U.S. patent application number 11/266239 was filed with the patent office on 2006-05-11 for axial flow pump.
This patent application is currently assigned to Toshiba TEC Kabushiki Kaisha. Invention is credited to Takahiko Manda, Yoshifumi Tanabe.
Application Number | 20060099068 11/266239 |
Document ID | / |
Family ID | 36316502 |
Filed Date | 2006-05-11 |
United States Patent
Application |
20060099068 |
Kind Code |
A1 |
Tanabe; Yoshifumi ; et
al. |
May 11, 2006 |
Axial flow pump
Abstract
Disclosed is an axial flow pump including a combined impeller
integrally formed of an axial impeller and a centrifugal impeller,
the axial impeller being composed of a first cylinder on which a
first groove is formed, the centrifugal impeller being composed of
a second cylinder on which a second groove is formed. The second
groove is smoothly connected with the first groove and a distance
between a bottom surface of the second groove and a centerline of
the second cylinder gradually increases to prevent turbulent flow
of liquid which may occur at the connection point between first and
second grooves thereby achieving a high pump performance and a
decreased external size of the pump.
Inventors: |
Tanabe; Yoshifumi; (Tokyo,
JP) ; Manda; Takahiko; (Tokyo, JP) |
Correspondence
Address: |
PILLSBURY WINTHROP SHAW PITTMAN, LLP
P.O. BOX 10500
MCLEAN
VA
22102
US
|
Assignee: |
Toshiba TEC Kabushiki
Kaisha
Tokyo
JP
|
Family ID: |
36316502 |
Appl. No.: |
11/266239 |
Filed: |
November 4, 2005 |
Current U.S.
Class: |
415/143 |
Current CPC
Class: |
F04D 1/025 20130101;
F04D 13/0606 20130101; F04D 13/12 20130101; H02K 7/14 20130101;
F04D 3/00 20130101 |
Class at
Publication: |
415/143 |
International
Class: |
F04D 13/12 20060101
F04D013/12 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 5, 2004 |
JP |
JP 2004-321469 |
Claims
1. A pump for transporting liquid, comprising: a housing having a
cylindrical wall defining a liquid passage inside the housing, the
housing having opposite sides; an inlet port, formed at one side of
the housing, which is fluidly communicated with the passage; an
outlet port, formed at the other side of the housing, which is
fluidly communicated the passage; and a combined impeller rotatably
arranged along a center line of the cylindrical wall to forcibly
generate flow of the liquid through the inlet port and discharge
the liquid out of the outlet port, the combined impeller including
an axial impeller and a centrifugal impeller which are located, in
order, along the passage from the inlet port to the outlet port,
the axial impeller being composed of a first cylinder having a
first outer diameter and a first groove spirally formed on the
first cylinder, and the centrifugal impeller being composed of a
second cylinder having a second outer diameter larger than the
first outer diameter and a second groove spirally formed on the
second cylinder, wherein the second groove is smoothly connected
with the first groove through a connection point and the second
groove is shaped such that a distance between a bottom surface of
the second groove and a rotational center of the centrifugal
impeller gradually increases from the connection point in a
direction opposite to the rotational direction of the combined
impeller.
2. A pump according to claim 1, wherein the second groove has a
bottom surface termination edge and includes a forcing surface,
formed on the bottom surface termination edge, which projects
toward the rotational direction of the combined impeller to push
out the liquid along with substantially a tangential direction of
the second cylinder.
3. A pump according to claim 2, wherein the projecting area of the
forcing surface is 30% or less to the entire area of the bottom
surface of the second groove from the connection point to the
bottom surface termination edge.
4. A pump according to claim 2, wherein the bottom surface of the
second groove is formed such that a width of the bottom surface in
a direction along the center line of the cylindrical wall gradually
decreases toward the bottom surface termination edge.
