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Claims  |
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We claim:
1. A hydraulic shock absorber for vehicles, comprising:
an inner tube and an outer tube, said inner and outer tubes being
telescopically fitted together;
a tapered rod supported by said outer tube and extending vertically and
axially therefrom, the diameter of said tapered rod progressively
decreasing from a proximal end thereof to a distal end thereof;
said inner tube including a partition member having a hole through which
said tapered rod substantially loosely extends;
an orifice angularly defined between said rod and said hole and variable in
response to relative movement of said rod and hole;
a piston provided on the distal end of said rod, and slidable with respect
to said inner tube;
a lower chamber defined below said piston, and a central chamber defined
above said piston and below said partition member;
said piston being provided with a valved portion adapted to open when said
tubes relatively move in one direction to permit substantially full
communication between said lower chamber and said central chamber, and
adapted to operate to gain a damping force when said tubes relatively move
in the opposite direction;
said piston including a spacer which spaces said valved portion from a
lower surface of said partition member when they abut against each other;
a spacer member separate and distinct from said partition member disposed
at an upper end of said inner tube and supported by said partition member
for supporting thereon means for breaking up air bubbles passing upwardly
and downwardly through said spacer member;
a tubular holder coaxially disposed around an upper outer peripheral
portion of said outer tube and having a diameter larger than the diameter
of said outer tube;
a partition membrane substantially vertically disposed between said holder
and said outer tube and mounted substantially coaxially therewith, said
partition membrane being fabricated of a substantially flexible and
resilient material and being disposed so as to divide a space defined
between said holder and said outer tube into a high-pressure gas chamber
outside of said membrane and a low-pressure gas chamber inside of said
membrane; and
an upper portion of said outer tube being provided with a number of
apertures through which said low-pressure chamber communicates with an
upper space within said outer tube.
2. A hydraulic shock absorber according to claim 1, wherein:
said spacer member includes a recess having a partition part disposed
therebelow;
said partition part is provided with a plurality of through holes extending
through to the bottom of said recess; and
said means for breaking up air bubbles comprises an air bubble suppressor
mounted in said recess.
3. A hydraulic shock absorber according to claim 1, wherein:
said partition member includes a downwardly opening annular space portion;
said spacer of said piston comprises an annular substantially skirt-shaped
spacer projecting upwardly from a peripheral bottom portion of said
piston; and
an upper distal end of said spacer of said piston is adapted to be fitted
within said annular space portion of said partition member so as to keep
said piston spaced from a lower surface of said partition member when said
upper distal end of said spacer substantially abuts against said lower
surface of said partition member.
4. A hydraulic shock absorber according to claim 3, wherein:
an axial span is defined between a lower end portion of said outer tube and
a portion of said inner tube adjacent said spacer member when said upper
distal end of said spacer substantially abuts against said lower surface
of said partition member; and
said partition member with said orifice is substantially centrally disposed
between said piston and said spacer member when said upper distal end of
said spacer substantially abuts against said lower surface of said
partition member, to prevent deformation of the shape of said orifice
around said tapered rod.
5. A hydraulic shock absorber according to claim 1, wherein:
said upper portion of said outer tube is provided with means for protecting
said partition membrane from deformation when said partition membrane is
compressed against said outer tube.
6. A hydraulic shock absorber according to claim 5, wherein:
said means for protecting said partition membrane comprises a metal mesh or
network substantially enclosing said upper portion of said outer tube
having said apertures, said metal mesh or network preventing entry of said
partition membrane into said apertures.
7. A hydraulic shock absorber according to claim 5 or 6, wherein:
said means for protecting said partition membrane comprises a plurality of
substantially elongated projections mounted on said upper portion of said
outer tube so as to be out of alignment with said apertures, to prevent
wrinkling of said partition membrane when said partition membrane is
compressed against said outer tube.
8. A hydraulic shock absorber according to claim 5 or 6, wherein:
said means for protecting said partition membrane comprises a plurality of
substantially elongated projections mounted on said upper portion of said
outer tube so as to be out of alignment with said apertures, to prevent
wrinkling of said partition membrane when said partition membrane is
compressed against said outer tube; and
each said projection has a tapered contour, with the thickness thereof
decreasing from the upper to the lower end thereof.
