U.S. patent application number 09/284467 was filed with the patent office on 2001-08-16 for commutateur of improved segment joinability.
Invention is credited to FUJII, SHINICHI, HARADA, TAKAHIRO, KATO, HIROTAKA, ONOZAKI, SEIJI, OTA, HARUYUKI.
Application Number | 20010013737 09/284467 |
Document ID | / |
Family ID | 16823852 |
Filed Date | 2001-08-16 |
United States Patent
Application |
20010013737 |
Kind Code |
A1 |
FUJII, SHINICHI ; et
al. |
August 16, 2001 |
COMMUTATEUR OF IMPROVED SEGMENT JOINABILITY
Abstract
A metallic ring 45 molded by punching a copper plate having
hooks 43, etc., and a carbon member 46 are brazed to each other by
a brazing material having a higher melting point than the
temperature for connecting a coil to conductive members 52, that
is, a brazing material containing, for example, nickel and
chromium. Next, resin is filled up inside the metallic ring 45 and
carbon member 46 to form a resin substrate 48. Next, slits 50 are
formed at the metallic ring 45 and the carbon member 46 in the
radial direction, so that generally fan-shaped segments 51
insulated from each other and conductive members 52 are formed.
Next, a coil is connected to hooks 43 of the conductive members 52
by soldering, welding, etc.
Inventors: |
FUJII, SHINICHI; (OBU-SHI,
JP) ; KATO, HIROTAKA; (OBU-SHI, JP) ; HARADA,
TAKAHIRO; (TOKYO-TO, JP) ; OTA, HARUYUKI;
(TOKYO-TO, JP) ; ONOZAKI, SEIJI; (TOKYO-TO,
JP) |
Correspondence
Address: |
DENNISON MESEROLE POLLACK & SCHEINER
1745 JEFFERSON DAVIS HIGHWAY
SUITE 612
ARLINGTON
VA
22202
|
Family ID: |
16823852 |
Appl. No.: |
09/284467 |
Filed: |
April 20, 1999 |
PCT Filed: |
August 21, 1998 |
PCT NO: |
PCT/JP98/03710 |
Current U.S.
Class: |
310/233 |
Current CPC
Class: |
H01R 43/02 20130101;
H01R 39/32 20130101; H01R 39/06 20130101; H01R 43/08 20130101; Y10T
29/49011 20150115 |
Class at
Publication: |
310/233 |
International
Class: |
H01R 039/06 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 21, 1997 |
JP |
9-225090 |
Claims
1. A commutator comprising segments formed of carbon, conductive
members to which a coil is connected, and a supporting member that
supports said segments and conductive members, wherein said
segments are brazed to said conductive members using a brazing
material, the brazing material having a melting point that is
higher than the temperature used to connect the coil to said
conductive members.
2. A commutator as set forth in claim 1, wherein said conductive
members are made of copper and said brazing material contains
nickel and chromium.
3. A commutator as set forth in claim 1, wherein said segments are
formed of a material having a firing temperature that is higher
than the brazing temperature.
4. A commutator as set forth in claim 1, wherein the brazing
temperature is less than the melting point of said conductive
members.
5. A commutator as set forth in claim 1, wherein the bending
strength of said segments is 200 kg/cm.sup.2 or more.
6. A commutator as set forth in claim 1, wherein hooks for
connecting a coil are integrally molded with said conductive
members.
7. A commutator as set forth in claim 6, wherein said supporting
member is formed of resin, and wherein a retaining member for
retaining said supporting member is integrally molded with said
conductive members.
8. A commutator for an electro-drive type fuel pump, comprising
segments formed of carbon, conductive members to which a coil is
connected, and a supporting member that supports said segments and
said conductive members, wherein said segments and said conductive
members are brazed together by a brazing material having a melting
point that is higher than a temperature for connecting the coil to
said conductive members.
9. A commutator for an electro-drive type fuel pump as set forth in
claim 8, wherein the bending strength of said segments is 200
kg/cm.sup.2.
10. A method for producing a commutator having segments formed of
carbon, conductive members to which a coil is connected, and a
supporting member that supports said segments and said conductive
members, comprising the steps of: brazing a metallic ring
comprising copper and a carbon member using a brazing material
having a higher melting point than the temperature for connecting
the coil to said conductive members; forming a resin substrate on
said metallic ring and said carbon member; and forming segments and
conductive members by making slits on said metallic ring and said
carbon member.
