U.S. patent application number 16/763383 was filed with the patent office on 2021-10-14 for sliding member and method for manufacturing same.
This patent application is currently assigned to KABUSHIKI KAISHA TOYOTA JIDOSHOKKI. The applicant listed for this patent is KABUSHIKI KAISHA TOYOTA JIDOSHOKKI. Invention is credited to Hidetaka HAYASHI, Atsushi ICHIKAWA, Tetsuya MITSUOKA, Shino OKUBO, Naoharu UEDA.
Application Number | 20210317379 16/763383 |
Document ID | / |
Family ID | 1000005705773 |
Filed Date | 2021-10-14 |
United States Patent
Application |
20210317379 |
Kind Code |
A1 |
HAYASHI; Hidetaka ; et
al. |
October 14, 2021 |
SLIDING MEMBER AND METHOD FOR MANUFACTURING SAME
Abstract
A sliding member in which a sliding layer is capable of
exhibiting excellent sliding characteristics in terms of seizure
resistance, wear resistance and heat resistance. A method for
manufacturing the sliding member of the present teachings is a
method for manufacturing a sliding member to manufacture a sliding
member sliding with a mating material. The manufacturing method
includes irradiating particulate ultra high molecular weight
polyethylene with radiation rays in a sealed state, and
crosslinking the ultra high molecular weight polyethylene,
preparing a composition for a sliding layer containing a solid
lubricant and a binder resin, and forming a sliding layer sliding
with the mating material by providing the composition for a sliding
layer on a base material, and obtaining the sliding member. The
solid lubricant includes the ultra high molecular weight
polyethylene crosslinked during the irradiating and the
crosslinking.
Inventors: |
HAYASHI; Hidetaka; (Aichi,
JP) ; OKUBO; Shino; (Aichi, JP) ; UEDA;
Naoharu; (Aichi, JP) ; ICHIKAWA; Atsushi;
(Chiba, JP) ; MITSUOKA; Tetsuya; (Aichi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KABUSHIKI KAISHA TOYOTA JIDOSHOKKI |
Aichi |
|
JP |
|
|
Assignee: |
KABUSHIKI KAISHA TOYOTA
JIDOSHOKKI
Aichi
JP
|
Family ID: |
1000005705773 |
Appl. No.: |
16/763383 |
Filed: |
August 21, 2018 |
PCT Filed: |
August 21, 2018 |
PCT NO: |
PCT/JP2018/030740 |
371 Date: |
May 12, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10M 107/04 20130101;
C10M 177/00 20130101; C10M 125/22 20130101; C10N 2050/08 20130101;
C10M 125/02 20130101; C10N 2010/10 20130101; C10M 149/18 20130101;
C10N 2070/00 20130101 |
International
Class: |
C10M 107/04 20060101
C10M107/04; C10M 149/18 20060101 C10M149/18; C10M 125/22 20060101
C10M125/22; C10M 125/02 20060101 C10M125/02; C10M 177/00 20060101
C10M177/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 14, 2017 |
JP |
2017-218843 |
Apr 19, 2018 |
JP |
2018-080500 |
Claims
1. A method for manufacturing a sliding member to manufacture a
sliding member sliding with a mating material, comprising:
irradiating particulate ultra high molecular weight polyethylene
with radiation rays in a sealed state, and crosslinking the ultra
high molecular weight polyethylene; preparing a composition for a
sliding layer containing a solid lubricant including the ultra high
molecular weight polyethylene crosslinked during the irradiating
and the crosslinking, and a binder resin; and forming a sliding
layer sliding with the mating material by providing the composition
for a sliding layer on a base material, and obtaining the sliding
member.
2. The method for manufacturing a sliding member according to claim
1, wherein the irradiating and the crosslinking is performed under
a condition that an absorbed dose of electron beams as the
radiation rays is more than or equal to 60 kGy and less than 500
kGy.
3. A sliding member comprising a base material, and a sliding layer
formed on the base material, and containing a binder resin and a
solid lubricant, the sliding layer sliding with a mating material,
wherein the solid lubricant includes crosslinked ultra high
molecular weight polyethylene that is particulate, and has a
melting point that is more than 126.4.degree. C. and less than or
equal to 132.0.degree. C.
4. The sliding member according to claim 3, wherein the ultra high
molecular weight polyethylene has a gel fraction of more than or
equal to 26%.
5. The sliding member according to claim 3, wherein in the sliding
layer, the solid lubricant is more than or equal to 25% by volume
and less than or equal to 100% by volume with respect to the binder
resin, in the sliding layer, the binder resin is polyamide-imide,
and the ultra high molecular weight polyethylene is more than or
equal to 5% by volume and less than or equal to 35% by volume with
respect to all solid components in the sliding layer.
6. The sliding member according to claim 5, wherein the solid
lubricant further includes molybdenum disulfide, and in the sliding
layer, the molybdenum disulfide is less than or equal to 26% by
volume with respect to all solid components in the sliding
layer.
7. The sliding member according to claim 6, wherein in the sliding
layer, the ultra high molecular weight polyethylene is more than or
equal to 23% by volume and less than or equal to 35% by volume with
respect to all solid components in the sliding layer, and the
molybdenum disulfide is less than or equal to 15% by volume with
respect to all solid components in the sliding layer.
