U.S. patent application number 12/917718 was filed with the patent office on 2011-02-24 for friction material and its manufacturing method.
This patent application is currently assigned to AISIN KAKO KABUSHIKI KAISHA. Invention is credited to Yoshihito FUJIMAKI, Yuko HIGASHIJIMA.
Application Number | 20110041412 12/917718 |
Document ID | / |
Family ID | 32828517 |
Filed Date | 2011-02-24 |
United States Patent
Application |
20110041412 |
Kind Code |
A1 |
FUJIMAKI; Yoshihito ; et
al. |
February 24, 2011 |
FRICTION MATERIAL AND ITS MANUFACTURING METHOD
Abstract
A friction material has a resin amount distribution that is the
largest at a portion near a non-friction surface, that becomes
lower toward an inside and that is the lowest at a portion near a
friction surface. For example, such friction material is
manufacture as follows. First, two friction materials are
overlapped while the friction surfaces faced with each other. Then,
the friction materials are dried at a room temperature. At this
time, the resin has such a characteristic as to move while dragged
by a solvent that dries from the non-friction surface located
outside. Using such characteristic, the resin amount at the portion
near the friction surface is lessened. Then, a temperature at the
friction surface is made low and a temperature at the non-friction
surface is made high in a drying step of the friction material.
Thereby, the resin amount at the portion near the friction surface
is lessened.
Inventors: |
FUJIMAKI; Yoshihito; (
Aichi-ken, JP) ; HIGASHIJIMA; Yuko; (Nagoya-shi,
JP) |
Correspondence
Address: |
WESTERMAN, HATTORI, DANIELS & ADRIAN, LLP
1250 CONNECTICUT AVENUE, NW, SUITE 700
WASHINGTON
DC
20036
US
|
Assignee: |
AISIN KAKO KABUSHIKI KAISHA
Aichi-ken
JP
|
Family ID: |
32828517 |
Appl. No.: |
12/917718 |
Filed: |
November 2, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12318184 |
Dec 23, 2008 |
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12917718 |
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|
11393950 |
Mar 31, 2006 |
7488440 |
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12318184 |
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10730249 |
Dec 9, 2003 |
7051858 |
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11393950 |
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Current U.S.
Class: |
51/295 |
Current CPC
Class: |
F16D 13/64 20130101;
F16D 69/025 20130101; Y10T 428/24942 20150115; Y10T 442/698
20150401; Y10T 428/249921 20150401; F16D 69/026 20130101; Y10T
428/213 20150115; Y10T 442/2344 20150401; Y10T 428/31 20150115;
Y10T 442/699 20150401; Y10T 428/24992 20150115; Y10T 428/24
20150115; F16D 2200/0091 20130101 |
Class at
Publication: |
51/295 |
International
Class: |
B24D 11/00 20060101
B24D011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 9, 2002 |
JP |
2002-357094 |
Dec 9, 2003 |
JP |
2003-410009 |
Claims
1. A manufacturing method of a friction material comprising the
steps of: impregnating a resin in a friction material; and drying
the friction material; wherein the drying step further includes a
step for rotating the friction material in drying at a
predetermined temperature condition so as to make a distribution of
an amount of the resin higher at an outer peripheral portion of the
friction material by a centrifugal force in rotating.
Description
RELATED APPLICATION
[0001] This application is a divisional application of U.S. patent
application Ser. No. 12/318,184 filed on Dec. 23, 2008, which is a
divisional application of U.S. patent application Ser. No.
11/393,950 filed on Mar. 31, 2006 now U.S. Pat. No. 7,488,440,
issued Feb. 10, 2009, which is a divisional application of U.S.
patent application Ser. No. 10/730,249 filed on Dec. 9, 2003 now
U.S. Pat. No. 7,051,858, issued May 30, 2006, which is hereby
incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to a friction material for a friction
clutch device that has a single friction plate or a plurality of
friction plates for use in an automatic transmission of an
automobile, a transmission of a motorcycle or the like, and to its
manufacturing method.
[0004] 2. Description of the Related Art
[0005] A wet friction clutch such as a multiplate clutch has one or
a plurality of wet friction plates that are used in a lubricant.
There are wet friction plates that are made of a sintered alloy, a
carbon or a cork. Still, a paper wet friction plate is called as "a
paper friction material" and is commonly used.
[0006] In manufacturing the paper wet friction material, a paper
body is made of a substrate fiber such as a pulp or an aramid fiber
and a filler such as a friction adjuster or a base filler. Next,
the paper body is impregnated with a resin binder made of a
thermosetting resin. Then, the paper body is heated to cure or
harden the resin binder, thereby resulting in the paper wet
friction material. Such paper wet friction material is advantageous
because it is lightweight and cheap. Moreover, the paper wet
friction material is made of a porous material and relatively rich
in elasticity with resultant high oil absorbency. Furthermore, the
paper wet friction material is excellent in heat resistance,
abrasion resistance and the like.
[0007] A resin existing near a friction surface of the friction
material is one of factors that determine the heat resistance
(particularly a heat spot resistance) of the friction material. If
an amount of the resin near the friction surface is large, the
friction material becomes hard and the heat resistance is lowered.
