U.S. patent application number 15/053659 was filed with the patent office on 2016-09-01 for composition for lubricating film, sliding member using the composition for lubricating film, and method of manufacturing the composition for lubricating film.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. The applicant listed for this patent is AKROS Co., Ltd., ART METAL MFG, CO., LTD., TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Nobuyuki FUJIWARA, Yoshio FUWA, Keiji HAYASHI, Masako JIMBO, Yuichiro KANAZAWA, Misato KISHI, Naoto KOYAMAISHI, Shin MAKINO, Keisuke MIYAMOTO, Koji SAITO, Shinya TERADA, Ichiro YAMAGUCHI.
Application Number | 20160251589 15/053659 |
Document ID | / |
Family ID | 56682700 |
Filed Date | 2016-09-01 |
United States Patent
Application |
20160251589 |
Kind Code |
A1 |
KISHI; Misato ; et
al. |
September 1, 2016 |
COMPOSITION FOR LUBRICATING FILM, SLIDING MEMBER USING THE
COMPOSITION FOR LUBRICATING FILM, AND METHOD OF MANUFACTURING THE
COMPOSITION FOR LUBRICATING FILM
Abstract
A composition for a lubricating film includes molybdenum
disulfide particles which are dispersed, and a binding resin, and
is a composition for coating a surface of a base material made of
metal with a lubricating film in which the molybdenum disulfide
particles are bound together by the binding resin. The composition
for a lubricating film contains 50 mass % to 70 mass % of the
molybdenum disulfide particles with respect to a total amount of
the molybdenum disulfide particles and the binding resin. An
average particle size of the molybdenum disulfide particles is in a
range of 0.1 .mu.m to 3.0 .mu.m.
Inventors: |
KISHI; Misato; (Nisshin-shi,
JP) ; FUWA; Yoshio; (Toyota-shi, JP) ; SAITO;
Koji; (Toyota-shi, JP) ; HAYASHI; Keiji;
(Nagoya-shi, JP) ; YAMAGUCHI; Ichiro; (Toyota-shi,
JP) ; KOYAMAISHI; Naoto; (Toyota-shi, JP) ;
TERADA; Shinya; (Toyota-shi, JP) ; FUJIWARA;
Nobuyuki; (Ueda-shi, JP) ; KANAZAWA; Yuichiro;
(Ueda-shi, JP) ; MAKINO; Shin; (Komaki-shi,
JP) ; MIYAMOTO; Keisuke; (Ichinomiya-shi, JP)
; JIMBO; Masako; (Kakamigahara-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOYOTA JIDOSHA KABUSHIKI KAISHA
ART METAL MFG, CO., LTD.
AKROS Co., Ltd. |
Toyota-shi
Ueda-shi
Komaki-shi |
|
JP
JP
JP |
|
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi
JP
ART METAL MFG, CO., LTD.
Ueda-shi
JP
AKROS Co., Ltd.
Komaki-shi
JP
|
Family ID: |
56682700 |
Appl. No.: |
15/053659 |
Filed: |
February 25, 2016 |
Current U.S.
Class: |
508/103 |
Current CPC
Class: |
C10M 107/44 20130101;
C10M 125/22 20130101; C10N 2080/00 20130101; C10M 2201/066
20130101; C10N 2050/02 20130101; C10M 2217/044 20130101; C10N
2020/06 20130101; C10N 2030/06 20130101; C10M 111/04 20130101 |
International
Class: |
C10M 125/22 20060101
C10M125/22; C10M 107/44 20060101 C10M107/44 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 27, 2015 |
JP |
2015-038150 |
Claims
1. A composition for a lubricating film, comprising: molybdenum
disulfide particles which are dispersed; and a binding resin,
wherein the composition for the lubricating film is a composition
for coating a surface of a base material made of metal with a
lubricating film in which the molybdenum disulfide particles are
bound together by the binding resin, the composition for the
lubricating film contains 50 mass % to 70 mass % of the molybdenum
disulfide particles with respect to a total amount of the
molybdenum disulfide particles and the binding resin, and an
average particle size of the molybdenum disulfide particles is in a
range of 0.1 .mu.m to 3.0 .mu.m.
2. The composition for the lubricating film according to claim 1,
wherein the binding resin is a polyamide-imide resin.
3. A sliding member, in which the surface of the base material is
coated with the lubricating film formed of the composition for a
lubricating film according to claim 1.
4. The sliding member according to claim 3, wherein a plurality of
dimples are formed on the surface, a projecting valley depth of the
surface is in a range of 0.4 .mu.m to 1.0 .mu.m, and a center-line
average roughness of the surface is in a range of 0.4 .mu.m to 1.0
.mu.m.
5. The sliding member according to claim 3, wherein the sliding
member is a piston of an internal-combustion engine, and the
lubricating film is formed on a surface of a skirt section of the
piston.
6. A method of manufacturing a sliding member, in which a surface
of the base material is coated with a lubricating film formed of
the composition for a lubricating film according to claim 1.
