressure in the upper working chamber
20 is increased according to tha upward movement of the
piston 18. This causes ~luid flow from the upper
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working chamber 20 to the fluid reservoir chamber 16 via
the clearance between the bearing sleeve 72, the grooves
70 of the seal member 68, the space 74, the through
opening 64 and the communication path 44. For the fluid
flowing from the upper working chamber 20 to the ~luid
reservoir 16, the grooves 70 in the seal member 68 serve
as flow restricting orifices for limiting fluid flow
therethrough and thus generates damping force. ~-
On the other hand, in the piæton rebounding
stroke, the pressure in the upper working chamber 20 is -
decreased by expansion of the volume. On the other ~-
hand, the fluid in the lower working chamber 22 is
compressed to flow into the upper working chamber 20 via -
the rebounding communication path 78 in a limited
amount. The fluid pressure in the lower working chamber
22 i5 also transmitted to the hydraulic fluid in the
fluid reservoir chamber to compress the pneumatic fluld.
~herefore, the pneumatic pressure at the upper section
of the fluid reservoir is increased. This causes gas
~0 Elow from the fluid reservoir chamber 16 through -the
communication path 44. However, the pressure
transmitted from the fluid reservoir chamber 16 serves
for increasing depression for the outer lip 5Ç onto the -~
wall section 58 to establish gas tight seal
therebetween. Therefore, the pneumatic fluid in the ~-~
fluid reservoir chamber 16 will never leaks into the
upper working chamber. ;-
Fig~ 3 shows the second embodiment of the
shock absorber according to the present invention. In
the following discussion for the second embodiment, the
component common to the foregoing first embodiment will
be represented by the same reference numerals.
In this embodiment, the seal housing member 90
has the modified configuration to that disclosed in the
former embodiment~ In this embodiment, a seal housing
member or retainer 90 is in-tegrally-formed with a flange sectio~ 92 :;
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which has a plane 94 mating with the outer lip 56 to
serve as the wall section to cooperate with the outer
lip to establish the gas tight seal.
With this construction, substantially the same
effect to the foregoing first embodiment can be
achieved.
Fig. 4 shows the third embodiment of the shock
absorber according to the present inven~ion. Similarly
to the foregoing second embodiment, the components
common to the foregoing first embodiment will be
represented by the same reference numerals.
In the shown embodiment,an upper end plug 100
serving as the rod guide has stepped groove 102
defining the lowermost small diameter section 104, an
uppermost large diameter section 106 and an intermediate
se~tion 108 between the lowermost and upperrnost sections
104 and 106. A stationary ri~g member or re-tainer 110 is rigidly
Eitted to the intermediate sectlon 108 and extends
radially inward. ~ This stationary ring member 110 is
cooperative with the wall section 112 of the upper end
plug 100 defining the lowermost section 104 to de~ine a
seal receptacle groove 114. In the seal receptacle
~roove 114, a seal ring 116 is disposed for thrusting
movement in axlal direction according to pressure
difference between the fluid reservoir chamber 16 and
the upper working chamber. In the seal receptacle
groove 114~ an orifice ring 118 and a spacer ring 120
are also disposed in axial alignment to each other. In
the shown embodiment, the spacer ring 120 is placed in
the uppermost orientation and the seal ring 116 is
placed in the lowermost orientation. The orifice ring
118 is placed between the spacer ring 120 and the seal
ring 116. The orifice ring 118 and the spacer ring 120
are provided substantially the same external diameters
which s~bstantially correspond to the internal diameter
of the lowermost sec~io~ 104.
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As shown in Fig. 5, the spacer ring 120 has
greater internal diameter than the outer diameter of the
piston rod 24 to define therearound an annular space
122. On the other hand, the orifice ring 118 has an
internal diameter slightly greater than the outer
diameter of the piston rod 24 but smaller than the
internal diameter of the spacer ring 120. The orifice
ring 118 is formed with a plurality of radially
extending cut-outs 124 inner portions oE which overlap
with the annular space 122 defined by the spacer ring.
