Sliding member and a method for manufacturing the same

A sliding member is provided which comprises a base body made of a firmly entangled and collapsed metal fine wire, with the voids formed between the metal fine wires constituting the metal mesh being filled compactly with a heat resistant material, the sliding surface of the base body being formed into a smooth surface with either a lubricant that fills a number of small holes formed in the heat resistant material as well as covering the surface thereof or the lubricant and the metal fine wires being exposed. A manufacturing method of the same is also disclosed which basically comprises the steps of preparing a metal mesh as a reinforcing material, preparing a sheet-like heat resistant material with a plurality of small holes being formed through the thickness, applying a lubricant on the sheet-like heat resistant material in a given thickness so as to simultaneously fill the small holes, putting the sheet-like heat resistant material on the metal mesh to provide a laminate in which the lubricant is directed towards the sliding surface to be formed, convoluting the laminate about a cylindrical mandrel so as to represent a cylindrical preform and putting the preform in a metal die to axially compress it to provide the final product.

BACKGROUND OF THE INVENTION 
The present invention relates to a sliding member and more particularly to 
a sliding member having heat resistance. The present invention relates 
also to a method for manufacturing the same. 
At this point, it is to be noted that throughout the Specification and 
claims the term "sliding member having heat resistance" is used to 
designate a product that is capable of carrying a load with a relatively 
low coefficient of friction even under conditions in which the application 
of normally utilized lubricants is difficult due to high temperatures and 
at the same time exhibits a sealing function, e.g. bearing bushes, 
washers, sliding plates, contact type packings, etc. 
Hitherto, as sliding members of this kind those that have been publicly 
known have metallic materials made of stainless steel or copper alloy 
within which are embedded solid lubricant pellets, or nonmetallic 
materials such as graphite, or ceramics, etc., or compound materials such 
as the so-called cermet, etc., or heat resistant plastic material such as 
polytetrafluoroethylene (PTFE), polyimide, etc. 
However, although all of those known materials are superior in heat 
resistance they have problems in friction and wear under dry friction 
conditions, and difficulties in mechanical strength, in particular 
resistance to impact, not necessarily having good conformability with 
mating members, and also problems in that they cannot exhibit their 
function sufficiently in regard to minute slippages. 
In order to resolve those problems or difficulties, e.g. as disclosed in 
U.S. Pat. No. 3,404,061 or Japanese Patent Publication No. 23,966/1969, a 
technique to manufacture a sliding member has been developed in which the 
sliding member is manufactured by shaping expanded graphite, which is 
obtainable by a special treatment of graphite, together with reinforcing 
materials. Although this sliding member reveals superior heat resistance 
and its impact strength is remarkably improved compared with conventional 
sliding members, the coefficient of friction is somewhat higher than that 
of conventional sliding members and it also has a defect in that it often 
makes abnormal frictional noises under dry friction conditions. 
Further, sliding members which are obtained by shaping mica or asbestos 
together with reinforcing materials also have been publicly known, but 
they have similar problems and difficulties. 
This is thought to reside in the fact that in these members the difference 
between the coefficient of static and dynamic friction is large, and that 
they possess somewhat soft characteristics, etc. It is also conceivable 
that the shapes of the respective parts constituting the sliding system 
and the natural vibrations of the materials influence these problems. 
Some of the present inventors have already proposed a sliding member in 
order to resolve the problems as above described in Japanese patent 
application No. 120,701/1981 which member has a lubricating property 
appropriate for use over a wide temperature range from room to high 
temperatures and which is characterized in that the surface of a basic 
sliding member which is obtainable by shaping heat resistant material 
together with metal meshes comprised of woven or knitted metal filaments 
as reinforcing material, is covered with lubricating compounds, and they 
confirmed that it, generally fulfils the expected objectives. 
SUMMARY OF THE INVENTION 
It is a principal object of the present invention to provide a sliding 
member which can further improve the various properties of the sliding 
material already proposed by some of the present inventors as described 
above. 
