U.S. patent application number 10/509763 was filed with the patent office on 2005-06-02 for dc motor type fuel pump.
Invention is credited to Inoue, Seizo, Matsuzaki, Hiroyuki, Yamamoto, Kazuyuki, Yonemori, Kei.
Application Number | 20050118044 10/509763 |
Document ID | / |
Family ID | 32866317 |
Filed Date | 2005-06-02 |
United States Patent
Application |
20050118044 |
Kind Code |
A1 |
Inoue, Seizo ; et
al. |
June 2, 2005 |
Dc motor type fuel pump
Abstract
A dc motor fuel pump pressurizes and outputs fuel at a pump
section (20) fixed to a yoke (3) of a motor section (10)
accompanied by drive of a dc motor of mentioned motor section (10).
The yoke (3) includes a first tubular yoke (4) provided with a
ring-shaped magnet (2) of rare earths on an inner circumference and
a second tubular yoke (5) provided on an outer circumference of the
first tubular yoke (4) at a position conforming to the magnet.
(2).
Inventors: |
Inoue, Seizo; (Tokyo,
JP) ; Yonemori, Kei; (Tokyo, JP) ; Matsuzaki,
Hiroyuki; (Tokyo, JP) ; Yamamoto, Kazuyuki;
(Tokyo, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Family ID: |
32866317 |
Appl. No.: |
10/509763 |
Filed: |
September 30, 2004 |
PCT Filed: |
December 9, 2003 |
PCT NO: |
PCT/JP03/15692 |
Current U.S.
Class: |
417/423.7 ;
417/423.3 |
Current CPC
Class: |
F02M 37/08 20130101;
H02K 5/12 20130101; H02K 1/17 20130101; H02K 23/04 20130101 |
Class at
Publication: |
417/423.7 ;
417/423.3 |
International
Class: |
F04B 017/00; F04B
035/04 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 14, 2003 |
JP |
2003-36223 |
Claims
1. A dc motor fuel pump that pressurizes and outputs fuel at a pump
section fixed to a yoke of a motor section accompanied by drive of
a dc motor of mentioned motor section; the dc motor fuel pump being
characterized in that said yoke comprises a first tubular yoke
provided with a ring-shaped magnet of rare earths on an inner
circumference and a second tubular yoke provided on an outer
circumference of said first tubular yoke at a position conforming
to said magnet.
2. The dc motor fuel pump according to claim 1, wherein said magnet
is formed by injection molding, and a gate portion thereof is
formed at an end face of said magnet.
3. The dc motor fuel pump according to claim 1, wherein said magnet
is provided with a convex portion or a concave portion at an end
face thereof, and said convex portion or concave portion engages
with a concave portion or a convex portion of the other member
fixed to said yoke.
4. The dc motor fuel pump according to claim 3, wherein the convex
portion of said magnet is a gate portion for the injection
molding.
5. The dc motor fuel pump according to claim 1, wherein at least
one end face of said first tubular yoke and said magnet is on the
same plane.
6. The dc motor fuel pump according to claim 1, wherein an axial
length of said first tubular yoke is substantially equal to an
axial length of said magnet.
7. The dc motor fuel pump according to claim 1, wherein said magnet
is formed by injection molding, and said first tubular yoke is 3 mm
in thickness.
Description
TECHNICAL FIELD
[0001] The present invention relates to a dc motor fuel pump in
which fuel is pressurized by the drive of a motor, and the fuel
within a fuel tank is fed under pressure to an engine.
BACKGROUND ART
[0002] For example, according to the Japanese Patent Publication
(unexamined) No. 262483/2002, a construction of a dc motor for use
in a dc motor fuel pump is disclosed.
[0003] In the conventional dc motor disclosed in the foregoing
official gazette, a cylindrical yoke and a magnet forming a
circumferential magnetic circuit are located on an outer
circumference of an armature.
[0004] In the yoke, a fixing hole for fixing the magnet is formed.
This fixing hole goes through the yoke from an inner
circumferential surface to an outer circumferential surface in a
thickness direction thereof, and an opening diameter opening on the
outer circumferential surface is formed to be larger than an
opening diameter opening on the inner circumferential surface.