9. A hydraulic shock absorber according to claim 1, wherein:
said partition membrane includes a lower end thereof of reduced diameter
sandwiched between an inner peripheral portion of said holder and an outer
peripheral portion of said outer tube;
a cap is disposed on said outer tube; and
said partition membrane further includes an upper end thereof sandwiched
between said cap disposed on said outer tube and said holder.
10. A hydraulic shock absorber according to claim 1, wherein:
said high-pressure chamber is connected to a separate chamber;
said high-pressure chamber and said separate chamber is filled with a
medium which is normally in both gas and liquid phases; and
the volume of said separate chamber is adjustable.
11. A hydraulic shock absorber according to claim 1, wherein:
said rod includes an enlarged base portion fitted in a base portion of said
outer tube;
said enlarged portion is supported on said base portion of said outer tube
by engagement means; and
said rod is slightly movable between said rod base portion and said outer
tube base portion.
12. A hydraulic shock absorber according to claim 11, wherein:
said enlarged portion includes a lower inclined surface including a
partially spherical surface.
13. A hydraulic shock absorber according to claim 11, wherein:
said enlarged portion is substantially spherical in shape.
14. A hydraulic shock absorber according to claim 11, wherein:
said rod base comprises a threaded portion and a nut threadedly disposed
therearound;
a cap is disposed on said outer tube;
said nut has a lower end engaged with said cap on said outer tube; and
said threaded portion includes an upper end projecting beyond an upper
surface of said nut into contact with a bottom of said cap.
15. A hydraulic shock absorber for vehicles, comprising:
an inner tube and an outer tube, said inner and outer tubes being
telescopically fitted together;
a tapered rod supported by said outer tube and extending vertically and
axially therefrom;
said inner tube including a partition member having a hole through which
said tapered rod substantially loosely extends;
an orifice annularly defined between said rod and said hole and variable in
response to relative movement of said rod and hole;
a piston provided on the distal end of said rod;
said piston being provided with a valve adapted to open when said tubes
relatively move in one direction and adapted to operate to gain a damping
force when said tubes relatively move in the opposite direction;
a tubular holder coaxially disposed around an upper outer peripheral
portion of said outer tube and having a diameter larger than the diameter
of said outer tube;
a partition membrane substantially vertically disposed between said holder
and said outer tube and mounted substantially coaxially therewith, said
partition membrane being fabricated of a substantially flexible and
resilient material and being disposed so as to divide a space defined
between said holder and said outer tube into a high-pressure gas chamber
outside of said membrane and a low-pressure gas chamber inside of said
membrane;
an upper portion of said outer tube being provided with a number of
apertures through which said low-pressure chamber communicates with an
upper space within said outer tube; and
said upper portion of said outer tube being provided with a metal mesh or
network substantially enclosing said upper portion of said outer tube
having said apertures, said metal mesh or network preventing entry of said
partition membrane into said apertures.
16. A hydraulic shock absorber for vehicles, comprising:
an inner tube and an outer tube, said inner and outer tubes being
telescopically fitted together;
a tapered rod supported by said outer tube and extending vertically and
axially therefrom;
said inner tube including a partition member having a hole through which
said tapered rod substantially loosely extends;
an orifice annularly defined between said rod and said hole and variable in
response to relative movement of said rod and hole;
a piston provided on the distal end of said rod;
said piston being provided with a valve adapted to open when said tubes
relatively move in one direction and adapted to operate to gain a damping
force when said tubes relatively move in the opposite direction;
a tubular holder coaxially disposed around an upper outer peripheral
portion of said outer tube and having a diameter larger than the diameter
of said outer tube;
a partition membrane substantially vertically disposed between said holder
and said outer tube and mounted substantially coaxially therewith, said
partition membrane being fabricated of a substantially flexible and
resilient material and being disposed so as to divide a space defined
between said holder and said outer tube into a high-pressure gas chamber
outside of said membrane and a low-pressure gas chamber inside of said
membrane;
an upper portion of said outer tube being provided with a number of
apertures through which said low-pressure chamber communicates with an
upper space within said outer tube; and
said upper portion of said outer tube being provided with a plurality of
substantially elongated projections mounted on said upper portion of said
outer tube so as to be out of alignment with said apertures, to prevent
wrinkling of said partition membrane when said partition membrane is
compressed against said outer tube.
17. A hydraulic shock absorber according to claim 16, wherein:
each said projection has a tapered contour, with the thickness thereof
decreasing from the upper to the lower end thereof. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a hydraulically and
pneumatically operated shock absorber for vehicles.