Description
TECHNICAL FIELD
[0001] The present invention relates to a commutator for a rotor,
and more particularly, to a commutator preferably used in an
electro-drive type fuel pump.
BACKGROUND ART
[0002] A known electro-drive type fuel pump for an in-tank system
is installed in a fuel tank. In such an electro-drive type fuel
pump of an in-tank system, a commutator formed of copper, silver,
etc., is used. However, if such a commutator is used in a mixed
fuel system containing alcohol, it may react with the fuel and may
corrode, and deterioration thereof is accelerated.
[0003] Therefore, a commutator made of carbon has been proposed.
Carbon has better corrosion-resisting properties and a long service
life. Because carbon has self-lubricating properties, satisfactory
operation with brushes can be achieved. FIG. 2 is a plan view
showing one example of a flat type commutator that is formed of
carbon and FIG. 3 is a perspective view thereof. As shown in FIGS.
2 and 3, the flat type commutator comprises a plurality of radially
disposed segments 31 that have a generally fan-shaped
configuration, conductive members 32, each electrically connected
to the respective segments 31 and formed from a conductive material
such as copper, and an insulative resin-made substrate 30 for
supporting the segments 31 and the conductive members 32.
[0004] Each of the segments 31 is formed by compressing and molding
carbon powder and by thermally treating the segments 31. Further, a
hook 33 that connects a coil of an armature 7 is formed on the
conductive members 32. The resin-made substrate 30 is formed at the
center of the axis of rotation of the segments 31. An axial hole
35, into which the armature (rotor) shaft of a motor is fitted, is
formed in the resin-made substrate 30 at the center axis of
rotation. Each of the segments 31 and conductive members 32 are
insulated from other segments 31 and conductive members 32 by slits
34 formed in the radial direction.
[0005] A method for producing such a commutator made of carbon is
disclosed in U.S. Pat. No. 5,175,463. In this fabrication method,
the surface of a ring-like carbon member having a parallel surface
is first treated so that a metallic ring may be joined thereto.
This metallic ring is made of a conductive material, such as
copper, and is attached to the surface of the ring-like carbon
member by soldering. The commutator is filled with resin to form a
resin substrate that supports the carbon member and the metallic
ring. Slits 34 are then formed in the carbon member and the
metallic ring in the radial direction in order to divide the carbon
member and the metallic ring into sections, so that the segments 31
and the conductive members 32 are formed. Subsequently, an armature
(rotor) coil is connected to the conductive member 32 by soldering
or welding.
[0006] In this fabrication method, because the carbon member and
the metallic ring are joined together by soldering, the solder can
sometimes melt, due to the heat that is necessary to connect the
coil, whether by soldering or welding, to the conductive members
that are formed by dividing the metallic ring. The bonding strength
between the segments, which are created by dividing the carbon
member and the conductive member, decreases as the solder melts.
Thus, the segments may separate from the conductive member, and
conductivity may be diminished.
DISCLOSURE OF THE INVENTION
[0007] It is, accordingly, an object of the invention to prevent
the bonding strength between the carbon member and the conductive
member from decreasing and to improve conductivity by reducing
differences in the thermal expansion coefficients between the
conductive member and the segments, even though heat is utilized to
connect a coil to the conductive members, and by improving the
bonding strength between the segments and the conductive
members.
[0008] With the invention, the segments (carbon member) and the
conductive member (metallic ring) are brazed together with a
brazing material that does not melt from the heat applied when
connecting the coil to the conductive member. For example, a
brazing material including nickel and chromium may be used as the
brazing material. Thus, the heat generated in connecting the coil
to the conductive member does not melt the brazing material.
[0009] The contact area between the segments and the conductive
members also is decreased. Further, the firing temperature of the
segments is higher than the melting point of the brazing material,
so as to prevent the segments from cracking when cooling the
brazing material.