It is an object of the present invention therefore to provide a sliding 
member which is suitable to be used under conditions in which the 
application of lubricating materials such as lubricating oil or wax or the 
like is not allowed, or in other words suitable for use under dry 
frictional conditions over a wide temperature range e.g. from room to high 
temperatures. 
It is another object of the present invention therefore to provide a 
sliding member which does not make abnormal frictional noises even though 
it is used under such conditions as above described. 
It is a further object of the present invention therefore to provide a 
sliding member which can reveal superior frictional properties even though 
it is used under such conditions as above described. 
It is a still further object of the present invention to provide a sliding 
member which easily conforms with a mating member and simultaneously has a 
sealing function 
It is also an object of the present invention to provide a method for 
manufacturing a sliding shifting member in accordance with the present 
invention. 
In accordance with the present invention a sliding member is provided which 
comprises a base body made of a firmly entangled and collapsed metal fine 
wire, with the voids formed between the metal fine wires constituting the 
metal mesh being filled compactly with a heat resistant material, the 
sliding surface of the base body being formed into a smooth surface with 
either a lubricant that fills a number of small holes, formed in the heat 
resistant material as well as covering the surface thereof or the 
lubricant and the metal fine wires being exposed. In a preferred aspect of 
the present invention the metal fine wires are selected from the group 
comprising austenitic or ferritic stainless steel, copper-nickel alloy, 
copper-nickel-zinc alloy, brass, beryllium copper, aluminium alloy, and 
the like, singularly or in combination, the heat resistant material being 
sheet-like expanded graphite, and the lubricant being 
polytetrafluoroethylene. 
According to the present invention a method for manufacturing the sliding 
member is provided which comprises the steps of preparing a reinforcing 
material in the form of metal meshes which are made by weaving or knitting 
metal fine wires so as to have a band-like shape or to be a metal mesh 
sleeve; preparing a sheet-like heat resistant material; forming a number 
of small holes in the thickness of the heat resistant material, applying a 
lubricant on one of the surfaces of the heat resistant material in a given 
thickness and simultaneously also filling the small holes; then (A) in the 
case of the band-like wire mesh, putting the sheet-like heat resistant 
material on the band-like metal mesh to constitute a band-like laminate, 
subsequently either (a) putting on one or more of another heat resistant 
materials each of which is constituted by putting or applying on another 
metal mesh a sheet-like, powder-formed or slurry-formed heat resistant 
material with the sheet-like heat resistant material of the band-like 
laminate being directed towards the sliding surface, thereby resulting in 
a rectangular preform, or (b) to spirally convolute the band-like laminate 
itself so as to result in a cylindrical preform, and (B) in the case of 
the metal mesh sleeve, winding the sheet-like heat resistant material 
around the outer periphery of the wire mesh sleeve so as to result in a 
cylindrical laminate, folding back said cylindrical laminate from one end 
so as to result in a ring-shaped preform; succeedingly in both cases (A) 
and (B), inserting the rectangular or cylindrical or ring-shaped preform 
into a metal die; and compressing the rectangular, cylindrical or 
ring-shaped preform in the lamination or axial direction to be shaped into 
a final product in the metal die. 
The most characteristic aspect of the present invention resides in that as 
the sheet-like heat resistant material sheet-like expanded graphite is 
selected, and as the lubricant polytetrafluoroethylene is adopted. 
