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 1 and 2 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 1 is formed from particulate
molybdenum disulfide (MoS
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
2 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 1 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 2 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.
CITATION LIST
PATENT LITERATURE
[0004]
Patent Literature 1: Japanese Patent Laid-Open No. 2013-189569
Patent Literature 2: Japanese Patent Laid-Open No. 2016-69508
SUMMARY OF INVENTION
TECHNICAL PROBLEM
[0005] 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.
[0006] The present invention has been made in the light of the above described conventional
circumstances, and an object of the present invention is 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.
SOLUTION TO PROBLEM
[0007] A method for manufacturing a sliding member of the present invention is a method
for manufacturing a sliding member to manufacture a sliding member sliding with a
mating material, and includes
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,
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
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.
[0008] According to test results of the inventors, in the sliding member obtained by the
manufacturing method of the present invention, excellent seizure resistance and wear
resistance can be improved by the ultra high molecular weight polyethylene properly
crosslinked. It is presumed the reason of this is that in the manufacturing method
of the present invention, the particulate ultra high molecular weight polyethylene
is irradiated with radiation rays in the sealed state in the crosslinking step, so
that the ultra high molecular weight polyethylene is hardly oxidized and is properly
crosslinked. When particulate ultra high molecular weight polyethylene is irradiated
with radiation rays in a state open to the atmosphere, the ultra high molecular weight
polyethylene is oxidized, and the ultra high molecular weight polyethylene is hardly
crosslinked.
[0009] According to the test results of the inventors, the crosslinking step is preferably
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. The electron beams are
convenient to handle. When the electron beams are irradiated at the absorbed dose
in this range, ultra high molecular weight polyethylene is properly crosslinked, and
the sliding layer exhibits excellent heat resistance and wear resistance. When the
crosslinking step is performed at the absorbed dose of electron beams of less than
60 kGy, crosslinking of the ultra high molecular weight polyethylene becomes insufficient,
and wear resistance of the sliding layer is not sufficient. When the crosslinking
step is performed at the absorbed dose of electron beams of 500 kGy or more, the crosslinked
ultra high molecular weight polyethylene becomes brittle, and the wear resistance
of the sliding layer deteriorates.
[0010] A sliding member of the present invention is a sliding member including 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°C and less than
or equal to 132.0°C.
[0011] According to the test results of the inventors, when the melting point of ultra high
molecular weight polyethylene is within this range, a friction coefficient of the
sliding layer is low, the wear amount is small, and the ultra high molecular weight
polyethylene is hardly liquated and drops out of the surface of the sliding layer
at high temperatures. It is presumed this is because the ultra high molecular weight
polyethylene is properly crosslinked. Accordingly, the sliding layer can improve excellent
seizure resistance and wear resistance.
[0012] According to the test result of the inventors, the ultra high molecular weight polyethylene
preferably has a gel fraction of more than or equal to 26%. In this case, the friction
coefficient of the sliding layer is low, the wear amount is small, and the ultra high
molecular weight polyethylene is hardly liquated from the surface of the sliding layer
at high temperatures. The ultra high molecular weight polyethylene with the gel fraction
in this range is presumed to be properly crosslinked.
[0013] According to the test results of the inventors, in the sliding layer, the solid
lubricant is preferably more than or equal to 25% by volume and less than or equal
to 100% by volume with respect to the binder resin. In this case, the binder resin
can retain the fixed lubricant better. Furthermore, in the sliding layer, the binder
resin is preferably polyamide-imide. Furthermore, the ultra high molecular weight
polyethylene is preferably 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. In this
case, the sliding layer can further improve the wear resistance under dry environments
or under oil environments.
[0014] According to the test results of the inventors, the solid lubricant preferably further
includes molybdenum disulfide. Furthermore, 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, the sliding layer can improve the wear resistance
under dry environments or under oil environments.
[0015] According to the test results of the inventors, 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 the 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 dry environments in particular.
[0016] According to the test results of the inventors, the solid lubricant preferably further
includes graphite. Furthermore, 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. In this case, the sliding layer can further
improve the wear resistance under dry environments or under oil environments.