[0010] The present invention will be better understood by reading
the description of preferred embodiments described below with
reference to the accompanying drawings or reading the scope of
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is an outline view of an electro-drive type fuel
pump;
[0012] FIG. 2 is a plan view showing a commutator formed of
carbon;
[0013] FIG. 3 is a perspective view showing a commutator formed of
carbon;
[0014] FIG. 4 is a view showing a metallic plate used to produce a
commutator according to a first preferred embodiment of the
invention;
[0015] FIG. 5 is a view showing a metallic ring formed of a
metallic plate illustrated in FIG. 4;
[0016] FIG. 6 is a view showing a state in which a carbon member is
joined to the metallic ring illustrated in FIG. 5;
[0017] FIG. 7 is a view in which a carbon member is joined to the
metallic ring illustrated in FIG. 5;
[0018] FIG. 8 is a view in which the metallic ring and the carbon
member illustrated in FIG. 7 are integrated with a resin
substrate;
[0019] FIG. 9 is a view showing a commutator according to the first
preferred embodiment of the invention;
[0020] FIG. 10 is a cross-sectional view taken along the line X-X
in FIG. 9;
[0021] FIG. 11 is a cross-sectional view taken along the line XI-XI
in FIG. 9;
[0022] FIG. 12 is view showing another example of a claw of the
metallic ring;
[0023] FIG. 13 is a view showing a construction for positioning the
metallic ring and the carbon member;
[0024] FIG. 14 is a view showing another construction for
positioning the metallic ring and the carbon member;
[0025] FIG. 15 is a view showing a metallic plate used to produce a
commutator according to a second preferred embodiment of the
invention;
[0026] FIG. 16 is a view showing a metallic ring formed from the
metallic plate illustrated in FIG. 15;
[0027] FIG. 17 is a view showing a state in which a carbon member
is joined to the metallic ring illustrated in FIG. 15;
[0028] FIG. 18 is a view in which a carbon member is jointed to the
metallic ring illustrated in FIG. 15;
[0029] FIG. 19 is a view in which the metallic ring and the carbon
member illustrated in FIG. 18 are integrated with a resin
substrate;
[0030] FIG. 20 is a view showing a commutator according to the
second preferred embodiment of the invention;
[0031] FIG. 21 is a cross-sectional view taken along the line
XXI-XXI in FIG. 20;
[0032] FIG. 22 is a cross-sectional view taken along the line
XXII-XXII in FIG. 21;
[0033] FIG. 23 is a view showing a metallic plate used to produce a
commutator according to a third preferred embodiment of the
invention;
[0034] FIG. 24 is a view showing a metallic ring formed from the
metallic plate illustrated in FIG. 23;
[0035] FIG. 25 is a view showing a state in which a carbon member
is joined to the metallic ring illustrated in FIG. 24;
[0036] FIG. 26 is a view in which a carbon member is jointed to the
metallic ring illustrated in FIG. 23;
[0037] FIG. 27 is a view in which the metallic ring and the carbon
member illustrated in FIG. 26 are integrated with a resin
substrate;
[0038] FIG. 28 is a view showing a commutator according to the
third preferred embodiment of the invention;
[0039] FIG. 29 is a cross-sectional view taken along the line
XXIX-XXIX in FIG. 28; and
[0040] FIG. 30 is a view showing a correlation between the bending
strength of the carbon member and the yield (non-defective ratio)
of the commutators.
BEST MODES FOR CARRYING OUT THE INVENTION
[0041] First Preferred Embodiment
[0042] FIG. 1 shows one example of an electro-drive type fuel pump
of in-tank system that is provided in a fuel tank.
[0043] An electro-drive type fuel pump illustrated in FIG. 1
comprises a motor section 1 that is incorporated within a
cylindrically formed housing 3, and a pump section 2 that is
incorporated below the housing 3. A motor cover 4 is attached to
the upper end of the housing 3 and a pump cover 5 is attached to
the lower end thereof. The upper and lower ends of a shaft 8 are
supported at the motor cover 4 and the pump cover 5 by bearings 9
and 10, so that an armature 7 is rotatably disposed within a motor
chamber 6. A magnet 11 is disposed on the inner circumferential
wall of the housing 3. A plurality of commutators 12 connected to a
coil are disposed on the armature 7 and are insulated from each
other. The motor cover 4 includes a brush 13, which can slidingly
contact the commutators 12 of the armature 7, and a spring 14 that
biases the brush 13. The brush 13 is connected to an external
connection terminal via a choke coil 15. A fuel supply pipe is
connected to a check valve 17 that is incorporated in a discharge
port 16 and is secured to the motor cover 4. Further, on the
underside of the pump cover 5, a pump body 18 is attached to the
lower end part of the housing 3 by caulking. A fuel inlet port 19
is provided in the pump body 18. A fuel outlet port 20 is provided
in the pump cover 5. A disk-shaped impeller 21 having a number of
blade grooves 22 formed in the circumferential direction is
disposed in the pump chamber formed by the pump body 18 and the
pump cover 5. The impeller 21 is fitted onto and connected to the
armature shaft 8.