5. A pump according to claim 1, wherein the second groove has a
bottom surface termination edge and the bottom surface of the
second groove is formed such that a width of the bottom surface in
a direction along the center line of the cylindrical wall gradually
decreases toward the bottom surface termination edge.
6. A pump according to claim 5, further comprising a circular top
plate having a diameter equal to or larger than the second diameter
and provided on a surface having the bottom surface termination
edge.
7. A pump according to claim 1, further including a driving unit
for supplying a driving current to drive the combined impeller and
a stator having windings, the stator being opposite to the combined
impeller through the cylindrical wall in the housing.
8. A pump according to claim 7, wherein the combined impeller
includes a plurality of magnets arranged at a distance along the
rotational direction inside the combined impeller, and the combined
impeller is rotated around the rotational center when the driving
unit supplies a driving current to the windings of the stator.
Description
CROSS REFERENCE OF THE INVENTION
[0001] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Application No. 2004-321469
filed on Nov. 5, 2004, the contents of which are incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a pump for transporting
liquid and more particularly to an axial flow pump having a
combined impeller including an axial impeller and centrifugal
impeller.
[0004] 2. Description of the Related Art
[0005] Conventionally, a pump including an impeller is employed to
transport liquid. As an example of the pump, Japanese patent
application Kokai publication No. 2000-262404 discloses an axial
flow pump in which an impeller formed to seemingly combine an axial
impeller with a centrifugal impeller is provided. In the pump
including the axial and centrifugal impellers, rotation of the
axial impeller causes liquid taken from an inlet port to move in a
direction along with a centerline of the axial impeller and
rotation of the centrifugal impeller subsequently causes the liquid
to discharge from an outlet port in a centrifugal direction
substantially perpendicular to the centerline of the axial
impeller.
[0006] When the liquid transported by the axial impeller reaches
the centrifugal impeller, a traveling direction of the liquid
suddenly changes from the direction along with the centerline of
the axial impeller to the centrifugal direction. Due to this rapid
change, a turbulent flow of the liquid occurs. This turbulent flow
of the liquid causes deterioration in the liquid discharge
performance by the pump.
[0007] To prevent the turbulent flow phenomenon, a rectifier plate
may be is needed to be set where the turbulent flow occurs.
However, such installation of the rectifier plate may also cause
complexity in the entire structure of the impeller and increase in
the external size of the pump, as well.
SUMMARY OF THE INVENTION
[0008] Accordingly, it is an object of the present invention to
prevent a turbulent flow of liquid in an axial flow pump.
[0009] It is another object of the invention to provide a unique
structure of a combined impeller including an axial impeller and a
centrifugal impeller in an axial flow pump.
[0010] To accomplish the above-described objects, an axial flow
pump comprises a housing having a cylindrical wall defining a
liquid passage inside the housing, the housing having opposite
sides; an inlet port, formed at one side of the housing, which is
fluidly communicated with the passage; an outlet port, formed at
the other side of the housing, which is fluidly communicated the
passage; and a combined impeller rotatably arranged along a center
line of the cylindrical wall to forcibly generate flow of the
liquid through the inlet port and discharge the liquid out of the
outlet port, the combined impeller including an axial impeller and
a centrifugal impeller which are located, in order, along the
passage from the inlet port to the outlet port, the axial impeller
being composed of a first cylinder having a first outer diameter
and a first groove spirally formed on the first cylinder, and the
centrifugal impeller being composed of a second cylinder having a
second outer diameter larger than the first outer diameter and a
second groove spirally formed on the second cylinder, wherein the
second groove is smoothly connected with the first groove through a
connection point and the second groove is shaped such that a
distance between a bottom surface of the second groove and a
rotational center of the centrifugal impeller gradually increases
from the connection point in a direction opposite to the rotational
direction of the combined impeller.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a longitudinal cross sectional view of a pump in a
first embodiment of the present invention.
[0012] FIG. 2 is a block diagram showing a circuit for driving the
pump.
[0013] FIG. 3 is a perspective view with a part of longitudinal
cross section of a combined impeller employed in a pump of the
first embodiment.