7. The method according to claim 6, comprising: forming a plurality
of dimples, the dimples being formed by propelling hard particles
against the surface of the base material through shot peening to
allow the surface to have a projecting valley depth in a range of
1.5 .mu.m to 2.0 .mu.m and a center-line average roughness in a
range of 1.5 .mu.m to 2.0 .mu.m, the hard particles being harder
than the base material; and forming the lubricating film on the
surface on which the dimples are formed, with the composition for a
lubricating film.
8. A method of manufacturing a piston using the sliding member as
the piston, according to the method of manufacturing a sliding
member according to claim 7, the method further comprising: after
forming the plurality of dimples on the surface of a skirt section
of the piston, coating the surface of the skirt section, on which
the dimples are formed, with the lubricating film.
Description
INCORPORATION BY REFERENCE
[0001] The disclosure of Japanese Patent Application No.
2015-038150 filed on Feb. 27, 2015 including the specification,
drawings and abstract is incorporated herein by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a composition for a
lubricating film for coating the surface of a base material with a
lubricating film in which molybdenum disulfide particles are
dispersed and the dispersed molybdenum disulfide particles are
bound together by a binding resin, a sliding member using the same,
and a method of manufacturing the same.
[0004] 2. Description of Related Art
[0005] Hitherto, in order to improve sliding characteristics of a
sliding member, the surface of a base material is coated with a
lubricating film. Such a lubricating film contains, for example,
polytetrafluoroethylene particles, graphite particles, molybdenum
disulfide particles, or the like as a solid lubricant, and the
particles are bound together by a binding resin (matrix resin) such
as a polyamide-imide resin, a polyimide resin, or the like. As
described above, by including the solid lubricant in the
lubricating film, the slidabiltiy of the sliding member can be
enhanced.
[0006] As a technology, for example, Japanese Patent Application
Publication No. 2010-196813 (JP 2010-196813 A) suggests a sliding
member in which a lubricating film formed of a resin binder and 40
mass % to 60 mass % of a solid lubricant with respect to total
amount is formed on the surface of a base material. Here, the solid
lubricant is formed of particles of graphite, molybdenum disulfide,
or the like, and as the resin binder, a polyamide-imide resin, a
polybenzimidazole resin, or a polyimide resin is used.
SUMMARY OF THE INVENTION
[0007] Here, as illustrated in FIG. 7, since a surface 91a of a
base material 91 made of metal is coated with a general lubricating
film 92 such as the lubricating film disclosed in JP 2010-196813 A,
the roughness of a surface 92a of the lubricating film 92 (that is,
the roughness of a surface 9a of a sliding member 9) is likely to
be dependent on the roughness of the surface 91a of the base
material 91.
[0008] However, in a case where the average particle size of
particles 93 that act as the solid lubricant contained in the
lubricating film 92 (the average particle size of the particles
contained in the composition for a lubricating film) is large, the
surface roughness of the lubricating film 92 may become coarser
than the surface roughness of the base material 91. In addition,
even in a case where the amount of the particles 93 (the amount of
particles contained in the composition for a lubricating film) is
increased in order to enhance seizure resistance, the same
phenomenon occurs.
[0009] Accordingly, even when the surface 91a of the base material
91 of the sliding member is further smoothened, the sliding surface
of the sliding member is less likely to become smooth. As a result,
there may be cases where it is difficult to obtain low friction
sliding characteristics.
[0010] The present invention provides a composition for a
lubricating film which reduces the surface roughness of a
lubricating film formed on the surface of a base material of a
sliding member and allows the surface of the lubricating film to be
easily smoothened during sliding, a sliding member using the same,
and a method of manufacturing the same.
[0011] According to an aspect of the present invention, a
composition for a lubricating film includes molybdenum disulfide
particles which are dispersed, and a binding resin. The composition
for a lubricating film is a composition for coating a surface of a
base material made of metal with a lubricating film in which the
molybdenum disulfide particles are bound together by the binding
resin. The composition for a lubricating film contains 50 mass % to
70 mass % of the molybdenum disulfide particles with respect to a
total amount of the molybdenum disulfide particles and the binding
resin. An average particle size of the molybdenum disulfide
particles is in a range of 0.1 .mu.m to 3.0 .mu.m.
[0012] According to the aspect, since 50 mass % to 70 mass % of the
molybdenum disulfide particles are contained, initial fitting
characteristics are enhanced, and thus, the surface of the
lubricating film is easily smoothened during sliding. Furthermore,
since the average particle size of the molybdenum disulfide
particles is 0.1 .mu.m to 3.0 .mu.m, the particles size is reduced,
and thus, the surface of the lubricating film is smoothened.
[0013] Accordingly, when the sliding member is used, the surface of
the lubricating film is easily worn, and thus, the initial fitting
characteristics of the lubricating film (sliding member) can be
enhanced.
[0014] In the aspect, the binding resin may be a polyamide-imide
resin.
[0015] In the aspect, particle binding properties, adhesion to the
surface of the base material, heat-resistance of the lubricating
film, and the like are considered.
[0016] In the aspect, there is provided a sliding member, in which
the surface of the base material is coated with the lubricating
film formed of the composition for a lubricating film.
[0017] In the aspect, a plurality of dimples may be formed on the
surface. A projecting valley depth of the surface may be in a range
of 0.4 .mu.m to 1.0 .mu.m, and a center-line average roughness of
the surface may be in a range of 0.4 .mu.m to 1.0 .mu.m.