8. The sliding member according to claim 5, wherein the solid
lubricant further includes graphite, and in the sliding layer, the
graphite is more than or equal to 5% by volume and less than or
equal to 30% by volume with respect to all solid components in the
sliding layer.
9. The sliding member according to claim 3, wherein the ultra high
molecular weight polyethylene has a gel fraction of more than or
equal to 26%, wherein in the sliding layer, the solid lubricant is
more than or equal to 25% by volume and less than or equal to 100%
by volume with respect to the binder resin, in the sliding layer,
the binder resin is polyamide-imide, and the ultra high molecular
weight polyethylene is more than or equal to 5% by volume and less
than or equal to 35% by volume with respect to all solid components
in the sliding layer.
10. The sliding member according to claim 9, wherein the solid
lubricant further includes molybdenum disulfide, and in the sliding
layer, the molybdenum disulfide is less than or equal to 26% by
volume with respect to all solid components in the sliding
layer.
11. The sliding member according to claim 10, wherein in the
sliding layer, the ultra high molecular weight polyethylene is more
than or equal to 23% by volume and less than or equal to 35% by
volume with respect to all solid components in the sliding layer,
and the molybdenum disulfide is less than or equal to 15% by volume
with respect to all solid components in the sliding layer.
12. The sliding member according to claim 9, wherein the solid
lubricant further includes graphite, and in the sliding layer, the
graphite is more than or equal to 5% by volume and less than or
equal to 30% by volume with respect to all solid components in the
sliding layer.
13. The sliding member according to claim 6, wherein the solid
lubricant further includes graphite, and in the sliding layer, the
graphite is more than or equal to 5% by volume and less than or
equal to 30% by volume with respect to all solid components in the
sliding layer.
Description
TECHNICAL FIELD
[0001] The present invention relates to a sliding member and a
method for manufacturing the same.
BACKGROUND ART
[0002] Conventionally, sliding members disclosed in Patent
Literatures Japanese Patent Laid-Open No. 2013-189569 and Japanese
Patent Laid-Open No. 2016-69508 are known. These sliding members
each include a base material formed of a steel material or an
aluminum material, and a sliding layer formed on the base material.
An underlayer may be provided between the base material and the
sliding layer. The sliding layer contains a binder resin and a
solid lubricant. The binder resin is formed of an epoxy resin or
the like. The solid lubricant in Patent Literature Japanese Patent
Laid-Open No. 2013-189569 is formed from particulate molybdenum
disulfide (MoS.sub.2), particulate polytetrafluoroethylene (PTFE),
and particulate polyethylene. In recent years, an ultra high
molecular weight polyethylene has been studied because of
characteristics of self-lubricity and wear resistance, and the
solid lubricant in Patent Literature Japanese Patent Laid-Open No.
2016-69508 includes particulate crosslinked ultra high molecular
weight polyethylene.
[0003] These sliding members can be adopted in a propeller shaft, a
piston and the like in which sliding layers slide with mating
material. In particular, the sliding layer in Patent Literature
Japanese Patent Laid-Open No. 2013-189569 includes polyethylene
that has good affinity for lubricants as a solid lubricant, and
therefore realizes a low friction coefficient and high wear
resistance. Furthermore, the sliding layer in Patent Literature
Japanese Patent Laid-Open No. 2016-69508 uses a crosslinked ultra
high molecular weight polyethylene as a solid lubricant, and
realize not only seizure resistance and wear resistance but also
high heat resistance.
[0004] However, for the sliding members, further improvement in the
sliding characteristics is desired to ensure reliability. In this
regard, according to the test result by the inventors, the sliding
layer cannot always exhibit high heat resistance when the
crosslinked ultra high molecular weight polyethylene is simply
irradiated with radiation rays even if the crosslinked ultra high
molecular weight polyethylene is adopted as a part of the solid
lubricant. In some cases, the crosslinked ultra high molecular
weight polyethylene becomes brittle, and lubrication
characteristics of the sliding layer rather deteriorate.
SUMMARY OF INVENTION
[0005] It is therefore one non-limiting object of the present
teachings to provide a sliding member in which a sliding layer can
exhibit excellent sliding characteristics in terms of seizure
resistance, wear resistance and heat resistance. This object is
achieved by the teachings of claim 1. Further developments of the
teachings are recited in the dependent claims.
[0006] A method for manufacturing a sliding member of the present
teachings is a method for manufacturing a sliding member to
manufacture a sliding member sliding with a mating material, and
includes
[0007] a crosslinking step of irradiating particulate ultra high
molecular weight polyethylene with radiation rays in a sealed
state, and crosslinking the ultra high molecular weight
polyethylene,
[0008] a composition preparing step of preparing a composition for
a sliding layer containing a solid lubricant including the ultra
high molecular weight polyethylene crosslinked in the crosslinking
step, and a binder resin, and
[0009] a sliding layer forming step of forming a sliding layer
sliding with the mating material by providing the composition for a
sliding layer on a base material, and obtaining the sliding
member.
BRIEF DESCRIPTION OF DRAWINGS
[0010] FIG. 1 is a schematic perspective view showing a state of a
pin-on-disk reciprocating test in test 1.