[0014] FIG. 4 is a perspective view of the combined impeller of the
first embodiment.
[0015] FIG. 5 is a plan view of the combined impeller of the first
embodiment.
[0016] FIG. 6 is a perspective view of a combined impeller employed
in a second embodiment of the present invention.
[0017] FIG. 7 is a plan view of the combined impeller of the second
embodiment.
[0018] FIG. 8 is a graph showing a relation among area ratio of a
forcing surface to an entire surface of a second groove, pump
performance of discharging air taken in liquid, and degree of a
load affecting the pump.
[0019] FIG. 9 is a perspective view of the combined impeller of a
third embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] Preferred embodiments of the present invention will now be
described in more detail with reference to the accompanying
drawings. However, the same numerals are applied to the similar
elements in the drawings, and therefore, the detailed descriptions
thereof are not repeated.
[0021] A first embodiment of the present invention will now be
described with reference to FIGS. 1 through 5.
[0022] FIG. 1 is a longitudinal cross sectional view of an axial
flow pump 1 which transports liquid. The pump 1 includes a housing
3 having a cylindrical can 12 that has opposite sides and defines a
liquid passage 2 therein. The pump 1 also has a combined impeller 4
rotatably arranged along a centerline of the cylindrical can 12. An
inlet port 5 at one side of the housing 3 and an outlet port 6 at
the other side of the housing 3 are respectively formed to fluidly
communicate with the liquid passage 2. Rotation of the combined
impeller 4 forcibly generates flow of the liquid along the liquid
passage 2 through the inlet port 5 and discharges the liquid out of
the outlet port 6.
[0023] To rotate the combined impeller 4,around the centerline, a
stator 7 is arranged in the housing 3 to be opposite to the
combined impeller 4 through the cylindrical can 12. The stator 7 is
formed of a stator core 8, a plurality of windings 9, and bobbins
10. The stator core 8 is formed by laminating a plurality of
silicon steel plates each shaped in a circular disk such that six
projections 8a protruding toward a centerline of the cylindrical
can 12 are radially allocated by 60 degrees. The six windings 9 are
set on the respective projections 8a, separating three pairs each
serially connected. One of the pairs of the windings 9 is aligned
on two projections opposite to each other. The three pairs of the
windings 9 are sequentially energized by supplying a driving
current to magnetize the respective projections 8a.
[0024] As shown in FIG. 2, the driving current is sequentially
supplied from a driving unit 30 to the pairs of windings 9 so that
the combined impeller 4 rotates by an associated operation between
magnetization of the respective projections 8a in sequence and
permanent magnet provided in the combined impeller as described
below. The bobbin 10 provided between the winding 9 and the
projection 8a is made of an insulating material to insulate both of
them.
[0025] Between the bobbin 10 and projection 8a a clearance is
formed, and silicon grease 11 having a viscosity and thermal
conductivity is introduced into the clearance. The silicon grease
11 is a gelled oil based material containing alumina powder having
a high thermal conductivity to fill the clearance.
[0026] The cylindrical can 12 defining the liquid passage 2 in the
housing 3 keeps the liquid away from contacting with the stator 7.
In addition to the waterproof of the stator 7, since the
cylindrical can 12 is made of highly thermal conductive material,
such as metal, heat generated by the stator 7 travels through the
cylindrical can 12 to the liquid passing through the liquid passage
2 thereby cooling the stator 7.
[0027] In the cylindrical can 12, a part of the combined impeller
is arranged as described later. The combined impeller 4 has a shaft
16 which is rotatably supported by two ball bearings 17 and 18
attached respectively to the inlet port 5 side and the outlet port
6 side of the housing 3.