[0018] As is apparent from an experiment by the inventors, which
will be described later, by establishing the relationship between
the projecting valley depth Rvk and the center-line average
roughness Ra of the surface of the lubricating film, that is, the
sliding surface of the sliding member, low friction characteristics
can be realized while enhancing the initial fitting characteristics
of the sliding surface of the sliding member.
[0019] In the aspect, the sliding member may be a piston of an
internal-combustion engine. In addition, the lubricating film may
be formed on a surface of a skirt section of the piston.
[0020] In the aspect, there is provided a method of manufacturing a
sliding member, in which a surface of a base material is coated
with a lubricating film formed of the composition for a lubricating
film.
[0021] In the aspect, the method may include forming a plurality of
dimples, and forming the lubricating film on the surface on which
the dimples are formed, with the composition for a lubricating
film. The dimples are formed by propelling hard particles against
the surface of the base material through shot peening to allow the
surface to have a projecting valley depth in a range of 1.5 .mu.m
to 2.0 .mu.m and a center-line average roughness in a range of 1.5
.mu.m to 2.0 .mu.m. The hard particles are harder than the base
material.
[0022] Accordingly, the sliding member having the above-described
characteristics can be easily manufactured.
[0023] In the aspect, there is provided a method of manufacturing
the sliding member as a piston, according to the method of
manufacturing a sliding member. The method may include, after
forming a plurality of dimples on a surface of a skirt section of
the piston, coating the surface of the skirt section, on which the
dimples are formed, with the lubricating film.
[0024] According to the aspects of the present invention, the
surface roughness of the lubricating film formed on the surface of
the base material of the sliding member is reduced, and the surface
of the lubricating film is easily smoothened during sliding.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Features, advantages, and technical and industrial
significance of exemplary embodiments of the invention will be
described below with reference to the accompanying drawings, in
which like numerals denote like elements, and wherein:
[0026] FIG. 1A is a schematic view illustrating a method of
manufacturing a sliding member according to an embodiment, and is a
view illustrating a surface treatment of a base material;
[0027] FIG. 1B is a schematic view illustrating the method of
manufacturing a sliding member according to the embodiment, and is
a view illustrating the surface-treated base material;
[0028] FIG. 1C is a schematic view illustrating the method of
manufacturing a sliding member according to the embodiment, and is
a view illustrating the sliding member in which the surface of the
base material is coated with a lubricating film;
[0029] FIG. 2 is a view illustrating the surface roughnesses of
sliding members according to Examples 1 to 3 and Comparative
Examples 1 to 5;
[0030] FIG. 3 is a view illustrating a wear test of the sliding
members according to Examples 1 to 3 and Comparative Examples 1 to
5;
[0031] FIG. 4 is a view illustrating the wear amounts of the
lubricating films of the sliding members according to Examples 1 to
3 and Comparative Examples 1 to 5;
[0032] FIG. 5 is a view illustrating the relationship between
rotation frequency-BMEP and FMEP when pistons according to Examples
4 and 5 and Comparative Example 6 are used;
[0033] FIG. 6 is a view illustrating the relationship between
rotation frequency-BMEP and FMEP when the pistons according to
Example 5 and Comparative Example 7 are used; and
[0034] FIG. 7 is a schematic view illustrating a sliding member
according to the related art.
DETAILED DESCRIPTION OF EMBODIMENTS
[0035] Hereinafter, an embodiment of the present invention will be
described using FIGS. 1A, 1B, and 1C. FIGS. 1A, 1B, and 1C are
schematic views illustrating a method of manufacturing a sliding
member according to the embodiment, and FIG. 1A is a view
illustrating a surface treatment of a base material. FIG. 1B is a
view illustrating the surface-treated base material. FIG. 1C is a
view illustrating the sliding member in which the surface of the
base material is coated with a lubricating film.
[0036] Regarding a composition for a lubricating film, a
composition for a lubricating film according to this embodiment is
composition for coating a surface 10b of a base material 10 made of
metal, with a lubricating film 20, as illustrated in FIG. 1C. The
composition for a lubricating film contains molybdenum disulfide
particles and a binding resin (resin binder) for binding the
particles.
[0037] The composition for a lubricating film contains 50 mass % to
70 mass % of the molybdenum disulfide particles with respect to the
total amount of the molybdenum disulfide particles and the binding
resin. In addition, the average particle size of the molybdenum
disulfide particles is in a range of 0.1 .mu.m to 3.0 .mu.m.
[0038] Here, "particle size" mentioned in the specification
represents a volume cumulative average particle size (D.sub.50)
measured by a laser diffraction/scattering type particle size
distribution measurement method, "center-line average roughness Ra"
represents a value measured according to JIS B 0601-1994, and
"projecting valley depth (oil accumulation depth) Rvk" represents a
value measured according to JIS B 0601-2001.
[0039] In this embodiment, by allowing 50 mass % to 70 mass % of
the molybdenum disulfide particles to be contained and allowing the
average particle size of the molybdenum disulfide particles to be
0.1 .mu.m to 3.0 .mu.m, the surface roughness of the lubricating
film 20 formed on the surface 10b of the base material 10 of a
sliding member 1, which will be described later, can be the same
degree of surface roughness as the roughness of the surface 10b of
the base material 10. Accordingly, the surface of the lubricating
film 20 can be smoothened. Furthermore, when the sliding member 1
is used, the surface of the lubricating film 20 is easily worn.