Thus, it is thought that it is desirable for the resin amount to be
small.
[0008] However, if the total resin amount in the friction material
is reduced so as to decrease the resin amount near the friction
surface, it is impossible to maintain strength required for the
friction material. Therefore, a minimum amount of resin is mixed
into the friction material so as to balance the heat resistance and
the strength.
[0009] Still, it is indispensable to remove the resin at the
friction surface in order to achieve an ultrahigh heat resistance
required for the friction material in these years. As a means to
solve such problem, a post-treatment process such as a surface
polishing or a high heat resin degradation (heat shearing) is added
to improve the heat resistance.
[0010] However, if such post-treatment process is added, the costs
increase. Moreover, there take place adverse effects in case of the
post-treatment process. That is, if the surface polishing is
adopted, the friction face of the friction material becomes rough
or fuzzy so as to increase a drag torque. On other hand, if the
heat shearing is adopted, even an inside of the friction material
reaches a high temperature so as to cause deterioration of strength
or the like. Thus, it is very hard at present to attain goals
recently required for the friction material such as the low costs
and the ultrahigh heat resistance.
BRIEF SUMMARY OF THE INVENTION
[0011] An object of the present invention is to provide a friction
material at low costs that has an ultrahigh heat resistance without
deterioration of strength and to provide a manufacturing method of
such friction material.
[0012] According to a first aspect of the invention, there is
provided a friction material comprising: a friction surface; a
non-friction surface located opposite to the friction surface; and
a resin contained in the friction material. A distribution of an
amount of the resin in a thickness direction from a side of the
friction surface to a side of the non-friction surface of the
friction material is made lower at a portion near the friction
surface than a portion having a highest amount of the resin in the
thickness direction.
[0013] Therefore, the resin amount at the portion near the friction
surface becomes lower than that of an inside of the friction
material or the portion near the non-friction surface.
Consequently, the friction material is improved very much in a heat
resistance and a heat spot resistance, thereby becoming ultrahigh
heart resistant. Moreover, a resin amount distribution in the
thickness direction of the friction material is determined by a
drying step of the friction material. Therefore, a post-treatment
process is unnecessary. Consequently, the friction material can be
ultrahigh heat resistant at low costs without deterioration of
strength.
[0014] The amount of the resin of the friction material may be made
about 5% or more lower at the side of the friction surface than at
the side of the non-friction surface.
[0015] In this case, the resin amount becomes lower at the portion
near the friction surface than at the portion near the non-friction
surface.
[0016] The amount of the resin of the friction material may be made
about 5% or more lower at the side of the friction surface than at
an inside of the friction material.
[0017] In this case, the resin amount becomes lower at the portion
near the friction surface than at the inside of the friction
surface.
[0018] The distribution of the amount of the resin of the friction
material may change in a continuous manner.
[0019] In this case, since the resin amount distribution changes
continuously, no mechanical stress is concentrated on a specific
part.
[0020] The distribution of the amount of the resin of the friction
material may change in a discontinuous manner.
[0021] In this case, the resin amount distribution in the thickness
direction can be determined by an overlapping. Consequently, the
friction material is improved very much in the heat resistance and
the heat spot resistance at desired low costs.
[0022] The distribution of the amount of the resin of the friction
material may be formed by impregnation of the resin.
[0023] In this case, if a temperature at the friction surface is
decreased and a temperature at the non-friction surface is
increased in a drying step after the resin is impregnated, the
resin in the friction material has such a characteristic as to move
from a low temperature part to a high temperature part while led by
a solvent that moves toward the high temperature part so as to be
dried. Consequently, the resin amount distribution in the thickness
direction becomes the highest at the portion near the non-friction
surface and the lowest at the portion near the friction
surface.
[0024] The distribution of the amount of the resin of the friction
material may be made about 1% or more lower at the side of the
friction surface than an average rate of the resin in the friction
material.
[0025] In this case, the resin amount becomes lower at the portion
near the friction surface than at the inside of the friction
surface or at the portion near the non-friction surface.
[0026] The distribution of the amount of the resin may change
two-dimensionally in a width direction and the thickness direction
of the friction material when the friction material is cut along a
largest length.
[0027] In this case, the friction material can obtain a mechanical
strength corresponding to a load direction, thereby having stable
strength.
[0028] The two-dimensional change in the distribution of the amount
of the resin may be such that the distribution of the amount of the
resin is made higher at an outer peripheral portion than at a
central portion of the friction material.
[0029] In this case, the friction material can obtain a mechanical
strength corresponding to a couple direction in which a load
becomes large, thereby having stable strength.
[0030] According to a second aspect of the invention, there is
provided a manufacturing method of a friction material comprising
the steps of: making a resin contained in the friction material;
and drying the friction material. The drying step includes a step
for making low a temperature at one surface of the friction
material and/or making high a temperature at another surface of the
friction material.