[0044] In such an electro-drive type fuel pump, the impeller 21 is
driven and rotated by supplying an electric current to the motor
section 1, which rotates the axis of the armature 7. Thus, fuel in
the fuel tank is suctioned through the inlet port 19 and is
supplied to the motor chamber 6 through the outlet port 20, so that
the fuel is discharged from the discharge port 16 into a fuel
supply pipe.
[0045] A description will now be given of a first preferred
embodiment of a commutator according to the invention with
reference to FIGS. 4 through 9. It will be noted in the
specification that segments formed by sectioning a carbon member
are called "segments," and members formed by sectioning a metallic
ring are called "conductive members."
[0046] First, as shown in FIG. 4, a conductive metallic plate is
punched and has a body section 40, claws (retaining members) 41 and
42 to retain a resin substrate, and a hook 43 for connecting to a
coil. Preferably, a metallic plate is used that is made of copper
or a copper alloy having a higher conductivity.
[0047] As shown in FIG. 5, the body section 40 of the metallic
plate is then curled into a cylindrical shape. Metallic ring 45 is
formed by folding the claws 41 and 42 towards the center of the
cylindrical body section and by folding the hook 43 outward
thereof. If the metallic plate is made of copper or a copper alloy,
the curling of the body section 40 and the folding of the claws 41
and 42 is further improved.
[0048] As shown in FIGS. 6 and 7, a disk-shaped carbon member 46 is
formed from carbon powder that is compressed molded and
heat-treated and is joined to the metallic ring 45 by brazing.
[0049] Titanium (Ti) and chromium (Cr) may be used as a brazing
material to provide good bonding characteristics with the carbon
material that forms the carbon member 46. Further, chromium reacts
with carbon to form chrome carbide, which is an inter-metallic
compound. However, because titanium can be easily oxidized, it can
be only brazed in a vacuum or in an inert gas atmosphere. As a
result, production costs using titanium are increased, and it is
not suitable for mass production. Therefore, chromium is preferable
as a brazing material that has good bonding characteristics with
the carbon materials 46. Moreover, gold (Au), silver (Ag), copper
(Cu), titanium (Ti), and nickel (Ni) also may be as brazing
materials that have good bonding characteristics with the copper
and copper alloy that forms metal ring 45. However, titanium (Ti)
alone is not suitable for the reason mentioned above.
[0050] An investigation was made with respect to the bonding
properties of mercury, copper, nickel, and chromium, and resulted
in a finding that the bonding properties between nickel and
chromium were better than the bonding properties between mercury,
copper and chromium. Further, as will be described below, in order
to prevent the bonding properties between the segments (carbon
member) and the conductive material (metallic rings) from
deteriorating, due to the heat that is applied when connecting the
coil to the conductive member, the melting point of the brazing
material should be higher than the temperature that the brazing
material reaches from the heat absorbed when connecting the coil to
the conductive member. If the melting point of the brazing material
is higher than the soldering or welding temperature (for example,
approx. 1,000 C), this condition is satisfied. Therefore, a brazing
material containing nickel and chromium is preferable as the
brazing material to join the carbon member 46 and the metallic
rings 45.
