U.S. patent application number 15/370852 was filed with the patent office on 2017-03-23 for sliding member and process for producing the same.
This patent application is currently assigned to NOK Corporation. The applicant listed for this patent is NOK Corporation. Invention is credited to Yoshiyuki ABE, Toshiyuki MAEDA, Yuhei Tabuchi.
Application Number | 20170082200 15/370852 |
Document ID | / |
Family ID | 42561763 |
Filed Date | 2017-03-23 |
United States Patent
Application |
20170082200 |
Kind Code |
A1 |
Tabuchi; Yuhei ; et
al. |
March 23, 2017 |
Sliding Member and Process for Producing the Same
Abstract
A sliding member comprising a polyamide resin and 10 to 50 wt %
of a fibrous filler selected from the group consisting of carbon
fibers, aramid fibers, and whiskers, and having fine dents formed
in a sliding surface thereof by dimpling using a laser; and a
process for producing a sliding member comprising adding 10 to 50
wt % of a fibrous filler selected from the group consisting of
carbon fibers, aramid fibers, and whiskers to a polyamide resin,
and forming fine dents in a sliding surface of the sliding member
by dimpling using a laser.
Inventors: |
Tabuchi; Yuhei; (lbaraki,
JP) ; ABE; Yoshiyuki; (lbaraki, JP) ; MAEDA;
Toshiyuki; (Tochigi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NOK Corporation |
Tokyo |
|
JP |
|
|
Assignee: |
NOK Corporation
Tokyo
JP
|
Family ID: |
42561763 |
Appl. No.: |
15/370852 |
Filed: |
December 6, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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13148339 |
Aug 8, 2011 |
9551421 |
|
|
PCT/JP2010/051774 |
Feb 8, 2010 |
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15370852 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08J 3/203 20130101;
C08K 2003/265 20130101; C08K 3/04 20130101; F16J 15/328 20130101;
C08K 7/06 20130101; C08K 7/02 20130101; C08L 77/00 20130101; F16J
15/3496 20130101; C08K 3/346 20130101; F16J 15/3284 20130101; C08L
77/06 20130101; C08K 7/08 20130101; Y10T 428/24355 20150115; C08L
2205/02 20130101; C08L 77/10 20130101; C08J 2377/06 20130101; F16J
15/102 20130101; C08K 3/34 20130101; C08L 77/00 20130101; C08L
2666/20 20130101; C08K 7/02 20130101; C08L 77/00 20130101; C08K
7/06 20130101; C08L 77/06 20130101; C08K 7/08 20130101; C08L 77/06
20130101; C08K 3/346 20130101; C08L 77/00 20130101 |
International
Class: |
F16J 15/328 20060101
F16J015/328; F16J 15/3284 20060101 F16J015/3284; C08K 3/04 20060101
C08K003/04; C08K 7/06 20060101 C08K007/06; C08K 7/02 20060101
C08K007/02; C08K 3/34 20060101 C08K003/34; F16J 15/34 20060101
F16J015/34; C08J 3/20 20060101 C08J003/20 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 10, 2009 |
JP |
2009028286 |
Claims
1. A process for producing a sliding member comprising adding 10 to
50 wt % of an inorganic filler selected from the group consisting
of talc, clay, and calcium carbonate to a polyamide resin, then
forming a sliding member into a predetermined shape, using a
molding means, then forming fine dents having a maximum depth of 5
to 50 mm in a sliding surface of the sliding member by applying a
dimpling process to the sliding member, using a laser, and forming
no raised portions projecting from the same sliding surface as said
sliding surface consisting of melted spheres and projections due to
laser heat inside of the fine dents and around the dents at the
time of the dimpling process.
Description
[0001] This application is a divisional application of U.S. patent
application Ser. No. 13/148,339 filed Aug. 8, 2011 which claims
priority to PCT Application PCT/JP2010/051774 filed Feb. 8,
2010.
FIELD OF THE INVENTIONS
[0002] The present invention relates to a sliding member such as
seal rings, which require low friction coefficients; and more
particularly to a sliding member with a low friction coefficient in
which, when fine dents are formed in a surface of the sliding
member by dimpling using a laser, no hard raised portions are
generated, and which does not damage a mating member; and a process
for producing the sliding member.
BACKGROUND OF THE INVENTIONS
[0003] Thermoplastic resins have recently been used as a sliding
member for use in high-load parts because of their low specific
gravity, wide range of options for the shapes of molded articles,
and excellent moldability.
[0004] Polyamide resins have been widely used as a sliding member
because of their high self-lubricating properties among
thermoplastic resins. Glass fibers have been added to polyamide
resins, in order to improve the mechanical strength and heat
resistance (Patent Literatures 1 and 2).
