U.S. patent application number 14/792141 was filed with the patent office on 2016-01-28 for electric pump.
This patent application is currently assigned to AISIN SEIKI KABUSHIKI KAISHA. The applicant listed for this patent is AISIN SEIKI KABUSHIKI KAISHA. Invention is credited to Shuji HATTORI, Naoki Kamiya, Hiroomi Ogawa.
Application Number | 20160025095 14/792141 |
Document ID | / |
Family ID | 53672992 |
Filed Date | 2016-01-28 |
United States Patent
Application |
20160025095 |
Kind Code |
A1 |
HATTORI; Shuji ; et
al. |
January 28, 2016 |
ELECTRIC PUMP
Abstract
An electric pump includes: a case; a shaft member fixed to the
case; a cylindrical bearing inserted on the outside of the shaft
member; a rotor configured as a member separate from the bearing,
and configured to rotate integrally with the bearing; and an
impeller fixed to one end of the rotor, wherein a discharge path is
formed between the bearing and the rotor along an axial direction,
and allows fluid to return to the impeller therethrough, the fluid
flowing from the outer circumference of the impeller into the case,
and circulating in the case.
Inventors: |
HATTORI; Shuji; (Nagoya-shi,
JP) ; Kamiya; Naoki; (Anjo-shi, JP) ; Ogawa;
Hiroomi; (Nagoya-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AISIN SEIKI KABUSHIKI KAISHA |
Kariya-shi |
|
JP |
|
|
Assignee: |
AISIN SEIKI KABUSHIKI
KAISHA
Kariya-shi
JP
|
Family ID: |
53672992 |
Appl. No.: |
14/792141 |
Filed: |
July 6, 2015 |
Current U.S.
Class: |
417/423.12 |
Current CPC
Class: |
F04D 13/06 20130101;
F04D 29/043 20130101; F04D 29/22 20130101; F05D 2300/44 20130101;
F04D 13/0633 20130101; F04D 29/026 20130101; F16C 17/02 20130101;
F01P 5/12 20130101; F04D 13/0606 20130101; F04D 29/588 20130101;
F04D 29/046 20130101; F05D 2300/121 20130101; F16C 33/1085
20130101; F16C 37/002 20130101; F04D 29/0462 20130101; F04D 1/00
20130101; F04D 29/5806 20130101 |
International
Class: |
F04D 13/06 20060101
F04D013/06; F01P 5/12 20060101 F01P005/12; F04D 29/046 20060101
F04D029/046; F04D 29/22 20060101 F04D029/22; F04D 1/00 20060101
F04D001/00; F04D 29/043 20060101 F04D029/043 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 24, 2014 |
JP |
2014-150968 |
Jul 24, 2014 |
JP |
2014-150969 |
Claims
1. An electric pump comprising: a case; a shaft member fixed to the
case; a cylindrical bearing inserted on the outside of the shaft
member; a rotor configured as a member separate from the bearing,
and configured to rotate integrally with the bearing; and an
impeller fixed to one end of the rotor, wherein a discharge path is
formed between the bearing and the rotor along an axial direction,
and allows fluid to return to the impeller therethrough, the fluid
flowing from the outer circumference of the impeller into the case,
and circulating in the case.
2. The electric pump according to claim 1, wherein an outlet of the
discharge path is provided closer to the center of the shaft member
than blade members of the impeller.
3. The electric pump according to claim 1, wherein the rotor is
made of a resin material into which the bearing is insert-molded,
and wherein a portion of the discharge path passes through an
inside portion of the rotor while not being in contact with the
external surface of the bearing along the axial direction.
4. The electric pump according to claim 2, wherein the rotor is
made of a resin material into which the bearing is insert-molded,
and wherein a portion of the discharge path passes through an
inside portion of the rotor while not being in contact with the
external surface of the bearing along the axial direction.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is based on and claims priority under 35
U.S.C. .sctn.119 to Japanese Patent Applications 2014-150968 and
2014-150969, both filed on Jul. 24, 2014, the entire contents of
which are incorporated herein by reference.
TECHNICAL FIELD
[0002] This disclosure relates to an electric pump including a
rotor rotatably supported by a shaft member, and an impeller fixed
to one end of the rotor.