[0051] However, if the thermal expansion coefficient of the carbon
member 46 is different from the thermal expansion coefficient of
the brazing material, cracks, etc., are likely to form in the
carbon member 46 when the brazing material cools. However, because
the difference in the thermal expansion coefficient between
chromium used in the brazing material and the carbon member 46 is
small (i.e., the thermal expansion coefficient of chromium is
8.4.times.10.sup.-6/C, and the thermal expansion coefficient of
carbon is 7.times.10.sup.-6/C), stress in the carbon member 46,
which results from a difference in the thermal expansion efficient
between the carbon material 46 and the brazing material, is
insignificant as the brazing material cools after the brazing step
is completed. Therefore, it is possible to prevent the carbon
member 46 from cracking, etc., when the brazing material cools. In
this aspect, it is advantageous to use a brazing material
containing chromium.
[0052] It is also necessary that the brazing temperature is less
than the melting point of the 10 metallic rings 45. In the
preferred embodiment, a brazing material, JIS Z 3265 BNi-7
(Japanese Industrial Standards) containing chromium, of which the
major constituent is nickel, was used as brazing material because
it satisfies the above-mentioned conditions.
[0053] Further, because cracks, etc., are likely to form in the
carbon member 46 during the brazing step, if the metallic rings 45
are brazed to a carbon member 46 having a low resistance to
bending, the yield (non-defective ratio) of commutators produced is
reduced. FIG. 30 shows a correlation between the bending strength
of the carbon member and the yield of commutators if brazing is
performed with a brazing material containing nickel and chromium.
As shown in FIG. 30, if the bending strength of the carbon member
is less than 200 kg/cm.sup.2, the yield decreases. Therefore, the
carbon member preferably has a bending strength of 200 kg/cm or
more.
[0054] Further, if the brazing temperature is higher than the
firing temperature of carbon member 46, cracks, etc., are likely to
form in carbon member 46 during the brazing step. Therefore, the
firing temperature of the carbon member 46 is preferably higher
than the brazing temperature. For example, carbon having a firing
temperature that is higher than the melting point of a brazing
material is used. Alternatively, a brazing material having a lower
melting point than the firing temperature of the carbon member is
used.
[0055] If carbon member 46 is brazed to the metallic ring 45 as
illustrated in FIG. 5, the brazing surface area of the carbon
member 46 is small, because the end face of the metallic rings 45,
i.e., the plate thickness face 44, is brazed. Thus, stress in the
carbon member 46, which may be generated by a difference in the
thermal expansion coefficients of carbon member 46 and the brazing
material when the brazing material cools, is reduced, and it is
possible to prevent cracks, etc., from forming in carbon member
46.
[0056] As shown in FIG. 8, the metallic rings 45 and the carbon
members 46 are filled with resin to form a resin substrate 48 that
supports the metallic rings 45 and the carbon members 46. At this
time, a fitting hole 49 is opened and the armature axis 8 is fitted
into the center of the rotational axis of the resin substrate 48.
Because claws 41 and 42 are formed on the metallic rings 45 as
retaining members that retain the resin substrate 48, the metallic
rings 45 are firmly supported by the resin substrate 48. Further, a
stepped portion 47 is formed in the carbon members 46, such that
the stepped portion 47 forms an anchoring portion for the resin
substrate 48. Thus, the carbon members 46 are firmly supported on
the resin substrate 48 by the anchoring portion that is formed in
the stepped portion 47.
[0057] As shown in FIG. 9, slits 50 are formed at the carbon
members 46 and the metallic rings 45 in the radial direction, so
that they are insulated from each other. A plurality of generally
fan-shaped and radially disposed segments 51 and a plurality of
conductive members 52, each joined to the respective segments 51,
are formed.
[0058] A coil is connected to the hook 43 of the conductive members
52 by soldering, welding, etc. Because the conductive members 52
are formed of a metallic plate made of copper or copper alloy, the
thermal conductivity is good, and the coil can be easily connected
by welding.
[0059] FIG. 10 is a cross-sectional view taken along the line X-X
in FIG. 9, and FIG. 11 is also a cross-sectional view taken along
the line XI-XI in FIG. 9.
[0060] As described above, because a brazing material having good
bonding properties between the carbon members 46 and the metallic
rings 45 is used as the brazing material to braze together the
carbon members 46 and the metallic rings 45, it is not necessary to
form any metal film, such as a plating, on the carbon members 46.