ADVANTAGEOUS EFFECTS OF INVENTION
[0017] According to the manufacturing method of the present invention, the sliding member
in which the sliding layer can exhibit excellent sliding characteristics in terms
of seizure resistance, wear resistance and heat resistance can be manufactured. Furthermore,
according to the sliding member of the present invention, the sliding layer can exhibit
excellent sliding characteristics in terms of self-lubricity, wear resistance and
heat resistance.
BRIEF DESCRIPTION OF DRAWINGS
[0018]
[FIG. 1] FIG. 1 is a schematic perspective view showing a state of a pin-on-disk reciprocating
test in test 1.
[FIG. 2] FIG. 2 is a sectional view showing a state of a swash plate-shoe test in
test 2.
[FIG. 3] FIG. 3 is a 500-power SEM image photograph in a sliding layer of test 1,
in a sliding member of embodiment 1.
[FIG. 4] FIG. 4 is a 500-power SEM image photograph in a sliding layer in test 1,
in a sliding member of embodiment 2.
[FIG. 5] FIG. 5 is a 500-power SEM image photograph in a sliding layer in test 1,
in a sliding member of embodiment 3.
[FIG. 6] FIG. 6 is a 500-power SEM image photograph in a sliding layer in test 1,
in a sliding member of embodiment 4.
[FIG. 7] FIG. 7 is a 500-power SEM image photograph in a sliding layer in test 1,
in a sliding member of comparative example 2.
[FIG. 8] FIG. 8 is a 500-power SEM image photograph in a sliding layer in test 1,
in a sliding member of comparative example 3.
[FIG. 9] FIG. 9 is a schematic perspective view showing a state of a ring-on-disk
friction and wear test in test 4.
[FIG. 10] FIG. 10 is a schematic perspective view showing a state of a pin-on-disk
friction and wear test in test 5.
DESCRIPTION OF EMBODIMENTS
<Crosslinking step>
[0019] 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.
[0020] As the radiation rays, X-rays, electron beams, and ion beams can be adopted in addition
to α-rays, β-rays, and γ-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)
[0021] 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)
[0022] 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.
[0023] 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 µm, and more preferably has a particle
size of less than or equal to 15 µm, in terms of surface smoothness and wear resistance.
(Additive, etc.)
[0024] 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.
[0025] The sliding layer can contain a metal compound containing sulfur such as ZnS and
Ag
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.
[0026] 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.
<Sliding layer forming step>
[0027] 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)
[0028] Hereinafter, embodiments 1 to 4 that embody the present invention, and comparative
examples 1 to 3 will be described. First, the following materials were prepared.
Binder resin: polyamide-imide resin (PAI) varnish
[0029] Solid lubricant: particulate ultra high molecular weight polyethylene (UHPE particle),
particulate fluorine compound (PTFE particle), MoS
2, graphite
[0030] 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 4 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.
[0031] Table 1 shows melting points (°C), gel fractions (%), and average particle sizes
(µm) of the respective UHPE particles. Furthermore, Table 1 also shows a melting point
(°C) and an average particle size (µm) of PTFE particles.
[Table 1]
|
Fluorine compound |
Particulate ultra high molecular weight polyethylene (UHPE particle) |
PTFE particle |
Uncrosslinked product |
Crosslinked product No. 1 |
Crosslinked product No. 2 |
Crosslinked product No. 3 |
Crosslinked product No. 4 |
Crosslinked product No. 5 |
Crosslinked product No. 6 |
Unsealed crosslinked product |
Electron beam irradiation atmosphere |
- |
- |
Sealed |
Sealed |
Sealed |
Sealed |
Sealed |
Sealed |
Open to atmosphere |
Electron beam absorbed dose [kGy] |
0 |
0 |
60 |
80 |
100 |
300 |
500 |
1000 |
100 |
Melting point [°C] |
323.8 |
134.6 |
132.0 |
131.6 |
131.2 |
128.2 |
126.4 |
123.0 |
133.2 |
Gel fraction [weight%] |
- |
0 |
26 |
69 |
66 |
69 |
68 |
71 |
0 |
Average particle size [µm] |
5 |
10 |
10 |
10 |
10 |
10 |
10 |
10 |
10 |
[0032] Here, measurement conditions of the melting point are as follows.