[0031] Therefore, the resin in the friction material has such a
characteristic as to move from a low temperature part to a high
temperature part while led by a solvent that moves toward the high
temperature part so as to be dried. Consequently, the resin amount
distribution in the thickness direction becomes the lowest at the
portion near the one surface. Thus, the friction material becomes
ultrahigh heat resistant. Moreover, the manufacturing method forms
a preferable resin amount distribution in the drying step that the
conventional art adopts except a characteristic feature of the
invention. Consequently, it is unnecessary to add steps, so that it
can be practiced at low costs.
[0032] The drying step may further include a step for rotating the
friction material in drying at a predetermined temperature
condition so as to make a distribution of an amount of the resin
higher at an outer peripheral portion of the friction material by a
centrifugal force in rotating.
[0033] In this case, the friction material can obtain a mechanical
strength corresponding to a couple direction in which a load
becomes large, thereby having stable strength.
[0034] According to a third aspect of the invention, there is
provided a manufacturing method of a friction material comprising
the steps of: making a resin contained in the friction material;
and drying the friction material. The drying step may include steps
for drying two friction materials with friction surfaces thereof
overlapped with each other and then hardening the friction
materials at a high temperature while separating the friction
materials or keeping the friction materials overlapped.
[0035] Therefore, a solvent does not dry from the friction surfaces
that are faced with each other. Rather, the solvent dries from the
non-friction surface that is located outside. Then, the resin in
the friction material moves while dragged by the solvent. Thus, a
resin amount distribution in a thickness direction becomes the
highest at a portion near the non-friction surface and the lowest
at the portion near the friction surface. Consequently, the
friction material becomes ultrahigh heat resistant. Moreover, the
manufacturing method forms a preferable resin amount distribution
in the drying step that the conventional art adopts except a
characteristic feature of the invention. Consequently, it is
unnecessary to add steps, so that it can be practiced at low
costs.
[0036] The drying step may further include a step for rotating the
friction material in drying at a predetermined temperature
condition so as to make a distribution of an amount of the resin
higher at an outer peripheral portion of the friction material by a
centrifugal force in rotating.
[0037] According to a fourth aspect of the invention, there is
provided a manufacturing method of a friction material comprising
the steps of: making two or more friction materials containing a
different amount of a resin; and overlapping the friction materials
so as to join the friction materials into one body before finishing
drying of at least one of the friction materials containing the
different amount of the resin.
[0038] Therefore, a plurality of friction materials that has a
desired resin amount and that is dried appropriately are joined to
make the resin amount distribution in the thickness direction the
highest at the portion near the non-friction surface and the lowest
at the portion near the friction surface. Thus, the friction
material becomes ultrahigh heat resistant. For example, the
friction materials are joined into one body during the drying step
in which they are dried to a certain or appropriate degree.
[0039] The drying step may further include a step for rotating the
friction material in drying at a predetermined temperature
condition so as to make a distribution of an amount of the resin
higher at an outer peripheral portion of the friction material by a
centrifugal force in rotating.
[0040] According to a fifth aspect of the invention, there is
provided a manufacturing method of a friction material comprising
the steps of: impregnating a resin in a friction material; and
drying the friction material. The impregnating step includes a step
for impregnating resins having different viscosities in a front
surface and a rear surface of the friction material, and the drying
step includes a step for drying the friction material at a
predetermined temperature condition while locating downward a side
of the friction material at which the resin having a larger
viscosity is contained.
[0041] Therefore, in case the predetermined temperature condition
and the viscosity have a certain relation, namely, in case the
temperature is low and the viscosity is high, a resin amount
distribution in a thickness direction from a friction surface side
to a non-friction surface side of the friction material can be made
lower at a portion near the friction surface than at a portion
having a highest resin amount in the thickness direction.
[0042] The drying step may further include a step for rotating the
friction material in drying at the predetermined temperature
condition so as to make a distribution of an amount of the resin
higher at an outer peripheral portion of the friction material by a
centrifugal force in rotating.
[0043] According to a sixth aspect of the invention, there is
provided a manufacturing method of a friction material comprising
the steps of: impregnating a resin in a friction material; and
drying the friction material. The impregnating step includes a step
for impregnating an additional resin on one surface of the friction
material, and the drying step includes a step for drying the
friction material at a predetermined temperature condition while
locating outside a side of the friction material in which the
additional resin is impregnated and giving a centrifugal force to
the friction material in a thickness of the friction material.
[0044] Therefore, a resin amount distribution in a thickness
direction from a friction surface side, in which the additional
resin is impregnated, to a non-friction surface side of the
friction material can be made lower at a portion near the friction
surface than at a portion having a highest resin amount in the
thickness direction.
[0045] The drying step may further include a step for rotating the
friction material in drying at the predetermined temperature
condition so as to make a distribution of an amount of the resin
higher at an outer peripheral portion of the friction material by a
centrifugal force in rotating.
[0046] Further objects and advantages of the invention will be
apparent from the following description, reference being had to the
accompanying drawings, wherein preferred embodiments of the
invention are clearly shown.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0047] FIG. 1 is a graph showing a distribution of a resin amount
in a thickness direction of a lining portion of a friction material
unit according to an embodiment and its modifications of the
invention.
[0048] FIG. 2 is a graph comparing a heat spot resistance of the
friction material according to the embodiment of the invention and
that of a conventional material.
