U.S. patent application number 10/351576 was filed with the patent office on 2003-07-31 for sintered alloy article, its production method and a motorized fuel pump comprising a bearing comprised of sintered alloy article.
Invention is credited to Maruyama, Tsuneo, Murakami, Youichi, Shimizu, Teruo, Takei, Hiroaki.
Application Number | 20030143096 10/351576 |
Document ID | / |
Family ID | 27606290 |
Filed Date | 2003-07-31 |
United States Patent
Application |
20030143096 |
Kind Code |
A1 |
Shimizu, Teruo ; et
al. |
July 31, 2003 |
Sintered alloy article, its production method and a motorized fuel
pump comprising a bearing comprised of sintered alloy article
Abstract
A sintered alloy article having superior corrosion resistance
while also ensuring product dimensional accuracy is provided. A
sintered alloy body is formed by molding and sintering (S2) a raw
material powder containing copper, and tin plating (S4) treatment
on this sintered alloy body is performed, followed by sizing (S5).
When the tin plating layer is compressed during sizing, the tin
plating layer is formed to a nearly uniform thickness, pores opened
in the outer surface of the sintered alloy body are blocked by the
above tin plating, as a result of said tin plating being compressed
by the above sizing. Moreover, by combining a copper-based sintered
alloy and tin plating, a sintered body is obtained provided with
both corrosion resistance to sulfur and its compounds as well as
corrosion resistance to formic acid, acetic acid and other organic
acids.
Inventors: |
Shimizu, Teruo;
(Niigata-shi, JP) ; Maruyama, Tsuneo;
(Niigata-shi, JP) ; Takei, Hiroaki; (Kariya-shi,
JP) ; Murakami, Youichi; (Ama-gun, JP) |
Correspondence
Address: |
RADER, FISHMAN & GRAUER PLLC
David T. Nikaido
Suite 501
1233 20th Street, N.W.
Washington
DC
20036
US
|
Family ID: |
27606290 |
Appl. No.: |
10/351576 |
Filed: |
January 27, 2003 |
Current U.S.
Class: |
419/9 ; 428/553;
428/647 |
Current CPC
Class: |
C25D 5/48 20130101; B22F
3/16 20130101; Y10T 428/12715 20150115; B22F 2003/242 20130101;
C25D 7/10 20130101; Y10T 428/12063 20150115; B22F 2003/166
20130101; F16C 33/128 20130101; B22F 3/24 20130101; F16C 33/145
20130101 |
Class at
Publication: |
419/9 ; 428/553;
428/647 |
International
Class: |
B22F 007/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 29, 2002 |
JP |
2002-020719 |
Claims
1. A sintered alloy article obtainable by providing a tin plating
layer on a sintered alloy body comprised by molding and sintering a
raw material powder containing copper, and sizing said sintered
alloy body having this tin plating layer.
2. The sintered alloy article according to claim 1 wherein, said
sintered alloy article is a sliding member.
3. A production method of a sintered alloy article comprising:
forming a sintered alloy body by molding and sintering a raw
material powder containing copper, and tin plating this sintered
alloy body followed by sizing.
4. A motorized fuel pump comprising a bearing composed of the
sintered alloy article according to claim 1.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a sintered alloy article,
its production method and a motorized fuel pump comprising a
bearing composed of sintered alloy article.
[0003] 2. Background Art
[0004] Motorized fuel pumps for gasoline engines of the prior art
are known to have a structure as exemplified in the schematic
cross-sectional drawing of FIG. 8. Namely, as shown in the drawing,
the above fuel pump 1 has a structure such that, in a casing 2, a
rotating shaft 2 arranged at both ends of a motor 3 is supported by
bearings 5, an impeller 6 is inserted in one end of the above
rotating shaft 4, and a narrow gasoline flow path 7 is formed along
the outer peripheral surface of the above impeller 6 and a motor
(armature) 3 and the space (not shown) between bearings 5 and
rotating shaft 4. This motorized fuel pump operates such that
impeller 6 rotates with the rotation of the above motor 3, gasoline
is introduced into casing 2 with the rotation of this impeller 6,
and the introduced gasoline is supplied into a separately arranged
gasoline engine by passing through the gasoline flow path formed
along the outer peripheral surface of impeller 6 and motor 3 and
the space not shown between the bearings 5 and rotating shaft 4.