Analysis equipment: DSC Q2000 (TA instrument)
Heating rate: 5°C/minute (After a temperature was raised to 210°C, the temperature
was cooled to 30°C at -20°C/minute, and measurement was performed again.)
Atmosphere: N2
Sample weight: 5 mg±0.1 mg each
Melting point reading conditions: a melting peak temperature when measuring again
[0033] The gel fractions were measured as follows. First, each powder was pressed at a constant
pressure while being heated at 180°C to 230°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°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 µm while the solution is in a high temperature state of 130°C. Insoluble
matters on the wire mesh were dried under vacuum at 140°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)×100/0.3 (g) .
[0034] 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
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 2]
Volume% |
Embodiment 1 |
Embodiment 2 |
Embodiment 3 |
Embodiment 4 |
Comparative example 1 |
Comparative example 2 |
Comparative example 3 |
PAI varnish |
50 |
50 |
50 |
50 |
50 |
50 |
50 |
Solid lubricant |
PTFE particle |
- |
- |
- |
- |
18 |
- |
- |
UHPE particle |
Uncrosslinked product |
- |
- |
- |
- |
- |
18 |
- |
Crosslinked product |
No.1 |
18 |
- |
- |
- |
- |
- |
- |
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% by volume of PAI resin |
100 |
100 |
100 |
100 |
100 |
100 |
100 |
[0035] 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°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 µm were formed. In this manner, the respective sliding members of embodiments
1 to 4 and comparative examples 1 to 3 were obtained.
[0036] 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)>
[0037] 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 2Hz, and a number of reciprocations of 3500. At this time, a temperature
of a substrate surface is controlled to 80°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)>
[0038] 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)>
[0039] 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.
[0040] 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 3]
|
Test 2 |
Test 3 |
Friction coefficient |
Seizure time [second] |
Seizure load [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 example 1 |
0.033 |
465 |
3600 |
Comparative example 2 |
0.038 |
235 |
4000 |
Comparative example 3 |
0.036 |
293 |
3600 |
[0041] 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.
[0042] 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°C and less than or equal to 132.0°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.
[0043] 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.
[0044] 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)
[0045] Next, embodiments 5 to 18 that embody the present invention, 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 4]
Volume% |
Embodiment 5 |
Embodiment 6 |
Embodiment 7 |
Embodiment 8 |
Embodiment 9 |
Embodiment 10 |
Embodiment 11 |
PAI varnish |
50 |
50 |
50 |
50 |
50 |
50 |
50 |
Solid lubricant |
PTFE particle |
- |
- |
- |
- |
- |
- |
- |
UHPE particle |
Uncrosslinked product |
- |
- |
- |
- |
- |
- |
- |
Crosslinked product |
No.1 |
- |
- |
- |
- |
- |
- |
- |
No.2 |
- |
- |
- |
- |
- |
- |
- |
No.3 |
25 |
35 |
28 |
23 |
22.5 |
15 |
10 |
No.4 |
- |
- |
- |
- |
- |
- |
- |
No.5 |
- |
- |
- |
- |
- |
- |
- |
No.6 |
- |
- |
- |
- |
- |
- |
- |
Molybdenum disulfide |
15 |
9 |
0 |
8 |
22.5 |
15 |
10 |
Graphite |
10 |
6 |
22 |
19 |
5 |
20 |
30 |
Volume% of solid lubricant per 100% by volume of PAI resin |
100 |
100 |
100 |
100 |
100 |
100 |
100 |
[Table 5]
Volume% |
Embodiment 12 |
Embodiment 13 |
Embodiment 14 |
Embodiment 15 |
Embodiment 16 |
Embodiment 17 |
Embodiment 18 |
PAI varnish |
80 |
50 |
50 |
50 |
50 |
80 |
80 |
Solid lubricant |
PTFE particle |
- |
- |
- |
- |
- |
- |
- |
UHPE particle |
Uncrosslinked product |
- |
- |
- |
- |
- |
- |
- |
Crosslinked product |
No.1 |
- |
- |
- |
- |
- |
- |
- |
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% by volume of PAI resin |
25 |
100 |
100 |
100 |
100 |
25 |
25 |
[Table 6]
Volume% |
Comparative example 4 |
Comparative example 5 |
Comparative example 6 |
Comparative example 7 |
Comparative example 8 |
PAI varnish |
50 |
50 |
40 |
40 |
40 |
Solid lubricant |
PTFE particle |
- |
- |
- |
- |
- |
UHPE particle |
Uncrosslinked product |
- |
- |
- |
- |
- |
Crosslinked product |
No.1 |
- |
- |
- |
- |
- |
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% by volume of PAI resin |
100 |
100 |
150 |
150 |
150 |
[0046] 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>
[0047] 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 µm. 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 (×10
-6mm
3/N·m) 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)>
[0048] 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 µm. 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.
