Inverted strut damper

An inverted strut damper includes an external cylinder which has an expanded midsection and a vertically moveable damper tube arranged concentrically within the outer cylinder. The outer cylinder and tube arrangement form a lubricating oil supply reservoir. Disposed at a top and a bottom of the outer cylinder is a respective oil seal and bearing arrangement. The upper bearing is adjacent to the lubricating oil reservoir and upon upper movement of the damper tube, oil is supplied to the upper bearings and seal.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an inverted strut damper. 
2. Discussion of the Background Art 
Conventionally, an inverted strut damper is a structure having a damper 
tube fitted movably upwards and downwards through upper and lower oil 
seals and upper and lower bearings in an outer cylinder, for lubricating 
the upper and the lower oil seals and the upper and lower bearings with 
oil. 
In Japanese Patent Application No. 8-227211, the applicant of the present 
invention has previously proposed a technique for improving lubrication of 
the upper bearings and the upper oil seals by filling a lubricating 
chamber storing oil to the full by putting a hollow elastic substance in 
the lubricating chamber. This technique will be explained below with 
reference to a drawing of this application. 
FIG. 7, labeled "PRIOR ART", is an enlarged diagram of an upper section of 
an outer cylinder for a conventional inverted strut damper. This diagram 
shows that an upper oil seal 102 is provided on the top end of an inner 
plane of an erected outer cylinder 101 of an inverted strut damper 100. 
Upper bearings 103 are fitted beneath this upper oil seal 102, lower 
bearings 104 are fitted in the middle of the inner plane of the outer 
cylinder 101, a lower oil seal 105 is fitted beneath the lower bearings 
104. A damper tube 106 is inserted movably upwards and downwards between 
these upper and lower oil seals 102 and 105 and upper and lower bearings 
103 and 104, and a space formed by encircling it with the upper and lower 
oil seals 102 and 105, and the outer cylinder 101. The damper tube 106 is 
used as a lubricating chamber 107 for lubricating the upper and lower oil 
seals 102 and 105 and the upper and lower bearings 103 and 104. 
A reference number 108 denotes a porous elastic substance and 109 denotes a 
distance collar. 
The volume of the oil within the lubricating chamber 107 gradually 
decreases along with its use over a long period of time, so that the upper 
oil seal 102 and the upper bearings 103 lose their oil impregnation. 
However, by the upward and downward movement of the damper tube 106, the 
oil adhered to the outer plane of the damper tube 106 is supplied to the 
upper oil seal 102 and the upper bearings 103 to lubricate the upper oil 
seal 102 and the upper bearings 103 without problem. 
Although it is always possible to lubricate the upper oil seal 102 and the 
upper bearings 103 as described above, a further improvement in 
lubrication is desired under severer lubricating conditions required for 
the bearings and the oil seals due to the increase in piston speed along 
with the higher speed of vehicles that occurred in recent years. 
The lower bearings 104 and the lower oil seal 105 can be fitted in a simple 
manner since they can be inserted without pressuring. However, since there 
is a long distance of the same diameter of the outer cylinder 101 from its 
upper end to the positions where the lower bearings 104 and the lower oil 
seal 105 are fitted, a further improvement in their fitting by shortening 
this distance is also desired. 
SUMMARY OF THE INVENTION 
It is, therefore, an object of the present invention to provide an inverted 
strut damper with an improved lubrication of the upper bearings and the 
upper oil seal and also with an improved fitting of the lower bearings and 
the lower oil seal. 
To achieve the above-mentioned object in the invention, there is provided 
an inverted strut damper having an upper oil seal fitted to an upper end 
of an inner plane of an erected external cylinder, having upper bearings 
fitted beneath thereof, having lower bearings in the middle of said inner 
plane of said outer cylinder, having a lower oil seal fitted beneath 
thereof, having a damper tube inserted movably upwards and downwards 
between said upper and lower oil seals and said upper and lower bearings, 
and having a space formed by encircling it with said upper and lower oil 
seals, with said outer cylinder and with said damper tube used as a 
lubricating oil chamber for lubricating said upper and lower oil seals and 
said upper and lower bearings, wherein a lubricating oil-impregnated 
member for enabling a lubricating oil to be supplied to said upper 
bearings and to said upper oil seal is fitted to a lower plane of said 
upper bearings. 