[0049] FIG. 3 is a graph comparing a .mu.-V positive inclination
characteristic of the friction material of the embodiment and that
of the conventional material.
[0050] FIG. 4 is a graph comparing an initial property of the
friction material of the embodiment and that of the conventional
material.
[0051] FIG. 5 is an explanatory drawing showing a specific example
of the manufacturing method of the friction material according to
the embodiment of the invention.
[0052] FIG. 6 is an explanatory drawing showing another specific
example of the manufacturing method of the friction material
according to the embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0053] One embodiment of the invention is described hereunder
referring to FIG. 1 to FIG. 4.
[0054] FIG. 1 is a graph showing a distribution of a resin amount
in a thickness direction of a lining portion of a friction material
unit according to an embodiment and its modifications of the
invention. FIG. 2 is a graph comparing a heat spot resistance of
the friction material according to the embodiment of the invention
and that of a conventional material. FIG. 3 is a graph comparing a
.mu.-V positive inclination characteristic of the friction material
of the embodiment and that of the conventional material. FIG. 4 is
a graph comparing an initial property of the friction material of
the embodiment and that of the conventional material.
[0055] A friction material as a raw material of a friction material
unit according to the present embodiment is a resin impregnated
friction material. The present embodiment of the friction material
can be manufactured by a variety of manufacturing methods.
[0056] For example, a first manufacturing method of the present
embodiment of the friction material has a drying step of the
friction material. In the drying step, a temperature at a friction
surface of the friction material is kept low, while a temperature
of an opposite surface (non-friction surface) being kept high. A
resin in the friction material has a characteristic or tends to
move from a low temperature portion to a high temperature portion
by trailing behind a solvent that moves to the high temperature
portion so as to be dried. Therefore, a distribution of a resin
amount in a thickness direction is the highest at a portion near
the non-friction surface while being the lowest at a portion near
the friction surface.
[0057] According to a second manufacturing method of the present
embodiment of the friction material, friction surfaces of two
friction materials are faced and overlapped with each other and
naturally dried thereafter for twenty-four hours or more as they
are. Then, the dried two pieces of the friction materials are cured
or hardened at a high temperature while being separated from each
other or being kept overlapped as they are. In this case, the
solvent does not dry from the faced friction surfaces of the two
friction materials but dries from the non-friction surfaces that
are disposed outside. Consequently, the distribution of the resin
amount in the thickness direction is the highest at the portion
near the non-friction surface while being the lowest at the portion
near the friction surface, as in the first manufacturing
method.
[0058] FIG. 1 show respectively the distribution of the resin
amount in the thickness direction in the friction materials "Aa"
and "Ab" made by the first and the second manufacturing methods. As
shown in FIG. 1, in the friction materials "Aa" and "Ab", the
distribution of the resin amount in the thickness direction is the
highest at the portion near the non-friction surface. The
distribution of the resin amount decreases as it goes towards
inside. Then, the distribution of the resin amount is the lowest at
the portion near the friction surface. The friction material having
such distribution of the resin amount has an excellent property as
the friction material starting with a heat spot resistance
mentioned below.
[0059] In a first modification "B" of a friction material of the
present embodiment, the distribution of the resin amount is not the
lowest at the portion near the friction surface. However, the
distribution of the resin amount is lower at the portion near the
friction surface than the other portion such as the portion near
the non-friction surface. In a second and a third modifications "C"
and "D" of friction materials of the present embodiment, the
distribution of the resin amount is lower at the portion near the
friction surface, though the distribution is not so smooth as seen
in the distribution in the embodiments "Aa" and "Ab". In those
cases, the friction materials show excellent heat spot resistance,
too.
[0060] Next, a test for a heat spot resistance was carried out for
a specific example of a friction material according to the present
embodiment of the invention and a conventional friction material as
a comparison example. The specific example of the friction material
was manufactured as follows. First, two of the above described
friction materials according to the embodiment or modifications
were overlapped on each other while the friction surfaces are face
with each other. Then, the two friction materials were naturally
dried for twenty-four hours or more while they are kept overlapped.
Thereafter, the resin in the friction materials was completely
hardened at a temperature of 200.degree. C. for one hour. Then, the
friction materials were stuck to a core metal on which an adhesive
was coated so as to obtain the friction material of the specific
example. Thereafter, the heat spot resistance test was carried out
on the specific example of the friction material according to the
present embodiment and the comparison example of the conventional
friction material. The heat spot resistance test is a test in which
a friction material is pressingly fitted to an iron material and
rotated while it is measured how many times the friction material
rotates until a scorch (heat spot) is generated first on a surface
of the iron material. Thus, the heat resistance of the friction
material is evaluated.
[0061] As a test machine, SAE#2 tester was used. The evaluation was
carried out under a condition of a rotating speed of 7800 rpm, an
inertia amount of 0.086 kgm2, a face pressure of 785 kPa and an oil
amount of 180 ml/min. A test result is shown in FIG. 2. It is seen
that the heat spot resistance of the present embodiment of the
friction material improves up to almost fifteen times as large as
that of the conventional friction material.