As a result, fabrication is simplified. In addition, because the
melting point of the brazing material is high, the brazing material
will not melt due to the heat applied to the brazing material when
connecting the coil to the hooks 43 of the conductive member 52 by
soldering, welding, etc. As a result, the bonding strength between
the segments 51 and the conductive member 52 is not decreased.
Further, because the carbon members 46 and the metallic rings 45
are joined together before forming the resin substrate 48, carbon
having a high firing temperature may be used. Therefore, the
resistance of the carbon members 46 can be reduced, thereby
reducing power loss. Still further, it is possible to prevent
cracks, etc., from forming in the carbon members 46 as a result of
the heat applied to the carbon member when the carbon members 46
are brazed.
[0061] Further, the number of retaining members (claws 41 and 42)
for retaining the resin substrate and installation place thereof
may be appropriately changed, and the retaining members may be
omitted. Further, the shape of the retaining members (claws 41 and
42) may modified in various ways. For example, as shown in FIG. 12,
retaining members 55 having a C-shaped cross section may be used.
Also, the supporting member is not limited to a resin substrate in
order to support the segments (carbon members) and the conductive
members (metallic rings). The shape, position, etc., of the stepped
portion 47 formed on the carbon members 46 may be appropriately
modified, and indeed the stepped portion 47 may be omitted.
[0062] Further, a construction may be utilized that facilitates the
positioning of the carbon members 46 and the metallic rings 45. For
example, as shown in FIG. 13, a tapered section 56 may be formed,
by which the carbon members 46 and the metallic rings 45 can be
attached at a position opposed to each other. The carbon members 46
and the metallic rings 45 may be brazed together after positioning
at the tapered section 56. Alternatively, as shown in FIG. 14, a
groove 57 is formed in the carbon members 46. After the end face of
the metallic ring 45 is inserted into the groove 57, and the carbon
members 46 and the metallic rings 45 are positioned, the engaging
portions may be brazed.
[0063] A description will now be given of a second preferred
embodiment of the invention with reference to FIGS. 15 through 20.
The second preferred embodiment differs from the first embodiment
only in the shapes of the metallic rings and the carbon
members.
[0064] As shown in FIG. 15, a conductive metallic plate is punched
and has a ring-like body section 60, and claw forming portions 61
and hooks 62. Further, the area of the body section 60 is made as
small as possible to prevent the carbon members from cracking,
etc., due to stress in the carbon members when the brazing material
cools. As shown in FIG. 16, the central part of the claw forming
portions 61 is divided, so as to form a metallic ring 64 having a
claw 63 as a retaining member to retain the resin substrate.
[0065] Next, as shown in FIGS. 17 and 18, the metallic rings 64 and
disk-shaped carbon members 65 are brazed together using a brazing
material. A base 66 and a fitting portion 67 are formed at the
carbon members 65. By inserting the fitting portion 67 of the
carbon members 65 into the inner circumferential hole of the
metallic ring 64, the carbon members 65 and the metallic rings 64
can be easily positioned. After the carbon members 65 and the
metallic rings 64 are positioned, the opposing portions of the body
section 60 of the metallic rings 64 and the base 66 of the carbon
members 65 are brazed and joined together.
[0066] As shown in FIG. 19, the metallic rings 64 and the carbon
members 65 are filled with resin, thus forming a resin substrate
68. At this time, a fitting hole 69 is opened, and the armature
axis 8 is fitted inside along the center of rotational axis of the
resin substrate 68. Further, a stepped portion 47, which is similar
to that in the first preferred embodiment, is formed in the carbon
members 65. Thus, the metallic rings 64 are firmly retained in the
resin substrate 68 by the claw 63 and the carbon members 65 are
firmly retained by the anchoring portion of the resin substrate
formed in the stepped portion 47.
[0067] As shown in FIG. 20, slits 70 are then formed in the carbon
members 65 and the metallic rings 64 in the radial direction, so as
to insulate each other and to form a plurality of radially disposed
and generally fan-shaped segments 71 and a plurality of conductive
members 72 joined to the respective segments 71. Hooks 62 of the
conductive members 71 are folded outward, and a coil is connected
to hooks 62.
[0068] FIG. 21 shows a cross-sectional view taken along the line
XXI-XXI in FIG. 20, and FIG. 22 shows a cross-sectional view taken
along the line that XXII-XXII in FIG. 21.