Moreover, there is provided an inverted strut damper having an upper oil 
seal fitted to an upper end of an inner plane of an erected external 
cylinder, having upper bearings fitted beneath thereof, having lower 
bearings in the middle of said inner plane of said outer cylinder, having 
a lower oil seal fitted beneath thereof, having a damper tube inserted 
movably upwards and downwards between said upper and lower oil seals and 
said upper and lower bearings, and having a space formed by encircling it 
with said upper and lower oil seals, with said outer cylinder and with 
said damper tube used as a lubricating oil chamber for lubricating said 
upper and lower oil seals and said upper and lower bearings. O-rings for 
guiding an oil within said lubricating oil chamber to the vicinity of said 
upper bearings by pushing up said oil, are provided in said damper tube. 
Furthermore, there is provided an inverted strut damper having an upper oil 
seal fitted to an upper end of an inner plane of an erected external 
cylinder, having upper bearings fitted beneath thereof, having lower 
bearings in the middle of said inner plane of said outer cylinder, having 
a lower oil seal fitted beneath thereof, having a damper tube inserted 
movably upwards and downwards between said upper and lower oil seals and 
said upper and lower bearings, and having a space formed by encircling it 
with said upper and lower oil seals, with said outer cylinder and with 
said damper tube used as a lubricating oil chamber for lubricating said 
upper and lower oil seals and said upper and lower bearings. A hollow or 
porous elastic substance is accommodated within said lubricating oil 
chamber, and when said lubricating oil filled in said lubricating oil 
chamber has been expanded due to a variation in temperature, said 
expansion is absorbed by a contraction of said hollow elastic substance 
and when said lubricating oil has been contracted, said hollow elastic 
substance is expanded. 
Moreover, there is provided an inverted strut damper having an upper oil 
seal fitted to an upper end of an inner plane of an erected external 
cylinder, having upper bearings fitted beneath thereof, having lower 
bearings in the middle of said inner plane of said outer cylinder, having 
a lower oil seal fitted beneath thereof, having a damper tube inserted 
movably upwards and downwards between said upper and lower oil seals and 
said upper and lower bearings, and having a space formed by encircling it 
with said upper and lower oil seals, with said outer cylinder and with 
said damper tube used as a lubricating oil chamber for lubricating said 
upper and lower oil seals and said upper and lower bearings, wherein a 
large diameter section is formed by expanding said outer cylinder between 
said upper bearings and said lower bearings. A spring sheet for supporting 
a suspension spring is welded on an outer plane of said larger diameter 
section, and said upper and lower bearings are fitted to said outer 
cylinder by insertion.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Modes of implementation of the present invention will be explained below 
based on the attached drawings. 
FIG. 1 is a cross sectional diagram of an inverted strut damper relating to 
the present invention when the strut damper is extended. An inverted strut 
damper 1 has a damper tube 4 inserted as an inner cylinder movably upwards 
and downwards into an outer cylinder 3 equipped with a fitting bracket 2 
(generally referred to as a strut tube). A damper piston 5 is included 
inside the damper tube 4. The damper piston 5 is fixed to a bottom section 
7 of the outer cylinder 3 through a rod 6. A bumping rubber 8 and a dust 
preventing boot 9 are fitted to face downward at the upper section of the 
damper tube 4, and a suspension spring 13 is fitted between an upper 
spring sheet 11 provided at the upper end of the damper tube 4 and a lower 
spring sheet 12 provided on the outer plane of the outer cylinder 3. 