Therefore, the initial fitting characteristics of the lubricating
film 20 (the sliding member 1) can be enhanced.
[0040] Here, in a case where the amount of the molybdenum disulfide
particles is more than 70 mass % or in a case where the average
particle size of the molybdenum disulfide particles is greater than
3.0 .mu.m, the surface roughness of the formed lubricating film 20
is increased, and the smoothening of a sliding surface 1a of the
sliding member 1 may be impeded.
[0041] On the other hand, in a case where the amount of the
molybdenum disulfide particles is less than 50 mass %, in an
initial fitting stage, the lubricating film 20 is less likely to be
worn, and the initial fitting characteristics of the sliding member
1 are degraded. It is difficult to manufacture molybdenum disulfide
particles having an average particle size of smaller than 0.1
.mu.m.
[0042] Here, molybdenum disulfide particles having an average
particle size in a range of 0.1 .mu.m to 3.0 .mu.m can be easily
obtained by crushing and classifying commercially available
molybdenum disulfide particles or the like. The average particle
size of molybdenum disulfide particles by which the above-described
effects can be further expected is 0.5 .mu.m to 1.5 .mu.m.
[0043] The binding resin is preferably a heat-resistant resin
capable of binding molybdenum disulfide particles. Examples thereof
include a resin selected from the group consisting of an epoxy
resin, a phenol resin, a polyamide resin, and a polyamide-imide
resin, or a polymer alloy containing one type or two or more types
thereof. Among these, the polyamide-imide resin has excellent heat
resistance, is less likely to deteriorate even when used for
various types of lubricating oil, and has good friction and wear
characteristics.
[0044] The composition for a lubricating film used for forming the
lubricating film can be prepared by preparing the molybdenum
disulfide particles and the binding resin at the above-described
mixing ratio, and stirring and mixing the resultant with an
appropriate organic solvent as the solvent using a kneader or the
like. During the manufacturing of the composition for a lubricating
film, it is preferable to mix the molybdenum disulfide particles in
a state in which the binding resin is preliminarily dissolved in
the organic solvent.
[0045] As the organic solvent, a volatile polar aprotic solvent or
the like is appropriately used. Specific examples include ketones
such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and
cyclohexanone, esters such as methyl acetate and ethyl acetate,
aromatic hydrocarbons such as xylene and toluene, organic halogen
compounds such as methyl chloroform, trichloroethylene, and
trichlorotrifluoroethane, N-methyl-2-pyrrolidone (NMP), methyl
iso-pyrrolidone (MIP), dimethylformamide (DMF), and
dimethylacetamide (DMAC). N-methyl-2-pyrrolidone (NMP) may be
particularly preferably used. A non-polar solvent may also be used
as the organic solvent.
[0046] Furthermore, the composition for a lubricating film may also
contain a dispersant which promotes the dispersion of a solid
lubricant, a silane coupling agent which enhances the adhesion of a
resin to the solid lubricant or the adhesion of a resin to the base
material, and a surfactant which controls the surface tension.
Moreover, an appropriate amount of additives (a suspending agent, a
thickener, an anti-foaming agent, a leveling agent, and the like)
for improving storage stability, film fitting properties, and the
like may be added without departing from the object of the present
invention.
[0047] For the sliding member and the manufacturing method, first,
a base material made of metal is prepared. The base material is
preferably a base material made of type or more types of metals
selected from aluminum, iron, copper, nickel, chromium, and
titanium, and may also be a base material made of an alloy
containing the metals. As desired, a metal base material subjected
to a surface treatment such as alkali degreasing may also be
used.
[0048] Here, the surface roughness of the surface of the base
material made of metal may be appropriately set depending on the
use environment. In this embodiment, when the lubricating film is
formed of the composition for a lubricating film, which will be
described later, the surface roughness of the lubricating film (the
surface roughness of the sliding member) becomes a value close to
the surface roughness of the base material.
[0049] For example, the lubricating film may be formed by applying
the composition for a lubricating film to the surface (cut or
ground surface) of the base material made of metal illustrated in
FIG. 1A. However, in this embodiment, a base surface treatment is
performed to smoothen the surface of the base material 10.
Specifically, as illustrated in FIG. 1A, hard particles 40, which
are harder than the base material 10, are propelled against the
surface 10a of the base material 10 through shot peening. By the
shot peening, the surface 10b in which dimples are formed to allow
the base material 10 to have a projecting valley depth Rvk in a
range of 1.5 .mu.m to 2.0 .mu.m and a center-line average roughness
Ra in a range of 1.5 .mu.m to 2.0 .mu.m is formed (see FIG. 1B).
Accordingly, the surface 10b of the base material 10, which is
optimal for exhibiting the effects of the composition for a
lubricating film according to this embodiment, can be obtained.