[0005] The magnet is a plastic magnet that is formed in a ring
shape by mixing magnetic particles with resin, is formed integrally
with the yoke, and a part of the yoke itself is inserted into the
fixing hole of the yoke.
[0006] Owing to this construction, a part of the magnet, which is
formed integrally with the yoke, is fitted to a fixing hole of the
yoke, and this fit portion is larger on the outer circumferential
side than on the inner circumferential side. Therefore, the magnet
is never released from the yoke even if the magnet contracts after
having been molded, and is reliably fixed to the yoke.
[0007] In the conventional dc motor (that is, motor section) for
use in a dc motor fuel pump, a magnet is fixed to a yoke with the
use of a fixing hole that goes through the yoke in thickness
direction, so that it is necessary to provide a through hole on the
yoke side face.
[0008] As a result, a problem exists in that a yoke deforms, or
burr is produced due to punching.
[0009] Further, when injecting any resin with which magnetic
particles are mixed on an inner circumferential side of the yoke to
mold an integral structure of the magnet and yoke, a problem exits
in that resin overflows from a through hole on the yoke side face,
and burr is formed on an outer circumference of the yoke.
[0010] Moreover, a magnet is located in the innermost viewed in an
axial direction from the yoke end portion, so that a problem exists
in that the gate processing is difficult to be done in case of
carrying out the injection molding of a magnet from the inner
circumferential side of yoke.
[0011] In addition, a gate is an inlet of die at the time of
injection molding, and a sol resin is injected into the die from
this inlet (that is, gate). The resin having been injected in the
die is kept for a predetermined time period under the conditions of
a predetermined pressure and a predetermined temperature to obtain
a complete molded article. At this time, since the resin is filled
in a portion of the inlet, a solid resin of an inlet configuration
(protrusion configuration) remains. This portion is removed by,
e.g., cutting since it is unnecessary. This removal processing is
called as gate processing.
[0012] Moreover, in the case of using a rare earth magnet of a high
retentive power requiring a large polarizing force as magnet, the
yoke constituting a magnetic circuit needs a large thickness.
However, a problem exists in that a polarizing apparatus grows in
size since the yoke is made up of one member.
[0013] This invention was made to solve the problems as described
above, and has an object of providing a dc motor fuel pump in which
it is unnecessary to provide a through hole for fixing a magnet to
a yoke on a yoke side face and, furthermore, in the case of using a
magnet of rare earths, a high degree of freedom in arrangement of a
magnetic circuit formed of the magnet and yoke is achieved, and
polarization of the magnet can be easily carried out with a
small-sized polarizing apparatus.
DISCLOSURE OF INVENTION
[0014] A dc motor fuel pump according to the present invention
pressurizes and outputs fuel at a pump section fixed to a yoke of a
motor section accompanied by drive of a dc motor of mentioned motor
section, and in which the mentioned yoke includes a first tubular
yoke provided with a ring-shaped magnet of rare earths on an inner
circumference and a second tubular yoke provided on an outer
circumference of the mentioned first tubular yoke at a position
conforming to the mentioned magnet.
[0015] As a result, in this dc motor fuel pump, it is unnecessary
to provide a through hole for fixing a magnet to a yoke on a yoke
side face. Furthermore, in the case of using a magnet of rare
earths, a high degree of freedom in arrangement of a magnetic
circuit formed of the magnet and yoke is achieved, and polarization
of the magnet can be easily carried out with a small-sized
polarizing apparatus.
BRIEF DESCRIPTION OF DRAWINGS
[0016] FIG. 1 is a cross sectional view of a dc motor fuel pump
according to a first preferred embodiment of the present
invention.
[0017] FIG. 2 is an explanatory view of polarization of a
magnet.
[0018] FIG. 3 is a cross sectional view schematically showing a
magnet and yoke of a dc motor fuel pump according to a second
embodiment of the invention.
[0019] FIG. 4 is a cross sectional view schematically showing a
magnet and a first tubular yoke of a dc motor fuel pump according
to a third embodiment of the invention.
[0020] FIG. 5 is a view schematically showing a magnet and a
bearing holder of a dc motor fuel pump according to a fourth
embodiment of the invention.
BEST MODE FOR CARRYING OUT THE INVENTION
EMBODIMENT 1
[0021] A first preferred embodiment of the present invention is
hereinafter described.