[0011] FIG. 2 is a sectional view showing a state of a swash
plate-shoe test in test 2.
[0012] FIG. 3 is a 500-power SEM image photograph in a sliding
layer of test 1, in a sliding member of embodiment 1.
[0013] FIG. 4 is a 500-power SEM image photograph in a sliding
layer in test 1, in a sliding member of embodiment 2.
[0014] FIG. 5 is a 500-power SEM image photograph in a sliding
layer in test 1, in a sliding member of embodiment 3.
[0015] FIG. 6 is a 500-power SEM image photograph in a sliding
layer in test 1, in a sliding member of embodiment 4.
[0016] FIG. 7 is a 500-power SEM image photograph in a sliding
layer in test 1, in a sliding member of comparative example 2.
[0017] FIG. 8 is a 500-power SEM image photograph in a sliding
layer in test 1, in a sliding member of comparative example 3.
[0018] FIG. 9 is a schematic perspective view showing a state of a
ring-on-disk friction and wear test in test 4.
[0019] FIG. 10 is a schematic perspective view showing a state of a
pin-on-disk friction and wear test in test 5.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
<Crosslinking Step>
[0020] As means for irradiating particulate ultra high molecular
weight polyethylene with radiant rays in a sealed state, (1) a
vacuum method to evacuate a container storing particulate ultra
high molecular weight polyethylene to reduce the proportion of
existence of air, (2) a gas purge method to fill a container with
inert gas or nitrogen to discharge air, and the like can be
adopted. An atmosphere may include some oxygen without using a
vacuum method or a gas purge method, as long as the atmosphere is
sealed.
[0021] As the radiation rays, X-rays, electron beams, and ion beams
can be adopted in addition to .alpha.-rays, .beta.-rays, and
.gamma.-rays. An amount of radiation rays is expressed as a dose
proportional to energy absorbed in a unit mass. A gray (Gy) is a
unit that represents an amount of energy absorbed by a certain
substance (referred to as an absorbed dose) when the radiation rays
strike the substance.
<Composition Preparing Step>
(Binder Resin)
[0022] A binder resin exhibits a retention property for a solid
lubricant that makes it difficult to detach the solid lubricant,
durability against a shearing force that repeatedly acts under a
layered coating film (hardness as a base), wear resistance with
which the binder resin is difficult to break, heat resistance and
the like. As the binder resin, a polyimide resin, an epoxy resin, a
phenol resin and the like can be adopted. As the polyimide resin,
polyamide-imide (PAI), polyimide and the like can be adopted.
Considering cost and characteristics, it is optimal to use PAI as
the binder resin
(Solid Lubricant)
[0023] A solid lubricant is held by the binder resin, and exhibits
a low shearing force and a low friction coefficient on an outermost
surface. As the solid lubricant, fluororesin, molybdenum dioxide,
graphite, ultra high molecular weight polyethylene and the like are
adoptable. Fluororesin and ultra high molecular weight polyethylene
improve slidability by forming a coating film on a sliding surface
of a sliding layer, and transferring to a mating material.
Molybdenum dioxide and graphite improve slidability by a crystal
structure having a low shearing force, and realizes low friction
under a high load. According to test results by the inventors,
fluororesin has sliding characteristics such as wear resistance and
seizure resistance, but has oil repellency, and has a relatively
large lubricating oil contact angle. On the other hand, ultra high
molecular weight polyethylene has lipophilic properties though it
is inferior to fluororesin in sliding characteristics, and has a
relatively small lubricating oil contact angle. Furthermore, as the
solid lubricant, melamine cyanurate (MCA), calcium fluoride, and
soft metals such as copper and tin can be adopted. In particular,
ultra high molecular weight polyethylene that is properly
crosslinked hardly liquates from a surface of a sliding layer at
high temperatures, and can improve excellent seizure resistance and
wear resistance.
[0024] The ultra high molecular weight polyethylene before
crosslinked preferably has an average molecular weight of 1,000,000
to 7,000,000. Furthermore, a specific gravity of the ultra high
molecular weight polyethylene before crosslinked is preferably 0.92
to 0.96. The ultra high molecular weight polyethylene before
crosslinked preferably has a particle size less than or equal to 30
.mu.m, and more preferably has a particle size of less than or
equal to 15 .mu.m, in terms of surface smoothness and wear
resistance.
(Additive, Etc.)
[0025] A sliding layer can have an additive in addition to the
binder resin and the solid lubricant. As the additive, additives
that increase hardness of the sliding layer can be adopted, such as
hard particles of titanium dioxide, tricalcium phosphate, alumina,
silica, silicon carbide and silicon nitride.
[0026] The sliding layer can contain a metal compound containing
sulfur such as ZnS and Ag.sub.2S as an extreme pressure agent.
Furthermore, the sliding layer can have a surfactant, a coupling
agent, a processing stabilizer, an antioxidant and the like.
[0027] As a silane coupling agent used for silane coupling
treatment, a functional group is preferably an epoxy group. As the
silane coupling agent having an epoxy group in the functional
group, 2-(3,4-Epoxycyclohexyl) ethyltrimethoxysilane,
3-Glycidoxypropyltrimethoxysilane,
3-Glycidoxypropylmethyldiethoxysilane, and
3-Glycidoxypropyltriethoxysilane are preferable. These silane
coupling agents also have excellent storage stability.