Furthermore, in FIG. 8, a trace amount of fuel passes over the
outer periphery of both bearings 5, and gasoline that has been
increased in pressure by impeller 6 reaches the outer peripheral
surface of motor 3 by passing through gasoline flow path 7 of
casing 1.
[0005] A copper-based sintered alloy article is used for bearings 5
serving as structural members of the above fuel pump, and in the
production of this sintered alloy article, a raw material powder
containing copper is compressed to form a green compact, this green
compact is then sintered to form a sintered alloy body, and this
sintered alloy body is then sized by additional compression to
obtain the prescribed dimensions.
[0006] Since the above bearings 5 are used in an environment in
which they are exposed to fuel, a copper-based sintered alloy
article, that comprises a raw material powder containing copper as
previously described, is used in consideration of resistance to
corrosion by fuel. However, even in the case of such a copper-based
sintered alloy article, there is the problem of decreased service
life due to corrosion if a fuel is used that contains sulfur or its
compounds, or a fuel is used that contains formic acid, acetic acid
or other organic acids.
[0007] Therefore, a copper-lead alloy bearing is described in
Japanese Unexamined Patent Application, First Publication No.
5-202938A in which the providing of tin plating, lead plating or
plating of an alloy thereof on the inner and outer surfaces of a
copper alloy bearing is effective for improving the resistance of
the bearing to corrosion (paragraph 0005 of the patent
publication).
[0008] However, in products requiring a dimensional accuracy of,
for example, 10 .mu.m or less, even if dimensions are within the
allowed dimensional tolerance by performing sizing prior to plating
treatment, there is the problem of being unable to secure the
required dimensional accuracy due to variations in the thickness of
the plating performed thereafter.
BRIEF SUMMARY OF THE INVENTION
[0009] In order to solve the above problems, the object of the
present invention is to provide a sintered alloy article having
superior corrosion resistance and which is able to ensure product
dimensional accuracy, its production method, and a motorized fuel
pump that uses bearings composed of the sintered alloy article.
[0010] In order to achieve the above object, the present invention
provide a sintered alloy article by providing a tin plating layer
on a sintered alloy body comprised by molding and sintering a raw
material powder containing copper, and sizing said sintered alloy
body having this tin plating layer.
[0011] A sintered alloy article can be obtained that has high
corrosion resistance by covering a copper-based sintered alloy body
with a tin plating layer having corrosion resistance. In
particular, corrosion resistance to both sulfur and its compounds
as well as formic acid, acetic acid and other organic acids can be
provided by combining a copper-based sintered alloy and tin
plating. In addition, since the sintered alloy body having a tin
plating layer is sized, product dimensions which include the tin
plating layer can be finished to within a prescribed dimensional
tolerance. Moreover, the tin plating layer is compressed by sizing,
and the tin plating layer is formed to a nearly uniform thickness,
while at the same time, the compressed tin plating layer blocks air
holes in the outer surface of the sintered alloy body.
[0012] The above sintered alloy article may be a sliding
member.
[0013] As a result, a sliding member is obtained that is provided
with corrosion resistance to both sulfur and its compounds as well
as formic acid, acetic acid and other organic acids.
[0014] The present invention also provide a method that comprises
forming a sintered alloy body by molding and sintering a raw
material powder containing copper, and tin plating this sintered
alloy body followed by sizing.
[0015] As a result of using this method, since the tin plating
layer is compressed during sizing, the tin plating layer is formed
to a nearly uniform thickness, and at the same time, air holes
opened in the outer surface of the sintered alloy body are covered
by said tin plating due to said tin plating being compressed by the
above sizing, the compressed tin plating layer blocks air holes in
the outer surface of the sintered alloy article, and improves
coverage by said tin plating layer. In addition, since a sintered
alloy body having a tin plating layer is sized, product dimensions
that include the tin plating layer can be finished to within a
prescribed dimensional tolerance. Moreover, by combining a
copper-based sintered alloy article and tin plating, a sintered
alloy article is obtained that is provided with corrosion
resistance to both sulfur and its compounds as well as formic acid,
acetic acid and other organic acids.
[0016] The present invention further provides a motorized fuel pump
that which comprises a bearing composed of the above sintered alloy
article.
[0017] As a result, the bearings of this motorized fuel pump have
an superior service life with respect to fuel containing sulfur and
its compounds or fuel containing formic acid, acetic acid or other
organic acids.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a flow chart that explains a production method
indicating a first embodiment of the present invention.