BACKGROUND DISCUSSION
[0003] In the related art, an electric pump, which includes a shaft
member fixed to a case, and a rotor inserted on the outside of the
shaft member, is known (for example, refer to JP 2006-296125A
(Reference 1)). A through path is formed to pass through a region
between the shaft member and the rotor along an axial direction. A
balancing hole for releasing fluid pressure in the case to the
impeller is formed radially outside of the through path so as to
pass through an end of the rotor and to communicate with blade
members of the impeller.
[0004] A portion of a fluid flowing due to the rotation of the
impeller cools electronic components and the like while circulating
in the case, and returns to the impeller via the through path or
the balancing hole. At this time, the fluid passing through the
through path works as a lubricant that lubricates the shaft member
and the rotor.
[0005] However, in the electric pump in the related art, the
through path is formed between the shaft member and the rotor, and
thus the size of the through path is limited to small dimensions
such that the rotor does not shake relative to the shaft member.
For this reason, foreign matter mixed into the fluid may block the
through path, and bite between the shaft member and the rotor.
Therefore, the rotation of the rotor is prevented, which is a
problem.
[0006] Since the balancing hole communicates with the blade members
of the impeller, a significant fluid pressure, resulting from the
rotation of the impeller, is exerted onto the fluid, and the fluid
flows backward into the case. As a result, there is a problem in
that the foreign matter mixed into the fluid is not discharged, and
remains in the case.
SUMMARY
[0007] Thus, a need exists for an electric pump which is not
suspectable to the drawback mentioned above.
[0008] An aspect of this disclosure is directed to an electric pump
including: a case; a shaft member fixed to the case; a cylindrical
bearing inserted on the outside of the shaft member; a rotor
configured as a member separate from the bearing, and configured to
rotate integrally with the bearing; and an impeller fixed to one
end of the rotor, in which a discharge path is formed between the
bearing and the rotor along an axial direction, and allows fluid to
return to the impeller therethrough, the fluid flowing from the
outer circumference of the impeller into the case, and circulating
in the case.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The foregoing and additional features and characteristics of
this disclosure will become more apparent from the following
detailed description considered with the reference to the
accompanying drawings, wherein:
[0010] FIG. 1 is a sectional view illustrating the entire
configuration of an electric pump in an embodiment;
[0011] FIG. 2 is a partial sectional view in the embodiment;
[0012] FIG. 3 is a view when the part in FIG. 2 is seen from the
front;
[0013] FIG. 4 is a side view of the embodiment;
[0014] FIG. 5 is a plan view of the embodiment;
[0015] FIG. 6 is a view when the part in FIG. 2 is seen from the
rear;
[0016] FIG. 7 is a side view of a bearing;
[0017] FIG. 8 is a sectional view taken along line VIII-VIII in
FIG. 2;
[0018] FIG. 9 is a view of one end of a rotor when seen from the
front;
[0019] FIG. 10 is a partial sectional view of another embodiment;
and
[0020] FIG. 11 is a view when the part in FIG. 10 is seen from the
rear.
DETAILED DESCRIPTION
[0021] Hereinafter, an electric pump P in an embodiment disclosed
here will be described with reference to the accompanying drawings.
In an example given in the embodiment, an electric water pump
(hereinafter, simply referred to as an "electric pump P") for
circulating coolant (an example of a fluid), which cools the engine
of a vehicle, will be described. However, this disclosure is not
limited to the embodiment to be described hereinbelow, and can be
modified in various forms insofar as the modifications do not
depart from the purport of this disclosure. In an explanation to be
given hereinbelow, the front and the rear in a longitudinal
direction of a rotor 5 in FIG. 1, respectively, refer to a side on
which an impeller 6 is disposed, and the opposite side to the
impeller 6.
[0022] FIG. 1 illustrates the entire configuration of the electric
pump P in the embodiment. The electric pump P includes a case 1
made of resin; a metal shaft (shaft member) 3 fixed to the case 1;
a cylindrical bush (bearing) 4 inserted on the outside of the shaft
3; the rotor 5 configured as a member separate from the bush 4, and
rotating integrally with the bush 4; and the impeller 6 fixed to a
flange-shaped end 51 of the rotor 5.
[0023] The bush 4, which directly slides against the shaft 3, is
made of a highly wear-resistant and high heat-resistant material,
and for example, is configured as a carbon bearing made of a
composite material consisting of carbon fiber and resin, or only
carbon. The rotor 5 is made of a resin material such as
polyphenylene sulfide (PPS), in which the bush 4 is insert-molded.
The material of the bush 4 is not limited to a specific material
insofar as the material yields a high wear resistance and a high
heat resistance, and the bush 4 may be made of resin or metal such
as aluminum.