A reference number 15 denotes a rod guide, 16 an oil seal, 17 an oil seal 
stopper, and 18 a mounting bracket. 
The basic operation of the above-described inverted strut damper 1 is 
explained below. 
Referring to FIG. 1, an upper first chamber 21 of the damper piston 5 is 
filled with a gas 23 in its upper section and a working oil 24 in its 
lower section. A lower second chamber 22 of the damper piston 5 is filled 
with a working oil 25 to the full. (The working oil 25 is the same oil as 
the working oil 24, and these reference numbers are different to 
discriminate their positions.) 
When a press-down force is applied relative to the damper tube 4, a part of 
the working oil 24 in the first chamber 21 starts moving toward the second 
chamber 22 through an orifice of the damper piston 5, so that a damping 
force is generated. 
FIG. 2 is a cross sectional diagram for showing the inverted strut damper 
relating to the present invention when the strut damper is compressed. 
This shows that the height position of the damper piston 5 remains 
unchanged but the damper tube 4 has been fully pressed down. In this case, 
an increase in the volume of the rod 6 moving into the second chamber 22 
is absorbed by a contraction of the gas 23 in the upper section of the 
first chamber 21 by being compressed. 
FIG. 3 is an enlarged diagram of the upper section of the outer cylinder 
relating to the present invention. This shows that a large diameter 
section 31 is formed by expanding the diameter of the upper section of the 
outer cylinder 3. An upper oil seal 32 is fitted at the upper end of an 
inner plane of the outer cylinder 3 at the upper side of this large 
diameter section 31. Upper bearings 33 are fitted beneath this upper oil 
seal 32. Lower bearings 34 are fitted on the inner plane of the outer 
cylinder 3 at the lower side of the large diameter section 31. A lower oil 
seal 35 is fitted beneath the lower bearings 34. A damp tube 4 is inserted 
movably upwards and downwards between the upper and lower oil seals 32 and 
35 and the upper and lower bearings 33 and 34. A space formed by the upper 
and lower oil seals 32 and 35, the outer cylinder 3 and the damper tube 4 
is used as a lubricating oil chamber 36 for lubricating the upper and 
lower oil seals 32 and 35 and the upper and lower bearings 33 and 34. 
Further, FIG. 3 also shows that a stopper collar 37 is fixed on the inner 
plane of the outer cylinder 3 by compressing or locally recessing the 
outer cylinder 3. The lower oil seal 35 is applied to the upper section of 
this stopper collar 37. The lower bearings 34 are fitted to the lower oil 
seal 35. The upper bearings 33 are fitted to the upper oil seal 32. A 
distance collar 38 is provided between the upper and lower bearings 33 and 
34, and a lubricating oil-impregnated material 41 attached to the upper 
bearings 34. O-rings 42 engaged on the outer plane of the damper tube 4 
and a hollow or porous elastic substance 43 provided at the lower section 
are accommodated within the lubricating oil chamber 36. 
In the outer cylinder 3, when the inner diameter of a position where the 
upper oil seal 32 and the upper bearings 33 are fitted is expressed as D1, 
the inner diameter of the large diameter section 31 is expressed as D2 and 
the inner diameter of a position where the lower bearings 34 and the lower 
oil seal 35 are fitted is expressed as D3, there is a relationship of 
D2&gt;D1=D3. 
The upper bearings 33 are provided by engaging a bearing body 33b in a 
housing 33a. The lower bearings 34 are also provided by engaging a bearing 
body 34b in a housing 34a. 
The outer diameters of the upper bearings 33 and the lower bearings 34 and 
the outer diameters of the upper oil seal 32 and the lower oil seal 35 are 
the same and common respectively. 
The lubricating oil chamber 36 is a sealed space, and in principle, the 
lubricating oil is filled to the full at the time of assembling. The 
volume of the lubricating oil changes according to a temperature change. 