[0050] For example, in a case where the base material is made of an
aluminum alloy (Al--Si-based alloy), the hard particles 40 of an
iron-based alloy having an average particle size of 20 .mu.m to 300
.mu.m are used during the shot peening. First, the above-mentioned
hard particles 40 are propelled against the surface 10a of the base
material 10 under the condition of a predetermined arc height value
in an atmosphere in which oxygen is present (for example, in the
air).
[0051] As described above, the surface 10b of the base material 10
in which a plurality of dimples having the above-described surface
properties are formed can be obtained. In addition, the projecting
valley depth Rvk and the center-line average roughness Ra can be
adjusted by changing the shot diameter, shot propelling conditions
during the propelling process, and the like.
[0052] Next, the surface 10b of the base material 10 in which the
dimples are formed is coated with the composition for a lubricating
film to form the lubricating film 20. Coating of the surface 10b of
the base material 10 may be performed by well-known methods such as
brush coating, spray coating, roll coating, coating using screen
printing, knife coating, coating according to a padding method, and
immersion coating. Industrially, coating may also be performed by
air spraying.
[0053] After the composition for a lubricating film is applied to
the surface 10b of the base material 10, a heating treatment is
performed to remove the organic solvent from the composition, such
that the surface of the base material 10 can be coated with the
lubricating film 20 as illustrated in FIG. 1C.
[0054] The projecting valley depth Rvk of the surface of the
obtained lubricating film 20 is in a range of 0.4 .mu.m to 1.0
.mu.m, and the center-line average roughness Ra of the surface of
the lubricating film 20 is in a range of 0.4 .mu.m to 1.0 .mu.m. As
a result, by allowing the relationship between the projecting
valley depth Rvk and the center-line average roughness Ra of the
sliding surface 1a of the sliding member 1 to be in the
above-described range, the sliding surface 1a can be enhanced in
the property of holding the lubricating oil in a state in which the
surface roughness of the sliding surface 1a is lower than that in
the related art. Accordingly, low friction characteristics can be
realized while enhancing the initial fitting characteristics of the
sliding surface 1a of the sliding member 1.
[0055] Here, the thickness of the lubricating film is arbitrary,
but is preferably 6 .mu.m to 16 .mu.m. By allowing the thickness to
be in the above-described range, in a case where the molybdenum
disulfide particles having the above-mentioned average particle
size are contained in the above-described range, the lubricating
film can be smoothened, so that the sliding surface is allowed to
be dependent on the surface of the base material and the sliding
surface is allowed to be in the above-described range. When the
composition for a lubricating film is applied to the sliding
surface of the skirt section of a piston and the lubricating film
is formed, a reduction in the thermal conductivity of the piston
can be suppressed.
[0056] In the related art, when the surface of the base material is
polished by a grindstone or the like, the surface has striation
marks and thus the actual surface pressure is increased.
Accordingly, the initial fitting characteristics cannot be enhanced
by allowing a large amount of the molybdenum disulfide particles to
be mixed. However, in this embodiment, the surface 10b of the base
material 10 smoothened by the base surface treatment described
above is coated with the lubricating film 20, and the actual
surface pressure of the sliding surface la is reduced by reducing
the average particle size of the molybdenum disulfide particles
contained in the lubricating film 20, thereby suppressing wear.
Accordingly, even when a larger amount of the molybdenum disulfide
particles is mixed, the wear resistance is ensured without the
separation or the like of the particles. Therefore, the initial
fitting characteristics of the lubricating film 20 are enhanced and
a smooth sliding surface can be formed at an early stage.
[0057] Hereinafter, Examples of the present invention will be
described.
EXAMPLE 1
[0058] As the base material of the sliding member, an aluminum
alloy casting (AC8B in JIS standards) having a size of 15.7
mm.times.6.5 mm.times.10.1 mm and a surface roughness Rz of 0.8
.mu.m (corresponding to an Ra of 0.2 .mu.m) was prepared, and the
surface of the base material was subjected to alkali
degreasing.
[0059] Subsequently, molybdenum disulfide particles having an
average particle size of 2 .mu.m were prepared as the solid
lubricant, and a polyamide-imide resin (PAI) dissolved in NMP as
the organic solvent was prepared as a resin for binding the
particles. 50 mass % of the molybdenum disulfide particles and 50
mass % (mass % of the resin excluding the organic solvent) of the
polyamide-imide resin were blended as shown in Table 1, and were
mixed, thereby producing a composition for a lubricating film.
Subsequently, the base material was preliminarily heated under the
condition of 80.degree. C..times.30 minutes, the composition for a
lubricating film was applied to the surface of the base material,
the resultant was heated under the condition of 180.degree.
C..times.90 minutes, thereby forming a lubricating film having a
thickness of 13 .mu.m on the base material.
[0060] Here, the average particle size of the molybdenum disulfide
particles was measured by a measurement method according to PIDS
(polarization intensity differential scattering) using a laser
diffraction/scattering type particle size distribution measurement
apparatus (Microtrac MT300 made by Nikkiso Co., Ltd.). The average
particle size is a volume cumulative average particle size D.sub.50
of the molybdenum disulfide particles measured by NMP. In addition,
the ratios (mass %) of the molybdenum disulfide particles and the
polyamide-imide resin were measured through weighing.