[0019] FIG. 2 is a perspective view of a sintered alloy body of a
first embodiment of the present invention.
[0020] FIG. 3 is a partially enlarged cross-sectional view of a
sintered alloy article of a first embodiment of the present
invention.
[0021] FIG. 4 is a cross-sectional view that explains sizing of a
first embodiment of the present invention.
[0022] FIG. 5 is an enlarged cross-sectional view of a tin plating
layer prior to sizing of a first embodiment of the present
invention.
[0023] FIG. 6 is an enlarged cross-sectional view of a tin plating
layer after sizing of a first embodiment of the present
invention.
[0024] FIG. 7 is a flow chart that explains a production method
indicating a second embodiment of the present invention.
[0025] FIG. 8 is a schematic cross-sectional view of a motorized
fuel pump for a gasoline engine.
DETAILED DESCRIPTION OF THE INVENTION
[0026] The following provides an explanation of embodiments of the
present invention with reference to the attached drawings. FIGS. 1
through 6 show one embodiment of the present invention, and
Cu--Ni--Zn--C-based or Cu--Sn--C-based raw materials can be used
for the raw material of the sintered alloy body. Furthermore, the
following explanation is provided using the example of the above
bearings 5 for the sintered alloy article. As shown in FIGS. 2 and
3, bearing 5 is composed of a roughly cylindrical sintered alloy
body 51, and cylindrical sliding surface 52 over which the above
rotating shaft 4 rotationally slides is formed in its center.
Moreover, tin plating layer 53 is provided that covers the entire
exposed outer surface of sintered alloy body 51. Furthermore, the
tin plating in the present invention refers to that which contains
plating of tin or tin alloy.
[0027] A composition containing, for example, 10 to 25% by weight
of Zn, 10 to 25% by weight of Ni, 0.1 to 0.9% by weight of P and 1
to 8% by weight of C, with the remainder consisting of Cu and
unavoidable impurities, and a graphite-dispersed Cu-based sintered
alloy having porosity of 5 to 25% can be used for sintered alloy
body 51 of the above bearing 5, while graphite-dispersed Cu-based
sintered alloy having a composition other than that described above
can also be used.
[0028] In providing an explanation of the production method of the
bearing 5 with reference to FIG. 1, bearings 5 composed of a
graphite-dispersed Cu-based sintered alloy were produced by
preparing as the raw material powder used for sintered alloy body
51 five types of Cu--Ni--Zn alloy powders, all of which are formed
by water atomization and which had an average particle diameter of
45 .mu.m, namely Cu-15.8% Ni-18.3% Zn alloy powder, Cu-16.9%
Ni-18.0% Zn alloy powder, Cu-18.8% Ni-18.4% Zn alloy powder,
Cu-17.4% Ni-16.4% Zn alloy powder and Cu-17.3% Ni-19.9% Zn alloy
powder, (thus five types of alloy powders), water-atomized Cu-P
alloy (containing 33% P) powder having an average particle diameter
of 45 .mu.m, and graphite powder having an average particle
diameter of 45 .mu.m, blending these raw material powders to a
prescribed blended composition, mixing for 40 minutes with a V
mixer (S1: Step 1), molding into a green compact of a prescribed
shape by compressing at a prescribed pressure within the range of
150 to 300 MPa (S2), and sintering this green compact in an ammonia
decomposed gas atmosphere under conditions of holding for 40
minutes at a prescribed temperature within the range of 750 to
900.degree. C. (S3). When the resulting bearings 5 were observed
using a light microscope (magnification: 200.times.), the Cu--P
alloy and graphite were finely dispersed in a base material
composed of a solid solution phase of Cu--Ni--Zn alloy in all
cases, and all exhibited a structure that contained pores. These
bearings 5 made of graphite-dispersed Cu-based sintered alloys
obtained in this manner demonstrated both the superior strength and
corrosion resistance possessed by the Cu--Ni--Zn alloys that form
their base materials, and also demonstrated superior wear
resistance in an atmosphere exposed to highly pressurized,
fast-flowing gasoline. In addition, a motorized fuel pump that uses
these graphite-dispersed Cu-based sintered alloy bearings has a
superior service life with respect to fuel containing sulfur or its
compounds in its impurities.