[0022] FIG. 1 is a cross sectional view of a dc motor fuel pump
(hereinafter, it is merely referred to as fuel pump as well)
according to the first embodiment of the invention. A fuel pump 1
is comprised of a motor section 10 and a pump section 20.
[0023] First, the motor section 10 is described. A magnet 2 is
formed in a cylindrical configuration, and is located with a
predetermined distance from an outer circumferential surface of an
armature 6 on an inner circumferential surface of a yoke 3 to form
a magnetic circuit along with the yoke 3 at an outer circumference
of the armature 6.
[0024] In addition, on the supposition that a magnet material, for
example, neodym of Sm Fe N is injected onto an inner
circumferential surface of the yoke 3 to form the magnet 2
integrally with the yoke 3, an adhesive between the magnet 2 and
the yoke 3 becomes unnecessary.
[0025] The yoke 3 consists of a first tubular yoke 4 and a second
tubular yoke 5 that are made of STKM (carbon steel tube for machine
structure). The first tubular yoke 4 is press-fitted into the
second tubular yoke 5 in an axial direction until coming in contact
with a convex portion 50a of the second tubular yoke 5.
[0026] Additionally, as described later, from the viewpoint of
easier polarization, in the case of forming the magnet 2 integrally
with the first tubular yoke 4 by the method of injection molding,
it is preferable to polarize the magnet 2 before the first tubular
yoke 4 is press-fitted into the second tubular yoke 5.
[0027] Further, a gate portion for the purpose of forming the
magnet 2 by injection molding is formed at an end face of the
magnet 2.
[0028] In this case, in view of accuracy in polarization, or low
likelihood of deformation at the time of machining the first
tubular yoke 4, a thickness of the first tubular yoke 4 is
preferably not more than 3 mm, more preferably not more than 2
mm.
[0029] The second tubular yoke 5 is bent toward a shaft center
direction of a shaft 7 at both ends thereof, thereby forming an
integral structure of a bearing holder 12, an inlet housing 21, and
an outlet housing 23.
[0030] Additionally, it is preferable that one end portion of the
second tubular yoke 5 is bent toward a shaft center direction of
the shaft 7.
[0031] In this case, either the bearing holder 12 or the housing
consisting of the inlet housing 21 and the outlet housing 23 is
press-fitted and fixed to the other end portion that has not been
bent.
[0032] For example, the bearing holder 12 that is made of an
insulating resin of which main component is poly-acetal houses a
check-valve 13, a bearing 8 to journal the shaft 7, a brush 9
having conductive properties, a coil spring 10 pressing this brush
9 to the commutator 6a, a lead wire 11 for supplying a current
outside of the fuel pump to the brush 9, and others.
[0033] Now, the pump section 20 is described. The inlet housing 21
is made of resin, houses a shaft stopper 28, and is provided with
an inlet for sucking fuel within the fuel tank not shown.
[0034] The outlet housing 23 is made of resin, is provided with an
outlet 24 for discharging fuel having been pressurized in a passage
27 to the side of the armature 6, and houses a bearing 25
journaling the shaft 7.
[0035] A D-shaped cut portion 7a, being an end portion of the shaft
7 of which cross section is formed in a D shape, is fitted into a
D-shaped bore at a center portion of an impeller 26 that is molded
of resin and provided with a plurality of blade grooves on an outer
circumference.
[0036] A passage 27 is formed by concave grooves 21a, 23a of the
inlet housing 21 and outlet housing 22, and a plurality of impeller
grooves of the impeller 26.
[0037] Now, operation of the fuel pump is described.
[0038] When current is fed from a battery, not shown, to the
armature 6 via a feed terminal (not shown), the lead wire 11, the
brush 9 and a commutator 6a, the armature 6 rotates along with the
impeller 26 using the shaft 7 as a rotary shaft.
[0039] Thus, fuel within a fuel tank, not shown, is induced from
the inlet 22 and pressurized to be 300 Kpa to 500 Kpa in the
passage 27, and thereafter passes through the outlet 24 and flows
into a space within the motor section 10. This pressurized fuel
cools the armature 6 when passing through between the armature 6
and the magnet 2 within the motor section 10, causes the check
valve 13 to open, and is discharged from a discharge pipe 12a of
the bearing holder 12. This pressurized fuel having been discharged
is fed to an internal combustion engine (engine), not shown.