[0062] Next, a .mu.-V positive inclination characteristic was
tested on the present embodiment of the friction material while
compared with the conventional friction material. A test result is
shown in FIG. 3. No .mu.-V positive inclination characteristic was
confirmed on the conventional friction material. On the other hand,
an outstanding .mu.-V positive inclination characteristic is
confirmed on the present embodiment of the friction material. Thus,
since the resin amount at the portion near the friction surface is
low in the friction material according to the present embodiment,
an actual driving feeling improves such as a clutch property or a
.mu.-V positive inclination characteristic.
[0063] Next, an initial property was tested on the present
embodiment of the friction material while compared with the
conventional friction material. A test result is shown in FIG. 4.
It is well seen that the present embodiment of the friction
material improves in the initial property far better than the
conventional friction material. Thus, since the resin amount at the
portion near the friction surface is low in the friction material
according to the present embodiment, the initial property improves.
Therefore, it is possible to stabilize a performance of an AT
(automatic transmission) from an initial stage.
[0064] As described above, in the present embodiment of the
friction material, the distribution of the resin amount in the
thickness direction at a lining portion is lower at the portion
near the friction surface than at a portion that has a highest
distribution of a resin amount. For example, in the resin
impregnated friction material, the drying is carried out so as to
make low the temperature at the friction surface of the friction
material and make high the temperature at the non-friction surface.
Thus, the distribution of the resin amount in the thickness
direction of the lining portion of the friction material unit
becomes lower at the portion near the friction surface than at the
portion that has the highest distribution of the resin amount. That
is, the resin amount at the portion near the friction surface is
lower than the inside of the friction material or the portion near
the non-friction surface. Consequently, the heat resistance and the
heat spot resistance improves very much. Thus, the present
embodiment of the friction material becomes ultra-high heat
resistant.
[0065] Moreover, the distribution of the resin amount in the
thickness direction of the friction material is determined by the
drying step of the friction material. Then, it is unnecessary to
carry out a post-treatment process. Consequently, it is possible to
provide a friction material of ultra-high heat resistance at low
costs without any deterioration of the strength. Furthermore, since
the resin amount near the friction surface is less, the clutch
property, the .mu.-V positive inclination characteristic and the
actual driving feeling improve. In addition, since the resin amount
near the friction surface is less, the initial property improves.
Therefore, the performance of the AT is made stable from the
initial stage.
[0066] The "portion near the friction surface" means a portion or a
range that has a depth of about 10% from the friction surface in
relation to the overall thickness of the friction material.
Moreover, a "resin rate" is defined to mean a "resin amount per a
unit volume". Thus, it can be defined that, in the present
embodiment of the friction material, an average resin rate within
the range having a depth of about 10% from the friction surface in
relation to the overall thickness of the friction material is lower
than an average resin rate of the entire friction material. The
same results are obtained if it is defined that an average resin
rate within a range having a depth of about 5% from the friction
surface in relation to the overall thickness of the friction
material is lower than the average resin rate of the entire
friction material. According to experiments of the inventors of the
present application, it was confirmed that an average resin rate
within a range having a depth of about 40% from the friction
surface in relation to the overall thickness of the friction
material is lower than the average resin rate of the entire
friction material. However, as judged from a property shown in FIG.
1, it is estimated that an average resin rate within a range having
a depth a little larger than about 40% from the friction surface in
relation to the overall thickness of the friction material is lower
than the average resin rate of the entire friction material.
[0067] In the present embodiment of the friction material unit, the
friction materials shown by "Aa", "Ab", "C" and "D" of FIG. 1 have
the lowest resin amount distribution in the thickness direction at
the portions near the friction surfaces, respectively. The
above-mentioned effects are obtained if the resin amount
distribution in the thickness direction of the lining portion of
the friction material is such that there exist at the portion near
the friction surface a portion having a high resin amount and a
portion having a low resin amount or portions having resin rate of
about plus 3% or more or minus 3% or less in relation to the
average resin rate. Particularly, the above-mentioned effects are
obtained if the resin amount distribution in the thickness
direction of the lining portion of the friction material is such
that there exist at the portion near the friction surface a portion
having a low resin amount or a resin rate less than about minus 3%
in relation to the average resin rate.
[0068] Moreover, according to test results of the inventors, the
present embodiment of the friction material can be specified as a
friction material that has an average resin rate of 0% to 50% at
the portion near the friction surface and that has a lower average
resin rate than the average resin rate of the entire friction
material. In this case, it is though that the same advantageous
effects are also obtained.
[0069] Particularly, if the resin amount distribution in the
thickness direction of the lining portion of the friction material
is the lowest at the portion near the friction surface, the
friction material can have an extremely high heat resistance and
hear spot resistance so as to be ultrahigh heat resistant.
Moreover, the resin amount distribution in the thickness direction
of the friction material is determined by the drying step of the
friction material. Therefore, no post-treatment process is
necessary. Consequently, the friction material can be manufactured
at low costs and no deterioration of strength is caused thereto.
Furthermore, even if a compounding rate or mixing amount of the
resin of the friction material is increased in order to heighten
the strength, the resin amount near the friction surface becomes
less than the convention one. Consequently, it is possible to
heighten the strength without affecting the heat resistance.