When the lubricating oil has expanded, the hollow or porous elastic 
substance 43 is compressed to absorb the expansion, and when the 
lubricating oil has been compressed, the hollow or porous elastic 
substance 43 is expanded. Accordingly, it is possible to fill the 
lubricating oil to the full. As a result, the upper oil seal 32 and the 
upper bearings 33 can be soaked with lubricating oil to enable a 
satisfactory lubrication. 
The stopper collar 37 is a member for stopping the lower bearings 34 from 
dropping, and this is a thin panel cylinder according to the present 
example. 
The distance collar 38 is a member for restricting the upper bearings 33 
from dropping and the lower bearings 34 from rising. In the present 
example, the distance collar 38 is a material having a thin-panel 
two-stage cylinder with a small diameter at its lower section and having a 
ring-shaped inward-facing projection 38a for restricting the lubricating 
oil-impregnated material 41 from dropping at the upper section. 
The lubricating oil impregnated-material 41 is a material impregnated with 
oil and for supplying this oil to the upper bearings 33 and the upper oil 
seal 32 to promote the lubrication of the upper bearings 33 and the upper 
oil seal 32. For example, a felt formed in a ring shape (generally called 
a felt ring) is suitable for the lubricating oil impregnated-material 41. 
The O-rings 42 move integrally with the damper tube 4 when moving in the 
oil within the lubricating oil chamber 36 and can move relatively together 
with the damper tube 4 when a mechanical external force is applied. 
With the above-described structure, when the damper tube 4 has moved 
upwards, the O-rings 42 push up the oil to supply the upper bearings 33 
and the upper oil seal 32. The drawing shows a state wherein the O-rings 
42 are in contact with the inward-facing projection section 38a of the 
distance collar 38 after the damper tube 4 has moved upwards. After the 
damper tube 4 has moved downwards, the O-rings 42 are brought into contact 
with the upper portion of the bent section 38b of the distance collar 38 
as shown by a phantom line. 
A movement volume L of the O-rings 42 is smaller than a stroke quantity of 
the inverted strut damper 1. In other words, when the damper tube 4 has 
moved upwards, the O-rings 42 at first move integrally with the damper 
tube 4, but when the O-rings 42 have brought into contact with the 
inward-facing projection section 38a of the distance collar 38, the 
O-rings 42 slide on the outer plane of the damper tube 4. When the damper 
tube 4 has moved downwards, the O-rings 42 at first move integrally with 
the damper tube 4, but when the O-rings 42 are brought into contact with 
the bent section 38b of the distance collar 38, the O-rings 42 slide on 
the outer plane of the damper tube 4. 
With the above-described arrangement, it becomes possible to make larger 
the stroke of the inverted strut damper 1 or to make smaller the overall 
length of the outer cylinder 3. 
The hollow or porous elastic substance 43 is an elastic material including 
one or a plurality of hollows 43a not communicating to the outside. An 
independent foamed elastic material or an urethane rubber or a foamed 
resin covered with a thin rubber or resin, for example, is suitable for 
the hollow elastic substance 43. 
The operation of the above-described inverted strut damper is explained 
next. 
FIGS. 4A to 4C are cross sectional diagrams for showing the operation of 
the inverted strut damper relating to the present invention; FIG. 4A shows 
a state wherein the O-rings are in the oil, FIG. 4B shows a state wherein 
the O-rings are out of the oil, and FIG. 4C shows a state wherein the 
O-rings reached the lower portion of the lubricating oil-impregnated 
member. 
Referring to FIG. 4A, when the damper tube 4 has moved upwards, the O-rings 
42 positioned at the outer plane of the damper tube 4 and the oil adhered 
to the outer plane of the damper tube 4 rise together with the damper tube 
4. 
In FIG. 4B, the O-rings 42 push up oil F by which it is surrounded. 
In FIG. 4C, when the damper tube 4 continues the rise, the O-rings 42 are 
brought into contact with the inward-facing projection section 38a of the 
distance collar 38 and supply oil F to the lubricating oil-impregnated 
material 41. 