[0028] The combined impeller 4 is to be integrally formed, as a one
piece, of an axial impeller 13 and a centrifugal impeller 14. The
axial impeller 13 is located inside the cylindrical can 12 at one
side of the housing 3 where the inlet port 6 is arranged. The
centrifugal impeller 14 is located at the other side of the housing
3 where the outlet port 6 is arranged. When the combined impeller 4
rotates by the magnetization of the projections 8a, the liquid
drawing via the inlet port 5 travels through the axial and
centrifugal impellers 13 and 14 in order.
[0029] The axial impeller is composed of a first cylinder 13a
having a first outer diameter slightly smaller than an inner
diameter of the cylindrical can 12 and a first groove 13b spirally
formed on a periphery of the first cylinder 13a. The centrifugal
impeller 14 is composed of a second cylinder 14a having a second
outer diameter larger than the first outer diameter and a second
groove 14b spirally formed on a periphery of the second cylinder
14a. The first groove 13b and the second groove 14b are smoothly
connected as described later.
[0030] In general, it may be understood that a groove is defined by
opposite walls and a bottom surface between walls. In this
embodiment, however, as shown in FIGS. 4 and 5, one of the walls of
the groove is eliminated to simplify the structure and the bottom
wall of the housing 3 facing the centrifugal impeller 14 acts as
the other wall of the groove in view of the operation of the pump.
Therefore, in this embodiment, such modified groove having one wall
and a bottom surface is also called as a groove.
[0031] In FIG. 3 the combined impeller 4 is manufactured by molding
polyphenylene sulfide to integrally form the axial and centrifugal
impellers 13 and 14. The axial impeller 13 includes two rotor cores
26 and a permanent magnet 25 which locates between the cores to
generate magnetic poles on the rotor cores. When molding, two rotor
cores 26 are positioned into the axial impeller 13 such that the
magnetic poles of the rotor cores 26 face, via the cylindrical can
12, to the projections 8a provided with the windings 9 when the
pump is assembled. The rotor cores 26 are radially allocated about
a centerline of the combined impeller 4 such that different
magnetic poles are alternately placed by 90 degrees.
[0032] As shown in FIG. 4, the first groove 13b on the axial
impeller 13 is shaped such that a distance between a bottom surface
13c of the first groove 13b and a rotational center of the axial
impeller 13 is uniformed over the entire region of the first groove
13b. The first groove 13b is also spirally shaped at an angle
ranging from 12 to 25 degrees with respect to the centerline of the
axial impeller 13.
[0033] The second groove 14b on the centrifugal impeller 14 is
smoothly connected with the first groove 13b through a connection
point A as indicated in FIG. 4. The second groove 14b is spirally
and extendedly shaped such that a distance between a bottom surface
14c of the second groove 14b and a rotational center of the
centrifugal impeller 14 gradually increases from the connection
point A in a direction opposite to the rotational direction of the
combined impeller 4. At the connection point A between the first
groove 13b and the second groove 14b, the bottom surface 13c of the
first groove 13b is smoothly connected with the bottom surface 14c
of the second groove 14b. Because the second groove 14b is spirally
and extendedly formed on the second cylinder 14a as stated above, a
termination edge 14d emerges at a position that the second groove
14b terminates on the second cylinder 14a. Besides, owing to the
spirally formed groove, a width B, B' of the bottom surface 14c of
the second groove 14b in a direction along the center line of the
combined impeller 4 gradually decreases toward the bottom surface
termination edge 14d.
[0034] In the pump 1 described above, the combined impeller 4 can
be driven in a rotational direction as indicated by an arrow C in
FIGS. 4 and 5 by means of the driving unit 30 that supplies a
driving current to the respective pairs of windings 9 to
sequentially change the magnetic poles of the respective
projections 8a in the stator 7.