[0005] With the recent growing concern for environmental issues, it
is necessary, even in the area of a sliding member such as seal
rings, to enhance energy efficiency, and, therefore, to improve
sliding properties, e.g., to reduce the friction coefficient.
[0006] As a means for improving sliding properties, e.g., reducing
the friction coefficient, the formation of fine dents in a sliding
surface using a laser is known (Patent Literature 3).
[0007] However, in the case of a sliding member made of a glass
fiber-reinforced polyamide resin, the glass fiber is melted by the
laser heat during laser processing, causing melted spheres to be
formed on the sliding surface. These melted spheres cause problems
such as damage to a mating member or an increased friction
coefficient.
CITATION LIST
Patent Literature
[0008] Patent Document 1: JP-A-H08-28572
[0009] Patent Document 2: JP-A-2007-224118
[0010] Patent Document 3: JP-A-2007-225105
SUMMARY
Technical Problem
[0011] Accordingly, an object of the present invention is to
provide a sliding member with a low friction coefficient that, when
fine dents are formed in a surface of the sliding member by
dimpling using a laser, no hard raised portions are generated, and
that does not damage a mating member.
[0012] Another object of the present invention is to provide a
process for producing a sliding member with a low friction
coefficient that, when fine dents are formed in a surface of the
sliding member by dimpling using a laser, no hard raised portions
are generated, and that does not damage a mating member.
[0013] Other objects of the present invention will become apparent
from the following description.
Solution to Problem
[0014] The foregoing objects will be solved by the present
inventions set forth below.
[0015] The invention is a sliding member comprising a polyamide
resin and 10 to 50 wt % of a fibrous filler selected from the group
consisting of carbon fibers, aramid fibers, and whiskers, and
having fine dents formed in a sliding surface thereof by dimpling
using a laser.
[0016] Another new member achieving these goals is a sliding member
comprising a polyamide resin and 10 to 50 wt % of an inorganic
filler selected from the group consisting of talc, clay, and
calcium carbonate, and having fine dents formed in a sliding
surface thereof by dimpling using a laser.
[0017] Another new member achieving these goals is the sliding
member defined in the preceding paragraphs, wherein the fine dents
have a maximum depth of 5 to 50 .mu.m.
[0018] Another new member achieving these goals is a process for
producing a sliding member comprising adding 10 to 50 wt % of a
fibrous filler selected from the group consisting of carbon fibers,
aramid fibers, and whiskers to a polyamide resin, and forming fine
dents in a sliding surface of the sliding member by dimpling using
a laser.
[0019] Another new member achieving these goals is a process for
producing a sliding member comprising adding 10 to 50 wt % of an
inorganic filler selected from the group consisting of talc, clay,
and calcium carbonate to a polyamide resin, and forming fine dents
in a sliding surface of the sliding member by dimpling using a
laser.
[0020] Another new member achieving these goals is the sliding
member defined in the preceding paragraphs, wherein the fine dents
have a maximum depth of 5 to 50 .mu.m.
Advantageous Effects of Invention
[0021] In accordance with the present invention, there is provided
a sliding member with a low friction coefficient that, when fine
dents are formed in a surface of the sliding member by dimpling
using a laser, no hard raised portions are generated, and that does
not damage a mating member.
[0022] In accordance with the present invention, there is also
provided a process for producing a sliding member with a low
friction coefficient that, when fine dents are formed in a surface
of the sliding member by dimpling using a laser, no hard raised
portions are generated, and that does not damage a mating
member.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is an electron micrograph showing the laser processed
surface of a sliding member (test sample 1);
[0024] FIG. 2 is an electron micrograph showing the laser processed
surface of a sliding member (test sample 2);
[0025] FIG. 3 is an electron micrograph showing the laser processed
surface of a sliding member (test sample 3);
[0026] FIG. 4 is an electron micrograph showing the laser processed
surface of a sliding member (test sample 4); and
[0027] FIG. 5 is an electron micrograph showing the laser processed
surface of a sliding member (comparative test sample 1).
DETAILED DESCRIPTION OF THE INVENTIONS
[0028] Embodiments of the present invention will be described
below.