More specifically, as stated above, the sliding member according to the 
present invention is fundamentally constituted by a band-like shaped metal 
mesh or a metal mesh sleeve which is obtainable by weaving or knitting 
metal fine wires as a reinforcing material and a sheet-like heat resistant 
material which is formed with a number of small holes in its thickness and 
has a lubricant applied on one surface in a given thickness so as to 
simultaneously fill the small holes, whereby the reinforcing material and 
the sheet-like heat resistant material are put one upon another so as to 
provide a band-like or cylindrical laminate, whereby (A) in the band-like 
laminate as a reinforcing material either (a) a band-like metal mesh or a 
band-like metal mesh which is obtained by radially crushing a metal mesh 
sleeve is used, and this laminate is shaped so as to resemble a 
rectangular laminate by putting it on one or more of another laminates 
which are constituted by putting or applying a sheet-like or powder-formed 
or slurry-formed heat resistant material on another metal mesh so that the 
lubricant applied to the heat resistant material of the laminate is 
directed towards the sliding surface, or (b) the band-like laminate itself 
is spirally convoluted so as to provide a cylindrical preform, and (B) as 
for the cylindrical laminate it is constituted by winding a sheet-like 
heat resistant material applied with a lubricant around the outer or inner 
periphery of the metal mesh sleeve, the cylindrical laminate being folded 
back from one end to form a ring-shaped preform, and the preform obtained 
by either one of the procedures (A) or (B) is put into a metal die the 
cavity of which corresponds to the dimension and shape of a final product, 
and compressed and shaped therein in the direction of the lamination, the 
axis of the convolution, or the axis of the cylindrical laminate. 
Thus, as a sheet-like heat resistant material applied with a lubricant 
sheet-like expanded graphite provided with a number of small holes in 
thickness is utilized with its surface having polytetrafluoroethylene 
(hereinafter referred to as "PTFE") applied as the lubricant in a given 
thickness together with the small holes being filled with PTFE (this 
treatment being hereinafter referred to as a "PTFE treatment"), and in the 
preform the surface applied with PTFE occupies the outermost layer which 
constitutes the sliding surface. In this case, in addition to the laminate 
comprising the reinforcing material and the PTFE treated sheet-like heat 
resistant material, either another assembly composed of a metal mesh 
identical to that of the reinforcing material or differing from that 
another sheet-like heat resistant material, or another laminate comprised 
by applying on a similar reinforcing material a powder-formed or 
slurry-formed heat resistant material and applying pressure thereon or 
simultaneously drying it so as to have the reinforcing material and the 
heat resistant material be integrally connected together, may be 
incorporated with any layer as an additional layer to constitute a layer 
other than the one forming the sliding surface.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to FIG. 1 of the attached drawings wherein a PTFE treated, 
e.g. rectangular band-shaped, sheet-like heat resistant material 1 has its 
PTFE applied surface (in the embodiment shown it is the rear surface as 
viewed in FIG. 1) put on a similar rectangular band-shaped metal mesh 2 as 
a reinforcing material which is obtained by weaving or knitting metal fine 
wires, resulting in a rectangular laminate 3. The laminate 3 thus formed 
is then convoluted around a suitable cylindrical mandrel with the 
sheet-like heat resistant material 1 inside so that a cylindrical preform 
30 is provided as shown in FIG. 2. Following this step, the preform 30 is 
put into a metal die the cavity of which corresponds to the shape and 
dimension of the final product, and compressed along the direction of the 
lamination, i.e. the axis of the convolution to be shaped to as for 
example the spherical-shell shaped sliding member 40 as shown in FIG. 3. 
On the outer periphery constituting the sliding surface in this sliding 
member 40 the reinforcing material 2 is exposed in a mesh-like pattern, 
and the voids formed between the metal wires are filled with the PTFE and 
the expanded graphite 1.sub.3 as the lubricant which has been generated by 
the destruction of the sheet-like heat resistant material 1, forming a 
smooth surface as a whole, while the cross section has such a structure 
that the metal fine meshes from which the metal mesh as the reinforcing 
material 2 has been formed are firmly entangled with each other and the 
heat resistant material tightly fills the voids formed around them. 
More specifically, the PTFE treated sheet-like heat resistant material 1 
has a constitution as shown in FIGS. 4 and 5. That is, the sheetlike 
expanded graphite 1 having e.g. a rectangular shape and a thickness of 0.1 
to 1.0 mm is formed with a number of small holes 1.sub.2 in its thickness 
at intervals of 2 to 6 mm, the diameter of the holes 1.sub.2 being e.g. 