2. Description of the Prior Art
Hydraulic shock absorbers which are widely used comprise a hydraulic damper
and a spring operatively combined therewith. Such prior shock absorbers
provided with a spring provide a dampening characteristic which is
commensurate with an applied force, and have a property not suitable for
vehicles of certain types. By including a spring, the diameter of the
shock absorbers must be enlarged and the size thereof made greater than
would otherwise be necessary. Further, the shock absorbers are heavy due
to addition of the spring and associated parts, and are complicated in
structure. An additional problem with the shock absorbers described above
is that spring-loading adjustment is relatively difficult, thereby
producing irregularly spring-loaded shock absorber products.
There has been proposed a hydraulically and pneumatically operated shock
absorber which utilizes a pneumatic spring. The shock absorber of this
type solves the above-mentioned difficulties in that it maintains an
increased degree of response during the compression stroke and is
hydraulically controlled to produce a large dampening force while in the
extension stroke. The pneumatic spring type of shock absorber is
especially suitable for automobiles for use on roads with many holes and
bumps, requiring shock absorbers which have a long compression stroke and
rapid responsiveness.
The hydraulically and pneumatically operated shock absorber includes an air
chamber and a fluid chamber which are generally divided by a free piston.
Such partitioning, however, results in difficulty in sealing between the
chambers, and the piston itself is not smoothly and reliably slidable.
Various efforts have been made to eliminate the above-discussed defects. As
a result, different types of flexible and resilient members have been
proposed for use as a partition between the air and fluid chambers. One
such type comprises a disc-shaped flexible partition member which
separates a compartment in an upper portion of the shock absorber body
into upper and lower parts. With this type of partition member, however,
the shock absorber becomes greater in overall length and larger in size.
In addition, attachment and centering of the flexible partition member
involves complex processes. Another type of partition member is composed
of a similar disc-shaped flexible separator which is vertically arranged
as a partition for a chamber mounted on a side of the shock absorber body.
This latter type causes the structure of the shock absorber to be
relatively complicated and large-sized. Further, it suffers from the same
problems as the former type in connection with attachment and centering.
Another type of hydraulic and pneumatic shock absorber comprises inner and
outer telescoping tubes, the inner tube having at its one end a partition
member having an orifice and the outer tube being equipped with a tapered
rod with a piston fixed thereto having an orifice. The fluid can be forced
to pass through one of the orifices during either the compression or the
extension stroke, the orifice with which the rod interferes being variable
by relative movement of the inner and outer tubes. One of the problems
attendant such shock absorber is that when the shock absorber is subjected
to lateral bending forces while it is at the end of the extension stroke
with the piston in abutment against the partition member and with the
sliding parts of the inner and outer tubes becoming closer to each other,
the cross-sectional shape of a clearance defined between the rod and the
orifice wall becomes irregular. Thus, oil is caused to flow irregularly
through the deformed cross-sectional shape of the orifice on the
compression stroke, with the consequence that the shock absorber will not
function properly. This difficulty also arises when the shock absorber is
in the vicinity of the end of the extension stroke. Other problems
include: the rod is frictionally engageable with the orifice wall; and the
piston, rod and inner tube are subjected to stresses, preventing smooth
and reliable shock absorbing operation.
Furthermore, with this latter type of shock absorber, there are three
points of contact; one between upper sliding surfaces of the inner and
outer tubes, one between lower sliding surfaces of the tubes, and one
between sliding surfaces of the inner tube and the piston. Thus, one extra
point of contact is provided as compared with other conventional shock
absorbers. Accordingly, if the parts are made of rigid material, they will
be subjected to severe stresses, especially when side forces in addition
to axial forces are applied to the shock absorbers, thereby impeding
smooth operation. Because the rod is relatively slender, it can be easily
bent when the piston is held by the inner tube with the rod fixedly
supported by the outer tube. At this time, irregular stresses are created
on the sliding surface of the piston, thus preventing the piston from
being able to slide smoothly. Such a condition can cause the rod to be
deformed, and when repeated, may even break a piston supporting portion on
the tube. The service life of the shock absorber may then be shortened,
and the durability thereof lessened.
The present invention provides a shock absorber of improved performance
which eliminates the above discussed various problems attendant the shock
absorbers of the conventional type and of the hydraulic and pneumatic
type.