[0028] <Sliding Layer Forming Step>
[0029] As a sliding layer forming step, it is possible to perform
viscosity adjustment and density adjustment of a solid content by
appropriately diluting a composition for a sliding layer with a
solvent such as n-methyl-2-pyrrolidone,
1,3-dimethyl-2-imidazolidinone, or xylene, depending on a kind of a
coating method such as spray coating and roll coating. It is
possible to form a sliding layer by performing drying and burning
after coating a base material with a diluent of the composition for
a sliding layer.
EMBODIMENTS
(First Experiment)
[0030] Hereinafter, embodiments 1 to 4 according to the present
teachings, and comparative examples 1 to 3 will be described.
First, the following materials were prepared.
[0031] Binder Resin: Polyamide-Imide Resin (PAI) Varnish
[0032] Solid lubricant: particulate ultra high molecular weight
polyethylene (UHPE particle), particulate fluorine compound (PTFE
particle), MoS.sub.2, graphite
[0033] A plurality of bags formed of vinyl that are capable of
being airtight and are of the same size were prepared, a fixed
amount of UHPE particles were put into each of these bags, and
respective bags were evacuated under the same conditions.
Thereafter, each of the bags was put into an electron beam
irradiation device, and UHPE particles were irradiated with
electron beams as radiation rays at an absorbed dose (kGy) shown in
Table 1. In this manner, UHPE particles of crosslinked products No.
1 to 6 were obtained. UHPE particles of an uncrosslinked product
were not irradiated with electron beams. UHPE particles of an
unsealed crosslinked product were irradiated with electron beams in
a state open to the atmosphere, that is, without being put into the
bag.
[0034] Table 1 shows melting points (.degree. C.), gel fractions
(%), and average particle sizes (.mu.m) of the respective UHPE
particles. Furthermore, Table 1 also shows a melting point
(.degree. C.) and an average particle size (.mu.m) of PTFE
particles.
TABLE-US-00001 TABLE 1 Particulate ultra high molecular weight
polyethylene (UHPE particle) Fluorine Crosslinked Crosslinked
Crosslinked Crosslinked Crosslinked Crosslinked Unsealed compound
Uncrosslinked product product product product product product
crosslinked PTFE particle product No. 1 No. 2 No. 3 No. 4 No. 5 No.
6 product Electron beam -- -- Sealed Sealed Sealed Sealed Sealed
Sealed Open to irradiation atmosphere atmosphere Electron beam 0 0
60 80 100 300 500 1000 100 absorbed dose [kGy] Melting point 323.8
134.6 132.0 131.6 131.2 128.2 126.4 123.0 133.2 [.degree. C.] Gel
fraction -- 0 26 69 66 69 68 71 0 [weight %] Average 5 10 10 10 10
10 10 10 10 particle size [.mu.m]
[0035] Here, measurement conditions of the melting point are as
follows.
[0036] Analysis equipment: DSC Q2000 (TA instrument)
[0037] Heating rate: 5.degree. C./minute (After a temperature was
raised to 210.degree. C., the temperature was cooled to 30.degree.
C. at -20.degree. C./minute, and measurement was performed
again.)
[0038] Atmosphere: N.sub.2
[0039] Sample weight: 5 mg.+-.0.1 mg each
[0040] Melting point reading conditions: a melting peak temperature
when measuring again
[0041] The gel fractions were measured as follows. First, each
powder was pressed at a constant pressure while being heated at
180.degree. C. to 230.degree. C., and thereby a sheet having a
thickness of 0.3 mm was formed. From each sheet, a small piece of
0.3 g was cut. Each small piece was put into a flask, and 500
milliliters of p-xylene was added into the flask. While heating
each flask to 130.degree. C., the mixture in the flask was stirred
for four hours to dissolve each small piece. The solution was
filtered with a wire mesh having a mesh of 106 .mu.m while the
solution is in a high temperature state of 130.degree. C. Insoluble
matters on the wire mesh were dried under vacuum at 140.degree. C.
for three hours, and a weight (g) of the insoluble matters after
the room temperature was measured. Subsequently, the gel fraction
was obtained by a formula of gel fraction (%)=insoluble matter
weight (g).times.100/0.3 (g).
[0042] As the composition preparing step, PAI varnish and each
solid lubricant were compounded at a compounding ratio shown in
Table 2, and after the compound was stirred well, the compound was
passed through three roll mills, whereby compositions for the
sliding layers in embodiments 1 to 4 and comparative examples 1 to
3 were prepared. The solid lubricant is formed from PTFE particles,
UHPE particles, MoS.sub.2 and graphite. The UHPE particles are any
one of an uncrosslinked product, crosslinked products No. 1 to 4 or
an unsealed crosslinked product.
TABLE-US-00002 TABLE 2 Embodiment Embodiment Embodiment Embodiment
Comparative Comparative Comparative Volume % 1 2 3 4 example 1
example 2 example 3 PAI varnish 50 50 50 50 50 50 50 Solid PTFE
particle -- -- -- -- 18 -- -- lubricant UHPE Uncrosslinked particle
product -- -- -- -- -- 18 -- Crosslinked No. 1 18 -- -- -- -- -- --
product No. 2 -- 18 -- -- -- -- -- No. 3 -- -- 18 -- -- -- -- No. 4
-- -- -- 18 -- -- -- Unsealed -- -- -- -- -- -- 18 Molybdenum
disulfide 18 18 18 18 18 18 18 Graphite 14 14 14 14 14 14 14 Volume
% of solid lubricant per 100% 100 100 100 100 100 100 100 by volume
of PAI resin
[0043] The following sliding layer forming step was performed.