EXAMPLE 2
[0061] A sliding member was produced in the same manner as in
Example 1. The difference from Example 1 is that as shown in Table
1, 60 mass % of the molybdenum disulfide particles and 40 mass % of
the polyamide-imide resin were blended to produce a composition for
a lubricating film.
EXAMPLE 3
[0062] A sliding member was produced in the same manner as in
Example 1. The difference from Example 1 is that as shown in Table
1, 70 mass % of the molybdenum disulfide particles and 30 mass % of
the polyamide-imide resin were blended to produce a composition for
a lubricating film.
COMPARATIVE EXAMPLE 1
[0063] A sliding member was produced in the same manner as in
Example 1. The difference from Example 1 is that as shown in Table
1, with respect to 70 mass % of the polyamide-imide resin, as the
solid lubricant, 20 mass % of molybdenum disulfide particles having
an average particle size of 7 .mu.m, 7 mass % of graphite particles
having an average particle size of 2.5 .mu.m, and 3 mass % of
polytetrafluoroethylene (PTFE) particles having an average particle
size of 4 .mu.m were blended to produce a composition for a
lubricating film.
COMPARATIVE EXAMPLE 2
[0064] A sliding member was produced in the same manner as in
Example 1. The difference from Example 1 is that as shown in Table
1, 40 mass % of the molybdenum disulfide particles and 60 mass % of
the polyamide-imide resin were blended to produce a composition for
a lubricating film.
COMPARATIVE EXAMPLE 3
[0065] A sliding member was produced in the same manner as in
Example 1. The difference from Example 1 is that as shown in Table
1, 80 mass % of the molybdenum disulfide particles and 20 mass % of
the polyamide-imide resin were blended to produce a composition for
a lubricating film.
COMPARATIVE EXAMPLE 4
[0066] A sliding member was produced in the same manner as in
Example 1. The difference from Example 1 is that as shown in Table
1, 50 mass % of the graphite particles used in Comparative Example
1 and 50 mass % of the polyamide-imide resin were blended to
produce a composition for a lubricating film.
COMPARATIVE EXAMPLE 5
[0067] A sliding member was produced in the same manner as in
Example 1. The difference from Example 1 is that as shown in Table
1, 50 mass % of the PTFE particles used in Comparative Example 1
and 50 mass % of the polyamide-imide resin were blended to produce
a composition for a lubricating film.
[0068] <Measurement of Surface Roughness of Lubricating
Film>
[0069] The surface roughnesses (center-line average roughnesses Ra)
of the lubricating films of the sliding members according to
Examples 1 to 3 and Comparative Examples 1 to 5 were measured. The
center-line average roughness Ra is a value measured according to
JIS B 0601-1994. The results are shown in Table 1 and FIG. 2. FIG.
2 is a view illustrating the surface roughnesses of the sliding
members according to Examples 1 to 3 and Comparative Examples 1 to
5. Broken line shown in FIG. 2 is the surface roughness of the base
material.
[0070] <Initial Fitting Test>
[0071] As shown in FIG. 3, a block test piece 51 corresponding to
the sliding member of Examples 1 to 3 an Comparative Examples 1 to
5 described above, a ring test piece 52, and a lubricating oil 53
were combined, and a friction and wear test (block-on-ring test
(LFW-1 test), made by Falex Corporation) was conducted.
[0072] Specifically, as the ring test piece 52, a test piece which
is made of gray cast iron (FC250 in JIS standards) and has an outer
diameter of 35 mm, a width of 8.8 mm, and a surface roughness Rz of
0.8 .mu.m was prepared. The lubricating oil 53 was poured into an
oil bath 54 to allow a portion of the ring test piece to be dipped
into the lubricating oil 53, and the ring test piece 52 was rotated
at a peripheral speed of 0.11 m/s while the oil temperature was
held at 80.degree. C. to form an oil film on the surface of the
ring test piece 52. A continuous test was conducted for 5 minutes
by allowing the block test piece 51 to come into contact with the
outer peripheral surface of the ring test piece 52 under a load of
22.5 N.
[0073] The wear depth of the lubricating film of the sliding
member, which was the block test piece 51, was measured after the
end of the test, and was represented as a wear amount. As the
lubricating oil, base oil (commercially available engine oil in the
SAE viscosity grade of 0W-20) was used. The results are shown in
Table 1 and FIG. 4. FIG. 4 is a view illustrating the wear amounts
of the lubricating films of the sliding members according to
Examples 1 to 3 and Comparative Examples 1 to 5. Broken line shown
in FIG. 4 is the lower limit of the wear amount determined from the
experience of the inventors or the like to provide good initial
fitting characteristics.
TABLE-US-00001 TABLE 1 Solid lubricant Surface roughness Wear Type
of PAI Ra depth particles mass % mass % .mu.m .mu.m Example 1
MoS.sub.2 50 50 0.13 8.1 Example 2 MoS.sub.2 60 40 0.18 8.2 Example
3 MoS.sub.2 70 30 0.20 9.5 Comparative MoS.sub.2 20 70 0.45 6.6
Example 1 Graphite 7 PTFE 3 Comparative MoS.sub.2 40 60 0.09 4.8
Example 2 Comparative MoS.sub.2 80 20 0.31 11.5 Example 3
Comparative Graphite 50 50 0.47 9.7 Example 4 Comparative PTFE 50
50 0.56 10.1 Example 5
[0074] (Result 1)
[0075] As shown in FIG. 2 and Table 1, the surface roughnesses of
the lubricating films formed of the compositions for a lubricating
film according to Examples 1 to 3 were lower than those of
Comparative Examples 1, 3, 4, and 5.