[0070] The manufacturing method of the friction material according
to the present embodiment includes a step for keeping low the
temperature at the friction surface while keeping high the
temperature at the non-friction surface in the drying step of the
friction material. Therefore, the resin in the friction material
has such a property as moving from the low temperature part to the
high temperature part while being led by the solvent that moves to
the high temperature part and that is dried thereafter.
Consequently, the resin amount distribution in the thickness
direction becomes the lowest at the portion near the friction
surface. Accordingly, the friction material can be ultrahigh heat
resistant while having the above-mentioned excellent
characteristics. Moreover, the present embodiment of the
manufacturing method forms a preferable resin amount distribution
in the drying step that is seen in the conventional art. Thus, it
is unnecessary to add special steps, so that the present embodiment
of the manufacture method can be practiced at low costs.
[0071] Particularly, the present embodiment has the step of drying
naturally or at a room temperature the two friction materials that
are overlapped on each other while faced at their friction surfaces
(First Method). The property tests were carried out on the friction
materials manufactured by such step. However, the property is
improved similarly also in case of the friction material that is
manufactured by decreasing the resin amount near the friction
surface by making low the temperature at the friction surface while
making high the temperature at the non-friction surface in the
drying step of the friction material (Second Method).
[0072] The method for decreasing the resin amount near the friction
surface is not limited to the above two methods. A variety of other
methods can be adopted such as a depressurization, a
pressurization, a centrifugal separation, a one-side coating by a
spray coating, a lip coating and a roller coating or the like, etc.
Moreover, while the present embodiment has been described on the
resin impregnated friction material, the friction material of the
invention is not limited to the resin impregnated one. The
invention can be embodied into any type of friction materials as
long as it contains a resin as a component starting with a resin
layered type.
[0073] Particularly, in case of using a powder resin, the inventive
friction material can be similarly manufactured also by a step for
mixing and kneading the powder resin so as to be evenly distributed
when forming the friction material and making low the temperature
at the friction surface while making high the temperature at the
non-friction surface in the drying step of the friction material.
Moreover, in the drying step of the friction material having such
even distribution, the power resin may be spread or dispersed on
one face of the friction material. Alternatively, the powder resin
may be stuck to the one face of the friction material so as to be
impregnated therein.
[0074] The invention is not limited to the above embodiment with
respect to the other structure, shape, number, material, dimension,
relative connection or the like. The invention is not limited to
the above embodiment with respect to the manufacturing method of
the friction material or the other steps.
[0075] Normally, the manufacturing method according to the above
embodiment of the friction material includes the step of making low
the temperature at the one surface and/or making high the
temperature at the other surface in the drying step of the friction
material. Then, the resin in the friction material has a
characteristic such that it moves from the low temperature part to
the high temperature part by being led or dragged by the solvent
that moves toward the high temperature part to be dried.
Consequently, the resin amount distribution in the thickness
direction becomes the lowest at the portion near the one surface.
Accordingly, the friction material becomes ultrahigh heat resistant
while having the above described excellent characteristics.
Moreover, the present embodiment of the manufacturing method forms
the preferable resin amount distribution in the conventional drying
step. Therefore, additional steps are unnecessary and it can be
practiced at low costs.
[0076] The above embodiment of the manufacturing method of the
friction material includes the step for drying the two friction
materials overlapped with the friction surfaces faced with each
other and thereafter hardening the friction materials while
separating them or keeping them overlapped. In this case, the
solvent does not dry from the faced friction surfaces but dries
from the non-friction surface disposed outside. Therefore, the
resin in the friction material moves while being led by the solvent
so that the resin amount distribution in the thickness direction
becomes the highest at the portion near the non-friction surface
and the lowest at the portion near the friction surface.
Accordingly, the friction material becomes the ultrahigh heat
resistant and has the above excellent characteristics. Moreover,
the present embodiment of the manufacturing method forms the
preferable resin amount distribution in the conventional drying
step. Therefore, additional steps are unnecessary and it can be
practiced at low costs.
[0077] The above-mentioned manufacturing method of the friction
material makes two or more friction materials having different
resin amounts overlapped and joined as one body. Specifically, two
or more friction materials having different resin amounts are
formed first. Then, the friction materials are overlapped on each
other in an appropriately dried state before finishing drying while
using at least one or more friction materials having a different
resin amount. Then, the friction materials are stuck to each other
via a binder so as to make one body. Thus, the resin amount
distribution in the thickness direction becomes the highest at the
portion near the non-friction material and the lowest at the
portion near the friction material. Consequently, the friction
material becomes ultrahigh heat resistant. That is, a friction
material can be dried while making the resin amount less at the
portion near the friction surface and mounted on another friction
material before drying so as to be integrally joined. As a result,
the resin amount distribution in the thickness direction from the
friction surface side to the non-friction surface side of the
friction material becomes lower at the portion near the friction
surface than at the portion having the highest resin amount in the
thickness direction. Moreover, it is possible that plural friction
materials be overlapped and the resin impregnated therein so as to
form a friction material having a non-continuous distribution
between the faces of plural friction materials.