0.3 to 1.5 mm, and the PTFE 1.sub.3 is applied such that the PTFE 
simultaneously fills all of the small holes 1.sub.2 In this case, in the 
embodiment shown in FIGS. 1 to 3 the metal mesh 2 as the reinforcing 
material confronts the PTFE 1.sub.3 applied on one of the surfaces of the 
sheet-like heat resistant material 1. Further, in this case, it is not 
necessary as a rule for the sheet-like expanded graphite 1.sub.1 to have 
both its surfaces applied with the PTFE 1.sub.3 . Instead the application 
on only one surface and yet over a length sufficient enough to surround 
the cylindrical preform 30 for at least one winding is sufficient. (See 
FIG. 4). 
FIG. 6 illustrates another form of the laminate. That is, this laminate is 
constituted such that the PTFE treated rectangular sheet-like heat 
resistant material 1 has its non-treated surface (the rear side as viewed 
in FIG. 6) put on the rectangular band-like metal mesh as the reinforcing 
material, and the laminate is spirally convoluted around a cylindrical 
mandrel with the metal mesh 2 inside, whereby a cylindrical preform 50 as 
shown in FIG. 7 is provided. 
When this preform 50 is put into a metal die and compressed in the 
direction of the lamination so as to shape a desired final product, a 
sliding member 60 in which no reinforcing material 2 is exposed on the 
sliding surface, i.e. the outer periphery, is obtained as shown in FIG. 8 
in a longitudinal sectional view on a larger scale. As can be seen from 
FIG. 8, on the outer periphery which forms the sliding surface in this 
sliding member 60 the PTFE treated heat resistant material 1 is exposed in 
a compressed state with the outer surface being covered with a thin layer 
of PTFE 1.sub.3. 
As a modification of the fundamental procedures for manufacturing a sliding 
member in accordance with the present invention, as shown in FIG. 9 a 
metal mesh 2' which is comprised by knitting metal fine wires in a sleeve 
form and cutting it to an appropriate length, has wound around its outer 
periphery a PTFE applied surface confronting the metal mesh 2', and the 
laminate thus prepared is folded back axially from one end so that the 
metal mesh 2' inside the laminate is exposed outside as shown in FIG. 9. 
Thus, the laminate is transformed to exhibit a ring-shaped (or 
doughnut-shaped) configuration depending upon the length of the fold back 
of the metal mesh as shown in FIG. 10, resulting in a ring-shaped preform 
70 having a somewhat tall height. In this case, in the preform 70 having a 
sheet-like heat resistant material 1' and the metal mesh 2' exist as 
alternate layers, the metal meshes 2' occupying the inner and outer 
peripheries as well as both ends, surrounding the sheet-like heat 
resistant materials 1'. When the ring-shaped preform 70 having such a 
constitution is put into a metal die, and compressed in the axial 
direction to provide a final desired product a sliding member 80 in 
accordance with the present invention is obtained as shown in FIG. 11. In 
the sliding member 80, the reinforcing material 2' is distributed 
regularly over the whole of the outer surface, and the PTFE and the 
expanded graphite continuously fill the voids formed between the metal 
fine wires constituting the reinforcing material 2', exhibiting a smooth 
outer surface as a whole. 
Also in this case, the PTFE treatment may be carried out only at the end 
portion of the parts to be folded back so that the PTFE treated portion 
appears around the inner and outer peripheries for at least one turn 
thereof, respectively. 
Further, although it has been referred to that in FIG. 9 the heat resistant 
material 1' is disposed around the knitted metal sleeve mesh 2', instead 
the heat resistant material 1' may be disposed inside the metal mesh 2' so 
as to come into contact therewith. However, in such a constitution of the 
laminate, since as the folding back of the assembly progresses the 
cylindrical part which has not yet been subjected to the folding back is 
folded back the diameter increases owing to its subjection to radial 
tension, in such a constitution of the laminate, it is important that 
either the heat resistant material 1' is disposed so as to be somewhat 
overlapped in the peripheral direction, or the heat resistant material 1' 
is formed in a narrow ribbon-shape so that it can be spirally wound inside 
the metal mesh 2'. Therefore, as the diameter increases due to the folding 
back the heat resistant material 1' there easily follows it. 