First, the respective compositions for sliding layers were diluted
with a solvent to make dilutions, the respective dilutions were
coated on the base material formed of a steel material, after
which, drying was performed, and burning was performed at
220.degree. C. for 1.5 hours. Thereafter, surface grinding was
performed to make film thicknesses the same, and sliding layers of
the film thickness of 15 .mu.m were formed. In this manner, the
respective sliding members of embodiments 1 to 4 and comparative
examples 1 to 3 were obtained.
[0044] The respective sliding members are each formed of the base
material and the sliding layer formed on the base material. The
sliding layer contains the binder resin and the solid lubricant.
The respective sliding members were provided to tests 1 to 3 as
follows.
<Test 1 (Pin-On-Disk Reciprocating Test)>
[0045] The test is to confirm a liquation (residual) state of the
UHPE particles in the sliding layer of each of the sliding members.
In other words, as shown in FIG. 1, each sliding member 10 is
placed on a plate 1 in which a top surface can be heated. In this
state, in each sliding member 10 has a sliding layer 10a as the top
surface. On the sliding layer 10a, a pin 2 made of SUJ2 with a
curvature of a tip end of 10R is reciprocated under conditions of a
load of 350 gf, a reciprocation distance 20 mm, a speed of 2 Hz,
and a number of reciprocations of 3500. At this time, a temperature
of a substrate surface is controlled to 80.degree. C., and a
lubricant 3 containing hydrocarbon oil is dropped onto the sliding
layer 10a. The test was performed to the sliding members of
embodiments 1 to 4 and comparative examples 1 to 3.
<Test 2 (Swash Plate-Shoe Test 1)>
[0046] The test is to evaluate a friction coefficient and seizure
under a dry environment in a swash plate type compressor. In other
words, as shown in FIG. 2, a base material 20 was formed into a
shape of a swash plate of a compressor, a sliding layer 20a was
formed on each of the base materials 20, and a swash plate was
obtained as described above. Meanwhile, a shoe 5 made of SUJ2 was
held by a holding tool 4. Subsequently, the swash plate was rotated
at a sliding speed of 10 m/second, a load of 1960 N was applied to
between the swash plate and the shoe 5, and a time (second)
required for the swash plate and the shoe 5 to seize was
investigated. The test was performed to the sliding members of
embodiments 1 to 4 and comparative examples 1 to 3.
<Test 3 (Swash Plate-Shoe Test 2)>
[0047] The test is to evaluate seizure at a time of applying a load
stepwise under lubrication in oil in a swash plate type compressor.
In other words, as shown in FIG. 2, the base material 20 was formed
into a shape of a swash plate of a compressor, a sliding layer 20a
was formed on each of the base materials 20, and a swash plate was
obtained as described above. Meanwhile, a shoe 5 made of SUJ2 was
held by a holding tool 4. Subsequently, the swash plate was rotated
at a sliding speed of 7 m/second while refrigerating machine oil
was attached to a surface of the swash plate by amount of 6
g/minute, a load of 400 N was applied to between the swash plate
and the shoe 5 every five minutes, and a load (N) under which the
swash plate and the shoe 5 were seized was investigated. The test
was performed to the sliding members of embodiments 1 to 4 and
comparative examples 1 to 3.
[0048] Table 3 shows results of the tests. Furthermore, remaining
states of UHPE particles in the sliding layers of the respective
sliding members of embodiments 1 to 4 and comparative examples 2
and 3 after test 1 were confirmed by SEM images. FIG. 3 shows a
500-power SEM image photograph in the sliding layer of test 1, in
the sliding member of embodiment 1. FIG. 4 shows a 500-power SEM
image photograph in the sliding layer of test 1, in the sliding
member of embodiment 2. FIG. 5 shows a 500-power SEM image
photograph in the sliding layer of test 1, in the sliding member of
embodiment 3. FIG. 6 shows a 500-power SEM image photograph in the
sliding layer of test 1, in the sliding member of embodiment 4.
FIG. 7 shows a 500-power SEM image photograph in the sliding layer
of test 1, in the sliding member of comparative example 2. FIG. 8
shows a 500-power SEM image photograph in the sliding layer of test
1, in the sliding member of comparative example 3.
TABLE-US-00003 TABLE 3 Test 2 Test 3 Friction Seizure time Seizure
load coefficient [second] [N] Embodiment 1 0.033 510 4000
Embodiment 2 0.033 479 5600 Embodiment 3 0.032 524 5600 Embodiment
4 0.033 451 4800 Comparative 0.033 465 3600 example 1 Comparative
0.038 235 4000 example 2 Comparative 0.036 293 3600 example 3
[0049] As can be seen from Table 3, the sliding members of
embodiments 1 to 4 can exhibit excellent seizure resistance and
wear resistance. It is presumed the reason of this is that since
the sliding members of embodiments 1 to 4 adopt UHPE particles
irradiated with radiation rays in the sealed state, the UHPE
particles are hardly oxidized, and are properly crosslinked.