[0078] As described above, the friction material according to the
invention has the resin material distribution in the thickness
direction of the lining portion, namely, in the thickness direction
from the friction surface side to the non-friction surface side.
The distribution is lower at the portion near the friction surface
than at the portion having the highest resin amount in the
thickness direction. In embodying the invention, the friction
surface and the non-friction surface or the front and the rear
surfaces of the friction materials that are dried appropriately in
the drying step are joined by the binder. Thus, it is possible to
make the resin amount distribution in the thickness direction from
the friction surface side to the non-friction surface side of the
friction material lower at the portion near the friction surface
than at the portion having the highest resin amount. In this case,
no post-treatment process is necessary. Consequently, the friction
material of ultrahigh heat resistance can be obtained at low costs
without deterioration of the strength.
[0079] As described above, the resin amount distribution in the
thickness direction from the friction surface side to the
non-friction surface side of the friction material is made lower at
the portion near the friction surface than at the portion having
the highest resin amount. Consequently, the friction material
improves its heat resistance and heat spot resistance so as to be
ultrahigh heat resistant. Moreover, the resin amount distribution
in the thickness direction is determined in the drying step of the
friction material. Accordingly, no post-treatment process is
necessary. Consequently, the friction material can be ultrahigh
heat resistant at low costs without deterioration of strength.
[0080] The resin of the above embodiment of the friction material
is 20% or more lower at the friction surface side than at the
non-friction surface side in the embodiment of the "Aa" of FIG. 1.
Therefore, the resin amount near the friction surface becomes lower
than that near the non-friction surface. Thus, the heat resistance
and the heat spot resistance improve very much, so that the
friction material becomes ultrahigh heat resistant. However,
according to the experiments of the inventors, even if the resin
amount is 5% or more lower at the friction surface side than at the
non-friction surface side, it was confirmed that the heat
resistance and the heat spot resistance improved and that the
property as the ultrahigh heat resistant friction material
improved. As a result, it was revealed that it was enough if the
resin amount distribution in the thickness direction from the
friction surface side to the non-friction surface side of the
friction material was made lower at the portion near the friction
surface than at the portion having the highest resin amount in the
thickness direction.
[0081] Particularly, in the above embodiment of the friction
material, the resin amount is made about 5% or more lower at the
friction surface side than at the inside of the friction material.
Since the resin amount is lower at the portion near the friction
surface than at the inside of the friction material. Consequently,
the friction material is improved very much in the heat resistance
and the heat spot resistance in the same manner as the embodiment
in which the resin amount is lower at the portion near the friction
surface than at the portion near the non-friction surface. As a
result, the friction material becomes ultrahigh heat resistant.
Moreover, the resin amount distribution in the thickness direction
is determined in the drying step of the friction material.
Accordingly, no post-treatment process is necessary. Consequently,
the friction material can be ultrahigh heat resistant at low costs
without deterioration of strength.
[0082] In the above embodiment, as shown in FIG. 1, the resin
amount distribution in the friction material is continuously
changed. Therefore, it is prevented that a mechanical stress is
applied to a specific portion.
[0083] Moreover, in the above embodiment, as shown in FIG. 1, the
friction material that changes the resin amount distribution
continuously can be manufactured as follows. That is, two or three
or more friction materials having different resin amounts are
formed first. Then, the friction materials are overlapped on each
other in an appropriately dried state before finishing drying while
using at least one or more friction materials having a different
resin amount. Then, the friction materials having the different
resin amounts are stuck to each other via a binder so as to make
one body.
[0084] In this case, the friction material changes the resin amount
distribution in a discontinuous manner. However, it is possible to
set a resin content rate as desired in the plural friction
materials having the different resin amounts. Consequently, the
friction material is improved very much in the heat resistance and
the heat spot resistance and becomes ultrahigh heat resistant.
Moreover, the resin amount distribution in the thickness direction
can be determined by the overlapping. As a result, it is possible
to obtain the ultrahigh heat resistant friction material at desired
low costs.
[0085] The above embodiment of the friction material is formed by
impregnation of the resin. That is, the temperature at the friction
surface of the friction material is decreased while the temperature
at the non-friction surface being increased after the resin is
impregnated therein. Then, the resin in the friction material has
such a property as to move from the low temperature portion to the
high temperature portion while being led by the solvent that moves
toward the high temperature portion and that is dried thereafter.
Consequently, the resin amount distribution in the thickness
direction becomes the highest at the portion near the non-friction
surface and the lowest at the portion near the friction surface.
Therefore, the friction material can be easily manufactured at low
costs.
[0086] According to the experiments of the inventors, with respect
to the resin amount distribution in the thickness direction of the
above embodiment of the friction material, if the resin amount is
about 1% lower at the portion near the friction surface than the
average resin rate, the resin amount becomes lower at the portion
near the friction surface than the inside of the friction material
or the portion near the non-friction surface. Thus, the friction
material is very much improved in the heat resistance and the heat
spot resistance so as to be ultrahigh heat resistant. Moreover, the
friction material can be ultrahigh heat resistant at low costs
without any deterioration of strength.