[0024] An engine control unit (ECU) (not illustrated) of the
vehicle performs control of the flow of current to a coil wound
around a stator 8, and as a result, a magnet 54 of the rotor 5 is
affected by alternating magnetic fields, and the bush 4 and the
rotor 5 rotate integrally.
[0025] When the bush 4 and the rotor 5 rotate integrally, the
impeller 6 fixed to the end 51 of the rotor 5 rotates as well. As
illustrated in FIGS. 1 to 5, the impeller 6 has a plurality of
curved blade members 63 inside of a shroud 64, and is covered with
an impeller cover 2 made of resin. For example, the blade members
63 are attached to the end 51 of the rotor 5 using vibration
welding. The electric pump P has the case 1; the impeller cover 2;
a welding portion 22 in which a first press contact surface 11
formed in the case 1 and a second press contact surface 21 formed
in the impeller cover 2 are welded together while being in press
contact therewith; a first pressing portion 13 of the first press
contact surface 11, and a second pressing portion 23 of the second
press contact surface 21 onto each of which a pressing force is
exerted so as to bring the first press contact surface 11 into
press contact with the second press contact surface 21. The second
pressing portion 23 has a convex portion 26a with a pressing
surface 23a having a height H1 set from the second press contact
surface 21, and a convex portion 26b with a pressing surface 23a
having a height H2 set from the second press contact surface
21.
[0026] As illustrated in FIG. 1, a washer 7 is disposed between the
impeller cover 2 and the bush 4 along an axial direction L, and is
fitted over the external surface of a leading end portion of the
shaft 3 such that the shaft 3 and the bush 4 cannot rotate relative
to each other. The washer 7 works as a retainer for the bush 4.
[0027] When the bush 4 and the rotor 5 rotate integrally, and the
impeller 6 rotates, the coolant flows in a spiral manner from a
suction port 61 to the outer circumference of the impeller 6. At
this time, as illustrated in FIG. 1, the majority of the coolant is
delivered to the outside via a discharge port 62, and a portion of
the coolant flows from the outer circumference of the impeller 6
into the case 1, and circulates therein. When the portion of the
coolant circulates in the case 1, the rotor 5, the stator 8, or the
like are cooled.
[0028] In contrast, foreign matter, for example, rust, metal
powder, or the like from metal components, may be mixed into the
coolant in a circulation path, clog up a narrow path formed in the
case 1, and remain therein. In particular, since it is necessary to
design the shaft 3 to have a vicinity which does not deteriorate
the support function of the shaft 3 which is performed for the
rotor 5, it is not possible to ensure a large flow path for the
coolant. As a result, there is a problem in that the coolant cannot
return from the inside of the case 1 to the impeller 6, a rotation
failure may occur due to foreign matter biting into a component, or
cooling function may deteriorate.
[0029] In the embodiment, a discharge path 52 is formed between the
bush 4 and the rotor 5 along the axial direction L, and allows the
coolant to return to the impeller 6 therethrough, the coolant
flowing from the outer circumference of the impeller 6 into the
case 1, and circulating in the case 1. In particular, in the
embodiment, the discharge path 52 is formed in the rotor 5 while
being in contact with the external surface of the bush 4.
Accordingly, it is possible to form the discharge path 52 by
inserting a core pin into a molding die when the bush 4 is
insert-molded, and thus it is not necessary to machine the bush 4,
and it is possible to obtain good manufacturing efficiency. Since
the discharge path 52 is formed between the bush 4 and the rotor 5,
it is possible to obtain a high degree of freedom in determining
the dimensions and shape of the discharge path 52. Therefore, it is
possible to solve the problem that foreign matter mixed into the
coolant clogs up a path.
[0030] In the embodiment, an outlet 52b of the discharge path 52 is
provided closer to the center of the shaft 3 than to the blade
members 63 of the impeller 6. The outlet 52b also works as a
so-called balancing hole for releasing fluid pressure in the case 1
to the impeller 6.
[0031] Typically, the balancing hole passes through the end 51 of
the rotor 5, and communicates with a region in which the blade
members 63 are present. For this reason, there is a problem in that
the coolant may receive fluid pressure resulting from the rotation
of the impeller 6, and flow backward into the case 1. As a result,
the fluid pressure in the case 1 is not released, and the rotating
function of the rotor 5 deteriorates. In addition, there is a
problem in that the coolant cannot circulate from the inside of the
case 1 to the impeller 6 and cooling function deteriorates.