SUMMARY OF THE INVENTION
The present invention provides a hydraulic shock absorber for vehicles
which includes an inner tube and an outer tube, the inner and outer tubes
being telescopically fitted together. Also included is orifice means
variable in response to relative movement of the inner and outer tubes,
and a piston adapted to produce a damping force in one direction during
relative movement of the tubes. A tubular holder is coaxially disposed
around an upper outer peripheral portion of the outer tube and has a
diameter larger than the diameter of the outer tube. A partition membrane
is substantially vertically disposed between the holder and the outer tube
and is mounted coaxially therewith. The partition membrane is fabricated
of a flexible and resilient material and is disposed so as to divide a
space defined between the holder and the outer tube into a high-pressure
gas chamber outside of the membrane and a low-pressure gas chamber inside
of the membrane. The low-pressure chamber is in communication with an
upper space within the outer tube.
A major object of the present invention is to provide a hydraulically and
pneumatically operated shock absorber for vehicles which comprises an
outer tube and a tubular holder mounted coaxially therewith and
surrounding the outer periphery of the outer tube. A space is provided
between the holder and the tube, the space being divided into inner and
outer portions by a tubular partition membrane of flexible and resilient
material which is concentric with the space. The outer space portion acts
as a high-pressure air chamber, and the inner space portion acts as a
low-pressure air chamber communicating with an upper portion of the tube.
Because the tubular partition membrane is concentrically disposed between
the tube and the tubular holder according to the invention, no centering
is required. The tubular partition membrane is fixed in place with its
upper and lower end portions sandwiched between the tube and the tubular
holder. With such an arrangement, the shock absorber of the hydraulic and
pneumatic type can be readily assembled and is of a simple structure. A
shock absorber of the above-mentioned type having high-pressure and
low-pressure chambers can easily be obtained according to the invention
with a high sealing property because the chambers are defined by the
tubular partition membrane coaxially disposed between the outer tube and
the holder member.
It is another object of the present invention to provide a hydraulic shock
absorber which is small in size, light in weight, and effective in
operation in that there are dual air chambers surrounding the tube. The
shock absorber is shorter, and the air chambers are provided all around
the tube, thereby keeping any increase in the overall diameter to a
minimum and maintaining a sufficient volume for the air chambers.
Still another object of the present invention is to provide a hydraulic
shock absorber having through holes in the tube for communication between
a space inside the partition membrane and the interior of the tube, there
being a network peripherally disposed around the perforated tube to
prevent the partition membrane from being squeezed into the holes, whereby
the longevity and durability of the partition membrane can be increased.
A still further object of the present invention is to provide a hydraulic
shock absorber having an outer high-pressure chamber bounded by a
partition membrane and containing a medium capable of both gas and liquid
phases, to which is connected a separate adjustment chamber containing the
medium. Latent heat of vaporization of the medium is utilized to take up
heat of friction generated when the inner and outer tubes are slidably
moved, thereby providing improved cooling characteristics for suppressing
an increase in spring force due to heating. Accordingly, the shock
absorber thus constructed is subjected to less changes in its
characteristics due to heat variations, and thus is thermally stable.
Yet a further object of the present invention is to provide a hydraulically
and pneumatically operated shock absorber for vehicles, having a partition
member disposed at a distal end of an inner tube and having an orifice,
through which vertically extends a tapered rod axially mounted on an outer
tube. The orifice is variable by relative movement of the tubes. The rod
has on its free end a piston having a first spacer which keeps the piston
spaced from the partition member when they abut against each other. The
inner tube has on its distal end an integral second spacer member disposed
on the partition member, and the second spacer member has around its outer
periphery a sliding portion against the inner wall of the outer tube. The
partition member with the orifice is adapted to be disposed between the
piston and the second spacer member when the tubes are at the end of the
extension stroke.
With such construction, the axial span of the sliding portions of the inner
and outer tubes at the end of the extension stroke is made sufficiently
large for stable interference between the orifice and the rod. Even when
the shock absorber is subjected to a bending force, the orifice is
normally functionally maintained and the cross section formed between the
rod and the orifice wall is constantly maintained to prevent the rod from
interfering with the orifice wall so as to permit smooth flow of oil
therethrough. Therefore, the shock absorber is reliably and normally
actuatable with smooth movement of the piston and other moving parts.