Quite similar to the procedure of obtaining a sliding member 80 as shown in 
FIG. 11 from the ring-shaped preform 70 shown in FIG. 10, the preform just 
described above can produce a sliding member having a somewhat different 
constitution through the same procedures. FIG. 12 shows the sliding member 
90 obtainable by such procedures, in a longitudinal sectional view on a 
larger scale. As can be seen from FIG. 12, in this sliding member 90 the 
PTFE treated heat resistant material 1 is exposed over the whole of the 
outer surface so that the PTFE 1.sub.3 is disposed on the outer surface, 
with no metal mesh 2' exposed. 
In the above manufacturing method the compressive or shaping pressure for 
the preforms 30, 50 or 70 is advantageously selected to be 2 to 2.5 
t/cm.sup.2. 
The sliding member in accordance with the present invention can be 
manufactured by the above procedures. The following is a more specific 
description of the principal components of the present invention. 
A. Reinforcing Materials 
As the metal for the metal fine wires constituting the reinforcing 
material, austenetic stainless steel such as defined by the Japanese 
Industrial Standard ("JIS") under the classifications SUS 304, 316, or 
ferritic stainless steel such as JIS SUS 403 are used as the ferrous 
material, and copper-nickel alloy (white copper), copper-nickel-zinc alloy 
(German silver), brass, or beryllium copper, or the like are used as the 
non-ferrous material and also it is possible to use aluminium alloy. 
The diameter of the metal fine wire is suitably about 0.1 to 0.5 mm, and as 
the reinforcing material the metal wire is applied in the form of a woven 
or knitted metal mesh, and in the shape of a band-like or cylindrical, 
i.e. sleeve metal mesh. The preferable void of the metal mesh formed 
between the metal wires is preferably on the order of 3 to 6 mm. 
B. Heat Resistant Materials 
As the heat resistant material expanded graphite, asbestos, mica, etc. are 
used, and they are preferably applied in the form of a sheet, as powder or 
as a slurry. Among these, although the sheet-like expanded graphite may be 
used either at the outermost layer and inside the reinforcing material, 
the expanded graphite and other materials in the form of powder or slurry 
can be used only inside the reinforcing material. 
Thus, as the outermost sheet-like heat resistant material which finally 
forms the sliding surface the expanded graphite is necessarily used. As 
the sheetlike expanded graphite at present that are now on the market, 
those under the trade name "Grafoil", sold by Union Carbide of the U.S.A. 
or those under the name "Nikafilm", sold by Nippon Carbon Co., Ltd., are 
suitable, preferably with a thickness of about 0.2 to 1.0 mm. 
As previously stated, when sheetlike expanded graphite is used as the 
outermost layer a number of small holes of about 0.3 to 1.5 mm in diameter 
should be formed through the thickness of the sheet at intervals of about 
2 to 6 mm. 
For the asbestos, filamental powders of a crysotile or amosite base, or 
asbestos paper or sheets made of these filamental powders are used. 
The mica is preferably powders of natural or synthesized mica, or mica 
paper which is made by bonding these powders with silicon resin. 
Further, when these heat resistant materials are in the form of powder or 
slurry, they are used as a band-like material in which after these heat 
resistant materials are spread on or applied to the metal mesh as the 
reinforcing material they are pressed together, or pressed and dried so as 
to become an integral substance. In this case, the metal mesh for the 
reinforcing material, may be identical to the reinforcing material for the 
surface layer, but, in general, it is preferable that a metal mesh of 
stainless steel be used regardless of the kind of reinforcing mateial to 
be used as the surface layer. 
C. Lubricants 
As the lubricant polytetrafluoroethylene (PTFE) is used. 