In the manner as described above, the lubricating oil-impregnated material 
41 can include oil F and can supply oil F to the upper bearings 33 and the 
upper oil seal 32 even after the O-rings 42 have dropped. 
FIGS. 5A to 5C are cross sectional diagrams for showing an example of a 
modification of the inverted strut damper relating to the present 
invention, which have the same structure as embodiment shown in FIG. 3 
except the O-rings are excluded from the embodiment. The same structural 
elements as those in FIG. 3 are identified by the same reference numbers 
so the detailed description will be omitted. 
FIG. 5A shows a state wherein the damper tube has stopped, FIG. 5B shows a 
state where the damper tube has move upwards, and FIG. 5C shows a state 
where the damper tube has stopped after having moved upward. 
In FIG. 5A, in the state where the damper tube 4 is stationary, the oil F 
stays within the lubricating oil chamber 36. 
In FIG. 5B, when the damper tube 4 has moved upward, the oil F adheres to 
the outer plane of the damper tube 4 and the oil F passes up and is 
supplied to the lubricating oil-impregnated material 41. 
In FIG. 5C, even if the damper tube 4 is stationary, the lubricating 
oil-impregnated material 41 holds oil F. 
In the manner as described above, the lubricating oil-impregnated material 
41 can include the oil F and can supply oil F to the upper bearings 33 and 
the upper oil seal 32 even after the damper tube 4 has become stationary. 
FIGS. 6A to 6C are cross sectional diagrams showing still another 
modification of the inverted strut damper relating to the present 
invention, which has the same structure as that of the mode of the 
embodiment shown in FIG. 3 except that the lubricating oil-impregnated 
material is excluded. The same structural elements as those in FIG. 3 are 
attached and identified by the same reference numbers so their detailed 
explanation will be omitted. 
FIG. 6A shows a state wherein the O-rings are in the oil, FIG. 6B shows a 
state where the O-rings are out of the oil and FIG. 6C shows a state where 
the damper tube is stationary. 
Referring to FIG. 6A, in the state where the damper tube 4 is stationary, 
the oil F stays within the lubricating oil chamber 36. 
Referring to FIG. 6B, where the damper tube 4 has moved upward, the O-ring 
42 passes out of the oil F and pushes oil upward. 
FIG. 6C shows a state wherein after the damper tube 4 continued the upward 
movement and the O-rings 42 are brought into contact with the lower 
portion of the upper bearings 33 to supply the uplifted oil F to the upper 
bearings 33 and the upper oil seal 32, the O-rings 42 are dropped. 
With the above-described structures, the present invention exhibits the 
following effects. 
The inverted strut damper has an upper oil seal fitted to an upper end of 
an inner plane of an erected external cylinder, with upper bearings fitted 
beneath thereof, and lower bearings in the middle of the inner plane of 
the outer cylinder, and a lower oil seal fitted beneath thereof, and a 
damper tube inserted movably upward and downward between the upper and 
lower oil seals and the upper and lower bearings, and having a space 
formed by encircling it with said upper and lower oil seals, with the 
outer cylinder and with the damper tube used as a lubricating oil chamber 
for lubricating the upper and lower oil seals and the upper and lower 
bearings, wherein a lubricating oil-impregnated member for enabling a 
lubricating oil to be supplied to the upper bearings and to the upper oil 
seal is fitted to a lower plane of the upper bearings. Lubrication is 
improved because the lubricating oil can always be supplied to the upper 
bearings and the upper oil seal. As a result, since the upper bearings and 
the upper oil seal can maintain a smooth sliding with the damper tube, the 
durability of the inverted strut damper is improved. 