These advantages can be obtained with a simple structure which includes a
skirt-like spacer on the piston and a spacer member on the partition
member.
A still further object of the present invention is to provide a shock
absorber of the type described above in which the spacer member acts as
means for holding a bubble breaker and suppressor of metal mesh or metal
fiber. In this manner, the flow of air bubbles into the orifice is
effectively prevented, the damping force is reduced, and air is trapped.
Still another object of the invention is to provide a hydraulic shock
absorber having an enlarged portion on the proximal end of the rod, the
enlarged portion being supported by engaging means on a base portion of
the tube so as to permit the rod to move slightly. With such an
arrangement, when the shock absorber is subjected to a lateral bending
force, the supported end of the rod is shifted in response to such forces,
thereby preventing generation of stresses between the piston and the tube
and thus minimizing friction caused thereby. Accordingly, the piston and
the tube are smoothly slidable on each other. The rod is thus protected
from excessive bending force and internal stresses.
A further object of the invention is to provide a simply constructed
hydraulic shock absorber for vehicles having a rod-mounting structure
which permits the shock absorber to be actuated smoothly and reliably and
has a long service life and an increased degree of durability for stable
operation over an extended period of time.
The invention will now be described in detail by way of example with
reference to the accompanying drawings. Other objects and advantages will
become apparent from the following description.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a vertical cross-sectional view of a hydraulic shock absorber
constructed in accordance with the present invention.
FIG. 2 is an enlarged cross-sectional view, with portions omitted, taken
along line 2--2 of FIG. 1.
FIG. 3 is an enlarged cross-sectional view, with portions omitted, taken
along line 3--3 of FIG. 1.
FIG. 4 is a view illustrating a modification according to the invention.
FIG. 5 is an enlarged fragmentary cross-sectional view of the shock
absorber at the end of the extension stroke.
FIG. 6 is a cross-sectional view taken along line 6--6 of FIG. 5.
FIG. 7 is an enlarged fragmentary view showing an embodiment of a rod
attachment structure according to the invention.
FIG. 8 is a view similar to FIG. 7, showing another embodiment of the
invention.
FIG. 9 is a view similar to FIGS. 7 and 8, of yet another embodiment
according to the invention.
DETAILED DESCRIPTION
With reference to FIG. 1, there is shown a hydraulic shock absorber 10
according to the present invention. The shock absorber 10 comprises inner
and outer tubes 11, 41 respectively, telescopically fitted together. The
inner tube 11 is disposed substantially downwardly of outer tube 41 which
is fitted over inner tube 11. The lower end of inner tube 11 is closed off
by a bottom plug 12 from which integrally extends a mounting portion 13
for attachment to a vehicle body. The bottom plug 12 is threaded at 15
into the lower end of the tube 11 with a sealing member 14 interposed
therebetween.
The inner tube 11 has at the upper portion thereof a partition member 20
having a central circular opening 21 provided therethrough. As shown in
FIG. 2, the partition member 20 is ring-shaped and has a flange 22 having
at its outer periphery an externally threaded portion engaging at 16 (FIG.
1) with an internally threaded portion of an inner periphery of the upper
portion of inner tube 11. Partition member 20 is provided with an annular
ring 23 projecting downwardly, there being an annular space 24 between the
outer periphery of ring 23 and the inner wall 17 of inner tube 11, with
annular space 24 opening downwardly. A sealing member 25 is located at a
proximal end of ring 23. An annular orifice 26 is defined by joining a
rod, described in detail below, in opening 21.
Located upwardly of partition member 20 is a cylindrical spacer 30, with
its lower portion threadedly engaging at 18 with the upper portion of
inner tube 11. Spacer 30 is provided in an intermediate portion thereof
with an annular projection 31 which is substantially equal in outside
diameter to inner tube 11. A sealing member 32 is disposed in an annular
recess above annular projection 31. The spacer 30 includes at its upper
portion a partition 33 having a central hole 34 around which there is
provided an annular recess 35. Partition 33 has a number of small holes 36
extending through the bottom of recess 35. An air bubble suppressor 37 of
metal fiber or metal mesh is disposed in recess 35 for breaking air
bubbles, the suppressor 37 clogging the small holes 36.