If as the PTFE the PTFE dispersion agent (solid constituent being 65 wt %) 
such as sold under the trade name "Teflon 30J" by Mitsui Fluorochemicals 
Co., Ltd. is used the application work is facilitated. 
That is, on the surface of the sheet-like expanded graphite in the 
thickness of which a number of small holes are formed the PTFE dispersion 
agent is (a) sprayed, or (b) brushed, or (c) applied by rollers, etc., and 
the thickness of the coating (after the solvent has been vaporized) is on 
the order of 10.sup.-2 mm, or on the order of 10.sup.-1 mm at the maximum. 
In this case, the PTFE should also fill the small holes formed in the 
sheet-like expanded graphite. When the thus coated sheet-like expanded 
graphite is heated at a temperature of 120.degree. C. for several minutes, 
the solvent is completely vaporized, and with this treatment a PTFE film 
is formed on the surface of the sheet-like expanded graphite so firmly 
that the film cannot be easily peeled off by a usual treatment. 
Also it is conceivable that as the PTFE a slurry form which is applied by 
mixing the minute powders of the PTFE sold under the trade name "PTFE Fine 
Powder" by Mitsui Fluorochemicals Co., Ltd. in water or volatile 
dispersing agent can be used, but in this case, a small amount of adhesive 
may be mixed or dissolved in the dispersing agent. 
D. Others 
As described above the PTFE treated sheet-like expanded graphite is 
combined with a metal mesh as a reinforcing material to form a laminate, 
and the graphite is located on the sliding surface at the outermost layer 
of the laminate, and in this case, a metal mesh as a reinforcing material 
singularly or with a sheet-like heat resistant material being put thereon 
can be interposed inside the assembly which constitutes the sliding 
surface. 
Alternatively, in place of the metal mesh last mentioned a metal mesh to 
which is applied a heat resistant material in the form of a powder or 
slurry which is made by the procedure as explained in item (B) above may 
be utilized. 
Next the results of the experiments which were carried out to prove the 
superiority of the sliding member in accordance with the present invention 
over the conventional ones will be explained. 
In accordance with the present invention sliding members were manufactured 
such that a plurality of expanded graphite sheets to constitute the 
sliding surfaces, each having a thickness of 0.4 mm, were formed with a 
number of small holes in their thickness, each having a diameter of 1.5 
mm, so that the ratios of the total area of the holes relative to the 
whole surface area varied from 3 to 50%, and the PTFE dispersion agent 
("Teflon 30J" of Mitsui Fluorohemicals Co., Ltd.) was applied to the 
surface so as to also fill the small holes, and then the sheet-like 
graphite was heated at 120.degree. C. to remove the volatile matters. 
The sliding members thus prepared were subjected to an oscillation test 
under the following conditions to measure the coefficient of friction 
(.mu.), wear amount and abnormal frictional noise. 
______________________________________ 
Test Conditions 
______________________________________ 
Mating Member: SUS 304 
Load (kg/cm.sup.2): 
20 
Oscillatory Velocity: 
20 
(cycle/min) 
Temperature (.degree.C.): 
100 
Time Period (hrs): 100, 300, 500, 1,000 
______________________________________ 
The criterion of the abnormal frictional noise was defined as follows: 
I: Only normal frictional sounds are generated, no abnormal noise being 
made; 
II: When the ear is positioned near the test piece, in addition to the 
frictional sound, abnormal frictional noise is faintly heard; 
III: Although at a definite position (1.5 m apart from the test piece) 
abnormal frictional noise is hard to identify due to the existence of 
sounds in the living environment it can be recognized by the tester; and 
IV: At a definite position anyone can recognize the abnormal frictional 
noise (unpleasant sound). 
The test results are given in the Table. 
TABLE 
__________________________________________________________________________ 
Test Period (hrs) 
100 300 500 1,000 
Coeff. 
Wear Coeff. 
Wear Coeff. 
Wear Coeff. 