[0035] By the rotation of the combined impeller 4, liquid is taken
through the inlet port 5, carried through the first groove 13a on
the axial impeller 13 and then transferred from the first groove
13a to the second groove 14b via the connection point A without
generating a turbulent flow of the liquid at the connection point
A. This is because that a flow direction of the liquid is gradually
and smoothly changed at the connection point A toward a centrifugal
direction indicated by an arrow D by the bottom surface 14c of the
second groove 14b as the combined impeller 4 (centrifugal impeller)
rotates. After that, the flow direction of the liquid is further
changed from the centrifugal direction to the rotational direction
of the combined impeller 4 as the centrifugal impeller further
rotates because of the absence of side wall extending from the can
12 and then the liquid is discharged from the outlet port 6.
[0036] In respect to a method of manufacturing the combined
impeller 4 in this embodiment, a molding method is employed to
integrally form the axial and centrifugal impellers 13 and 14 at
the same time without unevenness at the connection point A between
the first and second grooves 13b and 14b. Alternatively, after the
axial and centrifugal impellers are separately formed,
manufacturing method may be employed in which the axial and
centrifugal impellers are bonded to each other to smoothly connect
the first groove on the axial impeller with the second groove on
the centrifugal impeller.
[0037] The pump including the aforementioned combined impeller
achieves a smooth liquid transfer without occurrence of turbulent
flow at the connection point A from the axial impeller to the
centrifugal impeller. Due to a unique structure of the combined
impeller, applying a rectifier plate between an axial and
centrifugal impellers is not needed to achieve a smooth liquid
transfer. Therefore, performance of the pump can be improved
without the rectifier plate.
[0038] As the rectifier plate and room for setting the rectifier
plate are not needed, the external size of the pump can be
decreased compared with a pump which employs such rectifier
plate.
[0039] Besides, as indicated by B and B' in FIG.4, since a width of
the bottom surface 14c of the second groove 14b in a direction
along the center line of the cylindrical wall gradually decreases
toward a direction opposite to the rotational direction of the
combined impeller, load adversely affecting the rotation of the
combined impeller 4 which otherwise increases as the combined
impeller 4 rotates can be alleviated.
[0040] A second embodiment of the present invention is described
with reference to FIGS. 6 through 8. FIG. 6 is a perspective view
of a modified combined impeller 20 employed in an axial flow pump
of this embodiment. FIG. 7 is a plan view of the combined impeller
20.
[0041] A combined impeller 20 of the second embodiment is housed in
the housing 3 shown in FIG. 1, instead of the combined impeller 4.
A difference between the first embodiment and the second embodiment
is a structure of the combined impeller. In particular, a major
difference between the combined impeller 4 of the first embodiment
and the combined impeller 20 of the second embodiment is a
structure of the centrifugal impeller 14A. Therefore, description
will be given only to the structure of the combined impeller
20.
[0042] The combined impeller 20 is integrally formed, as one piece,
of an axial impeller 13 and a centrifugal impeller 14A. The axial
and centrifugal impellers 13 and 14A are placed such that liquid
taken from the inlet port 5 firstly goes through the axial impeller
13, and then goes through the centrifugal impeller 14A, as shown in
FIG. 1.
[0043] The axial impeller 13 is composed of a first cylinder 13a
having a first outer diameter slightly smaller than an inner
diameter of the cylindrical can 12 and a first groove 13b spirally
formed on a periphery of the first cylinder 13a.
[0044] The centrifugal impeller 14A is composed of a second
cylinder 14a having a second outer diameter larger than the first
outer diameter and a second groove 14b spirally and extendedly
formed on a periphery of the second cylinder 14a. The second groove
14b is smoothly connected with the first groove 13b at a connection
point A, as shown in FIG. 6. Thus, the combined impeller 20 in this
embodiment has two continuous grooves comprised of the first and
second grooves.