[0040] As described above, the yoke 3 consists of the first tubular
yoke 4 having a smaller thickness and the second tubular yoke 5
having a larger thickness.
[0041] Accordingly, in the case of using a magnet 2 of rare earths
having a large retentive power, first the magnet 2 of rare earths
is formed on an inner circumferential surface of the first tubular
yoke 4 by injection molding, and the magnet 2 is polarized in the
state as it is. Thereafter, the first tubular yoke 4 provided with
the magnet 2 on an inner surface can be fixed at a desired position
of the second tubular yoke 5.
[0042] In the meantime, as compared with the conventional fuel pump
employing a sintered magnet having a smaller retentive power than
the magnet of rare earths, the fuel pump 2 using the magnet 2 of
rare earths according to the first embodiment requires a yoke 3
having a larger thickness.
[0043] On the other hand, the fuel pump 1 needs to be provided with
a pump section 20 in an axial direction, being different from a
general dc motor. Further, a pressurized fuel passes through the
fuel pump 1, so that it is necessary to keep the bearing holder 12,
the inlet housing 21 and the outlet housing 23 fluid-tight (that
is, so as to prevent fluid from leakage) with the second tubular
yoke 5.
[0044] For this reason, as compared with a general dc motor, an
axial length (overall length of an axial direction) of the second
tubular yoke 5 becomes larger.
[0045] According to this first embodiment, since the yoke 3
consists of the first tubular yoke 4 and the second tubular yoke 5,
a magnetic circuit can be changed only by, for example, varying a
length of the first tubular yoke 4.
[0046] Thus, as compared with the case of a yoke having an integral
structure as the conventional one, a higher degree of freedom is
achieved in arrangement of a magnetic circuit.
[0047] Further, the first tubular yoke 4 is applicable to plural
types of fuel pumps of which required specifications are different
only by varying a length of the firs tubular yoke 4, so that it
comes to be also possible to use the second tubular yoke 5 commonly
with respect to plural types of fuel pumps.
[0048] Further, since the yoke 3 consists of two members of the
first tubular yoke 4 and the second tubular yoke 5 having a larger
axial length than the first tubular yoke 4, it is possible to make
smaller a thickness of an end portion of the second tubular yoke 5
exerting less influence on a magnetic circuit.
[0049] Further, bending of the second tubular yoke 5 to a shaft
center direction of the shaft 7 becomes easy by making smaller a
thickness of an end portion of the second tubular yoke 5, and an
easier assembling of the fuel pump 1 is achieved.
[0050] Furthermore, it is constructed such that the magnet 2 is
fixed onto an inner circumference of the first tubular yoke 4, so
that a position of the magnet 2 within the fuel pump 1 can be
adjusted by changing a fixed position of the first tubular yoke 4
relative to the second tubular yoke 5.
[0051] Consequently, the magnet 2 can be fixed to a position
convenient for product structure in the first tubular yoke 4.
[0052] Further, by making an axial length of the first tubular yoke
4 and the magnet 2 identical to make end face positions of an end
of the first tubular yoke 4 and magnet 2 the same, it is possible
to form a gate for injection molding in the proximity of an end
portion of the first tubular yoke 4.
[0053] In this case, it becomes unnecessary to provide a hole of a
gate for injection molding on a side face of the first tubular yoke
4, or to provide a gate for the injection molding from the inner
circumferential side of the first tubular yoke 4, being different
from the conventional art. In addition, gate processing comes to be
easy.
[0054] Further, since the first tubular yoke 4 and second tubular
yoke 5 acts as a magnetic circuit of a circumferential direction in
cooperation, the scope of thickness selection of the first tubular
yoke 4 and second tubular yoke 5 is expanded.
[0055] For example, it is possible to make the first tubular yoke 4
thinner by making the second tubular yoke 5 acting as a main
magnetic circuit thicker.
[0056] In the case of using a rare earth magnet having a large
coercive force that requires a large polarization as the magnet 2,
a magnetic circuit of a large thickness corresponding to the
coercive force thereof. However, thickness of the first tubular
yoke 4 and second tubular yoke 5 can be selected within a wide
range thereby enabling to meet easily.