[0049] 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 7]
|
Embodiment 1 |
Embodiment 2 |
Embodiment 3 |
Embodiment 4 |
Comparative example 1 |
Comparative example 2 |
Test 4 |
Specific wear amount ×10^-6[mm3/N·m] |
2.4 |
2.8 |
2.2 |
5.6 |
5.7 |
3.6 |
Test 5 |
Wear depth [µm] |
2.9 |
2.2 |
4.1 |
2.7 |
20.1 |
9.1 |
[Table 8]
|
Embodiment 5 |
Embodiment 6 |
Embodiment 7 |
Embodiment 8 |
Embodiment 9 |
Embodiment 10 |
Embodiment 11 |
Test 4 |
Specific wear amount ×10^-6[mm3/N·m] |
1.3 |
0.7 |
0.7 |
0.5 |
2.9 |
3.2 |
1.6 |
Test 5 |
Wear depth [µm] |
4.7 |
2.6 |
4.3 |
4.2 |
4.4 |
3.4 |
2.4 |
[Table 9]
|
Embodiment 12 |
Embodiment 13 |
Embodiment 14 |
Embodiment 15 |
Embodiment 16 |
Embodiment 17 |
Embodiment 18 |
Test 4 |
Specific wear amount ×10^-6[mm3/N·m] |
2.3 |
1.5 |
3.4 |
2.8 |
2.2 |
7.8 |
5.1 |
Test 5 |
Wear depth [µm] |
1.0 |
11.3 |
17.5 |
17.3 |
15.0 |
1.0 |
1.0 |
[Table 10]
|
Comparative example 4 |
Comparative example 5 |
Comparative example 6 |
Comparative example 7 |
Comparative example 8 |
Test 4 |
Specific wear amount ×10^-6[mm3/N·m] |
9.7 |
7.7 |
4.4 |
4.9 |
6.3 |
Test 5 |
Wear depth [µm] |
11.5 |
11.0 |
14.5 |
12.6 |
14.1 |
[0050] 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.
[0051] 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 (×10
-6mm
3/N·m), or wear depths are less than 9.1 (µm) 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.
[0052] 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°C
and less than or equal to 132.0°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.
[0053] 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
(×10
-6mm
3/N·m), and wear depths of more than or equal to 9.1 (µm), 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°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.
[0054] 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.
[0055] 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 (×10
-6mm
3/N·m), and the wear depths are more than 9.1 (µm) 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 fixed lubricants, and the solid lubricant dropped
out of the surface of the sliding layer at high temperatures.
[0056] 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.
[0057] 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 (×10
-6mm
3/N·m), and show remarkable effects as compared with the other embodiments in test
4.
[0058] 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.
[0059] Although the present invention has 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 invention.
[0060] For example, in the present invention, 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.
INDUSTRIAL APPLICABILITY
[0061] The present invention is applicable to various sliding members.
REFERENCE SIGNS LIST
[0062]
- 2, 5, 6, 7
- Mating material (2, 7...Pin, 5...Shoe, 6...Ring)
- 10
- Sliding member
- 20, 30, 40
- Base material
- 10a, 30a,
- 40aSliding layer