[0029] In order to further improve corrosion resistance in the
present invention, plating treatment (S4) is performed on sintered
alloy body 51 following sintering treatment (S3). In this plating
treatment (S4), a plating layer 53 containing tin (Sn) and having a
thickness of about 2 to 25.mu. is formed on the outer surface of
sintered alloy body 51 by electroplating and so forth.
[0030] Following plating treatment, bearing 5 is sized by
recompressing (S5) to finish to prescribed dimensions. As an
example, FIG. 4 shows a mold correcting apparatus 11 used for
sizing. This mold correcting apparatus 11 uses the vertical
direction as the axial direction (direction of the vertical axis of
compression), and is equipped with die 12, core rod 13, lower punch
14 and upper punch 15. Die 12 has a nearly cylindrical shape, and
nearly cylindrical core rod 13 is coaxially positioned within this
die 12. Lower punch 14 has a nearly cylindrical shape, and is
engaged between die 12 and core rod 13 so as to move up and down
freely from below. Upper punch 15 has a nearly cylindrical shape,
and is removably engaged between die 12 and core rod 13 so as to
move up and down freely from above. As shown in FIG. 4, the above
bearing 5 is loaded into die 12, and with core 13 inserted and
arranged on sliding surface 52 that forms a through hole of this
bearing 5, bearing 5 is pressurized by upper and lower punches 13
and 14 from above and below to correct to prescribed
dimensions.
[0031] Here, in order to confirm the status of plating layer 53
before sizing and plating layer 53 after sizing, a plurality of
sintered alloy bodies 51 were fabricated, and enlarged photographs
of their structure were taken. In actuality, after forming 20
sintered alloy bodies 51 through plating treatment under identical
conditions, sizing was performed on half, or 10, of the sintered
alloy bodies 51.
[0032] These ten sintered alloy bodies 51 were then cut as shown in
FIG. 3, and enlarged photographs of the structure of sliding
surface 52 were taken. As a result, in the ten sintered alloy
bodies 51 on which sizing was not performed, the average thickness
of tin plating layer 53 on sliding surface 52 was about 10 .mu.m,
and in the ten sintered alloy bodies 51 on which sizing was
performed, the average thickness of tin plating layer 53 was about
6 .mu.m. In this manner, sizing causes the thickness of tin plating
layer 53 to become thinner as a result of the tin plating layer
being drawn out, and the openings 54A of pores 54 are blocked by
this drawn out portion of tin plating layer 53.
[0033] In the sintered alloy bodies 51 on which sizing was not
performed, as shown in FIG. 5, pores 54 having openings 54A are
present in sliding surface 52, and these represent locations at
which pore blockage by plating is inadequate. In addition, surface
irregularities are observed in the outer surface of tin plating
layer 53, and these surface irregularities are formed due to
variations in the thickness of tin plating layer 53.
[0034] In contrast, in sintered alloy bodies 51 on which sizing was
performed, as shown in FIG. 6, openings 54A of pores 54 present in
sliding surface 52 are blocked by tin plating layer 53, while at
the same time, there are few surface irregularities in the outer
surface of tin plating layer 53.
[0035] In this manner, by performing sizing (S5) after plating,
pores 54 opened in the outer surface of sintered alloy body 51 are
blocked by tin plating 53 as a result of compressing and spreading
out said tin plating layer 53, thereby improving coverage by tin
plating layer 53. In addition, together with the outer surface of
tin plating layer 53 being formed flat by sizing (S5), it can also
be finished to a nearly uniform thickness.
[0036] In this manner, in the present embodiment, since a tin
plating layer 53 is provided on a sintered alloy body 51 comprised
by molding and sintering a raw material powder containing copper,
and a bearing 5 is sized that has this tin plating layer 53, a
bearing 5 can be obtained that is composed of a sintered alloy
article that has obtained a high corrosion resistance.
[0037] In particular, by combining a copper-based sintered alloy
with tin plating, bearing 5 can be provided with both corrosion
resistance to sulfur and its compounds, as well as corrosion
resistance to formic acid, acetic acid and other organic acids. In
addition, since a sintered alloy body 51 having tin plating layer
53 is sized, product dimensions which include tin plating layer 53
can be finished to within a prescribed dimensional tolerance.