On the other hand, the seal ring 116 has outer diameter
greater than the internal diameter of a radially
extending flange section 126 of the upper end plug 100.
With this construction, in the piston bounding
stroke where the hydraulic working fluid in the upper
working chamber is increased by compression of volume in
the upper working chamber, the seal ring 116 is shifted
upwardly and placed away from the flange section 126.
Then, the working fluid in the upper working chamber 20
i9 permitted to flow through the path defined by the
cut-outs 124 of the orifice ring 118 and the annular
space 122 of the spacer ring 120. The path area of the
path defined by the orifice ring 118 and the spacer ring
120 is s~all enough to restrict fluid flow therethrough,
damping force can be generatëd.
On the other hand, in the piston rebounding
stroke, the pressure in the upper working chamber 20
becomes lower than the pneumatic pressure in the
reservoir chamber 16. As a result, the seal ring 116
comes to contact with the flange section 126 of the
upper end plug 100 to establish gas tight seal.
Therefore, the pneumatic fluid in the fluid reservoir
chamber 16 can be prevented from leaking into the upper
worlcing chamber.
Figs. 6 and 7 shows the fourth embodiment of
the shock abso~ber according to the present invention
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In this embodiment, a seal assembly 130 which comprises
a seal retainer 132 and an elastic seal 134, is engaged
to esl-ablish liquid and gas-tight seal at the top oF the
outer cylinder 12. On the other hand, the top end of
the inner cylinder 10 is closed by an upper end plug
136. A chamber 138 is defined between the seal assembly
130 and the upper end plug 136. The cha~ber 138 is
constantly in communication with the fluid reservoir 16
via a communication path 140.
The upper end plug 136 serving as the road
guide has stepped sroove 1~2 defining the lower most
small diameter section 144, an uppermost large diameter
section 146 and an intermediate section 1~i8 between the
. lowermost and uppermost sections 144 and 146. A
stationary ring member or retainer 150 is rigidly fitted-to-the
intermediate section .L48 and extends radially inward.
This stationary ring member 15D i5 cooperative with the
wall section of the upper end plug 136 defining the --
lowermost section 144 to defi.ne a seal receptacle groove
154. In the seal receptacle groove 154, a seal ring 156
is disposed for thrusting movement in axial direction
according to pressure diff.erence between the fluid
reservoir chamber 16 and the upper working chamber. In
. order to permit thrusting movement, the seal ring 156
has a height ~1 smaller than the height ~ of the seal
receptacle groove 154. The seal receptacle groove 154
and an orif.ice ring 158 are also disposed in axial
align~ent to each other.
As shown in Fig. 7, an annular groove 160 and
.one or more radially extending grooves 162 are formed on
the lower surface of the stationary ring member 150.
The radially extending grooves 162 opens to the fluid
path lG4 defined between the inner peripheral edge of
the stationary ring member 150 and -the piston rod 24,
and the other end opens to the annular groove 160, as
shown in Fig. 8. The radius d1 of the seal
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receptacle groove 154 is greater than the sum of the radial
length d2 of the seal ring 156 and the possible transverse
offset magnitude d3 of th seal ring. On the other hand, as ~~
shown in Fig. 9, the orifice ring 15~ is formed with a
plurality of cut-outs 166.
With the grooves 160 and 162 of the stationary
ring member 150 and the cut-outs 166 of the orifice ring
158, the flow restricting path for permitting fluid flow
from the upper working chamber 20 and -the chamber 138 during
piston bounding stroke. On the other hand, in the piston
rebounding stroke, the seal ring 156 is depressed on the
flange s~ction 168 of the upper end plug for establishing
gas tight seal. Therefore, with this construction,
substantially the same effect to that obtained from the
~oregoing third embodiment can be obtained.
While the present invention has been disclosed in
terms of the preferred embodiment in order to facilitate
better understanding of the invention, it should be
appreciated that the invention can be embodied in various
ways without departing from the principle of the invention.
Therefore, the invention should be under6tood to include all
possible embodimenks and modifications to the shown
embodiments which can be embodied without departing from the
principle of the invention set out in the appended claims.
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