[0050] In particular, the sliding layers in the sliding members of
embodiments 2 to 4 exhibit excellent seizure resistance and wear
resistance. It is presumed this is because the sliding members of
embodiments 2 to 4 each adopt crosslinked UHPE particles having a
melting point of more than or equal to 128.2.degree. C. and less
than or equal to 132.0.degree. C., and a gel fraction of more than
or equal to 26% by having an absorbed dose of electron beams of
more than or equal to 60 kGy and less than or equal to 300 kGy as
shown in Table 1, so that the UHPE particles hardly liquate and
drop out of the surface of the sliding layer at high temperatures,
as shown in FIGS. 4 to 6.
[0051] On the other hand, as can be seen from Table 3, the sliding
members of comparative examples 2 and 3 each have a low seizure
load, and poor seizure resistance. It is presumed this is because
the sliding member of comparative example 2 adopts UHPE particles
of an uncrosslinked product, and therefore the UHPE particles
easily liquate and drop out of the surface of the sliding layer at
high temperatures as shown in FIG. 7. Furthermore, it is presumed
this is because the sliding member of comparative example 3 adopts
UHPE particles of an unsealed crosslinked product having a gel
fraction of 0%, so that the UHPE particles are oxidized and are not
properly crosslinked, and the UHPE particles easily liquate and
drop out of the surface of the sliding layer at high temperatures
as shown in FIG. 8.
[0052] Accordingly, it is found that in the sliding members of
embodiments 1 to 4, in particular, the sliding members of
embodiments 2 to 4, the sliding layers can exhibit excellent
sliding characteristics in terms of self-lubricity, wear resistance
and heat resistance. Therefore, it is found that, if these sliding
member are adopted in swash plates or the like of compressors, more
excellent compressors can be obtained.
(Second Experiment)
[0053] Next, embodiments 5 to 18 according to the present
teachings, and comparative examples 4 to 8 will be described.
First, as in the first experiment, as a composition preparing step,
PAI varnish and each solid lubricant were compounded at a
compounding ratio shown in Tables 4 to 6, and after the compound
was stirred well, the compound was passed through three roll mills,
whereby compositions for the sliding layers in embodiments 5 to 18
and comparative examples 4 to 8 were prepared. Subsequently, as in
the first experiment, a sliding layer forming step was performed.
In this manner, respective sliding members of embodiments 5 to 18
and comparative examples 4 to 8 were obtained.
TABLE-US-00004 TABLE 4 Embodiment Embodiment Embodiment Embodiment
Embodiment Embodiment Embodiment Volume % 5 6 7 8 9 10 11 PAI
varnish 50 50 50 50 50 50 50 Solid PTFE particle -- -- -- -- -- --
-- lubricant UHPE Unccosslinked product -- -- -- -- -- -- --
particle Crosslinked No. 1 -- -- -- -- -- -- -- product No. 2 -- --
-- -- -- -- -- No. 3 25 35 28 23 223 15 10 No. 4 -- -- -- -- -- --
-- No. 5 -- -- -- -- -- -- -- No. 6 -- -- -- -- -- -- -- Molybdenum
disulfide 15 9 0 5 22.5 15 10 Graphite 10 6 22 19 5 20 30 Volume %
of solid lubricant per 100% 100 100 100 100 100 100 100 by volume
of PAI resin
TABLE-US-00005 TABLE 5 Embodiment Embodiment Embodiment Embodiment
Embodiment Embodiment Embodiment Volume % 12 13 14 15 16 17 18 PAI
varnish 80 50 50 50 50 80 80 Solid PTFE particle -- -- -- -- -- --
-- lubricant UHPE Uncrosslinked product -- -- -- -- -- -- --
particle Crosslinked No. 1 -- -- -- -- -- -- -- product No. 2 -- --
-- -- -- -- -- No. 3 10 5 10 15 25 7.5 10 No. 4 -- -- -- -- -- --
-- No. 5 -- -- -- -- -- -- -- No. 6 -- -- -- -- -- -- -- Molybdenum
disulfide 0 26 23 25 25 7.5 10 Graphite 10 19 17 10 0 5 0 Volume %
of solid lubricant per 100% 25 100 100 100 100 25 25 by volume of
PAI resin
TABLE-US-00006 TABLE 6 Comparative Comparative Comparative
Comparative Comparative Volume % example 4 example 5 example 6
example 7 example 8 PAI varnish 50 50 40 40 40 Solid PTFE particle
-- -- -- -- -- lubricant UHPE Uncrosslinked product -- -- -- -- --
particle Crosslinked No. 1 -- -- -- -- -- product No. 2 -- -- -- --
-- No. 3 -- -- 22.5 30 30 No. 4 -- -- -- -- No. 5 18 -- -- -- --
No. 6 -- 18 -- -- -- Molybdenum disulfide 18 18 22.5 30 0 Graphite
14 14 15 0 30 Volume % of solid lubricant per 100% 100 100 150 150
150 by volume of PAI resin
[0054] The respective sliding members of embodiments 1 to 4 and
comparative examples 1 and 2 obtained by the first experiment, and
the respective sliding members of embodiments 5 to 18 and
comparative examples 4 to 8 obtained by the second experiment were
provided to tests 4 and 5 as follows.