[0029] The polyamide resin used in the present invention is a
polymer having a (--CO--NH--) bond. Examples of such polymers
include polyhexamethylene adipamide (nylon 66), polycapramide
(nylon 6), polytetramethylene adipamide (nylon 46),
polyhexamethylene sebacamide (nylon 610), polyhexamethylene
dodecamide (nylon 612), polyundecamethylene adipamide (nylon 116),
polyundecamide (nylon 11), polydodecamide (Nylon 12), polytrimethyl
hexamethylene terephthalamide (nylon TMDT), polyhexamethylene
isophthalamide (nylon 6I), polyhexamethylene
terephthal/isophthalamide (nylon 6T/6I),
polybis(4-aminocyclohexyl)methane dodecamide (nylon PACM12),
polybis(3-methyl-4-aminocyclohexyl)methane dodecamide (nylon
dimethyl PACM12), polymetaxylylene adipamide (nylon MXD6),
polynonamethylene terephthalamide (nylon 9T), polyundecamethylene
terephthalamide (nylon 11T), polyundecamethylene
hexahydroterephthalamide [nylon 11T(H)], and copolymerized
polyamides or mixed polyamides thereof. Among the above, nylon 66
is preferred.
[0030] Polyamide resins are commercially available, such as, for
example, "nylon 66" manufactured by Toray Industries, Inc.
[0031] The fibrous filler added to the polyamide resin is selected
from carbon fibers, aramid fibers, and whiskers, which may be used
alone or in combination.
[0032] The carbon fiber used in the present invention preferably
has a diameter of 5 to 20 .mu.m, and a length of 20 to 500
.mu.m.
[0033] The raw material of the carbon fiber may be any of a PAN
(polyacrylonitrile)-based, pitch-based, and like materials, but a
carbon fiber obtained by calcining at 1,200.degree. C. or lower is
preferably used, in order to attain an enhanced reinforcing effect
in the orientation direction in the polyamide resin.
[0034] The amount of the carbon fiber used is 10 to 50 wt %,
preferably 12 to 35 wt %, and more preferably 14 to 30 wt %, based
on the polyamide resin.
[0035] If the amount of the carbon fiber is less than 10 wt %, the
reinforcing effect will be poor, resulting in an insufficient
strength of the sliding member. Conversely, if the amount of the
carbon fiber is more than 50 wt %, the resulting sliding member
will be brittle and easily broken.
[0036] The aramid fiber preferably has a diameter of 5 to 20 .mu.m,
and a length of 20 to 500 .mu.m.
[0037] The amount of the aramid fiber used is 10 to 50 wt %,
preferably 12 to 35 wt %, and more preferably 14 to 30 wt %, based
on the polyamide resin.
[0038] If the amount of the aramid fiber is less than 10 wt %, the
reinforcing effect cannot be obtained; conversely, if the amount is
more than 50 wt %, the resulting sliding member will be brittle and
easily broken.
[0039] The whisker preferably has a diameter of 0.1 to 1 .mu.m, and
a length of 5 to 30 .mu.m.
[0040] The amount of the whisker used is 10 to 50 wt %, preferably
12 to 35 wt %, and more preferably 14 to 30 wt %, based on the
polyamide resin.
[0041] If the amount of the whisker is less than 10 wt %, the
reinforcing effect cannot be obtained; conversely, if the amount is
more than 50 wt %, the resulting sliding member will be brittle and
easily broken.
[0042] The whisker used in the present invention is a complete
single crystal that has grown in the form of an extremely fine
whisker, has very few lattice defects, and has a strength
approaching the theoretical value. Moreover, a whisker that is not
merely a single crystal, but also has only one screw dislocation in
the lengthwise direction, can also be used in the present
invention.
[0043] Examples of whiskers for use in the present invention
include aluminum borate whisker, zinc oxide whisker, and potassium
titanate whisker. Potassium titanate whisker is preferred.
[0044] Potassium titanate whisker is a special material whose
crystal is originally in a fibrous form. Therefore, the use of
potassium titanate whisker in the present invention provides the
effect of improving the dimensional stability and
reinforcement.
[0045] The use of a fibrous filler results in a sliding member
having excellent wear resistance, dimensional stability, and
strength; moreover, in the present invention, the use of, in
particular, a fibrous filler of the present invention results in a
sliding member having both excellent frictional and wear
properties.
[0046] In the present invention, one or a combination of inorganic
fillers selected from talc, calcium carbonate, and clay may be used
for adding to the polyamide resin.
[0047] Talc preferably has a mean particle size of 0.5 to 10 .mu.m,
and preferably 2 to 5 .mu.m. The mean particle size is measured by
a method of particle size distribution measurement.
[0048] The amount of the inorganic filler used is 10 to 50 wt %,
and preferably 20 to 40 wt %, based on the polyamide resin.
[0049] If the amount of the inorganic filler is less than 10 wt %,
the reinforcing effect cannot be obtained; conversely, if the
amount is more than 50 wt %, the resulting sliding member will be
brittle and easily broken.