Moreover, since tin plating layer 53 is compressed by sizing,
simultaneous to tin plating 53 being formed to nearly a uniform
thickness, the compressed tin plating layer 53 seals pores present
in the outer surface of sintered alloy body 51, thereby resulting
superior coverage by tin plating layer 53.
[0038] In addition, the above sintered alloy article may be a
sliding member, e.g. a bearing 5, and the bearing 5 is obtained
that is provided with both corrosion resistance to sulfur and its
compounds and corrosion resistance to formic acid, acetic acid and
other organic acids.
[0039] In this manner, in an embodiment of the present invention,
since a sintered alloy body 51 is formed by molding and sintering a
raw material powder containing copper, and this sintered alloy body
51 is tin plated followed by sizing, tin plating layer 53 is
compressed during sizing, and tin plating layer 53 is formed to a
nearly uniform thickness, while at the same time, pores 54 opened
in the outer surface of sintered alloy body 51 are blocked by tin
plating layer 53 as a result of said tin plating layer 53 being
compressed by the above sizing, thereby allowing compressed tin
plating layer 53 to seal pores in the outer surface of sintered
alloy body 51 resulting in improved coverage by tin plating layer
53. In addition, since sintered body alloy 51 having tin plating
layer 53 is sized, product dimensions matching tin plating layer 53
can be finished to within a prescribed dimensional tolerance.
Moreover, by combining a copper-based sintered alloy article and
tin plating, a sintered alloy article is obtained provided with
both corrosion resistance to sulfur and its compounds as well as
corrosion resistance to formic acid, acetic acid and other organic
acids.
[0040] In this manner, in an embodiment of the present invention,
since a bearing 5 composed of the sintered alloy article of the
present invention is used, the bearing 5 of a motorized fuel pump
has a superior service life with respect to fuel containing sulfur
and its compounds or formic acid, acetic acid or other organic
acids.
[0041] FIG. 7 shows a second embodiment of the present invention.
In providing a detailed description while using the same reference
numerals for the corresponding parts of the above first embodiment
and omitting a detailed explanation thereof, in this example, as a
result of performing sizing (S6) prior to plating sintered alloy
body 51 obtained by sintering (S3) treatment, the above plating(S4)
treatment is performed after finishing sintered alloy body 51 to
prescribed dimensions, and sizing (S5) is then performed after
plating (S4) treatment. By pre-compressing sintered alloy body 51
prior to plating treatment by sizing, a sintered alloy article can
be produced having even higher dimensional accuracy.
[0042] Furthermore, the present invention is not limited to the
above embodiments, and various variations of the present invention
can be carried out. For example, the present invention can be
applied to various raw material powders so long as they contain
copper or copper alloy, and is not limited to the above. In
addition, the bearing is not limited to that described in the
embodiments, but rather the present invention can be applied to
bearings of various shapes. In addition, the sliding member is also
not limited to a bearing, but rather the present invention can be
applied to various types of sliding members provided the member has
a sliding portion.
[0043] The sintered alloy article of present invention is composed
by providing a tin plating layer on a sintered alloy body comprised
by molding and sintering a raw material powder containing copper,
and then sizing this sintered alloy body having a tin plating
layer, and is provided with both corrosion resistance to sulfur and
its compounds as well as corrosion resistance to formic acid,
acetic acid and other organic acids. In addition, since a sintered
alloy body having a tin plating layer is sized, product dimensions
which include the tin plating layer can be finished to within a
prescribed dimensional tolerance.
[0044] When the above sintered alloy article is a sliding member,
the sliding member is provided with both corrosion resistance to
sulfur and its compounds as well as corrosion resistance to formic
acid, acetic acid and other organic acids.
[0045] The production method of the sintered alloy article is a
method in which a sintered alloy body is formed by molding and
sintering a raw material powder containing copper, and then tin
plating this sintered alloy body followed by sizing, wherein the
tin plating layer is compressed during sizing, and simultaneous to
the tin plating layer being formed to nearly a uniform thickness,
the above tin plating is compressed by the above sizing, and pores
opened in the outer surface of the sintered alloy body are blocked
by said tin plating, thereby enabling the compressed tin plating
layer to seal pores in the outer surface of the sintered alloy
body, and improve coverage by the tin plating layer.
[0046] The motorized fuel pump of the present invention comprises a
bearing comprised of the above sintered alloy article, and has a
superior service life with respect to fuel containing sulfur and
its compounds or formic acid, acetic acid and other organic
acids.
* * * * *