[0045] Since the second groove 14b is spirally and extendedly
formed on the second cylinder 14b, a bottom surface 14c of the
second groove 14b has a termination edge on the second cylinder
14a. At the termination edge, the bottom surface 14c projects
toward a rotational direction of the combined impeller 20 to form a
forcing surface 21. In more detail, the bottom surface 14c is
shaped such that a part of the bottom surface 14c near the
termination edge smoothly curves toward the rotational direction of
the combined impeller 20. By such a construction of the second
groove 14b, liquid which is conveyed along the second groove 14b as
the combined impeller 20 rotates is finally forced to change its
flow direction by the forcing surface 21 along with substantially a
tangential direction of the second cylinder 14a. A projecting area
G of the forcing surface 21 may be formed to be 30% or less to the
entire area F of the bottom surface 14c from the connection point A
to the termination edge as shown in FIG.7.
[0046] An operation of the forcing surface 21 will be described in
more detail. Rotation of the combined impeller 20 causes conveyance
of liquid from the inlet port 5 to the outlet port 6 through the
combined impeller 20, as shown in FIG. 1. When forwarding the
liquid from the centrifugal impeller 14A of the combined impeller
20 to the outlet port 6, the liquid is forwarded by the bottom
surface 14c toward the direction indicated by the arrow D and then
is forced to flow by the forcing surface 21 toward the tangential
direction of the second cylinder 14a indicated by an arrow E, i.e.,
the rotational direction of the combined impeller 20, as the
rotation of the combined impeller 20 advances. The flow direction
of the liquid is thus changed to the rotational direction of the
combined impeller 20 by the forcing surface 21 and the liquid is
finally discharged from the outlet port 6.
[0047] In general, pumps may draw liquid with air bubbles into the
inside thereof or air bubbles may be produced during transfer of
liquid within a pump. Such air bubbles may stay in the pump and
adversely affect performance of the pump. However, in this
embodiment, since the forcing surface 21 forcibly and smoothly
changes the flow direction of liquid from the axial direction to
the rotational direction of the combined impeller 20, air bubbles
are also forwarded together with the liquid to the outlet port 6
and are finally discharged out of the port 6. Therefore,
performance of the pump can be improved by the forcing surface.
[0048] FIG. 8 is a graph showing pump performance of discharging
air bubbles contained in liquid and degree of load affecting the
combined impeller 20 respectively in terms of each ratio in an area
of the forcing surface 21 to an entire area of the bottom surface
14c when the ratio is varied. As can be seen, the larger the area
ratio goes, the higher the pump performance becomes. However the
degree of the load adversely increases in accordance with the area
ratio. Thus, it is preferred to set the area ratio to be 30% or
less.
[0049] A third embodiment of the present invention is described
with reference to FIG. 9. In the above-described first and second
embodiments, the centrifugal impeller 14 (14A) includes the second
cylinder 14a on the outer surface of which the second groove 14b
having one wall and a bottom surface is formed. The third
embodiment includes a further modified combined impeller 30.
[0050] General structure of a pump in this embodiment is like the
pump described in the first embodiment. The further modified
combined impeller 30 is formed such that a circular top plate 14e
is set on the second cylinder 14a of the combined impeller 4 shown
in FIG. 1. The circular top plate 14e has a diameter equal to or
slightly larger than the outer diameter of the second cylinder
14a.
[0051] When manufacturing the combined impeller 30, it is possible
to fix the circular top plate 14e with the second cylinder 14a or
to integrally mold the combined impeller 30 including an axial and
centrifugal impellers 13, 14 and the circular top plate 14e.
[0052] The above-described combined impeller 30 is driven by the
driving unit 9 as similar to the first embodiment. When the
combined impeller 30 rotates in the pump, liquid transferred from
the first groove 13b is forwarded toward a radial direction of the
combined impeller 30 by the bottom surface 14c. Then the circular
top plate 14e functions to assist the centrifugal impeller 14 to
forcibly move the liquid, which otherwise flows in the axial
direction, toward the radial direction thereof. Therefore, the
circular top plate 14e of the centrifugal impeller 14 can improve
performance of the pump.
[0053] Numerous modifications and variations of the present
invention are possible in light of the above teachings. It is
therefore to be understood that, within the scope of the appended
claims, the present invention can be practiced in a manner other
than as specifically described therein.
* * * * *