Outer tube 41 supports at the top plug 42 thereof a rod 43 disposed
coaxially with tube 41 and projecting downwardly. The rod 43 is of a
tapered configuration with its diameter progressively smaller from the
upper proximal end toward the lower distal end thereof. Rod 43 vertically
extends through the hole 34 and the circular opening 21. The annular
orifice 26 is thus defined between the circumference of rod 43 and the
wall of circular opening 21, the cross section of orifice 26 being
variable by relative movement of rod 43 and opening 21. The rod 43 has at
its upper end an enlarged portion 44 located above plug 42, and extends
from just below the enlarged portion 44 through a central hole 45 in plug
42, whereby rod 43 is supported in place. The plug 42 includes an air
passage 46.
The rod 43 is provided on its lower end with a piston 60 secured thereto
and slidably fitted in inner tube 11. The piston 60 is provided with a
skirt-shaped spacer 62 which is annular and projects upwardly from a
peripheral portion of a bottom 61 of piston 60. The spacer 62 has an upper
distal end adapted to be fitted in annular space 24 opening downwardly
from partition member 20. The bottom 61 of piston 60 which extends
transversely of inner tube 11 has a plurality of orifices 63, 64 extending
therethrough and angularly spaced from each other. Orifices 63 are located
on an inner imaginary circle concentric with piston 60, and orifices 64
are located on an outer imaginary circle concentric with piston 60. The
orifices 63 are angularly spaced at equal intervals and are four in number
in the illustrated embodiment, and orifices 64 (also four in number) are
disposed intermediately of orifices 63. A slide valve 65 fitted over a
lower portion of rod 43 is disposed on piston 60, and is urged against an
upper surface of bottom 61 of piston 60 by a spring 67 interposed between
an upper surface of valve 65 and a spring seat 66 mounted on a lower
portion of rod 43. The outside diameter of valve 65 is such that valve 65
interferes with substantially half areas of outer orifices 64 to thereby
limit or reduce the opening thereof. At the same time, valve 65 closes the
inner orifices 63. A sealing member 68 is disposed around piston 60.
A cap 47 covering plug 42 of outer tube 41 is provided with an internal
mounting portion 48 for attachment to a vehicle body, and is of a larger
outside diameter than the outside diameter of outer tube 41, thereby
providing a flange 49. Flange 49 has an annular projection 50 extending
downwardly from a lower surface of flange 49, the annular projection 50
fitting over an upper end portion of outer tube 41. The cap 47 is provided
with an air introduction valve 51 and a passageway 52 communicating with
passage 46 in plug 42.
Disposed around the outer periphery of outer tube 41 is a tubular holder 70
having a much larger diameter than the diameter of outer tube 41. Holder
70 has an upper open end 71 fitted over and threadedly engaging with an
outer peripheral portion of projection 50 of cap 47. The body 72 of holder
70 is of substantially uniform diameter throughout its length, and the
lower end portion 73 thereof is tapered downwardly and threadedly engages
with an externally threaded portion 53 of an intermediate portion of outer
tube 41. Disposed below the threaded portion 53 of outer tube 41 is an
annular projection 54 supporting thereon a lower end of holder 70. Thus,
holder 70 is connected coaxially with outer tube 41, there being an
annular space A defined between an upper portion of holder 70 and outer
tube 41.
The space A is divided into an outer chamber B and an inner chamber C by a
partition membrane 80 made of a flexible and resilient material such as
rubber. Partition membrane 80 is a tapered hollow cylinder in shape with
its diameter being progressively smaller from its upper and central
portion toward its lower portion. The partition membrane 80 has at its
upper and lower ends thickened annular ribs 81, 82, respectively.
Partition membrane 80 is secured in place by inserting it from above
between the upper portion of outer tube 41 and holder 70, and then
sandwiching upper rib 81 between upper end portion 71 of holder 70 and
projection 50, and sandwiching lower rib 82 between an area above threaded
portion 53 of outer tube 41 and an inner peripheral wall of a lowest
portion 73 of holder 70. More specifically, holder 70 is fitted over outer
tube 41 from above and is threadedly mounted in position at its lower end,
and the cylindrical partition membrane 80 is inserted while holder 70 and
outer tube 41 are being connected at their upper ends by cap 47 threaded
in place. The partition membrane 80 can thus be attached concentrically
during such assembling process without requiring centering adjustment.
When the upper and lower ribs are sandwiched between holder 70 and outer
tube 41, partition membrane 80 provides air-tight sealing between chambers
B and C.