[0057] That is, in the case of using a rare earth magnet having a
large coercive force that requires a large polarization, it is
possible to make the first tubular yoke 4 thinner, to polarize the
magnet 2 having been injection-molded on the inside of this first
tubular yoke 4, and thereafter to mount the first tubular yoke 4 on
the second tubular yoke 5 functioning as a main magnetic
circuit.
[0058] In consequence, it is possible to polarize the magnet 2 with
a small-sized polarizing apparatus. In addition, an occupied volume
of the first tubular yoke 4, which is unnecessary for polarization
of the magnet 2, is small, so that it is possible to enhance
accuracy in polarization.
[0059] Now, polarization of the magnet is described referring to
FIG. 2.
[0060] FIG. 2 is a view for explaining the condition of when
polarizing the magnet 2 by the same polarizing force 41 with the
polarizing apparatus 40. FIG. 2(a) shows the case where the magnet
2 is formed on an inner circumference of the first tubular yoke 4
having a small thickness like this first embodiment. FIG. 2(b)
shows the case where the magnet 2 is formed on an inner
circumference of the tubular yoke having a large thickness like the
conventional art.
[0061] In the case of FIG. 2(a), a magnetic force 42 crosses over
the first tubular yoke 4 and the magnet 2 by a predetermined
polarizing force 41 of the polarizing apparatus 40, thereby
enabling to polarize the magnet 2 desirably.
[0062] On the other hand, in the case of FIG. 2(b), no magnetic
force 42 crosses over the magnet 2 by the same polarizing force 41
as FIG. 2(a) (the so-called short state), and the magnet 2 cannot
be polarized to the full.
[0063] Accordingly, as compared with the case of FIG. 2(a), a large
polarizing force is necessary for polarization of the magnet 2.
[0064] Further, on the supposition that a smaller coefficient of
linear expansion is selected for the second tubular yoke 5 than for
the first tubular yoke 4, the contact between the first tubular
yoke 4 and the second tubular yoke 5 is kept even if the first
tubular yoke 4 and second tubular yoke 5 expands due to an elevated
temperature by the operation of a fuel pump or by the influence of
service condition, resulting in low likelihood of division of a
magnetic circuit.
[0065] In addition, although the first tubular yoke 4 is
press-fitted into the second tubular yoke 5 to be fixed in the
foregoing example,, it is also preferable for the first tubular
yoke 4 to be shrinkage-fitted.
EMBODIMENT 2
[0066] A second preferred embodiment of this invention is
hereinafter described.
[0067] FIG. 3 is a cross sectional view schematically showing a
magnet and a yoke of a dc motor fuel pump according to the second
embodiment. FIG. 3(a) shows the case where an axial length of the
first tubular yoke is longer than that of the second tubular yoke.
FIG. 3(b) shows the case where an axial length of the first tubular
yoke is shorter than that of the second tubular yoke.
[0068] In the case shown in FIG. 3(a), an end face of a magnet 2a
is in contact with a rib 40a provided on an inner surface of lower
end of a first tubular yoke 4a, thereby preventing the magnet 2a
that is located within the first tubular yoke 4a from moving
downward when or after the magnet 2a is molded integrally with the
first tubular yoke 4a on an inner circumference by molding at the
time of use as the fuel pump 1.
[0069] A second tubular yoke 5a possesses the same construction as
the first tubular yoke 5 described in the foregoing first
embodiment, and the other constructions, not shown, are the same as
that of the first embodiment, so that descriptions thereof are
omitted herein (it is the same as in the embodiments described
hereinafter).
[0070] In addition, in the case where the magnet 2a is polarized
after it has been molded integrally with the fist tubular yoke 4a
by injection molding, an axial length of the first tubular yoke 4a
is short (that is, it is substantially the same axial length as the
magnet 2a) as compared with the case of FIG. 3(b), thereby enabling
easy polarization.
[0071] Particularly, in the case of a fuel pump, as compared with a
dc motor, a pump section 20 is required in an axial direction, and
an axial direction of the second tubular yoke 5a becomes longer, so
that function and advantage thereof are significant.
[0072] In the case shown in FIG. 3(b), a second tubular yoke 5b
covers a part of an outer circumference of the first tubular yoke
4b at a position conforming to a magnet 2b (i.e., at a position of
constituting a magnetic circuit along with the magnet 2b and a
first tubular yoke 4b).