[0076] That is, in a case where the lubricating films were formed
of the compositions for a lubricating film according to Comparative
Examples 1, 3, 4, and 5, the surface roughness of the lubricating
film is coarsened. It is thought that this is because in the case
of Comparative Examples 1, 4, and 5, the average particle sizes of
the solid lubricants contained in the compositions for a
lubricating film are greater than those of Examples 1 to 3. On the
other hand, the case of Comparative Example 3 is caused by that the
amount of the solid lubricant (molybdenum disulfide particles)
contained in the composition for a lubricating film is more than
those of Examples 1 to 3.
[0077] On the other hand, as shown in FIG. 4 and Table 1, the wear
amounts of the lubricating films of the sliding members according
to Examples 1 to 3 and Comparative Examples 3 to 5 are more than
those of Comparative Examples 1 and 2. It is thought that this is
because the amounts of the molybdenum disulfide particles of the
lubricating films of the sliding members according to Examples 1 to
3 and Comparative Examples 3 to 5 are more than those of
Comparative Examples 1 and 2. However, since the surface
roughnesses of the lubricating films of Comparative Examples 3 to 5
are higher than the surface roughnesses of those of Examples 1 to
3, the ability to form an oil film is low. Therefore, it can be
said that the lubricating films of the sliding members according to
Examples 1 to 3 have a higher ability to form an oil film than
those of Comparative Examples 1 to 5 and have good initial fitting
characteristics.
[0078] From the above description, it is thought that when 50 to 70
mass % of the molybdenum disulfide particles are contained in the
composition for a lubricating film and the average particle size
thereof is in a range of 0.1 .mu.m to 3.0 .mu.m, the lubricating
film has a surface roughness corresponding to the surface roughness
of the base material (smoothness is provided) and thus good initial
fitting characteristics are provided.
EXAMPLE 4
[0079] As the sliding member, a piston (base material) of an
internal-combustion engine formed of an AC8-based aluminum alloy
casting was prepared, and cutting work was performed on the surface
of the skirt section of the piston. Accordingly, a plurality of
striation marks were formed on the surface of the skirt section.
Next, the projecting valley depth (oil accumulation depths) Rvk at
a plurality of points on the surface of the skirt section was
measured according to JIS B 0601-2001, and the center-line average
roughness Ra thereof was measured according to the above-described
method. As a result, the maximum value of the projecting valley
depth Rvk was 1.0 .mu.m and the minimum value thereof was 0.2 .mu.m
(the projecting valley depth Rvk was 0.2 .mu.m to 1.0 .mu.m), and
the maximum value of the center-line average roughness Ra was 4.8
.mu.m and the minimum value thereof was 2.5 .mu.m (the center-line
average roughness Ra was 2.5 .mu.m to 4.8 .mu.m).
[0080] A lubricating film was formed on the surface using the same
composition for a lubricating film as that in Example 1 under the
same conditions as those of Example 1. The projecting valley depth
Rvk and the center-line average roughness Ra at the plurality of
points on the surface (sliding surface) of the lubricating film
after being formed were measured by the same method as the
above-described method. As a result, the projecting valley depth
Rvk was in a range of 0.2 .mu.m to 1.0 .mu.m, and the center-line
average roughness Ra was in a range of 2.5 .mu.m to 4.8 .mu.m.
EXAMPLE 5
[0081] In the same manner as in Example 4, a piston (base material)
of an internal-combustion engine formed of an AC8-based aluminum
alloy casting was prepared, and a surface treatment was performed
on the surface of the skirt section of the piston. Specifically,
using hard particles which are harder than those of the base
material (specifically, shot formed of an iron-based material
having an average particle size of 50 .mu.m), a plurality of
dimples were formed on the surface of the skirt section through
shot peening.
[0082] Subsequently, the projecting valley depth (oil accumulation
depth) Rvk and the center-line average roughness Ra at the
plurality of points on the surface of the skirt section were
measured. As a result, the maximum value of the projecting valley
depth Rvk was 2.0 .mu.m and the minimum value thereof was 1.5 .mu.m
(the projecting valley depth Rvk was 1.5 .mu.m to 2.0 .mu.m), and
the maximum value of the center-line average roughness Ra was 2.0
.mu.m and the minimum value thereof was 1.5 .mu.m (the center-line
average roughness Ra was 1.5 .mu.m to 2.0 .mu.m).
[0083] A lubricating film was formed on the surface using the same
composition for a lubricating film as that in Example 1 under the
same conditions as those of Example 1. The projecting valley depth
Rvk and the center-line average roughness Ra at the plurality of
points on the surface (sliding surface) of the lubricating film
after being formed were measured by the same method as the
above-described method. As a result, the projecting valley depth
Rvk was in a range of 0.4 .mu.m to 1.0 .mu.m, and the center-line
average roughness Ra was in a range of 0.4 .mu.m to 1.0 .mu.m.