[0069] A description will now be given of a third preferred
embodiment of the invention with reference to FIGS. 23 through 28.
The third preferred embodiment differs from the first and second
preferred embodiments only in the shape of the metallic ring and
the carbon member.
[0070] As shown in FIG. 23, a conductive metallic plate is punched
and has a ring-like body section 80, a hole 81, and a hook 82. As
shown in FIG. 24, the hook 82 is folded outward to form a metallic
ring 83.
[0071] Next, as shown in FIGS. 25 and 26, the metallic ring 83 and
a disk-shaped carbon member 84 are brazed together using a brazing
material containing chromium and nickel, so that a protrusion part
85 is formed on the carbon members 84. By inserting the protrusions
85 of the carbon member 84 into the holes 81 in the metallic ring
83, the carbon member 84 and the metallic ring 83 can be easily
positioned. After the carbon member 84 and the metallic ring 83 are
positioned, the hole 81 and the protrusions 85 are brazed together.
In order to prevent the carbon member 84 from cracking, etc. due to
stress in the carbon member 84 when the brazing material cools, the
end face of the metallic ring 83 to be brazed, i.e., the
circumferential surface of the hole 81, is as small as
possible.
[0072] As shown in FIG. 27, the metallic ring 83 and the carbon
member 84 are filled with resin in order to form a resin substrate
86. At this time, a fitting hole 87 is formed, into which the
armature axis 8 is fitted along the center of rotational axis of
the resin substrate 86. A stepped portion 47 is formed, as in the
first preferred embodiment, so that the metallic ring 83 is firmly
retained in the resin substrate 86 by the protrusions 85 of the
carbon member 84. The protrusions 85 protrude from the hole 81 of
the metallic ring 83 while the carbon member 65 is firmly retained
at the resin substrate 86 by the anchoring part of the resin
substrate, which is formed in the stepped portion 47.
[0073] As shown in FIG. 28, slits 88 are formed at the carbon
member 84 and the metallic ring 83 in the radial direction, so as
to insulate each other, and to form a plurality of radially
disposed and generally fan-shaped segments 89, and a plurality of
conductive members 90 respectively connected to the respective
segments 89. A coil is connected to the hooks 82 of the conductive
members 90. FIG. 29 shows a cross-sectional view taken along the
line XXIX-XXIX in FIG. 28.
[0074] The brazing material used in the present invention is not
limited to a brazing material containing nickel and chromium. It
also may be a brazing material that does not melt as a result of
the heat generated to connect the coil to the conductive members.
Thus, the brazing material used in the invention is not limited to
a brazing material containing nickel and chromium, and it may be a
brazing material in which a difference in the thermal expansion
coefficient between the brazing material and the carbon member is
small. Further, the shape of the metallic ring and the carbon
member, the structure of the brazing portions of the metallic ring
and the carbon member, and method thereof, etc. may be modified in
various ways.
[0075] As described above, in a commutator according to the
invention, the bonding strength between the carbon member
(segments) and the metallic ring (conductive members) is not
reduced, because the brazing material does not melt from the heat
applied to the brazing material when connecting a coil to the
conductive members. In addition, because a metallic film, such as
plating, is not required to be formed on the carbon member,
fabrication is simplified and costs can be reduced. Further,
because the difference in the thermal expansion coefficients
between the brazing material and the carbon member is small, the
carbon member can be prevented from cracking, etc., as a result of
stress generated after the brazing is finished and as the brazing
material cools. Still further, because the metallic ring is
configured so that the brazing surface area of the carbon member is
reduced, the carbon member can be prevented from cracking from
stress when the brazing material cools. Further, because the
metallic plate having the metallic ring can be produced by
punching, the production is simplified and costs thereof is
reduced. Further, because a resin substrate is formed after the
carbon member and the metallic ring are adhered together, the
firing temperature of the carbon member can be increased. Thus,
because the resistance of the carbon member can be decreased, power
loss can be reduced. As a result, the carbon member can be further
prevented from cracking, etc., from the heat when the carbon member
46 is brazed. A commutator according to the invention is useful,
not only for an electro-drive type fuel pump of in-tank system, but
is also useful for rotating machines such as motors, generators and
dynamos in a variety of fields.
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