[0050] The sliding member of the present invention is produced as
follows: A polyamide resin is mixed with the above-defined amount
of a fibrous filler or an inorganic filler. The mixture is molded
into a predetermined shape, such as a seal ring, using a molding
means such as an injection molding machine. Fine dents are
subsequently formed in the surface of the molded article by
dimpling using laser irradiation. In this manner, a sliding member
having fine dents formed in its sliding surface is obtained.
[0051] The fine dents preferably have a maximum depth of 5 to 50
.mu.m, in order to reduce friction.
[0052] When the depth of the fine dents is within this range, a
favorable oil film can be maintained between the sliding surface of
the sliding member of the present invention and the mating sliding
surface, such as the inner surface of a cylinder, thereby
preventing damage to the mating member.
[0053] Examples of laser media used for the laser irradiation
include infrared lasers such as CO.sub.2 and YAG, and UV lasers
such as ArF, KrF, and XeCl. The laser temperature is preferably
about 1,000.degree. C.
[0054] Previously, when a glass fiber was used, the laser heat
caused the glass fiber (glass melting point: 700.degree. C.) to
form hard raised portions, causing damage to the mating sliding
surface. However, when the materials of the present invention are
used, no such raised portions are formed, thus eliminating damage
to the mating sliding surface.
[0055] One example of a known dimpling method is a technique
wherein a pattern of oil reservoirs (dimples) is formed by a hot
press in a reciprocating PTFE seal ring for compressors
(JP-B-3114874). However, this technique has a problem in that, when
dimpling is performed using a mold, because dimpled dents are fine,
the use of a resin material containing a rigid filler results in a
degraded quality because of mold wear (the mold life is short).
[0056] Another example of a known dimpling method is a technique
wherein dimples are formed in a bearing sliding member by shot
peening (JP-A-2003-184883). However, this technique has a problem
in that, when dimples are formed with shot, although raised
portions and dents can be formed with shot alone, dents only cannot
be formed with shot alone.
[0057] In order to form only dents with shot, masking is required
between the shot and the article; however, masking has the problem
of being too costly.
[0058] In the present invention, because a laser is used for
dimpling, only dents having excellent wear resistance can be
formed, and a sliding member with a stable quality can be obtained
without degradation in quality due to, for example, mold wear.
[0059] Furthermore, according to the process of the present
invention, only dents of oil reservoirs (dimples) having excellent
wear resistance can be formed, and a sliding member with a stable
quality can be obtained.
EXAMPLES
[0060] Effects of the present invention will be demonstrated below,
referring to Examples.
Example 1
1. Production of Test Samples
<Production of Test Sample 1>
[0061] 85 wt % of "nylon 66" (a polyamide resin) was mixed with 15
wt % of a carbon fiber (diameter: 10 .mu.m, fiber length: 150
.mu.m), and the mixture was formed into a sliding member for seal
rings, using an injection molding machine (Toshiba IS80-EPN).
[0062] The resulting sliding member is denoted as "test sample
1".
<Production of Test Sample 2>
[0063] 85 wt % of "nylon 66" (a polyamide resin) was mixed with 15
wt % of an aramid fiber (diameter: 10 .mu.m, fiber length: 150
.mu.m), and the mixture was formed into a sliding member for seal
rings, using an injection molding machine (Toshiba IS80-EPN).
[0064] The resulting sliding member is denoted as "test sample
2".
<Production of Test Sample 3>
[0065] 70 wt % of "nylon 66" (a polyamide resin) was mixed with 30
wt % of potassium titanate whisker (diameter: 0.5 .mu.m, fiber
length: 20 .mu.m), and the mixture was formed into a sliding member
for seal rings, using an injection molding machine (Toshiba
IS80-EPN). The resulting sliding member is denoted as "test sample
3".
<Production of Test Sample 4>
[0066] 60 wt % of "nylon 66" (a polyamide resin) was mixed with 40
wt % of talc (mean particle size: 5 .mu.m), and the mixture was
formed into a sliding member for seal rings, using an injection
molding machine (Toshiba IS80-EPN). The resulting sliding member is
denoted as "test sample 4".
[0067] <Production of Comparative Test Sample 1>
[0068] 70 wt % of "nylon 66" (a polyamide resin), manufactured by
Toray Industries, Inc., was mixed with 30 wt % of a glass fiber
(diameter: 15 .mu.m, fiber length: 150 .mu.m), manufactured by
Toray Industries, Inc., and the mixture was formed into a sliding
member for seal rings, using an injection molding machine (Toshiba
IS80-EPN). The resulting sliding member is denoted as "comparative
test sample 1".