[0073] Owing to such a construction, it is sufficient that the
second tubular yoke 5b is located only in a region necessary for
constituting a magnetic circuit, thereby enabling to make an
overall contour of a fuel pump downsized.
[0074] Further, as compared with the case of FIG. 3(a), it is easy
to, e.g., weld together the first tubular yoke 4b and the second
tubular yoke 5b for reinforcing the fixation therebetween after the
first tubular yoke 4b and the second tubular yoke 5b have been
press-fitted.
[0075] In the case of FIG. 3(b), the first tubular yoke 4b serves
to fix the bearing holder 12 (refer to FIG. 1), the inlet housing
21 (refer to FIG. 1), and the outlet housing 23 (refer to FIG.
1).
[0076] Furthermore, in the same manner as in the prior art, the
magnet 2b of which axial length is so short as is less than about
half the first tubular yoke 4b is located substantially at the
axially central portion of the first tubular yoke 4b.
[0077] In consequence, it is preferable from the viewpoint of
efficiency in manufacturing that the magnet 2b is inserted in and
fixed to the first tubular yoke 4b after having been molded, or
that a through hole, not shown, is provided on a side face of the
first tubular yoke 4b, and the magnet 2b is molded integrally with
the first tubular yoke 4b on an inner circumference from the side
face of the first tubular yoke 4b through this through hole, in the
same manner as in the prior art.
EMBODIMENT 3
[0078] A third preferred embodiment of this invention is
hereinafter described. The third embodiment is modifications of the
magnet and the first tubular yoke in a fuel pump described in the
foregoing first and second embodiments. In these modifications, the
magnet is molded integrally with the first tubular yoke by
injection molding.
[0079] FIG. 4 is a cross sectional view schematically showing a
magnet and a first tubular yoke of a dc motor fuel pump according
to the third embodiment of this invention. FIG. 4(a) is an example
in which a magnet is taper-shaped. FIG. 4(b) is an example in which
a magnet is fixed to the first tubular yoke at both ends. FIG. 4(c)
is an example in which a convex portion is provided at both end
faces of the first tubular yoke. FIG. 4(d) is a view showing only
the yoke of FIG. 4(c).
[0080] In the case of FIG. 4(a), an inner circumferential surface
of a first tubular yoke 4c is formed in a taper shape, and
furthermore a lower end of the first tubular yoke 4c is covered
with a rib 40c at an end portion of a magnet 2c, thereby enabling
to prevent the magnet 2c from moving in the axial direction.
[0081] In the case of FIG. 4(b), both ends of a first tubular yoke
4d are covered with a rib at both end portions of a magnet 2d
integrated with the first tubular yoke 4d by injection molding,
thereby enabling to prevent the magnet 2d from moving in the axial
direction.
[0082] In the case of FIG. 4 (c), a convex FIG. 50e is provided on
an upper end surface of a first tubular yoke 4e in the same manner
as in FIG. 4(d), and both ends of the first tubular yoke 4e are
covered with a magnet 2e integrated with the first tubular yoke 4e
by injection molding, thereby enabling to prevent the magnet 2e
from moving in the axial direction and rotating. In addition, even
if a convex FIG. 50e of the first tubular yoke 4e is formed in a
concave configuration, the same function and advantage can be
obtained.
EMBODIMENT 4
[0083] A fourth preferred embodiment of this invention is
hereinafter described. This fourth embodiment is a modification of
preventing a magnet from rotation in the fuel pump described in the
foregoing Embodiments 1 to 3.
[0084] FIG. 5 is a view schematically showing a magnet and a
bearing holder of a dc motor fuel pump according to the fourth
embodiment of this invention. FIG. 5(a) is an example in which an
end face on the side opposite to the bearing holder 12 of a tubular
magnet (refer to FIG. 1) is flat. FIG. 5(b) is a cross sectional
view showing a magnet, bearing holder, and yoke of FIG. 5(a). FIG.
5(c) is an example of the case where an end face of a magnet is
corrugated. Figs. (d) to (g) are examples of the case where a
concave portion and a convex portion are provided at an end face of
a magnet.