However, in the embodiment, the balancing hole is provided inside
of the blade members 63 such that the coolant is less affected by
fluid pressure resulting from the rotation of the impeller 6, and
thus the coolant can smoothly flow from the inside of the case 1 to
the impeller 6.
[0032] As illustrated in FIG. 7, the bush 4 is formed in a
cylindrical shape, and a plurality (in the embodiment, three) of
protruding portions 41, surrounded by the insert-molding resin
material used to form the rotor 5, are provided on the external
circumferential surface of the bush 4 while being positioned at
equal intervals along a circumferential direction of the bush 4.
Since the protruding portions 41 are in close contact with
internal-surface concave portions 56 of the rotor 5, respectively,
relative rotation between the bush 4 and the rotor 5 is restricted,
and both the bush 4 and the rotor 5 rotate integrally.
[0033] As illustrated in FIGS. 6 and 7, the rear end surface of the
bush 4 opposite to the impeller 6 is cut away in a radial direction
of the bush 4 such that a plurality of positioning concave portions
42 are formed in the rear end surface. When the bush 4 is seen from
the rear, the positioning concave portions 42 are disposed at equal
intervals along the circumferential direction of the bush 4 while
being interposed between the three protruding portions 41. That is,
the protruding portions 41 and the positioning concave portions 42
are alternately disposed along the circumferential direction of the
bush 4.
[0034] When the rotor 5 is formed with the bush 4 being
insert-molded, core pins are inserted into the molding die so as to
align with the positions of the positioning concave portions 42
along the longitudinal direction. That is, the positioning concave
portions 42 work as guides in positioning the discharge paths 52
formed between the bush 4 and the rotor 5. Since the positioning
concave portions 42 are in contact with an insert-molding die, it
is possible to fix the position of the bush 4.
[0035] As illustrated in FIG. 3, a plurality of leading end grooves
43 are formed in the leading end surface of the bush 4 adjacent to
the impeller 6, and extend in a radiating shape around the center
of the bush 4. The leading end grooves 43 work as paths through
which carbon power, made by sliding friction between the shaft 3
and the bush 4, is guided to the outside in the radial direction.
The leading end grooves 43 communicate with the outlets 52b of the
discharge paths 52, and as illustrated in FIG. 7, when the bush 4
is seen from the front, the leading end grooves 43 are disposed at
the same circumferential positions as those of the three protruding
portions 41.
[0036] The quantities, dimensions, and shapes of the protruding
portions 41, the positioning concave portions 42, and the leading
end grooves 43 are not limited to specific quantities, dimensions
and shapes, and one or more protruding portions 41, one or more
positioning concave portions 42, and one or more leading end
grooves 43 may be provided along the circumferential direction of
the bush 4. When the bush 4 is seen from the rear, the protruding
portions 41 and the positioning concave portions 42 are disposed so
as to not overlap each other.
[0037] As illustrated in FIGS. 1 to 2, the magnet 54 is
insert-molded into the rotor 5 while being positioned on the
opposite side to the end 51. As illustrated in FIG. 8, the magnet
54 is configured as a multipolar magnet (6-pole magnet), and the
internal sectional surface of the magnet 54 is formed in a
hexagonal annular shape. The number of poles of the magnet 54 is
not limited to six poles, and may be an even number greater than
two.
[0038] The protruding portions 41 of the bush 4 and the discharge
paths 52 are alternately disposed at the apexes of the hexagonal
internal surface of the magnet 54. That is, since the protruding
portion 41 is disposed in a region in which a large thickness of
the resin material used to form the rotor 5 is ensured, it is
possible to increase the amount of protrusion of the protruding
portion 41. For this reason, it is possible to appropriately set
the dimensions and shape of the protruding portion 41 while taking
the rigidity of each of the bush 4 and the rotor 5 into
consideration. In addition, since the discharge path 52 is disposed
in a region in which a large thickness of the resin material used
to form the rotor 5 is ensured, it is possible to ensure a large
sectional area of the discharge path 52. Accordingly, even if large
pieces of foreign matter are mixed into the coolant, the discharge
path 52 is unlikely to be blocked. The foreign matter mixed into
the coolant is smoothly discharged to the impeller 6 without
remaining in the case 1.