A valve 74 is mounted on the lowest portion 73 of holder 70 for supplying
high-pressure gas into the outer chamber B defined by partition membrane
80.
An upper portion of outer tube 41 is provided with a number of apertures 55
of a relatively large diameter through which the inner chamber C, bounded
by partition membrane 80, communicates with an upper chamber D in outer
tube 41. The upper portion of tube 41 including the apertures 55 is
enclosed by a mesh or network 56 of metal for preventing forced entry of
partition membrane 80 into apertures 55.
Inner and outer tubes 11, 41 are supplied with a sealed amount of oil.
Inner chamber C and upper chamber D communicating therewith are loaded
with a sealed amount of low-pressure gas, and outer chamber B is loaded
with a sealed amount of high-pressure gas.
When shock absorber 10 is in the compression stroke, slide valve 65 on
piston 60 is lifted to open all of orifices 63, 64 in piston 60 for
allowing full communication between a chamber E below piston 60 and a
central chamber F above piston 60. Oil flow is restricted and controlled
by annular orifice 26 is partition member 20 above central chamber F,
thereby generating a damping force during the compression stroke. Orifice
26 is variable because its cross-sectional area is reduced as inner tube
11 is raised over tapered rod 43 during the compression stroke.
During the compression stroke, the low-pressure chamber D, C becomes
decreased in volume by an increasing amount of oil in a chamber G above
partition member 20. As the pressure in chambers D, C builds up, the
partition membrane 80 is bulged outwardly, thereby reducing the volume of
high-pressure chamber B. Such action is performed rapidly with preselected
pressures in the high-pressure and low-pressure chambers, whereby rapid
responsiveness can be assured during the compression stroke. When the
tubes have moved a predetermined stroke, reduction of the volume of
high-pressure chamber B is discontinued, whereupon a damping force is
increased.
During the extension stroke, slide valve 65 fully closes inner orifices 63
in piston 60 and half closes outer orifices 64, to thereby reduce the area
of orifices 64 and thus restrict the oil flow therethrough. Accordingly, a
damping force is increased during the extension stroke.
In the above described manner, a desired amount of damping force can be
obtained by the variable orifice 26 in partition member 20 on the
compression stroke, and by orifices 64 in piston 60 on the extension
stroke. Because the variable orifice produces a damping force during the
compression stroke, the amount of damping force depends on the relative
positions of tubes 11 and 41. The variable orifice 26 also provides the
same function during the extension stroke, provided that the
cross-sectional area of variable orifice 26 is equal to or smaller than
the cross-sectional area of orifices 64 controlled by slide valve 65.
During the extension stroke, the volume of chambers C, D increases, and the
pressure in chamber B causes partition membrane 80 to adhere to outer tube
41 having apertures 55. Partition membrane 80 is prevented by metal mesh
56 from intruding into apertures 55, and is thus protected against damage.
Even if partition membrane 80 is damaged, bubbles are substantially
prevented from entering the oil because chambers B, C and D are located
upwardly. The bubbles, as introduced into the oil, are broken up by bubble
breaker or suppressor 37 so that temporary removal of a damping force,
which would otherwise be caused by large bubbles, is prevented. Bubble
suppressor 37 can function when bubbles enter the oil during reciprocating
movement of inner and outer tubes 11 and 41. With bubble suppressor 37
being located on the side of the gas chambers and over orifice 26, large
bubbles are prevented from passing through orifice 26 so that smooth
operation of the shock absorber is ensured.
When piston 60 is raised on the extension stroke, oil forcibly flows
upwardly through orifice 26, or during the compression stroke, oil flows
up and down to create air bubbles due to such oil disturbances and
movements of the shock absorber. Such air bubbles, however, are broken up
by bubble suppressor 37 and are suppressed to such an extent that the
hydraulic damping action will not be adversely affected.
When inner and outer tubes 11, 41 of absorber 10 are at the end of the
extension stroke, the distal end of skirt-shaped spacer 62 of piston 60
enters into space 24 below partition member 20 and abuts against sealing
member 25 so as to be located in place. At this time, partition member 20
with orifice 26 is disposed centrally between piston 60 and spacer 30.
Accordingly, at the end of the extension stroke, an axial span l is
provided between a sliding portion a on a lower end portion of outer tube
41 and a sliding portion b on inner tube 11 adja | | |