[0085] In addition, although FIG. 5(b) is described showing an
example of a tubular yoke made up of one member for reasons of
description, it is also preferable that a tubular yoke is a tubular
yoke consisting of the first tubular yoke and the second tubular
yoke in the same manner as in the first to third embodiments.
[0086] FIG. 5(a) shows the case where an end face of both a bearing
holder 12f and magnet 2f is flat. As shown in FIG. 5(b), the magnet
2f is sandwiched at both end faces between a convex portion of a
yoke 3f (that is, a convex portion formed radially protruding from
an inner circumference of an end portion on the pump 20 side of the
yoke 3f) and the bearing holder 12f.
[0087] The bearing holder 12f houses the brush 9 (see FIG. 1), the
bearing 8 (see FIG. 1) of the armature 6 (see FIG. 1), and the like
of a dc motor, and is provided with the discharge pipe 12a (see
FIG. 1) of a pressurized fuel, and is an essential component for a
dc motor fuel pump. Therefore, it is possible to stop the movement
in an axial direction and the rotation of the magnet 2f without
increasing the number of parts.
[0088] FIG. 5(c) shows the case where an end face of a bearing
holder 12g and a magnet 2g is corrugated, and these corrugated
portions come in engagement with each other, thereby enabling to
stop the rotation of the magnet 2f.
[0089] FIG. 5(d) shows the case where a concave portion 70h is
provided at an end face of a bearing holder 12h and a convex
portion 60h is provided at an end face of a magnet 2h. These
concave portion and convex portion come in engagement with each
other, thereby enabling to stop the rotation of the magnet 2h.
[0090] FIG. 5(e) shows the case where a convex portion 61k is
provided at an end face of a bearing holder 12k, and a concave
portion 71k is provided at an end face of a magnet 2k. These
concave portion and convex portion come in engagement with each
other, thereby enabling to stop the rotation of the magnet 2k.
[0091] FIG. 5(f) shows the case where a concave portion 72m having
a spring property in a circumferential direction is provided at an
end face of a bearing holder 12m, and a convex portion 62m is
provided at a magnet 2m. These concave portion and convex portion
come in engagement with each other, thereby enabling to stop the
rotation of the magnet 2m.
[0092] FIG. 5(g) shows the case where a convex portion 73h having a
spring property is provided in a circumferential direction at a
bearing holder 12n and a concave portion 63n is provided at a
magnet 2n. These concave portion and convex portion come in
engagement with each other, thereby enabling to stop the rotation
of the magnet 2m.
[0093] Furthermore, the concave portion 72m in the case of FIG.
5(f) or the concave portion 73h in the case of FIG. 5(g) possess a
spring property, thereby enabling to bring the magnet and the
bearing holder in engagement without being loose as compared with
the case of FIG. 5(d) or 5(e).
[0094] In addition, the reason why the concave portion 72m of the
bearing holder 12m has a spring property is now described. The
concave portion 72m of the bearing holder 12m consists of an
inserted-portion (trapezoidal portion) of which opening, into which
the concave portion 62m of the magnet 2m is inserted, is narrower
than the convex portion 62m of the magnet 2m; a pair of protrusions
extending on both sides of this inserted-portion; and slits
provided between the foregoing protrusion and a side portion of the
bearing holder 12m. Then, when the convex portion 62m of the magnet
2m is inserted into the concave portion 72m of the bearing holder
12m, the magnet 2m and the bearing holder 12m are positioned under
the state that a pair of protrusions are elastically deformed to
the slit side (i.e., in the sate of having an axial spring
property) due to the fact that the opening of the inserted-portion
is narrower than the concave portion 72m.
[0095] In the case of molding the magnet 2h or the magnet 2m by
injection molding, when a gate portion having been made at the time
of molding is used as a convex portion of the magnet 2h of FIG.
5(d) or the magnet 2m of FIG. 5(f), the gate processing becomes
preferably unnecessary. A gate in this case is 1 to 2.6 mm in
diameter or side, and is of a cylindrical or prismatic
configuration of approximately 1 mm in height.
[0096] Industrial Applicability
[0097] The present invention is useful in putting into practice use
a dc motor fuel pump having a high degree of freedom in arrangement
of a magnetic circuit, and of which magnet can be easily polarized
with a small-sized polarizing apparatus.
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