The inverted strut damper has an upper oil seal fitted to an upper end of 
an inner plane of an erected external cylinder, with upper bearings fitted 
beneath thereof, and lower bearings in the middle of the inner plane of 
the outer cylinder, a lower oil seal fitted beneath thereof, and a damper 
tube inserted movably upward and downward between the upper and lower oil 
seals and upper and lower bearings, and a space formed by encircling it 
with the upper and lower oil seals, with the outer cylinder and with the 
damper tube used as a lubricating oil chamber for lubricating the upper 
and lower oil seals and the upper and lower bearings, wherein O-rings for 
guiding oil within the lubricating oil chamber to the vicinity of the 
upper bearings by forcing up the oil are provided in the damper tube. So, 
lubrication is improved because the lubricating oil can always be supplied 
to the upper bearings and the upper oil seal by the low-cost O-rings that 
can be fitted simply. As a result, since the upper bearings and the upper 
oil seal can maintain a smooth sliding with the damper tube, the 
durability of the inverted strut damper is improved. 
The inverted strut damper has an upper oil seal fitted to an upper end of 
an inner plane of an erected external cylinder, and upper bearings fitted 
beneath thereof, and lower bearings in the middle of the inner plane of 
the outer cylinder, and a lower oil seal fitted beneath thereof, and a 
damper tube inserted movably upward and downward between the upper and 
lower oil seals and the upper and lower bearings, and a space formed by 
encircling it with the upper and lower oil seals, with the outer cylinder 
and with the damper tube used as a lubricating oil chamber for lubricating 
the upper and lower oil seals and the upper and lower bearings, wherein a 
hollow elastic substance is accommodated within the lubricating oil 
chamber, and when the lubricating oil in the lubricating oil chamber has 
been expanded due to a variation in temperature, the expansion is absorbed 
by a contraction of the hollow elastic substance and when the lubricating 
oil has been contracted, the hollow elastic substance is expanded. So, the 
lubricating oil can be filled to the full. As a result, the upper oil seal 
and the upper bearings can be soaked with lubricating oil to enable a 
satisfactory lubrication. 
The inverted strut damper has an upper oil seal fitted to an upper end of 
an inner plane of an erected external cylinder, and a upper bearings 
fitted beneath thereof, and lower bearings in the middle of the inner 
plane of the outer cylinder, and a lower oil seal fitted beneath thereof, 
and a damper tube inserted movably upward and downward between the upper 
and lower oil seals and the upper and lower bearings, and has a space 
formed by encircling it with the upper and lower oil seals, with the outer 
cylinder and with the damper tube used as a lubricating oil chamber for 
lubricating the upper and lower oil seals and the upper and lower 
bearings, wherein a large diameter section is formed by expanding said 
outer cylinder between the upper bearings and the lower bearings, a spring 
sheet for supporting a suspension spring is welded on an outer plane of 
the larger diameter section, and the upper and lower bearings are fitted 
to the outer cylinder by insertion. So, the lower bearings and the lower 
oil seal can be simply fitted to the outer cylinder by insertion. 
Further, the outer diameters of the upper and lower bearings and the outer 
diameters of the upper and lower oil seals can be set to be equal and can 
be used commonly respectively. 
Moreover, even if a distortion has occurred in the inner plane of the 
larger diameter section by a welding of the lower spring sheet, the lower 
bearings and the lower oil seal can be fitted to the outer cylinder 
without being affected by this distortion. 
As described above, according to the present invention, it becomes possible 
to provide an inverted strut damper with an improved lubrication of the 
upper bearings and the upper oil seal and with an improved fitting of the 
lower bearings and the lower oil seal. 
Although the invention has been illustrated and described with respect to 
several exemplary embodiments thereof, it should be understood by those 
skilled in the art that the foregoing and various other changes, omissions 
and additions may be made to the present invention without departing from 
the spirit and scope thereof. Therefore, the present invention should not 
be understood as limited to the specific embodiment set out above but to 
include all possible embodiments which can be embodied within a scope 
encompassed and equivalents thereof with respect to the feature set out in 
the appended claims.