COMPARATIVE EXAMPLE 6
[0084] In the same manner as in Example 4, a piston (base material)
of an internal-combustion engine formed of an AC8-based aluminum
alloy casting was prepared, and cutting work was performed on the
surface of the skirt section of the piston as in Example 4.
Accordingly, a plurality of striation marks were formed on the
surface of the skirt section. The projecting valley depth Rvk and
the center-line average roughness Ra of the surface of the skirt
section were in the same ranges as those described in Example
4.
[0085] A lubricating film was formed on the surface using the same
composition for a lubricating film as that in Comparative Example 1
under the same conditions as those of Comparative Example 1. The
projecting valley depth Rvk and the center-line average roughness
Ra at the plurality of points on the surface (sliding surface) of
the lubricating film after being formed were measured. The
projecting valley depth Rvk and the center-line average roughness
Ra of Comparative Example 6 were in the same ranges as those
described in Example 4.
COMPARATIVE EXAMPLE 7
[0086] In the same manner as in Example 5, a piston (base material)
of an internal-combustion engine formed of an AC8-based aluminum
alloy casting was prepared, and for the surface of the skirt
section of the piston, a plurality of dimples were formed on the
surface of the skirt section through shot peening. The projecting
valley depth Rvk and the center-line average roughness Ra of the
surface of the skirt section were in the same ranges as those
described in Example 5.
[0087] A lubricating film was formed on the surface using the same
composition for a lubricating film as that in Comparative Example 1
under the same conditions as those of Comparative Example 1. The
projecting valley depth Rvk and the center-line average roughness
Ra at the plurality of points on the surface (sliding surface) of
the lubricating film after being formed were measured. The
projecting valley depth Rvk and the center-line average roughness
Ra of Comparative Example 7 were in the same ranges as those
described in Example 5.
[0088] <Actual Machine Test>
[0089] Using the pistons according to Examples 4 and 5 and
Comparative Examples 6 and 7, an actual machine test was conducted.
Specifically, the piston had an emission amount of about 660 cc, a
cylinder bore diameter of 94 mm, and a stroke of 95 mm, 0W-20 was
used as the engine oil, and an oil/water temperature was set to
80.degree. C..+-.1.degree. C. Subsequently, while increasing a
rotation frequency in stages to 2000 rpm, and changing a brake mean
effective pressure (BMEP), a friction mean effective pressure
(FMEP) was measured. The results are shown in FIGS. 5 and 6. FIG. 5
is a view illustrating the relationship between rotation
frequency-BMEP and FMEP when the pistons according to Examples 4
and 5 and Comparative Example 6 are used. FIG. 6 is a view
illustrating the relationship between rotation frequency-BMEP and
FMEP when the pistons according to Example 5 and Comparative
Example 7 are used.
[0090] (Result 2)
[0091] As shown in FIG. 5, the friction mean effective pressures
(FMEP) of Examples 4 and 5 are lower than that of Comparative
Example 6, and the friction mean effective pressure (FMEP) of
Example 5 was lower than that of Example 4. In addition, as shown
in FIG. 6, the friction mean effective pressure (FMEP) of Example 5
was lower than that of Comparative Example 7.
[0092] From this, it is thought that since the composition for a
lubricating film according to Example 1 was used in Examples 4 and
5, even when the molybdenum disulfide particles were contained
therein, the lubricating film could be formed without allowing a
surface roughness to be greater than the surface roughness of the
base material. Accordingly, it is thought that since the
lubricating films of Examples 4 and 5 easily form oil films, the
FMEPs of Examples 4 and 5 became lower than that of Comparative
Example 6.
[0093] Particularly, in the case of the lubricating film of Example
5, the projecting valley depth (oil accumulation depth) Rvk thereof
is greater than that in Example 4 regardless of that the
center-line average roughness Ra thereof is small. Accordingly, it
is thought that in the case of Example 5, a thicker oil film is
more easily formed than in Example 4, and the FMEP in Example 5
became lower than that in Example 4. However, it is thought that in
the case of Comparative Example 7, since the composition for a
lubricating film according to Comparative Example 1 was used, it is
difficult to be dependent on the surface properties of the base
material, and the FMEP in Comparative Example 7 became greater than
that in Example 5.
[0094] Furthermore, when a plurality of the surface roughnesses of
the lubricating film of the skirt section after the actual machine
test were measured, the surface roughness of the lubricating film
according to Example 4 (for example, an Ra of 2.1 .mu.m) was
smaller than that of Comparative Example 6 (for example, an Ra of
2.3 .mu.m). Similarly, the surface roughness of the lubricating
film according to Example 5 (for example, an Ra of 0.72 .mu.m) was
smaller than that of Comparative Example 7 (for example, an Ra of
1.01 .mu.m). The relationship between the surface roughnesses was
the same as the relationship therebetween before the actual machine
test. From this result and the result of the FMEP described above,
it is thought that the sliding members according to Examples 4 and
5 have higher initial fitting characteristics than those of
Comparative Examples 6 and 7.
[0095] While the embodiments of the present invention have been
described in detail, the present invention is not limited to the
above-described embodiments, and various changes in design can be
made without departing from the spirit of the present invention
described in the appended claims and the specification.
* * * * *