Wear 
of A- of A- of A- of A- 
Sliding Friction 
mount Friction 
mount Friction 
mount Friction 
mount 
Surface (.mu.) 
(mm) 
Noise 
(.mu.) 
(mm) 
Noise 
(.mu.) 
(mm) 
Noise 
(.mu.) 
(mm) 
Noise 
__________________________________________________________________________ 
Single 0.12 0.05 
IV 0.12 0.14 
IV -- -- -- -- -- -- 
Graphite Sheet 
20-25.mu. PTFE Film 
0.06 0.018 
I 0.06.about. 
0.08 
I -- -- -- -- -- 
Surface Thickness 0.12 IV 
PTFE Film + 3% 
0.06 0.017 
I 0.06 0.022 
I 0.06.about. 
0.10 
I.about. 
-- -- -- 
Area Filled Holes 0.11 IV 
PTFE Film + 5% 
0.06 0.019 
I 0.05 0.020 
I 0.06 0.05 
I 0.06 0.10 
I 
Area Filled Holes 
PTFE Film + 10% 
0.05 0.015 
I 0.06 0.022 
I 0.06 0.043 
I 0.06 0.09 
I 
Area Filled Holes 
PTFE Film + 15% 
0.05 0.014 
I 0.05 0.019 
I 0.05 0.038 
I 0.06 0.08 
I 
Area Filled Holes 
PTFE Film + 30% 
0.05 0.018 
I 0.05 0.035 
I 0.05 0.08 
I 0.06 0.13 
I 
Area Filled Holes 
PTFE Film + 40% 
0.05 0.020 
I 0.05 0.048 
I 0.05 0.12 
I 0.05 0.22 
I 
Area Filled Holes 
PTFE Film + 50% 
0.05 0.050 
I 0.10 0.06 
I 0.06 0.15 
I 0.06 0.28 
I 
Area Filled Holes 
15% Area Filled 
0.08 0.020 
I 0.09 0.030 
I 0.08 0.045 
I 0.09 0.65 
I 
Holes + 33% 
Exposed Metal Mesh 
__________________________________________________________________________ 
As can be seen from the Table the sliding members which are not PFTE 
treated make large sliding noises, and the coefficient of friction as well 
as the wear amounts are large. Incidentally, as to the sliding member in 
which the PTFE was applied merely on the sliding surface, since the PTFE 
applied on the surface was worn out when only 230 hrs. had lapsed and the 
graphite was excessively exposed, making abnormal noise, the test was 
suspended when the test time period of 300 hrs. had lapsed. Among the PTFE 
treated sliding members, the one in which the area ratio of the PTFE was 
3% made abnormal frictional noise after the lapse of 460 hrs. This is 
presumed to be because of the fact that the PTFE on the sliding surface 
was worn out and the powders of the graphite which was generated as a 
result of the wear covered the surface of the PTFE which had a small area 
ratios, so mutual friction between the graphite occurred. 
Contrarily, the sliding members in which the area ratio of the PTFE was 5 
to 50% did not entirely make abnormal frictional noise as apparent from 
the Table, but on the other hand, as the area ratio of the PTFE increased 
there arose the disadvantage of an increase in the amount of wear. 
Therefore, in general an area ratio of the PTFE from 5 to 40% is 
preferable, and an area ratio from 10 to 30% exhibits the most excellent 
characteristics. It will be also appreciated from the Table that although 
the exposure of the metal wires on the sliding surface slightly increases 
the coefficient of friction, it improves the strength of the sliding 
surface and increases the wear resistance all the more. 
From the foregoing it will be appreciated that the present invention 
provides a sliding member which is suitable for use under dry frictional 
conditions over a wide temperature range from room temperature to high 
temperatures, with no abnormal frictional noise occurring even under these 
conditions, and exhibits excellent wear properties. 
It is also to be understood that although certain forms of this invention 
have been illustrated and described it is not to be limited thereto except 
insofar as such limitations are included in the following claims.