2. Evaluation
[0069] The thus-obtained test samples and comparative test sample
were evaluated for their properties based on the following
evaluating tests.
[0070] (1) Roughness Ry of a Mating Member after Evaluation of
Damage Resistance to the Mating Member
<Measurement Method>
[0071] The roughness Ry of a mating member was determined under the
following conditions: load: 100 kgf, peripheral speed: 100 mm/s,
time: 12 min., and mating member: S45C (Ry: 0.3 to 0.5). The
results are shown in Table 1. Note that "Ry" represents the maximum
depth of profile (JIS B0601: 1994).
[0072] (2) Evaluation of Damage Resistance to the Mating Member
<Evaluation Method>
[0073] The roughness of the mating member after the evaluation of
damage resistance was measured using a surface roughness meter, and
the difference between the roughnesses before and after the test
was observed.
[0074] <Evaluation Criteria>
A: The roughness of the mating member was equal to that before the
evaluation. B: The roughness of the mating member was larger than
that before the evaluation (Rz was 0.6 or more)
[0075] The evaluation results are shown in Table 1. Note that "Rz"
represents the 10-point mean roughness (JIS B0601: 1994).
[0076] (3) Surface Conditions of the Sliding Member after Laser
Processing
[0077] The surface conditions of the sliding member were examined
using electron micrographs. FIGS. 1 to 5 show the electron
micrographs. The results revealed that the test samples 1 to 4 were
free of any raised portions. The comparative test sample shown in
FIG. 5 had glass spheres and projections generated by the melting
of the glass fiber due to the laser heat.
[0078] CO.sub.2 was used as the laser medium, and the laser
temperature was 1,000.degree. C.
(4) Frictional and Wear Properties
[0079] The friction coefficient [-] and wear coefficient [10.sup.-5
cms/(MPamh)] were determined under the following conditions:
surface pressure: 0.5 MPa, peripheral speed: 0.2 m/s, time: 24 hr,
and mating member: S45C (Rz: 1.5). The results are shown in Table
1.
(5) Qualitative Evaluation of Frictional and Wear Properties
<Evaluation Criteria>
[0080] A: Equal to or higher than the frictional and wear
properties of the comparative member B: The wear coefficient is
higher than that of the comparative member
[0081] The evaluation results are shown in Table 1.
(6) Mechanical Properties
[0082] The flexural strength [MPa] and flexural modulus of
elasticity [GPa] were determined according to ASTM D790. The
results are shown in Table 1.
TABLE-US-00001 TABLE 1 Comparative Test Test Test Test Test Sample
1 Sample 1 Sample 2 Sample 3 Sample 4 (Wt %) Composition Nylon 66
85 85 70 60 70 Glass Fiber 30 Carbon Fiber 15 Aramid Fiber 15
Potassium Titanate Whisker 30 Talc 40 Roughness of Mating Member Ry
0.4 .mu.m Ry 0.5 .mu.m Ry 0.3 .mu.m Ry 0.4 .mu.m Ry 4.9 .mu.m after
Evaluation of Damage Resistance to the Mating Member Evaluation of
Damage A A A A B Resistance to the Mating Member Frictional and
Wear Properties Friction Coefficiant [-] 0.24 0.23 0.15 0.37 0.41
Wear Coefficient 19 15 16 1415 152 [10.sup.-5 cm s/MPa m h]
Qualitative Evaluation of A A A B A Frictional and Wear Properties
Mechanical Properties Flexural Strength [MPa] 234 111 204 163 185
Flexural Modulus of Elasticity 9.2 3.8 8.3 5.9 6.2 [GPa]
[0083] It can be seen from Table 1 that the test samples 1 to 4
exhibit low friction coefficients. Moreover, with respect to the
evaluation of damage resistance to the mating member, the test
samples 1 to 4 exhibit mating member roughnesses that are equal to
those before the evaluation, i.e., the mating member roughnesses
after the evaluation of the damage resistance to the mating member
are small.
[0084] Furthermore, with respect to the qualitative evaluation of
frictional and wear properties, the test samples 1 to 3 exhibit
frictional and wear properties equal or better than those of the
comparative material and low wear coefficients, indicating that the
test samples 1 to 3 possess both low frictional and low wear
characteristics.
[0085] It can be seen that the comparative test sample 1, which do
not use the raw materials of the present invention, has a poor
result in the evaluation of damage resistance to the mating member,
and exhibits a quite large mating member roughness after the
evaluation of damage resistance to the mating member.
* * * * *