[0039] As illustrated in FIG. 9, rectangular insertion concave
portions 53 are formed in one end surface 51a of the rotor 5 with
the number (in the embodiment, seven) of rectangular insertion
concave portions 53 set to the same as the number of blade members
63, and rear end portions 63a of the blade members 63 are inserted
into the insertion concave portions 53. Convex portions 53a are
respectively formed in both side surfaces of some of the plurality
of the insertion concave portions 53, and are positioned separate
from each other in a longitudinal direction of the insertion
concave portion 53. For this reason, the displacement of the blade
member 63 relative to the axis of the rotor 5 is prevented when the
blade member 63 is attached to the one end surface 51a of the rotor
5 using vibration welding. In addition, since the blade member 63
comes into contact with the convex portion 53a when the impeller 6
rotates, the blade member 63 is prevented from moving relative to
the one end surface 51 a of the rotor 5 in a rotation
direction.
[0040] The convex portions 53a may be limitedly provided in some of
the insertion concave portions 53, or the convex portions 53a may
be provided in all the insertion concave portions 53. When the
insertion concave portion 53 is formed in substantially the same
size as that of the rear end of the blade member 63, the convex
portion 53a may not be provided.
Another Embodiment
[0041] Only points of difference in configuration between another
embodiment and the aforementioned embodiment will be described with
reference to FIGS. 10 to 11. In order to help easy understanding of
the drawings, the same names and reference signs of members as
those in the aforementioned embodiment are used in the explanation
to be given herein.
[0042] In this embodiment, a portion of the discharge path 52
passes through an inside portion of the rotor 5 while not being in
contact with the entire circumference of the bush 4 along the axial
direction L. In other words, a resin surrounding portion 55 is
formed in such a manner that the resin material used to form the
rotor 5 surrounds the entire circumference of a partial region on
the external surface of the bush 4 along the axial direction L. In
this embodiment, the partial region refers to a region of the
discharge path 52 not including the vicinity of an inlet 52a and
the outlet 52b, and the discharge path 52 is in contact with the
entire outer circumference of the bush 4 in the vicinity of the
inlet 52a and the outlet 52b.
[0043] Accordingly, since resin contracting pressure exerted on the
bush 4 is distributed along the circumferential direction of the
bush 4 when the insert-molding die is removed, the shape of the
internal sectional surface of the bush 4 is maintained in a
circular shape. For this reason, the bush 4 smoothly rotates
relative to the shaft 3.
[0044] When the discharge path 52 is configured such that the
discharge path 52 is in contact with the entire outer circumference
of the bush 4 in the vicinity of the outlet 52b, it is possible to
dispose the impeller 6 inward in the radial direction, and thus as
the electric pump P, a compact-sized pump can be used. Since it is
possible to ensure a large sectional area of the discharge path 52,
it is possible to smoothly discharge the coolant to the impeller
6.
[0045] In this embodiment, the resin surrounding portion 55 is
formed by providing a stepped portion 55a in the leading end
portion of the bush 4 along the circumferential direction, the
stepped portion 55a being formed by recessing the external surface
of the leading end portion in the radial direction. However, this
is just an example, and the resin surrounding portion 55 may be
provided on the external flush surface of the bush 4 instead of
recessing the external surface of the bush 4. Also in this case, it
is possible to ensure a large sectional area of the discharge path
52 compared to when the discharge paths 52 are provided between the
shaft 3 and the bush 4.
Other Embodiments
[0046] (1) In the aforementioned embodiment, the discharge paths 52
are formed in the rotor 5 side while being positioned between the
bush 4 and the rotor 5; however, the discharge paths 52 may be
formed in the bush 4 side while being positioned between the bush 4
and the rotor 5. The discharge paths 52 may be formed in the bush 4
and the rotor 5 astride.
[0047] (2) In the aforementioned embodiment, a portion of the
discharge path 52 is not in contact with the entire circumference
of the bush 4 along the axial direction L; however, the entire
discharge path 52 may not be in contact with the entire
circumference of the bush 4 along the axial direction L. The
portion of the discharge path 52 along the axial direction L is not
limited to a region not including the vicinity of the inlet 52a and
the outlet 52b, and may be provided in a region not including the
vicinity of the inlet 52a or the outlet 52b.
[0048] (3) A method for integrating the bush 4 and the rotor 5
together, the bush 4 and the rotor 5 being configured as separate
members, is not limited to an insert-molding method, and for
example, the rotor 5 may be press-fitted on the bush 4.