<Test 4 (Ring-On-Disk Friction and Wear Test: Under Dry
Environment>
[0055] The test is to evaluate wear resistance under a certain
level of a dry environment in the sliding layers of the respective
sliding members. In other words, as shown in FIG. 9, a sliding
layer 30a of each of the sliding members is formed on a top surface
of a base material 30 formed of S45C. A film thickness of the
sliding layer 30a is approximately 20 .mu.m. In this state, a ring
6 is placed on a top surface of the sliding layer 30a of each of
the sliding members. The ring 6 made of S45C is rotated under
conditions of a contact pressure of 5.4 MPa, a sliding speed of 0.9
m/second, and a sliding distance of 500 m. A specific wear amount
(.times.10.sup.-6 mm.sup.3/Nm) of the sliding layer 30a during this
while was measured. The test was performed to the sliding members
of embodiments 1 to 18 and comparative examples 1, 2 and 4 to
8.
<Test 5 (Pin-On-Disk Friction and Wear Test: Under Oil
Environment)>
[0056] The test is to evaluate wear resistance under a certain
level of an oil environment in the sliding layers of the respective
sliding members. In other words, as shown in FIG. 10, a sliding
layer 40a of each of the sliding members is formed on a top surface
of a base material 40 formed of S45C. A film thickness of the
sliding layer 40a is approximately 15 .mu.m. In this state, a pin 7
is placed on a top surface of the sliding layer 40a of each of the
sliding members. The pin 7 made of SUJ2 in which a curvature of a
tip end is 10R is rotated under conditions of a load of 20N, a
sliding speed of 0.25 m/second, and a sliding distance of 22.6 m.
At this time, 5 mg of a refrigerator oil 8 was dropped onto the
sliding layer 40a, and a wear depth of the sliding layer 40a during
this while was measured. The test was performed to the sliding
members of embodiments 1 to 18 and comparative examples 1, 2 and 4
to 8.
[0057] Table 7 shows results of test 4 and test 5 in the sliding
members of embodiments 1 to 4 and comparative examples 1 and 2.
Tables 8 to 10 show results of test 4 and test 5 in the sliding
members of embodiments 5 to 18 and comparative examples 4 to 8.
TABLE-US-00007 TABLE 7 Embodiment Embodiment Embodiment Embodiment
Comparative Comparative 1 2 3 4 example 1 example 2 Test 4 Specific
wear amount .times. 10{circumflex over ( )}-6 2.4 2.8 2.2 5.6 5.7
3.6 [mm3/N m] Test 5 Wear depth [.mu.m] 2.9 2.2 4.1 2.7 20.1
9.1
TABLE-US-00008 TABLE 8 Embodiment Embodiment Embodiment Embodiment
Embodiment Embodiment Embodiment 5 6 7 8 9 10 11 Test 4 Specific
wear amount .times.10{circumflex over ( )}-6 1.3 0.7 0.7 0.5 2.9
3.2 1.6 [mm3/N m] Test 5 Wear depth [.mu.m] 4.7 2.6 4.3 4.2 4.4 3.4
2.4
TABLE-US-00009 TABLE 9 Embodiment Embodiment Embodiment Embodiment
Embodiment Embodiment Embodiment 12 13 14 15 16 17 18 Test 4
Specific wear amount .times. 10{circumflex over ( )}-6[mm3/N m] 2.3
1.5 3.4 2.8 2.2 7.8 5.1 Test 5 Wear depth [.mu.m] 1.0 11.3 17.5
17.3 15.0 1.0 1.0
TABLE-US-00010 TABLE 10 Comparative Comparative Comparative
Comparative Comparative example 4 example 5 example 6 example 7
example 8 Test 4 Specific wear amount .times. 10{circumflex over (
)}-6[mm3/N m] 9.7 7.7 4.4 4.9 6.3 Test 5 Wear depth [.mu.m] 11.5
11.0 14.5 12.6 14.1
[0058] In evaluating the wear resistance of the sliding members of
embodiments 1 to 18, wear resistance of the sliding member of
comparative example 2 was used as a criteria. The reason of this is
that while the UHPE particles are properly crosslinked in the
sliding members of embodiments 1 to 18, the UHPE particles are not
crosslinked in the sliding member of comparative example 2 as can
be seen from Tables 2 and 4 to 6, and therefore presence or absence
of crosslinking of the UHPE particles was adopted as the
criteria.
[0059] As can be seen from Tables 7 to 10, in the respective
sliding members of embodiments 1 to 18, the specific wear amounts
are less than 3.6 (.times.10.sup.-6 mm.sup.3/Nm), or wear depths
are less than 9.1 (.mu.m) when the results of tests 4 and 5 in the
sliding member of comparative example 2 are the standards. In other
words, the sliding members of embodiments 1 to 18 can exhibit
excellent wear resistance under the dry environment or under the
oil environment. It is presumed the reason of this is that since
the sliding members of embodiments 1 to 18 adopt the UHPE particles
irradiated with radiation rays in the sealed state, the UHPE
particles are hardly oxidized, and are properly crosslinked. In
particular, in the sliding members of embodiments 1 to 3 and 5 to
12, the sliding layers exhibit excellent wear resistance under the
dry environment and under the oil environment.