[0087] The present embodiment of the manufacturing method of the
friction material can be practiced such that it includes the step
for making low the temperature of the one surface and/or making
high the temperature of the other surface in the drying step of the
friction material. The resin in the friction material has such a
characteristic as to move from the low temperature part to the high
temperature part while dragged by the solvent moving toward the
high temperature portion so as to be dried. Then, the resin amount
distribution in the thickness direction becomes the lowest at the
portion near the one surface. Accordingly, the friction material
becomes ultrahigh heat resistance while having the above excellent
characteristics. Moreover, the present embodiment of the
manufacturing method forms the preferable resin amount distribution
in the conventional drying step. Consequently, no additional steps
are necessary. As a result, it can be practiced at low costs.
[0088] The present embodiment of the manufacturing method of the
friction material includes the steps for drying two friction
materials or two or more friction materials with the friction
surfaces thereof overlapped with each other and then hardening the
friction materials at a high temperature while separating them or
keeping them overlapped. In this case, the solvent does not dry
from the friction surface faced and confronted to each other but
dries from the non-friction surface that is located outside.
Therefore, the resin in the friction material moves while dragged
by the solvent. Thus, the resin amount distribution in the
thickness direction becomes the highest at the portion near the
non-friction surface and the lowest at the portion near the
friction surface. Moreover, the present embodiment of the
manufacturing method forms the preferable resin amount distribution
in the conventional drying step. Consequently, no additional steps
are necessary. As a result, it can be practiced at low costs.
[0089] The present embodiment of the manufacturing method of the
friction material includes the steps for additionally impregnating
the resin into one surface of the friction material in the step of
impregnating the resin in the friction material, disposing the
side, to which the resin is additionally impregnated, of the
friction materials toward outside and drying the friction materials
at a predetermined temperature condition while giving a centrifugal
force in its thickness direction. Consequently, it is possible to
make the resin amount distribution in the thickness direction from
the friction surface side to the non-friction surface side at the
side to which the resin is additionally impregnated lower at the
portion near the friction surface than at the portion having the
highest resin amount in the thickness direction.
[0090] FIG. 5 is an explanatory drawing showing a specific example
of the manufacturing method of the friction material according to
the embodiment of the invention.
[0091] In the present embodiment of the manufacturing method of the
friction material, a friction material 10 is impregnated with a
resin. Next, in a drying step of the friction material 10, the
friction material 10 is disposed on a support 51. Then, the support
51 is mounted on a rotation drum 50 via an engagement means 52.
Thereafter, the rotation drum 50 is rotated to give a centrifugal
force to the friction material 10 in the thickness direction. At
the same time, the friction material 10 is dried at a predetermined
temperature condition. Therefore, the resin amount distribution in
the thickness direction from the friction surface side to the
non-friction surface side of the friction material 10 can be made
lower as desired at the portion near the friction surface than at
the portion having the highest resin amount in the thickness
direction depending on the temperature condition and the
centrifugal force. Alternatively, the drying step of the friction
material 10 may include a step for drying the friction material 10
at a predetermined temperature condition while making a side having
a larger viscosity resin of the friction material 10 disposed
outside and giving a centrifugal force thereto in the thickness
direction. In this case, the resin amount distribution in the
thickness direction from the friction surface side to the
non-friction surface side of the friction material 10 can be made
lower as desired at the portion near the friction surface than at
the portion having the highest resin amount in the thickness
direction depending on the viscosity condition, the temperature
condition and the centrifugal force in the front and the rear sides
of the friction material.
[0092] While the above embodiments are described on the premise
that the friction material is two-dimensionally processed, the
three-dimensional process is possible as shown in FIG. 5.
[0093] FIG. 6 is an explanatory drawing showing another specific
example of the manufacturing method of the friction material
according to the embodiment of the invention.
[0094] Specifically, the friction material 10 is disposed on a
center of a rotation bed 60 that rotates at a predetermined
rotation speed at the time of drying the friction material 10 at a
predetermined temperature condition. Thus, the resin amount
distribution at a peripheral portion of the friction material 10
becomes high by a centrifugal force thereof. Accordingly, in
addition to the above-mentioned embodiments, the resin amount
distribution becomes high at the peripheral portion of the friction
material 10. Consequently, it is possible to obtain a mechanical
strength in such a direction as to enlarge a couple of force
corresponding to a load. As a result, the friction material has a
stable strength.
[0095] That is, when the friction material 10 is cut along a
diameter that is the largest length thereof, the resin amount
distribution changes two-dimensionally in a width direction and a
thickness direction in its cross-section. For example, in the
embodiment of FIG. 6, such two-dimensional change in the resin
amount distribution means that the resin amount distribution is
made higher at the outer peripheral portion than the central
portion. Moreover, the resin amount distribution change can be
obtained as desired according to the thickness of the friction
material 10, the centrifugal force, the temperature and the resin
viscosity.
[0096] The preferred embodiments described herein are illustrative
and not restrictive, the scope of the invention being indicated in
the appended claims and all variations which come within the
meaning of the claims are intended to be embraced therein.
* * * * *