[0049] (4) A method for fixing the impeller 6 to the end 51 of the
rotor 5 is not limited to vibration welding, and for example, the
impeller 6 can be fixed to the rotor 5 using various methods such
as thermal welding or integration molding.
[0050] (5) The electric pump P is not limited to a pump for
circulating the coolant of the engine, and the electric pump P may
circulate engine oil, or may have applications other than a
vehiclular application. With regards to a motor drive method, the
electric pump P is not limited to a brushless motor that generates
alternating magnetic fields; alternatively, a brushed motor may be
used as the electric pump P.
[0051] An aspect of this disclosure is directed to an electric pump
including: a case; a shaft member fixed to the case; a cylindrical
bearing inserted on the outside of the shaft member; a rotor
configured as a member separate from the bearing, and configured to
rotate integrally with the bearing; and an impeller fixed to one
end of the rotor, in which a discharge path is formed between the
bearing and the rotor along an axial direction, and allows fluid to
return to the impeller therethrough, the fluid flowing from the
outer circumference of the impeller into the case, and circulating
in the case.
[0052] According to this configuration, the bearing and the rotor
rotate integrally around the fixed shaft member, the rotor being
configured as a member separate from the bearing. That is, since it
is not necessary to provide a through path for the sake of
lubrication between the shaft member and the rotor unlike the
related art, it is sufficient to make only the bearing of a highly
wear-resistant material, which is beneficial. In addition, foreign
matter biting between the shaft member and the bearing does not
prevent the rotation of the rotor.
[0053] According to this configuration, the discharge path is
provided between the bearing and the rotor which rotate integrally,
and the shaking of components relative to the shaft member occurs
less than in the related art in which the discharge path is
provided between the shaft member and the rotor which do not rotate
integrally. Therefore, it is possible to ensure a large sectional
area of the discharge path. That is, even if large pieces of
foreign matter are mixed into the fluid, the discharge path is not
blocked. Accordingly, foreign matter mixed into the fluid returns
to the impeller and is discharged to the outside without remaining
in the case.
[0054] As described above, it is possible to reasonably configure
an electric pump that can smoothly discharge foreign matter mixed
into the fluid without preventing the rotation of the rotor.
[0055] In the electric pump according to the aspect of this
disclosure, an outlet of the discharge path may be provided closer
to the center of the shaft member than to the blade members of the
impeller.
[0056] Centrifugal force, resulting from the rotation of the
impeller, is exerted onto the fluid, and the fluid flows to the
outer circumference of the impeller. That is, the flow rate (fluid
pressure) of the fluid increases toward the outer circumference of
the impeller in a region in which the blade members of the impeller
are present. In this configuration, the outlet of the discharge
path is provided closer to the center of the shaft member than to
the blade members of the impeller, that is, it is provided on the
inner circumference of the impeller on which fluid pressure is
exerted the least, and thus it is possible to make the fluid, into
which foreign matter is mixed, smoothly flow from the inside of the
case to the impeller.
[0057] In the electric pump according to the aspect of this
disclosure, the rotor may be made of a resin material into which
the bearing is insert-molded, and a portion of the discharge path
may pass through an inside portion of the rotor while not being in
contact with the external surface of the bearing along the axial
direction.
[0058] According to this configuration, when the rotor is formed
with the bearing being insert-molded, integrity between the rotor
and the bearing is increased. Since the discharge path is
configured such that a portion of the discharge path is not in
contact with the external surface of the bearing along the axial
direction, the entire circumference of the bearing is surrounded by
the resin material used to form the rotor. Accordingly, pressure,
induced by resin shrinkage, exerted on the bearing is distributed
along a circumferential direction of the bearing, the shape of the
internal sectional surface of the bearing is easily maintained in a
circular shape. As a result, the bearing and the rotor can smoothly
rotate relative to the shaft member.
[0059] This disclosure can be used in an electric pump for
circulating various types of fluid.
[0060] The principles, preferred embodiment and mode of operation
of the present invention have been described in the foregoing
specification. However, the invention which is intended to be
protected is not to be construed as limited to the particular
embodiments disclosed. Further, the embodiments described herein
are to be regarded as illustrative rather than restrictive.
Variations and changes may be made by others, and equivalents
employed, without departing from the spirit of the present
invention. Accordingly, it is expressly intended that all such
variations, changes and equivalents which fall within the spirit
and scope of the present invention as defined in the claims, be
embraced thereby.
* * * * *