[0060] Furthermore, it is presumed that since the sliding members
of embodiments 1 to 18 adopt the crosslinked UHPE particles having
the melting points of more than 126.4.degree. C. and less than or
equal to 132.0.degree. C., and gel fractions of more than or equal
to 26% by having the absorbed doses of electron beams of more than
or equal to 60 kGy and less than 500 kGy as shown in Table 1, the
UHPE particles hardly liquate and drop out of the surfaces of the
sliding layers at high temperatures.
[0061] On the other hand, as can be seen from Tables 7 to 10, the
sliding members of comparative examples 1, 2, 4 and 5 have the
specific wear amounts of more than or equal to 3.6
(.times.10.sup.-6=.sup.3/Nm), and wear depths of more than or equal
to 9.1 (.mu.m), in the results of tests 4 and 5. Accordingly, the
sliding members of comparative examples 1, 2, 4 and 5 have poor
wear resistance under either the dry environment or the oil
environment as compared with the sliding members of embodiments 1
to 18. It is presumed that the sliding member of comparative
example 1 adopts a fluorine compound (PTFE particles) instead of
the UHPE particles which are properly crosslinked, and therefore
has poor wear resistance. It is presumed that the sliding member of
comparative example 2 adopts the uncrosslinked UHPE particles with
a melting point of 134.6.degree. C., and therefore the UHPE
particles easily liquate and drop out of the surface of the sliding
layer at high temperatures. Furthermore, it is presumed that since
in the sliding members of comparative examples 4 and 5, the
absorbed doses of electron beams are more than or equal to 500 kGy,
the crosslinked UHPE particles are brittle, and wear resistance of
the sliding members rather deteriorate.
[0062] Accordingly, it is found that in the sliding members of
embodiments 1 to 18, the sliding layers can exhibit excellent wear
resistance under the dry environment or under the oil environment.
In particular, in the sliding members of embodiments 1 to 3 and 5
to 12, the sliding layers can exhibit excellent wear resistance
under the dry environment or under the oil environment.
[0063] In the sliding layer, the solid lubricant is preferably more
than or equal to 25% by volume and is less than or equal to 100% by
volume with respect to the binder resin, and the ultra high
molecular weight polyethylene is preferably more than or equal to
5% by volume and is less than or equal to 35% by volume with
respect to all solid components in the sliding layer. More
specifically, the sliding members of embodiments 1 to 18 can
exhibit excellent wear resistance under the dry environment or
under the oil environment to the sliding members of comparative
examples 6 to 8. In other words, in the siding members of
comparative examples 6 to 8, the specific wear amounts are more
than 3.6 (.times.10.sup.-6 mm.sup.3/Nm), and the wear depths are
more than 9.1 (.mu.m) in the results of tests 4 and 5. It is
presumed that since in the sliding members of comparative examples
6 to 8, the solid lubricants were 150% by volume with respect to
the binder resins, the binder resins were unable to retain the
solid lubricants, and the solid lubricant dropped out of the
surface of the sliding layer at high temperatures.
[0064] In the sliding layer, molybdenum disulfide is preferably
less than or equal to 26% by volume with respect to all solid
components in the sliding layer. In this case, in the sliding
layer, the wear resistance can be more improved under the dry
environment or under the oil environment. Furthermore, as in the
sliding members of embodiments 7 and 12, molybdenum disulfide does
not have to be included in the solid lubricant.
[0065] In the sliding layer, the ultra high molecular weight
polyethylene is preferably more than or equal to 23% by volume and
less than or equal to 35% by volume with respect to all solid
components in the sliding layer, and molybdenum disulfide is
preferably less than or equal to 15% by volume with respect to all
solid components in the sliding layer. In this case, the sliding
layer can further improve the wear resistance under the dry
environment in particular. More specifically, the sliding members
of embodiments 5 to 8 can exhibit excellent wear resistance under
the dry environment. In the siding members of embodiments 5 to 8,
the specific wear amounts are within a range of 0.5 to 1.3
(.times.10.sup.-6=.sup.3/Nm), and show remarkable effects as
compared with the other embodiments in test 4.
[0066] In the sliding layer, graphite is preferably more than or
equal to 5% by volume and less than or equal to 30% by volume with
respect to all solid components in the sliding layer. In this case,
the sliding layer can further improve the wear resistance under the
dry environment or under the oil environment. Furthermore, graphite
does not have to be included in the solid lubricant as in the
sliding members of embodiments 16 and 18.
[0067] Although the present teachings have been described above in
line with embodiments 1 to 18, it is needless to say that the
invention is not limited to the above-described embodiments 1 to
18, but may be appropriately modified in application without
departing from the gist of the teachings.
[0068] For example, in the present teachings, it is possible to
perform a degreasing step of contacting alkali or the like to the
base material to enhance adhesion of the base material and the
sliding layer. Furthermore, it is also possible to form an
underlayer formed from phosphate such as zinc phosphate, and
manganese phosphate after the degreasing step to further enhance
adhesion of the base material and the sliding layer.
[0069] The present teachings are applicable to various sliding
members.
* * * * *